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Biomedical subjects

W Halperin

Publications and source records attributed to W Halperin.

At least 37 records · Page 2Linked to original sources
PubMed1990

A chromosomal Agrobacterium tumefaciens gene required for effective plant signal transduction.

The vir gene products of Agrobacterium tumefaciens carry out the transfer of T-DNA to the plant genome. Effective transcriptional induction of the vir genes by plant signal molecules is controlled by two vir gene products, VirA and VirG. In this study we have identified and cloned a chromosomal region which is also required for vir gene induction. Transposon insertions within this region reduce induction significantly and strongly attenuate virulence, resulting in a restricted host range for infection. The reduction in vir gene transcription can be partially overcome by high concentrations of the inducer molecule acetosyringone. Expression of virG at low pH and low phosphate concentrations, which is independent of plant signals, is not affected by these mutations. Sequence analysis of the region revealed two divergent open reading frames, which we have designated chvE and ORF1. Several transposon insertions mapped in chvE; this resulted in attenuated virulence. chvE codes for a putative protein which is homologous to two periplasmic receptor proteins involved in chemotaxis and uptake of sugars. Whether ORF1 is required for virulence is uncertain. One transposon insertion resulting in avirulence maps in or near the 5' end of ORF1, and several which do not affect virulence map in its 3' end. ORF1 codes for a putative protein which is homologous to a family of transcriptional activator proteins.

Acetophenones↗
PubMed1989

Cohort and case-control analyses of workers exposed to vinyl chloride: an update.

The mortality in a cohort of workers at a vinyl chloride polymerization plant has been updated, extending the period of observation in the original study from 1974 to 1986. Workers at this plant may have been exposed to vinyl chloride monomer and/or polyvinyl chloride dust, or may have had no exposure to either substance. Seventy-six percent of the work force worked in jobs with potential exposure to vinyl chloride monomer. Among the total cohort, statistically significant excess risks were observed for liver, lung, and brain cancer. For the subcohort of workers exposed to vinyl chloride monomer, the standardized mortality ratio (SMR) for liver cancer was 333 (90% confidence interval (CI) 202 to 521). However, there were no significant excesses of either brain (SMR = 145, 90% CI 78 to 249) or lung cancer (SMR = 115, 90% CI 96 to 141). To investigate dose response, nested case-control studies for liver, brain, and lung cancer were conducted among the total cohort (including the nonexposed). For these studies there were two exposure variables, cumulative dose of vinyl chloride monomer and cumulative dose of polyvinyl chloride dust. Cumulative dose was defined as the product of level and duration of exposure. The only significant association between disease risk and cumulative dose was for liver cancer and cumulative dose of vinyl chloride monomer. Further division of the liver cancers into angiosarcoma (n = 12) and other liver cancers (n = 7), based on review of death certificates and medical records, showed that the dose response existed only for angiosarcomas.

Brain Neoplasms↗
PubMed1989

Nephropathy in cadmium workers: assessment of risk from airborne occupational exposure to cadmium.

To assess the quantitative relation between exposure to airborne cadmium and various markers of renal tubular and glomerular function, 45 male workers employed at a plant that recovers cadmium from industrial waste and 32 male hospital workers of similar age and geographical location were examined. Cumulative external exposure to airborne cadmium (dose) was estimated from historical air sampling data, adjusted for respirator use. Increasing cadmium dose was associated with multiple renal tubular functional abnormalities, including reduced reabsorption of beta-2-microglobulin (beta-2), retinol binding protein (RBP), calcium, and phosphate. Serum creatinine concentration also increased with cadmium dose, suggesting impaired glomerular function. Mean systolic and diastolic blood pressures were higher in the cadmium workers than in the unexposed (134 v 120 mm Hg and 80 v 73 mm Hg respectively), but only systolic blood pressure was significantly associated with cadmium dose in multivariate analyses. Cadmium dose remained the most important predictor of serum creatinine concentration after controlling for age, blood pressure, body size, and other extraneous factors. Logistic regression to model the probability (prevalence) of various renal abnormalities with increasing dose of cadmium was used. The probability of multiple tubular abnormalities and raised serum creatinine concentration increased sharply at cumulative cadmium exposures exceeding 300 mg/m3 days, corresponding to working for 4.3 years at the current permissible United States exposure limit for cadmium dust.

Air Pollutants, Occupational↗
PubMed1988

Study of mortality among chemical workers in the Kanawha Valley of West Virginia.

To assess the mortality experience of a cohort of chemical workers in the Kanawha Valley of West Virginia, 29,139 males who worked at any one of three facilities over a 39-year period were followed-up for vital status. The facilities include two chemical manufacturing plants and a research and development center. From this cohort, 5,785 men were found to have died as of the study end, December 31, 1978. This was less than the 6,148.5 men expected to have died, based upon the United States white male population (standardized mortality ratio (SMR) = 94, 95% confidence interval (CI) = 92-96). Eighty-six specific causes of death were examined. Statistically significant increased deaths were observed for two causes; cancers of the liver (not specified as primary or secondary) (SMR = 174; CI = 102-280) and lympho- and reticulosarcoma (SMR = 140; CI = 104-187). When all biliary and liver cancer was examined by duration and time since initial employment, the SMR for those who worked at least 25 years and whose deaths occurred 30 years or more after first employment was 301 (95% confidence limit = 168-497). The identification and follow-up of this complete cohort provides the basis for future study of subcohorts with specific chemical and process exposures and case control studies of specific causes of death.

Adult↗
PubMed1988

A retrospective cohort mortality study of workers exposed to formaldehyde in the garment industry.

In order to assess the possible human carcinogenicity of formaldehyde we conducted a retrospective cohort mortality study of workers exposed for at least three months to formaldehyde in three garment facilities which produced permanent press garments. A total of 11,030 workers contributing 188,025 person-years were included in the study. Vital status was successfully ascertained through 1982 for over 96% of the cohort. The average (TWA) formaldehyde exposure at the three plants monitored in 1981 and 1984 by NIOSH was 0.15 ppm but past exposures may have been substantially higher. In general, mortality from nonmalignant causes was less than expected. A statistically significant excess in mortality from cancers of the buccal cavity (SMR = 343) and connective tissue (SMR = 364) was observed. Statistically nonsignificant excesses in mortality were observed for cancers of the trachea, bronchus and lung (SMR = 114), pharynx (SMR = 112), bladder (SMR = 145), leukemia and aleukemia (SMR = 113), and other lymphopoietic neoplasms (SMR = 170). Mortality from cancers of the trachea, bronchus and lung was inversely related to duration of exposure and latency. In contrast, mortality from cancers of the buccal cavity, leukemias, and other lymphopoietic neoplasms increased with duration of formaldehyde exposure and/or latency. These neoplasms also were found to be highest among workers first exposed during a time period of high potential formaldehyde exposures in this industry (1955-1962). However, it should be recognized that these findings are based on relatively small numbers and that confounding by other factors may still exist. The results from this investigation, although far from conclusive, do provide evidence of a possible relationship between formaldehyde exposure and the development of upper respiratory cancers (buccal), leukemias, and other lymphopoietic neoplasms in humans.

Female↗
PubMed1988

Bladder tumors in two young males occupationally exposed to MBOCA.

MBOCA (4,4' methylenebis (2-chloroaniline) is a structural analogue of benzidine and is carcinogenic in mice, rats, and dogs. MBOCA has not yet been demonstrated to be carcinogenic in humans and is not regulated as an occupational carcinogen in the United States. We report two noninvasive papillary tumors of the bladder identified in a screening study of 540 workers exposed to MBOCA during its production at a Michigan chemical plant from 1968 to 1979. Both tumors occurred in men under 30 years old who had never smoked. Although the prevalence of grade 1-2 tumors among asymptomatic males in this age group is unknown, the incidence of clinically apparent tumors on U.S. males aged 25-29 is only 1 per 100,000 per year. The detection of the two tumors in young, nonsmoking males is consistent with the hypothesis that MBOCA induces bladder neoplasms in humans.

Adult↗
PubMed1988

Incidence of laryngeal cancer and exposure to acid mists.

To determine the relation between exposure to acid mist and laryngeal cancer, the smoking habits, drinking habits, and incidence of laryngeal cancer of 879 male steelworkers exposed to acid mists during pickling operations was ascertained. Sulphuric acid mist was the primary exposure for most men in this cohort. These men had all worked in a pickling operation for a minimum of six months before 1965, with an average duration of exposure of 9.5 years. Exposures to sulphuric acid in the 1970s averaged about 0.2 mg/m3, and earlier exposures were probably similar. Interviews were conducted with all cohort members or their next of kin in 1986 and medical records of decedents were reviewed. Nine workers were identified who had been diagnosed as having laryngeal cancer, using a conservative case definition that required medical record confirmation for any case among decedents and confirmation by a physician for any case among live individuals. Using data from national surveys of cancer incidence as referent rates, 3.44 laryngeal cancers would have been expected. Excess smoking by the exposed cohort compared with the United States population resulted in an upward adjustment of the expected number of cases of laryngeal cancer to 3.92. The standardised incidence rate ratio for laryngeal cancer was 2.30 (9/3.92), with a one sided p value of 0.01 (assuming a Poisson distribution). The finding of excess laryngeal cancer in this cohort is consistent with four other studies published since 1981.

Alcohol Drinking↗
PubMed1988

The estimated predictive value of screening for illicit drugs in the workplace.

This paper estimates the predictive values of screening tests for six illicit drugs of common concern in the workplace (amphetamines, barbiturates, cocaine, hallucinogens, marijuana, and opiates) using published information on test sensitivity and specificity and survey data on prevalence. Estimated predictive values (negative) were generally high, whereas the estimated predictive value of a positive test ranged from 1 per cent for amphetamines to 100 per cent for hallucinogens and was only 38 per cent for marijuana, the most prevalent drug.

Adult↗
PubMed1988

Use of workers' compensation claims data for surveillance of cumulative trauma disorders.

Workers' compensation claims in Ohio were evaluated as a source of surveillance data for identifying workplaces at high risk of cumulative trauma disorders (CTDs) and analyzed for their demographic and industrial characteristics. During a 5-year period (1980 to 1984), 6,849 workers' compensation claims met the case criteria for CTDs. Tenosynovitis due to continuous motion was the most frequently reported condition (58%), and the wrist was the body part most frequently affected (48%). The highest case rate was observed for female workers in the 36 to 45 age group. Incidence rates for individual companies were determined and those with the highest rates for CTDs were identified. The employer-specific rates for CTDs based on workers' compensation claims data can be used as an effective surveillance tool in locating high-risk operations where ergonomic interventions can be implemented to reduce CTD hazards.

Adolescent↗
PubMed1987

4,4'-Methylenebis (2-chloroaniline): an unregulated carcinogen.

4,4'-Methylenebis (2-chloroaniline) (MBOCA) is a confirmed animal carcinogen. It is used commercially as a curing agent for polymers containing isocyanate. There are no adequate studies documenting a carcinogenic risk for MBOCA in humans; however, studies in rats and dogs have shown that MBOCA is a carcinogen. Also, MBOCA is structurally similar to aromatic amines, which cause bladder cancer in workers with occupational exposure. Manufacture of MBOCA in the United States ceased in 1979. However, estimates of the number of workers potentially exposed range from 1,400 to 33,000 in the manufacture of MBOCA-cured products. Presently, there are no federal regulations limiting occupational exposure to MBOCA. An occupational standard for MBOCA proposed by the Occupational Safety and Health Administration was remanded by the Third Circuit Court of Appeals on procedural grounds in 1974. NIOSH recommended in 1978 that MBOCA be treated as a potential human carcinogen and that worker exposure be controlled so that it does not exceed 3 micrograms/m3 of air determined as a time-weighted average concentration for up to a 10-hour workshift (the lowest level that can be reliably measured). In this paper, we will review the literature in regard to MBOCA's carcinogenicity, describe industrial use and extent of worker exposure, and review MBOCA's status in relation to occupational regulations in the United States and abroad.

Animals↗
PubMed1987

Surveillance of work-related cold injuries using workers' compensation claims.

The usefulness of workers' compensation claims for the surveillance of occupational injuries was evaluated by analyzing claims for cold injury. Five hundred ten claims filed in 1983 from 23 states participating in the Bureau of Labor Statistics Supplementary Data System and an additional 147 claims filed with the Division of Safety and Hygiene of the Industrial Commission of Ohio from Jan 1, 1984, to June 30, 1985, were examined. As expected, the number of injuries per winter day increased as temperature decreased and wind speed increased. The rate of injury began to increase when temperatures fell below 10 degrees F and wind speeds exceeded 10 mph. These weather conditions were milder than previously published cold hazard charts suggest. Frostbite injuries of the lower extremities occurred at milder temperatures, required more lost workdays, and were more costly than cold injuries to the head and face or to the upper extremities. Industries with the highest rates of injury included agriculture, oil and gas extraction, trucking and warehousing, protective services, and interurban transportation. Injuries during nonwinter months involved the processing, distribution, and preparation of food. Vehicle breakdown or contact with water, gasoline, alcohol, or cold water were noted as contributing factors on many of the compensation claims. This probe suggests that claims for workers' compensation adequately reflect the expected association of environmental factors and the occurrence of cold injury.

Absenteeism↗
PubMed1986

Physical and functional map of supervirulent Agrobacterium tumefaciens tumor-inducing plasmid pTiBo542.

Agrobacterium tumefaciens strains carrying pTiBo542 induce large, fast-appearing tumors and have an unusually wide host range. A clone bank was made from this 250-kilobase plasmid in a wide-host-range vector, and restriction maps were determined for BamHI and SalI. The virulence genes, transferred DNA genes, plasmid incompatibility region, and a region that inhibits growth of certain A. tumefaciens strains were localized. The six virulence genes and two tms genes were highly homologous to the genes of pTiA6, but the tmr gene was not. Mutations in each of the six vir loci of pTiA6 were complemented by clones from the vir region of pTiBo542.

Chromosome Mapping↗
PubMed1985

Proportionate mortality study of workers in the garment industry exposed to formaldehyde.

In order to evaluate the human carcinogenicity of formaldehyde, we conducted a proportionate mortality study of garment workers engaged in the production of shirts from formaldehyde-treated cloth. This study included three plants, and was based upon 256 deaths identified from a death-benefit insurance fund. No deaths due to nasal cancer were observed, and the mortality from respiratory cancer (11 cases, PMR = 95) was slightly less than expected. Statistically significant (p less than .05) elevations in proportionate mortality were observed for malignant neoplasms of the "buccal cavity" (three cases, PMR = 750), for "biliary passages and liver" (four cases, PMR = 313) and for "other lymphatic and hematopoietic sites" (four cases, PMR = 400). A proportionate cancer mortality (PCMR) analysis also was conducted, and cancer of the "buccal cavity" (three cases, PCMR = 682), and other "lymphatic and hematopoietic sites" (four cases, PCMR = 342) were still significantly elevated. The observed excesses in cancer mortality were primarily experienced by white females, who made up the major portion of the workforce, and workers with more than 10 years of latency and duration of exposure, a criterion for inclusion for most workers in the study group. The neoplasms observed were not equally distributed among the three facilities included in the study. Because of the small number of deaths involved and the lack of consistency with other studies, we believe that these findings should be viewed cautiously, pending the outcome of more definitive studies.

Adolescent↗
PubMed1985

Specific attachment of Agrobacterium tumefaciens to bamboo cells in suspension cultures.

Agrobacterium tumefaciens was tested for its ability to attach to tissue culture cells of bamboo, a monocotyledonous plant. Phase-contrast microscopy and kinetic experiments with radiolabeled bacteria showed that attachment to bamboo cells was indistinguishable from attachment to cells of dicotyledonous plants. Bacterial mutants defective in attachment to dicotyledonous plants showed similar behavior with bamboo, and extensive washing of the bamboo cells had no effect on the number of bacteria which attached.

Adhesiveness↗
PubMed1985

Renal toxicity in uranium mill workers.

Although the kidney is the critical organ limiting occupational exposure to soluble uranium compounds, there have been no adequate studies evaluating renal tubular dysfunction in chronically exposed workers. The present investigation evaluated kidney function among 39 uranium mill workers and 36 local cement plant workers of equivalent age, sex, and race. The uranium workers showed a significantly higher excretion of beta-2-microglobulin and five amino acids than the reference group. Although the levels of tubular proteinuria were mild, a dose-effect relation existed between the clearance of beta-2-microglobulin, relative to that of creatinine, and the length of time that the uranium workers had spent in the yellowcake drying and packaging area, the work area with the highest exposures to soluble uranium. Age did not account for this relationship. Glomerular function was significantly better among the uranium workers than among the referents, though this may have been the result of differences in the physical activity of the groups during the collection period. The data presented suggest reduced renal proximal tubular reabsorbtion of amino acids and of low molecular weight proteins, consistent with uranium nephrotoxicity.

Adult↗