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Genetic variation at the Major Histocompatibility Complex locus DQ beta was
analyzed in 233 beluga whales (Delphinapterus leucas) from seven
populations: St. Lawrence Estuary, eastern Beaufort Sea, eastern Chukchi
Sea, western Hudson Bay, eastern Hudson Bay, southeastern Baffin Island,
and High Arctic and in 12 narwhals (Monodon monoceros) sympatric with the
High Arctic beluga population. Variation was assessed by amplification of
the exon coding for the peptide binding region via the polymerase chain
reaction, followed by either cloning and DNA sequencing or single-stranded
conformation polymorphism analysis. Five alleles were found across the
beluga populations and one in the narwhal. Pairwise comparisons of these
alleles showed a 5:1 ratio of nonsynonymous to synonymous substitutions per
site leading to eight amino acid differences, five of which were
nonconservative substitutions, centered around positions previously shown
to be important for peptide binding. Although the amount of allelic
variation is low when compared with terrestrial mammals, the nature of the
substitutions in the peptide binding sites indicates an important role for
the DQ beta locus in the cellular immune response of beluga whales.
Comparisons of allele frequencies among populations show the High Arctic
population to be different (P < or = .005) from the other beluga
populations surveyed. In these other populations an allele, Dele-DQ
beta*0101-2, was found in 98% of the animals, while in the High Arctic it
was found in only 52% of the animals. Two other alleles were found at high
frequencies in the High Arctic population, one being very similar to the
single allele found in narwhal.
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Calcrete aquifers from the Yilgarn region of arid central Western Australia contain an assemblage of obligate groundwater invertebrate species that are each endemic to single aquifers. Fine-scale phylogeographic and population genetic analyses of three sympatric and independently derived species of amphipod (Chiltoniidae) were carried out to determine whether there were common patterns of population genetic structure or evidence for past geographic isolation of populations within a single calcrete aquifer. Genetic diversity in amphipod mitochondrial DNA (cytochrome c oxidase subunit I gene) and allozymes were examined across a 3.5 km2 region of the Sturt Meadows calcrete, which contains a grid of 115 bore holes (=wells). Stygobiont amphipods were found to have high levels of mitochondrial haplotype diversity coupled with low nucleotide diversity. Mitochondrial phylogeographic structuring was found between haplogroups for one of the chiltoniid species, which also showed population structuring for nuclear markers. Signatures of population expansion in two of the three species, match previous findings for diving beetles at the same site, indicating that the system is dynamic. We propose isolation of populations in refugia within the calcrete, followed by expansion events, as the most likely source of intraspecific genetic diversity, due to changes in water level influencing gene flow across the calcrete. 相似文献
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A polyhydroxyalkanoates bioprocess improvement case study based on four fed-batch feeding strategies
Maciej W. Guzik Gearóid F. Duane Shane T. Kenny Eoin Casey Paweł Mielcarek Magdalena Wojnarowska Kevin E. O’Connor 《Microbial biotechnology》2022,15(3):996-1006
The modelling and optimization of a process for the production of the medium chain length polyhydroxyalkanoate (mcl-PHA) by the bacterium Pseudomonas putida KT2440 when fed a synthetic fatty acid mixture (SFAM) was investigated. Four novel feeding strategies were developed and tested using a constructed model and the optimum one implemented in further experiments. This strategy yielded a cell dry weight of 70.6 g l−1 in 25 h containing 38% PHA using SFAM at 5 l scale. A phosphate starvation strategy was implemented to improve PHA content, and this yielded 94.1 g l−1 in 25 h containing 56% PHA using SFAM at 5 l scale. The process was successfully operated at 20 l resulting in a cell dry weight of 91.2 g l−1 containing 65% PHA at the end of a 25-h incubation. 相似文献
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Microtubule-dependent transport in neurons: steps towards an understanding of regulation, function and dysfunction 总被引:13,自引:0,他引:13
Intracellular transport by microtubule-dependent motors is crucial for neuronal survival and function. Recent advances reveal novel strategies for the regulation of transport and the attachment of motors to cargoes. Current findings also illustrate the importance of directed transport in neuronal biology, including microtubule-motor-dependent transduction of neurotrophic signals and axonal damage signal complexes. Furthermore, recent data implicating the dysfunction of microtubule-dependent transport in the cause and development of several neurodegenerative diseases provides evidence for the vital role of transport in neuronal and organismal function. 相似文献
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High cell density cultivation of Pseudomonas putida KT2440 using glucose without the need for oxygen enriched air supply 下载免费PDF全文
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Thrombin plays a pivotal role in blood clotting as well as in the regulation of vascular remodeling and oxidative stress. Recent evidence suggests that auto-antibodies directed against prothrombin, may play an important role in the pathogenesis of atherosclerosis. It is however not clear, if prothrombin bound in an immune complex retains its clotting and regulatory properties or acts solely by increasing vascular inflammation. In order to answer this question, we used a newly developed stain for the detection of thrombin activity of such complexes. Plasma and serum samples were subjected to rocket immunoelectrophoresis in an anti-prothrombin antiserum containing agarose gel. Gel plates, covered with a nitrocellulose membrane were soaked with chromogenic thrombin substrate. The product of thrombin activity was diazotized to red azo dye bound to nitrocellulose. Activity stain revealed barely discernible rockets in plasma, but heavily stained ones in serum. Pre-incubation with trypsin enhanced activity of immunoprecipitates deriving from plasma, but not from serum. Densitometric analysis showed, that the trypsin-enhanced activity in plasma derived immune complexes was twice as high as in serum derived immunoprecipitates. Thrombin active centre is not blocked by anti-prothrombin antiserum allowing to retain thrombin activity. Moreover, prothrombin in immunoprecipitate is readily cleaved by proteolytic enzymes. This cleavage could potentially be enhanced by antibody binding, although these results need to be confirmed using different antibodies. 相似文献