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101.
Modeling the leech heartbeat elemental oscillator I. Interactions of intrinsic and synaptic currents
Farzan Nadim Øystein H. Olsen Erik de Schutter Ronald L. Calabrese 《Journal of computational neuroscience》1995,2(3):215-235
We have developed a biophysical model of a pair of reciprocally inhibitory interneurons comprising an elemental heartbeat oscillator of the leech. We incorporate various intrinsic and synaptic ionic currents based on voltage-clamp data. Synaptic transmission between the interneurons consists of both a graded and a spike-mediated component. By using maximal conductances as parameters, we have constructed a canonical model whose activity appears close to the real neurons. Oscillations in the model arise from interactions between synaptic and intrinsic currents. The inhibitory synaptic currents hyperpolarize the cell, resulting in activation of a hyperpolarization-activated inward currentI
h
and the removal of inactivation from regenerative inward currents. These inward currents depolarize the cell to produce spiking and inhibit the opposite cell. Spike-mediated IPSPs in the inhibited neuron cause inactivation of low-threshold Ca++ currents that are responsible for generating the graded synaptic inhibition in the opposite cell. Thus, although the model cells can potentially generate large graded IPSPs, synaptic inhibition during canonical oscillations is dominated by the spike-mediated component. 相似文献
102.
Location of the active site of the bean {alpha}-amylase inhibitor and involvement of a Trp, Arg, Tyr triad 总被引:1,自引:0,他引:1
Mirkov T.Erik; Evans Stephen V.; Washlstrom Janice; Gomez Luis; Young N.Martin; Chrispeels Maarten J. 《Glycobiology》1995,5(1):45-50
Seeds of the common bean contain three homologous proteins:phytohaemagglutinin E, phytohaemagglutinin L and the lectin-likeprotein 相似文献
103.
Defective regulation of the cytosolic Ca2+ activity in parathyroid cells from patients with hyperparathyroidism 总被引:2,自引:0,他引:2
Rolf Larsson Chris Wallfelt Håkan Abrahamsson Erik Gylfe Sverker Ljunghall Jonas Rastad Patrik Rorsman Leif Wide Göran Åkerström 《Bioscience reports》1984,4(11):909-915
The parathyroid hormone (PTH) release and cytosolic Ca2+ activity were determined in normal bovine parathyroid cells and parathyroid cells obtained from patients with hyperparathyroidism (HPT). There was a sigmoid relation between the cytosolic Ca2+ activity and the extracellular calcium concentration between 0.5 and 6.0 mmol/l. The PTH release was inhibited in parallel with the rise in the cytosolic Ca2+ activity. Both the hormone release and the cytosolic Ca2+ activity were lower in cells from human adenomas and hyperplastic glands~ and in comparison with the bovine preparations these ceils had higher set points for the cytosolic Ca2+ activity and PTH release. There was a close correlation between the individual set points for the cytosolic Ca2+ activity and PTH release in a material containing both normal and pathological cells. The results indicate that the abnormal PTH release characteristic of HPT is due to a defective regulation of the cytosolic Ca2+ activity. 相似文献
104.
Sven Erik Godtfredsen Anne Munk Rasmussen Martin Ottesen Peer Rafn Nicolai Peitersen 《Applied microbiology and biotechnology》1984,20(1):23-28
Summary Acetolactate decarboxylase activity has been detected among three genera, nine species and 263 strains of lactic acid bacteria tested in the course of a screening for acetolactate decarboxylases amenable for use in brewing as maturation aid. Streptococcus diacetylactis strain FD-64-D was found to generate a decarboxylase exhibiting a satisfactory activity and an excellent stability at the pH prevailing in beer and wort. This decarboxylase could not be solubilized but enzymatically active, freeze-dried cells were effective for satisfactory flavour maturation of beer although difficulties were encountered during attempts to remove the applied cell material by filtration of the beer. Lactobacillus casei DSM 2547 was likewise found to produce a decarboxylase exhibiting a satisfactory activity and stability at the low pH of beer and which, in addition, was readily solubilized. A method has been developed for pilot scale production of preparations of this decarboxylase suitable for use in brewing.Abbreviations DSM
Deutsche Sammlung von Microorganismen
- EDTA
Ethylene diaminetetra-acetic acid 相似文献
105.
Stephen J. H. Ashcroft Judy Bunce Martin Lowry Svend E. Hansen Carl J. Hedeskov 《The Biochemical journal》1978,174(2):517-526
Rates of incorporation of [4,5-(3)H]leucine into insulin plus proinsulin, designated ;(pro)insulin', and total protein in rat pancreatic islets were measured. Glucose stimulates rates of total protein and (pro)insulin biosynthesis, but (pro)insulin biosynthesis is stimulated preferentially. Mannose and N-acetylglucosamine also stimulate (pro)insulin and total protein biosynthesis; inosine and dihydroxyacetone stimulate (pro)insulin biosynthesis specifically. Fructose does not stimulate (pro)insulin biosynthesis when tested alone, but does so in the presence of low concentrations of glucose, mannose or N-acetylglucosamine. Many glucose analogues do not stimulate (pro)insulin biosynthesis. Mannoheptulose inhibits synthesis of (pro)insulin and total protein stimulated by glucose or mannose but not by dihydroxyacetone, inosine or N-acetylglucosamine; phloretin (9mum) inhibits N-acetylglucosamine-stimulated (pro)insulin biosynthesis preferentially. The data are in agreement with the view that the same glucose-sensor mechanism may control both insulin release and biosynthesis, and ;substrate-site' model is suggested. The threshold for stimulation of biosynthesis of (pro)insulin and total protein is lower than that found for glucose-stimulated insulin release; moreover the biosynthetic response to an elevation of glucose concentration is slower than that found for insulin release. The physiological implication of these findings is discussed. Caffeine and isobutylmethylxanthine, at concentrations known to increase islet 3':5'-cyclic AMP and potentiate glucose-induced insulin release, were without effect on rates of glucose-stimulated (pro)insulin biosynthesis. 相似文献
106.
The natural mortality rate of trout fry and the impact of weed cutting and cleaning out of weeds, branches and twigs from the stream-bed upon the mortality rate of trout fry was studied on several reaches in small streams. Above an initial density of 3.1 fry m–2 natural mortality rate was found to be density-dependent in the first few months of life. In reaches where weed cutting and cleaning out of the stream-bed had taken place the mortality rate was higher than that found under natural conditions in undisturbed reaches. The results support the suggestion that stream management works which make the stream more uniform will be in conflict with sound fishery management. 相似文献
107.
108.
Rino Cella Roberta Colombo Maria Grazia Galli Erik Nielsen Franco Rollo Francesco Sala 《Physiologia plantarum》1982,55(3):279-284
Rice ( Oryza sativa L.) cells returning to in vitro culture after preservation at superlow temperature in liquid nitrogen are characterized by a number of physiological alterations. These include: reduction in respiration and glucose uptake, loss of intracellular potassium, decrease in the cellular level of key metabolites (ATP, glucose-6-phosphate and pyruvate) and fragility of protoplasts following the action of cell wall-degrading enzymes.
Nevertheless, cell growth resumes after a short lag phase (2–4 days) with an actual 70–100% cell survival, thus indicating that the observed damage is not lethal and can be repaired in a short time. 相似文献
Nevertheless, cell growth resumes after a short lag phase (2–4 days) with an actual 70–100% cell survival, thus indicating that the observed damage is not lethal and can be repaired in a short time. 相似文献
109.
Jørn Erik Bjørndalen 《Nordic Journal of Botany》1981,1(5):665-670
The basiphilous pine forests in southern Telemark, SE Norway, have previously been classified according to the ordinary phytosociological methods of the Braun—Blanquet system. The same material was later treated by numerical analysis, i.e., TABORD—classification and the ordination technique 'reciprocal averaging'. No significant differences were found between the numerical and the non—numerical classification except for the classification of some transitional communities. Ordination by 'reciprocal averaging' gave a useful complement to the TABORD classification, and re—leves and species were distributed along interpretable gradients (i.e., along a dry—wet gradient and along a gradient from forest—rim conditions to forest conditions). 相似文献
110.
Nielsen Johannes Vetner Max Holm Vagn Askjær Svend Aage Reske-Nielsen Edith 《Human genetics》1977,38(3):357-362
Summary A case of Meckel or Gruber syndrome is reported, together with a survey of the relevant literature of recent years (1971–1977), in reference to a probably autosomal recessive inheritance of this malformation. 相似文献