PVA水凝胶在不同人体模拟液中的压缩蠕变行为

通过冷冻-解冻循环方法制备出聚乙烯醇（PVA）水凝胶人工髓核材料,研究了其在生理盐水和Hanks溶液两种模拟体液及去离子水中的压缩蠕变性能并进行了蠕变黏弹性模型分析.PVA水凝胶在不同模拟体液中都表现出良好的黏弹性能,达到蠕变平衡的快慢和应变量大小都与体液中的离子含量有关.等时线法的研究表明,水凝胶的力学行为符合线性黏弹性行为,选取的Kelvin-Voigt模型能够很好地模拟PVA水凝胶蠕变行为.拟合结果表明：体液中的一些盐离子抑制了水凝胶内部小尺寸单元的运动,蠕变平衡时间延长;体液中的Na⁺盐离子会促进水凝胶内部大尺寸单元的运动,使其快速达到蠕变平衡,满足临床医学使用要求.     

Clinicopathological studies on pseudosarcomatous lesion of the upper gastrointestinal tract

Thirty-seven cases of pseudosarcomatous lesion (PSL) are studied clinicopathologically on the upper gastrointestinal tract. Majority of the cases showed polypoid tumor lesions, and only minority of them showed non-polypoid lesions. All showed surface erosion or ulcer. Atypical proliferating cells, easily mistaken for sarcoma, were observed in the stroma. The cellular atypia of the stromal cells was related on site and shape; polypoid or non-polypoid. The lesions with severe atypia were observed mainly in the esophago-cardiac junction, lower portion of esophagus and cardia. Non-polypoid lesions showed mild atypia. Immunohistochemically, atypical stromal cells were positive only for vimentin, so considered to be fibroblastic cells. In order to avoid over-diagnosis on biopsy of the upper gastrointestinal tract, recognition of the clinicopathological features of PSL is very important.     

In vitro genotoxicity studies of chrysotile asbestos fibers dispersed in simulated pulmonary surfactant

Micronucleus (MN) formation and sister-chromatid exchange (SCE) assays were performed for asbestos in cultured Chinese hamster lung (V79) cells to determine the effect of surfactant treatment on the genotoxicity of two chrysotile asbestos samples of different fiber lengths. The cells were challenged in vitro with NIEHS intermediate- and short-length chrysotile fibers in both their native state and with surfactant pretreatment. For the surfactant pretreatment, the fibers were incubated in a simulated pulmonary surfactant which was prepared by ultrasonically dispersing dipalmitoyl lecithin (DPL), a primary component of pulmonary surfactant, in minimal essential medium (MEM). Chrysotile asbestos was ultrasonically mixed into the prepared surfactant dispersion or into MEM. V79 cells were exposed to DPL-treated intermediate-length chrysotile (TICA), intermediate-length chrysotile (ICA), DPL-treated short-length chrysotile (TSCA) or short-length chrysotile (SCA) fibers for 48 h. For each treatment, 2000 mononucleated cells were scored for MN formation, and 30 M2 metaphase cells were scored for SCE induction. The results showed that all samples, TICA, ICA, TSCA and SCA, caused significant elevation in the frequency of cells with micronuclei and of cells with two or more nuclei. The increase in micronucleus frequency was greatest in cells challenged with untreated intermediate-length fibers, and was greater for untreated than for DPL-treated short-length fibers. For the short-length fiber samples, DPL surfactant treatment decreased activity for multiple nucleus formation, while DPL treatment did not result in consistent changes in that activity for intermediate-length fibers. Results of SCE assays were either negative or inconclusive. Cells were more viable following TICA and TSCA than following ICA and SCA challenge as measured by cell counts after 48 h of incubation.     

In vitro polarographic studies of rat brain oxygen uptake in simulated uraemia and hepatic coma

The villi and crypts of the small intestine of the albino rat (Rattus norvigicus) have been enumerated and measured at different ages from 2 weeks to 8 months. The number of villi increased up to the third month of age and the number of crypts up to the eighth month. In the proximal intestine, the mean length of the villus base increased up to the fifth month as ridge-shaped villi were formed. Villus height was greater proximally than distally and this, and the crypt depth, remained constant from the end of the first month of age. The total villus circumference per unit area of intestine, and the villus circumference per crypt was the same proximally and distally, and was relatively constant after the first month of age. The total circumference of the crypt mouths per square millimeter of intestine was the same proximally and distally and, at all ages, was greater than the total villus circumference. The villus surface area per square millimeter of intestine, or per crypt, remained relatively constant after the first month and was greater proximally than distally, due only to the taller villi proximally. The change from finger-shaped to ridge-shaped villi did not affect the villus mucosal surface area. The changes in villus shape are probably not determined by differences in the rate of crypt cell production.     

Churg-Strauss syndrome diagnosed and followed with gastrointestinal fiberscopic studies and electroneuromyography

BACKGROUND: High immigration rates contribute to the high incidence of pediatric tuberculosis (TB) in San Diego, Calif. Adolescents frequently have poor access to health care and may not receive appropriate TB screening. School-based screening has been ineffective in detecting TB in other parts of the country. OBJECTIVE: To determine the prevalence of TB infection and disease in a high-risk population of high school students through school-based screening. DESIGN AND PARTICIPANTS: Cross-sectional study of TB prevalence and an analysis of risk factors for TB infection in students attending 2 San Diego high schools with high percentages of non-US-born students. MAIN OUTCOME MEASURES: Positive induration (> or =10 mm) with Mantoux tuberculin skin test. A chest radiograph or clinical findings consistent with active TB. RESULTS: A total of 744 (36%) students at high school 1 and 860 (57%) students at high school 2 participated. Ninety-five (12.8%) and 207 (24.1%) students, respectively, had positive tuberculin skin test results. One student had a chest radiograph that showed active TB. Smear for acid-fast bacteria and culture for Mycobacterium tuberculosis had negative results. Vietnamese, Filipino, and Latino ethnic groups were significantly more likely to have positive tuberculin skin test results than the white population (P<.05). Non-US-born students were significantly more likely to have positive tuberculin skin test results than US-born students in all ethnic groups except the Latino group. CONCLUSION: Although treatment of TB coupled with aggressive public health investigation is the most cost-beneficial way of preventing TB, targeted school-based screening may be an effective way of detecting TB infection in high-risk populations with poor access to health care.     

Is electrogastrography a substitute for manometric studies in children with functional gastrointestinal disorders?

We performed simultaneous fasting and fed antroduodenal manometry and EGG in 25 children with functional bowel disorders. Three patients (12%) had an uninterpretable EGG. The manometric studies showed severe neuropathy in six patients; milder neuropathic changes in five patients; postprandial hypomotility in one patient; myopathy in four patients, and normal motility in the remaining six patients. The percentage of tachygastria time (frequency > 3.5 cycles/min) was higher in the patiens with mild (44.1 +/- 15.8%) and severe (48 +/- 19.1%) neuropathy than in the patients with myopathy (20 +/- 16.2%, P < 0.05) or with normal motility (23 +/- 13.3%, P < 0.05). There was a considerable overlap in the percentage of tachygastria and total arrhythmia time among the different study groups. The ratio of post- to preprandial power was significantly higher (2.5 +/- 0.07) in children with normal motility than in the other patients groups. Every child with total arrhythmia time < 35% and a ratio of post- to preprandial power > 2.4 had normal manometry. In summary, EGG differentiated groups of children with normal manometry from others with neuropathic or myopathic changes, but in a minority of patients the study was not interpretable and there was overlap in EGG results between children with normal and abnormal manometry.     

Average causal effects from nonrandomized studies: A practical guide and simulated example.

In a well-designed experiment, random assignment of participants to treatments makes causal inference straightforward. However, if participants are not randomized (as in observational study, quasi-experiment, or nonequivalent control-group designs), group comparisons may be biased by confounders that influence both the outcome and the alleged cause. Traditional analysis of covariance, which includes confounders as predictors in a regression model, often fails to eliminate this bias. In this article, the authors review Rubin's definition of an average causal effect (ACE) as the average difference between potential outcomes under different treatments. The authors distinguish an ACE and a regression coefficient. The authors review 9 strategies for estimating ACEs on the basis of regression, propensity scores, and doubly robust methods, providing formulas for standard errors not given elsewhere. To illustrate the methods, the authors simulate an observational study to assess the effects of dieting on emotional distress. Drawing repeated samples from a simulated population of adolescent girls, the authors assess each method in terms of bias, efficiency, and interval coverage. Throughout the article, the authors offer insights and practical guidance for researchers who attempt causal inference with observational data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amylase thermolability in body fluids

The thermolability of amylase was measured in saliva, pancreatic juice, urine, adult and neonatal sera. The mean percentage thermolability from these fluids was 100%, 99%, 87%, 44% and 23% respectively. In patients with acute pancreatitis and mumps the amylase was 84% and 83% thermolabile during the acute phase. On resolution of the pancreatitis this dropped towards normal. Patients with a pancreatic pseudocyst showed a high mean percentage thermolability (82%). These results could suggest that a component of amylase in human serum is not of pancreatic or salivary origin. In addition, this simple technique may be helpful in the diagnosis of pancreatic pseudocyst.