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Extreme Variation (extreme + variation)
Selected AbstractsThree Common Intronic Variants in the Maternal and Fetal Thiamine Pyrophosphokinase Gene (TPK1) are Associated with Birth WeightANNALS OF HUMAN GENETICS, Issue 5 2007D. Fradin Summary Extreme variations in birth weight increase immediate postnatal mortality and morbidity, and are also associated with the predisposition to metabolic diseases in late adulthood. Birth weight in humans is influenced by yet unknown genetic factors. Since the 7q34-q35 region showed linkage with birth weight in a recent human genome scan (p = 8.10,5), this study investigated the TPK1 (thiamine pyrophosphokinase) gene locus, located in 7q34-36. Having found no coding variants in the TPK1 gene, we genotyped 43 non coding SNPs spanning a region of 420kb, and used the QTDT method to test their association with birth weight in 964 individuals from 220 families of European ancestry. Family-based tests detected association of 8 SNPs with birth weight (p<0.008), but after correction for multiple tests only rs228581 C/T (p = 0.03), rs228582 A/G (p = 0.04) and rs228584 C/T (p = 0.03) were still associated with birth weight, as well as their T-A-T haplotype (p = 0.03). In addition, we found an association between maternal rs228584 genotype and offspring birth weight (p = 0.027). These observations suggest that genomic variations in the fetal and maternal TPK1 gene could contribute to the variability of birth weight in normal humans. [source] Differentiating normal, abnormal, and disordered personalityEUROPEAN JOURNAL OF PERSONALITY, Issue 4 2005W. John Livesley Interest in the interface between normality and psychopathology was renewed with the publication of DSM-III more than 20 years ago. The use of a separate axis to classify disorders of personality brought increased attention to these conditions. At the same time, the definition of personality disorder as inflexible and maladaptive traits stimulated interest in the relationship between normal and disordered personality structure and functioning. The evidence suggests that the traits delineating personality disorder are continuous with normal variation and that the structural relationships among these traits resemble the structures described by normative trait theories. Recognition that personality disorder represents the extremes of trait dimensions emphasizes the importance of differentiating normal, abnormal, and disordered personality. It is argued that while abnormal personality may be considered extreme variation, personality disorder is more than statistical variation. A definition of personality disorder is suggested based on accounts of the adaptive functions of personality. Copyright © 2005 John Wiley & Sons, Ltd. [source] Test of an adaptive hypothesis for egg speckling along an elevational gradient in a population of Mexican jays Aphelocoma ultramarinaJOURNAL OF AVIAN BIOLOGY, Issue 4 2009Elena C. Berg The adaptive significance of avian egg speckling patterns has been a subject of ongoing debate. We examined speckling in a population of Mexican jays Aphelocoma ultramarina exhibiting extreme eggshell variability. We sampled 167 eggs at 55 nests from sites ranging across a steep elevation gradient within the Sierra del Carmen mountain range in Coahuila, Mexico, in order to test the recent hypothesis that egg speckling lends structural support to eggs and should therefore be more prevalent in females subject to reduced environmental calcium. Although we documented high variation in the amount and distribution of eggshell speckling within the Sierra del Carmen jays, we found no relationship between local soil calcium levels and the pattern of speckling. Our results indicate that explanations in addition to soil calcium levels are necessary to explain extreme variation in eggshell speckling in birds. [source] Evidence for selection on coloration in a Panamanian poison frog: a coalescent-based approachJOURNAL OF BIOGEOGRAPHY, Issue 5 2010Jason L. Brown Abstract Aim, The strawberry poison frog, Oophaga pumilio, has undergone a remarkable radiation of colour morphs in the Bocas del Toro archipelago in Panama. This species shows extreme variation in colour and pattern between populations that have been geographically isolated for < 10,000 years. While previous research has suggested the involvement of divergent selection, to date no quantitative test has examined this hypothesis. Location, Bocas del Toro archipelago, Panama. Methods, We use a combination of population genetics, phylogeography and phenotypic analyses to test for divergent selection in coloration in O. pumilio. Tissue samples of 88 individuals from 15 distinct populations were collected. Using these data, we developed a gene tree using the mitochondrial DNA (mtDNA) d-loop region. Using parameters derived from our mtDNA phylogeny, we predicted the coalescence of a hypothetical nuclear gene underlying coloration. We collected spectral reflectance and body size measurements on 94 individuals from four of the populations and performed a quantitative analysis of phenotypic divergence. Results, The mtDNA d-loop tree revealed considerable polyphyly across populations. Coalescent reconstructions of gene trees within population trees revealed incomplete genotypic sorting among populations. The quantitative analysis of phenotypic divergence revealed complete lineage sorting by colour, but not by body size: populations showed non-overlapping variation in spectral reflectance measures of body coloration, while variation in body size did not separate populations. Simulations of the coalescent using parameter values derived from our empirical analyses demonstrated that the level of sorting among populations seen in colour cannot reasonably be attributed to drift. Main conclusions, These results imply that divergence in colour, but not body size, is occurring at a faster rate than expected under neutral processes. Our study provides the first quantitative support for the claim that strong diversifying selection underlies colour variation in the strawberry poison frog. [source] Accounting for overlap of fractional cloud in infrared radiationTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 570 2000J. Li Abstract The cloud-matrix method for describing the mutual cloud-coverage relationship between any two levels is systematically discussed. A general method is devised for calculating the effective cloud emissivity for maximum-random overlap clouds. For several cloud configurations with extreme variation in fractional cloud amounts, the errors are generally very small (<5%). The radiative-transfer process that corresponds to the random-overlap cloud scheme is discussed. Compared with the purely random clouds scheme, the maximum-random overlap scheme always produces a smaller cooling rate in the lower layers of a cloud block and a smaller downward flux. The difference in cooling rate can be about 3 K d,1 and the difference in the downward flux near the surface can be as large as 20 W m,2. The calculations show that the scheme of effective cloud emissivity commonly used in general-circulation models could cause underestimation of cloud cooling rate. The clear-sky and the cloudy-sky radiation field can be obtained through a single calculation process but with different water-vapour profiles. The results show that for the all-sky case the separate treatment of the water-vapour profile for clear and cloudy portions makes only a very small difference in the cooling rate and upward flux at the top of the atmosphere in comparison with the results of an averaged water-vapour profile. [source] Reproductive strategies in some arctic Saxifraga (Saxifragaceae), with emphasis on the narrow endemic S. svalbardensis and its parental speciesBOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2001CHRISTIAN BROCHMANN Arctic saxifrages show conspicuous reproductive and chromosomal variation. We examined sexual and asexual traits in 43 phytotron-cultivated Svalbard populations of nine species, including the endemic, supposedly entirely asexual and aneupolyploid S. svalbardensis and its parental species, S. cernua and S. rivularis. All species were self-compatible hermaphrodites with low pollen/ovule ratios, including the strongly protandrous S. cernua, which previously has been reported as self-incompatible with an androdioecious mating system. Spontaneous selfing resulted in considerable seed set in several species and a few seeds in S. svalbardensis and S. cernua; hand-selfing and cross-pollination often increased seed set in the two latter species. Self-fertilized seeds of S. svalbardensis and S. cernua were viable and developed into normal, vigorous plants. Saxifraga rivularis and its close relative S. hyperborea were strongly autogamous. The bulbil-reproducing S. svalbardensis and S. cernua showed extreme variation in fertility, probably because of frequent aneuploidy. Many plants of S. cernua were fully fertile, suggesting that although natural seed set rarely has been observed, sexual reproduction is frequent enough to maintain its previously reported high levels of clonal diversity. Some plants of S. svalbardensis were also fairly fertile. This species may have considerable evolutionary potential; sexual events can lead to increasingly fertile genets with euploid chromosome numbers. [source] Effect of varying osmotic conditions on the response of bovine nucleus pulposus cells to growth factors and the activation of the ERK and Akt pathwaysJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 10 2010Eleni Mavrogonatou Abstract Intervertebral disc and especially nucleus pulposus is characterized by low cellularity. Additionally, extreme variations in osmolality are observed in this tissue, as a result of its specific physicochemical environment, daily activities, or degeneration. In this study, we investigated the role of osmotic fluctuations in the proliferative response of nucleus pulposus cells to exogenous growth factors. In particular, we examined the effect of platelet-derived growth factor (PDGF) and insulin-like growth factor-I (IGF-I) on the proliferation of bovine nucleus pulposus cells and on the activation of the MEK/ERK and PI-3-K/Akt pathways under varying osmotic conditions, in an effort to understand the mechanisms regulating cell proliferation in the intact and the degenerated intervertebral disc. Exposure of cells to high osmolality restrained novel DNA synthesis induced by PDGF or IGF-I in a dose-dependent manner and reduced ERK and Akt activation stimulated by serum or isolated growth factors. Our findings indicate that hyperosmolality imposes a strict control in intervertebral disc cells' proliferation, while hypo-osmotic conditions prevailing in degenerated discs may offer a more permissive environment for cellular proliferation. Published by Wiley Periodicals, Inc. J Orthop Res 28:1276,1282, 2010 [source] | ||||||||||