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Biomedical subjects

M Grimm

Publications and source records attributed to M Grimm.

At least 163 records · Page 9Linked to original sources
PubMed1990

Energy consumption in paraplegic ambulation using the reciprocating gait orthosis and electric stimulation of the thigh muscles.

The energy consumption of six thoracic paraplegic persons ambulating in the reciprocating gait orthosis (RGO) with and without functional electric stimulation (FES) of their thigh muscles was determined as a function of walking speed. Plots of Kcal/kg-min and Kcal/kg-m vs walking speed in the RGO and RGO & FES were experimentally determined in this study and compared with the energy cost of walking in the long leg brace (LLB), the hip guidance orthosis (HGO), and an FES walking aid from data available in the literature. The RGO powered with electric stimulation of the thigh muscles required the lowest energy expenditure in Kcal/kg-m across the full range of walking speeds. The RGO, HGO, LLB, and FES walking orthoses ranked second, third, fourth, and fifth respectively. The lowest energy costs in Kcal/kg-min were associated with the RGO & FES, followed by the RGO, HGO, LLB, and FES for walking speeds below .28m/sec. At walking speeds higher than .28m/sec the HGO demonstrates lower energy cost followed by the RGO & FES, RGO, FES, and LLB. At the end of a 30-m walk, patients using the RGO & FES had a mean heart rate (HR) which was 12 beats/min less than the mean HR when using the RGO without FES, 31 beats/min less than the HR when using the LLB, and 42 beats/min less than the HR when using FES only. It was concluded that the FES-powered RGO combines the advantages of a passive mechanical orthosis with those of FES to provide substantial improvements in energy cost which may provide paraplegic persons with a mode of independent ambulation superior to the wheelchair.

Adult↗
PubMed1989

Toxic effects of aldehydes released from fixed pericardium on bovine aortic endothelial cells.

Glutaraldehyde (GA) and formaldehyde (FA) were shown to be released from 1 cm2 fixed pericard patches into 2-mL storage solutions after three 2-min washings in concentrations of about 1 mg/L. The cytotoxicity of these aldehyde concentrations on bovine aortic endothelial cells (BAECs) was evaluated in vitro, by proliferation capacity, cellular ATP content, PGI2 release and cyclic AMP synthesis. Continuous incubation of BAECs with GA greater than 0.1 mg/L and FA greater than 0.5 mg/L resulted in a significantly inhibited proliferation and in an increase of the intracellular Ca2+ triggered parameters, PGI2 and cyclic AMP, up to three fold. This strongly suggests an aldehyde-induced inhibition of the plasma-membrane bound Ca2+-ATPase, an enzyme which normally maintains low intracellular Ca2+-level. From these findings there is evidence that aldehydes released from bioprosthetic valve tissue may contribute to the lack of endothelial cell coverage in human implants.

Adenosine Triphosphate↗
PubMed1989

Human endothelial cell seeding: evaluation of its effectiveness by platelet parameters after one year.

Platelet parameters were assessed in patients after implantation of polytetrafluoroethylene (PTFE) grafts, either nonseeded or seeded with autologous endothelial cells or reversed saphenous vein grafts, during the follow-up period of 1 year. The objective of this investigation was to compare the sensitivity of different noninvasive platelet parameters with the assessment of the result of endothelial cell seeding. Scanning electron microscopic investigation of circulating blood platelets showed a significantly higher incidence of activated platelets in patients with seeded or nonseeded PTFE grafts, compared with patients after reversed vein graft implantation. "Shape-changed" platelets, as well as membrane-perforated thrombocytes, were found exclusively in the circulating blood of patients after seeded or nonseeded PTFE graft implantation, indicative of platelet trauma by the artificial graft surface. Plasma levels of platelet factor IV and beta-thromboglobulin, as well as the uptake of indium-111-labeled platelets, failed to show statistically significant differences after 1 year of follow-up. The similar results for seeded and nonseeded grafts indicate the failure of endothelial cell seeding to induce the development of a nontraumatizing surface, comparable to that of saphenous vein grafts.

Blood Platelets↗
PubMed1988

Prognostic significance of signal-averaged ECGs during acute myocardial infarction: a preliminary report.

To gain insight into the prognostic significance of the presence of late potentials detected by body surface signal-averaged electrocardiography during acute myocardial infarction, the authors prospectively studied the relationship between the presence of late potentials and the occurrence of ventricular arrhythmias and sudden death in 52 patients from the initial presentation of myocardial infarction to 14 months after discharge from the hospital. Signal-averaged recordings were performed on admission and again at the time of discharge (mean, 12 days from initial tracing). Late potentials were present on the first recording in 10 patients, 6 of whom had late potentials on the second recording. Twelve patients had late potentials on the second recording, and six of these did not have late potentials on the first recording. Early in-hospital sustained ventricular tachycardia and ventricular fibrillation occurred in three patients, all in the late potential-negative group. There were 10 deaths, 7 in the hospital and 3 late. There was no significant difference in early or late mortality between the late potential-positive and the late potential-negative groups due to the small sample size, although there was a trend toward higher mortality in the late potential positive group. Late potentials detected by body surface signal-averaged electrocardiography did not predict the occurrence of early in-hospital ventricular tachycardia or fibrillation or sudden death. During the acute phase of myocardial infarction, late potentials are often variable and transient findings on signal-averaged electrocardiography.

Arrhythmias, Cardiac↗
PubMed1987

Location of the epitope for the alpha-tubulin monoclonal antibody TU-O1.

A cyanogen bromide peptide of pig brain alpha-tubulin with high reactivity to the monoclonal antibody TU-O1 has been isolated and identified. It corresponds to positions 37-154 of the alpha-tubulin sequence. A tryptic peptide within this region corresponding to positions 65-79 was also immunoreactive. Its relatively low reactivity, however, indicates that one or more important determinants are missing.

Amino Acid Sequence↗
PubMed1987

Narrow polarized components in the OH 1612-MHz maser emission from supergiant OH-IR sources.

High-resolution OH 1612-MHz spectra are presented of the supergiant OH-IR sources VY CMa, VX Sgr, IRC 10420 and NML Cyg. The spectra have a resolution of 300 Hz. Narrow components in the spectra have linewidths as small as 550 Hz (0.1 km s-1) but there is no evidence for components narrower than this. These results are in accord with present understanding of maser line-narrowing and of the physical conditions in the OH maser regions. Many of the narrow components have an appreciable degree of circular polarization which is not apparent at the lower frequency resolutions usually employed. The circular polarization indicates the presence of magnetic fields of approximately 1 mG in the circumstellar envelopes, at distances of approximately 3x10(16) cm from the central stars. These fields are strong enough to influence the outflow from the stars, and may help to explain some of the asymmetries which are seen in their circumstellar envelopes.

Astronomical Phenomena↗
PubMed1986

Interferon alfa-2b-cyclophosphamide combination studies: in vitro and phase I-II clinical results.

Since interferon alfa-2b (Intron A) is useful as a single agent, it is important to determine if interferon can be combined with standard chemotherapy to improve both response and survival in patients with cancer. Using clonogenic assays, interferon was tested alone and in combination with cyclophosphamide (Cytoxan) or melphalan (Alkeran) using several dose and exposure schedules to evaluate cytotoxicity. In vitro, continuous-exposure interferon produced optimal cell kill. Maximum enhancement of cytotoxicity occurred with cyclophosphamide or melphalan pretreatment (1 hour) and/or simultaneous interferon treatment. Based upon these data, a phase I-II study was designed to determine the tolerance of cancer patients to a fixed dose of cyclophosphamide (150 mg/m2 p.o. daily X 4 days [days 2 to 5]) combined with increasing doses of interferon. Interferon was administered subcutaneously on treatment cycle days 1 to 5, plus days 8, 10, 12, 15, 17, and 19 of the 21-day regimen. Three patients had partial responses: one breast cancer, one angiosarcoma, and one myeloma (mixed). All patients reported mild flu-like symptoms, fatigue, and anorexia. Leukopenia occurred in all patients; three required treatment interruption to allow recovery. Eight patients had a fall in hemoglobin (mean decrease 1.4 g/dL). The combination of cyclophosphamide and interferon was safe and deserves further trial in cancer treatment. However, using this combination schedule, interferon doses greater than or equal to 5 X 10(6) IU were poorly tolerated and compromised administration of full-dose cyclophosphamide.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1983

Correction of altered noradrenaline reactivity in essential hypertension by indapamide.

Fourteen patients with untreated mild to moderate essential hypertension had, on average, an abnormally high cardiovascular reactivity to exogenous noradrenaline and angiotensin II, while plasma noradrenaline, renin activity, exchangeable body sodium, and blood volume were normal. Treatment with a low dose of indapamide (2.5 mg/day) for 6 weeks decreased blood pressure by 10% in these hypertensive patients but not in 13 normal control subjects. Plasma or blood volume and exchangeable sodium were not changed significantly; nevertheless, the latter, and body weight, tended to be decreased slightly. Though a mild reduction in extracellular sodium in both normal and hypertensive subjects appears possible, it may not fully explain per se the blood pressure-lowering effect of indapamide in essential hypertension. Indapamide induced a mild decrease in angiotensin II pressor responsiveness in normal or hypertensive subjects, but a possible depressor influence from this change was probably antagonized by a concomitant pronounced increase in plasma renin activity. In hypertensive patients, the abnormally high noradrenaline reactivity was corrected by indapamide without an accompanying increase in endogenous plasma noradrenaline levels. Indapamide-induced changes in blood pressure correlated with those in noradrenaline pressor dose. It was concluded, therefore, that indapamide may decrease blood pressure in essential hypertension at least in part by lowering an abnormally high cardiovascular noradrenaline reactivity without causing an equivalent increase in adrenergic nervous activity.

Adolescent↗
PubMed1981

Chronic treatment with the new potent vasodilator Ro 12-4713 in moderate to severe hypertension: effects on blood pressure, endocrine function, sodium and plasma volume.

The antihypertensive efficacy and endocrine profile of the new antihypertensive agent, Ro 12-4713, were evaluated in 23 patients (17 men and 6 women) with moderate to severe arterial hypertension. Following addition of Ro 12-4713 to pre-existing therapy with diuretics and beta-blockers or sympatholytics, blood pressure in most of the patients was normalized within one month by a daily dose of 60 to 120 mg. Heart rate was only slightly increased. Orthostatic hypotension was not observed. Weight gain or oedema formation occurred in 14 patients within the first four weeks, but could be controlled satisfactorily by intensified diuretic therapy. Increased hair growth occurred in most of the patients. After a mean duration of treatment of 2.8 months, plasma volume and plasma and urine sodium were unaltered, and plasma potassium was slightly decreased. Plasma renin activity was doubled, whereas plasma aldosterone concentrations were unaltered. Plasma norepinephrine levels were high before and increased only slightly during chronic Ro 12-4713 treatment, whereas urinary norepinephrine excretion was unchanged. Plasma and urinary epinephrine were unaltered by Ro 12-4713. Ro 12-4713 appears to be a potent vasodilator for the combination treatment of hypertension in men.

Adult↗
PubMed1981

Correction of altered noradrenaline reactivity in essential hypertension by indapamide.

Fourteen patients with untreated mild to moderate essential hypertension had on average an abnormally high cardiovascular reactivity to exogenous noradrenaline and angiotension II, while plasma noradrenaline, renin activity, exchangeable body sodium, and blood volume were normal. Treatment with a low dose of indapamide (2.5 mg/day) for six weeks decreased blood pressure by 10% in these hypertensive patients but not in 13 normal control subjects. Plasma or blood volume and exchangeable sodium were not changed significantly; nevertheless, the latter, and body weight, tended to be decreased slightly. Though a mild reduction in extracellular sodium in both normal and hypertensive subjects appears possible, it may not per se fully explain indapamide's blood pressure-lowering effect in essential hypertension. Indapamide induced a mild decrease in angiotensin II pressor responsiveness in normal or hypertensive subjects, but a possible depressor influence from this change was probably antagonised by a concomitant pronounced increase in plasma renin activity. In hypertensive patients, the abnormally high noradrenaline reactivity was corrected by indapamide without an accompanying increase in endogenous plasma noradrenaline levels. Indapamide-induced changes in blood pressure correlated with those in noradrenaline pressor dose. It was concluded, therefore, that indapamide may decrease blood pressure in essential hypertension at least in part by lowering an abnormally high cardiovascular noradrenaline reactivity without causing an equivalent increase in adrenergic nervous activity.

Adolescent↗
PubMed1980

Norepinephrine clearance and pressor effect in normal and hypertensive man.

Whether and to what extent the sympathetic nervous system participates in the development of essential hypertension has remained largely unclear. The role of the adrenergic effector - cardiovascular response axis in the pathogenesis of essential hypertension was investigated by combined analysis of blood levels, total plasma clearance and cardiovascular pressor effects of norepinephrine (NE). Measurements of plasma NE and blood pressure were performed before, during and after an intravenous infusion of NE at stepwise increasing rates in approximately age and sex-matched groups of 28 normal subjects and 35 patients with essential hypertension. The threshold of the pressor effect of NE was lower in hypertensive than in normal subjects (20 +/- 10 vs. 42 +/- 26 ng/kg min; P < 0.001); but the slope of the dose - resonse curve and basal endogenous plasma NE were in the average similar. Total plasma NE clearance estimated under steady state conditions was similar in normal and hypertensive subjects (5.3 +/- 2.5 vs. 5.4 +/- 2.31/min). NE clearance corrleated inversely with basal plasma NE in normal subjects (r = 0.57; P < 0.005). The plasma half-life of NE was about 2 min. These findings demonstrate that basal blood levels and total plasma clearance of NE during NE infusion are usually normal in essential hypertension. A low threshold of the pressor effect of NE in the presence of normal adrenergic activity may contribute to the development and/or maintenance of essential hypertension.

Adolescent↗
PubMed1980

Age-rated profile of cardiovascular reactivity to norepinephrine and angiotensin II in normal and hypertensive man.

The interrelationships among age, cardiovascular pressor reactivity to intravenously infused norepinephrine (NE) or angiotensin II, and endogenous plasma NE or renin (PRA) levels were evaluated i 31 normal subjects and 37 patients with essential hypertension. In normal subjects both angiotensin II pressor dose and PRA decreased progressively with aging. Angiotensin pressor dose correlated positively with PRA (r = 0.41, P < 0.025) and inversely with age (r = -0.46, P < 0.02). NE pressor dose and basal plasma NE were also positively correlated (r = 0.53, P < 0.005), but the two factors remained largely unchanged with aging. Findings in essential hypertension differed in certain aspects. Angiotensin II pressor dose did not correlate with either basal PRA or age; and pressor doses of NE and angiotensin II tended to be lower in some patients than in normal subjects. These findings indicate that aging is accompanied by a physiologic increase in cardiovascular reactivity to angiotensin II, probably due to a concomitant decrease in circulating renin. The dissociation between angiotensin pressor dose and PRA in essential hypertension suggests an interference from an other factor.

Adult↗
PubMed1980

[Comparison of oral diazoxide and minoxidil in refractory hypertension].

The efficacy and side effects of two potent vasodilatators, namely diazoxide and minoxidil given orally, were compared in 11 patients who had hypertension refractory to conventional drug treatment. The latter included diuretics, betablockers and/or sympatholytics, and either dihydralazine or prazosin. In a crossover approach, dihydralazine and prazosin were withdrawn and replaced by diazoxide or minoxidil. In nine patients the diazoxide phase preceded the minoxidil treatment, while in two it followed minoxidil treatment. Before introduction of the more potent vasodilators blood pressure averaged 181/107 mm Hg in the supine and 161/103 mm Hg in the upright position. Both, oral diazoxide (median dose 400 mg/d( and minoxidil (medium dose 17.5 mg/d) produced similar decreases (p < 0.02) in mean arterial pressure (-15%) in the supine and (-11 vs. -12%) in the upright position. They caused a comparable tendency for sodium retention and weight gain which could be satisfactorily controlled with increased diuretic therapy, except in one patient. Hypertrichosis occurred with both drugs, but tended to be somewhat milder with diazoxide. Electrocardiograms remained generally unchanged. Plasma glucose levels were increased during diazoxide treatment in six patients necessitating interruption of this therapy in four patients. It is concluded that the antihypertensive potency and most side effect of orally administered diazoxide are comparable to those of minoxidil, except for diazoxide-related hyperglycemia which may limit the use of this substance.

Blood Glucose↗