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Biomedical subjects

D A Morrison

Publications and source records attributed to D A Morrison.

At least 91 records · Page 5Linked to original sources
PubMed1991

Left and right ventricular systolic function and exercise capacity with coronary artery disease.

This prospective study of symptom-limited supine ergometry was conducted to determine the contributions of right ventricular (RV) and left ventricular (LV) systolic function to the exercise capacity of a cohort of patients with coronary artery disease (CAD). Patients with unstable angina, angiographically proven CAD (n = 53) and stable symptoms after medical therapy or angioplasty were included. Documented myocardial infarction (greater than or equal to 2 weeks before exercise) was present in 43 of 53 patients. Angina was the limiting symptom in 11 of 53; the other 42 stopped exercise with dyspnea or fatigue, or both. Oxygen consumption was measured on-line during exercise with a metabolic cart. RV ejection fraction and LV ejection fraction were measured by validated methods from gated blood pool radionuclide ventriculography. There were weak but statistically significant correlations between exercise oxygen consumption and exercise RV ejection fraction (r = 0.30, p less than 0.05) and between exercise oxygen consumption and exercise LV ejection fraction (r = 0.38, p less than 0.01). Multivariate regression analysis, including exercise RV ejection fraction, exercise LV ejection fraction and exercise heart rate versus exercise oxygen consumption revealed a better relation (r = 0.48, p less than 0.005) than any variable in univariate regression. The values of RV and LV ejection fraction at rest did not correlate significantly (r = 0.2, difference not significant), but the exercise values did correlate weakly (r = 0.41, p less than 0.01). The reserve of LV ejection fraction, defined as exercise minus rest value, correlated weakly with exercise oxygen consumption (r = 0.32, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗
PubMed1991

Genetic transformation in Streptococcus pneumoniae: nucleotide sequence analysis shows comA, a gene required for competence induction, to be a member of the bacterial ATP-dependent transport protein family.

The complete nucleotide sequence of comA, a gene required for induction of competence for genetic transformation in Streptococcus pneumoniae, was determined by using plasmid DNA templates and synthetic oligonucleotide primers. The sequence contained a single large open reading frame, ORF1, of 2,151 bp. ORF1 was included within the comAB locus previously mapped genetically and accounted for 50% of its extent. The predicted molecular weight of the largest polypeptide encoded within ORF1, 80,290, coincided with that measured previously (77,000) for the product of in vitro transcription-translation of the cloned comA locus. A Shine-Dalgarno sequence (AAAGGAG, delta G = -14 kcal) lay immediately upstream of ORF1. A sequence (TTtAat-17 bp-TAaAAT) similar to the Escherichia coli sigma 70 promoter consensus was located 410 bp upstream of ORF1. The deduced protein sequence of ComA showed a very strong similarity to the E. coli hemolysin secretion protein, HlyB, and strong similarities to other members of the family of ATP-dependent transport proteins, including the mammalian multidrug resistance P-glycoprotein. These similarities suggest that ComA functions in the transport of some molecule, possibly pneumococcal competence factor itself.

Adenosine Triphosphate↗
PubMed1991

Relief of right ventricular angina and increased exercise capacity with long-term oxygen therapy.

Long-term low-flow oxygen therapy can lead to improved exercise capacity and improved hemodynamics in selected patients with pulmonary hypertension. We report a patient who presented with severe exercise limitation and anginal chest pain that appeared to result from pulmonary hypertension and predominantly right ventricular ischemia. Acute oxygen therapy led to relief of pain but no change in exercise capacity or of pulmonary hypertension. After eight months of oxygen therapy, the patient's pulmonary hypertension was unchanged, but right ventricular hypertrophy and marked increases in exercise cardiac output and exercise capacity developed. Thus, oxygen can relieve right ventricular angina and facilitate the development of compensatory hypertrophy.

Angina Pectoris↗
PubMed1991

Coronary bypass surgery for stable angina and unstable angina pectoris.

Large randomized trials have shown that surgical revascularization is more effective than medical therapy in relieving angina and improving exercise tolerance. Development of atherosclerosis in the vein grafts plus progression of disease in the native vessels, however, results in a return of angina in a substantial proportion of patients 5 to 10 years after the procedure. The better myocardial protection, more complete revascularization, and improved graft patency rates that have occurred in the last decade imply that survival following coronary artery bypass may be improved in a broader spectrum of coronary artery disease patients than documented in the randomized trials. Patients with unstable angina have higher operative mortality but clearly benefit symptomatically from revascularization. There is a need for randomized trials to compare the relative risks and benefits of angioplasty versus surgical revascularization.

Adult↗
PubMed1990

Percutaneous transluminal coronary angioplasty for rest angina pectoris requiring intravenous nitroglycerin and intraaortic balloon counterpulsation.

In selected patients with medically refractory rest angina, percutaneous transluminal coronary angioplasty (PTCA) might be a reasonable alternative to coronary artery bypass graft surgery. Between January 1987 and November 1989, 1 operator at a Veterans Administration center performed PTCA on 73 vessels in 56 patients with rest angina of sufficient severity to require intravenous nitroglycerin in all 56 and intraaortic balloon counter-pulsation (IABP) in 18. Of the 56 patients, 17 (30%) had 1-vessel disease, 14 (25%) had 2-vessel disease and 25 (45%) had 3-vessel disease; 14 (25%) had greater than or equal to 1 prior bypass surgery, 35 (62.5%) were within 30 days of an acute infarction, 12 (21%) had left ventricular ejection fraction less than 0.50 and 7 (12.5%) were greater than 70 years of age. PTCA was successful in 61 (84%) vessels and 47 (84%) patients (greater than or equal to 1 vessel plus relief of angina). During index hospitalization, there were 2 deaths (3.6%), 4 myocardial infarctions (7.2%), 4 emergent bypass surgeries (7.2%) and 1 semiemergent bypass (1.8%) for technically unsuccessful PTCA. In follow-up from 3 to 36 months, there has been 1 additional myocardial infarction (1.8%), 1 late death (1.8%), 2 repeat PTCAs (3.6%), 6 crossovers to bypass (10.7%) and 38 patients (68%) have remained cardiac-event free. Although this angioplasty cohort is small and selected, these data raise the possibility that a prospective randomized comparison of PTCA versus bypass surgery might be feasible and appropriate in a subset of unstable angina patients who require intravenous nitroglycerin or IABP.

Adult↗
PubMed1990

Coronary angioplasty for medically refractory unstable angina in patients with prior coronary bypass surgery.

Percutaneous transluminal coronary angioplasty (PTCA) has been applied with good results to selected patients with unstable angina and to selected patients who have had prior bypass surgery. The population with prior bypass and unstable angina has not been specifically evaluated. This report reviews the results of angioplasty of 45 vessels in 34 patients with medically refractory unstable angina and at least one prior bypass heart surgery. Of these 34 patients, 32 had rest angina; 14 had resting electrocardiographic changes, all 34 were on aspirin 325 mg QD, 31 were on a calcium blocker, 22 were on a beta blocker, 9 were on intravenous nitroglycerin, and 5 required intraaortic balloon counterpulsation for temporary stabilization. Angioplasty of a vein graft was attempted in 17 patients; the left internal mammary was attempted in 4 patients; 24 native coronary arteries in 15 patients were attempted; 3 of the native arteries were protected left main arteries. Of the LIMA angioplasties, 3 were successful; in the 1 unsuccessful case, the occluded anterior descending artery was opened. Of the 17 vein grafts, 16 were successful: 1 had an acute occlusive syndrome and went to surgery with a balloon pump and bail out catheter; his recovery was uneventful. Of the 24 native artery angioplasties, 22 were successful: one patient was technically unsuccessful in the only vessel attempted; he went to semiemergent surgery and recovered uneventfully. In the other, a right coronary lesion was successfully dilated, but an occluded anterior descending artery was not opened. There were no deaths or in-hospital myocardial infarctions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1990

Coronary angioplasty for medically refractory unstable angina within 30 days of acute myocardial infarction.

Percutaneous transluminal coronary angioplasty (PTCA) has been used with good results in selected patients with unstable angina. The population with recent (less than or equal to 30 days) infarction and unstable angina is a subject of controversy. This report reviews the results of angioplasty of 84 vessels in 66 patients with medically refractory unstable angina who had documented myocardial infarction within 30 days of the procedure. Of these 66 patients, 54 had rest angina. Of the 66 patients with angioplasties, 58 patients (88%) had successful procedures. Two patients had technically unsuccessful results in the only vessel attempted; one went to elective surgery and recovered uneventfully and the other patient was in cardiogenic shock at the time of the procedure and died 12 hours later. There were three acute occlusions of infarct-related arteries that were managed medically. There were two (3%) emergency coronary artery bypass graft (CABG) procedures. There were two (3%) deaths during the index hospitalization. Of the 58 of 66 patients with technically successful angioplasty, all 58 had no more rest angina, and 46 had a satisfactory predischarge exercise test. All 46 were without angina at exercise. In follow-up ranging from 4 months to 36 months (14 months mean), there have been six cases of restenosis with recurrence of angina treated successfully with repeat angioplasty. There have been five late bypass surgeries. There have been three late deaths. These data, generated by a single operator in a Veterans Administration (VA) center, support the use of angioplasty in patients with unstable angina and recent myocardial infarction. The data suggest that a VA prospective randomized trial of PTCA versus CABG for post-infarction angina may be feasible.

Angina Pectoris↗
PubMed1990

Streptococcus pneumoniae possesses canonical Escherichia coli (sigma 70) promoters.

Seventeen DNA fragments from Streptococcus pneumoniae were randomly cloned in Escherichia coli with selection for promoter activity. The fragments were sequenced and the promoter locations were determined by primer extension analysis. Examination for sites similar to the E. coli major consensus promoter sequence revealed such a site in each of the seventeen fragments, located five to eight base pairs upstream of the point at which transcription was initiated in the E. coli host. Thus, the abundance of promoter activity found in pneumococcal DNA cloned in E. coli hosts arises primarily from sigma-70-type promoter structures. Combined with the observation that such sequences are usually found just upstream of, but not within, pneumococcal genes, this implies that one class (perhaps the major class) of pneumococcal promoters closely resembles the canonical E. coli promoter consensus.

Base Sequence↗
PubMed1990

Genetic transformation in Streptococcus pneumoniae: nucleotide sequence and predicted amino acid sequence of recP.

We present the complete nucleotide sequence of recP, a locus required for high-efficiency recombination of chromosomal DNA during genetic transformation in Streptococcus pneumoniae. The sequence was determined by using plasmid DNA templates and synthetic oligonucleotide primers. The locus contained a single large open reading frame, ORF1, of 1,968 base pairs (bp). ORF1 is included within the recP locus previously mapped genetically and accounts for 94% of its extent. The predicted molecular weight of the largest polypeptide encoded within ORF1, 71,662, coincided with that measured previously (72,000) for the product of in vitro transcription-translation of the cloned recP locus. A Shine-Dalgarno sequence (AGAAAGGA; delta G = -17 kcal [ca. -71.1 kJ]) lay 6 bp upstream of ORF1. A sequence (TTGcat-17 bp-TATAAT) similar to the E. coli sigma-70 promoter consensus was located 52 bp upstream of ORF1. This putative promoter overlapped a structure consisting of two perfect inverted 10-bp repeats and a loop of 8 bp.

Amino Acid Sequence↗
PubMed1989

Reduced exercise capacity of chronic obstructive pulmonary disease patients exercising with noseclip/mouthpiece.

A noseclip and low resistance mouthpiece are often used to monitor exhaled gases during exercise. Because otolaryngologic studies suggest that 50% of airway resistance is in the nose and mouth, it was hypothesized that patients with advanced chronic obstructive pulmonary disease might be artifactually limited by exercise testing with a noseclip and mouthpiece. Accordingly, 12 patients with stable chronic obstructive pulmonary disease performed identical symptom-limited supine bicycle exercise tests with and without noseclip and mouthpiece. Right-sided cardiac hemodynamic measurements, radionuclide ventriculography and arterial and mixed venous gas sampling were performed during each exercise test. Exhaled gases were analyzed during the noseclip/mouthpiece exercise. The order of exercise tests was alternated. Comparing exercises with and without a noseclip, there were significant reductions in exercise duration (397 +/- 270 vs 300 +/- 230 seconds, p less than 0.01), exercise oxygen consumption (780 +/- 279 vs 638 +/- 200 ml/min, p less than 0.01) and exercise cardiac output (8.4 +/- 2.7 vs 7.3 +/- 2.0 liters/min, p less than 0.05), an increase in right ventricular ejection fraction (0.39 +/- 0.08 vs 0.43 +/- 0.08, p less than 0.01) and no change in exercise heart rate (106 +/- 14 vs 106 +/- 14), right-sided cardiac pressures or arterial and mixed venous blood gases. These data suggest that a noseclip/mouthpiece can limit exercise tolerance in advanced chronic obstructive pulmonary disease patients. This limitation may result from decreased right-sided cardiac preload (venous return).

Adult↗
PubMed1989

Effect of i.v. omeprazole on the pH and volume of gastric contents before surgery.

Gastric pH and volume were measured in 87 patients who had received i.v. omeprazole (a new gastric antisecretory agent) 40 mg or placebo 1 or 3 h before surgery. Omeprazole increased the pH of gastric contents in the majority of patients. Administration 1 h before surgery produced greater gastric pH and smaller volume than administration 3 h before surgery. There was a reduction in the number of patients with a pH of less than 2.5 and a volume of 25 ml or more in the treated groups compared with the combined placebo groups. Omeprazole may have a role in prophylaxis against acid aspiration syndrome.

Adolescent↗
PubMed1989

Changes in right ventricular relaxation during acute anterior myocardial infarction in pigs.

To determine the effect of an anteroseptal myocardial infarction on right ventricular systolic and diastolic function, we studied 12 pigs before and 1 h after left anterior descending coronary artery occlusion. Total arterial occlusion was achieved by the percutaneous, transcatheter placement of a 1 mm Teflon plug into the mid portion of the artery. The resulting infarction involved 28 (SEM 3)% of the left ventricular wall, in the anterior and septal regions. A small rim of the right ventricular free wall adjacent to the septum and the right ventricular apex were also affected. End diastolic pressures in both ventricles rose significantly: left ventricular from 12(1) to 20(2) mm Hg and right ventricular from 8(1) to 10(1) mm Hg. Right ventricular peak systolic pressure increased from 29(2) to 35(2) mm Hg while left ventricular peak systolic pressure did not change. One hour after infarction the half time of isovolumic relaxation of the right ventricle was prolonged from 6.9(0.5) to 8.7(0.4) ms. Ejection fraction in both ventricles was depressed: from 46(1) to 34(2)% in the right ventricle and from 69(3) to 49(3) in the left ventricle. There was no change in either right or left ventricular dP/dt. These data suggest that right ventricular systolic and diastolic dysfunction occurs as the result of an anteroseptal myocardial infarction in pigs.

Acute Disease↗
PubMed1988

Functional tricuspid regurgitation and right ventricular dysfunction in pulmonary hypertension.

This study examined the effects of tricuspid regurgitation (TR) on the relation between right ventricular (RV) ejection fraction and mean pulmonary pressure. The significant inverse relation between RV ejection fraction and pulmonary artery pressure for the entire group (n = 95, r = -0.38, p less than 0.001) was improved either by looking only at the subset without TR (n = 56, r = -0.54, p less than 0.001) or by combining the RV ejection fraction with the angiographic grade of TR using multivariate analysis (n = 95, r = -0.52, p less than 0.001). Pulmonary hypertension was associated with the development of angiographic TR. These data support the concept that in using the RV ejection fraction as a measure of RV systolic function, it is necessary to consider the presence or absence of TR.

Adult↗
PubMed1988

Construction and properties of a new insertion vector, pJDC9, that is protected by transcriptional terminators and useful for cloning of DNA from Streptococcus pneumoniae.

A new Escherichia coli plasmid cloning vector, pJDC9, was constructed by replacing the TcR determinant of pMB9 with the erythromycin-resistance ermB determinant and the lacZ alpha gene of pUC19. Efficient transcriptional terminator signals were positioned at both ends of lacZ alpha. Evidence is presented that protection of the vector by terminator signals enabled cloning of many fragments of DNA from Streptococcus pneumoniae that were unstable in vectors lacking such protection, including pBR322. At the pneumococcal mal locus, three promoter sites required such protection, while overexpression of the malX protein appeared to be lethal despite such protection.

Cloning, Molecular↗
PubMed1988

Genetic transformation in Streptococcus pneumoniae: molecular cloning and characterization of recP, a gene required for genetic recombination.

A 225-base-pair fragment of a recombination gene was identified by insertion-duplication mutagenesis and used as a radioactive probe to clone the corresponding rec locus from Streptococcus pneumoniae in Escherichia coli plasmid vectors. Attempts to clone large pieces of this locus were unsuccessful, but small pieces of DNA from this region were cloned in the E. coli transcriptional terminator vectors pKK232-8 and pJDC9. The extent of the rec region, 2.1 to 2.2 kilobases, was defined by determining the competence phenotype of insertion mutations constructed in vitro. A deletion of the rec locus showed it to be necessary for chromosomal integration but not for plasmid establishment. A plasmid carrying the entire locus encoded a 72-kilodalton polypeptide in a cell-free E. coli transcription-translation system.

Bacterial Proteins↗