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61.
62.
The effect of feeding endophyte infected tall fescue seed on reproductive performance in female rats 总被引:1,自引:0,他引:1
D R Varney M Ndefru S L Jones R Newsome M R Siegel P M Zavos 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1987,87(1):171-175
Female Sprague-Dawley rats (Rattus norvegicus) were randomly assigned to diets containing mixtures of rat chow and tall fescue (Festuca arundinacea) seed with 0, 5, 10, 20 and 40% infection levels of Acremonium coenophialum to assess the effect of the diets on the reproductive potential of rats. Rats fed 40% infected seed had decreased body weight, decreased mean percent body weight of uteri, failed to maintain normal estrous cycles and were unable to become pregnant. Animals fed a diet of 20% infected fescue seed had extended estrous cycles. There were no significant differences among the 0, 5 and 10% dietary treatments. 相似文献
63.
64.
A new class of low molecular weight, aminomethylimidazol-4-one (IQ-"like") mutagens have been produced by the reaction of creatinine with the amino acid L-threonine, in liquid-reflux models, mimicking cooking, of diethylene glycol:5% distilled water (2 h at 150 degrees C). Two mutagens, 2-amino-1-methyl-5-propylideneimidazol-4-one (AMPI) and 2-amino-5-ethylidene-1-methylimidazol-4-one (AEMI) were isolated and characterized by UV absorption spectra, mass spectra, and 1H-NMR. The mutagen AEMI was identical to that obtained from the reaction of creatinine with acetaldehyde. These mutagens were positive in all IQ-sensitive Ames tester strains and were not inactivated by acidic nitrosation at pH 1.0. Products displaying mutagenicity were also obtained by refluxing creatinine with other hydroxyamino acids such as L-serine, L-homoserine, and L-4-amino-3-hydroxybutyric acid, and aldehydes such as glyoxal, methylglyoxal, glycolaldehyde, but not formaldehyde. Simple model systems such as creatinine and acetaldehyde may be useful in more clearly defining the exact mechanism of formation of IQ-type mutagens (aminomethylimidazo-quinolines and -quinoxalines) produced during cooking, as well as in screening for potential inhibitors of IQ-type mutagen formation, and elucidating the mechanism of such inhibition. 相似文献
65.
66.
Regulation of mouse CYP1A1 gene expression by dioxin: requirement of two cis-acting elements during induction. 总被引:19,自引:12,他引:7 下载免费PDF全文
L A Neuhold Y Shirayoshi K Ozato J E Jones D W Nebert 《Molecular and cellular biology》1989,9(6):2378-2386
The mouse cytochrome P1450 (CYP1A1) gene is responsible for the metabolism of numerous carcinogens and toxic chemicals. Induction by the environmental contaminant tetrachlorodibenzo-p-dioxin (TCDD) requires a functional aromatic hydrocarbon (Ah) receptor. We examined the 5'-flanking region of the CYP1A1 gene in mouse hepatoma Hepa-1 wild-type cells and a mutant line having a defect in chromatin binding of the TCDD-receptor complex. We identified two cis-acting elements (distal, -1071 to -901 region; proximal, -245 to -50 region) required for constitutive and TCDD-inducible CYP1A1 gene expression. Three classes of DNA-protein complexes binding to the distal element were identified: class I, found only in the presence of TCDD and a functional Ah receptor, that was heat labile and not competed against by simian virus 40 (SV40) early promoter DNA; class II, consisting of at least three constitutive complexes that were heat stable and bound to SV40 DNA; and class III, composed of at least three constitutive complexes that were thermolabile and were not competed against by SV40 DNA. Essential contacts for these proteins were centered at -993 to -990 for the class I complex, -987, -986, or both for the class II complexes, and -938 to -927 for the class III complexes. The proximal element was absolutely essential for both constitutive and TCDD-inducible CYP1A1 gene expression, and at least two constitutive complexes bound to this region. These data are consistent with the proximal element that binds proteins being necessary but not sufficient for inducible gene expression; interaction of these proteins with those at the distal element was found to be required for full CYP1A1 induction by TCDD. 相似文献
67.
The problem of characterising liposomes with covalently attached proteins has been analysed theoretically in terms of a normal weight distribution of liposome diameters. The polydispersity of protein conjugation is considered in terms of the width (standard deviation) of the liposome size distribution. It is shown that the weight-average number of proteins per liposome is a convenient parameter to use to define the protein content of proteoliposomes. Two types of proteoliposome have been prepared (small unilamellar vesicles and reverse phase evaporation vesicles) in which wheat germ agglutinin is covalently coupled to the liposomal surface. The liposomes cover a range of weight average diameter from 65 to 240 nm and of polydispersity (weight to number average diameter (dw/dn) from 2.6 to 11.4. The liposomes have been characterised by chemical analysis and photon correlation spectroscopy and the results are discussed in terms of the theoretical consequences of an equivalent normal weight distribution of diameters. 相似文献
68.
A Monte Carlo investigation of homogeneity tests of the odds ratio under various sample size configurations 总被引:2,自引:0,他引:2
Epidemiologic data for case-control studies are often summarized into K 2 x 2 tables. Given a fixed number of cases and controls, the degree of sparseness in the data depends on the number of strata, K. The effect of increasing stratification on size and power of seven tests of homogeneity of the odds ratio is studied using Monte Carlo methods. In all the designs considered here, the numbers of cases and controls per stratum are the same. Considering both size and power in non-sparse-data settings, we recommend the Breslow-Day statistic (1980, Statistical Methods in Cancer Research, 1. The Analysis of Case-Control Studies, p. 142; Lyon: International Agency for Research on Cancer) for general use. In sparse-data settings the T4 statistic of Liang and Self (1985, Biometrika 72, 353-358) performs the best when all tables, regardless of sample size, have odds ratios generated from the same distribution. In sparse-data settings characterized by a large table with an odds ratio of 1 and many small tables with odds ratios greater than 1, the T5 statistic of Liang and Self (1985) performs the best. One of the most important results of this study is the generally low power for all homogeneity tests especially when the data are sparse. 相似文献
69.
P J Jones 《Canadian journal of physiology and pharmacology》1989,67(9):994-998
The comparative effects of feeding diets containing corn, olive, coconut, or menhaden fish oil on efficiency of energy deposition and on short term energy expenditure were examined in growing hamsters. Diets comprising oils mixed with laboratory diets at 10% oil w/w were fed ad libitum for 3 weeks. Animals fed laboratory diets were used as controls. Body composition was determined before and after the feeding period using 3H2O distribution space. Oxygen consumption was measured in each animal during the final week. Weight gains of groups fed corn and olive oil diets exceeded those of the group fed laboratory diet alone (p less than 0.05), although metabolizable energy intakes were similar across groups. Corn oil fed animals demonstrated higher carcass energy gains as fat compared with laboratory diet fed or menhaden oil fed groups. This was reflected in an increased fractional deposition of metabolizable energy intake in the group fed corn oil diet compared with the latter two groups. Fecal energy losses were lower in the group fed corn oil diet, and higher in the group fed laboratory diet alone, compared with other groups. Oxygen consumption did not differ between groups. These findings indicate that feeding dietary fish oil, compared with corn oil, favours energy substrate oxidation reducing the fraction of metabolizable energy partitioned for storage. 相似文献
70.
Local stimulation of prostaglandin production by corticotropin-releasing hormone in human fetal membranes and placenta 总被引:4,自引:0,他引:4
Corticotropin-releasing hormone is produced by the human placenta and fetal membranes, but its physiological significance is not established. We examined the possibility that CRH might affect prostaglandin output by these intra-uterine tissues. Primary cultures of amnion, chorion, decidua and placenta were established from tissue obtained from women at term elective cesarean section were maintained in the presence of increasing concentrations of synthetic hCRH. PG output at 48h was measured by radioimmunoassay. hCRH stimulated PGE2 output by amnion, chorion and placenta, but not by decidual tissue. PGF2 alpha output was stimulated in amnion, decidua and placenta but not chorion, whereas output of 13, 14-dihydro-15-keto PGF2 alpha was stimulated in all four tissues. We conclude that hCRH stimulates prostaglandin output by human placenta, decidua and the fetal membranes, raising the possibility of paracrine or autocrine interactions between CRH and prostaglandins in vivo. 相似文献