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1.
2.
A Krishan 《Cytometry》1987,8(6):642-645
The present study shows that staining of certain live cells, e.g., adriamycin-resistant P388 cells, by Hoechst 33342 is difficult because of the presence of a rapid efflux pump, which reduces intracellular dye concentration. Coincubation of these refractory cells in the presence of efflux blockers such as phenothiazines (trifluoperazine) or Ca++ channel blockers (verapamil) enhances dye retention and thus leads to generation of normal DNA distribution histograms. Laser flow cytometric data is confirmed by fluorometric assays, which show that P388/R cells retain one-third the amount of Hoechst 33342, and coincubation with efflux blockers increases Hoechst retention to values similar to those of drug-sensitive P388 cells. DNA histograms of mouse splenocytes incubated with Hoechst 33342 alone have a bimodal distribution possibly because of the presence of subpopulations that do not retain the fluorochrome owing to rapid efflux. Coincubation with an efflux blocker results in the generation of unimodal DNA histograms from these cells. These preliminary studies suggest that reduced retention of Hoechst 33342 in certain cell types (because of rapid efflux) can be blocked by efflux blockers, thus leading to generation of typical DNA distribution histograms. 相似文献
3.
The in vitro acetylation of HMG proteins was studied using liver slices of young (18-week) and old (138-week) male rats. Acetylation of total HMG proteins is lower in old age. The incorporation of (14C) acetate into individual HMG proteins varies remarkably with advancing age. Whereas acetylation of high mol. wt. proteins (HMG 1 and 2) is higher, that of low mol. wt. proteins (HMG 14 and 17) is lower in the liver of young rats as compared to the old ones. Spermine stimulates the acetylation of HMG 1 and 14 in young and HMG 1, 2 and 14 in old age. It inhibits the acetylation of HMG 17 in both ages. Dexamethasone decreases the level of incorporation of (14C) into HMG 1 and 17 in young and HMG 14 and 17 in old rats. On the other hand, it stimulates the acetylation of HMG 14 by two-fold in young and that of HMG 1 and 2 by more than three-fold in old rats. Such alteration in the acetylation of HMG proteins may account for age-related changes in the structure and function of chromatin. 相似文献
4.
Cell surface tubulin in leukemic cells: molecular structure, surface binding, turnover, cell cycle expression, and origin 下载免费PDF全文
We report here new characteristics of cell surface tubulin from a human leukemia cell line. These cells (CEM cells) possess tubulin that is readily iodinated on the surface of living cells, turns over at a rate identical to that of other surface proteins, and is present throughout the cell cycle. When removed with trypsin, it rapidly returns to the surface. Peptide mapping of iodinated surface tubulin indicates that it possesses a similar, but not identical, primary structure to total CEM and rat brain tubulin. Living CEM cells are able to bind specifically a subfraction of CEM tubulin from metabolically labeled high speed supernatants of lysed CEM cells. Surface tubulin is more basic than the total tubulin pool. The binding, which is saturable, is inhibited by unlabeled CEM high speed supernatants but not by excess thrice-cycled rat or bovine brain tubulin. Surface tubulin is also shown to bind to living nontransformed normal rat kidney cells but not to normal, circulating, mononuclear white cells. Activated lymphocytes produce a tubulin that binds to CEM cells. Since CEM tubulin was detected in the media of 6-h cultures of CEM cells, we must conclude that at least some of the surface tubulin comes from the media. We further conclude that these leukemic cells produce an unusual tubulin that may bind specifically to any membrane. The presence of iodinatable surface tubulin, however, appears to require both the production of a unique tubulin and the presence of a "receptor-like" surface binding component. 相似文献
5.
I S Thakur 《Biochemistry international》1986,13(5):915-925
In vivo and in vitro allergenic activities of Prosopis juliflora pollen allergens were measured in guinea pigs. Intracutaneous skin test showed an early wheal flare response and a late erythema-redness, sensitized with various concentrations (100, 50, 25, 5 and 1.5 micrograms/ml) of Prosopis juliflora pollen extract after administration of a challenging dose. A 50 micrograms/ml sensitizing dose of Prosopis juliflora pollen allergen gave optimum skin response as both early and late effects. The nature of immunochemical reactivity between pollen allergens and reaginic antibodies were further characterized by histamine release test, gel diffusion test, radioallergosorbent test and passive cutaneous anaphylaxis test. These tests confirm allergenicity caused by Prosopis juliflora pollen allergens and showed the binding of allergens with reaginic antibody and its regulation in guinea pigs. 相似文献
6.
Vipin K. Paliwal Krishan K. Kohli Mridula Sharma Ravindra Nath 《Molecular and cellular biochemistry》1986,71(2):139-147
Metallothionein (MT) a low molecular weight, Cd-binding, cysteine rich, cytosolic protein has been isolated, purified and characterized from cadmium exposed Rhesus monkeys maintained on protein calorie malnourished (PCM) diet. Metallothionein was resolved into three isoforms i.e. MTa, MTb and MTVc. The ratio of Cd, Zn and Cu varied in these isometallothioneins. MTc was the major isometallothionein. UV Spectra of MTc revealed the presence of mercaptide bonds and absence of aromatic amino acids. These observations were further confirmed by amino acid analysis of MTc which demonstrated high cysteine content (22.6) followed by serine, glycine and lysine. The molecular weight of MTc as determined by gel filtration and amino acid analysis was 13000 and 6398 daltons respectively. This demonstrates that MTc is a non-globular ellipsoid polypeptide. MTc showed a unique property of binding selenium. Monkey liver metallothionein was immunologically identical with human metallothionein. All the characteristics of MTc obtained in the present study reveal a similarity between monkey and human metallothionein probably due to closer phylogenetic relationship between the two species. 相似文献
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9.
Two new steroidal glycosides, agaveside A and B, isolated from the fruits of Agave cantala were characterized as 3 beta-O-[beta-D-xylopyranosyl-(1----2),beta-D-xylopyranosyl-(1----3), beta-D-glucopyranosyl-(1----3)-[beta-D-xylopyranosyl-(1----3)-beta-D- galactopyranosyl-(1----2)]-beta-D-glucopyranosyl]-(25R)-5 alpha-spirostane and 3 beta-O-[beta-D-xylopyranosyl-(1----2), beta-D-xylopyranosyl-(1----3)-beta-D-glucopyranosyl-(1----3)- [beta-D-galactopyranosyl-(1----2)]-beta-D-glucopyranosyl]-(25R)-5 alpha-spirostane. The structures were elucidated by a combination of 13CNMR spectroscopy, chemical degradation and fast atom bombardment mass spectrometry. 相似文献
10.
T Oka M K Thakur K Miyamoto T Sassa I Suzuki Y Natori 《Biochemical and biophysical research communications》1992,189(1):179-183
The degradation of H1 histone and high mobility group (HMG) nonhistone proteins was stimulated when the homogenate from chick liver was incubated in the presence of phenylmethylsulfonyl fluoride (PMSF). Two proteinase inhibitors, elastatinal and chymostatin, significantly inhibited the PMSF-stimulated degradation of H1 histone and HMG proteins. On the contrary, other proteinase inhibitors like leupeptin, pepstatin, trypsin inhibitor, antipain, o-phenanthroline and EDTA had no effect on the degradation of the nuclear proteins. These results warn the researcher to be cautious while using PMSF for preparation of nuclear proteins such as H1 histone and HMG proteins. 相似文献