The limits of thresholds: silica and the politics of science, 1935 to 1990.

Since the 1930s threshold limit values have been presented as an objectively established measure of US industrial safety. However, there have been important questions raised regarding the adequacy of these thresholds for protecting workers from silicosis. This paper explores the historical debates over silica threshold limit values and the intense political negotiation that accompanied their establishment. In the 1930s and early 1940s, a coalition of business, public health, insurance, and political interests formed in response to a widely perceived "silicosis crisis." Part of the resulting program aimed at containing the crisis was the establishment of threshold limit values. Yet silicosis cases continued to be documented. By the 1960s these cases had become the basis for a number of revisions to the thresholds. In the 1970s, following a National Institute for Occupational Safety and Health recommendation to lower the threshold limit value for silica and to eliminate sand as an abrasive in blasting, industry fought attempts to make the existing values more stringent. This paper traces the process by which threshold limit values became part of a compromise between the health of workers and the economic interests of industry.     

Anthropometric Characteristics of Mohawk Children Aged 6 to 11 Years: A Population Perspective

OBJECTIVE: Recent studies have concluded that Native North American children have higher proportions of overweight and obesity than children from the general North American population. This study presents anthropometric data on a representative sample of children from the Mohawk Nation that can be used for comparison with other Native American populations. DESIGN: This is a cross-sectional study comparing distributions of anthropometric characteristics of Mohawk children to the corresponding age and gender data from the Second National Health and Nutrition Examination Survey (NHANES II). Weight, height, triceps and subscapular skinfold thickness, and waist and hip circumferences were measured in 527 children. SUBJECTS/SETTING: All children in grades 1 to 6 (aged 6 to 11 years) in the 3 elementary schools of 2 Mohawk communities in Canada, for whom parental consent was obtained, were enrolled in the present study. There were no exclusion criteria. With a participation rate of 83%, the 527 children enrolled in this study represent an unbiased sample of the population from 2 Mohawk territories. RESULTS: Compared with children studied in NHANES II, Mohawk children were similar in height and triceps skinfolds but were generally heavier, had thicker subscapular skinfolds, and had greater waist and hip circumferences. These differences were greater in older children. Mohawk children who had extreme-high weight values compared with their population means were heavier than their NHANES II counterparts. APPLICATIONS/CONCLUSIONS: Results indicated that, on average, Mohawk children seem to be slightly heavier than children in NHANES II. Except for those with extreme overweight values, Mohawk children show less variation of weight and body mass index than children in NHANES II. Finally, overweight Mohawk children seem to be more likely to carry their excess body fat truncally, compared with overweight children from NHANES II. Health practitioners working with Native American populations should be careful when assessing childhood obesity. Simple comparisons of weight or body mass index with NHANES standards may lead to inappropriate risk assessments.     

Increased membrane-associated protein kinase C activity and translocation in blood platelets from bipolar affective disorder patients

BACKGROUND: recent investigations have suggested that the phosphoinositide (PI) signal transduction system may be involved in the pathophysiology of bipolar affective disorders. Earlier studies in our laboratory have implicated altered PKC-mediated phosphorylation in bipolar affective disorder and in the clinical action of lithium. In the present study, we compared PKC activity and its translocation in platelets from subjects with bipolar affective disorder and three other groups. METHODS: subjects included 44 with bipolar disorder (acute manic episode), 25 with acute major depression, 23 with schizophrenia in acute exacerbation and 43 controls free of personal or family history of an Axis I disorder. Blood platelet membrane and cytosol PKC activity was measured before and after in vitro stimulation with serotonin (5-HT), thrombin and the direct PKC activator, PMA. In addition, we examined 5-HT-, thrombin- and PMA-elicited translocations of PKC isozymes from cytosol to the membrane in platelets of control subjects. RESULTS: in the basal state, manic subjects demonstrated higher membrane PKC activity than depressive and control subjects. The ratio of membrane to cytosol PKC activity was significantly higher in manic (1.10), as compared to control (0.84), depressed (0.93) or schizophrenic (0.93) subjects. Stimulation of platelets with 5-HT in vitro, resulted in greater membrane to cytosol ratio in the manic subjects compared to the three other groups. The responsiveness of platelets to PMA and thrombin was greater for manic subjects than for depressed and schizophrenic subjects, but not greater than the controls. In this measure both the schizophrenic and depressive groups were less active than controls. The results also demonstrate that platelets contain alpha-, beta-, delta- and zeta-PKC isozymes. While alpha- and beta-PKC isoforms were translocated from cytosol to membrane in response to serotonin, PMA and thrombin, serotonin also elicited the redistribution of delta-PKC and thrombin also activated zeta-PKC. CONCLUSION: the results demonstrate that a heightened PKC-mediated signal transduction is associated with acute mania and suggest a decreased transduction in patients with unipolar depression or schizophrenia.     

Effects of a hybrid recombinant human alpha interferon (A/D) on in vitro cytotoxicity and in vivo localization of monoclonal antibody L6-cytosine deaminase conjugate in a colon cancer model

L6 is an IgG2a murine monoclonal antibody which we have demonstrated binds well to HT29 human colon carcinoma cells by flow cytometry, whole cell ELISA, and mixed hemadsorption. In vitro cytotoxicity studies revealed that the monoclonal antibody L6-cytosine deaminase (L6-CD) immunoconjugate plus the nontoxic prodrug, 5-fluorocytosine (5-FC), is equivalent to 5-fluorouracil (5-FU) in its ability to kill HT29 cells. Human alpha-interferon (A/D) was able to enhance this cytotoxic effect. The I.C.50's revealed that very small amounts of L6-CD are needed for this cytotoxic effect (approximately, 5 pg/ml resulted in 50% viability). The limiting factor was the amount of 5-FC employed with L6-CD (3 microM yielded 50% cell viability). alpha-Interferon (A/D) lowered the requirement of 5-FC to 1 microM to achieve 50% cell lethality. In vivo biodistribution experiments indicated that 1 microgram of L6-CD is nonspecifically taken up by the liver and spleen and cleared rapidly from the blood. Significant localization of L6-CD to HT29 tumors occurred only when 99 micrograms of unlabeled L6-CD was added to 1 microgram of 125I-labeled immunoconjugate injected intravenously. Further augmentation of tumor/blood ratios without reduction in percent injected dose per gram of tumor was possible with the intravenous injection of 100 micrograms of anti-idiotypic monoclonal antibody 13B, 24 hours after L6-CD, which bound unreacted L6-CD and cleared it from the blood. The addition of 100,000 U of alpha-interferon (A/D) given intraperitoneally every day increased the clearance of L6-CD by the liver and spleen, but impaired tumor localization (percent injected dose per gram). These studies demonstrated that in vivo localization of the L6-CD conjugate to HT29 tumors could be optimized by injecting excess L6-CD followed by an equal amount of L6 anti-idiotype mAb 13B, 24 hours after L6-CD.     

高效液相色谱法测定绿茶和饮料中的咖啡因

采用反相高效液相色谱法，固定相为十八烷基硅烷键合硅胶，以乙腈-水(20：80)为流动相，检测波长274nm，测定绿茶和饮料中的咖啡因含量。结果线性范围为3．9～3900ng，r=O.9999；绿茶和2种饮料的平均加样回收率分别为100．2％、100．1％和99．8％。该方法准确、简便、快速，适合绿茶和可乐型饮料中咖啡因的测定。     

银杏叶黄酮类化合物的研究进展

综述了近年来对银杏叶黄酮类化合物提取工艺、测定方法、应用等方面的研究进展，为开发利用银杏叶黄酮类化合物提供依据。     

Recruitment of patients into an internet-based clinical trials database: the experience of OncoLink and the National Colorectal Cancer Research Alliance.

PURPOSE: In March 2001, the National Colorectal Cancer Research Alliance (NCCRA) and OncoLink (http://www.oncolink.org) established a database to facilitate patient enrollment onto clinical trials. This study describes the population registering with the database and identifies discrepancies between individuals registering through the Internet and those registering through a telephone call center. METHODS: Participants registered with the NCCRA/OncoLink database through the Internet or a telephone call center. All participants entering the database completed a questionnaire regarding basic demographics, colon cancer risk factors, and indicated how they became aware of the database. Comparisons were made between individuals registering through the Internet and those registering through the telephone call center. RESULTS: A total of 2,162 participants registered during the first 16 months of the database. Most patients registered through the Internet rather than the telephone call center (88% v 12%; P < .001). More females than males registered (73% v 27%; P < .001). The majority (89%) were white. Participants registering through the Internet were younger than those registering through the call center (mean, 48.8 v 55.0 years; P < .001). There was no difference between the two groups with regard to sex or ethnicity. CONCLUSION: The Internet has the potential to increase the likelihood that interested individuals find appropriate clinical trials. Some of the discrepancies that are known to exist for access to the Internet were also seen for those registering with the database through the Internet. Despite these differences, the potential to increase clinical trial enrollment with this type of Internet-based database is high.     

Haemoptysis in healthy children due to unsuspected foreign body

Abstract: Haemoptysis in otherwise healthy children is an uncommon event. Two cases of massive haemoptysis, subsequently requiring lobectomy, are discussed. In each case, foreign vegetable matter was identified despite previously normal bronchoscopy and minimal changes on chest radiograph.