摘要:

Abstract:The effects of vasoactive intestinal peptide (VIP) and several other peptides have been examined on cyclic AMP accumulation in intact pieces and isolated horizontal cells of the teleost (carp) retina. VIP was the most effective peptide examined, inducing a dose‐related response, and an approximately fivefold increase in cyclic AMP production when used at a concentration of 10 μM. Porcine histidine isoleucine‐containing peptide and secretin, peptides structurally related to VIP, also stimulated cyclic AMP accumulation, but at concentrations of 10 μMinduced responses which were only approximately 40% and 10%, respectively, of the response observed with 10 μMVIP. In contrast, several other peptides, including glucagon, neurotensin, somatostatin, luteinizing hormone‐releasing hormone, α‐melanocyte‐stimulating hormone, cholecystokinin octapeptide26–33, gastrin‐releasing peptide, thyrotropin‐releasing hormone, and VIP10–28were totally inactive. The response to 10 μMVIP was not antagonized by several dopamine antagonists, indicating the presence of a population of specific VIP receptors coupled to adenylate cyclase, distinct from the population of dopamine receptors coupled to adenylate cyclase also known to be present in this tissue. Finally, experiments involving the use of fractions of isolated horizontal cells indicate that these neurons possess a population of VIP receptors coupled to cyclic AMP production which would appear to share a common pool of adenylate cyclase with a population of similarly coupled dopamine receptors. These data are discussed in terms of the presence, localization, and possible function of a putative VIP‐ergic innerv

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb00813.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Gangliosides were previously reported to induce neuritogenesis in primary neuronal cultures and in some neurally derived cell lines. Because isolated gangliosides usually contain variable quantities of peptides, we investigated the possibility that neurite‐stimulating activity could be caused by these contaminants. Ganglioside preparations from bovine brain and other sources were subjected to a three‐step purification procedure that eliminated at least 95% of the contaminating peptides. These purified preparations retained their capacity to induce extensive neurite growth in neuro‐2A murine neuroblastoma. Proteolytic digestion and a number of additional procedures were used to reduce residual contamination further without loss of activity. Several crude ganglioside samples had negative effects on neurite development until freed of their inhibitory factors, which were derived from the tissue and/or introduced during laboratory operations. This was particularly evident for bovine white matter gangliosides whose activity increased in proportion to peptide removal. When carefully purified, virtually all of 11 different gangliosides tested were highly active, with the possible exception of GM4, which demonstrated only moderate activity in a limited number of tests. All of the neutral glycolipids tested, as well as sulfatides and free sialic acid, were ina

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb00814.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Monospecific anti‐rat serum alpha‐fetoprotein (AFP) IgG was coupled to cyanogen bromide‐activated Sepharose‐4B (4.5 mg/ml packed volume of gel) to yield an immunoaffinity matrix. The immunoaffinity column was used to isolate AFP from feto‐neonatal rat brain. The purified AFP was immunologically and electrophoreti‐cally similar to serum AFP. It yielded a single band with a molecular weight of 70,000 on sodium dodecyl sulphate polyacrylamide gel electrophoresis. Polyacrylamide gel electrophoresis of the protein under nondenaturing conditions yielded two charge variants of AFP, reminiscent of AFP from feto‐neonatal rat serum. The AFP was observed to bind estradiol withKa= 5.8 × 108M−1and 1.3 × 108M−1by dextran‐coated charcoal adsorption and Sephadex gel filtration techniques, respectively. Newborn rat brain cells linearly incorporated [14C]leucine into immunoprecipitable AFP during 6 h in culture. It is, therefore, concluded that feto‐neonatal rat brain contains AFP similar to that present in fetal serum and that it may arise in brain as a result

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb00815.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:After intracarotid injection of [3H]β‐casomorphin‐5 (βCM5) in rats, the accumulation of radioactivity was determined in 18 brain regions and the anterior pituitary. The relative accumulation in all regions significantly exceeded that of [3H]inulin by a factor of 2.5, indicating a low but measurable brain uptake of the peptide. In blood‐brain barrier‐free areas, the accumulation of radioactivity was 15‐fold higher than in blood‐brain barrierprotected areas. The relative accumulation was not dependent on the total βCM5 concentration in the range of 0.3–1.1μM, and was not depressed by 400μML‐tyrosine. We conclude that βCM5, like other peptides, is accumulated in the blood‐brain barrier‐free areas to a relatively high but differing degree, whereas in the areas with a tight endothelium the accumulation is relatively low and nearly uniform. A binding to endothelial cells may contribute to the low accumulation of βCM5, especially in blood‐b

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb00816.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The biochemical and morphological effects of polyunsaturated fatty acids on fetal brain cells grown in a chemically defined medium were studied. Fetal brain cells were dissociated from mouse cerebral hemispheres taken on the 16th day of gestation. After cells had grown in chemically defined medium for 8 days, the proportion of polyunsaturated fatty acids of cultured cells was only one‐half of that observed at day 0 and about 1.5 times less than that of cells grown in serum‐supplemented medium. Fatty acid 20:3(n‐9) was present in cultured cells grown in either chemically defined or serum‐supplemented medium, demonstrating the deficiency of essential fatty acids. The reduced amount of polyunsaturated fatty acids in cells grown in the chemically defined medium was balanced by an increase in monounsaturated fatty acids. The saturated fatty acids were not affected. When added at the seeding time, linoleic, linolenic, arachidonic, or docosahexaenoic acid stimulated the proliferation of small dense cells. Besides, we demonstrate that each of the four fatty acids studied was incorporated into phospholipids. Adding fatty acids of the n‐6 series increased the content of n‐6 fatty acids in the cells, but also provoked an increase in the n‐3 fatty acids. Among several combinations of fatty acids, only 20:4 and 22:6, when added to the culture in a ratio of 2:1, restored a fatty acid profile similar to controls (i.e.in vivotissue taken at pos

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb00817.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Two distinct classes of acetylcholinesterase (AChE) from the fruit flyDrosophila melanogasterare reported: a soluble species that shows heterogeneity of forms and a particulate species. The subunit composition of the particulate enzyme was studied using the active site label [3H]diisopropylfIuorophosphate. Comparison of the electrophoretic patterns on nondenaturing gels using the activity stain and the active site label shows that the label is specific to AChE. The smallest active site‐containing subunit of the enzyme is a monomer of —60,000 daltons MW. Two such units are linked by disulphide bonds to produce a dimer of about 110,000 daltons. Another monomeric form of MW —64,000 daltons, although present, does not participate in the dimerisation. The particulate enzyme when solubilised exists as a 9–10S species as determined by sucrose gradient centrifugation. This species has a MW>200,000, as shown by its behaviour on a coarse‐bead Sephadex‐G200 column. Electrophoretic analysis suggests a MW of nearly 250,000 daltons for this form. Thus, this species is likely to be a tetramer. One possibility is that this tetramer is made up of two units of 64,000 daltons each and a dimer of 110,000 daltons. Preliminary data on mutant enzymes that support such a possibility are als

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb00818.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:The concentration of 6‐phosphogluconate in the brain increased from 0–24 nmol/g in the controls to 1430 and 1506 nmol/g in rats treated with 50 mg of 6‐aminonicotinamide/kg of body weight. A dose‐dependent increase in the concentrations of glucose and glucose 6 phosphate as well as of 6‐phosphogluconate was found in the brains of 6‐aminonicotinamide‐treated rats. The biochemical changes and symptoms of neurological disorder in 6‐aminonicotinamide‐treated rats were not due to hypothermia. The rate of utilization of glucose via the hexosemonophosphate shunt was determined by isolation of gluconate from 6‐phosphogluconate and measurement of its [14C]content at short time intervals after injection of [U‐14C]glucose into 6‐aminonicotinamide‐treated rats; it was 16.5 nmol of glucose utilized/min per g of brain, and represented approximately 2.3% of the overall utilization of glucose in the brain. A highly significant correlation was observed between the concentration of 6‐phosphogluconate and the concentration of glucose 6‐phosphate and free glucose. The validity of this correlation was supported by the results of previous investigations invol

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb00819.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Monolayer cultures of neuroblastoma × glioma hybrid (clonal) cell line NG108–15, synchronized by the isoleucine/glutamine deprivation method, showed maximal expression of opiate binding sites at the same point in the cell cycle at which prostaglandin E, (PGE1) had a maximum stimulatory effect on cyclic AMP synthesis. However, the capacity of enkephalin [D‐Ala2D‐Leu5] to block the stimulation of cyclic AMP synthesis by PGE1was not related to the number of opiate receptors expressed. TheKifor the inhibition of cyclic AMP synthesis by opioid peptides increased substantially during the period of the cell cycle at which maximal expression of opiate binding sites occurred, making the effective level of inhibition of adenylate cyclase activity by 0.1 μMenkephalin [D‐Ala2D‐Leu5] the same through the cell cycle. Data are presented to suggest that enkephalin receptor coupling to adenylate cyclase, via a GTP‐binding protein, is maximal during G1phase (which may approximate the state of the differentiated neuron) and minimal during S + G2phase, just prior to cell division, when many receptors

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb00820.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Bovine chromaffin secretory vesicle ghosts loaded with Na+were found to take up Ca2+when incubated in K+media or in sucrose media containing micromolar concentrations of free Ca2+. Li+‐ or choline+loaded ghosts did not take up Ca2+. The Ca2+accumulated by Na+‐loaded ghosts could be released by the Ca2+ionophore A23187, but not by EGTA. Ca2+uptake was inhibited by external Sr2+, Na+, Li+, or choline+. All the45Ca2+accumulated by Na+‐dependent Ca2+uptake could be released by external Na+, indicating that both Ca2+influx and efflux occur in a Na+‐dependent manner. Na+‐dependent Ca2+uptake and release were only slightly inhibited by Mg2+. In the presence of the Na+ionophore Monensin the Ca2+uptake by Na+‐loaded ghosts was reduced. Ca2+sequestered by the Na+‐dependent mechanism could also be released by external Ca2+or Sr2+but not by Mg2+, indicating the presence of a Ca2+/Ca2+exchange activity in secretory membrane vesicles. This Ca2+/Ca2+exchange system is inhibited by Mg2+, but not by Sr2+. The Na+‐dependent Ca2+uptake system in the presence of Mg2+is a saturable process with an apparentKmof 0.28 μMand a Vmax= 14.5 nmol min−1mg protein−1. Ruthenium red inhibited neither the Na+/Ca2+nor the Ca2+/Ca2+exchange, even at

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb00821.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Abstract:Radioiodinated lectins were used to detect glycoproteins of peripheral nervous system (PNS) myelin (rat, human, bovine) and cultured rat Schwann cells. Proteins were resolved by sodium dodecyl sulfate‐polyacrylamide slab gel electrophoresis and transferred to nitrocellulose filters. The filters were overlaid with radioiodinated lectins of known saccharide affinities. These included concanavalin A,Helix pomatia, Limulus polyphemus, Madura pomifera, peanut, soybean,Ulex europaeus, and wheat germ agglutinins. Inclusion of the appropriate monosaccharide in the overlay solution (0.2M) inhibited lectin binding to the nitrocellulose‐fixed proteins. Fluorography permitted identification of 26 myelin glycoproteins and many more in Schwann cells. All lectins labeled a band present in myelin, but not Schwann cells, corresponding to the major PNS myelin protein, P0. Our attention focused on a high‐molecular‐weight myelin glycoprotein [apparent molecular weight (Mr) 170,000], which appeared abundant by Coomassie Blue staining and which was heavily labeled by all lectins except concanavalin A. A protein with approximately this Mrand lectinbinding pattern was present in human and bovine PNS myelin as well, but not detected in rat Schwann cells, CNS myelin, liver and fibroblast homogenates, or cultured bovine oligodendroglia. Hence this 170,000 Mrglycoprotein is apparently unique to PNS

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1983.tb00822.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY