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951.
952.
Matthew E. Durnin Per J. Palsbøll Oliver A. Ryder Dale R. McCullough 《Conservation Genetics》2007,8(3):715-720
Extractions from non-invasive hair samples usually yield low amounts of highly degraded DNA. Previously developed mammal molecular
sexing methods were not designed with such sub-optimal conditions in mind. We developed a simple and reliable PCR-based sexing
method aimed at degraded, low yield DNA extractions from the giant panda (Ailuropoda melanoleuca). Comparisons of this new primer set with others showed that the reliability of sex determination from low-yield, degraded
DNA extractions was improved if; amplification products were short (<170 bp); and the Y-chromosome amplification product was
shorter than the X-chromosome amplification product. The primers developed in this study appear useful for sex determination
in other bear species. 相似文献
953.
We estimated the phylogenetic position of the pseudosegmented ribbon worm Annulonemertes minusculus to test proposed evolutionary hypotheses to explain these body constrictions. The analysis is based on 18S rDNA sequences and shows that the species belongs to an apomorphic clade of hoplonemertean species. The segmentation has no phylogenetic bearing as previously discussed, but is a derived character probably coupled to the species' interstitial habitat. 相似文献
954.
The tricyclic cytosine, tC, is a fluorescent base analogue with excellent properties for investigating intrinsic characteristics of nucleic acid as well as interactions between nucleic acids and other molecules. Its unique fluorescence properties and insignificant influence on overall structure and dynamics of nucleic acid after incorporation makes tC particularly interesting in fluorescence resonance energy transfer and anisotropy measurements. We here describe a straightforward synthesis of the standard monomer form of tC for DNA solid-phase synthesis, the tC phosphoramidite, and its subsequent incorporation into oligonucleotides. The total synthesis of the tC phosphoramidite takes approximately 8 days and its incorporation and the subsequent oligonucleotide purification an additional day. 相似文献
955.
Background
The FFAR1 receptor is expressed mainly in pancreatic beta cells and is activated by medium to long chain free fatty acids (FFAs), as well as by thiazolidinediones, resulting in elevated Ca2+ concentrations and promotion of insulin secretion. These properties suggest that FFAR1 could be a mediator of lipotoxicity and a potential candidate gene for Type 2 diabetes (T2D). We therefore investigated whether variations at the FFAR1 locus are associated with T2D and beta cell function.Methodology/Principal Findings
We re-sequenced the FFAR1 region in 96 subjects (48 healthy and 48 T2D individuals) and found 13 single nucleotide polymorphisms (SNPs) 8 of which were not previously described. Two SNPs located in the upstream region of the FFAR1 gene (rs1978013 and rs1978014) were chosen and genotyped in 1929 patients with T2D and 1405 healthy control subjects. We observed an association of rs1978013 and rs1978014 with insulinogenic index in males (p = 0.024) and females (p = 0.032), respectively. After Bonferroni corrections, no association with T2D was found in the case-control material, however a haplotype consisting of the T-G alleles conferred protection against T2D (p = 0.0010).Conclusions/Significance
Variation in the FFAR1 gene may contribute to impaired beta cell function in T2D. 相似文献956.
957.
MOTIVATION: Most gene-expression based studies aim to identify genes with the capability of distinguishing different phenotypes. Although analysis at the genomic level is important, results of the molecular/cellular level are essential for understanding biological mechanisms. To deliver molecular/cellular-level results, a two-stage scheme is widely employed. This scheme just evaluates biological processes/molecular activities individually, totally overlooking the relationship between processes/activities. This treatment conflicts with the fact that most biological processes/molecular activities do not work alone. In order to deliver improved results, this shortcoming should be addressed. RESULTS: We design a selection model from a novel perspective to directly detect important gene functional categories (each category represents a cellular process or a molecular activity). More importantly, the correlations between gene categories are considered. Contributed by this capability, the proposed method shows its advantages over others. AVAILABILITY: the source code in Matlab is accessible via http://www.ee.cityu.edu.hk/~twschow/category_selection/category_selection.htm 相似文献
958.
Induced Shift in Ecosystem Productivity? Extensive Scale Effects of Abundant Large Herbivores 总被引:3,自引:0,他引:3
Kari Anne Bråthen Rolf A. Ims Nigel G. Yoccoz Per Fauchald Torkild Tveraa Vera H. Hausner 《Ecosystems》2007,10(5):773-789
Abundant large herbivores can strongly alter vegetation composition, shifting the ecosystem into a lasting state of changed
productivity. Previous studies of the effects of abundant reindeer on alpine and arctic vegetation have yielded equivocal
results, probably due to differing environmental contexts. To overcome context dependency we devised a large-scale survey
in the region of Finnmark, northern Norway, possessing some of the most densely stocked reindeer herds in the world. The effects
of reindeer abundance on summer pasture vegetation were assessed by employing a quasi-experimental design, including site
fertility as a potential modifier of the reindeer–vegetation interaction. The study design comprised ten pairs of neighboring
management districts (encompassing 18,003 km2), where over the two last decades a high-density district on average had reindeer densities more than twice as high and calf
weights consistently lower than the low-density district. The abundance of different plant functional groups, ranging from
those having facilitating to retarding effects on ecosystem productivity, were quantified by the point intercept method on
plots selected according to a hierarchical, stratified random sampling design. Species with strong retarding effects on ecosystem
productivity (for example, ericoids) were by far the most abundant. However, we found no consistent effects of reindeer density
on their abundance. The most consistent differences between high- and low-density districts were found in plant functional
groups with facilitating to neutral effects on ecosystem productivity. In particular, the abundance of N-facilitators, large
dicotyledons and grasses were substantially reduced in the high-density districts. However, this reduction was restricted
to fertile sites. Thus, reindeer when present at high densities have homogenized the biomass of palatable plants across environmental
productivity gradients according to predictions from exploitation ecosystem models. Such reduction of plants with facilitating
to neutral effects on ecosystem productivity indicates a reduced state of ecosystem productivity in high-density districts.
Electronic supplementary material: The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
959.
The lantibiotic nisin is produced by Lactococcus lactis. In the biosynthesis of nisin, the enzyme NisB dehydrates nisin precursor, and the enzyme NisC is needed for lanthionine formation. In this study, the nisA gene encoding the nisin precursor, and the genes nisB and nisC of the lantibiotic modification machinery were expressed together in vitro by the Rapid Translation System (RTS). Analysis of the RTS mixture showed that fully modified nisin precursor was formed. By treating the mixture with trypsin, active nisin was obtained. However, no nisin could be detected in the mixture without zinc supplementation, explained by the fact that NisC requires zinc for its function. The results revealed that the modification of nisin precursor, which is supposed to occur at the inner side of the membrane by an enzyme complex consisting of NisB, NisC, and the transporter NisT, can take place without membrane association and without NisT. This in vitro production system for nisin opens up the possibility to produce nisin variants that cannot be producedin vivo. Moreover, the system is a promising tool for utilizing the NisB and NisC enzymes for incorporation of thioether rings into medical peptides and hormones for increased stability. 相似文献
960.
Ihlen EA Sletvold O Goihl T Wik PB Vereijken B Helbostad J 《Journal of biomechanics》2012,45(9):1559-1565
The present article investigates gait stability of healthy older persons during weight transfer. Ten healthy older persons and ten younger persons walked 10 min each on a treadmill at 3 different gait speeds. The intra-stride change in gait stability was defined by the local divergence exponent λ(t) estimated by a newly developed method. The intra-stride changes in λ(t) during weight transfer were identified by separating each stride into a single and double support phase. The intra-stride changes in λ(t) were also compared to changes in the variation of the gait kinematics, i.e., SD(t). The healthy older persons walked at the same preferred walking speed as the younger persons. However, they exhibited significantly larger λ(t) (p<0.001) during weight transfer in the double support phase. Local divergence was closely related to intra-stride changes in SD(t) of the feet in the anterior-posterior direction. Furthermore, a high correlation was found between local divergence and the variation in step length and step width for both older (R>0.67, p<0.05) and younger persons (R>0.67, p<0.05). The present results indicate that the gait kinematics of older adults are more dynamical unstable during the weight transfer compared to younger persons. Furthermore, a close relationship exists between intra-stride changes in dynamical stability and variation in step length and step width. Further work will validate the results of the present study using real-life perturbations of the gait kinematics of both younger and older adults. 相似文献