Search results for "Variation"
showing 10 items of 2124 documents
Characterization and classification of different genotypes in a population of Cucumis melo based on their ability to regenerate shoots from leaf expl…
1995
Variability of the in vitro organogenic response from leaf explants of a seed population of Cueumis melo L. ev. Cantaloupe Charentais was analyzed to detect genotypic variability among individual seeds for shoot regeneration. Variation in shoot regeneration frequency among plants from different seeds was compared to that found among clonal replicas of each original plant. Clonal propagation was performed using in vitro culture of apical and axillary buds of axenic plants to avoid somaclonal variation. Results demonstrate the existence of highly significant differences among plants from the seed population. Regeneration frequency of leaf explants derived from clonally propagated sets of a si…
Detection of ephemeral genetic sub-structure in the narrow endemic Abies nebrodensis (Lojac.) Mattei (Pinaceae) using RAPD markers
2004
A. nebrodensis (Nebrodi fir, Sicilian fir) is restricted to a small area of the Madonie Natural Park in Sicily. According to recent estimates, its only population consists of 30 adult individuals and a fluctuating number of juveniles derived from natural regeneration; besides, some hundreds of cultivated plants are preserved as ex situ collection. We used RAPD data from six 10-mer primers to examine the consequences of extensive historical clearance and human pressures on the extant population. Data from multiple life stages and different habitat conditions were considered, affording an opportunity to ascertain for the first time the structure of genetic variation in the extant uneven-aged …
Genetic population structure of two cryptic Gammarus fossarum types across a contact zone
1998
Previous studies have revealed inconsistent results about the taxonomic status of European Gammarus fossarum forms. The variability in morphology and hybridization ability has not shown clear geographic patterns, whereas on a genetical basis two Central European G. fossarum forms have been proposed. In the present study the genetic structure of G. fossarum populations was investigated across a natural contact zone. For the first time direct comparisons of allotopic versus syntopic populations were feasible. 24 Populations of G. fossarum plus 4 populations of G. pulex (as outgroup) were sampled along 2 transects across the contact zone. The genotypes of about 60 individuals per population we…
Genetic differentiation of three species of Matthiola (Brassicaceae) in the Sicilian insular system
2005
We examined the genetic variation of 12 isozyme loci in 14 populations of Matthiola (Brassicaceae) representing the geographic distribution of the species M. incana, M. fruticulosa ssp. fruticulosa and M. tricuspidata in the Sicilian insular system and the adjacent mainland areas to estimate the levels and apportionment of genetic variation in the insular populations and to understand their population dynamics. The disparity in the distribution of polymorphism in populations of M. incana ssp. incana (low within populations but with high values of F ST and G ST ) contrasts with the homogeneity in the inter-population distribution of the high genetic variation detected in M. tricuspidata and …
Limited effects of size-selective harvesting and harvesting-induced life-history changes on the temporal variability of biomass dynamics in complex f…
2023
Harvesting has been implicated in destabilizing the abundances of exploited populations. Because selective harvesting often targets large individuals, some studies have proposed that exploited populations often experience demographic shifts toward younger, smaller individuals and become more sensitive to environmental fluctuations. The theory of consumer–resource dynamics has been applied to address the impacts of harvesting in simple modular food webs, but harvested populations are embedded in a complex food web in nature. In addition, exploited populations have been shown to undergo trait evolution or phenotypic changes toward early maturation at smaller sizes. Using an empirically derive…
Diabetes: Genetic variation underpins metformin response.
2016
Metformin is the first-line antidiabetic drug with over 100 million users worldwide, yet its mechanism of action remains unclear1. Here the Metformin Genetics (MetGen) Consortium reports a three-stage genome-wide association study (GWAS), consisting of 13,123 participants of different ancestries. The C allele of rs8192675 in the intron of SLC2A2, which encodes the facilitated glucose transporter GLUT2, was associated with a 0.17% (p=6.6×10−14) greater metformin-induced in haemoglobin A1c (HbA1c) in 10,577 participants of European ancestry. rs8192675 is the top cis expression quantitative trait locus (cis-eQTL) for SLC2A2 in 1,226 human liver samples, suggesting a key role for hepatic GLUT2 …
Intra-individual variability in TSH levels of healthy women during the first half of pregnancy
2017
TSH is the parameter most widely accepted to assess thyroid function, especially in pregnant women. The aim of this current study was to analyze intra-individual changes in TSH during the first half of pregnancy in women with TSH levels higher than 2.5mIU/L in early pregnancy.An observational, prospective study was conducted on 243 healthy pregnant women in the first trimester of pregnancy. Thyroid function was assessed by testing TSH and free T4 levels. A subgroup of women with TSH levels2.5mIU/L underwent additional tests (TSH, free T4, peroxidase antibodies). Information on dietary iodine intake and/or iodine supplements was also recorded.Mean TSH level was 1.89mIU/L (range 0.024-6.48mIU…
A Diffractive Reading
2023
AbstractTowards the end of the editing process, we started to see the book as something more than a collection of chapters around a theme: as an assemblage, which included, of course, the community of authors. When we put out the first call for contributions in May 2018, most authors volunteered a contribution rather quickly, others joined a bit later, and some dropped out for different reasons, underlining the dynamic nature of our assemblage. In pre-pandemic times, we met on and off campus, introduced some of our ideas at conferences, and had a workshop day to brainstorm, plan chapters, and reflect on the process and the purpose of the book. We were connected by common meals, jokes, writi…
Development of an individualized familiarization method for vertical jumps
2013
OBJETIVO: Propor um método de familiarização individualizado para saltos verticais e verificar o seu efeito na variabilidade intrassujeito. MÉTODOS: Cinquenta e três homes (média ± DP; idade 23,5 ± 3,3 anos; estatura 1,76 ± 0,08 m; massa 72,8 ± 8,6 kg; percentual de gordura 12,9 ± 5,2%) realizaram sucessivos saltos até atingir o nível de estabilidade proposto. Após 48 h este processo era repetido e a estabilidade entre dias era verificada, se necessário, mais sessões eram realizadas. O nível de estabilidade foi determinado por um teste z, com intervalo de confiança de 95%. Após o processo de familiarização, duas sessões experimentais adicionais foram realizadas para determinar a confiabilid…
A posteriori error identities for nonlinear variational problems
2015
A posteriori error estimation methods are usually developed in the context of upper and lower bounds of errors. In this paper, we are concerned with a posteriori analysis in terms of identities, i.e., we deduce error relations, which holds as equalities. We discuss a general form of error identities for a wide class of convex variational problems. The left hand sides of these identities can be considered as certain measures of errors (expressed in terms of primal/dual solutions and respective approximations) while the right hand sides contain only known approximations. Finally, we consider several examples and show that in some simple cases these identities lead to generalized forms of the …