Showing papers in "Neurochemical Research in 1978"
TL;DR: The release of glutamate was much smaller than the uptake, and only little affected by an increase of the external glutamate concentration, suggesting a net accumulation of glutamate rather than a homoexchange, and may play a major role in brain metabolism and may keep the extracellular glutamate cohcentration below excitatory levels.
Abstract: Kinetics for uptake and release of glutamate were measured in normal, i.e., nontransformed, astrocytes in cultures obtained from the dissociated, cortexenriched superficial parts of the brain hemispheres of newborn DBA mice. The uptake kinetics indicated a minor, unsaturable component together with an intense uptake following Michaelis-Menten kinetics. TheK
m
(50 μM) was reasonably comparable to the corresponding values in brain slices and in other glial preparations. TheV
max (58.8 nmol min−1 mg−1 protein) was, however, much higher than that observed in glial cell lines or peripheral satellite cells, and also considerably higher than that generally reported for brain slices. The release of glutamate was much smaller than the uptake, and only little affected by an increase of the external glutamate concentration, suggesting a net accumulation of glutamate rather than a homoexchange. Such an intense accumulation of glutamate into normal astrocytes may play a major role in brain metabolism and may help keep the extracellular glutamate cohcentration below excitatory levels.
204 citations
TL;DR: This review stresses recent developments concerning the protein composition of myelin and the metabolism of these proteins.
Abstract: The chemical composition of myelin has long been of interest to neurochemists, in part because of the relevance of such information to an understanding of the many human diseases of myelin. In recent years the realization that myelin, although highly specialized in function, shares many of the morphological and chemical properties of other membranes, has focused attention on its suitability as a model system for the study of membrane biogenesis and metabolism. This review stresses recent developments concerning the protein composition of myelin and the metabolism of these proteins.
111 citations
TL;DR: Assays for NGF activity of all protein components separated by analytical isoelectric focusing showed that NGFactivity was associated only with the basic protein component.
Abstract: Nerve growth factor (NGF) has been isolated from human placental tissue. Using the chicken embryo dorsal root ganglia assay, we determined levels of NGF activity for the amnion, placental cotyledons, cord serum, fetal serum, and maternal serum. The highest levels of NGF activity were measured in placental cotyledons. After homogenization and centrifugation of the placental cotyledons, the supernatant was sequentially chromatographed, at neutral pH, on Sephadex G-100, DEAE-11, and Sephadex G-150. A high-molecular-weight protein fraction (≈150,000), which contained all the biological activity, was isolated in this fashion. Analytical isoelectric focusing of this fraction revealed a basic protein component (pI 9.5) of the high-molecular-weight species. Assays for NGF activity of all protein components separated by analytical isoelectric focusing showed that NGF activity was associated only with the basic protein component. Correspondingly, preparative isoelectric focusing of the high-molecular-weight species yielded a basic protein with very high biological activity (1–3 ng per biological unit) that was immunochemically active against rabbit IgG made against mouse β-NGF.
97 citations
TL;DR: A direct interaction of ACTH with SPM protein kinase(s) is likely to be responsible for its effect on phosphorylation.
Abstract: ACTH1–24 inhibits the endogenous phosphorylation in vitro of distinct SPM protein bands. Using N-terminal fragments of ACTH, the structure-activity requirements for this effect were studied. A rather complex interaction of the ACTH fragments with endogenous SPM phosphorylation was observed. The effects were not only dependent on the primary structure of the peptide used, but also on the protein band studied and the ATP/SPM ratio used in the incubation system. ACTH1–24 did not interfere with the ATP-hydrolyzing activity of the SPM preparation, nor did it influence the endogenous phosphatase activity. Therefore, a direct interaction of ACTH with SPM protein kinase(s) is likely to be responsible for its effect on phosphorylation.
97 citations
TL;DR: Kinetic analyses plotted in double reciprocal form reveal that berberine and 1,2,10,11-tetrahydroxyaporphine are simplelinear competitive inhibitors with respect to ATP, whereas sanguinarine and papaveroline are simple linear noncompetitive inhibitors.
Abstract: Representatives of eleven different classes of isoquinoline alkaloids inhibit Na+, K+-ATPase and Mg2+-ATPase in rat brain microsomal preparations In most cases the Na+, K+-ATPase is more sensitive than Mg2+-ATPase to inhibition by the alkaloids The classes of alkaloids can be ranked according to potency of inhibition of Na+, K+-ATPase Protoberberines are most effective, followed in decreasing order by benzophenanthridines, benzylisoquinolines, aporphines, tetrahydroprotoberberines, pavines, protopines, isoquinolines, tetrahydrobenzylisoquinolines, morphinanes, and tetrahydroisoquinolines As specific representatives of each of the first four classes of alkaloids, berberine, sanguinarine, papaveroline and 1,2,10,11-tetrahydroxyaporphine, respectively, prove most valuable in kinetic studies because they exhibit the greatest inhibitory action on brain Na+, K+-ATPase Kinetic analyses plotted in double reciprocal form reveal that berberine and 1,2,10,11-tetrahydroxyaporphine are simple linear competitive inhibitors with respect to ATP, whereas sanguinarine and papaveroline are simple linear noncompetitive inhibitors These four representative alkaloids exhibit non-linear competitive inhibition with respect to Na+-activation Additionally, these alkaloids significantly inhibit rat brain microsomal K+-activated pNPPase The results demonstrate that certain members of several classes of isoquinoline alkaloids markedly affect various cation-dependent phosphohydrolases in vitro
96 citations
TL;DR: The neurotoxicity of small doses of kainic acid was found to be influenced by injection time and volume, and an indirect mechanism involving glutamate release and inhibition of reuptake is suggested.
Abstract: Intrastriatal injections of kainic acid are known to destroy striatal neurons including many containing choline acetyltransferase (CAT) and glutamic acid decarboxylase (GAD). Using these enzymes as indices of neuronal loss, the neurotoxicity of small doses of kainic acid was found to be influenced by injection time and volume. It was partly blocked by coninjection of some but not all glutamate antagonists or by prior lesioning of the corticostriatal tract. Other adjuvants, drugs, or lesions tested had little modifying effect, except that changes in the dopaminergic system seemed to increase the toxicity towards cholinergic but not GABAnergic systems. High-affinity glutamate accumulation by neostriatal synaptosomes was significantly increased 1–7 days following kainic acid injections. MAO and acetylcholinesterase activities were depressed in kainic acid-lesioned striata but not nearly as much as were CAT and GAD. An indirect mechanism involving glutamate release and inhibition of reuptake is suggested for kainic acid neurotoxicity.
88 citations
TL;DR: Three specific enzymes are involved in the cerebral synthesis of 7,8-dihydrobiopterin from GTP, which was isolated, purified, and characterized.
Abstract: Three specific enzymes are involved in the cerebral synthesis of 7,8-dihydrobiopterin from GTP. These were isolated, purified, and characterized. The first enzyme, also catalyzing the rate-limiting step, is GTP-cyclohydrolase A-I or Mg2+-dependent A-II, which hydrolyze the GTP to the specific product 2-amino-6-(5-triphosphoribosyl)-amino-5-or-6-formamido-6-hydroxypyrimidine (FPyd-P3). FPyd-P3 is cyclized by a synthetase to D-erythro-7,8-dihydroneopterintriphosphate (NPTH2-P3). The new enzyme, D-erythro-7,8-dihydroneopterintriphosphate synthetase (enzyme B) is a basic protein of 9177 daltons containing three free SH groups, isoleucyl-seryl- as N- and valyl-glutamyl- as C-terminals. This enzyme of 69 amino acid residues from rat and 68 residues (one less aspartic acid) from guinea pig brain contains no hydroxyproline, methionine, or tryptophan. The enzyme from rat brain will gradually convert its product NPTH2-P3 to BH2, wherease the enzyme from guinea pig brain lacks this property. 2,4-amino-6-hydroxypyrimidine and dFPyd-P3 are effective inhibitors of this enzyme. The synthesis of BH2 from NPTH2-P3, but not from 7,8-dihydroneopterin, is catalyzed by L-erythro-7,8-dihydrobiopterin synthetase (enzyme C), which was purified to electrophoretic purity. This enzyme does not require pyridine nucleotides of Mc2+ for its catalysis.
83 citations
TL;DR: The results, in conjunction with others describing the potent pharmacological action of the nucleotide, seem to suggest that ATP could be a mediator in a “purinergic" system in the CNS.
Abstract: The steady-state level of brain ATP was measured after the tissue had been treated with a focused microwave irradiation system. The brain ATP content (1.50 nmol/mg tissue) obtained by microwave fixation is similar to that observed by others using fast-freezing and microwave fixation techniques. The concentrations of ATP in different brain regions show a rather uniform distribution, ranging from 1.918±0.059 (brainstem) to 2.393±0.19 (caudate) nmol/mg tissue; however, insufficient microwave fixation time seems to produce a greater regional variation of ATP. Release of ATP was investigated by placing a cup on the sensory-motor cortex. The rate for basal release of ATP is 1.43±0.14 femtomole/min/mm2. A 30-fold increase in ATP release was obtained by direct stimulation of the cortex with 5 mA pulses of 0.2 msec duration at a rate of 20/sec over a period of 10 min. These results, in conjunction with others describing the potent pharmacological action of the nucleotide, seem to suggest that ATP could be a mediator in a “purinergic” system in the CNS.
77 citations
TL;DR: The binding of [125I]alpha-bungarotoxin (ABTX) to homogenates of ciliary ganglia and irises from embryonic and posthatching chickens has been examined and follows a pattern similar to that of AChE activity.
Abstract: The binding of [125I]alpha-bungarotoxin (ABTX) to homogenates of ciliary ganglia and irises from embryonic and posthatching chickens has been examined. Specific, high-affinity binding was found in both tissues [K
D
(iris)=2.5 nM;K
D
(ganglion)=2.7 nM]. Binding is saturated above 10 nM toxin concentration and is inhibited by low concentrations of the nicotinic antagonistd-tubocurarine. The binding may be associated with a nicotinic cholinergic receptor in both tissues. The amount of binding in the iris begins to increase soon after functional innervation is first observed, at 12 days of incubation (d.i.), and continues to increase up to four months after hatching (a.h.), the oldest age tested. In contrast, ABTX binding in the ciliary ganglion increases fourfold between 7 and 11 d.i., after which the amount of binding remains unchanged up to four months a.h. When compared to the development of choline acetyltransferase (ChAc) and acetylcholinesterase (AChE) activities in the ganglion and iris, ABTX binding follows a pattern similar to that of AChE activity. The largest increases in ChAc activity occur later than those of the postsynaptic markers. After 16 d.i. there are approximately 3×106 toxin molecules bound per neuron in the ciliary ganglion.
72 citations
TL;DR: The high tissue/medium ratio and the lack of a GABA-induced enhancement of the release of radioactivity indicate that the previously observed high-affinity uptake of GABA in cultured astrocytes represents a net uptake and not a homoexchange with endogenous GABA.
Abstract: Content of GABA was measured in cultured, normal astrocytes (from the brain cortex of newborn mice) together with the effect of nonradioactive GABA on the efflux of labeled GABA from cells previously loaded with [14C]GABA. An increase of external GABA concentration from 0 to 25 μM evoked a rise of the GABA content in the cells to a level which was approximately 50 times that of the incubation medium. Neither 200 nor 2000 μM nonradioactive GABA had any effect on the rate of release of radioactivity from cells loaded with [14C]GABA. Both the high tissue/medium ratio and the lack of a GABA-induced enhancement of the release of radioactivity indicate that the previously observed high-affinity uptake of GABA in cultured astrocytes represents a net uptake and not a homoexchange with endogenous GABA. This uptake is sodium dependent but was found to be unaffected in potassium-free media; the quantitative correlation between GABA transport and sodium transport differed from that reported for synaptosomes.
72 citations
TL;DR: Analysis of the autoradiographs obtained from one SPM preparation under different ATP/SPM ratios revealed dependence of phosphorylation of individual protein bands on the conditions used.
Abstract: The time course of endogenous phosphorylation in vitro of total or separted synaptic plasma membrane proteins (SPM) has been correlated with that of hydrolysis of the phosphate donor (ATP) in the incubation medium. The ATP/SPM ratio in the medium was varied. In a low-ratio medium (7.5 μM ATP; 2.2 μg SPM/μl) a complete hydrolysis of ATP occurred almost instantaneously as was measured by the release of free phosphate in and the disappearance of ATP from the medium. As a consequence, only a very short peak of phosphorylation, followed by dephosphorylation was observed. However, when higher ATP/SPM ratios were used (200 μM ATP; 0.4 μg SPM/μl and 500 μM ATP; 0.4 μg SPM/μl), the incorporation of phosphate into SPM proteins was linear for 20 sec, and the maximum level of phosphate incorporation was increased. Similar results were obtained after separation of32P-labeled phosphoproteins by slab gel electrophoresis. However, analysis of the autoradiographs obtained fromone SPM preparation under different ATP/SPM ratios revealed dependence of phosphorylation of individual protein bands on the conditions used.
TL;DR: A modification of the tyrosine hydroxylase assay is described in which ascorbate is used as the reductant, rather than 2-mercaptoethanol or dihydropteridine reductase with NADPH, which is consistent with the biological and regulatory properties of the enzyme which have been determined with the other reducing systems.
Abstract: A modification of the tyrosine hydroxylase assay is described in which ascorbate, rather than 2-mercaptoethanol or dihydropteridine reductase with NADPH, is used as the reductant. Enzyme activity is 3–4 times higher with ascorbate than with the other reducing agents. Low blanks are obtained with the ascorbate system provided that catalase is also included. The tissue distribution and kinetic activation of the enzyme have been studied with the ascorbate assay. The results obtained are consistent with the biological and regulatory properties of the enzyme which have been determined with the other reducing systems.
TL;DR: The effect of depolarizing potassium concentration on the release of [14C]glycine, [3H]GABA, and [35S]taurine was investigated in the whole chick retina and in a synaptosomal fraction prepared from the chick retina.
Abstract: The effect of depolarizing potassium concentration on the release of [14C]glycine, [3H]GABA, and [35S]taurine was investigated in the whole chick retina and in a synaptosomal fraction prepared from the chick retina. In the whole retina, increasing potassium concentration above 40 mM resulted in an increased release of the three amino acids. The release of glycine was the most stimulated and that of taurine, the least. The potassium-evoked release of glycine and GABA was calcium dependent. In the synaptosomal fraction, 68.5 mM potassium significantly stimulated the efflux of GABA and glycine by a calcium-dependent mechanism. The release of taurine from this fraction was unaffected by high potassium.
TL;DR: In brain mitochondria the NAD-linked dehydrogenases, located in the matrix space, were more sensitive to inhibition by lead than were inner membrane enzymes, and all in vitro lead effects on mitochondrial respiration were comparable in cerebral and cerebellar mitochondria isolated from both immature and adult rats.
Abstract: The effects of lead acetate on respiration in cerebral and cerebellar mitochondria from immature and adult rats were studied polarographically. With all substrates low lead concentrations produced an increase in respiration. Higher concentrations produced an inhibition of both this lead-induced respiration and ADP-dependent (State 3) respiration. Lead-induced respiration required inorganic phosphate and was inhibited by oligomycin, suggesting a coupling to oxidative phosphorylation. Inhibition of respiration was produced by much lower lead concentrations with NAD-linked citric acid cycle substrates than with succinate or α-glycerophosphate. In partially disrupted mitochondria, NAD-linked substrate oxidation was inhibited at lead concentrations which did not affect NADH oxidation. Thus, in brain mitochondria the NAD-linked dehydrogenases, located in the matrix space, were more sensitive to inhibition by lead than were inner membrane enzymes. All in vitro lead effects on mitochondrial respiration were comparable in cerebral and cerebellar mitochondria isolated from both immature and adult rats.
TL;DR: It is concluded that 4-aminobutyrate aminotransferases from various tissues of the mouse are probably identical or closely related.
Abstract: A rapid and specific method for assaying 4-aminobutyrate-2-oxoglutarate aminotransferase was developed. The method was based on the selectivity of ion exchange resin and the speed of vacuum filtration. With this new method, the aminotransferase activity in various tissues has been determined as follows: brain, 10.2; spinal cord, 11.8; liver, 5.7; kidney, 4.6; heart, 0.5; lung, 0.4 nmol glutamate formed/min/mg. No activity could be detected in muscle preparations. When the aminotransferases were tested with the antibody, against the purified 4-aminobutyrate aminotransferase from brain, no difference could be detected among brain, spinal cord, and kidney preparations as judged from the results of immunodiffusion, inhibition of enzyme activity by antibody, and microcomplement fixation. It is concluded that 4-aminobutyrate aminotransferases from various tissues of the mouse are probably identical or closely related.
TL;DR: After injection of labeled glycerol, choline, or serine into the eye of goldfish, labeled lipids were axonally transported along the optic nerve to the optic tectum, indicating a fast rate of transport, but continued to accumulate over a period of 1–2 weeks, which presumably reflects the time course of their release from the cell body.
Abstract: After injection of labeled glycerol, choline, or serine into the eye of goldfish, labeled lipids were axonally transported along the optic nerve to the optic tectum. Although the different precursors were presumably incorporated into somewhat different lipid populations, all three were approximately equally effective in labeling the lipids transported to the tectum, but the amount of transported material remaining in the nerve was different, being highest with choline and lowest with serine. The labeled lipids appeared in the tectum within 6 hr of the injection, indicating a fast rate of transport, but continued to accumulate over a period of 1--2 weeks, which presumably reflects the time course of their release from the cell body. Since there was a gradual increase in the proportion of labeled lipid in the tectum during this period, some other process in addition to fast axonal transport may have affected the distribution of the lipids along the optic axons. When [3H]choline was used as precursor, the transported material included a small amount of TCA-soluble material, which was probably mainly phosphorylcholine, with labeled acetylcholine appearing in only insignificant amounts. With serine, which gave rise to a large amount of axonally transported protein in addition to lipid, a late increase in the amount of labeled lipid in the tectum was seen, accompanied by a decrease in labeling of the protein fraction.
TL;DR: The effects of one intraperitoneal injection of 60–65 mg/kg of 3-acetylpyridine on the levels of aspartate, glutamate, GABA, taurine, glycine, and alanine in the cerebellum, medulla, telencephalon, and diencephalon-mesencephalons of the rat were studied at various times after injection.
Abstract: The effects of one intraperitoneal injection of 60–65 mg/kg of 3-acetylpyridine (3-AP) on the levels of aspartate, glutamate, GABA, taurine, glycine, and alanine in the cerebellum, medulla, telencephalon, and diencephalon-mesencephalon of the rat were studied at various times (4–28 days) after injection. In the first 4–7 days, the levels of glutamate, GABA, glycine, and alanine in the cerebellum were 10–30% higher in the 3-AP-treated rats than in the control animals. By day 14, the levels of these four amino acids were normal (in the case of glutamate and glycine) or below normal (for GABA and alanine). By day 21, the values for GABA and alanine returned to normal. In the first 7 days, the level of aspartate in the cerebellum was the same in both the 3-AP- and saline-injected groups. From days 14 to 28, the level of aspartate in the cerebellum was 10–20% lower in the 3-AP-injected group than in the saline-treated animals. The level of taurine in the cerebellum was 15–30% lower in the 3-AP group than in the control group from days 7 to 28. The pattern of changes observed in the medulla in the first 7 days was similar to that found in the cerebellum for this period. However, unlike the data for the cerebellum, the level of aspartate in the medulla was unchanged by the 3-AP injection from day 14 to day 28, and the level of glutamate in the medulla remained higher (10–15%) from days 14 to 28 in the 3-AP-injected animals with respect to control values. The levels of taurine in the medulla were lower (10–15%) from day 7 to day 28 in the 3-AP injected group with respect to control values. The injection of 3-AP did not alter the levels of aspartate, glutamate, GABA, taurine, glycine, or alanine in the telencephalon on days 7, 14, 21, or 28 and in the diencephalon-mesencephalon on day 21 with respect to control levels.
TL;DR: In this paper, Norepinephrine added in vitro to nerve ending membranes from rat cerebral cortex stimulates the activity of (Na+, K+) adenosinetriphosphatase (ATPase) only in the presence of the soluble brain fraction.
Abstract: Norepinephrine added in vitro to nerve ending membranes from rat cerebral cortex stimulates the activity of (Na+, K+) adenosinetriphosphatase (ATPase) only in the presence of the soluble brain fraction. In its absence norepinephrine inhibits the enzyme. (Mg2+)ATPase also showed stimulation by norepinephrine in the presence of the soluble fraction, but of lesser magnitude. The activation of (Na+, K+)ATPase by norepinephrine is not reproduced by cyclic AMP and is not antagonized by either α- or β-adrenergic blocking agents. These results suggest that the stimulation caused by norepinephrine is a direct effect on the enzyme and is not mediated by cyclic AMP or adrenergic receptors.
TL;DR: A significant role for the γ-glutamyl cycle is demonstrated in the transport of large neutral amino acids from blood to brain and in the incorporation into protein when expressed in relation to the plasma specific activity.
Abstract: Two inhibitors of the γ-glutamyl cycle, methionine sulfoximine (MSO) and 2-imidazolidone-4-carboxylic acid (ICA) were administered to C57BL/6J mice. Both agents resulted in a reduced rate of transport of tyrosine from blood to brain and a decreased rate of incorporation of tyrosine from plasma into brain protein. MSO administration also diminished the concentrations of brain tyrosine, dopamine, and norepinephrine. MSO decreased the transport rate of valine by brain as well as the rate of its incorporation into protein when expressed in relation to the plasma specific activity. The results demonstrate a significant role for the γ-glutamyl cycle in the transport of large neutral amino acids from blood to brain.
TL;DR: Administration of pepstatin for shorter periods to Lewis rats, or BSVS mice, or guinea pigs challenged with myelin basic protein delayed, but did not prevent clinical signs of EAE, but was accompanied in all cases by a less severe histopathology.
Abstract: Intraperitoneal administration of pepstatin (2 mg/day for 5 weeks) to Lewis rats subjected to experimental allergic encephalomyelitis (EAE) (induced by guinea pig spinal cord and pertussis vaccine) suppressed the appearance of clinical signs of disease, and reduced the severity and incidence of CNS lesions normally associated with this disease. Administration of pepstatin for shorter periods to Lewis rats, or BSVS mice, or guinea pigs challenged with myelin basic protein delayed, but did not prevent clinical signs of EAE, but was accompanied in all cases by a less severe histopathology.
TL;DR: It appears that an hypoxic environment may provoke both early and long-term alterations in catecholamine and serotonin metabolism, thus neurotransmitter imbalances may explain some of the alterations in neurologic and endocrine development characteristic of the hypoxic animal.
Abstract: Exposure to high altitude (HA) affects neurotransmitter levels in the adult brain and induces a number of neurologic and behavioral disturbances. The present work was undertaken to investigate the effects of chronic exposure to a moderate hypoxic environment (natural altitude of 3800 m, 12.8% O2 in inspired air) on the development from birth until adulthood of brain monoamine enzymes in rats. The activity of synthesizing (tyrosine and tryptophan hydroxylase) and catabolizing (catechol-O-methyl transferase and monoamine oxidase) enzymes was studied in discrete brain areas (cerebral cortex, cerebellum, mesodiencephalon, hypothalamus, corpus striatum, and pons medulla) and was shown to be selectively affected by HA, depending on the age of the animal and the brain region. In general, enzyme activity was less susceptible to HA during the first week after birth than at later ages, some brain areas such as the hypothalamus showing significant alterations in some enzymes throughout development, and in all enzymes at adulthood. Furthermore, in all brain areas and at all ages, tyrosine and tryptophan hydroxylase were more affected by HA than the catabolizing enzymes, and their activity was increased in some areas (e.g., cerebral cortex and cerebellum) but decreased in other areas (e.g., hypothalamus, mesodiencephalon, corpus striatum). These enzymatic changes and the corresponding alterations in precursor amino acids, particularly tryptophan, seem to be due more to the direct effect of hypoxia on oxygen-dependent enzymes, than to the stress. It appears that an hypoxic environment may provoke both early and long-term alterations in catecholamine and serotonin metabolism, thus neurotransmitter imbalances may explain some of the alterations in neurologic and endocrine development characteristic of the hypoxic animal.
TL;DR: A functionally active T-lymphocyte subpopulation sensitized to myelin basic protein in patients with multiple sclerosis and in patientswith certain other CNS diseases is demonstrated.
Abstract: A subpopulation of T lymphocytes sensitized to human myelin basic protein in peripheral blood of patients with multiple sclerosis, central nervous system (CNS) tumors, and cerebrovascular accidents was demonstrated by the antigen-stimulated, rosette-forming T cell assay. A significant increase in the percent of active rosette-forming T cells was detected after in vitro exposure of peripheral blood lymphocytes to human myelin basic protein but not to histones. In contrast, peripheral blood lymphocytes from healthy controls and from patients with benign and malignant breast diseases were unresponsive to stimulation by either antigen. These results demonstrate a functionally active T-lymphocyte subpopulation sensitized to myelin basic protein in patients with multiple sclerosis and in patients with certain other CNS diseases.
TL;DR: The enzyme, most likely cathepsin D, may play an important role in the formation and breakdown of peptide hormones in the hypothalamus and be responsible for splitting somatostatin, substance P, and analogs of substance P.
Abstract: In a continuing study of the physiological role of protein breakdown in the hypothalamus, acid proteinase from bovine hypothalamus was purified about 1000-fold. The molecular weight of the enzyme was approximately 50,000. Maximal activity against hemoglobin was obtained at pH 3.2–3.5; serum albumin was split much more slowly. Hypothalamus acid proteinase was partially inhibited by β-phenyl pyruvate, or benzethonium Cl, and was completely inhibited by low concentrations of pepstatin. This proteinase splits somatostatin, substance P, and analogs of substance P. The probable sites of enzyme action on these peptides were determined by the end group dansyl technique. The enzyme, most likely cathepsin D, may play an important role in the formation and breakdown of peptide hormones in the hypothalamus.
TL;DR: The preincubation of tryptophan hydroxylase extracted from various areas of the central nervous system of the rat with 30 mM dithiothreitol and 50 μM ferrous ammonium sulfate under nitrogen atmosphere resulted in a persistent increase of its activity.
Abstract: The preincubation of tryptophan hydroxylase extracted from various areas of the central nervous system of the rat with 30 mM dithiothreitol and 50 μM ferrous ammonium sulfate under nitrogen atmosphere resulted in a persistent increase of its activity. Studies on the enzyme characteristics indicated that this activation was associated with a doubling in itsVmax and a shift (from 7.6 to 7.2) of the optimal pH for its activity. In contrast, the molecular weight and the apparent affinities of tryptophan hydroxylase for its pterin cofactor and for tryptophan were not significantly altered by the preincubation with dithiothreitol and ferrous ammonium sulfate. Since this treatment did not prevent the stimulatory effects of various compounds (phosphatidylserine, ATP and Mg2+, Ca2+) on tryptophan hydroxylase activity, this might be a good procedure to activate this enzyme with only minor changes in its regulatory properties.
TL;DR: It is not entirely clear why the nervous system appears to be more frequently affected, while other tissues apparently remain undamaged, but it may be related to the extensive development of the central nervous system postnatally when the individual no longer has the protection of the maternal metabolism.
Abstract: The genetic basis of metabolic disorders was recognized long before the structure of DNA, the genetic code, or the biochemical basis for genetic inheritance was elucidated. While studying alkaptonuria, cystinuria, albinism, and pentosuria, Garrod (1) developed the concept that certain diseases can arise because an enzyme, which controls a single metabolic step, is either missing or has been severely impaired in its function. The defective enzymes or inborn errors of metabolism as he termed them, which are responsible for these diseases, were not biochemically defined until 50 years after Garrod's first observations. Since 1950 so many metabolic diseases have been described that today there are 150 known inborn errors of metabolism (2). Central and peripheral nervous system damage occurs in many of these inborn enzymatic defects (3). It is not entirely clear why the nervous system appears to be more frequently affected, while other tissues apparently remain undamaged, but it may be related to the extensive development of the central nervous system postnatally when the individual no longer has the protection of the maternal metabolism. Although the enzyme defects responsible for many metabolic diseases have been elu-
TL;DR: It is reported that inbred susceptible mice (O'Grady strain) injected intraperitoneally with 6-OH-DA exhibited an unusual response pattern during audiogenic seizures, characterized mainly by delayed and prolonged clonic manifestations with a high incidence of deaths.
TL;DR: In the face of a severe diet-induced deficiency of taurine in kitten brain, there appears to be no conservation of t aurine by any particular subcellular pool of tauraine.
Abstract: Taurine concentration decreases rapidly in the tissues and physiological fluids of kittens fed a diet of partially purified casein which lacks taurine. We have studied the subcellular distribution in cerebrum of taurine and [35S]taurine administered intravenously to these animals. The taurine concentration of all the fractions isolated from the cerebrum of taurine-deficient kittens was approximately sevenfold less than that observed in the fractions of cerebrum isolated from control kittens. The [35S]taurine was approximately twofold greater in all the brain fractions isolated from the taurine-deficient kittens compared with those isolated from the control kittens. The percent distributions of taurine and [35S]taurine in the fractions isolated from the cerebrum of control and deficient kittens were identical. Thus, in the face of a severe diet-induced deficiency of taurine in kitten brain, there appears to be no conservation of taurine by any particular subcellular pool of taurine. These studies provide no evidence for differences in compartmentation of taurine in cerebrum of taurine-deficient kittens compared with control kittens.
TL;DR: It is demonstrated that cocaine and low concentrations of sodium ion also reduced these uptakes of meta-tyramine, para-tyramsine, and dopamine into rat striatal slices, and the removal of calcium either did not reduce or completely abolished the releases depending upon the duration of the calcium removal.
Abstract: The uptakes of high-affinity concentrations (10−8 M) ofmeta-tyramine (m-TA),para-tyramine (p-TA), and dopamine (DA) into rat striatal slices have been shown to be inhibited by DNP and ouabain. We now demonstrate that cocaine (5×10−6 M) and low concentrations of sodium ion (26×10−3 M) also reduced these uptakes. The spontaneous efflux and the release [induced by an elevated concentration of potassium ion (5×10−2 M)] of each of the previously accumulated amines were studied in the presence and absence of added calcium ions. The spontaneous efflux of each amine (especially the tyramines) was enhanced by the absence of calcium ions. Part of this enhancement seemed to be due to an inhibition of a calcium-dependent reuptake. The elevated concentration of potassium ion proved to be an effective releaser of each amine; and for DA, such release was decreased by the removal of calcium. Form- andp-TA, however, the removal of calcium either did not reduce or completely abolished the releases depending upon the duration of the calcium removal. The significance of these findings is discussed.
TL;DR: In this article, high enriched fractions of synaptic junctional complexes, synaptic vesicles, and coated vesicle were isolated from rat forebrains and compared, along with synaptosomal plasma membrane and its nonjunctional components, by discontinuous sodium dodecylsulfate-polyacrylamide gel electrophoresis.
Abstract: Highly enriched fractions of synaptic junctional complexes, synaptic vesicles, and coated vesicles were isolated from rat forebrains and compared, along with synaptosomal plasma membrane and its nonjunctional components, by discontinuous sodium dodecylsulfate-polyacrylamide gel electrophoresis. When stained for proteins with Coomassie blue, the gels all contained the same protein bands, only in different relative amounts. Mixing experiments revealed no additional bands. However, gel patterns of each fraction were not only quantitatively but also qualitatively different when stained for carbohydrate. These observations suggested that some of the protein bands may vary in their degree of glycosylation among the various synaptic fractions. Within the limits of resolution of the methods used here, these results are consistent with the morphological process of synaptic vesicle exocytosis and recycling but suggest the possibility of a reversible modification of certain membrane glycoproteins as they pass through the various membrane compartments.
TL;DR: Ornithine decarboxylase activity was increased about tenfold in adrenal glands and in brain regions preponderantly containing aminergic neurons, by a single dose of reserpine, and activity-time curves in the brain regions showed a concomitant polyphasic course.
Abstract: Ornithine decarboxylase activity was increased about tenfold in adrenal glands and in brain regions preponderantly containing aminergic neurons, by a single dose of 16 μmol/kg of reserpine. Maximal enzyme activity in the adrenal glands was observed at about 8 hr after reserpine administration. The ornithine decarboxylase activity-time curves in the brain regions showed a concomitant polyphasic course, with the highest maximum at 12 hr postinjection. Ornithine decarboxylase induction is discussed as an early event in the cascade of molecular events preceding the induction of cell typic enzymes.