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761.
Sergi Castellví-Bel Dr Montserrat Milà Anna Soler Ana Carrió Aurora Sánchez Margarita Villa M Dolores Jiménez Xavier Estivill 《黑龙江环境通报》1995,15(9):801-807
Fragile X syndrome is the most common form of inherited mental retardation, due to an expansion of the (CGG)n trinucleotide repeat in the FMR-1 gene and hypermethylation of its 5′ upstream CpG island. Two major problems remain to be resolved for fragile X prenatal diagnosis: the abnormal methylation patterns of chorionic villus samples (CVS) and the inability to predict the mental status of females with the full mutation. We present here the results of ten prenatal diagnoses of fragile X syndrome using Southern blotting and polymerase chain reaction (PCR) amplification, and the analysis of 50 further CVS to test the methylation status of the CpG island of the FMR-1 gene. In the ten ‘at-risk’ CVS, eight normal (five males and three females) and two affected male fetuses were detected. Absence of methylation in the CVS was observed in two cases, which was not found upon subsequent examination of the newborn or of fetal tissues. In the 50 CVS not ‘at risk’ for fragile X syndrome, abnormal fragment patterns for probe StB12.3 were detected in 32 per cent for female and 24 per cent for male fetuses. This abnormal pattern could be due to absent or partial methylation of the CpG island of the FMR-1 gene in chorionic villus tissues. 相似文献
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763.
Raimundo Real A. Márcia Barbosa J. Mario Vargas 《Environmental and Ecological Statistics》2006,13(2):237-245
Logistic regression is a statistical tool widely used for predicting species’ potential distributions starting from presence/absence
data and a set of independent variables. However, logistic regression equations compute probability values based not only
on the values of the predictor variables but also on the relative proportion of presences and absences in the dataset, which
does not adequately describe the environmental favourability for or against species presence. A few strategies have been used
to circumvent this, but they usually imply an alteration of the original data or the discarding of potentially valuable information.
We propose a way to obtain from logistic regression an environmental favourability function whose results are not affected
by an uneven proportion of presences and absences. We tested the method on the distribution of virtual species in an imaginary
territory. The favourability models yielded similar values regardless of the variation in the presence/absence ratio. We also
illustrate with the example of the Pyrenean desman’s (Galemys pyrenaicus) distribution in Spain. The favourability model yielded more realistic potential distribution maps than the logistic regression
model. Favourability values can be regarded as the degree of membership of the fuzzy set of sites whose environmental conditions
are favourable to the species, which enables applying the rules of fuzzy logic to distribution modelling. They also allow
for direct comparisons between models for species with different presence/absence ratios in the study area. This makes them
more useful to estimate the conservation value of areas, to design ecological corridors, or to select appropriate areas for
species reintroductions.
Received: June 2005 / Revised: July 2005 相似文献
764.
Mohammed S. Rahman Ana B. Payá-Pérez Helle Skejø-Andresen Bo R. Larsen 《Environmental science and pollution research international》1994,1(3):131-139
Reductions in the apparent soil-water partition coefficients (Kd *) for 28 polychlorinated biphenyls (PCBs) caused by the surfactant sodium dodecylsulphate (SDS) in the aqueous phase were studied. Above the critical micelle concentration (CMC) of the surfactant, Kd * was reduced by 2–3 orders of magnitude, but even far below CMC at environmentally relevant surfactant concentrations significant reductions in Kd * were observed. The plot of the soil-water partition coefficient (Kd) divided by Kd * versus the concentration of SDS allowed for the calculation of monomer (Kmn oc) and micellar (Kmc oc) surfactant-water partition coefficients normalized to organic carbon for each PCB congener. Kmn oc values were comparable with published values for the partition of PCBs between natural dissolved organic matter and lake water. Kmc oc values were up to 30 times higher than Kmn oc values and comparable with published octanol-water distribution coefficients. The findings of the present study underline the potential of surfactants at concentrations below their CMC to mobilize otherwise strongly bound hydrophobic compounds in soil-water systems. 相似文献
765.
Ana Marçalo Luísa Mateus José Henrique Duarte Correia Pedro Serra Rob Fryer Yorgos Stratoudakis 《Marine Biology》2006,149(6):1509-1518
Observations from the purse seine fishery off northern Portugal are used to describe the early dynamics of sardine (Sardina pilchardus) stress reactions and identify likely stressors during the commercial fishing operation. Sardine blood and muscle were sampled from the onset of fishing (school identification and encircling) to the end of fish transfer onboard (90–120 min later). The evolution of haematocrit, haemoglobin, cortisol, glucose, ionic concentrations, ATP and its catabolites were modelled using linear mixed models as a function of time spent in the net, biological (sex, reproductive state and condition) and operational variables (catch, light level and phase of fishing operation). Significant linear trends with time were detected for most stress variables and mean concentrations after 2 h in the net were similar to literature values corresponding to acute stress reactions for teleosts. Biological variables were rarely significant and explained a small proportion of variation, while operational variables were never significant. For each stress variable, levels varied considerably between trips but the temporal evolution was common across trips. Random trip effects were uncorrelated among most biochemical variables, suggesting that distinct factors affected each stress variable during the sampled trips. However, the linear trend with time spent in the net observed for most stress variables indicates that the duration of the fishing operation is an important stressor in purse seine fishing due to the progressive water volume restriction, crowding and manipulation associated to the fishing method. 相似文献
766.
767.
768.
Rodolfo Salm Lisa Feder Mario Augusto Gonçalves Jardim Nefertiti Hass Euphly Jalles-Filho Ana Maria Costa 《Environment, Development and Sustainability》2009,11(1):161-173
In a meeting between FUNAI (the Brazilian Indian National Foundation) and the Kayapo in the Kayapo village of Aukre, in October
2005, the Kayapo Indians requested support to increase the culture of coconuts (Cocos nucifera) in their lands. The introduction of exotic species is a cause of biological diversity loss throughout the world. However,
this is by no means applicable to all kinds of exotic species. We argue that the culture of coconuts may actually be a useful
tool for the conservation of this country’s indigenous lands, despite criticism to the contrary. It may also be useful as
source for raw material for the indigenous people who are presently experiencing a population boom. For the Kayapo of south-eastern
Amazonia, such a demographic explosion, coupled with their increasing dependence on money to purchase industrialized goods,
tend to substantially increase the pressure on their lands, which still contain a substantial amount of well-preserved seasonally-dry
Amazonian forests. We investigated the actual economic relevance of coconuts for the Kayapo by measuring human and coconut
populations and found that this exotic palm is not important for the subsistence of these Indians, due to coconut scarcity,
and that such importance is not forthcoming. In the Amazon, coconuts may be particularly useful for the Indians’ nutrition
due to the high energetic value of the solid endosperm of the mature fruit. Therefore, given the importance of indigenous
lands for the conservation of the Amazonian forests, the encouragement of subsistence coconut cultures in indigenous lands
is defensible as a measure for the conservation of biodiversity. 相似文献
769.