摘要:

Abstract—The kinetics of sodium dependent glutamic acid transport have been studied in desheathed frog sciatic nerve. Initial velocities have been measured as a function of both glulamic acid and sodium concentration. Lineweaver–Burk plots are constructed from these data, and the kinetic constants describing uptake are estimated.Vmaxis unaffected by sodium concentration, which implies that translocation is not directly affected by sodium.K1is sodium dependent, which implies that sodium affects the affinity of the carrier for glutamic acid. Reciprocal plots of velocity vs [Na] orK1vs 1/[Na] are linear, suggesting that glutamic acid and sodium are co‐transported on a one‐to‐one basis.t, the sodium concentration giving half maximal velocity of uptake, was found to vary from about 57 mmto 48 mmat glutamic acid concentrations of 1.0–10.0 ± 10−6m. A model of a mechanism by which sodium and glutamate could be co‐transported is presented; the model is in very good agreement with the e

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb04471.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—A method is described for detecting myelin in small amounts of tissue by density criteria. Samples are homogenized in 0.926m‐CsCl, 10 mm‐Tris‐HCl, (pH 7.4), 5 mm‐Ca2+solution and centrifuged to equilibrium at 52,000 rev./min and 4°C in the AN‐F rotor of the Model E analytical ultracentrifuge. Homogenates of white matter show a band of material in the density range of 1.20–1.130 g/ml, whereas gray matter homogenates do not show a band of material in this density region. A preparative method is described for isolating the material banding in the region of 1.120–1.130 g/ml from optic nerve homogenates of 21‐day old rats. This material has (1) a protein content of 22–24%, (2) an enzymatic activity for 2′,3′‐cyclic nucleotide phosphohydrolase of 13.1 μmol/min per mg protein and (3) a phospholipid‐cholesterol‐galactolipid molar ratio of 100:100:48. Plasmalogen accounted for 22% of the phospholipid, and sulfatide accounted for 31% of the galactolipid. This material is 85% soluble in chloroform:methanol (2:1. v:v). Developmental studies indicate that this myelin material can first be detected in the opt

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb04472.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—Analysis of lipids and proteins in whole optic nerves during initial stages of myelination indicate a sequential deposition of myelin components. During this period sulfatide levels increase from 4 nmol/pair of nerves at 9 days to 29 nmol/pair of nerves at 21 days. Cerebrosides are not detected until the 12th day and attain a level of 46 nmol/pair of nerves in the 21‐day old rat. Plasma‐logen values increase from 2.1 to 31 nmol/pair of nerves and cholesterol values from 12 to 158 nmol/pair of nerves between 9 and 21 days. High molecular weight proteins are present in samples from 9‐day old rats analyzed by discontinuous sodium dodecyl sulphate‐polyacrylamide gel electrophoresis. Under identical conditions myelin basic proteins are first observed in the 10 day sample, and the proteolipid protein is first detected in the 12 day sample. The 2′, 3′‐cyclic nucleotide 3′‐phosphohydrolase activity increases from 1.13 to 5.50 μmol/min per mg protein b

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb04473.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—Histidine decarboxylase activity is found in all parts of the hippocampal formation (subiculum, CA1, CA3 and area dentata), and a major portion of the enzyme is localized in a subcellular fraction containing the nerve terminal particles. The almost complete disppearance of HD (and histamine) after deafferentation of the hippocampal formation suggests that histamine synthesis in this region resides in terminals of extrinsic fibres. The results after selective lesions indicate that these alleged histaminergic fibres enter the hippocampus, like the monaminergic fibres, through a dorsal route (comprising fimbria, fornix superior and cingulum) as well as through a ventral route (via the amygdaloid area). The former was tentatively estimated to represent about 60% of the total hippocampal supply of alleged histaminergic fibre

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb04474.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—Adenylate cyclase activity of permeabilized neuroblastoma cells was measured by the conversion of [α32P]ATP into labelled cyclic AMP. Adenosine (10−6‐ 10−4m) induced a dose‐dependent increase in cyclic AMP formation. This effect could not be accounted for either by an adenosine‐induced inhibition of the phosphodiesterase activity present in the enzyme preparation, or by a direct conversion of adenosine into cyclic AMP. This indicates that the observed increase in cyclic AMP accumulation reflected an activation of adenylate cyclase. Adenosine is partially metabolized during the course of incubation with the enzyme preparation. However, none of the identified non‐phosphorylated adenosine metabolites were able to induce an adenylate cyclase activation. This suggests that adenosine itself is the stimulatory agent. The apparentKmof the adenylate cyclase for adenosine was 5 ± 10−6‐10−5m. Maximal activation represented 3‐4 times the basal value (10‐100 pmol cyclic AMP formed/10 min/mg protein). The adenosine effect was stereospecific, since structural analogues of adenosine were inactive. Adenosine increased the maximal velocity of the adenylate cyclase reaction. The stimulatory effect of adenosine was inhibited by theophylline. Prostaglandin PGE1had a stimulatory effect much more pronounced than that of adenosine (6‐10‐fold the basal value at 10−6m). Dopamine and norepinephrine induced a slight adenylate cyclase activation which was not potentiated by adenosine. It is concluded that adenosine is able to activate directly neuroblastoma cell adenylate cyclase. It seems very likely that such a direct activation is also present in intact nervous tissue and account, at least partly, for the observed cyclic AMP accumu

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb04475.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—1,2‐Diacyl‐, 1‐alk‐1′‐eny1‐2‐acyl‐ and 1‐alky1‐2‐acyl‐sn‐glycero‐3‐phosphorylcholine specifically labelled with different fatty acids at the 2 position, were prepared enzymically using the acyltransferase system of rabbit sarcoplasmic reticulum. The substrates were submitted to hydrolysis by phospholipase A2(phospholipid acyl‐hydrolase, EC 3.1.1.4) obtained from normal and brain tissue affected with subacute sclerosing panencephalitis. In the diseased tissue an increase of phospholipase A2activity ranging from 46 to 54% could be observed in comparison to the control brain for all substrates investigated. Among the investigated substrates phospholipase A2had the highest affinity for the 1,2‐diacylcompound, whereas alkenylacyl‐ and alkylacyl‐sn‐glycero‐3‐phosphorylcholine were cleaved at almost similar rates. The hydrolysis rate of choline‐plasmalogen and the corresponding diacyl compound by the enzyme was greatly influenced by the fatty acid m

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb04476.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—The spatial and temporal distribution of labelled protein in lateral eyes ofLimulus polyphemushas been followed after injection ofl‐[3H]leucine into the pericardial sinus. Labelled protein in the eyes rises for 3 h, for the first hour more rapidly in the cytoplasm but thereafter preferentially in the rhabdomal membranes of the visual receptor cells. In light, the label in the membrane reaches a peak at 3 h whereas in dark the peak is at 6 h. The subsequent decrease in label in light has a half life of about 2 h, but in dark is biphasic with halflives of 2 h and 8 days. These results can be interpreted on the basis that the major labelled protein in the rhabdomal membrane is rhodopsin, the degradation rate of which is enhanced when the membranes are depolarized by li

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb04477.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—Phospholipids of guinea‐pig inner ear tissues were labelledin vivoby perilymphatic perfusion of the cochlea with [32P]orthophosphate or myo‐[3H]inositol. After 20‐40 min the most highly labelled32P‐lipids were phosphatidylinositol phosphate and diphosphate. Incorporation of [3H]inositol proceeded in the order phosphatidylinositol>phosphatidylinositol phosphate>phosphatidylinositol diphosphate.After treatment of animals with neomycin for 3 weeks,32P‐incorporation into phosphatidylinositol diphosphate, but not into other lipids, was significantly decreased in the preparations of the organ of Corti and stria vascularis. In homogenates of inner ear tissues, the labelling of the polyphosphoinositides by [γ‐32P]ATP was increased and the hydrolysis of these lipids was blocked in the presence of 10−4m‐neomycin. Neomycin also competitively inhibited the binding of45Ca2+to homogenate

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb04478.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—Age‐related changes in acyl group composition of diacyl‐glycerophosphorylethanolamine (GPE), alkenylacyl‐GPE and diacyl‐glycerophosphorylcholine (GPC) were examined in myelin and microsomal fractions of mouse brain during development. In general, the phosphoglycerides in the myelin fraction showed an increase in the proportions of 18:1 and 20:1 and a decrease in the proportions of 16:0, 20:4(n‐6) and 22:6(n‐3) with increasing age. These changes were especially obvious with the acyl groups of alkenylacyl‐GPE. The acyl group profiles of phosphoglycerides in the microsomal fraction were different from those in the myelin fraction. During development, there was an increase in 22:6 and a decrease in 20:4 in the phosphoglycerides of microsomes. These changes were especially obvious with the diacyl‐GPE. Starting from 2 weeks of age, there was also an increase in the proportions of 18:1 and 20:1 in alkenylacyl‐GPE in the microsomal fraction but this change was not as dramatic as that in the myelin fraction. In general, the acyl groups of diacyl‐GPC in both myelin and microsomal fractions showed only little age‐related changes as compared to the ethanolamine phosphoglycerides. Results suggest an induction in the synthesis of monoenoic fatty acids in brain during development. The monoenoic fatty acids synthesized during this period are rapidly and preferentially incorporated into the ethanolamine plasmalogen for further utilization in synthesis

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb04479.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY

摘要:

Abstract—Synaptosomes which had taken up [14C]GABA were applied to a filter and rapidly perfused with various solutions in order to study the time course of release of this putative transmitter and the characteristics of its release. Depolarization of the synaptosomes with veratridine or 56mM‐K+or pretreatment with the Ca2+ionophore, A23187, increased the calcium‐dependent efflux of [14C]GABA. Release of [14C]GABA was increased by Ca2+within 0.3 s of exposure, and the maximal release rate was not maintained for longer than 0.6 s. The reduction in the rate of release was not attributable to a decrease in calcium influx, but rather appeared to reflect fatigue at some subsequent stage in release. Stimulation by 56mM‐K+also elicited a calcium‐independent increase in the efflux of radioactive GABA, which appeared to arise in part from subcellular particles other than syn

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1976.tb04480.x

出版商:Blackwell Publishing Ltd    

年代:1976

数据来源: WILEY