摘要:

AbstractAdrenal glands from embryonic day 11 (E‐11) chicks were cryostat‐sectiond, and it was determined that tyrosine hydroxylase‐like immunoreactive (TLI) cells, somatostain‐like immunoreactive (SLI) cells, and methionnie‐enkephalin‐like immunoreactive (ELI) cells occupied chromaffin regions of the gland. Similar age adrenals were dissociated, and the cells were cultured under serum‐free conditons. Cultured TLI cells, ELI cells, and SLI cells were characterized according to cell size, cell number, and neurite formation. ELI and SLI cells composed two largely separate populations, with SLI cells tending to have larger cell areas, to be more numerous, and to be less likely to from neurits than ELI cells. The population of TLI cells, although unique in itself, was diverse and numerous enough to include all or portions of the neuropeptide‐immunoreactive populations. Neurites of some cells from each of the above populations were strongly immunoreactive for alpha neurofilament protein, and for NAPA73 neurofilament‐associated protein. However, neurities could also be observed in all populations that showed poor immunoreactivity for these cytoskeletal proteins. Exogenously added NGF significantly increased nurite‐like process formation among TLI and ELI cells, but not among SLI cells. Reductions in the number of neurite‐like processes following treatment with anti‐nerve growth factor (NGF) were not singnificant for any of the populations. However, if shorter and broader process were included, ELI cells. Anti‐NGF inhibition of process formation among ELI cells could be reversed with exogenous NGF. Neither NGF or anti‐NGF treatments showed a significant effect on cell numbers among TLI and ELI populations. The implications are that a compound of antigenic and physiologic similarity to mouse salivary NGF is made by embryonic chick adrenal cells in culture, but the effects of NGF do not appear to be the same for all neural‐crest‐derived cells from the adrenal, and greater heterogeneity of phenotypes may exist among chromaffin cells than has previously been accepted. Some quesitons are also raised concerning the neurite‐like nature of processes formed

ISSN:0360-4012    

DOI:10.1002/jnr.490160202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractMyelin basic protein (MBP)‐specific protein‐arginine N‐methyltransferase (protein methylase I) activity in homozygous shiverer (shi/shi) mutant mouse brain is significantly higher than in than normal littermate brain at the onset of myelination. While the enzyme activity (expressed as pmol os S‐adenosyl‐L‐[methyl‐14C] methelination used /min/mg enzyme protein) increase coincidently during the period of myelination in the normal brain (15–18 days of age), it decreases significantly in the mutant brain during this period of time. These results are in contrast to those found with another dysmyelinating mutant, jimpy (jp/Y) mice, in which the enzyme activity in the mutant brain is similar to that in the normal animals but remains unchanged during the myelination process. There is no difference in the weight and protein concentration of the normal and shiverer mutant brains with corresponding ages, and the histone‐specific portein methylase I activity is also unaffected in t

ISSN:0360-4012    

DOI:10.1002/jnr.490160203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractSinefungin, a known inhibitore of protein methylation, inhibited the myelin basic protein (arginine) methyltransferase activity in homogenantes of cultured cererbral cells from embryonic mice. Fifty percent inhibition was achieved with 25μ M sinefungin. Electron microscopie examination of the myelin fraction, isolated by gradient density centifugation and obtained from untreated cells, revealed numerous ringlike multilamellaar membranous substructures that had a major dense line periodicity, compactness, and the general apperance expected of myelin obtained by the same technique from whole brain. Cells treated with 30 μM sinefungin, which inhibits myelin basic protein methyltrnasferase in broken cell preprations about 60%, produced ringlike structures that were devoid of multiameller periodicity and compactness reminiscent of the vacuolated myelin observed in subacute combined degeneration and in nitrous‐oxide‐ or cycloleucine‐treated animals in which methyltransferase activity is also inhibited. The sinefungin‐induced change in multiamellar periodicity cannot be attributed to a lack of myelin basic protein, since the ratio of myelin basic protein to total protein did not decrease in sinefungin‐treated cells. This primary culture system should be useful for further evaluting the hypothesis that the methylation of mylein basic protein is related to the formation of com

ISSN:0360-4012    

DOI:10.1002/jnr.490160204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractSeveral adrenergic effectors and neurotransmitters were tested as potential regulators of myelin basic protein (MBP) and histone methyltransferase activities. Both enzymes were specifically activated by β‐adrenergic agonists in a stereospecific manner. Cyclic AMP (but not AMP) stimulated the enzymes to the same extent as did the β‐adrenergic agonist, (−) isoproterenol. The studies suggest that β‐adrenergic agonists stimulate adenylate cyclase thereby causing an increased production of cyclic AMP which stimulates the methyltransferases. Cycloheximide addition to the reaction mixture did not affect the stimulation due to cyclic AMP, indicating that new protein synthesis is not involved in the cyclic AMP stimulation of the methyltransferases. Thyroid hormone (T3) has been shown to stimulate MBP methyltransferase [Amur et al, 1984] and could exert its stimulatory effect through β‐adrenergic‐dependent systems. Thus, the methylation of MBP seems to be regulated both by T3and by neurotransmitters and/or hormones mediating their effects through cyclic AMP production, whereas the methylation of histones seems to be regulated onl

ISSN:0360-4012    

DOI:10.1002/jnr.490160205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe functional association of astroglial footplates with blood vessels is important because astrocytes may provide a channel between the blood and neurons deeper in the brain parenchyma for the passage of ions and metabolites. This hypothesized function is very difficulty to study in vivo or in monolayer cultures. We have produced a three‐dimensional cell culture model of perivascular astroglia by means of an artificial capillary system. Conventional primary cultures of astroglia were first prerpard from neonatal rat cererbral hemispherers in 75‐cm2tissue culture flasks. After 25 days, the cells were seeded in Amicon Vitafiber hollow fiber culture vessels. Direct seeding of brain cell suspensions was not successful. A culture unit consists of a bundle of hollow, semi‐permeable polysulfone fibers encased in a plastic shell. The fibers were coated with fibronectin and bovine serum albumin, and astroglia were seeded on their outer surfaces. Warmed medium was pumped through the lumina of the fibers. After 13 days the cells were fixed with paraformaldehyde and examined. Scanning electron microscopy reevealed the tubes to be uniformly covered with astroglia with short processes that contacted nearby cells. Transmission electron microscopy showed glial filaments glioma cells in hollow fiber culture. The astrocytes formed a monolayer, whereas C6 cells formed a stratified culture. Furthermore, C6 cells did not form gap junctions. Astrocytes have been hypothesized to take up K+discharged to the extracellular space by deploarizing neurons and move it to areas of low concentration, i.e., to act as a K+spital buffer. Our culture system should permit direct testing of this hypot

ISSN:0360-4012    

DOI:10.1002/jnr.490160206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractCultures were prepared by dissociating 3‐day‐old whole chick embryos and plating the dispersed cells on poly‐L‐Iysine‐coated dishes in Dulbecco's Modified Eagle's Medium with 10% fetal calf serum. By 48 hr in culture, aggregates and neuritic sprouting were observed. Long neuritic bundles connecting cell aggregates were evident by 4 days in culture. Consistent patterns throughout the lifespan of the cultures were contacts bwtween neurites, and flat isolated cells, presumptively glial, emerged. Throughout the lifespan of the cultures, the cholinergic cell poopulation was characterized histochemically by the method of Karnovsky and Roots and biochemical by assaying choline acetyltransferase. By 4 days in culture, all aggregates showed light cholinesterase‐positive staining; however, with days in culture, several aggregates had no staining, and some positive‐stained aggregates were interconnected with other aggregates showing only spotted positive staining. Choline acetyltransferase activity showed a developmental profile in agreement with the histological findings. The early presence of choline acetyltransferase activity is taken as indication of the early commitment of cholin

ISSN:0360-4012    

DOI:10.1002/jnr.490160207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractDendrodendritic synapses occur between granule cell dendrites and secondary dendrites of mitral cells within the olfactory bulb and are attainable in a subcellular fraction (DDS). Since the mitral cells are thought to utilize an excitatory amino acid as a neurotransmitter, we determined the pharmacologic specificity of Na+‐independent L‐[3H]glutamate binding to fresh membrances of DDS in 50 mM Tris‐HCI, pH 7.1. Binding of L‐glutamate to membrances of DDS was specific, CI−dependent, and saturable. Scatchard plots were analyzed by nonlinear regression analysee using the computer program LIGAND, and the data was best‐fitted to a one‐site model with KDof 0.56 ± 0.04 μM and an apparent Bmaxof 48 ± 5 pmol/mg protein. Hill plots also indicated the presence of one site and no cooperativity (nH= 0.99 ± 0.03). However, the relative effictiveness of several compounds in inhibiting L‐glutamate binding to membranes of DDS clearly demonstrated the presence of more than one site. Electrophysiological studies suggest that 2‐amino‐4‐phosphonobutyrate (APB) is a potent antagonist of evoked responses elicited by simulation of mitral cell axons and that quisqualate is a potent agonist; both of these compounds were highly effective inhibitors of L‐glutamate binding to DDS membrances. APB displaced about 70% of tke sites labeled with 200 nM L‐glutamate with a K1of 1.6 μM, whereas quisqualate inhibition of L‐glutamate binding yielded a line that was curvilinear in the Scatchard plot and was resolved into two sites of relatively high affinity (K1values of 0.02 and 0.65 μM). Several other compounds, including N‐methyl‐D‐aspartate and kainate, were relatively ineffective inhibitors. Although a small amount of CI−‐independent L‐glutamate binding was demonstrable in the preparation, CI−‐dependent sites predominated and were stimulated by clacium. These results suggest an important role of L‐glutamate, or a closely related compound

ISSN:0360-4012    

DOI:10.1002/jnr.490160208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractThe adaptation of repeated periods of intermittent normobaric hypoxia (oxygen:nitrogen = 10:90, 12 hr daily for 5 days) of some specific enzymatic activities related to energy metabolism has been observed in different rat brain areas (cerebral cortex, hippocampus, corpus striatum, hypothalamus, cerebellum, and medulla oblongata).The evaluation of the maximum rate (Vmax) of the enzymes was carried out on: (1) the homogenate “in toto,” (2) the nonsynaptic mitochondrial fraction, and (3) the crude synaptosomal fraction. The adaptation to inermittent normobaric hypoxic exposure was characterized by significant modifications of some enzyme activities in the homogenate “in toto” (decrease of hexokinase activity in cerebellum), in the nonsynaptic mitochondrial fraction (increase of succinate dehydrogenase activity in corpus striatum and decrease of cytochrome oxidase activity in cererbral cortex), and, particularly, in the synaptosomal fraction (decrease of cytochrome oxidase activity in cerebral cortex, hippocampus, corpus striatum, and cerebellum, and decrease of malate dehydrogenase and lactate dehydrogenase activity in cererbellum).The adaptation to normobaric intermittent hypoxia differs according to the brain area, subcellular fraction, and enzyme activity

ISSN:0360-4012    

DOI:10.1002/jnr.490160209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractChronic pretreatment of mice with the monoamine oxidase type B inhibitor (–) deprenly resulted in an increase in the density of cerebral cortical3H‐imipramine binding sites and a decrease in the density of cerebral cortical beta‐adrenergic receptors. In contrast, pretreatment of mice with the tricyclie antidepresents imipramine and desipramine did not alter the density of cerebral cortical3‐Himipramine binding sites. Imipramine and desipramine treatment decreased the density of beta‐adrenergic receptors. Haloperidol pretreatment resulted in an increase in the density of striatal D‐2 dopamine receptors, but did not alter the density of cerebral cortical3H‐imipramine binding sites or beta‐adrenergic receptors. These data suggest that brain3H‐imipramine binding sites can be regulated by pharmacological pretreatment, but that this regulation may not occur for a

ISSN:0360-4012    

DOI:10.1002/jnr.490160210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractIn this commentary, the indirect sympathomimetic effect of tyramine and the phenomenon of tyramine tachiphylaxis are reinterpreted in terms of carriermediated excahange processes. Extracellular tyramine would exchange with intraterminal noradrenaline and, upon repeated tyramine administration, with a mixture of noradrenaline and tyramine progressively more enriched in the pharmacologically inactive amine.

ISSN:0360-4012    

DOI:10.1002/jnr.490160211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY