Effects of chemical and physical mutagens on the frequency of a large genetic duplication in Salmonella typhimurium. II. Stimulation of duplication-loss from merodiploids

Strains of Salmonella typhimurium which contain a duplication of approximately 30% of the genome may be obtained by a simple selective procedure. These strains are highly unstable, losing the duplication when grown on non-selective medium. In this paper we report that treatment of merodiploid bacteria with mutagenic agents stimulates the rate at which haploid segregants are obtained from merodiploid strains. The mutagens which have been tested for this effect are X-rays, ultraviolet light (UV), ethyl methanesulfonate (EMS), and the azaacridine half-mustard ICR-372.

A comparison of dietary methods in epidemiologic studies

Three methods of estimating group and individual dietary consumption have been developed and assessed in a case-control study of diet and breast cancer. The methods comprised a 24-hour recall, a detailed quantitative diet history directed to the most recent two-month period and the two-month period six months before, and a four-day diet diary. There is a high degree of correlation between the estimates of food consumption for the controls using each of the methods. The highest estimate was obtained from the diet history, with a slightly higher estimate in the period six months before than the current period, while the lowest is found in the 24-hour recall. The latter corresponds with the same method in a Nutrition Canada Survey. It is concluded that all methods ara applicable to case-control studies, but the diet history is preferred when current food intake may be influenced by a disease.

An epidemiologic study of breast cancer

A case-control study has been conducted in four areas of Canada in which 400 cases of breast cancer matched by age and marital status with neighborhood controls were administered medical and dietary questionnaires. The study is suggestive of an increased risk of breast cancer in post-menopausal women with younger age at menarche and an increased risk with delay of age at natural menopause. No protective effect of early age at first pregnancy was demonstrated in either pre- or post-menopausal women. An increased frequency of pregnancies of four months duration or less was found in cases compared to controls and a greater frequency in pre-menopausal cases compared to controls of a history of irregular menstrual periods. In pre-menopausal women no association has been found between increased height and weight as risk factors for breast cancer. For post-menopausal women, however, a weak association with increased height has been found, while a strong association with increased weight both at the time of menopause and the 12 months preceding diagnosis has ben confirmed.

A study of diet and breast cancer

A case-control study has been conducted in four areas in Canada in which 400 cases of breast cancer matched by age and marital status with neighborhood controls were administered a medical and dietary history questionnaire, a 24-hour recall for dietary information and a four-day diet record. The Study has produced evidence of an association between an increased intake of nutrients, especially total fat, in both pre-menopausal and post-menopausal women with breast cancer. Reasons why a weak association might have been anticipated are discussed, and it is concluded that in reality the association is stronger. Furthermore, its consistency with other evidence, both experimental and international, suggests that it is causal.

Estrogen profiles in young women: effect of maternal history of breast cancer

To examine the hypothesis that familial breast cancer risk is related to estrogen metabolism, we analyzed urines of daughters of breast cancer patients and their matched controls for estrone (E1), estradiol (E2), and estriol (E3). From this, we computed estriol proportions (E3/E1 + E2 + E3). "Patient-daughters" and the matched controls showed no differences in estriol proportions. Our results failed to support the hypothesis that high-risk women (those with a family history of breast cancer) have relatively lower estriol proportions, and we concluded that whatever family history contributes to breast cancer risk, that risk is not likely to be transmitted by the estrogen profile.

Asbestos, smoking, and laryngeal carcinoma

This study was designed to examine the relationship between exposure to asbestos and laryngeal cancer. A retrospective study of 43 pairs of patients with laryngeal cancer and their matched controls examined a number of variables, including smoking, exposure to asbestos, and other occupational factors. Patients with laryngeal cancer and the controls were matched for age, sex, and place of residence. The data indicate a substantial association between asbestos exposure and laryngeal cancer. Cigarette smoking was also associated with the disease, although the strength of association was not as high as that for asbestos. Exposure to uranium, chromium, nickel, cobalt, arsenic, x-rays, and alcohol did not appear related to later development of carcinoma of the larynx. We conclude that exposure to asbestos and cigarette smoking are potent factors in the development of this disease.

Chronic open-angle glaucoma and ocular hypertension. An epidemiological study

An epidermiological study of patients with chronic simple glaucoma or ocular hypertension suggests that the diagnosis of glaucoma is associated with a positive family history, acute blood loss, and diabetes mellitus. There was no association with other vascular disease or with smoking. Ocular hypertension was related to smoking habits but not to family history. The relationship of these variables to ocular hypertension/glaucoma status is discussed.

Inuit myopia: an environmentally induced "epidemic"?

Among Inuit less than 30 years old the prevalence of myopia is far in excess of that of their elders. This is especially true for females. There seems to be little, if any, genetic contribution to this "epidemic" of myopia in the young. The age and sex distribution indicates the likelihood of an environmental factor, probably cultural, being responsible for the current pattern. Other data implicate school attendance as a possible etiologic factor.

Bladder cancer: smoking, beverages and artificial sweeteners

A matched patient-control study of bladder cancer examined the relationship of the disease to occupation, smoking and intake of tea, coffee, cola, alcohol and artificial sweeteners.There was no association of disease with occupation for these patients. Heavy smoking gave relative risks of 6.37 and 4.36 for men and women respectively; there was evidence of a dose-response relationship. Tea and coffee intake did not increase the risk of disease nor did prolonged use of artificial sweeteners. Alcohol and cola intake increased the relative risk of bladder cancer among male smokers. There is some suggestion that smoking interacts with both alcohol and cola intake in the production of bladder cancer.

Etiology of breast cancer. III. Opportunities for prevention

Breast cancer, or its effects, may be preventable. Childbearing at an early age will confer some protection. Until there are other methods of primary prevention the physician must concentrate on secondary prevention, including screening. In presenting risk factors as criteria for screening we have attempted to make rational the use of screening technology. We should not easily accept screening for breast cancer as of proved value. Rather we must encourage clinical trials of various screening methods. In the meantime, while we engage in a moderate amount of screening we do so under the Scottish verdict of "not proven".

Etiology of breast cancer. II. Epidemiologic aspects

The epidemiology of breast cancer is reviewed with particular emphasis on its etiology. A number of studies suggest that differences in breast cancer incidence are associated with differences in marital status, number of pregnancies, age at menarche, age at menopause, height and weight, socioeconomic status, geographic location and residence. However, in no case is the evidence adequate to establish a "cause and effect" relationship. The genetic component of these associations may be of primary importance, while other conditions such as marital status are probably indirect reflections of the operation of more fundamental factors.There is a general consensus that endocrine factors play an important part in mammary cancer occurrence. At present, the association between breast cancer and the presence of the virus-like (type B) particles in human milk is not established.

Etiology of breast cancer. I. Genetic aspects

The subject of breast cancer is reviewed with particular emphasis on the genetic aspect of its etiology. A number of studies using various approaches gave the same results: the familial form occurs earlier and there is a higher risk in female members of the breast-cancer families. An association between breast cancer and cancer of certain other sites among women is reported. Cytogenetic studies of "cancer families" revealed increased frequency of aneuploidy in some members. However, the role of chromosome abnormalities in carcinogenesis is still not clear.