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Particular Population (particular + population)
Selected AbstractsAging-dependent generation of suppressive CD4+CD25,R123loCD103+ T,cells in miceEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 9 2003Jun Shimizu Abstract Advancing age is associated with significant alterations in immune functions, including a decline in CD4 T,cell function, in both mice and humans. In our previous report, we showed that CD4+CD25, T,cells in aged (24-month-old) mice, especially after in vitro pre-stimulation of these cells, exhibit hyporesponsive and suppressive properties. We examined here whether the suppressive activity of aged CD4+CD25, T,cells is ascribable to a particular population within these cells. In vitro analyses revealed that cell populations rapidly extruding Rhodamine-123 (R123) (referred to as R123lo cells) in aged CD4+CD25, T,cells have a more potent suppressive function compared with R123hi populations. In addition, CD103+ cells in freshly prepared aged CD4+CD25,R123lo T,cells had a most potent suppressive activity. Both R123hi and R123lo populations had individually stronger suppressive activity after pre-stimulation than before pre-stimulation. Furthermore, the R123lo population in young CD4+CD25, T,cells also had different properties from R123hi T cells: low responsiveness, no additive effect in proliferation assays, and the gain of a suppressive function after in vitro pre-stimulation. Takentogether, these results suggest that CD4+CD25,R123lo T,cells are a unique population within whole CD4+CD25, T,cells. This population exists in the earlystage of the life span, and the properties in this population become obvious with aging, that is the gain of their suppressive activity. [source] REINFORCEMENT AND THE GENETICS OF NONRANDOM MATINGEVOLUTION, Issue 1 2000Maria R. Servedio Abstract., The occurrence of reinforcement is compared when premating isolation is caused by the spread of a gene causing females to prefer to mate with males carrying a population-specific trait (a "preference" model) and by a gene that causes females to prefer to mate with males that share their own trait phenotype (an "assortative mating" model). Both two-island models, which have symmetric gene flow, and continent-island models, which have one-way gene flow, are explored. Reinforcement is found to occur much more easily in a two-island assortative mating model than in any of the other three models. This is due primarily to the fact that in this model the assortative mating allele will automatically become genetically associated in each population with the trait allele that is favored by natural selection on that island. In contrast, natural selection on the trait both favors and opposes the evolution of premating isolation in the two-island preference model, depending on the particular population. These results imply that species recognition in the context of mating may evolve particularly easily when it targets cues that are favored by natural selection in each population. In the continent-island models, reinforcement is found to occur more often under the preference model than the assortative mating model, thus reversing the trend from the two-island models. Patterns of population subdivision may therefore play a role in determining what types of premating isolation may evolve. [source] Relationship between cribra orbitalia and enamel hypoplasia in the early medieval Slavic population at Borovce, SlovakiaINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 3 2008Z. Obertová Abstract Cribra orbitalia and enamel hypoplasia were examined in an early medieval (8th to beginning of 12th century AD) skeletal sample of 451 individuals from Borovce, Slovakia. More than 40% of these individuals died before reaching 20 years of age. The relationship between the occurrence of orbital and enamel lesions was analysed by focusing on the age-specific distribution, and on its influence on demographic parameters. Both features were found in 11.2% of the observed skulls. The presence of orbital and dental lesions showed a considerable impact on mortality as well as the life expectancy. Generally, the highest mortality was observed among 0,4 year old individuals. The greatest discrepancy in the demographic parameters, however, appeared between the affected and unaffected individuals aged 10,14 and 15,19 years. In these two age groups the co-occurrence of both lesions was most frequently recorded. These individuals obviously had a history of sickness, and thus could not cope with further bouts of disease and with the increased physiological demands of pubertal growth. The missing correlation in younger age categories can be largely explained by the difficulty of macroscopically examining the permanent dentition, since an interrelationship between the age at hypoplasia development and the occurrence of cribra orbitalia was detected. Several differences between the individuals with enamel defects and both conditions were observed in the distribution of age at hypoplasia formation. According to these results, several factors, such as impaired health status, growth demands and diet, influence the development of enamel hypoplasia and cribra orbitalia in a particular population. It is possible that after reaching a certain threshold, the underlying factors act synergistically in a kind of vicious cycle as the balance between the immune system, metabolism, and exogenous factors such as pathogens and nutrition, is disturbed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Mailed urine samples are not an effective screening approach for Chlamydia trachomatis case finding among young menJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 6 2007M Domeika Abstract Background, Frequency of testing is known to be low for sexually transmitted infections (STIs) in men aged 20,24 years. The use of mailed, home-obtained urine specimens could increase the uptake of young men and facilitate screening programmes for the detection of asymptomatic Chlamydia trachomatis. Objective, The aim of the present study is to evaluate the home screening approach as a tool for recruitment of asymptomatic men for screening of genital C. trachomatis infections. Methods, Men aged 19,24 years old (n = 1936) were invited to participate in home-based testing for genital C. trachomatis infection. Persons who agreed to be tested were provided with a testing kit. Self-collected first void urine was sent for testing to the microbiology laboratory. The test result was accessible on the study's web-page 1 week after testing. Individuals with a diagnosed infection were instructed to contact the venereal disease department. Results, The response rate was 24% (462/1936). The responders' main reason for not participating was a feeling of being safe regarding STIs (87%; 159/182). The primary reason for this feeling of safety was that the responders were in a steady relationship (59%; 107/159). Having sex outside a steady relationship was reported by 36% (90/250) of the responders. The prevalence of C. trachomatis infection among the responders was 2.02% and the reported history of chlamydial infection was 36% (34/95). Out of the responders, 92% (229/249) were, to varying degrees, concerned about getting STIs; however, the majority (72%; 174/242) estimated the risk to be low. Conclusion, Home screening using web-based answer management is a feasible tool for STI screening, which lowers the threshold for people at risk. In this particular population, however, the response rate was too low to be routinely introduced. [source] The frequency and severity of catastrophic die-offs in vertebratesANIMAL CONSERVATION, Issue 2 2003David H. Reed Rare bouts of extreme environmental perturbations (catastrophes) have been predicted to have a major influence on the probability of extinction. Yet very little information is available on the frequency and severity of catastrophes. Improving the available information concerning catastrophe parameters would allow for an evaluation of their effect and a start towards understanding their causes. We used the Global Population Dynamics Database to determine the frequency and severity of die-offs in 88 species of vertebrates. We define a catastrophe as any 1-year decrease in population size of 50% or greater. The data yielded three findings. (1) The frequency of severe die-offs in vertebrate populations is strongly related to the generation length of the organism. (2) The probability of a severe die-off for a particular population is approximately 14% per generation. (3) The frequency of die-off severity can be modelled as a modified power function with the frequency of die-offs decreasing with increasing magnitude of effect. The distribution is not consistent with catastrophes stemming from environmental sources different than those responsible for smaller fluctuations, but seems to represent the tail of a continuous distribution of environmental perturbations. [source] Bacterial vaginosis , a laboratory and clinical diagnostics enigma,APMIS, Issue 3 2005Review article II Diagnosing bacterial vaginosis (BV) has long been based on the clinical criteria of Amsel et al., whereby three of four defined criteria must be satisfied. Though there are other criteria and scoring methods which function well in comparison (i.e. Nugent scoring), it is not certain that they will always identify the same category of patients. Point-of-care methods based on various combinations of microbial products, presence of RNA, or more complex laboratory instrumentations such as sensor arrays, have also been introduced for the diagnosis of BV. No method for diagnosing BV can at present be regarded as the best. It could be that , based partly on tacit knowledge on the part of the clinical investigators scoring in the clinic , various scoring systems have been chosen to fit a particular BV-related problem in a particular population. In this review we critically examine these pertinent issues influencing clinical scoring and laboratory diagnostics of BV. [source] Haptoglobin: a review of the major allele frequencies worldwide and their association with diseasesINTERNATIONAL JOURNAL OF LABORATORY HEMATOLOGY, Issue 2 2007KYMBERLEY CARTER Summary Haptoglobin (Hp) is a plasma ,2 -glycoprotein which binds free haemoglobin, thus preventing oxidative damage. The complex is rapidly removed from the circulation by a specific receptor (CD163) found on macrophages. Three major subtypes, Hp1-1, Hp2-1 and Hp2-2 are the product of two closely related genes HP1 and HP2. The frequency of the HP1 and HP2 genes varies worldwide depending on racial origin: the HP1frequency varying from about 0.07 in parts of India to over 0.7 in parts of West Africa and South America. Both HP1 and HP2 have been linked to susceptibility to various diseases. Such associations may be explained by functional differences between the subtypes in the binding of Hb and its rate of clearance from the plasma. However, there are also corresponding negative reports for disease associations. The conflicting evidence on disease association and the lack of association between disease and particular populations, despite the wide range of HP1 and HP2 gene frequencies across the world, may indicate that any associations are marginal. [source] Population Genetic Structure of the Medicinal Plant Vitex rotundifolia in China: Implications for its Use and ConservationJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2008Yuan Hu Abstract Vitex rotundifolia L. is an important plant species used in traditional Chinese medicine. For its efficient use and conservation, genetic diversity and clonal variation of V. rotundifolia populations in China were investigated using inter-simple sequence repeat markers. Fourteen natural populations were included to estimate genetic diversity, and a large population with 135 individuals was used to analyze clonal variation and fine-scale spatial genetic structure. The overall genetic diversity (GD) of V. rotundifolia populations in China was moderate (GD = 0.190), with about 40% within-population variation. Across all populations surveyed, the average within-population diversity was moderate (P = 22.6%; GD = 0.086). A relatively high genetic differentiation (Gst = 0.587) among populations was detected based on the analysis of molecular variance data. Such characteristics of V. rotundifolia are likely attributed to its sexual/asexual reproduction and limited gene flow. The genotypic diversity (D = 0.992) was greater than the average values of a clonal plant, indicating its significant reproduction through seedlings. Spatial autocorrelation analysis showed a clear within-population structure with gene clusters of approximately 20 m. Genetic diversity patterns of V. rotundifolia in China provide a useful guide for its efficient use and conservation by selecting particular populations displaying greater variation that may contain required medicinal compounds, and by sampling individuals in a population at >20 m spatial intervals to avoid collecting individuals with identical or similar genotypes. [source] Ethics and medical research in childrenPEDIATRIC ANESTHESIA, Issue 10 2009ANDREW J. DAVIDSON MBBS MD FANZCA Summary The ethics of clinical research is based on several well-known guidelines and documents. The guidelines vary between countries, but the principles of respect for persons, beneficence, and justice are constant. These principles are reflected in requirements to obtain free and informed consent, to minimize risk or harm, and to not overly burden or disadvantage particular populations. For research to be ethical, it must also be of such a standard, and be conducted in such a manner that it will generate knew and useful knowledge. Children have limited capacity for understanding and may be more open to coercion. Therefore, they are regarded as a particularly vulnerable population, and specific clauses regarding children are incorporated into many guidelines. A key concept in these clauses is the degree of risk acceptable for children involved in research. While it is generally agreed that children require particular attention because of their vulnerability, there is also increasing concern that children in general should not be disadvantaged by lack of knowledge due to reduced research activity. Finally, an increasingly active area of research in children involves genetics and biobanking. Research in these areas raises new and challenging ethical issues. [source] | |||||||||||||