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Biomedical subjects

D W Stewart

Publications and source records attributed to D W Stewart.

At least 19 recordsLinked to original sources
PubMed1994

Effect of ethidium binding and superhelix density on the apparent supercoiling free energy and torsion constant of pBR322 DNA.

The value of the twist energy parameter (ET) of pBR322 is determined near zero superhelix density from topoisomer distributions created under various conditions. The resulting value, ET = 1155 +/- 65, at 37 degrees C is essentially unaffected by adding 10 mM Mg2+, or by changing the kind of Topo I from chicken-red-cell to calf-thymus. This value significantly exceeds that (ET = 950 +/- 80) measured for p30 delta DNA under identical conditions by the same method in the preceding paper. Decreasing the temperature from 37 to 21 degrees C yields a slightly larger value, ET = 1340 +/- 130, but the statistical significance of the increase is marginal. Attempts to determine reliable ET values for pBR322 at higher superhelix densities by ethidium binding were frustrated by the fact that good fits of the equilibrium dialysis results could not be achieved using a single value of ET. Moreover, the curves of apparent ET versus binding ratio r vary considerably from one preparation to another, and for a given preparation vary with time after cell lysis up to about seven weeks, after which they settle in to nearly reproducible behavior. The apparent ET values obtained from competitive dialysis experiments are typically rather low (ET approximately 700) for small r and nearly native superhelix density, and rise up to 1300 to 1500 with increasing binding ratio (up to r = 0.055) and decreasing negative superhelix density.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Effect of ethidium binding and superhelix density on the supercoiling free energy and torsion and bending constants of p30 delta DNA.

Topoisomer distributions created by the action of topoisomerase I on p30 delta DNA in the presence of various concentrations of ethidium are measured and analyzed using recently developed theory to obtain the twist energy parameter (ET) that governs the free energy of supercoiling in each case. Competitive dialysis experiments to investigate the relative affinity of ethidium for linear and supercoiled DNAs at different binding ratios are assayed fluorometrically and the results are analyzed using related theory. The topoisomer distributions and fluorescence intensity ratios agree well with the theory, which is based on the assumption that the supercoiling free energy varies quadratically with the effective linking difference, regardless of ethidium binding or superhelix density. The topoisomer distribution experiments alone yield an average best-fit value, ET = 950 +/- 80, independent of ethidium binding ratio from r = 0 to 0.082, while the combined topoisomer distribution and ethidium binding experiments yield an average best-fit value, ET = 1030 +/- 90, which is essentially independent of ethidium binding ratio from r = 0 to 0.082 and superhelix density from sigma = 0 to (-)0.053. One may conclude that the supercoiling free-energy-varies quadratically with effective linking difference over the entire range of observed ethidium binding ratios and superhelix densities. The independently measured torsion constant (alpha) of p30 delta DNA is likewise essentially independent of superhelix density and ethidium binding ratio. The observed invariance of ET and alpha implies that the bending constant kappa beta is similarly invariant to superhelix density and ethidium binding ratio. The apparently ideal behavior displayed by p30 delta DNA is not exhibited by pBR322 DNA, which is discussed in the following companion paper.

Algorithms↗
PubMed1990

Salpingo-vesical fistula. Rare and unusual complication of vaginal hysterectomy.

A case of salpingo-vesical fistula is presented which occurred in a forty-six-year-old female two years after a vaginal hysterectomy. The patient's presenting complaints included pelvic and right lumbosacral discomfort, aggravated by urination. Cystoscopy revealed the fistula, and the patient was successfully treated with a salpingo-oophorectomy.

Fallopian Tube Diseases↗
PubMed1990

Suture material in bladder surgery: a comparison of polydioxanone, polyglactin, and chromic catgut.

A comparison of polydioxanone, polyglactin, and chromic catgut suture was performed in 120 rat bladders studying propensity for infection, degree of inflammation, calculogenic potential, changes in urine pH, and suture absorption. None of the sutures predisposed to infection and there was wide variability but no correlation in urine pH. Although initially the polydioxanone incited a greater inflammatory response, by six months all three sutures were similar. The absorption of polydioxanone was slower than chromic catgut suture, but similar to the absorption of polyglactin. There was no significant difference in calculogenic potential between the suture materials tested over a six-month period. Based on this study in rats, polydioxanone suture would appear to be equal to catgut and polyglactin suture in bladder surgery.

Animals↗
PubMed1988

First step in obtaining child health care: selecting a physician.

To investigate the process by which families identified and selected their children's current physicians, a close-ended questionnaire was administered to 750 families in a mail panel. Of 630 responses (84.0%), 244 had children in the home; 229 (93.9%) identified a regular and current physician for their youngest child. However, parents did not spend much time or energy selecting a physician and rarely explored medical expertise in their decisions. Families averaged 1.2 sources of information consulted per decision; few considered more than two physician choices and infrequently considered alternative types of doctors (pediatricians v family or general practitioners). Selection priorities ranked in order of importance concerned parents' perceptions of their doctors' communication skills, accessibility, and quality as determined by recommendations of friends or physicians. Parents appeared less concerned with issues of cost and convenience. Families selecting pediatricians differed from those selecting family and general practitioners in sources of information used and selection priorities. The survey also identified 84 families who had changed or seriously considered changing the physician who was caring for their youngest child. The most frequent dissatisfaction was the perception that an illness was not being managed adequately, followed by believing that the doctor or staff were rude or unconcerned. Families unhappy with pediatricians expressed different reasons from those unhappy with family or general practitioners. The study results provide insight about the first step in obtaining child health care services, a relatively unexplored area of patient decision making.

Adolescent↗
PubMed1986

The symptom as metaphor in Lacan's theory of the unconscious.

An analysis of Freud's forgetting of the name Signorelli provides a framework for an explication of some central concepts in Lacan's theory of the unconscious. The parapraxis is viewed as a symptom which is structured like a metaphor. The creation of a symptom during the process of repression produces a gap in conscious discourse. The analysis of such symptoms provides evidence for Lacan's assertion that the unconscious is structured like a language.

Freudian Theory↗