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161.
Uptake of Exogenous Glutamate and Aspartate by Circumventricular Organs but Not Other Regions of Brain 总被引:1,自引:1,他引:0
Madelon T. Price John W. Olney Oliver H. Lowry Susan Buchsbaum 《Journal of neurochemistry》1981,36(5):1774-1780
Abstract: Glutamate (Glu) and aspartate (Asp) concentrations in blood and selected regions of brain were measured at sequential intervals over a 3-h period following subcutaneous administration of Glu, Asp, or Glu plus Asp (2 mg/g body wt) to 4-day-old mouse or rat pups. Marked serum elevations of the administered amino acids (peak values exceeding 200 times control levels) were detected within 1 h. In circumventricular organ (CVO) regions of brain, which are thought to have no blood-brain barriers, a sharp and steady increase in tissue concentrations of the administered amino acids (peak values 4–10 times higher than control levels) occurred during a 15–120 min interval, whereas no appreciable increases were detected in other brain regions. When 2 mg/g Glu plus 2 mg/g Asp were administered, CVO tissue concentrations of each amino acid rose to approximately the same level obtained when the individual amino acids were given. It is concluded that blood-brain barriers preventing net entry of Glu or Asp into brain proper are relatively well established by the 4th postnatal day in rodents, but that CVO brain regions lack such barriers; selective access of blood-borne Glu or Asp to CVO neurons explains why these neurons are selectively destroyed by systemic administration of these neurotoxic amino acids. 相似文献
162.
Complete accounts of the natural products chemistry of Bonnemaisonia nootkana, B. asparagoides, B. hamifera and Trailliella intricata are described. In contrast to the chemistry of the closely related alga Asparagopsis, Bonnemaisonia spp. do not produce halomethanes, but instead an array of C7-C9 halogen-containing ketones, alcohols and carboxylic acids. Biomimetic syntheses of these compounds suggest they are precursors and products of in vivo Favorsky rearrangements. 相似文献
163.
The effect of glyoxylate on photosynthesis and photorespiration by isolated soybean mesophyll cells 总被引:2,自引:2,他引:0
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Oliver DJ 《Plant physiology》1980,65(5):888-892
Incubating isolated soybean leaf mesophyll cells with glyoxylate increased the rates of CO2 fixation by as much as 150%. In order to cause this stimulation, the glyoxylate must be presented to the cells before the NaHCO3. Significant stimulation was observed 15 seconds after beginning the glyoxylate treatment. The glyoxylate-dependent stimulation was increased by high O2 concentrations and decreased by high CO2 concentrations. Glyoxylate treatment resulted in a 71% inhibition in the rate of CO2 incorporation into glycolate and glycine. Glyoxylate may be stimulating net photosynthesis solely by decreasing photorespiration or it may be increasing the amount of CO2 fixed by both decreasing photorespiration and increasing gross photosynthesis. Ribulose bisphosphate carboxylase, when preactivated and assayed in situ, was unaffected by the glyoxylate treatment. 相似文献
164.
Cytogenetic and electrophoretic analyses on 2n = 28 strains ofAsphodelus cerasiferus strongly suggest that the basic number x = 14 of the genusAsphodelus is of secondary polyploid origin from x = 7. 相似文献
165.
166.
Constance Oliver 《In vitro cellular & developmental biology. Plant》1980,16(4):297-305
Summary Methods have been developed for isolating and maintaining differentiated rat exorbital lacrimal, parotid, and pancreatic acinar
cells for up to 1 month in culture. The dissociated cells retained their differentiated morphology when cultured as suspension
cultures at 35°C with the appropriate secretagogue (exorbital lacrimal, 10−6
M carbamyl choline; pancreas 10−5
M carbamyl choline; parotid, 10−6
M isoproterenol). Under these conditions the cells remained viable and differentiated for up to 4 weeks in culture and continued
to incorporate3H-leucine at rates similar to those of freshly isolated cells. If secretagogue was omitted from the medium, the cells rapidly
degenerated. These results indicate that differentiated from the medium, the cells rapidly degenerated. These results indicate
that differentiated exocrine gland acinar cells may be maintained in vitro and utilized as a model system for the study of
secretory processes. 相似文献
167.
Insulin antagonism of glucocorticoid induction of tyrosine aminotransferase in cultured foetal hepatocytes 总被引:7,自引:0,他引:7
Polyadenylated RNA from developing Artemia salina cysts was fractionated by centrifugation through a sucrose gradient containing methylmercuric hydroxide (CH3HgOH). Aliquots of each fraction were directly added to a rabbit reticulocyte lysate to program protein synthesis in vitro. The translation products were assayed for eukaryotic elongation factor Tu (eEF-Tu) by immunoprecipitation with an antibody raised in rabbits and purified by affinity chromatography. The immunoprecipitated radioactivity was analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecylsulphate. Sequences coding for eEF-Tu sediment in the 20-S region of the gradient and form a major component of the poly(A)-containing RNA. The mRNA of the 20-S region, comprising about 10% of the poly(a)-containing RNA fractionated on the gradient, has been translated in vitro and 30% of the translation products represent immunoprecipitable eEF-Tu protein chains with an Mr of 50000. 相似文献
168.
The marine opisthobranch molluscAplysia punctata was cultured at the Laboratoire de Biologie Marine in Concarneau, France.A. punctata veligers settled and underwent metamorphosis on the algaLomentaria articulata, but not onUlva spp., Palmaria marina, Laminaria spp. andFucus spp.Research supported by grants from The Arts Foundation and the Lerner Fund for Marine Research of the American Museum of Natural History. We wish to thank Director Yves Legal, College de France for his support and cooperation. 相似文献
169.
A carbamate herbicide causes microtubule and microfilament disruption and nuclear fragmentation in fibroblasts 总被引:1,自引:0,他引:1
Microtubule associated proteins (MAPs) are high molecular weight proteins that associate with microtubules during polymerization. This report describes a high molecular weight protein fraction with a molecular weight of approx. 290 000 from cultured mammalian fibroblasts that associates with polymerized rat brain tubulin. This protein(s), which is referred to as f-MAP, is enriched approx. 25-fold in a twice polymerized microtubules when compared with the original cell extract. Polymerization of rat brain extract in the presence of in vivo 32P-labeled fibroblast extract reveals the presence of a 32P-labeled protein in the polymerized pellet with the same electrophoretic mobility as f-MAP. The present study suggests that fibroblasts in culture contain a high molecular weight phosphoprotein with properties and a molecular weight very similar to the MAPs described in mammalian brain. 相似文献
170.
The oxidation of 3-hydroxy[3-14C]butyrate to CO2 and its incorporation into cerebral lipids by cortex slices from one-week old rats were markedly inhibited by methylmalonate. However, methylmalonate had no effect on the metabolism of labelled aceto- acetate, glucose and acetate by brain slices. Addition of propionate in the incubation medium reduced cerebral lipogenesis from labelled 3-hydroxybutyrate and acetate. Acute methylmalonic acidemia induced in one-week old pups by injecting 3% methylmalonate solution caused a reduction in the incorporation of labelled 3-hydroxybutyrate into cerebral lipids. However, acute methylmalonic acidemia had no effect on cerebral lipogensis from labelled acetate. These findings show (i) the conversion of 3-hydroxybutyrate to acetoacetate by 3-hydroxybutyrate dehydrogenase in the brain is inhibited by methylmalonate, and (ii) an inhibition of cerebral lipid synthesis by propionate, which also accumulates in patients with methylmalonic aciduria. 相似文献