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排序方式: 共有2567条查询结果,搜索用时 15 毫秒
91.
92.
FS vom Saal PS Cooke DL Buchanan P Palanza KA Thayer SC Nagel S Parmigiani WV Welshons 《Canadian Metallurgical Quarterly》1998,14(1-2):239-260
Two chemicals previously shown to have estrogenic activity, bisphenol A and octylphenol, were examined for their effects on accessory reproductive organs and daily sperm production in male offspring of mice fed these chemicals during pregnancy. These chemicals are used in the manufacture of plastics and other products, and have been detected in food and water consumed by animals and people. From gestation day 11-17 female mice were fed an average concentration (dissolved in oil) of bisphenol A or octylphenol of 2 ng/g body weight (2 ppb) and 20 ng/g (20 ppb). The 2 ppb dose of bisphenol A is lower than the amount reported to be swallowed during the first hour after application of a plastic dental sealant (up to 931 micrograms; 13.3 ppb in a 70 kg adult). We found that the 2 ng/g dose of bisphenol A permanently increased the size of the preputial glands, but reduced the size of the epididymides; these organs develop from different embryonic tissues. At 20 ng/g, bisphenol A significantly decreased efficiency of sperm production (daily sperm production per g testis) by 20% relative to control males. The only significant effect of octylphenol was a reduction in daily sperm production and efficiency of sperm production at the 2 ng/g dose. A new approach to studying physiologically relevant doses of environmental endocrine disruptors is discussed, particularly with regard to the development of the reproductive organs, the brain, and behavior. 相似文献
93.
Based on the study of 66 miners in the subclinical stage of manganotoxicosis the principle functional changes have been ascertained in the given condition. Revealed in the above series were an increased content of manganese in the hair of more than 3 mg% (95.5%-100.0%), the presence of neurosis-like condition presenting with elements of somatized depression, anxiety, asthenization, slight decline in the mnestic functions (69.6%-93.5%), mild impairment of the power of voluntary movement, parasympathetic type vegetative dystonia (42%-73.7%), slight changes in cerebral and peripheral hemodynamics (36.6%-68.6%), disordered bioelectrical activity of muscles of the extrapyramidal type (53.7%-83.2%), breakdown of mechanisms of adaptation of the sympathoadrenal (19.1%-49.3%) and cholinergic (26.3%-57.9%) systems. 相似文献
94.
Glutathione (GSH) is important in maintaining intracellular thiol status. The present study looked at the effect of GSH depletion on lipid composition of colon-derived HT-29 cells. GSH was depleted in HT-29 cells by incubation either with buthionine-S, R-sulfoximine (BSO) or diethylmaleate (DEM). GSH was restored during early periods of cells growth by supplementation of growth medium with either GSH ester or N-acetyl cysteine (NAC). Lipids were analysed following GSH depletion and supplementation. Among the neutral lipids, an increase in free cholesterol and diacylglycerol and decrease in cholesteryl ester and triacylglycerol were seen in GSH-depleted cells as compared to control cells. There were no detectable free fatty acids either in control or GSH-depleted cells. Among the phospholipids, a decrease in phosphatidylcholine and phosphatidylinositol and an increase in phosphatidylethanolamine were observed. These changes were a completely reversed by supplementation of BSO-treated cells with GSH ester and partially reversed by N-acetyl cysteine. These results suggest that the GSH status of the cell plays an important role in the lipid composition of the cells. 相似文献
95.
PURPOSE: To determine if ethnic and gender differences in smoking (lifetime prevalence and 30-day prevalence) exist among a cohort of Asian, black, Hispanic, and white inner-city adolescents during the 3-year middle school period. METHODS: Students in 22 urban schools completed self-report questionnaires and provided carbon monoxide breath samples at three annual assessments. Chi-square analyses were conducted to test for associations between ethnic group (Asian, black, Hispanic, and white) and smoking and to test for gender differences in smoking within each ethnic group. Additional analyses examined differences in smoking between two Hispanic subgroups (Puerto Rican and Dominican). RESULTS: Ethnicity was associated with lifetime smoking prevalence at all three assessment points but was only associated with 30-day smoking prevalence at the 2-year follow-up. However, there were no differences in smoking between Puerto Rican and Dominican youth. Black girls reported higher lifetime smoking prevalence than black boys at all three assessments. At the 2-year follow-up, Asian boys reported higher lifetime smoking prevalence than Asian girls; Hispanic girls reported higher 30-day prevalence than Hispanic boys. CONCLUSIONS: White and Hispanic adolescents were at higher risk for smoking relative to Asian and black adolescents. With the exception of white youth, gender differences were found within each ethnic group. 相似文献
96.
97.
JC Jacquier AV Gorelov DM McLoughlin KA Dawson 《Canadian Metallurgical Quarterly》1998,817(1-2):263-271
Due to the growing interest in the use of cationic surfactants for the construction of liposomal genetic delivery systems, the study of complex formation between DNA and quaternary ammonium detergents is of fundamental importance. In this context, we undertook the study of this complex formation using capillary zone electrophoresis (CZE) with suppressed electroosmotic flow, a technique that allowed us to both monitor the change in mobility of DNA as a function of added surfactant in a precise and reproducible manner and evaluate the potential of CZE to reflect the change in hydrodynamic friction upon binding. Nevertheless, CZE must be applied with caution for binding studies where strong cooperativity occurs, because of the presence of peak splitting at concentrations close to the half-point of binding. Also, a comparison between this experiment and Manning's polyelectrolyte transport properties theory on one hand and Tirado and Garcia de la Torre expression for hydrodynamic friction of rod-like molecules on the other hand is given. 相似文献
98.
99.
Mammalian cells are hypersensitive to very low doses of X-rays (< 0.2 Gy), a response which is followed by increased radioresistance up to 1 Gy. Increased radioresistance is postulated to be a response to DNA damage, possibly single-strand breaks, and it appears to be a characteristic of low linear energy transfer (LET) radiation. Here we demonstrate a correspondence between the extent of the increased radioresistance and linear energy transfer of 250 kVp X-rays and plateau and Bragg peak negative pi-mesons. The results support our hypothesis since the size of the increased radioresistant response appears to correspond to the number of radiation induced single-strand breaks. Furthermore, since survival prior to the increased radioresistant response (< 0.2 Gy) was LET-independent, these data support the notion that the increased radioresistant response may dictate the overall survival response to higher doses. However, while these data provide further circumstantial evidence for the involvement of DNA strand breaks in the triggering of increased radioresistance, more direct conclusions cannot be made. The data are not accurate enough to detect structure in the single-strand break profiles, the production of single-strand breaks being apparently linear with dose. 相似文献
100.
A 13-year-old girl underwent a right salpingo-o-ophorectomy and partial omentectomy for an ovarian tumor that on microscopic examination was a grade 1 immature teratoma. Mature glial implants were found in the omentum (Stage III). No additional treatment was given. Ten months later, grade 0 and grade 1 peritoneal glial implants were found on laparotomy. Chemotherapy with four cycles of vincristine/cisplatin/etoposide/bleomycin was administered. A second laparotomy 4 months later showed persistence of grade 0 and grade 1 peritoneal glial implants. The patient was well for the next 7 years, after which time she presented with a pelvic mass that on microscopic examination was a malignant neuroectodermal tumor resembling a glioblastoma multiforme. The tumor did not respond to debulking and chemotherapy, and the patient died 6 months later, 8 years after her initial presentation. This case represents the second report of malignant transformation of peritoneal glial implants. 相似文献