Mortality and cancer incidence of aircraft maintenance workers exposed to trichloroethylene and other organic solvents and chemicals: extended follow up

OBJECTIVES

To extend the follow up of a cohort of 14,457 aircraft maintenance workers to the end of 1990 to evaluate cancer risks from potential exposure to trichloroethylene and other chemicals.

METHODS

The cohort comprised civilians employed for at least one year between 1952 and 1956, of whom 5727 had died by 31 December 1990. Analyses compared the mortality of the cohort with the general population of Utah and the mortality and cancer incidence of exposed workers with those unexposed to chemicals, while adjusting for age, sex and calendar time.

RESULTS

In the combined follow up period (1952-90), mortality from all causes and all cancer was close to expected (standardised mortality ratios (SMRs) 97 and 96, respectively). Significant excesses occurred for ischaemic heart disease (SMR 108), asthma (SMR 160), and cancer of the bone (SMR 227), whereas significant deficits occurred for cerebrovascular disease (SMR 88), accidents (SMR 70), and cancer of the central nervous system (SMR 64). Workers exposed to trichloroethylene showed non-significant excesses for non-Hodgkin's lymphoma (relative risk (RR) 2.0), and cancers of the oesophagus (RR 5.6), colon (RR 1.4), primary liver (RR 1.7), breast (RR 1.8), cervix (RR 1.8), kidney (RR 1.6), and bone (RR 2.1). None of these cancers showed an exposure-response gradient and RRs among workers exposed to other chemicals but not trichloroethylene often had RRs as large as workers exposed to trichloroethylene. Workers exposed to solvents other than trichloroethylene had slightly increased mortality from asthma, non-Hodgkin's lymphoma, multiple myeloma, and breast cancer.

CONCLUSION

These findings do not strongly support a causal link with trichloroethylene because the associations were not significant, not clearly dose-related, and inconsistent between men and women. Because findings from experimental investigations and other epidemiological studies on solvents other than trichloroethylene provide some biological plausibility, the suggested links between these chemicals and non-Hodgkin's lymphoma, multiple myeloma, and breast cancer found here deserve further attention. Although this extended follow up cannot rule out a connection between exposures to solvents and some diseases, it seems clear that these workers have not experienced a major increase in cancer mortality or cancer incidence.

Non-hodgkin's lymphoma and agricultural use of the insecticide lindane

Data from population-based case-control studies of non-Hodgkin's lymphoma among white men from Kansas, Nebraska, Iowa, and Minnesota were pooled to evaluate potential risks from environmental exposures in more detail, while controlling for potential confounding factors. These data provided the opportunity to evaluate the risk of non-Hodgkin's lymphoma from potential exposures to lindane, a pesticide that causes cancer in laboratory animals and has been associated with human cancer in a few epidemiologic investigations. This pooled data set includes 987 individuals with non-Hodgkin's lymphoma and 2,895 population-based controls. Information was obtained by telephone or in person interviews, which included detailed questions on farm practices and agricultural use of chemicals. Logistic regression was used to calculate odds ratios (ORs) adjusted for age, state of residence, and subject or proxy interviews. Reported use of lindane significantly increased the risk of non-Hodgkin's's lymphoma by 50%. Some use characteristics were suggestive of an association. ORs were greater among persons who first used the pesticide 20 years before diagnosis (OR = 1.7) than more recently (OR = 1.3), among those who reported more frequent use (OR = 2.0 for use 5 or more days per year versus 1.6 for fewer than five days per year), and from use on crops (OR = 1.9), rather than from use on animals (OR = 1.3), although these differences were not statistically significant. On the other hand, ORs were lower when based on direct interviews (OR = 1.3) than on data from proxy respondents (OR = 2.1) and adjustment for potential confounding by use of 2,4-D and diazinon reduced the ORs associated with lindane use from 1.5 to 1.2 and 1.3, respectively. Lindane does not appear to be a major etiologic factor in the development of non-Hodgkin's's lymphoma, although a small role cannot be ruled out.

Long-term health effects of the occupational exposure to DDT. A preliminary report

We conducted a proportional mortality study of 1043 deaths among men who took part in an antimalarial campaign in Sardinia, Italy from 1946 to 1950. DDT comprised 94% of the insecticide used during the campaign, and was sprayed over the soil of the entire region at an average concentration of 10 mg/m2, as well as in all dwellings and animal shelters. Expected deaths were derived from the proportional mortality rates of the general Italian male population, specific by cause, 5-year age groups, and 5-year calendar periods in the period from 1956 to 1992. The proportional mortality ratio (PMR) for cardiovascular diseases was significantly decreased, while nonmalignant respiratory diseases showed a 22% increase in risk of borderline statistical significance. Significant increases in risk among workers exposed to DDT in application or inspection jobs were observed for liver and biliary tract cancer (PMR = 228; 95% C.I. = 143-345) and multiple myeloma (PMR = 341; 95% C.I. = 110-795). The PMR for myeloid leukemia was also increased (PMR = 189; 95% C.I. = 38-552), although it was not statistically significant. PMRs for liver and biliary tract cancer and myeloid leukemia were also elevated among workers who did not have direct occupational contact with DDT (liver and biliary cancer: PMR = 210; 95% C.I. = 117-346; myeloid leukemia: PMR = 170; 95% C.I. = 19-614). No trends occurred according to length of employment in exposed jobs. These preliminary results are somewhat in agreement with experimental studies in rodents and previous epidemiologic findings. Expansion of the cohort to include all applications, and collection of information to improve exposure assessment is needed to clarify these findings.

Preferential adhesion of fetal liver derived primitive haemopoietic progenitor cells to bone marrow stroma

The orderly transfer of haemopoiesis from the fetal liver to the medullary cavities during the ontogeny may result from a decrease in the capacity of the fetal liver to support haemopoiesis. Alternatively it could be facilitated by the preferential migration of primitive haemopoietic cells to the marrow. In this study we have compared the ability of high proliferative potential colony forming cells (HPP-CFC) derived from murine fetal liver (FL) on the 15th day of gestation and from murine adult bone marrow (BM) to adhere to either FL or BM derived stromal layers. Adhesion of FL HPP-CFC to bone marrow stromal layers was significantly greater than all other combinations tested. The remarkable affinity of HPP-CFC derived from FL for BM stromal layers is consistent with the preferential migration of haemopoietic cells from the fetal liver to the medullary cavities.

Tobacco, alcohol use, and risks of laryngeal and lung cancer by subsite and histologic type in Turkey

Effects of tobacco smoking and alcohol use on risks of cancers of the larynx and lung have been evaluated extensively in industrialized countries. Few studies on the effect of these risk factors have been reported from developing countries. We conducted a case-control study to evaluate risks of laryngeal and lung cancers in men by subsite and cell type in relation to smoking and alcohol drinking in Turkey, a country where smoking and alcohol consumption patterns are different from those in industrialized countries. We identified 832 laryngeal and 1,210 lung cancer cases and 829 controls with information on smoking and alcohol use (amount and duration) and histologic cell type from an oncology treatment center of a Social Security Agency hospital in Istanbul, Turkey, admitted between 1979 and 1984. Both laryngeal and lung cancer showed significant associations with smoking and alcohol drinking, but no monotonic dose-response was obtained for alcohol drinking. Among smokers, the highest risks were observed in the supraglottis region of the larynx (odds ratio [OR] = 4.1) after adjustment for age and alcohol use. Among alcohol drinkers, the highest risks were observed in the glottis region of the larynx (OR = 1.7) after adjustment for age and smoking. In the analysis by the cell type of lung cancer among ever-smokers, small cell type showed the highest risk (OR = 5.4), while it showed no association with alcohol drinking. Cumulative cigarette use (pack-years) and number of cigarettes per day showed stronger associations than years smoked for both cancer sites. The relative risks of joint exposure to smoking and alcohol were 12.2 for laryngeal cancer and 14.1 for lung cancer among heavy smokers and heavy alcohol drinkers. This study provides epidemiologic evidence from Turkey that smoking and alcohol use are associated with risks of cancers of the larynx and lung.

Dichlorodiphenyltrichloroethane serum levels and breast cancer risk: a case-control study from Mexico

Some, but not all, epidemiological studies have suggested that dichlorodiphenyltrichloroethane (DDT) may play a role in the development of breast cancer. These investigations have been conducted in countries where this substance has been banned for at least 20 years. We conducted a study in Mexico, a country in which DDT is still being used to control malaria. In a hospital-based case-control study, we compared 141 histologically confirmed cases of breast cancer with 141 age-matched controls (+/-3 years). All subjects were identified at three referral hospitals of Mexico City between March 1994 and April 1996. Reproductive histories and other variables were obtained by structured interviews, DDT/DDE levels were determined in serum by gas-liquid chromatography. The arithmetic mean of serum DDE in lipid basis was 562.48 +/- 676.18 ppb (range, 10.24-4661.44) for the cases and 505.46 +/- 567.22 ppb (range, 0.004 to 4361.75) for the controls, but this difference was not statistically significant. The age-adjusted odds ratios for breast cancer regarding the serum level of DDE were 0.69 (95% confidence interval, 0.38-1.24) and 0.97 (confidence interval, 0.55-1.70) for the contrasts between tertile 1 (lowest level) and tertiles 2 and 3, respectively. These estimates were unaffected by adjustment for body mass, accumulated time of breast-feeding and menopause, and other breast cancer risk factors. These results do not lend support to the hypothesis that DDT is causally related to breast cancer at the body-burden levels found in our study population but do not exclude the possibility that higher levels of exposure could still play a role in the etiology of this tumor.

A nested case-control study of non-Hodgkin lymphoma and serum organochlorine residues

BACKGROUND

The steady worldwide increase in the incidence of non-Hodgkin lymphoma during the past few decades remains mostly unexplained. Several studies suggest that there may be an association between the agricultural use of the organochlorine 1,1,1-trichloro-2,2'bis(p-chlorophenyl)ethane (DDT) and increased risk of non-Hodgkin lymphoma. We have investigated the association between risk of non-Hodgkin lymphoma and body burden of selected organochlorines in the general population in a nested case-control study.

METHODS

We measured prediagnostic serum concentrations of DDT, its metabolites, and other organochlorines, including polychlorinated biphenyls (PCBs), in 74 cases of non-Hodgkin lymphoma and 147 matched controls identified from a prospective cohort of 25,802 adults, established in 1974 in Washington County, Maryland, USA. We report results for total lipid-corrected serum concentrations of DDT and total PCBs.

FINDINGS

There was a strong dose-response relation between quartiles of total lipid-corrected serum PCB concentrations and risk of non-Hodgkin lymphoma overall (odds ratios by quartile: 1.0; 1.3 [95% CI 0.5-3.3]; 2.8 [1.1-7.6]); and 4.5 [1.7-12.0]; p for trend = 0.0008) and separately in men and in women. There was also evidence suggesting that seropositivity for the Epstein-Barr virus early antigen potentiated the effects of serum PCBs. By contrast, total lipid-corrected serum concentrations of DDT were not associated with risk of non-Hodgkin lymphoma.

INTERPRETATION

These results should be regarded as hypothesis-generating. Before causal inferences can be made about exposure to PCBs and increased risk of non-Hodgkin lymphoma, our findings require replication and the biological plausibility of the association needs further investigation.

Proportional mortality of dichloro-diphenyl-trichloroethane (DDT) workers: a preliminary report

The authors conducted a proportional mortality study of 1,043 deaths that occurred between 1956 and 1992 among men who used mainly dichloro-diphenyl-trichloroethane (DDT) in an anti-malarial campaign in Sardinia, Italy, during the late 1940s. For each cause of interest, investigators compared observed deaths with expected deaths. The estimated DDT exposure ranged from 170 to 600 mg/m3 in indoor operations and from 24 to 86 mg/m3 in outdoor operations. Workers directly exposed to DDT had a significant increase in risk for liver and biliary tract cancers (PMR = 228; 95% confidence interval = 143, 345) and multiple myeloma (PMR = 341; 95% confidence interval = 110, 795). However, the PMR for liver and biliary tract cancers was also elevated among workers who did not have direct occupational contact with DDT, and the authors observed no increase in either PMR, by number of days in exposed jobs. Perhaps DDT did not increase the risk or perhaps occupational exposure, although quite high, did not further increase the risk, compared with the heavy baseline exposure of the entire Sardinian population, (i.e., mainly through diet and drinking water). Expansion of the cohort to include all exposed workers, and collection of information to improve exposure assessment are needed to clarify these findings.

Why immunise. Care giver understanding of childhood immunisation

Currently in Australia, both the National Health and Medical Research Council (NHMRC) and the Public Health Association have stated that our immunisation uptake levels are not of a high enough percentage within the population to prevent outbreaks of childhood vaccine preventable diseases (1996). While the literature discusses factors that are believed to influence care givers' decisions to vaccinate their children, few Australian studies focus on care giver understanding of childhood diseases and vaccination. The purpose of this descriptive study was to profile care givers who presented their children for vaccination at public health clinics regarding their level of understanding of childhood vaccine preventable diseases. Two hundred and forty eight care givers attending one of six public clinics were asked to respond verbally to a researcher administered questionnaire. Demographic information as well as information related specifically to immunisation was collected from each participant. The major findings of this preliminary study indicate a very low level of knowledge among careers presenting their child for vaccination at the public health clinic. Twenty-three percent of carers had no knowledge regarding the vaccinations that their child was receiving and the disease for which the vaccination was administered. In fact, 18 percent of care givers were unsure of the relationship between vaccination and the likelihood of their child contracting an infectious disease. The personal health record was not found to be useful as an educational resource. Although 99 percent of care givers had the booklet in their possession only 8 percent had referred to it as a source of information. The major sources of information were identified as child health nurses (44%) and hospital midwives (34%). The results of this study highlight the disparity in knowledge levels among care givers with regards to vaccination and the diseases they prevent and the important role of the midwife and child health nurse in disseminating information relating to immunisation.

Informational needs of women with a recent diagnosis of breast cancer: development and initial testing of a tool

This study developed and tested the Toronto Informational Needs Questionnaire-Breast Cancer (TINQ-BC), a questionnaire designed to identify the information which women with a recent diagnosis of breast cancer need to deal with their illness. The 73-item questionnaire had content validity based on findings in the literature and opinions of expert oncology nurses. It was administered to 114 women with a recent diagnosis of breast cancer during chemotherapy (n = 39), radiation therapy (n = 40) or surgery (n = 35). Item analysis determined that 51 items in five subscales should be retained in the questionnaire. The subscales, labelled Disease, Investigative Tests, Treatments, Physical, and Psychosocial had good internal consistency reliabilities with Cronbach's alphas of 0.81 to 0.93. Informational needs of women were high with mean scores over 200 in a possible range of 51-255. Informational needs were greatest in either the Disease or Treatments subscales. Marital status, level of education, and level of income were not related to level of informational need. Younger women had a greater need for information than older women (r = -0.35, P = 0.003). The results suggest that information is important to help women with breast cancer manage their illness. Nurses should give women an opportunity to ask questions and be prepared to give accurate information.

Reactive chemicals and cancer

Epidemiologic evidence on the relation between reactive chemicals and cancer is reviewed. These highly reactive chemicals (acrylonitrile; bis[chloromethyl]ether and chloromethyl methyl ether; 1,3-butadiene, ethylene oxide; formaldehyde; mustard gas; sulfuric acid; and vinyl chloride) vary in use and exposure. All are animal carcinogens that also have received considerable epidemiologic attention. Acrylonitrile is a chemical of current economic importance. The epidemiologic evidence is quite weak, but the available studies were very small. Epidemiologic studies clearly demonstrate that bis (chloromethyl) ether and chloromethyl methyl ether cause lung cancer. Continued follow-up of exposed workers is encouraged to provide information on risks for other cancers. Results from epidemiologic studies of butadiene-exposed workers are somewhat inconsistent, but the largest study with the best exposure assessment found the largest relative risk for leukemia. The failure of several larger studies to replicate the early Swedish findings of a very strong association between leukemia and ethylene oxide has not been adequately explained. Epidemiologic studies of formaldehyde provide limited evidence for an association with cancer of the nasopharynx and possibly with nasal cancer. These very rare tumors, however, are difficult to study epidemiologically. Mustard gas is a well-established lung carcinogen, but a recent follow-up of the English cohort suggests that other sites also may be affected. Sulfuric acid appears to cause laryngeal cancer. A suggested relationship with lung cancer in a few studies is of concern because of the widespread opportunity for exposure from ambient air pollution. Vinyl chloride causes angiosarcoma of the liver, but a large, multi-country study provided no clear evidence that other sites are affected.

Lack of expression of Thy-1 (CD90) on acute myeloid leukemia cells with long-term proliferative ability in vitro and in vivo

Acute myeloid leukaemia (AML) is thought to be maintained by a small population of leukemic progenitor cells. To define the phenotype of such cells with long-term proliferative capacity in vitro and in vivo, we have used the production of leukemic clonogenic cells (CFU) after 2 to 8 weeks in suspension culture as a measure of these cells in vitro and compared their phenotype with that of cells capable of engrafting nonobese diabetic severe combined immune deficient (NOD/SCID) mice. Leukemic blast peripheral blood cells were evaluated for expression of CD34 and Thy-1 (CD90) antigens. The majority of AML blast cells at diagnosis lacked expression of Thy-1. Most primary CFU-blast and the CFU detected at up to 8 weeks from suspension cultures were CD34+/Thy-1-. AML cells that were capable of engrafting NOD/SCID mice were also found to have the CD34+/Thy-1- phenotype. However, significant engraftment was achieved using both CD34+/Thy-1- and CD34- subfractions from one AML M5 patient. These results suggest that while heterogeneity exists between individual patients, the leukemic progenitor cells that are capable of maintaining the disease in vitro and in vivo differ from normal hematopoietic progenitor cells in their lack of expression of Thy-1.

Pesticides and cancer

The authors discuss pesticide exposure in both agricultural and nonagricultural occupations, referring to a variety of studies on the cancer risks of specific pesticides. Adult and childhood cancer are addressed, and direction for future research efforts is offered.

Tobacco and non-Hodgkin's lymphoma: combined analysis of three case-control studies (United States)

The role of tobacco in the etiology of non-Hodgkin's lymphoma (NHL) was evaluated in a combined analysis of data from three population-based case-control studies conducted in four midwestern states of the United States: Nebraska, Iowa, Minnesota, and Kansas. Interviews were obtained from 1,177 cases (993 men, 184 women) and 3,625 controls (2,918 men, 707 women) or, if deceased, from their next-of-kin. Overall, there was no association between NHL and tobacco use (odds ratio [OR] = 1.0, 95 percent confidence interval [CI] = 0.8-1.1) or cigarette smoking (OR = 1.0, CI = 0.8-1.1). A slight negative association evident in analyses by intensity and duration of smoking was not present when interviews from proxy respondents were eliminated. There was a suggestion of a positive association between smoking and NHL among women (OR = 1.3, CI = 0.9-1.9), although there was no clear exposure-response relationship. This large case-control analysis provides no evidence that smoking is linked to the development of NHL among men. The possible role of smoking in the etiology of NHL among women needs further evaluation.

The Agricultural Health Study: factors affecting completion and return of self-administered questionnaires in a large prospective cohort study of pesticide applicators

Response rates were examined in a prospective epidemiologic study of individuals, mostly farmers, from Iowa and North Carolina seeking a pesticide applicator license during the period from 1994 through 1996. In the first year of enrollment 16,535 farmers (representing 77% of eligible farmer applicators) enrolled in the study by completing a 17-page questionnaire administered at a pesticide training session; 47% of the enrolled farmers completed and returned a much longer take-home questionnaire. The characteristics of farmers who completed only the enrollment questionnaire were quite similar to those of farmers who also completed and returned the take-home questionnaire. The most notable difference was the increased age of responders. Thus, the study population might have slightly higher cumulative farm exposures and slightly lower current farm exposures than the base population of all farmer applicators. The lack of evidence for substantial selection bias is reassuring for the Agricultural Health Study, and provides a measure of reassurance for other studies depending on the voluntary completion of self-administered questionnaires.

Avoided and avoidable risks of cancer

Despite the considerable efforts and funds devoted to cancer research over several decades, cancer still remains a mainly lethal disease. Cancer incidence and mortality have not declined at the same rate as other major causes of death, indicating that primary prevention remains a most valuable approach to decrease mortality. There is general agreement that environmental exposures are variously involved in the causation of the majority of cancer cases and that at least half of all cancers could be avoided by applying existing etiologic knowledge. There is disagreement, however, regarding the proportion of cancer risks attributable to specific etiological factors, including diet, occupation and pollution. Estimates of attributable risks are largely based today on unverified assumptions and the calculation of attributable risks involves taking very unequal evidence of various types of factors and treating them equally. Effective primary prevention resulting in a reduction of cancer risk can be obtained by: (i) a reduction in the number of carcinogens to which humans are exposed; or (ii) a reduction of the exposure levels to carcinogens. Exposure levels that could be seen as sufficiently low when based on single agents, may actually not be safe in the context of the many other concomitant carcinogenic and mutagenic exposures. The list of human carcinogens and of their target organs might be quite different if: (i) epidemiological data were available for a larger proportion of human exposures for which there is experimental evidence of carcinogenicity; (ii) more attention was paid to epidemiological evidence that is suggestive of an exposure-cancer association, but is less than sufficient, particularly in identifying target organs; and (iii) experimental evidence of carcinogenicity, supported by mechanistic considerations, were more fully accepted as predictions of human risk.

The challenges of assessing outcome in chronic pain

Clinicians in chronic pain services are facing the need to develop meaningful and methodologically adequate measures, not only to evaluate the effectiveness of interventions and to assure quality, but also to support the continued funding and future development of such services. Explores the problems inherent in assessing outcomes in chronic pain. These include the complexity of the chronic pain syndrome itself, the multidimensional nature of interventions and the challenges of defining outcomes in the chronic illness syndrome. The complexity and challenges of assessing outcomes may lead to some reticence in facing the challenges but it is the responsibility of the clinicians to continue developing measures and to communicate to purchasers and other stake holders the complexity of assessing outcomes in chronic pain.

Occupational epidemiologic study design and application

Occupational epidemiologic investigations have provided, and will continue to provide, important information to understand environmental causes of disease. High-quality investigations designed to test hypotheses have several requirements. They must include valid quantitative assessments of exposure, some information on lifestyle risk factors, and include biologic monitoring and marker components whenever possible. Availability of these data allows a clear evaluation of potential confounders and biases, assessment of interaction among risk factors, and provides the opportunity to identify susceptible subgroups.

Newborn screening for HLA markers associated with IDDM: diabetes autoimmunity study in the young (DAISY)

Autoimmunity causing insulin-dependent diabetes mellitus (IDDM) begins in early childhood due to interactions between genes and unknown environmental factors that may be identified through follow-up of a large cohort of genetically susceptible children. Such a cohort has been established using a simple and rapid cord blood screening for HLA alleles. The DRB1 and DQB1 second exon sequences were co-amplified using the polymerase chain reaction and hybridized with single and pooled sequence-specific oligonucleotide probes. Four individual probes were used to detect the susceptibility alleles DRB1*03, DRB1*04, and DQB1*0302 as well as the usually protective DRB1*15/16 (DR2) alleles. In addition, pooled probes allow the distinction of DR3/3 from the DR3/x genotype (where x is neither DR2, 3, nor 4) and DR4/4 from DR4/x. Among 5000 newborns from the general Denver population, we have found the high-risk genotype (DRB1*03/ DRB1*04, DQB1*0302) to be present in 2.4% of non-Hispanic whites, 2.8% of Hispanics, and 1.6% of African Americans. The moderate-risk genotypes (DRB1*04, DQB1*0302/DRB1*04, DQB1*0302, DRB1*04, DQB1*0302/x, or DRB1*03/DRB1*03) are present in 17% of American non-Hispanic whites, 24% of Hispanics and in 10% of African Americans. These results demonstrate the feasibility of a large-scale newborn screening for genes associated with IDDM. The ultimate role for such a screening in future routine prediction and prevention of IDDM will depend on the availability of an effective and acceptable form of clinical intervention.

Beta-cell autoantibodies in infants and toddlers without IDDM relatives: diabetes autoimmunity study in the young (DAISY)

Little is known concerning the natural history of beta-cell autoimmunity in infants and toddlers, especially in those without a first degree IDDM relative. A population-based cohort of Colorado infants at increased IDDM risk due to their HLA genotype has been identified through a PCR-based HLA screening of cord blood and is being prospectively studied. We report the distribution of insulin (IAA), GAD65 (GAA), and ICA512 autoantibody levels in 312 children aged 9 months and in 131 children aged 15 months from this cohort, without family history of IDDM. The levels of IAA, GAA and ICA512 did not differ by the HLA genotype (DR3/4,DQB1*0302 vs. DR3/3, vs. DR2/DR4,DQB1*0302 vs. DRx/4,DQB1*0302, where x is not DR3 or DR2), by ethnicity (non-Hispanic whites vs. other ethnic groups), or by age (9 vs. 15 months). The 95th and 99th percentiles of the IAA distribution were respectively 40 and 61 nU/ml at the age of 9 months and 38 and 59 nU/ml at the age of 15 months. The 95th and 99th percentiles of the GAA distribution were respectively 0.020 and 0.046 at the age of 9 months and 0.022 and 0.098 at the age of 15 months. We propose to use IAA levels greater than 60 nU/ml and GAA index greater than 0.05 to define the presence of beta-cell autoimmunity in children younger than 2 years.

Characterization of a hierarchy in human acute myeloid leukemia progenitor cells

Despite the usual uniform and primitive appearance of cells derived from the leukemic clone in most patients with acute myeloid leukemia (AML), there is considerable heterogeneity among leukemic blasts, particularly with respect to their capacity to proliferate and/or self renew. We have assessed whether these differences in proliferative potential are correlated with the phenotypic changes that characterize normal hematopoiesis, which might suggest an analogous hierarchy of AML progenitors. We have used the ability of primitive AML cells to persist or produce blast colony forming cells (CFU-blast) detected after 2 to 8 weeks in the presence of growth factors in suspension cultures (SC) termed SC-initiating cells (IC), or with stroma in long-term cultures (LTC-IC) as a quantitative assay for a cell that may have primitive characteristics. This SC assay is linear, cell concentration independent, and the frequency of SC-IC by limiting dilution analysis is lower than primary CFU-blast. The average output of CFU-blast after 2 to 8 weeks by individual SC-IC varied between 2 and more than 100 in individual patients. Leukemic blasts were sorted based on their expression of antigens previously found useful to characterize normal progenitor differentiation, and analyzed for the percentage of CFU-blast SC-IC, and leukemic LTC-IC within each fraction. All of these progenitor types were heterogeneous in their expression of CD45RA and CD33, but expressed uniformly low levels of CD15 and differed from normal primitive progenitors in their high expression of HLA-DR. CFU-blast had a significantly higher expression of CD71 and CD38 as compared with SC-IC or leukemic LTC-IC. In patients with CD34+ blasts, the majority of their SC-IC at 4 weeks were CD34+/CD38-; however, patients with CD34- blasts had at least some CD34- progenitors. These results show that while heterogeneity exists between patients, it is possible to physically separate subpopulations of AML cells with different proliferative potentials. It also provides some support for the concept that quantitation of leukemic cells capable of producing CFU-blast for 4 weeks or more in vitro measures a less frequent leukemic progenitor with higher proliferative potential that may be the only relevant cell for maintaining the leukemic clone in vivo.

Regulation of two pair-rule stripes by a single enhancer in the Drosophila embryo

Previous studies on the regulation of the segmentation gene even-skipped (eve) have centered on the transcription of stripe 2. Here, we characterize another enhancer module contained within the complex eve promoter that directs expression of stripes 3 and 7. This enhancer is approximately 500 bp in length and maps approximately 3.3 kb upstream of the transcription start site. The stripe 3 + 7 enhancer appears to be regulated by one or more ubiquitously distributed activators, including components of a JAK-Stat pathway. The two-stripe pattern results via multiple tiers of repressors which delimit this ubiquitous activation. The zinc finger repressor hunchback appears to be responsible for establishing the anterior border of stripe 3 and the posterior border of stripe 7. knirps, a member of the nuclear receptor family of transcription factors, appears to establish the posterior border of stripe 3 and the anterior border of stripe 7. Activator and repressor proteins bind in vitro to several sites within the enhancer. These findings suggest a general model for the regulation of segmentation stripes, whereby enhancers integrate positional information provided by broadly distributed activators and spatially restricted repressors.

The Agricultural Health Study

The Agricultural Health Study, a large prospective cohort study has been initiated in North Carolina and Iowa. The objectives of this study are to: 1) identify and quantify cancer risks among men, women, whites, and minorities associated with direct exposure to pesticides and other agricultural agents; 2) evaluate noncancer health risks including neurotoxicity reproductive effects, immunologic effects, nonmalignant respiratory disease, kidney disease, and growth and development among children; 3) evaluate disease risks among spouses and children of farmers that may arise from direct contact with pesticides and agricultural chemicals used in the home lawns and gardens, and from indirect contact, such as spray drift, laundering work clothes, or contaminated food or water; 4) assess current and past occupational and nonoccupational agricultural exposures using periodic interviews and environmental and biologic monitoring; 5) study the relationship between agricultural exposures, biomarkers of exposure, biologic effect, and genetic susceptibility factors relevant to carcinogenesis; and 6) identify and quantify cancer and other disease risks associated with lifestyle factors such as diet, cooking practices, physical activity, smoking and alcohol consumption, and hair dye use. In the first year of a 3-year enrollment period, 26,235 people have been enrolled in the study, including 19,776 registered pesticide applicators and 6,459 spouses of registered farmer applicators. It is estimated that when the total cohort is assembled in 1997 it will include approximately 75,000 adult study subjects. Farmers, the largest group of registered pesticide applicators comprise 77% of the target population enrolled in the study. This experience compares favorably with enrollment rates of previous prospective studies.