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Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
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A major difference between the divergence patterns within the lines-1 families in mice and voles 总被引:3,自引:0,他引:3
Vanlerberghe F; Bonhomme F; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1993,10(4):719-731
L1 retroposons are represented in mice by subfamilies of interspersed
sequences of varied abundance. Previous analyses have indicated that
subfamilies are generated by duplicative transposition of a small number of
members of the L1 family, the progeny of which then become a major
component of the murine L1 population, and are not due to any active
processes generating homology within preexisting groups of elements in a
particular species. In mice, more than a third of the L1 elements belong to
a clade that became active approximately 5 Mya and whose elements are >
or = 95% identical. We have collected sequence information from 13 L1
elements isolated from two species of voles (Rodentia: Microtinae: Microtus
and Arvicola) and have found that divergence within the vole L1 population
is quite different from that in mice, in that there is no abundant
subfamily of homologous elements. Individual L1 elements from voles are
very divergent from one another and belong to a clade that began a period
of elevated duplicative transposition approximately 13 Mya. Sequence
analyses of portions of these divergent L1 elements (approximately 250 bp
each) gave no evidence for concerted evolution having acted on the vole L1
elements since the split of the two vole lineages approximately 3.5 Mya;
that is, the observed interspecific divergence (6.7%-24.7%) is not larger
than the intraspecific divergence (7.9%-27.2%), and phylogenetic analyses
showed no clustering into Arvicola and Microtus clades.
相似文献
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Oylum Erkus Victor CL de Jager Maciej Spus Ingrid J van Alen-Boerrigter Irma MH van Rijswijck Lucie Hazelwood Patrick WM Janssen Sacha AFT van Hijum Michiel Kleerebezem Eddy J Smid 《The ISME journal》2013,7(11):2126-2136
Maintenance of a high degree of biodiversity in homogeneous environments is poorly understood. A complex cheese starter culture with a long history of use was characterized as a model system to study simple microbial communities. Eight distinct genetic lineages were identified, encompassing two species: Lactococcus lactis and Leuconostoc mesenteroides. The genetic lineages were found to be collections of strains with variable plasmid content and phage sensitivities. Kill-the-winner hypothesis explaining the suppression of the fittest strains by density-dependent phage predation was operational at the strain level. This prevents the eradication of entire genetic lineages from the community during propagation regimes (back-slopping), stabilizing the genetic heterogeneity in the starter culture against environmental uncertainty. 相似文献
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Irisin was first identified in muscle cells. We detected irisin immunoreactivity in various organs of the crested porcupine (Hystrix cristata). In the epidermis, irisin immunoreactivity was localized mainly in stratum basale, stratum spinosum and stratum granulosum layers; immunoreactivity was not observed in the stratum corneum. In the dermis, irisin was found in the external and internal root sheath, cortex and medulla of hair follicles, and in sebaceous glands. Irisin immunoreactivity was found in the neural retina and skeletal muscle fibers associated with the eye. The pineal and thyroid glands also exhibited irisin immunoreactivity. 相似文献
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Ethanol inhibits IgE-induced degranulation and cytokine production in cultured mouse and human mast cells 总被引:2,自引:0,他引:2
Activated mast cells (MC) can produce a wide variety of potent inflammatory mediators. Excessive alcohol consumption is known to lead to immune deficiency and propensity for pneumonias in particular. As MCs are important in the first line of defence of mucosal membranes we have studied the effect of ethanol (EtOH) on several MC functions. EtOH attenuated dose dependently IgE-induced degranulation of mouse bone marrow derived mast cells (mBMMC) as reflected by the release of granule associated beta-hexosaminidase (beta-hex). A mean of 26 +/- 7% inhibition of beta-hex release was observed in the presence of 5/1000 (86 mM) EtOH and nearly complete inhibition in the presence of 20/1000 (344 mM) ethanol. The IgE-induced degranulation of mBMMC cultured with EtOH for seven days was inhibited to a similar degree as the degranulation of mBMMC exposed to EtOH for only one hour. Inclusion of 5/1000 (86 mM) ethanol in the medium reduced tumour necrosis factor (TNF)-alpha and interleukin (IL)-8 production in human mast cell line (HMC-1) cells by 55 +/- 7% and 19 +/- 5%, respectively, and the presence of 20/1000 (344 mM) ethanol inhibited the expression 81 +/- 12% and 59 +/- 14% respectively. These results suggest that, in contrast to previous assumption, ethanol inhibits several critical MC functions at least in vitro. This inhibition of mediator, and cytokine release in particular, could contribute to the immune deficiency associated with chronic alcohol consumption. 相似文献
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Mervi H. Toivari Laura Ruohonen Peter Richard Merja Penttilä Marilyn G. Wiebe 《Applied microbiology and biotechnology》2010,88(3):751-760
Saccharomyces cerevisiae was engineered to produce D-xylonate by introducing the Trichoderma reesei xyd1 gene, encoding a D-xylose dehydrogenase. D-xylonate was not toxic to S. cerevisiae, and the cells were able to export D-xylonate produced in the cytoplasm to the supernatant. Up to 3.8 g of D-xylonate per
litre, at rates of 25–36 mg of D-xylonate per litre per hour, was produced. Up to 4.8 g of xylitol per litre was also produced.
The yield of D-xylonate from D-xylose was approximately 0.4 g of D-xylonate per gramme of D-xylose consumed. Deletion of the
aldose reductase encoding gene GRE3 in S. cerevisiae strains expressing xyd1 reduced xylitol production by 67%, increasing the yield of D-xylonate from D-xylose. However, D-xylose uptake was reduced
compared to strains containing GRE3, and the total amount of D-xylonate produced was reduced. To determine whether the co-factor NADP+ was limiting for D-xylonate production the Escherichia coli transhydrogenase encoded by udhA, the Bacillus subtilis glyceraldehyde 3-phosphate dehydrogenase encoded by gapB or the S. cerevisiae glutamate dehydrogenase encoded by GDH2 was co-expressed with xyd1 in the parent and GRE3 deficient strains. Although each of these enzymes enhanced NADPH consumption on D-glucose, they did not enhance D-xylonate production, suggesting
that NADP+ was not the main limitation in the current D-xylonate producing strains. 相似文献
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