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51.
Differentiation of glucose transport in human brain gray and white matter.   总被引:5,自引:0,他引:5  
Localized 1H nuclear magnetic resonance spectroscopy has been applied to determine human brain gray matter and white matter glucose transport kinetics by measuring the steady-state glucose concentration under normoglycemia and two levels of hyperglycemia. Nuclear magnetic resonance spectroscopic measurements were simultaneously performed on three 12-mL volumes, containing predominantly gray or white matter. The exact volume compositions were determined from quantitative T1 relaxation magnetic resonance images. The absolute brain glucose concentration as a function of the plasma glucose level was fitted with two kinetic transport models, based on standard (irreversible) or reversible Michaelis-Menten kinetics. The steady-state brain glucose levels were similar for cerebral gray and white matter, although the white matter levels were consistently 15% to 20% higher. The ratio of the maximum glucose transport rate, V(max), to the cerebral metabolic utilization rate of glucose, CMR(Glc), was 3.2 +/- 0.10 and 3.9 +/- 0.15 for gray matter and white matter using the standard transport model and 1.8 +/- 0.10 and 2.2 +/- 0.12 for gray matter and white matter using the reversible transport model. The Michaelis-Menten constant K(m) was 6.2 +/- 0.85 and 7.3 +/- 1.1 mmol/L for gray matter and white matter in the standard model and 1.1 +/- 0.66 and 1.7 +/- 0.88 mmol/L in the reversible model. Taking into account the threefold lower rate of CMR(Glc) in white matter, this finding suggests that blood--brain barrier glucose transport activity is lower by a similar amount in white matter. The regulation of glucose transport activity at the blood--brain barrier may be an important mechanism for maintaining glucose homeostasis throughout the cerebral cortex.  相似文献   
52.
PURPOSE: We assess the reliability of intraoperative cavernous nerve stimulation for producing an erectile response during radical prostatectomy. MATERIALS AND METHODS: In 61 patients cavernous nerve function was assessed during radical retropubic prostatectomy using a CaverMap nerve stimulator. Control stimulation was also performed before and after prostatic dissection by placing the nerve stimulator tip on the anterior bladder wall. An increase in penile circumference measured by the device was considered a tumescence response while any measurable detumescence was also categorized. RESULTS: Patient age ranged 43 to 72 years (mean 59.8). Before apical dissection 41% and 46% had tumescence, 31% and 21% had detumescence, and 28% and 33% had no response with stimulation of the neurovascular bundle and anterior bladder wall, respectively. After dissection 42% and 25% had tumescence, 16% and 18% had detumescence, and 42% and 57% had no response with stimulation of the neurovascular bundle and anterior bladder wall, respectively. CONCLUSIONS: A response to neurovascular bundle stimulation using this device does not necessarily correlate with the precise anatomical location of the cavernous nerves. There is considerable background variability related to anesthesia, surgical manipulation and other undefined factors that may cause minor but measurable changes in penile circumference.  相似文献   
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54.
Quantifying the disease impact of cigarette smoking with SAMMEC II software   总被引:10,自引:0,他引:10  
Smoking-Attributable Mortality, Morbidity, and Economic Costs Software, Release II (SAMMEC II) has been developed for the Office on Smoking and Health, Public Health Service, to permit rapid calculation of deaths, years of potential life lost, direct health-care costs, indirect mortality costs, and disability costs associated with cigarette smoking. For the mortality-related measures, age-specific and age-adjusted rates are also calculated. The pivotal epidemiologic measure in these calculations is the smoking-attributable fraction, and attributal risk measure. A multiple-measure approach (attributable mortality and economic costs) to quantifying a health problem is termed "disease impact estimation." Previously, national and State-specific estimates of smoking-attributable mortality and economic costs were calculated using SAMMEC software, the predecessor of SAMMEC II. SAMMEC II is completely menu-driven and operates within the Lotus 1-2-3 software as a set of linked spreadsheets. SAMMEC II adapts national epidemiologic methods for use by State and local health departments. Increased exposure of public health professionals to disease impact estimation techniques, as demonstrated by SAMMEC II, will lead to improvements in both methodology and the quality of smoking-related health data. The primary purpose of SAMMEC II, however, is to provide State or locality-specific data on the health consequences of smoking to policymakers and public health professionals in these jurisdictions.  相似文献   
55.
beta-Carotene, canthaxanthin, and beta-carotene plus canthaxanthin were administered to "chinchilla bastard" pigmented rabbits in their rabbit diet (approximately 200 ppm carotenoid per group). The effect of the carotenoids on retinal function and morphology was tested against a control group in the course of 11 months. Electroretinography showed that in contrast to the control animals, beta-carotene-treated rabbits produced increasing peak latencies of the scotopic b-waves. In the canthaxanthin-treated rabbits, a- and b-waves showed hypernormal amplitudes at low cumulative dosages (approximately 0.5-2 g) and reduced amplitudes at higher dosages (about 5 g). The peak latencies of the scotopic a- and b-waves increased remarkably. This effect was still stronger in the carotenoid combination. Histology and electron microscopy indicated that in contrast to the control animals, canthaxanthin-treated rabbits showed a reduction in retinal thickness in some samples. In particular, they exhibited alterations in the granular layers and a marked diminuation of the photoreceptor outer segments and morphological alterations of the photoreceptor inner segments with massive deposition of electron-dense material. In all animals treated with carotenoids, lipid droplets of the retinal pigment epithelium were enlarged in size and number.  相似文献   
56.
OBJECTIVE: To prospectively assess whether low-molecular-weight heparin (LMWH) provides a survival benefit in patients with advanced cancer. PATIENTS AND METHODS: Between December 1998 and June 2001, we performed a randomized controlled study of patients with advanced cancer. Initially, the study was double blinded and placebo controlled, with the patients receiving daily injections of 5000 U of LMWH or saline. However, because of low accrual midway through the study, the placebo injection arm was eliminated, and the study became open labeled, with patients receiving either LMWH injections plus standard clinical care or standard clinical care alone. The primary study end point was overall survival. RESULTS: Of 141 patients randomized to this clinical trial, 3 dropped out, leaving 138 patients. The median survival time was 10.5 months (95% confidence interval, 7.6-12.2 months) for the combined standard care and placebo groups. The median survival time for the combined LMWH arms was 7.3 months (95% confidence interval, 4.8-12.2 months). These median survival times were not significantly different (log-rank P = .46). The median survival times for the blinded and unblinded LMWH groups were 6.2 months and 9.0 months, respectively. The median survival times were 10.3 months for the blinded placebo arm and 10.5 months for the standard care arm. The rate of severe or life-threatening venous thromboembolism was 6% in the LMWH arms and 7% in the control arms. The rate of severe or life-threatening bleeding was 3% in the LMWH arms and 7% in the control arms.  相似文献   
57.
Rats with nitrofen-induced congenital diaphragmatic hernia (CDH) have heart hypoplasia and cardiovascular malformations. The mechanism of action of nitrofen involves changes in neural crest signaling. Pax3 function is required for cardiac neural crest cells to complete their migration to the developing heart. The aim of this study was to examine whether Pax3 expression is changed at two gestational endpoints in rat embryos or fetuses exposed to nitrofen. On day E9.5 of gestation, pregnant rats received either 100 mg of nitrofen (n=10) or vehicle alone (control, n=10). The fetuses were recovered on E15 or E21. Their hearts were dissected out and weighed. Pax3 mRNA expression was determined by real-time polymerase chain reaction. We used two-tailed Students t-tests to compare groups, with a threshold of significance of p<0.05. Compared with controls, nitrofen-exposed fetuses had heart hypoplasia in terms of heart/body weight ratio (0.62±0.10% vs. 0.77±0.17%, p<0.05). Pax3 mRNA expression in the heart was significantly decreased on E15 in nitrofen-treated embryos (32.94±17.11 U vs. 55.09±11.56 U, p<0.05), and it was still decreased, although not significantly, in the hearts of nitrofen-exposed fetuses recovered on E21 (15.67±5.56 U vs. 20.51±5.92 U, not significant). In conclusion, Pax3 is underexpressed in the hearts of nitrofen-exposed embryonal rats before the end of gestation. The mechanism of action of Pax3 should be further investigated because it could be one of the targets for future prenatal transplacental intervention.Paper presented at the XVIIth International Symposium of Pediatric Surgical Research, Liverpool, United Kingdom, 1–2 October, 2004.  相似文献   
58.
The extracellular part of ErbB-2 is formed by 4 domains, specifically, L1, L2 that adopt a beta-helical structure and S1, S2 that consist of several cysteine-rich, EGF-fold modules. These ectodomains mediate ErbB-2 dimerisation with itself or with other members of the epidermal growth factor receptor (EGFR) family, events essential to both ErbB-2 signaling and the development of certain malignancies. The anti-ErbB-2 monoclonal antibodies N12, N28 and L87 bind to the polypeptides C531-A586, T216-C235 and C220-C235 respectively. In this study, glycine walking and random mutagenesis were used to further delineate the critical residues involved in antibody binding. A molecular model of ErbB-2 ectodomains was then constructed based on the recently published coordinates of the EGFR (EGFR) model. This model rationalized successfully many features of our epitope mapping, including their location in modules within the S1 and S2 domains and the importance of Arg545, Gln548 and Leu561 for N12 binding. Further investigation of the functional effects of the anti-ErbB-2 monoclonal antibodies demonstrated that N28 strongly stimulated ErbB-2 phosphorylation and MAPK activation whereas N12 had no effect. As bivalency is required for the action of these antibodies we propose that at least 2 different kinds of ErbB-2 homodimers can be formed as relative rotational isomers and that the S1 and S2 domains are instrumental in determining the relative orientations of the ErbB-2 homodimers, such that different signaling effects are induced.  相似文献   
59.
Aim: Electrical burns account for up to 10% of burns admissions worldwide. Although a potentially serious mechanism of injury in children, there exists limited Australian data. This study aimed to describe the epidemiology, presentation, management and complications of electrical burn injuries in children. Methods: We performed a retrospective case note review of all children under 16 years of age with electrical burns admitted to the New South Wales Paediatric Burns Centre over an 8‐year, 2‐month study period between November 1995 and December 2003. Results: Twenty‐two cases were identified. The mean age at presentation was 7.6 years (range 8 months to 14.3 years). Eighty‐six percent of cases were sustained from a Low Voltage (<1000 W) power source and 55% occurred in males. The total body surface area burnt ranged from 0.5% to 35% with an average of 4%. Fourteen children had their burns managed non‐operatively, but eight required various surgical procedures ranging from local debridement and primary closure to full‐thickness skin grafting. The average length of hospital stay was 6 days (range 1–58 days). Complications occurred in 4 of the 22 patients (18%) and included wound infections, acute renal failure because of myoglobinuria, permanent electrocardiogram changes and long‐term paraesthesia. Three patients (14%) suffered continued morbidity because of scarring, amputation and psychological disturbance. There was no mortality. Conclusions: Electrical injury was an infrequent but potentially serious cause of injury in children. Minor injuries were successfully managed non‐operatively. Neurological sequelae, cardiac arrhythmias and renal failure remain serious complications in up to 20% of cases.  相似文献   
60.
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