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M C Pike

Publications and source records attributed to M C Pike.

At least 235 records · Page 13Linked to original sources
PubMed1983

Estimation of the distribution of age at natural menopause from prevalence data.

Nearly 30% of US women reach menopause (defined as cessation of menstrual periods) as a consequence of an operation. This biases the observable distribution of age at natural menopause. Another problem with estimating this distribution from a cross-sectional study is the clustering of reported age at natural menopause around ages ending in zero and five (Mac-Mahon B, Worcester J. Age at menopause, United States 1960-1962. Washington DC: National Center for Health Statistics, 1966. Vital and health statistics, Series 11: Data from the National Health Survey, no. 19. (DHEW publication no. (HSM) 66-1000)). This paper discusses the approach of Mac-Mahon and Worcester to this problem and compares it with a competing risks approach.

Adult↗
PubMed1983

Secular trends in the distributions of the breast cancer risk factors--menarche, first birth, menopause, and weight--in Hiroshima and Nagasaki, Japan.

The results of a mail survey completed by approximately 21,000 female atomic bomb survivors in Hiroshima and Nagasaki in 1970 are studied with respect to menarche, first birth, menopause, and weight. These known risk factors for breast cancer can be used to explain some but not all of the differences in Japanese and US breast cancer rates. The results for age at menarche are the most striking, with the presence of a strong secular trend. The average age at menarche in Japan was observed to decrease from 16.4 years for women born in 1902 to 14.4 years for women born in 1942. However, a temporary increase was observed in women whose menarche was expected to occur during the war years of the early 1940s. Differences between US and Japanese women were also observed in age at first birth and nulliparity rates. Age at menopause was similar for the two groups, although US women have a considerably higher rate of surgically induced menopause. Within each birth cohort, it is shown that body weight is negatively correlated with age at menarche and positively correlated with age at menopause.

Adult↗
PubMed1983

Estrogen exposure during gestation and risk of testicular cancer.

In this case--control study of 108 cases of testicular cancer in men under 30 years of age, cryptorchidism was a major risk factor [relative risk (RR) = 9.0]. Low birth weight was also associated with increased risk (RR = 3.2). Having severe acne at puberty was protective (RR = 0.37). Interviews with mothers of cases revealed that exposure of the mother to exogenous estrogen during pregnancy created a significant risk in the son (RR = 8.0). In first pregnancies, excessive nausea indicated an increased risk of testicular cancer (RR = 4.2). Increased body weight in the mother also increased the risk. The relation between these factors and testicular hypoplasia is discussed. Severe perimenopausal menorrhagia was a factor in the mother associated with reduced risk of testicular cancer in the son (RR = 0.10). A modified hormonal milieu in the mother appears to be important in the later development of testicular cancer in her sons.

Acne Vulgaris↗
PubMed1983

Hepatitis, alcohol consumption, cigarette smoking, and hepatocellular carcinoma in Los Angeles.

Seventy-eight black patients and white patients with primary hepatocellular carcinoma (PHC), 70 years or younger at diagnosis, and 78 age-, sex-, and race-matched neighborhood controls were interviewed. Information sought included usual dietary and drinking habits, cigarette smoking habits, prior medical conditions including a history of hepatitis, prior exposure to blood products, and occupational history. Cigarette smoking was a risk factor for PHC; the relative risk (RR) for current smokers of more than one pack/day compared to nonsmokers was 2.6. Alcohol consumption was also a significant risk factor for PHC; individuals who drank 80 g or more of ethanol per day had a RR of 4.2 compared to those drinking less than 10 g/day. In addition, a history of hepatitis (RR = 13.0) and a history of blood transfusions (RR = 7.0) were significant risk factors for PHC. Each of these factors remained significant after adjustment was made for the others.

Alcohol Drinking↗
PubMed1982

Descriptive epidemiology of cancers of the upper respiratory tract in Los Angeles.

The descriptive epidemiology of cancer of three upper respiratory tract sites (lip; mouth and pharynx, excluding nasopharynx; and nose, sinus and nasopharynx) was explored using data from 1972-1976 from the population-based cancer registry covering Los Angeles County, California. In addition, the proportion of Los Angeles cases at each site which are explained by tobacco use was estimated using attributable risks calculated from previously published case-control studies. Causes of nontobacco-related cases are considered. Lip cancer was found to be a disease predominantly of white males with a male/female ratio of 9.8 for the lower lip and of 1.0 for the upper lip. Tobacco use is responsible for 60% of male lip cancers, and incidence rates of lip cancer after subtraction of the proportion of the incidence due to tobacco use were more than three times greater in men than in women. A hypothesis is proposed that an important etiologic factor is exposure to sun, wind and cold which results in chapping; this exposure is most intense for the lower lip; and the use of lip coverings in women protects their lips both from the sun and from chapping. Cigarette smoking was responsible for 51% of mouth and pharynx cancer in men and women in Los Angeles County, and after subtraction of the proportion of the incidence due to smoking, rates in men and women were similar. Factors such as poor dentition and nutritional deficiencies may help explain demographic characteristics such as the higher rates of mouth and pharynx cancer among men and women in the lower social classes and the secular decline in incidence rates. Cancers of the nose, sinus and nasopharynx were found to occur among workers in a wide range of occupations and industries which involved inhalation of dust, fumes and vapors. High incidence rates of nasopharynx cancer were observed among Chinese in Los Angeles and high rates of sinus cancer among Spanish-surnamed residents. Cancers at these sites appear to be related to the action of carcinogens on tissue chronically irritated by repeated upper respiratory infections or allergic responses. In addition racial differences in the physical structure of the nasal passage may influence where inhaled particles are deposited.

California↗
PubMed1982

Transmethylation reactions regulate affinity and functional activity of chemotactic factor receptors on macrophages.

Methylation mediated by S-adenosyl-L-methionine is required for the chemotaxis of mononuclear leukocytes. We investigated whether transmethylation reactions are required for normal functioning of chemotactic factor receptors. Three chemoatractant-mediated functions in macrophages, chemotaxis, the stimulated release of arachidonic acid from membrane phospholipids and superoxide production, are markedly depressed by agents that inhibit cellular methylation reactions. Treatment of macrophages with methylation inhibitors decreased the affinity of the N-formylated chemoattractant receptor present on these cells by a factor of 4.5, but did not significantly alter the total receptor on macrophages can exist in more than one affinity state and that an ongoing methylation reaction is required for the maintenance of the receptor in its higher affinity form. Inhibition of methylation lowers the affinity of the receptor and renders it nonfunctional or "uncoupled" in its ability to produce chemotaxis, superoxide and the release of a arachidonic acid from leukocyte membranes.

Adenosine↗
PubMed1982

An empirical approach to the statistical analysis of mutagenesis data from the Salmonella test.

A number of recent papers have suggested basing the statistical analysis of Salmonella (Ames) mutagenicity test results on a mathematical model of the complete dose-response curve. For most mutagens at low doses the curve increases linearly; then, as the dose increases, the curve may flatten and finally turn downwards due primarily to effects of toxicity. The exact mechanism underlying this shape is, however, not well understood and is likely to vary for different chemicals. A different approach is to assume that the initial part of the curve is linear and to base the statistical analysis solely on this region, reasoning that it contains most of the interpretable information about the mutagenesis dose response. In this paper a formal method of deciding which points are on the initial linear part of the curve is described, and a statistical method is proposed for analyzing these points. Computer simulations are used to examine the properties of the procedure and comparisons are made with a previously proposed mathematical model of the whole curve. It is concluded that the method suggested here provides a very satisfactory, robust method for the standard analysis of Salmonella data.

Dose-Response Relationship, Drug↗
PubMed1982

Endogenous hormones as a major factor in human cancer.

Hormone-related cancers account for almost 30% of all cancer cases in the United States. Data from animal experiments and from epidemiological and endocrinological studies in humans support the hypothesis that the individual hormones which control normal growth of target organs can also create the proper conditions for neoplastic transformation. The concept that hormones can cause, i.e., increase the incidence of, human cancer is most developed for the four hormone-related cancers which are numerically the most important, namely, breast, prostate, endometrium, and ovary. Even for these sites, large gaps remain in our knowledge of the responsible hormones and the conditions which create the optimal opportunity for carcinogenesis. Although scanty, the available epidemiological evidence also suggests a hormonal role in the pathogenesis of testis cancer, thyroid cancer, and osteosarcoma. We believe that the primary prevention of all these cancers will probably depend on modification of the factors which affect the secretion and metabolism of the responsible hormones rather than on control of exposure to classical exogenous initiators.

Adolescent↗
PubMed1982

Approximate confidence intervals for probabilities of survival and quantiles in life-table analysis.

For survival probabilities with censored data, Rothman (1978, Journal of Chronic Diseases 31, 557-560) has recommended the use of quadratic confidence limits based on the assumption that the product of the 'effective' sample size at time t and the life-table estimate of the survival probability past time t follows a binomial distribution. This paper shows that the proposed confidence limits are asymptotically correct for continuous survival data. These intervals, as well as those based on the arcsine transformation, the logit transformation and the log(--log) transformation, are compared by simulation to those based on Greenwood's formula--the usual method of interval estimation in life-table analysis. With large amounts of data, the alternatives to the Greenwood method all produce acceptable intervals. On the basis of overall performance, the intervals suggested by Rothman are preferred for smaller samples. Any of these methods may be used to generate confidence sets for the median survival time or for any other quantile.

Actuarial Analysis↗
PubMed1982

Epidemiological characteristics of adenocarcinoma of the lung in Los Angeles County.

The descriptive epidemiology of adenocarcinoma of the lung was compared with that of squamous cell carcinoma with the use of data for 1972-76 from the population-based cancer registry serving Los Angeles County. Several differences in the demographic characteristics between these two types of lung cancer were observed, including low male-to-female ratios and lack of social class gradients for adenocarcinoma. Cigarette smoking was responsible for 90% of squamous cell carcinoma in both men and women and for 79% of male and 46% of female adenocarcinoma. We also studied incidence rates of lung cancer after subtraction of the proportion of the incidence due to smoking by using data from a previously conducted case-control study in Los Angeles County. These residual rates for squamous cell carcinoma showed a fivefold excess in males compared with females, whereas those for adenocarcinoma were almost the same in men and women. These findings indicate that 1) smoking is etiologically less important for adenocarcinoma than for squamous cell carcinoma, and 2) other etiologic factors for adenocarcinoma affect women as much as men.

Adenocarcinoma↗
PubMed1981

The effect on lipids and lipoproteins of a contraceptive vaginal ring containing levonorgestrel and estradiol.

Lipids and lipoproteins were studied in controls and women using contraceptive vaginal rings (CVRs). The groups were comparable for race, age, parity, obesity indices, alcohol ingestion, smoking, diet and exercise. Fasting blood samples were obtained twice before CVR treatment, after 2 and 7 weeks of treatment and 1 week thereafter. The women using the CVR had a significant incremental reduction of cholesterol from baseline to treatment which was distributed among all the lipoprotein classes. The cholesterol/HDL-C ratio was significantly increased with treatment. All mena changes were within the reference range. The reduction in HDL and especially in the subclasses HDL 2a and HDL 2b were significant and outside the reference range. The LDL/HDL ratio increased significantly, while the LDL/HDL 2a+2b ratio increased significantly outside the reference range with treatment. Of the lipid and lipoprotein measurements that changed significantly with treatment, HDL-C, HDL, HDL 2a LDL/HDL and LDL/HDL 2a+2b changed significantly towards baseline in the 1-week-off treatment. The potential reduction in predicted coronary risk with the use of the CVR suggested by a reduction in cholesterol was counterbalanced by a reduction in HDL-C and increases in the cholesterol/HDL-C and LDL/HDL ratios. The potential clinical implications of these findings remain to be determined.

Adult↗
PubMed1981

Oral contraceptive use and early abortion as risk factors for breast cancer in young women.

A case-control study was conducted in Los Angeles County, California, of 163 very young breast-cancer cases (all aged 32 or less at diagnosis) to investigate the role, if any, of oral contraceptives (OC) in the development of the disease. OC use before first full-term pregnancy (FFTP) was associated with an elevated risk, which increased with duration of OC use (relative risk approximately 2.2 at 6 years of use, P < 0.01). This increased risk could not be explained by other risk factors. OC use after FFTP was not associated with any change in risk. A first-trimester abortion before FFTP, whether spontaneous or induced, was associated with a 2.4-fold increase in breast-cancer risk (P < 0.005).

Abortion, Induced↗
PubMed1981

Elevated levels of prolactin in nulliparous women.

Follicular-phase (Day 11) plasma prolactin, and plasma and urinary oestrogen levels of 70 nulliparous nuns were compared with those of 80 of their sisters, of whom 62 were parous. The nuns and their nulliparous sisters did not differ significantly in their prolactin and oestrogen levels. No differences in plasma oestrogens or urinary oestriol ratio were found between the parous and the nulliparous women. However, the mean prolactin level of the nuns and their nulliparous sisters was 35% higher than that of the parous women in the sample taken approximately 1 3/4 h after rising (p less than 0.0005), and 24% higher (P less then 0.01) in the 2nd sample taken 2 h later. The elevation was independent of age, weight, and age at menarché. Age at first full-term pregnancy, at least up to the age of 30, and second or subsequent full-term pregnancies had no further effect on prolactin level. This study suggests that the effect of early first full-term pregnancy in lowering breast cancer risk may be mediated, at least in part, by permanently lowering the level of circulating prolactin.

Adult↗
PubMed1981

Alterations of new methylated phospholipid synthesis in the plasma membranes of macrophages exposed to chemoattractants.

Chemotactic factors have been shown to inhibit the methylation of phosphatidylethanolamine in macrophages without affecting total phospholipid synthesis. It would thus be anticipated that newly synthesized membranes of macrophages exposed to chemoattractants would have an increased ratio of phosphatidylethanolamine to its methylated derivatives. These ratios were measured directly in newly synthesized phospholipids of plasma membranes isolated from guinea pig peritoneal macrophages. The phosphatidylethanolamine: methylated phospholipid ratio in such plasma membranes was increased by 53 to 111% upon exposure of the cells to chemotactic factors. This increase was due to decreased synthesis of methylated phospholipids and not to altered formation of phosphatidylethanolamine or activation of phospholipases. Methylated phospholipid ratios were also studied in the leading front lamellipodia isolated from macrophages migrating under chemotactic and nonchemotactic conditions. The phosphatidylethanolamine:methylated phospholipid ratios were increased up to fourfold in lamellipodia of macrophages migrating towards chemotactic agents when compared to those from cells migrating randomly. Biophysical changes in the plasma membrane produced by an increase in the ratio of phosphatidylethanolamine:methylated phospholipids as a result of exposure of cells to chemoattractants may be required for sustained directed migration.

Animals↗