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排序方式: 共有63条查询结果,搜索用时 15 毫秒
1.
2.
Sampling properties of DNA sequence data in phylogenetic analysis 总被引:26,自引:6,他引:20
We inferred phylogenetic trees from individual genes and random samples of
nucleotides from the mitochondrial genomes of 10 vertebrates and compared
the results to those obtained by analyzing the whole genomes. Individual
genes are poor samples in that they infrequently lead to the whole-genome
tree. A large number of nucleotide sites is needed to exactly determine the
whole-genome tree. A relatively small number of sites, however, often
results in a tree close to the whole-genome tree. We found that blocks of
contiguous sites were less likely to lead to the whole-genome tree than
samples composed of sites drawn individually from throughout the genome.
Samples of contiguous sites are not representative of the entire genome, a
condition that violates a basic assumption of the bootstrap method as it is
applied in phylogenetic studies.
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3.
BACKGROUND: Morbidity management is a core component of the global programme for the elimination of lymphatic filariasis. In a double-blind clinical trial, the tolerability and efficacy of Daflon (500 mg) + DEC (25 mg) or DEC (25 mg) alone, twice daily for 90 days, was studied in 26 patients with bancroftian filarial lymphoedema. RESULTS: None of the patients in either drug group reported any adverse reaction throughout the treatment period (90 days). Haematological and biochemical parameters were within normal limits and there was no significant difference between the pre-treatment (day 0) and post-treatment (day 90) values. The group receiving Daflon showed significant reduction in oedema volume from day 90 (140.6 PlusMinus; 18.8 ml) to day 360 (71.8 PlusMinus; 20.7 ml) compared to the pre-treatment (day 0, 198.4 PlusMinus; 16.5 ml) value. This accounted for a 63.8% reduction in oedema volume by day 360 (considering the pre-treatment (day 0) as 100%). In the DEC group, the changes in oedema volume (between day 1 and day 360) were not significant when compared to the pre-treatment (day 0) value. The percentage reduction at day 360 was only 9%, which was not significant (P > 0.05). CONCLUSION: This study has shown that Daflon (500 mg, twice a day for 90 days) is both safe and efficacious in reducing oedema volume in bancroftian filarial lymphoedema. Further clinical trials are essential for strengthening the evidence base on the role of this drug in the morbidity management of lymphatic filariasis. 相似文献
4.
Conformation and glycosylation of a megalin fragment correlate with nephritogenicity in Heymann nephritis 总被引:2,自引:0,他引:2
Active Heymann nephritis (AHN), a rat model of autoimmune glomerulonephritis, is induced by immunization with autologous megalin, a 600-kDa cell surface glycoprotein isolated from crude renal extracts. Recombinant proteins containing a 563-residue N-terminal sequence of megalin were obtained from Escherichia coli and baculovirus-insect cell expression systems. Rats immunized with the soluble, secreted protein encoded by a baculovirus construct elicited high titer anti-megalin autoantibodies and developed glomerular immune deposits and elevated proteinuria consistent with AHN. Rats treated with the bacterial or nonsecreted insect cell proteins produced a milder anti-megalin response and did not develop the disease. Nephritogenicity appeared to correlate with conformational or other structural features of native megalin. All three recombinant proteins were reactive in Western blots with rabbit anti-megalin antiserum, whereas the insect cell-derived proteins reacted preferentially in Western blot and ELISA with anti-megalin autoantibodies from rats with AHN induced by native megalin. Only the secreted insect cell product was stained in a lectin blot, suggesting its specific glycosylation. These observations provide evidence that a megalin N-terminal domain includes B and T cell epitopes sufficient for a pathogenic autoimmune response and that a native-like conformation and glycosylation are essential for the induction of disease. The importance of conformational B cell epitopes for pathogenic autoantibodies recapitulates observations made in other models of organ-specific autoimmune disease. Glycosidic modifications could influence the presentation of either B or T cell epitopes in AHN, consistent with emerging evidence of the role of post-translational modifications in pathogenic autoimmune responses. 相似文献
5.
6.
The Kosi coastal lake system, a chain of four interconnected basins, is located in the subtropical north-eastern corner of South Africa. Little information is available on zooplankton of the system and the main aim of this study is to report on zooplankton samples collected during 2002 and 2003. The set of samples consists of seasonal, subsurface mesozooplankton samples that were collected during nighttime in each of the lakes. A well-developed salinity gradient was evident along the interconnected lakes in the subsurface water during all seasons, ranging from freshwater in the upper lake Amanzamnyama to a maximum of 22 recorded in Lake Makhawulani. The zooplankton community structures of the lakes reflected the salinity gradient of the system, with some coastal marine taxa recorded in the lakes closer to the mouth and only freshwater taxa recorded in Lake Amanzamnyama. Mesozooplankton diversity and abundance were relatively low compared to other estuarine systems along the eastern coast of South Africa. The dominant taxa were calanoid copepods Acartiella natalensis and Pseudodiaptomus stuhlmanni and the mysid Mesopodopsis africana in the lower lakes, whereas cyclopoids Mesocyclops sp. and Thermocyclops sp. dominated the freshwater lake Amanzamnyama. 相似文献
7.
Previous results have demonstrated the binding of a 76- and 80-kDa serum protein to the Heymann nephritis autoantigen, gp330. This 76-kDa serum protein was purified by column chromatography and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A rabbit polyclonal antibody for the serum protein was produced and used to screen a rat liver cDNA expression library. Sequence analysis of an isolated clone identified the serum protein as plasminogen. Plasminogen was isolated from rat serum by standard techniques, and the binding of plasminogen to gp330 was confirmed by Western analysis. Enzyme-linked immunosorbent assay results demonstrated a time-dependent, saturable, and specifically inhibitable binding of plasminogen to gp330. There was no significant difference in the binding of the two carbohydrate forms of plasminogen to gp330. Plasminogen binding to gp330 could be completely inhibited by the addition of exogenous gp330. This binding could also be partially inhibited by benzamidine but only slightly by the lysine analogue, epsilon-aminocaproic acid. However, even a combination of these two inhibitors could not completely block the binding of plasminogen to gp330 indicating that gp330 may be binding to plasminogen through some other unknown interactions. These results demonstrate that gp330 is a receptor site for plasminogen. 相似文献
8.
Singh RK Vikram P Makker J Jabeen T Sharma S Dey S Kaur P Srinivasan A Singh TP 《Biochemistry》2003,42(40):11701-11706
Phospholipase A(2) (PLA(2)) (E. C. 3.1.1.4) is a common enzyme in the two-way cascade mechanism leading to the production of proinflammatory compounds known as eicosanoids. The binding of phospholipase A(2) to the membrane surface and hydrolysis of phospholipids are thought to involve the formation of a hydrophobic channel into which a single substrate molecule diffuses before its cleavage. To regulate the production of proinflammatory compounds, a specific peptide inhibitor Val-Ala-Phe-Arg-Ser (VAFRS) for the group I PLA(2) enzymes has been designed and synthesized. PLA(2) was isolated from Indian cobra (Naja naja sagittifera) venom and purified to homogeneity. The binding studies indicated the K(i) value of 1.02 +/- 0.10 x 10(-8) M. The purified PLA(2) samples and the designed inhibitor VAFRS were cocrystallized. The crystal structure of the complex was determined and refined to 1.9 A resolution. The peptide binds to PLA(2) at the active site and fills the hydrophobic channel completely. However, its placement with respect to the channel is in the opposite direction as compared to those observed in group II PLA(2)'s. Furthermore, the predominant intermolecular interactions involve strong electrostatic interactions between the side chains of peptide Arg and Asp 49 of PLA(2) together with a number of van der Waals interactions with other residues. A good number of observed interactions between the peptide and the protein indicate the significance of a structure-based drug design approach. The novel factor in the present sequence of the peptide is related to the introduction of a positively charged residue at the C-terminal part of the peptide. 相似文献
9.
Type IX collagen is a key component of the extracellular matrix of
cartilage where it occurs at the surfaces of type II collagen fibrils as a
glycanated molecule. The function of the glycosaminoglycan (GAG) side chain
of the molecule is, however, unknown. We have shown that type IX collagen
in chicken sternal cartilage is synthesized with a unimodal distribution of
GAG chain size, but at post 17 days of development three predominant
glycanforms of type IX collagen accumulate. Such accumulation did not occur
in sterna from day 15 embryos. In day 17 embryos predominant glycanforms
were found in the caudal region of the sternum. By day 19 of development
the three predominant glycanforms are widespread throughout the caudal and
cephalic regions. The results indicate that developmental and anatomical
changes occur to type IX collagen that depend on the size of the GAG chain
attached to the alpha2(IX) chain of the molecule.
相似文献
10.
Annu Makker M. M. Singh S. R. Chowdhury S. C. Maitra V. P. Kamboj 《The Journal of steroid biochemistry and molecular biology》1994,48(5-6):535-543
Alterations in nuclear and cytosolic estradiol (ER) and progesterone (PR) receptor concentration in the antimesometrial (AM) and mesometrial (M) segments of the uterus in relation to circulating hormone levels, histology and surface topography during the period of high endometrial sensitivity and development of trauma-induced decidualization in cyclic guinea pigs were investigated. The period of high endometrial sensitivity (i.e. day 5 of the estrous cycle) was characterized by elevated plasma estradiol and progesterone and their receptors in the nuclear and cytosolic fractions of the uterus. There was, however, no difference in the concentration of these receptors or the surface ultrastructure in the AM and M segments. Unilateral traumatization by scissor cut along the AM length of the uterus on day 5 of the estrous cycle induced decidual cell reaction resulting in a marked increase in weight of the decidualized (traumatized) uterine horn with advancing decidualization to reach maximum levels (926% of the contralateral nontraumatized uterine horn) 7 days after traumatization. This was associated with decidual transformation and a marked increase in nuclear and cytosolic ER and PR concentration in the AM segment of the traumatized uterine horn. An increase in receptor concentration in the M segment of the traumatized uterine horn or the AM segment of the nontraumatized uterine horn was transitory and of a low order. Receptor concentration in the M segment of the nontraumatized uterine horn remained low throughout days 8–12 of the cycle. Findings indicate a possible role of both estradiol and progesterone in induction of endometrial sensitivity and development and maintenance of decidua in the guinea pig. 相似文献