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Defined Groups (defined + groups)

Distribution by Scientific Domains

Medical Sciences	40%

Selected Abstracts

Non-random reassortment in human influenza A viruses

INFLUENZA AND OTHER RESPIRATORY VIRUSES, Issue 1 2008
Raul Rabadan
Background, The influenza A virus has two basic modes of evolution. Because of a high error rate in the process of replication by RNA polymerase, the viral genome drifts via accumulated mutations. The second mode of evolution is termed a shift, which results from the reassortment of the eight segments of this virus. When two different influenza viruses co-infect the same host cell, new virions can be released that contain segments from both parental strains. This type of shift has been the source of at least two of the influenza pandemics in the 20th century (H2N2 in 1957 and H3N2 in 1968). Objectives, The methods to measure these genetic shifts have not yet provided a quantitative answer to questions such as: what is the rate of genetic reassortment during a local epidemic? Are all possible reassortments equally likely or are there preferred patterns? Methods, To answer these questions and provide a quantitative way to measure genetic shifts, a new method for detecting reassortments from nucleotide sequence data was created that does not rely upon phylogenetic analysis. Two different sequence databases were used: human H3N2 viruses isolated in New York State between 1995 and 2006, and human H3N2 viruses isolated in New Zealand between 2000 and 2005. Results, Using this new method, we were able to reproduce all the reassortments found in earlier works, as well as detect, with very high confidence, many reassortments that were not detected by previous authors. We obtain a lower bound on the reassortment rate of 2,3 events per year, and find a clear preference for reassortments involving only one segment, most often hemagglutinin or neuraminidase. At a lower frequency several segments appear to reassort in vivo in defined groups as has been suggested previously in vitro. Conclusions, Our results strongly suggest that the patterns of reassortment in the viral population are not random. Deciphering these patterns can be a useful tool in attempting to understand and predict possible influenza pandemics. [source]

Geography and segmented assimilation: examples from the New York Chinese

POPULATION, SPACE AND PLACE (PREVIOUSLY:-INT JOURNAL OF POPULATION GEOGRAPHY), Issue 1 2004
K. Bruce Newbold
Abstract Drawing upon the segmented assimilation framework, and using the 1990 5% PUMS file, the paper compares the assimilation of selected Chinese immigrant cohorts, based upon age and period of entry. Including a spatial component within the framework, we examine whether differences in the organisation and assimilation of immigrant groups exist across space. For each cohort, contrasts are made with reference to location in the New York Consolidated Metropolitan Statistical Area (CMSA), with the analysis focusing upon differences in spatial assimilation with respect to acculturation, socioeconomic characteristics, internal migration, and immigrant characteristics relative to other immigrant and native-born groups. The analysis is updated using Immigration and Naturalization Service (INS) data files from the 1990s. Results suggest that space, and location in space, alter the assimilation trajectory of similarly defined groups. Copyright © 2004 John Wiley & Sons, Ltd. [source]

How race becomes biology: Embodiment of social inequality

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2009
Clarence C. Gravlee
Abstract The current debate over racial inequalities in health is arguably the most important venue for advancing both scientific and public understanding of race, racism, and human biological variation. In the United States and elsewhere, there are well-defined inequalities between racially defined groups for a range of biological outcomes,cardiovascular disease, diabetes, stroke, certain cancers, low birth weight, preterm delivery, and others. Among biomedical researchers, these patterns are often taken as evidence of fundamental genetic differences between alleged races. However, a growing body of evidence establishes the primacy of social inequalities in the origin and persistence of racial health disparities. Here, I summarize this evidence and argue that the debate over racial inequalities in health presents an opportunity to refine the critique of race in three ways: 1) to reiterate why the race concept is inconsistent with patterns of global human genetic diversity; 2) to refocus attention on the complex, environmental influences on human biology at multiple levels of analysis and across the lifecourse; and 3) to revise the claim that race is a cultural construct and expand research on the sociocultural reality of race and racism. Drawing on recent developments in neighboring disciplines, I present a model for explaining how racial inequality becomes embodied,literally,in the biological well-being of racialized groups and individuals. This model requires a shift in the way we articulate the critique of race as bad biology. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source]

A New Group Contribution Method based on Equation of State Parameters to Evaluate the Critical Properties of Simple and Complex Molecules

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2006
José O. Valderrama
Abstract A new group contribution method to evaluate the critical properties (temperature, pressure and volume) is presented and applied to estimate the critical properties of biomolecules. Similar to other group contribution methods, the one proposed here divides the molecule into conveniently defined groups and evaluates the properties as the sum of the different contributions according to a specified model equation for each of the properties. The proposed method consists of a one-step calculation that uses simple model equations and does not require additional data besides the knowledge of the structure of the molecule, except for isomers. For these substances the normal boiling temperature, the molecular mass and the number of atoms in the molecule are used to distinguish among isomers. The method is applicable to high molecular weight compounds, as most biomolecules and large molecules present in natural products. On présente une nouvelle méthode de contribution de groupe pour évaluer les propriétés critiques (température, pression et volume) de biomolécules. Comme dans le cas d'autres méthodes de contribution de groupe, celle qu'on présente ici divise la molécule en groupes définis de manière pratique et évalue les propriétés comme la somme des différentes contributions selon une équation de modèle spécifique pour chacune des propriétés. La méthode proposée consiste en un calcul en une étape qui utilise des équations de modèle simple et, excepté pour les isomères, ne requiert pas de données supplémentaires hormis la structure de la molécule. Pour ces substances, on utilise la température d'ébullition normale, la masse moléculaire et le nombre d'atomes dans la molécule pour distinguer entre les isomères. La méthode est applicable à des composés de poids moléculaire élevé, comme la plupart des biomolécules et des molécules larges présentes dans les produits naturels. [source]

Sperm chromatin integrity in young men with no experiences of infertility and men from idiopathic infertility couples

ANDROLOGIA, Issue 3 2009
R. Rybar
Summary Damage to the genetic component of spermatozoa seems to play the main role in a majority of cases where current approaches fail to reveal the specific cause of male infertility. In this study, we compared semen quality in men assigned to two defined groups: men from couples with unexplained infertility , idiopathic infertility (A) and young men with no experiences of infertility (B). All samples were examined by standard ejaculate analysis and sperm chromatin structure assay (SCSA). Sperm chromatin damage was significantly higher in men from group A than in those from group B. Similar results were obtained by comparison of men from group A (all men were normozoospermic) with normozoospermic men from group B. According to these results, we can suppose that chromatin disorders may be the causal factor of subfertility or infertility in some of these men. No evidence for a strong association between chromatin disorders and standard parameters of ejaculates was found. We failed to confirm a relationship between smoking and sperm quality in men from any of the investigated groups. SCSA is a method that facilitates the identification of infertile men who otherwise show normal semen variables. [source]