摘要:

AbstractThe SK‐N‐SH cell line is a human neuroblastoma which when grown under standard culture conditions remains relatively undifferentiated. The undifferentiated SK‐N‐SH cells are relatively inexcitable: they show only partial active responses to injections of current pulses and lack the depolarizing component of the action potential generating mechanism [Kuramoto et al, 1977]. In this study we report on the membrane properties of two subclones of the SK‐N‐SH, the SK‐N‐SH‐IN (referred to as IN) and the SK‐N‐SH‐Sy5Y (referred to as 5Y) which exhibit extensive morphological differentiation when grown with 1mM dibutyryl cAMP. Fully differentiated IN and 5Y cells have higher resting membrane potentials, in the range of −50 to −80 mV, and higher input resistance and time constants than do the undifferentiated SK‐N‐SH parental cell line. After 1 week in culture the differentiated IN and 5Y cells exhibit spike potentials in response to injection of current to the cell body. The presence of the Na+‐dependent depolarization was verified directly by the use of tetrodotoxin (TTX) and indirectly in experiments where veratridine (0.1 mM) markedly enhanced the influx of22Na+. Taken together, the data indicate that generation of action potentials in these human neuroblastoma cells is to a large extent a function

ISSN:0360-4012    

DOI:10.1002/jnr.490060402

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

年代:1981

数据来源: WILEY

摘要:

AbstractNerve growth factor (NGF) has been purified from the guinea pig prostate using a modification of the Bocchini‐Angeletti method for isolating 2.5S NGF from mouse submaxillary glands. As with the mouse preparation, guinea pig prostate NGF appears to migrate as a high molecular weight entity at physiological pH. Following dissociation, NGF, active in neurite proliferation assays and similar in size to mouse 2.5S NGF, can be isolated by chromatography on a column of carboxymethyl‐cellulose at pH 4.8. Based on gel filtration, SDS‐polyacrylamide gel analysis, and amino‐terminal sequence studies, this material consists of two, noncovalently linked, identical polypeptide chains each with a molecular weight of about 13,000. The amino‐terminal third of the polypeptide chain is at least 90% identical to the corresponding region of the murine molecule, confirming the homology of the guinea pig prostate protein to NGFs obtained from different tissues in other species. However, in contrast to the mouse preparation, the putative high molecular weight form of guinea pig NGF does not contain a subunit with arginine esteropeptidase activity. Although there is an abundance of this enzymatic activity in the homogenate, it does not appear to be associated with the fractions containing NGF. This apparent difference in the mouse and guinea pig material is of interest because the mouse γ subunit, possessing the arginine esteropeptidase activity, has been alleged to participate in the processing of a precursor of the β NGF polype

ISSN:0360-4012    

DOI:10.1002/jnr.490060403

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe effect of intraperitoneally injected taurine against the convulsive activity induced by 4‐aminopyridine (4‐AP) was studied in 12‐ to 15‐day‐old mice. At a dose of 2.6 mg/kg, taurine increased the latency of clonic seizures from 7 to 20 minutes, reduced the incidence of tonic seizures from 92% to 30% and the postconvulsive mortality from 80% to 31%. The injection of EDTA prior to the administration of taurine prevented the protective effect of the amino acid. GABA and glycine at the same doses did not protect against 4‐AP‐induced seizures. 4‐AP caused a small increase (19%) in45Ca accumulation by mice brain synaptosomes incubated in a Krebs‐HEPES medium containing low CaCl2(0.1 mM) and also slightly potentiated the veratrine and potassium‐induced increase in calcium accumulation. 4‐AP at concentrations of 1–2 mM caused a marked increase (100%–500%) of45Ca acculation by synaptosomes incubated in a Krebs‐bicarbonate medium containing 2.5 mM CaCl2. This increase was completely antagonized by taurine but not by GABA or glycine. The present observations suggest that the anticonvulsant effect of taurine might be mediated by 4‐AP

ISSN:0360-4012    

DOI:10.1002/jnr.490060404

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

年代:1981

数据来源: WILEY

摘要:

Abstract[3H]‐taurine binding to membranes from different regions from rat brain was studied. Binding to membranes from cerebral cortex and its subcellular fractions, hypothalamus, olfactory bulb and cerebellum was measured. Binding to membranes from dorsal root ganglion was also determined. Na+‐dependent taurine binding was consistently observed in all the membranes except those from dorsal root ganglion. A KD= 4.06 μM was obtained for binding to membranes from cerebral cortex. Na+‐dependent taurine binding was displaced by 20 μM strychnine or bicuculline. Na+‐independent taurine binding with properties corresponding to a postsynaptic interaction could not be detected in any of the regions studied. The possibility of Na+‐dependent taurine binding, representing binding to uptake sites or to postsynaptic receptors for GABA and glycine, i

ISSN:0360-4012    

DOI:10.1002/jnr.490060405

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

年代:1981

数据来源: WILEY

摘要:

AbstractBovine and rabbit retina synaptosomal fractions bind the potent and specific GABA agonist, [3H]‐muscimol with high affinity and limited capacity. The high degree of pharmacological specificity and the subcellular distribution of these binidng sites are similar to those reported for [3H]‐GABA binding sites. These observations suggest that these sites represent the recongition sites for GABA receptors. The specific binding of [3H]‐muscimol in retinal homogenates from different aged rabbits reveal a distinct developmental profile with a fivefold to six fold increase in binding between days 5 and 13. Thus, it appears that GABA receptor development continues after eye opening in rabbits (day 9–10) and that receptor maturation is delayed by at least two to three days with respect to published reports of GABA uptake and evoked

ISSN:0360-4012    

DOI:10.1002/jnr.490060406

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

年代:1981

数据来源: WILEY

摘要:

AbstractAlteration of metabolism of taurine in prolonged light‐ and dark‐adapted frog retinae were studied in comparison with that of gamma‐aminobutyric acid (GABA) and the following results were obtained. (1) Statistically significant alterations in retinal taurine, an increase in dark‐adapted, and a decrease in light‐adapted states, respectively, occurred when frogs were adapted continuously to light or dark for more than 3 weeks. Under the same experimental conditions, no alteration in retinal GABA was noted. (2) At 3 weeks and thereafter, a significant increase of retinal cysteine sulfinic acid decarboxylase (CSD; EC 4.1.1.12) activity, an enzyme involved in the biosynthetic pathway of taurine, also occurred in the dark, whereas the activity in the light‐adapted retina was reduced. On the other hand, the retinal activity of L‐glutamate decarboxylase (GAD; EC 4.1.1.15), the rate‐limiting enzyme of GABA biosynthesis, was not altered in dark‐ as well as light‐adapted state. Similarly, retinal GABA‐transaminase (GABA‐T; EC 2.6.1.19)‐succinic semialdehyde dehydrogenase (SSADH; EC 1.2.1.16) was unaltered. (3) These alterations in retinal taurine were, however, unaccompanied by any changes in factors related to transmitter actions such as evoked release, high affinity uptake, and specific binding to synaptic membranes. The above results suggest that, different from GABA as a potent candidate for inhibitory neurotransmitter, retinal taurine may act as neuromodulator and/or may play an important role as a basic factor for maintaining cellular integrity under certain path

ISSN:0360-4012    

DOI:10.1002/jnr.490060407

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

年代:1981

数据来源: WILEY

摘要:

AbstractChronic ethanol ingestion or cycloheximide treatment results in alterations in the properties and synthesis of protein and RNA of polyribosomes in the whole brain. To analyze the effects on a homogeneous neural cell population, Cox astrocytoma (glioma) cells were grown in tissue culture media with 100 mM ethanol or 0.017 mg/ml of cycloheximide. When ethanol had been present for ten days, the cell densities remained unchanged but had markedly reduced RNA and protein contents. Furthermore, the ethanol treatment reduced the whole‐cell pulse‐labeling of RNA with (5–3H) orotic acid and protein with (14C) leucine in the postmitochondrial supernatant. These results suggest that chronic ethanol treatment reduced the whole cell synthesis of RNA and protein or increased their degradation. Analysis of the polyribosomes on sucrose density gradients showed that dense polyribosomal chains were decreased after the ethanol treatment, supporting the concept that the polyribosomes were degraded with an alteration in the metabolism of mRNA. The cell‐free incorporation of (14C) leucine into hot TCA precipitable protein by the purified polyribosomes in the presence of ATP, GTP, a heterologous source of soluble factors, and endogenous mRNA was also reduced following the ethanol treatment, further indicating that the previous chronic exposure to ethanol had inhibited the translation of mRNA. When the control cells were grown in the presence of cycloheximide for one hour prior to harvesting, the cell densities remained unchanged, but again, as with the ethanol treatment, the polyribosomal protein and RNA yields decreased. In contrast to ethanol, however, cycloheximide treatment caused increases both in the whole‐cell incorporation of labeled RNA and protein precursors into the supernatant fraction and in the cell‐free incorporation of (14C) leucine into protein. These results suggest that, like the ethanol effects, cycloheximide reduces the total polyribosomes, but unlike the ethanol effects, the remaining polyribosomes have stable mRNA and rapidly incorporate radioactive amino acids, even more than untreated controls. The one‐hour cycloheximide treatment also caused an increase in the ratio of dense polyribosomes to monosomes plus 40s and 60s ribosomal subunits of control cells. In addition, it increased the incorporation of the labeled precursor into protein in the polyribosomal region of the sucrose gradients of both control and ethanol treated cells, suggesting that cycloheximide inhibited the termination step of protein synthesis. When cycloheximide was present for 24 hours prior to harvesting, the ethanol treated cells, in contrast to the controls, still had increased cell‐free incorporation of amino acid into protein, indicating that the stimulatory effects of cycloheximide are prolonged to 24 hours when ethanol is present. Thus, while the ethanol treatment in general inhibits polyribosomal biogenesis in the cells, it alters the complex of stimulating and then inhibiting effects of cycloheximide by preserving cycloheximide's stimulating effects on the amino acid incorporation activities of th

ISSN:0360-4012    

DOI:10.1002/jnr.490060408

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

年代:1981

数据来源: WILEY

摘要:

AbstractThe transneuronal effect of bilateral, dorsal funicular lesions (T 12) on the frequency of boutons on cells in layer IV of hindlimb cortex was studies. Adult rats were utilized 1, 2, 3, 7, 14, 30, 45, 60, 90, or 120 days postoperative (DPO), and tissue was processed for the light microscopic visualization of silver‐impregnated boutons (Rasmussen method). Bouton counts were taken on soma, or along 5‐ and 10‐μm segments of proximal dendrite branching from soma. The soma diameter also was measured on those neurons chosen for bouton counts on the circumference of the soma. Statistically significant, increased afferentation on soma and proximal dendrite occurred during the first postlesion week relative to longer survival times; bouton counts on the proximal dendrite showed a trend (not statistically significant) toward increases above normal. These data mirror similar, consistent increases in bouton counts reported in thalamic ventroposterolateral nucleus of these same cases. At 14 DPO, bouton counts on the soma decreased below normal (P<0.005) and, except at 60 DPO, remained so through 120 DPO (P<0.025). Bouton counts on the proximal dendrite also decreased below normal at 14 DPO (P<0.005), thereafter exhibiting either periodic (along 5‐7μm) or extended (along 10‐7mu;m) periods in significant decreases from normal. Correlations in lesioned cases between the number of boutons on the soma and either bouton counts on proximal dendrite or soma diameter were positive and statistically significant (P<0.005 in all correlations). Possible anterograde (via the dorsal column‐medial lemniscal system) and/or retrograde (via the corticospinal tract) transneuronal mediation of these effects in hindlimb cortex

ISSN:0360-4012    

DOI:10.1002/jnr.490060409

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

年代:1981

数据来源: WILEY

摘要:

AbstractIsolated nerve endings have been demonstrated to undergo saturable, covalent interactions with [3H]‐dopamine under physiological conditions; and the reaction is greatly accelerated by flash photolysis with ultraviolet light. With intact nerve endings, under conditions where dopamine reuptake occurs, benztropine and cocaine (inhibitors of dopamine reuptake), but not atropine or haloperidol (a postsynaptic antagonist), prevent the reaction. The reaction also occurs in vivo following the intraventricular administration of [3H]‐dopamine, the reaction being greatest with mitochondria, followed by the nerve ending and myelin. With the use of sodium dodecylsulfate–gel electrophoresis, a number of proteins of varying molecular weight were labeled, and the pattern of labeling was similar in vitro and in vivo. One protein, with a MW of about 60,000 was labeled to an exceptionally high degree. A number of protein bands showed decreased radiolabeling in the presence of benztropine, a finding which suggests that they may be associated with the reuptake site. Both the addition of ascorbic acid and unlabeled dopamine inhibited the reactivity of [3H]‐dopamine, and the effects were concentration dependent. In the absence of photolysis, the reaction of [3H]‐dopamine to synaptic membranes attained saturation within 10 min, but with photolysis the reaction continued at a constant rate even after 20 min. The results are discussed in relation to the use of [3]‐dopamine as a photoaffinity label of the dopamine reuptake site and in relation to the nature of the reactions with and without

ISSN:0360-4012    

DOI:10.1002/jnr.490060410

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

年代:1981

数据来源: WILEY

摘要:

AbstractCerebral slices from rats subjected either to chronic (2‐ to 6‐month) administration of carbon tetrachloride or to prolonged (21‐day) portocaval shunting showed an increased above control ability to incorporate [3H]uridine in vitro into the RNA of the large cell nuclei, mostly derived from astrocytes but not the small oligodendroglial cell nuclei. This result is interpreted to indicate that brain reacts to extended periods of hepatogenic insult or chronic omission of hepatic circulation with a stimulation of RNA synthesis in the astrocytes. The possible relation of this phenomenon to the characteristic astrocytes response accompanying hepatogenic encephalopathy is disc

ISSN:0360-4012    

DOI:10.1002/jnr.490060411

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

年代:1981

数据来源: WILEY