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361.
Measurement of the microvillar enzymes, γ-glutamyltranspeptidase (GGTP), aminopeptidase M (APM) and alkaline phosphatase (ALP), in amniotic fluid supernatant has been proposed as a method for the early prenatal diagnosis of cystic fibrosis. The activities of these enzymes in a series of other fetal abnormalities have now been examined. GGTP activities were below the 5th percentile in 28 out of 54 cases of trisomy 21 and 9 of 14 cases of trisomy 18, while APM values were below this cut-off in 26 of 54 cases of trisomy 21 and 8 of 14 cases of trisomy 18. Abnormal ALP isoenzyme ratios were found in 6 of 54 cases of trisomy 21 and 4 of 14 cases of trisomy 18. If prenatal cytogenetic studies are routinely carried out on amniotic fluid cells, the occasional confounding effect of abnormal microvillar enzymes associated with fetal trisomies rather than with cystic fibrosis should be avoided.  相似文献   
362.
Direct detection of the fragile X mutation by DNA analysis has greatly simplified prenatal diagnosis of this disease. However, women carrying a fragile X premutation may pass their expanded trinucleotide repeat to sons without expansion to a full mutation. Such sons are predicted to be intellectually normal. In this situation, the accuracy with which the fetal status can be inferred from analysis of chorionic villus sample (CVS) DNA is unclear. We describe such a case, in which it was felt necessary to proceed to fetal blood sampling despite technically unambiguous DNA results from the CVS. The lack of prospective data means that this dilemma may be expected to recur over the next few years when performing prenatal diagnosis on fragile X premutation carriers.  相似文献   
363.
Prenatal diagnosis of cord defects by means of ultrasound examination is possible and highly accurate. Although this is a rare pathological finding, we report two cases in which umbilical cord pseudocysts were associated with trisomy 18. These observations underscore the need of umbilical blood sampling for establishing the karyotype in fetuses with such umbilical cord anomalies and the importance of careful examination of placentas and infants born with such defects.  相似文献   
364.
A biogeochemical model(DNDC) is combined with a plant ecological model to estimate N2O emission from rice paddy fields in the Yangtze River Delta region. The model is driven by local meteorological, soil, and physiological data and is validated for 1999 and 2000 at a site in the region, which showed that the simulated N2O emissions agree fairly well with the observed data. This adds some confidence in the estimated N2O emissions during 1950 and 2000 in the Hangzhou Region. A significant correlation between the N2O emissions and the population for the Hangzhou Region is found, which is due to a combination of increased application of fertilizers and cultivated area.Such a correlation can not be established for the whole Yangtze River Delta region when the data of both urban and rural are as areincluded. However, when the data from the heavily urbanized areas are excluded, a significant correlation between population and N2O emissions emerges. The results show clearly that both the temporal and the spatial N2O emissions have significant positive relationship with population under traditional farming practice. These results have implications for suitable mitigation options towards a sustainable agriculture and environment in this region.  相似文献   
365.
Environmental surveillance of poliovirus (PV) plays an important role in the global program for eradication of wild PV. The bag-mediated filtration system (BMFS) was first developed in 2014 and enhances PV surveillance when compared to the two-phase grab method currently recommended by the World Health Organization (WHO). In this study, the BMFS design was improved and tested for its usability in wastewater and wastewater-impacted surface waters in Nairobi, Kenya. Modifications made to the BMFS included the size, color, and shape of the collection bags, the filter housing used, and the device used to elute the samples from the filters. The modified BMFS concentrated 3–10 L down to 10 mL, which resulted in an effective volume assayed (900–3000 mL) that was 6–20 times greater than the effective volume assayed for samples processed by the WHO algorithm (150 mL). The system developed allows for sampling and in-field virus concentration, followed by transportation of the filter for further analysis with simpler logistics than the current methods. This may ultimately reduce the likelihood of false-negative samples by increasing the effective volume assayed compared to samples processed by the WHO algorithm, making the BMFS a valuable sampling system for wastewater and wastewater-impacted surface waters.  相似文献   
366.
It is the aim of plant functional research to generate general rules of species assembly and species reactions based on plant functional traits. Here we determined plant functional groups that are important with regard to land use types (grazing, mowing, mulching, burning, abandonment) and looked for mechanisms leading to changes in species composition after management changes in calcareous grasslands.To filter out the set of traits which best described the variation in plant composition along the studied land use gradient and to identify functional groups we chose an iterative three-table ordination method. We included traits related to persistence as well as traits describing the germination niche of a plant. To gain insight into underlying mechanisms which led to differing importance of these plant functional groups at different management regimes we investigated shifts in dominance of the identified functional groups at eight management regimes using long-term vegetation data of a site which was grazed before the onset of different management regimes in 1974. Ongoing unidirectional changes in cover of the four determined functional groups at most of the treatments indicated that even after almost 30 years new equilibria of functional group composition were still not reached.The study showed that other management treatments but grazing and mowing led to changes in functional group composition, which were mainly driven by increasing dominance of a highly competitive species group.  相似文献   
367.
Most monogamous male mammals display parental care, but the mechanism by which they become motivated to care for infants remains unknown. We used prairie voles (Microtus ochrogaster) as a model of biparental species to test the hypothesis that physical contact with a female enhances male parental responsiveness before the birth of offspring. We tested four groups of males: mated with physical contact with their mate, mated with only distal cues from their mate, mated with no cues, and unmated with distal cues from a female. The subjects were placed in an oversized cage divided into two compartments by a perforated barrier. At mid-gestation, the bedding and females were removed, and the males’ responses toward two infants were videotaped. Although most males behaved parentally, mated males exposed to their mate’s tactile or distal cues approached the young faster and were more likely to care for both infants than unmated males which received female distal cues. Males who had physical contact with their mate showed “kyphosis” (a crouching position over infants) and contacted infants more frequently than mated males which received no cues from their mate or unmated males which received female distal cues. Furthermore, the frequency of non-social behaviors was lowest in mated males that had physical contact with their mate. The data suggest that exposure to female distal cues after mating is sufficient to increase male parental attentiveness, but female somatosensory cues affect the male's tendency to remain in physical contact with infants.  相似文献   
368.
Angelini C  Silliman BR 《Ecology》2012,93(1):101-110
Massive anthropogenic and climate-related disturbances are now common in ecosystems worldwide, generating widespread die-off and subsequent community recovery dominated by remnant-patch dynamics rather than open-gap dynamics. Whether communities can recover and, if so, which factors mediate recolonization rate and extent remain unresolved. Here we evaluate recolonization dynamics of southern U.S. salt marshes that experienced extensive, drought-induced die-off of the foundation species Spartina alterniflora over the previous decade. Surveys of Georgia (USA) salt marshes showed little seedling recruitment in die-off areas but persistence of Spartina particularly in large, rather than small, remnant patches. Given this natural variation in remnant patch size, we conducted field experiments to test whether key plant-controlling biotic (grazing, plant neighbor presence) and abiotic (water availability) factors differentially impact Spartina recolonization at small and large-patch scales. In the small-patch (< 1 m2) experiment in 2009, removing grazers and plant neighbors prompted dramatically higher expansion and growth of Spartina relative to controls, while adding freshwater to reduce water limitation had little effect. In contrast, large-patch (> 20 m2 borders advanced significantly over the same time period regardless of grazer or neighbor removal. We continued the large-patch experiments in 2010, a year that experienced drought, and also added freshwater or salt to borders to modify ambient drought stress; overall, borders advanced less than the previous year but significantly more where neighbors were removed or freshwater added. Thus, water availability appears to mediate Spartina recovery by fueling large-patch expansion during wet summers and intensifying interspecific competition during drought. Combined, these findings suggest ecosystems can recover from massive disturbance if remnant foundation species' patches are large enough to overcome biotic inhibition and successfully expand during periods of relaxed abiotic stress.  相似文献   
369.
The fundamental data requirements for the authorization of plant protection products and the inclusion of active ingredients in Annex I of Council Directive 91/414/EEC are described in the Annexes II and III of the Directive. Definite guidelines concerning investigations with arthropods are partially deficient. The uniform principles for the registration of plant protection products in the Member States described in Annex VI of the directive were primarily developed to assess the effects on the beneficial capacity of arthropods in agriculture. However, the risk for arthopods as an essential part of the environment need to be assessed, too. Hence, the German Federal Environmental Agency has developed a tiered approach to assess the effects of plant protection products on arthopods based on the data requirements of Annex II and III of the Directive 91/414/EEC. The risk is assessed using the effect-concentration evaluated in ecotoxicological tests and the environmental concentration predicted by validated exposure models. To protect non-target species in terrestrial ecosystems assessment factors need to be considered.  相似文献   
370.
ABSTRACT: This research examines the sensitivity and vulnerability of community water systems (CWSs) to weather and climate in the Pennsylvania portion of the Susquehanna River Basin. Three key findings emerge from a survey of 506 CWS managers. First, CWSs are sensitive to extreme weather and climate, but that sensitivity is determined more by type of system than system size. CWSs that rely partly or wholly on surface water face more disruptions than do groundwater systems. Larger systems have more problems with flooding, and size is not a significant determinant of outages from storms or disruptions from droughts. Second, CWS managers are unsure about global warming. Few managers dismiss global warming; most think global warming could be a problem but are unwilling to consider it in their planning activities until greater scientific certainty exists. Third, the nature of the CWS, its sensitivity to weather and climate, and projected risks from weather and climate are insignificant determinants of how managers plan. Experienced, full-time managers are more likely to consider future weather and climate scenarios in their planning, while inexperienced and part-time managers are less likely to do so. Implications of these findings include support for efforts to move away from surface water, for clear communication of climate change information, and for the hiring and retention of full-time professional CWS managers.  相似文献   
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