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21.
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Ram Krishna Thakur Vinod Kumar Yadav Akinchan Kumar Ankita Singh Krishnendu Pal Luke Hoeppner Dhurjhoti Saha Gunjan Purohit Richa Basundra Anirban Kar Rashi Halder Pankaj Kumar Aradhita Baral MJ Mahesh Kumar Alfonso Baldi Bruno Vincenzi Laura Lorenzon Rajkumar Banerjee Praveen Kumar Viji Shridhar Debabrata Mukhopadhyay Shantanu Chowdhury 《Nucleic acids research》2014,42(18):11589-11600
23.
Marieke?Pingen Ramin?Sarrami-Forooshani Annemarie?MJ?Wensing Petra?van Ham Agata?Drewniak Charles?AB?Boucher Teunis?BH?GeijtenbeekEmail author Monique?NijhuisEmail author 《Retrovirology》2014,11(1):113
Background
Different patterns of drug resistance are observed in treated and therapy naïve HIV-1 infected populations. Especially the NRTI-related M184I/V variants, which are among the most frequently encountered mutations in treated patients, are underrepresented in the antiretroviral naïve population. M184I/V mutations are known to have a profound effect on viral replication and tend to revert over time in the new host. However it is debated whether a diminished transmission efficacy of HIV variants with a reduced replication capacity can also contribute to the observed discrepancy in genotypic patterns.As dendritic cells (DCs) play a pivotal role in HIV-1 transmission, we used a model containing primary human Langerhans cells (LCs) and DCs to compare the transmission efficacy M184 variants (HIV-M184V/I/T) to HIV wild type (HIV-WT). As control, we used HIV harboring the NNRTI mutation K103N (HIV-K103N) which has a minor effect on replication and is found at a similar prevalence in treated and untreated individuals.Results
In comparison to HIV-WT, the HIV-M184 variants were less efficiently transmitted to CCR5+ Jurkat T cells by both LCs and DCs. The transmission rate of HIV-K103N was slightly reduced to HIV-WT in LCs and even higher than HIV-WT in DCs. Replication experiments in CCR5+ Jurkat T cells revealed no apparent differences in replication capacity between the mutant viruses and HIV-WT. However, viral replication in LCs and DCs was in concordance with the transmission results; replication by the HIV-M184 variants was lower than replication by HIV-WT, and the level of replication of HIV-K103N was intermediate for LCs and higher than HIV-WT for DCs.Conclusions
Our data demonstrate that drug resistant M184-variants display a reduced replication capacity in LCs and DCs which directly impairs their transmission efficacy. As such, diminished transmission efficacy may contribute to the lower prevalence of drug resistant variants in therapy naive individuals.24.
The haplochromine cichlid fish communities of the rocky habitats of Lake Malawi are highly diverse; however, many species
live side by side with apparently very similar resource requirements. There is a long-standing debate concerning whether these
species partition their resources on a finer scale than has been previously reported or if species that are truly ecologically
indistinguishable can coexist. A field study of food resource use was conducted to determine whether coexisting species segregate
their diet and foraging sites. Significant differences between species were found, yet considerable inter-specific resource
use overlap was commonplace. The data indicate that these cichlid species coexist both with and without niche differentiation.
We propose that alternatives to niche differentiation should be considered to explain how many species coexist in Lake Malawi
cichlid communities.
Received: 5 October 1998 / Accepted: 30 June 1999 相似文献
25.
Niche segregation among Lake Malawi cichlid fishes? Evidence from stable isotope signatures 总被引:3,自引:0,他引:3
The fish communities of the rocky littoral zone of Lake Malawi contain a large number of ecologically similar cichlid species. It has been suggested that dietary niche segregation may play a role in the coexistence of these species, but previous studies have yielded ambiguous results. Stable isotope analysis was used to determine whether five sympatric species are segregated by diet. Significant differences were found between the mean isotopic signatures of the study species, but there was considerable interspecific overlap between three species from the same subgenus that were anatomically almost indistinguishable. The implication that this was due to substantial dietary similarity was supported by stomach content analysis. We propose that ecological segregation may not always be necessary to allow coexistence of Lake Malawi cichlids. 相似文献
26.
27.
28.
Asilatu Shechonge Benjamin P. Ngatunga Rashid Tamatamah Stephanie J. Bradbeer Jack Harrington Antonia G. P. Ford George F. Turner Martin J. Genner 《Conservation Genetics》2018,19(5):1199-1209
Among the many negative impacts of invasive species, hybridization with indigenous species has increasingly become recognized as a major issue. However, relatively few studies have characterized the phenotypic outcomes of hybridization following biological invasions. Here we investigate the genetic and morphological consequences of stocking invasive tilapia species in two water bodies in central Tanzania. We sampled individuals from the Mindu Reservoir on the Ruvu river system, and at Kidatu on the Great Ruaha–Rufiji river system. We screened individuals at 16 microsatellite loci, and quantified morphology using geometric morphometrics and linear measurements. In both the Mindu and Kidatu systems, we identified evidence of hybridization between indigenous Wami tilapia (Oreochromis urolepis) and the introduced Nile tilapia (Oreochromis niloticus) or blue-spotted tilapia (Oreochromis leucostictus). At both sites, purebred individuals could largely be separated using geometric morphometric variables, with hybrids occupying a broad morphospace among the parental species. Our data demonstrate that the gene pools and phenotypic identity of the indigenous O. urolepis have been severely impacted by the stocking of the invasive species. Given the lack of evidence for clear commercial benefits from stocking invasive tilapia species in waters already populated by indigenous congenerics, we suggest further spread of introduced species should be undertaken with considerable caution. 相似文献
29.
Current phylogenetic tree reconstruction methods assume that there is a
single underlying tree topology for all sites along the sequence. The
presence of mosaic sequences due to recombination violates this assumption
and will cause phylogenetic methods to give misleading results due to the
imposition of a single tree topology on all sites. The detection of mosaic
sequences caused by recombination is therefore an important first step in
phylogenetic analysis. A graphical method for the detection of
recombination, based on the least squares method of phylogenetic
estimation, is presented here. This method locates putative recombination
breakpoints by moving a window along the sequence. The performance of the
method is assessed by simulation and by its application to a real data set.
相似文献
30.
We used the repetitive character of transposable elements to isolate a
non-LTR retrotransposon in Drosophila subobscura. bilbo, as we have called
it, has homology to TRIM and LOA elements. Sequence analysis showed a 5'
untranslated region (UTR), an open reading frame (ORF) with no RNA-binding
domains, a downstream ORF that had structural homology to that of the I
factor, and, finally, a 3' UTR which ended in several 5-nt repeats. The
results of our phylogenetic and structural analyses shed light on the
evolution of Drosophila non-LTR retrotransposons and support the hypothesis
that an ancestor of these elements was structurally complex.
相似文献