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151.
Juvenile hormone bisepoxide (JHB3) and juvenile hormone III (JH III) both inhibited the in vitro production of ecdysteroids by ring glands and brain-ring gland complexes from third instar post-feeding larvae ofDrosophila melanogaster in a reversible manner, although JHB3 had greater efficacy. The JH III and JHB3 precursor, methyl farnesoate, did not affect ecdysteroid production. The in vitro synthesis of total detectable JH (JHB3+JH III+methyl farnesoate) by the corpus allatum portion of the isolated ring gland was also inhibited reversibly in the presence of exogenous JHB3 and JH III, but not by methyl farnesoate. These data indicating negative feedback are in agreement with the accepted dogma of endocrine gland regulation. 相似文献
152.
Konso-Gardula is a palaeoanthropological area discovered by the 1991 Palaeoanthropological Inventory of Ethiopia in the southern Main Ethiopian Rift. The Konso-Gardula sediments span the period about 1.3-1.9 million years ago. They contain rich Acheulean archaeological occurrences. Vertebrate fossils include early Homo. 相似文献
153.
P. Walter 《Cellular and molecular life sciences : CMLS》1991,47(2):178-181
Summary Some recent evidence on the benefits and hazards of elevated dosages of vitamins is summarized. Special emphasis is given on the safety of vitamins A, D, K1 and B6. Furthermore, the possibly beneficial effects of vitamins for athletic performance as well as the preventive potential of antioxidative vitamins and of carotenoids against cancer are discussed. 相似文献
154.
Juvenile hormone bisepoxide (JHB3) and juvenile hormone III (JH III) both inhibited the in vitro production of ecdysteroids by ring glands and brain-ring gland complexes from third instar post-feeding larvae of Drosophila melanogaster in a reversible manner, although JHB3 had greater efficacy. The JH III and JHB3 precursor, methyl farnesoate, did not affect ecdysteroid production. The in vitro synthesis of total detectable JH (JHB3 + JH III + methyl farnesoate) by the corpus allatum portion of the isolated ring gland was also inhibited reversibly in the presence of exogenous JHB3 and JH III, but not by methyl farnesoate. These data indicating negative feedback are in agreement with the accepted dogma of endocrine gland regulation. 相似文献
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158.
臭氧在食品保鲜和消毒杀菌上的应用越来越广,但有关臭氧处理对食品营养成份影响的研究极少。 研究了小白菜(Brassica chinensis)经低质量浓度臭氧水处理后几种营养成份的变化情况。结果表明:1.4 mg/L的臭氧水处理小白菜30 min, 67%(w)的脱氢维生素C被破坏,而总维生素C也损失近30%(w);其它营养成份如可溶性糖、可溶性蛋白和叶绿素则无显著性变化。研究结果说明应用臭氧水处理小白菜等叶类蔬菜时,需要考虑臭氧对蔬菜中维生素C等还原性成份的破坏作用。 相似文献
159.
Stability of the Larsen B ice shelf on the Antarctic Peninsula during the Holocene epoch 总被引:1,自引:0,他引:1
Domack E Duran D Leventer A Ishman S Doane S McCallum S Amblas D Ring J Gilbert R Prentice M 《Nature》2005,436(7051):681-685
The stability of the Antarctic ice shelves in a warming climate has long been discussed, and the recent collapse of a significant part, over 12,500 km2 in area, of the Larsen ice shelf off the Antarctic Peninsula has led to a refocus toward the implications of ice shelf decay for the stability of Antarctica's grounded ice. Some smaller Antarctic ice shelves have undergone periodic growth and decay over the past 11,000 yr (refs 7-11), but these ice shelves are at the climatic limit of ice shelf viability and are therefore expected to respond rapidly to natural climate variability at century to millennial scales. Here we use records of diatoms, detrital material and geochemical parameters from six marine sediment cores in the vicinity of the Larsen ice shelf to demonstrate that the recent collapse of the Larsen B ice shelf is unprecedented during the Holocene. We infer from our oxygen isotope measurements in planktonic foraminifera that the Larsen B ice shelf has been thinning throughout the Holocene, and we suggest that the recent prolonged period of warming in the Antarctic Peninsula region, in combination with the long-term thinning, has led to collapse of the ice shelf. 相似文献
160.
Human oestrogen receptor cDNA: sequence, expression and homology to v-erb-A 总被引:182,自引:0,他引:182
We have cloned and sequenced the complete complementary DNA of the oestrogen receptor (ER) present in the breast cancer cell line MCF-7. The expression of the ER cDNA in HeLa cells produces a protein that has the same relative molecular mass and binds oestradiol with the same affinity as the MCF-7 ER. There is extensive homology between the ER and the erb-A protein of the oncogenic avian erythroblastosis virus. 相似文献