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Biomedical subjects

R Dietz

Publications and source records attributed to R Dietz.

At least 217 records · Page 12Linked to original sources
PubMed1990

Intravenous thrombolytic therapy with a combination of single-chain urokinase-type plasminogen activator and recombinant tissue-type plasminogen activator in acute myocardial infarction.

The effects of simultaneous intravenous infusions of 12 mg recombinant tissue-type plasminogen activator (rt-PA) over 30 minutes and 48 mg single-chain urokinase-type plasminogen activator (scuPA) over 40 minutes were studied in 38 patients with acute myocardial infarction. Coronary arterial patency was assessed angiographically 60 minutes and 90 minutes after initiation of treatment. Patency was achieved in 19 of 31 patients (61.3%) (95% confidence limits, 42-78%) at 60 minutes and in 27 of 33 patients (81.8%) (95% confidence limits, 65-93%) at 90 minutes. Nonspecific plasminogen activation was monitored by measuring relevant plasma parameters. At 60 minutes and 120 minutes, the fibrinogen concentration decreased slightly to 82.8 +/- 24.3% and 91.2 +/- 17.4% of the preinfusion level, and the plasminogen concentration to 66.3 +/- 15.2% and 65.3 +/- 13.4%, respectively. A greater consumption of alpha 2-antiplasmin was observed, which decreased to 30.7 +/- 22.8% and 32.2 +/- 21.2% of the preinfusion level at 60 and 120 minutes, respectively. No bleeding necessitating transfusion was observed. Two patients (5.3%) died during hospitalization. The findings suggest that the combined intravenous infusion of rt-PA and scuPA at appropriate doses induces highly effective coronary thrombolysis equal to the best results obtained with either rt-PA or scuPA alone. This efficacy is coupled with high specificity. Thus, the data support the potential use of combinations of rt-PA and scuPA in place of monotherapy.

Drug Therapy, Combination↗
PubMed1990

[The multicentric glioblastoma multiforme].

The authors report on two cases of multicentric glioblastoma multiforme, one of them being a trilocular glioblastoma, whereas in the second case a second focus developed contralaterally. Both patients received whole skull radiation of 40 Gy. The patient who suffered from the primarily unilocal tumour was given a tumour boost. The article reports on the imaging via CT and MR.

Brain Neoplasms↗
PubMed1990

[Therapy of medulloblastomas--results from 1968 to 1985].

Between 1968 and 1985 35 patients with an histological proven medulloblastoma received radiotherapy after surgery. Patients are divided into three groups, showing the improvement in diagnostic procedures as well as in therapy. These changes result in a higher proportion of patients living longer without disease. Only a close cooperation between surgeon, radiotherapist and pediatric oncologist will give these patients the best chances of cure, if they are treated in multicenter studies.

Adolescent↗
PubMed1990

[The effect of positive end expiratory pressure on the blood flow velocity in the basal cerebral arteries during general anesthesia].

The effects of incremental positive end-expiratory pressure (PEEP) on middle cerebral artery (MCA) blood flow velocity and pulsatility index were studied in 20 patients scheduled for minor elective surgery. Transcranial Doppler sonography (TCD) was used to measure systolic (Vsyst) and mean flow velocity (Vmean) and the pulsatility index (PI). Heart rate (HR), mean arterial blood pressure (MAP), end-tidal CO2(PetCO2) and TCD parameters were recorded at control (PEEP = O) and following PEEP of 5 cm H2O, 10 cm H2O and 15 cm H2O for a period of 5 minutes for each PEEP level. Vsyst and Vmean were significantly reduced with each increment of PEEP. PI increased stepwise in response to each PEEP level. MAP decreased with PEEP 10 and 15 while HR and PetCO2 remained constant over time. These data suggest that PEEP-induced decreases in MCA blood flow velocity may represent decreases in CBF due to impairment of the intracranial venous flow if the diameter of the insonated vascular segment remains constant.

Adult↗
PubMed1990

[24-hour blood pressure and renal function in cardiac failure during the titration phase of captopril and enalapril].

In 33 patients with heart failure (NYHA II-III) 24-h blood pressure was examined during the titration of two ACE-inhibitors. Blood pressure was measured by the oscillometric method using the blood pressure monitor 90202 from SpaceLabs, Inc. The measurements were taken from 06.00 to 22.00 hours every 20 min, and from 22.00 to 06.00 hours every 1 h. All patients received an additional therapy, either with captopril (group 1, n = 17) or enalapril (group 2, n = 16) in random order. Serum-electrolytes, serum-creatinine, and plasma-renin activity were measured before and during therapy with both ACE-inhibitors. 24-h blood pressure measurements were taken before and on the first and fifth day of the treatment with ACE-inhibitors. The groups did not different in respect to the degree of heart failure, the concomitant medication, or the 24-h profiles of blood pressure and heart rate. The mean initial doses of captopril was 9.2 +/- 1.2 mg. Each patient of group 2 received an initial dose of 2.5 mg enalapril. The maximal decrease of diastolic blood pressure occurred after 1 h in group 1 and after 4 h in group 2 and was similar in both groups (8 vs, 7 mmHg). The 24-h blood pressure values on day 5 were consistently below the pretreatment values (p less than 0.005). Heart rate was not affected by either ACE-inhibitor. The groups did not differ significantly during ACE-inhibition in their 24-h blood pressure and heart rate profiles. Before treatment, serum-sodium, -potassium and -creatinine were within the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

[Tuberous sclerosis: family manifestations].

The authors report on 6 sisters and brothers with Bourneville's disease (tuberous sclerosis). The article describes the different morphologic manifestations of the illness in the patients and places them in relation with the generally assumed principal signs with special reference to the new imaging techniques such as cranial computed tomography and magnetic resonance imaging. These methods reveal pathognomonic patterns already very early, in association with specific clinical changes. Tuberous sclerosis must be excluded even in apparently healthy relatives by an exact diagnosis. Computed tomography is an absolutely indispensable indicator in this regard, since it is a highly sensitive method.

Brain↗
PubMed1989

Atrial natriuretic factor. Its possible role in hypertension and congestive heart failure.

The atrial natriuretic factor (ANF) is a circulating peptide, consisting of 24 to 28 amino acids. Atrial natriuretic factor is synthetized in atrial cardiomyocytes and stored in specific cytoplasmatic granules. It possesses potent diuretic, natriuretic, and vasorelexant properties. The possible role of ANF in the pathogenesis of hypertension and heart failure was investigated in animal models and in men. We were able to show that the release of ANF from cardiac atria is positively correlated with atrial pressures in both men and rats. In experimental studies, plasma levels of ANF measured by radioimmunoassay, were increased by up to four-fold after acute blood volume expansion. Atrial natriuretic factor release in response to volume loading was markedly attenuated in four-week-old spontaneously hypertensive rats as compared to age-matched normotensive Wistar-Kyoto rats, but a similar responsiveness was found in 16-week-old rats of both strains. This finding can be reconciled with the hypothesis that ANF plays a pathophysiological role in initiating but not maintaining high blood pressure. Clinical studies demonstrate elevated plasma concentrations of ANF in patients with organic heart disease. Further increments in plasma levels of ANF were obtained during physical exercise and after acute volume loading. In patients with congestive cardiomyopathy, the elevated plasma concentrations of ANF reached almost normal levels following improvement of their hemodynamic disturbances after treatment with converting-enzyme inhibitors. These findings suggest that in patients with organic heart disease, plasma concentrations of ANF reflect the hemodynamic burden of the heart and may, therefore, be used as a noninvasive marker of the efficacy of the current cardiac therapy.

Animals↗
PubMed1988

Role of right and left atrial dimensions for release of atrial natriuretic peptide in left-sided valvular heart disease and idiopathic dilated cardiomyopathy.

To evaluate the role of atrial dimensions for release of atrial natriuretic peptide (ANP), right and left atrial dimensions (cross-sections) were determined by 2-dimensional echocardiography in 50 patients with left-sided valvular heart disease or idiopathic dilated cardiomyopathy. All patients underwent right- and left-sided heart catheterization with measurement of central hemodynamics. Plasma samples for ANP were withdrawn from femoral vein (ANPv) and ascending aorta. An estimate of right and left meridional atrial wall stress was derived by multiplying cross-sectional areas with pressures of the respective atria. As expected ANPv was closely related to mean right (r = 0.63; p less than 0.001; n = 50) and left atrial pressures (r = 0.61; p less than 0.001; n = 47). Furthermore, a positive correlation between ANPv and right (r = 0.56; p less than 0.001; n = 48) and left (r = 0.30; p less than 0.05; n = 48) atrial cross-sections was obtained. Finally, an excellent relation was found between ANPv and right (r = 0.73; p less than 0.001; n = 48) as well as left (r = 0.58; p less than 0.001; n = 44) meridional atrial wall stress, indicating that atrial wall stress rather than atrial pressures or dimensions alone determines plasma ANP concentrations. However, for identical right and left meridional atrial wall stress 3- to 4-times higher plasma ANPv levels were obtained in patients with idiopathic dilated cardiomyopathy than in patients with left-sided valvular heart disease. This indicates that release of ANP to the same stimulus may be modulated by the nature of the underlying heart disease.

Adult↗
PubMed1988

[Percutaneous transfemoral valvuloplasty in patients with calcified aortic stenosis and significantly increased surgical risk: clinical course and value of Doppler sonography in assessment of therapeutic success].

Percutaneous transluminal valvuloplasty (PTV) was performed in 24 patients (aged 67-86 years, mean: 76 +/- 5.7 years) with calcific aortic stenosis and high operative risk. The gradient between maximal left ventricular and aortic pressures (peak-to-peak gradient, PPPG) could be reduced by 52% from 73 +/- 21 to 34 +/- 12 mmHg (p less than 0.001). Peak pressure gradient (PPG), as assessed by continuous wave Doppler, could be reduced from 80 +/- 28 to 58 +/- 21 mmHg (p less than 0.001). Aortic valve area (AVA) as determined by Doppler and two dimensional echocardiography increased significantly from 0.39 +/- 0.14 to 0.61 +/- 0.3 cm2 (p less than 0.05). Clinical symptoms were found to be improved in 5 of 8 patients with impaired ejection fraction and in 11 of 16 patients with normal ejection fraction during the first week after PTV. Complications due to the procedure were surgical revision of femoral artery puncture site in one patient and hemodynamic relevant pericardial effusion in another patient. Transmitral early (E) and late (L) diastolic filling integrals were measured by pulsed Doppler: the ratio E/L decreased significantly after PTV from 0.9 +/- 0.5 to 0.63 +/- 0.31 (p less than 0.03) indicating further reduction of left ventricular early diastolic filling. Ejection fraction, stroke volume and cardiac output did not significantly change immediately after PTV.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Higher oxidation states of prostaglandin H synthase. EPR study of a transient tyrosyl radical in the enzyme during the peroxidase reaction.

Purified prostaglandin H synthase (EC 1.14.99.1), reconstituted with hemin, was reacted with substrates of the cyclooxygenase and peroxidase reaction. The resulting EPR spectra were measured below 90 K. Arachidonic acid, added under anaerobic conditions, did not change the EPR spectrum of the native enzyme due to high-spin ferric heme. Arachidonic acid with O2, as well as prostaglandin G2 or H2O2, decreased the spectrum of the native enzyme and concomitantly a doublet signal at g = 2.005 was formed with maximal intensity of 0.35 spins/enzyme and a half-life of less than 20 s at -12 degrees C. From the conditions for the formation and the effect of inhibitors, this doublet signal was assigned to an enzyme intermediate of the peroxidase reaction, namely a higher oxidation state. The doublet signal with characteristic hyperfine structure was nearly identical to the signal of the tyrosyl radical in ribonucleotide reductase (EC 1.17.4.1). Hence the signal of prostaglandin H synthase was assigned to a tyrosyl radical. Electronic spectra as well as decreased power saturation of the tyrosyl radical signal indicated heme in its ferryl state which coupled to the tyrosyl radical weakly. [FeIVO(protoporphyrin IX)]...Tyr+. was suggested as the structure of this two-electron oxidized state of the enzyme. A hypothetical role for the tyrosyl radical could be the abstraction of a hydrogen at C-13 of arachidonic acid which is assumed to be the initial step of the cyclooxygenase reaction.

Animals↗
PubMed1988

Higher oxidation states of prostaglandin H synthase. Rapid electronic spectroscopy detected two spectral intermediates during the peroxidase reaction with prostaglandin G2.

The reaction of prostaglandin H synthase with prostaglandin G2, the physiological substrate for the peroxidase reaction, was examined by rapid reaction techniques at 1 degree C. Two spectral intermediates were observed and assigned to higher oxidation states of the enzymes. Intermediate I was formed within 20 ms in a bimolecular reaction between the enzyme and prostaglandin G2 with k1 = 1.4 x 10(7) M-1 s-1. From the resemblance to compound I of horseradish peroxidase, the structure of intermediate I was assigned to [(protoporphyrin IX)+.FeIVO]. Between 10 ms and 170 ms intermediate II was formed from intermediate I in a monomolecular reaction with k2 = 65 s-1. Intermediate II, spectrally very similar to compound II of horseradish peroxidase or complex ES of cytochrome-c peroxidase, was assigned to a two-electron oxidized state [(protoporphyrin IX)FeIVO] Tyr+. which was formed by an intramolecular electron transfer from tyrosine to the porphyrin-pi-cation radical of intermediate I. A reaction scheme for prostaglandin H synthase is proposed where the tyrosyl radical of intermediate II activates the cyclooxygenase reaction.

Animals↗
PubMed1988

Humoral adaptation mechanisms and clinical outcome during vasodilator therapy.

Administration of hydralazine and isosorbide dinitrate leads to a reduction of one-year mortality by 38%. However, a major disappointment has been the inability to predict the individual patient's response to these drugs. The aim of the present study, therefore, was to evaluate possible predictors for a favourable response to hydralazine treatment on the basis of the acute humoral and haemodynamic response to the drug. Stroke volume increased in all 37 patients with severe left ventricular dysfunction in response to acute intravenous hydralazine (0.4 mg kg-1). However, when re-investigated after 2 months of chronic oral hydralazine therapy, sustained haemodynamic and clinical improvement was observed in only 16 patients. Pretreatment values of either left ventricular filling pressure, cardiac index or systemic vascular resistance were not useful in predicting the outcome of treatment. However, when patients were subdivided on the basis of their heart rate response to acute hydralazine, better discrimination for a beneficial response, was possible. It is concluded that the haemodynamic and humoral responses to acute intravenous hydralazine allow discrimination between patients not responding to chronic vasodilator treatment and those who are likely to benefit. A reflex excitation of sympathetic outflow in response to acute vasodilation (indicated by a reflex acceleration of heart rate and increase in plasma noradrenaline levels) characterised best those patients who did not benefit from oral hydralazine. The data indicate a detrimental role of reflex sympathetic stimulation which may blunt at least part of the direct beneficial drug-induced effect in chronic vasodilator therapy.

Atrial Natriuretic Factor↗
PubMed1988

Influence of captopril on the arterial baroreceptor reflex in patients with heart failure.

In 16 male patients with heart failure (NYHA II-III), the influence of a single dose of 25 mg captopril on the carotid sinus baroreceptor reflex was examined. Blood pressure fell significantly by 11 +/- 1.7 mm Hg (P less than 0.001), whereas heart rate remained unchanged (85 +/- 3 vs. 83 +/- 3 beats min-1). Carotid sinus baroreceptors were stimulated by means of an airtight neck chamber. Two indices of baroreflex sensitivity were calculated. (1) The sensitivity to reflex heart rate slowing was increased by captopril from -2.9 +/- 0.7 to -5.0 +/- 1.3 ms mmHg-1 (P less than 0.02). The higher the initial sensitivity the more pronounced was the change after captopril with an increase of sensitivity by 46% (y = 1.46x -0.17, P less than 0.01). This increase in sensitivity cannot be explained by haemodynamic changes induced by captopril. (2) In eight patients the sensitivity of the baroreflex to increased transmural pressure gradients of the carotid sinus was evaluated by registration of the blood pressure response to neck suction; this demonstrated an unchanged responsiveness following captopril administration. From these data it can be concluded that captopril selectively augments a reflex bradycardia which is mediated by an increase in vagal efferent tone. The change in the reflex response depends on the initial reflex sensitivity and cannot be explained by haemodynamic changes caused by captopril.

Adult↗
PubMed1988

[Comparison of captopril with enalapril in the therapy of heart failure: effect on hemodynamics and kidney function].

24 patients with severe heart failure (NYHA III) were randomly assigned to an additional therapy with captopril or enalapril. The mean daily dose of captopril was 56 +/- 2 mg and of enalapril, 9.6 +/- 0.9 mg. After a mean of 9 days, the influence of both inhibitors of the angiotensin converting enzyme (ACE-inhibitors) on hemodynamics and renal function was evaluated. The mean arterial pressure in the group treated with captopril (group A) fell by 11 +/- 2 mm Hg (p less than 0.001), with enalapril (group B) by 13 +/- 3 mm Hg (p less than 0.01), the difference between the groups not being significant. Heart rate decreased in both groups to a similar degree. The change was significant only in the patients treated with enalapril (13 +/- 4/min; p less than 0.05 vs. 11 +/- 5/min in group A). Stroke volume index increased by 10 +/- 2 ml/m2 in group A vs. 12 +/- 2 ml/m2 in group B; both increases were highly significant (p less than 0.001). Mean decreases in pulmonary artery and right atrial pressure were comparable in both groups. The hemodynamic improvement was not different with both ACE-inhibitors. Serum sodium and potassium before therapy were 137 +/- 1 mmol/l and 4.1 +/- 0.2 mmol/l in group A and 139 +/- 1 mmol/l and 3.8 +/- 0.1 mmol/l in group B and serum creatinine was 1.2 +/- 0.1 mg/dl in both groups. Neither serum electrolytes nor serum creatinin were changed significantly by therapy with captopril or enalapril.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

[Does the measurement of plasma ANP have a diagnostic or prognostic value in patients with organic heart disease?].

Plasma levels of atrial natriuretic peptide (ANP) were measured in patients with organic heart disease undergoing diagnostic cardiac catheterization. Independent of nature and duration of the disease (valvular heart disease, congestive cardiomyopathy) plasma ANP levels were closely related to the severity of cardiac failure. Furthermore, plasma ANP levels were found to be negatively correlated with the cardiac index and to be positively correlated with right and/or left atrial and with pulmonary artery pressures. During physical exercise (bicycle ergometer) a marked increase of plasma ANP levels was observed, which was closely related to increments in mean pulmonary artery pressure. This rise in plasma ANP levels during physical exercise was not attenuated in patients with already elevated resting plasma concentrations of ANP. In patients with congestive cardiomyopathy, afterload-reduction by ACE-inhibition resulted in changes of central hemodynamics, which were closely reflected by venous concentrations of ANP. The measurement of plasma ANP levels may serve as an indicator of the severity of cardiac failure. Plasma concentrations of ANP, however, are neither helpful in establishing the etiology of the underlying heart disease nor in differentiating left and right heart failure. However, in cases of already established organic heart disease plasma ANP levels may be used as a marker for assessing the efficacy of the therapeutic regimen.

Atrial Natriuretic Factor↗