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At least 1,621 records · Page 90Linked to original sources
PubMed2005

[Spatial heterogeneity of soil moisture after raining at forest-grassland landscape boundary in hilly area of Loess Plateau].

Soil moisture is a main factor limiting vegetation restoration in semi-arid region. In this paper, the spatial variability of different layers soil moisture after raining at the forest-grassland boundary in hilly area of Loess Plateau were studied by traditional and geostatistical analysis methods. The results showed that the moisture content in surface (0 - 10 cm) and subsurface soil layer (10 - 20 cm) of grassland was higher than that of forestland. The two layers soil moisture content at forest-grassland boundary showed a small variation but an obvious ecological distribution. By using moving split-window techniques, it was obtained that the width of edge influence in surface and subsurface layer was 8 and 6 m, respectively. Geostatistical analyses showed that the spatial distribution of two layers soil moisture had a pure nugget effect in grassland, linear model in forestland, and spherical model in forest-grassland boundary. The spatial heterogeneity of two layers soil moisture was higher at forest-grassland boundary than at forestland and grassland, which had a stronger spatial dependence and autorelation. Kriging maps expressed the spatial structural characters. The distribution of soil moisture in two layers showed a strip shape near forest edge, and a patch shape far from the edge.

China↗
PubMed1992

Cultural barriers associated with large gene frequency differences among Italian populations.

Analysis of geographic variation for eight red cell markers in Italy shows significant spatial structure for most alleles. Effective population sizes estimated from FST values at these loci are much smaller than those predicted from data on consanguineous marriage, suggesting the presence of factors (presumably barriers) that have reduced gene flow and enhanced the evolutionary weight of genetic drift. Most regions of sharp gene frequency change correspond to geographic and linguistic barriers. Two allele frequencies are significantly correlated with measures of linguistic differentiation but not with indexes describing broad religious and social attitudes. The similarity between patterns of genetic and linguistic variation in Italy, also observed in a previous study, suggests that in specific areas linguistic diversity has acted as a biological barrier constraining mating, dispersal, or both. There is no evidence for a similar role of other extent cultural barriers.

Communication Barriers↗
PubMedDate not supplied

[The 4-dimensional spherical color space in the monkey].

Discrimination of colours by macaque rhesus was studied by the method of elaboration of differentiation inhibition of instrumental conditioned responses to colour stimuli. Matrix of probabilities of instrumental reactions to presentation of colour stimuli, the columns of which corresponded to the colours applied, and the lines--to series of experiments with definite reinforced colour--was processed by the method of factor analysis. Four factors describing the used colours in four-dimensional Euclidean space were singled out. Spatial structure of the seven used colours satisfies the equation of four-dimensional sphere. Two first factors are interpreted as colour-opponent red-green and yellow-blue and the third and fourth ones as achromatic light and dark neuronal channels. Perceptive space of colour stimuli based on the data of instrumental behaviour of the monkey corresponds to analogous results obtained by the method of multidimensional scaling of subjective evaluations of super-threshold colour differences for the man.

Animals↗
PubMed1991

[Spatial organization of cytochrome oxidase subunit II].

We have studied the tryptic digestion and cyanogen bromide cleavage of the tritium-labelled subunit II from bovine cytochrome oxidase. Basing on the radioactivity distribution in the peptides obtained we suggest a model for the spatial structure of the title subunit.

Amino Acid Sequence↗
PubMedDate not supplied

[The optical activity of the system cellulose acetate--mesophasogenic solvent in the formation of a lyotropic liquid-crystalline phase].

Vapors of a mesophasogenic solvent (which can form an liquid-crystalline phase with the polymer) have been found to actively affect the spatial structure and optical activity of natural polysaccharides (cellulose acetates). This process is accompanied by variations of the specific optical rotation value [alpha] within wide limits, including the inversion of the sign of [alpha]. The action of vapors obeys the dosage-effect rule, with lower doses producing a stronger effect. It was supposed that this approach can be applied to study the structural peculiarities of biopolymers such as DNA.

Cellulose↗
PubMed2006

[Dynamics of Sophora davidii population in a hilly region closed for thirty years in Loess Plateau].

Taking wild grass ground as the reference, this paper studied the dynamics of Sophora davidii population on the sunny, semi-sunny and semi-shady slopes of hilly region in Loess Plateau after 30 years closed for reforestation, and analyzed the age structure, spatial distribution pattern, life table, and survival curve of the population. The results showed that S. dvidii population in the region belonged to progressive type, with more young and less old individuals. Among the three habits, semi-sunny slope had the highest population density. The survival curve of S. dvidii population was approached to Deevey 11 type. The population pattern was of clustered distribution, with the aggregating intensity increased with age. Water and light were the main environmental factors affecting the recovery and development of S. davidii community. The better recovery of S. davidii population suggested that the measures of closing the land for reforestation were efficient.

China↗
PubMed2006

[Progress of researches on gene function of GSDMDC family].

The GSDMDC family,a novel protein superfamily, includes five members (DFNA5, DFNA5L, GSDM, GSDML and MLZE), all of them containing a Gasdermin domain. Many studies indicated that the GSDMDC family had many important physiological functions in development, tumorigenesis and genetic disease with deafness and hair loss phenotype. Many studies have focused on the DFNA5 gene because it is one of the disease genes of autosomal dominant non-syndromic hearingimpairment and it is also associated with melanoma and breast cancer. But it is still unclear of the molecular mechanism of DFNA5 in the genetic disease and tumorigenesis. And there are also few studies on the spatial structure , interacting proteins and physiological functions of the GSDMDC domain. So there are a lot of works to do for shedding light on the physiological functions and the relevance on genetic disease of the other members of the GSDMDC family.

Animals↗
PubMed2006

[Neighborhood comparison of Cryptomeria fortunei plantation by using different variables].

Neighborhood comparison is defined as the proportion of the nearest greater neighbors to a given reference tree measured by a certain variable. By this way, the dominant differentiation degree of individual wood could be measured well. In this paper, the variables DBH, biomass, canopy breadth, and tree height were used to make the neighborhood comparison of Cryptomeria fortunei plantation in Chongzhou forest farm. The results showed that the neighborhood comparison measured by DBH and biomass had a slight fluctuation range and the highest reliability. Nevertheless, due to the effects of various tree types, the neighborhood comparison measured by canopy breath and tree height was not as reliable as that measured by the former two variables. The average value of the neighborhood comparison measured by DBH and biomass was visibly higher than that by canopy breath and tree height, indicating that the differentiation degree of individual's DBH and biomass was further greater than that of individual's canopy breath and tree height. It was possible that increasing individual's DBH to enhance its biomass, and thus, to achieve its predominance status among individuals' competition was the main strategy of individual's differentiation. Neighborhood comparison should also be taken as an instructive reference in modifying the spatial structure of stand.

Biomass↗
PubMedDate not supplied

[The rule of "one migrant per generation" and genetic differentiation in subdivided populations].

The genetic differentiation in population with migration according island and two-dimensional stepping stone models was studied with simulation methods. It is shown that migration of one or few individuals per generation is insufficient for leveling differences between subpopulations in allele frequencies. Even if migration is estimated as m = 0.5 (exchange of 50 and 500 individuals per generation) statistically significant differences remain at least in the half of populations with insular structure. Spatial heterogeneity disappears completely only if m = 0.7-0.8. In case of two-dimensional step model the level of genetic differentiation is higher and statistically significant heterogeneity remains at all levels of genetic exchange including that which was estimated as m = 1.

Animal Migration↗
PubMedDate not supplied

[Oligomerization of L-asparaginase from Erwinia carotovora].

Bacterial L-asparaginases catalyzing hydrolysis of L-asparagine up to L-aspartate and ammonia, are used in medical practice for treatment of acute lymphoblastic leukemia. The long-term therapy with these preparations is accompanied by a number of side effects, which are attributed to glutaminase activity of L-asparaginase. Substrate specificity and activity of L-asparaginases are directly associated with the process of enzyme oligomerization. It is active only in the tetrameric form as the active sites are located in contact areas between monomers. The present work is devoted to homology modeling of spatial structure of L-asparaginase from Erwinia carotovora, the comparative molecular-graphic analysis of subunits interfaces, as well as development of experimental approach for enzyme oligomerization study. L-asparaginase was immobilized on a CM5 chip surface of optical biosensor Biacore 3000 based on the surface plasmon resonance technology. The dissociation process of enzyme tetrameric complexes up to monomers and subsequent oligomerization process have been registered.

Amino Acid Sequence↗
PubMedDate not supplied

[Heteroassociation of antibiotic norfloxacin with aromatic vitamins in aqueous solution].

The heteroassociation of the antibacterial antibiotic norfloxacin with aromatic vitamins nicotineamide and flavin mononucleotide in aqueous solution has been studied by 1H NMR spectroscopy (503 MHz). Equilibrium constants, induced proton chemical shifts, and the thermodynamic parameters (deltaH, deltaS) of the heteroassociation of molecules were determined from the concentration and temperature dependences of chemical shifts of protons of interacting aromatic molecules. An analysis of the results indicates the formation of heterocomplexes between the molecules of the vitamins and norfloxacin, which is caused by stacking interactions between aromatic chromophores and an additional intermolecular hydrogen bond in the norfloxacin-nicotinamide system. Based on the analysis of induced chemical shifts of protons of molecules, the most probable spatial structures 1:1 of norfloxacin-flavin mononucleitide and norfloxacin-nicotinamide heterocomolexes were determined by the methods of molecular modeling using the X-PLOR program.

Anti-Bacterial Agents↗
PubMed1991

[Socioecological determinants of the risk of accidents in young pedestrians].

We studied all traffic accidents to pedestrians under age 15 which occurred on the Island of Montreal during an eighteen months period. Data were collected from eleven hospitals and completed with accident police records. A spatial quadrat analysis, a Comparative Accident Index, and a comparative analysis of the means of different socio-ecological variables between high and low risk accident areas revealed interesting patterns. The location of traffic accidents is not random but rather presents a particular spatial structure. High risk zones are characterized by dense population, fast-moving traffic, and the absence of parks. Accidents often take place on two-way streets, far from traffic lights, on dry surfaces, in good weather, and with good visibility. The socio-economic status of the victim's family as measured by education, income, and unemployment, tends to be low. More boys than girls are victims. Children are often injured while getting out of a car or crossing unconventionally.

Accidents, Traffic↗
PubMed1991

[Conformational analysis of a segment in bacterioopsin by two-dimensional (1)H-NMR spectroscopy].

The spatial structure of a synthetic peptide, an analogue of the membrane spanning segment B (residues 34-65) of bacterioopsin from Halobacterium halobium, has been refined. Backbone torsion angles were derived from intensities of short-range interproton NOEs. These, together with a complete set of the NOEs integral intensities formed the basis for the three-dimensional structure refinement by the energy minimization with consideration of NOE penalty functions. Analysis indicates the right-handed alpha-helical conformation of segment B extending from Asp-38 to Tyr-64 with a kink of the helical axis (27 degrees) at Pro-50. The most stable region with an average root-mean-square deviation of 0.43 A between the backbone atoms includes residues 42-60 in six energy refined structures. The N-terminal part of segment B (residues 34-37) has no ordered conformation. The inferred structure is in close agreement with the electron cryomicroscopy structure of bacteriorhodopsin, differing from it in conformations of most of the side chains.

Amino Acid Sequence↗
PubMed1991

Contribution of vascular network transformation of the heart to the pathogenesis of ischaemic heart disease. Qualitative changes in myocardial angioarchitectonics.

Based on the idea of segmental arterial vascularization of the heart as well as qualitative assessment of angio- and microangiograms, transformations of intramyocardial vascularization induced by atherosclerotic lesions of the extramyocardial coronary arteries have been presented. Using various angiographic methods, vascularization was evaluated in 58 cases of acute and chronic ischaemic heart disease. Attention was paid to transformations of spatial structure of the vascular network and it was found that some morphological forms of ischaemic heart disease are characterized by a progressive remodelling of the peripheral vascular bed microangioarchitectonics which seems to be of major importance for exacerbation pathomechanisms. Two group of angiographic changes in the ischaemic myocardium have been distinguished, which consisted in disturbances of the segmental pattern of myocardial vascularization and disturbances of the intrasegmental structure of the arterial bundles and capillary vessels.

Adult↗
PubMed1991

Spatial differentiation of RH and GM haplotype frequencies in Sub-Saharan Africa and its relation to linguistic affinities.

This study analyzes patterns of variation in eight GM and seven Rhesus (RH) haplotypes across sub-Saharan Africa. We examine the concordance with genetic patterns of both geographic and language-family relationships by spatial analysis and ordination techniques. The genetic variation has significant spatial structure, but positive autocorrelation declines neither asymptotically nor proportionally with increasing distance. Evidently, neither isolation by distance with increasing distance. Evidently, neither isolation by distance nor clinical migration-selection models account for the observed genetic structure. Language-family relationship is the best predictor of genetic relationship and may reflect historic migrations and expansions of ethnically different peoples within sub-Saharan Africa. Yet the greatest part of the genetic variance remains unexplained by the models we have tested.

Africa, Central↗
PubMed1991

Modification of the cleavage activation of the influenza virus hemagglutinin by site-specific mutagenesis.

Factors determining cleavability of influenza virus hemagglutinin which is activated by ubiquitous cellular endoproteases were analysed by carrying out site-directed mutagenesis on the cloned hemaglutinin genes of strains A/FPV/Rostock/34 (subtype H7) and A/Port Chalmers/1/73 (subtype H3). Substitutions at the cleavage site of the H7 hemagglutinin indicate that the tetrapeptide Arg-X-Lys/Arg-Arg is the minimal consensus sequence recognized by the ubiquitous proteases. The H3 hemagglutinin also became susceptible to these enzymes, when additional arginines were inserted at the cleavage site. Three arginines were sufficient, when the carbohydrate was removed, whereas four additional arginines are needed when this carbohydrate was present, indicating that the accessibility of the cleavage motif is important for the protease. The appropriate localization of the basic cleavage motif within the amino acid sequence and the spatial structure of the hemagglutinin precursor is an additional prerequisite for cleavage.

Amino Acid Sequence↗
PubMedDate not supplied

[Polarity and hydropathic properties of natural amino acids].

A new classification of amino acids according to their polarity and symmetric location in the spatial structure of the genetic code is suggested. The polar amino acids are: R, S (codons AGC and AGU), K, N, Q, H, W, C, Y, G, E, D; apolar ones are: T, M, I, P, L, S (codons UCN). Polar and apolar amino acids are grouped into three families whose members possess complementarity with respect to the symmetric structure of the genetic code. Interaction of these complementary polar and apolar amino acids encodes formation of the space structures and ligand-receptor complexes of proteins. Correlation between the polar and hydropathic properties of amino acids is investigated. Normalization of 38 hydrophobicity scales of natural amino acids is carried out. A discrepancy between structures of polar/hydrophilic and apolar/hydrophobic groups of amino acids is demonstrated. According to the signature principle this discrepancy is due to different properties of amino acid side radicals which, in turn, depend on the second component of the reaction and on environmental conditions.

Amino Acids↗
PubMed1990

[Conformation analysis of carbohydrate chains of glycoconjugates].

A problem of conformations of carbohydrate chains of glycoconjugates-glycoproteins and glycolipids--is reviewed. Experimental data (NMR, X-Ray) and theoretical conformational analysis data are discussed. Spatial structures of O-linked oligosaccharides from blood-group glycoproteins, N-linked oligosaccharides of different types (oligomannosidic, complex, hybrid, bisect) and carbohydrate chains of glycosphingolipids are considered.

Carbohydrate Conformation↗