排序方式: 共有151条查询结果,搜索用时 15 毫秒
91.
Atanu Raha Susmita Das Kakoli Banerjee Abhijit Mitra 《Biodiversity and Conservation》2012,21(5):1289-1307
Climate change induced sea level rise (SLR) added with anthropogenically altered environment leads to rapid land dynamics
in terms of erosion and accretion; and alteration in species diversity and productivity, more pronouncedly in sensitive ecosystems
such as river deltas. Here, we tried to analyze the historical records to understand the SLR with respect to hydrological
conditions, sedimentation and morphological processes. We analyzed the land transformation of few islands in Indian Sunderbans
using maps and satellite images in increasing order of temporal frequency between 1924 and 2008, which revealed that both
the erosion and accretion processes go hand in hand. Increase of downstream salinity due obstruction in upstream has led to
decrease in transparency of water causing decrease in phytoplankton and fish, density and diversity in the central sector
of Indian Sunderbans. Analysis of the above ground biomass of three dominant mangrove species (Sonneratia apetala, Avicennia alba and Excoecaria agallocha) revealed better growth in the western sector compared to the central sector. The study reveals the cumulative effect of
climate change and anthropogenic disturbance on the diversity and productivity in World’s largest ecosystem; and advocates
mangrove plantation and effective management of freshwater resources for conservation of the most vulnerable and sensitive
ecosystem. 相似文献
92.
Programmed cell death (PCD) has been observed in many unicellular eukaryotes; however, in very few cases have the pathways been described. Recently the early divergent amitochondrial eukaryote Giardia has been included in this group. In this paper we investigate the processes of PCD in Giardia. We performed a bioinformatics survey of Giardia genomes to identify genes associated with PCD alongside traditional methods for studying apoptosis and autophagy. Analysis of Giardia genomes failed to highlight any genes involved in apoptotic-like PCD; however, we were able to induce apoptotic-like morphological changes in response to oxidative stress (H2O2) and drugs (metronidazole). In addition we did not detect caspase activity in induced cells. Interestingly, we did observe changes resembling autophagy when cells were starved (staining with MDC) and genome analysis revealed some key genes associated with autophagy such as TOR, ATG1 and ATG 16. In organisms such as Trichomonas vaginalis, Entamoeba histolytica and Blastocystis similar observations have been made but no genes have been identified. We propose that Giardia possess a pathway of autophagy and a form of apoptosis very different from the classical known mechanism; this may represent an early form of programmed cell death. 相似文献
93.
Parimelzaghan Anitha Vaideeswaran Sivasakthi Pandian Lavanya Susmita Bag Kalavathi Murugan Kumar Anand Anbarasu Sudha Ramaiah 《Bioinformation》2012,8(17):820-826
Metalloproteins have many different functions in cells such as enzymes; signal transduction, transport and storage proteins. About
one third of all proteins require metals to carry out their functions. In the present study we have analyzed the roles played by Arg
and Lys (cationic side chains) interactions with π (Phe, Tyr or Trp) residues and their role in the structural stability of
metalloproteins. These interactions might play an important role in the global conformational stability in metalloproteins. In spite
of its lower natural occurrence (1.76%) the number of Trp residues involved in energetically significant interactions is higher in
metalloproteins. 相似文献
94.
Paralanov V Lu J Duffy LB Crabb DM Shrivastava S Methé BA Inman J Yooseph S Xiao L Cassell GH Waites KB Glass JI 《BMC microbiology》2012,12(1):88
ABSTRACT: BACKGROUND: Ureaplasma urealyticum (UUR) and Ureaplasma parvum (UPA) are sexually transmitted bacteria among humans implicated in a variety of disease states including but not limited to: nongonococcal urethritis, infertility, adverse pregnancy outcomes, chorioamnionitis, and bronchopulmonary dysplasia in neonates. There are 10 distinct serotypes of UUR and 4 of UPA. Efforts to determine whether difference in pathogenic potential exists at the ureaplasma serovar level have been hampered by limitations of antibody-based typing methods, multiple cross-reactions and poor discriminating capacity in clinical samples containing two or more serovars. RESULTS: We determined the genome sequences of the American Type Culture Collection (ATCC) type strains of all UUR and UPA serovars as well as four clinical isolates of UUR for which we were not able to determine serovar designation. UPA serovars had 0.750.78 Mbp genomes and UUR serovars were 0.840.95 Mbp. The original classification of ureaplasma isolates into distinct serovars was largely based on differences in the major ureaplasma surface antigen called the multiple banded antigen (MBA) and reactions of human and animal sera to the organisms. Whole genome analysis of the 14 serovars and the 4 clinical isolates showed the mba gene was part of a large superfamily, which is a phase variable gene system, and that some serovars have identical sets of mba genes. Most of the differences among serovars are hypothetical genes, and in general the two species and 14 serovars are extremely similar at the genome level. CONCLUSIONS: Comparative genome analysis suggests UUR is more capable of acquiring genes horizontally, which may contribute to its greater virulence for some conditions. The 4 overwhelming evidence of extensive horizontal gene transfer among these organisms from our previous studies combined with our comparative analysis indicates that 6 ureaplasmas exist as quasispecies rather than as stable serovars in their native environment. Therefore, differential pathogenicity and clinical outcome of a ureaplasmal infection is most likely not on the serovar level, but rather may be due to the presence or absence of potential pathogenicity factors in an individual ureaplasma clinical isolate and/or patient to patient differences in terms of autoimmunity and microbiome. 相似文献
95.
Bharati S Mukherji D Pal M Som S Kumar Adak D Vasulu TS Bharati P 《Collegium antropologicum》2010,34(4):1207-1213
This paper analyzes the variation in the mean stature of adult males of a variety of population groups in India and examines the influence of geographical, climatic and ethnic factors on it. A considerable variation in mean stature has been found with respect to these three attributes. Variation "between" ethnic groups compared with "within" ethnic groups was found to be much more than that of geographical and climatic zones. Scheduled Castes (SC) and Scheduled Tribes (ST) populations have much low average height than that of General Castes (GC). Climatically dry and semiarid zones have a tendency to have higher stature than in the Monsoon areas. The mean height has been found to be the highest in north India. It is closely followed by west India. An interesting feature is that as one goes towards east and south the mean height gradually decreases. It is the lowest in islands. The mean heights have been regressed on geographical, climatic and ethnic factors, after converting these factors into binary variables. The regression analysis has strengthened the findings, that there is a highly significant relationship between height and geographical, climatic and ethnic factors. 相似文献
96.
A simple two-locus drift model for cytonuclear systems is developed, in which the stochastic dynamics of cytonuclear genotypic frequencies are specified. Random union of zygotes is assumed. Trajectories for the first two moments of both genotypic and allelic disequilibria are given under three scenarios: (i) random drift alone; (ii) random drift with mutation; and (iii) random drift with migration. Steady state solutions for the cytonuclear disequilibria are reported. The utility of this simple two-locus drift model in testing the neutrality of mitochondrial DNA markers in artificial hybrid zones is briefly illustrated 相似文献
97.
98.
Allergic reactions are triggered by the interaction between IgE and its high-affinity receptor, FcεRI. Various studies have mapped the interaction surface between IgE and its cellular receptors to the third constant domain of IgE (Cε3). The isolated Cε3 domain has been shown to exist as a molten globule, and the domain retains significant flexibility within the context of the IgE protein. Here we have analyzed the structural basis of the intrinsic flexibility of this domain. We have compared the sequence of the Cε3 domain to the sequences of other members of the C1 subset of the immunoglobulin superfamily and observed that Cε3 has an unusually high electrostatic charge and an unusually low content of hydrophobic residues. Mutations restoring Cε3 to a more canonical sequence were introduced in an attempt to derive a more structured domain, and several mutants display decreased levels of disorder. Engineered domains of Cε3 with a range of structural rigidities could serve as important tools for the elucidation of the role of flexibility of the Cε3 domain in IgE's biological functions. 相似文献
99.
The histone octamer induced bending of DNA into the super-helix structure in nucleosome core particle, is very unique and vital for DNA packing into chromatin. We collected 48 nucleosome crystal structures from PDB and applied a multivariate analysis on the nucleosome structural data. Based on the anisotropic nature of DNA structure, a principal conformational subspace (PCS) is derived from multiple properties to represent the most significant variances of nucleosome DNA structures. The coupling of base pair-oriented parameters with sugar phosphate backbone parameters presented in principal dimensionalities reveals two main deformation modes that have supplemented the existing physical model. By using sequence alignment-based statistics, a positiondependent conformational map for the super-helical DNA path is established. The result shows that the crystal structures of nucleosome DNA have much consistency in position-specific structural variations and certain periodicity is found to exist in these variations. Thus, the positions with obvious deformation patterns along the DNA path in nucleosome core particle are relatively conservative from the perspective of statistics. 相似文献
100.
Michael E. Bose Jie He Susmita Shrivastava Martha I. Nelson Jayati Bera Rebecca A. Halpin Christopher D. Town Hernan A. Lorenzi Daniel E. Noyola Valeria Falcone Giuseppe Gerna Hans De Beenhouwer Cristina Videla Tuckweng Kok Marietjie Venter John V. Williams Kelly J. Henrickson 《PloS one》2015,10(3)