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W Halperin

Publications and source records attributed to W Halperin.

At least 55 records · Page 3Linked to original sources
PubMed1984

Methods of control for smoking in occupational cohort mortality studies.

Cohort mortality studies, which compare the observed mortality of a historically exposed cohort to an expected mortality based on figures from a national population, are among the most common and useful types of studies done in occupational epidemiology. Such studies are primarily based on records which lack data on smoking. Hence it is often difficult to determine whether an observed excess of a given smoking-related disease is the result of occupational exposures, an excess consumption of cigarettes among the exposed, or an interaction between the two. The purpose of this paper is to outline the different types of control which may be exercised in cohort mortality studies to control for the effects of smoking. Indirect control, which uses only existing data, may be exercised through (i) analysis of other smoking-related causes of death besides the cause-of-death of primary interest, (ii) use of an internal reference group instead of the national population, (iii) adjustment of the excess risk based on hypothetical smoking habits, or (iv) analysis for a dose-response relationship between occupational exposure and disease. Direct control, which requires interviews, may be exercised through (i) a survey of the smoking habits of currently employed cohort members, (ii) a survey of all cohort members, or (iii) a "nested" case-referent study within the cohort. The choice of which method to use depends on the cost and the degree of accuracy required by the investigator.

Aged↗
PubMed1982

Agrobacterium tumefaciens mutants affected in attachment to plant cells.

An analysis of Agrobacterium tumefaciens mutants with Tn5 insertions in chromosomal DNA showed that the chromosome of A. tumefaciens codes for a specific ability of this bacterium to attach to plant cells. This ability is associated with tumorigenesis by A. tumefaciens, the ability of avirulent A. tumefaciens to inhibit tumorigenesis, and the ability to adsorb certain phages. A second class of chromosomal mutations affects tumorigenesis without altering the ability to attach to plant cells. The attachment of A. tumefaciens to plant cells was assayed by mixing radiolabeled bacteria with suspensions of tobacco tissue culture cells or freshly isolated Zinnia leaf mesophyll cells. Under the conditions of this assay, an avirulent Ti plasmid-cured strain attached to the same extent as the same strain containing pTiB6806. Six of eight avirulent mutants with Tn5 insertions in chromosomal DNA showed defective attachment, whereas two retained wild-type attachment ability. In contrast to the strains showing wild-type attachment, the attachment-defective mutants failed to inhibit tumorigenesis when inoculated onto Jerusalem artichoke slices before inoculation of a virulent strain and also showed a loss of sensitivity to two Agrobacterium phages. The loss of phage sensitivity appeared to be due to a loss of ability to adsorb the phages. Staining with Calcofluor indicated that the mutants retained the ability to synthesize cellulose fibrils, which have been implicated in the attachment process. Southern filter hybridizations demonstrated that each mutant contained a single Tn5 insertion, and genetic linkage between the Tn5 insertion in one mutant and the attachment phenotype has also been demonstrated.

Adsorption↗
PubMed1979

Factors Affecting Crown Gall Tumorigenesis in Tuber Slices of Jerusalem Artichoke (Helianthus tuberosus, L.).

Agrobacterium tumefaciens can induce tumors on thin slices which are excised from Jerusalem artichoke (Helianthus tuberosus) tubers and grown in culture on medium containing minerals and a carbon source. A comparative study was made of the kinetics of cell division in slices under three conditions: (a) slices which were untreated and showed only spontaneous (wound-induced) cell divisions; (b) slices treated with indoleacetic acid at several concentrations; and (c) slices treated with virulent or avirulent bacteria. The earliest spontaneous cell divisions were completed (as detected by the appearance of new daughter cell pairs) by about 3 hours. These cells divide only once. In indoleacetic acid-treated tissue, more cells divide, with the first cell pairs being detected slightly earlier than in slices not subjected to the hormone. The number of cells which divide is roughly proportional to auxin concentration. Tissue treated with virulent bacteria showed only the pattern of spontaneous cell division until about 72 hours, after which another burst of cell division commenced and continued indefinitely. The bacteria-induced growths produced the unusual amino acids which are characteristic of crown gall tumors. The percentage of slices with tumors was sharply reduced if certain avirulent A. tumefaciens strains were applied prior to virulent strains.

Journal Article↗
PubMed1979

A comparison of the intradermal and subcutaneous routes of influenza vaccination with A/New Jersey/76 (swine flu) and A/Victoria/75: report of a study and review of the literature.

A trail of influenza vaccination, with use of bivalent split virus vaccine (A/New Jersey/76 and A/Victoria/75), was conducted to compare the immunogenicity and reactions when vaccine was given by the subcutaneous and intradermal routes. Volunteers 18 to 24 years old were randomized into equal groups, one group receiving 0.1 ml of vaccine intradermally and the other receiving 0.5 ml subcutaneously. For the A/Victoria vaccine, the immunogenicity of the intradermal route seemed superior; for A/New Jersey vaccine, the routes were equivalent. Adverse reactions were minimal and equivalent for both groups. In times of vaccine shortage, the intradermal route is considered to stretch vaccine supplies. Field trials of new influenza vaccines should include evaluation of the immunogenicity of and adverse reactions caused by the same vaccine given by different routes in varied dosages.

Adolescent↗
PubMed1978

Conjunctivitis and skin erythema. Outbreak caused by a damaged high-intensity lamp.

Eighty-one members of girls' basketball teams were exposed to ultraviolet light while sitting in the bleachers of a school gymnasium. A mercury high-intensity discharge lamp lighting the bleacher area had a hole in its outer envelope that allowed the emission of ultraviolet light. Sixty-nine (85%) of the 81 girls were affected; 49 (71%) had symptoms of conjunctivitis and 63 (91%) had symptoms of erythema.

Accidents, Home↗
PubMed1976

MEU: measuring efficient utilization of hospital services.

MEU is a simple way of Measuring Efficient Utilization of hospital services. It looks at the part of the patient's hospital stay that depends on the tests and treatment required. Are these tests ordered in a way that does not waste time? Is the turnaround time from test ordering to reported results fast or slow? MEU produces a numerical index of efficient utilization; here are some of the ways it has been put to use.

Efficiency↗
PubMedDate not supplied

A retrospective cohort mortality study of a phosphate fertilizer production facility.

A retrospective cohort mortality study of phosphate fertilizer production workers was undertaken to determine whether this group is at increased risk of dying from any cause, particularly from lung cancer. A total of 3,199 workers who had ever been employed at one facility were included in this investigation. These workers were followed for vital status ascertainment from their first date of employment up to December 1, 1977, or the date of death, whichever occurred first. Overall, no statistically significant elevations in cause-specific mortality were observed for the entire study population. However, when the analysis was stratified by duration of employment, and length of follow-up, a statistically significant (P less than .05) excess in lung cancer mortality was observed among workers with more than 10 yr of employment and follow-up (standardized mortality ratio = 411). Because of the small number of deaths involved, and because we had prior knowledge of a lung cancer cluster at this plant, we believe that these findings should be viewed as suggestive, and that other investigations in plants with similar exposures are needed to clarify whether an occupationally related lung cancer excess truly exists.

Adolescent↗
PubMedDate not supplied

Green tobacco sickness: occupational nicotine poisoning in tobacco workers.

In this study the authors describe the investigation of a 1992 outbreak of green tobacco sickness, a form of nicotine poisoning from dermal exposure, among 47 tobacco workers in a five-county region of central and south-central Kentucky. Cases were identified through medical record searches at participating hospitals, as well as from reports submitted to the Occupational Health Nurses in Agricultural Communities program. A case-control study was undertaken to assess risk factors for green tobacco sickness. In a 20-min telephone interview, 40 cases and 83 controls responded to questions contained in a questionnaire. In 1992, 47 persons (3 were under age 16 y) in the study region sought medical treatment for green tobacco sickness. Twelve persons were hospitalized and 2 required intensive-care treatment. The crude incidence in 1992 was 10.0/1,000 tobacco workers. In 1993, 66 cases (7 were under age 16 y) of green tobacco sickness were identified in the study region (i.e., annual incidence of 14.0/1,000). A case-control study demonstrated that ill workers were younger, and were more likely to have worked in wet conditions, compared with workers who were not ill. Green tobacco sickness is a common problem among tobacco workers that may be prevented by avoiding work in wet tobacco or by use of protective clothing. Children younger than 16 y of age represented 9% of the green tobacco sickness cases in 1992 and 1993. Current occupational safety and health laws do not address protection of tobacco workers with respect to green tobacco sickness.

Adolescent↗