Bridge populations in the spread of HIV/AIDS in Thailand.

OBJECTIVE: To determine the extent to which men provide a bridge population between commercial sex workers (CSW) and the general female population in Thailand. DESIGN: Sexual network and serological data were collected from a systematic quota sample of low income men and truckers during 1992 in three Thailand provinces. Completed sample size was 1075 men aged 17-45 years and 330 truckers. METHODS: Sexual network information was used to identify those men who have sex with both female CSW and non-CSW partners (the 'bridge population'). A new method was used for calculating the partner acquisition rate and to establish the potential number of women exposed to HIV via inconsistent condom use among the bridge population. RESULTS: Approximately 17% of men and 25% of truckers can be included in the bridge population. These men are more likely to be HIV-positive and to have had at least one other sexually transmitted infection in the past year (odds ratio, 2.2 and 3.4, respectively). Consistent condom use with CSW is less than 30%, and is less than 1% with non-CSW partners. As a result, 30 women in the general population were potentially exposed to HIV per 100 sexually active men in the last year:nine women each additional year. Younger men and truckers expose almost twice as many women to HIV; more female peers than wives are exposed. CONCLUSION: Bridge populations may be as important as "core groups' for the spread of HIV into the general Thai population. Young men and women are strategic intervention targets because they have more partners, are more likely to be in bridging networks, and are more receptive to condom use.

Ras oncogene p21 levels parallel malignant potential of different human colonic benign conditions.

Ras oncogenes are a specific family of genes believed to play a role in malignant transformation and tumor growth in humans. To gain a better understanding of the role these oncogenes may play in malignant transformation, we evaluated the levels of a ras gene protein product (p21) in formaldehyde-fixed, paraffin-embedded specimens of normal human colonic mucosa, hyperplastic polyps, tubular adenomas, villous adenomas, and epithelium from a patient with ulcerative colitis. The p21 protein content was measured using the RAP-5 monoclonal antibody in a semiquantitative immunohistochemical assay. The titer value was expressed as the highest dilution of antibody giving definite staining using the avidin-biotin peroxidase method. Differences in p21 titer values among all classes of polyps were significant (hyperplastic polyps values were less than tubular adenomas values, which were less than villous adenoma values). The p21 titers obtained from ulcerative colitis specimens were similar to those obtained from villous adenomas. We conclude that the levels of ras oncogene protein product increase with the malignant potential of benign human colonic conditions. These findings suggest that the ras oncogene protein product may play an important role in the malignant transformation of benign lesions of the human colon. If these findings are confirmed, as technology progresses to allow molecular probes to measure gene products in biopsy specimens, high-risk patients could be monitored and treated before actual malignant transformation occurs.

Relationship between ras oncogene expression and clinical and pathological features of colonic carcinoma.

In order to investigate the value of ras oncogene expression as a prognostic indicator in colonic adenocarcinoma, we evaluated the level of ras gene protein product (p21) in the available material of 109 surgical specimens resected at our institution between 1978 and 1981. Pathology slides and archived paraffin blocks were retrieved for confirmation of the original diagnosis, determination of stage, and measurement of p21 content. P21 titers were obtained using the RAP-5 monoclonal antibody in a semiquantitative immunohistochemical assay. Titer was expressed as the highest dilution of antibody given definitive staining using the Avidin-Biotin peroxidase method. The analysis indicated that tumors with high (greater than or equal to 1:40,000) p21 titer had a lower five-year survival rate than tumors with low (less than 1:40,000) titers (34.3% vs 60.8%, p less than 0.02). When a logistic regression analysis was used with the dependent variable being five-year survival and the independent variables being age, sex, location of tumor. Dukes' stage, mucin production, p21 titer, differentiation degree and tumor size, the statistically significant relationship of the level of ras gene protein product to long-term survival was negated by the concomitant knowledge of Dukes' stage. On the other hand, when only the variables available in the preoperative period were entered in the multivariate analysis, p21 titers retained a significant relationship with long-term survival (p less than 0.05). We conclude that ras oncogene determination in colonic carcinomas may have clinical importance for the pre-operative identification of a group of colonic tumors with a more aggressive behavior and a poorer prognosis.

Spatial Distribution of Green Mold Foci in 30 Commercial Mushroom Crops.

Statistical analyses were performed on spatial distributions of mushroom green mold foci caused by Trichoderma spp. in 30 standard Pennsylvania doubles (743 m2 production surface) selected at random from over 900 total crops mapped. Mapped production houses were divided into four tiers of six beds each with 16 sections per bed (total = 384 sections per double). Each section contained approximately 2 m2. Green mold foci were mapped according to presence or absence in each section as they became visible during the course of the mushroom production. There was a trend toward higher disease incidence at the ends of the doubles, although this was not consistent from level to level. Spatial analysis revealed that green mold foci were more likely to occur in neighboring sections along the beds rather than above, below, or across from each other. Cultural practices that were associated with movement along the beds, i.e., nutrient supplementation, spawning, bed tamping, surface covering, etc., were considered the most likely factors influencing the incidence of green mold in spawned compost. Airborne contamination was considered a less likely source of inocula contributing to epidemic development. Sanitation practices that reduce spore loads along the beds are expected to provide the greatest degree of green mold control.

Statistical review of the henhouse experiments: the effects of a pulsed magnetic field on chick embryos.

This paper analyzes data from a study conducted by the United States Office of Naval Research on the effects of pulsed magnetic fields on chick embryos. The experiment involved incubation of eggs under carefully controlled conditions in six different laboratories. The original analysis included inappropriate statistical methodology for analyzing the experimental results. Since the conclusions from this study rest so heavily on the results of statistical analyses, choosing the proper methodology is imperative. The major aim of this paper then is to introduce more appropriate analytic tools and illustrate their use in the present context. Qualitatively our results agree with those of the original analysis; our findings about interactions between effects, however, makes interpretation of these effects more subtle. We apply linear logistic modeling to counts of damaged embryos, using as covariates factors corresponding to exposure, laboratory, incubator, run, and measurements of background radiation. This facilitates estimation of the size of the effects. The effects of laboratory, incubator, and run are explored both as fixed and random effects. We find statistically significant exposure and laboratory effects, in accordance with the original study. However, we also find that the inter-laboratory variation in exposure effect is at least as large as the exposure effect itself. The presence of such effects fundamentally alters the interpretation of the fitted model, as is graphically presented.

Combining registration-system and survey data to estimate birth probabilities.

With the widespread availability of event-history data, demographers have increasingly eschewed registration-system data in favor of survey data. We propose instead using survey and registration-system data in combination, via a constrained maximum-likelihood framework for demographic hazard modeling. As an application, we combine panel survey data and birth registration data to estimate annual birth probabilities by parity. The general fertility rate obtained from registration-system data constrains the weighted sum of parity-specific birth probabilities. The variances about the parity-specific birth probabilities are halved when registration-system data are used to constrain the estimates. Other demographic applications are discussed.

Experience with 647 consecutive tumors of the duodenum, ampulla, head of the pancreas, and distal common bile duct.

Between 1946 and 1987, 647 patients with periampullary tumors were diagnosed at the University of Chicago Medical Center. These included 549 tumors located in the head of the pancreas, 40 in the distal common bile duct, 29 in the duodenum, and 29 at the ampulla of Vater. Ninety-eight per cent of all tumors were adenocarcinoma, with 93% of the remaining being duodenal carcinoid or sarcoma. Operability rate ranged from 81% to 97%, according to the tumor location and histologic type. A combination of laparotomy, biopsy, and bypass was performed in 433 patients and only one survived 5 years (0.2%). Resectability rate ranged from 16.5% for pancreatic adenocarcinoma to 89.3% for ampullary tumors. Of the 133 resections, 80 were pancreatoduodenectomies, 29 total pancreatectomies, 7 duodenectomies, 2 gastrectomies, 8 common bile duct resections, and 7 local excisions. Overall 19% of patients who underwent radical resection died in the immediate postoperative period, although mortality has decreased to 5% since 1981. Mortality was 20% after a standard pancreatoduodenectomy and 24.1% after a total pancreatectomy. Five-year actuarial survival rates, including perioperative deaths, were 8.8%, 20%, and 32% for pancreatic, duodenal, and ampullary adenocarcinoma, respectively. One half of patients with sarcoma and two-thirds with carcinoid of the duodenum survived 5 years. No patient with distal common bile duct adenocarcinoma achieved a 5-year survival rate. Multivariate analysis on all patients operated on (n = 566) revealed that the 5-year survival rate was significantly related to intent of operation (palliative 0.2%, curative 12%; p less than 0.001), histologic type (adenocarcinoma 2%, carcinoid and sarcoma 31%; p less than 0.0001), and site (ampullary and duodenal 21%, biliary and pancreatic 0.9%; p less than 0.001). A second multivariate analysis, evaluating only those patients with adenocarcinoma who survived the perioperative period of the radical resection (n = 97) analyzed the influence of tumor size and differentiation, lymphatic, capillary, and perineural microinvasion, lymph node status, and type of procedure (pancreatoduodenectomy vs. total pancreatectomy) on 5-year survival. None of these additional variables was significantly associated with long-term survival rates. In addition we evaluated the presence of local or distant recurrence after resection by analyzing the findings from all autopsies performed on these patients (n = 49): 29.4% of patients died with local recurrence alone, 23.5% with distant recurrence alone, and 47.1% had both local and distant recurrences.(ABSTRACT TRUNCATED AT 400 WORDS)