Chromosome analysis of lymphocytes from workers at an ethylene oxide plant.

Samples of peripheral blood were collected from 33 men who had been employed in the manufacture of ethylene oxide for between 1 and 14 years, and from 32 men from other parts of the same plant who were used as controls. Their lymphocytes were analysed for chromosome damage. There were low frequencies of polyploidy, chromatid aberrations and chromosome breaks in the cells of the 65 men. A slightly higher frequency of chromatid aberrations was observed in the cells of the ethylene oxide workers than in those of the controls, but the difference between the two groups was not statistically significant. There was a positive correlation between length of employment in the ethylene oxide group and the numbers of aberrations in the cultures of each individual. This trend was not solely attributable to the age of the men. The levels of chromatid and chromosome damage observed in this study are consistent with those in humans who have not recently been exposed to known chromosome-breaking agents.

Cytogenetic, immunological, and haematological effects in workers in an ethylene oxide manufacturing plant.

Samples of blood were collected from a group of plant workers engaged in the manufacture of ethylene oxide (EO) for periods of up to 14 years and also from a group of control personnel matched by age and smoking habits. Peripheral blood lymphocytes were cultured for cytogenetic analysis. Selected immune and haematological parameters were also investigated. The results of these studies showed no statistically significant difference between the group of plant workers and the control group in respect of any of the biological parameters investigated in this study. Nevertheless, duration of employment in EO manufacturing was positively correlated (p less than 0.05) with the frequency of chromosome breaks and with the percentage of neutrophils in a differential white blood cell count and negatively correlated (p less than 0.05) with the percentage of lymphocytes. As the values of these parameters remained within the normal limits of control populations, the correlations were considered to have no significance for health. Atmospheric concentrations of EO were determined using personnel air samplers and were generally below the detection limit (less than 0.05 ppm) during stable plant operations, although transient concentrations of up to 8 ppm were occasionally recorded. The amount of alkylation (2-hydroxyethyl groups) of the Nt atom of histidinyl residues in haemoglobin was also measured in an attempt to gauge recent individual exposures to EO. Variable but, in most instances, readily measurable amounts of Nt-(2'-hydroxyethyl)-L-histidine (Nt represents the N3 atom of histidine) were found in the haemoglobin of plant workers and in the control group who had not knowingly been exposed to an exogenous source of EO. There was no statistically significant difference between the results obtained in the control group and in the group of plant workers.

Chromosome analysis from peripheral blood lymphocytes of workers after an acute exposure to benzene.

A spillage of about 1200 gallons of benzene occurred during the loading of a ship, and 10 workers on a single shift were exposed to benzene. Shortly afterwards, an assay of the urine of these individuals showed that substantial amounts of phenol were being excreted. About three months after the incident samples of venous blood were taken from 10 individuals exposed to benzene and 11 men on a comparable shift who acted as controls. The lymphocytes were stimulated to divide in short term cultures. For each subject, 200 cells at metaphase were examined for chromosome damage using 48 h cultures, and sister chromatid exchanges (SCE) were analysed from about 30 cells in their second division, using 72 h cultures. The most frequent types of aberrations in all the individuals were chromatid gaps, with occasional breaks of chromatids and chromosomes. There were few exchanges within or between the arms of chromatids or chromosomes. More cells in the control than in the exposed group showed damage, an effect that was especially noticeable for chromatid gaps. All values, however, were considered to be within a normal range. There were slightly more SCE in some of the exposed individuals than in the controls and there was a trend towards a positive association between the frequency of SCE recorded for each individual and the maximum value for the excretion of phenol in the urine on the day after the incident. There is no evidence to indicate that benzene induced any type of lasting chromosome damage in the lymphocytes of the 10 exposed workers when cells were examined about three months after the incident.

The quantitation of sister chromatid exchanges in lymphocytes of cancer patients at intervals after cytotoxic chemotherapy.

Venous blood was taken from patients with cancer, prior to and up to 42 days after the administration of cytotoxic chemotherapy. Lymphocytes were stimulated to divide in vitro, and examined for sister chromatid exchanges (SCEs). Cyclophosphamide rapidly increased the frequency of SCE, which returned to approximately double the control value 24 hr after administration. The remaining SCEs disappeared more slowly. There was a positive correlation between the dose of drug and the frequency of SCE measured immediately and 4 hr, 20 hr and 21 days after treatment. As patients received successive courses of treatment the number of SCEs generally increased from about 0.14 to 0.25 per chromosome. After this, further chemotherapy was often less effective in inducing them. The presence of SCEs in peripheral blood lymphocytes may be a useful indicator for the occurrence and persistence of alkylating metabolites, residual damage in the DNA and individual responses of patients to a standard regimen.

Sister chromatid exchanges in human lymphocytes exposed to single cytotoxic drugs in vivo or in vitro.

Venous blood was taken from apparently healthy volunteers and patients with cancer, the latter both before and at intervals after treatment with single cytotoxic drugs. Cells from untreated individuals were exposed to a range of concentrations of drugs in culture medium. Chlorambucil, treosulfan and cyclophosphamide (activated by hepatic microsomes) significantly increased the numbers of SCEs, both in vitro and in the lymphocytes of patients. While methotrexate and 5-fluorouracil had no effect, bleomycin slightly increased the number of SCEs, but only in vitro. Although the in vitro dose-effect relationship indicated which drugs would increase the frequency of SCE in vivo, the magnitude of the response tended to be overestimated. When patients were treated with drugs the frequency of SCE increased, then declined with time. Though this complicates the quantitative relationship between dose and damage, SCEs may be useful to monitor the effects of alkylating agents on normal tissues.

Sister chromatid exchanges in human lymphocytes treated with combinations of cytotoxic drugs.

Lymphocytes from peripheral blood of either 'normal' donors or patients with cancer were stimulated to divide in culture medium containing 5-bromo-2'-deoxyuridine. During 74 hr of incubation, the cells were exposed to single agents or to permutations of two combinations of chemotherapeutic drugs, namely MOPP or cyclophosphamide and methotrexate. Only mustine and cyclophosphamide (activated and not activated) increased the frequency of sister chromatid exchanges (SCE). Neither vincristine, procarbazine or prednisolone with mustine, nor methotrexate with cyclophosphamide altered the number of SCEs expected from the use of mustine or cyclophosphamide alone. There was no difference in the response of cells from cancer patients and 'normal' subjects to the drugs. If the drugs of these two regimens do interact with one another to enhance the amount of subcellular damage, this is not manifested by changes in the number of SCEs in human lymphocytes in vitro.