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Biomedical subjects

C M Bell

Publications and source records attributed to C M Bell.

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

Evaluation of breath alcohol measuring devices intended for evidential use in Victoria.

The accuracy, precision and specificity for ethanol of eight different evidential breath alcohol measuring devices were evaluated. Other factors of importance, such as susceptibility to radio frequency interference and variation in the power supply voltage were also examined. On the basis of the above criteria, three instruments were identified as more suitable than the remainder for evidential use. These three instruments are based on the principle of absorption of infra-red radiation in the 9.5 um region and are the Drager Alcotest 7110, Siemens Alcomat V5.2F and Seres Ethylometre 679. Although the specificity of these instruments was adequate for most substances tested, it was not absolute. As a result, if these devices were introduced for evidential purposes, arguments may arise in the courts with respect to specificity of the devices for ethanol. Such arguments could not be resolved without recourse to physiological and toxicological data.

Breath Tests↗
PubMed1989

Radiation dose and breast cancer risk in patients treated for cancer of the cervix.

The relationship between breast cancer and radiation treatment for cervical cancer was evaluated in an international study of 953 women who subsequently developed breast cancer and 1,806 matched controls. Radiation doses to the breast (average 0.31 Gy) and ovaries (average 32 Gy) were reconstructed for exposed subjects on the basis of their original radiotherapy records. Overall, 88% of the breast cancer cases and 89% of the controls received radiation treatment [relative risk (RR) = 0.88; 95% confidence interval (CI) = 0.7-1.2]. Among women with intact ovaries (561 cases, 1,037 controls), radiotherapy was linked to a significant 35% reduction in breast cancer risk, attributable in all likelihood to the cessation of ovarian function. Ovarian doses of 6 Gy were sufficient to reduce breast cancer risk but larger doses did not reduce risk further. This saturation-type response is probably due to the killing of a critical number of ovarian cells. Cervical cancer patients without ovaries (145 cases, 284 controls) were analyzed separately because such women are at especially low natural risk for breast cancer development. In theory, any effect of low-dose breast exposure, received incidentally during treatment for cervical cancer, should be more readily detectable. Among women without ovaries, there was a slight increase in breast cancer risk (RR = 1.07; 95% CI = 0.6-2.0), and a suggestion of a dose response with the RR being 1.0, 0.7, 1.5 and 3.1 for breast doses of 0, 0.01-0.24, 0.25-0.49 and 0.50+ Gy, respectively. However, this trend of increasing RR was not statistically significant. If low-dose radiation increases the risk of breast cancer among women over age 40 years, it appears that the risk is much lower than would be predicted from studies of younger women exposed to higher doses.

Adult↗
PubMed1989

Leukaemia and residence near electricity transmission equipment: a case-control study.

A population-based case-control study of leukaemia and residential proximity to electricity supply equipment has been carried out in south-east England. A total of 771 leukaemias was studied, matched for age, sex, year of diagnosis and district of residence to 1,432 controls registered with a solid tumour excluding lymphoma; 231 general population controls aged 18 and over from one part of the study area were also used. The potential for residential exposure to power frequency magnetic fields from power-lines and transformer substations was assessed indirectly from the distance, type and loading of the equipment near each subject's residence. Only 0.6% of subjects lived within 100 m of an overhead power-line, and the risk of leukaemia relative to cancer controls for residence within 100 m was 1.45 (95% confidence interval (CI) 0.54-3.88); within 50 m the relative risk was 2.0 but with a wider confidence interval (95% CI 0.4-9.0). Over 40% of subjects lived within 100 m of a substation, for which the relative risk of leukaemia was 0.99. Residence within 25 m carried a risk of 1.3 (95% CI 0.8-2.0). Weighted exposure indices incorporating measures of the current load carried by the substations did not materially alter these risks estimates. For persons aged less than 18 the relative risk of leukaemia from residence within 50 m of a substation was higher than in adults (PR = 1.5, 95% CI 0.7-3.4).

Electromagnetic Fields↗
PubMed1987

Models of the healthy worker effect in industrial cohorts.

The patterns of standardized mortality ratios (SMRs) with duration of follow-up and duration of service which are characteristic of the healthy worker effect in occupational cohort studies have been simulated using models of selection and survivor effects. The models support current theories about the population dynamics which underlie the selection effect but highlight inadequacies in our understanding of the survivor effect. Several possible models were tested and methods of generating appropriate data are discussed. It is important that the healthy worker effect should be better understood as it can present so large a problem in the interpretation of occupational risk estimates.

Adolescent↗
PubMed1987

Second primary malignancy after Hodgkin's disease, ovarian cancer and cancer of the testis: a population-based cohort study.

The risk of second primary malignancy was assessed in a population-based cohort study of all persons registered with Hodgkin's disease (n = 2,970), ovarian cancer (n = 11,802) and testicular cancer (n = 2,013) in the South Thames Cancer Registry during the period 1961-80, to identify for further study those second malignancies which might be treatment-related. A total of 244 second malignancies was observed. After adjustment for age, sex and calendar period, the relative risk of any second malignancy was 1.4 (90% confidence interval (CI) 1.1-1.7) after Hodgkin's disease, 1.1 (90% CI 1.0-1.2) after ovarian cancer and 0.7 (90% CI 0.5-1.0) after testicular cancer. In particular, the relative risk for leukaemia was 11.9 after Hodgkin's disease, 3.7 after ovarian cancer and 2.5 after testicular cancer. Excess risks were also observed for cancers of the cervix and lung after Hodgkin's disease, for cancers of the breast, lung and rectum after ovarian cancer, and for contralateral testicular cancer. Confounding by social class or smoking does not explain these observations. The excess risks of leukaemia and of second cancer were higher in patients first diagnosed with Hodgkin's disease and ovarian cancer in the 1970s than for those first diagnosed in the 1960s. Increased use of multiple-agent chemotherapy regimes for these tumours in the 1970s may have contributed to these increases in excess risk.

Antineoplastic Agents↗
PubMed1987

Aetiological factors in cutaneous malignant melanomas seen at a UK skin clinic.

A clinic-based case-control study was set up in 1961 to examine a variety of aetiological factors in malignant melanoma cases compared with controls with other non-malignant skin conditions. The 268 cases and 1577 controls showed odds ratios of 1.9 for red hair, 2.0 for skin that burns in the sun, and no difference between indoor and outdoor workers or between Celts and other Europeans, consistent with the results of more recent studies. Exposure to 16 specific chemicals was recorded in the study and, among these, men exposed to cutting oils were found to have a significantly raised odds ratio of 1.91. Other statistically significant findings were an elevated risk among women diabetics, particularly in the postmenopausal age group, and a reduced risk of 0.7 among cigarette smokers.

Diabetes Complications↗
PubMed1987

Radiation dose and leukemia risk in patients treated for cancer of the cervix.

To quantify the risk of radiation-induced leukemia and provide further information on the nature of the relationship between dose and response, a case-control study was undertaken in a cohort of over 150,000 women with invasive cancer of the uterine cervix. The cases either were reported to one of 17 population-based cancer registries or were treated in any of 16 oncologic clinics in Canada, Europe, and the United States. Four controls were individually matched to each of 195 cases of leukemia on the basis of age and calendar year when diagnosed with cervical cancer and survival time. Leukemia diagnoses were verified by one hematologist. Radiation dose to active bone marrow was estimated by medical physicists on the basis of the original radiotherapy records of study subjects. The risk of chronic lymphocytic leukemia, one of the few malignancies without evidence for an association with ionizing radiation, was not increased [relative risk (RR) = 1.03; n = 52]. However, for all other forms of leukemia taken together (n = 143), a twofold risk was evident (RR = 2.0; 90% confidence interval = 1.0-4.2). Risk increased with increasing radiation dose until average doses of about 400 rad (4 Gy) were reached and then decreased at higher doses. This pattern is consistent with experimental data for which the down-turn in risk at high doses has been interpreted as due to killing of potentially leukemic cells. The dose-response information was modeled with various RR functions, accounting for the nonhomogeneous distribution of radiation dose during radiotherapy. The local radiation doses to each of 14 bone marrow compartments for each patient were incorporated in the models, and the corresponding risks were summed. A good fit to the observed data was obtained with a linear-exponential function, which included a positive linear induction term and a negative exponential term. The estimate of the excess RR per rad was 0.9%, and the estimated RR at 100 rad (1 Gy) was 1.7. The model proposed in this study of risk proportional to mass exposed and of risk to an individual given by the sum of incremental risks to anatomic sites appears to be applicable to a wide range of dose distributions. Furthermore, the pattern of leukemia incidence associated with different levels of radiation dose is consistent with a model postulating increasing risk with increasing exposure, modified at high doses by increased frequency of cell death, which reduces risk.

Adult↗
PubMed1985

Lectin binding to psoriatic epidermis.

The lectin-binding properties of psoriatic epidermis were assessed using a wide range of lectins. Changes in these properties were found at all levels of differentiation in lesional tissue. There was no clear evidence for an expansion in the population of basal-type cells. Binding of some lectins demonstrated a normal basal-suprabasal boundary. Others bound closer to the dermal-epidermal junction than in normal tissue, and expression of certain normal suprabasal characteristics was found in the basal layer in psoriasis. These findings suggest that the detected changes in psoriatic glycoconjugates reflect a programme of differentiation which is altered rather than incomplete.

Adult↗
PubMed1984

Abnormal pattern of erythrocyte ageing in hereditary spherocytosis as shown by Percoll density gradient centrifugation.

Erythrocytes from individuals with Hereditary Spherocytosis (HS) were fractionated on Percoll density gradients. The osmotic fragility, mean cell volume, mean cell haemoglobin concentration, reticulocyte count and cell morphology of the fractions showed that the gradients separate the erythrocytes according to age, the older small spherocytes appearing in the dense fractions. Comparison of the well established parameters of erythrocyte ageing, pyruvate kinase activity, acetylcholinesterase activity and cell potassium content in normal and HS erythrocyte fractions of similar age revealed abnormalities in the senescence of HS erythrocytes both before and after splenectomy.

Acetylcholinesterase↗
PubMed1984

The release rate of 37Ar from human subjects following intravenous injection.

Two measurements of the exhalation rate of 37Ar following an intravenous bolus injection have been made on a volunteer, and compared with the exhalation rate of 133Xe for the same subject. The results are also compared with a previously reported pilot 37Ar injection study on a second volunteer. During the first 100 min following injection, the 37Ar washout rate was shown to resemble closely the 133Xe washout rate. This result shows that for short time periods after injection, the behaviour of 133Xe may be used to predict 37Ar behaviour.

Argon↗
PubMed1984

Factors affecting the binding of lectins to normal human skin.

Factors affecting the binding of a wide range of lectins to normal human skin were examined in order to evaluate current discrepancies in the literature. The profile of specific binding characteristic for each lectin was found to be variously influenced by the source of conjugate, tissue-processing method, the effectiveness of saccharide inhibitors, and by individual and minor body site variations. Most significantly, the use of routine histological processing not only greatly reduced binding intensity overall but also altered the binding pattern.

Arachis↗
PubMed1983

The retention and release of 37Ar from samples of human bone examined in vitro and a review of the implications for argon transfer from bone in vivo.

The release rates and long term retention of 37Ar produced by the reaction 40Ca(n, alpha) 37Ar, following fast neutron irradiation, have been measured in vitro, in three samples of dried human femur. For each sample, the release rates were fitted to three exponential curves, of half-times approximately 2, 20 and 300 min. Some 60-80% of the 37Ar released was contained in the first component. The release rates for samples of trabecular and cortical bone were qualitatively similar, but after some 20 h the retained fraction of 37Ar was 28 +/- 0.6% in a sample of predominantly trabecular bone, and 33 +/- 0.7% in samples of predominantly cortical bone. The processes affecting the trapping and release of 37Ar from bone crystals are discussed. It is suggested that 37Ar escapes from bone mineral by back-diffusion along recoil damage tracks. The factors affecting the release of 37Ar from bone into the venous blood supply are discussed in the context of in vivo measurements of body calcium by the 37Ar method. The physiological processes and compartments likely to give rise to the long 37Ar exhalation half-times following irradiation in vivo: transfer from the mineralised bone matrix to blood capillaries, and uptake and washout from bone marrow, are considered. Uptake in bone marrow may be responsible for both of the observed half-times.

Argon↗
PubMed1978

In vivo measurement of calcium by the 37Ar method: a study of the effect of recirculating breath collection systems on the exhalation rate.

A study has been made of the effect that different methods of breath collection have on the measurement of calcium in vivo by the 40Ca(n,alpha) 37Ar method. The effect of open and rebreathing breath collection methods has been examined by using intravenous injections of 133Xe. This study has indicated that comparison of calcium measurements between individuals and between centres is likely to be accurate only if breath is collected on 'open circuit'.

Argon↗