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991.
Paul A. Price Sharon A. Baukol 《Biochemical and biophysical research communications》1981,99(3):928-935
1,25-dihydroxyvitamin D3 increases serum levels of bone Gla protein (BGP). The maximal increase occurs 12 h after injection and is given by 350 ng 1,25(OH)2D3 per 180 g body weight. In both 2 and 11 month-old male rats, the maximal increase is about 3 times the normal level, while in 2 month old female rats, the maximal increase is 2 times the normal level. These effects of 1,25(OH)2D3 in rats parallel the previously described effects of the vitamin on BGP secretion by rat osteosarcoma cells in culture.BGP is the first bone-specific protein whose synthesis in animals is dramatically increased by 1,25(OH)2D3. The possible functions of BGP in the biological actions of 1,25(OH)2D3 on bone are discussed. 相似文献
992.
Douglas L. Currell Bernice Law Michael Stevens Paul Murata Carmela Ioppolo Filippo Martini 《Biochemical and biophysical research communications》1981,102(1):348-354
Human hemoglobin reacts with 4-Isothiocyanatobenzene sulfonic acid at the four amino groups of the N-terminal valines. The modified protein shows a decreased oxygen affinity over a wide pH range, a reduced alkaline Bohr effect, decreased co-operativity, and a reduced effect of inositol hexasulfate on the oxygen affinity. 相似文献
993.
994.
Primary cell cultures derived from mutants in seventeen different genes were analyzed for their ability to excise pyrimidine
dimers from DNA. Five of these mutagen-sensitive mutants [mus(2)205A1, mus(3)302D1, mus(3) 304D3, mus(3)306D1, mus(3)308D2] display a significantly reduced excision capacity relative to control cultures. In addition, two of the five [mus(3)306D1, mus(3)308D2] are defective in the accumulation of single-strand breaks normally seen after ultraviolet irradiation. This study, therefore,
brings the total number of Drosophila mutants known to be defective in excision repair to seven. The results are discussed relative to other genetic and biochemical
properties of these mutants.
This work is dedicated to Professor W. Beermann whose own contributions were instrumental in focusing a modern analysis of
the eukaryotic genome on the diptera. Those of us who benefitted so much from his personal guidance recognize that we did
so as a result of some sacrifice on his part. One of Boyd's contemporaries in Tübingen once remarked: “It's terrifying to
think what Professor Beermann could do if he were in the lab full time.” 相似文献
995.
Synthesis of histone H4 by mouse oocytes and unfertilized eggs has been examined by using a modified high-resolution two-dimensional gel electrophoresis procedure capable of resolving basic proteins (M. J. LaMarca and P. M. Wassarman, 1979, Develop. Biol.73, 103–119). Histones were separated on such gels and observed rates of incorporation of [35S]methionine into histone H4 were converted into absolute rates of synthesis by using previously determined values for the absolute rates of total protein synthesis in mouse oocytes and unfertilized eggs Schultz et al., 1979a, Schultz et al., 1979b. Histone H4 was synthesized at all stages of oogenesis examined, and accounted for 0.07, 0.05, and 0.04% of total protein synthesis in growing oocytes, fully grown oocytes, and unfertilized eggs, respectively. During oocyte maturation the absolute rate of histone H4 synthesis decreased by about 40%, as compared to a 23% decrease in the rate of total protein synthesis during the same period. These measurements indicate that enough histone is synthesized during oogenesis in the mouse to support two to three cell divisions. Examination of the intracellular location of newly synthesized proteins in fully grown oocytes revealed that histone H4 was highly concentrated in the nucleus (germinal vesicle), whereas total protein and tubulin were not. Nearly 50% of the histone H4 synthesized during a 5-hr period was located in the oocyte's germinal vesicle, as compared to 1.9 and 0.9% for total protein and tubulin, respectively. These results are compared with those obtained using oocytes and eggs from nonmammalian animal species. 相似文献
996.
Johannes Boonstra Paul T. Van Der Saag Wouter H. Moolenaar Siegfried W. De Laat 《Experimental cell research》1981,131(2):452-455
Nerve growth factor (NGF) induces neuronal differentiation of rat pheochromocytoma cells (PC12). Here we show that NGF causes a stimulation of Na+,K+-pump mediated K+ influx, with a maximum at 30 min after addition of NGF. The stimulation of the Na+,K+-pump is completely blocked by the Na+-flux inhibitor amiloride (0.2 mM) and can be mimicked by the Na+ ionophore monensin. These results suggest that NGF causes a rapid enhancement of Na+ influx leading to an activation of the Na+,K+-pump, a mechanism similar to the action of other growth factors. 相似文献
997.
Grard Morel Paul Dubois Claudine Benassayag Emmanuel Nunez Christine Radanyi Grard Redeuilh Hlne Richard-Foy Etienne-Emile Baulieu 《Experimental cell research》1981,132(2):249-257
Antiserum against calf uterus oestradiol receptor has been used for detecting oestradiol receptor in rat pituitary cells at the ultrastructural level after immunochemical reaction according to Sternberger. The gonadotropic, lactotropic and somatotropic cells were positive, but not the thyrotropic and corticotropic cells. In peripubertal and adult rats, both cytoplasmic and nuclear receptors were seen, but in a long-term castrated rat, the receptor was found only in the cytoplasm. After oestradiol administration to 21-day-old animals, the cytoplasmic receptor decreased and the nuclear receptor increased in gonadotropic cells, supporting the concept of hormone-receptor complex translocation. Antibodies against α1-foetoprotein demonstrated the presence of this oestrogen-binding plasma protein in all pituitary cells, but only in the cytoplasmic area. These results and the immunological controls related to antibody specificity give the first evidence of steroid receptor at the ultrastructural level. 相似文献
998.
The influence of exogenous thyroxine was studied on the hepatic glycogen content and glucose-6-phosphatase activity of rats of different age groups. The glycogen content and glucose-6-phosphatase activity were found to be decreased in the livers of 5, 15, 30 and 60-day-old rats after thyroxine treatment. In normal rats of 5, 15, 30 and 60-day-old, a gradual rise in both the hepatic glycogen content and glucose-6-phosphatase activity was noted as the age advanced from immature to adult. 相似文献
999.
Zooplankton species diversity and selected chemical parameters were investigated at three stations in Lake St. Clair, Ontario, Canada, from 15 June–26 August, 1971. Primary productivity and zooplankton species diversity were greatest at stations 1 and 2 which were enriched by the Thames River drainage. No significant correlation between total zooplankton diversity and chlorophyll a was found, however, within the Cladocera and Copepoda, positive correlations with chlorophyll a, reactive silicate and nitrate were shown at stations 2 and 3. Rotifer species diversity showed negative correlation with chlorophyll a, nitrate and reactive silicate. 相似文献
1000.
Paul J. Higgins 《Journal of experimental marine biology and ecology》1980,45(2):229-244
The effects of changes in the availability of algal food on the valve movements of juvenile Crassostrea virginica (Gmelin) were investigated. Individual oysters were subjected to different conditions: (1) unfed in filtered sea water; (2) continuously fed, in which oysters were given an algal suspension maintained at a constant level (50 000 cells/ml) by an automatic turbidostat; (3) discontinuously fed, where oysters were alternately fed with the turbidostat for 12 h and unfed for 12 h; and (4) batch fed, in which oysters were given specific daily rations at two ration levels (maximum and 40%). Valve movements were concurrently recorded and periods of activity (valves open) and quiescence (valves closed) measured.Oysters fed continuously remained open an average of 94.3% of the time, whereas unfed oysters were open 35.1% of the time. Discontinuously fed animals were open 95.7% of the time during the times of feeding, but 60.6% of the time during the unfed periods. Activity in the batch-fed oysters was related to the ambient algal concentration in that both the percentage time open/hour and the duration of valve openness decreased with decreasing concentration. Time series analysis of valve movements showed that oysters exhibited a 24-h periodicity of activity when subjected to a 24-h feeding schedule (discontinuous and batch groups) but exhibited no consistent periodicity under the continuous feeding or unfed conditions. 相似文献