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51.
Polymorphism and divergence at the 5' flanking region of the sex- determining locus, Sry, in mice 总被引:3,自引:0,他引:3
We have investigated patterns of evolution in the nonrecombining portion of
the Y chromosome in mice by comparing levels of polymorphism within Mus
domesticus with levels of divergence between M. domesticus and M. spretus.
A 1,277-bp fragment of noncoding sequence flanking the sex determining
locus (Sry) was PCR amplified, and 1,063 bases were sequenced and compared
among 20 M. domesticus and 1 M. spretus. Two polymorphic base substitutions
and two polymorphic insertion/deletion sites were identified within M.
domesticus; nucleotide diversity was estimated to be 0.1%. Divergence
between M. domesticus and M. spretus for this region (1.9%) was slightly
lower than the average divergence of single-copy nuclear DNA for these
species. Comparison of levels of polymorphism and divergence at Sry with
levels of polymorphism and divergence in the mitochondrial DNA control
region provided no evidence of a departure from the expectations of neutral
molecular evolution. These findings are consistent with the presumed lack
of function for much of the Y chromosome.
相似文献
52.
Summary The optimum temperatures for growth and respiration of an obligately psychrophilic Pseudomonas spec. were 14°C and 23°C, respectively. The maximum temperature for growth was between 19 and 20°C. When cells were grown in a chemostat with lactate as the growth-limiting substrate at a specific growth rate of 0.05 hr-1 over a temperature range of 5–19°C, it was found that RNA concentration was lowest at 14°C. At lower temperatures the cells compensated the decrease of reaction rates by increasing the concentration of RNA and of respiratory enzymes. A temperature raise above 14°C also increased cellular RNA, which probably counteracted an impairment of protein synthesis. Above 18°C the RNA increase ceased, resulting in a rapid decrease of protein synthesis, until between 19 and 20°C growth ceased entirely. Cells grown at 14°C showed a linear increase of RNA content and
values with growth rate, when this was varied from 0.025 to the maximum value of 0.2 hr-1.Dedicated to Prof. C. B. van Niel on the occasion of his 70th birthday. 相似文献
53.
Joshua J. Ziarek Christopher T. Veldkamp Fuming Zhang Nathan J. Murray Gabriella A. Kartz Xinle Liang Jidong Su John E. Baker Robert J. Linhardt Brian F. Volkman 《The Journal of biological chemistry》2013,288(1):737-746
The ability to interact with cell surface glycosaminoglycans (GAGs) is essential to the cell migration properties of chemokines, but association with soluble GAGs induces the oligomerization of most chemokines including CXCL12. Monomeric CXCL12, but not dimeric CXCL12, is cardioprotective in a number of experimental models of cardiac ischemia. We found that co-administration of heparin, a common treatment for myocardial infarction, abrogated the protective effect of CXCL12 in an ex vivo rat heart model for myocardial infarction. The interaction between CXCL12 and heparin oligosaccharides has previously been analyzed through mutagenesis, in vitro binding assays, and molecular modeling. However, complications from heparin-induced CXCL12 oligomerization and studies using very short oligosaccharides have led to inconsistent conclusions as to the residues involved, the orientation of the binding site, and whether it overlaps with the CXCR4 N-terminal site. We used a constitutively dimeric variant to simplify the NMR analysis of CXCL12-binding heparin oligosaccharides of varying length. Biophysical and mutagenic analyses reveal a CXCL12/heparin interaction surface that lies perpendicular to the dimer interface, does not involve the chemokine N terminus, and partially overlaps with the CXCR4-binding site. We further demonstrate that heparin-mediated enzymatic protection results from the promotion of dimerization rather than direct heparin binding to the CXCL12 N terminus. These results clarify the structural basis for GAG recognition by CXCL12 and lend insight into the development of CXCL12-based therapeutics. 相似文献
54.
Goldstein DB; Zhivotovsky LA; Nayar K; Linares AR; Cavalli-Sforza LL; Feldman MW 《Molecular biology and evolution》1996,13(9):1213-1218
It has recently been suggested that observed levels of variation at
microsatellite loci can be used to infer patterns of selection in genomes
and to assess demographic history. In order to evaluate the feasibility of
these suggestions it is necessary to know something about how levels of
variation at microsatellite loci are expected to fluctuate due simply to
stochasticity in the processes of mutation and inheritance (genetic
sampling). Here we use recently derived properties of the stepwise mutation
model to place confidence intervals around the variance in repeat score
that is expected at mutation-drift equilibrium and outline a statistical
test for whether an observed value differs significantly from expectation.
We also develop confidence intervals for the time course of the buildup of
variation following a complete elimination of variation, such as might be
caused by a selective sweep or an extreme population bottleneck. We apply
these methods to the variation observed at human Y-specific
microsatellites. Although a number of authors have suggested the
possibility of a very recent sweep, our analyses suggest that a sweep or
extreme bottleneck is unlikely to have occurred anytime during the last
approximately 74,000 years. To generate this result we use a recently
estimated mutation rate for microsatellite loci of 5.6 x 10(-4) along with
the variation observed at autosomal microsatellite loci to estimate the
human effective population size. This estimate is 18,000, implying an
effective number of 4,500 Y chromosomes. One important general conclusion
to emerge from this study is that in order to reject mutation-drift
equilibrium at a set of linked microsatellite loci it is necessary to have
an unreasonably large number of loci unless the observed variance is far
below that expected at mutation-drift equilibrium.
相似文献
55.
56.
Pauline MW van Kempen Rob Noorlag Weibel W Braunius Inge Stegeman Stefan M Willems Wilko Grolman 《Epigenetics》2014,9(2):194-203
Oropharyngeal squamous cell carcinoma (OPSCC) is associated with human papillomavirus (HPV). HPV-positive OPSCC is considered a distinct molecular entity with a better prognosis than HPV-negative cases of OPSCC. However, the exact pathogenic mechanisms underlying the differences in clinical and molecular behavior between HPV-positive and HPV-negative OPSCC remain poorly understood. Epigenetic events play an important role in the development of cancer. Hypermethylation of DNA in promoter regions and global hypomethylation are 2 epigenetic changes that have been frequently observed in human cancers. It is suggested that heterogeneous epigenetic changes play a role in the clinical and biological differences between HPV-positive and HPV-negative tumors. Unraveling the differences in methylation profiles of HPV-associated OPSCC may provide for promising clinical applications and may pave the road for personalized cancer treatment. This systematic review aims to assess the current state of knowledge regarding differences in promoter hypermethylation and global methylation between HPV-positive and HPV-negative OPSCC. 相似文献
57.
L. Barreto M.C. Ribeiro A. Veldkamp M. van Eupen K. Kok E. Pontes 《Ecological Indicators》2010,10(5):1055-1063
Nature conservation and restoration activities require delineation of effective conservation networks. This paper presents a methodology which allows a quick evaluation of different planning options for extensive areas. We analyzed the spatial structure of remaining patches of the natural Cerrado vegetation in the Balsás sub-basin, South of Maranhão State of Brazil (about 25,590 km2) in order to understand how the remaining habitats are distributed and spatially configured. Conservation area network scenarios are based on hexagonal cells, referred to as analysis unit (AU) cells. A multi-scale analysis of 10,000 ha and 50,000 ha AU cells was set up to represent local and regional scales, respectively. For each AU at both local and regional scales we computed landscape metrics of native vegetation: NATIVE VEGETATION COVER: percentage of native vegetation cover; (NV-NP): number of patches; (NV-MSI): mean shape index. Subsequently, five different conservation and restoration strategies were defined: (a) only enforce nature conservation within legally established units; (b) target nature conservation only within the local AU landscape; (c) target regional management by combining neighboring AU; (d) management of both local landscape and region; (e) protect the legal conservation areas and promote local and regional conservation. We also generated scenarios of habitat capacity for mammals and matched these results with the different vegetation conservation scenarios. Results indicate that only 12% of the study area is well conserved and that 43% of the region is in a very critical condition. The percentage of AU cells where native vegetation conservation actions are required differ for the five conservation strategies: These results allow policy makers and other stakeholders to target the locations and extent of conservation units required. We suggest that about 45% of the sub-basin could be managed at local, regional or both scales. Regarding a mammal species diversity scenario an even higher percentage of the average habitat capacity of the selected species occurs in open cerrado and valleys areas that coincide with critical areas. The proposed multi-scale analysis unit cell approach can support the planning process of extensive areas as necessary in Brazil. 相似文献
58.
M. S. Kiran Raj M. Sivadasan J. F. Veldkamp A. H. Alfarhan Jacob Thomas 《Nordic Journal of Botany》2013,31(2):161-165
The new genus Nanooravia Kiran Raj & Sivad. (Poaceae–Andropogoneae–Dimeriinae) from the southwestern Ghats in India is described and illustrated, and the new combination N. santapaui (M. R. Almeida) Kiran Raj & Sivad. is made. The genus is characterized by its usually unequal and intertwined racemes, triquetrous rachis, extremely oblique and glabrous pedicel tip, distantly arranged spikelets, long trigonous callus with oblique tip and densely covered with golden–yellow or yellowish–brown hairs along one angle, keel‐less glumes with a dorsally echinate apex and apically auricled margins, and an upper lemma with a stout awn having a long column. The new genus is distinct from Dimeria R. Br. in which the species was originally described, but is similar to the monotypic Indian genus Pogonachne Bor currently placed in the subtribe Ischaeminae. It occurs in Peninsular India, a region considered as the centre of diversity of the subtribe with more than 50% of the known Dimeria species, including numerous endemics. 相似文献
59.
Sarah K. Casper Scott J. Schoeller Danielle M. Zgoba Andrew J. Phillips Thomas J. Morien Gary R. Chaffee Peter C. Sackett Francis C. Peterson Kirsten Crossgrove Christopher T. Veldkamp 《Proteins》2014,82(12):3490-3496
Brugia malayi is a parasitic nematode that causes lymphatic filariasis in humans. Here the solution structure of the forkhead DNA binding domain of Brugia malayi DAF‐16a, a putative ortholog of Caenorhabditis elegans DAF‐16, is reported. It is believed to be the first structure of a forkhead or winged helix domain from an invertebrate. C. elegans DAF‐16 is involved in the insulin/IGF‐I signaling pathway and helps control metabolism, longevity, and development. Conservation of sequence and structure with human FOXO proteins suggests that B. malayi DAF‐16a is a member of the FOXO family of forkhead proteins. Proteins 2014; 82:3490–3496. © 2014 Wiley Periodicals, Inc. 相似文献
60.
Rogier AM Quax Jan W Koper Pascal HP de Jong Ramona van Heerebeek Angelique E Weel Anne M Huisman Derkjen van Zeben Frank H de Jong Steven WJ Lamberts Johanna MW Hazes Richard A Feelders 《Arthritis research & therapy》2012,14(4):R195