Is bigger always better? The optimal size of a group practice

The past decade saw several attempts to consolidate physician practices, but this sector remains one of the last cottage industries in the United States. This article develops a framework for analyzing the optimal size of a physician practice. The framework addresses technological factors (e.g., economies of scale and scope), behavioral factors (e.g., changing physician goals, costs of organizing and operating a practice), and market-driven factors (e.g., managed care contracting). Existing empirical research suggests three "optimal" sizes of practices: 5-10 physicians, based on economies of scale and decision-making; 20-30 physicians, based on economies of scope and initial development of a corporate structure; and 80+ (multi-specialty) physicians, which can create an system of referrals and utilization. The article concludes with observations about the challenges to physician practices as they grow.     

Physical activity and nutritional status of adolescents on Guam

The 1999 Safe & Drug Free Schools and Communities Youth Risk Behavior Study collected data from representative samples of both high school (n=590) and middle school students (n=643) on Guam in May, 1999. Results showed that the dietary and exercise habits of Guam's adolescents were sub-optimal. Out of the 643 middle school students surveyed, 26% consumed at least 3 meals per week at a fast food restaurant and 53.3% consumed at least 2 cans of sweetened soda per day. Guam adolescents had a very low intake of fruits and vegetables. As many as 75.3% of high school students reported consuming fruits and vegetables less than once a day. Students who practiced unsafe weight loss practices were significantly more likely to smoke cigarettes, and use illegal drugs. In addition, 26.9% of adolescents surveyed were considered 'overweight'--similar to the prevalence of overweight reported among U.S. Mainland adolescents. Finally, data from survey showed that adolescents on Guam spent more time watching television and less time performing various physical activities than adolescents in the U.S. mainland. These suboptimal practices put Guam's adolescents at increased risk for immediate and long-term health problems.     

Evaluation of kangaroo pericardium as an alternative substitute for reconstructive cardiac surgery

BACKGROUND: Bioprosthetic materials (human, bovine and porcine) are used in various cardio-thoracic repair and replacement procedures because of excellent performance and low thrombogenicity. These bioprosthetic substitutes fail due to degeneration and calcification. This study examines the morphology, tensile properties and calcification potential of kangaroo pericardium in vitro and in vivo. METHODS: Bovine (control tissue) and kangaroo pericardium, fixed in 0.625% buffered glutaraldehyde, were examined by light and scanning electron microscopy. A standard method was used for biaxial testing. Pericardial strips (10 x 5 mm) were implanted subcutaneously into male Wistar rats and retrieved after 4, 6 and 8 weeks and examined by Von Kossa's stain technique and atomic absorption spectrophotometry. RESULTS: Histology revealed serosa and fibrosa cell layers in both tissues. Electron microscopy showed a densely arranged collagen matrix in kangaroo pericardium. Kangaroo pericardium calcified significantly less than bovine pericardium at 4 weeks (0.80+/-0.28 versus 21.60+/-4.80 microg/mg) at 6 weeks (0.48+/-0.08 versus 32.80+/-14.4 microg/mg) and at 8 weeks (2.40+/-1.20 versus 30.40+/-17.20 microg/mg), respectively. CONCLUSIONS: Kangaroo pericardium has a densely arranged collagen matrix with a higher extensibility and significantly lower calcification potential. Therefore, kangaroo pericardium could be used as an alternative substitute in cardiac surgery because of its low calcification potential.     

Adenomatous polyp recurrence and physical activity in the Polyp Prevention Trial (United States)

Objective: To examine prospectively the association between physical activity and adenomatous polyp recurrence. Methods: Information on past year total physical activity was collected annually through an interview-administered questionnaire from the 1905 men and women enrolled in a randomized dietary intervention study, the Polyp Prevention Trial. Multiple logistic regression analysis was used to examine the association between physical activity and polyp recurrence in up to three years of follow-up from baseline colonoscopy. Results: There were no significant associations between moderate, vigorous, or total physical activity at the start of the trial and overall polyp recurrence in either men or women. Participants who reported consistent vigorous activity throughout the trial period had no significantly reduced risk of polyp recurrence compared to those who reported consistent sedentary activity (OR = 0.8, CI = 0.5–1.1). Consistent vigorous activity was also not significantly associated with either advanced or multiple polyps, nor with polyp recurrence at any specific anatomical location in the large bowel. Conclusions: These prospective data suggest that recent physical activity is not associated with polyp recurrence in a three-year period.     

Long-term and homogeneous regulation of the Escherichia coli araBAD promoter by use of a lactose transporter of relaxed specificity

Expression systems based on the Escherichia coli arabinose operon P(BAD) promoter exhibit the all-or-nothing (autocatalytic) induction of expression that was first documented in the lac operon. Under conditions of subsaturating levels of inducer, some of the cells of the population are fully induced, whereas other cells remain uninduced. Recently, a new AraE transporter system was reported to have circumvented the problem of autocatalytic expression in the pBAD expression vectors and to provide graded and homogeneous cell-to-cell expression in the presence of variable inducer concentrations [Khlebnikov, A., Risa, O., Skaug, T., Carrier, T. A. & Keasling, J. D. (2000) J. Bacteriol. 182, 7029-7034]. However, we report that nonuniform gene expression in the AraE system was readily detectable by the use of mutant green fluorescent proteins that are rapidly degraded in E. coli. We report an approach to avoid all-or-nothing induction of the pBAD promoter; the use of a mutant LacY transporter in a strain deficient in both arabinose transport (araE araFGH) and degradation (araBAD). This mutant LacY protein performs facilitated diffusion of arabinose resulting in homogeneous expression of an unstable GFP that is maintained over extended incubation times at subsaturating levels of inducer. This approach is readily adapted to other sugar-regulated expression systems.     

Consumption of aspartame-containing beverages and incidence of hematopoietic and brain malignancies.

BACKGROUND: In a few animal experiments, aspartame has been linked to hematopoietic and brain cancers. Most animal studies have found no increase in the risk of these or other cancers. Data on humans are sparse for either cancer. Concern lingers regarding this widely used artificial sweetener. OBJECTIVE: We investigated prospectively whether aspartame consumption is associated with the risk of hematopoietic cancers or gliomas (malignant brain cancer). METHODS: We examined 285,079 men and 188,905 women ages 50 to 71 years in the NIH-AARP Diet and Health Study cohort. Daily aspartame intake was derived from responses to a baseline self-administered food frequency questionnaire that queried consumption of four aspartame-containing beverages (soda, fruit drinks, sweetened iced tea, and aspartame added to hot coffee and tea) during the past year. Histologically confirmed incident cancers were identified from eight state cancer registries. Multivariable-adjusted relative risks (RR) and 95% confidence intervals (CI) were estimated using Cox proportional hazards regression that adjusted for age, sex, ethnicity, body mass index, and history of diabetes. RESULTS: During over 5 years of follow-up (1995-2000), 1,888 hematopoietic cancers and 315 malignant gliomas were ascertained. Higher levels of aspartame intake were not associated with the risk of overall hematopoietic cancer (RR for >/=600 mg/d, 0.98; 95% CI, 0.76-1.27), glioma (RR for >/=400 mg/d, 0.73; 95% CI, 0.46-1.15; P for inverse linear trend = 0.05), or their subtypes in men and women. CONCLUSIONS: Our findings do not support the hypothesis that aspartame increases hematopoietic or brain cancer risk.