The spatial variability of the intensity of the bioluminescence field in coastal waters of the Crimean Peninsula in the spring period

The spatial variability of the vertical structure of bioluminescence intensity has been studied along the Crimean coast in the spring period. The location of a layer with a high intensity of bioluminescence has been determined and its dependence on hydrological characteristics and thermohaline structure of waters is shown. Structurization of the spatial variability of bioluminescence intensity has been made. Four regions that are distinguished by the pattern of the vertical distribution of the bioluminescence intensity have been distinguished in coastal waters of the Crimean Peninsula.     

Removing the confounding effect of habitat specialization reveals the stabilizing contribution of diversity to species variability

Earlier studies have found that diversity, S, stabilizes the relative variability of combined biomass or abundance of species making up a community. However, the effect of S on variability of constituent species has been elusive. We hypothesize that the proportion of specialists increases with S and, because specialists are more variable, this shift in composition will mask the stabilizing effect of S on populations of species making up a community. The test uses data on variability and ecological specialization of species in 49 natural rock pool invertebrate communities. Initial analyses produced inconclusive results similar to earlier studies. However, when variability owing to species' specialization was factored out, S reduced species' abundance variability, although not in all communities. Our study explains why the stabilizing effect of diversity on populations has not been found earlier.     

Theoretical and clinical assessment of the sensitivity of heart rate variability indices

The application of modern methods of mathematical processing of non-stationary quasi-periodic data to the analysis of heart-rate variability is considered. Methods for the assessment of new parameters in non-linear variability analysis are described in detail. Mathematical models of heart rhythm are developed with the presence of various noise processes taken into account. A model of the state of the cardiovascular system based on the analysis of heart-rate variability has been developed. A theoretical estimate of the sensitivity of heart-rate variability indices to changes in the state of the cardiovascular system has been obtained for model data. Clinical studies of the parameters of heart-rate variability included in the analysis have been performed within the framework of cardiological screening for coronary heart disease.     

Use of Ranks in Comparisons of Variability in the Non-Normal Populations

A method of analysis for comparing the variability of two samples drawn from two populations has been developed. The method is also suitable for the nonnumeric form of data. A test based on ordered observations for testing the null hypothesis of equality of two variances has been given. The test statistic is a function of the sum of ranks assigned to smaller size sample. Ranking procedure has been modified to depict the variability in the data by the sum of ranks. The null distribution of the test-statistic has been worked out for small samples and it turns out to be chi-square distribution for large samples. The analytical procedure has been explained by a numerical example on the productivity and production of rice and wheat in India from 1950–51 to 1983–84.     

Distinct features of intraspecific and intrapopulation variability of the skull size in the red fox

The range of chronographic variability of the average size of the skull in the red fox (data collected by the authors) from a compact area in the Middle Urals has been assessed for a 30-year period, and the results obtained have been compared with the published data on the geographical variability within the vast species range. The range of changes of the average dimensions of the skull over time spanned almost the entire range of geographical variability. Therefore, the problem of search for factors that determine the morphological diversity arises.     

An analysis of the viability of clonal plants based on a morphometric approach (exemplified by Calamagrostis langsdorffii)

Clonal plants viability has been studied on the basis of morphostructure variability of clone modules. The research has been carried out on the Calamagrostis langsdorffii (Poaceae) in the flood-lands of the Amur River Basin (Khabarovsk Territory). Plants vitality has been evaluated by 26 morphometric parameters, characterizing their growth, productivity and reproduction. Clone ramets differed from each other by considerable variability and plasticity. Significant changes of all morphometric parameters according to humidity and alluvion gradients were very specific. Reproductive parameters were the most stable ones. Parameters of growth and dimension were characterised by increased variability. Wide reaction of morphometric parameters of C. langsdorffii to the changes in ecological conditions can be considered as an adaptation to the existence in dynamical environment of the flood-land.     

Extensive nucleotide variability within a 370 kb sequence from the central region of the major histocompatibility complex

The recent availability of the genomic sequence spanning the central and telomeric end of the major histocompatibility complex (MHC) has allowed a detailed study of its organisation, gene content and level of nucleotide variability. Previous analyses of nucleotide variability in the MHC have focused on the coding regions of the human leukocyte antigen (HLA) Class I and II genes. Non-coding nucleotide variability has been considered a by-product of exonic diversity. However, with the advent of genomic sequencing, the extent of non-coding nucleotide variability within the MHC has just begun to be appreciated. In this study, we compared different human haplotypes in 370 kb of sequence in the central region of the MHC to show the following: 1. unusually high levels of non-coding nucleotide variability, up to 80 times greater than elsewhere in the genome; 2. non-coding nucleotide variability greater than 1% at nucleotide sites distant to the Class I genes; 3. nucleotide variability greater than 1% maintained over regions containing highly linked loci; and 4. distinct troughs and peaks in the level of nucleotide variability. We will discuss these observations in relation to a possible role of nucleotide variability in the organisation of the MHC.     

Diffusion of the second messengers in the cytoplasm acts as a variability suppressor of the single photon response in vertebrate phototransduction

The single photon response in vertebrate phototransduction is highly reproducible despite a number of random components of the activation cascade, including the random activation site, the random walk of an activated receptor, and its quenching in a random number of steps. Here we use a previously generated and tested spatiotemporal mathematical and computational model to identify possible mechanisms of variability reduction. The model permits one to separate the process into modules, and to analyze their impact separately. We show that the activation cascade is responsible for generation of variability, whereas diffusion of the second messengers is responsible for its suppression. Randomness of the activation site contributes at early times to the coefficient of variation of the photoresponse, whereas the Brownian path of a photoisomerized rhodopsin (Rh*) has a negligible effect. The major driver of variability is the turnoff mechanism of Rh*, which occurs essentially within the first 2-4 phosphorylated states of Rh*. Theoretically increasing the number of steps to quenching does not significantly decrease the corresponding coefficient of variation of the effector, in agreement with the biochemical limitations on the phosphorylated states of the receptor. Diffusion of the second messengers in the cytosol acts as a suppressor of the variability generated by the activation cascade. Calcium feedback has a negligible regulatory effect on the photocurrent variability. A comparative variability analysis has been conducted for the phototransduction in mouse and salamander, including a study of the effects of their anatomical differences such as incisures and photoreceptors geometry on variability generation and suppression.     

Effects of black mustard population size on the taxonomic composition of pollinators

In plant species that are pollinated by a variety of animal species, spatial and temporal variability in the taxonomic composition of those pollinators may cause spatial and temporal variability in selection on floral traits. While temporal variation in pollinator composition has been widely reported, spatial variability, particularly on a local scale, has been studied less frequently; nevertheless, available evidence suggests that local spatial variability may be a widespread feature of plant-pollinator interactions. In addition, the causes of this spatial variability are poorly known. This study was undertaken to quantify variability in the taxonomic composition of pollinators visiting local populations of black mustard, Brassica nigra, and to determine some of the causes of this variability. Simultaneous observations were conducted in seven pairs of black mustard populations. The members of each pair were in close spatial proximity but differed in number of plants. Larger plant populations were visited by significantly greater numbers of honey bees and significantly fewer small bees than small populations on a per-plant basis. There was also a trend toward greater syrphid fly visitation in small populations. The increased numbers of honey bees at large plant populations is probably due to their ability to recruit long distances to the most rewarding plant populations. The lower number of small bees at large plant populations may be due to competition from honey bees and/or spreading a constant number of small bees over the larger number of plants in large populations.This paper is dedicated to the memory of George Eickwort     

Comparative analysis of genetic variation in two groups of Crimean pine trees with different levels of tolerance to industrial pollutants in the environs of the city of Mariupol

The comparative analysis of genetic variability of two groups of young Pinus pallasiana D. Don. trees with different degree of tolerance to industrial pollution, defined in plantations of Mariupol and its environs, has been performed on the basis of polymorphism investigations in 20 isoenzyme loci controlling 9 enzyme systems. In these groups of plants with high and low quantity of needles on the growing sprouts differences in the levels of genetic variability, as to average criteria, have not been found.     

Effects of estradiol and progesterone on the variability of the micronucleus assay

To investigate chromosomal radiosensitivity of lymphocytes the micronucleus (MN) assay has been used for many years. The results of these studies suggest the use of the MN assay as a biomarker for cancer predisposition. However, the MN assay has still some limitations associated with the reproducibility and sensitivity. Especially a high intra-individual variability has been observed. An explanation for this high intra-individual variability is not yet available. In literature it is suggested that the high variability among females is attributable to hormonal status. In this study we investigated if the high intra-individual variability in micronucleus formation in lymphocytes of females after in vitro exposure to ionising radiation is caused by variations in hormone levels of estradiol (E2) and progesterone (PROG). For this, the MN assay was performed on blood samples of 18 healthy women during 7 consecutive weeks while the estradiol and progesterone levels were determined at the same time. The MN assay was also examined in cultures of isolated blood lymphocytes with estradiol or progesterone levels added in vitro. The results demonstrated that estradiol and progesterone levels have no influence on the variations in radiation-induced MN yields observed in blood samples of healthy women. These conclusions were confirmed by the "in vitro" experiments as no correlation between the MN yields and the concentrations of hormones (estradiol or progesterone) added in vitro to isolated lymphocytes cultures was observed.     

DNA polymorphism in the genus Brucella

The genus Brucella has been described as consisting of six species, three of them including several biovars, which display a high degree of DNA homology by DNA-DNA hybridization. However, DNA polymorphism able to differentiate the six Brucella species and some of their biovars has been shown to exist. This work reviews the DNA variability in the genus Brucella and discusses the relationships between its members according to this genetic variability and a proposal for their evolution based on genetic diversity of the omp2 locus.     

Analysis of the nonlinear heart rate dynamics by two-contour mathematical model

Using a two-contour mathematical model, changes in the degree of heart rate variability induced by an increased extracardial impulsation in the sinoatrial node have been studied. The model is based on quantitative characteristics of impulse conduction in the cardiac conduction system. A mathematical and computer modeling revealed the following three regimes of heart rate variability: linear dynamics, the 1st-degree chaos, and the 2nd-degree chaos. Transitions between these regimes have been studied. A comparative analysis of the one- and two-contour models of heart rate regulation has been performed.     

Nonstationarity and duration of the R-R-segment in the diagnostics of functional states of operators

The effect of the nonstationarity of R-R interval series on the diagnostics of functional states of operators has been analyzed. The functional states were diagnosed by means of a factor model of heart rate variability. The heart rate was recorded in the supine position, before the performance of an important task, and after its completion. A high resistance of the diagnostics of functional states to nonstationarity was found for all periods. Indices of heart rate variability resistant to nonstationarity were defined. Also, the effect of R-R segment duration on functional states diagnostics was explored. The results obtained allow one to conclude that the diagnostics of functional states based on the three-factor model of heart rate variability can be used on short segments within a range of 256 divided 32 R-R intervals. The indices of the factor model of heart rate variability must be normalized for corresponding R-R segment duration before diagnostics. In addition, the effect of the duration of R-R segment on the indices of heart rate variability was analyzed for different functional states. The indices resistant to the duration of R-R segments and conditions necessary for heart rate recording were defined.     

Variability of the mitochondrial genome in mammals at the inter-species/intra-species boundary

Genomic variations represent the molecular basis of the biodiversity of living organisms on which selection operates to generate evolution. In eukaryotes, genomic variability can be experienced in both nuclear and organellar, i.e. mitochondrial and plastid (where present), genomes, which can follow completely different evolution pathways, as revealed by comparative genomics analyses. In Metazoa, for which a substantial number of complete genome sequences are available (nuclear, but mainly mitochondrial), we are just starting to grasp the selective pressures operating on some basic features of the genome as a whole. In this brief review, we discuss the variability of the mitochondrial metazoan genome, with particular reference to mitochondrial DNA in mammals. In light of the recent assumption that a small segment of mitochondrial DNA may be used, particularly in Metazoa, as a species marker, some data on mitochondrial gene variability at the inter-species/intra-species boundary are reported. Intra-species variability has been evaluated in four mammalian species, Homo sapiens, Bos taurus, Sus scrofa and Canis familiaris, whereas the relationship between intra- and inter-species variability has been investigated in Bos taurus and Bos indicus.     

血压波动性对主动脉夹层发生发展影响的研究进展

高血压病是严重威胁人类健康的一类疾病。近年来研究表明,血压波动对于靶器官的损伤较高血压本身更大。主动脉夹层是一种与高血压密切相关的疾病。近年来,主动脉夹层的发生发展与血压波动的关系,越来越受到关注。血压波动性可造成内膜损伤和中膜层退行性变,从而在局部影响主动脉夹层的发生;还可通过免疫反应,炎性变化等全身因素造成主动脉夹层的发生。血压波动性在已发生主动脉夹层的患者中也是影响预后的重要因素。本文主要介绍血压波动性的分类和测量方法,以及对主动脉夹层发生发展影响的研究进展,旨在为临床医生进行主动脉夹层与血压波动性的关系研究提供参考。     

Structural bases of the plasticity of the nervous system

The present state of morphological study of variability in the nervous elements under conditions of adaptive change under the influence of afferent effects, age changes during different periods of ontogenesis, under conditions of de- and regeneration of synapses have been considered. A question on correlation between structure and the function of synapses during the change has been analysed. The tasks of subsequent study of this problem have been outlined.     

Hsp90 inhibition and the expression of phenotypic variability in the rainforest species Drosophila birchii

Recently a heat shock protein (Hsp90) has been implicated as controlling the expression of cryptic genetic variation through buffering developmental processes. The release of variability in canalized characters following Hsp90 inhibition has been established in model species including Drosophila melanogaster and Arabidopsis thaliana , but has not yet been examined in species with limited distributions. To test if Hsp90 has a role in releasing phenotypic variation in rainforest Drosophila species, developing larvae from a large (> 1000 individuals) outbred population of Drosophila birchii were treated with the Hsp90 inhibitors geldanamycin and radicicol, and morphological traits, desiccation resistance, and life-history traits were measured. The means of all traits were influenced by inhibition. Although only the phenotypic variances of two canalized bristle traits were affected consistently, variability for two of the continuously varying traits (fecundity and development time) were also affected, albeit inconsistently. There was also no effect of Hsp90 inhibition on the developmental stability of the morphological traits as measured by fluctuating asymmetry. Hsp90 inhibition did not increase phenotypic variability in desiccation resistance, a trait previously shown to represent an evolutionary limit in this species. These results question the extent to which Hsp90 buffers variation for both quantitative and discrete traits, and highlight the need for further empirical studies to determine the involvement of Hsp90 in canalization and developmental stability. Nevertheless the results demonstrated increased variability in canalized traits, consistent with observations in model systems. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 92 , 457–465.     

Determination of the phenotypic variability of the autoantibody level in man]

The principles of determination of phenotypic variability of the autoantibodies levels in man were investigated using twin and cluster analyses. The component difference of common phenotypic variance of immunological traits considered has been shown. The component mentioned depended on the molecular origin of the autoantigen.     

The morphological variability of the maritae of Phyllodistomum umblae and Phyllodistomum folium (Trematoda: Gorgoderidae) from fish in the Lake Baikal basin

The host variability of adults of Phyllodistomum umblae and P. folium in fishes of the Baikal region has been studied. The absence of considerable geographical variability of P. umblae in Coregonus lavaretus (Lake Baikal, Lake Storsj?n in Sweden) has been shown. The complexes of most stable (the size of acetabulum and eggs, location of acetabulum, ovary and vitelline bodies) and variable (the distance from oral sucker to intestinal bifurcation, distance from intestinal back edge to body end, width of seminal vesicle) features of trematodes of the genus Phyllodistomum have been determined.