Home About us Contact
|
Home About us Contact | ||
|
|
||
Different Populations (different + population)
Terms modified by Different Populations Selected AbstractsVariability of the Needle Essential Oils of Pinus peuce from Different Populations in Montenegro and SerbiaCHEMISTRY & BIODIVERSITY, Issue 9 2008Biljana Nikoli No abstract is available for this article. [source] Selection of locations of knots for linear splines in random regression test-day modelsJOURNAL OF ANIMAL BREEDING AND GENETICS, Issue 2 2010J. Jamrozik Summary Using spline functions (segmented polynomials) in regression models requires the knowledge of the location of the knots. Knots are the points at which independent linear segments are connected. Optimal positions of knots for linear splines of different orders were determined in this study for different scenarios, using existing estimates of covariance functions and an optimization algorithm. The traits considered were test-day milk, fat and protein yields, and somatic cell score (SCS) in the first three lactations of Canadian Holsteins. Two ranges of days in milk (from 5 to 305 and from 5 to 365) were taken into account. In addition, four different populations of Holstein cows, from Australia, Canada, Italy and New Zealand, were examined with respect to first lactation (305 days) milk only. The estimates of genetic and permanent environmental covariance functions were based on single- and multiple-trait test-day models, with Legendre polynomials of order 4 as random regressions. A differential evolution algorithm was applied to find the best location of knots for splines of orders 4 to 7 and the criterion for optimization was the goodness-of-fit of the spline covariance function. Results indicated that the optimal position of knots for linear splines differed between genetic and permanent environmental effects, as well as between traits and lactations. Different populations also exhibited different patterns of optimal knot locations. With linear splines, different positions of knots should therefore be used for different effects and traits in random regression test-day models when analysing milk production traits. [source] ORIGINAL ARTICLE: Antigen-presenting Cells in Pregnant and Non-pregnant Human MyometriumAMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 3 2010Marina Ivanisevic Citation Ivanisevic M, Segerer S, Rieger L, Kapp M, Dietl J, Kämmerer U, Frambach T. Antigen-presenting cells in pregnant and non-pregnant human myometrium. Am J Reprod Immunol 2010; 64: 188,196 Problem, Inflammatory cells play a crucial role in human parturition. Different populations of leucocytes invade the reproductive tract. Numerous studies have described the decidual immune cell population in pregnant and non-pregnant endometrium. However, little is known about the presence of immune cells in human myometrium. Method of study, We herein analysed a spectrum of immune cells in human myometrium comparing tissue samples from non-pregnant (n = 8) and pregnant (n = 10) uteri. Applying immunohistochemistry with a panel of antibodies specific for T cells, monocytes, natural killer cells, B cells and antigen-presenting cells (CD4, CD8, CD14, CD15, CD16, CD19, CD56, CD68, CD83, HLA-DR, DC-Sign, mast cell tryptase), we characterized the immune cell population of human myometrium. Results, A significantly higher number of CD14, CD15, CD16, DC-SIGN as well as CD4-positive cells were found in myometrium of pregnant compared to non-pregnant uteri, while mast cells were significantly reduced in pregnant myometrium. Conclusion, All markers found increased in pregnant myometrium indicate monocyte/macrophage lineage cells and thus suggest a possible involvement of these cells in healthy pregnancy maintenance. Monocytes/macrophages might produce a microenvironment that permits a controlled invasion of trophoblast cells into the myometrium while preventing a rejection of the semiallogenic conceptus and providing an important barrier against invading pathogenes. [source] A Novel In Vitro Model of Canine Malignant HemangioendotheliomaANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2005D. Kühn Introduction and Aim:, Canine malignant haemangioendothelioma is an aggressive neoplasia that affects mostly older dogs of large breeds with a strong predilection for the spleen, liver, heart and skin. The tumour originates in the vascular endothelium and consists of transformed cells forming large and leaky vessel-like structures. Prognosis is poor because surgery and chemotherapy have limited success in prolonging survival times and increasing quality of patients. A new strategy to treat this malignancy could be anti-angiogenic therapy based on the inhibition of proliferation, migration and three-dimensional organization of transformed cells. In order to reduce animal experiments, in vitro -models are required to test the safety and efficacy of anti-angiogenic drugs. So far only few models of angiogenesis are available using mostly human, rodent and bovine cells. Therefore, the aim of our study was to establish an in vitro model of canine haemangioendothelioma. Materials and Methods:, Tumours were collected from dogs during surgery or immediately after euthanasia. Isolation of cells was done from different areas of the tumours and by enzymatic digestion of the tissue. Cells were incubated in culture media with and without endothelial growth factors. Cells were characterized by lectin histochemistry using Dolichos biflorus agglutinin, Ulex europaeus agglutinin and Bandeiraea simplicifolia agglutinin I. Moreover, RT-PCR (polymerase chain reaction) was employed to investigate the expression of vascular endothelial growth factor (VEGF) and its endothelium-specific receptors VEGF-R1 and -R2. Results and Conclusions:, Different populations of cells were isolated and cultured successfully from canine malignant haemangioendothelioma. Cells show characteristics of microvascular endothelial cells of an angiogenic phenotype, i.e. the formation of spheroids and tube-like structures as well as strong labelling for Bandeiraea simplicifolia agglutinin I. Thus, morphological and glycohistochemical results confirm the vascular character of the cells isolated. RT-PCR showed expression of VEGF. However, endothelium-specific VEGF receptors were not expressed. Loss of typical receptors is common in cancer and may correlate with increased tumour dedifferentiation. [source] Consequences of dispersal for the quantitative study of adaptation in small-scale plots: a case study of an avian island populationECOGRAPHY, Issue 5 2000M. M. Lambrechts Lifetime recruitment of breeding offspring estimated in small-scale study plots (i.e. local recruitment) is considered to be the best available ecological measure of contributions to following generations, and sufficient for the quantitative study of adaptation in natural populations. Recent investigations suggest that local recruitment of breeding offspring does not always reflect the total recruitment in the whole population, especially in small-scale plots where the majority of locally-born offspring leave these plots to breed elsewhere. We examined in an avian island population whether study plot size has an important impact on different population and fitness measures. We defined around a central nestbox seven plots, varying in radius from 100 to 700 m. We show that in the smallest plots, the local replacement rate of adults by breeding offspring is low, the number of locally-born offspring settling beyond the limits of a plot is high, and relationships between local and total recruitment are weak. This is especially true for daughters as more daughters than sons settle beyond the limits of local plots for breeding. Our interpretation is that the lifetime recruitment of breeding offspring in local plots does not necessarily reflect the lifetime recruitment of breeding offspring in the whole population, especially when plots do not cover the natal dispersal distance. Consequences of dispersal for the quantitative study of adaptation are discussed. [source] Understanding anorexia nervosa through analysis of thematic content of letters in an adolescent sampleEUROPEAN EATING DISORDERS REVIEW, Issue 5 2006Glen Freedman Abstract Objective Positive and negative themes about their illness have been identified in an adult population with anorexia nervosa. It was our goal to explore the thematic content of the letters written by an adolescent population in order to better our understanding of how this different population relates to the illness. Method Twenty-seven adolescents with anorexia nervosa were asked to write two letters to their eating disorder, one addressing it as a friend and the other, as an enemy. The coding scheme initially developed by Serpell and Treasure, with minor adjustments, was used to code the letters by two trained raters, with high inter-rater reliability. Results Many similarities and a few notable differences between the adolescent population and an adult population were noted. Compared to an adult population, adolescents valued to a greater degree the sense of feeling looked after by the disorder and the increased attention that they felt the disorder provided. In contrast, they did not view loss of periods as a benefit. Regarding perceived costs of anorexia nervosa, adolescents described a greater degree of psychological distress in relation to the disorder, and a greater sense of having been tricked by the disorder. They did not describe as much frustration with preoccupation with thoughts about food or of being controlled by food. All other themes were not considered appreciably different in terms of percentage of statements or of subjects. Discussion An understanding of how adolescents relate to their illness in terms of themes can help to provide the therapist with a sense of where a patient is in terms of motivation and readiness for recovery. This in turn can aid in the determination of an appropriate treatment approach that is most likely to foster an optimal therapeutic alliance and to enhance motivation to recover. Copyright © 2006 John Wiley & Sons, Ltd and Eating Disorders Association. [source] Constitutional Tax and Expenditure Limitation in Colorado: The Impact on Municipal GovernmentsPUBLIC BUDGETING AND FINANCE, Issue 3 2000Tom Rown Tax and expenditure limitations (TELs) have become a pervasive influence on local government fiscal affairs. Explanations for the spread of TELs suggest that voters thought local government was growing more than needed. Thus, TELs were intended to constrain growth and reduce the size of local governments. This article's purpose was to determine the impact of two separate kinds of TELs, one a property tax measure, and the other a comprehensive revenue and expenditure limit, upon the growth of municipal governments in Colorado. Using a panel data set on municipal budgets (1975,1996), the article demonstrates three major points: 1) the effectiveness of a TEL in achieving reductions in local government revenue and spending growth depends upon the nature of the TEL; 2) the comprehensive TEL did effectively constrain growth and reduce local government reliance on the property tax, despite the local options for exemption; and 3) TELs do not have uniform impacts among governments of different population. [source] Increased Behavioral Variation and the Calculation of Release Numbers for Reintroduction ProgramsCONSERVATION BIOLOGY, Issue 3 2004M. ELSBETH McPHEE This increased variation can translate into decreased survivorship upon reintroduction to native habitats. Data show that captive populations of oldfield mice (Peromyscus polionotus subgriseus) exhibit such an increase in variation. Motivated by these results, we developed a series of calculations for a "release ratio" that can be used to determine the number of captive-bred animals needed to compensate for the increased variance. We present calculations of release ratios for behavioral and morphological variables with different distributions and illustrate the functional relationship between release numbers, increased variation, and change in average behavior and morphology. Our calculations indicated that the release of 130,150 captive-bred oldfield mice is equivalent to the release of 100 wildlike animals. Release ratios will vary among species, however, and perhaps among different populations of the same species and should be calculated separately for each situation. Development of the release ratio is the first rigorous effort to incorporate behavioral and morphological changes due to captivity into reintroduction planning. Release ratios will help conservation biologists ensure that the appropriate number of animals is released, thus increasing the success of reintroduction programs. Resumen:,Las poblaciones cautivas pueden exhibir mayor variación conductual que sus contrapartes silvestres como resultado del relajamiento de presiones selectivas en el ambiente de cautiverio. Esta variación incrementada puede traducirse en una disminución de la supervivencia en la reintroducción a hábitats nativos. Hay datos que muestran que poblaciones cautivas de ratones Peromyscus polionotus subgriseus exhiben tal incremento en la variación. Motivados por estos resultados, desarrollamos una serie de cálculos para un "índice de liberación" que pueda utilizarse para determinar el número de animales criados en cautiverio requerido para compensar la variación incrementada. Presentamos los cálculos de 2 índices de liberación para variables conductuales y morfológicas con distribuciones diferentes e ilustramos la relación funcional entre el número de liberaciones, la variación incrementada y el cambio en la conducta promedio y la morfología. Nuestros cálculos indicaron que la liberación de 130 a 150 ratones es equivalente a la liberación de 100 animales silvestres. Sin embargo, los índices de liberación varían entre especies y quizás entre poblaciones diferentes de la misma especie y deben calcularse por separado en cada situación. El desarrollo de índices de liberación es el primer esfuerzo riguroso para incorporar cambios conductuales y morfológicos debido al cautiverio en la planificación de reintroducciones. Los índices de liberación ayudarán a que los biólogos de la conservación se aseguren que el número de animales liberados es el apropiado, incrementando con ello el éxito de los programas de reintroducción. [source] Impaired glucose regulation and type 2 diabetes in children and adolescentsDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 6 2008Kerstin Kempf Abstract Diabetes mellitus in paediatric patients used to be almost exclusively type 1, but in recent years, case series as well as hospital-based and population-based studies indicated that the number of children and adolescents with type 2 diabetes (T2DM) has been increasing. This development is alarming since T2DM in youth is usually not an isolated condition, but accompanied by other cardiovascular risk factors such as obesity, dyslipidaemia, hypertension and low-grade inflammation. In adults, numerous studies provided detailed data on prevalence, incidence and risk factors for the development of T2DM, but for children and adolescents clinical and experimental data are still rather limited. This review provides an overview about the epidemiology and pathogenesis of T2DM in youth and about impaired glucose regulation as major risk factor for diabetes development with a special focus on the recent literature on clinical and lifestyle-related risk factors. Differences in incidence and prevalence across different populations indicate that ethnic background and genetic pre-disposition may be important risk determinants. In addition, epigenetic factors and foetal programming appear to confer additional risk before birth. Among the environmental and lifestyle-related risk factors there is evidence that obesity, hypercaloric diet, physical inactivity, socio-economic position (SEP), smoking, low-grade inflammation, psychosocial stress and sleeping patterns contribute to the risk for T2DM. However, the assessment of the relevance of risk factors and of incidence or prevalence estimates in youth is complicated by methodological issues that are also discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Screening for gestational diabetes; past, present and futureDIABETIC MEDICINE, Issue 5 2002F. W. F. Hanna Abstract Gestational diabetes is carbohydrate intolerance, with onset or first recognition of hyperglycaemia during pregnancy. Several studies have suggested that gestational hyperglycaemia is associated with adverse maternal and fetal outcomes, promoting the case for screening. Conversely, others argue that screening for gestational diabetes may colour the clinical judgement, influencing further management, e.g. more ,unjustified' caesarean sections. Additionally, the lack of definitive data either on a clear-cut glycaemic threshold for the development of adverse outcomes or on the impact of intervention is emphasized by opponents of screening. This review attempts to evaluate the available data on screening for gestational diabetes. Oral glucose tolerance test is promoted on the basis that the diabetogenic stress of pregnancy is encountered during late gestation and is best recognized in the fed state. There are different tests, including the 1 h/50-g, 2 h/75-g and 3 h/100-g tests, with practical limitations, including the time and cost involved and the unpleasant supra-physiological glucose load that is unrelated to body weight, and issues of reproducibility and sensitivity/specificity profiles. Despite its convenience, the poor sensitivity of random glucose has precluded its routine use for screening. Fasting glucose appears to be promising but further testing is required to ensure satisfactory sensitivity/specificity in different populations. Despite its limitations, the oral glucose tolerance test has become established as the ,most acceptable' diagnostic test for gestational diabetes. More convenient methods, e.g. fasting or random or post-load glucose, have to be validated therefore against the oral glucose tolerance test to gain acceptance for routine screening. Diabet. Med 19, 351,358 (2002) [source] Sexual selection did not contribute to the evolution of male lifespan under curtailed age at reproduction in a seed beetleECOLOGICAL ENTOMOLOGY, Issue 5 2009ALEXEI A. MAKLAKOV Abstract. 1. Sexual selection is a powerful evolutionary force that is hypothesised to play an important role in the evolution of lifespan. Here we test for the potential contribution of sexual selection to the rapid evolution of male lifespan in replicated laboratory populations of the seed beetle, Callosobruchus maculatus. 2. For 35 generations, newly hatched virgin male beetles from eight different populations were allowed to mate for 24 h and then discarded. Sexual selection was removed in half of these populations by enforcing random monogamy. 3. Classic theory predicts that because of sexual competition, males from sexually selected lines would have higher age-specific mortality rates and shorter lifespan than males from monogamous lines. 4. Alternatively, condition-dependent sexual selection may also favour genes that have positive pleiotropic effects on lifespan and ageing. 5. Males from all eight populations evolved shorter lifespans compared with the source population. However, there was no difference in lifespan between males from populations with or without sexual selection. Thus, sexual selection did not contribute to the evolution of male lifespan despite the fact that such evolution did occur in our study populations. [source] Genetic and expression analysis of all non-synonymous single nucleotide polymorphisms in the human deoxyribonuclease I-like 1 and 2 genesELECTROPHORESIS, Issue 12 2010Misuzu Ueki Abstract Members of the human DNase I family, DNase I-like 1 and 2 (DNases 1L1 and 1L2), with physiological role(s) other than those of DNase I, possess three and one non-synonymous SNPs in the genes, respectively. However, only limited population data are available, and the effect of these SNPs on the catalytic activity of the enzyme remains unknown. Genotyping of all the non-synonymous SNPs was performed in three ethnic groups including six different populations using the PCR-RFLP method newly developed. Asian and African groups including Japanese, Koreans, Ghanaians and Ovambos were typed as a single genotype at each SNP, but polymorphism at only SNP V122I in DNase 1L1 was found in Caucasian groups including Germans and Turks; thus a Caucasian-specific allele was identified. The DNase 1L1 and 1L2 genes show relatively low genetic diversity with regard to these non-synonymous SNPs. The level of activity derived from the V122I, Q170H and D227A substituted DNase 1L1 corresponding to SNPs was similar to that of the wild-type, whereas replacement of the Asp residue at position 197 in the DNase 1L2 protein with Ala, corresponding to SNP D197A, reduced its activity greatly. Thus, SNP V122I in DNase 1L1 exhibiting polymorphism exerts no effect on the catalytic activity, and furthermore SNP D197A in DNase 1L2, affecting its catalytic activity, shows no polymorphism. These findings permit us to postulate that the non-synonymous SNPs identified in the DNase 1L1 and 1L2 genes may exert no influence on the activity levels of DNases 1L1 and 1L2 in human populations. [source] Genetic variation in Myzus persicae populations associated with host-plant and life cycle categoryENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2001Kiriaki Zitoudi Abstract Random amplified polymorphic DNA (RAPD) analysis was applied on 96 clones of Myzus persicae (Sulzer) (Homoptera: Aphididae) representing seven populations collected from different host-plants and regions of Greece. Ten decamer random primers were used to evaluate genetic variation among the examined samples. Despite the variability found between clones, no specific RAPD marker was detected to discriminate the different populations. A significant finding was that aphids from peach and pepper, which were collected far away from tobacco-growing regions, especially those from peach, showed genetic divergence from the tobacco-feeding clones. Moreover, data analysis revealed a significant genetic divergence between holocyclic and anholocyclic populations from tobacco. Lastly, holocyclic clones showed higher level of estimated heterozygosity than the nonholocyclic (anholocyclic, androcyclic and intermediate) ones. [source] Community heterogeneity and single-cell digestive activity of estuarine heterotrophic nanoflagellates assessed using lysotracker and flow cytometryENVIRONMENTAL MICROBIOLOGY, Issue 7 2010Eva Sintes Summary Heterotrophic nanoflagellates (HNFs) are an essential component of all aquatic microbial food webs, and yet the exploration of the numerical and single-cell responses of these organisms in mixed assemblages still represents a major technical challenge. LysoTracker Green staining combined with flow cytometry was recently proposed for the enumeration of aquatic HNFs. Here we show that LysoTracker Green not only allows the enumeration of HNFs in estuarine samples with a wide range of HNF abundances, but also allows the discrimination of distinct HNF populations in mixed assemblages. In addition, the resulting cytometric parameters can be used to characterize cell size and the level of activity of the cells in the different populations that are detected. LysoTracker Green accumulates preferentially in lysosomes, and we demonstrate that the green fluorescence emission from HNF cells stained with LysoTracker strongly correlates with cell-specific ,-glucosaminidase (,-Gam) activity, a key digestive enzyme of lysosomal origin in eukaryotic cells. Our results further show that different populations that develop in estuarine regrowth cultures are characterized by different intrinsic ranges of size and of feeding activity, and that there is a wide range of single-cell responses within these HNF populations. We found a large degree of uncoupling between cell size and feeding activity, both between and within HNF populations, and there appears to be no clear allometric scaling of feeding activity. We were able to reconstruct the succession of distinct HNF populations that developed during the regrowth experiments, and explore the complex interactions that occurred between numerical (change in abundance of the cytometric populations) and single-cell HNF responses. [source] Novelty detector neurons in the mammalian auditory midbrainEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2005David Pérez-González Abstract Novel stimuli in all sensory modalities are highly effective in attracting and focusing attention. Stimulus-specific adaptation (SSA) and brain activity evoked by novel stimuli have been studied using population measures such as imaging and event-related potentials, but there have been few studies at the single-neuron level. In this study we compare SSA across different populations of neurons in the inferior colliculus (IC) of the rat and show that a subclass of neurons with rapid and pronounced SSA respond selectively to novel sounds. These neurons, located in the dorsal and external cortex of the IC, fail to respond to multiple repetitions of a sound but briefly recover their excitability when some stimulus parameter is changed. The finding of neurons that respond selectively to novel stimuli in the mammalian auditory midbrain suggests that they may contribute to a rapid subcortical pathway for directing attention and/or orienting responses to novel sounds. [source] Two populations of glutamatergic axons in the rat dorsal raphe nucleus defined by the vesicular glutamate transporters 1 and 2EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2005Kathryn G. Commons Abstract Most glutamatergic neurons in the brain express one of two vesicular glutamate transporters, vGlut1 or vGlut2. Cortical glutamatergic neurons highly express vGlut1, whereas vGlut2 predominates in subcortical areas. In this study immunohistochemical detection of vGlut1 or vGlut2 was used in combination with tryptophan hydroxylase (TPH) to characterize glutamatergic innervation of the dorsal raphe nucleus (DRN) of the rat. Immunofluorescence labeling of both vGlut1 and vGlut2 was punctate and homogenously distributed throughout the DRN. Puncta labeled for vGlut2 appeared more numerous then those labeled for vGlut1. Ultrastructural analysis revealed axon terminals containing vGlut1 and vGlut2 formed asymmetric-type synapses 80% and 95% of the time, respectively. Postsynaptic targets of vGlut1- and vGlut2-containing axons differed in morphology. vGlut1-labeled axon terminals synapsed predominantly on small-caliber (distal) dendrites (42%, 46/110) or dendritic spines (46%, 50/110). In contrast, vGlut2-containing axons synapsed on larger caliber (proximal) dendritic shafts (> 0.5 µm diameter; 48%, 78/161). A fraction of both vGlut1- or vGlut2-labeled axons synapsed onto TPH-containing dendrites (14% and 34%, respectively). These observations reveal that different populations of glutamate-containing axons innervate selective dendritic domains of serotonergic and non-serotonergic neurons, suggesting they play different functional roles in modulating excitation within the DRN. [source] The subcellular localization of GABAB receptor subunits in the rat substantia nigraEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2003Justin Boyes Abstract The inhibitory effects of GABA within the substantia nigra (SN) are mediated in part by metabotropic GABAB receptors. To better understand the mechanisms underlying these effects, we have examined the subcellular localization of the GABAB receptor subunits, GABAB1 and GABAB2, in SN neurons and afferents using pre-embedding immunocytochemistry combined with anterograde or retrograde labelling. In both the SN pars compacta (SNc) and pars reticulata (SNr), GABAB1 and GABAB2 showed overlapping, but distinct, patterns of immunolabelling. GABAB1 was more strongly expressed by putative dopaminergic neurons in the SNc than by SNr projection neurons, whereas GABAB2 was mainly expressed in the neuropil of both regions. Immunogold labelling for GABAB1 and GABAB2 was localized in presynaptic and postsynaptic elements throughout the SN. The majority of labelling was intracellular or was associated with extrasynaptic sites on the plasma membrane. In addition, labelling for both subunits was found on the presynaptic and postsynaptic membranes at symmetric, putative GABAergic synapses, including those formed by anterogradely labelled striatonigral and pallidonigral terminals. Labelling was also observed on the presynaptic membrane and at the edge of the postsynaptic density at asymmetric, putative excitatory synapses. Double immunolabelling, using the vesicular glutamate transporter 2, revealed the glutamatergic nature of many of the immunogold-labelled asymmetric synapses. The widespread distribution of GABAB subunits in the SNc and SNr suggests that GABAB -mediated effects in these regions are likely to be more complex than previously described, involving presynaptic autoreceptors and heteroreceptors, and postsynaptic receptors on different populations of SN neurons. [source] Oral status indicators DMFT and FS-T: reflections on index selectionEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2001Annemarie A. Schuller Oral status in a population has traditionally been described by the DMFT index (decayed, filled, and missing teeth). There seems to be contradicting and confusing evidence in the literature with regard to the usefulness of different indices. Limitations of the DMFT are recognised, and attempts have been made to develop other indices. Two indices, DMFT and FS-T (filled and sound teeth) have been selected for analysis in the present paper. The purpose of this paper is to examine the relationship between DMFT and FS-T in different populations, and to show consequences of choice of index exemplified in analytical analysis. Data stem from the Trøndelag-83 and -94 studies that were follow-up studies of the Norwegian portion of the 1973 International Collaborative Study. Sunflower scatter plots and regression analyses were used to describe the variation in DMFT and FS-T in different populations. DMFT was more suitable for describing variation in populations with low levels of disease than FS-T, while FS-T was more suitable for describing variation in populations with high levels of disease. It may be concluded that both DMFT and FS-T should be presented when describing oral status in a population. However, choice of index depends first of all on the purpose of the investigation. If there are theoretical reasons to prefer one index instead of the other, the superiority of the alternative index in terms of variation must be disregarded. [source] HOW BRIGHT AND HOW NASTY: EXPLAINING DIVERSITY IN WARNING SIGNAL STRENGTHEVOLUTION, Issue 3 2007Michael P. Speed The conspicuous displays that warn predators of defenses carried by potential prey have been of interest to evolutionary biologists from the time of Wallace and Darwin to the present day. Although most studies implicitly assume that these "aposematic" warning signals simply indicate the presence of some repellent defense such as a toxin, it has been speculated that the intensity of the signal might reliably indicate the strength of defense so that, for example, the nastiest prey might "shout loudest" about their unprofitability. Recent phylogenetic and empirical studies of Dendrobatid frogs provide contradictory views, in one instance showing a positive correlation between toxin levels and conspicuousness, in another showing a breakdown of this relationship. In this paper we present an optimization model, which can potentially account for these divergent results. Our model locates the optimal values of defensive traits that are influenced by a range of costs and benefits. We show that optimal aposematic conspicuousness can be positively correlated with optimal prey toxicity, especially where population sizes and season lengths vary between species. In other cases, optimal aposematic conspicuousness may be negatively correlated with toxicity; this is especially the case when the marginal costs of aposematic displays vary between members of different populations. Finally, when displays incur no allocation costs there may be no single optimum value for aposematic conspicuousness, rather a large array of alternative forms of a display may have equal fitness. [source] POSTMATING SEXUAL SELECTION: ALLOPATRIC EVOLUTION OF SPERM COMPETITION MECHANISMS AND GENITAL MORPHOLOGY IN CALOPTERYGID DAMSELFLIES (INSECTA: ODONATA)EVOLUTION, Issue 2 2004A. Cordero Rivera Abstract Postmating sexual selection theory predicts that in allopatry reproductive traits diverge rapidly and that the resulting differentiation in these traits may lead to restrictions to gene flow between populations and, eventually, reproductive isolation. In this paper we explore the potential for this premise in a group of damselflies of the family Calopterygidae, in which postmating sexual mechanisms are especially well understood. Particularly, we tested if in allopatric populations the sperm competition mechanisms and genitalic traits involved in these mechanisms have indeed diverged as sexual selection theory predicts. We did so in two different steps. First, we compared the sperm competition mechanisms of two allopatric populations of Calopteryx haemorrhoidalis (one Italian population studied here and one Spanish population previously studied). Our results indicate that in both populations males are able to displace spermathecal sperm, but the mechanism used for sperm removal between both populations is strikingly different. In the Spanish population males seem to empty the spermathecae by stimulating females, whereas in the Italian population males physically remove sperm from the spermathecae. Both populations also exhibit differences in genital morphometry that explain the use of different mechanisms: the male lateral processes are narrower than the spermathecal ducts in the Italian population, which is the reverse in the Spanish population. The estimated degree of phenotypic differentiation between these populations based on the genitalic traits involved in sperm removal was much greater than the differentiation based on a set of other seven morphological variables, suggesting that strong directional postmating sexual selection is indeed the main evolutionary force behind the reproductive differentiation between the studied populations. In a second step, we examined if a similar pattern in genital morphometry emerge in allopatric populations of this and other three species of the same family (Calopteryx splendens, C. virgo and Hetaerina cruentata). Our results suggest that there is geographic variation in the sperm competition mechanisms in all four studied species. Furthermore, genitalic morphology was significantly divergent between populations within species even when different populations were using the same copulatory mechanism. These results can be explained by probable local coadaptation processes that have given rise to an ability or inability to reach and displace spermathecal sperm in different populations. This set of results provides the first direct evidence of intraspecific evolution of genitalic traits shaped by postmating sexual selection. [source] PERSPECTIVE: MODELS OF SPECIATION: WHAT HAVE WE LEARNED IN 40 YEARS?EVOLUTION, Issue 10 2003Sergey Gavrilets Abstract Theoretical studies of speciation have been dominated by numerical simulations aiming to demonstrate that speciation in a certain scenario may occur. What is needed now is a shift in focus to identifying more general rules and patterns in the dynamics of speciation. The crucial step in achieving this goal is the development of simple and general dynamical models that can be studied not only numerically but analytically as well. I review some of the existing analytical results on speciation. I first show why the classical theories of speciation by peak shifts across adaptive valleys driven by random genetic drift run into trouble (and into what kind of trouble). Then I describe the Bateson-Dobzhansky-Muller (BDM) model of speciation that does not require overcoming selection. I describe exactly how the probability of speciation, the average waiting time to speciation, and the average duration of speciation depend on the mutation and migration rates, population size, and selection for local adaptation. The BDM model postulates a rather specific genetic architecture of reproductive isolation. I then show exactly why the genetic architecture required by the BDM model should be common in general. Next I consider the multilocus generalizations of the BDM model again concentrating on the qualitative characteristics of speciation such as the average waiting time to speciation and the average duration of speciation. Finally, I consider two models of sympatric speciation in which the conditions for sympatric speciation were found analytically. A number of important conclusions have emerged from analytical studies. Unless the population size is small and the adaptive valley is shallow, the waiting time to a stochastic transition between the adaptive peaks is extremely long. However, if transition does happen, it is very quick. Speciation can occur by mutation and random drift alone with no contribution from selection as different populations accumulate incompatible genes. The importance of mutations and drift in speciation is augmented by the general structure of adaptive landscapes. Speciation can be understood as the divergence along nearly neutral networks and holey adaptive landscapes (driven by mutation, drift, and selection for adaptation to a local biotic and/or abiotic environment) accompanied by the accumulation of reproductive isolation as a by-product. The waiting time to speciation driven by mutation and drift is typically very long. Selection for local adaptation (either acting directly on the loci underlying reproductive isolation via their pleiotropic effects or acting indirectly via establishing a genetic barrier to gene flow) can significantly decrease the waiting time to speciation. In the parapatric case the average actual duration of speciation is much shorter than the average waiting time to speciation. Speciation is expected to be triggered by changes in the environment. Once genetic changes underlying speciation start, they go to completion very rapidly. Sympatric speciation is possible if disruptive selection and/or assortativeness in mating are strong enough. Sympatric speciation is promoted if costs of being choosy are small (or absent) and if linkage between the loci experiencing disruptive selection and those controlling assortative mating is strong. [source] EVOLUTION OF REPRODUCTIVE STRATEGIES IN THE SEXUALLY DECEPTIVE ORCHID OPHRYS SPHEGODES: HOW DOES FLOWER-SPECIFIC VARIATION OF ODOR SIGNALS INFLUENCE REPRODUCTIVE SUCCESS?EVOLUTION, Issue 6 2000Manfred Ayasse Abstract The orchid Ophrys sphegodes Miller is pollinated by sexually excited males of the solitary bee Andrena nigroaenea, which are lured to the flowers by visual cues and volatile semiochemicals. In O. sphegodes, visits by pollinators are rare. Because of this low frequency of pollination, one would expect the evolution of strategies that increase the chance that males will visit more than one flower on the same plant; this would increase the number of pollination events on a plant and therefore the number of seeds produced. Using gas chromatography-mass spectrometry (GC-MS) analyses, we identified more than 100 compounds in the odor bouquets of labellum extracts from O. sphegodes; 24 compounds were found to be biologically active in male olfactory receptors based on gas chromatography with electroantennographic detection (GC-EAD). Gas chromatography (GC) analyses of odors from individual flowers showed less intraspecific variation in the odor bouquets of the biologically active compounds as compared to nonactive compounds. This can be explained by a higher selective pressure on the pollinator-attracting communication signal. Furthermore, we found a characteristic variation in the GC-EAD active esters and aldehydes among flowers of different stem positions within an inflorescence and in the n-alkanes and n-alkenes among plants from different populations. In our behavioral field tests, we showed that male bees learn the odor bouquets of individual flowers during mating attempts and recognize them in later encounters. Bees thereby avoid trying to mate with flowers they have visited previously, but do not avoid other flowers either of a different or the same plant. By varying the relative proportions of saturated esters and aldehydes between flowers of different stem positions, we demonstrated that a plant may take advantage of the learning abilities of the pollinators and influence flower visitation behavior. Sixty-seven percent of the males that visited one flower in an inflorescence returned to visit a second flower of the same inflorescence. However, geitonogamy is prevented and the likelihood of cross-fertilization is enhanced by the time required for the pollinium deposited on the pollinator to complete its bending movement, which is necessary for pollination to occur. Cross-fertilization is furthermore enhanced by the high degree of odor variation between plants. This variation minimizes learned avoidance of the flowers and increases the likelihood that a given pollinator would visit several to many different plants within a population. [source] Thermal adaptation of Arctic charr: experimental studies of growth in eleven charr populations from Sweden, Norway and BritainFRESHWATER BIOLOGY, Issue 2 2005S. LARSSON Summary 1. Experimental growth data for Arctic charr (Salvelinus alpinus L.), all fed on excess rations, from 11 European watercourses between 54 and 70°N were analysed and fitted to a new general growth model for fish. The model was validated by comparing its predictions with the growth rate of charr in the wild. 2. Growth performance varied among populations, mainly because of variation in the maximum growth potential, whereas the thermal response curves were similar. The estimated lower and upper temperatures for growth varied between ,1.7 to 5.3 and 20.8,23.2 °C, respectively, while maximum growth occurred between 14.4 and 17.2 °C. 3. There was no geographical or climatic trend in growth performance among populations and therefore no indication of thermal adaptation. The growth potential of charr from different populations correlated positively with fish body length at maturity and maximum weight in the wild. Charr from populations including large piscivorous fish had higher growth rates under standardised conditions than those from populations feeding on zoobenthos or zooplankton. Therefore, the adaptive variation in growth potential was related to life-history characteristics and diet, rather than to thermal conditions. [source] Carotenoid and melanin-based ornaments signal similar aspects of male quality in two populations of the common yellowthroatFUNCTIONAL ECOLOGY, Issue 1 2010Peter O. Dunn Summary 1.,Female preferences for particular male ornaments may shift between populations as a consequence of ecological differences that change the reliability and detectability of the ornament, but few studies have examined how ornaments function in different populations. 2.,We examined the signalling function of male plumage ornaments in a warbler, the common yellowthroat (Geothlypis trichas), breeding in New York (NY) and Wisconsin (WI), USA. Males have two prominent ornaments: a black facial mask pigmented with melanin and a yellow bib pigmented by carotenoids. Previous studies in WI indicate that the size of the mask, and not the bib, is primarily related to female choice and male reproductive success. In NY, however, the pattern is reversed and attributes of the bib (size and colour), and not the mask, are the target of sexual selection. 3.,We found that brightness of the yellow bib was the best signal of humoral immunity (immunoglobulin G) in NY and mask size was the best signal in WI, after controlling for breeding experience and capture date. Thus, similar aspects of male quality appeared to be signalled by different ornaments in different populations. 4.,There was no difference between populations in the level of plasma carotenoids or the prevalence of malarial parasites, which may affect the costs and benefits of choosing males with particular ornaments in each location. 5.,Even though females in different populations prefer different ornaments produced by different types of pigments, these ornaments appear to be signalling similar aspects of male quality. Our results caution against inferring the function of particular ornaments based simply on their type of pigment. [source] Measuring natural abundance of 13C in respired CO2: variability and implications for non-invasive dietary analysisFUNCTIONAL ECOLOGY, Issue 6 2001S. E. PERKINS Summary 1,Three experiments were performed, using laboratory mice (Mus musculus) as a model species, to evaluate the potential of using measurements of carbon isotope ratios in expired CO2 for tracing diets. 2,Breath 13C signatures of mice fed a constant diet (,21·4, ± 0·35) reflected their diet, but were depleted by on average ,5·7,. Body mass, sex and age were independent and significant factors correlated with the variability of 13C enrichment in respired CO2. 3,Breath 13C signatures from starved mice (7 h) were lower than unstarved mice by 2·0,. Subsequently when starved mice were fed a small meal of a new diet, breath 13C signatures approached those of the new diets within 15 min, returning to preingestion levels after 105 min. 4,After a permanent diet switch 13C values of breath were not asymptotic within 6 days, possibly because of use of fat reserves during the daytime carrying an isotopic memory of the previous diet. Hence, individual breath 13C signatures may vary according to nutritive state and previous dietary history. 5,Interindividual variability was measured at 3·3,. The implications are that large samples of individuals will be required to distinguish between diets of different populations where the isotopic difference between their diets was small , for example, that expected between herbivorous and carnivorous diets. However, breath would be suitable for distinguishing between dietary intakes of individuals for food types that are isotopically more distinct , such as between C3 and C4 plants. [source] Pharmacoepidemiology of anabolic androgenic steroids: a reviewFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 1 2005Ingemar Thiblin Abstract Non-prescribed use of anabolic androgenic steroids (AAS) has been associated with a number of physical and psychiatric/behavioural complications, some of which are potentially lethal. Here, we review both observational and experimental studies on human subjects concerned with such side-effects. The only physical complication of AAS use that receives definitive support from such investigations is unfavourable changes in blood lipid profiles. Support for various psychiatric complications has also been provided by a number of cross-sectional studies, most involving comparisons between weight-training individuals who use or do not use AAS. Certain of these complications, in particular hypomania and increased aggressiveness, have been confirmed in some, but not all, randomized controlled studies. Epidemiological attempts to determine whether AAS use triggers violent behaviour have failed, primarily because of high rates of non-participation. Studies regarding the prevalence of AAS use in different populations typically report life-time prevalences of 1,5% among adolescents. However, the life-time prevalence (i.e. use on at least one occasion) is of doubtful relevance in attempting to estimate the number of individuals at risk for side-effects, as most of these complications appear to develop during prolonged use of AAS. Furthermore, it is reasonable to assume that the symptoms and signs of AAS use are often overlooked by healthcare professionals, so that the number of cases of possible AAS-related complications is virtually unknown. These limitations, together with an apparently low prevalence of prolonged AAS use among the general population, indicate that future epidemiological research in this area should focus on retrospective case,control studies and, perhaps, also on prospective cohort studies of populations selected for a high prevalence of AAS use, rather than attempting to perform large-scale population-based studies. [source] Interactions between genetic and reproductive factors in breast cancer risk in a population-based sample of African-American familiesGENETIC EPIDEMIOLOGY, Issue 4 2002Valérie Chaudru Abstract Incidence of breast cancer (BC) varies among ethnic groups, with higher rates in white than in African-American women. Until now, most epidemiological and genetic studies have been carried out in white women. To investigate whether interactions between genetic and reproductive risk factors may explain part of the ethnic disparity in BC incidence, a genetic epidemiology study was conducted, between 1989 and 1994, at the Howard University Cancer Center (Washington, DC), which led to the recruitment of 245 African-American families. Segregation analysis of BC was performed by use of the class D regressive logistic model that allows for censored data to account for a variable age of onset of disease, as implemented in the REGRESS program. Segregation analysis of BC was consistent with a putative dominant gene effect (P < 0.000001) and residual sister-dependence (P < 0.0001). This putative gene was found to interact significantly with age at menarche (P = 0.048), and an interaction with a history of spontaneous abortions was suggested (P = 0.08). A late age at menarche increased BC risk in gene carriers but had a protective effect in non-gene carriers. A history of spontaneous abortions had a protective effect in gene carriers and increased BC risk in non-gene carriers. Our findings agree partially with a similar analysis of French families showing a significant gene × parity interaction and a suggestive gene × age at menarche interaction. Investigating gene × risk factor interactions in different populations may have important implications for further biological investigations and for BC risk assessment. Genet. Epidemiol. 22:285,297, 2002. © 2002 Wiley-Liss, Inc. [source] Are local weather, NDVI and NAO consistent determinants of red deer weight across three contrasting European countries?GLOBAL CHANGE BIOLOGY, Issue 7 2009MARÍA MARTÍNEZ-JAUREGUI Abstract There are multiple paths via which environmental variation can impact herbivore ecology and this makes the identification of drivers challenging. Researchers have used diverse approaches to describe the association between environmental variation and ecology, including local weather, large-scale patterns of climate, and satellite imagery reflecting plant productivity and phenology. However, it is unclear to what extent it is possible to find a single measure that captures climatic effects over broad spatial scales. There may, in fact, be no a priori reason to expect populations of the same species living in different areas to respond in the same way to climate as their population may experience limiting factors at different times of the year, and the forms of regulation may differ among populations. Here, we examine whether the same environmental indices [seasonal Real Bioclimatic Index (RBI), seasonal Normalized Difference Vegetation Index (NDVI) and winter North Atlantic Oscillation (NAO)] influence body size in different populations of a large ungulate living in Mediterranean Spain, Western Scotland and Norway. We found substantial differences in the pattern of weight change over time in adult female red deer among study areas as well as different environmental drivers associated with variation in weight. The lack of general patterns for a given species at a continental scale suggest that detailed knowledge regarding the way climate affects local populations is often necessary to successfully predict climate impact. We caution against extrapolation of results from localized climate,population studies to broad spatial scales. [source] Effects of climate on population fluctuations of ibexGLOBAL CHANGE BIOLOGY, Issue 2 2008VIDAR GRØTAN Abstract Predicting the effects of the expected changes in climate on the dynamics of populations require that critical periods for climate-induced changes in population size are identified. Based on time series analyses of 26 Swiss ibex (Capra ibex) populations, we show that variation in winter climate affected the annual changes in population size of most of the populations after accounting for the effects of density dependence and demographic stochasticity. In addition, precipitation during early summer also influenced the population fluctuations. This suggests that the major influences of climate on ibex population dynamics operated either through loss of individuals during winter or early summer, or through an effect on fecundity. However, spatial covariation in these climate variables was not able to synchronize the population fluctuations of ibex over larger distances, probably due to large spatial heterogeneity in the effects of single climate variables on different populations. Such spatial variation in the influence of the same climate variable on the local population dynamics suggests that predictions of influences of climate change need to account for local differences in population dynamical responses to climatic conditions. [source] On the empirical association between poor health and low socioeconomic status at old ageHEALTH ECONOMICS, Issue 3 2002Christian Salas Abstract Epidemiologic studies using mortality rates as indicators of health fail to find any meaningful association between poor health and low socioeconomic status in older age-groups, whereas economic studies using self-assessed health consistently find a significant positive correlation, even after controlling for self-reporting errors. Such contradictory results have not been reported for working age individuals. A simple explanation might be that the elderly samples on which the epidemiologic and economic studies are based come from different populations. However, this paper shows that similar contradictory results are obtained even when the same samples are used, simply by switching between self-assessed health and mortality as health indicators. An alternative explanation is proposed, namely that these health indicators yield different results because they relate to different ranges of the latent health variable at old age. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||