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921.
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
922.
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
923.
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
924.
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
925.
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
926.
The effects of prostacyclin (PGI2) on the contractile frequency and on the isometric developed tension of spontaneously beating or paced isolated rat atria were explored. PGI2 enhanced frequency and contractile tension, both effects being blocked by the presence of propranolol, or following a pretreatment with 6-OHDopamine. 相似文献
927.
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
928.
929.
Genetically obese male Zucker rats (fa/fa) and their lean littermates (Fa/-) were used in this experiment. Fourteen-week-old obese and lean littermates were sacrificed and choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) enzymes were assayed in specific brain regions. The assays of these enzymes indicate that obese animals had a significantly lower ChAT activity in the cerebellum, pons, and cerebral cortex and a significant increase in ChAT activity in the thalamus and hypothalamus. Meanwhile, the cerebral cortex, cerebellum, midbrain, thalamus and hypothalamus of the obese animals showed significantly higher AChE activity than their lean littermates. It was concluded from this study that obesity may be associated with changes in the enzymes of the brain cholinergic system. 相似文献
930.
Histone H3 lysine 9 methylation is an epigenetic imprint of facultative heterochromatin. 总被引:20,自引:0,他引:20
Antoine H F M Peters Jacqueline E Mermoud Dónal O'Carroll Michaela Pagani Dieter Schweizer Neil Brockdorff Thomas Jenuwein 《Nature genetics》2002,30(1):77-80
Post-translational modifications of histone amino termini are an important regulatory mechanism that induce transitions in chromatin structure, thereby contributing to epigenetic gene control and the assembly of specialized chromosomal subdomains. Methylation of histone H3 at lysine 9 (H3-Lys9) by site-specific histone methyltransferases (Suv39h HMTases) marks constitutive heterochromatin. Here, we show that H3-Lys9 methylation also occurs in facultative heterochromatin of the inactive X chromosome (Xi) in female mammals. H3-Lys9 methylation is retained through mitosis, indicating that it might provide an epigenetic imprint for the maintenance of the inactive state. Disruption of the two mouse Suv39h HMTases abolishes H3-Lys9 methylation of constitutive heterochromatin but not that of the Xi. In addition, HP1 proteins, which normally associate with heterochromatin, do not accumulate with the Xi. These observations suggest the existence of an Suv39h-HP1-independent pathway regulating H3-Lys9 methylation of facultative heterochromatin. 相似文献