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Biomedical subjects

R W Morgan

Publications and source records attributed to R W Morgan.

At least 73 records · Page 4Linked to original sources
PubMed1982

Age at menarche, probability of ovulation and breast cancer risk.

An analysis is undertaken of the frequency of ovulation in 17 groups of women aged 15 to 19 who had been the subjects of other studies. A urine specimen of at least 8 h accumulation had been provided on the 20th or 21st day of a menstrual cycle by 681 women. Analysis is restricted to 431 specimens which had been collected between 11 and 3 days prior to the onset of the subsequent menstrual period. A pregnanediol concentration of less than 1 mg per litre in such a specimen was taken as evidence that the cycle was anovular. The probability of a cycle being anovular was inversely and significantly related to the number of years since menarche, and, with years since menarche held constant, was positively but not significantly associated with age at menarche. This observation indicates that women with early menarche do not have a longer duration of exposure to anovular cycles than do those whose menarche is delayed, and that variation in the duration of exposure to post-menarcheal anovular cycles does not explain the association of breast cancer risk with early age at menarche. The 17 groups of women were classified into four categories according to ethnic origin and breast cancer incidence in the populations from which they derived. Anovular cycles were not more common in the high-risk groups; indeed, the two centers in the lowest risk category had the highest proportion of anovular cycles.

Adolescent↗
PubMed1982

Smoking as a risk factor in cancer of the cervix: additional evidence from a case-control study.

The results of a case-control study in Toronto, Canada, demonstrated a two-fold risk of invasive squamous cell carcinoma of the cervix among current smokers relative to women who had never smoked. This significant effect of smoking was not diminished by simultaneously adjusting for age, education, and indices of sexual behavior. This association was further supported by the observations that ex-smokers were at a lower risk than current smokers (1.7 versus 2.3), and that the risk increased with the amount of cigarettes smoked (2.2 for less than half a pack per day to 2.9 for more than one pack per day).

Adult↗
PubMed1981

A general mortality study of production workers in the paint and coatings manufacturing industry. A preliminary report.

Information has been obtained on a cohort of 16,243 men employed for at least one year in the manufacture of paint or vanish after January 1, 1946, and for seven subgroups on the basis of exposure. These workers experienced a level of mortality that compares favorably with that of the U.S. white male population. The workers' pattern of mortality differed somewhat from the U.S. pattern, with considerably reduced mortality from psychiatric, metabolic, respiratory, and violent causes. There was an increased mortality due to bowel and rectal cancer. While the numbers are smaller, there are also increased rates for liver and skin cancer. Lung cancer rates, while not in excess of the national average, did not match the low mortality from nonmalignant, noninfectious respiratory disease. The authors have concluded that work in this industry presents no major health hazard.

Carcinogens, Environmental↗
PubMed1981

Mortality among ethylene oxide workers.

Because of reports linking an increased risk of leukemia with exposure to ethylene oxide, a mortality study of workers with potential exposure to ethylene oxide at the Texaco Chemical Company Plant in Port Neches, Tex., was undertaken. A total of 767 males with potential exposure to ethylene oxide were identified. Forty-six deaths occurred in this cohort with 80 expected (standardized mortality ratio; SMR = 58). No deaths from leukemia were seen, nor were there any statistically significant excesses from any specific causes of death.

Ethylene Oxide↗
PubMed1981

Airborne carcinogens and human cancer.

There is as yet little convincing evidence that air pollution contributes to cancer risk, save for the strong suspicion of an increase in risk for persons living adjacent to arsenic emitters. The lack of any demonstrated direct and strong relationship between pollution and cancer, as well as the absence of any easily identifiable cancer epidemic in polluted areas, leads us to suspect that if a relationship exists, it is relatively weak and contributes little to the total cancer burden, especially in comparison to hazards such as cigarette smoking. There is a need for further research to verify our conclusions.

Adult↗
PubMed1981

Aroclor 1254-induced intestinal metaplasia and adenocarcinoma in the glandular stomach of F344 rats.

Ingestion of diets containing Aroclor 1254, a mixture of polychlorinated biphenyls, for 2 years led to a dose-related increase in the incidence of focal lesions in the glandular stomachs of male and female F344 rats. The incidence of stomach lesions was 6% in control specimens and in specimens from rats fed a diet containing 25, 50, or 100 ppm Aroclor 1254, the incidences of stomach lesions were 10, 17, and 35%, respectively. The majority of gastric lesions in treated rats were histologically identified as intestinal metaplasia characterized by an architecture resembling that of intestinal crypts and particularly by goblet cells, which stained with Alcian blue and periodic acid-Schiff reagent. Adenocarcinomas were found in six specimens. Most (88%) of the lesions were located in the pyloric region of the glandular stomach. No multiple lesions were observed among 47 control specimens examined; however, nine cases of multiple lesions were observed in 30 lesion-containing specimens from Aroclor 1254-treated rats. Although the exact relationship between gastric intestinal metaplasia and adenocarcinoma remains to be established, they commonly coexist and may share initiating mechanisms.

Adenocarcinoma↗
PubMed1981

Detection of mutagens-carcinogens: carcinogen-induced lesions pinpointed by alkaline phosphatase activity in fixed gastric specimens from rats.

Alkaline phosphatase (AP) activity was not detectable by histochemical staining in the glandular stomachs of normal rats. However, AP activity was present at high levels in the brush borders of the intestine and persisted after fixation of the tissues in Formalin at room temperature. Foci of AP activity were detected in gross Formalin-fixed specimens of glandular stomachs of male and female inbred F344 rats exposed to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and killed over 6 years ago. The incidence of AP-positive foci increased in proportion to the dose of the carcinogen MNNG. Histologically, most of the grossly visible AP-positive foci corresponded to areas of intestinal metaplasia and adenocarcinoma. AP-positive foci localized sites of pathologic significance for microscopic examination and pinpointed gastric sites containing very early tumors that were missed by standard examination.

Adenocarcinoma↗
PubMed1981

Cystic disease, family history of breast cancer, and use of oral contraceptives.

Epidemiologic studies show a lower frequency of fibrocystic breast disease among users of oral contraceptives than among women who have never used them. Family history of breast cancer appears to be more common among benign breast disease patients than among their controls. To determine the use of oral contraceptives and the presence of family history of breast cancer, information was obtained from 211 cystic cases and their matched controls from the metropolitan Toronto area. Cystic cases compared to controls had a higher proportion of women with a family history of breast cancer (21% vs 15%). For both a positive and negative family history of breast cancer, as well as for all women combined, the mean duration of oral contraceptive use was lower for cystic cases than for controls. The odds ratio for oral contraceptive use according to family history of breast cancer for cystic cases and controls was 0.42 and 0.81 respectively. The possibility that a woman is more protected against benign breast disease by using oral contraceptives if she has a family history of breast cancer deserves more attention in future investigations on the long-term effects of birth control pills.

Breast Diseases↗
PubMed1981

Benign breast disease: estriol proportions and family history of breast cancer.

Urine samples were analyzed for estrone (E1), estradiol (E2), and Estriol (E3) to test the hypothesis that women diagnosed with benign breast disease (high risk for breast cancer?) will have lower estriol proportions (E3/E1 + E2 + E3) than a comparison control group. Luteal urine samples were collected from 64 women recently diagnosed with benign breast disease (cases) and from 64 controls matched for age and education. Compared to their controls, benign breast disease patients had a lower mean weight (P less than 0.05), lower Quetelet's index (P less than 0.02), and higher frequency of family history of breast cancer (P less than 0.01) and of family history of any breast disease (P less than 0.01). The mean estriol proportions were similar for cases and controls before and after stratification by family history and Quetelet's index. Results of this study indicate that if women with benign breast disease are at high risk of breast cancer, that risk is not transmitted by the estriol proportion.

Adult↗
PubMed1979

Exercise prescription: a clinical trial.

To assess the effectiveness of physician prescribed exercise, health education, and patient self-monitoring, 124 firefighters were medically screened and randomly allocated to a control and two treatment groups. Physiologic and reporting methods were employed to assess adherence to regular exercise at three months and six months after the initial exercise prescription. Addition of a health education program significantly improved compliance over that achieved by a physician consultation. Self-monitoring did not produce a further increase in compliance. Improvement in the treatment groups was limited to three months after prescription; at six months, the treatment and control populations had similar exercise patterns.

Adult↗
PubMed1978

Effects of chemical and physical mutagens on the frequency of a large genetic duplication in Salmonella typhimurium. I. Induction of duplications.

In Salmonella typhimurium a simple selection has been described to detect bacteria that are merodiploid for almost one-third of the chromosome. The selective procedure is based upon improved utilization of L-malate as the sole carbon source in merodiploid strains. The spontaneous frequency of the duplication in haploid strains is approximately 10(-4) per cell plated. Following the exposure of a haploid strain to mutagenic agents, there is a dose-dependent increase in the duplication frequency above the spontaneous level. In this paper we describe the induction of genetic duplications in Salmonella typhimurium by X-rays, ultraviolet light (UV), ethyl methanesulfonate (EMS), nitrous acid, and the azaacridine half mustard, ICR-372.

Acridines↗
PubMed1978

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.

Aza Compounds↗
PubMed1978

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.

Adolescent↗
PubMed1978

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.

Breast Neoplasms↗
PubMed1978

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.

Age Factors↗