Home About us Contact
|
Home About us Contact | ||
|
|
||
Taurine
Terms modified by Taurine Selected AbstractsDevelopmental shift in bidirectional functions of taurine-sensitive chloride channels during cortical circuit formation in postnatal mouse brainDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2004Mika Yoshida Abstract Taurine (2-aminoethanesulfonic acid) is the most abundant free amino acid in the developing mammalian cerebral cortex, however, few studies have reported its neurobiological functions during development. In this study, by means of whole-cell patch-clamp recordings, we examined the effects of taurine on chloride channel receptors in neocortical neurons from early to late postnatal stages, which cover a critical period in cortical circuit formation. We show here that taurine activates chloride channels in cortical neurons throughout the postnatal stages examined (from postnatal day 2 to day 36). The physiological effects of taurine changed from excitatory to inhibitory due to variations in the intracellular Cl, concentration during development. An antagonist blocking analysis also demonstrated a developmental shift in the receptor target of taurine, from glycine receptors to GABAA receptors. Taken together, these results may reflect genetically programmed, bidirectional functions of taurine. At the early developmental stage, taurine acting on glycine receptors would serve to promote cortical circuit formation. As cortical circuit has to be regulated in the later stages, taurine would serve as a safeguard against hyperexcitable circuit. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 166,175, 2004 [source] GABA and glycine are protective to mature but toxic to immature rat cortical neurons under hypoxiaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2005Peng Zhao Abstract Although recent studies suggest that ,-aminobutyric acid (GABA) and glycine may be ,inhibitory' to mature neurons, but ,excitatory' to immature neurons under normoxia, it is unknown whether inhibitory neurotransmitters are differentially involved in neuronal response to hypoxia in immature and mature neurons. In the present study, we exposed rat cortical neurons to hypoxia (1% O2) and examined the effects of three major inhibitory neurotransmitters (GABA, glycine and taurine) on the hypoxic neurons at different neuronal ages [days in vitro (DIV)4,20]. Our data showed that the cortical neurons expressed both GABAA and glycine receptors with differential developmental profiles. GABA (10,2000 µm) was neuroprotective to hypoxic neurons of DIV20, but enhanced hypoxic injury in neurons of <,DIV20. Glycine at low concentrations (10,100 µm) exhibited a similar pattern to GABA. However, higher concentrations of glycine (1000,2000 µm) for long-term exposure (48,72 h) displayed neuroprotection at all ages (DIV4,20). Taurine (10,2000 µm), unlike GABA and glycine, displayed protection only in DIV4 neurons, and was slightly toxic to neurons >,DIV4. In comparison with delta-opioid receptor (DOR)-induced protection in DIV20 neurons exposed to 72 h of hypoxia, glycine-induced protection was weaker than that of DOR but stronger than that of GABA and taurine. These data suggest that the effects of the inhibitory neurotransmitters on hypoxic cortical neurons are age-dependent, with GABA and glycine being neurotoxic to immature neurons and neuroprotective to mature neurons. [source] Taurine selectively modulates the secretory activity of vasopressin neurons in conscious ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2001Mario Engelmann Abstract Previous experiments have shown that a 10-min forced swimming session triggers the release of vasopressin from somata and dendrites, but not axon terminals, of neurons of the hypothalamic,neurohypophysial system. To further investigate regulatory mechanisms underlying this dissociated release, we forced male Wistar rats to swim in warm (20 °C) water and monitored release of the potentially inhibitory amino acids gamma amino butyric acid (GABA) and taurine into the hypothalamic supraoptic nucleus using microdialysis. Forced swimming caused a significant increase in the release of taurine (up to 350%; P < 0.05 vs. prestress release), but not GABA. To reveal the physiological significance of centrally released taurine, the specific taurine antagonist 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1-dioxide was administered into the supraoptic nucleus via retrodialysis. Administration of this antagonist caused a significant increase in the release of vasopressin within the supraoptic nucleus and into the blood both under basal conditions and during stress (up to 800%; P < 0.05 vs. basal values), without affecting hypothalamic or plasma oxytocin. Local administration of the GABAA receptor antagonist bicuculline, in contrast, failed to influence vasopressin secretion at either time point. In a separate series of in vivo electrophysiological experiments, administration of the same dosage of the taurine antagonist into the supraoptic nucleus via microdialysis resulted in an increased electrical activity of identified vasopressinergic, but not oxytocinergic, neurons. Taken together our data demonstrate that taurine is released within the supraoptic nucleus during physical/emotional stress. Furthermore, at the level of the supraoptic nucleus, taurine inhibits not only the electrical activity of vasopressin neurons but also acts as an inhibitor of both central and peripheral vasopressin secretion during different physiological states. [source] Expression Of O-Acetyl Sialic Acid On Cerebral Microcirculation In A Glycine Or Taurine Treated Diabetic Rat ModelJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 3 2000A Noe Expression of sialic acid is altered in Diabetes mellitus. This modification has also been involved with both vascular and neurologic diseases, and with the increase of no enzymatic glycosylation of proteins. In our opinion, the lectins were very useful with specificity for sialic acids in order to determine the level of sialic acid expression on cerebral microcirculation in a diabetic Wistar rat model with streptozotocin. In this model, the glycine (1%) and taurine (0.5%) aminoacids were placed in drinking-water by six months. At the end of this time, the animals were sacrificed, their brains surgically removed and frozen in liquid nitrogen, and the specimens cut in serial sections. Immediately, the sections were incubated with different biotin-labelled lectins specific to sialic acid using peroxidase-labelled avidin as second ligand and H2O2 chromogen. The results showed greater O-acetyl sialic acid expression in cerebral capillaries of untreated diabetic rats than in glycine-, taurine-treated diabetic rats or than in control animals. The minor sialic acid expression may be an indicator of degenerative diseases such as Alzheimer's or the vascular disease of diabetic patients and probably is related to cellular protective properties of the glycine and taurine aminoacids. These first protective characteristics that have been observed in both ischemia with cellular ATP depletion models, suggest the utilization of aminoacids glycine or taurine in diabetic patient in order to avoid the development of microinfarcts. [source] Effect of Taurine and Melatonin in the Culture Medium on Buffalo In Vitro Embryo DevelopmentREPRODUCTION IN DOMESTIC ANIMALS, Issue 1 2009BM Manjunatha Contents This study was carried out to investigate the effect of supplementing culture medium with different concentrations of taurine and melatonin, on buffalo oocyte in vitro meiotic maturation and embryo development. In experiment 1, oocytes were matured in vitro and the cleaved embryos were cultured in the same following seven culture medium; (i) control (TCM 199 + 10% SS); (ii) control + 0.5 mm taurine; (iii) control + 1 mm taurine; (iv) control + 3 mm taurine; (v) control + 5 ,m melatonin; (vi) control + 10 ,m melatonin and (vii) control + 50 ,m melatonin. In experiment 2, based on the results of experiment 1, to examine the synergistic effect of antioxidants, the oocytes were matured in culture medium (TCM199 + 10% SS), supplemented with both taurine at 1 mm and melatonin at 10 ,m concentration and the cleaved embryos were cultured in the same medium. Supplementation of taurine at 1 mm concentration in the culture medium resulted in a higher (p < 0.05) transferable embryo (TE) yield when compared with control (20.6% vs 14.1%). Supplementation of melatonin at 10 and 50 ,m concentration in the culture medium resulted in a higher (p < 0.05) meiotic maturation rate (90.3% and 88.8% respectively) and TE yield (28.4% and 27.2% respectively), than the other treatments. In experiment 2, the TE yield did not improve by supplementing the culture medium with both taurine and melatonin, when compared with melatonin alone. In conclusion, the results of this study demonstrated that, enriching the culture medium with taurine and melatonin, improves in vitro embryo production efficiency in buffaloes. In particular, a high TE yield was obtained by enriching the culture medium with 10 ,m melatonin. [source] Taurine uptake across the human intestinal brush-border membrane is via two transporters: H+ -coupled PAT1 (SLC36A1) and Na+ - and Cl, -dependent TauT (SLC6A6)THE JOURNAL OF PHYSIOLOGY, Issue 4 2009Catriona M. H. Anderson Taurine is an essential amino acid in some mammals and is conditionally essential in humans. Taurine is an abundant component of meat and fish-based foods and has been used as an oral supplement in the treatment of disorders such as cystic fibrosis and hypertension. The purpose of this investigation was to identity the relative contributions of the solute transporters involved in taurine uptake across the luminal membrane of human enterocytes. Distinct transport characteristics were revealed following expression of the candidate solute transporters in Xenopus laevis oocytes: PAT1 (SLC36A1) is a H+ -coupled, pH-dependent, Na+ - and Cl, -independent, low-affinity, high-capacity transporter for taurine and ,-alanine; TauT (SLC6A6) is a Na+ - and Cl, -dependent, high-affinity, low-capacity transporter of taurine and ,-alanine; ATB0,+ (SLC6A14) is a Na+ - and Cl, -dependent, high-affinity, low-capacity transporter which accepts ,-alanine but not taurine. Taurine uptake across the brush-border membrane of human intestinal Caco-2 cell monolayers showed characteristics of both PAT1- and TauT-mediated transport. Under physiological conditions, Cl, -dependent TauT-mediated uptake predominates at low taurine concentrations, whereas at higher concentrations typical of diet, Cl, -independent PAT1-mediated uptake is the major absorptive mechanism. Real-time PCR analysis of human duodenal and ileal biopsy samples demonstrates that PAT1, TauT and ATB0,+ mRNA are expressed in each tissue but to varying degrees. In conclusion, this study is the first to demonstrate both taurine uptake via PAT1 and functional coexpression of PAT1 and TauT at the apical membrane of the human intestinal epithelium. PAT1 may be responsible for bulk taurine uptake during a meal whereas TauT may be important for taurine supply to the intestinal epithelium and for taurine capture between meals. [source] Effects of oyster extract on the reproductive function of zinc-deficient mice: Bioavailability of zinc contained in oyster extractCONGENITAL ANOMALIES, Issue 4 2003Yoshikazu Matsuda ABSTRACT Zinc is a vital nutrient in the normal reproductive function and embryonic development of mammals, and it is well known that oyster extract contains significant amounts of zinc. The effects of oyster extract on reproductive function, such as embryonic development, serum levels of zinc and sperm maturation were examined in zinc-deficient mice. Zinc deficiency in dams during pregnancy induced a decrease in the successful pregnancy rate, maternal weight gain, the number of live fetuses and fetal body weight. Zinc deficiency for 12 weeks in male mice induced a decrease in body weight, testis weight and sperm count in the epididymis. However, reproductive failure, embryonic defects and decreased sperm motility in zinc-deficient mice were improved by supplementation with oyster extract. Some nutrients contained in oyster extract, such as taurine and glycogen, may be related to the recovery of reproductive function. There were significantly lower serum concentrations of zinc in dams fed a zinc-deficient diet However, the serum zinc concentration was normal in the oyster extract-supplemented group. No difference in the concentration of serum zinc was observed between the oyster extract- and zinc carbonate-supplemented groups. From these findings, it is suggested that oyster extract is a useful supplement that can prevent reproductive defects from zinc deficiency, and the bioavailability of zinc may be identical to zinc carbonate. [source] The taurine transporter: mechanisms of regulationACTA PHYSIOLOGICA, Issue 1-2 2006X. Han Abstract Taurine transport undergoes an adaptive response to changes in taurine availability. Unlike most amino acids, taurine is not metabolized or incorporated into protein but remains free in the intracellular water. Most amino acids are reabsorbed at rates of 98,99%, but reabsorption of taurine may range from 40% to 99.5%. Factors that influence taurine accumulation include ionic environment, electrochemical charge, and post-translational and transcriptional factors. Among these are protein kinase C (PKC) activation and transactivation or repression by proto-oncogenes such as WT1, c-Jun, c-Myb and p53. Renal adaptive regulation of the taurine transporter (TauT) was studied in vivo and in vitro. Site-directed mutagenesis and the oocyte expression system were used to study post-translational regulation of the TauT by PKC. Reporter genes and Northern and Western blots were used to study transcriptional regulation of the taurine transporter gene (TauT). We demonstrated that (i) the body pool of taurine is controlled through renal adaptive regulation of TauT in response to taurine availability; (ii) ionic environment, electrochemical charge, pH, and developmental ontogeny influence renal taurine accumulation; (iii) the fourth segment of TauT is involved in the gating of taurine across the cell membrane, which is controlled by PKC phosphorylation of serine 322 at the post-translational level; (iv) expression of TauT is repressed by the p53 tumour suppressor gene and is transactivated by proto-oncogenes such as WT1, c-Jun, and c-Myb; and (v) over-expression of TauT protects renal cells from cisplatin-induced nephrotoxicity. [source] Parasitoid wasp sting: A cocktail of GABA, taurine, and ,-alanine opens chloride channels for central synaptic block and transient paralysis of a cockroach hostDEVELOPMENTAL NEUROBIOLOGY, Issue 8 2006Eugene L. Moore Abstract The wasp Ampulex compressa injects venom directly into the prothoracic ganglion of its cockroach host to induce a transient paralysis of the front legs. To identify the biochemical basis for this paralysis, we separated venom components according to molecular size and tested fractions for inhibition of synaptic transmission at the cockroach cercal-giant synapse. Only fractions in the low molecular weight range (<2 kDa) caused synaptic block. Dabsylation of venom components and analysis by HPLC and MALDI-TOF-MS revealed high levels of GABA (25 mM), and its receptor agonists ,-alanine (18 mM), and taurine (9 mM) in the active fractions. Each component produces transient block of synaptic transmission at the cercal-giant synapse and block of efferent motor output from the prothoracic ganglion, which mimics effects produced by injection of whole venom. Whole venom evokes picrotoxin-sensitive chloride currents in cockroach central neurons, consistent with a GABAergic action. Together these data demonstrate that Ampulex utilizes GABAergic chloride channel activation as a strategy for central synaptic block to induce transient and focal leg paralysis in its host. © 2006 Wiley Periodicals, Inc. © 2006 Wiley Periodicals, Inc. J Neurobiol, 2006 [source] Developmental shift in bidirectional functions of taurine-sensitive chloride channels during cortical circuit formation in postnatal mouse brainDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2004Mika Yoshida Abstract Taurine (2-aminoethanesulfonic acid) is the most abundant free amino acid in the developing mammalian cerebral cortex, however, few studies have reported its neurobiological functions during development. In this study, by means of whole-cell patch-clamp recordings, we examined the effects of taurine on chloride channel receptors in neocortical neurons from early to late postnatal stages, which cover a critical period in cortical circuit formation. We show here that taurine activates chloride channels in cortical neurons throughout the postnatal stages examined (from postnatal day 2 to day 36). The physiological effects of taurine changed from excitatory to inhibitory due to variations in the intracellular Cl, concentration during development. An antagonist blocking analysis also demonstrated a developmental shift in the receptor target of taurine, from glycine receptors to GABAA receptors. Taken together, these results may reflect genetically programmed, bidirectional functions of taurine. At the early developmental stage, taurine acting on glycine receptors would serve to promote cortical circuit formation. As cortical circuit has to be regulated in the later stages, taurine would serve as a safeguard against hyperexcitable circuit. © 2004 Wiley Periodicals, Inc. J Neurobiol 60: 166,175, 2004 [source] The role of taurine in diabetes and the development of diabetic complicationsDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 5 2001Svend Høime Hansen Abstract The ubiquitously found ,-amino acid taurine has several physiological functions, e.g. in bile acid formation, as an osmolyte by cell volume regulation, in the heart, in the retina, in the formation of N -chlorotaurine by reaction with hypochlorous acid in leucocytes, and possibly for intracellular scavenging of carbonyl groups. Some animals, such as the cat and the C57BL/6 mouse, have disturbances in taurine homeostasis. The C57BL/6 mouse strain is widely used in diabetic and atherosclerotic animal models. In diabetes, the high extracellular levels of glucose disturb the cellular osmoregulation and sorbitol is formed intracellularly due to the intracellular polyol pathway, which is suspected to be one of the key processes in the development of diabetic late complications and associated cellular dysfunctions. Intracellular accumulation of sorbitol is most likely to cause depletion of other intracellular compounds including osmolytes such as myo -inositol and taurine. When considering the clinical complications in diabetes, several links can be established between altered taurine metabolism and the development of cellular dysfunctions in diabetes which cause the clinical complications observed in diabetes, e.g. retinopathy, neuropathy, nephropathy, cardiomyopathy, platelet aggregation, endothelial dysfunction and atherosclerosis. Possible therapeutic perspectives could be a supplementation with taurine and other osmolytes and low-molecular compounds, perhaps in a combinational therapy with aldose reductase inhibitors. Copyright © 2001 John Wiley & Sons, Ltd. [source] Insights into the acute cerebral metabolic changes associated with childhood diabetesDIABETIC MEDICINE, Issue 5 2005F. J. Cameron Abstract Aims Type 1 diabetes is a prevalent chronic disease in childhood with the commonest single cause of death being cerebral oedema in the context of diabetic ketoacidosis (DKA). The nature of the alterations in cerebral metabolism that may result in vulnerability to neuronal injury remains unknown. The aim of this study was to analyse the magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) brain data from eight children with diabetes following acute presentation with hyperglycaemia with or without ketoacidosis, to determine the nature and timing of any alterations in cerebral structure and metabolism. Methods This study used MRI and MRS to investigate regional cerebral abnormalities in a small series of diabetic patients with and without DKA. Changes were compared with the clinical and biochemical features of the patients studied. Results Our small series of patients all demonstrated abnormal signal changes in the frontal region on fluid attenuated inversion recovery (FLAIR) MR imaging, suggestive of oedema, and spectroscopic abnormalities of increased taurine, myoinositol and glucose levels. The MR abnormalities varied in severity but did not correlate with any clinical or biochemical parameters. Conclusions These changes indicate that many diabetic children, particularly at presentation, may have alterations in cerebral metabolism with implications for the pathogenesis and treatment of the cerebral complications of DKA. In addition, our findings suggest that increased taurine may be one of the important differentiating factors in the response of the brain of diabetic children to DKA that may reflect an increase in their vulnerability to cerebral oedema compared with diabetic adults. [source] Reflux and pH: ,alkaline' components are not neutralized by gastric pH variationsDISEASES OF THE ESOPHAGUS, Issue 1 2000P. Bechi The ability of the ,alkaline' components of reflux to cause harm in vivo is still open to debate, although these components have been shown in vitro to be capable of damaging the mucosa. The precipitation of bile acids and lysolecithin that occurs at low pH values is the main reason for questioning in vivo mucosal damage. This study was undertaken to determine the composition of gastric aspirates at different original pH values and the degree of solubility of the alkaline components when pH modifications are artificially induced. The samples for chemical analysis were collected from indwelling nasogastric tubes after surgical procedures that did not involve the upper gastrointestinal tract. Bile acid and lysolecithin concentrations were assessed by means of dedicated methods. Thirty-five samples were available for bile acid evaluation and 27 for lysolecithin evaluation. Bile acid and lysolecithin assessments were repeated after pH adjustment at 2, 3.5, 5.5 and 7. For easier assessment of the results, three ranges of the original pH were selected (pH,<,2, 2 , pH < 5, pH , 5). For each pH range, results were pooled together and compared with those in the other pH ranges. Bile acid concentrations were 113 ± 48, 339 ± 90 and 900 ± 303 (mean ± s.e.m. ,mol/L), respectively, in the three groups selected on account of the different original pH values. Differences were significant (p < 0.001). Both taurine- and glycine-conjugated bile acids were represented even at pH < 2. No major differences were observed in bile acid concentration with the artificially induced pH variations. Lysolecithin concentrations were 5.99 ± 3.27, 30.80 ± 8.43 and 108.37 ± 22.17 (mean ± SEM ,g/ml), respectively, in the three groups selected on account of the different original pH ranges. Differences were significant (p < 0.001). No significant differences in lysolecithin concentration were detected with the artificially induced pH variations. In conclusion, both bile acids and lysolecithin are naturally represented in the gastric environment even at very low pH values, although their concentrations decrease on lowering of the naturally occurring pH. Given the concentration variability of bile acids and lysolecithin, further studies are needed to assess the minimal concentration capable of mucosal damage in vivo. [source] Design, characterization, and utilization of a fast fluorescence derivatization reaction utilizing o -phthaldialdehyde coupled with fluorescent thiolsELECTROPHORESIS, Issue 7 2007Suminda Hapuarachchi Abstract We have developed a chemical derivatization scheme for primary amines that couples the fast kinetic properties of o -phthaldialdehyde (OPA) with the photophysical properties of visible, high quantum yield, fluorescent dyes. In this reaction, OPA is used as a cross-linking reagent in the labeling reaction of primary amines in the presence of a fluorescent thiol, 5-((2-(and-3)- S -(acetylmercapto)succinoyl)amino)fluorescein (SAMSA fluorescein), thereby incorporating fluorescein (,,=,78,000,M,1, quantum yield of 0.98) into the isoindole product. Detection is based on excitation and emission of the incorporated fluorescein using the 488,nm laser line of an Ar+ laser rather than the UV-excited isoindole, thereby eliminating the UV light sources for detection. Using this method, we have quantitatively labeled biologically important primary amines in less than 10,s. Detection limits for analysis of glutamate, glycine, GABA, and taurine were less than 2,nM. We present the characterization of OPA/SAMSA-F reaction and the potential utility of the derivatization reaction for dynamic chemical monitoring of biologically relevant analytes using CE. [source] A versatile electrophoresis system for the analysis of high- and low-molecular-weight proteinsELECTROPHORESIS, Issue 11 2003Christophe Tastet Abstract A new, versatile, multiphasic buffer system for high-resolution sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins in the relative molecular weight range of 300,000,3000 Da is described. The system, based on the theory of multiphasic zone electrophoresis, allows complete stacking and destacking of proteins in the above Mr range. The buffer system uses taurine and chloride as trailing and leading ion, respectively, and Tris, at a pH close to its pKa, as the buffering counterion. Coupled with limited variation in the acrylamide concentration, this electrophoresis system allows to tailor the resolution in the 6,200 kDa Mr range, with minimal difficulties in the post electrophoretic identification processes. [source] GABA and glycine are protective to mature but toxic to immature rat cortical neurons under hypoxiaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2005Peng Zhao Abstract Although recent studies suggest that ,-aminobutyric acid (GABA) and glycine may be ,inhibitory' to mature neurons, but ,excitatory' to immature neurons under normoxia, it is unknown whether inhibitory neurotransmitters are differentially involved in neuronal response to hypoxia in immature and mature neurons. In the present study, we exposed rat cortical neurons to hypoxia (1% O2) and examined the effects of three major inhibitory neurotransmitters (GABA, glycine and taurine) on the hypoxic neurons at different neuronal ages [days in vitro (DIV)4,20]. Our data showed that the cortical neurons expressed both GABAA and glycine receptors with differential developmental profiles. GABA (10,2000 µm) was neuroprotective to hypoxic neurons of DIV20, but enhanced hypoxic injury in neurons of <,DIV20. Glycine at low concentrations (10,100 µm) exhibited a similar pattern to GABA. However, higher concentrations of glycine (1000,2000 µm) for long-term exposure (48,72 h) displayed neuroprotection at all ages (DIV4,20). Taurine (10,2000 µm), unlike GABA and glycine, displayed protection only in DIV4 neurons, and was slightly toxic to neurons >,DIV4. In comparison with delta-opioid receptor (DOR)-induced protection in DIV20 neurons exposed to 72 h of hypoxia, glycine-induced protection was weaker than that of DOR but stronger than that of GABA and taurine. These data suggest that the effects of the inhibitory neurotransmitters on hypoxic cortical neurons are age-dependent, with GABA and glycine being neurotoxic to immature neurons and neuroprotective to mature neurons. [source] GABA selectively controls the secretory activity of oxytocin neurons in the rat supraoptic nucleusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2004Mario Engelmann Abstract Recently we reported that a single social defeat experience triggers the release of oxytocin (OXT) from somata and dendrites, but not axon terminals, of neurons of the hypothalamic,neurohypophysial system. To further investigate the regulatory mechanisms underlying this dissociated release, we exposed male Wistar rats to a 30-min social defeat and monitored release of the inhibitory amino acids gamma amino butyric acid (GABA) and taurine within the hypothalamic supraoptic nucleus (SON) using microdialysis. Social defeat caused a significant increase in the release of both GABA and taurine within the SON (up to 480%; P < 0.01 vs. prestress release). To reveal the physiological significance of centrally released GABA, the specific GABAA -receptor antagonist bicuculline (0.02 mm) was administered into the SON via retrodialysis. This approach caused a significant increase in the release of OXT both within the SON and into the blood under basal conditions and during stress (up to 300 and 200%, respectively; P < 0.05 vs. basal values), without affecting plasma vasopressin. Electrophysiological studies confirmed the selective action of bicuculline on the firing activity of OXT neurons in the SON. Taken together, our data demonstrate that GABA is released within the SON during emotional stress to act as a selective inhibitor of both central and peripheral OXT secretion. [source] Taurine selectively modulates the secretory activity of vasopressin neurons in conscious ratsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2001Mario Engelmann Abstract Previous experiments have shown that a 10-min forced swimming session triggers the release of vasopressin from somata and dendrites, but not axon terminals, of neurons of the hypothalamic,neurohypophysial system. To further investigate regulatory mechanisms underlying this dissociated release, we forced male Wistar rats to swim in warm (20 °C) water and monitored release of the potentially inhibitory amino acids gamma amino butyric acid (GABA) and taurine into the hypothalamic supraoptic nucleus using microdialysis. Forced swimming caused a significant increase in the release of taurine (up to 350%; P < 0.05 vs. prestress release), but not GABA. To reveal the physiological significance of centrally released taurine, the specific taurine antagonist 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1-dioxide was administered into the supraoptic nucleus via retrodialysis. Administration of this antagonist caused a significant increase in the release of vasopressin within the supraoptic nucleus and into the blood both under basal conditions and during stress (up to 800%; P < 0.05 vs. basal values), without affecting hypothalamic or plasma oxytocin. Local administration of the GABAA receptor antagonist bicuculline, in contrast, failed to influence vasopressin secretion at either time point. In a separate series of in vivo electrophysiological experiments, administration of the same dosage of the taurine antagonist into the supraoptic nucleus via microdialysis resulted in an increased electrical activity of identified vasopressinergic, but not oxytocinergic, neurons. Taken together our data demonstrate that taurine is released within the supraoptic nucleus during physical/emotional stress. Furthermore, at the level of the supraoptic nucleus, taurine inhibits not only the electrical activity of vasopressin neurons but also acts as an inhibitor of both central and peripheral vasopressin secretion during different physiological states. [source] Pharmacological "cross-inhibition" of connexin hemichannels and swelling activated anion channelsGLIA, Issue 3 2009Zu-Cheng Ye Abstract The study of ion channels has relied heavily on the use of pharmacological blocking agents. However, many of these agents have multiple effects, which may compromise interpretation of results when the affected mechanisms/pathways mediate similar functions. Volume regulated anion channels (VRAC) and connexin hemichannels can both mediate the release of glutamate and taurine, although these channels have distinct activation stimuli and hemichannels, but not VRAC, are permeable to Lucifer Yellow (LY). It has been reported that some anion channel blockers may inhibit connexin hemichannels. We further examined the effects of classic gap junction/hemichannel blockers and anion channel blockers on these channels. The typical VRAC blockers, NPPB, IAA-94, and tamoxifen blocked low divalent cation-induced glutamate and taurine release and LY loading, presumed due to hemichannel opening. The blocking action of these compounds on hemichannels was concentration dependent and fell within the same range where the drugs classically block VRACs. Conversely, carbenoxolone (CBX), the most widely used gap junction/hemichannel blocker, was an effective blocker of VRAC-mediated glutamate and taurine release, and blocked these channels at similar concentrations at which it blocked hemichannels. The CBX effect on VRACs was verified using astrocytes from connexin 43 knock out (Cx43 KO) animals. In these cells, the hypotonic induced amino acid flux was retained whereas the low divalent cation solution-induced flux was lost. These results extend our knowledge about "cross-inhibition" of VRACs and gap junctions/hemichannels by certain pharmacological agents. Given the overlap in function of these two types of channels, great care must be exerted in using pharmacological blockers to identify one channel from the other. © 2008 Wiley-Liss, Inc. [source] Novel biotransformation and physiological properties of norursodeoxycholic acid in humans,,HEPATOLOGY, Issue 6 2005Alan F. Hofmann Experiments were performed in 2 volunteers to define the biotransformation and physiological properties of norursodeoxycholic acid (norUDCA), the C23 (C24 -nor) homolog of UDCA. To complement the in vivo studies, the biotransformation of norUDCA ex vivo using precision-cut human liver slices was also characterized. In the human studies, both a tracer dose given intravenously and a physiological dose (7.9 mmol, 3.0 g) given orally were excreted equally in bile and urine. By chromatography and mass spectrometry, the dominant biotransformation product of norUDCA in bile and urine was the C-23 ester glucuronide. Little N -acyl amidation (with glycine or taurine) occurred. The oral dose induced a sustained bicarbonate-rich hypercholeresis, with total bile flow averaging 20 ,L/kg/min, a rate extrapolating to 2 L/d. The increased bile flow was attributed to cholehepatic shunting of norUDCA as well to the lack of micelles in bile. Phospholipid and cholesterol secretion relative to bile acid secretion decreased during secretion of norUDCA and its metabolites, presumably also because of the absence of micelles in canalicular bile. When incubated with human liver slices, norUDCA was glucuronidated, whereas UDCA was conjugated with glycine or taurine. In conclusion, in humans, norUDCA is glucuronidated rather than amidated. In humans, but not animals, there is considerable renal elimination of the C-23 ester glucuronide, the dominant metabolite. NorUDCA ingestion induces a bicarbonate-rich hypercholeresis and evokes less phospholipid and cholesterol secretion into bile than UDCA. Molecules that undergo cholehepatic shunting should be powerful choleretics in humans. (HEPATOLOGY 2005;42:1391,1398.) [source] Role of mitogen-activated protein kinases in tauroursodeoxycholic acid-induced bile formation in cholestatic rat liverHEPATOLOGY RESEARCH, Issue 7 2008Gerald Ulrich Denk Aim:, Ursodeoxycholic acid exerts anticholestatic effects in various cholestatic disorders and experimental models of cholestasis. Its taurine conjugate (TUDCA) stimulates bile salt secretion in isolated perfused rat livers (IPRL) under physiological, non-cholestatic conditions, in part by mitogen-activated protein kinase (MAPK)-dependent mechanisms. The role of MAPK in the anticholestatic effect of TUDCA, however, is unclear. Therefore, we studied the role of MAPK in the anticholestatic effect of TUDCA in IPRL and isolated rat hepatocytes (IRH) in taurolithocholic acid (TLCA)-induced cholestasis. Methods:, Bile flow, biliary levels of 2,4-dinitrophenyl-S-glutathione (GS-DNP) as a marker of hepatobiliary organic anion secretion and activity of lactate dehydrogenase (LDH) in hepatovenous effluate as a marker of hepatocellular damage in IPRL perfused with TUDCA and/or TLCA were determined in the presence or absence of MAPK inhibitors. In addition, phosphorylation of Erk 1/2 and p38MAPK induced by TUDCA and/or TLCA was studied by Western immunoblot in IPRL and IRH. Results:, TUDCA-induced bile flow was impaired by the Erk 1/2 inhibitor PD98059 in normal livers (,28%), but not in livers made cholestatic by TLCA. GS-DNP secretion was unaffected by PD98059 under both conditions. TUDCA-induced bile formation and organic anion secretion both in the presence and absence of TLCA were unaffected by the p38MAPK inhibitor SB202190. Erk 1/2 phosphorylation in liver tissue was unchanged after bile salt exposure for 70 min, but was transiently enhanced by TUDCA in IRH. Conclusion:, MAPK do not mediate the anticholestatic effects of TUDCA in TLCA-induced cholestasis. [source] A case of acute hepatitis E associated with multidrug hypersensitivity and cytomegalovirus reactivationHEPATOLOGY RESEARCH, Issue 2 2007Yasuhiro Takikawa A 65-year-old Japanese man was hospitalized because of acute hepatitis and severe cholestasis due to hepatitis E virus (HEV) infection combined with a drug reaction to a cold preparation. He died of disseminated intravascular coagulation and severe intestinal bleeding due to systemic cytomegalovirus reactivation following the development of severe eruptions with marked eosinophilia due to drug hypersensitivity to taurine and ursodeoxycholate preparations. The close interaction between viral infection or reactivation and drug hypersensitivity was considered as a pathophysiology in this case, which emphasizes the need for further study of the immunological mechanism of the interaction. [source] Taurine concentrations in animal feed ingredients; cooking influences taurine contentJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 7-8 2003A. R. Spitze Summary The aim of this study was to determine the taurine content in a variety of animal feeds. There is very little information on the taurine content of ingredients used in home-prepared diets for dogs and cats, and foods fed to wild animals in captivity. This study reports the taurine content of both common and alternative feed ingredients, and compares taurine loss as a result of different methods of food preparation. Foods were selected based on their use in commercial and home-prepared diets. Animal muscle tissue, particularly marine, contained high taurine concentrations. Plant products contained either low or undetectable amounts of taurine. The amount of taurine that remained in a feed ingredient after cooking depended upon the method of food preparation. When an ingredient was constantly surrounded by water during the cooking process, such as in boiling or basting, more taurine was lost. Food preparation methods that minimized water loss, such as baking or frying, had higher rates of taurine retention. [source] Cryopreservation of fish sperm: applications and perspectivesJOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2010E. Cabrita Summary Cryopreservation is of interest not only for fish farming but also for the conservation and genetic improvement of resources. This technique has been well established in some freshwater fish species mainly, salmonid, sturgeons and carps, however, only in the last decade research was focused in marine fish species. The benefits of sperm cryopreservation include: (i) synchronization of gamete availability of both sexes, (ii) sperm economy; (iii) simplification of broodstock management, (iv) transport of gametes from different fish farms, and (v) germplasm storage for genetic selection programs or conservation of species. These issues would certainly benefit the aquaculture industry. The tremendous impact that biotechnology is having in aquaculture has been particularly obvious in recent years. Several species are being used as research models not only for aquaculture development applications but also for medical research. Sperm cryopreservation can give an important contribution in the germ storage of all transgenic lines. However, in all applications in fish sperm, cryopreservation needs to overcome a lack in standardization of methodologies and procedures, a correct assay of seminal quality and the development of tools to characterize cryoinjury. Many efforts have recently been made in the study of DNA using different approaches such as the comet assay (single cell gel electrophoresis), TUNEL (terminal deoxynucleotidyl transferase-nick-end-labelling), SCSA (sperm chromatin structure assay) and the analysis of specific DNA sequences using RT-PCR, since DNA damage may impair fertility or embryo development. Cryopreservation of gametes would certainly benefit from a higher concern on male improvement, basically through nutrition or selection of resistant stocks (e.g. stress resistant individuals or highly adapted to captivity) producing gametes of higher quality. There is a huge window of opportunities for improve the resistance of cells to cryopreservation through diet supplementation of certain compounds such as amino acids (taurine and hypotaurine), vitamins (Vit. E and C) and lipids or through a direct supplementation of the extender media. An equilibrium of those compounds will improve spermatozoa and seminal plasma composition protecting cells against oxidative stress (lipid peroxidation, protein oxidation, DNA fragmentation, enzyme protection) that is gaining each day more importance in cryodamage research. [source] Adsorption and desorption behaviour of taurine on macroporous adsorption resinsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2001Tang Zhigang Abstract Adsorption of taurine on S-8, NKA2 and Amberlite XAD-1 resins was measured with respect to time and the results indicated that equilibrium was reached in 50,min. The adsorption isotherms of taurine on D4006, AB-8, S-8, NKA2 were recorded and compared with those using Amberlite XAD-1, XAD-3, XAD-6 and XAD-7 at 28,°C. For an aqueous concentration range of 0,100,mg,g,1, each isotherm could be represented as a straight line. S-8 and XAD-1 resins had the highest solid/liquid distribution coefficients of 0.92 and 0.9. Since the locally produced S-8 resin is less expensive than XAD-1 resin, it was selected for further studies with adsorption isotherms being measured over the aqueous concentration range of 0,160,mg,g,1. These experimental results could be fitted by the Langmuir equation. The effects of pH, salting-out and temperature on the adsorption were studied with the results showing that the influence of temperature was the most important. A temperature-swing adsorption process was then tested to separate taurine from aqueous solutions and gave a overall yield >90% when taurine was adsorbed at 28,°C and eluted by deionized water at 70,°C. © 2001 Society of Chemical Industry [source] Adding another spectral dimension to 1H magnetic resonance spectroscopy of hepatic encephalopathy,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2005Nader Binesh PhD Abstract Purpose To evaluate a localized two-dimensional correlated magnetic resonance spectroscopic (L-COSY) technique in patients with hepatic encephalopathy (HE) and healthy subjects, and to correlate the cerebral metabolite changes with neuropsychological (NP) test scores. Materials and Methods Eighteen minimal hepatic encephalopathy (MHE) patients and 21 healthy controls have been investigated. A GE 1.5-T magnetic resonance (MR) scanner was used in combination with a body MR coil for transmission and a 3-inch surface coil for reception. A 27-mL voxel was localized by three slice-selective radio frequency (RF) pulses (90°-180°-90°) in the anterior cingulate region. The total duration of each two-dimensional L-COSY spectrum was approximately 25 minutes. The NP battery included a total of 15 tests, which were grouped into six domains. Results MR spectroscopic results showed a statistically significant decrease in myo-inositol (mI) and choline (Ch) and an increase in glutamate/glutamine (Glx) in patients when compared to healthy controls. There was also an increase in taurine (Tau) in patients. The NP results indicated a significant correlation between motor function assessed by NP tests and mI ratios recorded using two-dimensional L-COSY. Conclusion The study demonstrated the feasibility of evaluating the two-dimensional L-COSY sequence in a clinical environment. The results showed additional cerebral metabolites that can be measured with the technique in comparison to one-dimensional study. J. Magn. Reson. Imaging 2005;21:398,405. © 2005 Wiley-Liss, Inc. [source] In vitro1H magnetic resonance spectroscopy differences between meningeoma and astrocytomaJOURNAL OF NEUROCHEMISTRY, Issue 2003K. Likav, anová Tumor transformation of the human brain cells causes different biochemical changes. Here we employed 1H magnetic resonance spectroscopy to compare the presence of low molecular weight metabolites in meningeoma and astrocytoma tumors by measuring perchloric acid extracts of the cells. In 1H spectra of meningeoma we detected high signal from lactate but were unable to detect any signal of NAA and creatine. In contrast, astrocytoma samples revealed significantly higher level of inositol and glycine and significant decrease in glutamate and glutamine compared with meningeoma but no presence of taurine. Our results suggest that 1H MRS can provide useful information about biochemical changes in different types of brain tumors. Acknowledgements: This work was supported by the Grant Category C and Comenius University Grant No. X/2003. [source] Characterization of a glycine receptor domain that controls the binding and gating mechanisms of the ,-amino acid agonist, taurineJOURNAL OF NEUROCHEMISTRY, Issue 3 2001Nian-Lin R. Han The ,-amino acid, taurine, is a full agonist of the human glycine receptor ,1 subunit when recombinantly expressed in a mammalian (HEK293) cell line, but a partial agonist of the same receptor when expressed in Xenopus oocytes. Several residues in the Ala101,Thr112 domain have previously been identified as determinants of ,-amino acid binding and gating mechanisms in Xenopus oocyte-expressed receptors. The present study used the substituted cysteine accessibility method to investigate the role of this domain in controlling taurine-specific binding and gating mechanisms of glycine receptors recombinantly expressed in mammalian cells. Asn102 and Glu103 are identified as taurine and glycine binding sites, whereas Ala101 is eliminated as a possible binding site. The N102C mutation also abolished the antagonistic actions of taurine, indicating that this site does not discriminate between the putative agonist- and antagonist-bound conformations of ,-amino acids. The effects of mutations from Lys104,Thr112 indicate that the mechanism by which this domain controls ,-amino acid-specific binding and gating processes differs substantially depending on whether the receptor is expressed in mammalian cells or Xenopus oocytes. Thr112 is the only domain element in mammalian cell-expressed GlyRs which was demonstrated to discriminate between glycine and taurine. [source] Studies on the effects of lactate transport inhibition, pyruvate, glucose and glutamine on amino acid, lactate and glucose release from the ischemic rat cerebral cortexJOURNAL OF NEUROCHEMISTRY, Issue 1 2001J. W. Phillis A rat four vessel occlusion model was utilized to examine the effects of ischemia/reperfusion on cortical window superfusate levels of amino acids, glucose, and lactate. Superfusate aspartate, glutamate, phosphoethanolamine, taurine, and GABA were significantly elevated by cerebral ischemia, then declined during reperfusion. Other amino acids were affected to a lesser degree. Superfusate lactate rose slightly during the initial ischemic period, declined during continued cerebral ischemia and then was greatly elevated during reperfusion. Superfusate glucose levels declined to near zero levels during ischemia and then rebounded beyond basal levels during the reperfusion period. Inhibition of neuronal lactate uptake with ,-cyano-4-hydroxycinnamate dramatically elevated superfusate lactate levels, enhanced the ischemia/reperfusion evoked release of aspartate but reduced glutamine levels. Topical application of an alternative metabolic fuel, glutamine, had a dose dependent effect. Glutamine (1 mm) elevated basal superfusate glucose levels, diminished the decline in glucose during ischemia, and accelerated its recovery during reperfusion. Lactate levels were elevated during ischemia and reperfusion. These effects were not evident at 5 mm glutamine. At both concentrations, glutamine significantly elevated the superfusate levels of glutamate. Topical application of sodium pyruvate (20 mm) significantly attenuated the decline in superfusate glucose during ischemia and enhanced the levels of both glucose and lactate during reperfusion. However, it had little effect on the ischemia-evoked accumulation of amino acids. Topical application of glucose (450 mg/dL) significantly elevated basal superfusate levels of lactate, which continued to be elevated during both ischemia and reperfusion. The ischemia-evoked accumulations of aspartate, glutamate, taurine and GABA were all significantly depressed by glucose, while phosphoethanolamine levels were elevated. These results support the role of lactate in neuronal metabolism during ischemia/reperfusion. Both glucose and glutamine were also used as energy substrates. In contrast, sodium pyruvate does not appear to be as effectively utilized by the ischemic/reperfused rat brain since it did not reduce ischemia-evoked amino acid efflux. [source] Protective function of taurine in glutamate-induced apoptosis in cultured neuronsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2009Rebecca Leon Abstract Previously, we showed that taurine protects neurons against glutamate-induced excitotoxicity by inhibiting the glutamate-induced increase of [Ca2+]i. In this study, we report that taurine prevents glutamate-induced chromosomal condensation, indicating that taurine inhibits glutamate-induced apoptosis. We found that Bcl-2 was down-regulated while Bax was up-regulated by glutamate treatment, and these changes were prevented in the presence of taurine. We have also shown that taurine inhibits glutamate-induced activation of calpain. Furthermore, calpastatin, a specific calpain inhibitor, also prevented glutamate-induced cell death. Here we propose the mechanisms underlying glutamate-induced apoptosis and taurine's inhibition of glutamate-induced apoptosis to be as follows: glutamate stimulation induces [Ca2+]i elevation, which in turn activates calpain; activation of calpain leads to a reduction of Bcl-2:Bax ratios; with decreased Bcl-2:Bax ratios Bax homodimers form, Bax homodimerization, and translocation to the mitochondria result in the release of cytochrome c; released cytochrome c in turn activates a downstream caspase cascade leading to apoptosis. The antiapoptotic function of taurine is due to its inhibition of glutamate-induced membrane depolarization. © 2008 Wiley-Liss, Inc. [source] | |||||||||||||||||||