摘要:

AbstractGlial fibrillary acidic protein (GFAP) is the major constituent of glial filaments and is restricted within the CNS to astrocytes. As with other classes of intermediate filament proteins, the regulation of GFAP expression is poorly understood. Utilizing highly purified cultures of astrocytes and a chemically defined (CD) medium, we have demonstrated that the expression of GFAP is subject to regulation by hormones and growth factors. The concentration of GFAP/mg protein was induced 2–4‐fold in the presence of hydrocortisone, putrescine, prostaglandin F‐2α (PGF2α), and pituitary fibroblast growth factor (FGF). Augmentation of the levels of GFAP continued for up to 3 weeks after conversion to CD medium and paralleled the morphological maturation of astrocytes. The accumulation of GFAP resulted from an increase in its specific rate of synthesis. Conversion of astrocytes from serum‐supplemented (SS) to CD medium did not alter its rate of degradation. GFAP appeared quite stable under both sets of conditions, exhibition a half‐life of approximately 7.5 days. The data demonstrate that GFAP expression in astrocytes is subject to hormonal regulation, which may have implications

ISSN:0360-4012    

DOI:10.1002/jnr.490140202

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe adult cat sciatic nerve was examined for Schwann cell biosynthesis of the major myelin glycoprotein (P0) in the distal segments after permanent nerve transection, where there is no axonal regeneration or myelin assembly. Endoneurial slices (intrafascicular tissue) from the distal segment of the desheathed cat sciatic nerves at 10 wk after transection and from normal adult desheathed brachial nerves were incubated with radioactive mannose; [3H]mannose incorporation into P0was observed by fluorography after sodium dodecyl sulphate‐pore gradient electrophoresis (SDS‐PGE). Analysis of immune precipitates by SDS‐PGE after incubation of an aliquot of an endoneurial fraction with rabbit antichick P0gamma globulin verified that the [3H]mannose‐labeled glycoprotein was P0. The level of incorporation of [3H]mannose into P0and into other endoneurial glycoproteins in the normal brachial nerve from the adult cat was at substantially reduced levels compared with the transected nerve. Such incorporation was detectable by fluorography only after prolonged exposure to X‐ray film (15 days). As a result, the level of biosynthesis of P0in the normal adult cat is substantially reduced, suggesting that the extent of active myelination in the adult cat nerve is at a low level. Furthermore, Schwann cells are capable of continued synthesis of P0in the adult, permanently transected nerve in the absence of axonal influence, suggesting that axonal association is not an absolute requirement for specifying myelin protein

ISSN:0360-4012    

DOI:10.1002/jnr.490140203

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

年代:1985

数据来源: WILEY

摘要:

AbstractPossible influences upon patterns of neurogenesis expressed in vitro were examined quantitatively by the use of microfragment cultures of embryonic day 10 mouse neural tube. Crude extracts were prepared either from whole embryos (day 13 or 15 of gestation) or from embryonic brains (day 18 of gestation) and added to the culture medium for the first 10 days of culturing. Neuronal outgrowth zones surrounding individual microfragments were reduced in area (indicating restricted neuronal migration) and in number of neurons present (indicating restricted production of neurons) following treatment with either of the extracts. The severity of reductions observed were related to the developmental age of embryonic tissue used for preparing the extract, as greatest reduction resulted from addition of embryonic day 18 brain extracts and to concentration employed, higher doses further restricting neuronal outgrowth. By increasing the concentrations of extract the proportional number of large‐sized neurons forming the outgrowth zones became greater relative to the small neuron contribution, indicating an enhanced survival for this neuronal population. The formation and migration of astroglial precursor cells was not affected by the addition of any of the extracts.The number of neurons remaining within the original portions of neural tube microfragments was not significantly altered following culturing in the presence of embryonic extract. This suggested that the reduction in neuron number in the outgrowth zone actually reflected a decreased neuron production and was not simply the result of a retention of neurons within the remaining portion of the microfragment .The results suggest the presence of substances within mouse embryos that have regulatory effects on aspects of development of the central nervous system. Indications are that survival and maturation of postmitotic neuroblasts are promoted in vitro while the formation of additional neuronal progenitor cells may be partially inhibited by the addition of embryonic mouse extracts to the medium. We propose that an endogenous negative feedback mechanism may be invloved in the coordination of patterns of neurogenesi

ISSN:0360-4012    

DOI:10.1002/jnr.490140204

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

年代:1985

数据来源: WILEY

摘要:

AbstractA procedure has been developed for the deacylation of the hydrophobic, myelin proteolipid apoprotein using hydroxylamine in an alkaline organic solvent medium. Complete removal of covalently bound fatty acids was obtained after 4 hr of treatment. After deacylation, no changes could be detected in the electrophoretic pattern or in the number of free sulfhydryl groups. The deacylated apoprotein remains soluble in chloroform‐methanol mixtures and is suitable for further physicochemical characterizatio

ISSN:0360-4012    

DOI:10.1002/jnr.490140205

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe rates of [6‐14C]‐glucose oxidation by reconstituted systems of cytosol and mitochondria or cytosol and synaptosomes were essentially the same as the rate of oxidation of [3‐14C]‐3‐hydroxybutyrate. However, the rate of [U‐14C]‐glutamine oxidation by mitochondria was 2.5 times that by synaptosomes. The addition of glutamine (5 mM) caused a reduction in the rates of oxidation of [6‐14C]‐glucose of 20% and 40% by mitochondria and synaptosomes, respectively. Conversely, the addition of glucose (5 mM) had little or no effect on the rate of [U‐14C]‐glutamine oxidation by either organelle. Amino‐oxyacetate decreased [U‐14C]‐glutamine oxidation by mitochondria more than 35% but had little or no effect on the rate of glutamine oxidation by synaptosomes. When glucose (5 mM) was added to [3‐14C]‐3‐hydroxybutyrate, the rates of oxidation by the mitochondria and synaptosomes were increased by 65% and 77%, respectively. However, in the reverse situation the addition of 3‐hydroxybutyrate decreased [6‐14C]‐glucose oxidation by synaptosomes (35%) but did not decrease the rate by mitochondria. These results suggest that differences in the rates of substrate utilization by mitochondria and synaptosomes and differences in substrate interactions in these two subcellular organelles may contribute to

ISSN:0360-4012    

DOI:10.1002/jnr.490140206

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

年代:1985

数据来源: WILEY

摘要:

AbstractWhen soluble proteins in cytosolic fractions of rat soleus muscles are32P‐phosphorylated in vitro by an ATP:protein phosphotransferase reaction, the major substrate is a 56‐kilodalton (56K) protein. As we have also reported previously, the onset and development of increased32P‐phosphorylation of this 56K protein, which are observed after the soleus is denervated, temporally correlate with the denervation period and length of the distal nerve stump [Held et al, 1983]. Conclusive evidence which identifies this neuroregulated muscle protein as the regulatory subunit of cyclic AMP‐dependent protein kinase type II (R‐II) is presented in this paper. The 56K soleus protein and purified bovine heart R‐II were32P‐phosphorylated and subjected to limited proteolysis with bovine pancreas trypsin. After resolution of the generated32P‐phosphopeptides by SDS slab PAGE and visualization by autoradiography, no tryptic products were observed from the 56K soleus protein which were not also produced by proteolysis of the purified R‐II. These tryptic phosphopeptides included 39, 16.5, and 12K fragments which retained the autophosphorylation site of R‐II. After denervation, the32P‐phosphorylation of the 56K soleus protein and of the 39K tryptic peptide product were comparably increased. The identification of the neuroregulated 56K soleus protein as R‐II was also confirmed by Western blotting with a specific anti‐R‐II sera. Taken together, our results demonstrate that the previously observed neuroregulation of the32P‐phosphorylation of the 56K soleus protein is identifiable with some alteration which affects the intramolecular32

ISSN:0360-4012    

DOI:10.1002/jnr.490140207

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe phosphorylative neuromodulation of the regulatory subunit of protein kinase type II (R‐II) in cytosolic fractions from denervated and sham‐operated, contralateral soleus muscles of the rat was evaluated. The denervation‐induced increase in the32P‐phosphorylation of R‐II is not related to an increased dephosphorylation by cation‐dependent or cation‐independent protein phosphatases in the cytosolic fractions. The level of32P‐phosphorylation of an exogenous heptapeptide substrate (Kemptide) by dissociated catalytic subunits of cyclic AMP‐dependent protein kinase in cytosolic fractions from denervated and sham‐operated solei did not differ. Also, no change in the concentration of cytosolic R‐II assessed by competitive enzyme‐linked immunosorbent assays (ELISA) was found after denervation. However, the in vitro32P‐phosphorylation of R‐II in these samples was increased. Taken together, our results suggest that the increased availability of autophosphorylatable sites reflects an in vivo modulation of R‐II phosphorylation rather than a significant

ISSN:0360-4012    

DOI:10.1002/jnr.490140208

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe present investigation sought to examine the importance of substance P in the altered respiratory activity after neonatal capsaicin administration. Halothaneanesthetized adult rats given capsaicin neonatally exhibit a decreased basal minute ventilation with PaCO2equal to and PaO2greater than vehicle injected controls. In addition, the minute ventilation‐PaCO2curve was displaced to the right. Acute bilateral cervical vagotomy severely blunted the minute ventilation response to PaCO2and abolished the differences in ventilation between capsaicin treated and control rats. Neonatal capsaicin significantly reduced pons‐medulla substance P content but not TRH, serotonin or 5‐hydroxyindole acetic acid. Immunohistochemical studies revealed that substance P fibers of the trigeminal spinal nucleus were the most severely affected in the brain stem and that substance P fibers in the lung were totally absent.The intracerebroventricular administration of substance P increased minute ventilation similarly in both control and capsaicin treated rats, largely as a result of increases in tidal volume. The minute ventilation‐PaCO2curve was similar in both groups after substance P administration. Simultaneous administration of the peptidase inhibitor captopril with substance P increased the respiratory response to substance P in normal rats. Administration of captopril to capsaicin treated rats restored the ventilation‐PaCO2curve to the position observed in normal rats. The hypotensive response to intracerebroventricular captopril alone in control rats was less profound in rats given neonatal capsaicin.These results are consistent with the thesis that respiratory depression after capsaicin treatment is at least in part due to the loss of substance P primary afferent nerve terminals in the brain stem, suggesting that substance P fibers in the brain stem may participate in the normal modulation of respiratory

ISSN:0360-4012    

DOI:10.1002/jnr.490140209

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

年代:1985

数据来源: WILEY

摘要:

AbstractBoth hyperammonemia and blood‐brain barrier (BBB) breakdown have been implicated in the evolution of hepatic encephalopathy. To define a possible relationship, Swiss Albino mice were subjected to sublethal encephalopathic doses of ammonium acetate; the integrity of the BBB was determined grossly with Evans blue and quantitatively with [14C]‐α‐aminoisobutyrate (AIB). Some animals were injecte with a dose of ammonium acetate sufficient to maintain coma for 1 hr (AC group). One group, termed stuporous (AS), received only enough ammonium acetate to interfere with grooming and exploratory activity; this dosage was insufficient to completely block the righting response, which was absent in the AC group. When compared to that of controls (CON) receiving normal saline instead of ammonium acetate, cerebral tisue from the AC group was stained blue and contained nearly double the amount of AIB; AS group brain tissue was unstained and the AIB content did not differ significantly from normal. Some of the AC group were pretreated with drugs known to retard BBB breakdown; one set received dexamethasone (AC‐DXMN), another the ornithine decarboxylase inhibitor difluoromethyl ornithine (AC‐DFMO), and a third L‐ornithine (AC‐ORN). Brain tissue from the AC‐ORN group stained blue and AIB content did not differ significantly from that of the untreated AC group. Cerebral tissue of the AC‐DXMN pretreatment group stained light blue; AIB content was significantly lower than in the AC group and greater than the CON group. The AC‐DFMO brains were unstained and AIB content was significantly lower than in the AC group but did not differ significantly from CON. These results indicate that hyperammonemia may induce BBB breakdown but that the disruption of barrier integrity is not antecedent to the development of coma, although it seems to coincide with coma in time. DFMO is more effective than DXMN in preventing ammonium acetate‐induced BBB breakdown, but in this study neither drug prevented t

ISSN:0360-4012    

DOI:10.1002/jnr.490140210

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe high‐affinity bindings of [3H]‐5‐hydroxytryptamine to serotonin S‐l receptors, [ H]‐ketanserin to serotonin S‐2 receptors in the cerebral cortex, [3H]‐fluphenazine to dopamine D‐l receptors, and [3H]‐spiroperidol to dopamine D‐2 receptors in the corpus striatum were studied in pyridoxine‐deficient rats and compared to pyridoxine‐supplemented controls. There was a significant increase in the maximal binding (Bmax) of serotonin S‐l and S‐2 receptors with a significant decrease in their binding affinities (Kd). However, there were no significant changes either in the maximal binding or binding affinity of striatal dopamine D‐1 and D‐2 receptors. Receptor sensitivity seems to correlate negatively with the corresponding neurotransmitter concentrations i

ISSN:0360-4012    

DOI:10.1002/jnr.490140211

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

年代:1985

数据来源: WILEY