摘要:

Abstract:Brain membranes contain several protein kinases, all of which appear to play a role in the regulation of neuronal functioning. These membranes also contain numerous (phospho) proteins. It has been proposed that the degree of phosphorylation of some of these proteins may affect neuronal membrane properties. In a series of previous reports we showed that ACTH1‐24inhibits the endogenous phosphorylation of several synaptosomal plasmamembrane (SPM) proteins including the B‐50 protein. Although we have speculated that the degree of phosphorylation of B‐50 may be important in regulating the turnover of membrane (poly)‐phosphoinositides, the exact nature of the interaction between ACTH1‐24and B‐50/B‐50 protein kinase is unknown. The purpose of the present study was to determine whether treatment of SPM with ACTH1‐24will lead to a specific release of proteins from SPM. We found that ACTH1‐24specifically releases a 41,000 Mrprotein from rat brain SPM. Although we are not certain about the biological significance of the release of this polypeptide, it is of sufficient interest for further research in view of the lack of success of finding binding of labeled ACTH t

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb05323.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Gonadectomy of male rats led to a threefold increase of 3α‐hydroxysteroid dehydrogenase (3α‐HSDH) activity in pituitary homogenates that could be completely reversed by chronic administration of estradiol or 5α‐dihydrotestosterone (DHT). 3α‐HSDH was found to be distributed mainly between the 10,000gand 100,000gsediments from whole homogenates. The microsomal enzyme activity showed a substantial specificity for NADH whereas the cytosolic enzyme (100,000gsupernatant) demonstrated a slight preference for NADPH. The changes inVmaxfound in homogenates following gonadectomy and gonadal steroid administration reflected changes in NADH‐ linked activity of the microsomal, but not the cytosolic enzyme. Estradiol‐induced suppression of NADH‐linked 3α‐HSDH activity in pituitary homogenates from gonadectomized rats of either sex was accompanied by a similar suppression of NADPH‐linked 5α‐reductase activity and a marked decrease of luteinizing hormone (LH) and follicle‐stimulating hormone (FSH) release. In the ovariectomized rat chronic administration of nonsteroidal antiestrogens had strong estrogenic effects on 3α‐HSDH activity and LH release, but not on 5α‐reductase activity and FSH release. In the gonadectomized male rat, which was much less sensitive to intrinsic estrogenicity of the antiestrogens tested, nafoxidine completely blocked estradiol‐induced suppression of 5α‐reductase activity and FSH release and partially antagonized suppression of LH release. Thetrans‐isomeric, substituted triphenylethylenes, tamoxifen, and enclomiphene, as well as nitromifene (mixture oftransandcisisomers) were able partially to counteract estradiol‐induced suppression of 5α‐reductase, but not 3α‐HSDH activity. It is concluded that estradiol action on pituitary 5α‐reductase, but not 3α‐

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb05324.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Two human brain surgery biopsies and one autopsy sample were subjected to subcellular fractionation. With either 0.12 or 6 mM‐acetaldehyde as substrate, about half of the total aldehyde dehydrogenase activity was found in the mitochondrial (+ synaptosomal) fraction and less activity in the cytosolic, nuclear, and microsomal fractions. High‐affinity activity was found only in the mitochondrial fraction. The enzyme in all fractions had a higher affinity for indole‐3‐acetaldehyde than for acetaldehyde. The kinetic data indicate the presence of several distinct aldehyde dehydrogenase isozymes that have ample capacity to oxidize both aliphatic and aromatic aldehydes in huma

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb05325.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:High‐affinity binding sites (apparentKD= 1.5 nM) for [3H]desipramine have been demonstrated and characterized in membranes prepared from rat brain. The binding of [3H]desipramine was found to be saturable, reversible, heat‐sensitive, sodium‐dependent, and regionally distributed among various regions of the brain. High concentrations of [3H]desipramine binding sites were found in the septum, cerebral cortex, and hypothalamus, whereas lower concentrations were found in the medulla, cerebellum, and corpus striatum. A very good correlation (r= 0.81,P<0.001) was observed between the potencies of a series of drugs in inhibiting high‐affinity [3H]desipramine binding and their capacity to block norepinephrine uptake into synaptosomes. In 6‐hydroxydopamine‐lesioned rats there was a marked decrease in [3H]norepinephrine uptake and [3H]desipramine binding with no significant alterations in either [3H]serotonin uptake or [3H]imipramine binding. These results suggest that the high‐affinity binding of [3HJdesipramine to rat brain membranes is pharmacologically and biochemically distinct from the high‐affinity binding of [3H]imipramine, and that there is a close relationship between the high‐affinity binding site for [3H]desipramine and the uptake site f

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb05326.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Neonatal changes in the activities of tyrosine hydroxylase (TH) and tryptophan hydroxylase (TrpH) and in the content of the co‐factor, biopterin, were studied in rat midbrain for the first 20 days after birth. Changes in TH activity in the parotid and submandibular glands were also examined. Changes in TH activity per unit weight in the developing rat brain were briefly similar to those in the salivary glands: the activity increased from day 2 or 4 to day 9 after birth, and remained constant or slightly decreased at day 12, then rapidly increased on day 16. TrpH activity in the midbrain increased about twofold up to day 16. The biopterin concentration in the brain increased, reached a maximum level on day 12 after birth, and thereafter decreased. The effect of hyperthyroidism in rats given 0.2 mg/kg i.p. of thyroxine every 2 days postnatally was studied on the activity of TH in rat salivary glands at 12‐day‐old rats. In parotid or submandibular gland of hyperthyroid rats, TH activity increased at day 12 postnatally. In comparison with the effect on TH activity in the salivary glands, TH activity in the midbrain on day 20 postnatally was not induced by hyperthyroidism. Furthermore, increase of the TrpH activity and biopterin and catecholamine levels in the midbrain of hyperthyroid rats was not found on day 20 after birth in comparison with the corresponding controls. From these data, we suppose that postnatal hyperthyroidism may cause precocious induction of TH in rat salivary gland, but may not increase the activity of TH or TrpH, and the level of their co‐factor, biopterin, in rat m

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb05327.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Ontogenetic development of specific [3H]spiperone binding to crude synaptic membranes and its regulation by Na+and GTP was investigated in the rat striatum, (d)‐Butaclamol more effectively inhibited [3H]spiperone binding than (l)‐butaclamol. The ratio of inhibitory activity of (d)‐ and (l)‐butaclamol for [3H]spiperone binding was not different between 1‐, 7‐, and 70‐day‐old animals but eight‐ to ninefold lower at 18 days of gestation than during the postnatal period. A Scatchard plot of specific binding indicated the presence of two types of binding: low‐affinity (KD=1.51 nm) and high‐affinity (KD= 0.09 nM) binding on day 70. Only one component (KD= 0.075 nM) was observed on days 1 and 7 and both types of binding were found on day 15. Bmaxgradually increased with age and reached a peak on day 30, followed by a decline on days 70 and 360. Na+, 100 mM, significantly increased specific binding on days 1, 7, 15, and 70. GTP, 50 μM, completely reversed the Na+‐induced decrease in IC50of apomor‐phine on both days 15 and 70, but not on day 7. It is suggested that receptors could recognize ligand stereospecificity on day 1. The density in dopamine receptors in the striatum reaches a peak on day 30, followed by a decrease on days 70 and 360. In addition, regulation by Na+and GTP in agonist binding to dopamine receptors seems to become functional between

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb05328.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:The development of cytoplasmic glycerol phosphate dehydrogenase (GPDH) activity in chick neural retina is compared with that in brain. GPDH converts dihydroxyacetone phosphate to glycerol 3‐phosphate, an intermediate in phospholipid synthesis. The enzyme is known to be under corticosteroid control in rat brain and spinal cord (but not muscle or liver) and in primary oligodendrocyte cultures. It has not been previously studied in the eye. In chick brain the GDPH specific activity rises fivefold from the early embryo to the adult, with nearly all the increase occurring between embryonic day 14 and hatching. This time course correlates well with the known maturation of chick adrenal cortex (which produces corticosteroids). On the other hand, in chick retina the GPDH specific activity remains at a low basal level throughout development. Furthermore, adult rat and beef retinas show much lower enzyme activity than do the corresponding brain tissues. GPDH can be induced precociously by hydrocortisone in embryonic chick brain from days 12 through 16, both in the intact embryo and in tissue culture; however, GPDH is not at all inducible in chick retina. The developmental increase in chick brain GPDH can be correlated qualitatively with myelin formation, as shown by luxol fast blue staining, whereas no myelin is seen in retina at any age. Our results are consistent with recent immunocytochemical studies demonstrating that GPDH in rat brain is associated with myelin‐producing oligodendroglial cells, absent in retina. In comparison, another glial enzyme, glutamine synthetase (GS), known to be inducible in both chick brain and retina, is localized in brain astrocytes and retinal Müller c

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb05329.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Brain glucose metabolism was studied in paralyzed, ventilated rats given electroconvulsive shock (ECS) under normocapnic and hypercapnic conditions. Brains were obtained with a freeze‐blowing apparatus. Rates of glucose utilization were determined with [2‐14C]glucose and[3H]deoxyglucose as tracers. In normocapnic rats, ECS caused a large increase in the rate of glycolysis to 5–6 μmol/g/min. Brain lactate levels increased three‐ to fourfold. The stimulation of glucose metabolism was reflected in decreased brain glucose 6‐phosphate concentration as early as 2–3 s after ECS. There were significant decreases in brain glucose and glycogen levels at 20 and 30 s after ECS. The decreases in endogenous brain glucose accounted for most of the increases in glucose utilization measured isotopically, implying that influx of glucose from blood into brain did not increase greatly over these time periods. Animals made hypercapnic by respiration with 10% CO2for 2 min prior to ECS were different in their metabolic responses to ECS in several ways. The increases in glycolyt‐ic rate and lactate content of brain were half of those found in normocapnic rats. Brain glycogen and glucose concentrations did not change significantly in the hypercapnic rats during seizure activity. Thus, hypercapnia lessened the stimulation of glycolysis caused by ECS, but increased net influx of glucose from blood to brain. The mechanisms of these effects of hypercapnia are uncertain, but it is postulated that the effect on glycolytic activity is due to the acidosis and that the effect on glucose transport is due to an increase in capillar

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb05330.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:The poly(adenylate)[poly(A)] polymerase of rat brain, as in rat liver, is located primarily in the nuclear sap when nuclei are prepared under hypertonic conditions. The enzyme can be released from nuclei in two forms. Form I is prepared by gentle incubation of nuclei at 0°C in hypotonic buffer. It has a Mn optimum of 0.6 mM and a pH optimum between 8 and 9. The ATP concentration curve plateaus at 0.2 mM. The optimal poly(A) primer concentration is 600 μg/ml, which is three times higher than that for the enzyme similarly prepared from liver. The time course of the reaction for the form I enzyme is increasing over the first 40 min and becomes nearly linear thereafter. Form I is not stimulated by either calcium or cyclic nucleotides, but is inhibited by polyamines, pyrophosphate, and high concentrations of GTP. Form II enzyme is prepared by homogenization of nuclei in hypotonic buffer. It has the same ATP and poly(A) optima as the form I enzyme but displays linear kinetics over a 60‐min time course. It is slightly stimulated by cGMP and cAMP and strongly inhibited by spermine, sodium pyrophosphate, and high concentrations of

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb05331.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Ubiquinone synthesis has been studied in cultured C‐6 glial and neuroblastoma cells by utilizing an inhibitor, 3‐β‐(2‐diethylaminoethoxy) androst‐5‐en‐17‐one hydrochloride (U18666A), of cholesterol biosynthesis. Exposure of C‐6 glial cells to nanomolar quantities of U18666A caused a marked inhibition of total sterol synthesis from [14C]acetate or [3H]mevalonate within minutes. A 95% inhibition was apparent after a 3‐h exposure to 200 ng/ml of U18666A. These observations, together with studies of the incorporation of radioactivity from the two precursors into cholesterol, desmosterol, lanosterol, and squalene, indicated that although the most sensitive site to inhibition by U18666A is desmosterol reduction to cholesterol, a major site of inhibition is demonstrable at a more proximal site, perhaps squalene synthetase. As a consequence of the latter inhibition, exposure of C‐6 glial cells to U18666A caused a marked stimulation of incorporation of [14C]acetate or [3H]mevalonate into ubiquinone. Over a wide range of U18666A concentrations, the increase in ubiquinone synthesis was accompanied by an approximately similar decrease in total sterol synthesis. Whereas in the absence of U18666A only approximately 7% of the radioactivity incorporated from [3H]mevalonate into isoprenoid compounds was found in ubiquinone, in the presence of the drug approximately 90% of incorporated radioactivity was found in ubiquinone. The reciprocal effects of U18666A on ubiquinone and sterol syntheses were apparent also in the neuronal cells. The data thus demonstrate a tight relationship between ubiquinone and sterol biosyntheses in cultured cells of neural origin. In such cells ubiquinone synthesis is exquisitely sensitive to the availability of isoprenoid precursors derived from the cholestero

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb05332.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY