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1

Respiratory metabolism: glycolysis, the TCA cycle and mitochondrial electron transport  

Microsoft Academic Search

The respiratory pathways of glycolysis, the tricarboxylic acid (TCA) cycle and the mitochondrial electron transport chain are ubiquitous throughout nature. They are essential for both energy provision in heterotrophic cells and a wide range of other physiological functions. Although the series of enzymes and proteins that participate in these pathways have long been known, their regulation and control are much

Alisdair R Fernie; Fernando Carrari; Lee J Sweetlove

2004-01-01

2

Revisiting the TCA cycle: signaling to tumor formation.  

PubMed

A role for mitochondria in tumor formation is suggested by mutations in enzymes of the TCA cycle: isocitrate dehydrogenase (IDH), succinate dehydrogenase (SDH) and fumarate hydratase (FH). Although they are all components of the TCA cycle, the resulting clinical presentations do not overlap. Activation of the hypoxia pathway can explain SDH phenotypes, but recent data suggest that FH and IDH mutations lead to tumor formation by repressing cellular differentiation. In this review, we discuss recent findings in the context of both mitochondrial and cytoplasmic components of the TCA cycle, and we propose that extrametabolic roles of TCA cycle metabolites result in reduced cellular differentiation. Furthermore, activation of the pseudohypoxia pathway likely promotes the growth of these neoplasias into tumors. PMID:21764377

Raimundo, Nuno; Baysal, Bora E; Shadel, Gerald S

2011-07-20

3

Revisiting the TCA cycle: signaling to tumor formation  

PubMed Central

A role for mitochondria in tumor formation is suggested by mutations in enzymes of the TCA cycle: isocitrate dehydrogenase (IDH), succinate dehydrogenase (SDH) and fumarate hydratase (FH). Although they are all components of the TCA cycle, the resulting clinical presentations do not overlap. Activation of the hypoxia pathway can explain SDH phenotypes, but recent data suggest that FH and IDH mutations lead to tumor formation by repressing cellular differentiation. Here we discuss recent findings in the context of both mitochondrial and cytoplasmic components of the TCA cycle, and we propose that extra-metabolic roles of TCA cycle metabolites result in the reduced cellular differentiation. Furthermore, the activation of the pseudo-hypoxia pathway likely promotes the growth of these neoplasias into tumors.

Raimundo, Nuno; Baysal, Bora E.; Shadel, Gerald S.

2011-01-01

4

TCA Cycle Defects and Cancer: When Metabolism Tunes Redox State  

PubMed Central

Inborn defects of the tricarboxylic acid (TCA) cycle enzymes have been known for more than twenty years. Until recently, only recessive mutations were described which, although resulted in severe multisystem syndromes, did not predispose to cancer onset. In the last ten years, a causal role in carcinogenesis has been documented for inherited and acquired alterations in three TCA cycle enzymes, succinate dehydrogenase (SDH), fumarate hydratase (FH), and isocitrate dehydrogenase (IDH), pointing towards metabolic alterations as the underlying hallmark of cancer. This paper summarizes the neoplastic alterations of the TCA cycle enzymes focusing on the generation of pseudohypoxic phenotype and the alteration of epigenetic homeostasis as the main tumor-promoting effects of the TCA cycle affecting defects. Moreover, we debate on the ability of these mutations to affect cellular redox state and to promote carcinogenesis by impacting on redox biology.

Cardaci, Simone; Ciriolo, Maria Rosa

2012-01-01

5

Succinate links TCA cycle dysfunction to oncogenesis by inhibiting HIF-? prolyl hydroxylase  

Microsoft Academic Search

Several mitochondrial proteins are tumor suppressors. These include succinate dehydrogenase (SDH) and fumarate hydratase, both enzymes of the tricarboxylic acid (TCA) cycle. However, to date, the mechanisms by which defects in the TCA cycle contribute to tumor formation have not been elucidated. Here we describe a mitochondrion-to-cytosol signaling pathway that links mitochondrial dysfunction to oncogenic events: succinate, which accumulates as

Mary A. Selak; Sean M. Armour; Elaine D. MacKenzie; Houda Boulahbel; David G. Watson; Kyle D. Mansfield; Yi Pan; M. Celeste Simon; Craig B. Thompson; Eyal Gottlieb

2005-01-01

6

Mitochondrial TCA cycle intermediates regulate body fluid and acid-base balance.  

PubMed

Intrarenal control mechanisms play an important role in the maintenance of body fluid and electrolyte balance and pH homeostasis. Recent discoveries of new ion transport and regulatory pathways in the distal nephron and collecting duct system have helped to better our understanding of these critical kidney functions and identified new potential therapeutic targets and approaches. In this issue of the JCI, Tokonami et al. report on the function of an exciting new paracrine mediator, the mitochondrial the citric acid(TCA) cycle intermediate ?-ketoglutarate (?KG), which via its OXGR1 receptor plays an unexpected, nontraditional role in the adaptive regulation of renal HCO(3?) secretion and salt reabsorption. PMID:23926603

Peti-Peterdi, János

2013-06-24

7

Modulation of TCA cycle enzymes and electron transport chain systems in experimental lung cancer  

Microsoft Academic Search

The modulatory effect of Withania somnifera along with paclitaxel on tricarboxylic acid (TCA) cycle key enzymes and electron transport chain complexes were investigated against lung cancer induced by benzo(a)pyrene in Swiss albino mice. Decreased activities of TCA cycle key enzymes such as isocitrate dehydrogenase (ICDH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH) and alpha-ketoglutarate dehydrogenase (alpha-KGDH) in lung cancer bearing animals

P. Senthilnathan; R. Padmavathi; V. Magesh; D. Sakthisekaran

2006-01-01

8

Role of Mitochondrial TCA Cycle Enzymes in Determining Prostate Cancer Chemosensitivity.  

National Technical Information Service (NTIS)

In the needle biopsy samples from high-risk prostate cancer patients, we further confirmed that TCA cycle enzymes MDH2 and CS are elevated in subsets of patients. In vitro, comparing three commonly used prostate cancer cell lines PC3, C42B and LNCaP to be...

D. Qian

2011-01-01

9

Micro-coulometric study of bioelectrochemical reaction coupled with TCA cycle.  

PubMed

The mediated electro-enzymatic electrolysis systems based on the tricarboxylic acid (TCA) cycle reaction were examined on a micro-bulk electrolytic system. A series of the enzyme-catalyzed reactions in the TCA cycle was coupled with electrode reaction. Electrochemical oxidation of NADH was catalyzed by diaphorase with an aid of a redox mediator with a formal potential of -0.15 V vs. Ag|AgCl. The mediator was also able to shuttle electrons between succinate dehydrogenase and electrode. The charge during the electrolysis increased on each addition of dehydrogenase reaction in a cascade of the TCA cycle. However, the electrolysis efficiencies were close to or less than 90% because of the product inhibition. Lactate oxidation to acetyl-CoA catalyzed by two NAD-dependent dehydrogenases was coupled with the bioelectrochemical TCA cycle reaction to achieve the 12-electron oxidation of lactate to CO(2). The charge passed in the bioelectrocatalytic oxidation of 5 nmol of lactate was 4 mC, which corresponds to 70% of the electrolysis efficiency. PMID:22391482

Tsujimura, Seiya; Fukuda, Jun; Shirai, Osamu; Kano, Kenji; Sakai, Hideki; Tokita, Yuichi; Hatazawa, Tsuyonobu

2012-02-17

10

A possible role of unique TCA cycles in wood-rotting basidiomycetes  

Microsoft Academic Search

We have reported that the copper tolerant brown-rot fungus, Fomitopsis palustris, acquires metabolic energy by use of the constitutively-occurring Kornberg's glyoxylate cycle coordinating with oxalate biosynthesis and glucose oxidation (Erman Munir et al. Proc. Natl. Acad. Sci. USA, (2001) 98, 11126-11130). Furthrmore, this fungus does not have the normal TCA cycle, lacking 2-oxoglutarate dehydrogenase which is a key enzyme of

Erman Munir; Takefumi Hattori; Mikio Shimada

11

Both forward and reverse TCA cycles operate in green sulfur bacteria.  

PubMed

The anoxygenic green sulfur bacteria (GSBs) assimilate CO(2) autotrophically through the reductive (reverse) tricarboxylic acid (RTCA) cycle. Some organic carbon sources, such as acetate and pyruvate, can be assimilated during the phototrophic growth of the GSBs, in the presence of CO(2) or HCO(3)(-). It has not been established why the inorganic carbonis required for incorporating organic carbon for growth and how the organic carbons are assimilated. In this report, we probed carbon flux during autotrophic and mixotrophic growth of the GSB Chlorobaculum tepidum. Our data indicate the following: (a) the RTCA cycle is active during autotrophic and mixotrophic growth; (b) the flux from pyruvate to acetyl-CoA is very low and acetyl-CoA is synthesized through the RTCA cycle and acetate assimilation; (c) pyruvate is largely assimilated through the RTCA cycle; and (d) acetate can be assimilated via both of the RTCA as well as the oxidative (forward) TCA (OTCA) cycle. The OTCA cycle revealed herein may explain better cell growth during mixotrophic growth with acetate, as energy is generated through the OTCA cycle. Furthermore, the genes specific for the OTCA cycle are either absent or down-regulated during phototrophic growth, implying that the OTCA cycle is not complete, and CO(2) is required for the RTCA cycle to produce metabolites in the TCA cycle. Moreover, CO(2) is essential for assimilating acetate and pyruvate through the CO(2)-anaplerotic pathway and pyruvate synthesis from acetyl-CoA. PMID:20650900

Tang, Kuo-Hsiang; Blankenship, Robert E

2010-07-22

12

A mitochondrial GABA permease connects the GABA shunt and the TCA cycle, and is essential for normal carbon metabolism.  

PubMed

In plants, ?-aminobutyric acid (GABA) accumulates in the cytosol in response to a variety of stresses. GABA is transported into mitochondria, where it is catabolized into TCA cycle or other intermediates. Although there is circumstantial evidence for mitochondrial GABA transporters in eukaryotes, none have yet been identified. Described here is an Arabidopsis protein similar in sequence and topology to unicellular GABA transporters. The expression of this protein complements a GABA-transport-deficient yeast mutant. Thus the protein was termed AtGABP to indicate GABA-permease activity. In vivo localization of GABP fused to GFP and immunobloting of subcellular fractions demonstrate its mitochondrial localization. Direct [(3) H]GABA uptake measurements into isolated mitochondria revealed impaired uptake into mitochondria of a gabp mutant compared with wild-type (WT) mitochondria, implicating AtGABP as a major mitochondrial GABA carrier. Measurements of CO(2) release, derived from radiolabeled substrates in whole seedlings and in isolated mitochondria, demonstrate impaired GABA-derived input into the TCA cycle, and a compensatory increase in TCA cycle activity in gabp mutants. Finally, growth abnormalities of gabp mutants under limited carbon availability on artificial media, and in soil under low light intensity, combined with their metabolite profiles, suggest an important role for AtGABP in primary carbon metabolism and plant growth. Thus, AtGABP-mediated transport of GABA from the cytosol into mitochondria is important to ensure proper GABA-mediated respiration and carbon metabolism. This function is particularly essential for plant growth under conditions of limited carbon. PMID:21501262

Michaeli, Simon; Fait, Aaron; Lagor, Kelly; Nunes-Nesi, Adriano; Grillich, Nicole; Yellin, Ayelet; Bar, Dana; Khan, Munziba; Fernie, Alisdair R; Turano, Frank J; Fromm, Hillel

2011-05-31

13

Reverse TCA cycle flux through isocitrate dehydrogenases 1 and 2 is required for lipogenesis in hypoxic melanoma cells  

PubMed Central

Summary The TCA cycle is the central hub of oxidative metabolism, running in the classic forward direction to provide carbon for biosynthesis and reducing agents for generation of ATP. Our metabolic tracer studies in melanoma cells showed that in hypoxic conditions the TCA cycle is largely disconnected from glycolysis. By studying the TCA branch point metabolites, acetyl CoA and citrate, as well as the metabolic endpoints glutamine and fatty acids, we developed a comprehensive picture of the rewiring of the TCA cycle that occurs in hypoxia. Hypoxic tumor cells maintain proliferation by running the TCA cycle in reverse. The source of carbon for acetyl CoA, citrate, and fatty acids switches from glucose in normoxia to glutamine in hypoxia. This hypoxic flux from glutamine into fatty acids is mediated by reductive carboxylation. This reductive carboxylation is catalyzed by two isocitrate dehydrogenases, IDH1 and IDH2. Their combined action is necessary and sufficient to effect the reverse TCA flux and maintain cellular viability.

Filipp, Fabian V.; Scott, David A.; Ronai, Ze'ev A.; Osterman, Andrei L.; Smith, Jeffrey W.

2012-01-01

14

Reverse TCA cycle flux through isocitrate dehydrogenases 1 and 2 is required for lipogenesis in hypoxic melanoma cells.  

PubMed

The tricarboxylic acid (TCA) cycle is the central hub of oxidative metabolism, running in the classic forward direction to provide carbon for biosynthesis and reducing agents for generation of ATP. Our metabolic tracer studies in melanoma cells showed that in hypoxic conditions the TCA cycle is largely disconnected from glycolysis. By studying the TCA branch point metabolites, acetyl CoA and citrate, as well as the metabolic endpoint glutamine and fatty acids, we developed a comprehensive picture of the rewiring of the TCA cycle that occurs in hypoxia. Hypoxic tumor cells maintain proliferation by running the TCA cycle in reverse. The source of carbon for acetyl CoA, citrate, and fatty acids switches from glucose in normoxia to glutamine in hypoxia. This hypoxic flux from glutamine into fatty acids is mediated by reductive carboxylation. This reductive carboxylation is catalyzed by two isocitrate dehydrogenases, IDH1 and IDH2. Their combined action is necessary and sufficient to effect the reverse TCA flux and maintain cellular viability. PMID:22360810

Filipp, Fabian V; Scott, David A; Ronai, Ze'ev A; Osterman, Andrei L; Smith, Jeffrey W

2012-03-27

15

TCA cycle inactivation in Staphylococcus aureus alters nitric oxide production in RAW 264.7 cells  

PubMed Central

Inactivation of the Staphylococcus aureus tricarboxylic acid (TCA) cycle delays the resolution of cutaneous ulcers in a mouse soft tissue infection model. In this study, it was observed that cutaneous lesions in mice infected with wild-type or isogenic aconitase mutant S. aureus strains contained comparable inflammatory infiltrates, suggesting the delayed resolution was independent of the recruitment of immune cells. These observations led us to hypothesize that staphylococcal metabolism can modulate the host immune response. Using an in vitro model system involving RAW 264.7 cells, the authors observed that cells cultured with S. aureus aconitase mutant strains produced significantly lower amounts of nitric oxide (NO•) and an inducible nitric oxide synthase as compared to those cells exposed to wild-type bacteria. Despite the decrease in NO• synthesis, the expression of antigen-presentation and costimulatory molecules was similar in cells cultured with wild-type and those cultured with aconitase mutant bacteria. The data suggest that staphylococci can evade innate immune responses and potentially enhance their ability to survive in infected hosts by altering their metabolism. This may also explain the occurrence of TCA cycle mutants in clinical S. aureus isolates.

Massilamany, Chandirasegaran; Gangaplara, Arunakumar; Gardner, Donald J.; Musser, James M.; Steffen, David; Somerville, Greg A.

2013-01-01

16

Improving the description of metabolic networks: the TCA cycle as example.  

PubMed

To collect the ever-increasing yet scattered knowledge on metabolism, multiple pathway databases like the Kyoto Encyclopedia of Genes and Genomes have been created. A complete and accurate description of the metabolic network for human and other organisms is essential to foster new biological discoveries. Previous research has shown, however, that the level of agreement among pathway databases is surprisingly low. We investigated whether the lack of consensus among databases can be explained by an inaccurate representation of the knowledge described in scientific literature. As an example, we focus on the well-known tricarboxylic acid (TCA) cycle and evaluated the description of this pathway as found in a comprehensive selection of 10 human metabolic pathway databases. Remarkably, none of the descriptions given by these databases is entirely correct. Moreover, consensus exists on only 3 reactions. Mistakes in pathway databases might lead to the propagation of incorrect knowledge, misinterpretation of high-throughput molecular data, and poorly designed follow-up experiments. We provide an improved description of the TCA cycle via the community-curated database WikiPathways. We review various initiatives that aim to improve the description of the human metabolic network and discuss the importance of the active involvement of biological experts in these. PMID:22661004

Stobbe, Miranda D; Houten, Sander M; van Kampen, Antoine H C; Wanders, Ronald J A; Moerland, Perry D

2012-06-01

17

Anaerobic respiration using a complete oxidative TCA cycle drives multicellular swarming in Proteus mirabilis.  

PubMed

Proteus mirabilis rapidly migrates across surfaces using a periodic developmental process of differentiation alternating between short swimmer cells and elongated hyperflagellated swarmer cells. To undergo this vigorous flagellum-mediated motility, bacteria must generate a substantial proton gradient across their cytoplasmic membranes by using available energy pathways. We sought to identify the link between energy pathways and swarming differentiation by examining the behavior of defined central metabolism mutants. Mutations in the tricarboxylic acid (TCA) cycle (fumC and sdhB mutants) caused altered patterns of swarming periodicity, suggesting an aerobic pathway. Surprisingly, the wild-type strain swarmed on agar containing sodium azide, which poisons aerobic respiration; the fumC TCA cycle mutant, however, was unable to swarm on azide. To identify other contributing energy pathways, we screened transposon mutants for loss of swarming on sodium azide and found insertions in the following genes that involved fumarate metabolism or respiration: hybB, encoding hydrogenase; fumC, encoding fumarase; argH, encoding argininosuccinate lyase (generates fumarate); and a quinone hydroxylase gene. These findings validated the screen and suggested involvement of anaerobic electron transport chain components. Abnormal swarming periodicity of fumC and sdhB mutants was associated with the excretion of reduced acidic fermentation end products. Bacteria lacking SdhB were rescued to wild-type pH and periodicity by providing fumarate, independent of carbon source but dependent on oxygen, while fumC mutants were rescued by glycerol, independent of fumarate only under anaerobic conditions. These findings link multicellular swarming patterns with fumarate metabolism and membrane electron transport using a previously unappreciated configuration of both aerobic and anaerobic respiratory chain components. Bacterial locomotion and the existence of microbes were the first scientific observations that followed the invention of the microscope. A bacterium can swim through a fluid environment or coordinate motion with a group of bacteria and swarm across a surface. The flagellar motor, which propels the bacterium, is fueled by proton motive force. In contrast to the physiology that governs swimming motility, much less is known about the energy sources required for multicellular swarming on surfaces. In this study, we used Proteus mirabilis as a model organism to study vigorous swarming behavior and genetic and biochemical approaches to define energy pathways and central metabolism that contribute to multicellular motility. We found that swarming bacteria use a complete aerobic tricarboxylic acid (TCA) cycle but do not respire oxygen as the terminal electron acceptor, suggesting that multicellular cooperation during swarming reduces the amount of energy required by individual bacteria to achieve rapid motility. PMID:23111869

Alteri, Christopher J; Himpsl, Stephanie D; Engstrom, Michael D; Mobley, Harry L T

2012-10-30

18

An Incomplete TCA Cycle Increases Survival of Salmonella Typhimurium during Infection of Resting and Activated Murine Macrophages  

PubMed Central

Background In comparison to the comprehensive analyses performed on virulence gene expression, regulation and action, the intracellular metabolism of Salmonella during infection is a relatively under-studied area. We investigated the role of the tricarboxylic acid (TCA) cycle in the intracellular replication of Salmonella Typhimurium in resting and activated macrophages, epithelial cells, and during infection of mice. Methodology/Principal Findings We constructed deletion mutations of 5 TCA cycle genes in S. Typhimurium including gltA, mdh, sdhCDAB, sucAB, and sucCD. We found that the mutants exhibited increased net intracellular replication in resting and activated murine macrophages compared to the wild-type. In contrast, an epithelial cell infection model showed that the S. Typhimurium ?sucCD and ?gltA strains had reduced net intracellular replication compared to the wild-type. The glyoxylate shunt was not responsible for the net increased replication of the TCA cycle mutants within resting macrophages. We also confirmed that, in a murine infection model, the S. Typhimurium ?sucAB and ?sucCD strains are attenuated for virulence. Conclusions/Significance Our results suggest that disruption of the TCA cycle increases the ability of S. Typhimurium to survive within resting and activated murine macrophages. In contrast, epithelial cells are non-phagocytic cells and unlike macrophages cannot mount an oxidative and nitrosative defence response against pathogens; our results show that in HeLa cells the S. Typhimurium TCA cycle mutant strains show reduced or no change in intracellular levels compared to the wild-type [1]. The attenuation of the S. Typhimurium ?sucAB and ?sucCD mutants in mice, compared to their increased net intracellular replication in resting and activated macrophages suggest that Salmonella may encounter environments within the host where a complete TCA cycle is advantageous.

Knudsen, Gitte M.; Hinton, Jay C. D.; Thompson, Arthur

2010-01-01

19

Anaerobic Respiration Using a Complete Oxidative TCA Cycle Drives Multicellular Swarming in Proteus mirabilis  

PubMed Central

ABSTRACT Proteus mirabilis rapidly migrates across surfaces using a periodic developmental process of differentiation alternating between short swimmer cells and elongated hyperflagellated swarmer cells. To undergo this vigorous flagellum-mediated motility, bacteria must generate a substantial proton gradient across their cytoplasmic membranes by using available energy pathways. We sought to identify the link between energy pathways and swarming differentiation by examining the behavior of defined central metabolism mutants. Mutations in the tricarboxylic acid (TCA) cycle (fumC and sdhB mutants) caused altered patterns of swarming periodicity, suggesting an aerobic pathway. Surprisingly, the wild-type strain swarmed on agar containing sodium azide, which poisons aerobic respiration; the fumC TCA cycle mutant, however, was unable to swarm on azide. To identify other contributing energy pathways, we screened transposon mutants for loss of swarming on sodium azide and found insertions in the following genes that involved fumarate metabolism or respiration: hybB, encoding hydrogenase; fumC, encoding fumarase; argH, encoding argininosuccinate lyase (generates fumarate); and a quinone hydroxylase gene. These findings validated the screen and suggested involvement of anaerobic electron transport chain components. Abnormal swarming periodicity of fumC and sdhB mutants was associated with the excretion of reduced acidic fermentation end products. Bacteria lacking SdhB were rescued to wild-type pH and periodicity by providing fumarate, independent of carbon source but dependent on oxygen, while fumC mutants were rescued by glycerol, independent of fumarate only under anaerobic conditions. These findings link multicellular swarming patterns with fumarate metabolism and membrane electron transport using a previously unappreciated configuration of both aerobic and anaerobic respiratory chain components.

Alteri, Christopher J.; Himpsl, Stephanie D.; Engstrom, Michael D.; Mobley, Harry L. T.

2012-01-01

20

Real Time Molecular Imaging of TCA Cycle Metabolism in vivo By Hyperpolarized 1-13C Diethyl Succinate  

PubMed Central

The Krebs tricarboxylic acid cycle (TCA) is central to metabolic energy production and is known to be altered in many disease states. Real time molecular imaging of TCA cycle in vivo will be important in understanding the metabolic basis of several diseases. Positron emission tomography (PET) using FDG-glucose (2-[18F]fluoro-2-deoxy-D-glucose) is already being used as a metabolic imaging agent in clinics. However, FDG-glucose does not reveal anything past glucose uptake and phosphorylation. We have developed a new metabolic imaging agent, hyperpolarized diethyl 1-13C 2,3-d2 succinate, that allows for real time in vivo imaging and spectroscopy of the TCA cycle. Diethyl succinate can be hyperpolarized using parahydrogen induced polarization (PHIP) in an aqueous solution with signal enhancement of 5000 compared to Boltzmann polarization. 13C magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) were achieved in vivo seconds after injection of 10 to 20 ?mol of hyperpolarized diethyl succinate into normal mice. The downstream metabolites of hyperpolarized diethyl succinate were identified in vivo as malate, succinate, fumarate and aspartate. The metabolism of diethyl succinate was altered after exposing the animal to 3-nitropropionate, a known irreversible inhibitor of succinate dehydrogenase. Based on our results, hyperpolarized diethyl succinate allows for in real time in vivo MRI and MRS with a high signal to noise ratio and with visualization of multiple steps of the TCA cycle. Hyperpolarization of diethyl succinate and its in vivo applications may reveal an entirely new regime wherein the local status of TCA cycle metabolism is interrogated on the time scale of seconds to minutes with unprecedented chemical specificity and MR sensitivity.

Zacharias, Niki M.; Chan, Henry R.; Sailasuta, Napapon; Ross, Brian D.

2011-01-01

21

Isotopomer Profiling of Leishmania mexicana Promastigotes Reveals Important Roles for Succinate Fermentation and Aspartate Uptake in Tricarboxylic Acid Cycle (TCA) Anaplerosis, Glutamate Synthesis, and Growth*  

PubMed Central

Leishmania parasites proliferate within nutritionally complex niches in their sandfly vector and mammalian hosts. However, the extent to which these parasites utilize different carbon sources remains poorly defined. In this study, we have followed the incorporation of various 13C-labeled carbon sources into the intracellular and secreted metabolites of Leishmania mexicana promastigotes using gas chromatography-mass spectrometry and 13C NMR. [U-13C]Glucose was rapidly incorporated into intermediates in glycolysis, the pentose phosphate pathway, and the cytoplasmic carbohydrate reserve material, mannogen. Enzymes involved in the upper glycolytic pathway are sequestered within glycosomes, and the ATP and NAD+ consumed by these reactions were primarily regenerated by the fermentation of phosphoenolpyruvate to succinate (glycosomal succinate fermentation). The initiating enzyme in this pathway, phosphoenolpyruvate carboxykinase, was exclusively localized to the glycosome. Although some of the glycosomal succinate was secreted, most of the C4 dicarboxylic acids generated during succinate fermentation were further catabolized in the TCA cycle. A high rate of TCA cycle anaplerosis was further suggested by measurement of [U-13C]aspartate and [U-13C]alanine uptake and catabolism. TCA cycle anaplerosis is apparently needed to sustain glutamate production under standard culture conditions. Specifically, inhibition of mitochondrial aconitase with sodium fluoroacetate resulted in the rapid depletion of intracellular glutamate pools and growth arrest. Addition of high concentrations of exogenous glutamate alleviated this growth arrest. These findings suggest that glycosomal and mitochondrial metabolism in Leishmania promastigotes is tightly coupled and that, in contrast to the situation in some other trypanosomatid parasites, the TCA cycle has crucial anabolic functions.

Saunders, Eleanor C.; Ng, William W.; Chambers, Jennifer M.; Ng, Milica; Naderer, Thomas; Kromer, Jens O.; Likic, Vladimir A.; McConville, Malcolm J.

2011-01-01

22

Comparison of Intact Arabidopsis thaliana Leaf Transcript Profiles during Treatment with Inhibitors of Mitochondrial Electron Transport and TCA Cycle  

PubMed Central

Plant mitochondria signal to the nucleus leading to altered transcription of nuclear genes by a process called mitochondrial retrograde regulation (MRR). MRR is implicated in metabolic homeostasis and responses to stress conditions. Mitochondrial reactive oxygen species (mtROS) are a MRR signaling component, but whether all MRR requires ROS is not established. Inhibition of the cytochrome respiratory pathway by antimycin A (AA) or the TCA cycle by monofluoroacetate (MFA), each of which initiates MRR, can increase ROS production in some plant cells. We found that for AA and MFA applied to leaves of soil-grown Arabidopsis thaliana plants, ROS production increased with AA, but not with MFA, allowing comparison of transcript profiles under different ROS conditions during MRR. Variation in transcript accumulation over time for eight nuclear encoded mitochondrial protein genes suggested operation of both common and distinct signaling pathways between the two treatments. Consequences of mitochondrial perturbations for the whole transcriptome were examined by microarray analyses. Expression of 1316 and 606 genes was altered by AA and MFA, respectively. A subset of genes was similarly affected by both treatments, including genes encoding photosynthesis-related proteins. MFA treatment resulted in more down-regulation. Functional gene category (MapMan) and cluster analyses showed that genes with expression levels affected by perturbation from AA or MFA inhibition were most similarly affected by biotic stresses such as pathogens. Overall, the data provide further evidence for the presence of mtROS-independent MRR signaling, and support the proposed involvement of MRR and mitochondrial function in plant responses to biotic stress.

Yu, Jianping; Ruckle, Michael E.; McIntosh, Lee; Hock, Jeffery J.; Bingham, Scott; White, Samuel J.; George, Rajani M.; Subbaiah, Chalivendra C.; Rhoads, David M.

2012-01-01

23

Exposure of Clinical MRSA Heterogeneous Strains to ?-Lactams Redirects Metabolism to Optimize Energy Production through the TCA Cycle  

PubMed Central

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as one of the most important pathogens both in health care and community-onset infections. The prerequisite for methicillin resistance is mecA, which encodes a ?-lactam-insensitive penicillin binding protein PBP2a. A characteristic of MRSA strains from hospital and community associated infections is their heterogeneous expression of resistance to ?-lactam (HeR) in which only a small portion (?0.1%) of the population expresses resistance to oxacillin (OXA) ?10 µg/ml, while in other isolates, most of the population expresses resistance to a high level (homotypic resistance, HoR). The mechanism associated with heterogeneous expression requires both increase expression of mecA and a mutational event that involved the triggering of a ?-lactam-mediated SOS response and related lexA and recA genes. In the present study we investigated the cellular physiology of HeR-MRSA strains during the process of ?-lactam-mediated HeR/HoR selection at sub-inhibitory concentrations by using a combinatorial approach of microarray analyses and global biochemical profiling employing gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/mass spectrometry (LC/MS) to investigate changes in metabolic pathways and the metabolome associated with ?-lactam-mediated HeR/HoR selection in clinically relevant heterogeneous MRSA. We found unique features present in the oxacillin-selected SA13011-HoR derivative when compared to the corresponding SA13011-HeR parental strain that included significant increases in tricarboxyl citric acid (TCA) cycle intermediates and a concomitant decrease in fermentative pathways. Inactivation of the TCA cycle enzyme cis-aconitase gene in the SA13011-HeR strain abolished ?-lactam-mediated HeR/HoR selection demonstrating the significance of altered TCA cycle activity during the HeR/HoR selection. These results provide evidence of both the metabolic cost and the adaptation that HeR-MRSA clinical strains undergo when exposed to ?-lactam pressure, indicating that the energy production is redirected to supply the cell wall synthesis/metabolism, which in turn contributes to the survival response in the presence of ?-lactam antibiotics.

Keaton, Mignon A.; Rosato, Roberto R.; Plata, Konrad B.; Singh, Christopher R.; Rosato, Adriana E.

2013-01-01

24

Fitness of Escherichia coli during Urinary Tract Infection Requires Gluconeogenesis and the TCA Cycle  

PubMed Central

Microbial pathogenesis studies traditionally encompass dissection of virulence properties such as the bacterium's ability to elaborate toxins, adhere to and invade host cells, cause tissue damage, or otherwise disrupt normal host immune and cellular functions. In contrast, bacterial metabolism during infection has only been recently appreciated to contribute to persistence as much as their virulence properties. In this study, we used comparative proteomics to investigate the expression of uropathogenic Escherichia coli (UPEC) cytoplasmic proteins during growth in the urinary tract environment and systematic disruption of central metabolic pathways to better understand bacterial metabolism during infection. Using two-dimensional fluorescence difference in gel electrophoresis (2D-DIGE) and tandem mass spectrometry, it was found that UPEC differentially expresses 84 cytoplasmic proteins between growth in LB medium and growth in human urine (P<0.005). Proteins induced during growth in urine included those involved in the import of short peptides and enzymes required for the transport and catabolism of sialic acid, gluconate, and the pentose sugars xylose and arabinose. Proteins required for the biosynthesis of arginine and serine along with the enzyme agmatinase that is used to produce the polyamine putrescine were also up-regulated in urine. To complement these data, we constructed mutants in these genes and created mutants defective in each central metabolic pathway and tested the relative fitness of these UPEC mutants in vivo in an infection model. Import of peptides, gluconeogenesis, and the tricarboxylic acid cycle are required for E. coli fitness during urinary tract infection while glycolysis, both the non-oxidative and oxidative branches of the pentose phosphate pathway, and the Entner-Doudoroff pathway were dispensable in vivo. These findings suggest that peptides and amino acids are the primary carbon source for E. coli during infection of the urinary tract. Because anaplerosis, or using central pathways to replenish metabolic intermediates, is required for UPEC fitness in vivo, we propose that central metabolic pathways of bacteria could be considered critical components of virulence for pathogenic microbes.

Alteri, Christopher J.; Smith, Sara N.; Mobley, Harry L. T.

2009-01-01

25

GC/TOFMS analysis of metabolites in serum and urine reveals metabolic perturbation of TCA cycle in db/db mice involved in diabetic nephropathy.  

PubMed

Early diagnosis of diabetic nephropathy (DN) is difficult although it is of crucial importance to prevent its development. To probe potential markers and the underlying mechanism of DN, an animal model of DN, the db/db mice, was used and serum and urine metabolites were profiled using gas chromatography/time-of-flight mass spectrometry. Metabolic patterns were evaluated based on serum and urine data. Principal component analysis of the data revealed an obvious metabonomic difference between db/db mice and controls, and db/db mice showed distinctly different metabolic patterns during the progression from diabetes to early, medium, and later DN. The identified metabolites discriminating between db/db mice and controls suggested that db/db mice have perturbations in the tricarboxylic acid cycle (TCA, citrate, malate, succinate, and aconitate), lipid metabolism, glycolysis, and amino acid turnover. The db/db mice were characterized by acidic urine, high TCA intermediates in serum at week 6 and a sharp decline thereafter, and gradual elevation of free fatty acids in the serum. The sharp drop of serum TCA intermediates from week 6 to 8 indicated the downregulated glycolysis and insulin resistance. However, urinary TCA intermediates did not decrease in parallel with those in the serum from week 6 to 10, and an increased portion of TCA intermediates in the serum was excreted into the urine at 8, 10, and 12 wk than at 6 wk, indicating kidney dysfunction occurred. The relative abundances of TCA intermediates in urine relative to those in serum were suggested as an index of renal damage. PMID:23467425

Li, Mengjie; Wang, Xufang; Aa, Jiye; Qin, Weisong; Zha, Weibin; Ge, Yongchun; Liu, Linsheng; Zheng, Tian; Cao, Bei; Shi, Jian; Zhao, Chunyan; Wang, Xinwen; Yu, Xiaoyi; Wang, Guangji; Liu, Zhihong

2013-03-06

26

Hypoxia Triggers Major Metabolic Changes in AML Cells without Altering Indomethacin-Induced TCA Cycle Deregulation  

PubMed Central

Our previous studies have shown that the nonsteroidal anti-inflammatory drug indomethacin exhibits antileukemic activity in vitro and can inhibit the aldo-keto reductase AKR1C3, which we identified as a novel target in acute myeloid leukemia. However, the antileukemic actions of indomethacin are likely to be complex and extend beyond inhibition of either AKR1C3 or cycloxygenases. To further understand the antileukemic activity of indomethacin we have used untargeted nuclear magnetic resonance-based metabolic analysis to characterize the responses of KG1a and K562 cell lines in both normal culture conditions and in hypoxia, which better represents the tumor environment in vivo. Hypoxia induced dramatic metabolic changes in untreated KG1a and K562, including adaptation of both phospholipid and glycolytic metabolism. Despite these changes, both cell lines sustained relatively unaltered mitochondrial respiration. The administration of indomethacin induced similar metabolic responses regardless of the oxygen level in the environment. Notable exceptions included metabolites associated with de novo fatty acid synthesis and choline phospholipid metabolism. Collectively, these results suggest that leukemia cells have the inherent ability to tolerate changes in oxygen tension while maintaining an unaltered mitochondrial respiration. However, the administration of indomethacin significantly increased oxidative stress in both KG1a and K562, inducing mitochondrial dysfunction, regardless of the oxygenation conditions. These findings emphasize the particular pertinence of the tricarboxylic acid cycle to the survival of cancer cells and may explain why some antileukemic drugs have been discovered and developed successfully despite the use of culture conditions that do not reflect the hypoxic environment of cancer cells in vivo.

2010-01-01

27

Possible links between stress defense and the tricarboxylic acid (TCA) cycle in Francisella pathogenesis.  

PubMed

Francisella tularensis is a highly infectious bacterium causing the zoonotic disease tularemia. In vivo, this facultative intracellular bacterium survives and replicates mainly in the cytoplasm of infected cells. We have recently identified a genetic locus, designated moxR that is important for stress resistance and intramacrophage survival of F. tularensis. In the present work, we used tandem affinity purification coupled to mass spectrometry to identify in vivo interacting partners of three proteins encoded by this locus: the MoxR-like ATPase (FTL_0200), and two proteins containing motifs predicted to be involved in protein-protein interactions, bearing von Willebrand A (FTL_0201) and tetratricopeptide (FTL_0205) motifs. The three proteins were designated here for simplification, MoxR, VWA1, and TPR1, respectively. MoxR interacted with 31 proteins, including various enzymes. VWA1 interacted with fewer proteins, but these included the E2 component of 2-oxoglutarate dehydrogenase and TPR1. The protein TPR1 interacted with one hundred proteins, including the E1 and E2 subunits of both oxoglutarate and pyruvate dehydrogenase enzyme complexes, and their common E3 subunit. Remarkably, chromosomal deletion of either moxR or tpr1 impaired pyruvate dehydrogenase and oxoglutarate dehydrogenase activities, supporting the hypothesis of a functional role for the interaction of MoxR and TPR1 with these complexes. Altogether, this work highlights possible links between stress resistance and metabolism in F. tularensis virulence. PMID:23669032

Dieppedale, Jennifer; Gesbert, Gael; Ramond, Elodie; Chhuon, Cerina; Dubail, Iharilalao; Dupuis, Marion; Guerrera, Ida Chiara; Charbit, Alain

2013-05-13

28

The Majority of Free-Living Autotrophic Bacteria use the Reductive TCA Cycle for Carbon Fixation at Deep-Sea Hydrothermal Vents  

NASA Astrophysics Data System (ADS)

Deep-sea hydrothermal vents support large micro and macroscopic communities, without the input of photosynthesis. Autotrophic production at these vents is based on hydrothermal vent fluid chemistry. Primary production has been thought to occur mainly via hydrogen sulfide oxidation through the Calvin-Benson pathway, as measured by the presence of Rubisco in endosymbionts of several invertebrate hosts. Recently, we characterized two fosmids from a large insert library of the epsilon Proteobacterial episymbionts of Alvinella pompejana. Both contained sequences encoding ATP citrate lyase, a key enzyme in the reverse TCA cycle, an alternate carbon dioxide fixation pathway. Previous investigators have demonstrated the dominance of the epsilon subdivision in the free-living bacterial communities at hydrothermal vents. Based on these results, our working hypothesis is: The rTCA cycle is the dominant pathway for carbon fixation in the free-living bacterial communities at hydrothermal vents. A selection of free-living bacterial communities from various geographic locations (9N, East Pacific Rise and Guaymas Basin) were screened for the presence, diversity and expression (via RT-PCR) of Rubisco (forms I and II) and ATP citrate lyase. Our results indicate that the ATP citrate lyase gene is diverse and is consistently expressed in several types of vent communities. The two forms of Rubisco are not consistently present or expressed in the same environments. These results indicate that chemoautotrophic production in the free-living bacterial communities at deep-sea hydrothermal vents is dominated by bacteria that utilize the rTCA cycle, and parallels the phylogenetic dominance of members of the epsilon subdivision of Proteobacteria.

Campbell, B. J.; Cary, C.

2003-12-01

29

Modulation of key enzymes of glycolysis, gluconeogenesis, amino acid catabolism, and TCA cycle of the tropical freshwater fish Labeo rohita fed gelatinized and non-gelatinized starch diet.  

PubMed

A 60-day experiment was conducted to study the effect of dietary gelatinized (G) and non-gelatinized (NG) starch on the key metabolic enzymes of glycolysis (hexokinase, glucokinase, pyruvate kinase, and lactate dehydrogenase), gluconeogenesis (glucose-6 phosphatase and fructose-1,6 bisphosphatase), protein metabolism (aspartate amino transferase and alanine amino transferase), and TCA cycle (malate dehydrogenase) in Labeo rohita juveniles. In the analysis, 234 juveniles (2.53 +/- 0.04 g) were randomly distributed into six treatment groups each with three replicates. Six semi-purified diets containing NG and G cornstarch, each at six levels of inclusion (0, 20, 40, 60, 80, and 100) were prepared viz., T1 (100% NG, 0% G starch), T2 (80% NG, 20% G starch), T3 (60% NG, 40% G starch), T4 (40% NG, 60% G starch), T5 (20% NG, 80% G starch), and T6 (0% NG, 100% G starch). Dietary G:NG starch ratio had a significant (P < 0.05) effect on the glycolytic enzymes, the highest activities were observed in the T6 group and lowest in the T1 group. On the contrary, the gluconeogenic enzymes, the glucose-6-phosphatase and fructose-1,6 bisphosphatase activities in the organs, liver and kidney were recorded highest in the T1 group and lowest in the T6 group. The liver aspartate amino transferase activity showed an increasing trend with the decrease in the dietary G level. However, the muscle aspartate amino transferase activity was not significantly (P > 0.05) influenced by the type of dietary starch. The alanine amino transferase activity in both liver and muscle showed an increasing trend with the decrease in the dietary G level. The liver and muscle malate dehydrogenase activities were lowest in the T6 group and highest in the T1 group. Results suggest that NG (100%) starch diet significantly induced more the enzyme activities of amino acid metabolism, gluconeogenesis, and TCA cycle, whereas partial or total replacement of raw starch by gelatinized starch increased the glycolytic enzyme activity. PMID:19340598

Kumar, Vikas; Sahu, N P; Pal, A K; Kumar, Shivendra; Sinha, Amit Kumar; Ranjan, Jayant; Baruah, Kartik

2009-04-02

30

Global Transcription Analysis of Krebs Tricarboxylic Acid Cycle Mutants Reveals an Alternating Pattern of Gene Expression and Effects on Hypoxic and Oxidative Genes  

Microsoft Academic Search

To understand the many roles of the Krebs tricarboxylic acid (TCA) cycle in cell function, we used DNA microarrays to examine gene expression in response to TCA cycle dysfunction. mRNA was analyzed from yeast strains harboring defects in each of 15 genes that encode subunits of the eight TCA cycle enzymes. The expression of 400 genes changed at least threefold

Mark T. McCammon; Charles B. Epstein; Beata Przybyla-Zawislak; Ronald A. Butow

2002-01-01

31

Chromosome-encoded gene cluster for the metabolic pathway that converts aniline to TCA-cycle intermediates in Delftia tsuruhatensis AD9.  

PubMed

Delftia tsuruhatensis AD9 was isolated as an aniline-degrading bacterium from the soil surrounding a textile dyeing plant. The gene cluster involved in aniline degradation was cloned from the total DNA of strain AD9 into Escherichia coli JM109. After shotgun cloning, two recombinant E. coli strains showing aniline oxidation activity or catechol meta-cleavage activity were obtained by simple plate assays. These strains contained 9.3 kb and 15.4 kb DNA fragments, respectively. Sequence analysis of the total 24.7 kb region revealed that this region contains a gene cluster (consisting of at least 17 genes, named tadQTA1A2BRD1C1D2C2EFGIJKL) responsible for the complete metabolism of aniline to TCA-cycle intermediates. In the gene cluster, the first five genes (tadQTA1A2B) and the subsequent gene (tadR) were predicted to encode a multi-component aniline dioxygenase and a LysR-type regulator, respectively, while the others (tadD1C1D2C2EFGIJKL) were expected to encode meta-cleavage pathway enzymes for catechol degradation. In addition, it was found that the gene cluster is surrounded by two IS1071 sequences, indicating that it has a class I transposon-like structure. PFGE and Southern hybridization analyses confirmed that the tad gene cluster is encoded on the chromosome of strain AD9 in a single copy. These results suggest that, in strain AD9, aniline is degraded via catechol through a meta-cleavage pathway by the chromosome-encoded tad gene cluster. The tad gene cluster showed significant similarity in nucleotide sequence and genetic organization to the plasmid-encoded aniline degradation gene cluster of Pseudomonas putida UCC22. PMID:16207925

Liang, Quanfeng; Takeo, Masahiro; Chen, Ming; Zhang, Wei; Xu, Yuquan; Lin, Min

2005-10-01

32

The Cc Chemokine Thymus-Derived Chemotactic Agent 4 (Tca-4, Secondary Lymphoid Tissue Chemokine, 6ckine, Exodus-2) Triggers Lymphocyte Function-Associated Antigen 1-Mediated Arrest of Rolling T Lymphocytes in Peripheral Lymph Node High Endothelial Venules  

PubMed Central

T cell homing to peripheral lymph nodes (PLNs) is defined by a multistep sequence of interactions between lymphocytes and endothelial cells in high endothelial venules (HEVs). After initial tethering and rolling via L-selectin, firm adhesion of T cells requires rapid upregulation of lymphocyte function–associated antigen 1 (LFA-1) adhesiveness by a previously unknown pathway that activates a G?i-linked receptor. Here, we used intravital microscopy of murine PLNs to study the role of thymus-derived chemotactic agent (TCA)-4 (secondary lymphoid tissue chemokine, 6Ckine, Exodus-2) in homing of adoptively transferred T cells from T-GFP mice, a transgenic strain that expresses green fluorescent protein (GFP) selectively in naive T lymphocytes (TGFP cells). TCA-4 was constitutively presented on the luminal surface of HEVs, where it was required for LFA-1 activation on rolling TGFP cells. Desensitization of the TCA-4 receptor, CC chemokine receptor 7 (CCR7), blocked TGFP cell adherence in wild-type HEVs, whereas desensitization to stromal cell–derived factor (SDF)-1? (the ligand for CXC chemokine receptor 4 [CXCR4]) did not affect TGFP cell behavior. TCA-4 protein was not detected on the luminal surface of PLN HEVs in plt/plt mice, which have a congenital defect in T cell homing to PLNs. Accordingly, TGFP cells rolled but did not arrest in plt/plt HEVs. When TCA-4 was injected intracutaneously into plt/plt mice, the chemokine entered afferent lymph vessels and accumulated in draining PLNs. 2 h after intracutaneous injection, luminal presentation of TCA-4 was detectable in a subset of HEVs, and LFA-1–mediated TGFP cell adhesion was restored in these vessels. We conclude that TCA-4 is both required and sufficient for LFA-1 activation on rolling T cells in PLN HEVs. This study also highlights a hitherto undocumented role for chemokines contained in afferent lymph, which may modulate leukocyte recruitment in draining PLNs.

Stein, Jens V.; Rot, Antal; Luo, Yi; Narasimhaswamy, Manjunath; Nakano, Hideki; Gunn, Michael D.; Matsuzawa, Akio; Quackenbush, Elizabeth J.; Dorf, Martin E.; von Andrian, Ulrich H.

2000-01-01

33

Integrated proteomic and metabolomic analysis reveals the NADH-mediated TCA cycle and energy metabolism disorders based on a new model of chronic progressive heart failure.  

PubMed

Background: Despite major advances in the treatment of heart failure (HF), it remains the major cause of mortality and morbidity worldwide. Experimental models of HF typically utilize acute myocardial infarction. However, the majority of clinical HFs occur gradually by a chronic progressive mechanism. Thus, more relevant models are required to aid identification, quantification, and characterization of HF, and its underlying mechanisms. Methods and findings: We developed a model of progressive chronic heart failure (CHF) in the mini-swine by placement of an ameroid constrictor on the left anterior descending coronary artery (LAD). This model demonstrated a steady decline in the cardiac function from 8 to 12 weeks, with a 50% reduction in the ejection fraction. Further, the proteomic, metabolomic and bioinformatic analyses of ischemic tissue and plasma revealed a significant alteration of the mitochondrial respiratory chain mediated by nicotinamide adenine dinucleotide (NADH), which resulted in down-regulation of malate dehydrogenase (MDH) and insufficient energy supply to support cardiac contractility and relaxation. Furthermore, significant changes in apolipoprotein A-I, low density lipoprotein (LDL), and very LDL (VLDL) in plasma indicated that lipid metabolism disorders occurred in mini-swines with myocardial ischemia via glycerolipid metabolism. Conclusions: We describe a stable and easily reproducible CHF model using an ameroid constrictor placed on the LAD. We found that the NADH-mediated tricarboxylic acid cycle and energy metabolism disorders are key pathophysiological mechanisms underlying CHF. These data will provide potential biomarkers for monitoring the therapeutic intervention of CHF. PMID:24108264

Wang, Yong; Li, Chun; Chuo, Wenjing; Liu, Zhongyang; Ouyang, Yulin; Li, Dong; Han, Jing; Wu, Yan; Guo, Shuzhen; Wang, Wei

2013-10-10

34

Lentivirus-mediated RNA interference of E2F-1 suppresses Tca8113 cell proliferation.  

PubMed

In most types of human cancer, inactivation of pRb/E2F complexes occurs, and released E2Fs initiate transcription of genes required for cell cycle progression. Evidence reveals that phosphorylated pRb deregulates E2F-1, and the levels of E2F-1 expression can accurately predict prognosis of oral squamous cell carcinoma (OSCC). Paradoxically, numerous reports indicate that E2F-1 is also capable of inducing apoptosis under certain cellular circumstances. In the present study, lentivirus-mediated shRNA was used to downregulate endogenous E2F-1 expression in order to study the function of E2F-1 in the pRb/E2F-1 pathway in the OSCC cell line Tca8113, and to investigate the alteration of Tca8113 cells in proliferation and apoptosis. The data from real-time quantitative RT-PCR and Western blot analysis showed that E2F-1-shRNA led to the inhibition of endogenous E2F-1 mRNA and protein expression, and E2F-1 may be associated with proliferation and apoptosis pathways. Growth kinetics data showed that Tca8113-E2F-1-shRNA cells presented more active proliferation properties than Tca8113-NC cells, and flow cytometry data demonstrated that the percentages of cells in the G1 phase, G2 phase and undergoing apoptosis differed between groups. In conclusion, silencing of E2F-1 inhibits proliferation and induces apoptosis. E2F-1 may also be involved in multi-level regulation networks; therefore, its role in OSCC requires further clarification. PMID:22076063

Yuan, Hua; Jiang, Fei; Wang, Ruixia; Shen, Ming; Chen, Ning

2011-11-07

35

ATCA/muTCA for Physics  

SciTech Connect

ATCA/{mu}TCA platforms are attractive because of the modern serial link architecture, high availability features and many packaging options. Less-demanding availability applications can be met economically by scaling back speed and redundancy. The ATCA specification was originally targeted for the Telecom industry but has gained recently a much wider user audience. The purpose of this paper is to report on present hardware and software R and D efforts where ATCA and {mu}TCA are planned, already being used or in development using selected examples for accelerator and detectors in the Physics community. It will present also the status of a proposal for physics extensions to ATCA/{mu}TCA specifications to promote inter-operability of laboratory and industry designs for physics.

Jezynski, Tomasz; /DESY; Larsen, Raymond; /SLAC; Le Du, Patrick; /Lyon, IPN

2012-06-14

36

Development of 2dTCA for the Detection of Irregular, Transient BOLD Activity  

PubMed Central

The temporal clustering algorithm (TCA) has been developed in order to detect irregular, transient functional MRI (fMRI) activation signals when the timings of the stimuli are unknown. Unfortunately, such methods are also sensitive to signal changes caused by motion and physiological noise. We have developed a modified TCA technique, 2dTCA, which can detect multiple different timing patterns within a dataset so that signals of interest can be separated from artifacts and those of no interest. The objective of this work was to further develop the 2dTCA methods and evaluate their performance in simulated functional MRI datasets. Comparisons were made with TCA and a freely-distributed independent component analysis algorithm (ICA). We created two different sets of six computer-generated phantoms with one and two different simulated activation time courses present in 10 regions of interest. The phantoms also contained real subject rigid and nonrigid body motion and noise. Sensitivity of detection, defined as the true-positive activation rate at false-positive activation rates varying between 0.0001 and 0.01, was compared between methods. Additionally, specificity of detection of the irregular, transient signal of interest was assessed by comparing the number of signal time courses detected by each algorithm. The results suggest that the increased sensitivity of 2dTCA over TCA in detecting this particular signal of interest is comparable to the detection with ICA, but with fewer other signals detected. A few examples of the successful application of 2dTCA to the localization of interictal activity in preliminary studies of temporal lobe epilepsy are also described.

Morgan, Victoria L.; Li, Yong; Abou-Khalil, Bassel; Gore, John C.

2009-01-01

37

Functional Family Therapy: A Life Cycle Perspective.  

ERIC Educational Resources Information Center

|Functional family therapy model assesses family behavior from perspectives of interactional process and functional payoffs for the individual family members. Illustrates that functional needs change as a result of development, and that by including a family life cycle perspective in the assessment process, clinicians will get a clearer picture of…

Wetchler, Joseph L.

1985-01-01

38

In folio respiratory fluxomics revealed by 13C isotopic labeling and H/D isotope effects highlight the noncyclic nature of the tricarboxylic acid "cycle" in illuminated leaves.  

PubMed

While the possible importance of the tricarboxylic acid (TCA) cycle reactions for leaf photosynthesis operation has been recognized, many uncertainties remain on whether TCA cycle biochemistry is similar in the light compared with the dark. It is widely accepted that leaf day respiration and the metabolic commitment to TCA decarboxylation are down-regulated in illuminated leaves. However, the metabolic basis (i.e. the limiting steps involved in such a down-regulation) is not well known. Here, we investigated the in vivo metabolic fluxes of individual reactions of the TCA cycle by developing two isotopic methods, (13)C tracing and fluxomics and the use of H/D isotope effects, with Xanthium strumarium leaves. We provide evidence that the TCA "cycle" does not work in the forward direction like a proper cycle but, rather, operates in both the reverse and forward directions to produce fumarate and glutamate, respectively. Such a functional division of the cycle plausibly reflects the compromise between two contrasted forces: (1) the feedback inhibition by NADH and ATP on TCA enzymes in the light, and (2) the need to provide pH-buffering organic acids and carbon skeletons for nitrate absorption and assimilation. PMID:19675152

Tcherkez, Guillaume; Mahé, Aline; Gauthier, Paul; Mauve, Caroline; Gout, Elizabeth; Bligny, Richard; Cornic, Gabriel; Hodges, Michael

2009-08-12

39

In Folio Respiratory Fluxomics Revealed by 13C Isotopic Labeling and H/D Isotope Effects Highlight the Noncyclic Nature of the Tricarboxylic Acid "Cycle" in Illuminated Leaves1[W  

PubMed Central

While the possible importance of the tricarboxylic acid (TCA) cycle reactions for leaf photosynthesis operation has been recognized, many uncertainties remain on whether TCA cycle biochemistry is similar in the light compared with the dark. It is widely accepted that leaf day respiration and the metabolic commitment to TCA decarboxylation are down-regulated in illuminated leaves. However, the metabolic basis (i.e. the limiting steps involved in such a down-regulation) is not well known. Here, we investigated the in vivo metabolic fluxes of individual reactions of the TCA cycle by developing two isotopic methods, 13C tracing and fluxomics and the use of H/D isotope effects, with Xanthium strumarium leaves. We provide evidence that the TCAcycle” does not work in the forward direction like a proper cycle but, rather, operates in both the reverse and forward directions to produce fumarate and glutamate, respectively. Such a functional division of the cycle plausibly reflects the compromise between two contrasted forces: (1) the feedback inhibition by NADH and ATP on TCA enzymes in the light, and (2) the need to provide pH-buffering organic acids and carbon skeletons for nitrate absorption and assimilation.

Tcherkez, Guillaume; Mahe, Aline; Gauthier, Paul; Mauve, Caroline; Gout, Elizabeth; Bligny, Richard; Cornic, Gabriel; Hodges, Michael

2009-01-01

40

Effect of siRNA-mediated downregulation of VEGF in Tca8113 cells on the activity of monocyte-derived dendritic cells  

PubMed Central

Vascular endothelial growth factor (VEGF) is a tumor angiogenesis factor that is important in immune regulation. In our previous study, we found that VEGF expression in the peripheral blood and neoplasm nest from patients with oral squamous cell carcinoma (OSCC) was positively correlated with the course of disease, while an inverse correlation between VEGF expression and dendritic cells (DCs) was identified in the peripheral blood. Therefore, in the present study, we investigated whether inhibition of human VEGF in the human tongue carcinoma cell line Tca8113 had effects on the activity of monocyte-derived DCs. We knocked down the expression of human VEGF in Tca8113 cells using the small interfering RNA (siRNA) technique. Tca8113 cells pre-transfected with siRNA targeting VEGF were co-cultured with monocyte?derived immature and mature DCs. Cell proliferation was evaluated by a WST-8 assay. Cell apoptosis, cell cycle and cell phenotypes were determined by flow cytometry. The data revealed that downregulation of the human VEGF significantly inhibited the proliferation of Tca8113 cells and increased apoptosis. Inhibition of human VEGF arrested the cell cycle of Tca8113 cells at the G0/G1 phase. Our results showed that the co-culture of DCs with Tca8113 cells markedly inhibited the expression of the mature markers of DCs including HLA-DR, CD80, CD86, CD40 and CD1a, as well as the immature marker CD83, while inhibition of human VEGF in Tca8113 cells significantly reversed these effects. Therefore, human VEGF in Tca8113 cells may not only regulate the cell proliferation and apoptosis of oral squamous cell carcinoma cells, but may also inhibit DC maturation.

Ni, Yan-Hong; Wang, Zhi-Yong; Huang, Xiao-Feng; Shi, Pei-Hua; Han, Wei; Hou, Ya-Yi; Hua, Zi-Chun; Hu, and Qin-Gang

2012-01-01

41

The Endoreduplication Cell Cycle: Regulation and Function  

Microsoft Academic Search

The endoreduplication cell cycle is a variant of the standard mitotic cell cycle in which reiterated\\u000a rounds of DNA synthesis occur in the absence of chromosome segregation and cell division. The resulting\\u000a polyploid cells are frequently found in plants and often occur in tissues with a high metabolic activity\\u000a that accumulate storage molecules. In this chapter we review the current understanding of

Paolo A. Sabelli; Brian Larkins

42

Monte Carlo simulations of neutron well-logging in granite and sand to detect water and trichloroethane (TCA)  

SciTech Connect

The Monte Carlo code MCNP is used in simulations of neutron well logging in granite to detect water and TCA (C{sub 2}H{sub 3}Cl{sub 3}), a common ground contaminant, in fractures of 1 cm and 1 mm thickness at various distances and orientations. Also simulated is neutron well logging in wet sand to detect TCA and lead (Pb) at various uniform concentrations. The {sup 3}H(d,n) (DT) and{sup 2}H(d,n) (DD) neutron producing reactions are used in the simulations to assess the relative performance of each. Simulations are also performed to determine the efficiency of several detector materials such as CdZnTe, Ge and NaI as a function of photon energy. Results indicate that, by examining the signal from the 6.11 MeV gamma from the thermal neutron capture of Cl in TCA, trace amounts (few ppm) are detectable in saline free media. Water and TCA filled fractures are also detectable. These results are summarized in Tables 7--21. Motivation for this work is based on the need for detection of trace environmental pollutants as well as possible fracture characterization of geologic media.

Hua, D.D. [Lawrence Berkeley National Lab., CA (United States)]|[Univ. of California, Berkeley, CA (United States). Dept. of Nuclear Engineering; Donahue, R.J.; Celata, C.M. [Lawrence Berkeley National Lab., CA (United States); Greenspan, E. [Univ. of California, Berkeley, CA (United States). Dept. of Nuclear Engineering

1998-01-01

43

Cell Cycle-Specific Function of Ikaros in Human Leukemia  

PubMed Central

Background The loss of Ikaros is associated with the development of B and T cell leukemia. Data on Ikaros function, including its role as a tumor suppressor and a regulator of cell cycle progression, come almost exclusively from murine studies; little is known of the mechanisms that regulate human Ikaros function. Our studies are the first to examine the function and regulation of human Ikaros isoforms during the cell cycle in human ALL. Procedures Electromobility shift assay (EMSA), confocal microscopy, and phosphopeptide mapping were used to study Ikaros function during different stages of the cell cycle. Results The DNA-binding activity of human Ikaros complexes undergoes dynamic changes as the cell cycle progresses. In S phase, Ikaros DNA-binding affinity for regulatory regions of its target genes decreases, while its binding to pericentromeric heterochromatin is preserved and correlates with Ikaros pericentromeric localization. These S phase-specific changes in Ikaros function are controlled by phosphorylation via the CK2 kinase pathway. During cell cycle progression, the subcellular pericentromeric localization of the largest human Ikaros isoforms is different from that in mouse cells, suggesting unique functions for human Ikaros. Conclusions Our results demonstrate that the function of Ikaros is cell cycle-specific and controlled by CK2-mediated phosphorylation during S phase of the cell cycle in human T-cell and B-cell ALL. The differences we observe in murine and human Ikaros function highlight the importance of using human cells in studies of ALL. These data identify the CK2 pathway as a target for therapies in ALL.

Li, Zhanjun; Song, Chunhua; Ouyang, Hongsheng; Lai, Liangxue; Payne, Kimberly J.; Dovat, Sinisa

2011-01-01

44

Drosophila Amphiphysin Functions during Synaptic Fasciclin II Membrane Cycling  

Microsoft Academic Search

Recent studies have revealed that endocytosis and exocytosis of postsynaptic receptors play a major role in the regulation of synaptic function, particularly during long-term potentiation and long-term depression. Interestingly, many of the proteins implicated in exocy- tosis and endocytosis of synaptic vesicles are also involved in postsynaptic protein cycling. In vertebrates, Amphiphysin is postulated to function during endocytosis in nerve

Dennis Mathew; Andrei Popescu; Vivian Budnik

2003-01-01

45

Proteomic analysis of protein expression profiles during hyperthermia-induced apoptosis in Tca8113 cells  

PubMed Central

The aim of the present study was to explore protein expression profiles during cancer cell apoptosis induced by hyperthermia. A hyperthermia-induced apoptosis model was established using a Tca8113 cell line derived from a human tongue squamous cell carcinoma, which underwent fluorescent differential display two-dimensional (2D) gel electrophoresis at 2, 6, 8, 12 and 24 h following the induction of hyperthermia. Proteins were identified by mass spectrometry analysis. Expression changes in the proteins were detected by western blot analysis. A total of 107 proteins were detected that exhibited different expression levels in the hyperthermia-treated cells compared with the controls, and 57 of these proteins were identified. Expression changes in the representative proteins were further verified by western blot analysis. These 57 proteins were identified according to the following functional groups: energy metabolism-related enzymes, cytoskeleton-related proteins, chaperones, transcription factors, protein synthesis-related proteins and cell division- and proliferation-related proteins. These groups included 44 upregulated and 13 downregulated proteins. Among the 44 upregulated proteins, 27 were upregulated continuously, eight were upregulated at an early time-point and nine were upregulated at a middle to late time-point. Among the 13 downregulated proteins, five were downregulated continuously, six were downregulated at an early time-point and two were downregulated at a middle to late time-point. These results indicate that hyperthermia-induced Tca8113 cell apoptosis is controlled by multiple factors, which include time and regulatory proteins.

JIANG, WEN; BIAN, LI; WANG, NING; HE, YONGWEN

2013-01-01

46

Intellectual Performance as a Function of Repression and Menstrual Cycle.  

ERIC Educational Resources Information Center

Performance on complex (Space Relations and Verbal Reasoning) and simple (Digit Symbol) tests was investigated as a function of Byrne's Repression-Sensitization (RS) dimension, phase of menstrual cycle and premenstrual-menstrual (PM) symptomatology in a group of females not taking oral contraceptives. Two control groups, consisting of males and…

Englander-Golden, Paula; And Others

47

A personal user's view of functional electrical stimulation cycling.  

PubMed

Two years of functional electrical stimulation cycling (FESC) as a researcher and subject have given me an insight into the direction that future FESC should take as well as providing me with significant health benefits and an enjoyable and functional ability to cycle. If FESC is to benefit spinal cord injured persons (SCIPs), researchers must turn their attention to making the activity convenient and enjoyable. What follows is a personal view and will be less scientifically rigorous than other presentations but hopefully still of value. It calls upon my experience as a general medical practitioner with a special interest in the value of exercise, a human powered vehicle enthusiast, an amateur FES researcher, but most importantly, an SCIP and FES cyclist. PMID:11940034

Fitzwater, Roger

2002-03-01

48

Measurement and Analysis of Reactivity Worth of Np Sample in Cores of TCA and FCA  

Microsoft Academic Search

The reactivity worth of 22.87 grams of Np oxide sample was measured and analyzed in seven uranium cores in the Tank-Type Critical Assembly (TCA) and two uranium cores in the Fast Critical Assembly (FCA) at the Japan Atomic Energy Agency. The TCA cores provided a systematic variation in the neutron spectrum between the thermal and resonance energy regions. The FCA

Takeshi SAKURAI; Takamasa MORI; Shigeaki OKAJIMA; Kazuhiro TANI; Takenori SUZAKI; Masaki SAITO

2009-01-01

49

Urea cycle defects and hyperammonemia: effects on functional imaging.  

PubMed

The urea-cycle disorders (UCDs) are a group of congenital enzyme and carrier deficiencies predisposing to hyperammonemia (HA). HA causes changes in the central nervous system (CNS) including alterations of neurotransmitter function, cell volume, and energy deprivation ultimately leading to cerebral edema. Neuropathological findings of UCDs primarily reflect changes in astrocyte morphology. Neurological features accompanying acute HA include changes in behavior and consciousness in the short term, and potential for impairments in memory and executive function as long-term effects. Plasma measures of ammonia and glutamine, although useful for clinical monitoring, prove poor markers of CNS function. Multimodal neuroimaging has potential to investigate impact on cognitive function by interrogating neural networks, connectivity and biochemistry. As neuroimaging methods become increasingly sophisticated, they will play a critical role in clinical monitoring and treatment of metabolic disease. We describe our findings in UCDs; with focus on Ornithine Transcarbamylase deficiency (OTCD) the only X linked UCD. PMID:23149878

Gropman, Andrea L; Prust, Morgan; Breeden, Andrew; Fricke, Stanley; VanMeter, John

2012-11-13

50

Vx-770 potentiates CFTR function by promoting decoupling between the gating cycle and ATP hydrolysis cycle  

PubMed Central

Vx-770 (Ivacaftor), a Food and Drug Administration (FDA)-approved drug for clinical application to patients with cystic fibrosis (CF), shifts the paradigm from conventional symptomatic treatments to therapeutics directly tackling the root of the disease: functional defects of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel caused by pathogenic mutations. The underlying mechanism for the action of Vx-770 remains elusive partly because this compound not only increases the activity of wild-type (WT) channels whose gating is primarily controlled by ATP binding/hydrolysis, but also improves the function of G551D-CFTR, a disease-associated mutation that abolishes CFTR’s responsiveness to ATP. Here we provide a unified theory to account for this dual effect of Vx-770. We found that Vx-770 enhances spontaneous, ATP-independent activity of WT-CFTR to a similar magnitude as its effects on G551D channels, a result essentially explaining Vx-770’s effect on G551D-CFTR. Furthermore, Vx-770 increases the open time of WT-CFTR in an [ATP]-dependent manner. This distinct kinetic effect is accountable with a newly proposed CFTR gating model depicting an [ATP]-dependent “reentry” mechanism that allows CFTR shuffling among different open states by undergoing multiple rounds of ATP hydrolysis. We further examined the effect of Vx-770 on R352C-CFTR, a unique mutant that allows direct observation of hydrolysis-triggered gating events. Our data corroborate that Vx-770 increases the open time of WT-CFTR by stabilizing a posthydrolytic open state and thereby fosters decoupling between the gating cycle and ATP hydrolysis cycle. The current study also suggests that this unique mechanism of drug action can be further exploited to develop strategies that enhance the function of CFTR.

Jih, Kang-Yang; Hwang, Tzyh-Chang

2013-01-01

51

Topology of Modified Helical Gears and Tooth Contact Analysis (TCA) Program.  

National Technical Information Service (NTIS)

The contents of this report covers: (1) development of optimal geometries for crowned helical gears; (2) a method for their generation; (3) tooth contact analysis (TCA) computer programs for the analysis of meshing and bearing contact of the crowned helic...

F. L. Litvin J. Zhang

1989-01-01

52

Functional study of the vitamin K cycle in mammalian cells.  

PubMed

We describe a cell-based assay for studying vitamin K-cycle enzymes. A reporter protein consisting of the gla domain of factor IX (amino acids 1-46) and residues 47-420 of protein C was stably expressed in HEK293 and AV12 cells. Both cell lines secrete carboxylated reporter when fed vitamin K or vitamin K epoxide (KO). However, neither cell line carboxylated the reporter when fed KO in the presence of warfarin. In the presence of warfarin, vitamin K rescued carboxylation in HEK293 cells but not in AV12 cells. Dicoumarol, an NAD(P)H-dependent quinone oxidoreductase 1 (NQO1) inhibitor, behaved similarly to warfarin in both cell lines. Warfarin-resistant vitamin K epoxide reductase (VKOR-Y139F) supported carboxylation in HEK293 cells when fed KO in the presence of warfarin, but it did not in AV12 cells. These results suggest the following: (1) our cell system is a good model for studying the vitamin K cycle, (2) the warfarin-resistant enzyme reducing vitamin K to hydroquinone (KH?) is probably not NQO1, (3) there appears to be a warfarin-sensitive enzyme other than VKOR that reduces vitamin K to KH?, and (4) the primary function of VKOR is the reduction of KO to vitamin K. PMID:21239697

Tie, Jian-Ke; Jin, Da-Yun; Straight, David L; Stafford, Darrel W

2011-01-14

53

Enzymatic mechanism of oxalate production in the TCA and ...  

Treesearch

Oxalate biosynthesis in copper-tolerant fungi has been linked to the ... Within these two cycles, it has been proposed that oxalate production relies on twelve ... well as attempt to establish a pathway involved in the direct production of oxalate.

54

Molecular evolution of SRP cycle components: functional implications.  

PubMed Central

Signal recognition particle (SRP) is a cytoplasmic ribonucleoprotein that targets a subset of nascent presecretory proteins to the endoplasmic reticulum membrane. We have considered the SRP cycle from the perspective of molecular evolution, using recently determined sequences of genes or cDNAs encoding homologs of SRP (7SL) RNA, the Srp54 protein (Srp54p), and the alpha subunit of the SRP receptor (SR alpha) from a broad spectrum of organisms, together with the remaining five polypeptides of mammalian SRP. Our analysis provides insight into the significance of structural variation in SRP RNA and identifies novel conserved motifs in protein components of this pathway. The lack of congruence between an established phylogenetic tree and size variation in 7SL homologs implies the occurrence of several independent events that eliminated more than half the sequence content of this RNA during bacterial evolution. The apparently non-essential structures are domain I, a tRNA-like element that is constant in archaea, varies in size among eucaryotes, and is generally missing in bacteria, and domain III, a tightly base-paired hairpin that is present in all eucaryotic and archeal SRP RNAs but is invariably absent in bacteria. Based on both structural and functional considerations, we propose that the conserved core of SRP consists minimally of the 54 kDa signal sequence-binding protein complexed with the loosely base-paired domain IV helix of SRP RNA, and is also likely to contain a homolog of the Srp68 protein. Comparative sequence analysis of the methionine-rich M domains from a diverse array of Srp54p homologs reveals an extended region of amino acid identity that resembles a recently identified RNA recognition motif. Multiple sequence alignment of the G domains of Srp54p and SR alpha homologs indicates that these two polypeptides exhibit significant similarity even outside the four GTPase consensus motifs, including a block of nine contiguous amino acids in a location analogous to the binding site of the guanine nucleotide dissociation stimulator (GDS) for E. coli EF-Tu. The conservation of this sequence, in combination with the results of earlier genetic and biochemical studies of the SRP cycle, leads us to hypothesize that a component of the Srp68/72p heterodimer serves as the GDS for both Srp54p and SR alpha. Using an iterative alignment procedure, we demonstrate similarity between Srp68p and sequence motifs conserved among GDS proteins for small Ras-related GTPases. The conservation of SRP cycle components in organisms from all three major branches of the phylogenetic tree suggests that this pathway for protein export is of ancient evolutionary origin. Images

Althoff, S; Selinger, D; Wise, J A

1994-01-01

55

High-Level Functional and Operational Requirements for the Advanced Fuel Cycle Facilty  

SciTech Connect

High-Level Functional & Operational Requirements for the AFCF -This document describes the principal functional and operational requirements for the proposed Advanced Fuel Cycle Facility (AFCF). The AFCF is intended to be the world's foremost facility for nuclear fuel cycle research, technology development, and demonstration. The facility will also support the near-term mission to develop and demonstrate technology in support of fuel cycle needs identified by industry, and the long-term mission to retain and retain U.S. leadership in fuel cycle operations. The AFCF is essential to demonstrate a more proliferation-resistant fuel cycle and make long-term improvements in fuel cycle effectiveness, performance and economy.

Charles Park

2006-12-01

56

Performance of Confocal Scanning Laser Tomograph Topographic Change Analysis (TCA) for Assessing Glaucomatous Progression  

PubMed Central

Purpose To determine the sensitivity and specificity of confocal scanning laser ophthalmoscope’s Topographic Change Analysis (TCA; Heidelberg Retina Tomograph [HRT]; Heidelberg Engineering, Heidelberg, Germany) parameters for discriminating between progressing glaucomatous and stable healthy eyes. Methods The 0.90, 0.95, and 0.99 specificity cutoffs for various (n = 70) TCA parameters were developed by using 1000 permuted topographic series derived from HRT images of 18 healthy eyes from Moorfields Eye Hospital, imaged at least four times. The cutoffs were then applied to topographic series from 36 eyes with known glaucomatous progression (by optic disc stereophotograph assessment and/or standard automated perimetry guided progression analysis, [GPA]) and 21 healthy eyes from the University of California, San Diego (UCSD) Diagnostic Innovations in Glaucoma Study (DIGS), all imaged at least four times, to determine TCA sensitivity and specificity. Cutoffs also were applied to 210 DIGS patients’ eyes imaged at least four times with no evidence of progression (nonprogressed) by stereophotography or GPA. Results The TCA parameter providing the best sensitivity/specificity tradeoff using the 0.90, 0.95, and 0.99 cutoffs was the largest clustered superpixel area within the optic disc margin (CAREAdisc mm2). Sensitivities/specificities for classifying progressing (by stereophotography and/or GPA) and healthy eyes were 0.778/0.809, 0.639/0.857, and 0.611/1.00, respectively. In nonprogressing eyes, specificities were 0.464, 0.570, and 0.647 (i.e., lower than in the healthy eyes). In addition, TCA parameter measurements of nonprogressing eyes were similar to those of progressing eyes. Conclusions TCA parameters can discriminate between progressing and longitudinally observed healthy eyes. Low specificity in apparently nonprogressing patients’ eyes suggests early progression detection using TCA.

Bowd, Christopher; Balasubramanian, Madhusudhanan; Weinreb, Robert N.; Vizzeri, Gianmarco; Alencar, Luciana M.; O'Leary, Neil; Sample, Pamela A.; Zangwill, Linda M.

2009-01-01

57

Functions of microtubules in the Saccharomyces cerevisiae cell cycle  

PubMed Central

We used the inhibitor nocodazole in conjunction with immunofluorescence and electron microscopy to investigate microtubule function in the yeast cell cycle. Under appropriate conditions, this drug produced a rapid and essentially complete disassembly of cytoplasmic and intranuclear microtubules, accompanied by a rapid and essentially complete block of cellular and nuclear division. These effects were similar to, but more profound than, the effects of the related drug methyl benzimidazole carbamate (MBC). In the nocodazole-treated cells, the selection of nonrandom budding sites, the formation of chitin rings and rings of 10-nm filaments at those sites, bud emergence, differential bud enlargement, and apical bud growth appeared to proceed normally, and the intracellular distribution of actin was not detectably perturbed. Thus, the cytoplasmic microtubules are apparently not essential for the establishment of cell polarity and the localization of cell-surface growth. In contrast, nocodazole profoundly affected the behavior of the nucleus. Although spindle-pole bodies (SPBs) could duplicate in the absence of microtubules, SPB separation was blocked. Moreover, complete spindles present at the beginning of drug treatment appeared to collapse, drawing the opposed SPBs and associated nuclear envelope close together. Nuclei did not migrate to the mother-bud necks in nocodazole-treated cells, although nuclei that had reached the necks before drug treatment remained there. Moreover, the double SPBs in arrested cells were often not oriented toward the budding sites, in contrast to the situation in normal cells. Thus, microtubules (cytoplasmic, intranuclear, or both) appear to be necessary for the migration and proper orientation of the nucleus, as well as for SPB separation, spindle function, and nuclear division.

1988-01-01

58

Comparative study of 15% TCA peel versus 35% glycolic acid peel for the treatment of melasma  

PubMed Central

Background: Chemical peels are the mainstay of a cosmetic practitioner's armamentarium because they can be used to treat some skin disorders and can provide aesthetic benefit. Objectives: To compare 15% TCA peel and 35% glycolic acid peel for the treatment of melasma. Material and Methods: We selected 30 participants of melasma aged between 20 and 50 years from the dermatology outpatient department and treated equal numbers with 15% TCA and 35% glycolic acid. Results: Subjective response as graded by the patient showed good or very good response in 70% participants in the glycolic acid group and 64% in the TCA group. Conclusions: There was statistically insignificant difference in the efficacy between the two groups for the treatment of melasma.

Puri, Neerja

2012-01-01

59

The Shape of Solar Cycle Described by a Modified Gaussian Function  

NASA Astrophysics Data System (ADS)

The shape of each sunspot cycle is found to be well described by a modified Gaussian function with four parameters: peak size A, peak timing t m, width B, and asymmetry ?. The four-parameter function can be further reduced to a two-parameter function by assuming that B and ? are quadratic functions of t m, computed from the starting time ( T 0). It is found that the shape can be better fitted by the four-parameter function, while the remaining behavior of the cycle can be better predicted by the two-parameter function when using the data from a few (about two) months after the starting time defined by the smoothed monthly mean sunspot numbers. As a new solar cycle is ongoing, its remaining behavior can be constructed by the above four- or two-parameter function. A running test shows that the maximum amplitude of the cycle can be predicted to within 15% at about 25 months into the cycle based on the two-parameter function. A preliminary modeling to the first 24 months of data available for the current cycle indicates that the peak of cycle 24 may probably occur around June 2013±7 months with a size of 72±11. The above results are compared to those by quasi-Planck functions.

Du, Zhanle

2011-10-01

60

Role of Mitochondrial TCA Cycle Enzymes in Determining Prostate Cancer Chemosensitivity.  

National Technical Information Service (NTIS)

Based on the results in preliminary data and in year No. 1 of the proposal, we hypothesize that MDH2 plays a crucial role in determining prostate cancer chemosensitivity. In year No. 2, we further determined the effect of inhibiting MDH2 on prostate cance...

D. Qian

2012-01-01

61

Multiple Targets of Nitric Oxide in the Tricarboxylic Acid (TCA) Cycle of Salmonella enterica Serovar Typhimurium  

PubMed Central

Host nitric oxide (NO·) production is important for controlling intracellular bacterial pathogens including Salmonella enterica serovar Typhimurium but the underlying mechanisms are incompletely understood. S. Typhmurium 14028s is prototrophic for all amino acids but cannot synthesize Methionine (M) or Lysine (K) during nitrosative stress. Here we show that NO·-induced MK auxotrophy results from reduced succinyl-CoA availability as a consequence of NO· targeting of lipoamide-dependent lipoamide dehydrogenase (LpdA) activity. LpdA is an essential component of the pyruvate and ?-ketoglutarate dehydrogenase complexes. Additional effects of NO· on gene regulation prevent compensatory pathways of succinyl-CoA production. Microarray analysis indicates that over 50% of the transcriptional response of S. Typhimurium to nitrosative stress is attributable to LpdA inhibition. Bacterial methionine transport is essential for virulence in NO·-producing mice, demonstrating that NO·-induced MK auxotrophy occurs in vivo. These observations underscore the importance of metabolic targets for antimicrobial actions of NO·.

Richardson, Anthony R.; Payne, Elizabeth C.; Younger, Noah; Karlinsey, Joyce E.; Thomas, Vinai C.; Becker, Lynne A.; Navarre, William W.; Castor, Margaret E.; Libby, Stephen J.; Fang, Ferric C.

2011-01-01

62

IRIS Toxicological Review of Trichloroacetic Acid (TCA) (Interagency Science Consultation Draft)  

EPA Science Inventory

On September 24, 2009, the Toxicological Review of Trichloroacetic Acid (TCA) and the charge to external peer reviewers were released for external peer review and public comment. The Toxicological Review and charge were reviewed internally by EPA and by other federal agencies an...

63

Influence of menstrual cycle phase on pulmonary function in asthmatic athletes  

Microsoft Academic Search

The main aim of this study was to investigate whether there is a relationship between menstrual cycle phase and exercise-induced\\u000a bronchoconstriction (EIB) in female athletes with mild atopic asthma. Seven eumenorrheic subjects with regular 28-day menstrual\\u000a cycles were exercised to volitional exhaustion on day 5 [mid-follicular (FOL)] and day 21 [mid-luteal (LUT)] of their menstrual\\u000a cycle. Pulmonary function tests were

Kristin I. Stanford; Timothy D. Mickleborough; Shahla Ray; Martin R. Lindley; David M. Koceja; Joel M. Stager

2006-01-01

64

Functional Responses of Coyotes and Lynx to the Snowshoe Hare Cycle  

Microsoft Academic Search

Coyotes and lynx are the two most important mammalian predators of snow- shoe hares throughout much of the boreal forest. Populations of hares cycle in abundance, with peaks in density occurring every 8-11 yr, and experimental results suggest that pre- dation is a necessary factor causing these cycles. We measured the functional responses of coyotes and lynx during a cyclic

Mark O’Donoghue; Stan Boutin; Charles J. Krebs; Gustavo Zuleta; Dennis L. Murray; Elizabeth J. Hofer

1998-01-01

65

Evaluation of Functional Electrical Stimulation to Assist Cycling in Four Adolescents with Spastic Cerebral Palsy  

PubMed Central

Introduction. Adolescents with cerebral palsy (CP) often have difficulty participating in exercise at intensities necessary to improve cardiovascular fitness. Functional electrical stimulation- (FES-) assisted cycling is proposed as a form of exercise for adolescents with CP. The aims of this paper were to adapt methods and assess the feasibility of applying FES cycling technology in adolescents with CP, determine methods of performing cycling tests in adolescents with CP, and evaluate the immediate effects of FES assistance on cycling performance. Materials/Methods. Four participants (12–14 years old; GMFCS levels III-IV) participated in a case-based pilot study of FES-assisted cycling in which bilateral quadriceps muscles were activated using surface electrodes. Cycling cadence, power output, and heart rate were collected. Results. FES-assisted cycling was well tolerated (n = 4) and cases are presented demonstrating increased cadence (2–43?rpm), power output (19–70%), and heart rates (4-5%) and decreased variability (8–13%) in cycling performance when FES was applied, compared to volitional cycling without FES assistance. Some participants (n = 2) required the use of an auxiliary hub motor for assistance. Conclusions. FES-assisted cycling is feasible for individuals with CP and may lead to immediate improvements in cycling performance. Future work will examine the potential for long-term fitness gains using this intervention.

Harrington, Ann Tokay; McRae, Calum G. A.; Lee, Samuel C. K.

2012-01-01

66

Flagellum assembly and function during the Leishmania life cycle.  

PubMed

During a complex digenetic life cycle flagellated Leishmania parasites alternate between promastigote and amastigote forms which differ significantly in cellular morphology and flagellum length. Recent studies have provided important new insights into mechanisms by which Leishmania regulate expression of genes required for flagellum assembly, and mechanisms used to modify flagellum length. While the critical role of the promastigote flagellum in parasite biology has long been appreciated, the importance of the amastigote flagellum has often been disregarded. However, recent work suggests that the 'rudimentary' amastigote flagellum may serve indispensable roles in cellular organisation, and/or sensory perception, which are critical for intracellular survival of Leishmania within host macrophages. PMID:20541962

Gluenz, Eva; Ginger, Michael L; McKean, Paul G

2010-06-11

67

The functional human neuroanatomy of food pleasure cycles.  

PubMed

Food ensures our survival and is a potential source of pleasure and general well-being. In order to survive, the human brain is required to optimize the resource allocation such that rewards are pursued when relevant. This means that food intake follows a similar cyclical time course to other rewards with phases related to expectation, consummation and satiety. Here we develop a multilevel model for the full cycle of eating behavior based on the evidence for the brain networks and mechanisms initiating, sustaining and terminating the various phases of eating. We concentrate on how the underlying reward mechanisms of wanting, liking and learning lead to how human food intake is governed by both hedonic and homeostatic principles. We describe five of the main processing principles controlling food intake: hunger and attentional signal processing; motivation-independent discriminative processing; reward representations; learning-dependent multimodal sensory representations and hedonic experience. Overall, the evidence shows that while human food intake is complex, we are making progress in understanding the underlying mechanisms and that the brain networks supporting the food pleasure cycle are remarkably similar to those underlying the processing of other rewards. PMID:22487544

Kringelbach, Morten L; Stein, Alan; van Hartevelt, Tim J

2012-03-28

68

New Functions for Parts of the Krebs Cycle in Procyclic Trypanosoma brucei, a Cycle Not Operating as a Cycle  

Microsoft Academic Search

We investigated whether substrate availability influ- ences the type of energy metabolism in procyclic Tryp- anosoma brucei. We show that absence of glycolytic sub- strates (glucose and glycerol) does not induce a shift from a fermentative metabolism to complete oxidation of substrates. We also show that glucose (and even gly- colysis) is not essential for normal functioning and pro- liferation

Susanne W. H. van Weelden; Jaap J. van Hellemond; Fred R. Opperdoes; Aloysius G. M. Tielens

2004-01-01

69

Control strategies for integration of electric motor assist and functional electrical stimulation in paraplegic cycling: utility for exercise testing and mobile cycling  

Microsoft Academic Search

Aim: The aim of this study was to investigate feedback control strategies for integration of electric motor assist and functional electrical stimulation (FES) for paraplegic cycling, with particular focus on development of a testbed for exercise testing in FES cycling, in which both cycling cadence and workrate are simultaneously well controlled and contemporary physiological measures of exercise performance derived. A

Kenneth J. Hunt; Barry Stone; N.-O. Negard; T. Schauer; M. H. Fraser; A. J. Cathcart; C. Ferrario; S. A. Ward; S. Grant

2004-01-01

70

Functional cooperation between FACT and MCM is coordinated with cell cycle and differential complex formation  

PubMed Central

Background Functional cooperation between FACT and the MCM helicase complex constitutes an integral step during DNA replication initiation. However, mode of regulation that underlies the proper functional interaction of FACT and MCM is poorly understood. Methods & Results Here we present evidence indicating that such interaction is coordinated with cell cycle progression and differential complex formation. We first demonstrate the existence of two distinct FACT-MCM subassemblies, FACT-MCM2/4/6/7 and FACT-MCM2/3/4/5. Both complexes possess DNA unwinding activity and are subject to cell cycle-dependent enzymatic regulation. Interestingly, analysis of functional attributes further suggests that they act at distinct, and possibly sequential, steps during origin establishment and replication initiation. Moreover, we show that the phosphorylation profile of the FACT-associated MCM4 undergoes a cell cycle-dependent change, which is directly correlated with the catalytic activity of the FACT-MCM helicase complexes. Finally, at the quaternary structure level, physical interaction between FACT and MCM complexes is generally dependent on persistent cell cycle and further stabilized upon S phase entry. Cessation of mitotic cycle destabilizes the complex formation and likely leads to compromised coordination and activities. Conclusions Together, our results correlate FACT-MCM functionally and temporally with S phase and DNA replication. They further demonstrate that enzymatic activities intrinsically important for DNA replication are tightly controlled at various levels, thereby ensuring proper progression of, as well as exit from, the cell cycle and ultimately euploid gene balance.

2010-01-01

71

Retinal degeneration depends on Bmi1 function and reactivation of cell cycle proteins.  

PubMed

The epigenetic regulator Bmi1 controls proliferation in many organs. Reexpression of cell cycle proteins such as cyclin-dependent kinases (CDKs) is a hallmark of neuronal apoptosis in neurodegenerative diseases. Here we address the potential role of Bmi1 as a key regulator of cell cycle proteins during neuronal apoptosis. We show that several cell cycle proteins are expressed in different models of retinal degeneration and required in the Rd1 photoreceptor death process. Deleting E2f1, a downstream target of CDKs, provided temporary protection in Rd1 mice. Most importantly, genetic ablation of Bmi1 provided extensive photoreceptor survival and improvement of retinal function in Rd1 mice, mediated by a decrease in cell cycle markers and regulators independent of p16(Ink4a) and p19(Arf). These data reveal that Bmi1 controls the cell cycle-related death process, highlighting this pathway as a promising therapeutic target for neuroprotection in retinal dystrophies. PMID:23359713

Zencak, Dusan; Schouwey, Karine; Chen, Danian; Ekström, Per; Tanger, Ellen; Bremner, Rod; van Lohuizen, Maarten; Arsenijevic, Yvan

2013-01-28

72

Menstrual Cycle-Related Changes of Functional Cerebral Asymmetries in Fine Motor Coordination  

ERIC Educational Resources Information Center

|Fluctuating sex hormone levels during the menstrual cycle have been shown to affect functional cerebral asymmetries in cognitive domains. These effects seem to result from the neuromodulatory properties of sex hormones and their metabolites on interhemispheric processing. The present study was carried out to investigate whether functional

Bayer, Ulrike; Hausmann, Markus

2012-01-01

73

Maximizing muscle force via low-cadence functional electrical stimulation cycling  

Microsoft Academic Search

Objective: This study investigated the effect of pedal cadence upon torque production, power output and muscle fatigue rates during functional electrical stimulation evoked cycling in spinal cord injured individuals. Subjects: All subjects had complete thoracic spinal cord injuries T4-T9 (ASIA A) and had been functional electrical stimulation training regularly for at least 6 months. Methods: One trial (n = 8)

Ché Fornusek; Glen Davis

2004-01-01

74

New Alleles of SIR2 Define Cell-Cycle-Specific Silencing Functions  

Microsoft Academic Search

The establishment of transcriptional silencing in yeast requires cell-cycle progression, but the nature of this requirement is unknown. Sir2 is a protein deacetylase that is required for gene silencing in yeast. We have used temperature-sensitive alleles of the SIR2 gene to assess Sir2's contribution to silencing as a function of the cell cycle. When examined in vivo, these conditional alleles

Mirela Matecic; Kristen Martins-Taylor; Merrit Hickman; Jason Tanny; Danesh Moazed; Scott G. Holmes

2006-01-01

75

Special function instruments for binary cycle geothermal power plants  

SciTech Connect

Three special instruments have been designed to support plant operations at the Heber geothermal power plant in Heber, California. All are aids to give operating information which no commercial instruments can provide. The first is a package for determining CO/sub 2/ breakout conditions for a particular brine. Brine is sampled continuously at either the wellhead or the plant inlet. A temperature-pressure curve is generated which will span all possible operating combinations. That information tells designers or operators what pump pressures must be used to keep the CO/sub 2/ in solution. A second package unit will detect the presence of ppM levels of isobutane in either brine or water streams. It samples actual flowing brine streams continuously. The function is to alert operators when leaks are occurring in heat exchangers. A final unit senses water in flowing hydrocarbon streams. The sampled streams can be either liquid or vapor. Sensitivity is close to actual solubility limit for water in isobutane. This device warns operators when their hydrocarbon has been contaminated with brine (or cooling water).

Robertus, R.J.; Shannon, D.W.; Sullivan, R.G.

1984-04-01

76

Effect of migratory cycle and 17ß-estradiol on splenic leukocyte functions in female black-headed gulls  

Microsoft Academic Search

The immune function of wild birds is practically unknown. We have studied several functions of splenic leukocytes from the gull Larus ridibundus. Considering that avian physiology is strikingly affected by the seasonal migratory cycle, those functions were analyzed throughout the seasonal cycle. The functions assayed were: adherence to substrate, chemotaxis and lymphoproliferative response to mitogens. Estrogens have been reported to

Francisco J. Muńoz; Mónica De la Fuente

2003-01-01

77

A Dysfunctional Tricarboxylic Acid Cycle Enhances Fitness of Staphylococcus epidermidis During ?-Lactam Stress.  

PubMed

ABSTRACT A recent controversial hypothesis suggested that the bactericidal action of antibiotics is due to the generation of endogenous reactive oxygen species (ROS), a process requiring the citric acid cycle (tricarboxylic acid [TCA] cycle). To test this hypothesis, we assessed the ability of oxacillin to induce ROS production and cell death in Staphylococcus epidermidis strain 1457 and an isogenic citric acid cycle mutant. Our results confirm a contributory role for TCA-dependent ROS in enhancing susceptibility of S. epidermidis toward ?-lactam antibiotics and also revealed a propensity for clinical isolates to accumulate TCA cycle dysfunctions presumably as a way to tolerate these antibiotics. The increased protection from ?-lactam antibiotics could result from pleiotropic effects of a dysfunctional TCA cycle, including increased resistance to oxidative stress, reduced susceptibility to autolysis, and a more positively charged cell surface. IMPORTANCE Staphylococcus epidermidis, a normal inhabitant of the human skin microflora, is the most common cause of indwelling medical device infections. In the present study, we analyzed 126 clinical S. epidermidis isolates and discovered that tricarboxylic acid (TCA) cycle dysfunctions are relatively common in the clinical environment. We determined that a dysfunctional TCA cycle enables S. epidermidis to resist oxidative stress and alter its cell surface properties, making it less susceptible to ?-lactam antibiotics. PMID:23963176

Chittezham Thomas, Vinai; Kinkead, Lauren C; Janssen, Ashley; Schaeffer, Carolyn R; Woods, Keith M; Lindgren, Jill K; Peaster, Jonathan M; Chaudhari, Sujata S; Sadykov, Marat; Jones, Joselyn; Mohamadi Abdelghani, Sameh M; Zimmerman, Matthew C; Bayles, Kenneth W; Somerville, Greg A; Fey, Paul D

2013-08-20

78

A synthetic biology approach to engineer a functional reversal of the ?-oxidation cycle.  

PubMed

While we have recently constructed a functional reversal of the ?-oxidation cycle as a platform for the production of fuels and chemicals by engineering global regulators and eliminating native fermentative pathways, the system-level approach used makes it difficult to determine which of the many deregulated enzymes are responsible for product synthesis. This, in turn, limits efforts to fine-tune the synthesis of specific products and prevents the transfer of the engineered pathway to other organisms. In the work reported here, we overcome the aforementioned limitations by using a synthetic biology approach to construct and functionally characterize a reversal of the ?-oxidation cycle. This was achieved through the in vitro kinetic characterization of each functional unit of the core and termination pathways, followed by their in vivo assembly and functional characterization. With this approach, the four functional units of the core pathway, thiolase, 3-hydroxyacyl-CoA dehydrogenase, enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydratase, and acyl-CoA dehydrogenase/trans-enoyl-CoA reductase, were purified and kinetically characterized in vitro. When these four functional units were assembled in vivo in combination with thioesterases as the termination pathway, the synthesis of a variety of 4-C carboxylic acids from a one-turn functional reversal of the ?-oxidation cycle was realized. The individual expression and modular construction of these well-defined core components exerted the majority of control over product formation, with only highly selective termination pathways resulting in shifts in product formation. Further control over product synthesis was demonstrated by overexpressing a long-chain thiolase that enables the operation of multiple turns of the reversal of the ?-oxidation cycle and hence the synthesis of longer-chain carboxylic acids. The well-defined and self-contained nature of each functional unit makes the engineered reversal of the ?-oxidation cycle "chassis neutral" and hence transferrable to the host of choice for efficient fuel or chemical production. PMID:23656231

Clomburg, James M; Vick, Jacob E; Blankschien, Matthew D; Rodríguez-Moyá, María; Gonzalez, Ramon

2012-10-24

79

Recovering Joy's Law as a Function of Solar Cycle, Hemisphere, and Longitude  

NASA Astrophysics Data System (ADS)

Bipolar active regions in both hemispheres tend to be tilted with respect to the East-West Equator of the Sun in accordance with Joy's law, which describes the average tilt angle as a function of latitude. Mt. Wilson Observatory data from 1917 - 1985 are used to analyze the active-region tilt angle as a function of solar cycle, hemisphere, and longitude, in addition to the more common dependence on latitude. Our main results are as follows: i) We recommend a revision of Joy's law towards a weaker dependence on latitude (slope of 0.13 - 0.26) and without forcing the tilt to zero at the Equator. ii) We determine that the hemispheric mean tilt value of active regions varies with each solar cycle, although the noise from a stochastic process dominates and does not allow for a determination of the slope of Joy's law on an 11-year time scale. iii) The hemispheric difference in mean tilt angles, 1.1?±0.27, over Cycles 16 to 21 was significant to a three- ? level, with average tilt angles in the Northern and Southern hemispheres of 4.7?±0.26 and 3.6?±0.27, respectively. iv) Area-weighted mean tilt angles normalized by latitude for Cycles 15 to 21 anticorrelate with cycle strength for the southern hemisphere and whole-Sun data, confirming previous results by Dasi-Espuig et al. ( Astron. Astrophys. 518, A7, 2010). The Northern Hemispheric mean tilt angles do not show a dependence on cycle strength. v) Mean tilt angles do not show a dependence on longitude for any hemisphere or cycle. In addition, the standard deviation of the mean tilt is 29 - 31? for all cycles and hemispheres, indicating that the scatter is due to the same consistent process even if the mean tilt angles vary.

McClintock, B. H.; Norton, A. A.

2013-10-01

80

Functional microarray analysis of nitrogen and carbon cycling genes across an Antarctic latitudinal transect.  

PubMed

Soil-borne microbial communities were examined via a functional gene microarray approach across a southern polar latitudinal gradient to gain insight into the environmental factors steering soil N- and C-cycling in terrestrial Antarctic ecosystems. The abundance and diversity of functional gene families were studied for soil-borne microbial communities inhabiting a range of environments from 51 degrees S (cool temperate-Falkland Islands) to 72 degrees S (cold rock desert-Coal Nunatak). The recently designed functional gene array used contains 24,243 oligonucleotide probes and covers >10,000 genes in >150 functional groups involved in nitrogen, carbon, sulfur and phosphorus cycling, metal reduction and resistance and organic contaminant degradation (He et al. 2007). The detected N- and C-cycle genes were significantly different across different sampling locations and vegetation types. A number of significant trends were observed regarding the distribution of key gene families across the environments examined. For example, the relative detection of cellulose degradation genes was correlated with temperature, and microbial C-fixation genes were more present in plots principally lacking vegetation. With respect to the N-cycle, denitrification genes were linked to higher soil temperatures, and N2-fixation genes were linked to plots mainly vegetated by lichens. These microarray-based results were confirmed for a number of gene families using specific real-time PCR, enzymatic assays and process rate measurements. The results presented demonstrate the utility of an integrated functional gene microarray approach in detecting shifts in functional community properties in environmental samples and provide insight into the forces driving important processes of terrestrial Antarctic nutrient cycling. PMID:18043626

Yergeau, Etienne; Kang, Sanghoon; He, Zhili; Zhou, Jizhong; Kowalchuk, George A

2007-05-24

81

Functional microarray analysis of nitrogen and carbon cycling genes across an Antarctic latitudinal transect  

Microsoft Academic Search

Soil-borne microbial communities were examined via a functional gene microarray approach across a southern polar latitudinal gradient to gain insight into the environmental factors steering soil N- and C-cycling in terrestrial Antarctic ecosystems. The abundance and diversity of functional gene families were studied for soil-borne microbial communities inhabiting a range of environments from 51°S (cool temperate – Falkland Islands) to

Etienne Yergeau; Sanghoon Kang; Zhili He; Jizhong Zhou; George A Kowalchuk

2007-01-01

82

The nuclear envelope in the plant cell cycle: structure, function and regulation  

PubMed Central

Background Higher plants are, like animals, organisms in which successful completion of the cell cycle requires the breakdown and reformation of the nuclear envelope in a highly controlled manner. Interestingly, however, while the structures and processes appear similar, there are remarkable differences in protein composition and function between plants and animals. Scope Recent characterization of integral and associated components of the plant nuclear envelope has been instrumental in understanding its functions and behaviour. It is clear that protein interactions at the nuclear envelope are central to many processes in interphase and dividing cells and that the nuclear envelope has a key role in structural and regulatory events. Conclusion Dissecting the mechanisms of nuclear envelope breakdown and reformation in plants is necessary before a better understanding of the functions of nuclear envelope components during the cell cycle can be gained.

Evans, D. E.; Shvedunova, M.; Graumann, K.

2011-01-01

83

Suppression of mitochondrial oxidative phosphorylation and TCA enzymes in discrete brain regions of mice exposed to high fluoride: amelioration by Panax ginseng (Ginseng) and Lagerstroemia speciosa (Banaba) extracts.  

PubMed

Chronic fluoride intoxication results in pathophysiological complications pertaining to soft tissues, called non-skeletal fluorosis. This study examined whether fluoride-induced alterations in selected parameters that are indicative of mitochondrial dysfunction accompany the toxic effects of fluoride in discrete brain regions in vivo and also explored the possibility of treatment with Ginseng (GE) and Banaba (BLE) either alone or with their co-exposure which is capable of reversing parameters indicative of fluoride-induced impairments in mitochondrial function. Swiss mice, Mus musculus, were given 270 ppm fluoride (600 ppm NaF) in their drinking water for 30 days, while continuing the fluoride exposure, toxicated animals were given differential doses (50-250 mg/kg body wt) of phytoextracts through oral gavage for 2 weeks. Discrete brain regions separated from dissected animals to perform biochemical assessments. Disturbances in mitochondrial enzyme complexes (I-IV) and decrements in TCA enzymes (ICDH, SDH, and aconitase) were noted in discrete brain regions upon F exposure, suggesting mitochondrial dysfunction. In addition, a significant reduction in oxidative stress indices with increased MDA content as well as decrease in reduced glutathione content and increases in catalase and SOD enzyme activity suggests the involvement of severe oxidative stress affecting the mitochondrial function(s). Treatment with either GE or BLE reversed F-induced alterations in augmenting the suppressed complex enzymes followed by TCA enzymes and oxidative stress indices in a dose independent manner. However, the co-exposure of GE and BLE at a dose of 150 mg/kgbw appeared to restore mitochondrial functioning. These results provide in vivo evidence supporting the hypothesis that fluoride induces impairments in mitochondrial function, which can be reversed by treatment with GE and BLE as well their co-exposure at 150 mg/kgbw. PMID:23392579

Mahaboob Basha, P; Saumya, S M

2013-02-08

84

Yeast UBL-UBA proteins have partially redundant functions in cell cycle control  

PubMed Central

Background Proteins containing ubiquitin-like (UBL) and ubiquitin associated (UBA) domains have been suggested to shuttle ubiquitinated substrates to the proteasome for degradation. There are three UBL-UBA containing proteins in budding yeast: Ddi1, Dsk2 and Rad23, which have been demonstrated to play regulatory roles in targeting ubiquitinated substrates to the proteasome for degradation. An involvement of these proteins in cell cycle related events has also been reported. We tested whether these three proteins act redundantly in the cell cycle. Results Here we show that the UBL-UBA proteins are partially redundant for cell cycle related roles. RAD23 is redundant with DDI1 and DSK2, but DDI1 and DSK2 are not redundant with each other and the triple deletion shows a synthetic effect, suggesting the existence of at least two roles for RAD23 in cell cycle control. The rad23?ddi1?dsk2? triple deletion strain delays both in G2/M-phase and in mid-anaphase at high temperatures with duplicated spindle pole bodies. Cell cycle progression in the triple deletion strain can only be partially rescued by a rad23 allele lacking the c-terminal UBA domain, suggesting that RAD23 requires its c-terminal UBA domain for full function. In addition to their ability to bind ubiquitin and the proteasome, the UBL-UBA proteins also share the ability to homodimerize. Rad23 and Dsk2 dimerization requires their UBL and/or UBA domains whereas Ddi1 dimerization does not. Here we show that Ddi1 homodimerization is necessary for its cell cycle related functions. Conclusion The three yeast UBL-UBA proteins have partially redundant roles required for progression through mitosis.

Diaz-Martinez, Laura A; Kang, Yang; Walters, Kylie J; Clarke, Duncan J

2006-01-01

85

Effect of fluid ingestion on neuromuscular function during prolonged cycling exercise  

PubMed Central

Objectives: To investigate the effects of fluid ingestion on neuromuscular function during prolonged cycling exercise. Methods: Eight well trained subjects exercised for 180 minutes in a moderate environment at a workload requiring ?60% maximal oxygen uptake. Two conditions, fluid (F) and no fluid (NF) ingestion, were investigated. Results: During maximal voluntary isometric contraction (MVC), prolonged cycling exercise reduced (p<0.05) the maximal force generating capacity of quadriceps muscles (after three hours of cycling) and root mean square (RMS) values (after two hours of cycling) with no difference between the two conditions despite greater body weight loss (p<0.05) in NF. The mean power frequency (MPF) for vastus lateralis muscle was reduced (p<0.05) and the rate of force development (RFD) was increased (p<0.05) only during NF. During cycling exercise, integrated electromyographic activity and perceived exertion were increased in both conditions (p<0.05) with no significant effect of fluid ingestion. Conclusions: The results suggest that fluid ingestion did not prevent the previously reported decrease in maximal force with exercise duration, but seems to have a positive effect on some indicators of neuromuscular fatigue such as mean power frequency and rate of force development during maximal voluntary contraction. Further investigations are needed to assess the effect of change in hydration on neural mechanisms linked to the development of muscular fatigue during prolonged exercise.

Vallier, J; Grego, F; Basset, F; Lepers, R; Bernard, T; Brisswalter, J

2005-01-01

86

Exercise pressor reflex function in female rats fluctuates with the estrous cycle.  

PubMed

In women, sympathoexcitation during static handgrip exercise is reduced during the follicular phase of the ovarian cycle compared with the menstrual phase. Previous animal studies have demonstrated that estrogen modulates the exercise pressor reflex, a sympathoexcitatory mechanism originating in contracting skeletal muscle. The present study was conducted in female rats to determine whether skeletal muscle contraction-evoked reflex sympathoexcitation fluctuates with the estrous cycle. The estrous cycle was judged by vaginal smear. Plasma concentrations of estrogen were significantly (P < 0.05) higher in rats during the proestrus phase of the estrus cycle than those during the diestrus phase. In decerebrate rats, either electrically induced 30-s continuous static contraction of the hindlimb muscle or 30-s passive stretch of Achilles tendon (a maneuver that selectively stimulates mechanically sensitive muscle afferents) evoked less renal sympathoexcitatory and pressor responses in the proestrus animals than in the diestrus animals. Renal sympathoexcitatory response to 1-min intermittent (1- to 4-s stimulation to relaxation) bouts of static contraction was also significantly less in the proestrus rats than that in the diestrus rats. In ovariectomized female rats, 17?-estradiol applied into a well covering the dorsal surface of the lumbar spinal cord significantly reduced skeletal muscle contraction-evoked responses. These observations demonstrate that the exercise pressor reflex function and its mechanical component fluctuate with the estrous cycle in rats. Estrogen may cause these fluctuations through its attenuating effects on the spinal component of the reflex arc. PMID:22723635

Koba, Satoshi; Yoshinaga, Kenshi; Fujita, Sayaka; Miyoshi, Michio; Watanabe, Tatsuo

2012-06-21

87

A Survey of Essential Gene Function in the Yeast Cell Division Cycle  

PubMed Central

Mutations impacting specific stages of cell growth and division have provided a foundation for dissecting mechanisms that underlie cell cycle progression. We have undertaken an objective examination of the yeast cell cycle through flow cytometric analysis of DNA content in TetO7 promoter mutant strains representing 75% of all essential yeast genes. More than 65% of the strains displayed specific alterations in DNA content, suggesting that reduced function of an essential gene in most cases impairs progression through a specific stage of the cell cycle. Because of the large number of essential genes required for protein biosynthesis, G1 accumulation was the most common phenotype observed in our analysis. In contrast, relatively few mutants displayed S-phase delay, and most of these were defective in genes required for DNA replication or nucleotide metabolism. G2 accumulation appeared to arise from a variety of defects. In addition to providing a global view of the diversity of essential cellular processes that influence cell cycle progression, these data also provided predictions regarding the functions of individual genes: we identified four new genes involved in protein trafficking (NUS1, PHS1, PGA2, PGA3), and we found that CSE1 and SMC4 are important for DNA replication.

Yu, Lisa; Castillo, Lourdes Pena; Mnaimneh, Sanie

2006-01-01

88

Oxidation of carbon sources via the tricarboxylic acid cycle during calcium-induced conidation of Penicillium notatum  

Microsoft Academic Search

The TCA cycle was examined during Ca2+-induced conidiation in Penicillium notatum over the 12-h period after addition of Ca2+ to vegetative cultures. Conidiation was independent of Ca2+ when certain intermediates and derivatives of the TCA cycle served as sole carbon sources. Arsenite and malonate augmented the effect of Ca2+ on conidiation but did not substitute for it. Mitochondria from vegetative

D. Pitt; M. J. Mosley

1986-01-01

89

A Kinase-Independent Function of CDK6 Links the Cell Cycle to Tumor Angiogenesis.  

PubMed

In contrast to its close homolog CDK4, the cell cycle kinase CDK6 is expressed at high levels in lymphoid malignancies. In a model for p185(BCR-ABL+) B-acute lymphoid leukemia, we show that CDK6 is part of a transcription complex that induces the expression of the tumor suppressor p16(INK4a) and the pro-angiogenic factor VEGF-A. This function is independent of CDK6's kinase activity. High CDK6 expression thus suppresses proliferation by upregulating p16(INK4a), providing an internal safeguard. However, in the absence of p16(INK4a), CDK6 can exert its full tumor-promoting function by enhancing proliferation and stimulating angiogenesis. The finding that CDK6 connects cell-cycle progression to angiogenesis confirms CDK6's central role in hematopoietic malignancies and could underlie the selection pressure to upregulate CDK6 and silence p16(INK4a). PMID:23948297

Kollmann, Karoline; Heller, Gerwin; Schneckenleithner, Christine; Warsch, Wolfgang; Scheicher, Ruth; Ott, Rene G; Schäfer, Markus; Fajmann, Sabine; Schlederer, Michaela; Schiefer, Ana-Iris; Reichart, Ursula; Mayerhofer, Matthias; Hoeller, Christoph; Zöchbauer-Müller, Sabine; Kerjaschki, Dontscho; Bock, Christoph; Kenner, Lukas; Hoefler, Gerald; Freissmuth, Michael; Green, Anthony R; Moriggl, Richard; Busslinger, Meinrad; Malumbres, Marcos; Sexl, Veronika

2013-08-12

90

Cellular and functional characterization of buffalo (Bubalus bubalis) corpus luteum during the estrous cycle and pregnancy.  

PubMed

In the present paper, cellular composition of buffalo corpus luteum (CL) with its functional characterization based on 3?-HSD and progesterone secretory ability at different stages of estrous cycle and pregnancy was studied. Buffalo uteri along with ovaries bearing CL were collected from the local slaughter house. These were classified into different stages of estrous cycle (Stage I, II, III and IV) and pregnancy (Stage I, II and III) based on morphological appearance of CL, surface follicles on the ovary and crown rump length of conceptus. Luteal cell population, progesterone content and steroidogenic properties were studied by dispersion of luteal cells using collagenase type I enzyme, RIA and 3?-HSD activity, respectively. Large luteal cells (LLC) appeared as polyhedral or spherical in shape with a centrally placed large round nucleus and an abundance of cytoplasmic lipid droplets. However, small luteal cells (SLC) appeared to be spindle shaped with an eccentrically placed irregular nucleus and there was paucity of cytoplasmic lipid droplets. The size of SLC (range 12-23?m) and LLC (range 25-55?m) increased (P<0.01) with the advancement of stage of estrous cycle and pregnancy. The mean progesterone concentration per gram and per CL increased (P<0.01) from Stage I to III of estrous cycle with maximum concentration at Stage III of estrous cycle and pregnancy. The progesterone concentration decreased at Stage IV (day 17-20) of estrous cycle coinciding with CL regression. Total luteal cell number (LLC and SLC) also increased (P<0.01) from Stage I to III of estrous cycle and decreased (P<0.05), thereafter, at Stage IV indicating degeneration of luteal cells and regression of the CL. Total luteal cell population during pregnancy also increased (P<0.01) from Stage I to II and thereafter decreased (P>0.05) indicating cessation of mitosis. Increased (P<0.05) large luteal cell numbers from Stage I to III of estrous cycle and pregnancy coincided with the increased progesterone secretion and 3?-HSD activity of CL. Thus, proportionate increases of large compared with small luteal cells were primarily responsible for increased progesterone secretion during the advanced stages of the estrous cycle and pregnancy. Total luteal cells and progesterone content per CL during the mid-luteal stage in buffalo as observed in the present study seem to be less than with cattle suggesting inherent luteal deficiency. PMID:23896394

Baithalu, Rubina Kumari; Singh, S K; Gupta, Chhavi; Raja, Anuj K; Saxena, Abhishake; Kumar, Yogendra; Singh, R; Agarwal, S K

2013-06-28

91

Feasibility of home-based functional electrical stimulation cycling: case report  

Microsoft Academic Search

Study design:Single-subject (male, 64 years of age) case.Objectives:To determine the feasibility of a home-based FES-LEC (functional electrical stimulation lower extremities cycling) program and effects on body composition, quality of life (QOL) and seat pressure mapping in an older individual with spinal cord injured (SCI).Setting:Home-based FES-LEC with internet connection. Southeastern United States.Methods:FES-LEC three sessions per week for 9 weeks in the

D R Dolbow; A S Gorgey; D X Cifu; J R Moore; D R Gater

2012-01-01

92

Sexual dimorphism in immune function changes during the annual cycle in house sparrows  

Microsoft Academic Search

Difference between sexes in parasitism is a common phenomenon among birds, which may be related to differences between males\\u000a and females in their investment into immune functions or as a consequence of differential exposure to parasites. Because life-history\\u000a strategies change sex specifically during the annual cycle, immunological responses of the host aiming to reduce the impact\\u000a of parasites may be

Péter László Pap; Gábor Árpád Czirják; Csongor István Vágási; Zoltán Barta; Dennis Hasselquist

2010-01-01

93

Functional unit, technological dynamics, and scaling properties for the life cycle energy of residences.  

PubMed

Prior LCA studies take the operational phase to include all energy use within a residence, implying a functional unit of all household activities, but then exclude related supply chains such as production of food, appliances, and household chemicals. We argue that bounding the functional unit to provision of a climate controlled space better focuses the LCA on the building, rather than activities that occur within a building. The second issue explored in this article is how technological change in the operational phase affects life cycle energy. Heating and cooling equipment is replaced at least several times over the lifetime of a residence; improved efficiency of newer equipment affects life cycle energy use. The third objective is to construct parametric models to describe LCA results for a family of related products. We explore these three issues through a case study of energy use of residences: one-story and two-story detached homes, 1,500-3,500 square feet in area, located in Phoenix, Arizona, built in 2002 and retired in 2051. With a restricted functional unit and accounting for technological progress, approximately 30% of a building's life cycle energy can be attributed to materials and construction, compared to 0.4-11% in previous studies. PMID:22192002

Frijia, Stephane; Guhathakurta, Subhrajit; Williams, Eric

2012-01-18

94

Seat Pressure Changes after Eight Weeks of Functional Electrical Stimulation Cycling: A Pilot Study  

PubMed Central

Background: Pressure ulcers (PUs) are a common secondary condition associated with spinal cord injury (SCI). PUs can potentially interfere with activities of daily living, occupational duties, and rehabilitation programs, and in severe cases they may threaten life. Functional electrical stimulation (FES) cycling has been proposed as an activity that may decrease the risk of PUs through the promotion of increased blood flow and thickening of the gluteus maximus. The purpose of this pilot study was to measure the effects of home-based FES cycling on the average and maximal seat pressure of wheelchair-reliant individuals with SCI. Method: Eight male veterans with C5-T6 SCI participated in FES cycling 3 times per week. Cycling parameters were individualized depending on the comfort of the participants and the amount of current needed to perform the cycling activity. Pressure mapping was completed immediately before and after the 8 weeks of FES cycling with the measurement performed by a force sensitive application (FSA) 4 pressure mapping system. Results: The mean average seat pressure decreased by 3.69 ± 4.46 mm Hg (35.57 ± 11.99 to 31.88 ± 13.02), while the mean maximum seat pressure decreased by 14.56 ±18.45 mm Hg (112 ± 34.73 to 98.36 ± 25.89). Although neither measurement was statistically significant, there was a strong trend toward a reduction in average and maximal seat pressure (P = .052 and P = .061, respectively). Conclusion: The positive trend of decreased seat pressure in our study creates incentive for further investigation of the effects of electrical stimulation activities on seat pressure and the prevention of PUs.

2013-01-01

95

Sexual dimorphism in immune function changes during the annual cycle in house sparrows  

NASA Astrophysics Data System (ADS)

Difference between sexes in parasitism is a common phenomenon among birds, which may be related to differences between males and females in their investment into immune functions or as a consequence of differential exposure to parasites. Because life-history strategies change sex specifically during the annual cycle, immunological responses of the host aiming to reduce the impact of parasites may be sexually dimorphic. Despite the great complexity of the immune system, studies on immunoecology generally characterise the immune status through a few variables, often overlooking potentially important seasonal and gender effects. However, because of the differences in physiological and defence mechanisms among different arms of the immune system, we expect divergent responses of immune components to environmental seasonality. In male and female house sparrows ( Passer domesticus), we measured the major components of the immune system (innate, acquired, cellular and humoral) during four important life-history stages across the year: (1) mating, (2) breeding, (3) moulting and (4) during the winter capture and also following introduction to captivity in aviary. Different individuals were sampled from the same population during the four life cycle stages. We found that three out of eight immune variables showed a significant life cycle stage × sex interaction. The difference in immune response between the sexes was significant in five immune variables during the mating stage, when females had consistently stronger immune function than males, while variables varied generally non-significantly with sex during the remaining three life cycle stages. Our results show that the immune system is highly variable between life cycle stages and sexes, highlighting the potential fine tuning of the immune system to specific physiological states and environmental conditions.

Pap, Péter László; Czirják, Gábor Árpád; Vágási, Csongor István; Barta, Zoltán; Hasselquist, Dennis

2010-10-01

96

Tricarboxylic acid cycle-sustained oxidative phosphorylation in isolated myelin vesicles.  

PubMed

The Central Nervous System (CNS) function was shown to be fueled exclusively by oxidative phosphorylation (OXPHOS). This is in line with the sensitivity of brain to hypoxia, but less with the scarcity of the mitochondria in CNS. Consistently with the ectopic expression of FoF1-ATP synthase and the electron transfer chain in myelin, we have reported data demonstrating that isolated myelin vesicles (IMV) conduct OXPHOS. It may suggest that myelin sheath could be a site for the whole aerobic degradation of glucose. In this paper, we assayed the functionality of glycolysis and of TCA cycle enzymes in IMV purified from bovine forebrain. We found the presence and activity of all of the glycolytic and TCA cycle enzymes, comparable to those in mitochondria-enriched fractions, in the same experimental conditions. IMV also contain consistent carbonic anhydrase activity. These data suggest that myelin may be a contributor in energy supply for the axon, performing an extra-mitochondrial aerobic OXPHOS. The vision of myelin as the site of aerobic metabolism may shed a new light on many demyelinating pathologies, that cause an a yet unresolved axonal degeneration and whose clinical onset coincides with myelin development completion. PMID:23851157

Ravera, Silvia; Bartolucci, Martina; Calzia, Daniela; Aluigi, Maria Grazia; Ramoino, Paola; Morelli, Alessandro; Panfoli, Isabella

2013-07-12

97

Fabrication of functionally gradient nanocomposite coatings by plasma electrolytic oxidation based on variable duty cycle  

NASA Astrophysics Data System (ADS)

Plasma electrolytic oxidation (PEO) was applied on the surface of commercially pure titanium substrates in a mixed aluminate-phosphate electrolyte in the presence of silicon nitride nanoparticles as suspension in the electrolyte in order to fabricate nanocomposite coatings. Pulsed current was applied based on variable duty cycle in order to synthesize functionally gradient coatings (FGC). Different rates of variable duty cycle (3, 1.5 and 1%/min), applied current densities (0.06-0.14 A/cm2) and concentrations of nanoparticles in the electrolyte (2, 4, 6, 8 and 10 g l-1) were investigated. The nanopowder and coated samples were analyzed by atomic force microscope, scanning electron microscope and transmission electron microscope. The influence of different rates of variable duty cycle (or treatment times) on the growth rate of nanocomposite coatings and their microhardness values was investigated. The experimental results revealed that the content of Si3N4 nanoparticulates in the layer increases with the increase of its concentration in the plasma electrolysis bath. Nanocomposite coatings fabricated with lower rate of variable duty cycle have higher microhardness with smoother microhardness profile.

Aliofkhazraei, M.; Rouhaghdam, A. Sabour

2012-01-01

98

HESS Opinions "Biological catalysis of the hydrological cycle: life's thermodynamic function"  

NASA Astrophysics Data System (ADS)

Darwinian theory depicts life as being overwhelmingly consumed by a fight for survival in a hostile environment. However, from a thermodynamic perspective, life is a dynamic, out of equilibrium process, stabilizing and coevolving in concert with its abiotic environment. The living components of the biosphere on the Earth's surface of greatest biomass, the plants and cyanobacteria, are involved in the transpiration of a vast amount of water. Transpiration is part of the global water cycle, and it is this cycle that distinguishes Earth from its apparently life-barren neighboring planets, Venus and Mars. The dissipation of sunlight into heat by organic molecules in the biosphere, and its coupling to the water cycle (as well as other abiotic processes), is by far the greatest entropy-producing process occurring on Earth. Life, from this perspective, can be viewed as performing an important thermodynamic function, acting as a dynamic catalyst by aiding irreversible abiotic processes such as the water cycle, hurricanes, and ocean and wind currents to produce entropy. The role of animals in this view is that of unwitting but dedicated servants of the plants and cyanobacteria, helping them to grow, and to spread into initially inhospitable areas.

Michaelian, K.

2012-08-01

99

Are response function representations of the global carbon cycle ever interpretable?  

NASA Astrophysics Data System (ADS)

Response function models are often used to represent the behaviour of complex, high order global carbon cycle (GCC) and climate models in applications which require short model run times. Although apparently black-box, these response function models need not necessarily be entirely opaque, but instead may also convey useful insights into the properties of the parent model or process. By exploiting a transfer function (TF) framework to analyse the Lenton GCC model, this paper attempts to demonstrate that response function representations of GCC models can sometimes also provide structural information on the parent model from which they are identified and calibrated. We take a fifth-order TF identified from the impulse response of the Lenton model atmospheric burden, and decompose this to show how it can be re-expresses in a generic five-box form in sympathy with the structure of the parent model.

Li, Sile; Jarvis, Andrew J.; Leedal, David T.

2009-04-01

100

H2A.Z Functions To Regulate Progression through the Cell Cycle  

PubMed Central

Histone H2A variants are highly conserved proteins found ubiquitously in nature and thought to perform specialized functions in the cell. Studies in yeast on the histone H2A variant H2A.Z have shown a role for this protein in transcription as well as chromosome segregation. Our studies have focused on understanding the role of H2A.Z during cell cycle progression. We found that htz1? cells were delayed in DNA replication and progression through the cell cycle. Furthermore, cells lacking H2A.Z required the S-phase checkpoint pathway for survival. We also found that H2A.Z localized to the promoters of cyclin genes, and cells lacking H2A.Z were delayed in the induction of these cyclin genes. Several different models are proposed to explain these observations.

Dhillon, Namrita; Oki, Masaya; Szyjka, Shawn J.; Aparicio, Oscar M.; Kamakaka, Rohinton T.

2006-01-01

101

Functional electrical stimulation cycling improves body composition, metabolic and neural factors in persons with spinal cord injury  

Microsoft Academic Search

Persons with spinal cord injury (SCI) are at a heightened risk of developing type II diabetes and cardiovascular disease. The purpose of this investigation was to conduct an analysis of metabolic, body composition, and neurological factors before and after 10weeks of functional electrical stimulation (FES) cycling in persons with SCI. Eighteen individuals with SCI received FES cycling 2–3 times per

L. Griffin; M. J. Decker; J. Y. Hwang; B. Wang; K. Kitchen; Z. Ding; J. L. Ivy

2009-01-01

102

Nitrogen cycling in Yellowstone National Park thermal features: using gene expression to reveal ecological function  

NASA Astrophysics Data System (ADS)

Studies of biodiversity, metabolic strategies, and functional ecology in modern hydrothermal systems have the potential to provide insight into the metabolism and evolution of life. The geochemical and microbial diversity present at Yellowstone National Park (YNP), Wyoming, USA, makes it an ideal place for studying the functional ecology and metabolic processes of prokaryotic organisms. While much work in terrestrial hydrothermal features is focused on phylogenetic and geochemical analyses, a few recent investigations in YNP and other hydrothermal areas have focused on “gene hunting”: screening thermal sediment and biofilm samples for the presence of genes utilized in specific metabolic processes [2, 3, 6, 7, 8]. Although research has evaluated and confirmed the presence of many of these genes in various thermophilic microbial communities, the existence of a gene in the DNA of an organism does not verify its use, and few researchers have done work to confirm the utilization (expression) of the genes discovered in thermal samples [1, 6, 7, 8]. Disequilibrium between reduced hydrothermal fluid of YNP thermal features and the atmosphere provides a copious source of potential energy to be harnessed through microbial metabolic processes, with NO3- and NO2- serving as the preferred electron acceptors and top energy sources after O2 [4, 5]. Consequentially, nitrogen cycling likely plays a vital role in microbial metabolic processes, as well as nutrient availability. This study explores the presence and utilization of functional genes that are key in steps of the nitrogen cycle, such as nitrogen fixation (NifH), denitrification (nirKS), and ammonia oxidation (amoA). Both DNA and RNA were extracted from thermal sediment and streamer biofilm communities collected in the chemosynthetic zone of various thermal features of the Sentinel Meadows Group in Lower Geyser Basin, YNP. Extracted DNA and reverse transcribed RNA (cDNA) were amplified using the polymerase chain reaction (PCR), and products were analyzed through gel electrophoresis to identify the presence and expression of the target functional nitrogen cycle genes. Results allow comparison of nitrogen cycling processes between different chemotrophic microbial communities both within and among the thermal features investigated in this study. [1] Botero et al., 2005. AEM 71: 1267-1275. [2] Hall et al., 2008. AEM 74: 4910-4922. [3] Meyer-Dombard et al., 2009. EOS Trans AGU 90. Abstract B23C-0390. [4] Reysenbach & Shock, 2002. Science 296: 1077-1082. [5] Shock et al., 2005. Geochim Cosmochim Acta 74: 4005-4043. [6] Steunou et al., 2006. PNAS 103:2398-2403. [7] Steunou et al., 2008. The ISME Journal 2: 364-378. [8] Zhang et al., 2008. AEM 74: 6417-6426.

Lafree, S. T.; Burton, M. S.; Meyer-Dombard, D. R.

2010-12-01

103

Biostimulation induces syntrophic interactions that impact C, S and N cycling in a sediment microbial community.  

PubMed

Stimulation of subsurface microorganisms to induce reductive immobilization of metals is a promising approach for bioremediation, yet the overall microbial community response is typically poorly understood. Here we used proteogenomics to test the hypothesis that excess input of acetate activates complex community functioning and syntrophic interactions among autotrophs and heterotrophs. A flow-through sediment column was incubated in a groundwater well of an acetate-amended aquifer and recovered during microbial sulfate reduction. De novo reconstruction of community sequences yielded near-complete genomes of Desulfobacter (Deltaproteobacteria), Sulfurovum- and Sulfurimonas-like Epsilonproteobacteria and Bacteroidetes. Partial genomes were obtained for Clostridiales (Firmicutes) and Desulfuromonadales-like Deltaproteobacteria. The majority of proteins identified by mass spectrometry corresponded to Desulfobacter-like species, and demonstrate the role of this organism in sulfate reduction (Dsr and APS), nitrogen fixation and acetate oxidation to CO2 during amendment. Results indicate less abundant Desulfuromonadales, and possibly Bacteroidetes, also actively contributed to CO2 production via the tricarboxylic acid (TCA) cycle. Proteomic data indicate that sulfide was partially re-oxidized by Epsilonproteobacteria through nitrate-dependent sulfide oxidation (using Nap, Nir, Nos, SQR and Sox), with CO2 fixed using the reverse TCA cycle. We infer that high acetate concentrations, aimed at stimulating anaerobic heterotrophy, led to the co-enrichment of, and carbon fixation in Epsilonproteobacteria. Results give an insight into ecosystem behavior following addition of simple organic carbon to the subsurface, and demonstrate a range of biological processes and community interactions were stimulated. PMID:23190730

Handley, Kim M; VerBerkmoes, Nathan C; Steefel, Carl I; Williams, Kenneth H; Sharon, Itai; Miller, Christopher S; Frischkorn, Kyle R; Chourey, Karuna; Thomas, Brian C; Shah, Manesh B; Long, Philip E; Hettich, Robert L; Banfield, Jillian F

2012-11-29

104

Influence of caffeine on metabolic and cardiovascular functions during sustained light intensity cycling and at rest.  

PubMed

This study assessed the influence of caffeine on metabolic and cardiovascular functions during sustained, light intensity cycling and at rest. Eight healthy, recreationally active adults participated in four randomly assigned, double-blind experimental trials of 60 min upright seated cycle exercise (30% VO2 max) or equivalent rest with caffeine (5 mg.kg-1) or placebo consumed 60 min prior to data collection. Gas exchange was measured by open-circuit spirometry indirect calorimetry. Global blood flow was evaluated by thoracic impedance cardiography and arterial blood pressure by auscultation. A repeated measures ANOVA indicated that pretrial caffeine increased oxygen uptake and energy expenditure rate (p < 0.05) but did not change respiratory exchange ratio. Systolic, diastolic, and mean arterial blood pressure were elevated following caffeine intake (p < 0.05). Cardiac output, heart rate, stroke volume, and systemic vascular resistance were not significantly different between caffeine and placebo sessions. For each of the metabolic and hemodynamic variables examined, the effects of caffeine were similar during constant-load, light intensity cycling and at rest. These data illustrate that caffeine's mild thermogenic influence can be mediated without a major shift in substrate oxidation mixture. Caffeine at this dosage level alters cardiovascular dynamics by augmenting arterial blood pressure. PMID:10660867

Engels, H J; Wirth, J C; Celik, S; Dorsey, J L

1999-12-01

105

Sparstolonin B inhibits pro-angiogenic functions and blocks cell cycle progression in endothelial cells.  

PubMed

Sparstolonin B (SsnB) is a novel bioactive compound isolated from Sparganium stoloniferum, an herb historically used in Traditional Chinese Medicine as an anti-tumor agent. Angiogenesis, the process of new capillary formation from existing blood vessels, is dysregulated in many pathological disorders, including diabetic retinopathy, tumor growth, and atherosclerosis. In functional assays, SsnB inhibited endothelial cell tube formation (Matrigel method) and cell migration (Transwell method) in a dose-dependent manner. Microarray experiments with human umbilical vein endothelial cells (HUVECs) and human coronary artery endothelial cells (HCAECs) demonstrated differential expression of several hundred genes in response to SsnB exposure (916 and 356 genes, respectively, with fold change ?2, p<0.05, unpaired t-test). Microarray data from both cell types showed significant overlap, including genes associated with cell proliferation and cell cycle. Flow cytometric cell cycle analysis of HUVECs treated with SsnB showed an increase of cells in the G1 phase and a decrease of cells in the S phase. Cyclin E2 (CCNE2) and Cell division cycle 6 (CDC6) are regulatory proteins that control cell cycle progression through the G1/S checkpoint. Both CCNE2 and CDC6 were downregulated in the microarray data. Real Time quantitative PCR confirmed that gene expression of CCNE2 and CDC6 in HUVECs was downregulated after SsnB exposure, to 64% and 35% of controls, respectively. The data suggest that SsnB may exert its anti-angiogenic properties in part by downregulating CCNE2 and CDC6, halting progression through the G1/S checkpoint. In the chick chorioallantoic membrane (CAM) assay, SsnB caused significant reduction in capillary length and branching number relative to the vehicle control group. Overall, SsnB caused a significant reduction in angiogenesis (ANOVA, p<0.05), demonstrating its ex vivo efficacy. PMID:23940584

Bateman, Henry R; Liang, Qiaoli; Fan, Daping; Rodriguez, Vanessa; Lessner, Susan M

2013-08-05

106

Sparstolonin B Inhibits Pro-Angiogenic Functions and Blocks Cell Cycle Progression in Endothelial Cells  

PubMed Central

Sparstolonin B (SsnB) is a novel bioactive compound isolated from Sparganium stoloniferum, an herb historically used in Traditional Chinese Medicine as an anti-tumor agent. Angiogenesis, the process of new capillary formation from existing blood vessels, is dysregulated in many pathological disorders, including diabetic retinopathy, tumor growth, and atherosclerosis. In functional assays, SsnB inhibited endothelial cell tube formation (Matrigel method) and cell migration (Transwell method) in a dose-dependent manner. Microarray experiments with human umbilical vein endothelial cells (HUVECs) and human coronary artery endothelial cells (HCAECs) demonstrated differential expression of several hundred genes in response to SsnB exposure (916 and 356 genes, respectively, with fold change ?2, p<0.05, unpaired t-test). Microarray data from both cell types showed significant overlap, including genes associated with cell proliferation and cell cycle. Flow cytometric cell cycle analysis of HUVECs treated with SsnB showed an increase of cells in the G1 phase and a decrease of cells in the S phase. Cyclin E2 (CCNE2) and Cell division cycle 6 (CDC6) are regulatory proteins that control cell cycle progression through the G1/S checkpoint. Both CCNE2 and CDC6 were downregulated in the microarray data. Real Time quantitative PCR confirmed that gene expression of CCNE2 and CDC6 in HUVECs was downregulated after SsnB exposure, to 64% and 35% of controls, respectively. The data suggest that SsnB may exert its anti-angiogenic properties in part by downregulating CCNE2 and CDC6, halting progression through the G1/S checkpoint. In the chick chorioallantoic membrane (CAM) assay, SsnB caused significant reduction in capillary length and branching number relative to the vehicle control group. Overall, SsnB caused a significant reduction in angiogenesis (ANOVA, p<0.05), demonstrating its ex vivo efficacy.

Bateman, Henry R.; Liang, Qiaoli; Fan, Daping; Rodriguez, Vanessa; Lessner, Susan M.

2013-01-01

107

Transcription-independent function of Polycomb group protein PSC in cell cycle control.  

PubMed

Polycomb group (PcG) proteins control development and cell proliferation through chromatin-mediated transcriptional repression. We describe a transcription-independent function for PcG protein Posterior sex combs (PSC) in regulating the destruction of cyclin B (CYC-B). A substantial portion of PSC was found outside canonical PcG complexes, instead associated with CYC-B and the anaphase-promoting complex (APC). Cell-based experiments and reconstituted reactions established that PSC and Lemming (LMG, also called APC11) associate and ubiquitylate CYC-B cooperatively, marking it for proteosomal degradation. Thus, PSC appears to mediate both developmental gene silencing and posttranslational control of mitosis. Direct regulation of cell cycle progression might be a crucial part of the PcG system's function in development and cancer. PMID:22491092

Mohd-Sarip, Adone; Lagarou, Anna; Doyen, Cecile M; van der Knaap, Jan A; Aslan, Ülkü; Bezstarosti, Karel; Yassin, Yasmin; Brock, Hugh W; Demmers, Jeroen A A; Verrijzer, C Peter

2012-04-05

108

Nutrient Restriction Preserves Calcium Cycling and Mitochondrial Function in Cardiac Myocytes During Ischemia and Reperfusion  

PubMed Central

Nutrient restriction (NR) prolongs longevity via enhanced mitochondrial function. To test the hypothesis that NR enhances resistance to ischemia/reperfusion (IR) arrhythmias via preserved calcium (Ca) cycling and mitochondrial function. We examined the protective effects of NR on regional IR in cultured neonatal rat ventricular myocyte monolayers. Optical mapping of intracellular Ca and mitochondrial membrane potential ??m was performed using Rhod 2-AM and TMRE, respectively. Regional ischemia was mimicked by covering a portion of monolayer with a glass coverslip until loss of Ca propagation, and reperfusion was mimicked by removing the coverslip. NR was mimicked by culture in serum- and glucose-free medium for 24 hours. Relative to controls, NR monolayers sustained Ca oscillations during longer periods of ischemia (19.2±1.8 min vs 10.4±1.4 min, p < 0.001); attenuated increases in Ca transient duration (CaD) and time decay Constant (Tau) during ischemia; preserved Conduction velocity (CV) during early reperfusion, leading to protection against reperfusion arrhythmias; had minimal “rebound” decreased CaD and Tau during reperfusion; and had no depolarization of ??m during IR. NR attenuates IR arrhythmias via 1) stable calcium cycling; and 2) prevention of ??m depolarization during IR. Enhanced mitochondrial resistance to IR arrhythmias may play a role in NR-induced longevity prolongation.

Wang, Sufen; Chen, Jiexiao; Valderrabano, Miguel

2012-01-01

109

The roles of predator maturation delay and functional response in determining the periodicity of predator-prey cycles.  

PubMed

Population cycles in small mammals have attracted the attention of several generations of theoretical and experimental biologists and continue to generate controversy. Top-down and bottom-up trophic regulations are two recent competing hypotheses. The principal purpose of this paper is to explore the relative contributions of a variety of ecological factors to predator-prey population cycles. Here we suggest that for some species - collared lemmings, snowshoe hares and moose in particular - maturation delay of predators and the functional response of predation appear to be the primary determinants. Our study suggests that maturation delay alone almost completely determines the cycle period, whereas the functional response greatly affects its amplitude and even its existence. These results are obtained from sensitivity analysis of all parameters in a mathematical model of the lemming-stoat delayed system, which is an extension of Gilg's model. Our result may also explain why lemmings have a 4-year cycle whereas snowshoe hares have a 10-year cycle. Our parameterized model supports and extends May's assertion that time delay impacts cycle period and amplitude. Furthermore, if maturation periods of predators are too short or too long, or the functional response resembles Holling Type I, then population cycles do not appear; however, suitable intermediate predator maturation periods and suitable functional responses can generate population cycles for both prey and predators. These results seem to explain why some populations are cyclic whereas others are not. Finally, we find parameterizations of our model that generate a 38-year population cycle consistent with the putative cycles of the moose-wolf interactions on Isle Royale, Michigan. PMID:19563815

Wang, Hao; Nagy, John D; Gilg, Olivier; Kuang, Yang

2009-06-27

110

Q-site inhibitor induced ROS production of mitochondrial complex II is attenuated by TCA cycle dicarboxylates.  

PubMed

The impact of complex II (succinate:ubiquinone oxidoreductase) on the mitochondrial production of reactive oxygen species (ROS) has been underestimated for a long time. However, recent studies with intact mitochondria revealed that complex II can be a significant source of ROS. Using submitochondrial particles from bovine heart mitochondria as a system that allows the precise setting of substrate concentrations we could show that mammalian complex II produces ROS at subsaturating succinate concentrations in the presence of Q-site inhibitors like atpenin A5 or when a further downstream block of the respiratory chain occurred. Upon inhibition of the ubiquinone reductase activity, complex II produced about 75% hydrogen peroxide and 25% superoxide. ROS generation was attenuated by all dicarboxylates that are known to bind competitively to the substrate binding site of complex II, suggesting that the oxygen radicals are mainly generated by the unoccupied flavin site. Importantly, the ROS production induced by the Q-site inhibitor atpenin A5 was largely unaffected by the redox state of the Q pool and the activity of other respiratory chain complexes. Hence, complex II has to be considered as an independent source of mitochondrial ROS in physiology and pathophysiology. PMID:23800966

Siebels, Ilka; Dröse, Stefan

2013-06-22

111

Regulation of the TCA cycle and the general amino acid permease by overflow metabolism in Rhizobium leguminosarum  

Microsoft Academic Search

Mutants of Rhizobium leguminosarum were selected that were altered in the uptake activity of the general amino acid permease (Aap). The main class of mutant maps to sud and suct), which are part of a gene cluster mdh-sucCDAB, which codes for malate dehydrogenase (mdh), succinyl-CoA synthetase (sucCD) and components of the 2-oxoglutarate dehydrogenase complex (sudB). Mutation of either SUCC or

David L. Walshaw; Adam Wilkinson; Mathius Mundy; Mary Smith; Philip S. Poole

1997-01-01

112

Midkine-A functions upstream of Id2a to regulate cell cycle kinetics in the developing vertebrate retina  

PubMed Central

Background Midkine is a small heparin binding growth factor expressed in numerous tissues during development. The unique midkine gene in mammals has two paralogs in zebrafish: midkine-a (mdka) and midkine-b (mdkb). In the zebrafish retina, during both larval development and adult photoreceptor regeneration, mdka is expressed in retinal stem and progenitor cells and functions as a molecular component of the retina’s stem cell niche. In this study, loss-of-function and conditional overexpression were used to investigate the function of Mdka in the retina of the embryonic zebrafish. Results The results show that during early retinal development Mdka functions to regulate cell cycle kinetics. Following targeted knockdown of Mdka synthesis, retinal progenitors cycle more slowly, and this results in microphthalmia, a diminished rate of cell cycle exit and a temporal delay of cell cycle exit and neuronal differentiation. In contrast, Mdka overexpression results in acceleration of the cell cycle and retinal overgrowth. Mdka gain-of-function, however, does not temporally advance cell cycle exit. Experiments to identify a potential Mdka signaling pathway show that Mdka functions upstream of the HLH regulatory protein, Id2a. Gene expression analysis shows Mdka regulates id2a expression, and co-injection of Mdka morpholinos and id2a mRNA rescues the Mdka loss-of-function phenotype. Conclusions These data show that in zebrafish, Mdka resides in a shared Id2a pathway to regulate cell cycle kinetics in retinal progenitors. This is the first study to demonstrate the function of Midkine during retinal development and adds Midkine to the list of growth factors that transcriptionally regulate Id proteins.

2012-01-01

113

Function of trehalose and glycogen in cell cycle progression and cell viability in Saccharomyces cerevisiae.  

PubMed

Trehalose and glycogen accumulate in Saccharomyces cerevisiae when growth conditions deteriorate. It has been suggested that aside from functioning as storage factors and stress protectants, these carbohydrates may be required for cell cycle progression at low growth rates under carbon limitation. By using a mutant unable to synthesize trehalose and glycogen, we have investigated this requirement of trehalose and glycogen under carbon-limited conditions in continuous cultures. Trehalose and glycogen levels increased with decreasing growth rates in the wild-type strain, whereas no trehalose or glycogen was detected in the mutant. However, the mutant was still able to grow and divide at low growth rates with doubling times similar to those for the wild-type strain, indicating that trehalose and glycogen are not essential for cell cycle progression. Nevertheless, upon a slight increase of extracellular carbohydrates, the wild-type strain degraded its reserve carbohydrates and was able to enter a cell division cycle faster than the mutant. In addition, wild-type cells survived much longer than the mutant cells when extracellular carbon was exhausted. Thus, trehalose and glycogen have a dual role under these conditions, serving as storage factors during carbon starvation and providing quickly a higher carbon and ATP flux when conditions improve. Interestingly, the CO2 production rate and hence the ATP flux were higher in the mutant than in the wild-type strain at low growth rates. The possibility that the mutant strain requires this steady higher glycolytic flux at low growth rates for passage through Start is discussed. PMID:9882651

Silljé, H H; Paalman, J W; ter Schure, E G; Olsthoorn, S Q; Verkleij, A J; Boonstra, J; Verrips, C T

1999-01-01

114

[Dynamic changes in functional genes for nitrogen bioremediation of petroleum-contaminated soil cycle during].  

PubMed

Microorganisms in nitrogen cycle serve as an important part of the ecological function of soil. The aim of this research was to monitor the abundance of nitrogen-fixing, denitrifying and nitrifying bacteria during bioaugmentation of petroleum-contaminated soil using real-time polymerase chain reaction (real-time PCR) of nifH, narG and amoA genes which encode the key enzymes in nitrogen fixation, nitrification and ammoniation respectively. Three different kinds of soils, which are petroleum-contaminated soil, normal soil, and remediated soil, were monitored. It was shown that the amounts of functional microorganisms in petroleum-contaminated soil were far less than those in normal soil, while the amounts in remediated soil and normal soil were comparable. Results of this experiment demonstrate that nitrogen circular functional bacteria are inhibited in petroleum-contaminated soil and can be recovered through bioremediation. Furthermore, copies of the three functional genes as well as total petroleum hydrocarbons (TPH) for soils with six different treatments were monitored. Among all treatments, the one, into which both E. cloacae as an inoculant and wheat straw as an additive were added, obtained the maximum copies of 2.68 x 10(6), 1.71 x 10(6) and 8.54 x 10(4) per gram dry soil for nifH, narG and amoA genes respectively, companying with the highest degradation rate (48% in 40 days) of TPH. The recovery of functional genes and removal of TPH were better in soil inoculated with E cloacae and C echinulata collectively than soil inoculated with E cloacae only. All above results suggest that the nitrogen circular functional genes could be applied to monitor and assess the bioremediation of petroleum-contaminated soil. PMID:22946197

Wu, Bin-Bin; Lu, Dian-Nan; Liu, Zheng

2012-06-01

115

Life-cycle cost analysis 200-West Weather Enclosure: Multi-function Waste Tank Facility  

SciTech Connect

The Multi-Function Waste Tank Facility (MWTF)will provide environmentally safe and acceptable storage capacity for handling wastes resulting from the remediation of existing single-shell and double-shell tanks on the Hanford Site. The MWTF will construct two tank farm facilities at two separate locations. A four-tank complex will be constructed in the 200-East Area of the Hanford Site; a two-tank complex will be constructed in the 200-West Area. This report documents the results of a life-cycle cost analysis performed by ICF Kaiser Hanford Company (ICF KH) for the Weather Enclosure proposed to be constructed over the 200-West tanks. Currently, all tank farm operations on the Hanford Site are conducted in an open environment, with weather often affecting tank farm maintenance activities. The Weather Enclosure is being proposed to allow year-round tank farm operation and maintenance activities unconstrained by weather conditions. Elimination of weather-related delays at the MWTF and associated facilities will reduce operational costs. The life-cycle cost analysis contained in this report analyzes potential cost savings based on historical weather information, operational and maintenance costs, construction cost estimates, and other various assumptions.

Umphrey, M.R. [Westinghouse Hanford Co., Richland, WA (United States)

1995-01-16

116

Defective cell cycle checkpoint functions in melanoma are associated with altered patterns of gene expression.  

PubMed

Defects in DNA damage responses may underlie genetic instability and malignant progression in melanoma. Cultures of normal human melanocytes (NHMs) and melanoma lines were analyzed to determine whether global patterns of gene expression could predict the efficacy of DNA damage cell cycle checkpoints that arrest growth and suppress genetic instability. NHMs displayed effective G1 and G2 checkpoint responses to ionizing radiation-induced DNA damage. A majority of melanoma cell lines (11/16) displayed significant quantitative defects in one or both checkpoints. Melanomas with B-RAF mutations as a class displayed a significant defect in DNA damage G2 checkpoint function. In contrast the epithelial-like subtype of melanomas with wild-type N-RAS and B-RAF alleles displayed an effective G2 checkpoint but a significant defect in G1 checkpoint function. RNA expression profiling revealed that melanoma lines with defects in the DNA damage G1 checkpoint displayed reduced expression of p53 transcriptional targets, such as CDKN1A and DDB2, and enhanced expression of proliferation-associated genes, such as CDC7 and GEMININ. A Bayesian analysis tool was more accurate than significance analysis of microarrays for predicting checkpoint function using a leave-one-out method. The results suggest that defects in DNA damage checkpoints may be recognized in melanomas through analysis of gene expression. PMID:17597816

Kaufmann, William K; Nevis, Kathleen R; Qu, Pingping; Ibrahim, Joseph G; Zhou, Tong; Zhou, Yingchun; Simpson, Dennis A; Helms-Deaton, Jennifer; Cordeiro-Stone, Marila; Moore, Dominic T; Thomas, Nancy E; Hao, Honglin; Liu, Zhi; Shields, Janiel M; Scott, Glynis A; Sharpless, Norman E

2007-06-28

117

Reliability and consistency of plantarflexor stretch-shortening cycle function using an adapted force sledge apparatus.  

PubMed

There are various limitations to existing methods of studying plantarflexor stretch-shortening cycle (SSC) function and muscle-tendon unit (MTU) mechanics, predominantly related to measurement validity and reliability. This study utilizes an innovative adaptation to a force sledge which isolates the plantarflexors and ankle for analysis. The aim of this study was to determine the sledge loading protocol to be used, most appropriate method of data analysis and measurement reliability in a group of healthy, non-injured subjects. Twenty subjects (11 males, 9 females; age: 23.5 ±2.3 years; height: 1.73 ±0.08 m; mass: 74.2 ±11.3 kg) completed 11 impacts at five different loadings rated on a scale of perceived exertion from 1 to 5, where 5 is a loading that the subject could only complete the 11 impacts using the adapted sledge. Analysis of impacts 4-8 or 5-7 using loading 2 provided consistent results that were highly reliable (single intra-class correlation, ICC > 0.85, average ICC > 0.95) and replicated kinematics found in hopping and running. Results support use of an adapted force sledge apparatus as an ecologically valid, reliable method of investigating plantarflexor SSC function and MTU mechanics in a dynamic controlled environment. PMID:23524578

Furlong, Laura-Anne M; Harrison, Andrew J

2013-03-22

118

Intellectual, Adaptive, and Behavioral Functioning in Children with Urea Cycle Disorders  

PubMed Central

Inborn errors of urea synthesis lead to an accumulation of ammonia in blood and brain, and result in high rates of mortality and neurodevelopmental disability. The current study seeks to characterize the cognitive, adaptive, and emotional/behavioral functioning of children with Urea Cycle Disorders (UCDs). These domains were measured through testing and parent questionnaires in 92 children with UCDs (33 neonatal onset, 59 late onset). Results indicate that children who present with neonatal onset have poorer outcome than those who present later in childhood. Approximately half of the children with neonatal onset performed in the range of intellectual disability (ID), including a substantial number (~30%) who were severely impaired. In comparison, only a quarter of the late onset group were in the range of ID. There is also evidence that the UCD group has difficulties in aspects of emotional/behavioral and executive skills domains. In conclusion, children with UCDs present with a wide spectrum of cognitive outcomes. Children with neonatal onset disease have a much higher likelihood of having an intellectual disability, which becomes even more evident with increasing age. However, even children with late onset UCDs demonstrate evidence of neurocognitive and behavioral impairment, particularly in aspects of attention and executive functioning.

Krivitzky, Lauren; Babikian, Talin; Lee, HyeSeung; Thomas, Nina Hattiangadi; Burk-Paull, Karen L.; Batshaw, Mark L.

2009-01-01

119

Atherosclerosis and cardiac function assessment in low-density lipoprotein receptor-deficient mice undergoing body weight cycling  

PubMed Central

Background: Obesity has become an epidemic in many countries and is supporting a billion dollar industry involved in promoting weight loss through diet, exercise and surgical procedures. Because of difficulties in maintaining body weight reduction, a pattern of weight cycling often occurs (so called ‘yo-yo' dieting) that may result in deleterious outcomes to health. There is controversy about cardiovascular benefits of yo-yo dieting, and an animal model is needed to better understand the contributions of major diet and body weight changes on heart and vascular functions. Our purpose is to determine the effects of weight cycling on cardiac function and atherosclerosis development in a mouse model. Methods: We used low-density lipoprotein receptor-deficient mice due to their sensitivity to metabolic syndrome and cardiovascular diseases when fed high-fat diets. Alternating ad libitum feeding of high-fat and low-fat (rodent chow) diets was used to instigate weight cycling during a 29-week period. Glucose tolerance and insulin sensitivity tests were done at 22 and 24 weeks, echocardiograms at 25 weeks and atherosclerosis and plasma lipoproteins assessed at 29 weeks. Results: Mice subjected to weight cycling showed improvements in glucose homeostasis during the weight loss cycle. Weight-cycled mice showed a reduction in the severity of atherosclerosis as compared with high-fat diet-fed mice. However, atherosclerosis still persisted in weight-cycled mice as compared with mice fed rodent chow. Cardiac function was impaired in weight-cycled mice and matched with that of mice fed only the high-fat diet. Conclusion: This model provides an initial structure in which to begin detailed studies of diet, calorie restriction and surgical modifications on energy balance and metabolic diseases. This model also shows differential effects of yo-yo dieting on metabolic syndrome and cardiovascular diseases.

McMillen, T S; Minami, E; LeBoeuf, R C

2013-01-01

120

Menstrual cycle phase modulates reward-related neural function in women  

PubMed Central

There is considerable evidence from animal studies that the mesolimbic and mesocortical dopamine systems are sensitive to circulating gonadal steroid hormones. Less is known about the influence of estrogen and progesterone on the human reward system. To investigate this directly, we used functional MRI and an event-related monetary reward paradigm to study women with a repeated-measures, counterbalanced design across the menstrual cycle. Here we show that during the midfollicular phase (days 4–8 after onset of menses) women anticipating uncertain rewards activated the orbitofrontal cortex and amygdala more than during the luteal phase (6–10 days after luteinizing hormone surge). At the time of reward delivery, women in the follicular phase activated the midbrain, striatum, and left fronto-polar cortex more than during the luteal phase. These data demonstrate augmented reactivity of the reward system in women during the midfollicular phase when estrogen is unopposed by progesterone. Moreover, investigation of between-sex differences revealed that men activated ventral putamen more than women during anticipation of uncertain rewards, whereas women more strongly activated the anterior medial prefrontal cortex at the time of reward delivery. Correlation between brain activity and gonadal steroid levels also revealed that the amygdalo-hippocampal complex was positively correlated with estradiol level, regardless of menstrual cycle phase. Together, our findings provide evidence of neurofunctional modulation of the reward system by gonadal steroid hormones in humans and establish a neurobiological foundation for understanding their impact on vulnerability to drug abuse, neuropsychiatric diseases with differential expression across males and females, and hormonally mediated mood disorders.

Dreher, Jean-Claude; Schmidt, Peter J.; Kohn, Philip; Furman, Daniella; Rubinow, David; Berman, Karen Faith

2007-01-01

121

Linking N Cycling to Microbial Function Within Soil Microenvironments in Cover Crop Systems  

NASA Astrophysics Data System (ADS)

Cover crops have emerged as a crop management strategy to achieve agricultural sustainability and maintain environmental quality. Thus, fundamental knowledge of microbial-mediated C and N cycling is vital to understanding soil organic matter (SOM) dynamics in cover cropped agroecosystems. We investigated the effects of short-term cover crop-C input on N processing by microbial communities within SOM microenvironments and in bulk soil, across a gradient of organic to conventional crop management. We hypothesized that cover crop C and N inputs promote soil aggregation, which increases the abundance of ammonia oxidizing bacteria (AOB) and stimulates greater microbial cycling of N within soil microenvironments, thereby leading to potential increases in N stabilization coupled with decreases in N loss. Our hypothesis was tested on the long-term organic, low-input, and conventional maize-tomato rotations at the Center for Integrated Farming Systems experiment (Davis, CA). We collected soil samples (0-15cm) across the cover crop and subsequent maize growing seasons and then isolated three SOM fractions soil: coarse particulate organic matter (cPOM; >250um), microaggregates (53-250um), and silt-and-clay (<53um). Total C and N were measured on both bulk soil and SOM fractions. Real-time polymerase chain reaction (PCR) using primers for the functional genes, amoA and nosZ, were employed to quantify AOB and denitrifier population sizes, respectively. We also measured gross ammonification and nitrification rates in short-term 15N-incubations of the bulk soil to link cover crop induced N cycling to N-transforming bacteria. Total soil C and N concentrations and soil aggregation were higher in the organic than conventional and low-input systems. The amoA and no Z copy numbers g-1 dry soil were highest in the microaggregate fraction and similar between the cPOM and silt-and-clay fractions, among all cropping treatments. Abundances of AOB and denitrifiers were lower in bulk soil from the conventional and low- input than organic system. Our study indicates that long-term, annual cover crop inputs to the organic system lead to greater aggregation and development of microaggregate structures. Consequently, the abundance of nitrifiers and denitrifiers as well as the rates of ammonification and nitrification are augmented in the organic system compared to the conventional, which does not receive a cover crop, and the low-input system, which receives cover crops only in alternate years. These results shed light on the specific mechanisms governing short-term N stabilization versus losses under long-term crop management.

Kong, A. Y.; Scow, K. M.; Hristova, K.; Six, J.

2007-12-01

122

Seasonal redistribution of immune function in a migrant shorebird: annual-cycle effects override adjustments to thermal regime.  

PubMed

Throughout the annual cycle, demands on competing physiological systems change, and animals must allocate resources to maximize fitness. Immune function is one such system and is important for survival. Yet detailed empirical data tracking immune function over the entire annual cycle are lacking for most wild animals. We measured constitutive immune indices once a month for a year on captive red knots (Calidris canutus). We also examined temperature as an environmental contributor to immune variation by manipulating ambient temperature to vary energy expenditure. To identify relationships among immune indices, we performed principal-component analysis. We found significant repeatability in immune indices over the annual cycle and covariation of immune indices within and among individuals. This covariation suggests immune strategies as individual traits among individuals and the use of different immune strategies during different annual-cycle stages within individuals. Over the annual cycle, both higher-cost phagocyte-based immunity and lower-cost lymphocyte-based immunity were high during mass change, but there was a clear shift toward lower-cost lymphocyte-based immunity during peak molt. Experimental manipulation of temperature had little effect on annual variation in immune function. This suggests that other environmental factors, such as food availability and disease, should also be examined in the future. PMID:18999941

Buehler, Deborah M; Piersma, Theunis; Matson, Kevin; Tieleman, B Irene

2008-12-01

123

Nitroxyl Improves Cellular Heart Function by Directly Enhancing Cardiac Sarcoplasmic Reticulum Ca2+ Cycling  

PubMed Central

Heart failure remains a leading cause of morbidity and mortality worldwide. Although depressed pump function is common, development of effective therapies to stimulate contraction has proven difficult. This is thought to be attributable to their frequent reliance on cAMP stimulation to increase activator Ca2+. A potential alternative is nitroxyl (HNO), the 1-electron reduction product of nitric oxide (NO) that improves contraction and relaxation in normal and failing hearts in vivo. The mechanism for myocyte effects remains unknown. Here, we show that this activity results from a direct interaction of HNO with the sarcoplasmic reticulum Ca2+ pump and the ryanodine receptor 2, leading to increased Ca2+ uptake and release from the sarcoplasmic reticulum. HNO increases the open probability of isolated ryanodine-sensitive Ca2+-release channels and accelerates Ca2+ reuptake into isolated sarcoplasmic reticulum by stimulating ATP-dependent Ca2+ transport. Contraction improves with no net rise in diastolic calcium. These changes are not induced by NO, are fully reversible by addition of reducing agents (redox sensitive), and independent of both cAMP/protein kinase A and cGMP/protein kinase G signaling. Rather, the data support HNO/thiolate interactions that enhance the activity of intracellular Ca2+ cycling proteins. These findings suggest HNO donors are attractive candidates for the pharmacological treatment of heart failure.

Tocchetti, Carlo G.; Wang, Wang; Froehlich, Jeffrey P.; Huke, Sabine; Aon, Miguel A.; Wilson, Gerald M.; Benedetto, Giulietta Di; O'Rourke, Brian; Gao, Wei Dong; Wink, David A.; Toscano, John P.; Zaccolo, Manuela; Bers, Donald M.; Valdivia, Hector H.; Cheng, Heping; Kass, David A.; Paolocci, Nazareno

2009-01-01

124

Mathematical modelling of steam-water cycle with auxiliary empirical functions application  

NASA Astrophysics Data System (ADS)

Research oriented on identification of operating states variations with the application of mathematical models of thermal processes has been developed in the field of energy processes diagnostics. Simple models, characterised by short calculation time, are necessary for thermal diagnostics needs. Such models can be obtained using empirical modelling methods. Good results brings the construction of analytical model with auxiliary empirical built-in functions. The paper presents a mathematical model of a steam-water cycle containing mass and energy balances and semiempirical models of steam expansion line in turbine as well as heat transfer in exchangers. A model of steam expansion line in a turbine is worked out with the application of a steam flow capacity equation and an internal efficiency of process equation for each group of stages for the analysed turbine. A model of a heat exchanger contains energy balance and the relation describing heat transfer in an exchanger, proposed by Beckman. Estimation of empirical equations coefficients was realised with the application of special and reliable measurements. Estimation criterion was a weighted relative sum of the remainder squares. There are exemplary calculations results presented in the final part of paper.

Szapajko, Grzegorz; Rusinowski, Henryk

2010-09-01

125

Review: nucleotide binding to the thermoplasma thermosome: implications for the functional cycle of group II chaperonins.  

PubMed

Structural information on group II chaperonins became available during recent years from electron microscopy and X-ray crystallography. Three conformational states have been identified for both archaeal and eukaryotic group II chaperonins: an open state, a spherical closed conformation, and an intermediate asymmetric bullet-shaped form. However, the functional cycle of group II chaperonins appears less well understood, although major principles are conserved when compared to group I chaperonins: binding of the substrate polypeptide to the apical domains of the open state and MgATP-driven conformational changes that result in encapsulation of the substrate where folding can proceed presumably in the closed ring of the bullet-shaped form. Binding of the transition state analogue MgADP-AlF3-H2O in the crystal structure of the Thermoplasma acidophilum thermosome suggests that the closed geometry is the enzymatically active conformation that performs ATP hydrolysis. Domain movements observed by electron microscopy suggest a coupling of ATP hydrolysis and domain movement similar to that in the GroE system. The hydrophilic interior of the closed thermosome corresponds to the cis-ring of the asymmetric GroEL-GroES complex implicated in protein folding. PMID:11580264

Steinbacher, S; Ditzel, L

2001-08-01

126

OVARIAN FUNCTION DURING THE ESTROUS CYCLE OF THE COW: OVARIAN BLOOD FLOW AND PROGESTERONE RELEASE RATE 1'2  

Microsoft Academic Search

Summary To study the function of the corpus luteum (CL) through its major secretory product, progesterone (P4), catheters were inserted into the carotid artery (via the facial artery) and the ovarian vein (n = 12), and electromagnetic flow transducers were placed around the ovarian artery in cycling Angus and Hereford cows (n = 6). Blood samples were taken four times

Thomas H. Wise; Donald Caton; William W. Thatcher; Donald H. Barton; Michael J. Fields

2010-01-01

127

Study of Rosmarinus officinalis L. Essential Oil Yield and Composition as a Function of the Plant Life Cycle  

Microsoft Academic Search

The yield and composition variation of the Algerian Rosmarinus officinalis as a function of plant life cycle was studied. Best period to collect the plant was found to be at full flowering stage. However, to obtain required oil quality, a compromise between oil yield and composition must be considered.

C. Boutekedjiret; R. Belabbes; F. Bentahar; J. M. Bessiere

1999-01-01

128

The fate and function of therapeutic antiaddiction monoclonal antibodies across the reproductive cycle of rats.  

PubMed

During preclinical development of neuroprotective antiaddiction therapeutic monoclonal antibodies (mAbs) against phencyclidine (PCP) and (+)-methamphetamine, we discovered novel, gestation stage-specific changes in mAb disposition spanning the entire reproductive cycle of female rats. Each pharmacological change was independent of mAb dose and antigen target but was precisely coincident with transitions between the gestational trimesters, parturition, and lactation periods of the female reproductive cycle. Whereas anti-PCP mAb6B5 terminal elimination half-life (t(1/2?z)) in nonpregnant females was 6.6 ± 1.6 days, the mAb6B5 t(1/2?z) significantly changed to 3.7 ± 0.4 days, then 1.4 ± 0.1 days, then 3.0 ± 0.4 days in the second trimester, third trimester, and postpartum periods, respectively (p < 0.05 for each change). Initially, these evolving changes in mAb6B5 clearance (3.3-fold), distribution volume (1.8-fold), and elimination half-life (4.7-fold) affected our ability to sustain sufficient mAb6B5 levels to sequester PCP in the bloodstream. However, understanding the mechanisms underlying each transition allowed development of an adaptive mAb-dosing paradigm, which substantially reduced PCP levels in dam brains and fetuses throughout pregnancy. These mAb functional studies also revealed that antidrug mAbs readily cross the placenta before syncytiotrophoblast barrier maturation, demonstrating the dynamic nature of mAb pharmacokinetics in pregnancy and the importance of maintaining maternal mAb levels. These studies provide the first preclinical pregnancy model in any species for chronic mAb dosing and could have important implications for the use of antibody therapies involving blood organ barriers (such as addiction) or other chronic diseases in women of childbearing age (e.g., irritable bowel diseases, multiple sclerosis, breast cancer, rheumatoid arthritis). PMID:20962030

Hubbard, Jonathan J; Laurenzana, Elizabeth M; Williams, D Keith; Gentry, W Brooks; Owens, S Michael

2010-10-20

129

Ovarian Cycle and Effect of Social Changes on Adrenal and Ovarian Function in Pygathrix nemaeus  

Microsoft Academic Search

To assist captive breeding of the endangered red-shanked douc langur (Pygathrix nemaeus), basic knowledge on female reproductive physiology is important. We aimed 1) to characterize the pattern of fecal estrogens and progestogens during the ovarian cycle and 2) to use the information to provide reliable data on ovarian cycle characteristics. Moreover, we examined the potential impact of a change in

Michael Heistermann; Christelle Ademmer; Werner Kaumanns

2004-01-01

130

A generalized harmonic function perturbation method for determining limit cycles and homoclinic orbits of Helmholtz—Duffing oscillator  

NASA Astrophysics Data System (ADS)

In this paper, a novel description of periodic solution and homoclinic orbit of undamped Helmholtz—Duffing oscillator is proposed via nonlinear time transformation. Based on this novel description, a generalized harmonic function perturbation method is presented to determine the limit cycles and homoclinic orbits of Helmholtz—Duffing oscillator with nonlinear damping. The amplitude of limit cycle and critical value of the homoclinic bifurcation parameter can be also predicted. To illustrate the accuracy of the present method, the solutions obtained in this paper are compared with those of Runge—Kutta method, which shows the method proposed in this paper is effective and feasible.

Li, Zhenbo; Tang, Jiashi; Cai, Ping

2013-10-01

131

Alternative electron flows (water-water cycle and cyclic electron flow around PSI) in photosynthesis: molecular mechanisms and physiological functions.  

PubMed

An electron flow in addition to the major electron sinks in C(3) plants [both photosynthetic carbon reduction (PCR) and photorespiratory carbon oxidation (PCO) cycles] is termed an alternative electron flow (AEF) and functions in the chloroplasts of leaves. The water-water cycle (WWC; Mehler-ascorbate peroxidase pathway) and cyclic electron flow around PSI (CEF-PSI) have been studied as the main AEFs in chloroplasts and are proposed to play a physiologically important role in both the regulation of photosynthesis and the alleviation of photoinhibition. In the present review, I discuss the molecular mechanisms of both AEFs and their functions in vivo. To determine their physiological function, accurate measurement of the electron flux of AEFs in vivo are required. Methods to assay electron flux in CEF-PSI have been developed recently and their problematic points are discussed. The common physiological function of both the WWC and CEF-PSI is the supply of ATP to drive net CO(2) assimilation. The requirement for ATP depends on the activities of both PCR and PCO cycles, and changes in both WWC and CEF-PSI were compared with the data obtained in intact leaves. Furthermore, the fact that CEF-PSI cannot function independently has been demonstrated. I propose a model for the regulation of CEF-PSI by WWC, in which WWC is indispensable as an electron sink for the expression of CEF-PSI activity. PMID:21068108

Miyake, Chikahiro

2010-11-10

132

Functional genes to assess nitrogen cycling and aromatic hydrocarbon degradation: primers and processing matter  

PubMed Central

Targeting sequencing to genes involved in key environmental processes, i.e., ecofunctional genes, provides an opportunity to sample nature's gene guilds to greater depth and help link community structure to process-level outcomes. Vastly different approaches have been implemented for sequence processing and, ultimately, for taxonomic placement of these gene reads. The overall quality of next generation sequence analysis of functional genes is dependent on multiple steps and assumptions of unknown diversity. To illustrate current issues surrounding amplicon read processing we provide examples for three ecofunctional gene groups. A combination of in silico, environmental and cultured strain sequences was used to test new primers targeting the dioxin and dibenzofuran degrading genes dxnA1, dbfA1, and carAa. The majority of obtained environmental sequences were classified into novel sequence clusters, illustrating the discovery value of the approach. For the nitrite reductase step in denitrification, the well-known nirK primers exhibited deficiencies in reference database coverage, illustrating the need to refine primer-binding sites and/or to design multiple primers, while nirS primers exhibited bias against five phyla. Amino acid-based OTU clustering of these two N-cycle genes from soil samples yielded only 114 unique nirK and 45 unique nirS genus-level groupings, likely a reflection of constricted primer coverage. Finally, supervised and non-supervised OTU analysis methods were compared using the nifH gene of nitrogen fixation, with generally similar outcomes, but the clustering (non-supervised) method yielded higher diversity estimates and stronger site-based differences. High throughput amplicon sequencing can provide inexpensive and rapid access to nature's related sequences by circumventing the culturing barrier, but each unique gene requires individual considerations in terms of primer design and sequence processing and classification.

Penton, C. Ryan; Johnson, Timothy A.; Quensen, John F.; Iwai, Shoko; Cole, James R.; Tiedje, James M.

2013-01-01

133

Functional genes to assess nitrogen cycling and aromatic hydrocarbon degradation: primers and processing matter.  

PubMed

Targeting sequencing to genes involved in key environmental processes, i.e., ecofunctional genes, provides an opportunity to sample nature's gene guilds to greater depth and help link community structure to process-level outcomes. Vastly different approaches have been implemented for sequence processing and, ultimately, for taxonomic placement of these gene reads. The overall quality of next generation sequence analysis of functional genes is dependent on multiple steps and assumptions of unknown diversity. To illustrate current issues surrounding amplicon read processing we provide examples for three ecofunctional gene groups. A combination of in silico, environmental and cultured strain sequences was used to test new primers targeting the dioxin and dibenzofuran degrading genes dxnA1, dbfA1, and carAa. The majority of obtained environmental sequences were classified into novel sequence clusters, illustrating the discovery value of the approach. For the nitrite reductase step in denitrification, the well-known nirK primers exhibited deficiencies in reference database coverage, illustrating the need to refine primer-binding sites and/or to design multiple primers, while nirS primers exhibited bias against five phyla. Amino acid-based OTU clustering of these two N-cycle genes from soil samples yielded only 114 unique nirK and 45 unique nirS genus-level groupings, likely a reflection of constricted primer coverage. Finally, supervised and non-supervised OTU analysis methods were compared using the nifH gene of nitrogen fixation, with generally similar outcomes, but the clustering (non-supervised) method yielded higher diversity estimates and stronger site-based differences. High throughput amplicon sequencing can provide inexpensive and rapid access to nature's related sequences by circumventing the culturing barrier, but each unique gene requires individual considerations in terms of primer design and sequence processing and classification. PMID:24062736

Penton, C Ryan; Johnson, Timothy A; Quensen, John F; Iwai, Shoko; Cole, James R; Tiedje, James M

2013-09-17

134

Glutamate is the major anaplerotic substrate in the tricarboxylic acid cycle of isolated rumen epithelial and duodenal mucosal cells from beef cattle.  

PubMed

In this study, we aimed to determine the contribution of substrates to tricarboxylic acid (TCA) cycle fluxes in rumen epithelial cells (REC) and duodenal mucosal cells (DMC) isolated from Angus bulls (n = 6) fed either a 75% forage (HF) or 75% concentrate (HC) diet. In separate incubations, [(13)C(6)]glucose, [(13)C(5)]glutamate, [(13)C(5)]glutamine, [(13)C(6)]leucine, or [(13)C(5)]valine were added in increasing concentrations to basal media containing SCFA and a complete mixture of amino acids. Lactate, pyruvate, and TCA cycle intermediates were analyzed by GC-MS followed by (13)C-mass isotopomer distribution analysis. Glucose metabolism accounted for 10-19% of lactate flux in REC from HF-fed bulls compared with 27-39% in REC from HC and in DMC from bulls fed both diets (P < 0.05). For both cell types, as concentration increased, an increasing proportion (3-63%) of alpha-ketoglutarate flux derived from glutamate, whereas glutamine contributed <3% (P < 0.05). Although leucine and valine were catabolized to their respective keto-acids, these were not further metabolized to TCA cycle intermediates. Glucose, glutamine, leucine, and valine catabolism by ruminant gastrointestinal tract cells has been previously demonstrated, but in this study, their catabolism via the TCA cycle was limited. Further, although glutamate's contribution to TCA cycle fluxes was considerable, it was apparent that other substrates available in the media also contributed to the maintenance of TCA fluxes. Lastly, the results suggest that diet composition alters glucose, glutamate, and leucine catabolism by the TCA cycle of REC and DMC. PMID:19282370

El-Kadi, Samer W; Baldwin, Ransom L; McLeod, Kyle R; Sunny, Nishanth E; Bequette, Brian J

2009-03-12

135

Regulation of glycolysis by Pdk functions as a metabolic checkpoint for cell cycle quiescence in hematopoietic stem cells.  

PubMed

Defining the metabolic programs that underlie stem cell maintenance will be essential for developing strategies to manipulate stem cell capacity. Mammalian hematopoietic stem cells (HSCs) maintain cell cycle quiescence in a hypoxic microenvironment. It has been proposed that HSCs exhibit a distinct metabolic phenotype under these conditions. Here we directly investigated this idea using metabolomic analysis and found that HSCs generate adenosine-5'-triphosphate by anaerobic glycolysis through a pyruvate dehydrogenase kinase (Pdk)-dependent mechanism. Elevated Pdk expression leads to active suppression of the influx of glycolytic metabolites into mitochondria. Pdk overexpression in glycolysis-defective HSCs restored glycolysis, cell cycle quiescence, and stem cell capacity, while loss of both Pdk2 and Pdk4 attenuated HSC quiescence, glycolysis, and transplantation capacity. Moreover, treatment of HSCs with a Pdk mimetic promoted their survival and transplantation capacity. Thus, glycolytic metabolic status governed by Pdk acts as a cell cycle checkpoint that modulates HSC quiescence and function. PMID:23290136

Takubo, Keiyo; Nagamatsu, Go; Kobayashi, Chiharu I; Nakamura-Ishizu, Ayako; Kobayashi, Hiroshi; Ikeda, Eiji; Goda, Nobuhito; Rahimi, Yasmeen; Johnson, Randall S; Soga, Tomoyoshi; Hirao, Atsushi; Suematsu, Makoto; Suda, Toshio

2013-01-01

136

Cytolytic T lymphocyte function is independent of growth phase and position in the mitotic cycle  

PubMed Central

We have investigated mitotic cell cycle and growth phase regulation of homogeneous cytolytic T lymphocytes (CTL). Two independently derived CTL clones were stained with the DNA-binding dye Hoechst 33342, sorted in a fluorescence-activated cell sorter according to their position in the cell cycle, and then assayed for specific lytic activity using a short-term (30 min) (51)Cr release assay. Results show that lytic activity remained unchanged throughout the cell cycle. Furthermore, there was no significant difference in the lytic activity of CTL clones growing exponentially or arrested in a plateau phase. These results demonstrate that T cell-mediated cytolysis is independent of growth phase and position in the cell cycle.

Sekaly, RP; MacDonald, HR; Zaech, P; Glasebrook, AL; Cerottini, J-C

1981-01-01

137

Computational functions in biochemical reaction networks.  

PubMed Central

In prior work we demonstrated the implementation of logic gates, sequential computers (universal Turing machines), and parallel computers by means of the kinetics of chemical reaction mechanisms. In the present article we develop this subject further by first investigating the computational properties of several enzymatic (single and multiple) reaction mechanisms: we show their steady states are analogous to either Boolean or fuzzy logic gates. Nearly perfect digital function is obtained only in the regime in which the enzymes are saturated with their substrates. With these enzymatic gates, we construct combinational chemical networks that execute a given truth-table. The dynamic range of a network's output is strongly affected by "input/output matching" conditions among the internal gate elements. We find a simple mechanism, similar to the interconversion of fructose-6-phosphate between its two bisphosphate forms (fructose-1,6-bisphosphate and fructose-2,6-bisphosphate), that functions analogously to an AND gate. When the simple model is supplanted with one in which the enzyme rate laws are derived from experimental data, the steady state of the mechanism functions as an asymmetric fuzzy aggregation operator with properties akin to a fuzzy AND gate. The qualitative behavior of the mechanism does not change when situated within a large model of glycolysis/gluconeogenesis and the TCA cycle. The mechanism, in this case, switches the pathway's mode from glycolysis to gluconeogenesis in response to chemical signals of low blood glucose (cAMP) and abundant fuel for the TCA cycle (acetyl coenzyme A). Images FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 7 FIGURE 10 FIGURE 12 FIGURE 13 FIGURE 14 FIGURE 15 FIGURE 16

Arkin, A; Ross, J

1994-01-01

138

Prediction of limit cycle pressure oscillations in gas turbine combustion systems using the flame describing function  

Microsoft Academic Search

Thermo-acoustic analysis is crucial for a successful development of new gas\\u000aturbine combustion systems. In this context, it becomes more and more\\u000anecessary to predict the limit cycle pressure amplitude of thermo-acoustic\\u000acombustion instabilities to figure out if they are within the critical design limit or will cause damage to the engine.\\u000aFor the prediction of limit cycle pressure amplitudes,

Harmen Jan Krediet

2012-01-01

139

Properties of TCA-insoluble peptides in kimoto (traditional seed mash for sake brewing) and conditions for liberation of the peptides from rice protein.  

PubMed

It was found that a large amount of TCA (trichloroacetic acid)-insoluble peptides were liberated into the supernatant of kimoto on the 7th-10th day of mashing. These TCA-insoluble peptides had five polypeptide groups (12, 21, 31, 38, and 55 kDa) on SDS-PAGE (SDS-polyacrylamide gel electrophoresis), and a large amount of high molecular weight peptides, higher than 10,000, were observed upon gel filtration chromatography using TSKgel G2000swxl (Tosoh Co.). Four of these peptides (12, 21, 31, and 38 kDa on SDS-PAGE) appeared specifically in kimoto, and were not detected at all either in sokujo-moto or in the main mash for sake brewing. These TCA-insoluble peptides were fractionated from the supernatant of kimoto on the 9th day, and it was revealed that free amino acids were produced abundantly from them in the presence of the enzyme of rice-koji. Therefore, it was assumed that the peptides are related to the abundant production of free amino acids in kimoto. For the liberation of these TCA-insoluble peptides from rice protein, the enzyme of rice-koji was indispensable. The enzyme liberating the TCA-insoluble peptides from rice protein was purified from rice-koji, and was presumed to be identical with acid protease (AP) of rice-koji. The presence of a high concentration of glucose (higher than 20%) was also indispensable for the liberation of the TCA-insoluble peptides. Furthermore, it was revealed that the peptides were liberated from rice protein under a limited pH of around 4.5. PMID:16232657

Iemura, Y; Takahashi, T; Yamada, T; Furukawa, K; Hara, S

1999-01-01

140

Gluconeogenesis is associated with high rates of tricarboxylic acid and pyruvate cycling in fasting northern elephant seals.  

PubMed

Animals that endure prolonged periods of food deprivation preserve vital organ function by sparing protein from catabolism. Much of this protein sparing is achieved by reducing metabolic rate and suppressing gluconeogenesis while fasting. Northern elephant seals (Mirounga angustirostris) endure prolonged fasts of up to 3 mo at multiple life stages. During these fasts, elephant seals maintain high levels of activity and energy expenditure associated with breeding, reproduction, lactation, and development while maintaining rates of glucose production typical of a postabsorptive mammal. Therefore, we investigated how fasting elephant seals meet the requirements of glucose-dependent tissues while suppressing protein catabolism by measuring the contribution of glycogenolysis, glycerol, and phosphoenolpyruvate (PEP) to endogenous glucose production (EGP) during their natural 2-mo postweaning fast. Additionally, pathway flux rates associated with the tricarboxylic acid (TCA) cycle were measured specifically, flux through phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate cycling. The rate of glucose production decreased during the fast (F(1,13) = 5.7, P = 0.04) but remained similar to that of postabsorptive mammals. The fractional contributions of glycogen, glycerol, and PEP did not change with fasting; PEP was the primary gluconeogenic precursor and accounted for ?95% of EGP. This large contribution of PEP to glucose production occurred without substantial protein loss. Fluxes through the TCA cycle, PEPCK, and pyruvate cycling were higher than reported in other species and were the most energetically costly component of hepatic carbohydrate metabolism. The active pyruvate recycling fluxes detected in elephant seals may serve to rectify gluconeogeneic PEP production during restricted anaplerotic inflow in these fasting-adapted animals. PMID:22673783

Champagne, Cory D; Houser, Dorian S; Fowler, Melinda A; Costa, Daniel P; Crocker, Daniel E

2012-06-06

141

Study of the damage evolution function of tin silver copper in cycling  

NASA Astrophysics Data System (ADS)

The present research focused on the assessment of solder joint fatigue life in microelectronics assemblies. A general concern of any reliability engineer is whether accelerated tests are relevant to field conditions. The risk of this was minimized by developing an approach to reduce the duration of an accelerated thermal cycling test, thus allowing for the use of less accelerated test conditions. For this purpose the conventional dye and pry technique was improved and used together with artificial neural networks to measure and characterize very early stages of crack growth. The same work also demonstrated a quantitative link between thermal cycling induced recrystallization and a strong acceleration of the subsequent fatigue crack growth and failure. A new study was conducted in which different combinations of annealing and isothermal cycling provided a systematic characterization of the effects of a range of individual parameters on the recrystallization. Experiments showed the ongoing coarsening of secondary precipitates to have a clear effect on recrystallization. The rate of recrystallization was also shown not to scale with the inelastic energy deposition. This means that the most popular current thermal cycling model cannot apply to SnAgCu solder joints. Recrystallization of the Sn grains is usually not the rate limiting mechanism in isothermal cycling. The crack initiation stage often takes up a much greater fraction of the overall life, and the eventual failure of BGA joints tends to involve transgranular crack growth instead. Cycling of individual solder joints allowed for monitoring of the evolution of the solder properties and the rate of inelastic energy deposition. Both the number of cycles to crack initiation and the subsequent number of cycles to failure were shown to be determined by the inelastic energy deposition. This provides for a simple model for the extrapolation of accelerated test results to the much milder cycling amplitudes characteristic of long term service conditions based on conventional Finite Element Modeling. It also offers a critical basis for the ongoing development of a practical model to account for the often dramatic break-down of Miner's rule of linear damage accumulation under variable cycling amplitudes as expected in realistic applications.

Qasaimeh, Awni

142

In vivo nuclear magnetic resonance spectroscopy studies of the relationship between the glutamate-glutamine neurotransmitter cycle and functional neuroenergetics.  

PubMed Central

In this article we review recent studies, primarily from our laboratory, using 13C NMR (nuclear magnetic resonance) to non-invasively measure the rate of the glutamate-glutamine neurotransmitter cycle in the cortex of rats and humans. In the glutamate-glutamine cycle, glutamate released from nerve terminals is taken up by surrounding glial cells and returned to the nerve terminals as glutamine. 13C NMR studies have shown that the rate of the glutamate-glutamine cycle is extremely high in both the rat and human cortex, and that it increases with brain activity in an approximately 1:1 molar ratio with oxidative glucose metabolism. The measured ratio, in combination with proposals based on isolated cell studies by P. J. Magistretti and co-workers, has led to the development of a model in which the majority of brain glucose oxidation is mechanistically coupled to the glutamate-glutamine cycle. This model provides the first testable mechanistic relationship between cortical glucose metabolism and a specific neuronal activity. We review here the experimental evidence for this model as well as implications for blood oxygenation level dependent magnetic resonance imaging and positron emission tomography functional imaging studies of brain function.

Rothman, D L; Sibson, N R; Hyder, F; Shen, J; Behar, K L; Shulman, R G

1999-01-01

143

Herbivores, the Functional Diversity of Plants Species, and the Cycling of Nutrients in Ecosystems  

PubMed

Numerous investigators have suggested that herbivores almost always increase rates of nutrient and energy flow through terrestrial ecosystems by returning to the soil fecal material and urine with faster turnover rate than shed plant litter. These previous theories and models always treat the producer compartment as a homogenous pool. Essentially, they assume that consumers feed through a pureed cream of vegetable soup. However, many field observations and experiments have shown that consumers feed selectively (i.e., in a cafeteria) and that consumer choice is made on the same chemical basis that determines decomposition rates. Plants that are preferred food sources often have higher nutrient content, higher growth rates, and faster decomposition rates. As consumption reduces dominance of these species in favor of unpreferred species with slower decomposition, rates of nutrient cycling and energy flow should therefore decline. We analyze a model in which the consumer is given a choice among producers that vary in nutrient uptake rates, rates of nutrient return to decomposers, and consumer preference, and which is parameterized for plants and consumers characteristic of boreal regions. In this model, in an open, well-mixed system with one consumer and two such producers, the nutrient/energy flow will not exceed that of a system without the consumer. If the consumer has a choice between two such producers, it must choose one plant over the other at a greater ratio than that between the two plants in uptake and decay rates. In contrast, in a closed system the consumer must be less selective to coexist with the two plants. The system behavior is determined by the level of nutrient return through the consumer and the differences between the plants in nutrient uptake rates and consumer preference. Species richness affects properties of this model system to the extent that species are functionally distinct (i.e., have different rate constants) in a multivariate space of life history traits (i.e., nutrient uptake and palatability). We suggest that the biochemical variability of plant tissues that simultaneously determines both consumer preference and decomposition rates is an essential feature of food webs that cannot be ignored. Thus, ecosystem models should, at minimum, consider more than one producer type with consumer preference. PMID:9245773

Pastor; Cohen

1997-06-01

144

Damage evolution in an electron beam physical vapor deposited thermal barrier coating as a function of cycle temperature and time  

Microsoft Academic Search

Failure of thermal barrier coatings (TBCs) deposited on a single-crystal superalloy with a grit-blasted platinum modified nickel aluminide [?-(Ni, Pt) Al] bond coat has been studied as a function of thermal cycling temperature and time. One-hour cyclic furnace tests were conducted at 1100°C, 1121°C and 1151°C, and 24-h tests were run at 1121°C. It was found that all the samples

Swetha Sridharan; Liangde Xie; Eric H. Jordan; Maurice Gell; K. S. Murphy

2005-01-01

145

Ovarian function in the elephant: luteinizing hormone and progesterone cycles in African and Asian elephants.  

PubMed

Serum samples were collected weekly for 3 yr from two female African elephants, for 18 mo from two other female African elephants, and for 2 yr from two female Asian elephants. Animals were not sedated at the time of blood collection. Ovarian cycles, characterized by changes in progesterone and immunoreactive luteinizing hormone (ILH) concentrations, averaged 15.9 +/- 0.6 wk (N = 25) for African females and 14.7 +/- 0.5 wk for Asian females (N = 10). The length of the active luteal phase averaged 10.0 +/- 0.3 wk for African elephants (range 8-14 wk) and 10.6 +/- 0.6 wk for Asian females (range 9-13 wk). Interluteal phases were 5.9 +/- 0.6 wk for African females and 4.2 +/- 0.5 wk for Asian females. One African female (Maliaca) had two extended interluteal phases, both occurring between the months of February and May. Excluding these two periods, there were no differences in the length of the ovarian cycle or the length of the luteal phase between species of elephant. Serum progesterone in both species ranged from less than 50 pg/ml to 933 pg/ml. Average progesterone concentrations during the luteal phase were significantly lower in African elephants compared with Asian elephants (328 +/- 13, N = 30 cycles vs. 456 +/- 23, N = 14 cycles; p less than 0.001). ILH ranged from nondetectable to 11.6 ng/ml. These data suggest that the length of the ovarian cycle in the African elephant is about 16 wk and confirm that the length of the ovarian cycle in the Asian elephant is about 15 wk. PMID:3358979

Plotka, E D; Seal, U S; Zarembka, F R; Simmons, L G; Teare, A; Phillips, L G; Hinshaw, K C; Wood, D G

1988-03-01

146

Functional requirement of AgRP and NPY neurons in ovarian cycle-dependent regulation of food intake.  

PubMed

In female mammals including rodents and humans, feeding decreases during the periovulatory period of the ovarian cycle, which coincides with a surge in circulating estrogen levels. Ovariectomy increases food intake, which can be normalized by estrogen treatment at a dose and frequency mimicking those during the estrous cycle. Furthermore, administration of estrogen to rodents potently inhibits food intake. Despite these well-known effects of estrogen, neuronal subtypes that mediate estrogen's anorexigenic effects have not been identified. In this study, we show that changes in hypothalamic expression of agouti-related protein (Agrp) and neuropeptide Y (Npy) coincide with the cyclic changes in feeding across the estrous cycle. These cyclic changes in feeding are abolished in mice with degenerated AgRP neurons even though these mice cycle normally. Central administration of 17beta-estradiol (E2) decreases food intake in controls but not in mice lacking the AgRP neurons. Furthermore, E2 treatment suppresses fasting-induced c-Fos activation in AgRP and NPY neurons and blunts the refeeding response. Surprisingly, although estrogen receptor alpha (ERalpha) is the key mediator of estrogen's anorexigenic effects, we find that expression of ERalpha is completely excluded from AgRP and NPY neurons in the mouse hypothalamus, suggesting that estrogen may regulate these neurons indirectly via presynaptic neurons that express ERalpha. This study indicates that neurons coexpressing AgRP and NPY are functionally required for the cyclic changes in feeding across estrous cycle and that AgRP and NPY neurons are essential mediators of estrogen's anorexigenic function. PMID:19805233

Olofsson, Louise E; Pierce, Andrew A; Xu, Allison W

2009-09-02

147

Report of practicability of a 6-month home-based functional electrical stimulation cycling program in an individual with tetraplegia  

PubMed Central

Background Sedentarism is common among people with spinal cord injury (SCI). However, new technologies such as functional electrical stimulation cycles with internet connectivity may provide incentive by removing some of the limitations and external barriers. Objective To determine the effectiveness of a long-term home-based functional electrical stimulation lower extremities cycling (FES-LEC) program on exercise adherence, body composition, energy expenditure, and quality of life (QOL) in an adult with chronic tetraplegia. Participant A 53-year-old man, 33 years post-motor complete C4 SCI participated in FES-LEC in his home, three sessions per week for 24 weeks. Methods Exercise adherence was calculated as the percentage of performed cycling sessions relative to the recommended number of cycling sessions. Body composition was measured by dual-energy X-ray absorptiometry. Energy expenditure was measured using a COSMED K4b2 and QOL via the World Health Organization Quality of Life (WHO-QOL) Brief Questionnaire. Testing was performed before and after the 24-week exercise program. Results The participant cycled 59 out of a recommended 72 sessions which is an exercise adherence rate of 82%. Body composition displayed increases in total body lean mass (LM) with an increase of 3.3% and an increase in leg LM of 7.1%. Energy expenditure increased by 1.26 kcal/minute or greater than 200%. The physical and psychological domain scores of QOL increased by 25 and 4.5%, respectively. Conclusion This case study provides encouragement concerning the practicality of a home-based FES-LEC program for those with SCI.

Dolbow, David R.; Gorgey, Ashraf S.; Moore, Jewel R.; Gater, David R.

2012-01-01

148

Variations of Heart Rate During Sleep as a Function of the Sleep Cycle.  

National Technical Information Service (NTIS)

The paper describes heart rate characteristics during sleep paying particular attention to the sleep cycle. Averages and variances of heart rate are presented on ten subjects during two entire nights of sleep using approximately 3200 epochs of R-R interva...

A. J. Welch J. L. Aldredge

1973-01-01

149

Heart rate variability during sleep as a function of the sleep cycle  

Microsoft Academic Search

In this work, in order to evaluate whether autonomic differences distinguish REM sleep and NREM sleep through the whole sleeping period, statistical analysis on spectral power associated with low frequency and high frequency bands were performed on the whole polysomnographic recording, considering the sleep cycle as a unit of sleep. Our results from nine subjects show that power associated with

Francesco Versace; Manola Mozzato; Giuliano De Min Tona; Corrado Cavallero; Luciano Stegagno

2003-01-01

150

A Chemical Fractionation for Structure–Function Relations of Soil Organic Matter in Nutrient Cycling  

Microsoft Academic Search

Chemical extractions of soil organic matter (SOM) have not been widely used to elucidate the dynamics of SOM in field settings, espe- cially to address issues of nutrient cycling. To illustrate potential ap- plications of chemical extractions to nutrient issues, this report reviews studies in which the extraction of SOM fractions was based on their binding to polyvalent soil cations.

Daniel C. Olk

2006-01-01

151

Decoupling of soil nutrient cycles as a function of aridity in global drylands.  

PubMed

The biogeochemical cycles of carbon (C), nitrogen (N) and phosphorus (P) are interlinked by primary production, respiration and decomposition in terrestrial ecosystems. It has been suggested that the C, N and P cycles could become uncoupled under rapid climate change because of the different degrees of control exerted on the supply of these elements by biological and geochemical processes. Climatic controls on biogeochemical cycles are particularly relevant in arid, semi-arid and dry sub-humid ecosystems (drylands) because their biological activity is mainly driven by water availability. The increase in aridity predicted for the twenty-first century in many drylands worldwide may therefore threaten the balance between these cycles, differentially affecting the availability of essential nutrients. Here we evaluate how aridity affects the balance between C, N and P in soils collected from 224 dryland sites from all continents except Antarctica. We find a negative effect of aridity on the concentration of soil organic C and total N, but a positive effect on the concentration of inorganic P. Aridity is negatively related to plant cover, which may favour the dominance of physical processes such as rock weathering, a major source of P to ecosystems, over biological processes that provide more C and N, such as litter decomposition. Our findings suggest that any predicted increase in aridity with climate change will probably reduce the concentrations of N and C in global drylands, but increase that of P. These changes would uncouple the C, N and P cycles in drylands and could negatively affect the provision of key services provided by these ecosystems. PMID:24172979

Delgado-Baquerizo, Manuel; Maestre, Fernando T; Gallardo, Antonio; Bowker, Matthew A; Wallenstein, Matthew D; Quero, Jose Luis; Ochoa, Victoria; Gozalo, Beatriz; García-Gómez, Miguel; Soliveres, Santiago; García-Palacios, Pablo; Berdugo, Miguel; Valencia, Enrique; Escolar, Cristina; Arredondo, Tulio; Barraza-Zepeda, Claudia; Bran, Donaldo; Carreira, José Antonio; Chaieb, Mohamed; Conceiçăo, Abel A; Derak, Mchich; Eldridge, David J; Escudero, Adrián; Espinosa, Carlos I; Gaitán, Juan; Gatica, M Gabriel; Gómez-González, Susana; Guzman, Elizabeth; Gutiérrez, Julio R; Florentino, Adriana; Hepper, Estela; Hernández, Rosa M; Huber-Sannwald, Elisabeth; Jankju, Mohammad; Liu, Jushan; Mau, Rebecca L; Miriti, Maria; Monerris, Jorge; Naseri, Kamal; Noumi, Zouhaier; Polo, Vicente; Prina, Aníbal; Pucheta, Eduardo; Ramírez, Elizabeth; Ramírez-Collantes, David A; Romăo, Roberto; Tighe, Matthew; Torres, Duilio; Torres-Díaz, Cristian; Ungar, Eugene D; Val, James; Wamiti, Wanyoike; Wang, Deli; Zaady, Eli

2013-10-31

152

Application of trichloroacetic acid (TCA) to extraction of soft body for the determination of tissue Cd, Cu, Pb and Zn in the prosobranch Hydrobia ulvae (Pennant)  

Microsoft Academic Search

The application of trichloroacetic acid (TCA) as a shell extractant for preparation of soft body parts with reference to tissue metal concentrations (Cd, Cu, Pb, Zn) in shellfish has been evaluated on the example of the mud snail Hydrobia ulvae, a small marine prosobranch densely present in rocky and soft-bottom habitats of the eastern Atlantic. A solution of 0.1 M

Adam Sokolowski; Pierre Richard; Denis Fichet; Gilles Radenac; Thierry Guyot

2003-01-01

153

Stabilization of mitochondrial and microsomal function by polysaccharide of Ulva lactuca on D-Galactosamine induced hepatitis in rats.  

PubMed

In this study we used liver mitochondrial and microsomal fraction from rats pretreated with seaweed Ulva lactuca polysaccharide extract (ULP - 200mg/kg body weight, daily for 21 days, oral gavage) on D-Galactosamine (500mg/kg body weight, intraperitoneally) challenge. Effectiveness of ULP was determined based on functional status of trichloro acetic acid (TCA), urea cycle, and microsomal enzymes. The composition of sulfate polysaccharide content such as total sugars, sulfate and uronic acid were examined. In addition the fine ultra structural changes were examined using electron microscopy (EM). We observed significant (p<0.001) mitochondrial and microsomal abnormalities during liver damage by D-Galactosamine, consequently altering enzymes of energy metabolism. Electron microscopy of D-Galactosamine intoxicated rat liver tissue revealed the swelling and loss of mitochondrial cristae. Conversely the rats pretreated with ULP against D-Galactosamine challenge prevented (p<0.05) the significant abnormality of TCA, microsomal enzymes and severity of mitochondria as observed in EM study in rats injected with D-Galactosamine alone. However no effective prevention was observed in urea cycle enzymes among D-Galactosamine and treatment group rats. These results showed the effectiveness of ULP in stabilizing the functional status of mitochondrial and microsomal membrane which might be due to the presence of sulfated polysaccharide that could prevented the oxidative stress induced by D-Galactosamine intoxication. PMID:19000663

Devaki, Thiruvengadam; Sathivel, Arumugam; BalajiRaghavendran, Hanumantha Rao

2008-10-18

154

13C NMR isotopomeric analysis and its application in the study of endocrine cell metabolism and function.  

PubMed

Defining mechanisms and enzymatic paths critical to cellular function (e.g., secretion) of endocrine cells is a key research goal that can lead toward novel avenues of therapeutic intervention for a variety of disorders. 13C NMR spectroscopy and isotopomer analysis of cell extracts are excellent tools to quantitatively assess metabolism through intermediate labeling and estimate carbon entry to the TCA cycle. Discussed are: cell lines and in vitro culturing; extraction of intracellular material; NMR spectroscopy of the extract; isotopomeric analysis and modeling to obtain relative metabolic fluxes to the TCA cycle. This paper describes issues related to the application of NMR spectroscopic techniques on cell line extracts. Included are results of two studies that illustrate considerations that must be taken when performing analogous studies on neuroendocrine tissue: one involving the effect of media composition on cell behavior and isotopomer labeling; the second looking at effects of applying different metabolic models to 13C data and inferences that may be drawn. NMR isotopomeric analysis is a powerful technique that may be applied to better understand endocrine cell function. PMID:17465328

Simpson, Nicholas E; Constantinidis, Ioannis

2007-01-01

155

Staphylococcus epidermidis Polysaccharide Intercellular Adhesin Production Significantly Increases during Tricarboxylic Acid Cycle Stress  

PubMed Central

Staphylococcal polysaccharide intercellular adhesin (PIA) is important for the development of a mature biofilm. PIA production is increased during growth in a nutrient-replete or iron-limited medium and under conditions of low oxygen availability. Additionally, stress-inducing stimuli such as heat, ethanol, and high concentrations of salt increase the production of PIA. These same environmental conditions are known to repress tricarboxylic acid (TCA) cycle activity, leading us to hypothesize that altering TCA cycle activity would affect PIA production. Culturing Staphylococcus epidermidis with a low concentration of the TCA cycle inhibitor fluorocitrate dramatically increased PIA production without impairing glucose catabolism, the growth rate, or the growth yields. These data lead us to speculate that one mechanism by which staphylococci perceive external environmental change is through alterations in TCA cycle activity leading to changes in the intracellular levels of biosynthetic intermediates, ATP, or the redox status of the cell. These changes in the metabolic status of the bacteria result in the attenuation or augmentation of PIA production.

Vuong, Cuong; Kidder, Joshua B.; Jacobson, Erik R.; Otto, Michael; Proctor, Richard A.; Somerville, Greg A.

2005-01-01

156

Systems-Level Metabolic Flux Profiling Elucidates a Complete, Bifurcated Tricarboxylic Acid Cycle in Clostridium acetobutylicum ? †  

PubMed Central

Obligatory anaerobic bacteria are major contributors to the overall metabolism of soil and the human gut. The metabolic pathways of these bacteria remain, however, poorly understood. Using isotope tracers, mass spectrometry, and quantitative flux modeling, here we directly map the metabolic pathways of Clostridium acetobutylicum, a soil bacterium whose major fermentation products include the biofuels butanol and hydrogen. While genome annotation suggests the absence of most tricarboxylic acid (TCA) cycle enzymes, our results demonstrate that this bacterium has a complete, albeit bifurcated, TCA cycle; oxaloacetate flows to succinate both through citrate/?-ketoglutarate and via malate/fumarate. Our investigations also yielded insights into the pathways utilized for glucose catabolism and amino acid biosynthesis and revealed that the organism's one-carbon metabolism is distinct from that of model microbes, involving reversible pyruvate decarboxylation and the use of pyruvate as the one-carbon donor for biosynthetic reactions. This study represents the first in vivo characterization of the TCA cycle and central metabolism of C. acetobutylicum. Our results establish a role for the full TCA cycle in an obligatory anaerobic organism and demonstrate the importance of complementing genome annotation with isotope tracer studies for determining the metabolic pathways of diverse microbes.

Amador-Noguez, Daniel; Feng, Xiao-Jiang; Fan, Jing; Roquet, Nathaniel; Rabitz, Herschel; Rabinowitz, Joshua D.

2010-01-01

157

Cell cycle regulation as a mechanism for functional separation of the apparently redundant uracil DNA glycosylases TDG and UNG2  

PubMed Central

Human Thymine-DNA Glycosylase (TDG) is a member of the uracil DNA glycosylase (UDG) superfamily. It excises uracil, thymine and a number of chemical base lesions when mispaired with guanine in double-stranded DNA. These activities are not unique to TDG; at least three additional proteins with similar enzymatic properties are present in mammalian cells. The successful co-evolution of these enzymes implies the existence of non-redundant biological functions that must be coordinated. Here, we report cell cycle regulation as a mechanism for the functional separation of apparently redundant DNA glycosylases. We show that cells entering S-phase eliminate TDG through the ubiquitin–proteasome system and then maintain a TDG-free condition until G2. Incomplete degradation of ectopically expressed TDG impedes S-phase progression and cell proliferation. The mode of cell cycle regulation of TDG is strictly inverse to that of UNG2, which peaks in and throughout S-phase and then declines to undetectable levels until it appears again just before the next S-phase. Thus, TDG- and UNG2-dependent base excision repair alternates throughout the cell cycle, and the ubiquitin–proteasome pathway constitutes the underlying regulatory system.

Hardeland, Ulrike; Kunz, Christophe; Focke, Frauke; Szadkowski, Marta; Schar, Primo

2007-01-01

158

DNA Damage-Induced Cell Cycle Regulation and Function of Novel Chk2 Phosphoresidues  

Microsoft Academic Search

Chk2 kinase is activated by DNA damage to regulate cell cycle arrest, DNA repair, and apoptosis. Phos- phorylation of Chk2 in vivo by ataxia telangiectasia-mutated (ATM) on threonine 68 (T68) initiates a phos- phorylation cascade that promotes the full activity of Chk2. We identified three serine residues (S19, S33, and S35) on Chk2 that became phosphorylated in vivo rapidly and

Giacomo Buscemi; Luigi Carlessi; Laura Zannini; Sofia Lisanti; Enrico Fontanella; Silvana Canevari; Domenico Delia

2006-01-01

159

Quadriceps and Diaphragmatic Function after Exhaustive Cycle Exercise in the Healthy Elderly  

Microsoft Academic Search

The purpose of this study was to determine whether quadriceps or diaphragmatic fatigue or both occur after high-intensity cycle ex- ercise to exhaustion in healthy elderly persons. Ten relatively sed- entary male subjects aged 68.3 6 1.4 yr (mean 6 SE) (range: 60 to 75 yr) exercised at 65% to 75% of their predetermined maximal work capacity to the limits

M. JEFFERY MADOR; THOMAS J. KUFEL; LILIBETH A. PINEDA

2000-01-01

160

Pneumocystis carinii Uses a Functional Cdc13 B-Type Cyclin Complex during Its Life Cycle  

Microsoft Academic Search

Pneumocystis carinii causes severe pneumonia in immunocom- promised patients. Recent studies indicate that P. carinii uses a Cdc2 cyclin-dependent kinase to control its proliferation. To further study the regulation of the life cycle of P. carinii , we characterized the P. carinii B-type cyclin termed Cdc13, whose binding to Cdc2 is necessary for kinase activity. Antibodies to B-type cyclins (Cdc13)

Theodore J. Kottom; Charles F. Thomas; Kamal K. Mubarak; Edward B. Leof; Andrew H. Limper

161

Functional interaction of mammalian target of rapamycin complexes in regulating mammalian cell size and cell cycle  

PubMed Central

Dysregulation of the mammalian target of rapamycin (mTOR) kinase pathway is centrally involved in a wide variety of cancers and human genetic diseases. In mammalian cells, mTOR is part of two different kinase complexes: mTORC1 composed of mTOR, raptor and mLST8, and mTORC2 containing mTOR, rictor, sin1 and mLST8. Whereas, mTORC1 is known to be a pivotal regulator of cell size and cell cycle control, the question whether the recently discovered mTORC2 complex is involved in these processes remains elusive. We report here that the mTORC1-mediated consequences on cell cycle and cell size are separable and do not involve effects on mTORC2 activity. However, we show that mTORC2 itself is a potent regulator of mammalian cell size and cell cycle via a mechanism involving the Akt/TSC2/Rheb cascade. Our data are of relevance for the understanding of the molecular development of the many human diseases caused by deregulation of upstream and downstream effectors of mTOR.

Rosner, Margit; Fuchs, Christiane; Siegel, Nicol; Valli, Alessandro; Hengstschlager, Markus

2009-01-01

162

The mechanism of sensory transduction in a mechanoreceptor. Functional stages in campaniform sensilla during the molting cycle  

PubMed Central

This paper describes the ultrastructural modifications that cockroach campaniform sensilla undergo at three major stages in the molting cycle and finds that the sensilla are physiological functional at all developmental stages leading to ecdysis. Late stage animals on the verge of ecdysis have two completely separate cuticles. The campaniform sensillum sends a 220-mum extension of the sensory process through a hole in its cap in the new (inner) cuticle across a fluid-filled molting space to its functional insertion in the cap in the old (outer) cuticle. Mechanical stimulation of the old cap excites the sensillum. The ultrastructural geometry of late stage sensilla, coupled with the observation they are physiolgically functional, supports the hypotheses (a) that sensory transduction occurs at the tip of the sensory process, and (b) that cap identation causes the cap cuticle to pinch the tip of the sensory process, thereby stimulating the sensillum.

1976-01-01

163

Loss of the retinoblastoma tumor suppressor: differential action on transcriptional programs related to cell cycle control and immune function.  

PubMed

Functional inactivation of the retinoblastoma tumor suppressor gene product (RB) is a common event in human cancers. Classically, RB functions to constrain cellular proliferation, and loss of RB is proposed to facilitate the hyperplastic proliferation associated with tumorigenesis. To understand the repertoire of regulatory processes governed by RB, two models of RB loss were utilized to perform microarray analysis. In murine embryonic fibroblasts harboring germline loss of RB, there was a striking deregulation of gene expression, wherein distinct biological pathways were altered. Specifically, genes involved in cell cycle control and classically associated with E2F-dependent gene regulation were upregulated via RB loss. In contrast, a program of gene expression associated with immune function and response to pathogens was significantly downregulated with the loss of RB. To determine the specific influence of RB loss during a defined period and without the possibility of developmental compensation as occurs in embryonic fibroblasts, a second system was employed wherein Rb was acutely knocked out in adult fibroblasts. This model confirmed the distinct regulation of cell cycle and immune modulatory genes through RB loss. Analyses of cis-elements supported the hypothesis that the majority of those genes upregulated with RB loss are regulated via the E2F family of transcription factors. In contrast, those genes whose expression was reduced with the loss of RB harbored different promoter elements. Consistent with these analyses, we found that disruption of E2F-binding function of RB was associated with the upregulation of gene expression. In contrast, cells harboring an RB mutant protein (RB-750F) that retains E2F-binding activity, but is specifically deficient in the association with LXCXE-containing proteins, failed to upregulate these same target genes. However, downregulation of genes involved in immune function was readily observed with disruption of the LXCXE-binding function of RB. Thus, these studies demonstrate that RB plays a significant role in both the positive and negative regulations of transcriptional programs and indicate that loss of RB has distinct biological effects related to both cell cycle control and immune function. PMID:17452985

Markey, M P; Bergseid, J; Bosco, E E; Stengel, K; Xu, H; Mayhew, C N; Schwemberger, S J; Braden, W A; Jiang, Y; Babcock, G F; Jegga, A G; Aronow, B J; Reed, M F; Wang, J Y J; Knudsen, E S

2007-04-23

164

Multi-function ring magnet power supply for rapid-cycling synchrotrons  

SciTech Connect

Ring magnet power supply (RMPS) circuits that produce a wide range of magnet current waveshapes for rapid-cycling synchrotrons (RCS) are described. The shapes range from long flat-tops separated by a biased dual frequency cosine wave to those having a flat-bottom (injection), followed by a lower frequency cosine half wave (acceleration), a flat-top (extraction), and a higher frequency cosine half wave (magnet reset). Applications of these circuits for proposed synchrotrons are outlined. Solid-state switching circuits and the results of proof-of-concept tests are shown. 8 refs., 12 figs.

Praeg, W.F.

1985-01-01

165

Functional relationships between spatio-temporal vegetation dynamics and the water cycle  

NASA Astrophysics Data System (ADS)

The land use / land cover of an area is a key parameter within the hydrological cycle. In the framework of IMPETUS (Integrated management project for a sustainable use of fresh water) the Vegetation Group are investigating the complex interactions between the hydrological cycle and vegetation in two river catchments, situated north and south of the Sahara (Draa in Morocco and Ouémé in Benin). A major research focus is the assessment of land use / land cover (LUCC) and the derivation of their key parameters such as leaf area index, transpiration and biomass production. This is achieved using satellite imagery of different resolutions (e.g.:LANDSAT, MODIS) that are analysed and verified by intensive ground-truthing and comprehensive in-situ measurements. The vegetation dynamics are also being investigated via a series of remote sensing images at different temporal scales. This is being undertaken in order to understand the underlying processes, and their impact on the hydrological cycle. Therefore, the ecosystem's stability and its regeneration potential are in focus of the research activities of the Vegetation Group. The importance of quantifying and understanding vegetation change is critical, given that the research sites there have experience dramatic land use / land cover change. Between 1986 and 2000 more than 32% of the dense forest in the research site in Benin has been cut. The results of these investigations are related to the output of climatological and hydrological models. Socio-economic factors driving land cover / land use changes are also considered, and integrated into a model describing land cover / land use changes. Land consumption and food security are closely related with the efficiency of agriculture. The Agricultural Group is therefore investigating the influence of different types of fertilisers on the yield across 150 research fields. Initial results show that water use efficiency of crops may be increased by more than 30% using special varieties and fertiliser addition. Based on results of these multi-dimensional research activities, scenarios for the development of the land cover / land use, and the impact on the hydrological cycle under different boundary conditions can be develop. This is an important step towards a sustainable development plan for the regions, particularly in regards to available fresh water resources.

Thamm, H.-P.; Menz, G.; Goldbach, H.; Poremski, S.; Juergens, N.; Burkhardt, J.; Finck, M.; Orthmann, B.; Staudinger, M.; Gresens, F.

2003-04-01

166

Nuclear magnetic resonance patterns of intracellular water as a function of HeLa cell cycle.  

PubMed

Nuclear magnetic resonance relaxation time (T1) of the intracellular water protons and water content were measured in synchronized HeLa cells. The T1 was maximum (1020 milliseconds) in mitotic and minimum (534 milliseconds) in S phase cells. The cyclic pattern of T1 values correlated well with the chromosome condensation cycle. By treating cells with spermine, it was possible to alter T1 without a significant change in the water content. The results of this study suggest that an additional variable, namely, the conformational state of macromolecules, should be incluced in any expression explaining the shortened relaxation times of water protons in biological systems. PMID:1273575

Beall, P T; Hazlewood, C F; Rao, P N

1976-05-28

167

A centrosomal function for the human Nek2 protein kinase, a member of the NIMA family of cell cycle regulators.  

PubMed Central

Nek2, a mammalian protein kinase of unknown function, is closely related to the mitotic regulator NIMA of Aspergillus nidulans. Here we show by both immunofluorescence microscopy and biochemical fractionation that human Nek2 localizes to the centrosome. Centrosome association occurs throughout the cell cycle, including all stages of mitosis, and is independent of microtubules. Overexpression of active Nek2 induces a striking splitting of centrosomes, whereas prolonged expression of either active or inactive Nek2 leads to dispersal of centrosomal material and loss of a focused microtubule-nucleating activity. Surprisingly, this does not prevent entry into mitosis, as judged by the accumulation of mitotically arrested cells induced by co-expression of a non-destructible B-type cyclin. These results bear on the dynamic function of centrosomes at the onset of mitosis. Moreover, they indicate that one function of mammalian Nek2 relates to the centrosome cycle and thus provide a new perspective on the role of NIMA-related kinases.

Fry, A M; Meraldi, P; Nigg, E A

1998-01-01

168

Radiation-induced cardiomyopathy as a function of radiation beam gating to the cardiac cycle  

NASA Astrophysics Data System (ADS)

Portions of the heart are often unavoidably included in the primary treatment volume during thoracic radiotherapy, and radiation-induced heart disease has been observed as a treatment-related complication. Such complications have been observed in humans following radiation therapy for Hodgkin's disease and treatment of the left breast for carcinoma. Recent attempts have been made to prevent re-stenosis following angioplasty procedures using external beam irradiation. These attempts were not successful, however, due to the large volume of heart included in the treatment field and subsequent cardiac morbidity. We suggest a mechanism for sparing the heart from radiation damage by synchronizing the radiation beam with the cardiac cycle and delivering radiation only when the heart is in a relatively hypoxic state. We present data from a rat model testing this hypothesis and show that radiation damage to the heart can be altered by synchronizing the radiation beam with the cardiac cycle. This technique may be useful in reducing radiation damage to the heart secondary to treatment for diseases such as Hodgkin's disease and breast cancer.

Gladstone, David J.; Flanagan, Michael F.; Southworth, Jean B.; Hadley, Vaughn; Thibualt, Melissa Wei; Hug, Eugen B.; Hoopes, P. Jack

2004-04-01

169

Oligonucleotide Microarray for the Study of Functional Gene Diversity in the Nitrogen Cycle in the Environment  

Microsoft Academic Search

The analysis of functional diversity and its dynamics in the environment is essential for understanding the microbial ecology and biogeochemistry of aquatic systems. Here we describe the development and optimization of a DNA microarray method for the detection and quantification of functional genes in the environment and report on their preliminary application to the study of the denitrification gene nirS

Gaspar Taroncher-Oldenburg; Erin M. Griner; Chris A. Francis; Bess B. Ward

2003-01-01

170

Nitrogen cycling in Yellowstone National Park thermal features: using gene expression to reveal ecological function  

Microsoft Academic Search

Studies of biodiversity, metabolic strategies, and functional ecology in modern hydrothermal systems have the potential to provide insight into the metabolism and evolution of life. The geochemical and microbial diversity present at Yellowstone National Park (YNP), Wyoming, USA, makes it an ideal place for studying the functional ecology and metabolic processes of prokaryotic organisms. While much work in terrestrial hydrothermal

S. T. Lafree; M. S. Burton; D. R. Meyer-Dombard

2010-01-01

171

Mechanisms of Beat-to-Beat Regulation of Cardiac Pacemaker Cell Function by Ca(2+) Cycling Dynamics.  

PubMed

Whether intracellular Ca(2+) cycling dynamics regulate cardiac pacemaker cell function on a beat-to-beat basis remains unknown. Here we show that under physiological conditions, application of low concentrations of caffeine (2-4 mM) to isolated single rabbit sinoatrial node cells acutely reduces their spontaneous action potential cycle length (CL) and increases Ca(2+) transient amplitude for several cycles. Numerical simulations, using a modified Maltsev-Lakatta coupled-clock model, faithfully reproduced these effects, and also the effects of CL prolongation and dysrhythmic spontaneous beating (produced by cytosolic Ca(2+) buffering) and an acute CL reduction (produced by flash-induced Ca(2+) release from a caged Ca(2+) buffer), which we had reported previously. Three contemporary numerical models (including the original Maltsev-Lakatta model) failed to reproduce the experimental results. In our proposed new model, Ca(2+) releases acutely change the CL via activation of the Na(+)/Ca(2+) exchanger current. Time-dependent CL reductions after flash-induced Ca(2+) releases (the memory effect) are linked to changes in Ca(2+) available for pumping into sarcoplasmic reticulum which, in turn, changes the sarcoplasmic reticulum Ca(2+) load, diastolic Ca(2+) releases, and Na(+)/Ca(2+) exchanger current. These results support the idea that Ca(2+) regulates CL in cardiac pacemaker cells on a beat-to-beat basis, and suggest a more realistic numerical mechanism of this regulation. PMID:24094396

Yaniv, Yael; Stern, Michael D; Lakatta, Edward G; Maltsev, Victor A

2013-10-01

172

c-Myb Regulates Cell Cycle-Dependent Expression of Erbin: An Implication for a Novel Function of Erbin  

PubMed Central

In the present study, we demonstrated the cell cycle periodicity of Erbin expression with the maximal expression of Erbin in G2/M phase. A significant increase in Erbin promoter activity was observed in G2/M phase-synchronized cells. Sequence analysis revealed a c-Myb site in the core promoter region of Erbin. Mutagenesis of c-Myb consensus sequences abrogated the increased Erbin promoter activity in G2/M phase. ChIP and oligonucleotide pull-down assays validated that the recruitment of c-Myb to the consensus sequences was specific. The interaction of c-Myb with c-Myb site in the Erbin promoter was significantly enhanced in G2/M phase. Ectopic overexpression of c-Myb led to the up-regulation of Erbin promoter activity and c-Myb silencing by small interfering RNA significantly decreased Erbin protein level. Transfection of c-Myb rescued Erbin expression that was impaired by c-Myb knockdown. It proves that c-Myb and the c-Myb response element mediate the cell cycle-dependent expression of Erbin. Inactivation of Erbin causes an acceleration of the G1/S transition, the formation of multipolar spindles and abnormal chromosome congression. These results unravel a critical role of c-Myb in promoting Erbin transcription in G2/M phase and also predict an unappreciated function of Erbin in cell cycle progression.

Zhang, Hao; Qian, Lu; Yu, Ming; Hu, Meiru; Zhang, Ruihong; Wang, Tianyou; Han, Caili; Duan, Huijun; Guo, Ning

2012-01-01

173

Expression and localization of nodal in bovine oviduct and uterus during different functional stages of oestrus cycle and pregnancy.  

PubMed

Members of TGF-? superfamily play a major role in the endometrial changes involved in the establishment and maintenance of pregnancy. Their deregulated expression and action could lead to absolute or partial failure of embryo implantation. Nonetheless, the precise function and mechanism of many of these cytokines remain unclear. Nodal, a transforming growth factor beta (TGF-?) superfamily member, was characterized in the human and rodent uterus and implicated in the tissue remodeling events during menstruation and embryo implantation. In order to study its possible role in the cattle reproductive process, we have analyzed Nodal expression pattern and localization in the oviduct and uterine horn during the oestrus cycle and early pregnancy (day 20). Nodal was detected both in oviduct and uterus during either the oestrus cycle or pregnancy; however, it shows a differential expression profile in the uterine horn at dioestrus and pregnancy, decreasing 1.5 and 1.4 folds in comparison with oestrus. Nodal immunostaining intensity was observed in stromal and in epithelial cells of the surface and the glandular epithelium. The staining pattern correlates with the RT-qPCR expression profile. This work is the first to evidence the presence of Nodal in the bovine reproductive tract; our data suggest that Nodal is a novel cytokine that would be involved in the remodelling occurring in the endometrium of cattle during the oestrus cycle and in the embryo implantation. The identification of new molecules that participate in endometrium cycling and/or pregnancy may be useful for predicting the ability of the uterine tissue to establish and maintain pregnancy or for detecting the infertility processes. These results highlight Nodal as a possible novel marker of the fertility process, nevertheless further studies should be done to determine its role in the reproductive system. PMID:23052837

Argańaraz, Martin Eduardo; Apichela, Silvana Andrea; Kenngott, Rebecca; Vermeheren, Margarethe; Rodler, Daniela; Palma, Gustavo Adolfo; Miceli, Dora Cristina; Sinowatz, Fred

2012-10-04

174

The tricarboxylic acid cycle in Shewanella oneidensis is independent of Fur and RyhB control  

SciTech Connect

It is well established in E. coli and Vibrio cholerae that strains harboring mutations in the ferric uptake regulator gene (fur) are unable to utilize tricarboxylic acid (TCA) compounds, due to the down-regulation of key TCA cycle enzymes, such as AcnA and SdhABCD. This down-regulation is mediated by a Fur-regulated small regulatory RNA named RyhB. In this study, we showed that a fur deletion mutant of the ?-proteobacterium S. oneidensis could utilize TCA compounds. In addition, expression of the TCA cycle genes acnA and sdhA was not down-regulated in the mutant. To explore this observation further, we identified a ryhB gene in Shewanella species and demonstrated its expression experimentally. Further experiments suggested that RyhB was up-regulated in fur mutant, but that AcnA and SdhA were not controlled by RyhB. This work delineates an important difference of the Fur-RyhB regulatory cycle between S. oneidensis and other ?-proteobacteria.

Yang, Yunfeng; McCue, Lee Ann; Parsons, Andrea B.; Feng, Sheng; Zhou, Jizhong

2010-10-26

175

The role of surface chemical analysis in a study to select replacement processes for TCA vapor degreasing  

NASA Astrophysics Data System (ADS)

The role of surface-sensitive chemical analysis (ESCA, AES, and SIMS) in a study to select a process to replace 1, 1, 1-trichloroethane (TCA) vapor degreasing as a steel and aluminum bonding surface preparation method is described. The effort was primarily concerned with spray-in-air cleaning processes involving aqueous alkaline and semi-aqueous cleaners and a contamination sensitive epoxy-to-metal bondline. While all five cleaners tested produced bonding strength results equal to or better than those produced by vapor degreasing, the aqueous alkaline cleaners yielded results which were superior to those produced by the semi-aqueous cleaners. The main reason for the enhanced performance appears to be a silicate layer left behind by the aqueous alkaline cleaners. The silicate layer increases the polarity of the surface and enhances epoxy-to-metal bonding. On the other hand, one of the semi-aqueous cleaners left a nonpolar carbonaceous residue which appeared to have a negative effect on epoxy-to-metal bonding. Differences in cleaning efficiency between cleaners/processes were also identified. These differences in surface chemistry, which were sufficient to affect bonding, were not detected by conventional chemical analysis techniques.

Lesley, Michael W.; Davis, Lawrence E.; Moulder, John F.; Carlson, Brad A.

1995-03-01

176

Functional anatomy of visuo-spatial working memory during mental rotation is influenced by sex, menstrual cycle, and sex steroid hormones  

Microsoft Academic Search

Recent observations indicate that sex and level of steroid hormones may influence cortical networks associated with specific cognitive functions, in particular visuo-spatial abilities.The present study probed the influence of sex, menstrual cycle, and sex steroid hormones on 3D mental rotation and brain function using 3-T fMRI. Twelve healthy women and 12 men were investigated. Menstrual cycle and hormone levels were

S. Schöning; A. Engelien; H. Kugel; S. Schäfer; H. Schiffbauer; P. Zwitserlood; E. Pletziger; P. Beizai; A. Kersting; P. Ohrmann; R. R. Greb; W. Lehmann; W. Heindel; V. Arolt; C. Konrad

2007-01-01

177

AtCDC5 regulates the G2 to M transition of the cell cycle and is critical for the function of Arabidopsis shoot apical meristem  

Microsoft Academic Search

As a cell cycle regulator, the Myb-related CDC5 protein was reported to be essential for the G2 phase of the cell cycle in yeast and animals, but little is known about its function in plants. Here we report the functional characterization of the CDC5 gene in Arabidopsis thaliana. Arabidopsis CDC5 (AtCDC5) is mainly expressed in tissues with high cell division

Zhiqiang Lin; Kangquan Yin; Danling Zhu; Zhangliang Chen; Hongya Gu; Li-Jia Qu

2007-01-01

178

Mitochondrial function and redox state in mammalian embryos.  

PubMed

Mitochondria play a central and multifaceted role in the mammalian egg and early embryo, contributing to many different aspects of early development. While the contribution of mitochondria to energy production is fundamental, other roles for mitochondria are starting to emerge. Mitochondria are central to intracellular redox metabolism as they produce reactive oxygen species (ROS, the mediators of oxidative stress) and they can generate TCA cycle intermediates and reducing equivalents that are used in antioxidant defence. A high cytosolic lactate dehydrogenase activity coupled with dynamic levels of cytosolic pyruvate is responsible for a very dynamic intracellular redox state in the oocyte and embryo. Mammalian embryos have a low glucose metabolism during the earliest stages of development, as both glycolysis and the pentose phosphate pathway are suppressed. The mitochondrial TCA cycle is therefore the major source of reducing equivalents in the cytosol so that any change in mitochondrial function in the embryo will be reflected in changes in the intracellular redox state. In the mouse, the metabolic substrates used by the oocyte and early embryo each have a different impact on the intracellular redox state. Pyruvate which oxidises the cytosolic redox state, acts as an energetic and redox substrate whereas lactate, which reduces the cytosolic redox state, acts only as a redox substrate. Mammalian early embryos are very sensitive to oxidative stress which can cause permanent developmental arrest before zygotic genome activation and apoptosis in the blastocyst. The oocyte stockpiles antioxidant defence for the early embryo to cope with exogenous and endogenous oxidant insults arising during early development. Mitochondria provide ATP for glutathione (GSH) production during oocyte maturation and also participate in the regeneration of NADPH and GSH during early development. Finally, a number of pathological conditions or environmental insults impair early development by altering mitochondrial function, illustrating the centrality of mitochondrial function in embryo development. PMID:19530278

Dumollard, R; Carroll, J; Duchen, M R; Campbell, K; Swann, K

2009-05-01

179

Endogenous and exogenous control of ecosystem function: N cycling in headwater streams  

SciTech Connect

Allochthonous inputs act as resource subsidies to many ecosystems, where they exert strong influences on metabolism and material cycling. At the same time, metabolic theory proposes endogenous thermal control independent of resource supply. To address the relative importance of exogenous and endogenous influences, we quantified spatial and temporal variation in ecosystem metabolism and nitrogen (N) uptake using seasonal releases of {sup 15}N as nitrate in six streams differing in riparian-stream interaction and metabolic character. Nitrate removal was quantified using a nutrient spiraling approach based on measurements of downstream decline in {sup 15}N flux. Respiration (R) and gross primary production (GPP) were measured with whole-stream diel oxygen budgets. Uptake and metabolism metrics were addressed as z scores relative to site means to assess temporal variation. In open-canopied streams, areal uptake (U; {micro}g N {center_dot} m{sup -2} {center_dot} s{sup -1}) was closely related to GPP, metabolic rates increased with temperature, and R was accurately predicted by metabolic scaling relationships. In forested streams, N spiraling was not related to GPP; instead, uptake velocity (v{sub f}; mm/s) was closely related to R. In contrast to open-canopied streams, N uptake and metabolic activity were negatively correlated to temperature and poorly described by scaling laws. We contend that streams differ along a gradient of exogenous and endogenous control that relates to the relative influences of resource subsidies and in-stream energetics as determinants of seasonal patterns of metabolism and N cycling. Our research suggests that temporal variation in the propagation of ecological influence between adjacent systems generates phases when ecosystems are alternatively characterized as endogenously and exogenously controlled.

Mulholland, Patrick J [ORNL; Valett, H. Maurice [Virginia Polytechnic Institute and State University (Virginia Tech); Thomas, Steve [University of Nebraska; Webster, Jackson [Virginia Polytechnic Institute and State University (Virginia Tech); Dahm, Cliff [University of New Mexico, Albuquerque; Fellows, Christine [Griffith University, Nathan, Queensland, Australia; Crenshaw, Chelsea [University of New Mexico, Albuquerque; Peterson, Chris G. [Loyola University

2008-01-01

180

Human liver methionine cycle: MAT1A and GNMT gene resequencing, functional genomics, and hepatic genotype-phenotype correlation.  

PubMed

The "methionine cycle" plays a critical role in the regulation of concentrations of (S)-adenosylmethionine (AdoMet), the major biological methyl donor. We set out to study sequence variation in genes encoding the enzyme that synthesizes AdoMet in liver, methionine adenosyltransferase 1A (MAT1A) and the major hepatic AdoMet using enzyme, glycine N-methyltransferase (GNMT), as well as functional implications of that variation. We resequenced MAT1A and GNMT using DNA from 288 subjects of three ethnicities, followed by functional genomic and genotype-phenotype correlation studies performed with 268 hepatic biopsy samples. We identified 44 and 42 polymorphisms in MAT1A and GNMT, respectively. Quantitative Western blot analyses for the human liver samples showed large individual variation in MAT1A and GNMT protein expression. Genotype-phenotype correlation identified two genotyped single-nucleotide polymorphisms (SNPs), reference SNP (rs) 9471976 (corrected p = 3.9 × 10(-10)) and rs11752813 (corrected p = 1.8 × 10(-5)), and 42 imputed SNPs surrounding GNMT that were significantly associated with hepatic GNMT protein levels (corrected p values < 0.01). Reporter gene studies showed that variant alleles for both genotyped SNPs resulted in decreased transcriptional activity. Correlation analyses among hepatic protein levels for methionine cycle enzymes showed significant correlations between GNMT and MAT1A (p = 1.5 × 10(-3)) and between GNMT and betaine homocysteine methyltransferase (p = 1.6 × 10(-7)). Our discovery of SNPs that are highly associated with hepatic GNMT protein expression as well as the "coordinate regulation" of methionine cycle enzyme protein levels provide novel insight into the regulation of this important human liver biochemical pathway. PMID:22807109

Ji, Yuan; Nordgren, Kendra K S; Chai, Yubo; Hebbring, Scott J; Jenkins, Gregory D; Abo, Ryan P; Peng, Yi; Pelleymounter, Linda L; Moon, Irene; Eckloff, Bruce W; Chai, Xiaoshan; Zhang, Jianping; Fridley, Brooke L; Yee, Vivien C; Wieben, Eric D; Weinshilboum, Richard M

2012-07-17

181

Human Liver Methionine Cycle: MAT1A and GNMT Gene Resequencing, Functional Genomics, and Hepatic Genotype-Phenotype Correlation  

PubMed Central

The “methionine cycle” plays a critical role in the regulation of concentrations of (S)-adenosylmethionine (AdoMet), the major biological methyl donor. We set out to study sequence variation in genes encoding the enzyme that synthesizes AdoMet in liver, methionine adenosyltransferase 1A (MAT1A) and the major hepatic AdoMet using enzyme, glycine N-methyltransferase (GNMT), as well as functional implications of that variation. We resequenced MAT1A and GNMT using DNA from 288 subjects of three ethnicities, followed by functional genomic and genotype-phenotype correlation studies performed with 268 hepatic biopsy samples. We identified 44 and 42 polymorphisms in MAT1A and GNMT, respectively. Quantitative Western blot analyses for the human liver samples showed large individual variation in MAT1A and GNMT protein expression. Genotype-phenotype correlation identified two genotyped single-nucleotide polymorphisms (SNPs), reference SNP (rs) 9471976 (corrected p = 3.9 × 10?10) and rs11752813 (corrected p = 1.8 × 10?5), and 42 imputed SNPs surrounding GNMT that were significantly associated with hepatic GNMT protein levels (corrected p values < 0.01). Reporter gene studies showed that variant alleles for both genotyped SNPs resulted in decreased transcriptional activity. Correlation analyses among hepatic protein levels for methionine cycle enzymes showed significant correlations between GNMT and MAT1A (p = 1.5 × 10?3) and between GNMT and betaine homocysteine methyltransferase (p = 1.6 × 10?7). Our discovery of SNPs that are highly associated with hepatic GNMT protein expression as well as the “coordinate regulation” of methionine cycle enzyme protein levels provide novel insight into the regulation of this important human liver biochemical pathway.

Ji, Yuan; Nordgren, Kendra K. S.; Chai, Yubo; Hebbring, Scott J.; Jenkins, Gregory D.; Abo, Ryan P.; Peng, Yi; Pelleymounter, Linda L.; Moon, Irene; Eckloff, Bruce W.; Chai, Xiaoshan; Zhang, Jianping; Fridley, Brooke L.; Yee, Vivien C.; Wieben, Eric D.

2012-01-01

182

Elucidating Structure and Catalytic Cycles of Anti- or Ferro-magnetic Iron Enzymes from Spin Density Functional Theory  

NASA Astrophysics Data System (ADS)

Nature uses metal-containing enzymes to catalyze important biochemical reactions. Some enzymes, such as methane monooxygenase hydroxylase (MMOH), contain (anti)ferromagnetic binuclear iron centers that interact with dioxygen and/or other substrates to facilitate biochemical functions. We have studied the electronic and magnetic structures of several enzyme binuclear iron centers and predicted their spectroscopic properties. We have used spin density functional theory (SDFT) to predict ^57Fe M"ossbauer and other spectral parameters of MMOH and structurally related iron-containing enzymes. Upon dioxygen binding, the diiron center of MMOH undergoes a ferromagnetic to antiferromagnetic transition which may play an important role in its catalytic activity. In addition, based on our ability to predict spectroscopic data, we have been able to predict the structure of a key reaction intermediate in the MMOH catalytic cycle for which there is no X-ray structure.

Rodriguez, Jorge H.

2012-02-01

183

Dual functions of ?-ketoglutarate dehydrogenase E2 in the Krebs cycle and mitochondrial DNA inheritance in Trypanosoma brucei.  

PubMed

The dihydrolipoyl succinyltransferase (E2) of the multisubunit ?-ketoglutarate dehydrogenase complex (?-KD) is an essential Krebs cycle enzyme commonly found in the matrices of mitochondria. African trypanosomes developmentally regulate mitochondrial carbohydrate metabolism and lack a functional Krebs cycle in the bloodstream of mammals. We found that despite the absence of a functional ?-KD, bloodstream form (BF) trypanosomes express ?-KDE2, which localized to the mitochondrial matrix and inner membrane. Furthermore, ?-KDE2 fractionated with the mitochondrial genome, the kinetoplast DNA (kDNA), in a complex with the flagellum. A role for ?-KDE2 in kDNA maintenance was revealed in ?-KDE2 RNA interference (RNAi) knockdowns. Following RNAi induction, bloodstream trypanosomes showed pronounced growth reduction and often failed to equally distribute kDNA to daughter cells, resulting in accumulation of cells devoid of kDNA (dyskinetoplastic) or containing two kinetoplasts. Dyskinetoplastic trypanosomes lacked mitochondrial membrane potential and contained mitochondria of substantially reduced volume. These results indicate that ?-KDE2 is bifunctional, both as a metabolic enzyme and as a mitochondrial inheritance factor necessary for the distribution of kDNA networks to daughter cells at cytokinesis. PMID:23125353

Sykes, Steven E; Hajduk, Stephen L

2012-11-02

184

Dual Functions of ?-Ketoglutarate Dehydrogenase E2 in the Krebs Cycle and Mitochondrial DNA Inheritance in Trypanosoma brucei  

PubMed Central

The dihydrolipoyl succinyltransferase (E2) of the multisubunit ?-ketoglutarate dehydrogenase complex (?-KD) is an essential Krebs cycle enzyme commonly found in the matrices of mitochondria. African trypanosomes developmentally regulate mitochondrial carbohydrate metabolism and lack a functional Krebs cycle in the bloodstream of mammals. We found that despite the absence of a functional ?-KD, bloodstream form (BF) trypanosomes express ?-KDE2, which localized to the mitochondrial matrix and inner membrane. Furthermore, ?-KDE2 fractionated with the mitochondrial genome, the kinetoplast DNA (kDNA), in a complex with the flagellum. A role for ?-KDE2 in kDNA maintenance was revealed in ?-KDE2 RNA interference (RNAi) knockdowns. Following RNAi induction, bloodstream trypanosomes showed pronounced growth reduction and often failed to equally distribute kDNA to daughter cells, resulting in accumulation of cells devoid of kDNA (dyskinetoplastic) or containing two kinetoplasts. Dyskinetoplastic trypanosomes lacked mitochondrial membrane potential and contained mitochondria of substantially reduced volume. These results indicate that ?-KDE2 is bifunctional, both as a metabolic enzyme and as a mitochondrial inheritance factor necessary for the distribution of kDNA networks to daughter cells at cytokinesis.

Sykes, Steven E.

2013-01-01

185

An Examination of the Stretch-Shortening Cycle of the Dorsiflexors and Evertors in Uninjured and Functionally Unstable Ankles  

PubMed Central

Objective: To determine if there were differences in concentric peak torque/body-weight (PT/BW) ratios and concentric time to peak torque (TPT) of the dorsiflexors and evertors in uninjured and functionally unstable ankles using a stretch-shortening cycle (SSC) protocol on an isokinetic dynamometer. Design and Setting: We employed a case-control study design to examine the test subjects in a climate-controlled athletic training/sports medicine research laboratory. Subjects: Thirty subjects volunteered to participate in this study, 15 with unilateral functional ankle instability and 15 matched controls. Measurements: Participants were assessed isokinetically using an SSC protocol for the dorsiflexors and evertors at 120 and 240°·s?1, bilaterally. Strength was assessed using PT values normalized for body mass. Concentric TPT measurements were also compared between the groups. Results: No differences in concentric PT/BW ratios or concentric TPT were evident between the groups (P > .05). Additionally, there were no differences in these measurements between the ankles for the same motion and speed between the ankles in the subjects with functional instability. Conclusions: Using the SSC protocol as a measure of ankle function and the stretch-reflex phenomenon, we found no evidence to support the notion that differences in strength and TPT in the active, conscious state exist between those with functional ankle instability and a group of healthy control subjects.

Porter, Gary K.; Kaminski, Thomas W.; Hatzel, Brian; Powers, Michael E.; Horodyski, MaryBeth

2002-01-01

186

Some evidence on determinants of fuel economy as a function of driving cycle and test type  

SciTech Connect

Statistical methods are used with 107 vehicles whose fuel economy was presented and reported for five test types in a single publication by Consumers Union (CU) for 1986--1988 vehicles. Standard loglinear statistical formulations (i.e., multiplicative models of interactions) are used with data from this and supplementary sources to develop coefficients estimating the percent fuel economy gain per percent change in engine/vehicle design characteristic. The coefficients are developed for the five different test conditions evaluated by CU and are compared with each other on the basis of attributes of the tests. The insights of engineering models are used to develop expectations regarding the shift in size of coefficients as driving cycles change. In both the engineering models and the statistical model, the effect of weight is estimated to be higher in urban driving than in highway driving. For two test categories -- field tests and dynamometer tests -- the benefits of weight reduction are statistically estimated to be greatest in urban driving conditions. The effect on idle fuel flow rate of designing vehicles to hold performance roughly constant by maintaining power per kilogram and/or displacement per kilogram is examined, and its implication for the size of the weight effect is simply approximated from Sovran`s 1983 engineering model results. The fuel-economy-decreasing effect of the desire for performance is estimated to be somewhat larger in the statistical analysis than in the NAS study, when engine technology is held constant.

Santini, D.J.; Anderson, J.

1993-08-01

187

Dosage-Sensitive Function of RETINOBLASTOMA RELATED and Convergent Epigenetic Control Are Required during the Arabidopsis Life Cycle  

PubMed Central

The plant life cycle alternates between two distinct multi-cellular generations, the reduced gametophytes and the dominant sporophyte. Little is known about how generation-specific cell fate, differentiation, and development are controlled by the core regulators of the cell cycle. In Arabidopsis, RETINOBLASTOMA RELATED (RBR), an evolutionarily ancient cell cycle regulator, controls cell proliferation, differentiation, and regulation of a subset of Polycomb Repressive Complex 2 (PRC2) genes and METHYLTRANSFERASE 1 (MET1) in the male and female gametophytes, as well as cell fate establishment in the male gametophyte. Here we demonstrate that RBR is also essential for cell fate determination in the female gametophyte, as revealed by loss of cell-specific marker expression in all the gametophytic cells that lack RBR. Maintenance of genome integrity also requires RBR, because diploid plants heterozygous for rbr (rbr/RBR) produce an abnormal portion of triploid offspring, likely due to gametic genome duplication. While the sporophyte of the diploid mutant plants phenocopied wild type due to the haplosufficiency of RBR, genetic analysis of tetraploid plants triplex for rbr (rbr/rbr/rbr/RBR) revealed that RBR has a dosage-dependent pleiotropic effect on sporophytic development, trichome differentiation, and regulation of PRC2 subunit genes CURLY LEAF (CLF) and VERNALIZATION 2 (VRN2), and MET1 in leaves. There were, however, no obvious cell cycle and cell proliferation defects in these plant tissues, suggesting that a single functional RBR copy in tetraploids is capable of maintaining normal cell division but is not sufficient for distinct differentiation and developmental processes. Conversely, in leaves of mutants in sporophytic PRC2 subunits, trichome differentiation was also affected and expression of RBR and MET1 was reduced, providing evidence for a RBR-PRC2-MET1 regulatory feedback loop involved in sporophyte development. Together, dosage-sensitive RBR function and its genetic interaction with PRC2 genes and MET1 must have been recruited during plant evolution to control distinct generation-specific cell fate, differentiation, and development.

Johnston, Amal J.; Kirioukhova, Olga; Barrell, Philippa J.; Rutten, Twan; Moore, James M.; Baskar, Ramamurthy; Grossniklaus, Ueli; Gruissem, Wilhelm

2010-01-01

188

An N-Myristoylated Globin with a Redox-Sensing Function That Regulates the Defecation Cycle in Caenorhabditis elegans  

PubMed Central

Globins occur in all kingdoms of life where they fulfill a wide variety of functions. In the past they used to be primarily characterized as oxygen transport/storage proteins, but since the discovery of new members of the globin family like neuroglobin and cytoglobin, more diverse and complex functions have been assigned to this heterogeneous family. Here we propose a function for a membrane-bound globin of C. elegans, GLB-26. This globin was predicted to be myristoylated at its N-terminus, a post-translational modification only recently described in the globin family. In vivo, this globin is found in the membrane of the head mesodermal cell and in the tail stomato-intestinal and anal depressor muscle cells. Since GLB-26 is almost directly oxidized when exposed to oxygen, we postulate a possible function as electron transfer protein. Phenotypical studies show that GLB-26 takes part in regulating the length of the defecation cycle in C. elegans under oxidative stress conditions.

Tilleman, Lesley; De Henau, Sasha; Pauwels, Martje; Nagy, Nora; Pintelon, Isabel; Braeckman, Bart P.; De Wael, Karolien; Van Doorslaer, Sabine; Adriaensen, Dirk; Timmermans, Jean-Pierre; Moens, Luc; Dewilde, Sylvia

2012-01-01

189

Soil warming alters nitrogen cycling in a New England forest: implications for ecosystem function and structure.  

PubMed

Global climate change is expected to affect terrestrial ecosystems in a variety of ways. Some of the more well-studied effects include the biogeochemical feedbacks to the climate system that can either increase or decrease the atmospheric load of greenhouse gases such as carbon dioxide and nitrous oxide. Less well-studied are the effects of climate change on the linkages between soil and plant processes. Here, we report the effects of soil warming on these linkages observed in a large field manipulation of a deciduous forest in southern New England, USA, where soil was continuously warmed 5°C above ambient for 7 years. Over this period, we have observed significant changes to the nitrogen cycle that have the potential to affect tree species composition in the long term. Since the start of the experiment, we have documented a 45% average annual increase in net nitrogen mineralization and a three-fold increase in nitrification such that in years 5 through 7, 25% of the nitrogen mineralized is then nitrified. The warming-induced increase of available nitrogen resulted in increases in the foliar nitrogen content and the relative growth rate of trees in the warmed area. Acer rubrum (red maple) trees have responded the most after 7 years of warming, with the greatest increases in both foliar nitrogen content and relative growth rates. Our study suggests that considering species-specific responses to increases in nitrogen availability and changes in nitrogen form is important in predicting future forest composition and feedbacks to the climate system. PMID:21983640

Butler, S M; Melillo, J M; Johnson, J E; Mohan, J; Steudler, P A; Lux, H; Burrows, E; Smith, R M; Vario, C L; Scott, L; Hill, T D; Aponte, N; Bowles, F

2011-10-05

190

Elevated atmospheric CO2 impacts abundance and diversity of nitrogen cycling functional genes in soil.  

PubMed

The concentration of CO(2) in the Earth's atmosphere has increased over the last century. Although this increase is unlikely to have direct effects on soil microbial communities, increased atmospheric CO(2) may impact soil ecosystems indirectly through plant responses. This study tested the hypothesis that exposure of plants to elevated CO(2) would impact soil microorganisms responsible for key nitrogen cycling processes, specifically denitrification and nitrification. We grew trembling aspen (Populus tremuloides) trees in outdoor chambers under ambient (360 ppm) or elevated (720 ppm) levels of CO(2) for 5 years and analyzed the microbial communities in the soils below the trees using quantitative polymerase chain reaction and clone library sequencing targeting the nitrite reductase (nirK) and ammonia monooxygenase (amoA) genes. We observed a more than twofold increase in copy numbers of nirK and a decrease in nirK diversity with CO(2) enrichment, with an increased predominance of Bradyrhizobia-like nirK sequences. We suggest that this dramatic increase in nirK-containing bacteria may have contributed to the significant loss of soil N in the CO(2)-treated chambers. Elevated CO(2) also resulted in a significant decrease in copy numbers of bacterial amoA, but no change in archaeal amoA copy numbers. The decrease in abundance of bacterial amoA was likely a result of the loss of soil N in the CO(2)-treated chambers, while the lack of response for archaeal amoA supports the hypothesis that physiological differences in these two groups of ammonia oxidizers may enable them to occupy distinct ecological niches and respond differently to environmental change. PMID:22961365

Kelly, John J; Peterson, Emily; Winkelman, Jonathan; Walter, Teagan J; Rier, Steven T; Tuchman, Nancy C

2012-09-08

191

Influence of Cell Cycle Checkpoints and p53 Function on the Toxicity of Temozolomide in Human Pancreatic Cancer Cells  

PubMed Central

Background Though an increased efficacy of carmustine and temozolomide (TMZ) has been demonstrated by inactivation of O6-methylguanine-DNA methyltransferase (MGMT) with O6-benzyl-guanine (BG) in human pancreatic tumors refractive to alkylating agents, the regulatory mechanisms have not been explored. Methods The effects of TMZ and BG on apoptosis, cell growth, the mitotic index, cell cycle distribution, and protein expression were studied by TUNEL, cell counting, flow cytometry, and Western blot analysis, respectively. Results The wt-p53 human pancreatic tumor cell line Capan-2 and p53-efficient mouse embryonic fibroblasts (MEFs) were more responsive to treatment with TMZ + BG than mutant p53 Capan-1 and p53-null MEFs. S phase delay with a subsequent G2/M arrest was observed in Capans in response to BG + TMZ. The G1-to-S transition delay in Capan-2 was associated with p53-dependent apoptosis and was distinctly different from the presumed mismatch repair (MMR) killing operative during the G2/M arrest. The effect of p53 on BG + TMZ toxicity was supported by a marked change in apoptosis when p53 function was restored/inactivated. There was an early induction of MMR proteins in p53-efficient lines. Conclusion p53 provokes a classic proapoptotic response by delaying G1-to-S progression, but it may also facilitate cell killing by enhancing MMR-related cell cycle arrest and cell death.

Gupta, Seema; Sathishkumar, Sabapathi; Ahmed, Mansoor M.

2010-01-01

192

Normal Proliferation and Tumorigenesis but Impaired Pancreatic Function in Mice Lacking the Cell Cycle Regulator Sei1  

PubMed Central

Sei1 is a positive regulator of proliferation that promotes the assembly of Cdk4-cyclin D complexes and enhances the transcriptional activity of E2f1. The potential oncogenic role of Sei1 is further suggested by its overexpression in various types of human cancers. To study the role of Sei1, we have generated a mouse line deficient for this gene. Sei1-null fibroblasts did not show abnormalities regarding proliferation or susceptibility to neoplastic transformation, nor did we observe defects on Cdk4 complexes or E2f activity. Sei1-null mice were viable, did not present overt pathologies, had a normal lifespan, and had a normal susceptibility to spontaneous and chemically-induced cancer. Pancreatic insulin-producing cells are known to be particularly sensitive to Cdk4-cyclin D and E2f activities, and we have observed that Sei1 is highly expressed in pancreatic islets compared to other tissues. Interestingly, Sei1-null mice present lower number of islets, decreased ?-cell area, impaired insulin secretion, and glucose intolerance. These defects were associated to nuclear accumulation of the cell-cycle inhibitors p21Cip1 and p27Kip1 in islet cells. We conclude that Sei1 plays an important role in pancreatic ?-cells, which supports a functional link between Sei1 and the core cell cycle regulators specifically in the context of the pancreas.

Fernandez-Marcos, Pablo J.; Pantoja, Cristina; Gonzalez-Rodriguez, Agueda; Martin, Nicholas; Flores, Juana M.; Valverde, Angela M.; Hara, Eiji; Serrano, Manuel

2010-01-01

193

Stability, chromatin association and functional activity of mammalian pre-replication complex proteins during the cell cycle.  

PubMed

We have examined the behavior of pre-replication complex (pre-RC) proteins in relation to key cell cycle transitions in Chinese Hamster Ovary (CHO) cells. ORC1, ORC4 and Cdc6 were stable (T1/2 >2 h) and associated with a chromatin-containing fraction throughout the cell cycle. Green fluorescent protein-tagged ORC1 associated with chromatin throughout mitosis in living cells and co-localized with ORC4 in metaphase spreads. Association of Mcm proteins with chromatin took place during telophase, approximately 30 min after the destruction of geminin and cyclins A and B, and was coincident with the licensing of chromatin to replicate in geminin-supplemented Xenopus egg extracts. Neither Mcm recruitment nor licensing required protein synthesis throughout mitosis. Moreover, licensing could be uncoupled from origin specification in geminin-supplemented extracts; site-specific initiation within the dihydrofolate reductase locus required nuclei from cells that had passed through the origin decision point (ODP). These results demonstrate that mammalian pre-RC assembly takes place during telophase, mediated by post-translational modifications of pre-existing proteins, and is not sufficient to select specific origin sites. A subsequent, as yet undefined, step selects which pre-RCs will function as replication origins. PMID:11483529

Okuno, Y; McNairn, A J; den Elzen, N; Pines, J; Gilbert, D M

2001-08-01

194

Second messenger function of nicotinic acid adenine dinucleotide phosphate revealed by an improved enzymatic cycling assay.  

PubMed

Nicotinic acid adenine dinucleotide phosphate (NAADP) is the most potent activator of Ca2+ release from intracellular stores known today. Although recent reports have suggested an important function of NAADP in human T lymphocytes, direct evidence for receptor-induced formation of NAADP is yet missing in these cells. Thus, we developed a highly sensitive and specific enzyme assay capable of quantifying low fmol amounts of NAADP. In unstimulated T cells, the NAADP concentration amounted to 4.4 +/- 1.6 nm (0.055 +/- 0.028 pmol/mg of protein). Stimulation of the cells via the T cell receptor/CD3 complex resulted in biphasic elevation kinetics of cellular NAADP levels and was characterized by a bell-shaped concentration-response curve for NAADP. In contrast, the NAADP concentration was elevated neither upon activation of the ADP-ribose/TRPM2 channel Ca2+ signaling system nor by an increase of the intracellular Ca2+ concentration upon thapsigargin stimulation. T cell receptor/CD3 complex-mediated NAADP formation was dependent on the activity of tyrosine kinases because genistein completely blocked NAADP elevation. Thus, we propose a regulated formation of NAADP upon specific stimulation of the T cell receptor/CD3 complex, suggesting a function of NAADP as a Ca2+-mobilizing second messenger during T cell activation. PMID:16627475

Gasser, Andreas; Bruhn, Sören; Guse, Andreas H

2006-04-20

195

Mitochondrial dynamics, biogenesis, and function are coordinated with the cell cycle by APC/C CDH1.  

PubMed

Cell proliferation is associated with a high rate of aerobic glycolysis, which has been widely interpreted as a compensatory mechanism for suppressed mitochondrial function, despite reports of high respiration rates. The molecular mechanisms that link cell proliferation with mitochondrial metabolism, dynamics, and biogenesis remain obscure. Here, we show that proliferation is associated with an increase in both glycolysis and respiration, in conjunction with mitochondrial fusion and biogenesis. Changes in mitochondrial morphology and mass are due to accumulation of OPA1, MFN1, and TFAM, silencing any of which hinders cell proliferation. Moreover, the levels of OPA1, MFN1, and TFAM are regulated by the ubiquitin ligase APC/C(CDH1), which also controls proteasomal degradation of key glycolytic, glutaminolytic, and cell-cycle proteins. Thus, we have identified an important component of the molecular mechanism that coordinates cell proliferation with activation of the mitochondrial metabolic machinery that provides the necessary energy and biosynthetic substrates. PMID:22482729

Garedew, Assegid; Andreassi, Catia; Moncada, Salvador

2012-04-01

196

A functional and morphological approach to evaluate the vertical migration of estuarine intertidal nematodes during a tidal cycle  

NASA Astrophysics Data System (ADS)

We tested herein the hypothesis that exposure time significantly contributes to the vertical distribution profile of nematodes during a tidal cycle as a function of distinct feeding and locomotion behaviors, conditioned by body morphology. We showed that the vertical distribution profile of the slender with filiform tail, numerically dominant Terschellingia longicaudata is in fact significantly correlated with sediment changes induced by tidal variation. Conversely, none of the other nematode species showed unequivocal evidence of vertical migration. Horizontal spatial heterogeneity also influenced the vertical distribution of nematode associations, probably as a response to varying temperature and desiccation levels at the sediment surface. The resulting vertical profiles for individual or species groups are a trade-off among locomotory and feeding strategies and concordant morphological adaptations.

Brustolin, M. C.; Thomas, M. C.; Lana, P. C.

2013-03-01

197

F3-LAYER Seasonal Variations Near the Southern Crest of the Equatorial Ionospheric Anomaly as a Function of Solar Cycle  

NASA Astrophysics Data System (ADS)

The occurrence of an additional F3-layer has been reported at Brazilian, Indian and Asian sectors by several investigators. In this paper, we report F3-layer seasonal variations carried out at Săo José dos Campos (23.2 S, 45.0 W; dip latitude 17.6 S), near the southern crest of the equatorial ionospheric anomaly (EIA), Brazil, as a function of solar cycle. The period from September 2000 to August 2001 is used as representative of high solar activity (HSA) and the period from January 2006 to December 2006 as representative of low solar activity (LSA). This investigation shows that the frequency of occurrence of the F3-layer during HSA is 11 times more than during LSA.

Fagundes, P. R.; Klausner, V.; Bittencourt, J. A.; Sahai, Y.; Abalde, J. R.

2011-12-01

198

Nickel mine spoils revegetation attempts: effect of pioneer plants on two functional bacterial communities involved in the N-cycle.  

PubMed

Nickel mine spoils in New Caledonia represent an extreme environment, rich in nickel and strongly deficient in elementary elements such as carbon and nitrogen. To rehabilitate these sites, revegetation attempts are performed with endemic plant species establishing dinitrogen-fixation symbiosis (Gymnostoma webbianum and Serianthes calycina). As this biological fixation process provides the major source of available nitrogen in this extreme environment, it could be expected that nitrogen cycling would be stimulated. To study the revegetation effect on mine spoils, the effect of the two pioneer plants on the structure and activity of two functional bacterial communities involved in the N-cycle was investigated. nifH and narG genes were used as molecular markers for dinitrogen-fixers and dissimilatory nitrate reducers respectively. In order to assess the influence of the plants on both communities, nine clone libraries were constructed for each targeted gene. Libraries containing 602 and 513 nifH and narG clones, respectively, were screened by restriction fragment length polymorphism (RFLP) analysis. One hundred and forty-one and 78 representative clones from at least all RFLP families containing more than one clone were sequenced from nifH and narG clone libraries respectively. Both pioneer plants modified the diversity and activity of the two functional communities. However, distinct effects were observed depending on the plant species and the community considered. Serianthes calycina strongly selected a diazotroph phylotype and restored the potential activity of both communities. In contrast, G. webbianum selected no particular phylotype and only restored a fixing activity. PMID:15816926

Héry, Marina; Philippot, Laurent; Mériaux, Eve; Poly, Franck; Le Roux, Xavier; Navarro, Elisabeth

2005-04-01

199

ZYG-9, TAC-1 and ZYG-8 together ensure correct microtubule function throughout the cell cycle of C. elegans embryos.  

PubMed

The early Caenorhabditis elegans embryo is well suited for investigating microtubule-dependent cell division processes. In the one-cell stage, the XMAP215 homologue ZYG-9, associated with the TACC protein TAC-1, promotes microtubule growth during interphase and mitosis, whereas the doublecortin domain protein ZYG-8 is required for anaphase spindle positioning. How ZYG-9, TAC-1 and ZYG-8 together ensure correct microtubule-dependent processes throughout the cell cycle is not fully understood. Here, we identify new temperature-sensitive alleles of zyg-9 and tac-1. Analysis of ZYG-9 and TAC-1 distribution in these mutants identifies amino acids important for centrosomal targeting and for stability of the two proteins. This analysis also reveals that TAC-1 is needed for correct ZYG-9 centrosomal enrichment. Moreover, we find that ZYG-9, but not TAC-1, is limiting for microtubule-dependent processes in one-cell-stage embryos. Using two of these alleles to rapidly inactivate ZYG-9-TAC-1 function, we establish that this complex is required for correct anaphase spindle positioning. Furthermore, we uncover that ZYG-9-TAC-1 and ZYG-8 function together during meiosis, interphase and mitosis. We also find that TAC-1 physically interacts with ZYG-8 through its doublecortin domain, and that in vivo TAC-1 and ZYG-8 are part of a complex that does not contain ZYG-9. Taken together, these findings indicate that ZYG-9-TAC-1 and ZYG-8 act in a partially redundant manner to ensure correct microtubule assembly throughout the cell cycle of early C. elegans embryos. PMID:17666432

Bellanger, Jean-Michel; Carter, J Clayton; Phillips, Jennifer B; Canard, Coralie; Bowerman, Bruce; Gönczy, Pierre

2007-07-31

200

In situ Expression of Functional Genes Reveals Nitrogen Cycling at High Temperatures in Terrestrial Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

An essential element for life, nitrogen occurs in all living organisms and is critical for the synthesis of amino acids, proteins, nucleic acids, and other forms of biomass. Thus, nitrogen cycling likely plays a vital role in microbial metabolic processes as well as nutrient availability. For microorganisms in "extreme" environments, this means developing adaptations that allow them to survive in harsh conditions and still perform the metabolisms essential to sustain life. Recent studies have screened biofilms and thermal sediments of Yellowstone National Park (YNP) thermal features for the presence of nifH genes, which code for a key enzyme in the nitrogen fixation process [1-4]. Furthermore, analysis of nitrogen isotopes in biofilms across a temperature and chemical gradient revealed that nitrogen fixation likely varies across the chemosynthetic/photosynthetic ecotone [5]. Although research has evaluated and confirmed the presence of nifH genes in various thermophilic microbial communities, the existence of a gene in the DNA of an organism does not verify its use. Instead, other methods, such as culturing, isotope tracer assays, and gene expression studies are required to provide direct evidence of biological nitrogen fixation. Culturing and isotope tracer approaches have successfully revealed high-temperature biological nitrogen fixation in both marine hydrothermal vent microbial communities [6] and in acidic, terrestrial hydrothermal sediment [3]. Transcriptomics-based techniques (using mRNA extracted from samples to confirm in situ expression of targeted genes) have been much more limited in number, and only a few studies have, to date, investigated in situ expression of the nifH gene in thermophilic microbial communities [2, 7]. This study explores the presence and expression of nifH genes in several features of the Lower Geyser Basin (LGB) of YNP. Nucleic acids from chemosynthetic and photosynthetic microbial communities were extracted and then amplified using (reverse-transcription) polymerase chain reaction to identify the presence and expression of nifH genes, and resultant (RT-)PCR product was cloned and sequenced. Results reveal high-temperature in situ expression of nifH in select LGB features [7] which is, to the authors' knowledge, the first direct evidence of nifH transcription in the chemosynthetic zones of terrestrial hydrothermal systems. Results also indicate the presence of novel nifH sequences and allow phylogenetic comparison of nifH genes along geochemical gradients within individual hot spring features and between various thermal features in the LGB. Collectively, these results provide evidence for microbial adaptations that have led to the ability to support basic metabolic processes under "extreme" conditions. [1] Hall et al., 2008. AEM 74: 4910-4922. [2] Steunou et al., 2008. The ISME Journal 2: 364-378. [3] Hamilton et al., 2011. Microb Ecol DOI 10.1007/s00248-011-9824-9. [4] Raymond et al., 2008. EOS Trans AGU. Abstract B14A-03. [5] Havig et al., 2010. J Geophys Res-Biogeo 116: G01005. [6] Mehta & Baross, 2006. Science 314: 1783-1786. [7] Loiacono et al., 2011. Submitted FEMS Microbiol Ecol.

Loiacono, S. T.; Meyer-Dombard, D. R.

2011-12-01

201

Sexual reproduction in the Candida clade: cryptic cycles, diverse mechanisms, and alternative functions.  

PubMed

To have sex, or not to have sex, is a question posed by many microorganisms. In favor of a sexual lifestyle is the associated rearrangement of genetic material that confers potential fitness advantages, including resistance to antimicrobial agents. The asexual lifestyle also has benefits, as it preserves complex combinations of genes that may be optimal for pathogenesis. For this reason, it was thought that several pathogenic fungi favored strictly asexual modes of reproduction. Recent approaches using genome sequencing, population analysis, and experimental techniques have now revised this simplistic picture. It is now apparent that many pathogenic fungi have retained the ability to undergo sexual reproduction, although reproduction is primarily clonal in origin. In this review, we highlight the current understanding of sexual programs in the Candida clade of species. We also examine evidence that sexual-related processes can be used for functions in addition to mating and recombination in these organisms. PMID:20552251

Alby, Kevin; Bennett, Richard J

2010-06-15

202

Effect of peptide-conjugated near-infrared fluorescent quantum dots (NIRF-QDs) on the invasion and metastasis of human tongue squamous cell carcinoma cell line Tca8113 in vitro.  

PubMed

In this study we investigated the effect of near-infrared fluorescent quantum dots (NIRF-QDs, QTracker) on the proliferation, adherence, invasion and chemotaxis of human tongue squamous cell carcinoma cell line Tca8113 in vitro. Cell proliferation and colony formation rate were determined by using a hemocytometer and culture plate. A transwell chamber assay was used to determine the cell invasion, adherence and chemotaxis. The results showed that there was no significant difference between the results of Tca8113 cells labeled with NIRF-QD800 and those of unlabeled Tca8113 cells, suggesting that the proliferation, invasion, adherence and chemotaxis of Tca8113 cells were not affected by NIRF-QD800. These results provide a basis for the further utilization of NIRF-QDs in non-invasive imaging and tracking of tumor cells in vivo. PMID:20057952

Yang, Kai; Li, Zhigang; Cao, Yuan; Yu, Xiuli; Mei, Jie

2009-11-20

203

Outcomes of a Home Cycling Program Using Functional Electrical Stimulation or Passive Motion for Children With Spinal Cord Injury: A Case Series  

PubMed Central

Background/Objective: Children with spinal cord injury (SCI) are at risk for musculoskeletal and cardiovascular complications. Stationary cycling using functional electrical stimulation (FES) or passive motion has been suggested to address these complications. The purpose of this case series is to report the outcomes of a 6-month at-home cycling program for 4 children with SCI. Methods: Two children cycled with FES and 2 cycled passively at home for 1 hour, 3 times per week. Outcome Measures: Data collected included bone mineral density of the left femoral neck, distal femur, and proximal tibia; quadriceps and hamstring muscle volume; stimulated quadriceps and hamstring muscle strength; a fasting lipid profile; and heart rate and oxygen consumption during incremental upper extremity ergometry testing. Results: The 2 children cycling with FES and 1 child cycling passively exhibited improved bone mineral density, muscle volume, stimulated quadriceps strength, and lower resting heart rate. For the second child cycling passively, few changes were realized. Overall, the lipid results were inconsistent, with some positive and some negative changes seen. Conclusions: This case series suggests that cycling with or without FES may have positive health benefits and was a practical home exercise option for these children with SCI.

Johnston, Therese E; Smith, Brian T; Oladeji, Oluwabunmi; Betz, Randal R; Lauer, Richard T

2008-01-01

204

Rho proteins of plants--functional cycle and regulation of cytoskeletal dynamics.  

PubMed

Rho-related ROP proteins are molecular switches that essentially regulate a wide variety of processes. Of central interest is their influence on the plant cytoskeleton by which they affect vital processes like cell division, growth, morphogenesis, and pathogen defense. ROPs switch between GTP- and GDP-bound conformations by strictly regulated nucleotide exchange and GTP-hydrolysis, and only the active GTP-form interacts with downstream effectors to ultimately provoke a biological response. However, the mode of action of the engaged regulators and effectors as well as their upstream and downstream interaction partners have long been largely unknown. As opposed to analogous systems in animals and fungi, plants use specific GTPase activating proteins (RopGAPs) with a unique domain composition and novel guanine nucleotide exchange factors (RopGEFs) with a probable link to cell surface receptors. Moreover, plants comprise novel effector molecules and adapters connecting ROPs to mostly unknown downstream targets on the route to the cytoskeleton. This review aims to summarize recent knowledge on the molecular mechanisms and reaction cascades involved in ROP dependent cytoskeletal rearrangements, addressing the structure and function of the unusual RopGAPs, RopGEFs and effectors, and the upstream and downstream pathways linking ROPs to cell receptor-like kinases, actin filaments, and microtubules. PMID:21277045

Mucha, Elena; Fricke, Inka; Schaefer, Antje; Wittinghofer, Alfred; Berken, Antje

2011-01-28

205

A Functional Analysis of the Influence of ?3-adrenoceptors on the Rat Micturition Cycle.  

PubMed

Dysfunctions of the lower urinary tract, such as overactive bladder syndrome and incontinence, are the product of storage failure. Spontaneous regional bladder wall movements [nonmicturition contractions (NMCs)] are proposed to generate afferent activity that signals volume status to the central nervous system. The sympathetic nervous system, via activation of ?-adrenoceptors (?-ARs), causes bladder relaxation and promotes urine storage. We hypothesized that ?-AR regulation of micturition is mediated by suppression of NMCs. We used an unanesthetized, decerebrate, artificially perfused rat preparation that allows simultaneous cystometry with external urethral sphincter and pelvic afferent nerve recordings. Systemic isoprenaline (10 nM to 1 µM) increased intervoid interval and bladder compliance accompanied by a decrease in NMC amplitude, voiding pressure, and voiding threshold. Isoprenaline also reduced arterial pressure and increased heart rate. The ?3-AR agonist mirabegron (10-100 nM) increased intervoid interval and bladder compliance and reduced NMC amplitude, yet preserved active voiding function and had no effect on arterial pressure or heart rate. All of these effects of mirabegron were blocked by the selective ?3-AR antagonist N-[[3-[(2S)-2-hydroxy-3-[[2-[4-[(phenylsulfonyl)amino] phenyl]ethyl]amino]propoxy]phenyl]methyl]-acetamide (L748,337), which alone shortened intervoid interval and decreased bladder compliance-suggesting the presence of a basal ?3-AR-mediated sympathetic tone. Similar effects of mirabegron were seen in an acetic acid-sensitized bladder preparation and in preparations after loss of spinobulbar reflex bladder control. The ?3-AR-mediated increase in intervoid interval correlated with increased bladder compliance but not with the decrease in NMC amplitude. These findings indicate that ?3-adrenoceptors have a selective effect that improves urine storage by increasing compliance without affecting the active components of voiding. PMID:24008334

Sadananda, Prajni; Drake, Marcus J; Paton, Julian F R; Pickering, Anthony E

2013-09-05

206

Dosage-Sensitive Function of RETINOBLASTOMA RELATED and Convergent Epigenetic Control Are Required during the Arabidopsis Life Cycle  

Microsoft Academic Search

The plant life cycle alternates between two distinct multi-cellular generations, the reduced gametophytes and the dominant sporophyte. Little is known about how generation-specific cell fate, differentiation, and development are controlled by the core regulators of the cell cycle. In Arabidopsis, RETINOBLASTOMA RELATED (RBR), an evolutionarily ancient cell cycle regulator, controls cell proliferation, differentiation, and regulation of a subset of Polycomb

Amal J. Johnston; Olga Kirioukhova; Philippa J. Barrell; Twan Rutten; James M. Moore; Ramamurthy Baskar; Ueli Grossniklaus; Wilhelm Gruissem

2010-01-01

207

Representing key phytoplankton functional groups in ocean carbon cycle models: Coccolithophorids  

NASA Astrophysics Data System (ADS)

Carbonates are the largest reservoirs of carbon on Earth. From mid-Mesozoic time, the biologically catalyzed precipitation of calcium carbonates by pelagic phytoplankton has been primarily due to the production of calcite by coccolithophorids. In this paper we address the physical and chemical processes that select for coccolithophorid blooms detected in Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color imagery. Our primary goal is to develop both diagnostic and prognostic models that represent the spatial and temporal dynamics of coccolithophorid blooms in order to improve our knowledge of the role of these organisms in mediating fluxes of carbon between the ocean, the atmosphere, and the lithosphere. On the basis of monthly composite images of classified coccolithophorid blooms and global climatological maps of physical variables and nutrient fields, we developed a probability density function that accounts for the physical chemical variables that predict the spatiotemporal distribution of coccolithophorids in the world oceans. Our analysis revealed that areas with sea surface temperatures (SST) between 3° and 15°C, a critical irradiance between 25 and 150 ?mol quanta m-2 s-1, and decreasing nitrate concentrations (?N/?t < 0) are selective for upper ocean large-scale coccolithophorid blooms. While these conditions favor both Northern and Southern Hemisphere blooms of the most abundant coccolithophorid in the modern oceans, Emiliania huxleyi, the Northern and Southern Hemisphere populations of this organism are genetically distinct. Applying amplified fragment length polymorphism as a marker of genetic diversity, we identified two major taxonomic clades of E. huxleyi; one is associated with the Northern Hemisphere blooms, while the other is found in the Southern Hemisphere. We suggest a rule of "universal distribution and local selection": that is, coccolithophorids can be considered cosmopolitan taxa, but their genetic plasticity provides physiological accommodation to local environmental selection pressure. Sea surface temperature, critical irradiance, and ?N/?t were predicted for the years 2060-2070 using the NCAR Community Climate System Model to generate future monthly probability distributions of coccolithophorids based upon the relationships observed between the environmental variables and coccolithophorid blooms in modern oceans. Our projected probability distribution analysis suggests that in the North Atlantic, the largest habitat for coccolithophorids on Earth, the areal extent of blooms will decrease by up to 50% by the middle of this century. We discuss how the magnitude of carbon fluxes may be affected by the evolutionary success of coccolithophorids in future climate scenarios.

Iglesias-RodríGuez, M. DéBora; Brown, Christopher W.; Doney, Scott C.; Kleypas, Joan; Kolber, Dorota; Kolber, Zbigniew; Hayes, Paul K.; Falkowski, Paul G.

2002-12-01

208

Tricarboxylic-acid-cycle intermediates and cycle endurance capacity.  

PubMed

The purpose of this study was to determine whether ingestion of a multinutrient supplement containing 3 tricarboxylic-acid-cycle intermediates (TCAIs; pyridoxine-alpha-ketoglutarate, malate, and succinate) and other substances potentially supporting the TCA cycle (such as aspartate and glutamate) would improve cyclists' time to exhaustion during a submaximal endurance-exercise test (approximately 70 % to 75 % VO2peak) and rate of recovery. Seven well-trained male cyclists (VO2max 67.4 2.1 mL x kg(-1) x in(-1), 28.6 +/- 2.4 y) participated in a randomized, double-blind crossover study for 7 wk. Each took either the treatment or a placebo 30 min before and after their normal training sessions for 3 wk and before submaximal exercise tests. There were no significant differences between the TCAI group (KI) and placebo group (P) in time to exhaustion during cycling (KI = 105 +/- 18, P = 113 +/- 11 min); respiratory-exchange ratio at 20-min intervals; blood lactate and plasma glucose before, after, and at 30-min intervals during exercise; perceived exertion at 20-min intervals during exercise; or time to fatigue after the 30-min recovery (KI = 16.1 +/- 3.2, P = 15 +/- 2 min). Taking a dietary sport supplement containing several TCAIs and supporting substances for 3 wk does not improve cycling performance at 75 % VO2peak or speed recovery from previously fatiguing exercise. PMID:15657476

Brown, Amy C; Macrae, Holden S H; Turner, Nathan S

2004-12-01

209

Selective 13C labeling of nucleotides for large RNA NMR spectroscopy using an E. coli strain disabled in the TCA cycle  

PubMed Central

Escherichia coli (E. coli) is an ideal organism to tailor-make labeled nucleotides for biophysical studies of RNA. Recently, we showed that adding labeled formate enhanced the isotopic enrichment at protonated carbon sites in nucleotides. In this paper, we show that growth of a mutant E. coli strain DL323 (lacking succinate and malate dehydrogenases) on 13C-2-glycerol and 13C-1,3-glycerol enables selective labeling at many useful sites for RNA NMR spectroscopy. For DL323 E. coli grown in 13C-2-glycerol without labeled formate, all the ribose carbon atoms are labeled except the C3? and C5? carbon positions. Consequently the C1?, C2? and C4? positions remain singlet. In addition, only the pyrimidine base C6 atoms are substantially labeled to ~96% whereas the C2 and C8 atoms of purine are labeled to ~5%. Supplementing the growth media with 13C-formate increases the labeling at C8 to ~88%, but not C2. Not unexpectedly, addition of exogenous formate is unnecessary for attaining the high enrichment levels of ~88% for the C2 and C8 purine positions in a 13C-1,3-glycerol based growth. Furthermore, the ribose ring is labeled in all but the C4? carbon position, such that the C2? and C3? positions suffer from multiplet splitting but the C5? position remains singlet and the C1? position shows a small amount of residual C1?–C2? coupling. As expected, all the protonated base atoms, except C6, are labeled to ~90%. In addition, labeling with 13C-1,3-glycerol affords an isolated methylene ribose with high enrichment at the C5? position (~90%) that makes it particularly attractive for NMR applications involving CH2-TROSY modules without the need for decoupling the C4? carbon. To simulate the tumbling of large RNA molecules, perdeuterated glycerol was added to a mixture of the four nucleotides, and the methylene TROSY experiment recorded at various temperatures. Even under conditions of slow tumbling, all the expected carbon correlations were observed, which indicates this approach of using nucleotides obtained from DL323 E. coli will be applicable to high molecular weight RNA systems.

Thakur, Chandar S.; Sama, Jacob N.; Jackson, Melantha E.; Chen, Bin

2010-01-01

210

Glutamate is the major anaplerotic substrate in the tricarboxylic acid cycle of isolated rumen epithelial and duodenal mucosal cells from beef cattle  

Technology Transfer Automated Retrieval System (TEKTRAN)

This study aimed to determine the contribution of substrates to tricarboxylic acid (TCA) cycle fluxes in rumen epithelial (REC) and duodenal mucosal (DMC) cells isolated from bulls (n = 6) fed either a 75% forage (HF) or 75% concentrate (HC) diet. In separate incubations, [13C6]glucose, [13C5]glutam...

211

Essential Dosage-Dependent Functions of the Transcription Factor Yin Yang 1 in Late Embryonic Development and Cell Cycle Progression†  

PubMed Central

Constitutive ablation of the Yin Yang 1 (YY1) transcription factor in mice results in peri-implantation lethality. In this study, we used homologous recombination to generate knockout mice carrying yy1 alleles expressing various amounts of YY1. Phenotypic analysis of yy1 mutant embryos expressing ?75%, ?50%, and ?25% of the normal complement of YY1 identified a dosage-dependent requirement for YY1 during late embryogenesis. Indeed, reduction of YY1 levels impairs embryonic growth and viability in a dose-dependent manner. Analysis of the corresponding mouse embryonic fibroblast cells also revealed a tight correlation between YY1 dosage and cell proliferation, with a complete ablation of YY1 inducing cytokinesis failure and cell cycle arrest. Consistently, RNA interference-mediated inhibition of YY1 in HeLa cells prevents cytokinesis, causes proliferative arrest, and increases cellular sensitivity to various apoptotic agents. Genome-wide expression profiling identified a plethora of YY1 target genes that have been implicated in cell growth, proliferation, cytokinesis, apoptosis, development, and differentiation, suggesting that YY1 coordinates multiple essential biological processes through a complex transcriptional network. These data not only shed new light on the molecular basis for YY1 developmental roles and cellular functions, but also provide insight into the general mechanisms controlling eukaryotic cell proliferation, apoptosis, and differentiation.

Affar, El Bachir; Gay, Frederique; Shi, Yujiang; Liu, Huifei; Huarte, Maite; Wu, Su; Collins, Tucker; Li, En; Shi, Yang

2006-01-01

212

The multimerization of human immunodeficiency virus type I Vif protein: a requirement for Vif function in the viral life cycle.  

PubMed

The Vif (virion infectivity factor protein of human immunodeficiency virus type I (HIV-1) is essential for viral replication in vivo and productive infection of peripheral blood mononuclear cells, macrophages, and H9 T-cells. However, the molecular mechanism(s) of Vif remains unknown and needs to be further determined. In this report, we show that, like many other proteins encoded by HIV-1, Vif proteins possess a strong tendency toward self-association. In relatively native conditions, Vif proteins formed multimers in vitro, including dimers, trimers, or tetramers. Through in vivo binding assays such as coimmunoprecipitation and the mammalian two-hybrid system, we also demonstrated that Vif proteins could interact with each other within a cell, indicating that the multimerization of Vif proteins is not simply due to fortuitous aggregation. Further studies indicated that the domain affecting Vif self-association is located at the C terminus of this protein, especially the proline-enriched 151-164 region. Moreover, we found that a Vif mutant with deletion at amino acid 151-164 was unable to rescue the infectivity of vif-defective viruses generated from H9 T-cells, suggesting that the multimerization of Vif proteins could be important for Vif function in the viral life cycle. Our studies identified a new feature of Vif and should accelerate our understanding of its role in HIV-1 pathogenesis. PMID:11071884

Yang, S; Sun, Y; Zhang, H

2000-11-08

213

The Cdk1-APC/C cell cycle oscillator circuit functions as a time-delayed, ultrasensitive switch  

PubMed Central

Despite the complexity and variety of biological oscillators, their core design invariably includes an essential negative feedback loop. In the Xenopus laevis embryonic cell cycle oscillator, this loop consists of the kinase cyclin B-Cdk1 and the ubiquitin ligase APC/CCdc20; active Cdk1 activates APC/CCdc20, which then brings about cyclin B degradation and inactivates Cdk1. Here we ask how this negative feedback loop functions quantitatively, with the aim of understanding what mechanisms keep the Cdk1-APC/CCdc20 system from settling into a stable steady state with intermediate levels of Cdk1 and APC/CCdc20 activity. We found that the system operates as a time-delayed, digital switch, with a time lag of ~15 min between Cdk1 and APC/CCdc20 activation and a tremendously high degree of ultrasensitivity (nH ? 17). Computational modeling shows how these attributes contribute to the generation of robust, clock-like oscillations. Principles uncovered here may also apply to other activator-repressor oscillators and help in designing robust synthetic clocks.

Yang, Qiong; Ferrell, James E.

2013-01-01

214

Rates of insulin secretion in INS-1 cells are enhanced by coupling to anaplerosis and Kreb's cycle flux independent of ATP synthesis  

PubMed Central

Mechanistic models of glucose stimulated insulin secretion (GSIS) established in minimal media in vitro, may not accurately describe the complexity of coupling metabolism with insulin secretion that occurs in vivo. As a first approximation, we have evaluated metabolic pathways in a typical growth media, DMEM as a surrogate in vivo medium, for comparison to metabolic fluxes observed under the typical experimental conditions using the simple salt-buffer of KRB. Changes in metabolism in response to glucose and amino acids and coupling to insulin secretion were measured in INS-1 832/13 cells. Media effects on mitochondrial function and the coupling efficiency of oxidative phosphorylation were determined by fluorometrically measured oxygen consumption rates (OCR) combined with 31P-NMR measured rates of ATP synthesis. Substrate preferences and pathways into the TCA cycle, and the synthesis of mitochondrial 2nd messengers by anaplerosis were determined by 13C-NMR isotopomer analysis of the fate of [U-13C]glucose metabolism. Despite similar incremental increases in insulin secretion, the changes of OCR in response to increasing glucose from 2.5 to 15 mM were blunted in DMEM relative to KRB. Basal and stimulated rates of insulin secretion rates were consistently higher in DMEM, while ATP synthesis rates were identical in both DMEM and KRB, suggesting greater mitochondrial uncoupling in DMEM. The relative rates of anaplerosis, and hence synthesis and export of 2nd messengers from the mitochondria were found to be similar in DMEM to those in KRB. And, the correlation of total PC flux with insulin secretion rates in DMEM was found to be congruous with the correlation in KRB. Together, these results suggest that signaling mechanisms associated with both TCA cycle flux and with anaplerotic flux, but not ATP production, may be responsible for the enhanced rates of insulin secretion in more complex, and physiologically-relevant media.

Cline, Gary W.; Pongratz, Rebecca L.; Zhao, Xiaojian; Papas, Klearchos K.

2011-01-01

215

Effect of Chronic Renal Failure on Cardiac Contractile Function, Calcium Cycling, and Gene Expression of Proteins Important for Calcium Homeostasis in the Rat  

Microsoft Academic Search

Patients with chronic renal failure frequently develop cardiac hypertrophy and diastolic dysfunction; however, the mechanisms by which this occurs are still unclear. Male Sprague-Dawley rats were subjected to 5\\/6 nephrectomy and studied for their isolated myocyte function, calcium cycling, and gene expression of proteins important in calcium ho- meostasis after 4 wk. Comparable rats subjected to suprarenal aortic banding for

DAVID KENNEDY; EIAD OMRAN; SANKARIDRUG M. PERIYASAMY; JAMES C. WILLEY; DEEPAK MALHOTRA; ZIJIAN XIE; JOSEPH I. SHAPIRO

2003-01-01

216

Color-coded measures of myocardial velocity throughout the cardiac cycle by tissue Doppler imaging to quantify regional left ventricular function  

Microsoft Academic Search

TDI is a new echocardiographic technique that calculates and displays color-coded myocardial velocity on-line. To determine the feasibility of endocardial velocity throughout the cardiac cycle as a means to quantify regional function, 20 normal subjects aged 30 ± 5 years and 12 patients with heart disease aged 62 ± 17 years were studied with a prototype TDI system. TDI M-mode

John Gorcsan; Vijay K. Gulati; William A. Mandarino; William E. Katz

1996-01-01

217

A weight function-critical plane approach for low-cycle fatigue under variable amplitude multiaxial loading  

Microsoft Academic Search

Low-cycle fatigue data of type 304 stainless steel obtained under axial-torsional loading of variable amplitudes are analyzed using four multiaxial fatigue parameters: SWT, KBM, FS and LKN. Rainflow cycle counting and Morrow's plastic work interaction rule are used to calculate fatigue damage. The performance of a fatigue model is dependent on the fatigue parameter, the critical plane and the damage

X. C HEN; D. J IN; K. S. KIM

2006-01-01

218

Analysis of altered gait cycle duration in amyotrophic lateral sclerosis based on nonparametric probability density function estimation.  

PubMed

Human locomotion is regulated by the central nervous system (CNS). The neurophysiological changes in the CNS due to amyotrophic lateral sclerosis (ALS) may cause altered gait cycle duration (stride interval) or other gait rhythm. This article used a statistical method to analyze the altered stride interval in patients with ALS. We first estimated the probability density functions (PDFs) of stride interval from the outlier-processed gait rhythm time series, by using the nonparametric Parzen-window approach. Based on the PDFs estimated, the mean of the left-foot stride interval and the modified Kullback-Leibler divergence (MKLD) can be computed to serve as dominant features. In the classification experiments, the least squares support vector machine (LS-SVM) with Gaussian kernels was applied to distinguish the stride patterns in ALS patients. According to the results obtained with the stride interval time series recorded from 16 healthy control subjects and 13 patients with ALS, the key findings of the present study are summarized as follows. (1) It is observed that the mean of stride interval computed based on the PDF for the left foot is correlated with that for the right foot in patients with ALS. (2) The MKLD parameter of the gait in ALS is significantly different from that in healthy controls. (3) The diagnostic performance of the nonlinear LS-SVM, evaluated by the leave-one-out cross-validation method, is superior to that obtained by the linear discriminant analysis. The LS-SVM can effectively separate the stride patterns between the groups of healthy controls and ALS patients with an overall accurate rate of 82.8% and an area of 0.869 under the receiver operating characteristic curve. PMID:21130016

Wu, Yunfeng; Shi, Lei

2010-12-03

219

Mad2 Haploinsufficiency Protects Hematopoietic Progenitor Cells Subjected to Cell Cycle Stress In Vivo and to Inhibition of Redox Function of Ape1/Ref-1 In Vitro  

PubMed Central

Objective Cell cycle checkpoints guarantee movement through the cell cycle. Mitotic arrest deficiency 2 (Mad2), a mitotic checkpoint protein, appears crucial for generating the wait anaphase signal to prevent onset of anaphase. We evaluated effects of Mad2 haploinsufficiency on hematopoietic stem (HSC) and progenitor (HPC) function in response to stress. Materials and Methods We studied effects of Mad2+/? on in vivo recovery of bone marrow HPC from cytotoxic effects and also effects of cytostatic agents on HPC growth in vitro using Mad2+/? mice. Results Mad2+/? HPCs were protected from cytotoxic effects in vivo of a cell cycle specific agent, Ara-C, events consistent with Mad2+/? HPCs being in a slow or noncycling state, but not from recovery of functional HPC after treatment with non-cycle specific cyclophosphamide or sub-lethal irradiation. There were no differences in phenotyped HSCs in Mad2+/? & Mad2+/+ mice, information confirmed by no changes in short or long term repopulating HSC assay. To better understand Mad2+/? HPC function, E3330, a cytostatic agent, was used to assess redox function of Ape1/Ref-1; colony growth was examined under 5% and 20% O2 tension. Mad2+/? HPCs were less responsive to E3330 than Mad2+/+ HPCs, and E3330 was more effective under lowered O2 tension. Mad2+/? HPCs were not enhanced at lowered oxygen, as were Mad2+/+ HPCs. Conclusions Our studies have unexpectedly found that Mad2 haploinsufficiency is protective in the presence of a cycle specific DNA synthesis agent in vivo, and Ape1/Ref-1 inhibitor in vitro.

Rohrabaugh, Sara L.; Hangoc, Giao; Kelley, Mark R.; Broxmeyer, Hal E.

2011-01-01

220

Analysis of effects of an objective function on environmental and economic performance of a water network system using life cycle assessment and life cycle costing methods  

Microsoft Academic Search

Water network synthesis has been used to conserve water resources and reduce economic costs. In this study, all contributors to environmental burdens and economic costs of water network systems were estimated to analyze the effects of objective functions on their environmental and economic performances. A total freshwater flowrate-minimized water network system (FWNS) and a total freshwater cost-minimized water network system

Seong-Rin Lim; Donghee Park; Jong Moon Park

2008-01-01

221

Coulometric bioelectrocatalytic reactions based on NAD-dependent dehydrogenases in tricarboxylic acid cycle  

Microsoft Academic Search

This paper describes the characterization of mediated electro-enzymatic electrolysis systems based on NAD-dependent dehydrogenase reactions in the tricarboxylic acid (TCA) cycle. A micro-bulk electrolysis system with a carbon felt anode immersed in an electrolysis solution with a value of about 10?L was constructed for coulometric analysis of the substrate oxidation. Diaphorase (DI) was used to couple the NAD-dependent dehydrogenase reaction

Jun Fukuda; Seiya Tsujimura; Kenji Kano

2008-01-01

222

Perturbation of Cell Cycle Progression and Cellular Gene Expression as a Function of Herpes Simplex Virus ICP0  

Microsoft Academic Search

Herpes simplex virus type 1 is capable of inhibiting host cell DNA synthesis following lytic infection. However, the mechanism and nature of potential effects on cell cycle progression have not been described. In this report, we characterize the dysregulation of the cell cycle following infection with the replication-incom- petent virus d106, where immediate-early gene expression is restricted to infected-cell polypeptide

WILLIAM E. HOBBS; NEAL A. DELUCA

1999-01-01

223

The tRNA-modifying function of MnmE is controlled by post-hydrolysis steps of its GTPase cycle  

PubMed Central

MnmE is a homodimeric multi-domain GTPase involved in tRNA modification. This protein differs from Ras-like GTPases in its low affinity for guanine nucleotides and mechanism of activation, which occurs by a cis, nucleotide- and potassium-dependent dimerization of its G-domains. Moreover, MnmE requires GTP hydrolysis to be functionally active. However, how GTP hydrolysis drives tRNA modification and how the MnmE GTPase cycle is regulated remains unresolved. Here, the kinetics of the MnmE GTPase cycle was studied under single-turnover conditions using stopped- and quench-flow techniques. We found that the G-domain dissociation is the rate-limiting step of the overall reaction. Mutational analysis and fast kinetics assays revealed that GTP hydrolysis, G-domain dissociation and Pi release can be uncoupled and that G-domain dissociation is directly responsible for the ‘ON’ state of MnmE. Thus, MnmE provides a new paradigm of how the ON/OFF cycling of GTPases may regulate a cellular process. We also demonstrate that the MnmE GTPase cycle is negatively controlled by the reaction products GDP and Pi. This feedback mechanism may prevent inefficacious GTP hydrolysis in vivo. We propose a biological model whereby a conformational change triggered by tRNA binding is required to remove product inhibition and initiate a new GTPase/tRNA-modification cycle.

Prado, Silvia; Villarroya, Magda; Medina, Milagros; Armengod, M.-Eugenia

2013-01-01

224

13C NMR isotopomer analysis reveals a connection between pyruvate cycling and glucose-stimulated insulin secretion (GSIS).  

PubMed

Cellular metabolism of glucose is required for stimulation of insulin secretion from pancreatic beta cells, but the precise metabolic coupling factors involved in this process are not known. In an effort to better understand mechanisms of fuel-mediated insulin secretion, we have adapted 13C NMR and isotopomer methods to measure influx of metabolic fuels into the tricarboxylic acid (TCA) cycle in insulinoma cells. Mitochondrial metabolism of [U-13C3]pyruvate, derived from [U-13C6]glucose, was compared in four clonal rat insulinoma cell 1-derived cell lines with varying degrees of glucose responsiveness. A 13C isotopomer analysis of glutamate isolated from these cells showed that the fraction of acetyl-CoA derived from [U-13C6]glucose was the same in all four cell lines (44 +/- 5%, 70 +/- 3%, and 84 +/- 4% with 3, 6, or 12 mM glucose, respectively). The 13C NMR spectra also demonstrated the existence of two compartmental pools of pyruvate, one that exchanges with TCA cycle intermediates and a second pool derived from [U-13C6]glucose that feeds acetyl-CoA into the TCA cycle. The 13C NMR spectra were consistent with a metabolic model where the two pyruvate pools do not randomly mix. Flux between the mitochondrial intermediates and the first pool of pyruvate (pyruvate cycling) varied in proportion to glucose responsiveness in the four cell lines. Furthermore, stimulation of pyruvate cycling with dimethylmalate or its inhibition with phenylacetic acid led to proportional changes in insulin secretion. These findings indicate that exchange of pyruvate with TCA cycle intermediates, rather than oxidation of pyruvate via acetyl-CoA, correlates with glucose-stimulated insulin secretion. PMID:11880625

Lu, Danhong; Mulder, Hindrik; Zhao, Piyu; Burgess, Shawn C; Jensen, Mette V; Kamzolova, Svetlana; Newgard, Christopher B; Sherry, A Dean

2002-03-01

225

Radiolabelled proteomics to determine differential functioning of Accumulibacter during the anaerobic and aerobic phases of a bioreactor operating for enhanced biological phosphorus removal.  

PubMed

Proteins synthesized by the mixed microbial community of two sequencing batch reactors run for enhanced biological phosphorus removal (EBPR) during aerobic and anaerobic reactor phases were compared, using mass spectrometry-based proteomics and radiolabelling. Both sludges were dominated by polyphosphate-accumulating organisms belonging to Candidatis Accumulibacter and the majority of proteins identified matched closest to these bacteria. Enzymes from the Embden-Meyerhof-Parnas pathway were identified, suggesting this is the major glycolytic pathway for these Accumulibacter populations. Enhanced aerobic synthesis of glyoxylate cycle enzymes suggests this cycle is important during the aerobic phase of EBPR. In one sludge, several TCA cycle enzymes showed enhanced aerobic synthesis, suggesting this cycle is unimportant anaerobically. The second sludge showed enhanced synthesis of TCA cycle enzymes under anaerobic conditions, suggesting full or partial TCA cycle operation anaerobically. A phylogenetic analysis of Accumulibacter polyphosphate kinase genes from each sludge demonstrated different Accumulibacter populations dominated the two sludges. Thus, TCA cycle activity differences may be due to Accumulibacter strain differences. The major fatty acids present in Accumulibacter-dominated sludge include palmitic, hexadecenoic and cis-vaccenic acid and fatty acid content increased by approximately 20% during the anaerobic phase. We hypothesize that this is associated with increased anaerobic phospholipid membrane biosynthesis, to accommodate intracellular polyhydroxyalkanoate granules. PMID:19650829

Wexler, Margaret; Richardson, David J; Bond, Philip L

2009-07-24

226

The ethylmalonyl-CoA pathway is used in place of the glyoxylate cycle by Methylobacterium extorquens AM1 during growth on acetate.  

PubMed

Acetyl-CoA assimilation was extensively studied in organisms harboring the glyoxylate cycle. In this study, we analyzed the metabolism of the facultative methylotroph Methylobacterium extorquens AM1, which lacks isocitrate lyase, the key enzyme in the glyoxylate cycle, during growth on acetate. MS/MS-based proteomic analysis revealed that the protein repertoire of M. extorquens AM1 grown on acetate is similar to that of cells grown on methanol and includes enzymes of the ethylmalonyl-CoA (EMC) pathway that were recently shown to operate during growth on methanol. Dynamic 13C labeling experiments indicate the presence of distinct entry points for acetate: the EMC pathway and the TCA cycle. 13C steady-state metabolic flux analysis showed that oxidation of acetyl-CoA occurs predominantly via the TCA cycle and that assimilation occurs via the EMC pathway. Furthermore, acetyl-CoA condenses with the EMC pathway product glyoxylate, resulting in malate formation. The latter, also formed by the TCA cycle, is converted to phosphoglycerate by a reaction sequence that is reversed with respect to the serine cycle. Thus, the results obtained in this study reveal the utilization of common pathways during the growth of M. extorquens AM1 on C1 and C2 compounds, but with a major redirection of flux within the central metabolism. Furthermore, our results indicate that the metabolic flux distribution is highly complex in this model methylotroph during growth on acetate and is fundamentally different from organisms using the glyoxylate cycle. PMID:22105076

Schneider, Kathrin; Peyraud, Rémi; Kiefer, Patrick; Christen, Philipp; Delmotte, Nathanaël; Massou, Stéphane; Portais, Jean-Charles; Vorholt, Julia A

2011-11-21

227

C1 metabolism and the Calvin cycle function simultaneously and independently during HCHO metabolism and detoxification in Arabidopsis thaliana treated with HCHO solutions.  

PubMed

Formaldehyde (HCHO) is suggested to be detoxified through one-carbon (C1) metabolism or assimilated by the Calvin cycle in plants. To further understand the function of the Calvin cycle and C1 metabolism in HCHO metabolism in plants, HCHO elimination and metabolism by Arabidopsis thaliana in HCHO solutions was investigated in this study. Results verified that Arabidopsis could completely eliminate aqueous HCHO from the HCHO solutions. Carbon-13 nuclear magnetic resonance ((13)C-NMR) analysis showed that H(13)CHO absorbed by Arabidopsis was first oxidized to H(13)COOH. Subsequently, a clear increase in [U-(13)C]Gluc peaks accompanied by a strong enhancement in peaks of [2-(13)C]Ser and [3-(13)C]Ser appeared in Arabidopsis. Pretreatment with cyclosporin A or L-carnitine, which might inhibit the transport of (13)C-enriched compounds into chloroplasts and mitochondria, caused a remarkable decline in yields of both [U-(13)C]Gluc and [3-(13)C]Ser in H(13)CHO-treated Arabidopsis. These results suggested that both the Calvin cycle and the C1 metabolism functioned simultaneously during HCHO detoxification. Moreover, both functioned more quickly under high H(13)CHO stress than low H(13)CHO stress. When a photorespiration mutant was treated in 6 mm H(13)CHO solution, formation of [U-(13)C]Gluc and [2-(13)C]Ser was completely inhibited, but generation of [3-(13)C]Ser was not significantly affected. This evidence suggested that the Calvin cycle and C1 metabolism functioned independently in Arabidopsis during HCHO metabolism. PMID:23421623

Song, Zhong-Bang; Xiao, Su-Qin; You, Lan; Wang, Sha-Sha; Tan, Hao; Li, Kun-Zhi; Chen, Li-Mei

2013-03-25

228

Effect of glycerol-induced hyperhydration on thermoregulatory and cardiovascular functions and endurance performance during prolonged cycling in a 25°C environment  

Microsoft Academic Search

We compared the effect of glycerol-induced hyperhydration (GIH) to that of water-induced hyperhydration (WIH) on cardiovascular and thermoregulatory functions and endurance performance (EP) during prolonged cycling in a temperate climate in subjects consuming fluid during exercise. At weekly intervals, 6 trained male subjects ingested, in a randomized, double-blind, counterbalanced fashion, either a glycerol (1.2 g glycerol\\/kg bodyweight (BW) with 26

Eric D. B. Goulet; Robert A. Robergs; Susan Labrecque; Donald Royer; Isabelle J. Dionne

2006-01-01

229

Pre-B cell receptor-mediated cell cycle arrest in Philadelphia chromosome-positive acute lymphoblastic leukemia requires IKAROS function  

PubMed Central

B cell lineage acute lymphoblastic leukemia (ALL) arises in virtually all cases from B cell precursors that are arrested at pre–B cell receptor–dependent stages. The Philadelphia chromosome–positive (Ph+) subtype of ALL accounts for 25–30% of cases of adult ALL, has the most unfavorable clinical outcome among all ALL subtypes and is defined by the oncogenic BCR-ABL1 kinase and deletions of the IKAROS gene in >80% of cases. Here, we demonstrate that the pre–B cell receptor functions as a tumor suppressor upstream of IKAROS through induction of cell cycle arrest in Ph+ ALL cells. Pre–B cell receptor–mediated cell cycle arrest in Ph+ ALL cells critically depends on IKAROS function, and is reversed by coexpression of the dominant-negative IKAROS splice variant IK6. IKAROS also promotes tumor suppression through cooperation with downstream molecules of the pre–B cell receptor signaling pathway, even if expression of the pre–B cell receptor itself is compromised. In this case, IKAROS redirects oncogenic BCR-ABL1 tyrosine kinase signaling from SRC kinase-activation to SLP65, which functions as a critical tumor suppressor downstream of the pre–B cell receptor. These findings provide a rationale for the surprisingly high frequency of IKAROS deletions in Ph+ ALL and identify IKAROS-mediated cell cycle exit as the endpoint of an emerging pathway of pre–B cell receptor–mediated tumor suppression.

Trageser, Daniel; Iacobucci, Ilaria; Nahar, Rahul; Duy, Cihangir; von Levetzow, Gregor; Klemm, Lars; Park, Eugene; Schuh, Wolfgang; Gruber, Tanja; Herzog, Sebastian; Kim, Yong-mi; Hofmann, Wolf-Karsten; Li, Aihong; Storlazzi, Clelia Tiziana; Jack, Hans-Martin; Groffen, John; Martinelli, Giovanni; Heisterkamp, Nora; Jumaa, Hassan

2009-01-01

230

Use of response surface methodology in a fed-batch process for optimization of tricarboxylic acid cycle intermediates to achieve high levels of canthaxanthin from Dietzia natronolimnaea HS-1.  

PubMed

In this work, we applied statistical experimental design to a fed-batch process for optimization of tricarboxylic acid cycle (TCA) intermediates in order to achieve high-level production of canthaxanthin from Dietzia natronolimnaea HS-1 cultured in beet molasses. A fractional factorial design (screening test) was first conducted on five TCA cycle intermediates. Out of the five TCA cycle intermediates investigated via screening tests, alfaketoglutarate, oxaloacetate and succinate were selected based on their statistically significant (P<0.05) and positive effects on canthaxanthin production. These significant factors were optimized by means of response surface methodology (RSM) in order to achieve high-level production of canthaxanthin. The experimental results of the RSM were fitted with a second-order polynomial equation by means of a multiple regression technique to identify the relationship between canthaxanthin production and the three TCA cycle intermediates. By means of this statistical design under a fed-batch process, the optimum conditions required to achieve the highest level of canthaxanthin (13172 + or - 25 microg l(-1)) were determined as follows: alfaketoglutarate, 9.69 mM; oxaloacetate, 8.68 mM; succinate, 8.51 mM. PMID:20226378

Nasri Nasrabadi, Mohammad Reza; Razavi, Seyed Hadi

2009-11-08

231

Response to Functional Electrical Stimulation Cycling in Women With Spinal Cord Injuries Using Dual-Energy X-ray Absorptiometry and Peripheral Quantitative Computed Tomography: A Case Series  

PubMed Central

Background: Loss of bone mass is common after spinal cord injury (SCI). One rehabilitation modality that has shown some promise for maintaining bone health is the functional electrical stimulation (FES) cycle ergometer. Although there has been some research investigating bone health and FES cycle ergometry, few have provided a detailed description of the changes that can occur in bone mass and soft-tissue mass. Objective: To use 2 types of bone imaging, peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA), to provide a detailed description of bone and soft-tissue response to FES cycle ergometry training in women with SCI. Study Design: Case series; a 6-month program of FES cycle ergometry for women with chronic motor complete (n ?=? 2) and incomplete (n ?=? 1) SCI. Setting: Outpatient rehabilitation center in Canada. Methods: Three women participated in a thrice weekly 6-month exercise program of FES cycle ergometry. We used DXA (lower extremity) and pQCT at the midshaft (50%) and distal (5%) sites of the tibia to assess bone density and soft-tissue mass before and after the exercise program. Results: There was an increase or maintenance in bone mineral density by DXA and pQCT in the lower extremity for all 3 participants. Muscle mass by DXA increased in the lower extremity in 2 participants. Conclusion: In this case series, we note a positive response in bone mass and soft-tissue mass in the lower extremity after a 6-month FES cycle ergometry program.

Ashe, Maureen C; Eng, Janice J; Krassioukov, Andrei V; Warburton, Darren E.R; Hung, Chihya; Tawashy, Amira

2010-01-01

232

Cassia tora L. (Jue-ming-zi) has anticancer activity in TCA8113 cells in vitro and exerts anti-metastatic effects in vivo  

PubMed Central

Cassia tora L. (Jue-ming-zi) is a traditional Chinese medicine widely used in East Asia. The in vitro anticancer effects of Jue-ming-zi were evaluated in TCA8113 human tongue carcinoma cells using a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay. At a concentration of 1.0 mg/ml, Cassia tora L. inhibited the growth of TCA8113 cells by 72%; this inhibiton was greater than that by 0.5 and 0.25 mg/ml Cassia tora L. (43 and 16%, respectively). To elucidate the inhibitory mechanisms underlying the anticancer effect of Cassia tora L. in cancer cells, the expression of genes associated with apoptosis, inflammation and metastasis were measured using RT-PCR and western blot analysis. Cassia tora L. significantly induced apoptosis in cancer cells (P<0.05) by upregulating Bax, caspase-3 and caspase-9, and by downregulating Bcl-2. The expression of genes associated with inflammation, including NF-?B, iNOS and COX-2, was significantly downregulated (P<0.05) by Cassia tora L., demonstrating its anti-inflammatory properties. Cassia tora L. also exerted a significant anti-metastatic effect on cancer cells as demonstrated by decreased mRNA expression of matrix metalloprotease (MMP) genes and increased expression of tissue inhibitors of metalloproteinases (TIMPs), and as confirmed by the inhibition of induced tumor metastasis induced in 26-M3.1 colon cells in BALB/c mice. Our results demonstrated that Cassia tora L. exhibited the most potent in vitro anticancer effects, induced apoptosis, had anti-inflammatory activities and exerted in vivo anti-metastatic effects. Additionally, the anticancer, anti-inflammatory and anti-metastatic effects of the higher Cassia tora L. concentrations were stronger compared with those of the lower Cassia tora L. concentrations tested.

ZHAO, XIN; WANG, QIANG; QIAN, YU; PANG, LIANG

2013-01-01

233

Responses of Antarctic soil microbial communities and associated functions to temperature and freeze-thaw cycle frequency  

Microsoft Academic Search

Climatic changes will not only result in higher overall temperature, but also in greater variability in weather conditions. Antarctic soils are subjected to extremely variable conditions in the form of frequent freeze–thaw cycles (FTCs), but the importance of alteration in FTC frequency, compared with increases in average temperature and indirect vegetation-mediated effects on soil microorganisms, is still unknown. We therefore

Etienne Yergeau; George A. Kowalchuk

2008-01-01

234

Krebs Cycle Function is Required for Activation of the SpoOA Transcription Factor in Bacillus subtilis  

Microsoft Academic Search

Expression of genes early during sporulation in Bacillus subtilis requires the activity of the transcription factor encoded by spo0A. The active, phosphorylated form of Spo0A is produced through the action of a multicomponent pathway, the phosphorelay. A mutant defective in the first three enzymes of the Krebs citric acid cycle was unable to express early sporulation genes, apparently because of

Keith Ireton; Shengfang Jin; Alan D. Grossman; Abraham L. Sonenshein

1995-01-01

235

Surveillance of Salmonella populations, prevalence and serotype diversity in layer feces as a function of production cycle and molting  

Microsoft Academic Search

Salmonella species are recognized as a major cause of foodborne illnesses that are closely associated with the consumption of contaminated poultry and egg products. The objective of this study was to determine whether the hen's laying cycle and the practice of reduced caloric intake molting influenced the prevalence and populations of Salmonella in layer feces and to evaluate the serotype

B. W. SHELDON; X. LI; J. B. PAYNE; F. B. O. SANTOS; K. E. ANDERSON

236

Geodetic data inversion using ABIC to estimate slip history during one earthquake cycle with viscoelastic slip-response functions  

Microsoft Academic Search

We developed a new method of geodetic data inversion to estimate slip history at a plate interface by using Akaike's Bayesian Information Criterion (ABIC). In this method we considered the effects of viscoelastic stress relaxation in the asthenosphere, which cannot be neglected to estimate slip history at a plate interface during one earthquake cycle. We also introduced a proper formulation

Yukitoshi Fukahata; Akira Nishitani; Mitsuhiro Matsu'ura

2004-01-01

237

Predicting VO[subscript 2max] in College-Aged Participants Using Cycle Ergometry and Perceived Functional Ability  

ERIC Educational Resources Information Center

|The purpose of this study was to develop a multiple linear regression model to predict treadmill VO[subscript 2max] scores using both exercise and non-exercise data. One hundred five college-aged participants (53 male, 52 female) successfully completed a submaximal cycle ergometer test and a maximal graded exercise test on a motorized treadmill.…

Nielson, David E.; George, James D.; Vehrs, Pat R.; Hager, Ron L.; Webb, Carrie V.

2010-01-01

238

Multiple limit cycles in a Gause type predator-prey model with Holling type III functional response and Allee effect on prey.  

PubMed

This work aims to examine the global behavior of a Gause type predator-prey model considering two aspects: (i) the functional response is Holling type III and, (ii) the prey growth is affected by the Allee effect. We prove the origin of the system is an attractor equilibrium point for all parameter values. It has also been shown that it is the ?-limit of a wide set of trajectories of the system, due to the existence of a separatrix curve determined by the stable manifold of the equilibrium point (m,0), which is associated to the Allee effect on prey. When a weak Allee effect on the prey is assumed, an important result is obtained, involving the existence of two limit cycles surrounding a unique positive equilibrium point: the innermost cycle is unstable and the outermost stable. This property, not yet reported in models considering a sigmoid functional response, is an important aspect for ecologists to acknowledge as regards the kind of tristability shown here: (1) the origin; (2) an interior equilibrium; and (3) a limit cycle of large amplitude. These models have undoubtedly been rather sensitive to disturbances and require careful management in applied conservation and renewable resource contexts. PMID:20830610

González-Olivares, Eduardo; Rojas-Palma, Alejandro

2010-09-10

239

Uniqueness of limit cycles and multiple attractors in a Gause-type predator-prey model with nonmonotonic functional response and Allee effect on prey.  

PubMed

The main purpose of this work is to analyze a Gause type predator-prey model in which two ecological phenomena are considered: the Allee effect affecting the prey growth function and the formation of group defence by prey in order to avoid the predation. We prove the existence of a separatrix curves in the phase plane, determined by the stable manifold of the equilibrium point associated to the Allee effect, implying that the solutions are highly sensitive to the initial conditions. Trajectories starting at one side of this separatrix curve have the equilibrium point (0,0) as their ?-limit, while trajectories starting at the other side will approach to one of the following three attractors: a stable limit cycle, a stable coexistence point or the stable equilibrium point (K,0) in which the predators disappear and prey attains their carrying capacity. We obtain conditions on the parameter values for the existence of one or two positive hyperbolic equilibrium points and the existence of a limit cycle surrounding one of them. Both ecological processes under study, namely the nonmonotonic functional response and the Allee effect on prey, exert a strong influence on the system dynamics, resulting in multiple domains of attraction. Using Liapunov quantities we demonstrate the uniqueness of limit cycle, which constitutes one of the main differences with the model where the Allee effect is not considered. Computer simulations are also given in support of the conclusions. PMID:23458304

González-Olivares, Eduardo; González-Yańez, Betsabé; Mena-Lorca, Jaime; Flores, Jose D

2013-04-01

240

The Arabidopsis thaliana Homolog of Yeast BRE1 Has a Function in Cell Cycle Regulation during Early Leaf and Root Growth[W][OA  

PubMed Central

Chromatin modification and transcriptional activation are novel roles for E3 ubiquitin ligase proteins that have been mainly associated with ubiquitin-dependent proteolysis. We identified HISTONE MONOUBIQUITINATION1 (HUB1) (and its homolog HUB2) in Arabidopsis thaliana as RING E3 ligase proteins with a function in organ growth. We show that HUB1 is a functional homolog of the human and yeast BRE1 proteins because it monoubiquitinated histone H2B in an in vitro assay. Hub knockdown mutants had pale leaf coloration, modified leaf shape, reduced rosette biomass, and inhibited primary root growth. One of the alleles had been designated previously as ang4-1. Kinematic analysis of leaf and root growth together with flow cytometry revealed defects in cell cycle activities. The hub1-1 (ang4-1) mutation increased cell cycle duration in young leaves and caused an early entry into the endocycles. Transcript profiling of shoot apical tissues of hub1-1 (ang4-1) indicated that key regulators of the G2-to-M transition were misexpressed. Based on the mutant characterization, we postulate that HUB1 mediates gene activation and cell cycle regulation probably through chromatin modifications.

Fleury, Delphine; Himanen, Kristiina; Cnops, Gerda; Nelissen, Hilde; Boccardi, Tommaso Matteo; Maere, Steven; Beemster, Gerrit T.S.; Neyt, Pia; Anami, Sylvester; Robles, Pedro; Micol, Jose Luis; Inze, Dirk; Van Lijsebettens, Mieke

2007-01-01

241

Animation of the Dynamical Events of the Elongation Cycle Based on Cryoelectron Microscopy of Functional Complexes of the Ribosome  

Microsoft Academic Search

Using three-dimensional cryoelectron microscopy, the binding positions of tRNA and elongation factors EF-G and EF-Tu (the latter complexed with aminoacyl tRNA and GTP) on the ribosome were determined in previous studies. On the basis of these studies, the dynamical events that take place in the course of the elongation cycle of protein synthesis have been animated. The resulting 3-min movie

Joachim Frank; Amy B Heagle; Rajendra K Agrawal

1999-01-01

242

Cycle and function-related changes in lectin binding to human endometrium: a histochemical study with pronase treatment  

Microsoft Academic Search

Forty-eight endometrial biopsy specimens were obtained during a normal menstrual cycle, during pregnancy and from patients with dysfunctional bleeding. The specimens were examined for Peanut (PNA), Soybean (SBA), Vicia villosa (VVA), Phytohem-(PHA), Lens culinaris (LCA) and Concanavalin (succ. Con A) agglutinin binding. The study was performed on paraffin sections using the pronase digestion and either the peroxidase-antiperoxidase or the avidin-biotin-peroxidase

J. Kupryjaficzyk

1989-01-01

243

Cycle inhibiting factors (CIFs) are a growing family of functional cyclomodulins present in invertebrate and mammal bacterial pathogens.  

PubMed

The cycle inhibiting factor (Cif) produced by enteropathogenic and enterohemorrhagic Escherichia coli was the first cyclomodulin to be identified that is injected into host cells via the type III secretion machinery. Cif provokes cytopathic effects characterized by G(1) and G(2) cell cycle arrests, accumulation of the cyclin-dependent kinase inhibitors (CKIs) p21(waf1/cip1) and p27(kip1) and formation of actin stress fibres. The X-ray crystal structure of Cif revealed it to be a divergent member of a superfamily of enzymes including cysteine proteases and acetyltransferases that share a conserved catalytic triad. Here we report the discovery and characterization of four Cif homologs encoded by different pathogenic or symbiotic bacteria isolated from vertebrates or invertebrates. Cif homologs from the enterobacteria Yersinia pseudotuberculosis, Photorhabdus luminescens, Photorhabdus asymbiotica and the beta-proteobacterium Burkholderia pseudomallei all induce cytopathic effects identical to those observed with Cif from pathogenic E. coli. Although these Cif homologs are remarkably divergent in primary sequence, the catalytic triad is strictly conserved and was shown to be crucial for cell cycle arrest, cytoskeleton reorganization and CKIs accumulation. These results reveal that Cif proteins form a growing family of cyclomodulins in bacteria that interact with very distinct hosts including insects, nematodes and humans. PMID:19308257

Jubelin, Grégory; Chavez, Carolina Varela; Taieb, Frédéric; Banfield, Mark J; Samba-Louaka, Ascel; Nobe, Rika; Nougayrčde, Jean-Philippe; Zumbihl, Robert; Givaudan, Alain; Escoubas, Jean-Michel; Oswald, Eric

2009-03-24

244

Carbon and nitrogen cycling in thermally heated sediments  

NASA Astrophysics Data System (ADS)

Hydrothermally heated sediment environments, such as are found in abundance throughout Yellowstone National Park, host fully functional microbial ecosystems. As with any ecosystem, both sources and sinks of carbon, nitrogen, and a myriad of other nutrients and energy-driving factors must be supplied. While we know microbial communities in hydrothermal environments can be surprisingly diverse, we know little about basic ecological functions such as carbon and nitrogen cycling. Previous work has shown that carbon cycling in one hot spring in Yellowstone National Park [“Bison Pool”] and its associated runoff channel functions as a complex system. Analysis of carbon and nitrogen isotopes in sediments and biofilms across a temperature and chemical gradient at this location revealed that the four best studied carbon fixation pathways [Calvin, reverse tricarboxylic acid, acetyl-CoA, 3-hydroxypropionate cycles] may all be functioning in this system, and nitrogen fixation varies across the chemosynthetic/photosynthetic ecotone [1]. Microcosm experiments using biofilms from this hot spring as inoculae with 13C labeled carbon substrates indicate heterotrophic growth [2]. In addition, metagenomic analysis of environmental DNA has indicated the presence of genes involved in carbon fixation [both phototrophic and autotrophic], and heterotrophy, as well as nitrogen fixation [3]. Studies from other Yellowstone locations have also found genetic evidence for carbon and nitrogen fixation [4, 5]. Of particular interest is the role of individuals in carbon and nitrogen cycling as environmental conditions suitable for chemosynthetic and photosynthetic growth vary. This study explores the diversity of cbbM/cbbL [Calvin cycle], aclB/oor/porA [rTCA cycle], nifH [nitrogen fixation], nirK [nitrite reduction] and amoA [ammonia oxidation] genes across a variety of Yellowstone environments. The transition of genetic diversity within sediments and biofilms is focused on the chemosynthetic/photosynthetic ecotone from a variety of hot springs spanning a range of pH and geochemical conditions. By sampling across this ecotone, changes in carbon and nitrogen fixation as a function of changing community structure become apparent. Environmental DNA was extracted from these samples, and the presence/absence of Bacteria and Archaea determined by PCR. In addition, PCR-directed screens reveal the presence or absence of the aforementioned functional genes. Further, comparison across a broad spectrum of environmental conditions supplies context for phylogenetic analysis of diversity. [1] Havig, J.R., 2009. Geochemistry of Hydrothermal Biofilms: Composition of Biofilms in Siliceous Sinter-Deposting Hot Springs. Doctoral Dissertation, Arizona State University. [2] Meyer-Dombard et al., 2007. Microbial Diversity and SIP Investigations of Streamer Biofilm Communities in Yellowstone. Goldschmidt Geochemical Conference. [3] Raymond et al., 2008. EOS Trans AGU. Abstract B14A-03. [4] Hall et al., 2008. AEM 74:4910-4922. [5] Steunou et al., 2006. PNAS 103:2398-2403.

Meyer-Dombard, D. R.; Burton, M.; Vennelakanti, S.; Havig, J. R.; Shock, E.

2009-12-01

245

Hepatitis C virus core functions as a suppressor of cyclin-dependent kinase-activating kinase and impairs cell cycle progression.  

PubMed

We investigated how the hepatitis C virus (HCV) core protein affects the cell cycle profile and cell cycle-related molecules by using the HCV core-expressing stable transfectant. Analysis of the cell cycle profile showed that HCV core impaired G(1) to S transition. The E2F-mediated transcription, phosphorylation of the retinoblastoma protein, and cyclin-dependent kinase (CDK) 4 and CDK2 activities were suppressed in HCV core-expressing cells. The expression levels of G(1) phase-related CDKs/cyclins and various CDK inhibitors were not substantially affected by expression of HCV core. When influences of HCV core on CDK-activating kinase (CAK) were examined, the expression levels of the CAK components, CDK7, cyclin H, and MAT1, were not affected. However, formation of the ternary CAK complex, CAK activity, and the CDK2 level with activating phosphorylation were inhibited by expression of the HCV core. The direct effect of HCV core on CAK was further assessed in the cell-free system by adding the in vitro translated HCV core protein to the anti-CDK7 immunoprecipitate from the cell. The results showed that HCV core led to dissociation of MAT1 from the CAK complex and suppressed the CAK activity. Furthermore, the binding assay revealed that the HCV core was directed against CDK7. Their interaction occurred mainly in the nucleus by the immunostaining. In conclusion, the HCV core protein interacts with CAK and functions as an extrinsic suppressor of CAK. This may be the molecular basis of HCV core-mediated suppression of cell cycle progression. Our findings suggest a novel mechanism concerning HCV core-mediated alteration in the cell cycle machinery. PMID:14711830

Ohkawa, Kazuyoshi; Ishida, Hisashi; Nakanishi, Fumihiko; Hosui, Atsushi; Ueda, Keiji; Takehara, Tetsuo; Hori, Masatsugu; Hayashi, Norio

2004-01-07

246

RNAi Targeting CXCR4 Inhibits Tumor Growth Through Inducing Cell Cycle Arrest and Apoptosis  

PubMed Central

CXC chemokine receptor 4 (CXCR4) is involved in many human malignant tumors and plays an important role in tumor growth and metastasis. To explore the effects of CXCR4 expression on the malignant cells of oral squamous cell carcinoma (OSCC), Tca8113 and SCC-9 cell lines, as well as their xenograft models, of nude mice were used to detect cancer cell proliferation alteration. This study also examined the corresponding molecular mechanism after CXCR4 knockdown using a recombinant lentiviral vector expressing small interference RNA (siRNA) for CXCR4. RNA interference-mediated knockdown of CXCR4 in highly aggressive (Tca8113 and SCC-9) tumor cells significantly inhibited the proliferation of the two cell lines in vitro and in vivo. The expression levels of >1,500 genes involved in cell cycle, apoptosis, and multiple signaling pathways were also altered. These results provide new evidence of CXCR4 as a promising tumor gene therapeutic target.

Yu, Tao; Wu, Yingying; Huang, Yi; Yan, Chaoran; Liu, Ying; Wang, Zongsheng; Wang, Xiaoyi; Wen, Yuming; Wang, Changmei; Li, Longjiang

2012-01-01

247

The Influence of Biospheric Temperature Acclimation and Choice of Temperature Response Function on Feedbacks in Coupled Climate-Carbon Cycle Models  

NASA Astrophysics Data System (ADS)

Future CO2 concentrations and global mean temperatures are higher in general circulation models that include an interactive global carbon cycle than in those without the coupling. However, the magnitude of this positive climate-carbon cycle feedback varies among models. The differences can largely be attributed to terrestrial biosphere response, with higher ecosystem respiration at higher temperatures an important contributor. We are thus investigating the impact of different models of the temperature response of ecosystem respiration on simulated climate-carbon feedbacks. We focus on temperature acclimation of heterotrophic (soil) respiration (Rh), because acclimation of Rh to warmer temperatures is hypothesized to reduce climate-carbon feedbacks. We have implemented alternative temperature functions for Rh, including those with temperature acclimation, in a site-scale ecosystem model (LoTEC), a global terrestrial biogeochemistry model (GTEC 2.0), a global integrated terrestrial biosphere model (IBIS 2.5), and a coupled climate-carbon cycle model (INCCA), which couples the Parallel Climate Model (PCM) with IBIS. Simulations with the ecosystem and uncoupled biosphere models show that the choice of temperature function strongly influences the accumulation of carbon in soil over time and space, and these differences in soil carbon stocks influence the release of CO2 to the atmosphere via first order, mass-dependent decay dynamics. These indirect effects are more important in determining climate-carbon feedbacks at warmer temperatures than the primary effects of temperature on rates of respiration per unit mass of carbon. In some simulations, total respiratory flux of carbon to the atmosphere in projected warmer climates was virtually the same with or without acclimation because of compensating differences in carbon accumulation at earlier cooler temperatures. When the coupled climate-carbon model is forced by historical fossil-fuel emissions, total global soil carbon increases at 0.5 Gt C y-1 when Rh is modeled with a temperature response function exhibiting moderate acclimation to temperature but declines at 0.3 Gt C y-1 when Rh is modeled with a simple Q10 temperature function showing no acclimation. These results suggest that the choice of temperature functions for terrestrial Rh can influence simulated climate-carbon feedbacks in coupled models. However, the influence is largely through indirect effects on soil carbon stocks, rather than acclimation or other differences in temperature dependent rates per se. Differences among temperature functions in the range of 10-35 0C are likely more important than differences under warmer, but rarely experienced, conditions. Accordingly, when choosing a temperature response function, careful attention should be given to accurate simulation of soil respiration at historically prevailing temperatures.

King, A. W.; Post, W. M.; Tharp, M. L.; Erickson, D. J.; Thompson, S. L.

2004-12-01

248

The large tumor antigen: a "Swiss Army knife" protein possessing the functions required for the polyomavirus life cycle.  

PubMed

The SV40 large tumor antigen (L-Tag) is involved in the replication and cell transformation processes that take place during the polyomavirus life cycle. The ability of the L-Tag to interact with and to inactivate the tumor suppressor proteins p53 and pRb, makes this polyfunctional protein an interesting target in the search for compounds with antiviral and/or antiproliferative activities designed for the management of polyomavirus-associated diseases. The severe diseases caused by polyomaviruses, mainly in immunocompromised hosts, and the absence of licensed treatments, make the discovery of new antipolyomavirus drugs urgent. Parallels can be made between the SV40 L-Tag and the human papillomavirus (HPV) oncoproteins (E6 and E7) as they are also able to deregulate the cell cycle in order to promote cell transformation and its maintenance. In this review, a presentation of the SV40 L-Tag characteristics, regarding viral replication and cellular transformation, will show how similar these two processes are between the polyoma- and papillomavirus families. Insights at the molecular level will highlight similarities in the binding of polyoma- and papillomavirus replicative helicases to the viral DNA and in their disruptions of the p53 and pRb tumor suppressor proteins. PMID:23201316

Topalis, D; Andrei, G; Snoeck, R

2012-11-28

249

Adaptation in the Ventral Eye of Limulus is Functionally Independent of the Photochemical Cycle, Membrane Potential, and Membrane Resistance  

PubMed Central

The early receptor potential (ERP), membrane potential, membrane resistance, and sensitivity were measured during light and/or dark adaptation in the ventral eye of Limulus. After a bright flash, the ERP amplitude recovered with a time constant of 100 ms, whereas the sensitivity recovered with an initial time constant of 20 s. When a strong adapting light was turned off, the recovery of membrane potential and of membrane resistance had time-courses similar to each other, and both recovered more rapidly than the sensitivity. The receptor depolarization was compared during dark adaptation after strong illumination and during light adaptation with weaker illumination; at equal sensitivities the cell was more depolarized during light adaptation than during dark adaptation. Finally, the waveforms of responses to flashes were compared during dark adaptation after strong illumination and during light adaptation with weaker illumination. At equal sensitivities (equal amplitude responses for identical flashes), the responses during light adaptation had faster time-courses than the responses during dark adaptation. Thus neither the photochemical cycle nor the membrane potential nor the membrane resistance is related to sensitivity changes during dark adaptation in the photoreceptors of the ventral eye. By elimination, these results imply that there are (unknown) intermediate process(es) responsible for adaptation interposed between the photochemical cycle and the electrical properties of the photoreceptor.

Fein, A.; DeVoe, R. D.

1973-01-01

250

Menstrual Cycle Effects on Hypothalamic Dopamine Receptor Function in Women with a History of Puerperal Bipolar Disorder  

Microsoft Academic Search

Neuroendocrine challenge tests of hypothalamic dopamine receptor function in the early postpartum period suggest that the sensitivity of these receptors is increased in women with a history of bipolar disorder after childbirth. We tested the hypothesis that, in women predisposed to bipolar disorder in the puerperium, hypothalamic dopamine receptor function is more sensitive to changes in circulating ovarian hormone concentrations

A. Wieck; R. A. Davies; A. D. Hirst; N. Brown; A. Papadopoulos; M. N. Marks; S. A. Checkley; R. C. Kumar; I. C. Campbell

2003-01-01

251

Loss of the retinoblastoma tumor suppressor: differential action on transcriptional programs related to cell cycle control and immune function  

Microsoft Academic Search

Functional inactivation of the retinoblastoma tumor suppressor gene product (RB) is a common event in human cancers. Classically, RB functions to constrain cellular proliferation, and loss of RB is proposed to facilitate the hyperplastic proliferation associated with tumorigenesis. To understand the repertoire of regulatory processes governed by RB, two models of RB loss were utilized to perform microarray analysis. In

M P Markey; J Bergseid; E E Bosco; K Stengel; H Xu; C N Mayhew; S J Schwemberger; W A Braden; Y Jiang; G F Babcock; A G Jegga; B J Aronow; M F Reed; J Y J Wang; E S Knudsen

2007-01-01

252

Global Analysis of Host Cell Gene Expression Late during Cytomegalovirus Infection Reveals Extensive Dysregulation of Cell Cycle Gene Expression and Induction of Pseudomitosis Independent of US28 Function  

PubMed Central

Replication of human cytomegalovirus (CMV) depends on host cell gene products working in conjunction with viral functions and leads to a dramatic dysregulation of cell cycle gene expression. Comprehensive transcriptional profiling was used to identify pathways most dramatically modulated by CMV at late times during infection and to determine the extent to which expression of the viral chemokine receptor US28 contributed to modulating cellular gene expression. Cells infected with the AD169 strain of virus or a fully replication competent US28-deficient derivative (RV101) were profiled throughout the late phase of infection (50, 72, and 98 h postinfection). Although sensitive statistical analysis showed striking global changes in transcript levels in infected cells compared to uninfected cells, the expression of US28 did not contribute to these alterations. CMV infection resulted in lower levels of transcripts encoding cytoskeletal, extracellular matrix, and adhesion proteins, together with small GTPases and apoptosis regulators, and in higher levels of transcripts encoding cell cycle, DNA replication, energy production, and inflammation-related gene products. Surprisingly, a large number of cellular transcripts encoding mitosis-related proteins were upmodulated at late times in infection, and these were associated with the formation of abnormal mitotic spindles and the appearance of pseudomitotic cells. These data extend our understanding of how broadly CMV alters the regulation of host cell cycle gene products and highlight the establishment of a mitosis-like environment in the absence of cellular DNA replication as important for viral replication and maturation.

Hertel, Laura; Mocarski, Edward S.

2004-01-01

253

Sometimes "Newton's Method" Always "Cycles"  

ERIC Educational Resources Information Center

|Are there functions for which Newton's method cycles for all non-trivial initial guesses? We construct and solve a differential equation whose solution is a real-valued function that two-cycles under Newton iteration. Higher-order cycles of Newton's method iterates are explored in the complex plane using complex powers of "x." We find a class of…

Latulippe, Joe; Switkes, Jennifer

2012-01-01

254

Liberation of functional p53 by proteasome inhibition in human papilloma virus-positive head and neck squamous cell carcinoma cells promotes apoptosis and cell cycle arrest.  

PubMed

Human papilloma virus (HPV) infection represents an emerging risk factor in head and neck squamous cell carcinoma (HNSCC). In contrast to HPV-negative HNSCC, most cases of HPV-positive HNSCC encode wild-type p53, although the p53 protein in these cells is rapidly degraded via HPV E6-mediated ubiquitination and subsequent proteasomal degradation. This unique feature of HPV-positive HNSCC has raised hope that liberation of wild-type p53 from the E6 protein may have therapeutic benefit in this disease. Indeed, suppression of E6 expression promotes apoptosis in HPV-positive HNSCC cell lines. However, the role of p53 in mediating this cell death has not been determined. Here, we demonstrate that siRNAs targeting the E6/E7 RNA, or treatment with the proteasome inhibitor bortezomib, resulted in upregulation of functional p53 and p53 gene targets in three HPV-positive HNSCC cell lines, but not in HPV-negative HNSCC cells. Apoptosis induced by E6/E7 siRNA in HPV-positive cells was found to be dependent on p53, while bortezomib-induced cell death was modestly p53-dependent. Treatment with subtoxic doses of bortezomib led to cell cycle arrest in HPV-positive, but not HPV-negative HNSCC cells. Moreover, this cell cycle arrest was mediated by p53 and the cell cycle inhibitor p21, the product of a p53 target gene. Collectively, these findings establish that wild-type p53 encoded by HPV-positive HNSCC cells, once liberated from HPV E6, can play important roles in promoting apoptosis and cell cycle arrest. PMID:23421999

Li, Changyou; Johnson, Daniel E

2013-02-19

255

The activity of the glyoxylate cycle in peroxisomes of Candida albicans depends on a functional beta-oxidation pathway: evidence for reduced metabolite transport across the peroxisomal membrane.  

PubMed

The glyoxylate cycle, a metabolic pathway required for generating C(4) units from C(2) compounds, is an important factor in virulence, in both animal and plant pathogens. Here, we report the localization of the key enzymes of this cycle, isocitrate lyase (Icl1; EC 4.1.3.1) and malate synthase (Mls1; EC 2.3.3.9), in the human fungal pathogen Candida albicans. Immunocytochemistry in combination with subcellular fractionation showed that both Icl1 and Mls1 are localized to peroxisomes, independent of the carbon source used. Although Icl1 and Mls1 lack a consensus type I peroxisomal targeting signal (PTS1), their import into peroxisomes was dependent on the PTS1 receptor Pex5p, suggesting the presence of non-canonical targeting signals in both proteins. Peroxisomal compartmentalization of the glyoxylate cycle is not essential for proper functioning of this metabolic pathway because a pex5Delta/Delta strain, in which Icl1 and Mls1 were localized to the cytosol, grew equally as well as the wild-type strain on acetate and ethanol. Previously, we reported that a fox2Delta/Delta strain that is completely deficient in fatty acid beta-oxidation, but has no peroxisomal protein import defect, displayed strongly reduced growth on non-fermentable carbon sources such as acetate and ethanol. Here, we show that growth of the fox2Delta/Delta strain on these carbon compounds can be restored when Icl1 and Mls1 are relocated to the cytosol by deleting the PEX5 gene. We hypothesize that the fox2Delta/Delta strain is disturbed in the transport of glyoxylate cycle products and/or acetyl-CoA across the peroxisomal membrane and discuss the possible relationship between such a transport defect and the presence of giant peroxisomes in the fox2Delta/Delta mutant. PMID:18832312

Piekarska, Katarzyna; Hardy, Guy; Mol, Els; van den Burg, Janny; Strijbis, Karin; van Roermund, Carlo; van den Berg, Marlene; Distel, Ben

2008-10-01

256

Hsp70 and Hsp40 Functionally Interact with Soluble Mutant Huntingtin Oligomers in a Classic ATP-dependent Reaction Cycle*  

PubMed Central

Inclusion bodies of aggregated mutant huntingtin (htt) fragments are a neuropathological hallmark of Huntington disease (HD). The molecular chaperones Hsp70 and Hsp40 colocalize to inclusion bodies and are neuroprotective in HD animal models. How these chaperones suppress mutant htt toxicity is unclear but might involve direct effects on mutant htt misfolding and aggregation. Using size exclusion chromatography and atomic force microscopy, we found that mutant htt fragments assemble into soluble oligomeric species with a broad size distribution, some of which reacted with the conformation-specific antibody A11. Hsp70 associated with A11-reactive oligomers in an Hsp40- and ATP-dependent manner and inhibited their formation coincident with suppression of caspase 3 activity in PC12 cells. Thus, Hsp70 and Hsp40 (DNAJB1) dynamically target specific subsets of soluble oligomers in a classic ATP-dependent reaction cycle, supporting a pathogenic role for these structures in HD.

Lotz, Gregor P.; Legleiter, Justin; Aron, Rebecca; Mitchell, Emily J.; Huang, Shao-Yi; Ng, Cheping; Glabe, Charles; Thompson, Leslie M.; Muchowski, Paul J.

2010-01-01

257

Serum-dependent transcriptional networks identify distinct functional roles for H-Ras and N-Ras during initial stages of the cell cycle  

PubMed Central

Background Using oligonucleotide microarrays, we compared transcriptional profiles corresponding to the initial cell cycle stages of mouse fibroblasts lacking the small GTPases H-Ras and/or N-Ras with those of matching, wild-type controls. Results Serum-starved wild-type and knockout ras fibroblasts had very similar transcriptional profiles, indicating that H-Ras and N-Ras do not significantly control transcriptional responses to serum deprivation stress. In contrast, genomic disruption of H-ras or N-ras, individually or in combination, determined specific differential gene expression profiles in response to post-starvation stimulation with serum for 1 hour (G0/G1 transition) or 8 hours (mid-G1 progression). The absence of N-Ras caused significantly higher changes than the absence of H-Ras in the wave of transcriptional activation linked to G0/G1 transition. In contrast, the absence of H-Ras affected the profile of the transcriptional wave detected during G1 progression more strongly than did the absence of N-Ras. H-Ras was predominantly functionally associated with growth and proliferation, whereas N-Ras had a closer link to the regulation of development, the cell cycle, immunomodulation and apoptosis. Mechanistic analysis indicated that extracellular signal-regulated kinase (ERK)-dependent activation of signal transducer and activator of transcription 1 (Stat1) mediates the regulatory effect of N-Ras on defense and immunity, whereas the pro-apoptotic effects of N-Ras are mediated through ERK and p38 mitogen-activated protein kinase signaling. Conclusions Our observations confirm the notion of an absolute requirement for different peaks of Ras activity during the initial stages of the cell cycle and document the functional specificity of H-Ras and N-Ras during those processes.

2009-01-01

258

Cytokine mediated immune responses in the Japanese pufferfish (Takifugu rubripes) administered with heat-killed Lactobacillus paracasei spp. paracasei (06TCa22) isolated from the Mongolian dairy product.  

PubMed

The important role played by cytokines in host innate immunity and the interaction of subsets of immune and inflammatory cells through cytokines offer avenues for immune interventions. We investigated 16 cytokine gene responses in the Japanese pufferfish, Takifugu rubripes orally treated with a heat-killed lactic acid bacterium (LAB), Lactobacillus paracasei spp. paracasei (strain 06TCa22) (Lpp) isolated from a Mongolian dairy product at 1mgg(-1)body weightd(-1) for 3days. Additionally, we assessed superoxide anion production (SAP) and phagocytic activity (PA) of head kidney cells and resistance to Vibrio harveyi infection in treated fish. Significant up-regulation of pro-inflammatory (IL-1?, IL-6, IL-17A/F-3, TNF-? and TNF-N), cell-mediated immunity inducing (IL-12p35, IL-12p40 and IL-18), antiviral/intra-cellular pathogen killing (I-IFN-1 and IFN-?), anti-inflammatory (IL-10) and peripheral T cell expansion and survival controlling (IL-2, IL-7, IL-15, IL-21 and TGF-?1) cytokines was observed in the treated fish. Furthermore, significantly increased SAP, PA and pathogen resistance were observed in the treated fish compared to untreated fish. Our results indicate the enhancement of cytokine mediated immunity in T. rubripes by the use of the heat-killed Lpp as a potential immunostimulant and would be of great use in immunomodulation trials with the possibility to monitor positive immune response. PMID:23867289

Biswas, G; Korenaga, H; Nagamine, R; Kawahara, S; Takeda, S; Kikuchi, Y; Dashnyam, B; Yoshida, T; Kono, T; Sakai, M

2013-07-15

259

Laboratory batch experiments of the combined effects of ultrasound and air stripping in removing CCl4 and 1,1,1-TCA from water.  

PubMed

Ultrasonic and air-stripping techniques for removal of carbon tetrachloride (CCl4) and 1,1,1-trichloroethane (1,1,1-TCA) from water were studied in batch experiments. Ultrasound (US) is effective for destroying organic compounds in aqueous solutions whereas air stripping (AS) efficiently transfers volatile compounds from the liquid to the gas phase. In simultaneous US and AS experiments, synergistic effects were observed and attributed to the effect of US on the mass transfer process. Using a photographic method, ultrasonic break up of gas bubbles and changes in gas holdup ratios were examined. In the two different gas-sparging systems studied, ultrasonic waves did not break up gas bubbles. In contrast, bubbles from the smaller porous size diffuser were coalesced due to sonication. In addition, both photographic and gas holdup experiments demonstrated that ultrasonic irradiation increased the gas holdup ratio. The enhancement observed in the removal of the compounds appeared to be due to this greater ultrasonic gas holdup ratio. PMID:15811676

Ayyildiz, Onder; Anderson, Paul R; Peters, Robert W

2005-04-11

260

How do migratory species stay healthy over the annual cycle? A conceptual model for immune function and for resistance to disease.  

PubMed

Migration has fascinated researchers for years and many active areas of study exist. However, the question of how migratory species stay healthy within the context of their annual cycle remains relatively unexplored. This article addresses this question using Red Knots (Calidris canutus) as a model migrant species. We review recent research on immune function in Red Knots and integrate this work with the broader eco-immunological literature to introduce a conceptual model. This model synthesizes earlier ideas about resource allocation and the costs of immunity with recent increases in our knowledge about the vertebrate immune system and then puts these concepts into the context of defense against real pathogens in environments where a myriad of factors change in time and space. We also suggest avenues for further research, which will help to test the model and better link measures of immune function to pressure from pathogens and to optimal defense against disease. PMID:21558209

Buehler, Deborah M; Tieleman, B Irene; Piersma, Theunis

2010-05-21

261

Water Cycle  

NSDL National Science Digital Library

4th Grade Science - Water Cycle Water Cycle two day interactive lesson plan. DAY 1: Welcome to the Water Cycle! Today we are going to be exploring and finding out more about the wonderful Water Cycle! For starters we are going to start with a movie, click the following link and watch the video and ...

Staley, Mrs.

2009-11-09

262

A novel role for fatty acid transport protein 1 in the regulation of tricarboxylic acid cycle and mitochondrial function in 3T3-L1 adipocytes  

PubMed Central

Fatty acid transport proteins (FATPs) are integral membrane acyl-CoA synthetases implicated in adipocyte fatty acid influx and esterification. Whereas some FATP1 translocates to the plasma membrane in response to insulin, the majority of FATP1 remains within intracellular structures and bioinformatic and immunofluorescence analysis of FATP1 suggests the protein primarily resides in the mitochondrion. To evaluate potential roles for FATP1 in mitochondrial metabolism, we used a proteomic approach following immunoprecipitation of endogenous FATP1 from 3T3-L1 adipocytes and identified mitochondrial 2-oxoglutarate dehydrogenase. To assess the functional consequence of the interaction, purified FATP1 was reconstituted into phospholipid-containing vesicles and its effect on 2-oxoglutarate dehydrogenase activity evaluated. FATP1 enhanced the activity of 2-oxoglutarate dehydrogenase independently of its acyl-CoA synthetase activity whereas silencing of FATP1 in 3T3-L1 adipocytes resulted in decreased activity of 2-oxoglutarate dehydrogenase. FATP1 silenced 3T3-L1 adipocytes exhibited decreased tricarboxylic acid cycle activity, increased cellular NAD+/NADH, increased fatty acid oxidation, and increased lactate production indicative of altered mitochondrial energy metabolism. These results reveal a novel role for FATP1 as a regulator of tricarboxylic acid cycle activity and mitochondrial function.

Wiczer, Brian M.; Bernlohr, David A.

2009-01-01

263

Function of the pentose phosphate pathway and its key enzyme, transketolase, in the regulation of the meiotic cell cycle in oocytes  

PubMed Central

Objective Previously, we identified that transketolase (Tkt), an important enzyme in the pentose phosphate pathway, is highly expressed at 2 hours of spontaneous maturation in oocytes. Therefore, this study was performed to determine the function of Tkt in meiotic cell cycle regulation, especially at the point of germinal vesicle breakdown (GVBD). Methods We evaluated the loss-of-function of Tkt by microinjecting Tkt double-stranded RNAs (dsRNAs) into germinal vesicle-stage oocytes, and the oocytes were cultured in vitro to evaluate phenotypic changes during oocyte maturation. In addition to maturation rates, meiotic spindle and chromosome rearrangements, and changes in expression of other enzymes in the pentose phosphate pathway were determined after Tkt RNA interference (RNAi). Results Despite the complete and specific knockdown of Tkt expression, GVBD occurred and meiosis was arrested at the metaphase I (MI) stage. The arrested oocytes exhibited spindle loss, chromosomal aggregation, and declined maturation promoting factor and mitogen-activated protein kinase activities. The modified expression of two enzymes in the pentose phosphate pathway, Prps1 and Rbks, after Tkt RNAi and decreased maturation rates were amended when ribose-5-phosphate was supplemented in the culture medium, suggesting that the Tkt and pentose phosphate pathway are important for the maturation process. Conclusion We concluded that Tkt and its associated pentose phosphate pathway play an important role in the MI-MII transition of the oocytes' meiotic cell cycle, but not in the process of GVBD.

Kim, Yunna; Kim, Eun-Young; Seo, You-Mi; Yoon, Tae Ki; Lee, Woo-Sik

2012-01-01

264

A Genetic Screen for Dominant Enhancers of the Cell-Cycle Regulator ?-Endosulfine Identifies Matrimony as a Strong Functional Interactor in Drosophila  

PubMed Central

The coordination of cell-cycle events with developmental processes is essential for the reproductive success of organisms. In Drosophila melanogaster, meiosis is tightly coupled to oocyte development, and early embryos undergo specialized S-M mitoses that are supported by maternal products. We previously showed that the small phosphoprotein ?-endosulfine (Endos) is required for normal oocyte meiotic maturation and early embryonic mitoses in Drosophila. In this study, we performed a genetic screen for dominant enhancers of endos00003 and identified several genomic regions that, when deleted, lead to impaired fertility of endos00003/+ heterozygous females. We uncovered matrimony (mtrm), which encodes a Polo kinase inhibitor, as a strong dominant enhancer of endos. mtrm126 +/+ endos00003 females are sterile because of defects in early embryonic mitoses, and this phenotype is reverted by removal of one copy of polo. These results provide compelling genetic evidence that excessive Polo activity underlies the strong functional interaction between endos00003 and mtrm126. Moreover, we show that endos is required for the increased expression of Mtrm in mature oocytes, which is presumably loaded into early embryos. These data are consistent with the model that maternal endos antagonizes Polo function in the early embryo to ensure normal mitoses through its effects on Mtrm expression during late oogenesis. Finally, we also identified genomic deletions that lead to loss of viability of endos00003/+ heterozygotes, consistent with recently published studies showing that endos is required zygotically to regulate the cell cycle during development.

Von Stetina, Jessica R.; LaFever, Kimberly S.; Rubin, Mayer; Drummond-Barbosa, Daniela

2011-01-01

265

A Genetic Screen for Dominant Enhancers of the Cell-Cycle Regulator ?-Endosulfine Identifies Matrimony as a Strong Functional Interactor in Drosophila.  

PubMed

The coordination of cell-cycle events with developmental processes is essential for the reproductive success of organisms. In Drosophila melanogaster, meiosis is tightly coupled to oocyte development, and early embryos undergo specialized S-M mitoses that are supported by maternal products. We previously showed that the small phosphoprotein ?-endosulfine (Endos) is required for normal oocyte meiotic maturation and early embryonic mitoses in Drosophila. In this study, we performed a genetic screen for dominant enhancers of endos(00003) and identified several genomic regions that, when deleted, lead to impaired fertility of endos(00003)/+ heterozygous females. We uncovered matrimony (mtrm), which encodes a Polo kinase inhibitor, as a strong dominant enhancer of endos. mtrm(126) +/+ endos(00003) females are sterile because of defects in early embryonic mitoses, and this phenotype is reverted by removal of one copy of polo. These results provide compelling genetic evidence that excessive Polo activity underlies the strong functional interaction between endos(00003) and mtrm(126). Moreover, we show that endos is required for the increased expression of Mtrm in mature oocytes, which is presumably loaded into early embryos. These data are consistent with the model that maternal endos antagonizes Polo function in the early embryo to ensure normal mitoses through its effects on Mtrm expression during late oogenesis. Finally, we also identified genomic deletions that lead to loss of viability of endos(00003)/+ heterozygotes, consistent with recently published studies showing that endos is required zygotically to regulate the cell cycle during development. PMID:22384372

Von Stetina, Jessica R; Lafever, Kimberly S; Rubin, Mayer; Drummond-Barbosa, Daniela

2011-12-01

266

A functional asymmetry in the Leech Heartbeat Timing Network is revealed by driving the network across various cycle periods.  

PubMed

We tested predictions of a computational model (Hill et al., 2002) of the leech heartbeat timing network. The timing network consists of two segmental oscillators located in the third (G3) and fourth (G4) segmental ganglia. Each oscillator consists of two reciprocally inhibitory oscillator interneurons along with the coordinating interneuron fibers that link them. In the model, the network was driven to cycle periods around the normal period of the network by repeatedly stimulating one of the paired oscillator interneurons in G3 or G4. Here we replicate these experiments in the biological system. The model predicts that the G3 and G4 oscillators can entrain the timing network to periods faster but not slower than the inherent period of the nondriven ("follower") oscillator and that they can do so symmetrically. The biological system can be driven to periods both faster (such that the driven oscillator leads in phase) and slower (such that the driven oscillator lags in phase) than the inherent period of the timing network. Although both oscillators can entrain the network, the G4 oscillator does so over a narrower range of periods. Two differences between the assumptions of the model and the properties of the biological network, spike frequency adaptation in coordinating interneurons and asymmetry in the connections from the oscillator interneurons to the coordinating interneurons, may account for these discrepancies. Individual coordinating interneurons were also able to entrain the oscillators but with little effect of the phase relationship between the oscillators, suggesting that phase relations are determined by properties inherent to the oscillator interneurons. PMID:12040049

Masino, Mark A; Calabrese, Ronald L

2002-06-01

267

Functional cloning of SPIN2, a nuclear anti-apoptotic protein with roles in cell cycle progression  

Microsoft Academic Search

The balance between hematopoietic cell viability and apoptosis is regulated by exogenous growth factors, however, the molecular mechanisms by which these trophic factors exert their effects remain obscure. A functional retroviral cDNA library-based screen was employed to identify genes that prevent growth factor withdrawal-mediated apoptosis in the myeloid progenitor cell 32Dcl3. This approach identified three classes of genes: those with

BS Fletcher; C Dragstedt; L Notterpek; GP Nolan

2002-01-01

268

Estrogenic environmental endocrine-disrupting chemical effects on reproductive neuroendocrine function and dysfunction across the life cycle  

Microsoft Academic Search

Endocrine disrupting chemicals (EDCs) are natural or synthetic compounds that interfere with the normal function of an organism’s\\u000a endocrine system. Many EDCs are resistant to biodegradation, due to their structural stability, and persist in the environment.\\u000a The focus of this review is on natural and artificial EDCs that act through estrogenic mechanisms to affect reproductive neuroendocrine\\u000a systems. This endocrine axis

Sarah M. Dickerson; Andrea C. Gore

2007-01-01

269

CCR7 Ligands, SLC\\/6Ckine\\/Exodus2\\/TCA4 and CK?-11\\/MIP3?\\/ELC, Are Chemoattractants for CD56 +CD16 ?NK Cells and Late Stage Lymphoid Progenitors  

Microsoft Academic Search

Two human CC chemokines, SLC\\/6Ckine\\/Exodus2\\/TCA4 and CK?-11\\/MIP-3?\\/ELC, are previously reported as efficacious chemoattractants for T- and B-cells and dendritic cells. SLC and CK?-11 share only 32% amino acid identity, but are ligands for the same chemokine receptor, CCR7. In this study, we examined chemotactic activity of SLC and CK?-11 for NK cells and lymphoid progenitors in bone marrow and thymus.

Chang H. Kim; Louis M. Pelus; Edward Appelbaum; Kyung Johanson; Naoyuki Anzai; Hal E. Broxmeyer

1999-01-01

270

SLC\\/Exodus2\\/6Ckine\\/TCA4 induces chemotaxis of hematopoietic progenitor cells: differential activity of ligands of CCR7, CXCR3, or CXCR4 in chemotaxis vs. suppression of progenitor proliferation  

Microsoft Academic Search

Chemokines induce chemotaxis of hema- topoietic progenitor cells (HPC), and suppress their proliferation. In this study we report that SLC\\/ Exodus2\\/6Ckine\\/TCA4 (hereafter termed SLC) is a chemoattractant for human CD341 HPC. SLC mainly induces preferential chemotaxis of macro- phage progenitors. We examined the chemotactic activity of CXCR3 ligands on CD341 HPC because it has been reported that SLC is a

Chang H. Kim; Hal E. Broxmeyer

271

Functional Characterization of Rpn3 Uncovers a Distinct 19S Proteasomal Subunit Requirement for Ubiquitin-Dependent Proteolysis of Cell Cycle Regulatory Proteins in Budding Yeast  

PubMed Central

By selectively eliminating ubiquitin-conjugated proteins, the 26S proteasome plays a pivotal role in a large variety of cellular regulatory processes, particularly in the control of cell cycle transitions. Access of ubiquitinated substrates to the inner catalytic chamber within the 20S core particle is mediated by the 19S regulatory particle (RP), whose subunit composition in budding yeast has been recently elucidated. In this study, we have investigated the cell cycle defects resulting from conditional inactivation of one of these RP components, the essential non-ATPase Rpn3/Sun2 subunit. Using temperature-sensitive mutant alleles, we show that rpn3 mutations do not prevent the G1/S transition but cause a metaphase arrest, indicating that the essential Rpn3 function is limiting for mitosis. rpn3 mutants appear severely compromised in the ubiquitin-dependent proteolysis of several physiologically important proteasome substrates. Thus, RPN3 function is required for the degradation of the G1-phase cyclin Cln2 targeted by SCF; the S-phase cyclin Clb5, whose ubiquitination is likely to involve a combination of E3 (ubiquitin protein ligase) enzymes; and anaphase-promoting complex targets, such as the B-type cyclin Clb2 and the anaphase inhibitor Pds1. Our results indicate that the Pds1 degradation defect of the rpn3 mutants most likely accounts for the metaphase arrest phenotype observed. Surprisingly, but consistent with the lack of a G1 arrest phenotype in thermosensitive rpn3 strains, the Cdk inhibitor Sic1 exhibits a short half-life regardless of the RPN3 genotype. In striking contrast, Sic1 turnover is severely impaired by a temperature-sensitive mutation in RPN12/NIN1, encoding another essential RP subunit. While other interpretations are possible, these data strongly argue for the requirement of distinct RP subunits for efficient proteolysis of specific cell cycle regulators. The potential implications of these data are discussed in the context of possible Rpn3 function in multiubiquitin-protein conjugate recognition by the 19S proteasomal regulatory particle.

Bailly, Eric; Reed, Steven I.

1999-01-01

272

Measurement of human tricarboxylic acid cycle rates during visual activation by (13)C magnetic resonance spectroscopy.  

PubMed

Measurement by (13)C magnetic resonance spectroscopy (MRS) of the incorporation of label from [1-(13)C] glucose, initially into C4 of glutamate, allows the regional tricarboxylic acid (TCA) cycle flux (F(TCA)) to be determined in the human brain. In this study, a direct (13)C MRS approach was used at 3T, with NOE enhancement and (1)H decoupling with WALTZ16, to determine basal F(TCA) in six volunteers. The values found in the visual cortex are similar to those reported in previous (13)C MRS studies, and consistent with PET measurements of the cerebral metabolic rate for glucose, CMRglc. In two preliminary activation studies using light emitting diode (LED) goggles flashing at 8 Hz, compared to darkness as control, increases in F(TCA) were found from 0.60 +/- 0.10 to 0.94 +/- 0.03 micromol/min/g (56%) and from 0.34 +/- 0.14 to 0.56 +/- 0.07 micromol/min/g (65%). These are upper estimates, but they are similar to the increases in CMRglc reported in PET studies, and strongly suggest, in contrast to these PET studies, that cerebral glucose is metabolized oxidatively, even during intense visual stimulation. This is supported by the observation that very little (13)C label is incorporated into C3 lactate, as would be expected if glucose were metabolized anaerobically. There is evidence for incorporation of glucose into cerebral glycogen, but this is a relatively minor component of cerebral glucose metabolism. PMID:11746397

Chhina, N; Kuestermann, E; Halliday, J; Simpson, L J; Macdonald, I A; Bachelard, H S; Morris, P G

2001-12-01

273

The trophic biology of the holothurian Molpadia musculus: implications for organic matter cycling and ecosystem functioning in a deep submarine canyon  

NASA Astrophysics Data System (ADS)

Megafaunal organisms play a key role in ecosystem functioning in the deep-sea through bioturbation, bioirrigation and organic matter cycling. At 3500 m water depth in the Nazaré Canyon, NE Atlantic, very high abundances of the infaunal holothurian Molpadia musculus were observed. To quantify the role of M. musculus in sediment cycling, sediment samples and holothurians were collected using an ROV and in situ experiments were conducted with incubation chambers. The biochemical composition of the sediment (in terms of proteins, carbohydrates and lipids), the holothurians' gut contents and holothurians' faecal material were analysed. In the sediments, proteins were the dominant organic compound, followed by carbohydrates and lipids. In the holothurian's gut contents, protein concentrations were higher than the other compounds, decreasing significantly as the material passed through the digestive tract. Approximately 33±1% of the proteins were digested by the time sediment reached the mid gut, with a total digestion rate equal to 67±1%. Carbohydrates and lipids were ingested in smaller amounts and digested with lower efficiencies (23±11% and 50±11%, respectively). As a result, the biopolymeric C digestion rate was on average 62±3%. We estimated that the population of M. musculus could remove approximately 0.49±0.13 g biopolymeric C and 0.13±0.03 g N m-2 d-1 from the sediments. These results suggest that M. musculus plays a key role in the benthic tropho-dynamics and biogeochemical processes in the Nazaré Canyon.

Amaro, T.; Bianchelli, S.; Billett, D. S. M.; Cunha, M. R.; Pusceddu, A.; Danovaro, R.

2010-08-01

274

Elevated cytokine responses to Vibrio harveyi infection in the Japanese pufferfish (Takifugu rubripes) treated with Lactobacillus paracasei spp. paracasei (06TCa22) isolated from the Mongolian dairy product.  

PubMed

With the aim of evaluating the effect of a Mongolian dairy product derived Lactobacillus paracasei spp. paracasei (strain 06TCa22) (Lpp) on the cytokine-mediated immune responses to Vibrio harveyi infection, we examined 16 cytokine expressions in the Japanese pufferfish, Takifugu rubripes. Fish were orally treated with the heat-killed Lpp at 1 mg g(-1) body weight d(-1) for 3 days. At 24 h posttreatment, fish were infected by an intramuscular injection of 0.1 mL V. harveyi bacterial suspension (10(8) cfu mL(-1)). Additionally, superoxide anion production (SAP) and phagocytic activity (PA) of head kidney cells were assessed during 120 h postinfection period. Significant up-regulation of pro-inflammatory (IL-1?, IL-6, IL-17A/F-3, TNF-? and TNF-N), cell-mediated immune inducing (IL-12p35, IL-12p40 and IL-18), antiviral/intra-cellular pathogen killing (I-IFN-1 and IFN-?), anti-inflammatory (IL-10) and lymphocyte agonistic (IL-2, IL-7, IL-15, IL-21 and TGF-?1) cytokines was observed in the treated fish compared to control ones during the pathogen infection. Furthermore, significantly increased SAP and PA (P < 0.01; 0.05) were recorded in the treated fish compared to untreated fish. These results suggest the beneficial role of Lpp in enhancement of cytokine-mediated immunity in the Japanese pufferfish against V. harveyi infection and application of this product as a potential fish immunostimulant. PMID:23769874

Biswas, G; Korenaga, H; Nagamine, R; Kawahara, S; Takeda, S; Kikuchi, Y; Dashnyam, B; Yoshida, T; Kono, T; Sakai, M

2013-06-12

275

Purple bamboo salt has anticancer activity in TCA8113 cells in vitro and preventive effects on buccal mucosa cancer in mice in vivo  

PubMed Central

Bamboo salt is a traditional healthy salt known in Korea. The in vitro anticancer effects of the salt were evaluated using a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay in TCA8113 human tongue carcinoma cells. At 1% concentration, the growth inhibitory rate of purple bamboo salt was 61% higher than that of sea salt (27%). Apoptosis analysis of the cancer cells was carried out using 4,6-diamidino-2-phenylindole (DAPI) staining to investigate the mechanism of the anticancer effects in tongue carcinoma cells. Purple bamboo salt induced a stronger apoptotic effect than sea salt. An Institute of Cancer Research (ICR) mouse buccal mucosa cancer model was established by injecting mice with U14 squamous cell carcinoma cells. Following injection, the wound at the injection site was smeared with salt samples. It was observed that the tumor volumes for the group treated with purple bamboo salt were smaller than those from the sea salt treatment and control groups. The sections of buccal mucosa cancer tissue showed that canceration in the purple bamboo salt group was weaker compared with that in the sea salt group. Similar results were observed in the lesion section of the cervical lymph. Using reverse transcription-polymerase chain reaction (RT-PCR) and western blotting, the purple bamboo salt group demonstrated an increase in Bcl-2-associated X protein (Bax) and a decrease in B cell lymphoma-2 (Bcl-2), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression, compared with the sea salt and control groups. The results demonstrated that purple bamboo salt had improved in vivo buccal mucosa cancer preventive activity compared with sea salt in mice.

ZHAO, XIN; DENG, XIAOXIAO; PARK, KUN-YOUNG; QIU, LIHUA; PANG, LIANG

2013-01-01

276

Numerical simulation of the diurnal cycle of rainfall in SW Amazon basin during the 1999 rainy season: the role of convective trigger function  

NASA Astrophysics Data System (ADS)

In continental areas, the maximum rainfall simulated with the Brazilian developments on the Regional Atmospheric Modeling System (BRAMS) occurs around 4 h earlier than the one observed with rain gauges. This work presents the successful implementation of a new convective trigger function (CTF) in the convective parameterization scheme used in BRAMS that corrects this misfit between model and observations. The importance of the CTF formulation on the diurnal cycle of rainfall over the Amazon Basin is reflected by the following numbers: Over Rondonia (SW Amazonia), the original version of BRAMS simulates the maximum rainfall at 1400 UTC (1000 LST), with the new CTF maximum shifting to 1800 UTC (1400 LST), while the S-band radar rainfall maximum is at 1900 UTC (1500 LST). This is attributed to two factors: (1) the new CTF is now coupled to the sensible and latent heat fluxes at surface; (2) during the early morning, the convective available potential energy is reduced.

e Silva, Cláudio Moisés Santos; de Freitas, Saulo Ribeiro; Gielow, Ralf

2012-08-01

277

A tricarboxylic acid cycle intermediate regulating transcription of a chloroaromatic biodegradative pathway: fumarate-mediated repression of the clcABD operon.  

PubMed

The ortho-cleavage pathways of catechol and 3-chlorocatechol are central catabolic pathways of Pseudomonas putida that convert aromatic and chloroaromatic compounds to tricarboxylic acid (TCA) cycle intermediates. They are encoded by the evolutionarily related catBCA and clcABD operons, respectively. Expression of the cat and clc operons requires the LysR-type transcriptional activators CatR and ClcR, respectively, and the inducer molecules cis,cis-muconate and 2-chloro-cis,cis-muconate, respectively. The regulation of the cat and clc promoters has been well studied, but the extent to which these operons are repressed by growth in TCA cycle intermediates has not been explored. We demonstrate by transcriptional fusion studies that the expression from the clc promoter is repressed when the cells are grown on succinate, citrate, or fumarate and that this repression is ClcR dependent and occurs at the transcriptional level. The presence of these organic acids did not affect the expression from the cat promoter. In vitro transcription assays demonstrate that the TCA cycle intermediate fumarate directly and specifically inhibits the formation of the clcA transcript. No such inhibition was observed when CatR was used as the activator on either the cat or clc template. Titration studies of fumarate and 2-chloromuconate show that the fumarate effect is concentration dependent and reversible, indicating that fumarate and 2-chloromuconate most probably compete for the same binding site on ClcR. This is an interesting example of the transcriptional regulation of a biodegradative pathway by the intracellular sensing of the state of the TCA cycle. PMID:9352923

McFall, S M; Abraham, B; Narsolis, C G; Chakrabarty, A M

1997-11-01

278

A tricarboxylic acid cycle intermediate regulating transcription of a chloroaromatic biodegradative pathway: fumarate-mediated repression of the clcABD operon.  

PubMed Central

The ortho-cleavage pathways of catechol and 3-chlorocatechol are central catabolic pathways of Pseudomonas putida that convert aromatic and chloroaromatic compounds to tricarboxylic acid (TCA) cycle intermediates. They are encoded by the evolutionarily related catBCA and clcABD operons, respectively. Expression of the cat and clc operons requires the LysR-type transcriptional activators CatR and ClcR, respectively, and the inducer molecules cis,cis-muconate and 2-chloro-cis,cis-muconate, respectively. The regulation of the cat and clc promoters has been well studied, but the extent to which these operons are repressed by growth in TCA cycle intermediates has not been explored. We demonstrate by transcriptional fusion studies that the expression from the clc promoter is repressed when the cells are grown on succinate, citrate, or fumarate and that this repression is ClcR dependent and occurs at the transcriptional level. The presence of these organic acids did not affect the expression from the cat promoter. In vitro transcription assays demonstrate that the TCA cycle intermediate fumarate directly and specifically inhibits the formation of the clcA transcript. No such inhibition was observed when CatR was used as the activator on either the cat or clc template. Titration studies of fumarate and 2-chloromuconate show that the fumarate effect is concentration dependent and reversible, indicating that fumarate and 2-chloromuconate most probably compete for the same binding site on ClcR. This is an interesting example of the transcriptional regulation of a biodegradative pathway by the intracellular sensing of the state of the TCA cycle.

McFall, S M; Abraham, B; Narsolis, C G; Chakrabarty, A M

1997-01-01

279

Cloning of the amphibolic Calvin cycle\\/OPPP enzyme d-ribulose-5-phosphate 3-epimerase (EC 5.1.3.1) from spinach chloroplasts: functional and evolutionary aspects  

Microsoft Academic Search

Exploiting the differential expression of genes for Calvin cycle enzymes in bundle-sheath and mesophyll cells of the C4 plant Sorghum bicolor L., we isolated via subtractive hybridization a molecular probe for the Calvin cycle enzyme d-ribulose-5-phosphate 3-epimerase (R5P3E) (EC 5.1.3.1), with the help of which several full-size cDNAs were isolated from spinach. Functional identity of the encoded mature subunit was

Ulrich Nowitzki; Ralf Wyrich; Peter Westhoff; Katrin Henze; Claus Schnarrenberger; William Martin

1995-01-01

280

A novel function of RNAs arising from the long terminal repeat of human endogenous retrovirus 9 in cell cycle arrest.  

PubMed

The human genome contains approximately 50 copies of the replication-defective human endogenous retrovirus 9 (ERV-9) and thousands of copies of its solitary long term repeat (sLTR) element. While some sLTRs are located upstream of critical genes and have enhancer activity, other sLTRs are located within introns and may be transcribed as RNAs. We found that intronic RNAs arising from U3 sLTRs of ERV-9 were expressed as both sense (S) and antisense (AS) transcripts in all human cells tested but that expression levels differed in malignant versus nonmalignant cells. In nonmalignant cells, AS was expressed at higher levels than S and at higher levels than in malignant cells; in malignant cells, AS was expressed at amounts equivalent to those of S RNA. Critically, U3 AS RNA was found to physically bind to key transcription factors for cellular proliferation, including NF-Y, p53, and sp1, indicating that such RNA transcripts may function as decoy targets or traps for NF-Y and thus inhibit the growth of human cancer cells. Indeed, short U3 oligodeoxynucleotides (ODNs) based on these RNA sequences ably inhibited proliferation of cancer cell lines driven by cyclins B1/B2, the gene targets of NF-Y. PMID:23097441

Xu, Lai; Elkahloun, Abdel G; Candotti, Fabio; Grajkowski, Andrzej; Beaucage, Serge L; Petricoin, Emanuel F; Calvert, Valerie; Juhl, Hartmut; Mills, Frederick; Mason, Karen; Shastri, Neal; Chik, Josh; Xu, Cynthia; Rosenberg, Amy S

2012-10-24

281

Systematic investigation of the catalytic cycle of a single site ruthenium oxygen evolving complex using density functional theory.  

PubMed

The mechanism of water oxidation by a single site ruthenium oxygen evolving complex is investigated using fully unrestricted pseudospectral B3LYP with the effective core potential LACV3P in continuum solvent with some quantum mechanical waters. Guess wave functions have been used that allow greater flexibility in sampling different electronic configurations of the complex. Systematic comparison with experiment is improved using these guesses because they provide a complete analysis of the low energy manifold and help to alleviate the formal disconnect between theory and experiment in assigning Lewis structures for transition metal complexes. In agreement with results from the literature, the challenging 4e(-)and 4H(+) oxidation of water is accomplished using a mechanism that features three proton coupled electron transfers, one electron transfer, one atom proton transfer (APT), and one ligand exchange (LE). Calculations on a large database of ruthenium complexes allows us to benchmark the computation of reduction half potentials and free energies of activation and to investigate systematic ligand variations and their effect on the reaction mechanism. Mean unsigned errors of reduction half potentials in comparison to experiment are generally small (100-200 mV). The APT and LE steps are found to be rate limiting with free energy barriers of 19.27 and 19.53 kcal/mol respectively, which is in excellent agreement with the ?20 kcal/mol barrier obtained from experimental rate constants using classical transition state theory. PMID:21678966

Hughes, Thomas F; Friesner, Richard A

2011-06-30

282

The yeast gene ERG6 is required for normal membrane function but is not essential for biosynthesis of the cell-cycle-sparking sterol.  

PubMed Central

In Saccharomyces cerevisiae, methylation of the principal membrane sterol at C-24 produces the C-28 methyl group specific to ergosterol and represents one of the few structural differences between ergosterol and cholesterol. C-28 in S. cerevisiae has been suggested to be essential for the sparking function (W. J. Pinto and W. R. Nes, J. Biol. Chem. 258:4472-4476, 1983), a cell cycle event that may be required to enter G1 (C. Dahl, H.-P. Biemann, and J. Dahl, Proc. Natl. Acad. Sci. USA 84:4012-4016, 1987). The sterol biosynthetic pathway in S. cerevisiae was genetically altered to assess the functional role of the C-28 methyl group of ergosterol. ERG6, the putative structural gene for S-adenosylmethionine: delta 24-methyltransferase, which catalyzes C-24 methylation, was cloned, and haploid strains containing erg6 null alleles (erg6 delta 1 and erg6 delta ::LEU2) were generated. Although erg6 delta cells are unable to methylate ergosterol precursors at C-24, they exhibit normal vegatative growth, suggesting that C-28 sterols are not essential in S. cerevisiae. However, erg6 delta cells exhibit pleiotropic phenotypes that include defective conjugation, hypersensitivity to cycloheximide, resistance to nystatin, a severely diminished capacity for genetic transformation, and defective tryptophan uptake. These phenotypes reflect the role of ergosterol as a regulator of membrane permeability and fluidity. Genetic mapping experiments revealed that ERG6 is located on chromosome XIII, tightly linked to sec59. Images

Gaber, R F; Copple, D M; Kennedy, B K; Vidal, M; Bard, M

1989-01-01

283

RanBP2 and SENP3 function in a mitotic SUMO2/3 conjugation-deconjugation cycle on Borealin.  

PubMed

The ubiquitin-like SUMO system controls cellular key functions, and several lines of evidence point to a critical role of SUMO for mitotic progression. However, in mammalian cells mitotic substrates of sumoylation and the regulatory components involved are not well defined. Here, we identify Borealin, a component of the chromosomal passenger complex (CPC), as a mitotic target of SUMO. The CPC, which additionally comprises INCENP, Survivin, and Aurora B, regulates key mitotic events, including chromosome congression, the spindle assembly checkpoint, and cytokinesis. We show that Borealin is preferentially modified by SUMO2/3 and demonstrate that the modification is dynamically regulated during mitotic progression, peaking in early mitosis. Intriguingly, the SUMO ligase RanBP2 interacts with the CPC, stimulates SUMO modification of Borealin in vitro, and is required for its modification in vivo. Moreover, the SUMO isopeptidase SENP3 is a specific interaction partner of Borealin and catalyzes the removal of SUMO2/3 from Borealin. These data thus delineate a mitotic SUMO2/3 conjugation-deconjugation cycle of Borealin and further assign a regulatory function of RanBP2 and SENP3 in the mitotic SUMO pathway. PMID:18946085

Klein, Ulf R; Haindl, Markus; Nigg, Erich A; Muller, Stefan

2008-10-22

284

A protein required for RNA processing and splicing in Neurospora mitochondria is related to gene products involved in cell cycle protein phosphatase functions.  

PubMed

The Neurospora crassa cyt-4 mutants have pleiotropic defects in mitochondrial RNA splicing, 5' and 3' end processing, and RNA turnover. Here, we show that the cyt-4+ gene encodes a 120-kDa protein with significant similarity to the SSD1/SRK1 protein of Saccharomyces cerevisiae and the DIS3 protein of Schizosaccharomyces pombe, which have been implicated in protein phosphatase functions that regulate cell cycle and mitotic chromosome segregation. The CYT-4 protein is present in mitochondria and is truncated or deficient in two cyt-4 mutants. Assuming that the CYT-4 protein functions in a manner similar to the SSD1/SRK1 and DIS3 proteins, we infer that the mitochondrial RNA splicing and processing reactions defective in the cyt-4 mutants are regulated by protein phosphorylation and that the defects in the cyt-4 mutants result from failure to normally regulate this process. Our results provide evidence that RNA splicing and processing reactions may be regulated by protein phosphorylation. PMID:1311848

Turcq, B; Dobinson, K F; Serizawa, N; Lambowitz, A M

1992-03-01

285

FabQ, a Dual-Function Dehydratase/Isomerase, Circumvents the Last Step of the Classical Fatty Acid Synthesis Cycle.  

PubMed

In the classical anaerobic pathway of unsaturated fatty acid biosynthesis, that of Escherichia coli, the double bond is introduced into the growing acyl chain by the FabA dehydratase/isomerase. Another dehydratase, FabZ, functions in the chain elongation cycle. In contrast, Aerococcus viridans has only a single FabA/FabZ homolog we designate FabQ. FabQ can not only replace the function of E. coli FabZ in vivo, but it also catalyzes the isomerization required for unsaturated fatty acid biosynthesis. Most strikingly, FabQ in combination with E. coli FabB imparts the surprising ability to bypass reduction of the trans-2-acyl-ACP intermediates of classical fatty acid synthesis. FabQ allows elongation by progressive isomerization reactions to form the polyunsaturated fatty acid, 3-hydroxy-cis-5, 7-hexadecadienoic acid, both in vitro and in vivo. FabQ therefore provides a potential pathway for bacterial synthesis of polyunsaturated fatty acids. PMID:23972938

Bi, Hongkai; Wang, Haihong; Cronan, John E

2013-08-22

286

RanBP2 and SENP3 Function in a Mitotic SUMO2/3 Conjugation-Deconjugation Cycle on Borealin  

PubMed Central

The ubiquitin-like SUMO system controls cellular key functions, and several lines of evidence point to a critical role of SUMO for mitotic progression. However, in mammalian cells mitotic substrates of sumoylation and the regulatory components involved are not well defined. Here, we identify Borealin, a component of the chromosomal passenger complex (CPC), as a mitotic target of SUMO. The CPC, which additionally comprises INCENP, Survivin, and Aurora B, regulates key mitotic events, including chromosome congression, the spindle assembly checkpoint, and cytokinesis. We show that Borealin is preferentially modified by SUMO2/3 and demonstrate that the modification is dynamically regulated during mitotic progression, peaking in early mitosis. Intriguingly, the SUMO ligase RanBP2 interacts with the CPC, stimulates SUMO modification of Borealin in vitro, and is required for its modification in vivo. Moreover, the SUMO isopeptidase SENP3 is a specific interaction partner of Borealin and catalyzes the removal of SUMO2/3 from Borealin. These data thus delineate a mitotic SUMO2/3 conjugation–deconjugation cycle of Borealin and further assign a regulatory function of RanBP2 and SENP3 in the mitotic SUMO pathway.

Klein, Ulf R.; Haindl, Markus; Nigg, Erich A.

2009-01-01

287

In vitro mimicking of estrous cycle stages in porcine oviduct epithelium cells: estradiol and progesterone regulate differentiation, gene expression, and cellular function.  

PubMed

Throughout the estrous cycle the oviduct epithelium undergoes dramatic morphological and functional changes. To elucidate cyclic cellular events and associated regulation mechanisms of 17beta estradiol (E2) and progesterone (P4), we mimicked estrous cycle stages in vitro using a culture system of primary porcine oviduct epithelium cells (POEC). Cells were polarized in an air/liquid interface and then treated with E2 and P4 for physiological time periods: In experiment 1, high concentration of P4 with low concentration of E2 for 10 days resembled diestrus; in experiment 2, following the previous diestrus, sequential high E2 with low P4 for 2.5 days represented estrus. Histomorphometry and electron microscopy showed cyclic changes in cellular height, cell population, and cilia density under the influence of hormone stimulation. Transepithelial electrical resistance was high in simulated diestrus but reduced in estrus. Thus, E2 and P4 affect cellular polarity, transformation of ciliated and secretory cells, as well as electrical conductivity of oviduct epithelium. Simulation of diestrus led to significant decrease in expression of hormone receptors (PGR and ESR1) and other epithelial markers (MUC16, OVGP1, and HSP90B1), while sequential simulated estrus caused an increase in these markers. The hormonal regulation of some marker genes was clearly time-dependent. Furthermore, POEC showed increased sperm-binding capacity in simulated estrus. In this study, we also present a novel approach based on the AndroVision software, which can be routinely utilized as a parameter for ciliary activity, and for the first time, we showed fluid movement patterns along the epithelium lining in vitro. PMID:23904510

Chen, Shuai; Einspanier, Ralf; Schoen, Jennifer

2013-09-12

288

Functional genomics and SNP analysis of human genes encoding proline metabolic enzymes  

PubMed Central

Proline metabolism in mammals involves two other amino acids, glutamate and ornithine, and five enzymatic activities, ?1-pyrroline-5-carboxylate (P5C) reductase (P5CR), proline oxidase, P5C dehydrogenase, P5C synthase and ornithine-?-aminotransferase (OAT). With the exception of OAT, which catalyzes a reversible reaction, the other 4 enzymes are unidirectional, suggesting that proline metabolism is purpose-driven, tightly regulated, and compartmentalized. In addition, this tri-amino-acid system also links with three other pivotal metabolic systems, namely the TCA cycle, urea cycle, and pentose phosphate pathway. Abnormalities in proline metabolism are relevant in several diseases: six monogenic inborn errors involving metabolism and/or transport of proline and its immediate metabolites have been described. Recent advances in the Human Genome Project, in silico database mining techniques, and research in dissecting the molecular basis of proline metabolism prompted us to utilize functional genomic approaches to analyze human genes which encode proline metabolic enzymes in the context of gene structure, regulation of gene expression, mRNA variants, protein isoforms, and single nucleotide polymorphisms.

Williams, D. Bart; Zhaorigetu, Siqin; Khalil, Shadi; Wan, Guanghua; Valle, David

2009-01-01

289

carbon cycle  

NSDL National Science Digital Library

Life on earth is based on carbon. Living things acquire carbon from their environment - from air, water, soil, and rock and from other living things - through processes such as photosynthesis, respiration and decomposition. The carbon cycle model is a representation of the movement of carbon from sources to sinks through chemical and physical transfers. The carbon cycle activity allows students to see the effect of fossil fuel burning on the carbon cycle.

School, Maryland V.

290

Metaproteomics Provides Functional Insight into Activated Sludge Wastewater Treatment  

PubMed Central

Background Through identification of highly expressed proteins from a mixed culture activated sludge system this study provides functional evidence of microbial transformations important for enhanced biological phosphorus removal (EBPR). Methodology/Principal Findings A laboratory-scale sequencing batch reactor was successfully operated for different levels of EBPR, removing around 25, 40 and 55 mg/l P. The microbial communities were dominated by the uncultured polyphosphate-accumulating organism “Candidatus Accumulibacter phosphatis”. When EBPR failed, the sludge was dominated by tetrad-forming ?-Proteobacteria. Representative and reproducible 2D gel protein separations were obtained for all sludge samples. 638 protein spots were matched across gels generated from the phosphate removing sludges. 111 of these were excised and 46 proteins were identified using recently available sludge metagenomic sequences. Many of these closely match proteins from “Candidatus Accumulibacter phosphatis” and could be directly linked to the EBPR process. They included enzymes involved in energy generation, polyhydroxyalkanoate synthesis, glycolysis, gluconeogenesis, glycogen synthesis, glyoxylate/TCA cycle, fatty acid ? oxidation, fatty acid synthesis and phosphate transport. Several proteins involved in cellular stress response were detected. Conclusions/Significance Importantly, this study provides direct evidence linking the metabolic activities of “Accumulibacter” to the chemical transformations observed in EBPR. Finally, the results are discussed in relation to current EBPR metabolic models.

Wilmes, Paul; Wexler, Margaret; Bond, Philip L.

2008-01-01

291

Match/X, A gene expression pattern recognition algorithm used to identify genes which may be related to CDC2 function and cell cycle regulation.  

PubMed

Large-scale microarray gene expression studies can provide insight into complex genetic networks and biological pathways. A comprehensive gene expression database was constructed using Affymetrix GeneChip microarrays and RNA isolated from more than 6,400 distinct normal and diseased human tissues. These individual patient samples were grouped into over 700 sample sets based on common tissue and disease morphologies, and each set contained averaged expression data for over 45,000 gene probe sets representing more than 33,000 known human genes. Sample sets were compared to each other in more than 750 normal vs. disease pairwise comparisons. Relative up or downregulation patterns of genes across these pairwise comparisons provided unique expression fingerprints that could be compared and matched to a gene of interest using the Match/X trade mark algorithm. This algorithm uses the kappa statistic to compute correlations between genes and calculate a distance score between a gene of interest and all other genes in the database. Using cdc2 as a query gene, we identified several hundred genes that had similar expression patterns and highly correlated distance scores. Most of these genes were known components of the cell cycle involved in G2/M progression, spindle function or chromosome arrangement. Some of the identified genes had unknown biological functions but may be related to cdc2 mediated mechanism based on their closely correlated distance scores. This algorithm may provide novel insights into unknown gene function based on correlation to expression profiles of known genes and can identify elements of cellular pathways and gene interactions in a high throughput fashion. PMID:15136762

Coberley, Carter; Elashoff, Michael; Mertz, Lawrence

2004-06-02

292

Control and Regulation of Integrated Mitochondrial Function in Metabolic and Transport Networks  

PubMed Central

The pattern of flux and concentration control coefficients in an integrated mitochondrial energetics model is examined by applying a generalized matrix method of control analysis to calculate control coefficients, as well as response coefficients The computational model of Cortassa et al. encompasses oxidative phosphorylation, the TCA cycle, and Ca2+ dynamics. Control of ATP synthesis, TCA cycle, and ANT fluxes were found to be distributed among various mitochondrial processes. Control is shared by processes associated with ATP/ADP production and transport, as well as by Ca2+ dynamics. The calculation also analyzed the control of the concentrations of key regulatory ions and metabolites (Ca2+, NADH, ADP). The approach we have used demonstrates how properties of integrated systems may be understood through applications of computational modeling and control analysis.

Cortassa, Sonia; O'Rourke, Brian; Winslow, Raimond L.; Aon, Miguel A.

2009-01-01

293

Control and regulation of integrated mitochondrial function in metabolic and transport networks.  

PubMed

The pattern of flux and concentration control coefficients in an integrated mitochondrial energetics model is examined by applying a generalized matrix method of control analysis to calculate control coefficients, as well as response coefficients The computational model of Cortassa et al. encompasses oxidative phosphorylation, the TCA cycle, and Ca(2+) dynamics. Control of ATP synthesis, TCA cycle, and ANT fluxes were found to be distributed among various mitochondrial processes. Control is shared by processes associated with ATP/ADP production and transport, as well as by Ca(2+) dynamics. The calculation also analyzed the control of the concentrations of key regulatory ions and metabolites (Ca(2+), NADH, ADP). The approach we have used demonstrates how properties of integrated systems may be understood through applications of computational modeling and control analysis. PMID:19468321

Cortassa, Sonia; O'Rourke, Brian; Winslow, Raimond L; Aon, Miguel A

2009-04-01

294

Thermochemical safety evaluation of tertiary pyridine resin for the application to multi-functional reprocessing process “Adv.ORIENT cycle development”  

Microsoft Academic Search

As part of “Adv.-ORIENT” (Advanced Optimization by Recycling Instructive ElemeNTs) cycle technologies, which aim to develop a new fuel cycle based on a fast reactor cycle system, the reactivity between a tertiary pyridine resin (TPR) and a methanol-nitric acid solution at elevated temperatures has been investigated in order to prevent runaway reactions. The influence of metal ions, which simulate metallic

Yoshihiko Sato; Ken Okada; Miyako Akiyoshi; Takehiro Matsunaga; Shin-ichi Koyama; Tatsuya Suzuki; Masaki Ozawa

2011-01-01

295

The Association of Cell Cycle Checkpoint 2 Variants and Kidney Function: Findings of the Family Blood Pressure Program and the Atherosclerosis Risk in Communities Study  

PubMed Central

BACKGROUND Recent experimental evidence suggests that DNA damage and cell cycle regulatory proteins are involved in kidney injury and apoptosis. The checkpoint 2 gene (CHEK2) is an important transducer in DNA damage signaling pathways in response to injury, and therefore, CHEK2 variants may affect susceptibility to kidney disease. METHODS We used tag-single-nucleotide polymorphisms (tag-SNPs) to evaluate the association of the CHEK2 with kidney function (estimated glomerular filtration rate, eGFR) in 1,549 African-American and 1,423 white Hypertension Genetic Epidemiology Network (HyperGEN) participants. We performed replication analyses in the Genetic Epidemiology Network of Arteriopathy (GENOA) participants (1,746 African Americans and 1,418 whites), GenNet participants (706 whites), and Atherosclerosis Risk in Communities (ARIC) study participants (3,783 African Americans and 10,936 whites). All analyses were race-stratified and used additive genetic models with adjustments for covariates and for family structure, if needed. RESULTS One tag-SNP, rs5762764, was associated with eGFR in HyperGEN P = (0.003) and GENOA white participants (P = 0.009), and it was significantly associated with eGFR in meta-analyses (P = 0.002). The associations were independent of type 2 diabetes. CONCLUSIONS These results suggest that CHEK2 variants may influence eGFR in the context of hypertension.

Franceschini, Nora; North, Kari E.; Arnett, Donna; Pankow, James S.; Chung, Jay H.; Baird, Lisa; Leppert, Mark F.; Eckfeldt, John H.; Boerwinkle, Eric; Gu, C. Charles; Lewis, Cora E.; Myers, Richard H.; Turner, Stephen T.; Weder, Alan; Kao, W.H. Linda; Mosley, Thomas H.; Chakravarti, Aravinda; Kramer, Holly; Zhang, Jinghui; Hunt, Steven C.

2009-01-01

296

Role for a region of helically unstable DNA within the Epstein-Barr virus latent cycle origin of DNA replication oriP in origin function  

SciTech Connect

The minimal replicator of the Epstein-Barr virus (EBV) latent cycle origin of DNA replication oriP is composed of two binding sites for the Epstein-Barr virus nuclear antigen-1 (EBNA-1) and flanking inverted repeats that bind the telomere repeat binding factor TRF2. Although not required for minimal replicator activity, additional binding sites for EBNA-1 and TRF2 and one or more auxiliary elements located to the right of the EBNA-1/TRF2 sites are required for the efficient replication of oriP plasmids. Another region of oriP that is predicted to be destabilized by DNA supercoiling is shown here to be an important functional component of oriP. The ability of DNA fragments of unrelated sequence and possessing supercoiled-induced DNA duplex destabilized (SIDD) structures, but not fragments characterized by helically stable DNA, to substitute for this component of oriP demonstrates a role for the SIDD region in the initiation of oriP-plasmid DNA replication.

Polonskaya, Zhanna [Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794 (United States); Benham, Craig J. [Department of Mathematics, University of California at Davis, Davis, CA 95616 (United States); Hearing, Janet [Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794 (United States)]. E-mail: jhearing@ms.cc.sunysb.edu

2004-10-25

297

A decay function model for the integrity loss of rock when subjected to recurrent cycles of freezing–thawing and heating–cooling  

Microsoft Academic Search

Rocks are used in engineering works as monument or building stone and as architectural covering stone. As a result, they can be subjected to recurrent cycles of freezing and thawing and will be subjected to heating and cooling. They loose some of their integrity under these cyclic temperature variations and the more frequent and severe these cycles, the higher the

M Mutlutürk; R Altindag; G Türk

2004-01-01

298

Thermal Fatigue of SnPb and SAC Resistor Joints: Analysis of Stress-Strain as a Function of Cycle Parameters  

Microsoft Academic Search

Accelerated thermal cycling (ATC) has been widely used in the microelectronics industry for reliability assessment. The relative effects of thermal cycling parameters (temperature range, dwell time, and ramp rate) and the failure mechanisms they induce have been the subject of many studies; however, uncertainty remains, particularly regarding the role of a very high ramp rate such as encountered in a

Yan Qi; Hamid R. Ghorbani; Jan K. Spelt

2006-01-01

299

Estimating Seasonal Cycles of Atmospheric CO2 and APO Resulting from Terrestrial NEE and Air-Sea O2 Fluxes using the Transcom T3L2 Pulse-Response Functions  

NASA Astrophysics Data System (ADS)

We present a method for translating modeled terrestrial net ecosystem exchange (NEE) fluxes of carbon into the corresponding annual mean cycles in atmospheric CO2. The method is based on the pulse-response functions from the Transcom 3 atmospheric tracer transport model (ATM) intercomparison. An oceanic version of the method is applied to air-sea O2 fluxes to estimate the corresponding annual mean cycles in atmospheric potential oxygen (APO). The estimated atmospheric seasonal cycles can be evaluated against observed atmospheric CO2 and APO data, which are measured at high precision at a wide range of monitoring sites and reflect the integrated impact of surface CO2 and O2 fluxes, respectively, across broad regions. The pulse-response function method is considerably faster than a full forward ATM simulation, allowing seasonal cycles from 13 different ATMS to be computed in minutes, rather than the days or weeks required for a single forward simulation. We evaluate the method against the results of full forward ATM simulations and examine the uncertainties associated with neglecting additional surface fluxes, e.g., from fossil fuel combustion, that may contribute to the observed seasonal cycles of CO2 and APO.

Nevison, C. D.

2011-12-01

300

Determining novel functions of Arabidopsis 14-3-3 proteins in central metabolic processes  

PubMed Central

Background 14-3-3 proteins are considered master regulators of many signal transduction cascades in eukaryotes. In plants, 14-3-3 proteins have major roles as regulators of nitrogen and carbon metabolism, conclusions based on the studies of a few specific 14-3-3 targets. Results In this study, extensive novel roles of 14-3-3 proteins in plant metabolism were determined through combining the parallel analyses of metabolites and enzyme activities in 14-3-3 overexpression and knockout plants with studies of protein-protein interactions. Decreases in the levels of sugars and nitrogen-containing-compounds and in the activities of known 14-3-3-interacting-enzymes were observed in 14-3-3 overexpression plants. Plants overexpressing 14-3-3 proteins also contained decreased levels of malate and citrate, which are intermediate compounds of the tricarboxylic acid (TCA) cycle. These modifications were related to the reduced activities of isocitrate dehydrogenase and malate dehydrogenase, which are key enzymes of TCA cycle. In addition, we demonstrated that 14-3-3 proteins interacted with one isocitrate dehydrogenase and two malate dehydrogenases. There were also changes in the levels of aromatic compounds and the activities of shikimate dehydrogenase, which participates in the biosynthesis of aromatic compounds. Conclusion Taken together, our findings indicate that 14-3-3 proteins play roles as crucial tuners of multiple primary metabolic processes including TCA cycle and the shikimate pathway.

2011-01-01

301

Weather Cycles  

NASA Astrophysics Data System (ADS)

This completely updated edition explores in detail the unresolved debate on the existence of weather cycles. It provides a different perspective on one of the most difficult questions in the current global warming debate: how much of the recent temperature rise can be attributed to natural causes? The book examines the complex analysis required to assess the evidence for cycles with a minimum of mathematics. First Edition Hb (1992): 0-521-38178-9 First Edition Pb (1995): 0-521-47869-3

Burroughs, William James

2003-12-01

302

Vapor Compression Cycle Design Program (CYCLE_D)  

National Institute of Standards and Technology Data Gateway

SRD 49 NIST Vapor Compression Cycle Design Program (CYCLE_D) (PC database for purchase)   The CYCLE_D database package simulates the vapor compression refrigeration cycles. It is fully compatible with REFPROP 9.0 and covers the 62 single-compound refrigerants . Fluids can be used in mixtures comprising up to five components.

303

Transcriptome alterations following developmental atrazine exposure in zebrafish are associated with disruption of neuroendocrine and reproductive system function, cell cycle, and carcinogenesis.  

PubMed

Atrazine, a herbicide commonly applied to agricultural areas and a common contaminant of potable water supplies, is implicated as an endocrine-disrupting chemical (EDC) and potential carcinogen. Studies show that EDCs can cause irreversible changes in tissue formation, decreased reproductive potential, obesity, and cancer. The U.S. Environmental Protection Agency considers an atrazine concentration of ? 3 ppb in drinking water safe for consumption. The specific adverse human health effects associated with a developmental atrazine exposure and the underlying genetic mechanisms of these effects are not well defined. In this study, zebrafish embryos were exposed to a range of atrazine concentrations to establish toxicity. Morphological, transcriptomic, and protein alterations were then assessed at 72h postfertilization following developmental atrazine exposure at 0, 0.3, 3, or 30 ppb. A significant increase in head length was observed in all three atrazine treatments. Transcriptomic profiles revealed 21, 62, and 64 genes with altered expression in the 0.3, 3, and 30 ppb atrazine treatments, respectively. Altered genes were associated with neuroendocrine and reproductive system development, function, and disease; cell cycle control; and carcinogenesis. There was a significant overlap (42 genes) between the 3 and 30 ppb differentially expressed gene lists, with two of these genes (CYP17A1 and SAMHD1) present in all three atrazine treatments. Increased transcript levels were translated to significant upregulation in protein expression. Overall, this study identifies genetic and molecular targets altered in response to a developmental atrazine exposure to further define the biological pathways and mechanisms of toxicity. PMID:23358194

Weber, Gregory J; Sepúlveda, Maria S; Peterson, Samuel M; Lewis, Solange S; Freeman, Jennifer L

2013-01-28

304

A functional link between the human cell cycle-regulatory phosphatase Cdc14A and the atypical mitogen-activated kinase Erk3.  

PubMed

Cdc14 is a member of the dual-specificity phosphatase family, which is essential for faithful cell cycle progression in eukaryotic cells of different origin. The function of human Cdc14A (hCdc14A), however, has not been fully elucidated as only few physiological substrates have been identified. To gain insight into the biological role of Cdc14A, we performed a yeast two-hybrid screen designed to isolate substrates of this human phosphatase. Using this genetic approach, we here report the identification of Erk3, an atypical mitogen-activated protein kinase (MAPK), as a specific binding partner of hCdc14A. GST pull-down assays show that Erk3 interacts directly with hCdc14A in vitro via its unique C-terminal domain. Furthermore, biochemical analysis reveals that hCdc14A can remove cyclin-dependent kinase (Cdk)-mediated phosphorylation of Erk3 in vitro raising the possibility that Erk3 may be a potential substrate for hCdc14A in vivo. Consistent with a physiologically relevant cross-talk in vivo, we find that Cdc14A forms a stable complex with Erk3 in human cells independent of its intrinsic phosphatase activity but mediated by its regulatory C-terminal domain. We show that hCdc14A impacts the emerging signaling pathway between Erk3 and MK5, a MAPK-activated protein kinase. We document that hCdc14A upregulation leads to redistribution of the Erk3 substrate MK5 from the nucleus to the cytoplasm. In addition, we find that hCdc14A stabilizes complex formation between Erk3 and its binding partner cyclin D3, a D-type cyclin implicated in both cellular proliferation and differentiation. Collectively, our findings suggest an intimate functional relationship between the Cdc14A phosphatase and the Erk3 kinase in signaling pathways that regulate key cell-fate decisions in human cells. PMID:18235225

Hansen, Christina Aaen; Bartek, Jiri; Jensen, Sanne

2007-11-30

305

Sn-Ag-Cu Solder Joint Microstructure and Orientation Evolution as a Function of Position and Thermal Cycles in Ball Grid Arrays Using Orientation Imaging Microscopy  

NASA Astrophysics Data System (ADS)

Thermally cycled plastic ball grid array (PBGA) packages with full arrays of 196 solder joints after various preconditions were examined to observe the microstructure evolution of Sn-Ag-Cu solder joints during aging and thermal cycling, focusing on Sn grain orientation. Each PBGA package was polished to obtain a plan-view cross-section of every solder joint, and characterized using both polarized optical microscopy and orientation imaging microscopy (OIM). By OIM observations, distribution maps were obtained based on Sn crystal c-axis orientations. Each precondition showed a characteristic distribution related to the combined thermal aging and thermal cycling history. This study on Sn grain orientation using OIM provides further understanding about deformation and microstructure evolution processes that occur during thermal cycling, and the impact of isothermal aging as a precondition.

Lee, Tae-Kyu; Zhou, Bite; Blair, Lauren; Liu, Kuo-Chuan; Bieler, Thomas R.

2010-12-01

306

Hydrological cycle.  

PubMed

The Pantanal hydrological cycle holds an important meaning in the Alto Paraguay Basin, comprising two areas with considerably diverse conditions regarding natural and water resources: the Plateau and the Plains. From the perspective of the ecosystem function, the hydrological flow in the relationship between plateau and plains is important for the creation of reproductive and feeding niches for the regional biodiversity. In general, river declivity in the plateau is 0.6 m/km while declivity on the plains varies from 0.1 to 0.3 m/km. The environment in the plains is characteristically seasonal and is home to an exuberant and abundant diversity of species, including some animals threatened with extinction. When the flat surface meets the plains there is a diminished water flow on the riverbeds and, during the rainy season the rivers overflow their banks, flooding the lowlands. Average annual precipitation in the Basin is 1,396 mm, ranging from 800 mm to 1,600 mm, and the heaviest rainfall occurs in the plateau region. The low drainage capacity of the rivers and lakes that shape the Pantanal, coupled with the climate in the region, produce very high evaporation: approximately 60% of all the waters coming from the plateau are lost through evaporation. The Alto Paraguay Basin, including the Pantanal, while boasting an abundant availability of water resources, also has some spots with water scarcity in some sub-basins, at different times of the year. Climate conditions alone are not enough to explain the differences observed in the Paraguay River regime and some of its tributaries. The complexity of the hydrologic regime of the Paraguay River is due to the low declivity of the lands that comprise the Mato Grosso plains and plateau (50 to 30 cm/km from east to west and 3 to 1.5 cm/km from north to south) as well as the area's dimension, which remains periodically flooded with a large volume of water. PMID:21537597

Gonçalves, H C; Mercante, M A; Santos, E T

2011-04-01

307

Oscillation of ADP-ribosyl cyclase activity during the cell cycle and function of cyclic ADP-ribose in a unicellular organism, Euglena gracilis  

Microsoft Academic Search

In Euglena gracilis, the activity of ADP-ribosyl cyclase, which produces cyclic ADP-ribose, oscillated during the cell cycle in a synchronous culture induced by a light-dark cycle, and a marked increase in the activity was observed in the G2 phase. Similarly, the ADP-ribosyl cyclase activity rose extremely immediately before cell division started, when synchronous cell division was induced by adding cobalamin

Wataru Masuda; Shigeo Takenaka; Kiyoshi Inageda; Hiroshi Nishina; Katsunobu Takahashi; Toshiaki Katada; Shingo Tsuyama; Hiroshi Inui; Kazutaka Miyatake; Yoshihisa Nakano

1997-01-01

308

Final Report - The Xanthophyll Cycle  

Microsoft Academic Search

The xanthophyll cycle is a ubiquitous activity in higher plants. A major function of the cycle is to protect the photosynthetic system from the potentially damaging effects of high light by dissipating excess energy that might otherwise damage the photosynthetic apparatus harmlessly as heat by a process termed non-photochemical quenching (NFQ). This research focused on investigating the dynamics of the

Harry Yamamato

2005-01-01

309

A comparative look at sunspot cycles  

NASA Astrophysics Data System (ADS)

On the basis of cycles 8 through 20, spanning about 143 years, observations of sunspot number, smoothed sunspot number, and their temporal properties were used to compute means, standard deviations, ranges, and frequency of occurrence histograms for a number of sunspot cycle parameters. The resultant schematic sunspot cycle was contrasted with the mean sunspot cycle, obtained by averaging smoothed sunspot number as a function of time, tying all cycles (8 through 20) to their minimum occurence date. A relatively good approximation of the time variation of smoothed sunspot number for a given cycle is possible if sunspot cycles are regarded in terms of being either HIGH- or LOW-R(MAX) cycles or LONG- or SHORT-PERIOD cycles, especially the latter. Linear regression analyses were performed comparing late cycle parameters with early cycle parameters and solar cycle number. The early occurring cycle parameters can be used to estimate later occurring cycle parameters with relatively good success, based on cycle 21 as an example. The sunspot cycle record clearly shows that the trend for both R(MIN) and R(MAX) was toward decreasing value between cycles 8 through 14 and toward increasing value between cycles 14 through 20. Linear regression equations were also obtained for several measures of solar activity.

Wilson, R. M.

1984-05-01

310

Cycle Sequencing  

NSDL National Science Digital Library

This animation from Cold Spring Harbor Laboratory's Dolan DNA Learning Center presents the cycle sequencing. The animation contains instructions on how to sequence a piece of DNA beginning with the raw materials needed, and details on the process: "Fluorescent dyes are added to the reactions, and a laser within an automated DNA sequencing machine is used to analyze the DNA fragments produced."

2011-11-23

311

Menu Cycles.  

ERIC Educational Resources Information Center

The curriculum guide for commercial foods instruction is designed to aid the teacher in communicating the importance of menu cycles in commercial food production. It also provides information about the necessary steps in getting food from the raw form to the finished product, and then to the consumer. In addition to providing information on how to…

Clayton, Alfred; Almony, John

312

Phosphorylation of minichromosome maintenance protein 7 (MCM7) by cyclin/cyclin-dependent kinase affects its function in cell cycle regulation.  

PubMed

MCM7 is one of the subunits of the MCM2-7 complex that plays a critical role in DNA replication initiation and cell proliferation of eukaryotic cells. After forming the pre-replication complex (pre-RC) with other components, the MCM2-7 complex is activated by DDK/cyclin-dependent kinase to initiate DNA replication. Each subunit of the MCM2-7 complex functions differently under regulation of various kinases on the specific site, which needs to be investigated in detail. In this study, we demonstrated that MCM7 is a substrate of cyclin E/Cdk2 and can be phosphorylated on Ser-121. We found that the distribution of MCM7-S121A is different from wild-type MCM7 and that the MCM7-S121A mutant is much less efficient to form a pre-RC complex with MCM3/MCM5/cdc45 compared with wild-type MCM7. By using the Tet-On inducible HeLa cell line, we revealed that overexpression of wild-type MCM7 but not MCM7-S121A can block S phase entry, suggesting that an excess of the pre-RC complex may activate the cell cycle checkpoint. Further analysis indicates that the Chk1 pathway is activated in MCM7-overexpressed cells in a p53-dependent manner. We performed experiments with the human normal cell line HL-7702 and also observed that overexpression of MCM7 can cause S phase block through checkpoint activation. In addition, we found that MCM7 could also be phosphorylated by cyclin B/Cdk1 on Ser-121 both in vitro and in vivo. Furthermore, overexpression of MCM7-S121A causes an obvious M phase exit delay, which suggests that phosphorylation of MCM7 on Ser-121 in M phase is very important for a proper mitotic exit. These data suggest that the phosphorylation of MCM7 on Ser-121 by cyclin/Cdks is involved in preventing DNA rereplication as well as in regulation of the mitotic exit. PMID:23720738

Wei, Qian; Li, Junhui; Liu, Ting; Tong, Xiaomei; Ye, Xin

2013-05-17

313

Ultrafast thermal cycling of solar panels  

SciTech Connect

Two new cyclers that utilize a novel hybrid approach to perform fast thermal cycling of solar panels have been built and are now operational in the Mechanics and Materials Technology Center at The Aerospace Corporation. These cyclers are part of a continuing effort to minimize solar cell life test durations by accelerating the cycling rates. These fully automated cyclers, which provide continuous unmanned cycling in a gaseous nitrogen atmosphere, can execute 5 min cycles, thus yielding in excess of 100,000 cycles per year. They also have a unique capability of verifying solar panel functionality without interruption of cycling, so that cycling doesn`t continue on nonfunctioning panels.

Wall, T.S.; Valenzuela, P.R.; Sue, C.

1998-08-15

314

A Functional Calvin Cycle Is Not Indispensable for the Light Activation of C4 Phosphoenolpyruvate Carboxylase Kinase and Its Target Enzyme in the Maize Mutant bundle sheath defective2-mutable1  

Microsoft Academic Search

We used a pale-green maize (Zea mays L.) mutant that fails to accumulate ribulose-1,5-bisphosphate carboxylase\\/oxygenase (Rubisco) to test the working hypothesis that the regulatory phos- phorylation of C4 phosphoenolpyruvate carboxylase (PEPC) by its Ca21-insensitive protein-serine\\/threonine kinase (PEPC kinase) in the C4 mesophyll cytosol depends on cross-talk with a functional Calvin cycle in the bundle sheath. Wild-type (W22) and bundle sheath

Lucy H. Smith; Jane A. Langdale; Raymond Chollet

1998-01-01

315

Technology Life Cycle.  

National Technical Information Service (NTIS)

OUTLINE: DoD Life Cycle - NASA Life Cycle - Generic Life Cycle - Technology Readiness Levels - Exceptions - Product Life Cycle - Product and Technology Life Cycles Together. CONCLUSION: Technology Maturity Measures Where You are in the Technology Life Cyc...

B. Nolte

2006-01-01

316

The Water Cycle  

NSDL National Science Digital Library

4th Grade Science Learn all about the Water Cycle! The Water Cycle: Water Storage Learn about Evaporation, Condensation, Precipitation, and Collection! The Water Cycle Here are some activites to learn about the water cycle. Hydrologic Cycle ...

Andrus, Ms.

2007-10-12

317

Carbon Cycle  

NSDL National Science Digital Library

Elementary students often successfully memorize and repeat back the stages in cycles, with no deep conceptual understanding of the complexities of the processes involved. Their ability to synthesize knowledge of the cycles with a wider breadth of information related to real-world, unresolved environmental issues such as global warming, greenhouse gas emissions or the burning of biomass for fuel is probably less well developed. In order to engage in meaningful discussions of carbon-related environmental issues, students also need an understanding of the changing nature of the earth s atmosphere. The relative proportion of nitrogen, carbon dioxide, oxygen, ozone and other gases is neither consistent around the world nor constant over time. What factors contribute to the variability in atmospheric content? Which of the factors should be controlled? What are the possible approaches to controlling them? What are the possible and probable outcomes of such controlling measures?

Lefever, Mary

2007-01-01

318

In vivo effects of the soluble fraction of light cycle oil on immune functions in the European sea bass, Dicentrarchus labrax (Linné)  

Microsoft Academic Search

Hydrocarbons are major contaminants that may affect biota at various trophic levels in estuaries and coastal ecosystems. The effects of accidental pollution by light cycle oil (LCO), a refined product of heavy fuel oil, on bioaccumulation, depuration processes and immune-related parameters in the European sea bass, Dicentrarchus labrax, were investigated in the laboratory after 7 days of exposure and a

Anne Bado-Nilles; Claire Quentel; David Mazurais; José Luis Zambonino-Infante; Michel Auffret; Hélčne Thomas-Guyon; Stéphane Le Floch

2011-01-01

319

Effects of neonatal treatment with phytoestrogens, genistein and daidzein, on sex difference in female rat brain function: estrous cycle and lordosis  

Microsoft Academic Search

It is well known that neonatal exposure to estrogen induces masculinization or defeminization of the brain. In this study, the effects of neonatal treatment with two kinds of soybean isoflavone aglycone, genistein (GS) and daidzein (DZ), on the estrous cycle and lordosis behavior were investigated. Female rats were injected subcutaneously with 1 mg GS, 1 mg DZ, 100 ?g estradiol

Tom Kouki; Miki Kishitake; Miho Okamoto; Izumi Oosuka; Minoru Takebe; Korehito Yamanouchi

2003-01-01

320

A methodology for estimating seasonal cycles of atmospheric CO2 resulting from terrestrial net ecosystem exchange (NEE) fluxes using the Transcom T3L2 pulse-response functions  

NASA Astrophysics Data System (ADS)

We present a method for translating modeled terrestrial net ecosystem exchange (NEE) fluxes of carbon into the corresponding seasonal cycles in atmospheric CO2. The method is based on the pulse-response functions from the Transcom 3 Level 2 (T3L2) atmospheric tracer transport model (ATM) intercomparison. The new pulse-response method is considerably faster than a full forward ATM simulation, allowing CO2 seasonal cycles to be computed in seconds, rather than the days or weeks required for a forward simulation. Further, the results provide an estimate of the range of transport uncertainty across 13 different ATMs associated with the translation of surface NEE fluxes into an atmospheric signal. We evaluate the method against the results of archived forward ATM simulations from T3L2. The latter are also used to estimate the uncertainties associated with oceanic and fossil fuel influences. We present a regional breakdown at selected monitoring sites of the contribution to the atmospheric CO2 cycle from the 11 different T3L2 land regions. A test case of the pulse-response code, forced by NEE fluxes from the Community Land Model, suggests that for many terrestrial models, discrepancies between model results and observed atmospheric CO2 cycles will be large enough to clearly transcend ATM uncertainties.

Nevison, C. D.; Baker, D. F.; Gurney, K. R.

2012-09-01

321

FOXO1-mediated upregulation of pyruvate dehydrogenase kinase-4 (PDK4) decreases glucose oxidation and impairs right ventricular function in pulmonary hypertension: therapeutic benefits of dichloroacetate.  

PubMed

Pyruvate dehydrogenase kinase (PDK) is activated in right ventricular hypertrophy (RVH), causing an increase in glycolysis relative to glucose oxidation that impairs right ventricular function. The stimulus for PDK upregulation, its isoform specificity, and the long-term effects of PDK inhibition are unknown. We hypothesize that FOXO1-mediated PDK4 upregulation causes bioenergetic impairment and RV dysfunction, which can be reversed by dichloroacetate. Adult male Fawn-Hooded rats (FHR) with pulmonary arterial hypertension (PAH) and right ventricular hypertrophy (RVH; age 6-12 months) were compared to age-matched controls. Glucose oxidation (GO) and fatty acid oxidation (FAO) were measured at baseline and after acute dichloroacetate (1 mM × 40 min) in isolated working hearts and in freshly dispersed RV myocytes. The effects of chronic dichloroacetate (0.75 g/L drinking water for 6 months) on cardiac output (CO) and exercise capacity were measured in vivo. Expression of PDK4 and its regulatory transcription factor, FOXO1, were also measured in FHR and RV specimens from PAH patients (n = 10). Microarray analysis of 168 genes related to glucose or FA metabolism showed >4-fold upregulation of PDK4, aldolase B, and acyl-coenzyme A oxidase. FOXO1 was increased in FHR RV, whereas HIF-1 ? was unaltered. PDK4 expression was increased, and the inactivated form of FOXO1 decreased in human PAH RV (P < 0.01). Pyruvate dehydrogenase (PDH) inhibition in RVH increased proton production and reduced GO's contribution to the tricarboxylic acid (TCA) cycle. Acutely, dichloroacetate reduced RV proton production and increased GO's contribution (relative to FAO) to the TCA cycle and ATP production in FHR (P < 0.01). Chronically dichloroacetate decreased PDK4 and FOXO1, thereby activating PDH and increasing GO in FHR. These metabolic changes increased CO (84 ± 14 vs. 69 ± 14 ml/min, P < 0.05) and treadmill-walking distance (239 ± 20 vs. 171 ± 22 m, P < 0.05). Chronic dichloroacetate inhibits FOXO1-induced PDK4 upregulation and restores GO, leading to improved bioenergetics and RV function in RVH. PMID:23247844

Piao, Lin; Sidhu, Vaninder K; Fang, Yong-Hu; Ryan, John J; Parikh, Kishan S; Hong, Zhigang; Toth, Peter T; Morrow, Erik; Kutty, Shelby; Lopaschuk, Gary D; Archer, Stephen L

2012-12-18

322

Oscillation of ADP-ribosyl cyclase activity during the cell cycle and function of cyclic ADP-ribose in a unicellular organism, Euglena gracilis.  

PubMed

In Euglena gracilis, the activity of ADP-ribosyl cyclase, which produces cyclic ADP-ribose, oscillated during the cell cycle in a synchronous culture induced by a light-dark cycle, and a marked increase in the activity was observed in the G2 phase. Similarly, the ADP-ribosyl cyclase activity rose extremely immediately before cell division started, when synchronous cell division was induced by adding cobalamin (which is an essential growth factor and participates in DNA synthesis in this organism) to its deficient culture. Further, cADPR in these cells showed a maximum level immediately before cell division started. A dose-dependent Ca2+ release was observed when microsomes were incubated with cADPR. PMID:9094434

Masuda, W; Takenaka, S; Inageda, K; Nishina, H; Takahashi, K; Katada, T; Tsuyama, S; Inui, H; Miyatake, K; Nakano, Y

1997-03-17

323

The evolution of the Calvin cycle from prokaryotic to eukaryotic chromosomes: a case study of functional redundancy in ancient pathways through endosymbiosis  

Microsoft Academic Search

The evolutionary histories of the 12 enzymes that catalyze the reactions of the Calvin cycle in higher-plant chloroplasts\\u000a are summarized. They are shown to be encoded by a mixture of nuclear genes of cyanobacterial and proteobacterial origin. Moreover,\\u000a where cytosolic isoforms of these enzymes are found they are almost invariably encoded by genes of clearly endosymbiont origin.\\u000a We infer that

William Martin; Claus Schnarrenberger

1997-01-01

324

Chromium(III) Triggers the DNA-Damaged Checkpoint of the Cell Cycle and Induces a Functional Increase of 4EBP  

Microsoft Academic Search

Using sea urchin early embryos as a pertinent model, chromium(III) provoked cell cycle arrest and induced apoptosis. The molecular machinery of translation initiation was investigated. Chromium provoked a time- and dose-dependent increase in the level of 4E-BP protein, the natural regulator of the cap- dependent initiation factor 4E (eIF4E). The 4E-BP increase was the result of 4E-BP stabilization and appeared

Ronan Le Bouffant; Odile Mulner-Lorillon; Julia Morales; Patrick Cormier; Robert Bellé

2008-01-01

325

Serial Regulation of Transcriptional Regulators in the Yeast Cell Cycle  

Microsoft Academic Search

Genome-wide location analysis was used to determine how the yeast cell cycle gene expression program is regulated by each of the nine known cell cycle transcriptional activators. We found that cell cycle transcriptional activators that function during one stage of the cell cycle regulate transcriptional activators that function during the next stage. This serial regulation of transcriptional activators forms a

Itamar Simon; John Barnett; Nancy Hannett; Christopher T Harbison; Nicola J Rinaldi; Thomas L Volkert; John J Wyrick; Julia Zeitlinger; David K Gifford; Tommi S Jaakkola; Richard A Young

2001-01-01

326

The Usher 1B protein, MYO7A, is required for normal localization and function of the visual retinoid cycle enzyme, RPE65.  

PubMed

Mutations in the MYO7A gene cause a deaf-blindness disorder, known as Usher syndrome 1B.  In the retina, the majority of MYO7A is in the retinal pigmented epithelium (RPE), where many of the reactions of the visual retinoid cycle take place.  We have observed that the retinas of Myo7a-mutant mice are resistant to acute light damage. In exploring the basis of this resistance, we found that Myo7a-mutant mice have lower levels of RPE65, the RPE isomerase that has a key role in the retinoid cycle.  We show for the first time that RPE65 normally undergoes a light-dependent translocation to become more concentrated in the central region of the RPE cells.  This translocation requires MYO7A, so that, in Myo7a-mutant mice, RPE65 is partly mislocalized in the light.  RPE65 is degraded more quickly in Myo7a-mutant mice, perhaps due to its mislocalization, providing a plausible explanation for its lower levels.  Following a 50-60% photobleach, Myo7a-mutant retinas exhibited increased all-trans-retinyl ester levels during the initial stages of dark recovery, consistent with a deficiency in RPE65 activity.  Lastly, MYO7A and RPE65 were co-immunoprecipitated from RPE cell lysate by antibodies against either of the proteins, and the two proteins were partly colocalized, suggesting a direct or indirect interaction.  Together, the results support a role for MYO7A in the translocation of RPE65, illustrating the involvement of a molecular motor in the spatiotemporal organization of the retinoid cycle in vision. PMID:21493626

Lopes, Vanda S; Gibbs, Daniel; Libby, Richard T; Aleman, Tomas S; Welch, Darcy L; Lillo, Concepción; Jacobson, Samuel G; Radu, Roxana A; Steel, Karen P; Williams, David S

2011-04-14

327

The Usher 1B protein, MYO7A, is required for normal localization and function of the visual retinoid cycle enzyme, RPE65  

PubMed Central

Mutations in the MYO7A gene cause a deaf-blindness disorder, known as Usher syndrome 1B.  In the retina, the majority of MYO7A is in the retinal pigmented epithelium (RPE), where many of the reactions of the visual retinoid cycle take place.  We have observed that the retinas of Myo7a-mutant mice are resistant to acute light damage. In exploring the basis of this resistance, we found that Myo7a-mutant mice have lower levels of RPE65, the RPE isomerase that has a key role in the retinoid cycle.  We show for the first time that RPE65 normally undergoes a light-dependent translocation to become more concentrated in the central region of the RPE cells.  This translocation requires MYO7A, so that, in Myo7a-mutant mice, RPE65 is partly mislocalized in the light.  RPE65 is degraded more quickly in Myo7a-mutant mice, perhaps due to its mislocalization, providing a plausible explanation for its lower levels.  Following a 50–60% photobleach, Myo7a-mutant retinas exhibited increased all-trans-retinyl ester levels during the initial stages of dark recovery, consistent with a deficiency in RPE65 activity.  Lastly, MYO7A and RPE65 were co-immunoprecipitated from RPE cell lysate by antibodies against either of the proteins, and the two proteins were partly colocalized, suggesting a direct or indirect interaction.  Together, the results support a role for MYO7A in the translocation of RPE65, illustrating the involvement of a molecular motor in the spatiotemporal organization of the retinoid cycle in vision.

Lopes, Vanda S.; Gibbs, Daniel; Libby, Richard T.; Aleman, Tomas S.; Welch, Darcy L.; Lillo, Concepcion; Jacobson, Samuel G.; Radu, Roxana A.; Steel, Karen P.; Williams, David S.

2011-01-01

328

Cell cycle regulators cyclin D1 and CDK4/6 have estrogen receptor-dependent divergent functions in breast cancer migration and stem cell-like activity.  

PubMed

Cyclin D1 and its binding partners CDK4/6 are essential regulators of cell cycle progression and are implicated in cancer progression. Our aim was to investigate a potential regulatory role of these proteins in other essential tumor biological characteristics. Using a panel of breast cancer cell lines and primary human breast cancer samples, we have demonstrated the importance of these cell cycle regulators in both migration and stem-like cell activity. siRNA was used to target cyclin D1 and CDK4/6 expression, having opposing effects on both migration and stem-like cell activity dependent upon estrogen receptor (ER) expression. Inhibition of cyclin D1 or CDK4/6 increases or decreases migration and stem-like cell activity in ER-ve (ER-negative) and ER+ve (ER-positive) breast cancer, respectively. Furthermore, overexpressed cyclin D1 caused decreased migration and stem-like cell activity in ER-ve cells while increasing activity in ER+ve breast cancer cells. Treatment of breast cancer cells with inhibitors of cyclin D1 and CDK4/6 (Flavopiridol/PD0332991), currently in clinical trials, mimicked the effects observed with siRNA treatment. Re-expression of ER in two ER-ve cell lines was sufficient to overcome the effects of either siRNA or clinical inhibitors of cyclin D1 and CDK4/6.   In conclusion, cyclin D1 and CDK4/6 have alternate roles in regulation of migration and stem-like cell activity. Furthermore, these effects are highly dependent upon expression of ER. The significance of these results adds to our general understanding of cancer biology but, most importantly, could be used diagnostically to predict treatment response to cell cycle inhibition in breast cancer. PMID:23839043

Lamb, Rebecca; Lehn, Sophie; Rogerson, Lynsey; Clarke, Robert B; Landberg, Göran

2013-06-26

329

Metabolic engineering of Lactobacillus plantarum for succinic acid production through activation of the reductive branch of the tricarboxylic acid cycle.  

PubMed

Biosynthesis of succinic acid is an alternative method from conventional chemical synthesis. For this application, several bacteria and fungi have been employed and genetically modified. Lactic acid bacteria (LAB) are gaining recognition as novel producers of useful compounds by metabolic engineering. Among LAB, Lactobacillus plantarum NCIMB 8826 is an interesting candidate for succinic acid production by metabolic engineering since it has an incomplete tricarboxylic acid (TCA) cycle and naturally produces small amounts of succinic acid. In this study, we constructed recombinant LAB and evaluated them as hosts of succinic acid production. We examined the enzymes pyruvate carboxylase (PC), phosphoenolpyruvate carboxykinase (PEPCK), and malic enzyme for their potential to improve metabolic flux from glycolysis to the reductive TCA cycle in a lactate dehydrogenase-deficient strain of L. plantarum NCIMB 8826 (VL103). We investigated the effects of overexpression or coexpression of each enzyme on succinic acid production. Our results suggested that PC is the key enzyme for succinic acid production by L. plantarum VL103, whereas PEPCK is critical for increasing biomass. The highest yield of succinic acid was obtained through coexpression of PC and PEPCK in L. plantarum VL103. This recombinant strain produced a 22-fold higher amount of succinic acid than the wild-type and converted 25.3% of glucose to succinic acid. PMID:23769309

Tsuji, Akira; Okada, Sanae; Hols, Pascal; Satoh, Eiichi

2013-05-09

330

A single transcription factor regulates evolutionarily diverse but functionally linked metabolic pathways in response to nutrient availability  

PubMed Central

During evolution, enzyme-coding genes are acquired and/or replaced through lateral gene transfer and compiled into metabolic pathways. Gene regulatory networks evolve to fine tune biochemical fluxes through such metabolic pathways, enabling organisms to acclimate to nutrient fluctuations in a competitive environment. Here, we demonstrate that a single TrmB family transcription factor in Halobacterium salinarum NRC-1 globally coordinates functionally linked enzymes of diverse phylogeny in response to changes in carbon source availability. Specifically, during nutritional limitation, TrmB binds a cis-regulatory element to activate or repress 113 promoters of genes encoding enzymes in diverse metabolic pathways. By this mechanism, TrmB coordinates the expression of glycolysis, TCA cycle, and amino-acid biosynthesis pathways with the biosynthesis of their cognate cofactors (e.g. purine and thiamine). Notably, the TrmB-regulated metabolic network includes enzyme-coding genes that are uniquely archaeal as well as those that are conserved across all three domains of life. Simultaneous analysis of metabolic and gene regulatory network architectures suggests an ongoing process of co-evolution in which TrmB integrates the expression of metabolic enzyme-coding genes of diverse origins.

Schmid, Amy K; Reiss, David J; Pan, Min; Koide, Tie; Baliga, Nitin S

2009-01-01

331

Cell cycle regulation of the activity and subcellular localization of Plk1, a human protein kinase implicated in mitotic spindle function  

Microsoft Academic Search

Correct assembly and function of the mitotic spindle during cell division is essential for the accurate partitioning of the duplicated genome to daughter cells. Protein phosphorylation has long been implicated in controlling spindle function and chromosome segrega- tion, and genetic studies have identified several protein kinases and phosphatases that are likely to regulate these processes. In particular, mutations in the

Roy M. Golsteyn; Kirsten E. Mundt; Andrew M. Fry; Erich A. Nigg

1995-01-01

332

Pain Perception during Menstrual Cycle  

Microsoft Academic Search

Sexual hormones influence complex brain function and pain perception. Many psychophysical studies attempted to establish pain\\u000a perception changes across menstrual cycle in animal models and healthy women or those with chronic pain. General results are\\u000a quite uncertain in regard to consistent menstrual-related fluctuations of pain perception. The few studies applying neurophysiological\\u000a procedures to test pain-related changes during menstrual cycle suggested

Marina de Tommaso

333

The mammalian Cut homeodomain protein functions as a cell-cycle-dependent transcriptional repressor which downmodulates p21WAF1/CIP1/SDI1 in S phase.  

PubMed Central

Cut is a homeodomain transcription factor which has the unusual property of containing several DNA-binding domains: three regions called Cut repeats and the Cut homeodomain. Genetic studies in Drosophila melanogaster indicate that cut plays important roles in the determination and maintenance of cell-type specificity. In the present study, we show that mammalian Cut proteins may yet play another biological role, specifically in proliferating cells. We found that the binding of Cut to a consensus binding site varies during the cell cycle. Binding was virtually undetectable in G0 and early G1, but became very strong as cells reached S phase. This was shown to result both from an increase in Cut expression and dephosphorylation of the Cut homeodomain by the Cdc25A phosphatase. We also show that the increase in Cut activity coincides with a decrease in p21WAF1/CIP1/SDI1 mRNAs. In co-transfection experiments, Cut proteins repressed p21WAF1/CIP1/SDI1 gene expression through binding to a sequence that overlaps the TATA box. Moreover, p21WAF1/CIP1/SDI1 expression was repressed equally well by either Cdc25A or Cut. Altogether, these results suggest a model by which Cdc25A activates the Cut repressor which then downregulates transcription of p21WAF1/CIP1/SDI1 in S phase. Thus, in addition to their role during cellular differentiation, Cut proteins also serve as cell-cycle-dependent transcriptional factors in proliferating cells.

Coqueret, O; Berube, G; Nepveu, A

1998-01-01

334

Clinical Response to Tricyclic Antidepressants in Functional Bowel Disorders is not Related to Dosage  

Microsoft Academic Search

BACKGROUND:As shown in the per protocol analysis of a recent randomized, controlled trial, when tolerated, Desipramine (DES) is effective over placebo (PLA) in treating moderate-to-severe functional bowel disorders (FBD). Clinical experience suggests that the benefit from tricyclic antidepressants (TCA) in FBD can be achieved at doses lower than those used to treat major depression. Within psychiatry, when using higher dosage

Albena Halpert; Christine B. Dalton; Nicholas E. Diamant; Brenda B. Toner; Yuming Hu; Carolyn B. Morris; Shrikant I. Bangdiwala; William E. Whitehead; Douglas A. Drossman

2005-01-01

335

The Nitrogen Cycle  

NSDL National Science Digital Library

You are going to learn about the nitrogen cycle. After finishing these activities, you will be able to draw the nitrogen cycle and explain how human activity affects it. 1. Explore this website to learn some basic information about the nitrogen cycle. The Nitrogen Cycle 2. Discover additional information about the nitrogen cycle by looking at more websites. The Nitrogen Cycle: Of Microbes and Men Introduction to the Biosphere: The Nitrogen Cycle 3. Draw your own diagram ...

Bates, Albion M.

2006-10-06

336

Large-scale brain functional modularity is reflected in slow electroencephalographic rhythms across the human non-rapid eye movement sleep cycle.  

PubMed

Large-scale brain functional networks (measured with functional magnetic resonance imaging, fMRI) are organized into separated but interacting modules, an architecture supporting the integration of distinct dynamical processes. In this work we study how the aforementioned modular architecture changes with the progressive loss of vigilance occurring in the descent to deep sleep and we examine the relationship between the ensuing slow electroencephalographic rhythms and large-scale network modularity as measured with fMRI. Graph theoretical methods are used to analyze functional connectivity graphs obtained from fifty-five participants at wakefulness, light and deep sleep. Network modularity (a measure of functional segregation) was found to increase during deeper sleep stages but not in light sleep. By endowing functional networks with dynamical properties, we found a direct link between increased electroencephalographic (EEG) delta power (1-4 Hz) and a breakdown of inter-modular connectivity. Both EEG slowing and increased network modularity were found to quickly decrease during awakenings from deep sleep to wakefulness, in a highly coordinated fashion. Studying the modular structure itself by means of a permutation test, we revealed different module memberships when deep sleep was compared to wakefulness. Analysis of node roles in the modular structure revealed an increase in the number of locally well-connected nodes and a decrease in the number of globally well-connected hubs, which hinders interactions between separated functional modules. Our results reveal a well-defined sequence of changes in brain modular organization occurring during the descent to sleep and establish a close parallel between modularity alterations in large-scale functional networks (accessible through whole brain fMRI recordings) and the slowing of scalp oscillations (visible on EEG). The observed re-arrangement of connectivity might play an important role in the processes underlying loss of vigilance and sensory awareness during deep sleep. PMID:23313420

Tagliazucchi, Enzo; von Wegner, Frederic; Morzelewski, Astrid; Brodbeck, Verena; Borisov, Sergey; Jahnke, Kolja; Laufs, Helmut

2013-01-09

337

Module structure of interphotoreceptor retinoid-binding protein (IRBP) may provide bases for its complex role in the visual cycle - structure/function study of Xenopus IRBP  

PubMed Central

Background Interphotoreceptor retinoid-binding protein's (IRBP) remarkable module structure may be critical to its role in mediating the transport of all-trans and 11-cis retinol, and 11-cis retinal between rods, cones, RPE and Müller cells during the visual cycle. We isolated cDNAs for Xenopus IRBP, and expressed and purified its individual modules, module combinations, and the full-length polypeptide. Binding of all-trans retinol, 11-cis retinal and 9-(9-anthroyloxy) stearic acid were characterized by fluorescence spectroscopy monitoring ligand-fluorescence enhancement, quenching of endogenous protein fluorescence, and energy transfer. Finally, the X-ray crystal structure of module-2 was used to predict the location of the ligand-binding sites, and compare their structures among modules using homology modeling. Results The full-length Xenopus IRBP cDNA codes for a polypeptide of 1,197 amino acid residues beginning with a signal peptide followed by four homologous modules each ~300 amino acid residues in length. Modules 1 and 3 are more closely related to each other than either is to modules 2 and 4. Modules 1 and 4 are most similar to the N- and C-terminal modules of the two module IRBP of teleosts. Our data are consistent with the model that vertebrate IRBPs arose through two genetic duplication events, but that the middle two modules were lost during the evolution of the ray finned fish. The sequence of the expressed full-length IRBP was confirmed by liquid chromatography-tandem mass spectrometry. The recombinant full-length Xenopus IRBP bound all-trans retinol and 11-cis retinaldehyde at 3 to 4 sites with Kd's of 0.2 to 0.3 ?M, and was active in protecting all-trans retinol from degradation. Module 2 showed selectivity for all-trans retinol over 11-cis retinaldehyde. The binding data are correlated to the results of docking of all-trans-retinol to the crystal structure of Xenopus module 2 suggesting two ligand-binding sites. However, homology modeling of modules 1, 3 and 4 indicate that both sites may not be available for binding of ligands in all four modules. Conclusion Although its four modules are homologous and each capable of supporting ligand-binding activity, structural differences between their ligand-binding domains, and interactions between the modules themselves will be critical to understanding IRBP's complex role in the visual cycle.

Gonzalez-Fernandez, Federico; Baer, Claxton A; Ghosh, Debashis

2007-01-01

338

Cycling through transcription with the RNA polymerase F/E (RPB4/7) complex: structure, function and evolution of archaeal RNA polymerase.  

PubMed

RNA polymerases (RNAPs) from the three domains of life, Bacteria, Archaea and Eukarya, are evolutionarily related and thus have common structural and functional features. Despite the radically different morphology of Archaea and Eukarya, their RNAP subunit composition and utilisation of basal transcription factors are almost identical. This review focuses on the multiple functions of the most prominent feature that differentiates these enzymes from the bacterial RNAP--a stalk-like protrusion, which consists of the heterodimeric F/E subcomplex. F/E is highly versatile, it facilitates DNA strand-separation during transcription initiation, increases processivity during the elongation phase of transcription and ensures efficient transcription termination. PMID:20863887

Grohmann, Dina; Werner, Finn

2010-09-21

339

Modeling the Nuclear Fuel Cycle  

SciTech Connect

A review of existing nuclear fuel cycle systems analysis codes was performed to determine if any existing codes meet technical and functional requirements defined for a U.S. national program supporting the global and domestic assessment, development and deployment of nuclear energy systems. The program would be implemented using an interconnected architecture of different codes ranging from the fuel cycle analysis code, which is the subject of the review, to fundamental physical and mechanistic codes. Four main functions are defined for the code: (1) the ability to characterize and deploy individual fuel cycle facilities and reactors in a simulation, while discretely tracking material movements, (2) the capability to perform an uncertainty analysis for each element of the fuel cycle and an aggregate uncertainty analysis, (3) the inclusion of an optimization engine able to optimize simultaneously across multiple objective functions, and (4) open and accessible code software and documentation to aid in collaboration between multiple entities and facilitate software updates. Existing codes, categorized as annualized or discrete fuel tracking codes, were assessed according to the four functions and associated requirements. These codes were developed by various government, education and industrial entities to fulfill particular needs. In some cases, decisions were made during code development to limit the level of detail included in a code to ease its use or to focus on certain aspects of a fuel cycle to address specific questions. The review revealed that while no two of the codes are identical, they all perform many of the same basic functions. No code was able to perform defined function 2 or several requirements of functions 1 and 3. Based on this review, it was concluded that the functions and requirements will be met only with development of a new code, referred to as GENIUS.

Jacob J. Jacobson; Mary Lou Dunzik-Gougar; Christopher A. Juchau

2010-08-01

340

The Water Cycle  

NSDL National Science Digital Library

Students will learn the process of the water cycle. Alabama Course of Study: Science. Second Grade: Standard 9: Describe evaporation, condensation, and precipitation in the water cycle. What is the water cycle? On the worksheet provided, list the 4 parts of the water cycle. Between the parts draw a small picture to represent what is happening during this cycle. The Water Cycle See how we use the water in the water cycle. Thirstins Water Cycle Name 3 ways water changes form. This is an animated diagram of the Water Cycle Here is a ...

Lopez, Mrs.

2009-07-09

341

THE WATER CYCLE/ CLOUDS  

NSDL National Science Digital Library

Students will learn about the water cycle and how it works. You will explore many resources to find out many new factors about the water cycle. What is the water cycle? National water cycle Name the 4 water parts of the water cycle? Weather wonders Where are 3 places that the water cycle exists- What happens after condensation? animated water cycle Name 4 types of clouds? What is the highest level cloud called? Which cloud is associated with powerful thunderstorms? Cloud Types What do clouds have to do with the water cycle? National water cycle What is ...

Ms.brown

2009-04-06

342

Sensitivity of C3H 10T1/2 cells to radiation-induced killing and neoplastic transformation as a function of cell cycle.  

PubMed

Cell-age sensitivity to both cell killing and neoplastic transformation induced by radiation was investigated using synchronized populations of C3H10T1/2 cells. Mitotic-cell suspensions, collected using a mitotic shake-off procedure, were irradiated with 4Gy 250 kVp X-rays or 0.5 Gy fission neutrons from the RSV-TAPIRO reactor at CR-Casaccia. For study of cell killing the mitotic-cell suspensions were either irradiated immediately after collection, or plated for subsequent irradiation, which was performed every hour, covering an interval of 17 h. The response pattern observed was similar after X-rays and neutron irradiation, but the magnitude of the variation through the cell cycle was smaller in the case of neutrons (1.3- compared with 5-fold). For study of neoplastic transformation induction the irradiation was performed immediately after collection, i.e. in M phase, or at later times corresponding to mid-G1, G1/S and G2 phases. The sensitivity of the G2/M phase was examined by irradiating the cells with 4Gy X-rays while still attached to the flask bottom, and dislodging them after 25 min. SimilarLy to cell survival, the transformation frequency showed a small variation after neutron irradiation (1.4- compared with 3.1-fold) for the phases examined. PMID:8601756

Pazzaglia, S; Saran, A; Pariset, L; Rebessi, S; Di Majo, V; Coppola, M; Covelli, V

1996-01-01

343

Discovering the Water Cycle!  

NSDL National Science Digital Library

We will be learning about what the water cycle is and how it works. Resources! The Hydrologic Cycle: Water's journey through time The Water Cycle Thirstin's Water Cycle Activity Water evaporates from the surface Water Wonders These are a collection of websites that are going to help us in our journey of discovering what the water cycle is. ...

Mortensen, Miss

2009-10-09

344

INCUBATION TEMPERATURE AND EGGSHELL CONDUCTANCE EFFECTS ON THE INTESTINAL MATURATION AND THYROID FUNCTION IN COMMERCIAL TURKEY POULTS HATCHING FROM THE FIRST CYCLE FLOCK  

Technology Transfer Automated Retrieval System (TEKTRAN)

Eggshell conductance (G) and egg white (EW) affect poult viability. Poor livability may be related intestinal maturation and thyroid function of the neonate. The objectives of this study were to test if incubator temperature and G determine poult maturity among egg from a young turkey flock. Matu...

345

Reformulation, as a Function of Only Working Temperatures, of Performance Parameters of a Solar Driven Ejector-Absorption Cycle Using Artificial Neural Networks  

Microsoft Academic Search

Theoretical thermodynamic analysis of the absorption thermal systems is too complex because of analytic functions calculating the thermodynamic properties of fluid couples involving the solution of complex differential equations and simulations programs. This article proposes a new approach to performance analysis of solar driven ejector-absorption refrigeration system (EARS) operated aqua\\/ammonia. Use of artificial neural networks (ANNs) has been proposed to

Adnan Sözen; M. Ali Akçayol

2005-01-01

346

Force cycles and force chains.  

PubMed

We examine the coevolution of N cycles and force chains as part of a broader study which is designed to quantitatively characterize the role of the laterally supporting contact network to the evolution of force chains. Here, we elucidate the rheological function of these coexisting structures, especially in the lead up to failure. In analogy to force chains, we introduce the concept of force cycles: N cycles whose contacts each bear above average force. We examine their evolution around force chains in a discrete element simulation of a dense granular material under quasistatic biaxial loading. Three-force cycles are shown to be stabilizing structures that inhibit relative particle rotations and provide strong lateral support to force chains. These exhibit distinct behavior from other cycles. Their population decreases rapidly during the initial stages of the strain-hardening regime-a trend that is suddenly interrupted and reversed upon commencement of force chain buckling prior to peak shear stress. Results suggest that the three-force cycles are called upon for reinforcements to ward off failure via shear banding. Ultimately though, the resistance to buckling proves futile; buckling wins under the combined effects of dilatation and increasing compressive load. The sudden increase in three-force cycles may thus be viewed as an indicator of imminent failure via shear bands. PMID:20365363

Tordesillas, Antoinette; Walker, David M; Lin, Qun

2010-01-13

347

Three cycle engine with varying combustion chamber volume  

Microsoft Academic Search

A piston type internal combustion engine of novel three cycle variety, in which the intake and compression functions are divorced from the combustion cylinder entirely and are carried out by a separate high pressure compressor; with a high pressure charging cycle, a power cycle and an exhaust cycle carried out in the combustion chamber in a positive manner. The gas

1985-01-01

348

Genetic evidence for bacterial chemolithoautotrophy based on the reductive tricarboxylic acid cycle in groundwater systems.  

PubMed

Geologically and chemically distinct aquifers were screened for the presence of two genes coding for key enzymes of the reverse tricarboxylic acid (rTCA) cycle in autotrophic bacteria, 2-oxoglutarate : ferredoxin oxidoreductase (oorA) and the beta subunit of ATP citrate lyase enzymes (aclB). From 42 samples investigated, aclB genes were detected in two and oorA genes in six samples retrieved from polluted and sulfidic aquifers. aclB genes were represented by a single phylotype of almost identical sequences closely affiliated with chemolithoautotrophic Sulfurimonas species. In contrast, sequences analysis of oorA genes revealed diverse phylotypes mainly related to sequences from cultivation-independent studies. PMID:22791056

Alfreider, Albin; Vogt, Carsten

2012-01-01

349

Mitochondria-targeted antioxidant promotes recovery of skeletal muscle mitochondrial function after burn trauma assessed by in vivo 31P nuclear magnetic resonance and electron paramagnetic resonance spectroscopy.  

PubMed

Burn injury causes a major systemic catabolic response that is associated with mitochondrial dysfunction in skeletal muscle. We investigated the effects of the mitochondria-targeted peptide antioxidant Szeto-Schiller 31 (SS-31) on skeletal muscle in a mouse burn model using in vivo phosphorus-31 nuclear magnetic resonance ((31)P NMR) spectroscopy to noninvasively measure high-energy phosphate levels; mitochondrial aconitase activity measurements that directly correlate with TCA cycle flux, as measured by gas chromatography mass spectrometry (GC-MS); and electron paramagnetic resonance (EPR) to assess oxidative stress. At 6 h postburn, the oxidative ATP synthesis rate was increased 5-fold in burned mice given a single dose of SS-31 relative to untreated burned mice (P=0.002). Furthermore, SS-31 administration in burned animals decreased mitochondrial aconitase activity back to control levels. EPR revealed a recovery in redox status of the SS-31-treated burn group compared to the untreated burn group (P<0.05). Our multidisciplinary convergent results suggest that SS-31 promotes recovery of mitochondrial function after burn injury by increasing ATP synthesis rate, improving mitochondrial redox status, and restoring mitochondrial coupling. These findings suggest use of noninvasive in vivo NMR and complementary EPR offers an approach to monitor the effectiveness of mitochondrial protective agents in alleviating burn injury symptoms. PMID:23482635

Righi, Valeria; Constantinou, Caterina; Mintzopoulos, Dionyssios; Khan, Nadeem; Mupparaju, S P; Rahme, Laurence G; Swartz, Harold M; Szeto, Hazel H; Tompkins, Ronald G; Tzika, A Aria

2013-03-12

350

Slip history during one earthquake cycle at the Nankai subduction zone, inferred from the inversion analysis of levelling data with a viscoelastic slip response function  

Microsoft Academic Search

We developed a new method of geodetic data inversion with a viscoelastic slipresponse function for estimating slip history at plate interfaces. By applyingthis inversion method to levelling data for 1893-1983 in Shikoku, southwesternJapan, we reconstructed the pattern of spatiotemporal variation in slip motionat the interface between the Eurasian plate and the Philippine Sea plate.In the deep portion (40km ! d)

Akira Nishitani; Yukitoshi Fukahata

351

Final Report - The Xanthophyll Cycle  

SciTech Connect

The xanthophyll cycle is a ubiquitous activity in higher plants. A major function of the cycle is to protect the photosynthetic system from the potentially damaging effects of high light by dissipating excess energy that might otherwise damage the photosynthetic apparatus harmlessly as heat by a process termed non-photochemical quenching (NFQ). This research focused on investigating the dynamics of the relationship between PsbS, subunit PSII protein required for NPQ, and zeaxanthin by perturbing the natural relationship of these components by overexpression of PsbS, violaxanthin de-epoxidase (VDE), and PsbS-VDE in tobacco. The effects of these treatments showed that the relationship between NPQ and zeaxanthin formation is more complex than previously indicated from studies carried out under high light. It is postulated that the xanthophyll cycle functions as a type of signal-transduction system within the thylakoid membrane. Recent studies in model lipid systems demonstrated that zeaxanthin exerts feedback inhibition on violaxanthin de-epoxidase. This feedback inhibition is consistent with the lipid phase functioning as a modulating factor in the dynamics of the cycle's operation. While this research and those in other laboratories have defined both the biochemistry and molecular mechanism of the cycle's operation, especially for violaxanthin de-epoxidase, there is yet insufficient knowledge that explains the ubiquitous presence of the cycle in all higher plants and a related cycle in diatoms. Antisense VDE tobacco plants (work carried out under another grant) withstood the high-light environment in Hawaii over one generation. Thus, it is speculated that the protective system was essential for survival in earth's high-light earth environment over multiple generations. The proposed signal transduction protective system, however, may explain the ability of the protective system to modulate or adapt to a range of environments.

Harry Yamamato

2005-04-21

352

The Q-cycle reviewed: how well does a monomeric mechanism of the bc1 complex account for the function of a dimeric complex?  

PubMed Central

Recent progress in understanding the Q-cycle mechanism of the bc1 complex is reviewed. The data strongly support a mechanism in which the Qo-site operates through a reaction in which the first electron transfer from ubiquinol to the oxidized iron-sulfur protein is the rate determining step for the overall process. The reaction involves a proton-coupled electron transfer down a hydrogen bond between the ubiquinol and a histidine ligand of the [2Fe-2S] cluster, in which the unfavorable protonic configuration contributes a substantial part of the activation barrier. The reaction is endergonic, and the products are an unstable ubisemiquinone at the Qo-site, and the reduced iron-sulfur protein, the extrinsic mobile domain of which is now free to dissociate and move away from the site to deliver an electron to cyt c1 and liberate the H+. When oxidation of the semiquinone is prevented, it participates in bypass reactions, including superoxide generation if O2 is available. When the b-heme chain is available as acceptor, the semiquinone is oxidized in a process in which the proton is passed to the glutamate of the conserved –PEWY- sequence, and the semiquinone anion passes its electron to heme bL to form the product ubiquinone. The rate is rapid compared to the limiting reaction, and would require movement of the semiquinone closer to heme bL to enhance the rate constant. The acceptor reactions at the Qi-site are still controversial, but likely involve a “two-electron gate” in which a stable semiquinone stores an electron. Possible mechanisms to explain the cytb150 phenomenon are discussed, and the information from pulsed EPR studies about the structure of the intermediate state is reviewed. The mechanism discussed is applicable to a monomeric bc1 complex. We discuss evidence in the literature that has been interpreted as shown that the dimeric structure participates in a more complicated mechanism involving electron transfer across the dimer interface. We show from myxothiazol titrations and mutational analysis of Tyr-199, which is at the interface between monomers, that no such inter-monomer electron transfer is detected at the level of the bL hemes. We show from analysis of strains with mutations at Asn-221 that there are coulombic interactions between the b-hemes in a monomer. The data can also be interpreted as showing similar coulombic interaction across the dimer interface, and we discuss mechanistic implications.

Crofts, Antony R.; Holland, J. Todd; Victoria, Doreen; Kolling, Derrick R.J.; Dikanov, Sergei A.; Gilbreth, Ryan; Lhee, Sangmoon; Kuras, Richard; Kuras, Mariana Guergova

2008-01-01

353

Inhibition of the alpha-ketoglutarate dehydrogenase complex alters mitochondrial function and cellular calcium regulation.  

PubMed

Mitochondrial dysfunction occurs in many neurodegenerative diseases. The alpha-ketoglutarate dehydrogenase complex (KGDHC) catalyzes a key and arguably rate-limiting step of the tricarboxylic acid cycle (TCA). A reduction in the activity of the KGDHC occurs in brains and cells of patients with many of these disorders and may underlie the abnormal mitochondrial function. Abnormalities in calcium homeostasis also occur in fibroblasts from Alzheimer's disease (AD) patients and in cells bearing mutations that lead to AD. Thus, the present studies test whether the reduction of KGDHC activity can lead to the alterations in mitochondrial function and calcium homeostasis. alpha-Keto-beta-methyl-n-valeric acid (KMV) inhibits KGDHC activity in living N2a cells in a dose- and time-dependent manner. Surprisingly, concentration of KMV that inhibit in situ KGDHC by 80% does not alter the mitochondrial membrane potential (MMP). However, similar concentrations of KMV induce the release of cytochrome c from mitochondria into the cytosol, reduce basal [Ca(2+)](i) by 23% (P<0.005), and diminish the bradykinin (BK)-induced calcium release from the endoplasmic reticulum (ER) by 46% (P<0.005). This result suggests that diminished KGDHC activities do not lead to the Ca(2+) abnormalities in fibroblasts from AD patients or cells bearing PS-1 mutations. The increased release of cytochrome c with diminished KGDHC activities will be expected to activate other pathways including cell death cascades. Reductions in this key mitochondrial enzyme will likely make the cells more vulnerable to metabolic insults that promote cell death. PMID:12527416

Huang, Hsueh-Meei; Zhang, Hui; Xu, Hui; Gibson, Gary E

2003-01-20

354

Life cycle analysis: A critique  

Microsoft Academic Search

Life cycle analysis (LCA) is an increasingly important tool for environmental policy, and even for industry. Analysts are also interested in forecasting future materials\\/energy fluxes on regional and global scales, as a function of various economic growth and regulatory scenarios. A fundamental tenet of LCA is that every material product must eventually become a waste. To choose the ‘greener’ of

Robert U. Ayres

1995-01-01

355

5-AED enhances survival of irradiated mice in a G-CSF-dependent manner, stimulates innate immune cell function, reduces radiation-induced DNA damage and induces genes that modulate cell cycle progression and apoptosis.  

PubMed

The steroid androst-5-ene-3ß,17ß-diol (5-androstenediol, 5-AED) elevates circulating granulocytes and platelets in animals and humans, and enhances survival during the acute radiation syndrome (ARS) in mice and non-human primates. 5-AED promotes survival of irradiated human hematopoietic progenitors in vitro through induction of Nuclear Factor-?B (NF?B)-dependent Granulocyte Colony-Stimulating Factor (G-CSF) expression, and causes elevations of circulating G-CSF and interleukin-6 (IL-6). However, the in vivo cellular and molecular effects of 5-AED are not well understood. The aim of this study was to investigate the mechanisms of action of 5-AED administered subcutaneously (s.c.) to mice 24 h before total body ?- or X-irradiation (TBI). We used neutralizing antibodies, flow cytometric functional assays of circulating innate immune cells, analysis of expression of genes related to cell cycle progression, DNA repair and apoptosis, and assessment of DNA strand breaks with halo-comet assays. Neutralization experiments indicated endogenous G-CSF but not IL-6 was involved in survival enhancement by 5-AED. In keeping with known effects of G-CSF on the innate immune system, s.c. 5-AED stimulated phagocytosis in circulating granulocytes and oxidative burst in monocytes. 5-AED induced expression of both bax and bcl-2 in irradiated animals. Cdkn1a and ddb1, but not gadd45a expression, were upregulated by 5-AED in irradiated mice. S.c. 5-AED administration caused decreased DNA strand breaks in splenocytes from irradiated mice. Our results suggest 5-AED survival enhancement is G-CSF-dependent, and that it stimulates innate immune cell function and reduces radiation-induced DNA damage via induction of genes that modulate cell cycle progression and apoptosis. PMID:22843381

Grace, Marcy B; Singh, Vijay K; Rhee, Juong G; Jackson, William E; Kao, Tzu-Cheg; Whitnall, Mark H

2012-07-22

356

5-AED enhances survival of irradiated mice in a G-CSF-dependent manner, stimulates innate immune cell function, reduces radiation-induced DNA damage and induces genes that modulate cell cycle progression and apoptosis  

PubMed Central

The steroid androst-5-ene-3ß,17ß-diol (5-androstenediol, 5-AED) elevates circulating granulocytes and platelets in animals and humans, and enhances survival during the acute radiation syndrome (ARS) in mice and non-human primates. 5-AED promotes survival of irradiated human hematopoietic progenitors in vitro through induction of Nuclear Factor-?B (NF?B)-dependent Granulocyte Colony-Stimulating Factor (G-CSF) expression, and causes elevations of circulating G-CSF and interleukin-6 (IL-6). However, the in vivo cellular and molecular effects of 5-AED are not well understood. The aim of this study was to investigate the mechanisms of action of 5-AED administered subcutaneously (s.c.) to mice 24 h before total body ?- or X-irradiation (TBI). We used neutralizing antibodies, flow cytometric functional assays of circulating innate immune cells, analysis of expression of genes related to cell cycle progression, DNA repair and apoptosis, and assessment of DNA strand breaks with halo-comet assays. Neutralization experiments indicated endogenous G-CSF but not IL-6 was involved in survival enhancement by 5-AED. In keeping with known effects of G-CSF on the innate immune system, s.c. 5-AED stimulated phagocytosis in circulating granulocytes and oxidative burst in monocytes. 5-AED induced expression of both bax and bcl-2 in irradiated animals. Cdkn1a and ddb1, but not gadd45a expression, were upregulated by 5-AED in irradiated mice. S.c. 5-AED administration caused decreased DNA strand breaks in splenocytes from irradiated mice. Our results suggest 5-AED survival enhancement is G-CSF-dependent, and that it stimulates innate immune cell function and reduces radiation-induced DNA damage via induction of genes that modulate cell cycle progression and apoptosis.

Grace, Marcy B.; Singh, Vijay K.; Rhee, Juong G.; Jackson, William E.; Kao, Tzu-Cheg; Whitnall, Mark H.

2012-01-01

357

The Arabidopsis Cell Division Cycle  

PubMed Central

Plant cells have evolved a complex circuitry to regulate cell division. In many aspects, the plant cell cycle follows a basic strategy similar to other eukaryotes. However, several key issues are unique to plant cells. In this chapter, both the conserved and unique cellular and molecular properties of the plant cell cycle are reviewed. In addition to division of individual cells, the specific characteristic of plant organogenesis and development make that cell proliferation control is of primary importance during development. Therefore, special attention should be given to consider plant cell division control in a developmental context. Proper organogenesis depends on the formation of different cell types. In plants, many of the processes leading to cell differentiation rely on the occurrence of a different cycle, termed the endoreplication cycle, whereby cells undergo repeated full genome duplication events in the absence of mitosis and increase their ploidy. Recent findings are focusing on the relevance of changes in chromatin organization for a correct cell cycle progression and, conversely, in the relevance of a correct functioning of chromatin remodelling complexes to prevent alterations in both the cell cycle and the endocycle.

Gutierrez, Crisanto

2009-01-01

358

The Water Cycle  

NSDL National Science Digital Library

Today you will explore the water cycle. Please visit the following websites (in order!) to gather information about the water cycle. Fill out your Information Sheet as you go. 1. Water cycle story 2. Water Cycle--heat 3. animation (Make sure to read the captions at the bottom!) ...

Hauck, Mrs.

2006-08-26

359

Introduction to combined cycles  

Microsoft Academic Search

Ideas and concepts underlying the technology of combined cycles including the scientific principles involved and the reasons these cycles are in fashion at the present time, are presented. A cycle is a steady flow process for conversion of heat energy into work, in which a working medium passes through a range of states, returning to its original state. Cycles for

M. J. Moore

1993-01-01

360

The Water Cycle  

NSDL National Science Digital Library

Students will understand and explain parts of the water cycle. First watch the video to get a background about the water cycle: water cycle video Draw and explain the water cycle in your own words (include the terms: evaporation, condensation, precipitation, at least 3 bodies of water, the sun). Before reading the experiment record your predictions: If you put a small amount of water ...

Amanda, Miss

2011-02-14

361

Life Cycle Effects on Residential Area Evaluation  

Microsoft Academic Search

This study examines the effects of the family life cycle on residential area evaluation. The analysis is based on a revised conceptualization of residential area evaluation that departs from previous research in two respects. First, life cycle status is hypothesized to affect two components of the evaluation process: residential area aspirations and the evaluation function. Residential area aspirations designate the

Valerie Ann Preston

1978-01-01

362

Using Phospholipids and Stable Carbon Isotopes to Assess Microbial Community Structures and Carbon Cycle Pathways in Kamchatka Hot Springs  

NASA Astrophysics Data System (ADS)

Phospholipid fatty acid (PLFA) and stable carbon isotopes were used to assess the microbial community structures in Kamchatka hot springs. Eighteen mats or surface sediments were collected from hot springs having temperatures of 31 to 91°C and pHs of 4.9 to 8.5. These samples were clearly separated into three groups according to the bacterial PLFA: 1) those dominated by terminally branched odd-numbered fatty acids, 2) those dominated by C18:1 and 3) those dominated by C20:1. With support from other minor PLFA components, group 2 may be used as biomarkers for Chloroflexales or other phototrophic bacteria and group 3 for Aquificales, respectively. Among the sampled hot springs, the Arkashin pool represents the simplest microbial structure with members of Aquificales being the dominant primary producers. On the other hand, the Zavarzin pool may represent the most heterogeneous pool that may include members of Chloroflexales and Aquificales as primary producers. Bacterial 16S rDNA clone libraries confirmed the presence of these microbial groups in the two pools. Results of stable carbon isotope fractionation between CO2 source, bulk biomass and total PLFA showed that primary producers in the Arkashin pool primarily used the reductive tricarboxylic acid (rTCA) cycle (e.g., members of Aquificales); whereas the Zavarzin pool may be a mixture of the 3-hydroxypropionate (3-HP) pathway (e.g. members of Chloroflexales) and the rTCA cycle. Bacterial contribution using the Calvin cycle was not significant and may be less important in Kamchatka hot springs.

Zhao, W.; Romanek, C. S.; Burgess, E. A.; Wiegel, J.; Mills, G.; Zhang, C. L.

2006-12-01

363

Rapid cycling bipolar disorder.  

PubMed

Rapid cycling bipolar disorder (RCBD) is defined in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) as a type of manic-depressive illness in which the patient experiences four or more episodes of mania and/or major depression per year. It was first reported as a consequence of the reduced effectiveness of lithium carbonate in the treatment and prophylaxis of this form of bipolar disorder (BD) in contrast to those with less frequent cycling. Among the anticonvulsants, there have been reports with different degrees of controlled data concerning carbamazepine, valproate, lamotrigine, topiramate, gabapentin and primidone. There is a paucity of double-blind studies, but what is available supports the use of lamotrigine. There is open data supporting the use of carbamazepine, valproate and topiramate. Regarding other classes, nimodipine may have specific utility in ultradian- (ultra-ultra-) or ultra-RCBD and there is double-blind data regarding the specific utility of olanzapine in RCBD. Low thyroid function may be a factor in development of RCBD; therapies aimed at elevating thyroid levels, even beyond the usual range, have frequently produced benefits in open trials. More research is needed into the possible therapeutic benefits of verapamil, bupropion, choline, light therapy and electroconvulsive therapy (ECT). PMID:11825328

Barrios, C; Chaudhry, T A; Goodnick, P J

2001-12-01

364

Multiple Rankine topping cycles  

SciTech Connect

The efficiency of a Rankine cycle is primarily determined by the temperatures of heat addition and rejection. However, no working fluid has been identified which will operate in a Rankine cycle over an extremely wide temperature range. Multiple Rankine topping cycles offer a technique for achieving high thermal efficiencies in power plants by allowing the use of several working fluids. This paper gives a history of Rankine topping cycles, presents an analysis for the calculation of the overall efficiency of a three-module multiple Rankine cycle, and presents results from a case study for a sodium-mercury-water cycle.

McWhirter, J.D. [Argonne National Lab., Idaho Falls, ID (United States). Engineering Div.]|[Idaho State Univ., Pocatello, ID (United States). Coll. of Engineering

1995-07-01

365

Functional laser speckle imaging of cerebral blood flow under hypothermia  

NASA Astrophysics Data System (ADS)

Hypothermia can unintentionally occur in daily life, e.g., in cardiovascular surgery or applied as therapeutics in the neurosciences critical care unit. So far, the temperature-induced spatiotemporal responses of the neural function have not been fully understood. In this study, we investigated the functional change in cerebral blood flow (CBF), accompanied with neuronal activation, by laser speckle imaging (LSI) during hypothermia. Laser speckle images from Sprague-Dawley rats (n = 8, male) were acquired under normothermia (37°C) and moderate hypothermia (32°C). For each animal, 10 trials of electrical hindpaw stimulation were delivered under both temperatures. Using registered laser speckle contrast analysis and temporal clustering analysis (TCA), we found a delayed response peak and a prolonged response window under hypothermia. Hypothermia also decreased the activation area and the amplitude of the peak CBF. The combination of LSI and TCA is a high-resolution functional imaging method to investigate the spatiotemporal neurovascular coupling in both normal and pathological brain functions.

Li, Minheng; Miao, Peng; Zhu, Yisheng; Tong, Shanbao

2011-08-01

366

Immunology and the menstrual cycle.  

PubMed

Sex and gender differences in disease prevalence, pathogenesis and modulation have been frequently reported. The menstrual cycle represents the opportunity to study the physiological effect of hormonal fluctuations in vivo on the immune function and chronic disease modulation. Reports on the effect of the cycle on immune cell numbers and activity fluctuations are scarce, but recent publications demonstrate an increasing interest in the subject. The menstrual cycle might affect immune cell numbers and modulate their activity throughout the 4-week cycle, as demonstrated in the case of regulatory T cells. The implications of these fluctuations are particularly relevant in the field of chronic diseases affecting women of reproductive age. In fact, baseline inflammation and immune cell activation in association with other mechanisms, such as regulation of receptor expression, modulation of muscular contraction and behavioral aspects might explain the menstrual-associated fluctuations described in chronic and acute diseases. In the following review the current knowledge about the modulatory effects of the menstrual cycle on both immune cells and systemic diseases, such as autoimmune diseases, asthma, diabetes, cardiac arrhythmia and schizophrenia, is reported. Most of these diseases display worsening of symptoms premenstrually or during menses due to physiologic effects on the target tissue mediated by progesterone and estrogen fluctuations and, thus, display paradigmatic changes potentially relevant to numerous other conditions. PMID:22155200

Oertelt-Prigione, Sabine

2011-12-03

367

Glucose metabolism, energetics, and function of rat hearts exposed to ischemic preconditioning and oxygenated cardioplegia.  

PubMed

We examined changes induced during ischemia-reperfusion on myocardial metabolism and function by oxygenated warm cardioplegia (CP) and ischemic preconditioning (IP). The postischemic hemodynamic recovery was comparable and significantly better in IP and CP groups, than in untreated hearts (e.g., LVDP recovery was threefold that of the control). The IP hearts reached a pH plateau earlier during ischemia and at considerably higher pH value (pH approximately 6) compared to the other groups (pH approximately 5.5). Postischemic phosphocreatine (PCr) and ATP recoveries were comparable and better in protected groups (approximately 72% and approximately 30% vs approximately 25% and approximately 10% in control, p < 0.0001). Preischemic glycogen was significantly reduced in IP to 49% and increased in CP hearts to 127%. However, the lactate levels at the end of ischemia were similar in all the groups, indicating glucose utilization from extracellular space during ischemia in IP hearts. Thus, similar hemodynamic protection by CP and IP is observed despite increased energy depletion during ischemia in IP. IP and CP protection is expressed through better energetic status and by higher recovery of the TCA cycle activity or enhanced mitochondria-cytosol transport of alpha-ketoglutarate on reperfusion in addition to metabolic changes during ischemia. Glycogen store recovered significantly better in IP than in CP and Control. These results exhibit similar and improved postischemic hemodynamic protection by CP and IP. Increased recovery of postischemic glycogen pool is a protective feature of IP, whereas slightly higher lactate metabolism during reperfusion is a protection component of CP. PMID:12489906

Olivson, Abira; Berman, Elisha; Houminer, Ester; Borman, Joseph B; Merin, Gideon; Karck, Matthias; Haverich, Axel; Chisin, Roland; Schwalb, Herzl

368

Low cycle fatigue loads.  

National Technical Information Service (NTIS)

A simple approximative algorithm for taking into account low cycle fatigue loads, related to transitions between the basic load cases forming the traditional duty cycle description, is outlined. The algorithm allows inclusion of contributions associated w...

G. C. Larsen K. Thomsen

1996-01-01

369

What-a-cycle  

NSDL National Science Digital Library

In this activity, students act as water molecules and travel through parts of the water cycle (ocean, atmosphere, clouds, glaciers, snow, rivers, lakes, ground, aquifer), noting on a hydrological cycle diagram the pathway traveled.

Weather, Jetstream -.; Service, Noaa -.

370

Global Material Cycles  

Microsoft Academic Search

\\u000a This chapter discusses prominent examples of global material cycles. This is of major significance in order to understand\\u000a potential perturbation of the natural material cycles caused by man’s production or use of energy. As selected examples, carbon,\\u000a water, nitrogen and oxygen cycles will be treated, and in addition aspects of some other material cycles (sulfur, phosphorus,\\u000a chlorine) as well as

Georg Schaub; Thomas Turek

371

Low cycle fatigue  

Microsoft Academic Search

The papers contained in this volume focus on various aspects of low cycle fatigue, including cyclic deformation, crack propagation, high-temperature low cycle fatigue, microstructural defects, multiaxial and variable amplitude loading, and life prediction. Papers are presented on the low cycle fatigue of some aluminum alloys, prediction of crack growth under creep-fatigue loading conditions, high-temperature low cycle fatigue behavior and lifetime

H. D. Solomon; L. R. Kaisand; G. R. Halford; B. N. Leis

1988-01-01

372

Amazon Water Cycle Roleplay  

NSDL National Science Digital Library

In this creative roleplay activity, learners will explore the various processes of the water cycle using movement, sound, and props to aid in comprehension. Learners will understand that water changes forms throughout the water cycle, and that this cycle runs continuously throughout all the cycles at the same time. This standards-based lesson, which is great for the classroom, camps, or afterschool programs, includes roleplay cards and ideas for props.

Sciences, California A.

2008-01-01

373

Cell Cycle Phase Regulates Glucocorticoid Receptor Function  

Microsoft Academic Search

The glucocorticoid receptor (GR) is a member of the nuclear hormone receptor superfamily of ligand-activated transcription factors. In contrast to many other nuclear receptors, GR is thought to be exclusively cytoplasmic in quiescent cells, and only translocate to the nucleus on ligand binding. We now demonstrate significant nuclear GR in the absence of ligand, which requires nuclear localisation signal 1

Laura Matthews; James Johnson; Andrew Berry; Peter Trebble; Ann Cookson; Dave Spiller; Caroline Rivers; Michael Norman; Mike White; David Ray

2011-01-01

374

Marine biodiversity, ecosystem functioning, and carbon cycles  

PubMed Central

Although recent studies suggest that climate change may substantially accelerate the rate of species loss in the biosphere, only a few studies have focused on the potential consequences of a spatial reorganization of biodiversity with global warming. Here, we show a pronounced latitudinal increase in phytoplanktonic and zooplanktonic biodiversity in the extratropical North Atlantic Ocean in recent decades. We also show that this rise in biodiversity paralleled a decrease in the mean size of zooplanktonic copepods and that the reorganization of the planktonic ecosystem toward dominance by smaller organisms may influence the networks in which carbon flows, with negative effects on the downward biological carbon pump and demersal Atlantic cod (Gadus morhua). Our study suggests that, contrary to the usual interpretation of increasing biodiversity being a positive emergent property promoting the stability/resilience of ecosystems, the parallel decrease in sizes of planktonic organisms could be viewed in the North Atlantic as reducing some of the services provided by marine ecosystems to humans.

Beaugrand, Gregory; Edwards, Martin; Legendre, Louis

2010-01-01

375

The Anderson Quin Cycle  

Microsoft Academic Search

The objective of this study was to make a more refined evaluation of the Anderson Quin Cycle based on most recent information on the performance of various elements that will be used in the Anderson Quin Cycle. My original estimate of the work plan for evaluating and optimizing the Anderson Quin Cycle called for 7000 man hours of work. Since

J. H. Anderson; W. M. Bilbow

1993-01-01

376

Potassium vapor topping cycle  

Microsoft Academic Search

The potassium vapor topping cycle is a concept for increasing the efficiency of the Rankine vapor cycle by raising the peak temperature by employing a potassium vapor cycle with a turbine inlet temperature of 1500 to 1600 F (815 to 870 C) in which the waste heat rejected from the condensing potassium vapor is transferred to boiling water and steam

R. S. Holcomb

1978-01-01

377

An Initial Study of Direct Relationships between Life-Cycle Modularity and Life-Cycle Cost  

Microsoft Academic Search

This work shows the relationship between product life-cycle modularity and product life-cycle costs. Previous statements tying increased modularity to improved costs, specifically product retirement costs, motivated this work.The benefits of modularity with respect to product functionality, product development, production, the supply chain, and other life-cycle elements have been expounded by many works in several fields. Increased modularity has been widely

Y. Zhang; John K. Gershenson

2003-01-01

378

Studies on the cycle life of commercial lithium ion batteries during rapid charge–discharge cycling  

Microsoft Academic Search

The impedance spectra of Li-ion batteries as a function of the number of charge–discharge cycles have been measured to study the cycle life of the commercial Li-ion battery (prismatic Sanyo UF653467) during cycling at 1C charge–discharge rate. The individual electrodes in the batteries have been examined using XRD, transmission electron microscopy (TEM) and SEM. The results show that the Nyquist

J Li; E Murphy; J Winnick; P. A Kohl

2001-01-01

379

Women's voice attractiveness varies across the menstrual cycle  

Microsoft Academic Search

We investigated ratings of female voice attractiveness as a function of menstrual cycle phase. Women had their voices recorded at four different times during their menstrual cycle. Voice samples were categorized from low to high conception risk based on menstrual cycle phase and empirical pregnancy data. Results showed a significant increase in voice attractiveness ratings as the risk of conception

R. Nathan Pipitone; Gordon G. Gallup Jr

2008-01-01

380

The enigmatic effects of caffeine in cell cycle and cancer  

Microsoft Academic Search

Caffeine may very well be the most frequently ingested neuroactive drug in the world. Mechanistically, caffeine has been reported to affect cell cycle function, induce programmed cell death or apoptosis and perturb key cell cycle regulatory proteins. Although the effects of caffeine have been heavily investigated, much of the research data regarding caffeine's effects on cell cycle and proliferation seem

Ann M. Bode; Zigang Dong

2007-01-01

381

Introduction to combined cycles  

NASA Astrophysics Data System (ADS)

Ideas and concepts underlying the technology of combined cycles including the scientific principles involved and the reasons these cycles are in fashion at the present time, are presented. A cycle is a steady flow process for conversion of heat energy into work, in which a working medium passes through a range of states, returning to its original state. Cycles for power production are the steam cycle, which is a closed cycle, and the gas turbine, which represents an open cycle. Combined cycle thermodynamic parameters, are discussed. The general arrangement of the plant is outlined and important features of their component parts described. The scope for future development is discussed. It is concluded that for the next few years the natural gas fired combined cycle will be the main type of plant installed for electricity generation and cogeneration. Whilst gas turbines may not increase substantially in unit size, there remains scope for further increase in firing temperature with consequent increase in cycle performance. However the larger global reserves of coal are providing an incentive to the development of plant for clean coal combustion using the inherent advantage of the combined cycle to attain high efficiencies.

Moore, M. J.

382

Functional cell-cycle chromatin conformation changes in the presence of DNA damage result into chromatid breaks: a new insight in the formation of radiation-induced chromosomal aberrations based on the direct observation of interphase chromatin.  

PubMed

Experiments were carried out to explore the correlation between chromatin conformation changes in the presence of DNA lesions and the formation of radiation-induced chromosomal aberrations. To modulate the onset and dynamics of chromatin conformation changes following irradiation, premature chromosome condensation (PCC) was induced by means of cell fusion. G2-check point abrogation by caffeine or elevated heat treatment was also applied. In addition, transfer of irradiated mitotic cells was employed either into depleted media to restrain them from proceeding through G1/S, or holding them further in colcemid to avoid M/G1 transition. To investigate the correlation between efficiency of chromosomal conformation changes and chromosomal breakage in irradiated G0 peripheral blood lymphocytes, cell fusion with different mitotic PCC-inducer cells was used. The experimental evidence supports the hypothesis that functional cell-cycle chromatin conformation changes in the presence of DNA damage are important determinants in the formation of radiation-induced chromosomal aberrations. Specifically, it is proposed here that following irradiation, chromatin structure may not be broken but instead it unfolds to a conformation that is more accessible to repair enzymes at the sites of DNA lesions. If subsequent chromosomal conformation changes occur while DNA is still being repaired, such changes will lead into an energetically unfavorable state, thus exerting mechanical stress on the unfolded chromatin at the damaged sites, which will in turn result into chromatid breaks that may not be able to restitute or mis-rejoin. Therefore, this biophysical conversion process of DNA damage into chromatid breaks as such is antagonistic to the DNA repair process. Alternatively, in the absence of chromosomal conformation changes, either DNA repair will take place efficiently or DNA misrepair will cause the formation of exchanges and chromosomal rearrangements. Consequently, the type and yield of radiation-induced chromosomal aberrations at a given cell cycle stage will be the combined effect of the interaction, at that particular stage, of the DNA repair process and the proposed conversion process of DNA lesions into chromatid breaks. PMID:20398788

Pantelias, Gabriel E; Terzoudi, Georgia I

2010-04-14

383

Limit cycles and conformal invariance  

NASA Astrophysics Data System (ADS)

There is a widely held belief that conformal field theories (CFTs) require zero beta functions. Nevertheless, the work of Jack and Osborn implies that the beta functions are not actually the quantites that decide conformality, but until recently no such behavior had been exhibited. Our recent work has led to the discovery of CFTs with nonzero beta functions, more precisely CFTs that live on recurrent trajectories, e.g., limit cycles, of the beta-function vector field. To demonstrate this we study the S function of Jack and Osborn. We use Weyl consistency conditions to show that it vanishes at fixed points and