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Biomedical subjects

A C Upton

Publications and source records attributed to A C Upton.

At least 19 recordsLinked to original sources
PubMed1991

Radiation, diagnosis, and management.

The biomedical effects of ionizing and nonionizing radiations include responses that are known to have thresholds ("nonstochastic" effects) as well as responses that are presumed to have no thresholds ("stochastic" effects). The latter include mutagenic, carcinogenic, and teratogenic effects. Present radiation risk management strategies seek to protect completely against nonstochastic effects by preventing anyone from accumulating a dose of radiation in excess of the relevant threshold. Protection against stochastic effects, on the other hand, is sought by limiting the level of radiation exposure sufficiently to keep the resulting risks of such effects within acceptable bounds. For this purpose, a limit is placed on the cumulative dose that may be received by any tissue of the body.

Background Radiation↗
PubMed1990

Environmental medicine: introduction and overview.

Human health and longevity have long been known to depend on a complex interplay between hereditary and nonhereditary determinants. The latter include various lifestyle factors, as well as physical and chemical agents encountered in air, food, water, consumer products, the workplace, and the environment at large. Knowledge of these determinants is becoming increasingly important to the physician and other members of society in the maintenance of human health and in the diagnosis and treatment of the diseases of modern life.

Diet↗
PubMed1988

Evolving perspectives on the concept of dose in radiobiology and radiation protection.

Since the discovery of the x ray more than 90 y ago, the biological effects of radiation have been a subject of intensive and continuing study. At the outset, such study was severely hampered by the lack of a suitable method of dosimetry. More than a quarter of a century elapsed before the introduction of a quantitative system for measuring exposure, and another quarter of a century elapsed before the introduction of quantitative units of absorbed dose. In the meantime, the effects of a given dose had long since been found to depend on its distribution in space and time; that is, on the precise spatial and temporal patterns of energy deposition within absorbing tissues and cells. Study of the biological effects of radiation thus led to elaboration of the concept of dose, to take into account relevant microdosimetric parameters. Advances in ongoing research on the molecular mechanisms of radiation effects can be expected to result in further evolution of such coNcepts.

Animals↗
PubMed1988

Carcinogenic risk assessment in proper perspective.

The evidence that human cancers result in large measure from factors related to life style, working conditions, or other extrinsic variables--and are thus, in principle, preventable (Doll and Peto, 1981)--and the hypothesis that there is no threshold for the carcinogenic effects of many cancer-causing agents (Office of Science and Technology Policy, 1985) have spurred efforts to minimize human exposure to carcinogens. In pursuit of this goal, attempts have been made to identify airborne and other extrinsic carcinogens and to assess the extent to which they contribute to the occurrence of cancer. The status of such endeavors is summarized in the following, without any attempt at a comprehensive review, which would be beyond the scope of this report.

Carcinogens, Environmental↗
PubMed1987

Prevention of work-related injuries and diseases: lessons from experience with ionizing radiation.

Almost immediately after the discovery of the Roentgen ray, in 1895, radiation injuries of various kinds began to be encountered in early X-ray workers, radium handlers, radiologists, and exposed patients. The injuries, which were predominantly acute reactions resulting from the killing of cells in affected tissues, were found to be preventable merely by keeping exposures below relevant threshold levels. By the middle of the twentieth century, however, it was realized that thresholds might not exist for certain effects of ionizing radiation, such as mutagenic, carcinogenic, and teratogenic effects. The risks of such effects in workers and other populations exposed to low-level radiation have thus been of increasing concern in recent years. The scientific basis for assessing such risks and the principles that have evolved for their control have important implications for occupational and environmental health in general.

Bone Marrow↗
PubMed1987

Cancer induction and non-stochastic effects.

The mechanisms of carcinogenesis are not known in detail, but there is strong evidence that cancer usually arises from a single transformed cell. Hence, although the process of carcinogenesis appears to require a multiplicity of changes in the affected cancer-forming cell, such as may be associated with successive stages of tumour initiation, tumour promotion, and tumour progression, only one such change induced by radiation in an appropriate cell may be conceived to increase the probability of neoplasia in a suitably susceptible individual. For this reason, carcinogenic effects of radiation, like mutagenic effects of radiation, are considered for purposes of radiological protection to have no threshold and to behave as stochastic phenomena. In contrast, certain other effects of radiation, such as cataract of the lens, infertility, and depression of the bone marrow, require the killing of many cells in the affected organs. Thus, they vary in severity with the extent of cell loss and have thresholds of detectability which depend on the sensitivity with which the consequences of cell loss can be measured.

Cell Survival↗
PubMed1987

The physician in industry.

This article surveys the major types of work-related injuries and diseases, their principal causes, methods for their prevention or control, and the multifaceted role of the physician in occupational medicine.

Accidents, Occupational↗
PubMed1986

Evolving perspectives on the biology and mechanisms of carcinogenesis.

From experimental and epidemiological evidence, radiation-induced cancers appear to arise as multistage, monoclonal growths, which are elicited through various mechanisms, depending on the neoplasm in question and the conditions of exposure. At the molecular level, the process of carcinogenesis may involve the activation of oncogenes and/or the inactivation or loss of anti-oncogenes, through chromosomal rearrangements, point mutations, and other effects of radiation on DNA. In contrast to these mechanisms of carcinogenesis, which result from the absorption of radiation by the tumor-forming cells themselves, abscopal effects resulting from irradiation of other cells may contribute to carcinogenesis under certain conditions, e.g. in the induction of tumors of endocrine target cells through radiation-induced disturbances of hormonal balance. Effects of the latter type, which require the killing of substantial numbers of cells, are not elicited at low doses, thus contrasting with effects of the former type, which may be presumed to have no thresholds. Because radiation carcinogenesis may be mediated through a diversity of effects, the relationship between incidence and dose can vary accordingly. The relationship between the incidence of radiation-induced tumors and the time elapsing after irradiation also varies, depending on the type of tumor in question, species, age at irradiation, exposure conditions, and other factors. Although the variations with dose and time are consistent with multistage models of tumor initiation, tumor promotion, and tumor progression, the precise nature of the successive steps that are involved remains to be determined. The tendency for the tumors to resemble their spontaneous counterparts in age-distribution points to interactions between radiation and other carcinogenic risk factors which are as yet poorly understood. Also poorly understood are species- and organ-differences in susceptibility to radiation carcinogenesis, which bear no consistent relationship to corresponding 'spontaneous' cancer rates.

Age Factors↗