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Biomedical subjects

S McKay

Publications and source records attributed to S McKay.

At least 19 recordsLinked to original sources
PubMed1992

Reliving birth: maternal responses to viewing videotape of their second stage labors.

To learn about women's responses to their second stage labors and the care they received, women (N = 20) whose second stage labors had been videotaped were interviewed postpartally and shown their videotapes. Often women found the videotape viewing to be intensely emotional, especially when they heard noises they made. Women frequently commented upon details they hadn't remembered, their reactivated memory for labor pain, and the "weird" experience of watching themselves in labor. The authors recommend that women who watch their labor videotapes do so with a caregiver or supportive companion. They should be forewarned that the experience may be intense; details of their labors may be vividly recalled or women may see labor events on the videotape of which they were previously unaware.

Adolescent↗
PubMed1992

Idiopathic edema.

This article describes idiopathic edema, alias fluid retention syndrome, cyclical edema, or orthostatic edema. It occurs solely in women in the absence of any currently recognized cause and its symptoms are usually dismissed as premenstrual or "minor." In severe cases, it can be both crippling and limiting. This article describes the proposed pathophysiology and the resulting effects on the fluid and sodium excretion by the kidney. Two types of idiopathic edema are depicted: orthostatic sodium retention and orthostatic water retention. A case study is presented to better illustrate this syndrome.

Adult↗
PubMed1990

The structure of a subterminal repeated sequence present on many human chromosomes.

All telomeres which have been studied consist of an array of simple G/C rich repeats. Human telomeres were shown to share sequence similarity with those of lower eukaryotes by cross-hybridization and human telomeric sequences have been cloned by complementation of telomere function in yeast. Analysis of human telomeric sequences cloned in this way is described here. The terminal part of the cloned human telomeric DNA consists of an array of simple repeats, principally of the sequence TTAGGG and derivatives. The very terminal part consists of yeast-type telomeric repeats which suggests that the human telomeric sequences have acted as a primer for the addition of additional telomeric repeats in the yeast. Subterminal sequences are shared between a number of clones and in situ data shows that these subterminal sequences are present at several different chromosomal ends. Related sequences are present at internal as well as telomeric positions. Differences in the hybridization patterns of subterminal sequences in somatic compared to germ-line tissues are described which indicate differential modification of these sequences during development.

Base Composition↗
PubMed1990

A nuclear protein that binds preferentially to methylated DNA in vitro may play a role in the inaccessibility of methylated CpGs in mammalian nuclei.

The effects of DNA methylation on gene expression and chromatin structure suggest the existence of a mechanism in the nucleus capable of distinguishing methylated and non-methylated sequences. We report the finding of a nuclear protein in several vertebrate tissues and cell lines that binds preferentially to methylated DNA in vitro. Its lack of sequence-specific requirements makes it potentially capable of binding to any methylated sequence in mammalian nuclei. An in vivo counterpart of these results is that methylated CpGs are inaccessible to nucleases within nuclei. In contrast, non-methylated CpG sites, located mainly at CpG islands, and restriction sites not containing this dinucleotide, are relatively accessible. The possibility that DNA methylation acts through binding to specific proteins that could alter chromatin structure is discussed.

Animals↗
PubMed1990

Women's views of second-stage labor as assessed by interviews and videotapes.

Twenty women were selected from public and private maternity services and interviewed by nurses and nurse-midwives on a research team. The women were shown videotapes of their second-stage labors that for 15 of them had been recorded by 2 other members of the research team. Four videos were provided by mothers who had had home births and one from a mother whose birth was filmed at a birth center. The interviews were analyzed for major themes; the theme reported here is women's experiences of pushing. Women reported wide variations in sensations during the second stage. Whereas 9 of 16 women expressed feelings of relief or pressure and stretching, 7 described pushing as painful, miserable, or horrible. Thirteen of 19 women had well defined urges to push, 1 had an intermittent urge, and 5 had no urge. Women often felt unprepared for the sensations and work of second-stage labor, and caregivers' instructions commonly did not seem to be in synchrony with physiological responses. We conclude that childbirth educators and caregivers must prepare women more realistically for the second stage. They would be more effective if they responded to maternal behavior, rather than giving arbitrary instructions about pushing.

Adolescent↗
PubMed1989

Identification of a mammalian protein that binds specifically to DNA containing methylated CpGs.

The effects of DNA methylation on transcription and chromatin structure require that nuclear factors be able to distinguish methylated and nonmethylated DNA. We describe a methyl-CpG binding protein (MeCP) that complexes with a variety of unrelated DNA sequences when they are methylated at CpG. Fifteen or more symmetrically methylated CpG moieties per molecule are required for strong binding under our conditions. Competition experiments show that vertebrate DNAs bind to MeCP, whereas naturally nonmethylated genomes or cloned vertebrate genomes do not bind. Cross-linking experiments detect a 120 kd protein that correlates stringently with MeCP activity. Species and tissue comparisons show that MeCP is widely distributed in mammals except in embryonal carcinoma cell lines, which have very low levels.

5-Methylcytosine↗
PubMed1988

Metabolic activation of 7-ethyl- and 7-methylbenz[a]anthracene in mouse skin.

The carcinogen 7-methylbenz[a]anthracene (7-MBA) is considered to be metabolically activated via its bay-region dihydrodiol-epoxide, trans-3,4-dihydro-3,4-dihydroxy-7-methyl-benz[a]anthracene 1,2-oxide (7-MBA-3,4-diol 1,2-oxide). When tested on mouse skin, a target tissue for polycylic aromatic hydrocarbon carcinogenesis, 7-ethylbenz[a]anthracene (7-EBA) was much less active than 7-MBA, and this difference may be due to differences in the pathways by which the two compounds are metabolized and activated. In the present work, the metabolism by mouse-skin microsomes of both hydrocarbons to dihydrodiols has been examined. Both were metabolized to a similar extent with the 8,9-dihydrodiols being detected as the predominant metabolites. The 3,4-, 5,6-and 10,11-dihydrodiols of 7-MBA and the 3,4- and 10, 11-dihydrodiols of 7-EBA, were also detected. 7-MBA was found to bind covalently to microsomal protein at 10 times the level of 7-EBA. The covalent binding of benz[a]anthracene (BA), 7-EBA and 7-MBA to DNA in mouse skin following topical application was determined using the 32P-postlabelling assay. The results correlated with the relative carcinogenic activities of the compounds with 7-MBA binding at five and nine times the level of 7-EBA and BA respectively. For all three hydrocarbons, the major hydrocarbon: 32P-labelled nucleoside bisphosphate, eluted in the same area of the TLC maps, suggesting the involvement of a common type of bay-region dihydrodiol-epoxide intermediate.

Animals↗
PubMed1987

Comparative metabolism of 7-methyl- and 7-ethylbenz[a]anthracene by rat-liver preparations.

The metabolism of 7-ethyl (7-EBA) and 7-methylbenz[a]anthracene (7-MBA) to dihydrodiols has been compared in incubations with hepatic microsomal fractions prepared from untreated rats. Although both hydrocarbons were found to be metabolised to similar extents, the relative proportions of their diols that were detected differed. For 7-MBA, the principal diols identified were the 8,9- and 5,6-derivatives, whereas for 7-EBA the 8,9- and 1,2-diols predominated; the 5,6-diol was only present as a minor product. These results imply that the presence of the sterically bulky ethyl group at position seven in the benz[a]anthracene ring system may, when compared to the analogous methyl derivative, enhance diol formation on the angular 1,2,3,4 benzo-ring, at the expense of metabolism at the K-region.

Animals↗
PubMed1986

The metabolism of 9-methylanthracene by rat-liver microsomal preparations.

The metabolism of 9-methylanthracene by liver microsomal preparations from 3-methylcholanthrene-treated rats was examined. The principal metabolites identified were 9-hydroxymethylanthracene, the 1,2- and 3,4-dihydrodiols of the parent hydrocarbon and the 3,4-dihydrodiol of the 9-hydroxymethyl derivative. A small amount of a product that appeared to be a phenolic derivative of the hydrocarbon was also formed. The structures of the major metabolites were confirmed by u.v., n.m.r., and mass-spectral analysis and, wherever possible, by direct comparison of their chromatographic properties with those of the authentic compounds. 9-Hydroxymethylanthracene was further metabolized by rat-liver microsomal preparations to the 3,4-dihydrodiol but not to the related 1,2-dihydrodiol.

Animals↗
PubMed1976

Effects of staphylococcal products on locomotion and chemotaxis of human blood neutrophils and monocytes.

The effects of staphylococcal products as chemo-attractants for human blood neutrophils and monocytes and as inhibitors of locomotion of these cells were studied with bacterial cells, culture filtrates and isoelectrically focused fractions from culture filtrates of nine strains of Staphylococcus aureus. Little direct chemotactic activity of staphylococcal products for neutrophils was observed, although a chloroform-soluble extract of the whole organisms contained such activity. The major chemotactic effect of staphylococci for neutrophils was indirect, i.e., generated when the organisms or their products were incubated with plasma, perhaps due to activation of complement. In contrast, direct chemotactic activity for monocytes was found in a large number of staphylococcal fractions. Staphylococci also produced inhibitors of locomotion of both neutrophils and monocytes. Isoelectric focusing showed more fractions inhibitory for neutrophils than for monocytes. Some of the inhibitors could be identified. Staphylococcal alpha-toxin inhibited migration of both neutrophils and monocytes. Sphingomyelinase C (beta toxin) inhibited migration of monocytes but not of neutrophils. Leucocidin-rich strains were strongly active as inhibitors of neutrophil locomotion but less so as inhibitors of monocyte locomotion.

Cell Migration Inhibition↗
PubMed1974

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Alberta↗