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At least 307 records · Page 17Linked to original sources
PubMed2001

Microsatellite analysis of the Queensland fruit fly Bactrocera tryoni (Diptera: Tephritidae) indicates spatial structuring: implications for population control.

The population structure of a tephritid pest species, the Queensland fruit fly Bactrocera tryoni (Froggatt), has been analysed over a five year period (1994-1998), using six microsatellites. Adult fly samples were collected to cover most regions of eastern and central Australia where the flies are regularly found. Tests for heterogeneity indicated that flies within geographically defined regions were homogeneous. The samples were allocated into five regions, including one very large region, Queensland, which encompasses that portion of the fly's range where breeding can occur year-round. With one exception, the collections from different regions were homogeneous between years, showing a fairly static distribution of the species. However, differences between regions were highly significant. The one case of a change in frequency between years indicated a gradual replacement of flies in a marginal region by flies from the main part of the range. The finding of stability in the distribution of a highly mobile insect is of interest, potentially also for other species which have expanded beyond their native range. It is argued that a contributing reason for this stability may be adaptation to different climatic regimes, and that strategies for control based on this hypothesis afford a reasonable chance of success.

Animals↗
PubMedDate not supplied

[Differences in the spatial structure of an envelope protein from tobacco mosaic virus and its mutant, detected by tritium planigraphy].

Mutant ts21-66 of the tobacco mosaic virus (TMV) differs from the wild-type TMV-U1 by two mutations (Ile-21-->Thr and Asp-66-->Gly) in the coat protein (CP) gene and in symptoms produced in infected N' plants. The CP structure in TMV-U1 and ts21-66 virions was probed by tritium planigraphy. Compared with the wild-type CP, labeling of the N-terminal region of mutant CP was half as high and suggested its greater shielding. A role of this CP region in virus interactions with the N' resistance system is discussed.

Amino Acid Sequence↗
PubMedDate not supplied

[Ontogeny of different life forms of plants and specific features of age and spatial structure of their populations].

Materials have been generalized that were accumulated in population-ontogenetic studies of plants and leading features of the ontogeny of plants have been noted that determine specific structural features of their populations. The described patterns allowed the authors to develop simulation models of plant population dynamics. The results of simulation are provided, and they are compared to the empirical data. Problems have been considered that concern the influence of specific features of development of different plant biomorphs on the genetic structure of populations and biocoenotic processes.

Biological Evolution↗
PubMedDate not supplied

[Study of the spatial structure of globular proteins by tritium planigraphy. Short peptides as a model of a fully extended polypeptide chain].

The interaction of tritium atoms with amino acid residue from short peptides was studied. The short peptides were considered as a model of extended polypeptides chain. Every residue in this chain has 100% steric accessibility. It was shown that: 1. The linear correlation exists between the residue accessible surface area (that is composed of hydrocarbon fragments) and the amount of tritium interacting with this residue; 2. The presence of the tertiary carbon atom in the residue side chain influences on the reactivity of this residue; 3. The N- or C-terminal residue presence does not influences on the possibility of interaction of this residue with tritium atoms. The obtained reactivity scale of amino acid residues is compared with other theoretical and experimental data.

Amino Acids↗
PubMed1992

[Folding of peptide chains during formation of the spatial structure of protein molecules is determined by the code of amino acid codon roots].

Basing on the analysis of a large number of protein sequences (Cserzo M., Simon I., 1989), the structure of the amino acid nearest neighbour pair whose occurrence has a maximal positive deviation from the mean statistical value, is shown to correspond in most cases to the code of the amino acid codon roots. It reveals particularly amino acid pairs in n and n+5 positions of polypeptide chains. Amino acids belonging to A/U family contribute mostly to the folding of peptide chains.

Amino Acids↗
PubMed1992

Analysis of spatial structure of thymocytes and of their contacts with thymic non-lymphoid cells.

The study aimed et determining morphological relations between thymic cells and thymocytes. The studies were performed on 16 days old rats of Wistar strain. The material was processed for ultrastructural studies in a routine manner. For 50 thymocytes computer reconstruction was performed which allowed to define cell volume, volume of cell nucleus and of condensed chromatin. The value characterizing three-dimensional morphology of thymocytes provided grounds for analysis using graph theory. The stereological methods allowed to examine microarchitecture of individual thymic zones. Thymocytes in contact with dendritic cells or with macrophages were found to differ in morphology from thymocytes with no such contacts. The results indicated direct effect of dendritic cells and of macrophages on thymocytes.

Animals↗
PubMedDate not supplied

[De novo proteins with a given spatial structure: new approaches to design and analysis].

Based on the molecular theory of protein structure the de novo protein was designed in order to obtain the tertiary fold which has not yet been observed in natural proteins, namely four-stranded antiparallel beta-sheet covered by two alpha-helixes. The gene coding for this protein (named albebetin) was chemically synthesized, cloned in plasmid with SP6 phage promoter and expressed in mRNA-dependent cell-free translation system. An approach was developed to study albebetin using only nanogram amounts of radio labelled protein without previous purification. The preliminary analysis of its structure by gel-filtration, urea-gradient electrophoresis and limited proteolysis revealed compactness and stability of the de novo protein.

Amino Acid Sequence↗
PubMed2005

Evolutionary dynamics of a spatially structured host-parasite association: Drosophila innubila and male-killing Wolbachia.

The mode and tempo of host-parasite evolution depend on population structure and history and the strength of selection that the species exert on each other. Here we genetically and epidemiologically characterize populations of the mycophagous fly Drosophila innubila and its male-killing Wolbachia endosymbiont, with the aim of integrating the local through global nature of this association. Drosophila innubila inhabit the forested "sky island" regions of the of the southwestern United States and northern Mexico, where its distribution is highly fragmented. We examine geographically isolated sky island populations of D. innubila, surveying the frequency and expression of Wolbachia infection as well as the distribution of genetic variation within and among populations of the host and parasite. In all populations, Wolbachia infection is associated with virtually complete male-killing, thus providing no evidence for the evolution of population-specific interaction phenotypes or local resistance. Although Wolbachia infection occurs in each of the main populations, there is variation among populations in the prevalence of infection and the resulting population-level sex ratio of D. innubila. Among these populations, the nuclear genes of D. innubila show moderate, though significant, differentiation. In contrast, the host mitochondrial DNA (mtDNA), which shares transmission with Wolbachia, exhibits substantially greater geographic differentiation, even after accounting for differences in transmission between nuclear and mitochondrial genes. We suggest that this pattern is caused by local Wolbachia--but not D. innubila--fluctuations in prevalence that increase the severity of drift experienced only by the mtDNA. Overall, our data suggest that the association between D. innubila and male-killing Wolbachia is ecologically dynamic within local populations, but evolutionarily coherent across the species as a whole.

Analysis of Variance↗
PubMed1991

[The genetic-demographic approach in anthropological research. IX. The spatial structure of Khakass populations].

The rural population of Khakassia is characterized by genetic isolation due to marital traditions and ethnic-territorial subdivisions. The type of Khakass settling limits the choice of a marital partner within the territory occupied by one ethnographic group, preventing an active migration of alleles from one population to another. Formation of local zonal anthropologic type (84% of marital couples) occurs on the territory approximately equal to the area of one administrative district.

Alleles↗