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排序方式: 共有118条查询结果,搜索用时 46 毫秒
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G Xu L Huan I Khatri U S Sajjan D McCool D Wang C Jones G Forstner J Forstner 《Biochemical and biophysical research communications》1992,183(2):821-828
A cDNA specific for a human intestinal mucin (MLP) was amplified by PCR from cDNA of cultured human colonic adenocarcinoma cells, LS174T. The human cDNA shared high sequence homology with a corresponding rat intestinal mucin (MLP) cDNA in the 3' terminal region, and hybridized to the same mRNA (approximately 9.0 Kb) that was recognized by a probe for the MUC-2 human intestinal mucin gene. The gene encoding our human mucin peptide also mapped to chromosome 11 p 15.5, the known locus of MUC-2. Our findings suggest that human MLP and MUC-2 are encoded by the same gene and that rat and human intestinal mucin share a common C-terminal amino acid structure. 相似文献
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Positions of multiple insertions in SSU rDNA of lichen-forming fungi 总被引:11,自引:3,他引:8
Lichen-forming fungi, in symbiotic associations with algae, frequently have
nuclear small subunit ribosomal DNA (SSU rDNA) longer than the 1,800
nucleotides typical for eukaryotes. The lichen-forming ascomycetous fungus
Lecanora dispersa contains insertions at eight distinct positions of its
SSU rDNA; the lichen-forming fungi Calicium tricolor and Porpidia
crustulata each contain one insertion. Insertions are not limited to fungi
that form lichens; the lichen ally Mycocalicium albonigrum also contains
two insertions. Of the 11 insertion positions now reported for
lichen-forming fungi and this ally, 6 positions are known only from
lichen-forming fungi. Including the 4 newly reported in this study,
insertions are now known from at least 17 positions among all reported SSU
rDNA sequences. Insertions, most of which are Group I introns, are reported
in fungal and protistan lineages and occur at corresponding positions in
genomes as phylogenetically distant as the nuclei of fungi, green algae,
and red algae. Many of these positions are exposed in the mature rRNA
tertiary structure and may be subject to independent insertion of introns.
Insertion of introns, accompanied by their sporadic loss, accounts for the
scattered distribution of insertions observed within the SSU rDNA of these
diverse organisms.
相似文献
46.
The extent of polylactosamine glycosylation of MDCK LAMP-2 is determined by its Golgi residence time 总被引:2,自引:1,他引:1
The increased polylactosamine glycosylation of LAMP-2 in MDCK cells
cultured for 1 day relative to cells cultured for 3 days has been
correlated with its slower rate of Golgi transit (Nabi and Rodriguez-
Boulan, 1993, Mol. Biol. Cell., 4, 627-635). To determine if the
differential polylactosamine glycosylation of LAMP-2 is a consequence of
glycosyltransferase expression levels, the activities of beta1- 6GlcNAc-TV,
beta1-3GlcNAc-T(i), beta1-2GlcNAc-TI, beta1, 4Gal-T, alpha2- 6sialyl-T, and
alpha2-3sialyl-T were assayed and no significant differences in the
activities of these enzymes in 1 and 3 day cell extracts were detected.
During MDCK epithelial polarization, the Golgi apparatus undergoes
morphological changes and apiconuclear Golgi networks were more evident in
3 day cells. Treatment with nocodazole disrupted Golgi networks and
generated numerous Golgi clusters in both 1 day and 3 day cells. In the
presence of nocodazole the differential migration of LAMP-2 in 1 and 3 day
MDCK cells was maintained and could be eliminated by treatment with
endo-beta-galactosidase, indicating that gross Golgi morphology did not
influence the extent of LAMP-2 polylactosamine glycosylation. Nocodazole
treatment did, however, result in the faster migration of LAMP-2 which was
not due to modification of core N-glycans as the precursor form of the
glycoprotein migrated with an identical molecular size. Following
incubation at 20 degrees C, which prevents the exit of proteins from the
trans-Golgi network, the molecular size of LAMP-2 increased to a similar
extent in both 1 and 3 day MDCK cells. Extending the time of incubation at
20 degrees C did not influence the size of LAMP-2, demonstrating that its
glycosylation is modified not by its retention within the Golgi but rather
by its equivalent slower Golgi passage at the lower temperature in both 1
and 3 day cells. An identical effect was observed in nocodazole treated
cells, demonstrating that Golgi residence time determines the extent of
LAMP-2 polylactosamine glycosylation, even in isolated Golgi clusters.
相似文献
47.
Testes from 47 juvenile Swamp buffalo bulls were examined for puberty and sexual maturity histologically and daily sperm production per gram of testis parenchyma was determined by enumeration of elongated spermatids in homogenates of testis parenchyma. Puberty was defined as the attainment of a daily sperm production per gram of testis parenchyma >0.5 x 10(6). In most bulls, puberty is attained by 24 mo of age, when scrotal circumference (SC) is approximately 16 cm, and liveweight exceeds 135 kg. Sexual maturity was defined as the attainment of adult levels of daily sperm production per gram of testis parenchyma (14 x 10(6)). In most bulls, this occurs at 30 to 33 mo of age, when SC is in the 17-to 20-cm range, and liveweight generally exceeds 250 kg. There was marked individual variation in age, liveweight and SC at both puberty and sexual maturity. 相似文献
48.
Incorporation of axonally transported glycoproteins into axolemma during nerve regeneration 总被引:14,自引:4,他引:10
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The insertion of axonally transported fucosyl glycoproteins into the axolemma of regenerating nerve sprouts was examined in rat sciatic motor axons at intervals after nerve crush. [(3)H]Fucose was injected into the lumbar ventral horns and the nerves were removed at intervals between 1 and 14 d after labeling. To follow the fate of the “pulse- labeled” glycoproteins, we examined the nerves by correlative radiometric and EM radioautographic approaches. The results showed, first, that rapidly transported [(3)H]fucosyl glycoproteins were inserted into the axolemma of regenerating sprouts as well as parent axons. At 1 d after delivery, in addition to the substantial mobile fraction of radioactivity still undergoing bidirectional transport within the axon, a fraction of label was already associated with the axolemma. Insertion of labeled glycoproteins into the sprout axolemma appeared to occur all along the length of the regenerating sprouts, not just in sprout terminals. Once inserted, labeled glycoproteins did not undergo extensive redistribution, nor did they appear in sprout regions that formed (as a result of continued outgrowth) after their insertion. The amount of radioactivity in the regenerating nerves decreased with time, in part as a result of removal of transported label by retrograde transport. By 7-14 d after labeling, radioautography showed that almost all the remaining radioactivity was associated with axolemma. The regenerating sprouts retained increased amounts of labeled glycoproteins; 7 or 14 d after labeling, the regenerating sprouts had over twice as much of radioactivity as comparable lengths of control nerves or parent axons. One role of fast axonal transport in nerve regeneration is the contribution to the regenerating sprout of glycoproteins inserted into the axolemma; these membrane elements are added both during longitudinal outgrowth and during lateral growth and maturation of the sprout. 相似文献
49.
JW Mills ADC MacKnight JA Jarrell JM Dayer DA Ausiello 《The Journal of cell biology》1981,88(3):637-643
To determine the specificity and efficacy of [(3)H]ouabain binding as a quantitative measure of the Na(+) pump (Na(+), K(+)-ATPase) and as a marker for the localization of pumps involved in transepithelial Na(+)-transport, we analyzed the interaction of [(3)H]ouabain with its receptor in pig kidney epithelial (LLC-PK(1)) cells. When these epithelial cells are depleted of Na(+) and exposed to 2 muM [(3)H]ouabain in a Na(+)-free medium, binding is reduced by 90 percent. When depleted of K(+) and incubated in a K(+)- free medium, the ouabain binding rate is increase compared with that measured at 5 mM. This increase is only demonstable when Na(+) is present. The increased rate could be attributed to the predominance of the Na(+)-stimulated phosphorylated form of the pump, as K(+) is not readily available to stimulate dephosphorylation. However, some binding in the K(+)-free medium is attributable to pump turnover (and therefore, recycling of K(+)), because analysis of K(+)-washout kinetics demonstrated that addition of 2 muM ouabain to K(+)-depleted cells increased the rate of K(+) loss. These results indicate that in intact epithelial cells, unlike isolated membrane preparations, the most favorable condition for supporting ouabain binding occurs when the Na(+), K(+)-ATPase is operating in the Na(+)-pump mode or is phosphorylated in the presence of Na(+). When LLC-PK(1) cells were exposed to ouabain at 4 degrees C, binding was reduced by 97 percent. Upon rewarming, the rate of binding was greater than that obtained on cells kept at a constant 37 degrees C. However, even at this accelerated rate, the time to reach equilibrium was beyond what is required for cells, swollen by exposure to cold, to recover normal volume. Thus, results from studies that have attempted to use ouabain to eliminate the contribution of the conventional Na(+) pump to volume recovery must be reevaluated if the exposure to ouabain was done in the cold or under conditions in which the Na(+) pump is not operating. 相似文献
50.