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Biomedical subjects

G Schmidt

Publications and source records attributed to G Schmidt.

At least 217 records · Page 12Linked to original sources
PubMed1991

Lateral order in binary lipid alloys and its coupling to membrane functions.

Densitometry, Raman spectroscopy and small angle neutron scattering are employed to elucidate the miscibility behavior of lipid mixtures organized as liposomal dispersions. First, temperature-composition-phase diagrams for several binary alloys of dialkyl-lecithins differing in chain lengths by an increasing number of CH2-groups are derived. A mixture of dimyristoyllecithin and distearoyllecithin (delta CH2 = 4) shows a peritectic phase behavior with a miscibility gap in the gel state. In the fluid phase, at high enough temperatures, homogeneous mixtures of the two components are formed at all molar ratios. However, upon approaching a critical point by either lowering the temperature or increasing the hydrostatic pressure, critical concentration fluctuations are observed. If one component of a binary mixture is charged, electrostatic interactions can be used to induce phase separation at constant temperature. This is demonstrated for Ca2(+)-driven demixing in alloys of lecithin and negatively charged phosphatidylglycerol. The influence of the various concepts for the induction of lateral structure formation in lipid membranes on integral functional units like ionophores is demonstrated by analysing the single channel current fluctuations of gramicidin in bimolecular lipid membranes. Ca2+, as well as polyelectrolyte-induced phase separations are shown and discussed as examples for the important (lateral) order-function relationship in biomembranes.

Electrochemistry↗
PubMed1991

Pilot study of teniposide in combination chemotherapy for small cell lung cancer.

Teniposide is one of the most active agents in small cell lung cancer (SCLC). Because of the experimental evidence of synergistic activity between teniposide and methotrexate and between vincristine and methotrexate, 34 SCLC patients were treated with a combination of teniposide, vincristine, methotrexate and cyclophosphamide. Chest radiotherapy was given to responding patients with limited disease and prophylactic cranial irradiation was given to complete responders only. Most patients had extensive disease and good performance status. The main side-effects were myelosuppression, mucositis and peripheral neuropathy, which were all common and often severe. A response rate of 78% with 22% complete responses was obtained in 32 evaluable patients. Median durations of responses and survival were 252 and 311 days, respectively. Patients with limited disease had a median survival of 556 days while extensive disease patients had a median survival of 240 days. 2 patients with limited disease have been in continuous complete remission for more than 2 years from start of treatment.

Adult↗
PubMed1991

Evaluation of antiarrhythmic drug effects with simultaneous analysis of single ventricular premature contractions, couplets and salvos.

To improve the clinical value of ambulatory Holter electrocardiographic (ECG) monitoring as a tool of antiarrhythmic therapy control, a new statistical model was developed. In a patient group at increased risk of sudden cardiac death, the spontaneous variability of ventricular arrhythmias was assessed, with simultaneous consideration of single ventricular premature complexes, couplets and salvos. The study included 100 patients who suffered from coronary heart disease or idiopathic dilated cardiomyopathy and for whom greater than 30 ventricular premature complexes/h and couplets had been demonstrated on the last Holter ECG before the study. Between 3 and 12 Holter recordings were made for each patient in a drug-free state; the mean follow-up period was 260 days (maximum 1,403). The mean hourly values of the ectopic events (EE) were assessed separately for ventricular premature complexes, couplets and salvos. The spontaneous variability (SV) was calculated for single ventricular premature complexes, couplets and salvos as SV = log (EEday 2 + 0.01/EEday 1 + 0.01) and linked in one, two and three dimensions. Compared with the consideration of only one type of arrhythmia (one-dimensional model), the simultaneous use of two or three types of arrhythmia (two- or three-dimensional model) resulted in considerably lower reduction and aggravation rates as sufficient proof of drug effects. With control intervals up to 1 week, the one-dimensional model yielded reduction rates for ventricular premature complexes, couplets and salvos of -63%, -90% and -95%, respectively. In contrast, with the three-dimensional model, the rates were -28%, -72% and -88%. The corresponding aggravation values were +370, +1,114% and +2,189% versus +38%, +256% and +747%.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Arrhythmia Agents↗
PubMed1991

[Alfonso Corti (1822-1876), some of his biographers and his relationship to Vienna].

Biographical data and the evaluation of the scientific work of Corti taken from Austrian, German, Italian, Swiss and American medical historiographers are summarised and completed by details and documents of the time Corti spent in Vienna. It is pointed out that Corti received important impulse for his later research when he was Hyrtl's assistant.

Anatomy↗
PubMed1991

[Digital luminescence radiography (DLR) for skeletal diagnosis in traumatology].

170 patients who had suffered trauma to bones or soft tissues were examined by a digital and a conventional film/screen technique. In addition to "standard" and edge-enhanced images, post-processing was carried out and compared with conventional radiographs. Four radiologists and two surgeons evaluated the compacta, spongiosa, soft tissues, fractures and osteo-synthetic materials as shown on the two systems. The "standard" digital images are inferior to film images, but edge-enhanced images showed definite advantages for demonstrating soft tissues. Evaluation of osteo-synthetic material is limited by the creation of artifacts. Recognition of detail can be significantly improved by using post-processing with optimized parameters.

Adolescent↗
PubMed1991

Action of rHuEpo on mechanical membrane properties of red blood cells in children with end-stage renal disease.

By means of a micropipette aspiration technique mechanical membrane properties of RBC in ten uraemic children undergoing haemodialysis were compared to those of nine healthy children. In contrast to the healthy reference group (mu = 4.01 +/- 0.71 microN/m), the mean apparent elastic shear modulus of RBC membrane mu as a parameter of static deformability was significantly increased to 9.05 +/- 1.61 microN/m in children with chronic renal failure measured in the pre-study period. At the 7th week of the correction period of rHuEpo therapy, the haematocrit of treated patients is enhanced to a mean of 0.30 +/- 0.03, whereas mean mu is decreased to 5.41 +/- 0.63 microN/m. Within the maintenance period of rHuEpo treatment (30th week), the parameter mu did not show significant differences to the reference value 3.78 +/- 0.31 microN/m. Additionally, a significant increase in red cell mean corpuscular volume was obtained during rHuEpo therapy. Improved deformability of uraemic RBC induced by the rHuEpo therapy can only be explained by the assumption that in the course of this therapy an increasing number of cells with normalised viscoelastic properties have been formed by stimulated erythropoiesis.

Adolescent↗
PubMed1991

Achalasia of the oesophagus: results of treatment.

Achalasia of the oesophagus is an uncommon neuromuscular disorder characterized by symptoms of dysphagia and regurgitation of undigested food. The results of treatment of 43 patients with achalasia over 10 years are presented. Clinical data on presenting complaints and duration, and all subsequent treatments, were recorded. Patients were contacted to assess their current symptomatic status.

Adolescent↗
PubMed1991

A followup study of manic-depressive and schizoaffective psychoses after systemic family therapy.

The authors report the results of a followup study of manic-depressive and schizoaffective psychoses after systemic family therapy. They describe the development of inpatient relapse rates, familial interactional patterns, and prescriptions of medication in a sample of 30 cases treated with family therapy and followed up after a mean interval of 3 years. Finally, they assess the effectiveness of systemic family therapy with manic-depressive and schizoaffective psychoses.

Adolescent↗
PubMed1991

The standard Romanowsky-Giemsa stain in histology.

A new and technically simple Romanowsky-Giemsa (RG) stain is proposed as a standardized technique for use in histology. An RG stock solution (pure azure B 7.5 g/l, eosin Y as eosinic acid 1.2 g/l in dimethylsulfoxide) is diluted to form the working solution with HEPES-buffer, pH 6. Staining time is 30-90 min after formol-calcium solution (or 2-4 hr after formaldehyde-organic acid mixtures). The resulting overstained sections are to be differentiated. A tannic acid-acetic acid combination in an isopropanol-water mixture was found to give optimum results within 100 sec. Subsequent dehydration is in isopropanol only. The staining pattern obtained is polychrome. The distribution of colors in detail is influenced by the modes of pre- and posttreatment. Of practical interest is the development of green and greenish blue colors on collagen fibrils which contrast strongly against the pink of sarcoplasm. For this and other reasons, this RG stain version seems suitable to replace the trichrome Gomori-type trichrome stains under appropriate processing conditions.

Animals↗
PubMed1991

[Long-term treatment with amiodarone].

The aim of this study was to investigate the efficacy and the side effects of a long-term treatment with amiodarone. We analyzed the data of 41 patients in whom amiodarone therapy had been initiated between 1974 and 1984. Twenty-one patients had dilative cardiomyopathy, 14 patients had chronic myocardial infarction, four patients suffered from WPW syndrome with intermittent atrial fibrillation, one patient had aortic valve surgery, whereas in one patient there was no clinical evidence of a heart disease. All patients had salvos of ventricular extrasystoles, ventricular tachycardia or documented intermittent ventricular fibrillation. There have been seven drop-outs up to the present time. In each patient, the lowest antiarrhythmically effective dose was applied, which was generally higher in patients with low ejection fraction. Effective treatment of the ventricular tachycardia was achieved in 55-92% of patients and did not depend on the duration of treatment. In 10 patients in whom amiodarone therapy had to be stopped for various reasons. Sudden cardiac death was slightly more frequent than in the 24 patients treated with amiodarone, though the difference was not significant. In cases with a history of syncope the prognosis was poor, even with amiodarone therapy. Due to side effects, a dosage reduction or discontinuation of amiodarone treatment became necessary in 14 patients. Amiodarone proved to be an effective drug also for the long-term treatment of ventricular tachycardia, and possibly for the prevention of sudden cardiac death. With the exception of blue skin color, there was no accumulation of side effects, even during long-term treatment of several years.

Adult↗
PubMed1991

[Effect of amiodarone on signal-averaged and long-term ECG].

This prospective study examined the influence of long-term amiodarone therapy on the parameters of the signal-averaged ECG and their relation to simultaneously derived Holter monitoring data. For this purpose, 23 patients with angiographically confirmed dilated cardiomyopathy or coronary heart disease and high-grade ventricular arrhythmias, in whom an average of four class I antiarrhythmic drugs had proven ineffective, were stabilized on amiodarone. Before the beginning of therapy, as well as after 2 months and, subsequently, every 3 months, a resting ECG, a signal-averaged ECG by Simson's method, and Holter monitoring were performed. Compared to the initial measurement, we found a significant increase in the duration of the total filtered QRS complex from an average of 114 +/- 24 ms to 127 +/- 35 ms, while the change in voltage did not reach the significance level. The incidence of late potentials remained largely constant under amiodarone; 10 patients showed a constant late potential, 12 patients had no late potential, and one patient with coronary heart disease developed a new late potential. In the long-term follow-up, we ascertained a relatively high responder rate under amiodarone between 41% and 81%. No relation could be detected between the results of the signal-averaged ECG and those of 24-h Holter monitoring.

Aged↗
PubMed1991

Acute changes in microvascular blood flow distribution in the myocardium of the rat during partial occlusion of the right coronary artery; effects of dihydroergotamine.

Changes in blood flow during restricted right coronary perfusion were studied in anesthetized rats. By use of a carotid-coronary shunt system, coronary perfusion pressure could be reduced to 40 mm Hg, leading to a fall in flow from 0.9 ml/min to 0.3 ml/min. The perfusion pattern within the flow-restricted area was determined by labelling the blood plasma with fluoresceinisothiocyanate (FITC) globulin (demonstration of the entire vascular system) and lissamine-rhodamine B200 (RB200) globulin (demonstration of actually perfused myocardial capillaries). In histological sections, arterial ramifications were evaluated with respect to the arrival of RB200 in their branches. Large filling defects were observed when flow was obstructed. After 10s labelling, in ramifications with a feeding artery larger than 15 microns in diameter, 10.5% of the vessels displayed dye in only one of the branches, and 13.5% in neither of the two branches. For smaller ramifications (less than 8 microns), these values amounted to 17.5% and 41.5%, respectively. A similar pattern was observed after vascular labelling for 60 s. When dihydroergotamine (2.0 micrograms/kg i.v.) was applied one minute after onset of occlusion, the perfusion inhomogeneity was significantly reduced (labelling in one branch and in none of the two, respectively: greater than 15 microns: 60% and 10.0%; less than 8 microns: 13.5%, and 26%). It can therefore be concluded that dihydroergotamine reduces hypoperfusion-induced inhomogeneity in myocardial blood flow.

Animals↗
PubMed1991

Influence of decorin on fibroblast adhesion to fibronectin.

Decorin is a ubiquitous small dermatan sulfate proteoglycan carrying a single glycosaminoglycan chain. It is known for its ability to bind, via its core protein, to interstitial collagens. Decorin was purified from the secretions of cultured human skin fibroblasts under non-denaturing conditions. The intact proteoglycan and its glycosaminoglycan-free core protein were tested for their interference with fibroblast adhesion to a fibronectin substrate. Concentrations of 40 nmoles or more of hexuronic acid/ml of decorin or equivalent amounts of core protein inhibited cell adhesion. Inhibition was caused by an interaction of core protein with fibronectin and not by masking of the fibronectin receptor. When cell-binding fragments of fibronectin were used as substrates, a similar inhibition of cell adhesion by decorin core protein was found, and in vitro assays demonstrated an interaction of core protein with the cell-binding domain of fibronectin. Decorin core protein also inhibited the low degree of cell adhesion to heparin-binding fragments on the N-terminus and near the C-terminus of the fibronectin molecules.

Cell Adhesion↗
PubMed1991

Relation between epicardial electrograms and signal-averaged electrocardiograms after acute myocardial infarction in dogs.

Signal-averaged electrocardiograms allow the non-invasive detection of late potentials which represent locally delayed conduction in the myocardium. To validate this method, it is necessary to compare the signal-averaged data with electrograms recorded directly from the heart. However, the studies performed to date involve only a consecutive collection of the invasively and non-invasively obtained data. To obtain a more direct comparison, we examined this relation at operation by simultaneous epicardial and signal-averaged measurements. Acute infarction in animals was chosen, because the ischemic area is a zone of delayed conduction whose presence can be verified in a signal-averaged electrocardiogram. For this purpose, the left anterior descending artery, proximal of large septal and diagonal branches, was tied off in nine mongrel dogs after thoracotomy. Before infarction, a signal-averaged electrocardiogram was recorded from the body surface. At the same time, epicardial electrograms were performed using bipolar electrodes both from the supply area of the left anterior descending artery and from that of the circumflex artery. Five minutes after coronary ligation, both the epicardial measurements and the signal-averaged electrocardiogram were repeated on the open thorax. Before occlusion of the left anterior descending artery, narrow activation complexes occurred in general in the epicardial electrograms and no late potentials were recorded in any dog by the signal-averaged electrocardiogram. Five minutes after coronary ligation, fractionated and prolonged electrograms occurred in the epicardial recordings from the ischemic zone, while the activation complexes in the uninfarcted supply area of the circumflex artery remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[Karl Landsteiner (1868-1943) in memoriam].

Apart from the discovery of the human blood groups and the Rhesus factor Landsteiner developed the visualization of Spirochaeta pallida by the method of dark field microscopy. Furthermore, he demonstrated the transmission of poliomyelitis to monkeys, which made it possible to prove the viral origin of this disease. He gave fundamental impulses to the development of immunobiology (e.g. concept of haptens, specificity of antigens etc.).

Austria↗
PubMed1991

[Precision of blood alcohol determination using GC and ADH methods].

For the precision testing of the gas-chromatographic and the ADH-enzymatic method respectively we used commercially available control sera. During one year of testing (1990) they were daily and routinely used together with the specimen analysed. With the automatized GC-method the precision required according to the jurisdiction of the Bundesgerichtshof was better than with the manual ADH-method. The precision of the ADH-method should be improved using an autoanalyzer. Systematical errors between the two different methods (GC and ADH) can be minimized by a double GC-determination. Our investigation also aimed at a possible lower threatening threshold of 0.5% (BAK) as a consequence of the german "Wiedervereinigung". The precision for this concentration is 0.02% for the GC- and the ADH-method.

Alcohol Dehydrogenase↗