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Biomedical subjects

M K White

Publications and source records attributed to M K White.

At least 55 records · Page 3Linked to original sources
PubMed1984

The effects of exercise on the bones of postmenopausal women.

The effects of walking and aerobic dancing on the bones of 73 recently postmenopausal women have been compared by photon absorptiometry of the distal radius with a control group who did not exercise. The period of observation was six months. Results showed that the control group and the walking group lost statistically significant amounts of bone mineral content (1.6%, and 1.7% respectively), but that the dancing group did not (0.8%). The control group did not show a significant increase in the bone width (0.9%), but both the dancing (1.3%) and walking (1.6%) groups did. Changes in the cross-sectional moment of inertia of the radius were estimated for each subject based on bone mineral content and bone width values. Both exercise groups experienced significant increases in this variable, while the control group did not. Plasma oestrogen levels were not influenced by exercise. The results support the hypothesis that mechanical loading due to exercise may be effective in preventing postmenopausal osteoporosis.

Biomechanical Phenomena↗
PubMed1984

Association of an integral membrane protein with glucose transport and with anion transport.

A monoclonal antibody that recognizes a cell-surface glycoprotein associated with glucose transport was reported previously. Additional information about the function and intracellular distribution of the antigen recognized by this antibody is presented. The monoclonal antibody recognizes a cell-surface and a cytoplasmic determinant. The density of the cell-surface determinant is heterogeneous within the cell population. The subpopulation of cells that carry the cell-surface determinant at high density correspond with a subset of cells that incorporate 2-deoxy-D-[3H]glucose more rapidly than the population as a whole. The monoclonal antibody is used, with cell-affinity chromatography, to isolate this subset of cells. The cytoplasmic determinant, to which the antibody binds, is associated with the cytoplasmic microfilaments but the antibody is not absorbed by actin. The cell-surface and cytoplasmic components are not identical since the apparent affinity of the antibody for each site is different. The portion of the antigen in the membrane behaves as an integral membrane protein while the remainder is tightly associated with the detergent-insoluble cytoskeleton. The expression of the antigen on the cell surface is modified by covalent attachment of an inhibitor of anion transport, 4,4'-diisothiocyano-2,2'-disulphonic stilbene. The possible interaction of the anion/lactate transporter with the glucose transporter is discussed.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1984

Kinetic parameters of neutral amino acid transport in hybrids between malignant and non-malignant cells.

The kinetics of neutral amino acid transport were examined in isogeneic matched pairs of hybrid cells, one member of each pair being tumorigenic, the other not. The L system of transport, which is sodium-independent, was measured by the uptake of leucine, and the A system, which is sodium-dependent, by the uptake of methylaminoisobutyric acid. Although there was variation from one cell type to another in both Km and Vmax for the transport of these amino acids, no systematic change was found to be associated with tumorigenicity. This is in marked contrast with hexose uptake where tumorigenicity was invariably found to be associated with a reduction in Km. It thus appears that whatever molecular change is responsible for the alteration in the kinetics of hexose transport, it is specific, at least to the extent that it does not affect either sodium-dependent or sodium-independent transport of neutral amino acids.

Amino Acids↗
PubMed1984

Alterations induced by glucose deprivation and tunicamycin in the kinetic parameters of hexose transport in hybrid cells.

Matched pairs of malignant and non-malignant hybrid cells were compared in their response to glucose deprivation and to tunicamycin. Glucose deprivation induced an increase in the maximum velocity in the malignant cells, but not in the non-malignant cells. The Michaelis constant of hexose uptake was largely unchanged by glucose deprivation except in the case of one melanoma derivative, PG19 G-, which showed a large increase in Michaelis constant when deprived of glucose. Tunicamycin increased the Michaelis constant of hexose uptake in both malignant and non-malignant cell lines. It is therefore possible that the Michaelis constant of hexose uptake is affected by the extent of glycosylation of one or more of the cell membrane glycoproteins.

Animals↗
PubMed1983

Kinetic parameters of hexose transport in hybrids between malignant and nonmalignant cells.

Matched pairs of isogeneic hybrid cells, in which one member of the pair was malignant and the other not, were used to examine the linkage between malignancy and functional alterations in hexose transport. The kinetic parameters of uptake of 2-deoxy-D-glucose were measured in a range of such hybrids, both human and murine. Some other malignant cell lines were also examined and were compared with non-tumorigenic derivatives of tumour cells selected by exposure to the lectin, wheat-germ agglutinin. In every case, malignancy, as defined by the ability of cells to grow progressively in vivo, was found to be linked to a decrease in the Michaelis constant of hexose uptake. Independent measurement of the transport and phosphorylation reactions involved in hexose uptake revealed that this decrease was determined by the membrane transport system. The difference in Michaelis constant between malignant and non-malignant cells was observed with 3-O-methylglucose, a hexose that is transported into the cell but not further metabolized. The activity of hexokinase in cell homogenates was higher than the level that would be required to cope with transport and showed no correlation with tumorigenicity. Measurement of the uptake of D-glucose itself, by a rapid filtration centrifugation method, gave results similar to those obtained with 2-deoxy-D-glucose.

3-O-Methylglucose↗
PubMed1981

Hexose transport in hybrids between malignant and normal cells.

The kinetic parameters of hexose uptake were measured in matched pairs of hybrids between malignant and normal cells. Each pair consisted of a hybrid in which malignancy was initially suppressed and a segregant tumour derived from it. Comparisons were also made between tumour cells and non-tumorigenic derivatives selected from the tumour cell populations in vitro. Without exception, malignancy, as defined by the ability of the cell to grow progressively in vivo, was found to be linked to a systematic decrease in the Michaelis constant of the hexose transport system.

Animals↗
PubMed1980

Intrauterine device termination rates and the menstrual cycle day of insertion.

World-wide clinicians apparently prefer to insert the intrauterine device (IUD) during the bleeding phase of the menstrual cycle. To examine the benefits and risks of inserting IUDs at various times during the menstrual cycle, data on over 9000 women having copper T-200 IUD insertions were analyzed. During the first 2 months after IUD insertion: 1) rates of IUD expulsion are lower the later in the menstrual cycle ;he IUD is inserted; 2) rates of IUD removal for pain and bleeding and rates of accidental pregnancy, are higher the later in the menstrual cycle IUD is inserted, particularly after day 17. The present analysis suggests that the above are probably causal associations. It is estimated that 1000 insertions before day 11 will result in 9 more terminations of IUD use for expulsion, pain and bleeding, and accidental pregnancy than if the insertions are done after day 11. Furthermore, the copper T-200 IUD can be inserted with relative safety on the day it is requested if the woman's history indicates that she is unlikely to be pregnant. There is no justification for a blanket policy of inserting IUDs only during the menses.

Adult↗
PubMed1979

Complementation analysis of eleven tryptophanase mutations in Escherichia coli.

Nine independent mutants deficient in tryptophanase activity were isolated. Each mutation was transferred to a specialized transducing phage that carries the tryptophanase region of the Escherichia coli chromosome. The nine phages thus produced, and a tenth carrying a previously characterized tryptophanase mutation, were used to lysogenize a bacterial strain harbouring a mutation in the tryptophanase structural gene and also a suppressor of polarity. In no case was complementation observed; we conclude that there is no closely linked positive regulatory gene for tryptophanase.

Bacteriophage lambda↗
PubMed1977

A case-control study of uterine perforations documented at laparoscopy.

A case-control analysis was done of 19 cases of uterine perforations which occurred during laparoscopic sterilization at Gardy Memorial Hospital in Atlanta, between February 1, 1974, and January 31, 1976. The over-all perforation rate, 30.4 per 1,000 procedures, is three to 30 times that commonly reported for dilatation and suction or sharp curettage (D&C) of the uterus. Case women were 10.4 times more likely than control women to combine two of the following three characteristics: age greater than 34, parity greater than 4, and obesity greater than 20 per cent above the ideal body weight for height. Surgeons with fewer months of formal Ob/Gyn training were no more likely than their relatively more experienced colleagues to perforate the uterus. No other risk factors were delineated. It is believed that the perforation rate, higher in this study than in earlier ones, reflects better ascertainment of perforations. The bleeding site was always visualized with the laparoscope in this series.

Adult↗
PubMedDate not supplied

Teaching clinician-patient communication in the treatment of breast diseases.

In 1998, some 179,000 women in the United States were newly diagnosed with breast cancer, and 48,500 women died from it. Early detection by mammography, physical examination, and breast self-examination improves survival rates and can decrease mortality. The clinician's level of comfort with discussing education and prevention with patients can influence patients' adherence to preventive measures. Improved clinician-patient interpersonal communication has a demonstrated positive impact on adherence and health outcomes. We developed and pilot tested a core curriculum on breast health aimed at primary care community physicians and resident house staff. The goal was to improve interpersonal communication between clinician and patient. Two groups of participants attended either a week-long or a 2-week-long training program consisting of four components: a brief demonstration of an interview and breast examination, interviews and breast examinations with a standardized patient, and two separate workshops of varying length. This pilot program had a significant impact on clinician behavior and knowledge. We recommend further investigation of this area with larger sample sizes.

Breast Diseases↗