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941.
942.
943.
F D Reilly 《Experientia》1985,41(2):187-192
944.
Titres of juvenile hormone (JH) have been determined in both hemolymph and whole body extracts of female Diploptera punctata during the first gonotrophic cycle using a method employing gas chromatography/mass spectrometry for qualitative and quantitative analysis. JH III is the sole JH found in both adult and last instar D. punctata. Maximum values of approximately 1500 ng/ml (approximately 6 microM) were observed at the middle of the gonotrophic cycle, when basal oocyte growth rate was greatest. Changes in rates of JH release in vitro by corpora allata paralleled closely the changes in JH titre, suggesting that biosynthesis is a major regulator of titre. JH levels per animal were calculated from observed JH titres, and at certain time points in the gonotrophic cycle JH obtained from analysis of whole bodies were significantly greater than those predicted from hemolymph titres. These results suggest the existence of a nonhemolymph JH pool in D. punctata. Decay in JH titre after allatectomy of 5 day females has also been studied. Following a rapid initial decline, the rate of decay slowed appreciably 4 h post-operation. Thus, use of a first-order rate constant to estimate half-life of JH significantly underestimated the longevity of the hormone. The apparent persistence of JH following allatectomy may be due to the existence of a nonhemolymph JH pool. 相似文献
945.
Following oral or intravenous administration, a representative cognition activator drug, pramiracetam sulfate, is shown to have a pharmacologic therapeutic window at three different levels of study: learned behavior, gross EEG activity of the frontal cortex and hippocampus, and firing rate of single hippocampal neurons. 相似文献
946.
Summary Reflex autonomic changes which occur after cigarette smoke enters the upper airways are partially due to peripheral chemoreceptor stimulation. Chemoreceptor denervation attenuates but does not abolish smoke induced bradycardia. Denervation nearly abolishes bradycardia induced by tracheal occlusion. Hypertension accompanies smoke induced apnea but does not occur during tracheal occlusion.Acknowledgments. This study was supported by Oral Roberts University research funds. 相似文献
947.
M. Aglietta A. Stacchini F. Sanavio W. Piacibello 《Cellular and molecular life sciences : CMLS》1985,41(3):375-376
Summary The effect of 2 H2 receptor antagonists (ranitidine and cimetidine) on the in vitro growth of human granulomonopoietic precursors (CFU-GM) was studied. Ranitidine, although having an anti H2 receptor activity much greater than that of cimetidine, displays the same toxicity for CFU-GM.Acknowledgments. This work was supported by CNR, Rome, PFCCN and AIRC, Milan. 相似文献
948.
Focus formation in rat fibroblasts exposed to a tumour promoter after transfer of polyoma plt and myc oncogenes 总被引:1,自引:0,他引:1
The gene encoding the large-T protein of polyoma virus (plt), the E1A genes of adenoviruses, the viral myc gene (v-myc) or rearranged forms of the cellular c-myc gene confer on rat embryo fibroblast (REF) cells in primary culture a series of new properties ('immortality', reduced serum requirement and sensitivity to transformation by viral and activated cellular oncogenes) but do not induce the appearance of transformed foci. We now report that focus formation can be induced after transfer of these genes into either REF or established FR3T3 rat cells by subsequent exposure to the tumour promoter 12-O-tetradecanoylphorbol 13-acetate (TPA). Frequencies of transformation are in the same range as those usually observed for transformation with complete polyoma DNA or with a mixture of cloned myc and ras oncogenes. These results further characterize the 'immortalized' state induced by plt and myc as one in which the cells maintain a normal growth control in many respects but can be further acted upon to produce a neoplastic progeny. 相似文献
949.
Fenton F. Robb 《Systemic Practice and Action Research》1997,10(3):321-341
‘As it is now clear that Hume is the Author of theAbstract, this short work can be enthusiastically recommended to those who wish to consider Hume's own account of the chief argument
of theTreatise’ (Norton, 1993a). This ‘simplification’ of Hume'sAbstract aims to make it more accessible to a wider audience, especially to readers who do not have English as their first language.
Some of Hume's own invented terms have been translated, many of his longer sentences divided, and most of his expressions
simplified. The sequence of his arguments is preserved. Where needed, his arguments have been set out in traditional form.
Topic headings have been added and some definitions appended. To ease reference to theAbstract, as published in Hume (1740b), the page numbers have been inserted near their correct position in square brackets. 相似文献
950.
N S Yamamoto A M Kelmer Bracht E L Ishii F S Kemmelmeier M Alvarez A Bracht 《Experientia》1985,41(1):55-57
The effect of several natural products of Stevia rebaudiana on glucose production and oxygen uptake in rat renal cortical tubules was investigated. Steviol, isosteviol and glucosilsteviol decreased glucose production and inhibited oxygen uptake. The sweet principle stevioside, and steviolbioside, however, were without effect on gluconeogenesis and oxygen uptake. 相似文献