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991.
992.
BACKGROUND: Uraemia and chronical haemodialysis are associated with an abnormal growth hormone (GH)-insulin-like growth factor (IGF) axis which may contribute to malnutrition and renal bone disease. Short-term studies have shown a beneficial effect of treatment with recombinant human growth hormone (rhGH) on nutritional status in patients on haemodialysis. In the present study, we evaluated the effect of rhGH on bone and mineral metabolism. METHODS: Twenty chronic malnourished patients on haemodialysis took part in a double-blind, placebo controlled trial with subcutaneous injections of rhGH (4 IU/m2/day) or placebo for 6 months. RESULTS: During rhGH treatment, serum IGF-1 increased 264 +/- 52% (mean +/- SEM) (P < 0.008). There were no significant changes in biochemical markers of mineral metabolism (serum ionized calcium, phosphate and parathyroid hormone). Among markers of bone metabolism, there was a significant increase in serum procollagen type I C-terminal propeptide (maximum 155 +/- 8%, P < 0.001) and no significant changes in serum alkaline phosphatase. Bone densitometry showed a significant decrease in whole body bone mineral content (95.7 +/- 1.2%) after 6 months treatment. The effects on the proximal femur were not significant. CONCLUSION: The effects of 6 months treatment with rhGH seen in this study are best explained by a GH- or IGF-1-induced increased bone turnover. Long-term treatment in larger cohorts followed by bone densitometry and, preferentially, bone histomorphometry are needed to evaluate whether this is a beneficial effect in haemodialysis patients.  相似文献   
993.
994.
The present study assessed whether prenatal androgen and estrogen exposure affected adult spatial learning and hippocampal morphology. Water maze performance, the CA1 and CA3 pyramidal cell field, and the dentate gyrus-granule cell layer (DG-GCL) morphology were assessed at adulthood (70+ days of age) in males, females, androgen-treated (testosterone propionate, TP, or dihydrotestosterone propionate, DHTP) females (2-4 mg/day), estradiol benzoate (EB)-treated females (100 microgram/day), and males treated with the antiandrogen flutamide (8 mg/day). Pregnant rats were injected daily (sc) between Embryonic Day 16 and birth; all pups were delivered by cesarean section. Flutamide-treated males were castrated upon delivery, and adult castrates were used to control for activational effects. Steroid-sensitive sex differences were observed in water maze performance in favor of males. Males had larger CA1 and CA3 pyramidal cell field volumes and soma sizes than females, which were feminized with flutamide treatment. TP and EB, but not DHTP, masculinized CA1 pyramidal cell field volume and neuronal soma size; CA3 was masculinized in both TP- and DHTP-treated females, while EB was ineffective. No effects were observed in cell density, number, or DG-GCL volume or due to adult hormone levels. Thus, prenatal androgens and estrogen influence sex differences in adult spatial navigation and exert differential effects on CA1 and CA3 pyramidal cell morphology. Hence, in addition to the previously reported postnatal component, there is also a prenatal component to the critical period in which gonadal steroids organize the neural mechanisms underlying sex differences in adult spatial ability.  相似文献   
995.
PURPOSE: To examine parental influences on two transitions in the adolescent smoking uptake process: from never having smoked to experimentation and from experimentation to established smoking. METHODS: Using data from the longitudinal Teenage Attitudes and Practices Survey of 1989-1993, we related perceived parental concern about their adolescents' future smoking, parental smoking status, problem-solving communication between parent and adolescent, demographics, and other factors at baseline to experimentation by follow-up among those who had never puffed on a cigarette (n = 4149). We also related these factors at baseline to reaching a lifetime level of smoking of at least 100 cigarettes by follow up among those who had experimented but smoked < 100 cigarettes (n = 2684) in univariate and multivariate analyses. RESULTS: Among never-smokers, baseline susceptibility to smoking and having male best friends who smoke predicted experimentation in the next 4 years. Among experimenters, susceptibility to smoking, having male or female best friends who smoked, and lack of parental concern about future smoking distinguished those who progressed to established smoking by follow-up. Furthermore, communicating with parents first about serious problems was protective against progression from experimentation to established smoking. CONCLUSION: Interventions aimed at reducing adolescent smoking should encourage cessation for parents who smoke and help parents communicate strong anti-smoking norms to children and adolescents and maintain strong lines of communication with them.  相似文献   
996.
The results from previous studies have provided evidence to support the hypothesised association between intrauterine oestrogen exposure and subsequent risk of breast cancer. Information has not been available to study this relationship for several perinatal factors thought to be related to pregnancy oestrogen levels. Data collected from the mothers of women in two population-based case-control studies of breast cancer in women under the age of 45 years (510 case mothers, 436 control mothers) who were diagnosed between 1983 and 1992 in three western Washington counties were used to investigate further the relationship between intrauterine oestrogen exposure and risk of breast cancer. A pregnancy weight gain of 25-34 pounds was associated with breast cancer risk (odds ratio [OR] = 1.5; 95% confidence interval [CI] 1.1, 2.0); however, women whose mothers gained 35 pounds or more were not at increased risk. Use of antiemetic medication in women with any nausea and vomiting (OR = 2.9; 95% CI 1.1, 8.1) and use of diethylstilboestrol (DES) (OR = 2.3; 95% CI 0.8, 6.4) appeared to be positively associated with breast cancer risk. The results from this study provide limited support for the hypothesis that in utero oestrogen exposure may be related to subsequent breast cancer risk among young women.  相似文献   
997.
1. The microcirculation of the kidney is arranged in a manner that facilitates separation of blood flow to the cortex, outer medulla and inner medulla. 2. Resistance vessels in the renal vascular circuit include arcuate and interlobular arteries, glomerular afferent and efferent arterioles and descending vasa recta. 3. Vasoactive hormones that regulate smooth muscle cells of the renal circulation can originate outside the kidney (e.g. vasopressin), can be generated from nearby regions within the kidney (e.g. kinins, endothelins, adenosine) or they can be synthesized by adjacent endothelial cells (e.g. nitric oxide, prostacyclin, endothelins). 4. Vasoactive hormones released into the renal inner medullary microcirculation may be trapped by countercurrent exchange to act upon descending vasa recta within outer medullary vascular bundles. 5. Countercurrent blood flow within the renal medulla creates a hypoxic environment. Relative control of inner versus outer medullary blood flow may play a role to abrogate the hypoxia that arises from O2 consumption by the thick ascending limb of Henle. 6. Cortical blood flow is autoregulated. In contrast, the extent of autoregulation of medullary blood flow appears to be influenced by the volume status of the animal. Lack of medullary autoregulation during volume expansion may be part of fundamental processes that regulate salt and water excretion.  相似文献   
998.
Two-dimensional (2-D) gel electrophoresis with immobilized pH gradient 4-8 in the first dimension was applied in the analysis of Alzheimer's disease brain proteins. The silver-stained 2-D maps of extracts from the frontal cerebral cortex were examined. About 800 and 550 protein spots could be observed on the electrophoretograms from the total and buffer-soluble fractions, respectively. In comparing the gels, four protein spots could now be detected which had either been hitherto undetectable (one spot) or which were weaker (two spots) or stronger (one spot) in density (in the controls) [corrected].  相似文献   
999.
Inter- and intra-limb coordination in arm tremor was examined in adult subjects under vision and no vision conditions using accelerometery techniques. The accelerometer data were analyzed using standard time and frequency domain analyses and the regularity of the acceleration time series was determined using an approximate entropy (Ap En) measure. The data analysis was structured to examine the hypothesis that there is a functional compensatory relation between the motion (tremor) of the limb segments in the arm coordination postural pointing task. The results showed that the level of acceleration increased in a proximal to distal direction within a single arm and was symmetrical across homologous arm segments. The frequency analysis showed the established power spectral profiles for each limb segment in postural tremor tasks, but the finger motion included (beyond the normal 8-12 Hz and 20 Hz tremor) a third slower peak at around 2-3 Hz, due possibly to the reactive forces of the other arm links. There was no effect of vision on the level or frequency patterns of accleration in the limb segments. The coordination analysis showed that there was no linkage between the arms in either the time or frequency domain in the execution of this postural task. This result would tend to suggest that the neuronal commands underlying normal tremor are not derived from a common central oscillator within the central nervous system but are organized in a parallel fashion. The strength of the coupling of intra-limb coordination varied according to the particular adjacent limb links. There were significant correlations in the time domain and coherence in the frequency domain in the acceleration signals between upper arm and forearm, and between hand and finger. The phase lag of the arm units within each of these respective segment pairs was close to in phase or 0 deg. Significant coherence in the frequency domain was also evident between upper arm and hand motion, with the phase lag between these segments being close to 180 deg out of phase. The Ap En analysis of the acceleration signals revealed that there was more regularity to the upper arm and hand accelerometer signals than the forearm and finger signals. The findings show that the intra-limb coordination of the arm links in a two-limb postural pointing task is effected by a compensatory synergy organized about the action of the wrist and shoulder joints. This compensatory synergy reduces the coordination of the 4 within-limb degrees of freedom (arm links) to, in effect, a single degree of freedom arm control task that is not coupled in organization to the motion of the other limb or the torso. It is proposed that this coordination solution reduces the degrees of freedom independently regulated for realization of the task goal but preserves independent body segment control in critical degrees of freedom for potential adaptation to postural perturbations.  相似文献   
1000.
The increasing miniaturisation on the field of electronics and information generation requires evaluation of new concepts and technologies. One method to fulfil the demands is use of single molecular units for data storage and processing. The primary research field of our work group are the properties of conducting polymers and switching molecules. The work includes synthesis of new organic materials for molecular electronics as well as the study of conductivity under different conditions, their dynamics upon optical excitation and their suitability for electronic devices. Materials to be studied are, above all, molecules with extended systems of conjugated double bonds. It covers one-dimensional conductors like polyacetylene and related polymers or oligomers whose structure are based on a polyacetylene backbone, but also more complex structures like graphite[1-4].  相似文献   
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