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961.
Numerous women are treated with a combination of oestrogen and progestogen for contraception and hormone replacement therapy worldwide. A possible increased risk of cancer in target organs has been discussed vividly for many years. While oestrogens are clearly mitogenic for breast epithelial cells, there has been considerable uncertainty about the effects of progestogens. This article reviews current knowledge on this field, including our own data. Oestrogen receptors are down-regulated during the luteal phase, while progesterone receptors remain at a high level throughout the menstrual cycle. According to most studies, in vivo proliferation of normal breast epithelial cells is higher during the luteal phase in the vast majority of women. Normal breast tissue can convert oestrone sulphate to oestradiol. A negative correlation between the levels of circulating oestradiol and the enzyme converting oestrone into oestradiol suggests a local regulatory mechanism of tissue oestradiol formation. Serum progesterone levels correlate positively with sulphatase activity while 19-norsteroid progestogens may be inhibitory. We found that long-term continuous combined hormonal treatment with conjugated equine oestrogens and medroxyprogesterone acetate induced a proliferative response in the breasts of surgically postmenopausal macaques. The effect of combined treatment was more pronounced than that of oestrogen treatment alone. Both endogenous progesterone and exogenous progestogens increase proliferation of breast epithelial cells. Exogenous progestogens down-regulate both oestrogen and progesterone receptors. Oestrogen and progestogens may have both direct and indirect stimulating effects on proliferation. The finding of a positive correlation between insulin-like growth factor I messenger RNA and proliferation found in hormonally treated women with low receptor levels suggests the possibility of nonreceptor-mediated effects of sex steroids on proliferation, which needs to be investigated further.  相似文献   
962.
The ferredoxin (fdx) and lectin (hgl5) promoters of Entamoeba histolytica contain the DNA sequence motif TATTCTATT (URE3). Previously we showed that mutation of the URE3 motif in the hgl5 lectin promoter results in an increase in promoter reporter activity. Mutation of this motif in the fdx promoter led to a 40-to-50% decrease in fdx promoter activity as measured by reporter gene activity and abundance of mRNA. E. histolytica nuclear proteins exhibited sequence-specific binding to the URE3 motif in electrophoretic mobility shift assays. These results support the regulation of both ferredoxin and lectin promoters by a nuclear protein(s) which recognizes the URE3 motif.  相似文献   
963.
964.
An analysis of the distribution of trace metals in the kidney cortex in normal and brindled male mice has been carried out with a scanning proton microprobe. Enzyme histochemical staining techniques were used to distinguish between proximal and distal tubules. Average copper levels were increased in brindled kidney tissue sections, with the above-normal Cu accumulation found to occur entirely within the proximal tubules. Therefore, the proximal tubule is now regarded as the location where the defect in Cu transport in brindled mice is manifested the most clearly. The distribution of Fe was found to be non-uniform with some tubule cross-sections exhibiting high concentrations in both genotypes. The distribution of Zn was found to be uniform, and the concentration was similar for each genotype.  相似文献   
965.
We report on partial dup(22q), growth deficiency, and the facioauriculovertebral sequence including hemifacial microsomia, cleft lip and palate, preauricular tags, and hearing loss in one patient. No endocrine or systemic cause for growth deficiency was identified. The case illustrates applicability of chromosome analysis in syndrome-associated growth failure, and a previously unreported associated chromosome abnormality.  相似文献   
966.
This study compared catalytic and immunochemical properties of drug metabolizing phase I and II enzyme systems in houbara bustard (Chlamydotis undulata) liver and kidney and rat liver. P450 content in bustard liver (0.34 +/- 0.03 nmol mg-1 protein) was 50% lower than that of rat liver (0.70 +/- 0.02 nmol mg-1 protein). With the exception of aniline hydroxylase activity, monooxygenase activities using aminopyrine, ethoxyresorufin and ethoxycoumarin as substrates were all significantly lower than corresponding rat liver enzymes. As found in mammalian systems the P450 activities in the bird liver were higher than in the kidney. Immunohistochemical analysis of microsomes using antibodies to rat hepatic P450 demonstrated that bustard liver and kidney express P4502C11 homologous protein; no appreciable cross-reactivity was observed in bustards using antibodies to P4502E1, 1A1 or 1A2 isoenzymes. Glutathione content and glutathione S-transferase (GST) activity in bustard liver were comparable with those of rat liver. GST activity in the kidney was 65% lower than the liver. Western blotting of liver and kidney cytosol with human GST isoenzyme-specific antibodies revealed that the expression of alpha-class of antibodies exceeds mu in the bustard. In contrast, the pi-class of GST was not detected in the bustard liver. This data demonstrates that hepatic and renal microsomes from the bustard have multiple forms of phase I and phase II enzymes. The multiplicity and tissue specific expression of xenobiotic metabolizing enzymes in bustards may play a significant role in determining the pharmacokinetics of drugs and susceptibility of the birds to various environmental pollutants and toxic insults.  相似文献   
967.
BACKGROUND: It has been suggested that patients with unipolar depression show abnormal responses to negative feedback in the performance of cognitive tasks. Positron emission tomography (PET) has previously identified blood flow abnormalities in depressed patients during cognitive performance. We have also used PET to identify regions where there is differential neural response to performance feedback in normal volunteers. In this study we aimed to test the hypothesis that blood flow in these regions, the medial caudate and ventromedial prefrontal cortex, would be abnormal in depressed patients. METHODS: Six patients with unipolar depression and six matched controls were scanned using PET while performing cognitive tasks in the presence and absence of feedback. RESULTS: Compared with controls, depressed patients failed to show significant activation in the medial caudate and ventromedial orbitofrontal cortex. Blood flow was lower and a differential response, observed in normals, under different task and feedback conditions was not seen in the patients. DISCUSSION: The findings suggest that the behavioural response to feedback in depressed patients is associated with an abnormal neural response within the medial caudate and ventromedial orbitofrontal cortex, regions implicated in reward mechanisms. We argue that the observed abnormalities may depend on a combination of psychological factors, with both cognitive and emotive components.  相似文献   
968.
Wear behavior correlations with morphology and orientation directions have been established from commercially produced nylon 6 with different draw ratios between 1 and 7 approximately. The wear rate is least in a direction perpendicular to the draw direction for highly drawn samples. It correlates with surface microstructure and the inherent molecular characteristics induced by sample preparation. Well-characterized polymer specimens were used in this investigation.  相似文献   
969.
The previously cloned CER2 gene is required for the normal accumulation of cuticular waxes and encodes a novel protein. Earlier reports suggested that the CER2 protein is either a membrane-bound component of the fatty acid elongase complex or a regulatory protein. Cell fractionation and immunoblot analyses using polyclonal antibodies raised against a chemically synthesized peptide with a sequence based on the predicted CER2 protein sequence have demonstrated that the 47-kD CER2 protein is soluble and nuclear localized. These results are consistent with CER2 being a regulatory protein. Detailed studies of plants harboring a CER2 promoter/GUS transgene (CER2-GUS), in combination with immunoblot analyses, revealed that CER2 is expressed and the CER2 protein accumulates in a variety of organs and cell types. Expression is highest early in the development of these organs and is epidermis specific in most tissues. In agreement with the activity of the CER2 promoter in hypocotyls, cuticular wax accumulates on this organ in a CER2-dependent fashion. In leaves CER2 expression is confined to the guard cells, trichomes, and petioles. However, application of the cytokinin 6-benzylaminopurine induces ectopic expression of CER2-GUS in all cell types of leaves that emerge following treatment.  相似文献   
970.
To examine the preventive oral health behavior levels of randomly-selected dentate and edentulous adults, age 18 and over, a mail survey was conducted in North York, Ontario, a multicultural suburb of Metropolitan Toronto (n = 1,050). High optimal levels of at least daily tooth brushing were reported by the majority of the dentate (96 per cent). Lower rates were evident for yearly preventive visiting (69 per cent), daily flossing (22 per cent), daily use of an interdental device (25 per cent), not snacking between meals (12 per cent) and eating one or no cariogenic foods on the previous day (36 per cent). Logistic regression results indicated higher levels on an additive index of oral preventive behaviors for females, those having a higher education and non-Italian respondents. Edentulous respondents reported high daily denture cleaning rates (87 per cent), but less frequent night removal (51 per cent), checking for oral lesions (68 per cent) and preventive visiting (12 per cent). Oral disease is one of the most common and costly chronic disorders affecting modern populations. However, unlike most other chronic diseases, it is largely preventable. These data indicate a clear need for determined oral health promotion efforts to inform and encourage increased levels of preventive behaviors in addition to tooth and denture brushing, particularly among specific sociodemographic and ethnic groups.  相似文献   
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