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101.
Effects of Neuronal Activity on Inositol Phospholipid Metabolism in the Rat Autonomic Nervous System 总被引:4,自引:4,他引:0
Clark A. Briggs Joel Horwitz† Donald A. McAfee Sophia Tsymbalov† Robert L. Perlman† 《Journal of neurochemistry》1985,44(3):731-739
The effect of nerve stimulation on inositol phospholipid hydrolysis in autonomic tissue was assessed by direct measurement of [3H]inositol phosphate production in ganglia that had been preincubated with [3H]inositol. Within minutes, stimulation of the preganglionic nerve increased the [3H]inositol phosphate content of the superior cervical sympathetic ganglion indicating increased hydrolysis of inositol phospholipids. This effect was blocked in a low Ca2+, high Mg2+ medium. It was also greatly reduced when nicotinic and muscarinic antagonists were present together in normal medium. However, neither the nicotinic antagonist nor the muscarinic antagonist alone appeared to be as effective as both in combination. In other experiments, stimulation of the vagus nerve caused dramatic increases in [3H]inositol phosphate in the nodose ganglion but did not increase [3H]inositol phosphate in the nerve itself. This effect was insensitive to the cholinergic antagonists. Thus, neuronal activity increased inositol phospholipid hydrolysis in a sympathetic ganglion rich in synapses, as well as in a sensory ganglion that contains few synapses. In the sympathetic ganglion, synaptic stimulation activated inositol phospholipid hydrolysis and this was primarily due to cholinergic transmission; both nicotinic and muscarinic pathways appeared to be involved. 相似文献
102.
103.
Saprophytic fungi have degradative abilities and interspecific interactions which suggest that resource use and yield should increase as species number increases, but previous studies show the opposite. As a test of the possibility that invertebrate activity changes fungal resource use patterns, we grew coprophilous fungi on rabbit feces at the same initial density singly or in mixtures of 2, 4, or 6 species, with or without activity of larvalLycoriella mali (Diptera: Sciaridae). Fungi in mixtures without larvae caused less weight loss in one mixture, and greater weight loss in 2 mixtures than when growing alone; fungi in 4 of 6 mixtures produced fewer spores than when growing alone. Overall, without larvae, weight loss did not increase as number of fungal species increased. Larvae did not change the pattern of weight loss or proportions of spores caused by mixing fungal species. Numbers of larvae surviving to pupate rose as fungal species numbers increased; as a result, weight loss increased with fungal species number in cultures with larvae. 相似文献
104.
An observation of episodic feeding and growth of larval Leiostomus xanthurus in the northern Gulf of Mexico 总被引:1,自引:0,他引:1
Govoni John J.; Chester Alexander J.; Hoss Donald E.; Ortner Peter B. 《Journal of plankton research》1985,7(1):137-146
Four cruises were conducted in the northern Gulf of Mexico overtwo spawning seasons of the sciaenid fish Leiostomus xanthurus.On only one occasion did unusually high densities of larvaeand their principal microzooplanktonic foods co-occur. Peakdensities of larvae and microzooplankton were observed in athin lens of cool surface water that characterized a hydrographicdiscontinuity, and all larvae contained high numbers of foodorganisms in their guts. Instantaneous exponential growth ratesestimated from measurements of otolith growth increments, indicatedaccelerated growth on the day that larvae were collected. Alaboratory experiment verified that larval L. xanthurus respondsto an increased ration with accelerated growth that is detectableon otoliths. Together these data suggest that the spatial distributionof L. xanthurus larvae and their microzooplanktonic food ispatchy and that interactions of larvae and microzooplanktonmay be episodic. 相似文献
105.
Abstract The penicillin binding proteins (PBPs) of 4 representative isolates of Haemophilus influenzae were studied using crude membrane preparations and whole cells grown to the logarithmic and stationary phases of growth. Relative binding, % of total bound, and binding affinities were compared. The PBP patterns were similar for crude membranes and whole cells for all 4 strains tested at each phase of growth. However, PBP 2 was slightly reduced and PBP 4 was markedly reduced with whole-cell labelling in comparison to crude membranes. 8 PBPs were detected in cells labelled during the logarithmic phase of growth, while 6 were detected in stationary phase cells. The pBPs 'lost' in stationary phase (PBPs 4 and 6) with apparent M r of 62 000 and 45 000, respectively, have a high affinity for ampicillin ( I 50 ≃ 0.04 μ g/ml). This suggests that these proteins may have an important role in cell growth, and are targets for β-lactam substrates. 相似文献
106.
Steven D. Woods Richard H. Rand H. David Block Donald C. Lewis 《Journal of mathematical biology》1985,21(3):273-283
A mathematical examination of retinal photochemistry leads to a hypothesis for Mach band phenomena based on eye movements. This retinal model suggests why minimally distinct borders fade under eye fixation and agrees qualitatively with subjective measures of border contrast as a function of overall field luminance.Deceased 相似文献
107.
Rhizobium sp. strain ORS571 ammonium assimilation and nitrogen fixation. 总被引:15,自引:13,他引:2
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Among rhizobia studied, Rhizobium sp. strain ORS571 alone grew unambiguously on N2 as sole N source. In ORS571 , only the glutamine synthetase (GS)-glutamate synthase ( GOGAT ) pathway assimilated ammonium. However, ORS571 exhibited two unique physiological aspects of this pathway: ORS571 had only GS I, whereas all other Rhizobiaceae studied had both GS I and GS II, and both NADPH- and NADH-dependent GOGAT activities were present. ORS571 GS-affected and NADPH- GOGAT -affected mutant strains were defective in both ammonium assimilation (Asm-) and N2 fixation (Nif-) in culture and in planta ; NADH- GOGAT mutants were Asm- but Nif+. "Bacteroid" GS activity was essentially nil, suggesting symbiotic ammonium export. Physiological studies on effects of glutamine, ammonium, methionine sulfoximine, and diazo-oxo-norleucine on nitrogenase induction in culture implied a regulatory role for the intracellular glutamine pool. 相似文献
108.
The effects of mineral salts constituting water hardness on fecundity ofDaphnia magna were assessed. Of the salts tested, increased concentrations of NaHCO3 and MgSO4 had no effect on fecundity, CaSO4 significantly increased fecundity, and KCl significantly reduced fecundity. The number of offspring produced per daphnid
was correlative to the CaSO4 concentration at CaSO4 concentrations between 91 and 2100 mg/ℓ. The effects of CaSO4 on daphnid fecundity could influence the interpretive outcome of industrial wastewater toxicity tests using this species
when the waste and dilution waters contain different concentrations of CaSO4. It is recommended that when performing these tests, dilution water be sampled at the intake site of the industry's water
source, thus assuring initial comparability of the waste and dilution waters. The CaSO4 content of the water prior to and after industrial use should be determined to identify any alterations of CaSO4 concentration during use. Identification of CaSO4 concentration differences can aid in the interpretation of effects associated with the wastewater. 相似文献
109.
Fusayuki Kanda Sei-ichi Matsui Donald E. Sykes Avery A. Sandberg 《Biochemical and biophysical research communications》1984,122(3):1296-1306
Isopeptidase is a novel eukaryotic enzyme that cleaves a structural chromatin protein, A24, stoichiometrically into H2A and ubiquitin. To understand the rapid turnover of ubiquitin in mitosis as wells as the high specific activity of the enzyme associated with metaphase chromosomes, attempts were made to determine chromatin constituents that show high affinity for this enzyme. Endogenous protease-free isopeptidase was prepared from calf thymus and applied to a Sepharose 4B affinity column on which histones, DNA, NHCP and ubiquitin were respectively immobilized. The enzyme proved to bind only histones. To further determine which of the histone fractions is involved, affinity columns with each histone fraction were also used. The enzyme showed affinity for all histone fractions. However, the strength of affinity varied in the order H2A>H3 H2B≥H4?H1, being inversely correlated with the ratio of basic/acidic amino acids in these molecules. These results suggest that the turnover of A24 in mitosis is controlled, at least in part, by the affinity of enzyme for histones, and also that such affinity is caused by a mechanism which cannot be explained simply by the electrostatic interaction between negatively charged enzyme molecules and positively charged histones. 相似文献
110.
Allen W. Archer Donald E. Hattin 《Palaeogeography, Palaeoclimatology, Palaeoecology》1984,45(2):165-187
Argillaceous strata of the Greenhorn and Niobrara depositional cycles contain an extensive, though spottily developed, record of tracemaking organisms. These beds are assignable to five facies, four of which represent the gradation from nearshore sandy shales to far offshore calcareous shales, the fifth representing anoxic or nearly anoxic bottom conditions. In strata studied by us the best potential for trace fossil preservation was in deposits characterized by pronounced textural variation, such as shales with sandstone interbeds, shales with thin lenses of siltstone or sandstone, or sandy and silty shales (= mudstones). In pure clayey shales and calcareous shales, trace fossils are preserved best in concretionary structures. Our study suggests that except for shales rich in organics, trace-making organisms were common and widespread in argillaceous muds of the Western Interior. Initial fluidity, high degree of compaction, and textural homogeneity are principal reasons for the poor record of trace makers in pure, clayey shales. 相似文献