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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.
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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
5.
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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To evaluate the role of aromatic amino-acids residues, four analogues of the mu-selective opioid peptide agonist DALDA (H-Tyr-D-Arg-Phe-Lys-NH2) containing the amphiphilic, a,a-disubstituted amino acid (R)- or (S)-alpha-hydroxymethyltyrosine (HmTyr) in position 1 and (R)- or (S)-alpha-hydroxymethylphenylalanine (HmPhe) in position 3 of the peptide sequence were synthesized. Only the [(R)-HmPhe3)]DALDA analogue displayed full agonistic activity in both the guinea pig ileum and the mouse vas deferens assays and turned out to be a delta receptor-selective opioid agonist. 相似文献
8.
New analogues of deltorphin I (DT I), in which the phenylalanine residue in position 3 is substituted with amphiphilic alpha,alpha-disubstituted amino acid enantiomers, (R) and (S)-alpha-hydroxymethylnaphtylalanine, were synthesized and tested for mu and delta opioid receptor affinity and selectivity. Although both analogues have lower affinity to delta receptors than DT I, they both expressed specificity to delta receptors. 相似文献
9.
New analogues of deltorphin I (DT I), in which the Phe residue in position 3, and the Val residue in position 5 or 6 are replaced with respective amphiphilic alpha-hydroxymethylamino acid residues (HmAA), were synthesized and tested for receptor affinity and selectivity to mu and delta opioid receptors. The analogue with (R)-HmPhe at position 3 lost receptor selectivity, as a result of a partial decrease of affinity to delta and a significant increase of affinity to mu receptors. In contrast, an analogue with (S)-HmPhe in the same position, was very potent and more specific to delta receptors than parent DT I. The analogue with (R)-HmVal at position 5 expressed higher delta affinity and selectivity than parent DT I. The analogue with other possible isomer (S)-HmVal was less selective for delta opioid receptors, as a result of decreasing affinity to delta and increasing affinity to mu receptors. The analogues with (R)- or (S)-HmVal in position 6 expressed equally low receptor affinity and selectivity. The data obtained support a previously proposed model of active conformation of deltorphins. 相似文献
10.
To what extent are the left and right visual hemifields spatially coded in the dorsal frontoparietal attention network? In many experiments with neglect patients, the left hemisphere shows a contralateral hemifield preference, whereas the right hemisphere represents both hemifields. This pattern of spatial coding is often used to explain the right-hemispheric dominance of lesions causing hemispatial neglect. However, pathophysiological mechanisms of hemispatial neglect are controversial because recent experiments on healthy subjects produced conflicting results regarding the spatial coding of visual hemifields. We used an fMRI paradigm that allowed us to distinguish two attentional subprocesses during a visual search task. Either within the left or right hemifield subjects first attended to stationary locations (spatial orienting) and then shifted their attentional focus to search for a target line. Dynamic changes in spatial coding of the left and right hemifields were observed within subregions of the dorsal front-parietal network: During stationary spatial orienting, we found the well-known spatial pattern described above, with a bilateral hemifield representation in the right hemisphere and a contralateral preference in the left hemisphere. However, during search, the right hemisphere had a contralateral preference and the left hemisphere equally represented both hemifields. This finding leads to novel perspectives regarding models of visuospatial attention and hemispatial neglect. 相似文献