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Biomedical subjects

M E Thompson

Publications and source records attributed to M E Thompson.

At least 73 records · Page 4Linked to original sources
PubMed1987

Differential effect of stimulation of nucleus ambiguus on atrial and ventricular rates.

Acute experiments were performed on open-chest male mongrel dogs that were anesthetized with thiopental sodium and respired. An average of 10 penetrations per side was used to explore the rostral-caudal organization of the nucleus ambiguus (NA) and the area ventrolateral to it. Atrial pacing was performed on some trials to clarify the occurrence of atrioventricular (AV) block. In addition, the vagi were sectioned in some animals to confirm the peripheral pathway of the observed effects. Finally, the twin-pulse technique was used to classify the neurons underlying the observed effects according to their refractory periods. Stimulation in the area of the NA and lateral to it produced bradycardia and bradyarrhythmias without altering blood pressure. Stimulation of either the left or right NA produced slowing of both atrial and ventricular rates. However, slowing of the atrial rate was greatest with right NA stimulation, whereas slowing of the ventricular rate was predominant with left-side stimulation. The presence of AV block was evident from dropped QRS complexes with and without pacing. Vagotomy demonstrated that these effects were conducted by ipsilateral but not contralateral nerves. Measurement of the refractory periods showed that the neurons underlying both atrial and ventricular slowing were characteristic of B-fibers.

Analysis of Variance↗
PubMed1987

The possible effects of a change to master's entry level in occupational therapy.

One of the most challenging debates facing the profession of occupational therapy centers on whether or not the standard for entry level into the field should be upgraded. The occupational therapy baccalaureate degree has been viewed as too limited in scope and professional training, and the master's degree has been forwarded as the standard for entry into the profession. However, upgrading the entry level standard raises several questions. This study considered 25 areas that would be affected by upgrading the entry level from the baccalaureate to the master's level in occupational therapy and in related health professions. A model was developed to provide a framework for analyzing how a change in entry level will affect the current status of occupational therapy as a profession. Although the parallel material is drawn from other health professions, the considerations are similar to the ones faced by occupational therapy. This comparison is especially important because a major change in entry level education has far-reaching repercussions that must be considered before any groundwork is laid for upgrading educational requirements.

Clinical Competence↗
PubMed1987

Cardiac transplantation: improved quality of survival with a modified immunosuppressive protocol.

The effects on renal function on two different immunosuppressive protocols were evaluated retrospectively in two subsequent groups of heart transplant recipients. In group I, cyclosporine was given before the procedure at a loading dose of 17.5 mg/kg and then continued after the procedure to keep a whole blood level about 1000 ng/ml. In group II, cyclosporine was started only after the procedure at a lower dosage and was complemented by azathioprine, which was used for the first postoperative week. Group II showed a better perioperative renal function as determined by serum blood urea nitrogen and serum creatinine levels. Group II also showed a significant decrease of chronic nephrotoxicity secondary to long-term therapy with cyclosporine. Despite this improvement in late renal function, group II still shows a slow rise in serum creatinine. We think that even these lower dosages of cyclosporine can cause chronic nephrotoxicity and that further modification of the immunosuppressive regimen is required to completely abolish this toxic side effect.

Actuarial Analysis↗
PubMed1987

Speech discrimination skills in the elderly: a critical review.

Traditionally, investigators have claimed that speech discrimination skills decline with increasing age more than would be expected, given hearing sensitivity. These effects are magnified under difficult listening conditions. Evidence is presented which both supports and refutes this claim of decreased speech discrimination ability in the elderly. Other possible explanations for this phenomenon including reaction time, response bias, hearing threshold, memory, learning, selective attention and social expectation are discussed. The question of whether this effect represents central or peripheral processing is explored. It is suggested that further evidence is necessary before conclusive statements can be made.

Aged↗
PubMed1987

Endocrine factors of blood pressure regulation in different age groups.

Systolic and diastolic blood pressures were measured and blood and urine were collected at 4-hr intervals over a 24-hr span in 194 diurnally active children 11 +/- 1.5 years of age and in 278 elderly subjects 77 +/- 8 years of age. Plasma aldosterone and cortisol were determined by radioimmunoassay, serum calcium and magnesium on a Dupont ACA, and urinary epinephrine and norepinephrine by high-pressure liquid chromatography. In the children, there was a slight but statistically significant positive correlation between the circadian means in systolic blood pressure and norepinephrine excretion and serum calcium, and between diastolic blood pressure and norepinephrine excretion and serum calcium and magnesium. In the elderly subjects, there was a positive correlation between the circadian mean in diastolic blood pressure and aldosterone. In contrast to the findings in the children, however, the elderly subjects showed a negative correlation between the circadian means in norepinephrine excretion and in systolic and diastolic blood pressures. These investigations indicate differences in the regulation of the blood pressure within the "usual range" between children and elderly subjects. This has to be kept in mind in the study of essential hypertension, a syndrome that may be caused by different mechanisms in different age groups.

Age Factors↗
PubMed1986

Extent of myocardial fibrosis and cellular hypertrophy in dilated cardiomyopathy.

The distribution of fibrosis and cellular hypertrophy was studied in the hearts of patients with dilated cardiomyopathy (DC). Transmural sections were removed from the left and right ventricular free walls and the ventricular septum of 9 patients with heart failure and 6 control subjects. These sections were stained with hematoxylin-eosin (to determine cell size) and trichrome (to determine percent fibrosis). The sections were separated into equal areas from epicardium to endocardium in the free walls and right to left across the septum. Percent fibrosis was greater in patients with DC (20 +/- 4%) than control subjects (4 +/- 1%, p = 0.0001). A pattern of increasing fibrosis in the left ventricular free wall from epicardium (14 +/- 6%) to endocardium (22 +/- 9%, p less than 0.05) was documented. Fibrosis was greater on the left (21 +/- 12%) than the right (15 +/- 6%, p less than 0.05) side of the septum. No pattern was evident in the right ventricular free wall or in the control group. Myocardial cell diameter was greater in the heart failure group (22 +/- 5 micron) than the control group (17 +/- 2 micron, p less than 0.05), but no pattern of hypertrophy across the walls was seen. The increased fibrosis, the pattern of fibrosis and the increased cell diameter in patients with DC help to characterize DC.

Adult↗
PubMed1986

The contrasting effects of cyclosporin-A and azathioprine on arterial blood pressure and renal function following cardiac transplantation.

The effects of cyclosporin-A and azathioprine on the postoperative development of systemic hypertension and renal dysfunction in patients undergoing cardiac transplantation were compared retrospectively in 18 patients receiving cyclosporin-A and in 12 patients receiving azathioprine. Twelve months postoperatively, the average mean blood pressure was 116 +/- 13 mm Hg and 98 +/- 7.5 mm Hg; the average preoperative serum creatinine was 1.2 +/- 0.3 mg% and 1.5 +/- 0.3 mg%; and the postoperative serum creatinine was 2.2 +/- 0.8 mg% and 1.1 +/- 0.2 mg% (P less than 0.0001) in the cyclosporin-A-and azathioprine-treated groups respectively. Hemodynamic studies were done to characterize the de novo postoperative hypertension developing in the cyclosporin-A group. The pre- and postoperative cardiac output was 3.7 and 4.91/min, respectively (P less than 0.01). The pre- and postoperative systemic vascular resistance was 1707 and 1941 dynes sec X cm-5, respectively (P greater than 0.2). Peripheral renin activity and 24-hour urinary catecholamine excretion were not elevated. The mechanism of the hypertension developing in cyclosporin-A-treated patients is unknown, but is associated with normalization of cardiac output, an abnormally elevated systemic vascular resistance, and modest impairment of renal function. These findings are in marked contrast to azathioprine-treated patients, in whom postoperative hypertension and renal dysfunction do not occur. These observations implicate cyclosporin-A as the major contributing factor in the development of hypertension and renal dysfunction.

Adult↗
PubMed1986

Mortally ill patients and excellent survival following cardiac transplantation.

Cardiac transplantation was resumed in 1980 at the University Health Center of Pittsburgh. Generally accepted criteria for selection of patients were used, one being the expectation that survival would not reach 6 months. All of the initial recipients were in New York Heart Association Functional Class IV, but many were ambulant. We soon saw patients who were more clearly terminally ill. They were characterized by a systolic arterial pressure of less than 80 mm Hg, a cardiac index of less than 2 L/min/m2, evidence of reduced blood flow as indicated by urine output of less than 20 ml per hour, impaired mental function, and signs of decreased peripheral perfusion. The initial success of cardiac transplantation in these patients prompted us to reconsider selection criteria to include them among less strikingly ill candidates and to develop a therapeutic protocol designed to maintain peripheral perfusion and adequate renal and hepatic function until transplantation could be accomplished. Actuarial survival at 30 months for the group of terminally ill patients was 75% compared with 67% for the less critically ill group. Actuarial survival at 30 months for the combined group of 77 patients was 67%. Twenty-nine of the 33 mortally ill patients were alive and active at the time of writing, January, 1985.

Adult↗
PubMed1986

Blood pressure in the puerperium.

Blood pressure was measured by random zero sphygmomanometer in the morning and afternoon for 5 days after normal delivery in a group of 136 previously normotensive women. The number of women studied each day varied from 32 to 125. The afternoon blood pressure was higher than the morning blood pressure (differences: 1.7 mmHg systolic, 2.6 mmHg diastolic; P less than 0.05). Both systolic and diastolic blood pressures rose for the first 4 days after delivery. The average rise over the whole period was about 6 mmHg systolic and 4 mmHg diastolic (P less than 0.05). A considerable number of previously normotensive women displayed elevations of blood pressure in the puerperium. Twelve per cent of all patients exceeded a diastolic blood pressure of 100 mmHg.

Adolescent↗
PubMed1986

Loss of nocturnal decline in blood pressure after cardiac transplantation.

Twenty-four hour noninvasive ambulatory blood pressure and heart rate monitoring was performed on patients who underwent orthotopic cardiac transplantation, as part of the investigation of the de novo hypertension that developes in such patients. Patients with essential hypertension served as control subjects. The results demonstrated a highly significant loss of the usual decline in blood pressure and heart rate during sleep in the transplant patients. A similar loss of nocturnal decline in blood pressure was noted in a group of 10 patients with autonomic neuropathy secondary to diabetes mellitus. The de novo hypertension associated with cardiac transplantation is probably multicausal. Impairment of renal function by cyclosporin-A with associated salt and water retention and persistent elevation of the systemic vascular resistance in the presence of a restored normal cardiac output by the "new" heart are major factors. In addition, loss of the normal nocturnal decline in blood pressure and heart rate, which probably is related to the denervated state of the transplanted heart, may play an important role in blood pressure control.

Adult↗
PubMed1986

Subarachnoid hemorrhage and the heart.

Electrocardiographic abnormalities, both morphological and rhythmic, are frequently seen in association with spontaneous subarachnoid hemorrhage. These changes, which often reflect subendocardial damage, seem to be caused by hypothalamic stimulation leading to an acute increase in sympathetic tone. As a result, potentially life-threatening ventricular arrhythmias may develop in subarachnoid hemorrhage patients. These arrhythmias have responded to sympathetic blocking agents, which may also have a protective effect on subendocardial tissue in this setting. There is no evidence that the prophylactic administration of propranolol or other autonomic blockers significantly alters outcome in these patients. Ultimate morbidity and mortality are clearly related to the degree of intracerebral-intraventricular hemorrhage and vasospasm. This article reviews experimental and clinical evidence regarding the causes of cardiac abnormalities after subarachnoid hemorrhage, the types of abnormalities most frequently seen, their relationship with subendocardial lesions, and the role of autonomic blockers.

Adult↗
PubMed1986

Human and canine ventricular vasoactive intestinal polypeptide: decrease with heart failure.

Vasoactive intestinal polypeptide (VIP) is a systemic and coronary vasodilator that may have positive inotropic properties. Myocardial levels of VIP were assayed before and after the development of heart failure in two canine models. In the first, cobalt cardiomyopathy was induced in eight dogs; VIP (by radioimmunoassay) decreased from 35 +/- 11 pg/mg protein (mean +/- SD) to 5 +/- 4 pg/mg protein (P less than 0.05). In six dogs with doxorubicin-induced heart failure, VIP decreased from 31 +/- 7 to 11 +/- 4 pg/mg protein (P less than 0.05). In addition, VIP content of left ventricular muscle of resected failing hearts in 10 patients receiving a heart transplant was compared with the papillary muscles in 14 patients (five with rheumatic disease, nine with myxomatous degeneration) receiving mitral valve prostheses. The lowest myocardial VIP concentration was found in the hearts of patients with coronary disease (one patient receiving a transplant and three receiving mitral prostheses) (6.3 +/- 1.9 pg/mg protein). The other patients undergoing transplantation had an average ejection fraction of 17% +/- 6% and a VIP level of 8.8 +/- 3.9 pg/mg protein. The hearts without coronary artery disease (average ejection fraction of this group 62% +/- 10%) had a VIP concentration of 14.1 +/- 7.9 pg/mg protein, and this was greater than in hearts of the patients with coronary disease and the hearts of patients receiving a transplant (P less than 0.05). Myocardial catecholamines were also determined in 14 subjects; a weak correlation (r = 0.57, P less than 0.05) between the tissue concentrations of VIP and norepinephrine was noted.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Elevated plasma vasopressin in cardiomyopathic hamsters.

Hamsters of the BIO 14.6 strain characteristically develop cardiomyopathy as they age, and hamsters of this strain have overt signs of heart failure by 11 months of age. Plasma levels of the posterior pituitary hormone arginine-vasopressin (AVP) were found to be elevated (approximately 2-fold) in 11 month old BIO 14.6 hamsters, compared to age-matched hamsters of a control strain. AVP appeared inappropriately elevated in these animals, since they were neither hyperosmotic nor markedly hypotensive. The elevated levels of AVP observed in these animals appears to contribute to vasomotor tone, since intravenous administration of a specific antagonist of the vasoconstrictor action of AVP [d(CH2)5Ome(TYR)AVP] elicited a fall in arterial pressure (9 +/- 2 mm Hg, n = 6, p less than 0.05). The AVP antagonist had no effect on arterial pressure in hamsters of a control strain, and vehicle administration had no effect on arterial pressure in either strain. These data indicate that inappropriately elevated levels of AVP contribute to the cardiovascular state of myopathic hamsters. Since elevated plasma AVP has been noted in human congestive heart failure, these results suggest that AVP may contribute to the cardiovascular status during congestive heart failure.

Age Factors↗
PubMed1985

Reasons for the disagreements on the impact of smoking on medical care expenditures: a proposal for a uniform approach.

A recent paper suggested that smoking does not increase medical care expenditures and, therefore, that reduced smoking is unlikely to decrease it. This conclusion differs from that of most other studies in this area and the reasons for this disagreement are investigated. It is pointed out that medical care expenditure estimates yield different results depending on whether they are estimated on a per capita basis or in total for populations which change in size as smoking is reduced or eliminated. To avoid disagreement in future studies of this type, some specific proposals are made which should facilitate the comparison of results obtained from different studies.

Accident Prevention↗
PubMed1985

Thiopental after brain ischemia in monkeys. Cardiovascular and electroencephalographic effects.

The cardiovascular and electroencephalographic (EEG) effects of thiopental were investigated, with and without preceding global brain ischemia (GBI). Four groups of pigtailed monkeys were used: Group I received thiopental 90 mg/kg over 1 h after 16 min GBI. Group II received thiopental 90 mg/kg over 1 h without preceding brain ischemia. Group III received 90 mg/kg over 1, 3, 6, or 8 h with varying infusion rates and no brain ischemia. Group IV, after 16 min GBI, received thiopental 90 mg/kg over 12 h with a gradually reduced infusion rate, keeping thiopental serum levels around 120-140 mumol X l-1 throughout the infusion. Large doses of thiopental (Group II) produced serious cardiovascular side-effects. With co-existing brain ischemia (Group I), these side-effects were much worse; five of six animals not receiving lidocaine prophylaxis suffered circulatory arrest. A prolongation of the Q-T interval on the electrocardiogram may be of pathogenetic importance. In contrast, lower thiopental blood levels, sufficient to depress the EEG to burst suppression or isoelectricity, were well tolerated with and without preceding brain ischemia (Groups IV and III).

Animals↗
PubMed1985

Long-term hemodynamic follow-up of cardiac transplant patients treated with cyclosporine and prednisone.

To evaluate the long-term hemodynamic results in cardiac transplant patients treated with cyclosporine and prednisone, 19 patients were studied by cardiac catheterization and endomyocardial biopsy 13 +/- 3 months after transplantation. Immunosuppression consisted of 6 +/- 4 mg/kg/day cyclosporine and 20 +/- 8 mg/day prednisone. Eighteen patients were asymptomatic but had developed postoperative systemic hypertension (17 on antihypertensive therapy). These patients were compared with a normotensive control group of 18 patients without cardiovascular disease. Significant differences were found in heart rate; right atrial, pulmonary arterial, pulmonary arterial wedge, systemic arterial, and left ventricular end-diastolic pressures; cardiac index and stroke volume index; systemic and pulmonary vascular resistance; and end-diastolic volume index and left ventricular ejection fraction. The most frequent hemodynamic abnormalities included an elevated arterial pressure in 10 patients (56%), an elevated left ventricular end-diastolic pressure in six patients (33%), and a reduced ejection fraction in five patients (28%). Hemodynamic abnormalities tended to resolve or improve in the five patients restudied 2 years after transplantation. There was no significant relationship between fibrosis or inflammation on endomyocardial biopsy and hemodynamic abnormalities. We conclude that mild-to-moderate hemodynamic abnormalities are common in asymptomatic cardiac transplant patients receiving cyclosporine and prednisone.

Adult↗