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Acid Transport (acid + transport)
Kinds of Acid Transport Terms modified by Acid Transport Selected AbstractsEpidermal Growth Factor Regulates Amino Acid Transport in Chick Embryo Hepatocytes via Protein Kinase CEXPERIMENTAL PHYSIOLOGY, Issue 4 2000Maria Marino System A-mediated amino acid transport, activation of different steps of signal transduction and involvement of different isoforms of protein kinase C (PKC) have been investigated in chick embryo hepatocytes after epidermal growth factor (EGF) stimulation. EGF rapidly (10 min) increased the rate of aminoisobutyric acid (AIB) uptake in chick embryo hepatocytes freshly isolated on the 19th day of embryonic life, while no change was detectable at other embryonal stages. The growth factor stimulation was abolished by PKC and tyrosine kinase inhibitors and was mimicked by 4-phorbol-12-myristate-13-acetate, dimethyl-2 (PMA). EGF treatment did not modify the phosphorylation of the , isoform of phospholipase C (PLC-,), and inositol trisphosphate (IP3) and intracellular calcium levels, but it induced an increase in PKC activity. Our data show that EGF regulates amino acid uptake, via PKC and without PLC-, activation, only in the last period of chick embryo hepatocyte development. The effects of growth factor on PKC activity suggest the involvement of PKC-, and -, isoforms in EGF modulation of amino acid transport. [source] The Mechanisms and Regulation of Placental Amino Acid Transport to the Human FoetusJOURNAL OF NEUROENDOCRINOLOGY, Issue 4 2008J. K. Cleal The mechanisms by which amino acids are transferred across the human placenta are fundamental to our understanding of foetal nutrition. Amino acid transfer across the human placenta is dependent on transport across both the microvillous and basal plasma membranes of the placental syncytiotrophoblast, and on metabolism within the syncytiotrophoblast. Although the principles underlying uptake of amino acids across the microvillous plasma membrane are well understood, the extent to which amino acids are metabolised within human placenta and the mechanisms by which amino acids are transported out of the placenta across the basal plasma membrane are not well understood. Understanding the mechanisms and regulation of amino acid transport is necessary to understand the causes of intrauterine growth restriction in human pregnancy. [source] Human herpes virus 6B: A possible role in epilepsy?EPILEPSIA, Issue 11 2008William H. Theodore Summary Human herpes virus 6 (HHV6) infection is nearly ubiquitous in childhood and may include central nervous system invasion. There are two variants, HHV6A and HHV6B. Usually asymptomatic, it is associated with the common, self-limited childhood illness roseola infantum and rarely with more severe syndromes. In patients with immune compromise, subsequent reactivation of viral activity may lead to severe limbic encephalitis. HHV6 has been identified as a possible etiologic agent in multiple sclerosis, myocarditis, and encephalitis. A preponderance of evidence supports an association between HHV6 and febrile seizures. An ongoing multicenter study is investigating possible links between HHV6 infection, febrile status epilepticus, and development of mesial temporal sclerosis (MTS). Investigation of temporal lobectomy specimens showed evidence of active HHV6B but not HHV6A replication in hippocampal astrocytes in about two-thirds of patients with MTS but not other causes of epilepsy. It has been suggested that HHV6B may cause "excitotoxicity" by interfering with astrocyte excitatory amino acid transport. Although conventional inflammatory changes are not found in most MTS specimens, inflammatory modulators may play a role in neuronal injury leading to MTS as well. If the link between early viral infection, complex or prolonged febrile seizures, and later development of intractable temporal lobe epilepsy is confirmed, new therapeutic approaches to a common intractable epilepsy syndrome may be possible. [source] Effects of Endotoxin Exposure on Cationic Amino Acid Transporter Function in Ovine Peripheral Blood Mononuclear CellsEXPERIMENTAL PHYSIOLOGY, Issue 2 2003Megan F. Clark Rodent models of sepsis differ from clinical human disease in that humans make substantially less whole-body nitric oxide and have different cellular responses to endotoxin. Sheep, when exposed to endotoxin, behave in a manner more similar to humans. Many studies of rodent peripheral blood mononuclear cells (PBMCs) exposed to endotoxin demonstrate increased cationic amino acid transporter function (particularly through the y+ transporter) to supply arginine substrate to upregulated nitric oxide synthase. Whether this is true in sheep is not known. We have studied cationic amino acid transport in sheep PBMCs stimulated with endotoxin, using labelled lysine. PBMCs stimulated both in vitro and in vivo show an initial reduction in total and y+ lysine transport (after 1-2 h exposure to endotoxin): a previously undescribed effect of endotoxin. In in vitro activated cells, the reduction in y+ transport was prevented by the lipoxygenase inhibitor, nordihydroguaretic acid (NDGA), and the phospholipase inhibitor 4-bromophenacyl bromide (4-BPAB), but not cyclohexamide or a number of other inhibitors of intracellular second-messenger pathways. In contrast after 14 h incubation, the expected increase in total and y+ lysine transport was seen. The increase in y+ transport could be prevented by cyclohexamide, dexamethasone, ibuprofen, the protein kinase C inhibitor sphingosine, NDGA and 4-BPAB. These results suggest that in response to endotoxin exposure there is an initial decrease in y+ activity mediated by a lipoxygenase product, followed by a substantial increase in y+ activity mediated by the products of either cyclo-oxygenase or lipoxygenase. Cyclo-oxygenase and/or lipoxygenase inhibition might be useful in reducing arginine transport, and hence nitric oxide production, in these cells. [source] Epidermal Growth Factor Regulates Amino Acid Transport in Chick Embryo Hepatocytes via Protein Kinase CEXPERIMENTAL PHYSIOLOGY, Issue 4 2000Maria Marino System A-mediated amino acid transport, activation of different steps of signal transduction and involvement of different isoforms of protein kinase C (PKC) have been investigated in chick embryo hepatocytes after epidermal growth factor (EGF) stimulation. EGF rapidly (10 min) increased the rate of aminoisobutyric acid (AIB) uptake in chick embryo hepatocytes freshly isolated on the 19th day of embryonic life, while no change was detectable at other embryonal stages. The growth factor stimulation was abolished by PKC and tyrosine kinase inhibitors and was mimicked by 4-phorbol-12-myristate-13-acetate, dimethyl-2 (PMA). EGF treatment did not modify the phosphorylation of the , isoform of phospholipase C (PLC-,), and inositol trisphosphate (IP3) and intracellular calcium levels, but it induced an increase in PKC activity. Our data show that EGF regulates amino acid uptake, via PKC and without PLC-, activation, only in the last period of chick embryo hepatocyte development. The effects of growth factor on PKC activity suggest the involvement of PKC-, and -, isoforms in EGF modulation of amino acid transport. [source] Effect of fatty acid-binding proteins on intermembrane fatty acid transportFEBS JOURNAL, Issue 19 2000Studies on different types, mutant proteins Liposomes of different charge fixed to nitrocellulose filters were used to study the transfer of fatty acids to rat heart or liver mitochondria in the presence of fatty acid-binding protein (FABP) or albumin. [14C]Palmitate oxidation was used as a parameter. Different FABP types and heart FABP mutants were tested. The charge of the liposomes did not influence the solubilization and mitochondrial oxidation of palmitate without FABP and the amount of solubilized palmitate in the presence of FABP. Mitochondria did not show a preference for oxidation of FABP-bound palmitate over their tissue-specific FABP type. All FABP types increased palmitate oxidation by heart and liver mitochondria with neutral, positive and negative liposomes by 2.5-fold, 3.2-fold and twofold, respectively. Ileal lipid-binding protein and H-FABP mutants that do not bind fatty acid had no effect. Other H-FABP mutants had different effects, dependent on the site of mutation. The effect of albumin was similar to, but not dependent on, liposome charge. The ionic strength had only a slight effect. In conclusion, the transfer of palmitate from liposomal membranes to mitochondria was increased by all FABP types to a similar extent. The membrane charge had a large effect in contrast to the origin of the mitochondria. [source] Amino Acid Transport Kinetics and Protein Turnover in HemodialysisHEMODIALYSIS INTERNATIONAL, Issue 1 2003Raj Dominic Background: Protein metabolism is abnormal in patients with end-stage renal disease. However, the etiology of abnormal protein turnover is unclear. Also the role of hemodialysis on protein turnover remains controversial. Abnormal protein metabolism could be due to malnutrition or due to abnormal amino acid transport kinetics Hypothesis: 1) Amino acid transport is abnormal in uremia, 2) Hemodialysis increases fractional protein synthesis rate and c) Net protein accretion is negative during hemodialysis because of increased catabolism. Aim: 1) To study the impact of uremia and hemodialysis on intracellular amino acid transport kinetics and 2) Quantify the fractional protein synthesis rate and degradation in a uremic state and during hemodialysis Methods: Protein turnover and amino acid transport kinetics using stable isotopes of phenylalanine in 2 patients and 2 controls. The patients were placed on a standard diet (1.2 gm/Kg protein and 35 Kcal/Kg) for 2 weeks prior to the study. Acidosis as corrected by NaHCO3 supplementation. Amino acid transport and protein turnover were estimated by compartmental model and precursor product approach respectively. Results: Mean protein intake and HCO3 were 1.4 ± 1 gm/day and 26.8 ± 4.1 meq/L respectively. Inward transport (11.2 ± 2.6 vs. 9.8 ± 2.1 nmol/min,1/100 ml leg,1) and outward transport (10.2 ± 1.2 vs.11.0 ± 1.6 l nmol/min,1/100 ml leg,1) were not different before and during HD. Inward and outward transport in controls were 12.6 ± 3.7 and 16.2 ± 3.5 nmol/min,1/100 ml leg,1 respectively. Protein synthesis was higher than catabolism in the pre-dialysis phase (156.8 ± 66.1 vs. 144.3 ± 53.7 nmol/min/ml leg-1, p = NS), but catabolism was higher than synthesis during HD (172.3 ± 20.5 vs. 186.8 ± 25.8 nmol/min/ml leg-1, p = NS). Protein synthesis and catabolism in controls were 110.8 ± 13.5 and 127.4 ± 12.7 nmol/min/ml leg-1. Conclusion: 1. Inward and outward transport of amino acids are not altered by renal failure or hemodialysis. 2. Protein turnover is increased during hemodialysis, with net balance favoring catabolism [source] Biliary physiology and disease: Reflections of a physician-scientist,HEPATOLOGY, Issue 4 2010Gustav Paumgartner A review is presented of Gustav Paumgartner's five decades of research and practice in hepatology focusing on biliary physiology and disease. It begins with studies of the excretory function of the liver including hepatic uptake of indocyanine green, bilirubin, and bile acids. The implications of these studies for diagnosis and understanding of liver diseases are pointed out. From there, the path of scientific research leads to investigations of hepatobiliary bile acid transport and the major mechanisms of bile formation. The therapeutic effects of the hydrophilic bile acid, ursodeoxycholic acid, have greatly stimulated these studies. Although ursodeoxycholic acid therapy for dissolution of cholesterol gallstones and some other nonsurgical treatments of gallstones were largely superseded by surgical techniques, ursodeoxycholic acid is currently considered the mainstay of therapy of some chronic cholestatic liver diseases, such as primary biliary cirrhosis. The major mechanisms of action of ursodeoxycholic acid therapy in cholestatic liver diseases are discussed. An attempt is made to illustrate how scientific research can lead to advances in medical practice that help patients. (HEPATOLOGY 2010:51:1095,1106.) [source] Bile acid treatment alters hepatic disease and bile acid transport in peroxisome-deficient PEX2 Zellweger mice,HEPATOLOGY, Issue 4 2007Megan H. Keane The marked deficiency of peroxisomal organelle assembly in the PEX2,/, mouse model for Zellweger syndrome provides a unique opportunity to developmentally and biochemically characterize hepatic disease progression and bile acid products. The postnatal survival of homozygous mutants enabled us to evaluate the response to bile acid replenishment in this disease state. PEX2 mutant liver has severe but transient intrahepatic cholestasis that abates in the early postnatal period and progresses to steatohepatitis by postnatal day 36. We confirmed the expected reduction of mature C24 bile acids, accumulation of C27,bile acid intermediates, and low total bile acid level in liver and bile from these mutant mice. Treating the PEX2,/, mice with bile acids prolonged postnatal survival, alleviated intrahepatic cholestasis and intestinal malabsorption, reduced C27,bile acid intermediate production, and prevented older mutants from developing severe steatohepatitis. However, this therapy exacerbated the degree of hepatic steatosis and worsened the already severe mitochondrial and cellular damage in peroxisome-deficient liver. Both untreated and bile acid,fed PEX2,/, mice accumulated high levels of predominantly unconjugated bile acids in plasma because of altered expression of hepatocyte bile acid transporters. Significant amounts of unconjugated bile acids were also found in the liver and bile of PEX2 mutants, indicating a generalized defect in bile acid conjugation. Conclusion: Peroxisome deficiency widely disturbs bile acid homeostasis and hepatic functioning in mice, and the high sensitivity of the peroxisome-deficient liver to bile acid toxicity limits the effectiveness of bile acid therapy for preventing hepatic disease. (HEPATOLOGY 2007;45:982,997.) [source] Secretin activation of the apical Na+ -dependent bile acid transporter is associated with cholehepatic shunting in rats,HEPATOLOGY, Issue 5 2005Gianfranco Alpini The role of the cholangiocyte apical Na+ -dependent bile acid transporter (ASBT) in bile formation is unknown. Bile acid absorption by bile ducts results in cholehepatic shunting, a pathway that amplifies the canalicular osmotic effects of bile acids. We tested in isolated cholangiocytes if secretin enhances ASBT translocation to the apical membrane from latent preexisting intracellular stores. In vivo, in bile duct,ligated rats, we tested if increased ASBT activity (induced by secretin pretreatment) results in cholehepatic shunting of bile acids. We determined the increment in taurocholate-dependent bile flow and biliary lipid secretion and taurocholate (TC) biliary transit time during high ASBT activity. Secretin stimulated colchicine-sensitive ASBT translocation to the cholangiocyte plasma membrane and 3H-TC uptake in purified cholangiocytes. Consistent with increased ASBT promoting cholehepatic shunting, with secretin pretreatment, we found TC induced greater-than-expected biliary lipid secretion and bile flow and there was a prolongation of the TC biliary transit time. Colchicine ablated secretin pretreatment-dependent bile acid,induced choleresis, increased biliary lipid secretion, and the prolongation of the TC biliary transit. In conclusion, secretin stimulates cholehepatic shunting of conjugated bile acids and is associated with increased cholangiocyte apical membrane ASBT. Bile acid transport by cholangiocyte ASBT can contribute to hepatobiliary secretion in vivo. (HEPATOLOGY 2005.) [source] The nuclear bile acid receptor FXR as a novel therapeutic target in cholestatic liver diseases: Hype or hope?HEPATOLOGY, Issue 1 2004Michael Trauner M.D. Farnesoid X receptor (FXR) is a bile acid,activated transcription factor that is a member of the nuclear hormone receptor superfamily. FXR-null mice exhibit a phenotype similar to Byler disease, an inherited cholestatic liver disorder. In the liver, activation of FXR induces transcription of transporter genes involved in promoting bile acid clearance and represses genes involved in bile acid biosynthesis. We investigated whether the synthetic FXR agonist GW4064 could protect against cholestatic liver damage in rat models of extrahepatic and intrahepatic cholestasis. In the bile duct ligation and alpha-naphthylisothiocyanate models of cholestasis, GW4064 treatment resulted in significant reductions in serum alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase, as well as other markers of liver damage. Rats that received GW4064 treatment also had decreased incidence and extent of necrosis, decreased inflammatory cell infiltration, and decreased bile duct proliferation. Analysis of gene expression in livers from GW4064-treated cholestatic rats revealed decreased expression of bile acid biosynthetic genes and increased expression of genes involved in bile acid transport, including the phospholipid flippase MDR2. The hepatoprotection seen in these animal models by the synthetic FXR agonist suggests FXR agonists may be useful in the treatment of cholestatic liver disease. [source] Ursodeoxycholic acid: Mechanism of action and novel clinical applicationsHEPATOLOGY RESEARCH, Issue 2 2008Tadashi Ikegami Ursodeoxycholic acid (UDCA) is used in the treatment of cholestatic liver diseases, gallstone dissolution, and for patients with hepatitis C virus infection to ameliorate elevated alanine aminotransferase levels. The efficacy of UDCA treatment has been debated and the mechanisms of action in humans have still not defined. Suggested mechanisms include the improvement of bile acid transport and/or detoxification, cytoprotection, and anti-apoptotic effects. In this review, we summarize the proposed molecular mechanisms for the action of UDCA, especially in hepatocytes, and also discuss the putative future clinical usage of this unique drug. [source] Cellular localization of epidermal-type and brain-type fatty acid-binding proteins in adult hippocampus and their response to cerebral ischemiaHIPPOCAMPUS, Issue 7 2010Dexuan Ma Abstract This study aimed at an analysis of expression of epidermal-type and brain-type fatty acid-binding proteins (E-FABP and B-FABP, also called FABP5 and FABP7, respectively) in adult hippocampus and their potential value as neuroprotective factors after ischemic brain damage in monkey model. The immunostaining and Western blotting results show that FABP5 was mainly expressed in neurons, whereas FABP7 was primarily expressed in astrocytes and progenitors of the subgranular zone (SGZ). Interestingly, FABP5 expression in neurons increased in cornu Ammonis 1 (CA1) and remains stable within dentate gyrus (DG) after ischemia; FABP7 expression increased within both CA1 and SGZ. This indicates a potential role for FABP5 and FABP7 in intracellular fatty acid transport within different neural cells. The change in FABP5,7 expression within CA1 and DG of the adult postischemic hippocampus was compatible with previous findings of downregulation in CA1 neurons and upregulation in SGZ progenitor cells after ischemia. Altogether, the present data suggest that polyunsaturated fatty acids, such as docosahexaenoic acid, may act via FABP5 or 7 to regulate adult postischemic hippocampal neuronal antiapoptosis or neurogenesis in primates. © 2009 Wiley-Liss, Inc. [source] The Complementary Membranes Forming the Blood-Brain BarrierIUBMB LIFE, Issue 3 2002Richard A. Hawkins Abstract Brain capillary endothelial cells form the blood-brain barrier. They are connected by extensive tight junctions, and are polarized into luminal (blood-facing) and abluminal (brain-facing) plasma membrane domains. The polar distribution of transport proteins allows for active regulation of brain extracellular fluid. Experiments on isolated membrane vesicles from capillary endothelial cells of bovine brain demonstrated the polar arrangement of amino acid and glucose transporters, and the utility of such arrangements have been proposed. For instance, passive carriers for glutamine and glutamate have been found only in the luminal membrane of blood-brain barrier cells, while Na-dependent secondary active transporters are at the abluminal membrane. This organization could promote the net removal of nitrogen-rich amino acids from brain, and account for the low level of glutamate penetration into the central nervous system. Furthermore, the presence of a ,-glutamyl cycle at the luminal membrane and Na-dependent amino acid transporters at the abluminal membrane may serve to modulate movement of amino acids from blood-to-brain. Passive carriers facilitate amino acid transport into brain. However, activation of the ,-glutamyl cycle by increased plasma amino acids is expected to generate oxoproline within the blood-brain barrier. Oxoproline stimulates secondary active amino acid transporters (Systems A and B o,+ ) at the abluminal membrane, thereby reducing net influx of amino acids to brain. Finally, passive glucose transporters are present in both the luminal and abluminal membranes of the blood-brain barrier. Interestingly, a high affinity Na-dependent glucose carrier has been described only in the abluminal membrane. This raises the question whether glucose entry may be regulated to some extent. Immunoblotting studies suggest more than one type of passive glucose transporter exist in the blood-brain barrier, each with an asymmetrical distribution. In conclusion, it is now clear that the blood-brain barrier participates in the active regulation of brain extracellular fluid, and that the diverse functions of each plasma membrane domain contributes to these regulatory functions. [source] Effects of Cyclosporine on Osteoclast Activity: Inhibition of Calcineurin Activity With Minimal Effects on Bone Resorption and Acid Transport Activity,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2003John P Williams Abstract Cyclosporine results in rapid and profound bone loss in transplant patients, an effect ascribed to osteoclasts. Cyclosporine, complexed with the appropriate immunophilin, inhibits calcineurin (the calcium/calmodulin dependent serine/threonine phosphatase) activity. We tested the hypothesis that cyclosporine inhibits calcineurin activity in osteoclasts, resulting in stimulation of osteoclast activity. We compared the effects of cyclosporine A and the calmodulin antagonist, tamoxifen, on bone resorption by avian osteoclasts. Tamoxifen inhibits bone resorption ,60%, whereas cyclosporine A only inhibited bone resorption 12%. One-hour treatment with 100 nM cyclosporine inhibited osteoclast calcineurin activity 70% in whole cell lysates, whereas 10 ,M tamoxifen only inhibited calcineurin activity 25%. We compared the effects of cyclosporine A and tamoxifen on acid transport activity in isolated membrane vesicles and in isolated membrane vesicles obtained from osteoclasts treated with cyclosporine A or tamoxifen under conditions that inhibit calcineurin activity. Direct addition of cyclosporine A in the acid transport assay, or pretreatment of cells with cyclosporine A followed by membrane isolation, had no effect on acid transport activity in membrane vesicles. In contrast, direct addition of tamoxifen to membranes inhibits acid transport activity, an effect that can be prevented by addition of exogenous calmodulin. Furthermore, acid transport activity was also inhibited in membrane vesicles isolated from cells treated with tamoxifen. In conclusion, cyclosporine A inhibits osteoclast calcineurin activity; however, calcineurin inhibition does not correspond to a significant effect on acid transport activity in isolated membrane vesicles or bone resorption by osteoclasts. [source] Essential role of PSM/SH2-B variants in insulin receptor catalytic activation and the resulting cellular responsesJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2008Manchao Zhang Abstract The positive regulatory role of PSM/SH2-B downstream of various mitogenic receptor tyrosine kinases or gene disruption experiments in mice support a role of PSM in the regulation of insulin action. Here, four alternative PSM splice variants and individual functional domains were compared for their role in the regulation of specific metabolic insulin responses. We found that individual PSM variants in 3T3-L1 adipocytes potentiated insulin-mediated glucose and amino acid transport, glycogenesis, lipogenesis, and key components in the metabolic insulin response including p70 S6 kinase, glycogen synthase, glycogen synthase kinase 3 (GSK3), Akt, Cbl, and IRS-1. Highest activity was consistently observed for PSM alpha, followed by beta, delta, and gamma with decreasing activity. In contrast, dominant-negative peptide mimetics of the PSM Pro-rich, pleckstrin homology (PH), or src homology 2 (SH2) domains inhibited any tested insulin response. Potentiation of the insulin response originated at the insulin receptor (IR) kinase level by PSM variant-specific regulation of the Km (ATP) whereas the Vmax remained unaffected. IR catalytic activation was inhibited by peptide mimetics of the PSM SH2 or dimerization domain (DD). Either peptide should disrupt the complex of a PSM dimer linked to IR via SH2 domains as proposed for PSM activation of tyrosine kinase JAK2. Either peptide abolished downstream insulin responses indistinguishable from PSM siRNA knockdown. Our results implicate an essential role of the PSM variants in the activation of the IR kinase and the resulting metabolic insulin response. PSM variants act as internal IR ligands that in addition to potentiating the insulin response stimulate IR catalytic activation even in the absence of insulin. J. Cell. Biochem. 103: 162,181, 2008. © 2007 Wiley-Liss, Inc. [source] The Mechanisms and Regulation of Placental Amino Acid Transport to the Human FoetusJOURNAL OF NEUROENDOCRINOLOGY, Issue 4 2008J. K. Cleal The mechanisms by which amino acids are transferred across the human placenta are fundamental to our understanding of foetal nutrition. Amino acid transfer across the human placenta is dependent on transport across both the microvillous and basal plasma membranes of the placental syncytiotrophoblast, and on metabolism within the syncytiotrophoblast. Although the principles underlying uptake of amino acids across the microvillous plasma membrane are well understood, the extent to which amino acids are metabolised within human placenta and the mechanisms by which amino acids are transported out of the placenta across the basal plasma membrane are not well understood. Understanding the mechanisms and regulation of amino acid transport is necessary to understand the causes of intrauterine growth restriction in human pregnancy. [source] ANALYSIS OF EXPRESSED SEQUENCE TAGS (ESTS) FROM THE POLAR DIATOM FRAGILARIOPSIS CYLINDRUS,JOURNAL OF PHYCOLOGY, Issue 1 2006Thomas Mock Analysis of expressed sequence tags (ESTs) was performed to gain insights into cold adaptation in the polar diatom Fragilariopsis cylindrus Grunow. The EST library was generated from RNA isolated 5 days after F. cylindrus cells were shifted from approximately +5° C to ,1.8°C. A total of 1376 ESTs were sequenced from a non-normalized cDNA library and assembled into 996 tentative unique sequences. About 27% of the ESTs displayed similarity (tBLASTX, e -value of ,10,4) to predicted proteins in the centric diatom Thalassiosira pseudonana Hasle & Heindal. Eleven additional algae and plant data bases were used for annotation of sequences not covered by Thalassiosira sequences (7%). Most of the ESTs were similar to genes encoding proteins responsible for translation, ribosomal structure, and biogenesis (3%), followed by genes encoding proteins for amino acid transport and metabolism and post-translational modifications. Interestingly, 66% of all the EST sequences from F. cylindrus displayed no similarity (e -value ,10,4) to sequences from the 12 non-redundant databases. Even 6 of the 10 strong to moderately expressed sequences in this EST library could not be identified. Adaptation of F. cylindrus to freezing temperatures of seawater may require a complex protein metabolism and possibly also genes, which were highly expressed but still unknown. However, it could also mean that due to low temperatures, there might have been a stronger pressure to adapt amino acid sequences, making it more difficult to identify these unknown sequences and/or that there are still few protist sequences available for comparison. [source] Calluna vulgaris root cells show increased capacity for amino acid uptake when colonized with the mycorrhizal fungus Hymenoscyphus ericaeNEW PHYTOLOGIST, Issue 3 2002Sergei G. Sokolovski Summary ,,Ericoid mycorrhizas are believed to improve N nutrition of many ericaceous plant species that typically occur in habitats with impoverished nutrient status, by releasing amino acids from organic N forms. Despite the ubiquity of mycorrhizal formation the mechanisms and regulation of nutrient transport in mycorrhizal associations are poorly understood. ,,We used an electrophysiological approach to study how amino acid transport characteristics of Calluna vulgaris were affected by colonization with the ericoid mycorrhiza fungus Hymenoscyphus ericae . ,,Both the Vmax and Km parameters of amino acid uptake were affected by fungal colonization in a manner consistent with an increased availability of amino acid to the plant. ,,The ecophysiological significance of altered amino acid transport in colonized root cells of C. vulgaris is discussed. [source] Placental insulin-like growth factor II (IGF-II) and its relation to litter size in the common marmoset monkey (Callithrix jacchus)AMERICAN JOURNAL OF PRIMATOLOGY, Issue 12 2009Julienne N. Rutherford Abstract The primate placenta produces a wide variety of hormones throughout gestation that regulate placental function and fetal growth. One such hormone is insulin-like growth factor-II (IGF-II), a peptide implicated in cell division, differentiation, and amino acid transport. IGF-II concentrations were measured in 23 common marmoset (Callithrix jacchus) term placentas from twin and triplet litters in order to determine whether previously described differences in fetoplacental phenotype such as placental and litter mass and placental surface area were related to differences in endocrine function. IGF-II was extracted from frozen tissue samples and measured using an enzyme-linked immunosorbent assay kit designed for human tissue, which was validated for marmoset placenta. IGF-II concentrations were not related to placental or litter mass, and twin and triplet placentas did not differ in total concentration. However, per individual fetus, triplets were associated with a significant 42% reduction in IGF-II concentration (P=0.03), and IGF-II concentration per gram of fetal mass was a third lower in triplet litters. The triplet placenta exhibits a global expansion of the surface area which was contrasted by a per unit area reduction in IGF-II concentration (r=,0.75, P=0.01), a pattern that explains why twin and triplet placentas overall did not differ in concentration. Per fetus, triplet pregnancies are associated with relatively less maternal mass, placental mass and microscopic surface area suggesting that the intrauterine growth of triplets is supported by systems that increase the efficiency of nutrient transfer. The finding that individual triplet fetuses are also associated with significantly lower IGF-II concentrations is consistent with the view that the marmoset fetoplacental unit exhibits a flexible pattern of placental allocation and metabolism. Plasticity in placental endocrine and metabolic function is likely to play an important role in the ability of the fetus to sense and accommodate the intrauterine environment and, by extension, the external ecology. Am. J. Primatol. 71:969,975, 2009. © 2009 Wiley-Liss, Inc. [source] Novel mechanism causing restricted fetal growth: does maternal homocysteine impair placental amino acid transport?THE JOURNAL OF PHYSIOLOGY, Issue 17 2009Thomas Jansson No abstract is available for this article. [source] Rosiglitazone increases fatty acid oxidation and fatty acid translocase (FAT/CD36) but not carnitine palmitoyltransferase I in rat muscle mitochondriaTHE JOURNAL OF PHYSIOLOGY, Issue 6 2008Carley R. Benton Peroxisome proliferator-activated receptors (PPARs) alter the expression of genes involved in regulating lipid metabolism. Rosiglitazone, a PPAR, agonist, induces tissue-specific effects on lipid metabolism; however, its mode of action in skeletal muscle remains unclear. Since fatty acid translocase (FAT/CD36) was recently identified as a possible regulator of skeletal muscle fatty acid transport and mitochondrial fatty acid oxidation, we examined in this tissue the effects of rosiglitazone infusion (7 days, 1 mg day,1) on FAT/CD36 mRNA and protein, its plasmalemmal content and fatty acid transport. In addition, in isolated subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria we examined rates of fatty acid oxidation, FAT/CD36 and carnitine palmitoyltransferase I (CPTI) protein, and CPTI and ,-hydroxyacyl CoA dehydrogenase (,-HAD) activities. Rosiglitazone did not alter FAT/CD36 mRNA or protein expression, FAT/CD36 plasmalemmal content, or the rate of fatty acid transport into muscle (P > 0.05). In contrast, rosiglitazone increased the rates of fatty acid oxidation in both SS (+21%) and IMF mitochondria (+36%). This was accompanied by concomitant increases in FAT/CD36 in subsarcolemmal (SS) (+43%) and intermyofibrillar (IMF) mitochondria (+46%), while SS and IMF CPTI protein content, and CPTI submaximal and maximal activities (P > 0.05) were not altered. Similarly, citrate synthase (CS) and ,-HAD activities were also not altered by rosiglitazone in SS and IMF mitochondria (P > 0.05). These studies provide another example whereby changes in mitochondrial fatty oxidation are associated with concomitant changes in mitochondrial FAT/CD36 independent of any changes in CPTI. Moreover, these studies identify for the first time a mechanism by which rosiglitazone stimulates fatty acid oxidation in skeletal muscle, namely the chronic, subcellular relocation of FAT/CD36 to mitochondria. [source] Gene duplication, exon gain and neofunctionalization of OEP16 -related genes in land plantsTHE PLANT JOURNAL, Issue 5 2006Sinéad C. Drea Summary OEP16, a channel protein of the outer membrane of chloroplasts, has been implicated in amino acid transport and in the substrate-dependent import of protochlorophyllide oxidoreductase A. Two major clades of OEP16-related sequences were identified in land plants (OEP16-L and OEP16-S), which arose by a gene duplication event predating the divergence of seed plants and bryophytes. Remarkably, in angiosperms, OEP16-S genes evolved by gaining an additional exon that extends an interhelical loop domain in the pore-forming region of the protein. We analysed the sequence, structure and expression of the corresponding Arabidopsis genes (atOEP16-S and atOEP16-L) and demonstrated that following duplication, both genes diverged in terms of expression patterns and coding sequence. AtOEP16-S, which contains multiple G-box ABA-responsive elements (ABREs) in the promoter region, is regulated by ABI3 and ABI5 and is strongly expressed during the maturation phase in seeds and pollen grains, both desiccation-tolerant tissues. In contrast, atOEP-L, which lacks promoter ABREs, is expressed predominantly in leaves, is induced strongly by low-temperature stress and shows weak induction in response to osmotic stress, salicylic acid and exogenous ABA. Our results indicate that gene duplication, exon gain and regulatory sequence evolution each played a role in the divergence of OEP16 homologues in plants. [source] Redox regulation of ascorbic acid transport: Role of transporter and intracellular sulfhydrylsBIOFACTORS, Issue 4 2004James M. May Abstract Ascorbic acid is one of the most sensitive cellular defenses against oxidant damage. However, it requires a sodium- and energy-dependent transporter to enter cells against a concentration gradient. To test the hypothesis that ascorbate transport is sensitive to redox stress, we studied changes in transport of the vitamin in response to sulfhydryl modification of the protein and to GSH depletion in cultured endothelial cells. Transport of ascorbic acid, measured as the uptake of radiolabeled ascorbate, was inhibited by the membrane-impermeant sulfhydryl reagents thorin, p -chloromercuribenzene sulfonic acid, and 5,5,-dithiobis-(2-nitrobenzoic acid) in a dose-dependent manner without significant depletion of intracellular GSH. Sulfhydryl reagents capable of penetrating the plasma membrane, including phenylarsine oxide, p -chloromercuribenzoic acid, and N-ethylmaleimide, inhibited transport and lowered cellular GSH. Diamide, which induces disulfide formation, increased ascorbate transport over a narrow concentration range under conditions in which GSH was not depleted. On the other hand, specific depletion of intracellular GSH by several different mechanisms did inhibit transport. Together, these results suggest that the ascorbate transporter is sensitive to redox modulation. This relates in part to sulfhydryl groups exposed on the exofacial ascorbate transporter, and to sulfhydryl groups that are sensitive to changes in the redox state of intracellular GSH. [source] Developmental consequences of abnormal folate transport during murine heart morphogenesis ,BIRTH DEFECTS RESEARCH, Issue 7 2004Louisa S. Tang Abstract BACKGROUND Folic acid is essential for the synthesis of nucleotides and methyl transfer reactions. Folic acid,binding protein one (Folbp1) is the primary mediator of folic acid transport into murine cells. Folbp1 knockout mouse embryos die in utero with multiple malformations, including severe congenital heart defects (CHDs). Although maternal folate supplementation is believed to prevent human conotruncal heart defects, its precise role during cardiac morphogenesis remains unclear. In this study, we examined the role of folic acid on the phenotypic expression of heart defects in Folbp1 mice, mindful of the importance of neural crest cells to the formation of the conotruncus. METHODS To determine if the Folbp1 gene participates in the commitment and differentiation of the cardiomyocytes, relative levels of dead and proliferating precursor cells in the heart were examined by flow cytometry, Western blot, and immunohistostaining. RESULTS Our studies revealed that impaired folic acid transport results in extensive apoptosis-mediated cell death, which concentrated in the interventricular septum and truncus arteriosus, thus being anatomically restricted to the two regions of congenital heart defects. Together with a reduced proliferative capacity of the cardiomyocytes, the limited size of the available precursor cell pool may contribute to the observed cardiac defects. Notably, there is a substantial reduction in Pax-3 expression in the region of the presumptive migrating cardiac neural crest, suggesting that this cell population may be the most severely affected by the massive cell death. CONCLUSIONS Our findings demonstrate for the first time a prominent role of the Folbp1 gene in mediating susceptibility to heart defects. Birth Defects Research (Part A), 2004. © 2004 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||