摘要:

Abstract—Several isotopic precursors have been monocularly injected into chick embryos and into day‐old or 15‐day‐old chicks. After various intervals, the incorporation of various isotopes into acid insoluble material within the retina of the injected eye and within the optic lobes, was determined. Radioactive proline and fucose were used as precursors of protein and glycoprotein respectively while uridine was used as an RNA precursor. The proportion of rapidly migrating proteins and glycoproteins was reduced during maturation. The extent of RNA migrating also appeared to decline during development. The proportion of synthesized protein that was transported was relatively constant and independent of the amino acid used. Around 30 per cent of retinally synthesized glycoprotein migrated distally and this migrating material appeared to contain very few sialic acid residues. A considerable amount of retinally synthesized gangliosides also appeared rapidly in the distal regions of the opti

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb10741.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Equilibrium or incomplete equilibrium density gradient centrifugation was used to characterize the subcellular localization of exogenous [3 5S]taurine which was taken up by minces or homogenates of rat cerebral cortex. [3 5S]Taurine is accumulated in synaptosomes, which sediment more slowly thanl‐[3H]norepinephrine‐accumulating particles. When [3 5S]taurine and [3H]GABA are accumulated by minces, a small difference in the sedimentation profile of taurine and GABA was observed, but no difference was found when taurine and intrasynaptosomal potassium were compared. However, potassium sedimented more slowly after incubation of homogenates than of minces. These data give evidence for the accumulation of [3 5S]taurine by a specific synaptosomal popul

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb10742.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—A method is described by which the rate of glucose utilization by whole brain of conscious rats may be measured. The basis is the uptake of14C derived front [2‐14C] glucose into the acid‐soluble metabolite pool of brain. Catheters are placed in the femoral artery and vein under light ether anesthesia. After full recovery of consciousness a single intravenous injection of [2‐14C] glucose is given and arterial blood samples taken at intervals. Simultaneous with the last sample the brain is removed and frozen within 1 s. The accumulation of14C into the acid‐soluble metabilite pool is measured and the rate of glucose utilization is calculated according to the equation:The integral is calculated from the plasma glucose specific activity curve and evidence is presented to justify this procedure. The rate of glucose utilization measured by this method was 0·62 μmol/min per g in conscious rats and 0·28 μmol/min per g in sodium pentobarbital anes

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb10743.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Ovariectomized female rats were treated daily with oestradiol‐17β benzoate for intervals up to one week and enzyme activities were measured in the pituitary and various brain regions. Brain regions were selected for study on the basis of their previously demonstrated content of putative oestradiol receptor sites. (1) Pituitary showed oestrogen‐dependent increases in glucose‐6‐phosphate dehydrogenase (G6PDH), 6‐phosphogluconate dehydrogenase (6PGDH) and lactic dehydrogenase (LDH), and no change in NADP+‐dependent isocitric dehydrogenase (ICDH), NADP+‐dependent malic dehydrogenase (MDH) or hexokinase (HK). MDH and ICDH were elevated in whole hypothalamus. Enzyme activities did not change significantly in whole amygdala, cerebral cortex, or hippocampus. (2) Sub‐regions of the preoptic area, hypothalamus and amygdala were dissected to obtain more highly concentrated populations of cells containing putative oestrogen receptor sites. In the basomedial sub‐region of hypothalamus, activities of MDH, ICDH and G6PDH were elevated by oestrogen treatment. In the corticomedial sub‐region of amygdala, MDH and ICDH were elevated by oestrogen treatment. No change was observed in any of the six enzymes in medial preoptic area. (3) Increases in enzyme activities were related to the totalin vivodose of oestradiol benzoate given. (4) Hypophysectomy or adrenalectomy did not prevent the enzymatic responses to oestrogen. (S) Oestrogen added directly to the enzyme incubation medium did not change enzyme activities. (6) Weight loss in ovariectomized rats due to reduced food intake did not increase enzyme activities. (7) In the pituitary, good correlation was obtained between the known receptor binding properties of various oestrogenic and non‐oestrogenic steroids and the elevation in G6PDH activity. The results indicate that oestradiol acts directly to cause changes in activities of some brain and pituitary enzymes. The possibility is discussed that these changes may result from oestrogen interaction with putative receptor sites found in pituitary a

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb10744.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The hereditary motor neuron degeneration found in the wobbler (wr) mouse was studied as a model of secondary demyelination. Lysosomal enzymes (acid phosphatase, acid proteinase, β‐glucuronidase and β‐galactosidase) were found elevated about three‐fold in the white matter of the affected cervical spinal cord as compared with normal controls; but they were either not increased, or increased much less, in the anterior horn. Since gliosis and influx of phagocytic cells are minimal in this model, the high hydrolase levels are believed to arise primarily from (a) the accumulations of axonal dense bodies seen in involved areas, and (b) from indigenous cells engaged in breaking down the myelin fragments. Thus, secondary demyelination may, at least in this case, be initiated by enzymes of local origin.DNA levels per unit weight of tissue in both white and gray matter of wobbler cervical cord were elevated 40‐50 per cent over controls. However, this was considered to reflect the stunted growth of wobbler mice rather than proliferation or influx of cells (an altered ratio of DNA to protein was demonstrated in the brain).Wobbler mice had similar levels of lactic dehydrogenase as controls; glucose‐6‐phosphate dehydrogenase was moderately elevated, and glycerol‐3‐phosphate dehydrogenase was less active in the anterior horn but more active in the white matter

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb10745.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Synaptosomes were prepared from rat brain on a continuous gradient of sodium diatrizoate and compared with synaptosomes obtained on a discontinuous sucrose gradient. The yield of synaptosomal protein using diatrizoate was double that obtained with sucrose. No significant differences in quality between the two preparations were found based on measurement of: β‐glucuronidase, RNA polymerase, 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase, total and Na+, K+‐ATPase, acetylcholinesterase, lactic acid dehydrogenase, glucose utilization, and serotonin uptake. Electron microscopy showed the vesicles in the diatrizoate synaptosomes to be better preserved. Vesicles prepared on diatrizoate segregated into two distinct bands which differed in electron microscopic appearance and enzyme activity. The less dense vesicles were smaller, had much higher Mg2+‐ATPase activity, and a lower content of acetylcholinesterase than the more dense vesicles. The less dense vesicle preparation was very homogeneous morphologically, free of myelin and mitochondria, and contained occasional organelle fragments and double m

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb10746.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Acetylcholine, its precursor (choline), and the enzymes of its biosynthesis and degradation (choline acetyltransferase and acetylcholinesterase, respectively) have been studied and quantified in extracts of several regions of the nervous system of the lobster and in single, isolated axons of identified efferent excitatory, efferent inhibitory and afferent sensory neurons. The choline acetyltransferase is a soluble enzyme similar to that from other species. The predominant acetylcholine‐hydrolysing enzyme is largely membrane‐bound and has been characterized as a specific acetylcholinesterase. A single peak of acetylcholinesterase activity can be detected upon velocity sedimentation analysis of Triton X‐100‐treated extracts of all regions of the nervous system. Choline acetyltransferase distribution parallels that of sensory neural elements, and its specific activity shows nearly a 500‐fold difference from the richest to the poorest neural source. Acetylcholinesterase levels span only a 23‐fold range, and activity is found in all neural regions, including those free of known sensory components. A radiochemical microassay for choline and acetylcholine in the range of 20–2000 pmol is described in detail. All 3 types of axons contain comparable levels of choline (ca.2 pmol/μg protein), but acetylcholine is asymmetrically distributed. Efferent axons contain no detectable acetylcholine, while sensory axons from abdominal muscle receptor organs have an average of 1·9 pmol/μg protein. Choline acetyltransferase is similarly distributed; sensory axons show at least 500‐fold greater activity than efferent axons. Acetylcholinesterase is nearly uniformly distributed among the three types of fibres. These results are discussed in terms of a general view of transmitter accumulati

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb10747.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Visible lesions from monkeys with acute experimental allergic encephalomyelitis (EAE) induced by injection of purified myelin basic protein were assayed for acid proteinase, for a neutral proteinase at pH 6·5, and one lesion was measured for cathepsin A. Acid proteinase was increased to 152–176 per cent of levels in normal‐appearing brain areas, neutral proteinase increased to 220–258 per cent, and the one lesion assayed for cathepsin A was 840 per cent of control. These enzymes were measured in the brain stem of Lewis rats with acute EAE as a result of basic protein injection and compared to Freund's adjuvant‐injected controls. Acid proteinase was increased significantly to an average level of 128 per cent of control, the increase in neutral proteinase was not significant, and cathepsin A levels were 258 per cent of control, a highly significant increase. The rise in cathepsin A levels was not seen until the onset of paralytic symptoms. The brain stem of Wistar rats treated with whole spinal cord which show EAE in a milder form than the Lewis rat did not contain significantly higher enzyme levels than the control. The increases in acid proteinase and cathepsin A in brain stems were compared to levels of these enzymes in lymph nodes of EAE, Freund's adjuvant‐injected controls and uninjected controls. The level of acid proteinase of lymph nodes/g protein did not change appreciably in the course of EAE development in the Lewis and Wistar rats and was about 3–4 times the activity in the brain stem. The cathepsin A in the inguinal lymph nodes of Wistar and Lewis rats injected with whole spinal cord in Freund's adjuvant increases to a level 2× that of the lymph nodes of the uninjected control. The cathepsin A levels in these activated lymph nodes was 6–8 × that of the control brain stem. The lymph nodes of Lewis and Wistar rats injected with Freund's adjuvant alone showed the same increase in cathepsin A as those from rats injected with spinal cord. The brain stem of rats undergoing severe demyelination as a result of chronic administration of triethyl tin did not show the enzyme increases. These results are compatible with the theory that proteolytic enzyme increases in EAE (and probably multiple sclerosis) are due to the invasion of mononuclear cells, some of which are probably lymphocytes. Whether or not these enzymes participate in the actual dissolution of

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb10748.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—Two basic peptides (B1 and B2) were derived from bovine spinal cord followingin situproteolysis at 37°C for 10–24 h. These peptides do not arise as degradation products from the A1 protein as shown by amino acid composition and end group analysis; rather they appear to originate from some larger basic protein in the spinal cord having similarities to the P2 protein, a basic protein found in peripheral nerve myelin. The peptides were purified following defatting, acid extraction, and ammonium sulphate fractionation, by chromatography on Amberlite IRC‐50 resin using guanidinium chloride. The peptides, found generally in a 4:1 ratio of B1 to B2, appeared homogeneous on gel electrophoresis and immunodiffusion. Approximately 25–60 mg of peptides was obtained per 100 g wet spinal cord.In contrast to the basic A1 protein from myelin, neither of these peptides nor their pepsin digests were encephalitogenic. They do not cross‐react immunologically with the basic A1 protein, but cross‐react with each other. These peptides further differ from the A1 protein in their tryptic peptide map, size (B1, 63 residues; B2, 54 residues), and composition particularly the high lysine: arginine ratio, and low histidine content. Like the A1 protein, however, they contain a tryptophan residue and a blocked NH2‐terminal amino acid; peptide Bl has COOH‐terminal valine. It was concluded that the basic peptides represent a fragment of a hitherto unidentified protein(s) of th

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb10749.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

Abstract—The influx and efflux of [3H]GABA were investigated in synaptosomes. Two efflux components were detected. The first, termed spontaneous efflux, was not affected by the external sodium chloride concentration. The second, termed GABA‐stimulated efflux, was observed when low levels of GABA were added to the incubation medium and was found to require external sodium chloride. The rate of spontaneous efflux at 0°C was about 37 per cent of the rate at 27°C but both GABA‐stimulated efflux and GABA influx were completely inhibited at 0°C. The stimulation of efflux by external GABA followed simple Michaelis–Menten kinetics with respect to external GABA. The concentration of external GABA required for half‐maximal stimulation was 4·9 ± 1·4 μmand theVmaxfor efflux was 1·0 ± 0·6 nmol. min‐1.mg‐1of protein. A similar stimulation of efflux was observed with GABA analoguel‐2,4‐diamino‐butyric acid which is a competitive inhibitor of influx. The concentration of externall‐2,4‐diaminobutyric acid required for half‐maximal stimulation of efflux was 51 ± 12 μmand theVmaxfor efflux was 0·8 ± 0·5 nmol.min‐1.mg‐1of protein. Since the sodium‐dependency, temperature sensitivity, and kinetic properties of the GABA‐stimulated efflux system were similar to the influx system, GABA‐stimulated efflux was attributed to carrier‐mediated exchange diffusion. Measurement of efflux and influx in the same preparation showed there was a net efflux when total fluxes were considered and that the exchange ratio (influx to GABA‐stimulated efflux) was 0·9 when carrier‐mediated fluxes were considered. The effect of the temperature of the fluid used to rinse synaptosomes collected on filters in influx experiments was investigated. There was no detectable difference in measured values of influx between samples rinsed with cold fluid (0°C) and warm fluid (27°C). The endogenous GABA content of synaptosomes was found to be 20·3 ± 2·5 nmol GABA per mg of protein. From this value, the cytoplasmic concentration of GABA in synaptosomes was estimated to be a maximum of 40 mm. About 5 per cent of total

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1974.tb10750.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY