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It has been reported that vitamin K deficiency in the rat markedly increases the 1,25-dihydroxyvitamin D3 receptor (VDR) binding to DNA and that vitamin K-dependent gamma-carboxylation of endogenous substrates of the intestinal and renal cytosol, also containing VDR, sharply reduced that binding (Sergeev, I.N., and Spirichev, V.B. (1989) Nutr. Res. 9, 725-733). In the present study we have evaluated vitamin K-dependent 14CO2 incorporation to VDR quantitated by immunoprecipitation with anti-VDR monoclonal antibodies. The results obtained strongly suggest that VDR in vitro can undergo gamma-carboxylation in the presence of vitamin K1 and that 15-25% of Glu residues in the VDR are carboxylated in vivo. Taking into account our earlier findings, it is likely that the VDR gamma-carboxylation modulates its binding to DNA. 相似文献
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Ellen J. Lehning Renu Doshi Norman Isaksson Peter K. Stys Richard M. LoPachin Jr. 《Journal of neurochemistry》1996,66(2):493-500
Abstract: To investigate the route of axonal Ca2+ entry during anoxia, electron probe x-ray microanalysis was used to measure elemental composition of anoxic tibial nerve myelinated axons after in vitro experimental procedures that modify transaxolemmal Na+ and Ca2+ movements. Perfusion of nerve segments with zero-Na+/Li+-substituted medium and Na+ channel blockade by tetrodotoxin (1 µM) prevented anoxia-induced increases in Na and Ca concentrations of axoplasm and mitochondria. Incubation with a zero-Ca2+/EGTA perfusate impeded axonal and mitochondrial Ca accumulation during anoxia but did not affect characteristic Na and K responses. Inhibition of Na+-Ca2+ exchange with bepridil (50 µM) reduced significantly the Ca content of anoxic axons although mitochondrial Ca remained at anoxic levels. Nifedipine (10 µM), an L-type Ca2+ channel blocker, did not alter anoxia-induced changes in axonal Na, Ca, and K. Exposure of normoxic control nerves to tetrodotoxin, bepridil, or nifedipine did not affect axonal elemental composition, whereas both zero-Ca2+ and zero-Na+ solutions altered normal elemental content characteristically and significantly. The findings of this study suggest that during anoxia, Na+ enters axons via voltage-gated Na+ channels and that subsequent increases in axoplasmic Na+ are coupled functionally to extraaxonal Ca2+ import. Intracellular Na+-dependent, extraaxonal Ca2+ entry is consistent with reverse operation of the axolemmal Na+-Ca2+ exchanger, and we suggest that this mode of Ca2+ influx plays a general role in peripheral nerve axon injury. 相似文献
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Norman D. Levine 《International journal for parasitology》1977,7(2):101-108
A checklist is given of the 45 named species of the family Urosporidae (phylum Protozoa, subphylum Apicomplexa, class Sporozoa, subclass Gregarinia, order Eugregarinida, suborder Aseptatina) together with their synonyms, the names of their hosts, their locations in the hosts, their known geographic distribution, and key references. Another list is given of synonyms, lapsi calami, nomina nuda, etc. associated with the genera of this family. The following taxonomic-nomenclatural innovations are introduced—NEW NAME: Gonospora good-richae nom. nov. in the polychaete Arenicola ecaudata; NEW COMBINATIONS: Urospora grassei (Changeux, 1961) in the sea cucumbers Holothuria spp.; Urospora schneideri (Mingazzini, 1891) in the sea cucumbers Holothuria spp; Gonospora gonadipertha (Djakonov, 1923) in the sea cucumber Cucumaria frondosa; Gonospora stichopi (Lützen, 1967) in the sea cucumber Stichopus tremulus. 相似文献
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Norman R. Drinkwater Rebecca C. Corner J. Justin McCormick Veronica M. Maher 《Mutation research》1982,106(2):277-289
The sensitivity of diploid human fibroblasts to the cytotoxic effects of diphtheria toxin (DT) depended on the cell growth status. Exponentially growing cells treated with 10?3-1 lethal flocculating units (LF) of DT/ml for 4 days survived with a frequency of 4 × 10?4. However, the DT-resistant phenotype of colonies isolated under these conditions was not stable. When the growth of the cells had been arrested by confluence or deprivation of serum growth factors prior to treatment with DT (4 days, 10?3-0.6 LF/ml), the survival decreased to 2 × 10?6 and the resistance of isolated colonies was stable. An in situ assay for induced DT-resistant mutants was developed in order to avoid problems associated with the possible reduced viability of the mutants relative to that of wild-type cells. A reproducible and linear dose response was obtained for the induction of DT-resistant mutants by ethylnitrosourea. The mutants were induced with high frequency by this compound (e.g., 10?3 mutants/viable cell at a 37% survival dose); complete expression of the mutant phenotype occurred after 6 generations of growth under nonselective conditions. Isolated mutant colonies showed stable resistance to DT and were cross-resistant to Pseudomonas aeruginosa exotoxin A. 相似文献
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Accessibility of sialo components in a murine tumor cell to extracellular glycohydrolase (sialidase)
Lipid-bound sialic acid in the murine melanoma cell is not totally inaccessible to an exogenous macromolecular probe, as formerly believed. Roughly 30% of the sialic acid bound to lipid, and an equal proportion of the sialic acid bound to protein is cleaved by the action of Clostridium perfringens glycohydrolase (neuraminidase, sialidase) when the purified enzyme is added to the suspension medium of intact murine melanoma cells freshly derived from the tumor. Cleavage of lipid-bound sialic acid is indifferent to the presence of Ca2+ in the medium. However, maximum release from protein requires a physiological concentration of this divalent cation. Variation in ionic strength has no effect on release of sialic acid. These findings show that a restricted portion of the bound sialic acid may be released from the intact murine melanama cell by the extracellularly supplied enzyme acting topographically. 相似文献
30.
Turner SA Bossart MI Klima T Leachman RD Cooley DA Norman JC 《Cardiovascular diseases》1980,7(3):272-277
Persistent atrial paralysis in a patient with complete heart block and mild mitral insufficiency is presented. Left atrial specimens obtained during implantation of a permanent cardiac pulse generator showed evidence of hypertrophy and fibrosis; subcellular degenerative changes ranged from near normal to irreversible, thus suggesting that atrial paralysis may be due to the replacement of normal atrial muscle with nonfunctional fibrous tissue. 相似文献