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1.
The potential physiological impact of morphological changes in the active dendritic spines, which are believed to be associated
with altered synaptic efficacy, was investigated in a computer simulation study using the NEURON package [1]. A compartmental
model of a simplified neuron was built, which included 30 complex spines (neck, head, and active zone) and accommodating AMPA-type
synaptic inputs with alpha-function conductances. Hodgkin-Huxley type excitable membranes were inserted into the spine heads.
It was shown that arranging spines in dense clusters, as opposed to a uniformly random spine distribution, has a negligible
effect on the synaptic signal transfer (other model conditions, including synaptic input and spine density, remained unchanged).
However, if a proportion (e.g., 3–20%) of the spines partly fuse with their neighbors forming branched spines, this could
increase dramatically the cell response to the unchanged synaptic input. Results of this pilot study provide the basis for
a more detailed investigation of the relationship between the spine arrangement and synaptic function, considering dual-component
synaptic currents and mechanisms controlling ion fluxes in the dendritic compartments. 相似文献
2.
Yu. I. Rusakov A. P. Kolychev V. N. Shipilov V. M. Bondareva 《Journal of Evolutionary Biochemistry and Physiology》2003,39(4):425-432
Cerebropleural ganglia from 4000 individuals of the mollusc Anodonta cygnea were submitted to procedures developed for isolation of vertebrate pancreatic insulins: homogenization and extraction, stage-like isoelectrical sedimentation, and ion-exchange chromatography. As a result of purification of the obtained preparation, using high-effective liquid chromatography, there were identified 7 protein peaks differing by time of retention on the reverse-phase sorbent in acetonitryl gradient and designated as insulin-related peptides (IRP), IRP1-IRP7. The material was characterized by the peptide ability to inhibit specific binding of 125I-insulin and of insulin-related factor-1 (125I-IGF-1) by plasma membranes of the rat liver and brain. The IC50 value of peptide concentration (nM) able to replace 50% of the labeled hormone bound with the receptor amounted in the insulin radioreceptor system for IRP1 to 330, for IRP3 to 130, for IRP4 to 17, for IRP5 to130, for IRP6 to 420 nM. Peptide IRP7 at a maximal concentration (104 ng/ml) replaced less than 50% of labeled hormone, whereas in IRP2 no inhibitory ability was detected under these experimental conditions. The IC50 value in the case of 125I-IGF-1 amounted for IRP1, IRP4, and IRP5 to17, for IRP2 to 50, for IRP3 to 83, for IRP6 to 133 nM. IRP7 at a concentration of 104 ng/ml replaced less than 50% of labeled hormone. The same high relative affinity of the peptide IRP4 (12% of activity of standard insulin and IGF-1) to both receptor types is revealed. The results of analysis in two types of hormonal test systems indicate the ability of the insulin-related peptides of the anodonta cerebropleural ganglion to interact with the vertebrate receptor of insulin and IGF-1. This gives grounds to suggest the presence of the metabolic and growth-stimulating properties in these peptides. For the first time, the IGF-1 activity is revealed in insulin-like molecules in invertebrates. Taking into account the chromatographically revealed differences of physicochemical characteristics of individual IRP as well as predominance of their IGF-1-binding properties, there is suggested another organization of the IRP receptor-binding domains in IPR of this mollusc species, as compared with mammalian insulins. 相似文献
3.
Payant V; Abukashawa S; Sasseville M; Benkel BF; Hickey DA; David J 《Molecular biology and evolution》1988,5(5):560-567
Nuclear DNA was extracted from each of the eight species comprising the
Drosophila melanogaster species subgroup. Southern hybridization of this
DNA by using a molecular probe specific for the alpha-amylase coding region
showed that the duplicated structure of the amylase locus, first found in
D. melanogaster, is conserved among all species of the melanogaster
subgroup. Evidence is also presented for the concerted evolution of the
duplicated genes within each species. In addition, it is shown that the
glucose repression of amylase gene expression, which has been extensively
studied in D. melanogaster, is not confined to this species but occurs in
all eight members of the species subgroup. Thus, both the duplicated gene
structure and the glucose repression of Drosophila amylase gene activity
are stable over extended periods of evolutionary time.
相似文献
4.
An electron-microscopic study of the topography of carbohydrate residues on the surface of the cell body membrane of cultured spinal neurons was carried out using lectins from wheat (WGA) and snail (HPL), labeled with colloidal gold, as specific molecular probes. Mathematical methods of analysis suggested a set of surface markers, from the distribution of particles observed in electron micrographs of random sections, corresponding to two random functions. Analysis of these functions allows the required quantitative characteristics to be obtained. The Monte Carlo reconstructing model is described, and results of its use (based on the aforementioned experimental data) are demonstrated in the form of "averaged" surface topography of the studied markers in a limited section of the membrane. The results obtained are discussed in connection with cooperative properties of the membrane.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 595–603, September–October, 1991. 相似文献
5.
JOÃO BATISTA TAVARES DA SILVA ISAAC ROITMAN 《The Journal of eukaryotic microbiology》1990,37(6):521-523
ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme. 相似文献
6.
Borrelia burgdorferi is a spirochete pathogen transmitted among warm-
blooded hosts by ixodid ticks. Frequency-dependent selection for variant
outer-surface proteins might be expected to arise in this species, since
rare variants are more likely to avoid immune surveillance in previously
infected hosts. We sequenced the OspA and OspB genes of nine North American
strains and compared them with nine strains previously described. For each
gene, the mean number of synonymous substitutions per synonymous site and
the mean number of nonsynonymous substitutions per nonsynonymous site show
only a twofold excess of silent mutations. Synonymous rates vary widely
along the OspB protein. Some regions show a significant excess of silent
substitutions, while divergence in other regions is constrained by biased
base composition or selection. The presence, in antigenically important
regions of the protein, of significant variation among strains, as well as
evidence for recombination among strains, should be considered in attempts
to develop vaccines against this disease.
相似文献
7.
M P ROBINSON G BUTCHER R H CURTIS K G DA VIES K EVANS 《The Annals of applied biology》1993,123(2):337-347
Two monoclonal antibodies, which differentially recognise the two species of potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, are described. They have been shown to have potential for quantification of these two species, recognising proteins of the same molecular weight (34 kD) in both species. Further investigation showed these proteins to have isoelectric points at pH values of 5.7 in G. pallida and 5.9 in G. rostochiensis, in common with the proteins used by Fleming & Marks (1983) to differentiate the species of PCN. They are likely to be structurally very similar, with the same physiological function (and therefore similar concentrations) in the two species. In cross-reactivity tests with a wide range of soil nematode species, the antibodies reacted strongly only with species of the genus Globodera, and thereby confirmed their potential as the basis of a quantitative immunoassay likely to be useful in management of PCN populations. 相似文献
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