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Biomedical subjects

D B Thomas

Publications and source records attributed to D B Thomas.

At least 199 records · Page 11Linked to original sources
PubMed1982

Proposal for a collaborative epidemiology study of prostate cancer in the Pacific Basin.

Incidence rates of invasive prostate cancer vary markedly among countries of the Pacific Basin, and migrant studies have shown that this is at least partly due to environmental factors. Future epidemiology studies in these countries should be conducted so that this variability in incidence can be explained. Prevalence ratios of latent prostate carcinomas of the infiltrative type vary with incidence rates of invasive carcinomas, and a collaborative case-control study of infiltrative and noninfiltrative latent carcinomas in the Pacific Basin, combined with a standardized pathological review of specimens obtained at autopsy, could provide new etiological clues. Factors that should be investigated include fertility and sexual practices; exposure to zinc, cadmium, and mercury compounds; prior benign prostatic hypertrophy; diet; conditions that may alter endogenous levels of androgens and estrogens; and family history of diseases of the prostate. Events during the fourth decade of life may be of particular importance. Case-control studies of invasive prostate cancer in high- and low-risk populations are currently being conducted, and additional ones are not warranted until results from these are available. Investigators should use these results in planning the proposed study of latent prostate carcinoma.

Alaska↗
PubMed1982

Epidemiology of testicular cancer in the Pacific Basin.

Although a rare tumor, testicular cancer shows substantial international variation in incidence. In whites, the peak incidence occurs at 25-30 years of age, with a second increase in old age. Blacks have much lower rates than do whites. The rate of increase in the incidence and mortality of this cancer has been consistent but low during the past 40 years. Risk factors identified in epidemiology studies of testicular cancer include cryptorchidism (best documented), inguinal hernia, testicular injury, wearing of tight-fitting underclothing, obesity, maternal use of exogenous estrogens during pregnancy, higher social class, and professional occupations. Epidemiological evidence provides two etiologic hypotheses: a relative hormone imbalance, particularly an excess of estrogen, and a failure of normal thermal regulation of the testis. In the Pacific Basin region, notable variation in incidence rates is also seen. High-risk populations include whites, Polynesians (in Hawaii and New Zealand), and Native Alaskans. Low-risk groups include Filipinos (in Hawaii and Manila), Japanese (in Hawaii and Japan), Indians, and Malays. Most of this variation occurs in the younger ages (0-54 yr). Several areas for potentially fruitful research on this cancer in the Pacific region are given.

Adolescent↗
PubMed1981

Infantile colic.

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Anesthesia, Obstetrical↗
PubMed1981

Kinetic studies of the murine foetal thymus using vincristine sulphate.

The turnover time of the foetal thymus has been evaluated in CD1 mice using the metaphase arrest drug vincristine sulphate and also by direct cell counting and found to be 18 h (range 12--26) and 11.9 h (range 10.9--13.1) respectively. Vincristine sulphate can be used for cell kinetic studies on foetal thymus provided an appropriate dose (5 mgm per kgm body weight given intravenously) and time scale (less than 1 hour after injection) are used for these measurements. These conditions are different from those used for adult tissues. Using 125I-iododeoxyuridine uptake measurements, it was found that vincristine sulphate suppressed DNA synthesis in the foetal thymus but not in the maternal thymus at this dose. Only the G2 cohort of cells in the thymus entered mitosis.

Animals↗
PubMed1981

Effects of epidural anesthesia on newborns and their mothers.

The effects of epidural anesthesia on newborns were studied using a sample of babies from mothers having (a) little or no medication during childbirth (N = 15), (b) epidurals with bupivacaine (N = 20), and (c) epidurals in combination with oxytocin to stimulate labor (N = 20). Outcome measures included assessments of neonatal behavior (Brazelton Scale), mother-baby interaction during feeding, and mothers' perceptions of their babies' behavior during the first month after delivery. Effects of drugs on the neonatal behavior were strongest on the first day. By the fifth day, there was evidence of behavioral recovery, but the medicated babies continued to exhibit poor state organization. At 1 month, examiners observed few differences between groups, but unmedicated mothers reported their babies to be more sociable, rewarding, and easy to care for, and these mothers were more responsive to their babies' cries. The importance of the first encounters with a disorganized baby in shaping maternal expectations and interactive styles was discussed.

Anesthesia, Epidural↗
PubMed1980

In vivo cyclic change in B-lymphocyte susceptibility to T-cell control.

The humoral response to hapten-protein conjugates is an invaluable model for dissecting the cellular elements of lymphocyte cooperation, and the Mitchison secondary adoptive transfer system provides convincing evidence of cooperation between hapten-specific B cells and carrier-specific T cells in the production of anti-hapten antibody. Recently, attention has focused on the role of suppressor T cells in the regulation of antibody production. Several workers have shown that carrier-priming may, in some instances, suppress a subsequent hapten antibody response, both in vivo and in vitro. This effect is attributed to a suppressor T-cell population, generated during the initial phase of the immune response. Gershon and co-workers have postulated that such suppressor T cells function in a feedback regulatory loop to limit the duration of an immune response. We have examined the suppressive effect of carrier immunization in a secondary anti-hapten response in vivo and demonstrate a cyclic change in susceptibility of memory B cells to T-help and suppression. Such variation presents a severe restriction to any model of feedback control by suppressor T cells.

Animals↗
PubMed1980

Vital DNA staining and cell sorting by flow microfluorometry.

A procedure has been investigated for sorting viable cells according to their DNA content. Cells are stained with the U.V. activated fluorochromes 4'6-diamidino-2-phenylindole (DAPI), Hoechst 33258 or Hoechst 33342, and sorted with a Fluorescence Activated Cell Sorter. Hoechst 33342 is a suitable vital stain for a variety of cell types. Hoechst 33258 and DAPI, however, are quantitative vital stains for CHO cells only. Cloning efficiency is unaffected by the sorting procedure, and these stains are not mutagenic at concentrations suitable for vital staining. Potential applications of this procedure to cell biology are discussed.

Amidines↗
PubMed1980

Risk of breast cancer in women with benign breast disease.

A group of 1,489 white women were treated in a private surgery practice from 1940 through 1975 for biopsy-proved benign breast disease, and 1,441 were followed through 1976 for the development of breast cancer. Average duration of follow-up was 12.9 years for a total of 18,617 person-years of observation. Information was collected from a set of questions devised in 1941 and asked of all subjects at the time of their initial office visit, follow-up interview conducted in 1976, and a standardized histology review of the slides from the initial benign lesions and the subsequent cancers. The current pathology review indicated that 66 of the women developed breast cancer. The incidence rate was 3.55 per 1,000 person-years, which is 2.10 times that of the general population. When multiple disease types and other variables were controlled for, excess risk of breast cancer was related to the presence of fibrocystic disease. In women with fibrocystic disease, excess risk was particularly related to the presence of epithelial hyperplasia and/or papias not related to the presence of fibroadenoma alone, but it was related to the presence of fibroadenoma in women with concomitant fibrocystic disease. The excess risk was also directly related to the estimated size of the initial benign mass and was greater for women with bilateral than with unilateral benign lesions.

Adult↗
PubMed1979

Method of delivery and developmental outcome at five years of age.

A controlled follow-up study examined the impact of delivery method on developmental outcome of the child. The modes of delivery investigated were low forceps delivery (188 infants), midcavity forceps delivery (51 infants), forceps rotation with forceps delivery (57 infants), manual rotation with forceps delivery (67 infants), elective caesarean section (101 infants) and spontaneous delivery (control, 207 infants). Breech presentation (100 infants) was separately compared with the vertex presentation groups. Sample selection controlled for complications during pregnancy and low birthweight and was restricted to married English-speaking mothers. The children were assessed at the age of five years on verbal and non-verbal subtests of a standardized intelligence scale, tests of gross motor coordination, and auditory and visual tests. A full paediatric examination was also performed. Breech presentation children performed less well on tests of balance and fine motor coordination and on visual acuity and stereopsis testing than children who presented in the vertex position. No deleterious effect of delivery method was found. In the absence of other complicating events (like a poor antenatal history, prematurity, and a disorganized home environment) delivery complication constitutes an early risk factor which the growing child is able to overcome.

Cesarean Section↗