摘要:

AbstractA genetic element called the identifier (ID) sequence, highly repeated in the rat genome, has previously been reported to be located in the introns of some genes transcribed in the adult rat brain by RNA polymerase II (Pol II). We show that nuclear RNA isolated from neurons of cerebral hemispheres (cortex) of 14‐day old rats is enrlched more than 10‐fold in ID sequences compared to nuclear RNA from liver, kidney, cerebellum, or cortical glia. The developmental onset of the difference is during the first 2 weeks after birth. Mouse cortical neuronal nuclear RNA is similarly enriched in an element related but not identical to the rat ID element, and the enrichment also has postnatal onset. The enriched appearnce of ID sequences in transcripts whose expression is increased postnatally in cortical neurons correlates developmentally and spatially with the transcription of ID elements by RNA polymerase III (Pol III) and with a change in chromatin struct

ISSN:0360-4012    

DOI:10.1002/jnr.490180202

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe present study examined trophic activities in normal and injured brain which affect the survival and growth of central neurons in culture. Adult rats received bilateral lesions through the angular bundle, severing projections between the entorhinal cortex and the hippocampus. Ten days later, extracts were prepared from the entorhinal or hippocampal regions of the injured brains and compared with extract prepared from analogous regions of normal brains for trophic activities in cultures of either entorhinal or septal tissues.At least three activities were observed: (1) a trophic activity which bound to polylysine‐treated wells, which was>10,000 Da in size, heat labile, and sensitive to trypsin, and which supported the survival of both septal and entorhinal neurons in culture; (2) a trophic activity which did not bind to polylysine‐treated wells, which was>10,000 Da in size, heat labile, and sensitive to trypsin, and which, in the presence of polylysine‐bindable material, facilitated the survival and growth of entorhinal cells in culture, and (3) an inhibitory activity which significantly reduced survival in entorhinal cultures when cells were plated in the presence of high concentrations of extract prepared from normal brain. These effects were not due to nonspecific effects of plating the cells in, or treating the wells with, large amounts of protein.A significant injury‐related increase in nonpolylysine‐bindable trophic activity was also observed. Extracts prepared from either the hippocampus or the entorhinal area of the injured brains contained more non‐polylusine‐bindable trophic activity than extract prepared from normal brains. Injury‐related changes in trophic activities were more prominent in entorhinal than in septal cultures. This increase in activity may account for the injury‐related effects on the survival of entorhinal transplants reported previously [Gibbs and Cotman:Neuroscience(in press) 1987], and may represent an endogenous mechanism by which the brain attempts to selectively support the survival of injured cells

ISSN:0360-4012    

DOI:10.1002/jnr.490180203

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

年代:1987

数据来源: WILEY

摘要:

AbstractTryptic peptides and cyanogen bromide fragments of dopamine beta‐monooxygenase (DBH) were prepared and separated on C‐8 reverse phase columns by high pressure liquid chromatography. Absorbance profiles at both 220 nm and 280 nm were monitored so that peptides with aromatic residues could be isolated. These peptides were subjected to automated Edman degradation with a gas phase microsequen

ISSN:0360-4012    

DOI:10.1002/jnr.490180204

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

年代:1987

数据来源: WILEY

摘要:

AbstractWe have cloned and sequenced an NGF cDNA from the cobra venom gland. The structure of the predicted cobra precursor resembles that of the mouse prohormone, with a highly conserved mature NGF protein at the C‐terminus. In the non‐NGF moiety, a putative signal peptide and two sets of basic residues presumably reflecting cleavage sites that are more conserved, while large interstitial regions are poorly conserved. This moiety may be involved in defining the folding of the precursor for subsequent proteolytic maturation and/or encode a bioactive polypeptide(s). Primer extension analysis indicates a single NGF transcript in the cobra venom gl

ISSN:0360-4012    

DOI:10.1002/jnr.490180205

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe perfusion of rat brain with125I‐transferrin resulted in a receptor‐mediated uptake of transferrin into the endothelium of the blood‐brain barrier followed by its detecation in the brain. During a pulsechase experiment,125I‐transferrin accumulated in the endothelial cells during the pulse, with a decrease of this intraendothelial radioactivity during the chase associated a concomitant increase in the nonvascular elements of the brain. The receptor‐mediated movement of transferrin across the blood‐brain barrier suggests that the brain may derive its iron through the transcytosis of iron‐loaded transferrin across the brain microvasculature. We discuss the likelihood that aluminum and other potentially toxic heavy metals, which also bind tightly to transferrin, may enter the brain by this pathway. We also discuss the possibility that other large molecules including neuroactive peptides and neurotrophic viruses may enter the brain through a similar receptor‐mediated, vesicular tra

ISSN:0360-4012    

DOI:10.1002/jnr.490180206

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

年代:1987

数据来源: WILEY

摘要:

AbstractGlutamate dehydrogenase (GDH) is primarily a mitochondrial enzyme involved in the metabolism of glutamate. We have recently shown by light microscopic immunocytochemistry that, within detergent‐permeabilized brain tissue, GDH is enriched in glial cells, particularly in regions utilizing L‐glutamate as a neurotransmitter. In this study, we used immunogold labeling to quantitatively establish that the forms of the enzyme recognized by the presently used GDH antiserum is associated primarily with a subpopulation of mitochondria in ultrathin, plastic‐embedded sections of the rat cortex and striatum. Permeabilization with detergents was omitted in these studies, so as to preserve the ultrastructure. As expected, labeled mitochondria occurred both in neurons and glia. Furthermore, light microscopic comparisons of the regional distributions of peroxidase immunoreactivity for GDH and a histochemical reaction product for a second mitochondrial enzyme, cytochrome oxidase (CO), were used to demonstrate that high levels of GDH in glia of glutamate‐receptive areas do not necessarily reflect the areas's demand for elevated oxidative metabolism. While all showing intense labeling for glial GDH also exhibited high levels of CO activity, many additional regions showing high levels of CO activity contained no detectable immunoreactivity for glial GDH. These light‐microscopic comparisons reveal that the energy requirments are not the only factors accounting for the regional heterogeneity of the enzyme. We conclude that glial mitochondria are heterogeneous withe respect to their GDH content and that GDH is enriched in areas exhibiting chronically active glutamatergic tra

ISSN:0360-4012    

DOI:10.1002/jnr.490180207

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

年代:1987

数据来源: WILEY

摘要:

AbstractMetabolism of free and esterfied cholesterol and triacylglycerol was compard in cultured neuronal cells, glial cells, and fibroblasts grown from chick embryos. Cellular contents of free and esterified cholesterol were comparable in these cells and triactlglycerol content in the neuronal cells was about 40% of that in the other cell types. Cholesterol synthesis from [3H]acetate was high in all these cells and was not affected by fetal calf serum in the culture medium. Monensin, which has been shown to influence cholesterol metabolism through the inhibition of low‐density liporprotein receptor recycling in human fibroblasts, did not induce profound effects on cholesterol metabolism in these cells. Higher incorporation of [3H] oleic acid into esterified cholesterol was observed in the glial cells and fibroblasts when fetal calf serum was removed from the culture medium. Cellular content of the esterified cholesterol also increased in the glial cells under a serum‐free arrangement. 25‐Hydroxy‐cholesterol induced higher incorporation of both [3H]acetic acid and [3H]oleic acid into esterified cholesterol in all of these cells. The results indicate that the active metabolism of cholesterol found in cultured chick neural cells and fibroblasts may not be regulated by and LDL receptor‐mediated system and some factors in fetal calf serum inhibit cellular accumulation of esterified ch

ISSN:0360-4012    

DOI:10.1002/jnr.490180208

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

年代:1987

数据来源: WILEY

摘要:

AbstractA brain to blood carrier‐mediated transport system for agrinine vasopressin (AVP) was investigated in mice after intraventricular injection of iodinated AVP and varying amounts of unlabeled material or candidate inhibitors. Residual activity in the brain detected after decaptiation was used as the main determinant ot transport activity. The half‐time disappearance of iodinated AVP from the brain was 12.4 min, the Vmaxwas 1.41 nmol/g min, and the apparent Kmwas 28.7 nmol/g. A 30‐nmol dose of AVP, mestocin, arginine vasotocin, pressionoic, amide, pressinoic acid, tocinoic acid, and lysine vasotocin, but not oxytocin, lysine vasopressin, AVP free acid, tocinoic amide, Tyr‐MIF‐1, or cyclo Leu‐Gly, significantly (P<0.05) inhibited the transport of iodinated AVP out of the brain. The 30 nmol dose of AVP had no effect on the tranport of iodide or iodotyrosine out of the brain. High‐preformance liquid chromatography showed that 59.2% of the radioactivity found in the blood 2 min after an i.c.v. injection of labeld AVP eluted at same postiton as labeled AVP compared with 68.8% of radioactivity eluting at that postition after material was infused i.v. for 2 min. This indicates that intact peptide is transported across the blood‐brain barrier and that most of the degradation of AVP occurs during circulation in the blood. Calculations based on the appearance of radioactivity in the periphery showed that 56.2% of the material injected centrally would have been transported into the periphery by 10 min. This appearance of material in the periphery was inhibited by the simulataneous injection of an excess of unlabeled peptide. Water loading significantly decreased the brain to blood transport rate of AVP by 40%. It is concluded that a saturable system exists for brain to blood transport of AVP and some structurally s

ISSN:0360-4012    

DOI:10.1002/jnr.490180209

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

年代:1987

数据来源: WILEY

摘要:

AbstractTorpedoelectric organ contains high concentrations of angiotensin converting enzyme (ACE) like activity, cleaving [Leu5]enkephalin at the Gly3‐Phe4peptide bond. Most of the activity cosediments with the cell membranes. The enzymatic preparation from membranes is inhibited by low concentrations of the ACE inhibitors, AQ 14225 and SQ 20881 (IC50of 0.6 and 15 nM, respectively), and is weakly inhibited by the neutral endopeptidase inhibitors, phosphoramidon and thiorphan (IC50of 30 μM and ca. 70 nM, respectively). The enzyme degrades hippuryl‐His‐Leu and is activated by NaCl. Hippuryl‐His‐Leu and [Leu5]enkephalin are degraded with Km of 93 and 41 μM, and Vmaxof 21 and 10 nmol/mg protein/min, respectively. The specific activity of the ACE‐like activity in homogenates ofTorpedoelectric organ is relatively high (6.3 nmol hippuryl‐His‐Leu/mg protein/min); this value is similar to that obtained for rat lung

ISSN:0360-4012    

DOI:10.1002/jnr.490180210

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe effect of organic Ca2+channel blockers and Co2+on kainate‐induced in45Ca2+efflux and amino acid release was studied in the rabbit hippocampus with the dialysis‐perfusion technique. Administration of 1 mM kainate caused a transient, 50% drop of extracellular Ca2+. This effect was insensitive to 100 μM flunarizine or verapamil, 10 μM nimodipine, and 6 mM CoCl2. The organic Ca2+entry blockers did not significantly influence kainate‐induced changes in extracellular amino acid, whereas Ca2+affected both basal and kainic acid stimulated release of amino acids. These results indicate that kainate‐regulated Ca2+ionophores differ from Ca2+channels in peripheral tissues in terms of sensitivity to Ca2+entry i

ISSN:0360-4012    

DOI:10.1002/jnr.490180211

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

年代:1987

数据来源: WILEY