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51.
Local and regional trends in the ground vegetation of beech forests   总被引:1,自引:0,他引:1  
We sampled moss and vascular forest vegetation in five ancient beech forests from northwest France, embracing in each a wide array of environmental conditions. Indirect (PCA) and direct (RDA) gradient analysis were used to discern local and regional ecological factors which explain the observed variation in species composition. Our results point to a global factor encompassing a large array of soil and light conditions, unravelled when local particularities of studied forests are singled out. The humus form, numerically expressed by the Humus Index, explains a large part of the observed variation in ground vegetation. Our study confirmed opposite trends in vascular and moss species richness according to humus condition. Ecological factors to which vascular and moss forest species respond at the regional level can be estimated directly in the field by visually inspecting humus forms and vegetation strata despite of the confounding influence of local factors.  相似文献   
52.
Rodent transgenesis and human‐assisted reproductive programs involve multistep handling of preimplantation embryos. The efficacy of production and quality of results from conventionally scheduled programs are limited by temporal constraints other than the quality and quantities of embryos per se. The emergence of vitrification, a water ice‐free cryopreservation technique, as a reliable way to arrest further growth of preimplantation embryos, provides an option to eliminate the time constraint. In this article, current and potential applications of cryopreservation to facilitate laboratory animal experiments, colony management, and human‐assisted reproductive programs are reviewed. Carrier devices developed for vitrification in the last two decades are compared with an emphasis on their physical properties that infer cooling rate of samples and sterility assurance. Biological impacts of improved cryopreservation on preimplantation embryos are also discussed. Birth Defects Research (Part C) 90:163–175, 2010. © 2010 Wiley‐Liss, Inc.  相似文献   
53.
本实验探讨赤楠果实红色素的理化性质及提取条件。结果表明,该色素属花色苷类;其最佳提取工艺是:1%HCl-乙醇(1ml HCl:99ml 95%乙醇)溶液作为提取剂,料液比1/10,温度35℃,提取时间3h,提取次数3次。  相似文献   
54.
This is the third of a series of articles detailing the development of near-infrared spectroscopy methods for solid dosage form analysis. Experiments were conducted at the Duquesne University Center for Pharmaceutical Technology to develop a system for continuous calibration monitoring and formulate an appropriate strategy for calibration transfer. Indcators of high-flux noise (noise factor level) and wave-length uncertainty were developed. These measurements, in combination with Hotelling’s T2 and Q residual, are used to continuously monitor instrument performance and model relevance. Four calibration transfer techniques were compared. Three established techniques, finite impulse response filtering, generalized least squares weighting, and piecewise direct standardization were evaluated. A fourth technique, baseline subtraction, was the most effective for calibration transfer. Using as few as 15 transfer samples, predictive capability of the analytical method was maintained across multiple instruments and major instrument maintenance.  相似文献   
55.
Two new facilities for in vivo activation analysis of patients have been designed, developed, and constructed at Toronto General Hospital. One of these is for the determination of body calcium for the diagnosis of osteoporosis and other diseases associated with bone loss. The other is for the measurement of total body nitrogen for the determination of protein status. These facilities replace old university facilities and take into account the comfort and management of patients. In addition, in the case of the calcium facility, the precision of the measurements has been improved because of larger detector volume and increased neutron source strength. Both the facilities are now in routine hospital clinical use.  相似文献   
56.
We investigated the influence of mesohabitats on fish communities and on attributes of a multimetric index of fish integrity in the River Meuse basin. Three consecutive 150 m sectors in a Meuse tributary (Ourthe, Belgium), each divided in two or three sub-sections presenting various percentages of mesohabitats (riffles, runs and pools), were sampled by electrofishing. In each sub-section, relative and absolute biomasses of each fish species were estimated. The presence of limnophilic cyprinids was inversely correlated (r 2 = 0.70 and 0.56 for absolute and relative biomass, respectively) with the percentage of riffles. Salmonids preferred runs and their absolute biomass was highly dependent (r 2 = 0.71) on the proportion of this mesohabitat, whereas biomass of limnophilic cyprinids was highly correlated (r 2 = 0.75 and r 2 = 0.82 for absolute and relative biomass, respectively) with pools. A positive correlation (r 2 = 0.58) was established between relative biomass of predators and the percentage of this mesohabitat. An IBI was calculated for the three sectors on the basis of results from the entire Meuse catchment. Scores of most metrics showed low variation among sectors but values of two metrics (% of individuals as tolerant, % of individuals as ubiquitous spawners) were greatest in sector 2, where pools predominated. Further, the lowest IBI score (51/65, integrity class: fair to good) was recorded in sector 2 where pools dominated, while sector 1 (where runs dominated) obtained the highest score (63/65, integrity class: excellent). Sector 3 which has a balanced proportion of riffles and runs obtained an intermediate score (57/65). Considering the response of IBI to the natural variation of mesohabitat proportions, it appears that an accurate sampling requires the prospection of a variety of mesohabitats (with a majority of runs) for the evaluation of river quality.  相似文献   
57.
Clathrin plays important roles in intracellular membrane traffic including endocytosis of plasma membrane proteins and receptors and protein sorting between the trans-Golgi network (TGN) and endosomes. Whether clathrin serves additional roles in receptor recycling, degradative sorting, or constitutive secretion has remained somewhat controversial. Here we have used acute pharmacological perturbation of clathrin terminal domain (TD) function to dissect the role of clathrin in intracellular membrane traffic. We report that internalization of major histocompatibility complex I (MHCI) is inhibited in cells depleted of clathrin or its major clathrin adaptor complex 2 (AP-2), a phenotype mimicked by application of Pitstop® inhibitors of clathrin TD function. Hence, MHCI endocytosis occurs via a clathrin/AP-2-dependent pathway. Acute perturbation of clathrin also impairs the dynamics of intracellular clathrin/adaptor complex 1 (AP-1)- or GGA (Golgi-localized, γ-ear-containing, Arf-binding protein)-coated structures at the TGN/endosomal interface, resulting in the peripheral dispersion of mannose 6-phosphate receptors. By contrast, secretory traffic of vesicular stomatitis virus G protein, recycling of internalized transferrin from endosomes, or degradation of EGF receptor proceeds unperturbed in cells with impaired clathrin TD function. These data indicate that clathrin is required for the function of AP-1- and GGA-coated carriers at the TGN but may be dispensable for outward traffic en route to the plasma membrane.  相似文献   
58.
An epithermal neutron activation method is used to determine the concentration of mineral elements in human dental enamel. A large number (252) of samples from ancient and modern origins are analyzed. The analytical results are mathematically processed using a statistical multivariant method. This allows to differentiate deciduous from permanent teeth and decayed from sound enamel. It is also possible to distinguish the teeth coming from two different necropoles. The origin and the localization of determined elements in the mineralized part, or in the aqueous-organic part, of enamel is suggested. Their role, as witnessed in the physiopathological phenomena of dental enamel, is discussed.  相似文献   
59.
Using data for 27 Texas counties from 1978-1987, it is shown that the incidence rates of suicide, homicide, and rape are significantly higher in counties whose drinking water supplies contain little or no lithium than in counties with water lithium levels ranging from 70-170 micrograms/L; the differences remain statistically significant (p less than 0.01) after corrections for population density. The corresponding associations with the incidence rates of robbery, burglary, and theft were statistically significant with p less than 0.05. These results suggest that lithium has moderating effects on suicidal and violent criminal behavior at levels that may be encountered in municipal water supplies. Comparisons of drinking water lithium levels, in the respective Texas counties, with the incidences of arrests for possession of opium, cocaine, and their derivatives (morphine, heroin, and codeine) from 1981-1986 also produced statistically significant inverse associations, whereas no significant or consistent associations were observed with the reported arrest rates for possession of marijuana, driving under the influence of alcohol, and drunkenness. These results suggest that lithium at low dosage levels has a generally beneficial effect on human behavior, which may be associated with the functions of lithium as a nutritionally-essential trace element. Subject to confirmation by controlled experiments with high-risk populations, increasing the human lithium intakes by supplementation, or the lithiation of drinking water is suggested as a possible means of crime, suicide, and drug-dependency reduction at the individual and community level.  相似文献   
60.
In the present study we report on the effects of commonly used nonsteroidal antiinflammatory drugs on metallothionein (MT) and MT-I mRNA levels. A single dose of chloroquine (100 mg/kg), diclofenac (100 mg/kg), indomethacin (10 mg/kg), or piroxicam (100 mg/kg) was administered ip to C57B1 mice. After 18 h, MT levels were determined with a Cd-saturation radioassay. MT-I mRNA levels were measured by Northern Blot analyses using a probe containing the mouse MT-I gene. All drugs tested caused an increase in the MT content of the liver but not of the kidneys and lung. The lowest and highest effects were observed with chloroquine (8 times the control value) and diclofenac (18 times), respectively. In accordance with the stimulation of MT synthesis, increased accumulation of hepatic MT-I mRNA could be demonstrated. These results indicate that elevated MT levels may contribute to the effectiveness of nonsteroidal antiinflammatory drugs in the treatment of rheumatoid arthritis (RA).  相似文献   
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