Home About us Contact
|
Home About us Contact | ||
|
|
||
Descent
Kinds of Descent Selected AbstractsINCOMPLETE UNDERSTANDING OF INCOMPLETE DESCENTANZ JOURNAL OF SURGERY, Issue 11 2008FRACS, MS (Melb), Spencer W. Beasley MBChB (Otago) No abstract is available for this article. [source] Contextualism, Scepticism, and the Problem of Epistemic DescentDIALECTICA, Issue 4 2001Duncan Pritchard Perhaps the most dominant anti-sceptical proposal in recent literature ,advanced by such figures as Stewart Cohen, Keith DeRose and David Lewis ,is the contextualist response to radical scepticism. Central to the contextualist thesis is the claim that, unlike other non-contextualist anti-sceptical theories, contextualism offers a dissolution of the sceptical paradox that respects our common sense epistemological intuitions. Taking DeRose's view as representative of the contextualist position, it is argued that instead of offering us an intuitive response to scepticism, contextualism is actually committed to a revisionist stance as regards our everyday usage of epistemic terms. In particular, it is argued that the thesis fails to present a satisfactory explication of a notion ,that of,epistemic descent', that is pivotal to the anti-sceptical import of the account. On the positive side, however, it is claimed that although the contextualist response to scepticism is ultimately unsatisfying, DeRose's theory does contain within it the framework for a completely different - and far more persuasive - account of the,phenomenology'of scepticism which runs along non-contextualist lines. [source] Parental investment, sexual selection and sex ratiosJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2008HANNA KOKKO Abstract Conventional sex roles imply caring females and competitive males. The evolution of sex role divergence is widely attributed to anisogamy initiating a self-reinforcing process. The initial asymmetry in pre-mating parental investment (eggs vs. sperm) is assumed to promote even greater divergence in post-mating parental investment (parental care). But do we really understand the process? Trivers [Sexual Selection and the Descent of Man 1871,1971 (1972), Aldine Press, Chicago] introduced two arguments with a female and male perspective on whether to care for offspring that try to link pre-mating and post-mating investment. Here we review their merits and subsequent theoretical developments. The first argument is that females are more committed than males to providing care because they stand to lose a greater initial investment. This, however, commits the ,Concorde Fallacy' as optimal decisions should depend on future pay-offs not past costs. Although the argument can be rephrased in terms of residual reproductive value when past investment affects future pay-offs, it remains weak. The factors likely to change future pay-offs seem to work against females providing more care than males. The second argument takes the reasonable premise that anisogamy produces a male-biased operational sex ratio (OSR) leading to males competing for mates. Male care is then predicted to be less likely to evolve as it consumes resources that could otherwise be used to increase competitiveness. However, given each offspring has precisely two genetic parents (the Fisher condition), a biased OSR generates frequency-dependent selection, analogous to Fisherian sex ratio selection, that favours increased parental investment by whichever sex faces more intense competition. Sex role divergence is therefore still an evolutionary conundrum. Here we review some possible solutions. Factors that promote conventional sex roles are sexual selection on males (but non-random variance in male mating success must be high to override the Fisher condition), loss of paternity because of female multiple mating or group spawning and patterns of mortality that generate female-biased adult sex ratios (ASR). We present an integrative model that shows how these factors interact to generate sex roles. We emphasize the need to distinguish between the ASR and the operational sex ratio (OSR). If mortality is higher when caring than competing this diminishes the likelihood of sex role divergence because this strongly limits the mating success of the earlier deserting sex. We illustrate this in a model where a change in relative mortality rates while caring and competing generates a shift from a mammalian type breeding system (female-only care, male-biased OSR and female-biased ASR) to an avian type system (biparental care and a male-biased OSR and ASR). [source] Descent with Modification: Bioanthropological Identities in 2009AMERICAN ANTHROPOLOGIST, Issue 2 2010Julienne Rutherford ABSTRACT, In the year of Darwin, what were the emerging themes and events that united disparate manifestations of bioanthropological identities? In this review, I draw from conference proceedings, the literature, and electronic social networking to assess six major developments in 2009: the bioanthropological legacy of Darwin on the 200th anniversary of his birth; the efforts of primatologists from a multitude of backgrounds to grapple with the construction of a unified ethics; the remediation of philosophical tensions between field and captive primatology; the coalescence of an explicitly comparative evolutionary anthropology; the role of conference attendance and collaborations in forging disciplinary identity; and the provocative implications of the Ardipithecus ramidus story. The field of biological anthropology continues to evolve and diversify, obscuring a common identity, but as in other organic fractal systems, a common origin as anthropologists leads to descent with modification. [source] Life and Words: Violence and the Descent into the OrdinaryAMERICAN ANTHROPOLOGIST, Issue 1 2009CABEIRI DEBERGH ROBINSON No abstract is available for this article. [source] The Noble House in Colonial Puebla, Mexico: Descent, Inheritance, and the Nahua TraditionAMERICAN ANTHROPOLOGIST, Issue 3 2000John K. Chance Claude Lévi-Strauss's concept of the 'house" has proven to be a viable alternative to traditional lineage theory in the study of many societies, and this paper applies the house concept to a Mesoamencan case. The teccalli, or noble house, was an important aspect of Nahua (Aztec) sociopolitical organization in prchispanic and early colonial central Mexico, particularly in the Puebla-Tlaxcala Valley. It is often characterized as a lineage with rights in land and commoner labor, yet the nature of descent, succession, and inheritance are little understood. Late colonial wills and lawsuits from the (formerly) Nahua community of Santiago Tecali in the Puebla-Tlaxcala Valley provide valuable insights into these matters that can also help us to understand earlier periods. It is argued that the Nahua noble house can be better understood as a house than as a lineage, [house, kinship, inheritance, Nahuas, Mesoamerica] [source] Instrument Development of the Confidence in Home Care Services Questionnaire for Use With Elders and Caregivers of Mexican DescentPUBLIC HEALTH NURSING, Issue 3 2006Janice D. Crist ABSTRACT Mexican American elders use home care services less than non-Hispanic white elders, and a larger study is testing whether lack of confidence in home care services, measured by the Community Service Attitude Inventory, is a factor. In order to further develop the questionnaire for use with Mexican American elders and caregivers, qualitative interviews were conducted with Mexican American elders (n=5), Mexican American caregivers (n=5), and home care providers (n=5). Content analysis of interviews supported 2 dimensions: confidence and fear/worry. The research team developed 29 items from the dimensions. Testing of the items (n=15) suggested content validity and two additional items. The revised questionnaire was translated and tested for language equivalence in Spanish and English, assisted by a local community advisory council (n=9). Through collaboration, bicultural/bilingual teams and community partners refined 1 instrument that can be used to measure one of many barriers to equity in health care services with vulnerable populations. Thematic findings may be incorporated into nurses' interventions as they offer home care services to families. [source] Introduction: Protistan Biology, Horizontal Gene Transfer, and Common Descent Uncover Faulty Logic in Intelligent Design,THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 1 2010AVELINA ESPINOSA No abstract is available for this article. [source] Descent with modification: the unity underlying homology and homoplasy as seen through an analysis of development and evolutionBIOLOGICAL REVIEWS, Issue 3 2003BRIAN K. HALL ABSTRACT Homology is at the foundation of comparative studies in biology at all levels from genes to phenotypes. Homology similarity because of common descent and ancestry, homoplasy is similarity arrived at via independent evolution However, given that there is but one tree of life, all organisms, and therefore all features of organisms, share degree of relationship and similarity one to another. That sharing may be similarity or even identity of structure the sharing of a most recent common ancestor,as in the homology of the arms of humans and apes,or it reflect some (often small) degree of similarity, such as that between the wings of insects and the wings of groups whose shared ancestor lies deep within the evolutionary history of the Metazoa. It may reflect sharing entire developmental pathways, partial sharing, or divergent pathways. This review compares features classified homologous with the classes of features normally grouped as homoplastic, the latter being convergence, parallelism, reversals, rudiments, vestiges, and atavisms. On the one hand, developmental mechanisms may be conserved, when a complete structure does not form (rudiments, vestiges), or when a structure appears only in some individuals (atavisms). On the other hand, different developmental mechanisms can produce similar (homologous) features Joint examination of nearness of relationship and degree of shared development reveals a continuum within expanded category of homology, extending from homology , reversals , rudiments , vestiges , atavisms , parallelism, with convergence as the only class of homoplasy, an idea that turns out to be surprisingly old. realignment provides a glimmer of a way to bridge phylogenetic and developmental approaches to homology homoplasy, a bridge that should provide a key pillar for evolutionary developmental biology (evo-devo). It will and in a practical sense cannot, alter how homoplastic features are identified in phylogenetic analyses. But rudiments, reversals, vestiges, atavisms and parallelism as closer to homology than to homoplasy should guide toward searching for the common elements underlying the formation of the phenotype (what some have called deep homology of genetic and/or cellular mechanisms), rather than discussing features in terms of shared independent evolution. [source] Daily Variation in Ethnic Identity, Ethnic Behaviors, and Psychological Well,Being among American Adolescents of Chinese DescentCHILD DEVELOPMENT, Issue 5 2002Tiffany Yip This study examined the links among Chinese American adolescents' (N= 96) global ethnic identity and their ethnic behaviors, ethnic identity salience, and psychological well,being based on daily diaries collected over a 2,week period. The daily association between engagement in ethnic behaviors and ethnic salience was positive regardless of overall ethnic identity. The daily,level association between ethnic identity salience and well,being, however, was dependent on adolescents' global ethnic identity. Among adolescents who were moderate or high in global ethnic identity, ethnic identity salience was consistently associated with positive well,being at the daily level. In contrast, the daily association between ethnic identity salience and well,being was less strong for youths who were low in ethnic identity. Additionally, a higher level of salience and a weaker association between salience and negative symptoms was found for girls than for boys, and older youths reported a weaker association between salience and positive symptoms than did younger youths. [source] Sinai Tschulok (1875,1945),a pioneer of CladisticsCLADISTICS, Issue 1 2010Olivier Rieppel Sinai Tschulok emigrated from the Ukraine to Switzerland, where he studied natural sciences, in particular biology. He founded and managed his own high school, which prepared students for entry to university-level education. This left him little time for research, which may explain why his work largely fell into oblivion. He did publish two influential books, however (Tschulok, S., 1910, Das System der Biologie in Forschung und Lehre, Gustav Fischer, Jena and Tschulok, S., 1922, Deszendenzlehre, Gustav Fischer, Jena), which were cited and commented upon favourably by both Walter Zimmermann and Willi Hennig. The most important point, in their opinion, was how Tschulok's explication of biological systematics had turned the "natural system" into a proof for the "Theory of Descent". The influence of Walter Zimmermann on Willi Hennig and the development of phylogenetic systematics is well known. Here some parts of Tschulok's writings are discussed that render him a pioneer in Cladistics. © The Willi Hennig Society 2009. [source] Writing the History of Humanity: The Role of Museums in Defining Origins and Ancestors in a Transnational WorldCURATOR THE MUSEUM JOURNAL, Issue 1 2005Monique Scott ABSTRACT This article explores the question of how transnational audiences experience anthropology exhibitions in particular, and the natural history museum overall. Of interest are the ways in which natural history museums reconcile anthropological notions of humanity's shared evolutionary history,in particular, African origins accounts,with visitors' complex cultural identities. Through case studies of British, American, and Kenyan museum audiences, this research probed the cultural preconceptions that museum visitors bring to the museum and use to interpret their evolutionary heritage. The research took special notice of audiences of African descent, and their experiences in origins exhibitions and the natural history museums that house them. The article aims to draw connections between natural history museums and the dynamic ways in which museum visitors make meaning. As museums play an increasing role in the transnational homogenization of cultures, human origins exhibitions are increasingly challenged to communicate an evolutionary prehistory that we collectively share, while validating the cultural histories that make us unique. [source] Obsessive-compulsive disorder among African Americans and blacks of Caribbean descent: results from the national survey of American life,DEPRESSION AND ANXIETY, Issue 12 2008Joseph A. Himle Ph.D. Abstract Background: There is limited research regarding the nature and prevalence of obsessive-compulsive disorder (OCD) among various racial and ethnic subpopulations within the United States, including African Americans and blacks of Caribbean descent. Although heterogeneity within the black population in the United States has largely been ignored, notable differences exist between blacks of Caribbean descent and African Americans with respect to ethnicity, national heritage, and living circumstances. This is the first comprehensive examination of OCD among African Americans and blacks of Caribbean descent. Methods: Data from the National Survey of American Life, a national household probability sample of African Americans and Caribbean blacks in the United States, were used to examine rates of OCD among these groups. Results: Lifetime and 12-month OCD prevalence estimates were very similar for African Americans and Caribbean blacks. Persistence of OCD and rates of co-occurring psychiatric disorders were very high and also similar between African American and Caribbean black respondents. Both groups had high levels of overall mental illness severity and functional impairment. Use of services was low for both groups, particularly in specialty mental health settings. Use of anti-obsessional medications was also rare, especially among the Caribbean black OCD population. Conclusions: OCD among African Americans and Caribbean blacks is very persistent, often accompanied by other psychiatric disorders, and is associated with high overall mental illness severity and functional impairment. It is also likely that very few blacks in the United States with OCD are receiving evidence-based treatment and thus considerable effort is needed to bring treatment to these groups. Depression and Anxiety, 2008. Published 2008 Wiley-Liss, Inc. [source] Botulinum Toxin for the Treatment of Facial FlushingDERMATOLOGIC SURGERY, Issue 1 2004Melanie Yuraitis MS Background. Facial flushing is a common problem that is encountered by fair-skinned patients of Celtic and Northern European descent. Although usually transient in nature, some patients display a persistent reddened skin tone, with periods of increased erythema. Treatment of this condition is limited. Objective. To describe a novel method for the treatment of persistent facial flushing. Method. We report a case of persistent facial flushing that was resistant to multiple pulsed dye laser treatments and was successfully treated with botulinum toxin A. Results. The posttreatment appearance was dramatic, and the patient was highly satisfied with the cosmetic outcome. Conclusion. Botulinum toxin A can be used in small quantities to decrease persistent facial flushing temporarily. [source] Fixing the Hole in the Bucket: Household Poverty Dynamics in the Peruvian AndesDEVELOPMENT AND CHANGE, Issue 5 2006Anirudh Krishna ABSTRACT Achieving the Millennium Development Goal of halving poverty will require simultaneous action on two separate fronts: helping poor people escape from poverty, and stemming the flow of people into poverty. This article examines forty Peruvian communities, and finds that descents into poverty have occurred alongside escapes in every one of them. Escape and descent are asymmetric in terms of reasons: while one set of reasons is responsible for escapes from poverty, another and different set of reasons is associated with descent. Making progress in poverty reduction will require measures to accelerate escapes whilst at the same time slowing down descents. The article looks at the different policies which will be required to serve these two separate purposes. [source] Differing aspects of insulin resistance in diabetes complications: the shape of things to come.DIABETIC MEDICINE, Issue 12 2002RD Lawrence lecture 2000 Abstract The anticipated global epidemic of diabetes, largely as a consequence of increased rates of obesity, will particularly impact on people of South Asian and African Caribbean descent, two populations at elevated risk of insulin resistance. This article contrasts the consequent heightened risk of heart disease on the one hand in South Asians, and the paradoxical protection from heart disease in African Caribbeans on the other. Protection from the hypertriglyceridaemic effects of insulin resistance is likely to account for much of the African Caribbean paradox, although the mechanisms remain unclear. The growing evidence that insulin resistance is commonly observed in people with Type 1 diabetes, as well as those with Type 2 diabetes, and that features of insulin resistance may play a crucial role in the development of microvascular, as well as macrovascular complications, is also discussed. This indicates novel targets for the prevention and treatment of diabetes complications. Diabet. Med. 19, 973,977 (2002) [source] The transformation of kinship and the family in late Anglo-Saxon EnglandEARLY MEDIEVAL EUROPE, Issue 3 2001Andrew Wareham The development of the family into a small unit in which descent was traced almost exclusively through the male line is regarded as a major turning point in medieval European history. The early stages of the formation of agnatic kinship have usually been connected to strategies designed to preserve and retain control of patrimonies and castles, arising from the breakdown of public order. In this article it is suggested that the emergence of new kinship values was connected to the investment of aristocratic energy and resources in monastic programmes, and to subtle changes in lay involvement with the rituals associated with death and the salvation of souls. [source] The origins of kingship in early medieval KentEARLY MEDIEVAL EUROPE, Issue 1 2000Charlotte Behr In this article, it is argued that Bede's famous account of the origin and early development of the people and kings of Kent in Historia ecclesiastica (I.15) does not report historical events, but reflects eighth-century concepts of migration-period kingship with mythical links to the Jutes of Scandinavia. Bracteate evidence shows that the veneration of Woden existed in Kent by the sixth century. Support for a contemporary belief in the Scandinavian origin of Kentish kings is found in locally produced bracteates, which imitate Scandinavian styles, and where several recovered from Kentish cemeteries are found in close proximity to places with royal connections. These include the only known Kentish site linked to the veneration of Woden. Evidence suggests that Kentish genealogy reflects a mythical belief in ancestry from Woden, rather than historical descent from Scandinavian Jutes. Finally, it is argued that Kentish bracteates, usually found in exceptionally rich female graves, were worn by high status women. These women may have played a significant role in legitimizing new royal claims. [source] Evidence of Robust Coupling of Atrioventricular Mechanical Function of the Right Side of the Heart: Insights from M-Mode Analysis of Annular MotionECHOCARDIOGRAPHY, Issue 6 2008Raveen Bazaz M.D. Background: Extensive data exist regarding annular descent and ventricular function. We have already demonstrated significant differences in amplitude and timing of events between maximal mitral (MAPSE) and tricuspid (TAPSE) annular plane systolic excursion as well as described quantitative temporal differences in annular ascent (AA) between the right and left sides of the heart. However, whether any relationship exists between annular ascent and descent components remains uninvestigated. Methods: Left ventricular ejection fraction (LVEF), right ventricular fractional area change (RVFAC), MAPSE, TAPSE, MV, and TV AA as well as pulsed tissue Doppler of the lateral MV and TV annuli were recorded from 53 patients. Results: In this population (age 55 ± 17 years) mean LVEF was 55 ± 19%, mean RVFAC was 47 ± 20%, mean MAPSE was 2.11 ± 0.72 cm, mean TAPSE was 1.48 ± 0.44 cm, mean MV AA was 0.52 ± 0.17 cm, TV AA was 0.96 ± 0.47, MV A-wave 0.10 ± 0.04 cm/s, and TV A-wave was 0.13 ± 0.05 cm/s. A more robust correlation was seen between TV AA and RVFAC than between MV AA and LVEF and also between TV AA and pulsed TDI TV A-wave velocity than between MV AA and pulsed TDI MV A-wave. Conclusion: Our data reveal that mechanical systolic functions of the atria and the ventricles are more closely coupled on the right than on the left side of the heart. Whether this is a result of anatomic linking or chamber geometry will require further study. [source] Assessment of Acute Right Ventricular Dysfunction Induced by Right Coronary Artery Occlusion Using Echocardiographic Atrioventricular Plane DisplacementECHOCARDIOGRAPHY, Issue 6 2000Alpesh R. Shah M.D. Right ventricular (RV) systolic function analysis by echocardiography has traditionally required RV endocardial border definition with subsequent tracing and is often inaccurate or impossible in technically poor studies. The atrioventricular plane displacement (AVPD) method attempts to use the descent of the tricuspid annular ring, a reflection of the longitudinal shortening of the right ventricle, as a surrogate marker for RV systolic function. We hypothesized that RV ischemia induced during right coronary artery occlusion proximal to the major right ventricular branches would result in severe right ventricular systolic dysfunction detectable by the AVPD method. During this pilot study, seven patients undergoing elective proximal RCA angioplasty had echocardiographic measurement of RV AVPD performed at baseline (i.e., immediately prior to RCA balloon inflation), during the last 30 seconds of first RCA balloon inflation, and at 1 minute after balloon deflation (recovery). Lateral and medial RV AVPD were significantly reduced from baseline values during intracoronary balloon inflation. (Lateral: 2.45 cm ± 0.22 vs 1.77 cm ± 0.13, P < 0.001; medial: 1.46 cm ± 0.37 vs 1.28 cm ± 0.32, P < 0.05). Additionally, lateral and medial RV AVPD significantly returned towards baseline values during recovery. (Lateral: 2.39 cm ± 0.20, P < 0.001; medial: 1.58 cm ± 0.27, P = 0.01). At baseline, all lateral RV AVPD values were > 2.0 cm, whereas during balloon inflation all were < 2.0 cm. No such clear distinction was found in medial RV AVPD values. Proximal RCA angioplasty is associated with a significant reduction in lateral and medial RV AVPD. Thus RV AVPD may serve as a marker for RV systolic dysfunction. [source] Osmoadaptation in bacteria and archaea: common principles and differencesENVIRONMENTAL MICROBIOLOGY, Issue 12 2001Markus Roeßler The availability of water is the most important prerequisite for life of any living cell, and exposure of cells to hypersaline conditions always threatens the cells with a drastic loss of water. To re-establish the essential turgor pressure, cells increase the water activity of their cytoplasm by accumulation of compatible solutes, either by synthesis or by uptake. The ability to respond to increasing osmolality is well conserved in all three lines of descent and, here, we compare the osmoadaptive strategies of Bacteria and Archaea. The temporal sequence of events after an osmotic upshock will be discussed, with a focus on the most rapid response, notably the mechanisms of transport activation at the protein level, and different signals for osmolality will be compared. The spectrum of compatible solutes used by different organisms is rather diverse and a comparison of ,bacterial' and ,archaeal' compatible solutes will be given. [source] GENETIC STUDY: FULL ARTICLE: Incorporating age at onset of smoking into genetic models for nicotine dependence: evidence for interaction with multiple genesADDICTION BIOLOGY, Issue 3 2010Richard A. Grucza ABSTRACT Nicotine dependence is moderately heritable, but identified genetic associations explain only modest portions of this heritability. We analyzed 3369 SNPs from 349 candidate genes and investigated whether incorporation of SNP-by-environment interaction into association analyses might bolster gene discovery efforts and prediction of nicotine dependence. Specifically, we incorporated the interaction between allele count and age at onset of regular smoking (AOS) into association analyses of nicotine dependence. Subjects were from the Collaborative Genetic Study of Nicotine Dependence and included 797 cases ascertained for Fagerström nicotine dependence and 811 non-nicotine-dependent smokers as controls, all of European descent. Compared with main effect models, SNP × AOS interaction models resulted in higher numbers of nominally significant tests, increased predictive utility at individual SNPs and higher predictive utility in a multi-locus model. Some SNPs previously documented in main effect analyses exhibited improved fits in the joint analysis, including rs16969968 from CHRNA5 and rs2314379 from MAP3K4. CHRNA5 exhibited larger effects in later-onset smokers, in contrast with a previous report that suggested the opposite interaction (Weiss et al. 2008). However, a number of SNPs that did not emerge in main effect analyses were among the strongest findings in the interaction analyses. These include SNPs located in GRIN2B (P = 1.5 × 10,5), which encodes a subunit of the N-methyl-D-aspartate receptor channel, a key molecule in mediating age-dependent synaptic plasticity. Incorporation of logically chosen interaction parameters, such as AOS, into genetic models of substance use disorders may increase the degree of explained phenotypic variation and constitutes a promising avenue for gene discovery. [source] LIKELIHOOD-BASED INFERENCE IN ISOLATION-BY-DISTANCE MODELS USING THE SPATIAL DISTRIBUTION OF LOW-FREQUENCY ALLELESEVOLUTION, Issue 11 2009John Novembre Estimating dispersal distances from population genetic data provides an important alternative to logistically taxing methods for directly observing dispersal. Although methods for estimating dispersal rates between a modest number of discrete demes are well developed, methods of inference applicable to "isolation-by-distance" models are much less established. Here, we present a method for estimating ,,2, the product of population density (,) and the variance of the dispersal displacement distribution (,2). The method is based on the assumption that low-frequency alleles are identical by descent. Hence, the extent of geographic clustering of such alleles, relative to their frequency in the population, provides information about ,,2. We show that a novel likelihood-based method can infer this composite parameter with a modest bias in a lattice model of isolation-by-distance. For calculating the likelihood, we use an importance sampling approach to average over the unobserved intraallelic genealogies, where the intraallelic genealogies are modeled as a pure birth process. The approach also leads to a likelihood-ratio test of isotropy of dispersal, that is, whether dispersal distances on two axes are different. We test the performance of our methods using simulations of new mutations in a lattice model and illustrate its use with a dataset from Arabidopsis thaliana. [source] THE FITNESS EFFECTS OF SPONTANEOUS MUTATIONS IN CAENORHABDITIS ELEGANSEVOLUTION, Issue 4 2000Larissa L. Vassilieva Abstract. Spontaneous mutation to mildly deleterious alleles has emerged as a potentially unifying component of a variety of observations in evolutionary genetics and molecular evolution. However, the biological significance of hypotheses based on mildly deleterious mutation depends critically on the rate at which new mutations arise and on their average effects. A long-term mutation-accumulation experiment with replicate lines of the nematode Caenorhabditis elegans maintained by single-progeny descent indicates that recurrent spontaneous mutation causes approximately 0.1% decline in fitness per generation, which is about an order of magnitude less than that suggested by previous studies with Drosophila. Two rather different approaches, Bateman-Mukai and maximum likelihood, suggest that this observation, along with the observed rate of increase in the variance of fitness among lines, is consistent with a genomic deleterious mutation rate for fitness of approximately 0.03 per generation and with an average homozygous effect of approximately 12%. The distribution of mutational effects for fitness appears to have a relatively low coefficient of variation, being no more extreme than expected for a negative exponential, and for one composite fitness measure (total progeny production) approaches constancy of effects. These results are derived from assays in a benign environment. At stressful temperatures, estimates of the genomic deleterious mutation rate (for genes expressed at such temperatures) is sixfold lower, whereas those for the average homozygous effect is approximately eightfold higher. Our results are reasonably compatible with existing estimates for flies, when one considers the differences between these species in the number of germ-line cell divisions per generation and the magnitude of transposable element activity. [source] Evolutionary archeology: Current status and future prospectsEVOLUTIONARY ANTHROPOLOGY, Issue 1 2002Michael J. O'Brien Abstract Darwinian evolution can be defined minimally as "any net directional change or any cumulative change in the characteristics of , populations over many generations,in other words, descent with modification"1 (p. 5). In archeology the population comprises artifacts, which are conceived of as phenotypic.2,4 Extension of the human phenotype to include ceramic vessels, projectile points, and the like is based on the notion that artifacts are material expressions of behavior, which itself is phenotypic. Archeology's unique claim within the natural sciences is its access to past phenotypic characters. Thus, historical questions are the most obvious ones archeologists can ask, although admittedly this is hardly a strong warrant for asking them. But if the issue is evolution, then historical questions must be asked. Posing and answering historical questions is the goal of evolutionary archeology.5. [source] Recombinant expression of an insulin-like peptide 3 (INSL3) precursor and its enzymatic conversion to mature human INSL3FEBS JOURNAL, Issue 18 2009Xiao Luo Insulin-like peptide 3 (INSL3), which is primarily expressed in the Leydig cells of the testes, is a member of the insulin superfamily of peptide hormones. One of its primary functions is to initiate and mediate descent of the testes of the male fetus via interaction with its G protein-coupled receptor, RXFP2. Study of the peptide has relied upon chemical synthesis of the separate A- and B-chains and subsequent chain recombination. To establish an alternative approach to the preparation of human INSL3, we designed and recombinantly expressed a single-chain INSL3 precursor in Escherichia coli cells. The precursor was solubilized from the inclusion body, purified almost to homogeneity by immobilized metal-ion affinity chromatography and refolded efficiently in vitro. The refolded precursor was subsequently converted to mature human INSL3 by sequential endoproteinase Lys-C and carboxypeptidase B treatment. CD spectroscopic analysis and peptide mapping showed that the refolded INSL3 possessed an insulin-like fold with the expected disulfide linkages. Recombinant human INSL3 demonstrated full activity in stimulating cAMP activity in RXFP2-expressing cells. Interestingly, the activity of the single-chain precursor was comparable with that of the mature two-chain INSL3, suggesting that the receptor-binding region within the mid- to C-terminal of B-chain is maintained in an active conformation in the precursor. This study not only provides an efficient approach for mature INSL3 preparation, but also resulted in the acquisition of a useful single-chain template for additional structural and functional studies of the peptide. [source] Pax6 transcription factor is required for the interkinetic nuclear movement of neuroepithelial cellsGENES TO CELLS, Issue 9 2007Hiroshi Tamai The mammalian cerebral cortex develops from proliferative neuroepithelial cells that exhibit a cell cycle-dependent nuclear movement (interkinetic nuclear migration; INM). Pax6 transcription factor plays pivotal roles in various aspects of corticogenesis. From live observation using cultured cortical slices from the Pax6 mutant rat, we identified the premature descent of S phase cells, the unsteady ascent or descent of G2 phase cells, and ectopic cell division within the basal side of the ventricular zone (VZ). The centrosome normally stayed at the most apical side, apart from the nucleus, in the neuroepithelial cell during the S to G2 phase, while the Pax6 mutant showed unstable movement of the centrosome associated with an abnormal INM. Our results suggest the possibility that Pax6 regulates the INM by stabilizing the centrosome at the apical side. [source] Detection of SNP-SNP interactions in trios of parents with schizophrenic childrenGENETIC EPIDEMIOLOGY, Issue 5 2010Qing Li Abstract Schizophrenia (SZ) is a heritable and complex psychiatric disorder with an estimated worldwide prevalence of about 1%. Research on the risk factors for SZ has thus far yielded few clues to causes, but has pointed to a heterogeneous etiology that likely involves multiple genes and gene-environment interactions. In this manuscript, we apply a novel method (trio logic regression, Li et al., 2009) to case-parent trio data from a SZ candidate gene study conducted on families of Ashkenazi Jewish descent, and demonstrate the method's ability to detect multi-gene models for SZ risk in the family-based design. In particular, we demonstrate how this method revealed a genotype-phenotype association that includes an allele without marginal effect. Genet. Epidemiol. 34: 396,406, 2010. © 2010 Wiley-Liss, Inc. [source] Replication of genetic associations as pseudoreplication due to shared genealogyGENETIC EPIDEMIOLOGY, Issue 6 2009Noah A. Rosenberg Abstract The genotypes of individuals in replicate genetic association studies have some level of correlation due to shared descent in the complete pedigree of all living humans. As a result of this genealogical sharing, replicate studies that search for genotype-phenotype associations using linkage disequilibrium between marker loci and disease-susceptibility loci can be considered as "pseudoreplicates" rather than true replicates. We examine the size of the pseudoreplication effect in association studies simulated from evolutionary models of the history of a population, evaluating the excess probability that both of a pair of studies detect a disease association compared to the probability expected under the assumption that the two studies are independent. Each of nine combinations of a demographic model and a penetrance model leads to a detectable pseudoreplication effect, suggesting that the degree of support that can be attributed to a replicated genetic association result is less than that which can be attributed to a replicated result in a context of true independence. Genet. Epidemiol. 33:479,487, 2009. © 2009 Wiley-Liss, Inc. [source] A common cortactin gene variation confers differential susceptibility to severe asthmaGENETIC EPIDEMIOLOGY, Issue 8 2008Shwu-Fan Ma Abstract Genomic regions with replicated linkage to asthma-related phenotypes likely harbor multiple susceptibility loci with relatively minor effects on disease susceptibility. The 11q13 chromosomal region has repeatedly been linked to asthma with five genes residing in this region with reported replicated associations. Cortactin, an actin-binding protein encoded by the CTTN gene in 11q13, constitutes a key regulator of cytoskeletal dynamics and contractile cell machinery, events facilitated by interaction with myosin light chain kinase; encoded by MYLK, a gene we recently reported as associated with severe asthma in African Americans. To evaluate potential association of CTTN gene variation with asthma susceptibility, CTTN exons and flanking regions were re-sequenced in 48 non-asthmatic multiethnic samples, leading to selection of nine tagging polymorphisms for case-control association studies in individuals of European and African descent. After ancestry adjustments, an intronic variant (rs3802780) was significantly associated with severe asthma (odds ratio [OR]: 1.71; 95% confidence interval [CI]: 1.20,2.43; p=0.003) in a joint analysis. Further analyses evidenced independent and additive effects of CTTN and MYLK risk variants for severe asthma susceptibility in African Americans (accumulated OR: 2.93, 95% CI: 1.40,6.13, p=0.004). These data suggest that CTTN gene variation may contribute to severe asthma and that the combined effects of CTTN and MYLK risk polymorphisms may further increase susceptibility to severe asthma in African Americans harboring both genetic variants. Genet. Epidemiol. 2008. © 2008 Wiley-Liss, Inc. [source] | ||||||||||||||||||||||||||||||||||||||||||||||