Taurine in the developing cat: Uptake and release in different brain areas

Taurine is an important modulator of neuronal activity in the immature brain. In kittens, taurine deficiency causes serious dysfunction in the cerebellar and cerebral visual cortex. The processes of taurine transport in vitro were now studied for the first time in different brain areas in developing and adult cats. The uptake of taurine consisted initially of two saturable components, high- and low-affinity, in synaptosomal preparations from the developing cerebral cortex and cerebellum, but the high-affinity uptake component completely disappeared during maturation. The release of both endogenous and preloaded labeled taurine from brain slices measured in a superfusion system was severalfold stimulated with a slow onset by depolarizing K⁺ (50 mM) concentrations. K⁺ stimulation released markedly more taurine from the cerebral cortex, cerebellum and brain stem in kittens than in adult cats. The responses were largest in the cerebellum. Both uptake and release of taurine are thus highly efficient in the brain of kittens and may be of significance in view of the vulnerability of cats to taurine deficiency.     

Taurine release in mouse brain stem slices under cell-damaging conditions

Summary. Taurine has been thought to be essential for the development and survival of neural cells and to protect them under cell-damaging conditions. In the brain stem taurine regulates many vital functions, including cardiovascular control and arterial blood pressure. We have recently characterized the release of taurine in the adult and developing brain stem under normal conditions. Now we studied the properties of preloaded [³H]taurine release under various cell-damaging conditions (hypoxia, hypoglycemia, ischemia, the presence of metabolic poisons and free radicals) in slices prepared from the mouse brain stem from developing (7-day-old) and young adult (3-month-old) mice, using a superfusion system. Taurine release was greatly enhanced under these cell-damaging conditions, the only exception being the presence of free radicals in both age groups. The ischemia-induced release was characterized to consist of both Ca²⁺-dependent and -independent components. Moreover, the release was mediated by Na⁺-, Cl⁻-dependent transporters operating outwards, particularly in the immature brain stem. Cl⁻ channel antagonists reduced the release at both ages, indicating that a part of the release occurs through ion channels, and protein kinase C appeared to be involved. The release was also modulated by cyclic GMP second messenger systems, since inhibitors of soluble guanylyl cyclase and phosphodiesterases suppressed ischemic taurine release. The inhibition of phospholipases also reduced taurine release at both ages. This ischemia-induced taurine release could constitute an important mechanism against excitotoxicity, protecting the brain stem under cell-damaging conditions.     

Role of feline maternal taurine nutrition in fetal cerebellar development: An immunohistochemical study

Summary We report the effects of four levels of maternal dietary taurine on the cerebellum of 45-day gestation fetuses. As we have previously reported for newborn and 8-week-old kittens, maternal dietary taurine content has a profound effect also on fetal cerebellum. Fetuses from queens fed the lowest amount of taurine had the greatest density of granule cells, probably because of smallest brain size, and had a high proportion of morphological abnormalities. Somewhat surprising was the observation that the fetuses from the lowest maternal dietary taurine group had the highest proportion of taurine-positive granule cells. In addition, these results confirm the vulnerability of developing fetal brain to its intrauterine environment.     

几种海产品中氨基酸及牛磺酸含量的比较

通过对几种海产品进行氨基酸分析,确证海产品中除了含有常见的１８种氨基酸外,还有含量较高的牛磺酸,对其进行了研究探讨。     

Taurine bromamine: a potent oxidant of tryptophan residues in albumin

Taurine is the most abundant free amino acid in leukocytes and can react with HOBr to produce taurine bromamine (Tau-NHBr). The aim of this study was to assess the ability of Tau-NHBr to oxidize tryptophan, either free or as a residue in albumin. We have demonstrated that Tau-NHBr is a powerful oxidant for tryptophan. Importantly, in comparison to taurine chloramine, HOCl or HOBr, Tau-NHBr exhibits a degree of selectivity for tryptophan. Oxidation of albumin by Tau-NHBr resulted in emission of light, and the quantum yield was more than 10-fold more efficient than that of the other oxidants. The fluorescence band corresponding to oxidized albumin (λ_ex 350/λ_em 450), which is characteristic of the formation of formylkynurenine, was significantly higher in reactions using Tau-NHBr. Excitation of the fluorescent probe 8-anilino-1-naphthalenesulfonate at 295 nm was used to assess the depletion of tryptophan residues in albumin. Results from this experiment further supported a higher efficiency of oxidation of tryptophan residues by Tau-NHBr. Other parameters of protein oxidation, including cysteine depletion and formation of carbonyl groups, were not significantly different between the oxidants tested. In conclusion, these results indicate that Tau-NHBr has a higher affinity for tryptophan residues in proteins.     

Sperm viability in the black-footed ferret (Mustela nigripes) is influenced by seminal and medium osmolality

Fundamental knowledge of spermatozoa cryobiology can assist with optimizing cryopreservation protocols needed for genetic management of the endangered black-footed ferret. Objectives were to characterize semen osmolality and assess the influence of two media at various osmolalities on sperm viability. We examined the influence of Ham's F10 +Hepes medium (H) at 270, 400, 500 or 700 mOsm (adjusted with sucrose, a nonpermeating cryoprotectant) and TEST Yolk Buffer (TYB) with 0% (300 mOsm) versus 4% (900 mOsm) glycerol (a permeating cryoprotectant). Electroejaculates (n=16) were assessed for osmolality using a vapor pressure osmometer. For media comparison, semen (n=5) was collected in TYB 0%, split into six aliquots, and diluted in H270, H400, H500, H700, and TYB 0% or TYB 4%. Each sample was centrifuged (300 g, 8 min), resuspended in respective medium, and maintained at 37 degrees C for 3h. Sperm motility and forward progression were monitored every 30 min for 3h post-washing. Acrosomal integrity was monitored at 0 and 60 min post-washing. Results demonstrated that black-footed ferret semen has a comparatively high osmolality (mean+/-SEM, 513.1+/-32.6 mOsm; range, 366-791 mOsm). Ferret spermatozoa were sensitive to hyperosmotic stress. Specifically, sperm motility was more susceptible (P<0.01) to hyperosmotic conditions than acrosomal integrity, and neither were influenced (P>0.05) by hypotonic solutions. Exposure to TYB 4% glycerol retained more (P<0.01) sperm motility than a hyperosmotic Ham's (700 mOsm). These findings will guide the eventual development of assisted breeding with cryopreserved sperm contributing to genetic management of this rare species.     

Taurine deficiency,synthesis and transport in the mdx mouse model for Duchenne Muscular Dystrophy

The amino acid taurine is essential for the function of skeletal muscle and administration is proposed as a treatment for Duchenne Muscular Dystrophy (DMD). Taurine homeostasis is dependent on multiple processes including absorption of taurine from food, endogenous synthesis from cysteine and reabsorption in the kidney. This study investigates the cause of reported taurine deficiency in the dystrophic mdx mouse model of DMD. Levels of metabolites (taurine, cysteine, cysteine sulfinate and hypotaurine) and proteins (taurine transporter [TauT], cysteine deoxygenase and cysteine sulfinate dehydrogenase) were quantified in juvenile control C57 and dystrophic mdx mice aged 18 days, 4 and 6 weeks. In C57 mice, taurine content was much higher in both liver and plasma at 18 days, and both cysteine and cysteine deoxygenase were increased. As taurine levels decreased in maturing C57 mice, there was increased transport (reabsorption) of taurine in the kidney and muscle. In mdx mice, taurine and cysteine levels were much lower in liver and plasma at 18 days, and in muscle cysteine was low at 18 days, whereas taurine was lower at 4: these changes were associated with perturbations in taurine transport in liver, kidney and muscle and altered metabolism in liver and kidney. These data suggest that the maintenance of adequate body taurine relies on sufficient dietary intake of taurine and cysteine availability and metabolism, as well as retention of taurine by the kidney. This research indicates dystrophin deficiency not only perturbs taurine metabolism in the muscle but also affects taurine metabolism in the liver and kidney, and supports targeting cysteine and taurine deficiency as a potential therapy for DMD.     

Taurine Interaction with Neurotransmitter Receptors in the CNS: An Update

Taurine appears to have multiple functions in the brain participating both in volume regulation and neurotransmission. In the latter context it may exert its actions by serving as an agonist at receptors of the GABAergic and glycinergic neurotransmitter systems. Its interaction with GABA_A and GABA_B receptors as well as with glycine receptors is reviewed and the physiological relevance of such interactions is evaluated. The question as to whether local extracellular concentrations of taurine are likely to reach the threshold level for the pertinent receptor populations cannot presently be answered satisfactorily. Hence more sophisticated analytical methods are warranted in order to obtain a definite answer to this important question. Special issue dedicated to Dr. Simo S. Oja     

Effect of different salinity on serum osmolality,ion levels and hematological parameters of East Java strain tilapia Oreochromis niloticus

This study evaluated the effect of different salinity levels on the physiology of East Java strain tilapia (Oreochromis niloticus) by measuring the serum osmolalities (SO), ion levels and hematological parameters. Their SOs above the external medium (hyper-osmotic) at 0 and 5 ppt, becoming iso-osmotic at 10 ppt and hypo-osmotic at 15 ppt. The concentrations of serum Na⁺, K⁺, Cl^? and Ca²⁺ in fish acclimated in 0 and 5 ppt were not significantly different. The levels of Na⁺, Cl^– and Ca²⁺ in fish exposed to 10 and 15 ppt were higher than those in fish acclimated at 0 and 5 ppt. In contrast, the levels of K⁺ in fish exposed to 10 and 15 ppt were lower than those in fish exposed to 0 and 5 ppt. The levels of red blood cell, hematocrit and hemoglobin of fish exposed to salinity of 0, 5, 10 and 15 ppt were not significantly different. The levels of white blood cell increased significantly at fish exposed to 10 and 15 ppt. These data provide useful information for future reference and farming practice.     

Plasma osmolality, urine composition and tissue water content of the toad Bufo viridis Laur. in nature and under controlled laboratory conditions

The compositions of plasma and urine were studied in toads (Bufo viridis) which were collected from three locations in Israel, and compared with toads which were kept under constant laboratory conditions for nearly 2 years. Plasma osmolality was rather constant (over 310 mOsm kg-1 H2O) during the whole year in the active toads. Urea was the most variable osmolyte in the plasma, and accounted for the higher osmolality in southern population. Urine osmolality fluctuated in a circannual fashion both in freshly captured and in the toads under constant laboratory conditions. Water content of the tissues was constant throughout the year, independent of the plasma osmolality. It is concluded that high plasma urea concentration and the excretory system (kidneys and the urinary bladder) are important in sustaining constant plasma osmolality in active toads. Both mechanisms change annually and form the basis for the high terrestriality of this species.     

Metabolism of Cysteine in Astroglial Cells: Synthesis of Hypotaurine and Taurine

Abstract: The synthesis of hypotaurine and taurine was investigated in astroglia-rich primary cultures obtained from brains of neonatal Wistar rats using ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. Cell extracts of astroglial cultures analyzed by ¹H NMR spectroscopy show prominent signals of hypotaurine. To identify cysteine as precursor for hypotaurine and taurine synthesis in astroglial cells, primary cultures were incubated with [3-¹³C]cysteine for 24 or 72 h. Cell extracts and incubation media were then analyzed with ¹³C NMR spectroscopy. Labeled hypotaurine, taurine, glutathione, and lactate were identified in the cell extracts. Within 72 h, 35.0% of the total intracellular hypotaurine and 22.5% of taurine were newly synthesized from [3-¹³C]cysteine. The presence of [1-¹³C]hypotaurine and [1-¹³C]taurine in the incubation medium proves the release of those products of cysteine metabolism into the medium. Minor amounts of the [3-¹³C]cysteine were used for the synthesis of glutathione in astroglial cells or metabolized to [3-¹³C]lactate, which was found in cell extracts and media. These results indicate that the formation of hypotaurine and taurine is a major pathway of cysteine metabolism in astroglial cells.     

Building Biosynthetic Schools: Reviewing Compartmentation of CNS Taurine Synthesis

Taurine is one of the mammalian brain's most abundant and indispensable amino acids. Considerable strides have been made in understanding taurine biosynthesis within the brain, but many disputed issues nonetheless remain. Heading the list is the cellular origin of biosynthetically derived taurine: glial or neuronal? This article reviews the competing theories surrounding cellular compartmentation of taurine biosynthesis in the brain. It concludes that while in vitro systems clearly show astrocytes to be fully capable of taurine synthesis and neurons to be limited to synthesizing taurine from hypotaurine, there is insufficient evidence to attribute these processes to any one cell type in vivo. Instead, there is a growing body of evidence that suggests brain taurine biosynthesis is occurring via a more cooperative metabolic interaction between astrocytes and neurons.

     

Taurine concentration in the brain and in the plasma following intraperitoneal injections

Summary. The effect of different taurine doses (0.050, 0.125, 0.250, 0.500 and 1.000g/kg) administered intraperitoneally to Wistar rats was studied in both the plasma and the hippocampal microdialysate content.The samples were analyzed by reverse phased HPLC for the microdialysate samples and by HPLC with ion-exchange post-column derivatization (ninhydrin) for the plasma samples.In both plasma and microdialysate, we observed a dose dependent increase of taurine concentration. The AUC curves obtained from both microdialysate and plasma samples showed that the increase of taurine concentrations were linear. The mean ratio between AUCs microdialysate and plasma was 1.63±0.21 showing thus an unbalance between plasma and brain taurine content; a mechanism which enhance taurine transfer from the plasma to the brain was assumed.     

黄芪联合牛磺酸治疗病毒性心肌炎临床观察

目的:探讨黄芪联合牛磺酸治疗病毒性心肌炎的临床疗效。方法:80例病毒性心肌炎患儿随机分成对照组和治疗组各40例,对照组予常规治疗,治疗组在此治疗基础上加用黄芪注射液和牛磺酸,进行临床疗效比较。结果:治疗组主要症状及体征改善情况明显优于对照组,治疗组治疗后血清肌酸磷酸激酶(CPK)、天冬氨酸转氨酶(AST)及血清乳酸脱氢酶(LDH)较治疗前明显降低(P＜0．05),而对照组CPK、AST、LDH治疗前后比较差异均无显著性(P＞0．05),治疗组总有效率明显高于对照组,差异有显著性(P＜0．05)。结论:黄芪联合牛磺酸对病毒性心肌炎具有明显的治疗作用。     

Influence of medium osmolality on the in vitro growth ofPlasmodium falciparum: A morphologic and radioisotopic study

Summary The study of the growth rate and incorporation of [³H]hypoxanthine and [¹⁴C]isoleucine showed that in vitro variations ofPlasmodium falciparum parasitemia levels and incorporation rates of the two radiolabeled molecules have been correlated. In our experimental conditions,P. falciparum blood forms in vitro tolerate osmolalities ranging from 180 to 360 mOsm. A weak hypo-osmolality (241 mOsm) favored the development of the parasite. The highest sensitivity of the parasite to osmotic variations was observed during schizogony. The merozoite stage and reinvasion process seemed less affected by hypo-osmolalities than by hyperosmolalities. The minor alterations in morphology of the parasites in hypo- and hyperosmotic media suggested thatP. falciparum may have efficient osmoregulatory power.     

Taurine and Its Chloramine: Modulators of Immunity

Taurine is a semiessential amino acid that is not incorporated into proteins. In mammalian tissues, taurine is ubiquitous and is the most abundant free amino acid in the heart, retina, skeletal muscle, and leukocytes. Taurine reaches up to 50 mM concentration in leukocytes. Taurine has been shown to be tissue-protective in many models of oxidant-induced injury. One possibility is that taurine reacts with HOCl, produced by the myeloperoxidase (MPO) pathway, to produce the more stable but less toxic taurine chloramine (Tau-Cl). However, data from several laboratories demonstrate that Tau-Cl is a powerful regulator of the immune system. Specifically, Tau-Cl has been shown to downregulate the production of proinflammatory mediators in both rodent and human leukocytes. Recent molecular studies on the function of taurine provide evidence that taurine is a constituent of biological macromolecules. Specifically, two novel taurine-containing modified uridines have been found in both human and bovine mitrochondria. In studies on mechanism of action, Tau-Cl inhibits the activation of NFkappaB, a potent signal transducer for inflammatory cytokines, by oxidation of IkappaB alpha at methionine45. Taurine transporter knockout mice show reduced taurine, reduced fertility, and loss of vision resulting from severe retinal degeneration, which was found to be due to apoptosis. Apoptosis induced by amino chloramines is a current and important finding because oxidants derived from leukocytes play a key role in killing pathogens. The fundamental importance of taurine in adaptive and acquired immunity will be revealed using genetic manipulation.     

Taurine Levels in Discrete Brain Nuclei of Rats

Concentrations of taurine have been measured in 44 microdissected rat brain nuclei or areas. Taurine is ubiquitously present and distributed unevenly in the rat brain: the ratio of the highest (pyriform cortex) to lowest (midbrain reticular formation) concentrations is 4.7:1. High taurine levels were found in cerebral cortical areas, caudate-putamen, cerebellum, median eminence, and supraoptic nucleus. Acute pain stress reduced taurine levels in the hypothalamus and the lower brainstem nuclei but not in cortical areas. Increased locomotor and behavioral activities following a high dose of amphetamine elevated taurine concentrations significantly in the substantia nigra and locus ceruleus.