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Tatiana Sitnikova Ellinor Michel Yulia Tulupova Igor Khanaev Valentina Parfenova Larisa Prozorova 《Symbiosis (Philadelphia, Pa.)》2012,56(3):103-110
We describe the first records of spirochetes in the gut of fourteen species of continental gastropods from a range of habitats and representing six families (Amnicolidae, Baicaliidae, Bithyniidae, Pyrgulidae, Lithoglyphidae and Benedictiidae). The bacteria were mainly found in the crystalline style sac, as has been reported in marine bivalves. The surveyed habitats include water bodies in North America and Eurasia, including deep water hydrothermal vent and gas hydrate zones in Lake Baikal. Spirochetes were present both in mature and young snails, but were not detected in embryos before hatching, indicating lateral transfer. The surveyed gastropods range in trophic strategy, including phyto-, detrito- and bacteriophagous grazers and filter feeders. Our results indicate that spirochetes are commensal in the surveyed gastropods with potential limited benefit and no detriment to the host animal. We suggest that the specialized internal habitat of the crystalline style sac in molluscs is likely to reveal unrecognized spirochete diversity that will shed new light on gastropod trophic ecology and spirochete diversity. 相似文献
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Interior-branch and bootstrap tests of phylogenetic trees 总被引:19,自引:3,他引:16
We have compared statistical properties of the interior-branch and
bootstrap tests of phylogenetic trees when the neighbor-joining tree-
building method is used. For each interior branch of a predetermined
topology, the interior-branch and bootstrap tests provide the confidence
values, PC and PB, respectively, that indicate the extent of statistical
support of the sequence cluster generated by the branch. In phylogenetic
analysis these two values are often interpreted in the same way, and if PC
and PB are high (say, > or = 0.95), the sequence cluster is regarded as
reliable. We have shown that PC is in fact the complement of the P-value
used in the standard statistical test, but PB is not. Actually, the
bootstrap test usually underestimates the extent of statistical support of
species clusters. The relationship between the confidence values obtained
by the two tests varies with both the topology and expected branch lengths
of the true (model) tree. The most conspicuous difference between PC and PB
is observed when the true tree is starlike, and there is a tendency for the
difference to increase as the number of sequences in the tree increases.
The reason for this is that the bootstrap test tends to become
progressively more conservative as the number of sequences in the tree
increases. Unlike the bootstrap, the interior-branch test has the same
statistical properties irrespective of the number of sequences used when a
predetermined tree is considered. Therefore, the interior-branch test
appears to be preferable to the bootstrap test as long as unbiased
estimators of evolutionary distances are used. However, when the
interior-branch is applied to a tree estimated from a given data set, PC
may give an overestimate of statistical confidence. For this case, we
developed a method for computing a modified version (P'C) of the PC value
and showed that this P'C tends to give a conservative estimate of
statistical confidence, though it is not as conservative as PB. In this
paper we have introduced a model in which evolutionary distances between
sequences follow a multivariate normal distribution. This model allowed us
to study the relationships between the two tests analytically.
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I E Kudriashov I V Kudriashova E Iu Sitnikova V V Raevski? 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1999,49(4):629-634
Hippocampal slices from 15-20-day-old Wistar rats were used to study the development of some features of synaptic transmission in hippocampus and the influence of partial limitation of the sensory inflow in the early ontogeny of this transmission. The dynamics of population spike changes was observed in the CA1 hippocampal field in response to stimulation of Schaffer collaterals. The early ontogenetic limitation of the sensory inflow was accomplished by cutting n. medianus on the 13th day. Between the 15th and 20th days, the dynamics of the population spike amplitude increase in the control and experimental animals was similar, however, the response amplitude of the control rats remained higher than in the experimental animals throughout the whole period of observation. It is suggested that the partial limitation of sensory inflow from a forelimb at the early stages of the ontogeny alters the formation of synaptic transmission in hippocampus. 相似文献
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Bj?rn Stelbrink Alena A. Shirokaya Catharina Clewing Tatiana Y. Sitnikova Larisa A. Prozorova Christian Albrecht 《Biology letters》2015,11(7)
Lake Baikal is the deepest, oldest and most speciose ancient lake in the world. The lake is characterized by high levels of molluscan species richness and endemicity, including the limpet family Acroloxidae with 25 endemic species. Members of this group generally inhabit the littoral zone, but have been recently found in the abyssal zone at hydrothermal vents and oil-seeps. Here, we use mitochondrial and nuclear data to provide a first molecular phylogeny of the Lake Baikal limpet radiation, and to date the beginning of intra-lacustrine diversification. Divergence time estimates suggest a considerably younger age for the species flock compared with lake age estimates, and the beginning of extensive diversification is possibly related to rapid deepening and cooling during rifting. Phylogenetic relationships and divergence time estimates do not clearly indicate when exactly the abyssal was colonized but suggest a timeframe coincident with the formation of the abyssal in the northern basin (Middle to Late Pleistocene). 相似文献
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Ivanova AS Sitnikova OG Nazarov SB 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2012,98(3):388-394
The activity of peritoneal macrophages, nitrotyrosine concentration and condition of free radical processes in normal pregnancy in white rats against the background of the introduction of donator (sodium nitrite) and inhibitor (Nw-nitro-L-arginine methyl ester) of nitric oxide was studied. During normal pregnancy in animals, nitrotyrosine concentration, the activity of free radical processes, and phagocytosis increase. With the introduction of nitric oxide donator, NO level increases and after the injection of antagonist of nitric oxide it is reduced. These changes are accompanied by increased lipid peroxidation and activation of phagocytic activity of macrophages. 相似文献
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The gene families encoding the immunoglobulin variable regions of heavy
(VH) and light (VL) chains in vertebrates are composed of many genes.
However, the gene number and the extent of diversity among VH and VL gene
copies vary with species. To examine the causes of this variation and the
evolutionary forces for these multigene families, we conducted a
phylogenetic analysis of VH and VL genes from the species of amniotes. The
results of our analysis showed that for each species, VH and VL genes have
the same pattern of clustering in the trees, and, according to this
clustering pattern, the species can be divided into two groups. In the
first group of species (humans and mice), VH and VL genes were extensively
intermingled with genes from other organisms; in the second group of
species (chickens, rabbits, cattle, sheep, swine, and horses), the genes
tended to form clusters within the same group of organisms. These results
suggest that the VH and VL multigene families have evolved in the same
fashion: they have undergone coordinated contraction and expansion of gene
repertoires such that each group of organisms is characterized by a certain
level of diversity of VH and VL genes. The extent of diversity among copies
of VH and VL genes in each species is related to the mechanism of
generation of antibody variety. In humans and mice, DNA rearrangement of
immunoglobulin variable, diversity, and joining-segment genes is a main
source of antibody diversity, whereas in chickens, rabbits, cattle, sheep,
swine, and horses, somatic hypermutation and somatic gene conversion play
important roles. The evolutionary pattern of VH and VL multigene families
is consistent with the birth-and-death model of evolution, yet different
levels of diversifying selection seem to operate in the VH and VL genes of
these two groups of species.
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It is suggested that existence of "dwarfs" and "giants" among Baikal gastropods depends on several factors. "Dwarfs" occurs in habitats 1) where sedimentation rate is low and thick silt layer is absent (the small shell without long periostracal nodules does not allow the animal to stay on the soft sediment surface; 2) where there is hard substratum suitable for laying egg capsules; 3) where there is intensive water exchange assuring supply of food (detritus and phytoplankton). Distribution of "giants" capable to lay egg capsules on their own shells is not confined by availability of hard substratum. They dwell on soft sediments because they have large light shell with high whorl allowing them to migrate on silt surface. "Giants" live in places with high sedimentation rates, constant supply of food (including died fish), and higher degree of water mineralization. "Giants" and "dwarfs" inhabit only oxidized substrates. Neither "giants", nor "dwarfs" inhabit the flat bottom of Baikal. "Giants" occur on near-slope parts of the lake, while the "dwarfs" prefer underwater elevations. 相似文献