Introduction and uptake of new medical technologies in the Australian health care system: a qualitative study.

PubMed

Gallego, Gisselle; Casey, Robert; Norman, Richard; Goodall, Stephen

2011-10-01

The aim of this study was to explore the views and perceptions of stakeholders about the current national health technology assessment process conducted by the Medical Services Advisory Committee (MSAC) and its role in the uptake and diffusion of new medical technologies in Australia. Data collection occurred over a nine month period (August 2008-April 2009). Twenty in-depth, semi-structured interviews were conducted with individuals from four stakeholders groups: (i) MSAC members and evaluators, (ii) academic and health technology assessment experts, (iii) medical industry representatives and (iv) medical specialists. Interviews were digitally recorded, transcribed verbatim and coded using a constant comparative method. Respondents expressed a consensus opinion that the MSAC process is generally fair and transparent, and has been increasingly so over time. The process was described as "flexible" and "intuitive" yet also "idiosyncratic" due to the nature of the technologies being appraised. Approval by MSAC was generally reported to be increasingly important once a technology becomes more widely used. While successful MSAC approval was felt to be important for widespread distribution of a new technology, it was viewed more as a "facilitator of the uptake of new technologies" as opposed to a primary "driver" of technology uptake. Instead, other factors were identified as providing the actual impetus for the uptake of new technologies, with MSAC approval and reimbursement eventually helping facilitate more widespread diffusion. MSAC's decision making process is perceived as fair but with room for improvement. Its role in the uptake and diffusion of new medical technologies in Australia is limited. MSAC does not act as a barrier to significant market penetration of new procedures and medical technologies. However reimbursement is a trigger for increased use. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

The Rate and Clinical Significance of Incidental Thyroid Uptake as Detected by Gallium-68 DOTATATE Positron Emission Tomography/Computed Tomography

PubMed Central

Nockel, Pavel; Millo, Corina; Keutgen, Xavier; Klubo-Gwiezdzinska, Joanna; Shell, Jasmine; Patel, Dhaval; Nilubol, Naris; Herscovitch, Peter; Sadowski, Samira M.

2016-01-01

Background: Gallium-68 (Ga-68) DOTATATE is a radiolabeled peptide–imaging modality that targets the somatostatin receptor (SSTR), especially subtype 2 (SSTR2). Benign and malignant thyroid tumors have been observed to express SSTR. The aim of this study was to evaluate the frequency and clinical significance of incidental atypical thyroid uptake as detected by Ga-68 DOTATATE positron emission tomography/computed tomography (PET/CT). Methods: A retrospective analysis was conducted of a prospective study in which 237 patients underwent Ga-68 DOTATATE PET/CT as part of a work-up for metastatic and unknown primary neuroendocrine tumors. The types of uptake in the thyroid gland (focal/diffuse) and maximum standardized uptake value (SUVmax) levels were evaluated and compared with the background uptake in the liver and salivary glands. Results: Of 237 patients, 26 (11%) had atypical thyroid uptake as detected by Ga-68 DOTATATE PET/CT. There were no significant clinical or biochemical variables associated with atypical thyroid uptake. Fourteen (54%) patients had positive focal uptake, and 12 (46%) patients had diffuse uptake. Of the 14 patients with atypical focal uptake, 10 (71%) had thyroid nodules on the corresponding side, as detected by anatomic imaging. Three of 10 patients (21%) were found to have papillary thyroid cancer, and seven (70%) had adenomatoid nodules. Of the 12 patients with diffuse increased uptake, six (50%) had a history of hypothyroidism, five (42%) had chronic lymphocytic thyroiditis, and one (8%) had nontoxic multinodular goiter. Conclusions: Patients with an incidental focal abnormal thyroid uptake on Ga-68 DOTATATE PET/CT scan should have further clinical evaluation to exclude a diagnosis of thyroid cancer. PMID:27094616

Synergistic Skin Penetration Enhancer and Nanoemulsion Formulations Promote the Human Epidermal Permeation of Caffeine and Naproxen.

PubMed

Abd, Eman; Namjoshi, Sarika; Mohammed, Yousuf H; Roberts, Michael S; Grice, Jeffrey E

2016-01-01

We examined the extent of skin permeation enhancement of the hydrophilic drug caffeine and lipophilic drug naproxen applied in nanoemulsions incorporating skin penetration enhancers. Infinite doses of fully characterized oil-in-water nanoemulsions containing the skin penetration enhancers oleic acid or eucalyptol as oil phases and caffeine (3%) or naproxen (2%) were applied to human epidermal membranes in Franz diffusion cells, along with aqueous control solutions. Caffeine and naproxen fluxes were determined over 8 h. Solute solubility in the formulations and in the stratum corneum (SC), as well as the uptake of product components into the SC were measured. The nanoemulsions significantly enhanced the skin penetration of caffeine and naproxen, compared to aqueous control solutions. Caffeine maximum flux enhancement was associated with a synergistic increase in both caffeine SC solubility and skin diffusivity, whereas a formulation-increased solubility in the SC was the dominant determinant for increased naproxen fluxes. Enhancements in SC solubility were related to the uptake of the formulation excipients containing the active compounds into the SC. Enhanced skin penetration in these systems is largely driven by uptake of formulation excipients containing the active compounds into the SC with impacts on SC solubility and diffusivity.

Modeling the effect of glutamate diffusion and uptake on NMDA and non-NMDA receptor saturation.

PubMed Central

Holmes, W R

1995-01-01

One- and two-dimensional models of glutamate diffusion, uptake, and binding in the synaptic cleft were developed to determine if the release of single vesicles of glutamate would saturate NMDA and non-NMDA receptors. Ranges of parameter values were used in the simulations to determine the conditions when saturation could occur. Single vesicles of glutamate did not saturate NMDA receptors unless diffusion was very slow and the number of glutamate molecules in a vesicle was large. However, the release of eight vesicles at 400 Hz caused NMDA receptor saturation for all parameter values tested. Glutamate uptake was found to reduce NMDA receptor saturation, but the effect was smaller than that of changes in the diffusion coefficient or in the number of glutamate molecules in a vesicle. Non-NMDA receptors were not saturated unless diffusion was very slow and the number of glutamate molecules in a vesicle was large. The release of eight vesicles at 400 Hz caused significant non-NMDA receptor desensitization. The results suggest that NMDA and non-NMDA receptors are not saturated by single vesicles of glutamate under usual conditions, and that tetanic input, of the type typically used to induce long-term potentiation, will increase calcium influx by increasing receptor binding as well as by reducing voltage-dependent block of NMDA receptors. Images FIGURE 1 PMID:8580317

Bilateral symmetrical adrenal hypermetabolism on FDG PET/CT due to Cushing syndrome in well differentiated neuroendocrine carcinoma.

PubMed

Aktas, G E; Soyluoglu Demir, S; Sarikaya, A

2016-01-01

The (18)F-FDG PET/CT scan has been suggested for whole-body imaging to identify ectopic adrenocorticotrophic hormone secreting tumours, but there are some challenges involved. The case of a patient is presented, who was admitted with the pre-diagnosis of ectopic ACTH syndrome. On the CT, a nodular lesion was detected in the medial segment of the right lung. The FDG uptake of the lesion seemed to be increased visually, but was not pathological quantitatively (SUVmax: 1.8) on the PET/CT. There was also diffuse increased uptake (SUVmax: 14.2) in the enlarged adrenal glands. The lesion was reported as a possible malignant lesion with low FDG affinity, such as a low grade neuroendocrine tumour, while the diffuse enlarged adrenal glands with high uptake were interpreted as diffusely hyperplasic, due to Cushing's syndrome. The patient was treated with a surgical wedge resection. The histopathological diagnosis confirmed that the tumour was a grade 1 well-differentiated neuroendocrine carcinoma. Copyright © 2015 Elsevier España, S.L.U. and SEMNIM. All rights reserved.

Evaluation of a low-carbohydrate diet-based preparation protocol without fasting for cardiac PET/MR imaging.

PubMed

Nensa, Felix; Tezgah, E; Schweins, K; Goebel, J; Heusch, P; Nassenstein, K; Schlosser, T; Poeppel, T D

2017-06-01

Assessment of increased glucose uptake in inflammatory or malignant myocardial disease using PET/MRI relies on uptake suppression in normal myocardium. We evaluated the efficacy of a ≥24 hours high-fat, low-carbohydrate, and protein-permitted diet (HFLCPP) in combination with unfractionated heparin for suppression of "physiologic" myocardial glucose uptake. PET/MRI was successfully performed in 89 patients. HFLCPP was started ≥24 hours prior to PET/MRI. All patients received i.v. injection of unfractionated heparin (50 IU·kg -1 ) 15 minutes prior to FDG administration. Left ventricular FDG uptake was visually evaluated by two readers. Diffuse myocardial uptake exceeding liver uptake, isolated uptake in the lateral wall, or diffuse uptake in the entire circumference of the heart base were defined as failed suppression. Homogeneous myocardial uptake below liver uptake with/without focal uptake was defined as successful suppression. Success rate was 84%. Suppression was unsuccessful in 14 patients. No significant influence of gender (P = .40) or age (P = .21) was found. However, insufficient suppression was more common in patients younger than 45 years (20% vs 7%). PET/MR imaging completion rate was >97%. A HFLCPP diet in combination with unfractionated heparin was successfully implemented for cardiac PET/MRI and resulted in a sufficient suppression of myocardial FDG uptake in 84% of patients.

Pulmonary uptake in Indium-111 leukocyte imaging: clinical significance in patients with suspected occult infections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cook, P.S.; Datz, F.L.; Disbro, M.A.

1984-02-01

A retrospective review was undertaken to evaluate the frequency and significance of pulmonary activity noted on 306 indium-111 leukocyte studies involving 232 patients with suspected occult infections. Forty-eight studies showed pulmonary activity in one of two patterns of uptake, focal or diffuse. Fourteen of 27 studies (52%) with focal uptake and two of 21 studies (10%) with diffuse uptake were associated with infectious processes. Lung uptake of indium-111-labeled leukocytes was a poor predictor of pulmonary infection in patients studied for occult infection, although the focal pattern was more likely than the diffuse pattern to be associated with infection.

Multiphase chemical kinetics of OH radical uptake by molecular organic markers of biomass burning aerosols: humidity and temperature dependence, surface reaction, and bulk diffusion.

PubMed

Arangio, Andrea M; Slade, Jonathan H; Berkemeier, Thomas; Pöschl, Ulrich; Knopf, Daniel A; Shiraiwa, Manabu

2015-05-14

Multiphase reactions of OH radicals are among the most important pathways of chemical aging of organic aerosols in the atmosphere. Reactive uptake of OH by organic compounds has been observed in a number of studies, but the kinetics of mass transport and chemical reaction are still not fully understood. Here we apply the kinetic multilayer model of gas-particle interactions (KM-GAP) to experimental data from OH exposure studies of levoglucosan and abietic acid, which serve as surrogates and molecular markers of biomass burning aerosol (BBA). The model accounts for gas-phase diffusion within a cylindrical coated-wall flow tube, reversible adsorption of OH, surface-bulk exchange, bulk diffusion, and chemical reactions at the surface and in the bulk of the condensed phase. The nonlinear dependence of OH uptake coefficients on reactant concentrations and time can be reproduced by KM-GAP. We find that the bulk diffusion coefficient of the organic molecules is approximately 10(-16) cm(2) s(-1), reflecting an amorphous semisolid state of the organic substrates. The OH uptake is governed by reaction at or near the surface and can be kinetically limited by surface-bulk exchange or bulk diffusion of the organic reactants. Estimates of the chemical half-life of levoglucosan in 200 nm particles in a biomass burning plume increase from 1 day at high relative humidity to 1 week under dry conditions. In BBA particles transported to the free troposphere, the chemical half-life of levoglucosan can exceed 1 month due to slow bulk diffusion in a glassy matrix at low temperature.

The influence of hepatic transport on the distribution volumes and mean residence time of drug in the body and the accuracy of estimating these parameters by the traditional pharmacokinetic calculations.

PubMed

Berezhkovskiy, Leonid M

2011-11-01

The influence of hepatic uptake and efflux, which includes passive diffusion and transporter-mediated component, on drug distribution volumes [steady-state volume of distribution (V(ss)) and terminal volume of distribution (V(β))], mean residence time (MRT), clearance, and terminal half-life is considered using a simplified physiologically based pharmacokinetic model. To account for hepatic uptake, liver is treated as two-compartmental unit with drug transfer from extracellular water into hepatocytes. The exactly calculated distribution volumes and MRT are compared with that obtained by the traditional equations based on the assumption of central elimination. It was found that V(ss) may increase more than 10-fold and V(β) more than 100-fold due to the contribution of transporter-mediated uptake. The terminal half-life may be substantially shortened (more than 100-fold) due to transporters. It may also decrease significantly due to the increase of intrinsic hepatic clearance (CL(int)), whereas hepatic clearance has already reached saturation (and stays close to the possible maximum value). It is shown that in case of transporter-mediated uptake of compound into hepatocytes, in the absence of efflux and passive diffusion (unidirectional uptake), hepatic clearance is independent of CL(int) and is determined by hepatic blood flow and uptake rate constant. The effects of transporter-mediated uptake are mostly pronounced for hydrophilic acidic compounds and moderately lipophilic neutral compounds. For basic compounds and lipophilic neutral compounds the change of distribution volumes due to transporters is rather unlikely. It was found that the traditional equations provide very accurate values of V(ss), V(β), and MRT in the absence of transporter action even for very low rates of passive diffusion. On the other hand, the traditional equations fail to provide the correct values of these parameters when the increase of distribution volumes due to transporters takes place, and actually yield the values substantially smaller than the true ones (up to an order of magnitude for V(ss) and MRT, and three orders of magnitude for V(β)). Copyright © 2011 Wiley-Liss, Inc.

Uptake of 2, 4-Dichlorophenoxyacetic acid by Pseudomonas fluorescens

USGS Publications Warehouse

Wedemeyer, G.A.

1966-01-01

Factors influencing the uptake of the sodium salt of 2,4-dichlorophenoxyacetic acid (2,4-D), under conditions in which no net metabolism occurred, were investigated in an effort to determine both the significance of “nonmetabolic” uptake as a potential agent in reducing pesticide levels and the mechanisms involved. Uptake of 2,4-D was affected by pH, temperature, and the presence of other organic and inorganic compounds. Uptake was more pronounced at pH values less than 6, which implies that there may be some interaction between charged groups on the cell and the ionized carboxyl group of 2,4-D. Active transport, carriermediated diffusion, passive diffusion, and adsorption were considered as possible mechanisms. Though uptake was inhibited by glucose, sodium azide, and fluorodinitrobenzene (but not by uranylion), 2,4-D was not accumulated against a concentration gradient, a necessary consequence of an active transport system, nor was isotope counterflow found to occur. Thus, carrier-mediated diffusion was finally precluded, implying that uptake probably occurs by a two-step process: sorption onto the cell wall followed by passive diffusion into the cytoplasm.

Uptake of 2,4-dichlorophenoxyacetic acid by Pseudomonas fluorescens

USGS Publications Warehouse

Wedemeyer, Gary

1966-01-01

Factors influencing the uptake of the sodium salt of 2,4-dichlorophenoxyacetic acid (2,4-D), under conditions in which no net metabolism occurred, were investigated in an effort to determine both the significance of “non-metabolic” uptake as a potential agent in reducing pesticide levels and the mechanisms involved. Uptake of 2,4-D was affected by pH, temperature, and the presence of other organic and inorganic compounds. Uptake was more pronounced at pH values less than 6, which implies that there may be some interaction between charged groups on the cell and the ionized carboxyl group of 2,4-D. Active transport, carrier-mediated diffusion, passive diffusion, and adsorption were considered as possible mechanisms. Though uptake was inhibited by glucose, sodium azide, and fluorodinitrobenzene (but not by uranyl ion), 2,4-D was not accumulated against a concentration gradient, a necessary consequence of an active transport system, nor was isotope counterflow found to occur. Thus, carrier-mediated diffusion was finally precluded, implying that uptake probably occurs by a two-step process: sorption onto the cell wall followed by passive diffusion into the cytoplasm.

Hierarchically porous organic polymers: highly enhanced gas uptake and transport through templated synthesis† †Electronic supplementary information (ESI) available: Complete procedures for the synthesis of hierarchically porous organic polymers and characterization data (gas adsorption–desorption isotherms, pore size distribution graphs, SEM images, and density data). Detailed procedures for propane uptake experiments and calculation of diffusion constants. See DOI: 10.1039/c4sc02502d Click here for additional data file.

PubMed Central

Chakraborty, Sanjiban; Colón, Yamil J.; Snurr, Randall Q.

2015-01-01

Porous organic polymers (POPs) possessing meso- and micropores can be obtained by carrying out the polymerization inside a mesoporous silica aerogel template and then removing the template after polymerization. The total pore volume (tpv) and specific surface area (ssa) can be greatly enhanced by modifying the template (up to 210% increase for tpv and 73% for ssa) as well as by supercritical processing of the POPs (up to an additional 142% increase for tpv and an additional 32% for ssa) to include larger mesopores. The broad range of pores allows for faster transport of molecules through the hierarchically porous POPs, resulting in increased diffusion rates and faster gas uptake compared to POPs with only micropores. PMID:28966764

Including carrier-mediated transport in oral uptake prediction of nutrients and pharmaceuticals in humans.

PubMed

O'Connor, Isabel A; Veltman, Karin; Huijbregts, Mark A J; Ragas, Ad M J; Russel, Frans G M; Hendriks, A Jan

2014-11-01

Most toxicokinetic models consider passive diffusion as the only mechanism when modeling the oral uptake of chemicals. However, the overall uptake of nutrients and xenobiotics, such as pharmaceuticals and environmental pollutants, can be increased by influx transport proteins. We incorporated carrier-mediated transport into a one-compartment toxicokinetic model originally developed for passive diffusion only. The predictions were compared with measured oral uptake efficiencies of nutrients and pharmaceuticals, i.e. the fraction of the chemical reaching systemic circulation. Including carrier-mediated uptake improved model predictions for hydrophilic nutrients (RMSE=10% vs. 56%, Coefficient of Efficiency CoE=0.5 vs. -9.6) and for pharmaceuticals (RMSE=21% vs. 28% and CoE=-0.4 vs. -1.1). However, the negative CoE for pharmaceuticals indicates that further improvements are needed. Most important in this respect is a more accurate estimation of vMAX and KM as well as the determination of the amount of expressed and functional transport proteins both in vivo and in vitro. Copyright © 2014 Elsevier B.V. All rights reserved.

The effect of stress on hydrogen uptake and desorption by A-286

NASA Technical Reports Server (NTRS)

Danford, Merlin D.

1991-01-01

The uptake and desorption of hydrogen by A-286 as a function of stress was studied using electrochemical methods. It was found that the apparent surface hydrogen concentration, the mean hydrogen concentration, and the hydrogen distribution uniformity all increased up to a stress level 50 percent of yield and decreased thereafter. The value of the hydrogen diffusion coefficient was relatively unaffected by stress while the percent of trapped hydrogen appeared to decrease with increasing stress.

Molecular Dynamics Simulations for Loading-Dependent Diffusion of CO2, SO2, CH4, and Their Binary Mixtures in ZIF-10: The Role of Hydrogen Bond.

PubMed

Li, Li; Yang, Deshuai; Fisher, Trevor R; Qiao, Qi; Yang, Zhen; Hu, Na; Chen, Xiangshu; Huang, Liangliang

2017-10-24

The loading-dependent diffusion behavior of CH 4 , CO 2 , SO 2 , and their binary mixtures in ZIF-10 has been investigated in detail by using classical molecular dynamics simulations. Our simulation results demonstrate that the self-diffusion coefficient D i of CH 4 molecules decreases sharply and monotonically with the loading while those of both CO 2 and SO 2 molecules initially display a slight increase at low uptakes and follow a slow decrease at high uptakes. Accordingly, the interaction energies between CH 4 molecules and ZIF-10 remain nearly constant regardless of the loading due to the absence of hydrogen bonds (HBs), while the interaction energies between CO 2 (or SO 2 ) and ZIF-10 decease rapidly with the loading, especially at small amounts of gas molecules. Such different loading-dependent diffusion and interaction mechanisms can be attributed to the relevant HB behavior between gas molecules and ZIF-10. At low loadings, both the number and strength of HBs between CO 2 (or SO 2 ) molecules and ZIF-10 decrease obviously as the loading increases, which is responsible for the slight increase of their diffusion coefficients. However, at high loadings, their HB strength increases with the loading. Similar loading-dependent phenomena of diffusion, interaction, and HB behavior can be observed for CH 4, CO 2 , and SO 2 binary mixtures in ZIF-10, only associated with some HB competition between CO 2 and SO 2 molecules in the case of the CO 2 /SO 2 mixture.

IDH mutation is paradoxically associated with higher 18F-FDOPA PET uptake in diffuse grade II and grade III gliomas.

PubMed

Verger, A; Metellus, Ph; Sala, Q; Colin, C; Bialecki, E; Taieb, D; Chinot, O; Figarella-Branger, D; Guedj, E

2017-08-01

The World Health Organization Classification of Tumors of the Central Nervous System has recently been updated by the integration of diagnostic and prognostic molecular parameters, giving pivotal attention to IDH mutation as a favourable factor. Amino acid PET is increasingly used in the management of gliomas, but its prognostic value is a matter of debate. The aim of this study was to assess the relationship between IDH mutation and 18 F-FDOPA uptake on PET in newly diagnosed gliomas. A total of 43 patients, presenting with diffuse astrocytic and oligodendroglial grade II and III gliomas, reclassified according to the 2016 WHO classification of tumours of the CNS, were retrospectively included. They had all undergone 18 F-FDOPA PET at an initial stage before surgery and histological diagnosis. 18 F-FDOPA uptake values were compared between patients with and without IDH mutation in terms of maximum standardized uptake value (SUVmax) ratios between tumour and normal contralateral brain (T/N), and between tumour and striatum (T/S). Patients with IDH mutation showed higher 18 F-FDOPA T/N SUVmax ratios (1.6 vs. 1.2) and T/S SUVmax ratios (0.9 vs. 0.6) than patients without IDH mutation (p < 0.05). This study showed paradoxically higher 18 F-FDOPA uptake in diffuse grade II and III gliomas with IDH mutation. Despite evident interest in the management of gliomas, and especially in relation to posttherapy evaluation, our findings raise the question of the prognostic value of 18 F-FDOPA uptake on PET uptake in this group of patients. This may be related to differences in amino acid integration, metabolism, or cell differentiation.

Glossosoma nigrior (Trichoptera: Glossosomatidae) respiration in moving fluid.

PubMed

Morris, Mark W L; Hondzo, Miki

2013-08-15

Laboratory measurements of dissolved oxygen (DO) uptake by Glossosoma nigrior Banks were conducted in a sealed, recirculating flume under variable fluid flow velocities. Measurements were performed in similar water temperatures, DO concentrations and fluid flow velocities to field conditions in the stream where the larvae were obtained. Total oxygen uptake by both cased larvae and corresponding cases without larvae were quantified. An increased fluid flow velocity corresponded to an increased larval DO uptake rate. Oxygen uptake by the larval cases alone was not as sensitive to changes in the Peclet (Pe) number, the dimensionless ratio of advective to diffusive DO transport, as uptake by larvae themselves. The flux of DO to larvae and their cases was up to seven times larger in a moving fluid in comparison to non-moving fluid conditions in the proximity of larvae for 087, larvae typically remained in their cases. This indicates that oxygen delivery to the larvae at low Pe is insufficient to satisfy the respiratory demands of cased larvae.

Diffuse abdominal uptake of Ga-67 citrate in a patient with hypoproteinemia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, E.K.; Gobuty, A.; Guiterrez, C.

1983-06-01

A 3-wk-old male, with abdominal distention and severe hypoproteinemia from poor nutrition, underwent a study that showed a persistent diffuse abdominal uptake of Ga-67 citrate, indicating pyogenic or tuberculous peritonitis. However, there were no corresponding clinical or laboratory findings. After a 1-wk course of hyperalimentation with albumin, furosemide, and protein, repeat radiographs showed reduction in bowel gas. It is suggested that hypoproteinemia should be considered as a possibility in the differential diagnosis when there is diffuse abdominal uptake of Ga-67 citrate, with careful clinical correlation. Possible mechanism of Ga-67 uptake in the peritoneal cavity is suggested.

Diffuse abdominal gallium-67 citrate uptake in salmonella infections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garty, I.; Koren, A.

1987-11-01

Two pediatric patients with salmonella infections (one with typhoid fever and the second with salmonella C2 gastroenteritis), had a diffuse abdominal uptake of Ga-67 citrate. The possible explanation for this finding is discussed. Salmonella infection should be included as a cause in the differential diagnosis of diffuse accumulation of Ga-67 citrate.

Oceanic Uptake of Oxygen During Deep Convection Events Through Diffusive and Bubble-Mediated Gas Exchange

NASA Astrophysics Data System (ADS)

Sun, Daoxun; Ito, Takamitsu; Bracco, Annalisa

2017-10-01

The concentration of dissolved oxygen (O2) plays fundamental roles in diverse chemical and biological processes throughout the oceans. The balance between the physical supply and the biological consumption controls the O2 level of the interior ocean, and the O2 supply to the deep waters can only occur through deep convection in the polar oceans. We develop a theoretical framework describing the oceanic O2 uptake during open-ocean deep convection events and test it against a suite of numerical sensitivity experiments. Our framework allows for two predictions, confirmed by the numerical simulations. First, both the duration and the intensity of the wintertime cooling contribute to the total O2 uptake for a given buoyancy loss. Stronger cooling leads to deeper convection and the oxygenation can reach down to deeper depths. Longer duration of the cooling period increases the total amount of O2 uptake over the convective season. Second, the bubble-mediated influx of O2 tends to weaken the diffusive influx by shifting the air-sea disequilibrium of O2 toward supersaturation. The degree of compensation between the diffusive and bubble-mediated gas exchange depends on the dimensionless number measuring the relative strength of oceanic vertical mixing and the gas transfer velocity. Strong convective mixing, which may occur under strong cooling, reduces the degree of compensation so that the two components of gas exchange together drive exceptionally strong oceanic O2 uptake.

Spectrally resolved visualization of fluorescent dyes permeating into skin

NASA Astrophysics Data System (ADS)

Maeder, Ulf; Bergmann, Thorsten; Beer, Sebastian; Burg, Jan Michael; Schmidts, Thomas; Runkel, Frank; Fiebich, Martin

2012-03-01

We present a spectrally resolved confocal imaging approach to qualitatively asses the overall uptake and the penetration depth of fluorescent dyes into biological tissue. We use a confocal microscope with a spectral resolution of 5 nm to measure porcine skin tissue after performing a Franz-Diffusion experiment with a submicron emulsion enriched with the fluorescent dye Nile Red. The evaluation uses linear unmixing of the dye and the tissue autofluorescence spectra. The results are combined with a manual segmentation of the skin's epidermis and dermis layers to assess the penetration behavior additionally to the overall uptake. The diffusion experiments, performed for 3h and 24h, show a 3-fold increased dye uptake in the epidermis and dermis for the 24h samples. As the method is based on spectral information it does not face the problem of superimposed dye and tissue spectra and therefore is more precise compared to intensity based evaluation methods.

Diffusion of D-glucose measured in the cytosol of a single astrocyte.

PubMed

Kreft, Marko; Lukšič, Miha; Zorec, Tomaž M; Prebil, Mateja; Zorec, Robert

2013-04-01

Astrocytes interact with neurons and endothelial cells and may mediate exchange of metabolites between capillaries and nerve terminals. In the present study, we investigated intracellular glucose diffusion in purified astrocytes after local glucose uptake. We used a fluorescence resonance energy transfer (FRET)-based nano sensor to monitor the time dependence of the intracellular glucose concentration at specific positions within the cell. We observed a delay in onset and kinetics in regions away from the glucose uptake compared with the region where we locally super-fused astrocytes with the D-glucose-rich solution. We propose a mathematical model of glucose diffusion in astrocytes. The analysis showed that after gradual uptake of glucose, the locally increased intracellular glucose concentration is rapidly spread throughout the cytosol with an apparent diffusion coefficient (D app) of (2.38 ± 0.41) × 10(-10) m(2) s(-1) (at 22-24 °C). Considering that the diffusion coefficient of D-glucose in water is D = 6.7 × 10(-10) m(2) s(-1) (at 24 °C), D app determined in astrocytes indicates that the cytosolic tortuosity, which hinders glucose molecules, is approximately three times higher than in aqueous solution. We conclude that the value of D app for glucose measured in purified rat astrocytes is consistent with the view that cytosolic diffusion may allow glucose and glucose metabolites to traverse from the endothelial cells at the blood-brain barrier to neurons and neighboring astrocytes.

Advances in modeling sorption and diffusion of moisture in porous reactive materials.

PubMed

Harley, Stephen J; Glascoe, Elizabeth A; Lewicki, James P; Maxwell, Robert S

2014-06-23

Water-vapor-uptake experiments were performed on a silica-filled poly(dimethylsiloxane) (PDMS) network and modeled by using two different approaches. The data was modeled by using established methods and the model parameters were used to predict moisture uptake in a sample. The predictions are reasonably good, but not outstanding; many of the shortcomings of the modeling are discussed. A high-fidelity modeling approach is derived and used to improve the modeling of moisture uptake and diffusion. Our modeling approach captures the physics and kinetics of diffusion and adsorption/desorption, simultaneously. It predicts uptake better than the established method; more importantly, it is also able to predict outgassing. The material used for these studies is a filled-PDMS network; physical interpretations concerning the sorption and diffusion of moisture in this network are discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The diffusive boundary layer of sediments: oxygen microgradients over a microbial mat

NASA Technical Reports Server (NTRS)

Jorgensen, B. B.; Des Marais, D. J.

1990-01-01

Oxygen microelectrodes were used to analyze the distribution of the diffusive boundary layer (DBL) at the sediment-water interface in relation to surface topography and flow velocity. The sediment, collected from saline ponds, was covered by a microbial mat that had high oxygen consumption rate and well-defined surface structure. Diffusion through the DBL constituted an important rate limitation to the oxygen uptake of the sediment. The mean effective DBL thickness decreased from 0.59 to 0.16 mm as the flow velocity of the overlying water was increased from 0.3 to 7.7 cm s-1 (measured 1 cm above the mat). The oxygen uptake rate concurrently increased from 3.9 to 9.4 nmol cm-2 min-1. The effects of surface roughness and topography on the thickness and distribution of the DBL were studied by three-dimensional mapping of the sediment-water interface and the upper DBL boundary at 0.1-mm spatial resolution. The DBL boundary followed mat structures that had characteristic dimensions > 1/2 DBL thickness but the DBL had a dampened relief relative to the mat. The effective surface area of the sediment-water interface and of the upper DBL boundary were 31 and 14% larger, respectively, than a flat plane. Surface topography thereby increased the oxygen flux across the sediment-water interface by 49% relative to a one-dimensional diffusion flux calculated from the vertical oxygen microgradients.

Correlation of dopaminergic terminal dysfunction and microstructural abnormalities of the basal ganglia and the olfactory tract in Parkinson's disease.

PubMed

Scherfler, Christoph; Esterhammer, Regina; Nocker, Michael; Mahlknecht, Philipp; Stockner, Heike; Warwitz, Boris; Spielberger, Sabine; Pinter, Bernadette; Donnemiller, Eveline; Decristoforo, Clemens; Virgolini, Irene; Schocke, Michael; Poewe, Werner; Seppi, Klaus

2013-10-01

Signal abnormalities of the substantia nigra and the olfactory tract detected either by diffusion tensor imaging, including measurements of mean diffusivity, a parameter of brain tissue integrity, and fractional anisotropy, a parameter of neuronal fibre integrity, or transcranial sonography, were recently reported in the early stages of Parkinson's disease. In this study, changes in the nigral and olfactory diffusion tensor signal, as well as nigral echogenicity, were correlated with clinical scales of motor disability, odour function and putaminal dopamine storage capacity measured with 6-[(18)F] fluorolevodopa positron emission tomography in early and advanced stages of Parkinson's disease. Diffusion tensor imaging, transcranial sonography and positron emission tomography were performed on 16 patients with Parkinson's disease (mean disease duration 3.7 ± 3.7 years, Hoehn and Yahr stage 1 to 4) and 14 age-matched healthy control subjects. Odour function was measured by the standardized Sniffin' Sticks Test. Mean putaminal 6-[(18)F] fluorolevodopa influx constant, mean nigral echogenicity, mean diffusivity and fractional anisotropy values of the substantia nigra and the olfactory tract were identified by region of interest analysis. When compared with the healthy control group, the Parkinson's disease group showed significant signal changes in the caudate and putamen by 6-[(18)F] fluorolevodopa positron emission tomography, in the substantia nigra by transcranial sonography, mean diffusivity and fractional anisotropy (P < 0.001, P < 0.01, P < 0.05, respectively) and in the olfactory tract by mean diffusivity (P < 0.05). Regional mean diffusivity values of the substantia nigra and the olfactory tract correlated significantly with putaminal 6-[(18)F] fluorolevodopa uptake (r = -0.52, P < 0.05 and r = -0.71, P < 0.01). Significant correlations were also found between nigral mean diffusivity values and the Unified Parkinson's Disease Rating Scale motor score (r = -0.48, P < 0.01) and between mean putaminal 6-[(18)F] fluorolevodopa uptake and the total odour score (r = 0.58; P < 0.05) as well as the Unified Parkinson's Disease Rating Scale motor score (r = -0.53, P < 0.05). This study reports a significant association between increased mean diffusivity signal and decreased 6-[(18)F] fluorolevodopa uptake, indicating that microstructural degradation of the substantia nigra and the olfactory tract parallels progression of putaminal dopaminergic dysfunction in Parkinson's disease. Since increases in nigral mean diffusivity signal also correlated with motor dysfunction, diffusion tensor imaging may serve as a surrogate marker for disease progression in future studies of putative disease modifying therapies.

Transport rather than diffusion-dependent route for nitric oxide gas activity in alveolar epithelium.

PubMed

Brahmajothi, Mulugu V; Mason, S Nicholas; Whorton, A Richard; McMahon, Timothy J; Auten, Richard L

2010-07-15

The pathway by which inhaled NO gas enters pulmonary alveolar epithelial cells has not been directly tested. Although the expected mechanism is diffusion, another route is the formation of S-nitroso-L-cysteine, which then enters the cell through the L-type amino acid transporter (LAT). To determine if NO gas also enters alveolar epithelium this way, we exposed alveolar epithelial-rat type I, type II, L2, R3/1, and human A549-cells to NO gas at the air liquid interface in the presence of L- and D-cysteine+/-LAT competitors. NO gas exposure concentration dependently increased intracellular NO and S-nitrosothiol levels in the presence of L- but not D-cysteine, which was inhibited by LAT competitors, and was inversely proportional to diffusion distance. The effect of L-cysteine on NO uptake was also concentration dependent. Without preincubation with L-cysteine, NO uptake was significantly reduced. We found similar effects using ethyl nitrite gas in place of NO. Exposure to either gas induced activation of soluble guanylyl cylase in a parallel manner, consistent with LAT dependence. We conclude that NO gas uptake by alveolar epithelium achieves NO-based signaling predominantly by forming extracellular S-nitroso-L-cysteine that is taken up through LAT, rather than by diffusion. Augmenting extracellular S-nitroso-L-cysteine formation may augment pharmacological actions of inhaled NO gas. Copyright 2010 Elsevier Inc. All rights reserved.

Diverse bone scan abnormalitites in "shin splints".

PubMed

Spencer, R P; Levinson, E D; Baldwin, R D; Sziklas, J J; Witek, J T; Rosenberg, R

1979-12-01

Four young patients who presented with pain over the anterior compartment of the legs, gave a recent athletic history suggesting stress fractures. Although radiographs were initially normal in all four cases, the bone scintigrams were positive. The individual findings, however, were quite different. In one there was a single focal area of increased radioactivity in each of the tibias; the second patient had uneven uptake of radiotracer and several foci of accumulation in the fibulas; the third showed diffuse linear tibial uptake suggesting periosteal lesions; and the fourth case revealed uptake in the lateral malleolus and in bones of the foot.

Low rate loading-induced convection enhances net transport into the intervertebral disc in vivo.

PubMed

Gullbrand, Sarah E; Peterson, Joshua; Mastropolo, Rosemarie; Roberts, Timothy T; Lawrence, James P; Glennon, Joseph C; DiRisio, Darryl J; Ledet, Eric H

2015-05-01

The intervertebral disc primarily relies on trans-endplate diffusion for the uptake of nutrients and the clearance of byproducts. In degenerative discs, diffusion is often diminished by endplate sclerosis and reduced proteoglycan content. Mechanical loading-induced convection has the potential to augment diffusion and enhance net transport into the disc. The ability of convection to augment disc transport is controversial and has not been demonstrated in vivo. To determine if loading-induced convection can enhance small molecule transport into the intervertebral disc in vivo. Net transport was quantified via postcontrast enhanced magnetic resonance imaging (MRI) into the discs of the New Zealand white rabbit lumbar spine subjected to in vivo cyclic low rate loading. Animals were administered the MRI contrast agent gadodiamide intravenously and subjected to in vivo low rate loading (0.5 Hz, 200 N) via a custom external loading apparatus for either 2.5, 5, 10, 15, or 20 minutes. Animals were then euthanized and the lumbar spines imaged using postcontrast enhanced MRI. The T1 constants in the nucleus, annulus, and cartilage endplates were quantified as a measure of gadodiamide transport into the loaded discs compared with the adjacent unloaded discs. Microcomputed tomography was used to quantify subchondral bone density. Low rate loading caused the rapid uptake and clearance of gadodiamide in the nucleus compared with unloaded discs, which exhibited a slower rate of uptake. Relative to unloaded discs, low rate loading caused a maximum increase in transport into the nucleus of 16.8% after 5 minutes of loading. Low rate loading increased the concentration of gadodiamide in the cartilage endplates at each time point compared with unloaded levels. Results from this study indicate that forced convection accelerated small molecule uptake and clearance in the disc induced by low rate mechanical loading. Low rate loading may, therefore, be therapeutic to the disc as it may enhance the nutrient uptake and waste product clearance. Copyright © 2015 Elsevier Inc. All rights reserved.

Strategies of dissolved inorganic carbon use in macroalgae across a gradient of terrestrial influence: implications for the Great Barrier Reef in the context of ocean acidification

NASA Astrophysics Data System (ADS)

Diaz-Pulido, Guillermo; Cornwall, Christopher; Gartrell, Patrick; Hurd, Catriona; Tran, Dien V.

2016-12-01

Macroalgae are generally used as indicators of coral reef status; thus, understanding the drivers and mechanisms leading to increased macroalgal abundance are of critical importance. Ocean acidification (OA) due to elevated carbon dioxide (CO2) concentrations has been suggested to stimulate macroalgal growth and abundance on reefs. However, little is known about the physiological mechanisms by which reef macroalgae use CO2 from the bulk seawater for photosynthesis [i.e., (1) direct uptake of bicarbonate (HCO3 -) and/or CO2 by means of carbon concentrating mechanisms (CCM) and (2) the diffusive uptake of CO2], which species could benefit from increased CO2 or which habitats may be more susceptible to acidification-induced algal proliferations. Here, we provide the first quantitative examination of CO2-use strategies in coral reef macroalgae and provide information on how the proportion of species and the proportional abundance of species utilising each of the carbon acquisition strategies varies across a gradient of terrestrial influence (from inshore to offshore reefs) in the Great Barrier Reef (GBR). Four macroalgal groups were identified based on their carbon uptake strategies: (1) CCM-only (HCO3 - only users); (2) CCM-HCO3 -/CO2 (active uptake HCO3 - and/or CO2 use); (3) Non-CCM species (those relying on diffusive CO2 uptake); and (4) Calcifiers. δ13C values of macroalgae, confirmed by pH drift assays, show that diffusive CO2 use is more prevalent in deeper waters, possibly due to low light availability that limits activity of CCMs. Inshore shallow reefs had a higher proportion of CCM-only species, while reefs further away from terrestrial influence and exposed to better water quality had a higher number of non-CCM species than inshore and mid-shelf reefs. As non-CCM macroalgae are more responsive to increased seawater CO2 and OA, reef slopes of the outer reefs are probably the habitats most vulnerable to the impacts of OA. Our results suggest a potentially important role of carbon physiology in structuring macroalgal communities in the GBR.

Facilitation of cytosolic calcium wave propagation by local calcium uptake into the sarcoplasmic reticulum in cardiac myocytes.

PubMed

Maxwell, Joshua T; Blatter, Lothar A

2012-12-01

The widely accepted paradigm for cytosolic Ca(2+) wave propagation postulates a 'fire-diffuse-fire' mechanism where local Ca(2+)-induced Ca(2+) release (CICR) from the sarcoplasmic reticulum (SR) via ryanodine receptor (RyR) Ca(2+) release channels diffuses towards and activates neighbouring release sites, resulting in a propagating Ca(2+) wave. A recent challenge to this paradigm proposed the requirement for an intra-SR 'sensitization' Ca(2+) wave that precedes the cytosolic Ca(2+) wave and primes RyRs from the luminal side to CICR. Here, we tested this hypothesis experimentally with direct simultaneous measurements of cytosolic ([Ca(2+)](i); rhod-2) and intra-SR ([Ca(2+)](SR); fluo-5N) calcium signals during wave propagation in rabbit ventricular myocytes, using high resolution fluorescence confocal imaging. The increase in [Ca(2+)](i) at the wave front preceded depletion of the SR at each point along the calcium wave front, while during this latency period a transient increase of [Ca(2+)](SR) was observed. This transient elevation of [Ca(2+)](SR) could be identified at individual release junctions and depended on the activity of the sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA). Increased SERCA activity (β-adrenergic stimulation with 1 μM isoproterenol (isoprenaline)) decreased the latency period and increased the amplitude of the transient elevation of [Ca(2+)](SR), whereas inhibition of SERCA (3 μM cyclopiazonic acid) had the opposite effect. In conclusion, the data provide experimental evidence that local Ca(2+) uptake by SERCA into the SR facilitates the propagation of cytosolic Ca(2+) waves via luminal sensitization of the RyR, and supports a novel paradigm of a 'fire-diffuse-uptake-fire' mechanism for Ca(2+) wave propagation in cardiac myocytes.

Facilitation of cytosolic calcium wave propagation by local calcium uptake into the sarcoplasmic reticulum in cardiac myocytes

PubMed Central

Maxwell, Joshua T; Blatter, Lothar A

2012-01-01

The widely accepted paradigm for cytosolic Ca2+ wave propagation postulates a ‘fire-diffuse-fire’ mechanism where local Ca2+-induced Ca2+ release (CICR) from the sarcoplasmic reticulum (SR) via ryanodine receptor (RyR) Ca2+ release channels diffuses towards and activates neighbouring release sites, resulting in a propagating Ca2+ wave. A recent challenge to this paradigm proposed the requirement for an intra-SR ‘sensitization’ Ca2+ wave that precedes the cytosolic Ca2+ wave and primes RyRs from the luminal side to CICR. Here, we tested this hypothesis experimentally with direct simultaneous measurements of cytosolic ([Ca2+]i; rhod-2) and intra-SR ([Ca2+]SR; fluo-5N) calcium signals during wave propagation in rabbit ventricular myocytes, using high resolution fluorescence confocal imaging. The increase in [Ca2+]i at the wave front preceded depletion of the SR at each point along the calcium wave front, while during this latency period a transient increase of [Ca2+]SR was observed. This transient elevation of [Ca2+]SR could be identified at individual release junctions and depended on the activity of the sarco-endoplasmic reticulum Ca2+-ATPase (SERCA). Increased SERCA activity (β-adrenergic stimulation with 1 μm isoproterenol (isoprenaline)) decreased the latency period and increased the amplitude of the transient elevation of [Ca2+]SR, whereas inhibition of SERCA (3 μm cyclopiazonic acid) had the opposite effect. In conclusion, the data provide experimental evidence that local Ca2+ uptake by SERCA into the SR facilitates the propagation of cytosolic Ca2+ waves via luminal sensitization of the RyR, and supports a novel paradigm of a ‘fire-diffuse-uptake-fire’ mechanism for Ca2+ wave propagation in cardiac myocytes. PMID:22988145

Influence of substrate diffusion on degradation of dibenzofuran and 3-chlorodibenzofuran by attached and suspended bacteria.

PubMed Central

Harms, H; Zehnder, A J

1994-01-01

Dibenzofuran uptake-associated kinetic parameters of suspended and attached Sphingomonas sp. strain HH19k cells were compared. The suspended cells were studied in a batch system, whereas glass beads in percolated columns were used as the solid support for attached cells. The maximum specific activities of cells in the two systems were the same. The apparent half-maximum uptake rate-associated concentrations (Kt') of attached cells, however, were considerably greater than those of suspended cells and depended on cell density and on percolation velocity. A mathematical model was developed to explain the observed differences in terms of substrate transport to the cells. This model was based on the assumptions that the intrinsic half-maximum uptake rate-associated concentration (Kt) was unchanged and that deviations of Kt' from Kt resulted from the stereometry and the hydrodynamics around the cells. Our calculations showed that (i) diffusion to suspended cells and to single attached cells is efficient and therefore only slightly affects Kt'; (ii) diffusion to cells located on crowded surfaces is considerably lower than that to single attached cells and greatly increases Kt', which depends on the cell density; (iii) the convective-diffusive transport to attached cells that occurs in a percolated column is influenced by the liquid flow and results in dependency of Kt' on the flow rate; and (iv) higher specific affinity of cells correlates with higher susceptibility to diffusion limitation. Properties of the experimental system which limited quantitative proof of exclusively transport-controlled variations of Kt' are discussed. PMID:8085817

Influence of extrinsic operational parameters on salt diffusion during ultrasound assisted meat curing.

PubMed

Inguglia, Elena S; Zhang, Zhihang; Burgess, Catherine; Kerry, Joseph P; Tiwari, Brijesh K

2018-02-01

The present study investigated the effect of geometric parameters of the ultrasound instrument during meat salting in order to enhance salt diffusion and salt distribution in pork meat on a lab scale. The effects of probe size (∅2.5 and 1.3cm) and of different distances between the transducer and the meat sample (0.3, 0.5, and 0.8cm) on NaCl diffusion were investigated. Changes in the moisture content and NaCl gain were used to evaluate salt distribution and diffusion in the samples, parallel and perpendicular to ultrasound propagation direction. Results showed that 0.3cm was the most efficient distance between the probe and the sample to ensure a higher salt diffusion rate. A distance of 0.5cm was however considered as a trade-off distance to ensure salt diffusion and maintenance of meat quality parameters. The enhancement of salt diffusion by ultrasound was observed to decrease with increased horizontal distance from the probe. This study is of valuable importance for meat processing industries willing to apply new technologies on a larger scale and with defined operational standards. The data suggest that the geometric parameters of ultrasound systems can have strong influence on the efficiency of ultrasonic enhancement of NaCl uptake in meat and can be a crucial element in determining salt uptake during meat processing. Copyright © 2017 Elsevier B.V. All rights reserved.

Stomatal control of leaf fluxes of carbonyl sulfide and CO2 in a Typha freshwater marsh

NASA Astrophysics Data System (ADS)

Sun, Wu; Maseyk, Kadmiel; Lett, Céline; Seibt, Ulli

2018-06-01

Carbonyl sulfide (COS) is an emerging tracer to constrain land photosynthesis at canopy to global scales, because leaf COS and CO2 uptake processes are linked through stomatal diffusion. The COS tracer approach requires knowledge of the concentration normalized ratio of COS uptake to photosynthesis, commonly known as the leaf relative uptake (LRU). LRU is known to increase under low light, but the environmental controls over LRU variability in the field are poorly understood due to scant leaf scale observations. Here we present the first direct observations of LRU responses to environmental variables in the field. We measured leaf COS and CO2 fluxes at a freshwater marsh in summer 2013. Daytime leaf COS and CO2 uptake showed similar peaks in the mid-morning and late afternoon separated by a prolonged midday depression, highlighting the common stomatal control on diffusion. At night, in contrast to CO2, COS uptake continued, indicating partially open stomata. LRU ratios showed a clear relationship with photosynthetically active radiation (PAR), converging to 1.0 at high PAR, while increasing sharply at low PAR. Daytime integrated LRU (calculated from daytime mean COS and CO2 uptake) ranged from 1 to 1.5, with a mean of 1.2 across the campaign, significantly lower than the previously reported laboratory mean value (˜ 1.6). Our results indicate two major determinants of LRU - light and vapor deficit. Light is the primary driver of LRU because CO2 assimilation capacity increases with light, while COS consumption capacity does not. Superimposed upon the light response is a secondary effect that high vapor deficit further reduces LRU, causing LRU minima to occur in the afternoon, not at noon. The partial stomatal closure induced by high vapor deficit suppresses COS uptake more strongly than CO2 uptake because stomatal resistance is a more dominant component in the total resistance of COS. Using stomatal conductance estimates, we show that LRU variability can be explained in terms of different patterns of stomatal vs. internal limitations on COS and CO2 uptake. Our findings illustrate the stomata-driven coupling of COS and CO2 uptake during the most photosynthetically active period in the field and provide an in situ characterization of LRU - a key parameter required for the use of COS as a photosynthetic tracer.

Coexistent Superscan and Lincoln Sign on Bone Scintigraphy.

PubMed

Kulkarni, Mukta; Soni, Atul; Shetkar, Shubhangi; Amer, Momin; Mulavekar, Amruta; Joshi, Prathamesh

2017-08-01

A 70-year-old man underwent Tc-methylene diphosphonate scintigraphy for staging of adenocarcinoma prostate. Scintigraphy revealed diffuse increased tracer uptake in skeletal system along with faint renal visualization, a pattern compatible with metastatic superscan. The scintigraphy also revealed increased radiotracer uptake in the body of the mandible-Lincoln sign or black beard sign. Radiological imaging revealed sclerotic lesions throughout the skeleton including the mandible, confirming widespread skeletal metastases. Lincoln sign is previously described in monostotic Paget disease of the mandible and in contiguous spread of oral malignancy. We describe this pattern in distant metastatic involvement from carcinoma prostate with coexistent superscan pattern.

Scintigraphic findings in ankylosing spondylitis.

PubMed

Lentle, B C; Russell, A S; Percy, J S; Jackson, F I

1977-06-01

A prospective study of bone scintigraphic findings has been carried out in 63 patients, firmly diagnosed as having ankylosing spondylitis. In addition to abnormal uptake of the radiotracer at the sacroiliac joints, a peripheral arthropathy has been a common finding, particularly in the proximal joints, occurring in up to 50% of patients. Increased uptake of radiotracer in the spine has also been found both diffusely and focally. Focal increases have been noted at the apophyseal joints in 40% of patients and in three patients with a sterile intervertebral diskitis, an unusual complication of this disease only diagnosed in two patients after bone scintigraphy.

The Impact of Atmospheric Aerosols on the Fraction of absorbed Photosynthetically Active Radiation

NASA Astrophysics Data System (ADS)

Veroustraete, Frank

2010-05-01

Aerosol pollution attracts a growing interest from atmospheric scientists with regard to their impact on health, the global climate and vegetation stress. A hypothesis, less investigated, is whether atmospheric aerosol interactions in the solar radiation field affect the amount of radiation absorbed by vegetation canopies and hence terrestrial vegetation productivity. Typically, aerosols affect vegetation canopy radiation absorption efficiency by altering the physical characteristics of solar radiation incoming on for example a forest canopy. It has been illustrated, that increasing mixing ratio's of atmospheric particulate matter lead to a higher fraction of diffuse sunlight as opposed to direct sunlight. It can be demonstrated, based on the application of atmospheric (MODTRAN) and leaf/canopy radiative transfer (LIBERTY/SPRINT) models, that radiation absorption efficiency in the PAR band of Picea like forests increases with increasing levels of diffuse radiation. It can be documented - on a theoretical basis - as well, that increasing aerosol loads in the atmosphere, induce and increased canopy PAR absorption efficiency. In this paper it is suggested, that atmospheric aerosols have to be taken into account when estimating vegetation gross primary productivity (GPP). The results suggest that Northern hemisphere vegetation CO2 uptake magnitude may increase with increasing atmospheric aerosol loads. Many climate impact scenario's related to vegetation productivity estimates, do not take this phenomenon into account. Boldly speaking, the results suggest a larger sink function for terrestrial vegetation than generally accepted. Keywords: Aerosols, vegetation, fAPAR, CO2 uptake, diffuse radiation.

pH-Dependent Uptake of Fumaric Acid in Saccharomyces cerevisiae under Anaerobic Conditions

PubMed Central

Jamalzadeh, Elaheh; Verheijen, Peter J. T.; Heijnen, Joseph J.

2012-01-01

Microbial production of C4 dicarboxylic acids from renewable resources has gained renewed interest. The yeast Saccharomyces cerevisiae is known as a robust microorganism and is able to grow at low pH, which makes it a suitable candidate for biological production of organic acids. However, a successful metabolic engineering approach for overproduction of organic acids requires an incorporation of a proper exporter to increase the productivity. Moreover, low-pH fermentations, which are desirable for facilitating the downstream processing, may cause back diffusion of the undissociated acid into the cells with simultaneous active export, thereby creating an ATP-dissipating futile cycle. In this work, we have studied the uptake of fumaric acid in S. cerevisiae in carbon-limited chemostat cultures under anaerobic conditions. The effect of the presence of fumaric acid at different pH values (3 to 5) has been investigated in order to obtain more knowledge about possible uptake mechanisms. The experimental results showed that at a cultivation pH of 5.0 and an external fumaric acid concentration of approximately 0.8 mmol · liter−1, the fumaric acid uptake rate was unexpectedly high and could not be explained by diffusion of the undissociated form across the plasma membrane alone. This could indicate the presence of protein-mediated import. At decreasing pH levels, the fumaric acid uptake rate was found to increase asymptotically to a maximum level. Although this observation is in accordance with protein-mediated import, the presence of a metabolic bottleneck for fumaric acid conversion under anaerobic conditions could not be excluded. PMID:22113915

Diverse bone scan abnormalities in shin splints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spencer, R.P.; Levinson, E.D.; Baldwin, R.D.

1979-12-01

Four young patients who presented with pain over the anterior compartment of the legs, gave a recent athletic history suggesting stress fractures. Although radiographs were initially normal in all four cases, the bone scintigrams were positive. The individual findings, however, were quite different. In one there was a single focal area of increased radioactivity in each of the tibias; the second patient had uneven uptake of radiotracer and several foci of accumulation in the fibulas; the third showed diffuse linear tibial uptake suggesting periosteal lesions; and the fourth case revealed uptake in the lateral malleolus and in bones of themore » foot.« less

In vitro hypoglycemic effects of Albizzia lebbeck and Mucuna pruriens

PubMed Central

Bhutkar, Mangesh; Bhise, Satish

2013-01-01

Objective To verify the antidiabetic potential of stem bark of Albizzia lebbeck (A. lebbeck) and seeds of Mucuna pruriens (M. pruriens) using various in vitro techniques. Methods The plant extracts were studied for their effects on glucose adsorption, diffusion amylolysis kinetics and glucose transport across yeast cells. Results Both the plant extracts adsorbed glucose and the adsorption of glucose increased remarkably with an increase in glucose concentration. No significant (P≤0.05) differences were observed between the adsorption capacities of A. lebbeck and M. pruriens. In amylolysis kinetic experimental model the rate of glucose diffusion was found to increase with time from 30 to 180 min, and both the plant extracts demonstrated significant inhibitory effects on movement of glucose into external solution across dialysis membrane as compared to control. The retardation of glucose diffusion by A. lebbeck extract was significantly higher (P≤0.05) than M. pruriens. These effects were reflected with higher glucose dialysis retardation index values for A. lebbeck than M. pruriens. The plant extracts also promoted glucose uptake by yeast cells. The rate of uptake of glucose into yeast cells was linear in all the 5 glucose concentrations used in the study. M. pruriens extract exhibited significantly higher (P≤0.05) activity than the extract of A. lebbeck at all concentrations. Conclusions The results verified the antidiabetic potential of A. lebbeck and M. pruriens. The hypoglycemic effect exhibited by the extracts is mediated by increasing glucose adsorption, decreasing glucose diffusion rate and at the cellular level by promoting glucose transport across the cell membrane as revealed by simple in vitro model of yeast cells.

Isopycnal mixing by mesoscale eddies significantly impacts oceanic anthropogenic carbon uptake

NASA Astrophysics Data System (ADS)

Gnanadesikan, Anand; Pradal, Marie-Aude; Abernathey, Ryan

2015-06-01

Anthropogenic carbon dioxide uptake varies across Earth System Models for reasons that have remained obscure. When varied within a single model, the lateral eddy mixing coefficient ARedi produces a range of uptake similar to the modeled range. The highest uptake, resulting from a simulation with a constant ARedi of 2400 m2/s, simulates 15% more historical carbon uptake than a model with ARedi = 400 m2/s. A sudden doubling in carbon dioxide produces a 21% range in carbon uptake across the models. Two spatially dependent representations of ARedi produce uptake that lies in the middle of the range of constant values despite predicting very large values in the subtropical gyres. One-dimensional diffusive models of the type used for integrated assessments can be fit to the simulations, with ARedi accounting for a substantial fraction of the effective vertical diffusion. Such models, however, mask significant regional changes in stratification and biological carbon storage.

The Association Between Liver and Tumor [18F]FDG Uptake in Patients with Diffuse Large B Cell Lymphoma During Chemotherapy.

PubMed

Wu, Xingchen; Bhattarai, Abhisek; Korkola, Pasi; Pertovaara, Hannu; Eskola, Hannu; Kellokumpu-Lehtinen, Pirkko-Liisa

2017-10-01

The aim of this study was to explore the association between liver, mediastinum and tumor 2-deoxy-2-[ 18 F]fluoro-D-glucose ([ 18 F]FDG) uptake during chemotherapy in diffuse large B cell lymphoma (DLBCL). Nineteen patients with proven DLBCL underwent positron emission tomography (PET)/X-ray computed tomography scan at baseline, 1 week and 2 cycles after rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP) therapy, and again after chemotherapy completion. The mean and maximal standardized uptake value (SUVmean and SUVmax) of the liver and mediastinum were measured and correlated with the tumor SUVmax, SUVsum, whole-body metabolic tumor volume (MTVwb), and total lesion glycolysis (TLG). At baseline, both the liver and mediastinum SUVmean and SUVmax correlated inversely with the tumor MTVwb or TLG (p < 0.01 or 0.001). The liver SUVmean and SUVmax increased significantly after 1 week of R-CHOP therapy and remained at the high level until chemotherapy completion. The mediastinum SUVmean and SUVmax remained stable during chemotherapy. The tumor SUVmax, SUVsum, MTVwb, and TLG decreased significantly after 1 week of R-CHOP therapy. The change of the liver SUVmean correlated inversely with the change of tumor MTVwb and TLG after 1 week of chemotherapy (p < 0.05, respectively). The intersubject variability of liver and mediastinum [ 18 F]FDG uptake ranged from 11 to 26 %. The liver [ 18 F]FDG uptake increased significantly after R-CHOP therapy. One of the possible reasons is the distribution of a greater fraction of the tracer to healthy tissues rather than tumor after effective chemotherapy. The variability of the liver [ 18 F]FDG uptake during chemotherapy might affect the visual analysis of the interim PET scan and this needs to be confirmed in future studies with a large patient cohort. In addition, the intersubject variability of the liver and mediastinum [ 18 F]FDG uptake should be considered.

Fungal inoculation and elevated CO2 mediate growth of Lolium mutiforum and Phytolacca americana, metal uptake, and metal bioavailability in metal-contaminated soil: evidence from DGT measurement.

PubMed

Song, Ningning; Wang, Fangli; Zhang, Changbo; Tang, Shirong; Guo, Junkang; Ju, Xuehai; Smith, Donald L

2013-01-01

Fungal inoculation and elevated CO2 may mediate plant growth and uptake of heavy metals, but little evidence from Diffusive Gradients in Thin-films (DGT) measurement has been obtained to characterize the process. Lolium mutiforum and Phytolacca americana were grown at ambient and elevated CO2 on naturally Cd and Pb contaminated soils inoculated with and without Trichoderma asperellum strain C3 or Penicillium chrysogenum strain D4, to investigate plant growth, metal uptake, and metal bioavailability responses. Fungal inoculation increased plant biomass and shoot/root Cd and Pb concentrations. Elevated CO2 significantly increased plants biomass, but decreased Cd and Pb concentrations in shoot/root to various extents, leading to a metal dilution phenomenon. Total Cd and Pb uptake by plants, and DGT-measured Cd and Pb concentrations in rhizosphere soils, were higher in all fungal inoculation and elevated CO2 treatments than control treatments, with the combined treatments having more influence than either treatment alone. Metal dilution phenomenon occurred because the increase in DGT-measured bioavailable metal pools in plant rhizosphere due to elevated CO2 was unable to match the increase in requirement for plant uptake of metals due to plant biomass increase.

Molecular Binding Contributes to Concentration Dependent Acrolein Deposition in Rat Upper Airways: CFD and Molecular Dynamics Analyses

PubMed Central

Hu, Qin; Si, Xiuhua April

2018-01-01

Existing in vivo experiments show significantly decreased acrolein uptake in rats with increasing inhaled acrolein concentrations. Considering that high-polarity chemicals are prone to bond with each other, it is hypothesized that molecular binding between acrolein and water will contribute to the experimentally observed deposition decrease by decreasing the effective diffusivity. The objective of this study is to quantify the probability of molecular binding for acrolein, as well as its effects on acrolein deposition, using multiscale simulations. An image-based rat airway geometry was used to predict the transport and deposition of acrolein using the chemical species model. The low Reynolds number turbulence model was used to simulate the airflows. Molecular dynamic (MD) simulations were used to study the molecular binding of acrolein in different media and at different acrolein concentrations. MD results show that significant molecular binding can happen between acrolein and water molecules in human and rat airways. With 72 acrolein embedded in 800 water molecules, about 48% of acrolein compounds contain one hydrogen bond and 10% contain two hydrogen bonds, which agreed favorably with previous MD results. The percentage of hydrogen-bonded acrolein compounds is higher at higher acrolein concentrations or in a medium with higher polarity. Computational dosimetry results show that the size increase caused by the molecular binding reduces the effective diffusivity of acrolein and lowers the chemical deposition onto the airway surfaces. This result is consistent with the experimentally observed deposition decrease at higher concentrations. However, this size increase can only explain part of the concentration-dependent variation of the acrolein uptake and acts as a concurrent mechanism with the uptake-limiting tissue ration rate. Intermolecular interactions and associated variation in diffusivity should be considered in future dosimetry modeling of high-polarity chemicals such as acrolein. PMID:29584651

Changes in soil moisture drive soil methane uptake along a fire regeneration chronosequence in a eucalypt forest landscape.

PubMed

Fest, Benedikt; Wardlaw, Tim; Livesley, Stephen J; Duff, Thomas J; Arndt, Stefan K

2015-11-01

Disturbance associated with severe wildfires (WF) and WF simulating harvest operations can potentially alter soil methane (CH4 ) oxidation in well-aerated forest soils due to the effect on soil properties linked to diffusivity, methanotrophic activity or changes in methanotrophic bacterial community structure. However, changes in soil CH4 flux related to such disturbances are still rarely studied even though WF frequency is predicted to increase as a consequence of global climate change. We measured in-situ soil-atmosphere CH4 exchange along a wet sclerophyll eucalypt forest regeneration chronosequence in Tasmania, Australia, where the time since the last severe fire or harvesting disturbance ranged from 9 to >200 years. On all sampling occasions, mean CH4 uptake increased from most recently disturbed sites (9 year) to sites at stand 'maturity' (44 and 76 years). In stands >76 years since disturbance, we observed a decrease in soil CH4 uptake. A similar age dependency of potential CH4 oxidation for three soil layers (0.0-0.05, 0.05-0.10, 0.10-0.15 m) could be observed on incubated soils under controlled laboratory conditions. The differences in soil CH4 uptake between forest stands of different age were predominantly driven by differences in soil moisture status, which affected the diffusion of atmospheric CH4 into the soil. The observed soil moisture pattern was likely driven by changes in interception or evapotranspiration with forest age, which have been well described for similar eucalypt forest systems in south-eastern Australia. Our results imply that there is a large amount of variability in CH4 uptake at a landscape scale that can be attributed to stand age and soil moisture differences. An increase in severe WF frequency in response to climate change could potentially increase overall forest soil CH4 sinks. © 2015 John Wiley & Sons Ltd.

Cell wall pH and auxin transport velocity

NASA Technical Reports Server (NTRS)

Hasenstein, K. H.; Rayle, D.

1984-01-01

According to the chemiosmotic polar diffusion hypothesis, auxin pulse velocity and basal secretion should increase with decreasing cell wall pH. Experiments were designed to test this prediction. Avena coleoptile sections were preincubated in either fusicoccin (FC), cycloheximide, pH 4.0, or pH 8.0 buffer and subsequently their polar transport capacities were determined. Relative to controls, FC enhanced auxin (IAA) uptake while CHI and pH 8.0 buffer reduced IAA uptake. Nevertheless, FC reduced IAA pulse velocity while cycloheximide increased velocity. Additional experiments showed that delivery of auxin to receivers is enhanced by increased receiver pH. This phenomenon was overcome by a pretreatment of the tissue with IAA. Our data suggest that while acidic wall pH values facilitate cellular IAA uptake, they do not enhance pulse velocity or basal secretion. These findings are inconsistent with the chemiosmotic hypothesis for auxin transport.

Monosaccharide uptake by erythrocytes of the embryonic and adult chicken.

PubMed

Ingermann, R L; Stock, M K; Metcalfe, J; Bissonnette, J M

1985-01-01

Rates of monosaccharide uptake by adult and 10-18 day old embryonic chicken erythrocytes were quantitated. The rate of carrier-mediated, stereospecific transport decreased 28% from day 10 to day 14 of incubation and was unchanged thereafter. At no time, however, did the rate of carrier-mediated transport by embryonic erythrocytes differ significantly from that of the adult cells. The rate of transfer by simple diffusion was 3-5 fold faster in embryonic than in adult erythrocytes. Uptake by simple diffusion decreased slightly as the embryo developed. Chronic hyperoxic incubation (70% O2) had little influence on total monosaccharide uptake by embryonic erythrocytes.

Uptake of the antileishmania drug tafenoquine follows a sterol-dependent diffusion process in Leishmania.

PubMed

Manzano, José Ignacio; Carvalho, Luis; García-Hernández, Raquel; Poveda, José Antonio; Ferragut, José Antonio; Castanys, Santiago; Gamarro, Francisco

2011-11-01

The present study was designed to elucidate the mechanism of tafenoquine uptake in Leishmania and its sterol dependence. Because tafenoquine is a fluorescent compound, spectrofluorimetric analysis allowed us to monitor its uptake by Leishmania promastigotes and intracellular amastigotes, and to evaluate the effect of temperature, energy and H+ gradient on drug entry. The influence of sterols on tafenoquine uptake in Leishmania parasites was determined in experiments using sterol-depleting agents such as methyl-β-cyclodextrin or cholesterol oxidase. Tafenoquine exhibited fast entry kinetics into Leishmania in an energy-independent, but pH- and temperature-dependent, non-saturable process. Furthermore, sterol depletion decreased tafenoquine uptake. These findings suggest that Leishmania takes up tafenoquine by a diffusion process and that decreases in membrane sterol content may induce a decrease in drug uptake.

Plants may alter competition by modifying nutrient bioavailability in rhizosphere: a modeling approach.

PubMed

Raynaud, Xavier; Jaillard, Benoît; Leadley, Paul W

2008-01-01

Plants modify nutrient availability by releasing chemicals in the rhizosphere. This change in availability induced by roots (bioavailability) is known to improve nutrient uptake by individual plants releasing such compounds. Can this bioavailability alter plant competition for nutrients and under what conditions? To address these questions, we have developed a model of nutrient competition between plant species based on mechanistic descriptions of nutrient diffusion, plant exudation, and plant uptake. The model was parameterized using data of the effects of root citrate exudation on phosphorus availability. We performed a sensitivity analysis for key parameters to test the generality of these effects. Our simulations suggest the following. (1) Nutrient uptake depends on the number of roots when nutrients and exudates diffuse little, because individual roots are nearly independent in terms of nutrient supply. In this case, bioavailability profits only species with exudates. (2) Competition for nutrients depends on the spatial arrangement of roots when nutrients diffuse little but exudates diffuse widely. (3) Competition for nutrients depends on the nutrient uptake capacity of roots when nutrients and exudates diffuse widely. In this case, bioavailability profits all species. Mechanisms controlling competition for bioavailable nutrients appear to be diverse and strongly depend on soil, nutrient, and plant properties.

A high 18F-FDOPA uptake is associated with a slow growth rate in diffuse Grade II-III gliomas.

PubMed

Isal, Sibel; Gauchotte, Guillaume; Rech, Fabien; Blonski, Marie; Planel, Sophie; Chawki, Mohammad B; Karcher, Gilles; Marie, Pierre-Yves; Taillandier, Luc; Verger, Antoine

2018-04-01

In diffuse Grade II-III gliomas, a high 3,4-dihydroxy-6-( 18 F)-fluoro-L-phenylalanine ( 18 F-FDOPA) positron emission tomography (PET) uptake, with a standardized uptake value (SUV max )/contralateral brain tissue ratio greater than 1.8, was previously found to be consistently associated with the presence of an isocitrate dehydrogenase (IDH) mutation, whereas this mutation is typically associated with a better prognosis. This pilot study was aimed to ascertain the prognostic value of this high 18 F-FDOPA uptake in diffuse Grade II-III gliomas with regard to the velocity of diameter expansion (VDE), which represents an established landmark of better prognosis when below 4 mm per year. 20 patients (42 ± 10 years, 10 female) with newly-diagnosed diffuse Grade II-III gliomas (17 with IDH mutation) were retrospectively included. All had a 18 F-FDOPA PET, quantified with SUV max ratio, along with a serial MRI enabling VDE determination. SUV max ratio was above 1.8 in 5 patients (25%) all of whom had a VDE <4 mm/year (100%) and IDH mutation (100%). Moreover, a SUV max ratio above 1.8 was associated with higher rates of VDE <4 mm/year in the overall population (45 vs 0%, p = 0.04) and also in the subgroup of patients with IDH mutation (45 vs 0%, p = 0.10). This pilot study shows that in diffuse Grade II-III gliomas, a high 18 F-FDOPA uptake would be predictive of low tumour growth, with a different prognostic significance than IDH mutation. Advances in knowledge: 18 F-FDOPA PET in a single session imaging could have prognostic value in initial diagnosis of diffuse Grade II-III gliomas.

Microdialysis of Soil P: A means to mimic root uptake?

NASA Astrophysics Data System (ADS)

Schack-Kirschner, Helmer; Demand, Dominic; Lang, Friederike

2017-04-01

Standard procedures to assess P availability in soils are based on batch experiments with various extractants. However, in most soils P nutrition is less limited by bulk stocks but by slow diffusion of phosphate through the soil solution. More comparable to the root's approach is to strip phosphate locally from the solid phase by lowering the soil-solution concentration, which can be achieved by establishing an infinite diffusional sink, such as DGT. An alternative diffusive sampling technique is microdialysis (MD), well established in pharmacokinetics. Briefly, this method uses miniaturized flow-through probes where the perfusate gets in diffusive contact to the external solution by a semipermeable membrane. Important aspects of P supply to roots resemble MD sampling. This is not only the mostly diffusive transport, but also an elongated capillary tube-like geometry of absorption. The diameter of typical commercial MD probes is around 500μm. One additional inherent feature of microdialysis is the possibility to release low-molecular substances from the perfusate by diffusion into the matrix, such as carboxylates. However, microdialysis has yet not been used for P in soils. We tested microdialysis in topsoils of an acid beech forest, of an unfertilized grassland and of a fertilized crop site. Three perfusates have been used: 1 mM KNO3, electrolyte + 0.1 mM citric acid, and electrolyte + 1 mM citric acid. We observed rates of uptake into the probes in a range between 1.5*10-15 and 6.7*10-14 mol s-1cm-1 in case of no citrate addition. Surprisingly, these uptake rates were mostly independent of the bulk stocks. Citrate addition increased P yields only in the higher concentration but not in the forest soil. The order of magnitude of MD uptake rates from the soil samples matched root-length related uptake rates from other studies. The micro-radial citrate release in MD reflects the processes controlling phosphate mobilization in the rhizosphere better than measurements based on "flooding" of soil samples with citric acid in batch experiments. Important challenges in MD with phosphate are small volumes of dialysate with extremely low concentrations and a high variability of results due to soil heterogeneity and between-probe variability. We conclude that MD is a promising tool to complement existing P-analytical procedures, especially when spatial aspects or the release of mobilizing substances are in focus.

Highly Viscous States Affect the Browning of Atmospheric Organic Particulate Matter

PubMed Central

2018-01-01

Initially transparent organic particulate matter (PM) can become shades of light-absorbing brown via atmospheric particle-phase chemical reactions. The production of nitrogen-containing compounds is one important pathway for browning. Semisolid or solid physical states of organic PM might, however, have sufficiently slow diffusion of reactant molecules to inhibit browning reactions. Herein, organic PM of secondary organic material (SOM) derived from toluene, a common SOM precursor in anthropogenically affected environments, was exposed to ammonia at different values of relative humidity (RH). The production of light-absorbing organonitrogen imines from ammonia exposure, detected by mass spectrometry and ultraviolet–visible spectrophotometry, was kinetically inhibited for RH < 20% for exposure times of 6 min to 24 h. By comparison, from 20% to 60% RH organonitrogen production took place, implying ammonia uptake and reaction. Correspondingly, the absorption index k across 280 to 320 nm increased from 0.012 to 0.02, indicative of PM browning. The k value across 380 to 420 nm increased from 0.001 to 0.004. The observed RH-dependent behavior of ammonia uptake and browning was well captured by a model that considered the diffusivities of both the large organic molecules that made up the PM and the small reactant molecules taken up from the gas phase into the PM. Within the model, large-molecule diffusivity was calculated based on observed SOM viscosity and evaporation. Small-molecule diffusivity was represented by the water diffusivity measured by a quartz-crystal microbalance. The model showed that the browning reaction rates at RH < 60% could be controlled by the low diffusivity of the large organic molecules from the interior region of the particle to the reactive surface region. The results of this study have implications for accurate modeling of atmospheric brown carbon production and associated influences on energy balance. PMID:29532020

Highly Viscous States Affect the Browning of Atmospheric Organic Particulate Matter.

PubMed

Liu, Pengfei; Li, Yong Jie; Wang, Yan; Bateman, Adam P; Zhang, Yue; Gong, Zhaoheng; Bertram, Allan K; Martin, Scot T

2018-02-28

Initially transparent organic particulate matter (PM) can become shades of light-absorbing brown via atmospheric particle-phase chemical reactions. The production of nitrogen-containing compounds is one important pathway for browning. Semisolid or solid physical states of organic PM might, however, have sufficiently slow diffusion of reactant molecules to inhibit browning reactions. Herein, organic PM of secondary organic material (SOM) derived from toluene, a common SOM precursor in anthropogenically affected environments, was exposed to ammonia at different values of relative humidity (RH). The production of light-absorbing organonitrogen imines from ammonia exposure, detected by mass spectrometry and ultraviolet-visible spectrophotometry, was kinetically inhibited for RH < 20% for exposure times of 6 min to 24 h. By comparison, from 20% to 60% RH organonitrogen production took place, implying ammonia uptake and reaction. Correspondingly, the absorption index k across 280 to 320 nm increased from 0.012 to 0.02, indicative of PM browning. The k value across 380 to 420 nm increased from 0.001 to 0.004. The observed RH-dependent behavior of ammonia uptake and browning was well captured by a model that considered the diffusivities of both the large organic molecules that made up the PM and the small reactant molecules taken up from the gas phase into the PM. Within the model, large-molecule diffusivity was calculated based on observed SOM viscosity and evaporation. Small-molecule diffusivity was represented by the water diffusivity measured by a quartz-crystal microbalance. The model showed that the browning reaction rates at RH < 60% could be controlled by the low diffusivity of the large organic molecules from the interior region of the particle to the reactive surface region. The results of this study have implications for accurate modeling of atmospheric brown carbon production and associated influences on energy balance.

Relationship between pretreatment FDG-PET and diffusion-weighted MRI biomarkers in diffuse large B-cell lymphoma

PubMed Central

de Jong, Antoinette; Kwee, Thomas C; de Klerk, John MH; Adam, Judit A; de Keizer, Bart; Fijnheer, Rob; Kersten, Marie José; Ludwig, Inge; Jauw, Yvonne WS; Zijlstra, Josée M; den Bos, Indra C Pieters - Van; Stoker, Jaap; Hoekstra, Otto S; Nievelstein, Rutger AJ

2014-01-01

The purpose of this study was to determine the correlation between the 18F-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) standardized uptake value (SUV) and the diffusion-weighted magnetic resonance imaging (MRI) apparent diffusion coefficient (ADC) in newly diagnosed diffuse large B-cell lymphoma (DLBCL). Pretreatment FDG-PET and diffusion-weighted MRI of 21 patients with histologically proven DLBCL were prospectively analyzed. In each patient, maximum, mean and peak standardized uptake value (SUV) was measured in the lesion with visually highest FDG uptake and in the largest lesion. Mean ADC (ADCmean, calculated with b-values of 0 and 1000 s/mm2) was measured in the same lesions. Correlations between FDG-PET metrics (SUVmax, SUVmean, SUVpeak) and ADCmean were assessed using Pearson’s correlation coefficients. In the lesions with visually highest FDG uptake, no significant correlations were found between the SUVmax, SUVmean, SUVpeak and the ADCmean (P=0.498, P=0.609 and P=0.595, respectively). In the largest lesions, there were no significant correlations either between the SUVmax, SUVmean, SUVpeak and the ADCmean (P=0.992, P=0.843 and P=0.894, respectively). The results of this study indicate that the glycolytic rate as measured by FDG-PET and changes in water compartmentalization and water diffusion as measured by the ADC are independent biological phenomena in newly diagnosed DLBCL. Further studies are warranted to assess the complementary roles of these different imaging biomarkers in the evaluation and follow-up of DLBCL. PMID:24795837

Development of an Mg-Based Alloy with a Hydrogen-Storage Capacity over 6 wt% by Adding Graphene

NASA Astrophysics Data System (ADS)

Choi, Eunho; Kwak, Young Jun; Song, Myoung Youp

2018-06-01

Graphene (multilayer graphene) was chosen as an additive to improve the hydrogen uptake and release properties of magnesium (Mg). Five weight percent of graphene was added to pre-milled Mg by milling in hydrogen (reaction-involving milling). The hydrogen uptake and release properties of the graphene-added Mg were investigated. The activation of Mg-5graphene, which was prepared by adding 5 wt% graphene to Mg pre-milled for 24 h, was completed after the second cycle (cycle number, CN = 2). Mg-5graphene had a high effective hydrogen-storage capacity (the quantity of hydrogen absorbed for 60 min) of 6.21 wt% at CN = 3 at 593 K in 12 bar H2. At CN = 1, Mg-5graphene released 0.46 wt% hydrogen for 10 min and 4.99 wt% hydrogen for 60 min. Milling in hydrogen is believed to create defects (leading to facilitation of nucleation), produce cracks and clean surfaces (leading to increase in reactivity), and decrease particle size (leading to diminution of diffusion distances or increasing the flux of diffusing hydrogen atoms). The added graphene is believed to have helped the sample have higher hydrogen uptake and release rates, weakly but partly, by dispersing heat rapidly.

Mapping trace element distribution in fossil teeth and bone with LA-ICP-MS

NASA Astrophysics Data System (ADS)

Hinz, E. A.; Kohn, M. J.

2009-12-01

Trace element profiles were measured in fossil bones and teeth from the late Pleistocene (c. 25 ka) Merrell locality, Montana, USA, by using laser-ablation ICP-MS. Laser-ablation ICP-MS can collect element counts along predefined tracks on a sample’s surface using a constant ablation speed allowing for rapid spatial sampling of element distribution. Key elements analyzed included common divalent cations (e.g. Sr, Zn, Ba), a suite of REE (La, Ce, Nd, Sm, Eu, Yb), and U, in addition to Ca for composition normalization and standardization. In teeth, characteristic diffusion penetration distances for all trace elements are at least a factor of 4 greater in traverses parallel to the dentine-enamel interface (parallel to the growth axis of the tooth) than perpendicular to the interface. Multiple parallel traverses in sections parallel and perpendicular to the tooth growth axis were transformed into trace element maps, and illustrate greater uptake of all trace elements along the central axis of dentine compared to areas closer to enamel, or within the enamel itself. Traverses in bone extending from the external surface, through the thickness of cortical bone and several mm into trabecular bone show major differences in trace element uptake compared to teeth: U and Sr are homogeneous, whereas all REE show a kinked profile with high concentrations on outer surfaces that decrease by several orders of magnitude within a few mm inward. The Eu anomaly increases uniformly from the outer edge of bone inward, whereas the Ce anomaly decreases slightly. These observations point to major structural anisotropies in trace element transport and uptake during fossilization, yet transport and uptake of U and REE are not resolvably different. In contrast, transport and uptake of U in bone must proceed orders of magnitude faster than REE as U is homogeneous whereas REE exhibit strong gradients. The kinked REE profiles in bone unequivocally indicate differential transport rates, consistent with a double-medium diffusion model in which microdomains with slow diffusivities are bounded by fast-diffusing pathways.

Abdominal and hepatic uptake of /sup 99m/Tc-pyrophosphate in neonatal necrotizing enterocolitis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caride, V.J.; Touloukian, R.J.; Ablow, R.C.

1981-04-01

Abdominal /sup 99m/Tc-pyrophosphate (/sup 99m/Tc-PYP) scans were obtained in 15 neonates: 12 with neonatal necrotizing enterocolitis (NEC), two with osteomyelitis, and one with myocarditis. Ten of the babies with NEC had at least one positive scan; of these 10 studies, seven (Group A) showed both diffuse abdominal uptake and localized hepatic activity, two (Group B) showed abdominal uptake and questionable hepatic uptake, and one (Group C) demonstrated diffuse abdominal uptake only. The other two babies with NEC had normal scans (Group D). All NEC patients had normal scans. A patient with myocarditis had hepatic uptake of /sup 99m/Tc-PYP while themore » abdominal scan in the two infants with osteomyelitis was normal. These preliminary observations suggest that further study of a relationship between abdominal scan findings and the course of NEC is warranted.« less

Novel mucus-penetrating liposomes as a potential oral drug delivery system: preparation, in vitro characterization, and enhanced cellular uptake

PubMed Central

Li, Xiuying; Chen, Dan; Le, Chaoyi; Zhu, Chunliu; Gan, Yong; Hovgaard, Lars; Yang, Mingshi

2011-01-01

Background The aim of this study was to investigate the intestinal mucus-penetrating properties and intestinal cellular uptake of two types of liposomes modified by Pluronic F127 (PF127). Methods The two types of liposomes, ie, PF127-inlaid liposomes and PF127-adsorbed liposomes, were prepared by a thin-film hydration method followed by extrusion, in which coumarin 6 was loaded as a fluorescence marker. A modified Franz diffusion cell mounted with the intestinal mucus of rats was used to study the diffusion characteristics of the two types of PF127 liposomes. Cell uptake studies were conducted in Caco-2 cells and analyzed using confocal laser scanning microcopy as well as flow cytometry. Results The diffusion efficiency of the two types of PF127-modified liposomes through intestinal rat mucus was 5–7-fold higher than that of unmodified liposomes. Compared with unmodified liposomes, PF127-inlaid liposomes showed significantly higher cellular uptake of courmarin 6. PF127-adsorbed liposomes showed a lower cellular uptake. Moreover, and interestingly, the two types of PF127-modified liposomes showed different cellular uptake mechanisms in Caco-2 cells. Conclusion PF127-inlaid liposomes with improved intestinal mucus-penetrating ability and enhanced cellular uptake might be a potential carrier candidate for oral drug delivery. PMID:22163166

Cadmium and Zn availability as affected by pH manipulation and its assessment by soil extraction, DGT and indicator plants.

PubMed

Muhammad, Iqbal; Puschenreiter, Markus; Wenzel, Walter W

2012-02-01

Manipulation of soil pH by soil additives and / or rhizosphere processes may enhance the efficiency of metal phytoextraction. Here we report on the effect of nitric acid additions to four polluted soils on Cd and Zn concentrations in soil solution (C(soln)) and 0.005M Ca(NO(3))(2) extracts, and related changes in the diffusive fluxes and resupply of the metals as assessed by diffusive gradients in thin films (DGT). The responses of these chemical indicators of bioavailability were compared to metal uptake in two indicator plant species, common dandelion (Taraxacum officinale F.H. Wigg) and narrow leaf plantain (Plantago lanceolata L.) grown for 75days in a pot experiment. Lowering soil pH increased C(soln), the 0.005M Ca(NO(3))(2)-soluble fractions and the DGT-measured Cd and Zn concentrations (C(DGT)) in the experimental soils. This was associated with enhanced uptake of Cd and Zn on soils acidified to pH 4.5 whereas plants did not survive at pH 3.5. Toxicity along with decreased kinetics of metal resupply (calculated by the 2D DIFS model) in the strong acidification treatment suggests that moderate acidification is more appropriate to enhance the phytoextraction process. Each of the chemical indicators of bioavailability predicted well (R(2)>0.70) the Cd and Zn concentrations in plantain shoots but due to metal toxicity not for dandelion. Concentration factors, i.e. the ratio between metal concentrations in shoots and in soil solution (CF) indicate that Cd and Zn uptake in plantain was not limited by diffusion which may explain that DGT did not perform better than C(soln). However, DGT is expected to predict plant uptake better in diffusion-limited conditions such as in the rhizosphere of metal-accumulating phytoextraction crops. Copyright © 2011 Elsevier B.V. All rights reserved.

Mechanically triggered solute uptake in soft contact lenses.

PubMed

Tavazzi, Silvia; Ferraro, Lorenzo; Fagnola, Matteo; Cozza, Federica; Farris, Stefano; Bonetti, Simone; Simonutti, Roberto; Borghesi, Alessandro

2015-06-01

Molecular arrangement plays a role in the diffusion of water and solutes across soft contact lenses. In particular, the uptake of solutes in hydrated contact lenses can occur as long as free water is available for diffusion. In this work, we investigated the effect of mechanical vibrations of low frequency (200 Hz) on the solute uptake. Hyaluronan, a polysaccharide of ophthalmic use, was taken as example of solute of interest. For a specific water-hydrated hydrogel material, differential scanning calorimetry experiments showed that a large fraction of the hydration water accounted for loosely-bound water, both before and after one week of daily-wear of the lenses. The size (of the order of magnitude of few hundreds of nanometers) of hyaluronan in aqueous solution was found to be less than the size of the pores of the lens observed by scanning electron microscopy. However, solute uptake in already-hydrated lenses was negligible by simple immersion, while a significant increase occurred under mechanical vibrations of 200 Hz, thus providing experimental evidence of mechanically triggered enhanced solute uptake, which is attributed to the release of interfacial loosely-bound water. Also other materials were taken into consideration. However, the effectiveness of mechanical vibrations for hyaluronan uptake is restricted to lenses containing interfacial loosely-bound water. Indeed, loosely-bound water is expected to be bound to the polymer with bonding energies of the order of magnitude of 10-100 J/g, which are compatible with the energy input supplied by the vibrations. Copyright © 2015 Elsevier B.V. All rights reserved.

Diffusion Performance of Fertilizer Nutrient through Polymer Latex Film.

PubMed

An, Di; Yang, Ling; Liu, Boyang; Wang, Ting-Jie; Kan, Chengyou

2017-12-20

Matching the nutrient release rate of coated fertilizer with the nutrient uptake rate of the crop is the best way to increase the utilization efficiency of nutrients and reduce environmental pollution from the fertilizer. The diffusion property and mechanism of nutrients through the film are the theoretical basis for the product pattern design of coated fertilizers. For the coated fertilizer with a single-component nutrient, an extended solution-diffusion model was used to describe the difference of nutrient release rate, and the release rate is proportional to the permeation coefficient and the solubility of the nutrient. For the double- and triple-component fertilizer of N-K, N-P, and N-P-K, because of the interaction among nutrient molecules and ions, the release rates of different nutrients were significantly affected by the components in the composite fertilizer. Coating the single-component fertilizer (i.e., nitrogen fertilizer, phosphate fertilizer, and potash fertilizer) first and subsequently bulk blending is expected to be a promising way to adjust flexibly the nutrient release rate to meet the nutrient uptake rate of the crop.

Kinetics and equilibrium of solute diffusion into human hair.

PubMed

Wang, Liming; Chen, Longjian; Han, Lujia; Lian, Guoping

2012-12-01

The uptake kinetics of five molecules by hair has been measured and the effects of pH and physical chemical properties of molecules were investigated. A theoretical model is proposed to analyze the experimental data. The results indicate that the binding affinity of solute to hair, as characterized by hair-water partition coefficient, scales to the hydrophobicity of the solute and decreases dramatically as the pH increases to the dissociation constant. The effective diffusion coefficient of solute depended not only on the molecular size as most previous studies suggested, but also on the binding affinity as well as solute dissociation. It appears that the uptake of molecules by hair is due to both hydrophobic interaction and ionic charge interaction. Based on theoretical considerations of the cellular structure, composition and physical chemical properties of hair, quantitative-structure-property-relationships (QSPR) have been proposed to predict the hair-water partition coefficient (PC) and the effective diffusion coefficient (D (e)) of solute. The proposed QSPR models fit well with the experimental data. This paper could be taken as a reference for investigating the adsorption properties for polymeric materials, fibres, and biomaterials.

Diffusivity of dicarboxylic acids molecules to secondary organic material governed by particle phase state

NASA Astrophysics Data System (ADS)

Han, Y.; Gong, Z.; Liu, P.; de Sá, S. S.; McKinney, K. A.; Martin, S. T.

2017-12-01

Atmospheric secondary organic material (SOM) from oxidation of volatile organic compounds can exist in amorphous solid, semisolid, and liquid states depending on a range of factors such as relative humidity (RH), temperature, and reaction history. The phase state of SOM affects the dynamic exchange and reactivity between particles and gas-phase molecules. Dicarboxylic acids are ubiquitous in ambient atmosphere and the uptake of which may lead to substantial changes in hygroscopicity, absorption property, and light scattering of aerosol particles. This study investigates the diffusivity of dicarboxylic acids to the matrix of SOM particles. SOM was generated from dark ozonolysis of a-pinene in Harvard Environmental Chamber. The produced SOM particles were passed through an ozone scrubber to remove gas-phase chemistry before being led into a flask reactor, where gas-phase dicarboxylic acid was injected continuously and RH was varied from 5% to 85%. The probe dicarboxylic acids molecules including malonic acid and a-ketoglutaric acid have been investigated for the uptake to SOM particles. Organic composition in the outflow of the flask was measured with a high-resolution time-of-flight aerosol mass spectrometer. The mass fractions of tracer ions in total organic mass for both malonic acid and a-ketoglutaric acid increased substantially with the increase of RH values. The tracer ions of malonic acid were also more abundant in a-pinene SOM particles with increased gas-phase concentrations. These results suggest that the diffusion of the studied dicarboxylic acids molecules to a-pinene SOM particles was enhanced at increased RH values, which is possibly due to the phase transition of a-pinene SOM particles from non-liquid to liquid states. Therefore, particle phase state may be an important factor governing the diffusivity of dicarboxylic acids molecules to a-pinene SOM. Further dicarboxylic acids with various functional groups will be investigated to understand the effects of volatility and structure on their diffusivity.

Increased diffuse radiation fraction does not significantly accelerate plant growth

NASA Astrophysics Data System (ADS)

Angert, Alon; Krakauer, Nir

2010-05-01

A recent modelling study (Mercado et al., 2009) claims that increased numbers of scattering aerosols are responsible for a substantial fraction of the terrestrial carbon sink in recent decades because higher diffuse light fraction enhances plant net primary production (NPP). Here we show that observations of atmospheric CO2 seasonal cycle and tree ring data indicate that the relation between diffuse light and NPP is actually quite weak on annual timescales. The inconsistency of these data with the modelling results may arise because the relationships used to quantify the enhancement of NPP were calibrated with eddy covariance measurements of hourly carbon uptake. The effect of diffuse-light fraction on carbon uptake could depend on timescale, since this effect varies rapidly as sun angle and cloudiness change, and since plants can respond dynamically over various timescales to change in incoming radiation. Volcanic eruptions, such as the eruption of Mount Pinatubo in 1991, provide the best available tests for the effect of an annual-scale increase in the diffuse light fraction. Following the Pinatubo Eruption, in 1992 and 1993, a sharp decrease in the atmospheric CO2 growth rate was observed. This could have resulted from enhanced plant carbon uptake. Mercado et al. (2009) argue that largely as a result of the (volcanic aerosol driven) increase in diffuse light fraction, NPP was elevated in 1992, particularly between 25° N-45° N where annual NPP was modelled to be ~0.8 PgC (~10%) above average. In a previous study (Angert et al., 2004) a biogeochemical model (CASA) linked to an atmospheric tracer model (MATCH), was used to show that a diffuse-radiation driven increase in NPP in the extratropics will enhance carbon uptake mostly in summer, leading to a lower CO2 seasonal minimum. Here we use a 'toy model' to show that this conclusion is general and model-independent. The model shows that an enhanced sink of 0.8 PgC, similar to that modelled by Mercado et al. (2009), will result in a measurable decrease (~0.6ppm) in the seasonal CO2 minimum. This holds regardless of whether the sink is the result of 1) An increase in NPP, or 2) The combined effect of a temperature-driven decrease in heterotrophic respiration (Rh) and no change in NPP. This is since both NPP and Rh peak in summer. By contrast, observations from the NOAA global CO2 monitoring network show the opposite change in the seasonal minimum in 1992 and 1993 (~0.2ppm increase) both at Mauna Loa, and in the Marine Boundary Layer mean (>20° N), which is hard to reconcile with increased NPP in northern summer. Another indicator of annual NPP is tree wood increment. Previous work (Krakauer et al., 2003) showed that the average response in tree ring series after past Pinatubo-size volcanic eruptions implied lower NPP north of 45° N, presumably as a result of shorter growing season and lower total irradiance induced by scattering aerosols, and no significant change in NPP at lower latitudes. Here we show that In 1992, after the Pinatubo eruption, ring width in the 25° N-45° N band was 99.3±2.9% of average (n=351 sites), similar to the average of 100.4±2.2% over past eruptions (n=15 eruptions) (Uncertainty is given as 2 SE.). These results are also inconsistent with substantial NPP enhancement, although a limitation of the tree-ring approach is that available measurements do not uniformly sample the latitude band. The combined evidence of tree rings and the CO2 seasonal cycle shows that the enhancement of NPP by scattering aerosols on annual timescales is weak. This result suggests that reducing aerosols through stricter pollution controls may strengthen the land carbon sink, while geo-engineering schemes which aim to mitigate global warming by spreading scattering aerosols in the stratosphere may weaken it.

Hierarchically porous organic polymers: highly enhanced gas uptake and transport through templated synthesis.

PubMed

Chakraborty, Sanjiban; Colón, Yamil J; Snurr, Randall Q; Nguyen, SonBinh T

2015-01-01

Porous organic polymers (POPs) possessing meso- and micropores can be obtained by carrying out the polymerization inside a mesoporous silica aerogel template and then removing the template after polymerization. The total pore volume (tpv) and specific surface area (ssa) can be greatly enhanced by modifying the template (up to 210% increase for tpv and 73% for ssa) as well as by supercritical processing of the POPs (up to an additional 142% increase for tpv and an additional 32% for ssa) to include larger mesopores. The broad range of pores allows for faster transport of molecules through the hierarchically porous POPs, resulting in increased diffusion rates and faster gas uptake compared to POPs with only micropores.

Bromelain Surface Modification Increases the Diffusion of Silica Nanoparticles in the Tumor Extracellular Matrix

PubMed Central

2015-01-01

Tumor extracellular matrix (ECM) represents a major obstacle to the diffusion of therapeutics and drug delivery systems in cancer parenchyma. This biological barrier limits the efficacy of promising therapeutic approaches including the delivery of siRNA or agents intended for thermoablation. After extravasation due to the enhanced penetration and retention effect of tumor vasculature, typical nanotherapeutics are unable to reach the nonvascularized and anoxic regions deep within cancer parenchyma. Here, we developed a simple method to provide mesoporous silica nanoparticles (MSN) with a proteolytic surface. To this extent, we chose to conjugate MSN to Bromelain (Br–MSN), a crude enzymatic complex, purified from pineapple stems, that belongs to the peptidase papain family. This surface modification increased particle uptake in endothelial, macrophage, and cancer cell lines with minimal impact on cellular viability. Most importantly Br–MSN showed an increased ability to digest and diffuse in tumor ECM in vitro and in vivo. PMID:25119793

Bromelain surface modification increases the diffusion of silica nanoparticles in the tumor extracellular matrix.

PubMed

Parodi, Alessandro; Haddix, Seth G; Taghipour, Nima; Scaria, Shilpa; Taraballi, Francesca; Cevenini, Armando; Yazdi, Iman K; Corbo, Claudia; Palomba, Roberto; Khaled, Sm Z; Martinez, Jonathan O; Brown, Brandon S; Isenhart, Lucas; Tasciotti, Ennio

2014-10-28

Tumor extracellular matrix (ECM) represents a major obstacle to the diffusion of therapeutics and drug delivery systems in cancer parenchyma. This biological barrier limits the efficacy of promising therapeutic approaches including the delivery of siRNA or agents intended for thermoablation. After extravasation due to the enhanced penetration and retention effect of tumor vasculature, typical nanotherapeutics are unable to reach the nonvascularized and anoxic regions deep within cancer parenchyma. Here, we developed a simple method to provide mesoporous silica nanoparticles (MSN) with a proteolytic surface. To this extent, we chose to conjugate MSN to Bromelain (Br-MSN), a crude enzymatic complex, purified from pineapple stems, that belongs to the peptidase papain family. This surface modification increased particle uptake in endothelial, macrophage, and cancer cell lines with minimal impact on cellular viability. Most importantly Br-MSN showed an increased ability to digest and diffuse in tumor ECM in vitro and in vivo.

Effect of summer throughfall exclusion, summer drought, and winter snow cover on methane fluxes in a temperate forest soil

USGS Publications Warehouse

Borken, W.; Davidson, E.A.; Savage, K.; Sundquist, E.T.; Steudler, P.

2006-01-01

Soil moisture strongly controls the uptake of atmospheric methane by limiting the diffusion of methane into the soil, resulting in a negative correlation between soil moisture and methane uptake rates under most non-drought conditions. However, little is known about the effect of water stress on methane uptake in temperate forests during severe droughts. We simulated extreme summer droughts by exclusion of 168 mm (2001) and 344 mm (2002) throughfall using three translucent roofs in a mixed deciduous forest at the Harvard Forest, Massachusetts, USA. The treatment significantly increased CH4 uptake during the first weeks of throughfall exclusion in 2001 and during most of the 2002 treatment period. Low summertime CH4 uptake rates were found only briefly in both control and exclusion plots during a natural late summer drought, when water contents below 0.15 g cm-3 may have caused water stress of methanotrophs in the A horizon. Because these soils are well drained, the exclusion treatment had little effect on A horizon water content between wetting events, and the effect of water stress was smaller and more brief than was the overall treatment effect on methane diffusion. Methane consumption rates were highest in the A horizon and showed a parabolic relationship between gravimetric water content and CH4 consumption, with maximum rate at 0.23 g H2O g-1 soil. On average, about 74% of atmospheric CH4 was consumed in the top 4-5 cm of the mineral soil. By contrast, little or no CH4 consumption occurred in the O horizon. Snow cover significantly reduced the uptake rate from December to March. Removal of snow enhanced CH4 uptake by about 700-1000%, resulting in uptake rates similar to those measured during the growing season. Soil temperatures had little effect on CH4 uptake as long as the mineral soil was not frozen, indicating strong substrate limitation of methanotrophs throughout the year. Our results suggest that the extension of snow periods may affect the annual rate of CH4 oxidation and that summer droughts may increase the soil CH4 sink of temperate forest soils. ?? 2005 Elsevier Ltd. All rights reserved.

Uptake of L-nicotine and of 6-hydroxy-L-nicotine by Arthrobacter nicotinovorans and by Escherichia coli is mediated by facilitated diffusion and not by passive diffusion or active transport.

PubMed

Ganas, Petra; Brandsch, Roderich

2009-06-01

The mechanism by which l-nicotine is taken up by bacteria that are able to grow on it is unknown. Nicotine degradation by Arthrobacter nicotinovorans, a Gram-positive soil bacterium, is linked to the presence of the catabolic megaplasmid pAO1. l-[(14)C]Nicotine uptake assays with A. nicotinovorans showed transport of nicotine across the cell membrane to be energy-independent and saturable with a K(m) of 6.2+/-0.1 microM and a V(max) of 0.70+/-0.08 micromol min(-1) (mg protein)(-1). This is in accord with a mechanism of facilitated diffusion, driven by the nicotine concentration gradient. Nicotine uptake was coupled to its intracellular degradation, and an A. nicotinovorans strain unable to degrade nicotine (pAO1(-)) showed no nicotine import. However, when the nicotine dehydrogenase genes were expressed in this strain, import of l-[(14)C]nicotine took place. A. nicotinovorans pAO1(-) and Escherichia coli were also unable to import 6-hydroxy-l-nicotine, but expression of the 6-hydroxy-l-nicotine oxidase gene allowed both bacteria to take up this compound. l-Nicotine uptake was inhibited by d-nicotine, 6-hydroxy-l-nicotine and 2-amino-l-nicotine, which may indicate transport of these nicotine derivatives by a common permease. Attempts to correlate nicotine uptake with pAO1 genes possessing similarity to amino acid transporters failed. In contrast to the situation at the blood-brain barrier, nicotine transport across the cell membrane by these bacteria was not by passive diffusion or active transport but by facilitated diffusion.

Integrated MRI and [11 C]-PBR28 PET Imaging in Amyotrophic Lateral sclerosis.

PubMed

Alshikho, Mohamad J; Zürcher, Nicole R; Loggia, Marco L; Cernasov, Paul; Reynolds, Beverly; Pijanowski, Olivia; Chonde, Daniel B; Izquierdo Garcia, David; Mainero, Caterina; Catana, Ciprian; Chan, James; Babu, Suma; Paganoni, Sabrina; Hooker, Jacob M; Atassi, Nazem

2018-05-08

To characterize [ 11 C]-PBR28 brain uptake using positron emission tomography (PET) in people with amyotrophic lateral sclerosis (ALS), and primary lateral sclerosis (PLS). We have previously shown increased [ 11 C]-PBR28 uptake in the precentral gyrus in a small group of ALS patients. Herein, we confirm our initial finding, study the longitudinal changes, and characterize the gray vs. white matter distribution of [ 11 C]-PBR28 uptake in a larger cohort of patients with ALS and PLS. Eighty-five participants including 53 ALS, 11 PLS and 21 healthy controls underwent integrated [ 11 C]-PBR28 PET-MR brain imaging. Patients were clinically assessed using the upper motor neuron burden (UMNB), and the revised ALS functional rating scale (ALSFRS-R). [ 11 C]-PBR28 uptake was quantified as standardized uptake value ratio (SUVR), and compared between groups. Cortical thickness, and fractional anisotropy were compared between groups and correlated with SUVR and the clinical data. [ 11 C]-PBR28 uptake and ALSFRS-R were compared longitudinally over six-month in ten ALS individuals. Whole brain voxel-wise, surface-based and region of interest analyses revealed increased [ 11 C]-PBR28 uptake in the precentral and paracentral gyri in ALS, and in the sub-cortical white matter for the same regions in PLS, compared to controls. The increase in [ 11 C]-PBR28 uptake co-localized and correlated with cortical thinning, reduced fractional anisotropy, increased mean diffusivity, and correlated with higher UMNB score. No significant changes were detected in [ 11 C]-PBR28 uptake over six-month despite clinical progression. Glial activation measured by in vivo [ 11 C]-PBR28 PET is increased in pathologically relevant regions in people with ALS and correlates with clinical measures. This article is protected by copyright. All rights reserved. © 2018 American Neurological Association.

Fluorine-18 fluorodeoxyglucose splenic uptake from extramedullary hematopoiesis after granulocyte colony-stimulating factor stimulation.

PubMed

Abdel-Dayem, H M; Rosen, G; El-Zeftawy, H; Naddaf, S; Kumar, M; Atay, S; Cacavio, A

1999-05-01

Two patients with sarcoma, one with recurrent osteosarcoma of the spine and the other with metastatic synovial cell sarcoma, were treated with high-dose chemotherapy that produced severe leukopenia. The patients received granulocyte colony-stimulating factor (G-CSF) to stimulate the bone marrow (480 mg given subcutaneously twice daily for 5 to 7 days); their responses were seen as a marked increase in peripheral leukocyte count with no change in the erythrocyte or platelet counts. The patients had fluorine-18 fluorodeoxyglucose (F-18 FDG) imaging 24 hours after the end of G-CSF treatment. Diffusely increased uptake of F-18 FDG was seen in the bone marrow in both patients. In addition, markedly increased uptake in the spleen was noted in both, indicating that the spleen was the site of extramedullary hematopoiesis. The patients had no evidence of splenic metastases. The first patient had a history of irradiation to the dorsal spine, which was less responsive to G-CSF administration than was the nonirradiated lumbar spine.

Diffusion of small molecules into medaka embryos improved by electroporation

PubMed Central

2013-01-01

Background Diffusion of small molecules into fish embryos is essential for many experimental procedures in developmental biology and toxicology. Since we observed a weak uptake of lithium into medaka eggs we started a detailed analysis of its diffusion properties using small fluorescent molecules. Results Contrary to our expectations, not the rigid outer chorion but instead membrane systems surrounding the embryo/yolk turned out to be the limiting factor for diffusion into medaka eggs. The consequence is a bi-phasic uptake of small molecules first reaching the pervitelline space with a diffusion half-time in the range of a few minutes. This is followed by a slow second phase (half-time in the range of several hours) during which accumulation in the embryo/yolk takes place. Treatment with detergents improved the uptake, but strongly affected the internal distribution of the molecules. Testing electroporation we could establish conditions to overcome the diffusion barrier. Applying this method to lithium chloride we observed anterior truncations in medaka embryos in agreement with its proposed activation of Wnt signalling. Conclusions The diffusion of small molecules into medaka embryos is slow, caused by membrane systems underneath the chorion. These results have important implications for pharmacologic/toxicologic techniques like the fish embryo test, which therefore require extended incubation times in order to reach sufficient concentrations in the embryos. PMID:23815821

Limited effects of exogenous glucose during severe hypoxia and a lack of hypoxia-stimulated glucose uptake in isolated rainbow trout cardiac muscle

PubMed Central

Becker, Tracy A.; DellaValle, Brian; Gesser, Hans; Rodnick, Kenneth J.

2013-01-01

SUMMARY We examined whether exogenous glucose affects contractile performance of electrically paced ventricle strips from rainbow trout under conditions known to alter cardiomyocyte performance, ion regulation and energy demands. Physiological levels of d-glucose did not influence twitch force development for aerobic preparations (1) paced at 0.5 or 1.1 Hz, (2) at 15 or 23°C, (3) receiving adrenergic stimulation or (4) during reoxygenation with or without adrenaline after severe hypoxia. Contractile responses to ryanodine, an inhibitor of Ca2+ release from the sarcoplasmic reticulum, were also not affected by exogenous glucose. However, glucose did attenuate the fall in twitch force during severe hypoxia. Glucose uptake was assayed in non-contracting ventricle strips using 2-[3H] deoxy-d-glucose (2-DG) under aerobic and hypoxic conditions, at different incubation temperatures and with different inhibitors. Based upon a lack of saturation of 2-DG uptake and incomplete inhibition of uptake by cytochalasin B and d-glucose, 2-DG uptake was mediated by a combination of facilitated transport and simple diffusion. Hypoxia stimulated lactate efflux sixfold to sevenfold with glucose present, but did not increase 2-DG uptake or reduce lactate efflux in the presence of cytochalasin B. Increasing temperature (14 to 24°C) also did not increase 2-DG uptake, but decreasing temperature (14 to 4°C) reduced 2-DG uptake by 45%. In conclusion, exogenous glucose improves mechanical performance under hypoxia but not under any of the aerobic conditions applied. The extracellular concentration of glucose and cold temperature appear to determine and limit cardiomyocyte glucose uptake, respectively, and together may help define a metabolic strategy that relies predominantly on intracellular energy stores. PMID:23685969

Interstitial diffusion and the relationship between compartment modelling and multi-scale spatial-temporal modelling of (18)F-FLT tumour uptake dynamics.

PubMed

Liu, Dan; Chalkidou, Anastasia; Landau, David B; Marsden, Paul K; Fenwick, John D

2014-09-07

Tumour cell proliferation can be imaged via positron emission tomography of the radiotracer 3'-deoxy-3'-18F-fluorothymidine (18F-FLT). Conceptually, the number of proliferating cells might be expected to correlate more closely with the kinetics of 18F-FLT uptake than with uptake at a fixed time. Radiotracer uptake kinetics are standardly visualized using parametric maps of compartment model fits to time-activity-curves (TACs) of individual voxels. However the relationship between the underlying spatiotemporal accumulation of FLT and the kinetics described by compartment models has not yet been explored. In this work tumour tracer uptake is simulated using a mechanistic spatial-temporal model based on a convection-diffusion-reaction equation solved via the finite difference method. The model describes a chain of processes: the flow of FLT between the spatially heterogeneous tumour vasculature and interstitium; diffusion and convection of FLT within the interstitium; transport of FLT into cells; and intracellular phosphorylation. Using values of model parameters estimated from the biological literature, simulated FLT TACs are generated with shapes and magnitudes similar to those seen clinically. Results show that the kinetics of the spatial-temporal model can be recovered accurately by fitting a 3-tissue compartment model to FLT TACs simulated for those tumours or tumour sub-volumes that can be viewed as approximately closed, for which tracer diffusion throughout the interstitium makes only a small fractional change to the quantity of FLT they contain. For a single PET voxel of width 2.5-5 mm we show that this condition is roughly equivalent to requiring that the relative difference in tracer uptake between the voxel and its neighbours is much less than one.

The OprB porin plays a central role in carbohydrate uptake in Pseudomonas aeruginosa.

PubMed Central

Wylie, J L; Worobec, E A

1995-01-01

Using interposon mutagenesis, we have generated strains of Pseudomonas aeruginosa which lack or overexpress the substrate-selective OprB porin of this species. A marked decrease or increase in the initial uptake of glucose by these strains verified the role of OprB in facilitating the diffusion of glucose across the outer membrane of P. aeruginosa. However, we also demonstrated that the loss or overexpression of OprB had a similar effect on the uptake of three other sugars able to support the growth of this bacterium (mannitol, glycerol, and fructose). This effect was restricted to carbohydrate transport; arginine uptake was identical in mutant and wild-type strains. These results indicated that OprB cannot be considered strictly a glucose-selective porin; rather, it acts as a central component of carbohydrate transport and is more accurately described as a carbohydrate-selective porin. PMID:7768797

The OprB porin plays a central role in carbohydrate uptake in Pseudomonas aeruginosa.

PubMed

Wylie, J L; Worobec, E A

1995-06-01

Using interposon mutagenesis, we have generated strains of Pseudomonas aeruginosa which lack or overexpress the substrate-selective OprB porin of this species. A marked decrease or increase in the initial uptake of glucose by these strains verified the role of OprB in facilitating the diffusion of glucose across the outer membrane of P. aeruginosa. However, we also demonstrated that the loss or overexpression of OprB had a similar effect on the uptake of three other sugars able to support the growth of this bacterium (mannitol, glycerol, and fructose). This effect was restricted to carbohydrate transport; arginine uptake was identical in mutant and wild-type strains. These results indicated that OprB cannot be considered strictly a glucose-selective porin; rather, it acts as a central component of carbohydrate transport and is more accurately described as a carbohydrate-selective porin.

Numerical Evaluation of Lateral Diffusion Inside Diffusive Gradients in Thin Films Samplers

PubMed Central

2015-01-01

Using numerical simulation of diffusion inside diffusive gradients in thin films (DGT) samplers, we show that the effect of lateral diffusion inside the sampler on the solute flux into the sampler is a nonlinear function of the diffusion layer thickness and the physical sampling window size. In contrast, earlier work concluded that this effect was constant irrespective of parameters of the sampler geometry. The flux increase caused by lateral diffusion inside the sampler was determined to be ∼8.8% for standard samplers, which is considerably lower than the previous estimate of ∼20%. Lateral diffusion is also propagated to the diffusive boundary layer (DBL), where it leads to a slightly stronger decrease in the mass uptake than suggested by the common 1D diffusion model that is applied for evaluating DGT results. We introduce a simple correction procedure for lateral diffusion and demonstrate how the effect of lateral diffusion on diffusion in the DBL can be accounted for. These corrections often result in better estimates of the DBL thickness (δ) and the DGT-measured concentration than earlier approaches and will contribute to more accurate concentration measurements in solute monitoring in waters. PMID:25877251

Imaging and modelling root water uptake

NASA Astrophysics Data System (ADS)

Zarebanadkouki, M.; Meunier, F.; Javaux, M.; Kaestner, A.; Carminati, A.

2017-12-01

Spatially resolved measurement and modelling of root water uptake is urgently needed to identify root traits that can improve capture of water from the soil. However, measuring water fluxes into roots of transpiring plants growing in soil remains challenging. Here, we describe an in-situ technique to measure local fluxes of water into roots. The technique consists of tracing the transport of deuterated water (D2O) in soil and roots using time series neutron radiography and tomography. A diffusion-convection model was used to model the transport of D2O in roots. The model includes root features such as the endodermis, xylem and the composite flow of water in the apoplastic and symplastic pathways. Diffusion permeability of root cells and of the endodermis were estimated by fitting the experiment during the night, when transpiration was negligible. The water fluxes at different position of the root system were obtained by fitting the experiments at daytime. The results showed that root water uptake was not uniform along root system and varied among different root types. The measured profiles of root water uptake into roots were used to estimate the radial and axial hydraulic of the roots. A three-dimensional model of root water uptake was used to fit the measured water fluxes by adjusting the root radial and axial hydraulic conductivities. We found that the estimated radial conductivities decreased with root age, while the axial conducances increased, and they are different among root types. The significance of this study is the development of a method to estimate 1) water uptake and 2) the radial and axial hydraulic conductivities of roots of transpiring plants growing in the soil.

The Capacity for Thermal Protection of Photosynthetic Electron Transport Varies for Different Monoterpenes in Quercus ilex1

PubMed Central

Copolovici, Lucian O.; Filella, Iolanda; Llusià, Joan; Niinemets, Ülo; Peñuelas, Josep

2005-01-01

Heat stress resistance of foliar photosynthetic apparatus was investigated in the Mediterranean monoterpene-emitting evergreen sclerophyll species Quercus ilex. Leaf feeding with fosmidomycin, which is a specific inhibitor of the chloroplastic isoprenoid synthesis pathway, essentially stopped monoterpene emission and resulted in the decrease of the optimum temperature of photosynthetic electron transport from approximately 38°C to approximately 30°C. The heat stress resistance was partly restored by fumigation with 4 to 5 nmol mol−1 air concentrations of monoterpene α-pinene but not with fumigations with monoterpene alcohol α-terpineol. Analyses of monoterpene physicochemical characteristics demonstrated that α-pinene was primarily distributed to leaf gas and lipid phases, while α-terpineol was primarily distributed to leaf aqueous phase. Thus, for a common monoterpene uptake rate, α-terpineol is less efficient in stabilizing membrane liquid-crystalline structure and as an antioxidant in plant membranes. Furthermore, α-terpineol uptake rate (U) strongly decreased with increasing temperature, while the uptake rates of α-pinene increased with increasing temperature, providing a further explanation of the lower efficiency of thermal protection by α-terpineol. The temperature-dependent decrease of α-terpineol uptake was both due to decreases in stomatal conductance, gw, and increased volatility of α-terpineol at higher temperature that decreased the monoterpene diffusion gradient between the ambient air (FA) and leaf (FI; U = gw[FA − FI]). Model analyses suggested that α-pinene reacted within the leaf at higher temperatures, possibly within the lipid phase, thereby avoiding the decrease in diffusion gradient, FA − FI. Thus, these data contribute to the hypothesis of the antioxidative protection of leaf membranes during heat stress by monoterpenes. These data further suggest that fumigation with the relatively low atmospheric concentrations of monoterpenes that are occasionally observed during warm windless days in the Mediterranean canopies may significantly improve the heat tolerance of nonemitting vegetation that grows intermixed with emitting species. PMID:16126854

Effects of solvent evaporation on water sorption/solubility and nanoleakage of adhesive systems.

PubMed

Chimeli, Talita Baumgratz Cachapuz; D'Alpino, Paulo Henrique Perlatti; Pereira, Patrícia Nóbrega; Hilgert, Leandro Augusto; Di Hipólito, Vinicius; Garcia, Fernanda Cristina Pimentel

2014-01-01

To evaluate the influence of solvent evaporation in the kinetics of water diffusion (water sorption-WS, solubility-SL, and net water uptake) and nanoleakage of adhesive systems. Disk-shaped specimens (5.0 mm in diameter x 0.8 mm in thickness) were produced (N=48) using the adhesives: Clearfil S3 Bond (CS3)/Kuraray, Clearfil SE Bond - control group (CSE)/Kuraray, Optibond Solo Plus (OS)/Kerr and Scotchbond Universal Adhesive (SBU)/3M ESPE. The solvents were either evaporated for 30 s or not evaporated (N=24/per group), and then photoactivated for 80 s (550 mW/cm2). After desiccation, the specimens were weighed and stored in distilled water (N=12) or mineral oil (N=12) to evaluate the water diffusion over a 7-day period. Net water uptake (%) was also calculated as the sum of WS and SL. Data were submitted to 3-way ANOVA/Tukey's test (α=5%). The nanoleakage expression in three additional specimens per group was also evaluated after ammoniacal silver impregnation after 7 days of water storage under SEM. Statistical analysis revealed that only the factor "adhesive" was significant (p<0.05). Solvent evaporation had no influence in the WS and SL of the adhesives. CSE (control) presented significantly lower net uptake (5.4%). The nanoleakage was enhanced by the presence of solvent in the adhesives. Although the evaporation has no effect in the kinetics of water diffusion, the nanoleakage expression of the adhesives tested increases when the solvents are not evaporated.

Size-related bioconcentration kinetics of hydrophobic chemicals in fish

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sijm, D.T.H.M.; Linde, A. van der

1994-12-31

Uptake and elimination of hydrophobic chemicals by fish can be regarded as passive diffusive transport processes. Diffusion coefficients, lipid/water partitioning, diffusion pathlenghts, concentration gradients and surface exchange areas are key parameters describing this bioconcentration distribution process. In the present study two of these parameters were studied: the influence of lipid/water partitioning was studied by using hydrophobic chemicals of different hydrophobicity, and the surface exchange area by using different sizes of fish. By using one species of fish it was assumed that all other parameters were kept constant. Seven age classes of fish were exposed to a series of hydrophobic, formore » five days, which was followed by a deputation phase lasting up to 6 months. Bioconcentration parameters, such as uptake and elimination rate constants, and bioconcentration factors were determined. Uptake of the hydrophobic compounds was compared to that of oxygen. Uptake and elimination rates were compared to weight and estimated (gill) exchange areas. The role of weight and its implications for extrapolations of bioconcentration parameters to other species and sizes will be discussed.« less

The yeast H+-ATPase Pma1 promotes Rag/Gtr-dependent TORC1 activation in response to H+-coupled nutrient uptake.

PubMed

Saliba, Elie; Evangelinos, Minoas; Gournas, Christos; Corrillon, Florent; Georis, Isabelle; André, Bruno

2018-03-23

The yeast Target of Rapamycin Complex 1 (TORC1) plays a central role in controlling growth. How amino acids and other nutrients stimulate its activity via the Rag/Gtr GTPases remains poorly understood. We here report that the signal triggering Rag/Gtr-dependent TORC1 activation upon amino-acid uptake is the coupled H + influx catalyzed by amino-acid/H + symporters. H + -dependent uptake of other nutrients, ionophore-mediated H + diffusion, and inhibition of the vacuolar V-ATPase also activate TORC1. As the increase in cytosolic H + elicited by these processes stimulates the compensating H + -export activity of the plasma membrane H + -ATPase (Pma1), we have examined whether this major ATP-consuming enzyme might be involved in TORC1 control. We find that when the endogenous Pma1 is replaced with a plant H + -ATPase, H + influx or increase fails to activate TORC1. Our results show that H + influx coupled to nutrient uptake stimulates TORC1 activity and that Pma1 is a key actor in this mechanism. © 2018, Saliba et al.

The effect of atmospheric sulfate reductions on diffuse radiation and photosynthesis in the United States during 1995-2013

NASA Astrophysics Data System (ADS)

Keppel-Aleks, G.; Washenfelder, R. A.

2016-09-01

Aerosol optical depth (AOD) has been shown to influence the global carbon sink by increasing the fraction of diffuse light, which increases photosynthesis over a greater fraction of the vegetated canopy. Between 1995 and 2013, U.S. SO2 emissions declined by over 70%, coinciding with observed AOD reductions of 3.0 ± 0.6% yr-1 over the eastern U.S. In the Community Earth System Model (CESM), these trends cause diffuse light to decrease regionally by almost 0.6% yr-1, leading to declines in gross primary production (GPP) of 0.07% yr-1. Integrated over the analysis period and domain, this represents 0.5 Pg C of omitted GPP. A separate upscaling calculation that used published relationships between GPP and diffuse light agreed with the CESM model results within 20%. The agreement between simulated and data-constrained upscaling results strongly suggests that anthropogenic sulfate trends have a small impact on carbon uptake in temperate forests due to scattered light.

Longitudinal distribution of ozone and chlorine in the human respiratory tract: simulation of nasal and oral breathing with the single-path diffusion model.

PubMed

Bush, M L; Zhang, W; Ben-Jebria, A; Ultman, J S

2001-06-15

In the single-path model of the respiratory system, gas transport occurs within a conduit of progressively increasing cross-sectional and surface areas by a combination of flow, longitudinal dispersion, and lateral absorption. The purpose of this study was to use bolus inhalation data previously obtained for chlorine (Cl(2)) and for ozone (O(3)) to test the predictive capability of the single-path model and to adjust input parameters for applying the model to other exposure conditions. The data, consisting of uptake fraction as a function of bolus penetration volume, were recorded on 10 healthy nonsmokers breathing orally as well as nasally at alternative air flows of 150, 250, and 1000 ml/s. By employing published data for airway anatomy, gas-phase dispersion coefficients, and gas-phase mass transfer coefficients while neglecting diffusion limitations in the mucus phase, the single-path model was capable of predicting the uptake distribution for O(3) but not the steeper distribution that was observed for Cl(2). To simultaneously explain the data for these two gases, it was necessary to increase gas-phase mass transfer coefficients and to include a finite diffusion resistance of O(3) within the mucous layer. The O(3) reaction rate constants that accounted for this diffusion resistance, 2 x 10(6) s(-1) in the mouth and 8 x 10(6) s(-1) in the nose and lower airways, were much greater than previously reported reactivities of individual substrates found in mucus. Copyright 2001 Academic Press.

A Simplified Model of Moisture Transport in Hydrophilic Porous Media With Applications to Pharmaceutical Tablets.

PubMed

Klinzing, Gerard R; Zavaliangos, Antonios

2016-08-01

This work establishes a predictive model that explicitly recognizes microstructural parameters in the description of the overall mass uptake and local gradients of moisture into tablets. Model equations were formulated based on local tablet geometry to describe the transient uptake of moisture. An analytical solution to a simplified set of model equations was solved to predict the overall mass uptake and moisture gradients with the tablets. The analytical solution takes into account individual diffusion mechanisms in different scales of porosity and diffusion into the solid phase. The time constant of mass uptake was found to be a function of several key material properties, such as tablet relative density, pore tortuosity, and equilibrium moisture content of the material. The predictions of the model are in excellent agreement with experimental results for microcrystalline cellulose tablets without the need for parameter fitting. The model presented provides a new method to analyze the transient uptake of moisture into hydrophilic materials with the knowledge of only a few fundamental material and microstructural parameters. In addition, the model allows for quick and insightful predictions of moisture diffusion for a variety of practical applications including pharmaceutical tablets, porous polymer systems, or cementitious materials. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Ozone and haze pollution effects on the contemporary land carbon cycle

NASA Astrophysics Data System (ADS)

Unger, N.

2016-12-01

Atmospheric pollutants have both beneficial and detrimental effects on carbon uptake by land ecosystems. Surface ozone damages leaf photosynthesis by oxidizing plant cells, while aerosols promote carbon uptake by increasing diffuse radiation and exert additional influences through concomitant perturbations to meteorology and hydrology. Here, I present new results from three assessment studies that employ Earth system modeling and multiple measurement datasets. First, we quantify the separate and combined effects of anthropogenic ozone and aerosol pollution on the global land carbon uptake. Second, we evaluate benefits to land ecosystem health from selective emission reductions in specific pollution sources and sectors. Finally, I show that the long-term climatic effects of mid-latitude air pollution boosts plant productivity in the Amazon by 10% on the annual average today.

POLUTE. Forest Air Pollutant Uptake Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murphy, C.E. Jr.; Sinclair, T.R.

1992-02-13

POLUTE is a computer model designed to estimate the uptake of air pollutants by forests. The model utilizes submodels to describe atmospheric diffusion immediately above and within the canopy, and into the sink areas within or on the trees. The program implementing the model is general and can be used, with only minor changes, for any gaseous pollutant. The model provides an estimate describing the response of the vegetarian-atmosphere system to the environment as related to three types of processes: atmospheric diffusion, diffusion near and inside the absorbing plant, and the physical and chemical processes at the sink on ormore » within the plant.« less

Comparison between numeric and approximate analytic solutions for the prediction of soil metal uptake by roots. Example of cadmium.

PubMed

Schneider, André; Lin, Zhongbing; Sterckeman, Thibault; Nguyen, Christophe

2018-04-01

The dissociation of metal complexes in the soil solution can increase the availability of metals for root uptake. When it is accounted for in models of bioavailability of soil metals, the number of partial differential equations (PDEs) increases and the computation time to numerically solve these equations may be problematic when a large number of simulations are required, for example for sensitivity analyses or when considering root architecture. This work presents analytical solutions for the set of PDEs describing the bioavailability of soil metals including the kinetics of complexation for three scenarios where the metal complex in solution was fully inert, fully labile, or partially labile. The analytical solutions are only valid i) at steady-state when the PDEs become ordinary differential equations, the transient phase being not covered, ii) when diffusion is the major mechanism of transport and therefore, when convection is negligible, iii) when there is no between-root competition. The formulation of the analytical solutions is for cylindrical geometry but the solutions rely on the spread of the depletion profile around the root, which was modelled assuming a planar geometry. The analytical solutions were evaluated by comparison with the corresponding PDEs for cadmium in the case of the French agricultural soils. Provided that convection was much lower than diffusion (Péclet's number<0.02), the cumulative uptakes calculated from the analytic solutions were in very good agreement with those calculated from the PDEs, even in the case of a partially labile complex. The analytic solutions can be used instead of the PDEs to predict root uptake of metals. The analytic solutions were also used to build an indicator of the contribution of a complex to the uptake of the metal by roots, which can be helpful to predict the effect of soluble organic matter on the bioavailability of soil metals. Copyright © 2017 Elsevier B.V. All rights reserved.

Nonlinear Porous Diffusion Modeling of Hydrophilic Ionic Agrochemicals in Astomatous Plant Cuticle Aqueous Pores: A Mechanistic Approach.

PubMed

Tredenick, Eloise C; Farrell, Troy W; Forster, W Alison; Psaltis, Steven T P

2017-01-01

The agricultural industry requires improved efficacy of sprays being applied to crops and weeds in order to reduce their environmental impact and deliver improved financial returns. Enhanced foliar uptake is one means of improving efficacy. The plant leaf cuticle is known to be the main barrier to diffusion of agrochemicals within the leaf. The usefulness of a mathematical model to simulate uptake of agrochemicals in plant cuticles has been noted previously in the literature, as the results of each uptake experiment are specific to each formulation of active ingredient, plant species and environmental conditions. In this work we develop a mathematical model and numerical simulation for the uptake of hydrophilic ionic agrochemicals through aqueous pores in plant cuticles. We propose a novel, nonlinear, porous diffusion model for ionic agrochemicals in isolated cuticles, which extends simple diffusion through the incorporation of parameters capable of simulating: plant species variations, evaporation of surface droplet solutions, ion binding effects on the cuticle surface and swelling of the aqueous pores with water. We validate our theoretical results against appropriate experimental data, discuss the key sensitivities in the model and relate theoretical predictions to appropriate physical mechanisms. Major influencing factors have been found to be cuticle structure, including tortuosity and density of the aqueous pores, and to a lesser extent humidity and cuticle surface ion binding effects.

Nonlinear Porous Diffusion Modeling of Hydrophilic Ionic Agrochemicals in Astomatous Plant Cuticle Aqueous Pores: A Mechanistic Approach

PubMed Central

Tredenick, Eloise C.; Farrell, Troy W.; Forster, W. Alison; Psaltis, Steven T. P.

2017-01-01

The agricultural industry requires improved efficacy of sprays being applied to crops and weeds in order to reduce their environmental impact and deliver improved financial returns. Enhanced foliar uptake is one means of improving efficacy. The plant leaf cuticle is known to be the main barrier to diffusion of agrochemicals within the leaf. The usefulness of a mathematical model to simulate uptake of agrochemicals in plant cuticles has been noted previously in the literature, as the results of each uptake experiment are specific to each formulation of active ingredient, plant species and environmental conditions. In this work we develop a mathematical model and numerical simulation for the uptake of hydrophilic ionic agrochemicals through aqueous pores in plant cuticles. We propose a novel, nonlinear, porous diffusion model for ionic agrochemicals in isolated cuticles, which extends simple diffusion through the incorporation of parameters capable of simulating: plant species variations, evaporation of surface droplet solutions, ion binding effects on the cuticle surface and swelling of the aqueous pores with water. We validate our theoretical results against appropriate experimental data, discuss the key sensitivities in the model and relate theoretical predictions to appropriate physical mechanisms. Major influencing factors have been found to be cuticle structure, including tortuosity and density of the aqueous pores, and to a lesser extent humidity and cuticle surface ion binding effects. PMID:28539930

Surface chemistry of ferrihydrite: Part 2. Kinetics of arsenate adsorption and coprecipitation

USGS Publications Warehouse

Fuller, C.C.; Dadis, J.A.; Waychunas, G.A.

1993-01-01

The kinetics of As(V) adsorption by ferrihydrite was investigated in coprecipitation and postsynthesis adsorption experiments conducted in the pH range 7.5-9.0. In coprecipitation experiments, As(V) was present in solution during the hydrolysis and precipitation of iron. In adsorption experiments, a period of rapid (<5 min) As(V) uptake from solution was followed by continued uptake for at least eight days, as As(V) diffused to adsorption sites on ferrihydrite surfaces within aggregates of colloidal particles. The time dependence of As(V) adsorption is well described by a general model for diffusion into a sphere if a subset of surface sites located near the exterior of aggregates is assumed to attain adsorptive equilibrium rapidly. The kinetics of As(V) desorption after an increase in pH were also consistent with diffusion as a rate-limiting process. Aging of pure ferrihydrite prior to As(V) adsorption caused a decrease in adsorption sites on the precipitate owing to crystallite growth. In coprecipitation experiments, the initial As(V) uptake was significantly greater than in post-synthesis adsorption experiments, and the rate of uptake was not diffusion limited because As(V) was coordinated by surface sites before crystallite growth and coagulation processes could proceed. After the initial adsorption, As(V) was slowly released from coprecipitates for at least one month, as crystallite growth caused desorption of As(V). Adsorption densities as high as 0.7 mole As(V) per mole of Fe were measured in coprecipitates, in comparison to 0.25 mole As(V) per mole of Fe in post-synthesis adsorption experiments. Despite the high Concentration of As(V) in the precipitates, EXAFS spectroscopy (Waychunas et al., 1993) showed that neither ferric arsenate nor any other As-bearing surface precipitate or solid solution was formed. The high adsorption densities are possible because the ferrihydrite particles are extremely small, approaching the size of small dioctahedral chains at the highest As(V) adsorption density. The results suggest that the solid solution model proposed by Fox (1989, 1992) for control of arsenate and phosphate concentrations in natural waters may be invalid. ?? 1993.

Cerebral Proliferative Angiopathy (CPA): Imaging Findings and Response to Therapy.

PubMed

Lopci, Egesta; Olivari, Laura; Bello, Lorenzo; Navarria, Pierina; Chiti, Arturo

2016-12-01

We report the case of a 55-year-old woman with cerebral proliferative angiopathy (CPA). Her medical history included brain surgery for small vascular lesions and suspicion of cerebral malignancy. C methionine PET (C-METH PET) demonstrated a diffusely increased uptake on the right hemisphere. Contrast-enhanced MRI documented a massive lesion with a diffuse "nidus" appearance, involving the right cerebral hemisphere (sparing the inferior frontal gyrus and the anterior frontal lobe), the brainstem, and the middle cerebellar peduncle. Pathology confirmed the diagnosis of CPA and, after radiation treatment, the patient presented with clinical and radiological response.

Mathematical Description of the Uptake of Hydrocarbons in Jet Fuel into the Stratum Corneum of Human Volunteers

PubMed Central

Kim, David; Farthing, Matthew W.; Miller, Cass T.; Nylander-French, Leena A.

2008-01-01

The objective of this research was to develop a mathematical description of uptake of aromatic and aliphatic hydrocarbons into the stratum corneum of human skin in vivo. A simple description based on Fick’s Laws of diffusion was used to predict the spatiotemporal variation of naphthalene, 1- and 2-methylnaphthalene, undecane, and dodecane in the stratum corneum of human volunteers. The estimated values of the diffusion coefficients for each chemical were comparable to values predicted using in vitro skin systems and biomonitoring studies. These results demonstrate the value of measuring dermal exposure using the tape-strip technique and the importance of quantifying of dermal uptake. PMID:18423910

Water Uptake Behavior and Young Modulus Prediction of Composites Based on Treated Sisal Fibers and Poly(Lactic Acid)

PubMed Central

Orue, Ander; Eceiza, Arantxa; Peña-Rodriguez, Cristina; Arbelaiz, Aitor

2016-01-01

The main aim of this work was to study the effect of sisal fiber surface treatments on water uptake behavior of composites based on untreated and treated fibers. For this purpose, sisal fibers were treated with different chemical treatments. All surface treatments delayed the water absorption of fibers only for a short time of period. No significant differences were observed in water uptake profiles of composites based on fibers with different surface treatments. After water uptake period, tensile strength and Young modulus values of sisal fiber/poly(lactic acid) (PLA) composites were decreased. On the other hand, composites based on NaOH + silane treated fibers showed the lowest diffusion coefficient values, suggesting that this treatment seemed to be the most effective treatment to reduce water diffusion rate into the composites. Finally, Young modulus values of composites, before water uptake period, were predicted using different micromechanical models and were compared with experimental data. PMID:28773524

The effect of sedimentation and diffusion on cellular uptake of gold nanoparticles

PubMed Central

Cho, Eun Chul; Zhang, Qiang; Xia, Younan

2011-01-01

In vitro experiments typically measure the uptake of nanoparticles by exposing cells at the bottom of a culture plate to a suspension of nanoparticles, which is assumed to be well-dispersed. However, nanoparticles can sediment and this means the concentration of particles on the cell surface and those actually taken up by the cells may be higher than the initial bulk concentration. Here we use upright and inverted cell culture configurations to show that cellular uptake of gold nanoparticles depends on the sedimentation and diffusion velocities of the nanoparticles and is independent of size, shape, density, surface coating and initial concentration of the nanoparticles. Generally more nanoparticles are taken up in the upright configuration than the inverted one and nanoparticles that sediment faster showed greater differences in uptake between the two configurations. Our results suggest that cellular uptake of nanoparticles is sensitive to the way cells are positioned and sedimentation need to be considered when performing in vitro studies for large and heavy nanoparticles. PMID:21516092

Altered carnitine transport in pressure-overload hypertrophied rat hearts

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Rourke, B.; Foster, K.; Reibel, D.K.

1986-03-01

The authors have previously observed reduced carnitine levels in hypertrophied hearts of rats subjected to aortic constriction. In an attempt to determine the mechanism for reduced myocardial carnitine content, carnitine transport was examined in isolated perfused hearts. Hearts were excised from sham-operated and aortic-constricted rats 3 weeks following surgery and perfused at 60 mm Hg aortic pressure with buffer containing various concentrations of L-/sup 14/C-carnitine. Carnitine uptake by control and hypertrophied hearts was linear throughout 30 minutes of perfusion with 40 ..mu..M carnitine. Total carnitine uptake was significantly reduced by 25% in hypertrophied hearts at each time point examined. Themore » reduction in uptake by hypertrophied hearts was also evident when hearts were perfused with 100 or 200 ..mu..M carnitine. When 0.05 mM mersalyl acid was included in the buffer to inhibit the carrier-mediated component of transport, no difference in carnitine uptake was observed indicating that the transport of carnitine by diffusion was unaltered in the hypertrophied myocardium. Carrier-mediated carnitine uptake (total uptake - uptake by diffusion) was significantly reduced by approximately 40% in hypertrophied hearts at all concentrations examined. Thus, the reduction in carnitine content in the pressure-overload hypertrophied rat heart appears to be due to a reduction in carrier-mediated carnitine uptake by the heart.« less

99mTc Sestamibi Thyroid Scan in Amiodarone-Induced Thyrotoxicosis Type I.

PubMed

Patel, Niraj R; Tamara, Luis A; Lee, Ho

2016-07-01

Amiodarone-induced thyrotoxicosis (AIT) type I describes inducement of clinical hyperthyroidism by excessive thyroidal iodine in the setting of latent Graves disease, and therapy differs from that used for AIT type II. A 65-year-old man previously on amiodarone for atrial fibrillation developed clinical hyperthyroidism. Diagnosis of AIT was made, but the type was not clear. Tc sestamibi thyroid scan showed diffusely increased uptake and retention in an enlarged thyroid gland, a pattern consistent with AIT type I. Methimazole was initiated and controlled the thyrotoxicosis. I iodide thyroid scan and uptake study performed later was consistent with Graves disease.

Modelling the effect of intervillous flow on solute transfer based on 3D imaging of the human placental microstructure.

PubMed

Perazzolo, S; Lewis, R M; Sengers, B G

2017-12-01

A healthy pregnancy depends on placental transfer from mother to fetus. Placental transfer takes place at the micro scale across the placental villi. Solutes from the maternal blood are taken up by placental villi and enter the fetal capillaries. This study investigated the effect of maternal blood flow on solute uptake at the micro scale. A 3D image based modelling approach of the placental microstructures was undertaken. Solute transport in the intervillous space was modelled explicitly and solute uptake with respect to different maternal blood flow rates was estimated. Fetal capillary flow was not modelled and treated as a perfect sink. For a freely diffusing small solute, the flow of maternal blood through the intervillous space was found to be limiting the transfer. Ignoring the effects of maternal flow resulted in a 2.4 ± 0.4 fold over-prediction of transfer by simple diffusion, in absence of binding. Villous morphology affected the efficiency of solute transfer due to concentration depleted zones. Interestingly, less dense microvilli had lower surface area available for uptake which was compensated by increased flow due to their higher permeability. At super-physiological pressures, maternal flow was not limiting, however the efficiency of uptake decreased. This study suggests that the interplay between maternal flow and villous structure affects the efficiency of placental transfer but predicted that flow rate will be the major determinant of transfer. Copyright © 2017 Elsevier Ltd. All rights reserved.

When Future Change Matters: Modeling Future Price and Diffusion in Health Technology Assessments of Medical Devices.

PubMed

Grimm, Sabine E; Dixon, Simon; Stevens, John W

Health technology assessments (HTAs) that take account of future price changes have been examined in the literature, but the important issue of price reductions that are generated by the reimbursement decision has been ignored. To explore the impact of future price reductions caused by increasing uptake on HTAs and decision making for medical devices. We demonstrate the use of a two-stage modeling approach to derive estimates of technology price as a consequence of changes in technology uptake over future periods on the basis of existing theory and supported by empirical studies. We explore the impact on cost-effectiveness and expected value of information analysis in an illustrative example on the basis of a technology in development for preterm birth screening. The application of our approach to the case study technology generates smaller incremental cost-effectiveness ratios compared with the commonly used single cohort approach. The extent of this reduction in the incremental cost-effectiveness ratio depends on the magnitude of the modeled price reduction, the speed of diffusion, and the length of the assumed technology life horizon. Results of value of information analysis are affected through changes in the expected net benefit calculation, the addition of uncertain parameters, and the diffusion-adjusted estimate of the affected patient population. Because modeling future changes in price and uptake has the potential to affect HTA outcomes, modeling techniques that can address such changes should be considered for medical devices that may otherwise be rejected. Copyright © 2016 International Society for Pharmacoeconomics and Outcomes Research (ISPOR). Published by Elsevier Inc. All rights reserved.

Effects of solvent evaporation on water sorption/solubility and nanoleakage of adhesive systems

PubMed Central

CHIMELI, Talita Baumgratz Cachapuz; D'ALPINO, Paulo Henrique Perlatti; PEREIRA, Patrícia Nóbrega; HILGERT, Leandro Augusto; DI HIPÓLITO, Vinicius; GARCIA, Fernanda Cristina Pimentel

2014-01-01

Objective To evaluate the influence of solvent evaporation in the kinetics of water diffusion (water sorption-WS, solubility-SL, and net water uptake) and nanoleakage of adhesive systems. Material and Methods Disk-shaped specimens (5.0 mm in diameter x 0.8 mm in thickness) were produced (N=48) using the adhesives: Clearfil S3 Bond (CS3)/Kuraray, Clearfil SE Bond - control group (CSE)/Kuraray, Optibond Solo Plus (OS)/Kerr and Scotchbond Universal Adhesive (SBU)/3M ESPE. The solvents were either evaporated for 30 s or not evaporated (N=24/per group), and then photoactivated for 80 s (550 mW/cm2). After desiccation, the specimens were weighed and stored in distilled water (N=12) or mineral oil (N=12) to evaluate the water diffusion over a 7-day period. Net water uptake (%) was also calculated as the sum of WS and SL. Data were submitted to 3-way ANOVA/Tukey's test (α=5%). The nanoleakage expression in three additional specimens per group was also evaluated after ammoniacal silver impregnation after 7 days of water storage under SEM. Results Statistical analysis revealed that only the factor "adhesive" was significant (p<0.05). Solvent evaporation had no influence in the WS and SL of the adhesives. CSE (control) presented significantly lower net uptake (5.4%). The nanoleakage was enhanced by the presence of solvent in the adhesives. Conclusions Although the evaporation has no effect in the kinetics of water diffusion, the nanoleakage expression of the adhesives tested increases when the solvents are not evaporated. PMID:25141201

Organic N cycling in Arctic ecosystems: Quantifying root uptake kinetics and temporal variability of soil amino acids.

NASA Astrophysics Data System (ADS)

Homyak, P. M.; Iverson, S. L.; Slessarev, E.; Marchus, K.; Schimel, J.

2017-12-01

Arctic ecosystems are undergoing shifts in plant community composition with increased warming. How these changes may alter ecosystem function is not well constrained, owing in part to uncertainties on how plant-soil feedbacks influence nutrient cycling. For nitrogen (N), in particular, understanding how these feedbacks may alter cycling rates is challenging because i) Arctic plants take up organic N (i.e., amino acids; AA) when inorganic N is limiting, yet ii) it has never been quantified, for any plant species growing in the wild, how much of its N demand is actually met by taking up AA. To advance fundamental understanding of plant-soil feedbacks as the Arctic warms, we are integrating field measurements of AA availability in N-limited tussock tundra (E. vaginatum) and a comparably less N-limited birch shrub tundra (Betula nana and Salix spp.) with a root uptake model. We used soil microdialysis to determine available AA concentrations in the soil solution and potential rates of AA diffusion and mass flow to roots at the Toolik Field Station in Alaska. These measurements are being combined with AA root uptake kinetic experiments using E. vaginatum to establish actual AA root uptake rates. We found that in the early growing season (June), total AA concentrations in the soil solution averaged 104 µg N L-1 and were similar to NH4+ across sites. In the late growing season (August), AA were the dominant form of N averaging 75 µg N L-1 while NH4+ decreased to 13 µg N L-1. In the early growing season AA diffusion rates in the soil averaged 200 ng N cm-2 s-1 and declined to 150 ng N cm-2 s-1 in the late growing season. Lysine, serine, and arginine were the most abundant AA and differences in the N status of sites did not affect total AA concentrations. Amino acids made up at least half of the N diffusing through the soil solution, suggesting they can subsidize the N demand of arctic plants. Ongoing field experiments at Toolik will be used to constrain actual AA root uptake rates.

Comparison of measurement methods for benzene and toluene

NASA Astrophysics Data System (ADS)

Wideqvist, U.; Vesely, V.; Johansson, C.; Potter, A.; Brorström-Lundén, E.; Sjöberg, K.; Jonsson, T.

Diffusive sampling and active (pumped) sampling (tubes filled with Tenax TA or Carbopack B) were compared with an automatic BTX instrument (Chrompack, GC/FID) for measurements of benzene and toluene. The measurements were made during differing pollution levels and different weather conditions at a roof-top site and in a densely trafficked street canyon in Stockholm, Sweden. The BTX instrument was used as the reference method for comparison with the other methods. Considering all data the Perkin-Elmer diffusive samplers, containing Tenax TA and assuming a constant uptake rate of 0.406 cm3 min-1, showed about 30% higher benzene values compared to the BTX instrument. This discrepancy may be explained by a dose-dependent uptake rate with higher uptake rates at lower dose as suggested by laboratory experiments presented in the literature. After correction by applying the relationship between uptake rate and dose as suggested by Roche et al. (Atmos. Environ. 33 (1999) 1905), the two methods agreed almost perfectly. For toluene there was much better agreement between the two methods. No sign of a dose-dependent uptake could be seen. The mean concentrations and 95% confidence intervals of all toluene measurements (67 values) were (10.80±1.6) μg m -3 for diffusive sampling and (11.3±1.6) μg m -3 for the BTX instrument, respectively. The overall ratio between the concentrations obtained using diffusive sampling and the BTX instrument was 0.91±0.07 (95% confidence interval). Tenax TA was found to be equal to Carbopack B for measuring benzene and toluene in this concentration range, although it has been proposed not to be optimal for benzene. There was also good agreement between the active samplers and the BTX instrument.

Use of Inert Gases to Study the Interaction of Blood Flow and Diffusion during Passive Absorption from the Gastrointestinal Tract of the Rat

PubMed Central

Levitt, Michael D.; Levitt, David G.

1973-01-01

Measurement of the relative absorption rates of inert gases (H2, He, CH4, SF6, and 133Xe) was used to investigate the interaction between diffusion and blood flow during passive absorption from the stomach, small bowel, and colon of the rat. If uptake is blood flow limited, the gases should be absorbed in proportion to their solubilities in blood, but if diffusion limited, uptake should be proportional to the diffusion rate of the gases in mucosal tissues. The observed absorption data were fitted to a series of models of interaction between perfusion and diffusion. A simple model accurately predicted the absorption rates of the gases from all segments of bowel. In this model, gas is absorbed into two distinct blood flows: one which flows in proximity to the lumen and completely equilibrates with the lumen, and a second which is sufficiently rapid and distant from the lumen that its gas uptake is entirely diffusion limited. The fraction of the total absorption attributable to the equilibrating flow can be readily calculated and equalled 93%, 77%, and 33% for the small bowel, colon, and stomach, respectively. Thus the rate of passive absorption of gases from the small bowel is limited almost entirely by the blood flow to the mucosa, and absorption from the stomach is largely limited by the diffusion rate of the gases. The flow which equilibrates with the lumen can be quantitated, and this flow may provide a useful measure of “effective” mucosal blood flow. Images PMID:4719667

Diffusion and cellular uptake of drugs in live cells studied with surface-enhanced Raman scattering probes

NASA Astrophysics Data System (ADS)

Bálint, Štefan; Rao, Satish; Sánchez, Mónica Marro; Huntošová, Veronika; Miškovský, Pavol; Petrov, Dmitri

2010-03-01

An understanding of the mechanisms of drug diffusion and uptake through cellular membranes is critical for elucidating drug action and in the development of effective drug delivery systems. We study these processes for emodin, a potential anticancer drug, in live cancer cells using surface-enhanced Raman scattering. Micrometer-sized silica beads covered by nanosized silver colloids are passively embedded into the cell and used as sensors of the drug. We demonstrate that the technique offers distinct advantages: the possibility to study the kinetics of drug diffusion through the cellular membrane toward specific cell organelles, the detection of lower drug concentrations compared to fluorescence techniques, and less damage imparted on the cell.

POLUTE; forest air pollutant uptake model. [IBM360,370; CSMP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murphy, C.E.

POLUTE is a computer model designed to estimate the uptake of air pollutants by forests. The model utilizes submodels to describe atmospheric diffusion immediately above and within the canopy, and into the sink areas within or on the trees. The program implementing the model is general and can be used, with only minor changes, for any gaseous pollutant. The model provides an estimate describing the response of the vegetarian-atmosphere system to the environment as related to three types of processes: atmospheric diffusion, diffusion near and inside the absorbing plant, and the physical and chemical processes at the sink on ormore » within the plant.IBM360,370; CSMP; OS/370.« less

Diffuse thyroid uptake incidentally found on 18F-fluorodeoxyglucose positron emission tomography in subjects without cancer history.

PubMed

Lee, Ji Young; Choi, Joon Young; Choi, Yoon-Ho; Hyun, Seung Hyup; Moon, Seung Hwan; Jang, Su Jin; Choe, Yearn Seong; Lee, Kyung-Han; Kim, Byung-Tae

2013-01-01

We investigated the clinical significance of incidental diffuse thyroid uptake (DTU) on (18)F-FDG PET in subjects without a history of cancer. This study included 2062 studies from adults who underwent (18)F-FDG PET as a cancer screening program. Subjects were divided into the following two groups: with (group I) or without (group II) DTU. The presence of DTU and the thyroid visual grading score were compared with thyroid function tests, serum anti-microsomal antibody (AMA) levels, and the presence of diffuse parenchymal change (DPC) on ultrasonography (USG). DTU was found in 6.6% of the scans (137/2062). Serum thyroid stimulating hormone (TSH) and AMA levels were significantly higher in group I than in group II. Increased AMA level (55.1%) and DPC (48.7%) were more frequently found in group I (p < 0.001). The proportion of subjects with any abnormal results in serum free thyroxine, triiodothyronine, TSH, or AMA levels or DPC on USG was significantly higher in group I than in group II (71.5% vs. 10.6%, p < 0.001), and was significantly and gradually increased according to the visual grading score group (0 vs. 1-2 vs. 3-4 = 10.6% vs. 58.5% vs. 90.9%, p < 0.001). TSH and is AMA levels were significantly increased according to the visual grading score. The presence or degree of incidental DTU on (18)F-FDG PET is closely correlated with increased serum AMA and TSH levels, and the presence of DPC on USG. Therefore, the most plausible pathological cause of DTU may be cell damage by an autoimmune mechanism.

Bicarbonate uptake by Southern Ocean phytoplankton

NASA Astrophysics Data System (ADS)

Cassar, Nicolas; Laws, Edward A.; Bidigare, Robert R.; Popp, Brian N.

2004-06-01

Marine phytoplankton have the potential to significantly buffer future increases in atmospheric carbon dioxide levels. However, in order for CO2 fertilization to have an effect on carbon sequestration to the deep ocean, the increase in dissolved CO2 must stimulate primary productivity; that is, marine phototrophs must be CO2 limited [, 1993]. Estimation of the extent of bicarbonate (HCO3-) uptake in the oceans is therefore required to determine whether the anthropogenic carbon sources will enhance carbon flux to the deep ocean. Using short-term 14CO2-disequilibrium experiments during the Southern Ocean Iron Experiment (SOFeX), we show that HCO3- uptake by Southern Ocean phytoplankton is significant. Since the majority of dissolved inorganic carbon (DIC) in the ocean is in the form of bicarbonate, the biological pump may therefore be insensitive to anthropogenic CO2. Approximately half of the DIC uptake observed was attributable to direct HCO3- uptake, the other half being direct CO2 uptake mediated either by passive diffusion or active uptake mechanisms. The increase in growth rates and decrease in CO2 concentration associated with the iron fertilization did not trigger any noticeable changes in the mode of DIC acquisition, indicating that under most environmental conditions the carbon concentrating mechanism (CCM) is constitutive. A low-CO2 treatment induced an increase in uptake of CO2, which we attributed to increased extracellular carbonic anhydrase activity, at the expense of direct HCO3- transport across the plasmalemma. Isotopic disequilibrium experimental results are consistent with Southern Ocean carbon stable isotope fractionation data from this and other studies. Although iron fertilization has been shown to significantly enhance phytoplankton growth and may potentially increase carbon flux to the deep ocean, an important source of the inorganic carbon taken up by phytoplankton in this study was HCO3-, whose concentration is negligibly affected by the anthropogenic rise in CO2. We conclude that biological productivity in this region of the world's ocean is unlikely to be directly regulated by natural or anthropogenic variations in atmospheric CO2 concentrations because of the presence of a constitutive CCM.

Simultaneous uptake of NOM and Microcystin-LR by anion exchange resins: Effect of inorganic ions and resin regeneration.

PubMed

Dixit, Fuhar; Barbeau, Benoit; Mohseni, Madjid

2018-02-01

This study investigated the efficiency of a strongly basic macroporous anion exchange resin for the co-removal of Microcystin-LR (MCLR) and natural organic matter (NOM) in waters affected by toxic algal blooms. Environmental factors influencing the uptake behavior included MCLR and resin concentrations, NOM and anionic species, specifically nitrate, sulphate and bicarbonate. A860 resin exhibited an excellent adsorption capacity of 3800 μg/g; more than 60% of the MCLR removal was achieved within 10 min with a resin dosage of 200 mg/L (∼1 mL/L). Further, kinetic studies revealed that the overall removal of MCLR is influenced by both external diffusion and intra-particle diffusion. Increasing NOM concentration resulted in a significant reduction of MCLR uptake, especially at lower resin dosages, where a competitive uptake between the charged NOM fractions and MCLR was observed due to limited active sites. In addition, MCLR uptake was significantly reduced in the presence of sulphate and nitrate in the water matrix. Moreover, performance of the resin proved to be stable from one regeneration cycle to another. Approximately 80% of MCLR and 50% of dissolved organic carbon (DOC) were recovered in the regenerated brine. Evidences of resin saturation and site reduction were also observed after 2000 bed volumes (BV) of operation. For all the investigated water matrices, a resin dosage of 1000 mg/L (∼4.5 mL/L) was sufficient to lower MCLR concentration from 100 μg/L to below the World Health Organization guideline of 1 μg/L, while simultaneously providing more than 80% NOM removal. Copyright © 2017 Elsevier Ltd. All rights reserved.

Increased technetium uptake is not equivalent to muscle necrosis: scintigraphic, morphological and intramuscular pressure analyses of sore muscles after exercise

NASA Technical Reports Server (NTRS)

Crenshaw, A. G.; Friden, J.; Hargens, A. R.; Lang, G. H.; Thornell, L. E.

1993-01-01

A scintigraphic technique employing technetium pyrophosphate uptake was used to identify the area of skeletal muscle damage in the lower leg of four runners 24 h after an ultramarathon footrace (160 km). Most of the race had been run downhill which incorporated an extensive amount of eccentric work. Soreness was diffuse throughout the posterior region of the lower leg. In order to interpret what increased technetium uptake reflects and to express extreme endurance related damages, a biopsy was taken from the 3-D position of abnormal uptake. In addition, intramuscular pressures were determined in the deep posterior compartment. Scintigraphs revealed increased technetium pyrophosphate uptake in the medial portion of the gastrocnemius muscle. For 3698 fibres analysed, 33 fibres (1%) were necrotic, while a few other fibres were either atrophic or irregular shaped. A cluster of necrotic fibres occurred at the fascicular periphery for one subject and fibre type grouping occurred for another. Ultrastructural analysis revealed Z-line streaming near many capillaries and variously altered subsarcolemmal mitochondria including some with paracrystalline inclusions. The majority of the capillaries included thickened and irregular shaped endothelial cells. Intramuscular pressures of the deep posterior compartment were slightly elevated (12-15 mmHg) for three of the four subjects. Increased technetium uptake following extreme endurance running does not just reflect muscle necrosis but also subtle fibre abnormalities. Collectively, these pathological findings are attributed to relative ischaemia occurring during the race and during pre-race training, whereas, intramuscular pressure elevations associated with muscle soreness are attributed to mechanical stress caused by extensive eccentric work during the race.

Modeling and Uncertainty Quantification of Vapor Sorption and Diffusion in Heterogeneous Polymers

DOE PAGES

Sun, Yunwei; Harley, Stephen J.; Glascoe, Elizabeth A.

2015-08-13

A high-fidelity model of kinetic and equilibrium sorption and diffusion is developed and exercised. The gas-diffusion model is coupled with a triple-sorption mechanism: Henry’s law absorption, Langmuir adsorption, and pooling or clustering of molecules at higher partial pressures. Sorption experiments are conducted and span a range of relative humidities (0-95%) and temperatures (30-60°C). Kinetic and equilibrium sorption properties and effective diffusivity are determined by minimizing the absolute difference between measured and modeled uptakes. Uncertainty quantification and sensitivity analysis methods are described and exercised herein to demonstrate the capability of this modeling approach. Water uptake in silica-filled and unfilled poly(dimethylsiloxane) networksmore » is investigated; however, the model is versatile enough to be used with a wide range of materials and vapors.« less

Convective and Diffusive O2 Transport Components of Peak Oxygen Uptake Following Long-duration Spaceflight

NASA Technical Reports Server (NTRS)

Ade, Carl J.; Moore, A. D.

2014-01-01

Spaceflight reduces aerobic capacity and may be linked with maladaptations in the O2 transport pathway. The aim was to 1) evaluate the cardiorespiratory adaptations following 6 months aboard the International Space Station and 2) model the contributions of convective (Q (raised dot) O2) and peripheral diffusive (DO2) components of O2 transport to changes in peak O2 uptake (V (raised dot) O2PEAK). To date, 1 male astronaut (XX yrs) completed an incremental exercise test to measure V (raised dot) O2PEAK prior to and 2 days post-flight. Cardiac output (Q (raised dot) ) was measured at three submaximal work rates via carbon dioxide rebreathing. The Q (raised dot) :V (raised dot) O2 relationship was extrapolated to V (raised dot) O2PEAK to determine Q (raised dot) PEAK. Hemoglobin concentration was measured at rest via a venous blood sample. These measurements were used to model the changes in Q (raised dot) O2 and DO2 using Fick's principle of mass conservation and Law of Diffusion as established by Wagner and colleagues (Annu. Rev. Physiol 58: 21-50, 1996 and J. Appl. Physiol. 73: 1067-1076, 1992). V (raised dot) O2PEAK decreased postflight from 3.72 to 3.45 l min-1, but Q (raised dot) PEAK increased from 24.5 to 27.7 l min-1. The decrease in V (raised dot) O2PEAK post-flight was associated with a 21.2% decrease in DO2, an 18.6% decrease in O2 extraction, but a 3.4% increase in Q (raised dot) O2. These preliminary data suggest that long-duration spaceflight reduces peripheral diffusing capacity and that it largely contributes to the post-flight decrease in aerobic capacity.

Hydroxyl/bile acid exchange. A new mechanism for the uphill transport of cholate by basolateral liver plasma membrane vesicles.

PubMed

Blitzer, B L; Terzakis, C; Scott, K A

1986-09-15

In order to characterize the driving forces for the concentrative uptake of unconjugated bile acids by the hepatocyte, the effects of pH gradients on the uptake of [3H]cholate by rat basolateral liver plasma membrane vesicles were studied. In the presence of an outwardly directed hydroxyl gradient (pH 6.0 outside and pH 7.5 inside the vesicle), cholate uptake was markedly stimulated and the bile acid was transiently accumulated at a concentration 1.5- to 2-fold higher than at equilibrium ("overshoot"). In the absence of a pH gradient (pH 6.0 or 7.5 both inside and outside the vesicle), uptake was relatively slower and no overshoot was seen. Reductions in the magnitude of the transmembrane pH gradient were associated with slower initial uptake rates and smaller overshoots. Cholate uptake under pH gradient conditions was inhibited by furosemide and bumetanide but not by 4, 4'-diisothiocyano-2,2'-disulfonic stilbene (SITS), 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (DIDS), or probenecid. In the absence of a pH gradient, an inside-positive valinomycin-induced K+ diffusion potential caused a slight increase in cholate uptake which was insensitive to furosemide. Moreover, in the presence of an outwardly directed hydroxyl gradient, uphill cholate transport was observed even under voltage clamped conditions. These findings suggest that pH gradient-driven cholate uptake was not due to associated electrical potentials. Despite an identical pKa to that of cholate, an outwardly directed hydroxyl gradient did not drive uphill transport of three other unconjugated bile acids (deoxycholate, chenodeoxycholate, ursodeoxycholate), suggesting that a non-ionic diffusion mechanism cannot account for uphill cholate transport. In canalicular vesicles, although cholate uptake was relatively faster in the presence of a pH gradient than in the absence of a gradient, peak uptake was only slightly above that found at equilibrium under voltage clamped conditions. These findings suggest a specific carrier on the basolateral membrane of the hepatocyte which mediates hydroxyl/cholate exchange (or H+-cholate co-transport). A model for uphill cholate transport is discussed in which the Na+ pump would ultimately drive Na+/H+ exchange which in turn would drive hydroxyl/cholate exchange.

Hybrid atomistic simulation of fluid uptake in a deformable solid

NASA Astrophysics Data System (ADS)

Moghadam, Mahyar M.; Rickman, J. M.

2014-01-01

Fluid imbibition via diffusion in a deformable solid results in solid stresses that may, in turn, alter subsequent fluid uptake. To examine this interplay between diffusional and elastic fields, we employed a hybrid Monte Carlo-molecular dynamics scheme to model the coupling of a fluid reservoir to a deformable solid, and then simulated the resulting fluid permeation into the solid. By monitoring the instantaneous structure factor and solid dimensions, we were able to determine the compositional strain associated with imbibition, and the diffusion coefficient in the Fickian regime was obtained from the time dependence of the fluid uptake. Finally, for large, mobile fluid atoms, a non-Fickian regime was highlighted and possible mechanisms for this behavior were identified.

Solvent and solute ingress into hydrogels resolved by a combination of imaging techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagner, D.; Burbach, J.; Egelhaaf, S. U.

2016-05-28

Using simultaneous neutron, fluorescence, and optical brightfield transmission imaging, the diffusion of solvent, fluorescent dyes, and macromolecules into a crosslinked polyacrylamide hydrogel was investigated. This novel combination of different imaging techniques enables us to distinguish the movements of the solvent and fluorescent molecules. Additionally, the swelling or deswelling of the hydrogels can be monitored. From the sequence of images, dye and solvent concentrations were extracted spatially and temporally resolved. Diffusion equations and different boundary conditions, represented by different models, were used to quantitatively analyze the temporal evolution of these concentration profiles and to determine the diffusion coefficients of solvent andmore » solutes. Solute size and network properties were varied and their effect was investigated. Increasing the crosslinking ratio or partially drying the hydrogel was found to hinder solute diffusion due to the reduced pore size. By contrast, solvent diffusion seemed to be slightly faster if the hydrogel was only partially swollen and hence solvent uptake enhanced.« less

Calcium-ion transport by intact Ehrlich ascites-tumour cells. Role of respiratory substrates, Pi and temperature.

PubMed

Charlton, R R; Wenner, C E

1978-03-15

1. The interaction of intact Ehrlich ascites-tumour cells with Ca2+ at 37 degrees C consists of Ca2+ uptake followed by efflux from the cells. Under optimum conditions, two or three cycles of uptake and efflux are observed in the first 15 min after Ca2+ addition. 2. The respiratory substrates malate, succinate and ascorbate plus p-phenylenediamine support Ca2+ uptake. Ca2+ uptake at 37 degrees C is sensitive to the respiratory inhibitors rotenone and antimycin A when appropriate substrates are present. Ca2+ uptake and retention are inhibited by the uncoupler S-13. 3. Increasing extracellular Pi (12 to 30 mM) stimulates uncoupler-sensitive Ca2+ uptake, which reaches a maximum extent of 15 nmol/mg of protein when supported by succinate respiration. Ca2+ efflux is partially inhibited at 30 mM-Pi. 4. Optimum Ca2+ uptake occurs in the presence of succinate and Pi, suggesting that availability of substrate and Pi are rate-limiting. K. Ca2+ uptake occurs at 4 degrees C and is sensitive to uncouplers and oligomycin. Ca2+ efflux at this temperature is minimal. These data are consistent with a model in which passive diffusion of Ca2+ through the plasma membrane is followed by active uptake by the mitochondria. Ca2+ uptake is supported by substrates entering respiration at all three energy-coupling sites. Ca2+ efflux appears to be an active process with a high temperature coefficient.

Small global effect on terrestrial net primary production due to increased fossil fuel aerosol emissions from East Asia since the turn of the century.

PubMed

O'Sullivan, M; Rap, A; Reddington, C L; Spracklen, D V; Gloor, M; Buermann, W

2016-08-16

The global terrestrial carbon sink has increased since the start of this century at a time of growing carbon emissions from fossil fuel burning. Here we test the hypothesis that increases in atmospheric aerosols from fossil fuel burning enhanced the diffuse light fraction and the efficiency of plant carbon uptake. Using a combination of models, we estimate that at global scale changes in light regimes from fossil fuel aerosol emissions had only a small negative effect on the increase in terrestrial net primary production over the period 1998-2010. Hereby, the substantial increases in fossil fuel aerosol emissions and plant carbon uptake over East Asia were effectively canceled by opposing trends across Europe and North America. This suggests that if the recent increase in the land carbon sink would be causally linked to fossil fuel emissions, it is unlikely via the effect of aerosols but due to other factors such as nitrogen deposition or nitrogen-carbon interactions.

Accelerated Analyte Uptake on Single Beads in Microliter-scale Batch Separations using Acoustic Streaming: Plutonium Uptake by Anion Exchange for Analysis by Mass Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paxton, Walter F.; O'Hara, Matthew J.; Peper, Shane M.

2008-06-01

The use of acoustic streaming as a non-contact mixing platform to accelerate mass transport-limited diffusion processes in small volume heterogeneous reactions has been investigated. Single bead anion exchange of plutonium at nanomolar and sub-picomolar concentrations in 20 microliter liquid volumes was used to demonstrate the effect of acoustic mixing. Pu uptake rates on individual ~760 micrometer diameter AG 1x4 anion exchange resin beads were determined using acoustic mixing and compared with Pu uptake rates achieved by static diffusion alone. An 82 MHz surface acoustic wave (SAW) device was placed in contact with the underside of a 384-well microplate containing flat-bottomedmore » semiconical wells. Acoustic energy was coupled into the solution in the well, inducing acoustic streaming. Pu uptake rates were determined by the plutonium remaining in solution after specific elapsed time intervals, using liquid scintillation counting (LSC) for nanomolar concentrations and thermal ionization mass spectrometry (TIMS) analysis for the sub-picomolar concentration experiments. It was found that this small batch uptake reaction could be accelerated by a factor of about five-fold or more, depending on the acoustic power applied.« less

Diffusional limits to the consumption of atmospheric methane by soils

USGS Publications Warehouse

Striegl, Robert G.

1993-01-01

Net transport of atmospheric gases into and out of soil systems is primarily controlled by diffusion along gas partial pressure gradients. Gas fluxes between soil and the atmosphere can therefore be estimated by a generalization of the equation for ordinary gaseous diffusion in porous unsaturated media. Consumption of CH4 by methylotrophic bacteria in the top several centimeters of soil causes the uptake of atmospheric CH4 by aerated soils. The capacity of the methylotrophs to consume CH4 commonly exceeds the potential of CH4 to diffuse from the atmosphere to the consumers. The maximum rate of uptake of atmospheric CH4 by soil is, therefore, limited by diffusion and can be calculated from soil physical properties and the CH4 concentration gradient. The CH4 concentration versus depth profile is theoretically described by the equation for gaseous diffusion with homogeneous chemical reaction in porous unsaturated media. This allows for calculation of the in situ rate of CH4 consumption within specified depth intervals.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willemin, Marie-Emilie; Lumen, Annie, E-mail: Anni

Thyroid homeostasis can be disturbed due to thiocyanate exposure from the diet or tobacco smoke. Thiocyanate inhibits both thyroidal uptake of iodide, via the sodium-iodide symporter (NIS), and thyroid hormone (TH) synthesis in the thyroid, via thyroid peroxidase (TPO), but the mode of action of thiocyanate is poorly quantified in the literature. The characterization of the link between intra-thyroidal thiocyanate concentrations and dose of exposure is crucial for assessing the risk of thyroid perturbations due to thiocyanate exposure. We developed a PBPK model for thiocyanate that describes its kinetics in the whole-body up to daily doses of 0.15 mmol/kg, withmore » a mechanistic description of the thyroidal kinetics including NIS, passive diffusion, and TPO. The model was calibrated in a Bayesian framework using published studies in rats. Goodness-of-fit was satisfactory, especially for intra-thyroidal thiocyanate concentrations. Thiocyanate kinetic processes were quantified in vivo, including the metabolic clearance by TPO. The passive diffusion rate was found to be greater than NIS-mediated uptake rate. The model captured the dose-dependent kinetics of thiocyanate after acute and chronic exposures. Model behavior was evaluated using a Morris screening test. The distribution of thiocyanate into the thyroid was found to be determined primarily by the partition coefficient, followed by NIS and passive diffusion; the impact of the latter two mechanisms appears to increase at very low doses. Extrapolation to humans resulted in good predictions of thiocyanate kinetics during chronic exposure. The developed PBPK model can be used in risk assessment to quantify dose-response effects of thiocyanate on TH. - Highlights: • A PBPK model of thiocyanate (SCN{sup −}) was calibrated in rats in a Bayesian framework. • The intra-thyroidal kinetics of thiocyanate including NIS and TPO was modeled. • Passive diffusion rate for SCN{sup −} seemed to be greater than the NIS-mediated uptake. • The dose-dependent kinetics of SCN{sup −} was captured after an acute and chronic exposure. • The PBPK model of thiocyanate was successfully extrapolated to humans.« less

Uptake of aromatic hydrocarbon vapors (benzene and phenanthrene) at the air-water interface of micron-size water droplets.

PubMed

Raja, Suresh; Valsaraj, Kalliat T

2004-12-01

Uptake of aromatic hydrocarbon vapors (benzene and phenanthrene) by typical micrometer-sized fog-water droplets was studied using a falling droplet reactor at temperatures between 296 and 316 K. Uptake of phenanthrene vapor greater than that predicted by bulk (air-water)-phase equilibrium was observed for diameters less than 200 microm, and this was attributed to surface adsorption. The experimental values of the droplet-vapor partition constant were used to obtain the overall mass transfer coefficient and the mass accommodation coefficient for both benzene and phenanthrene. Mass transfer of phenanthrene was dependent only on gas-phase diffusion and mass accommodation at the interface. However, for benzene, the mass transfer was limited by liquid-phase diffusion and mass accommodation. A large value of the mass accommodation coefficient, alpha = (1.4 +/- 0.4) x 10(-2) was observed for the highly surface-active (hydrophobic) phenanthrene, whereas a small alpha = (9.7 +/- 1.8) x 10(-5) was observed for the less hydrophobic benzene. Critical cluster numbers ranging from 2 for benzene to 5.7 for phenanthrene were deduced using the critical cluster nucleation theory for mass accommodation. The enthalpy of mass accommodation was more negative for phenanthrene than it was for benzene. Consequently, the temperature effect was more pronounced for phenanthrene. A linear correlation was observed for the enthalpy of accommodation with the excess enthalpy of solution. A natural organic carbon surrogate (Suwannee Fulvic acid) in the water droplet increased the uptake for phenanthrene and benzene, the effect being more marked for phenanthrene. A characteristic time constant analysis showed that uptake and droplet scavenging would compete for the fog deposition of phenanthrene, whereas deposition would be unimpeded by the uptake rate for benzene vapor. For both compounds, the characteristic atmospheric reaction times were much larger and would not impact fog deposition.

Kinetics of Uptake and Washout of Lidocaine in Rat Sciatic Nerve In Vitro

PubMed Central

Leeson, Stanley; Strichartz, Gary

2012-01-01

Background The potency and efficacy of local anesthetics injected clinically for peripheral nerve block depends strongly on the rate of neural drug uptake. However, since diffusion into surrounding tissues and removal by the vascular system are major factors in the overall distribution of lidocaine in vivo, true kinetics of drug/neural tissue interactions must be studied in the absence of those confounding factors. Methods Uptake: Ensheathed or desheathed isolated rat sciatic nerves were exposed to [14C]-lidocaine for 0-180min and then removed and the lidocaine content of nerve and sheath analyzed. Washout: Isolated nerves were soaked in [14C]-lidocaine for 60min and then placed in lidocaine-free solution for 0-30min, with samples removed at different times to assess the drug content. Experimental variables included the effects of the ensheathing epineurium, lidocaine concentration, pH, presence of CO2-bicarbonate, and incubation duration. Results The equilibrium uptake of lidocaine increased with incubation time, concentration and the fraction of molecules in the non-ionized form. The uptake rate was unaffected by drug concentration, but was about halved by the presence of the epineurial sheath, with the washout rate slowed less. Slight alkalinization, from pH 6.8 to pH 7.4, by bicarbonate-CO2 buffer or a non-bicarbonate buffer, enhanced the neural uptake, and to the same degree. The washout of lidocaine was faster after shorter incubations at high concentrations than when equal amounts of lidocaine were taken up after long incubations at low lidocaine concentrations. Conclusion Lidocaine enters a nerve by a process other than free diffusion, through an epineurial sheath that is a slight obstacle. Given the rapid entry in vitro compared to the much smaller and transient content measured in vivo, it seems highly unlikely that lidocaine equilibrates with the nerve during a peripheral blockade. PMID:23400993

Ozone and haze pollution weakens net primary productivity in China

NASA Astrophysics Data System (ADS)

Yue, Xu; Unger, Nadine; Harper, Kandice; Xia, Xiangao; Liao, Hong; Zhu, Tong; Xiao, Jingfeng; Feng, Zhaozhong; Li, Jing

2017-05-01

Atmospheric pollutants have both beneficial and detrimental effects on carbon uptake by land ecosystems. Surface ozone (O3) damages leaf photosynthesis by oxidizing plant cells, while aerosols promote carbon uptake by increasing diffuse radiation and exert additional influences through concomitant perturbations to meteorology and hydrology. China is currently the world's largest emitter of both carbon dioxide and short-lived air pollutants. The land ecosystems of China are estimated to provide a carbon sink, but it remains unclear whether air pollution acts to inhibit or promote carbon uptake. Here, we employ Earth system modeling and multiple measurement datasets to assess the separate and combined effects of anthropogenic O3 and aerosol pollution on net primary productivity (NPP) in China. In the present day, O3 reduces annual NPP by 0.6 Pg C (14 %) with a range from 0.4 Pg C (low O3 sensitivity) to 0.8 Pg C (high O3 sensitivity). In contrast, aerosol direct effects increase NPP by 0.2 Pg C (5 %) through the combination of diffuse radiation fertilization, reduced canopy temperatures, and reduced evaporation leading to higher soil moisture. Consequently, the net effects of O3 and aerosols decrease NPP by 0.4 Pg C (9 %) with a range from 0.2 Pg C (low O3 sensitivity) to 0.6 Pg C (high O3 sensitivity). However, precipitation inhibition from combined aerosol direct and indirect effects reduces annual NPP by 0.2 Pg C (4 %), leading to a net air pollution suppression of 0.8 Pg C (16 %) with a range from 0.6 Pg C (low O3 sensitivity) to 1.0 Pg C (high O3 sensitivity). Our results reveal strong dampening effects of air pollution on the land carbon uptake in China today. Following the current legislation emission scenario, this suppression will be further increased by the year 2030, mainly due to a continuing increase in surface O3. However, the maximum technically feasible reduction scenario could drastically relieve the current level of NPP damage by 70 % in 2030, offering protection of this critical ecosystem service and the mitigation of long-term global warming.

Mass Conservation in Modeling Moisture Diffusion in Multi-Layer Carbon Composite Structures

NASA Technical Reports Server (NTRS)

Nurge, Mark A.; Youngquist, Robert C.; Starr, Stanley O.

2009-01-01

Moisture diffusion in multi-layer carbon composite structures is difficult to model using finite difference methods due to the discontinuity in concentrations between adjacent layers of differing materials. Applying a mass conserving approach at these boundaries proved to be effective at accurately predicting moisture uptake for a sample exposed to a fixed temperature and relative humidity. Details of the model developed are presented and compared with actual moisture uptake data gathered over 130 days from a graphite epoxy composite sandwich coupon with a Rohacell foam core.

Guava (Psidium guajava) leaf powder: novel adsorbent for removal of methylene blue from aqueous solutions.

PubMed

Ponnusami, V; Vikram, S; Srivastava, S N

2008-03-21

Batch sorption experiments were carried out using a novel adsorbent, guava leaf powder (GLP), for the removal of methylene blue (MB) from aqueous solutions. Potential of GLP for adsorption of MB from aqueous solution was found to be excellent. Effects of process parameters pH, adsorbent dosage, concentration, particle size and temperature were studied. Temperature-concentration interaction effect on dye uptake was studied and a quadratic model was proposed to predict dye uptake in terms of concentration, time and temperature. The model conforms closely to the experimental data. The model was used to find optimum temperature and concentration that result in maximum dye uptake. Langmuir model represent the experimental data well. Maximum dye uptake was found to be 295mg/g, indicating that GLP can be used as an excellent low-cost adsorbent. Pseudo-first-order, pseudo-second order and intraparticle diffusion models were tested. From experimental data it was found that adsorption of MB onto GLP follow pseudo second order kinetics. External diffusion and intraparticle diffusion play roles in adsorption process. Free energy of adsorption (DeltaG degrees ), enthalpy change (DeltaH degrees ) and entropy change (DeltaS degrees ) were calculated to predict the nature of adsorption. Adsorption in packed bed was also evaluated.

Quantitative characterization of organic diffusion using an analytical diffusion-reaction model and its application to assessing BOD removal when treating municipal wastewater in a plug flow reactor.

PubMed

Fan, Chihhao; Kao, Chen-Fei; Liu, Yu-Hsi

2017-09-15

The present study aimed to derive an analytical formula to quantify the diffusion of organic contaminant in a biofilm. The experiments were conducted to investigate the BOD degradation under the conditions of influent COD concentration from 50 to 300 mg/L, COD:N:P ratios of 100:5:1 and 100:15:3, with and without auxiliary aeration. The BOD removal rate was around 73% for non-aerated influent COD of 50 mg/L with 1-h hydraulic retention time. The BOD removal rate increased as the influent loading and hydraulic retention time increased while the influent COD was no more than 150 mg/L. Without aeration, the removal rate dropped significantly when influent COD increased to the range no less than 200 mg/L, due to the fact that the BOD diffusive flux driven by the biomass uptake was not further enhanced by higher ambient organic loading. The diffusion coefficient was calculated to be 1.12 × 10 -6  m 2 /d with influent COD of 50 mg/L at COD:N:P ratio of 100:5:1 and 1 h hydraulic retention time and aeration, and the coefficient increased to 3.35 × 10 -6  m 2 /d as the influent COD concentration increased to 300 mg/L. The diffusion coefficient decreased to 4.09 × 10 -7  m 2 /d as the retention time increased to 3 h. The overall diffusion coefficients showed an increasing trend as the influent organic loading increased. The difference in diffusion coefficients between 1 and 2 h was apparently greater than that between 2 and 3 h, indicating a smaller overall diffusive flux due to a longer retention time. Further analysis revealed that BOD diffusion activity exhibited a declining trend as the wastewater travelled through the system. An analytical diffusion-reaction model was developed to characterize the diffusion behaviour, and applied to estimating the treatment efficiency for real domestic sewage. The result showed that the estimated effluent BOD concentrations were quite comparable to those from experimental measurements. Copyright © 2017 Elsevier Ltd. All rights reserved.

Inhibitory effect on the uptake and diffusion of Cd(2+) onto soybean hull sorbent in Cd-Pb binary sorption systems.

PubMed

Módenes, Aparecido N; Espinoza-Quiñones, Fernando R; Colombo, Andréia; Geraldi, Claudinéia L; Trigueros, Daniela E G

2015-05-01

The uptake of Cd(2+) and Pb(2+) ions by a soybean hull (SH) biosorbent in single and binary systems has been investigated. Sorption tests regarding SH in natura and chemically treated were carried out testing a suitable value range of solution pH, sorption temperature and shaking velocity. Sorption capacity is improved at pH 4, 30 °C temperature and 100 rpm. When a strong base is applied, a related-to-untreated SH increasing of 20% in the sorption capacity of Pb(2+) ions was observed, but with poor results for Cd(2+) uptake. Additionally, a relatively strong decreasing in both sorption capacities of Pb(2+) and Cd(2+) ions was evidenced for all acidic treatments. Regarding untreated SH, kinetic sorption data of both metals were well-interpreted by a pseudo second-order model and a rate-limiting step on the basis of an intra-particle diffusion model was suggested to occur. An inhibitory effect of Pb(2+) diffusion over Cd(2+) one was observed, limiting to reach the obtained maximum sorption capacity in single system. Maximum adsorption capacities of 0.49 and 0.67mequivg(-1) for Cd(2+) and Pb(2+), respectively, were predicted by the Langmuir isotherm model that reproduced well the equilibrium sorption data for single systems. The inhibitory effect of one metal over the other one was verified in equilibrium sorption data for binary systems interpreted on the basis of a modified extended Langmuir isotherm model, predicting changes in metal affinity onto the SH surface. Finally, SH is an alternative biosorbent with a great potential for the wastewater treatment containing cadmium and lead ions. Copyright © 2015 Elsevier Ltd. All rights reserved.

Amino acid tracers in PET imaging of diffuse low-grade gliomas: a systematic review of preoperative applications.

PubMed

Näslund, Olivia; Smits, Anja; Förander, Petter; Laesser, Mats; Bartek, Jiri; Gempt, Jens; Liljegren, Ann; Daxberg, Eva-Lotte; Jakola, Asgeir Store

2018-05-24

Positron emission tomography (PET) imaging using amino acid tracers has in recent years become widely used in the diagnosis and prediction of disease course in diffuse low-grade gliomas (LGG). However, implications of preoperative PET for treatment and prognosis in this patient group have not been systematically studied. The aim of this systematic review was to evaluate the preoperative diagnostic and prognostic value of amino acid PET in suspected diffuse LGG. Medline, Cochrane Library, and Embase databases were systematically searched using keywords "PET," "low-grade glioma," and "amino acids tracers" with their respective synonyms. Out of 2137 eligible studies, 28 met the inclusion criteria. Increased amino acid uptake (lesion/brain) was consistently reported among included studies; in 25-92% of subsequently histopathology-verified LGG, in 83-100% of histopathology-verified HGG, and also in some non-neoplastic lesions. No consistent results were found in studies reporting hot spot areas on PET in MRI-suspected LGG. Thus, the diagnostic value of amino acid PET imaging in suspected LGG has proven difficult to interpret, showing clear overlap and inconsistencies among reported results. Similarly, the results regarding the prognostic value of PET in suspected LGG and the correlation between uptake ratios and the molecular tumor status of LGG were conflicting. This systematic review illustrates the difficulties with prognostic studies presenting data on group-level without adjustment for established clinical prognostic factors, leading to a loss of additional prognostic information. We conclude that the prognostic value of PET is limited to analysis of histological subgroups of LGG and is probably strongest when using kinetic analysis of dynamic FET uptake parameters.

Nonlinear Layer-by-Layer Films: Effects of Chain Diffusivity on Film Structure and Swelling

DOE PAGES

Selin, Victor; Ankner, John F.; Sukhishvili, Svetlana A.

2017-08-09

Here in this paper, we report on the role of molecular diffusivity in the formation of nonlinearly growing polyelectrolyte multilayers (nlPEMs). Electrostatically bound polyelectrolyte multilayers were assembled from poly(methacrylic acid) (PMAA) as a polyanion and quaternized poly(2-(dimethylamino)ethyl methacrylate) (QPC) as a polycation. Film growth as measured by ellipsometry was strongly dependent on the time allowed for each polymer deposition step, suggesting that the diffusivities of the components are crucial in controlling the rate of film growth. Uptake of polyelectrolytes within nlPEMs was relatively slow and occurred on time scales ranging from minutes to hours, depending on the film thickness. Spectroscopicmore » ellipsometry measurements with nlPEM films exposed to aqueous solutions exhibited high (severalfold) degrees of film swelling and different swelling values for films exposed to QPC or PMAA solutions. FTIR spectroscopy showed that the average ionization of film-assembled PMAA increased upon binding of QPC and decreased upon binding of PMAA, in agreement with the charge regulation mechanism for weak polyelectrolytes. The use of neutron reflectometry (NR) enabled quantification of chain intermixing within the film, which was drastically enhanced when longer times were allowed for polyelectrolyte deposition. Diffusion coefficients of the polycation derived from the uptake rates of deuterated chains within hydrogenated films were of the order of 10 –14 cm 2/s, i.e., 5–6 orders of magnitude smaller than those found for diffusion of free polymer chains in solution. Exchange of the polymer solutions to buffer inhibited film intermixing. Taken together, these results contribute to understanding the mechanism of the growth of nonlinear polyelectrolyte multilayers and demonstrate the possibility of controlling film intermixing, which is highly desirable for potential future applications.« less

Quantitative assessment of the hepatic metabolic volume product in patients with diffuse hepatic steatosis and normal controls through use of FDG-PET and MR imaging: a novel concept.

PubMed

Bural, Gonca G; Torigian, Drew A; Burke, Anne; Houseni, Mohamed; Alkhawaldeh, Khaled; Cucchiara, Andrew; Basu, Sandip; Alavi, Abass

2010-06-01

The aim of this study was to compare hepatic standardized uptake values (SUVs) and hepatic metabolic volumetric products (HMVP) between patients of diffuse hepatic steatosis and control subjects with normal livers. Twenty-seven subjects were included in the study (13 men and 14 women; age range, 34-72 years). All had 18F-2-fluoro-2-D-deoxyglucose-positron emission tomography (FDG-PET) and magnetic resonance imaging (MRI) scans with an interscan interval of 0-5 months. Twelve of 27 subjects had diffuse hepatic steatosis on MRI. The remaining 15 were selected as age-matched controls based on normal liver parenchyma on MRI. Mean and maximum hepatic SUVs were calculated for both patient groups on FDG-PET images. Hepatic volumes were measured from MRI. HMVP in each subject was subsequently calculated by multiplication of hepatic volume by mean hepatic SUV. HMVPs as well as mean and maximum hepatic SUVs were compared between the two study groups. HMVPs, mean hepatic SUVs, and maximum hepatic SUVs were greater (statistically significant, p < 0.05) in subjects with diffuse hepatic steatosis compared to those in the control group. The increase in HMVP is the result of increased hepatic metabolic activity likely related to the diffuse hepatic steatosis. The active inflammatory process related to the diffuse hepatic steatosis is the probable explanation for the increase in hepatic metabolic activity on FDG-PET study.

A simple model of the effect of ocean ventilation on ocean heat uptake

NASA Astrophysics Data System (ADS)

Nadiga, Balu; Urban, Nathan

2017-11-01

Transport of water from the surface mixed layer into the ocean interior is achieved, in large part, by the process of ventilation-a process associated with outcropping isopycnals. Starting from such a configuration of outcropping isopycnals, we derive a simple model of the effect of ventilation on ocean uptake of anomalous radiative forcing. This model can be seen as an improvement of the popular anomaly-diffusing class of energy balance models (AD-EBM) that are routinely employed to analyze and emulate the warming response of both observed and simulated Earth system. We demonstrate that neither multi-layer, nor continuous-diffusion AD-EBM variants can properly represent both surface-warming and the vertical distribution of ocean heat uptake. The new model overcomes this deficiency. The simplicity of the models notwithstanding, the analysis presented and the necessity of the modification is indicative of the role played by processes related to the down-welling branch of global ocean circulation in shaping the vertical distribution of ocean heat uptake.

Transporters, channels, or simple diffusion? Dogmas, atypical roles and complexity in transport systems.

PubMed

Conde, Artur; Diallinas, George; Chaumont, François; Chaves, Manuela; Gerós, Hernâni

2010-06-01

The recent breakthrough discoveries of transport systems assigned with atypical functions provide evidence for complexity in membrane transport biochemistry. Some channels are far from being simple pores creating hydrophilic passages for solutes and can, unexpectedly, act as enzymes, or mediate high-affinity uptake, and some transporters are surprisingly able to function as sensors, channels or even enzymes. Furthermore, numerous transport studies have demonstrated complex multiphasic uptake kinetics for organic and mineral nutrients. The biphasic kinetics of glucose uptake in Saccharomyces cerevisiae, a result of several genetically distinct uptake systems operating simultaneously, is a classical example that is a subject of continuous debate. In contrast, some transporters display biphasic kinetics, being bona fidae dual-affinity transporters, their kinetic properties often modulated by post-translational regulation. Also, aquaporins have recently been reported to exhibit diverse transport properties and can behave as highly adapted, multifunctional channels, transporting solutes such as CO(2), hydrogen peroxide, urea, ammonia, glycerol, polyols, carbamides, purines and pyrimidines, metalloids, glycine, and lactic acid, rather than being simple water pores. The present review provides an overview on some atypical functions displayed by transporter proteins and discusses how this novel knowledge on cellular uptake systems may be related to complex multiphasic uptake kinetics often seen in a wide variety of living organisms and the intriguing diffusive uptake of sugars and other solutes. Copyright 2009 Elsevier Ltd. All rights reserved.

Ozone Uptake During Inspiratory Flow in a Model of the Larynx, Trachea and Primary Bronchial Bifurcation

PubMed Central

Padaki, Amit; Ultman, James S.; Borhan, Ali

2009-01-01

Three-dimensional simulations of the transport and uptake of a reactive gas such as O3 were compared between an idealized model of the larynx, trachea, and first bifurcation and a second “control” model in which the larynx was replaced by an equivalent, cylindrical, tube segment. The Navier-Stokes equations, Spalart-Allmaras turbulence equation, and convection-diffusion equation were implemented at conditions reflecting inhalation into an adult human lung. Simulation results were used to analyze axial velocity, turbulent viscosity, local fractional uptake, and regional uptake. Axial velocity data revealed a strong laryngeal jet with a reattachment point in the proximal trachea. Turbulent viscosity data indicated that jet turbulence occurred only at high Reynolds numbers and was attenuated by the first bifurcation. Local fractional uptake data affirmed hotspots previously reported at the first carina, and suggested additional hotspots at the glottal constriction and jet reattachment point in the proximal trachea. These laryngeal effects strongly depended on inlet Reynolds number, with maximal effects (approaching 15%) occurring at maximal inlet flow rates. While the increase in the regional uptake caused by the larynx subsided by the end of the model, the effect of the larynx on cumulative uptake persisted further downstream. These results suggest that with prolonged exposure to a reactive gas, entire regions of the larynx and proximal trachea could show signs of tissue injury. PMID:22949744

Aerosols and their influence on radiation partitioning and savanna productivity in northern Australia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanniah, K. D.; Beringer, J.; Tapper, N. J.

2010-05-01

We investigated the effect of aerosols and clouds on the Net Ecosystem Productivity (NEP) of savannas in northern Australia using aerosol optical depth, clouds and radiation data from the Atmospheric Radiation Measurement (ARM) site in Darwin and carbon flux data measured from eddy covariance techniques from a site at Howard Springs, 35km southeast of Darwin. Generally we found that the concentration of aerosols in this region was relatively low than observed at other sites, therefore the proportion of diffuse radiation reaching the earths surface was only ~ 30%. As a result, we observed only a modest change in carbon uptakemore » under aerosol laden skies and there was no significant difference for dry season Radiation Use Efficiency (RUE) between clear sky, aerosols or thin clouds. On the other hand thick clouds in the wet season produce much more diffuse radiation than aerosols or thin clouds and therefore the initial canopy quantum efficiency was seen to increase 45 and 2.5 times more than under thin clouds and aerosols respectively. The normalized carbon uptake under thick clouds is 57% and 50% higher than under aerosols and thin clouds respectively even though the total irradiance received under thick clouds was reduced 59% and 50% than under aerosols and thin clouds respectively. However, reduction in total irradiance decreases the mean absolute carbon uptake as much as 22% under heavy cloud cover compared to thin clouds or aerosols. Thus, any increase in aerosol concentration or cloud cover that can enhance the diffuse component may have large impacts on productivity in this region.« less

Model for Microcapsule Drug Release with Ultrasound-Activated Enhancement.

PubMed

Tsao, Nadia H; Hall, Elizabeth A H

2017-11-14

Microbubbles and microcapsules of silane-polycaprolactone (SiPCL) have been filled with a fluorescent acridium salt (lucigenin) as a model for a drug-loaded delivery vehicle. The uptake and delivery were studied and compared with similar microbubbles and microcapsules of silica/mercaptosilica (S/M/S). Positively charged lucigenin was encapsulated through an electrostatic mechanism, following a Type I Langmuir isotherm as expected, but with an additional multilayer uptake that leads to a much higher loading for the SiPCL system (∼280 μg/2.4 × 10 9 microcapsules compared with ∼135 μg/2.4 × 10 9 microcapsules for S/M/S). Whereas the lucigenin release from the S/M/S bubbles and capsules loaded below the solubility limit is consistent with diffusion from a monolithic structure, the SiPCL structures show distinct release patterns; the Weibull function predicts a general trend for diffusion from normal Euclidean space at short times tending toward diffusion out of fractal spaces with increasing time. As a slow release system, the dissolution time (T d ) increases from 1 to 2 days for the S/M/S and for the low concentration, loaded SiPCl vehicles to ∼10 days for the high loaded microcapsules. However, T d can be reduced on insonation to 2 days, indicating the potential to gain control over the local enhanced release with ultrasound. This was tested for a docetaxel model and its effect on C4-2B prostate cancer cells, showing improved cell toxicity for concentrations below the normal EC 50 in solution.

Contrasting Diffusion Patterns for PC and Mobile Videos: A User-Centric View of the Influencing Factors

ERIC Educational Resources Information Center

Wu, Baixue

2010-01-01

As both computer and mobile phone reach nearly ubiquity in the U.S. market, the slow uptake of mobile video, in contrast to the thriving usage of PC-based video, warrants a deeper understanding of user-oriented factors contributing to the two diffusion paths. Unlike the majority of existing diffusion research practices, the dissertation…

[Effects of sub-micro emulsion composition on cellular disposition of incorporated lipophilic drug].

PubMed

Sun, Xiao-Yi; Xiang, Zhi-Qiang; Wu, Shuo; Lv, Yuan-Yuan; Liang, Wen-Quan

2013-09-01

To investigate the effects of sub-micro emulsion composition on cellular uptake and disposition of incorporated lipophilic drug. Sub-micro emulsions containing 10 % oil, 1.2 % lecithin and 2.25 % glycerol were prepared, and the fluorescent agent coumarin 6 was used as a model drug. The effects of oil types, co-surfactants and cationic lipid on uptake and elimination kinetics of 6-coumarin in HeLa cells were studied. The uptake mechanism of sub-micro emulsions was further investigated. Oil type and Tweens had no influence on the cellular uptake. Modifications of surfactants with Span series increased the cellular influx, among which Span 20 with hydrophilic-lipophilic balance (HLB) value of 8.6 was the best enhancer. The intracellular drug level reached up to (46.09 ± 1.98)ng/μg protein which had significant difference with control group [(38.54 ± 0.34)ng/μg protein]. The positively charged emulsions significantly increased the uptake rate constant and elimination rate constant which were 4 times and 1.5 times of those in anionic groups, respectively. The uptake enhancement was also observed in cationic emulsions, cellular concentrations at plateau were (42.73 ± 0.84)ng/μg protein, which was about 3 times of that in anionic emulsions [(15.71 ± 0.74)ng/μg protein], when extracellular drug concentration kept at 100 ng/ml. Cationic emulsions delivered the payload mainly by direct drug transfer to contacted cells, while the negative ones depended on both drug passive diffusion and clathrin-mediated endocytosis of drug containing oil droplets which accounted for 20% of the intracellular drug. Interfacial characteristic of sub-micro emulsions such as co-surfactants HLB as well as zeta potentials can influence lipophilic drug both in cellular uptake and elimination.

Studies on gallium accumulation in inflammatory lesions: I. Gallium uptake by human polymorphonuclear leukocytes. [/sup 67/Ga, rabbits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsan, M.F.; Chen, W.Y.; Scheffel, U.

1978-01-01

The mechanism of ionic gallium-67 localization in inflammatory lesions was studied. Human polymorphonuclear leukocytes (PMN) had higher Ga-67 uptake than lymphocytes, whereas red blood cells had no affinity for Ga-67. Uptake by PMN showed temperature dependence, was independent of Ga-67 concentrations, and was not inhibited by metabolic inhibitors. However, its binding to PMN could be removed by trypsin but not by neuraminidase. These results are consistent with the hypothesis that the plasma membrane serves as a diffusion barrier and Ga-67 only binds to the surface of the PMN plasma membrane. When this membrane's permeability barrier was disrupted, as in heat-killedmore » PMN, Ga-67 uptake increased markedly. Experimental abscesses were induced with E. coli or turpentine in rabbits. Twenty-four hours after i.v. injection, only 20 percent of Ga-67 in abscesses was in fractions containing intact PMN, cell debris or bacteria; the remainder was in a soluble, non-cellular fraction (2,500-g supernatant).« less

Study on kinetics of glucose uptake by some species of plankton

NASA Astrophysics Data System (ADS)

Li, Wenquan; Wang, Xian; Zhang, Yaohua

1993-03-01

The rates of glucose uptake by some species of plankton were determined by3H-glucose tracer method. Experimental results indicated that the observed glucose uptake at natural seawater concentrations by Platymonas subcordiformis and Brachionus plicatilis was principally a metabolic process fitted with the Michaelis-Menten equation in the range of adaptive temperatures. Heterotrophic uptake by Platymonas subcordiformis was mainly dependent on diffusion at high glucose levels. The uptake by Brachionus plicatilis showed active transport even at high glucose levels, indicating its high heterotrophic activity. The uptake rate by Artemia salina was lower, and its V m/K ratio was lower than those of the other two species of plankton.

Ultrasound findings of diffuse metastasis of gastric signet-ring-cell carcinoma to the thyroid gland.

PubMed

Morita, Koji; Sakamoto, Takahiko; Ota, Shuji; Masugi, Hideo; Chikuta, Ikumi; Mashimo, Yamato; Edo, Naoki; Tokairin, Takuo; Seki, Nobuhiko; Ishikawa, Toshio

2017-01-01

It has been shown that metastases to the thyroid from extrathyroidal malignancies occur as solitary or multiple nodules, or may involve the whole thyroid gland diffusely. However, diffuse metastasis of gastric cancer to the thyroid is extremely rare. Here, we report a case of a 74-year-old woman with diffuse infiltration of gastric adenocarcinoma (signet-ring-cell carcinoma/poorly differentiated adenocarcinoma) cells in the thyroid. The pathological diagnosis was made based on upper gastrointestinal endoscopy with biopsy and fine-needle aspiration cytology of the thyroid. An 18F-FDG PET/CT revealed multiple lesions with increased uptake, including the bilateral thyroid gland. On thyroid ultrasound examination, diffuse enlargement with internal heterogeneity and hypoechoic reticular lines was observed. On color Doppler imaging, a blood-flow signal was not detected in these hypoechoic lines. These findings were similar to those of diffuse metastases caused by other primary cancers, such as lung cancer, as reported earlier. Therefore, the presence of hypoechoic reticular lines without blood-flow signals is probably common to diffuse thyroid metastasis from any origin and an important diagnostic finding. This is the first report to show detailed ultrasound findings of diffuse gastric cancer metastasis to the thyroid gland using color Doppler.

How drugs get into cells: tested and testable predictions to help discriminate between transporter-mediated uptake and lipoidal bilayer diffusion

PubMed Central

Kell, Douglas B.; Oliver, Stephen G.

2014-01-01

One approach to experimental science involves creating hypotheses, then testing them by varying one or more independent variables, and assessing the effects of this variation on the processes of interest. We use this strategy to compare the intellectual status and available evidence for two models or views of mechanisms of transmembrane drug transport into intact biological cells. One (BDII) asserts that lipoidal phospholipid Bilayer Diffusion Is Important, while a second (PBIN) proposes that in normal intact cells Phospholipid Bilayer diffusion Is Negligible (i.e., may be neglected quantitatively), because evolution selected against it, and with transmembrane drug transport being effected by genetically encoded proteinaceous carriers or pores, whose “natural” biological roles, and substrates are based in intermediary metabolism. Despite a recent review elsewhere, we can find no evidence able to support BDII as we can find no experiments in intact cells in which phospholipid bilayer diffusion was either varied independently or measured directly (although there are many papers where it was inferred by seeing a covariation of other dependent variables). By contrast, we find an abundance of evidence showing cases in which changes in the activities of named and genetically identified transporters led to measurable changes in the rate or extent of drug uptake. PBIN also has considerable predictive power, and accounts readily for the large differences in drug uptake between tissues, cells and species, in accounting for the metabolite-likeness of marketed drugs, in pharmacogenomics, and in providing a straightforward explanation for the late-stage appearance of toxicity and of lack of efficacy during drug discovery programmes despite macroscopically adequate pharmacokinetics. Consequently, the view that Phospholipid Bilayer diffusion Is Negligible (PBIN) provides a starting hypothesis for assessing cellular drug uptake that is much better supported by the available evidence, and is both more productive and more predictive. PMID:25400580

Coupled elasticity–diffusion model for the effects of cytoskeleton deformation on cellular uptake of cylindrical nanoparticles

PubMed Central

Wang, Jizeng; Li, Long

2015-01-01

Molecular dynamic simulations and experiments have recently demonstrated how cylindrical nanoparticles (CNPs) with large aspect ratios penetrate animal cells and inevitably deform cytoskeletons. Thus, a coupled elasticity–diffusion model was adopted to elucidate this interesting biological phenomenon by considering the effects of elastic deformations of cytoskeleton and membrane, ligand–receptor binding and receptor diffusion. The mechanism by which the binding energy drives the CNPs with different orientations to enter host cells was explored. This mechanism involved overcoming the resistance caused by cytoskeleton and membrane deformations and the change in configurational entropy of the ligand–receptor bonds and free receptors. Results showed that deformation of the cytoskeleton significantly influenced the engulfing process by effectively slowing down and even hindering the entry of the CNPs. Additionally, the engulfing depth was determined quantitatively. CNPs preferred or tended to vertically attack target cells until they were stuck in the cytoskeleton as implied by the speed of vertically oriented CNPs that showed much faster initial engulfing speeds than horizontally oriented CNPs. These results elucidated the most recent molecular dynamics simulations and experimental observations on the cellular uptake of carbon nanotubes and phagocytosis of filamentous Escherichia coli bacteria. The most efficient engulfment showed the stiffness-dependent optimal radius of the CNPs. Cytoskeleton stiffness exhibited more significant influence on the optimal sizes of the vertical uptake than the horizontal uptake. PMID:25411410

The effect of tissue structure and soil chemistry on trace element uptake in fossils

NASA Astrophysics Data System (ADS)

Hinz, Emily A.; Kohn, Matthew J.

2010-06-01

Trace element profiles for common divalent cations (Sr, Zn, Ba), rare-earth elements (REE), Y, U, and Th were measured in fossil bones and teeth from the c. 25 ka Merrell locality, Montana, USA, by using laser-ablation ICP-MS. Multiple traverses in teeth were transformed into 2-D trace element maps for visualizing structural influences on trace element uptake. Trace element compositions of different soils from the fossil site were also analyzed by solution ICP-MS, employing progressive leaches that included distilled H 2O, 0.1 M acetic acid, and microwave digestion in concentrated HCl-HNO 3. In teeth, trace element uptake in enamel is 2-4 orders of magnitude slower than in dentine, forming an effective trace element barrier. Uptake in dentine parallel to the dentine-enamel interface is enhanced by at least 2 orders of magnitude compared to transverse, causing trace element "plumes" down the tooth core. In bone, U, Ba and Sr are nearly homogeneous, implying diffusivities ˜5 orders of magnitude faster than in enamel and virtually complete equilibration with host soils. In contrast all REE show strong depletions inward, with stepwise linear segments in log-normal or inverse complementary error function plots; these data require a multi-medium diffusion model, with about 2 orders of magnitude difference in slowest vs. fastest diffusivities. Differences in REE diffusivities in bone (slow) vs. dentine (fast) reflect different partition coefficients ( Kd's). Although acid leaches and bulk digestion of soils yield comparable fossil-soil Kd's among different elements, natural solutions are expected to be neutral to slightly basic. Distilled H 2O leachates instead reveal radically different Kd's in bone for REE than for U-Sr-Ba, suggest orders of magnitude lower effective diffusivities for REE, and readily explain steep vs. flat profiles for REE vs. U-Sr-Ba, respectively. Differences among REE Kd's and diffusivities may explain inward changes in Ce anomalies. Acid washes and bulk soil compositions yield misleading Kd's for many trace elements, especially the REE, and H 2O-leaches are preferred. Patterns of trace element distributions indicate diagenetic alteration at all scales, including enamel, and challenge the use of trace elements in paleodietary studies.

Flagella-Driven Flows Circumvent Diffusive Bottlenecks that Inhibit Metabolite Exchange

NASA Astrophysics Data System (ADS)

Short, Martin; Solari, Cristian; Ganguly, Sujoy; Kessler, John; Goldstein, Raymond; Powers, Thomas

2006-03-01

The evolution of single cells to large and multicellular organisms requires matching the organisms' needs to the rate of exchange of metabolites with the environment. This logistic problem can be a severe constraint on development. For organisms with a body plan that approximates a spherical shell, such as colonies of the volvocine green algae, the required current of metabolites grows quadratically with colony radius whereas the rate at which diffusion can exchange metabolites grows only linearly with radius. Hence, there is a bottleneck radius beyond which the diffusive current cannot keep up with metabolic demands. Using Volvox carteri as a model organism, we examine experimentally and theoretically the role that advection of fluid by surface-mounted flagella plays in enhancing nutrient uptake. We show that fluid flow driven by the coordinated beating of flagella produces a convective boundary layer in the concentration of a diffusing solute which in turn renders the metabolite exchange rate quadratic in the colony radius. This enhanced transport circumvents the diffusive bottleneck, allowing increase in size and thus evolutionary transitions to multicellularity in the Volvocales.

Gallium-positive Lyme disease myocarditis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alpert, L.I.; Welch, P.; Fisher, N.

1985-09-01

In the course of a work-up for fever of unknown origin associated with intermittent arrhythmias, a gallium scan was performed which revealed diffuse myocardial uptake. The diagnosis of Lyme disease myocarditis subsequently was confirmed by serologic titers. One month following recovery from the acute illness, the abnormal myocardial uptake completely resolved.

In vitro investigation of intestinal transport mechanism of silicon, supplied as orthosilicic acid-vanillin complex.

PubMed

Sergent, Thérèse; Croizet, Karine; Schneider, Yves-Jacques

2017-02-01

Silicon (Si) is one of the most abundant trace elements in the body. Although pharmacokinetics data described its absorption from the diet and its body excretion, the mechanisms involved in the uptake and transport of Si across the gut wall have not been established. Caco-2 cells were used as a well-accepted in vitro model of the human intestinal epithelium to investigate the transport, across the intestinal barrier in both the absorption and excretion directions, of Si supplied as orthosilicic acid stabilized by vanillin complex (OSA-VC). The transport of this species was found proportional to the initial concentration and to the duration of incubation, with absorption and excretion mean rates similar to those of Lucifer yellow, a marker of paracellular diffusion, and increasing in the presence of EGTA, a chelator of divalents cations including calcium. A cellular accumulation of Si, polarized from the apical side of cells, was furthermore detected. These results provide evidence that Si, ingested as a food supplement containing OSA-VC, crosses the intestinal mucosa by passive diffusion via the paracellular pathway through the intercellular tight junctions and accumulates intracellularly, probably by an uptake mechanism of facilitated diffusion. This study can help to further understand the kinetic of absorption of Si. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Uptake of Fluorescent Gentamicin by Peripheral Vestibular Cells after Systemic Administration

PubMed Central

Liu, Jianping; Kachelmeier, Allan; Dai, Chunfu; Li, Hongzhe; Steyger, Peter S.

2015-01-01

Objective In addition to cochleotoxicity, systemic aminoglycoside pharmacotherapy causes vestibulotoxicity resulting in imbalance and visual dysfunction. The underlying trafficking routes of systemically-administered aminoglycosides from the vasculature to the vestibular sensory hair cells are largely unknown. We investigated the trafficking of systemically-administered gentamicin into the peripheral vestibular system in C56Bl/6 mice using fluorescence-tagged gentamicin (gentamicin-Texas-Red, GTTR) imaged by scanning laser confocal microscopy to determine the cellular distribution and intensity of GTTR fluorescence in the three semicircular canal cristae, utricular, and saccular maculae at 5 time points over 4 hours. Results Low intensity GTTR fluorescence was detected at 0.5 hours as both discrete puncta and diffuse cytoplasmic fluorescence. The intensity of cytoplasmic fluorescence peaked at 3 hours, while punctate fluorescence was plateaued after 3 hours. At 0.5 and 1 hour, higher levels of diffuse GTTR fluorescence were present in transitional cells compared to hair cells and supporting cells. Sensory hair cells typically exhibited only diffuse cytoplasmic fluorescence at all time-points up to 4 hours in this study. In contrast, non-sensory cells rapidly exhibited both intense fluorescent puncta and weaker, diffuse fluorescence throughout the cytosol. The numbers and size of fluorescent puncta in dark cells and transitional cells increased over time. There is no preferential GTTR uptake by the five peripheral vestibular organs’ sensory cells. Control vestibular tissues exposed to Dulbecco’s phosphate-buffered saline or hydrolyzed Texas Red had negligible fluorescence. Conclusions All peripheral vestibular cells rapidly take up systemically-administered GTTR, reaching peak intensity 3 hours after injection. Sensory hair cells exhibited only diffuse fluorescence, while non-sensory cells displayed both diffuse and punctate fluorescence. Transitional cells may act as a primary pathway for trafficking of systemic GTTR from the vasculature to endolymph prior to entering hair cells. PMID:25793391

Enhanced dopamine release by dopamine transport inhibitors described by a restricted diffusion model and fast scan cyclic voltammetry

PubMed Central

Hoffman, Alexander F.; Spivak, Charles E.; Lupica, Carl R.

2016-01-01

Fast-scan cyclic voltammetry (FSCV) using carbon fiber electrodes is widely used to rapidly monitor changes in dopamine (DA) levels in vitro and in vivo. Current analytical approaches utilize parameters such as peak oxidation current amplitude and decay times to estimate release and uptake processes, respectively. However, peak amplitude changes are often observed with uptake inhibitors, thereby confounding the interpretation of these parameters. To overcome this limitation, we demonstrate that a simple, 5 parameter, two compartment model mathematically describes DA signals as a balance of release (r/ke) and uptake (ku), summed with adsorption (kads and kdes) of DA to the carbon electrode surface. Using non-linear regression, we demonstrate that our model precisely describes measured DA signals obtained in brain slice recordings. The parameters extracted from these curves were then validated using pharmacological manipulations that selectively alter vesicular release or DA transporter (DAT)-mediated uptake. Manipulation of DA release through altered Ca2+/Mg2+ ratio or tetrodotoxin (TTX), reduced the release parameter with no effect on the uptake parameter. The DAT inhibitors methylenedioxypyrovalerone (MDPV), cocaine, and nomifensine significantly reduced uptake and increased vesicular DA release. In contrast, a low concentration of amphetamine reduced uptake but had no effect on DA release. Finally, the kappa-opioid receptor (KOR) agonist U50,488 significantly reduced vesicular DA release but had no effect on uptake. Together, these data demonstrate a novel analytical approach to distinguish the effects of manipulations on DA release or uptake that can be used to interpret FSCV data. PMID:27018734

Enhanced Dopamine Release by Dopamine Transport Inhibitors Described by a Restricted Diffusion Model and Fast-Scan Cyclic Voltammetry.

PubMed

Hoffman, Alexander F; Spivak, Charles E; Lupica, Carl R

2016-06-15

Fast-scan cyclic voltammetry (FSCV) using carbon fiber electrodes is widely used to rapidly monitor changes in dopamine (DA) levels in vitro and in vivo. Current analytical approaches utilize parameters such as peak oxidation current amplitude and decay times to estimate release and uptake processes, respectively. However, peak amplitude changes are often observed with uptake inhibitors, thereby confounding the interpretation of these parameters. To overcome this limitation, we demonstrate that a simple five-parameter, two-compartment model mathematically describes DA signals as a balance of release (r/ke) and uptake (ku), summed with adsorption (kads and kdes) of DA to the carbon electrode surface. Using nonlinear regression, we demonstrate that our model precisely describes measured DA signals obtained in brain slice recordings. The parameters extracted from these curves were then validated using pharmacological manipulations that selectively alter vesicular release or DA transporter (DAT)-mediated uptake. Manipulation of DA release through altering the Ca(2+)/Mg(2+) ratio or adding tetrodotoxin reduced the release parameter with no effect on the uptake parameter. DAT inhibitors methylenedioxypyrovalerone, cocaine, and nomifensine significantly reduced uptake and increased vesicular DA release. In contrast, a low concentration of amphetamine reduced uptake but had no effect on DA release. Finally, the kappa opioid receptor agonist U50,488 significantly reduced vesicular DA release but had no effect on uptake. Together, these data demonstrate a novel analytical approach to distinguish the effects of manipulations on DA release or uptake that can be used to interpret FSCV data.

An improved procedure for reconstitution of the uncoupling protein and in-depth analysis of H+/OH- transport.

PubMed

Winkler, E; Klingenberg, M

1992-07-01

An improved procedure for reincorporation of isolated uncoupling protein (UCP) from brown adipose tissue into phospholipid vesicles is reported and H+ uptake in K(+)-driven exchange diffusion quantitatively analyzed. UCP is isolated and reconstituted with medium-length linear-chain alkyl polyoxyethylene. In the critical step of vesicle formation, the stepwise removal of the detergent by polystyrene beads is applied. Vesicles are generated in the presence of solutes and buffers to be internalized which are then removed by gel filtration. The internal volume is about 4 microliters/mg phospholipid with a vesicle diameter of 100 nm. One vesicle contains, on average, six molecules UCP. The best results are obtained with purified egg yolk phosphatidylcholine. Addition of PtdEtn, PtdSer decreases the vesicle size and, still more, H(+)-transport activity by UCP. Asolectin completely inactivates UCP. K(+)-gradient-driven H+ uptake is 80% inhibited by external GTP and 95% by internal plus external GTP. When H+ transport is recorded externally by a pH electrode and internally by pyranine, the kinetics show no delay resulting from intervening membrane-bound H+ pools. Total H+ uptake after addition of carbonylcyanine m-chlorophenylhydrazone (CCCP) and valinomycin corresponds to the diffusion between H+ and K+ and is unchanged by GTP. The linear correlation of H(+)-transport inhibition to GTP binding demonstrates that all UCP molecules incorporated are equally active. The exchange diffusion between H+ uptake and K+ efflux is demonstrated using a K+ electrode and 86Rb measurements. Recording delta psi using 3,3'-diispropylthiadicarbocyanine shows a rapid generation of delta psi on valinomycin addition, which decreases only slightly with H+ uptake, even after addition of CCCP or gramicidin. The delta psi collapses only after addition of external K+. By demonstrating that valinomycin-induced K+ and H+ fluxes reflect relaxation into the diffusion equilibrium state, the transport rate of UCP can be evaluated as a first-order rate, VH+/CH+, in which the rate, VH+, is related to H(+)-uptake capacity, CH+. This allows quantitative comparison of transport rates independently of the variable CH+. The dependence on delta psi of H+ transport is measured by varying external K+ concentration. A virtually linear relation of the rate to the K(+)-diffusion potential is observed, although the capacity is only slightly changed. The linear VH+/delta psi relationship resembles an open-channel type of transport, but is discussed in terms of a low-activation-barrier type of carrier mechanism, in contrast to the log (VH+/delta psi) relation found for the ADP/ATP carrier with high activation barriers.

Small global effect on terrestrial net primary production due to increased fossil fuel aerosol emissions from East Asia since the turn of the century

DOE PAGES

O'Sullivan, M.; Rap, A.; Reddington, C. L.; ...

2016-07-29

The global terrestrial carbon sink has increased since the start of this century at a time of growing carbon emissions from fossil fuel burning. Here we test the hypothesis that increases in atmospheric aerosols from fossil fuel burning enhanced the diffuse light fraction and the efficiency of plant carbon uptake. Using a combination of models, we estimate that at global scale changes in light regimes from fossil fuel aerosol emissions had only a small negative effect on the increase in terrestrial net primary production over the period 1998–2010. Hereby, the substantial increases in fossil fuel aerosol emissions and plant carbonmore » uptake over East Asia were effectively canceled by opposing trends across Europe and North America. This suggests that if the recent increase in the land carbon sink would be causally linked to fossil fuel emissions, it is unlikely via the effect of aerosols but due to other factors such as nitrogen deposition or nitrogen-carbon interactions.« less

Small global effect on terrestrial net primary production due to increased fossil fuel aerosol emissions from East Asia since the turn of the century

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Sullivan, M.; Rap, A.; Reddington, C. L.

The global terrestrial carbon sink has increased since the start of this century at a time of growing carbon emissions from fossil fuel burning. Here we test the hypothesis that increases in atmospheric aerosols from fossil fuel burning enhanced the diffuse light fraction and the efficiency of plant carbon uptake. Using a combination of models, we estimate that at global scale changes in light regimes from fossil fuel aerosol emissions had only a small negative effect on the increase in terrestrial net primary production over the period 1998–2010. Hereby, the substantial increases in fossil fuel aerosol emissions and plant carbonmore » uptake over East Asia were effectively canceled by opposing trends across Europe and North America. This suggests that if the recent increase in the land carbon sink would be causally linked to fossil fuel emissions, it is unlikely via the effect of aerosols but due to other factors such as nitrogen deposition or nitrogen-carbon interactions.« less

Characterization of metal adsorption kinetic properties in batch and fixed-bed reactors.

PubMed

Chen, J Paul; Wang, Lin

2004-01-01

Copper adsorption kinetic properties in batch and fixed-bed reactors were studied in this paper. The isothermal adsorption experiments showed that the copper adsorption capacity of a granular activated carbon (Filtrasorb 200) increased when ionic strength was higher. The presence of EDTA diminished the adsorption. An intraparticle diffusion model and a fixed-bed model were successfully used to describe the batch kinetic and fixed-bed operation behaviors. The kinetics became faster when the solution pH was not controlled, implying that the surface precipitation caused some metal uptake. The external mass transfer coefficient, the diffusivity and the dispersion coefficient were obtained from the modeling. It was found that both external mass transfer and dispersion coefficients increased when the flow rate was higher. Finally effects of kinetic parameters on simulation of fixed-bed operation were conducted.

Secretion of Sparfloxacin from the Human Intestinal Caco-2 Cell Line Is Altered by P-Glycoprotein Inhibitors

PubMed Central

Cormet-Boyaka, Estelle; Huneau, Jean-François; Mordrelle, Agnès; Boyaka, Prosper N.; Carbon, Claude; Rubinstein, Ethan; Tomé, Daniel

1998-01-01

The mechanism of intestinal secretion of the difluorinated quinolone sparfloxacin was investigated with the epithelial cell line Caco-2 and was compared to that of the P-glycoprotein (P-gp) substrate vinblastine. The P-gp inhibitors verapamil and progesterone significantly increased the epithelial cell accumulation of both vinblastine and sparfloxacin. This increase is likely to result from an inhibition of drug secretion since both vinblastine uptake and sparfloxacin uptake are known to proceed through a passive transmembrane diffusion. The unidirectional fluxes across cell monlayers grown on permeable filters indicated that a net secretion of sparfloxacin and vinblastine occurred across Caco-2 cells. These secretions were significantly inhibited by the MDR-reversing agent verapamil. We conclude that the P-gp is likely to be involved in the intestinal elimination of the difluorinated quinolone sparfloxacin. PMID:9756763

Distribution of polycyclic aromatic hydrocarbons in subcellular root tissues of ryegrass (Lolium multiflorum Lam.)

PubMed Central

2010-01-01

Background Because of the increasing quantity and high toxicity to humans of polycyclic aromatic hydrocarbons (PAHs) in the environment, several bioremediation mechanisms and protocols have been investigated to restore PAH-contaminated sites. The transport of organic contaminants among plant cells via tissues and their partition in roots, stalks, and leaves resulting from transpiration and lipid content have been extensively investigated. However, information about PAH distributions in intracellular tissues is lacking, thus limiting the further development of a mechanism-based phytoremediation strategy to improve treatment efficiency. Results Pyrene exhibited higher uptake and was more recalcitrant to metabolism in ryegrass roots than was phenanthrene. The kinetic processes of uptake from ryegrass culture medium revealed that these two PAHs were first adsorbed onto root cell walls, and they then penetrated cell membranes and were distributed in intracellular organelle fractions. At the beginning of uptake (< 50 h), adsorption to cell walls dominated the subcellular partitioning of the PAHs. After 96 h of uptake, the subcellular partition of PAHs approached a stable state in the plant water system, with the proportion of PAH distributed in subcellular fractions being controlled by the lipid contents of each component. Phenanthrene and pyrene primarily accumulated in plant root cell walls and organelles, with about 45% of PAHs in each of these two fractions, and the remainder was retained in the dissolved fraction of the cells. Because of its higher lipophilicity, pyrene displayed greater accumulation factors in subcellular walls and organelle fractions than did phenanthrene. Conclusions Transpiration and the lipid content of root cell fractions are the main drivers of the subcellular partition of PAHs in roots. Initially, PAHs adsorb to plant cell walls, and they then gradually diffuse into subcellular fractions of tissues. The lipid content of intracellular components determines the accumulation of lipophilic compounds, and the diffusion rate is related to the concentration gradient established between cell walls and cell organelles. Our results offer insights into the transport mechanisms of PAHs in ryegrass roots and their diffusion in root cells. PMID:20860818

Determination of deployment specific chemical uptake rates for SDB-RPD Empore disk using a passive flow monitor (PFM).

PubMed

O'Brien, Dominique; Bartkow, Michael; Mueller, Jochen F

2011-05-01

The use of the adsorbent styrenedivinylbenzene-reverse phase sulfonated (SDB-RPD) Empore disk in a chemcatcher type passive sampler is routinely applied in Australia when monitoring herbicides in aquatic environments. One key challenge in the use of passive samplers is mitigating the potentially confounding effects of varying flow conditions on chemical uptake by the passive sampler. Performance reference compounds (PRCs) may be applied to correct sampling rates (R(s)) for site specific changed in flow and temperature however evidence suggests the use of PRCs is unreliable when applied to adsorbent passive samplers. The use of the passive flow monitor (PFM) has been introduced for the assessment of site-specific changes in water flow. In the presented study we have demonstrated that the R(s) at which both atrazine and prometryn are accumulated within the SDB-RPD-Empore disk is dependent on the flow conditions. Further, the calibration of the measured R(s) for chemical uptake by the SDB-RPD-Empore disk to the mass lost from the PFM has shown that the PFM provides an accurate measure of R(s) for flow velocities from 0 to 16cms(-1). Notably, for flow rates >16cms(-1), a non linear increase in the R(s) of both herbicides was observed which indicates that the key resistance to uptake into the SDB-RPD Empore disk is associated with the diffusion through the overlying diffusion limiting membrane. Overall the greatest uncertainty remains at very low flow conditions, which are unlikely to often occur in surface waters. Validation of the PFM use has also been undertaken in a limited field study. Copyright © 2011 Elsevier Ltd. All rights reserved.

Incidence of Thyroid-Related Adverse Events in Melanoma Patients Treated With Pembrolizumab

PubMed Central

Jansen, Yanina; Schreuer, Max; Everaert, Hendrik; Velkeniers, Brigitte; Neyns, Bart; Bravenboer, Bert

2016-01-01

Context: Immune checkpoint blockade is associated with endocrine-related adverse events. Thyroid dysfunction during pembrolizumab therapy, an anti-programmed cell death 1 (PD-1) receptor monoclonal antibody, remains to be fully characterized. Objective: To assess the incidence and characteristics of pembrolizumab-associated thyroid dysfunction. Design and Setting: Thyroid function was monitored prospectively in melanoma patients who initiated pembrolizumab within an expanded access program at a referral oncology center. 18Fluorodeoxyglucose uptake on positron emission tomography/computed tomography (18FDG-PET/CT) was reviewed in cases compatible with inflammatory thyroiditis. Patients: Ninety-nine patients with advanced melanoma (age, 26.3–93.6 years; 63.6% females) who received at least one administration of pembrolizumab. Main Outcome Measures: Patient characteristics, thyroid function (TSH, free T4), thyroid autoantibodies, and 18FDG-PET/CT. Results: Eighteen adverse events of thyroid dysfunction were observed in 17 patients. Thyrotoxicosis occurred in 12 patients, of which nine evolved to hypothyroidism. Isolated hypothyroidism was present in six patients. Levothyroxine therapy was required in 10 of 15 hypothyroid patients. Thyroid autoantibodies were elevated during thyroid dysfunction in four of 10 cases. Diffuse increased 18FDG uptake by the thyroid gland was observed in all seven thyrotoxic patients who progressed to hypothyroidism. Conclusions: Thyroid dysfunction is common in melanoma patients treated with pembrolizumab. Hypothyroidism and thyrotoxicosis related to inflammatory thyroiditis are the most frequent presentations. Serial measurements of thyroid function tests are indicated during anti-PD-1 monoclonal antibody therapy. Thyrotoxicosis compatible with inflammatory thyroiditis was associated with diffuse increased 18FDG uptake by the thyroid gland. The prospective role of thyroid autoantibodies should be further investigated, together with the histopathological correlates. PMID:27571185

Glycerol uptake is by passive diffusion in the heart but by facilitated transport in RBCs at high glycerol levels in cold acclimated rainbow smelt (Osmerus mordax).

PubMed

Clow, Kathy A; Driedzic, William R

2012-04-15

Rainbow smelt (Osmerus mordax) is a small fish that accumulates glycerol at low winter seawater temperatures. In laboratory-held fish, glycerol concentration typically reaches 225 mM in plasma and in all cells. Glycerol uptake by the heart and red blood cells (RBCs) was assessed by tracking [(14)C(U)]glycerol into the acid-soluble pool. In fish acclimated to 9-10°C a decrease in perfusion/incubation temperature from 8 to 1°C resulted in a decrease in glycerol uptake with a Q(10) of 3.2 in heart and 2.4 in RBCs. Acclimation to ∼1.5°C did not result in an adaptive enhancement of glycerol uptake as rates were unchanged in heart and RBCs. Glycerol uptake at 1°C was by passive diffusion in heart as evidenced by a linear relationship between glycerol uptake and extracellular glycerol concentration and a lack of inhibition by phloretin. In contrast, in RBCs, glycerol uptake with respect to glycerol concentration showed two linear relationships with a transition point around 50 mM extracellular glycerol. The slope of the second phase was much steeper and eliminated with the inclusion of phloretin. In RBCs from Atlantic salmon (Salmo salar), a related species that does not accumulate glycerol, glycerol uptake showed only a single linear curve and was not inhibited by phloretin. The data imply a strong facilitated component to glycerol uptake in rainbow smelt RBCs at high glycerol concentrations. We propose this is related to cyclic changes in RBC glycerol content involving a loss of glycerol at the gill and a reaccumulation during passage through the liver.

Optical tracer size differences allow quantitation of active pumping rate versus Stokes-Einstein diffusion in lymphatic transport

NASA Astrophysics Data System (ADS)

DSouza, Alisha V.; Marra, Kayla; Gunn, Jason R.; Samkoe, Kimberley S.; Pogue, Brian W.

2016-10-01

Lymphatic uptake of interstitially administered agents occurs by passive convective-diffusive inflow driven by interstitial concentration and pressure, while the downstream lymphatic transport is facilitated by active propulsive contractions of lymphatic vessel walls. Near-infrared fluorescence imaging in mice was used to measure these central components of lymphatic transport for the first time, using two different-sized molecules-methylene blue (MB) and fluorescence-labeled antibody immunoglobulin G (IgG)-IRDye 680RD. This work confirms the hypothesis that lymphatic passive inflow and active propulsion rates can be separated based upon the relative differences in Stokes-Einstein diffusion coefficient. This coefficient specifically affects the passive-diffusive uptake when the interstitial volume and pressure are constant. Parameters such as mean time-to-peak signal, overall fluorescence signal intensities, and number of active peristaltic pulses, were estimated from temporal imaging data. While the mean time to attain peak signal representative of diffusion-dominated flow in the lymph vessels was 0.6±0.2 min for MB and 8±6 min for IgG, showing a size dependence, the active propulsion rates were 3.4±0.8 pulses/min and 3.3±0.5 pulses/min, respectively, appearing size independent. The propulsion rates for both dyes decreased with clearance from the interstitial injection-site, indicating intrinsic control of the smooth muscles in response to interstitial pressure. This approach to size-comparative agent flow imaging of lymphatic function can enable noninvasive characterization of diseases related to uptake and flow in lymph networks.

Synthesis and hydriding properties of Li 2Mg(NH) 2

NASA Astrophysics Data System (ADS)

Markmaitree, Tippawan; Shaw, Leon L.

The phase pure Li 2Mg(NH) 2 has been synthesized via a dehydriding treatment of a ball milled 2LiNH 2 + MgH 2 mixture. This phase pure Li 2Mg(NH) 2 has been utilized to investigate its hydriding kinetics at the temperature range 180-220 °C. It is found that the hydriding process of Li 2Mg(NH) 2 is very sluggish even though it has favorable thermodynamic properties for near the ambient temperature operation. Holding at 200 °C for 10 h only results in 3.75 wt.% H 2 uptake. The detailed kinetic analysis reveals that the hydriding process of Li 2Mg(NH) 2 is diffusion-controlled. Thus, this study unambiguously indicates that the future direction to enhance the hydriding kinetics of this promising hydrogen storage material system should be to minimize the diffusion distance and increase the diffusion rate.

The effect of atmospheric sulfate reductions on diffuse radiation and photosynthesis in the eastern United States

NASA Astrophysics Data System (ADS)

Keppel-Aleks, G.; Washenfelder, R. A.

2016-12-01

Aerosol optical depth (AOD) has been shown to influence ecosystem carbon uptake by increasing the fraction of diffuse light, which increases photosynthesis over a greater fraction of the vegetated canopy. Several modeling studies have hypothesized that this effect may be a significant driver of the historical terrestrial carbon sink, and may therefore be an important climate feedback associated with changing air quality. In this study, we quantify the impact of anthropogenic aerosols on gross primary production (GPP) in the eastern United States. We focus on the eastern U.S. because 1) rapid decreases in SO2 emissions over the past two decades create an opportunity to examine the effects of reduced SO4 mass and aerosol optical depth; 2) SO2 emissions in the United States have been well quantified; 3) carbon fluxes within temperate ecosystems in the eastern United States have been well observed. We use accurate SO2 emission data for 1995-2013 in the Community Earth System Model (CESM) to determine trends in AOD, surface radiation, and photosynthesis. Between 1995 and 2013, U.S. SO2 emissions declined by over 70%, coinciding with observed AOD reductions of 3.0 ± 0.6% y-1 over the eastern U.S. In the Community Earth System Model (CESM), these trends cause diffuse light to decrease regionally by almost 0.6% y-1, leading to declines GPP of 0.07% y-1. Integrated over the analysis period and domain, this represents 0.5 PgC of omitted GPP. A separate upscaling calculation that used published relationships between GPP and diffuse light agreed with the CESM model results within 20%. The agreement between simulated and data-constrained upscaling results strongly suggests that anthropogenic sulfate trends have a small impact on carbon uptake in temperate forests due to scattered light.

An analytical procedure for the determination of aluminum used in antiperspirants on human skin in Franz™ diffusion cell.

PubMed

Guillard, Olivier; Fauconneau, Bernard; Favreau, Frédéric; Marrauld, Annie; Pineau, Alain

2012-04-01

A local case report of hyperaluminemia (aluminum concentration: 3.88 µmol/L) in a woman using an aluminum-containing antiperspirant for 4 years raises the question of possible transdermal uptake of aluminum salt as a future public health problem. Prior to studying the transdermal uptake of three commercialized cosmetic formulas, an analytical assay of aluminum (Al) in chlorohydrate form (ACH) by Zeeman Electrothermal Atomic Absorption Spectrophotometer (ZEAAS) in a clean room was optimized and validated. This analysis was performed with different media on human skin using a Franz(™) diffusion cell. The detection and quantification limits were set at ≤ 3 µg/L. Precision analysis as within-run (n = 12) and between-run (n = 15-68 days) yield CV ≤ 6%. The high analytic sensitivity (2-3 µg/L) and low variability should allow an in vitro study of the transdermal uptake of ACH.

Striatal dopamine neurotransmission: regulation of release and uptake

PubMed Central

Sulzer, David; Cragg, Stephanie J.; Rice, Margaret E.

2016-01-01

Dopamine (DA) transmission is governed by processes that regulate release from axonal boutons in the forebrain and the somatodendritic compartment in midbrain, and by clearance by the DA transporter, diffusion, and extracellular metabolism. We review how axonal DA release is regulated by neuronal activity and by autoreceptors and heteroreceptors, and address how quantal release events are regulated in size and frequency. In brain regions densely innervated by DA axons, DA clearance is due predominantly to uptake by the DA transporter, whereas in cortex, midbrain, and other regions with relatively sparse DA inputs, the norepinephrine transporter and diffusion are involved. We discuss the role of DA uptake in restricting the sphere of influence of DA and in temporal accumulation of extracellular DA levels upon successive action potentials. The tonic discharge activity of DA neurons may be translated into a tonic extracellular DA level, whereas their bursting activity can generate discrete extracellular DA transients. PMID:27141430

Membrane transport of amino acid enantiomers in protoscoleces of Echinococcus granulosus (Cestoda).

PubMed

Allen, J T; Arme, C

1991-02-01

Protoscoleces of Echinococcus granulosus absorb both L- and D-alanine. Concentration ratios exceed 1 with values for D-alanine exceeding those for the L-isomer, suggesting that both are absorbed by active mechanisms. Uptake of both isomers involves both diffusion and carrier-mediated components. Values for the diffusion component (Kd) for L- and D-alanine were 0.21 and 0.38 nmol mg-1 protein/1.5 min mM-1 respectively, and values for Kt, the transport constants, 0.17 mM and 0.21 mM respectively. Uptake of both isomers was inhibited competitively by a number of other amino acids.

Analysis of 11C-methionine uptake in low-grade gliomas and correlation with proliferative activity.

PubMed

Kato, T; Shinoda, J; Oka, N; Miwa, K; Nakayama, N; Yano, H; Maruyama, T; Muragaki, Y; Iwama, T

2008-11-01

The relationship of (11)C-methionine (MET) uptake and tumor activity in low-grade gliomas (those meeting the criteria for World Health Organization [WHO] grade II gliomas) remains uncertain. The aim of this study was to compare MET uptake in low-grade gliomas and to analyze whether MET positron-emission tomography (PET) can estimate tumor viability and provide evidence of malignant transformation. We studied glioma metabolic activity in 49 consecutive patients with newly diagnosed grade II gliomas by using MET PET before surgical resection. On MET PET, we measured tumor/normal brain uptake ratio (T/N ratio) in 21 diffuse astrocytomas (DAs), 12 oligodendrogliomas (ODs), and 16 oligoastrocytomas (OAs). We compared MET T/N ratio among these 3 tumors and investigated possible correlation with proliferative activity, as measured by Mib-1 labeling index (LI). MET T/N ratios of DA, OD, and OA were 2.11 +/- 0.87, 3.75 +/- 1.43, and 2.76 +/- 1.27, respectively. The MET T/N ratio of OD was significantly higher than that of DA (P < .005). In comparison of MET T/N ratios with the Mib-1 LI, a significant correlation was shown in DA (r = 0.63; P < .005) but not in OD and OA. MET uptake in DAs may be closely associated with tumor viability, which depends on increased amino acid transport by an activated carrier-mediated system. DAs with lower MET uptake were considered more quiescent lesions, whereas DA with higher MET uptake may act more aggressively.

Alveolar epithelial cell processing of nanoparticles activates autophagy and lysosomal exocytosis.

PubMed

Sipos, Arnold; Kim, Kwang-Jin; Chow, Robert H; Flodby, Per; Borok, Zea; Crandall, Edward D

2018-05-03

Utilizing confocal microscopy, we quantitatively assessed uptake, processing and egress of near infrared (NIR)-labeled carboxylated polystyrene nanoparticles (PNP) in live alveolar epithelial cells (AEC) during interactions with primary rat AEC monolayers (RAECM). PNP fluorescence intensity (content) and colocalization with intracellular vesicles in a cell were determined over the entire cell volume via z-stacking. Isotropic cuvette-based microfluorimetry was used to determine PNP concentration ([PNP]) from anisotropic measurements of PNP content assessed by confocal microscopy. Results showed that PNP uptake kinetics and steady state intracellular content decreased as diameter increased from 20 to 200 nm. For 20 nm PNP, uptake rate and steady state intracellular content increased with increased apical [PNP], but were unaffected by inhibition of endocytic pathways. Intracellular PNP increasingly co-localized with autophagosomes and/or lysosomes over time. PNP egress exhibited fast [Ca2+]-dependent release and a slower diffusion-like process. Inhibition of microtubule polymerization curtailed rapid PNP egress, resulting in elevated vesicular and intracellular PNP content. Interference with autophagosome formation led to slower PNP uptake and markedly decreased steady state intracellular content. At steady state, cytosolic [PNP] was higher than apical [PNP] and vesicular [PNP] (~80% of intracellular PNP content) exceeded both cytosolic [PNP] and intracellular [PNP]. These data are consistent with the hypotheses that (1) autophagic processing of nanoparticles is essential for maintenance of AEC integrity, (2) altered autophagy and/or lysosomal exocytosis may lead to AEC injury and (3) intracellular [PNP] in AEC is regulable, suggesting strategies for enhancement of nanoparticle-driven AEC gene/drug delivery and/or amelioration of AEC nanoparticle-related cellular toxicity.

Innovation Diffusion: Implications for Evaluation

ERIC Educational Resources Information Center

Ashley, Shena R.

2009-01-01

Whether looking at the spread and adoption of an intervention across a community, across multiple units, or within a single unit, an understanding of diffusion theory can help evaluators uncover patterns and impacts that might otherwise be overlooked. The theory alerts evaluators to examine why uptake of an intervention appeared different in…

Amino Acid Transporters and Release of Hydrophobic Amino Acids in the Heterocyst-Forming Cyanobacterium Anabaena sp. Strain PCC 7120.

PubMed

Pernil, Rafael; Picossi, Silvia; Herrero, Antonia; Flores, Enrique; Mariscal, Vicente

2015-04-23

Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that can use inorganic compounds such as nitrate or ammonium as nitrogen sources. In the absence of combined nitrogen, it can fix N2 in differentiated cells called heterocysts. Anabaena also shows substantial activities of amino acid uptake, and three ABC-type transporters for amino acids have been previously characterized. Seven new loci encoding predicted amino acid transporters were identified in the Anabaena genomic sequence and inactivated. Two of them were involved in amino acid uptake. Locus alr2535-alr2541 encodes the elements of a hydrophobic amino acid ABC-type transporter that is mainly involved in the uptake of glycine. ORF all0342 encodes a putative transporter from the dicarboxylate/amino acid:cation symporter (DAACS) family whose inactivation resulted in an increased uptake of a broad range of amino acids. An assay to study amino acid release from Anabaena filaments to the external medium was set up. Net release of the alanine analogue α-aminoisobutyric acid (AIB) was observed when transport system N-I (a hydrophobic amino acid ABC-type transporter) was engaged in the uptake of a specific substrate. The rate of AIB release was directly proportional to the intracellular AIB concentration, suggesting leakage from the cells by diffusion.

Role of (18)F-FDG PET-CT in Monitoring the Cyclophosphamide Induced Pulmonary Toxicity in Patients with Breast Cancer - 2 Case Reports.

PubMed

Taywade, Sameer Kamalakar; Kumar, Rakesh; Bhethanabhotla, Sainath; Bal, Chandrasekhar

2016-09-01

Drug induced pulmonary toxicity is not uncommon with the use of various chemotherapeutic agents. Cyclophosphamide is a widely used chemotherapeutic drug in the treatment of breast cancer. Although rare, lung toxicity has been reported with cyclophosphamide use. Detection of bleomycin induced pulmonary toxicity and pattern of (18)F-fluorodeoxyglucose ((18)F-FDG) uptake in lungs on fluorodeoxyglucose positron emission tomography-computed tomography ((18)F-FDG PET-CT) has been elicited in literature in relation to lymphoma. However, limited data is available regarding the role of (18)F-FDG PET-CT in monitoring drug induced pulmonary toxicity in breast cancer. We here present two cases of cyclophosphamide induced drug toxicity. Interim (18)F-FDG PET-CT demonstrated diffusely increased tracer uptake in bilateral lung fields in both these patients. Subsequently there was resolution of lung uptake on (18)F-FDG PET-CT scan post completion of chemotherapy. These patients did not develop significant respiratory symptoms during chemotherapy treatment and in follow up.

Application of the diffusive gradients in thin films technique for available potassium measurement in agricultural soils: effects of competing cations on potassium uptake by the resin gel.

PubMed

Zhang, Yulin; Mason, Sean; McNeill, Ann; McLaughlin, Michael J

2014-09-09

The utilization of Amberlite (IRP-69 ion-exchange resin, 100-500 wet mesh) as the binding phase in the diffusive gradients in thin films (DGT) technique has shown potential to improve the assessment of plant-available K in soils. The binding phase has recently been optimized by using a mixed Amberlite and ferrihydrite (MAF) gel which results in linear K uptake over extended deployment periods and in solutions with higher K concentrations. As restriction of K uptake by Ca on the Amberlite based resin gel has been previously proposed, potential competing effects of Ca(2+), Mg(2+) and NH(4+) on K uptake by the MAF gel were investigated. These cations had no effect on K elution efficiency which was 85%. However, K uptake by the MAF gel was restricted in the presence of competing cations in solution. Consequently, the diffusion coefficient of K decreased in the presence of cations compared to previous studies but was stable at 1.12×10(-5)cm(2)s(-1) at 25°C regardless of cation concentrations. Uptake of K by the DGT device was affected by the presence of excessive Ca in more than 30% of twenty typical Australian agricultural soils. However, this problem could be circumvented by using a shorter deployment time than the normal 24 h. Moderate correlation of concentrations of K extracted by DGT with Colwell K (extracted by NaHCO(3), R(2)=0.69) and NH4OAc K (R(2)=0.61) indicates that DGT measures a different pool of K in soils than that measured by the standard extractants used. In addition, the MAF gel has the ability to measure Ca and Mg simultaneously. Copyright © 2014 Elsevier B.V. All rights reserved.

Coupled elasticity-diffusion model for the effects of cytoskeleton deformation on cellular uptake of cylindrical nanoparticles.

PubMed

Wang, Jizeng; Li, Long

2015-01-06

Molecular dynamic simulations and experiments have recently demonstrated how cylindrical nanoparticles (CNPs) with large aspect ratios penetrate animal cells and inevitably deform cytoskeletons. Thus, a coupled elasticity-diffusion model was adopted to elucidate this interesting biological phenomenon by considering the effects of elastic deformations of cytoskeleton and membrane, ligand-receptor binding and receptor diffusion. The mechanism by which the binding energy drives the CNPs with different orientations to enter host cells was explored. This mechanism involved overcoming the resistance caused by cytoskeleton and membrane deformations and the change in configurational entropy of the ligand-receptor bonds and free receptors. Results showed that deformation of the cytoskeleton significantly influenced the engulfing process by effectively slowing down and even hindering the entry of the CNPs. Additionally, the engulfing depth was determined quantitatively. CNPs preferred or tended to vertically attack target cells until they were stuck in the cytoskeleton as implied by the speed of vertically oriented CNPs that showed much faster initial engulfing speeds than horizontally oriented CNPs. These results elucidated the most recent molecular dynamics simulations and experimental observations on the cellular uptake of carbon nanotubes and phagocytosis of filamentous Escherichia coli bacteria. The most efficient engulfment showed the stiffness-dependent optimal radius of the CNPs. Cytoskeleton stiffness exhibited more significant influence on the optimal sizes of the vertical uptake than the horizontal uptake. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Prediction of methyl mercury uptake by rice plants ( Oryza sativa L.) using the diffusive gradient in thin films technique.

PubMed

Liu, Jinling; Feng, Xinbin; Qiu, Guangle; Anderson, Christopher W N; Yao, Heng

2012-10-16

Rice consumption is the primary pathway for methyl mercury (MeHg) exposure at inland mercury (Hg) mining areas of SW China. Mechanistic information on MeHg accumulation in rice is, however, limited. The process of MeHg exchange between paddy soil and rice plants predominantly occurs in pore water. The detection of bioavailable MeHg in pore water is therefore important to predict MeHg uptake by rice plants ( Oryza sativa L.). This study investigated MeHg dynamics and spatial MeHg trends in pore water during the rice growing season using the diffusive gradient in thin films (DGT) technique and tested the ability of DGT to predict MeHg uptake by rice. The MeHg uptake flux from soil to rice plants via roots was significantly correlated with the DGT-measured MeHg flux (R = 0.853, p < 0.01). Our study implies that DGT can predict the bioavailability of MeHg in rice paddy soil and that the DGT method can provide quantitative description of the rate of uptake of this bioavailable MeHg. The DGT technique is demonstrated as a useful indicator of the likely ecotoxicological risk that might be apparent where paddy rice is grown in MeHg contaminated soil.

Gill structural change in response to turbidity has no effect on the oxygen uptake of a juvenile sparid fish.

PubMed

Cumming, H; Herbert, N A

2016-01-01

Turbidity as a result of increased suspended sediments in coastal waters is an environmental stress of worldwide concern. Recent research on fish suggests that detrimental changes to gill structure can occur in turbid waters, with speculation that these alterations diminish fitness variables, such as growth and development, by negatively impacting the O 2 uptake capacity (respiration) of fish. Specifically to address this unknown, the impact of turbid water on the gill structure, somatic growth rate and O 2 uptake rates of a juvenile sparid species ( Pagrus auratus ) was addressed following exposure to five different turbidity treatments (<10, 20, 40, 60 or 80 nephelometric turbidity units) for 30 days. Significant gill structural change was apparent with a progressive increase in turbidity and was quantified as a reduction in lamellar density, as well as an increase in basal hyperplasia, epithelial lifting and increased oxygen diffusion distance across the lamellae. The weight of control fish did not change throughout the experiment, but all fish exposed to turbid waters lost weight, and weight loss increased with nephelometric turbidity units, confirming that long-term turbidity exposure is detrimental to growth productivity. The growth of fish could be impacted in a variety of ways, but the specific hypothesis that structural alteration of the gills impairs O 2 uptake across the gills and limits growth fitness was not supported because there was no measurable difference in the standard metabolic rate, maximal metabolic rate, aerobic metabolic scope or critical oxygen saturation limit of fish measured in clear water after 30 days of exposure. Although impaired O 2 uptake as a result of structurally adjusted gills is unlikely to be the cause of poor fish growth, the exact mechanism by which growth productivity is affected in turbid conditions remains unclear and warrants further investigation.

Gill structural change in response to turbidity has no effect on the oxygen uptake of a juvenile sparid fish

PubMed Central

Cumming, H.; Herbert, N. A.

2016-01-01

Turbidity as a result of increased suspended sediments in coastal waters is an environmental stress of worldwide concern. Recent research on fish suggests that detrimental changes to gill structure can occur in turbid waters, with speculation that these alterations diminish fitness variables, such as growth and development, by negatively impacting the O2 uptake capacity (respiration) of fish. Specifically to address this unknown, the impact of turbid water on the gill structure, somatic growth rate and O2 uptake rates of a juvenile sparid species (Pagrus auratus) was addressed following exposure to five different turbidity treatments (<10, 20, 40, 60 or 80 nephelometric turbidity units) for 30 days. Significant gill structural change was apparent with a progressive increase in turbidity and was quantified as a reduction in lamellar density, as well as an increase in basal hyperplasia, epithelial lifting and increased oxygen diffusion distance across the lamellae. The weight of control fish did not change throughout the experiment, but all fish exposed to turbid waters lost weight, and weight loss increased with nephelometric turbidity units, confirming that long-term turbidity exposure is detrimental to growth productivity. The growth of fish could be impacted in a variety of ways, but the specific hypothesis that structural alteration of the gills impairs O2 uptake across the gills and limits growth fitness was not supported because there was no measurable difference in the standard metabolic rate, maximal metabolic rate, aerobic metabolic scope or critical oxygen saturation limit of fish measured in clear water after 30 days of exposure. Although impaired O2 uptake as a result of structurally adjusted gills is unlikely to be the cause of poor fish growth, the exact mechanism by which growth productivity is affected in turbid conditions remains unclear and warrants further investigation. PMID:27766155

Adenosine uptake by the isolated epithelium of guine pig jejunum.

PubMed

Kolassa, N; Stengg, R; Turnheim, K

1977-10-01

The uptake of [8-14C]adenosine by the isolated epithelium of guinea pig jejunum was faster than that of inosine, hypoxanthine, or adenine. The initial velocity of adenosine uptake from both the luminal and the antiluminal side of the epithelium exhibited saturation kinetics. The apparent Km, V, and passive permeability of luminal adenosine uptake were all lower than the corresponding values of antiluminal uptake. p-Nitrobenzyl-thioguanosine inhibited adenosine uptake from both the luminal and the antiluminal side, whilst hexobendine decreased the uptake only from the antiluminal side of the epithelium. The results suggest that adenosine enters the intestinal epithelium by a carrier-mediated process in addition to passive diffusion. The antiluminal transport system for adenosine seems similar to that of other tissues with respect to hexobendine inhibition; the luminal transport mechanism, however, exhibits different properties, being insensitive to hexobendine.

Carbonation and CO{sub 2} uptake of concrete

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Keun-Hyeok, E-mail: yangkh@kgu.ac.kr; Seo, Eun-A, E-mail: ssooaa@naver.com; Tae, Sung-Ho, E-mail: jnb55@hanyang.ac.kr

This study developed a reliable procedure to assess the carbon dioxide (CO{sub 2}) uptake of concrete by carbonation during the service life of a structure and by the recycling of concrete after demolition. To generalize the amount of absorbable CO{sub 2} per unit volume of concrete, the molar concentration of carbonatable constituents in hardened cement paste was simplified as a function of the unit content of cement, and the degree of hydration of the cement paste was formulated as a function of the water-to-cement ratio. The contribution of the relative humidity, type of finishing material for the concrete surface, andmore » the substitution level of supplementary cementitious materials to the CO{sub 2} diffusion coefficient in concrete was reflected using various correction factors. The following parameters varying with the recycling scenario were also considered: the carbonatable surface area of concrete crusher-runs and underground phenomena of the decreased CO{sub 2} diffusion coefficient and increased CO{sub 2} concentration. Based on the developed procedure, a case study was conducted for an apartment building with a principal wall system and an office building with a Rahmen system, with the aim of examining the CO{sub 2} uptake of each structural element under different exposure environments during the service life and recycling of the building. As input data necessary for the case study, data collected from actual surveys conducted in 2012 in South Korea were used, which included data on the surrounding environments, lifecycle inventory database, life expectancy of structures, and recycling activity scenario. Ultimately, the CO{sub 2} uptake of concrete during a 100-year lifecycle (life expectancy of 40 years and recycling span of 60 years) was estimated to be 15.5%–17% of the CO{sub 2} emissions from concrete production, which roughly corresponds to 18%–21% of the CO{sub 2} emissions from the production of ordinary Portland cement. - Highlights: • CO{sub 2} uptake assessment approach owing to the concrete carbonation is developed. • An equation to directly determine the absorbable CO{sub 2} amount in concrete is proposed. • The carbonatable surface area of concrete crusher-runs for CO{sub 2} uptake is ascertained. • This study provides typical data for uptake and emission of CO{sub 2} in concrete building.« less

Wildfire Effects on In-stream Nutrient Processing and Hydrologic Transport

NASA Astrophysics Data System (ADS)

Rhea, A.; Covino, T. P.; Rhoades, C.; Fegel, T.

2017-12-01

In many forests throughout the Western U.S., drought, climate change, and growing fuel loads are contributing to increased fire frequency and severity. Wildfires can influence watershed nutrient retention as they fundamentally alter the biological composition and physical structure in upland landscapes, riparian corridors, and stream channels. While numerous studies have documented substantial short-term increases in stream nutrient concentrations and export (particularly reactive nitrogen, N) following forest fires, the long-term implications for watershed nutrient cycling remain unclear. For example, recent work indicates that nitrate concentrations and export can remain elevated for a decade or more following wildfire, yet the controls on these processes are unknown. In this research, we use empirical observations from nutrient tracer injections, nutrient diffusing substrates, and continuous water quality monitoring to isolate biological and physical controls on nutrient export across a burn-severity gradient. Tracer results demonstrate substantial stream-groundwater exchange, but little biological nutrient uptake in burned streams. This in part explains patterns of elevated nutrient export. Paired nutrient diffusing substrate experiments allow us to further investigate shifts in N, phosphorus, and carbon limitation that may suppress post-fire stream nutrient uptake. By isolating the mechanisms that reduce the capacity of fire-affected streams to retain and transform nutrient inputs, we can better predict dynamics in post-fire water quality and help prioritize upland and riparian restoration.

Vertebral sarcoidosis: demonstration of bone involvement by computerized axial tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dinerstein, S.L.; Kovarsky, J.

1984-08-01

A report is given of a rare case of vertebral sarcoidosis with negative conventional spinal x-ray films, yet with typical cystic lesions of the spine found incidentally during abdominal computerized axial tomography (CAT). The patient was a 28-year-old black man, who was admitted for evaluation of a 1 1/2-year history of diffuse myalgias, intermittent fever to 102 F orally, bilateral hilar adenopathy, and leukopenia. A technetium polyphosphate bone scan revealed diffuse areas of increased uptake over the sternum, entire vertebral column, and pelvis. Conventional x-ray films of the cervical, thoracic, and lumbar spine, and an AP view of the pelvismore » were all normal. Chest x-ray film revealed only bilateral hilar adenopathy. During the course of an extensive negative evaluation for infection, an abdominal CAT scan was done, showing multiple, small, sclerotic-rimmed cysts at multiple levels of the lower thoracic and lumbar spine. Bone marrow biopsy revealed only changes consistent with anemia of chronic disease. Mediastinal lymph node biopsy revealed noncaseating granulomas. A tentative diagnosis of sarcoidosis was made, and treatment with prednisone, isoniazid and rifampin was begun. Within two weeks of initiation of prednisone therapy, the patient was symptom-free. A repeat technetium polyphosphate bone scan revealed only a small residual area of mildly increased uptake over the upper thoracic vertebrae.« less

Confocal analysis of hepatocellular long-chain fatty acid uptake.

PubMed

Elsing, C; Winn-Börner, U; Stremmel, W

1995-12-01

Transmembrane transport and cytosolic accumulation of fatty acids were investigated using confocal laser scanning microscopy (cLSM). A Zeiss LSM 310 system was used to determine the uptake of the fluorescent fatty acid derivative 12-(N-methyl)-N-[(7-nitrobenz-2-oxa-1,3- diazol-4-yl)amino]octadecanoic acid (12-NBD stearate) (C18) in single rat hepatocytes. Uptake was a saturable process with a Michaelis-Menten constant value of 68 nM. Initial uptake velocity was dependent on extracellular presence of albumin and beta-lactoglobulin. Absence of albumin reduced uptake to 32 +/- 16% (P < 0.01) of control values. In the presence of unlabeled stearate, uptake of 12-NBD stearate was lowered to 49 +/- 12% (P < 0.01). Ion substitution experiments showed no sodium dependency of uptake. Increase in membrane potential led to a pronounced accumulation of the fatty acid derivative within the plasma membrane and in the adjacent cytoplasmic compartment, whereas membrane depolarization had no effect on uptake rates. In separate experiments line scans through representative hepatocytes were analyzed to generate "x-t" plots. 12-NBD stearate showed a fluorescence pattern with prominent staining of the area of the plasma membrane and the adjacent cytoplasm, dependent on the presence of extracellular albumin. For the hepatocellular cytosolic accumulation process of 12-NBD stearate a diffusion constant of 22.2 +/- 6.2 x 10(-9) cm2/s was calculated. In contrast to the long-chain fatty acid derivative 12-NBD stearate, short (C5)- and medium (C11)-chain fatty acids revealed no membrane interaction with hepatocytes. Erythrocytes also lacked a membrane interaction process for 12-NBD stearate. In conclusion, it was demonstrated that cLSM is capable of directly evaluating the cellular fatty acid uptake process at a subcellular level.

Heat uptake in the Southern Ocean in a warmer, windier world: a process-based analysis using an AOGCM with an eddy-permitting ocean

NASA Astrophysics Data System (ADS)

Kuhlbrodt, T.; Gregory, J. M.

2016-02-01

About 90% of the anthropogenic increase in heat stored in the climate system is found the oceans. Therefore it is relevant to understand the details of ocean heat uptake. Here we present a detailed, process-based analysis of ocean heat uptake (OHU) processes in HiGEM1.2, an atmosphere-ocean general circulation model (AOGCM) with an eddy-permitting ocean component of 1/3° resolution. Similarly to various other models, HiGEM1.2 shows that the global heat budget is dominated by a downward advection of heat compensated by upward isopycnal diffusion. This upward isopycnal diffusion of heat is located mostly in the Southern Ocean (Fig. 1a).We compare the responses to a 4xCO2 forcing and an enhancement of the windstress forcing in the Southern Ocean. In line with the CMIP5 models, HiGEM1.2 shows a band of strong OHU in the mid-latitude Southern Ocean in the 4xCO2 run, which is mostly advective. By contrast, in the high-latitude Southern Ocean regions it is the suppression of convection that leads to OHU (Fig. 1b). In the enhanced windstress run, convection is strengthened at high Southern latitudes (Fig. 1c), leading to heat loss, while the magnitude of the OHU in the Southern mid-latitudes is very similar to the 4xCO2 results. Remarkably, there is only very small global OHU in the enhanced windstress run. The wind stress forcing just leads to a redistribution of heat. We relate the ocean changes at high southern latitudes to the effect of climate change on the Antarctic Circumpolar Current (ACC). It weakens in the 4xCO2 run and strengthens in the wind stress run. The weakening is due to a narrowing of the ACC, caused by an expansion of the Weddell Gyre, and a flattening of the isopycnals, which are explained by a combination of the wind stress forcing and increased precipitation. The presentation will also try to clarify the definitions of terms like "advective", "diffusive" and "eddy-induced" when used for observed and modelled (at various resolutions) ocean heat uptake processes. Fig. 1: Horizontally averaged temperature tendency diagnostics for the high-latitude Southern Ocean, for (a) the control run, (b) the 4xCO2 anomalies and (c) the windstress anomalies. Both axes are scaled according to a power law. "VM"- vertical mixing, which includes convection ("conv").

Kinetic study of heterogeneous reaction of deliquesced NaCl particles with gaseous HNO3 using particle-on-substrate stagnation flow reactor approach.

PubMed

Liu, Y; Cain, J P; Wang, H; Laskin, A

2007-10-11

Heterogeneous reaction kinetics of gaseous nitric acid with deliquesced sodium chloride particles NaCl(aq) + HNO3(g) --> NaNO3(aq) + HCl(g) were investigated with a novel particle-on-substrate stagnation flow reactor (PS-SFR) approach under conditions, including particle size, relative humidity, and reaction time, directly relevant to the atmospheric chemistry of sea salt particles. Particles deposited onto an electron microscopy grid substrate were exposed to the reacting gas at atmospheric pressure and room temperature by impingement via a stagnation flow inside the reactor. The reactor design and choice of flow parameters were guided by computational fluid dynamics to ensure uniformity of the diffusion flux to all particles undergoing reaction. The reaction kinetics was followed by observing chloride depletion in the particles by computer-controlled scanning electron microscopy with energy-dispersive X-ray analysis (CCSEM/EDX). The validity of the current approach was examined first by conducting experiments with median dry particle diameter D(p) = 0.82 microm, 80% relative humidity, particle loading densities 4 x 10(4)

Use of a chemical equilibrium model to describe surface properties and uptake of cadmium, strontium, and lead by Chlorella (UTEX 252)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassett, J.M.

1988-01-01

Metal-aquatic biota interactions are important in both natural and engineered systems. In this study, the uptake of cadmium, strontium and lead by the unicellular green alga Chlorella (UTEX 252) was investigated. Variables included metal concentration, pH, and ionic strength. Data gathered included dry weights (mg/l), cell counts (cells/ml), electrophoretic mobilities (EPMs, {mu}m/sec/V/cm) of metal-free and metal-exposed cells, and metal uptake - difference in concentration in filtrate of cell-metal and cell-free metal solutions. Derived data included cell volumes and surface area, uptake on a {mu}M/m{sup 2} basis, {zeta}-potentials, diffuse layer potentials and charge densities. Typical uptake values were 1.1, 5.2, andmore » 6 {mu}M/m{sup 2} for Cd, Pb, and Sr, respectively, from solutions of pH 6, ionic strength 0.02M, and metal concentration 10{sup {minus}4} M. Cell EPMs were insensitive to metal; under certain conditions, however, (pM > 4, pH > 8), cadmium exposed cells exhibited a reversal in surface charge from negative to positive. The chemical equilibrium model MINEQL1 + STANFORD was used to model algal surface properties and metal uptake. Input data included site pK, density, and {Delta}pK, estimated from EPM-pH data. The model described surface properties of Chlorella (UTEX 252) as judged by a close fit of {zeta}-potentials and model-derived diffuse layer potentials. Metal uptake was modelled by adjusting site density and/or metal-surface site equilibrium constants. Attempts to model surface properties and metal uptake simultaneously were not successful.« less

Influence of physical state on the ozonolysis of shikimic acid

NASA Astrophysics Data System (ADS)

Steimer, Sarah; Krieger, Ulrich; Lampimäki, Markus; Peter, Thomas; Ammann, Markus

2014-05-01

Atmospheric aerosols are an important focus of environmental research due to their effect on climate, air quality and human health. They undergo continuous transformation, changing their physical and chemical properties. Recent findings show that secondary organic aerosol (SOA) particles can form amorphous solids and semi-solids under atmospheric conditions [1]. Since such physical states are highly viscous, diffusivity within the bulk decreases. The decrease in mass transport could slow down chemical reactions, thereby increasing the lifetime of the organic compounds involved. First indications of such behavior were recently shown for reaction of thin protein films with ozone [2], formation of organonitrogen from ammonia uptake to α-pinene secondary organic material [3] and reaction of SOA-coated benzo[a]pyrene with ozone [4]. In this study, we investigated the influence of physical state on the ozonolysis of shikimic acid. Said carboxylic acid is a constituent of biomass burning aerosols and used here as a proxy for oxygenated organic material. Its viscosity was adjusted by varying the humidity of the system between 0% and 92% RH, assuming correlation between the two parameters since water acts as a plasticizer. The system was probed with three complementary techniques: an electrodynamic balance (EDB), measuring the response of single particles to changes in humidity, coated wall flow tube measurements, where uptake of ozone is measured via loss from the gas phase and in situ X-ray microspectroscopy on single particles, where oxidation of the bulk can be observed. Additionally, a kinetic model was used to facilitate data analysis. EDB measurements showed clear evidence of humidity dependent glass formation and correlation of water content and water diffusivity. The dependence of the ozonolysis on relative humidity was observed with both flow tube and microspectroscopy measurements. The coated wall flow tube experiments showed a long term, gradually changing ozone uptake over more than 15 hours, the magnitude of which varied over nearly two orders between lowest and highest humidity. It was possible to separate the uptake into two distinct kinetic regimes, the first of which displayed a Langmuir-Hinshelwood type behavior regarding the ozone gas phase concentration. Microspectroscopy showed that the speed at which the characteristic double bond peak of shikimic acid disappeared was humidity dependent. The measured dependence of the reaction kinetics on humidity supports the hypothesis that the uptake coefficient is highly dependent on the diffusion coefficients of ozone and/or shikimic acid in the organic film. [1] Virtanen, A., et al., An amorphous solid state of biogenic secondary organic aerosol particles. Nature, 2010. 467(7317): p. 824-827. [2] Shiraiwa, M., et al., Gas uptake and chemical aging of semisolid organic aerosol particles. Proceedings of the National Academy of Sciences of the United States of America, 2011. 108(27): p. 11003-11008. [3] Kuwata, M. and Martin, S. T., Phase of atmospheric secondary organic material affects its reactivity. Proceedings of the National Academy of Sciences of the United States of America, 109(43): p. 17354-17359. [4] Zhou, S., et al., Kinetic limitations in gas-particle reactions arising from slow diffusion in secondary organic aerosol. Faraday Discussions, 2013. 165: p. 391-406.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Selin, Victor; Ankner, John F.; Sukhishvili, Svetlana A.

Here in this paper, we report on the role of molecular diffusivity in the formation of nonlinearly growing polyelectrolyte multilayers (nlPEMs). Electrostatically bound polyelectrolyte multilayers were assembled from poly(methacrylic acid) (PMAA) as a polyanion and quaternized poly(2-(dimethylamino)ethyl methacrylate) (QPC) as a polycation. Film growth as measured by ellipsometry was strongly dependent on the time allowed for each polymer deposition step, suggesting that the diffusivities of the components are crucial in controlling the rate of film growth. Uptake of polyelectrolytes within nlPEMs was relatively slow and occurred on time scales ranging from minutes to hours, depending on the film thickness. Spectroscopicmore » ellipsometry measurements with nlPEM films exposed to aqueous solutions exhibited high (severalfold) degrees of film swelling and different swelling values for films exposed to QPC or PMAA solutions. FTIR spectroscopy showed that the average ionization of film-assembled PMAA increased upon binding of QPC and decreased upon binding of PMAA, in agreement with the charge regulation mechanism for weak polyelectrolytes. The use of neutron reflectometry (NR) enabled quantification of chain intermixing within the film, which was drastically enhanced when longer times were allowed for polyelectrolyte deposition. Diffusion coefficients of the polycation derived from the uptake rates of deuterated chains within hydrogenated films were of the order of 10 –14 cm 2/s, i.e., 5–6 orders of magnitude smaller than those found for diffusion of free polymer chains in solution. Exchange of the polymer solutions to buffer inhibited film intermixing. Taken together, these results contribute to understanding the mechanism of the growth of nonlinear polyelectrolyte multilayers and demonstrate the possibility of controlling film intermixing, which is highly desirable for potential future applications.« less

A novel passive water sampler for in situ sampling of antibiotics.

PubMed

Chen, Chang-Er; Zhang, Hao; Jones, Kevin C

2012-05-01

Passive water sampling has several advantages over active methods; it provides time-integrated data, can save on time and cost compared to active methods, and yield high spatial resolution data through co-deployment of simple, cheap units. However, one problem with many sampler designs in current use is that their uptake rates for trace substances of interest are flow-rate dependent, thereby requiring calibration data and other information to enable water concentrations to be derived from the mass per sampler. However, the 'family' of samplers employing the principle of diffusive gradients in thin films (DGT) provides an in situ means of quantitatively measuring labile species in aquatic systems without field calibration. So far, this technique has only been tested and applied in inorganic substances: metals, radionuclides, nutrients, etc. Design and applications of DGT to trace organic contaminants ('o-DGT') would be of widespread interest. This study describes the laboratory testing and performance characteristics of o-DGT, with the antibiotic sulfamethoxazole (SMX) as a model compound and XAD18 as the novel binding agent. o-DGT uptake of SMX increased with time and decreased with diffusion layer thickness, confirming the principle for SMX. XAD18 showed sufficiently high capacity for SMX for routine field applications. o-DGT measurement of SMX was independent of pH (6-9) and ionic strength (0.001-0.1 M) and not affected by flow rate once above static conditions. The diffusion coefficient of SMX in the sampler was measured using an independent diffusion cell and information is presented to allow temperature correction and derivation of aqueous concentrations from deployed samplers. The potential use of o-DGT for in situ measurement of pharmaceutical antibiotics is confirmed by this study and applications are briefly discussed.

Chemotaxis migration and morphogenesis of living colonies.

PubMed

Ben Amar, Martine

2013-06-01

Development of forms in living organisms is complex and fascinating. Morphogenetic theories that investigate these shapes range from discrete to continuous models, from the variational elasticity to time-dependent fluid approach. Here a mixture model is chosen to describe the mass transport in a morphogenetic gradient: it gives a mathematical description of a mixture involving several constituents in mechanical interactions. This model, which is highly flexible can incorporate many biological processes but also complex interactions between cells as well as between cells and their environment. We use this model to derive a free-boundary problem easier to handle analytically. We solve it in the simplest geometry: an infinite linear front advancing with a constant velocity. In all the cases investigated here as the 3 D diffusion, the increase of mitotic activity at the border, nonlinear laws for the uptake of morphogens or for the mobility coefficient, a planar front exists above a critical threshold for the mobility coefficient but it becomes unstable just above the threshold at long wavelengths due to the existence of a Goldstone mode. This explains why sparsely bacteria exhibit dendritic patterns experimentally in opposition to other colonies such as biofilms and epithelia which are more compact. In the most unstable situation, where all the laws: diffusion, chemotaxis driving and chemoattractant uptake are linear, we show also that the system can recover a dynamic stability. A second threshold for the mobility exists which has a lower value as the ratio between diffusion coefficients decreases. Within the framework of this model where the biomass is treated mainly as a viscous and diffusive fluid, we show that the multiplicity of independent parameters in real biologic experimental set-up may explain varieties of observed patterns.

Correlation of the apparent diffusion coefficient and the standardized uptake value in neoplastic lesions: a meta-analysis.

PubMed

Shen, Guohua; Ma, Huan; Liu, Bin; Ren, Pengwei; Kuang, Anren

2017-12-01

Diffusion-weighted imaging and fluorine-18-fluorodeoxyglucose PET are increasingly being recognized as feasible oncological techniques. The apparent diffusion coefficient (ADC) measured by diffusion-weighted imaging and the standardized uptake value (SUV) from fluorine-18-fluorodeoxyglucose PET have similar clinical applications. The aim of this study was to assess the correlation between these two parameters in various cancers. Several major databases were searched for eligible studies. The correlation coefficient (ρ) values were pooled in a random-effects model. Begg's test was used to analyze the existence of publication bias and the sources of heterogeneity were explored in subgroup analyses on the basis of study design, diagnostic method, scanning modality, and tumor type. Thirty-five articles were accepted. The pooled ρ value of all of the accepted studies was -0.30 (95% confidence interval: -0.33 to -0.27), and notable heterogeneity was present (I=69.4%, P<0.001), which indicated a relatively weak negative correlation. The pooled ρ values were -0.26, -0.33, -0.32, and -0.33 for the SUVmax/ADCmean, SUVmax/ADCmin, SUVmean/ADCmean, and SUVmean/ADCmin relationships, respectively. The study design and diagnostic method were potential sources of heterogeneity. Lung cancer showed a stronger correlation (ρ=-0.42) than head and neck cancer (ρ=-0.27), cervical cancer (ρ=-0.21), and breast cancer (ρ=-0.23). A Begg's test indicated no significant publication bias among the accepted studies (P>0.05). The two functional parameters of ADC and SUV showed a very weak inverse correlation, which may contribute toward a sophisticated characterization of tumor biology. However, the findings require further validation with trials with large samples and different tumor types.

Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 2. Assessing Charge Site Location and Isotope Scrambling

NASA Astrophysics Data System (ADS)

Khakinejad, Mahdiar; Ghassabi Kondalaji, Samaneh; Donohoe, Gregory C.; Valentine, Stephen J.

2016-03-01

Ion mobility spectrometry (IMS) coupled with gas-phase hydrogen deuterium exchange (HDX)-mass spectrometry (MS) and molecular dynamic simulations (MDS) has been used for structural investigation of anions produced by electrospraying a sample containing a synthetic peptide having the sequence KKDDDDDIIKIIK. In these experiments the potential of the analytical method for locating charge sites on ions as well as for utilizing collision-induced dissociation (CID) to reveal the degree of deuterium uptake within specific amino acid residues has been assessed. For diffuse (i.e., more elongated) [M - 2H]2- ions, decreased deuterium content along with MDS data suggest that the D4 and D6 residues are charge sites, whereas for the more diffuse [M - 3H]3- ions, the data suggest that the D4, D7, and the C-terminus are deprotonated. Fragmentation of mobility-selected, diffuse [M - 2H]2- ions to determine deuterium uptake at individual amino acid residues reveals a degree of deuterium retention at incorporation sites. Although the diffuse [M - 3H]3- ions may show more HD scrambling, it is not possible to clearly distinguish HD scrambling from the expected deuterium uptake based on a hydrogen accessibility model. The capability of the IMS-HDX-MS/MS approach to provide relevant details about ion structure is discussed. Additionally, the ability to extend the approach for locating protonation sites on positively-charged ions is presented.

NMR 1D-imaging of water infiltration into mesoporous matrices.

PubMed

Le Feunteun, Steven; Diat, Olivier; Guillermo, Armel; Poulesquen, Arnaud; Podor, Renaud

2011-04-01

It is shown that coupling nuclear magnetic resonance (NMR) 1D-imaging with the measure of NMR relaxation times and self-diffusion coefficients can be a very powerful approach to investigate fluid infiltration into porous media. Such an experimental design was used to study the very slow seeping of pure water into hydrophobic materials. We consider here three model samples of nuclear waste conditioning matrices which consist in a dispersion of NaNO(3) (highly soluble) and/or BaSO(4) (poorly soluble) salt grains embedded in a bitumen matrix. Beyond studying the moisture progression according to the sample depth, we analyze the water NMR relaxation times and self-diffusion coefficients along its 1D-concentration profile to obtain spatially resolved information on the solution properties and on the porous structure at different scales. It is also shown that, when the relaxation or self-diffusion properties are multimodal, the 1D-profile of each water population is recovered. Three main levels of information were disclosed along the depth-profiles. They concern (i) the water uptake kinetics, (ii) the salinity and the molecular dynamics of the infiltrated solutions and (iii) the microstructure of the water-filled porosities: open networks coexisting with closed pores. All these findings were fully validated and enriched by NMR cryoporometry experiments and by performing environmental scanning electronic microscopy observations. Surprisingly, results clearly show that insoluble salts enhance the water progression and thereby increase the capability of the material to uptake water. Copyright © 2011 Elsevier Inc. All rights reserved.

Decreases in maximal oxygen uptake following long-duration spaceflight: Role of convective and diffusive O2 transport mechanisms.

PubMed

Ade, C J; Broxterman, R M; Moore, A D; Barstow, T J

2017-04-01

We have previously predicted that the decrease in maximal oxygen uptake (V̇o 2max ) that accompanies time in microgravity reflects decrements in both convective and diffusive O 2 transport to the mitochondria of the contracting myocytes. The aim of this investigation was therefore to quantify the relative changes in convective O 2 transport (Q̇o 2 ) and O 2 diffusing capacity (Do 2 ) following long-duration spaceflight. In nine astronauts, resting hemoglobin concentration ([Hb]), V̇o 2max , maximal cardiac output (Q̇ Tmax ), and differences in arterial and venous O 2 contents ([Formula: see text]-[Formula: see text]) were obtained retrospectively for International Space Station Increments 19-33 (April 2009-November 2012). Q̇o 2 and Do 2 were calculated from these variables via integration of Fick's Principle of Mass Conservation and Fick's Law of Diffusion. V̇o 2max significantly decreased from pre- to postflight (-53.9 ± 45.5%, P = 0.008). The significant decrease in Q̇ Tmax (-7.8 ± 9.1%, P = 0.05), despite an unchanged [Hb], resulted in a significantly decreased Q̇o 2 (-11.4 ± 10.5%, P = 0.02). Do 2 significantly decreased from pre- to postflight by -27.5 ± 24.5% ( P = 0.04), as did the peak [Formula: see text]-[Formula: see text] (-9.2 ± 7.5%, P = 0.007). With the use of linear regression analysis, changes in V̇o 2max were significantly correlated with changes in Do 2 ( R 2  = 0.47; P = 0.04). These data suggest that spaceflight decreases both convective and diffusive O 2 transport. These results have practical implications for future long-duration space missions and highlight the need to resolve the specific mechanisms underlying these spaceflight-induced changes along the O 2 transport pathway. NEW & NOTEWORTHY Long-duration spaceflight elicited a significant decrease in maximal oxygen uptake. Given the adverse physiological adaptations to microgravity along the O 2 transport pathway that have been reported, an integrative approach to the determinants of postflight maximal oxygen uptake is needed. We demonstrate that both convective and diffusive oxygen transport are decreased following ~6 mo International Space Station missions. Copyright © 2017 the American Physiological Society.

Need-based activation of ammonium uptake in Escherichia coli

PubMed Central

Kim, Minsu; Zhang, Zhongge; Okano, Hiroyuki; Yan, Dalai; Groisman, Alexander; Hwa, Terence

2012-01-01

The efficient sequestration of nutrients is vital for the growth and survival of microorganisms. Some nutrients, such as CO2 and NH3, are readily diffusible across the cell membrane. The large membrane permeability of these nutrients obviates the need of transporters when the ambient level is high. When the ambient level is low, however, maintaining a high intracellular nutrient level against passive back diffusion is both challenging and costly. Here, we study the delicate management of ammonium (NH4+/NH3) sequestration by E. coli cells using microfluidic chemostats. We find that as the ambient ammonium concentration is reduced, E. coli cells first maximize their ability to assimilate the gaseous NH3 diffusing into the cytoplasm and then abruptly activate ammonium transport. The onset of transport varies under different growth conditions, but always occurring just as needed to maintain growth. Quantitative modeling of known interactions reveals an integral feedback mechanism by which this need-based uptake strategy is implemented. This novel strategy ensures that the expensive cost of upholding the internal ammonium concentration against back diffusion is kept at a minimum. PMID:23010999

Influence of wind-speed on short-duration NO2 measurements using Palmes and Ogawa passive diffusion samplers

NASA Astrophysics Data System (ADS)

Masey, Nicola; Gillespie, Jonathan; Heal, Mathew R.; Hamilton, Scott; Beverland, Iain J.

2017-07-01

We assessed the precision and accuracy of nitrogen dioxide (NO2) concentrations over 2-day, 3-day and 7-day exposure periods measured with the following types of passive diffusion samplers: standard (open) Palmes tubes; standard Ogawa samplers with commercially-prepared Ogawa absorbent pads (Ogawa[S]); and modified Ogawa samplers with absorbent-impregnated stainless steel meshes normally used in Palmes tubes (Ogawa[P]). We deployed these passive samplers close to the inlet of a chemiluminescence NO2 analyser at an urban background site in Glasgow, UK over 32 discrete measurement periods. Duplicate relative standard deviation was <7% for all passive samplers. The Ogawa[P], Ogawa[S] and Palmes samplers explained 93%, 87% and 58% of temporal variation in analyser concentrations respectively. Uptake rates for Palmes and Ogawa[S] samplers were positively and linearly associated with wind-speed (P < 0.01 and P < 0.05 respectively). Computation of adjusted uptake rates using average wind-speed observed during each sampling period increased the variation in analyser concentrations explained by Palmes and Ogawa[S] estimates to 90% and 92% respectively, suggesting that measurements can be corrected for shortening of diffusion path lengths due to wind-speed to improve the accuracy of estimates of short-term NO2 exposure. Monitoring situations where it is difficult to reliably estimate wind-speed variations, e.g. across multiple sites with different unknown exposures to local winds, and personal exposure monitoring, are likely to benefit from protection of these sampling devices from the effects of wind, for example by use of a mesh or membrane across the open end. The uptake rate of Ogawa[P] samplers was not associated with wind-speed resulting in a high correlation between estimated concentrations and observed analyser concentrations. The use of Palmes meshes in Ogawa[P] samplers reduced the cost of sampler preparation and removed uncertainty associated with the unknown manufacturing process for the commercially-prepared collection pads.

Effect of CO2 absorption on ion and water mobility in an anion exchange membrane

NASA Astrophysics Data System (ADS)

Peng, Jing; Roy, Asa L.; Greenbaum, Steve G.; Zawodzinski, Thomas A.

2018-03-01

We report the measured water uptake, density, ionic conductivity and water transport properties in Tokuyama A201 membrane in OH-, HCO3- and Cl- forms. The water uptake of the AEM varies with anion type in the order λ(OH-) > λ(HCO3-) > λ(Cl-) for samples equilibrated with the same water vapor activity (aw). The conductivity of the AEM is reduced by absorption of CO2. Pulsed-field gradient nuclear magnetic resonance (PFG-NMR) measurements were utilized to characterize the diffusivity of water and HCO3- ion. The anion diffusion coefficient and membrane conductivity are used to probe the applicability of the Nernst-Einstein equation in these AEMs.

[Eco-physiological investigations on wild and cultivated plants in the Negev Desert : II. The influence of climatic factors on carbon dioxide exchange and transpiration at the end of the dry period].

PubMed

Schulze, E -D; Lange, O L; Koch, W

1972-12-01

The influence of climatic factors on net photosynthesis, dark respiration and transpiration was investigated in the Negev Desert at the end of the dry summer period when plant water stress was at a maximum. Species studied included: dominant species of the natural vegetation (Artemisia herba-alba, Hammada scoparia, Noaea mucronata, Reaumuria negevensis, Salsola inermis, Zygophyllum dumosum), cultivated plants receiving rainfall and run-off water during the winter season in the run-off farm Avdat (Prunus armeniaca, Vitis vinifera), and irrigated cultivated plants receiving additional water during the summer season (Citrullus colocynthis, Datura metel). 1. Light saturation of net photosynthesis was reached at 60-90 klx conforming to the high solar radiation intensities of the desert. 2. Maximum rates of CO 2 uptake per unit of dry weight for the irrigated mesomorphic plants was ten times that of the wild plants. However, in comparison to the other species, maximal rates of CO 2 uptake for wild plants were higher when calculated on a leaf area basis than when represented on a dry weight basis. Maximum rates of net photosynthesis per unit chlorophyll content for some of the wild plants (Salsola and Noaea) were comparable to those of the cultivated Vitis and irrigated Citrullus and Datura, Hammada exhibited even higher rates than Prunus. This demonstrates the great photosynthetic capacity of the wild plants even at the end of the dry season. 3. The upper temperature compensation point for net photosynthesis of the wild plants was unusually high as an adaptation to the temperatures of the habitat. Compensation points higher than 49°C exceed the maxima known so far for other flowering species. Maximum rates of net photosynthesis of Hammada were measured when the temperature of the photosynthetic organs was 37°C; at 49°C photosynthesis was only reduced by 50%. 4. Leaf temperature affects plant gas exchange by influencing stomatal aperture. Diffusion resistance of leaves to water vapour was reduced at low temperatures and increased at high temperatures. Reduction of net photosynthesis and transpiration of desert plants at midday may, therefore, be the result of temperature-induced stomatal closure. The possible influence of peristomatal transpiration on stomatal aperture is also discussed. Peristomatal transpiration is directly related to the vapour pressure gradient between the leaf mesophyll and the ambient air which increases with increasing temperatures. 5. Diffusion resistance to water vapour was reduced at high temperatures approaching the limits of heat resistance, due to increased stomatal aperture. This resulted in greater transpirational cooling. 6. Under conditions of increased leaf water stress, diffusion resistance increased, either by sudden stomatal closure at specific threshold values of water stress or through a continuous increase in resistance. This increased resistance is coupled with decreases in transpiration and photosynthesis. 7. In several plant species increased diffusion resistance during the course of the day caused decreased transpiration without a corresponding decrease in photosynthesis. Under these conditions, the ratio of CO 2 uptake to transpiration became more favourable as the day progressed. The possibility that this favourable gas exchange response is the result of an increased mesophyll resistance to water vapour loss is discussed.

Uptake of divalent ions (Mn+2 and Ca+2) by heat-set whey protein gels.

PubMed

Oztop, Mecit H; McCarthy, Kathryn L; McCarthy, Michael J; Rosenberg, Moshe

2012-02-01

Divalent salts are used commonly for gelation of polymer molecules. Calcium, Ca(+2), is one of the most common divalent ions that is used in whey protein gels. Manganese, Mn(+2), is also divalent, but paramagnetic, enhancing relaxation decay rates in magnetic resonance imaging (MRI) and can be used as a probe to understand the behavior of Ca(+2) in whey protein gels. The objective of this study was to investigate the diffusion of Ca(+2) and Mn(+2) ions in heat-set whey protein gels by using MRI and nuclear magnetic resonance (NMR) relaxometry. Whey protein gels were immersed in solutions containing MnCl(2) and CaCl(2) at neutral pH. Images obtained with gels immersed in MnCl(2) solution revealed a relaxation sink region in the gel's surface and the thickness of the region increased with time. These "no signal" regions in the MR images were attributed to uptake of Mn(+2) by the gel. Results obtained with CaCl(2) solution indicated that since Ca(+2) did not have the paramagnetic effect, the regions where Ca(+2) diffused into the gel exhibited a slight decrease in signal intensity. The relaxation spectrums exhibited 3 populations of protons, for gels immersed in MnCl(2) solution, and 2 populations for gels in CaCl(2) solution. No significant change in T(2) distributions was observed for the gels immersed in CaCl(2) solution. The results demonstrated that MRI and NMR relaxometry can be used to understand the diffusion of ions into the whey protein gel, which is useful for designing gels of different physical properties for controlled release applications. Design of food systems for delivery of bioactive compounds requires knowledge of diffusion rates and structure. Utilizing magnetic resonance imaging the diffusion rates of ions can be measured. Relaxation spectra could yield information concerning molecular interactions. © 2012 Institute of Food Technologists®

Cancer: a profit-driven biosystem?

PubMed

Deisboeck, Thomas S

2008-08-01

The argument is made that solid malignant tumors behave as profit-driven biological systems in that they expand their nutrient-uptaking surface to increase energetic revenue, at a comparably low metabolic cost. Within this conceptual framework, cancer cell migration is a critical mechanism as it maximizes systemic surface expansion while minimizing diffusion distance. Treating these tumor systems with adjuvant anti-proliferative regimen only should increase the energetic net gain of the viable cancer cells left behind, hence would facilitate tumor recurrence. Therapeutic attempts to better control tumor (re)growth should therefore aim primarily at containing its surface expansion, thus reducing its energetic revenue, or increasing its metabolic costs or better yet, both.

Cancer: A profit-driven biosystem ?

PubMed Central

Deisboeck, Thomas S.

2008-01-01

The argument is made that solid malignant tumors behave as profit-driven biological systems in that they expand their nutrient-uptaking surface to increase energetic revenue, at a comparably low metabolic cost. Within this conceptual framework, cancer cell migration is a critical mechanism as it maximizes systemic surface expansion while minimizing diffusion distance. Treating these tumor systems with adjuvant anti-proliferative regimen only should increase the energetic net gain of the viable cancer cells left behind, hence would facilitate tumor recurrence. Therapeutic attempts to better control tumor (re)growth should therefore aim primarily at containing its surface expansion, thus reducing its energetic revenue, or increasing its metabolic costs or better yet, both. PMID:18420354

Experimental and Modeling Study of Solvent Diffusion in PDMS for Nanoparticle-Polymer Cosuspension Imprint Lithography.

PubMed

Gervasio, Michelle; Lu, Kathy; Davis, Richey

2015-09-15

This study is the first that focuses on solvent migration in a polydimethylsiloxane (PDMS) stamp during the imprint lithography of ZnO-poly(methyl methacrylate) (PMMA) hybrid suspensions. Using suspensions with varying solids loading levels and ZnO/PMMA ratios, the uptake of the anisole solvent in the stamp is evaluated as a function of time. Laser confocal microscopy is employed as a unique technique to measure the penetration depth of the solvent into the stamp. The suspension solids loading affects the anisole saturation depth in the PDMS stamp. For the suspensions with low solids loading, the experimental data agree with the model for non-Fickian diffusion through a rubbery-elastic polymer. For the suspensions with high solids loading, the data agree more with a sigmoidal diffusion curve, reflecting the rubbery-viscous behavior of a swelling polymer. This difference is due to the degree of swelling in the PDMS. Higher solids loadings induce more swelling because the rate of anisole diffusing into the stamp is increased, likely due to the less dense buildup of the solids as the suspension dries.

Prognostic Value of Bone Marrow Tracer Uptake Pattern in Baseline PET Scans in Hodgkin Lymphoma: Results from an International Collaborative Study.

PubMed

Zwarthoed, Colette; El-Galaly, Tarec Cristoffer; Canepari, Maria; Ouvrier, Matthieu John; Viotti, Julien; Ettaiche, Marc; Viviani, Simonetta; Rigacci, Luigi; Trentin, Livio; Rusconi, Chiara; Luminari, Stefano; Cantonetti, Maria; Bolis, Silvia; Borra, Anna; Darcourt, Jacques; Salvi, Flavia; Subocz, Edyta; Tajer, Joanna; Kulikowski, Waldemar; Malkowski, Bogdan; Zaucha, Jan Maciej; Gallamini, Andrea

2017-08-01

PET/CT-ascertained bone marrow involvement (BMI) constitutes the single most important reason for upstaging by PET/CT in Hodgkin lymphoma (HL). However, BMI assessment in PET/CT can be challenging. This study analyzed the clinicopathologic correlations and prognostic meaning of different patterns of bone marrow (BM) 18 F-FDG uptake in HL. Methods: One hundred eighty newly diagnosed early unfavorable and advanced-stage HL patients, all scanned at baseline and after 2 adriamycin-bleomycin-vinblastine-dacarbazine (ABVD) courses with 18 F-FDG PET, enrolled in 2 international studies aimed at assessing the role of interim PET scanning in HL, were retrospectively included. Patients were treated with ABVD × 4-6 cycles and involved-field radiation when needed, and no treatment adaptation on interim PET scanning was allowed. Two masked reviewers independently reported the scans. Results: Thirty-eight patients (21.1%) had focal lesions (fPET + ), 10 of them with a single (unifocal) and 28 with multiple (multifocal) BM lesions. Fifty-three patients (29.4%) had pure strong (>liver) diffuse uptake (dPET + ) and 89 (48.4%) showed no or faint (≤liver) BM uptake (nPET + ). BM biopsy was positive in 6 of 38 patients (15.7%) for fPET + , in 1 of 53 (1.9%) for dPET + , and in 5 of 89 (5.6%) for nPET + dPET + was correlated with younger age, higher frequency of bulky disease, lower hemoglobin levels, higher leukocyte counts, and similar diffuse uptake in the spleen. Patients with pure dPET + had a 3-y progression-free survival identical to patients without any 18 F-FDG uptake (82.9% and 82.2%, respectively, P = 0.918). However, patients with fPET+ (either unifocal or multifocal) had a 3-y progression-free survival significantly inferior to patients with dPET+ and nPET+ (66.7% and 82.5%, respectively, P = 0.03). The κ values for interobserver agreement were 0.84 for focal uptake and 0.78 for diffuse uptake. Conclusion: We confirmed that 18 F-FDG PET scanning is a reliable tool for BMI assessment in HL, and BM biopsy is no longer needed for routine staging. Moreover, the interobserver agreement for BMI in this study proved excellent and only focal 18 F-FDG BM uptake should be considered as a harbinger of HL. © 2017 by the Society of Nuclear Medicine and Molecular Imaging.

Designing herbicide formulation characteristics to maximize efficacy and minimize rice injury in paddy environments.

PubMed

Cryer, S A; Mann, R K; Erhardt-Zabik, S; Keeney, F N; Handy, P R

2001-06-01

Mathematical descriptors, coupled with experimental observations, are used to quantify differential uptake of an experimental herbicide in Japonica and Indica rice (Oryza sativa, non-target) and barnyardgrass (Echinochloa crus-galli, target). Partitioning, degradation, plant uptake and metabolism are described using mass-balance conservation equations in the form of kinetic approximations. Estimated environmental concentrations, governed by the pesticide formulation, are described using superimposed analytical solutions for the one-dimensional diffusion equation in spherical coordinates and by a finite difference representation of the two-dimensional diffusion equation in Cartesian coordinates. Formulation attributes from granules include active ingredient release rates, particle sizes, pesticide loading, and granule spacing. The diffusion model for pesticide transport is coupled with the compartment model to follow the fate and transport of a pesticide from its initial application location to various environmental matrices of interest. Formulation effects, partitioning and degradation in the various environmental matrices, differential plant uptake and metabolism, and dose-response information for plants are accounted for. This novel model provides a mechanism for selecting formulation delivery systems that optimize specific attributes (such as weed control or the therapeutic index) for risk-assessment procedures. In this report we describe how this methodology was used to explore the factors affecting herbicide efficacy and to define an optimal release rate for a granule formulation.

Effect of Pore Clogging on Kinetics of Lead Uptake by Clinoptilolite.

PubMed

Inglezakis; Diamandis; Loizidou; Grigoropoulou

1999-07-01

The kinetics of lead-sodium ion exchange using pretreated natural clinoptilolite are investigated, more specifically the influence of agitation (0, 210, and 650 rpm) on the limiting step of the overall process, for particle sizes of 0.63-0.8 and 0.8-1 mm at ambient temperature and initial lead solutions of 500 mg l-1 without pH adjustment. The isotopic exchange model is found to fit the ion exchange process. Particle diffusion is shown to be the controlling step for both particle sizes under agitation, while in the absence of agitation film diffusion is shown to control. The ion exchange process effective diffusion coefficients are calculated and found to depend strongly on particle size in the case of agitation at 210 rpm and only slightly on particle size at 650 rpm. Lead uptake rates are higher for smaller particles only at rigorous agitation, while at mild agitation the results are reversed. These facts are due to partial clogging of the pores of the mineral during the grinding process. This is verified through comparison of lead uptake rates for two samples of the same particle size, one of which is rigorously washed for a certain time before being exposed to the ion exchange. Copyright 1999 Academic Press.

Quantitative diffusion and swelling kinetic measurements using large-angle interferometric refractometry.

PubMed

Saunders, John E; Chen, Hao; Brauer, Chris; Clayton, McGregor; Chen, Weijian; Barnes, Jack A; Loock, Hans-Peter

2015-12-07

The uptake and release of sorbates into films and coatings is typically accompanied by changes of the films' refractive index and thickness. We provide a comprehensive model to calculate the concentration of the sorbate from the average refractive index and the film thickness, and validate the model experimentally. The mass fraction of the analyte partitioned into a film is described quantitatively by the Lorentz-Lorenz equation and the Clausius-Mosotti equation. To validate the model, the uptake kinetics of water and other solvents into SU-8 films (d = 40-45 μm) were explored. Large-angle interferometric refractometry measurements can be used to characterize films that are between 15 μm to 150 μm thick and, Fourier analysis, is used to determine independently the thickness, the average refractive index and the refractive index at the film-substrate interface at one-second time intervals. From these values the mass fraction of water in SU-8 was calculated. The kinetics were best described by two independent uptake processes having different rates. Each process followed one-dimensional Fickian diffusion kinetics with diffusion coefficients for water into SU-8 photoresist film of 5.67 × 10(-9) cm(2) s(-1) and 61.2 × 10(-9) cm(2) s(-1).

Kinetic Modelling of Infection Tracers [18F]FDG, [68Ga]Ga-Citrate, [11C]Methionine, and [11C]Donepezil in a Porcine Osteomyelitis Model.

PubMed

Jødal, Lars; Jensen, Svend B; Nielsen, Ole L; Afzelius, Pia; Borghammer, Per; Alstrup, Aage K O; Hansen, Søren B

2017-01-01

Positron emission tomography (PET) is increasingly applied for infection imaging using [ 18 F]FDG as tracer, but uptake is unspecific. The present study compares the kinetics of [ 18 F]FDG and three other PET tracers with relevance for infection imaging. A juvenile porcine osteomyelitis model was used. Eleven pigs underwent PET/CT with 60-minute dynamic PET imaging of [ 18 F]FDG, [ 68 Ga]Ga-citrate, [ 11 C]methionine, and/or [ 11 C]donepezil, along with blood sampling. For infectious lesions, kinetic modelling with one- and two-tissue-compartment models was conducted for each tracer. Irreversible uptake was found for [ 18 F]FDG and [ 68 Ga]Ga-citrate; reversible uptake was found for [ 11 C]methionine (two-tissue model) and [ 11 C]donepezil (one-tissue model). The uptake rate for [ 68 Ga]Ga-citrate was slow and diffusion-limited. For the other tracers, the uptake rate was primarily determined by perfusion (flow-limited uptake). Net uptake rate for [ 18 F]FDG and distribution volume for [ 11 C]methionine were significantly higher for infectious lesions than for correspondingly noninfected tissue. For [ 11 C]donepezil in pigs, labelled metabolite products appeared to be important for the analysis. The kinetics of the four studied tracers in infection was characterized. For clinical applications, [ 18 F]FDG remains the first-choice PET tracer. [ 11 C]methionine may have a potential for detecting soft tissue infections. [ 68 Ga]Ga-citrate and [ 11 C]donepezil were not found useful for imaging of osteomyelitis.

Application of nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, UV-Visible spectroscopy and kinetic modeling for elucidation of adsorption chemistry in uptake of tetracycline by zeolite beta.

PubMed

Kang, Jin; Liu, Huijuan; Zheng, Yu-Ming; Qu, Jiuhui; Chen, J Paul

2011-02-01

Extensive usage of tetracycline has resulted in its contamination in surface water and groundwater. The adsorption of tetracycline on zeolite beta was systematically investigated for the decontamination of the antibiotic polluted water in this study. Ninety percent of uptake by the zeolite beta occured in 0.25h, and the adsorption equilibrium was obtained within 3h, which was well described by an intraparticle diffusion model. The adsorption generally increased when pH was increased from 4.0 to 5.0, and then decreased significantly as the pH was further increased, which was caused by the pH-dependent speciation of tetracycline and surface charge of zeolite beta. Both Freundlich and Langmuir equations well described the adsorption isotherm. A thermodynamic analysis showed that the sorption process was spontaneous and endothermic. Aluminum atoms in the zeolite played a crucial role in the uptake; the adsorption increased with the increasing aluminum content in zeolite. The UV-Visible spectroscopy study showed that the spectra of tetracycline changed upon the interaction with zeolite beta, which could be ascribed to the formation of complexes of tetracycline and aluminum atoms in the zeolite surface. Nuclear magnetic resonance spectroscopy study further confirmed the participation of Al in the tetracycline adsorption. Fourier transform infrared spectroscopy studies showed that the amino functional groups in tetracycline were involved in the complexation with the zeolite surface. Copyright © 2010 Elsevier Inc. All rights reserved.

On wettability of shale rocks.

PubMed

Roshan, H; Al-Yaseri, A Z; Sarmadivaleh, M; Iglauer, S

2016-08-01

The low recovery of hydraulic fracturing fluid in unconventional shale reservoirs has been in the centre of attention from both technical and environmental perspectives in the last decade. One explanation for the loss of hydraulic fracturing fluid is fluid uptake by the shale matrix; where capillarity is the dominant process controlling this uptake. Detailed understanding of the rock wettability is thus an essential step in analysis of loss of the hydraulic fracturing fluid in shale reservoirs, especially at reservoir conditions. We therefore performed a suit of contact angle measurements on a shale sample with oil and aqueous ionic solutions, and tested the influence of different ion types (NaCl, KCl, MgCl2, CaCl2), concentrations (0.1, 0.5 and 1M), pressures (0.1, 10 and 20MPa) and temperatures (35 and 70°C). Furthermore, a physical model was developed based on the diffuse double layer theory to provide a framework for the observed experimental data. Our results show that the water contact angle for bivalent ions is larger than for monovalent ions; and that the contact angle (of both oil and different aqueous ionic solutions) increases with increase in pressure and/or temperature; these increases are more pronounced at higher ionic concentrations. Finally, the developed model correctly predicted the influence of each tested variable on contact angle. Knowing contact angle and therefore wettability, the contribution of the capillary process in terms of water uptake into shale rocks and the possible impairment of hydrocarbon production due to such uptake can be quantified. Copyright © 2016 Elsevier Inc. All rights reserved.

Cyanobacterial carbon concentrating mechanisms facilitate sustained CO2 depletion in eutrophic lakes

NASA Astrophysics Data System (ADS)

Morales-Williams, Ana M.; Wanamaker, Alan D., Jr.; Downing, John A.

2017-06-01

Phytoplankton blooms are increasing in frequency, intensity, and duration in aquatic ecosystems worldwide. In many eutrophic lakes, these high levels of primary productivity correspond to periods of CO2 depletion in surface waters. Cyanobacteria and other groups of phytoplankton have the ability to actively transport bicarbonate (HCO3-) across their cell membrane when CO2 concentrations are limiting, possibly giving them a competitive advantage over algae not using carbon concentrating mechanisms (CCMs). To investigate whether CCMs can maintain phytoplankton bloom biomass under CO2 depletion, we measured the δ13C signatures of dissolved inorganic carbon (δ13CDIC) and phytoplankton particulate organic carbon (δ13Cphyto) in 16 mesotrophic to hypereutrophic lakes during the ice-free season of 2012. We used mass-balance relationships to determine the dominant inorganic carbon species used by phytoplankton under CO2 stress. We found a significant positive relationship between phytoplankton biomass and phytoplankton δ13C signatures as well as a significant nonlinear negative relationship between water column ρCO2 and isotopic composition of phytoplankton, indicating a shift from diffusive uptake to active uptake by phytoplankton of CO2 or HCO3- during blooms. Calculated photosynthetic fractionation factors indicated that this shift occurs specifically when surface water CO2 drops below atmospheric equilibrium. Our results indicate that active HCO3- uptake via CCMs may be an important mechanism in maintaining phytoplankton blooms when CO2 is depleted. Further increases in anthropogenic pressure, eutrophication, and cyanobacteria blooms are therefore expected to contribute to increased bicarbonate uptake to sustain primary production.

Contribution of aerial hyphae of Aspergillus oryzae to respiration in a model solid-state fermentation system.

PubMed

Rahardjo, Yovita S P; Weber, Frans J; le Comte, E Paul; Tramper, Johannes; Rinzema, Arjen

2002-06-05

Oxygen transfer is for two reasons a major concern in scale-up and process control in industrial application of aerobic fungal solid-state fermentation (SSF): 1) heat production is proportional to oxygen uptake and it is well known that heat removal is one of the main problems in scaled-up fermenters, and 2) oxygen supply to the mycelium on the surface of or inside the substrate particles may be hampered by diffusion limitation. This article gives the first experimental evidence that aerial hyphae are important for fungal respiration in SSF. In cultures of A. oryzae on a wheat-flour model substrate, aerial hyphae contributed up to 75% of the oxygen uptake rate by the fungus. This is due to the fact that A. oryzae forms very abundant aerial mycelium and diffusion of oxygen in the gas-filled pores of the aerial hyphae layer is rapid. It means that diffusion limitation in the densely packed mycelium layer that is formed closer to the substrate surface and that has liquid-filled pores is much less important for A. oryzae than was previously reported for R. oligosporus and C. minitans. It also means that the overall oxygen uptake rate for A. oryzae is much higher than the oxygen uptake rate that can be predicted in the densely packed mycelium layer for R. oligosporus and C. minitans. This would imply that cooling problems become more pronounced. Therefore, it is very important to clarify the physiological role of aerial hyphae in SSF. Copyright 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 539-544, 2002.

Diffusive gradient in thin FILMS (DGT) compared with soil solution and labile uranium fraction for predicting uranium bioavailability to ryegrass.

PubMed

Duquène, L; Vandenhove, H; Tack, F; Van Hees, M; Wannijn, J

2010-02-01

The usefulness of uranium concentration in soil solution or recovered by selective extraction as unequivocal bioavailability indices for uranium uptake by plants is still unclear. The aim of the present study was to test if the uranium concentration measured by the diffusive gradient in thin films (DGT) technique is a relevant substitute for plant uranium availability in comparison to uranium concentration in the soil solution or uranium recovered by ammonium acetate. Ryegrass (Lolium perenne L. var. Melvina) is grown in greenhouse on a range of uranium spiked soils. The DGT-recovered uranium concentration (C(DGT)) was correlated with uranium concentration in the soil solution or with uranium recovered by ammonium acetate extraction. Plant uptake was better predicted by the summed soil solution concentrations of UO(2)(2+), uranyl carbonate complexes and UO(2)PO(4)(-). The DGT technique did not provide significant advantages over conventional methods to predict uranium uptake by plants. Copyright 2009 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skyhar, M.J.; Danzig, L.A.; Hargens, A.R.

Twelve freshly killed mature male rabbits were used to study the effects of continuous passive motion (CPM) on regional and overall nonvascular nutritional pathways of the anterior cruciate ligament (ACL). One hundred fifty microcuries of /sup 35/S-sulfate was injected intraarticularly into each knee joint. The right knee underwent CPM for 1 hour, while the left knee remained immobilized. Both knee joints were then isolated and immediately frozen. The ACLs were removed while still mostly frozen, and sectioned into anterior, middle, and posterior thirds for the six rabbits in Group 1, and proximal, middle, and distal thirds for the six rabbitsmore » in Group 2. In addition, quadriceps tendon samples were harvested from each limb of three rabbits. After appropriate processing, all samples were counted in a scintillation counter, and counts per minute per milligram of tissue were calculated. There was significantly higher uptake in rest extremity ACLs compared to CPM extremity ACLs (P = 0.0001). No significant difference was demonstrated in regional uptake comparing respective thirds of the ACL in either Group 1 or Group 2. Quadriceps tendon uptake trended higher in the limbs exposed to CPM compared to those maintained at rest (P = 0.14). The ACL uses diffusion as a primary nutrient pathway. CPM does not increase nutrient uptake by the ACL in this avascular model, but CPM may facilitate transport of metabolites out of the joint. No regional differences in uptake within the ACL occurred in either group.« less

Carrier-mediated uptake of nobiletin, a citrus polymethoxyflavonoid, in human intestinal Caco-2 cells.

PubMed

Kimura, Osamu; Ohta, Chiho; Koga, Nobuyuki; Haraguchi, Koichi; Kato, Yoshihisa; Endo, Tetsuya

2014-07-01

The mechanism of intestinal absorption of nobiletin (NBL) was investigated using Caco-2 cells. The uptake of NBL from the apical membranes of Caco-2 cells was rapid and temperature-dependent and the presence of metabolic inhibitors, NaN3 and carbonylcyanide p-trifluoromethoxyphenylhydrazone, did not cause a decrease in NBL uptake. The relationship between the initial uptake of NBL and its concentration was saturable, suggesting the involvement of a carrier-mediated process. The Km and uptake clearance (Vmax/Km) values for NBL were 50.6 and 168.1μl/mg protein/min, respectively. This clearance value was about 9-fold greater than that of the non-saturable uptake clearance (Kd: 18.5μl/mg protein/min). The presence of structurally similar compounds, such as quercetin and luteolin, competitively inhibited NBL uptake. These results suggest that uptake of NBL from the apical membranes of Caco-2 cells is mainly mediated by an energy-independent facilitated diffusion process. Copyright © 2013 Elsevier Ltd. All rights reserved.

Functional imaging in hyperinsulinemic hypoglycemia after gastric bypass surgery for morbid obesity.

PubMed

de Heide, Loek J M; Glaudemans, Andor W J M; Oomen, Peter H N; Apers, Jan A; Totté, Eric R E; van Beek, André P

2012-06-01

Hyperinsulinemic hypoglycemia after Roux-en-Y gastric bypass (RYGB) has been increasingly reported. It is induced by β-cell hyperplasia often referred to as nesidioblastosis. Positron emission tomography (PET) with [11C]-5-hydroxytryptophan ((11)C-HTP) and 6-[18F]fluoro-3,4-dihydroxy-l-phenylalanine ((18)F-DOPA) has been successfully applied to image neuroendocrine tumors. No data are available of the usefulness of these functional imaging techniques in post-RYGB in this new endocrine disorder, neither for diagnostic purposes nor for follow-up. We present a patient with post-RYGB hypoglycemia who underwent (11)C-HTP and (18)F-DOPA PET scintigraphy for diagnostic purposes and to evaluate the effect of additional laparoscopic adjustable banding of the pouch as a surgical therapy for this disorder. We describe a woman with biochemically confirmed post-RYGB hypoglycemia who showed diffuse uptake of the (11)C-HTP and (18)F-DOPA tracers in the entire pancreas. After failure of dietary and medical treatment options, she underwent a laparoscopic adjustable banding for pouch dilatation. Subjective improvement was noted, which coincided with decreased uptake of (18)F-DOPA and (11)C-HTP in the head of the pancreas. Functional imaging by (18)F-DOPA- and (11)C-HTP-PET can accurately visualize diffuse endocrine pancreatic activity in post-gastric bypass hyperinsulinemic hypoglycemia. Both (11)C-HTP- and (18)F-DOPA-PET imaging appear to have a similar diagnostic performance in the presented case, and uptake of both tracers potentially relates to disease activity after surgical intervention.

Modelling bioaccumulation of semi-volatile organic compounds (SOCs) from air in plants based on allometric principles.

PubMed

Steyaert, Nils L L; Hauck, Mara; Van Hulle, Stijn W H; Hendriks, A Jan

2009-10-01

A model was developed for gaseous plant-air exchange of semi-volatile organic compounds. Based on previous soil-plant modelling, uptake and elimination kinetics were scaled as a function of plant mass and octanol-air partition ratios. Exchange of chemicals was assumed to be limited by resistances encountered during diffusion through a laminar boundary layer of air and permeation through the cuticle of the leaf. The uptake rate constant increased and the elimination rate constant decreased with the octanol-air partition ratio both apparently levelling off at high values. Differences in kinetics between species could be explained by their masses. Validation on independent data showed that bio-concentration factors of PCBs, chlorobenzenes and other chemicals were predicted well by the model. For pesticides, polycyclic aromatic hydrocarbons and dioxins deviations occurred.

Sea-level haemoglobin concentration is associated with greater exercise capacity in Tibetan males at 4200 m.

PubMed

Wagner, P D; Simonson, T S; Wei, G; Wagner, H E; Wuren, T; Qin, G; Yan, M; Ge, R L

2015-11-01

What is the topic of this review? Recent developments link relatively lower hemoglobin concentration in Tibetans at high altitude to exercise capacity and components of oxygen transport. What advances does it highlight? Haemoglobin concentration (ranging from 15.2 to 22.9 g dl(-1) ) in Tibetan males was negatively associated with peak oxygen (O2 ) uptake per kilogram, cardiac output and muscle O2 diffusion conductance. Most variance in the peak O2 uptake per kilogram of Tibetan males was attributed to cardiac output, muscle diffusional conductance and arterial partial pressure of CO2 . The mechanisms underlying these differences in oxygen transport in Tibetans require additional analyses. Despite residence at >4000 m above sea level, many Tibetan highlanders, unlike Andean counterparts and lowlanders at altitude, exhibit haemoglobin concentration ([Hb]) within the typical sea-level range. Genetic adaptations in Tibetans are associated with this relatively low [Hb], yet the functional relevance of the lower [Hb] remains unknown. To address this, we examined each major step of the oxygen transport cascade [ventilation (VE), cardiac output (QT) and diffusional conductance in lung (DL) and muscle (DM)] in Tibetan males at maximal exercise on a cycle ergometer. Ranging from 15.2 to 22.9 g dl(-1) , [Hb] was negatively associated with peak O2 uptake per kilogram (r = -0.45, P < 0.05) and both cardiac output (QT/kg: r = -0.54, P < 0.02) and muscle O2 diffusion conductance (DM/kg: r = -0.44, P < 0.05) but not ventilation, arterial partial pressure of O2 or pulmonary diffusing capacity. Most variance in peak O2 uptake per kilogram was attributed to QT, DM and arterial partial pressure of CO2 (r(2)  = 0.90). In summary, lack of polycythaemia in Tibetans is associated with increased exercise capacity, which is explained by elevated cardiac, muscle and, to a small extent, ventilatory responses rather than pulmonary gas exchange. Whether lower [Hb] is the cause or result of these changes in O2 transport or is causally unrelated will require additional study. © 2015 The Authors. Experimental Physiology © 2015 The Physiological Society.

D-amphetamine (A)-induced dopamine (DA) release is not strictly dependent on newly-synthesized transmitter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, E.; Cubeddu, L.

1986-03-05

A is thought to exert its stimulant effects by releasing DA from a newly synthesized transmitter pool. This hypothesis was evaluated directly by measuring the basal efflux and electrically-evoked release of endogenous DA and dihydroxyphenylacetic acid (DOPAC). In striatal slices from reserpine-treated rabbits A increased DA efflux, reduced DOPAC efflux, and inhibited electrically-evoked /sup 3/H-ACh release in a concentration-dependent manner. These effects could not be mimicked by inhibition of neuronal uptake or MAO, but were blocked by inhibition of DA synthesis or neuronal uptake, and were potentiated by inhibition of MAO. In slices with intact vesicular transmitter stores A inducedmore » DA efflux was 2-fold greater than that seen in slices having no vesicular stores. Inhibition of DA synthesis reduced A-induced DA efflux by 60%, but had little effect on the ability of A to inhibit /sup 3/H-ACh release. A also increased the electrical stimulation-evoked overflow of DA (an effect which was attenuated slightly by synthesis inhibition), and potently inhibited DOPAC overflow. These results suggest that: 1) A facilitates efflux of axoplasmic DA by an accelerated exchange diffusion mechanism. The releasable axoplasmic pool is derived from newly synthesized and vesicular transmitter pools; 2) postsynaptic indices of transmitter release may be misleading; and 3) A increases electrically-evoked DA release possibly by inhibiting neuronal uptake.« less

Bridging evidence, policy, and practice to strengthen health systems for improved maternal and newborn health in Pakistan.

PubMed

Hirose, Atsumi; Hall, Sarah; Memon, Zahid; Hussein, Julia

2015-11-25

Policy and decision making should be based on evidence, but translating evidence into policy and practice is often sporadic and slow. It is recognised that the relationship between research and policy uptake is complex and that dissemination of research findings is necessary, but insufficient, for policy uptake. Political, social, and economic context, use of (credible) data and dialogues between and across networks of researchers and policymakers play important roles in evidence uptake. Advocacy is the process of mobilising political and public opinions to achieve specific aims and its role is crucial in mobilising key actors to push for policy uptake. Advocacy and research groups (i.e. those who would like to see research evidence used by policymakers) may use different approaches and tools to stimulate the diffusion of research findings. The use of mass- and social media, communication with study participants, and the involvement of stakeholders at the early stages of research development are examples of the approaches that can be employed to stimulate diffusion of evidence and increase evidence uptake. The Research and Advocacy Fund (RAF) for Maternal and Newborn Health (MNH) worked within the health system context in Pakistan with the aim of espousing the principles of evidence, advocacy, and dissemination to improve MNH outcomes. The articles included in this special issue are outputs of RAF and highlight where RAF's approaches contributed to MNH policy reforms. The papers discuss critical health system issues facing Pakistan, including service delivery components, demand creation, equitable access, transportation interventions for improved referrals, availability of medicines and equipment, and health workforce needs. In addition to these tangible elements, the health system 'software', i.e. the power and the political and social contexts, is also represented in the collection. These articles highlight three considerations for the future: the growing importance of implementation research, the crucial need for participation and ownership, and the recognition that policymaking can be 'informed' by rather than 'based-on' evidence. The future challenge will be to continue the momentum RAF has created and to welcome a new era of health, wealth, and growth for Pakistan.

Mathematical modelling of the uptake and transport of salt in plant roots.

PubMed

Foster, Kylie J; Miklavcic, Stanley J

2013-11-07

In this paper, we present and discuss a mathematical model of ion uptake and transport in roots of plants. The underlying physical model of transport is based on the mechanisms of forced diffusion and convection. The model can take account of local variations in effective ion and water permeabilities across the major tissue regions of plant roots, represented through a discretized coupled system of governing equations including mass balance, forced diffusion, convection and electric potential. We present simulation results of an exploration of the consequent enormous parameter space. Among our findings we identify the electric potential as a major factor affecting ion transport across, and accumulation in, root tissues. We also find that under conditions of a constant but realistic level of bulk soil salt concentration and plant-soil hydraulic pressure, diffusion plays a significant role even when convection by the water transpiration stream is operating. Crown Copyright © 2013 Published by Elsevier Ltd. All rights reserved.

Sensitivity of technetium-99m-pyrophosphate scintigraphy in diagnosing cardiac amyloidosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Falk, R.H.; Lee, V.W.; Rubinow, A.

1983-03-01

To determine the value of technetium-99m-pyrophosphate myocardial scintigraphy in the diagnosis of amyloid heart disease this procedure was prospectively performed in 20 consecutive patients with biopsy-proven primary amyloidosis. Eleven patients had echocardiographic abnormalities compatible with amyloid cardiomyopathy, 9 of whom had congestive heart failure. Diffuse myocardial pyrophosphate uptake was of equal or greater intensity than that of the ribs in 9 of the 11 patients with echocardiograms suggestive of amyloidosis, but in only 2 of the 9 with normal echocardiograms, despite abnormal electrocardiograms (p less than 0.01). Increased wall thickness measured by M-mode echocardiography correlated with myocardial pyrophosphate uptake (rmore » . 0.68, p less than 0.01). None of 10 control patients with nonamyloid, nonischemic heart disease had a strongly positive myocardial pyrophosphate uptake. Thus, myocardial technetium-99m-pyrophosphate scanning is a sensitive and specific test for the diagnosis of cardiac amyloidosis in patients with congestive heart failure of obscure origin. It does not appear to be of value for the early detection of cardiac involvement in patients with known primary amyloidosis without echocardiographic abnormalities.« less

Uptake of 18F-DCFPyL in Paget's Disease of Bone, an Important Potential Pitfall in Clinical Interpretation of PSMA PET Studies.

PubMed

Rowe, Steven P; Deville, Curtiland; Paller, Channing; Cho, Steve Y; Fishman, Elliot K; Pomper, Martin G; Ross, Ashley E; Gorin, Michael A

2015-12-01

Prostate-specific membrane antigen (PSMA)-targeted PET imaging is an emerging technique for evaluating patients with prostate cancer (PCa) in a variety of clinical contexts. As with any new imaging modality, there are interpretive pitfalls that are beginning to be recognized. In this image report, we describe the findings in a 63-year-old male with biochemically recurrent PCa after radical prostatectomy who was imaged with 18 F-DCFPyL, a small molecule inhibitor of PSMA. Diffuse radiotracer uptake was noted throughout the sacrum, corresponding to imaging findings on contrast-enhanced CT, bone scan, and pelvic MRI consistent with Paget's disease of bone. The uptake of 18 F-DCFPyL in Paget's disease is most likely due to hyperemia and increased radiotracer delivery. In light of the overlap in patients affected by PCa and Paget's, it is important for nuclear medicine physicians and radiologists interpreting PSMA PET/CT scans to be aware of the potential for this diagnostic pitfall. Correlation to findings on conventional imaging such as diagnostic CT and bone scan can help confirm the diagnosis.

Differences in influence patterns between groups predicting the adoption of a solar disinfection technology for drinking water in Bolivia.

PubMed

Moser, Stephanie; Mosler, Hans-Joachim

2008-08-01

The lack of safe drinking water is one of the major problems faced by developing countries. The consequences of contaminated water are diseases such as diarrhea, one of the main causes of infant mortality. Because of its simplicity, solar water-disinfection technology provides a good way of treating water at the household level. Despite its obvious advantages and considerable promotional activities, this innovation has had rather a slow uptake. We conducted a field survey in which 644 households in Bolivia were interviewed in order to gain insights on motivations that resulted in adopting the technology. The aim was to examine possible differences in the predictors for adopting this technology during the diffusion process using the theory of innovation diffusion. Our findings indicate that early adoption was predicted by increased involvement in the topic of drinking water and that adoption in the middle of the diffusion process was predicted by increased involvement by opinion leaders and by recognition of a majority who supported the technology. Finally, late adoption was predicted by recognition that a majority had already adopted. Suggestions for future promotional strategies are outlined.

Assessing trace element diffusion models in fossil and sub-fossil bone

NASA Astrophysics Data System (ADS)

Suarez, C. A.; Kohn, M. J.

2012-12-01

Three different diffusion models have been proposed to explain trace element uptake during fossilization of bone: diffusion-adsorption (DA), diffusion-recrystallization (DR), and double-medium diffusion (DMD). Theoretically, differences in trace element profiles, particularly the rare earth elements (REE) and U, can discriminate among these possibilities. In this study, we tested which model best explains natural samples by analyzing trace element profiles in natural bone using laser-ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS). Fossil bones ranging in age from a few ka to over 100 Ma were analyzed along traverses from the outer cortical edge to the inner marrow cavity margin. Forty major, minor and trace elements were analyzed, notably Ca, P, transition metals, Sr, Ba, REE, U, Th and Pb. Spatial and analytical resolutions were ~10 μm and ~100 ppb respectively. Many specimens show commonly observed exponential decreases in REE from the outer edge and marrow cavity, with relatively homogeneous U distributions. Yet, most significantly, specimens from American Falls (last interglacial) and Duck Point (last glacial maximum) show distinctive U plateaus adjacent to the outer and inner cortical bone margins. Whereas exponential profiles can be produced by different uptake processes, such plateaus are diagnostic of a DR mechanism. Our work is consistent with recent investigation of trace element diffusivities in modern fresh and deproteinated bone. These studies show similar diffusion rates for REE and U, so the profound disparity in U vs. REE profiles in most fossils cannot result solely from differences in volume diffusion within the context of DA and DMD. Rather, as a recrystallization front propagates into bone, the bone appears to encode changing soil water compositions with earlier vs. later compositions reflected in the bone margin vs. interior. Soil water U concentrations apparently remain nearly fixed during fossilization, whereas REE are rapidly stripped from the surrounding matrix, leading to nearly homogeneous U vs. steep REE profiles. However in our Pleistocene bones (American Falls and Duck Point), changes to U concentrations on the bone margin reveal more complex changes to boundary compositions, and eliminate both DA and DMD (alone) as the dominant mechanisms of trace element uptake. Our work reconciles disparate zoning patterns observed in fossil bone, and simplifies interpretations of soil or sediment water chemistry, but complicates U-series dating of fossils.

Uptake of VOC by sunflower

NASA Astrophysics Data System (ADS)

Folkers, A.; Miebach, M.; Kleist, E.; Wildt, J.

2003-04-01

To study potential VOC uptake by plants we exposed sunflower (Helianthus annuus) to different VOC in continuously stirred tank reactors. For many VOC like methanol, ethanol, acetone, methylvinylketone, isoprene or limonene no uptake was detectable within the accuracy of our analytic set up. Other VOC like hexanal, octanal, (E)-3-hexenol and nopinone were taken up by sunflower. The uptake was related to stomatal aperture. Obviously, these VOC enter the plants through stomata. In case of hexanal, octanal, and (E)-3-hexenol the uptake was only limited by stomatal aperture implying that these VOC are rapidly metabolised. For nopinone the uptake seems to be limited by a slow metabolization. Estimations of deposition velocities showed that dry deposition of these compounds cannot be neglected as sink if diffusion through stomata is the limiting step for dry deposition. In such cases the lifetime with respect to dry deposiotion is comparable to the lifetime with respect to oxidation by hydroxyl radicals.

Effects of homogenization process parameters on physicochemical properties of astaxanthin nanodispersions prepared using a solvent-diffusion technique

PubMed Central

Anarjan, Navideh; Jafarizadeh-Malmiri, Hoda; Nehdi, Imededdine Arbi; Sbihi, Hassen Mohamed; Al-Resayes, Saud Ibrahim; Tan, Chin Ping

2015-01-01

Nanodispersion systems allow incorporation of lipophilic bioactives, such as astaxanthin (a fat soluble carotenoid) into aqueous systems, which can improve their solubility, bioavailability, and stability, and widen their uses in water-based pharmaceutical and food products. In this study, response surface methodology was used to investigate the influences of homogenization time (0.5–20 minutes) and speed (1,000–9,000 rpm) in the formation of astaxanthin nanodispersions via the solvent-diffusion process. The product was characterized for particle size and astaxanthin concentration using laser diffraction particle size analysis and high performance liquid chromatography, respectively. Relatively high determination coefficients (ranging from 0.896 to 0.969) were obtained for all suggested polynomial regression models. The overall optimal homogenization conditions were determined by multiple response optimization analysis to be 6,000 rpm for 7 minutes. In vitro cellular uptake of astaxanthin from the suggested individual and multiple optimized astaxanthin nanodispersions was also evaluated. The cellular uptake of astaxanthin was found to be considerably increased (by more than five times) as it became incorporated into optimum nanodispersion systems. The lack of a significant difference between predicted and experimental values confirms the suitability of the regression equations connecting the response variables studied to the independent parameters. PMID:25709435

BioFVM: an efficient, parallelized diffusive transport solver for 3-D biological simulations

PubMed Central

Ghaffarizadeh, Ahmadreza; Friedman, Samuel H.; Macklin, Paul

2016-01-01

Motivation: Computational models of multicellular systems require solving systems of PDEs for release, uptake, decay and diffusion of multiple substrates in 3D, particularly when incorporating the impact of drugs, growth substrates and signaling factors on cell receptors and subcellular systems biology. Results: We introduce BioFVM, a diffusive transport solver tailored to biological problems. BioFVM can simulate release and uptake of many substrates by cell and bulk sources, diffusion and decay in large 3D domains. It has been parallelized with OpenMP, allowing efficient simulations on desktop workstations or single supercomputer nodes. The code is stable even for large time steps, with linear computational cost scalings. Solutions are first-order accurate in time and second-order accurate in space. The code can be run by itself or as part of a larger simulator. Availability and implementation: BioFVM is written in C ++ with parallelization in OpenMP. It is maintained and available for download at http://BioFVM.MathCancer.org and http://BioFVM.sf.net under the Apache License (v2.0). Contact: paul.macklin@usc.edu. Supplementary information: Supplementary data are available at Bioinformatics online. PMID:26656933

Diffusion of volatile organics through porous snow: impact of surface adsorption and grain boundaries

NASA Astrophysics Data System (ADS)

Bartels-Rausch, T.; Wren, S. N.; Schreiber, S.; Riche, F.; Schneebeli, M.; Ammann, M.

2013-07-01

Release of trace gases from surface snow on earth drives atmospheric chemistry, especially in the polar regions. The gas-phase diffusion of methanol and of acetone through the interstitial air of snow was investigated in a well-controlled laboratory study in the temperature range of 223 to 263 K. The aim of this study was to evaluate how the structure of the snowpack, the interaction of the trace gases with the snow surface, and the grain boundaries influence the diffusion on timescales up to 1 h. The diffusive loss of these two volatile organics into packed snow samples was measured using a chemical ionization mass spectrometer. The structure of the snow was analysed by means of X-ray-computed micro-tomography. The observed diffusion profiles could be well described based on gas-phase diffusion and the known structure of the snow sample at temperatures ≥ 253 K. At colder temperatures, surface interactions start to dominate the diffusive transport. Parameterizing these interactions in terms of adsorption to the solid ice surface, i.e. using temperature-dependent air-ice partitioning coefficients, better described the observed diffusion profiles than the use of air-liquid partitioning coefficients. No changes in the diffusive fluxes were observed by increasing the number of grain boundaries in the snow sample by a factor of 7, indicating that for these volatile organic trace gases, uptake into grain boundaries does not play a role on the timescale of diffusion through porous surface snow. For this, a snow sample with an artificially high amount of ice grains was produced and the grain boundary surface measured using thin sections. In conclusion, we have shown that the diffusivity can be predicted when the structure of the snowpack and the partitioning of the trace gas to solid ice is known.

Diffusion of volatile organics through porous snow: impact of surface adsorption and grain boundaries

NASA Astrophysics Data System (ADS)

Bartels-Rausch, T.; Wren, S. N.; Schreiber, S.; Riche, F.; Schneebeli, M.; Ammann, M.

2013-03-01

Release of trace gases from surface snow on Earth drives atmospheric chemistry, especially in the polar regions. The gas-phase diffusion of methanol and of acetone through the interstitial air of snow was investigated in a well-controlled laboratory study in the temperature range of 223 to 263 K. The aim of this study was to evaluate how the structure of the snowpack, the interaction of the trace gases with the snow surface, and the grain boundaries influence the diffusion on timescales up to 1 h. The diffusive loss of these two volatile organics into packed snow samples was measured using a chemical ionization mass spectrometer. The structure of the snow was analyzed by means of X-ray computed micro-tomography. The observed diffusion profiles could be well described based on gas-phase diffusion and the known structure of the snow sample at temperatures ≥ 253 K. At colder temperatures surface interactions start to dominate the diffusive transport. Parameterizing these interactions in terms of adsorption to the solid ice surface, i.e. using temperature dependent air-ice partitioning coefficients, better described the observed diffusion profiles than the use of air-liquid partitioning coefficients. No changes in the diffusive fluxes were observed by increasing the number of grain boundaries in the snow sample by a factor of 7, indicating that for these volatile organic trace gases, uptake into grain boundaries does not play a role on the timescale of diffusion through porous surface snow. In conclusion, we have shown that the diffusivity can be predicted when the structure of the snowpack and the partitioning of the trace gas to solid ice is known.

Towards an improved understanding of processes controlling absorption efficiency and biomagnification of organic chemicals by fish.

PubMed

Xiao, Ruiyang; Arnot, Jon A; MacLeod, Matthew

2015-11-01

Dietary exposure is considered the dominant pathway for fish exposed to persistent, hydrophobic chemicals in the environment. Here we present a dynamic, fugacity-based three-compartment bioaccumulation model that describes the fish body as one compartment and the gastrointestinal tract (GIT) as two compartments. The model simulates uptake from the GIT by passive diffusion and micelle-mediated diffusion, and chemical degradation in the fish and the GIT compartments. We applied the model to a consistent measured dietary uptake and depuration dataset for rainbow trout (n=215) that is comprised of chlorinated benzenes, biphenyls, dioxins, diphenyl ethers, and polycyclic aromatic hydrocarbons (PAHs). Model performance relative to the measured data is statistically similar regardless of whether micelle-mediated diffusion is included; however, there are considerable uncertainties in modeling this process. When degradation in the GIT is assumed to be negligible, modeled chemical elimination rates are similar to measured rates; however, predicted concentrations of the PAHs are consistently higher than measurements by up to a factor of 20. Introducing a kinetic limit on chemical transport from the fish compartment to the GIT and increasing the rate constant for degradation of PAHs in tissues of the liver and/or GIT are required to achieve good agreement between the modelled and measured concentrations for PAHs. Our results indicate that the apparent low absorption efficiency of PAHs relative to the chemicals with similar hydrophobicity is attributable to biotransformation in the liver and/or the GIT. Our results provide process-level insights about controls on the extent of bioaccumulation of chemicals. Copyright © 2015 Elsevier Ltd. All rights reserved.

Functional analysis of two genes coding for distinct cation diffusion facilitators of the ectomycorrhizal Zn-accumulating fungus Russula atropurpurea.

PubMed

Sácký, Jan; Leonhardt, Tereza; Kotrba, Pavel

2016-04-01

Russula atropurpurea can accumulate remarkably high concentrations of Zn in its sporocarps. We have previously demonstrated that 40 % of the intracellular Zn in this species is sequestered by MT-like RaZBP peptides. To see what other mechanisms for the handling of the accumulated Zn are available to R. atropurpurea, we searched its transcriptome for cDNAs coding for transporters of the cation diffusion facilitator (CDF) family. The transcriptome search enabled us to identify RaCDF1 and RaCDF2, which were further subjected to functional studies in metal sensitive Saccharomyces cerevisiae. The expression of RaCDF1 and its translational fusion with green fluorescent protein (GFP) protected the yeasts against Zn and Co, but not Cd or Mn, toxicity and led to increased Zn accumulation in the cells. The GFP fluorescence, observed in the RaCDF1::GFP-expressing yeasts on tonoplasts, indicated that the RaCDF1-mediated Zn and Co tolerance was a result of vacuolar sequestration of the metals. The expression of RaCDF2 supported Zn, but not Mn, tolerance in the yeasts and reduced the cellular uptake of Zn, which is congruent with the proposed idea of the Zn-efflux function of RaCDF2, supported by the localization of GFP-derived fluorescence on the plasma membrane of the yeasts expressing functional RaCDF2::GFP. Contrarily, RaCDF2 increased the sensitivity to Co and Cd in the yeasts and significantly promoted Cd uptake, which suggested that it can act as a bidirectional metal transporter. The notion that RaCDF1 and RaCDF2 are genuine CDF transporters in R. atropurputrea was further reinforced by the fact that the RaCDF-associated metal tolerance and uptake phenotypes were lost upon the replacement of histidyl (in RaCDF1) and aspartyl (in RaCDF2), which are highly conserved in the second transmembrane domain and known to be essential for the function of CDF proteins.

Methane uptake in urban forests and lawns.

PubMed

Groffman, Peter M; Pouyat, Richard V

2009-07-15

The largest natural biological sink for the radiatively active trace gas methane (CH4) is bacteria in soils that consume CH4 as an energy and carbon source. This sink has been shown to be sensitive to nitrogen (N) inputs and alterations of soil physical conditions. Given this sensitivity, conversion of native ecosystems to urban, suburban, and exurban managed lawns thus has potential to affect regional CH4 budgets. We measured CH4 fluxes monthly from four urban forest, four rural forest and four urban lawn plots in the Baltimore, MD, metropolitan area from 2001 to 2005. Our objectives were to evaluate the effects of urban atmospheric and land use change on CH4 uptake and the importance of these changes relative to other greenhouse forcings in the urban landscape. Rural forests had a high capacity for CH4 uptake (1.68 mg m(-2) day(-1)). This capacity was reduced in urban forests (0.23 mg m(-2) day(-1)) and almost completely eliminated in lawns. Possible mechanisms for these reductions include increases in atmospheric N deposition and CO2 levels, fertilization of lawns, and alteration of soil physical conditions that influence diffusion. Although conversion of native forests to lawns had dramatic effects on CH4 uptake, these effects do not appear to be significant to statewide greenhouse gas forcing.

Critical Determinants of Uptake and Translocation of Nanoparticles by the Human Pulmonary Alveolar Epithelium

PubMed Central

2015-01-01

The ability to manipulate the size and surface properties of nanomaterials makes them a promising vector for improving drug delivery and efficacy. Inhalation is a desirable route of administration as nanomaterials preferentially deposit in the alveolar region, a large surface area for drug absorption. However, as yet, the mechanisms by which particles translocate across the alveolar epithelial layer are poorly understood. Here we show that human alveolar type I epithelial cells internalize nanoparticles, whereas alveolar type II epithelial cells do not, and that nanoparticles translocate across the epithelial monolayer but are unable to penetrate the tight junctions between cells, ruling out paracellular translocation. Furthermore, using siRNA, we demonstrate that 50 nm nanoparticles enter largely by passive diffusion and are found in the cytoplasm, whereas 100 nm nanoparticles enter primarily via clathrin- and also caveolin-mediated endocytosis and are found in endosomes. Functionalization of nanoparticles increases their uptake and enhances binding of surfactant which further promotes uptake. Thus, we demonstrate that uptake and translocation across the pulmonary epithelium is controlled by alveolar type I epithelial cells, and furthermore, we highlight a number of factors that should be considered when designing new nanomedicines in order to improve drug delivery to the lung. PMID:25360809

Intravascular Drug Release Kinetics Dictate Arterial Drug Deposition, Retention, and Distribution

PubMed Central

Balakrishnan, Brinda; Dooley, John F.; Kopia, Gregory; Edelman, Elazer R.

2007-01-01

Millions of patients worldwide have received drug-eluting stents to reduce their risk for in-stent restenosis. The efficacy and toxicity of these local therapeutics depend upon arterial drug deposition, distribution, and retention. To examine how administered dose and drug release kinetics control arterial drug uptake, a model was created using principles of computational fluid dynamics and transient drug diffusion-convection. The modeling predictions for drug elution were validated using empiric data from stented porcine coronary arteries. Inefficient, minimal arterial drug deposition was predicted when a bolus of drug was released and depleted within seconds. Month-long stent-based drug release efficiently delivered nearly continuous drug levels, but the slow rate of drug presentation limited arterial drug uptake. Uptake was only maximized when the rates of drug release and absorption matched, which occurred for hour-long drug release. Of the two possibly means for increasing the amount of drug on the stent, modulation of drug concentration potently impacts the magnitude of arterial drug deposition, while changes in coating drug mass affect duration of release. We demonstrate the importance of drug release kinetics and administered drug dose in governing arterial drug uptake and suggest novel drug delivery strategies for controlling spatio-temporal arterial drug distribution. PMID:17868948

Filter-feeding, near-field flows, and the morphologies of colonial choanoflagellates

NASA Astrophysics Data System (ADS)

Kirkegaard, Julius B.; Goldstein, Raymond E.

2016-11-01

Efficient uptake of prey and nutrients from the environment is an important component in the fitness of all microorganisms, and its dependence on size may reveal clues to the origins of evolutionary transitions to multicellularity. Because potential benefits in uptake rates must be viewed in the context of other costs and benefits of size, such as varying predation rates and the increased metabolic costs associated with larger and more complex body plans, the uptake rate itself is not necessarily that which is optimized by evolution. Uptake rates can be strongly dependent on local organism geometry and its swimming speed, providing selective pressure for particular arrangements. Here we examine these issues for choanoflagellates, filter-feeding microorganisms that are the closest relatives of the animals. We explore the different morphological variations of the choanoflagellate Salpingoeca rosetta, which can exist as a swimming cell, as a sessile thecate cell, and as colonies of cells in various shapes. In the absence of other requirements and in a homogeneously nutritious environment, we find that the optimal strategy to maximize filter-feeding by the collar of microvilli is to swim fast, which favors swimming unicells. In large external flows, the sessile thecate cell becomes advantageous. Effects of prey diffusion are discussed and also found to be to the advantage of the swimming unicell.

Viscous organic aerosol particles in the upper troposphere: diffusivity-controlled water uptake and ice nucleation?

DOE PAGES

Lienhard, D. M.; Huisman, A. J.; Krieger, U. K.; ...

2015-01-01

New measurements of water diffusion in secondary organic aerosol (SOA) material produced by oxidation of α-pinene and in a number of organic/inorganic model mixtures (3-methylbutane-1,2,3-tricarboxylic acid (3-MBTCA), levoglucosan, levoglucosan/NH 4HSO 4, raffinose) are presented. These indicate that water diffusion coefficients are determined by several properties of the aerosol substance and cannot be inferred from the glass transition temperature or bouncing properties. Our results suggest that water diffusion in SOA particles is faster than often assumed and imposes no significant kinetic limitation on water uptake and release at temperatures above 220 K. The fast diffusion of water suggests that heterogeneous icemore » nucleation on a glassy core is very unlikely in these systems. At temperatures below 220 K, model simulations of SOA particles suggest that heterogeneous ice nucleation may occur in the immersion mode on glassy cores which remain embedded in a liquid shell when experiencing fast updraft velocities. The particles absorb significant quantities of water during these updrafts which plasticize their outer layers such that these layers equilibrate readily with the gas phase humidity before the homogeneous ice nucleation threshold is reached. Glass formation is thus unlikely to restrict homogeneous ice nucleation. Only under most extreme conditions near the very high tropical tropopause may the homogeneous ice nucleation rate coefficient be reduced as a consequence of slow condensed-phase water diffusion. Since the differences between the behavior limited or non limited by diffusion are small even at the very high tropical tropopause, condensed-phase water diffusivity is unlikely to have significant consequences on the direct climatic effects of SOA particles under tropospheric conditions.« less

Dermal uptake directly from air under transient conditions: advances in modeling and comparisons with experimental results for human subjects.

PubMed

Morrison, G C; Weschler, C J; Bekö, G

2016-12-01

To better understand the dermal exposure pathway, we enhance an existing mechanistic model of transdermal uptake by including skin surface lipids (SSL) and consider the impact of clothing. Addition of SSL increases the overall resistance to uptake of SVOCs from air but also allows for rapid transfer of SVOCs to sinks like clothing or clean air. We test the model by simulating di-ethyl phthalate (DEP) and di-n-butyl phthalate (DnBP) exposures of six bare-skinned (Weschler et al. 2015, Environ. Health Perspect., 123, 928) and one clothed participant (Morrison et al. 2016, J. Expo. Sci. Environ. Epidemiol., 26, 113). The model predicts total uptake values that are consistent with the measured values. For bare-skinned participants, the model predicts a normalized mass uptake of DEP of 3.1 (μg/m 2 )/(μg/m 3 ), whereas the experimental results range from 1.0 to 4.3 (μg/m 2 )/(μg/m 3 ); uptake of DnBP is somewhat overpredicted: 4.6 (μg/m 2 )/(μg/m 3 ) vs. the experimental range of 0.5-3.2 (μg/m 2 )/(μg/m 3 ). For the clothed participant, the model predicts higher than observed uptake for both species. Uncertainty in model inputs, including convective mass transfer coefficients, partition coefficients, and diffusion coefficients, could account for overpredictions. Simulations that include transfer of skin oil to clothing improve model predictions. A dynamic model that includes SSL is more sensitive to changes that impact external mass transfer such as putting on and removing clothes and bathing. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Studies on choline permeation through the plasma membrane and its incorporation into phosphatidyl choline of Ehrlich-Lettré-ascites tumor cells in vitro.

PubMed

Haeffner, E W

1975-02-03

The initial rate of incorporation of 14C or 3H-labeled choline into Ehrlich-Lettre ascites cells of the glycogen-free strain seven days after inoculation was investigated in vitro. 1. At choline concentrations in the medium between 6 to 30 muM and 100 to 500 muM the choline uptake by the cells followed Michaelis-Menton Kinetics with V values between 31 to 100 and 59 to 500 pmol per minute at a given cell density, and average Q10-values of 2.1 at the high and of 2.4 at the low choline molarity. The K-m-values increased from 27 muM to 58.8 muM at low and from 0.11 mM to 0.22 mM at high choline concentrations over a temperature range between 15 degrees C and 37 degrees C. Arrhenius plot of the V values gave two lines, one with a transition temperature at 25 degrees C at low and one straight line at high choline concentrations, from which the energy of activation for choline uptake was determined to be 16 kcal/mol. 2. It is assumed that two systems exist for the choline uptake by the ascites cells. One, operative at low substrate concentrations, which is saturable and probably is to be classified as a carrier-mediated facilitated diffusion process, can be strongly inhibited by deoxyglucose or 2,4-dinitrophenol and also by substrate analogues such as chlorocholine or benzoylcholine. Ouabain affects this system to a lesser extent. The other system functioning at high choline concentrations may be a simple diffusion process, which is little inhibited by substrate analogues, ouabain and deoxyglucose; however, it is also inhibited by 2,4-dinitrophenol and p-chloromercuribenzoate. 3. Choline incorporation into the acid-insoluble material (lecithin) gave linear Michaelis-Menton kinetics at the low and the high substrate concentration respectively. K-m-values decreased with an increase in temperature at low and increased with rising temperature at high substrate concentrations thus reflecting a close relationship between choline uptake and its metabolism. Labeling of lecithin choline in the various subcellular fractions under the conditions of the functioning of a carrier-mediated process was in the order: mitochondria (50%) greater than plasma membranes (25%) greater nuclei (14%) greater than microsomes (9%) greater than supernatant (1.5%). 4. Treatment of the cells with p-chloromercuribenzoate or heat shock at 50 degrees C markedly reduced the cholinee uptake and concomitantly its conversion into lecithin. Kinetic analysis revealed that the inhibitory effect of p-chloromercuribenzoate was competitive and that of the heat shock non-competitive in nature. Further the choline uptake by the cells was found to be the rate-limiting step, since the rate of choline phosphorylation was determined by the extracellular choline concentration. Pulse chase experiments showed a rapid turnover of the choline moiety with a concomitant increase in activity of the lecithin fraction and little change within the choline phosphate pool.

A model for estimating air-pollutant uptake by forests: calculation of absorption of sulfur dioxide from dispersed sources

Treesearch

C. E., Jr. Murphy; T. R. Sinclair; K. R. Knoerr

1977-01-01

The computer model presented in this paper is designed to estimate the uptake of air pollutants by forests. The model utilizes submodels to describe atmospheric diffusion immediately above and within the canopy, and into the sink areas within or on the trees. The program implementing the model is general and can be used with only minor changes for any gaseous pollutant...

The Global Influence of Cloud Optical Thickness on Terrestrial Carbon Uptake

NASA Astrophysics Data System (ADS)

Zhu, P.; Cheng, S. J.; Keppel-Aleks, G.; Butterfield, Z.; Steiner, A. L.

2016-12-01

Clouds play a critical role in regulating Earth's climate. One important way is by changing the type and intensity of solar radiation reaching the Earth's surface, which impacts plant photosynthesis. Specifically, the presence of clouds modifies photosynthesis rates by influencing the amount of diffuse radiation as well as the spectral distribution of solar radiation. Satellite-derived cloud optical thickness (COT) may provide the observational constraint necessary to assess the role of clouds on ecosystems and terrestrial carbon uptake across the globe. Previous studies using ground-based observations at individual sites suggest that below a COT of 7, there is a greater increase in light use efficiency than at higher COT values, providing evidence for higher carbon uptake rates than expected given the reduction in radiation by clouds. However, the strength of the COT-terrestrial carbon uptake correlation across the globe remains unknown. In this study, we investigate the influence of COT on terrestrial carbon uptake on a global scale, which may provide insights into cloud conditions favorable for plant photosynthesis and improve our estimates of the land carbon sink. Global satellite-derived MODIS data show that tropical and subtropical regions tend to have COT values around or below the threshold during growing seasons. We find weak correlations between COT and GPP with Fluxnet MTE global GPP data, which may be due to the uncertainty of upscaling GPP from individual site measurements. Analysis with solar-induced fluorescence (SIF) as a proxy for GPP is also evaluated. Overall, this work constructs a global picture of the role of COT on terrestrial carbon uptake, including its temporal and spatial variations.

Water uptake coefficients and deliquescence of NaCl nanoparticles at atmospheric relative humidities from molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Bahadur, Ranjit; Russell, Lynn M.

2008-09-01

Deliquescence properties of sodium chloride are size dependent for particles smaller than 100 nm. Molecular dynamics (MD) simulations are used to determine deliquescence relative humidity (DRH) for particles in this size range by modeling idealized particles in contact with humid air. Constant humidity conditions are simulated by inclusion of a liquid reservoir of NaCl solution in contact with the vapor phase, which acts as a source of water molecules as uptake by the nanoparticle proceeds. DRH is bounded between the minimum humidity at which sustained water accumulation is observed at the particle surface and the maximum humidity at which water accumulation is not observed. Complete formation of a liquid layer is not observed due to computational limitations. The DRH determined increases with decreasing particle diameter, rising to between 91% and 93% for a 2.2 nm particle and between 81% and 85% for an 11 nm particle, higher than the 75% expected for particles larger than 100 nm. The simulated size dependence of DRH agrees well with predictions from bulk thermodynamic models and appears to converge with measurements for sizes larger than 10 nm. Complete deliquescence of nanoparticles in the 2-11 nm size range requires between 1 and 100 μs, exceeding the available computational resources for this study. Water uptake coefficients are near 0.1 with a negligible contribution from diffusion effects. Planar uptake coefficients decrease from 0.41 to 0.09 with increasing fractional water coverage from 0.002 to 1, showing a linear dependence on the logarithm of the coverage fraction with a slope of -0.08+/-0.01 (representing the effect of solvation). Particle uptake coefficients increase from 0.13 at 11 nm to 0.65 at 2.2 nm, showing a linear dependence on the logarithm of the edge fraction (which is a function of diameter) with a slope of 0.74+/-0.04 (representing larger edge effects in smaller particles).

Influence of humidity on performance and microscopic dynamics of an ionic liquid in supercapacitor

NASA Astrophysics Data System (ADS)

Osti, Naresh C.; Dyatkin, Boris; Thompson, Matthew W.; Tiet, Felix; Zhang, Pengfei; Dai, Sheng; Tyagi, Madhusudan; Cummings, Peter T.; Gogotsi, Yury; Wesolowski, David J.; Mamontov, Eugene

2017-08-01

We investigated the influence of water molecules on the diffusion, dynamics, and electrosorption of a room temperature ionic liquid (RTIL), [BMI m+] [T f2N-] , confined in carbide-derived carbon with a bimodal nanoporosity. Water molecules in pores improved power densities and rate handling abilities of these materials in supercapacitor electrode configurations. We measured the water-dependent microscopic dynamics of the RTIL cations using quasielastic neutron scatting (QENS). The ionic liquid demonstrated greater mobility with increasing water uptake, facilitated by the nanoporous carbon environment, up to a well-defined saturation point. We concluded that water molecules displaced RTIL ions attached to the pore surfaces and improved the diffusivity of the displaced cations. This effect consequently increased capacitance and rate handling of the electrolyte in water-containing pores. Our findings suggest the possible effect of immiscible co-solvents on energy and power densities of energy storage devices, as well as the operating viability of nonaqueous supercapacitor electrolytes in humid environments.

Looking skyward to study ecosystem carbon dynamics

USGS Publications Warehouse

Dye, Dennis G.

2012-01-01

Between May and October 2011 the U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program, conducted a field campaign at the ARM Southern Great Plains site in north central Oklahoma to evaluate a new instrument for quantitative image-based monitoring of sky conditions and solar radiation. The High Dynamic Range All-Sky Imaging System (HDR-ASIS) was developed by USGS to support studies of cloud- and aerosol-induced variability in the geometric properties of solar radiation (the sky radiance distribution) and its effects on photosynthesis and uptake of carbon dioxide (CO2) by terrestrial ecosystems. Under a clean, cloudless atmosphere when the Sun is above the horizon, most of the solar radiation reaching an area of the Earth's surface is concentrated in a beam coming directly from the Sun; a relatively small proportion arrives as diffuse radiation from the rest of the sky. Clouds and atmospheric aerosols cause increased scattering of the beam radiation, which increases the proportion of diffuse radiation at the surface.

Digesting a Path Forward: The Utility of Collagenase Tumor Treatment for Improved Drug Delivery.

PubMed

Dolor, Aaron; Szoka, Francis C

2018-06-04

Collagen and hyaluronan are the most abundant components of the extracellular matrix (ECM) and their overexpression in tumors is linked to increased tumor growth and metastasis. These ECM components contribute to a protective tumor microenvironment by supporting a high interstitial fluid pressure and creating a tortuous setting for the convection and diffusion of chemotherapeutic small molecules, antibodies, and nanoparticles in the tumor interstitial space. This review focuses on the research efforts to deplete extracellular collagen with collagenases to normalize the tumor microenvironment. Although collagen synthesis inhibitors are in clinical development, the use of collagenases is contentious and clinically untested in cancer patients. Pretreatment of murine tumors with collagenases increased drug uptake and diffusion 2-10-fold. This modest improvement resulted in decreased tumor growth, but the benefits of collagenase treatment are confounded by risks of toxicity from collagen breakdown in healthy tissues. In this review, we evaluate the published in vitro and in vivo benefits and limitations of collagenase treatment to improve drug delivery.

Reflectance spectroscopy can quantify cutaneous haemoglobin oxygenation by oxygen uptake from the atmosphere after epidermal barrier disruption.

PubMed

Heise, H M; Lampen, P; Stücker, M

2003-11-01

The supply of oxygen to the viable skin tissue within the upper layers is not only secured by the cutaneous blood vascular system, but to a significant part also by oxygen diffusion from the atmosphere through the horny layer. The aim of this study was to examine whether changes in haemoglobin oxygenation can be observed within the isolated perfused bovine udder skin used as a skin model by removing the upper horny layer by adhesive tape stripping. Diffuse reflectance spectroscopy in the visible spectral range was used for non-invasive characterisation of haemoglobin oxygenation in skin under in vitro conditions. Mid-infrared attenuated total reflectance spectroscopy was employed for analysing the surface layer of the stratum corneum with respect to keratin, water and lipid components. Skin barrier disruption was achieved by repeated stripping of superficial corneocyte layers by adhesive tape. Significant changes in skin haemoglobin oxygenation were observed for skin areas with reduced lipid concentration and a reduced stratum corneum layer, as determined from the quantitative evaluation of the diffuse reflectance skin spectra. The result can be interpreted as an increase of oxygen diffusion after the removal of the upper horny layer.

Direct estimation of mass flow and diffusion of nitrogen compounds in solution and soil.

PubMed

Oyewole, Olusegun Ayodeji; Inselsbacher, Erich; Näsholm, Torgny

2014-02-01

Plant nutrient uptake from soil is mainly governed by diffusion and transpirationally induced mass flow, but the current methods for assessing the relative importance of these processes are indirect. We developed a microdialysis method using solutions of different osmotic potentials as perfusates to simulate diffusion and mass flow processes, and assessed how induced mass flow affected fluxes of nitrogen (N) compounds in solution and in boreal forest soil. Varying the osmotic potential of perfusates induced vertical fluxes in the direction of the dialysis membranes at rates of between 1 × 10(-8) and 3 × 10(-7)  m s(-1) , thus covering the estimated range of water velocities perpendicular to root surfaces and induced by transpiration. Mass flow increased N fluxes in solution but even more so in soil. This effect was explained by an indirect effect of mass flow on rates of diffusive fluxes, possibly caused by the formation of steeper gradients in concentrations of N compounds from membrane surfaces out in the soil. Our results suggest that transpiration may be an essential driver of plant N acquisition. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

Mechanism of uptake of nitrosoureas by L5178Y lymphoblasts in vitro.

PubMed

Begleiter, A; Lam, H P; Goldenberg, G J

1977-04-01

The mechanism of uptake of nitrosoureas by L5178Y cells in vitro was investigated. A time course of the uptake of radioactivity on incubation of L5178Y lymphoblast with [14C]-1,3-bis(2-chloroethyl)-1-nitrosourea was linear for 30 min and then entered a plateau phase; it was markedly temperature dependent. A similar time course for cells incubated with [14C]ethylene-labeled 1-(2-chlorethyl)-3-cyclohexyl-1-nitrosourea reached equilibrium rapidly, was temperature independent, and resulted in a relatively low level of uptake of radioactivity. However, cells treated with 3-[cyclohexyl-14C]-1-(2-chlorethyl)-1-nitrosourea had a time course that was linear for 30 min, resulted in much higher levels of uptake of radioactivity, and was strongly temperature dependent. These findings, at least for 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea, suggest that some drug decomposition precedes uptake. The percentage of radioactivity found in the cell sap fraction was at least 85% of total cell activity when cells were incubated with any of the three 14C-labeled nitrosoureas. Furthermore, thin-layer chromatography of the cell sap fraction revealed the presence of free intact drug. These findings indicate that intracellular uptake of intact nitrosoureas occurred. A time course of uptake of intact 1,3-bis(2-chloroethyl)-1-nitrosourea reached equilibrium rapidly with cell/medium distribution ratios of 0.2 to 0.6 and was temperature independent. The addition of excess unlabeled 1,3-bis(2-chlorethyl)-1-nitrosourea or 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea had no effect on uptake of [14C]-1,3-bis(2-chloroethyl)-1-nitrosourea, These findings suggest that uptake of intact 1,3-bis(2-chloroethyl)-1-nitrosourea was by passive diffusion. A time course of the uptake of intact 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea with either [14C]ethylene- or ring-labeled drug rapidly reached equilibrium, was temperature independent, and attained a cell/medium ratio greater than unity. Uptake of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea was sodium independent and was unaffected by the metabolic inhibitors (sodium fluoride, sodium cyanide, or 2,4-dinitrophenol) or by urea, a potential physiological competitor. Furthermore, addition of unlabeled 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea or 1,3-bis(2-chlorethyl)-1-nitrosourea had no effect on uptake of labeled 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea. These findings suggest that uptake of 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea also occurs by passive diffusion.

Echinococcus granulosus (Cestoda): uptake of L-amino acids by secondary hydatid cysts.

PubMed

Jeffs, S A; Arme, C

1988-02-01

The uptake of cycloleucine, L-proline, L-alanine and L-threonine by secondary hydatid cysts of Echinococcus granulosus (U.K. horse strain 3-8 mm in diameter, derived from Balb/c mice infected 300-400 days previously) occurs by passive diffusion into the cyst wall (laminated layer plus germinal layer) and by mediated mechanisms into the fluid-filled interior. The maximal concentrations of these compounds are achieved after incubation for 2 h in vitro and approach those in vivo. Kt and Vmax values describing the uptake of these compounds are given. The flux rates for these compounds are extremely slow compared to those obtained with the protoscolex. A rationale for standardizing the experimental method for uptake studies with hydatid cysts is described.

Uptake and distribution of Zn65 in the coho salmon egg (Oncorhynchus kisutch)

USGS Publications Warehouse

Wedemeyer, Gary

1968-01-01

1. Zinc uptake and distribution in the developing coho salmon egg was measured using radioisotope tracer techniques.2. The uptake was affected by pH, temperature, Cu2+, 2,4-fluorodinitrobenzene and the azo dye, malachite green; but not by azide ion or 2,4-dinitrophenol.3. About 70 per cent of the total accumulated zinc was bound, rather firmly, to the chorion; about 26 per cent was found in the perivitelline fluid, about 2 per cent in the yolk, and about 1 per cent in the embryo.4. Temperature, pH, inhibitor and kinetic studies indicated that zinc uptake involves physicochemical sorption to the chorion together with passive diffusion into the yolk and embryo.

Characterization of Cadmium Uptake by Plant Tissue 12

PubMed Central

Cutler, Jay M.; Rains, Donald W.

1974-01-01

The uptake of cadmium by excised root tissue of barley (Hordeum vulgare L. cv. Arivat) was investigated with respect to kinetics, concentration, and interactions with various cations. The role of metabolism in Cd absorption was examined using a range of temperatures, anaerobic treatments, and chemical inhibitors. The uptake and distribution of Cd in intact barley plants was also determined. A large fraction of the Cd taken up by excised barley roots was apparently the result of exchange adsorption and was displaced by subsequent desorption with unlabeled Cd, Zn, Cu, or Hg. Another fraction of Cd which could not be displaced by desorption in unlabeled Cd was thought to result from strong irreversible binding of Cd, perhaps on sites of the cell wall. The fraction of the Cd taken up beyond that by exchange adsorption by fresh roots was a linear function of temperature, and inhibited by conditions of low oxygen and by the presence of 2,4-dinitrophenol. It was concluded that this fraction of Cd entered excised barley roots by diffusion. Diffusion, when followed by sequestering, probably accounts for the accumulation of Cd observed in intact barley plants. PMID:16658840

Soil Methane uptake Model (MeMo): a process based model for global methane consumption by soils

NASA Astrophysics Data System (ADS)

Murguia-Flores, F.; Arndt, S.; Ganesan, A.; Hornibrook, E. R. C.; Murray-Tortarolo, G.

2016-12-01

Atmospheric methane (CH4) is a powerful greenhouse gas, responsible for 20% of global warming. The only terrestrial and biological sink is the uptake in the soils by methanotrophic bacteria, however there is large spatial and temporal heterogeneity in the magnitude of this sink. One way to provide a global understanding of this process is by using a mathematical model to simulate the mechanisms of the underlying physical and biological drivers. Here we present the soil Methane uptake Model (MeMo) a process-based model for the global methane consumption by soils. We have built on previous models by Ridgwell et al., (1999) and Curry et al., (2007), by making several advances. First, a general analytical solution of the one-dimensional diffusion-reaction equation was implemented that accounts for a maximum uptake depth and for a CH4 flux coming from below the surface (i.e. CH4 production in the soil). Secondly, we revisited and improved the effect of nitrogen inhibition, soil moisture and soil temperature on CH4 uptake in the light of newly available data and advances in our understanding of these drivers. Using observed forcing data, we estimated a global mean CH4 uptake of 31.2±1.2 Tg y-1 for the period 1990-2009 with an increasing trend of 0.1 Tg y-2. Our model represented the latitudinal pattern of uptake shown by field observations, with the highest uptake per unit area occurring over dry tropical forest and the lowest uptake in the polar desert. The highest seasonality occurred in the Northern Hemisphere, showing that the main driver of variability in a given year is from a combination of temperature and soil moisture. Our model showed that CH4 uptake is reduced from previous studies by approximately 10% at the regions with the highest nitrogen deposition: East Asia and Europe. Finally, our results suggest that more field measurements are needed to improve the modelling of the process, such as the basal oxidation rate for different ecosystems, the Q10 temperature response across different conditions and long term field CH4 uptake records.

Measuring Hydrogen Concentrations in Metals

NASA Technical Reports Server (NTRS)

Danford, M. D.

1985-01-01

Commercial corrosion-measurement system adapted to electrochemical determination of hydrogen concentrations in metals. New technique based on diffusion of hydrogen through foil specimen of metal. In sample holder, hydrogen produced on one side of foil, either by corrosion reaction or by cathodic current. Hydrogen diffused through foil removed on other side by constant anode potential, which leads to oxidation of hydrogen to water. Anode current is measure of concentration of hydrogen diffusing through foil. System used to study hydrogen uptake, hydrogen elimination by baking, effect of heat treatment, and effect of electroplating on high-strength steels.

Rational Targeting of Cellular Cholesterol in Diffuse Large B-Cell Lymphoma (DLBCL) Enabled by Functional Lipoprotein Nanoparticles: A Therapeutic Strategy Dependent on Cell of Origin.

PubMed

Rink, Jonathan S; Yang, Shuo; Cen, Osman; Taxter, Tim; McMahon, Kaylin M; Misener, Sol; Behdad, Amir; Longnecker, Richard; Gordon, Leo I; Thaxton, C Shad

2017-11-06

Cancer cells have altered metabolism and, in some cases, an increased demand for cholesterol. It is important to identify novel, rational treatments based on biology, and cellular cholesterol metabolism as a potential target for cancer is an innovative approach. Toward this end, we focused on diffuse large B-cell lymphoma (DLBCL) as a model because there is differential cholesterol biosynthesis driven by B-cell receptor (BCR) signaling in germinal center (GC) versus activated B-cell (ABC) DLBCL. To specifically target cellular cholesterol homeostasis, we employed high-density lipoprotein-like nanoparticles (HDL NP) that can generally reduce cellular cholesterol by targeting and blocking cholesterol uptake through the high-affinity HDL receptor, scavenger receptor type B-1 (SCARB1). As we previously reported, GC DLBCL are exquisitely sensitive to HDL NP as monotherapy, while ABC DLBCL are less sensitive. Herein, we report that enhanced BCR signaling and resultant de novo cholesterol synthesis in ABC DLBCL drastically reduces the ability of HDL NPs to reduce cellular cholesterol and induce cell death. Therefore, we combined HDL NP with the BCR signaling inhibitor ibrutinib and the SYK inhibitor R406. By targeting both cellular cholesterol uptake and BCR-associated de novo cholesterol synthesis, we achieved cellular cholesterol reduction and induced apoptosis in otherwise resistant ABC DLBCL cell lines. These results in lymphoma demonstrate that reduction of cellular cholesterol is a powerful mechanism to induce apoptosis. Cells rich in cholesterol require HDL NP therapy to reduce uptake and molecularly targeted agents that inhibit upstream pathways that stimulate de novo cholesterol synthesis, thus, providing a new paradigm for rationally targeting cholesterol metabolism as therapy for cancer.

Electrodiffusive Model for Astrocytic and Neuronal Ion Concentration Dynamics

PubMed Central

Halnes, Geir; Østby, Ivar; Pettersen, Klas H.; Omholt, Stig W.; Einevoll, Gaute T.

2013-01-01

The cable equation is a proper framework for modeling electrical neural signalling that takes place at a timescale at which the ionic concentrations vary little. However, in neural tissue there are also key dynamic processes that occur at longer timescales. For example, endured periods of intense neural signaling may cause the local extracellular K+-concentration to increase by several millimolars. The clearance of this excess K+ depends partly on diffusion in the extracellular space, partly on local uptake by astrocytes, and partly on intracellular transport (spatial buffering) within astrocytes. These processes, that take place at the time scale of seconds, demand a mathematical description able to account for the spatiotemporal variations in ion concentrations as well as the subsequent effects of these variations on the membrane potential. Here, we present a general electrodiffusive formalism for modeling of ion concentration dynamics in a one-dimensional geometry, including both the intra- and extracellular domains. Based on the Nernst-Planck equations, this formalism ensures that the membrane potential and ion concentrations are in consistency, it ensures global particle/charge conservation and it accounts for diffusion and concentration dependent variations in resistivity. We apply the formalism to a model of astrocytes exchanging ions with the extracellular space. The simulations show that K+-removal from high-concentration regions is driven by a local depolarization of the astrocyte membrane, which concertedly (i) increases the local astrocytic uptake of K+, (ii) suppresses extracellular transport of K+, (iii) increases axial transport of K+ within astrocytes, and (iv) facilitates astrocytic relase of K+ in regions where the extracellular concentration is low. Together, these mechanisms seem to provide a robust regulatory scheme for shielding the extracellular space from excess K+. PMID:24367247

Microenvironmental pH is a key factor for exosome traffic in tumor cells.

PubMed

Parolini, Isabella; Federici, Cristina; Raggi, Carla; Lugini, Luana; Palleschi, Simonetta; De Milito, Angelo; Coscia, Carolina; Iessi, Elisabetta; Logozzi, Mariantonia; Molinari, Agnese; Colone, Marisa; Tatti, Massimo; Sargiacomo, Massimo; Fais, Stefano

2009-12-04

Exosomes secreted by normal and cancer cells carry and deliver a variety of molecules. To date, mechanisms referring to tumor exosome trafficking, including release and cell-cell transmission, have not been described. To gain insight into this, exosomes purified from metastatic melanoma cell medium were labeled with a lipid fluorescent probe, R18, and analyzed by spectrofluorometry and confocal microscopy. A low pH condition is a hallmark of tumor malignancy, potentially influencing exosome release and uptake by cancer cells. Using different pH conditions as a modifier of exosome traffic, we showed (i) an increased exosome release and uptake at low pH when compared with a buffered condition and (ii) exosome uptake by melanoma cells occurred by fusion. Membrane biophysical analysis, such as fluidity and lipid composition, indicated a high rigidity and sphingomyelin/ganglioside GM3 (N-acetylneuraminylgalactosylglucosylceramide) content in exosomes released at low pH. This was likely responsible for the increased fusion efficiency. Consistent with these results, pretreatment with proton pump inhibitors led to an inhibition of exosome uptake by melanoma cells. Fusion efficiency of tumor exosomes resulted in being higher in cells of metastatic origin than in those derived from primary tumors or normal cells. Furthermore, we found that caveolin-1, a protein involved in melanoma progression, is highly delivered through exosomes released in an acidic condition. The results of our study provide the evidence that exosomes may be used as a delivery system for paracrine diffusion of tumor malignancy, in turn supporting the importance of both exosomes and tumor pH as key targets for future anti-cancer strategies.

Taking their breath away: metabolic responses to low-oxygen levels in anchialine shrimps (Crustacea: Atyidae and Alpheidae).

PubMed

Havird, Justin C; Vaught, Rebecca C; Weeks, Jeffrey R; Fujita, Yoshihisa; Hidaka, Michio; Santos, Scott R; Henry, Raymond P

2014-12-01

Crustaceans generally act as oxy-regulators, maintaining constant oxygen uptake as oxygen partial pressures decrease, but when a critical low level is reached, ventilation and aerobic metabolism shut down. Cave-adapted animals, including crustaceans, often show a reduced metabolic rate possibly owing in part to the hypoxic nature of such environments. However, metabolic rates have not been thoroughly explored in crustaceans from anchialine habitats (coastal ponds and caves), which can experience variable oxygenic regimes. Here, an atypical oxy-conforming pattern of oxygen uptake is reported in the Hawaiian anchialine atyid Halocaridina rubra, along with other unusual metabolic characteristics. Ventilatory rates are near-maximal in normoxia and did not increase appreciably as PO₂ declined, resulting in a decline in VO₂ during progressive hypoxia. Halocaridina rubra maintained in anoxic waters survived for seven days (the duration of the experiment) with no measureable oxygen uptake, suggesting a reliance on anaerobic metabolism. Supporting this, lactate dehydrogenase activity was high, even in normoxia, and oxygen debts were quickly repaid by an unusually extreme increase in oxygen uptake upon exposure to normoxia. In contrast, four related anchialine shrimp species from the Ryukyu Islands, Japan, exhibited physiological properties consistent with previously studied crustaceans. The unusual respiratory patterns found in H. rubra are discussed in the context of a trade-off in gill morphology for osmoregulatory ion transport vs. diffusion of respiratory gasses. Future focus on anchialine species may offer novel insight into the diversity of metabolic responses to hypoxia and other physiological challenges experienced by crustaceans. Published by Elsevier Inc.

Oxygen uptake and vertical transport during deep convection events

NASA Astrophysics Data System (ADS)

Sun, D.; Ito, T.; Bracco, A.

2016-02-01

Dissolved oxygen (O2) is essential for the chemistry and living organisms of the oceans. O2 is consumed in the interior ocean due to the respiration of organic matter, and must be replenished by physical ventilation with the O2-rich surface waters. The O2 supply to the deep waters happens only through the subduction and deep convection during cold seasons at high latitude oceans. The Labrador Sea is one of the few regions where deep ventilation occurs. According to observational and modeling studies, the intensity, duration and timing of deep convection events have varied significantly on the interannual and decadal timescales. In this study we develop a theoretical framework to understand the air-sea transfer of O2 during open-ocean deep convection events. The theory is tested against a suite of numerical integrations using MITgcm in non-hydrostatic configuration including the parameterization of diffusive and bubble mediated gas transfer. Forced with realistic air-sea buoyancy fluxes, the model can reproduce the evolution of temperature, salinity and dissolved O2 observed by ARGO floats in the Labrador Sea. Idealized sensitivity experiments are performed changing the intensity and duration of the buoyancy forcing as well as the wind speed for the gas exchange parameterizations. The downward transport of O2 results from the combination of vertical homogenization of existing O2 and the uptake from the air-sea flux. The intensity of the buoyancy forcing controls the vertical extent of convective mixing which brings O2 to the deep ocean. Integrated O2 uptake increases with the duration of convection even when the total buoyancy loss is held constant. The air-sea fluxes are highly sensitive to the wind speed especially for the bubble injection flux, which is a major addition to the diffusive flux under strong winds. However, the bubble injection flux can be partially compensated by the diffusive outgassing in response to the elevated saturation state. Under strong buoyancy forcing, this compensation is suppressed by the entrainment of relatively O2-poor deep waters. These results imply and allow to quantify the direct link between variability of deep convection and the supply of O2 in the North Atlantic.

Factors affecting the uptake of new medicines: a systematic literature review.

PubMed

Lublóy, Ágnes

2014-10-20

The successful diffusion of new drugs is crucial for both pharmaceutical companies and patients-and of wider stakeholder concern, including for the funding of healthcare provision. Micro-level characteristics (the socio-demographic and professional characteristics of medical professionals), meso-level characteristics (the prescribing characteristics of doctors, the marketing efforts of pharmaceutical companies, interpersonal communication among doctors, drug attributes, and the characteristics of patients), and macro-level characteristics (government policies) all influence the diffusion of new drugs. This systematic literature review examines the micro- and meso-level characteristics of early prescribers of newly introduced drugs. Understanding the characteristics of early adopters may help to speed up the diffusion process, promote cost-efficient prescribing habits, forecast utilisation, and develop targeted intervention strategies. The PubMed and Scopus electronic databases were chosen for their extensive coverage of the pertinent literature and used to identify 205 potentially relevant studies by means of a four-layered search string. The 35 studies deemed eligible were then synthetized carefully and critically, to extract variables relevant to this review. Early adoption of new drugs is not a personal trait, independent of drug type, but early adopters share both micro- and meso-level characteristics. At prescriber level, doctors' interest in particular therapeutic areas, participation in clinical trials, and volume of prescribing-either in total or within the therapeutic class of the new drug-increase the likelihood of early adoption. The marketing efforts of pharmaceutical companies and doctors' professional and social interactions leading to prescribing contagion are very powerful predictors of new drug uptake. At patient level, doctors with younger patients, patients with higher socioeconomic statuses and/or patients with poorer health statuses are more inclined to prescribe new drugs early. In contrast, the socio-demographic characteristics of prescribers and many practice-related factors play little role in the adoption process. The most powerful predictors of new drug uptake include the doctors' strong scientific commitment, high prescribing volume in total or in within the therapeutic class of the new drug, high exposure to marketing, and intense communication with colleagues.

Targeting transferrin receptors at the blood-brain barrier improves the uptake of immunoliposomes and subsequent cargo transport into the brain parenchyma.

PubMed

Johnsen, Kasper Bendix; Burkhart, Annette; Melander, Fredrik; Kempen, Paul Joseph; Vejlebo, Jonas Bruun; Siupka, Piotr; Nielsen, Morten Schallburg; Andresen, Thomas Lars; Moos, Torben

2017-09-04

Drug delivery to the brain is hampered by the presence of the blood-brain barrier, which excludes most molecules from freely diffusing into the brain, and tightly regulates the active transport mechanisms that ensure sufficient delivery of nutrients to the brain parenchyma. Harnessing the possibility of delivering neuroactive drugs by way of receptors already present on the brain endothelium has been of interest for many years. The transferrin receptor is of special interest since its expression is limited to the endothelium of the brain as opposed to peripheral endothelium. Here, we investigate the possibility of delivering immunoliposomes and their encapsulated cargo to the brain via targeting of the transferrin receptor. We find that transferrin receptor-targeting increases the association between the immunoliposomes and primary endothelial cells in vitro, but that this does not correlate with increased cargo transcytosis. Furthermore, we show that the transferrin receptor-targeted immunoliposomes accumulate along the microvessels of the brains of rats, but find no evidence for transcytosis of the immunoliposome. Conversely, the increased accumulation correlated both with increased cargo uptake in the brain endothelium and subsequent cargo transport into the brain. These findings suggest that transferrin receptor-targeting is a relevant strategy of increasing drug exposure to the brain.

Alveolar ventilation to perfusion heterogeneity and diffusion impairment in a mathematical model of gas exchange

NASA Technical Reports Server (NTRS)

Vidal Melo, M. F.; Loeppky, J. A.; Caprihan, A.; Luft, U. C.

1993-01-01

This study describes a two-compartment model of pulmonary gas exchange in which alveolar ventilation to perfusion (VA/Q) heterogeneity and impairment of pulmonary diffusing capacity (D) are simultaneously taken into account. The mathematical model uses as input data measurements usually obtained in the lung function laboratory. It consists of two compartments and an anatomical shunt. Each compartment receives fractions of alveolar ventilation and blood flow. Mass balance equations and integration of Fick's law of diffusion are used to compute alveolar and blood O2 and CO2 values compatible with input O2 uptake and CO2 elimination. Two applications are presented. The first is a method to partition O2 and CO2 alveolar-arterial gradients into VA/Q and D components. The technique is evaluated in data of patients with chronic obstructive pulmonary disease (COPD). The second is a theoretical analysis of the effects of blood flow variation in alveolar and blood O2 partial pressures. The results show the importance of simultaneous consideration of D to estimate VA/Q heterogeneity in patients with diffusion impairment. This factor plays an increasing role in gas alveolar-arterial gradients as severity of COPD increases. Association of VA/Q heterogeneity and D may produce an increase of O2 arterial pressure with decreasing QT which would not be observed if only D were considered. We conclude that the presented computer model is a useful tool for description and interpretation of data from COPD patients and for performing theoretical analysis of variables involved in the gas exchange process.

Uptake of NO, NO 2 and O 3 by sunflower ( Helianthus annuus L.) and tobacco plants ( Nicotiana tabacum L.): dependence on stomatal conductivity

NASA Astrophysics Data System (ADS)

Neubert, A.; Kley, D.; Wildt, J.; Segschneider, H. J.; Förstel, H.

The uptake of NO, NO 2 and O 3 by sunflowers ( Helianthus annuus L. var. giganteus) and tobacco plants ( Nicotiana tabacum L. var. Bel W3), using concentrations representative for moderately polluted air, has been determined by gas exchange experiments. Conductivities for these trace gases were measured at different light fluxes ranging from 820 μEm -2s -1 to darkness. The conductivities to water vapor and the trace gases are highly correlated. It is concluded that the uptake of NO, NO 2 and O 3 by sunflowers and tobacco plants is linearly dependent on stomatal opening. While the uptake of NO is limited by the mesophyll resistance, the uptake of NO 2 is only by diffusion through the stomata. Loss processes by deposition to the leaf surfaces are more pronounced for O 3 than for NO and NO 2.

Temperature- and composition-dependent hydrogen diffusivity in palladium from statistically-averaged molecular dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Xiaowang; Heo, Tae Wook; Wood, Brandon C.

Solid-state hydrogen storage materials undergo complex phase transformations whose kinetics is often limited by hydrogen diffusion. Among metal hydrides, palladium hydride undergoes a diffusional phase transformation upon hydrogen uptake, during which the hydrogen diffusivity varies with hydrogen composition and temperature. Here we perform robust statistically-averaged molecular dynamics simulations to obtain a well-converged analytical expression for hydrogen diffusivity in bulk palladium that is valid throughout all stages of the reaction. Our studies confirm significant dependence of the diffusivity on composition and temperature that elucidate key trends in the available experimental measurements. Whereas at low hydrogen compositions, a single process dominates, atmore » high hydrogen compositions, diffusion is found to exhibit behavior consistent with multiple hopping barriers. Further analysis, supported by nudged elastic band computations, suggests that the multi-barrier diffusion can be interpreted as two distinct mechanisms corresponding to hydrogen-rich and hydrogen-poor local environments.« less

Temperature- and composition-dependent hydrogen diffusivity in palladium from statistically-averaged molecular dynamics

DOE PAGES

Zhou, Xiaowang; Heo, Tae Wook; Wood, Brandon C.; ...

2018-03-09

Solid-state hydrogen storage materials undergo complex phase transformations whose kinetics is often limited by hydrogen diffusion. Among metal hydrides, palladium hydride undergoes a diffusional phase transformation upon hydrogen uptake, during which the hydrogen diffusivity varies with hydrogen composition and temperature. Here we perform robust statistically-averaged molecular dynamics simulations to obtain a well-converged analytical expression for hydrogen diffusivity in bulk palladium that is valid throughout all stages of the reaction. Our studies confirm significant dependence of the diffusivity on composition and temperature that elucidate key trends in the available experimental measurements. Whereas at low hydrogen compositions, a single process dominates, atmore » high hydrogen compositions, diffusion is found to exhibit behavior consistent with multiple hopping barriers. Further analysis, supported by nudged elastic band computations, suggests that the multi-barrier diffusion can be interpreted as two distinct mechanisms corresponding to hydrogen-rich and hydrogen-poor local environments.« less

Influence of Permeant Lipophilicity on Permeation Across Human Sclera

PubMed Central

Wen, He; Li, S. Kevin

2010-01-01

Purpose The objectives of this study were to determine the effects of permeant lipophilicity on permeant uptake into and transport across human sclera for transscleral delivery. Methods Model permeants with a wide range of lipophilicities were selected and studied with human sclera. Uptake experiments were carried out to measure permeant partitioning into the sclera. Transport experiments were performed in side-by-side diffusion cells, and the permeability coefficients and transport lag times of the permeants across the sclera were evaluated. Results Permeants with higher lipophilicity showed higher partition coefficients to human sclera, and the apparent transport lag time also increased significantly as the permeant lipophilicity increased. No correlation between the permeability coefficients and lipophilicity of the model permeants was observed in this study with human sclera. A hypothesis on the different findings between the present and previous studies was proposed. Conclusions Permeants with higher lipophilicity exhibited stronger binding to human sclera and would therefore lead to larger permeant partitioning to the sclera and longer transport lag time. The steady-state permeability coefficients of the permeants were not significantly affected by permeant lipophilicity. PMID:20734114

Dual-tracer background subtraction approach for fluorescent molecular tomography

PubMed Central

Holt, Robert W.; El-Ghussein, Fadi; Davis, Scott C.; Samkoe, Kimberley S.; Gunn, Jason R.; Leblond, Frederic

2013-01-01

Abstract. Diffuse fluorescence tomography requires high contrast-to-background ratios to accurately reconstruct inclusions of interest. This is a problem when imaging the uptake of fluorescently labeled molecularly targeted tracers in tissue, which can result in high levels of heterogeneously distributed background uptake. We present a dual-tracer background subtraction approach, wherein signal from the uptake of an untargeted tracer is subtracted from targeted tracer signal prior to image reconstruction, resulting in maps of targeted tracer binding. The approach is demonstrated in simulations, a phantom study, and in a mouse glioma imaging study, demonstrating substantial improvement over conventional and homogenous background subtraction image reconstruction approaches. PMID:23292612

Intestinal absorption and biomagnification of organochlorines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gobas, F.A.P.C.; McCorquodale, J.R.; Haffner, G.D.

1993-03-01

Dietary uptake rates of several organochlorines from diets with different lipid contents were measured in goldfish (Carassius auratus) to investigate the mechanism of intestinal absorption and biomagnification of organic chemical. The results suggest that intestinal absorption is predominantly controlled by chemical diffusion rather than lipid cotransport. Data for chemical uptake in human infants are presented to illustrate that biomagnification is caused by the digestion of food in the gastrointestinal tract. The findings are discussed in the context of two conflicting theories for the mechanism of biomagnification, and a mechanistic model is presented for the dietary uptake and biomagnification of organicmore » chemicals in fish and mammals.« less

Value of 18F-3,4-dihydroxyphenylalanine PET/MR image fusion in pediatric supratentorial infiltrative astrocytomas: a prospective pilot study.

PubMed

Morana, Giovanni; Piccardo, Arnoldo; Milanaccio, Claudia; Puntoni, Matteo; Nozza, Paolo; Cama, Armando; Zefiro, Daniele; Cabria, Massimo; Rossi, Andrea; Garrè, Maria Luisa

2014-05-01

Infiltrative astrocytomas (IAs) represent a group of astrocytic gliomas ranging from low-grade to highly malignant, characterized by diffuse invasion of the brain parenchyma. When compared with their adult counterpart, pediatric IAs may be considered biologically distinct entities; nevertheless, similarly to those in adults they represent a complex oncologic challenge. The aim of this study was to investigate the diagnostic role, clinical contribution, and prognostic value of fused (18)F-3,4-dihydroxyphenylalanine ((18)F-DOPA) PET/MR images in pediatric supratentorial IAs. Pediatric patients with supratentorial IAs involving at least 2 cerebral lobes, either newly diagnosed or with suspected disease progression, prospectively underwent (18)F-DOPA PET and conventional MR imaging, performed within 10 d of each other. (18)F-DOPA PET data were interpreted qualitatively and semiquantitatively, fusing images with MR images. PET scans were classified as positive if tumors identified on MR imaging exhibited tracer uptake above the level of the corresponding contralateral normal brain. Maximum standardized uptake values, tumor-to-normal contralateral tissue ratios, and tumor-to-normal striatum ratios were calculated for all tumors. Correlations between the degree and extent of (18)F-DOPA uptake, MR imaging tumor characteristics, and histologic results were investigated. The contribution of (18)F-DOPA PET/MR image fusion was considered relevant if it enabled one to select the most appropriate biopsy site, discriminate between disease progression and treatment-related changes, or influence treatment strategy. The patient's outcome was finally correlated with (18)F-DOPA uptake. Thirteen patients (8 boys and 5 girls) were included (5 diffuse astrocytomas, 2 anaplastic astrocytomas, 5 gliomatosis cerebri, and 1 glioblastoma multiforme). The (18)F-DOPA uptake pattern was heterogeneous in all positive scans (9/13), revealing metabolic heterogeneities within each tumor. Significant differences in terms of (18)F-DOPA uptake were found between low- and high-grade lesions (P < 0.05). The diagnostic and therapeutic contribution of (18)F-DOPA PET/MR image fusion was relevant in 9 of 13 patients (69%). (18)F-DOPA uptake correlated significantly with progression-free survival (P = 0.004). Our results indicate that (18)F-DOPA PET/MR image fusion may be a reliable imaging biomarker of pediatric IAs. Information gathered by this combined imaging approach can be readily transferred to the everyday practice and may help clinicians to better stratify patients with IAs, especially diffuse astrocytomas and gliomatosis cerebri, for diagnostic, therapeutic, and prognostic purposes.

YouTube as a platform for publishing clinical skills training videos.

PubMed

Topps, David; Helmer, Joyce; Ellaway, Rachel

2013-02-01

The means to share educational materials have grown considerably over the years, especially with the multitude of Internet channels available to educators. This article describes an innovative use of YouTube as a publishing platform for clinical educational materials.The authors posted online a series of short videos for teaching clinical procedures anticipating that they would be widely used. The project Web site attracted little traffic, alternatives were considered, and YouTube was selected for exploration as a publication channel. YouTube's analytics tools were used to assess uptake, and viewer comments were reviewed for specific feedback in support of evaluating and improving the materials posted.The uptake was much increased with 1.75 million views logged in the first 33 months. Viewer feedback, although limited, proved useful. In addition to improving uptake, this approach also relinquishes control over how materials are presented and how the analytics are generated. Open and anonymous access also limits relationships with end users.In summary, YouTube was found to provide many advantages over self-publication, particularly in terms of technical simplification, increased audience, discoverability, and analytics. In contrast to the transitory interest seen in most YouTube content, the channel has seen sustained popularity. YouTube's broadcast model diffused aspects of the relationship between educators and their learners, thereby limiting its use for more focused activities, such as continuing medical education.

Membrane formation and drug loading effects in high amylose starch tablets studied by NMR imaging.

PubMed

Thérien-Aubin, Héloïse; Zhu, X X; Ravenelle, François; Marchessault, Robert H

2008-04-01

Cross-linked high amylose starch is used as an excipient in the preparation of pharmaceutical tablets for the sustained release of drugs. NMR imaging with contrast enhanced by proton density and by self-diffusion coefficient was used to follow the water uptake and swelling, two critical parameters controlling the drug release of the cross-linked starch tablets containing 10 wt % of ciprofloxacin and of acetaminophen, respectively. The drug-loaded tablets were studied in a H2O/D2O mixture at 37 degrees C in comparison to the tablets without any drug loading. The diffusion of water in the tablets all showed a Fickian behavior, but the kinetics of water uptake was faster in the case of the drug-loaded tablets. The formation of a membrane at the water/tablet interface was observed.

Theoretic criteria for antibody penetration into solid tumors and micrometastases.

PubMed

Thurber, Greg M; Zajic, Stefan C; Wittrup, K Dane

2007-06-01

Targeting tumors with antibody-based therapeutics is a complex task presenting multiple kinetic barriers. Antibody internalization and clearance inhibit uptake both in solid tumors, limited by tumor vascular permeability, and in micrometastases, limited by diffusion. A modeling exercise is used to introduce 2 simple criteria that must be less than unity for saturation of both tumors and micrometastases. The clearance modulus and the Thiele modulus are ratios of the plasma clearance rate and antibody catabolism, respectively, to the tumor tissue penetration rate. Even low rates of antigen internalization from constitutive membrane turnover can significantly retard antibody penetration. Rapid clearance of single-chain variable fragments also hinders uptake, often more than counterbalancing their more rapid extravasation and diffusion. The model illustrates that with the large resistance from the tumor capillary, antibodies may be more suitable for targeting micrometastases than vascularized tumors.

Diffuse lung uptake (DLU) on Ga-67 scintigraph: Clinical, radiologic and pathologic correlation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sy, W.M.; Seo, I.S.; Vieira, J.

1985-05-01

Review, analysis and correlation (clinical, radiologic and pathologic) of 29 consecutive adults (16 drug addicts and/or homosexuals) with DLU on Ga-67 scintigraph were made. Diffuse increased uptake of at least 75% of both lungs was considered as DLU. WFOF cameras were used to obtain 24 to 96 hr. scintigraphs after IV injection of 3-5 mCi of Ga-67 citrate. In 26, tissue diagnosis established: pneumocystis carinii (PC) 15, miliary tuberculosis (TB) 3, sarcoidosis (SR) 3, drug-induced toxicity 2, and toxoplasmosis (TX), primary hyperparathyroidism and nonspecific lymphocytic pneumonia-one each. In two with breast and one with esophageal carcinomas, no lung tissue diagnosismore » was sought. Concurrent chest x-rays were negative in 16, but in 7/16, lung infiltrate was later documented. An average of 31 days elapsed before x-rays became positive in four with PC, 7 days in two with TB, and 22 days in one with TX. In 13, concurrent x-rays showed lung infiltrate, but in 6, only subtle, localized rather than diffuse infiltrate was noted. Fourteen of 29 had at least two Ga-67 studies. In 12 (7 PC, 2 TB, 3 SR) of 14 whose repeat studies showed significant to total disappearance of DLU, all did well clinically. In two whose initial studies were negative or equivocal, they became clinically worse when the repeat study showed DLU. In three others (2 PC, 1 TX) who died, their single studies recorded intense DLU. DLU on gallium scintigraph indicated a variety of pathology. In 55.2%, gallium scintigraph predated x-ray findings by a few days to weeks. In 20.3%, x-ray findings were only subtle or localized. Scintigraphic changes correlated well with the clinical courses in various diseases.« less

Personal Health Record Use in the United States: Forecasting Future Adoption Levels

PubMed Central

Huerta, Timothy R

2016-01-01

Background Personal health records (PHRs) offer a tremendous opportunity to generate consumer support in pursing the triple aim of reducing costs, increasing access, and improving care quality. Moreover, surveys in the United States indicate that consumers want Web-based access to their medical records. However, concerns that consumers’ low health information literacy levels and physicians’ resistance to sharing notes will limit PHRs’ utility to a relatively small portion of the population have reduced both the product innovation and policy imperatives. Objective The purpose of our study was 3-fold: first, to report on US consumers’ current level of PHR activity; second, to describe the roles of imitation and innovation influence factors in determining PHR adoption rates; and third, to forecast future PHR diffusion uptake among US consumers under 3 scenarios. Methods We used secondary data from the Health Information National Trends Survey (HINTS) of US citizens for the survey years 2008, 2011, and 2013. Applying technology diffusion theory and Bass modeling, we evaluated 3 future PHR adoption scenarios by varying the introduction dates. Results All models displayed the characteristic diffusion S-curve indicating that the PHR technology is likely to achieve significant market penetration ahead of meaningful use goals. The best-performing model indicates that PHR adoption will exceed 75% by 2020. Therefore, the meaningful use program targets for PHR adoption are below the rates likely to occur without an intervention. Conclusions The promise of improved care quality and cost savings through better consumer engagement prompted the US Institute of Medicine to call for universal PHR adoption in 1999. The PHR products available as of 2014 are likely to meet and exceed meaningful use stage 3 targets before 2020 without any incentive. Therefore, more ambitious uptake and functionality availability should be incorporated into future goals. PMID:27030105

Transport of Palmitic Acid Across the Tegument of the Entomophilic Nematode Romanomermis culicivorax.

PubMed

Gordon, R; Burford, I R

1984-01-01

Romanomermis culicivorax juveniles, dissected out of Aedes aegypti larvae 7 days after infection, were incubated under controlled conditions in isotonic saline containing (1)C-U-palmitic acid to investigate the nature of the transport mechanism(s) used by the nematode for transcuticular uptake of palmitic acid. Net uptake of the isotope by the nematode was of a logarithmic nature with respect to time. Uptake of palmitic acid was accomplished by a combination of diffusion and a mediated process which was substrate saturable and competitively inhibited by myristic and stearic acids. Both 2,4-dinitrophenol and ouabain inhibited uptake of palmitic acid and thus supported the hypothesis that the carrier system is of the active transport variety and is coupled to a NaK ATPase pump.

Uptake of pharmaceuticals by plants grown under hydroponic conditions and natural occurring plant species: A review.

PubMed

Madikizela, Lawrence Mzukisi; Ncube, Somandla; Chimuka, Luke

2018-04-27

Sizeable amount of research has been conducted on the possible uptake of pharmaceuticals by plants from contaminated soil and water used for irrigation of crops. In most cases, pharmaceuticals are taken by roots and translocated into various tissues by transpiration and diffusion. Due to the plant uptake, the occurrence of pharmaceuticals in food sources such as vegetables is a public concern. Few review papers focusing on the uptake of pharmaceuticals, in particular antibiotics, and their translocation in plant tissues have been published. In the current review paper, the work conducted on the uptake of pharmaceuticals belonging to different therapeutic groups such as antibiotics, non-steroidal anti-inflammatory drugs, β-blockers and antiepileptics is reviewed. Such work includes the occurrence of pharmaceuticals in plants, translocation once taken by plants, toxicity studies as well as implications and future studies. Furthermore, the advantages and drawbacks associated with the detection and uptake of these pharmaceuticals by plants are discussed. In addition, the physico-chemical properties that could influence the plant uptake of pharmaceuticals are deliberated. Copyright © 2018 Elsevier B.V. All rights reserved.

Clinical utility of FDG PET/CT in acute complicated pyelonephritis-results from an observational study.

PubMed

Wan, Chih-Hsing; Tseng, Jing-Ren; Lee, Ming-Hsun; Yang, Lan-Yan; Yen, Tzu-Chen

2018-03-01

Acute complicated pyelonephritis (ACP) is an upper urinary tract infection associated with coexisting urinary tract abnormalities or medical conditions that could predispose to serious outcomes or treatment failures. Although CT and magnetic resonance imaging (MRI) are frequently used in patients with ACP, the clinical value of 18 F-fluorodeoxyglucose positron emission tomography and computed tomography (FDG PET/CT) has not been systematically investigated. This single-center retrospective study was designed to evaluate the potential usefulness of FDG PET/CT in patients with ACP. Thirty-one adult patients with ACP who underwent FDG PET/CT were examined. FDG PET/CT imaging characteristics, including tracer uptake patterns, kidney volumes, and extrarenal imaging findings, were reviewed in combination with clinical data and conventional imaging results. Of the 31 patients, 19 (61%) showed focal FDG uptake. The remaining 12 study participants showed a diffuse FDG uptake pattern. After volumetric approximation, the affected kidneys were found to be significantly enlarged. Patients who showed a focal uptake pattern had a higher frequency of abscess formation requiring drainage. ACP patients showing diffuse tracer uptake patterns had a more benign clinical course. Seven patients had suspected extrarenal coinfections, and FDG PET/CT successfully confirmed the clinical suspicion in five cases. FDG PET/CT was as sensitive as CT in identifying the six patients (19%) who developed abscesses. Notably, FDG PET/CT findings caused a modification to the initial antibiotic regimen in nine patients (29%). FDG PET/CT may be clinically useful in the assessment of patients with ACP who have a progressive disease course.

Diffusion in inhomogeneous polymer membranes

NASA Astrophysics Data System (ADS)

Kasargod, Sameer S.; Adib, Farhad; Neogi, P.

1995-10-01

The dual mode sorption solubility isotherms assume, and in instances Zimm-Lundberg analysis of the solubilities show, that glassy polymers are heterogeneous and that the distribution of the solute in the polymer is also inhomogeneous. Under some conditions, the heterogeneities cannot be represented as holes. A mathematical model describing diffusion in inhomogeneous polymer membranes is presented using Cahn and Hilliard's gradient theory. The fractional mass uptake is found to be proportional to the fourth root of time rather than the square root, predicted by Fickian diffusion. This type of diffusion is classified as pseudo-Fickian. The model is compared with one experimental result available. A negative value of the persistence factor is obtained and the results are interpreted.

Arsenic enhanced plant growth and altered rhizosphere characteristics of hyperaccumulator Pteris vittata.

PubMed

Xu, Jia Yi; Li, Hong Bo; Liang, Shuang; Luo, Jun; Ma, Lena Q

2014-11-01

We investigated the effects of arsenic species on As accumulation, plant growth and rhizospheric changes in As-hyperaccumulator Pteris vittata (PV). PV was grown for 60-d in a soil spiked with 200 mg kg(-1) arsenate (AsV-soil) or arsenite (AsIII-soil). Diffusive gradients in thin-films technique (DGT) were used to monitor As uptake by PV. Interestingly AsIII-soil produced the highest PV biomass at 8.6 g plant(-1), 27% and 46% greater than AsV-soil and the control. Biomass increase was associated with As-induced P uptake by PV. Although AsIII was oxidized to AsV during the experiment, As species impacted As accumulation by PV, with 17.5% more As in AsIII-soil than AsV-soil (36 vs. 31 mg plant(-1)). As concentration in PV roots was 30% higher in AsV-soil whereas As concentration in PV fronds was 7.9% greater in AsIII-soil, suggesting more rapid translocation of AsIII than AsV. These findings were important to understand the mechanisms of As uptake, accumulation and translocation by PV. Published by Elsevier Ltd.

Loss Aversion Reflects Information Accumulation, Not Bias: A Drift-Diffusion Model Study.

PubMed

Clay, Summer N; Clithero, John A; Harris, Alison M; Reed, Catherine L

2017-01-01

Defined as increased sensitivity to losses, loss aversion is often conceptualized as a cognitive bias. However, findings that loss aversion has an attentional or emotional regulation component suggest that it may instead reflect differences in information processing. To distinguish these alternatives, we applied the drift-diffusion model (DDM) to choice and response time (RT) data in a card gambling task with unknown risk distributions. Loss aversion was measured separately for each participant. Dividing the participants into terciles based on loss aversion estimates, we found that the most loss-averse group showed a significantly lower drift rate than the other two groups, indicating overall slower uptake of information. In contrast, neither the starting bias nor the threshold separation (barrier) varied by group, suggesting that decision thresholds are not affected by loss aversion. These results shed new light on the cognitive mechanisms underlying loss aversion, consistent with an account based on information accumulation.

Loss Aversion Reflects Information Accumulation, Not Bias: A Drift-Diffusion Model Study

PubMed Central

Clay, Summer N.; Clithero, John A.; Harris, Alison M.; Reed, Catherine L.

2017-01-01

Defined as increased sensitivity to losses, loss aversion is often conceptualized as a cognitive bias. However, findings that loss aversion has an attentional or emotional regulation component suggest that it may instead reflect differences in information processing. To distinguish these alternatives, we applied the drift-diffusion model (DDM) to choice and response time (RT) data in a card gambling task with unknown risk distributions. Loss aversion was measured separately for each participant. Dividing the participants into terciles based on loss aversion estimates, we found that the most loss-averse group showed a significantly lower drift rate than the other two groups, indicating overall slower uptake of information. In contrast, neither the starting bias nor the threshold separation (barrier) varied by group, suggesting that decision thresholds are not affected by loss aversion. These results shed new light on the cognitive mechanisms underlying loss aversion, consistent with an account based on information accumulation. PMID:29066987

(18)F-FDG dynamic PET/CT in patients with multiple myeloma: patterns of tracer uptake and correlation with bone marrow plasma cell infiltration rate.

PubMed

Sachpekidis, Christos; Mai, Elias K; Goldschmidt, Hartmut; Hillengass, Jens; Hose, Dirk; Pan, Leyun; Haberkorn, Uwe; Dimitrakopoulou-Strauss, Antonia

2015-06-01

The value of F-FDG PET in the diagnostic approach of multiple myeloma (MM) remains incompletely elicited. Little is known about the kinetics of F-FDG in the bone marrow and extramedullary sites in MM. This study aimed to evaluate quantitative data on kinetics and distribution patterns of F-FDG in MM patients with regard to pelvic bone marrow plasma cell infiltration. The study included 40 patients with primary MM. Dynamic PET/CT scanning of the lower lumbar spine and pelvis was performed after the administration of F-FDG. Whole-body PET/CT studies were performed. Sites of focal increased tracer uptake were considered as highly suggestive of myelomatous involvement after taking into account the patient history and CT findings. Bone marrow of the os ilium without pathologic tracer accumulation served as reference. The evaluation of dynamic PET/CT studies was based in addition to the conventional visual (qualitative) assessment, on semiquantitative (SUV) calculations, as well as on absolute quantitative estimations after application of a 2-tissue compartment model and a noncompartmental approach. F-FDG quantitative information and corresponding distribution patterns were correlated with pelvic bone marrow plasma cell infiltration. Fifty-two myelomatous lesions were detected in the pelvis. All parameters in suspected MM lesions ranged in significantly higher levels than in reference tissue (P < 0.01). Correlative analyses revealed that bone marrow plasma cell infiltration rate correlated significantly with SUVaverage, SUVmax, and the parameters K1, influx, and fractal dimension of F-FDG in reference bone marrow (P < 0.01). In addition, whole-body static PET/CT imaging demonstrated 4 patterns of tracer uptake; these are as follows: negative, focal, diffuse, and mixed (focal/diffuse) tracer uptake. Patients with a mixed pattern of radiotracer uptake had the highest mean plasma cell infiltration rate in their bone marrow, whereas those with negative PET/CT scans demonstrated the lowest bone marrow plasma cell infiltration. In total, 265 focal myeloma-indicative F-FDG-avid lesions were detected, 129 of which correlated with low-dose CT osteolytic findings. No significant correlation between the number of focal lesions detected in PET/CT and bone marrow infiltration was detected. The F-FDG kinetic parameters K1, influx, and fractal dimension as well as SUVaverage from reference tissue correlated significantly with bone marrow malignant plasma cell infiltration rate. Patients with negative PET/CT demonstrated the lowest bone marrow infiltration by malignant plasma cells, whereas those with a mixed pattern of tracer uptake had the highest infiltration.

Shikimic Acid Ozonolysis is Influenced by its Physical State

NASA Astrophysics Data System (ADS)

Steimer, S.; Krieger, U. K.; Lampimäki, M.; Peter, T.; Ammann, M.

2013-12-01

Atmospheric aerosols play an important role in climate, air quality and human health. They undergo continuous transformation, changing their physical and chemical properties. Recent findings show that secondary organic aerosol (SOA) particles can form amorphous solids and semi-solids under atmospheric conditions [1]. Such physical states are highly viscous, leading to a decreased diffusivity within the bulk of the material. Inhibited mass transport could slow down chemical reactions, thereby increasing the lifetime of the organic compounds involved. First indications of such behavior were recently shown for the reaction of thin protein films with ozone [2] and formation of organonitrogen from ammonia uptake to α-pinene secondary organic material [3]. In this study, we investigated the influence of physical state on the ozonolysis of shikimic acid. This carboxylic acid is a constituent of biomass burning aerosols and used here as a proxy for oxygenated organic aerosol. The viscosity of the organic material was adjusted by varying the humidity of the system between 0% and 92% RH, assuming a correlation between the two parameters since water acts as a plasticizer. The system was probed with two complementary techniques: coated wall flow tube measurements, where the uptake of ozone is measured via loss from the gas phase and in situ X-ray microspectroscopy on single particles, where oxidation of the bulk can be observed. Additionally, data from electrodynamic balance measurements and kinetic modeling were used to facilitate data analysis. The dependence of the ozonolysis on relative humidity was clearly observed with both techniques. The coated wall flow tube measurements showed a long term, gradually changing ozone uptake over more than 15 hours, the magnitude of which varied over nearly two orders between driest and wettest conditions. It was possible to separate the uptake into two distinct kinetic regimes, the first of which displayed a Langmuir-Hinshelwood type behavior regarding the ozone gas phase concentration. Microspectroscopy showed that the speed at which the characteristic double bond peak of shikimic acid disappeared was humidity dependent. The measured humidity dependence supports the hypothesis that the uptake coefficient is highly dependent on the diffusion coefficients of ozone and/or shikimic acid in the organic film. [1] Nature, 2010, 467, 824-827. [2] Proc. Natl. Acad. Sci. U. S. A., 2011, 108, 11003-11008. [3] Proc. Natl. Acad. Sci. U. S. A., 2012, 109, 17354-17359.

PET/CT incidental detection of second tumor in patients investigated for pancreatic neoplasms.

PubMed

Moletta, Lucia; Bissoli, Sergio; Fantin, Alberto; Passuello, Nicola; Valmasoni, Michele; Sperti, Cosimo

2018-05-04

Positron Emission Tomography/computed tomography (PET/CT) is an imaging technique which has a role in the detection and staging malignancies (both in first diagnosis and follow-up). The finding of an unexpected region of FDG (Fluorodeoxyglucose) uptake can occur when performing whole-body FDG-PET, raising the possibility of a second primary tumor. The aim of this study was to evaluate our experience of second primary cancer incidentally discovered during PET/CT examination performed for pancreatic diseases, during the initial work-up or follow-up after surgical resection. In this study, a retrospective evaluation of a prospectively collected data base was performed. Three hundred ninety- nine patients with pancreatic pathology were evaluated by whole body PET/CT imaging from January 2004 to December 2014. Among them, 348 patients were scanned before surgical resection and 51 during the course of their follow-up (pancreatic cancer). Median follow-up time was 29 months (range 14-124). Fifty-six patients (14%) had incidental uptake of FDG in their organs: 31 patients had focal uptake and 25 showed diffuse with or without focal uptake. All patients with focal uptake were investigated, and invasive malignancy was diagnosed in 22 patients: 14 colon, 4 lung, 1 larynx, 1 urothelial, 1 breast cancer, and 1 colon metastasis from pancreatic cancer. Twenty patients underwent resection, and 6 endoscopic removal of colonic polyps. Three patients were not operated for advanced disease, and two patients did not show any pathology (PET/CT false positive). Of the 10 patients investigated for diffuse uptake, no malignancy was found; none of these patients developed a second cancer during the follow-up. As in other malignancies, unexpected FDG uptake can occur in patients having PET/CT investigation for pancreatic diseases. Focal uptake is likely to be a malignancy and deserves further investigations, although the stage and the poor prognosis of primary pancreatic cancer should be kept in mind. Some selected patients may benefit from the aggressive treatment of incidental lesions and show survival benefit.

Impact of physical properties on ozone removal by several porous materials.

PubMed

Gall, Elliott T; Corsi, Richard L; Siegel, Jeffrey A

2014-04-01

Models of reactive uptake of ozone in indoor environments generally describe materials through aerial (horizontal) projections of surface area, a potentially limiting assumption for porous materials. We investigated the effect of changing porosity/pore size, material thickness, and chamber fluid mechanic conditions on the reactive uptake of ozone to five materials: two cellulose filter papers, two cementitious materials, and an activated carbon cloth. Results include (1) material porosity and pore size distributions, (2) effective diffusion coefficients for ozone in materials, and (3) material-ozone deposition velocities and reaction probabilities. At small length scales (0.02-0.16 cm) increasing thickness caused increases in estimated reaction probabilities from 1 × 10(-6) to 5 × 10(-6) for one type of filter paper and from 1 × 10(-6) to 1 × 10(-5) for a second type of filter paper, an effect not observed for materials tested at larger thicknesses. For high porosity materials, increasing chamber transport-limited deposition velocities resulted in increases in reaction probabilities by factors of 1.4-2.0. The impact of physical properties and transport effects on values of the Thiele modulus, ranging across all materials from 0.03 to 13, is discussed in terms of the challenges in estimating reaction probabilities to porous materials in scenarios relevant to indoor environments.

Systemic delivery of the anticancer agent arenobufagin using polymeric nanomicelles.

PubMed

Yuan, Xue; Xie, Qian; Su, Keyu; Li, Zhijie; Dong, Dong; Wu, Baojian

2017-01-01

Arenobufagin (ABG) is a major active component of toad venom, a traditional Chinese medicine used for cancer therapy. However, poor aqueous solubility limits its pharmacological studies in vivo due to administration difficulties. In this study, we aimed to develop a polymeric nanomicelle (PN) system to enhance the solubility of ABG for effective intravenous delivery. ABG-loaded PNs (ABG-PNs) were prepared with methoxy poly (ethylene glycol)-block-poly (d,l-lactic-co-glycolic acid) (mPEG-PLGA) using the solvent-diffusion technique. The obtained ABG-PNs were 105 nm in size with a small polydispersity index of 0.08. The entrapment efficiency and drug loading were 71.9% and 4.58%, respectively. Cellular uptake of ABG-PNs was controlled by specific clathrin-mediated endocytosis. In addition, ABG-PNs showed improved drug pharmacokinetics with an increased area under the curve value (a 1.73-fold increase) and a decreased elimination clearance (37.8% decrease). The nanomicelles showed increased drug concentrations in the liver and lung. In contrast, drug concentrations in both heart and brain were decreased. Moreover, the nanomicelles enhanced the anticancer effect of the pure drug probably via increased cellular uptake of drug molecules. In conclusion, the mPEG-PLGA-based nanomicelle system is a satisfactory carrier for the systemic delivery of ABG.

Nanostructure of tetrafunctional epoxy resins and composites: Correlation to moisture absorption properties

NASA Astrophysics Data System (ADS)

Bolan, Brett Andrew

The effect that changes in network topology, while maintaining a constant network polarity (i.e. thermodynamic driving force was kept constant), had upon the moisture absorption properties of an aerospace grade tetrafunctional epoxy (TGMDA) cured with multifunctional amines were investigated. Utilizing Positron Annihilation Lifetime Spectroscopy (PALS) to characterize the nanoscale structure of these epoxies, it was found that as the "static" hole volume (a measurement of packing defects at 0K) increased so did the equilibrium uptake. PALS studies of one of these resins cured to varying extents, found that this static amount increased with degree of cure indicating that the network becomes more open as a direct consequence of crosslinking. Polar groups, which are the attractive force for diffusion, are in the vicinity of these crosslinks, therefore it is believed that the increase in static hole volume results in exposing more polar groups for absorption. The diffusion coefficient, which is representative of the kinetic aspect of diffusion, was also investigated. It was discovered that the amount of nanohole volume in the polymer; whether the total, the static, or dynamic (i.e. thermally activated) does not correlate to the diffusion coefficient in anyway. Furthermore, at an isotherm the diffusion coefficients for all these materials were relatively constant. From this it is hypothesized that it is the similar sub-Tsb{g} motions of these resins which is the rate limiting step in diffusion. This was bolstered by the fact that the activation energy for diffusion and for the sub-Tsb{g} motions for these epoxies are of the same order of magnitude. The nanostructure of fiber reinforced epoxy composites (i.e. a boron/epoxy and a graphite/epoxy) were probed with the bulk PALS technique as well. It was observed that for the graphite/epoxy composite and its flash (i.e. no fibers present) cured under identical conditions, that the nanoholes in the composite were larger than those present in the flash at temperatures below the epoxy's Tsb{g}. Curiously the boron/epoxy composite and its flash showed an opposite trend. Several potential explanations were examined. The only viable explanation for the observed nanostructural differences between the flash and the resin in these composites utilizes a micromechanics approach involving the CTE mismatch between the fibers and the matrix material. In this approach it is proposed that the fibers in the composite act as a constraint, preventing the nanohole from freely contracting (upon cooling through Tsb{g}) in the axial direction, while Poisson's ratio forces the holes to contract more in the transverse direction than the unrestrained hole in the flash. Therefore the resultant nanoholes in the composite maybe elongated in the fiber direction and shortened in the transverse direction when below the curing temperature. When the PALS technique probed these elongated holes it averaged their dimensions (but weighted the shortest dimension more heavily), thereby yielding the observed results. Despite slightly smaller static holes in the boron/epoxy composite than its flash, no difference in equilibrium uptake was noticed. The diffusion coefficient for the epoxy resin in this composite was found to be an order of magnitude higher than its flash. Nanostructure is not believed to be the cause of this but rather the glass fiber scrim cloth utilized in the processing of the prepreg.

Cerebral glucose uptake in patients with chronic mental and cognitive sequelae following a single blunt mild TBI without visible brain lesions.

PubMed

Komura, Akifumi; Kawasaki, Tomohiro; Yamada, Yuichi; Uzuyama, Shiho; Asano, Yoshitaka; Shinoda, Jun

2018-06-19

The aim of this study is to investigate glucose uptake on FDG-PET in patients with chronic mental and cognitive symptoms following a single blunt mild traumatic brain injury (TBI) and without visible brain lesions on CT/MRI. Eighty-nine consecutive patients (mean age 43.8±10.75) who had a single blunt mild TBI from a traffic accident and suffering from chronic mental and cognitive symptoms without visible brain lesions on CT/MRI were enrolled in the study. Patients underwent FDG-PET imaging, and the mean interval between the TBI and FDG-PET was 50.0 months. The Wechsler Adult Intelligence Scale version III testing was performed within one month of the FDG-PET. A control group consisting of 93 healthy adult volunteers (mean age 42.2±14.3 years) also underwent FDG-PET. The glucose uptake pattern from FDG-PET in the patient group was compared to that from normal controls using statistical parametric mapping. Glucose uptake was significantly decreased in the bilateral prefrontal area and significantly increased around the limbic system in the patient group compared to normal controls. This topographical pattern of glucose uptake is different from that reported previously in patients with diffuse axonal injury (DAI), but may be similar to that seen in patients with major depression disorder. These results suggest that the pathological mechanism causing chronic mental and cognitive symptoms in patients with a single blunt mild TBI and without visible brain lesions might be different from that due to primary axonopathy in patients with DAI.

Movement of Cations through Cuticles of Citrus aurantium and Acer saccharum1

PubMed Central

Tyree, Melvin T.; Tabor, Christopher A.; Wescott, Charles R.

1990-01-01

We examined some biophysical mechanisms of ion migration across leaf cuticles enzymatically isolated from Acer saccharum L. and Citrus aurantium L. leaves. Diffusion potential measurements were used to calculate the permeabilities of Cl-, Li+, Na+, and Cs+ ions all as a ratio with respect to the permeability of K+ in cuticles. In 2 millimolar ionic strength solutions the permeability sequence from high to low was K = Cs > Na > Li » Cl. When the outer and inner surfaces of cuticles were bathed in artificial precipitation and artificial apoplast, respectively, diffusion potentials ranging from −52 to −91 millivolts were measured (inside negative). The Goldman equation predicted that the measured potentials were enough to increase the driving force on the accumulation of heavy metals by a factor of 4 to 7. Other ions migrate with forces 3 to 10 times less than predicted by the Goldman equation for concentration differences alone. Our analysis showed that Ca2+, and perhaps Mg2+, might even be accumulated against concentration gradients under some circumstances. Their uptake was apparently driven by the diffusion potentials created by the outward migration of monovalent salts. We feel that future models predicting leaching of nutrients from trees during acid rain events must be modified to account for the probable influence of diffusion potentials on ion migration. PMID:16667677

Impact of diffusion barriers to small cytotoxic molecules on the efficacy of immunotherapy in breast cancer.

PubMed

Das, Hiranmoy; Wang, Zhihui; Niazi, M Khalid Khan; Aggarwal, Reeva; Lu, Jingwei; Kanji, Suman; Das, Manjusri; Joseph, Matthew; Gurcan, Metin; Cristini, Vittorio

2013-01-01

Molecular-focused cancer therapies, e.g., molecularly targeted therapy and immunotherapy, so far demonstrate only limited efficacy in cancer patients. We hypothesize that underestimating the role of biophysical factors that impact the delivery of drugs or cytotoxic cells to the target sites (for associated preferential cytotoxicity or cell signaling modulation) may be responsible for the poor clinical outcome. Therefore, instead of focusing exclusively on the investigation of molecular mechanisms in cancer cells, convection-diffusion of cytotoxic molecules and migration of cancer-killing cells within tumor tissue should be taken into account to improve therapeutic effectiveness. To test this hypothesis, we have developed a mathematical model of the interstitial diffusion and uptake of small cytotoxic molecules secreted by T-cells, which is capable of predicting breast cancer growth inhibition as measured both in vitro and in vivo. Our analysis shows that diffusion barriers of cytotoxic molecules conspire with γδ T-cell scarcity in tissue to limit the inhibitory effects of γδ T-cells on cancer cells. This may increase the necessary ratios of γδ T-cells to cancer cells within tissue to unrealistic values for having an intended therapeutic effect, and decrease the effectiveness of the immunotherapeutic treatment.

Effects of training on muscle O2 transport at VO2max

NASA Technical Reports Server (NTRS)

Roca, J.; Agusti, A. G.; Alonso, A.; Poole, D. C.; Viegas, C.; Barbera, J. A.; Rodriguez-Roisin, R.; Ferrer, A.; Wagner, P. D.

1992-01-01

To quantify the relative contributions of convective and peripheral diffusive components of O2 transport to the increase in leg O2 uptake (VO2leg) at maximum O2 uptake (VO2max) after 9 wk of endurance training, 12 sedentary subjects (age 21.8 +/- 3.4 yr, VO2max 36.9 +/- 5.9 ml.min-1.kg-1) were studied. VO2max, leg blood flow (Qleg), and arterial and femoral venous PO2, and thus VO2leg, were measured while the subjects breathed room air, 15% O2, and 12% O2. The sequence of the three inspirates was balanced. After training, VO2max and VO2leg increased at each inspired O2 concentration [FIO2; mean over the 3 FIO2 values 25.2 +/- 17.8 and 36.5 +/- 33% (SD), respectively]. Before training, VO2leg and mean capillary PO2 were linearly related through the origin during hypoxia but not during room air breathing, suggesting that, at 21% O2, VO2max was not limited by O2 supply. After training, VO2leg and mean capillary PO2 at each FIO2 fell along a straight line with zero intercept, just as in athletes (Roca et al. J. Appl. Physiol. 67: 291-299, 1989). Calculated muscle O2 diffusing capacity (DO2) rose 34% while Qleg increased 19%. The relatively greater rise in DO2 increased the DO2/Qleg, which led to 9.9% greater O2 extraction. By numerical analysis, the increase in Qleg alone (constant DO2) would have raised VO2leg by 35 ml/min (mean), but that of DO2 (constant Qleg) would have increased VO2leg by 85 ml/min, more than twice as much. The sum of these individual effects (120 ml/min) was less (P = 0.013) than the observed rise of 164 ml/min (mean). This synergism (explained by the increase in DO2/Qleg) seems to be an important contribution to increases in VO2max with training.

The influence of physical state on shikimic acid ozonolysis: a case for in situ microspectroscopy

NASA Astrophysics Data System (ADS)

Steimer, S. S.; Lampimäki, M.; Coz, E.; Grzinic, G.; Ammann, M.

2014-03-01

Atmospheric soluble organic aerosol material can become solid or semi-solid. Due to increasing viscosity and decreasing diffusivity, this can impact important processes such as gas uptake and reactivity within aerosols containing such substances. This work explores the dependence of shikimic acid ozonolysis on humidity and thereby viscosity. Shikimic acid, a proxy for oxygenated reactive organic material, reacts with O3 in a Criegee-type reaction. We used an environmental microreactor embedded in a Scanning Transmission X-ray Microscope (STXM) to probe this oxidation process. This technique facilitates in situ measurements with single micron-sized particles and allows to obtain Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra with high spatial resolution. Thus, the chemical evolution of the interior of the particles can be followed under reaction conditions. The experiments show that the overall degradation rate of shikimic acid is depending on the relative humidity in a way that is controlled by the decreasing diffusivity of ozone with decreasing humidity. This decreasing diffusivity is most likely linked to the increasing viscosity of the shikimic acid-water mixture. The degradation rate was also depending on particle size, most congruent with a reacto-diffusion limited kinetic case where the reaction progresses only in a shallow layer within the bulk. No gradient in the shikimic acid concentration was observed within the bulk material at any humidity indicating that the diffusivity of shikimic acid is still high enough to allow its equilibration throughout the particles on the time scale of hours at higher humidity and that the thickness of the oxidized layer under dry conditions, where the particles are solid, is beyond the resolution of STXM.

The influence of physical state on shikimic acid ozonolysis: a case for in situ microspectroscopy

NASA Astrophysics Data System (ADS)

Steimer, S. S.; Lampimäki, M.; Coz, E.; Grzinic, G.; Ammann, M.

2014-10-01

Atmospheric soluble organic aerosol material can become solid or semi-solid. Due to increasing viscosity and decreasing diffusivity, this can impact important processes such as gas uptake and reactivity within aerosols containing such substances. This work explores the dependence of shikimic acid ozonolysis on humidity and thereby viscosity. Shikimic acid, a proxy for oxygenated reactive organic material, reacts with O3 in a Criegee-type reaction. We used an environmental microreactor embedded in a scanning transmission X-ray microscope (STXM) to probe this oxidation process. This technique facilitates in situ measurements with single micron-sized particles and allows to obtain near-edge X-ray absorption fine structure (NEXAFS) spectra with high spatial resolution. Thus, the chemical evolution of the interior of the particles can be followed under reaction conditions. The experiments show that the overall degradation rate of shikimic acid is depending on the relative humidity in a way that is controlled by the decreasing diffusivity of ozone with decreasing humidity. This decreasing diffusivity is most likely linked to the increasing viscosity of the shikimic acid-water mixture. The degradation rate was also depending on particle size, most congruent with a reacto-diffusion limited kinetic case where the reaction progresses only in a shallow layer within the bulk. No gradient in the shikimic acid concentration was observed within the bulk material at any humidity indicating that the diffusivity of shikimic acid is still high enough to allow its equilibration throughout the particles on the timescale of hours at higher humidity and that the thickness of the oxidized layer under dry conditions, where the particles are solid, is beyond the resolution of STXM.

Comparison of precursor infiltration into polymer thin films via atomic layer deposition and sequential vapor infiltration using in-situ quartz crystal microgravimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Padbury, Richard P.; Jur, Jesse S., E-mail: jsjur@ncsu.edu

Previous research exploring inorganic materials nucleation behavior on polymers via atomic layer deposition indicates the formation of hybrid organic–inorganic materials that form within the subsurface of the polymer. This has inspired adaptations to the process, such as sequential vapor infiltration, which enhances the diffusion of organometallic precursors into the subsurface of the polymer to promote the formation of a hybrid organic–inorganic coating. This work highlights the fundamental difference in mass uptake behavior between atomic layer deposition and sequential vapor infiltration using in-situ methods. In particular, in-situ quartz crystal microgravimetry is used to compare the mass uptake behavior of trimethyl aluminummore » in poly(butylene terephthalate) and polyamide-6 polymer thin films. The importance of trimethyl aluminum diffusion into the polymer subsurface and the subsequent chemical reactions with polymer functional groups are discussed.« less

Water absorption characteristics of novel Cu/LDPE nanocomposite for use in intrauterine devices.

PubMed

Xia, Xianping; Cai, Shuizhou; Hu, Junhui; Xie, Changsheng

2006-11-01

Intrauterine devices (IUDs), especially the copper-containing IUDs (Cu-IUDs), are one of the worldwide used forms for birth control, owing to their advantages of long-lasting and high efficacy, economy, safety, and reversibility. However, it is not perfect for the existing Cu-IUDs; some shortcomings related to its side effects have not been overcome yet. For this reason, a new Cu-IUDs material, the copper/low-density polyethylene (Cu/LDPE) nanocomposite, has been developed in our research team. The structure and water uptake characteristics of this new Cu-IUDs material have been investigated by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), and gravimetric analysis in this paper. The results of XRD, SEM, EDS, and FT-IR show three important outcomes associated with the structure of the nanocomposite. First, the nanocomposite is hybrid of the polymer and the copper nanoparticles (nano-Cu). Second, porosities, nano-Cu aggregates, and primary alcohol (R--CH(2)--OH) are existed in the nanocomposite. Third, the nano-Cu aggregates are distributed uniformly in the polymer matrix in general. The results of Gravimetric analysis, which associated with the water uptake characteristics of the nanocomposite, exhibit that the water absorption behavior of the nanocomposite obeys the classical diffusion theory very well, the water uptake of the nanocomposite increases with the increasing of the nano-Cu loading, and that the water uptake ability of the nanocomposite with 15.0 wt % nano-Cu (50 nm in diameter) is about 150 times larger than that of the base resin and about 45 times higher than that of the Cu/LDPE microcomposite with 15.0 wt % copper microparticles (5 microm in diameter). These water uptake characteristics are mainly attributed to the structure of the Cu/LDPE composites and the size effect of the nano-Cu. (c) 2006 Wiley Periodicals, Inc.

Influence of Structural Heterogeneity on Diffusion of CH4 and CO2 in Silicon Carbide-Derived Nanoporous Carbon

PubMed Central

2015-01-01

We investigate the influence of structural heterogeneity on the transport properties of simple gases in a Hybrid Reverse Monte Carlo (HRMC) constructed model of silicon carbide-derived carbon (SiC-DC). The energy landscape of the system is determined based on free energy analysis of the atomistic model. The overall energy barriers of the system for different gases are computed along with important properties, such as Henry constant and differential enthalpy of adsorption at infinite dilution, and indicate hydrophobicity of the SiC-DC structure and its affinity for CO2 and CH4 adsorption. We also study the effect of molecular geometry, pore structure and energy heterogeneity considering different hopping scenarios for diffusion of CO2 and CH4 through ultramicropores using the Nudged Elastic Band (NEB) method. It is shown that the energy barrier of a hopping molecule is very sensitive to the shape of the pore entry. We provide evidence for the influence of structural heterogeneity on self-diffusivity of methane and carbon dioxide using molecular dynamics simulation, based on a maximum in the variation of self-diffusivity with loading. A comparison of the MD simulation results with self-diffusivities from quasi-elastic neutron scattering (QENS) measurements and, with macroscopic uptake-based low-density transport coefficients, reveals the existence of internal barriers not captured in MD simulation and QENS experiments. Nevertheless, the simulation and macroscopic uptake-based diffusion coefficients agree within a factor of 2–3, indicating that our HRMC model structure captures most of the important energy barriers affecting the transport of CH4 in the nanostructure of SiC-DC. PMID:24932319

Influence of Structural Heterogeneity on Diffusion of CH4 and CO2 in Silicon Carbide-Derived Nanoporous Carbon.

PubMed

Farmahini, Amir H; Shahtalebi, Ali; Jobic, Hervé; Bhatia, Suresh K

2014-06-05

We investigate the influence of structural heterogeneity on the transport properties of simple gases in a Hybrid Reverse Monte Carlo (HRMC) constructed model of silicon carbide-derived carbon (SiC-DC). The energy landscape of the system is determined based on free energy analysis of the atomistic model. The overall energy barriers of the system for different gases are computed along with important properties, such as Henry constant and differential enthalpy of adsorption at infinite dilution, and indicate hydrophobicity of the SiC-DC structure and its affinity for CO 2 and CH 4 adsorption. We also study the effect of molecular geometry, pore structure and energy heterogeneity considering different hopping scenarios for diffusion of CO 2 and CH 4 through ultramicropores using the Nudged Elastic Band (NEB) method. It is shown that the energy barrier of a hopping molecule is very sensitive to the shape of the pore entry. We provide evidence for the influence of structural heterogeneity on self-diffusivity of methane and carbon dioxide using molecular dynamics simulation, based on a maximum in the variation of self-diffusivity with loading. A comparison of the MD simulation results with self-diffusivities from quasi-elastic neutron scattering (QENS) measurements and, with macroscopic uptake-based low-density transport coefficients, reveals the existence of internal barriers not captured in MD simulation and QENS experiments. Nevertheless, the simulation and macroscopic uptake-based diffusion coefficients agree within a factor of 2-3, indicating that our HRMC model structure captures most of the important energy barriers affecting the transport of CH 4 in the nanostructure of SiC-DC.

Microenvironmental pH Is a Key Factor for Exosome Traffic in Tumor Cells*

PubMed Central

Parolini, Isabella; Federici, Cristina; Raggi, Carla; Lugini, Luana; Palleschi, Simonetta; De Milito, Angelo; Coscia, Carolina; Iessi, Elisabetta; Logozzi, Mariantonia; Molinari, Agnese; Colone, Marisa; Tatti, Massimo; Sargiacomo, Massimo; Fais, Stefano

2009-01-01

Exosomes secreted by normal and cancer cells carry and deliver a variety of molecules. To date, mechanisms referring to tumor exosome trafficking, including release and cell-cell transmission, have not been described. To gain insight into this, exosomes purified from metastatic melanoma cell medium were labeled with a lipid fluorescent probe, R18, and analyzed by spectrofluorometry and confocal microscopy. A low pH condition is a hallmark of tumor malignancy, potentially influencing exosome release and uptake by cancer cells. Using different pH conditions as a modifier of exosome traffic, we showed (i) an increased exosome release and uptake at low pH when compared with a buffered condition and (ii) exosome uptake by melanoma cells occurred by fusion. Membrane biophysical analysis, such as fluidity and lipid composition, indicated a high rigidity and sphingomyelin/ganglioside GM3 (N-acetylneuraminylgalactosylglucosylceramide) content in exosomes released at low pH. This was likely responsible for the increased fusion efficiency. Consistent with these results, pretreatment with proton pump inhibitors led to an inhibition of exosome uptake by melanoma cells. Fusion efficiency of tumor exosomes resulted in being higher in cells of metastatic origin than in those derived from primary tumors or normal cells. Furthermore, we found that caveolin-1, a protein involved in melanoma progression, is highly delivered through exosomes released in an acidic condition. The results of our study provide the evidence that exosomes may be used as a delivery system for paracrine diffusion of tumor malignancy, in turn supporting the importance of both exosomes and tumor pH as key targets for future anti-cancer strategies. PMID:19801663

Predicting the oral uptake efficiency of chemicals in mammals: Combining the hydrophilic and lipophilic range

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Connor, Isabel A., E-mail: i.oconnor@science.ru.nl; Huijbregts, Mark A.J., E-mail: m.huijbregts@science.ru.nl; Ragas, Ad M.J., E-mail: a.ragas@science.ru.nl

Environmental risk assessment requires models for estimating the bioaccumulation of untested compounds. So far, bioaccumulation models have focused on lipophilic compounds, and only a few have included hydrophilic compounds. Our aim was to extend an existing bioaccumulation model to estimate the oral uptake efficiency of pollutants in mammals for compounds over a wide K{sub ow} range with an emphasis on hydrophilic compounds, i.e. compounds in the lower K{sub ow} range. Usually, most models use octanol as a single surrogate for the membrane and thus neglect the bilayer structure of the membrane. However, compounds with polar groups can have different affinitiesmore » for the different membrane regions. Therefore, an existing bioaccumulation model was extended by dividing the diffusion resistance through the membrane into an outer and inner membrane resistance, where the solvents octanol and heptane were used as surrogates for these membrane regions, respectively. The model was calibrated with uptake efficiencies of environmental pollutants measured in different mammals during feeding studies combined with human oral uptake efficiencies of pharmaceuticals. The new model estimated the uptake efficiency of neutral (RMSE = 14.6) and dissociating (RMSE = 19.5) compounds with logK{sub ow} ranging from − 10 to + 8. The inclusion of the K{sub hw} improved uptake estimation for 33% of the hydrophilic compounds (logK{sub ow} < 0) (r{sup 2} = 0.51, RMSE = 22.8) compared with the model based on K{sub ow} only (r{sup 2} = 0.05, RMSE = 34.9), while hydrophobic compounds (logK{sub ow} > 0) were estimated equally by both model versions with RMSE = 15.2 (K{sub ow} and K{sub hw}) and RMSE = 15.7 (K{sub ow} only). The model can be used to estimate the oral uptake efficiency for both hydrophilic and hydrophobic compounds. -- Highlights: ► A mechanistic model was developed to estimate oral uptake efficiency. ► Model covers wide logK{sub ow} range (- 10 to + 8) and several mammalian species. ► K{sub ow} and the heptane water partition coefficient K{sub hw} were combined. ► K{sub ow} and K{sub hw} reflect the inner and the outer membrane diffusion resistance. ► Combining K{sub ow} and K{sub hw} improved uptake estimation for hydrophilic compounds.« less

The acellular matrix (ACM) for bladder tissue engineering: A quantitative magnetic resonance imaging study.

PubMed

Cheng, Hai-Ling Margaret; Loai, Yasir; Beaumont, Marine; Farhat, Walid A

2010-08-01

Bladder acellular matrices (ACMs) derived from natural tissue are gaining increasing attention for their role in tissue engineering and regeneration. Unlike conventional scaffolds based on biodegradable polymers or gels, ACMs possess native biomechanical and many acquired biologic properties. Efforts to optimize ACM-based scaffolds are ongoing and would be greatly assisted by a noninvasive means to characterize scaffold properties and monitor interaction with cells. MRI is well suited to this role, but research with MRI for scaffold characterization has been limited. This study presents initial results from quantitative MRI measurements for bladder ACM characterization and investigates the effects of incorporating hyaluronic acid, a natural biomaterial useful in tissue-engineering and regeneration. Measured MR relaxation times (T(1), T(2)) and diffusion coefficient were consistent with increased water uptake and glycosaminoglycan content observed on biochemistry in hyaluronic acid ACMs. Multicomponent MRI provided greater specificity, with diffusion data showing an acellular environment and T(2) components distinguishing the separate effects of increased glycosaminoglycans and hydration. These results suggest that quantitative MRI may provide useful information on matrix composition and structure, which is valuable in guiding further development using bladder ACMs for organ regeneration and in strategies involving the use of hyaluronic acid.

Passive lipoidal diffusion and carrier-mediated cell uptake are both important mechanisms of membrane permeation in drug disposition.

PubMed

Smith, Dennis; Artursson, Per; Avdeef, Alex; Di, Li; Ecker, Gerhard F; Faller, Bernard; Houston, J Brian; Kansy, Manfred; Kerns, Edward H; Krämer, Stefanie D; Lennernäs, Hans; van de Waterbeemd, Han; Sugano, Kiyohiko; Testa, Bernard

2014-06-02

Recently, it has been proposed that drug permeation is essentially carrier-mediated only and that passive lipoidal diffusion is negligible. This opposes the prevailing hypothesis of drug permeation through biological membranes, which integrates the contribution of multiple permeation mechanisms, including both carrier-mediated and passive lipoidal diffusion, depending on the compound's properties, membrane properties, and solution properties. The prevailing hypothesis of drug permeation continues to be successful for application and prediction in drug development. Proponents of the carrier-mediated only concept argue against passive lipoidal diffusion. However, the arguments are not supported by broad pharmaceutics literature. The carrier-mediated only concept lacks substantial supporting evidence and successful applications in drug development.

The influence of clouds and diffuse radiation on ecosystem-atmosphere CO2 and CO18O exhanges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Still, C.J.; Riley, W.J.; Biraud, S.C.

2009-05-01

This study evaluates the potential impact of clouds on ecosystem CO{sub 2} and CO{sub 2} isotope fluxes ('isofluxes') in two contrasting ecosystems (a broadleaf deciduous forest and a C{sub 4} grassland), in a region for which cloud cover, meteorological, and isotope data are available for driving the isotope-enabled land surface model, ISOLSM. Our model results indicate a large impact of clouds on ecosystem CO{sub 2} fluxes and isofluxes. Despite lower irradiance on partly cloudy and cloudy days, predicted forest canopy photosynthesis was substantially higher than on clear, sunny days, and the highest carbon uptake was achieved on the cloudiest day.more » This effect was driven by a large increase in light-limited shade leaf photosynthesis following an increase in the diffuse fraction of irradiance. Photosynthetic isofluxes, by contrast, were largest on partly cloudy days, as leaf water isotopic composition was only slightly depleted and photosynthesis was enhanced, as compared to adjacent clear sky days. On the cloudiest day, the forest exhibited intermediate isofluxes: although photosynthesis was highest on this day, leaf-to-atmosphere isofluxes were reduced from a feedback of transpiration on canopy relative humidity and leaf water. Photosynthesis and isofluxes were both reduced in the C{sub 4} grass canopy with increasing cloud cover and diffuse fraction as a result of near-constant light limitation of photosynthesis. These results suggest that some of the unexplained variation in global mean {delta}{sup 18}O of CO{sub 2} may be driven by large-scale changes in clouds and aerosols and their impacts on diffuse radiation, photosynthesis, and relative humidity.« less

Oxygen, water, and sodium chloride transport in soft contact lenses materials.

PubMed

Gavara, Rafael; Compañ, Vicente

2017-11-01

Oxygen permeability, diffusion coefficient of the sodium ions and water flux and permeability in different conventional hydrogel (Hy) and silicone-hydrogel (Si-Hy) contact lenses have been measured experimentally. The results showed that oxygen permeability and transmissibility requirements of the lens have been addressed through the use of siloxane containing hydrogels. In general, oxygen and sodium chloride permeability values increased with the water content of the lens but there was a percolation phenomenon from a given value of water uptake mainly in the Si-Hy lenses which appeared to be related with the differences between free water and bound water contents. The increase of ion permeability with water content did not follow a unique trend indicating a possible dependence of the chemical structure of the polymer and character ionic and non-ionic of the lens. Indeed, the salt permeability values for silicone hydrogel contact lenses were one order of magnitude below those of conventional hydrogel contact lenses, which can be explained by a diffusion of sodium ions occurring only through the hydrophilic channels. The increase of the ionic permeability in Si-Hy materials may be due to the confinement of ions in nanoscale water channels involving possible decreased degrees of freedom for diffusion of both water and ions. In general, ionic lenses presented values of ionic permeability and diffusivity higher than most non-ionic lenses. The tortuosity of the ionic lenses is lower than the non-ionic Si-Hy lenses. Frequency 55 and PureVision exhibited the highest water permeability and flux values and, these parameters were greater for ionic Si-Hy lenses than for ionic conventional hydrogel lenses. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2218-2231, 2017. © 2016 Wiley Periodicals, Inc.

Cutaneous sarcoidosis evaluated by FDG PET.

PubMed

Li, Yuxin; Berenji, Gholam R

2011-07-01

A 50-year-old man presented with initial complaints of diffuse skin pain and pruritus. Physical examination revealed scattered skin plaques and subcutaneous nodules with mild tenderness throughout the body. Skin biopsy demonstrated noncaseating epithelioid granulomas. Patient soon developed cough, fever with hot flashes, and shortness of breath on exertion. FDG PET/CT demonstrated diffuse cutaneous involvement throughout the body. Follow-up FDG PET/CT after treatment revealed a decrease in FDG uptake suggesting a good response to therapy.

[Chronic recurrent multifocal osteomyelitis of the mandible: report of three cases].

PubMed

Paim, Luciana B; Liphaus, Bernadete Lourdes; Rocha, André C; Castellanos, Aura Ligia Z; Silva, Clovis Artur A

2003-01-01

To report three cases of chronic recurrent multifocal osteomyelitis of the mandible, an inflammatory disease affecting one or more bones with absence of isolated microorganisms in affected areas. The first case is a 13 year-old female presenting with pain and fever after dental treatment. The patient received antibiotic treatment for osteomyelitis, but developed progressive enlargement of the mandible and palmoplantar pustulosis. Bone scintigraphy showed intense and diffuse uptake in the mandible. The swelling decreased after indomethacin and hyperbaric oxygen therapy. Case 2 is a 9 year-old female patient with recurrent pain and edema of the right mandible for three years. The diagnosis of osteomyelitis was established and amoxicillin introduced. After three months, tomography showed diffuse mandible osteolysis. Indomethacin and hyperbaric oxygen therapy were introduced, however the patient presented a relapse and was treated with prednisone, rofecoxib and methotrexate. Patient 3, a 10 year-old male, had palmoplantar pustulosis and recurrent enlargement of the mandible. Tomography showed diffuse mandible osteolysis and scintigraphy revealed intense and diffuse uptake in the mandible. The patient was treated with prednisone. Rofecoxib was replaced after two relapses. Chronic recurrent multifocal osteomyelitis of the mandible is often associated with prolonged pain periods and periods of activity and remission of the inflammatory process. Its recognition is important to prevent the patient from being submitted to prolonged antibiotic therapy and unnecessary invasive procedures.

Correlation between tissue metabolism and cellularity assessed by standardized uptake value and apparent diffusion coefficient in peritoneal metastasis.

PubMed

Yu, Xue; Lee, Elaine Yuen Phin; Lai, Vincent; Chan, Queenie

2014-07-01

To evaluate the correlation between standardized uptake value (SUV) (tissue metabolism) and apparent diffusion coefficient (ADC) (water diffusivity) in peritoneal metastases. Patients with peritoneal dissemination detected on (18)F-fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG-PET/CT) were prospectively recruited for MRI examinations with informed consent and the study was approved by the local Institutional Review Board. FDG-PET/CT, diffusion-weighted imaging (DWI), MRI, and DWI/MRI images were independently reviewed by two radiologists based on visual analysis. SUVmax/SUVmean and ADCmin/ADCmean were obtained manually by drawing ROIs over the peritoneal metastases on FDG-PET/CT and DWI, respectively. Diagnostic characteristics of each technique were evaluated. Pearson's coefficient and McNemar and Kappa tests were used for statistical analysis. Eight patients were recruited for this prospective study and 34 peritoneal metastases were evaluated. ADCmean was significantly and negatively correlated with SUVmax (r = -0.528, P = 0.001) and SUVmean (r = -0.548, P = 0.001). ADCmin had similar correlation with SUVmax (r = -0.508, P = 0.002) and SUVmean (r = -0.513, P = 0.002). DWI/MRI had high diagnostic performance (accuracy = 98%) comparable to FDG-PET/CT, in peritoneal metastasis detection. Kappa values were excellent for all techniques. There was a significant inverse correlation between SUV and ADC. © 2013 Wiley Periodicals, Inc.

Current knowledge on the sensitivity of the (68)Ga-somatostatin receptor positron emission tomography and the SUVmax reference range for management of pancreatic neuroendocrine tumours.

PubMed

Virgolini, Irene; Gabriel, Michael; Kroiss, Alexander; von Guggenberg, Elisabeth; Prommegger, Rupert; Warwitz, Boris; Nilica, Bernhard; Roig, Llanos Geraldo; Rodrigues, Margarida; Uprimny, Christian

2016-10-01

Physiologically increased pancreatic uptake at the head/uncinate process is observed in more than one-third of patients after injection of one of the three (68)Ga-labelled octreotide-based peptides used for somatostatin (sst) receptor (r) imaging. There are minor differences between these (68)Ga-sstr-binding peptides in the imaging setting. On (68)Ga-sstr-imaging the physiological uptake can be diffuse or focal and usually remains stable over time. Differences in the maximal standardised uptake values (SUVmax) reported for the normal pancreas as well as for pancreatic neuroendocrine tumour (PNET) lesions may be related to several factors, including (a) differences in the peptide binding affinities as well as differences in sstr subtype expression of pancreatic α- and β-cells, and heterogeneity / density of tumour cells, (b) differences in scanner resolution, image reconstruction techniques and acquisition protocols, (c) mostly retrospective study designs, (d) mixed patient populations, or (e) interference with medications such as treatment with long-acting sst analogues. The major limitation in most of the studies lies in the lack of histopathological confirmation of abnormal findings. There is a significant overlap between the calculated SUVmax-values for physiological pancreas and PNET-lesions of the head/uncinate process that do not favour the use of quantitative parameters in the clinical setting. Anecdotal long-term follow-up studies have even indicated that increased uptake in the head/uncinate process still can turn out to be malignant over years of follow up. SUVmax-data for the pancreatic body and tail are limited. Therefore, any visible focal tracer uptake in the pancreas must be considered as suspicious for malignancy irrespective of quantitative parameters. In general, sstr-PET/CT has significant implications for the management of NET patients leading to a change in treatment decision in about one-third of patients. Therefore, follow-up with (68)Ga-sstr-PET/CT is mandatory in the clinical setting if uptake in the head/uncinate process is observed.

Zeolite Y Adsorbents with High Vapor Uptake Capacity and Robust Cycling Stability for Potential Applications in Advanced Adsorption Heat Pumps.

PubMed

Li, Xiansen; Narayanan, Shankar; Michaelis, Vladimir K; Ong, Ta-Chung; Keeler, Eric G; Kim, Hyunho; McKay, Ian S; Griffin, Robert G; Wang, Evelyn N

2015-01-01

Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg 2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg,Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the labscale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N 2 sorption, 27 Al/ 29 Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2 nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H 2 O and N 2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications.

Rad4 recognition-at-a-distance: Physical basis of conformation-specific anomalous diffusion of DNA repair proteins.

PubMed

Kong, Muwen; Van Houten, Bennett

2017-08-01

Since Robert Brown's first observations of random walks by pollen particles suspended in solution, the concept of diffusion has been subject to countless theoretical and experimental studies in diverse fields from finance and social sciences, to physics and biology. Diffusive transport of macromolecules in cells is intimately linked to essential cellular functions including nutrient uptake, signal transduction, gene expression, as well as DNA replication and repair. Advancement in experimental techniques has allowed precise measurements of these diffusion processes. Mathematical and physical descriptions and computer simulations have been applied to model complicated biological systems in which anomalous diffusion, in addition to simple Brownian motion, was observed. The purpose of this review is to provide an overview of the major physical models of anomalous diffusion and corresponding experimental evidence on the target search problem faced by DNA-binding proteins, with an emphasis on DNA repair proteins and the role of anomalous diffusion in DNA target recognition. Copyright © 2016 Elsevier Ltd. All rights reserved.

Equilibrium and Kinetic Studies of Cd2+ Biosorption by the Brown Algae Sargassum fusiforme

PubMed Central

Zou, Hui-Xi; Li, Nan; Wang, Li-Hua; Yu, Ping; Yan, Xiu-Feng

2014-01-01

A fundamental investigation of the biosorption of Cd2+ from aqueous solution by the edible seaweed Sargassum fusiforme was performed under batch conditions. The influences of experimental parameters, such as the initial pH, sorption time, temperature, and initial Cd2+ concentration, on Cd2+ uptake by S. fusiforme were evaluated. The results indicated that the biosorption of Cd2+ depended on the initial Cd2+ concentration, as well as the pH. The uptake of Cd2+ could be described by the Langmuir isotherm model, and both the Langmuir biosorption equilibrium constant and the maximum biosorption capacity of the monolayer decreased with increasing temperature, thereby confirming the exothermic character of the sorption process. The biosorption kinetics follows the pseudo-second-order kinetic model, and intraparticle diffusion is the sole rate-limiting step for the entire biosorption period. These fundamental equilibrium and kinetic results can support further studies to the removal of cadmium from S. fusiforme harvested from cadmium-polluted waters. PMID:24736449

Defining the Subcellular Interface of Nanoparticles by Live-Cell Imaging

PubMed Central

Hemmerich, Peter H.; von Mikecz, Anna H.

2013-01-01

Understanding of nanoparticle-bio-interactions within living cells requires knowledge about the dynamic behavior of nanomaterials during their cellular uptake, intracellular traffic and mutual reactions with cell organelles. Here, we introduce a protocol of combined kinetic imaging techniques that enables investigation of exemplary fluorochrome-labelled nanoparticles concerning their intracellular fate. By time-lapse confocal microscopy we observe fast, dynamin-dependent uptake of polystyrene and silica nanoparticles via the cell membrane within seconds. Fluorescence recovery after photobleaching (FRAP) experiments reveal fast and complete exchange of the investigated nanoparticles at mitochondria, cytoplasmic vesicles or the nuclear envelope. Nuclear translocation is observed within minutes by free diffusion and active transport. Fluorescence correlation spectroscopy (FCS) and raster image correlation spectroscopy (RICS) indicate diffusion coefficients of polystyrene and silica nanoparticles in the nucleus and the cytoplasm that are consistent with particle motion in living cells based on diffusion. Determination of the apparent hydrodynamic radii by FCS and RICS shows that nanoparticles exert their cytoplasmic and nuclear effects mainly as mobile, monodisperse entities. Thus, a complete toolkit of fluorescence fluctuation microscopy is presented for the investigation of nanomaterial biophysics in subcellular microenvironments that contributes to develop a framework of intracellular nanoparticle delivery routes. PMID:23637951

Measurement of Passive Uptake Rates for Volatile Organic Compounds on Commercial Thermal Desorption Tubes and the Effect of Ozone on Sampling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maddalena, Randy; Parra, Amanda; Russell, Marion

Diffusive or passive sampling methods using commercially filled axial-sampling thermal desorption tubes are widely used for measuring volatile organic compounds (VOCs) in air. The passive sampling method provides a robust, cost effective way to measure air quality with time-averaged concentrations spanning up to a week or more. Sampling rates for VOCs can be calculated using tube geometry and Fick’s Law for ideal diffusion behavior or measured experimentally. There is evidence that uptake rates deviate from ideal and may not be constant over time. Therefore, experimentally measured sampling rates are preferred. In this project, a calibration chamber with a continuous stirredmore » tank reactor design and constant VOC source was combined with active sampling to generate a controlled dynamic calibration environment for passive samplers. The chamber air was augmented with a continuous source of 45 VOCs ranging from pentane to diethyl phthalate representing a variety of chemical classes and physiochemical properties. Both passive and active samples were collected on commercially filled Tenax TA thermal desorption tubes over an 11-day period and used to calculate passive sampling rates. A second experiment was designed to determine the impact of ozone on passive sampling by using the calibration chamber to passively load five terpenes on a set of Tenax tubes and then exposing the tubes to different ozone environments with and without ozone scrubbers attached to the tube inlet. During the sampling rate experiment, the measured diffusive uptake was constant for up to seven days for most of the VOCs tested but deviated from linearity for some of the more volatile compounds between seven and eleven days. In the ozone experiment, both exposed and unexposed tubes showed a similar decline in terpene mass over time indicating back diffusion when uncapped tubes were transferred to a clean environment but there was no indication of significant loss by ozone reaction.« less

Advective and diffusive dermal processes for estimating terrestrial amphibian pesticide exposure

EPA Science Inventory

Background/Question/Methods Dermal exposure presents a potentially significant but understudied route for pesticide uptake in terrestrial amphibians. Historically, evaluation of pesticide risk to both amphibians and reptiles has been achieved by comparing ingestion and inhalat...

Transport of aspartic acid, arginine, and tyrosine by the opportunistic protist Pneumocystis carinii.

PubMed

Basselin, M; Lipscomb, K J; Qiu, Y H; Kaneshiro, E S

2001-04-02

In order to improve culture media and to discover potential drug targets, uptake of an acidic, a basic, and an aromatic amino acid were investigated. Current culture systems, axenic or co-cultivation with mammalian cells, do not provide either the quantity or quality of cells needed for biochemical studies of this organism. Insight into nutrient acquisition can be expected to lead to improved culture media and improved culture growth. Aspartic acid uptake was directly related to substrate concentration, Q(10) was 1.10 at pH 7.4. Hence the organism acquired this acidic amino acid by simple diffusion. Uptake of the basic amino acid arginine and the aromatic amino acid tyrosine exhibited saturation kinetics consistent with carrier-mediated mechanisms. Kinetic parameters indicated two carriers (K(m)=22.8+/-2.5 microM and K(m)=3.6+/-0.3 mM) for arginine and a single carrier for tyrosine (K(m)=284+/-23 microM). The effects of other L-amino acids showed that the tyrosine carrier was distinct from the arginine carriers. Tyrosine and arginine transport were independent of sodium and potassium ions, and did not appear to require energy from ATP or a proton motive force. Thus facilitated diffusion was identified as the mechanism of uptake. After 30 min of incubation, these amino acids were incorporated into total lipids and the sedimentable material following lipid extraction; more than 90% was in the cellular soluble fraction.

Biophysical elucidation of the mechanism of enhanced drug release and topical delivery from polymeric film-forming systems.

PubMed

Garvie-Cook, Hazel; Frederiksen, Kit; Petersson, Karsten; Guy, Richard H; Gordeev, Sergey N

2015-08-28

The effect of incorporating the lipidic medium-chain triglyceride (MCT) into polymeric film-forming systems (FFS) for topical drug delivery has been evaluated. First, the in vitro release of betamethasone-17-valerate (BMV), a representative dermatological drug, was determined from FFS comprising either hydrophobic polyacrylate co-polymers, or hydrophilic hydroxypropyl cellulose, with and without MCT. Release was enhanced from both polymers in the presence of MCT. Atomic force microscopy imaging and nanoindentation of FFS with MCT revealed two-phase structured films with softer inclusions (0.5 to 4μm in diameter) surrounded by a more rigid structure. Chemical mapping with Raman micro-spectroscopy showed that MCT was primarily confined to the inclusions within the polymer, which predominated in the surrounding film. BMV was distributed throughout the film but was more concentrated outside the inclusions. Furthermore, while BMV dissolved better into the hydrophobic films, it was more soluble in the MCT inclusions in hydrophilic films, suggesting its increased availability for diffusion from these softer regions of the polymer and explaining the release enhancement observed. Second, ex vivo skin penetration studies clearly revealed that uptake of BMV was higher from hydrophobic FFS than that from the more hydrophilic polymer due, at least in part, to the superior anti-nucleation efficiency of the former. Drug was quickly taken up into the SC from which it then diffused continuously over a sustained period into the lower, viable skin layers. In the presence of MCT, the overall uptake of BMV was increased and provides the basis for further optimisation of FFS as simple, convenient and sustained formulations for topical therapy. Copyright © 2015 Elsevier B.V. All rights reserved.

Model development and verification for mass transport to Escherichia coli cells in a turbulent flow

NASA Astrophysics Data System (ADS)

Hondzo, Miki; Al-Homoud, Amer

2007-08-01

Theoretical studies imply that fluid motion does not significantly increase the molecular diffusive mass flux toward and away from microscopic organisms. This study presents experimental and theoretical evidence that small-scale turbulence modulates enhanced mass transport to Escherichia coli cells in a turbulent flow. Using the technique of inner region and outer region expansions, a model for dissolved oxygen and glucose uptake by E. coli was developed. The mass transport to the E. coli was modeled by the Sherwood (Sh)-Péclet (Pe) number relationship with redefined characteristic length and velocity scales. The model Sh = (1 + Pe1/2 + Pe) agreed with the laboratory measurements well. The Péclet number that quantifies the role and function of small-scale turbulence on E. coli metabolism is defined by Pe = (?) where Ezz is the root mean square of fluid extension in the direction of local vorticity, ηK is the Kolmogorov length scale, Lc is the length scale of E. coli, and D is the molecular diffusion coefficient. An alternative formulation for the redefined Pe is given by Pe = (?) where ? = 0.5(ɛν)1/4 is the Kolmogorov velocity averaged over the Kolmogorov length scale, ɛ is dissipation of turbulent kinetic energy, and ν is the kinematic viscosity of fluid. The dissipation of turbulent kinetic energy was estimated directly from measured velocity gradients and was within the reported range in engineered and natural aquatic ecosytems. The specific growth of E. coli was up to 5 times larger in a turbulent flow in comparison to the still water controls. Dissolved oxygen and glucose uptake were enhanced with increased ɛ in the turbulent flow.

Phosphorus removal from aqueous solution in parent and aluminum-modified eggshells: thermodynamics and kinetics, adsorption mechanism, and diffusion process.

PubMed

Guo, Ziyan; Li, Jiuhai; Guo, Zhaobing; Guo, Qingjun; Zhu, Bin

2017-06-01

Parent and aluminum-modified eggshells were prepared and characterized with X-ray diffraction, specific surface area measurements, infrared spectroscopy, zeta potential, and scanning electron microscope, respectively. Besides, phosphorus adsorptions in these two eggshells at different temperatures and solution pH were carried out to study adsorption thermodynamics and kinetics as well as the mechanisms of phosphorus adsorption and diffusion. The results indicated that high temperature was favorable for phosphorus adsorption in parent and aluminum-modified eggshells. Alkaline solution prompted phosphorus adsorption in parent eggshell, while the maximum adsorption amount was achievable at pH 4 in aluminum-modified eggshell. Adsorption isotherms of phosphorus in these eggshells could be well described by Langmuir and Freundlich models. Phosphorus adsorption amounts in aluminum-modified eggshell were markedly higher compared to those in parent eggshell. Adsorption heat indicated that phosphorus adsorption in parent eggshell was a typically physical adsorption process, while chemical adsorption mechanism of ion exchange between phosphorus and hydroxyl groups on the surface of eggshells was dominated in aluminum-modified eggshell. The time-resolved uptake curves showed phosphorus adsorption in aluminum-modified eggshell was significantly faster than that in parent eggshell. Moreover, there existed two clear steps in time-resolved uptake curves of phosphorus in parent eggshell. Based on pseudo-second order kinetic model and intraparticle diffusion model, we inferred more than one process affected phosphorus adsorption. The first process was the diffusion of phosphorus through water to external surface and the opening of pore channel in the eggshells, and the second process was mainly related to intraparticle diffusion.

Diffuse pulmonary gallium accumulation with a normal chest radiogram in a homosexual man with pneumocystis carinii pneumonia. A case report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moses, S.C.; Baker, S.R.; Seldin, M.F.

1983-12-01

A homosexual man with A.I.D.S. (acquired immunologic deficiency syndrome) and pneumocystis infestation was found to have diffuse Ga-67 uptake in the lungs with a coincident negative chest x-ray. While Ga-67 accumulates diffusely in the lungs in a variety of conditions, the present case is the first described in a patient with A.I.D.S. in which Ga-67 was positive before roentgenographic abnormalities were demonstrated. Thus, the use of Ga-67 scan, when A.I.D.S. is suspected, could help establish a diagnosis more promptly.

18F-DOPA PET and enhanced CT imaging for congenital hyperinsulinism: initial UK experience from a technologist's perspective.

PubMed

Meintjes, Marguerite; Endozo, Raymond; Dickson, John; Erlandsson, Kjel; Hussain, Khalid; Townsend, Caroline; Menezes, Leon; Bomanji, Jamshed

2013-06-01

Congenital hyperinsulinism (CHI) is the most common cause of persistent hypoglycaemia in infants and children. Histologically, there are two subgroups, diffuse and focal. The aim of this study was to evaluate the accuracy of (18)F-fluoro-L-dihydroxyphenylalanine ((18)F-DOPA) PET/computed tomography (CT) and contrast-enhanced CT in distinguishing between focal and diffuse lesions in infants with CHI who are unresponsive to medical therapy. In addition, this paper describes the detailed protocol used for imaging and analysis of (18)F-DOPA PET/CT images in our clinical practice. Twenty-two (18)F-DOPA PET/CT and contrast-enhanced CT imaging studies were carried out on 18 consecutive patients (nine boys and nine girls) with CHI (median age, 2 years and 1 month; range, 1-84 months) who had positive dominant ABCC8 mutation genetic results or negative ABCC8/t results but did not respond to first-line medical therapy with high-dose diazoxide. (18)F-DOPA was produced by the cyclotron unit of Woolfson Molecular Imaging Centre, Manchester, and transported to our centre in central London after synthesis and implementation of quality control measures. (18)F-DOPA was administered intravenously at a dose of 4 MBq/kg, and iodine contrast medium was injected intravenously at a dose of 1.5 ml/kg. Single bed position PET/CT images of the pancreas were acquired under light sedation with oral chloral hydrate. Four PET dynamic data acquisition scans were taken 20, 40, 50 and 60 min after injection for a duration of 10 min each. The results were assessed by visual interpretation and quantitative measurements of standardized uptake values (SUVs) in the head, body, and tail of the pancreas. Of the 18 patients, 13 showed diffuse and five showed focal (18)F-DOPA PET pancreatic uptake. Three regions of interest were drawn over the head, body and tail of the pancreas to calculate the SUV(max). Using the formula - highest SUV(max)/next highest SUV(max) - a ratio was calculated. Five patients had an accumulation of F-DOPA in the pancreas and an SUV ratio greater than 1.5, indicating focal disease with an SUV(max) more than 50% higher than that of the unaffected areas of the pancreas. The remaining 13 patients had diffuse accumulation of (18)F-DOPA in the pancreas (SUV ratio<1.3). Using this ratio, a focal lesion can be distinguished from diffuse uptake and normal pancreatic uptake. The sizes of these regions of interest varied according to the age of the child. All patients diagnosed with focal lesions underwent surgery and were cured eventually. Lesions were accurately localized by PET/CT and confirmed by histological results after surgery. Three of these patients had to undergo second (18)F-DOPA scans and second surgeries after unsuccessful excision during their first surgery. Three patients with diffuse disease underwent a partial pancreatectomy, and histological results confirmed diffuse disease. One patient was cured and two remain on high-dose diazoxide therapy because of persistent hypoglycaemia. (18)F-DOPA PET/CT offers excellent differentiation of focal from diffuse CHI, and the contrast-enhanced CT technique permits precise preoperative localization of the lesion and anatomical landmarks.

Dynamics of canopy stomatal conductance, transpiration, and evaporation in a temperate deciduous forest, validated by carbonyl sulfide uptake

DOE PAGES

Wehr, Richard; Commane, Roisin; Munger, J. William; ...

2017-01-26

Stomatal conductance influences both photosynthesis and transpiration, thereby coupling the carbon and water cycles and affecting surface–atmosphere energy exchange. The environmental response of stomatal conductance has been measured mainly on the leaf scale, and theoretical canopy models are relied on to upscale stomatal conductance for application in terrestrial ecosystem models and climate prediction. Here we estimate stomatal conductance and associated transpiration in a temperate deciduous forest directly on the canopy scale via two independent approaches: (i) from heat and water vapor exchange and (ii) from carbonyl sulfide (OCS) uptake. We use the eddy covariance method to measure the net ecosystem–atmosphere exchange ofmore » OCS, and we use a flux-gradient approach to separate canopy OCS uptake from soil OCS uptake. We find that the seasonal and diurnal patterns of canopy stomatal conductance obtained by the two approaches agree (to within ±6 % diurnally), validating both methods. Canopy stomatal conductance increases linearly with above-canopy light intensity (in contrast to the leaf scale, where stomatal conductance shows declining marginal increases) and otherwise depends only on the diffuse light fraction, the canopy-average leaf-to-air water vapor gradient, and the total leaf area. Based on stomatal conductance, we partition evapotranspiration (ET) and find that evaporation increases from 0 to 40 % of ET as the growing season progresses, driven primarily by rising soil temperature and secondarily by rainfall. Counterintuitively, evaporation peaks at the time of year when the soil is dry and the air is moist. Our method of ET partitioning avoids concerns about mismatched scales or measurement types because both ET and transpiration are derived from eddy covariance data. Neither of the two ecosystem models tested predicts the observed dynamics of evaporation or transpiration, indicating that ET partitioning such as that provided here is needed to further model development and improve our understanding of carbon and water cycling.« less

Dynamics of canopy stomatal conductance, transpiration, and evaporation in a temperate deciduous forest, validated by carbonyl sulfide uptake

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wehr, Richard; Commane, Roisin; Munger, J. William

Stomatal conductance influences both photosynthesis and transpiration, thereby coupling the carbon and water cycles and affecting surface–atmosphere energy exchange. The environmental response of stomatal conductance has been measured mainly on the leaf scale, and theoretical canopy models are relied on to upscale stomatal conductance for application in terrestrial ecosystem models and climate prediction. Here we estimate stomatal conductance and associated transpiration in a temperate deciduous forest directly on the canopy scale via two independent approaches: (i) from heat and water vapor exchange and (ii) from carbonyl sulfide (OCS) uptake. We use the eddy covariance method to measure the net ecosystem–atmosphere exchange ofmore » OCS, and we use a flux-gradient approach to separate canopy OCS uptake from soil OCS uptake. We find that the seasonal and diurnal patterns of canopy stomatal conductance obtained by the two approaches agree (to within ±6 % diurnally), validating both methods. Canopy stomatal conductance increases linearly with above-canopy light intensity (in contrast to the leaf scale, where stomatal conductance shows declining marginal increases) and otherwise depends only on the diffuse light fraction, the canopy-average leaf-to-air water vapor gradient, and the total leaf area. Based on stomatal conductance, we partition evapotranspiration (ET) and find that evaporation increases from 0 to 40 % of ET as the growing season progresses, driven primarily by rising soil temperature and secondarily by rainfall. Counterintuitively, evaporation peaks at the time of year when the soil is dry and the air is moist. Our method of ET partitioning avoids concerns about mismatched scales or measurement types because both ET and transpiration are derived from eddy covariance data. Neither of the two ecosystem models tested predicts the observed dynamics of evaporation or transpiration, indicating that ET partitioning such as that provided here is needed to further model development and improve our understanding of carbon and water cycling.« less

Supercritical CO2 uptake by nonswelling phyllosilicates

PubMed Central

Tokunaga, Tetsu K.; Ashby, Paul D.; Kim, Yongman; Voltolini, Marco; Gilbert, Benjamin; DePaolo, Donald J.

2018-01-01

Interactions between supercritical (sc) CO2 and minerals are important when CO2 is injected into geologic formations for storage and as working fluids for enhanced oil recovery, hydraulic fracturing, and geothermal energy extraction. It has previously been shown that at the elevated pressures and temperatures of the deep subsurface, scCO2 alters smectites (typical swelling phyllosilicates). However, less is known about the effects of scCO2 on nonswelling phyllosilicates (illite and muscovite), despite the fact that the latter are the dominant clay minerals in deep subsurface shales and mudstones. Our studies conducted by using single crystals, combining reaction (incubation with scCO2), visualization [atomic force microscopy (AFM)], and quantifications (AFM, X-ray photoelectron spectroscopy, X-ray diffraction, and off-gassing measurements) revealed unexpectedly high CO2 uptake that far exceeded its macroscopic surface area. Results from different methods collectively suggest that CO2 partially entered the muscovite interlayers, although the pathways remain to be determined. We hypothesize that preferential dissolution at weaker surface defects and frayed edges allows CO2 to enter the interlayers under elevated pressure and temperature, rather than by diffusing solely from edges deeply into interlayers. This unexpected uptake of CO2, can increase CO2 storage capacity by up to ∼30% relative to the capacity associated with residual trapping in a 0.2-porosity sandstone reservoir containing up to 18 mass % of illite/muscovite. This excess CO2 uptake constitutes a previously unrecognized potential trapping mechanism. PMID:29339499

Supercritical CO2 uptake by nonswelling phyllosilicates.

PubMed

Wan, Jiamin; Tokunaga, Tetsu K; Ashby, Paul D; Kim, Yongman; Voltolini, Marco; Gilbert, Benjamin; DePaolo, Donald J

2018-01-30

Interactions between supercritical (sc) CO 2 and minerals are important when CO 2 is injected into geologic formations for storage and as working fluids for enhanced oil recovery, hydraulic fracturing, and geothermal energy extraction. It has previously been shown that at the elevated pressures and temperatures of the deep subsurface, scCO 2 alters smectites (typical swelling phyllosilicates). However, less is known about the effects of scCO 2 on nonswelling phyllosilicates (illite and muscovite), despite the fact that the latter are the dominant clay minerals in deep subsurface shales and mudstones. Our studies conducted by using single crystals, combining reaction (incubation with scCO 2 ), visualization [atomic force microscopy (AFM)], and quantifications (AFM, X-ray photoelectron spectroscopy, X-ray diffraction, and off-gassing measurements) revealed unexpectedly high CO 2 uptake that far exceeded its macroscopic surface area. Results from different methods collectively suggest that CO 2 partially entered the muscovite interlayers, although the pathways remain to be determined. We hypothesize that preferential dissolution at weaker surface defects and frayed edges allows CO 2 to enter the interlayers under elevated pressure and temperature, rather than by diffusing solely from edges deeply into interlayers. This unexpected uptake of CO 2 , can increase CO 2 storage capacity by up to ∼30% relative to the capacity associated with residual trapping in a 0.2-porosity sandstone reservoir containing up to 18 mass % of illite/muscovite. This excess CO 2 uptake constitutes a previously unrecognized potential trapping mechanism. Copyright © 2018 the Author(s). Published by PNAS.

Supercritical CO 2 uptake by nonswelling phyllosilicates

DOE PAGES

Wan, Jiamin; Tokunaga, Tetsu K.; Ashby, Paul D.; ...

2018-01-16

Interactions between supercritical (sc) CO 2 and minerals are important when CO 2 is injected into geologic formations for storage and as working fluids for enhanced oil recovery, hydraulic fracturing, and geothermal energy extraction. It has previously been shown that at the elevated pressures and temperatures of the deep subsurface, scCO 2 alters smectites (typical swelling phyllosilicates). However, less is known about the effects of scCO 2 on nonswelling phyllosilicates (illite and muscovite), despite the fact that the latter are the dominant clay minerals in deep subsurface shales and mudstones. Our studies conducted by using single crystals, combining reaction (incubationmore » with scCO 2 ), visualization [atomic force microscopy (AFM)], and quantifications (AFM, X-ray photoelectron spectroscopy, X-ray diffraction, and off-gassing measurements) revealed unexpectedly high CO 2 uptake that far exceeded its macroscopic surface area. Results from different methods collectively suggest that CO 2 partially entered the muscovite interlayers, although the pathways remain to be determined. We hypothesize that preferential dissolution at weaker surface defects and frayed edges allows CO 2 to enter the interlayers under elevated pressure and temperature, rather than by diffusing solely from edges deeply into interlayers. This unexpected uptake of CO 2, can increase CO 2 storage capacity by up to ~30% relative to the capacity associated with residual trapping in a 0.2-porosity sandstone reservoir containing up to 18 mass % of illite/muscovite. This excess CO 2 uptake constitutes a previously unrecognized potential trapping mechanism.« less

Rapid transporter regulation prevents substrate flow traffic jams in boron transport

PubMed Central

Sotta, Naoyuki; Duncan, Susan; Tanaka, Mayuki; Sato, Takafumi

2017-01-01

Nutrient uptake by roots often involves substrate-dependent regulated nutrient transporters. For robust uptake, the system requires a regulatory circuit within cells and a collective, coordinated behaviour across the tissue. A paradigm for such systems is boron uptake, known for its directional transport and homeostasis, as boron is essential for plant growth but toxic at high concentrations. In Arabidopsis thaliana, boron uptake occurs via diffusion facilitators (NIPs) and exporters (BORs), each presenting distinct polarity. Intriguingly, although boron soil concentrations are homogenous and stable, both transporters manifest strikingly swift boron-dependent regulation. Through mathematical modelling, we demonstrate that slower regulation of these transporters leads to physiologically detrimental oscillatory behaviour. Cells become periodically exposed to potentially cytotoxic boron levels, and nutrient throughput to the xylem becomes hampered. We conclude that, while maintaining homeostasis, swift transporter regulation within a polarised tissue context is critical to prevent intrinsic traffic-jam like behaviour of nutrient flow. PMID:28870285

Rapid transporter regulation prevents substrate flow traffic jams in boron transport.

PubMed

Sotta, Naoyuki; Duncan, Susan; Tanaka, Mayuki; Sato, Takafumi; Marée, Athanasius Fm; Fujiwara, Toru; Grieneisen, Verônica A

2017-09-05

Nutrient uptake by roots often involves substrate-dependent regulated nutrient transporters. For robust uptake, the system requires a regulatory circuit within cells and a collective, coordinated behaviour across the tissue. A paradigm for such systems is boron uptake, known for its directional transport and homeostasis, as boron is essential for plant growth but toxic at high concentrations. In Arabidopsis thaliana , boron uptake occurs via diffusion facilitators (NIPs) and exporters (BORs), each presenting distinct polarity. Intriguingly, although boron soil concentrations are homogenous and stable, both transporters manifest strikingly swift boron-dependent regulation. Through mathematical modelling, we demonstrate that slower regulation of these transporters leads to physiologically detrimental oscillatory behaviour. Cells become periodically exposed to potentially cytotoxic boron levels, and nutrient throughput to the xylem becomes hampered. We conclude that, while maintaining homeostasis, swift transporter regulation within a polarised tissue context is critical to prevent intrinsic traffic-jam like behaviour of nutrient flow.

A sensitivity study of diffusional mass transfer of gases in tropical storm hydrometeors

NASA Astrophysics Data System (ADS)

Ghosh, Satyajit; Gumber, Siddharth; Varotsos, C.

2017-11-01

This paper quantifies mass transfer and diffusional uptake rates of gases in liquid and solid hydrometeors within a cyclonic system. The non-availability of transfer rates for trace gases diffusing into storm hydrometeors, particularly over polluted urban conurbations, often constrain modellers the world over; however, this is an essential requirement to quantify the scavenging rates over the region concerned. The present paper seeks to provide modellers with such rates. Further, all of the earlier studies apply only to temperate regimes, and surprisingly identical formulations are assumed even for tropical conditions. The present analysis fills this research gap and couples cloud morphology with the associated thermodynamics through Weather Research and Forecasting (WRF) runs for cyclone Chapala (27 October 2015-04 November 2015) which battered the coasts of Yemen (Skamarock et al. 2008). It was a good example for undertaking this sensitivity study because the vertical extent spanned from around 0.75 to 16 km—enabling uptake rate calculations over both droplet and ice phases. Many of the diffusing gases were polar; the dipole moment of sulphur dioxide (SO2) and water vapour (H2O) was also included using a full Lennard-Jones model to compute the binary diffusivities of these gases as they diffused into the droplets mixed with water vapour. The first-order uptake rate constants ranged from 2.08 × 10-07 to 3.44 × 10-06 (s-1) and 1.97 × 10-07 to 7.81 × 10-07 (s-1) for H2O and SO2 respectively. The rates are of the order of 10-09 (s-1) for diffusion of water vapour into ice crystals further aloft. Closely linked with the gas uptake rates is another crucial parameter—the mass accommodation coefficient, α. The most widely used values are 1 and 0.036 (Pruppacher and Klett 1998)—the chosen values are restrictive and warrants a closer look. In storm systems, the vertical extents are in the kilometre range. Chapala with a large vertical extent warrants a full profile calculation. This study shows that for H2O vapour, α values range from a low of 0.004 reaching up to 0.046, and for SO2 impacting the liquid droplets, they are 0.004 to 0.077. Using these values in cloud droplet growth equations showed large changes in the positioning of the cloud base height up to about a maximum of 30%—a classic example illustrating the coupling of microphysics with dynamics suggesting that even large-scale models should cautiously use standard un-corrected accommodation and diffusion coefficients. Over polluted environments, aerosol number concentrations are very high—several hundreds of particles in a cubic centimetre—the cumulative effect involving such large-scale scavenging ends up in causing substantive changes in the actual scavenging rates. This is likely to affect overall radiative transfer calculations and must be corrected.

Diffusion Analysis Of Hydrogen-Desorption Measurements

NASA Technical Reports Server (NTRS)

Danford, Merlin D.

1988-01-01

Distribution of hydrogen in metal explains observed desorption rate. Report describes application of diffusion theory to anaylsis of experimental data on uptake and elimination of hydrogen in high-strength alloys of 25 degree C. Study part of program aimed at understanding embrittlement of metals by hydrogen. Two nickel-base alloys, Rene 41 and Waspaloy, and one ferrous alloy, 4340 steel, studied. Desorption of hydrogen explained by distribution of hydrogen in metal. "Fast" hydrogen apparently not due to formation of hydrides on and below surface as proposed.

Preparation of folate-modified pullulan acetate nanoparticles for tumor-targeted drug delivery.

PubMed

Zhang, Hui-zhu; Li, Xue-min; Gao, Fu-ping; Liu, Ling-rong; Zhou, Zhi-min; Zhang, Qi-qing

2010-01-01

The purpose of this work was to develop a novel nano-carrier with targeting property to tumor. In this study, pullulan acetate (PA) was synthesized by the acetylation of pullulan to simplify the preparation technique of nanoparticles. Folic acid (FA) was conjugated to PA in order to improve the cancer-targeting activity. The products were characterized by proton nuclear magnetic resonance (¹H NMR) spectroscopy. Epirubicin-loaded nanoparticles were prepared by a solvent diffusion method. The loading efficiencies and EPI content increased with the amount of triethylamine (TEA) increasing in some degree. FPA nanoparticles could incorporate more epirubicin than PA nanoparticles. The folate-modified PA nanoparticles (FPA/EPI NPs) exhibited faster drug release than PA nanoparticles (PA/EPI NPs) in vitro. Confocal image analysis and flow cytometry test revealed that FPA/EPI NPs exhibited a greater extent of cellular uptake than PA/EPI NPs against KB cells over-expressing folate receptors on the surface. FPA/EPI NPs also showed higher cytotoxicity than PA/EPI NPs. The cytotoxic effect of FPA/EPI NPs to KB cells was inhibited by an excess amount of folic acid, suggesting that the binding and/or uptake were mediated by the folate receptor.

An evaluation of the phosphorus storage capacity of an anaerobic/aerobic sequential batch biofilm reactor.

PubMed

Chiou, Ren-Jie; Yang, Yi-Rong

2008-07-01

The aim of this work was to assess the phosphorus storage capability of the polyphosphate (poly-P) accumulating organisms (PAO) in the biofilm using a sequential batch biofilm reactor (SBBR). In the anaerobic phase, the specific COD uptake rates increases from 0.05 to 0.22 (mg-COD/mg-biomass/h) as the initial COD increases and the main COD uptake activity occurs in the initial 30 min. The polyhydroxyalkanoates (PHAs) accumulation from 18 to 38 (mg-PHA/g-biomass) and phosphorus release from 20 to 60 (mg-P/L) share a similar trend. The adsorbed COD cannot be immediately transformed to PHAs. Since the PHAs' demand per released phosphorus is independent of the initial COD, the enhancement of the PHA accumulation would be of benefit to phosphorus release. The only requirement is to have an initial amount of substrate that will result in sufficient PHA accumulation (approximately 20 mg-PHA/g-biomass) for phosphorus release. During the aerobic phase, the aeration should not only provide sufficient dissolved oxygen, but should also enhance the mass transfer and the diffusion. In other words, the limitation to the phosphorus storage capability always occurs during the anaerobic phase, not the aerobic phase.

Multimodal Imaging of Brain Connectivity Using the MIBCA Toolbox: Preliminary Application to Alzheimer's Disease

NASA Astrophysics Data System (ADS)

Ribeiro, André Santos; Lacerda, Luís Miguel; Silva, Nuno André da; Ferreira, Hugo Alexandre

2015-06-01

The Multimodal Imaging Brain Connectivity Analysis (MIBCA) toolbox is a fully automated all-in-one connectivity analysis toolbox that offers both pre-processing, connectivity, and graph theory analysis of multimodal images such as anatomical, diffusion, and functional MRI, and PET. In this work, the MIBCA functionalities were used to study Alzheimer's Disease (AD) in a multimodal MR/PET approach. Materials and Methods: Data from 12 healthy controls, and 36 patients with EMCI, LMCI and AD (12 patients for each group) were obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database (adni.loni.usc.edu), including T1-weighted (T1-w), Diffusion Tensor Imaging (DTI) data, and 18F-AV-45 (florbetapir) dynamic PET data from 40-60 min post injection (4x5 min). Both MR and PET data were automatically pre-processed for all subjects using MIBCA. T1-w data was parcellated into cortical and subcortical regions-of-interest (ROIs), and the corresponding thicknesses and volumes were calculated. DTI data was used to compute structural connectivity matrices based on fibers connecting pairs of ROIs. Lastly, dynamic PET images were summed, and the relative Standard Uptake Values calculated for each ROI. Results: An overall higher uptake of 18F-AV-45, consistent with an increased deposition of beta-amyloid, was observed for the AD group. Additionally, patients showed significant cortical atrophy (thickness and volume) especially in the entorhinal cortex and temporal areas, and a significant increase in Mean Diffusivity (MD) in the hippocampus, amygdala and temporal areas. Furthermore, patients showed a reduction of fiber connectivity with the progression of the disease, especially for intra-hemispherical connections. Conclusion: This work shows the potential of the MIBCA toolbox for the study of AD, as findings were shown to be in agreement with the literature. Here, only structural changes and beta-amyloid accumulation were considered. Yet, MIBCA is further able to process fMRI and different radiotracers, thus leading to integration of functional information, and supporting the research for new multimodal biomarkers for AD and other neurodegenerative diseases.

Regulation of glucose and ketone-body metabolism in brain of anaesthetized rats

PubMed Central

Ruderman, Neil B.; Ross, Peter S.; Berger, Michael; Goodman, Michael N.

1974-01-01

1. The effects of starvation and diabetes on brain fuel metabolism were examined by measuring arteriovenous differences for glucose, lactate, acetoacetate and 3-hydroxybutyrate across the brains of anaesthetized fed, starved and diabetic rats. 2. In fed animals glucose represented the sole oxidative fuel of the brain. 3. After 48h of starvation, ketone-body concentrations were about 2mm and ketone-body uptake accounted for 25% of the calculated O2 consumption: the arteriovenous difference for glucose was not diminished, but lactate release was increased, suggesting inhibition of pyruvate oxidation. 4. In severe diabetic ketosis, induced by either streptozotocin or phlorrhizin (total blood ketone bodies >7mm), the uptake of ketone bodies was further increased and accounted for 45% of the brain's oxidative metabolism, and the arteriovenous difference for glucose was decreased by one-third. The arteriovenous difference for lactate was increased significantly in the phlorrhizin-treated rats. 5. Infusion of 3-hydroxybutyrate into starved rats caused marked increases in the arteriovenous differences for lactate and both ketone bodies. 6. To study the mechanisms of these changes, steady-state concentrations of intermediates and co-factors of the glycolytic pathway were determined in freeze-blown brain. 7. Starved rats had increased concentrations of acetyl-CoA. 8. Rats with diabetic ketosis had increased concentrations of fructose 6-phosphate and decreased concentrations of fructose 1,6-diphosphate, indicating an inhibition of phosphofructokinase. 9. The concentrations of acetyl-CoA, glycogen and citrate, a potent inhibitor of phosphofructokinase, were increased in the streptozotocin-treated rats. 10. The data suggest that cerebral glucose uptake is decreased in diabetic ketoacidosis owing to inhibition of phosphofructokinase as a result of the increase in brain citrate. 11. The inhibition of brain pyruvate oxidation in starvation and diabetes can be related to the accelerated rate of ketone-body metabolism; however, we found no correlation between the decrease in glucose uptake in the diabetic state and the arteriovenous difference for ketone bodies. 12. The data also suggest that the rates of acetoacetate and 3-hydroxybutyrate utilization by brain are governed by their concentrations in plasma. 13. The finding of very low concentrations of acetoacetate and 3-hydroxybutyrate in brain compared with plasma suggests that diffusion across the blood–brain barrier may be the rate-limiting step in their metabolism. PMID:4275704

Polymeric nanoparticles of siRNA prepared by a double-emulsion solvent-diffusion technique: Physicochemical properties, toxicity, biodistribution and efficacy in a mammary carcinoma mice model.

PubMed

Ben David-Naim, Meital; Grad, Etty; Aizik, Gil; Nordling-David, Mirjam M; Moshel, Ofra; Granot, Zvi; Golomb, Gershon

2017-11-01

siRNA-loaded nanoparticles (NPs) administered systemically can overcome the poor stability and rapid elimination of free double-stranded RNA in circulation, resulting in increased tumor accumulation and efficacy. siRNA against osteopontin (siOPN), a protein involved in breast cancer development, was encapsulated in poly(D,L-lactic-co-glycolic acid) NPs by a double emulsion solvent diffusion (DESD) technique. We also compared the effect of polyethylenimine (PEI) molecular weight (800 Da and 25 kDa), used as the counter-ion for siRNA complexation, on the physicochemical properties of the NPs, cytotoxicity, and cellular uptake. NPs prepared by the DESD technique were obtained at the desired size (∼170 nm) using both types of PEIs, and were characterized with a neutral surface charge, high encapsulation yield (up to ∼60%), siOPN concentration of 5.6-8.4 μg/mg, stability in physiologic conditions in vitro and in vivo, and long-term shelf-life stability (> 3 years). The NPs prepared using both PEIs exhibited no cytotoxicity in primary smooth muscle culture, and no detrimental effect on mice liver enzymes following their IV administration. Following cellular uptake and biodistribution studies, the therapeutic potential of the NPs was demonstrated by a significant decrease of tumor progression and size in an ectopic xenograft model of mammary carcinoma in mice. Copyright © 2017 Elsevier Ltd. All rights reserved.

Improved cellular uptake of functionalized single-walled carbon nanotubes.

PubMed

Antonelli, A; Serafini, S; Menotta, M; Sfara, C; Pierigé, F; Giorgi, L; Ambrosi, G; Rossi, L; Magnani, M

2010-10-22

Single-walled carbon nanotubes (SWNTs) due to their unique structural and physicochemical properties, have been proposed as delivery systems for a variety of diagnostic and therapeutic agents. However, SWNTs have proven difficult to solubilize in aqueous solution, limiting their use in biological applications. In an attempt to improve SWNTs' solubility, biocompatibility, and to increase cell penetration we have thoroughly investigated the construction of carbon scaffolds coated with aliphatic carbon chains and phospholipids to obtain micelle-like structures. At first, oxidized SWNTs (2370 ± 30 nmol mg(-1) of SWNTs) were covalently coupled with an alcoholic chain (stearyl alcohol, C(18)H(37)OH; 816 nmol mg(-1) of SWNTs). Subsequently, SWNTs-COOC(18)H(37) derivatives were coated with phosphatidylethanolamine (PE) or -serine (PS) phospholipids obtaining micelle-like structures. We found that cellular uptake of these constructs by phagocytic cells occurs via an endocytotic mechanism for constructs larger than 400 nm while occurs via diffusion through the cell membrane for constructs up to 400 nm. The material that enters the cell by phagocytosis is actively internalized by macrophages and localizes inside endocytotic vesicles. In contrast the material that enters the cells by diffusion is found in the cell cytosol. In conclusion, we have realized new biomimetic constructs based on alkylated SWNTs coated with phospholipids that are efficiently internalized by different cell types only if their size is lower than 400 nm. These constructs are not toxic to the cells and could now be explored as delivery systems for non-permeant cargoes.

High waterborne Mg does not attenuate the toxic effects of Fe, Mn, and Ba on Na+ regulation of Amazonian armored catfish tamoatá (Hoplosternum litoralle).

PubMed

Duarte, Rafael M; Benaduce, Ana Paula; Garcia, Luciano; Gomes, Levy C; Gomes, Adriana Chippari; Val, Adalberto L; Baldisserotto, Bernardo

2018-04-24

Formation water (FoW) is a by-product from oil and gas production and usually has high concentrations of soluble salts and metals. Calcium (Ca) and magnesium (Mg) have been shown to reduce the toxicity of metals to aquatic animals, and previous study showed that high waterborne Ca exerts mild effect against disturbances on Na + regulation in Amazonian armored catfish tamoatá (Hoplosternum littorale) acutely exposed to high Fe, Mn, and Ba levels. Here, we hypothesized that high Mg levels might also reduce the toxic effects of these metals on Na + regulation of tamoatá. The exposure to 5% FoW promoted an increase in Na + uptake and a rapid accumulation of Na + in all tissues analyzed (kidney

Aqueous pathways dominate permeation of solutes across Pisum sativum seed coats and mediate solute transport via diffusion and bulk flow of water.

PubMed

Niemann, Sylvia; Burghardt, Markus; Popp, Christian; Riederer, Markus

2013-05-01

The permeability of seed coats to solutes either of biological or anthropogenic origin plays a major role in germination, seedling growth and seed treatment by pesticides. An experimental set-up was designed for investigating the mechanisms of seed coat permeation, which allows steady-state experiments with isolated seed coats of Pisum sativum. Permeances were measured for a set of organic model compounds with different physicochemical properties and sizes. The results show that narrow aqueous pathways dominate the diffusion of solutes across pea seed coats, as indicated by a correlation of permeances with the molecular sizes of the compounds instead of their lipophilicity. Further indicators for an aqueous pathway are small size selectivity and a small effect of temperature on permeation. The application of an osmotic water potential gradient across isolated seed coats leads to an increase in solute transfer, indicating that the aqueous pathways form a water-filled continuum across the seed coat allowing the bulk flow of water. Thus, the uptake of organic solutes across pea testae has two components: (1) by diffusion and (2) by bulk water inflow, which, however, is relevant only during imbibition. © 2012 Blackwell Publishing Ltd.

Dependence of Plant Uptake and Diffusion of Polycyclic Aromatic Hydrocarbons on the Leaf Surface Morphology and Micro-structures of Cuticular Waxes

NASA Astrophysics Data System (ADS)

Li, Qingqing; Li, Yungui; Zhu, Lizhong; Xing, Baoshan; Chen, Baoliang

2017-04-01

The uptake of organic chemicals by plants is considered of great significance as it impacts their environmental transport and fate and threatens crop growth and food safety. Herein, the dependence of the uptake, penetration, and distribution of sixteen polycyclic aromatic hydrocarbons (PAHs) on the morphology and micro-structures of cuticular waxes on leaf surfaces was investigated. Plant surface morphologies and wax micro-structures were examined by scanning emission microscopy, and hydrophobicities of plant surfaces were monitored through contact angle measurements. PAHs in the cuticles and inner tissues were distinguished by sequential extraction, and the cuticle was verified to be the dominant reservoir for the accumulation of lipophilic pollutants. The interspecies differences in PAH concentrations cannot be explained by normalizing them to the plant lipid content. PAHs in the inner tissues became concentrated with the increase of tissue lipid content, while a generally negative correlation between the PAH concentration in cuticles and the epicuticular wax content was found. PAHs on the adaxial and abaxial sides of a leaf were differentiated for the first time, and the divergence between these two sides can be ascribed to the variations in surface morphologies. The role of leaf lipids was redefined and differentiated.

Slow acidification of the winter mixed layer in the subarctic western North Pacific

NASA Astrophysics Data System (ADS)

Wakita, Masahide; Nagano, Akira; Fujiki, Tetsuichi; Watanabe, Shuichi

2017-08-01

We used carbon dioxide (CO2) system data collected during 1999-2015 to investigate ocean acidification at time series sites in the western subarctic region of the North Pacific Ocean. The annual mean pH at station K2 decreased at a rate of 0.0025 ± 0.0010 year-1 mostly in response to oceanic uptake of anthropogenic CO2. The Revelle factor increased rapidly (0.046 ± 0.022 year-1), an indication that the buffering capacity of this region of the ocean has declined faster than at other time series sites. In the western subarctic region, the pH during the winter decline at a slower rate of 0.0008 ± 0.0004 year-1. This was attributed to a reduced rate of increase of dissolved inorganic carbon (DIC) and an increase of total alkalinity (TA). The reduction of DIC increase was caused by the decline of surface water density associated with the pycnocline depression and the reduction of vertical diffusion flux from the upper pycnocline. These physical changes were probably caused by northward shrinkage of the western subarctic gyre and global warming. Meanwhile, the contribution of the density decline to the TA increase is canceled out by that of the reduced vertical diffusive flux. We speculated that the winter TA increase is caused mainly by the accumulation of TA due to the weakened calcification by organisms during the winter.

Uptake of oleate by isolated rat adipocytes is mediated by a 40-kDa plasma membrane fatty acid binding protein closely related to that in liver and gut

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schwieterman, W.; Sorrentino, D.; Potter, B.J.

1988-01-01

A portion of the hepatocellular uptake of nonesterified long-chain fatty acids is mediated by a specific 40-kDa plasma membrane fatty acid binding protein, which has also been isolated from the gut. To investigate whether a similar transport process exists in other tissues with high transmembrane fatty acid fluxes, initial rates (V/sub O/) of (/sup 3/H)-oleate uptake into isolated rat adipocytes were studied as a function of the concentration of unbound (/sup 3/H)oleate in the medium. V/sub O/ reached a maximum as the concentration of unbound oleate was increased and was significantly inhibited both by phloretin and by prior incubation ofmore » the cells with Pronase. A rabbit antibody to the rat liver plasma membrane fatty acid binding protein inhibited adipocyte fatty acid uptake by up to 63% in dose-dependent fashion. Inhibition was noncompetitive; at an immunoglobulin concentration of 250 ..mu..g/ml V/sub max/ was reduced from 2480 /plus minus/ 160 to 1870 /plus minus/ 80 pmol/min per 5 /times/ 10/sup 4/ adipocytes, with no change in K/sub m/. A basic kDa adipocyte plasma membrane fatty acid binding protein, isolated from crude adipocyte plasma membrane fractions, reacted strongly in both agar gel diffusion and electrophoretic blots with the antibody raised against the corresponding hepatic plasma membrane protein. These data indicate that the uptake of oleate by rat adipocytes is mediated by a 40-kDa plasma membrane fatty acid binding protein closely related to that in liver and gut.« less

Healing of polymer interfaces: Interfacial dynamics, entanglements, and strength

NASA Astrophysics Data System (ADS)

Ge, Ting; Robbins, Mark O.; Perahia, Dvora; Grest, Gary S.

2014-07-01

Self-healing of polymer films often takes place as the molecules diffuse across a damaged region, above their melting temperature. Using molecular dynamics simulations we probe the healing of polymer films and compare the results with those obtained for thermal welding of homopolymer slabs. These two processes differ from each other in their interfacial structure since damage leads to increased polydispersity and more short chains. A polymer sample was cut into two separate films that were then held together in the melt state. The recovery of the damaged film was followed as time elapsed and polymer molecules diffused across the interface. The mass uptake and formation of entanglements, as obtained from primitive path analysis, are extracted and correlated with the interfacial strength obtained from shear simulations. We find that the diffusion across the interface is significantly faster in the damaged film compared to welding because of the presence of short chains. Though interfacial entanglements increase more rapidly for the damaged films, a large fraction of these entanglements are near chain ends. As a result, the interfacial strength of the healing film increases more slowly than for welding. For both healing and welding, the interfacial strength saturates as the bulk entanglement density is recovered across the interface. However, the saturation strength of the damaged film is below the bulk strength for the polymer sample. At saturation, cut chains remain near the healing interface. They are less entangled and as a result they mechanically weaken the interface. Chain stiffness increases the density of entanglements, which increases the strength of the interface. Our results show that a few entanglements across the interface are sufficient to resist interfacial chain pullout and enhance the mechanical strength.

Tackling agricultural diffuse pollution: What might uptake of farmer-preferred measures deliver for emissions to water and air?

PubMed

Collins, A L; Zhang, Y S; Winter, M; Inman, A; Jones, J I; Johnes, P J; Cleasby, W; Vrain, E; Lovett, A; Noble, L

2016-03-15

Mitigation of agricultural diffuse pollution poses a significant policy challenge across Europe and particularly in the UK. Existing combined regulatory and voluntary approaches applied in the UK continue to fail to deliver the necessary environmental outcomes for a variety of reasons including failure to achieve high adoption rates. It is therefore logical to identify specific on-farm mitigation measures towards which farmers express positive attitudes for higher future uptake rates. Accordingly, a farmer attitudinal survey was undertaken during phase one of the Demonstration Test Catchment programme in England to understand those measures towards which surveyed farmers are most receptive to increasing implementation in the future. A total of 29 on-farm measures were shortlisted by this baseline farm survey. This shortlist comprised many low cost or cost-neutral measures suggesting that costs continue to represent a principal selection criterion for many farmers. The 29 measures were mapped onto relevant major farm types and input, assuming 95% uptake, to a national scale multi-pollutant modelling framework to predict the technically feasible impact on annual agricultural emissions to water and air, relative to business as usual. Simulated median emission reductions, relative to current practise, for water management catchments across England and Wales, were estimated to be in the order sediment (20%)>ammonia (16%)>total phosphorus (15%) ≫ nitrate/methane (11%)>nitrous oxide (7%). The corresponding median annual total cost of the modelled scenario to farmers was £3 ha(-1)yr(-1), with a corresponding range of -£84 ha(-1)yr(-1) (i.e. a net saving) to £33 ha(-1)yr(-1). The results suggest that those mitigation measures which surveyed farmers are most inclined to implement in the future would improve the environmental performance of agriculture in England and Wales at minimum to low cost per hectare. Copyright © 2015 Elsevier B.V. All rights reserved.

A study of water uptake by selected superdisintegrants from the sub-molecular to the particulate level.

PubMed

Barmpalexis, P; Syllignaki, P; Kachrimanis, K

2018-06-01

Water diffusion through the matrix of three superdisintegrants, namely sodium starch glycolate (SSG), croscarmellose sodium (cCMC-Na) and crospovidone (cPVP), was studied at the sub-molecular level using Attenuated Total Reflectance (ATR)-FTIR spectroscopy and molecular dynamics simulations, and the results were correlated to water uptake studies conducted at the particulate level using Parallel Exponential Kinetics (PEK) modeling in dynamic moisture sorption studies and optical microscopy. ATR-FTIR studies indicated that water diffuses inside cPVP by a single fast acting process, while in SSG and cCMC-Na, a slow and a fast process acting simultaneously, were identified. The same pattern regarding the rate of water uptake for all superdisintegrants was found also at the particulate level by PEK modeling. Moreover, molecular dynamics simulation helped elucidate the hydrogen bonding patterns formed between water-SSG and water-cCMC-Na, mainly via their carboxylic oxygen atoms and secondarily via their hydroxyl groups, while cPVP formed hydrogen bonds only through carbonyl oxygen. Finally, cPVP chains showed significant flexibility during hydration, while cCMC-Na and SSG chains retain their conformation to some extent, explaining the extensive swelling observed also at the particulate level by optical microscopy hydration studies.

Field measures show methanotroph sensitivity to soil moisture follows precipitation regime of the grassland sites across the US Great Plains

NASA Astrophysics Data System (ADS)

Koyama, A.; Webb, C. T.; Johnson, N. G.; Brewer, P. E.; von Fischer, J. C.

2015-12-01

Methane uptake rates are known to have temporal variation in response to changing soil moisture levels. However, the relative importance of soil diffusivity vs. methanotroph physiology has not been disentangled to date. Testing methanotroph physiology in the laboratory can lead to misleading results due to changes in the fine-scale habitat where methanotrophs reside. To assay the soil moisture sensitivity of methanotrophs under field conditions, we studied 22 field plots scattered across eight Great Plains grassland sites that differed in precipitation regime and soil moisture, making ca. bi-weekly measures during the growing seasons over three years. Quantification of methanotroph activity was achieved from chamber-based measures of methane uptake coincident with SF6-derived soil diffusivity, and interpretation in a reaction-diffusion model. At each plot, we also measured soil water content (SWC), soil temperature and inorganic nitrogen (N) contents. We also assessed methanotroph community composition via 454 sequencing of the pmoA gene. Statistical analyses showed that methanotroph activity had a parabolic response with SWC (concave down), and significant differences in the shape of this response among sites. Moreover, we found that the SWC at peak methanotroph activity was strongly correlated with mean annual precipitation (MAP) of the site. The sequence data revealed distinct composition patterns, with structure that was associated with variation in MAP and soil texture. These results suggest that local precipitation regime shapes methanotroph community composition, which in turn lead to unique sensitivity of methane uptake rates with soil moisture. Our findings suggest that methanotroph activity may be more accurately modeled when the biological and environmental responses are explicitly described.

Colony patterning and collective hyphal growth of filamentous fungi

NASA Astrophysics Data System (ADS)

Matsuura, Shu

2002-11-01

Colony morphology of wild and mutant strains of Aspergillus nidulans at various nutrient and agar levels was investigated. Two types of colony patterning were found for these strains. One type produced uniform colonies at all nutrient and agar levels tested, and the other exhibited morphological change into disordered ramified colonies at low nutrient levels. Both types showed highly condensed compact colonies at high nutrient levels on low agar media that was highly diffusive. Disordered colonies were found to develop with low hyphal extension rates at low nutrient levels. To understand basic pattern selection rules, a colony model with three parameters, i.e., the initial nutrient level and the step length of nutrient random walk as the external parameters, and the frequency of nutrient uptake as an internal parameter, was constructed. At low nutrient levels, with decreasing nutrient uptake frequency under diffusive conditions, the model colony exhibited onsets of disordered ramification. Further, in the growth process of A. nidulans, reduction of hyphal extension rate due to a population effect of hyphae was found when hyphae form three-dimensional dense colonies, as compared to the case in which hyphal growth was restricted into two-dimensional space. A hyphal population effect was introduced in the colony model. Thickening of colony periphery due to the population effect became distinctive as the nutrient diffusion effect was raised at high nutrient levels with low hyphal growth rate. It was considered that colony patterning and onset of disorder were strongly governed by the combination of nutrient diffusion and hyphal growth rate.

A modelling approach for the heterogeneous oxidation of elastomers

NASA Astrophysics Data System (ADS)

Herzig, A.; Sekerakova, L.; Johlitz, M.; Lion, A.

2017-09-01

The influence of oxygen on elastomers, known as oxidation, is one of the most important ageing processes and becomes more and more important for nowadays applications. The interaction with thermal effects as well as antioxidants makes oxidation of polymers a complex process. Based on the polymer chosen and environmental conditions, the ageing processes may behave completely different. In a lot of cases the influence of oxygen is limited to the surface layer of the samples, commonly referred to as diffusion-limited oxidation. For the lifetime prediction of elastomer components, it is essential to have detailed knowledge about the absorption and diffusion behaviour of oxygen molecules during thermo-oxidative ageing and how they react with the elastomer. Experimental investigations on industrially used elastomeric materials are executed in order to develop and fit models, which shall be capable of predicting the permeation and consumption of oxygen as well as changes in the mechanical properties. The latter are of prime importance for technical applications of rubber components. Oxidation does not occur homogeneously over the entire elastomeric component. Hence, material models which include ageing effects have to be amplified in order to consider heterogeneous ageing, which highly depends on the ageing temperature. The influence of elevated temperatures upon accelerated ageing has to be critically analysed, and influences on the permeation and diffusion coefficient have to be taken into account. This work presents phenomenological models which describe the oxygen uptake and the diffusion into elastomers based on an improved understanding of ongoing chemical processes and diffusion limiting modifications. On the one side, oxygen uptake is modelled by means of Henry's law in which solubility is a function of the temperature as well as the ageing progress. The latter is an irreversible process and described by an inner differential evolution equation. On the other side, further diffusion of oxygen into the material is described by a model based on Fick's law, which is modified by a reaction term. The evolved diffusion-reaction equation depends on the ageing temperature as well as on the progress of ageing and is able to describe diffusion-limited oxidation.

Imaging and quantification of trans-membrane protein diffusion in living bacteria.

PubMed

Oswald, Felix; L M Bank, Ernst; Bollen, Yves J M; Peterman, Erwin J G

2014-07-07

The cytoplasmic membrane forms the barrier between any cell's interior and the outside world. It contains many proteins that enable essential processes such as the transmission of signals, the uptake of nutrients, and cell division. In the case of prokaryotes, which do not contain intracellular membranes, the cytoplasmic membrane also contains proteins for respiration and protein folding. Mutual interactions and specific localization of these proteins depend on two-dimensional diffusion driven by thermal fluctuations. The experimental investigation of membrane-protein diffusion in bacteria is challenging due to their small size, only a few times larger than the resolution of an optical microscope. Here, we review fluorescence microscopy-based methods to study diffusion of membrane proteins in living bacteria. The main focus is on data-analysis tools to extract diffusion coefficients from single-particle tracking data obtained by single-molecule fluorescence microscopy. We introduce a novel approach, IPODD (inverse projection of displacement distributions), to obtain diffusion coefficients from the usually obtained 2-D projected diffusion trajectories of the highly 3-D curved bacterial membrane. This method provides, in contrast to traditional mean-squared-displacement methods, correct diffusion coefficients and allows unravelling of heterogeneously diffusing populations.

Monte Carlo based method for fluorescence tomographic imaging with lifetime multiplexing using time gates

PubMed Central

Chen, Jin; Venugopal, Vivek; Intes, Xavier

2011-01-01

Time-resolved fluorescence optical tomography allows 3-dimensional localization of multiple fluorophores based on lifetime contrast while providing a unique data set for improved resolution. However, to employ the full fluorescence time measurements, a light propagation model that accurately simulates weakly diffused and multiple scattered photons is required. In this article, we derive a computationally efficient Monte Carlo based method to compute time-gated fluorescence Jacobians for the simultaneous imaging of two fluorophores with lifetime contrast. The Monte Carlo based formulation is validated on a synthetic murine model simulating the uptake in the kidneys of two distinct fluorophores with lifetime contrast. Experimentally, the method is validated using capillaries filled with 2.5nmol of ICG and IRDye™800CW respectively embedded in a diffuse media mimicking the average optical properties of mice. Combining multiple time gates in one inverse problem allows the simultaneous reconstruction of multiple fluorophores with increased resolution and minimal crosstalk using the proposed formulation. PMID:21483610

Side-by-Side Comparison of Commonly Used Biomolecules That Differ in Size and Affinity on Tumor Uptake and Internalization

PubMed Central

Leelawattanachai, Jeerapond; Kwon, Keon-Woo; Michael, Praveesuda; Ting, Richard; Kim, Ju-Young; Jin, Moonsoo M.

2015-01-01

The ability to use a systemically injected agent to image tumor is influenced by tumor characteristics such as permeability and vascularity, and the size, shape, and affinity of the imaging agent. In this study, six different imaging biomolecules, with or without specificity to tumor, were examined for tumor uptake and internalization at the whole body, ex-vivo tissue, and cellular levels: antibodies, antibody fragments (Fab), serum albumin, and streptavidin. The time of peak tumor uptake was dependent solely on the size of molecules, suggesting that molecular size is the major factor that influences tumor uptake by its effect on systemic clearance and diffusion into tumor. Affinity to tumor antigen failed to augment tumor uptake of Fab above non-specific accumulation, which suggests that Fab fragments of typical monoclonal antibodies may fall below an affinity threshold for use as molecular imaging agents. Despite abundant localization into the tumor, albumin and streptavidin were not found on cell surface or inside cells. By comparing biomolecules differing in size and affinity, our study highlights that while pharmacokinetics are a dominant factor in tumor uptake for biomolecules, affinity to tumor antigen is required for tumor binding and internalization. PMID:25901755

Uptake of Sulfate but Not Phosphate by Mycobacterium tuberculosis Is Slower than That for Mycobacterium smegmatis

PubMed Central

Song, Houhui

2012-01-01

Knowledge of the metabolic pathways used by Mycobacterium tuberculosis during infection is important for understanding its nutrient requirements and host adaptation. However, uptake, the first step in the utilization of nutrients, is poorly understood for many essential nutrients, such as inorganic anions. Here, we show that M. tuberculosis utilizes nitrate as the sole nitrogen source, albeit at lower efficiency than asparagine, glutamate, and arginine. The growth of the porin triple mutant M. smegmatis ML16 in media with limiting amounts of nitrate and sulfate as sole nitrogen and sulfur sources, respectively, was delayed compared to that of the wild-type strain. The uptake of sulfate was 40-fold slower than that of the wild-type strain, indicating that the efficient uptake of these anions is dependent on porins. The uptake by M. tuberculosis of sulfate and phosphate was approximately 40- and 10-fold slower than that of M. smegmatis, respectively, which is consistent with the slower growth of M. tuberculosis. However, the uptake of these anions by M. tuberculosis is orders of magnitude faster than diffusion through lipid membranes, indicating that unknown outer membrane proteins are required to facilitate this process. PMID:22194452

The contribution of water soluble and water insoluble organic fractions to oxygen uptake rate during high rate composting.

PubMed

Giuliana, D'Imporzano; Fabrizio, Adani

2007-02-01

This study aims to establish the contribution of the water soluble and water insoluble organic fractions to total oxygen uptake rate during high rate composting process of a mixture of organic fraction of municipal solid waste and lignocellulosic material. This mixture was composted using a 20 l self-heating pilot scale composter for 250 h. The composter was fully equipped to record both the biomass-temperature and oxygen uptake rate. Representative compost samples were taken at 0, 70, 100, 110, 160, and 250 h from starting time. Compost samples were fractionated in water soluble and water insoluble fractions. The water soluble fraction was then fractionated in hydrophilic, hydrophobic, and neutral hydrophobic fractions. Each fraction was then studied using quantitative (total organic carbon) and qualitative analysis (diffuse reflectance infrared spectroscopy and biodegradability test). Oxygen uptake rates were high during the initial stages of the process due to rapid degradation of the soluble degradable organic fraction (hydrophilic plus hydrophobic fractions). Once this fraction was depleted, polymer hydrolysis accounted for most of the oxygen uptake rate. Finally, oxygen uptake rate could be modeled using a two term kinetic. The first term provides the oxygen uptake rate resulting from the microbial growth kinetic type on easily available, no-limiting substrate (soluble fraction), while the second term considers the oxygen uptake rate caused by the degradation of substrate produced by polymer hydrolysis.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, XS; Narayanan, S; Michaelis, VK

Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapormore » diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg, Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the lab-scale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N-2 sorption, Al-27/Si-29 MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N-2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications. (C) 2014 Elsevier Inc. All rights reserved.« less

Comparative study of silver nanoparticle permeation using Side-Bi-Side and Franz diffusion cells

NASA Astrophysics Data System (ADS)

Trbojevich, Raul A.; Fernandez, Avelina; Watanabe, Fumiya; Mustafa, Thikra; Bryant, Matthew S.

2016-03-01

Better understanding the mechanisms of nanoparticle permeation through membranes and packaging polymers has important implications for the evaluation of drug transdermal uptake, in food safety and the environmental implications of nanotechnology. In this study, permeation of 21 nm diameter silver nanoparticles (AgNPs) was tested using Side-Bi-Side and Franz static diffusion cells through hydrophilic 0.1 and 0.05 µm pore diameter 125 µm thick synthetic cellulose membranes, and 16 and 120 µm thick low-density polyethylene (LDPE) films. Experiments performed with LDPE films discarded permeation of AgNPs or Ag ions over the investigated time-frame in both diffusion systems. But controlled release of AgNPs has been quantified using semipermeable hydrophilic membranes. The permeation followed a quasi-linear time-dependent model during the experimental time-frame, which represents surface reaction-limited permeation. Diffusive flux, diffusion coefficients, and membrane permeability were determined as a function of pore size and diffusion model. Concentration gradient and pore size were key to understand mass transfer phenomena in the diffusion systems.

Sorption isotherm and kinetic modeling of aniline on Cr-bentonite.

PubMed

Zheng, Hong; Liu, Donghong; Zheng, Yan; Liang, Shuping; Liu, Zhe

2009-08-15

In this paper, the sorption characteristics of aniline on Cr-bentonite prepared using synthetic wastewater containing chromium was investigated in a batch system at 30 degrees C. The effects of relevant parameters, such as pH value of solution, adsorbent dosage and initial aniline concentration were examined. The experimental data were analyzed by the Langmuir and Freundlich, and Temkin models of sorption. The sorption isotherm data were fitted well to Langmuir isotherm and the monolayer sorption capacity was found to be 21.60 mg/g at 30 degrees C. Dubinin-Redushkevich (D-R) isotherm was applied to describe the nature of aniline uptake and it was found that it occurred chemically. The kinetic data obtained at different concentrations were analyzed using a pseudo first-order, pseudo second-order kinetic equation and intraparticle diffusion model. The experimental data fitted very well the pseudo second-order kinetic model. Intraparticle diffusion affects aniline uptake. The results indicate that there is significant potential for Cr-bentonite as an adsorbent material for aniline removal from aqueous solutions.

Bronchoalveolar carcinoma of lung masquerading as iodine avid metastasis in a patient with minimally invasive follicular carcinoma of thyroid.

PubMed

Malhotra, Gaurav; Nair, Narendra; Menon, Hari; Gujral, Sumit; Abhyankar, Amit; Baghel, Nawab S; Awasare, Sushama; Nabar, Swapna J; Abhyankar, Suman; Kand, Purushottam G

2008-01-01

A 52-year-old man with follicular thyroid carcinoma was administered 182 mCi of radioiodine (I-131) a month after total thyroidectomy. Post-therapy scan revealed diffuse uptake of radioiodine in the apical left lung. CT-guided biopsy of this mass revealed mucinous bronchoalveolar carcinoma. Immunohistochemistry for thyroglobulin was negative. An FDG PET scan showed avid uptake in the lung mass. Surgery was ruled out, so he was given chemotherapy, without benefit. The lesion continued to show I-131 uptake even while on daily T3 substitution, suggesting that the mass was thyroid stimulating hormone-independent. Because the mass showed I-131 uptake and chemotherapy was not beneficial, it was decided to treat with I-131. He was continued on T3 substitution therapy and was given 209 mCi of I-131. Follow-up CT scan a few weeks later reported a 1-cm all round reduction of the mass. I-131 scan showed avid tracer uptake in the mass. This case suggests the possibility of this therapeutic option in nonthyroidal tumors that may concentrate radioiodine.

Uptake and Accumulation of the Herbicides Chlorsulfuron and Clopyralid in Excised Pea Root Tissue 1

PubMed Central

Devine, Malcolm D.; Bestman, Hank D.; Vanden Born, William H.

1987-01-01

The herbicides chlorsulfuron and clopyralid were taken up rapidly by excised pea root tissue and accumulated in the tissue to concentrations ten and four times those in the external medium, respectively. Uptake was related linearly to external herbicide concentration over a wide concentration range, implying that transport across the membrane is by nonfacilitated diffusion. Uptake of both compounds was influenced by pH, with greatest uptake at low pH. The pH dependence of uptake suggests that the herbicides (both of which are weak acids) are transported across the plasma membrane in the undissociated form, and accumulate in the cytoplasm by an ion trap mechanism. Most of the absorbed herbicide effluxed from the tissue when it was transferred to herbicide-free buffer, indicating that the accumulation was not due to irreversible binding. Consequently, both herbicides remain available for transfer to the phloem. These results can explain the high reported phloem mobility of clopyralid in intact plants. The low phloem mobility of chlorsulfuron must be accounted for by factors that override its ability to accumulate in the symplast. PMID:16665689

Three-compartment model for contaminant accumulation by semipermeable membrane devices

USGS Publications Warehouse

Gale, Robert W.

1998-01-01

Passive sampling of dissolved hydrophobic contaminants with lipid (triolein)-containing semipermeable membrane devices (SPMDs) has been gaining acceptance for environmental monitoring. Understanding of the accumulation process has employed a simple polymer film-control model of uptake by the polymer-enclosed lipid, while aqueous film control has been only briefly discussed. A more complete three-compartment model incorporating both aqueous film (turbulent-diffusive) and polymer film (diffusive) mass transfer is developed here and is fit to data from accumulation studies conducted in constant-concentration, flow-through dilutors. This model predicts aqueous film control of the whole device for moderate to high Kow compounds, rather than polymer film control. Uptake rates for phenanthrene and 2,2‘,5,5‘-tetrachlorobiphenyl were about 4.8 and 4.2 L/day/standard SPMD, respectively. Maximum 28 day SPMD concentration factors of 30 000 are predicted for solutes with log Kow values of >5.5. Effects of varying aqueous and polymer film thicknesses and solute diffusivities in the polymer film are modeled, and overall accumulation by the whole device is predicted to remain under aqueous film control, although accumulation in the triolein may be subject to polymer film control. The predicted half-life and integrative response of SPMDs to pulsed concentration events is proportional to log KSPMD.

Modeling uptake of hydrophobic organic contaminants into polyethylene passive samplers.

PubMed

Thompson, Jay M; Hsieh, Ching-Hong; Luthy, Richard G

2015-02-17

Single-phase passive samplers are gaining acceptance as a method to measure hydrophobic organic contaminant (HOC) concentration in water. Although the relationship between the HOC concentration in water and passive sampler is linear at equilibrium, mass transfer models are needed for nonequilibrium conditions. We report measurements of organochlorine pesticide diffusion and partition coefficients with respect to polyethylene (PE), and present a Fickian approach to modeling HOC uptake by PE in aqueous systems. The model is an analytic solution to Fick's second law applied through an aqueous diffusive boundary layer and a polyethylene layer. Comparisons of the model with existing methods indicate agreement at appropriate boundary conditions. Laboratory release experiments on the organochlorine pesticides DDT, DDE, DDD, and chlordane in well-mixed slurries support the model's applicability to aqueous systems. In general, the advantage of the model is its application in the cases of well-agitated systems, low values of polyethylene-water partioning coefficients, thick polyethylene relative to the boundary layer thickness, and/or short exposure times. Another significant advantage is the ability to estimate, or at least bound, the needed exposure time to reach a desired CPE without empirical model inputs. A further finding of this work is that polyethylene diffusivity does not vary by transport direction through the sampler thickness.

Nearly total absence of pulmonary perfusion with corresponding technetium-99m MDP and gallium-67 uptake in a patient with mediastinal neuroblastoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garty, I.; Koren, A.; Moguilner, G.

1985-08-01

A case of unilateral nearly total hypoperfusion of the left lung in a 13-month-old girl is presented. The combination of the lung hypoperfusion and accumulation of the Tc-99m MDP and Ga-67 citrate in the same area suggested the preoperative diagnosis of mediastinal neuroblastoma. Explorative thoracotomy revealed the presence of a neuroblastoma compressing the left lung pedicle. The described scintigraphic appearance in the pediatric age group is suggested as typical of mediastinal neuroblastoma. This pathology should be included in the following gamuts in nuclear medicine: unilateral decrease or absent lung perfusion, unilateral diffuse chest uptake of Ga-67 citrate, and unilateral pulmonarymore » uptake in bone scintigraphy.« less

Tissue Permeability Effects Associated with the Use of Mucoadhesive Cationic Nanoformulations of Docetaxel in the Bladder.

PubMed

Pandey, Rakhi; Jackson, John K; Mugabe, Clement; Liggins, Richard; Burt, Helen M

2016-08-01

Recently, efficacy studies in mice have shown that amine-terminated cationic (CNP) nanoparticulate carriers of DTX offer an improved formulation of the drug for intravesical delivery. It is hypothesized that this improved efficacy may arise from a carrier mediated bladder exfoliation process that removes the urothelial barrier allowing for increased drug uptake into bladder tissue. The objective of this study was to investigate exfoliation processes in fresh pig's bladders (ex vivo) exposed to three cationic polyglycerols with increasing degrees of amination (denoted 350, 580 and 780). The study also compared the tissue depth profile of DTX uptake into these tissues using these different carriers. Aminated polyglycerols were synthesized and characterized in the laboratory with low (CNP-360), medium (CNP-580) and high (CNP-780) levels of amine content. CNP-based DTX solutions and commercial DTX solutions in polysorbate 80 (Taxotere®) were doped with (3)H-radiolabeled DTX and prepared by solvent evaporation from acetonitrile, followed by drying and reconstitution in pH 6.4 buffer. Sections of fresh pig's bladder tissue were clamped into Franz diffusion cells and the urothelial side was exposed to the DTX solutions for 2 h. Tissue sections were then frozen for sectioning by cryotome sectioning and subsequently processed for drug analysis by liquid scintillation counting. Alternatively tissue sections were fixed in 2% glutaraldehyde and 2% paraformaldehyde in 0.1 M sodium cacodylate buffer for the purposes of scanning electron microscopy (SEM). Exposure of the urothelial surface to the amine-terminated polyglycerol solutions resulted in the exfoliation of bladder tissues in a time- and concentration-dependent manner. Exfoliation was significantly more pronounced when using CNPs with a medium or high levels of amination whereas only minor levels of exfoliation were seen with low levels. Following incubation of tissues in Tween-based commercial formulations (Taxotere) of DTX (0.5 mg/mL) the drug was detectable at low levels (10-40 μg/g tissue) in all depths of tissue. Similar drug uptake was observed using the CNP-360 formulation. However drug uptake levels were increased to 60-100 μg/g tissue when samples were incubated with either the CNP-580 or CNP-780 formulations. The use of cationic polyglycerols with higher levels of amine termination allows for an enhanced uptake of DTX into bladder tissues as compared to commercial (Taxotere) formulations. These increased drug levels probably arise from exfoliation processes resulting in a temporary elimination of the urothelial permeability barrier and increased drug penetration into the tissue.

Equilibrium sorption and diffusion rate studies with halogenated organic chemical and sandy aquifer material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ball, W.P.

1990-01-01

Concepts for rate limitation of sorptive uptake of hydrophobic organic solutes by aquifer solids are reviewed, emphasizing physical diffusion models and in the context of effects on contaminant transport. Data for the sorption of tetrachloroethene (PCE) and 1,2,4,5-tetrachlorobenzene (TeCB) on Borden sand are presented, showing that equilibrium is attained very slowly, requiring equilibration times on the order of tens of days for PCE and hundreds of days for TeCB. The rate of approach to equilibrium decreased with increasing particle size and sorption distribution coefficient, in accordance with retarded intragranular diffusion models. Pulverization of the samples significantly decreased the required timemore » to equilibrium without changing the sorption capacity of the solids. Batch sorption methodology was refined to allow accurate measurement of long-term distribution coefficients, using purified {sup 14}C-labelled solute spikes and sealed glass ampules. Sorption isotherms for PCE and TeCB were conducted with size fractions of Borden sand over four to five orders of magnitude in aqueous concentration, and were found to be slightly nonlinear (Freundlich exponent = 0.8). A concentrated set of data in the low concentration range (<50 ug/L) revealed that sorption in this range could be equally well described by a linear isotherm. Distribution coefficients of the two solutes with seven size fractions of Borden sand, measured at low concentration and at full equilibrium, were between seven and sixty times the value predicted on the basis of recent correlations with organic carbon content. Rate results for coarse size fractions support a simple pore diffusion model, with pore diffusion coefficients estimated to be approximately 3 {times} 10{sup {minus}8} cm{sup 2}/sec, more than 200{times} lower than the aqueous diffusivities.« less

iCHAMPSS: Usability and Psychosocial Impact for Increasing Implementation of Sexual Health Education.

PubMed

Hernandez, Belinda F; Peskin, Melissa F; Shegog, Ross; Gabay, Efrat K; Cuccaro, Paula M; Addy, Robert C; Ratliff, Eric; Emery, Susan T; Markham, Christine M

2017-05-01

Diffusion of sexual health evidence-based programs (EBPs) in schools is a complex and challenging process. iCHAMPSS ( CHoosing And Maintaining effective Programs for Sex education in Schools) is an innovative theory- and Web-based decision support system that may help facilitate this process. The purpose of this study was to pilot-test iCHAMPSS for usability and short-term psychosocial impact. School district stakeholders from across Texas were recruited ( N = 16) and given access to iCHAMPSS for 3 weeks in fall 2014. Pre- and posttests were administered to measure usability parameters and short-term psychosocial outcomes. Data were analyzed using descriptive statistics and the Wilcoxon signed-rank test. Most participants reported that iCHAMPSS was easy to use, credible, helpful, and of sufficient motivational appeal. iCHAMPSS significantly increased participants' self-efficacy to obtain approval from their board of trustees to implement a sexual health EBP. Positive, though nonsignificant, trends included increased knowledge to locate EBPs, skills to prioritize sexual health education at the district level, and ability to choose an EBP that best meets district needs. iCHAMPSS is an innovative decision support system that could accelerate uptake of EBPs by facilitating diffusion and advance the field of dissemination and implementation science for the promotion of sexual health EBPs.

Bioavailable cadmium during the bioremediation of phenanthrene-contaminated soils using the diffusive gradients in thin-film technique.

PubMed

Amezcua-Allieri, M A; Rodríguez-Vázquez, R

2006-03-01

To study the impact of fungal bioremediation of phenanthrene on trace cadmium solid-solution fluxes and solution phase concentration. The bioremediation of phenanthrene in soils was performed using the fungus Penicillium frequentans. Metal behaviour was evaluated by the techniques of diffusive gradient in thin-films (DGT) and filtration. Fluxes of cadmium (Cd) show a significant (P < 0.002) increase after the start of bioremediation, indicating that the bioremediation process itself releases significant amount of Cd into solution from the soil solid-phase. Unlike DGT devices, the solution concentration from filtration shows a clear bimodal distribution. We postulate that the initial action of the fungi is most likely to breakdown the surface of the solid phase to smaller, 'solution-phase' material (<0.45 microm) leading to a peak in Cd concentration in solution. Phenanthrene removal from soils by bioremediation ironically results in the mobilization of another toxic pollutant (Cd). Bioremediation of organic pollutants in contaminated soil will likely lead to large increases in the mobilization of toxic metals, increasing metal bio-uptake and incorporation into the wider food chain. Bioremediation strategies need to account for this behaviour and further research is required both to understand the generality of this behaviour and the operative mechanisms.

Light distribution in plant canopies: A comparison between 1-D multi-layer modeling approach and 3-D ray tracing

NASA Astrophysics Data System (ADS)

Srinivasan, V.; Yiwen, X.; Ellis, A.; Christensen, A.; Borkiewic, K.; Cox, D.; Hart, J.; Long, S.; Marshall-Colon, A.

2016-12-01

The distribution of absorbed solar radiation in the photosynthetically active region wavelength (PAR) within plant canopies plays a critical role in determining photosynthetic carbon uptake and its associated transpiration. The vertical distribution of leaf area, leaf angles, leaf absorptivity and reflectivity within the canopy, affect the distribution of PAR absorbed throughout the canopy. While the upper canopy sunlit leaves absorb most of the incoming PAR and hence contribute most towards total canopy carbon uptake, the lower canopy shaded leaves which receive mostly lower intensity diffuse PAR make significant contributions towards plant carbon uptake. Most detailed vegetation models use a 1-D vertical multi-layer approach to model the sunlight and shaded canopy leaf fractions, and quantify the direct and diffuse radiation absorbed by the respective leaf fractions. However, this approach is only applicable under canopy closure conditions, and furthermore it fails to accurately capture the effects of diurnally varying leaf angle distributions in some plant canopies. Here, we show by using a 3-D ray tracing model which uses an explicit 3-D canopy structure that enforces no conditions about canopy closure, that the effects of diurnal variation of canopy leaf angle distributions better match with observed data. Our comparative analysis performed on soybean crop canopies between 3-D ray tracing model and the multi-layer model shows that the distribution of absorbed direct PAR is not exponential while, the distribution of absorbed diffuse PAR radiation within plant canopies is exponential. These results show the multi-layer model to significantly over-predict canopy PAR absorbed, and in turn significantly overestimate photosynthetic carbon uptake by up to 13% and canopy transpiration by 7% under mid-day sun conditions as verified through our canopy chamber experiments. Our results indicate that current detailed 1-D multi-layer canopy radiation attenuation models significantly over predict canopy radiation absorption and its associated canopy photosynthetic and transpiration fluxes, and use of a 3-D ray tracing model provides more realistic predictions of leaf canopy integrated fluxes of carbon and water.

Evaluation of organic amendment on the effect of cadmium bioavailability in contaminated soils using the DGT technique and traditional methods.

PubMed

Yao, Yu; Sun, Qin; Wang, Chao; Wang, Pei-Fang; Ding, Shi-Ming

2017-03-01

Organic amendments have been widely proposed as a remediation technology for metal-contaminated soils, but there exist controversial results on their effectiveness. In this study, the effect of pig manure addition on cadmium (Cd) bioavailability in Cd-contaminated soils was systematically evaluated by one dynamic, in situ technique of diffusive gradients in thin films (DGT) and four traditional methods based on the equilibrium theory (soil solution concentration and the three commonly used extractants, i.e., acetic acid (HAc), ethylenediamine tetraacetic acid (EDTA), and calcium chloride (CaCl 2 ). Wheat and maize were selected for measurement of plant Cd uptake. The results showed that pig manure addition could promote the growth of two plants, accompanied by increasing biomasses of shoots and roots with increasing doses of pig manure addition. Correspondingly, increasing additions of pig manure reduced plant Cd uptake and accumulation, as indicated by the decreases of Cd concentrations in shoots and roots. The bioavailable concentrations of Cd in Cd-contaminated soils reflected by the DGT technique obviously decreased with increasing doses of pig manure addition, following the same changing trend as plant Cd uptake. Changes in soil solution Cd concentration and extractable Cd by HAc, EDTA, and CaCl 2 in soils were similar to DGT measurement. Meanwhile, the capability of Cd resupply from solid phase to soil solution decreased with increasing additions of pig manure, as reflected by the decreases in the ratio (R) value of C DGT to C sol . Positive correlations were observed between various bioavailable indicators of Cd in soils and Cd concentrations in the tissues of the two plants. These findings provide stronger evidence that pig manure amendment is effective in reducing Cd mobility and bioavailability in soils and it is an ideal organic material for remediation of Cd-contaminated soils.

Transepithelial glucose transport and Na+/K+ homeostasis in enterocytes: an integrative model

PubMed Central

Drengstig, Tormod; Ruoff, Peter

2014-01-01

The uptake of glucose and the nutrient coupled transcellular sodium traffic across epithelial cells in the small intestine has been an ongoing topic in physiological research for over half a century. Driving the uptake of nutrients like glucose, enterocytes must have regulatory mechanisms that respond to the considerable changes in the inflow of sodium during absorption. The Na-K-ATPase membrane protein plays a major role in this regulation. We propose the hypothesis that the amount of active Na-K-ATPase in enterocytes is directly regulated by the concentration of intracellular Na+ and that this regulation together with a regulation of basolateral K permeability by intracellular ATP gives the enterocyte the ability to maintain ionic Na+/K+ homeostasis. To explore these regulatory mechanisms, we present a mathematical model of the sodium coupled uptake of glucose in epithelial enterocytes. Our model integrates knowledge about individual transporter proteins including apical SGLT1, basolateral Na-K-ATPase, and GLUT2, together with diffusion and membrane potentials. The intracellular concentrations of glucose, sodium, potassium, and chloride are modeled by nonlinear differential equations, and molecular flows are calculated based on experimental kinetic data from the literature, including substrate saturation, product inhibition, and modulation by membrane potential. Simulation results of the model without the addition of regulatory mechanisms fit well with published short-term observations, including cell depolarization and increased concentration of intracellular glucose and sodium during increased concentration of luminal glucose/sodium. Adding regulatory mechanisms for regulation of Na-K-ATPase and K permeability to the model show that our hypothesis predicts observed long-term ionic homeostasis. PMID:24898586

Estimating the Cost-Effectiveness of Implementation: Is Sufficient Evidence Available?

PubMed

Whyte, Sophie; Dixon, Simon; Faria, Rita; Walker, Simon; Palmer, Stephen; Sculpher, Mark; Radford, Stefanie

2016-01-01

Timely implementation of recommended interventions can provide health benefits to patients and cost savings to the health service provider. Effective approaches to increase the implementation of guidance are needed. Since investment in activities that improve implementation competes for funding against other health generating interventions, it should be assessed in term of its costs and benefits. In 2010, the National Institute for Health and Care Excellence released a clinical guideline recommending natriuretic peptide (NP) testing in patients with suspected heart failure. However, its implementation in practice was variable across the National Health Service in England. This study demonstrates the use of multi-period analysis together with diffusion curves to estimate the value of investing in implementation activities to increase uptake of NP testing. Diffusion curves were estimated based on historic data to produce predictions of future utilization. The value of an implementation activity (given its expected costs and effectiveness) was estimated. Both a static population and a multi-period analysis were undertaken. The value of implementation interventions encouraging the utilization of NP testing is shown to decrease over time as natural diffusion occurs. Sensitivity analyses indicated that the value of the implementation activity depends on its efficacy and on the population size. Value of implementation can help inform policy decisions of how to invest in implementation activities even in situations in which data are sparse. Multi-period analysis is essential to accurately quantify the time profile of the value of implementation given the natural diffusion of the intervention and the incidence of the disease. Copyright © 2016 International Society for Pharmacoeconomics and Outcomes Research (ISPOR). Published by Elsevier Inc. All rights reserved.

Uptake and elimination of poliovirus by West Coast oysters.

PubMed

Di Girolamo, R; Liston, J; Matches, J

1975-02-01

Accumulation of poliovirus Lsc-2ab by West Coast oysters was determined by using a stationary seawater system, and depuration was determined by using both stationary and free-flow systems. Results indicate that these shellfish have the same pattern of accumulation and localization of viruses as do East Coast species. However, uptake appeared to occur more rapidly than described for East Coast shellfish. There appeared to be a gradual diffusion of virus from the digestive area into the body. Depuration was found to occur more rapidly and completely under free-flow conditions than in a stationary system.

Uptake and Elimination of Poliovirus by West Coast Oysters

PubMed Central

Girolamo, Rudolph Di; Liston, John; Matches, J.

1975-01-01

Accumulation of poliovirus Lsc-2ab by West Coast oysters was determined by using a stationary seawater system, and depuration was determined by using both stationary and free-flow systems. Results indicate that these shellfish have the same pattern of accumulation and localization of viruses as do East Coast species. However, uptake appeared to occur more rapidly than described for East Coast shellfish. There appeared to be a gradual diffusion of virus from the digestive area into the body. Depuration was found to occur more rapidly and completely under free-flow conditions than in a stationary system. PMID:163615

Theoretical Study of Molecular Transport Through a Permeabilized Cell Membrane in a Microchannel.

PubMed

Mahboubi, Masoumeh; Movahed, Saeid; Hosseini Abardeh, Reza; Hoshyargar, Vahid

2017-06-01

A two-dimensional model is developed to study the molecular transport into an immersed cell in a microchannel and to investigate the effects of finite boundary (a cell is suspended in a microchannel), amplitude of electric pulse, and geometrical parameter (microchannel height and size of electrodes) on cell uptake. Embedded electrodes on the walls of the microchannel generate the required electric pulse to permeabilize the cell membrane, pass the ions through the membrane, and transport them into the cell. The shape of electric pulses is square with the time span of 6 ms; their intensities are in the range of 2.2, 2.4, 2.6, 3 V. Numerical simulations have been performed to comprehensively investigate the molecular uptake into the cell. The obtained results of the current study demonstrate that calcium ions enter the cell from the anodic side (the side near positive electrode); after a while, the cell faces depletion of the calcium ions on a positive electrode-facing side within the microchannel; the duration of depletion depends on the amplitude of electric pulse and geometry that lasts from microseconds to milliseconds. By keeping geometrical parameters and time span constant, increment of a pulse intensity enhances molecular uptake and rate of propagation inside the cell. If a ratio of electrode size to cell diameter is larger than 1, the transported amount of Ca 2+ into the cell, as well as the rate of propagation, will be significantly increased. By increasing the height of the microchannel, the rate of uptake is decreased. In an infinite domain, the peak concentration becomes constant after reaching the maximum value; this value depends on the intra-extracellular conductivity and diffusion coefficient of interior and exterior domains of the cell. In comparison, the maximum concentration is changed by geometrical parameters in the microchannel. After reaching the maximum value, the peak concentration reduces due to the depletion of Ca 2+ ions within the microchannel. Electrophoretic velocity has a significant effect on the cell uptake.

Bacterial uptake of antibiotics in model unsaturated systems

NASA Astrophysics Data System (ADS)

Zhang, W.; Chen, Z.; Zhang, Y.; Zhao, Z.; Wang, G.; Gao, Y.; Boyd, S. A.; Zhu, D.; Li, H.

2016-12-01

Anthropogenic antibiotics are ubiquitously present in the environment due to large uses in human medicine and animal agriculture, and are causing unintended consequence to human and ecosystem health. Bacterial uptake of antibiotics could exert selection pressure on antibiotic resistance development among bacteria population. Therefore, understanding environmental factors controlling bioavailability of antibiotics to bacteria is critical to better assessing exposure risks and developing mitigation strategies. Nonetheless, conventional bioavailability assays are often performed in water-saturated systems that do not represent unsaturated soils where most bacteria live, therefore neglecting soil water as a controlling factor in determining the extent of antibiotic bacterial uptake. Therefore, we propose to study bacterial uptake of antibiotics in model unsaturated systems using GFP-tagged Escherichia coli bioreporter for tetracyclines. Our preliminary studies demonstrated the important role of water content (or water matric potential) in determining the bioavailability of antibiotics, and complex interactions of water potential, tetracycline diffusion, and E. coli growth. Therefore, unsaturated processes are important for understanding antibiotic resistance development and developing mitigation strategies.

Modelling oral up-take of hydrophobic and super-hydrophobic chemicals in fish.

PubMed

Larisch, Wolfgang; Goss, Kai-Uwe

2018-01-24

We have extended a recently published toxicokinetic model for fish (TK-fish) towards the oral up-take of contaminants. Validation with hydrophobic chemicals revealed that diffusive transport through aqueous boundary layers in the gastro-intestinal tract and in the blood is the limiting process. This process can only be modelled correctly if facilitated transport by albumin or bile micelles through these boundary layers is accounted for. In a case study we have investigated the up-take of a super hydrophobic chemical, Dechlorane Plus. Our results suggest that there is no indication of a hydrophobicity or size cut-off in the bioconcentration of this chemical. Based on an extremely high, but mechanistically sound facilitation factor we received model results in good agreement with experimental values from the literature. The results also indicate that established experimental procedures for BCF determination cannot cover the very slow up-take and clearance kinetics that are to be expected for such a chemical.

Genome-wide assessment of the carriers involved in the cellular uptake of drugs: a model system in yeast

PubMed Central

2011-01-01

Background The uptake of drugs into cells has traditionally been considered to be predominantly via passive diffusion through the bilayer portion of the cell membrane. The recent recognition that drug uptake is mostly carrier-mediated raises the question of which drugs use which carriers. Results To answer this, we have constructed a chemical genomics platform built upon the yeast gene deletion collection, using competition experiments in batch fermenters and robotic automation of cytotoxicity screens, including protection by 'natural' substrates. Using these, we tested 26 different drugs and identified the carriers required for 18 of the drugs to gain entry into yeast cells. Conclusions As well as providing a useful platform technology, these results further substantiate the notion that the cellular uptake of pharmaceutical drugs normally occurs via carrier-mediated transport and indicates that establishing the identity and tissue distribution of such carriers should be a major consideration in the design of safe and effective drugs. PMID:22023736

Transport routes of metalloids into and out of the cell: a review of the current knowledge.

PubMed

Zangi, Ronen; Filella, Montserrat

2012-04-15

Except for their extra- and intra-cellular interfaces, cell membranes are hydrophobic and inhibit the transport of hydrophilic molecules. Metalloids in aqueous solutions form chemical species with oxygen and hydroxyl groups and, therefore, exist as hydrophilic neutral polar solutes or as hydrophilic anions. This characteristic of metalloids introduces a large barrier for their passage through the cell membrane via unaided diffusion. The necessity for an uptake mechanism for metalloids arises from the requirement of these species for the maintenance of life, such as the need of boron for plant cells. Conversely, the transport of these species out of the cell is necessary because some metalloids are toxic, such as arsenic and antimony, and their entrance into the cell is undesirable. The undesired uptake of these toxic species is possible via pathways designed for the uptake of other structurally and chemically similar essential compounds. Therefore, the extrusion of arsenic and antimony out of the cell is an example of a detoxification mechanism. As a consequence of the hydrophobic character of the cell membrane in all living systems, the main route for the uptake and efflux of metalloids is facilitated by transmembrane proteins, driven either by concentration gradients or by energy-fueled pumps. However, metalloids forming or embedded in nano-sized particles escape the need to cross the cell membrane because these particles can be taken into the cell by endocytosis. Here, we review the uptake and efflux pathways of boron, silicon, arsenic, and antimony through the cell membranes of different organisms and the protein channels involved in these processes. In particular, passive diffusion via aquaglyceroporins, active transport via primary and secondary ion pumps, extrusion into vacuoles of metalloid-thiol conjugates via ATP-binding cassette, the efflux of methylated metalloids, and endocytosis are summarized. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Mechanisms That Modulate Peripheral Oxygen Delivery during Exercise in Heart Failure.

PubMed

Kisaka, Tomohiko; Stringer, William W; Koike, Akira; Agostoni, Piergiuseppe; Wasserman, Karlman

2017-07-01

Oxygen uptake ([Formula: see text]o 2 ) measured at the mouth, which is equal to the cardiac output (CO) times the arterial-venous oxygen content difference [C(a-v)O 2 ], increases more than 10- to 20-fold in normal subjects during exercise. To achieve this substantial increase in oxygen uptake [[Formula: see text]o 2  = CO × C(a-v)O 2 ] both CO and the arterial-venous difference must simultaneously increase. Although this occurs in normal subjects, patients with heart failure cannot achieve significant increases in cardiac output and must rely primarily on changes in the arterial-venous difference to increase [Formula: see text]o 2 during exercise. Inadequate oxygen delivery to the tissue during exercise in heart failure results in tissue anaerobiosis, lactic acid accumulation, and reduction in exercise tolerance. H + is an important regulatory and feedback mechanism to facilitate additional oxygen delivery to the tissue (Bohr effect) and further aerobic production of ATP when tissue anaerobic metabolism increases the production of lactate (anaerobic threshold). This H + production in the muscle capillary promotes the continued unloading of oxygen (oxyhemoglobin desaturation) while maintaining the muscle capillary Po 2 (Fick principle) at a sufficient level to facilitate aerobic metabolism and overcome the diffusion barriers from capillary to mitochondria ("critical capillary Po 2 ," 15-20 mm Hg). This mechanism is especially important during exercise in heart failure where cardiac output increase is severely constrained. Several compensatory mechanisms facilitate peripheral oxygen delivery during exercise in both normal persons and patients with heart failure.

Transport mechanisms of a novel antileukemic and antiviral compound 9-norbornyl-6-chloropurine.

PubMed

Plačková, Pavla; Hřebabecký, Hubert; Šála, Michal; Nencka, Radim; Elbert, Tomáš; Mertlíková-Kaiserová, Helena

2015-02-01

6-Chloropurines substituted at the position 9 with variously modified bicyclic skeletons represent promising antiviral and anticancer agents. This work aimed to investigate the transport mechanisms of 9-[(1R*,2R*,4S*)-bicyclo[2.2.1]hept-2-yl]-6-chloro-9H-purine (9-norbornyl-6-chloropurine, NCP) and their relationship to the metabolism and biological activity of the compound. Transport experiments were conducted in CCRF-CEM cells using radiolabeled compound ([(3)H]NCP). The pattern of the intracellular uptake of [(3)H]NCP in CCRF-CEM cells pointed to a combination of passive and facilitated diffusion as prevailing transport mechanisms. NCP intracellular metabolism was found to enhance its uptake by modifying NCP concentration gradient. The transport kinetics reached steady state under the conditions of MRP and MDR proteins blockade, indicating that NCP is a substrate for these efflux pumps. Their inhibition also increased the cytotoxicity of NCP. Our findings suggest that the novel nucleoside analog NCP has potential to become a new orally available antileukemic agent due to its rapid membrane permeation.

Cation trapping by cellular acidic compartments: Beyond the concept of lysosomotropic drugs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marceau, François, E-mail: francois.marceau@crchul.ulaval.ca; Bawolak, Marie-Thérèse; Lodge, Robert

“Lysosomotropic” cationic drugs are known to concentrate in acidic cell compartments due to low retro-diffusion of the protonated molecule (ion trapping); they draw water by an osmotic mechanism, leading to a vacuolar response. Several aspects of this phenomenon were recently reexamined. (1) The proton pump vacuolar (V)-ATPase is the driving force of cationic drug uptake and ensuing vacuolization. In quantitative transport experiments, V-ATPase inhibitors, such as bafilomycin A1, greatly reduced the uptake of cationic drugs and released them in preloaded cells. (2) Pigmented or fluorescent amines are effectively present in a concentrated form in the large vacuoles. (3) Consistent withmore » V-ATPase expression in trans-Golgi, lysosomes and endosomes, a fraction of the vacuoles is consistently labeled with trans-Golgi markers and protein secretion and endocytosis are often inhibited in vacuolar cells. (4) Macroautophagic signaling (accumulation of lipidated and membrane-bound LC3 II) and labeling of the large vacuoles by the autophagy effector LC3 were consistently observed in cells, precisely at incubation periods and amine concentrations that cause vacuolization. Vacuoles also exhibit late endosome/lysosome markers, because they may originate from such organelles or because macroautophagosomes fuse with lysosomes. Autophagosome persistence is likely due to the lack of resolution of autophagy, rather than to nutritional deprivation. (5) Increased lipophilicity decreases the threshold concentration for the vacuolar and autophagic cytopathology, because simple diffusion into cells is limiting. (6) A still unexplained mitotic arrest is consistently observed in cells loaded with amines. An extended recognition of relevant clinical situations is proposed for local or systemic drug administration.« less

Canopy Flow Analysis Reveals the Advantage of Size in the Oldest Communities of Multicellular Eukaryotes

PubMed Central

Ghisalberti, Marco; Gold, David A.; Laflamme, Marc; Clapham, Matthew E.; Narbonne, Guy M.; Summons, Roger E.; Johnston, David T.; Jacobs, David K.

2015-01-01

Summary At Mistaken Point, Newfoundland, Canada, rangeomorph “fronds” dominate the earliest (579–565 million years ago) fossil communities of large (0.1 to 2 m height) multicellular benthic eukaryotes. They lived in low-flow environments, fueled by uptake [1–3] of dissolved reactants (osmotrophy). However, prokaryotes are effective osmotrophs, and the advantage of taller eukaryotic osmotrophs in this deepwater community context has not been addressed. We reconstructed flow-velocity profiles and vertical mixing using canopy flow models appropriate to the densities of the observed communities. Further modeling of processes at organismal surfaces documents increasing uptake with height in the community as a function of thinning of the diffusive boundary layer with increased velocity. The velocity profile, produced by canopy flow in the community, generates this advantage of upward growth. Alternative models of upward growth advantage based on redox/resource gradients fail, given the efficiency of vertical mixing. In benthic communities of osmotrophs of sufficient density, access to flow in low-flow settings provides an advantage to taller architecture, providing a selectional driver for communities of tall eukaryotes in contexts where phototropism cannot contribute to upward growth. These Ediacaran deep-sea fossils were preserved during the increasing oxygenation prior to the Cambrian radiation of animals and likely represent an important phase in the ecological and evolutionary transition to more complex eukaryotic forms. PMID:24462003

Characterization of vanadium ion uptake in sulfonated diels alder poly(phenylene) membranes

DOE PAGES

Lawton, Jamie; Jones, Amanda; Tang, Zhijiang; ...

2015-11-28

Sulfonated diels alder poly(phenylene) (SDAPP), alternative aromatic hydrocarbon membranes for vanadium redox flow batteries (VRFBs) are characterized using electron paramagnetic resonance (EPR). Membranes soaked in sulfuric acid and vanadyl sulfate are analyzed to determine the membrane environment in which the vanadyl ion (VO 2+) diffuses in the membranes. These results are compared to Nafion 117 membranes. In contrast to Nafion, the VO 2+ in SDAPP membranes exists in two different environments. The results of analysis of rotational diffusion determined from fits the EPR spectral lineshapes in comparison with previously reported permeation studies and measurements of partitioning functions reported here suggestmore » that the diffusion pathways in SDAPP are very different than in Nafion.« less

Lack of gallium uptake in primary hepatic amyloidosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Georgen, T.G.; Taylor, A.; Alazraki, N.

1976-06-01

Technetium-99m-sulfur colloid and /sup 67/Ga citrate hepatic scintigrams showed matching defects in a patient with diffuse primary amyloidosis. Amyloidosis should be added to the usual differential diagnosis of such matching lesions which includes cysts, fibrosis, most benign tumors, and occasional metastatic lesions which do not concentrate gallium.

Divergent alfalfa root system architecture is maintained across environment and nutrient supply

USDA-ARS?s Scientific Manuscript database

Plant root system architecture can alter and be altered by soil fertility and other environmental conditions. In soils with suboptimal fertility, plant root length often is correlated with P and K uptake because these nutrients are supplied by diffusion. We developed alfalfa (Medicago sativa L.) pop...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patel, TN; Park, AHA; Bantat, S

The limited permeability of the E. coli outer membrane can significantly hinder whole-cell biocatalyst performance. In this study, the SARS coronavirus small envelope protein (SCVE) was expressed in E. coli cells previously engineered for periplasmic expression of carbonic anhydrase (CA) activity. This maneuver increased small molecule uptake by the cells, resulting in increased apparent CA activity of the biocatalysts. The enhancements in activity were quantified using methods developed for traditional heterogeneous catalysis. The expression of the SCVE protein was found to significantly reduce the Thiele moduli (phi), as well as increase the effectiveness factors (eta), effective diffusivities (D-e), and permeabilitiesmore » (P) of the biocatalysts. These catalytic improvements translated into superior performance of the biocatalysts for the precipitation of calcium carbonate from solution which is an attractive strategy for long-term sequestration of captured carbon dioxide. Overall, these results demonstrate that synthetic biology approaches can be used to enhance heterogeneous catalysts incorporated into microbial whole-cell scaffolds.« less

Water sorption in microfibrillated cellulose (MFC): The effect of temperature and pretreatment.

PubMed

Meriçer, Çağlar; Minelli, Matteo; Giacinti Baschetti, Marco; Lindström, Tom

2017-10-15

Water sorption behavior of two different microfibrillated cellulose (MFC) films, produced by delamination of cellulose pulp after different pretreatment methods, is examined at various temperatures (16-65°C) and up to 70% RH. The effect of drying temperature of MFC films on the water uptake is also investigated. The obtained solubility isotherms showed the typical downward curvature at moderate RH, while no upturn is observed at higher RH; the uptakes are in line with characteristic values for cellulose fibers. Enzymatically pretreated MFC dispersion showed lower solubility than carboxymethylated MFC, likely due to the different material structure, which results from the different preparation methods The experimental results are analyzed by Park and GAB models, which proved suitable to describe the observed behaviors. Interestingly, while no significant thermal effect is detected on water solubility above 35°C, the uptake at 16 and 25°C, at a given RH, is substantially lower than that at higher temperature, indicating that, in such range, sorption process is endothermic. Such unusual behavior for a cellulose-based system seems to be related mainly to the structural characteristics of MFC films, and to relaxation phenomena taking place upon water sorption. The diffusion kinetics, indeed, showed a clear Fickian behavior at low temperature and RH, whereas a secondary process seems to occur at high temperature and higher RH, leading to anomalous diffusion behaviors. Copyright © 2017 Elsevier Ltd. All rights reserved.

Brain lactate kinetics: Modeling evidence for neuronal lactate uptake upon activation.

PubMed

Aubert, Agnès; Costalat, Robert; Magistretti, Pierre J; Pellerin, Luc

2005-11-08

A critical issue in brain energy metabolism is whether lactate produced within the brain by astrocytes is taken up and metabolized by neurons upon activation. Although there is ample evidence that neurons can efficiently use lactate as an energy substrate, at least in vitro, few experimental data exist to indicate that it is indeed the case in vivo. To address this question, we used a modeling approach to determine which mechanisms are necessary to explain typical brain lactate kinetics observed upon activation. On the basis of a previously validated model that takes into account the compartmentalization of energy metabolism, we developed a mathematical model of brain lactate kinetics, which was applied to published data describing the changes in extracellular lactate levels upon activation. Results show that the initial dip in the extracellular lactate concentration observed at the onset of stimulation can only be satisfactorily explained by a rapid uptake within an intraparenchymal cellular compartment. In contrast, neither blood flow increase, nor extracellular pH variation can be major causes of the lactate initial dip, whereas tissue lactate diffusion only tends to reduce its amplitude. The kinetic properties of monocarboxylate transporter isoforms strongly suggest that neurons represent the most likely compartment for activation-induced lactate uptake and that neuronal lactate utilization occurring early after activation onset is responsible for the initial dip in brain lactate levels observed in both animals and humans.

Potassium-based sorbents from fly ash for high-temperature CO2 capture.

PubMed

Sanna, Aimaro; Maroto-Valer, M Mercedes

2016-11-01

Potassium-fly ash (K-FA) sorbents were investigated for high-temperature CO 2 sorption. K-FAs were synthesised using coal fly ash as source of silica and aluminium. The synthesised materials were also mixed with Li 2 CO 3 and Ca(OH) 2 to evaluate their effect on CO 2 capture. Temperature strongly affected the performance of the K-FA sorbents, resulting in a CO 2 uptake of 1.45 mmol CO 2 /g sorbent for K-FA 1:1 at 700 °C. The CO 2 sorption was enhanced by the presence of Li 2 CO 3 (10 wt%), with the K-FA 1:1 capturing 2.38 mmol CO 2 /g sorbent at 700 °C in 5 min. This sorption was found to be similar to previously developed Li-Na-FA (2.54 mmol/g) and Li-FA (2.4 mmol/g) sorbents. The presence of 10 % Li 2 CO 3 also accelerated sorption and desorption. The results suggest that the increased uptake of CO 2 and faster reaction rates in presence of K-FA can be ascribed to the formation of K-Li eutectic phase, which favours the diffusion of potassium and CO 2 in the material matrix. The cyclic experiments showed that the K-FA materials maintained stable CO 2 uptake and reaction rates over 10 cycles.

Brain lactate kinetics: Modeling evidence for neuronal lactate uptake upon activation

PubMed Central

Aubert, Agnès; Costalat, Robert; Magistretti, Pierre J.; Pellerin, Luc

2005-01-01

A critical issue in brain energy metabolism is whether lactate produced within the brain by astrocytes is taken up and metabolized by neurons upon activation. Although there is ample evidence that neurons can efficiently use lactate as an energy substrate, at least in vitro, few experimental data exist to indicate that it is indeed the case in vivo. To address this question, we used a modeling approach to determine which mechanisms are necessary to explain typical brain lactate kinetics observed upon activation. On the basis of a previously validated model that takes into account the compartmentalization of energy metabolism, we developed a mathematical model of brain lactate kinetics, which was applied to published data describing the changes in extracellular lactate levels upon activation. Results show that the initial dip in the extracellular lactate concentration observed at the onset of stimulation can only be satisfactorily explained by a rapid uptake within an intraparenchymal cellular compartment. In contrast, neither blood flow increase, nor extracellular pH variation can be major causes of the lactate initial dip, whereas tissue lactate diffusion only tends to reduce its amplitude. The kinetic properties of monocarboxylate transporter isoforms strongly suggest that neurons represent the most likely compartment for activation-induced lactate uptake and that neuronal lactate utilization occurring early after activation onset is responsible for the initial dip in brain lactate levels observed in both animals and humans. PMID:16260743

Improving prediction of metal uptake by Chinese cabbage (Brassica pekinensis L.) based on a soil-plant stepwise analysis.

PubMed

Zhang, Sha; Song, Jing; Gao, Hui; Zhang, Qiang; Lv, Ming-Chao; Wang, Shuang; Liu, Gan; Pan, Yun-Yu; Christie, Peter; Sun, Wenjie

2016-11-01

It is crucial to develop predictive soil-plant transfer (SPT) models to derive the threshold values of toxic metals in contaminated arable soils. The present study was designed to examine the heavy metal uptake pattern and to improve the prediction of metal uptake by Chinese cabbage grown in agricultural soils with multiple contamination by Cd, Cu, Ni, Pb, and Zn. Pot experiments were performed with 25 historically contaminated soils to determine metal accumulation in different parts of Chinese cabbage. Different soil bioavailable metal fractions were determined using different extractants (0.43M HNO3, 0.01M CaCl2, 0.005M DTPA, and 0.01M LWMOAs), soil moisture samplers, and diffusive gradients in thin films (DGT), and the fractions were compared with shoot metal uptake using both direct and stepwise multiple regression analysis. The stepwise approach significantly improved the prediction of metal uptake by cabbage over the direct approach. Strongly pH dependent or nonlinear relationships were found for the adsorption of root surfaces and in root-shoot uptake processes. Metals were linearly translocated from the root surface to the root. Therefore, the nonlinearity of uptake pattern is an important explanation for the inadequacy of the direct approach in some cases. The stepwise approach offers an alternative and robust method to study the pattern of metal uptake by Chinese cabbage (Brassica pekinensis L.). Copyright © 2016. Published by Elsevier B.V.

Prediction and validation of diffusion coefficients in a model drug delivery system using microsecond atomistic molecular dynamics simulation and vapour sorption analysis.

PubMed

Forrey, Christopher; Saylor, David M; Silverstein, Joshua S; Douglas, Jack F; Davis, Eric M; Elabd, Yossef A

2014-10-14

Diffusion of small to medium sized molecules in polymeric medical device materials underlies a broad range of public health concerns related to unintended leaching from or uptake into implantable medical devices. However, obtaining accurate diffusion coefficients for such systems at physiological temperature represents a formidable challenge, both experimentally and computationally. While molecular dynamics simulation has been used to accurately predict the diffusion coefficients, D, of a handful of gases in various polymers, this success has not been extended to molecules larger than gases, e.g., condensable vapours, liquids, and drugs. We present atomistic molecular dynamics simulation predictions of diffusion in a model drug eluting system that represent a dramatic improvement in accuracy compared to previous simulation predictions for comparable systems. We find that, for simulations of insufficient duration, sub-diffusive dynamics can lead to dramatic over-prediction of D. We present useful metrics for monitoring the extent of sub-diffusive dynamics and explore how these metrics correlate to error in D. We also identify a relationship between diffusion and fast dynamics in our system, which may serve as a means to more rapidly predict diffusion in slowly diffusing systems. Our work provides important precedent and essential insights for utilizing atomistic molecular dynamics simulations to predict diffusion coefficients of small to medium sized molecules in condensed soft matter systems.

Effects of molecular weight on the diffusion coefficient of aquatic dissolved organic matter and humic substances.

PubMed

Balch, J; Guéguen, C

2015-01-01

In situ measurements of labile metal species using diffusive gradients in thin films (DGT) passive samplers are based on the diffusion rates of individual species. Although most studies have dealt with chemically isolated humic substances, the diffusion of dissolved organic matter (DOM) across the hydrogel is not well understood. In this study, the diffusion coefficient (D) and molecular weight (MW) of 11 aquatic DOM and 4 humic substances (HS) were determined. Natural, unaltered aquatic DOM was capable of diffusing across the diffusive gel membrane with D values ranging from 2.48×10(-6) to 5.31×10(-6) cm(2) s(-1). Humic substances had diffusion coefficient values ranging from 3.48×10(-6) to 6.05×10(-6) cm(2) s(-1), congruent with previous studies. Molecular weight of aquatic DOM and HS samples (∼500-1750 Da) measured using asymmetrical flow field-flow fractionation (AF4) strongly influenced D, with larger molecular weight DOM having lower D values. No noticeable changes in DOM size properties were observed during the diffusion process, suggesting that DOM remains intact following diffusion across the diffusive gel. The influence of molecular weight on DOM mobility will assist in further understanding and development of the DGT technique and the uptake and mobility of contaminants associated with DOM in aquatic environments. Copyright © 2014 Elsevier Ltd. All rights reserved.

Can ligand addition to soil enhance Cd phytoextraction? A mechanistic model study.

PubMed

Lin, Zhongbing; Schneider, André; Nguyen, Christophe; Sterckeman, Thibault

2014-11-01

Phytoextraction is a potential method for cleaning Cd-polluted soils. Ligand addition to soil is expected to enhance Cd phytoextraction. However, experimental results show that this addition has contradictory effects on plant Cd uptake. A mechanistic model simulating the reaction kinetics (adsorption on solid phase, complexation in solution), transport (convection, diffusion) and root absorption (symplastic, apoplastic) of Cd and its complexes in soil was developed. This was used to calculate plant Cd uptake with and without ligand addition in a great number of combinations of soil, ligand and plant characteristics, varying the parameters within defined domains. Ligand addition generally strongly reduced hydrated Cd (Cd(2+)) concentration in soil solution through Cd complexation. Dissociation of Cd complex ([Formula: see text]) could not compensate for this reduction, which greatly lowered Cd(2+) symplastic uptake by roots. The apoplastic uptake of [Formula: see text] was not sufficient to compensate for the decrease in symplastic uptake. This explained why in the majority of the cases, ligand addition resulted in the reduction of the simulated Cd phytoextraction. A few results showed an enhanced phytoextraction in very particular conditions (strong plant transpiration with high apoplastic Cd uptake capacity), but this enhancement was very limited, making chelant-enhanced phytoextraction poorly efficient for Cd.

Competitive Al3+ Inhibition of Net Mg2+ Uptake by Intact Lolium multiflorum Roots 1

PubMed Central

Rengel, Zdenko; Robinson, Donald L.

1989-01-01

Aluminum impairs uptake of Mg2+, but the mechanisms of this inhibition are not understood. The depletion technique was used to monitor net Mg2+ uptake from nutrient solution by intact, 23-day-old plants of ryegrass (Lolium multiflorum Lam., cv Gulf and Wilo). Activities of Mg2+ and monomeric Al species in nutrient solution were calculated and used as the basis for expressing the results. The kinetics of net Mg2+ absorption was resolved into (a) a transpiration-dependent uptake component, (b) a metabolically mediated, discontinuous saturable component that is Al3+ sensitive and p-chloromercuribenzene sulfonic acid (PCMBS) resistant, and (c) a linear, carbonyl cyanide m-chlorophenylhydrazone resistant, Al3+ sensitive component that might be a type of facilitated diffusion. Lowering the pH from 6.0 to 4.2 exerted a noncompetitive inhibition of net Mg2+ uptake, while aluminum at 6.6 micromolar Al3+ activity exerted competitive inhibition of net Mg2+ uptake at pH 4.2. The Al3+-induced effect was obvious after 30 minutes. Cultivar-specific ability to retain a higher affinity for Mg2+ by postulated transport proteins in the presence of Al3+ might be one of the mechanisms of differential Al tolerance among ryegrass cultivars. PMID:16667193

Poor accumulation of technetium-99m glucoheptonate in sarcoidosis and other diffuse infiltrative lung diseases as compared with gallium-67 citrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vorne, M.; Sahlstroem, K.A.; Alanko, K.

1988-02-01

Forty-two patients with diffuse infiltrative lung diseases were imaged with Ga-67 citrate and Tc-99m glucoheptonate (GH). Twenty patients had sarcoidosis, six had fibrosis, six had tuberculosis, nine had lung infiltration, and one had pleural empyema. The main difference between Ga-67 and Tc-99m GH was the much greater uptake of Ga-67 in sarcoidosis than that of Tc-99m GH. Fifteen patients with sarcoidosis had positive Ga-67 scans but only six had positive Tc-99m GH scans. The results in other diffuse infiltrative lung diseases were almost equal with Ga-67 and Tc-99m GH. Although Tc-99m GH is less expensive and simpler to use, itmore » is not an adequate substitute for Ga-67 in diffuse infiltrative lung diseases.« less

Health care technology adoption and diffusion in a social context.

PubMed

Coyte, Peter C; Holmes, Dave

2007-02-01

This article highlights mechanisms that may further sustainable technological development for the 21st century. The distributional effects associated with the adoption and diffusion of health care technologies are addressed wherein the capacity to capitalize on the health gains from the adoption of technology varies in society. These effects are caused by the actions of individuals as they segment themselves into distinct social groups. The circumstances under which social institutions are further segmented are explored and may motivate public sector limits on the funding for and diffusion of health care technologies. Safety and efficacy benchmarks are necessary but insufficient conditions for sustainability as product advantage on grounds of cost-effectiveness must also be demonstrated. Furthermore, given the substantial role played by public sector decision makers in purchasing health care technologies, the distributional consequences associated with the uptake and diffusion of technology need to be gauged by product designers and those responsible for marketing.

Fatty acid transport protein-2 inhibitor Grassofermata/CB5 protects cells against lipid accumulation and toxicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saini, Nipun; Black, Paul N.; Montefusco, David

The inhibition of the fatty acid uptake into non-adipose tissues provides an attractive target for prevention of lipotoxicity leading to obesity-associated non-alcoholic fatty liver disease and type 2 diabetes. Fatty acid transport proteins (FATPs) are bifunctional proteins involved in the uptake and activation of fatty acids by esterification with coenzyme A. Here we characterize Grassofermata/CB5, previously identified as a fatty acid uptake inhibitor directed against HsFATP2. The compound was effective in inhibiting the uptake of fatty acids in the low micro-molar range (IC{sub 50} 8–11 μM) and prevented palmitate-mediated lipid accumulation and cell death in cell lines that are models formore » intestines, liver, muscle and pancreas. In adipocytes, uptake inhibition was less effective (IC{sub 50} 58 μM). Inhibition was specific for long chain fatty acids and was ineffective toward medium chain fatty acids, which are transported by diffusion. Kinetic analysis of Grassofermata-dependent FA transport inhibition verified a non-competitive mechanism. By comparison with Grassofermata, several atypical antipsychotic drugs previously implicated as inhibitors of FA uptake were ineffectual. In mice Grassofermata decreased absorption of {sup 13}C-oleate demonstrating its potential as a therapeutic agent. - Highlights: • Grassofermata is a small compound inhibitor of FATP2. • Uptake inhibition is specific for long chain fatty acids. • Uptake kinetics shows low specificity for adipocytes compared to other cell types. • Inhibition is by a non-competitive mechanism. • Atypical antipsychotics do not inhibit FA uptake by comparison with Grassofermata.« less

Water sorption studies of hybrid biofiber-reinforced natural rubber biocomposites.

PubMed

Jacob, Maya; Varughese, K T; Thomas, Sabu

2005-01-01

Hybrid biofibers (sisal and oil palm) were incorporated into natural rubber matrix. The water absorption characteristics of the composites were evaluated with reference to fiber loading. The influence of temperature on water sorption of the composites is also analyzed. Moisture uptake was found to be dependent on the properties of the biofibers. The mechanism of diffusion in the gum sample was found to be Fickian in nature, while in the loaded composites, it was non-Fickian. Sisal and oil palm fibers were subjected to different treatments such as mercerization and silanation. The effect of chemical modification on moisture uptake was also analyzed. Chemical modification was seen to decrease the water uptake in the composites. The thermodynamic parameters of the sorption process were also evaluated. Activation energy was found to be maximum for the gum sample.

Fluorination of silicone rubber by plasma polymerization

NASA Astrophysics Data System (ADS)

Fielding, Jennifer Chase

Plasma polymerized fluorocarbon (PPFC) films were deposited onto various silicone rubber substrates, including O-rings, to decrease oil uptake. Depositions were performed using a radio frequency (rf)-powered plasma reactor and various fluorocarbon monomers, such as C2F6, C2F 5H, C3F6, and 1H,1H,2H-perfluoro-1-dodecene. PPFC films which were most promising for inhibiting oil uptake were deposited with 1H,1H,2H-perfluoro-1-dodecene, and were composed predominantly of perfluoromethylene (CF2) species. These films displayed low critical surface energies (as low as 2.7 mJ/m2), and high contact angles with oil (84°), which were correlated with the amount of CF2 species present in the film. For the films with the highest degree of CF2 (up to 67%), CF2 chains may have been oriented slightly perpendicular to the substrate and terminated by CF3 species. Adhesion of the PPFC films directly to silicone rubber was found to be poor. However, when a plasma polymerized hydrocarbon interlayer was deposited on the silicone rubber prior to the fluorocarbon films, adhesion was excellent. O-rings coated with multilayer fluorocarbon films showed 2.6% oil uptake after soaking in oil for 100 hrs at 100°C. Due to variability in data, and the low quality of the industrial grade silicone rubber, the oil uptake mechanism was determined to be from oil flowing through flaws in the film due to defects within the substrate, not from generalized diffusion through the film. This mechanism was confirmed using higher quality silicone rubber, which showed little or no oil diffusion. Therefore, this film may perform well as an oil-repelling barrier when deposited on a high quality silicone rubber.

In vitro study of percutaneous absorption of aluminum from antiperspirants through human skin in the Franz™ diffusion cell.

PubMed

Pineau, Alain; Guillard, Olivier; Favreau, Frédéric; Marty, Marie-Hélène; Gaudin, Angeline; Vincent, Claire Marie; Marrauld, Annie; Fauconneau, Bernard; Marty, Jean-Paul

2012-05-01

Aluminum salts such as aluminum chlorohydrate (ACH) are known for use as an active antiperspirant agent that blocks the secretion of sweat. A local case report of hyperaluminemia in a woman using an aluminum-containing antiperspirant for 4 years raises the problem of transdermal absorption of aluminum (Al). Only a very limited number of studies have shown that the skin is an effective barrier to transdermal uptake of Al. In accordance with our analytical procedure, the aim of this study with an in vitro Franz™ diffusion cell was to measure aluminum uptake from three cosmetic formulations of antiperspirant: the base for an "aerosol" (38.5% of ACH), a "roll-on" emulsion (14.5% ACH), and a "stick" (21.2%), by samples of intact and stripped human skin (5 donors). The Al assays were performed by Zeeman Electrothermal Atomic Absorption Spectrophotometry (ZEAAS). Following contacts lasting 6, 12 and 24h, the Al assays showed only insignificant transdermal absorption of Al (≤0.07% of the quantity of Al deposited) and particularly low cutaneous quantities that varied according to the formulations (1.8 μg/cm² for "aerosol base" and "stick" - 0.5 μg/cm² for the "roll-on"). On stripped skin, for which only the "stick" formulation was tested, the measured uptake was significantly higher (11.50 μg/cm² versus 1.81 μg/cm² for normal skin). These results offer reassurance as regards to the use of antiperspirants for topical application of ACH-containing cosmetic formulations on healthy skin over a limited time span (24h). On the other hand, high transdermal Al uptake on stripped skin should compel antiperspirant manufacturers to proceed with the utmost caution. Copyright © 2012 Elsevier Inc. All rights reserved.

Direct determination of the driving forces for taurocholate uptake into rat liver plasma membrane vesicles.

PubMed

Duffy, M C; Blitzer, B L; Boyer, J L

1983-10-01

To determine directly the driving forces for bile acid entry into the hepatocyte, the uptake of [3H]taurocholic acid into rat liver plasma membrane vesicles was studied. The membrane preparation contained predominantly right-side-out vesicles, and was highly enriched in plasma membrane marker enzymes. The uptake of taurocholate at equilibrium was inversely related to medium osmolarity, indicating transport into an osmotically sensitive space. In the presence of an inwardly directed sodium gradient (NaCl or sodium gluconate), the initial rate of uptake was rapid and taurocholate was transiently accumulated at a concentration twice that at equilibrium (overshoot). Other inwardly directed cation gradients (K+, Li+, choline+) or the presence of sodium in the absence of a gradient (Na+ equilibrated) resulted in a slower initial uptake rate and did not sustain an overshoot. Bile acids inhibited sodium-dependent taurocholate uptake, whereas bromsulphthalein inhibited both sodium-dependent and sodium-independent uptake and D-glucose had no effect on uptake. Uptake was temperature dependent, with maximal overshoots occurring at 25 degrees C. Imposition of a proton gradient across the vesicle (pHo less than pHi) in the absence of a sodium gradient failed to enhance taurocholate uptake, indicating that double ion exchange (Na+-H+, OH- -anion) is unlikely. Creation of a negative intravesicular potential by altering accompanying anions or by valinomycin-induced K+-diffusion potentials did not enhance taurocholate uptake, suggesting an electroneutral transport mechanism. The kinetics of taurocholate uptake demonstrated saturability with a Michaelis constant at 52 microM and maximum velocity of 4.5 nmol X mg-1 X protein X min-1. These studies provide definitive evidence for a sodium gradient-dependent, carrier-mediated, electrically neutral transport mechanism for hepatic taurocholate uptake. These findings are consistent with a model for bile secretion in which the basolateral enzyme Na+,K+-ATPase provides the driving force for "uphill" bile acid transport by establishing a trans-membrane sodium gradient.

Protein adsorption to poly(ethylenimine)-modified Sepharose FF: VI. Partial charge neutralization drastically increases uptake rate.

PubMed

Zhao, Yangyang; Dong, Xiaoyan; Yu, Linling; Sun, Yan

2016-01-04

The adsorption and elution behaviors of bovine serum albumin (BSA) on poly(ethylenimine) (PEI)-grafted Sepharose FF resins were recently studied and a critical ionic capacity (cIC; 600 mmol/L) was found, above which the uptake rate increased drastically due to the occurrence of significant "chain delivery" effect. Moreover, above the cIC value, higher salt concentrations were required for protein elution due to the high charge density of the resins. In this work, we have reduced the charge density on the PEI chains of a PEI-grafted resin by neutralization of the amine groups with sodium acetate. PEI-modified resin with IC of 740 mmol/L (FF-PEI-L740, IC>cIC) was chosen as the starting material, and three resins with residual IC values of 660, 560 and 440 mmol/L (FF-PEI-R440) were obtained. The adsorption and chromatographic behaviors of these resins for BSA were investigated. It was found that, with IC decreasing from 740 to 440 mmol/L, the adsorption capacity kept almost unchanged; the effective protein diffusivity (De) also showed negligible variations as IC decreased from 740 to 560 mmol/L (De/D0=0.38 ± 0.04). However, it was interesting to observe a three-fold increase of the De value for FF-PEI-R440 (De/D0=1.23 ± 0.08). It is considered that the occurrence of the drastic uptake rate increase in FF-PEI-R440 was attributed to the decreased available binding sites for protein molecule, which led to the decrease of binding strength, thus facilitated the happenings of "chain delivery" effect of bound proteins. Besides, a study on the effect of ionic strength clarified that the lower the IC value, the higher the sensitivity of protein binding to salt concentration due to the easily screened electrostatic interactions at low surface charge densities. The ionic strength at the elution peak also decreased with decreasing IC in accordance with the salt sensitivity order. Column breakthrough studies demonstrated that the dynamic adsorption capacity of FF-PEI-R440 was much higher than the other three resins at flow rates higher than 30 cm/h because of its high uptake rate. The findings in this work provided new insights into the effects of the interactions between proteins and grafted polymers on adsorption equilibria and uptake kinetics, which would help the selection and design of suitable media for high-performance protein chromatography. Copyright © 2015. Published by Elsevier B.V.

The significance of folic acid, tissue iron stores, and tissue viability in determining iron uptake from serum by thyroid tissue slices

PubMed Central

Buchanan, W. M.

1971-01-01

This paper describes an attempt to measure in vitro iron uptake from serum by human thyroid slices and to relate the uptake to tissue iron stores, folic acid status, and tissue viability. It is an extension of work previously reported (Buchanan, 1969). Thyroids were obtained from patients undergoing partial thyroidectomy for colloid goitre and serum from clinically normal healthy adults. The haemoglobin, serum iron, and folic acid levels of both thyroid and serum donors were measured and thyroids examined histologically for the presence of stainable iron. Viable and non-viable tissue slices were incubated in sera treated with radioactive iron so as to produce high and normal levels of transferrin saturation. Iron was taken up both from sera with normal and high transferrin saturation but the amount was, in almost all cases, greater from the more highly saturated. The uptake by non-viable tissue was appreciable but did not vary to any great extent from one serum to the next, and was attributed to simple diffusion of ionic iron into the tissue. There was, however, marked variation in uptake from different sera by viable tissue. It was concluded therefore that viability is a factor affecting the uptake. As the variation in uptake by viable tissue incubated in a single serum was significantly less than tissue incubated in a number of different sera it was further concluded that there was also a factor in the serum itself affecting iron uptake. The nature of the factor was not elucidated but neither folic acid nor levels of iron stores appeared to influence uptake because no correlation was found between iron uptake and iron stores or folic acid. Images PMID:5556118

Coupled Mo-U abundances and isotopes in a small marine euxinic basin: Constraints on processes in euxinic basins

NASA Astrophysics Data System (ADS)

Bura-Nakić, Elvira; Andersen, Morten B.; Archer, Corey; de Souza, Gregory F.; Marguš, Marija; Vance, Derek

2018-02-01

Sedimentary molybdenum (Mo) and uranium (U) abundances, as well as their isotope systematics, are used to reconstruct the evolution of the oxygenation state of the surface Earth from the geological record. Their utility in this endeavour must be underpinned by a thorough understanding of their behaviour in modern settings. In this study, Mo-U concentrations and their isotope compositions were measured in the water column, sinking particles, sediments and pore waters of the marine euxinic Lake Rogoznica (Adriatic Sea, Croatia) over a two year period, with the aim of shedding light on the specific processes that control Mo-U accumulation and isotope fractionations in anoxic sediment. Lake Rogoznica is a 15 m deep stratified sea-lake that is anoxic and euxinic at depth. The deep euxinic part of the lake generally shows Mo depletions consistent with near-quantitative Mo removal and uptake into sediments, with Mo isotope compositions close to the oceanic composition. The data also, however, show evidence for periodic additions of isotopically light Mo to the lake waters, possibly released from authigenic precipitates formed in the upper oxic layer and subsequently processed through the euxinic layer. The data also show evidence for a small isotopic offset (∼0.3‰ on 98Mo/95Mo) between particulate and dissolved Mo, even at highest sulfide concentrations, suggesting minor Mo isotope fractionation during uptake into euxinic sediments. Uranium concentrations decrease towards the bottom of the lake, where it also becomes isotopically lighter. The U systematics in the lake show clear evidence for a dominant U removal mechanism via diffusion into, and precipitation in, euxinic sediments, though the diffusion profile is mixed away under conditions of increased density stratification between an upper oxic and lower anoxic layer. The U diffusion-driven precipitation is best described with an effective 238U/235U fractionation of +0.6‰, in line with other studied euxinic basins. Combining the Mo and U systematics in Lake Rogoznica and other euxinic basins, it is apparent that the two different uptake mechanisms of U and Mo can lead to spatially and temporally variable Mo/U and Mo-U isotope systematics that depend on the rate of water renewal versus removal to sediment, the sulfide concentration, and the geometry of the basin. This study further emphasises the potential of combining multiple observations, from Mo-U enrichment and isotope systematics, for disentangling the various processes via which redox conditions control the chemistry of modern and ancient sediments.

Lipopolysaccharide endotoxemia induces amyloid-β and p-tau formation in the rat brain.

PubMed

Wang, Li-Ming; Wu, Qi; Kirk, Ryan A; Horn, Kevin P; Ebada Salem, Ahmed H; Hoffman, John M; Yap, Jeffrey T; Sonnen, Joshua A; Towner, Rheal A; Bozza, Fernando A; Rodrigues, Rosana S; Morton, Kathryn A

2018-01-01

Amyloid beta (Aβ) plaques are not specific to Alzheimer's disease and occur with aging and neurodegenerative disorders. Soluble brain Aβ may be neuroprotective and increases in response to neuroinflammation. Sepsis is associated with neurocognitive compromise. The objective was to determine, in a rat endotoxemia model of sepsis, whether neuroinflammation and soluble Aβ production are associated with Aβ plaque and hyperphosphorylated tau deposition in the brain. Male Sprague Dawley rats received a single intraperitoneal injection of 10 mg/kg of lipopolysaccharide endotoxin (LPS). Brain and blood levels of IL-1β, IL-6, and TNFα and cortical microglial density were measured in LPS-injected and control animals. Soluble brain Aβ and p-tau were compared and Aβ plaques were quantified and characterized. Brain uptake of [ 18 F]flutemetamol was measured by phosphor imaging. LPS endotoxemia resulted in elevations of cytokines in blood and brain. Microglial density was increased in LPS-treated rats relative to controls. LPS resulted in increased soluble Aβ and in p-tau levels in whole brain. Progressive increases in morphologically-diffuse Aβ plaques occurred throughout the interval of observation (to 7-9 days post LPS). LPS endotoxemia resulted in increased [ 18 F]flutemetamol in the cortex and increased cortex: white matter ratios of activity. In conclusion, LPS endotoxemia causes neuroinflammation, increased soluble Aβ and Aβ diffuse plaques in the brain. Aβ PET tracers may inform this neuropathology. Increased p-tau in the brain of LPS treated animals suggests that downstream consequences of Aβ plaque formation may occur. Further mechanistic and neurocognitive studies to understand the causes and consequences of LPS-induced neuropathology are warranted.

Ligand-Receptor Interaction-Mediated Transmembrane Transport of Dendrimer-like Soft Nanoparticles: Mechanisms and Complicated Diffusive Dynamics.

PubMed

Liang, Junshi; Chen, Pengyu; Dong, Bojun; Huang, Zihan; Zhao, Kongyin; Yan, Li-Tang

2016-05-09

Nearly all nanomedical applications of dendrimer-like soft nanoparticles rely on the functionality of attached ligands. Understanding how the ligands interact with the receptors in cell membrane and its further effect on the cellular uptake of dendrimer-like soft nanoparticles is thereby a key issue for their better application in nanomedicine. However, the essential mechanism and detailed kinetics for the ligand-receptor interaction-mediated transmembrane transport of such unconventional nanoparticles remain poorly elucidated. Here, using coarse-grained simulations, we present the very first study of molecular mechanism and kinetics behaviors for the transmembrane transport of dendrimer-like soft nanoparticles conjugated with ligands. A phase diagram of interaction states is constructed through examining ligand densities and membrane tensions that allows us to identify novel endocytosis mechanisms featured by the direct wrapping and the penetration-extraction vesiculation. The results provide an in-depth insight into the diffusivity of receptors and dendrimer in the membrane plane and demonstrate how the ligand density influences receptor diffusion and uptake kinetics. It is interesting to find that the ligand-conjugated dendrimers present superdiffusive behaviors on a membrane, which is revealed to be driven by the random fluctuation dynamics of the membrane. The findings facilitate our understanding of some recent experimental observations and could establish fundamental principles for the future development of such important nanomaterials for widespread nanomedical applications.

Meta-Analysis of the Correlation between Apparent Diffusion Coefficient and Standardized Uptake Value in Malignant Disease

PubMed Central

Deng, Shengming; Wu, Zhifang; Wu, Yiwei; Zhang, Wei; Li, Jihui; Dai, Na

2017-01-01

The objective of this meta-analysis is to explore the correlation between the apparent diffusion coefficient (ADC) on diffusion-weighted MR and the standard uptake value (SUV) of 18F-FDG on PET/CT in patients with cancer. Databases such as PubMed (MEDLINE included), EMBASE, and Cochrane Database of Systematic Review were searched for relevant original articles that explored the correlation between SUV and ADC in English. After applying Fisher's r-to-z transformation, correlation coefficient (r) values were extracted from each study and 95% confidence intervals (CIs) were calculated. Sensitivity and subgroup analyses based on tumor type were performed to investigate the potential heterogeneity. Forty-nine studies were eligible for the meta-analysis, comprising 1927 patients. Pooled r for all studies was −0.35 (95% CI: −0.42–0.28) and exhibited a notable heterogeneity (I2 = 78.4%; P < 0.01). In terms of the cancer type subgroup analysis, combined correlation coefficients of ADC/SUV range from −0.12 (lymphoma, n = 5) to −0.59 (pancreatic cancer, n = 2). We concluded that there is an average negative correlation between ADC and SUV in patients with cancer. Higher correlations were found in the brain tumor, cervix carcinoma, and pancreas cancer. However, a larger, prospective study is warranted to validate these findings in different cancer types. PMID:29097924

Meta-Analysis of the Correlation between Apparent Diffusion Coefficient and Standardized Uptake Value in Malignant Disease.

PubMed

Deng, Shengming; Wu, Zhifang; Wu, Yiwei; Zhang, Wei; Li, Jihui; Dai, Na; Zhang, Bin; Yan, Jianhua

2017-01-01

The objective of this meta-analysis is to explore the correlation between the apparent diffusion coefficient (ADC) on diffusion-weighted MR and the standard uptake value (SUV) of 18 F-FDG on PET/CT in patients with cancer. Databases such as PubMed (MEDLINE included), EMBASE, and Cochrane Database of Systematic Review were searched for relevant original articles that explored the correlation between SUV and ADC in English. After applying Fisher's r -to- z transformation, correlation coefficient ( r ) values were extracted from each study and 95% confidence intervals (CIs) were calculated. Sensitivity and subgroup analyses based on tumor type were performed to investigate the potential heterogeneity. Forty-nine studies were eligible for the meta-analysis, comprising 1927 patients. Pooled r for all studies was -0.35 (95% CI: -0.42-0.28) and exhibited a notable heterogeneity ( I 2 = 78.4%; P < 0.01). In terms of the cancer type subgroup analysis, combined correlation coefficients of ADC/SUV range from -0.12 (lymphoma, n = 5) to -0.59 (pancreatic cancer, n = 2). We concluded that there is an average negative correlation between ADC and SUV in patients with cancer. Higher correlations were found in the brain tumor, cervix carcinoma, and pancreas cancer. However, a larger, prospective study is warranted to validate these findings in different cancer types.

Comparative study of expression and activity of glucose transporters between stem cell-derived brain microvascular endothelial cells and hCMEC/D3 cells.

PubMed

Al-Ahmad, Abraham J

2017-10-01

Glucose constitutes a major source of energy of mammalian brains. Glucose uptake at the blood-brain barrier (BBB) occurs through a facilitated glucose transport, through glucose transporter 1 (GLUT1), although other isoforms have been described at the BBB. Mutations in GLUT1 are associated with the GLUT1 deficiency syndrome, yet none of the current in vitro models of the human BBB maybe suited for modeling such a disorder. In this study, we investigated the expression of glucose transporters and glucose diffusion across brain microvascular endothelial cells (BMECs) derived from healthy patient-derived induced pluripotent stem cells (iPSCs). We investigated the expression of different glucose transporters at the BBB using immunocytochemistry and flow cytometry and measured glucose uptake and diffusion across BMEC monolayers obtained from two iPSC lines and from hCMEC/D3 cells. BMEC monolayers showed expression of several glucose transporters, in particular GLUT1, GLUT3, and GLUT4. Diffusion of glucose across the monolayers was mediated via a saturable transcellular mechanism and partially inhibited by pharmacological inhibitors. Taken together, our study suggests the presence of several glucose transporters isoforms at the human BBB and demonstrates the feasibility of modeling glucose across the BBB using patient-derived stem cells. Copyright © 2017 the American Physiological Society.

Gas Sorption and Storage Properties of Calixarenes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patil, Rahul S.; Banerjee, Debasis; Atwood, Jerry L.

2016-12-01

Calixarenes, a class of organic macrocyclic molecules have shown interesting gas sorption properties towards industrially important gases such as carbon di-oxide, hydrogen, methane and acetylene. These macrocycles are involved in weak van der Waals interaction to form multidimensional supramolecular frameworks. The gas-diffusion and subsequent sorption occurs due to a cooperative behavior between neighboring macrocycles. Furthermore, the flexibility at the upper rim functional group also plays a key role in the overall gas uptake of calixarene. In this book chapter, we give a brief account of interaction and diffusion of gases in calixarene and selected derivatives.

Experimental setup for radon exposure and first diffusion studies using gamma spectroscopy

NASA Astrophysics Data System (ADS)

Maier, Andreas; van Beek, Patrick; Hellmund, Johannes; Durante, Marco; Schardt, Dieter; Kraft, Gerhard; Fournier, Claudia

2015-11-01

In order to measure the uptake and diffusion of 222Rn in biological material, an exposure chamber was constructed where cell cultures, biological tissues and mice can be exposed to 222Rn-activities similar to therapy conditions. After exposure, the material is transferred to a gamma spectrometer and the decay of 214Pb and 214Bi is analyzed. From the time kinetics of these decays the total amount of the initial 222Rn concentration can be calculated. In this paper the design and construction as well as first test measurements are reported.

Diffuse FDG uptake due to fat necrosis following transverse rectus abdominus myocutaneous (TRAM) flap reconstruction.

PubMed

Dobbs, Nathan B; Latifi, Hamid R

2013-08-01

We report a case of a 57-year-old female patient with right breast invasive ductal carcinoma. Bilateral mastectomy and TRAM flap reconstructions were performed. Postoperatively, a palpable focus was identified within the left breast. PET/CT showed hypermetabolism throughout the reconstructed left breast, correlating with mixed fat attenuation and inflammatory soft tissue. MRI showed extensive fat necrosis/oil cyst formation in the left breast. As a TRAM flap reconstruction with fat-rich tissue can be damaged intraoperatively due to surgical manipulation, abnormal FDG uptake in this setting is more likely related to fat necrosis than recurrent tumor.

Elements of the iron and manganese cycles in Lake Baikal

USGS Publications Warehouse

Granina, L.Z.; Callender, E.

2007-01-01

Using data obtained in recent years, we considered the external mass balance and characteristics of internal iron and manganese cycles in Lake Baikal (biological uptake, remineralization, sedimentary and diffusive fluxes, accumulation in sediments, time of renewal, etc.). Some previous results and common concepts were critically reevaluated. ?? Pleiades Publishing, Ltd. 2007.

Novel biosynthesized silver nanoparticles from cobweb as adsorbent for Rhodamine B: equilibrium isotherm, kinetic and thermodynamic studies

NASA Astrophysics Data System (ADS)

Azeez, Luqmon; Lateef, Agbaje; Adebisi, Segun A.; Oyedeji, Abdulrasaq O.

2018-03-01

This study has investigated the adsorption of Rhodamine B (Rh-B) dye on novel biosynthesized silver nanoparticles (AgNPs) from cobweb. The effects of contact time, initial pH, initial dye concentration, adsorbent dosage and temperature were studied on the removal of Rh-B and they significantly affected its uptake. Adsorption isotherms were evaluated using Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models. The adsorption process was best described by Langmuir isotherm with R 2 of 0.9901, indicating monolayer adsorption. The maximum adsorption capacity ( q max) of 59.85 mg/g showed that it has relatively high performance, while adsorption intensity showed a favourable adsorption process. Pseudo-second-order kinetics fitted best the rate of adsorption and intra-particle diffusion revealed both surface adsorption and intra-particle diffusion-controlled adsorption process. Negative values of thermodynamic parameters (Δ H°, Δ S° and Δ G°) indicated an exothermic and spontaneous adsorption process. The mean sorption energy ( E) and activation energy ( E a) suggested the uptake of Rh-B onto AgNPs was chemical in nature (chemosorption).

KCl stimulation increases norepinephrine transporter function in PC12 cells.

PubMed

Mandela, Prashant; Ordway, Gregory A

2006-09-01

The norepinephrine transporter (NET) plays a pivotal role in terminating noradrenergic signaling and conserving norepinephrine (NE) through the process of re-uptake. Recent evidence suggests a close association between NE release and regulation of NET function. The present study evaluated the relationship between release and uptake, and the cellular mechanisms that govern these processes. KCl stimulation of PC12 cells robustly increased [3H]NE uptake via the NET and simultaneously increased [3H]NE release. KCl-stimulated increases in uptake and release were dependent on Ca2+. Treatment of cells with phorbol-12-myristate-13-acetate (PMA) or okadaic acid decreased [3H]NE uptake but did not block KCl-stimulated increases in [3H]NE uptake. In contrast, PMA increased [3H]NE release and augmented KCl-stimulated release, while okadaic acid had no effects on release. Inhibition of Ca2+-activated signaling cascades with KN93 (a Ca2+ calmodulin-dependent kinase inhibitor), or ML7 and ML9 (myosin light chain kinase inhibitors), reduced [3H]NE uptake and blocked KCl-stimulated increases in uptake. In contrast, KN93, ML7 and ML9 had no effect on KCl-stimulated [3H]NE release. KCl-stimulated increases in [3H]NE uptake were independent of transporter trafficking to the plasma membrane. While increases in both NE release and uptake mediated by KCl stimulation require Ca2+, different intracellular mechanisms mediate these two events.

Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane.

PubMed

Pohlman, John W; Greinert, Jens; Ruppel, Carolyn; Silyakova, Anna; Vielstädte, Lisa; Casso, Michael; Mienert, Jürgen; Bünz, Stefan

2017-05-23

Continued warming of the Arctic Ocean in coming decades is projected to trigger the release of teragrams (1 Tg = 10 6 tons) of methane from thawing subsea permafrost on shallow continental shelves and dissociation of methane hydrate on upper continental slopes. On the shallow shelves (<100 m water depth), methane released from the seafloor may reach the atmosphere and potentially amplify global warming. On the other hand, biological uptake of carbon dioxide (CO 2 ) has the potential to offset the positive warming potential of emitted methane, a process that has not received detailed consideration for these settings. Continuous sea-air gas flux data collected over a shallow ebullitive methane seep field on the Svalbard margin reveal atmospheric CO 2 uptake rates (-33,300 ± 7,900 μmol m -2 ⋅d -1 ) twice that of surrounding waters and ∼1,900 times greater than the diffusive sea-air methane efflux (17.3 ± 4.8 μmol m -2 ⋅d -1 ). The negative radiative forcing expected from this CO 2 uptake is up to 231 times greater than the positive radiative forcing from the methane emissions. Surface water characteristics (e.g., high dissolved oxygen, high pH, and enrichment of 13 C in CO 2 ) indicate that upwelling of cold, nutrient-rich water from near the seafloor accompanies methane emissions and stimulates CO 2 consumption by photosynthesizing phytoplankton. These findings challenge the widely held perception that areas characterized by shallow-water methane seeps and/or strongly elevated sea-air methane flux always increase the global atmospheric greenhouse gas burden.

Clusters of Low (18)F-Fluorodeoxyglucose Uptake Voxels in Combat Veterans with Traumatic Brain Injury and Post-Traumatic Stress Disorder.

PubMed

Buchsbaum, Monte S; Simmons, Alan N; DeCastro, Alex; Farid, Nikdokht; Matthews, Scott C

2015-11-15

Individuals with mild traumatic brain injury (TBI) show diminished metabolic activity when studied with positron emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG). Since blast injury may not be localized in the same specific anatomical areas in every patient or may be diffuse, significance probability mapping may be vulnerable to false-negative detection of abnormalities. To address this problem, we used an anatomically independent measure to assess PET scans: increased numbers of contiguous voxels that are 2 standard deviations below values found in an uninjured control group. We examined this in three age-matched groups of male patients: 16 veterans with a history of mild TBI, 17 veterans with both mild TBI and post-traumatic stress disorder (PTSD), and 15 veterans without either condition. After FDG administration, subjects performed a modified version of the California Verbal Learning Task. Clusters of low uptake voxels were identified by computing the mean and standard deviation for each voxel in the healthy combat veteran group and then determining the voxel-based z-score for the patient groups. Abnormal clusters were defined as those that contained contiguous voxels with a z-score <-2. Patients with mild TBI alone and patients with TBI+PTSD had larger clusters of low uptake voxels, and cluster size significantly differentiated the mild TBI groups from combat controls. Clusters were more irregular in shape in patients, and patients also had a larger number of low-activity voxels throughout the brain. In mild TBI and TBI+PTSD patients, but not healthy subjects, cluster volume was significantly correlated with verbal learning during FDG uptake.

Studies on stabilization mechanism and stealth effect of poloxamer 188 onto PLGA nanoparticles.

PubMed

Jain, Darshana; Athawale, Rajani; Bajaj, Amrita; Shrikhande, Shruti; Goel, Peeyush N; Gude, Rajiv P

2013-09-01

In nanoparticulate engineering for drug delivery systems, poloxamers tri block copolymers are employed as adsorbing molecules to modify the aggregation state and impart stability to products. The aim was to prepare nanoparticles using poloxamer188 as stabiliser and investigate the mechanism of stabilisation of the prepared particles. Nanoparticles were prepared by solvent diffusion method with poloxamer 188 as stabiliser. Hydrodynamic thickness and zeta potential of the prepared nanoparticles were determined by photon correlation spectroscopy. To study the extent of adsorption of poloxamer onto the prepared nanoparticles, adsorption isotherms were constructed. The adsorbed amount of poloxamer 188 onto the particles was determined by depletion method. Macrophageal uptake study was performed to assess the uptake of the prepared nanoparticles using RAW 264.7 cell lines. Nanoparticles were prepared with slight increase in particle size and in absolute value of zeta potential compared to uncoated particles suggesting that this effect was due to adsorption of poloxamer 188. TEM studies and surface area analysis supported the results obtained from particle size analysis indicating preparation of particles with a thin layer of adsorbed poloxamer 188. Adsorption kinetics modeling suggested that at low concentrations (0.001-0.010 g/L), Langmuir monolayer equation fits quite well and at higher concentrations (above 0.010 g/L) multilayer adsorption of poloxamer 188 onto the prepared particles occurred. Thus the nanoparticles had multilayer of poloxamer 188 adsorbed onto the non uniform surface of PLGA. Results of macrophageal uptake and liver cell study exhibits adsorbed concentration dependent bypass of RES uptake of nanoparticles. Hence, results substantiate the application of adsorption isotherms for designing nanoparticles possessing potential to exhibit prolonged circulation when administered in vivo. Copyright © 2013 Elsevier B.V. All rights reserved.

Lack of appropriate stoichiometry: Strong evidence against an energetically important astrocyte-neuron lactate shuttle in brain.

PubMed

Dienel, Gerald A

2017-11-01

Glutamate-stimulated aerobic glycolysis in astrocytes coupled with lactate shuttling to neurons where it can be oxidized was proposed as a mechanism to couple excitatory neuronal activity with glucose utilization (CMR glc ) during brain activation. From the outset, this model was not viable because it did not fulfill critical stoichiometric requirements: (i) Calculated glycolytic rates and measured lactate release rates were discordant in cultured astrocytes. (ii) Lactate oxidation requires oxygen consumption, but the oxygen-glucose index (OGI, calculated as CMR O2 /CMR glc ) fell during activation in human brain, and the small rise in CMR O2 could not fully support oxidation of lactate produced by disproportionate increases in CMR glc . (iii) Labeled products of glucose metabolism are not retained in activated rat brain, indicating rapid release of a highly labeled, diffusible metabolite identified as lactate, thereby explaining the CMR glc -CMR O2 mismatch. Additional independent lines of evidence against lactate shuttling include the following: astrocytic oxidation of glutamate after its uptake can help "pay" for its uptake without stimulating glycolysis; blockade of glutamate receptors during activation in vivo prevents upregulation of metabolism and lactate release without impairing glutamate uptake; blockade of β-adrenergic receptors prevents the fall in OGI in activated human and rat brain while allowing glutamate uptake; and neurons upregulate glucose utilization in vivo and in vitro under many stimulatory conditions. Studies in immature cultured cells are not appropriate models for lactate shuttling in adult brain because of their incomplete development of metabolic capability and astrocyte-neuron interactions. Astrocyte-neuron lactate shuttling does not make large, metabolically significant contributions to energetics of brain activation. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane

PubMed Central

Greinert, Jens; Silyakova, Anna; Vielstädte, Lisa; Casso, Michael; Mienert, Jürgen; Bünz, Stefan

2017-01-01

Continued warming of the Arctic Ocean in coming decades is projected to trigger the release of teragrams (1 Tg = 106 tons) of methane from thawing subsea permafrost on shallow continental shelves and dissociation of methane hydrate on upper continental slopes. On the shallow shelves (<100 m water depth), methane released from the seafloor may reach the atmosphere and potentially amplify global warming. On the other hand, biological uptake of carbon dioxide (CO2) has the potential to offset the positive warming potential of emitted methane, a process that has not received detailed consideration for these settings. Continuous sea−air gas flux data collected over a shallow ebullitive methane seep field on the Svalbard margin reveal atmospheric CO2 uptake rates (−33,300 ± 7,900 μmol m−2⋅d−1) twice that of surrounding waters and ∼1,900 times greater than the diffusive sea−air methane efflux (17.3 ± 4.8 μmol m−2⋅d−1). The negative radiative forcing expected from this CO2 uptake is up to 231 times greater than the positive radiative forcing from the methane emissions. Surface water characteristics (e.g., high dissolved oxygen, high pH, and enrichment of 13C in CO2) indicate that upwelling of cold, nutrient-rich water from near the seafloor accompanies methane emissions and stimulates CO2 consumption by photosynthesizing phytoplankton. These findings challenge the widely held perception that areas characterized by shallow-water methane seeps and/or strongly elevated sea−air methane flux always increase the global atmospheric greenhouse gas burden. PMID:28484018

Uptake of gaseous formaldehyde by soil surfaces: a combination of adsorption/desorption equilibrium and chemical reactions

NASA Astrophysics Data System (ADS)

Li, Guo; Su, Hang; Li, Xin; Kuhn, Uwe; Meusel, Hannah; Hoffmann, Thorsten; Ammann, Markus; Pöschl, Ulrich; Shao, Min; Cheng, Yafang

2016-08-01

Gaseous formaldehyde (HCHO) is an important precursor of OH radicals and a key intermediate molecule in the oxidation of atmospheric volatile organic compounds (VOCs). Budget analyses reveal large discrepancies between modeled and observed HCHO concentrations in the atmosphere. Here, we investigate the interactions of gaseous HCHO with soil surfaces through coated-wall flow tube experiments applying atmospherically relevant HCHO concentrations of ˜ 10 to 40 ppbv. For the determination of uptake coefficients (γ), we provide a Matlab code to account for the diffusion correction under laminar flow conditions. Under dry conditions (relative humidity = 0 %), an initial γ of (1.1 ± 0.05) × 10-4 is determined, which gradually drops to (5.5 ± 0.4) × 10-5 after 8 h experiments. Experiments under wet conditions show a smaller γ that drops faster over time until reaching a plateau. The drop of γ with increasing relative humidity as well as the drop over time can be explained by the adsorption theory in which high surface coverage leads to a reduced uptake rate. The fact that γ stabilizes at a non-zero plateau suggests the involvement of irreversible chemical reactions. Further back-flushing experiments show that two-thirds of the adsorbed HCHO can be re-emitted into the gas phase while the residual is retained by the soil. This partial reversibility confirms that HCHO uptake by soil is a complex process involving both adsorption/desorption and chemical reactions which must be considered in trace gas exchange (emission or deposition) at the atmosphere-soil interface. Our results suggest that soil and soil-derived airborne particles can either act as a source or a sink for HCHO, depending on ambient conditions and HCHO concentrations.

In vitro determination of transdermal permeation of synthetic musks and estimated dermal uptake through usage of personal care products.

PubMed

Zhang, Xiaolan; Yu, Yuling; Gu, Yue; Li, Xiaojing; Zhang, Xinyu; Yu, Yingxin

2017-04-01

Synthetic musks, chemical constituents of personal care products, enter the human body through dermal contact. Elucidation of the mechanisms underlying transdermal permeation of synthetic musks should enhance our understanding of their uptake and distribution in human skin and allow accurate evaluation of associated human exposure. Here, the transdermal permeation dynamics and distribution of galaxolide (HHCB) and tonalide (AHTN) were investigated using an in vitro skin diffusion model. The transdermal permeation amounts of HHCB and AHTN increased rapidly during the first 6 h. The applied HHCB and AHTN amounts did not affect percutaneous absorption rates. HHCB and AHTN remained primarily in the stratum corneum, accounting for 70.0% and 70.3% of the totals during the 24-h period, respectively. The percutaneous absorption rate of both chemicals was ∼11%. HHCB, AHTN, musk ketone, musk xylene, and Musk-T were detected in 29 personal care products. The average total concentrations of the musks were 3990, 54.0, 17.7, and 9.8 μg g -1 in perfume, shampoo, lotion, and shower gel, respectively. Among the four product categories, HHCB was dominant (57.4%-99.6%), followed by AHTN. The data clearly indicate that polycyclic and nitro musks are most commonly used in personal care products. The total estimated dermal intake (51.6 μg kg -1 bw  day -1 ) was markedly higher than total dermal uptake (5.9 μg kg -1 bw  day -1 ) when percutaneous absorption rates of the chemicals were added into the calculation. Uptake of HHCB and AHTN via dermal contact of personal care products was significantly higher than that from dust inhalation calculated according to earlier literature data. Copyright © 2017 Elsevier Ltd. All rights reserved.

Persistent halogenated compounds in aquaculture environments of South China: implications for global consumers' health risk via fish consumption.

PubMed

Yu, Huan-Yun; Zhang, Bao-Zhong; Giesy, John P; Zeng, Eddy Y

2011-10-01

This study examined the potential sources of persistent halogenated compounds (PHCs), including organochlorine pesticides, mainly DDXs (sum of o,p'- and p,p'-DDT, -DDD, and -DDE and p,p'-DDMU) and polybrominated diphenyl ethers, to typical aquaculture environments of South China, determined the relative importance of gill diffusion and fish feeding for exposure of fish to these contaminants and assessed potential health risk for global consumers via consumption of fish from South China. Fish feed is generally a direct and important source of PHCs in both freshwater and seawater aquaculture. In addition, gill diffusion is the predominant uptake route for PHCs (except p,p'-DDMU, o,p'-DDD and -DDT) in farmed freshwater fish, whereas accumulation from the diet is the major route for farmed marine fish. Risks to health of global consumers via consumption of fish from South China are minimal. However, increased risk can be foreseen due to continuous use of brominated fire retardants and electronic waste importation to China. Copyright © 2011 Elsevier Ltd. All rights reserved.

Prediction of mercury bioavailability to common carp (Cyprinus carpio L.) using the diffusive gradient in thin film technique.

PubMed

Pelcová, Pavlína; Vičarová, Petra; Ridošková, Andrea; Dočekalová, Hana; Kopp, Radovan; Mareš, Jan; Poštulková, Eva

2017-11-01

The mercury bioaccumulation by common carp (Cyprinus carpio L.) tissues (gills, skin, eyes, scales, muscle, brain, kidneys, liver, and spleen) and the capability of the diffusive gradient in thin film (DGT) technique to predict bioavailability of mercury for individual carp's tissues were evaluated. Carp and DGT units were exposed to increasing concentrations of mercury (Hg 2+ : 0 μg L -1 , 0.5 μg L -1 , 1.5 μg L -1 and 3.0 μg L -1 ) in fish tanks for 14 days. In the uncontaminated fish group, the highest mercury concentration was determined in the muscle tissues and, in fish groups exposed to mercury, the highest mercury concentration was determined in the detoxification (kidneys) and input (gills) organs. A strong and positive correlation between the rate of mercury uptake by the DGT technique and the rate of mercury accumulation by fish tissues (gills, skin, scales, and eyes) was observed. Copyright © 2017 Elsevier Ltd. All rights reserved.

A model predicting waterborne cadmium bioaccumulation in Gammarus pulex: the effects of dissolved organic ligands, calcium, and temperature.

PubMed

Pellet, Bastien; Geffard, Olivier; Lacour, Céline; Kermoal, Thomas; Gourlay-francé, Catherine; Tusseau-vuillemin, Marie-hélène

2009-11-01

Metal bioavailability depends on the presence of organic ligands in the water and on the concentrations of competitive cations. The present study aims at testing whether the diffusive gradient in thin films technique (DGT) could be used to take into account Cd speciation and its consequences on bioavailability in a bioaccumulation model and whether the influences of the Ca concentration and temperature also should be considered. Four kinetic experiments were conducted on Gammarus pulex: a calibration of Cd turnover rates and of the DGT lability in mineral water, a study of the influence f ethylenediaminetetraacetic acid (EDTA) and humic acids (HA) on uptake rates, and two experiments testing the influence of the Ca concentrations and temperature on Cd uptake clearance rates (ku). In mineral water, where Cd was considered fully labile, the ku was 0.46 L g⁻¹ d⁻¹, and the depuration rate was 0.032 d⁻¹. The initial Cd influxes were lowered significantly by additions of 10 μg L⁻¹ of EDTA or 10 mg L⁻¹ of HA in the water but not at 5 mg L⁻¹HA, even if DGT measurements proved that Cd formed Cd-HA complexes in that treatment. Increasing Ca concentrations lowered ku values, and a competitive inhibition model between Ca and Cd fitted the data. A 30% enhancement of k, values was observed when the temperature was increased by 8°C, which appeared comparatively as a weak effect. Thus, taking into account the metal speciation and the influence of the Ca concentration should improve Cd bioaccumulation modeling in amphipods. In freshwater, where metal bioavailability is reduced by the presence of dissolved organic matter, forecasting Cd waterborne uptake using the labile concentrations should allow robust comparisons between laboratory and field studies.

Echinococcus granulosus: absorption of cycloleucine and alpha-aminoisobutyric acid by protoscoleces.

PubMed

Jeffs, S A; Arme, C

1986-02-01

Protoscoleces of Echinococcus granulosus absorb the amino acids cycloleucine and alpha-aminoisobutyric acid (AIB) by a combination of mediated uptake and diffusion. After correcting for the latter, values for Kt and Vmax of 0.124 mM and 0.947 nmoles/mg protein/2 min for cycloleucine were calculated; corresponding values for AIB were 0.039 mM and 0.139 nmoles/mg protein/2 min. Both amino acids were accumulated against a concentration gradient and a comparison of Kt and Ki values determined in mutual inhibition experiments suggested that both cycloleucine and AIB share a common uptake locus (loci). Cycloleucine uptake was pH-dependent and could be inhibited by a variety of other amino acids. Neither D- nor L-proline inhibited cycloleucine absorption but D-methionine, D-alanine, D-leucine, D-valine and D-serine were much more effective inhibitors than their L-counterparts.

Use of Inert Gases and Carbon Monoxide to Study the Possible Influence of Countercurrent Exchange on Passive Absorption from the Small Bowel

PubMed Central

Bond, John H.; Levitt, David G.; Levitt, Michael D.

1974-01-01

The purpose of the present study was to quantitate the influence of countercurrent exchange on passive absorption of highly diffusible substances from the small intestine of the rabbit. The absorption of carbon monoxide, which is tightly bound to hemoglobin and therefore cannot exchange, was compared to the absorption of four unbound gases (H2, He, CH4, and 133Xe), which should exchange freely. The degree to which the observed absorption of the unbound gases falls below that predicted from CO absorption should provide a quantitative measure of countercurrent exchange. CO uptake at high luminal Pco is flow-limited and, assuming that villus and central hemoglobin concentrations are equal, the flow that equilibrates with CO (Fco) was calculated to equal 7.24 ml/min/100 g. The observed absorption rate of the unbound gases was from two to four times greater than would have been predicted had their entire uptake been accounted for by equilibration with Fco. This is the opposite of what would occur if countercurrent exchange retarded absorption of the unbound gases. The unbound gases have both flow- and diffusion-limited components, and Fco should account for only the fraction of absorption that is flow limited. A simple model of perfusion and diffusion made it possible to calculate the fraction of the total uptake of unbound gases that was flow limited. This fraction of the total observed absorption rate was still about 1.8 times greater than predicted by CO absorption. A possible explanation for this discrepancy is that plasma skimming reduces the hemoglobin of villus blood to about 60% of that of central blood. Thus, Fco is actually about 1.7 times greater than initially calculated, and with this correction, there is close agreement between the predicted and observed rates of absorption of each of the unbound gases. We conclude that countercurrent exchange does not influence passive absorption under the conditions of this study. PMID:4436431

Drifting through Basic Subprocesses of Reading: A Hierarchical Diffusion Model Analysis of Age Effects on Visual Word Recognition

PubMed Central

Froehlich, Eva; Liebig, Johanna; Ziegler, Johannes C.; Braun, Mario; Lindenberger, Ulman; Heekeren, Hauke R.; Jacobs, Arthur M.

2016-01-01

Reading is one of the most popular leisure activities and it is routinely performed by most individuals even in old age. Successful reading enables older people to master and actively participate in everyday life and maintain functional independence. Yet, reading comprises a multitude of subprocesses and it is undoubtedly one of the most complex accomplishments of the human brain. Not surprisingly, findings of age-related effects on word recognition and reading have been partly contradictory and are often confined to only one of four central reading subprocesses, i.e., sublexical, orthographic, phonological and lexico-semantic processing. The aim of the present study was therefore to systematically investigate the impact of age on each of these subprocesses. A total of 1,807 participants (young, N = 384; old, N = 1,423) performed four decision tasks specifically designed to tap one of the subprocesses. To account for the behavioral heterogeneity in older adults, this subsample was split into high and low performing readers. Data were analyzed using a hierarchical diffusion modeling approach, which provides more information than standard response time/accuracy analyses. Taking into account incorrect and correct response times, their distributions and accuracy data, hierarchical diffusion modeling allowed us to differentiate between age-related changes in decision threshold, non-decision time and the speed of information uptake. We observed longer non-decision times for older adults and a more conservative decision threshold. More importantly, high-performing older readers outperformed younger adults at the speed of information uptake in orthographic and lexico-semantic processing, whereas a general age-disadvantage was observed at the sublexical and phonological levels. Low-performing older readers were slowest in information uptake in all four subprocesses. Discussing these results in terms of computational models of word recognition, we propose age-related disadvantages for older readers to be caused by inefficiencies in temporal sampling and activation and/or inhibition processes. PMID:27933029

NagA-dependent uptake of N-acetyl-glucosamine and N-acetyl-chitin oligosaccharides across the outer membrane of Caulobacter crescentus.

PubMed

Eisenbeis, Simone; Lohmiller, Stefanie; Valdebenito, Marianne; Leicht, Stefan; Braun, Volkmar

2008-08-01

Among the 67 predicted TonB-dependent outer membrane transporters of Caulobacter crescentus, NagA was found to be essential for growth on N-acetyl-beta-D-glucosamine (GlcNAc) and larger chitin oligosaccharides. NagA (93 kDa) has a predicted typical domain structure of an outer membrane transport protein: a signal sequence, the TonB box EQVVIT, a hatch domain of 147 residues, and a beta-barrel composed of 22 antiparallel beta-strands linked by large surface loops and very short periplasmic turns. Mutations in tonB1 and exbBD, known to be required for maltose transport via MalA in C. crescentus, and in two additional predicted tonB genes (open reading frames cc2327 and cc3508) did not affect NagA-mediated GlcNAc uptake. nagA is located in a gene cluster that encodes a predicted PTS sugar transport system and two enzymes that convert GlcNAc-6-P to fructose-6-P. Since a nagA insertion mutant did not grow on and transport GlcNAc, diffusion of GlcNAc through unspecific porins in the outer membrane is excluded. Uptake of GlcNAc into tonB and exbBD mutants and reduction but not abolishment of GlcNAc transport by agents which dissipate the electrochemical potential of the cytoplasmic membrane (0.1 mM carbonyl cyanide 3-chlorophenylhydrazone and 1 mM 2,4-dinitrophenol) suggest diffusion of GlcNAc through a permanently open pore of NagA. Growth on (GlcNAc)(3) and (GlcNAc)(5) requires ExbB and ExbD, indicating energy-coupled transport by NagA. We propose that NagA forms a small pore through which GlcNAc specifically diffuses into the periplasm and functions as an energy-coupled transporter for the larger chitin oligosaccharides.

Drifting through Basic Subprocesses of Reading: A Hierarchical Diffusion Model Analysis of Age Effects on Visual Word Recognition.

PubMed

Froehlich, Eva; Liebig, Johanna; Ziegler, Johannes C; Braun, Mario; Lindenberger, Ulman; Heekeren, Hauke R; Jacobs, Arthur M

2016-01-01

Reading is one of the most popular leisure activities and it is routinely performed by most individuals even in old age. Successful reading enables older people to master and actively participate in everyday life and maintain functional independence. Yet, reading comprises a multitude of subprocesses and it is undoubtedly one of the most complex accomplishments of the human brain. Not surprisingly, findings of age-related effects on word recognition and reading have been partly contradictory and are often confined to only one of four central reading subprocesses, i.e., sublexical, orthographic, phonological and lexico-semantic processing. The aim of the present study was therefore to systematically investigate the impact of age on each of these subprocesses. A total of 1,807 participants (young, N = 384; old, N = 1,423) performed four decision tasks specifically designed to tap one of the subprocesses. To account for the behavioral heterogeneity in older adults, this subsample was split into high and low performing readers. Data were analyzed using a hierarchical diffusion modeling approach, which provides more information than standard response time/accuracy analyses. Taking into account incorrect and correct response times, their distributions and accuracy data, hierarchical diffusion modeling allowed us to differentiate between age-related changes in decision threshold, non-decision time and the speed of information uptake. We observed longer non-decision times for older adults and a more conservative decision threshold. More importantly, high-performing older readers outperformed younger adults at the speed of information uptake in orthographic and lexico-semantic processing, whereas a general age-disadvantage was observed at the sublexical and phonological levels. Low-performing older readers were slowest in information uptake in all four subprocesses. Discussing these results in terms of computational models of word recognition, we propose age-related disadvantages for older readers to be caused by inefficiencies in temporal sampling and activation and/or inhibition processes.

Use of Mechanistic Modeling to Assess Interindividual Variability and Interspecies Differences in Active Uptake in Human and Rat Hepatocytes

PubMed Central

Ménochet, Karelle; Kenworthy, Kathryn E.; Houston, J. Brian

2012-01-01

Interindividual variability in activity of uptake transporters is evident in vivo, yet limited data exist in vitro, confounding in vitro-in vivo extrapolation. The uptake kinetics of seven organic anion-transporting polypeptide substrates was investigated over a concentration range in plated cryopreserved human hepatocytes. Active uptake clearance (CLactive, u), bidirectional passive diffusion (Pdiff), intracellular binding, and metabolism were estimated for bosentan, pitavastatin, pravastatin, repaglinide, rosuvastatin, telmisartan, and valsartan in HU4122 donor using a mechanistic two-compartment model in Matlab. Full uptake kinetics of rosuvastatin and repaglinide were also characterized in two additional donors, whereas for the remaining drugs CLactive, u was estimated at a single concentration. The unbound affinity constant (Km, u) and Pdiff values were consistent across donors, whereas Vmax was on average up to 2.8-fold greater in donor HU4122. Consistency in Km, u values allowed extrapolation of single concentration uptake activity data and assessment of interindividual variability in CLactive across donors. The maximal contribution of active transport to total uptake differed among donors, for example, 85 to 96% and 68 to 87% for rosuvastatin and repaglinide, respectively; however, in all cases the active process was the major contributor. In vitro-in vivo extrapolation indicated a general underprediction of hepatic intrinsic clearance, an average empirical scaling factor of 17.1 was estimated on the basis of seven drugs investigated in three hepatocyte donors, and donor-specific differences in empirical factors are discussed. Uptake Km, u and CLactive, u were on average 4.3- and 7.1-fold lower in human hepatocytes compared with our previously published rat data. A strategy for the use of rat uptake data to facilitate the experimental design in human hepatocytes is discussed. PMID:22665271

Taurine transport across hepatocyte plasma membranes: analysis in isolated rat liver sinusoidal plasma membrane vesicles.

PubMed

Inoue, M; Arias, I M

1988-07-01

To elucidate the mechanism of taurine transport across the hepatic plasma membranes, rat liver sinusoidal plasma membrane vesicles were isolated and the transport process was analyzed. In the presence of a sodium gradient across the membranes (vesicle inside less than vesicle outside), an overshooting uptake of taurine occurred. In the presence of other ion gradients (K+, Li+, and choline+), taurine uptake was very small and no such overshoot was observed. Sodium-dependent uptake of taurine occurred into an osmotically active intravesicular space. Taurine uptake was stimulated by preloading vesicles with unlabeled taurine (transstimulation) in the presence of NaCl, but not in the presence of KCl. Sodium-dependent transport followed saturation kinetics with respect to taurine concentration; double-reciprocal plots of uptake versus taurine concentration gave a straight line from which an apparent Km value of 0.38 mM and Vmax of 0.27 nmol/20 s x mg of protein were obtained. Valinomycin-induced K+-diffusion potential failed to enhance the rate of taurine uptake, suggesting that taurine transport does not depend on membrane potential. Taurine transport was inhibited by structurally related omega-amino acids, such as beta-alanine and gamma-aminobutyric acid, but not by glycine, epsilon-aminocaproic acid, or other alpha-amino acids, such as L-alanine. These results suggest that Na+-dependent uptake of taurine might occur across the hepatic sinusoidal plasma membranes via a transport system that is specific for omega-amino acids having 2-3 carbon chain length.

The effect of hydrate promoters on gas uptake.

PubMed

Xu, Chun-Gang; Yu, Yi-Song; Ding, Ya-Long; Cai, Jing; Li, Xiao-Sen

2017-08-16

Gas hydrate technology is considered as a promising technology in the fields of gas storage and transportation, gas separation and purification, seawater desalination, and phase-change thermal energy storage. However, to date, the technology is still not commercially used mainly due to the low gas hydrate formation rate and the low gas uptake. In this study, the effect of hydrate promoters on gas uptake was systematically studied and analyzed based on hydrate-based CH 4 storage and CO 2 capture from CO 2 /H 2 gas mixture experiments. Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and gas chromatography (GC) were employed to analyze the microstructures and gas compositions. The results indicate that the effect of the hydrate promoter on the gas uptake depends on the physical and chemical properties of the promoter and gas. A strong polar ionic promoter is not helpful towards obtaining the ideal gas uptake because a dense hydrate layer is easily formed at the gas-liquid interface, which hinders gas diffusion from the gas phase to the bulk solution. For a weak polar or non-polar promoter, the gas uptake depends on the dissolution characteristics among the different substances in the system. The lower the mutual solubility among the substances co-existing in the system, the higher the independence among the substances in the system; this is so that each phase has an equal chance to occupy the hydrate cages without or with small interactions, finally leading to a relatively high gas uptake.

Swelling behaviour in n-pentane and mechanical properties of epoxidized natural rubber with different epoxide content

NASA Astrophysics Data System (ADS)

Kinasih, N. A.; Fathurrohman, M. I.; Winarto, D. A.

2017-07-01

Epoxidized natural rubber (ENR) with different level of epoxidation (i.e. 10, 20, 30, 40 and 50 mol% indicated as ENR ENR10, ENR20, ENR30, ENR40 and ENR50, respectively) were prepared. They were then vulcanized by using efficient system vulcanization. The effect of epoxide content on curing characteristic, swelling and mechanical properties in N-pentane was investigated. The Attenuated Resonance Fourier Transform Infrared (ATR-FTIR) and H-Nuclear Magnetic Resonance (H-NMR) were used to determine the epoxidation level. Glass transition (Tg) of ENR samples was determined by using Direct Scanning Calorimetry (DSC). The result revealed that the resistance of ENR in N-pentane increased with increasing epoxidation level, which indicated by decreasing equilibrium mol uptake and diffusion coefficient. The compression set of ENR and aging resistance increased with increasing epoxide content, except ENR50 was due to ENR 50 have two Tg value. However, the value of hardness and tensile strength were not effected by epoxidation level.

Healing of polymer interfaces: Interfacial dynamics, entanglements, and strength

DOE PAGES

Ge, Ting; Robbins, Mark O.; Perahia, Dvora; ...

2014-07-25

Self-healing of polymer films often takes place as the molecules diffuse across a damaged region, above their melting temperature. Using molecular dynamics simulations we probe the healing of polymer films and compare the results with those obtained for thermal welding of homopolymer slabs. These two processes differ from each other in their interfacial structure since damage leads to increased polydispersity and more short chains. A polymer sample was cut into two separate films that were then held together in the melt state. The recovery of the damaged film was followed as time elapsed and polymer molecules diffused across the interface.more » The mass uptake and formation of entanglements, as obtained from primitive path analysis, are extracted and correlated with the interfacial strength obtained from shear simulations. We find that the diffusion across the interface is signifcantly faster in the damaged film compared to welding because of the presence of short chains. Though interfacial entanglements increase more rapidly for the damaged films, a large fraction of these entanglements are near chain ends. As a result, the interfacial strength of the healing film increases more slowly than for welding. For both healing and welding, the interfacial strength saturates as the bulk entanglement density is recovered across the interface. However, the saturation strength of the damaged film is below the bulk strength for the polymer sample. At saturation, cut chains remain near the healing interface. They are less entangled and as a result they mechanically weaken the interface. When the strength of the interface saturates, the number of interfacial entanglements scales with the corresponding bulk entanglement density. Chain stiffness increases the density of entanglements, which increases the strength of the interface. Our results show that a few entanglements across the interface are sufficient to resist interfacial chain pullout and enhance the mechanical strength.« less

Occult Breast Cancer: Scintimammography with High-Resolution Breast-specific Gamma Camera in Women at High Risk for Breast Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rachel F. Brem; Jocelyn A. Rapelyea; , Gilat Zisman

2005-08-01

To prospectively evaluate a high-resolution breast-specific gamma camera for depicting occult breast cancer in women at high risk for breast cancer but with normal mammographic and physical examination findings. MATERIALS AND METHODS: Institutional Review Board approval and informed consent were obtained. The study was HIPAA compliant. Ninety-four high-risk women (age range, 36-78 years; mean, 55 years) with normal mammographic (Breast Imaging Reporting and Data System [BI-RADS] 1 or 2) and physical examination findings were evaluated with scintimammography. After injection with 25-30 mCi (925-1110 MBq) of technetium 99m sestamibi, patients were imaged with a high-resolution small-field-of-view breast-specific gamma camera in craniocaudalmore » and mediolateral oblique projections. Scintimammograms were prospectively classified according to focal radiotracer uptake as normal (score of 1), with no focal or diffuse uptake; benign (score of 2), with minimal patchy uptake; probably benign (score of 3), with scattered patchy uptake; probably abnormal (score of 4), with mild focal radiotracer uptake; and abnormal (score of 5), with marked focal radiotracer uptake. Mammographic breast density was categorized according to BI-RADS criteria. Patients with normal scintimammograms (scores of 1, 2, or 3) were followed up for 1 year with an annual mammogram, physical examination, and repeat scintimammography. Patients with abnormal scintimammograms (scores of 4 or 5) underwent ultrasonography (US), and those with focal hypoechoic lesions underwent biopsy. If no lesion was found during US, patients were followed up with scintimammography. Specific pathologic findings were compared with scintimammographic findings. RESULTS: Of 94 women, 78 (83%) had normal scintimammograms (score of 1, 2, or 3) at initial examination and 16 (17%) had abnormal scintimammograms (score of 4 or 5). Fourteen (88%) of the 16 patients had either benign findings at biopsy or no focal abnormality at US; in two (12%) patients, invasive carcinoma was diagnosed at US-guided biopsy (9 mm each at pathologic examination). CONCLUSION: High-resolution breast-specific scintimammography can depict small (<1-cm), mammographically occult, nonpalpable lesions in women at increased risk for breast cancer not otherwise identified at mammography or physical examination.« less

Diffusion and related transport mechanisms in brain tissue

NASA Astrophysics Data System (ADS)

Nicholson, Charles

2001-07-01

Diffusion plays a crucial role in brain function. The spaces between cells can be likened to the water phase of a foam and many substances move within this complicated region. Diffusion in this interstitial space can be accurately modelled with appropriate modifications of classical equations and quantified from measurements based on novel micro-techniques. Besides delivering glucose and oxygen from the vascular system to brain cells, diffusion also moves informational substances between cells, a process known as volume transmission. Deviations from expected results reveal how local uptake, degradation or bulk flow may modify the transport of molecules. Diffusion is also essential to many therapies that deliver drugs to the brain. The diffusion-generated concentration distributions of well-chosen molecules also reveal the structure of brain tissue. This structure is represented by the volume fraction (void space) and the tortuosity (hindrance to diffusion imposed by local boundaries or local viscosity). Analysis of these parameters also reveals how the local geometry of the brain changes with time or under pathological conditions. Theoretical and experimental approaches borrow from classical diffusion theory and from porous media concepts. Earlier studies were based on radiotracers but the recent methods use a point-source paradigm coupled with micro-sensors or optical imaging of macromolecules labelled with fluorescent tags. These concepts and methods are likely to be applicable elsewhere to measure diffusion properties in very small volumes of highly structured but delicate material.

Role of Diffusion-Weighted Magnetic Resonance (MR) Imaging in Differentiation Between Graves’ Disease and Painless Thyroiditis

PubMed Central

Abdel Razek, Ahmed Abdel Khalek; El-Said, Amr Abd El-hamid

2017-01-01

Summary Background To assess the role of diffusion-weighted MR imaging in differentiation between Graves’ disease and painless thyroiditis. Material/Methods A prospective study was conducted among 37 consecutive patients with untreated thyrotoxicosis (25 female and 12 male; mean age of 44 years) and 15 ageand sex-matched controls. Diffusion-weighted MR imaging of the thyroid gland was performed in patients and controls. The apparent diffusion coefficient (ADC) value of the thyroid gland was calculated and correlated with Tc-99m uptake and thyroid function tests of the patients. Results There was a significant difference in the ADC value of the thyroid gland between patients and the control group (P=0.001). The mean ADC value of the thyroid gland in Graves’ disease was 2.03±0.28×10–3 mm2/sec, and in patients with painless thyroiditis 1.46±0.22×10–3 mm2/sec, respectively. There was a significant difference in the ADC values between Graves’ disease and painless thyroiditis (P=0.001). When the ADC value of 1.45×10–3 mm2/sec was used as a threshold value for differentiating Graves’ disease from painless thyroiditis, the best result was obtained with area under the curve of 0.934, accuracy of 83.8%, sensitivity of 95.8%, and specificity of 61.5%. The mean ADC value of the thyroid gland in patients positively correlated with serum TRAb and Tc-99m uptake (r=0.57, P=0.001 and r=0.74, P=0.001, respectively). Conclusions We concluded that ADC values of the thyroid gland can be used to differentiate Graves’ disease from painless thyroiditis in patients with untreated thyrotoxicosis. PMID:29662585

Role of Diffusion-Weighted Magnetic Resonance (MR) Imaging in Differentiation Between Graves' Disease and Painless Thyroiditis.

PubMed

Abdel Razek, Ahmed Abdel Khalek; Abd Allah, Sieza Samir; El-Said, Amr Abd El-Hamid

2017-01-01

To assess the role of diffusion-weighted MR imaging in differentiation between Graves' disease and painless thyroiditis. A prospective study was conducted among 37 consecutive patients with untreated thyrotoxicosis (25 female and 12 male; mean age of 44 years) and 15 ageand sex-matched controls. Diffusion-weighted MR imaging of the thyroid gland was performed in patients and controls. The apparent diffusion coefficient (ADC) value of the thyroid gland was calculated and correlated with Tc-99m uptake and thyroid function tests of the patients. There was a significant difference in the ADC value of the thyroid gland between patients and the control group ( P =0.001). The mean ADC value of the thyroid gland in Graves' disease was 2.03±0.28×10 -3 mm 2 /sec, and in patients with painless thyroiditis 1.46±0.22×10 -3 mm 2 /sec, respectively. There was a significant difference in the ADC values between Graves' disease and painless thyroiditis ( P =0.001). When the ADC value of 1.45×10 -3 mm 2 /sec was used as a threshold value for differentiating Graves' disease from painless thyroiditis, the best result was obtained with area under the curve of 0.934, accuracy of 83.8%, sensitivity of 95.8%, and specificity of 61.5%. The mean ADC value of the thyroid gland in patients positively correlated with serum TRAb and Tc-99m uptake ( r =0.57, P =0.001 and r =0.74, P =0.001, respectively). We concluded that ADC values of the thyroid gland can be used to differentiate Graves' disease from painless thyroiditis in patients with untreated thyrotoxicosis.

Transcellular movement of hydroxyurea is mediated by specific solute carrier transporters

PubMed Central

Walker, Aisha L.; Franke, Ryan M.; Sparreboom, Alex; Ware, Russell E.

2015-01-01

Objective Hydroxyurea has proven laboratory and clinical therapeutic benefits for sickle cell anemia (SCA) and other diseases, yet many questions remain regarding its in vivo pharmacokinetic and pharmacodynamic profiles. Previous reports suggest that hydroxyurea passively diffuses across cells, but its observed rapid absorption and distribution are more consistent with facilitated or active transport. We investigated the potential role of solute carrier (SLC) transporters in cellular uptake and accumulation of hydroxyurea. Materials and Methods Passive diffusion of hydroxyurea across cell membranes was determined using the parallel artificial membrane permeability assay. SLC transporter screens were conducted using in vitro intracellular drug accumulation and transcellular transport assays in cell lines and oocytes overexpressing SLC transporters. Gene expression of SLC transporters was measured by real-time PCR in human tissues and cell lines. Results Hydroxyurea had minimal diffusion across a lipid bilayer but was a substrate for 5 different SLC transporters belonging to the OCTN and OATP families of transporters and urea transporters A and B. Further characterization of hydroxyurea transport revealed that cellular uptake by OATP1B3 is time and temperature dependent and inhibited by known substrates of OATP1B3. Urea transporters A and B are expressed differentially in human tissues and erythroid cells, and transport hydroxyurea bidirectionally via facilitated diffusion. Conclusions These studies provide new insight into drug transport proteins that may be involved in the in vivo absorption, cellular distribution, and elimination of hydroxyurea. Elucidation of hydroxyurea transcellular movement should improve our understanding of its pharmacokinetics and pharmacodynamics, and may help explain some of the inter-patient drug variability observed in patients with SCA. PMID:21256917

FDG-PET/CT and diffusion-weighted imaging for resected lung cancer: correlation of maximum standardized uptake value and apparent diffusion coefficient value with prognostic factors.

PubMed

Usuda, Katsuo; Funasaki, Aika; Sekimura, Atsushi; Motono, Nozomu; Matoba, Munetaka; Doai, Mariko; Yamada, Sohsuke; Ueda, Yoshimichi; Uramoto, Hidetaka

2018-04-09

Diffusion-weighted magnetic resonance imaging (DWI) is useful for detecting malignant tumors and the assessment of lymph nodes, as FDG-PET/CT is. But it is not clear how DWI influences the prognosis of lung cancer patients. The focus of this study is to evaluate the correlations between maximum standardized uptake value (SUVmax) of FDG-PET/CT and apparent diffusion coefficient (ADC) value of DWI with known prognostic factors in resected lung cancer. A total of 227 patients with resected lung cancers were enrolled in this study. FEG-PET/CT and DWI were performed in each patient before surgery. There were 168 patients with adenocarcinoma, 44 patients with squamous cell carcinoma, and 15 patients with other cell types. SUVmax was a factor that was correlated to T factor, N factor, or cell differentiation. ADC of lung cancer was a factor that was not correlated to T factor, or N factor. There was a significantly weak inverse relationship between SUVmax and ADC (Correlation coefficient r = - 0.227). In analysis of survival, there were significant differences between the categories of sex, age, pT factor, pN factor, cell differentiation, cell type, and SUVmax. Univariate analysis revealed that SUVmax, pN factor, age, cell differentiation, cell type, sex, and pT factor were significant factors. Multivariate analysis revealed that SUVmax and pN factor were independent significant prognostic factors. SUVmax was a significant prognostic factor that is correlated to T factor, N factor, or cell differentiation, but ADC was not. SUVmax may be more useful for predicting the prognosis of lung cancer than ADC values.

Feeding ducks, bacterial chemotaxis, and the Gini index

NASA Astrophysics Data System (ADS)

Peaudecerf, François J.; Goldstein, Raymond E.

2015-08-01

Classic experiments on the distribution of ducks around separated food sources found consistency with the "ideal free" distribution in which the local population is proportional to the local supply rate. Motivated by this experiment and others, we examine the analogous problem in the microbial world: the distribution of chemotactic bacteria around multiple nearby food sources. In contrast to the optimization of uptake rate that may hold at the level of a single cell in a spatially varying nutrient field, nutrient consumption by a population of chemotactic cells will modify the nutrient field, and the uptake rate will generally vary throughout the population. Through a simple model we study the distribution of resource uptake in the presence of chemotaxis, consumption, and diffusion of both bacteria and nutrients. Borrowing from the field of theoretical economics, we explore how the Gini index can be used as a means to quantify the inequalities of uptake. The redistributive effect of chemotaxis can lead to a phenomenon we term "chemotactic levelling," and the influence of these results on population fitness are briefly considered.

Minimizing antibody surface density on liposomes while sustaining cytokine-activated EC targeting.

PubMed

Almeda, Dariela; Wang, Biran; Auguste, Debra T

2015-02-01

Liposomes may be engineered to target inflamed endothelium by mimicking ligand-receptor interactions between leukocytes and cytokine-activated endothelial cells (ECs). The upregulation and assembly of vascular cell adhesion molecule-1 (VCAM1) and E-selectin on the cell membrane upon exposure to cytokines have shown potential for drug delivery vehicles to target sites of chronic endothelial inflammation, such as atherosclerosis and cancer. Herein, we characterized EC surfaces by measuring the E-selectin and VCAM1 surface densities and adhesion forces of aVCAM1 and aE-selectin to ECs. We quantified the antibody density, ratio, and diffusivity of liposomes to achieve significant binding and internalization. At 1 h, the 1:1 ratio of VCAM1:E-selectin antibodies was significantly higher than 1:0 and 0:1. Significant binding and uptake was achieved at aE-selectin densities as low as 400 molecules/μm(2). The highest levels of binding and uptake were achieved when using a 1:1 ratio of VCAM1:E-selectin antibodies at a density of 1000 molecules/μm(2); this density is 85% lower than previous reports. The binding and uptake of functionalized liposomes were reduced to levels comparable to IgG functionalized liposomes upon a 10-fold reduction in liposome membrane diffusivity. We conclude with a liposomal design that discriminates between healthy and inflamed endothelium while reducing antibody surface presentation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Hexose transport by brain slices: further studies on energy dependence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kyle-Lillegard, J.; Gold, B.I.

1983-04-01

We studied the uptake of (/sup 3/H)2-deoxyglucose ((/sup 3/H)2DG) by slices of rat cerebral cortex in vitro as a model of glucose transport by brain. Slices were incubated with (/sup 3/H)2DG, or with L-(/sup 3/H)glucose as a marker for diffusion; the difference between (/sup 3/H)2DG uptake and L-(/sup 3/H)glucose uptake was defined as net (/sup 3/H)2DG transport. Net (/sup 3/H)2DG transport was a function of incubation temperature, with an estimated temperature coefficient of 1.87 from 15 degrees C to 25 degrees C. The net uptake of (/sup 3/H)2DG was not inhibited by phlorizin or phloretin in concentrations well above themore » reported Ki of these inhibitors for hexose uptake in other systems. To examine the hypothesis that (/sup 3/H)2DG transport by brain slices is dependent on mitochondrial energy, we studied net (/sup 3/H)2DG uptake by slices which had been preincubated in media designed to alter intracellular ATP stores. The transport process was very sensitive to inhibition by DNP, but the correlation between (/sup 3/H)2DG transport and ATP levels was unclear. In contrast to our published hypothesis that the transport process required mitochondrial energy, these data indicate that dependence on energy is not absolute.« less

Characterization of loxoprofen transport in Caco-2 cells: the involvement of a proton-dependent transport system in the intestinal transport of loxoprofen.

PubMed

Narumi, Katsuya; Kobayashi, Masaki; Kondo, Ayuko; Furugen, Ayako; Yamada, Takehiro; Takahashi, Natsuko; Iseki, Ken

2016-11-01

Loxoprofen, a propionate non-steroidal anti-inflammatory drug (NSAID), is used widely in East Asian countries. However, little is known about the transport mechanisms contributing to its intestinal absorption. The objectives of this study were to characterize the intestinal transport of loxoprofen using the human intestinal Caco-2 cell model. The transport of loxoprofen was investigated in cellular uptake studies. The uptake of loxoprofen into Caco-2 cells was pH- and concentration-dependent, and was described by a Michaelis-Menten equation with passive diffusion (K m : 4.8 mm, V max : 142 nmol/mg protein/30 s, and K d : 2.2 μl/mg protein/30 s). Moreover, the uptake of loxoprofen was inhibited by a typical monocarboxylate transporter (MCT) inhibitor as well as by various monocarboxylates. The uptake of [ 14 C] l-lactic acid, a typical MCT substrate, in Caco-2 cells was saturable with relatively high affinity for MCT. Because loxoprofen inhibited the uptake of [ 14 C] l-lactic acid in a noncompetitive manner, it was unlikely that loxoprofen uptake was mediated by high-affinity MCT(s). Our results suggest that transport of loxoprofen in Caco-2 cells is, at least in part, mediated by a proton-dependent transport system. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Glial activation colocalizes with structural abnormalities in amyotrophic lateral sclerosis.

PubMed

Alshikho, Mohamad J; Zürcher, Nicole R; Loggia, Marco L; Cernasov, Paul; Chonde, Daniel B; Izquierdo Garcia, David; Yasek, Julia E; Akeju, Oluwaseun; Catana, Ciprian; Rosen, Bruce R; Cudkowicz, Merit E; Hooker, Jacob M; Atassi, Nazem

2016-12-13

In this cross-sectional study, we aimed to evaluate brain structural abnormalities in relation to glial activation in the same cohort of participants. Ten individuals with amyotrophic lateral sclerosis (ALS) and 10 matched healthy controls underwent brain imaging using integrated MR/PET and the radioligand [ 11 C]-PBR28. Diagnosis history and clinical assessments including Upper Motor Neuron Burden Scale (UMNB) were obtained from patients with ALS. Diffusion tensor imaging (DTI) analyses including tract-based spatial statistics and tractography were applied. DTI metrics including fractional anisotropy (FA) and diffusivities (mean, axial, and radial) were measured in regions of interest. Cortical thickness was assessed using surface-based analysis. The locations of structural changes, measured by DTI and the areas of cortical thinning, were compared to regional glial activation measured by relative [ 11 C]-PBR28 uptake. In this cohort of individuals with ALS, reduced FA and cortical thinning colocalized with regions demonstrating higher radioligand binding. [ 11 C]-PBR28 binding in the left motor cortex was correlated with FA (r = -0.68, p < 0.05) and cortical thickness (r = -0.75, p < 0.05). UMNB was correlated with glial activation (r = +0.75, p < 0.05), FA (r = -0.77, p < 0.05), and cortical thickness (r = -0.75, p < 0.05) in the motor cortex. Increased uptake of the glial marker [ 11 C]-PBR28 colocalizes with changes in FA and cortical thinning. This suggests a link between disease mechanisms (gliosis and inflammation) and structural changes (cortical thinning and white and gray matter changes). In this multimodal neuroimaging work, we provide an in vivo model to investigate the pathogenesis of ALS. © 2016 American Academy of Neurology.

Glial activation colocalizes with structural abnormalities in amyotrophic lateral sclerosis

PubMed Central

Alshikho, Mohamad J.; Zürcher, Nicole R.; Loggia, Marco L.; Cernasov, Paul; Chonde, Daniel B.; Izquierdo Garcia, David; Yasek, Julia E.; Akeju, Oluwaseun; Catana, Ciprian; Rosen, Bruce R.; Cudkowicz, Merit E.

2016-01-01

Objective: In this cross-sectional study, we aimed to evaluate brain structural abnormalities in relation to glial activation in the same cohort of participants. Methods: Ten individuals with amyotrophic lateral sclerosis (ALS) and 10 matched healthy controls underwent brain imaging using integrated MR/PET and the radioligand [11C]-PBR28. Diagnosis history and clinical assessments including Upper Motor Neuron Burden Scale (UMNB) were obtained from patients with ALS. Diffusion tensor imaging (DTI) analyses including tract-based spatial statistics and tractography were applied. DTI metrics including fractional anisotropy (FA) and diffusivities (mean, axial, and radial) were measured in regions of interest. Cortical thickness was assessed using surface-based analysis. The locations of structural changes, measured by DTI and the areas of cortical thinning, were compared to regional glial activation measured by relative [11C]-PBR28 uptake. Results: In this cohort of individuals with ALS, reduced FA and cortical thinning colocalized with regions demonstrating higher radioligand binding. [11C]-PBR28 binding in the left motor cortex was correlated with FA (r = −0.68, p < 0.05) and cortical thickness (r = −0.75, p < 0.05). UMNB was correlated with glial activation (r = +0.75, p < 0.05), FA (r = −0.77, p < 0.05), and cortical thickness (r = −0.75, p < 0.05) in the motor cortex. Conclusions: Increased uptake of the glial marker [11C]-PBR28 colocalizes with changes in FA and cortical thinning. This suggests a link between disease mechanisms (gliosis and inflammation) and structural changes (cortical thinning and white and gray matter changes). In this multimodal neuroimaging work, we provide an in vivo model to investigate the pathogenesis of ALS. PMID:27837005

Enhanced anticancer activity and oral bioavailability of ellagic acid through encapsulation in biodegradable polymeric nanoparticles.

PubMed

Mady, Fatma M; Shaker, Mohamed A

2017-01-01

Despite the fact that various studies have investigated the clinical relevance of ellagic acid (EA) as a naturally existing bioactive substance in cancer therapy, little has been reported regarding the efficient strategy for improving its oral bioavailability. In this study, we report the formulation of EA-loaded nanoparticles (EA-NPs) to find a way to enhance its bioactivity as well as bioavailability after oral administration. Poly(ε-caprolactone) (PCL) was selected as the biodegradable polymer for the formulation of EA-NPs through the emulsion-diffusion-evaporation technique. The obtained NPs have been characterized by measuring particle size, zeta potential, Fourier transform infrared, differential scanning calorimetry, and X-ray diffraction. The entrapment efficiency and the release profile of EA was also determined. In vitro cellular uptake and cytotoxicity of the obtained NPs were evaluated using Caco-2 and HCT-116 cell lines, respectively. Moreover, in vivo study has been performed to measure the oral bioavailability of EA-NPs compared to free EA, using New Zealand white rabbits. NPs with distinct shape were obtained with high entrapment and loading efficiencies. Diffusion-driven release profile of EA from the prepared NPs was determined. EA-NP-treated HCT-116 cells showed relatively lower cell viability compared to free EA-treated cells. Fluorometric imaging revealed the cellular uptake and efficient localization of EA-NPs in the nuclear region of Caco-2 cells. In vivo testing revealed that the oral administration of EA-NPs produced a 3.6 times increase in the area under the curve compared to that of EA. From these results, it can be concluded that incorporation of EA into PCL as NPs enhances its oral bioavailability and activity.

Moisture diffusion and permeability characteristics of hydroxypropylmethylcellulose and hard gelatin capsules.

PubMed

Barham, Ahmad S; Tewes, Frederic; Healy, Anne Marie

2015-01-30

The primary objective of this paper is to compare the sorption characteristics of hydroxypropylmethylcellulose (HPMC) and hard gelatin (HG) capsules and their ability to protect capsule contents. Moisture sorption and desorption isotherms for empty HPMC and HG capsules have been investigated using dynamic vapour sorption (DVS) at 25°C. All sorption studies were analysed using the Young-Nelson model equations which distinguishes three moisture sorption types: monolayer adsorption moisture, condensation and absorption. Water vapour diffusion coefficients (D), solubility (S) and permeability (P) parameters of the capsule shells were calculated. ANOVA was performed with the Tukey comparison test to analyse the effect of %RH and capsule type on S, P, and D parameters. The moisture uptake of HG capsules were higher than HPMC capsules at all %RH conditions studied. It was found that values of D and P across HPMC capsules were greater than for HG capsules at 0-40 %RH; whereas over the same %RH range S values were higher for HG than for HPMC capsules. S values decreased gradually as the %RH was increased up to 60% RH. To probe the effect of moisture ingress, spray dried lactose was loaded into capsules. Phase evolution was characterised by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and differential scanning calorimetry (DSC). The capsules under investigation are not capable of protecting spray dried lactose from induced solid state changes as a result of moisture uptake. For somewhat less moisture sensitive formulations, HPMC would appear to be a better choice than HG in terms of protection of moisture induced deterioration. Copyright © 2014 Elsevier B.V. All rights reserved.

Gastrointestinal uptake and distribution of copper in rainbow trout.

PubMed

Clearwater, S J; Baskin, S J; Wood, C M; McDonald, D G

2000-08-01

A single dose of radioactive copper ((64)Cu or new Cu) was infused into the stomach of rainbow trout (Oncorhynchus mykiss) to model dietary copper (Cu) uptake under conditions of a normal nutritional dose and optimum environmental temperature (16 degrees C, 0.117 microg Cu g(-)(1 )body mass). The distribution of new Cu to the gut and internal organs occurred in two phases: rapid uptake by the gut tissues (almost complete by 24 h post-infusion) followed by slower uptake by the internal organs. By 72 h, 60 % of the dose had been excreted, 19 % was still retained in the gut tissue, 10 % remained in the lumen and 12 % had been absorbed across the gut and partitioned amongst the internal organs. A reduction in water temperature of 10 degrees C (to 6 degrees C) significantly retarded components of new Cu distribution (movement of the bolus along the gut and excretion); nonetheless, by 72 h, the fraction absorbed by all the internal organs was similar to that at 16 degrees C. An increase in water temperature of 3 degrees C (to 19 degrees C) caused a pronounced increase in internal organ uptake by 24 h to approximately double the uptake occurring at 16 degrees C. The uptake of new Cu by the gut tissue had a low temperature coefficient (Q(10)<1) consistent with simple diffusion, while the temperature coefficient for transfer of new Cu from gut tissue to the internal organs was high (Q(10)>2), consistent with facilitated transport. Internally, the liver and gall bladder (including bile) were the target organs for dietary Cu partitioning since they were the only organs that concentrated new Cu from the plasma. Individual tissues differed in terms of the exchange of their background Cu pools with new Cu. The background Cu in the walls of the gastrointestinal tract (excluding stomach) exchanged 45-94 % with new Cu from the gut lumen, while tissues such as the stomach, gills, kidney, carcass and fat had 5-7 % exchangeable background Cu. The liver, heart, spleen, ovary, bile and plasma had only 0.2-0.8 % exchangeable background Cu. The gastrointestinal tissues appear to act as a homeostatic organ, regulating the absorption of nutritional (non-toxic) doses of Cu (0. 117 microg g(-)(1 )body mass day(-)(1)) by the internal organs. Within the dose range we used and at optimal temperature (16 degrees C), the new Cu content of the gut tissues fluctuated, but absorption of new Cu by the internal organs remained relatively constant. For example, predosing the fish with non-radioactive Cu caused new Cu absorption by the gut tissues to double and decreased new Cu excretion from 38 to 1.5 %, but had no effect on new Cu uptake by the internal organs. Feeding fish after application of the normal liquid dose of new Cu also had no effect on new Cu uptake by the internal organs, even though the presence of food in the digestive tract reduced the binding of new Cu to the gut tissues and assisted with the excretion of new Cu. The gut was therefore able to regulate new Cu internalization at this dosage. Higher new Cu doses (10, 100 and 1000 times the normal dose), however, evoked regurgitation and increased new Cu excretion within 4 h of application but did not elevate new Cu levels in gut tissue beyond a threshold of approximately 40 microg of new Cu. Only at the highest dose (1000 times the normal dose, 192 microg g(-)(1 )body mass), equivalent to toxic concentrations in the daily diet (7000 microg Cu g(-)(1 )dry mass food), was the buffering capacity of the gut overwhelmed, resulting in an increase in internal new Cu uptake.

Translational diffusion of cumene and 3-methylpentane on free surfaces and pore walls studied by time-of-flight secondary ion mass spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Souda, Ryutaro

2010-12-07

Mobility of molecules in confined geometry has been studied extensively, but the origins of finite size effects on reduction of the glass transition temperature, T{sub g}, are controversial especially for supported thin films. We investigate uptake of probe molecules in vapor-deposited thin films of cumene, 3-methylpentane, and heavy water using secondary ion mass spectrometry and discuss roles of individual molecular motion during structural relaxation and glass-liquid transition. The surface mobility is found to be enhanced for low-density glasses in the sub-T{sub g} region because of the diffusion of molecules on pore walls, resulting in densification of a film via poremore » collapse. Even for high-density glasses without pores, self-diffusion commences prior to the film morphology change at T{sub g}, which is thought to be related to decoupling between translational diffusivity and viscosity. The diffusivity of deeply supercooled liquid tends to be enhanced when it is confined in pores of amorphous solid water. The diffusivity of molecules is further enhanced at temperatures higher than 1.2-1.3 T{sub g} irrespective of the confinement.« less

Molecular simulation of gas adsorption and diffusion in a breathing MOF using a rigid force field.

PubMed

García-Pérez, E; Serra-Crespo, P; Hamad, S; Kapteijn, F; Gascon, J

2014-08-14

Simulation of gas adsorption in flexible porous materials is still limited by the slow progress in the development of flexible force fields. Moreover, the high computational cost of such flexible force fields may be a drawback even when they are fully developed. In this work, molecular simulations of gas adsorption and diffusion of carbon dioxide and methane in NH2-MIL-53(Al) are carried out using a linear combination of two crystallographic structures with rigid force fields. Once the interactions of carbon dioxide molecules and the bridging hydroxyls groups of the framework are optimized, an excellent match is found for simulations and experimental data for the adsorption of methane and carbon dioxide, including the stepwise uptake due to the breathing effect. In addition, diffusivities of pure components are calculated. The pore expansion by the breathing effect influences the self-diffusion mechanism and much higher diffusivities are observed at relatively high adsorbate loadings. This work demonstrates that using a rigid force field combined with a minimum number of experiments, reproduces adsorption and simulates diffusion of carbon dioxide and methane in the flexible metal-organic framework NH2-MIL-53(Al).

Neuroendocrine regulation of osmoregulation and the evolution of air-breathing in decapod crustaceans.

PubMed

Morris, S

2001-03-01

Gills are the primary organ for salt transport, but in land crabs they are removed from water and thus ion exchanges, as well as CO(2) and ammonia excretion, are compromised. Urinary salt loss is minimised in land crabs by redirecting the urine across the gills where salt reabsorption occurs. Euryhaline marine crabs utilise apical membrane branchial Na(+)/H(+) and Cl(-)/HCO(3)(-) exchange powered by a basal membrane Na(+)/K(+)-ATPase, but in freshwater crustaceans an apical V-ATPase provides for electrogenic uptake of Cl(-) in exchange for HCO(3)(-). The HCO(3)(-) is provided by carbonic anhydrase facilitating CO(2) excretion while NH(4)(+) can substitute for K(+) in the basal ATPase and for H(+) in the apical exchange. Gecarcinid land crabs and the terrestrial anomuran Birgus latro can lower the NaCl concentration of the urine to 5 % of that of the haemolymph as it passes across the gills. This provides a filtration-reabsorption system analogous to the vertebrate kidney. Crabs exercise hormonal control over branchial transport processes. Aquatic hyper-regulators release neuroamines from the pericardial organs, including dopamine and 5-hydroxytryptamine (5-HT), which via a cAMP-mediated phosphorylation stimulate Na(+)/K(+)-ATPase activity and NaCl uptake. Freshwater species utilise a V-ATPase, and additional mechanisms of control have been suggested. Crustacean hyperglycaemic hormone (CHH) has now also been confirmed to have effects on hydromineral regulation, and a putative role for neuropeptides in salt and water balance suggests that current models for salt regulation are probably incomplete. In a terrestrial crabs there may be controls on both active uptake and diffusive loss. The land crab Gecarcoidea natalis drinking saline water for 3 weeks reduced net branchial Na(+) uptake but not Na(+)/K(+)-ATPase activity, thus implying a reduction in diffusive Na(+) loss. Further, in G. natalis Na(+) uptake and Na(+)/K(+)-ATPase were stimulated by 5-HT independently of cAMP. Conversely, in the anomuran B. latro, branchial Na(+) and Cl(-) uptake and Na(+)/K(+)-ATPase are inhibited by dopamine, mediated by cAMP. There has been a multiple evolution of a kidney-type system in terrestrial crabs capable of managing salt, CO(2) and NH(3) movements.

Precipitation of CaCO3 due to the Uptake of CO2 in Aqueous Solutions - Mechanisms and Rates

NASA Astrophysics Data System (ADS)

Dietzel, M.; Purgstaller, B.; Rinder, T.; Niedermayr, A.

2012-12-01

In natural and man-made environments the exchange of CO2 between aqueous solutions and the atmosphere frequently induces precipitation of CaCO3 polymorphs. Liberation of gaseous CO2 is well known to induce carbonate formation and extensively studied. In contrast significant gaps of knowledge exist with respect to the combined CO2 uptake and CaCO3 formation, although it is known to be highly valid for many natural and man-made surroundings causing e.g. travertine and scaling in analogy to CO2 liberation. Recently CO2 uptake is also discussed for biomineralization issues and debated for CO2 sequestration by using alkaline residue materials. In the present study CO2 uptake and CaCO3 precipitation mechanisms and rates were experimentally studied by diffusion of CO2 through a polyethylene membrane from an inner to an outer solution containing carbonic acid and CaCl2 (10 mM), respectively. The pH of the outer solution was kept constant between 8.3 and 11.5 by pH stat. technique (25°C). At a critical Ion Activity Product (IAP) CaCO3 is formed in the outer solution. The NaOH titration curve and Ca2+ concentrations reflect CO2 uptake and CaCO3 precipitation rates. To discover the impact of a drift in pH due to CO2 uptake on CaCO3 precipitation hydrogeochemical modeling was applied. XRD, (micro)Raman pattern and SEM imaging reveal the formation of calcite and vaterite at pH 8.3 and 9, whereas at pH > 10 vaterite is additionally formed. However at a given pH the formation of individual CaCO3 polymorphs strongly depends on the CO2 uptake rate (adjusted by membrane thickness), which controls carbonate accumulation in the solution. At elevated pH of the outer solution the uptake rate of CO2 is significantly higher and less time for nucleation of CaCO3 is required compared to lower pH. Surprisingly at the total experimental time of ≈ 20 h the amount of precipitated CaCO3 is similar for all experiments. This can be explained by significant higher CaCO3 precipitation rates at low versus high pH if once a critical IAP is reached. If a drift in pH is permitted the internal Pco2 value can be used as a reliable proxy to evaluate whether uptake of CO2 results in an increase or decrease of IAP with a threshold value of 10-6.15 atm at 25°C (pH ≈ 11). The obtained relationships for CaCO3 formation through CO2 uptake are discussed for selected alkaline environments.

Pulmonary and Cutaneous O[subscript 2] Gas Exchange: A Student Laboratory Exercise in the Frog

ERIC Educational Resources Information Center

Tattersall, Glenn J.; Currie, Suzanne; LeBlanc, Danielle M.

2013-01-01

Gas exchange in animals is ultimately diffusion based, generally occurring across dedicated respiratory organs. In many aquatic amphibians, however, multiple modes of gas exchange exist, allowing for the partitioning of O[subscript 2] uptake and CO[subscript 2] excretion between respiratory organs with different efficiencies. For example, due to…

Corrosion control and disinfection studies in spacecraft water systems. [considering Saturn 5 orbital workshop

NASA Technical Reports Server (NTRS)

Shea, T. G.

1974-01-01

Disinfection and corrosion control in the water systems of the Saturn 5 Orbital Workshop Program are considered. Within this framework, the problem areas of concern are classified into four general areas: disinfection; corrosion; membrane-associated problems of disinfectant uptake and diffusion; and taste and odor problems arising from membrane-disinfectant interaction.

A scalable multi-process model of root nitrogen uptake

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walker, Anthony P.

This article is a Commentary on McMurtrie & Näsholm et al., 218: 119–130. Roots are represented in Terrestrial Ecosystem Models (TEMs) in much less detail than their equivalent above-ground resource acquisition organs – leaves. Often roots in TEMs are simply resource sinks, and below-ground resource acquisition is commonly simulated without any relationship to root dynamics at all, though there are exceptions (e.g. Zaehle & Friend, 2010). The representation of roots as carbon (C) and nitrogen (N) sinks without complementary source functions can lead to strange sensitivities in a model. For example, reducing root lifespans in the Community Land Model (versionmore » 4.5) increases plant production as N cycles more rapidly through the ecosystem without loss of plant function (D. M. Ricciuto, unpublished). The primary reasons for the poorer representation of roots compared with leaves in TEMs are three-fold: (1) data are much harder won, especially in the field; (2) no simple mechanistic models of root function are available; and (3) scaling root function from an individual root to a root system lags behind methods of scaling leaf function to a canopy. Here in this issue of New Phytologist, McMurtrie & Näsholm (pp. 119–130) develop a relatively simple model for root N uptake that mechanistically accounts for processes of N supply (mineralization and transport by diffusion and mass flow) and N demand (root uptake and microbial immobilization).« less

The effect of hardness on the stability of citrate-stabilized gold nanoparticles and their uptake by Daphnia magna.

PubMed

Lee, Byung-Tae; Ranville, James F

2012-04-30

The stability and uptake by Daphnia magna of citrate-stabilized gold nanoparticles (AuNPs) in three different hardness-adjusted synthetic waters were investigated. Negatively charged AuNPs were found to aggregate and settle in synthetic waters within 24 h. Sedimentation rates depended on initial particle concentrations of 0.02, 0.04, and 0.08 nM AuNPs. Hardness of the synthetic waters affected the aggregation of AuNPs and is explained by the compression of diffuse double layer of AuNPs due to the increasing ionic strength. The fractal dimension of AuNPs in the reaction-limited regime of synthetic waters averaged 2.228±0.126 implying the rigid structures of aggregates driven by the collision of small particles with the growing aggregates. Four-day old D. magna accumulated more than 90% of AuNPs in 0.04 nM AuNP suspensions without any observed mortality. Exposure to pre-aggregated AuNP for 48 h in hard water did not show any significant difference in uptake, suggesting D. magna can also ingest settled AuNP aggregates. D. magna exposed to AuNPs shed their exoskeleton whereas the control did not generate any molts over 48 h. This implies that D. magna removed AuNPs on their exoskeleton by producing molts to decrease any adverse effects of adhered AuNPs. Copyright © 2012 Elsevier B.V. All rights reserved.

A scalable multi-process model of root nitrogen uptake

DOE PAGES

Walker, Anthony P.

2018-02-28

This article is a Commentary on McMurtrie & Näsholm et al., 218: 119–130. Roots are represented in Terrestrial Ecosystem Models (TEMs) in much less detail than their equivalent above-ground resource acquisition organs – leaves. Often roots in TEMs are simply resource sinks, and below-ground resource acquisition is commonly simulated without any relationship to root dynamics at all, though there are exceptions (e.g. Zaehle & Friend, 2010). The representation of roots as carbon (C) and nitrogen (N) sinks without complementary source functions can lead to strange sensitivities in a model. For example, reducing root lifespans in the Community Land Model (versionmore » 4.5) increases plant production as N cycles more rapidly through the ecosystem without loss of plant function (D. M. Ricciuto, unpublished). The primary reasons for the poorer representation of roots compared with leaves in TEMs are three-fold: (1) data are much harder won, especially in the field; (2) no simple mechanistic models of root function are available; and (3) scaling root function from an individual root to a root system lags behind methods of scaling leaf function to a canopy. Here in this issue of New Phytologist, McMurtrie & Näsholm (pp. 119–130) develop a relatively simple model for root N uptake that mechanistically accounts for processes of N supply (mineralization and transport by diffusion and mass flow) and N demand (root uptake and microbial immobilization).« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wan, Jiamin; Tokunaga, Tetsu K.; Ashby, Paul D.

Interactions between supercritical (sc) CO 2 and minerals are important when CO 2 is injected into geologic formations for storage and as working fluids for enhanced oil recovery, hydraulic fracturing, and geothermal energy extraction. It has previously been shown that at the elevated pressures and temperatures of the deep subsurface, scCO 2 alters smectites (typical swelling phyllosilicates). However, less is known about the effects of scCO 2 on nonswelling phyllosilicates (illite and muscovite), despite the fact that the latter are the dominant clay minerals in deep subsurface shales and mudstones. Our studies conducted by using single crystals, combining reaction (incubationmore » with scCO 2 ), visualization [atomic force microscopy (AFM)], and quantifications (AFM, X-ray photoelectron spectroscopy, X-ray diffraction, and off-gassing measurements) revealed unexpectedly high CO 2 uptake that far exceeded its macroscopic surface area. Results from different methods collectively suggest that CO 2 partially entered the muscovite interlayers, although the pathways remain to be determined. We hypothesize that preferential dissolution at weaker surface defects and frayed edges allows CO 2 to enter the interlayers under elevated pressure and temperature, rather than by diffusing solely from edges deeply into interlayers. This unexpected uptake of CO 2, can increase CO 2 storage capacity by up to ~30% relative to the capacity associated with residual trapping in a 0.2-porosity sandstone reservoir containing up to 18 mass % of illite/muscovite. This excess CO 2 uptake constitutes a previously unrecognized potential trapping mechanism.« less

Root type matters: measurements of water uptake by seminal, crown and lateral roots of maize

NASA Astrophysics Data System (ADS)

Ahmed, Mutez Ali; Zarebanadkouki, Mohsen; Kaestner, Anders; Carminati, Andrea

2016-04-01

Roots play a key role in water acquisition and are a significant component of plant adaptation to different environmental conditions. Although maize (Zea mays L.) is one of the most important crops worldwide, there is limited information on the function of different root segments and types in extracting water from soils. Aim of this study was to investigate the location of root water uptake in mature maize. We used neutron radiography to image the spatial distribution of maize roots and trace the transport of injected deuterated water (D2O) in soil and roots. Maize plants were grown in aluminum containers filled with a sandy soil that was kept homogeneously wet throughout the experiment. When the plants were five weeks-old, we injected D2O into selected soil regions. The transport of D2O was simulated using a diffusion-convection numerical model. By fitting the observed D2O transport we quantified the diffusion coefficient and the water uptake of the different root segments. The model was initially developed and tested with two weeks-old maize (Ahmed et. al. 2015), for which we found that water was mainly taken up by lateral roots and the water uptake of the seminal roots was negligible. Here, we used this method to measure root water uptake in a mature maize root system. The root architecture of five weeks-old maize consisted of primary and seminal roots with long laterals and crown (nodal) roots that emerged from the above ground part of the plant two weeks after planting. The crown roots were thicker than the seminal roots and had fewer and shorter laterals. Surprisingly, we found that the water was mainly taken up by the crown roots and their laterals, while the lateral roots of seminal roots, which were the main location of water uptake of younger plants, stopped to take up water. Interestingly, we also found that in contrast to the seminal roots, the crown roots were able to take up water also from their distal segments. We conclude that for the two weeks-old maize the function of lateral roots is to absorb water from the soil, while the function of the primary and seminal roots is to axially transport water to the shoot. For the five weeks-old maize, water was mainly taken up by the crown roots and their associated laterals. The ability of crown roots to uptake water from the distal segments can help maize to extract water from deep soil layers and better tolerate drought. Reference Ahmed MA, Zarebanadkouki M, Kaestner A, Carminati A (2015) Measurements of water uptake of maize roots: the key function of lateral roots. Plant and Soil 1-19. doi: 10.1007/s11104-015-2639-6

Classification and Segmentation of Nanoparticle Diffusion Trajectories in Cellular Micro Environments

PubMed Central

Kroll, Alexandra; Haramagatti, Chandrashekara R.; Lipinski, Hans-Gerd; Wiemann, Martin

2017-01-01

Darkfield and confocal laser scanning microscopy both allow for a simultaneous observation of live cells and single nanoparticles. Accordingly, a characterization of nanoparticle uptake and intracellular mobility appears possible within living cells. Single particle tracking allows to measure the size of a diffusing particle close to a cell. However, within the more complex system of a cell’s cytoplasm normal, confined or anomalous diffusion together with directed motion may occur. In this work we present a method to automatically classify and segment single trajectories into their respective motion types. Single trajectories were found to contain more than one motion type. We have trained a random forest with 9 different features. The average error over all motion types for synthetic trajectories was 7.2%. The software was successfully applied to trajectories of positive controls for normal- and constrained diffusion. Trajectories captured by nanoparticle tracking analysis served as positive control for normal diffusion. Nanoparticles inserted into a diblock copolymer membrane was used to generate constrained diffusion. Finally we segmented trajectories of diffusing (nano-)particles in V79 cells captured with both darkfield- and confocal laser scanning microscopy. The software called “TraJClassifier” is freely available as ImageJ/Fiji plugin via https://git.io/v6uz2. PMID:28107406

Effect of metabolic alterations on the accumulation of technetium-99m-labeled d, l-HMPAO in slices of rat cerebral cortex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahn, C.S.; Tow, D.E.; Yu, C.C.

1994-03-01

It is widely recognized that the distribution of technetium-99m-labeled d,l-hexamethylpropylene amine oxime ({sup 99m}Tc-HMPAO) in the brain is determined by the regional blood flow. However, other factors may affect this process including the metabolism of the brain tissue. To examine this possibility we studied the effects of metabolic alterations on {sup 99m}Tc-HMPAO uptake in rat brain cortex slices, with concurrent measurement of oxygen consumption (QO{sub 2}). {sup 99m}Tc-HMPAO uptake was determined by incubating slices of rat cerebral cortex at 37{degrees}C in Krebs-Ringer phosphate glucose medium containing {sup 99m}Tc-HMPAO with and without test substances. Differential gradients for {sup 99m}Tc activity betweenmore » the tissue and the suspending medium (T/M ratio) were derived from the equation T/M[{sup 99m}Tc] = counts per gram of tissue/counts per milliliter of medium. The QO{sub 2} of the brain slices was measured using a biological oxygen monitor equipped with a polarographic oxygen probe. Inhibitors affecting oxidative phosphorylation caused parallel suppression of the T/M ratio and QO{sub 2}. Agents that uncouple oxidation from phosphorylation increased the QO{sub 2} and decreased the T/M ratio. Incubation of slices at 22{degrees}C depressed the T/M ratio and QO{sub 2}. The presence of inhibitors of oxidative phosphorylation in the incubation medium increased the release of {sup 99m}Tc activity from slices that had been prelabeled with {sup 99m}Tc-HMPAO. These findings suggest that the altered metabolic status of the brain tissue modulates the kinetics and net accumulation of {sup 99m}Tc-HMPAO at the cellular level by either depressing uptake, increasing back-diffusion, or both. 33 refs., 4 figs., 3 tabs.« less

Whole-Body Diffusion-weighted MR Imaging of Iron Deposits in Hodgkin, Follicular, and Diffuse Large B-Cell Lymphoma.

PubMed

Cottereau, Anne-Ségolène; Mulé, Sébastien; Lin, Chieh; Belhadj, Karim; Vignaud, Alexandre; Copie-Bergman, Christiane; Boyez, Alice; Zerbib, Pierre; Tacher, Vania; Scherman, Elodie; Haioun, Corinne; Luciani, Alain; Itti, Emmanuel; Rahmouni, Alain

2018-02-01

Purpose To analyze the frequency and distribution of low-signal-intensity regions (LSIRs) in lymphoma lesions and to compare these to fluorodeoxyglucose (FDG) uptake and biologic markers of inflammation. Materials and Methods The authors analyzed 61 untreated patients with a bulky lymphoma (at least one tumor mass ≥7 cm in diameter). When a LSIR within tumor lesions was detected on diffusion-weighted images obtained with a b value of 50 sec/mm 2 , a T2-weighted gradient-echo (GRE) sequence was performed and calcifications were searched for with computed tomography (CT). In two patients, Perls staining was performed on tissue samples from the LSIR. LSIRs were compared with biologic inflammatory parameters and baseline FDG positon emission tomography (PET)/CT parameters (maximum standardized uptake value [SUV max ], total metabolic tumor volume [TMTV]). Results LSIRs were detected in 22 patients and corresponded to signal void on GRE images; one LSIR was due to calcifications, and three LSIRS were due to a recent biopsy. In 18 patients, LSIRs appeared to be related to focal iron deposits; this was proven with Perls staining in two patients. The LSIRs presumed to be due to iron deposits were found mostly in patients with aggressive lymphoma (nine of 26 patients with Hodgkin lymphoma and eight of 20 patients with diffuse large B-cell lymphoma vs one of 15 patients with follicular lymphoma; P = .047) and with advanced stage disease (15 of 18 patients). LSIRS were observed in spleen (n = 14), liver (n = 3), and nodal (n = 8) lesions and corresponded to foci FDG uptake, with mean SUV max of 9.8, 6.7, and 16.2, respectively. These patients had significantly higher serum levels of C-reactive protein, α 1 -globulin, and α 2 -globulin and more frequently had microcytic anemia than those without such deposits (P = .0072, P = .003, P = .0068, and P < .0001, respectively). They also had a significantly higher TMTV (P = .0055) and higher levels of spleen involvement (P < .0001). Conclusion LSIRs due to focal iron deposits are detected in lymphoma lesions and are associated with a more pronounced biologic inflammatory syndrome. © RSNA, 2017 Online supplemental material is available for this article.

Removal of Cu(II) from leachate using natural zeolite as a landfill liner material.

PubMed

Turan, N Gamze; Ergun, Osman Nuri

2009-08-15

All hazardous waste disposal facilities require composite liner systems to act as a barrier against migration of contaminated leachate into the subsurface environment. Removal of copper(II) from leachate was studied using natural zeolite. A serial of laboratory systems on bentonite added natural zeolite was conducted and copper flotation waste was used as hazardous waste. The adsorption capacities and sorption efficiencies were determined. The sorption efficiencies increased with increasing natural zeolite ratio. The pseudo-first-order, the pseudo-second-order, Elovich and the intra-particle diffusion kinetic models were used to describe the kinetic data to estimate the rate constants. The second-order model best described adsorption kinetic data. The results indicated that natural zeolite showed excellent adsorptive characteristics for the removal of copper(II) from leachate and could be used as very good liner materials due to its high uptake capacity and the abundance in availability.

Comparative Physiological Studies of the Yeast and Mycelial Forms of Histoplasma capsulatum: Uptake and Incorporation of l-Leucine

PubMed Central

Gupta, Rishab K.; Howard, Dexter H.

1971-01-01

l-Leucine entered the cells of both morphological forms of Histoplasma capsulatum by a permease-like system at low external concentrations of substrate. However, at levels greater than 5 × 10−5m l-leucine, the amino acid entered the cells both through a simple diffusion-like process and the permease-like system. The rate of the amino acid diffusion into yeast and mycelial forms appeared to be the same, whereas the initial rate of accumulation through the permease-like system was 5 to 10 times faster in the mycelial phase than it was in the yeast phase. The Michaelis constants were 2.2 × 10−5m in yeast phase and 2 × 10−5m in mycelial phase cells. Transport of l-leucine at an external concentration of 10−5m showed all of the characteristics of a system of active transport, which was dependent on temperature and pH. Displacement or removal of the α-amino group, or modification of the α-carboxyl group abolished amino acid uptake. The process was competitively inhibited by neutral aliphatic side-chain amino acids (inhibition constants ranged from 1.5 × 10−5 to 6.2 × 10−5m). Neutral aromatic side-chain amino acids and the d-isomers of leucine and valine did not inhibit l-leucine uptake. These data were interpreted to mean that the l-leucine transport system is stereospecific and is highly specific for neutral aliphatic side-chain amino acids. Incorporation of l-leucine into macromolecules occurred at almost the same rate in both morphological forms of the fungus. The mycelial phase but not the yeast phase showed a slight initial lag in incorporation. In both morphological forms the intracellular pool of l-leucine was of limited capacity, and the total uptake of the amino acid was a function of intracellular pool size. The initial rate of l-leucine uptake was independent of the level of intracellular pool. Both morphological forms deaminated and degraded only a minor fraction of the accumulated leucine. PMID:4323295

The Impact of Radiation Changes on the Terrestrial Carbon Sink over the Post Pinatubo Period

NASA Astrophysics Data System (ADS)

Sitch, S.; Mercado, L. M.; Bellouin, N.; Boucher, O.; Huntingford, C.; Cox, P. M.

2008-12-01

The amount of solar radiation reaching the earth surface is one of the major drivers of plant photosynthesis and therefore changes in radiation are likely to indirectly have an effect on the terrestrial carbon cycle. For example, changes in surface radiation that lead to increasing diffuse surface irradiance are reported to enhance plant photosynthesis (Gu et al., 2003, Niyogi et al., 2004, Oliveira et al., 2007, Roderick et al., 2001). Solar radiation reaching the land surface has changed over the industrial era due to aerosols emitted from volcanoes and various anthropogenic sources (Kvalevag and Myhre, 2007). Such changes in total surface radiation are accompanied by changes in direct and diffuse surface solar radiation. Recent major volcanic events include the eruptions of el Chichón in 1986 and Mount Pinatubo in 1991. In this study we estimate the impact of changes in surface radiation on photosynthetic carbon uptake during the Post Pinatubo period. We use an offline version of the Hadley Centre land surface scheme (Mercado et al., 2007) modified to account for variations in direct and diffuse radiation on sunlit and shaded canopy photosynthesis. We use meteorological forcing from the Climate Research Unit Data set. Additionally short wave and photosynthetic active radiation are reconstructed from the Hadley centre climate model, which accounts for the scattering and absorption of light by tropospheric and stratospheric aerosols. We describe the development of the land carbon cycle through the Pinatubo event and diagnose the impact of changes in diffuse radiation on the atmospheric [CO2] growth-rate

Detection of Explosive Vapors: The Roles of Exciton and Molecular Diffusion in Real-Time Sensing.

PubMed

Ali, Mohammad A; Shoaee, Safa; Fan, Shengqiang; Burn, Paul L; Gentle, Ian R; Meredith, Paul; Shaw, Paul E

2016-11-04

Time-resolved quartz crystal microbalance with in situ fluorescence measurements are used to monitor the sorption of the nitroaromatic (explosive) vapor, 2,4-dinitrotoluene (DNT) into a porous pentiptycene-containing poly(phenyleneethynylene) sensing film. Correlation of the nitroaromatic mass uptake with fluorescence quenching shows that the analyte diffusion follows the Case-II transport model, a film-swelling-limited process, in which a sharp diffusional front propagates at a constant velocity through the film. At a low vapor pressure of DNT of ≈16 ppb, the analyte concentration in the front is sufficiently high to give an average fluorophore-analyte separation of ≈1.5 nm. Hence, a long exciton diffusion length is not required for real-time sensing in the solid state. Rather the diffusion behavior of the analyte and the strength of the binding interaction between the analyte and the polymer play first-order roles in the fluorescence quenching process. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effects of heterogeneities on memory-dependent diffusion

NASA Astrophysics Data System (ADS)

Adib, Farhad; Neogi, P.

1993-07-01

Case II diffusion is often seen in glassy polymers, where the mass uptake in sorption is proportional to time t instead of sqrt{t}. A memory dependent diffusion is needed to explain such effects, where the relaxation function used to describe the memory effect has a characteristic time. The ratio of this time to the overall diffusion times is the diffusional Deborah number. Simple models show that case II results when the Deborah number is around one, that is, when the two time scales are comparable. Under investigation are the possible effects of the fact that the glassy polymers are heterogeneous over molecular scales. The averaging form given by DiMarzio and Sanchez has been used to obtain the averaged response. The calculated dynamics of sorption show that whereas case II is still observed, the long term tails change dramatically from the oscillatory to torpid, to chaotic, which are all observed in the experiments. The Deborah number defined here in a self-consistent manner collapses in those cases, but causes no other ill-effects.

Lung function parameters improve prediction of VO2peak in an elderly population: The Generation 100 study.

PubMed

Hassel, Erlend; Stensvold, Dorthe; Halvorsen, Thomas; Wisløff, Ulrik; Langhammer, Arnulf; Steinshamn, Sigurd

2017-01-01

Peak oxygen uptake (VO2peak) is an indicator of cardiovascular health and a useful tool for risk stratification. Direct measurement of VO2peak is resource-demanding and may be contraindicated. There exist several non-exercise models to estimate VO2peak that utilize easily obtainable health parameters, but none of them includes lung function measures or hemoglobin concentrations. We aimed to test whether addition of these parameters could improve prediction of VO2peak compared to an established model that includes age, waist circumference, self-reported physical activity and resting heart rate. We included 1431 subjects aged 69-77 years that completed a laboratory test of VO2peak, spirometry, and a gas diffusion test. Prediction models for VO2peak were developed with multiple linear regression, and goodness of fit was evaluated. Forced expiratory volume in one second (FEV1), diffusing capacity of the lung for carbon monoxide and blood hemoglobin concentration significantly improved the ability of the established model to predict VO2peak. The explained variance of the model increased from 31% to 48% for men and from 32% to 38% for women (p<0.001). FEV1, diffusing capacity of the lungs for carbon monoxide and hemoglobin concentration substantially improved the accuracy of VO2peak prediction when added to an established model in an elderly population.

Atmospheric pressure synthesis of photoluminescent hybrid materials by sequential organometallic vapor infiltration into polyethylene terephthalate fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Akyildiz, Halil I.; Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695; Mousa, Moataz Bellah M.

Exposing a polymer to sequential organometallic vapor infiltration (SVI) under low pressure conditions can significantly modify the polymer's chemical, mechanical, and optical properties. We demonstrate that SVI of trimethylaluminum into polyethylene terephthalate (PET) can also proceed readily at atmospheric pressure, and at 60 °C the extent of reaction determined by mass uptake is independent of pressure between 2.5 Torr and 760 Torr. At 120 °C, however, the mass gain is 50% larger at 2.5 Torr relative to that at 760 Torr, indicating that the precursor diffusion in the chamber and fiber matrix decreases at higher source pressure. Mass gain decreases, in general, as the SVI processmore » temperature increases both at 2.5 Torr and 760 Torr attributed to the faster reaction kinetics forming a barrier layer, which prevents further diffusion of the reactive species. The resulting PET/Al-O{sub x} product shows high photoluminescence compared to untreated fibers. A physical mask on the polymer during infiltration at 760 Torr is replicated in the underlying polymer, producing an image in the polymer that is visible under UV illumination. Because of the reduced precursor diffusivity during exposure at 760 Torr, the image shows improved resolution compared to SVI performed under typical 2.5 Torr conditions.« less

Scaling of physical constraints at the root-soil interface to macroscopic patterns of nutrient retention in ecosystems.

PubMed

Gerber, Stefan; Brookshire, E N Jack

2014-03-01

Nutrient limitation in terrestrial ecosystems is often accompanied with maintaining a nearly closed vegetation-soil nutrient cycle. The ability to retain nutrients in an ecosystem requires the capacity of the plant-soil system to draw down nutrient levels in soils effectually such that export concentrations in soil solutions remain low. Here we address the physical constraints of plant nutrient uptake that may be limited by the diffusive movement of nutrients in soils, by the uptake at the root/mycorrhizal surface, and from interactions with soil water flow. We derive an analytical framework of soil nutrient transport and uptake and predict levels of plant available nutrient concentration and residence time. Our results, which we evaluate for nitrogen, show that the physical environment permits plants to lower soil solute concentration substantially. Our analysis confirms that plant uptake capacities in soils are considerable, such that water movement in soils is generally too small to significantly erode dissolved plant-available nitrogen. Inorganic nitrogen concentrations in headwater streams are congruent with the prediction of our theoretical framework. Our framework offers a physical-based parameterization of nutrient uptake in ecosystem models and has the potential to serve as an important tool toward scaling biogeochemical cycles from individual roots to landscapes.

Phosphate uptake studies of cross-linked chitosan bead materials.

PubMed

Mahaninia, Mohammad H; Wilson, Lee D

2017-01-01

A systematic experimental study is reported that provides a molecular based understanding of cross-linked chitosan beads and their adsorption properties in aqueous solution containing phosphate dianion (HPO 4 2- ) species. Synthetically modified chitosan using epichlorohydrin and glutaraldehyde cross-linkers result in surface modified beads with variable hydrophile-lipophile character and tunable HPO 4 2- uptake properties. The kinetic and thermodynamic adsorption properties of cross-linked chitosan beads with HPO 4 2- species were studied in aqueous solution. Complementary structure and physicochemical characterization of chitosan beads via potentiometry, Raman spectroscopy, DSC, and dye adsorption measurements was carried out to establish structure-property relationships. The maximum uptake (Q m ) of bead systems with HPO 4 2- at equilibrium was 52.1mgg -1 ; whereas, kinetic uptake results for chitosan bead/phosphate systems are relatively rapid (0.111-0.113min -1 ) with an intraparticle diffusion rate-limiting step. The adsorption process follows a multi-step pathway involving inner- and outer-sphere complexes with significant changes in hydration. Phosphate uptake strongly depends on the composition and type of cross-linker used for preparation of chitosan beads. The adsorption isotherms and structural characterization of bead systems illustrate the role of surface charge, hydrophile-lipophile balance, adsorption site accessibility, and hydration properties of the chitosan bead surface. Copyright © 2016 Elsevier Inc. All rights reserved.

3D Time-lapse Imaging and Quantification of Mitochondrial Dynamics

NASA Astrophysics Data System (ADS)

Sison, Miguel; Chakrabortty, Sabyasachi; Extermann, Jérôme; Nahas, Amir; James Marchand, Paul; Lopez, Antonio; Weil, Tanja; Lasser, Theo

2017-02-01

We present a 3D time-lapse imaging method for monitoring mitochondrial dynamics in living HeLa cells based on photothermal optical coherence microscopy and using novel surface functionalization of gold nanoparticles. The biocompatible protein-based biopolymer coating contains multiple functional groups which impart better cellular uptake and mitochondria targeting efficiency. The high stability of the gold nanoparticles allows continuous imaging over an extended time up to 3000 seconds without significant cell damage. By combining temporal autocorrelation analysis with a classical diffusion model, we quantify mitochondrial dynamics and cast these results into 3D maps showing the heterogeneity of diffusion parameters across the whole cell volume.

Chronic mandibular osteomyelitis with suspected underlying synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome: a case report

PubMed Central

Mochizuki, Yumi; Omura, Ken; Hirai, Hideaki; Kugimoto, Takuma; Osako, Toshimitu; Taguchi, Takahide

2012-01-01

Chronic mandibular osteomyelitis is an intractable disease. In recent years, some case reports have related this disease process to synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome, which is chronic with frequent remissions and exacerbations. This report describes a case of chronic mandibular osteomyelitis suspected to be SAPHO syndrome. A 68-year-old woman presented with pain on the left side of the mandible. On the basis of clinical and radiological findings, chronic mandibular diffuse sclerosing osteomyelitis was initially diagnosed. We administrated oral clarithromycin (400 mg daily) and levofloxacin (500 mg daily), and her pain subsequently resolved. On 99mTc-labeled methylene diphosphonate scintigraphy, tracer uptake in the asymptomatic mandible was unchanged, but there was increasing tracer uptake in the sternocostal and sternoclavicular joints, compared with 99mTc-labeled methylene diphosphonate scintigraphic findings of the first visit. We diagnosed SAPHO syndrome and administrated oral sodium risedronate hydrate (2.5 mg daily). Although there has been no pain or swelling in the area of the left mandibular lesion, we have followed up on other skin and osteoarticular manifestations in conjunction with other medical departments. PMID:22427727

Appearance of Graves' disease after percutaneous ethanol injection for the treatment of hyperfunctioning thyroid adenoma.

PubMed

Monzani, F; Del Guerra, P; Caraccio, N; Casolaro, A; Lippolis, P V; Goletti, O

1997-05-01

In this report we describe an unusual patient with hyperfunctioning thyroid adenoma in whom percutaneous ethanol injection (p.e.i.) therapy was followed by typical Graves' disease. His history revealed the presence of a sister with Hashimoto's thyroiditis. 99-mTc thyroid scintiscan showed focal uptake in the nodule, with suppression of extranodular parenchyma. P.e.i. therapy was followed by the development of severe hyperthyroidism. One month after a second p.e.i. cycle, recurrence of hyperthyroidism associated with diffuse 99-mTc uptake by the gland was observed. TSH-receptor and thyroglobulin autoantibodies were undetectable before p.e.i. therapy, appeared during the first cycle, and showed a further increase after the second p.e.i. therapy cycle. Though spontaneous switch to Graves' disease cannot be excluded in patients with toxic nodules, the massive release of thyroid materials from follicular cells, among these TSH-receptor antigenic components partially denatured by ethanol, may indeed trigger an autoimmune response to the TSH-receptor, thus accounting for this observation. Patients with possible autoimmune disposition, as selected by familiar history and/or laboratory markers should be carefully monitored during p.e.i. treatment.

Controlled release from a composite silicone/hydrogel membrane.

PubMed

Hu, Z; Wang, C; Nelson, K D; Eberhart, R C

2000-01-01

To enhance the drug uptake and release capacity of silicone rubber (SR), N-isopropylacrylamide (NIPA) hydrogel particles have been incorporated into a SR membrane. The NIPA particles were thoroughly blended with uncured SR with a certain ratio at room temperature. The mixture was then cast in a Petri dish to 1 mm thickness and cured 10 hours at 90 degrees C. The SR/NIPA composite gel can absorb water approximately equal to its dry weight. Brilliant blue, used as a mock drug, was loaded into the composite gel. Drug release increased exponentially to a final value that is temperature dependent: low at T> =34 degrees C, and high at T< 34 degrees C. This finding is because the hydrophobicity of NIPA changes with temperature. Pulsed release in response to temperature switching between 20 and 39 degrees C has been achieved. Drug uptake and release capability strongly depends upon the structure of the composite gel. The optimal range of NIPA composition is between 75 and 87% by volume. In the cited range, the NIPA particles form an interconnected network that provides a channel for diffusion of drug solution. The SR/NIPA composite gel has promising attributes as a wound dressing and other uses.

Modulation of a pulsatile release drug delivery system using different swellable/rupturable materials.

PubMed

El-Maradny, Hoda A

2007-11-01

Diclofenac sodium tablets consisting of core coated with two layers of swelling and rupturable coatings were prepared and evaluated as a pulsatile drug delivery system. Cores containing the drug were prepared by direct compression using microcrystalline cellulose and Ludipress as hydrophilic excipients with the ratio of 1:1. Cores were then coated sequentially with an inner swelling layer of different swellable materials; either Explotab, Croscarmellose sodium, or Starch RX 1500, and an outer rupturable layer of different levels of ethylcellulose. The effect of the nature of the swelling layer and the level of the rupturable coating on the lag time and the water uptake were investigated. Drug release rate studies were performed using USP paddle method. Results showed the dependence of the lag time and water uptake prior to tablet rupture on the nature of the swelling layer and the coating levels. Explotab showed a significant decrease in the lag time, followed by Croscarmellose sodium and finally by Starch RX 1500. Increasing the level of ethylcellulose coating retarded the diffusion of the release medium to the swelling layer and the rupture of the coat, thus prolonging the lag time.

Characterization of the ZAT1p zinc transporter from Arabidopsis thaliana in microbial model organisms and reconstituted proteoliposomes.

PubMed

Bloss, Tanja; Clemens, Stephan; Nies, Dietrich H

2002-03-01

The ZAT1p zinc transporter from Arabidopsis thaliana (L.) Heynh. is a member of the cation diffusion facilitator (CDF) protein family. When heterologously expressed in Escherichia coli, ZAT1p bound zinc in a metal blot. Binding of zinc occurred mainly to the hydrophilic amino acid region from H182 to H232. A ZAT1p/ZAT1p*Delta(M1-I25) protein mixture was purified and reconstituted into proteoliposomes. Uptake of zinc into the proteoliposomes did not require a proton gradient across the liposomal membrane. ZAT1p did not transport cobalt, and transported cadmium at only 1% of the zinc transport rate. ZAT1p functioned as an uptake system for 65Zn2+ in two strains of the Gram-negative bacterium Ralstonia metallidurans, which were different in their content of zinc-efflux systems. The ZAT1 gene did not rescue increased zinc sensitivity of a Delta ZRC1single-mutant strain or of a Delta ZRC1 Delta COT1 double-mutant strain of Saccharomyces cerevisiae, but ZAT1 complemented this phenotype in a Delta SpZRC1 mutant strain of Schizosaccharomyces pombe.

Diffusion of biostimulators into plant tissues

NASA Astrophysics Data System (ADS)

Kolomazník, Karel; Pecha, Jiří; Friebrová, Veronika; Janáčová, Dagmar; Vašek, Vladimír

2012-09-01

Biostimulators are substances able to enhance the immune system of cultivated crops and support plant metabolism. Their utilization helps to reduce the amount of chemicals used in agriculture. To perform the desired effect, a biostimulator must be able to penetrate into the plant tissue. The time of penetration however, is limited, since the biostimulator must remain in a liquid state. This is of great importance—especially in field conditions, where the treated plants are exposed to different weather condition and other extrinsic factors. A mathematical model based on diffusion mechanisms has been elaborated to describe the biostimulator transport process from penetration of the leaves into the plant's inner tissues. By means of the effective diffusion coefficient of the prepared specific protein hydrolyzate, this model can be used to estimate the time necessary for the uptake of the minimal active amount of the biostimulator.

Understanding the Effect of Na in Improving the Performance of CuInSe 2 Based Photovoltaics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dobson, Kevin D.

Cu(In,Ga)Se 2 (CIGS) thin film photovoltaic technology is in the early stages of commercialization with an annual manufacturing capacity over 1 GW and has demonstrated the highest module efficiency of any of the thin film technologies. However there still is a lack of fundamental understanding of the relationship between the material properties and solar cell device operation. It is well known that the incorporation of a small amount of Na into the CIGS film during processing is essential for high efficiency devices. However, there are conflicting explanations for how Na behaves at the atomic scale. This report investigates how Namore » is incorporated into the CIGS device structure and evaluates the diffusion of Na into CIGS grain boundaries (GBs) and bulk crystallites. Participants: This project was carried out at the Institute of Energy Conversion at the University of Delaware, collaborating with the Rockett group at the University of Illinois Urbana-Champagne. Significant Findings: The significant outcomes of this project for each task include; Task 1.0: Effect of Na in Devices Fabricated on PVD Deposited CIGS; Na diffusion occurs through the Mo back contact via GBs driven by the presence of oxygen; Na reversibly compensates donor defects in CIGS GBs,Task 2.0: Na Incorporation in Single Crystal CIGS; and bulk Na diffusion proceeds rapidly such that grains are Na-saturated immediately following CIGS thin film manufacture. Industry Guidance: The presented results offer interesting concepts for modification of manufacturing processes of CIGS-based PV modules. Possible approaches to improve control of Na uptake and uniformly increase levels in CIGS films are highlighted for processes that employ either soda-lime glass or NaF as the Na source. Concepts include the potential of O 2 or oxidative based treatments of Mo back contacts to improve Na diffusion through the metal film and increase Na uptake into the growing CIGS. This project has also offered fundamental understanding of the behavior of Na in CIGS grains and GBs, particularly the confirmation that CIGS grains will be saturated with Na immediately following manufacture Summary of Results: Most commercially available CIGS modules are fabricated on soda-lime glass coated with Mo as the back electric contact, and Na in the glass diffuses through the Mo layer into the CIGS during film growth. In Task 1 the transport of Na through Mo was evaluated using x-ray photoelectron surface spectroscopy along with diffusion modeling to obtain diffusion coefficients at several temperatures. It was determined that Na diffusion in Mo only occurs along GBs and that oxygen provides an additional driving force to enhance Na transport. Device data revealed that older Mo substrates with a greater amount of surface oxide resulted in slightly higher efficiencies due to enhanced Na incorporation caused by the oxide. This finding shows that Mo substrates could potentially undergo an oxidation treatment prior to CIGS deposition to further improve and control the incorporation of Na. To determine if in-grain Na affects device performance, in Task 1 Na was selectively removed from GBs using heat/rinse cycles. Due to the low temperature of this treatment, Na at GBS remained mobile while diffusion within the bulk was too slow for Na removal from the grain interiors. Changes in electrical properties were evaluated using conductivity and Seebeck coefficient measurements, with both decreasing as Na was removed to reach values similar to Na-free controls samples. This can be explained by the compensation of donor defects by Na, causing an increase in the free carrier concentration. Devices showed a decrease in open-circuit voltage after Na removal confirming that the beneficial effects of GB Na. The findings of this project will provide guidance for rational optimization of Na incorporation procedures in the manufacturing of CIGS solar cells. While it is known that Na segregates at CIGS GBs, the nature and role of Na diffusion into grain interiors was less clear. In Task 2, single crystal CuInSe 2 was used as a model system to represent the grain interiors of CIGS. Crystals processed by two different methods of different compositions and dislocation densities, were evaluated. Diffusion coefficients were obtained at two temperatures after Na diffusion, giving near identical values, ~2x10 11 cm 2/s and ~6x10 11 cm2/s at 420°C and 480°C, respectively, for each crystal. Characterization confirmed that dislocation densities were too low to significantly impact the effective diffusion coefficient. The Cu-poor crystal had a higher solubility suggesting that Na diffusion is mediated by Cu-vacancies, but was not accompanied by an expected increase in diffusion coefficient. The activation energy for diffusion was similar to values expected for interstitial diffusion, but the large size of Na + ions should result in a solubility that is much lower than what was experimentally measured. A hybrid interstitial-substitutional mechanism is proposed that combines the fast diffusion of interstitial atoms with the high solubility common for substitutional impurities. Lattice diffusion of Na proceeds fast enough that CIGS grain interiors will have Na concentrations near the solubility limit of 1018 cm -3 when manufactured under standard conditions. Na and K treated epitaxial CIS films showed a significant increase in cathodoluminescence emission intensity, indicating a reduction of non-radiative recombination pathways, which is consistent with improvements in CIGS device performance, though the mechanism is not clear. Pathways forward: Despite the success of this project, there are a number of questions remaining related to further the understanding of the chemistry of Na in CIGS films and devices. These include further elucidation of the mechanisms of Na passivation in CIGS GBs, with identification of which defects are involved and confirmation of the possible effects of in-grain Na on device performance. To complete analysis of the cell structure, conformation of the presence and possible chemistries of Na at the CIGS/CdS junction and/or in the front transparent contacts, and its effects on device performance, is needed.« less

Water absorption behaviour of hybrid interwoven cellulosic fibre composites

NASA Astrophysics Data System (ADS)

Maslinda, A. B.; Majid, M. S. Abdul; Ridzuan, M. J. M.; Syayuthi, AR. A.

2017-10-01

The present paper investigated the water absorption behaviour of hybrid interwoven cellulosic fibre composites. Hybrid composites consisting of interwoven kenaf/jute and kenaf/hemp yarns were prepared by an infusion manufacturing technique that used epoxy as the polymer matrix. Water absorption test was conducted as elucidated in ASTM D570 standard by immersing the composite samples in tap water at room temperature until reaching their water content saturation point. For each composite type, average from five samples was recorded and the percentage of water uptake against the square root of time was plotted. As the effect of hybridization, the water uptake, diffusion and permeability coefficient of the hybrid composites were lesser than the individual woven composites.

The Spatial Relationship between Apparent Diffusion Coefficient and Standardized Uptake Value of 18F-Fluorodeoxyglucose Has a Crucial Influence on the Numeric Correlation of Both Parameters in PET/MRI of Lung Tumors

PubMed Central

Stieltjes, Bram; Weikert, Thomas; Gatidis, Sergios; Wiese, Mark; Wild, Damian; Lardinois, Didier

2017-01-01

The minimum apparent diffusion coefficient (ADCmin) derived from diffusion-weighted MRI (DW-MRI) and the maximum standardized uptake value (SUVmax) of FDG-PET are markers of aggressiveness in lung cancer. The numeric correlation of the two parameters has been extensively studied, but their spatial interplay is not well understood. After FDG-PET and DW-MRI coregistration, values and location of ADCmin- and SUVmax-voxels were analyzed. The upper limit of the 95% confidence interval for registration accuracy of sequential PET/MRI was 12 mm, and the mean distance (D) between ADCmin- and SUVmax-voxels was 14.0 mm (average of two readers). Spatial mismatch (D > 12 mm) between ADCmin and SUVmax was found in 9/25 patients. A considerable number of mismatch cases (65%) was also seen in a control group that underwent simultaneous PET/MRI. In the entire patient cohort, no statistically significant correlation between SUVmax and ADCmin was seen, while a moderate negative linear relationship (r = −0.5) between SUVmax and ADCmin was observed in tumors with a spatial match (D ≤ 12 mm). In conclusion, spatial mismatch between ADCmin and SUVmax is found in a considerable percentage of patients. The spatial connection of the two parameters SUVmax and ADCmin has a crucial influence on their numeric correlation. PMID:29391862

Turbulent mixing and removal of ozone within an Amazon rainforest canopy

NASA Astrophysics Data System (ADS)

Freire, L. S.; Gerken, T.; Ruiz-Plancarte, J.; Wei, D.; Fuentes, J. D.; Katul, G. G.; Dias, N. L.; Acevedo, O. C.; Chamecki, M.

2017-03-01

Simultaneous profiles of turbulence statistics and mean ozone mixing ratio are used to establish a relation between eddy diffusivity and ozone mixing within the Amazon forest. A one-dimensional diffusion model is proposed and used to infer mixing time scales from the eddy diffusivity profiles. Data and model results indicate that during daytime conditions, the upper (lower) half of the canopy is well (partially) mixed most of the time and that most of the vertical extent of the forest can be mixed in less than an hour. During nighttime, most of the canopy is predominantly poorly mixed, except for periods with bursts of intermittent turbulence. Even though turbulence is faster than chemistry during daytime, both processes have comparable time scales in the lower canopy layers during nighttime conditions. Nonchemical loss time scales (associated with stomatal uptake and dry deposition) for the entire forest are comparable to turbulent mixing time scale in the lower canopy during the day and in the entire canopy during the night, indicating a tight coupling between turbulent transport and dry deposition and stomatal uptake processes. Because of the significant time of day and height variability of the turbulent mixing time scale inside the canopy, it is important to take it into account when studying chemical and biophysical processes happening in the forest environment. The method proposed here to estimate turbulent mixing time scales is a reliable alternative to currently used models, especially for situations in which the vertical distribution of the time scale is relevant.

The Spatial Relationship between Apparent Diffusion Coefficient and Standardized Uptake Value of 18F-Fluorodeoxyglucose Has a Crucial Influence on the Numeric Correlation of Both Parameters in PET/MRI of Lung Tumors.

PubMed

Sauter, Alexander W; Stieltjes, Bram; Weikert, Thomas; Gatidis, Sergios; Wiese, Mark; Klarhöfer, Markus; Wild, Damian; Lardinois, Didier; Bremerich, Jens; Sommer, Gregor

2017-01-01

The minimum apparent diffusion coefficient (ADC min ) derived from diffusion-weighted MRI (DW-MRI) and the maximum standardized uptake value (SUV max ) of FDG-PET are markers of aggressiveness in lung cancer. The numeric correlation of the two parameters has been extensively studied, but their spatial interplay is not well understood. After FDG-PET and DW-MRI coregistration, values and location of ADC min - and SUV max -voxels were analyzed. The upper limit of the 95% confidence interval for registration accuracy of sequential PET/MRI was 12 mm, and the mean distance ( D ) between ADC min - and SUV max -voxels was 14.0 mm (average of two readers). Spatial mismatch ( D > 12 mm) between ADC min and SUV max was found in 9/25 patients. A considerable number of mismatch cases (65%) was also seen in a control group that underwent simultaneous PET/MRI. In the entire patient cohort, no statistically significant correlation between SUV max and ADC min was seen, while a moderate negative linear relationship ( r = -0.5) between SUV max and ADC min was observed in tumors with a spatial match ( D ≤ 12 mm). In conclusion, spatial mismatch between ADC min and SUV max is found in a considerable percentage of patients. The spatial connection of the two parameters SUV max and ADC min has a crucial influence on their numeric correlation.

Ventilation-perfusion matching during exercise

NASA Technical Reports Server (NTRS)

Wagner, P. D.

1992-01-01

In normal subjects, exercise widens the alveolar-arterial PO2 difference (P[A-a]O2) despite a more uniform topographic distribution of ventilation-perfusion (VA/Q) ratios. While part of the increase in P(A-a)O2 (especially during heavy exercise) is due to diffusion limitation, a considerable amount is caused by an increase in VA/Q mismatch as detected by the multiple inert gas elimination technique. Why this occurs is unknown, but circumstantial evidence suggests it may be related to interstitial pulmonary edema rather than to factors dependent on ventilation, airway gas mixing, airway muscle tone, or pulmonary vascular tone. In patients with lung disease, the gas exchange consequences of exercise are variable. Thus, arterial PO2 may increase, remain the same, or fall. In general, patients with advanced chronic obstructive pulmonary disease (COPD) or interstitial fibrosis who exercise show a fall in PO2. This is usually not due to worsening VA/Q relationships but mostly to the well-known fall in mixed venous PO2, which itself results from a relatively smaller increase in cardiac output than VO2. However, in interstitial fibrosis (but not COPD), there is good evidence that a part of the fall in PO2 on exercise is caused by alveolar-capillary diffusion limitation of O2 transport; in COPD (but not interstitial fibrosis), a frequent additional contributing factor to the hypoxemia of exercise is an inadequate ventilatory response, such that minute ventilation does not rise as much as does CO2 production or O2 uptake, causing arterial PCO2 to increase and PO2 to fall.

18F-FDG uptake in the colon is modulated by metformin but not associated with core body temperature and energy expenditure.

PubMed

Bahler, Lonneke; Holleman, Frits; Chan, Man-Wai; Booij, Jan; Hoekstra, Joost B; Verberne, Hein J

2017-01-01

Physiological colonic 18F-fluorodeoxyglucose (18F-FDG) uptake is a frequent finding on 18F-FDG positron emission tomography computed tomography (PET-CT). Interestingly, metformin, a glucose lowering drug associated with moderate weight loss, is also associated with an increased colonic 18F-FDG uptake. Consequently, increased colonic glucose use might partly explain the weight losing effect of metformin when this results in an increased energy expenditure and/or core body temperature. Therefore, we aimed to determine whether metformin modifies the metabolic activity of the colon by increasing glucose uptake. In this open label, non-randomized, prospective mechanistic study, we included eight lean and eight overweight males. We measured colonic 18F-FDG uptake on PET-CT, energy expenditure and core body temperature before and after the use of metformin. The maximal colonic 18F-FDG uptake was measured in 5 separate segments (caecum, colon ascendens,-transversum,-descendens and sigmoid). The maximal colonic 18F-FDG uptake increased significantly in all separate segments after the use of metformin. There was no significant difference in energy expenditure or core body temperature after the use of metformin. There was no correlation between maximal colonic 18F-FDG uptake and energy expenditure or core body temperature. Metformin significantly increases colonic 18F-FDG uptake, but this increased uptake is not associated with an increase in energy expenditure or core body temperature. Although the colon might be an important site of the glucose plasma lowering actions of metformin, this mechanism of action does not explain directly any associated weight loss.

Development of fluorescent glucose bioprobes and their application on real-time and quantitative monitoring of glucose uptake in living cells.

PubMed

Lee, Hyang Yeon; Lee, Jae Jeong; Park, Jongmin; Park, Seung Bum

2011-01-03

We developed a novel fluorescent glucose bioprobe, GB2-Cy3, for the real-time and quantitative monitoring of glucose uptake in living cells. We synthesized a series of fluorescent glucose analogues by adding Cy3 fluorophores to the α-anomeric position of D-glucose through various linkers. Systematic and quantitative analysis of these Cy3-labeled glucose analogues revealed that GB2-Cy3 was the ideal fluorescent glucose bioprobe. The cellular uptake of this probe competed with the cellular uptake of D-glucose in the media and was mediated by a glucose-specific transport system, and not by passive diffusion. Flow cytometry and fluorescence microscopy analyses revealed that GB2-Cy3 is ten times more sensitive than 2-NBDG, a leading fluorescent glucose bioprobe. GB2-Cy3 can also be utilized for the quantitative flow cytometry monitoring of glucose uptake in metabolically active C2C12 myocytes under various treatment conditions. As opposed to a glucose uptake assay performed by using radioisotope-labeled deoxy-D-glucose and a scintillation counter, GB2-Cy3 allows the real-time monitoring of glucose uptake in living cells under various experimental conditions by using fluorescence microscopy or confocal laser scanning microscopy (CLSM). Therefore, we believe that GB2-Cy3 can be utilized in high-content screening (HCS) for the discovery of novel therapeutic agents and for making significant advances in biomedical studies and diagnosis of various diseases, especially metabolic diseases. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Predicting Human Clearance of OATP substrates using Cynomolgus monkey: In vitro-in vivo scaling of hepatic uptake clearance.

PubMed

de Bruyn, Tom; Ufuk, Ayse; Cantrill, Carina; Kosa, Rachel E; Bi, Yi-An; Niosi, Mark; Modi, Sweta; Rodrigues, A David; Tremaine, Larry M; Varma, Manthena Vs; Galetin, Aleksandra; Houston, J Brian

2018-05-02

This work explores the utility of the cynomolgus monkey as a preclinical model to predict hepatic uptake clearance mediated by organic anion transporting polypeptide (OATP) transporters. Nine OATP substrates (rosuvastatin, pravastatin, repaglinide, fexofenadine, cerivastatin, telmisartan, pitavastatin, bosentan and valsartan) were investigated in plated cynomolgus monkey and human hepatocytes. Total uptake clearance and passive diffusion were measured in vitro from initial rates in the absence and presence of the OATP inhibitor rifamycin SV, respectively. Total uptake clearance values in plated hepatocytes ranged over three orders of magnitude in both species with a similar rank order and good agreement in the relative contribution of active transport to total uptake between cynomolgus monkey and human. In vivo hepatic clearance for these nine drugs was determined in cynomolgus monkey after intravenous dosing. Hepatic clearances showed a similar range to human parameters and good predictions from respective hepatocyte parameters (with 2.7 and 3.8-fold bias on average, respectively). The use of cross species empirical scaling factors (based on either dataset average or individual drug scaling factor from cynomolgus monkey data) improved prediction (less bias, better concordance) of human hepatic clearance from human hepatocyte data alone. In vitro intracellular binding in hepatocytes also correlated well between species. It is concluded that the minimal species differences observed for the current dataset between cynomolgus monkey and human hepatocyte uptake, both in vitro and in vivo, support future use of this preclinical model to delineate drug hepatic uptake and enable prediction of human in vivo intrinsic hepatic clearance. The American Society for Pharmacology and Experimental Therapeutics.

Mechanistic insights from DGT and soil solution measurements on the uptake of Ni and Cd by radish.

PubMed

Luo, Jun; Cheng, Hao; Ren, Jinghua; Davison, William; Zhang, Hao

2014-07-01

This work tests the previously proposed hypothesis that plant uptake of metals is determined dominantly by diffusional controlled or plant limiting uptake mechanisms at, respectively, low and high metal concentrations. Radish (Raphanus sativus) was grown in 13 soils spiked with Ni (10 and 100 mg kg(-1)) and Cd (0.5 and 4 mg kg(-1)) for 4 weeks to investigate the mechanisms affecting plant uptake. Soil solution concentrations, Css, of Ni and Cd were measured, along with the DGT interfacial concentration, CDGT, and the derived effective concentration in soil solution, CE. Free ion activities, aNi(2+) and aCd(2+), were obtained using WHAM 6. Although there was a poor relationship between Ni in radish roots and either Css or aNi(2+) in unamended soils, the distribution of data could be rationalized in terms of the extent of release of Ni from the soil solid phase, as identified by DGT and soil solution measurements. By contrast Ni in radish was linearly related to CE, demonstrating diffusion limited uptake. For soils amended with high concentrations of Ni, linear relationships were obtained for Ni in radish plotted against, Css, aNi(2+), and CE, consistent with the plant controlling uptake. For Ni the hypothesis concerning dominant diffusional and plant limiting uptake mechanisms was demonstrated. Poor relationships between Cd in radish and Css, aCd(2+), and CE, irrespective of amendment by Cd, showed the importance of factors other than diffusional supply, such as rhizosphere and inhibitory processes, and that fulfilment of this hypothesis is plant and metal specific.

Passive sampling for the isotopic fingerprinting of atmospheric mercury

NASA Astrophysics Data System (ADS)

Bergquist, B. A.; MacLagan, D.; Spoznar, N.; Kaplan, R.; Chandan, P.; Stupple, G.; Zimmerman, L.; Wania, F.; Mitchell, C. P. J.; Steffen, A.; Monaci, F.; Derry, L. A.

2017-12-01

Recent studies show that there are variations in the mercury (Hg) isotopic signature of atmospheric Hg, which demonstrates the potential for source tracing and improved understanding of atmospheric cycling of Hg. However, current methods for both measuring atmospheric Hg and collecting enough atmospheric Hg for isotopic analyses require expensive instruments that need power and expertise. Additionally, methods for collecting enough atmospheric Hg for isotopic analysis require pumping air through traps for long periods (weeks and longer). Combining a new passive atmospheric sampler for mercury (Hg) with novel Hg isotopic analyses will allow for the application of stable Hg isotopes to atmospheric studies of Hg. Our group has been testing a new passive sampler for gaseous Hg that relies on the diffusion of Hg through a diffusive barrier and adsorption onto a sulphur-impregnated activated carbon sorbent. The benefit of this passive sampler is that it is low cost, requires no power, and collects gaseous Hg for up to one year with linear, well-defined uptake, which allows for reproducible and accurate measurements of atmospheric gaseous Hg concentrations ( 8% uncertainty). As little as one month of sampling is often adequate to collect sufficient Hg for isotopic analysis at typical background concentrations. Experiments comparing the isotopic Hg signature in activated carbon samples using different approaches (i.e. by passive diffusion, by passive diffusion through diffusive barriers of different thickness, by active pumping) and at different temperatures confirm that the sampling process itself does not impose mass-independent fractionation (MIF). However, sampling does result in a consistent and thus correctable mass-dependent fractionation (MDF) effect. Therefore, the sampler preserves Hg MIF with very high accuracy and precision, which is necessary for atmospheric source tracing, and reasonable MDF can be estimated with some increase in error. In addition to experimental work, initial field data will be presented including a transect of increasing distance from a known strong source of Hg (Mt. Amiata mine, Italy), downwind of Kilauea volcano in Hawaii, and several other locales including the Arctic station Alert and various sites across Ontario, Canada.