Biomedical subjects

D Stockwell

Publications and source records attributed to D Stockwell.

3 recordsLinked to original sources

PubMed2000

Transcription of the transfer genes traY and traM of the antibiotic resistance plasmid R100-1 is linked.

Three separate traY deletion mutants of R100-1 were prepared by allele replacement. These mutants retained the ability to transfer at a level 100 times greater than R100 and 1/50 that of the parental R100-1. The mutants were complemented to normal R100-1 transfer levels by pDSP06, a multicopy traY clone. Comparison of transcripts initiated at the traY promoter, P(Y), by primer extension experiments showed that there was no detectable P(Y) activity in R100 and that the level of P(Y) activity in the traY deletion mutants was lower than that in R100-1. Similar measurements performed on RNA from a set of previously described traM deletion mutants showed that those traM deletion mutants that produced more traM and finM (M) transcripts than the parental R100-1 also produced more traY transcripts than R100-1 and that those traM mutants that produced fewer M transcripts than R100-1 also produced fewer traY transcripts than R100-1. We conclude that in R100, TraY regulates P(Y) activity and that transcripts originating in traM affect P(Y) activity.

Amino Acid Sequence↗

PubMed1995

Renal function during antihypertensive treatment.

To determine the association of renal function and the course of blood pressure in antihypertensive therapy, we studied the changes in serum creatinine as a measure of renal function and in-treatment blood pressure in black and white hypertensive patients. We measured serum creatinine in 2125 mild and moderately hypertensive men during treatment over an average of 5 years. Both unadjusted mean initial and final serum creatinine of 758 blacks (113 and 117 mumol/L respectively) were significantly higher than those of 1367 whites (108 and 107 mumol/L), with a small increase of 4 mumol/L (p < 0.01) for blacks and a fall of 0.9 mumol/L (p > 0.05) for whites. Less than 2% of all patients attained or remained at a final serum creatinine of 177 mumol/L or more. Of this small group (3% blacks, 1.4% whites), 31% had proteinuria at entry. After stratification by in-treatment diastolic blood pressure (< 95 and > or = 95 mm Hg) in each race, mean slopes of reciprocal serum creatinine were estimated, adjusting for age at entry, initial serum creatinine, diastolic pressure, and body-mass index by analysis of covariance. The two adjusted mean slopes did not differ significantly within each race. Multiple regression analysis confirmed that in-treatment diastolic pressure was not independently associated with final serum creatinine. The change in renal function was most likely a reflection of regression towards the mean, and does not support the view that antihypertensive treatment is an important determinant of renal function in mild-to-moderate hypertensive patients. Patients with substantial renal insufficiency may have pre-existing intrinsic renal disease.

Antihypertensive Agents↗

PubMed1990

Superiority of substrate enhancement over oxygen free-radical scavengers during extended periods of cold storage for cardiac transplantation.

When cold storage techniques used in cardiac transplantation are extended beyond 3 hours, there is significant depression in ventricular function. This study was undertaken to determine whether the addition of the amino acid L-glutamate or the oxygen free-radical scavengers superoxide dismutase (SOD) and catalase (CAT) during extended periods of cold storage would improve ventricular function. Fifteen rabbit hearts were placed on a Langendorff apparatus, arrested with crystalloid potassium cardioplegia, stored in iced saline solution (3 degrees C) for 5 hours, and then reperfused at 37 degrees C for 1 hour. In five hearts L-glutamate (4 mmol/L) was added to the cardioplegic and reperfusate solutions, and five hearts received SOD (1500 units/kg/L) and CAT (3500 units/kg/L), whereas in five others the cardioplegic and reperfusate solutions were unmodified. Hearts treated with L-glutamate had the best recovery of positive dP/dt (79%* glutamate vs 49%* SOD and CAT vs 36% unmodified), negative dP/dt (76%* glutamate vs 53% SOD and CAT vs 45% unmodified), developed pressure (67%* glutamate vs 51% SOD and CAT vs 45% unmodified), and coronary flow (81%* glutamate vs 79%* SOD and CAT vs 62% unmodified). We conclude that substrate enhancement with L-glutamate provides superior myocardial protection than is possible with the oxygen free-radical scavengers SOD and CAT during extended periods of cold storage for cardiac transplantation.

Animals↗