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Biomedical subjects

M Winkler

Publications and source records attributed to M Winkler.

At least 199 records · Page 11Linked to original sources
PubMed1992

Polyethylene glycol enhanced protein refolding.

Previous studies on the refolding of recombinant bovine carbonic anhydrase B (CAB) indicated that polyethylene glycol (PEG) significantly enhanced the recovery of active protein by reducing aggregation. To further test the ability of PEG to enhance refolding, three recombinant human proteins, deoxyribonuclease (rhDNAse), tissue plasminogen activator (rhtPA), and interferon-gamma (rhIFN-gamma) were refolded in the presence of PEG (3350 MW). rhDNAse produced from CHO cells was denatured in 7.2 M urea and refolded by rapid dilution to 4.0 M urea and 0.20 mg/ml protein. When a final PEG to rhDNAse molar ratio of 5 to 1 (0.1 milligram PEG, 3350 MW) was used in the dilution buffer, refolding was improved by 30% to yield complete recovery of active protein. Impure E. coli derived inclusion body preparations of rhDNAse were solubilized in 8 M urea and refolded by dilution to 4 M urea and 0.10 mg/ml protein. Refolding with a dilution buffer which yielded a final PEG to rhDNAse molar ratio of 10 to 1 (0.1 milligram PEG, 3350 MW) resulted in a three-fold increase in the recovery of active protein. When PEG was used in the dilution buffer, aggregation of rhDNAse did not occur during refolding in either case. rhtPA produced from CHO cells was denatured in 5 M guanidine hydrochloride (GuHCl) and refolded by rapid dilution to 0.10 M GuHCl and 0.20 mg/ml protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Specific and sensitive measurement of FK506 and its metabolites in blood and urine of liver-graft recipients.

A specific and sensitive assay for quantifying the immunosuppressant FK506 and its metabolites in blood and urine was developed. 32-O-Acetyl FK506 was synthesized and used as internal standard. FK506 and its metabolites were purified from the samples by solid-liquid extraction and were injected into a high-performance liquid chromatographic (HPLC) system linked to a mass spectrometer (MS) by particle-beam interface. The FK506 derivatives were separated from interfering material by use of a 100 x 4 mm C8 analytical column and water/acetonitrile or water/methanol gradient elution; they were detected by negative chemical ionization with methane as reagent gas. The limit of detection was 25 pg in a standard solution, and the limit of quantification in blood was 250 pg (extracted from 1 mL of blood). The CV was 11.3% at 5 ng, and no interferences with other drugs were found.

Chromatography, High Pressure Liquid↗
PubMed1992

Monoclonal fluorescence polarization immunoassay evaluated for monitoring cyclosporine in whole blood after kidney, heart, and liver transplantation.

In a prospective study we evaluated a novel fluorescence polarization immunoassay (FPIA) for determining cyclosporine (CsA) in whole blood. FPIA uses a monoclonal antibody and is performed on the TDx (Abbott). The within-series (CV less than 2%) and between-days (CV less than 3.3%) precision of the assay was excellent. The results obtained by the monoclonal FPIA in samples from transplant patients (n = 100) averaged 31.9% and 20.2% higher than those by HPLC and a specific radioimmunoassay (INCStar), respectively. Results by all three methods correlated well. Follow-up studies during the early course after liver transplantation, however, suggested that high metabolite concentrations affect FPIA results. This is explained by previously described cross-reactions of the monoclonal antibody with some CsA metabolites. The FPIA results in samples of such patients should be interpreted cautiously.

Chromatography, High Pressure Liquid↗
PubMed1991

The group IIB intron from the green alga Scenedesmus obliquus mitochondrion: molecular characterization of the in vitro splicing products.

In the presence of high molar salt concentrations, the mitochondrial group IIB intron (rI1) from the green alga Scenedesmus obliquus is capable of splicing in vitro. After establishing the optimal conditions for RNA processing the in vitro splicing products were unequivocally identified in self-splicing experiments by Northern hybridization analysis employing 3'end-labelled RNAs or exon- and/or intron-specific probes. Finally, two trans-esterification products were identified by sequencing of the spliced RNA. From our data we conclude that the processing of group II introns from both algal and yeast mitochondria is preceded by identical consecutive trans-esterification steps. The predicted secondary and tertiary structure of intron rI1 of S. obliquus contains all the motifs necessary for optimal self-splicing and which are characteristic of other group IIB introns from different species.

Base Sequence↗
PubMed1991

Sonographic demonstration of septicaemia with gas-forming organisms after liver transplantation.

Sepsis with gas-forming organisms, e.g. Clostridium perfringens and anaerobic streptococci occurred in three of 120 liver-transplant recipients (2.5%). The diagnosis was made in all three patients by bedside ultrasound, before blood cultures revealed bacterial growth. Floating high amplitude echoes within the extra- and intrahepatic portal veins and persistent small high amplitude echoes in the non-dependent portion of the liver are indicative of portal venous gas and should prompt further laboratory investigations.

Adult↗
PubMed1991

Muscle biopsy for diagnosis of malignant hyperthermia susceptibility in two patients with severe exercise-induced myolysis.

Muscle biopsy and in vitro contracture tests for diagnosis of susceptibility to malignant hyperthermia (MH) were performed in two patients who had developed fever and severe myolysis during exercise. MH susceptibility was confirmed in one patient, but in the other, exercise-induced heat stroke proved to be the correct diagnosis. Clinical presentation and epidemiology of exercise-induced MH and its relation to the heat stroke syndrome are discussed.

Adult↗
PubMed1991

[Reproducibility of the Doppler ultrasound blood flow profile of the umbilical artery with special reference to threatened premature labor].

The reproducibility of Doppler blood velocity profiles of the umbilical arteries within the umbilical cord is a special problem because of the difficult separation and extreme torsion of both vessels. Resistance-(RI) and pulsatility index (PI) have been assessed on two different locations immediately one after the other in 90 pregnancies with signs for premature labor, including 16 cases with premature rupture of membrane. For comparison the same measurements have been performed in 33 normal pregnancies. There was a significant correlation between the first and second assessment. However, the correlation coefficients of cases with premature labor are lower than in normal pregnancy. This underlines the necessity of at least two repeated measurements for these patients with signs of premature labor.

Blood Flow Velocity↗
PubMed1990

[Social medicine importance and treatment strategy of chronic venous diseases].

In European states chronic diseases of the veins are a remarkable social medical problem. Representative random investigations of the population in the GDR resulted in a medically significant chronic venous insufficiency of the legs in 14% of the adult population. The annual fresh disease rate concerning the medically significant type varicosis is 1.5%. The highest incidence rates are between the 20th and 40th year of age. A therapeutic need of recovery is the result. Only the early active therapy in the sense of a sanation of the disease is able to prevent severe forms of the course. Effective primary preventive measures are not yet known. The treatment of patients suffering from venous diseases is part of the basic medical care in the territory. The basis therapy should remain in the hands of the general practitioners.

Adult↗
PubMed1990

Efficacy of nitroglycerin in stress-induced regional myocardial dysfunction is dependent on the chosen model: investigations in anesthetized and conscious dogs.

The antianginal efficacy of nitroglycerin (1 microgram/kg per min) was investigated in two different experimental models, one using chloralose-anesthetized open-chest dogs, the other using conscious, chronically instrumented dogs. Heart rate, arterial pressure, left ventricular dp/dtmax, and left ventricular end-diastolic pressure were registered. Left ventricular regional contractile function in the area supplied by the left circumflex coronary artery (LCX) and the left anterior descending artery (LAD) were assessed using sonomicrometry. In both models, the coronary flow reserve was limited by a hydraulic occluder around the LCX. Cardiac stimulation was achieved by a bolus injection of isoproterenol (ISO 0.5 microgram/kg) in the anesthetized animals and by graded treadmill exercise in the conscious animals. In both cases, transient contractile dysfunction occurred in the area supplied by the stenosed vessel. This contractile dysfunction was completely abolished by nitroglycerin in the conscious animals, while nitroglycerin failed to show any antianginal effect in the anesthetized dogs. Although hemodynamic differences in open and closed chest should be considered, remarkable differences in mechanisms of blood-pressure regulation according to the mode of stimulation were observed: in contrast to the situation during treadmill exercise, the ISO-induced decrease in arterial blood pressure does not correspond to the clinical picture of an anginal attack. These results show that it is most important to mimic the complex pathophysiological reactions of angina pectoris in man as closely as possible in the experimental model.

Anesthesia, General↗
PubMed1990

Prospective study on the prevalence of sudden infant death and possible risk factors in Brussels: preliminary results (1987-1988).

A prospective study was carried out to assess the frequency of sudden infant death (SID) in the Brussels area. The study was conducted between January and December 1987 on infants presented to the health clinics of the Brussels "Office de la Naissance et de l'Enfance" (ONE). The infants entered the study if: (a) they were born between January 1 and December 31, 1987; (b) they attended an ONE consultation in the Brussels area between January 1987 and December 1988; (c) visits were repeated monthly during the first 12 months of life, or until death occurred; and (d) standard questionnaires were completed for each visit. For 4,064 infants these four criteria were fulfilled. During the study period 7 infants died of SID. Their deaths were unexpected and remained unexplained despite post-mortem investigations. For each SID case, 10 control infants were selected from the same health clinics. Controls matched the SID cases in the following respects: (a) dates of visits; (b) sex; (c) gestational age; (d) legal age; and (e) the profession of both parents. For most of the 65 items studied no significant difference was seen between the 7 SID infants and their 70 matched controls. Only two variables significantly differentiated the two groups. Repeated fatigue during feeding was seen in 4 of the 7 SID cases, but only in 10 of the 70 control infants (Fisher P = 0.017). Profuse sweating during sleep was reported in 2 of the 7 SID infants, and in none of the 70 controls (Fischer P = 0.007). These two infants' bedclothes were repeatedly wet with sweat.(ABSTRACT TRUNCATED AT 250 WORDS)

Belgium↗
PubMed1990

[Pneumothorax in intensive care patients. The value of tangential views].

In 55 intensive-care patients an additional tangential view of the chest was taken to demonstrate or exclude a pneumothorax in patients with sudden deterioration of gas exchange and negative ap-chest x-ray, if there was a suspicion of pneumothorax or a confirmed small pneumothorax in the ap-view. In 14 of 42 cases (33.3%) with negative or suspected ap-chest x-ray the tangential view revealed a pneumothorax. 6 of these 14 pneumothoraces were under tension. In 7 out of 11 patients (63.6%) with small pneumothorax, the tangential view showed additionally a tension pneumothorax.

Adult↗
PubMed1990

Prediction of malignant hyperthermia susceptibility: statistical evaluation of clinical signs.

The anaesthetic records of 61 patients who had experienced adverse reactions thought to be malignant hyperthermia (MH) were reviewed retrospectively to evaluate the diagnostic importance of clinical symptoms. Using the in vitro contracture test, 38 (62%) patients were identified as MH susceptible (MHS), the remainder showing normal test results (MHN). Generalized rigidity, ventricular arrhythmias, cyanosis and postoperative myoglobinuria were observed significantly more often in MHS patients. Median values of body temperature and creatine kinase serum concentrations were significantly greater in the MHS group. Masseter spasm and sinus tachycardia were as common in MHS as in MHN individuals. Statistical models using generalized rigidity, ventricular arrhythmias, cyanosis and fever exceeding 38 degrees C for prediction of MH showed a maximum sensitivity and specificity of 78% and thus are not acceptable for clinical use. For definitive diagnosis of MH, the well established in vitro contracture test remains essential.

Adolescent↗