EFFECT OF ELECTRICAL STIMULATION AND CHLORPROMAZINE ON THE UPTAKE AND RELEASE OF TAURINE, γ-AMINOBUTYRIC ACID AND GLUTAMIC ACID IN MOUSE BRAIN SYNAPTOSOMES

—The concentrations of taurine and GABA were determined in isolated mouse brain synaptosomes incubated in Krebs-Ringer phosphate medium (pH 7·4). The concentration of GABA gradually decreased during incubation, but that of taurine remained approximately unchanged. In the presence of chlorpromazine the amount of GABA in the synaptosomes increased, but the efflux and influx of GABA were slightly reduced. The content and efflux of both taurine and GABA increased in electrically stimulated synaptosomes, and the influx of taurine, GABA and glutamate into the synaptosomes similarly increased. All three amino acids are taken up by the synaptosomes through at least two mechanisms: low-affinity and high-affinity. In the high-affinity system the K_m values were 33 μm for taurine, 24 μm for GABA and 68 μm for glutamate, and in the low-affinity one 1·1 mil, 0·9 mm and 1·2mm , respectively. The influx capacity (V_max) was highest for glutamate, second highest for GABA and lowest for taurine.     

GABA IN THE OLFACTORY BULB AND OLFACTORY NUCLEUS OF THE RAT: THE DISTRIBUTION OF GAMMA-AMINOBUTYRIC ACID, GLUTAMIC ACID DECARBOXYLASE, GABA TRANSAMINASE AND SUCCINATE SEMIALDEHYDE DEHYDROGENASE

Abstract— The distribution of GABA and enzymes involved in its metabolism was investigated in the different regions of the olfactory bulb and olfactory nucleus. The highest levels of GABA in the olfactory bulb were found in the layers rich in nerve terminals (31 μmol/g dry wt.). A similar distribution was found in the olfactory nucleus although the overall level of GABA was only a quarter of that measured in the bulb. Glutamic acid decarboxylase (GAD) levels in the various layers of the olfactory nucleus were similar in distribution to those of GABA. However, the correlation between GAD and GABA did not hold for the olfactory bulb, particularly in the granule cell layer and the medulla. The activities of GAD and the levels of GABA are significantly higher in the bulb than in the nucleus but succinic acid scmialdehyde dehydrogenase and GABA aminotransaminase activities are almost identical in both regions.     

乙酰胆碱,谷氨酸与GABA对丘脑腹内侧核神经元活动的影响

本文采用微电泳方法观察到在大鼠丘脑腹内侧核（ＶＭ）,微电泳给予乙酰胆碱（ＡＣＨ）使所有受试神经元自发放电频率加快,谷氨酸（ＧＬＵ）使大多数神经元放电加快,它们的作用依赖于电流强度;而γ氨基丁酸（ＧＡＢＡ）和氯苯氨丁酸则抑制大多数神经元的放电活动,但前者的作用快速而暂短,而后者的作用相对缓慢而持久。在微电泳ＡＣＨ或ＧＬＵ的过程中,给予ＧＡＢＡ可拮抗它们的兴奋作用。双钴碱使大多数神经元的自发放电频率加快,而阿托品和ＭＫ８０１对自发放电的影响较小。这些结果表明ＧＡＢＡ,ＡＣＨ和ＧＬＵ等递质活动在同一ＶＭ神经元有重要的会聚作用;ＧＡＢＡ对ＶＭ神经元有紧张性抑制作用。     

METABOLISM OF GLUTAMIC ACID AND RELATED AMINO ACIDS IN THE BRAIN STUDIED WITH 14C-LABELLED GLUCOSE, BUTYRIC ACID AND GLUTAMIC ACID IN HYPERCAPNIC RATS

Abstract— The influence of hypercapnia on the metabolism of glutamic acid, aspartic acid, glutamine and GABA in rat brain was studied using three different precursors. Acute hypercapnia induced a fall in the concentration of glutamic and aspartic acid, and a rise in the concentration of glutamine and GABA. Acute hypercapnia had a profound effect on the relative specific radioactivity of glutamine indicating that the excess glutamine, present in the brain in hypercapnia, was synthetized from glutamic acid in the compartment where it could become quickly labelled from butyric and glutamic acid, but not from glucose. This effect was maintained in chronic hypercapnia.     

天花粉蛋白与膜脂相互作用的研究

天花粉蛋白（ＴＣＳ）在≥２．２２μｍｏｌ／Ｌ时能引起大豆磷脂脂质体内含物释放,Ｃａ＾２＋对这种释放有一定的促进作用,低ＰＨ值也能促进ＴＣＳ与脂质体的作用;将ＴＣＳ与细细胞一起保温;当ＴＣＳ终浓度达１４．７μｍｏｌ／Ｌ时能损伤红细胞膜,产生溶血作用;ＴＣＳ还能作用于红细胞血影膜,改变其脂双层的不对称性。     

谷氨酸发酵废液培育高锌酵母

利用生产味精的废液、糖蜜、适量营养盐,以啤酒酵母2016为菌种,经摇瓶、2.6升、30升发酵罐试验,干酵母产率达14克/升,平均含锌量4500ppm。产品的蛋白质、灰分、水分符合规定指标,产品安全无毒。发酵后废液中COD降低60%。     

THE FIXATION OF TETANUS TOXIN BY SYNAPTIC MEMBRANES

—The ability of subfractions of disrupted synaptosomes to bind tetanus toxin has been studied. Synaptic vesicles had little toxin-fixing capacity, but a fraction believed on morphological appearance and enzymic composition to be rich in external synaptosome membranes had a toxin-fixing capacity about 10 times that of the synaptic vesicles and over twice that of the initial brain homogenate. Mitochondria also had a low toxin-fixing capacity and other membrane fractions had an intermediate value. The results are discussed in relation to the known role of ganglioside in fixing toxin.     

TAURINE IN DEVELOPING RAT BRAIN: SUBCELLULAR DISTRIBUTION AND ASSOCIATION WITH SYNAPTIC VESICLES OF [35S]TAURINE IN MATERNAL, FETAL AND NEONATAL RAT BRAIN

The concentration of taurine in the brain of the fetus in several species is higher than that found in the mature animal. In order to explore the functional significance of this, we have studied the subcellular distribution of taurine and [³⁵S]taurine in the brain of the mother, the fetus and the neonate after [³⁵S]taurine was administered to pregnant rats. In maternal brain, the distribution of taurine and of radioactivity (all of which was recovered from brain as taurine) in the subcellular fractions of maternal brain were essentially identical and were recovered primarily in two fractions (72% taurine, 71% [³⁵S]taurine was soluble, S₃; 16% and 17%, respectively, was in the crude mitochondrial and synaptosomal fraction, P₂). After further fractionation of P₂, most of the taurine and [³⁵S]taurine were in the cytoplasmic, O, and the synaptosomal, B, fractions. In the neonatal brain, shortly after birth there was a decrease in taurine and [³⁵S]taurine recovered in the supernatant fraction, S₃, accompanied by an increase in the percentage of taurine and [³⁵S]taurine recovered in the crude mitochondrial fraction. A small percentage of taurine and [³⁵S]taurine was consistently recovered in the synaptic vesicle fraction. Fractionation of the synaptic vesicles on a gel column separated the vesicle bound taurine completely from the free taurine: approx 1% of the taurine in the synaptic vesicle fraction was eluted with vesicles and could not be released by hypo-osmotic shock. The pattern of development in subcellular fractions of neonatal rat brain labelled with [³⁵S]taurine via intraperitoneal injections of the pregnant mother may be an indication of maturation or protection of putative taurinergic nerve endings.     

INTRACELLULAR AMINO ACID CONTENT OF NEURONAL, GLIAL, AND NON-NEURAL CELL CULTURES: THE RELATIONSHIP TO GLUTAMIC ACID COMPARTMENTATION

Abstract— A protocol for the accurate determination of intracellular levels of amino acids in tissue cultured cells has been developed and used in the measurement of intracellular amino acids levels in neuronal, glial, and non-neural cell lines, with the objective of establishing morphological correlates for large and small glutamic acid compartments and of examining hypotheses for the morphological basis of glutamic acid compartmentation. This survey of intracellular amino acid levels has revealed striking differences among the cell lines tested, but these differences did not correlate with cell type, i.e. neuronal vs glial, in contrast to earlier results (R ose , 1968) based on bulk separated neuronal and pial fractions from rat brain. Amino acid levels were found to be dependent upon tissue culture conditions, yet reproducible differences could be observed when growth and experimental conditions were carefully controlled. Glutamic acid levels for various cell lines ranged from 50.8 ± 14.3 to 158 ± 8.5 nmol/mg protein. Intracellular glutamine levels demonstrated even greater difference, with values ranging from 0.8 ± 0.2 to 107 ± 42.4 nmol/mg protein. Statistically significant differences in intracellular amino acid levels between cell lines were also observed for aspartic acid, praline, glycine, alanine, valine, cystathionine, isoleucine, and leucine. A number of cell lines demonstrating highly elevated elevated levels of γ-aminobutyrate and β-alanine were identified. The significance of neuronal and glial levels of glutamic acid, glutamine and γ-aminobutyrate to models for glutamic acid compartmentation is discussed.     

MOUSE BRAIN TYROSINE HYDROXYLASE AND GLUTAMIC ACID DECARBOXYLASE FOLLOWING TREATMENT WITH ADRENOCORTICOTROPHIC HORMONE, VASOPRESSIN OR CORTICOSTERONE

The activities of tyrosine hydroxylase (TH) and glutamic acid decarboxylase (GAD) from several mouse brain regions were assayed following repeated administration of adrenocorticotrophic hormone (ACTH), lysine vasopressin (LVP) or corticosterone. Although similar treatments with ACTH have been shown to result in changes of catecholamine turnover and GABA content, no changes in the activity of either TH or GAD were observed in any brain region. Likewise LVP had no effect on either enzyme. Since the assays for TH were performed with concentrations of tyrosine and tetrahydrobiopterin cofactor below their respective Michaelis constants, this suggests that the changes of catecholamine turnover are not mediated by changes of TH activity. Twice daily corticosterone adrninistration for four days increased TH activity in the hypothalamus but not in any other brain region.     

ON THE MECHANISM OF TAURINE TRANSPORT AT BRAIN CELL MEMBRANES

One non-saturable and two saturable transport systems were demonstrated for taurine in rat brain slices. One of the saturable systems, designated β, is characterized by a high asnity for taurine and a low transport capacity, while the other, designated ω, by a low affinity and a high transport capacity. 2,4-Dinitrophenol inhibited the saturable transport of taurine non-competitively, while hypotaurine. β-alanine, γ-aminobutyric acid, N-methyl-taurine and L-cysteic acid inhibited transport competitively. It is thus inferred that the hypothetical carrier sites of taurine at cell membrane recognize to an equal degree strongly ionized electropositive and electronegative ends of an acceptable molecule separated by two or three carbon atoms. Two is the minimal and also the optimal carbon chain length in an acceptable molecule.     

EFFECTS OF AMINO-OXYACETIC ACID, ETHANOLAMINE-O-SULPHATE AND GABA ON THE CONTENTS OF GABA AND VARIOUS AMINES IN BRAIN SLICES

—The effects of amino-oxyacetic acid, ethanolamine-O-sulphate and γ-aminobutyric acid (GABA) on the contents of GABA, noradrenaline, dopamine and serotonin (5-HT) in slices of rat hypothalamus and midbrain were studied in vitro using a simultaneous fluorimetric assay procedure. Following control incubations the levels of 5-HT were raised, while the levels of the other substances remained steady. Amino-oxyacetic acid caused a reduction in the contents of noradrenaline and 5-HT, but had no effect on either GABA or dopamine. Ethanolamine-O-sulphate both raised the GABA content and lowered the noradrenaline content of slices, while the levels of dopamine and 5-HT were not altered. The presence of GABA in the incubation medium produced complex changes in these levels, depending both on the dose of GABA used and the brain area studied. In the hypothalamus, 0·07 mm -GABA caused an elevation in 5-HT, a drop in noradrenaline, and no change in either GABA or dopamine. With 5 mm -GABA, the noradrenaline level was raised slightly above control values and the endogenous GABA level doubled, while 5-HT and dopamine levels were not different from controls. Similar changes in 5-HT and GABA contents were observed with midbrain slices, but noradrenaline and dopamine were not affected. The possible modes of action of amino-oxyacetic acid and ethanolamine-O-sulphate on the amino acid and amine systems in the brain are discussed.     

蟾蜍脑突触质膜对精氨酸-催产素(AVT)的酶促转化

本文研究了蟾蜍脑突触质膜对精氨酸-催产素(AVT,Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Arg-GlyNH_2)的酶促转化过程。利用高压液相层析(HPLC)对降解产物进行了分离,并分析了这些产物的氨基酸组成。发现最主要的一个降解产物为AVT_(1-8)(Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Arg)。其降解机制与大白鼠脑突触质膜降解AVT的不同。还用二种不同类型的蛋白酶抑制剂,即对氯汞苯甲酸(PCMB)和苯甲基磺酰氟(PMSF),对该酶促转化过程的抑制作用进行了比较,结果表明该水解酶的活性中心可能含有丝氨酸。