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Biomedical subjects

C R Ayers

Publications and source records attributed to C R Ayers.

At least 37 records · Page 2Linked to original sources
PubMed1987

Limitation of deuterium labelled methoximes as internal standards in the mass spectral analysis of prostaglandins.

A reported method for the preparation of d3-methoxime derivatives as internal standards for prostaglandin assays by gas chromatography-mass spectrometry was evaluated. Sample derivatization resulted in 1.5-86% exchange of the d3-methoxime in a series of prostaglandins. Exchange was minimal when the methoxime was on the 5-membered ring; whereas, acyclic methoximes exhibited extensive exchange. Induced strain energy due to the steric interaction of the hydroxyl group and the C13-C20 alkyl side chain with the gem-dimethoxylamine transition state is offered as an explanation for the unusual stability of PGE2. The use of 18O exchange of the carboxylic acid function is presented as an alternative for the preparation of unavailable labelled eicosanoids.

Deuterium↗
PubMed1985

Measures of knowledge and attitude toward preventive cardiology.

In this paper, the authors describe the development and validation of an inventory of preventive cardiology at the University of Virginia. The inventory contains two instruments designed to measure medical students' preinstructional and postinstructional knowledge of and attitude toward preventive cardiology. The knowledge test subscales provide unique and significant information about knowledge in preventive cardiology and can discriminate among groups differing in level of instruction and expertise in preventive cardiology. The attitude survey provides information about two attitude factors: cardiovascular disease prevention and cardiovascular disease research priorities. In the study reported here, attitudes appeared not to differ among groups of students with different preventive cardiology instructional levels and expertise. Both instruments were demonstrated to be useful measures of medical students' knowledge and attitudes concerning preventive cardiology educational programs.

Adult↗
PubMed1985

Enalapril maleate versus captopril. A comparison of the hormonal and antihypertensive effects.

24 hypertensive patients were randomised into 2 groups to compare the antihypertensive effects of enalapril and captopril over a 10-week period. In the hydrochlorothiazide run-in period, blood pressure was reduced from 171 +/- 4/109 +/- 1mm Hg to 160 +/- 4/103 +/- 1mm Hg (p less than 0.05). Angiotensin-converting enzyme (ACE) inhibition decreased blood pressure to 132 +/- 3/87 +/- 2mm Hg. Captopril decreased diastolic blood pressure significantly more after 3 hours than enalapril (-24 versus -17mm Hg, p less than 0.05). After 10 weeks of therapy, this antihypertensive response was maintained at 134 +/- 3/83 +/- 1mm Hg. There was no difference between the captopril and enalapril treated groups. Acute and chronic responses of plasma renin activity, plasma aldosterone and ACE were determined. There was an acute positive correlation between the rise in plasma renin activity and the fall in blood pressures with captopril but not with enalapril. With chronic treatment there was no difference in the ability of either of the 2 drugs to reduce blood pressure, inhibit ACE, reduce aldosterone or stimulate plasma renin activity.

Adult↗
PubMed1985

Captopril versus enalapril maleate: a comparison of antihypertensive and hormonal effects.

The antihypertensive effects of captopril and enalapril maleate were studied over a 10-week period in 24 hypertensive patients randomized into captopril or enalapril treatment groups. Prestudy blood pressure was 171 +/- 4/109 +/- 1 mm Hg and after 4 weeks of hydrochlorothiazide 160 +/- 4/103 +/- 1 (p less than 0.05). With the addition of converting enzyme inhibitor to hydrochlorothiazide the blood pressure decreased at 3 h to 132 +/- 3/87 +/- 2 in the subjects. The diastolic blood pressure decreased acutely more with captopril (-24) than with enalapril (-17) (p less than 0.05). After 10 weeks of combined therapy the depressor response was maintained (134 +/- 3/83 +/- 1) and there was no difference between the diastolic blood pressure in the two groups treated with captopril and enalapril. Acute and chronic responses of plasma renin activity, plasma aldosterone, and converting enzyme to the angiotensin-converting enzyme inhibitor were determined. There was a significant correlation between the acute fall in diastolic blood pressure and rise in plasma renin activity in patients treated with captopril but not with enalapril. In conclusion, there is an acute depressor response with converting enzyme inhibition which is more pronounced with captopril than with enalapril and which correlates with an increase in plasma renin activity. With more prolonged treatment, the two drugs show equivalent efficacy in reducing blood pressure, inhibiting angiotensin-converting enzyme, reducing aldosterone, and stimulating plasma renin activity.

Adult↗
PubMed1983

Relation of therapeutic response to nifedipine to coronary anatomy and motion of S-T segment during unstable angina pectoris.

Of 77 patients hospitalized for unstable angina pectoris and failure of oral, dermal, or intravenous nitrates and/or beta blockade, 81 percent with negligible or single-vessel disease and 55 percent with two- or three-vessel disease showed response (p less than 0.05) to nifedipine therapy. Patients with either S-T elevation or no change during pain responded better (31 of 45) than those with any S-T depression (16 of 32; p less than 0.05). Patients with negligible or single-vessel disease had a higher prevalence of S-T elevation (13 of 16) than patients with two- or three-vessel disease (15 of 31; p = 0.004). S-T motion did not predict response in patients with two- or three-vessel disease, but did predict response in patients with negligible or single-vessel disease. On follow-up study at 9 +/- 8 (range one to 33) months, 39 of 42 who had shown response were free from pain. Three died from infarction without unstable angina. (range one to 33) months, 39 of 42 who had shown response were free from pain. Three died from infarction without unstable angina. Five who showed response had elective bypass surgery. The addition of nifedipine abolished or reduced pain episodes by more than 50 percent in 61 percent of patients with refractory unstable angina pectoris. Patients with negligible or single-vessel disease with S-T elevation benefit most. In patients with two- or three-vessel disease, the type of S-T motion did not predict response. Follow-up of all those with response indicated sustained amelioration by nifedipine therapy. Failure of nifedipine therapy should not be accepted until a dose of 120 mg per day has been achieved, or until intolerable side effects appear.

Adult↗
PubMed1983

Effects of percutaneous transluminal angioplasty on renal plasma flow.

Percutaneous transluminal angioplasty is being used with increasing frequency for the treatment of renal artery stenosis. Several noninvasive techniques that utilize radioactive tracers have been used for monitoring the effects of angioplasty and progression of disease. Forty-one patients were studied before and after renal angioplasty by using renograms and fractionated measurements of effect renal plasma flow. Although there were striking examples of improvement in effective renal plasma flow following angioplasty, this was not a consistent finding. There was a tendency for effective renal plasma flow to revert to the baseline level on follow-up studies. Cure of hypertension was more likely in patients without renal insufficiency and in patients with shorter periods of sustained hypertension. Fractionated effective renal plasma flow studies did not reliably differentiate patients who were cured from those who were improved nor were we able to delineate clearly those requiring repeat dilatation. Nevertheless, this technique is useful for noninvasively measuring fractionated renal function in the immediate postoperative or postdilatation recovery period and for detecting the difference between occlusion of the renal artery and transient renal insufficiency due to contrast material. Also, long-term measurement of fractionated function has value in following potential progression of the basic disease process.

Adult↗
PubMed1983

Measurement of plasma prostaglandin E2 using capillary gas chromatography negative ion chemical ionization mass spectrometry.

A stable isotope dilution assay for the measurement of plasma prostaglandin E2 (PGE2) employing capillary column gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICIMS) is described. PGE2 was extracted from plasma using C18 and silica SEP-PAKS. Further purification and separation was accomplished by thin layer chromatography. The prostaglandin was analyzed as its pentafluorobenzyl ester-methoxime-trimethyl-silyl ether, using fragment ions at m/e 524 (protium) and m/e 528 (deuterium) for quantitation. The mean plasma concentration of PGE2 determined in 8 healthy volunteers was 2.8 +/- 2.0 pg/ml.

Adult↗
PubMed1982

Percutaneous transluminal angioplasty: the treatment of choice for renovascular hypertension due to fibromuscular dysplasia.

Twenty-three renal artery stenoses in 21 hypertensive patients, caused by fibromuscular dysplasia, were treated with percutaneous transluminal angioplasty (PTA). Follow-up over a period of 1 to 30 months, including angiography, renal vein renin assay, and radionuclide flow studies, was performed in 8 patients, each with one stenosis. Dilatation was initially successful in all cases and was successfully repeated in 1 case. The mean systolic pressure decreased by 61.81 mm Hg and the mean diastolic pressure by 36.28 mm Hg in response to treatment. Thirteen patients were cured, 8 were felt to have better control of blood pressure on medication, and there was no failures. This study demonstrates that PTA is a clinically effective method of treating renovascular hypertension due to fibromuscular dysplasia.

Adult↗
PubMed1981

Percutaneous transluminal angioplasty in patients with renal artery stenosis: follow-up studies.

Fifty renal artery stenoses in 38 hypertensive patients were treated with percutaneous transluminal angioplasty. Follow-up over a period of 1 to 24 months (mean, 9 mo.), including angiography, renal vein renin determinations, and radionuclide flow studies, were performed in 24 patients (32 stenoses). The initial dilatation was successful in 90% of stenoses and redilatation was necessary in 22% with a success rate of 84%. The mean systolic pressure decreased by 65.83 mm Hg and the mean diastolic pressure by 35.88 mm Hg in response to the treatment. Sixteen patients were cured, 18 were felt to have better control of blood pressure on medication, and 4 were not helped. Percutaneous transluminal angioplasty appears to be a technically feasible and clinically effective method of treating renovascular hypertension.

Adolescent↗
PubMed1981

Left ventricular mural thrombus in a patient with thrombocytosis and agnogenic myeloid metaplasia.

The two factors responsible for the development of left ventricular mural thrombi are endocardial injury secondary to old or recent anterior myocardial infarction and left ventricular dysfunction. Endothelial damage also is thought to be the initial event in the development of arterial thrombi. However, arterial thrombi may develop in patients with thrombocytosis secondary to myeloproliferative disorders in the absence of endothelial injury. A patient had thrombocytosis secondary to agnogenic myeloid metaplasia and a left ventricular mural thrombus developed in the absence of clinical or laboratory evidence of old or coronary angiogram and left ventricular function. To our knowledge, this is the first such case reported.

Aged↗
PubMed1980

Percutaneous transluminal dilatation of the renal arteries: techniques and results.

The techniques and results of percutaneous transluminal angioplasty (TPA) of the renal arteries were evaluated in 20 hypertensive patients with 25 renal artery stenoses. Follow-up angiograms have been obtained in nine patients. Many patients had evidence of both essential and angiotensinogenic hypertension. Eleven patients had evidence of severe diffuse atherosclerotic disease, and nine patients had evidence of renal insufficiency. The mean systolic pressures before and after PTA were 203.80 and 150.30, respectively. The mean diastolic pressures before and after PTA were 117.45 and 85.95, respectively. Ten patients were cured. Six patients with long histories of hypertension and a recent increase in blood pressure were classified as having blood pressure easier to control with antihypertensive medication following PTA. Three patients failed to respond to PTA, and one patient was a technical failure. The advantages of this technique include avoidance of general anesthesia and a major surgical procedure, decreased cost, and a shortened hospital stay. The technique can be easily repeated if necessary, and future surgical intervention is not precluded if the method is unsuccessful.

Adult↗
PubMed1979

Identification and differentiation of surgically correctable hypertension due to primary aldosteronism.

During a protocol study for the evaluation of patients with primary aldosteronism, a variety of diagnostic studies were employed in an attempt to identify patients with primary aldosteronism and to differentiate patients with adrenal adenoma from patients with idiopathic adrenal hyperplasia. In this study, we are able to demonstrate the utility of (1) absent postural increase in plasma aldosterone concentration, (2) adrenal scanning and (3) normalization of blood pressure with spironolactone therapy in identifying patients with primary aldosterone excess who have an adrenal adenoma, surgical removal of which results in eliminating their hypertension.

Adenoma↗
PubMed1979

Activity of [des-aspartyl1]-angiotensin II in primary aldosteronism.

This study describes the effects of [des-Aspartyl(1)]-angiotensin II ([des-Asp]-AII) on blood pressure and aldosterone production in patients with primary aldosteronism due to aldosterone-producing adrenal adenoma (APA) and idiopathic adrenal hyperplasia (IHA), and in normotensive control subjects. 10 patients with primary aldosteronism, 7 with APA and 3 with IHA, and 6 normotensive control subjects were placed on a constant 150-meq sodium diet for 4 days. [des-Asp]-AII was infused for 30 min at 6, 12, and 18 pmol/kg per min. Three groups of patients were identified on the basis of aldosterone response to [des-Asp]-AII. Group I, composed of normotensive control subjects, showed incremental increases in plasma aldosterone concentration from 6+/-1 to 14+/-3 ng/100 ml (P < 0.01) with [des-Asp]-AII infusion. Group II, composed of patients with primary aldosteronism, showed incremental increases in plasma aldosterone concentration from 33+/-8 to 65+/-13 ng/100 ml (P < 0.05) with 12 pmol/kg per min of [des-Asp]-AII. Group III, also composed of patients with primary aldosteronism, showed no increase of plasma aldosterone concentration with [des-Asp]-AII. Groups I and II showed similar percentage increases in plasma aldosterone concentration (P = NS). Group III showed significantly lower aldosterone responses than group I (P < 0.01). Group II included all patients with IHA and two patients with APA. Group III included only patients with APA. The blood pressure responses to [des-Asp]-AII of subjects in group I did not differ significantly from those of groups II or III.Thus, patients with IHA and a subgroup of patients with APA showed responsiveness to [des-Asp]-AII which was limited to adrenal cortical stimulation of aldosterone biosynthesis. This suggests that adrenal responsiveness to angiotensin is a major control mechanism in some forms of primary aldosteronism. The differential adrenal responsiveness to [des-Asp]-AII in patients with APA indicates either that there are two distinct subpopulations of APA, or that alteration in tumor response to angiotensin occurs during the natural progression of the disease history.

Adrenal Glands↗