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Biomedical subjects

D C Thomas

Publications and source records attributed to D C Thomas.

At least 163 records · Page 9Linked to original sources
PubMed1981

Considerations in determining matching criteria and stratum sizes for case-control studies.

Despite considerable research into the statistical properties of matching in case-control studies, much disagreement remains regarding practical guidelines for the employment of the procedure. We critically examine some recent statistical recommendations, and review a number of theoretical and practical considerations that should be employed in designing matched studies. We conclude that determination of matching criteria and stratum sizes should always involve practical as well as theoretical considerations, and that global recommendations regarding matching cannot be justified on the basis of statistical considerations alone.

Epidemiologic Methods↗
PubMed1979

Patients' understanding of prescribed drugs.

Patients must understand their physicians' recommendations if they are to follow medical advice. This study assesses the degree to which patients and physicians share basic information about medications. Patients who regularly attended the medical clinics of a large, urban teaching hospital were asked to recall the identity, purpose, and dose schedule of medications that were prescribed for them. Patients' responses were compared to the medications actually prescribed by their physicians. Patients identified 90% of medications prescribed during the visits, knew the purpose 83%, and the correct dose schedule for 80%. Only 58% of patients knew the dosage schedule of all their medications correctly. Patients' knowledge of prescribed drugs was inversely related to the number of their medical problems and the number of medications prescribed. Lack of effective communication between physicians and patients about medications may be an important reason why patients do not follow medical advice.

Aged↗
PubMed1975

Thymidine kinase activity in cerebrospinal fluid of rabbits with Herpesvirus hominis encephalitis.

The rabbit model of Herpesvirus hominis (HVH) encephalitis was utilized to determine whether thymidine (TdR) kinase (EC. 2.7.1.2.1), AN EARLY ENZYME IN THe HVH replicative cycle, is present in the cerebrospinal fluid (CSF) of rabbits with HVH encephalitis. The mean TdR kinase activity in CSF from infected rabbits was 2.30 plus or minus 1.69 pmol product/120 min/100 mul CSF, while the mean TdR kinase activity of uninfected CSF was 0.34 plus or minus 0.25. The enzyme appeared to be cell associated since the TdR kinase activity in the sedimented cell suspension was 5.08 plus or minus 2.93 (seven values) while the supernatant activity was 0.14 plus or minus 0.31 (seven values). To allow a comparison of TdR kinase from infected rabbit CSF with HVH and rabbit mononuclear cell TdR kinase, the mean ratio of TdR kinase activity at pH 6.0/pH 8.0, for infected rabbit CSF is intermediate between the ratio for HVH TdR kinase (P less than 0.001) and rabbit mononuclear cell TdR kinase (P less than 0.05).

Animals↗
PubMed1975

The pattern of reproduction in female Columbian black-tailed deer, Odocoileus hemionus columbianus.

Ovarian cycles and the pattern of reproduction in female black-tailed deer in British Columbia were ascertained largely through examination of the ovaries from 444 females. Cyclic development and degeneration of single follicles of ovulatory size occurred several weeks before first ovulation. As the breeding season approached, a second or third large follicle developed in each cycle but in 48% of adult females the follicles were at different stages of maturation. Those failing to rupture at first ovulation luteinized 1 to 2 days thereafter. The first ovulation of the season, in November, never resulted in a lasting pregnancy even though some ova were penetrated by spermatozoa and began to cleave. First ovulation was apparently 'silent' in five of seven females for their ova lacked spermatozoa. Of sixty-one pregnant females, fifty-nine conceived at second ovulation; the other two conceived at subsequent ovulations more widely spaced than the 8- to 9-day interval between first and second ovulations. The synchrony of ovulatory cycles among adult females was such that half of them ovulated for the second time in a span of 7 or 8 days. Primary CL that formed after first ovulation grew to an average maximum volume of only about 45 mm3, whereas those originating at second ovulation grew to twice that size within 5 to 8 days. First generation CL shrank from 35 mm3 to 10 mm3 within 2 days. They disappeared within 18 months but corpora albicantia persisted for the life of the female. The possible ecological significance of the reproductive pattern is discussed.

Animals↗
PubMedDate not supplied

Statistical methods for relating several exposure factors to several diseases in case-heterogeneity studies.

Statistical methods for characterizing risks are now well-developed, although little attention has focussed on the problem of risk identification, as in the surveillance of adverse drug reactions or occupational cancers. In this paper we consider the analysis of studies in which one ascertains and compares cases of several disease groups in terms of exposure histories. We address the problem of adjusting each risk for the confounding effects of all the other risks in the data. Data analysis consists of multidimensional contingency tables or polychotomous logistic regression. The latter approach focuses attention on the exposure-disease relations of primary interest rather than on those among the exposure factors and higher-order interactions, and applies easily to many exposure variables and to continuous exposure variables. We describe a stepwise approach to selecting effects for inclusion in the model. Application to preliminary data from a study aimed at identification of hitherto unsuspected occupational carcinogens illustrates the general approach.

Biometry↗
PubMedDate not supplied

Domainal evolution of a prokaryotic DNA repair protein and its relationship to active-transport proteins.

The ABC excision nuclease of Escherichia coli is an ATP-dependent DNA repair enzyme composed of three protein subunits, UvrA, UvrB and UvrC. The DNA sequences of all three genes have been reported. UvrA, the component that binds directly to the DNA, and UvrB, which attaches itself to the UvrA-DNA complex, both contain consensus sequences though to be diagnostic of ATP-binding sites, although the UvrC sequence does not. We now report that a computer analysis of the UvrA sequence has revealed an unusual series of internal duplications centering around putative metal-binding sites which may be involved in the interaction with DNA. We also find a strong evolutionary relationship to a family of prokaryotic membrane-associated active-transport proteins.

Amino Acid Sequence↗