Constructing Inexpensive, Flexible, and Versatile Microdialysis Probes in an Undergraduate Microdialysis Research Lab

PubMed Central

Steffes, Sally; Sandstrom, Michael

2008-01-01

Several challenges await new assistant professors setting up a neuroscience lab, and obtaining sufficient research help is typically a top priority. A secondary, but no less daunting, challenge is juggling accuracy and reliability with costs and limited start-up funds. These concerns are particularly crucial for those engaging technically sophisticated measurements, such as microdialysis. We have developed straightforward procedures that our undergraduate students have utilized to successfully construct high-quality, low-cost microdialysis probes. Students mastering the various steps involved have also gained valuable insight into their use, troubleshooting, and the implications of data obtained from these constructed probes. These procedures are explained here to foster increased use in neuroscience labs that involve undergraduates, along with pointers about teaching the technique to newcomers. Students who master the techniques can pass them on to new students easily. These procedures train students in the overall research technique of microdialysis more thoroughly than when manufactured probes are used, they save money, and will eventually save the principal investigator time when students develop independence with troubleshooting and repairs. PMID:23493044

Methodological issues in microdialysis sampling for pharmacokinetic studies.

PubMed

de Lange, E C; de Boer, A G; Breimer, D D

2000-12-15

Microdialysis is an in vivo technique that permits monitoring of local concentrations of drugs and metabolites at specific sites in the body. Microdialysis has several characteristics, which makes it an attractive tool for pharmacokinetic research. About a decade ago the microdialysis technique entered the field of pharmacokinetic research, in the brain, and later also in peripheral tissues and blood. Within this period much has been learned on the proper use of this technique. Today, it has outgrown its child diseases and its potentials and limitations have become more or less well defined. As microdialysis is a delicate technique for which experimental factors appear to be critical with respect to the validity of the experimental outcomes, several factors should be considered. These include the probe; the perfusion solution; post-surgery interval in relation to surgical trauma, tissue integrity and repeated experiments; the analysis of microdialysate samples; and the quantification of microdialysate data. Provided that experimental conditions are optimized to give valid and quantitative results, microdialysis can provide numerous data points from a relatively small number of individual animals to determine detailed pharmacokinetic information. An example of one of the added values of this technique compared with other in vivo pharmacokinetic techniques, is that microdialysis reflects free concentrations in tissues and plasma. This gives the opportunity to assess information on drug transport equilibration across membranes such as the blood-brain barrier, which already has provided new insights. With the progress of analytical methodology, especially with respect to low volume/low concentration measurements and simultaneous measurement of multiple compounds, the applications and importance of the microdialysis technique in pharmacokinetic research will continue to increase.

Development of an On-animal Separation-based Sensor for Monitoring Drug Metabolism in Freely Roaming Sheep

PubMed Central

Scott, David E.; Willis, Sean D.; Gabbert, Seth; Johnson, Dave A.; Naylor, Erik; Janle, Elsa M.; Krichevsky, Janice E.; Lunte, Craig E.; Lunte, Susan M.

2015-01-01

The development of an on-animal separation-based sensor that can be employed for monitoring drug metabolism in a freely roaming sheep is described. The system consists of microdialysis sampling coupled directly to microchip electrophoresis with electrochemical detection (MD-ME-EC). Separations were accomplished using an all-glass chip with integrated platinum working and reference electrodes. Discrete samples from the microdialysis flow were introduced into the electrophoresis chip using a flow-gated injection approach. Electrochemical detection was accomplished in-channel using a two-electrode isolated potentiostat. Nitrite was separated by microchip electrophoresis using reverse polarity and a run buffer consisting of 50 mM phosphate at pH 7.4. The entire system was under telemetry control. The system was first tested with rats to monitor the production of nitrite following introduction of nitroglycerin into the subdermal tissue using a linear probe. The data acquired using the on-line MD-ME-EC system was compared to that obtained off-line analysis by liquid chromatography with electrochemical detection (LC-EC), using a second microdialysis probe implanted parallel to the first probe in the same animal. The MD-ME-EC device was then used on-animal to monitor the subdermal metabolism of nitroglycerin in sheep. The ultimate goal is to use this device to simultaneously monitor drug metabolism and behavior in a freely roaming animal. PMID:25697221

Estimation of in-vivo neurotransmitter release by brain microdialysis: the issue of validity.

PubMed

Di Chiara, G.; Tanda, G.; Carboni, E.

1996-11-01

Although microdialysis is commonly understood as a method of sampling low molecular weight compounds in the extracellular compartment of tissues, this definition appears insufficient to specifically describe brain microdialysis of neurotransmitters. In fact, transmitter overflow from the brain into dialysates is critically dependent upon the composition of the perfusing Ringer. Therefore, the dialysing Ringer not only recovers the transmitter from the extracellular brain fluid but is a main determinant of its in-vivo release. Two types of brain microdialysis are distinguished: quantitative micro-dialysis and conventional microdialysis. Quantitative microdialysis provides an estimate of neurotransmitter concentrations in the extracellular fluid in contact with the probe. However, this information might poorly reflect the kinetics of neurotransmitter release in vivo. Conventional microdialysis involves perfusion at a constant rate with a transmitter-free Ringer, resulting in the formation of a steep neurotransmitter concentration gradient extending from the Ringer into the extracellular fluid. This artificial gradient might be critical for the ability of conventional microdialysis to detect and resolve phasic changes in neurotransmitter release taking place in the implanted area. On the basis of these characteristics, conventional microdialysis of neurotransmitters can be conceptualized as a model of the in-vivo release of neurotransmitters in the brain. As such, the criteria of face-validity, construct-validity and predictive-validity should be applied to select the most appropriate experimental conditions for estimating neurotransmitter release in specific brain areas in relation to behaviour.

Metronidazole and hydroxymetronidazole central nervous system distribution: 1. microdialysis assessment of brain extracellular fluid concentrations in patients with acute brain injury.

PubMed

Frasca, Denis; Dahyot-Fizelier, Claire; Adier, Christophe; Mimoz, Olivier; Debaene, Bertrand; Couet, William; Marchand, Sandrine

2014-01-01

The distribution of metronidazole in the central nervous system has only been described based on cerebrospinal fluid data. However, extracellular fluid (ECF) concentrations may better predict its antimicrobial effect and/or side effects. We sought to explore by microdialysis brain ECF metronidazole distribution in patients with acute brain injury. Four brain-injured patients monitored by cerebral microdialysis received 500 mg of metronidazole over 0.5 h every 8 h. Brain dialysates and blood samples were collected at steady state over 8 h. Probe recoveries were evaluated by in vivo retrodialysis in each patient for metronidazole. Metronidazole and OH-metronidazole were assayed by high-pressure liquid chromatography, and a noncompartmental pharmacokinetic analysis was performed. Probe recovery was equal to 78.8% ± 1.3% for metronidazole in patients. Unbound brain metronidazole concentration-time curves were delayed compared to unbound plasma concentration-time curves but with a mean metronidazole unbound brain/plasma AUC0-τ ratio equal to 102% ± 19% (ranging from 87 to 124%). The unbound plasma concentration-time profiles for OH-metronidazole were flat, with mean average steady-state concentrations equal to 4.0 ± 0.7 μg ml(-1). This microdialysis study describes the steady-state brain distribution of metronidazole in patients and confirms its extensive distribution.

[Microdialysis cerebral. Main application of this technique].

PubMed

Blanco-Lezcano, L; Pavón-Fuentes, N; Blanco-Lezcano, V

Microdialysis cerebral technique has been widely employed in order to study the neurotransmitter release. This technique present numerous advantages such as: allow to work with sample in vivo from animals freely moving, by means of microdialysis can be infused simultaneously different drugs in different points implanted probes in several coordinates; also allow carry out pharmacokinetics studies that show correlation with behavior patter as well as to study metabolic changes, which is not possible when this determination are carry out in tissue, in post mortem stadio. In the present work is carry out a review about the main results obtaining in the sensitization and abstinence to several drug study and approach to biochemical characteristics to Parkinson s disease (PD) by means of microdialysis technique. In relation to sensibilization studies, the temporal changes in different behavior pattern that modify after amphetamine administration have been studied. Microdialysis study allowed correlationate dopamine concentration with behavior pattern above mentioned. In relation with PD, dopamine concentration after systemic and central (intracerebral) administration of levodopa and another dopaminergic drugs have been studied in different nucleus of basal ganglia as well as its respectively behavior correlates.

IN VIVO MEASUREMENT OF PHENYLGLUCUCURONIDE IN RAINBOW TROUT BY ON-LINE INJECTION MICRODIALYSIS

EPA Science Inventory

Phenylglucuronide (PG) was measured in vivo in arterial blood of rainbow trout using on-line injection microdialysis. A microdialysis probe was surgically implanted in the dorsal aorta of spinally-transected trout. The trout were dosed continuously with PG for 24 h using a ventra...

Modulation of the Foreign Body Reaction for Implants in the Subcutaneous Space: Microdialysis Probes as Localized Drug Delivery/Sampling Devices

PubMed Central

Mou, Xiaodun; Lennartz, Michelle R; Loegering, Daniel J; Stenken, Julie A

2011-01-01

Modulation of the foreign body reaction is considered to be an important step toward creation of implanted sensors with reliable long-term performance. In this work, microdialysis probes were implanted into the subcutaneous space of Sprague-Dawley rats. The probe performance was evaluated by comparing collected endogenous glucose concentrations with internal standard calibration (2-deoxyglucose, antipyrine, and vitamin B12). Probes were tested until failure, which for this work was defined as loss of fluid flow. In order to determine the effect of fibrous capsule formation on probe function, monocyte chemoattractant protein-1/CC chemokine ligand 2 (MCP-1/CCL2) was delivered locally via the probe to increase capsule thickness and dexamethasone 21-phosphate was delivered to reduce capsule thickness. Probes delivering MCP-1 had a capsule that was twice the thickness (500–600 μm) of control probes (200–225 μm) and typically failed 2 days earlier than control probes. Probes delivering dexamethasone 21-phosphate had more fragile capsules and the probes typically failed 2 days later than controls. Unexpectedly, extraction efficiency and collected glucose concentrations exhibited minor differences between groups. This is an interesting result in that the foreign body capsule formation was related to the duration of probe function but did not consistently relate to probe calibration. PMID:21722577

Critical evaluation of colon submucosal microdialysis in awake, mobile rats.

PubMed

Cibicek, Norbert; Ehrmann, Jiri; Proskova, Jitka; Vecera, Rostislav

2018-01-01

Sensors able to record large bowel physiology and biochemistry in situ in awake rodents are lacking. Microdialysis is a mini-invasive technique that may be utilized to continuously deliver or recover low-molecular substances from various tissues. In this experiment we evaluated the feasibility of in vivo microdialysis to monitor extracellular fluid chemistry in the descending colon submucosa of conscious, freely moving rodents. Following surgical implantation of a microdialysis probe, male Wistar rats were housed in metabolic cages where they were analgized and clinically followed for four days with free access to standard diet and water. To assess local microcirculation and probe function, glucose, lactate, glucose-to-lactate ratio and urea clearance were determined in the dialysates from the three postoperative days with focus on the final 24-h period. In an attempt to mitigate the expected tissue inflammatory response, one group of animals had the catheters perfused with 5-aminosalicylic acid-enriched medium with final concentration 1 μmol/L. For verification of probe position and the assessment of the surrounding foreign body reaction, standard histological and immunohistochemical methods were employed. Microdialysis of rat gut is associated with considerable technical challenges that may lead to the loss of probe function and high drop-out rate. In this setting, limited data did not allow to draw any firm conclusion regarding local anti-inflammatory effectiveness of 5-aminosalicylic acid perfusion. Although intestinal microdialysis may be suitable for larger anesthetized animals, low reproducibility of the presented method compromises its routine experimental use in awake and freely moving small-sized rodents.

Exploring Thermoresponsive Affinity Agents to Enhance Microdialysis Sampling Efficiency of Proteins

NASA Astrophysics Data System (ADS)

Vasicek, Thaddeus

Affinity agents increase microdialysis protein relative recovery, yet they have not seen widespread use within the microdialysis community due to their additional instrumentation requirements and prohibitive cost. This dissertation describes new affinity agents for microdialysis that require no additional instrumentation to use, have nearly 100% particle recovery, are 7 times more cost efficient than alternatives, and have low specificity enabling their use for a wide variety of proteins. Initially gold nanoparticles were chosen as an affinity ligand support due to their high surface area/volume ratio and colloidal stability. Poly (N-isopropylacrylamide) was immobilized to the gold nanoparticles, which served to sterically stabilize the particles and to act as a generic, reversible protein capture agent. A method was developed to reproducibly vary and quantify poly (N-isopropylacrylamide) graft density from 0.09 to 0.40 ligands/nm2 on gold nanoparticles. During characterization of the polymer coated gold nanoparticles, irreversible particle agglomeration was observed at low polymer graft density in ionic solutions, which prevented further development as a protein capture agent. Poly (N-isopropylacrylamide) nanogels, which have low nonspecific adsorption, low interparticle attractive forces owing to the low curvature of the particle, and a low Hamaker constant, were synthesized to overcome the agglomeration problem. A generic protein affinity ligand cibacron blue, was immobilized to the nanogels, which enabled rapid determination of particle recovery. The perfusion of the nanogels through a microdialysis probe was optimized yielding 100% particle recovery using a combination of a syringe and peristaltic pump. The microdialysis collection efficiency of CCL2, a physiologically relevant cytokine, was increased 3-fold with addition of the nanogel to the microdialysis perfusion fluid. The reduction in instrumentation requirements, low cost, and low specificity obtained with the new affinity agents will lead to increased affinity agent use for microdiaylsis protein sampling.

Dermal microdialysis of inflammatory markers induced by aliphatic hydrocarbons in rats

PubMed Central

Patlolla, Ram R.; Mallampati, Ramya; Fulzele, Suniket V.; Babu, R. Jayachandra; Singh, Mandip

2010-01-01

In the present study we made an attempt to understand the skin irritation cascade of selected aliphatic hydrocarbons using microdialysis technique. Microdialysis probes were inserted into dermis in the dorsal skin of hairless rats. After 2 h of probes insertion, occlusive dermal exposure (2 h) was carried out with 230 μl of nonane, dodecane and tetradecane, using Hill top chambers®. Inflammatory biomarkers such as substance P (SP), α-melanocyte stimulating hormone (α-MSH) Interleukin 6 (IL-6) and prostaglandin E2 (PGE2) were analyzed in the dialysis samples by enzyme immunoassay (EIA). SP, α-MSH and IL6 were released in significant amounts following the dermal exposure of nonane and dodecane, whereas tetradecane did not induce any of these markers in significant amounts compared to control. Nonane increased the PGE2 levels in significant amounts within 2 h of chemical exposure compared to dodecane and tetradecane. IL-6 response was found to be slow and 2–3-fold increase in IL-6 levels was observed after 5 h following nonane and dodecane application. The magnitude of skin irritation exerted by all three chemicals was in the order of nonane ≥ dodecane ≥ tetradecane. The results demonstrate that microdialysis can be used to measure the inflammatory biomarkers in the skin irritation studies and irritation response of chemicals was quantifiable by this method. In conclusion, microdialysis was found to be an excellent tool to measure several inflammatory biomarkers as a function of time after dermal exposures with irritant chemicals. PMID:19152832

Cochlear microdialysis for quantification of dexamethasone and fluorescein entry into scala tympani during round window administration.

PubMed

Hahn, Hartmut; Kammerer, Bernd; DiMauro, Andre; Salt, Alec N; Plontke, Stefan K

2006-02-01

Before new drugs for the treatment of inner ear disorders can be studied in controlled clinical trials, it is important that their pharmacokinetics be established in inner ear fluids. Microdialysis allows drug levels to be measured in perilymph without the volume disturbances and potential cerebrospinal fluid contamination associated with fluid sampling. The aims of this study were to show: (i) that despite low recovery rates from miniature dialysis probes, significant amounts of drug are removed from small fluid compartments, (ii) that dialysis sampling artifacts can be accounted for using computer simulations and (iii) that microdialysis allows quantification of the entry rates through the round window membrane (RWM) into scala tympani (ST). Initial experiments used microdialysis probes in small compartments in vitro containing sodium fluorescein. Stable concentrations were observed in large compartments (1000 microl) but significant concentration declines were observed in smaller compartments (100, 10 and 5.6 microl) comparable to the size of the inner ear. Computer simulations of these experiments closely approximated the experimental data. In in vivo experiments, sodium fluorescein 10 mg/ml and dexamethasone-dihydrogen-phosphate disodium salt 8 mg/ml were simultaneously applied to the RWM of guinea pigs. Perilymph concentration in the basal turn of ST was monitored using microdialysis. The fluorescein concentration reached after 200 min application (585+/-527 microg/ml) was approximately twice that of dexamethasone phosphate (291+/-369 microg/ml). Substantial variation in concentrations was found between animals by approximately a factor of 34 for fluorescein and at least 41 for dexamethasone phosphate. This is, to a large extent, thought to be the result of the RWM permeability varying in different animals. It was not caused by substance analysis variations, because two different analytic methods were used and the concentration ratio between the two substances remained nearly constant across the experiments and because differences were apparent for the repeated samples obtained in each animal. Interpretation of the results using computer simulations allowed RWM permeability to be quantified. It also demonstrated, however, that cochlear clearance values could not be reliably obtained with microdialysis because of the significant contribution of dialysis to clearance. The observed interanimal variation, e.g., in RWM permeability, is likely to be clinically relevant to the local application of drugs in patients.

Cochlear Microdialysis for Quantification of Dexamethasone and Fluorescein Entry into Scala Tympani During Round Window Administration

PubMed Central

Hahn, Hartmut; Kammerer, Bernd; DiMauro, Andre; Salt, Alec N.; Plontke, Stefan K.

2006-01-01

Before new drugs for the treatment of inner ear disorders can be studied in controlled clinical trials, it is important that their pharmacokinetics be established in inner ear fluids. Microdialysis allows drug levels to be measured in perilymph without the volume disturbances and potential cerebrospinal fluid contamination associated with fluid sampling. The aims of this study were to show: (i) that despite low recovery rates from miniature dialysis probes, significant amounts of drug are removed from small fluid compartments, (ii) that dialysis sampling artifacts can be accounted for using computer simulations and (iii) that microdialysis allows quantification of the entry rates through the round window membrane (RWM) into scala tympani (ST). Initial experiments used microdialysis probes in small compartments in vitro containing sodium fluorescein. Stable concentrations were observed in large compartments (1000 μl) but significant concentration declines were observed in smaller compartments (100, 10 and 5.6 μl) comparable to the size of the inner ear. Computer simulations of these experiments closely approximated the experimental data. In in vivo experiments, sodium fluorescein 10 mg/ml and dexamethasone-dihydrogen-phosphate disodium salt 8 mg/ml were simultaneously applied to the RWM of guinea pigs. Perilymph concentration in the basal turn of ST was monitored using microdialysis. The fluorescein concentration reached after 200 min application (585 ± 527 μg/ml) was approximately twice that of dexamethasone phosphate (291 ± 369 μg/ml). Substantial variation in concentrations was found between animals by approximately a factor of 34 for fluorescein and at least 41 for dexamethasone phosphate. This is, to a large extent, thought to be the result of the RWM permeability varying in different animals. It was not caused by substance analysis variations, because two different analytic methods were used and the concentration ratio between the two substances remained nearly constant across the experiments and because differences were apparent for the repeated samples obtained in each animal. Interpretation of the results using computer simulations allowed RWM permeability to be quantified. It also demonstrated, however, that cochlear clearance values could not be reliably obtained with microdialysis because of the significant contribution of dialysis to clearance. The observed interanimal variation, e.g., in RWM permeability, is likely to be clinically relevant to the local application of drugs in patients. PMID:16442251

Metronidazole and Hydroxymetronidazole Central Nervous System Distribution: 1. Microdialysis Assessment of Brain Extracellular Fluid Concentrations in Patients with Acute Brain Injury

PubMed Central

Frasca, Denis; Dahyot-Fizelier, Claire; Adier, Christophe; Mimoz, Olivier; Debaene, Bertrand; Couet, William

2014-01-01

The distribution of metronidazole in the central nervous system has only been described based on cerebrospinal fluid data. However, extracellular fluid (ECF) concentrations may better predict its antimicrobial effect and/or side effects. We sought to explore by microdialysis brain ECF metronidazole distribution in patients with acute brain injury. Four brain-injured patients monitored by cerebral microdialysis received 500 mg of metronidazole over 0.5 h every 8 h. Brain dialysates and blood samples were collected at steady state over 8 h. Probe recoveries were evaluated by in vivo retrodialysis in each patient for metronidazole. Metronidazole and OH-metronidazole were assayed by high-pressure liquid chromatography, and a noncompartmental pharmacokinetic analysis was performed. Probe recovery was equal to 78.8% ± 1.3% for metronidazole in patients. Unbound brain metronidazole concentration-time curves were delayed compared to unbound plasma concentration-time curves but with a mean metronidazole unbound brain/plasma AUC0–τ ratio equal to 102% ± 19% (ranging from 87 to 124%). The unbound plasma concentration-time profiles for OH-metronidazole were flat, with mean average steady-state concentrations equal to 4.0 ± 0.7 μg ml−1. This microdialysis study describes the steady-state brain distribution of metronidazole in patients and confirms its extensive distribution. PMID:24277041

Integration of Microdialysis Sampling and Microchip Electrophoresis with Electrochemical Detection

PubMed Central

Mecker, Laura C.; Martin, R. Scott

2009-01-01

Here we describe the fabrication, optimization, and application of a microfluidic device that integrates microdialysis (MD) sampling, microchip electrophoresis (ME), and electrochemical detection (EC). The manner in which the chip is produced is reproducible and enables the fixed alignment of the MD/ME and ME/EC interfaces. Poly(dimethylsiloxane) (PDMS) -based valves were used for the discrete injection of sample from the hydrodynamic MD dialysate stream into a separation channel for analysis with ME. To enable the integration of ME with EC detection, a palladium decoupler was used to isolate the high voltages associated with electrophoresis from micron-sized carbon ink detection electrodes. Optimization of the ME/EC interface was needed to allow the use of biologically appropriate perfusate buffers containing high salt content. This optimization included changes in the fabrication procedure, increases in the decoupler surface area, and a programmed voltage shutoff. The ability of the MD/ME/EC system to sample a biological system was demonstrated by using a linear probe to monitor the stimulated release of dopamine from a confluent layer of PC 12 cells. To our knowledge, this is the first report of a microchip-based system that couples microdialysis sampling with microchip electrophoresis and electrochemical detection. PMID:19551945

[In vitro and in vivo recoveries of cutaneous micro-dialysis probe of paeonol, eugenol and piperine].

PubMed

Yang, Chang; Bai, Jie; Du, Shou-Ying; Cui, Ya-Hua; Zhang, Qin-Shuai; Ma, Jun-Ming

2016-11-01

To establish a method for detecting micro-dialysis recovery of paeonol, eugenol and piperine in Huoxue Zhitong patch, in order to provide the basis for further percutaneous pharmacokinetics studies. The concentrations of paeonol, eugenol and piperine in dialysates were determined by HPLC, and probe deliveries were calculated respectively. The effects of concentration and calibration approaches on the micro-dialysis probe deliveries of the three components were investigated, and their probe absorbability, in vitro and in vivo probe stability and repeatability were also studied.The results indicated that little paeonol, eugenol and piperine were observed in probes with 30% alcohol as the perfusate, and could be cleaned from probe in a short time. And the in vivo and in vitro probe deliveries of three components were stable within 8 h, drug-containing solution and blank perfusate were alternatively used for three times, and the in vivo and in vitro probe deliveries of three components were basically unchanged. The in vitro recoveries of paeonol, eugenol and piperine with a range of concentration were respectively (45.7±4.66)%, (27.82±2.95)%, (41.3±3.96)%, which indicated no concentration independent. Under the same conditions, the similar delivery was observed by dialysis, retrodialysis and no-net flux. Therefore, the concentrations of analyses of the collected fraction could be calibrated by in vitro or in vivo recoveries. Meanwhile, this also proved that the micro-dialysis method built by this study is applicable to the study on percutaneous pharmacokinetics of Huoxue Zhitong patch. Copyright© by the Chinese Pharmaceutical Association.

A high-accuracy measurement method of glucose concentration in interstitial fluid based on microdialysis

NASA Astrophysics Data System (ADS)

Li, Dachao; Xu, Qingmei; Liu, Yu; Wang, Ridong; Xu, Kexin; Yu, Haixia

2017-11-01

A high-accuracy microdialysis method that can provide the reference values of glucose concentration in interstitial fluid for the accurate evaluation of non-invasive and minimally invasive continuous glucose monitoring is reported in this study. The parameters of the microdialysis process were firstly optimized by testing and analyzing three main factors that impact microdialysis recovery, including the perfusion rate, temperature, and glucose concentration in the area surrounding the microdialysis probe. The precision of the optimized microdialysis method was then determined in a simulation system that was designed and established in this study to simulate variations in continuous glucose concentration in the human body. Finally, the microdialysis method was tested for in vivo interstitial glucose concentration measurement.

Application of intracerebral microdialysis to study regional distribution kinetics of drugs in rat brain.

PubMed Central

de Lange, E. C.; Bouw, M. R.; Mandema, J. W.; Danhof, M.; de Boer, A. G.; Breimer, D. D.

1995-01-01

1. The purpose of the present study was to determine whether intracerebral microdialysis can be used for the assessment of local differences in drug concentrations within the brain. 2. Two transversal microdialysis probes were implanted in parallel into the frontal cortex of male Wistar rats, and used as a local infusion and detection device respectively. Within one rat, three different concentrations of atenolol or acetaminophen were infused in randomized order. By means of the detection probe, concentration-time profiles of the drug in the brain were measured at interprobe distances between 1 and 2 mm. 3. Drug concentrations were found to be dependent on the drug as well as on the interprobe distance. It was found that the outflow concentration from the detection probe decreased with increasing lateral spacing between the probes and this decay was much steeper for acetaminophen than for atenolol. A model was developed which allows estimation of kbp/Deff (transfer coefficient from brain to blood/effective diffusion coefficient in brain extracellular fluid), which was considerably larger for the more lipohilic drug, acetaminophen. In addition, in vivo recovery values for both drugs were determined. 4. The results show that intracerebral microdialysis is able to detect local differences in drug concentrations following infusion into the brain. Furthermore, the potential use of intracerebral microdialysis to obtain pharmacokinetic parameters of drug distribution in brain by means of monitoring local concentrations of drugs in time is demonstrated. PMID:8581296

HISTOLOGICAL STUDIES OF THE EFFECTS OF CHRONIC IMPLANTATION OF CERAMIC-BASED MICROELECTRODE ARRAYS AND MICRODIALYSIS PROBES IN RAT PREFRONTAL CORTEX

PubMed Central

Hascup, Erin R.; Bjerkén, Sara af; Hascup, Kevin N.; Pomerleau, Francois; Huettl, Peter; Strömberg, Ingrid; Gerhardt, Greg A.

2010-01-01

Chronic implantation of neurotransmitter measuring devices is essential for awake, behavioral studies occurring over multiple days. Little is known regarding the effects of long term implantation on surrounding brain parenchyma and the resulting alterations in the functional properties of this tissue. We examined the extent of tissue damage produced by chronic implantation of either ceramic microelectrode arrays (MEAs) or microdialysis probes. Histological studies were carried out on fixed tissues using stains for neurons (cresyl violet), astrocytes (GFAP), microglia (Iba-1), glutamatergic nerve fibers (VGLUT1), and the blood-brain barrier (SMI-71). Nissl staining showed pronounced tissue body loss with microdialysis implants compared to MEAs. The MEAs produced mild gliosis extending 50–100 µm from the tracks, with a significant change in the affected areas starting at 3 days. By contrast, the microdialysis probes produced gliosis extending 200–300 µm from the track, which was significant at 3 and 7 days. Markers for microglia and glutamatergic fibers supported that the MEAs produce minimal damage with significant changes occurring only at 3 and 7 days that return to control levels by one month. SMI-71 staining supported integrity of the blood brain barrier out to 1 week for both the microdialysis probes and the MEAs. This data support that the ceramic MEAs small size and biocompatibility are necessary to accurately measure neurotransmitter levels in the intact brain. The minimal invasiveness of the MEAs reduce tissue loss, allowing for long term (>6 month) electrochemical and electrophysiological monitoring of brain activity. PMID:19577548

Application of Light-cured Dental Adhesive Resin for Mounting Electrodes or Microdialysis Probes in Chronic Experiments

PubMed Central

Okumura, Tetsu; Okanoya, Kazuo; Tani, Jun

2007-01-01

In chronic recording experiments, self-curing dental acrylic resins have been used as a mounting base of electrodes or microdialysis-probes. Since these acrylics do not bond to the bone, screws have been used as anchors. However, in small experimental animals like finches or mouse, their craniums are very fragile and can not successfully hold the anchors. In this report, we propose a new application of light-curing dental resins for mounting base of electrodes or microdialysis probes in chronic experiments. This material allows direct bonding to the cranium. Therefore, anchor screws are not required and surgical field can be reduced considerably. Past experiences show that the bonding effect maintains more than 2 months. Conventional resin's window of time when the materials are pliable and workable is a few minutes. However, the window of working time for these dental adhesives is significantly wider and adjustable. PMID:18997897

In Vivo Microdialysis for Dynamic Monitoring of the Effectiveness of Nano-liposomes as Vehicles for Topical Psoralen Application.

PubMed

Zhang, Hongyu; Zhang, Kai; Li, Zhe; Zhao, Jihui; Zhang, Yongtai; Feng, Nianping

2017-01-01

In this study, the skin permeation of liposomes containing psoralen was investigated by in vivo skin microdialysis. Psoralen-loaded nano-sized liposomes were prepared with a mean size of 117.5 nm and a polydispersity index of 0.21, indicating the uniform dispersion of phosphatidylcholine vesicles in the liposomal solution. Based on in vivo microdialysis experiments, the drug concentration in local deep skin of rat increased rapidly and reached a peak concentration (C max ) of 319.35±23.72 µg/mL at 180 min, and decreased slowly thereafter. The local area under the concentration-time curve (AUC) 0-t was 3.81-fold higher than the compared aqueous suspension. The in vivo systemic pharmacokinetics were in agreement with the microdialysis results, in view of the C max and AUC 0-t from liposomal group were both significantly higher (p<0.05) than the compared group. Liposome-associated transdermal psoralen delivery was significantly more effective than delivery via an aqueous suspension. The enhanced skin permeability may be associated with improved skin hydration, lipid exchange and fusion with the stratum corneum (SC), and changes in SC structure, promoting drug permeation into deep skin. After 10 h of treatment with the perfusate, the microstructure of the microdialysis probe exhibited no obvious differences with control probes. The skin surface and the tissue around the probe showed no swelling or inflammation. These findings indicated that liposomes effectively enhanced the skin deposition of psoralen and showed good biocompatibility with skin tissues; additionally, ethanol at a low concentration in ringer's solution is an alternative perfusate for in vivo skin microdialysis studies.

Investigating local and long-range neuronal network dynamics by simultaneous optogenetics, reverse microdialysis and silicon probe recordings in vivo

PubMed Central

Taylor, Hannah; Schmiedt, Joscha T.; Çarçak, Nihan; Onat, Filiz; Di Giovanni, Giuseppe; Lambert, Régis; Leresche, Nathalie; Crunelli, Vincenzo; David, Francois

2014-01-01

Background The advent of optogenetics has given neuroscientists the opportunity to excite or inhibit neuronal population activity with high temporal resolution and cellular selectivity. Thus, when combined with recordings of neuronal ensemble activity in freely moving animals optogenetics can provide an unprecedented snapshot of the contribution of neuronal assemblies to (patho)physiological conditions in vivo. Still, the combination of optogenetic and silicone probe (or tetrode) recordings does not allow investigation of the role played by voltage- and transmitter-gated channels of the opsin-transfected neurons and/or other adjacent neurons in controlling neuronal activity. New method and results We demonstrate that optogenetics and silicone probe recordings can be combined with intracerebral reverse microdialysis for the long-term delivery of neuroactive drugs around the optic fiber and silicone probe. In particular, we show the effect of antagonists of T-type Ca2+ channels, hyperpolarization-activated cyclic nucleotide-gated channels and metabotropic glutamate receptors on silicone probe-recorded activity of the local opsin-transfected neurons in the ventrobasal thalamus, and demonstrate the changes that the block of these thalamic channels/receptors brings about in the network dynamics of distant somatotopic cortical neuronal ensembles. Comparison with existing methods This is the first demonstration of successfully combining optogenetics and neuronal ensemble recordings with reverse microdialysis. This combination of techniques overcomes some of the disadvantages that are associated with the use of intracerebral injection of a drug-containing solution at the site of laser activation. Conclusions The combination of reverse microdialysis, silicone probe recordings and optogenetics can unravel the short and long-term effects of specific transmitter- and voltage-gated channels on laser-modulated firing at the site of optogenetic stimulation and the actions that these manipulations exert on distant neuronal populations. PMID:25004203

Investigating local and long-range neuronal network dynamics by simultaneous optogenetics, reverse microdialysis and silicon probe recordings in vivo.

PubMed

Taylor, Hannah; Schmiedt, Joscha T; Carçak, Nihan; Onat, Filiz; Di Giovanni, Giuseppe; Lambert, Régis; Leresche, Nathalie; Crunelli, Vincenzo; David, Francois

2014-09-30

The advent of optogenetics has given neuroscientists the opportunity to excite or inhibit neuronal population activity with high temporal resolution and cellular selectivity. Thus, when combined with recordings of neuronal ensemble activity in freely moving animals optogenetics can provide an unprecedented snapshot of the contribution of neuronal assemblies to (patho)physiological conditions in vivo. Still, the combination of optogenetic and silicone probe (or tetrode) recordings does not allow investigation of the role played by voltage- and transmitter-gated channels of the opsin-transfected neurons and/or other adjacent neurons in controlling neuronal activity. We demonstrate that optogenetics and silicone probe recordings can be combined with intracerebral reverse microdialysis for the long-term delivery of neuroactive drugs around the optic fiber and silicone probe. In particular, we show the effect of antagonists of T-type Ca(2+) channels, hyperpolarization-activated cyclic nucleotide-gated channels and metabotropic glutamate receptors on silicone probe-recorded activity of the local opsin-transfected neurons in the ventrobasal thalamus, and demonstrate the changes that the block of these thalamic channels/receptors brings about in the network dynamics of distant somatotopic cortical neuronal ensembles. This is the first demonstration of successfully combining optogenetics and neuronal ensemble recordings with reverse microdialysis. This combination of techniques overcomes some of the disadvantages that are associated with the use of intracerebral injection of a drug-containing solution at the site of laser activation. The combination of reverse microdialysis, silicone probe recordings and optogenetics can unravel the short and long-term effects of specific transmitter- and voltage-gated channels on laser-modulated firing at the site of optogenetic stimulation and the actions that these manipulations exert on distant neuronal populations. Copyright © 2014. Published by Elsevier B.V.

Determination of muscle-specific glucose flux using radioactive stereoisomers and microdialysis

NASA Technical Reports Server (NTRS)

MacLean, D. A.; Ettinger, S. M.; Sinoway, L. I.; Lanoue, K. F.

2001-01-01

The purpose of the present study was to evaluate a novel approach for determining skeletal muscle-specific glucose flux using radioactive stereoisomers and the microdialysis technique. Microdialysis probes were inserted into the vastus lateralis muscle of human subjects and perfused (4 microl/min) with a Ringer solution containing small amounts of radioactive D- and L-glucose as the internal reference markers for determining probe recovery as well as varying concentrations of insulin (0-10 microM). The rationale behind this approach was that both stereoisomers would be equally affected by the factors that determine probe recovery, with the exception of L-glucose, which is nonmetabolizable and would not be influenced by tissue uptake. Therefore, any differences in the probe recovery ratios between the D- and L-stereoisomers represent changes in skeletal muscle glucose uptake directly at the tissue level. There were no differences in probe recovery between the D- (42.3 +/- 3.5%) and L- (41.2 +/- 3.5) stereoisomers during the control period (no insulin), which resulted in a D/L ratio of 1.04 +/- 0.03. However, during insulin perfusion (1 microM), The D/L ratio increased to 1.62 +/- 0.08 and 1.58 +/- 0.07 (P < 0.05) during the two collection (0-15 and 15-30 min) periods, respectively. This was accomplished solely by an increase (P < 0.05) in D-glucose probe recovery, as L-glucose probe recovery remained unchanged. In a second set of experiments, the perfusion of 10 microM insulin did not increase the D/L ratio (1.40 +/- 0.11) above that observed during 1.0 microM (1.41 +/- 0.07) insulin perfusion. These data suggest that this method is sufficiently sensitive to detect differences in insulin-stimulated glucose uptake; thus the use of radioactive stereoisomers in conjunction with the microdialysis technique provides a novel and useful technique for determining tissue-specific glucose flux and insulin sensitivity.

A review of microdialysis coupled to microchip electrophoresis for monitoring biological events

PubMed Central

Saylor, Rachel A.; Lunte, Susan M.

2015-01-01

Microdialysis is a powerful sampling technique that enables monitoring of dynamic processes in vitro and in vivo. The combination of microdialysis with chromatographic or electrophoretic methods yields along with selective detection methods yields a “separation-based sensor” capable of monitoring multiple analytes in near real time. Analysis of microdialysis samples requires techniques that are fast (<1 min), have low volume requirements (nL–pL), and, ideally, can be employed on-line. Microchip electrophoresis fulfills these requirements and also permits the possibility of integrating sample preparation and manipulation with detection strategies directly on-chip. Microdialysis coupled to microchip electrophoresis has been employed for monitoring biological events in vivo and in vitro. This review discusses technical considerations for coupling microdialysis sampling and microchip electrophoresis, including various interface designs, and current applications in the field. PMID:25637011

Sodium ion transport participates in non-neuronal acetylcholine release in the renal cortex of anesthetized rabbits.

PubMed

Shimizu, Shuji; Akiyama, Tsuyoshi; Kawada, Toru; Sata, Yusuke; Turner, Michael James; Fukumitsu, Masafumi; Yamamoto, Hiromi; Kamiya, Atsunori; Shishido, Toshiaki; Sugimachi, Masaru

2017-09-01

This study examined the mechanism of release of endogenous acetylcholine (ACh) in rabbit renal cortex by applying a microdialysis technique. In anesthetized rabbits, a microdialysis probe was implanted into the renal cortex and perfused with Ringer's solution containing high potassium concentration, high sodium concentration, a Na + /K + -ATPase inhibitor (ouabain), or an epithelial Na + channel blocker (benzamil). Dialysate samples were collected at baseline and during exposure to each agent, and ACh concentrations in the samples were measured by high-performance liquid chromatography. High potassium had no effect on renal ACh release. High sodium increased dialysate ACh concentrations significantly. Ouabain increased dialysate ACh concentration significantly. Benzamil decreased dialysate ACh concentrations significantly both at baseline and under high sodium. The finding that high potassium-induced depolarization does not increase ACh release suggests that endogenous ACh is released in renal cortex mainly by non-neuronal mechanism. Sodium ion transport may be involved in the non-neuronal ACh release.

Microdialysis of glucose in subcutaneous adipose tissue up to 3 weeks in healthy volunteers.

PubMed

Wientjes, K J; Vonk, P; Vonk-van Klei, Y; Schoonen, A J; Kossen, N W

1998-09-01

To measure possible changes in dialysate glucose concentrations over time, to validate the diffusional model for glucose transport from tissue to the probe, and to evaluate the actual glucose concentration in adipose tissue. Glucose concentrations in the subcutaneous adipose tissue of five healthy subjects (age 25 +/- 2.7 years, BMI 23.2 +/- 2.3 kg/m2 [mean +/- SD]) were measured by the microdialysis technique and compared with blood glucose. We applied microdialysis probes with hollow fibers of various membrane length (10-35 mm), used eight perfusion flow rates (0.5-20 microl/min), and perfused four glucose solutions (0.0, 2.8, 8.3, 11.1 mmol/l). After implantation, a substantial decrease in glucose recovery to the lowest value of 26 +/- 10% of the final plateau value was noted during the first few hours (n = 4). Recovery increased and stabilized after 5-9 days at 84.0 +/- 7.4% of capillary blood glucose when a flow rate of 0.5 microl/min was applied. According to the zero net-flux method, the glucose concentration in equilibrium, Cequi, with the surrounding tissue can be obtained. This concentration also decreases; however, 1 h after recovery, Cequi increases again over 1 or 2 days to a stable value that is not significantly different from the measured capillary blood glucose (P < 0.05). Using various perfusion flow rates and probes (membrane length 10-35 mm), it is shown that diffusion is the rate-limiting process for glucose transport through tissue. Insertion of the microdialysis probes causes damage to the adipose cells and the vascular bed around the probe. Glucose recovery decreases because of a lower blood supply. In 5-9 days, glucose recovery increases; apparently, this time is needed to repair the microstructure of tissue around the probe. After stabilization of the recovery, no loss of probe permeability, which is due to biocompatibility problems, was seen. The change during the 2 days in equilibrium concentration is probably caused by an inflammation reaction that consumes glucose around the probe. The individual increase in recovery during the 1st days after probe insertion until a stable plateau value is reached (flow rate >0 microl/min) is complicated for short-term clinical glucose measurements in adipose tissue. After stabilization, the mean equilibrium concentration of all subjects was equal to the mean capillary blood glucose concentration. Therefore, we conclude that capillary blood glucose concentration probably is the driving force for diffusion through the capillary wall into the probe and is not some interstitial concentration.

Microdialysis assessment of shock wave lithotripsy-induced renal injury.

PubMed

Brown, S A; Munver, R; Delvecchio, F C; Kuo, R L; Zhong, P; Preminger, G M

2000-09-01

Shock wave lithotripsy (SWL) is the primary treatment modality for managing the majority of symptomatic renal calculi. However, the fundamental mechanisms for stone fragmentation and the resultant morphologic changes that occur are not fully understood. Furthermore, a thorough understanding of the complex biologic pathways involved in SWL-induced renal injury does not exist at present. To elucidate the biologic processes involved in tissue injury after SWL, an animal model was designed to mimic the pathogenesis of high-energy SWL in humans. Juvenile female swine were anesthetized, and a midline laparotomy incision was performed to expose the right kidney. Using an introducer apparatus, a microdialysis probe was placed into the renal parenchyma of the right kidney lower pole and a tunnel was generated to exit the distal ends of the inlet and outlet tubing outside the body. After a 72-hour postoperative recovery period, SWL was performed to the lower pole renal region of the kidney, as a microdialysis pump continuously infused dialysate through the inlet tubing. Microdialysis fluids were collected during SWL, and lipid peroxidation, as measured by conjugated diene concentrations, was monitored. All microdialysis probes remained patent for a total of 2000 shock waves. A significant elevation in conjugated diene levels was observed in the SWL versus untreated kidneys after 1000 shock waves were administered (P <0.02). This animal model is unique in that it represents the first system for the real-time collection of renal interstitial fluids during SWL. Analysis of this fluid may provide insight into the physiologic mechanisms responsible for shock wave-induced renal injury.

Local opiate receptors in the sinoatrial node moderate vagal bradycardia.

PubMed

Farias, M; Jackson, K; Stanfill, A; Caffrey, J L

2001-02-20

Met-enkephalin-arg-phe (MEAP) interrupts vagal bradycardia when infused into the systemic circulation. This study was designed to locate the opiate receptors functionally responsible for this inhibition. Previous observations suggested that the receptors were most likely located in either intracardiac parasympathetic ganglia or the pre-junctional nerve terminals innervating the sinoatrial node. In this study 10 dogs were instrumented with a microdialysis probe inserted into the sinoatrial node. The functional position of the probe was tested by briefly introducing norepinephrine into the probe producing an increase in heart rate of more than 30 beats/min. Vagal stimulations were conducted at 0.5, 1.2 and 4 Hz during vehicle infusion (saline ascorbate). Cardiovascular responses during vagal stimulation were recorded on-line. MEAP was infused directly into the sinoatrial node via the microdialysis probe. The evaluation of vagal bradycardia was repeated during the nodal application of MEAP, diprenorphine (opiate antagonist), and diprenorphine co-infused with MEAP. MEAP introduced into the sinoatrial node via the microdialysis probe reduced vagal bradycardia by more than half. Simultaneous local nodal blockade of these receptors with the opiate antagonist, diprenorphine, eliminated the effect of MEAP demonstrating the participation by opiate receptors. Systemic infusions of MEAP produced a reduction in vagal bradycardia nearly identical to that observed during nodal administration. When local nodal opiate receptors were blocked with diprenorphine, the systemic effect of MEAP was eliminated. These data lead us to suggest that the opiate receptors responsible for the inhibition of vagal bradycardia are located within the sinoatrial node with few, if any, participating extra-nodal or ganglionic receptors.

Changes in blood flow and cellular metabolism at a myofascial trigger point with trigger point release (ischemic compression): a proof-of-principle pilot study

PubMed Central

Moraska, Albert F.; Hickner, Robert C.; Kohrt, Wendy M.; Brewer, Alan

2012-01-01

Objective To demonstrate proof-of-principle measurement for physiological change within an active myofascial trigger point (MTrP) undergoing trigger point release (ischemic compression). Design Interstitial fluid was sampled continuously at a trigger point before and after intervention. Setting A biomedical research clinic at a university hospital. Participants Two subjects from a pain clinic presenting with chronic headache pain. Interventions A single microdialysis catheter was inserted into an active MTrP of the upper trapezius to allow for continuous sampling of interstitial fluid before and after application of trigger point therapy by a massage therapist. Main Outcome Measures Procedural success, pain tolerance, feasibility of intervention during sample collection, determination of physiologically relevant values for local blood flow, as well as glucose and lactate concentrations. Results Both patients tolerated the microdialysis probe insertion into the MTrP and treatment intervention without complication. Glucose and lactate concentrations were measured in the physiological range. Following intervention, a sustained increase in lactate was noted for both subjects. Conclusions Identifying physiological constituents of MTrP’s following intervention is an important step toward understanding pathophysiology and resolution of myofascial pain. The present study forwards that aim by showing proof-of-concept for collection of interstitial fluid from an MTrP before and after intervention can be accomplished using microdialysis, thus providing methodological insight toward treatment mechanism and pain resolution. Of the biomarkers measured in this study, lactate may be the most relevant for detection and treatment of abnormalities in the MTrP. PMID:22975226

Overview of Brain Microdialysis

PubMed Central

Chefer, Vladimir I.; Thompson, Alexis C.; Zapata, Agustin; Shippenberg, Toni S.

2010-01-01

The technique of microdialysis enables sampling and collecting of small-molecular-weight substances from the interstitial space. It is a widely used method in neuroscience and is one of the few techniques available that permits quantification of neurotransmitters, peptides, and hormones in the behaving animal. More recently, it has been used in tissue preparations for quantification of neurotransmitter release. This unit provides a brief review of the history of microdialysis and its general application in the neurosciences. The authors review the theoretical principles underlying the microdialysis process, methods available for estimating extracellular concentration from dialysis samples (i.e., relative recovery), the various factors that affect the estimate of in vivo relative recovery, and the importance of determining in vivo relative recovery to data interpretation. Several areas of special note, including impact of tissue trauma on the interpretation of microdialysis results, are discussed. Step-by-step instructions for the planning and execution of conventional and quantitative microdialysis experiments are provided. PMID:19340812

The potential of flow-through microdialysis for probing low-molecular weight organic anions in rhizosphere soil solution.

PubMed

Sulyok, Michael; Miró, Manuel; Stingeder, Gerhard; Koellensperger, Gunda

2005-08-01

In this paper, flow-through microdialysis is presented as a novel analytical tool for automatic sampling of low molecular weight organic anions (LMWOA), such as oxalate and citrate, in solid samples of environmental concern. The microsampling methodology involves the implantation of dedicated capillary-type probes offering unrivalled spatial resolution (ca. 200μm) in definite soil sites. These passive samplers are aimed at monitoring local processes, such as the release of organic acids occurring in the rhizosphere environment, in nearly real-time. The influence of chemical and physical variables (composition and flow rate of the perfusion liquid, ionic strength and pH of the outer medium and presence of metal ions therein) was assessed in vitro using liquid-phase assays. On the other hand, the resistance of the external solid medium to mass transfer, and the actual applicability of in vivo calibration methods were investigated using quartz sand as an inert model soil. Microdialysers furnished with 3cm long semipermeable tubular membranes were perfused with 0.01M NaNO 3 at a flow rate of 2.0μl/min, yielding dialysis recoveries ≥45% for both assayed LMWOAs in simulated background soil electrolyte solutions, and ≥24% in the interstitial liquid of complex solid samples. Full knowledge of the fate of LMWOAs in soils was obtained through the application of stimulus-response approaches that mimic the discrete exudation pulses of roots. Highly time-resolved microdialysates were used to discern readily available species such as free carboxylic anions and LMW metal-organic acid complexes from adsorbed, precipitated or mineralised analyte species in a variety of soil samples containing variable amounts of organic matter, exchangeable cations and different levels of metal pollution.

Physiologically Relevant Changes in Serotonin Resolved by Fast Microdialysis

PubMed Central

2013-01-01

Online microdialysis is a sampling and detection method that enables continuous interrogation of extracellular molecules in freely moving subjects under behaviorally relevant conditions. A majority of recent publications using brain microdialysis in rodents report sample collection times of 20–30 min. These long sampling times are due, in part, to limitations in the detection sensitivity of high performance liquid chromatography (HPLC). By optimizing separation and detection conditions, we decreased the retention time of serotonin to 2.5 min and the detection threshold to 0.8 fmol. Sampling times were consequently reduced from 20 to 3 min per sample for online detection of serotonin (and dopamine) in brain dialysates using a commercial HPLC system. We developed a strategy to collect and to analyze dialysate samples continuously from two animals in tandem using the same instrument. Improvements in temporal resolution enabled elucidation of rapid changes in extracellular serotonin levels associated with mild stress and circadian rhythms. These dynamics would be difficult or impossible to differentiate using conventional microdialysis sampling rates. PMID:23614776

First plasma and tissue pharmacokinetic study of the YSNSG cyclopeptide, a new integrin antagonist, using microdialysis.

PubMed

Slimano, Florian; Djerada, Zoubir; Bouchene, Salim; Van Gulick, Laurence; Brassart-Pasco, Sylvie; Dukic, Sylvain

2017-07-15

The YSNSG peptide is a synthetic peptide targeting α v β 3 integrin. This peptide exhibits promising activity in vitro and in vivo against melanoma. To determine pharmacokinetic parameters and predictive active doses in the central nervous system (CNS) and subcutaneous tissue (SC), we conducted microdialysis coupled with pharmacokinetic modeling and Monte Carlo simulation. After a recovery period of surgical procedures, a microdialysis probe was inserted in the caudate and in subcutaneous tissue. Plasma samples and dialysates collected 5h after YSNSG intravenous administration (10mg/kg) were analyzed by UPLC-MS/MS. A nonlinear mixed-effect modeling approach implemented in Monolix® 2016R1 was performed. Model selection and evaluation were based on the usual diagnostic plot, precision and information criteria. The primary plasma and tissue pharmacokinetic parameters were comparable with those of other integrin antagonists, such as cilengitide or ATN-161. Tissue/plasma and brain/plasma area under the curve (AUC) ratio were 66.2±21.6% and 3.6±4.7%, respectively. Two models of 2-compartments with an additional microdialysis compartment, parameterized as rate constants (k for elimination, k12/k21 and k13/k31 for distribution) and volumes (central V1 and peripheral microdialysis compartment V3) with zero-order input were selected to describe the dialysate concentrations in CNS and SC. The inter-individual variability (IIV) was described by exponential terms, and residual variability was described by a combined additive and proportional error model. Individual AUC (plasma and tissues) values were derived for each animal using the Empirical-Bayes-Estimates of the individual parameters. The regimens needed to achieve an in vitro predetermined target concentration in tissues were studied by Monte Carlo simulations using Monolix® 2016R1. YSNSG pharmacokinetic parameters show promising results in terms of subcutaneous disposition. Further investigations into such processes as encapsulation and intratumoral disposition are currently being conducted. Copyright © 2017 Elsevier B.V. All rights reserved.

Water-soluble cyclodextrin polymers for enhanced relative recovery of hydrophobic analytes during microdialysis sampling.

PubMed

Ao, Xiaoping; Stenken, Julie A

2003-09-01

Microdialysis relative recovery (RR) enhancement using different water-soluble, epichlorohydrin-based cyclodextrin polymers (CD-EPS) was studied in vitro for different analytes, amitryptiline, carbamazepine, hydroquinone, ibuprofen, and 4-nitrophenol. When compared to the native CDs (alpha, beta, and gamma) on a per mole basis, the CD-EPS enhanced microdialysis RR was either statistically greater or the same. beta-CD-EPS was more highly retained than native beta-CD by a 20 000 Da molecular weight cutoff (MWCO) polycarbonate membrane, but showed no statistical difference for loss across a 100 000 Da MWCO polyethersulfone membrane (PES). When the same weight percent of beta-CD or beta-CD-EPS was included in the microdialysis perfusion fluid, the beta-CD-EPS produced a higher microdialysis RR than native beta-CD for all analytes across the PES membrane. However, enhancements for the PC membrane were statistically insignificant when beta-CD and beta-CD-EPS were compared on a per mole basis. These results suggest that CD-EPS may be used as effective enhancement agents during microdialysis sampling and for some membranes provide the additional advantage of being retained more than native CDs.

Blockade of glutamate release by botulinum neurotoxin type A in humans: A dermal microdialysis study

PubMed Central

da Silva, Larissa Bittencourt; Karshenas, Ali; Bach, Flemming W; Rasmussen, Sten; Arendt-Nielsen, Lars; Gazerani, Parisa

2014-01-01

BACKGROUND: The analgesic action of botulinum neurotoxin type A (BoNTA) has been linked to the blockade of peripheral release of neuropeptides and neurotransmitters in animal models; however, there is no direct evidence of this in humans. OBJECTIVES: To investigate the effect of BoNTA on glutamate release in humans, using an experimental model of pain and sensitization provoked by capsaicin plus mild heat. METHODS: Twelve healthy volunteers (six men, six women) were pretreated with BoNTA (10 U) on the volar forearm and with a saline control on the contralateral side. Dermal microdialysis was applied one week later to collect interstitial samples before and after the application of a capsaicin patch (8%) plus mild heat (40°C/60 min) to provoke glutamate release, pain and vasodilation. Samples were collected every hour for 3 h using linear microdialysis probes (10 mm, 100 kD). Dialysate was analyzed for glutamate concentration. Pain intensity and skin vasomotor reactions (temperature and blood flow changes) were also recorded. RESULTS: BoNTA significantly reduced glutamate release compared with saline (P<0.05). The provoked pain intensity was lower in the BoNTA-pretreated arm (P<0.01). The reduction in pain scores was not correlated with glutamate level. Cutaneous blood flow (P<0.05), but not cutaneous temperature (P≥0.05), was significantly reduced by BoNTA. There was a correlation between glutamate level and skin blood flow (r=0.58/P<0.05) but not skin temperature (P≥0.05). No differences according to sex were observed in any response. CONCLUSIONS: The present study provided the first direct evidence supporting the inhibitory effect of BoNTA on glutamate release in human skin, which is potentially responsible for some of the analgesic action of BoNTA. PMID:24851237

Bioactive nitric oxide concentration does not increase during reactive hyperemia in human skin.

PubMed

Zhao, J L; Pergola, P E; Roman, L J; Kellogg, D L

2004-02-01

This study examined whether nitric oxide (NO) is involved in the cutaneous response to reactive hyperemia (RH) in the human forearm. We enrolled seven healthy volunteers. NO concentrations were monitored using a NO selective amperometric electrode (ISO-NOP200, World Precision Instruments) inserted into the skin of the forearm. Laser-Doppler flowmetry (Moor Instruments) was used for monitoring skin blood flow (SkBF) at the same site. SkBF and NO levels were monitored and recorded continuously throughout the experiment. An intradermal microdialysis probe was inserted adjacent to the NO electrode for drug delivery. Data collection began 140 min after the NO electrodes and microdialysis probes were inserted. RH was achieved by the inflation of a blood pressure cuff to 25 mmHg above systolic pressure for 7 min after which the pressure in the cuff was abruptly released. Acetylcholine (ACh) was given by microdialysis probe at the end of RH study to verify the ability of the electrode system to detect changes in the NO concentration. SkBF and NO data before RH and immediately, 2, 5, 7, and 10 min after cuff deflation were used for analysis. SkBF increased immediately after release of the occlusion (P < 0.0001) and remained elevated for 2 min. No significant NO changes occurred with the increases in LDF. ACh induced increases in both SkBF and NO (P < 0.000 and P < 0.037, respectively). We conclude that RH increases SkBF by mechanisms that do not require a measurable increase in NO concentrations.

A Review on Microdialysis Calibration Methods: the Theory and Current Related Efforts.

PubMed

Kho, Chun Min; Enche Ab Rahim, Siti Kartini; Ahmad, Zainal Arifin; Abdullah, Norazharuddin Shah

2017-07-01

Microdialysis is a sampling technique first introduced in the late 1950s. Although this technique was originally designed to study endogenous compounds in animal brain, it is later modified to be used in other organs. Additionally, microdialysis is not only able to collect unbound concentration of compounds from tissue sites; this technique can also be used to deliver exogenous compounds to a designated area. Due to its versatility, microdialysis technique is widely employed in a number of areas, including biomedical research. However, for most in vivo studies, the concentration of substance obtained directly from the microdialysis technique does not accurately describe the concentration of the substance on-site. In order to relate the results collected from microdialysis to the actual in vivo condition, a calibration method is required. To date, various microdialysis calibration methods have been reported, with each method being capable to provide valuable insights of the technique itself and its applications. This paper aims to provide a critical review on various calibration methods used in microdialysis applications, inclusive of a detailed description of the microdialysis technique itself to start with. It is expected that this article shall review in detail, the various calibration methods employed, present examples of work related to each calibration method including clinical efforts, plus the advantages and disadvantages of each of the methods.

An in vitro Comparison of Microdialysis Relative Recovery of Met- and Leu-Enkephalin Using Cyclodextrins and Antibodies as Affinity Agents

PubMed Central

Fletcher, Heidi J.; Stenken, Julie A.

2008-01-01

Cyclodextrins and antibodies have been used as affinity agents to improve relative recovery during microdialysis sampling. Two neuropeptides, methionine-enkephalin (ME) and leucine-enkephalin (LE), were chosen to compare the use of cyclodextrins and antibodies as possible affinity agents for improving their relative recovery across polycarbonate and polyethersulfone membranes during in vitro sampling. Cyclodextrins (CD) including β-CD, 2-hydroxypropyl-β-cyclodextrin (2HPβ-CD), and γ-CD gave improvements of relative recovery for both peptides of less than 2-fold as compared to controls. Comparisons of relative recovery between tyrosine-glycine-glycine, tyrosine, and phenylalanine using different cyclodextrins in the perfusion fluid were also obtained. Inclusion of an antibody against met-enkephalin in the microdialysis perfusion fluid resulted in relative recovery increases of up to 2.5-fold. These results show that using antibodies as affinity agents during microdialysis sampling may be more effective agents to improve the relative recovery of these opioid neuropeptides. PMID:18558138

Urea clearance: a new technique based on microdialysis to assess liver blood flow studied in a pig model of ischemia/reperfusion.

PubMed

Farnebo, S; Winbladh, A; Zettersten, E K; Sandström, P; Gullstrand, P; Samuelsson, A; Theodorson, E; Sjöberg, F

2010-01-01

Delayed detection of ischemia is one of the most feared postoperative complications. Early detection of impaired blood flow and close monitoring of the organ-specific metabolic status may therefore be critical for the surgical outcome. Urea clearance is a new technique for continuous monitoring of alterations in blood flow and metabolic markers with acceptable temporal characteristics. We compare this new microdialysis technique with the established microdialysis ethanol technique to assess hepatic blood flow. Six pigs were used in a liver ischemia/reperfusion injury model. Microdialysis catheters were placed in liver segment IV and all circulation was stopped for 80 min, followed by reperfusion for 220 min. Urea and ethanol clearance was calculated from the dialysate and correlated with metabolic changes. A laser Doppler probe was used as reference of restoration of blood flow. Both urea and ethanol clearance reproducibly depicted changes in liver blood flow in relation to metabolic changes and laser Doppler measurements. The two techniques highly correlated both overall and during the reperfusion phase (r = 0.8) and the changes were paralleled by altered perfusion as recorded by laser Doppler. Copyright © 2010 S. Karger AG, Basel.

Feeding-associated alterations in striatal neurotransmitter release

NASA Technical Reports Server (NTRS)

Acworth, I. N.; Ressler, K.; Wurtman, R. J.

1989-01-01

Published evidence suggests a role for dopaminergic (DA) brain pathways in feeding-associated behaviors. Using the novel technique of brain microdialysis of striatal extracellular fluid (ECF) as an index of DA release, Church et al. described increases in levels of DA when animals had limited access to pellets, but not with free access. Dopamine release from the nucleus accumbens did increase with free access to pellets post starvation or after food reward. We used permanently implanted microdialysis probes to measure ECF levels of DA, DOPAC, HVA, and large neutral amino acids (LNAA) for up to 72 hours after implantation among rats experiencing different dietary regimens.

Microdialysis measurements of lamellar perfusion and energy metabolism during the development of laminitis in the oligofructose model.

PubMed

Medina-Torres, C E; Underwood, C; Pollitt, C C; Castro-Olivera, E M; Hodson, M P; Richardson, D W; van Eps, A W

2016-03-01

Failure of lamellar energy metabolism, with or without ischaemia, may be important in the pathophysiology of sepsis-associated laminitis. To examine lamellar perfusion and energy balance during laminitis development in the oligofructose model using tissue microdialysis. In vivo experiment. Six Standardbred horses underwent laminitis induction using the oligofructose model (OFT group) and 6 horses were untreated controls (CON group). Microdialysis probes were placed in the lamellar tissue of one forelimb (all horses) as well as the skin dermis of the tail in OFT horses. Dialysate and plasma samples were collected every 2 h for 24 h and concentrations of energy metabolites (glucose, lactate, pyruvate) and standard indices of energy metabolism (lactate to glucose ratio [L:G] and lactate to pyruvate ratio [L:P]) determined. Microdialysis urea clearance was used to estimate changes in tissue perfusion. Data were analysed nonparametrically. Median glucose concentration decreased to <30% of baseline by 8 h in OFT lamellar (P = <0.01) and skin (P<0.01) dialysate. Lactate increased mildly in skin dialysate (P = 0.04) and plasma (P = 0.05) but not lamellar dialysate in OFT horses. Median pyruvate concentration decreased to <50% of baseline in OFT lamellar dialysate (P = 0.03). A >5-fold increase in median L:G compared with baseline occurred in OFT lamellar and skin dialysate (P<0.03). From a baseline of <20, median L:P increased to a peak of 80 in OFT skin and 38.7 in OFT lamellar dialysates (P<0.02); however, OFT lamellar dialysate L:P was not significantly different from CON. Urea concentration decreased significantly in OFT lamellar dialysate (increased urea clearance) but not in OFT skin or CON lamellar dialysate. Increased lamellar perfusion occurred during the development of sepsis-associated laminitis in the oligofructose model. Glucose concentrations in the lamellar interstitium decreased, suggesting increased glucose consumption but there was no definitive evidence of lamellar energy failure. © 2015 EVJ Ltd.

Use of rapid sampling microdialysis for intraoperative monitoring of bowel ischemia.

PubMed

Deeba, S; Corcoles, E P; Hanna, G B; Hanna, B G; Pareskevas, P; Aziz, O; Boutelle, M G; Darzi, A

2008-09-01

Intestinal ischemia is a major cause of anastomotic leak and death and remains a clinical challenge as the physician relies on several nonspecific signs, biologic markers, and radiologic studies to make the diagnosis. This study used rapid sampling online microdialysis to evaluate the biochemical changes occurring in a segment of human bowel during and after resection, and assessed for the feasibility and reproducibility of this technique in monitoring intestinal ischemia. A custom made, rapid sampling online microdialysis analyzer was used to monitor the changes in the bowel wall of specimens being resected intraoperatively. Two patients were recruited for the pilot study to optimize the analyzer and seven patients undergoing colonic resections were recruited for the data collection and analysis. The concentration of glucose in the extracellular bowel wall fluid decreased transiently after division of individual feeding arteries followed by a rebound increase in the concentration back to baseline concentrations. After completion of resection, glucose concentrations continued to decrease while lactate concentrations increased constantly. Rapid sampling microdialysis was feasible in the clinical environment. These results suggest that tissue responds to ischemic insult by mobilizing glucose stores which later decrease again, whereas lactate concentrations constantly increased.

A comparative study on the skin penetration of pure tryptanthrin and tryptanthrin in Isatis tinctoria extract by dermal microdialysis coupled with isotope dilution ESI-LC-MS.

PubMed

Oberthür, Christine; Heinemann, Christian; Elsner, Peter; Benfeldt, Eva; Hamburger, Matthias

2003-05-01

The indolo[2,1- b]quinazoline alkaloid tryptanthrin has recently been identified as a pharmacologically active compound in Isatis tinctoria, with potent dual inhibitory activity on prostaglandin and leukotriene synthesis. To investigate the skin penetration of tryptanthrin from solutions of pure compound and Isatis extracts, we developed and validated a cutaneous microdialysis model using ex vivo pig foreleg. Microdialysis was performed by placing linear probes in the dermis of the skin in situ, and tryptanthrin concentrations in the dialysates were determined by isotope dilution electrospray ionization LC-MS in the selected ion mode. Measurable concentrations of tryptanthrin were detected 30 min after application. A dose-dependent increase in tryptanthrin concentrations in the dialysate was observed for the Isatis extracts, but not for pure tryptanthrin. Microscopic analysis showed that the pure compound crystallized from the solution but remained in an amorphous state in the extracts.

Toward continuous glucose monitoring with planar modified biosensors and microdialysis. Study of temperature, oxygen dependence and in vivo experiment.

PubMed

Ricci, Francesco; Caprio, Felice; Poscia, Alessandro; Valgimigli, Francesco; Messeri, Dimitri; Lepori, Elena; Dall'Oglio, Giorgio; Palleschi, Giuseppe; Moscone, Danila

2007-04-15

Glucose biosensors based on the use of planar screen-printed electrodes modified with an electrochemical mediator and with glucose oxidase have been optimised for their application in the continuous glucose monitoring in diabetic patients. A full study of their operative stability and temperature dependence has been accomplished, thus giving useful information for in vivo applications. The effect of dissolved oxygen concentration in the working solution was also studied in order to evaluate its effect on the linearity of the sensors. Glucose monitoring performed with serum samples was performed to evaluate the effect of matrix components on operative stability and demonstrated an efficient behaviour for 72 h of continuous monitoring. Finally, these studies led to a sensor capable of detecting glucose at concentrations as low as 0.04 mM and with a good linearity up to 2.0 mM (at 37 degrees C) with an operative stability of ca. 72 h, thus demonstrating the possible application of these sensors for continuous glucose monitoring in conjunction with a microdialysis probe. Moreover, preliminary in vivo experiments for ca. 20 h have demonstrated the feasibility of this system.

GABA release in the zona incerta of the sheep in response to the sight and ingestion of food and salt.

PubMed

Kendrick, K M; Hinton, M R; Baldwin, B A

1991-05-31

In order to establish which neurotransmitters may influence the activity of zona incerta neurones in the sheep which respond selectively to the sight or ingestion of food, we have measured the release of amino acid and monoamine neurotransmitters from this region using microdialysis sampling. Co-ordinates for the placement of microdialysis probes in regions of the zona incerta where cells respond to the sight or ingestion of food were first established by making single-unit extracellular recordings. When animals were food-deprived results showed that release of gamma-aminobutyric acid (GABA) was increased in response to the sight and ingestion of food but not of aspartate, glutamate, taurine, noradrenaline, dopamine or serotonin. This release of GABA was absent when the animals were shown non-food objects or saw or ingested salt solutions. When the same animals were physiologically sodium-depleted GABA release was evoked by the sight and ingestion of salt solutions and release following the sight and ingestion of food was significantly reduced. These results provide further evidence that GABA is an important neurotransmitter in neural circuits controlling the regulation of food intake.

Sequential enzymatic derivatization coupled with online microdialysis sampling for simultaneous profiling of mouse tumor extracellular hydrogen peroxide, lactate, and glucose.

PubMed

Su, Cheng-Kuan; Tseng, Po-Jen; Chiu, Hsien-Ting; Del Vall, Andrea; Huang, Yu-Fen; Sun, Yuh-Chang

2017-03-01

Probing tumor extracellular metabolites is a vitally important issue in current cancer biology. In this study an analytical system was constructed for the in vivo monitoring of mouse tumor extracellular hydrogen peroxide (H 2 O 2 ), lactate, and glucose by means of microdialysis (MD) sampling and fluorescence determination in conjunction with a smart sequential enzymatic derivatization scheme-involving a loading sequence of fluorogenic reagent/horseradish peroxidase, microdialysate, lactate oxidase, pyruvate, and glucose oxidase-for step-by-step determination of sampled H 2 O 2 , lactate, and glucose in mouse tumor microdialysate. After optimization of the overall experimental parameters, the system's detection limit reached as low as 0.002 mM for H 2 O 2 , 0.058 mM for lactate, and 0.055 mM for glucose, based on 3 μL of microdialysate, suggesting great potential for determining tumor extracellular concentrations of lactate and glucose. Spike analyses of offline-collected mouse tumor microdialysate and monitoring of the basal concentrations of mouse tumor extracellular H 2 O 2 , lactate, and glucose, as well as those after imparting metabolic disturbance through intra-tumor administration of a glucose solution through a prior-implanted cannula, were conducted to demonstrate the system's applicability. Our results evidently indicate that hyphenation of an MD sampling device with an optimized sequential enzymatic derivatization scheme and a fluorescence spectrometer can be used successfully for multi-analyte monitoring of tumor extracellular metabolites in living animals. Copyright © 2016 Elsevier B.V. All rights reserved.

A pilot microdialysis study in brain tumor patients to assess changes in intracerebral cytokine levels after craniotomy and in response to treatment with a targeted anti-cancer agent.

PubMed

Portnow, Jana; Badie, Behnam; Liu, Xueli; Frankel, Paul; Mi, Shu; Chen, Mike; Synold, Timothy W

2014-05-01

Intracerebral microdialysis enables continuous measurement of changes in brain biochemistry. In this study intracerebral microdialysis was used to assess changes in cytokine levels after tumor resection and in response to treatment with temsirolimus. Brain tumor patients undergoing craniotomy participated in this non-therapeutic study. A 100 kDa molecular weight cut-off microdialysis catheter was placed in peritumoral tissue at the time of resection. Cohort 1 underwent craniotomy only. Cohort 2 received a 200 mg dose of intravenous temsirolimus 48 h after surgery. Dialysate samples were collected continuously for 96 h and analyzed for the presence of 30 cytokines. Serial blood samples were collected to measure systemic cytokine levels. Dialysate samples were obtained from six patients in cohort 1 and 4 in cohort 2. Seventeen cytokines could be recovered in dialysate samples from at least 8 of 10 patients. Concentrations of interleukins and chemokines were markedly elevated in peritumoral tissue, and most declined over time, with IL-8, IP-10, MCP-1, MIP1β, IL-6, IL-12p40/p70, MIP1α, IFN-α, G-CSF, IL-2R, and vascular endothelial growth factor significantly (p < 0.05) decreasing over 96 h following surgery. No qualitative changes in intracerebral or serum cytokine concentrations were detected after temsirolimus administration. This is the first intracerebral microdialysis study to evaluate the time course of changes in macromolecule levels in the peritumoral microenvironment after a debulking craniotomy. Initial elevations of peritumoral interleukins and chemokines most likely reflected an inflammatory response to both tumor and surgical trauma. These findings have implications for development of cellular therapies that are administered intracranially at the time of surgery.

Cortical damage following traumatic brain injury evaluated by iomazenil SPECT and in vivo microdialysis.

PubMed

Koizumi, Hiroyasu; Fujisawa, Hirosuke; Suehiro, Eiichi; Iwanaga, Hideyuki; Nakagawara, Jyoji; Suzuki, Michiyasu

2013-01-01

[(123)I] iomazenil (IMZ) single photon emission computed tomography (SPECT) has been reported to be a useful marker of neuronal integrity. We evaluated cortical damage following traumatic brain injury (TBI) with IMZ SPECT at the acute stage. After conventional therapy for a cranial trauma, an IMZ SPECT re-evaluation was performed at the chronic stage. A reduction in IMZ uptake in the location of cerebral contusions was observed during the TBI acute phase; however, images of IMZ SPECT obtained during the chronic phase showed that areas with decreased IMZ distribution were remarkably reduced compared with those obtained during the acute phase. As a result of in vivo microdialysis study, the extracellular levels of glutamate in the cortex, where decreased IMZ distribution was shown during the acute phase, were increased during the 168-h monitoring period. During the chronic phase, IMZ uptake in the region with the microdialysis probes was recovered. The results suggest that this reduction in IMZ uptake might not be a sign of irreversible tissue damage in TBI.

Quantitative assessments of traumatic axonal injury in human brain: concordance of microdialysis and advanced MRI.

PubMed

Magnoni, Sandra; Mac Donald, Christine L; Esparza, Thomas J; Conte, Valeria; Sorrell, James; Macrì, Mario; Bertani, Giulio; Biffi, Riccardo; Costa, Antonella; Sammons, Brian; Snyder, Abraham Z; Shimony, Joshua S; Triulzi, Fabio; Stocchetti, Nino; Brody, David L

2015-08-01

Axonal injury is a major contributor to adverse outcomes following brain trauma. However, the extent of axonal injury cannot currently be assessed reliably in living humans. Here, we used two experimental methods with distinct noise sources and limitations in the same cohort of 15 patients with severe traumatic brain injury to assess axonal injury. One hundred kilodalton cut-off microdialysis catheters were implanted at a median time of 17 h (13-29 h) after injury in normal appearing (on computed tomography scan) frontal white matter in all patients, and samples were collected for at least 72 h. Multiple analytes, such as the metabolic markers glucose, lactate, pyruvate, glutamate and tau and amyloid-β proteins, were measured every 1-2 h in the microdialysis samples. Diffusion tensor magnetic resonance imaging scans at 3 T were performed 2-9 weeks after injury in 11 patients. Stability of diffusion tensor imaging findings was verified by repeat scans 1-3 years later in seven patients. An additional four patients were scanned only at 1-3 years after injury. Imaging abnormalities were assessed based on comparisons with five healthy control subjects for each patient, matched by age and sex (32 controls in total). No safety concerns arose during either microdialysis or scanning. We found that acute microdialysis measurements of the axonal cytoskeletal protein tau in the brain extracellular space correlated well with diffusion tensor magnetic resonance imaging-based measurements of reduced brain white matter integrity in the 1-cm radius white matter-masked region near the microdialysis catheter insertion sites. Specifically, we found a significant inverse correlation between microdialysis measured levels of tau 13-36 h after injury and anisotropy reductions in comparison with healthy controls (Spearman's r = -0.64, P = 0.006). Anisotropy reductions near microdialysis catheter insertion sites were highly correlated with reductions in multiple additional white matter regions. We interpret this result to mean that both microdialysis and diffusion tensor magnetic resonance imaging accurately reflect the same pathophysiological process: traumatic axonal injury. This cross-validation increases confidence in both methods for the clinical assessment of axonal injury. However, neither microdialysis nor diffusion tensor magnetic resonance imaging have been validated versus post-mortem histology in humans. Furthermore, future work will be required to determine the prognostic significance of these assessments of traumatic axonal injury when combined with other clinical and radiological measures. © The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

[Analysis on microdialysis probe recovery of baicalin in vitro and in vivo based on LC-MS/MS].

PubMed

Chen, Teng-Fei; Liu, Jian-Xun; Zhang, Ying; Lin, Li; Song, Wen-Ting; Yao, Ming-Jiang

2017-06-01

To further study the brain behavior and the pharmacokinetics of baicalin in intercellular fluid of brain, and study the recovery rate and stability of brain and blood microdialysis probe of baicalin in vitro and in vivo. The concentration of baicalin in brain and blood microdialysates was determined by LC-MS/MS and the probe recovery for baicalin was calculated. The effects of different flow rates (0.50, 1.0, 1.5, 2.0，3.0 μL•min⁻¹) on recovery in vitro were determined by incremental method and decrement method. The effects of different drug concentrations (50.00, 200.0, 500.0, 1 000 μg•L⁻¹) and using times (0, 1, 2) on recovery in vitro were determined by incremental method. The probe recovery stability and effect of flow rate on recovery in vivo were determined by decrement method, and its results were compared with those in in vitro trial. The in vitro recovery of brain and blood probe of baicalin was decreased with the increase of flow rate under the same concentration; and at the same flow rate, different concentrations of baicalin had little influence on the recovery. The probe which had been used for 2 times showed no obvious change in probe recovery by syringe with 2% heparin sodium and ultrapure water successively. In vitro recovery rates obtained by incremental method and decrement method were approximately equal under the same condition, and the in vivo recovery determined by decrement method was similar with the in vitro results and they were showed a good stability within 10 h. The results showed that decrement method can be used for pharmacokinetic study of baicalin, and can be used to study probe recovery in vivo at the same time. Copyright© by the Chinese Pharmaceutical Association.

Transcranial direct-current stimulation increases extracellular dopamine levels in the rat striatum

PubMed Central

Tanaka, Tomoko; Takano, Yuji; Tanaka, Satoshi; Hironaka, Naoyuki; Kobayashi, Kazuto; Hanakawa, Takashi; Watanabe, Katsumi; Honda, Manabu

2013-01-01

Background: Transcranial direct-current stimulation (tDCS) is a non-invasive procedure that achieves polarity-dependent modulation of neuronal membrane potentials. It has recently been used as a functional intervention technique for the treatment of psychiatric and neurological diseases; however, its neuronal mechanisms have not been fully investigated in vivo. Objective/Hypothesis: To investigate whether the application of cathodal or anodal tDCS affects extracellular dopamine and serotonin levels in the rat striatum. Methods: Stimulation and in vivo microdialysis were carried out under urethane anesthesia, and microdialysis probes were slowly inserted into the striatum. After the collection of baseline fractions in the rat striatum, cathodal or anodal tDCS was applied continuously for 10 min with a current intensity of 800 μA from an electrode placed on the skin of the scalp. Dialysis samples were collected every 10 min until at least 400 min after the onset of stimulation. Results: Following the application of cathodal, but not anodal, tDCS for 10 min, extracellular dopamine levels increased for more than 400 min in the striatum. There were no significant changes in extracellular serotonin levels. Conclusion: These findings suggest that tDCS has a direct and/or indirect effect on the dopaminergic system in the rat basal ganglia. PMID:23596399

SYSTEMIC ADMINISTRATION OF KAINIC ACID INCREASES GABA LEVELS IN PERFUSATE FROM THE HIPPOCAMPUS OF RATS IN VIVO

EPA Science Inventory

The ventral hippocampi of male, Fischer-344 rats were implanted with microdialysis probes and the effects of systemically administered kainic acid (KA) (8 mg/kg, s.c.) on the in vivo release of amino acids were measured for four hours after administration. n order to measure GABA...

Reliable glucose monitoring by ex-vivo blood microdialysis and infrared spectrometry for patients in critical care

NASA Astrophysics Data System (ADS)

Vahlsing, Thorsten; Delbeck, Sven; Budde, Janpeter; Ihrig, Dieter; Leonhardt, Steffen; Heise, H. Michael

2017-02-01

Blood glucose monitoring has been realised by biosensors in combination with micro-dialysis, using either subcutaneously or intravascularly implanted catheters. Another alternative is ex-vivo micro-dialysis of continuously sampled heparinized whole blood available from the patient even under critical care conditions. However, most devices suffer from inaccuracies due to variable recovery rates. Infrared spectrometry has been suggested for analyte quantification, since besides glucose other clinically relevant analytes can be simultaneously determined that are, e.g., important for intensive care patients. Perfusates with acetate and mannitol have been investigated as recovery markers (internal standards). In contrast to the previously used acetate, an almost linear dependency between mannitol loss and glucose recovery was observed for micro-dialysis of glucose spiked aqueous albumin solutions or porcine heparinized whole blood when testing flat membranes within a custom-made micro-dialysator. By this, a straightforward compensation of any dialysis recovery rate variation during patient monitoring is possible. The combination of microdialysis with infrared spectrometry provides a calibration-free assay for accurate continuous glucose monitoring, as reference spectra of dialysate components can be a-priori allocated.

Characterization of dopamine release in the substantia nigra by in vivo microdialysis in freely moving rats.

PubMed

Robertson, G S; Damsma, G; Fibiger, H C

1991-07-01

Dopamine (DA) is released not only from the terminals of the nigrostriatal projection, but also from the dendrites of these neurons, which arborize in the substantia nigra pars reticulata (SNR). Although striatal DA release has been extensively studied by in vivo microdialysis, dendritic DA release in the SNR has not been characterized by this technique. Extracellular DA was monitored simultaneously in the ipsilateral striatum and SNR. The nigral probe was implanted at a 50 degree angle, permitting 2.5 mm of SNR to be dialyzed. Delivery of the tracer Fluoro-Gold into the striatal probe retrogradely labeled tyrosine hydroxylase-positive cell bodies and dendrites in the vicinity of the nigral probe. Hence, it could be demonstrated that dopaminergic neurons near the nigral probe projected to the vicinity of the striatal probe. Addition of 50 mM KCl to the SNR perfusion solution produced a 3.5-fold increase in DA and a 50% reduction in dihydroxyphenylacetic acid (DOPAC) in the SNR; in contrast, this manipulation in the SNR caused DA release in the striatum to be decreased by 20%, while striatal DOPAC was increased by 50%. Local administration of nomifensine (10 microM) in the SNR produced a sevenfold increase in SNR DA but had no effect on striatal DA. Systemic injection of d-amphetamine (2 mg/kg, s.c.) elevated DA in the SNR and striatum five- to sevenfold, while DOPAC was decreased in both structures by at least 40%. To determine the effect of tetrodotoxin (TTX), basal concentrations of DA in the SNR were first elevated threefold by including nomifensine (1 microM) in the nigral perfusion solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuropeptide Signaling in Crustaceans Probed by Mass Spectrometry

NASA Astrophysics Data System (ADS)

Liang, Zhidan

Neuropeptides are one of the most diverse classes of signaling molecules whose identities and functions are not yet fully understood. They have been implicated in the regulation of a wide range of physiological processes, including feeding-related and motivated behaviors, and also environmental adaptations. In this work, improved mass spectrometry-based analytical platforms were developed and applied to the crustacean systems to characterize signaling molecules. This dissertation begins with a review of mass spectrometry-based neuropeptide studies from both temporal- and spatial-domains. This review is then followed by several chapters detailing a few research projects related to the crustacean neuropeptidomic characterization and comparative analysis. The neuropeptidome of crayfish, Orconectes rusticus is characterized for the first time using mass spectrometry-based tools. In vivo microdialysis sampling technique offers the capability of direct sampling from extracellular space in a time-resolved manner. It is used to investigate the secreted neuropeptide and neurotransmitter content in Jonah crab, Cancer borealis, in this work. A new quantitation strategy using alternative mass spectrometry data acquisition approach is developed and applied for the first time to quantify neuropeptides. Coupling of this method with microdialysis enables the study of neuropeptide dynamics concurrent with different behaviors. Proof-of-principle experiments validating this approach have been carried out in Jonah crab, Cancer borealis to study feeding- and circadian rhythm-related neuropeptide changes using micoridialysis in a time-resolved manner. This permits a close correlation between behavioral and neurochemical changes, providing potential candidates for future validation of regulatory roles. In addition to providing spatial information, mass spectrometry imaging (MSI) technique enables the characterization of signaling molecules while preserving the temporal resolution. A novel MSI-based platform is developed by interfacing with microdialysis sample collection and is applied to the study of in vivo neuropeptide degradation profiles in an off-line 'real-time' fashion. This unique platform provides novel insights into neuropeptide inactivation/elimination process, which is an essential step to understand peptidergic signaling pathway. In addition to neuropeptides, this platform has been further modified to study secreted neurotransmitters, and small molecule metabolites that might interact with neuropeptides in crustacean for the first time. This work not only reports improvements upon neuropeptides identification and quantitation by developing improved analytical strategies, but also provides important evidence for the potential roles of several neuropeptides in regulating food intake and circadian rhythm behaviors. Novel platform that integrates MALDI-MSI with microdialysis in exploring neurochemical changes in dynamic biological events is also presented, which could be potentially applied to many other systems in future research. Collectively this dissertation research develops new analytical methods and improves our fundamental understanding of neuropeptide signaling.

Characterization of beta-phenylethylamine-induced monoamine release in rat nucleus accumbens: a microdialysis study.

PubMed

Nakamura, M; Ishii, A; Nakahara, D

1998-05-22

In vivo microdialysis was used to investigate the effect of beta-phenylethylamine on extracellular levels of monoamines and their metabolites in the nucleus accumbens of conscious rats. At all doses tested (1, 10 and 100 microM), infusion of beta-phenylethylamine through the microdialysis probe significantly increased extracellular levels of dopamine in the nucleus accumbens. These increases were dose-related. The increase in dopamine levels induced by 100 microM beta-phenylethylamine was not affected by co-perfusion of 4 microM tetrodotoxin. The ability of 100 microM beta-phenylethylamine to increase the extracellular level of dopamine was comparable to that of the same dose of methamphetamine. On the other hand, beta-phenylethylamine had a much less potent enhancing effect on 5-hydroxytryptamine (5-HT) than dopamine levels. Only the highest dose (100 microM) caused a statistically significant effect on 5-HT levels. Over the dose range tested (1, 10 and 100 microM), beta-phenylethylamine had no effect on extracellular metabolite levels of dopamine and 5-HT. The results suggest that beta-phenylethylamine increases the efflux of monoamines, preferentially dopamine, without affecting monoamine metabolism, in the nucleus accumbens.

New method for monitoring nitric oxide in vivo using microdialysis sampling and chemiluminescence reaction

NASA Astrophysics Data System (ADS)

Yao, Dachun; Evmiridis, Nick P.; Zhou, Yikai; Xu, Shunqing; Zhou, Huarong

2001-09-01

A new method employing a combination of micro dialysis sampling and chemiluminescence reaction was developed to monitor nitric oxide (NO) in vivo. A special probe was designed with an interference-free membrane to achieve a very high selectivity for NO. High sensitivity was achieved by optimizing the working system and improving the NO sampling time. This system was used in vivo to monitor blood and brain tissue in rats and rabbits. We have established that this system is sensitive enough to detect variations in NO production in difference physiological state. The system can detect NO in the linear range of 5nM-1(mu) M, with a detection limit of 1nM, and real NO concentrations in our experimental animals were found to be in the range of 1-5 nM or even less. Finally, the effects of body temperature, NO donors, Viagra, NO activators, NO cofactors, NO interference were investigated carefully in different physiological situations.

Anandamide enhances extracellular levels of adenosine and induces sleep: an in vivo microdialysis study.

PubMed

Murillo-Rodriguez, Eric; Blanco-Centurion, Carlos; Sanchez, Cristina; Piomelli, Daniele; Shiromani, Priyattam J

2003-12-15

The principal component of marijuana, delta-9-tetrahydrocannabinol increases sleep in humans. Endogenous cannabinoids, such as N-arachidonoylethanolamine (anandamide), also increase sleep. However, the mechanism by which these molecules promote sleep is not known but might involve a sleep-inducing molecule such as adenosine. Microdialysis samples were collected from the basal forebrain in order to detect levels of adenosine before and after injection of anandamide. Rats were implanted for sleep studies, and a cannula was placed in the basal forebrain to collect microdialysis samples. Samples were analyzed using high-performance liquid chromatography. Basic neuroscience research laboratory. Three-month-old male F344 rats. At the start of the lights-on period, animals received systemic injections of dimethyl sulfoxide (vehicle), anandamide, SR141716A (cannabinoid receptor 1 [CB1] antagonist), or SR141716A and anandamide. One hour after injections, microdialysis samples were collected (5 microL) from the basal forebrain every hour over a 20-minute period for 5 hours. The samples were immediately analyzed via high-performance liquid chromatography for adenosine levels. Sleep was also recorded continuously over the same period. Anandamide increased adenosine levels compared to vehicle controls with the peak levels being reached during the third hour after drug injection. There was a significant increase in slow-wave sleep during the third hour. The induction in sleep and the rise in adenosine were blocked by the CB1-receptor antagonist, SR141716A. Anandamide increased adenosine levels in the basal forebrain and also increased sleep. The soporific effects of anandamide were mediated by the CB1 receptor, since the effects were blocked by the CB1-receptor antagonist. These findings identify a potential therapeutic use of endocannabinoids to induce sleep in conditions where sleep may be severely attenuated.

Microsomal metabolism of calycosin, formononetin and drug-drug interactions by dynamic microdialysis sampling and HPLC-DAD-MS analysis.

PubMed

Wen, Xiao-Dong; Qi, Lian-Wen; Li, Bin; Li, Ping; Yi, Ling; Wang, Ya-Qiong; Liu, E-Hu; Yang, Xiao-Lin

2009-08-15

A dynamic microdialysis sampling method with liquid chromatography-diode array detection and time-of-flight mass spectrometry (LC-DAD-TOF/MS) analysis was developed to investigate rat microsomal metabolisms of calycosin and formononetin, and their drug-drug interactions. Two hydroxylated metabolites from calycosin, and three hydroxylated or 4'-O-demethylated derivatives from formononetin were detected and identified after co-incubation with microsomes. Calibration curves offered linear ranges of two orders of magnitude with r(2)>0.999 for calycosin, formononetin and daidzein. The quantitative LC method provides a range of 0.028-0.034microg/mL for limits of detection, overall precision less than 5% and accuracy less than 3% by RSD. Besides, calycosin and formononetin were found to produce the depressive effect on the CYP450 enzyme reaction, and inhibit phase I enzyme reaction of each other when they are concurrent. Dynamic microdialysis sampling with LC-DAD-TOF/MS analysis developed in this work is a powerful tool for in vitro metabolism studies of drugs and metabolic interactions.

Non-invasive determination of glucose directly in raw fruits using a continuous flow system based on microdialysis sampling and amperometric detection at an integrated enzymatic biosensor.

PubMed

Vargas, E; Ruiz, M A; Campuzano, S; Reviejo, A J; Pingarrón, J M

2016-03-31

A non-destructive, rapid and simple to use sensing method for direct determination of glucose in non-processed fruits is described. The strategy involved on-line microdialysis sampling coupled with a continuous flow system with amperometric detection at an enzymatic biosensor. Apart from direct determination of glucose in fruit juices and blended fruits, this work describes for the first time the successful application of an enzymatic biosensor-based electrochemical approach to the non-invasive determination of glucose in raw fruits. The methodology correlates, through previous calibration set-up, the amperometric signal generated from glucose in non-processed fruits with its content in % (w/w). The comparison of the obtained results using the proposed approach in different fruits with those provided by other method involving the same commercial biosensor as amperometric detector in stirred solutions pointed out that there were no significant differences. Moreover, in comparison with other available methodologies, this microdialysis-coupled continuous flow system amperometric biosensor-based procedure features straightforward sample preparation, low cost, reduced assay time (sampling rate of 7 h(-1)) and ease of automation. Copyright © 2016 Elsevier B.V. All rights reserved.

Microdialysis as a New Technique for Extracting Phenolic Compounds from Extra Virgin Olive Oil.

PubMed

Bazzu, Gianfranco; Molinu, Maria Giovanna; Dore, Antonio; Serra, Pier Andrea

2017-03-01

The amount and composition of the phenolic components play a major role in determining the quality of olive oil. The traditional liquid-liquid extraction (LLE) method requires a time-consuming sample preparation to obtain the "phenolic profile" of extra virgin olive oil (EVOO). This study aimed to develop a microdialysis extraction (MDE) as an alternative to the LLE method to evaluate the phenolic components of EVOO. To this purpose, a microdialysis device and dialysis procedure were developed. "Dynamic-oil" microdialysis was performed using an extracting solution (80:20 methanol/water) flow rate of 2 μL min -1 and a constant EVOO stream of 4 μL min -1 . The results indicated a strong positive correlation between MDE and the LLE method, providing a very similar phenolic profile obtained with traditional LLE. In conclusion, the MDE approach, easier and quicker in comparison to LLE, provided a reliable procedure to determine the phenolic components used as a marker of the quality and traceability of EVOO.

Determination of Serotonin and Dopamine Metabolites in Human Brain Microdialysis and Cerebrospinal Fluid Samples by UPLC-MS/MS: Discovery of Intact Glucuronide and Sulfate Conjugates

PubMed Central

Suominen, Tina; Uutela, Päivi; Ketola, Raimo A.; Bergquist, Jonas; Hillered, Lars; Finel, Moshe; Zhang, Hongbo; Laakso, Aki; Kostiainen, Risto

2013-01-01

An UPLC-MS/MS method was developed for the determination of serotonin (5-HT), dopamine (DA), their phase I metabolites 5-HIAA, DOPAC and HVA, and their sulfate and glucuronide conjugates in human brain microdialysis samples obtained from two patients with acute brain injuries, ventricular cerebrospinal fluid (CSF) samples obtained from four patients with obstructive hydrocephalus, and a lumbar CSF sample pooled mainly from patients undergoing spinal anesthesia in preparation for orthopedic surgery. The method was validated by determining the limits of detection and quantification, linearity, repeatability and specificity. The direct method enabled the analysis of the intact phase II metabolites of 5-HT and DA, without hydrolysis of the conjugates. The method also enabled the analysis of the regioisomers of the conjugates, and several intact glucuronide and sulfate conjugates were identified and quantified for the first time in the human brain microdialysis and CSF samples. We were able to show the presence of 5-HIAA sulfate, and that dopamine-3-O-sulfate predominates over dopamine-4-O-sulfate in the human brain. The quantitative results suggest that sulfonation is a more important phase II metabolism pathway than glucuronidation in the human brain. PMID:23826355

Short-term dopaminergic regulation of GABA release in dopamine deafferented caudate-putamen is not directly associated with glutamic acid decarboxylase gene expression.

PubMed

O'Connor, W T; Lindefors, N; Brené, S; Herrera-Marschitz, M; Persson, H; Ungerstedt, U

1991-07-08

In vivo microdialysis and in situ hybridization were combined to study dopaminergic regulation of gamma-amino butyric acid (GABA) neurons in rat caudate-putamen (CPu). Potassium-stimulated GABA release in CPu was elevated following a dopamine deafferentation. Local perfusion with exogenous dopamine (50 microM) for 3 h via the microdialysis probe attenuated the potassium-stimulated increase in extracellular GABA in CPu. Expression of glutamic acid decarboxylase (GAD) mRNA was also increased in the dopamine deafferented CPu. However, local perfusion with dopamine had no significant attenuating effect on the increased GAD mRNA expression. These findings indicate that dopaminergic regulation of GABA neurons in the dopamine deafferented CPu includes both a short-term effect at the level of GABA release independent of changes in GAD mRNA expression and a long-term modulation at the level of GAD gene expression.

Detection of basal acetylcholine release in the microdialysis of rat frontal cortex by high-performance liquid chromatography using a horseradish peroxidase-osmium redox polymer electrode with pre-enzyme reactor.

PubMed

Kato, T; Liu, J K; Yamamoto, K; Osborne, P G; Niwa, O

1996-06-28

To determine the basal acetylcholine level in the dialysate of rat frontal cortex, a horseradish peroxidase-osmium redox polymer-modified glassy carbon electrode (HRP-GCE) was employed instead of the conventional platinum electrode used in high-performance liquid chromatography-electrochemical detection (HPLC-ED). In initial experiments, an oxidizable unknown compound interfered with the detection of basal acetylcholine release on HPLC-HRP-GCE. An immobilized peroxidase-choline oxidase precolumn (pre-reactor) was included in the HPLC system, to eliminate the interference from the unknown compound. This combination could detect less than 10 fmol of standard acetylcholine and basal acetylcholine levels in the dialysate from a conventional concentric design microdialysis probe, without the use of cholinesterase inhibitor, and may facilitate physiological investigation of cholinergic neuronal activity in the central nervous system.

Central l-proline attenuates stress-induced dopamine and serotonin metabolism in the chick forebrain.

PubMed

Hamasu, Kousuke; Shigemi, Kazutaka; Kabuki, Yusuke; Tomonaga, Shozo; Denbow, D Michael; Furuse, Mitsuhiro

2009-08-21

Using microdialysis, we investigated the effect of l-proline on monoamine release in the medio-rostral neostriatum/hyperstriatum ventrale (MNH) of freely moving and restricted chicks. A 30 min handling-stress resulted in a significant increase in extracellular homovallinic acid (HVA), a dopamine metabolite, and 5-hydroxyindoleacetic acid (5-HIAA), a serotonin metabolite, in the MNH. l-Proline, perfused through the microdialysis probe into the MNH during the stressed condition, significantly attenuated the average dialysate concentration of HVA produced by handling-stress. Handling-stress resulted in a significant increase in 5-HIAA levels in the control group, which were attenuated by profusion with l-proline. l-Proline did not significantly modify basal concentrations of HVA or 5-HIAA in the MNH during control conditions. These results show that perfusion of l-proline modified the turnover/metabolism of dopamine and serotonin in the MNH caused by handling-stress.

Nose-to-brain transport of melatonin from polymer gel suspensions: a microdialysis study in rats.

PubMed

Jayachandra Babu, R; Dayal, Pankaj Patrick; Pawar, Kasturi; Singh, Mandip

2011-11-01

Exogenous melatonin (MT) has significant neuroprotective roles in Alzheimer's and Parkinson's diseases. This study investigates the delivery MT to brain via nasal route as a polymeric gel suspension using central brain microdialysis in anesthetized rats. Micronized MT suspensions using polymers [carbopol, carboxymethyl cellulose (CMC)] and polyethylene glycol 400 (PEG400) were prepared and characterized for nasal administration. In vitro permeation of the formulations was measured across a three-dimensional tissue culture model EpiAirway(™). The central brain delivery into olfactory bulb of nasally administered MT gel suspensions was studied using brain microdialysis in male Wistar rats. The MT content of microdialysis samples was analyzed by high performance liquid chromatography (HPLC) using electrochemical detection. The nose-to-brain delivery of MT formulations was compared with intravenously administered MT solution. MT suspensions in carbopol and CMC vehicles have shown significantly higher permeability across Epiairway(™) as compared to control, PEG400 (P < 0.05). The brain (olfactory bulb) levels of MT after intranasal administration were 9.22, 6.77 and 4.04-fold higher for carbopol, CMC and PEG400, respectively, than that of intravenous MT in rats. In conclusion, microdialysis studies demonstrated increased brain levels of MT via nasal administration in rats.

Nose-to-brain transport of melatonin from polymer gel suspensions: a microdialysis study in rats

PubMed Central

Babu, R. Jayachandra; Dayal, Pankaj Patrick; Pawar, Kasturi; Singh, Mandip

2012-01-01

Purpose Exogenous melatonin (MT) has significant neuroprotective roles in Alzheimer’s and Parkinson’s diseases. This study investigates the delivery MT to brain via nasal route as a polymeric gel suspension using central brain microdialysis in anesthetized rats. Methods Micronized MT suspensions using polymers [carbopol, carboxymethyl cellulose (CMC)] and polyethylene glycol 400 (PEG400) were prepared and characterized for nasal administration. In vitro permeation of the formulations was measured across a three-dimensional tissue culture model EpiAirway™. The central brain delivery into olfactory bulb of nasally administered MT gel suspensions was studied using brain microdialysis in male Wistar rats. The MT content of microdialysis samples was analyzed by high performance liquid chromatography (HPLC) using electrochemical detection. The nose-to-brain delivery of MT formulations was compared with intravenously administered MT solution. Results MT suspensions in carbopol and CMC vehicles have shown significantly higher permeability across Epiairway™ as compared to control, PEG400 (P < 0.05). The brain (olfactory bulb) levels of MT after intranasal administration were 9.22, 6.77 and 4.04-fold higher for carbopol, CMC and PEG400, respectively, than that of intravenous MT in rats. In conclusion, microdialysis studies demonstrated increased brain levels of MT via nasal administration in rats. PMID:21428693

Effects of variation in cerebral haemodynamics during aneurysm surgery on brain tissue oxygen and metabolism.

PubMed

Kett-White, R; Hutchinson, P J; Czosnyka, M; al-Rawi, P; Gupta, A; Pickard, J D; Kirkpatrick, P J

2002-01-01

This study explores the sensitivities of multiparameter tissue gas sensors and microdialysis to variations in blood pressure, CSF drainage and to well-defined periods of ischaemia accompanying aneurysm surgery, and their predictive value for infarction. A Neurotrend sensor [brain tissue partial pressure of oxygen (PBO2), carbon dioxide (PBCO2), brain pH (pHB) and temperature] and microdialysis catheter were inserted into the appropriate vascular territory prior to craniotomy. Baseline data showed a clear correlation between PBO2 and mean arterial pressure (MAP) below a threshold of 80 mmHg. PBO2 improved with CSF drainage in 20 out of 28 (Wilcoxon: P < 0.05) cases where data was available. In 26 patients the effects of temporary vascular clipping (TC) (mean duration 16 minutes) were assessed. 2 patients subsequently declared infarction in the region of the probes. PBO2 fell from a mean 3.2 (95% CI 2.4-4.1) kPa to a minimum of 1.5 (95% CI 1.0-2.0) kPa in the non-infarct group. There was a lower baseline PBO2 (mean 0.8 kPa) in the patients who infarcted. PBCO2 mirrored PBO2 changes, whereas pHB did not change significantly in either group. Microdialysis changes associated with decreased PBO2 included a delayed increase in lactate, a raised lactate/pyruvate ratio and more rarely an increased glutamate. These changes were seen in 11 patients but were not predictive of infarction. Hypotension during aneurysm surgery is associated with a low PBO2. Multiparameter sensors can be sensitive to acute ischaemia. Microdialysis shows potential in the detection of metabolic changes during tissue hypoxia.

Characterization of peripheral-compartment kinetics of antibiotics by in vivo microdialysis in humans.

PubMed Central

Müller, M; Haag, O; Burgdorff, T; Georgopoulos, A; Weninger, W; Jansen, B; Stanek, G; Pehamberger, H; Agneter, E; Eichler, H G

1996-01-01

The calculation of pharmacokinetic/pharmacodynamic surrogates from concentrations in serum has been shown to yield important information for the evaluation of antibiotic regimens. Calculations based on concentrations in serum, however, may not necessarily be appropriate for peripheral-compartment infections. The aim of the present study was to apply the microdialysis technique for the study of the peripheral-compartment pharmacokinetics of select antibiotics in humans. Microdialysis probes were inserted into the skeletal muscle and adipose tissue of healthy volunteers and into inflamed and noninflamed dermis of patients with cellulitis. Thereafter, volunteers received either cefodizime (2,000 mg as an intravenous bolus; n = 6), cefpirome (2,000 mg as an intravenous bolus; n = 6), fleroxacin (400 mg orally n = 6), or dirithromycin (250 mg orally; n = 4); the patients received phenoxymethylpenicillin (4.5 x 10(6) U orally; n = 3). Complete concentration-versus-time profiles for serum and tissues could be obtained for all compounds. Major pharmacokinetic parameters (elimination half-life, peak concentration in serum, time to peak concentration, area under the concentration-time curve [AUC], and AUC/MIC ratio) were calculated for tissues. For cefodizime and cefpirome, the AUCtissue/AUCserum ratios were 0.12 to 0.35 and 1.20 to 1.79, respectively. The AUCtissue/AUCserum ratios were 0.34 to 0.38 for fleroxacin and 0.42 to 0.49 for dirithromycin. There was no visible difference in the time course of phenoxymethylpenicillin in inflamed and noninflamed dermis. We demonstrated, by means of microdialysis, that the concept of pharmacokinetic/pharmacodynamic surrogate markers for evaluation of antibiotic regimens originally developed for serum pharmacokinetics can be extended to peripheral-tissue pharmacokinetics. This novel information may be useful for the rational development of dosage schedules and may improve predictions regarding therapeutic outcome. PMID:9124826

Ultrasonic microdialysis coupled with capillary electrophoresis electrochemiluminescence study the interaction between trimetazidine dihydrochloride and human serum albumin.

PubMed

Sun, Shuangjiao; Long, Chanjuan; Tao, Chunyao; Meng, Sa; Deng, Biyang

2014-12-03

The paper describes a homemade ultrasonic microdialysis device coupled with capillary electrophoresis electrochemiluminescence (CE-ECL) for studying the interaction between human serum albumin (HSA) and trimetazidine dihydrochloride (TMZ). The time required for equilibrium by ultrasonic microdialysis was 45min, which was far less than that by traditional dialysis (240min). It took 80min to achieve the required combination equilibrium by normal incubation and only 20min by ultrasonic. Compared with traditional dialysis, the use of ultrasonic microdialysis simplified experimental procedures, shortened experimental time and saved consumption of sample. A simple, sensitive and selective determination of TMZ was developed using CE-ECL and the parameters that affected ECL intensity were optimized. Under the optimized conditions, the linear range of TMZ was from 0.075 to 80μmol/L (r(2)=0.9974). The detection limit was 26nmol/L with RSD of 2.8%. The number of binding sites and binding constant were 1.54 and 15.17L/mol, respectively. Copyright © 2014 Elsevier B.V. All rights reserved.

Substance P release in the spinal cord during the exercise pressor reflex in anaesthetized cats.

PubMed Central

Wilson, L B; Fuchs, I E; Matsukawa, K; Mitchell, J H; Wall, P T

1993-01-01

1. The purpose of this study was to determine if static skeletal muscle contraction causes the release of substance P(SP) in the L7-dorsal horn region of the spinal cord. A laminectomy was performed to expose the spinal cord of alpha-chloralose anaesthetized cats. The L6 spinal root was cut. A microdialysis probe was inserted into the L7 dorsal horn region ipsilateral to the contracting triceps surae muscle. The probe was perfused with a buffer solution at 3 microliters/min. Substance P-like immunoreactivity (SP-LI) was measured, from the microdialysis samples, by radioimmunoassay. 2. A 5-9 min contraction of the triceps surae muscle was evoked by alternate electrical stimulation of the peripheral ends of the cut L7 and S1 ventral roots. Basal SP-LI release was 0.20 +/- 0.03 fmol/100 microliters and was increased to 0.54 +/- 0.05 fmol/100 microliters (mean +/- S.D.) by static muscle contraction. This increase was greatly attenuated after cutting the L7 and S1 dorsal roots (0.23 +/- 0.03 to 0.39 +/- 0.08 fmol/100 microliters) or completely abolished by muscle paralysis (0.27 +/- 0.03 to 0.31 +/- 0.01 fmol/100 microliters). Muscle contraction also increased mean arterial blood pressure (MAP) 29 +/- 20 mmHg and heart rate (HR) 11 +/- 5 beats/min (mean +/- S.D.). These cardiovascular changes to muscle contraction were abolished by sectioning the dorsal roots or when the ventral roots were electrically stimulated after the cats were paralysed. 3. These results demonstrate that static contraction of skeletal muscle increases the release of SP-LI in the dorsal horn of the spinal cord. Furthermore, these data support the hypothesis that SP plays a role in mediating the cardiovascular responses evoked during static exercise. PMID:7683719

Image-guided intracranial cannula placement for awake in vivo microdialysis in nonhuman primates

NASA Astrophysics Data System (ADS)

Chen, Antong; Bone, Ashleigh; Hines, Catherine D. G.; Dogdas, Belma; Montgomery, Tamara O.; Michener, Maria; Winkelmann, Christopher T.; Ghafurian, Soheil; Lubbers, Laura S.; Renger, John; Bagchi, Ansuman; Uslaner, Jason M.; Johnson, Colena; Zariwala, Hatim A.

2016-03-01

Intracranial microdialysis is used for sampling neurochemicals and large peptides along with their metabolites from the interstitial fluid (ISF) of the brain. The ability to perform this in nonhuman primates (NHP) e.g., rhesus could improve the prediction of pharmacokinetic (PK) and pharmacodynamics (PD) action of drugs in human. However, microdialysis in rhesus brains is not as routinely performed as in rodents. One challenge is that the precise intracranial probe placement in NHP brains is difficult due to the richness of the anatomical structure and the variability of the size and shape of brains across animals. Also, a repeatable and reproducible ISF sampling from the same animal is highly desirable when combined with cognitive behaviors or other longitudinal study end points. Toward that end, we have developed a semi-automatic flexible neurosurgical method employing MR and CT imaging to (a) derive coordinates for permanent guide cannula placement in mid-brain structures and (b) fabricate a customized recording chamber to implant above the skull for enclosing and safeguarding access to the cannula for repeated experiments. In order to place the intracranial guide cannula in each subject, the entry points in the skull and the depth in the brain were derived using co-registered images acquired from MR and CT scans. The anterior/posterior (A/P) and medial-lateral (M/L) rotation in the pose of the animal was corrected in the 3D image to appropriately represent the pose used in the stereotactic frame. An array of implanted fiducial markers was used to transform stereotactic coordinates to the images. The recording chamber was custom fabricated using computer-aided design (CAD), such that it would fit the contours of the individual skull with minimum error. The chamber also helped in guiding the cannula through the entry points down a trajectory into the depth of the brain. We have validated our method in four animals and our results indicate average placement error of cannula to be 1.20 +/- 0.68 mm of the targeted positions. The approach employed here for derivation of the coordinates, surgical implantation and post implant validation is built using traditional access to surgical and imaging methods without the necessity of intra-operative imaging. The validation of our method lends support to its wider application in most nonhuman primate laboratories with onsite MR and CT imaging capabilities.

Microdialysis Sampling Techniques Applied to Studies of the Foreign Body Reaction

PubMed Central

Sides, Cynthia R.; Stenken, Julie A.

2014-01-01

Implanted materials including drug delivery devices and chemical sensors undergo what is termed the foreign body reaction (FBR). Depending on the device and its intended application, the FBR can have differing consequences. An extensive scientific research effort has been devoted to elucidating the cellular and molecular mechanisms that drive the FBR. Important, yet relatively unexplored, research includes the localized tissue biochemistry and the chemical signaling events that occur throughout the FBR. This review provides an overview of the mechanisms of the FBR, describes how the FBR affects different implanted devices, and illustrates the role that microdialysis sampling can play in further elucidating the chemical communication processes that drive FBR outcomes. PMID:24269987

Evaluation of a Portable Microchip Electrophoresis Fluorescence Detection System for the Analysis of Amino Acid Neurotransmitters in Brain Dialysis Samples

PubMed Central

OBORNY, Nathan J.; COSTA, Elton E. Melo; SUNTORNSUK, Leena; ABREU, Fabiane C.; LUNTE, Susan M.

2016-01-01

A portable fluorescence detection system for use with microchip electrophoresis was developed and compared to a benchtop system. Using this system, six neuroactive amines commonly found in brain dialysate—arginine, citrulline, taurine, histamine, glutamate, and aspartate—were derivatized offline with naphthalene-2,3-dicarboxaldehyde/cyanide, separated electrophoretically, and detected by fluorescence. Limits of detection for the analytes of interest were 50nM – 250nM for the benchtop system and 250 nM – 1.3 μM for the portable system, both of which were adequate for analyte determination in brain microdialysis samples. The portable system was then demonstrated for the detection of the same six amines in a rat brain microdialysis sample. PMID:26753703

Extracellular metabolites in the cortex and hippocampus of epileptic patients.

PubMed

Cavus, Idil; Kasoff, Willard S; Cassaday, Michael P; Jacob, Ralph; Gueorguieva, Ralitza; Sherwin, Robert S; Krystal, John H; Spencer, Dennis D; Abi-Saab, Walid M

2005-02-01

Interictal brain energy metabolism and glutamate-glutamine cycling are impaired in epilepsy and may contribute to seizure generation. We used the zero-flow microdialysis method to measure the extracellular levels of glutamate, glutamine, and the major energy substrates glucose and lactate in the epileptogenic and the nonepileptogenic cortex and hippocampus of 38 awake epileptic patients during the interictal period. Depth electrodes attached to microdialysis probes were used to identify the epileptogenic and the nonepileptogenic sites. The epileptogenic hippocampus had surprisingly high basal glutamate levels, low glutamine/glutamate ratio, high lactate levels, and indication for poor glucose utilization. The epileptogenic cortex had only marginally increased glutamate levels. We propose that interictal energetic deficiency in the epileptogenic hippocampus could contribute to impaired glutamate reuptake and glutamate-glutamine cycling, resulting in persistently increased extracellular glutamate, glial and neuronal toxicity, increased lactate production together with poor lactate and glucose utilization, and ultimately worsening energy metabolism. Our data suggest that a different neurometabolic process underlies the neocortical epilepsies.

DERMAL DRUG LEVELS OF ANTIBIOTIC (CEPHALEXIN) DETERMINED BY ELECTROPORATION AND TRANSCUTANEOUS SAMPLING (ETS) TECHNIQUE

PubMed Central

Sammeta, SM; Vaka, SRK; Murthy, S. Narasimha

2009-01-01

The purpose of this project was to assess the validity of a novel “Electroporation and transcutaneous sampling (ETS)” technique for sampling cephalexin from the dermal extracellular fluid (ECF). This work also investigated the plausibility of using cephalexin levels in the dermal ECF as a surrogate for the drug level in the synovial fluid. In vitro and in vivo studies were carried out using hair less rats to assess the workability of ETS. Cephalexin (20mg/kg) was administered i.v. through tail vein and the time course of drug concentration in the plasma was determined. In the same rats, cephalexin concentration in the dermal ECF was determined by ETS and microdialysis techniques. In a separate set of rats, only intraarticular microdialysis was carried out determine the time course of cephalexin concentration in synovial fluid. The drug concentration in the dermal ECF determined by ETS and microdialysis did not differ significantly from each other and so as were the pharmacokinetic parameters. The results provide validity to the ETS technique. Further, there was a good correlation (~0.9) between synovial fluid and dermal ECF levels of cephalexin indicating that dermal ECF levels could be used as a potential surrogate for cephalexin concentration in the synovial fluid. PMID:19067398

Involvement of intracellular Zn2+ signaling in LTP at perforant pathway-CA1 pyramidal cell synapse.

PubMed

Tamano, Haruna; Nishio, Ryusuke; Takeda, Atsushi

2017-07-01

Physiological significance of synaptic Zn 2+ signaling was examined at perforant pathway-CA1 pyramidal cell synapses. In vivo long-term potentiation (LTP) at perforant pathway-CA1 pyramidal cell synapses was induced using a recording electrode attached to a microdialysis probe and the recording region was locally perfused with artificial cerebrospinal fluid (ACSF) via the microdialysis probe. Perforant pathway LTP was not attenuated under perfusion with CaEDTA (10 mM), an extracellular Zn 2+ chelator, but attenuated under perfusion with ZnAF-2DA (50 μM), an intracellular Zn 2+ chelator, suggesting that intracellular Zn 2+ signaling is required for perforant pathway LTP. Even in rat brain slices bathed in CaEDTA in ACSF, intracellular Zn 2+ level, which was measured with intracellular ZnAF-2, was increased in the stratum lacunosum-moleculare where perforant pathway-CA1 pyramidal cell synapses were contained after tetanic stimulation. These results suggest that intracellular Zn 2+ signaling, which originates in internal stores/proteins, is involved in LTP at perforant pathway-CA1 pyramidal cell synapses. Because the influx of extracellular Zn 2+ , which originates in presynaptic Zn 2+ release, is involved in LTP at Schaffer collateral-CA1 pyramidal cell synapses, synapse-dependent Zn 2+ dynamics may be involved in plasticity of postsynaptic CA1 pyramidal cells. © 2017 Wiley Periodicals, Inc.

Analytical and Biological Methods for Probing the Blood-Brain Barrier

PubMed Central

Sloan, Courtney D. Kuhnline; Nandi, Pradyot; Linz, Thomas H.; Aldrich, Jane V.; Audus, Kenneth L.; Lunte, Susan M.

2013-01-01

The blood-brain barrier (BBB) is an important interface between the peripheral and central nervous systems. It protects the brain against the infiltration of harmful substances and regulates the permeation of beneficial endogenous substances from the blood into the extracellular fluid of the brain. It can also present a major obstacle in the development of drugs that are targeted for the central nervous system. Several methods have been developed to investigate the transport and metabolism of drugs, peptides, and endogenous compounds at the BBB. In vivo methods include intravenous injection, brain perfusion, positron emission tomography, and microdialysis sampling. Researchers have also developed in vitro cell-culture models that can be employed to investigate transport and metabolism at the BBB without the complication of systemic involvement. All these methods require sensitive and selective analytical methods to monitor the transport and metabolism of the compounds of interest at the BBB. PMID:22708905

Screening and analysis of bioactive compounds with biofingerprinting chromatogram analysis of traditional Chinese medicines targeting DNA by microdialysis/HPLC.

PubMed

Su, Xingye; Kong, Liang; Li, Xin; Chen, Xueguo; Guo, Ming; Zou, Hanfa

2005-05-27

Biofingerprinting chromatogram analysis, which is defined as the comparison of fingerprinting chromatograms of the extract of traditional Chinese medicines (TCMs) before and after the interaction with biological systems (DNA, protein, cell, etc.), was proposed for screening and analysis of the multiple bioactive compounds in TCMs. A method of microdialysis sampling combined with high performance liquid chromatography (HPLC) was applied to the study of DNA-binding property for the extracts of TCMs. Seven compounds were found to bind to calf thymus DNA (ct-DNA) from the TCMs of Coptis chinensis Franch (Coptis), but only three ones from Phellodendron amurense Rupr. (Phellodendron) and none from Sophoraflavescens Ait. (Sophora) to bind to ct-DNA, respectively. Three of them were identified as berberine, palmatine and jatrorrhizine and their association constants (K) to ct-DNA were determined by microdialysis/HPLC. Competitive binding behaviors of them to ct-DNA were also investigated.

Microdialysis as an Important Technique in Systems Pharmacology-a Historical and Methodological Review.

PubMed

Hammarlund-Udenaes, Margareta

2017-09-01

Microdialysis has contributed with very important knowledge to the understanding of target-specific concentrations and their relationship to pharmacodynamic effects from a systems pharmacology perspective, aiding in the global understanding of drug effects. This review focuses on the historical development of microdialysis as a method to quantify the pharmacologically very important unbound tissue concentrations and of recent findings relating to modeling microdialysis data to extrapolate from rodents to humans, understanding distribution of drugs in different tissues and disease conditions. Quantitative microdialysis developed very rapidly during the early 1990s. Method development was in focus in the early years including development of quantitative microdialysis, to be able to estimate true extracellular concentrations. Microdialysis has significantly contributed to the understanding of active transport at the blood-brain barrier and in other organs. Examples are presented where microdialysis together with modeling has increased the knowledge on tissue distribution between species, in overweight patients and in tumors, and in metabolite contribution to drug effects. More integrated metabolomic studies are still sparse within the microdialysis field, although a great potential for tissue and disease-specific measurements is evident.

Cholinergic Neurons in the Basal Forebrain Promote Wakefulness by Actions on Neighboring Non-Cholinergic Neurons: An Opto-Dialysis Study.

PubMed

Zant, Janneke C; Kim, Tae; Prokai, Laszlo; Szarka, Szabolcs; McNally, James; McKenna, James T; Shukla, Charu; Yang, Chun; Kalinchuk, Anna V; McCarley, Robert W; Brown, Ritchie E; Basheer, Radhika

2016-02-10

Understanding the control of sleep-wake states by the basal forebrain (BF) poses a challenge due to the intermingled presence of cholinergic, GABAergic, and glutamatergic neurons. All three BF neuronal subtypes project to the cortex and are implicated in cortical arousal and sleep-wake control. Thus, nonspecific stimulation or inhibition studies do not reveal the roles of these different neuronal types. Recent studies using optogenetics have shown that "selective" stimulation of BF cholinergic neurons increases transitions between NREM sleep and wakefulness, implicating cholinergic projections to cortex in wake promotion. However, the interpretation of these optogenetic experiments is complicated by interactions that may occur within the BF. For instance, a recent in vitro study from our group found that cholinergic neurons strongly excite neighboring GABAergic neurons, including the subset of cortically projecting neurons, which contain the calcium-binding protein, parvalbumin (PV) (Yang et al., 2014). Thus, the wake-promoting effect of "selective" optogenetic stimulation of BF cholinergic neurons could be mediated by local excitation of GABA/PV or other non-cholinergic BF neurons. In this study, using a newly designed opto-dialysis probe to couple selective optical stimulation with simultaneous in vivo microdialysis, we demonstrated that optical stimulation of cholinergic neurons locally increased acetylcholine levels and increased wakefulness in mice. Surprisingly, the enhanced wakefulness caused by cholinergic stimulation was abolished by simultaneous reverse microdialysis of cholinergic receptor antagonists into BF. Thus, our data suggest that the wake-promoting effect of cholinergic stimulation requires local release of acetylcholine in the basal forebrain and activation of cortically projecting, non-cholinergic neurons, including the GABAergic/PV neurons. Optogenetics is a revolutionary tool to assess the roles of particular groups of neurons in behavioral functions, such as control of sleep and wakefulness. However, the interpretation of optogenetic experiments requires knowledge of the effects of stimulation on local neurotransmitter levels and effects on neighboring neurons. Here, using a novel "opto-dialysis" probe to couple optogenetics and in vivo microdialysis, we report that optical stimulation of basal forebrain (BF) cholinergic neurons in mice increases local acetylcholine levels and wakefulness. Reverse microdialysis of cholinergic antagonists within BF prevents the wake-promoting effect. This important result challenges the prevailing dictum that BF cholinergic projections to cortex directly control wakefulness and illustrates the utility of "opto-dialysis" for dissecting the complex brain circuitry underlying behavior. Copyright © 2016 the authors 0270-6474/16/362058-11$15.00/0.

Cholinergic Neurons in the Basal Forebrain Promote Wakefulness by Actions on Neighboring Non-Cholinergic Neurons: An Opto-Dialysis Study

PubMed Central

Zant, Janneke C.; Kim, Tae; Prokai, Laszlo; Szarka, Szabolcs; McNally, James; McKenna, James T.; Shukla, Charu; Yang, Chun; Kalinchuk, Anna V.; McCarley, Robert W.; Brown, Ritchie E.

2016-01-01

Understanding the control of sleep–wake states by the basal forebrain (BF) poses a challenge due to the intermingled presence of cholinergic, GABAergic, and glutamatergic neurons. All three BF neuronal subtypes project to the cortex and are implicated in cortical arousal and sleep–wake control. Thus, nonspecific stimulation or inhibition studies do not reveal the roles of these different neuronal types. Recent studies using optogenetics have shown that “selective” stimulation of BF cholinergic neurons increases transitions between NREM sleep and wakefulness, implicating cholinergic projections to cortex in wake promotion. However, the interpretation of these optogenetic experiments is complicated by interactions that may occur within the BF. For instance, a recent in vitro study from our group found that cholinergic neurons strongly excite neighboring GABAergic neurons, including the subset of cortically projecting neurons, which contain the calcium-binding protein, parvalbumin (PV) (Yang et al., 2014). Thus, the wake-promoting effect of “selective” optogenetic stimulation of BF cholinergic neurons could be mediated by local excitation of GABA/PV or other non-cholinergic BF neurons. In this study, using a newly designed opto-dialysis probe to couple selective optical stimulation with simultaneous in vivo microdialysis, we demonstrated that optical stimulation of cholinergic neurons locally increased acetylcholine levels and increased wakefulness in mice. Surprisingly, the enhanced wakefulness caused by cholinergic stimulation was abolished by simultaneous reverse microdialysis of cholinergic receptor antagonists into BF. Thus, our data suggest that the wake-promoting effect of cholinergic stimulation requires local release of acetylcholine in the basal forebrain and activation of cortically projecting, non-cholinergic neurons, including the GABAergic/PV neurons. SIGNIFICANCE STATEMENT Optogenetics is a revolutionary tool to assess the roles of particular groups of neurons in behavioral functions, such as control of sleep and wakefulness. However, the interpretation of optogenetic experiments requires knowledge of the effects of stimulation on local neurotransmitter levels and effects on neighboring neurons. Here, using a novel “opto-dialysis” probe to couple optogenetics and in vivo microdialysis, we report that optical stimulation of basal forebrain (BF) cholinergic neurons in mice increases local acetylcholine levels and wakefulness. Reverse microdialysis of cholinergic antagonists within BF prevents the wake-promoting effect. This important result challenges the prevailing dictum that BF cholinergic projections to cortex directly control wakefulness and illustrates the utility of “opto-dialysis” for dissecting the complex brain circuitry underlying behavior. PMID:26865627

A novel dynamic approach for automatic microsampling and continuous monitoring of metal ion release from soils exploiting a dedicated flow-through microdialyser.

PubMed

Miró, Manuel; Jimoh, Modupe; Frenzel, Wolfgang

2005-05-01

In this paper, a novel concept is presented for automatic microsampling and continuous monitoring of metal ions in soils with minimum disturbance of the sampling site. It involves a hollow-fiber microdialyser that is implanted in the soil body as a miniaturized sensing device. The idea behind microdialysis in this application is to mimic the function of a passive sampler to predict the actual, rather than potential, mobility and bioavailability of metal traces. Although almost quantitative dialysis recoveries were obtained for lead (> or = 98%) from aqueous model solutions with sufficiently long capillaries (l > or = 30 mm, 200 microm i.d.) at perfusion rates of 2.0 microL min(-1), the resistance of an inert soil matrix was found to reduce metal uptake by 30%. Preliminary investigation of the potential of the microdialysis analyser for risk assessment of soil pollution, and for metal partitioning studies, were performed by implanting the dedicated probe in a laboratory-made soil column and hyphenating it with electrothermal atomic absorption spectrometry (ETAAS), so that minute, well-defined volumes of clean microdialysates were injected on-line into the graphite furnace. A noteworthy feature of the implanted microdialysis-based device is the capability to follow the kinetics of metal release under simulated natural scenarios or anthropogenic actions. An ancillary flow set-up was arranged in such a way that a continuous flow of leaching solution--mild extractant (10(-2) mol L(-1) CaCl2), acidic solution (10(-3) mol L(-1) HNO3), or chelating agent (10(-4) or 10(-2) mol L(-1) EDTA)--was maintained through the soil body, while the concentration trends of inorganic (un-bound) metal species at the soil-liquid interface could be monitored at near real-time. Hence, relevant qualitative and quantitative information about the various mobile fractions is obtained, and metal-soil phase associations can also be elucidated. Finally, stimulus-response schemes adapted from neurochemical applications and pharmacokinetic studies are to be extended to soil research as an alternative means of local monitoring of extraction processes after induction of a chemical change in the outer boundary of the permselective dialysis membrane.

Effects of beta-phenylethylamine on dopaminergic neurons of the ventral tegmental area in the rat: a combined electrophysiological and microdialysis study.

PubMed

Ishida, Kota; Murata, Mikio; Katagiri, Nobuyuki; Ishikawa, Masago; Abe, Kenji; Kato, Masatoshi; Utsunomiya, Iku; Taguchi, Kyoji

2005-08-01

The effects of systemic administration of beta-phenylethylamine (beta-PEA) and microiontophoretically applied beta-PEA on the spontaneous discharge of dopamine (DA) neurons in the ventral tegmental area (VTA) of the anesthetized rat were examined. Intravenous administration of beta-PEA (1.0, 2.5, and 5.0 mg/kg) and microiontophoretic applications of beta-PEA caused inhibitory responses in DA neurons. Systemic administration and microiontophoretic applications of beta-PEA induced dose- or current-dependent responses. The systemic beta-PEA-induced inhibitory responses were reversed by pretreatment with the DA D(2) receptor antagonists haloperidol (0.5 mg/kg i.p.) and sulpiride (10 mg/kg i.p). Pretreatment with reserpine (5 mg/kg i.p. 24 h earlier) did not completely block the systemic administration of beta-PEA (2.5 mg/kg) inhibition. A microdialysis study of freely moving rats demonstrated that the extracellular DA level increased significantly in response to local application of beta-PEA (100 muM) in the VTA via a microdialysis probe, and local application of beta-PEA-stimulated somatodendritic DA release in the VTA. The beta-PEA-induced release of DA was calcium ion-independent and was enhanced by pretreatment with pertussis toxin. These findings indicate that beta-phenylethylamine inhibits DA neuron activity via DA D(2) autoreceptors in the rat VTA and that this inhibitory effect is mediated by the somatodendritic DA release.

Aspects on the Physiological and Biochemical Foundations of Neurocritical Care

PubMed Central

Nordström, Carl-Henrik; Koskinen, Lars-Owe; Olivecrona, Magnus

2017-01-01

Neurocritical care (NCC) is a branch of intensive care medicine characterized by specific physiological and biochemical monitoring techniques necessary for identifying cerebral adverse events and for evaluating specific therapies. Information is primarily obtained from physiological variables related to intracranial pressure (ICP) and cerebral blood flow (CBF) and from physiological and biochemical variables related to cerebral energy metabolism. Non-surgical therapies developed for treating increased ICP are based on knowledge regarding transport of water across the intact and injured blood–brain barrier (BBB) and the regulation of CBF. Brain volume is strictly controlled as the BBB permeability to crystalloids is very low restricting net transport of water across the capillary wall. Cerebral pressure autoregulation prevents changes in intracranial blood volume and intracapillary hydrostatic pressure at variations in arterial blood pressure. Information regarding cerebral oxidative metabolism is obtained from measurements of brain tissue oxygen tension (PbtO2) and biochemical data obtained from intracerebral microdialysis. As interstitial lactate/pyruvate (LP) ratio instantaneously reflects shifts in intracellular cytoplasmatic redox state, it is an important indicator of compromised cerebral oxidative metabolism. The combined information obtained from PbtO2, LP ratio, and the pattern of biochemical variables reveals whether impaired oxidative metabolism is due to insufficient perfusion (ischemia) or mitochondrial dysfunction. Intracerebral microdialysis and PbtO2 give information from a very small volume of tissue. Accordingly, clinical interpretation of the data must be based on information of the probe location in relation to focal brain damage. Attempts to evaluate global cerebral energy state from microdialysis of intraventricular fluid and from the LP ratio of the draining venous blood have recently been presented. To be of clinical relevance, the information from all monitoring techniques should be presented bedside online. Accordingly, in the future, the chemical variables obtained from microdialysis will probably be analyzed by biochemical sensors. PMID:28674514

Locomotor stimulation produced by 3,4-methylenedioxymethamphetamine (MDMA) is correlated with dialysate levels of serotonin and dopamine in rat brain

PubMed Central

Baumann, Michael H.; Clark, Robert D.; Rothman, Richard B.

2008-01-01

(±)-3,4-Methylenedioxymethamphetmine (MDMA, or Ecstasy) is an illicit drug that evokes transporter-mediated release of monoamines, including serotonin (5-HT) and dopamine (DA). Here we monitored the effects of MDMA on neurochemistry and motor activity in rats, as a means to evaluate relationships between 5-HT, DA, and behavior. Male rats undergoing in vivo microdialysis were housed in chambers equipped with photobeams for measurement of ambulation (i.e., forward locomotion) and stereotypy (i.e., head weaving and forepaw treading). Microdialysis probes were placed into the n. accumbens, striatum or prefrontal cortex in separate groups of rats. Dialysate samples were assayed for 5-HT and DA by microbore HPLC-ECD. Rats received two i.v. injections of MDMA, 1 mg/kg followed by 3 mg/kg 60 min later; neurochemical and locomotor parameters were measured concurrently. MDMA produced dose-related elevations in extracellular 5-HT and DA in all regions, with the magnitude of 5-HT release always exceeding that of DA release. MDMA-induced ambulation was positively correlated with dialysate DA levels in all regions (P<0.05-0.0001) and with dialysate 5-HT in striatum and cortex (P<0.001-0.0001). Stereotypy was strongly correlated with dialysate 5-HT in all areas (P<0.001-0.0001) and with dialysate DA in accumbens and striatum (P<0.001-0.0001). These data support previous work and suggest the complex spectrum of behaviors produced by MDMA involves 5-HT and DA in a region- and modality-specific manner. PMID:18403002

Association of brain metabolites with blood lactate and glucose levels with respect to neurological outcomes after out-of-hospital cardiac arrest: A preliminary microdialysis study.

PubMed

Hifumi, Toru; Kawakita, Kenya; Yoda, Takeshi; Okazaki, Tomoya; Kuroda, Yasuhiro

2017-01-01

Out-of-hospital cardiac arrest (OHCA) is associated with poor prognosis. Cerebral microdialysis (CMD) is an efficient sampling technique to detect neurochemical changes in brain interstitial tissue. In this retrospective study, we hypothesised that there are different CMD levels between patients with favourable and unfavourable neurological outcomes. Data of patients with OHCA admitted to Kagawa University Hospital and administered therapeutic hypothermia (TH) were collected. Using a CMD probe, extracellular glucose, lactate and pyruvate levels were measured hourly along with intracranial perfusion pressure (ICP) and cerebral perfusion pressure (CPP) for the initial 72h during TH. The lactate/pyruvate (LP) ratio was calculated. Patients were divided into favourable [Glasgow-Pittsburgh cerebral performance category 1-2 at 30days after cardiac arrest] or unfavourable neurological outcome groups. CMD biochemical markers and blood lactate and glucose levels were compared between two groups. Ten patients were included. ICP was significantly higher in the unfavourable than in the favourable neurological outcome group; there were no significant differences with respect to CPP. The CMD LP ratio in the unfavourable outcome group progressively increased; significant differences were observed on days 2, 3 and 4 (p<0.01). Significant differences in blood lactate levels were observed between the groups only on day 3.5. CMD and blood glucose levels were higher in the unfavourable than in the favourable outcome group during TH. The association of CMD levels with long-term outcomes would be better defined in a large randomised prospective study. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Differences in the neurochemical and behavioural profiles of lisdexamfetamine methylphenidate and modafinil revealed by simultaneous dual-probe microdialysis and locomotor activity measurements in freely-moving rats.

PubMed

Rowley, Helen L; Kulkarni, Rajiv S; Gosden, Jane; Brammer, Richard J; Hackett, David; Heal, David J

2014-03-01

Lisdexamfetamine dimesylate is a novel prodrug approved in North America, Europe and Brazil for treating attention deficit hyperactivity disorder (ADHD). It undergoes rate-limited hydrolysis by red blood cells to yield d-amphetamine. Following our previous work comparing lisdexamfetamine with d-amphetamine, the neurochemical and behavioural profiles of lisdexamfetamine, methylphenidate and modafinil were compared by dual-probe microdialysis in the prefrontal cortex (PFC) and striatum of conscious rats with simultaneous locomotor activity measurement. We employed pharmacologically equivalent doses of all compounds and those that spanned the therapeutically relevant and psychostimulant range. Lisdexamfetamine (0.5, 1.5, 4.5 mg/kg d-amphetamine base, per os (po)), methylphenidate (3, 10, 30 mg/kg base, po) and modafinil (100, 300, 600 mg/kg base, po) increased efflux of dopamine and noradrenaline in PFC, and dopamine in striatum. Only lisdexamfetamine increased 5-hydroxytryptamine (5-HT) efflux in PFC and striatum. Lisdexamfetamine had larger and more sustained effects on catecholaminergic neurotransmission than methylphenidate or modafinil. Linear correlations were observed between striatal dopamine efflux and locomotor activity for lisdexamfetamine and methylphenidate, but not modafinil. Regression slopes revealed greater increases in extracellular dopamine could be elicited without producing locomotor activation by lisdexamfetamine than methylphenidate. These results are consistent with clinical findings showing that lisdexamfetamine is an effective ADHD medication with prolonged duration of action and good separation between its therapeutic actions and stimulant side-effects.

Ethyl cellulose nanocarriers and nanocrystals differentially deliver dexamethasone into intact, tape-stripped or sodium lauryl sulfate-exposed ex vivo human skin - assessment by intradermal microdialysis and extraction from the different skin layers.

PubMed

Döge, Nadine; Hönzke, Stefan; Schumacher, Fabian; Balzus, Benjamin; Colombo, Miriam; Hadam, Sabrina; Rancan, Fiorenza; Blume-Peytavi, Ulrike; Schäfer-Korting, Monika; Schindler, Anke; Rühl, Eckart; Skov, Per Stahl; Church, Martin K; Hedtrich, Sarah; Kleuser, Burkhard; Bodmeier, Roland; Vogt, Annika

2016-11-28

Understanding penetration not only in intact, but also in lesional skin with impaired skin barrier function is important, in order to explore the surplus value of nanoparticle-based drug delivery for anti-inflammatory dermatotherapy. Herein, short-term ex vivo cultures of (i) intact human skin, (ii) skin pretreated with tape-strippings and (iii) skin pre-exposed to sodium lauryl sulfate (SLS) were used to assess the penetration of dexamethasone (Dex). Intradermal microdialysis was utilized for up to 24h after drug application as commercial cream, nanocrystals or ethyl cellulose nanocarriers applied at the therapeutic concentration of 0.05%, respectively. In addition, Dex was assessed in culture media and extracts from stratum corneum, epidermis and dermis after 24h, and the results were compared to those in heat-separated split skin from studies in Franz diffusion cells. Providing fast drug release, nanocrystals significantly accelerated the penetration of Dex. In contrast to the application of cream and ethyl cellulose nanocarriers, Dex was already detectable in eluates after 6h when applying nanocrystals on intact skin. Disruption of the skin barrier further accelerated and enhanced the penetration. Encapsulation in ethyl cellulose nanocarriers delayed Dex penetration. Interestingly, for all formulations highly increased concentrations in the dialysate were observed in tape-stripped skin, whereas the extent of enhancement was less in SLS-exposed skin. The results were confirmed in tissue extracts and were in line with the predictions made by in vitro release studies and ex vivo Franz diffusion cell experiments. The use of 45kDa probes further enabled the collection of inflammatory cytokines. However, the estimation of glucocorticoid efficacy by Interleukin (IL)-6 and IL-8 analysis was limited due to the trauma induced by the probe insertion. Ex vivo intradermal microdialysis combined with culture media analysis provides an effective, skin-sparing method for preclinical assessment of novel drug delivery systems at therapeutic doses in models of diseased skin. Copyright © 2016 Elsevier B.V. All rights reserved.

Tau elevations in the brain extracellular space correlate with reduced amyloid-β levels and predict adverse clinical outcomes after severe traumatic brain injury.

PubMed

Magnoni, Sandra; Esparza, Thomas J; Conte, Valeria; Carbonara, Marco; Carrabba, Giorgio; Holtzman, David M; Zipfel, Greg J; Stocchetti, Nino; Brody, David L

2012-04-01

Axonal injury is believed to be a major determinant of adverse outcomes following traumatic brain injury. However, it has been difficult to assess acutely the severity of axonal injury in human traumatic brain injury patients. We hypothesized that microdialysis-based measurements of the brain extracellular fluid levels of tau and neurofilament light chain, two low molecular weight axonal proteins, could be helpful in this regard. To test this hypothesis, 100 kDa cut-off microdialysis catheters were placed in 16 patients with severe traumatic brain injury at two neurological/neurosurgical intensive care units. Tau levels in the microdialysis samples were highest early and fell over time in all patients. Initial tau levels were >3-fold higher in patients with microdialysis catheters placed in pericontusional regions than in patients in whom catheters were placed in normal-appearing right frontal lobe tissue (P = 0.005). Tau levels and neurofilament light-chain levels were positively correlated (r = 0.6, P = 0.013). Neurofilament light-chain levels were also higher in patients with pericontusional catheters (P = 0.04). Interestingly, initial tau levels were inversely correlated with initial amyloid-β levels measured in the same samples (r = -0.87, P = 0.000023). This could be due to reduced synaptic activity in areas with substantial axonal injury, as amyloid-β release is closely coupled with synaptic activity. Importantly, high initial tau levels correlated with worse clinical outcomes, as assessed using the Glasgow Outcome Scale 6 months after injury (r = -0.6, P = 0.018). Taken together, our data add support for the hypothesis that axonal injury may be related to long-term impairments following traumatic brain injury. Microdialysis-based measurement of tau levels in the brain extracellular space may be a useful way to assess the severity of axonal injury acutely in the intensive care unit. Further studies with larger numbers of patients will be required to assess the reproducibility of these findings and to determine whether this approach provides added value when combined with clinical and radiological information.

Design and characterization of poly(dimethylsiloxane)-based valves for interfacing continuous-flow sampling to microchip electrophoresis.

PubMed

Li, Michelle W; Huynh, Bryan H; Hulvey, Matthew K; Lunte, Susan M; Martin, R Scott

2006-02-15

This work describes the fabrication and evaluation of a poly(dimethyl)siloxane (PDMS)-based device that enables the discrete injection of a sample plug from a continuous-flow stream into a microchannel for subsequent analysis by electrophoresis. Devices were fabricated by aligning valving and flow channel layers followed by plasma sealing the combined layers onto a glass plate that contained fittings for the introduction of liquid sample and nitrogen gas. The design incorporates a reduced-volume pneumatic valve that actuates (on the order of hundreds of milliseconds) to allow analyte from a continuously flowing sampling channel to be injected into a separation channel for electrophoresis. The injector design was optimized to include a pushback channel to flush away stagnant sample associated with the injector dead volume. The effect of the valve actuation time, the pushback voltage, and the sampling stream flow rate on the performance of the device was characterized. Using the optimized design and an injection frequency of 0.64 Hz showed that the injection process is reproducible (RSD of 1.77%, n = 15). Concentration change experiments using fluorescein as the analyte showed that the device could achieve a lag time as small as 14 s. Finally, to demonstrate the potential uses of this device, the microchip was coupled to a microdialysis probe to monitor a concentration change and sample a fluorescein dye mixture.

In vivo brain microdialysis: advances in neuropsychopharmacology and drug discovery.

PubMed

Darvesh, Altaf S; Carroll, Richard T; Geldenhuys, Werner J; Gudelsky, Gary A; Klein, Jochen; Meshul, Charles K; Van der Schyf, Cornelis J

2011-02-01

INTRODUCTION: Microdialysis is an important in vivo sampling technique, useful in the assay of extracellular tissue fluid. The technique has both pre-clinical and clinical applications but is most widely used in neuroscience. The in vivo microdialysis technique allows measurement of neurotransmitters such as acetycholine (ACh), the biogenic amines including dopamine (DA), norepinephrine (NE) and serotonin (5-HT), amino acids such as glutamate (Glu) and gamma aminobutyric acid (GABA), as well as the metabolites of the aforementioned neurotransmitters, and neuropeptides in neuronal extracellular fluid in discrete brain regions of laboratory animals such as rodents and non-human primates. AREAS COVERED: In this review we present a brief overview of the principles and procedures related to in vivo microdialysis and detail the use of this technique in the pre-clinical measurement of drugs designed to be used in the treatment of chemical addiction, neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) and as well as psychiatric disorders such as attention-deficit/hyperactivity disorder (ADHD) and schizophrenia. This review offers insight into the tremendous utility and versatility of this technique in pursuing neuropharmacological investigations as well its significant potential in rational drug discovery. EXPERT OPINION: In vivo microdialysis is an extremely versatile technique, routinely used in the neuropharmacological investigation of drugs used for the treatment of neurological disorders. This technique has been a boon in the elucidation of the neurochemical profile and mechanism of action of several classes of drugs especially their effects on neurotransmitter systems. The exploitation and development of this technique for drug discovery in the near future will enable investigational new drug candidates to be rapidly moved into the clinical trial stages and to market thus providing new successful therapies for neurological diseases that are currently in demand.

Hydrodynamic sample injection into short electrophoretic capillary in systems with a flow-gating interface.

PubMed

Opekar, František; Tůma, Petr

2017-01-13

An electrophoretic apparatus with a flow-gating interface has been developed, enabling hydrodynamic sequence injection of the sample into the separation capillary from the liquid flow by underpressure generated in the outlet electrophoretic vessel. The properties of the apparatus were tested on an artificial sample of an equimolar mixture of 100μM potassium and sodium ions and arginine. The repeatability of the injection of the tested ions expressed as RSD (in%) for the peak area, peak height and migration time was in the range 0.76-2.08, 0.18-0.68 and 0.28-0.48, respectively. Under optimum conditions, the apparatus was used for sequence monitoring of the reaction between the antidiabetic drug phenyl biguanide and the glycation agent methyl glyoxal. The reaction solution was continuously sampled by a microdialysis probe from a thermostated external vessel using a syringe pump at a flow rate of 3μLmin -1 and was injected into a separation capillary at certain time intervals. The electrophoretic separation progressed in a capillary with an internal diameter of 50μm with a length of 11.5cm and was monitored using a contactless conductivity detector. Copyright © 2016 Elsevier B.V. All rights reserved.

INTERSTITIAL PLASMIN ACTIVITY WITH EPSILON AMINOCAPROIC ACID: TEMPORAL AND REGIONAL HETEROGENEITY

PubMed Central

Reust, Daryl L.; Reeves, Scott T.; Abernathy, James H.; Dixon, Jennifer A.; Gaillard, William F.; Mukherjee, Rupak; Koval, Christine N.; Stroud, Robert E.; Spinale, Francis G.

2010-01-01

Background Epsilon aminocaproic acid (EACA) is used in cardiac surgery to modulate plasmin activity (PLact). The present study developed a fluorogenic-microdialysis system to measure in-vivo region specific temporal changes in PLact following EACA administration. Methods Pigs (25-35kg) received EACA (75mg/kg, n=7) or saline in which microdialysis probes were placed in the liver, myocardium, kidney and quadricep muscle. The microdialysate contained a plasmin specific fluorogenic peptide and fluorescence emission, which directly reflected PLact, determined at baseline, 30, 60, 90 and 120 minutes following EACA/vehicle infusion. Results EACA caused significant decreases in liver and quadricep PLact at 60, 90, 120 minutes and at 30, 60, 120 minutes respectively (p<0.05). In contrast, EACA induced significant biphasic changes in heart and kidney PLact profiles with initial increases followed by decreases at 90 and 120 minutes (p<0.05). The peak EACA interstitial concentrations for all compartments occurred at 30 minutes post infusion, and were 5-fold higher in the renal compartment and 4-fold higher in the myocardium, when compared to the liver or muscle (p<0.05). Conclusions Using a large animal model and in-vivo microdialysis measurements of plasmin activity, the unique findings from this study were 2-fold. First, EACA induced temporally distinct plasmin activity profiles within the plasma and interstitial compartments. Second, EACA caused region specific changes in plasmin activity profiles. These temporal and regional heterogeneic effects of EACA may have important therapeutic considerations when managing fibrinolysis in the perioperative period. PMID:20417774

Interstitial plasmin activity with epsilon aminocaproic acid: temporal and regional heterogeneity.

PubMed

Reust, Daryl L; Reeves, Scott T; Abernathy, James H; Dixon, Jennifer A; Gaillard, William F; Mukherjee, Rupak; Koval, Christine N; Stroud, Robert E; Spinale, Francis G

2010-05-01

Epsilon aminocaproic acid (EACA) is used in cardiac surgery to modulate plasmin activity (PLact). The present study developed a fluorogenic-microdialysis system to measure in vivo region specific temporal changes in PLact after EACA administration. Pigs (25 to 35 kg) received EACA (75 mg/kg, n = 7) or saline in which microdialysis probes were placed in the liver, myocardium, kidney, and quadricep muscle. The microdialysate contained a plasmin-specific fluorogenic peptide and fluorescence emission, which directly reflected PLact, determined at baseline, 30, 60, 90, and 120 minutes after EACA/vehicle infusion. Epsilon aminocaproic acid caused significant decreases in liver and quadricep PLact at 60, 90, 120 minutes, and at 30, 60, and 120 minutes, respectively (p < 0.05). In contrast, EACA induced significant biphasic changes in heart and kidney PLact profiles with initial increases followed by decreases at 90 and 120 minutes (p < 0.05). The peak EACA interstitial concentrations for all compartments occurred at 30 minutes after infusion, and were fivefold higher in the renal compartment and fourfold higher in the myocardium, when compared with the liver or muscle (p < 0.05). Using a large animal model and in vivo microdialysis measurements of plasmin activity, the unique findings from this study were twofold. First, EACA induced temporally distinct plasmin activity profiles within the plasma and interstitial compartments. Second, EACA caused region-specific changes in plasmin activity profiles. These temporal and regional heterogeneic effects of EACA may have important therapeutic considerations when managing fibrinolysis in the perioperative period. Copyright (c) 2010 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Three-dimensional printed sample load/inject valves enabling online monitoring of extracellular calcium and zinc ions in living rat brains.

PubMed

Su, Cheng-Kuan; Hsia, Sheng-Chieh; Sun, Yuh-Chang

2014-08-01

We have developed a simple and low-cost flow injection system coupled to a quadruple ICP-MS for the direct and continuous determination of multi-element in microdialysates. To interface microdialysis sampling to an inductively coupled plasma mass spectrometer (ICP-MS), we employed 3D printing to manufacture an as-designed sample load/inject valve featuring an in-valve sample loop for precise handling of microliter samples with a dissolved solids content of 0.9% NaCl (w/v). To demonstrate the practicality of our developed on-line system, we applied the 3D printed valve equipped a 5-μL sample loop to minimize the occurrence of salt matrix effects and facilitate an online dynamic monitoring of extracellular calcium and zinc ions in living rat brains. Under the practical condition (temporal resolution: 10h(-1)), dynamic profiling of these two metal ions in living rat brain extracellular fluid after probe implantation (the basal values for Ca and Zn were 12.11±0.10mg L(-1) and 1.87±0.05μg L(-1), respectively) and real-time monitoring of the physiological response to excitotoxic stress elicited upon perfusing a solution of 2.5mM N-methyl-d-aspartate were performed. Copyright © 2014 Elsevier B.V. All rights reserved.

Differential Acetylcholine Release in the Prefrontal Cortex and Hippocampus During Pavlovian Trace and Delay Conditioning

PubMed Central

Flesher, M. Melissa; Butt, Allen E.; Kinney-Hurd, Brandee L.

2011-01-01

Pavlovian trace conditioning critically depends on the medial prefrontal cortex (mPFC) and hippocampus (HPC), whereas delay conditioning does not depend on these brain structures. Given that the cholinergic basal forebrain system modulates activity in both the mPFC and HPC, it was reasoned that the level of acetylcholine (ACh) release in these regions would show distinct profiles during testing in trace and delay conditioning paradigms. To test this assumption, microdialysis probes were implanted unilaterally into the mPFC and HPC of rats that were pre-trained in appetitive trace and delay conditioning paradigms using different conditional stimuli in the two tasks. On the day of microdialysis testing, dialysate samples were collected during a quiet baseline interval before trials were initiated, and again during performance in separate blocks of trace and delay conditioning trials in each animal. ACh levels were quantified using high performance liquid chromatography and electrochemical detection techniques. Consistent with our hypothesis, results showed that ACh release in the mPFC was greater during trace conditioning than during delay conditioning. The level of ACh released during trace conditioning in the HPC was also greater than the levels observed during delay conditioning. While ACh efflux in both the mPFC and HPC selectively increased during trace conditioning, ACh levels in the mPFC during trace conditioning testing showed the greatest increases observed. These results demonstrate a dissociation in cholinergic activation of the mPFC and HPC during performance in trace but not delay appetitive conditioning, where this cholinergic activity may contribute to attentional mechanisms, adaptive response timing, or memory consolidation necessary for successful trace conditioning. PMID:21514394

Effect of local acetylcholinesterase inhibition on sweat rate in humans

NASA Technical Reports Server (NTRS)

Shibasaki, M.; Crandall, C. G.

2001-01-01

ACh is the neurotransmitter responsible for increasing sweat rate (SR) in humans. Because ACh is rapidly hydrolyzed by acetylcholinesterase (AChE), it is possible that AChE contributes to the modulation of SR. Thus the primary purpose of this project was to identify whether AChE around human sweat glands is capable of modulating SR during local application of various concentrations of ACh in vivo, as well as during a heat stress. In seven subjects, two microdialysis probes were placed in the intradermal space of the forearm. One probe was perfused with the AChE inhibitor neostigmine (10 microM); the adjacent membrane was perfused with the vehicle (Ringer solution). SR over both membranes was monitored via capacitance hygrometry during microdialysis administration of various concentrations of ACh (1 x 10(-7)-2 M) and during whole body heating. SR was significantly greater at the neostigmine-treated site than at the control site during administration of lower concentrations of ACh (1 x 10(-7)-1 x 10(-3) M, P < 0.05), but not during administration of higher concentrations of ACh (1 x 10(-2)-2 M, P > 0.05). Moreover, the core temperature threshold for the onset of sweating at the neostigmine-treated site was significantly reduced relative to that at the control site. However, no differences in SR were observed between sites after 35 min of whole body heating. These results suggest that AChE is capable of modulating SR when ACh concentrations are low to moderate (i.e., when sudomotor activity is low) but is less effective in governing SR after SR has increased substantially.

A novel microdialysis-dissolution/permeation system for testing oral dosage forms: A proof-of-concept study.

PubMed

Fong, Sophia Yui Kau; Poulsen, Jessie; Brandl, Martin; Bauer-Brandl, Annette

2017-01-01

A novel microdialysis-dissolution/permeation (M-D/P) system was developed for the biopharmaceutical assessment of oral drug formulations. This system consists of a side-by-side diffusion chamber, a microdialysis unit fixed within the dissolution chamber for continuous sampling, and a biomimetic Permeapad® as the intestinal barrier. In the M-D/P system, the concentration of the molecularly dissolved drug (with MWCO <20kDa) was measured over time in the dissolution compartment (representing the gastrointestinal tract) while the concentration of the permeated drug was measured in the acceptor compartment (representing the blood). The kinetics of both the dissolution process and the permeation process were simultaneously quantified under circumstances that mimic physiological conditions. For the current proof-of-concept study, hydrocortisone (HCS) in the form of slowly dissolving solvate crystals and buffer and the biorelevant fasted state simulated intestinal fluids (FaSSIF), were employed as the model drug and dissolution media, respectively. The applicability of the M-D/P system to dissolution and permeation profiling of HCS in buffer and in FaSSIF has been successfully demonstrated. Compared to the conventional direct sampling method (using filter of 0.1-0.45μm), sampling by the M-D/P system exhibited distinct advantages, including (1) showing minimal disturbance of the permeation process, (2) differentiating "molecularly" dissolved drugs from "apparently" dissolved drugs during dissolution of HCS in FaSSIF, and (3) being less laborious and having better sampling temporal resolution. M-D/P system appeared to be a promising, simple and routine tool that allows for the researchers' intensive comprehension of the interplay of dissolution and permeation thus helping for better oral formulation screening and as an ultimate goal, for better dosage forms assessment. Copyright © 2016. Published by Elsevier B.V.

Lactate and the Lactate-to-Pyruvate Molar Ratio Cannot Be Used as Independent Biomarkers for Monitoring Brain Energetic Metabolism: A Microdialysis Study in Patients with Traumatic Brain Injuries

PubMed Central

Sahuquillo, Juan; Merino, Maria-Angels; Sánchez-Guerrero, Angela; Arikan, Fuat; Vidal-Jorge, Marian; Martínez-Valverde, Tamara; Rey, Anna; Riveiro, Marilyn; Poca, Maria-Antonia

2014-01-01

Background For decades, lactate has been considered an excellent biomarker for oxygen limitation and therefore of organ ischemia. The aim of the present study was to evaluate the frequency of increased brain lactate levels and the LP ratio (LPR) in a cohort of patients with severe or moderate traumatic brain injury (TBI) subjected to brain microdialysis monitoring to analyze the agreement between these two biomarkers and to indicate brain energy metabolism dysfunction. Methods Forty-six patients with an admission Glasgow coma scale score of ≤13 after resuscitation admitted to a dedicated 10-bed Neurotraumatology Intensive Care Unit were included, and 5305 verified samples of good microdialysis data were analyzed. Results Lactate levels were above 2.5 mmol/L in 56.9% of the samples. The relationships between lactate and the LPR could not be adequately modeled by any linear or non-linear model. Neither Cohen’s kappa nor Gwet’s statistic showed an acceptable agreement between both biomarkers to classify the samples in regard to normal or abnormal metabolism. The dataset was divided into four patterns defined by the lactate concentrations and the LPR. A potential interpretation for these patterns is suggested and discussed. Pattern 4 (low pyruvate levels) was found in 10.7% of the samples and was characterized by a significantly low concentration of brain glucose compared with the other groups. Conclusions Our study shows that metabolic abnormalities are frequent in the macroscopically normal brain in patients with traumatic brain injuries and a very poor agreement between lactate and the LPR when classifying metabolism. The concentration of lactate in the dialysates must be interpreted while taking into consideration the LPR to distinguish between anaerobic metabolism and aerobic hyperglycolysis. PMID:25025772

Beta-phenylethylamine stimulates striatal acetylcholine release through activation of the AMPA glutamatergic pathway.

PubMed

Ishida, Kota; Murata, Mikio; Kato, Masatoshi; Utsunomiya, Iku; Hoshi, Keiko; Taguchi, Kyoji

2005-09-01

Using an in vivo intra-striatal microdialysis technique, we examined the effects of systemically administered beta-phenylethylamine (beta-PEA), a psychomotor stimulating trace amine, on striatal acetylcholine release in freely moving rats. Infusion of N-methyl-D-aspartic acid (NMDA; 10(-5) M) significantly increased acetylcholine release. In addition, locally applied amino-3-hydroxy-5-methylisozasole-4-propionic acid (AMPA; 10(-5) M) significantly increased acetylcholine release in the striatum. Intra-striatal application of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 10(-5) M), an AMPA-type glutamatergic receptor antagonist, had little effect on acetylcholine release, while application of MK-801 (10(-5) M, 10(-6) M), an NMDA-type glutamatergic receptor antagonist, significantly reduced acetylcholine release. Acetylcholine within striatal perfusate was significantly increased by intraperitoneal administration of beta-PEA in a dose-dependent manner. This increase in acetylcholine release was completely blocked by application of CNQX (10(-5) M) through the microdialysis probe into the striatum. However, increased acetylcholine response to systemic beta-PEA was unaltered by addition of MK-801 to the perfusion medium. These results suggest a regulatory function of beta-PEA, mediated by AMPA-type glutamatergic receptors, on the release of acetylcholine in the rat striatum.

Reliable long-term continuous blood glucose monitoring for patients in critical care using microdialysis and infrared spectrometry

NASA Astrophysics Data System (ADS)

Heise, H. Michael; Damm, Uwe; Kondepati, Venkata R.

2006-02-01

For clinical research, in-vivo blood glucose monitoring is an ongoing important topic to improve glycemic control in patients with non-adequate blood glucose regulation. Critically ill patients received much interest, since the intensive insulin therapy treatment, as established for diabetics, reduces mortality significantly. Despite the existence of commercially available, mainly amperometric biosensors, continued interest is in infrared spectroscopic techniques for reagent-free glucose monitoring. For stable long-term operation, avoiding also sensor recalibration, a bed-side device coupled to a micro-dialysis probe was developed for quasi-continuous glucose monitoring. Multivariate calibration is required for glucose concentration prediction due to the complex composition of dialysates from interstitial body fluid. Measurements were carried out with different test persons, each experiment lasting for more than 8 hours. Owing to low dialysis recovery rates, glucose concentrations in the dialysates were between 0.83 and 4.44 mM. Standard errors of prediction (SEP) obtained with Partial Least Squares (PLS) calibration and different cross-validation strategies were mainly between 0.13 and 0.18 mM based on either full interval data or specially selected spectral variables.

Cholinergic basal forebrain structures are not essential for mediation of the arousing action of glutamate.

PubMed

Lelkes, Zoltán; Abdurakhmanova, Shamsiiat; Porkka-Heiskanen, Tarja

2017-09-18

The cholinergic basal forebrain contributes to cortical activation and receives rich innervations from the ascending activating system. It is involved in the mediation of the arousing actions of noradrenaline and histamine. Glutamatergic stimulation in the basal forebrain results in cortical acetylcholine release and suppression of sleep. However, it is not known to what extent the cholinergic versus non-cholinergic basal forebrain projection neurones contribute to the arousing action of glutamate. To clarify this question, we administered N-methyl-D-aspartate (NMDA), a glutamate agonist, into the basal forebrain in intact rats and after destruction of the cholinergic cells in the basal forebrain with 192 immunoglobulin (Ig)G-saporin. In eight Han-Wistar rats with implanted electroencephalogram/electromyogram (EEG/EMG) electrodes and guide cannulas for microdialysis probes, 0.23 μg 192 IgG-saporin was administered into the basal forebrain, while the eight control animals received artificial cerebrospinal fluid. Two weeks later, a microdialysis probe targeted into the basal forebrain was perfused with cerebrospinal fluid on the baseline day and for 3 h with 0.3 mmNMDA on the subsequent day. Sleep-wake activity was recorded for 24 h on both days. NMDA exhibited a robust arousing effect in both the intact and the lesioned rats. Wakefulness was increased and both non-REM and REM sleep were decreased significantly during the 3-h NMDA perfusion. Destruction of the basal forebrain cholinergic neurones did not abolish the wake-enhancing action of NMDA. Thus, the cholinergic basal forebrain structures are not essential for the mediation of the arousing action of glutamate. © 2017 European Sleep Research Society.

Influx of extracellular Zn(2+) into the hippocampal CA1 neurons is required for cognitive performance via long-term potentiation.

PubMed

Takeda, A; Suzuki, M; Tempaku, M; Ohashi, K; Tamano, H

2015-09-24

Physiological significance of synaptic Zn(2+) signaling was examined in the CA1 of young rats. In vivo CA1 long-term potentiation (LTP) was induced using a recording electrode attached to a microdialysis probe and the recording region was locally perfused with artificial cerebrospinal fluid (ACSF) via the microdialysis probe. In vivo CA1 LTP was inhibited under perfusion with CaEDTA and ZnAF-2DA, extracellular and intracellular Zn(2+) chelators, respectively, suggesting that the influx of extracellular Zn(2+) is required for in vivo CA1 LTP induction. The increase in intracellular Zn(2+) was chelated with intracellular ZnAF-2 in the CA1 1h after local injection of ZnAF-2DA into the CA1, suggesting that intracellular Zn(2+) signaling induced during learning is blocked with intracellular ZnAF-2 when the learning was performed 1h after ZnAF-2DA injection. Object recognition was affected when training of object recognition test was performed 1h after ZnAF-2DA injection. These data suggest that intracellular Zn(2+) signaling in the CA1 is required for object recognition memory via LTP. Surprisingly, in vivo CA1 LTP was affected under perfusion with 0.1-1μM ZnCl2, unlike the previous data that in vitro CA1 LTP was enhanced in the presence of 1-5μM ZnCl2. The influx of extracellular Zn(2+) into CA1 pyramidal cells has bidirectional action in CA1 LTP. The present study indicates that the degree of extracellular Zn(2+) influx into CA1 neurons is critical for LTP and cognitive performance. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

Brain microdialysis as a tool to explore the ionic profile of the brain extracellular space in neurocritical patients: a methodological approach and feasibility study.

PubMed

Martínez-Valverde, Tamara; Vidal-Jorge, Marian; Montoya, Noelia; Sánchez-Guerrero, Angela; Manrique, Susana; Munar, Francisca; Pellegri, Maria-Dolors; Poca, Maria-Antonia; Sahuquillo, Juan

2015-01-01

Our aim is to determine whether the ionic concentration in brain microdialysate enables calculations of the actual Na(+), K(+), and Cl(-) concentrations in vitro and whether this method can be applied to determine the ionic concentrations in the brain extracellular fluid. We designed an experiment using CMA-71 probes (M Dialysis, Stockholm, Sweden) and the standard conditions used in a clinical setting. Nine CMA-71 probes were inserted in different matrices and perfused with mock cerebrospinal fluid containing 3% albumin at the standard infusion rate used in the clinical setting (0.3 μL/min). Microvials were replaced every 12 h, and the ionic concentrations, both in the dialysate and the matrix, were analyzed. For each ion, scatter plots were built, with [Na(+)], [K(+)], and [Cl(-)] in the dialysate as the predictor variables and the matrix concentrations as the outcome variables. A linear regression model allowed us to calculate the true ionic concentrations in the matrix. To demonstrate the feasibility of the method, we present the calculated ionic profile of one patient with a malignant infarction and a second with a severe traumatic brain injury. Our results confirm that the ionic concentration in microdialysate can be used to calculate the true concentrations of ions in a matrix and the actual concentrations in the extracellular fluid. Microdialysis offers the unique possibility of monitoring the dynamic changes of ions in the brain over time and opens a new avenue to explore the brain's ionic profile, its changes in brain edema, and how this profile can be modified with different therapies.

In vivo microdialysis for the evaluation of transfersomes as a novel transdermal delivery vehicle for cinnamic acid.

PubMed

Zhang, Yong-Tai; Xu, Yue-Ming; Zhang, Su-Juan; Zhao, Ji-Hui; Wang, Zhi; Xu, Ding-Qin; Feng, Nian-Ping

2014-03-01

In this study, cinnamic acid-loaded transfersomes were prepared and dermal microdialysis sampling was used in Sprague-Dawley rats to compare the amount of drug released into the skin using transfersomes as transdermal carriers with that released on using conventional liposomes. The formulation of cinnamic acid-loaded transfersomes was optimized by a uniform design through in vitro transdermal permeation studies. Hydration time was confirmed as a significant factor influencing the entrapment efficiency of transfersomes, further affecting their transdermal flux in vitro. The fluxes of cinnamic acid from transfersomes were all higher than those from conventional liposomes, and the flux from the optimal transfersome formulation was 3.01-fold higher than that from the conventional liposomes (p < 0.05). An in vivo microdialysis sampling method revealed that the dermal drug concentrations from transfersomes applied on various skin regions were much lower than those required with conventional liposomes. After the administration of drug-containing transfersomes and liposomes on abdominal skin regions of rats for a period of 10 h, the Cmax of cinnamic acid from the compared liposomes was 3.21 ± 0.25 μg/mL and that from the transfersomes was merely 0.59 ± 0.02 μg/mL. The results suggest that transfersomes can be used as carriers to enhance the transdermal delivery of cinnamic acid, and that these vehicles may penetrate the skin in the complete form, given their significant deformability.

[Amino acid changes following intraperitoneal administration of Tityus zulianus scorpion venom in mice. Study with subcutaneous microdialysis and capillary electrophoresis].

PubMed

Páez, Ximena; Mazzei-Dávila, Carmen Amalia; Quiñonez, Belkis; D'Suze, Gina; Hernández, Luis

2003-12-01

Scorpion human envenoming is a public health hazard in the southwest of Venezuela. Tityus zulianus is one of the scorpion species whose venom causes lung edema and cardiac failure in children. These occasionally deadly manifestations have been attributed to a massive sympathetic discharge. The intraperitoneal administration of T. zulianus venom (20 micrograms/g mouse) to anesthetized mice during subcutaneous microdialysis caused increased secretions, dyspnea, seizures and death between 30 min to 2 h. Seven amino acids were analyzed by capillary electrophoresis with laser induced fluorescence detection (CE-LIFD) in the collected samples before and after the venom administration. We found an increase of arginine (39%), phenylalanine (40%) and glutamate (94%), with no changes in valine, serine and aspartate, changes were significant when the injection of venom and vehicle were compared and before vs after venom injection. Further investigation is needed to know if the observed changes could be related to the molecular mechanisms of the venom or some of its components and therefore with the envenoming symptoms. To our knowledge, this is the first report with subcutaneous microdialysis and CE-LIFD coupling in scorpion envenomation studies in vivo, in mice.

Lack of utility of arteriojugular venous differences of lactate as a reliable indicator of increased brain anaerobic metabolism in traumatic brain injury.

PubMed

Poca, Maria A; Sahuquillo, Juan; Vilalta, Anna; Garnacho, Angel

2007-04-01

Ischemic lesions are highly prevalent in patients with traumatic brain injuries (TBIs) and are the single most important cause of secondary brain damage. The prevention and early treatment of these lesions is the primary aim in the modem treatment of these patients. One of the most widely used monitoring techniques at the bedside is quantification of brain extracellular level of lactate by using arteriojugular venous differences of lactate (AVDL). The purpose of this study was to determine the sensitivity, specificity, and predictive value of AVDL as an indicator of increases in brain lactate production in patients with TBIs. Arteriojugular venous differences of lactate were calculated every 6 hours using samples obtained though a catheter placed in the jugular bulb in 45 patients with diffuse head injuries (57.8%) or evacuated brain lesions (42.2%). Cerebral lactate concentration obtained with a 20-kD microdialysis catheter implanted in undamaged tissue was used as the de facto gold standard. Six hundred seventy-three AVDL determinations and cerebral microdialysis samples were obtained simultaneously; 543 microdialysis samples (81%) showed lactate values greater than 2 mmol/L, but only 21 AVDL determinations (3.1%) showed an increase in brain lactate. No correlation was found between AVDL and cerebral lactate concentration (p = 0.014, p = 0.719). Arteriojugular venous differences of lactate had a sensitivity and specificity of 3.3 and 97.7%, respectively, with a false-negative rate of 96.7% and a false-positive rate of 2.3%. Arteriojugular venous differences of lactate do not reliably reflect increased cerebral lactate production and consequently are not reliable in ruling out brain ischemia in patients with TBIs. The clinical use of this monitoring method in neurocritical care should be reconsidered.

Biodegradable nanoparticles for improved kidney bioavailability of rhein: preparation, characterization, plasma, and kidney pharmacokinetics.

PubMed

Wei, Yinghui; Luo, Xiaoting; Guan, Jiani; Ma, Jianping; Zhong, Yicong; Luo, Jingwen; Li, Fanzhu

2017-11-01

The aim of this work is to develop biodegradable nanoparticles for improved kidney bioavailability of rhein (RH). RH-loaded nanoparticles were prepared using an emulsification solvent evaporation method and fully characterized by several techniques. Kidney pharmacokinetics was assessed by implanting a microdialysis probe in rat's kidney cortex. Blood samples were simultaneously collected (via femoral artery) for assessing plasma pharmacokinetics. Optimized nanoparticles were small, with a mean particle size of 132.6 ± 5.95 nm, and homogeneously dispersed. The charge on the particles was nearly zero, the encapsulation efficiency was 62.71 ± 3.02%, and the drug loading was 1.56 ± 0.15%. In vitro release of RH from the nanoparticles showed an initial burst release followed by a sustained release. Plasma and kidney pharmacokinetics showed that encapsulation of RH into nanoparticles significantly increased its kidney bioavailability (AUC kidney /AUC plasma  = 0.586 ± 0.072), clearly indicating that nanoparticles are a promising strategy for kidney drug delivery.

LC–MS/MS determination of carbamathione in microdialysis samples from rat brain and plasma

PubMed Central

Kaul, Swetha; Williams, Todd D.; Lunte, Craig E.; Faiman, Morris D.

2009-01-01

A selective liquid chromatography–tandem mass spectrometric (LC–MS/MS) method was developed for the determination of S-(N, N-diethylcarbamoyl) glutathione (carbamathione) in microdialysis samples from rat brain and plasma. S-(N, N-Diethylcarbamoyl) glutathione (carbamathione) is a metabolite of disulfiram. This metabolite may be responsible for disulfiram’s effectiveness in the treatment of cocaine dependence. An analytical method using liquid chromatography–tandem mass spectrometric (LC–MS/MS) was developed to determine carbamathione in vivo using microdialysis sampling from rat brain and plasma. Chromatographic separations were carried out on an Alltech Altima C-18 (50 mm long × 2.1 mm i.d., 3 μm particles) analytical column at a flow rate of 0.3 ml/min. Solvent A consisted of 10 mM ammonium formate, methanol, and formic acid (99:1:0.06, v/v/v). Solvent B consisted of methanol, 10 mM ammonium formate and formic acid (99:1:0.06, v/v/v). A 20 min linear gradient from 95% aqueous to 95% organic was used. Tandem mass spectra were acquired on a Micromass Quattro Ultima “triple” quadrupole mass spectrometer equipped with an ESI interface. Quantitative mass spectrometric analysis was conducted in positive ion mode selected reaction monitoring (SRM) mode looking at the transition of m/z 407–100 and 175 for carbamathione and m/z 392–263 for the internal standard S-hexyl glutathione. The simultaneous collection of microdialysate from blood and brain was used to monitor carbamathione concentrations centrally and peripherally. Good linearity was obtained over a concentration range of 0.25–10,000 nM. The lowest limit of quantification (LLOQ) was determined to be 1 nM and the lowest limit of detection (LLOD) was calculated to be 0.25 nM. Intra- and inter-day accuracy and precision were determined and for all the samples evaluated, the variability was less that 10% (R.S.D.). PMID:19709836

Amphetamine regulation of mesolimbic dopamine/cholecystokinin neurotransmission.

PubMed

Hurd, Y L; Lindefors, N; Brodin, E; Brené, S; Persson, H; Ungerstedt, U; Hökfelt, T

1992-04-24

The effects of acute and repeated amphetamine administration on mesolimbic dopamine (DA) neurons was assessed by studying DA and cholecystokinin (CCK) release in the nucleus accumbens (Acc), as well as effects on mRNA genes regulating DA and CCK synthesis in ventral tegmental area (VTA) cells in rats. Amphetamine (1.5 mg/kg) markedly increased extracellular levels of DA in the medial Acc (assessed by in vivo microdialysis) in drug-naive animals, about twice the amount released in animals repeatedly administered the drug for the previous 7 days (twice daily). CCK overflow was found to mirror the DA responses in that the very transient elevation of CCK monitored in drug-naive animals was attenuated in those with prior amphetamine use. The attenuation of both DA and CCK overflow in the medial Acc was found to be associated with a decrease in the number of CCK mRNA-positive VTA neurons (assessed by in situ hybridization histochemistry). Although the number of cells expressing CCK mRNA were decreased, the gene expression in those positive CCK and tyrosine hydroxylase mRNA cells in the VTA was significantly increased. The CCK mRNA neurons in the VTA were positively identified as those projecting to the medial Acc by the local perfusion of Fluoro-gold retrograde tracer via microdialysis probes located in the Acc.

Minimally invasive monitoring of skeletal muscle hypermetabolism induced by the phosphodiesterase-III-inhibitor milrinone and sodium fluoride.

PubMed

Schuster, Frank; Johannsen, Stephan; Roewer, Norbert; Anetseder, Martin

2013-04-01

We hypothesized that the phosphodiesterase-III-inhibitor milrinone and the non-specific G-protein activator sodium fluoride increase the skeletal muscular lactate levels as a sign of a hypermetabolic response. With approval of the local animal care committee Sprague-Dawley rats were killed and artificially perfused either with Ringer's solution or sodium fluoride 110 mM, while milrinone 1.32 mM or Ringer's solution at 1 μl/min was applied via microdialysis probes in both hind limbs. Lactate was measured spectrophotometrically in the dialysate. Baseline lactate levels before drug application did not differ between hind limbs. Local infusion of milrinone via microdialysis did not significantly increase intramuscular lactate concentrations compared with the Ringer control group. Muscular perfusion with sodium fluoride resulted in a significant increase of lactate and was potentiated by combination with local milrinone. Phosphodiesterase-III-inhibition alone does not significantly influence the lactate levels in skeletal muscle of sacrificed rats. Sodium fluoride infusion leads to an intramuscular lactate increase, which was further potentiated by local inhibition of phosphodiesterase-III. The fluoride-mediated hypermetabolic response following sodium fluoride could be a possible explanation for the observed myotoxic adverse effects in individuals treated by fluoride-containing agents. © 2012 The Authors. JPP © 2012. Royal Pharmaceutical Society.

P-glycoprotein and multidrug resistance-associated protein are involved in the regulation of extracellular levels of the major antiepileptic drug carbamazepine in the brain.

PubMed

Potschka, H; Fedrowitz, M; Löscher, W

2001-11-16

Despite considerable advances in the pharmacotherapy of epilepsy, about 30% of epileptic patients are refractory to antiepileptic drugs (AEDs). In most cases, a patient who is resistant to one major AED is also refractory to other AEDs, although these drugs act by different mechanisms. The mechanisms that lead to drug resistance in epilepsy are not known. Recently, over-expression of multidrug transporters, such as P-glycoprotein (PGP) and multidrug resistance-associated protein (MRP), has been reported in surgically resected epileptogenic human brain tissue and suggested to contribute to the drug resistance of epilepsy. However, it is not known to what extent multidrug transporters such as PGP or MRP are involved in transport of AEDs. In the present study, we used in vivo microdialysis in rats to study whether the concentration of carbamazepine in the extracellular fluid of the cerebral cortex can be enhanced by inhibition of PGP or MRP, using the PGP inhibitor verapamil and the MRP inhibitor probenecid. Local perfusion with verapamil or probenecid via the microdialysis probe increased the extracellular concentration of carbamazepine. The data indicate that both PGP and MRP participate in the regulation of extracellular brain concentrations of the major AED carbamazepine.

Cholinesterase inhibition and acetylcholine accumulation following intracerebral administration of paraoxon in rats

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

Ray, A.; Liu, J.; Karanth, S.

2009-05-01

We evaluated the inhibition of striatal cholinesterase activity following intracerebral administration of paraoxon assaying activity either in tissue homogenates ex vivo or by substrate hydrolysis in situ. Artificial cerebrospinal fluid (aCSF) or paraoxon in aCSF was infused unilaterally (0.5 {mu}l/min for 2 h) and ipsilateral and contralateral striata were harvested for ChE assay ex vivo. High paraoxon concentrations were needed to inhibit ipsilateral striatal cholinesterase activity (no inhibition at < 0.1 mM; 27% at 0.1 mM; 79% at 1 mM paraoxon). With 3 mM paraoxon infusion, substantial ChE inhibition was also noted in contralateral striatum. ChE histochemistry generally confirmed thesemore » concentration- and side-dependent effects. Microdialysates collected for up to 4 h after paraoxon infusion inhibited ChE activity when added to striatal homogenate, suggesting prolonged efflux of paraoxon. Since paraoxon efflux could complicate acetylcholine analysis, we evaluated the effects of paraoxon (0, 0.03, 0.1, 1, 10 or 100 {mu}M, 1.5 {mu}l/min for 45 min) administered by reverse dialysis through a microdialysis probe. ChE activity was then monitored in situ by perfusing the colorimetric substrate acetylthiocholine through the same probe and measuring product (thiocholine) in dialysates. Concentration-dependent inhibition was noted but reached a plateau of about 70% at 1 {mu}M and higher concentrations. Striatal acetylcholine was below the detection limit at all times with 0.1 {mu}M paraoxon but was transiently elevated (0.5-1.5 h) with 10 {mu}M paraoxon. In vivo paraoxon (0.4 mg/kg, sc) in adult rats elicited about 90% striatal ChE inhibition measured ex vivo, but only about 10% inhibition measured in situ. Histochemical analyses revealed intense AChE and glial fibrillary acidic protein staining near the cannula track, suggesting proliferation of inflammatory cells/glia. The findings suggest that ex vivo and in situ cholinesterase assays can provide very different views into enzyme-inhibitor interactions. Furthermore, the proliferation/migration of cells containing high amounts of cholinesterase just adjacent to a dialysis probe could affect the recovery and thus detection of extracellular acetylcholine in microdialysis studies.« less

Monitoring vigabatrin in head injury patients by cerebral microdialysis: obtaining pharmacokinetic measurements in a neurocritical care setting

PubMed Central

Shannon, Richard J; Timofeev, Ivan; Nortje, Jürgens; Hutchinson, Peter J; Carpenter, Keri L H

2014-01-01

Aims The aims were to determine blood–brain barrier penetration and brain extracellular pharmacokinetics for the anticonvulsant vigabatrin (VGB; γ-vinyl-γ-aminobutyric acid) in brain extracellular fluid and plasma from severe traumatic brain injury (TBI) patients, and to measure the response of γ-aminobutyric acid (GABA) concentration in brain extracellular fluid. Methods Severe TBI patients (n = 10) received VGB (0.5 g enterally, every 12 h). Each patient had a cerebral microdialysis catheter; two patients had a second catheter in a different region of the brain. Plasma samples were collected 0.5 h before and 2, 4 and 11.5 h after the first VGB dose. Cerebral microdialysis commenced before the first VGB dose and continued through at least three doses of VGB. Controls were seven severe TBI patients with microdialysis, without VGB. Results After the first VGB dose, the maximum concentration of VGB (Cmax) was 31.7 (26.9–42.6) μmol l−1 (median and interquartile range for eight patients) in plasma and 2.41 (2.03–5.94) μmol l−1 in brain microdialysates (nine patients, 11 catheters), without significant plasma–brain correlation. After three doses, median Cmax in microdialysates increased to 5.22 (4.24–7.14) μmol l−1 (eight patients, 10 catheters). Microdialysate VGB concentrations were higher close to focal lesions than in distant sites. Microdialysate GABA concentrations increased modestly in some of the patients after VGB administration. Conclusions Vigabatrin, given enterally to severe TBI patients, crosses the blood–brain barrier into the brain extracellular fluid, where it accumulates with multiple dosing. Pharmacokinetics suggest delayed uptake from the blood. PMID:24802902

Neurotransmitters and pathophysiology of stroke: evidence for the release of glutamate and other transmitters/mediators in animals and humans.

PubMed

Dávalos, A; Shuaib, A; Wahlgren, N G

2000-11-01

There is convincing evidence from animal models of stroke that ischemia leads to an increase in the extracellular concentrations of excitatory amino acids (EAAs), especially glutamate. This accumulation of glutamate, which can reach up to 80 times normal at the centre of an ischemic lesion, is believed to be an important factor for the premature death of neurons that would otherwise survive the ischemic conditions and recover when flow is restored. In the technique of microdialysis, a small probe is inserted into the brain tissue. Fluid passing through the probe is separated from the brain parenchyma by a semipermeable membrane, through which substances released into the brain can diffuse. Analysis of the dialysate allows the nature and time course of release of substances, such as glutamate, to be determined. This technique has been used in patients undergoing resection of cerebral tumors, surgery for epilepsy, head trauma, subarachnoid hemorrhage, and cerebral infarction. Clamping or ligating the blood supply to the lobe about to be excised leads to a rapid accumulation in the dialysate of, among other substances, glutamate. Similar findings have been obtained during lobar resection for the treatment of severe epilepsy. Accumulations of glutamate to approximately 100 times the basal concentration have been found. There are also a few reports of microdialysis being performed in patients undergoing lobectomy after severe strokes or extracranial-intracranial bypass surgery. Again, high concentrations of glutamate have been reported. Another approach is to examine the blood and cerebrospinal fluid (CSF) for traces of EAAs. High concentrations of glutamate have been found in the blood and CSF within 24 hours of the onset of stroke. In animal models, plasma concentrations of glutamate begin to rise some 4 to 6 hours after middle cerebral artery (MCA) occlusions, reaching a peak at about 8 to 24 hours. Similarly, when glutamate is injected into the CSF of rats, there is a lag of approximately 4 hours before the concentration of glutamate in the blood rises. Therefore, it may be possible to detect the ongoing release of glutamate into the brain as a result of cerebral ischemia, which may aid in the selection of the most appropriate treatment. The results of microdialysis and plasma EAA analyses suggest that excitotoxic damage can occur over many hours. This implies that effective neuroprotectant strategies could provide clinical benefits over similarly prolonged periods.

An in situ method to quantitatively determine dissolved free drug concentrations in vitro in the presence of polymer excipients using pulsatile microdialysis (PMD).

PubMed

Vejani, Charchil; Bellantone, Robert A

2015-12-30

In drug formulations containing polymer excipients, the effects of the polymer on the dissolved free drug concentration and resulting dissolution or release can be important, especially for poorly soluble drugs. In this study, an in vitro method based on pulsatile microdialysis (PMD) was developed to quantitatively determine dissolved free concentrations of drugs in the presence of polymers in aqueous media in situ (e.g., in place within the system being characterized). Formulations were made by dissolving various ratios of the drug griseofulvin and polymer PVP K30 in water and allowing the mix to equilibrate. A PMD probe was immersed in each mixture and the dissolved free drug concentrations were determined in the PMD samples. The experimental procedure and the equations used for data analysis are presented. To assess the consistency of data, a binding model was fit to the data obtained using PMD by calculating the dissolved free drug fraction fD for each drug-polymer ratio in solution, and obtaining the product of the binding stoichiometry and binding constant (νK per mole of polymer) from the slope of a plot of (1-fD)/fD vs. the molar polymer concentration. For comparison, equilibrium binding experiments were also performed at 23C, and the determined value of νK was similar to the value found using PMD. Experiments were performed at three temperatures, and a plot of ln (νK) vs. 1/T was linear and a binding enthalpy of -110.9±4.4J/mol of monomer was calculated from its slope. It was concluded that PMD can be used to determine the dissolved free drug concentrations in situ, which allows characterization of the drug-polymer interaction, even for low drug concentrations. This information may be important in modeling the dissolution or release of drugs from formulations containing polymers. Copyright © 2015 Elsevier B.V. All rights reserved.

Ocular silicon distribution and clearance following intravitreal injection of porous silicon microparticles

PubMed Central

Nieto, Alejandra; Hou, Huiyuan; Sailor, Michael J.; Freeman, William R.; Cheng, Lingyun

2013-01-01

Porous silicon (pSi) microparticles have been investigated for intravitreal drug delivery and demonstrated good biocompatibility. With the appropriate surface chemistry, pSi can reside in vitreous for months or longer. However, ocular distribution and clearance pathway of its degradation product, silicic acid, are not well understood. In the current study, rabbit ocular tissue was collected at different time point following fresh pSi (day 1, 5, 9, 16, and 21) or oxidized pSi (day 3, 7, 14, 21, and 35) intravitreal injection. In addition, dual-probe simultaneous microdialysis of aqueous and vitreous humor was performed following a bolus intravitreal injection of 0.25 mL silicic acid (150 μg/mL) and six consecutive microdialysates were collected every 20 min. Silicon was quantified from the samples using inductively coupled plasma-optical emission spectroscopy. The study showed that following the intravitreal injection of oxidized pSi, free silicon was consistently higher in the aqueous than in the retina (8.1 ± 6.5 vs. 3.4 ± 3.9 μg/mL, p = 0.0031). The area under the concentration-time curve (AUC) of the retina was only about 24% that of the aqueous. The mean residence time was 16 days for aqueous, 13 days for vitreous, 6 days for retina, and 18 days for plasma. Similarly, following intravitreal fresh pSi, free silicon was also found higher in aqueous than in retina (7 ± 4.7 vs. 3.4 ± 4.1 μg/mL, p = 0.014). The AUC for the retina was about 50% of the AUC for the aqueous. The microdialysis revealed the terminal half-life of free silicon in the aqueous was 30 min and 92 min in the vitreous; the AUC for aqueous accounted for 38% of the AUC for vitreous. Our studies indicate that aqueous humor is a significant pathway for silicon egress from the eye following intravitreal injection of pSi crystals. PMID:24036388

Alpha3beta4 nicotinic acetylcholine receptors in the medial habenula modulate the mesolimbic dopaminergic response to acute nicotine in vivo

PubMed Central

McCallum, Sarah E.; Cowe, Matthew A.; Lewis, Samuel W.; Glick, Stanley D.

2012-01-01

Habenulo-interpeduncular nicotinic receptors, particularly those containing α3, β4 and α5 subunits, have recently been implicated in the reinforcing effects of nicotine. Our laboratory has shown that injection of α3β4 nicotinic receptor antagonists into the medial habenula (MHb) decreases self-administration of multiple abused drugs, including nicotine (Glick et al., 2006; 2008; 2011). However, it is unclear whether blockade of MHb nicotinic receptors has a direct effect on mesolimbic dopamine. Here, we performed in vivo microdialysis in female rats. Microdialysis probes were implanted into the nucleus accumbens (NAcc) and α3β4 nicotinic receptor antagonists (18-methoxycoronaridine; 18-MC or α-conotoxin AuIB; AuIB), were injected into the ipsilateral MHb, just prior to systemic nicotine (0.4 mg/kg, s.c.). Dialysate samples were collected before and after drug administration and levels of extracellular dopamine and its metabolites were measured using HPLC. Acute nicotine administration increased levels of extracellular dopamine and its metabolites in the NAcc. Pre-treatment with intra-habenular AuIB or 18-MC prevented nicotine-induced increases in accumbal dopamine. Neither drug had an effect on nicotine-induced increases in dopamine metabolites, suggesting that α3β4 receptors do not play a role in dopamine metabolism. The effect of intra-habenular blockade of α3β4 receptors on NAcc dopamine was selective for acute nicotine: neither AuIB nor 18-MC prevented increases in NAcc dopamine stimulated by acute d-amphetamine or morphine. These results suggest the mesolimbic response to acute nicotine, but not to acute administration of other drugs of abuse, is directly modulated by α3β4 nicotinic receptors in the MHb, and emphasize a critical role for habenular nicotinic receptors in nicotine’s reinforcing effects. PMID:22561751

Relationships among the behavioral, noradrenergic, and pituitary–adrenal responses to interleukin-1 and the effects of indomethacin

PubMed Central

Wieczorek, Marek; Dunn, Adrian J.

2007-01-01

Peripheral administration of interleukin-1 (IL-1) is known to activate the hypothalamo–pituitary–adrenal axis (HPA axis) and brain noradrenergic systems. We studied the relationship between these responses using in vivo microdialysis to assess the release of hypothalamic norepinephrine (NE), while simultaneously sampling blood for ACTH and corticosterone, and monitoring body temperature and behavior in freely moving rats. Rats were implanted with microdialysis probes in the medial hypothalamus, with intravenous catheters, and with telethermometers in the abdomen. Each rat was injected with saline and IL-1β (1 μg ip) in random order, monitoring microdialysate NE, body temperature and plasma ACTH and corticosterone for 2–4 h after injection. Saline injections were followed by transient increases in microdialysate NE and in plasma ACTH and corticosterone. IL-1β injections resulted in prolonged elevations of microdialysate NE, as well as plasma ACTH and corticosterone, and body temperature. IL-1β also induced shivering and a prolonged depression of locomotor activity. Pretreatment with indomethacin (10 mg/kg sc) prevented the IL-1β-induced increases in body temperature and the apparent increase in hypothalamic NE release, but only attenuated the IL-1β-induced shivering and the increase in plasma ACTH. The results indicate a close temporal relationship between the release of NE and HPA axis activation. Such a relationship is also supported by the similar effects of indomethacin pretreatment on NE and ACTH. The shivering is likely involved in the increase in body temperature, but indomethacin only attenuated the shivering while it blocked the fever. However, the effects of indomethacin clearly indicate that neither the increase in body temperature nor the increase in hypothalamic NE release was essential for HPA axis activation. These results suggest that hypothalamic NE is involved in the IL-1-induced HPA axis activation, but that this is not the only mechanism by which the HPA axis is activated by intraperitoneally injected IL-1. PMID:16330180

IL-15 concentrations in skeletal muscle and subcutaneous adipose tissue in lean and obese humans: local effects of IL-15 on adipose tissue lipolysis

PubMed Central

Pierce, Joseph R.; Maples, Jill M.

2015-01-01

Animal/cell investigations indicate that there is a decreased adipose tissue mass resulting from skeletal muscle (SkM) IL-15 secretion (e.g., SkM-blood-adipose tissue axis). IL-15 could regulate fat mass accumulation in obesity via lipolysis, although this has not been investigated in humans. Therefore, the purpose was to examine whether SkM and/or subcutaneous adipose tissue (SCAT) IL-15 concentrations were correlated with SCAT lipolysis in lean and obese humans and determine whether IL-15 perfusion could induce lipolysis in human SCAT. Local SkM and abdominal SCAT IL-15 (microdialysis) and circulating IL-15 (blood) were sampled in lean (BMI: 23.1 ± 1.9 kg/m2; n = 10) and obese (BMI: 34.7 ± 3.5 kg/m2; n = 10) subjects at rest/during 1-h cycling exercise. Lipolysis (SCAT interstitial glycerol concentration) was compared against local/systemic IL-15. An additional probe in SCAT was perfused with IL-15 to assess direct lipolytic responses. SkM IL-15 was not different between lean and obese subjects (P = 0.45), whereas SCAT IL-15 was higher in obese vs. lean subjects (P = 0.02) and was correlated with SCAT lipolysis (r = 0.45, P = 0.05). Exercise increased SCAT lipolysis in lean and obese (P < 0.01), but exercise-induced SCAT lipolysis changes were not correlated with exercise-induced SCAT IL-15 changes. Microdialysis perfusion resulting in physiological IL-15 concentrations in the adipose tissue interstitium increased lipolysis in lean (P = 0.04) but suppressed lipolysis in obese (P < 0.01). Although we found no support for a human IL-15 SkM-blood-adipose tissue axis, IL-15 may be produced in/act on the abdominal SCAT depot. The extent to which this autocrine/paracrine IL-15 action regulates human body composition remains unknown. PMID:25921578

Relationships among the behavioral, noradrenergic, and pituitary-adrenal responses to interleukin-1 and the effects of indomethacin.

PubMed

Wieczorek, Marek; Dunn, Adrian J

2006-09-01

Peripheral administration of interleukin-1 (IL-1) is known to activate the hypothalamo-pituitary-adrenal axis (HPA axis) and brain noradrenergic systems. We studied the relationship between these responses using in vivo microdialysis to assess the release of hypothalamic norepinephrine (NE), while simultaneously sampling blood for ACTH and corticosterone, and monitoring body temperature and behavior in freely moving rats. Rats were implanted with microdialysis probes in the medial hypothalamus, with intravenous catheters, and with telethermometers in the abdomen. Each rat was injected with saline and IL-1beta (1 microg ip) in random order, monitoring microdialysate NE, body temperature and plasma ACTH and corticosterone for 2-4 h after injection. Saline injections were followed by transient increases in microdialysate NE and in plasma ACTH and corticosterone. IL-1beta injections resulted in prolonged elevations of microdialysate NE, as well as plasma ACTH and corticosterone, and body temperature. IL-1beta also induced shivering and a prolonged depression of locomotor activity. Pretreatment with indomethacin (10 mg/kg sc) prevented the IL-1beta-induced increases in body temperature and the apparent increase in hypothalamic NE release, but only attenuated the IL-1beta-induced shivering and the increase in plasma ACTH. The results indicate a close temporal relationship between the release of NE and HPA axis activation. Such a relationship is also supported by the similar effects of indomethacin pretreatment on NE and ACTH. The shivering is likely involved in the increase in body temperature, but indomethacin only attenuated the shivering while it blocked the fever. However, the effects of indomethacin clearly indicate that neither the increase in body temperature nor the increase in hypothalamic NE release was essential for HPA axis activation. These results suggest that hypothalamic NE is involved in the IL-1-induced HPA axis activation, but that this is not the only mechanism by which the HPA axis is activated by intraperitoneally injected IL-1.

The Brain In Vivo Expresses the 2′,3′-cAMP-Adenosine Pathway

PubMed Central

Verrier, Jonathan D.; Jackson, Travis C.; Bansal, Rashmi; Kochanek, Patrick M.; Puccio, Ava M.; Okonkwo, David O.; Jackson, Edwin K.

2012-01-01

Although multiple biochemical pathways produce adenosine, studies suggest that the 2′,3′-cAMP-adenosine pathway (2′,3′-cAMP → 2′-AMP/3′-AMP → adenosine) contributes to adenosine production in some cells/tissues/organs. To determine whether the 2′,3′-cAMP-adenosine pathway exists in vivo in the brain, we delivered to the brain (gray matter and white matter separately) via the inflow perfusate of a microdialysis probe either 2′,3′-cAMP, 3′,5′-cAMP, 2′-AMP, 3′-AMP, or 5′-AMP and measured the recovered metabolites in the microdialysis outflow perfusate with mass spectrometry. In both gray and white matter, 2′,3′-cAMP increased 2′-AMP, 3′-AMP and adenosine, and 3′,5′-cAMP increased 5′-AMP and adenosine. In both brain regions, 2′-AMP, 3-AMP and 5′-AMP were converted to adenosine. Microdialysis experiments in 2′,3′-cyclic nucleotide-3′-phosphodiesterase (CNPase) wild-type mice demonstrated that traumatic brain injury (TBI; controlled cortical impact model) activated the brain 2,3′-cAMP-adenosine pathway; similar experiments in CNPase knockout mice indicated that CNPase was involved in the metabolism of endogenous 2′,3′-cAMP to 2′-AMP and to adenosine. In CSF from TBI patients, 2′,3′-cAMP was significantly increased in the initial 12 hours after injury and strongly correlated with CSF levels of 2′-AMP, 3′-AMP, adenosine and inosine. We conclude that in vivo, 2′,3′-cAMP is converted to 2′-AMP/3′-AMP, and these AMPs are metabolized to adenosine. This pathway exists endogenously in both mice and humans. PMID:22360621

Use of Subcutaneous and Intraperitoneal Administration Methods to Facilitate Cassette Dosing in Microdialysis Studies in Rats.

PubMed

Durk, Matthew R; Deshmukh, Gauri; Valle, Nicole; Ding, Xiao; Liederer, Bianca M; Liu, Xingrong

2018-07-01

Microdialysis is a powerful technique allowing for real-time measurement of unbound drug concentrations in brain interstitial fluid in conscious animals. Use of microdialysis in drug discovery is limited by high resource requirement and low throughput, but this may be improved by cassette dosing. Administering multiple compounds intravenously of diverse physiochemical properties, it is often very challenging and time consuming to identify a vehicle that can dissolve all of the compounds. To overcome this limitation, the present study explores the possibility of administering a cassette dose of nine diverse compounds (carbamazepine, citalopram, desmethylclozapine, diphenhydramine, gabapentin, metoclopramide, naltrexone, quinidine, and risperidone) in suspension, rather than in solution, by intraperitoneal and subcutaneous routes, and determining if this is a viable option for assessing blood-brain barrier penetration in microdialysis studies. Repeated hourly subcutaneous dosing during the 6-hour microdialysis study allowed for the best attainment of distributional equilibrium between brain and plasma, resulting in less than a 2-fold difference in the unbound brain to unbound plasma concentration ratio for the cassette dosing method versus discrete dosing. Both subcutaneous and intraperitoneal repeated dosing can provide a more practical substitute for intravenous dosing in determining brain penetration of a cassette of diverse compounds in brain microdialysis studies. The results from the present study demonstrate that dosing compounds in suspension represents a practical approach to eliminating the technical challenge and labor-intensive step of preparation of solutions of a mixture of compounds and will enable the use of the cassette brain microdialysis method in a central nervous system drug discovery setting. Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics.

In Vivo Microdialysis and Electroencephalographic Activity in Freely Moving Guinea Pigs Exposed to Organophosphorus Nerve Agents Sarin and VX: Analysis of Acetylcholine and Glutamate

DTIC Science & Technology

2011-01-01

3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE In vivo microdialysis and electroencephalographic activity in freely moving guinea pigs 5a...microdialysis and electroencephalographic activity in freely moving guinea pigs exposed to organophosphorus nerve agents sarin and VX: analysis of...brain seizure activity . This robust double multi- variate design provides greater fidelity when comparing data while also reducing the required number

Acetylcholine Release in the Hippocampus and Striatum during Place and Response Training

ERIC Educational Resources Information Center

Pych, Jason C.; Chang, Qing; Colon-Rivera, Cynthia; Haag, Renee; Gold, Paul E.

2005-01-01

These experiments examined the release of acetylcholine in the hippocampus and striatum when rats were trained, within single sessions, on place or response versions of food-rewarded mazes. Microdialysis samples of extra-cellular fluid were collected from the hippocampus and striatum at 5-min increments before, during, and after training. These…

Methods to measure target site penetration of antibiotics in critically ill patients.

PubMed

Schwameis, Richard; Zeitlinger, Markus

2013-02-01

While several tools are necessary to repair a car, the engineer knows exactly which instrument he has to utilize at different parts of the broken machine. Likewise, depending on the information we are interested in, we have to choose different tools to investigate and consecutively understand the multiple aspects that are involved in pharmacokinetics of antimicrobial agents in critically ill patients. Some techniques, like blood sampling, microdialysis or positrons emission tomography (PET) will allow for obtaining continues concentration time profiles while others like bronchoalveolar lavage (BAL), biopsy or surgical tissue samples can only be used a limited number of times per subject. PET and methods based on tissue homogenization will deliver an average of the actual concentrations in intra - and extracellular compartments while investigations in isolated blood cells or microdialysis allow for more distinguished allocation of a concentration to a defined compartment. The present review aims at discussing the advantages and disadvantages of the various methods used for assessing pharmacokinetics in critically ill patients with regard to specific aspects of pharmacokinetic research and further reviews data of selected antibiotics as examples for applications of the individual techniques.

LC-MS/MS method for the quantification of almotriptan in dialysates: application to rat brain and blood microdialysis study.

PubMed

Nirogi, Ramakrishna; Ajjala, Devender Reddy; Kandikere, Vishwottam; Aleti, Raghupathi; Pantangi, Hanumanth Rao; Srikakolapu, Surya Rao; Benade, Vijay; Bhyrapuneni, Gopinadh; Vurimindi, Himabindu

2013-01-01

A sensitive LC-MS/MS method was developed and validated for the quantification of almotriptan in rat brain and blood dialysates. Almotriptan is a 5HT1B/1D receptor agonist used for the treatment of migraine pain. Method consists of rapid gradient elution program with 10mM ammonium formate (pH 3) and acetonitrile on a Xbridge column. The MRM transitions monitored were m/z 336.2-58.1 for almotriptan and m/z 448.2-285.3 for the IS. The assay was linear in the range of 0.1-20 ng/ml, with acceptable precision and accuracy along with adequate sensitivity. The between batch accuracy was in the range of 99.0-104.3% with precision in between 0.6% and 5.8%. Microdialysis is an important sampling technique, with the capability of capturing the concentrations of various analytes in different bio fluids, at a single time point. This method was applied to quantify brain and blood dialysate samples obtained from a microdialysis study of rats treated with almotriptan (10mg/kg, p.o.). In vivo recovery experiments were performed to correct the dialysate concentrations into extracellular concentrations. Mean peak dialysate concentrations of almotriptan were found to be 152 ± 78 and 7.4 ± 1.0 ng/ml in blood and prefrontal cortex, respectively. The brain penetration of almotriptan is characterized by the AUCbrain/AUCblood found to be 0.07 ± 0.05. The results revealed the importance of measuring the unbound almotriptan concentrations in the brain over the blood for understanding its PK/PD relationship. Copyright © 2013 Elsevier B.V. All rights reserved.

Carbon dioxide, oxygen, and pH detection in animal adipose tissue by means of extracorporeal microdialysis

NASA Astrophysics Data System (ADS)

Baldini, F.; Bizzarri, A.; Cajlakovic, M.; Feichtner, F.; Gianesello, L.; Giannetti, A.; Gori, G.; Konrad, C.; Mencaglia, A. A.; Mori, E.; Pavoni, V.; Perna, A. M.; Trono, C.

2007-05-01

Atypical physiological symptoms can be developed in healthy people under critically ill conditions. pH, pO II and pCO II are informative indicators of the conditions of a living system and can be valuable in determining the physiologic status of the critically ill patients. The continuous monitoring of these small molecules into the interstitial fluid (ISF) is a promising approach to reduce diagnostic blood loss and painful stress associated with blood sampling. Microdialysis is the approach followed for the extraction of the sample from the subcutaneous adipose tissue; the drawn interstitial fluid flows through a microfluidic circuit formed by the microdialysis catheter in series with a glass capillary on the internal wall of which the appropriate chemistry for sensing is immobilised. Absorption changes for pH sensor and modulation of the fluorescence lifetime for pO II and pCO II are the working principle. Phenol red covalently bound into the internal wall of a glass capillary by means of the Mannich reaction and platinum(II) tetrakis-pentafluorophenyl-porphyrine entrapped within a polymerised polystyrene layer are the chemical transducers used for pH and oxygen detection; the ion pair 8- hydroxypyrene-1,3,6-trisulfonic acid trisodium salt/ tetraoctylammonium hydroxide, dissolved in a silicon-based polymeric matrix, is used for the carbon dioxide detection. A suitable hemorrhagic shock model was developed in order to validate clinically the developed sensors in the condition of extreme stress and the obtained results show that the adipose tissue can become an alternative site for the continuous oitoring of pH, pO II and pCO II.

Microdialysis pharmacokinetic study of scopolamine in plasma, olfactory bulb and vestibule after intranasal administration.

PubMed

Wei, Yan; Ying, Mingzhen; Xu, Shuai; Wang, Feng; Zou, Aifeng; Cao, Shilei; Jiang, Xinguo; Wang, Yajie

2016-01-01

The purpose of this study was to investigate the microdialysis pharmacokinetic of scopolamine in plasma, olfactory bulb and vestibule after intranasal administration. The pharmacokinetic study of subcutaneous and oral administration was also performed in rats. From the in vivo results, scopolamine intranasal administration can avoid hepatic first-pass effect. Tmax plasma samples after intranasal administration were significantly faster than oral administration and subcutaneous injection. The relative bioavailability of intranasal administrations was 51.8-70% when compared with subcutaneous injection. Moreover, one can see that in comparison with scopolamine subcutaneous administration, scopolamine intranasal gel and solutions can increased drug target index (DTI) with olfactory bulb 1.69 and 2.05, vestibule 1.80 and 2.15, respectively. The results indicated that scopolamine can be absorbed directly through the olfactory mucosa into the olfactory bulb, and then transported to various brain tissue after intranasal administration, with the characteristics of brain drug delivery.

Caffeine potentiates the enhancement by choline of striatal acetylcholine release

NASA Technical Reports Server (NTRS)

Johnson, D. A.; Ulus, I. H.; Wurtman, R. J.

1992-01-01

We investigated the effect of peripherally administered caffeine (50 mg/kg), choline (30, 60, or 120 mg/kg) or combinations of both drugs on the spontaneous release of acetylcholine (ACh) from the corpus striatum of anesthetized rats using in vivo microdialysis. Caffeine alone or choline in the 30 or 60 mg/kg dose failed to increase ACh in microdialysis samples; the 120 mg/kg choline dose significantly enhanced ACh during the 80 min following drug administration. Coadministration of caffeine with choline significantly increased ACh release after each of the choline doses tested. Peak microdialysate levels with the 120 mg/kg dose were increased 112% when caffeine was additionally administered, as compared with 54% without caffeine. These results indicate that choline administration can enhance spontaneous ACh release from neurons, and that caffeine, a drug known to block adenosine receptors on these neurons, can amplify the choline effect.

Microdialysis unit for molecular weight separation

DOEpatents

Smith, Richard D.; Liu, Chuanliang

1999-01-01

The present invention relates generally to an apparatus and method for separating high molecular weight molecules from low molecular weight molecules. More specifically, the invention relates to the use of microdialysis for removal of the salt (low molecular weight molecules) from a nucleotide sample (high molecular weight molecules) for ESI-MS analysis. The dialysis or separation performance of the present invention is improved by (1) increasing dialysis temperature thereby increasing desalting efficiency and improving spectrum quality; (2) adding piperidine and imidazole to the dialysis buffer solution and reducing charge states and further increasing detection sensitivity for DNA; (3) using low concentrations (0-2.5 mM NH4OAc) of dialysis buffer and shifting the DNA negative ions to higher charge states, producing a nearly 10-fold increase in detection sensitivity and a slightly decreased desalting efficiency, or (4) any combination of (1), (2), and (3).

Age-dependent changes at the blood-brain barrier. A Comparative structural and functional study in young adult and middle aged rats.

PubMed

Bors, Luca; Tóth, Kinga; Tóth, Estilla Zsófia; Bajza, Ágnes; Csorba, Attila; Szigeti, Krisztián; Máthé, Domokos; Perlaki, Gábor; Orsi, Gergely; Tóth, Gábor K; Erdő, Franciska

2018-05-01

Decreased beta-amyloid clearance in Alzheimer's disease and increased blood-brain barrier permeability in aged subjects have been reported in several articles. However, morphological and functional characterization of blood-brain barrier and its membrane transporter activity have not been described in physiological aging yet. The aim of our study was to explore the structural changes in the brain microvessels and possible functional alterations of P-glycoprotein at the blood-brain barrier with aging. Our approach included MR imaging for anatomical orientation in middle aged rats, electronmicroscopy and immunohistochemistry to analyse the alterations at cellular level, dual or triple-probe microdialysis and SPECT to test P-glycoprotein functionality in young and middle aged rats. Our results indicate that the thickness of basal lamina increases, the number of tight junctions decreases and the size of astrocyte endfeet extends with advanced age. On the basis of microdialysis and SPECT results the P-gp function is reduced in old rats. With our multiparametric approach a complex regulation can be suggested which includes elements leading to increased permeability of blood-brain barrier by enhanced paracellular and transcellular transport, and factors working against it. To verify the role of P-gp pumps in brain aging further studies are warranted. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Regulation of striatal nitric oxide synthesis by local dopamine and glutamate interactions

PubMed Central

Park, Diana J.; West, Anthony R.

2009-01-01

Nitric oxide (NO) is a key neuromodulator of corticostriatal synaptic transmission. We have shown previously that dopamine (DA) D1/5 receptor stimulation facilitates neuronal NO synthase (nNOS) activity in the intact striatum. To study the impact of local manipulations of D1/5 and glutamatergic NMDA receptors on striatal nNOS activity, we combined the techniques of in vivo amperometry and reverse microdialysis. Striatal NO efflux was monitored proximal to the microdialysis probe in urethane anesthetized rats during local infusion of vehicle or drug. NO efflux elicited by systemic administration of SKF-81297 was blocked following intrastriatal infusion of: 1) the D1/5 receptor antagonist SCH-23390, 2) the nNOS inhibitor 7-nitroindazole, 3) the nonspecific ionotropic glutamate receptor antagonist kynurenic acid, and 4) the selective NMDA receptor antagonist 3-phosphonopropyl-piperazine-2-carboxylic acid. Glycine coperfusion did not affect SKF-81297-induced NO efflux. Furthermore, intrastriatal infusion of SKF-81297 potentiated NO efflux evoked during electrical stimulation of the motor cortex. The facilitatory effects of cortical stimulation and SKF-81297 were both blocked by intrastriatal infusion of SCH-23390, indicating that striatal D1/5 receptor activation is necessary for the activation of nNOS by corticostriatal afferents. These studies demonstrate for the first time that reciprocal DA-glutamate interactions play a critical role in stimulating striatal nNOS activity. PMID:19799710

Agmatine reduces extracellular glutamate during pentylenetetrazole-induced seizures in rat brain: A potential mechanism for the anticonvulsive effects

PubMed Central

Feng, Yangzheng; LeBlanc, Michael H.; Regunathan, Soundar

2010-01-01

Glutamate has been implicated in the initiation and spread of seizure activity. Agmatine, an endogenous neuromodulator, is an antagonist of NMDA receptors and has anticonvulsive effects. Whether agmatine regulate glutamate release, as measured by in vivo microdialysis, is not known. In this study, we used pentylenetetrazole (PTZ)-induced seizure model to determine the effect of agmatine on extracellular glutamate in rat brain. We also determined the time course and the amount of agmatine that reached brain after peripheral injection. After i.p. injection of agmatine (50 mg/kg), increase of agmatine in rat cortex and hippocampus was observed in 15 min with levels returning to baseline in one hour. Rats, naïve and implanted with microdialysis cannula into the cortex, were administered PTZ (60 mg/kg, i.p.) with prior injection of agmatine (100 mg/kg, i.p.) or saline. Seizure grades were recorded and microdialysis samples were collected every 15 min for 75 min. Agmatine pre-treatment significantly reduced the seizure grade and increased the onset time. The levels of extracellular glutamate in frontal cortex rose two- to three-fold after PTZ injection and agmatine significantly inhibited this increase. In conclusion, the present data suggest that the anticonvulsant activity of agmatine, in part, could be related to the inhibition glutamate release. PMID:16125317

Studies on the role of dopamine in the degeneration of 5-HT nerve endings in the brain of Dark Agouti rats following 3,4-methylenedioxymethamphetamine (MDMA or ‘ecstasy') administration

PubMed Central

Colado, M I; O'Shea, E; Granados, R; Esteban, B; Martín, A B; Green, A R

1999-01-01

We investigated whether dopamine plays a role in the neurodegeneration of 5-hydroxytryptamine (5-HT) nerve endings occurring in Dark Agouti rat brain after 3,4-methylenedioxymethamphetamine (MDMA or ‘ecstasy') administration. Haloperidol (2 mg kg−1 i.p.) injected 5 min prior and 55 min post MDMA (15 mg kg−1 i.p.) abolished the acute MDMA-induced hyperthermia and attenuated the neurotoxic loss of 5-HT 7 days later. When the rectal temperature of MDMA+haloperidol treated rats was kept elevated, this protective effect was marginal. MDMA (15 mg kg−1) increased the dopamine concentration in the dialysate from a striatal microdialysis probe by 800%. L-DOPA (25 mg kg−1 i.p., plus benserazide, 6.25 mg kg−1 i.p.) injected 2 h after MDMA (15 mg kg−1) enhanced the increase in dopamine in the dialysate, but subsequent neurodegeneration was unaltered. L-DOPA (25 mg kg−1) injected before a sub-toxic dose of MDMA (5 mg kg−1) failed to induce neurodegeneration. The MDMA-induced increase in free radical formation in the hippocampus (indicated by increased 2,3- and 2,5-dihydroxybenzoic acid in a microdialysis probe perfused with salicylic acid) was unaltered by L-DOPA. The neuroprotective drug clomethiazole (50 mg kg−1 i.p.) did not influence the MDMA-induced increase in extracellular dopamine. These data suggest that previous observations on the protective effect of haloperidol and potentiating effect of L-DOPA on MDMA-induced neurodegeneration may have resulted from effects on MDMA-induced hyperthermia. The increased extracellular dopamine concentration following MDMA may result from effects of MDMA on dopamine re-uptake, monoamine oxidase and 5-HT release rather than an ‘amphetamine-like' action on dopamine release, thus explaining why the drug does not induce degeneration of dopamine nerve endings. PMID:10193771

Quantification of Phenol, Phenyl Glucuronide, and Phenyl Sulfate in Blood of Unanesthetized Rainbow Trout by On-line Microdialysis Sampling

EPA Science Inventory

In this study we have developed a novel method to estimate in vivo rates of metabolism in unanesthetized fish. This method provides a basis for evaluating the accuracy of in vitro-in vivo metabolism extrapolations. As such, this research will lead to improved risk assessments f...

IN VIVO KINETICS OF PHENYLGLUCURONIDE, A PHASE II CONJUGATE OF PHENOLE, IN BLOOD AND URINE OF RAINBOW TROUT

EPA Science Inventory

The kinetics of phenylglucuronide (PG) in blood and urine of spinally-transected rainbow trout were investigated using microdialysis sampling techniques. Trout weighing 0.9 to 1.3 kg were dosed continuously with PG for an additional 48 h. PG could not be detected in expired branc...

A new minimal-stress freely-moving rat model for preclinical studies on intranasal administration of CNS drugs.

PubMed

Stevens, Jasper; Suidgeest, Ernst; van der Graaf, Piet Hein; Danhof, Meindert; de Lange, Elizabeth C M

2009-08-01

To develop a new minimal-stress model for intranasal administration in freely moving rats and to evaluate in this model the brain distribution of acetaminophen following intranasal versus intravenous administration. Male Wistar rats received one intranasal cannula, an intra-cerebral microdialysis probe, and two blood cannulas for drug administration and serial blood sampling respectively. To evaluate this novel model, the following experiments were conducted. 1) Evans Blue was administered to verify the selectivity of intranasal exposure. 2) During a 1 min infusion 10, 20, or 40 microl saline was administered intranasally or 250 microl intravenously. Corticosterone plasma concentrations over time were compared as biomarkers for stress. 3) 200 microg of the model drug acetaminophen was given in identical setup and plasma, and brain pharmacokinetics were determined. In 96% of the rats, only the targeted nasal cavity was deeply colored. Corticosterone plasma concentrations were not influenced, neither by route nor volume of administration. Pharmacokinetics of acetaminophen were identical after intravenous and intranasal administration, although the Cmax in microdialysates was reached a little earlier following intravenous administration. A new minimal-stress model for intranasal administration in freely moving rats has been successfully developed and allows direct comparison with intravenous administration.

Monitoring vigabatrin in head injury patients by cerebral microdialysis: obtaining pharmacokinetic measurements in a neurocritical care setting.

PubMed

Shannon, Richard J; Timofeev, Ivan; Nortje, Jürgens; Hutchinson, Peter J; Carpenter, Keri L H

2014-11-01

The aims were to determine blood-brain barrier penetration and brain extracellular pharmacokinetics for the anticonvulsant vigabatrin (VGB; γ-vinyl-γ-aminobutyric acid) in brain extracellular fluid and plasma from severe traumatic brain injury (TBI) patients, and to measure the response of γ-aminobutyric acid (GABA) concentration in brain extracellular fluid. Severe TBI patients (n = 10) received VGB (0.5 g enterally, every 12 h). Each patient had a cerebral microdialysis catheter; two patients had a second catheter in a different region of the brain. Plasma samples were collected 0.5 h before and 2, 4 and 11.5 h after the first VGB dose. Cerebral microdialysis commenced before the first VGB dose and continued through at least three doses of VGB. Controls were seven severe TBI patients with microdialysis, without VGB. After the first VGB dose, the maximum concentration of VGB (Cmax ) was 31.7 (26.9-42.6) μmol l(-1) (median and interquartile range for eight patients) in plasma and 2.41 (2.03-5.94) μmol l(-1) in brain microdialysates (nine patients, 11 catheters), without significant plasma-brain correlation. After three doses, median Cmax in microdialysates increased to 5.22 (4.24-7.14) μmol l(-1) (eight patients, 10 catheters). Microdialysate VGB concentrations were higher close to focal lesions than in distant sites. Microdialysate GABA concentrations increased modestly in some of the patients after VGB administration. Vigabatrin, given enterally to severe TBI patients, crosses the blood-brain barrier into the brain extracellular fluid, where it accumulates with multiple dosing. Pharmacokinetics suggest delayed uptake from the blood. © 2014 The Authors. British Journal of Clinical Pharmacology published by John Wiley & Sons Ltd on behalf of The British Pharmacological Society.

Alteration of glutamate/GABA balance during acute alcohol intoxication in rats: effect of Xingnaojing injection.

PubMed

Wei, Jingjing; Yao, Limei; Yang, Lei; Zhao, Wei; Shi, Si; Cai, Qingyan; Chen, Dingsheng; Li, Weirong; Wang, Qi

2015-05-26

Xingnaojing Injection (XNJI) is a modern Chinese formula came from famous Chinese medicine An Gong Niu Huang Pill. XNJI has been used for treatment of cerebral diseases and stroke in China, and is approved by the State Food and Drug Administration of China for the treatment of acute alcohol intoxication (AAI). XNJI belongs to the ethnopharmacological family of medicines. In this study, we investigated the mechanisms of the XNJI effect on AAI. To investigate the effects of XNJI on glutamate, gamma-aminobutyric acid (GABA) and related receptor in lateral hypothalamic area (LHA) of AAI rat. Adult male Sprague-Dawley rats were implanted with microdialysis probes in LHA. Rats were randomly divided into control, model, 1.36mg/kg XNJI, 0.68mg/kg XNJI and 0.34mg/kg XNJI groups. During microdialysis, baseline samples were collected from 1h to 2.5h; thereafter, the rats were given an intraperitoneal injection of 52% ethanol, 5.2g/kg, or saline for control group. Twenty minutes later, three doses of XNJI was given by unilateral injection respectively, while saline for control and model groups, and samples were collected for the next 4h. The extracellular glutamate and GABA levels were measured in the LHA by a high performance liquid chromatography coupled with fluorescence detector (HPLC-FLU). The expression levels of related receptors N-methyl-d-aspartate receptor (NR) subunit NR2A, NR2B and GABAA were analyzed by reverse transcription polymerase chain reaction (RT-PCR). Ethanol (5.2g/kg) significantly decreased the extracellular levels of glutamate and increased extracellular GABA in LHA. On the other hand ethanol significantly decreased NR2A and NR2B mRNAs expression, and increase GABAA mRNA expression. XNJI could increase the extracellular level of glutamate and decrease that of GABA; moreover, induced an increase in NR2A and NR2B mRNA expression, and a decrease in GABAA mRNA expression in LHA. The current changes in glutamate, GABA and mRNA expressions of related receptors in LHA after injection of XNJI suggest that changes in these neurotransmitters and receptors as a potential mechanism of action for AAI. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Effects of microdialyzed oxotremorine, carbachol, epibatidine, and scopolamine on intraspinal release of acetylcholine in the rat.

PubMed

Höglund, A U; Hamilton, C; Lindblom, L

2000-10-01

Intrathecally administered cholinergic agonists such as oxotremorine (muscarinic), carbachol (mixed nicotinic and muscarinic agonist), and epibatidine (nicotinic) have all been shown to reduce nociception in behavioral studies. Thus, there is substantial evidence for a role of acetylcholine (ACh) in the control of nociception in the spinal cord, but the mechanisms regulating ACh release are not known. The present study was initiated to establish a rat model to study which mechanisms are involved in the control of ACh release. Spinal microdialysis probes were inserted intraspinally at the C1-C5 spinal level in isoflurane-anesthetized rats. The probes were perfused with Ringer's solution containing 10 microM neostigmine to prevent degradation of ACh. Oxotremorine, carbachol, epibatidine, and scopolamine, dissolved in Ringer's solution, were administered intraspinally via dialysis and 30 microliter/10-min samples of dialysate were collected for HPLC analysis of ACh content. The release of ACh was found to be constant in the control (Ringer's only) situation during the experimental period of 150 min. Oxotremorine (100-1000 microM), carbachol (1 mM), and epibatidine (50-5000 microM) enhanced but scopolamine (50-200 nM) decreased the intraspinal release of ACh. Oxotremorine (ED(50) = 118 microM) and epibatidine (ED(50) = 175 microM) were found to produce a dose-dependent increase of ACh release. Cholinergic agonists caused an increase of intraspinal ACh and the antagonist scopolamine caused a decreased release of ACh. The data do not support an autoreceptor function of either nicotinic or muscarinic receptors in the spinal cord, contrary to what has been observed in the brain.

Skin microdialysis coupled with laser speckle contrast imaging to assess microvascular reactivity.

PubMed

Cracowski, J L; Gaillard-Bigot, F; Cracowski, C; Roustit, M; Millet, C

2011-11-01

Laser speckle contrast imaging (LSCI) can be used to assess real-time responses of skin microcirculation to pharmacological interventions. The main objective of this study was to determine whether intradermal or subdermal microdialysis fiber insertion, coupled with skin flux recording using LSCI, can be used to assess baseline cutaneous flux and the post-occlusive reactive hyperemic response. The microdialysis sites were compared to control area without microdialysis fibers. One dermal and two subdermal microdialysis fibers were randomly inserted in the right forearm skin of six healthy volunteers. We performed consecutively tests of post-occlusive hyperemia, infusion of 29 mM sodium nitroprusside (SNP), local thermal hyperemia at 43°C and a second 29 mM SNP infusion at the end of the experiment. Two hours after fiber insertion, cutaneous vascular conductances (CVC) at the subdermal fiber sites were not different from their respective control regions of interest, while at the dermal site CVC remained higher (0.48+/-0.15 versus 0.37+/-0.1 PU.mm Hg(-1), P=0.003). The peak CVC and area under the curve observed during post-occlusive reactive hyperemia were similar at all fiber sites and their respective controls. We observed a similar increase in CVC using 29 mM SNP infusion, 40 min local heating at 43°C, and their combination. Finally, physiological and pharmacological responses of the subdermal sites were reproducible in terms of amplitude, whether expressed as raw CVC or as % CVCmax. We showed that studying skin microvascular physiological or pharmacological responses using inserted subdermal microdialysis fibers coupled with LSCI is feasible and reproducible, and provides two-dimensional information. This technique will be useful for future mechanistic studies of skin microcirculation. Copyright © 2011 Elsevier Inc. All rights reserved.

In vivo assessment of high-grade glioma biochemistry using microdialysis: a study of energy-related molecules, growth factors and cytokines.

PubMed

Marcus, Hani J; Carpenter, Keri L H; Price, Stephen J; Hutchinson, Peter J

2010-03-01

Microdialysis enables measurement of the chemistry of the cerebral extracellular fluid. This study's objective was to utilise microdialysis to monitor levels of glucose, lactate, pyruvate, glutamate and glycerol in patients following surgery for intrinsic brain tumours, and to assess the concentration of growth factors, cytokines and other proteins involved in the pathogenesis of high-grade gliomas in vivo. Eight patients with suspected high-grade gliomas were studied. Seven of these underwent resection with one microdialysis catheter placed at the tumour resection margin and, in six of these seven cases, a second microdialysis catheter in macroscopically normal peritumour tissue. The remaining glioma patient had an image-guided biopsy with a single catheter inserted stereotactically at the tumour margin. Histology demonstrated WHO IV glioblastoma in five cases, WHO III anaplastic astrocytoma in two cases, and one cerebral lymphoma. In the high-grade gliomas (WHO IV and III), tumour margin microdialysates consistently showed significantly lower glucose, higher lactate/pyruvate (L/P) ratio, higher glutamate and higher glycerol, relative to peritumour microdialysates (P < 0.05). These results indicate that malignant glioma margin tissue is metabolically extremely active. There was great variability in the microdialysate concentrations of growth factors (TGFalpha, EGF, VEGF), cytokines (IL-1alpha, IL-1beta, IL-1ra, IL-6, IL-8), matrix metalloproteinases (MMP-2, MMP-9) and their endogenous inhibitors (TIMP-1, TIMP-2). Notably, microdialysates from the glioma resection margin demonstrated significantly higher IL-8 concentration and higher MMP-2/TIMP-1 ratio when compared to peritumour microdialysates (P < 0.05), suggesting an environment favouring invasion and angiogenesis at the tumour margin. Microdialysis is a promising technique to study in vivo glioma metabolism, and may assist in the development of new therapies.

Inhibition of P-glycoprotein enhances transport of imipramine across the blood-brain barrier: microdialysis studies in conscious freely moving rats.

PubMed

O'Brien, F E; Clarke, G; Fitzgerald, P; Dinan, T G; Griffin, B T; Cryan, J F

2012-06-01

Recent studies indicate that efflux of antidepressants by the multidrug resistance transporter P-glycoprotein (P-gp) at the blood-brain barrier (BBB) may contribute to treatment-resistant depression (TRD) by limiting intracerebral antidepressant concentrations. In addition, clinical experience shows that adjunctive treatment with the P-gp inhibitor verapamil may improve the clinical outcome in TRD. Therefore, the present study aimed to investigate the effect of P-gp inhibition on the transport of the tricyclic antidepressant imipramine and its active metabolite desipramine across the BBB. Intracerebral microdialysis in rats was used to monitor brain levels of imipramine and desipramine following i.v. imipramine administration, with or without pretreatment with one of the P-gp inhibitors verapamil or cyclosporin A (CsA). Plasma drug levels were also determined at regular intervals. Pretreatment with either verapamil or CsA resulted in significant increases in imipramine concentrations in the microdialysis samples, without altering imipramine plasma pharmacokinetics. Furthermore, pretreatment with verapamil, but not CsA, led to a significant elevation in plasma and brain levels of desipramine. The present study demonstrated that P-gp inhibition enhanced the intracerebral concentration of imipramine , thus supporting the hypothesis that P-gp activity restricts brain levels of certain antidepressants, including imipramine. These findings may help to explain reports of a beneficial response to adjunctive therapy with verapamil in TRD. © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.

Enteral nutrition increases interstitial brain glucose levels in poor-grade subarachnoid hemorrhage patients.

PubMed

Kofler, Mario; Schiefecker, Alois J; Beer, Ronny; Gaasch, Maxime; Rhomberg, Paul; Stover, John; Pfausler, Bettina; Thomé, Claudius; Schmutzhard, Erich; Helbok, Raimund

2018-03-01

Low brain tissue glucose levels after acute brain injury are associated with poor outcome. Whether enteral nutrition (EN) reliably increases cerebral glucose levels remains unclear. In this retrospective analysis of prospectively collected observational data, we investigate the effect of EN on brain metabolism in 17 poor-grade subarachnoid hemorrhage (SAH) patients undergoing cerebral microdialysis (CMD) monitoring. CMD-values were obtained hourly. A nutritional intervention was defined as the clinical routine administration of EN without supplemental parenteral nutrition. Sixty-three interventions were analyzed. The mean amount of EN per intervention was 472.4 ± 10.7 kcal. CMD-glucose levels significantly increased from 1.59 ± 0.13 mmol/l at baseline to a maximum of 2.03 ± 0.2 mmol/l after 5 h (p < 0.001), independently of insulin-treatment, baseline serum glucose, baseline brain metabolic distress (CMD-lactate-to-pyruvate-ratio (LPR) > 40) and the microdialysis probe location. The increase in CMD-glucose was directly dependent on the magnitude of increase of serum glucose levels (p = 0.007). No change in CMD-lactate, CMD-pyruvate, CMD-LPR, or CMD-glutamate (p > 0.4) was observed. Routine EN also increased CMD-glucose even if baseline concentrations were critically low ( < 0.7 mmol/l, neuroglucopenia; p < 0.001). These results may have treatment implications regarding glucose management of poor-grade aneurysmal SAH patients.

Estimation of skeletal muscle interstitial adenosine during forearm dynamic exercise in humans

NASA Technical Reports Server (NTRS)

Costa, F.; Heusinkveld, J.; Ballog, R.; Davis, S.; Biaggioni, I.

2000-01-01

It has been proposed that adenosine is a metabolic signal that triggers activation of muscle afferents involved in the exercise pressor reflex. Furthermore, exogenous adenosine induces sympathetic activation that mimics the exercise pressor reflex, and blockade of adenosine receptors inhibits sympathetic activation induced by exercise. Thus, we hypothesize that adenosine is released locally by the muscle during exercise. We used microdialysis probes, placed in the flexor digitorium superficialis muscle, to estimate muscle interstitial adenosine levels in humans. We estimated resting in vivo muscle interstitial adenosine concentrations (0.292+/-0.058 micromol/L, n=4) by perfusing increasing concentrations of adenosine to determine the gradient produced in the dialysate. Muscle interstitial adenosine concentrations increased from 0.23+/-0.04 to 0.82+/-0.14 micromol/L (n=14, P<0.001) during intermittent dynamic exercise at 50% of maximal voluntary contraction. Lactate increased from 0.8+/-0.1 to 2.3+/-0.3 mmol/L (P<0.001). Lower intensity (15% maximal voluntary contraction) intermittent dynamic exercise increased adenosine concentrations from 0.104+/-0.02 to 0.42+/-0.16 micromol/L (n=7). The addition of ischemia to this low level of exercise produced a greater increase in adenosine (from 0.095+/-0.02 to 0.48+/-0.2 micromol/L) compared with nonischemic exercise (0. 095+/-0.02 to 0.25+/-0.12 micromol/L). These results indicate that microdialysis is useful in estimating adenosine concentrations and in reflecting changes in muscle interstitial adenosine during dynamic exercise in humans.

Effects of the neurotoxin MPTP and pargyline protection on extracellular energy metabolites and dopamine levels in the striatum of freely moving rats.

PubMed

Bazzu, Gianfranco; Rocchitta, Gaia; Migheli, Rossana; Alvau, Maria Domenica; Zinellu, Manuel; Puggioni, Giulia; Calia, Giammario; Mercanti, Giulia; Giusti, Pietro; Desole, Maria Speranza; Serra, Pier Andrea

2013-11-13

The neurotoxin MPTP is known to induce dopamine release and depletion of ATP in the striatum of rats. Therefore, we studied the changes induced by MPTP and pargyline protection both on striatal dopamine release and on extracellular energy metabolites in freely moving rats, using dual asymmetric-flow microdialysis. A dual microdialysis probe was inserted in the right striatum of rats. MPTP (25mg/kg, 15mg/kg, 10mg/kg) was intraperitoneally administered for three consecutive days. MAO-B inhibitor pargyline (15mg/kg) was systemically administered before neurotoxin administration. The first MPTP dose induced an increase in dialysate dopamine and a decrease of DOPAC levels in striatal dialysate. After the first neurotoxin administration, increases in striatal glucose, lactate, pyruvate, lactate/pyruvate (L/P) and lactate/glucose (L/G) ratios were observed. Subsequent MPTP administrations showed a progressive reduction of dopamine, glucose and pyruvate levels with a concomitant further increase in lactate levels and L/P and L/G ratios. At day 1, pargyline pre-treatment attenuated the MPTP-induced changes in all studied analytes. Starting from day 2, pargyline prevented the depletion of dopamine, glucose and pyruvate while reduced the increase of lactate, L/P ratio and L/G ratio. These in vivo results suggest a pargyline neuroprotection role against the MPTP-induced energetic impairment consequent to mitochondrial damage. This neuroprotective effect was confirmed by TH immunostaining of the substantia nigra. © 2013 Elsevier B.V. All rights reserved.

Is chlormethiazole neuroprotective in experimental global cerebral ischemia? A microdialysis and behavioral study.

PubMed

Thaminy, S; Reymann, J M; Heresbach, N; Allain, H; Lechat, P; Bentué-Ferrer, D

1997-04-01

Chlormethiazole, an anticonvulsive agent, has been shown to have a possible neuroprotective effect against cerebral ischemia. In addition, chlormethiazole inhibits methamphetamine-induced release of dopamine, protecting against this neurotransmitter's neurotoxicity. The aim of this work was to ascertain whether, in experimental cerebral ischemia, chlormethiazole administration attenuated the ischemia-induced rise of the extracellular concentration of aminergic neurotransmitters and whether it reduces ischemia-induced deficits in memory and learning. Histology for assessment of ischemic damage was a so included. The four-vessel occlusion rat model was used to induce global cerebral ischemia. Aminergic neurotransmitters and their metabolites in the striatal extracellular fluid obtained by microdialysis were assayed by high-performance liquid chromatography-electrochemical detection. The drug was administered either IP (50 mg/kg-1) or directly through the dialysis probe (30 microM) 80 min before ischemia. For the behavioral test and histology, the drug was given IP (100 mg/kg-1) 1 h postischemia. The results obtained did not demonstrate any statistically significant evidence that chlormethiazole has an effect on the ischemia-induced rise in extracellular dopamine and serotonin levels. There was also no variation in metabolite levels. Behavioral measures (learning, recall) were not changed appreciably by the treatment. We observed no significant cell protection in the hippocampus (CA1, CA1), striatum, and entorhinal cortex in animals treated with chlormethiazole. We conclude that, under our experimental conditions, chlormethiazole has little or no effect on the neurochemical, neurobehavioral, and histological consequences of global cerebral ischemia.

Low dose naltrexone administration in morphine dependent rats attenuates withdrawal-induced norepinephrine efflux in forebrain.

PubMed

Van Bockstaele, Elisabeth J; Qian, Yaping; Sterling, Robert C; Page, Michelle E

2008-05-15

The administration of low dose opioid antagonists has been explored as a potential means of detoxification in opiate dependence. Previous results from our laboratory have shown that concurrent administration of low dose naltrexone in the drinking water of rats implanted with subcutaneous morphine pellets attenuates behavioral and biochemical signs of withdrawal in brainstem noradrenergic nuclei. Noradrenergic projections originating from the nucleus tractus solitarius (NTS) and the locus coeruleus (LC) have previously been shown to be important neural substrates involved in the somatic expression of opiate withdrawal. The hypothesis that low dose naltrexone treatment attenuates noradrenergic hyperactivity typically associated with opiate withdrawal was examined in the present study by assessing norepinephrine tissue content and norepinephrine efflux using in vivo microdialysis coupled to high performance liquid chromatography (HPLC) with electrochemical detection (ED). The frontal cortex (FC), amygdala, bed nucleus of the stria terminalis (BNST) and cerebellum were analyzed for tissue content of norepinephrine following withdrawal in morphine dependent rats. Naltrexone-precipitated withdrawal elicited a significant decrease in tissue content of norepinephrine in the BNST and amygdala. This decrease was significantly attenuated in the BNST of rats that received low dose naltrexone pre-treatment compared to controls. No significant difference was observed in the other brain regions examined. In a separate group of rats, norepinephrine efflux was assessed with in vivo microdialysis in the BNST or the FC of morphine dependent rats or placebo treated rats subjected to naltrexone-precipitated withdrawal that received either naltrexone in their drinking water (5 mg/L) or unadulterated water. Following baseline dialysate collection, withdrawal was precipitated by injection of naltrexone and sample collection continued for an additional 4 h. At the end of the experiment, animals were transcardially perfused and the brains were removed for verification of probe placement. Low dose naltrexone pre-treatment significantly attenuated withdrawal-induced increases of extracellular norepinephrine in the BNST, with a smaller effect in the FC. These findings suggest that alterations in norepinephrine release associated with withdrawal may be attenuated in forebrain targets of noradrenergic brainstem neurons that may underlie reduced behavioral signs of withdrawal following low dose naltrexone administration.

Osmoregulatory processes and skeletal muscle metabolism

NASA Astrophysics Data System (ADS)

Boschmann, Michael; Gottschalk, Simone; Adams, Frauke; Luft, Friedrich C.; Jordan, Jens

Prolonged microgravity during space flight is associated with a decrease in blood and extracellular volume. These changes in water and electrolyte balance might activate catabolic processes which contribute finally to the loss of muscle and bone mass and strength. Recently, we found a prompt increase that energy expenditure by about 30% in both normal and overweight men and women after drinking 500 ml water. This effect is mediated by an increased sympathetic nervous system activity, obviously secondary to stimulation of osmosensitive afferent neurons in the liver, and skeletal muscle is possibly one effector organ. Therefore, we tested the hypothesis that this thermogenic response to water is accompanied by a stimulation of aerobic glucose metabolism in skeletal muscle. To this end, 16 young healthy volunteers (8 men) were studied. After an overnight fast (12h), a microdialysis probe was implanted into the right M. quadriceps femoris vastus lateralis and subsequently perfused with Ringer's solution (+50 mM ethanol). After 1h, volunteers were asked to drink 500 ml water (22° C) followed by continuing microdialysis for another 90 min. Dialysates (15 min fractions) were analyzed for [ethanol], [glucose], [lactate], [pyruvate], and [glycerol] in order to assess changes in muscle tissue perfusion (ethanol dilution technique), glycolysis and lipolysis. Blood samples were taken and heart rate (HR) and blood pressure (BP) were monitored. Neither HR and systolic and diastolic BP, nor plasma [glucose], [lactate], [insulin], and [C peptide] changed significantly after water drinking. Also, tissue perfusion and dialysate [glucose] did not change significantly. However, dialysate [lactate] increased by about 10 and 20% and dialysate [pyruvate] by about 100 and 200% in men and women, respectively. In contrast, dialysate [glycerol] decreased by about 30 and 20% in men and women, respectively. Therefore, drinking of 500 ml water stimulates aerobic glucose metabolism and inhibits lipolysis in skeletal muscle and this to a greater extent in women than men. These insulin-like effects after water drinking originate possibly from regulatory cell volume swelling in osmosensitive organs such as muscle. Therefore, a well-balanced water homeostasis might be important for preventing catabolic processes during long-term space expeditions.

Ocular silicon distribution and clearance following intravitreal injection of porous silicon microparticles.

PubMed

Nieto, Alejandra; Hou, Huiyuan; Sailor, Michael J; Freeman, William R; Cheng, Lingyun

2013-11-01

Porous silicon (pSi) microparticles have been investigated for intravitreal drug delivery and demonstrated good biocompatibility. With the appropriate surface chemistry, pSi can reside in vitreous for months or longer. However, ocular distribution and clearance pathway of its degradation product, silicic acid, are not well understood. In the current study, rabbit ocular tissue was collected at different time point following fresh pSi (day 1, 5, 9, 16, and 21) or oxidized pSi (day 3, 7, 14, 21, and 35) intravitreal injection. In addition, dual-probe simultaneous microdialysis of aqueous and vitreous humor was performed following a bolus intravitreal injection of 0.25 mL silicic acid (150 μg/mL) and six consecutive microdialysates were collected every 20 min. Silicon was quantified from the samples using inductively coupled plasma-optical emission spectroscopy. The study showed that following the intravitreal injection of oxidized pSi, free silicon was consistently higher in the aqueous than in the retina (8.1 ± 6.5 vs. 3.4 ± 3.9 μg/mL, p = 0.0031). The area under the concentration-time curve (AUC) of the retina was only about 24% that of the aqueous. The mean residence time was 16 days for aqueous, 13 days for vitreous, 6 days for retina, and 18 days for plasma. Similarly, following intravitreal fresh pSi, free silicon was also found higher in aqueous than in retina (7 ± 4.7 vs. 3.4 ± 4.1 μg/mL, p = 0.014). The AUC for the retina was about 50% of the AUC for the aqueous. The microdialysis revealed the terminal half-life of free silicon in the aqueous was 30 min and 92 min in the vitreous; the AUC for aqueous accounted for 38% of the AUC for vitreous. Our studies indicate that aqueous humor is a significant pathway for silicon egress from the eye following intravitreal injection of pSi crystals. Copyright © 2013 Elsevier Ltd. All rights reserved.

In vivo monitoring of neuronal loss in traumatic brain injury: a microdialysis study

PubMed Central

Tisdall, Martin M.; Girbes, Armand R.; Martinian, Lillian; Thom, Maria; Kitchen, Neil; Smith, Martin

2011-01-01

Traumatic brain injury causes diffuse axonal injury and loss of cortical neurons. These features are well recognized histologically, but their in vivo monitoring remains challenging. In vivo cortical microdialysis samples the extracellular fluid adjacent to neurons and axons. Here, we describe a novel neuronal proteolytic pathway and demonstrate the exclusive neuro-axonal expression of Pavlov’s enterokinase. Enterokinase is membrane bound and cleaves the neurofilament heavy chain at positions 476 and 986. Using a 100 kDa microdialysis cut-off membrane the two proteolytic breakdown products, extracellular fluid neurofilament heavy chains NfH476−986 and NfH476−1026, can be quantified with a relative recovery of 20%. In a prospective clinical in vivo study, we included 10 patients with traumatic brain injury with a median Glasgow Coma Score of 9, providing 640 cortical extracellular fluid samples for longitudinal data analysis. Following high-velocity impact traumatic brain injury, microdialysate extracellular fluid neurofilament heavy chain levels were significantly higher (6.18 ± 2.94 ng/ml) and detectable for longer (>4 days) compared with traumatic brain injury secondary to falls (0.84 ± 1.77 ng/ml, <2 days). During the initial 16 h following traumatic brain injury, strong correlations were found between extracellular fluid neurofilament heavy chain levels and physiological parameters (systemic blood pressure, anaerobic cerebral metabolism, excessive brain tissue oxygenation, elevated brain temperature). Finally, extracellular fluid neurofilament heavy chain levels were of prognostic value, predicting mortality with an odds ratio of 7.68 (confidence interval 2.15–27.46, P = 0.001). In conclusion, this study describes the discovery of Pavlov’s enterokinase in the human brain, a novel neuronal proteolytic pathway that gives rise to specific protein biomarkers (NfH476−986 and NfH476−1026) applicable to in vivo monitoring of diffuse axonal injury and neuronal loss in traumatic brain injury. PMID:21278408

Integration of Microchip Electrophoresis with Electrochemical Detection Using an Epoxy-Based Molding Method to Embed Multiple Electrode Materials

PubMed Central

Johnson, Alicia S.; Selimovic, Asmira; Martin, R. Scott

2012-01-01

This paper describes the use of epoxy-encapsulated electrodes to integrate microchip-based electrophoresis with electrochemical detection. Devices with various electrode combinations can easily be developed. This includes a palladium decoupler with a downstream working electrode material of either gold, mercury/gold, platinum, glassy carbon, or a carbon fiber bundle. Additional device components such as the platinum wires for the electrophoresis separation and the counter electrode for detection can also be integrated into the epoxy base. The effect of the decoupler configuration was studied in terms of the separation performance, detector noise, and the ability to analyze samples of a high ionic strength. The ability of both glassy carbon and carbon fiber bundle electrodes to analyze a complex mixture was demonstrated. It was also shown that a PDMS-based valving microchip can be used along with the epoxy embedded electrodes to integrate microdialysis sampling with microchip electrophoresis and electrochemical detection, with the microdialysis tubing also being embedded in the epoxy substrate. This approach enables one to vary the detection electrode material as desired in a manner where the electrodes can be polished and modified in a similar fashion to electrochemical flow cells used in liquid chromatography. PMID:22038707

In vivo microdialysis and electroencephalographic activity in freely moving guinea pigs exposed to organophosphorus nerve agents sarin and VX: analysis of acetylcholine and glutamate.

PubMed

O'Donnell, John C; McDonough, John H; Shih, Tsung-Ming

2011-12-01

Organophosphorus nerve agents such as sarin (GB) and VX irreversibly inhibit acetylcholinesterase, causing a buildup of acetylcholine (ACh) in synapses and neuromuscular junctions, which leads to excess bronchial secretions, convulsions, seizures, coma, and death. Understanding the unique toxic characteristics of different nerve agents is vital in the effort to develop broad spectrum medical countermeasures. To this end, we employed a repeated measure multivariate design with striatal microdialysis collection and high-performance liquid chromatography analysis to measure changes in concentrations of several neurotransmitters (ACh, glutamate, aspartate, GABA) in the same samples during acute exposure to GB or VX in freely moving guinea pigs. Concurrent with microdialysis collection, we used cortical electrodes to monitor brain seizure activity. This robust double multivariate design provides greater fidelity when comparing data while also reducing the required number of subjects. No correlation between nerve agents' propensity for causing seizure and seizure-related lethality was observed. The GB seizure group experienced more rapid and severe cholinergic toxicity and lethality than that of the VX seizure group. Seizures generated from GB and VX exposure resulted in further elevation of ACh level and then a gradual return to baseline. Glutamate levels increased in the GB, but not in the VX, seizure group. There were no consistent changes in either aspartate or GABA as a result of either nerve agent. These observations reinforce findings with other nerve agents that seizure activity per se contributes to the elevated levels of brain ACh observed after nerve agent exposure.

Extracellular N-Acetylaspartate in Human Traumatic Brain Injury

PubMed Central

Shannon, Richard J.; Carter, Eleanor L.; Jalloh, Ibrahim; Menon, David K.; Hutchinson, Peter J.; Carpenter, Keri L.H.

2016-01-01

Abstract N-acetylaspartate (NAA) is an amino acid derivative primarily located in the neurons of the adult brain. The function of NAA is incompletely understood. Decrease in brain tissue NAA is presently considered symptomatic and a potential biomarker of acute and chronic neuropathological conditions. The aim of this study was to use microdialysis to investigate the behavior of extracellular NAA (eNAA) levels after traumatic brain injury (TBI). Sampling for this study was performed using cerebral microdialysis catheters (M Dialysis 71) perfused at 0.3 μL/min. Extracellular NAA was measured in microdialysates by high-performance liquid chromatography in 30 patients with severe TBI and for comparison, in radiographically “normal” areas of brain in six non-TBI neurosurgical patients. We established a detailed temporal eNAA profile in eight of the severe TBI patients. Microdialysate concentrations of glucose, lactate, pyruvate, glutamate, and glycerol were measured on an ISCUS clinical microdialysis analyzer. Here, we show that the temporal profile of microdialysate eNAA was characterized by highest levels in the earliest time-points post-injury, followed by a steady decline; beyond 70 h post-injury, average levels were 40% lower than those measured in non-TBI patients. There was a significant inverse correlation between concentrations of eNAA and pyruvate; eNAA showed significant positive correlations with glycerol and the lactate/pyruvate (L/P) ratio measured in microdialysates. The results of this on-going study suggest that changes in eNAA after TBI relate to the release of intracellular components, possibly due to neuronal death or injury, as well as to adverse brain energy metabolism. PMID:26159566

Vitamin D receptor activation induces P-glycoprotein and increases brain efflux of quinidine: an intracerebral microdialysis study in conscious rats.

PubMed

Durk, Matthew R; Fan, Jianghong; Sun, Huadong; Yang, Yingbo; Pang, Henrianna; Pang, K Sandy; de Lannoy, Inés A M

2015-03-01

Since the vitamin D receptor (VDR) was found to up-regulate cerebral P-glycoprotein expression in vitro and in mice, we extend our findings to rats by assessing the effect of rat Vdr activation on brain efflux of quinidine, a P-gp substrate that is eliminated primarily by cytochrome P450 3a. We treated rats with vehicle or the active VDR ligand, 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3] (4.8 or 6.4 nmol/kg i.p. every 2nd day × 4) and examined P-gp expression and cerebral quinidine disposition via microdialysis in control and treatment studies conducted longitudinally in the same rat. The 6.4 nmol/kg 1,25(OH)2D3 dose increased cerebral P-gp expression 1.75-fold whereas hepatic Cyp3a remained unchanged. Although there was no change in systemic clearance elicited by 1,25(OH)2D3, brain extracellular fluid quinidine concentrations were lower in treated rats. We noted that insertion of indwelling catheters increased plasma protein binding of quinidine and serial sampling decreased the blood:plasma concentration ratio, factors that alter distribution ratios in microdialysis studies. After appropriate correction, KECF/P,uu and KECF/B,uu, or ratios of quinidine unbound concentrations in brain extracellular fluid to plasma or blood at steady-state, were more than halved. We demonstrate that VDR activation increases cerebral P-gp expression and delimits brain penetration of P-gp substrates.

Functional role of striatal A2A, D2, and mGlu5 receptor interactions in regulating striatopallidal GABA neuronal transmission.

PubMed

Beggiato, Sarah; Tomasini, Maria Cristina; Borelli, Andrea Celeste; Borroto-Escuela, Dasiel Oscar; Fuxe, Kjell; Antonelli, Tiziana; Tanganelli, Sergio; Ferraro, Luca

2016-07-01

In this study, the functional role of individual striatal receptors for adenosine (A2AR), dopamine (D2R), and the metabotropic glutamate receptor mGlu5R in regulating rat basal ganglia activity was characterized in vivo using dual-probe microdialysis in freely moving rats. In particular, intrastriatal perfusion with the D2R agonist quinpirole (10 μM, 60 min) decreased ipsilateral pallidal GABA and glutamate levels, whereas intrastriatal CGS21680 (A2AR agonist; 1 μM, 60 min) was ineffective on either pallidal GABA and glutamate levels or the quinpirole-induced effects. Intrastriatal perfusion with the mGlu5R agonist (RS)-2-chloro-5-hydroxyphenylglycine (600 μM, 60 min), by itself ineffective on pallidal GABA and glutamate levels, partially counteracted the effects of quinpirole. When combined with CGS21680 (1 μM, 60 min), (RS)-2-chloro-5-hydroxyphenylglycine (CHPG; 600 μM, 60 min) fully counteracted the quinpirole (10 μM, 60 min)-induced reduction in ipsilateral pallidal GABA and glutamate levels. These effects were fully counteracted by local perfusion with the mGlu5R antagonist MPEP (300 μM) or the A2AR antagonist ZM 241385 (100 nM). These results suggest that A2ARs and mGlu5Rs interact synergistically in modulating the D2R-mediated control of striatopallidal GABA neurons. Using dual-probe microdialysis, we characterized the functional role of striatal adenosine A2A receptor (A2AR), dopamine D2 receptor (D2R), and metabotropic glutamate receptor 5 (mGluR5) interactions in regulating rat basal ganglia activity. The results suggest the possible usefulness of using an A2AR antagonist and mGluR5 antagonist combination in the treatment of Parkinson's disease to increase the inhibitory D2 signaling on striatopallidal GABA neurons. © 2016 International Society for Neurochemistry.

Early metabolic responses to lithium/pilocarpine-induced status epilepticus in rat brain.

PubMed

Imran, Imran; Hillert, Markus H; Klein, Jochen

2015-12-01

The lithium-pilocarpine model of status epilepticus is a well-known animal model of temporal lobe epilepsy. We combined this model with in vivo microdialysis to investigate energy metabolites and acute cellular membrane damage during seizure development. Rats were implanted with dialysis probes and pretreated with lithium chloride (127 mg/kg i.p.). Twenty-four hours later, they received pilocarpine (30 mg/kg s.c.) which initiated seizures within 30 min. In the dialysate from rat hippocampus, we observed a transient increase in glucose and a prominent, five-fold increase in lactate during seizures. Lactate release was because of neuronal activation as it was strongly reduced by infusion of tetrodotoxin, administration of atropine or when seizures were terminated by diazepam or ketamine. In ex vivo assays, mitochondrial function as measured by respirometry was not affected by 90 min of seizures. Extracellular levels of choline, however, increased two-fold and glycerol levels 10-fold, which indicate cellular phospholipid breakdown during seizures. Within 60 min of pilocarpine administration, hydroxylation of salicylate increased two-fold and formation of isoprostanes 20-fold, revealing significant oxidative stress in hippocampal tissue. Increases in lactate, glycerol and isoprostanes were abrogated, and increases in choline were completely prevented, when hippocampal probes were perfused with calcium-free solution. Similarly, administration of pregabalin (100 mg/kg i.p.), a calcium channel ligand, 15 min prior to pilocarpine strongly attenuated parameters of membrane damage and oxidative stress. We conclude that seizure development in a rat model of status epilepticus is accompanied by increases in extracellular lactate, choline and glycerol, and by oxidative stress, while mitochondrial function remains intact for at least 90 min. Membrane damage depends on calcium influx and can be prevented by treatment with pregabalin. Status epilepticus (SE) was induced in rats by lithium-pilocarpine ('Pilo') administration, and extracellular metabolites were measured by microdialysis. Seizures caused several-fold increases in lactate levels which were attenuated by diazepam ('Diaz'), ketamine, atropine and tetrodotoxin (TTX). Indicators of oxidative stress and membrane damage were also increased during seizures. Omission of calcium and pregabalin, a calcium channel blocker, reduced cellular damage induced by SE. © 2015 International Society for Neurochemistry.

beta-Phenylethylamine modulates acetylcholine release in the rat striatum: involvement of a dopamine D(2) receptor mechanism.

PubMed

Kato, M; Ishida, K; Chuma, T; Abe, K; Shigenaga, T; Taguchi, K; Miyatake, T

2001-04-20

We examined the effects of beta-phenylethylamine on striatal acetylcholine release in freely moving rats using in vivo microdialysis. beta-Phenylethylamine at 12.5 mg/kg, i.p. did not affect acetylcholine release in the striatum, whereas 25 and 50 mg/kg, i.p. immediately induced an increase in acetylcholine release in the striatum at 15-45 min. This increase following intraperitoneal administration of beta-phenylethylamine (25 mg/kg) was not affected by locally applied SCH-23390 (R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine, 10 microM), a dopamine D(1) receptor antagonist, nor by raclopride (10 microM), a dopamine D(2) receptor antagonist. The increased release of acetylcholine induced by beta-phenylethylamine was suppressed by local infusion of tetrodotoxin (1 microM). In contrast, the extracellular acetylcholine level in the striatum was significantly decreased by local application of beta-phenylethylamine (10 and 100 microM) in the striatum via a microdialysis probe. The decrease was completely blocked by local co-application of raclopride (10 microM). The beta-phenylethylamine-induced decrease in striatal acetylcholine release was not affected by co-perfusion with SCH-23390 (10 microM). These results indicate that systemic administration of beta-phenylethylamine increases acetylcholine release, whereas locally applied beta-phenylethylamine decreases striatal acetylcholine release in freely moving rats. Furthermore, the dopaminergic system, through the dopamine D(2) receptor, is involved in the locally applied beta-phenylethylamine-induced decrease in acetylcholine in the striatum.

Mode of action of cupping--local metabolism and pain thresholds in neck pain patients and healthy subjects.

PubMed

Emerich, M; Braeunig, M; Clement, H W; Lüdtke, R; Huber, R

2014-02-01

Cupping worldwide has been part of traditional medicine systems and is in the western world used as CAM therapy mainly for treating pain syndromes. The mode of action is up to now unclear. In order to investigate its mechanism we measured in parallel metabolic changes in the tissue under the cupping glass and pressure pain thresholds. In 12 volunteers (6 healthy subjects and 6 patients with chronic neck pain) a microdialysis system was implanted subcutaneously on both sides (left and right) above the trapezius muscle. After baseline measures cupping was performed at one randomly selected side (left or right), the other side served as control. Every 20 min during baseline measures and for 280 min after cupping, microdialysis probes for detection of lactate, pyruvate, glucose and glycerin were taken. In addition, pain thresholds were measured before and after cupping with algometry. Cupping resulted in a strong increase of lactate (beginning 160 min after cupping until the end of the measurements) and the lactate/pyruvate ratio, indicating an anaerobe metabolism in the surrounding tissue. Baseline pain thresholds were non-significantly lower in neck pain patients compared to healthy controls and slightly increased immediately after cupping (p<0.05 compared to baseline close to the area of cupping in healthy subjects and on the foot in neck pain patients). After 280 min no more significant changes of pain thresholds were detected. Cupping induces >280 min lasting anaerobe metabolism in the subcutaneous tissue and increases immediate pressure pain thresholds in some areas. Copyright © 2014 Elsevier Ltd. All rights reserved.

Differential impact of pavlovian drug conditioned stimuli on in vivo dopamine transmission in the rat accumbens shell and core and in the prefrontal cortex.

PubMed

Bassareo, Valentina; De Luca, Maria Antonietta; Di Chiara, Gaetano

2007-04-01

Conditioned stimuli (CSs) by pavlovian association with reinforcing drugs (US) are thought to play an important role in the acquisition, maintenance and relapse of drug dependence. The aim of this study was to investigate by microdialysis the impact of pavlovian drug CSs on behaviour and on basal and drug-stimulated dopamine (DA) in three terminal DA areas: nucleus accumbens shell, core and prefrontal cortex (PFCX). Conditioned rats were trained once a day for 3 days by presentation of Fonzies filled box (FFB, CS) for 10 min followed by administration of morphine (1 mg/kg), nicotine (0.4 mg/kg) or saline, respectively. Pseudo-conditioned rats were presented with the FFB 10 h after drug or saline administration. Rats were implanted with microdialysis probes in the shell, core and PFCX. The effect of stimuli conditioned with morphine and nicotine on DA and on DA response to drugs was studied. Drug CSs elicited incentive reactions and released DA in the shell and PFCX but not in the core. Pre-exposure to morphine CS potentiated DA release to morphine challenge in the shell but not in the core and PFCX. This effect was related to the challenge dose of morphine and was stimulus-specific since a food CS did not potentiate the shell DA response to morphine. Pre-exposure to nicotine CS potentiated DA release in the shell and PFCX. The results show that drug CSs stimulate DA release in the shell and medial PFCX and specifically potentiate the primary stimulant drug effects on DA transmission.

Brain Damage Caused by Chemical Warfare Agents: Are Free Radicals a Final Common Pathway?

DTIC Science & Technology

1998-08-01

to methemoglobin (Fe(III); MetHb), simultaneously releasing nitrate (Feelisch and Noack, 1987; Archer, 1993,). An analytical approach to measure NO...NO analysis such as measurement of nitrite and nitrate by the Griess assay or HPLC-conductivity detection (Green et al., 1982; Lippsmeyer et al., 1990...enzyme nitrate reductase. Although other groups have claimed to use the Griess reaction with microdialysis samples, we have found the Griess reaction

Effects of the combination of metyrapone and oxazepam on cocaine-induced increases in corticosterone in the medial prefrontal cortex and nucleus accumbens.

PubMed

Keller, Courtney M; Breaux, Kelly N; Goeders, Nicholas E

2017-03-01

We have previously demonstrated that a combination of drugs (i.e., metyrapone and oxazepam) known to attenuate HPA-axis activity effectively decreases cocaine self-administration and cue reactivity in rats. However, we did not find changes in plasma corticosterone that matched the behavioral effects we observed, indicating that a different mechanism of action must be involved. Therefore, we hypothesized that the combination of metyrapone and oxazepam attenuates cocaine taking and seeking by decreasing cocaine-induced increases in corticosterone in the brain. Male rats were implanted with guide cannulae targeting the medial prefrontal cortex or nucleus accumbens. After the rats recovered from surgery, the microdialysis session was conducted. Rats were housed in the experimental chamber and the dialysis probes inserted into the guide cannulae the night before the session. The following day, dialysate samples were collected over a five-hour session. Baseline samples were collected for the first two hours, every 20min. Samples were then collected following administration of cocaine (15mg/kg, ip). Before injections of cocaine, rats were pretreated with either vehicle or the combination of metyrapone (50mg/kg, ip) and oxazepam (10mg/kg, ip). The administration of cocaine resulted in an increase in corticosterone in the medial prefrontal cortex following vehicle pretreatment, which was not observed in the nucleus accumbens. This cocaine-induced increase in corticosterone was attenuated by metyrapone/oxazepam. Reducing cocaine-induced increases in corticosterone in the medial prefrontal cortex might represent a novel mechanism through which the combination of metyrapone/oxazepam produces its behavioral effects. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaluation of intraprostatic metabolism of 1,25-dihydroxyvitamin D(3) (calcitriol) using a microdialysis technique.

PubMed

Konety, Badrinath R; Somogyi, George; Atan, Ali; Muindi, Josephia; Chancellor, Michael B; Getzenberg, Robert H

2002-06-01

1,25-dihydroxyvitamin D(3) (calcitriol) inhibits prostate cancer growth in vitro and in vivo. We used a prostate microdialysis technique to better understand the intraprostatic pharmacokinetics of calcitriol, which in turn would facilitate planning for systemic calcitriol therapy in patients with prostate cancer. Male Sprague-Dawley rats were treated with 5 microg of calcitriol intravenously. Animals were either intact (group 1, n = 6) or castrated (group 2, n = 3). Prostate microdialysis was performed by perfusing Krebs solution through a 5-mm linear probe. Effluents were collected hourly from 0 to 20 hours or until death. Serum was collected at baseline and at the end of the experiment. Serum was also obtained from untreated rats at 0, 1, 2, 3, 4, 6, 8, 12, and 24 hours after intraperitoneal injection of calcitriol. Calcitriol levels were measured by radioimmunoassay. The average baseline intraprostatic level of calcitriol in prostate dialysate in intact rats was 21.1 pg/mL (+/-7.5); it was 88 pg/mL (+/-98.4) after calcitriol administration. In castrated animals, the values were 16.6 pg/mL (+/-5.3) and 25.3 pg/mL (+/-10.7). Two peaks in intraprostatic calcitriol levels were observed after intravenous administration: at less than 6 hours after injection and at more than 13 hours after injection. The mean total calcitriol exposure (area under the concentration versus time curve) in the prostate was 297.6 (+/-159) pg/hr/mL (intact) and 272.7 (+/-123.6) pg/hr/mL (castrated). The baseline serum levels were 0.1 to 1 ng/mL and reached a peak of more than 100 ng/mL within 1 hour of intraperitoneal injection. This technique permits real-time measurement of intraprostatic pharmacokinetics of calcitriol. The ratio of the intraprostatic area under the concentration versus time curve to the serum area under the concentration versus time curve of calcitriol was less than 1:100. Hence, within 24 hours of calcitriol administration, only a fraction (less than 1%) of the serum level is detectable in prostatic tissue. A bimodal peak in intraprostatic calcitriol levels is observed. This technique could be used to determine the tissue levels of calcitriol more accurately and to conduct additional studies to better elucidate the effects of castration on the intraprostatic pharmacokinetics of calcitriol.

Intracerebral microdialysis coupled to LC-MS/MS for the determination tramadol and its major pharmacologically active metabolite O-desmethyltramadol in rat brain microdialysates.

PubMed

Liu, Mingzhou; Wang, Peng; Yu, Xuming; Dong, Guicheng; Yue, Jiang

2017-08-01

A rapid and sensitive method involving liquid chromatography electrospray tandem mass spectrometry (LC-ESI-MS/MS) coupled to an intracerebral microdialysis technique was developed for the determination and pharmacokinetic investigation of tramadol and its major active metabolite O-desmethyltramadol (ODT) in rat brain. The microdialysis samples were separated on a C18 column and eluted with a mobile phase of acetonitrile-water-formic acid (50:50:0.1; v/v/v) at a flow rate of 0.3 mL/min. The ESI-MS/MS spectra were performed in electrospray positive ion mode, and the analytes were detected by multiple reaction monitoring (MRM) of the transitions m/z [M + H] + 264.3 → 58.2 for tramadol, m/z [M + H] + 250.3 → 58.3 for ODT, and m/z [M + H] + 379.4 → 264.0 for ambroxol (internal standard; IS). The total run time was 4.0 min. A lower limit of quantitation (LLOQ) was achieved as 1 ng/mL for tramadol and 0.5 ng/mL for ODT, with excellent linearity over a concentration range of 1 ~ 500 ng/mL (r > 0.99) for tramadol and 0.5 ~ 50 ng/mL for ODT (r > 0.99), respectively. The proposed method was successfully applied to the pharmacokinetic studies of tramadol and ODT in rat brain. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Hypertonic Lactate to Improve Cerebral Perfusion and Glucose Availability After Acute Brain Injury.

PubMed

Carteron, Laurent; Solari, Daria; Patet, Camille; Quintard, Hervé; Miroz, John-Paul; Bloch, Jocelyne; Daniel, Roy T; Hirt, Lorenz; Eckert, Philippe; Magistretti, Pierre J; Oddo, Mauro

2018-06-19

Lactate promotes cerebral blood flow and is an efficient substrate for the brain, particularly at times of glucose shortage. Hypertonic lactate is neuroprotective after experimental brain injury; however, human data are limited. Prospective study (clinicaltrials.gov NCT01573507). Academic ICU. Twenty-three brain-injured subjects (13 traumatic brain injury/10 subarachnoid hemorrhage; median age, 59 yr [41-65 yr]; median Glasgow Coma Scale, 6 [3-7]). Three-hour IV infusion of hypertonic lactate (sodium lactate, 1,000 mmol/L; concentration, 30 µmol/kg/min) administered 39 hours (26-49 hr) from injury. We examined the effect of hypertonic lactate on cerebral perfusion (using transcranial Doppler) and brain energy metabolism (using cerebral microdialysis). The majority of subjects (13/23 = 57%) had reduced brain glucose availability (baseline pretreatment cerebral microdialysis glucose, < 1 mmol/L) despite normal baseline intracranial pressure (10 [7-15] mm Hg). Hypertonic lactate was associated with increased cerebral microdialysis lactate (+55% [31-80%]) that was paralleled by an increase in middle cerebral artery mean cerebral blood flow velocities (+36% [21-66%]) and a decrease in pulsatility index (-21% [13-26%]; all p < 0.001). Cerebral microdialysis glucose increased above normal range during hypertonic lactate (+42% [30-78%]; p < 0.05); reduced brain glucose availability correlated with a greater improvement of cerebral microdialysis glucose (Spearman r = -0.53; p = 0.009). No significant changes in cerebral perfusion pressure, mean arterial pressure, systemic carbon dioxide, and blood glucose were observed during hypertonic lactate (all p > 0.1). This is the first clinical demonstration that hypertonic lactate resuscitation improves both cerebral perfusion and brain glucose availability after brain injury. These cerebral vascular and metabolic effects appeared related to brain lactate supplementation rather than to systemic effects.

Medullary serotonergic neurones modulate the ventilatory response to hypercapnia, but not hypoxia in conscious rats.

PubMed

Taylor, Natalie C; Li, Aihua; Nattie, Eugene E

2005-07-15

Serotonergic neurones in the mammalian medullary raphe region (MRR) have been implicated in central chemoreception and the modulation of the ventilatory response to hypercapnia, and may also be involved in the ventilatory response to hypoxia. In this study, we ask whether ventilatory responses across arousal states are affected when the 5-hydroxytryptamine 1A receptor (5-HT1A) agonist (R)-(+)-8-hydroxy-2(di-n-propylamino)tetralin (DPAT) is microdialysed into the MRR of the unanaesthetized adult rat. Microdialysis of 1, 10 and 30 mM DPAT into the MRR significantly decreased absolute ventilation values(VE) during 7% CO2 breathing by 21%, 19% and 30%, respectively, in wakefulness compared to artificial cerebrospinal fluid (aCSF) microdialysis, due to decreases in tidal volume (VT) and not in frequency (f), similar to what occurred during non-rapid eye movement (NREM) sleep. The concentration-dependence of the hypercapnic ventilatory effect might be due to differences in tissue distribution of DPAT. DPAT (30 mM) changed room air breathing pattern by increasing f and decreasing VT. As evidenced by a sham control group, repeated experimentation and microdialysis of aCSF alone had no effect on the ventilatory response to 7% CO2 during wakefulness or sleep. Unlike during hypercapnia, microdialysis of 30 mM DPAT into the MRR did not change the ventilatory response to 10% O2. Additionally, 10 and 30 mM DPAT MRR microdialysis decreased body temperature, and 30 mM DPAT increased the percentage of experimental time in wakefulness. We conclude that serotonergic activity in the MRR plays a role in the ventilatory response to hypercapnia, but not to hypoxia, and that MRR 5-HT1A receptors are also involved in thermoregulation and arousal.

Programmable carbon nanotube membrane-based transdermal nicotine delivery with microdialysis validation assay.

PubMed

Gulati, Gaurav Kumar; Chen, Tao; Hinds, Bruce Jackson

2017-01-01

To evaluate the performance of switchable carbon nanotubes (CNT) membrane devices for transdermal nicotine delivery, we have developed an in-vitro microdialysis method that allow us to detect variable transdermal fluxes of nicotine through CNT devices and can be applied directly to in-vivo studies. Microdialysis membranes were placed beneath the porcine skin and its nicotine levels increased 6-8 times when the CNT membrane on skin was turned from OFF to ON state by application of bias. Fluxes in the ON state were approximately 3 times that of commercial nicotine patches and switching times were less than two hours, thus suggesting the improved therapeutic potential of our device. Blue tooth enabled CNT devices that can be programmed by smartphone and coupled with remote counseling application for enhanced smoking cessation treatments. Copyright © 2016. Published by Elsevier Inc.

Mechanisms and time course of menthol-induced cutaneous vasodilation

PubMed Central

Craighead, Daniel H.; McCartney, Nathaniel B.; Tumlinson, James H.; Alexander, Lacy M.

2017-01-01

Menthol is a vasoactive compound that is widely used in topical analgesic agents. Menthol induces cutaneous vasodilation, however the underlying mechanisms are unknown. Determining the rates of appearance and clearance of menthol in the skin is important for optimizing topical treatment formulation and dosing. The purpose of this study was to determine the mechanisms contributing to menthol-mediated cutaneous vasodilation and to establish a time course for menthol appearance/clearance in the skin. Ten young (23±1 years, 5 males 5 females) subjects participated in two protocols. In study 1, four intradermal microdialysis fibers were perfused with increasing doses of menthol (0.1-500mM) and inhibitors for nitric oxide (NO), endothelium derived hyperpolarizing factors (EDHFs), and sensory nerves. Skin blood flow was measured with laser Doppler flowmetry and normalized to %CVCmax. In study 2, two intradermal microdialysis fibers were perfused with lactated Ringer's solution. 0.017mL•cm-2 of a 4% menthol gel was placed over each fiber. 5μL samples of dialysate from the microdialysis fibers were collected every 30 minutes and analyzed for the presence of menthol with high performance gas chromatography/mass spectrometry. Skin blood flow (laser speckle contrast imaging) and subjective ratings of menthol sensation were simultaneously obtained with dialysate samples. In study 1, menthol induced cutaneous vasodilation at all doses ≥100mM (all p<0.05). However, inhibition of either NO, EDHFs, or sensory nerves fully inhibited menthol-mediated vasodilation (all p>0.05). In study 2, significant menthol was detected in dialysate 30 minutes post menthol application (0.89ng, p=0.0002). Relative to baseline, cutaneous vasodilation was elevated from minutes 15-45 and ratings of menthol sensation were elevated from minute 5-60 post menthol application (all p<0.05). Menthol induces cutaneous vasodilation in the skin through multiple vasodilator pathways, including NO, EDHF, and sensory nerves. Topical menthol is detectable in the skin within 30 minutes and is cleared by 60 minutes. Skin blood flow and perceptual measures follow a similar time course as menthol appearance/clearance. PMID:27899298

Phasic Dopaminergic Signaling and the Presymptomatic Phase of Parkinson’s Disease

DTIC Science & Technology

2005-07-01

provides an ambient , steady- state level of extracellular dopamine, whereas phasic signaling results in a transient increase (i.e., a short-lived...certain ambient extracellular level of dopamine is essential for movement to occur [116]. Phasic signaling involves synchronized high frequency firing of...microdialysis. A measurement of the ambient level of dopamine by microdialysis in animal studies shows that extracellular dopamine levels are normal

A neuropharmacokinetic assessment of bafetinib, a second generation dual BCR-Abl/Lyn tyrosine kinase inhibitor, in patients with recurrent high-grade gliomas.

PubMed

Portnow, Jana; Badie, Behnam; Markel, Susan; Liu, An; D'Apuzzo, Massimo; Frankel, Paul; Jandial, Rahul; Synold, Timothy W

2013-05-01

The primary objective of this study was to use intracerebral microdialysis (ICMD) to determine the neuropharmacokinetics of bafetinib, a dual BCR-Abl/Lyn tyrosine kinase inhibitor that may have activity against gliomas. A microdialysis catheter was placed into either peritumoural or enhancing brain tissue of seven patients at the time of tumour resection or biopsy. Twenty-four hours later, bafetinib was administered, 240 or 360 mg po, repeating the same dose 12 h later. Dialysate samples were continuously collected for 24h, with plasma samples obtained in parallel. One to two weeks after finishing ICMD, patients were allowed to resume taking bafetinib continuously while being observed for toxicity and tumour response. Twenty-six dialysate samples per patient were collected (n=6) and analysed for bafetinib by tandem mass spectrometry. Bafetinib concentrations in the brain were below the lower limit of detection of the assay (0.1 ng/ml) in all samples except one from a single subject that was 0.52 ng/ml. The mean plasma bafetinib maximum concentrations after dose 1 and 2 were 143±99 and 247±73 ng/ml, respectively. Only one patient remained on treatment past two cycles, and no radiographic responses were seen. Bafetinib does not sufficiently cross intact or disrupted blood-brain barrier, and therefore, systemic administration of bafetinib is not recommended when investigating this drug as a treatment for brain tumours. ICMD can be a valuable research tool in early drug development. Lead-in ICMD studies can be performed relatively quickly, requiring only a small number of patients, and without significantly disrupting standard cancer care. Copyright © 2013 Elsevier Ltd. All rights reserved.

A novel liquid chromatography/tandem mass spectrometry method for the quantification of glycine as biomarker in brain microdialysis and cerebrospinal fluid samples within 5min.

PubMed

Voehringer, Patrizia; Fuertig, René; Ferger, Boris

2013-11-15

Glycine is an important amino acid neurotransmitter in the central nervous system (CNS) and a useful biomarker to indicate biological activity of drugs such as glycine reuptake inhibitors (GRI) in the brain. Here, we report how a liquid chromatography/tandem mass spectrometry (LC-MS/MS) method for the fast and reliable analysis of glycine in brain microdialysates and cerebrospinal fluid (CSF) samples has been established. Additionally, we compare this method with the conventional approach of high performance liquid chromatography (HPLC) coupled to fluorescence detection (FD). The present LC-MS/MS method did not require any derivatisation step. Fifteen microliters of sample were injected for analysis. Glycine was detected by a triple quadrupole mass spectrometer in the positive electrospray ionisation (ESI) mode. The total running time was 5min. The limit of quantitation (LOQ) was determined as 100nM, while linearity was given in the range from 100nM to 100μM. In order to demonstrate the feasibility of the LC-MS/MS method, we measured glycine levels in striatal in vivo microdialysates and CSF of rats after administration of the commercially available glycine transporter 1 (GlyT1) inhibitor LY 2365109 (10mg/kg, p.o.). LY 2365109 produced 2-fold and 3-fold elevated glycine concentrations from 1.52μM to 3.6μM in striatal microdialysates and from 10.38μM to 36μM in CSF, respectively. In conclusion, we established a fast and reliable LC-MS/MS method, which can be used for the quantification of glycine in brain microdialysis and CSF samples in biomarker studies. Copyright © 2013 Elsevier B.V. All rights reserved.

Alteration in plasma and striatal levels of d-serine after d-serine administration with or without nicergoline: An in vivo microdialysis study.

PubMed

Onozato, Mayu; Nakazawa, Hiromi; Ishimaru, Katsuyuki; Nagashima, Chihiro; Fukumoto, Minori; Hakariya, Hitomi; Sakamoto, Tatsuya; Ichiba, Hideaki; Fukushima, Takeshi

2017-09-01

d-Serine (d-Ser), a co-agonist of N -methyl-d-aspartate receptor (NMDAR), is effective for treating schizophrenia. The present study investigated changes in plasma and striatal d-Ser levels in Sprague-Dawley (SD) rats after intraperitoneal d-Ser administration alone or together with nicergoline (Nic), a commercial cerebral ameliorating drug, using in vivo microdialysis (MD) to explore the function of Nic. Phosphate-buffered saline (PBS) or Nic (0, 1.0, or 3.0 mg/kg) followed by d-Ser (5.0, 10.0, 20.0, and 50.0 mg/kg for PBS or 20.0 mg/kg for Nic) was administered intraperitoneally to male SD rats, and the profiles of d-Ser levels in plasma and striatal MD samples were examined by high-performance liquid chromatography (HPLC) with fluorescence detection. The area under the curve (AUC) for the MD and plasma samples was also calculated and statistically compared among groups. AUC values of d-Ser increased in a d-Ser dose-dependent manner in plasma samples, while a proportional increase in the AUC values of striatal MD samples was only observed in d-Ser doses up to 20 mg/kg. The Nic co-administered group showed a significant increase in the AUC of plasma d-Ser in a Nic dose-dependent manner, but the AUC in striatal d-Ser significantly decreased with increasing Nic doses suggesting that Nic may prevent excess d-Ser from penetrating the central nervous system (CNS). Nic may prevent an excessive distribution of exogenous d-Ser, such as that from a dietary origin, into the CNS by suppressing excitatory neurotransmission through NMDAR.

Effects of sarizotan on the corticostriatal glutamate pathways.

PubMed

Antonelli, Tiziana; Fuxe, Kjell; Tomasini, Maria C; Bartoszyk, Gerd D; Seyfried, Christoph A; Tanganelli, Sergio; Ferraro, Luca

2005-12-01

The effects of sarizotan, a 5-HT(1A) agonist with additional affinity for D(3) and D(4) receptors, have been studied on the corticostriatal glutamate pathways using dual-probe microdialysis in the awake rat. Sarizotan given systemically (0.1-10 mg/kg s.c.) or perfused into the motor cortex (10 microM) produced 20-30% reduction of cortical and striatal glutamate levels. The inhibitory effects of the systemic sarizotan on cortical and striatal glutamate levels were counteracted by intracortical perfusion with the 5-HT(1A) antagonist WAY100135 (10 microM). These findings suggest that the anti-dyskinetic properties of sarizotan could be mediated via its 5-HT(1A) agonist actions in the motor cortex, leading to reduced activity in the corticostriatal glutamate pathways with reduced activation of the striatopallidal GABA pathway mediating motor inhibition. Synapse 58:193-199, 2005. (c) 2005 Wiley-Liss, Inc.

Thiopental sodium reduces glutamate extracellular levels in rat intact prefrontal cortex.

PubMed

Liu, Hongliang; Yao, Shanglong

2005-12-01

To investigate the effect of thiopental sodium on glutamate extracellular levels in the prefrontal cortex (PFC) of rats, a microdialysis probe was inserted into the PFC, the perfusate was collected every 10 min throughout the experiment with thiopental sodium ip or perfused into the PFC locally. The concentrations of glutamate in the perfusate were determined by reversed-phase high performance liquid chromatography. Thiopental sodium 30 mg kg(-1) ip significantly decreased glutamate levels in the perfusate after 10, 20, 30, and 40 min; glutamate levels in the perfusate were also decreased from 10 to 90 min after thiopental sodium 50 mg kg(-1) ip. Thiopental sodium with concentrations of 30, 100, or 300 microM perfused into the PFC also decreased glutamate levels in the perfusate significantly. The results suggest that thiopental sodium decreases glutamate extracellular levels in rat intact PFC.

Lesion of medial prefrontal dopamine terminals abolishes habituation of accumbens shell dopamine responsiveness to taste stimuli.

PubMed

Bimpisidis, Zisis; De Luca, Maria Antonietta; Pisanu, Augusta; Di Chiara, Gaetano

2013-02-01

Taste stimuli increase extracellular dopamine (DA) in the nucleus accumbens (NAc) and in the medial prefrontal cortex (mPFC). This effect shows single-trial habituation in NAc shell but not in core or in mPFC. Morphine sensitization abolishes habituation of DA responsiveness in NAc shell but induces it in mPFC. These observations support the hypothesis of an inhibitory influence of mPFC DA on NAc DA. To test this hypothesis, we used in vivo microdialysis to investigate the effect of mPFC 6-hydroxy-dopamine (6-OHDA) lesions on the NAc DA responsiveness to taste stimuli. 6-OHDA was infused bilaterally in the mPFC of rats implanted with guide cannulae. After 1 week, rats were implanted with an intraoral catheter, microdialysis probes were inserted into the guide cannulae, and dialysate DA was monitored in NAc shell/core after intraoral chocolate. 6-OHDA infusion reduced tissue DA in the mPFC by 75%. Tyrosine hydroxylase immunohistochemistry showed that lesions were confined to the mPFC. mPFC 6-OHDA lesion did not affect the NAc shell DA responsiveness to chocolate in naive rats but abolished habituation in rats pre-exposed to the taste. In the NAc core, mPFC lesion potentiated, delayed and prolonged the stimulatory DA response to taste but failed to affect DA in pre-exposed rats. Behavioural taste reactions and motor activity were not affected. The results indicate a top-down control of NAc DA by mPFC and a reciprocal relationship between DA transmission in these two areas. Moreover, habituation of DA responsiveness in the NAc shell is dependent upon an intact DA input to the mPFC. © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Neuropathological Consequences of Exposure to Sublethal Doses of Cyanide

DTIC Science & Technology

1992-11-01

identify by block number) Experiments focused on the effects of cyanide on brain energy metabolism , microdialysis studies (to measure acid products of...Discussion 15 Brain metabolism studies 15 Table L Effect of cyanide on local cerebral glucose 17 use (pmol/lO0 glmin). Microdialysis studies 18 Figure 2. Local...Brain metabolism studies: To determine the brain regions affected by sublethal doses of cyanide, male rats were given saline or NaCN by controlled iv

Study of the interaction of 6-mercaptopurine with protein by microdialysis coupled with LC and electrochemical detection based on functionalized multi-wall carbon nanotubes modified electrode.

PubMed

Cao, Xu-Ni; Lin, Li; Zhou, Yu-Yan; Zhang, Wen; Shi, Guo-Yue; Yamamoto, Katsunobu; Jin, Li-Tong

2003-07-14

Microdialysis sampling coupled with liquid chromatography and electrochemical detection (LC-ECD) was developed and applied to study the interaction of 6-Mercaptopurine (6-MP) with bovine serum albumin (BSA). In the LC-ECD, the multi-wall carbon nanotubes fuctionalized with carboxylic groups modified electrode (MWNT-COOH CME) was used as the working electrode for the determination of 6-MP. The results indicated that this chemically modified electrode (CME) exhibited efficiently electrocatalytic oxidation for 6-MP with relatively high sensitivity, stability and long-life. The peak currents of 6-MP were linear to its concentrations ranging from 4.0 x 10(-7) to 1.0 x 10(-4) mol l(-1) with the calculated detection limit (S/N = 3) of 2.0 x 10(-7) mol l(-1). The method had been successfully applied to assess the association constant (K) and the number of the binding sites (n) on a BSA molecular, which calculated by Scatchard equation, were 3.97 x 10(3) mol(-1) l and 1.51, respectively. This method provided a fast, sensible and simple technique for the study of drug-protein interactions.

Substantial Metabolic Activity of Human Brown Adipose Tissue during Warm Conditions and Cold-Induced Lipolysis of Local Triglycerides.

PubMed

Weir, Graeme; Ramage, Lynne E; Akyol, Murat; Rhodes, Jonathan K; Kyle, Catriona J; Fletcher, Alison M; Craven, Thomas H; Wakelin, Sonia J; Drake, Amanda J; Gregoriades, Maria-Lena; Ashton, Ceri; Weir, Nick; van Beek, Edwin J R; Karpe, Fredrik; Walker, Brian R; Stimson, Roland H

2018-06-05

Current understanding of in vivo human brown adipose tissue (BAT) physiology is limited by a reliance on positron emission tomography (PET)/computed tomography (CT) scanning, which has measured exogenous glucose and fatty acid uptake but not quantified endogenous substrate utilization by BAT. Six lean, healthy men underwent 18 fluorodeoxyglucose-PET/CT scanning to localize BAT so microdialysis catheters could be inserted in supraclavicular BAT under CT guidance and in abdominal subcutaneous white adipose tissue (WAT). Arterial and dialysate samples were collected during warm (∼25°C) and cold exposure (∼17°C), and blood flow was measured by 133 xenon washout. During warm conditions, there was increased glucose uptake and lactate release and decreased glycerol release by BAT compared with WAT. Cold exposure increased blood flow, glycerol release, and glucose and glutamate uptake only by BAT. This novel use of microdialysis reveals that human BAT is metabolically active during warm conditions. BAT activation substantially increases local lipolysis but also utilization of other substrates such as glutamate. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

In vivo monitoring of multiple trace metals in the brain extracellular fluid of anesthetized rats by microdialysis-membrane desalter-ICPMS.

PubMed

Chung, Y T; Ling, Y C; Yang, C S; Sun, Y C; Lee, P L; Lin, C Y; Hong, C C; Yang, M H

2007-12-01

We have developed an on-line analytical system involving microdialysis (MD) sampling, a carbohydrate membrane desalter (CMD), and an inductively coupled plasma mass spectrometer (ICPMS) system for the simultaneous determination of multiple trace metals in the extracellular fluid (ECF) in the brains of anesthetized rats. The microdialysate that perfused from the animal at a flow rate of 0.5 microL/min was on-line transferred to the CMD to remove the high-sodium matrix, followed by ICPMS measurement. The role of the CMD in this on-line system was investigated in detail. With prior addition of EDTA to the microdialysate to form anionic complexes of the metal analytes and the use of NH4Cl as a regenerant to exchange Na(+) with NH4(+) ions, both quantitative recovery of the trace metal analytes and quantitative removal of the sodium matrix could be achieved. Two experimental modes of the monitoring system were constructed. For those metals (e.g., Cu, Zn, and Mn) that existed at (sub)nanogram-per-milliliter concentrations in the microdialysate, the temporal resolution was 10 min when using a 10 microL loop for sample collection, followed by CMD and ICPMS; for those elements (e.g., Ca and Mg) that existed at microgram-per-milliliter levels (or greater), near-real-time analysis was possible because the microdialysate could be led, bypassing the sample loop, directly to the CMD for desalting without any time delay. Further improvement of the temporal resolution for the low-concentration elements was not possible without decreasing the detection limits of mass detection. Among the eight trace metals tested using this on-line system, the method detection limits for Cu, Zn, Mn, Co, Ni, and Pb reached subnanogram-per-milliliter levels; for electrolyte species such as Ca and Mg, the detection limits were in the range of 50-100 ng/mL. Analytical accuracy, expressed as spike recovery, was 100% +/- 15% for all of the elements tested. We demonstrate the applicability of the proposed system through the successful measurement of the basal values of Ca, Mg, Cu, Zn, and Mn in the ECF of a living rat brain and through in vivo monitoring of the concentration profiles of Mn and Pt in the ECF after the injection of drugs (MnCl2 and cisplatin) into the rats. This microdialysis system is the first to offer real-time, in vivo monitoring of trace elements such as Ca and Mg.

Stimulus-dependent changes of extracellular glucose in the rat hippocampus determined by in vivo microdialysis.

PubMed

Rex, A; Bert, B; Fink, H; Voigt, J-P

2009-10-19

Neuronal activity is tightly coupled with brain energy metabolism; and glucose is an important energy substrate for neurons. The present in vivo microdialysis study was aimed at investigating changes in extracellular glucose concentrations in the rat ventral hippocampus due to exposure to the elevated plus maze. Determination of basal hippocampal glucose and lactate/pyruvate ratio in male Wistar rats was conducted in the home cage using in vivo microdialysis. Rats were exposed to the elevated plus maze, a rodent model of anxiety-related behaviour, or to unspecific stress induced by white noise (95dB) as a control condition. Basal hippocampal levels of glucose, as determined by zero-net-flux, and the basal lactate/pyruvate ratio were 1.49+/-0.05mmol/l and 13.8+/-1.1, respectively. In rats without manipulation, glucose levels remained constant throughout the experiment (120min). By contrast, exposure to the elevated plus maze led to a temporary decline in hippocampal glucose (-33.2+/-4.4%) which returned to baseline level in the home cage. White noise caused only a non-significant decrease in extracellular glucose level (-9.3+/-3.5%). In all groups, the lactate/pyruvate ratio remained unchanged by the experimental procedures. Our microdialysis study demonstrates that exposure to the elevated plus maze induces a transient decrease in extracellular hippocampal glucose concentration. In contrast, an unspecific stimulus did not change hippocampal glucose. The latter suggests that only specific behavioural stimuli increase hippocampal glucose utilization in the ventral hippocampus.

Intravenously administered oxotremorine and atropine, in doses known to affect pain threshold, affect the intraspinal release of acetylcholine in rats.

PubMed

Abelson, Klas S P; Höglund, A Urban

2002-04-01

Both systemically and intrathecally administered cholinergic agonists produce antinociception while cholinergic antagonists decrease pain threshold. The mechanism and the site of action of these substances are not known. In the present study it was hypothesized that systemically administered muscarinic agonists and antagonists modify nociceptive threshold by affecting intraspinal release of acetylcholine (ACh). Catheters were inserted into the femoral vein in rats maintained on isoflurane anaesthesia for administration of oxotremorine (10-300 microg/kg) and atropine (0.1, 10, 5000 microg/kg). Spinal microdialysis probes were placed intraspinally at approximately the C2-C5 spinal level for sampling of acetylcholine and dialysis delivery of atropine (0.1, 1, 10 nM). Additionally, the tail-flick behaviour was tested on conscious rats injected intraperitoneally with saline, atropine (10, 100 and 5000 microg/kg), or subcutaneously with oxotremorine (30, 100, 300 microg/kg). Subcutaneous administration of oxotremorine (30, 100, 300 microg/kg) significantly increased the tail-flick latency. These doses of oxotremorine dose-dependently increased the intraspinal release of acetylcholine. Intravenously administered atropine, in a dose that produced hyperalgesia (5000 microg/kg) in the tail-flick test, significantly decreased the intraspinal release of acetylcholine. Our results suggest an association between pain threshold and acetylcholine release in spinal cord. It is also suggested that an approximately 30% increase in basal ACh release produces antinociception and that a 30% decrease in basal release produces hyperalgesia.

Determination of protein-unbound rhynchiphylline brain distribution by microdialysis and ultra-performance liquid chromatography with tandem mass spectrometry.

PubMed

Lee, Chia-Jung; Hsueh, Thomas Y; Lin, Lie-Chwen; Tsai, Tung-Hu

2014-06-01

The stem with hook of Uncaria rhynchophylla (Chinese herbal name Gou-Teng) is a traditional Chinese medicine that has been ethnopharmacologically used to extinguish wind and clean interior heat. Rhynchophylline (RHY), a tetracyclic oxindole alkaloid isolated from U. rhynchophylla, displays significant antineuroinflammatory effects. However, there is no evidence to indicate that rhynchophylline can cross the blood-brain barrier and be detected in the brain. In this study, an in vivo microdialysis sampling method coupled with UPLC/MS/MS was employed for the continuous simultaneous monitoring of unbound RHY in rat blood and brain. The precursor ion → product ion transition at m/z 385.2 → 160.0 for rhynchophylline was monitored. A calibration curve gave good linearity (r>0.996) over the concentration range from 0.5 to 1000 ng/mL. The results demonstrated that rhynchophylline could be detected in the brain and plasma from 15 min to 6 h after its administration (1 or 10 mg/kg, i.v.). All the pharmacokinetic parameters of rhynchophylline in the brain and plasma were obtained. These results show that rhynchophylline can cross the blood-brain barrier and they provide useful clinical information. Copyright © 2014 John Wiley & Sons, Ltd.

Fast and sensitive HPLC/UV method for cefazolin quantification in plasma and subcutaneous tissue microdialysate of humans and rodents applied to pharmacokinetic studies in obese individuals.

PubMed

Palma, Eduardo Celia; Laureano, João Victor; de Araújo, Bibiana Verlindo; Meinhardt, Nelson Guardiola; Stein, Airton Tetelbom; Dalla Costa, Teresa

2018-04-14

Antimicrobial prophylactic dosing of morbidly obese patients may differ from normal weighted individuals owing to alterations in drug tissue distribution. Drug subcutaneous tissue distribution can be investigated by microdialysis patients and animals. The need for cefazolin prophylactic dose adjustment in obese patients remains under discussion. The paper describes the validation of an HPLC-UV method for cefazolin quantification in plasma and microdialysate samples from clinical and pre-clinical studies. A C 18 column with an isocratic mobile phase was used for drug separation, with detection at 272 nm. Total and unbound cefazolin lower limit of quantitation was 5 μg/mL in human plasma, 2 μg/mL in rat plasma, and 0.5 and 0.025 μg/mL in human and rat microdialysate samples, respectively. The maximum intra- and inter-day imprecisions were 10.7 and 8.1%, respectively. The inaccuracy was <9.7%. The limit of quantitation imprecision and inaccuracy were < 15%. Cefazolin stability in the experimental conditions was confirmed. Cefazolin plasma concentrations and subcutaneous tissue penetration were determined by microdialysis in morbidly obese patients (2 g i.v. bolus) and diet-induced obese rats (30 mg/kg i.v. bolus) using the method. This method has the main advantages of easy plasma clean-up and practicability and has proven to be useful in cefazolin clinical and pre-clinical pharmacokinetic investigations. Copyright © 2018 John Wiley & Sons, Ltd.

Microdialysis Sampling from Wound Fluids Enables Quantitative Assessment of Cytokines, Proteins, and Metabolites Reveals Bone Defect-Specific Molecular Profiles.

PubMed

Förster, Yvonne; Schmidt, Johannes R; Wissenbach, Dirk K; Pfeiffer, Susanne E M; Baumann, Sven; Hofbauer, Lorenz C; von Bergen, Martin; Kalkhof, Stefan; Rammelt, Stefan

2016-01-01

Bone healing involves a variety of different cell types and biological processes. Although certain key molecules have been identified, the molecular interactions of the healing progress are not completely understood. Moreover, a clinical routine for predicting the quality of bone healing after a fracture in an early phase is missing. This is mainly due to a lack of techniques to comprehensively screen for cytokines, growth factors and metabolites at their local site of action. Since all soluble molecules of interest are present in the fracture hematoma, its in-depth assessment could reveal potential markers for the monitoring of bone healing. Here, we describe an approach for sampling and quantification of cytokines and metabolites by using microdialysis, combined with solid phase extractions of proteins from wound fluids. By using a control group with an isolated soft tissue wound, we could reveal several bone defect-specific molecular features. In bone defect dialysates the neutrophil chemoattractants CXCL1, CXCL2 and CXCL3 were quantified with either a higher or earlier response compared to dialysate from soft tissue wound. Moreover, by analyzing downstream adaptions of the cells on protein level and focusing on early immune response, several proteins involved in the immune cell migration and activity could be identified to be specific for the bone defect group, e.g. immune modulators, proteases and their corresponding inhibitors. Additionally, the metabolite screening revealed different profiles between the bone defect group and the control group. In summary, we identified potential biomarkers to indicate imbalanced healing progress on all levels of analysis.

Microdialysis Sampling from Wound Fluids Enables Quantitative Assessment of Cytokines, Proteins, and Metabolites Reveals Bone Defect-Specific Molecular Profiles

PubMed Central

Wissenbach, Dirk K.; Pfeiffer, Susanne E. M.; Baumann, Sven; Hofbauer, Lorenz C.; von Bergen, Martin; Kalkhof, Stefan; Rammelt, Stefan

2016-01-01

Bone healing involves a variety of different cell types and biological processes. Although certain key molecules have been identified, the molecular interactions of the healing progress are not completely understood. Moreover, a clinical routine for predicting the quality of bone healing after a fracture in an early phase is missing. This is mainly due to a lack of techniques to comprehensively screen for cytokines, growth factors and metabolites at their local site of action. Since all soluble molecules of interest are present in the fracture hematoma, its in-depth assessment could reveal potential markers for the monitoring of bone healing. Here, we describe an approach for sampling and quantification of cytokines and metabolites by using microdialysis, combined with solid phase extractions of proteins from wound fluids. By using a control group with an isolated soft tissue wound, we could reveal several bone defect-specific molecular features. In bone defect dialysates the neutrophil chemoattractants CXCL1, CXCL2 and CXCL3 were quantified with either a higher or earlier response compared to dialysate from soft tissue wound. Moreover, by analyzing downstream adaptions of the cells on protein level and focusing on early immune response, several proteins involved in the immune cell migration and activity could be identified to be specific for the bone defect group, e.g. immune modulators, proteases and their corresponding inhibitors. Additionally, the metabolite screening revealed different profiles between the bone defect group and the control group. In summary, we identified potential biomarkers to indicate imbalanced healing progress on all levels of analysis. PMID:27441377

Impact of simulated microgravity and caloric restriction on autonomic nervous system function in adipose tissue

NASA Astrophysics Data System (ADS)

Boschmann, Michael; Adams, Frauke; Tank, Jens; Schaller, Karin; Boese, Andrea; Heer, Martina; Klause, Susanne; Luft, Friedrich C.; Jordan, Jens

2005-08-01

Long term immobilization and reduced food intake is often associated with development of orthostatic intolerance. Blocking the norepinephrine transporter (NET) can also mimic symptoms of orthostatic intolerance. Therefore, we hypothesized that simulated microgravity (14 days bed rest at head down tilt, BR) can cause changes in postganglionic NET function and adrenoreceptor (AR) sensitivity and these changes can be aggravated by hypocaloric food intake. For testing, two microdialysis probes were inserted into subcutaneous adipose tissue of eight young healthy men at day 1 and 14 of BR and perfused with Ringer's solution and increasing doses of tyramine and isoproterenol in order to simulate NET blockade and stimulate AR, respectively. At day 14 of eucaloric diet and BR, isoproterenol induced lipolysis was greater, whereas at day 14 of hypocaloric diet and BR, tyramine induced lipolysis was greater when compared to day 1. Therefore, the nutritional state affects NET function and AR sensitivity differently during BR.

Principal component analysis of the cytokine and chemokine response to human traumatic brain injury.

PubMed

Helmy, Adel; Antoniades, Chrystalina A; Guilfoyle, Mathew R; Carpenter, Keri L H; Hutchinson, Peter J

2012-01-01

There is a growing realisation that neuro-inflammation plays a fundamental role in the pathology of Traumatic Brain Injury (TBI). This has led to the search for biomarkers that reflect these underlying inflammatory processes using techniques such as cerebral microdialysis. The interpretation of such biomarker data has been limited by the statistical methods used. When analysing data of this sort the multiple putative interactions between mediators need to be considered as well as the timing of production and high degree of statistical co-variance in levels of these mediators. Here we present a cytokine and chemokine dataset from human brain following human traumatic brain injury and use principal component analysis and partial least squares discriminant analysis to demonstrate the pattern of production following TBI, distinct phases of the humoral inflammatory response and the differing patterns of response in brain and in peripheral blood. This technique has the added advantage of making no assumptions about the Relative Recovery (RR) of microdialysis derived parameters. Taken together these techniques can be used in complex microdialysis datasets to summarise the data succinctly and generate hypotheses for future study.

In vivo detection of fluctuating brain steroid levels SHORT

PubMed Central

Ikeda, Maaya; Rensel, Michelle A.; Schlinger, Barney A.; Remage-Healey, Luke

2015-01-01

This protocol describes a method for in vivo measurement of steroid hormones in brain circuits of the zebra finch. In vivo microdialysis has been used successfully to detect fluctuating neurosteroids in the auditory forebrain (Remage-Healey et al., 2008; 2012; Ikeda et al., 2012) and in the hippocampus (Rensel et al., 2012; 2013) of behaving adult zebra finches. In some cases, the steroids measured are derived locally (e.g., ‘neurosteroids’ like estrogens in males) whereas in other cases the steroids measured reflect systemic circulating levels and/or central conversion (e.g., the primary androgen testosterone and the primary glucocorticoid corticosterone). We also describe the method of reverse-microdialysis (‘retrodialysis’) of compounds that can influence local steroid neurochemistry as well as behavior. In vivo microdialysis can now be used to study steroid signaling in the brain for a variety of experimental purposes. Furthermore, similar methods have been developed to examine changing levels of catecholamines in behaving zebra finches (e.g., Sasaki et al., 2006). Thus, the combined study of neurochemistry and behavior in a vocal learning species now has a new set of powerful tools. PMID:25342066

Noradrenergic facilitation of shock-probe defensive burying in lateral septum of rats, and modulation by chronic treatment with desipramine.

PubMed

Bondi, Corina O; Barrera, Gabriel; Lapiz, M Danet S; Bedard, Tania; Mahan, Amy; Morilak, David A

2007-03-30

We have previously shown that acute stress-induced release of norepinephrine (NE) facilitates anxiety-like behavioral responses to stress, such as reduction in open-arm exploration on the elevated-plus maze and in social behavior on the social interaction test. Since these responses represent inhibition of ongoing behavior, it is important to also address whether NE facilitates a response that represents an activation of behavior. Correspondingly, it is unknown how a chronic elevation in tonic steady-state noradrenergic (NA) neurotransmission induced by NE reuptake blockade might alter this acute modulatory function, a regulatory process that may be pertinent to the anxiolytic effects of NE reuptake blockers such as desipramine (DMI). Therefore, in this study, we investigated noradrenergic modulation of the shock-probe defensive burying response in the lateral septum (LS). In experiment 1, shock-probe exposure induced an acute 3-fold increase in NE levels measured in LS of male Sprague-Dawley rats by microdialysis. Shock-probe exposure also induced a modest rise in plasma ACTH, taken as an indicator of perceived stress, that returned to baseline more rapidly in rats that were allowed to bury the probe compared to rats prevented from burying by providing them with minimal bedding, indicating that the active defensive burying behavior is an effective coping strategy that reduces the impact of acute shock probe-induced stress. In experiment 2, blockade of either alpha(1)- or beta-adrenergic receptors in LS by local antagonist microinjection immediately before testing reduced defensive burying and increased immobility. In the next experiment, chronic DMI treatment increased basal extracellular NE levels in LS, and attenuated the acute shock probe-induced increase in NE release in LS relative to baseline. Chronic DMI treatment decreased shock-probe defensive burying behavior in a time-dependent manner, apparent only after 2 weeks or more of drug treatment. Moreover, rats treated chronically with DMI showed no significant rise of plasma ACTH in response to shock-probe exposure. Thus, acute stress-induced release of NE in LS facilitated defensive burying, an active, adaptive behavioral coping response. Chronic treatment with the NE reuptake blocker and antidepressant drug DMI attenuated acute noradrenergic facilitation of the active burying response, and also attenuated the level of perceived stress driving that response. These results suggest that long-term regulation of the acute modulatory function of NE by chronic treatment with reuptake blockers may contribute to the mechanisms by which such drugs exert their anxiolytic effects in the treatment of stress-related psychiatric conditions, including depression and anxiety.

Functional neuroanatomy of the ventral striopallidal GABA pathway. New sites of intervention in the treatment of schizophrenia.

PubMed

O'Connor, W T

2001-08-15

Microdialysis was employed to investigate the dopamine, cholecystokinin (CCK) and neurotensin receptor regulation of ventral striopallidal GABA transmission by intra-accumbens perfusion with selective receptor ligands and monitoring local or ipsilateral ventral pallidal GABA release. In the dual probe studies intra-accumbens perfusion with the dopamine D1 and D2 receptor agonists SKF28293 and pergolide had no effect on ventral pallidal GABA, while both the D1 and D2 receptor antagonists SCH23390 and raclopride increased ventral pallidal GABA release. In contrast, intra-accumbens CCK decreased ventral pallidal GABA release and this was reversed by local perfusion with the CCK2 receptor antagonist PD134308 but not the CCK1 receptor antagonist L-364,718. In a single probe study intra-accumbens neurotensin increased local GABA release, which was strongly potentiated when the peptidase inhibitor phosphodiepryl 08 was perfused together with neurotensin. In addition, the neurotensin receptor antagonist SR48692 counteracted this phosphodiepryl 08 induced potentiated increased in GABA release. Taken together, these findings indicate that mesolimbic dopamine and CCK exert a respective tonic and phasic inhibition of ventral pallidal GABA release while the antipsychotic activity associated with D1 and D2 receptor antagonists may be explained by their ability to increase ventral striopallidal GABA transmission. Furthermore, the findings suggest that CCK2 receptor antagonists and neurotensin endopeptidase inhibitors may be useful antipsychotics.

Microdialysis as a way to measure antibiotics concentration in tissues.

PubMed

Marchand, Sandrine; Chauzy, Alexia; Dahyot-Fizelier, Claire; Couet, William

2016-09-01

As for all other drugs, antibiotics must reach their pharmacodynamic target in order to exert their effect, but because infection may occur in various tissues the distribution of antibiotics has always been of particular concern. In this article, we will first critically review the various methodologies available to study antibiotics tissue distribution, including microdialysis, secondly we will show how basic pharmacokinetic concepts may help to predict or interpret antibiotics tissue distribution and third we will address the question of linking antibiotics tissue distribution with their antimicrobial effect, using modern pharmacokinetic-pharmacodynamic methods. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ferrum nano particles and multiwall carbon nano tubes based electrode as FIA detector for determination of amino acids in hypothalamus microdialysis fluids

NASA Astrophysics Data System (ADS)

Sun, L.; Wang, J.; Wang, Y. T.; Yu, L.; Peng, H.; Zhu, J. Z.

2017-01-01

An amperometric electrode based on multiwall carbon nanotubes (MWCNTs) and Fe nanoparticles (NPs) has been successfully fabricated. Combined with Flow Injection Analysis (FIA) and chromatography separation column, the electrode exhibits linear response in the concentration range of 0.1 -12 μM and the sensitivity of 30.0 nA μM-1 for most of amino acids. The determination of 17 amino acids in the hypothalamus microdialysis fluids of guinea pigs, illustrates that the electrode is a powerful tool to investigate physiology and pathology mechanisms

Effects of methiothepin on changes in brain serotonin release induced by repeated administration of high doses of anorectic serotoninergic drugs

NASA Technical Reports Server (NTRS)

Gardier, A. M.; Kaakkola, S.; Erfurth, A.; Wurtman, R. J.

1992-01-01

We previously observed, using in vivo microdialysis, that the potassium-evoked release of frontocortical serotonin (5-HT) is suppressed after rats receive high doses (30 mg/kg, i.p., daily for 3 days) of fluoxetine, a selective blocker of 5-HT reuptake. We now describe similar impairments in 5-HT release after repeated administration of two other 5-HT uptake blockers, zimelidine and sertraline (both at 20 mg/kg, i.p. for 3 days) as well as after dexfenfluramine (7.5 mg/kg, i.p. daily for 3 days), a drug which both releases 5-HT and blocks its reuptake. Doses of these indirect serotonin agonists were about 4-6 times the drug's ED50 in producing anorexia, a serotonin-related behavior. In addition, methiothepin (20 microM), a non-selective receptor antagonist, locally perfused through the dialysis probe 24 h after the last drug injection, enhanced K(+)-evoked release of 5-HT at serotoninergic nerve terminals markedly in control rats and slightly in rats treated with high doses of dexfenfluramine or fluoxetine. On the other hand, pretreatment with methiothepin (10 mg/kg, i.p.) one hour before each of the daily doses of fluoxetine or dexfenfluramine given for 3 days, totally prevented the decrease in basal and K(+)-evoked release of 5-HT. Finally, when methiothepin was injected systemically the day before the first of 3 daily injections of dexfenfluramine, it partially attenuated the long-term depletion of brain 5-HT and 5-HIAA levels induced by repeated administration of high doses of dexfenfluramine. These data suggest that drugs which bring about the prolonged blockade of 5-HT reuptake - such as dexfenfluramine and fluoxetine - can, by causing prolonged increases in intrasynaptic 5-HT levels as measured by in vivo microdialysis, produce receptor-mediated long-term changes in the processes controlling serotonin levels and dynamics.

Transdermal permeation of drugs with differing lipophilicity: Effect of penetration enhancer camphor.

PubMed

Xie, Feng; Chai, Jia-Ke; Hu, Quan; Yu, Yong-Hui; Ma, Li; Liu, Ling-Ying; Zhang, Xu-Long; Li, Bai-Ling; Zhang, Dong-Hai

2016-06-30

The aim of the present study was to investigate the potential application of (+)-camphor as a penetration enhancer for the transdermal delivery of drugs with differing lipophilicity. The skin irritation of camphor was evaluated by in vitro cytotoxicity assays and in vivo transdermal water loss (TEWL) measurements. A series of model drugs with a wide span of lipophilicity (logP value ranging from 3.80 to -0.95), namely indometacin, lidocaine, aspirin, antipyrine, tegafur and 5-fluorouracil, were tested using in vitro transdermal permeation experiments to assess the penetration-enhancing profile of camphor. Meanwhile, the in vivo skin microdialysis was carried out to further investigate the enhancing effect of camphor on the lipophilic and hydrophilic model drugs (i.e. lidocaine and tegafur). SC (stratum corneum)/vehicle partition coefficient and Fourier transform infrared spectroscopy (FTIR) were performed to probe the regulation action of camphor in the skin permeability barrier. It was found that camphor produced a relatively low skin irritation, compared with the frequently-used and standard penetration enhancer laurocapram. In vitro skin permeation studies showed that camphor could significantly facilitate the transdermal absorption of model drugs with differing lipophilicity, and the penetration-enhancing activities were in a parabola curve going downwards with the drug logP values, which displayed the optimal penetration-enhancing efficiency for the weak lipophilic or hydrophilic drugs (an estimated logP value of 0). In vivo skin microdialysis showed that camphor had a similar penetration behavior on transdermal absorption of model drugs. Meanwhile, the partition of lipophilic drugs into SC was increased after treatment with camphor, and camphor also produced a shift of CH2 vibration of SC lipid to higher wavenumbers and decreased the peak area of the CH2 vibration, probably resulting in the alteration of the skin permeability barrier. This suggests that camphor might be a safe and effective penetration enhancer for transdermal drug delivery. Copyright © 2016 Elsevier B.V. All rights reserved.

Microdialysis Monitoring of CSF Parameters in Severe Traumatic Brain Injury Patients: A Novel Approach

PubMed Central

Thelin, Eric P.; Nelson, David W.; Ghatan, Per Hamid; Bellander, Bo-Michael

2014-01-01

Background: Neuro-intensive care following traumatic brain injury (TBI) is focused on preventing secondary insults that may lead to irreversible brain damage. Microdialysis (MD) is used to detect deranged cerebral metabolism. The clinical usefulness of the MD is dependent on the regional localization of the MD catheter. The aim of this study was to analyze a new method of continuous cerebrospinal fluid (CSF) monitoring using the MD technique. The method was validated using conventional laboratory analysis of CSF samples. MD-CSF and regional MD-Brain samples were correlated to patient outcome. Materials and Methods: A total of 14 patients suffering from severe TBI were analyzed. They were monitored using (1) a MD catheter (CMA64-iView, n = 7448 MD samples) located in a CSF-pump connected to the ventricular drain and (2) an intraparenchymal MD catheter (CMA70, n = 8358 MD samples). CSF-lactate and CSF-glucose levels were monitored and were compared to MD-CSF samples. MD-CSF and MD-Brain parameters were correlated to favorable (Glasgow Outcome Score extended, GOSe 6–8) and unfavorable (GOSe 1–5) outcome. Results: Levels of glucose and lactate acquired with the CSF-MD technique could be correlated to conventional levels. The median MD recovery using the CMA64 catheter in CSF was 0.98 and 0.97 for glucose and lactate, respectively. Median MD-CSF (CMA 64) lactate (p = 0.0057) and pyruvate (p = 0.0011) levels were significantly lower in the favorable outcome group compared to the unfavorable group. No significant difference in outcome was found using the lactate:pyruvate ratio (LPR), or any of the regional MD-Brain monitoring in our analyzed cohort. Conclusion: This new technique of global MD-CSF monitoring correlates with conventional CSF levels of glucose and lactate, and the MD recovery is higher than previously described. Increase in lactate and pyruvate, without any effect on the LPR, correlates to unfavorable outcome, perhaps related to the presence of erythrocytes in the CSF. PMID:25228896

Retrograde Cerebral Perfusion Results in Better Perfusion to the Striatum Than the Cerebral Cortex During Deep Hypothermic Circulatory Arrest: A Microdialysis Study.

PubMed

Liang, Meng-Ya; Chen, Guang-Xian; Tang, Zhi-Xian; Rong, Jian; Yao, Jian-ping; Wu, Zhong-Kai

2016-03-01

It remains controversial whether contemporary cerebral perfusion techniques, utilized during deep hypothermic circulatory arrest (DHCA), establish adequate perfusion to deep structures in the brain. This study aimed to investigate whether selective antegrade cerebral perfusion (SACP) or retrograde cerebral perfusion (RCP) can provide perfusion equally to various anatomical positions in the brain using metabolic evidence obtained from microdialysis. Eighteen piglets were randomly assigned to 40 min of circulatory arrest (CA) at 18°C without cerebral perfusion (DHCA group, n = 6) or with SACP (SACP group, n = 6) or RCP (RCP group, n = 6). Microdialysis parameters (glucose, lactate, pyruvate, and glutamate) were measured every 30 min in cortex and striatum. After 3 h of reperfusion, brain tissue was harvested for Western blot measurement of α-spectrin. After 40 min of CA, the DHCA group showed marked elevations of lactate and glycerol and a reduction in glucose in the microdialysis perfusate (all P < 0.05). The changes in glucose, lactate, and glycerol in the perfusate and α-spectrin expression in brain tissue were similar between cortex and striatum in the SACP group (all P > 0.05). In the RCP group, the cortex exhibited lower glucose, higher lactate, and higher glycerol in the perfusate and higher α-spectrin expression in brain tissue compared with the striatum (all P < 0.05). Glutamate showed no difference between cortex and striatum in all groups (all P > 0.05). In summary, SACP provided uniform and continuous cerebral perfusion to most anatomical sites in the brain, whereas RCP resulted in less sufficient perfusion to the cortex but better perfusion to the striatum. Copyright © 2015 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Proof of mechanism study of a novel serotonin transporter blocker, DA-8031, using [11C]DASB positron emission tomography and in vivo microdialysis.

PubMed

Park, Hyun Soo; Jung, In Soon; Lim, Nam Hee; Sung, Ji Hyun; Lee, Sukhyang; Moon, Byung Seok; Lee, Byung Chul; Kang, Kyung Koo; Kim, Sang Eun

2014-07-01

To investigate the efficacy of DA-8031, a novel compound for the treatment of premature ejaculation, we measured serotonin transporter (SERT) occupancy by DA-8031, as well as DA-8031-induced changes in extracellular serotonin levels, in the rat brain using positron emission tomography (PET) and 11C-N,N-dimethyl-2-(2-amino-4-cyanophenylthio) benzylamine ([11C]DASB) and in vivo microdialysis, respectively. [11C]DASB PET scans were performed in rats with graded doses of DA-8031 (vehicle: 10, 30, and 100 mg/kg). SERT occupancy in the midbrain was determined using binding potentials for [11C]DASB calculated by the multilinear reference tissue model. Extracellular serotonin levels were monitored in the dorsal raphe nucleus of rats after the administration of DA-8031 (10-100 mg/kg) using in vivo microdialysis. PET data indicated a reduction of [11C]DASB binding to SERTs in the midbrain as a function of DA-8031 dose. SERT occupancy for each DA-8031 dose (10-100 mg/kg) ranged between 31% and 84%. The drug dose required for 50% occupancy of SERT was 13.5 mg/kg in the midbrain, comparable with previous preclinical behavioral data (∼10-30 mg/kg). In vivo microdialysis showed that DA-8031 produced a dose-dependent increase in extracellular serotonin levels in the dorsal raphe nucleus (33%-81% increase for doses of 10-100 mg/kg). These preclinical data provide a proof of mechanism for DA-8031 as a novel compound of targeting the SERT for the treatment of premature ejaculation, warranting further clinical trials. They also offer insight into the optimal drug dose needed to exert therapeutic effects while minimizing adverse effects in humans. Copyright © 2014 Elsevier Inc. All rights reserved.

Rapid analysis of glutamate, glutamine and GABA in mice frontal cortex microdialysis samples using HPLC coupled to electrospray tandem mass spectrometry.

PubMed

Defaix, Celine; Solgadi, Audrey; Pham, Thu Ha; Gardier, Alain M; Chaminade, Pierre; Tritschler, Laurent

2018-04-15

In vivo measurement of multiple neurotransmitters is highly interesting but remains challenging in the field of neuroscience. GABA and l-glutamic acid are the major inhibitory and excitatory neurotransmitters, respectively, in the central nervous system, and their changes are related to a variety of diseases such as anxiety and major depressive disorder. This study described a simple method allowing the simultaneous LC-MS/MS quantification of l-glutamic acid, glutamine and GABA. Analytes were acquired from samples of the prefrontal cortex by microdialysis technique in freely moving mice. The chromatographic separation was performed by hydrophilic interaction liquid chromatography (HILIC) with a core-shell ammonium-sulfonic acid modified silica column using a gradient elution with mobile phases consisting of a 25 mM pH 3.5 ammonium formate buffer and acetonitrile. The detection of l-glutamic acid, glutamine and GABA, as well as the internal standards [d6]-GABA and [d5]-glutamate was performed on a triple quadrupole mass spectrometer in positive electrospray ionization and multiple reaction monitoring mode. The limit of quantification was 0.63 ng/ml for GABA, 1.25 ng/ml for l-glutamic acid and 3.15 ng/ml for glutamine, and the intra-day and inter-day accuracy and precision have been assessed for the three analytes. Therefore, the physiological relevance of the method was successfully applied for the determination of basal extracellular levels and potassium-evoked release of these neuroactive substances in the prefrontal cortex in adult awake C57BL/6 mice. Copyright © 2018 Elsevier B.V. All rights reserved.

THE NEUROPHARMACOKINETICS OF TEMOZOLOMIDE IN PATIENTS WITH RESECTABLE BRAIN TUMORS: POTENTIAL IMPLICATIONS FOR THE CURRENT APPROACH TO CHEMORADIATION

PubMed Central

Portnow, Jana; Badie, Behnam; Chen, Mike; Liu, An; Blanchard, Suzette; Synold, Timothy W.

2010-01-01

Purpose Intracerebral microdialysis (ICMD) is an accepted methodology for monitoring changes in neurochemistry from acute brain injury. The goal of this pilot study was to determine the feasibility of using ICMD to examine the neuropharmacokinetics (nPK) of temozolomide (TMZ) in brain interstitium (BI) following oral administration. Experimental Design Patients with primary or metastatic brain tumors had a microdialysis catheter placed in peritumoral brain tissue at the time of surgical debulking. CT scan confirmed the catheter location. Patients received a single oral dose of TMZ (150 mg/m2) on the first post-operative day, serial plasma and ICMD samples were collected over 24 hrs, and TMZ concentrations were determined by tandem mass spectrometry. Results Nine patients were enrolled. Dialysate and plasma samples were successfully collected from 7 of the 9 patients. The mean TMZ area-under-the-concentration-time-curve (AUC) in plasma and BI were 17.1 and 2.7 μg/ml × hr, with an average BI/plasma AUC ratio of 17.8%. The mean peak TMZ concentration in brain was 0.6 ± 0.3 μg/ml, and the mean time to reach peak level in brain was 2.0 ± 0.8 hrs. Conclusions The use of ICMD to measure the nPK of systemically administered chemotherapy is safe and feasible. Concentrations of TMZ in BI obtained by ICMD are consistent with published data obtained in a pre-clinical ICMD model, as well as from clinical studies of cerebrospinal fluid. However, the delayed time required to achieve maximum TMZ concentrations in brain suggests that current chemoradiation regimens may be improved by administering TMZ 2-3 hours before radiation. PMID:19861433

The neuropharmacokinetics of temozolomide in patients with resectable brain tumors: potential implications for the current approach to chemoradiation.

PubMed

Portnow, Jana; Badie, Behnam; Chen, Mike; Liu, An; Blanchard, Suzette; Synold, Timothy W

2009-11-15

Intracerebral microdialysis (ICMD) is an accepted method for monitoring changes in neurochemistry from acute brain injury. The goal of this pilot study was to determine the feasibility of using ICMD to examine the neuropharmacokinetics of temozolomide in brain interstitium following oral administration. Patients with primary or metastatic brain tumors had a microdialysis catheter placed in peritumoral brain tissue at the time of surgical debulking. Computerized tomography scan confirmed the catheter location. Patients received a single oral dose of temozolomide (150 mg/m2) on the first postoperative day, serial plasma and ICMD samples were collected over 24 hours, and temozolomide concentrations were determined by tandem mass spectrometry. Nine patients were enrolled. Dialysate and plasma samples were successfully collected from seven of the nine patients. The mean temozolomide areas under the concentration-time curve (AUC) in plasma and brain interstitium were 17.1 and 2.7 microg/mL x hour, with an average brain interstitium/plasma AUC ratio of 17.8%. The mean peak temozolomide concentration in the brain was 0.6 +/- 0.3 microg/mL, and the mean time to reach peak level in brain was 2.0 +/- 0.8 hours. The use of ICMD to measure the neuropharmacokinetics of systemically administered chemotherapy is safe and feasible. Concentrations of temozolomide in brain interstitium obtained by ICMD are consistent with published data obtained in a preclinical ICMD model, as well as from clinical studies of cerebrospinal fluid. However, the delayed time required to achieve maximum temozolomide concentrations in brain suggests that current chemoradiation regimens may be improved by administering temozolomide 2 to 3 hours before radiation.

Influence of peptide transporter 2 (PEPT2) on the distribution of cefadroxil in mouse brain: A microdialysis study.

PubMed

Chen, Xiaomei; Keep, Richard F; Liang, Yan; Zhu, Hao-Jie; Hammarlund-Udenaes, Margareta; Hu, Yongjun; Smith, David E

2017-05-01

Peptide transporter 2 (PEPT2) is a high-affinity low-capacity transporter belonging to the proton-coupled oligopeptide transporter family. Although many aspects of PEPT2 structure-function are known, including its localization in choroid plexus and neurons, its regional activity in brain, especially extracellular fluid (ECF), is uncertain. In this study, the pharmacokinetics and regional brain distribution of cefadroxil, a β-lactam antibiotic and PEPT2 substrate, were investigated in wildtype and Pept2 null mice using in vivo intracerebral microdialysis. Cefadroxil was infused intravenously over 4h at 0.15mg/min/kg, and samples obtained from plasma, brain ECF, cerebrospinal fluid (CSF) and brain tissue. A permeability-surface area experiment was also performed in which 0.15mg/min/kg cefadroxil was infused intravenously for 10min, and samples obtained from plasma and brain tissues. Our results showed that PEPT2 ablation significantly increased the brain ECF and CSF levels of cefadroxil (2- to 2.5-fold). In contrast, there were no significant differences between wildtype and Pept2 null mice in the amount of cefadroxil in brain cells. The unbound volume of distribution of cefadroxil in brain was 60% lower in Pept2 null mice indicating an uptake function for PEPT2 in brain cells. Finally, PEPT2 did not affect the influx clearance of cefadroxil, thereby, ruling out differences between the two genotypes in drug entry across the blood-brain barriers. These findings demonstrate, for the first time, the impact of PEPT2 on brain ECF as well as the known role of PEPT2 in removing peptide-like drugs, such as cefadroxil, from the CSF to blood. Copyright © 2017 Elsevier Inc. All rights reserved.

A microdialysis study of the novel antiepileptic drug levetiracetam: extracellular pharmacokinetics and effect on taurine in rat brain

PubMed Central

Tong, X; Patsalos, P N

2001-01-01

Using a rat model which allows serial blood sampling and concurrent brain microdialysis sampling, we have investigated the temporal kinetic inter-relationship of levetiracetam in serum and brain extracellular fluid (frontal cortex and hippocampus) following systemic administration of levetiracetam, a new antiepileptic drug. Concurrent extracellular amino acid concentrations were also determined. After administration (40 or 80 mg kg−1), levetiracetam rapidly appeared in both serum (Tmax, 0.4 – 0.7 h) and extracellular fluid (Tmax, 2.0 – 2.5 h) and concentrations rose linearly and dose-dependently, suggesting that transport across the blood-brain barrier is rapid and not rate-limiting. The serum free fraction (free/total serum concentration ratio; mean±s.e.mean range 0.93 – 1.05) was independent of concentration and confirms that levetiracetam is not bound to blood proteins. The kinetic profiles for the hippocampus and frontal cortex were indistinguishable suggesting that levetiracetam distribution in the brain is not brain region specific. However, t1/2 values were significantly larger than those for serum (mean range, 3.0 – 3.3 h vs 2.1 – 2.3 h) and concentrations did not attain equilibrium with respect to serum. Levetiracetam (80 mg kg−1) was associated with a significant reduction in taurine in the hippocampus and frontal cortex. Other amino acids were unaffected by levetiracetam. Levetiracetam readily and rapidly enters the brain without regional specificity. Its prolonged efflux from and slow equilibration within the brain may explain, in part, its long duration of action. The concurrent changes in taurine may contribute to its mechanism of action. PMID:11454660

Optical coherence tomography: imaging architect for dermal microdialysis in psoriasis

NASA Astrophysics Data System (ADS)

O'Connell, M.-L.; O'Connor, W.; Ramsay, B.; Guihen, E.; Ho, W. L.; Leahy, M. J.

2011-03-01

Optical coherence tomography (OCT) has been used as part of a ground breaking translational study to shed some light on one of the worlds most prevalent autoimmune diseases; psoriasis. The work successfully integrates the fields of optical imaging, biochemistry and dermatology in conducting a dermal microdialysis (DMD) trial for quantitative histamine assessment amongst a group of psoriasis sufferers. The DMD process involves temporary insertion of microscopic hollow tubes into a layer of skin to measure the levels of histamine and other important biological molecules in psoriasis. For comparison purposes, DMD catheters were implanted into healthy, peri-lesional and lesional skin regions. The catheters' entry and exit points and their precise locations in the epidermal layer of the skin were confirmed using OCT thus obtaining high resolution, wide-field images of the affected skin as well as catheter placement whilst local microdialysis enabled a tissue chemistry profile to be obtained from these three skin regions including histamine, a local immune system activator known to contribute towards itch and inflammation. Together these tools offer a synergistic approach in the clinical assessment of the disease. In addition, OCT delivered a non-invasive and rapid method for analyzing the affected skin architecture.

Effects on sleep and dopamine levels of microdialysis perfusion of cannabidiol into the lateral hypothalamus of rats.

PubMed

Murillo-Rodríguez, Eric; Palomero-Rivero, Marcela; Millán-Aldaco, Diana; Mechoulam, Raphael; Drucker-Colín, René

2011-03-14

The major non-psychoactive component of Cannabis sativa, cannabidiol (CBD), displays a plethora of actions including wakefulness. In the present study, we addressed whether perfusing CBD via microdialysis into lateral hypothalamus (LH) during the lights-on period would modify the sleep-wake cycle of rats as well as the contents of dopamine (DA) collected from nucleus accumbens (AcbC). Additionally, we tested whether perfusion of CBD into LH would block the sleep rebound after a sleep deprivation period. Electroencephalogram and electromyogram electrodes were implanted in rats as well as a guide-cannula aimed to LH or AcbC. CBD perfusion was carried out via cannulae placed into LH whereas contents of DA were collected from AcbC and analyzed using HPLC means. We found that microdialysis perfusion of CBD (30, 60, or 90 nM) into LH of rat enhances alertness and suppresses sleep. This effect was accompanied with an increase in DA extracellular levels collected from the AcbC. Furthermore, perfusion of CBD into LH after total sleep deprivation prevented the sleep rebound. These findings enhance the investigation about the neurobiological properties of CBD on sleep modulation. Copyright © 2011 Elsevier Inc. All rights reserved.

Comparison of the Levels of Pro-Inflammatory Cytokines Released in the Vastus Lateralis Muscle of Patients with Fibromyalgia and Healthy Controls during Contractions of the Quadriceps Muscle – A Microdialysis Study

PubMed Central

Christidis, Nikolaos; Ghafouri, Bijar; Larsson, Anette; Palstam, Annie; Mannerkorpi, Kaisa; Bileviciute-Ljungar, Indre; Löfgren, Monika; Bjersing, Jan; Kosek, Eva; Gerdle, Björn; Ernberg, Malin

2015-01-01

Objective Fibromyalgia is associated with central hyperexcitability, but it is suggested that peripheral input is important to maintain central hyperexcitability. The primary aim was to investigate the levels of pro-inflammatory cytokines released in the vastus lateralis muscle during repetitive dynamic contractions of the quadriceps muscle in patients with fibromyalgia and healthy controls. Secondarily, to investigate if the levels of pro-inflammatory cytokines were correlated with pain or fatigue during these repetitive dynamic contractions. Material and Methods 32 women with fibromyalgia and 32 healthy women (controls) participated in a 4 hour microdialysis session, to sample IL-1β, IL-6, IL-8, and TNF from the most painful point of the vastus lateralis muscle before, during and after 20 minutes of repeated dynamic contractions. Pain (visual analogue scale; 0–100) and fatigue Borg’s Rating of Perceived Exertion Scale; 6–20) were assessed before and during the entire microdialysis session. Results The repetitive dynamic contractions increased pain in the patients with fibromyalgia (P < .001) and induced fatigue in both groups (P < .001). Perceived fatigue was significantly higher among patients with fibromyalgia than controls (P < .001). The levels of IL-1β did not change during contractions in either group. The levels of TNF did not change during contractions in patients with fibromyalgia, but increased in controls (P < .001) and were significantly higher compared to patients with fibromyalgia (P = .033). The levels of IL-6 and IL-8 increased in both groups alike during and after contractions (P’s < .001). There were no correlations between pain or fatigue and cytokine levels after contractions. Conclusion There were no differences between patients with fibromyalgia and controls in release of pro-inflammatory cytokines, and no correlations between levels of pro-inflammatory cytokines and pain or fatigue. Thus, this study indicates that IL-1β, IL-6, IL-8, and TNF do not seem to play an important role in maintenance of muscle pain in fibromyalgia. PMID:26624891

Ultrafast scanning probe microscopy

DOEpatents

Weiss, S.; Chemla, D.S.; Ogletree, D.F.; Botkin, D.

1995-05-16

An ultrafast scanning probe microscopy method is described for achieving subpicosecond-temporal resolution and submicron-spatial resolution of an observation sample. In one embodiment of the present claimed invention, a single short optical pulse is generated and is split into first and second pulses. One of the pulses is delayed using variable time delay means. The first pulse is then directed at an observation sample located proximate to the probe of a scanning probe microscope. The scanning probe microscope produces probe-sample signals indicative of the response of the probe to characteristics of the sample. The second pulse is used to modulate the probe of the scanning probe microscope. The time delay between the first and second pulses is then varied. The probe-sample response signal is recorded at each of the various time delays created between the first and second pulses. The probe-sample response signal is then plotted as a function of time delay to produce a cross-correlation of the probe sample response. In so doing, the present invention provides simultaneous subpicosecond-temporal resolution and submicron-spatial resolution of the sample. 6 Figs.

Ultrafast scanning probe microscopy

DOEpatents

Weiss, Shimon; Chemla, Daniel S.; Ogletree, D. Frank; Botkin, David

1995-01-01

An ultrafast scanning probe microscopy method for achieving subpicosecond-temporal resolution and submicron-spatial resolution of an observation sample. In one embodiment of the present claimed invention, a single short optical pulse is generated and is split into first and second pulses. One of the pulses is delayed using variable time delay means. The first pulse is then directed at an observation sample located proximate to the probe of a scanning probe microscope. The scanning probe microscope produces probe-sample signals indicative of the response of the probe to characteristics of the sample. The second pulse is used to modulate the probe of the scanning probe microscope. The time delay between the first and second pulses is then varied. The probe-sample response signal is recorded at each of the various time delays created between the first and second pulses. The probe-sample response signal is then plotted as a function of time delay to produce a cross-correlation of the probe sample response. In so doing, the present invention provides simultaneous subpicosecond-temporal resolution and submicron-spatial resolution of the sample.

Brain Tissue Responses to Neural Implants Impact Signal Sensitivity and Intervention Strategies

PubMed Central

2015-01-01

Implantable biosensors are valuable scientific tools for basic neuroscience research and clinical applications. Neurotechnologies provide direct readouts of neurological signal and neurochemical processes. These tools are generally most valuable when performance capacities extend over months and years to facilitate the study of memory, plasticity, and behavior or to monitor patients’ conditions. These needs have generated a variety of device designs from microelectrodes for fast scan cyclic voltammetry (FSCV) and electrophysiology to microdialysis probes for sampling and detecting various neurochemicals. Regardless of the technology used, the breaching of the blood–brain barrier (BBB) to insert devices triggers a cascade of biochemical pathways resulting in complex molecular and cellular responses to implanted devices. Molecular and cellular changes in the microenvironment surrounding an implant include the introduction of mechanical strain, activation of glial cells, loss of perfusion, secondary metabolic injury, and neuronal degeneration. Changes to the tissue microenvironment surrounding the device can dramatically impact electrochemical and electrophysiological signal sensitivity and stability over time. This review summarizes the magnitude, variability, and time course of the dynamic molecular and cellular level neural tissue responses induced by state-of-the-art implantable devices. Studies show that insertion injuries and foreign body response can impact signal quality across all implanted central nervous system (CNS) sensors to varying degrees over both acute (seconds to minutes) and chronic periods (weeks to months). Understanding the underlying biological processes behind the brain tissue response to the devices at the cellular and molecular level leads to a variety of intervention strategies for improving signal sensitivity and longevity. PMID:25546652

Applications of tapered flat silver halide fiber elements for infrared biospectroscopy with aspects of optical stability and biocompatibility

NASA Astrophysics Data System (ADS)

Delbeck, Sven; Küpper, Lukas; Heise, Herbert M.

2018-02-01

Spectroscopic analysis of different biofluids and bodyfluid-like media has been realized by using tapered flat silver halide fiber elements as infrared biosensors. Optical stability and biocompatibility testing of the sensor elements have been performed with in-vitro samples under representative physiological conditions. After improving the reproducibility of manufacturing the sensor elements, the incoupling of radiation and the general handling including their chemical composition characterization, the fiber sensors were further optimized for the experiments. Stability tests in physiological solutions as well as porcine blood have shown that best results for biospectroscopic applications are available for the mid-IR fingerprint region, with the most stable behaviour as analyzed by the single-beam spectra. Despite several contrary reports, the silver halide material tested is toxic to cell lines chosen from the DIN standard specification for biocompatibility testing. Spectral changes as well as the results based on the DIN standard showed that pretreatment of the fibers is unavoidable to prevent direct contact of cells or human tissue and the silver halide material. Further applications of tapered flat silver halide fibers for the quantification of analytes in bodyfluids have also been tested by ensheathing the fiber-optic sensor element with a dialysis membrane. With the successfully produced prototype, results of diffusion rates and performance of a membrane-ensheathed fiber probe have been obtained. An invitro monitoring fiber sensor was developed aiming at the implantation of a microdialysis system for the analytical quantification of biomolecules such as glucose, lactate and others.

Optimal approaches for inline sampling of organisms in ballast water: L-shaped vs. Straight sample probes

NASA Astrophysics Data System (ADS)

Wier, Timothy P.; Moser, Cameron S.; Grant, Jonathan F.; Riley, Scott C.; Robbins-Wamsley, Stephanie H.; First, Matthew R.; Drake, Lisa A.

2017-10-01

Both L-shaped ("L") and straight ("Straight") sample probes have been used to collect water samples from a main ballast line in land-based or shipboard verification testing of ballast water management systems (BWMS). A series of experiments was conducted to quantify and compare the sampling efficiencies of L and Straight sample probes. The findings from this research-that both L and Straight probes sample organisms with similar efficiencies-permit increased flexibility for positioning sample probes aboard ships.

Gas sampling system for reactive gas-solid mixtures

DOEpatents

Daum, Edward D.; Downs, William; Jankura, Bryan J.; McCoury, Jr., John M.

1989-01-01

An apparatus and method for sampling a gas containing a reactive particulate solid phase flowing through a duct and for communicating a representative sample to a gas analyzer. A sample probe sheath 32 with an angular opening 34 extends vertically into a sample gas duct 30. The angular opening 34 is opposite the gas flow. A gas sampling probe 36 concentrically located within sheath 32 along with calibration probe 40 partly extend in the sheath 32. Calibration probe 40 extends further in the sheath 32 than gas sampling probe 36 for purging the probe sheath area with a calibration gas during calibration.

Gas sampling system for reactive gas-solid mixtures

DOEpatents

Daum, Edward D.; Downs, William; Jankura, Bryan J.; McCoury, Jr., John M.

1990-01-01

An apparatus and method for sampling gas containing a reactive particulate solid phase flowing through a duct and for communicating a representative sample to a gas analyzer. A sample probe sheath 32 with an angular opening 34 extends vertically into a sample gas duct 30. The angular opening 34 is opposite the gas flow. A gas sampling probe 36 concentrically located within sheath 32 along with calibration probe 40 partly extends in the sheath 32. Calibration probe 40 extends further in the sheath 32 than gas sampling probe 36 for purging the probe sheath area with a calibration gas during calibration.

Study of probe-sample distance for biomedical spectra measurement.

PubMed

Wang, Bowen; Fan, Shuzhen; Li, Lei; Wang, Cong

2011-11-02

Fiber-based optical spectroscopy has been widely used for biomedical applications. However, the effect of probe-sample distance on the collection efficiency has not been well investigated. In this paper, we presented a theoretical model to maximize the illumination and collection efficiency in designing fiber optic probes for biomedical spectra measurement. This model was in general applicable to probes with single or multiple fibers at an arbitrary incident angle. In order to demonstrate the theory, a fluorescence spectrometer was used to measure the fluorescence of human finger skin at various probe-sample distances. The fluorescence spectrum and the total fluorescence intensity were recorded. The theoretical results show that for single fiber probes, contact measurement always provides the best results. While for multi-fiber probes, there is an optimal probe distance. When a 400- μm excitation fiber is used to deliver the light to the skin and another six 400- μm fibers surrounding the excitation fiber are used to collect the fluorescence signal, the experimental results show that human finger skin has very strong fluorescence between 475 nm and 700 nm under 450 nm excitation. The fluorescence intensity is heavily dependent on the probe-sample distance and there is an optimal probe distance. We investigated a number of probe-sample configurations and found that contact measurement could be the primary choice for single-fiber probes, but was very inefficient for multi-fiber probes. There was an optimal probe-sample distance for multi-fiber probes. By carefully choosing the probe-sample distance, the collection efficiency could be enhanced by 5-10 times. Our experiments demonstrated that the experimental results of the probe-sample distance dependence of collection efficiency in multi-fiber probes were in general agreement with our theory.

Breathing is affected by dopamine D2-like receptors in the basolateral amygdala.

PubMed

Sugita, Toshihisa; Kanamaru, Mitsuko; Iizuka, Makito; Sato, Kanako; Tsukada, Setsuro; Kawamura, Mitsuru; Homma, Ikuo; Izumizaki, Masahiko

2015-04-01

The precise mechanisms underlying how emotions change breathing patterns remain unclear, but dopamine is a candidate neurotransmitter in the process of emotion-associated breathing. We investigated whether basal dopamine release occurs in the basolateral amygdala (BLA), where sensory-related inputs are received and lead to fear or anxiety responses, and whether D1- and D2-like receptor antagonists affect breathing patterns and dopamine release in the BLA. Adult male mice (C57BL/6N) were perfused with artificial cerebrospinal fluid, a D1-like receptor antagonist (SCH 23390), or a D2-like receptor antagonist ((S)-(-)-sulpiride) through a microdialysis probe in the BLA. Respiratory variables were measured using a double-chamber plethysmograph. Dopamine release was measured by an HPLC. Perfusion of (S)-(-)-sulpiride in the BLA, not SCH 23390, specifically decreased respiratory rate without changes in local release of dopamine. These results suggest that basal dopamine release in the BLA, at least partially, increases respiratory rates only through post-synaptic D2-like receptors, not autoreceptors, which might be associated with emotional responses. Copyright © 2014 Elsevier B.V. All rights reserved.

[C3(OH)2mim][BF4]-Au/Pt biosensor for glutamate sensing in vivo integrated with on-line microdialysis system.

PubMed

Yu, Yanyan; Liu, Xiaoqian; Jiang, Dawei; Sun, Qian; Zhou, Tianshu; Zhu, Min; Jin, Litong; Shi, Guoyue

2011-03-15

A new type of hydroxyl functionalized room temperature ionic liquid (RTIL), [C(3)(OH)(2)mim][BF(4)], was synthesized herein and a novel H(2)O(2) biosensor is fabricated with [C(3)(OH)(2)mim][BF(4)] as the substrate and electrodepositing bimetallic Au/Pt nanoparticles (NPs) onto the [C(3)(OH)(2)mim][BF(4)] film. The functionalization of RTIL with hydroxyl groups provided an appropriate environment for the preparation of more uniform and smaller Au/Pt NPs with the diameter of 2.5 nm±0.2 nm. Immobilized with glutamate oxidase (GlutaOx), the resulting GlutaOx-[C(3)(OH)(2)mim][BF(4)]-Au/Pt-Nafion biosensor displayed excellent electrocatalytic response to glutamate at a potential of -200 mV. An effective on-line microdialysis system, which was powered by a microdialysis pump, was set up and used for the detection of glutamate successively in the striatum of rats. The glutamate biosensor in on-line microdialysis system showed good linear range from 0.5 μM to 20.0 μM with the detection limit of 0.17 μM (S/N=3). The basal level of glutamate in the striatum of anaesthetic rats was calculated to be 3.01±0.67 μM (n=3). The application of the GlutaOx-[C(3)(OH)(2)mim][BF(4)]-Au/Pt-Nafion electrode is further demonstrated for in vivo sensing of the variation of glutamate level in the striatum when rats received intraperitoneal (i.p.) injection of 100 mM KCl and brain electrical stimulation of the subthalamic nucleus area (STN). Both of the two kinds of stimulation resulted in an increase in the extracellular concentration of glutamate. This method has proved to be sensitive and reproducible, which enables its promising application in physiology and pathology. Copyright © 2010 Elsevier B.V. All rights reserved.

Finite element and analytical solutions for van der Pauw and four-point probe correction factors when multiple non-ideal measurement conditions coexist

NASA Astrophysics Data System (ADS)

Reveil, Mardochee; Sorg, Victoria C.; Cheng, Emily R.; Ezzyat, Taha; Clancy, Paulette; Thompson, Michael O.

2017-09-01

This paper presents an extensive collection of calculated correction factors that account for the combined effects of a wide range of non-ideal conditions often encountered in realistic four-point probe and van der Pauw experiments. In this context, "non-ideal conditions" refer to conditions that deviate from the assumptions on sample and probe characteristics made in the development of these two techniques. We examine the combined effects of contact size and sample thickness on van der Pauw measurements. In the four-point probe configuration, we examine the combined effects of varying the sample's lateral dimensions, probe placement, and sample thickness. We derive an analytical expression to calculate correction factors that account, simultaneously, for finite sample size and asymmetric probe placement in four-point probe experiments. We provide experimental validation of the analytical solution via four-point probe measurements on a thin film rectangular sample with arbitrary probe placement. The finite sample size effect is very significant in four-point probe measurements (especially for a narrow sample) and asymmetric probe placement only worsens such effects. The contribution of conduction in multilayer samples is also studied and found to be substantial; hence, we provide a map of the necessary correction factors. This library of correction factors will enable the design of resistivity measurements with improved accuracy and reproducibility over a wide range of experimental conditions.

Finite element and analytical solutions for van der Pauw and four-point probe correction factors when multiple non-ideal measurement conditions coexist.

PubMed

Reveil, Mardochee; Sorg, Victoria C; Cheng, Emily R; Ezzyat, Taha; Clancy, Paulette; Thompson, Michael O

2017-09-01

This paper presents an extensive collection of calculated correction factors that account for the combined effects of a wide range of non-ideal conditions often encountered in realistic four-point probe and van der Pauw experiments. In this context, "non-ideal conditions" refer to conditions that deviate from the assumptions on sample and probe characteristics made in the development of these two techniques. We examine the combined effects of contact size and sample thickness on van der Pauw measurements. In the four-point probe configuration, we examine the combined effects of varying the sample's lateral dimensions, probe placement, and sample thickness. We derive an analytical expression to calculate correction factors that account, simultaneously, for finite sample size and asymmetric probe placement in four-point probe experiments. We provide experimental validation of the analytical solution via four-point probe measurements on a thin film rectangular sample with arbitrary probe placement. The finite sample size effect is very significant in four-point probe measurements (especially for a narrow sample) and asymmetric probe placement only worsens such effects. The contribution of conduction in multilayer samples is also studied and found to be substantial; hence, we provide a map of the necessary correction factors. This library of correction factors will enable the design of resistivity measurements with improved accuracy and reproducibility over a wide range of experimental conditions.

40 CFR 89.412 - Raw gaseous exhaust sampling and analytical system description.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) Sample probe. (1) The sample probe shall be a straight, closed-end, stainless steel, multi-hole probe... wall thickness of the probe shall not be greater than 0.10 cm. The fitting that attaches the probe to the exhaust pipe shall be as small as practical in order to minimize heat loss from the probe. (2) The...

40 CFR 89.412 - Raw gaseous exhaust sampling and analytical system description.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) Sample probe. (1) The sample probe shall be a straight, closed-end, stainless steel, multi-hole probe... wall thickness of the probe shall not be greater than 0.10 cm. The fitting that attaches the probe to the exhaust pipe shall be as small as practical in order to minimize heat loss from the probe. (2) The...

40 CFR 89.412 - Raw gaseous exhaust sampling and analytical system description.

Code of Federal Regulations, 2012 CFR

2012-07-01

...) Sample probe. (1) The sample probe shall be a straight, closed-end, stainless steel, multi-hole probe... wall thickness of the probe shall not be greater than 0.10 cm. The fitting that attaches the probe to the exhaust pipe shall be as small as practical in order to minimize heat loss from the probe. (2) The...

Effects of sarizotan in animal models of ADHD: challenging pharmacokinetic-pharmacodynamic relationships.

PubMed

Danysz, Wojciech; Flik, Gunnar; McCreary, Andrew; Tober, Carsten; Dimpfel, Wilfried; Bizot, Jean C; Kostrzewa, Richard; Brown, Russell W; Jatzke, Claudia C; Greco, Sergio; Jenssen, Ann-Kristin; Parsons, Christopher G

2015-09-01

Sarizotan 1-[(2R)-3,4-dihydro-2H-chromen-2-yl]-N-[[5-(4-fluorophenyl) pyridin-3-yl]methyl] methenamine, showed an in vivo pharmaco-EEG profile resembling that of methylphenidate which is used in attention deficit/hyperactivity disorder (ADHD). In turn, we tested sarizotan against impulsivity in juvenile rats measuring the choice for large delayed vs. a small immediate reward in a T-maze and obtained encouraging results starting at 0.03 mg/kg (plasma levels of ~11 nM). Results from rats treated neonatally with 6-hydroxydopamine (6-OHDA), also supported anti-ADHD activity although starting at 0.3 mg/kg. However, microdialysis studies revealed that free brain concentration of sarizotan at active doses were below its affinity for 5-HT1A receptors, the assumed primary target. In contrast, electrophysiological experiments in mid-brain Raphé serotonergic cells paralleled by plasma sampling showed that there was ~60% inhibition of firing rate—indicating significant activation of 5-HT1A receptors—at a plasma concentration of 76 nM. In line with this, we observed that sarizotan concentrations in brain homogenates were similar to total blood levels but over 500 fold higher than free extracellular fluid (ECF) concentrations as measured using brain microdialysis. These data suggest that sarizotan may have potential anti-ADHD effects at low doses free of the previously reported side-effects. Moreover, in this case a classical pharmacokinetic-pharmacodynamic relationship based on free brain concentrations seems to be less appropriate than target engagement pharmacodynamic readouts.

Brain interstitial fluid TNF-α after subarachnoid hemorrhage

PubMed Central

Hanafy, Khalid A.; Grobelny, Bartosz; Fernandez, Luis; Kurtz, Pedro; Connolly, ES; Mayer, Stephan A.; Schindler, Christian; Badjatia, Neeraj

2010-01-01

Objective: TNF-α is an inflammatory cytokine that plays a central role in promoting the cascade of events leading to an inflammatory response. Recent studies have suggested that TNF-α may play a key role in the formation and rupture of cerebral aneurysms, and that the underlying cerebral inflammatory response is a major determinate of outcome following subrarachnoid hemorrhage (SAH). Methods: We studied 14 comatose SAH patients who underwent multimodality neuromonitoring with intracranial pressure (ICP) and cerebral microdialysis as part of their clinical care. Continuous physiological variables were time-locked every 8 hours and recorded at the same point that brain interstitial fluid TNF-α was measured in brain microdialysis samples. Significant associations were determined using generalized estimation equations. Results: Each patient had a mean of 9 brain tissue TNF-α measurements obtained over an average of 72 hours of monitoring. TNF-α levels rose progressively over time. Predictors of elevated brain interstitial TNF-α included higher brain interstitial fluid glucose levels (β=0.066, P<0.02), intraventricular hemorrhage (β=0.085, P<0.021), and aneurysm size >6 mm (β=0.14, p<0.001). There was no relationship between TNF-α levels and the burden of cisternal SAH; concurrent measurements of serum glucose, or lactate-pyruvate ratio. Interpretation: Brain interstitial TNF-α levels are elevated after SAH, and are associated with large aneurysm size, the burden of intraventricular blood, and elevation brain interstitial glucose levels. PMID:20110094

AFM fluid delivery/liquid extraction surface sampling/electrostatic spray cantilever probe

DOEpatents

Van Berkel, Gary J.

2015-06-23

An electrospray system comprises a liquid extraction surface sampling probe. The probe comprises a probe body having a liquid inlet and a liquid outlet, and having a liquid extraction tip. A solvent delivery conduit is provided for receiving solvent liquid from the liquid inlet and delivering the solvent liquid to the liquid extraction tip. An open liquid extraction channel extends across an exterior surface of the probe body from the liquid extraction tip to the liquid outlet. An electrospray emitter tip is in liquid communication with the liquid outlet of the liquid extraction surface sampling probe. A system for analyzing samples, a liquid junction surface sampling system, and a method of analyzing samples are also disclosed.

Sparse sampling and reconstruction for electron and scanning probe microscope imaging

DOEpatents

Anderson, Hyrum; Helms, Jovana; Wheeler, Jason W.; Larson, Kurt W.; Rohrer, Brandon R.

2015-07-28

Systems and methods for conducting electron or scanning probe microscopy are provided herein. In a general embodiment, the systems and methods for conducting electron or scanning probe microscopy with an undersampled data set include: driving an electron beam or probe to scan across a sample and visit a subset of pixel locations of the sample that are randomly or pseudo-randomly designated; determining actual pixel locations on the sample that are visited by the electron beam or probe; and processing data collected by detectors from the visits of the electron beam or probe at the actual pixel locations and recovering a reconstructed image of the sample.

40 CFR 90.414 - Raw gaseous exhaust sampling and analytical system description.

Code of Federal Regulations, 2013 CFR

2013-07-01

... savers” or “protectors” with nonreactive diaphragms to reduce dead volumes is permitted. (b) Sample probe. (1) The sample probe must be a straight, closed end, stainless steel, multi-hole probe. The inside... probe may not be greater than 0.10 cm. The fitting that attaches the probe to the exhaust pipe must be...

40 CFR 90.414 - Raw gaseous exhaust sampling and analytical system description.

Code of Federal Regulations, 2012 CFR

2012-07-01

... savers” or “protectors” with nonreactive diaphragms to reduce dead volumes is permitted. (b) Sample probe. (1) The sample probe must be a straight, closed end, stainless steel, multi-hole probe. The inside... probe may not be greater than 0.10 cm. The fitting that attaches the probe to the exhaust pipe must be...

40 CFR 90.414 - Raw gaseous exhaust sampling and analytical system description.

Code of Federal Regulations, 2014 CFR

2014-07-01

... savers” or “protectors” with nonreactive diaphragms to reduce dead volumes is permitted. (b) Sample probe. (1) The sample probe must be a straight, closed end, stainless steel, multi-hole probe. The inside... probe may not be greater than 0.10 cm. The fitting that attaches the probe to the exhaust pipe must be...

Extracellular adenosine 5'-triphosphate concentrations changes in rat spinal cord associated with the activation of urinary bladder afferents. A microdialysis study.

PubMed

Rocha, Jeová Nina

2016-01-01

To determine adenosine 5'-triphosphate levels in the interstice of spinal cord L6-S1 segment, under basal conditions or during mechanical and chemical activation of urinary bladder afferents. A microdialysis probe was transversally implanted in the dorsal half of spinal cord L6-S1 segment in female rats. Microdialysate was collected at 15 minutes intervals during 135 minutes, in anesthetized animals. Adenosine 5'-triphosphate concentrations were determined with a bioluminescent assay. In one group of animals (n=7) microdialysate samples were obtained with an empty bladder during a 10-minutes bladder distension to 20 or 40cmH2O with either saline, saline with acetic acid or saline with capsaicin. In another group of animals (n=6) bladder distention was performed and the microdialysis solution contained the ectonucleotidase inhibitor ARL 67156. Basal extracellular adenosine triphosphate levels were 110.9±35.34fmol/15 minutes, (mean±SEM, n=13), and bladder distention was associated with a significant increase in adenosine 5'-triphosphate levels which was not observed after bladder distention with saline solution containing capsaicin (10µM). Microdialysis with solution containing ARL 67156 (1mM) was associated with significantly higher extracellular adenosine 5'-triphosphate levels and no further increase in adenosine 5'-triphosphate was observed during bladder distension. Adenosine 5'-triphosphate was present in the interstice of L6-S1 spinal cord segments, was degraded by ectonucleotidase, and its concentration increased following the activation of bladder mechanosensitive but not of the chemosensitive afferents fibers. Adenosine 5'-triphosphate may originate either from the central endings of bladder mechanosensitive primary afferent neurons, or most likely from intrinsic spinal neurons, or glial cells and its release appears to be modulated by capsaicin activated bladder primary afferent or by adenosine 5'-triphosphate itself. Determinar as concentrações extracelulares do 5'-trifosfato de adenosina no interstício dos segmentos medulares L6-S1, em condições basais ou durante a ativação mecânica e química das fibras aferentes vesicais. Um cateter de microdiálise foi implantado no sentido transversal na parte dorsal da medula espinal, entre os segmentos L6-S1 de ratas. O microdialisado foi coletado em intervalos de 15 minutos, durante 135 minutos, com os animais anestesiados. A concentração de 5'-trifosfato de adenosina nas amostras foi determinada mediante ensaio de bioluminescência. Em um grupo de animais (n=7), as amostras de microdialisado foram obtidas com a bexiga vazia, com distensão da bexiga para volume de 20 ou 40cmH2O, com solução salina, solução salina com ácido acético, ou solução salina com capsaicina. Em outro grupo (n=6), foi realizada com a bexiga distendida, e a solução para microdiálise continha o inibidor de ectonucleotidase ARL 67156. Os níveis extracelulares de trifosfato de adenosina no início do estudo foram 110,9±35,36fmol/15 minutos (média±EPM, n=13), e a distensão da bexiga causou um aumento nos níveis de 5'-trifosfato de adenosina, o que não foi observado após a distensão da bexiga com solução salina contendo capsaicina (10µM). A microdiálise com solução contendo ARL 67156 (1mM) foi associada com significante aumento dos níveis de trifosfato de adenosina extracelular, e nenhum aumento do trifosfato de adenosina foi observado durante a distensão da bexiga. O 5'-trifosfato de adenosina está presente no interstício do segmento L6-S1 da medula espinal, é degradado por ectonucleotidases, e sua concentração aumentou com a ativação das fibras aferentes mecanossensíveis da bexiga, mas não das quimiossensíveis. O 5'-trifosfato de adenosina pode ter sido liberado das terminações centrais dos neurônios aferentes primários mecanossensíveis ou, mais provavelmente, de neurônios espinais intrínsecos, ou ainda de células gliais. Sua liberação parece ser modulada por fibras aferentes primárias da bexiga ativadas pela capsaicina ou pelo próprio 5'-trifosfato de adenosina.

Combining Microdialysis and Electrophysiology in Cerebral Cortex to Delineate Functional Implications of Acetylcholine Gradients

NASA Astrophysics Data System (ADS)

Nelson, Kari L.

The neuronal network in cerebral cortex is a dynamic system that can undergo changes in collective neural activity as the organism changes its behavior. For example, during sleep and quiet restful awake state, many neurons tend to fire together in synchrony. In contrast, during alert awake states, firing patterns of neurons tend to be more asynchronous, firing more independently. These changes in population-level synchrony are defined as changes in cortical state. Response to sensory input is state-dependent, i.e., change in cortical state can impact the sensory information processing in cortex and introduce trial-to-trial variability in response to the same repeated stimuli. How the brain maintains reliable perception in spite of such trial-to-trial variability is a longstanding important question in neuroscience research. This dissertation is centered on two hypotheses. The first hypothesis is that different parts of the cortex can be in different states simultaneously. The second hypothesis is that inhomogeneity in cortical states can benefit the system by enabling the cortical network to maintain reliable sensory detection. If one part of the system is in a state that is not good for detection, then another part of the system could be in a different state that is good for detection, thus compensating and maintaining good detection for the system as a whole. These hypotheses were tested on anesthetized rats and awake mice. In anesthetized rats, cholinergic neuromodulation via microdialysis (muD) probes was used to induce cortical state changes in the somatosensory barrel cortex. Changes in cortical state and response to whisker stimulus was recorded with a microelectrode array (MEA). In awake mice, nucleus basalis was optogenetically stimulated by inserting an optic fiber in basal forebrain and response to visual stimulus was analyzed. The results demonstrated heterogeneity in cortical state across the spatial extent of cortical network. Changes in sensory response followed this heterogeneity and sensory detection was not reliable at the level of single neurons or small regions of cortex. The greater population of neurons, on the other hand, maintained reliable sensory detection, suggesting that heterogeneous state can be functionally beneficial for the cortical network.

Ethanol drinking reduces extracellular dopamine levels in the posterior ventral tegmental area of nondependent alcohol-preferring rats.

PubMed

Engleman, Eric A; Keen, Elizabeth J; Tilford, Sydney S; Thielen, Richard J; Morzorati, Sandra L

2011-09-01

Moderate ethanol exposure produces neuroadaptive changes in the mesocorticolimbic dopamine (DA) system in nondependent rats and increases measures of DA neuronal activity in vitro and in vivo. Moreover, moderate ethanol drinking and moderate systemic exposure elevates extracellular DA levels in mesocorticolimbic projection regions. However, the neuroadaptive changes subsequent to moderate ethanol drinking on basal DA levels have not been investigated in the ventral tegmental area (VTA). In the present study, adult female alcohol-preferring (P) rats were divided into alcohol-naive, alcohol-drinking, and alcohol-deprived groups. The alcohol-drinking group had continuous access to water and ethanol (15%, vol/vol) for 8 weeks. The alcohol-deprived group had 6 weeks of access followed by 2 weeks of ethanol deprivation, 2 weeks of ethanol re-exposure, followed again by 2 weeks of deprivation. The deprived rats demonstrated a robust alcohol deprivation effect (ADE) on ethanol reinstatement. The alcohol-naïve group had continuous access to water only. In the last week of the drinking protocol, all rats were implanted with unilateral microdialysis probes aimed at the posterior VTA and no-net-flux microdialysis was conducted to quantify extracellular DA levels and DA clearance. Results yielded significantly lower basal extracellular DA concentrations in the posterior VTA of the alcohol-drinking group compared with the alcohol-naive and alcohol-deprived groups (3.8±0.3nM vs. 5.0±0.5nM [P<.02] and 4.8±0.4nM, [P<.05], respectively). Extraction fractions were significantly (P<.0002) different between the alcohol-drinking and alcohol-naive groups (72±2% vs. 46±4%, respectively) and not significantly different (P=.051) between alcohol-deprived and alcohol-naive groups (61±6% for the alcohol-deprived group). The data indicate that reductions in basal DA levels within the posterior VTA occur after moderate chronic ethanol intake in nondependent P rats. This reduction may result, in part, from increased DA uptake and may be important for the maintenance of ethanol drinking. These adaptations normalize with ethanol deprivation and may not contribute to the ADE. Copyright © 2011 Elsevier Inc. All rights reserved.

13C-labelled microdialysis studies of cerebral metabolism in TBI patients☆

PubMed Central

Carpenter, Keri L.H.; Jalloh, Ibrahim; Gallagher, Clare N.; Grice, Peter; Howe, Duncan J.; Mason, Andrew; Timofeev, Ivan; Helmy, Adel; Murphy, Michael P.; Menon, David K.; Kirkpatrick, Peter J.; Carpenter, T. Adrian; Sutherland, Garnette R.; Pickard, John D.; Hutchinson, Peter J.

2014-01-01

Human brain chemistry is incompletely understood and better methodologies are needed. Traumatic brain injury (TBI) causes metabolic perturbations, one result of which includes increased brain lactate levels. Attention has largely focussed on glycolysis, whereby glucose is converted to pyruvate and lactate, and is proposed to act as an energy source by feeding into neurons’ tricarboxylic acid (TCA) cycle, generating ATP. Also reportedly upregulated by TBI is the pentose phosphate pathway (PPP) that does not generate ATP but produces various molecules that are putatively neuroprotective, antioxidant and reparative, in addition to lactate among the end products. We have developed a novel combination of 13C-labelled cerebral microdialysis both to deliver 13C-labelled substrates into brains of TBI patients and recover the 13C-labelled metabolites, with high-resolution 13C NMR analysis of the microdialysates. This methodology has enabled us to achieve the first direct demonstration in humans that the brain can utilise lactate via the TCA cycle. We are currently using this methodology to make the first direct comparison of glycolysis and the PPP in human brain. In this article, we consider the application of 13C-labelled cerebral microdialysis for studying brain energy metabolism in patients. We set this methodology within the context of metabolic pathways in the brain, and 13C research modalities addressing them. PMID:24361470

40 CFR 86.310-79 - Sampling and analytical system; component specifications.

Code of Federal Regulations, 2012 CFR

2012-07-01

... temperature specification applies. (b) Sample probe. (1) The sample probe shall be a straight, closed end, stainless steel, multi-hole probe. The Inside Diameter (I.D.) shall not be greater than the I.D. of the sample line (=.010 in.). The wall thickness of the probe shall not be greater than .040 inch. The fitting...

40 CFR 86.310-79 - Sampling and analytical system; component specifications.

Code of Federal Regulations, 2013 CFR

2013-07-01

... temperature specification applies. (b) Sample probe. (1) The sample probe shall be a straight, closed end, stainless steel, multi-hole probe. The Inside Diameter (I.D.) shall not be greater than the I.D. of the sample line (=.010 in.). The wall thickness of the probe shall not be greater than .040 inch. The fitting...

40 CFR 91.414 - Raw gaseous exhaust sampling and analytical system description.

Code of Federal Regulations, 2012 CFR

2012-07-01

... “protectors” with nonreactive diaphragms to reduce dead volumes is permitted. (b) Sample probe. (1) The sample probe shall be a straight, closed end, stainless steel, multi-hole probe. The inside diameter shall not be greater than the inside diameter of the sample line + 0.03 cm. The wall thickness of the probe...

40 CFR 86.310-79 - Sampling and analytical system; component specifications.

Code of Federal Regulations, 2011 CFR

2011-07-01

... temperature specification applies. (b) Sample probe. (1) The sample probe shall be a straight, closed end, stainless steel, multi-hole probe. The Inside Diameter (I.D.) shall not be greater than the I.D. of the sample line (=.010 in.). The wall thickness of the probe shall not be greater than .040 inch. The fitting...

40 CFR 86.310-79 - Sampling and analytical system; component specifications.

Code of Federal Regulations, 2010 CFR

2010-07-01

... temperature specification applies. (b) Sample probe. (1) The sample probe shall be a straight, closed end, stainless steel, multi-hole probe. The Inside Diameter (I.D.) shall not be greater than the I.D. of the sample line (=.010 in.). The wall thickness of the probe shall not be greater than .040 inch. The fitting...

40 CFR 91.414 - Raw gaseous exhaust sampling and analytical system description.

Code of Federal Regulations, 2014 CFR

2014-07-01

... “protectors” with nonreactive diaphragms to reduce dead volumes is permitted. (b) Sample probe. (1) The sample probe shall be a straight, closed end, stainless steel, multi-hole probe. The inside diameter shall not be greater than the inside diameter of the sample line + 0.03 cm. The wall thickness of the probe...

40 CFR 91.414 - Raw gaseous exhaust sampling and analytical system description.

Code of Federal Regulations, 2013 CFR

2013-07-01

... “protectors” with nonreactive diaphragms to reduce dead volumes is permitted. (b) Sample probe. (1) The sample probe shall be a straight, closed end, stainless steel, multi-hole probe. The inside diameter shall not be greater than the inside diameter of the sample line + 0.03 cm. The wall thickness of the probe...

On-line preconcentration of fluorescent derivatives of catecholamines in cerebrospinal fluid using flow-gated capillary electrophoresis.

PubMed

Zhang, Qiyang; Gong, Maojun

2016-06-10

Flow-gated capillary electrophoresis (CE) coupled with microdialysis has become an important tool for in vivo bioanalytical measurements because it is capable of performing rapid and efficient separations of complex biological mixtures thus enabling high temporal resolution in chemical monitoring. However, the limit of detection (LOD) is often limited to a micro- or nano-molar range while many important target analytes have picomolar or sub-nanomolar levels in brain and other tissues. To enhance the capability of flow-gated CE for catecholamine detection, a novel and simple on-line sample preconcentration method was developed exclusively for fluorescent derivatives of catecholamines that were fluorogenically derivatized with naphthalene-2,3-dicarboxaldehyde (NDA) in the presence of cyanide. The effective preconcentration coupled with the sensitive laser-induced fluorescence (LIF) detection lowered the LOD down to 20pM for norepinephrine (NE) and 50pM for dopamine (DA) at 3-fold of S/N ratio, and the signal enhancement was estimated to be over 100-fold relative to normal injection when standard analytes were dissolved in artificial cerebrospinal fluid (aCSF). The basic focusing principle is novel since the sample plug contains borate while the background electrolyte (BGE) is void of borate. This strategy took advantage of the complexation between diols and borate, through which one negative charge was added to the complex entity. The sample derivatization mixture was electrokinetically injected into a capillary via the flow-gated injection, and then NE and DA derivatives were selectively focused to a narrow zone by the reversible complexation. Separation of NE and DA derivatives was executed by incoming surfactants of cholate and deoxycholate mixed in the front BGE plug. This on-line preconcentration method was finally applied to the detection of DA in rat cerebrospinal fluid (CSF) via microdialysis and on-line derivatization. It is anticipated that the method would be valuable for in vivo monitoring of DA and NE in various brain regions of live animals on flow-gated CE or microchip platforms. Published by Elsevier B.V.

METAL RESISTIVITY MEASURING DEVICE

DOEpatents

Renken, J. Jr.; Myers, R.G.

1960-12-20

An eddy current device is offered for detecting discontinuities in metal samples. Alternate short and long duration pulses are inductively applied to a metal sample via the outer coil of a probe. The long pulses give a resultant signal from the metal sample responsive to probe-tosample spacing and discontinuities within the sample and the shont pulses give a resultant signal responsive only to probe -to-sample spacing. The inner coil of the probe detects the two resultant signals and transmits them to a separation network where the two signals are separated. The two separated signals are then transmitted to a compensation network where the detected signals due to the short pulses are used to compensate for variations due to probe-to-sample spacing contained in the detected signals from the long pulses. Thus, a resultant signal is obtained responsive to discontinuities within the sample and independent of probe-to- sample spacing.

Analyzing Thioflavin T Binding to Amyloid Fibrils by an Equilibrium Microdialysis-Based Technique

PubMed Central

Kuznetsova, Irina M.; Sulatskaya, Anna I.; Uversky, Vladimir N.; Turoverov, Konstantin K.

2012-01-01

A new approach for the determination of the amyloid fibril – thioflavin T (ThT) binding parameters (the number of binding modes, stoichiometry, and binding constants of each mode) is proposed. This approach is based on the absorption spectroscopy determination of the concentration of free and bound to fibril dye in solutions, which are prepared by equilibrium microdialysis. Furthermore, the proposed approach allowed us, for the first time, to determine the absorption spectrum, molar extinction coefficient, and fluorescence quantum yield of the ThT bound to fibril by each binding modes. This approach is universal and can be used for determining the binding parameters of any dye interaction with a receptor, such as ANS binding to proteins in the molten globule state or to protein amorphous aggregates. PMID:22383971

Analyzing thioflavin T binding to amyloid fibrils by an equilibrium microdialysis-based technique.

PubMed

Kuznetsova, Irina M; Sulatskaya, Anna I; Uversky, Vladimir N; Turoverov, Konstantin K

2012-01-01

A new approach for the determination of the amyloid fibril - thioflavin T (ThT) binding parameters (the number of binding modes, stoichiometry, and binding constants of each mode) is proposed. This approach is based on the absorption spectroscopy determination of the concentration of free and bound to fibril dye in solutions, which are prepared by equilibrium microdialysis. Furthermore, the proposed approach allowed us, for the first time, to determine the absorption spectrum, molar extinction coefficient, and fluorescence quantum yield of the ThT bound to fibril by each binding modes. This approach is universal and can be used for determining the binding parameters of any dye interaction with a receptor, such as ANS binding to proteins in the molten globule state or to protein amorphous aggregates.

NONDESTRUCTIVE EDDY CURRENT TESTING

DOEpatents

Renken, C.J. Jr.

1961-05-23

An eddy current testing device is described for measuring metal continuity independent of probe-to-sample spacing. An inductance would test probe is made a leg of a variable impedance bridge and the bridge is balanced with the probe away from the sample. An a-c signal is applied across the input terminals of the bridge circuit. As the probe is brought into proximity with the metal sample, the resulting impedance change in the probe gives an output signal from the bridge whose phase angle is proportional to the sample continuity and amplitude is proportional to the probe-tosample spacing. The output signal from the bridge is applied to a compensating network where, responsive to amplitude changes from the bridge output signal, a constant phased voltage output is maintained when the sample is continuous regardless of probe-to-sample spacing. A phase meter calibrated to read changes in resistivity of the metal sample measures the phase shift between the output of the compensating network and the original a-c signal applied to the bridge.

Origin and Properties of Striatal Local Field Potential Responses to Cortical Stimulation: Temporal Regulation by Fast Inhibitory Connections

PubMed Central

Galiñanes, Gregorio L.; Braz, Barbara Y.; Murer, Mario Gustavo

2011-01-01

Evoked striatal field potentials are seldom used to study corticostriatal communication in vivo because little is known about their origin and significance. Here we show that striatal field responses evoked by stimulating the prelimbic cortex in mice are reduced by more than 90% after infusing the AMPA receptor antagonist CNQX close to the recording electrode. Moreover, the amplitude of local field responses and dPSPs recorded in striatal medium spiny neurons increase in parallel with increasing stimulating current intensity. Finally, the evoked striatal fields show several of the basic known properties of corticostriatal transmission, including paired pulse facilitation and topographical organization. As a case study, we characterized the effect of local GABAA receptor blockade on striatal field and multiunitary action potential responses to prelimbic cortex stimulation. Striatal activity was recorded through a 24 channel silicon probe at about 600 µm from a microdialysis probe. Intrastriatal administration of the GABAA receptor antagonist bicuculline increased by 65±7% the duration of the evoked field responses. Moreover, the associated action potential responses were markedly enhanced during bicuculline infusion. Bicuculline enhancement took place at all the striatal sites that showed a response to cortical stimulation before drug infusion, but sites showing no field response before bicuculline remained unresponsive during GABAA receptor blockade. Thus, the data demonstrate that fast inhibitory connections exert a marked temporal regulation of input-output transformations within spatially delimited striatal networks responding to a cortical input. Overall, we propose that evoked striatal fields may be a useful tool to study corticostriatal synaptic connectivity in relation to behavior. PMID:22163020

40 CFR 91.420 - CVS concept of exhaust gas sampling system.

Code of Federal Regulations, 2013 CFR

2013-07-01

... that complete mixing of the engine exhaust and background air is assured prior to the sampling probe.... The background probe must draw a representative sample of the background air during each sampling mode...) sampling system. If a critical flow venturi (CFV) is used on the dilute exhaust sample probe, this system...

40 CFR 90.420 - CVS concept of exhaust gas sampling system.

Code of Federal Regulations, 2013 CFR

2013-07-01

... sampling probe. (2) Exhaust flow metering system. A dilute exhaust flow metering system must be used to... exhaust. The background probe must draw a representative sample of the background air during each sampling... (bag) sampling system. If a critical flow venturi (CFV) is used on the dilute exhaust sample probe...

40 CFR 91.420 - CVS concept of exhaust gas sampling system.

Code of Federal Regulations, 2010 CFR

2010-07-01

... that complete mixing of the engine exhaust and background air is assured prior to the sampling probe.... The background probe must draw a representative sample of the background air during each sampling mode...) sampling system. If a critical flow venturi (CFV) is used on the dilute exhaust sample probe, this system...

40 CFR 90.420 - CVS concept of exhaust gas sampling system.

Code of Federal Regulations, 2011 CFR

2011-07-01

... sampling probe. (2) Exhaust flow metering system. A dilute exhaust flow metering system must be used to... exhaust. The background probe must draw a representative sample of the background air during each sampling... (bag) sampling system. If a critical flow venturi (CFV) is used on the dilute exhaust sample probe...

40 CFR 90.420 - CVS concept of exhaust gas sampling system.

Code of Federal Regulations, 2014 CFR

2014-07-01

... sampling probe. (2) Exhaust flow metering system. A dilute exhaust flow metering system must be used to... exhaust. The background probe must draw a representative sample of the background air during each sampling... (bag) sampling system. If a critical flow venturi (CFV) is used on the dilute exhaust sample probe...

40 CFR 90.420 - CVS concept of exhaust gas sampling system.

Code of Federal Regulations, 2012 CFR

2012-07-01

... sampling probe. (2) Exhaust flow metering system. A dilute exhaust flow metering system must be used to... exhaust. The background probe must draw a representative sample of the background air during each sampling... (bag) sampling system. If a critical flow venturi (CFV) is used on the dilute exhaust sample probe...

40 CFR 90.420 - CVS concept of exhaust gas sampling system.

Code of Federal Regulations, 2010 CFR

2010-07-01

... sampling probe. (2) Exhaust flow metering system. A dilute exhaust flow metering system must be used to... exhaust. The background probe must draw a representative sample of the background air during each sampling... (bag) sampling system. If a critical flow venturi (CFV) is used on the dilute exhaust sample probe...

40 CFR 91.420 - CVS concept of exhaust gas sampling system.

Code of Federal Regulations, 2014 CFR

2014-07-01

... that complete mixing of the engine exhaust and background air is assured prior to the sampling probe.... The background probe must draw a representative sample of the background air during each sampling mode...) sampling system. If a critical flow venturi (CFV) is used on the dilute exhaust sample probe, this system...

40 CFR 91.420 - CVS concept of exhaust gas sampling system.

Code of Federal Regulations, 2011 CFR

2011-07-01

... that complete mixing of the engine exhaust and background air is assured prior to the sampling probe.... The background probe must draw a representative sample of the background air during each sampling mode...) sampling system. If a critical flow venturi (CFV) is used on the dilute exhaust sample probe, this system...

40 CFR 91.420 - CVS concept of exhaust gas sampling system.

Code of Federal Regulations, 2012 CFR

2012-07-01

... that complete mixing of the engine exhaust and background air is assured prior to the sampling probe.... The background probe must draw a representative sample of the background air during each sampling mode...) sampling system. If a critical flow venturi (CFV) is used on the dilute exhaust sample probe, this system...

The Preignition and Autoignition Oxidation of Alternatives to Petroleum Derived JP-8 and their Surrogate Components in a Pressurized Flow Reactor and Single Cylinder Research Engine

DTIC Science & Technology

2009-09-01

sample probe consisted of TIG welding the 3/8” sample probe shaft to the sample probe tip (Koert, 1990 and Lenhert, 2004b). Silver solder was...was performed in the Drexel University Machine Shop. Conventional TIG welding was sufficient for welding the 3/8” O.D. tube to the sample probe tip...However, to TIG weld the thermocouple and the glass lined tube to the sample probe tip, extreme care had to be taken so as not to damage the

Characterization of power induced heating and damage in fiber optic probes for near-field scanning optical microscopy

NASA Astrophysics Data System (ADS)

Dickenson, Nicholas E.; Erickson, Elizabeth S.; Mooren, Olivia L.; Dunn, Robert C.

2007-05-01

Tip-induced sample heating in near-field scanning optical microscopy (NSOM) is studied for fiber optic probes fabricated using the chemical etching technique. To characterize sample heating from etched NSOM probes, the spectra of a thermochromic polymer sample are measured as a function of probe output power, as was previously reported for pulled NSOM probes. The results reveal that sample heating increases rapidly to ˜55-60°C as output powers reach ˜50nW. At higher output powers, the sample heating remains approximately constant up to the maximum power studied of ˜450nW. The sample heating profiles measured for etched NSOM probes are consistent with those previously measured for NSOM probes fabricated using the pulling method. At high powers, both pulled and etched NSOM probes fail as the aluminum coating is damaged. For probes fabricated in our laboratory we find failure occurring at input powers of 3.4±1.7 and 20.7±6.9mW for pulled and etched probes, respectively. The larger half-cone angle for etched probes (˜15° for etched and ˜6° for pulled probes) enables more light delivery and also apparently leads to a different failure mechanism. For pulled NSOM probes, high resolution images of NSOM probes as power is increased reveal the development of stress fractures in the coating at a taper diameter of ˜6μm. These stress fractures, arising from the differential heating expansion of the dielectric and the metal coating, eventually lead to coating removal and probe failure. For etched tips, the absence of clear stress fractures and the pooled morphology of the damaged aluminum coating following failure suggest that thermal damage may cause coating failure, although other mechanisms cannot be ruled out.

Characterization of power induced heating and damage in fiber optic probes for near-field scanning optical microscopy.

PubMed

Dickenson, Nicholas E; Erickson, Elizabeth S; Mooren, Olivia L; Dunn, Robert C

2007-05-01

Tip-induced sample heating in near-field scanning optical microscopy (NSOM) is studied for fiber optic probes fabricated using the chemical etching technique. To characterize sample heating from etched NSOM probes, the spectra of a thermochromic polymer sample are measured as a function of probe output power, as was previously reported for pulled NSOM probes. The results reveal that sample heating increases rapidly to approximately 55-60 degrees C as output powers reach approximately 50 nW. At higher output powers, the sample heating remains approximately constant up to the maximum power studied of approximately 450 nW. The sample heating profiles measured for etched NSOM probes are consistent with those previously measured for NSOM probes fabricated using the pulling method. At high powers, both pulled and etched NSOM probes fail as the aluminum coating is damaged. For probes fabricated in our laboratory we find failure occurring at input powers of 3.4+/-1.7 and 20.7+/-6.9 mW for pulled and etched probes, respectively. The larger half-cone angle for etched probes ( approximately 15 degrees for etched and approximately 6 degrees for pulled probes) enables more light delivery and also apparently leads to a different failure mechanism. For pulled NSOM probes, high resolution images of NSOM probes as power is increased reveal the development of stress fractures in the coating at a taper diameter of approximately 6 microm. These stress fractures, arising from the differential heating expansion of the dielectric and the metal coating, eventually lead to coating removal and probe failure. For etched tips, the absence of clear stress fractures and the pooled morphology of the damaged aluminum coating following failure suggest that thermal damage may cause coating failure, although other mechanisms cannot be ruled out.

Sampling probe for microarray read out using electrospray mass spectrometry

DOEpatents

Van Berkel, Gary J.

2004-10-12

An automated electrospray based sampling system and method for analysis obtains samples from surface array spots having analytes. The system includes at least one probe, the probe including an inlet for flowing at least one eluting solvent to respective ones of a plurality of spots and an outlet for directing the analyte away from the spots. An automatic positioning system is provided for translating the probe relative to the spots to permit sampling of any spot. An electrospray ion source having an input fluidicly connected to the probe receives the analyte and generates ions from the analyte. The ion source provides the generated ions to a structure for analysis to identify the analyte, preferably being a mass spectrometer. The probe can be a surface contact probe, where the probe forms an enclosing seal along the periphery of the array spot surface.

Nanomechanical testing system

DOEpatents

Vodnick, David James; Dwivedi, Arpit; Keranen, Lucas Paul; Okerlund, Michael David; Schmitz, Roger William; Warren, Oden Lee; Young, Christopher David

2014-07-08

An automated testing system includes systems and methods to facilitate inline production testing of samples at a micro (multiple microns) or less scale with a mechanical testing instrument. In an example, the system includes a probe changing assembly for coupling and decoupling a probe of the instrument. The probe changing assembly includes a probe change unit configured to grasp one of a plurality of probes in a probe magazine and couple one of the probes with an instrument probe receptacle. An actuator is coupled with the probe change unit, and the actuator is configured to move and align the probe change unit with the probe magazine and the instrument probe receptacle. In another example, the automated testing system includes a multiple degree of freedom stage for aligning a sample testing location with the instrument. The stage includes a sample stage and a stage actuator assembly including translational and rotational actuators.

Nanomechanical testing system

DOEpatents

Vodnick, David James; Dwivedi, Arpit; Keranen, Lucas Paul; Okerlund, Michael David; Schmitz, Roger William; Warren, Oden Lee; Young, Christopher David

2015-01-27

An automated testing system includes systems and methods to facilitate inline production testing of samples at a micro (multiple microns) or less scale with a mechanical testing instrument. In an example, the system includes a probe changing assembly for coupling and decoupling a probe of the instrument. The probe changing assembly includes a probe change unit configured to grasp one of a plurality of probes in a probe magazine and couple one of the probes with an instrument probe receptacle. An actuator is coupled with the probe change unit, and the actuator is configured to move and align the probe change unit with the probe magazine and the instrument probe receptacle. In another example, the automated testing system includes a multiple degree of freedom stage for aligning a sample testing location with the instrument. The stage includes a sample stage and a stage actuator assembly including translational and rotational actuators.

Nanomechanical testing system

DOEpatents

Vodnick, David James; Dwivedi, Arpit; Keranen, Lucas Paul; Okerlund, Michael David; Schmitz, Roger William; Warren, Oden Lee; Young, Christopher David

2015-02-24

An automated testing system includes systems and methods to facilitate inline production testing of samples at a micro (multiple microns) or less scale with a mechanical testing instrument. In an example, the system includes a probe changing assembly for coupling and decoupling a probe of the instrument. The probe changing assembly includes a probe change unit configured to grasp one of a plurality of probes in a probe magazine and couple one of the probes with an instrument probe receptacle. An actuator is coupled with the probe change unit, and the actuator is configured to move and align the probe change unit with the probe magazine and the instrument probe receptacle. In another example, the automated testing system includes a multiple degree of freedom stage for aligning a sample testing location with the instrument. The stage includes a sample stage and a stage actuator assembly including translational and rotational actuators.

Analysis of non-contact and contact probe-to-sample thermal exchange for quantitative measurements of thin film and nanostructure thermal conductivity by the scanning hot probe method

NASA Astrophysics Data System (ADS)

Wilson, Adam A.

The ability to measure thermal properties of thin films and nanostructured materials is an important aspect of many fields of academic study. A strategy especially well-suited for nanoscale investigations of these properties is the scanning hot probe technique, which is unique in its ability to non-destructively interrogate the thermal properties with high resolution, both laterally as well as through the thickness of the material. Strategies to quantitatively determine sample thermal conductivity depend on probe calibration. State of the art calibration strategies assume that the area of thermal exchange between probe and sample does not vary with sample thermal conductivity. However, little investigation has gone into determining whether or not that assumption is valid. This dissertation provides a rigorous study into the probe-to-sample heat transfer through the air gap at diffusive distances for a variety of values of sample thermal conductivity. It is demonstrated that the thermal exchange radius and gap/contact thermal resistance varies with sample thermal conductivity as well as tip-to-sample clearance in non-contact mode. In contact mode, it is demonstrated that higher thermal conductivity samples lead to a reduction in thermal exchange radius for Wollaston probe tips. Conversely, in non-contact mode and in contact mode for sharper probe tips where air contributes the most to probe-to-sample heat transfer, the opposite trend occurs. This may be attributed to the relatively strong solid-to-solid conduction occurring between probe and sample for the Wollaston probes. A three-dimensional finite element (3DFE) model was developed to investigate how the calibrated thermal exchange parameters vary with sample thermal conductivity when calibrating the probe via the intersection method in non-contact mode at diffusive distances. The 3DFE model was then used to explore the limits of sensitivity of the experiment for a range of simulated experimental conditions. It is determined that, when operating the scanning hot probe technique in air at standard temperature and pressure using Wollaston probes, the technique is capable of measuring, within 20% uncertainty, samples with values of thermal conductivity up to 10 Wm-1K-1 in contact mode and up to 2 Wm-1K-1 in non-contact mode. By increasing the thermal conductivity of the probe's surroundings (i.e. changing air to a more conductive gas), sensitivity in non-contact mode to sample thermal conductivity is improved, which suggests potential for future investigations using non-contact scanning hot probe to measure thermal conductivity of higher thermal conductivity samples. The ability of the technique to differentiate thin films from the substrate is investigated, and the sensitivity of the technique to thin films and samples with anisotropic properties is explored. The models (both analytical and finite element) developed and reported in this dissertation lead to the ability to measure samples which, by the standard procedure before this work, were unable to be accurately measured. While other techniques failed to be able to successfully interrogate the film thermal conductivity of a full set of double-wall carbon nanotubes infused into polymers, the methods developed in this work allowed non-contact scanning hot probe measurements to be successfully performed to obtain the film thermal conductivity for each sample. Finite element simulations accounting for the anisotropy of these thin film on sample materials show similar trends with independently measured in-plane thermal conductivity for the only two (of five) samples in the set which were successfully able to be measured by the independent technique. Investigations in contact mode with high resolution Pd probes, whose probe-to-sample clearance is difficult to control in a repeatable fashion, show that surface roughness affects the thermal contact resistance. This can lead to values of reported sample thermal conductivity which are misleading, when using the standard calibrated thermal exchange parameters on samples with significantly different surface roughness than the calibration samples. This affect was taken into account to report sample thermal conductivity of Bi2Te3 nanoflakes.

Analysis of Glutamate, GABA, Noradrenaline, Dopamine, Serotonin, and Metabolites Using Microbore UHPLC with Electrochemical Detection

PubMed Central

2013-01-01

The applicability of microbore ultrahigh performance liquid chromatography (UHPLC) with electrochemical detection for offline analysis of a number of well-known neurotransmitters in less than 10 μL microdialysis fractions is described. Two methods are presented for the analysis of monoamine or amino acid neurotransmitters, using the same UHPLC instrument. Speed of analysis of noradrenaline (NA), dopamine (DA), serotonin (5-HT), and the metabolites homovanillic acid (HVA), 5-hydroxyindole aceticacid (5-HIAA), and 3,4-dihydroxyphenylacetic acid (DOPAC) was predominated by the retention behavior of NA, the nonideal behavior of matrix components, and the loss in signal of 5-HT. This method was optimized to meet the requirements for detection sensitivity and minimizing the size of collected fractions, which determines temporal resolution in microdialysis. The amino acid neurotransmitters glutamate (Glu) and γ-aminobutyric acid (GABA) were analyzed after an automated derivatization procedure. Under optimized conditions, Glu was resolved from a number of early eluting system peaks, while the total runtime was decreased to 15 min by a 4-fold increase of the flow rate under UHPLC conditions. The detection limit for Glu and GABA was 10 nmol/L (15 fmol in 1.5 μL); the monoamine neurotransmitters had a detection limit between 32 and 83 pmol/L (0.16–0.42 fmol in 5 μL) in standard solutions. Using UHPLC, the analysis times varied from 15 min to less than 2 min depending on the complexity of the samples and the substances to be analyzed. PMID:23642417

The GABA uptake inhibitor beta-alanine reduces pilocarpine-induced tremor and increases extracellular GABA in substantia nigra pars reticulata as measured by microdialysis.

PubMed

Ishiwari, Keita; Mingote, Susana; Correa, Merce; Trevitt, Jennifer T; Carlson, Brian B; Salamone, John D

2004-12-30

Substantia nigra pars reticulata (SNr) is a major output nucleus of the basal ganglia that receives GABAergic projections from neostriatum and globus pallidus. Previous research has shown that local pharmacological manipulations of GABA in SNr can influence tremulous jaw movements in rats. Tremulous jaw movements are defined as rapid vertical deflections of the lower jaw that resemble chewing but are not directed at a particular stimulus, and evidence indicates that these movements share many characteristics with parkinsonian tremor in humans. In order to investigate the role of GABA in motor functions related to tremor, the present study tested the GABA uptake blocker beta-alanine for its ability to reduce pilocarpine-induced tremulous jaw movements. In a parallel experiment, the effect of an active dose of beta-alanine on dialysate levels of GABA in SNr was assessed using microdialysis methods. GABA levels in dialysis samples were measured using high performance liquid chromatography with electrochemical detection. beta-Alanine (250-500 mg/kg) significantly reduced tremulous jaw movements induced by pilocarpine (4.0 mg/kg). Moreover, systemic administration of beta-alanine at a dose that reduced tremulous jaw movements (500 mg/kg) resulted in a substantial increase in extracellular levels of GABA in SNr compared to the pre-injection baseline. Thus, the present results are consistent with the hypothesis that GABAergic tone in SNr plays a role in the regulation of tremulous jaw movements. This research may lead to a better understanding of how parkinsonian symptoms are modulated by SNr GABA mechanisms.

Galanin Mediates Features of Neural and Behavioral Stress Resilience Afforded by Exercise

PubMed Central

Sciolino, N. R.; Smith, J.M.; Stranahan, A.M.; Freeman, K.G.; Edwards, G. L.; Weinshenker, D.; Holmes, P.V.

2014-01-01

Exercise promotes resilience to stress and increases galanin in the locus coeruleus (LC), but the question of whether changes in galanin signaling mediate the stress-buffering effects of exercise has never been addressed. To test the contributions of galanin to stress resilience, male Sprague Dawley rats received intracerebroventricular (ICV) cannulation for drug delivery and frontocortical cannulation for microdialysis, and were housed with or without a running wheel for 21d. Rats were acutely injected with vehicle or the galanin receptor antagonist M40 and exposed to a single session of either footshock or no stress. Other groups received galanin, the galanin receptor antagonist M40, or vehicle chronically for 21d prior to the stress session. Microdialysis sampling occurred during stress exposure and anxiety-related behavior was measured on the following day in the elevated plus maze. Dendritic spines were visualized by Golgi impregnation in medial prefrontal cortex (mPFC) pyramidal neurons and quantified. Exercise increased galanin levels in the LC. Under non-stressed conditions, anxiety-related behavior and dopamine levels were comparable between exercised and sedentary rats. In contrast, exposure to stress reduced open arm exploration in sedentary rats but not in exercise rats or those treated chronically with ICV galanin, indicating improved resilience. Both exercise and chronic, ICV galanin prevented the increased dopamine overflow and loss of dendritic spines observed after stress in sedentary rats. Chronic, but not acute M40 administration blocked the resilience-promoting effects of exercise. The results indicate that increased galanin levels promote features of resilience at both behavioral and neural levels. PMID:25301278

The complexity of minocycline serum protein binding.

PubMed

Zhou, Jian; Tran, Brian T; Tam, Vincent H

2017-06-01

Serum protein binding is critical for understanding the pharmacology of antimicrobial agents. Tigecycline and eravacycline were previously reported to have atypical non-linear protein binding; the percentage of free fraction decreased with increasing total concentration. In this study, we extended the investigation to other tetracyclines and examined the factors that might impact protein binding. Different minocycline concentrations (0.5-50 mg/L) and perfusion media (saline, 0.1 M HEPES buffer and 0.1 and 1 M PBS) were examined by in vitro microdialysis. After equilibration, two dialysate samples were taken from each experiment and the respective antimicrobial agent concentrations were analysed by validated LC-MS/MS methods. For comparison, the serum protein bindings of doxycycline and levofloxacin were also determined. The free fraction of minocycline decreased with increasing total concentration, and the results depended on the perfusion media used. The trends of minocycline protein binding in mouse and human sera were similar. In addition, serum protein binding of doxycycline showed the same concentration-dependent trend as minocycline, while the results of levofloxacin were concentration independent. The serum protein bindings of minocycline and doxycycline are negatively correlated with their total concentrations. It is possible that all tetracyclines share the same pharmacological property. Moreover, the specific perfusion media used could also impact the results of microdialysis. Additional studies are warranted to understand the mechanism(s) and clinical implications of serum protein binding of tetracyclines. © The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Tensiometer, drive probe for use with environmental testing equipment, and methods of inserting environmental testing equipment into a sample

DOEpatents

Hubbell, Joel M.; Sisson, James B.

2005-07-26

A method of inserting a tensiometer into a sample, comprises providing a drive probe configured to be engaged by direct push equipment; supporting a porous member from the drive probe; and driving the drive probe into the sample using a cone penetrometer. A tensiometer comprises a drive probe configured to be engaged by direct push equipment or a cone penetrometer; a porous member supported by the drive probe; and a pressure sensor in pressure sensing relation to the porous member.

Probe Heating Method for the Analysis of Solid Samples Using a Portable Mass Spectrometer

PubMed Central

Kumano, Shun; Sugiyama, Masuyuki; Yamada, Masuyoshi; Nishimura, Kazushige; Hasegawa, Hideki; Morokuma, Hidetoshi; Inoue, Hiroyuki; Hashimoto, Yuichiro

2015-01-01

We previously reported on the development of a portable mass spectrometer for the onsite screening of illicit drugs, but our previous sampling system could only be used for liquid samples. In this study, we report on an attempt to develop a probe heating method that also permits solid samples to be analyzed using a portable mass spectrometer. An aluminum rod is used as the sampling probe. The powdered sample is affixed to the sampling probe or a droplet of sample solution is placed on the tip of the probe and dried. The probe is then placed on a heater to vaporize the sample. The vapor is then introduced into the portable mass spectrometer and analyzed. With the heater temperature set to 130°C, the developed system detected 1 ng of methamphetamine, 1 ng of amphetamine, 3 ng of 3,4-methylenedioxymethamphetamine, 1 ng of 3,4-methylenedioxyamphetamine, and 0.3 ng of cocaine. Even from mixtures consisting of clove powder and methamphetamine powder, methamphetamine ions were detected by tandem mass spectrometry. The developed probe heating method provides a simple method for the analysis of solid samples. A portable mass spectrometer incorporating this method would thus be useful for the onsite screening of illicit drugs. PMID:26819909

40 CFR 85.2224 - Exhaust analysis system-EPA 81.

Code of Federal Regulations, 2012 CFR

2012-07-01

... probe, moisture separator and analyzers for HC and CO. (2) Dual sample probe requirements. If used, a dual sample probe must provide equal flow in each leg. The equal flow criterion is considered to be met if the flow rate in each leg of the probe (or an identical model) has been measured under two sample...

40 CFR 85.2224 - Exhaust analysis system-EPA 81.

Code of Federal Regulations, 2013 CFR

2013-07-01

... probe, moisture separator and analyzers for HC and CO. (2) Dual sample probe requirements. If used, a dual sample probe must provide equal flow in each leg. The equal flow criterion is considered to be met if the flow rate in each leg of the probe (or an identical model) has been measured under two sample...

40 CFR 85.2224 - Exhaust analysis system-EPA 81.

Code of Federal Regulations, 2011 CFR

2011-07-01

... probe, moisture separator and analyzers for HC and CO. (2) Dual sample probe requirements. If used, a dual sample probe must provide equal flow in each leg. The equal flow criterion is considered to be met if the flow rate in each leg of the probe (or an identical model) has been measured under two sample...

Probing dimensionality using a simplified 4-probe method.

PubMed

Kjeldby, Snorre B; Evenstad, Otto M; Cooil, Simon P; Wells, Justin W

2017-10-04

4-probe electrical measurements have been in existence for many decades. One of the most useful aspects of the 4-probe method is that it is not only possible to find the resistivity of a sample (independently of the contact resistances), but that it is also possible to probe the dimensionality of the sample. In theory, this is straightforward to achieve by measuring the 4-probe resistance as a function of probe separation. In practice, it is challenging to move all four probes with sufficient precision over the necessary range. Here, we present an alternative approach. We demonstrate that the dimensionality of the conductive path within a sample can be directly probed using a modified 4-probe method in which an unconventional geometry is exploited; three of the probes are rigidly fixed, and the position of only one probe is changed. This allows 2D and 3D (and other) contributions the to resistivity to be readily disentangled. The required experimental instrumentation can be vastly simplified relative to traditional variable spacing 4-probe instruments.

Skin glucose metabolism and microvascular blood flow during local insulin delivery and after an oral glucose load.

PubMed

Iredahl, Fredrik; Högstedt, Alexandra; Henricson, Joakim; Sjöberg, Folke; Tesselaar, Erik; Farnebo, Simon

2016-10-01

Insulin causes capillary recruitment in muscle and adipose tissue, but the metabolic and microvascular effects of insulin in the skin have not been studied in detail. The aim of this study was to measure glucose metabolism and microvascular blood flow in the skin during local insulin delivery and after an oral glucose load. Microdialysis catheters were inserted intracutanously in human subjects. In eight subjects two microdialysis catheters were inserted, one perfused with insulin and one with control solution. First the local effects of insulin was studied, followed by a systemic provocation by an oral glucose load. Additionally, as control experiment, six subjects did not recieve local delivery of insulin or the oral glucose load. During microdialysis the local blood flow was measured by urea clearance and by laser speckle contrast imaging (LSCI). Within 15 minutes of local insulin delivery, microvascular blood flow in the skin increased (urea clearance: P=.047, LSCI: P=.002) paralleled by increases in pyruvate (P=.01) and lactate (P=.04), indicating an increase in glucose uptake. An oral glucose load increased urea clearance from the catheters, indicating an increase in skin perfusion, although no perfusion changes were detected with LSCI. The concentration of glucose, pyruvate and lactate increased in the skin after the oral glucose load. Insulin has metabolic and vasodilatory effects in the skin both when given locally and after systemic delivery through an oral glucose load. © 2016 John Wiley & Sons Ltd.

Nonconvulsive electrographic seizures after traumatic brain injury result in a delayed, prolonged increase in intracranial pressure and metabolic crisis.

PubMed

Vespa, Paul M; Miller, Chad; McArthur, David; Eliseo, Mathew; Etchepare, Maria; Hirt, Daniel; Glenn, Thomas C; Martin, Neil; Hovda, David

2007-12-01

To determine whether nonconvulsive electrographic post-traumatic seizures result in increases in intracranial pressure and microdialysis lactate/pyruvate ratio. Prospective monitoring with retrospective data analysis. Single center academic neurologic intensive care unit. Twenty moderate to severe traumatic brain injury patients (Glasgow Coma Score 3-13). Continuous electroencephalography and cerebral microdialysis were performed for 7 days after injury. Ten patients had seizures and were compared with a matched cohort of traumatic brain injury patients without seizures. The seizures were repetitive and constituted status epilepticus in seven of ten patients. Using a within-subject design, post-traumatic seizures resulted in episodic increases in intracranial pressure (22.4 +/- 7 vs. 12.8 +/- 4.3 mm Hg; p < .001) and an episodic increase in lactate/pyruvate ratio (49.4 +/- 16 vs. 23.8 +/- 7.6; p < .001) in the seizure group. Using a between-subjects comparison, the seizure group demonstrated a higher mean intracranial pressure (17.6 +/- 6.5 vs. 12.2 +/- 4.2 mm Hg; p < .001), a higher mean lactate/pyruvate ratio (38.6 +/- 18 vs. 27 +/- 9; p < .001) compared with nonseizure patients. The intracranial pressure and lactate/pyruvate ratio remained elevated beyond postinjury hour 100 in the seizure group but not the nonseizure group (p < .02). Post-traumatic seizures result in episodic as well as long-lasting increases in intracranial pressure and microdialysis lactate/pyruvate ratio. These data suggest that post-traumatic seizures represent a therapeutic target for patients with traumatic brain injury.

7 CFR 800.82 - Sampling provisions by level of service.

Code of Federal Regulations, 2014 CFR

2014-01-01

... criteria, and a sample obtained with a probe at the time of the reinspection or appeal, generally, shall be... instances where original inspection results are based on samples obtained by probe, the decision as to whether file samples or new samples obtained by probe are to be used shall be made by the official...

Sample rotating turntable kit for infrared spectrometers

DOEpatents

Eckels, Joel Del [Livermore, CA; Klunder, Gregory L [Oakland, CA

2008-03-04

An infrared spectrometer sample rotating turntable kit has a rotatable sample cup containing the sample. The infrared spectrometer has an infrared spectrometer probe for analyzing the sample and the rotatable sample cup is adapted to receive the infrared spectrometer probe. A reflectance standard is located in the rotatable sample cup. A sleeve is positioned proximate the sample cup and adapted to receive the probe. A rotator rotates the rotatable sample cup. A battery is connected to the rotator.

Review of recent advances in analytical techniques for the determination of neurotransmitters

PubMed Central

Perry, Maura; Li, Qiang; Kennedy, Robert T.

2009-01-01

Methods and advances for monitoring neurotransmitters in vivo or for tissue analysis of neurotransmitters over the last five years are reviewed. The review is organized primarily by neurotransmitter type. Transmitter and related compounds may be monitored by either in vivo sampling coupled to analytical methods or implanted sensors. Sampling is primarily performed using microdialysis, but low-flow push-pull perfusion may offer advantages of spatial resolution while minimizing the tissue disruption associated with higher flow rates. Analytical techniques coupled to these sampling methods include liquid chromatography, capillary electrophoresis, enzyme assays, sensors, and mass spectrometry. Methods for the detection of amino acid, monoamine, neuropeptide, acetylcholine, nucleoside, and soluable gas neurotransmitters have been developed and improved upon. Advances in the speed and sensitivity of these methods have enabled improvements in temporal resolution and increased the number of compounds detectable. Similar advances have enabled improved detection at tissue samples, with a substantial emphasis on single cell and other small samples. Sensors provide excellent temporal and spatial resolution for in vivo monitoring. Advances in application to catecholamines, indoleamines, and amino acids have been prominent. Improvements in stability, sensitivity, and selectivity of the sensors have been of paramount interest. PMID:19800472

Systems and methods for laser assisted sample transfer to solution for chemical analysis

DOEpatents

Van Berkel, Gary J.; Kertesz, Vilmos; Ovchinnikova, Olga S.

2014-06-03

Systems and methods are described for laser ablation of an analyte from a specimen and capturing of the analyte in a dispensed solvent to form a testing solution. A solvent dispensing and extraction system can form a liquid microjunction with the specimen. The solvent dispensing and extraction system can include a surface sampling probe. The laser beam can be directed through the surface sampling probe. The surface sampling probe can also serve as an atomic force microscopy probe. The surface sampling probe can form a seal with the specimen. The testing solution including the analyte can then be analyzed using an analytical instrument or undergo further processing.

Systems and methods for laser assisted sample transfer to solution for chemical analysis

DOEpatents

Van Berkel, Gary J.; Kertesz, Vilmos; Ovchinnikova, Olga S.

2015-09-29

Systems and methods are described for laser ablation of an analyte from a specimen and capturing of the analyte in a dispensed solvent to form a testing solution. A solvent dispensing and extraction system can form a liquid microjunction with the specimen. The solvent dispensing and extraction system can include a surface sampling probe. The laser beam can be directed through the surface sampling probe. The surface sampling probe can also serve as an atomic force microscopy probe. The surface sampling probe can form a seal with the specimen. The testing solution including the analyte can then be analyzed using an analytical instrument or undergo further processing.

Systems and methods for laser assisted sample transfer to solution for chemical analysis

DOEpatents

Van Berkel, Gary J; Kertesz, Vilmos; Ovchinnikova, Olga S

2013-08-27

Systems and methods are described for laser ablation of an analyte from a specimen and capturing of the analyte in a dispensed solvent to form a testing solution. A solvent dispensing and extraction system can form a liquid microjunction with the specimen. The solvent dispensing and extraction system can include a surface sampling probe. The laser beam can be directed through the surface sampling probe. The surface sampling probe can also serve as an atomic force microscopy probe. The surface sampling probe can form a seal with the specimen. The testing solution including the analyte can then be analyzed using an analytical instrument or undergo further processing.

Self-referencing remote optical probe

DOEpatents

O'Rourke, Patrick E.; Prather, William S.; Livingston, Ronald R.

1991-01-01

A probe for remote spectrometric measurements of fluid samples having a hollow probe body with a sliding reflective plug therein and a lens at one end, ports for admitting and expelling the fluid sample and a means for moving the reflector so that reference measurement can be made with the reflector in a first position near the lens and a sample measurement can be made with the reflector away from the lens and the fluid sample between the reflector and the lens. Comparison of the two measurements will yield the composition of the fluid sample. The probe is preferably used for remote measurements and light is carried to and from the probe via fiber optic cables.

Self-referencing remote optical probe

DOEpatents

O'Rourke, P.E.; Prather, W.S.; Livingston, R.R.

1991-08-13

A probe is described for remote spectrometric measurements of fluid samples having a hollow probe body with a sliding reflective plug therein and a lens at one end, ports for admitting and expelling the fluid sample and a means for moving the reflector so that reference measurement can be made with the reflector in a first position near the lens and a sample measurement can be made with the reflector away from the lens and the fluid sample between the reflector and the lens. Comparison of the two measurements will yield the composition of the fluid sample. The probe is preferably used for remote measurements and light is carried to and from the probe via fiber optic cables. 3 figures.

Metal Resistivity Measuring Device

DOEpatents

Renken, Jr, C. J.; Myers, R. G.

1960-12-20

An eddy current device is designed for detecting discontinuities in metal samples. Alternate short and long duration pulses are inductively applied to a metal sample via the outer coil of a probe. The lorg pulses give a resultant signal from the metal sample responsive to probe-tosample spacing and discontinuities with the sample, and the short pulses give a resultant signal responsive only to probe-to-sample spacing. The inner coil of the probe detects the two resultant signals and transmits them to a separation network where the two signals are separated. The two separated signals are then transmitted to a compensation network where the detected signals due to the short pulses are used to compensate for variations due to probeto-sample spacing contained in the detected signals from the long pulses. Thus a resultant signal is obtained responsive to discontinuities within the sample and independent of probe-to- sample spacing.

Scanning optical microscope with long working distance objective

DOEpatents

Cloutier, Sylvain G.

2010-10-19

A scanning optical microscope, including: a light source to generate a beam of probe light; collimation optics to substantially collimate the probe beam; a probe-result beamsplitter; a long working-distance, infinity-corrected objective; scanning means to scan a beam spot of the focused probe beam on or within a sample; relay optics; and a detector. The collimation optics are disposed in the probe beam. The probe-result beamsplitter is arranged in the optical paths of the probe beam and the resultant light from the sample. The beamsplitter reflects the probe beam into the objective and transmits resultant light. The long working-distance, infinity-corrected objective is also arranged in the optical paths of the probe beam and the resultant light. It focuses the reflected probe beam onto the sample, and collects and substantially collimates the resultant light. The relay optics are arranged to relay the transmitted resultant light from the beamsplitter to the detector.

An Optimized Set of Fluorescence In Situ Hybridization Probes for Detection of Pancreatobiliary Tract Cancer in Cytology Brush Samples.

PubMed

Barr Fritcher, Emily G; Voss, Jesse S; Brankley, Shannon M; Campion, Michael B; Jenkins, Sarah M; Keeney, Matthew E; Henry, Michael R; Kerr, Sarah M; Chaiteerakij, Roongruedee; Pestova, Ekaterina V; Clayton, Amy C; Zhang, Jun; Roberts, Lewis R; Gores, Gregory J; Halling, Kevin C; Kipp, Benjamin R

2015-12-01

Pancreatobiliary cancer is detected by fluorescence in situ hybridization (FISH) of pancreatobiliary brush samples with UroVysion probes, originally designed to detect bladder cancer. We designed a set of new probes to detect pancreatobiliary cancer and compared its performance with that of UroVysion and routine cytology analysis. We tested a set of FISH probes on tumor tissues (cholangiocarcinoma or pancreatic carcinoma) and non-tumor tissues from 29 patients. We identified 4 probes that had high specificity for tumor vs non-tumor tissues; we called this set of probes pancreatobiliary FISH. We performed a retrospective analysis of brush samples from 272 patients who underwent endoscopic retrograde cholangiopancreatography for evaluation of malignancy at the Mayo Clinic; results were available from routine cytology and FISH with UroVysion probes. Archived residual specimens were retrieved and used to evaluate the pancreatobiliary FISH probes. Cutoff values for FISH with the pancreatobiliary probes were determined using 89 samples and validated in the remaining 183 samples. Clinical and pathologic evidence of malignancy in the pancreatobiliary tract within 2 years of brush sample collection was used as the standard; samples from patients without malignancies were used as negative controls. The validation cohort included 85 patients with malignancies (46.4%) and 114 patients with primary sclerosing cholangitis (62.3%). Samples containing cells above the cutoff for polysomy (copy number gain of ≥2 probes) were classified as positive in FISH with the UroVysion and pancreatobiliary probes. Multivariable logistic regression was used to estimate associations between clinical and pathology findings and results from FISH. The combination of FISH probes 1q21, 7p12, 8q24, and 9p21 identified cancer cells with 93% sensitivity and 100% specificity in pancreatobiliary tissue samples and were therefore included in the pancreatobiliary probe set. In the validation cohort of brush samples, pancreatobiliary FISH identified samples from patients with malignancy with a significantly higher level of sensitivity (64.7%) than the UroVysion probes (45.9%) (P < .001) or routine cytology analysis (18.8%) (P < .001), but similar specificity (92.9%, 90.8%, and 100.0% respectively). Factors significantly associated with detection of carcinoma, in adjusted analyses, included detection of polysomy by pancreatobiliary FISH (P < .001), a mass by cross-sectional imaging (P < .001), cancer cells by routine cytology (overall P = .003), as well as absence of primary sclerosing cholangitis (P = .011). We identified a set of FISH probes that detects cancer cells in pancreatobiliary brush samples from patients with and without primary sclerosing cholangitis with higher levels of sensitivity than UroVysion probes. Cytologic brushing test results and clinical features were independently associated with detection of cancer and might be used to identify patients with pancreatobiliary cancers. Copyright © 2015 AGA Institute. Published by Elsevier Inc. All rights reserved.

Interpretation of discrepancies in mass spectroscopy data obtained from different experimental configurations

NASA Technical Reports Server (NTRS)

Russell, John M.

1993-01-01

Many helium mass spectrometer leak detectors at KSC employ sampling systems that feature hand held sniffer probes. Authors of general leakage-testing literature recommend sniffer probes for leak location but not for quantitative leakage measurement. Their use in the latter application at KSC involves assumptions that may be subtle. The purpose of the research effort reported herein was to establish the significance of indicated leak rates displayed by sniffer-probe equipped leak detectors and to determine whether the use of alternative hardware or testing procedures may reduce the uncertainty of leakage measurements made with them. The report classifies probe-type sampling systems for helium leak detectors according to their internal plumbing (direct or branched), presents a basic analysis of the fluid dynamics in the sampling system in the branched-conduit case, describes the usual test method for measuring the internal supply-to-sample flowrate ratio (a.k.a permeation ratio), and describes a concept for a sponge-tipped probe whose external supply-to-sample flowrate ratio promises to be lower than that of a simple-ended probe. One conclusion is that the main source of uncertainty in the use of probe-type sampling systems for leakage measurement is uncertainty in the external supply-to-sample flowrate ratio. In contrast, the present method for measuring the internal supply-to-sample flowrate ratio is quantitative and satisfactory. The implication is that probes of lower external supply-to-sample flowrate ratio must be developed before this uncertainty may be reduced significantly.

Method and apparatus for chemical and topographical microanalysis

NASA Technical Reports Server (NTRS)

Kossakovski, Dmitri A. (Inventor); Baldeschwieler, John D. (Inventor); Beauchamp, Jesse L. (Inventor)

2002-01-01

A scanning probe microscope is combined with a laser induced breakdown spectrometer to provide spatially resolved chemical analysis of the surface correlated with the surface topography. Topographical analysis is achieved by scanning a sharp probe across the sample at constant distance from the surface. Chemical analysis is achieved by the means of laser induced breakdown spectroscopy by delivering pulsed laser radiation to the sample surface through the same sharp probe, and consequent collection and analysis of emission spectra from plasma generated on the sample by the laser radiation. The method comprises performing microtopographical analysis of the sample with a scanning probe, selecting a scanned topological site on the sample, generating a plasma plume at the selected scanned topological site, and measuring a spectrum of optical emission from the plasma at the selected scanned topological site. The apparatus comprises a scanning probe, a pulsed laser optically coupled to the probe, an optical spectrometer, and a controller coupled to the scanner, laser and spectrometer for controlling the operation of the scanner, laser and spectrometer. The probe and scanner are used for topographical profiling the sample. The probe is also used for laser radiation delivery to the sample for generating a plasma plume from the sample. Optical emission from the plasma plume is collected and delivered to the optical spectrometer so that analysis of emission spectrum by the optical spectrometer allows for identification of chemical composition of the sample at user selected sites.

Liquid Microjunction Surface Sampling Probe Fluid Dynamics: Computational and Experimental Analysis of Coaxial Intercapillary Positioning Effects on Sample Manipulation

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

ElNaggar, Mariam S; Barbier, Charlotte N; Van Berkel, Gary J

A coaxial geometry liquid microjunction surface sampling probe (LMJ-SSP) enables direct extraction of analytes from surfaces for subsequent analysis by techniques like mass spectrometry. Solution dynamics at the probe-to-sample surface interface in the LMJ-SSP has been suspected to influence sampling efficiency and dispersion but has not been rigorously investigated. The effect on flow dynamics and analyte transport to the mass spectrometer caused by coaxial retraction of the inner and outer capillaries from each other and the surface during sampling with a LMJ-SSP was investigated using computational fluid dynamics and experimentation. A transparent LMJ-SSP was constructed to provide the means formore » visual observation of the dynamics of the surface sampling process. Visual observation, computational fluid dynamics (CFD) analysis, and experimental results revealed that inner capillary axial retraction from the flush position relative to the outer capillary transitioned the probe from a continuous sampling and injection mode through an intermediate regime to sample plug formationmode caused by eddy currents at the sampling end of the probe. The potential for analytical implementation of these newly discovered probe operational modes is discussed.« less

Fiber optic probe for light scattering measurements

DOEpatents

Nave, Stanley E.; Livingston, Ronald R.; Prather, William S.

1995-01-01

A fiber optic probe and a method for using the probe for light scattering analyses of a sample. The probe includes a probe body with an inlet for admitting a sample into an interior sample chamber, a first optical fiber for transmitting light from a source into the chamber, and a second optical fiber for transmitting light to a detector such as a spectrophotometer. The interior surface of the probe carries a coating that substantially prevents non-scattered light from reaching the second fiber. The probe is placed in a region where the presence and concentration of an analyte of interest are to be detected, and a sample is admitted into the chamber. Exciting light is transmitted into the sample chamber by the first fiber, where the light interacts with the sample to produce Raman-scattered light. At least some of the Raman-scattered light is received by the second fiber and transmitted to the detector for analysis. Two Raman spectra are measured, at different pressures. The first spectrum is subtracted from the second to remove background effects, and the resulting sample Raman spectrum is compared to a set of stored library spectra to determine the presence and concentration of the analyte.

Fiber optic probe for light scattering measurements

DOEpatents

Nave, S.E.; Livingston, R.R.; Prather, W.S.

1993-01-01

This invention is comprised of a fiber optic probe and a method for using the probe for light scattering analyses of a sample. The probe includes a probe body with an inlet for admitting a sample into an interior sample chamber, a first optical fiber for transmitting light from a source into the chamber, and a second optical fiber for transmitting light to a detector such as a spectrophotometer. The interior surface of the probe carries a coating that substantially prevents non-scattered light from reaching the second fiber. The probe is placed in a region where the presence and concentration of an analyte of interest are to be detected, and a sample is admitted into the chamber. Exciting light is transmitted into the sample chamber by the first fiber, where the light interacts with the sample to produce Raman-scattered light. At least some of the Raman- scattered light is received by the second fiber and transmitted to the detector for analysis. Two Raman spectra are measured, at different pressures. The first spectrum is subtracted from the second to remove background effects, and the resulting sample Raman spectrum is compared to a set of stored library spectra to determine the presence and concentration of the analyte.

The Effects of Sampling Probe Design and Sampling Techniques on Aerosol Measurements

DTIC Science & Technology

1975-05-01

Schematic of Extraction and Sampling System 39 16. Filter Housing 40 17. Theoretical Isokinetic Flow Requirements of the EPA Sampling...from the flow parameters based on a zero-error assumption at isokinetic sampling conditions. Isokinetic , or equal velocity sampling, was...prior to testing the probes. It was also used to measure the flow field adjacent to the probe inlets to determine the isokinetic condition of the

Performance Evaluation of Particle Sampling Probes for Emission Measurements of Aircraft Jet Engines

NASA Technical Reports Server (NTRS)

Lee, Poshin; Chen, Da-Ren; Sanders, Terry (Technical Monitor)

2001-01-01

Considerable attention has been recently received on the impact of aircraft-produced aerosols upon the global climate. Sampling particles directly from jet engines has been performed by different research groups in the U.S. and Europe. However, a large variation has been observed among published data on the conversion efficiency and emission indexes of jet engines. The variation results surely from the differences in test engine types, engine operation conditions, and environmental conditions. The other factor that could result in the observed variation is the performance of sampling probes used. Unfortunately, it is often neglected in the jet engine community. Particle losses during the sampling, transport, and dilution processes are often not discussed/considered in literatures. To address this issue, we evaluated the performance of one sampling probe by challenging it with monodisperse particles. A significant performance difference was observed on the sampling probe evaluated under different temperature conditions. Thermophoretic effect, nonisokinetic sampling and turbulence loss contribute to the loss of particles in sampling probes. The results of this study show that particle loss can be dramatic if the sampling probe is not well designed. Further, the result allows ones to recover the actual size distributions emitted from jet engines.

40 CFR 1065.145 - Gaseous and PM probes, transfer lines, and sampling system components.

Code of Federal Regulations, 2012 CFR

2012-07-01

... measuring sample flows by designing a passive sampling system that meets the following requirements: (A) The... number of bends, and have no filters. (B) If probes are designed such that they are sensitive to stack... design and construction. Use sample probes with inside surfaces of 300 series stainless steel or, for raw...

40 CFR 1065.145 - Gaseous and PM probes, transfer lines, and sampling system components.

Code of Federal Regulations, 2010 CFR

2010-07-01

... measuring sample flows by designing a passive sampling system that meets the following requirements: (A) The... number of bends, and have no filters. (B) If probes are designed such that they are sensitive to stack... design and construction. Use sample probes with inside surfaces of 300 series stainless steel or, for raw...

40 CFR 1065.145 - Gaseous and PM probes, transfer lines, and sampling system components.

Code of Federal Regulations, 2014 CFR

2014-07-01

... measuring sample flows by designing a passive sampling system that meets the following requirements: (A) The... number of bends, and have no filters. (B) If probes are designed such that they are sensitive to stack... design and construction. Use sample probes with inside surfaces of 300 series stainless steel or, for raw...

40 CFR 1065.145 - Gaseous and PM probes, transfer lines, and sampling system components.

Code of Federal Regulations, 2013 CFR

2013-07-01

... measuring sample flows by designing a passive sampling system that meets the following requirements: (A) The... number of bends, and have no filters. (B) If probes are designed such that they are sensitive to stack... design and construction. Use sample probes with inside surfaces of 300 series stainless steel or, for raw...

40 CFR 1065.145 - Gaseous and PM probes, transfer lines, and sampling system components.

Code of Federal Regulations, 2011 CFR

2011-07-01

... measuring sample flows by designing a passive sampling system that meets the following requirements: (A) The... number of bends, and have no filters. (B) If probes are designed such that they are sensitive to stack... design and construction. Use sample probes with inside surfaces of 300 series stainless steel or, for raw...

Application of porous metal enrichment probe sampling to single cell analysis using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS).

PubMed

Fu, Qiang; Tang, Jun; Cui, Meng; Xing, Junpeng; Liu, Zhiqiang; Liu, Shuying

2016-01-01

There is an increasing need for analyzing metabolism in a single cell, which is important to understand the nature of cellular heterogeneity, disease, growth and specialization, etc. However, single cell analysis is often challenging for the traces of samples. In the present study, porous metal enrichment probe sampling combined with matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) has been applied for in situ analysis of live onion epidemic cell. Porous probe, treated by corroding copper wire with HCl, was directly inserted into a single cell to get cell solution. A self-made linear actuator was enough to control the penetration of probe into the target cell accurately. Then samples on the tip of probe were eluted and detected by a commercial MALDI-TOF-MS directly. The formation of porous microstructure on the probe surface increased the adsorptive capacity of cell solution. The sensitivity of porous probe sampling was 6 times higher than uncorroded probes generally. This method provides a sensitive and convenient way for the sampling and detection of single cell solution. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Surface sampling concentration and reaction probe with controller to adjust sampling position

DOEpatents

Van Berkel, Gary J.; ElNaggar, Mariam S.

2016-07-19

A method of analyzing a chemical composition of a specimen is described. The method can include providing a probe comprising an outer capillary tube and an inner capillary tube disposed co-axially within the outer capillary tube, where the inner and outer capillary tubes define a solvent capillary and a sampling capillary in fluid communication with one another at a distal end of the probe; contacting a target site on a surface of a specimen with a solvent in fluid communication with the probe; maintaining a plug volume proximate a solvent-specimen interface, wherein the plug volume is in fluid communication with the probe; draining plug sampling fluid from the plug volume through the sampling capillary; and analyzing a chemical composition of the plug sampling fluid with an analytical instrument. A system for performing the method is also described.

7 CFR 800.84 - Inspection of grain in land carriers, containers, and barges in single lots.

Code of Federal Regulations, 2011 CFR

2011-01-01

... each probe, the grain shall be sampled as thoroughly as possible with an approved probe. The grain in... show a statement, as specified in the instructions, indicating the depth probed. Any inspection which... and is loaded in such a manner that it is possible to secure only door-probe or shallow-probe samples...

7 CFR 800.84 - Inspection of grain in land carriers, containers, and barges in single lots.

Code of Federal Regulations, 2012 CFR

2012-01-01

... each probe, the grain shall be sampled as thoroughly as possible with an approved probe. The grain in... show a statement, as specified in the instructions, indicating the depth probed. Any inspection which... and is loaded in such a manner that it is possible to secure only door-probe or shallow-probe samples...

7 CFR 800.84 - Inspection of grain in land carriers, containers, and barges in single lots.

Code of Federal Regulations, 2014 CFR

2014-01-01

... probe, the grain shall be sampled as thoroughly as possible with an approved probe. The grain in the... statement, as specified in the instructions, indicating the depth probed. Any inspection which is based on a... manner that it is possible to secure only door-probe or shallow-probe samples, the container shall be...

7 CFR 800.84 - Inspection of grain in land carriers, containers, and barges in single lots.

Code of Federal Regulations, 2013 CFR

2013-01-01

... each probe, the grain shall be sampled as thoroughly as possible with an approved probe. The grain in... show a statement, as specified in the instructions, indicating the depth probed. Any inspection which... and is loaded in such a manner that it is possible to secure only door-probe or shallow-probe samples...

Characteristics of basal taurine release in the rat striatum measured by microdialysis.

PubMed

Molchanova, S; Oja, S S; Saransaari, P

2004-12-01

Taurine is a sulfur-containing amino acid thought to be an osmoregulator, neurotransmitter or neuromodulator in the brain. Our objective was to establish how much taurine is released in the striatum and examine the mechanisms controlling extracellular taurine concentrations under resting conditions. The experiments were made on rats by microdialysis in vivo. Changes in taurine were compared with those in glutamate, glycine and the non-neuroactive amino acid threonine. Using the zero net flux approach we showed the extracellular concentration of taurine to be 25.2 +/- 5.1 muM. Glutamate was increased by tetrodotoxin and decreased by Ca2+ omission, glycine and threonine were not affected and both treatments increased extracellular taurine. The basal taurine release was increased by the taurine transport inhibitor guanidinoethanesulfonate and reduced by the anion channel blocker 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid.

Scanning drop sensor

DOEpatents

Jin, Jian; Xiang, Chengxiang; Gregoire, John

2017-05-09

Electrochemical experiments are performed on a collection of samples by suspending a drop of electrolyte solution between an electrochemical experiment probe and one of the samples that serves as a test sample. During the electrochemical experiment, the electrolyte solution is added to the drop and an output solution is removed from the drop. The probe and collection of samples can be moved relative to one another so the probe can be scanned across the samples.

Fast and reliable method of conductive carbon nanotube-probe fabrication for scanning probe microscopy

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

Dremov, Vyacheslav, E-mail: dremov@issp.ac.ru; Fedorov, Pavel; Grebenko, Artem

2015-05-15

We demonstrate the procedure of scanning probe microscopy (SPM) conductive probe fabrication with a single multi-walled carbon nanotube (MWNT) on a silicon cantilever pyramid. The nanotube bundle reliably attached to the metal-covered pyramid is formed using dielectrophoresis technique from the MWNT suspension. It is shown that the dimpled aluminum sample can be used both for shortening/modification of the nanotube bundle by applying pulse voltage between the probe and the sample and for controlling the probe shape via atomic force microscopy imaging the sample. Carbon nanotube attached to cantilever covered with noble metal is suitable for SPM imaging in such modulationmore » regimes as capacitance contrast microscopy, Kelvin probe microscopy, and scanning gate microscopy. The majority of such probes are conductive with conductivity not degrading within hours of SPM imaging.« less

Sealed magic angle spinning nuclear magnetic resonance probe and process for spectroscopy of hazardous samples

DOEpatents

Cho, Herman M.; Washton, Nancy M.; Mueller, Karl T.; Sears, Jr., Jesse A.; Townsend, Mark R.; Ewing, James R.

2016-06-14

A magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) probe is described that includes double containment enclosures configured to seal and contain hazardous samples for analysis. The probe is of a modular design that ensures containment of hazardous samples during sample analysis while preserving spin speeds for superior NMR performance and convenience of operation.

Single point aerosol sampling: evaluation of mixing and probe performance in a nuclear stack.

PubMed

Rodgers, J C; Fairchild, C I; Wood, G O; Ortiz, C A; Muyshondt, A; McFarland, A R

1996-01-01

Alternative reference methodologies have been developed for sampling of radionuclides from stacks and ducts, which differ from the methods previously required by the United States Environmental Protection Agency. These alternative reference methodologies have recently been approved by the U.S. EPA for use in lieu of the current standard techniques. The standard EPA methods are prescriptive in selection of sampling locations and in design of sampling probes whereas the alternative reference methodologies are performance driven. Tests were conducted in a stack at Los Alamos National Laboratory to demonstrate the efficacy of some aspects of the alternative reference methodologies. Coefficients of variation of velocity, tracer gas, and aerosol particle profiles were determined at three sampling locations. Results showed that numerical criteria placed upon the coefficients of variation by the alternative reference methodologies were met at sampling stations located 9 and 14 stack diameters from the flow entrance, but not at a location that was 1.5 diameters downstream from the inlet. Experiments were conducted to characterize the transmission of 10 microns aerodynamic diameter liquid aerosol particles through three types of sampling probes. The transmission ratio (ratio of aerosol concentration at the probe exit plane to the concentration in the free stream) was 107% for a 113 L min-1 (4-cfm) anisokinetic shrouded probe, but only 20% for an isokinetic probe that follows the existing EPA standard requirements. A specially designed isokinetic probe showed a transmission ratio of 63%. The shrouded probe performance would conform to the alternative reference methodologies criteria; however, the isokinetic probes would not.

Biochemical changes related to hypoxia during cerebral aneurysm surgery: combined microdialysis and tissue oxygen monitoring: case report.

PubMed

Hutchinson, P J; Al-Rawi, P G; O'Connell, M T; Gupta, A K; Pickard, J D; Kirkpatrick, P J

2000-01-01

The objective of this study was to monitor brain metabolism on-line during aneurysm surgery, by combining the use of a multiparameter (brain tissue oxygen, brain carbon dioxide, pH, and temperature) sensor with microdialysis (extracellular glucose, lactate, pyruvate, and glutamate). The case illustrates the potential value of these techniques by demonstrating the effects of adverse physiological events on brain metabolism and the ability to assist in both intraoperative and postoperative decision-making. A 41-year-old woman presented with a World Federation of Neurological Surgeons Grade I subarachnoid hemorrhage. Angiography revealed a basilar artery aneurysm that was not amenable to coiling, so the aneurysm was clipped. Before the craniotomy was performed, a multiparameter sensor and a microdialysis catheter were inserted to monitor brain metabolism. During the operation, the brain oxygen level decreased, in relation to biochemical changes, including the reduction of extracellular glucose and pyruvate and the elevation of lactate and glutamate. These changes were reversible. However, when the craniotomy was closed, a second decrease in brain oxygen occurred in association with brain swelling, which immediately prompted a postoperative computed tomographic scan. The scan demonstrated acute hydrocephalus, requiring external ventricular drainage. The patient made a full recovery. The monitoring techniques influenced clinical decision-making in the treatment of this patient. On-line measurement of brain tissue gases and extracellular chemistry has the potential to assist in the perioperative and postoperative management of patients undergoing complex cerebrovascular surgery and to establish the effects of intervention on brain homeostasis.

Novel integrated microdialysis-amperometric system for in vitro detection of dopamine secreted from PC12 cells: design, construction, and validation.

PubMed

Migheli, Rossana; Puggioni, Giulia; Dedola, Sonia; Rocchitta, Gaia; Calia, Giammario; Bazzu, Gianfranco; Esposito, Giovanni; Lowry, John P; O'Neill, Robert D; Desole, M S; Miele, Egidio; Serra, Pier A

2008-09-15

A novel dual channel in vitro apparatus, derived from a previously described design, has been coupled with dopamine (DA) microsensors for the flow-through detection of DA secreted from PC12 cells. The device, including two independent microdialysis capillaries, was loaded with a solution containing PC12 cells while a constant phosphate-buffered saline (PBS) medium perfusion was carried out using a dual channel miniaturized peristaltic pump. One capillary was perfused with normal PBS, whereas extracellular calcium was removed from extracellular fluid of the second capillary. After a first period of stabilization and DA baseline recording, KCl (75 mM) was added to the perfusion fluid of both capillaries. In this manner, a simultaneous "treatment-control" experimental design was performed to detect K+-evoked calcium-dependent DA secretion. For this purpose, self-referencing DA microsensors were developed, and procedures for making, testing, and calibrating them are described in detail. The electronic circuitry was derived from previously published schematics and optimized for dual sensor constant potential amperometry applications. The microdialysis system was tested and validated in vitro under different experimental conditions, and DA secretion was confirmed by high-performance liquid chromatography with electrochemical detection (HPLC-EC). PC12 cell viability was quantified before and after each experiment. The proposed apparatus serves as a reliable model for studying the effects of different drugs on DA secretion through the direct comparison of extracellular DA increase in treatment-control experiments performed on the same initial PC12 cell population.

A multi-enzyme microreactor-based online electrochemical system for selective and continuous monitoring of acetylcholine.

PubMed

Lin, Yuqing; Yu, Ping; Mao, Lanqun

2015-06-07

This study demonstrates an online electrochemical system (OECS) for selective and continuous measurements of acetylcholine (ACh) through efficiently integrating in vivo microdialysis, a multi-enzyme microreactor and an electrochemical detector. A multi-enzyme microreactor was prepared first by co-immobilizing two kinds of enzymes, i.e. choline oxidase (ChOx) and catalase (Cat), onto magnetite nanoparticles and then confining the as-formed nanoparticles into a fused-silica capillary with the assistance of an external magnet. The multi-enzyme microreactor was settled between an in vivo microdialysis sampling system and an electrochemical detector to suppress the interference from choline toward ACh detection. Selective detection of ACh was accomplished using the electrochemical detector with ACh esterase (AChE) and ChOx as the recognition units for ACh and Prussian blue (PB) as the electrocatalyst for the reduction of hydrogen peroxide (H2O2). The current recorded with the OECS was linear with the concentration of ACh (I/nA = -3.90CACh/μM + 1.21, γ = 0.998) within a concentration range of 5 μM to 100 μM. The detection limit, based on a signal-to-noise ratio of 3, was calculated to be 1 μM. Interference investigation demonstrates that the OECS did not produce an observable current response toward physiological levels of common electroactive species, such as ascorbic acid (AA), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and uric acid (UA). The high selectivity and the good linearity in combination with the high stability may enable the OECS developed here as a potential system for continuous monitoring of cerebral ACh release in some physiological and pathological processes.

Effects of two different specific neck exercise interventions on palmitoylethanolamide and stearoylethanolamide concentrations in the interstitium of the trapezius muscle in women with chronic neck shoulder pain.

PubMed

Ghafouri, Nazdar; Ghafouri, Bijar; Fowler, Christopher J; Larsson, Britt; Turkina, Maria V; Karlsson, Linn; Gerdle, Björn

2014-08-01

Chronic neck/shoulder pain (CNSP) is one of the most common pain conditions. The understanding of mechanisms, including the peripheral balance between nociceptive and antinociceptive processes, is incomplete. N-acylethanolamines (NAEs) are a class of endogenous compounds that regulate inflammation and pain. The aim of this study was to investigate the levels of two NAEs: the peroxisome proliferator-activated receptor type-α ligand palmitoylethanolamide (PEA) and stearoylethanolamide (SEA) in the muscle interstitium of the trapezius muscle in women with CNSP randomized to two different neck specific training programs and in a healthy pain-free control group (CON). Fifty-seven women with CNSP were randomized to strength + stretch or stretch alone exercise programs. Twenty-nine subjects underwent microdialysis procedure before and after 4-6 months of exercise. Twenty-four CON subjects underwent microdialysis procedure before and after 4-6 months without any intervention in between. Microdialysate samples were collected from the trapezius muscle and analyzed by mass spectrometry for PEA and SEA levels. PEA and SEA levels were significantly higher in CNSP patients compared with CON. PEA was significantly higher in CNSP than in CON after both training programs. SEA was significantly higher in CNSP than in CON after stretch alone but not after strength + stretch training. A significant positive correlation was found between changes in pain intensity and in SEA levels in the strength + stretch group, but not in the stretch alone group. Our results indicate that exercise interventions differentially affect the levels of the bioactive lipids PEA and SEA in the interstitium of the trapezius muscle in women with CNSP. Wiley Periodicals, Inc.

Preclinical examination of clofarabine in pediatric ependymoma: intratumoral concentrations insufficient to warrant further study.

PubMed

Patel, Yogesh T; Jacus, Megan O; Boulos, Nidal; Dapper, Jason D; Davis, Abigail D; Vuppala, Pradeep K; Freeman, Burgess B; Mohankumar, Kumarasamypet M; Throm, Stacy L; Gilbertson, Richard J; Stewart, Clinton F

2015-05-01

Clofarabine, a deoxyadenosine analog, was an active anticancer drug in our in vitro high-throughput screening against mouse ependymoma neurospheres. To characterize the clofarabine disposition in mice for further preclinical efficacy studies, we evaluated the plasma and central nervous system disposition in a mouse model of ependymoma. A plasma pharmacokinetic study of clofarabine (45 mg/kg, IP) was performed in CD1 nude mice bearing ependymoma to obtain initial plasma pharmacokinetic parameters. These estimates were used to derive D-optimal plasma sampling time points for cerebral microdialysis studies. A simulation of clofarabine pharmacokinetics in mice and pediatric patients suggested that a dosage of 30 mg/kg IP in mice would give exposures comparable to that in children at a dosage of 148 mg/m(2). Cerebral microdialysis was performed to study the tumor extracellular fluid (ECF) disposition of clofarabine (30 mg/kg, IP) in the ependymoma cortical allografts. Plasma and tumor ECF concentration-time data were analyzed using a nonlinear mixed effects modeling approach. The median unbound fraction of clofarabine in mouse plasma was 0.79. The unbound tumor to plasma partition coefficient (K pt,uu: ratio of tumor to plasma AUCu,0-inf) of clofarabine was 0.12 ± 0.05. The model-predicted mean tumor ECF clofarabine concentrations were below the in vitro 1-h IC50 (407 ng/mL) for ependymoma neurospheres. Thus, our results show the clofarabine exposure reached in the tumor ECF was below that associated with an antitumor effect in our in vitro washout study. Therefore, clofarabine was de-prioritized as an agent to treat ependymoma, and further preclinical studies were not pursued.

Preclinical examination of clofarabine in pediatric ependymoma: Intratumoral concentrations insufficient to warrant further study

PubMed Central

Patel, Yogesh T.; Jacus, Megan O.; Boulos, Nidal; Dapper, Jason D.; Davis, Abigail D.; Vuppala, Pradeep K.; Freeman, Burgess B.; Mohankumar, Kumarasamypet M.; Throm, Stacy L.; Gilbertson, Richard J.; Stewart, Clinton F.

2015-01-01

Clofarabine, a deoxyadenosine analog, was an active anticancer drug in our in vitro high-throughput screening against mouse ependymoma neurospheres. To characterize the clofarabine disposition in mice for further preclinical efficacy studies, we evaluated the plasma and central nervous system (CNS) disposition in a mouse model of ependymoma. A plasma pharmacokinetic study of clofarabine (45 mg/kg, IP) was performed in CD1 nude mice bearing ependymoma to obtain initial plasma pharmacokinetic parameters. These estimates were used to derive D-optimal plasma sampling time-points for cerebral microdialysis studies. A simulation of clofarabine pharmacokinetics in mice and pediatric patients suggested that a dosage of 30 mg/kg, IP in mice would give exposures comparable to that in children at a dosage of 148 mg/m2. Cerebral microdialysis was performed to study the tumor extracellular fluid (ECF) disposition of clofarabine (30 mg/kg, IP) in the ependymoma cortical allografts. Plasma and tumor ECF concentration-time data were analyzed using a nonlinear mixed effects modeling approach. The median unbound fraction of clofarabine in mouse plasma was 0.79. The unbound tumor to plasma partition coefficient (Kpt,uu: ratio of tumor to plasma AUCu,0-inf) of clofarabine was 0.12±0.05. The model predicted mean tumor ECF clofarabine concentrations were below the in vitro 1-hr IC50 (407 ng/mL) for ependymoma neurospheres. Thus, our results show the clofarabine exposure reached in the tumor ECF was below that associated with an antitumor effect in our in vitro washout study. Therefore, clofarabine was de-prioritized as an agent to treat ependymoma, and further preclinical studies were not pursued. PMID:25724157

Alterations in brain extracellular dopamine and glycine levels following combined administration of the glycine transporter type-1 inhibitor Org-24461 and risperidone.

PubMed

Nagy, Katalin; Marko, Bernadett; Zsilla, Gabriella; Matyus, Peter; Pallagi, Katalin; Szabo, Geza; Juranyi, Zsolt; Barkoczy, Jozsef; Levay, Gyorgy; Harsing, Laszlo G

2010-12-01

The most dominant hypotheses for the pathogenesis of schizophrenia have focused primarily upon hyperfunctional dopaminergic and hypofunctional glutamatergic neurotransmission in the central nervous system. The therapeutic efficacy of all atypical antipsychotics is explained in part by antagonism of the dopaminergic neurotransmission, mainly by blockade of D(2) dopamine receptors. N-methyl-D-aspartate (NMDA) receptor hypofunction in schizophrenia can be reversed by glycine transporter type-1 (GlyT-1) inhibitors, which regulate glycine concentrations at the vicinity of NMDA receptors. Combined drug administration with D(2) dopamine receptor blockade and activation of hypofunctional NMDA receptors may be needed for a more effective treatment of positive and negative symptoms and the accompanied cognitive deficit in schizophrenia. To investigate this type of combined drug administration, rats were treated with the atypical antipsychotic risperidone together with the GlyT-1 inhibitor Org-24461. Brain microdialysis was applied in the striatum of conscious rats and determinations of extracellular dopamine, DOPAC, HVA, glycine, glutamate, and serine concentrations were carried out using HPLC/electrochemistry. Risperidone increased extracellular concentrations of dopamine but failed to influence those of glycine or glutamate measured in microdialysis samples. Org-24461 injection reduced extracellular dopamine concentrations and elevated extracellular glycine levels but the concentrations of serine and glutamate were not changed. When risperidone and Org-24461 were added in combination, a decrease in extracellular dopamine concentrations was accompanied with sustained elevation of extracellular glycine levels. Interestingly, the extracellular concentrations of glutamate were also enhanced. Our data indicate that coadministration of an antipsychotic with a GlyT-1 inhibitor may normalize hypofunctional NMDA receptor-mediated glutamatergic neurotransmission with reduced dopaminergic side effects characteristic for antipsychotic medication.

Capillary electrophoresis with laser-induced fluorescence detection: a sensitive method for monitoring extracellular concentrations of amino acids in the periaqueductal grey matter.

PubMed

Bergquist, J; Vona, M J; Stiller, C O; O'Connor, W T; Falkenberg, T; Ekman, R

1996-03-01

The use of capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) for the analysis of microdialysate samples from the periaqueductal grey matter (PAG) of freely moving rats is described. By employing 3-(4-carboxybenzoyl)-2-quinoline-carboxaldehyde (CBQCA) as a derivatization agent, we simultaneously monitored the concentrations of 8 amino acids (arginine, glutamine, valine, gamma-amino-n-butyric acid (GABA), alanine, glycine, glutamate, and aspartate), with nanomolar and subnanomolar detection limits. Two of the amino acids (GABA and glutamate) were analysed in parallel by conventional high-performance liquid chromatography (HPLC) in order to directly compare the two analytical methods. Other CE methods for analysis of microdialysate have been previously described, and this improved method offers greater sensitivity, ease of use, and the possibility to monitor several amino acids simultaneously. By using this technique together with an optimised form of microdialysis technique, the tiny sample consumption and the improved detection limits permit the detection of fast and transient transmitter changes.

Scanning drop sensor

DOEpatents

Jin, Jian; Xiang, Chengxiang; Gregoire, John M.; Shinde, Aniketa A.; Guevarra, Dan W.; Jones, Ryan J.; Marcin, Martin R.; Mitrovic, Slobodan

2017-05-09

Electrochemical or electrochemical and photochemical experiments are performed on a collection of samples by suspending a drop of electrolyte solution between an electrochemical experiment probe and one of the samples that serves as a test sample. During the electrochemical experiment, the electrolyte solution is added to the drop and an output solution is removed from the drop. The probe and collection of samples can be moved relative to one another so the probe can be scanned across the samples.

High temperature probe

DOEpatents

Swan, Raymond A.

1994-01-01

A high temperature probe for sampling, for example, smokestack fumes, and is able to withstand temperatures of 3000.degree. F. The probe is constructed so as to prevent leakage via the seal by placing the seal inside the water jacket whereby the seal is not exposed to high temperature, which destroys the seal. The sample inlet of the probe is also provided with cooling fins about the area of the seal to provide additional cooling to prevent the seal from being destroyed. Also, a heated jacket is provided for maintaining the temperature of the gas being tested as it passes through the probe. The probe includes pressure sensing means for determining the flow velocity of an efficient being sampled. In addition, thermocouples are located in various places on the probe to monitor the temperature of the gas passing there through.

Metallized Capillaries as Probes for Raman Spectroscopy

NASA Technical Reports Server (NTRS)

Pelletier, Michael

2003-01-01

A class of miniature probes has been proposed to supplant the fiber-optic probes used heretofore in some Raman and fluorescence spectroscopic systems. A probe according to the proposal would include a capillary tube coated with metal on its inside to make it reflective. A microlens would be hermetically sealed onto one end of the tube. A spectroscopic probe head would contain a single such probe, which would both deliver laser light to a sample and collect Raman or fluorescent light emitted by the sample.

A versatile rotary-stage high frequency probe station for studying magnetic films and devices

NASA Astrophysics Data System (ADS)

He, Shikun; Meng, Zhaoliang; Huang, Lisen; Yap, Lee Koon; Zhou, Tiejun; Panagopoulos, Christos

2016-07-01

We present a rotary-stage microwave probe station suitable for magnetic films and spintronic devices. Two stages, one for field rotation from parallel to perpendicular to the sample plane (out-of-plane) and the other intended for field rotation within the sample plane (in-plane) have been designed. The sample probes and micro-positioners are rotated simultaneously with the stages, which allows the field orientation to cover θ from 0∘ to 90∘ and φ from 0∘ to 360∘. θ and φ being the angle between the direction of current flow and field in a out-of-plane and an in-plane rotation, respectively. The operation frequency is up to 40 GHz and the magnetic field up to 1 T. The sample holder vision system and probe assembly are compactly designed for the probes to land on a wafer with diameter up to 3 cm. Using homemade multi-pin probes and commercially available high frequency probes, several applications including 4-probe DC measurements, the determination of domain wall velocity, and spin transfer torque ferromagnetic resonance are demonstrated.

GUIDELINES FOR INSTALLATION AND SAMPLING OF SUB-SLAB VAPOR PROBES TO SUPPORT ASSESSMENT OF VAPOR INTRUSION

EPA Science Inventory

The purpose of this paper is to provide guidelines for sub-slab sampling using dedicated vapor probes. Use of dedicated vapor probes allows for multiple sample events before and after corrective action and for vacuum testing to enhance the design and monitoring of a corrective m...

Relative quantification of 40 nucleic acid sequences by multiplex ligation-dependent probe amplification

PubMed Central

Schouten, Jan P.; McElgunn, Cathal J.; Waaijer, Raymond; Zwijnenburg, Danny; Diepvens, Filip; Pals, Gerard

2002-01-01

We describe a new method for relative quantification of 40 different DNA sequences in an easy to perform reaction requiring only 20 ng of human DNA. Applications shown of this multiplex ligation-dependent probe amplification (MLPA) technique include the detection of exon deletions and duplications in the human BRCA1, MSH2 and MLH1 genes, detection of trisomies such as Down’s syndrome, characterisation of chromosomal aberrations in cell lines and tumour samples and SNP/mutation detection. Relative quantification of mRNAs by MLPA will be described elsewhere. In MLPA, not sample nucleic acids but probes added to the samples are amplified and quantified. Amplification of probes by PCR depends on the presence of probe target sequences in the sample. Each probe consists of two oligonucleotides, one synthetic and one M13 derived, that hybridise to adjacent sites of the target sequence. Such hybridised probe oligonucleotides are ligated, permitting subsequent amplification. All ligated probes have identical end sequences, permitting simultaneous PCR amplification using only one primer pair. Each probe gives rise to an amplification product of unique size between 130 and 480 bp. Probe target sequences are small (50–70 nt). The prerequisite of a ligation reaction provides the opportunity to discriminate single nucleotide differences. PMID:12060695

Relative quantification of 40 nucleic acid sequences by multiplex ligation-dependent probe amplification.

PubMed

Schouten, Jan P; McElgunn, Cathal J; Waaijer, Raymond; Zwijnenburg, Danny; Diepvens, Filip; Pals, Gerard

2002-06-15

We describe a new method for relative quantification of 40 different DNA sequences in an easy to perform reaction requiring only 20 ng of human DNA. Applications shown of this multiplex ligation-dependent probe amplification (MLPA) technique include the detection of exon deletions and duplications in the human BRCA1, MSH2 and MLH1 genes, detection of trisomies such as Down's syndrome, characterisation of chromosomal aberrations in cell lines and tumour samples and SNP/mutation detection. Relative quantification of mRNAs by MLPA will be described elsewhere. In MLPA, not sample nucleic acids but probes added to the samples are amplified and quantified. Amplification of probes by PCR depends on the presence of probe target sequences in the sample. Each probe consists of two oligonucleotides, one synthetic and one M13 derived, that hybridise to adjacent sites of the target sequence. Such hybridised probe oligonucleotides are ligated, permitting subsequent amplification. All ligated probes have identical end sequences, permitting simultaneous PCR amplification using only one primer pair. Each probe gives rise to an amplification product of unique size between 130 and 480 bp. Probe target sequences are small (50-70 nt). The prerequisite of a ligation reaction provides the opportunity to discriminate single nucleotide differences.

Casingless down-hole for sealing an ablation volume and obtaining a sample for analysis

DOEpatents

Noble, Donald T.; Braymen, Steven D.; Anderson, Marvin S.

1996-10-01

A casing-less down hole sampling system for acquiring a subsurface sample for analysis using an inductively coupled plasma system is disclosed. The system includes a probe which is pushed into the formation to be analyzed using a hydraulic ram system. The probe includes a detachable tip member which has a soil point mad a barb, with the soil point aiding the penetration of the earth, and the barb causing the tip member to disengage from the probe and remain in the formation when the probe is pulled up. The probe is forced into the formation to be tested, and then pulled up slightly, to disengage the tip member and expose a column of the subsurface formation to be tested. An instrumentation tube mounted in the probe is then extended outward from the probe to longitudinally extend into the exposed column. A balloon seal mounted on the end of the instrumentation tube allows the bottom of the column to be sealed. A source of laser radiation is emitted from the instrumentation tube to ablate a sample from the exposed column. The instrumentation tube can be rotated in the probe to sweep the laser source across the surface of the exposed column. An aerosol transport system carries the ablated sample from the probe to the surface for testing in an inductively coupled plasma system. By testing at various levels in the down-hole as the probe is extracted from the soil, a profile of the subsurface formation may be obtained.

Discrepancy between culture and DNA probe analysis for the detection of periodontal bacteria.

PubMed

van Steenbergen, T J; Timmerman, M F; Mikx, F H; de Quincey, G; van der Weijden, G A; van der Velden, U; de Graaff, J

1996-10-01

The purpose of this study was to compare a commercially available DNA probe technique with conventional cultural techniques for the detection of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia in subgingival plaque samples. Samples from 20 patients with moderate to severe periodontitis were evaluated at baseline and during a 15 months period of periodontal treatment. Paperpoints from 4 periodontal pockets per patient were forwarded to Omnigene for DNA probe analysis, and simultaneously inserted paperpoints from the same pockets were analyzed by standard culture techniques. In addition, mixed bacterial samples were constructed harbouring known proportions of 25 strains of A. actinomycetemcomitans, P. gingivalis and P. intermedia each. A relatively low concordance was found between both methods. At baseline a higher detection frequency was found for A. actinomycetemcomitans and P. gingivalis for the DNA probe technique; for P. intermedia the detection frequency by culture was higher. For A. actinomycetemcomitans, 21% of the culture positive samples was positive with the DNA probe. Testing the constructed bacterial samples with the DNA probe method resulted in about 16% false positive results for the 3 species tested. Furthermore, 40% of P. gingivalis strains were not detected by the DNA probe. The present data suggest that at least part of the discrepancies found between the DNA probe technique used and cultural methods are caused by false positive and false negative DNA probe results. Therefore, the value of this DNA probe method for the detection of periodontal pathogens is questionable.

Surface sampling concentration and reaction probe

DOEpatents

Van Berkel, Gary J; Elnaggar, Mariam S

2013-07-16

A method of analyzing a chemical composition of a specimen is described. The method can include providing a probe comprising an outer capillary tube and an inner capillary tube disposed co-axially within the outer capillary tube, where the inner and outer capillary tubes define a solvent capillary and a sampling capillary in fluid communication with one another at a distal end of the probe; contacting a target site on a surface of a specimen with a solvent in fluid communication with the probe; maintaining a plug volume proximate a solvent-specimen interface, wherein the plug volume is in fluid communication with the probe; draining plug sampling fluid from the plug volume through the sampling capillary; and analyzing a chemical composition of the plug sampling fluid with an analytical instrument. A system for performing the method is also described.

Persistence of Microbial Contamination on Transvaginal Ultrasound Probes despite Low-Level Disinfection Procedure

PubMed Central

M'Zali, Fatima; Bounizra, Carole; Leroy, Sandrine; Mekki, Yahia; Quentin-Noury, Claudine; Kann, Michael

2014-01-01

Aim of the Study In many countries, Low Level Disinfection (LLD) of covered transvaginal ultrasound probes is recommended between patients' examinations. The aim of this study was to evaluate the antimicrobial efficacy of LLD under routine conditions on a range of microorganisms. Materials and Methods Samples were taken over a six month period in a private French Radiology Center. 300 specimens derived from endovaginal ultrasound probes were analyzed after disinfection of the probe with wipes impregnated with a quaternary ammonium compound and chlorhexidine. Human papillomavirus (HPV) was sought in the first set of s100 samples, Chlamydia trachomatis and mycoplasmas were searched in the second set of 100 samples, bacteria and fungi in the third 100 set samples. HPV, C. trachomatis and mycoplasmas were detected by PCR amplification. PCR positive samples were subjected to a nuclease treatment before an additional PCR assay to assess the likely viable microorganisms. Bacteria and fungi were investigated by conventional methods. Results A substantial persistence of microorganisms was observed on the disinfected probes: HPV DNA was found on 13% of the samples and 7% in nuclease-resistant form. C. trachomatis DNA was detected on 20% of the probes by primary PCR but only 2% after nuclease treatment, while mycoplasma DNA was amplified in 8% and 4%, respectively. Commensal and/or environmental bacterial flora was present on 86% of the probes, occasionally in mixed culture, and at various levels (10->3000 CFU/probe); Staphylococcus aureus was cultured from 4% of the probes (10-560 CFU/probe). No fungi were isolated. Conclusion Our findings raise concerns about the efficacy of impregnated towels as a sole mean for disinfection of ultrasound probes. Although the ultrasound probes are used with disposable covers, our results highlight the potential risk of cross contamination between patients during ultrasound examination and emphasize the need for reviewing the disinfection procedure. PMID:24695371

Laser interferometry force-feedback sensor for an interfacial force microscope

DOEpatents

Houston, Jack E.; Smith, William L.

2004-04-13

A scanning force microscope is provided with a force-feedback sensor to increase sensitivity and stability in determining interfacial forces between a probe and a sample. The sensor utilizes an interferometry technique that uses a collimated light beam directed onto a deflecting member, comprising a common plate suspended above capacitor electrodes situated on a substrate forming an interference cavity with a probe on the side of the common plate opposite the side suspended above capacitor electrodes. The probe interacts with the surface of the sample and the intensity of the reflected beam is measured and used to determine the change in displacement of the probe to the sample and to control the probe distance relative to the surface of the sample.

Microdialysis combined blood sampling technique for the determination of rosiglitazone and glucose in brain and blood of gerbils subjected to cerebral ischemia.

PubMed

Sheu, Wayne H-H; Chuang, Hsiu-Chun; Cheng, Shiu-Min; Lee, Maw-Rong; Chou, Chi-Chi; Cheng, Fu-Chou

2011-03-25

Rosiglitazone is a potent synthetic peroxisome proliferator-activated receptor-gamma (PPAR-γ) agonist which improves glucose control in the plasma and reduces ischemic brain injury. However, the pharmacokinetics of rosiglitazone in the brain is still unclear. In this study, a method using liquid chromatography-mass spectrometry coupled with microdialysis and an auto-blood sampling system was developed to determine rosiglitazone and glucose concentration in the brain and blood of gerbils subjected to treatment with rosiglitazone (3.0 mg kg(-1), i.p.). The results showed the limit of detection was 0.04 μg L(-1) and the correlation coefficient was 0.9997 for the determination of rosiglitazone in the brain. The mean parameters, maximum drug concentration (C(max)) and the area under the concentration-time curve from time zero to time infinity (AUC(inf)), following rosiglitazone administration were 1.06±0.28 μg L(-1) and 296.82±44.67 μg min L(-1), respectively. The time to peak concentration (C(max) or T(max)) of rosiglitazone occurred at 105±17.10 min, and the mean elimination half-life (t(1/2)) from brain was 190.81±85.18 min after administration of rosiglitazone. The brain glucose levels decreased to 71% of the basal levels in the rosiglitazone-treated group when compared with those in the control (p<0.01). Treatment with rosiglitazone decreased blood glucose levels to 80% at 1h after pretreatment of rosiglitazone (p<0.05). In addition, pretreatment with rosiglitazone significantly reduced the cerebral infarct volume compared with that of the control group. These findings suggest that this method may be useful for simultaneous and continuous determination of rosiglitazone and glucose concentrations in brain and plasma. Rosiglitazone was effective at penetrating the blood-brain barrier as evidenced by the rapid appearance of rosiglitazone in the brain, and rosiglitazone may contribute to a reduction in the extent of injuries related to cerebral ischemic stroke via its hypoglycemic effect. Copyright © 2010 Elsevier B.V. All rights reserved.

Controlled microaspiration for high-pressure freezing: a new method for ultrastructural preservation of fragile and sparse tissues for TEM and electron tomography

PubMed Central

Triffo, W. J.; Palsdottir, H.; McDonald, K. L.; Lee, J. K.; Inman, J. L.; Bissell, M. J.; Raphael, R. M.; Auer, M.

2009-01-01

Summary High-pressure freezing is the preferred method to prepare thick biological specimens for ultrastructural studies. However, the advantages obtained by this method often prove unattainable for samples that are difficult to handle during the freezing and substitution protocols. Delicate and sparse samples are difficult to manipulate and maintain intact throughout the sequence of freezing, infiltration, embedding and final orientation for sectioning and subsequent transmission electron microscopy. An established approach to surmount these difficulties is the use of cellulose microdialysis tubing to transport the sample. With an inner diameter of 200 µm, the tubing protects small and fragile samples within the thickness constraints of high-pressure freezing, and the tube ends can be sealed to avoid loss of sample. Importantly, the transparency of the tubing allows optical study of the specimen at different steps in the process. Here, we describe the use of a micromanipulator and microinjection apparatus to handle and position delicate specimens within the tubing. We report two biologically significant examples that benefit from this approach, 3D cultures of mammary epithelial cells and cochlear outer hair cells. We illustrate the potential for correlative light and electron microscopy as well as electron tomography. PMID:18445158

Casingless down-hole for sealing an ablation volume and obtaining a sample for analysis

DOEpatents

Noble, D.T.; Braymen, S.D.; Anderson, M.S.

1996-10-01

A casing-less down hole sampling system for acquiring a subsurface sample for analysis using an inductively coupled plasma system is disclosed. The system includes a probe which is pushed into the formation to be analyzed using a hydraulic ram system. The probe includes a detachable tip member which has a soil point and a barb, with the soil point aiding the penetration of the earth, and the barb causing the tip member to disengage from the probe and remain in the formation when the probe is pulled up. The probe is forced into the formation to be tested, and then pulled up slightly, to disengage the tip member and expose a column of the subsurface formation to be tested. An instrumentation tube mounted in the probe is then extended outward from the probe to longitudinally extend into the exposed column. A balloon seal mounted on the end of the instrumentation tube allows the bottom of the column to be sealed. A source of laser radiation is emitted from the instrumentation tube to ablate a sample from the exposed column. The instrumentation tube can be rotated in the probe to sweep the laser source across the surface of the exposed column. An aerosol transport system carries the ablated sample from the probe to the surface for testing in an inductively coupled plasma system. By testing at various levels in the down-hole as the probe is extracted from the soil, a profile of the subsurface formation may be obtained. 9 figs.

A versatile rotary-stage high frequency probe station for studying magnetic films and devices

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

He, Shikun; Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371; Meng, Zhaoliang

We present a rotary-stage microwave probe station suitable for magnetic films and spintronic devices. Two stages, one for field rotation from parallel to perpendicular to the sample plane (out-of-plane) and the other intended for field rotation within the sample plane (in-plane) have been designed. The sample probes and micro-positioners are rotated simultaneously with the stages, which allows the field orientation to cover θ from 0{sup ∘} to 90{sup ∘} and φ from 0{sup ∘} to 360{sup ∘}. θ and φ being the angle between the direction of current flow and field in a out-of-plane and an in-plane rotation, respectively. Themore » operation frequency is up to 40 GHz and the magnetic field up to 1 T. The sample holder vision system and probe assembly are compactly designed for the probes to land on a wafer with diameter up to 3 cm. Using homemade multi-pin probes and commercially available high frequency probes, several applications including 4-probe DC measurements, the determination of domain wall velocity, and spin transfer torque ferromagnetic resonance are demonstrated.« less

Preventing probe induced topography correlated artifacts in Kelvin Probe Force Microscopy.

PubMed

Polak, Leo; Wijngaarden, Rinke J

2016-12-01

Kelvin Probe Force Microscopy (KPFM) on samples with rough surface topography can be hindered by topography correlated artifacts. We show that, with the proper experimental configuration and using homogeneously metal coated probes, we are able to obtain amplitude modulation (AM) KPFM results on a gold coated sample with rough topography that are free from such artifacts. By inducing tip inhomogeneity through contact with the sample, clear potential variations appear in the KPFM image, which correlate with the surface topography and, thus, are probe induced artifacts. We find that switching to frequency modulation (FM) KPFM with such altered probes does not remove these artifacts. We also find that the induced tip inhomogeneity causes a lift height dependence of the KPFM measurement, which can therefore be used as a check for the presence of probe induced topography correlated artifacts. We attribute the observed effects to a work function difference between the tip and the rest of the probe and describe a model for such inhomogeneous probes that predicts lift height dependence and topography correlated artifacts for both AM and FM-KPFM methods. This work demonstrates that using a probe with a homogeneous work function and preventing tip changes is essential for KPFM on non-flat samples. From the three investigated probe coatings, PtIr, Au and TiN, the latter appears to be the most suitable, because of its better resistance against coating damage. Copyright © 2016 Elsevier B.V. All rights reserved.

A novel reaction-based fluorescent probe for the detection of cysteine in milk and water samples.

PubMed

Wang, Jialin; Wang, Hao; Hao, Yanfeng; Yang, Shaoxiang; Tian, Hongyu; Sun, Baoguo; Liu, Yongguo

2018-10-01

A novel fluorescent probe 3'-hydroxy-3-oxo-3H-spiro [isobenzofuran-1,9'-xanthene]-6'-yl-2,4-dinitrobenzenesulfonate (probe 1) was designed and synthesized as a visual sensor for the detection of cysteine levels in milk and water samples. The addition of cysteine to the solution of probe 1 resulted in an increase in fluorescence intensity and color change, from light yellow to yellow-green. The distinct color response indicated that probe 1 could be used as a visual sensor for cysteine. Cysteine can be detected quantitatively at concentrations between 0 and 400 μM and the detection limit of the fluorescence response to the probe was 6.5 μM. This suggests that probe 1 could be used as a signaling tool to determine the cysteine levels in samples, such as milk and water. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dual recognition unit strategy improves the specificity of the adenosine triphosphate (ATP) aptamer biosensor for cerebral ATP assay.

PubMed

Yu, Ping; He, Xiulan; Zhang, Li; Mao, Lanqun

2015-01-20

Adenosine triphosphate (ATP) aptamer has been widely used as a recognition unit for biosensor development; however, its relatively poor specificity toward ATP against adenosine-5'-diphosphate (ADP) and adenosine-5'-monophosphate (AMP) essentially limits the application of the biosensors in real systems, especially in the complex cerebral system. In this study, for the first time, we demonstrate a dual recognition unit strategy (DRUS) to construct a highly selective and sensitive ATP biosensor by combining the recognition ability of aptamer toward A nucleobase and of polyimidazolium toward phosphate. The biosensors are constructed by first confining the polyimidazolium onto a gold surface by surface-initiated atom transfer radical polymerization (SI-ATRP), and then the aptamer onto electrode surface by electrostatic self-assembly to form dual-recognition-unit-functionalized electrodes. The constructed biosensor based on DRUS not only shows an ultrahigh sensitivity toward ATP with a detection limit down to the subattomole level but also an ultrahigh selectivity toward ATP without interference from ADP and AMP. The constructed biosensor is used for selective and sensitive sensing of the extracellular ATP in the cerebral system by combining in vivo microdialysis and can be used as a promising neurotechnology to probing cerebral ATP concentration.

Tetrodotoxin-dependent glutamate release in the rat nucleus accumbens during concurrent presentation of appetitive and conditioned aversive stimuli.

PubMed

Saulskaya, Natalia B; Soloviova, Nina A

2004-12-30

In vivo microdialysis combined with a high-performance liquid chromatography was used to monitor extracellular glutamate (GLU) levels in the nucleus accumbens (N.Acc) of Sprague-Dawley rats during their behavioral responses to the concurrent presentation of appetitive and conditioned aversive stimuli. The presentation of a highly palatable diet followed by a tone previously paired with footshock to rats trained to take a pellet of the diet under these experimental conditions resulted in a marked and short lasting increase in extracellular glutamate, whereas the tone alone had no effect. A similar increase of the glutamate release was observed during the presentation of a piece of rubber instead of the diet. In both cases, the increase in extracellular glutamate was completely prevented by intra-accumbal infusions through the dialysis probe of 1 microM tetrodotoxin (a voltage-dependent Na(+) channel blocker), whereas (S)-4-carboxyphenylglycine (a cystine/glutamate exchange blocker, 5 microM) had no effect. The data obtained suggest that behavioral responses to unpredicted change in motivational value of expected reward appear to be associated with an increase of the extracellular glutamate level in the nucleus accumbens, and impulse-dependent synaptic release, rather than non-vesicular glutamate release via cystine/glutamate exchange, is responsible for this phenomenon.

A dark mode in scanning thermal microscopy

NASA Astrophysics Data System (ADS)

Ramiandrisoa, Liana; Allard, Alexandre; Joumani, Youssef; Hay, Bruno; Gomés, Séverine

2017-12-01

The need for high lateral spatial resolution in thermal science using Scanning Thermal Microscopy (SThM) has pushed researchers to look for more and more tiny probes. SThM probes have consequently become more and more sensitive to the size effects that occur within the probe, the sample, and their interaction. Reducing the tip furthermore induces very small heat flux exchanged between the probe and the sample. The measurement of this flux, which is exploited to characterize the sample thermal properties, requires then an accurate thermal management of the probe-sample system and to reduce any phenomenon parasitic to this system. Classical experimental methodologies must then be constantly questioned to hope for relevant and interpretable results. In this paper, we demonstrate and estimate the influence of the laser of the optical force detection system used in the common SThM setup that is based on atomic-force microscopy equipment on SThM measurements. We highlight the bias induced by the overheating due to the laser illumination on the measurements performed by thermoresistive probes (palladium probe from Kelvin Nanotechnology). To face this issue, we propose a new experimental procedure based on a metrological approach of the measurement: a SThM "dark mode." The comparison with the classical procedure using the laser shows that errors between 14% and 37% can be reached on the experimental data exploited to determine the heat flux transferred from the hot probe to the sample.

Sex differences in abuse-related neurochemical and behavioral effects of 3,4-methylenedioxymethamphetamine (MDMA) in rats.

PubMed

Lazenka, M F; Suyama, J A; Bauer, C T; Banks, M L; Negus, S S

2017-01-01

3,4-Methylenedioxymethamphetamine (MDMA) is a substrate for dopamine (DA), norepinephrine and serotonin (5HT) transporters that produces greater pharmacological effects on certain endpoints in females than males in both clinical and rodent preclinical studies. To evaluate potential for sex differences in abuse-related MDMA effects, the present study compared MDMA effects on intracranial self-stimulation (ICSS) and on in vivo microdialysis measurements of DA or 5HT in the nucleus accumbens (NAc) in female and male Sprague-Dawley rats. For ICSS studies, electrodes were implanted in the medial forebrain bundle and rats trained to press for electrical stimulation over a range of frequencies (56-158Hz, 0.05 log increments) under a fixed-ratio 1 schedule, and the potency (0.32-3.2mg/kg, 10min pretreatment) and time course (3.2. mg/kg, 10-180min pretreatment) of MDMA effects were determined. For in vivo microdialysis, rats were implanted with bilateral guide cannulae targeting the NAc, and the time course of MDMA effects (1.0-3.2mg/kg, 0-180min) on DA and 5HT was determined. MDMA produced qualitatively similar effects in both sexes on ICSS (both increases in low ICSS rates maintained by low brain-stimulation frequencies and decreases in high ICSS rates maintained by high brain-stimulation frequencies) and microdialysis (increases in both DA and 5HT). The duration and peak levels of both abuse-related ICSS facilitation and increases in NAc DA were longer in females. MDMA was also more potent to increase 5HT in females. These results provide evidence for heightened sensitivity of females to abuse-related behavioral and neurochemical effects of MDMA in rats. Copyright © 2016 Elsevier Inc. All rights reserved.

Increased adipose tissue lipolysis after a 2-week high-fat diet in sedentary overweight/obese men.

PubMed

Howe, Harold R; Heidal, Kimberly; Choi, Myung Dong; Kraus, Ray M; Boyle, Kristen; Hickner, Robert C

2011-07-01

The purpose of this study was to determine if a high-fat diet would result in a higher lipolytic rate in subcutaneous adipose tissue than a lower-fat diet in sedentary nonlean men. Six participants (healthy males; 18-40 years old; body mass index, 25-37 kg/m(2)) underwent 2 weeks on a high-fat or well-balanced diet of similar energy content (approximately 6695 kJ) in randomized order with a 10-day washout period between diets. Subcutaneous abdominal adipose tissue lipolysis was determined over the course of a day using microdialysis after both 2-week diet sessions. Average interstitial glycerol concentrations (index of lipolysis) as determined using microdialysis were higher after the high-fat diet (210.8 ± 27.9 μmol/L) than after a well-balanced diet (175.6 ± 23.3 μmol/L; P = .026). There was no difference in adipose tissue microvascular blood flow as determined using the microdialysis ethanol technique. These results demonstrate that healthy nonlean men who diet on the high-fat plan have a higher lipolytic rate in subcutaneous abdominal adipose tissue than when they diet on a well-balanced diet plan. This higher rate of lipolysis may result in a higher rate of fat mass loss on the high-fat diet; however, it remains to be determined if this higher lipolytic rate in men on the high-fat diet results in a more rapid net loss of triglyceride from the abdominal adipose depots, or if the higher lipolytic rate is counteracted by an increased rate of lipid storage. Copyright © 2011 Elsevier Inc. All rights reserved.

Acute Effects of Muscarinic M1 Receptor Modulation on AβPP Metabolism and Amyloid-β Levels in vivo: A Microdialysis Study.

PubMed

Welt, Tobias; Kulic, Luka; Hoey, Sarah E; McAfoose, Jordan; Späni, Claudia; Chadha, Antonella Santuccione; Fisher, Abraham; Nitsch, Roger M

2015-01-01

Indirect modulation of cholinergic activity by cholinesterase inhibition is currently a widely established symptomatic treatment for Alzheimer's disease (AD). Selective activation of certain muscarinic receptor subtypes has emerged as an alternative cholinergic-based amyloid-lowering strategy for AD, as selective muscarinic M1 receptor agonists can reduce amyloid-β (Aβ) production by shifting endoproteolytic amyloid-β protein precursor (AβPP) processing toward non-amyloidogenic pathways. In this study, we addressed the hypothesis that acute stimulation of muscarinic M1 receptors can inhibit Aβ production in awake and freely moving AβPP transgenic mice. By combining intracerebral microdialysis with retrodialysis, we determined hippocampal Aβ concentrations during simultaneous pharmacological modulation of brain M1 receptor function. Infusion with a M1 receptor agonist AF102B resulted in a rapid reduction of interstitial fluid (ISF) Aβ levels while treatment with the M1 antagonist dicyclomine increased ISF Aβ levels reaching significance within 120 minutes of treatment. The reduction in Aβ levels was associated with PKCα and ERK activation resulting in increased levels of the α-secretase ADAM17 and a shift in AβPP processing toward the non-amyloidogenic processing pathway. In contrast, treatment with the M1 receptor antagonist dicyclomine caused a decrease in levels of phosphorylated ERK that was independent of PKCα, and led to an elevation of β-secretase levels associated with increased amyloidogenic AβPP processing. The results of this study demonstrate rapid effects of in vivo M1 receptor modulation on the ISF pool of Aβ and suggest that intracerebral microdialysis with retrodialysis is a useful technical approach for monitoring acute treatment effects of muscarinic receptor modulators on AβPP/Aβ metabolism.

In vivo evaluation of glucose permeability of an immunoisolation device intended for islet transplantation: a novel application of the microdialysis technique.

PubMed

Rafael, E; Wernerson, A; Arner, P; Wu, G S; Tibell, A

1999-01-01

Immunoisolation devices consist of semipermeable membranes chosen to protect the islets from the immune system but still allow sufficient passage of nutrients, oxygen, and the therapeutic products, insulin. The exchange between the device and the microcirculation will influence the survival of the graft as well as the metabolic efficacy of the islet implant. Glucose is the important trigger factor for insulin secretion. In this study, we evaluate the in vivo glucose permeability of the Theracyte immunoisolation device at various times after implantation. Empty devices were implanted s.c. in rats. The glucose kinetics in the device was compared to that in the SC tissue during i.v. glucose tolerance tests (IVGTTs), using the microdialysis technique. In rats studied on day 1, or 1, 2, and 4 weeks after implantation, the peak glucose levels (Cmax) were significantly lower, the times-to-peak (TTP) were significantly longer, and the areas under the curve during the first 40 min (AUC(0-40)) were significantly smaller in the device than in the SC fat. However, at 3 months all parameters improved and Cmax, TTP, and AUC(0-40) in the device did not differ significantly from those measured in the SC fat. Thus, during the first 4 weeks the device constitutes a significant diffusion barrier, but at 3 months the exchange between the lumen of devices and the blood stream improves. Our data indicate that implantation of the device several months before transplantation of the cellular graft would improve the exchange across the membrane during the early posttransplant period. This should have positive effects on graft survival and function. We also suggest that microdialysis is a useful tool for evaluating the in vivo performance of macroencapsulation devices.

In vivo release of non-neuronal acetylcholine from the human skin as measured by dermal microdialysis: effect of botulinum toxin

PubMed Central

Schlereth, Tanja; Birklein, Frank; Haack, Katrin an; Schiffmann, Susanne; Kilbinger, Heinz; Kirkpatrick, Charles James; Wessler, Ignaz

2005-01-01

Acetylcholine is synthesized in the majority of non-neuronal cells, for example in human skin. In the present experiments, the in vivo release of acetylcholine was measured by dermal microdialysis. Two microdialysis membranes were inserted intradermally at the medial shank of volunteers. Physiological saline containing 1 μM neostigmine was perfused at a constant rate of 4 μl min−1 and the effluent was collected in six subsequent 20 min periods. Acetylcholine was measured by high-pressure liquid chromatography (HPLC) combined with bioreactors and electrochemical detection. Analysis of the effluent by HPLC showed an acetylcholine peak that disappeared, when the analytical column was packed with acetylcholine-specific esterase, confirming the presence of acetylcholine. In the absence of neostigmine, 71±51 pmol acetylcholine (n=4) was found during a 120 min period. The amount increased to 183±43 pmol (n=34), when the perfusion medium contained 1 μM neostigmine. Injection of 100 MU botulinum toxin subcutaneously blocked sweating completely, but the release of acetylcholine was not affected (botulinum toxin treated skin: 116±70 pmol acetylcholine/120 min; untreated skin: 50±20 pmol; n=4). Quinine (1 mM), inhibitor of organic cation transporters, and carnitine (0.1 mM), substrate of the Na+-dependent carnitine transporter OCTN2, tended to reduce acetylcholine release (by 40%, not significant). Our experiments demonstrate, for the first time, the in vivo release of non-neuronal acetylcholine in human skin. Organic cation transporters are not predominantly involved in the release of non-neuronal acetylcholine from the human skin. PMID:16273117

Increased adipose tissue lipolysis after a two-week high-fat diet in sedentary overweight/obese men

PubMed Central

Howe, Harold R; Heidal, Kimberly; Choi, Myung Dong; Kraus, Ray M.; Boyle, Kristen; Hickner, Robert C.

2013-01-01

Background/Objectives The purpose of this study was to determine if a high fat diet would result in a higher lipolytic rate in subcutaneous adipose tissue than a lower fat diet in sedentary non-lean men. Subjects/Methods Six participants (healthy males: 18-40 yrs old: body mass index 25-37 kg/m2) underwent two weeks on a high-fat or well-balanced diet of similar caloric content (approx. 1600 kcal) in randomized order with a ten-day washout period between diets. Subcutaneous abdominal adipose tissue lipolysis was determined over the course of a day using microdialysis after both two-week diet sessions. Results Average interstitial glycerol concentrations (index of lipolysis) as determined using microdialysis were higher following the high-fat diet (210.8 ±27.9 μM) than following a well-balanced diet (175.6 ± 23.3 μM; P = 0.026). There was no difference in adipose tissue microvascular blood flow as determined using the microdialysis ethanol technique. Conclusions These results demonstrate that healthy non-lean men who diet on the high-fat plan have a higher lipolytic rate in subcutaneous abdominal adipose tissue than when they diet on a well-balanced diet plan. This higher rate of lipolysis may result in a higher rate of fat mass loss on the high-fat diet; however, it remains to be determined if this higher lipolytic rate in men on the high-fat diet results in a more rapid net loss of triglyceride from the abdominal adipose depots, or if the higher lipolytic rate is counteracted by an increased rate of lipid storage. PMID:21040937

Sex Differences in Abuse-Related Neurochemical and Behavioral Effects of 3,4-methylenedioxymethamphetamine (MDMA) in Rats

PubMed Central

Lazenka, MF; Suyama, JA; Bauer, CT; Banks, ML; Negus, SS

2016-01-01

3,4-methylenedioxymethamphetamine (MDMA) is a substrate for the dopamine (DA), norepinephrine and serotonin (5HT) transporters that produces greater pharmacological effects on certain endpoints in females than males in both clinical and rodent preclinical studies. To evaluate potential for sex differences in abuse-related MDMA effects, the present study compared MDMA effects on intracranial self-stimulation (ICSS) and on in vivo microdialysis measurements of DA or 5HT in the nucleus accumbens (NAc) in female and male Sprague-Dawley rats. For ICSS studies, electrodes were implanted in the medial forebrain bundle and rats trained to press for electrical stimulation over a range of frequencies (56–158 Hz, 0.05 log increments) under a fixed-ratio 1 schedule, and the potency (0.32–3.2 mg/kg, 10 min pretreatment) and time course (3.2. mg/kg, 10–180 min pretreatment) of MDMA effects were determined. For in vivo microdialysis, rats were implanted with bilateral guide cannulae targeting the NAc, and the time course of MDMA effects (1.0–3.2 mg/kg, 0–180 min) on DA and 5HT was determined. MDMA produced qualitatively similar effects in both sexes on ICSS (both increases in low ICSS rates maintained by low brain-stimulation frequencies and decreases in high ICSS rates maintained by high brain-stimulation frequencies) and microdialysis (increases in both DA and 5HT). The duration and peak levels of both abuse-related ICSS facilitation and increases in NAc DA were longer in females. MDMA was also more potent to increase 5HT in females. These results provide evidence for heightened sensitivity of females to abuse-related behavioral and neurochemical effects of MDMA in rats. PMID:27566288

Muscle oxygenation and glycolysis in females with trapezius myalgia during stress and repetitive work using microdialysis and NIRS.

PubMed

Sjøgaard, Gisela; Rosendal, Lars; Kristiansen, Jesper; Blangsted, Anne K; Skotte, Jørgen; Larsson, Britt; Gerdle, Björn; Saltin, Bengt; Søgaard, Karen

2010-03-01

The aim of this investigation was to study female workers active in the labour market for differences between those with trapezius myalgia (MYA) and without (CON) during repetitive pegboard (PEG) and stress (STR) tasks regarding (1) relative muscle load, (2) trapezius muscle blood flow, (3) metabolite accumulation, (4) oxygenation, and (5) pain development. Among 812 female employees (age 30-60 years) at 7 companies with high prevalence of neck/shoulder complaints, clinical examination identified 43 MYA and 19 CON. At rest, during PEG, and STR the trapezius muscle was measured using (1) EMG and MMG, (2) microdialysis, and (3) NIRS. Further, subjective pain ratings were scored (VAS). EMGrms in %MVE (Maximal Voluntary EMG-activity), was significantly higher among MYA than CON during PEG (11.74 +/- 9.09 vs. 7.42 +/- 5.56%MVE) and STR (5.47 +/- 5.00 vs. 3.28 +/- 1.94%MVE). MANOVA showed a group and time effect regarding data from the microdialysis: for MYA versus CON group differences demonstrated lower muscle blood flow and higher lactate and pyruvate concentrations. Potassium and glucose only showed time effects. NIRS showed similar initial decreases in oxygenation with PEG in both groups, but only in CON a significant increase back to baseline during PEG. VAS score at rest was highest among MYA and increased during PEG, but not for CON. The results showed significant differences between CON and MYA regarding muscle metabolism at rest and with PEG and STR. Higher relative muscle load during PEG and STR, insufficient muscle blood flow and oxygenation may account for the higher lactate, pyruvate and pain responses among MYA versus CON.

In vivo continuous glucose monitoring using a chip based near infrared sensor

NASA Astrophysics Data System (ADS)

Ben Mohammadi, L.; Sigloch, S.; Frese, I.; Welzel, K.; Göddel, M.; Klotzbücher, T.

2014-05-01

Diabetes is a serious health condition considered to be one of the major healthcare epidemics of modern era. An effective treatment of this disease can be only achieved by reliable continuous information on blood glucose levels. In this work we present a minimally invasive, chip-based near infrared (NIR) sensor, combined with microdialysis, for continuous glucose monitoring (CGM). The sensor principle is based on difference absorption spectroscopy in the 1st overtone band of the near infrared spectrum. The device features a multi-emitter LED and InGaAs-Photodiodes, which are located on a single electronic board (non-disposable part), connected to a personal computer via Bluetooth. The disposable part consists of a chip containing the fluidic connections for microdialysis, two fluidic channels acting as optical transmission cells and total internally reflecting mirrors for in- and out-coupling of the LED light to the chip and to the detectors. The sensor is combined with an intraveneous microdialysis to separate the glucose from the cells and proteins in the blood and operates without any chemical consumption. In vitro measurements showed a linear relationship between glucose concentration and the integrated difference signal with a coefficient of determination of 99 % in the relevant physiological concentration range from 0 to 400 mg/dl. In vivo measurements on 10 patients showed that the NIR-CGM sensor data reflects the blood reference values adequately, if a proper calibration and signal drift compensation is applied. The MARE (mean absolute relative error) value taken over all patient data is 13.8 %. The best achieved MARE value is at 4.8 %, whereas the worst is 25.8 %, with a standard deviation of 5.5 %.

Direct and quantitative broadband absorptance spectroscopy with multilayer cantilever probes

DOEpatents

Hsu, Wei-Chun; Tong, Jonathan Kien-Kwok; Liao, Bolin; Chen, Gang

2015-04-21

A system for measuring the absorption spectrum of a sample is provided that includes a broadband light source that produces broadband light defined within a range of an absorptance spectrum. An interferometer modulates the intensity of the broadband light source for a range of modulation frequencies. A bi-layer cantilever probe arm is thermally connected to a sample arm having at most two layers of materials. The broadband light modulated by the interferometer is directed towards the sample and absorbed by the sample and converted into heat, which causes a temperature rise and bending of the bi-layer cantilever probe arm. A detector mechanism measures and records the deflection of the probe arm so as to obtain the absorptance spectrum of the sample.

What do you measure when you measure the Hall effect?

NASA Astrophysics Data System (ADS)

Koon, D. W.; Knickerbocker, C. J.

1993-02-01

A formalism for calculating the sensitivity of Hall measurements to local inhomogeneities of the sample material or the magnetic field is developed. This Hall weighting function g(x,y) is calculated for various placements of current and voltage probes on square and circular laminar samples. Unlike the resistivity weighting function, it is nonnegative throughout the entire sample, provided all probes lie at the edge of the sample. Singularities arise in the Hall weighting function near the current and voltage probes except in the case where these probes are located at the corners of a square. Implications of the results for cross, clover, and bridge samples, and the implications of our results for metal-insulator transition and quantum Hall studies are discussed.

Quantification of different Eubacterium spp. in human fecal samples with species-specific 16S rRNA-targeted oligonucleotide probes.

PubMed

Schwiertz, A; Le Blay, G; Blaut, M

2000-01-01

Species-specific 16S rRNA-targeted, Cy3 (indocarbocyanine)-labeled oligonucleotide probes were designed and validated to quantify different Eubacterium species in human fecal samples. Probes were directed at Eubacterium barkeri, E. biforme, E. contortum, E. cylindroides (two probes), E. dolichum, E. hadrum, E. lentum, E. limosum, E. moniliforme, and E. ventriosum. The specificity of the probes was tested with the type strains and a range of common intestinal bacteria. With one exception, none of the probes showed cross-hybridization under stringent conditions. The species-specific probes were applied to fecal samples obtained from 12 healthy volunteers. E. biforme, E. cylindroides, E. hadrum, E. lentum, and E. ventriosum could be determined. All other Eubacterium species for which probes had been designed were under the detection limit of 10(7) cells g (dry weight) of feces(-1). The cell counts obtained are essentially in accordance with the literature data, which are based on colony counts. This shows that whole-cell in situ hybridization with species-specific probes is a valuable tool for the enumeration of Eubacterium species in feces.

Quantification of Different Eubacterium spp. in Human Fecal Samples with Species-Specific 16S rRNA-Targeted Oligonucleotide Probes

PubMed Central

Schwiertz, Andreas; Le Blay, Gwenaelle; Blaut, Michael

2000-01-01

Species-specific 16S rRNA-targeted, Cy3 (indocarbocyanine)-labeled oligonucleotide probes were designed and validated to quantify different Eubacterium species in human fecal samples. Probes were directed at Eubacterium barkeri, E. biforme, E. contortum, E. cylindroides (two probes), E. dolichum, E. hadrum, E. lentum, E. limosum, E. moniliforme, and E. ventriosum. The specificity of the probes was tested with the type strains and a range of common intestinal bacteria. With one exception, none of the probes showed cross-hybridization under stringent conditions. The species-specific probes were applied to fecal samples obtained from 12 healthy volunteers. E. biforme, E. cylindroides, E. hadrum, E. lentum, and E. ventriosum could be determined. All other Eubacterium species for which probes had been designed were under the detection limit of 107 cells g (dry weight) of feces−1. The cell counts obtained are essentially in accordance with the literature data, which are based on colony counts. This shows that whole-cell in situ hybridization with species-specific probes is a valuable tool for the enumeration of Eubacterium species in feces. PMID:10618251

Fluorescence suppression using wavelength modulated Raman spectroscopy in fiber-probe-based tissue analysis.

PubMed

Praveen, Bavishna B; Ashok, Praveen C; Mazilu, Michael; Riches, Andrew; Herrington, Simon; Dholakia, Kishan

2012-07-01

In the field of biomedical optics, Raman spectroscopy is a powerful tool for probing the chemical composition of biological samples. In particular, fiber Raman probes play a crucial role for in vivo and ex vivo tissue analysis. However, the high-fluorescence background typically contributed by the auto fluorescence from both a tissue sample and the fiber-probe interferes strongly with the relatively weak Raman signal. Here we demonstrate the implementation of wavelength-modulated Raman spectroscopy (WMRS) to suppress the fluorescence background while analyzing tissues using fiber Raman probes. We have observed a significant signal-to-noise ratio enhancement in the Raman bands of bone tissue, which have a relatively high fluorescence background. Implementation of WMRS in fiber-probe-based bone tissue study yielded usable Raman spectra in a relatively short acquisition time (∼30  s), notably without any special sample preparation stage. Finally, we have validated its capability to suppress fluorescence on other tissue samples such as adipose tissue derived from four different species.

Microwave resonances in dielectric samples probed in Corbino geometry: simulation and experiment.

PubMed

Felger, M Maximilian; Dressel, Martin; Scheffler, Marc

2013-11-01

The Corbino approach, where the sample of interest terminates a coaxial cable, is a well-established method for microwave spectroscopy. If the sample is dielectric and if the probe geometry basically forms a conductive cavity, this combination can sustain well-defined microwave resonances that are detrimental for broadband measurements. Here, we present detailed simulations and measurements to investigate the resonance frequencies as a function of sample and probe size and of sample permittivity. This allows a quantitative optimization to increase the frequency of the lowest-lying resonance.

A LOW-E MAGIC ANGLE SPINNING PROBE FOR BIOLOGICAL SOLID STATE NMR AT 750 MHz

PubMed Central

McNeill, Seth A.; Gor’kov, Peter L.; Shetty, Kiran; Brey, William W.; Long, Joanna R.

2009-01-01

Crossed-coil NMR probes are a useful tool for reducing sample heating for biological solid state NMR. In a crossed-coil probe, the higher frequency 1H field, which is the primary source of sample heating in conventional probes, is produced by a separate low-inductance resonator. Because a smaller driving voltage is required, the electric field across the sample and the resultant heating is reduced. In this work we describe the development of a magic angle spinning (MAS) solid state NMR probe utilizing a dual resonator. This dual resonator approach, referred to as “Low-E,” was originally developed to reduce heating in samples of mechanically aligned membranes. The study of inherently dilute systems, such as proteins in lipid bilayers, via MAS techniques requires large sample volumes at high field to obtain spectra with adequate signal-to-noise ratio under physiologically relevant conditions. With the Low-E approach, we are able to obtain homogeneous and sufficiently strong radiofrequency fields for both 1H and 13C frequencies in a 4 mm probe with a 1H frequency of 750 MHz. The performance of the probe using windowless dipolar recoupling sequences is demonstrated on model compounds as well as membrane embedded peptides. PMID:19138870

Amperometric determination of 6-mercaptopurine on functionalized multi-wall carbon nanotubes modified electrode by liquid chromatography coupled with microdialysis and its application to pharmacokinetics in rabbit.

PubMed

Cao, Xu-Ni; Lin, Li; Zhou, Yu-Yan; Shi, Guo-Yue; Zhang, Wen; Yamamoto, Katsunobu; Jin, Li-Tong

2003-07-27

In this paper, multi-wall carbon nanotubes functionalized with carboxylic groups modified electrode (MWNT-COOH CME) was fabricated. This chemically modified electrode (CME) can be used as the working electrode in the liquid chromatography for the determination of 6-mercaptopurine (6-MP). The results indicate that the CME exhibits efficiently electrocatalytic oxidation for 6-MP with relatively high sensitivity, stability and long-life. The peak currents of 6-MP are linear to its concentrations ranging from 4.0 x 10(-7) to 1.0 x 10(-4) mol l(-1) with the calculated detection limit (S/N=3) of 2.0 x 10(-7) mol l(-1). Coupled with microdialysis, the method has been successfully applied to the pharmacokinetic study of 6-MP in rabbit blood. This method provides a fast, sensible and simple technique for the pharmacokinetic study of 6-MP in vivo.

Design of a dynamic optical tissue phantom to model extravasation pharmacokinetics

NASA Astrophysics Data System (ADS)

Zhang, Jane Y.; Ergin, Aysegul; Andken, Kerry Lee; Sheng, Chao; Bigio, Irving J.

2010-02-01

We describe an optical tissue phantom that enables the simulation of drug extravasation from microvessels and validates computational compartmental models of drug delivery. The phantom consists of a microdialysis tubing bundle to simulate the permeable blood vessels, immersed in either an aqueous suspension of titanium dioxide (TiO2) or a TiO2 mixed agarose scattering medium. Drug administration is represented by a dye circulated through this porous microdialysis tubing bundle. Optical pharmacokinetic (OP) methods are used to measure changes in the absorption coefficient of the scattering medium due to the arrival and diffusion of the dye. We have established particle sizedependent concentration profiles over time of phantom drug delivery by intravenous (IV) and intra-arterial (IA) routes. Additionally, pharmacokinetic compartmental models are implemented in computer simulations for the conditions studied within the phantom. The simulated concentration-time profiles agree well with measurements from the phantom. The results are encouraging for future optical pharmacokinetic method development, both physical and computational, to understand drug extravasation under various physiological conditions.

Cerebral taurine release mechanisms in vivo: pharmacological investigations in rats using microdialysis for proof of principle.

PubMed

Scheller, D; Korte, M; Szathmary, S; Tegtmeier, F

2000-06-01

Cerebral taurine acts as neurotransmitter, as neuromodulator, or as osmoregulator. To investigate its release mechanisms in vivo, we combined the microdialysis technique with a variety of experimental paradigms. Taurine release was stimulated by either NMDA, NO or a hypotonic solution locally with or without the addition of the NMDA antagonists APV or Ketamine, or the NO synthase inhibitor L-NAME. Alternatively, the neuroprotective drug lubeluzole was applied i.v. NMDA, NO or the hypotonic solution stimulated the release of taurine. NMDA-mediated taurine release was inhibited by either APV, Ketamine or the NO synthase inhibitor L-NAME. Lubeluzole had no effect. Under the hypotonic conditions only lubeluzole was effective. These data confirm in vivo that the NMDA-induced taurine release is mediated via the NO cascade. By contrast, the release after a hypotonic stimulus is not related to the NO cascade. Instead, Na(+)- and/or Ca(2+)-mediated events might have been attenuated by lubeluzole.

A ketogenic diet modifies glutamate, gamma-aminobutyric acid and agmatine levels in the hippocampus of rats: A microdialysis study.

PubMed

Calderón, Naima; Betancourt, Luis; Hernández, Luis; Rada, Pedro

2017-03-06

The ketogenic diet (KD) is acknowledged as an unconventional option in the treatment of epilepsy. Several lines of investigation point to a possible role of glutamate and gamma-aminobutyric acid (GABA) as main contributors in this protective effect. Other biomolecules could also be involved in the beneficial consequence of the KD, for example, the diamine agmatine has been suggested to block imidazole and glutamate NMDA receptor and serves as an endogenous anticonvulsant in different animal models of epilepsy. In the present report, we have used microdialysis coupled to capillary electrophoresis to monitor microdialysate levels of GABA, glutamate and agmatine in the hippocampus of rats submitted to a KD for 15days compared to rats on a normal rat chow diet. A significant increase in GABA and agmatine levels while no change in glutamate levels was observed. These results support the notion that the KD modifies different transmitters favoring inhibitory over excitatory neurotransmitters. Copyright © 2017 Elsevier B.V. All rights reserved.

Inhibition of neuropeptide degradation suppresses sweating but increases the area of the axon reflex flare.

PubMed

Schlereth, Tanja; Breimhorst, Markus; Werner, Nicolas; Pottschmidt, Katrin; Drummond, Peter D; Birklein, Frank

2013-04-01

The neuropeptides CGRP (calcitonin gene-elated peptide) and substance P (SP) mediate neurogenic inflammation. Both are degraded by the neutral endopeptidase (NEP) which can be blocked by phosphoramidon. The aim was to evaluate the effect of NEP inhibition on sweating and vasodilatation. Dermal microdialysis was performed on the skin of 39 subjects. Two fibres were perfused with phosphoramidon (0.01%, 0.02% or 0.2%), two with saline. Acetylcholine (ACh) was either added to the microdialysis perfusate (n = 30, 10(-2)  m) or thermoregulatory sweating was induced (n = 9). Co-application of phosphoramidon reduced cholinergic and thermoregulatory sweating. However, the flare size - a localized increase in superficial blood flow after ACh-application - was significantly increased. The increase in flare size is most probably due to increased CGRP levels. The inhibition of sweating by phosphoramidon may involve an increase in SP, a reduction in CGRP-degradation fragments or a direct inhibitory action of phosphoramidon. © 2013 John Wiley & Sons A/S.

A critical review of 5-HT brain microdialysis and behavior.

PubMed

Rueter, L E; Fornal, C A; Jacobs, B L

1997-01-01

Serotonin (5-HT) has been implicated in many central nervous system-mediated functions including sleep, arousal, feeding, motor activity and the stress response. In order to help establish the precise role of 5-HT in physiology and behavior, in vivo microdialysis studies have sought to identify the conditions under which the release of 5-HT is altered. Extracellular 5-HT levels have been monitored in more than fifteen regions of the brain during a variety of spontaneous behaviors, and in response to several physiological, environmental, and behavioral manipulations. The vast majority of these studies found increases (30-100%) in 5-HT release in almost all brain regions studied. Since electrophysiological studies have shown that behavioral arousal is the primary determinant of brain serotonergic neuronal activity, we suggest that the increase in 5-HT release seen during a wide variety of experimental conditions is largely due to one factor, namely an increase in behavioral arousal/motor activity associated with the manipulation.

Forced swimming-induced oxytocin release into blood and brain: Effects of adrenalectomy and corticosterone treatment.

PubMed

Torner, Luz; Plotsky, Paul M; Neumann, Inga D; de Jong, Trynke R

2017-03-01

The oxytocin (OXT) system is functionally linked to the HPA axis in a reciprocal and complex manner. Certain stressors are known to cause the simultaneous release of OXT and adrenocorticotrophic hormone (ACTH) followed by corticosterone (CORT). Furthermore, brain OXT attenuates ACTH and CORT responses. Although there are some indications of CORT influencing OXT neurotransmission, specific effects of CORT on neurohypophyseal or intra-hypothalamic release of OXT have not been studied in detail. In the present set of experiments, adult male rats were adrenalectomized (ADX) or sham-operated and fitted with a jugular vein catheter and/or microdialysis probe targeting the hypothalamic paraventricular nucleus (PVN). Blood samples and dialysates were collected before and after forced swimming (FS) and analyzed for CORT, ACTH and AVP concentrations (in plasma) and OXT concentrations (in plasma and dialysates). Experimental treatments included acute infusion of CORT (70 or 175μg/kg i.v.) 5min prior to FS, or subcutaneous placement of 40% CORT pellets resulting in stable CORT levels in the normal basal range. Although ADX did not alter basal OXT concentrations either in plasma or in microdialysates from the PVN, it did cause an exaggerated peripheral secretion of OXT and a blunted intra-PVN release of OXT in response to FS. CORT pellets did not influence either of these ADX-induced effects, while acute infusion of 175μg/kg CORT rescued the stress-induced rise in OXT release within the PVN and modestly increased peripheral OXT secretion. In conclusion, these results indicate that CORT regulates both peripheral and intracerebral OXT release, but in an independent manner. Whereas the peripheral secretion of OXT occurs simultaneously to HPA axis activation in response to FS and is modestly influenced by CORT, HPA axis activation and circulating CORT strongly contribute to the stress-induced stimulation of OXT release within the PVN. Copyright © 2016 Elsevier Ltd. All rights reserved.

Four-probe measurements with a three-probe scanning tunneling microscope.

PubMed

Salomons, Mark; Martins, Bruno V C; Zikovsky, Janik; Wolkow, Robert A

2014-04-01

We present an ultrahigh vacuum (UHV) three-probe scanning tunneling microscope in which each probe is capable of atomic resolution. A UHV JEOL scanning electron microscope aids in the placement of the probes on the sample. The machine also has a field ion microscope to clean, atomically image, and shape the probe tips. The machine uses bare conductive samples and tips with a homebuilt set of pliers for heating and loading. Automated feedback controlled tip-surface contacts allow for electrical stability and reproducibility while also greatly reducing tip and surface damage due to contact formation. The ability to register inter-tip position by imaging of a single surface feature by multiple tips is demonstrated. Four-probe material characterization is achieved by deploying two tips as fixed current probes and the third tip as a movable voltage probe.

Development of combination tapered fiber-optic biosensor dip probe for quantitative estimation of interleukin-6 in serum samples

NASA Astrophysics Data System (ADS)

Wang, Chun Wei; Manne, Upender; Reddy, Vishnu B.; Oelschlager, Denise K.; Katkoori, Venkat R.; Grizzle, William E.; Kapoor, Rakesh

2010-11-01

A combination tapered fiber-optic biosensor (CTFOB) dip probe for rapid and cost-effective quantification of proteins in serum samples has been developed. This device relies on diode laser excitation and a charged-coupled device spectrometer and functions on a technique of sandwich immunoassay. As a proof of principle, this technique was applied in a quantitative estimation of interleukin IL-6. The probes detected IL-6 at picomolar levels in serum samples obtained from a patient with lupus, an autoimmune disease, and a patient with lymphoma. The estimated concentration of IL-6 in the lupus sample was 5.9 +/- 0.6 pM, and in the lymphoma sample, it was below the detection limit. These concentrations were verified by a procedure involving bead-based xMAP technology. A similar trend in the concentrations was observed. The specificity of the CTFOB dip probes was assessed by analysis with receiver operating characteristics. This analysis suggests that the dip probes can detect 5-pM or higher concentration of IL-6 in these samples with specificities of 100%. The results provide information for guiding further studies in the utilization of these probes to quantify other analytes in body fluids with high specificity and sensitivity.

33 CFR 157.12d - Technical specifications.

Code of Federal Regulations, 2014 CFR

2014-07-01

... section. The sampling probes located in the overboard discharge lines and the piping system connecting the sampling probes to the oil content meter must meet the requirements of this paragraph. (2) The piping and probes must be— (i) Of a material resistant to fire, corrosion, and oil; and (ii) Of adequate strength...

Liquid microjunction surface sampling probe fluid dynamics: Characterization and application of an analyte plug formation operational mode

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

ElNaggar, Mariam S.; Van Berkel, Gary J.

2011-08-10

The recently discovered sample plug formation and injection operational mode of a continuous flow, coaxial tube geometry, liquid microjunction surface sampling probe (LMJ-SSP) (J. Am. Soc. Mass Spectrom, 2011) was further characterized and applied for concentration and mixing of analyte extracted from multiple areas on a surface and for nanoliter-scale chemical reactions of sampled material. A transparent LMJ-SSP was constructed and colored analytes were used so that the surface sampling process, plug formation, and the chemical reactions could be visually monitored at the sampling end of the probe before being analyzed by mass spectrometry of the injected sample plug. Injectionmore » plug peak widths were consistent for plug hold times as long as the 8 minute maximum attempted (RSD below 1.5%). Furthermore, integrated injection peak signals were not significantly different for the range of hold times investigated. The ability to extract and completely mix individual samples within a fixed volume at the sampling end of the probe was demonstrated and a linear mass spectral response to the number of equivalent analyte spots sampled was observed. Lastly, using the color and mass changing chemical reduction of the redox dye 2,6-dichlorophenol-indophenol with ascorbic acid, the ability to sample, concentrate, and efficiently run reactions within the same plug volume within the probe was demonstrated.« less

40 CFR 89.419 - Dilute gaseous exhaust sampling and analytical system description.

Code of Federal Regulations, 2010 CFR

2010-07-01

...) Continuous HC measurement system. (i) The continuous HC sample system (as shown in Figure 2 or 3 in appendix... this is not required. (ii) No other analyzers may draw a sample from the continuous HC sample probe... continuous HC sampling system shall consist of a probe (which must raise the sample to the specified...

Quantification of in-contact probe-sample electrostatic forces with dynamic atomic force microscopy.

PubMed

Balke, Nina; Jesse, Stephen; Carmichael, Ben; Okatan, M Baris; Kravchenko, Ivan I; Kalinin, Sergei V; Tselev, Alexander

2017-01-04

Atomic force microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe in the probe-sample junction in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can produce signals equivalent to a few pm of surface displacement. In combination with modeling, the measurements of the force were used to access the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junction can reach ca. 1 V nm -1 at a bias voltage of a few volts and is limited by non-ideality of the tip-sample contact. This field is sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids.

Use of the polymerase chain reaction to directly detect malaria parasites in blood samples from the Venezuelan Amazon.

PubMed

Laserson, K F; Petralanda, I; Hamlin, D M; Almera, R; Fuentes, M; Carrasquel, A; Barker, R H

1994-02-01

We have examined the reproducibility, sensitivity, and specificity of detecting Plasmodium falciparum using the polymerase chain reaction (PCR) and the species-specific probe pPF14 under field conditions in the Venezuelan Amazon. Up to eight samples were field collected from each of 48 consenting Amerindians presenting with symptoms of malaria. Sample processing and analysis was performed at the Centro Amazonico para la Investigacion y Control de Enfermedades Tropicales Simon Bolivar. A total of 229 samples from 48 patients were analyzed by PCR methods using four different P. falciparum-specific probes. One P. vivax-specific probe and by conventional microscopy. Samples in which results from PCR and microscopy differed were reanalyzed at a higher sensitivity by microscopy. Results suggest that microscopy-negative, PCR-positive samples are true positives, and that microscopy-positive and PCR-negative samples are true negatives. The sensitivity of the DNA probe/PCR method was 78% and its specificity was 97%. The positive predictive value of the PCR method was 88%, and the negative predictive value was 95%. Through the analysis of multiple blood samples from each individual, the DNA probe/PCR methodology was found to have an inherent reproducibility that was highly statistically significant.

Four-probe measurements with a three-probe scanning tunneling microscope

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

Salomons, Mark; Martins, Bruno V. C.; Zikovsky, Janik

2014-04-15

We present an ultrahigh vacuum (UHV) three-probe scanning tunneling microscope in which each probe is capable of atomic resolution. A UHV JEOL scanning electron microscope aids in the placement of the probes on the sample. The machine also has a field ion microscope to clean, atomically image, and shape the probe tips. The machine uses bare conductive samples and tips with a homebuilt set of pliers for heating and loading. Automated feedback controlled tip-surface contacts allow for electrical stability and reproducibility while also greatly reducing tip and surface damage due to contact formation. The ability to register inter-tip position bymore » imaging of a single surface feature by multiple tips is demonstrated. Four-probe material characterization is achieved by deploying two tips as fixed current probes and the third tip as a movable voltage probe.« less

Spectrophotometric probe

DOEpatents

Prather, W.S.; O'Rourke, P.E.

1994-08-02

A support structure is described bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe. 3 figs.

Spectrophotometric probe

DOEpatents

Prather, William S.; O'Rourke, Patrick E.

1994-01-01

A support structure bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe.

Direct Surface and Droplet Microsampling for Electrospray Ionization Mass Spectrometry Analysis with an Integrated Dual-Probe Microfluidic Chip

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

Huang, Cong-Min; Zhu, Ying; Jin, Di-Qiong

Ambient mass spectrometry (MS) has revolutionized the way of MS analysis and broadened its application in various fields. This paper describes the use of microfluidic techniques to simplify the setup and improve the functions of ambient MS by integrating the sampling probe, electrospray emitter probe, and online mixer on a single glass microchip. Two types of sampling probes, including a parallel-channel probe and a U-shaped channel probe, were designed for dryspot and liquid-phase droplet samples, respectively. We demonstrated that the microfabrication techniques not only enhanced the capability of ambient MS methods in analysis of dry-spot samples on various surfaces, butmore » also enabled new applications in the analysis of nanoliter-scale chemical reactions in an array of droplets. The versatility of the microchip-based ambient MS method was demonstrated in multiple different applications including evaluation of residual pesticide on fruit surfaces, sensitive analysis of low-ionizable analytes using postsampling derivatization, and high-throughput screening of Ugi-type multicomponent reactions.« less

Cryogenic sample exchange NMR probe for magic angle spinning dynamic nuclear polarization

PubMed Central

Barnes, Alexander B.; Mak-Jurkauskas, Melody L.; Matsuki, Yoh; Bajaj, Vikram S.; van der Wel, Patrick C. A.; DeRocher, Ronald; Bryant, Jeffrey; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Lugtenburg, Johan; Herzfeld, Judith; Griffin, Robert G.

2009-01-01

We describe a cryogenic sample exchange system that dramatically improves the efficiency of magic angle spinning (MAS) dynamic nuclear polarization (DNP) experiments by reducing the time required to change samples and by improving long-term instrument stability. Changing samples in conventional cryogenic MAS DNP/NMR experiments involves warming the probe to room temperature, detaching all cryogenic, RF, and microwave connections, removing the probe from the magnet, replacing the sample, and reversing all the previous steps, with the entire cycle requiring a few hours. The sample exchange system described here — which relies on an eject pipe attached to the front of the MAS stator and a vacuum jacketed dewar with a bellowed hole — circumvents these procedures. To demonstrate the excellent sensitivity, resolution, and stability achieved with this quadruple resonance sample exchange probe, we have performed high precision distance measurements on the active site of the membrane protein bacteriorhodopsin. We also include a spectrum of the tripeptide N-f-MLF-OH at 100 K which shows 30 Hz linewidths. PMID:19356957

System and method for liquid extraction electrospray-assisted sample transfer to solution for chemical analysis

DOEpatents

Kertesz, Vilmos; Van Berkel, Gary J.

2016-07-12

A system for sampling a surface includes a surface sampling probe comprising a solvent liquid supply conduit and a distal end, and a sample collector for suspending a sample collection liquid adjacent to the distal end of the probe. A first electrode provides a first voltage to solvent liquid at the distal end of the probe. The first voltage produces a field sufficient to generate electrospray plume at the distal end of the probe. A second electrode provides a second voltage and is positioned to produce a plume-directing field sufficient to direct the electrospray droplets and ions to the suspended sample collection liquid. The second voltage is less than the first voltage in absolute value. A voltage supply system supplies the voltages to the first electrode and the second electrode. The first electrode can apply the first voltage directly to the solvent liquid. A method for sampling for a surface is also disclosed.

AN IN VIVO MICRODIALYSIS METHOD FOR THE QUALITATIVE ANALYSIS OF HEPATIC PHASE I METABOLITES OF PHENOL IN RAINBOW TROUT (ONCORHYNCHUS MYKISS)

EPA Science Inventory

Development of reliable and accurate methodologies for determination of xenobiotic hepatic biotransformation rate and capacity parameters is important to the derivation of precise physiologically-based toxicokinetic (PB-TK) models. Biotransformation data incorporated into PB-TK m...

Ball assisted device for analytical surface sampling

DOEpatents

ElNaggar, Mariam S; Van Berkel, Gary J; Covey, Thomas R

2015-11-03

A system for sampling a surface includes a sampling probe having a housing and a socket, and a rolling sampling sphere within the socket. The housing has a sampling fluid supply conduit and a sampling fluid exhaust conduit. The sampling fluid supply conduit supplies sampling fluid to the sampling sphere. The sampling fluid exhaust conduit has an inlet opening for receiving sampling fluid carried from the surface by the sampling sphere. A surface sampling probe and a method for sampling a surface are also disclosed.

Four-point probe measurements using current probes with voltage feedback to measure electric potentials

NASA Astrophysics Data System (ADS)

Lüpke, Felix; Cuma, David; Korte, Stefan; Cherepanov, Vasily; Voigtländer, Bert

2018-02-01

We present a four-point probe resistance measurement technique which uses four equivalent current measuring units, resulting in minimal hardware requirements and corresponding sources of noise. Local sample potentials are measured by a software feedback loop which adjusts the corresponding tip voltage such that no current flows to the sample. The resulting tip voltage is then equivalent to the sample potential at the tip position. We implement this measurement method into a multi-tip scanning tunneling microscope setup such that potentials can also be measured in tunneling contact, allowing in principle truly non-invasive four-probe measurements. The resulting measurement capabilities are demonstrated for \

Measurements of glucose on the skin surface, in stratum corneum and in transcutaneous extracts: implications for physiological sampling.

PubMed

Cunningham, David D; Young, Douglas F

2003-09-01

Obtaining representative physiological samples for glucose analysis remains a challenge especially when developing less invasive glucose monitoring systems for diabetic patients. In the present study the glucose content of the stratum corneum was compared with the amount of glucose obtained by short aqueous extractions from a site on the dorsal wrist, using high pressure liquid chromatography with pulsed amperometric detection. Ten successive aqueous 1-minute extractions of the site yielded a total of 60 ng cm(-2). The total glucose content of the stratum corneum of the site, determined from 30 successive tape-strippings of the site, was 360 ng cm(-2). After tape-stripping, the transcutaneous aqueous extraction rate was 86 +/- 13 ng cm(-2) min(-1), compared with rates of 80-600 ng cm(-2) min(-1) obtained with suction effusion or microdialysis after tape-stripping. Glucose on the surface of the skin and within the stratum corneum should be considered as sources of extraneous glucose contamination during testing of less invasive glucose monitoring devices.

Effects of salt loading and flow blockage on the WIPP shrouded probe

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

Chandra, S.; Ortiz, C.A.; McFarland, A.R.

1993-08-01

The shrouded probes at the WIPP site operate in a salt aerosol environment that can cause a buildup of salt deposits on exposed surfaces of the probes that, in turn, could produce changes in the sampling performance of the probes. At Station A, three probes had been operated for a period of approximately 2 1/2 years when they were inspected with a remote television camera. There were visible deposits of unknown thickness on the probes, so WIPP removed the probes for inspection and cleanup. Measurements were made on the probes and they showed the buildups to be approximately 2.5 mmmore » thick on the most critical dimension of a shrouded probe, which is the inside diameter of the inner probe. For reference, the diameter of a clean probe is 30 mm. The sampling performance of this particular shrouded probe had been previously evaluated in a wind tunnel at Aerosol Technology Laboratory (ATL) of Texas A&M University for two free stream velocities (14 and 21 m/s) and three particle sizes (5, 10 and 15 {mu}m AED).« less

Optimal probes for withdrawal of uncontaminated fluid samples

NASA Astrophysics Data System (ADS)

Sherwood, J. D.

2005-08-01

Withdrawal of fluid by a composite probe pushed against the face z =0 of a porous half-space z >0 is modeled assuming incompressible Darcy flow. The probe is circular, of radius a, with an inner sampling section of radius αa and a concentric outer guard probe αa βa is saturated with fluid 2; the two fluids have the same viscosity. It is assumed that the interface between the two fluids is sharp and remains so as it moves through the rock. The pressure in the probe is lower than that of the pore fluid in the rock, so that the fluid interface is convected with the fluids towards the probe. This idealized axisymmetric problem is solved numerically, and it is shown that an analysis based on far-field spherical flow towards a point sink is a good approximation when the nondimensional depth of fluid 1 is large, i.e., β ≫1. The inner sampling probe eventually produces pure fluid 2, and this technique has been proposed for sampling pore fluids in rock surrounding an oil well [A. Hrametz, C. Gardner, M. Wais, and M. Proett, U.S. Patent No. 6,301,959 B1 (16 October 2001)]. Fluid 1 is drilling fluid filtrate, which has displaced the original pore fluid (fluid 2), a pure sample of which is required. The time required to collect an uncontaminated sample of original pore fluid can be minimized by a suitable choice of the probe geometry α [J. Sherwood, J. Fitzgerald and B. Hill, U.S. Patent No. 6,719,049 B2 (13 April 2004)]. It is shown that the optimal choice of α depends on the depth of filtrate invasion β and the volume of sample required.

Open Probe fast GC-MS - combining ambient sampling ultra-fast separation and in-vacuum ionization for real-time analysis.

PubMed

Keshet, U; Alon, T; Fialkov, A B; Amirav, A

2017-07-01

An Open Probe inlet was combined with a low thermal mass ultra-fast gas chromatograph (GC), in-vacuum electron ionization ion source and a mass spectrometer (MS) of GC-MS for obtaining real-time analysis with separation. The Open Probe enables ambient sampling via sample vaporization in an oven that is open to room air, and the ultra-fast GC provides ~30-s separation, while if no separation is required, it can act as a transfer line with 2 to 3-s sample transfer time. Sample analysis is as simple as touching the sample, pushing the sample holder into the Open Probe oven and obtaining the results in 30 s. The Open Probe fast GC was mounted on a standard Agilent 7890 GC that was coupled with an Agilent 5977A MS. Open Probe fast GC-MS provides real-time analysis combined with GC separation and library identification, and it uses the low-cost MS of GC-MS. The operation of Open Probe fast GC-MS is demonstrated in the 30-s separation and 50-s full analysis cycle time of tetrahydrocannabinol and cannabinol in Cannabis flower, sub 1-min analysis of trace trinitrotoluene transferred from a finger onto a glass surface, vitamin E in canola oil, sterols in olive oil, polybrominated flame retardants in plastics, alprazolam in Xanax drug pill and free fatty acids and cholesterol in human blood. The extrapolated limit of detection for pyrene is <1 fg, but the concentration is too high and the software noise calculation is untrustworthy. The broad range of compounds amenable for analysis is demonstrated in the analysis of reserpine. The possible use with alternate standard GC-MS and Open Probe fast GC-MS is demonstrated in the analysis of heroin in its street drug powder. The use of Open Probe with the fast GC acting as a transfer line is demonstrated in <10-s analysis without separation of ibuprofen and estradiol. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Methods for making nucleotide probes for sequencing and synthesis

DOEpatents

Church, George M; Zhang, Kun; Chou, Joseph

2014-07-08

Compositions and methods for making a plurality of probes for analyzing a plurality of nucleic acid samples are provided. Compositions and methods for analyzing a plurality of nucleic acid samples to obtain sequence information in each nucleic acid sample are also provided.

Capacitance-level/density monitor for fluidized-bed combustor

DOEpatents

Fasching, George E.; Utt, Carroll E.

1982-01-01

A multiple segment three-terminal type capacitance probe with segment selection, capacitance detection and compensation circuitry and read-out control for level/density measurements in a fluidized-bed vessel is provided. The probe is driven at a high excitation frequency of up to 50 kHz to sense quadrature (capacitive) current related to probe/vessel capacitance while being relatively insensitive to the resistance current component. Compensation circuitry is provided for generating a negative current of equal magnitude to cancel out only the resistive component current. Clock-operated control circuitry separately selects the probe segments in a predetermined order for detecting and storing this capacitance measurement. The selected segment acts as a guarded electrode and is connected to the read-out circuitry while all unselected segments are connected to the probe body, which together form the probe guard electrode. The selected probe segment capacitance component signal is directed to a corresponding segment channel sample and hold circuit dedicated to that segment to store the signal derived from that segment. This provides parallel outputs for display, computer input, etc., for the detected capacitance values. The rate of segment sampling may be varied to either monitor the dynamic density profile of the bed (high sampling rate) or monitor average bed characteristics (slower sampling rate).

Tapered Optical Fiber Probe Assembled with Plasmonic Nanostructures for Surface-Enhanced Raman Scattering Application.

PubMed

Huang, Zhulin; Lei, Xing; Liu, Ye; Wang, Zhiwei; Wang, Xiujuan; Wang, Zhaoming; Mao, Qinghe; Meng, Guowen

2015-08-12

Optical fiber-Raman devices integrated with plasmonic nanostructures have promising potentials for in situ probing remote liquid samples and biological samples. In this system, the fiber probe is required to simultaneously demonstrate stable surface enhanced Raman scattering (SERS) signals and high sensitivity toward the target species. Here we demonstrate a generic approach to integrate presynthesized plasmonic nanostructures with tapered fiber probes that are prepared by a dipping-etching method, through reversed electrostatic attraction between the silane couple agent modified silica fiber probe and the nanostructures. Using this approach, both negatively and positively charged plasmonic nanostructures with various morphologies (such as Au nanosphere, Ag nanocube, Au nanorod, Au@Ag core-shell nanorod) can be stably assembled on the tapered silica fiber probes. Attributed to the electrostatic force between the plasmonic units and the fiber surface, the nanostructures do not disperse in liquid samples easily, making the relative standard deviation of SERS signals as low as 2% in analyte solution. Importantly, the detection sensitivity of the system can be optimized by adjusting the cone angle (from 3.6° to 22°) and the morphology of nanostructures assembled on the fiber. Thus, the nanostructures-sensitized optical fiber-Raman probes show great potentials in the applications of SERS-based environmental detection of liquid samples.

Situ soil sampling probe system with heated transfer line

DOEpatents

Robbat, Jr., Albert

2002-01-01

The present invention is directed both to an improved in situ penetrometer probe and to a heated, flexible transfer line. The line and probe may be implemented together in a penetrometer system in which the transfer line is used to connect the probe to a collector/analyzer at the surface. The probe comprises a heater that controls a temperature of a geologic medium surrounding the probe. At least one carrier gas port and vapor collection port are located on an external side wall of the probe. The carrier gas port provides a carrier gas into the geologic medium, and the collection port captures vapors from the geologic medium for analysis. In the transfer line, a flexible collection line that conveys a collected fluid, i.e., vapor, sample to a collector/analyzer. A flexible carrier gas line conveys a carrier gas to facilitate the collection of the sample. A system heating the collection line is also provided. Preferably the collection line is electrically conductive so that an electrical power source can generate a current through it so that the internal resistance generates heat.

Results and Conclusions from the NASA Isokinetic Total Water Content Probe 2009 IRT Test

NASA Technical Reports Server (NTRS)

Reehorst, Andrew; Brinker, David

2010-01-01

The NASA Glenn Research Center has developed and tested a Total Water Content Isokinetic Sampling Probe. Since, by its nature, it is not sensitive to cloud water particle phase nor size, it is particularly attractive to support super-cooled large droplet and high ice water content aircraft icing studies. The instrument comprises the Sampling Probe, Sample Flow Control, and Water Vapor Measurement subsystems. Results and conclusions are presented from probe tests in the NASA Glenn Icing Research Tunnel (IRT) during January and February 2009. The use of reference probe heat and the control of air pressure in the water vapor measurement subsystem are discussed. Several run-time error sources were found to produce identifiable signatures that are presented and discussed. Some of the differences between measured Isokinetic Total Water Content Probe and IRT calibration seems to be caused by tunnel humidification and moisture/ice crystal blow around. Droplet size, airspeed, and liquid water content effects also appear to be present in the IRT calibration. Based upon test results, the authors provide recommendations for future Isokinetic Total Water Content Probe development.

Enhancement of low-temperature thermometry by strong coupling

NASA Astrophysics Data System (ADS)

Correa, Luis A.; Perarnau-Llobet, Martí; Hovhannisyan, Karen V.; Hernández-Santana, Senaida; Mehboudi, Mohammad; Sanpera, Anna

2017-12-01

We consider the problem of estimating the temperature T of a very cold equilibrium sample. The temperature estimates are drawn from measurements performed on a quantum Brownian probe strongly coupled to it. We model this scenario by resorting to the canonical Caldeira-Leggett Hamiltonian and find analytically the exact stationary state of the probe for arbitrary coupling strength. In general, the probe does not reach thermal equilibrium with the sample, due to their nonperturbative interaction. We argue that this is advantageous for low-temperature thermometry, as we show in our model that (i) the thermometric precision at low T can be significantly enhanced by strengthening the probe-sampling coupling, (ii) the variance of a suitable quadrature of our Brownian thermometer can yield temperature estimates with nearly minimal statistical uncertainty, and (iii) the spectral density of the probe-sample coupling may be engineered to further improve thermometric performance. These observations may find applications in practical nanoscale thermometry at low temperatures—a regime which is particularly relevant to quantum technologies.

Apparatus for molecular weight separation

DOEpatents

Smith, Richard D.; Liu, Chuanliang

2001-01-01

The present invention relates generally to an apparatus and method for separating high molecular weight molecules from low molecular weight molecules. More specifically, the invention relates to the use of microdialysis for removal of the salt (low molecular weight molecules) from a nucleotide sample (high molecular weight molecules) for ESI-MS analysis. The dialysis or separation performance of the present invention is improved by (1) increasing dialysis temperature thereby increasing desalting efficiency and improving spectrum quality; (2) adding piperidine and imidazole to the dialysis buffer solution and reducing charge states and further increasing detection sensitivity for DNA; (3) using low concentrations (0-2.5 mM NH4OAc) of dialysis buffer and shifting the DNA negative ions to higher charge states, producing a nearly 10-fold increase in detection sensitivity and a slightly decreased desalting efficiency, (4) conducting a two-stage separation or (5) any combination of (1), (2), (3) and (4).

Quantification of in-contact probe-sample electrostatic forces with dynamic atomic force microscopy

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

Balke, Nina Wisinger; Jesse, Stephen; Carmichael, Ben D.

Here, atomic force microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe in the probe-sample junction in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can produce signals equivalent to a few pm of surface displacement. Inmore » combination with modeling, the measurements of the force were used to access the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junction can reach ca. 1 V nm –1 at a bias voltage of a few volts and is limited by non-ideality of the tip-sample contact. This field is sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids.« less

Quantification of In-Contact Probe-Sample Electrostatic Forces with Dynamic Atomic Force Microscopy.

PubMed

Balke, Nina; Jesse, Stephen; Carmichael, Ben; Okatan, M; Kravchenko, Ivan; Kalinin, Sergei; Tselev, Alexander

2016-12-13

Atomic Force Microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe in the probe-sample junction in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can produce signals equivalent to a few pm of surface displacement. In combination with modeling, the measurements of the force were used to access the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junction can reach ca. 1 V/nm at a bias voltage of a few volts and is limited by non-ideality of the tip-sample contact. This field is sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids. Copyright 2016 IOP Publishing Ltd.

Quantification of in-contact probe-sample electrostatic forces with dynamic atomic force microscopy

DOE PAGES

Balke, Nina Wisinger; Jesse, Stephen; Carmichael, Ben D.; ...

2017-01-04

Here, atomic force microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe in the probe-sample junction in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can produce signals equivalent to a few pm of surface displacement. Inmore » combination with modeling, the measurements of the force were used to access the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junction can reach ca. 1 V nm –1 at a bias voltage of a few volts and is limited by non-ideality of the tip-sample contact. This field is sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids.« less

Nuclear Quadrupole Resonance (NQR) Method and Probe for Generating RF Magnetic Fields in Different Directions to Distinguish NQR from Acoustic Ringing Induced in a Sample

DTIC Science & Technology

1997-08-01

77,719 TITLE OF THE INVENTION NUCLEAR QUADRUPOLE RESONANCE ( NQR ) METHOD AND PROBE FOR GENERATING RF MAGNETIC FIELDS IN DIFFERENT DIRECTIONS TO...DISTINGUISH NQR FROM ACOUSTIC RINGING INDUCED IN A SAMPLE BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a...nuclear quadrupole 15 resonance ( NQR ) method and probe for generating RF magnetic fields in different directions towards a sample. More specifically

Long-Term Implanted cOFM Probe Causes Minimal Tissue Reaction in the Brain

PubMed Central

Hochmeister, Sonja; Asslaber, Martin; Kroath, Thomas; Pieber, Thomas R.; Sinner, Frank

2014-01-01

This study investigated the histological tissue reaction to long-term implanted cerebral open flow microperfusion (cOFM) probes in the frontal lobe of the rat brain. Most probe-based cerebral fluid sampling techniques are limited in application time due to the formation of a glial scar that hinders substance exchange between brain tissue and the probe. A glial scar not only functions as a diffusion barrier but also alters metabolism and signaling in extracellular brain fluid. cOFM is a recently developed probe-based technique to continuously sample extracellular brain fluid with an intact blood-brain barrier. After probe implantation, a 2 week healing period is needed for blood-brain barrier reestablishment. Therefore, cOFM probes need to stay in place and functional for at least 15 days after implantation to ensure functionality. Probe design and probe materials are optimized to evoke minimal tissue reaction even after a long implantation period. Qualitative and quantitative histological tissue analysis revealed no continuous glial scar formation around the cOFM probe 30 days after implantation and only a minor tissue reaction regardless of perfusion of the probe. PMID:24621608

Using membrane composition to fine-tune the pKa of an optical liposome pH sensor.

PubMed

Clear, Kasey J; Virga, Katelyn; Gray, Lawrence; Smith, Bradley D

2016-04-14

Liposomes containing membrane-anchored pH-sensitive optical probes are valuable sensors for monitoring pH in various biomedical samples. The dynamic range of the sensor is maximized when the probe p K a is close to the expected sample pH. While some biomedical samples are close to neutral pH there are several circumstances where the pH is 1 or 2 units lower. Thus, there is a need to fine-tune the probe p K a in a predictable way. This investigation examined two lipid-conjugated optical probes, each with appended deep-red cyanine dyes containing indoline nitrogen atoms that are protonated in acid. The presence of anionic phospholipids in the liposomes stabilized the protonated probes and increased the probe p K a values by < 1 unit. The results show that rational modification of the membrane composition is a general non-covalent way to fine-tune the p K a of an optical liposome sensor for optimal pH sensing performance.

Open-target sparse sensing of biological agents using DNA microarray

PubMed Central

2011-01-01

Background Current biosensors are designed to target and react to specific nucleic acid sequences or structural epitopes. These 'target-specific' platforms require creation of new physical capture reagents when new organisms are targeted. An 'open-target' approach to DNA microarray biosensing is proposed and substantiated using laboratory generated data. The microarray consisted of 12,900 25 bp oligonucleotide capture probes derived from a statistical model trained on randomly selected genomic segments of pathogenic prokaryotic organisms. Open-target detection of organisms was accomplished using a reference library of hybridization patterns for three test organisms whose DNA sequences were not included in the design of the microarray probes. Results A multivariate mathematical model based on the partial least squares regression (PLSR) was developed to detect the presence of three test organisms in mixed samples. When all 12,900 probes were used, the model correctly detected the signature of three test organisms in all mixed samples (mean(R2)) = 0.76, CI = 0.95), with a 6% false positive rate. A sampling algorithm was then developed to sparsely sample the probe space for a minimal number of probes required to capture the hybridization imprints of the test organisms. The PLSR detection model was capable of correctly identifying the presence of the three test organisms in all mixed samples using only 47 probes (mean(R2)) = 0.77, CI = 0.95) with nearly 100% specificity. Conclusions We conceived an 'open-target' approach to biosensing, and hypothesized that a relatively small, non-specifically designed, DNA microarray is capable of identifying the presence of multiple organisms in mixed samples. Coupled with a mathematical model applied to laboratory generated data, and sparse sampling of capture probes, the prototype microarray platform was able to capture the signature of each organism in all mixed samples with high sensitivity and specificity. It was demonstrated that this new approach to biosensing closely follows the principles of sparse sensing. PMID:21801424

Population Pharmacokinetic Modeling of the Unbound Levofloxacin Concentrations in Rat Plasma and Prostate Tissue Measured by Microdialysis

PubMed Central

Hurtado, Felipe K.; Weber, Benjamin; Derendorf, Hartmut; Hochhaus, Guenther

2014-01-01

Levofloxacin is a broad-spectrum fluoroquinolone used in the treatment of both acute and chronic bacterial prostatitis. Currently, the treatment of bacterial prostatitis is still difficult, especially due to the poor distribution of many antimicrobials into the prostate, thus preventing the drug to reach effective interstitial concentrations at the infection site. Newer fluoroquinolones show a greater penetration into the prostate. In the present study, we compared the unbound levofloxacin prostate concentrations measured by microdialysis to those in plasma after a 7-mg/kg intravenous bolus dose to Wistar rats. Plasma and dialysate samples were analyzed using a validated high-pressure liquid chromatography-fluorescence method. Both noncompartmental analysis (NCA) and population-based compartmental modeling (NONMEM 6) were performed. Unbound prostate tissue concentrations represented 78% of unbound plasma levels over a period of 12 h by comparing the extent of exposure (unbound AUC0–∞) of 6.4 and 4.8 h·μg/ml in plasma and tissue, respectively. A three-compartment model with simultaneous passive diffusion and saturable distribution kinetics from the prostate to the central compartment gave the best results in terms of curve fitting, precision of parameter estimates, and model stability. The following parameter values were estimated by the population model: V1 (0.38 liter; where V1 represents the volume of the central compartment), CL (0.22 liter/h), k12 (2.27 h−1), k21 (1.44 h−1), k13 (0.69 h−1), Vmax (7.19 μg/h), kM (0.35 μg/ml), V3/fuprostate (0.05 liter; where fuprostate represents the fraction unbound in the prostate), and k31 (3.67 h−1). The interindividual variability values for V1, CL, Vmax, and kM were 21, 37, 42, and 76%, respectively. Our results suggest that levofloxacin is likely to be substrate for efflux transporters in the prostate. PMID:24217697

Neural Stem Cell-Based Anticancer Gene Therapy: A First-in-Human Study in Recurrent High-Grade Glioma Patients.

PubMed

Portnow, Jana; Synold, Timothy W; Badie, Behnam; Tirughana, Revathiswari; Lacey, Simon F; D'Apuzzo, Massimo; Metz, Marianne Z; Najbauer, Joseph; Bedell, Victoria; Vo, Tien; Gutova, Margarita; Frankel, Paul; Chen, Mike; Aboody, Karen S

2017-06-15

Purpose: Human neural stem cells (NSC) are inherently tumor tropic, making them attractive drug delivery vehicles. Toward this goal, we retrovirally transduced an immortalized, clonal NSC line to stably express cytosine deaminase (HB1.F3.CD.C21; CD-NSCs), which converts the prodrug 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU). Experimental Design: Recurrent high-grade glioma patients underwent intracranial administration of CD-NSCs during tumor resection or biopsy. Four days later, patients began taking oral 5-FC every 6 hours for 7 days. Study treatment was given only once. A standard 3 + 3 dose escalation schema was used to increase doses of CD-NSCs from 1 × 10 7 to 5 × 10 7 and 5-FC from 75 to 150 mg/kg/day. Intracerebral microdialysis was performed to measure brain levels of 5-FC and 5-FU. Serial blood samples were obtained to assess systemic drug concentrations as well as to perform immunologic correlative studies. Results: Fifteen patients underwent study treatment. We saw no dose-limiting toxicity (DLT) due to the CD-NSCs. There was 1 DLT (grade 3 transaminitis) possibly related to 5-FC. We did not see development of anti-CD-NSC antibodies and did not detect CD-NSCs or replication-competent retrovirus in the systemic circulation. Intracerebral microdialysis revealed that CD-NSCs produced 5-FU locally in the brain in a 5-FC dose-dependent manner. Autopsy data indicate that CD-NSCs migrated to distant tumor sites and were nontumorigenic. Conclusions: Collectively, our results from this first-in-human study demonstrate initial safety and proof of concept regarding the ability of NSCs to target brain tumors and locally produce chemotherapy. Clin Cancer Res; 23(12); 2951-60. ©2016 AACR . ©2016 American Association for Cancer Research.

Deriving Therapies for Children with Primary CNS Tumors Using Pharmacokinetic Modeling and Simulation of Cerebral Microdialysis Data

PubMed Central

Jacus, M.O.; Throm, S.L.; Turner, D.C.; Patel, Y.T.; Freeman, B.B.; Morfouace, M.; Boulos, N.; Stewart, C. F.

2014-01-01

The treatment of children with primary central nervous system (CNS) tumors continues to be a challenge despite recent advances in technology and diagnostics. In this overview, we describe our approach for identifying and evaluating active anticancer drugs through a process that enables rational translation from the lab to the clinic. The preclinical approach we discuss uses tumor subgroup-specific models of pediatric CNS tumors, cerebral microdialysis sampling of tumor extracellular fluid (tECF), and pharmacokinetic modeling and simulation to overcome challenges that currently hinder researchers in this field. This approach involves performing extensive systemic (plasma) and target site (CNS tumor) pharmacokinetic studies. Pharmacokinetic modeling and simulation of the data derived from these studies are then used to inform future decisions regarding drug administration, including dosage and schedule. Here, we also present how our approach was used to examine two FDA approved drugs, simvastatin and pemetrexed, as candidates for new therapies for pediatric CNS tumors. We determined that due to unfavorable pharmacokinetic characteristics and insufficient concentrations in tumor tissue in a mouse model of ependymoma, simvastatin would not be efficacious in further preclinical trials. In contrast to simvastatin, pemetrexed was advanced to preclinical efficacy studies after our studies determined that plasma exposures were similar to those in humans treated at similar tolerable dosages and adequate unbound concentrations were found in tumor tissue of medulloblastoma-bearing mice. Generally speaking, the high clinical failure rates for CNS drug candidates can be partially explained by the fact that therapies are often moved into clinical trials without extensive and rational preclinical studies to optimize the transition. Our approach addresses this limitation by using pharmacokinetic and pharmacodynamic modeling of data generated from appropriate in vivo models to support the rational testing and usage of innovative therapies in children with CNS tumors. PMID:24269626

Crystallization and preliminary X-ray analysis of a novel thermoalkalophilic poly(3-hydroxybutyrate) depolymerase (PhaZ7) from Paucimonas lemoignei

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

Kapetaniou, Evangelia G.; Braaz, Reinhard; Jendrossek, Dieter

2005-05-01

A novel thermoalkalophilic depolymerase, PhaZ7, from P. lemoignei was crystallized by the microdialysis technique. Crystals belong to space group C2 and diffract to 2.75 Å resolution at a synchrotron source. Polyhydroxyalkanoates (PHA) are biodegradable polyesters that have attracted commercial and academic interest as environmentally friendly materials. A number of enzymes are able to degrade polyhydroxyalkanoates to water-soluble products. PhaZ7 poly(3-hydroxybutyrate) (PHB) depolymerase (EC 3.1.1.75), a 342-amino-acid hydrolase from the PHA-degrading bacterium Paucimonas lemoignei, has been found to possess substrate specificity for amorphous PHA. PhaZ7 was crystallized by the microdialysis method. Thin rod-like crystals were grown in low ionic strength solutionmore » and found to belong to the monoclinic space group C2, with unit-cell parameters a = 225.8, b = 46.5, c = 171.3, β = 128.9°. A complete data set was collected to 2.75 Å resolution at 100 K using synchrotron radiation.« less

Effects of aniracetam on extracellular levels of transmitter amino acids in the hippocampus of the conscious gerbils: an intracranial microdialysis study.

PubMed

Yu, Siming; Cai, Jingxia

2003-03-27

The effects of aniracetam on extracellular amino acid levels in the hippocampus of conscious gerbils, with or without transient cerebral ischemia/reperfusion, were measured by microdialysis and reverse phase-high performance liquid chromatography. Increased extracellular levels of aspartate and glutamate that were observed in the hippocampus of conscious gerbils during transient global forebrain ischemia were reversed by aniracetam. In contrast, the level of extracellular gamma-aminobutyric acid was increased, while taurine was maintained at a higher level than other amino acids by administration of aniracetam (100 mg/kg, p.o.) 60 min before ischemia. Further, in contrast to ischemic animals, administration of aniracetam (100 mg/kg, p.o.) enhanced the release of glutamate and aspartate in the normal gerbil hippocampus. The results suggest that these effects might be due to a partial calcium agonist activity of aniracetam, and that the effects of aniracetam on amino acid levels might be a mechanism of protection against delayed neuronal death in the ischemic hippocampus, thereby improving memory dysfunction induced by ischemia/reperfusion.

Extracellular levels of amino acids and choline in human high grade gliomas: an intraoperative microdialysis study.

PubMed

Bianchi, L; De Micheli, E; Bricolo, A; Ballini, C; Fattori, M; Venturi, C; Pedata, F; Tipton, K F; Della Corte, L

2004-01-01

The concentrations of endogenous amino acids and choline in the extracellular fluid of human cerebral gliomas have been measured, for the first time, by in vivo microdialysis. Glioblastoma growth was associated with increased concentrations of choline, GABA, isoleucine, leucine, lysine, phenylalanine, taurine, tyrosine, and valine. There was no difference between grade III and grade IV tumors in the concentrations of phenylalanine, isoleucine, tyrosine, valine, and lysine, whereas the concentrations of choline, aspartate, taurine, GABA, leucine, and glutamate were significantly different in the two tumor-grade subgroups. In contrast to the other compounds, the concentration of glutamate was decreased in glioma. The parenchyma adjacent to the tumor showed significant changes only in the extracellular concentration of glutamate, isoleucine, and valine. The concentrations of choline and the amino acids, glutamate, leucine, taurine, and tyrosine showed significant positive correlations with the degree of cell proliferation. Epilepsy, which is relatively common in subjects with gliomas, was shown to be a significant confounding variable when the extracellular concentrations of aspartate, glutamate and GABA were considered.

In vivo studies on insulin permeability of an immunoisolation device intended for islet transplantation using the microdialysis technique.

PubMed

Rafael, E; Wernerson, A; Arner, P; Tibell, A

1999-01-01

In this study, insulin was injected into Theracyte immunoisolation devices to analyze changes in the permeability of the device over time after implantation. The recovery of insulin was studied after subcutaneous implantation of the devices in rats, using the microdialysis technique. The area under the insulin concentration vs. time curves (AUC) after insulin injection in devices implanted 1 day previously did not differ significantly from the AUC after subcutaneous injection. At 1, 2 and 4 weeks after implantation, the recovery of insulin was significantly reduced, but at 3 months, the AUC was not significantly different from that in the control group. Histological examination showed that the number of vascular profiles within 15 microm of the device were significantly higher at 2, 4 weeks and 3 months after transplantation when compared to numbers at 1 week. The design of the device allows transplantation of cells at a chosen time point after its implantation. Delayed filling of the device would allow neovascularization of the device surface before graft implantation and we suggest that such a schedule might improve function of the encapsulated graft.

Role of inhibitory amino acids in control of hypoglossal motor outflow to genioglossus muscle in naturally sleeping rats.

PubMed

Morrison, Janna L; Sood, Sandeep; Liu, Hattie; Park, Eileen; Liu, Xia; Nolan, Philip; Horner, Richard L

2003-11-01

The hypoglossal motor nucleus innervates the genioglossus (GG) muscle of the tongue, a muscle that helps maintain an open airway for effective breathing. Rapid-eye-movement (REM) sleep, however, recruits powerful neural mechanisms that can abolish GG activity even during strong reflex stimulation such as by hypercapnia, effects that can predispose to sleep-related breathing problems in humans. We have developed an animal model to chronically manipulate neurotransmission at the hypoglossal motor nucleus using in vivo microdialysis in freely behaving rats. This study tests the hypothesis that glycine receptor antagonism at the hypoglossal motor nucleus, either alone or in combination with GABAA receptor antagonism, will prevent suppression of GG activity in natural REM sleep during room air and CO2-stimulated breathing. Rats were implanted with electroencephalogram and neck muscle electrodes to record sleep-wake states, and GG and diaphragm electrodes for respiratory muscle recording. Microdialysis probes were implanted into the hypoglossal motor nucleus for perfusion of artificial cerebrospinal fluid (ACSF) and strychnine (glycine receptor antagonist, 0.1 mM) either alone or combined with bicuculline (GABAA antagonist, 0.1 mM) during room air and CO2-stimulated breathing. Compared to ACSF controls, glycine receptor antagonism at the hypoglossal motor nucleus increased respiratory-related GG activity in room air (P = 0.010) but not hypercapnia (P = 0.221). This stimulating effect of strychnine in room air did not depend on the prevailing sleep-wake state (P = 0.625) indicating removal of a non-specific background inhibitory glycinergic tone. Nevertheless, GG activity remained minimal in those REM sleep periods without phasic twitches in GG muscle, with GG suppression from non-REM (NREM) sleep being > 85 % whether ACSF or strychnine was at the hypoglossal motor nucleus or the inspired gas was room air or 7 % CO2. While GG activity was minimal in these REM sleep periods, there was a small but measurable increase in GG activity after strychnine (P < 0.05). GG activity was also minimal, and effectively abolished, in the REM sleep periods without GG twitches with combined glycine and GABAA receptor antagonism at the hypoglossal motor nucleus. We conclude that these data in freely behaving rats confirm that inhibitory glycine and GABAA receptor mechanisms are present at the hypoglossal motor nucleus and are tonically active, but that such inhibitory mechanisms make only a small contribution to the marked suppression of GG activity and reflex responses observed in periods of natural REM sleep.

Assessment of the LV-S2 & LV-S3 Stack Sampling Probe Locations for Compliance with ANSI/HPS N13.1-1999

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

Glissmeyer, John A.; Antonio, Ernest J.; Flaherty, Julia E.

2014-09-30

This document reports on a series of tests conducted to assess the proposed air sampling locations for the Hanford Tank Waste Treatment and Immobilization Plant (WTP) Group 1-2A exhaust stacks with respect to the applicable criteria regarding the placement of an air sampling probe. The LV-C2, LV-S2, and LV-S3 exhaust stacks were tested together as a group (Test Group 1-2A). This report only covers the results of LV-S2 and LV-S3; LV-C2 will be reported on separately. Federal regulations1 require that a sampling probe be located in the exhaust stack according to the criteria established by the American National Standards Institute/Healthmore » Physics Society (ANSI/HPS) N13.1-1999, Sampling and Monitoring Releases of Airborne Radioactive Substances from the Stack and Ducts of Nuclear Facilities. 2 These criteria address the capability of the sampling probe to extract a sample that represents the effluent stream.« less

Regional relation between skin blood flow and sweating to passive heating and local administration of acetylcholine in young, healthy humans.

PubMed

Smith, Caroline J; Kenney, W Larry; Alexander, Lacy M

2013-04-01

Regional variation in sweating over the human body is widely recognized yet variation in vasomotor responses and mechanisms causing this variation remain unclear. This study aimed to explore the relation between regional sweating rates (RSR) and skin blood flow (SkBF) responses to thermal and pharmacological stimuli in young, healthy subjects. In nine subjects (23 ± 3 yr), intradermal microdialysis (MD) probes were inserted into the ventral forearm, abdomen, thigh, and lower back and perfused with lactated Ringer solution. RSR over each MD membrane were measured using ventilated capsules with a laser Doppler probe housed in each capsule for measurement of red cell flux (laser Doppler flux, LDF) as an index of SkBF. Subjects completed a whole body heating protocol to 1°C rise in oral temperature and an acetylcholine dose response (ACh 1 × 10(-7)-0.1 M; mean skin temperature 34°C). Maximal LDF were obtained at the end of both protocols (50 mM sodium nitroprusside).During heating RSR varied among sites (P < 0.0001) and was greater on the back versus other sites (P < 0.05), but LDF was similar between sites (P = 0.343). RSR and SkBF showed a strong relation during initial (arm: r = 0.77 ± 0.09, thigh: r = 0.81 ± 0.08, abdomen: r = 0.89 ± 0.04, back: r = 0.86 ± 0.04) but not latter stages of heating. No differences in RSR (P = 0.160) or SkBF (LDF, P = 0.841) were observed between sites during ACh perfusion. Taken together, these data suggest that increases in SkBF are necessary to initiate and increase sweating, but further rises in RSR are not fully dependent on SkBF in a dose-response manner. Furthermore, RSR cannot be explained by cholinergic sensitivity or variation in SkBF.

NR2A contributes to genesis and propagation of cortical spreading depression in rats.

PubMed

Bu, Fan; Du, Ruoxing; Li, Yi; Quinn, John P; Wang, Minyan

2016-03-22

Cortical spreading depression (CSD) is a transient propagating excitation of synaptic activity followed by depression, which is implicated in migraine. Increasing evidence points to an essential role of NR2A-containing NMDA receptors in CSD propagation in vitro; however, whether these receptors mediate CSD genesis in vivo requires clarification and the role of NR2A on CSD propagation is still under debate. Using in vivo CSD in rats with electrophysiology and in vitro CSD in chick retina with intrinsic optical imaging, we addressed the role of NR2A in CSD. We demonstrated that NVP-AAM077, a potent antagonist for NR2A-containing receptors, perfused through microdialysis probes, markedly reduced cortex susceptibility to CSD, but also reduced magnitude of CSD genesis in rats. Additionally, NVP-AAM077 at 0.3 nmol perfused into the contralateral ventricle, considerably suppressed the magnitude of CSD propagation wave and propagation rate in rats. This reduction in CSD propagation was also observed with TCN-201, a negative allosteric modulator selective for NR2A, at 3 μM, in the chick retina. Our data provides strong evidence that NR2A subunit contributes to CSD genesis and propagation, suggesting drugs selectively antagonizing NR2A-containing receptors might constitute a highly specific strategy treating CSD associated migraine with a likely better safety profile.

NR2A contributes to genesis and propagation of cortical spreading depression in rats

PubMed Central

Bu, Fan; Du, Ruoxing; Li, Yi; Quinn, John P; Wang, Minyan

2016-01-01

Cortical spreading depression (CSD) is a transient propagating excitation of synaptic activity followed by depression, which is implicated in migraine. Increasing evidence points to an essential role of NR2A-containing NMDA receptors in CSD propagation in vitro; however, whether these receptors mediate CSD genesis in vivo requires clarification and the role of NR2A on CSD propagation is still under debate. Using in vivo CSD in rats with electrophysiology and in vitro CSD in chick retina with intrinsic optical imaging, we addressed the role of NR2A in CSD. We demonstrated that NVP-AAM077, a potent antagonist for NR2A-containing receptors, perfused through microdialysis probes, markedly reduced cortex susceptibility to CSD, but also reduced magnitude of CSD genesis in rats. Additionally, NVP-AAM077 at 0.3 nmol perfused into the contralateral ventricle, considerably suppressed the magnitude of CSD propagation wave and propagation rate in rats. This reduction in CSD propagation was also observed with TCN-201, a negative allosteric modulator selective for NR2A, at 3 μM, in the chick retina. Our data provides strong evidence that NR2A subunit contributes to CSD genesis and propagation, suggesting drugs selectively antagonizing NR2A-containing receptors might constitute a highly specific strategy treating CSD associated migraine with a likely better safety profile. PMID:27001011

Longitudinal studies on the microcirculation around the TheraCyte immunoisolation device, using the laser Doppler technique.

PubMed

Rafael, E; Gazelius, B; Wu, G S; Tibell, A

2000-01-01

Encapsulation of cellular grafts in an immunoisolation membrane device may make it possible to perform transplantation without having to give immunosuppressive drugs. A common problem is the development of an avascular fibrotic zone around the implants, leading to impaired graft survival. The TheraCyte macroencapsulation device has therefore been designed to facilitate neovascularization of the device's surface. In this study, we evaluated the microcirculation around empty TheraCyte devices implanted SC in rats at various times after implantation, using a laser Doppler probe introduced via the device port. Studies were performed on day 1 or at 1, 2, and 4 weeks or at 2, 3, and 12 months after implantation. The mean flow was 158+/-42, 148+/-50, 133+/-28, 72+/-17, 138+/-41, 165+/-43, and 160+/-29 perfusion units (PU), respectively. Thus, the microcirculation around the device was significantly reduced at 4 weeks after implantation (p < 0.01) while, from 2 months onwards the circulation had improved and did not differ significantly from that on day 1. The present study shows time-related changes in the microcirculatory flow around TheraCyte macroencapsulation devices that agree with our previous microdialysis studies on in vivo exchange of insulin and glucose between the device and the circulation. Laser Doppler flowmetry seems to provide a reliable technique for screening blood perfusion around macroencapsulation devices.

The activation of metabotropic glutamate 5 receptors in the rat ventral tegmental area increases dopamine extracellular levels.

PubMed

Ferrada, Carla; Sotomayor-Zárate, Ramón; Abarca, Jorge; Gysling, Katia

2017-01-01

The mesocorticolimbic circuit projects to the prefrontal cortex, hippocampus, amygdala, and nucleus accumbens, among others, and it originates in the dopaminergic neurons of the ventral tegmental area (VTA). The VTA receives glutamatergic inputs from the prefrontal cortex and several subcortical regions. The glutamate released activates dopaminergic neurons and its action depends on the activation of ionotropic and metabotropic glutamate receptors. VTA dopaminergic neurons release dopamine (DA) from axon terminals in the innervated regions and somatodendritically in the VTA itself. DA release in the VTA is directly correlated with the activity of dopaminergic neurons. We hypothesized that metabotropic glutamate 5 receptors (mGlu5) directly regulate the activity of VTA dopaminergic neurons. To test this hypothesis, the extracellular levels of VTA DA and glutamate were studied by in-vivo microdialysis after an intra-VTA perfusion of (R,S)-2-chloro-5-hydroxyphenylglycine (CHPG), selective mGlu5 agonist. We observed that CHPG induced a significant increase in VTA DA and glutamate extracellular levels. To determine whether the effect of CHPG on DA levels is because of the increase in glutamate release, we perfused kynurenic acid, an ionotropic glutamate receptor antagonist, through the probe. Our results showed that kynurenic acid did not block the ability of CHPG to cause DA release. Thus, our results suggest that CHPG acts directly on mGlu5 in dopaminergic neurons to induce the release of DA.

Extracellular cyclic AMP-adenosine pathway in isolated adipocytes and adipose tissue.

PubMed

Strouch, Marci B; Jackson, Edwin K; Mi, Zaichuan; Metes, Nicole A; Carey, Gale B

2005-06-01

Our goal was to evaluate the presence and lipolytic impact of the extracellular cyclic adenosine monophosphate (AMP)-adenosine pathway in adipose tissue. Sixteen miniature Yucatan swine (Sus scrofa) were used for these in vitro and in situ experiments. Four microdialysis probes were implanted into subcutaneous adipose tissue and perfused at 2 microL/min with Ringer's solution containing no addition, varying levels of cyclic AMP, 10 microM isoproterenol, or 10 microM isoproterenol plus 1 mM alpha,beta-methylene adenosine 5'-diphosphate (AMPCP), a 5'-nucleotidase inhibitor. Dialysate was assayed for AMP, adenosine, inosine, hypoxanthine, and glycerol. Freshly isolated adipocytes were incubated with buffer, 1 microM isoproterenol, or 1 microM isoproterenol plus 0.1 mM AMPCP, and extracellular levels of AMP, adenosine, inosine, hypoxanthine, and glycerol were measured. Perfusion of adipose tissue with exogenous cyclic AMP caused a significant increase in AMP and adenosine appearance. Perfusion with AMPCP, in the presence or absence of isoproterenol, significantly increased the levels of AMP and glycerol, whereas it significantly reduced the level of adenosine and its metabolites. However, the AMPCP-provoked increase in lipolysis observed in situ and in vitro was not temporally associated with a decrease in adenosine. These data suggest the existence of a cyclic AMP-adenosine pathway in adipocytes and adipose tissue. The role of this pathway in the regulation of lipolysis remains to be clarified.

Modulation of genioglossus muscle activity across sleep-wake states by histamine at the hypoglossal motor pool.

PubMed

Bastedo, Timothy; Chan, Erin; Park, Eileen; Liu, Hattie; Horner, Richard L

2009-10-01

Histamine neurons comprise a major component of the aminergic arousal system and significantly influence sleep-wake states, with antihistamines widely used as sedative hypnotics. Unlike the serotonergic and noradrenergic components of this arousal system, however, the role of histamine in the central control of respiratory motor activity has not been determined. The aims of this study were to characterize the effects of histamine receptor agonists and antagonists at the hypoglossal motor pool on genioglossus muscle activity across sleep and awake states, and also determine if histamine contributes an endogenous excitatory drive to modulate hypoglossal motor outflow to genioglossus muscle. Thirty-three rats were implanted with electroencephalogram and neck electrodes to record sleep-wake states, and genioglossus and diaphragm electrodes for respiratory muscle recordings. Microdialysis probes were inserted into the hypoglossal motor nucleus. Histamine at the hypoglossal motor nucleus significantly increased tonic genioglossus muscle activity in wakefulness, non-REM sleep and REM sleep. The activating effects of histamine on genioglossus muscle activity also occurred with a histamine type-1 (H1) but not H2 receptor agonist. However, H1 receptor antagonism at the hypoglossal motor nucleus did not decrease genioglossus muscle activity in wakefulness or sleep. The results suggest that histamine at the hypoglossal motor pool increases genioglossus muscle activity in freely behaving rats in wakefulness, non-REM, and REM sleep via an H1 receptor mechanism.

Probe for high resolution NMR with sample reorientation

DOEpatents

Pines, Alexander; Samoson, Ago

1990-01-01

An improved NMR probe and method are described which substantially improve the resolution of NMR measurements made on powdered or amorphous or otherwise orientationally disordered samples. The apparatus mechanically varies the orientation of the sample such that the time average of two or more sets of spherical harmonic functions are zero.

Comparing Cognitive Interviewing and Online Probing: Do They Find Similar Results?

ERIC Educational Resources Information Center

Meitinger, Katharina; Behr, Dorothée

2016-01-01

This study compares the application of probing techniques in cognitive interviewing (CI) and online probing (OP). Even though the probing is similar, the methods differ regarding typical mode setting, sample size, level of interactivity, and goals. We analyzed probing answers to the International Social Survey Programme item battery on specific…

Modulated microwave microscopy and probes used therewith

DOEpatents

Lai, Keji; Kelly, Michael; Shen, Zhi-Xun

2012-09-11

A microwave microscope including a probe tip electrode vertically positionable over a sample and projecting downwardly from the end of a cantilever. A transmission line connecting the tip electrode to the electronic control system extends along the cantilever and is separated from a ground plane at the bottom of the cantilever by a dielectric layer. The probe tip may be vertically tapped near or at the sample surface at a low frequency and the microwave signal reflected from the tip/sample interaction is demodulated at the low frequency. Alternatively, a low-frequency electrical signal is also a non-linear electrical element associated with the probe tip to non-linearly interact with the applied microwave signal and the reflected non-linear microwave signal is detected at the low frequency. The non-linear element may be semiconductor junction formed near the apex of the probe tip or be an FET formed at the base of a semiconducting tip.

Design of planar microcoil-based NMR probe ensuring high SNR

NASA Astrophysics Data System (ADS)

Ali, Zishan; Poenar, D. P.; Aditya, Sheel

2017-09-01

A microNMR probe for ex vivo applications may consist of at least one microcoil, which can be used as the oscillating magnetic field (MF) generator as well as receiver coil, and a sample holder, with a volume in the range of nanoliters to micro-liters, placed near the microcoil. The Signal-to-Noise ratio (SNR) of such a probe is, however, dependent not only on its design but also on the measurement setup, and the measured sample. This paper introduces a performance factor P independent of both the proton spin density in the sample and the external DC magnetic field, and which can thus assess the performance of the probe alone. First, two of the components of the P factor (inhomogeneity factor K and filling factor η ) are defined and an approach to calculate their values for different probe variants from electromagnetic simulations is devised. A criterion based on dominant component of the magnetic field is then formulated to help designers optimize the sample volume which also affects the performance of the probe, in order to obtain the best SNR for a given planar microcoil. Finally, the P factor values are compared between different planar microcoils with different number of turns and conductor aspect ratios, and planar microcoils are also compared with conventional solenoids. These comparisons highlight which microcoil geometry-sample volume combination will ensure a high SNR under any external setup.

A broad range assay for rapid detection and etiologic characterization of bacterial meningitis: performance testing in samples from sub-Sahara.

PubMed

Won, Helen; Yang, Samuel; Gaydos, Charlotte; Hardick, Justin; Ramachandran, Padmini; Hsieh, Yu-Hsiang; Kecojevic, Alexander; Njanpop-Lafourcade, Berthe-Marie; Mueller, Judith E; Tameklo, Tsidi Agbeko; Badziklou, Kossi; Gessner, Bradford D; Rothman, Richard E

2012-09-01

This study aimed to conduct a pilot evaluation of broad-based multiprobe polymerase chain reaction (PCR) in clinical cerebrospinal fluid (CSF) samples compared to local conventional PCR/culture methods used for bacterial meningitis surveillance. A previously described PCR consisting of initial broad-based detection of Eubacteriales by a universal probe, followed by Gram typing, and pathogen-specific probes was designed targeting variable regions of the 16S rRNA gene. The diagnostic performance of the 16S rRNA assay in "127 CSF samples was evaluated in samples from patients from Togo, Africa, by comparison to conventional PCR/culture methods. Our probes detected Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae. Uniprobe sensitivity and specificity versus conventional PCR were 100% and 54.6%, respectively. Sensitivity and specificity of uniprobe versus culture methods were 96.5% and 52.5%, respectively. Gram-typing probes correctly typed 98.8% (82/83) and pathogen-specific probes identified 96.4% (80/83) of the positives. This broad-based PCR algorithm successfully detected and provided species level information for multiple bacterial meningitis agents in clinical samples. Copyright © 2012 Elsevier Inc. All rights reserved.

A broad range assay for rapid detection and etiologic characterization of bacterial meningitis: performance testing in samples from sub-Sahara☆, ☆☆,★

PubMed Central

Won, Helen; Yang, Samuel; Gaydos, Charlotte; Hardick, Justin; Ramachandran, Padmini; Hsieh, Yu-Hsiang; Kecojevic, Alexander; Njanpop-Lafourcade, Berthe-Marie; Mueller, Judith E.; Tameklo, Tsidi Agbeko; Badziklou, Kossi; Gessner, Bradford D.; Rothman, Richard E.

2012-01-01

This study aimed to conduct a pilot evaluation of broad-based multiprobe polymerase chain reaction (PCR) in clinical cerebrospinal fluid (CSF) samples compared to local conventional PCR/culture methods used for bacterial meningitis surveillance. A previously described PCR consisting of initial broad-based detection of Eubacteriales by a universal probe, followed by Gram typing, and pathogen-specific probes was designed targeting variable regions of the 16S rRNA gene. The diagnostic performance of the 16S rRNA assay in “”127 CSF samples was evaluated in samples from patients from Togo, Africa, by comparison to conventional PCR/culture methods. Our probes detected Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae. Uniprobe sensitivity and specificity versus conventional PCR were 100% and 54.6%, respectively. Sensitivity and specificity of uniprobe versus culture methods were 96.5% and 52.5%, respectively. Gram-typing probes correctly typed 98.8% (82/83) and pathogen-specific probes identified 96.4% (80/83) of the positives. This broad-based PCR algorithm successfully detected and provided species level information for multiple bacterial meningitis agents in clinical samples. PMID:22809694

Rapid detection of Listeria monocytogenes in foods, by a combination of PCR and DNA probe.

PubMed

Ingianni, A; Floris, M; Palomba, P; Madeddu, M A; Quartuccio, M; Pompei, R

2001-10-01

Listeria monocytogenes is a frequent contaminant of water and foods. Its rapid detection is needed before some foods can be prepared for marketing. In this work L. monocytogenes has been searched for in foods, by a combination of polymerase chain reaction (PCR) and a DNA probe. Both PCR and the probe were prepared for recognizing a specific region of the internalin gene, which is responsible for the production of one of the most important pathogenic factors of Listeria. The combined use of PCR and the DNA probe was used for the detection of L. monocytogenes in over 180 environmental and food samples. Several detection methods were compared in this study, namely conventional culture methods; direct PCR; PCR after an enrichment step; a DNA probe alone; a DNA probe after enrichment and another commercially available gene-probe. Finally PCR and the DNA probe were used in series on all the samples collected. When the DNA probe was associated with the PCR, specific and accurate detection of listeria in the samples could be obtained in about a working-day. The present molecular method showed some advantages in terms of rapidity and specificity in comparison to the other aforementioned tests. In addition, it resulted as being easy to handle, even for non-specialized personnel in small diagnostic microbiology laboratories. Copyright 2001 Academic Press.

Spatial-scanning hyperspectral imaging probe for bio-imaging applications

NASA Astrophysics Data System (ADS)

Lim, Hoong-Ta; Murukeshan, Vadakke Matham

2016-03-01

The three common methods to perform hyperspectral imaging are the spatial-scanning, spectral-scanning, and snapshot methods. However, only the spectral-scanning and snapshot methods have been configured to a hyperspectral imaging probe as of today. This paper presents a spatial-scanning (pushbroom) hyperspectral imaging probe, which is realized by integrating a pushbroom hyperspectral imager with an imaging probe. The proposed hyperspectral imaging probe can also function as an endoscopic probe by integrating a custom fabricated image fiber bundle unit. The imaging probe is configured by incorporating a gradient-index lens at the end face of an image fiber bundle that consists of about 50 000 individual fiberlets. The necessary simulations, methodology, and detailed instrumentation aspects that are carried out are explained followed by assessing the developed probe's performance. Resolution test targets such as United States Air Force chart as well as bio-samples such as chicken breast tissue with blood clot are used as test samples for resolution analysis and for performance validation. This system is built on a pushbroom hyperspectral imaging system with a video camera and has the advantage of acquiring information from a large number of spectral bands with selectable region of interest. The advantages of this spatial-scanning hyperspectral imaging probe can be extended to test samples or tissues residing in regions that are difficult to access with potential diagnostic bio-imaging applications.

New Insights on Different Response of MDMA-Elicited Serotonin Syndrome to Systemic and Intracranial Administrations in the Rat Brain

PubMed Central

Shokry, Ibrahim M.; Callanan, John J.; Sousa, John; Tao, Rui

2016-01-01

In spite of the fact that systemic administration of MDMA elicits serotonin syndrome, direct intracranial administration fails to reproduce the effect. To reconcile these findings, it has been suggested that the cause of serotonin syndrome is attributed mainly to MDMA hepatic metabolites, and less likely to MDMA itself. Recently, however, this explanation has been challenged, and alternative hypotheses need to be explored. Here, we tested the hypothesis that serotonin syndrome is the result of excessive 5HT simultaneously in many brain areas, while MDMA administered intracranially fails to cause serotonin syndrome because it produces only a localized effect at the delivery site and not to other parts of the brain. This hypothesis was examined using adult male Sprague Dawley rats by comparing 5HT responses in the right and left hemispheric frontal cortices, right and left hemispheric diencephalons, and medullar raphe nucleus. Occurrence of serotonin syndrome was confirmed by measuring change in body temperature. Administration routes included intraperitoneal (IP), intracerebroventricular (ICV) and reverse microdialysis. First, we found that IP administration caused excessive 5HT in all five sites investigated and induced hypothermia, suggesting the development of the serotonin syndrome. In contrast, ICV and reverse microdialysis caused excessive 5HT only in regions of delivery sites without changes in body-core temperature, suggesting the absence of the syndrome. Next, chemical dyes were used to trace differences in distribution and diffusion patterns between administration routes. After systemic administration, the dyes were found to be evenly distributed in the brain. However, the dyes administered through ICV or reverse microdialysis injection still remained in the delivery sites, poorly diffusing to the brain. In conclusion, intracranial MDMA administration in one area has no or little effect on other areas, which must be considered a plausible reason for the difference in MDMA-elicited serotonin syndrome between systemic and intracranial administrations. PMID:27192423

New Insights on Different Response of MDMA-Elicited Serotonin Syndrome to Systemic and Intracranial Administrations in the Rat Brain.

PubMed

Shokry, Ibrahim M; Callanan, John J; Sousa, John; Tao, Rui

2016-01-01

In spite of the fact that systemic administration of MDMA elicits serotonin syndrome, direct intracranial administration fails to reproduce the effect. To reconcile these findings, it has been suggested that the cause of serotonin syndrome is attributed mainly to MDMA hepatic metabolites, and less likely to MDMA itself. Recently, however, this explanation has been challenged, and alternative hypotheses need to be explored. Here, we tested the hypothesis that serotonin syndrome is the result of excessive 5HT simultaneously in many brain areas, while MDMA administered intracranially fails to cause serotonin syndrome because it produces only a localized effect at the delivery site and not to other parts of the brain. This hypothesis was examined using adult male Sprague Dawley rats by comparing 5HT responses in the right and left hemispheric frontal cortices, right and left hemispheric diencephalons, and medullar raphe nucleus. Occurrence of serotonin syndrome was confirmed by measuring change in body temperature. Administration routes included intraperitoneal (IP), intracerebroventricular (ICV) and reverse microdialysis. First, we found that IP administration caused excessive 5HT in all five sites investigated and induced hypothermia, suggesting the development of the serotonin syndrome. In contrast, ICV and reverse microdialysis caused excessive 5HT only in regions of delivery sites without changes in body-core temperature, suggesting the absence of the syndrome. Next, chemical dyes were used to trace differences in distribution and diffusion patterns between administration routes. After systemic administration, the dyes were found to be evenly distributed in the brain. However, the dyes administered through ICV or reverse microdialysis injection still remained in the delivery sites, poorly diffusing to the brain. In conclusion, intracranial MDMA administration in one area has no or little effect on other areas, which must be considered a plausible reason for the difference in MDMA-elicited serotonin syndrome between systemic and intracranial administrations.

Sexual odor preference and dopamine release in the nucleus accumbens by estrous olfactory cues in sexually naïve and experienced male rats.

PubMed

Fujiwara, Masaya; Chiba, Atsuhiko

2018-03-01

Sexual behavior is a natural reward that activates mesolimbic dopaminergic system. Microdialysis studies have shown that extracellular level of dopamine (DA) in the nucleus accumbens (NAcc) significantly increases during copulation in male rats. The NAcc DA level is also known to be increased during the presentation of a sexually receptive female before mating. This rise in DA was probably associated with sexual motivation elicited by incentive stimuli from the receptive female. These microdialysis studies, however, did not thoroughly investigated if olfactory stimuli from estrous females could significantly increase the extracellular DA in the NAcc of male rats. The present study was designed to examine systematically the relationship between the expression of preference for the olfactory stimuli from estrous females and the effects of these stimuli on the extracellular DA levels in the NAcc measured by in vivo microdialysis in male Long-Evans (LE) rats. We used two types of olfactory stimuli, either airborne odors (volatile stimuli) or soiled bedding (volatile plus nonvolatile stimuli). The sexually experienced male rats, which experienced six ejaculations, significantly preferred both of these olfactory stimuli from estrous females as opposed to males. Exposure to these female olfactory stimuli gradually increased extracellular DA in the NAcc, which reached significantly higher level above baseline during the period following the removal of the stimuli although not during the 15-min stimulus presentation period. The sexually naïve male rats, on the other hand, showed neither preference for olfactory stimuli from estrous females nor increase in the NAcc DA after exposure to these stimuli. These data suggest that in male LE rats olfactory stimuli from estrous females in and of themselves can be conditional cues that induce both incentive motivation and a significant increase in the NAcc DA probably as a result of being associated with sexual reward through copulatory experience. Copyright © 2017. Published by Elsevier Inc.

40 CFR 60.386 - Test methods and procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

.... The sample volume for each run shall be at least 1.70 dscm (60 dscf). The sampling probe and filter... probe and filter temperature slightly above the effluent temperature (up to a maximum filter temperature...

40 CFR 60.386 - Test methods and procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

.... The sample volume for each run shall be at least 1.70 dscm (60 dscf). The sampling probe and filter... probe and filter temperature slightly above the effluent temperature (up to a maximum filter temperature...

40 CFR 60.386 - Test methods and procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

.... The sample volume for each run shall be at least 1.70 dscm (60 dscf). The sampling probe and filter... probe and filter temperature slightly above the effluent temperature (up to a maximum filter temperature...

40 CFR 89.413 - Raw sampling procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) The gaseous emission sampling probe must be installed at least 0.5 m or 3 times the diameter of the... multi-cylinder engine with a branched exhaust manifold, the inlet of the probe shall be located...

40 CFR 60.386 - Test methods and procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

.... The sample volume for each run shall be at least 1.70 dscm (60 dscf). The sampling probe and filter... probe and filter temperature slightly above the effluent temperature (up to a maximum filter temperature...

Thin Cu film resistivity using four probe techniques: Effect of film thickness and geometrical shapes

NASA Astrophysics Data System (ADS)

Choudhary, Sumita; Narula, Rahul; Gangopadhyay, Subhashis

2018-05-01

Precise measurement of electrical sheet resistance and resistivity of metallic thin Cu films may play a significant role in temperature sensing by means of resistivity changes which can further act as a safety measure of various electronic devices during their operation. Four point probes resistivity measurement is a useful approach as it successfully excludes the contact resistance between the probes and film surface of the sample. Although, the resistivity of bulk samples at a particular temperature mostly depends on its materialistic property, however, it may significantly differ in the case of thin films, where the shape and thickness of the sample can significantly influence on it. Depending on the ratio of the film thickness to probe spacing, samples are usually classified in two segments such as (i) thick films or (ii) thin films. Accordingly, the geometric correction factors G can be related to the sample resistivity r, which has been calculated here for thin Cu films of thickness up to few 100 nm. In this study, various rectangular shapes of thin Cu films have been used to determine the shape induced geometric correction factors G. An expressions for G have been obtained as a function of film thickness t versus the probe spacing s. Using these expressions, the correction factors have been plotted separately for each cases as a function of (a) film thickness for fixed linear probe spacing and (b) probe distance from the edge of the film surface for particular thickness. Finally, we compare the experimental results of thin Cu films of various rectangular geometries with the theoretical reported results.

Development, fabrication and testing of a magnetically connected plastic vacuum probe surface sampler

NASA Technical Reports Server (NTRS)

Phillips, G. B.; Pace, V. A., Jr.

1972-01-01

The sampler utilizes permanent magnets and soft metal pole pieces to connect the cone/filter assembly to the sampling head and vacuum supply. The cone/filter assembly is packaged in a plastic container and presterilized so that the need for any human contact during the sampling procedure is completely eliminated. Microbiological tests have demonstrated that the sampling efficiency is not affected by the magnetic coupling apparatus and that the probe appears to function as efficiently as the conventional plastic and Sandia vacuum probes.

Genus Level Identification of Mycobacteria from Clinical Specimens by Using an Easy-To-Handle Mycobacterium-Specific PCR Assay

PubMed Central

Stauffer, Fritz; Haber, Heinrich; Rieger, Armin; Mutschlechner, Robert; Hasenberger, Petra; Tevere, Vincent J.; Young, Karen K. Y.

1998-01-01

An easy-to-handle Mycobacterium-specific PCR assay for detection of the presence of a wide range of mycobacterial species in clinical samples was evaluated. The performance of the genus probe was compared with the performance of probes specific for Mycobacterium tuberculosis and Mycobacterium avium and with that of standard culture. In addition, the utility of an internal control in monitoring amplification inhibitors was studied. Of 545 respiratory and 325 nonrespiratory specimens (a total of 870 specimens), 58 (6.7%) showed the presence of amplification inhibitors, as determined by a negative result for the internal control. Of these 58 specimens, 31 (53%) were stool specimens; other material, even citrate blood after lysis of erythrocytes, did not pose a problem with regard to inhibition of PCR amplification. Eighty-one of the remaining 812 specimens had a positive Mycobacterium culture result. Of these culture-positive specimens, 58 (71.6%) showed a positive result with the Mycobacterium genus-specific probe. Seventy-two samples had a positive result with the Mycobacterium-specific probe but a negative culture result. Of these 72 samples, 26 samples were regarded as true positive, either because the M. tuberculosis- or M. avium-specific probe was also positive at the same time or because other specimens from the same patient taken at the same time were culture positive. The sensitivity of the Mycobacterium-specific probe was 78.5% and the specificity was 93.5%. This study showed that pretesting of clinical specimens for mycobacteria to the genus level with a Mycobacterium-specific probe offers the routine clinical laboratory the possibility of detecting tuberculous and nontuberculous mycobacteria with one test. Furthermore, specimens testing positive with the genus-specific probe can be immediately identified with species-specific probes. PMID:9508282

The effects of postnatal alcohol exposure and galantamine on the context pre-exposure facilitation effect and acetylcholine efflux using in vivo microdialysis

PubMed Central

Perkins, Amy E.; Fadel, Jim R.; Kelly, Sandra J.

2015-01-01

Fetal alcohol spectrum disorders (FASD) affect 2–5% of children. FASD have been shown to cause damage to multiple brain regions, but damage to the hippocampus specifically may explain deficits in learning and memory that are hallmark symptoms of FASD. The acetylcholine neurotransmitter system is a major input to the hippocampus and is a possible target of developmental alcohol exposure. Alcohol (3.0 g/kg/day) was administered via intragastric intubation to developing male rat pups (postnatal day [PD] 2–10; ethanol-treated [ET]), with controls receiving a sham intubation (IC) or no treatment (NC). In Experiment 1, in vivo microdialysis was used to measure acetylcholine efflux in adolescents (PD 32–35). During microdialysis, the effects of a high K+/Ca2+ aCSF solution (PD 32–33) and an acute galantamine (acetylcholinesterase [AChE] inhibitor) injection (2.0 mg/kg; PD 34–35) on acetylcholine efflux were measured. Alcohol-exposed animals did not differ in acetylcholine efflux at baseline. However, alcohol-exposed animals had a decrease in K+/Ca2+-induced acetylcholine efflux compared to non-treated controls, and an enhanced acetylcholine response to galantamine compared to both control groups. Experiment 2 tested whether chronic administration of galantamine (2.0 mg/kg; PD 11–30) could attenuate alcohol-induced learning deficits in the context pre-exposure facilitation effect (CPFE; PD 30–32). Neither chronic galantamine nor postnatal alcohol exposure influenced performance in the CPFE task. Immunohistochemistry was used to measure expression of choline acetyltransferase (ChAT; medial septum), vesicular acetylcholine transporter (vAChT; ventral CA1), and the alpha7 nicotinic acetylcholine receptor (α7 nAChR; ventral CA1) following microdialysis (Exp. 1) or chronic galantamine and behavioral testing (Exp. 2). Neither alcohol exposure nor behavioral testing significantly altered the density of vAChT or α7 nAChRs in the ventral CA1 region of the hippocampus. The average number of ChAT+ cells was increased in the ET animals that displayed the context-shock association; there were no changes in the IC and NC animals that learned the context-shock association or in any of the animals that were in the control task that entailed no learning. Taken together, these results indicate that the hippocampal acetylcholine system is significantly disrupted under conditions of pharmacological manipulations (e.g., galantamine) in alcohol-exposed animals. Furthermore, ChAT was up-regulated in alcohol-exposed animals that learned to associate the context and shock, which may account for their ability to perform this task. Developmental alcohol exposure may disrupt learning and memory in adolescence via a cholinergic mechanism. PMID:25837482

Theoretical analysis of a dual-probe scanning tunneling microscope setup on graphene.

PubMed

Settnes, Mikkel; Power, Stephen R; Petersen, Dirch H; Jauho, Antti-Pekka

2014-03-07

Experimental advances allow for the inclusion of multiple probes to measure the transport properties of a sample surface. We develop a theory of dual-probe scanning tunneling microscopy using a Green's function formalism, and apply it to graphene. Sampling the local conduction properties at finite length scales yields real space conductance maps which show anisotropy for pristine graphene systems and quantum interference effects in the presence of isolated impurities. Spectral signatures in the Fourier transforms of real space conductance maps include characteristics that can be related to different scattering processes. We compute the conductance maps of graphene systems with different edge geometries or height fluctuations to determine the effects of nonideal graphene samples on dual-probe measurements.

Pump-probe nonlinear phase dispersion spectroscopy.

PubMed

Robles, Francisco E; Samineni, Prathyush; Wilson, Jesse W; Warren, Warren S

2013-04-22

Pump-probe microscopy is an imaging technique that delivers molecular contrast of pigmented samples. Here, we introduce pump-probe nonlinear phase dispersion spectroscopy (PP-NLDS), a method that leverages pump-probe microscopy and spectral-domain interferometry to ascertain information from dispersive and resonant nonlinear effects. PP-NLDS extends the information content to four dimensions (phase, amplitude, wavelength, and pump-probe time-delay) that yield unique insight into a wider range of nonlinear interactions compared to conventional methods. This results in the ability to provide highly specific molecular contrast of pigmented and non-pigmented samples. A theoretical framework is described, and experimental results and simulations illustrate the potential of this method. Implications for biomedical imaging are discussed.

Pump-probe nonlinear phase dispersion spectroscopy

PubMed Central

Robles, Francisco E.; Samineni, Prathyush; Wilson, Jesse W.; Warren, Warren S.

2013-01-01

Pump-probe microscopy is an imaging technique that delivers molecular contrast of pigmented samples. Here, we introduce pump-probe nonlinear phase dispersion spectroscopy (PP-NLDS), a method that leverages pump-probe microscopy and spectral-domain interferometry to ascertain information from dispersive and resonant nonlinear effects. PP-NLDS extends the information content to four dimensions (phase, amplitude, wavelength, and pump-probe time-delay) that yield unique insight into a wider range of nonlinear interactions compared to conventional methods. This results in the ability to provide highly specific molecular contrast of pigmented and non-pigmented samples. A theoretical framework is described, and experimental results and simulations illustrate the potential of this method. Implications for biomedical imaging are discussed. PMID:23609646

Carbon nanotube scanning probe for imaging in aqueous environment

NASA Technical Reports Server (NTRS)

Stevens, Ramsey M.; Nguyen, Cattien V.; Meyyappan, M.

2004-01-01

Carbon nanotubes (CNTs) used as a probe for scanning probe microscopy has become one of the many potential usages of CNTs that is finding real applications in scientific research and industrial communities. It has been proposed that the unique mechanical buckling properties of the CNT would lessen the imaging force exerted on the sample and, thus, make CNT scanning probes ideal for imaging soft materials, including biological samples in liquid environments. The hydrophobic nature of the CNT graphitic sidewall is clearly chemically incompatible with the aqueous solution requirements in some biological imaging applications. In this paper, we present electron micrograph results demonstrating the instability of CNT scanning probes when submerged in aqueous solution. Moreover, we also introduce a novel approach to resolve this chemical incompatibility problem. By coating the CNT probe with ethylenediamine, thus rendering the CNT probe less hydrophobic, we demonstrate the liquid imaging capability of treated CNT probes. Experimental data for imaging in aqueous solutions are presented, which include an ultrathin Ir film and DNA molecules on a mica surface.

Probe for high resolution NMR with sample reorientation

DOEpatents

Pines, A.; Samoson, A.

1990-02-06

An improved NMR probe and method are described which substantially improve the resolution of NMR measurements made on powdered or amorphous or otherwise orientationally disordered samples. The apparatus mechanically varies the orientation of the sample such that the time average of two or more sets of spherical harmonic functions are zero. 8 figs.

Sensitive and simultaneous determination of HIV protease inhibitors in rat biological samples by liquid chromatography-mass spectrometry.

PubMed

Gao, Weihua; Kishida, Tomoyuki; Kimura, Keisuke; Kageyama, Michiharu; Sumi, Masaki; Yoshikawa, Yukako; Shibata, Nobuhito; Takada, Kanji

2002-06-01

A sensitive and simultaneous liquid chromatographic-mass spectrometric (LC/MS) method for the determination of current four HIV protease inhibitors (PIs), indinavir (IDV), saquinavir (SQV), nelfinavir (NFV) and amprenavir (APV) in rat plasma and liver dialysate by a microdialysis method was described. An isocratic LC/MS method in combination with atmospheric pressure chemical ionization was developed for the determination of these four PIs in biological samples in the same run. The analytes including an internal standard were extracted from 100 microL of plasma or 150 microL of liver dialysate samples by salting-out with 100 microL of ice-cold 2 M K(3)PO(4) followed by ether extraction. The separation of analytes was carried out on a reversed-phase semi-micro column using 50% of acetonitrile containing 1% acetic acid as mobile phase at a flow rate of 0.2mL/min(-1). The separation was completed within 5 min. Precision, recovery and limits of detection indicated that the method was suitable for the quantitative determination of these PIs in rat plasma or liver dialysate. This simple, sensitive and highly specific LC/MS method is suitable for pharmacokinetic studies and therapeutic drug monitoring in AIDS patients who receive double protease therapy. Copyright 2002 John Wiley & Sons, Ltd.

Switching-angle sample spinning NMR probe with a commercially available 20 kHz spinning system

NASA Astrophysics Data System (ADS)

Mizuno, Takashi; Takegoshi, K.; Terao, Takehiko

2004-11-01

A switching-angle sample spinning (SASS) probe workable at high spinning speeds was developed using a commercially available rotor/housing system. Details of the construction are described. As application examples of the SASS probe, we report experiments of powder pattern separation at the spinning speed of 20 kHz and broadband 13C- 13C polarization transfer at 16 kHz.

Total RNA Sequencing Analysis of DCIS Progressing to Invasive Breast Cancer

DTIC Science & Technology

2015-09-01

EPICOPY to obtain reliable copy number variation ( CNV ) data from the methylome array data, thereby decreasing the DNA requirements in half...in the R statistical environment. Samples were assessed for good performance on the array using detection p-values, a metric implemented by...Illumina to identify probes detected with confidence. Samples less than 90% of probes detected were removed from the analysis and probes undetected in any

Nonisotopic detection of human papillomavirus DNA in clinical specimens using a consensus PCR and a generic probe mix in an enzyme-linked immunosorbent assay format.

PubMed

Kornegay, J R; Shepard, A P; Hankins, C; Franco, E; Lapointe, N; Richardson, H; Coutleé, F

2001-10-01

We assessed the value of a new digoxigenin (DIG)-labeled generic probe mix in a PCR-enzyme-linked immunosorbent assay format to screen for the presence of human papillomavirus (HPV) DNA amplified from clinical specimens. After screening with this new generic assay is performed, HPV DNA-positive samples can be directly genotyped using a reverse blotting method with product from the same PCR amplification. DNA from 287 genital specimens was amplified via PCR using biotin-labeled consensus primers directed to the L1 gene. HPV amplicons were captured on a streptavidin-coated microwell plate (MWP) and detected with a DIG-labeled HPV generic probe mix consisting of nested L1 fragments from types 11, 16, 18, and 51. Coamplification and detection of human DNA with biotinylated beta-globin primers served as a control for both sample adequacy and PCR amplification. All specimens were genotyped using a reverse line blot assay (13). Results for the generic assay using MWPs and a DIG-labeled HPV generic probe mix (DIG-MWP generic probe assay) were compared with results from a previous analysis using dot blots with a radiolabeled nested generic probe mix and type-specific probes for genotyping. The DIG-MWP generic probe assay resulted in high intralaboratory concordance in genotyping results (88% versus 73% agreement using traditional methods). There were 207 HPV-positive results using the DIG-MWP method and 196 positives using the radiolabeled generic probe technique, suggesting slightly improved sensitivity. Only one sample failed to test positive with the DIG-MWP generic probe assay in spite of a positive genotyping result. Concordance between the two laboratories was nearly 87%. Approximately 6% of samples that were positive or borderline when tested with the DIG-MWP generic probe assay were not detected with the HPV type-specific panel, perhaps representing very rare or novel HPV types. This new method is easier to perform than traditional generic probe techniques and uses more objective interpretation criteria, making it useful in studies of HPV natural history.

Determining confounding sensitivities in eddy current thin film measurements

NASA Astrophysics Data System (ADS)

Gros, Ethan; Udpa, Lalita; Smith, James A.; Wachs, Katelyn

2017-02-01

Eddy current (EC) techniques are widely used in industry to measure the thickness of non-conductive films on a metal substrate. This is done by using a system whereby a coil carrying a high-frequency alternating current is used to create an alternating magnetic field at the surface of the instrument's probe. When the probe is brought near a conductive surface, the alternating magnetic field will induce ECs in the conductor. The substrate characteristics and the distance of the probe from the substrate (the coating thickness) affect the magnitude of the ECs. The induced currents load the probe coil affecting the terminal impedance of the coil. The measured probe impedance is related to the lift off between coil and conductor as well as conductivity of the test sample. For a known conductivity sample, the probe impedance can be converted into an equivalent film thickness value. The EC measurement can be confounded by a number of measurement parameters. It was the goal of this research to determine which physical properties of the measurement set-up and sample can adversely affect the thickness measurement. The eddy-current testing was performed using a commercially available, hand-held eddy-current probe (ETA3.3H spring-loaded eddy probe running at 8 MHz) that comes with a stand to hold the probe. The stand holds the probe and adjusts the probe on the z-axis to help position the probe in the correct area as well as make precise measurements. The signal from the probe was sent to a hand-held readout, where the results are recorded directly in terms of liftoff or film thickness. Understanding the effect of certain factors on the measurements of film thickness, will help to evaluate how accurate the ETA3.3H spring-loaded eddy probe was at measuring film thickness under varying experimental conditions. This research studied the effects of a number of factors such as i) conductivity, ii) edge effect, iii) surface finish of base material and iv) cable condition.

'FloraArray' for screening of specific DNA probes representing the characteristics of a certain microbial community.

PubMed

Yokoi, Takahide; Kaku, Yoshiko; Suzuki, Hiroyuki; Ohta, Masayuki; Ikuta, Hajime; Isaka, Kazuichi; Sumino, Tatsuo; Wagatsuma, Masako

2007-08-01

To investigate uncharacterized microbial communities, a custom DNA microarray named 'FloraArray' was developed for screening specific probes that would represent the characteristics of a microbial community. The array was prepared by spotting 2000 plasmid DNAs from a genomic shotgun library of a sludge sample on a DNA microarray. By comparative hybridization of the array with two different samples of genomic DNA, one from the activated sludge and the other from a nonactivated sludge sample of an anaerobic ammonium oxidation (anammox) bacterial community, specific spots were visualized as a definite fluctuating profile in an MA (differential intensity ratio vs. spot intensity) plot. About 300 spots of the array accounted for the candidate probes to represent anammox reaction of the activated sludge. After sequence analysis of the probes and examination of the results of blastn searches against the reported anammox reference sequence, complete matches were found for 161 probes (58.3%) and >90% matches were found for 242 probes (87.1%). These results demonstrate that 'FloraArray' could be a useful tool for screening specific DNA molecules of unknown microbial communities.

In situ identification of nocardioform actinomycetes in activated sludge using fluorescent rRNA-targeted oligonucleotide probes.

PubMed

Schuppler, M; Wagner, M; Schön, G; Göbel, U B

1998-01-01

Hitherto, few environmental samples have been investigated by a 'full cycle rRNA analysis'. Here the results of in situ hybridization experiments with specific rRNA-targeted oligonucleotide probes developed on the basis of new sequences derived from a previously described comparative 16S rRNA analysis of nocardioform actinomycetes in activated sludge are reported. Application of the specific probes enabled identification and discrimination of the distinct populations of nocardioform actinomycetes in activated sludge. One of the specific probes (DLP) detected rod-shaped bacteria which were found in 13 of the 16 investigated sludge samples from various wastewater treatment plants, suggesting their importance in the wastewater treatment process. Another probe (GLP2) hybridized with typically branched filaments of nocardioforms mainly found in samples from enhanced biological phosphorus removal plants, suggesting that these bacteria are involved in sludge foaming. The combination of in situ hybridization with fluorescently labelled rRNA-targeted oligonucleotide probes and confocal laser scanning microscopy improved the detection of nocardioform actinomycetes, which often showed only weak signals inside the activated-sludge flocs.

Pump and probe spectroscopy with continuous wave quantum cascade lasers.

PubMed

Kirkbride, James M R; Causier, Sarah K; Dalton, Andrew R; Weidmann, Damien; Ritchie, Grant A D

2014-02-07

This paper details infra-red pump and probe studies on nitric oxide conducted with two continuous wave quantum cascade lasers both operating around 5 μm. The pump laser prepares a velocity selected population in a chosen rotational quantum state of the v = 1 level which is subsequently probed using a second laser tuned to a rotational transition within the v = 2 ← v = 1 hot band. The rapid frequency scan of the probe (with respect to the molecular collision rate) in combination with the velocity selective pumping allows observation of marked rapid passage signatures in the transient absorption profiles from the polarized vibrationally excited sample. These coherent transient signals are influenced by the underlying hyperfine structure of the pump and probe transitions, the sample pressure, and the coherent properties of the lasers. Pulsed pump and probe studies show that the transient absorption signals decay within 1 μs at 50 mTorr total pressure, reflecting both the polarization and population dephasing times of the vibrationally excited sample. The experimental observations are supported by simulation based upon solving the optical Bloch equations for a two level system.

Aerosols and Particulates Workshop Sampling Procedures and Venues Working Group Summary

NASA Technical Reports Server (NTRS)

Pachlhofer, Peter; Howard, Robert

1999-01-01

The Sampling Procedures and Venues Workgroup discussed the potential venues available and issues associated with obtaining measurements. Some of the issues included Incoming Air Quality, Sampling Locations, Probes and Sample Systems. The following is a summary of the discussion of the issues and venues. The influence of inlet air to the measurement of exhaust species, especially trace chemical species, must be considered. Analysis procedures for current engine exhaust emissions regulatory measurements require adjustments for air inlet humidity. As a matter of course in scientific investigations, it is recommended that "background" measurements for any species, particulate or chemical, be performed during inlet air flow before initiation of combustion, if possible, and during the engine test period as feasible and practical. For current regulatory measurements, this would be equivalent to setting the "zero" level for conventional gas analyzers. As a minimum, it is recommended that measurements of the humidity and particulates in the incoming air be taken at the start and end of each test run. Additional measurement points taken during the run are desirable if they can be practically obtained. It was felt that the presence of trace gases in the incoming air is not a significant problem. However, investigators should consider the ambient levels and influences of local air pollution for species of interest. Desired measurement locations depend upon the investigation requirements. A complete investigation of phenomenology of particulate formation and growth requires measurements at a number of locations both within the engine and in the exhaust field downstream of the nozzle exit plane. Desirable locations for both extractive and in situ measurements include: (1) Combustion Zone (Multiple axial locations); (2) Combustor Exit (Multiple radial locations for annular combustors); (3) Turbine Stage (Inlet and exit of the stage); (4) Exit Nozzle (Multiple axial locations downstream of the nozzle). Actual locations with potential for extractive or non-intrusive measurements depend upon the test article and test configuration. Committee members expressed the importance of making investigators aware of various ports that could allow access to various stages of the existing engines. Port locations are engine si)ecific and might allow extractive sampling or innovative hybrid optical-probe access. The turbine stage region was one the most desirable locations for obtaining samples and might be accessed through boroscope ports available in some engine designs. Discussions of probes and sampling systems quickly identified issues dependent on particular measurement quantities. With general consensus, the group recommends SAE procedures for measurements and data analyses of currently regulated exhaust species (CO2, CO, THC, NO(x),) using conventional gas sampling techniques. Special procedures following sound scientific practices must be developed as required for species and/or measurement conditions not covered by SAE standards. Several issues arose concerning short lived radicals and highly reactive species. For conventional sampling, there are concerns of perturbing the sample during extraction, line losses, line-wall reactions, and chemical reactions during the sample transport to the analyzers. Sample lines coated with quartz.or other materials should be investigated for minimization of such effects. The group advocates the development of innovative probe techniques and non-intrusive optical techniques for measurement of short lived radicals and highly reactive species that cannot be sampled accurately otherwise. Two innovative probe concepts were discussed. One concept uses specially designed probes to transfer optical beams to and from a region of flow inaccessible by traditional ports or windows. The probe can perturb the flow field but must have a negligible impact on the region to be optically sampled. Such probes are referred to as hybrid probes and are under development at AEDC for measurement in the high pressure, high temperature of a combustor under development for power generation. The other concept consists of coupling an instrument directly to the probe. The probe would isolate a representative sample stream, freeze chemical reactions and direct the sample into the analyzer portion of the probe. Thus, the measurement would be performed in situ without sample line losses due either to reactions or binding at the wall surfaces. This concept was used to develop a fast, in situ, time-of-flight mass spectrometer measurement system for temporal quantification of NO in the IMPULSE facility at AEDC. Additional work is required in this area to determine the best probe and sampling technique for each species measurement requirement identified by the Trace Chemistry Working Group. A partial list of Venues was used as a baseline for discussion. Additional venues were added to the list and the list was broken out into the following categories: (1)Engines (a) Sea Level Test Stands (b) Altitude Chambers; (2) Annular Combustor Test Stands, (3) Sector Flametube Test Stands, (4) Fundamentals Rigs/Experiments.

A multi-probe thermophoretic soot sampling system for high-pressure diffusion flames

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

Vargas, Alex M.; Gülder, Ömer L.

Optical diagnostics and physical probing of the soot processes in high pressure combustion pose challenges that are not faced in atmospheric flames. One of the preferred methods of studying soot in atmospheric flames is in situ thermophoretic sampling followed by transmission electron microscopy imaging and analysis for soot sizing and morphology. The application of this method of sampling to high pressures has been held back by various operational and mechanical problems. In this work, we describe a rotating disk multi-probe thermophoretic soot sampling system, driven by a microstepping stepper motor, fitted into a high-pressure chamber capable of producing sooting laminarmore » diffusion flames up to 100 atm. Innovative aspects of the sampling system design include an easy and precise control of the sampling time down to 2.6 ms, avoidance of the drawbacks of the pneumatic drivers used in conventional thermophoretic sampling systems, and the capability to collect ten consecutive samples in a single experimental run. Proof of principle experiments were performed using this system in a laminar diffusion flame of methane, and primary soot diameter distributions at various pressures up to 10 atm were determined. High-speed images of the flame during thermophoretic sampling were recorded to assess the influence of probe intrusion on the flow field of the flame.« less

40 CFR 89.413 - Raw sampling procedures.

Code of Federal Regulations, 2013 CFR

2013-07-01

... emissions. (a) The gaseous emission sampling probe must be installed at least 0.5 m or 3 times the diameter... the case of a multi-cylinder engine with a branched exhaust manifold, the inlet of the probe shall be...

40 CFR 89.413 - Raw sampling procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

... emissions. (a) The gaseous emission sampling probe must be installed at least 0.5 m or 3 times the diameter... the case of a multi-cylinder engine with a branched exhaust manifold, the inlet of the probe shall be...

Importance of the efficiency of double-stranded DNA formation in cDNA synthesis for the imprecision of microarray expression analysis.

PubMed

Thormar, Hans G; Gudmundsson, Bjarki; Eiriksdottir, Freyja; Kil, Siyoen; Gunnarsson, Gudmundur H; Magnusson, Magnus Karl; Hsu, Jason C; Jonsson, Jon J

2013-04-01

The causes of imprecision in microarray expression analysis are poorly understood, limiting the use of this technology in molecular diagnostics. Two-dimensional strandness-dependent electrophoresis (2D-SDE) separates nucleic acid molecules on the basis of length and strandness, i.e., double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), and RNA·DNA hybrids. We used 2D-SDE to measure the efficiency of cDNA synthesis and its importance for the imprecision of an in vitro transcription-based microarray expression analysis. The relative amount of double-stranded cDNA formed in replicate experiments that used the same RNA sample template was highly variable, ranging between 0% and 72% of the total DNA. Microarray experiments showed an inverse relationship between the difference between sample pairs in probe variance and the relative amount of dsDNA. Approximately 15% of probes showed between-sample variation (P < 0.05) when the dsDNA percentage was between 12% and 35%. In contrast, only 3% of probes showed between-sample variation when the dsDNA percentage was 69% and 72%. Replication experiments of the 35% dsDNA and 72% dsDNA samples were used to separate sample variation from probe replication variation. The estimated SD of the sample-to-sample variation and of the probe replicates was lower in 72% dsDNA samples than in 35% dsDNA samples. Variation in the relative amount of double-stranded cDNA synthesized can be an important component of the imprecision in T7 RNA polymerase-based microarray expression analysis. © 2013 American Association for Clinical Chemistry

Development of a multichannel hyperspectral imaging probe for food property and quality assessment

NASA Astrophysics Data System (ADS)

Huang, Yuping; Lu, Renfu; Chen, Kunjie

2017-05-01

This paper reports on the development, calibration and evaluation of a new multipurpose, multichannel hyperspectral imaging probe for property and quality assessment of food products. The new multichannel probe consists of a 910 μm fiber as a point light source and 30 light receiving fibers of three sizes (i.e., 50 μm, 105 μm and 200 μm) arranged in a special pattern to enhance signal acquisitions over the spatial distances of up to 36 mm. The multichannel probe allows simultaneous acquisition of 30 spatially-resolved reflectance spectra of food samples with either flat or curved surface over the spectral region of 550-1,650 nm. The measured reflectance spectra can be used for estimating the optical scattering and absorption properties of food samples, as well as for assessing the tissues of the samples at different depths. Several calibration procedures that are unique to this probe were carried out; they included linearity calibrations for each channel of the hyperspectral imaging system to ensure consistent linear responses of individual channels, and spectral response calibrations of individual channels for each fiber size group and between the three groups of different size fibers. Finally, applications of this new multichannel probe were demonstrated through the optical property measurement of liquid model samples and tomatoes of different maturity levels. The multichannel probe offers new capabilities for optical property measurement and quality detection of food and agricultural products.

Self-sensing cantilevers with integrated conductive coaxial tips for high-resolution electrical scanning probe metrology

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

Haemmerli, Alexandre J.; Pruitt, Beth L., E-mail: pruitt@stanford.edu; Harjee, Nahid

The lateral resolution of many electrical scanning probe techniques is limited by the spatial extent of the electrostatic potential profiles produced by their probes. Conventional unshielded conductive atomic force microscopy probes produce broad potential profiles. Shielded probes could offer higher resolution and easier data interpretation in the study of nanostructures. Electrical scanning probe techniques require a method of locating structures of interest, often by mapping surface topography. As the samples studied with these techniques are often photosensitive, the typical laser measurement of cantilever deflection can excite the sample, causing undesirable changes electrical properties. In this work, we present the design,more » fabrication, and characterization of probes that integrate coaxial tips for spatially sharp potential profiles with piezoresistors for self-contained, electrical displacement sensing. With the apex 100 nm above the sample surface, the electrostatic potential profile produced by our coaxial tips is more than 2 times narrower than that of unshielded tips with no long tails. In a scan bandwidth of 1 Hz–10 kHz, our probes have a displacement resolution of 2.9 Å at 293 K and 79 Å at 2 K, where the low-temperature performance is limited by amplifier noise. We show scanning gate microscopy images of a quantum point contact obtained with our probes, highlighting the improvement to lateral resolution resulting from the coaxial tip.« less

Impact of science objectives and requirements on probe mission and system design

NASA Technical Reports Server (NTRS)

Ledbetter, K. W.

1974-01-01

Problem areas in probe science technology are discussed that require a solution before probe systems can actually be designed. Considered are the effects of the model atmospheres on probe design; secondly, the effects of implementing the requirements to locate and measure the clouds and, trade-offs between descent sampling and measurement criteria as they affect probe system design.

Radio-frequency powered glow discharge device and method with high voltage interface

DOEpatents

Duckworth, D.C.; Marcus, R.K.; Donohue, D.L.; Lewis, T.A.

1994-06-28

A high voltage accelerating potential, which is supplied by a high voltage direct current power supply, is applied to the electrically conducting interior wall of an RF powered glow discharge cell. The RF power supply desirably is electrically grounded, and the conductor carrying the RF power to the sample held by the probe is desirably shielded completely excepting only the conductor's terminal point of contact with the sample. The high voltage DC accelerating potential is not supplied to the sample. A high voltage capacitance is electrically connected in series between the sample on the one hand and the RF power supply and an impedance matching network on the other hand. The high voltage capacitance isolates the high DC voltage from the RF electronics, while the RF potential is passed across the high voltage capacitance to the plasma. An inductor protects at least the RF power supply, and desirably the impedance matching network as well, from a short that might occur across the high voltage capacitance. The discharge cell and the probe which holds the sample are configured and disposed to prevent the probe's components, which are maintained at ground potential, from bridging between the relatively low vacuum region in communication with the glow discharge maintained within the cell on the one hand, and the relatively high vacuum region surrounding the probe and cell on the other hand. The probe and cell also are configured and disposed to prevent the probe's components from electrically shorting the cell's components. 11 figures.

Radio-frequency powered glow discharge device and method with high voltage interface

DOEpatents

Duckworth, Douglas C.; Marcus, R. Kenneth; Donohue, David L.; Lewis, Trousdale A.

1994-01-01

A high voltage accelerating potential, which is supplied by a high voltage direct current power supply, is applied to the electrically conducting interior wall of an RF powered glow discharge cell. The RF power supply desirably is electrically grounded, and the conductor carrying the RF power to the sample held by the probe is desirably shielded completely excepting only the conductor's terminal point of contact with the sample. The high voltage DC accelerating potential is not supplied to the sample. A high voltage capacitance is electrically connected in series between the sample on the one hand and the RF power supply and an impedance matching network on the other hand. The high voltage capacitance isolates the high DC voltage from the RF electronics, while the RF potential is passed across the high voltage capacitance to the plasma. An inductor protects at least the RF power supply, and desirably the impedance matching network as well, from a short that might occur across the high voltage capacitance. The discharge cell and the probe which holds the sample are configured and disposed to prevent the probe's components, which are maintained at ground potential, from bridging between the relatively low vacuum region in communication with the glow discharge maintained within the cell on the one hand, and the relatively high vacuum region surrounding the probe and cell on the other hand. The probe and cell also are configured and disposed to prevent the probe's components from electrically shorting the cell's components.

Chemical characterization of diesel and hydrotreated vegetable oil (HVO) soot after reactive gas probing using diffuse reflectance FTIR spectroscopy (DRIFTS).

PubMed

Tapia, A; Salgado, M S; Martín, M P; Rodríguez-Fernández, J; Rossi, M J; Cabañas, B

2017-03-01

A chemical characterization of diesel and hydrotreated vegetable oil (HVO) soot has been developed using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) before and after the reaction with different probe gases. Samples were generated under combustion conditions corresponding to an urban operation mode of a diesel engine and were reacted with probe gas-phase molecules in a Knudsen flow reactor. Specifically, NH 2 OH, O 3 and NO 2 were used as reactants (probes) and selected according to their reactivities towards specific functional groups on the sample surface. Samples of previously ground soot were diluted with KBr and were introduced in a DRIFTS accessory. A comparison between unreacted and reacted soot samples was made in order to establish chemical changes on the soot surface upon reaction. It was concluded that the interface of diesel and HVO soot before reaction mainly consists polycyclic aromatic hydrocarbons, nitro and carbonyl compounds, as well as ether functionalities. The main difference between both soot samples was observed in the band of the C=O groups that in diesel soot was observed at 1719 cm -1 but not in HVO soot. After reaction with probe gases, it was found that nitro compounds remain on the soot surface, that the degree of unsaturation decreases for reacted samples, and that new spectral bands such as hydroxyl groups are observed.

DC thermal microscopy: study of the thermal exchange between a probe and a sample

NASA Astrophysics Data System (ADS)

Gomès, Séverine; Trannoy, Nathalie; Grossel, Philippe

1999-09-01

The Scanning Thermal Microscopic (SThM) probe, a thin Pt resistance wire, is used in the constant force mode of an Atomic Force Microscope (AFM). Thermal signal-distance curves for differing degrees of relative humidity and different surrounding gases demonstrate how heat is transferred from the heated probe to the sample. It is known that water affects atomic force microscopy and thermal measurements; we report here on the variation of the water interaction on the thermal coupling versus the probe temperature. Measurements were taken for several solid materials and show that the predominant heat transfer mechanisms taking part in thermal coupling are dependent on the thermal conductivity of the sample. The results have important implications for any quantitative interpretation of thermal images made in air.

75 FR 13486 - Application(s) for Duty-Free Entry of Scientific Instruments

Federal Register 2010, 2011, 2012, 2013, 2014

2010-03-22

... nanostructures. This instrument combines an optical microscope with a scanning probe imaging system. Specifically... soft materials than other instruments, as it detects the probe coming close to the sample surface by... conventional AFM type silicon cantilevers as well as cantilevered optical fiber probes with exposed probe...

Method for replicating an array of nucleic acid probes

DOEpatents

Cantor, Charles R.; Przetakiewicz, Marek; Smith, Cassandra L.; Sano, Takeshi

1998-01-01

The invention relates to the replication of probe arrays and methods for replicating arrays of probes which are useful for the large scale manufacture of diagnostic aids used to screen biological samples for specific target sequences. Arrays created using PCR technology may comprise probes with 5'- and/or 3'-overhangs.

Full information acquisition in scanning probe microscopy and spectroscopy

DOEpatents

Jesse, Stephen; Belianinov, Alex; Kalinin, Sergei V.; Somnath, Suhas

2017-04-04

Apparatus and methods are described for scanning probe microscopy and spectroscopy based on acquisition of full probe response. The full probe response contains valuable information about the probe-sample interaction that is lost in traditional scanning probe microscopy and spectroscopy methods. The full probe response is analyzed post data acquisition using fast Fourier transform and adaptive filtering, as well as multivariate analysis. The full response data is further compressed to retain only statistically significant components before being permanently stored.

Unlabeled probes for the detection and typing of herpes simplex virus.

PubMed

Dames, Shale; Pattison, David C; Bromley, L Kathryn; Wittwer, Carl T; Voelkerding, Karl V

2007-10-01

Unlabeled probe detection with a double-stranded DNA (dsDNA) binding dye is one method to detect and confirm target amplification after PCR. Unlabeled probes and amplicon melting have been used to detect small deletions and single-nucleotide polymorphisms in assays where template is in abundance. Unlabeled probes have not been applied to low-level target detection, however. Herpes simplex virus (HSV) was chosen as a model to compare the unlabeled probe method to an in-house reference assay using dual-labeled, minor groove binding probes. A saturating dsDNA dye (LCGreen Plus) was used for real-time PCR. HSV-1, HSV-2, and an internal control were differentiated by PCR amplicon and unlabeled probe melting analysis after PCR. The unlabeled probe technique displayed 98% concordance with the reference assay for the detection of HSV from a variety of archived clinical samples (n = 182). HSV typing using unlabeled probes was 99% concordant (n = 104) to sequenced clinical samples and allowed for the detection of sequence polymorphisms in the amplicon and under the probe. Unlabeled probes and amplicon melting can be used to detect and genotype as few as 10 copies of target per reaction, restricted only by stochastic limitations. The use of unlabeled probes provides an attractive alternative to conventional fluorescence-labeled, probe-based assays for genotyping and detection of HSV and might be useful for other low-copy targets where typing is informative.

40 CFR 86.328-79 - Leak checks.

Code of Federal Regulations, 2013 CFR

2013-07-01

... flows may be used to estimate the in-use flow rates. (3) The sample probe and the connection between the sample probe and valve V2 (Figure D79-1) may be excluded from the leak check. (b) Pressure side leak...

40 CFR 91.324 - Analyzer leakage check.

Code of Federal Regulations, 2013 CFR

2013-07-01

... flows and bypass flows may be used to estimate the in-use flow rates. (3) The sample probe and the connection between the sample probe and valve V2 (see Figure 1 in appendix B of this subpart) may be excluded...

40 CFR 91.324 - Analyzer leakage check.

Code of Federal Regulations, 2010 CFR

2010-07-01

... flows and bypass flows may be used to estimate the in-use flow rates. (3) The sample probe and the connection between the sample probe and valve V2 (see Figure 1 in appendix B of this subpart) may be excluded...

40 CFR 86.328-79 - Leak checks.

Code of Federal Regulations, 2012 CFR

2012-07-01

... flows may be used to estimate the in-use flow rates. (3) The sample probe and the connection between the sample probe and valve V2 (Figure D79-1) may be excluded from the leak check. (b) Pressure side leak...

40 CFR 86.328-79 - Leak checks.

Code of Federal Regulations, 2010 CFR

2010-07-01

... flows may be used to estimate the in-use flow rates. (3) The sample probe and the connection between the sample probe and valve V2 (Figure D79-1) may be excluded from the leak check. (b) Pressure side leak...

40 CFR 86.328-79 - Leak checks.

Code of Federal Regulations, 2011 CFR

2011-07-01

... flows may be used to estimate the in-use flow rates. (3) The sample probe and the connection between the sample probe and valve V2 (Figure D79-1) may be excluded from the leak check. (b) Pressure side leak...

40 CFR 91.324 - Analyzer leakage check.

Code of Federal Regulations, 2011 CFR

2011-07-01

... flows and bypass flows may be used to estimate the in-use flow rates. (3) The sample probe and the connection between the sample probe and valve V2 (see Figure 1 in appendix B of this subpart) may be excluded...

40 CFR 91.324 - Analyzer leakage check.

Code of Federal Regulations, 2014 CFR

2014-07-01

... flows and bypass flows may be used to estimate the in-use flow rates. (3) The sample probe and the connection between the sample probe and valve V2 (see Figure 1 in appendix B of this subpart) may be excluded...

40 CFR 91.324 - Analyzer leakage check.

Code of Federal Regulations, 2012 CFR

2012-07-01

... flows and bypass flows may be used to estimate the in-use flow rates. (3) The sample probe and the connection between the sample probe and valve V2 (see Figure 1 in appendix B of this subpart) may be excluded...

The vector homology problem in diagnostic nucleic acid hybridization of clinical specimens.

PubMed Central

Ambinder, R F; Charache, P; Staal, S; Wright, P; Forman, M; Hayward, S D; Hayward, G S

1986-01-01

Nucleic acid hybridization techniques using cloned probes are finding application in assays of clinical specimens in research and diagnostic laboratories. The probes that we and others have used are recombinant plasmids composed of viral inserts and bacterial plasmid vectors such as pBR322. We suspected that there was material homologous to pBR322 present in many clinical samples. because hybridization occurred in samples which lacked evidence of virus by other techniques. If the presence of this vector-homologous material was unrecognized, hybridization in the test sample might erroneously be interpreted as indicating the presence of viral sequences. In this paper we demonstrate specific hybridization of labeled pBR322 DNA with DNA from various clinical samples. Evidence is presented that nonspecific probe trapping could not account for this phenomenon. In mixing experiments, it is shown that contamination of clinical samples with bacteria would explain such a result. Approaches tested to circumvent this problem included the use of isolated insert probes, alternate cloning vectors, and cold competitor pBR322 DNA in prehybridization and hybridization mixes. None proved entirely satisfactory. We therefore emphasize that it is essential that all hybridization detection systems use a control probe of the vector alone in order to demonstrate the absence of material with vector homology in the specimen tested. Images PMID:3013928

Thermal protection system development, testing, and qualification for atmospheric probes and sample return missions. Examples for Saturn, Titan and Stardust-type sample return

NASA Astrophysics Data System (ADS)

Venkatapathy, E.; Laub, B.; Hartman, G. J.; Arnold, J. O.; Wright, M. J.; Allen, G. A.

2009-07-01

The science community has continued to be interested in planetary entry probes, aerocapture, and sample return missions to improve our understanding of the Solar System. As in the case of the Galileo entry probe, such missions are critical to the understanding not only of the individual planets, but also to further knowledge regarding the formation of the Solar System. It is believed that Saturn probes to depths corresponding to 10 bars will be sufficient to provide the desired data on its atmospheric composition. An aerocapture mission would enable delivery of a satellite to provide insight into how gravitational forces cause dynamic changes in Saturn's ring structure that are akin to the evolution of protoplanetary accretion disks. Heating rates for the "shallow" Saturn probes, Saturn aerocapture, and sample Earth return missions with higher re-entry speeds (13-15 km/s) from Mars, Venus, comets, and asteroids are in the range of 1-6 KW/cm 2. New, mid-density thermal protection system (TPS) materials for such probes can be mission enabling for mass efficiency and also for use on smaller vehicles enabled by advancements in scientific instrumentation. Past consideration of new Jovian multiprobe missions has been considered problematic without the Giant Planet arcjet facility that was used to qualify carbon phenolic for the Galileo probe. This paper describes emerging TPS technologies and the proposed use of an affordable, small 5 MW arcjet that can be used for TPS development, in test gases appropriate for future planetary probe and aerocapture applications. Emerging TPS technologies of interest include new versions of the Apollo Avcoat material and a densified variant of Phenolic Impregnated Carbon Ablator (PICA). Application of these and other TPS materials and the use of other facilities for development and qualification of TPS for Saturn, Titan, and Sample Return missions of the Stardust class with entry speeds from 6.0 to 28.6 km/s are discussed.

Detection of the Light Organ Symbiont, Vibrio fischeri, in Hawaiian Seawater by Using lux Gene Probes †

PubMed Central

Lee, Kyu-Ho; Ruby, Edward G.

1992-01-01

Symbiotic bacteria that inhabit the light-emitting organ of the Hawaiian squid Euprymna scolopes are distinctive from typical Vibrio fischeri organisms in that they are not visibly luminous when grown in laboratory culture. Therefore, the abundance of these bacteria in seawater samples cannot be estimated simply by identifying them among luminous colonies that arise on nutrient agar plates. Instead, we have used luxR and polymerase chain reaction generated luxA gene probes to identify both luminous and non-visibly luminous V. fischeri colonies by DNA-DNA hybridization. The probes were specific, hybridizing at least 50 to 100 times more strongly to immobilized DNAs from V. fischeri strains than to those of pure cultures of other related species. Thus, even non-visibly luminous V. fischeri colonies could be identified among colonies obtained from natural seawater samples by their probe-positive reaction. Bacteria in seawater samples, obtained either within or distant from squid habitats, were collected on membrane filters and incubated until colonies appeared. The filters were then observed for visibly luminous V. fischeri colonies and hybridized with the lux gene probes to determine the number of total V. fischeri colonies (both luminous and non-visibly luminous). We detected no significant differences in the abundance of luminous V. fischeri CFU in any of the water samples observed (≤1 to 3 CFU/100 ml). However, probe-positive colonies of V. fischeri (up to 900 CFU/100 ml) were found only in seawater collected from within the natural habitats of the squids. A number of criteria were used to confirm that these probe-positive strains were indistinguishable from symbiotic V. fischeri. Therefore, the luxA and luxR gene probes were species specific and gave a reliable estimate of the number of culturable V. fischeri colonies in natural water samples. Images PMID:16348678

Detection of the Light Organ Symbiont, Vibrio fischeri, in Hawaiian Seawater by Using lux Gene Probes.

PubMed

Lee, K H; Ruby, E G

1992-03-01

Symbiotic bacteria that inhabit the light-emitting organ of the Hawaiian squid Euprymna scolopes are distinctive from typical Vibrio fischeri organisms in that they are not visibly luminous when grown in laboratory culture. Therefore, the abundance of these bacteria in seawater samples cannot be estimated simply by identifying them among luminous colonies that arise on nutrient agar plates. Instead, we have used luxR and polymerase chain reaction generated luxA gene probes to identify both luminous and non-visibly luminous V. fischeri colonies by DNA-DNA hybridization. The probes were specific, hybridizing at least 50 to 100 times more strongly to immobilized DNAs from V. fischeri strains than to those of pure cultures of other related species. Thus, even non-visibly luminous V. fischeri colonies could be identified among colonies obtained from natural seawater samples by their probe-positive reaction. Bacteria in seawater samples, obtained either within or distant from squid habitats, were collected on membrane filters and incubated until colonies appeared. The filters were then observed for visibly luminous V. fischeri colonies and hybridized with the lux gene probes to determine the number of total V. fischeri colonies (both luminous and non-visibly luminous). We detected no significant differences in the abundance of luminous V. fischeri CFU in any of the water samples observed (

Thermal probe design for Europa sample acquisition

NASA Astrophysics Data System (ADS)

Horne, Mera F.

2018-01-01

The planned lander missions to the surface of Europa will access samples from the subsurface of the ice in a search for signs of life. A small thermal drill (probe) is proposed to meet the sample requirement of the Science Definition Team's (SDT) report for the Europa mission. The probe is 2 cm in diameter and 16 cm in length and is designed to access the subsurface to 10 cm deep and to collect five ice samples of 7 cm3 each, approximately. The energy required to penetrate the top 10 cm of ice in a vacuum is 26 Wh, approximately, and to melt 7 cm3 of ice is 1.2 Wh, approximately. The requirement stated in the SDT report of collecting samples from five different sites can be accommodated with repeated use of the same thermal drill. For smaller sample sizes, a smaller probe of 1.0 cm in diameter with the same length of 16 cm could be utilized that would require approximately 6.4 Wh to penetrate the top 10 cm of ice, and 0.02 Wh to collect 0.1 g of sample. The thermal drill has the advantage of simplicity of design and operations and the ability to penetrate ice over a range of densities and hardness while maintaining sample integrity.

Assessment of the National Research Universal Reactor Proposed New Stack Sampling Probe Location for Compliance with ANSI/HPS N13.1-1999

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

Glissmeyer, John A.; Antonio, Ernest J.; Flaherty, Julia E.

2016-02-29

This document reports on a series of tests conducted to assess the proposed air sampling location for the National Research Universal reactor (NRU) complex exhaust stack, located in Chalk River, Ontario, Canada, with respect to the applicable criteria regarding the placement of an air sampling probe. Due to the age of the equipment in the existing monitoring system, and the increasing difficulty in acquiring replacement parts to maintain this equipment, a more up-to-date system is planned to replace the current effluent monitoring system, and a new monitoring location has been proposed. The new sampling probe should be located within themore » exhaust stack according to the criteria established by the American National Standards Institute/Health Physics Society (ANSI/HPS) N13.1-1999, Sampling and Monitoring Releases of Airborne Radioactive Substances from the Stack and Ducts of Nuclear Facilities. These criteria address the capability of the sampling probe to extract a sample that represents the effluent stream. The internal Pacific Northwest National Laboratory (PNNL) project for this task was 65167, Atomic Energy Canada Ltd. Chalk River Effluent Duct Flow Qualification. The testing described in this document was guided by the Test Plan: Testing of the NRU Stack Air Sampling Position (TP-STMON-032).« less

Assessment of the LV-C2 Stack Sampling Probe Location for Compliance with ANSI/HPS N13.1-1999

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

Glissmeyer, John A.; Antonio, Ernest J.; Flaherty, Julia E.

2015-09-01

This document reports on a series of tests conducted to assess the proposed air sampling location for the Hanford Tank Waste Treatment and Immobilization Plant (WTP) Low-Activity Waste (LAW) C2V (LV-C2) exhaust stack with respect to the applicable criteria regarding the placement of an air sampling probe. Federal regulations require that a sampling probe be located in the exhaust stack according to the criteria established by the American National Standards Institute/Health Physics Society (ANSI/HPS) N13.1-1999, Sampling and Monitoring Releases of Airborne Radioactive Substances from the Stack and Ducts of Nuclear Facilities. These criteria address the capability of the sampling probemore » to extract a sample that represents the effluent stream. The tests were conducted on the LV-C2 scale model system. Based on the scale model tests, the location proposed for the air sampling probe in the scale model stack meets the requirements of the ANSI/HPS N13.1-1999 standard for velocity uniformity, flow angle, gas tracer and particle tracer uniformity. Additional velocity uniformity and flow angle tests on the actual stack will be necessary during cold startup to confirm the validity of the scale model results in representing the actual stack.« less

A strip-shield improves the efficiency of a solenoid coil in probes for high-field solid-state NMR of lossy biological samples.

PubMed

Wu, Chin H; Grant, Christopher V; Cook, Gabriel A; Park, Sang Ho; Opella, Stanley J

2009-09-01

A strip-shield inserted between a high inductance double-tuned solenoid coil and the glass tube containing the sample improves the efficiency of probes used for high-field solid-state NMR experiments on lossy aqueous samples of proteins and other biopolymers. A strip-shield is a coil liner consisting of thin copper strips layered on a PTFE (polytetrafluoroethylene) insulator. With lossy samples, the shift in tuning frequency is smaller, the reduction in Q, and RF-induced heating are all significantly reduced when the strip-shield is present. The performance of 800MHz (1)H/(15)N and (1)H/(13)C double-resonance probes is demonstrated on aqueous samples of membrane proteins in phospholipid bilayers.

Scanning fiber angle-resolved low coherence interferometry

PubMed Central

Zhu, Yizheng; Terry, Neil G.; Wax, Adam

2010-01-01

We present a fiber-optic probe for Fourier-domain angle-resolved low coherence interferometry for the determination of depth-resolved scatterer size. The probe employs a scanning single-mode fiber to collect the angular scattering distribution of the sample, which is analyzed using the Mie theory to obtain the average size of the scatterers. Depth sectioning is achieved with low coherence Mach–Zehnder interferometry. In the sample arm of the interferometer, a fixed fiber illuminates the sample through an imaging lens and a collection fiber samples the backscattered angular distribution by scanning across the Fourier plane image of the sample. We characterize the optical performance of the probe and demonstrate the ability to execute depth-resolved sizing with subwavelength accuracy by using a double-layer phantom containing two sizes of polystyrene microspheres. PMID:19838271