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Biomedical subjects

G Livshits

Publications and source records attributed to G Livshits.

At least 73 records · Page 4Linked to original sources
PubMed1988

Environmental and sibling resemblance components of variance and covariance in traits of early child development.

The multiple regression analyses were undertaken to elucidate the significance and relative importance of different potential determinants of several child development traits (i.e. age at which child 1. turns himself over; 2. sits up; 3. stands up; 4. walks, and 5. cuts his first tooth). Despite the fact that we used a relatively wide gamut of potential determinants (such as parental age, geographic origin, occupation, current residence, or family size) of trait variability, the results of multiple regression analysis (N = 300 families) indicate an almost complete absence of significant factors and studied variables of development. Sibling resemblance component of variance and covariance for five mentioned traits of development and some morphological characters (weight, length and head circumference at day of birth and at 16 months) were studied in 66 families. The transmissibility ("heritability") values for the development traits were small, ranging from 0 ("Turn") to 0.42 ("Walked"). The Findings suggest that there are significant inverse relationship between some of the developmental traits and inborn morphological characters.

Body Height↗
PubMed1987

Dermatoglyphic traits as possible markers of developmental processes in humans.

Here we provide data on the relationship in variability between common anthropometric characters (stature, interocular diameter, mesosternal chest circumference, bi-trochanteric diameter, and palm length) and dermatoglyphic traits in groups of young healthy individuals. Our working hypothesis was that quantitative variables of fluctuating asymmetry, diversity, and variability involving dermatoglyphic traits, will be higher in more homozygous groups than in heterozygous ones. It was found that individuals who were in the center (average +/- 0.67 SD) of the morphological trait distribution (and therefore perhaps more heterozygous at loci determining the aforementioned morphological traits), have reduced fluctuating asymmetry in their ridge counts (RC). These heterozygous individuals tended to have lower values of the RC-diversity-indices and the Shanon information-measures of discrete digital patterns. On the basis of the present results and a large body of literature data, the use of dermatoglyphic traits as "markers" of developmental processes are discussed.

Adolescent↗
PubMed1987

Sibling similarity in development of covariation among physical traits in early childhood.

We studied the sibling similarity in development of covariation among body size characters (body weight (W), body length (S) and head circumference (HC) in Tel Aviv infants from birth up to 2 years of age. We investigated the effects of parental geographic origin, profession, age, current residence, and of family size. Multiple regression analysis with "dummy" procedure established that none of these variables had any significant effect on the aforementioned anthropometric traits. The matrices of phenotypic and genetic correlations, based on sibling similarity data, among age-specific W, S, and HC (measured for 12 different ages) were subjected to principal component analysis in order to elucidate patterns over the age groups. The patterns of both analyses, phenotypic and genetic, were quite similar: one factor in each (first genetic and second phenotypic) had a high positive correlation with early, first 2-3 months of life, W, S, and HC. Three other extracted factors correlated strongly, each with late W, S, and HC, respectively. The results of additional principal component analyses of age-specific W, S, and HC matrices separately, indicate the possibility of existence of two genetic subsystems, the first determining early postnatal stages of human ontogeny, and the second, later phases of child development.

Body Height↗
PubMed1986

Anthropometric multivariate structure and dermatoglyphic peculiarities in biochemically and morphologically different heterozygous groups.

Multivariate analysis of the relationship between degree of heterozygosity at four blood group loci and the morphological variability in a human population was carried out. Additionally, the possibility that dermatoglyphic patterns correlate with biochemical and anthropometric variables was also investigated. A strong and significant increase in the frequency of morphologically multimodal individuals was observed, which paralleled the heterozygosity level. Discriminant analysis, by quantitative characters, of the closest pair of biochemically different samples yielded a satisfactory discrimination. Multiple correlations of each variable with all the others (18 traits), the communality of characters, the index of integration, and the Mahalanobis distances of the factor scores for each individual (all extracted from principal component analysis) were all indicative of the different multivariate structures of homo- and heterozygous individuals and thus supported the hypothesis that heterozygotes tend to cluster near the center of the joint multivariate distribution. The dermatoglyphic patterns showed a certain relationship with the morphological makeup of individuals. Correlations between biochemical heterozygosity at blood group loci and patterns of digital dermatoglyphics were rather irregular.

Adolescent↗
PubMed1986

Multivariate structure of human populations: sedentary versus migrants.

The rate change of gene frequency in a population subject to emigration obviously depends on differences in the effective reproductive size (and resulting random genetic drift effects) between emigrants and natives. An important additional force may be the different selection pressures of the original and the new environment into which the population penetrates. Discrete traits and monolocus systems have been studied in many natural populations of various species. However, knowledge about the migration influence on quantitative, i.e. polygenic, characters is very limited. The present study set out to answer the following biological questions: (1) Does migration induce changes in sets of phenotypic, genetic and environmental correlations? (2) If so, are these changes expressed in levels and/or structure of the correlation matrices? Data on 20 anthropometric traits in 305 Mexican families [129 families from Mexico (sedentary population) and 176 families living in Texas (migrant population)] were used for analysis. The curves of distribution and average values of phenotypic, genetic and environmental correlations remained unchanged between the two populations. However, qualitatively (i.e., as far as the agreement between matrix compositions is concerned), all three matrices changed significantly. The phenotypic correlations appear to be the most highly canalized, the correspondence between the two matrices being 62.1%. The environmental matrices had the highest variation, and although 26.3% of the correlations were in agreement, this was statistically nonsignificant. The most important finding in the present study was the relatively low correspondence between the two genetic matrices (35.6%). We suggest that these changes were provoked by preselection (i.e., by a nonrandom sample) of migrating individuals.

Anthropometry↗
PubMed1985

Lerner's concept of developmental homeostasis and the problem of heterozygosity level in natural populations.

In recent years adherents of the neutral mutation hypothesis have conducted a variety of statistical tests concerning the applicability of their theory to data of biochemical genetic polymorphism in natural populations. From the other side, the involvement of natural selection as a main evolutionary force responsible for the observed levels of polymorphism and heterozygosity have also been proposed in numerous field studies and theoretical considerations. However, none of these hypotheses completely and satisfactorily explains the collected data. We believe that one of the main causes of the discrepancy in theories is that the variability at each locus is considered independently in both of the above-mentioned approaches. Yet, it was suggested long ago, and now there is an increasing amount of evidence indicating cooperation between different loci which can influence the variability at each of them. Thus we think that the use of models considering the genome as a suit of independent genes is a priori expected to decrease the efficacy of the approximation. In the present review we attempt to draw attention to findings of interdependence of the variability of different characters and its possible limiting action on the growth of genetic diversity in natural populations. We do not try to give a universal explanation for the processes acting in populations and determining levels of heterozygosity. However, to our mind, the solution of the discussed question requires consideration of genes in their interactions.

Alleles↗
PubMed1984

Developmental homeostasis and heterozygosity for blood group loci in a human population.

Relationship between the variability of 5 independent morphological characters and the heterozygosity level at 4 blood group loci were determined in Israel. An increase in the heterozygosity level led to a reduction of the range and coefficient of variation of the morphological traits and also led to an increase of modal phenotype frequencies in the group.

Adolescent↗
PubMed1984

Biochemical heterozygosity as a predictor of developmental homeostasis in man.

The relationships between the variability of 48 morphological traits and the heterozygosity of four blood group loci were studied in 200 Israeli Jewish males of Eastern European origin aged 18-22 years. A definite correlation was observed between the level of heterozygosity and the variability of 17 traits and two indices. Of the latter traits only 10 were chosen for further analysis. Principal component analysis showed that seven of these traits were independent. For six of them, the frequency of modal individuals (average +/- 0.67 S.D.) in the tetraheterozygous group was the highest, diminishing proportionally with decreasing heterozygosity levels. The degree of heterozygosity also had a significant negative correlation with the coefficient of variation of the morphological characters and was positively associated with the kurtosis values. Only the variability of one of 10 traits showed an opposite trend and a correlation with biochemical homozygosity. The results are discussed in terms of developmental homeostasis.

Adolescent↗
PubMed1984

Changes in the heritability components of anthropometric characters due to preselection and environment during migration.

Changes in the genetic and environmental components of the phenotypic variance of 20 morphological characters were studied in Mexican migrant and sedentary populations. As far as the changes in variance components and the average values of traits were concerned, it was found that some traits were subjected to different forms of selection pressure, some changed within the limits of the norm reaction, and some remained unchanged.

Adolescent↗
PubMed1983

Relationship between levels of biochemical heterozygosity and morphological variability in human populations.

The relationships between the heterozygosity of the loci of biochemical and morphological traits were compared in seven Jewish populations. This comparison was based, on the one hand, on the average heterozygosity of seven biochemical loci (four blood group and two enzymatic ones) and, on the other hand, on five morphological characters. To assess the heterozygosity level for quantitative traits (normal distribution), we found it useful to measure h = CV mu, where CV is the coefficient of variation, and mu is the deviation of the population mean from the general average divided by the standard deviation of the general distribution. Actually, 'h' represents an inverse measure of the heterozygosity. Marked negative correlation was detected between the biochemical and morphological heterozygosity. This negative correlation was attributed to the convergent influence of inbreeding on different loci, but other possible mechanisms are discussed.

Acid Phosphatase↗
PubMedDate not supplied

Genetic analysis of growth curve parameters of body weight, height and head circumference.

A sample of 681 Israeli boys and girls, including 355 regular siblings (SB), 112 pairs of dizygotic (DZ) and 51 pairs of monozygotic (MZ) twins, was measured for body weight (WT), length (HT) and head circumference (HC) at birth and during the first year of life. The Count model with three parameters was chosen as the best fitting and most parsimonious function to approximate growth of the studied traits. The curves' fitting parameters were estimated for WT, HT and HC for each individual. To test the assumption that there is a genetic source influencing the pattern of growth for each trait, familial correlations between parameter estimates were computed for MZ, DZ twins and SB. In all instances MZ twins showed the highest within-pair correlation in parameters of growth (from 0.58 to 0.86), while SB showed the lowest ones (from 0.10 to 0.70). Variance decomposition analysis was used to simultaneously assess the contribution of gender, gestational age, additive genetic factor, common sibs and common intrauterine environmental effects on total variance of each studied trait separately. All these sources of variation were statistically significant, though the effect of intrauterine environment played a substantial role in early stages of child physical development, explaining from 18.1% to 70.6% of the total variance of the growth curve parameters. Further analyses are needed to clarify how this environment affects child growth and for how long.

Anthropometry↗
PubMedDate not supplied

Bone ageing: genetics versus environment.

Bone ageing results from a complex interaction between genetic and environmental factors (such as diet, climate and physical exercise) throughout human life. According to current literature, the most popular measures of bone ageing are osseometric measurements (OSM), bone mineral density (BMD) and osseographic scores (OSS), based on descriptive criteria of bone age. Plain roentgenography allows simultaneous assessment of all three measures. Ethnic differences with regard to these bone ageing characteristics have prompted us to study to the process anew, with the aim of elucidation the nature of the genetic and environmental components involved, and the possible interaction(s) between them. Despite abundant data on ethnic differences regarding these measures, modern knowledge on the genetics of these processes has derived primarily from the family studies of BMD, which pointed to strong involvement of the familial factors on bone mass. Segregation analysis performed by us in two ethnically different samples of pedigrees revealed a significant effect of the putative major gene on BMD of both compact and cancellous bone. The major finding of our bivariate segregation analysis was that it lead to the acceptance of the hypothesis predicating a single major locus with pleiotropy to both cancellous and compact BMD, but clearly rejecting the polygenic hypotheses. Our study of cortical index (CI) provided evidence that a single potential major gene controls not only the baseline trait level, but also the age at onset of the involutive bone changes, and the rate of the CI change with age. When we examined the environmental vs genetic influences on OSS variation in 32 human populations, we found very little environmental effect on the rate of bone change (r2 = 0.107), but a substantial effect on this rate of the genetic differences between populations (r = 0.480). Clarification of the genetic basis of bone ageing could have wide-ranging applications in the prevention and treatment of bone degenerative diseases such as osteoporosis and osteoarthritis, before irreversible damage takes place. There is thus a need to target the genetic analysis of BMD and the biochemical regulating factors of bone turnover through the use of molecular genetic techniques.

Aging↗
PubMedDate not supplied

Modelling of age-related bone loss using cross-sectional data.

BACKGROUND: Current applications of bone mineral density (BMD) data in age studies are not free of certain drawbacks. Since it is well established that age-related patterns of BMD changes involve three distinct periods (bone acquisition in youth, stabilization at maturity, and decrease with ageing), adjusting for age via an inappropriate mathematical function may lead to inconsistencies and wrong conclusions. HYPOTHESIS: The piecewise model, which encompasses the above three periods, will accurately describe the BMD dependence on age. OBJECTIVE: To examine age-related patterns of BMD changes using a number of possible mathematical functions and to find among them the best-fitting function. Next, to test whether the chosen function is universally applicable or if there are diverse population-specific functions. MATERIAL AND METHODS: Thirteen ethnic samples from various regions of Europe and Asia, assigned into five ethnic-geographic groups, were examined. The total sample included 2430 males and 2515 females. Compact BMD of hand phalanges was measured by photodensitometry from plain radiographs of each individual studied. Statistical software was developed for the purposes of the present study; this software gave a maximum likelihood of the parameter estimates for various statistical models (functions). RESULTS: In all samples of sufficient size and representative age range, a two-interval function was found as the best fitting and most parsimonious model to describe the BMD age-related changes. This two-interval function was characterized by age-related bone mass increase, positive slope beta(1s) in young age or a plateau (beta(1s) = 0, i.e. no age-related changes) until a sex-specific age threshold, T(0), after which annual bone loss ensued with a slope coefficient beta(2s). Threshold of BMD loss in women of different ethnic groups ranged between 37.85 and 47.77 years, and roughly coincided with perimenopausal age. In males, the age T(0) varied between 27.85 and 49.07 years. The ensuing cortical bone loss appeared to be linear in both sexes, averaging between 0.51% and 1.15% in men and between 0.74% and 1.77% per year of young age BMD value in females. CONCLUSIONS: The change of phalangeal BMD with age may be best described by a two-interval function, regardless of sex and ethnic background. However, specific parameter estimates depend both on gender and ethnic affiliation. This study has yielded a well-fitted model of BMD dependence on age suitable for further use in population studies.

Adolescent↗
PubMedDate not supplied

Genetic composition of Jewish populations: diversity and inbreeding.

Genetic diversity and F statistics analysis, using 9 and 5 blood group loci, respectively, were carried out on 16 Jewish populations from 5 geographic regions: East Europe, Central Europe, South Europe, Middle East and North Africa. The proportion of total diversity found within populations was 98.9% while that between populations, within geographic groups and between groups altogether was only 1.1%. The average heterozygosity between geographic groups ranged from 0.3867 to 0.4150. There were no significant differences between geographic groups of populations in heterozygosity or in its variance. Average estimates of inbreeding were as follows: Fis = 0.0419, Fst = 0.0084 and Fit = 0.0498. Because the heterogeneity and relative proportion of diversity were less between Jewish populations than between non-Jewish ones, we conclude that genetic similarity between Jews is higher than between Gentiles. The findings are in agreement with our previously obtained calculations of genetic distances (Kobyliansky, Micle, Goldschmidt-Nathan, Arensburg and Nathan 1982).

Africa, Northern↗
PubMedDate not supplied

A morphological approach to the problem of the biological similarity of Jewish and non-Jewish populations.

The genetic kinship between various Jewish and non-Jewish groups, from the biochemical standpoint, has been much investigated, frequently with very contradictory conclusions. The present paper reports the results of two comparative analyses of several Jewish and non-Jewish populations as based on morphological measurements of adult males. The first analysis employed data on Jewish and non-Jewish communities from five geographic regions of the world. The dendrogram resulting from the cluster analysis clearly indicates that Jewish populations are much closer to one another than to non-Jewish neighbour groups. In the second analysis, 25 ethnoterritorial groups of the USSR (one Jewish and the rest non-Jewish) were evaluated on the basis of 27 anthropometric characters. The latter Jewish group was markedly separate from the other 24 ethnic groups, and especially distinct when only traits with high coefficients of heritability were employed.

Adult↗