摘要:

Abstract:We report the distribution of choline acetyltransferase (ChAT) activity in the laminae of the rat olfactory tubercle. Within its posterior medial portion, the tubercle contains three parallel histological laminae that can be separated by cutting tangential sections from frozen tissue. ChAT was measured in homogenates of consecutive sections (16 μm) cut parallel to these laminae. The distribution of ChAT activity, as a function of tubercle depth, showed a broad peak centered at 500 μm from the ventral surface of the brain. Enzyme activity measured at this depth (85 pmol acetylcholine formed/μg protein/h) was 2 1/2 times greater than that measured in the outermost, plexiform, layer. Stereotaxic injections of kainic acid (1 μg in 1 μ1) made directly into the tubercle were used to eliminate intrinsic neurons. Three days after injection, histological examination revealed the almost total absence of neuronal cell bodies and the proliferation of glial cells. The greatest decreases in ChAT activity (50%) were seen at depths of 300–600 μm whereas no loss of activity occurred in the plexifor

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12655.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Arachidonate incorporation into synaptosomal phospholipids was shown to be affected by factors including the procedure for preparation of the membrane fractions and preincubation of synaptosomes prior to assay of incorporation activity. Preincubation of synaptosomes gave rise to a decrease in incorporation of arachidonate into both phosphatidylcholine (PC) and phosphatidylinositol (PI). However, the inhibition toward incorporation into PIs, but not PCs, was fully reversed when the membranes were washed with bovine serum albumin. A twofold increase in arachidonate incorporation into PIs was also observed when freshly prepared synaptosomes were washed with serum albumin immediately before assay of incorporation activity. The inhibitory action is thought to be due to an increase in polyunsaturated fatty acids and/or their oxidation products which may then elicit a special effect on the acyltransferase responsible for transferring arachidonate into phosphatidylinositols. The differences in fatty acid uptake and response to serum albumin also suggest the presence of different acyltransferases for acyl transfer to PIs and PCs.

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12656.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The acetylcholine (ACh) content of sympathetic ganglia increases above its normal level following a period of preganglionic nerve stimulation. In the present experiments, this extra ACh that accumulates following activity was labeled radioactively from [3H]choline and its specific activity was compared with that of ACh subsequently released during preganglionic nerve stimulation. The specific activity of the released ACh was similar to that of the total tissue ACh, suggesting that the extra ACh mixes fully with endogenous stores. The present experiments also show that transmitter release during neuronal stimulation is necessary for the poststimulation increase in transmitter store. However, the increase was not evident when transmitter release was induced by K+. It is concluded that both transmitter release and impulse invasion of the nerve terminals are necessary for the adaptive phenomenon to manifest itself. The role of choline delivery and choline acetyltransferase activity in generating the poststimulation increase in transmitter store was tested. When choline transport activity measured as choline analogue (homocholine) accumulation increased, ACh synthesis was increased and when transport activity was not increased, neither was ACh synthesis. There was no poststimulation increase in measured choline acetyltransferase activity.

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12657.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Oxidation of ketone bodies (KBs) generates acetyl coenzyme A (AcCoA), which can be further incorporated into fatty acid. We have determined the rates of lipogenesis from ketone bodies in developing rats and their relation to the activities of enzymes involved in the production of cytoplasmic AcCoA via different pathways in brain regions. In the cerebrum (Cbr), rates of fatty acid synthesis from [3‐14C]acetoacetate ([3‐14C]AcAc) were high during the early postnatal period but decreased rapidly thereafter until weaning. Although similar developmental patterns of synthesis characterized the cerebellum (Cbl), midbrain (Mb), brain stem (Bs), and thalamus (Th), maximal rates were highest in the Cbr and lowest in the Th. In all regions, synthetic rates were higher throughout the entire suckling period than in adulthood. There were no appreciable differences in synthetic rates among brain regions of adult rats. The developmental changes in rates of AcAc incorporation into fatty acids were closely related to AcAcCoA synthetase activity, but not to activities of ATP‐citrate lyase or AcCoA synthetase. During the early postnatal stage the enhanced rates of lipogenesis were accompanied by increased activities of AcAcCoA synthetase in all regions, with the highest activity occurring in the Cbr. The sequence of reactions coupling AcAcCoA synthetase and AcAcCoA thiolase in cytoplasm may be an important pathway for generation of AcCoA from KBs for fatty acid synthesis in all regions of the developing brain. This interpretation is strengthened by evidence of concomitant increases in the activities of fatty acid synthetase and AcCoA carbox

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12658.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Synaptosomes from normoxic and hypoxic rats were incubated aerobically in the presence and absence of veratridine. In the absence of veratridine, no significant difference was observed between the two types of preparation regarding either ATP/ADP ratio or14CO2or [14C]acetylcholine synthesis from D‐[U‐14C]glucose. However, in the presence of veratridine, significant reductions in the output of14CO2and [14C]acetylcholine by synaptosomes from hypoxic rats were apparent. It was concluded that irreversible metabolic lesions occur at the synapse as a result of hypoxia, which are apparent only when the metabolism of the preparation is accelerated to a level comparable with the maximal rate occurringin vivo.The presence of such lesions is further evidenced by the significant reductions in ATP/ADP ratio,14CO2output, and [14C]acetylcholine synthesis that occur in synaptosomes from hypoxic rats made anoxicin vitroand permitted to recover. Such decreases are not seen when synaptosomes from normoxic rats are similarly trea

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12659.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:γ‐Aminobutyrylcholine (GABACh) has been reported to exist in mammalian brain tissue, but not, as yet, given a specific physiological role in the CNS. In order to investigate further its occurrence and function in the CNS, two new methods have been developed for its isolation and determination at the picomole level. Its isolation has been achieved by ammonium Reineckate precipitation or by cation‐exchange followed by HPLC determination of the dansyl andO‐phthaldialdehyde derivatives. Using these methods, no free endogenous GABACh (<80 pmol/g) was found in rat, guinea pig, cat, pig, marmoset, or human brain tissue. No evidence was obtained, eitherin vitroorin vivo, for the incorporation of [14C]choline or [14C]γ‐aminobutyric acid into GABACh. GABACh was hydrolysed at a low rate (maximum of 45 nmol/h/g of brain tissue) after incubation with rat, guinea pig, or cat brain minces and homogenates. These results fail to confirm the data of other investigators, and the possible reasons for this are

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12660.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The activities of three myelin‐associated enzymes, carbonic anhydrase, 5′‐nucleotidase, and 2′,3′‐cyclic nucleotide‐3′‐phosphodiesterase (CNP), were measured in oligodendrocytes, neurons, and astrocytes isolated from the brains of rats 10, 20, 60, and 120 days old. The carbonic anhydrase specific activity in oligodendrocytes was three‐ to fivefold higher than that in brain homogenates at each age, and, at all the ages, low activities of this enzyme were measured in neurons and astrocytes. The oligodendrocytes and astrocytes from the brains of rats at all ages had higher activities of the membrane‐bound enzyme 5′‐nucleotidase than was observed in neurons. In oligodendrocytes from 10‐ and 20‐day‐old rats, the 5′‐nucleotidase activity was two‐ to threefold the activity in the homogenates (i.e., relative specific activity = 2.0–3.0), and the relative specific activity of this enzyme in the oligodendrocytes declined to less than 1.0 at the later ages, concomitant with the accumulation of 5′‐nucleotidase in myelin. The CNP activity was always higher in oligodendrocytes than in neurons, but not appreciably different from that in astrocytes from 20 days of age onward. The relative specific activity of CNP was highest in the oligodendrocytes from 10‐day‐old rats but was lower, at all ages, than we had observed in bovine oligodendrocytes. These enzyme activities in oligodendroglia are quite different in amount and developmental pa

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12661.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Glycogen metabolism was studied in primary and Herpesvirus‐transformed cultures of neonatal rat brain astrocytes. A small fraction of the glucose consumed was coaserved in glycogen in both the primary and the transformed astrocytic cell cultures. After addition of culture medium containing 5.5 mMglucose, glycogen increased to maximal levels within 2.5 h, the approximate time at which half of the medium glucose was consumed, and rapidly declined thereafter in both the primary and transformed astrocytic cultures. Maximum levels of glycogen were apparently related to the cell density of the Herpesvirus‐transformed cultures, but primary cultures did not show this behavior. At any given cell density, maximal levels of glycogen were dependent on the concentration of extracellular glucose. Administration of glucose caused a transient activation of glycogen synthaseaand a rapid inactivation of glycogen phosphoryla

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12662.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Cultured astrocytes, transformed by Herpesvirus, were used as a model system to study several aspects of the control of glycogenolysis. Adrenergic agonists such as norepinephrine and isoproterenol caused an immediate and dose‐dependent increase in the intracellular levels of cyclic AMP. Concomitant with the initial phase of cyclic AMP increase, conversion of phosphorylasebtoaand glycogenolysis were observed. The elevation of cyclic AMP, phosphorylase conversion, and glycogenolysis were simultaneously blocked by β‐adrenergic blockers, but not by α‐adrenergic blocking agents. Repeated administration of norepinephrine caused an attenuated response in both cyclic AMP accumulation and glycogenolysis. Glycogen degradation is also partially regulated by glucose availability. In the presence of glucose, norepinephrine‐induced glycogenolysis is blocked, despite elevations in cyclic AMP. The direct role of glucose is postulated, since glucose analogs mimic the effects o

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12663.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Three S100 protein species (S100a, S100b, S100a′) have been purified from bovine brain using a modification of standard preparative methods. A higher yield for each protein was obtained at the last separation step. Characterization by urea/sodium dodecyl sulfate/polyacrylamide gel electrophoresis, UV absorption spectra, and fluorescence parameters provided evidence of anew tryptophan‐containing S100 protein called S100a′, which exhibits, as S100a and S100b, the properties of a Ca2+binding pr

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb12664.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY