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Biomedical subjects

J B Keller

Publications and source records attributed to J B Keller.

At least 19 recordsLinked to original sources
PubMed1991

Low-grade, latent prostate cancer volume: predictor of clinical cancer incidence?

We hypothesize that each cell in low-grade (Gleason grade 1-3) prostate cancer tissue is at risk of transformation into a cell which produces a high-grade (Gleason grade 4-5) clinical cancer after a short period of growth. As a consequence, the volume of low-grade, latent cancer tissue in the prostate glands of men at any age determines their incidence rate for high-grade, clinical cancer a few years later. Autopsy and incidence data for both white men and black men support this conclusion, with a tumor growth period of about 7 years. The transformation rate is similar for black men and for white men, about 0.024 high-grade cancers per year per cm3 of low-grade, latent cancer volume. Our hypothesis explains the infrequent occurrence of clinical cancer despite the high prevalence of latent cancer, the steep rise of clinical cancer incidence with age despite the slow rise of latent cancer prevalence with age, and the disparities in clinical cancer incidence among some populations despite their similar latent cancer prevalence. This hypothesis suggests that low-grade cancer volume is a critical determinant of clinical cancer risk.

Adult↗
PubMed1991

Mathematical model of granulocytopoiesis and chronic myelogenous leukemia.

We present a mathematical model of granulocytopoiesis that depends on certain physiologically meaningful parameters. By choosing different values of these parameters, the model describes both the normal process and that in chronic myelogenous leukemia (CML). The model fits all the available experimental data tested. Furthermore, it shows how the CML cells can ultimately outnumber the normal cells and how this process can be very slow. The model provides a quantitative approach to the relationship between proliferation and maturation and resolves the apparent contradiction between decreased proliferation and increased production, by assuming that a greater fraction of CML cells is produced by division rather than by maturation. The model should be helpful in designing experiments to better define the abnormalities of proliferation and maturation in CML and in seeking to define the specific alterations in the cell regulatory networks resulting from the production of the chimeric p210bcr-abl protein characteristic of CML.

Granulocytes↗
PubMed1991

Family data determine all parameters in Mendelian incomplete penetrance models.

We show that data on the frequency of occurrence of an hereditary trait in family members can be used to determine all four parameters in a Mendelian genetic model with incomplete penetrance. Thus previous statements in the literature that such data can determine only three combinations of the parameters are incorrect.

Alleles↗
PubMed1991

Pulmonary function and cardiovascular risk factor relationships in black and in white young men and women. The CARDIA Study.

Pulmonary function is known to be related inversely to incidence of coronary heart disease, congestive heart failure, chronic obstructive lung disease, lung cancer, and death from all causes. Reasons for some of these associations are poorly understood. Relationships between cardiovascular disease risk factors and pulmonary function were examined in 5,115 18- to 30-year-old black and white male and female participants in the study of Coronary Artery Risk Development in Young Adults (CARDIA). Forced expiratory volume in 1 s adjusted for height (FEV1/Ht2) was significantly lower in smokers than nonsmokers and in persons who reported shortness of breath; FEV1/Ht2 was correlated positively with a history of strenuous physical activity, duration of exercise on the treadmill, and high-density lipoprotein cholesterol. It was associated negatively with skinfold thicknesses, serum triglycerides, fasting serum insulin, and the Cook Medley scale of hostility. The association between pulmonary function and heart disease risk may reflect associations with physical fitness, vigor, fatness, and lipid profiles, as well as with cigarette smoking.

Adolescent↗
PubMed1991

Comparison of respiratory symptoms and pulmonary function between two communities; Tecumseh (US) and Bordeaux (France).

Respiratory symptoms, pulmonary function and smoking habits in two adult populations, aged 20-59 years, are compared in Tecumseh (Michigan) and Bordeaux (France). Personal, demographic, and medical characteristics were ascertained by self-administered questionnaires; Forced vital capacity and Forced expiratory volume in one second (FEV1) were measured. In Tecumseh, the proportion of smokers was higher, people started to smoke earlier and the number of cigarettes per day was higher, the differences were significant. The prevalences of respiratory symptoms tended to be higher in Tecumseh than in Bordeaux although the differences did not reach statistical significance. The age-adjusted odds ratios according to smoking and socio-economic status for respiratory conditions, or relating FEV1 less than 80% predicted did not differ significantly but tended to be greater in Tecumseh. These trends might suggest a greater morbidity and/or a greater impact of risk factors in Tecumseh.

Adult↗
PubMed1990

Health and other characteristics of employed women and homemakers in Tecumseh, 1959-1978. I. Demographic characteristics, smoking habits, alcohol consumption, and pregnancy outcomes and conditions.

Using data collected in 1959-60 and 1978-79 in the Tecumseh Community Health Study, characteristics of 866 women aged 20-44 years at baseline were analyzed according to employment status at baseline and follow-up (employed/employed, homemaker/employed, employed/homemaker and homemaker/homemaker). To avoid the bias of including unhealthy women with homemakers, disabled and retired women were excluded. Women employed at both exams more frequently reported current alcohol consumption than other women, and the association persisted after controlling for covariables. Smoking habits, rates of reported pregnancy outcomes and conditions, and rates of gynecological problems did not differ significantly among employment groups.

Adult↗
PubMed1990

Health and other characteristics of employed women and homemakers in Tecumseh, 1959-1978. II. Prevalence of respiratory and cardiovascular symptoms and illnesses, mortality rates and physical and physiological measurements.

Using data collected in 1959-60 and 1978-79 in the Tecumseh Community Health Study, characteristics of 866 women aged 20-44 years at baseline were analyzed according to employment status, at baseline and follow-up (employed/employed, homemaker/employed, employed/homemaker, and homemaker/homemaker). To avoid the bias of including unhealthy women with homemakers, disabled and retired women were excluded. There were few significant differences in health among the groups. Prevalence rates of respiratory conditions were slightly higher at follow-up for women employed at both exams, while prevalence rates of cardiovascular conditions were slightly higher for homemakers at follow-up. The rate of reporting heart attacks was significantly higher for homemakers at both exams, although rates of diagnosed coronary heart disease were similar among employment groups.

Adult↗
PubMed1989

Ocular dominance column development: analysis and simulation.

The visual cortex of many adult mammals has patches of cells that receive inputs driven by the right eye alternating with patches that receive inputs driven by the left eye. These ocular dominance patches (or "columns") form during early life as a consequence of competition between the activity patterns of the two eyes. A mathematical model of several biological mechanisms that can account for this development is presented. Analysis of this model reveals the conditions under which ocular dominance segregation will occur and determines the resulting patch width. Simulations of the model also exhibit other phenomena associated with early visual development, such as topographic refinement of cortical receptive fields, the confinement of input cell connections to patches, monocular deprivation plasticity including a critical period, and the effect of artificially induced strabismus. The model can be used to predict the results of proposed experiments and to discriminate among various mechanisms of plasticity.

Afferent Pathways↗
PubMed1989

Leisure time physical activity in the Framingham Offspring Study. Description, seasonal variation, and risk factor correlates.

Self-reported leisure time physical activity was analyzed for 1,598 men and 1,762 women aged 20-69 years in the Framingham Offspring Cycle 2 exam in 1979-1983. Walking for pleasure was generally the most common physical activity for both sexes throughout the year. Substantial seasonal variation was noted for the most common activities: gardening, carpentry, lawn mowing, golf, and running for men; and gardening, swimming, health club exercise, dancing, and bicycling for women. Both sexes expended more kilocalories in physical activities in summer than in winter (p less than 0.001). Frequency of participation in activities sufficient to induce perspiration was associated with frequency of participation in at least one hour of conditioning (greater than or equal to 7.5 kilocal/minute) activities per week (p less than 0.001). Based on age-adjusted mean levels, higher high density lipoprotein cholesterol, lower heart rate, lower body mass index and fewer cigarettes smoked per day were consistently observed across four quartiles of increasing physical activity levels (p less than 0.01). Men who participated in at least one hour of conditioning activities per week had significantly different mean levels for these four risk factors than men who reported less than one hour of such activities per week (p less than 0.001). Results substantiate previous reports of an inverse relation between physical activity levels and cardiovascular risk, and suggest seasonal variation in activity levels should be considered in future studies which explore the relation between physical activity and cardiovascular disease.

Adolescent↗
PubMed1989

Trends in COPD morbidity and mortality in Tecumseh, Michigan.

Trends in COPD morbidity and mortality were investigated among the population of Tecumseh, Michigan, for the period 1959 to 1987. COPD was mentioned on the death certificates of 11% (102) of deceased men and 13% (24) of deceased women. Forty-one percent of these deaths was attributed to COPD as the underlying cause and the remainder to COPD as a contributory cause. Usage of diagnostic terms changed during the course of the study; emphysema was mentioned on 81% of certificates completed prior to 1968, whereas COPD was entered on 77% of the certificates written after 1978. Proportional mortality rates of COPD increased from 8% during 1959 to 1967 to 13.3% during 1979 to 1987 among men, and from 2.7% during the earlier years to 4.3% during the later years among women. Death rates for COPD and for all causes combined increased among men from the early 1960s to the late 1970s, then declined. Death rates for all causes combined were stable among women, but COPD death rates may have increased. Prevalence rates for chronic bronchitis were lower at the third examination than at the second in both sexes. Prevalence of obstructive airway disease was highest at the first and lower at the second and third examinations in men but not in women. Agreement between study diagnoses of COPD and entry of COPD on death certificates was poor. COPD was recorded on the death certificate for only 21% of men and only 6% of women who had COPD diagnosed at a study examination.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Is chronic lung disease in low birth weight infants preventable? A survey of eight centers.

Chronic lung disease in prematurely born infants, defined as the need for increased inspired oxygen at 28 days of age, was thought to be more common in some institutions than in others. To test this hypothesis, we surveyed the experience in the intensive care nurseries at Columbia and Vanderbilt Universities, the Universities of Texas at Dallas, Washington at Seattle, and California at San Francisco, the Brigham and Women's Hospital in Boston, Texas Children's Hospital in Houston, and Mt Sinai Hospital in Toronto. The survey included 1,625 infants with birth weights of 700 to 1,500 g. We confirmed the relationship of risk to low birth weight, white race, and male sex. Significant differences in the incidence of chronic lung disease were found between institutions even when birth weight, race, and sex were taken into consideration through a multivariate logistic regression analysis. Columbia had one of the best outcomes for low birth weight infants and the lowest incidence of chronic lung disease.

Bronchopulmonary Dysplasia↗
PubMed1986

Adult respiratory distress syndrome in neutropenic patients.

The precise pathophysiologic mechanisms that cause the adult respiratory distress syndrome are unknown. Indirect evidence from human studies and extrapolations from animal models have suggested that phagocytic neutrophils are important in the pathogenesis of this disease. To further evaluate the role of neutrophils, the frequency of neutropenia in 18 bacteremic patients who had the adult respiratory distress syndrome was compared with that in a control group who had bacteremia alone. Three of 18 patients in the group with the adult respiratory distress syndrome were neutropenic as opposed to one of 18 in the control group (p greater than 0.6). Histologic examination of the lungs from two patients with the adult respiratory distress syndrome and neutropenia demonstrated the absence of neutrophils. It is likely that there are many pathways that lead to the adult respiratory distress syndrome. Although neutrophils may be involved in some of these processes, this study demonstrates that neutrophils are not required for the development of the syndrome. In the appropriate clinical setting, the diagnosis of the adult respiratory distress syndrome should not be excluded solely because of neutropenia.

Adult↗
PubMed1986

Passive smoking in childhood. Respiratory conditions and pulmonary function in Tecumseh, Michigan.

The relationship of passive smoking to respiratory conditions and pulmonary function was assessed using a cross-sectional design in the defined population of Tecumseh, Michigan. The study population was made up of 3,482 children who were 0 to 19 yr of age at the 1962-1965 examination and for whom questionnaire information was available for both parents. Nearly 62% of children in this age group were exposed at the time of examination to at least 1 parent who smoked. Passive exposure to cigarette smoke was associated with an elevated prevalence of phlegm, wheeze, asthma, and chest colds among males and wheeze, bronchitis, and chest colds among females. Using logistic regression, offspring were shown to be 1.5 to 2.0 times more likely to have a respiratory condition if both their parents currently smoked than if both parents never smoked. FEV1, and FVC among males and Vmax50 among females were significantly lower by 5% in nonsmokers 10 to 19 yr of age whose parents were current smokers compared with similar offspring of never smoking parents. Respiratory conditions were generally more frequent and the level of lung function was generally lower for males from households where only mothers smoked compared with males from households where only fathers smoked, although sample size was limited. In females similar relationships were less consistent. Differences tended to be larger and more often significant for males than for females when respiratory symptoms and illnesses were examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Survival estimation using splines.

A nonparametric maximum likelihood procedure is given for estimating the survivor function from right-censored data. It approximates the hazard rate by a simple function such as a spline, with different approximations yielding different estimators. A special case is that proposed by Nelson (1969, Journal of Quality Technology 1, 27-52) and Altshuler (1970, Mathematical Biosciences 6, 1-11). The estimators are uniformly consistent and have the same asymptotic weak convergence properties as the Kaplan-Meier (1958, Journal of the American Statistical Association 53, 457-481) estimator. However, in small and in heavily censored samples, the simplest spline estimators have uniformly smaller mean squared error than do the Kaplan-Meier and Nelson-Altshuler estimators. The procedure is extended to estimate the baseline hazard rate and regression coefficients in the Cox (1972, Journal of the Royal Statistical Society, Series B 34, 187-220) proportional hazards model and is illustrated using experimental carcinogenesis data.

Animals↗