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Biomedical subjects

F Mayer

Publications and source records attributed to F Mayer.

At least 145 records · Page 8Linked to original sources
PubMed1992

[A combined endoscopic surgical treatment concept in acute biliary pancreatitis].

This paper presents the results of a combined endoscopic-surgical approach with management of acute biliary pancreatitis in 91 patients. The diagnosis was always made by means of endoscopic-retrograde cholangiography. Papillary or bile duct stones, or unmistakable signs of previous stone passage, and in exceptional cases flow obstruction due to preiampullary diverticuli were considered criteria for a positive diagnosis. All 91 patients were subjected to endoscopic sphincterotomy with/without stone extraction subsequent to the diagnostic cholangiogram. Endoscopic intervention was performed as soon as possible after admission to hospital, but by 48 hours at the latest. Cholecystectomy was carried out in all patients who were free of risk factors and without previous cholecystectomy, during the disease-free interval. The complication rate of this combined endoscopic-surgical approach amounted to 10.9%; the mortality rate was 3.3%. The achieved results suggest that endoscopic sphincterotomy with stone extraction in the acute phase of biliary pancreatitis is the method of choice in order to interrupt the process of this disease. In combination with the final surgical treatment of gallstone disease by cholecystectomy to avoid recurrences, the prognosis of acute biliary pancreatitis can be significantly improved by using this combined endoscopic-surgical management.

Adult↗
PubMed1991

Simplified, rapid and inexpensive extraction procedure for a high-performance liquid chromatographic method for determination of disopyramide and its main metabolite mono-N-dealkylated disopyramide in serum.

A simplified, rapid and inexpensive extraction procedure for the determination of the antiarrhythmic drug disopyramide and its main metabolite mono-N-desalkylated disopyramide in serum by high-performance liquid chromatography has been developed. The analysis uses ultraviolet detection at 254 nm, and a 5 micron reversed-phase column with a mobile phase of water-triethylamine-acetonitrile-PIC-B8 reagent. Serum extraction is performed with dichloromethane and 1 M sodium hydroxide. p-Chlorodisopyramide is used as internal standard. Recovery rates were 94.5% (S.D. 5.7%) for disopyramide, 96.8% (S.D. 2.2%) for mono-N-desalkylated disopyramide and 97.9% (S.D. 2.8%) for the internal standard.

Chromatography, High Pressure Liquid↗
PubMed1991

Amino acid 55 plays a central role in tetramerization and function of Escherichia coli single-stranded DNA binding protein.

The histidine at position 55 of the amino acid sequence of the Escherichia coli single-stranded DNA binding protein was replaced by tyrosine, glutamic acid, lysine, phenylalanine, and isoleucine. The properties of the mutant proteins were determined using analytical ultracentrifugation, NMR spectroscopy, gel filtration, and fluorimetric detection of their single-stranded DNA binding ability. While the phenylalanine and isoleucine substitutions did not change the properties of the protein measurably, tyrosine and lysine mutants dissociate into subunits and loose some of their binding affinity for poly(dT). For the lysine mutant we show by electron microscopy that the protein, although fully dissociated and possibly denatured in the free state, binds to poly(dT) as a tetramer indistinguishable from the wild-type protein. The process of tetramerization as observed via single-stranded DNA binding ability is composed of a variety of steps ranging in time from some milliseconds to several hours; it probably involves several forms of dissociated and non-native protein.

DNA, Single-Stranded↗
PubMed1991

Properties of matrix-assisted laser desorption. Measurements with a time-to-digital converter.

Some properties of matrix-assisted laser desorption have been studied using single-ion-counting methods and a time-to-digital converter. The methods allow examination of the process for irradiances near the reported threshold for observation with a transient recorder. All measurements were made using bovine insulin as a test compound. We present direct evidence that an irradiance threshold near 10(6) W cm-2 exists for ion production, and that the process is a collective effect, either involving a large number of molecular ions (approximately 10(4) in a successful event or none at all. Above the threshold, the yield is found to scale with a high power (4th to 6th) of the irradiance. Measurements of initial velocity distributions indicate an axial velocity spread corresponding to approximately 50 eV and a radial velocity spread corresponding to approximately 2.4 eV. Thus the ejection or extraction mechanism appears to be strongly asymmetric.

Animals↗
PubMed1991

The application of the statistical study in the morphometric characterization of a Colombian strain of Trypanosoma cruzi.

After morphological and histopathological characterization, the Cali strain of T. cruzi isolated from a patient in Cali (Colombia), was also submitted to a morphometrical characterization. For this we estimated 16 cellular parameters in 30 samples of each evolutive form of T. cruzi in blood in NNN medium through planimetry by the IBAS-1 (Image Basic Analytic System). This morphometrical study was completed with a statistical one through the application of the variance (ANOVA-1). This made it possible to evidence a great number of significant differences between the slender, broad and stout forms and also between the short and large epimastigotes from the NNN medium. These data have a real interest for classifying some features of the biological cycle of T. cruzi as well as the future development of diagnosis techniques or therapeutical and prophylactic experiments.

Analysis of Variance↗
PubMed1991

Immunocytochemical Identification and Localization of Active and Inactive alpha-Amylase and Pullulanase in Cells of Clostridium thermosulfurogenes EM1.

Clostridium thermosulfurogenes EM1 formed blebs, i.e., protrusions still in contact with the cytoplasmic membrane, that originated from the cytoplasmic membrane during growth in batch culture and continuous culture. They could be observed squeezed between the cell wall and cytoplasmic membrane in cells with seemingly intact wall layers (surface layer and peptidoglycan layer) as well as in cells with wall layers in different states of degradation caused by phosphate limitation or high dilution rates. Blebs were found to turn into membrane vesicles by constriction in cases when the cell wall was heavily degraded. Bleb and vesicle formation was also observed in the absence of substrates that induce alpha-amylase and pullulanase synthesis. No correlations existed between bleb formation and the presence of active enzyme. Similar blebs could also be observed in a number of other gram-positive bacteria not producing these enzymes, but they were not observed in gram-negative bacteria. For immunoelectron-microscopic localization of alpha-amylase and pullulanase in C. thermosulfurogenes EM1, two different antisera were applied. One was raised against the enzymes isolated from the culture fluid; the other was produced against a peptide synthesized, as a defined epitope, in analogy to the N-terminal amino acid sequence (21 amino acids) of the native extracellular alpha-amylase. By using these antisera, alpha-amylase and pullulanase were localized at the cell periphery in samples taken from continuous culture or batch culture. In samples prepared for electron microscopy by freeze substitution followed by ultrathin sectioning, blebs could be seen, and the immunolabel pinpointing alpha-amylase enzyme particles was seen not only randomly distributed in the cell periphery, but also lining the surface of the cytoplasmic membrane and the blebs. Cells exhibiting high or virtually no enzyme activity were labeled similarly with both antisera. This finding strongly suggests that alpha-amylase and pullulanase may occur in both active and inactive forms, depending on growth conditions.

Journal Article↗
PubMed1991

Purification and Properties of a Thermoactive Glucoamylase from Clostridium thermosaccharolyticum.

A bacterial glucoamylase was purified from the anaerobic thermophilic bacterium Clostridium thermosaccharolyticum and characterized. The enzyme, which was purified 63-fold, with a yield of 36%, consisted of a single subunit with an apparent molecular mass of 75 kDa. The purified enzyme was able to attack alpha-1,4- and alpha-1,6-glycosidic linkages in various alpha-glucans, liberating glucose with a beta-anomeric configuration. The purified glucoamylase, which was optimally active at 70 degrees C and pH 5.0, attacked preferentially polysaccharides such as starch, glycogen, amylopectin, and maltodextrin. The velocity of oligosaccharide hydrolysis decreased with a decrease in the size of the substrate. The K(m) values for starch and maltose were 18 mg/ml and 20 mM, respectively. Enzyme activity was not significantly influenced by Ca, EDTA, or alpha- or beta-cyclodextrins.

Journal Article↗
PubMed1991

[Use of preventive intra-operative antibiotic administration in appendectomy. A pharmacokinetic study].

Studies on Cefazedone-kinetics in serum and subcutaneous fat tissue showed an early and lasting tissue concentration high above minimal inhibitation concentrations so that intraoperative single-shot administration of antibiotics are proven to be effective. Due to these pharmacokinetic patterns the results of an earlier prospective trial is confirmed that single-shot antibiotics during surgery are useful to reduce postoperative wound sepsis rate after appendectomy.

Adipose Tissue↗
PubMed1990

Localization of membrane-associated (NiFe) and (NiFeSe) hydrogenases of Desulfovibrio vulgaris using immunoelectron microscopic procedures.

The intracellular location of membrane-associated (NiFe) and (NiFeSe) hydrogenases of Desulfovibrio vulgaris was determined using pre-embedding and post-embedding immunoelectron microscopic procedures. Polyclonal antisera directed against the purified (NiFe) and (NiFeSe) hydrogenases were raised in rabbits. One-day-old cultures of D. vulgaris, grown on a lactate/sulfate medium, were used for all experiments in these studies. For post-embedding labeling studies cells were fixed with 0.2% glutaraldehyde and 0.3% formaldehyde, dehydrated with methanol, and embedded in the low-temperature resin Lowicryl K4M. Our post-embedding studies using antibody-gold or protein-A-gold as electron-dense markers revealed the location of the two hydrogenases exclusively at the cell periphery; the precise membrane location was then demonstrated by pre-embedding labeling. Spheroplasts were incubated with the polyclonal antisera against (NiFe) and (NiFeSe) hydrogenase followed by ferritin-linked secondary antibodies prior to embedding and sectioning. The observed labeling pattern unequivocally revealed that the antigenic reactive sites of the (NiFe) hydrogenase are located in the near vicinity of the cytoplasmic membrane facing into the periplasmic space, whereas the (NiFeSe) hydrogenase is associated with the cytoplasmic side of the cytoplasmic membrane.

Binding Sites↗
PubMed1990

Electron microscopy of native and artificial methylreductase high-molecular-weight complexes in strain Gö 1 and Methanococcus voltae.

The preparation of inside-out vesicles from methanogenic bacteria with protein cell walls was improved with regard to the preservation of structure and localization of membrane-bound proteins. Complexes similar to the methanoreductosome in the methanogenic bacterium Gö 1 were also found attached to the inner aspect of the cytoplasmic membrane of Methanococcus voltae. Methanoreductosomes were purified from crude extracts of Gö 1-cells by affinity chromatography. Under specific conditions at high protein concentrations methyl-CoM-methylreductase molecules isolated from Gö 1-cells could be reassociated to spherical complexes of various sizes, with an appearance similar to that of methanoreductosomes isolated from strain Gö 1.

Euryarchaeota↗
PubMed1990

Electrophysiologic effects and efficacy of cibenzoline on stimulation-induced atrial fibrillation and flutter and implications for treatment of paroxysmal atrial fibrillation.

The effects of intravenous cibenzoline (1.5 mg/kg) on atrial vulnerability and electrophysiology were assessed in 25 patients with documented paroxysmal atrial fibrillation (AF), in whom sustained (greater than 30 seconds) AF was induced by atrial stimulation with up to 2 extrastimuli and paced rates between 100 and 180 beats/min. In 7 patients AF persisted despite the application of cibenzoline, and in 8 patients the induction of sustained AF was prevented by cibenzoline. Intraatrial conduction time, flutter cycle length and shortest ventricular cycle length during AF were increased by cibenzoline (p less than or equal to 0.01). Sinus cycle length was decreased (p less than or equal to 0.05), whereas sinus node recovery time remained unchanged. The effective refractory period of the right atrium was not significantly affected. Eight patients with frequent episodes of paroxysmal AF received oral cibenzoline for control of paroxysmal AF irrespective of the efficacy of intravenous cibenzoline. Prevention of stimulation-induced AF predicted successful treatment of paroxysmal AF (p = 0.018). Cibenzoline could be effective in the treatment of atrial arrhythmias, and selection of an antiarrhythmic therapy for recurrent AF seems to be useful.

Administration, Oral↗
PubMed1990

Effects of intravenous cibenzoline on ventricular vulnerability and electrophysiology in patients with sustained ventricular tachycardia in comparison to a control group.

The electrophysiologic effects of intravenous (i.v. 1.5 mg/kg) cibenzoline were investigated in 13 patients with organic heart disease and supraventricular arrhythmias (control group) and 13 patients with drug refractory sustained ventricular tachycardia (VT group). In both groups, cibenzoline increased the effective refractory period (ERP) of the right ventricle (p less than or equal to 0.05), QRS duration (p less than or equal to 0.01), and QTc duration (p less than or equal to 0.01). Cycle length of the VT was increased from 311 +/- 73 to 393 +/- 119 ms (p less than or equal to 0.05) as well. The increase in QTc duration was more pronounced (p less than or equal to 0.05) in the VT group as compared with the control group. In four patients in the VT group with the largest increase in QRS-, QTc duration and cycle length of the VT proarrhythmia was noted after i.v. cibenzoline. Cibenzoline plasma levels were not significantly different between the two study groups. In the VT group, induction of VT was prevented in 2 patients, more difficult in 2 patients, easier in 1 patient, and unchanged in 5 patients. Spontaneous occurrence of the VT or induction by atrial stimulation was noted in 4 patients. In the control group, ventricular vulnerability remained unchanged. Cibenzoline may be effective in selected patients with drug refractory VT. In such patients, the increase in QTc duration was more pronounced as compared with a control group.

Anti-Arrhythmia Agents↗
PubMed1990

Subunit Composition and Glycosidic Activities of the Cellulase Complex from Clostridium thermocellum JW20.

The subunit composition of the extracellular complex from Clostridium thermocellum was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Twenty-six bands, representing proteins with apparent molecular sizes ranging from 37,500 to 185,000 Da, could be detected by silver staining. Cultivation of the bacteria with the substrate Avicel, Sigma cellulose, Solka floc, or cellobiose as the carbon source had no influence on the number of detectable protein bands. By activity staining with the substrate carboxymethyl cellulose or xylan added to the SDS-polyacrylamide gels, 15 of the 26 bands exhibited endoglucanase activity and 13 showed xylanase activity. In 8 of the 26 bands, both activities could be found. As minor activities, beta-glucosidase, beta-xylosidase, beta-galactosidase, and beta-mannosidase activities could be demonstrated in the cellulase complex. Upon measuring the release of para-nitrophenol (PNP) from PNP-cellobioside and determining the amount of glucose formed, the presence of exoglucanase activity was indicated. Upon glycoprotein staining of SDS-polyacrylamide gels, 14 of the 26 bands reacted positive, indicating the glycoprotein nature of the respective proteins. Four proteins (apparent molecular sizes, 58,000, 72,500, 94,000, and 110,000 Da) could be enriched from the originally bound cellulase complex by preparative SDS-PAGE. The two smaller proteins exhibited xylanase activity, whereas the 94,000-Da protein had endo- and exoglucanase activity, and the 110,000-Da protein degraded PNP-pyranosides.

Journal Article↗
PubMed1990

[Isolated rupture of the anterior distal syndesmosis. A diagnostic problem].

Referring to one case of isolated rupture of the distal tibiofibular syndesmosis the mechanism of accident, findings, differential diagnosis and therapy of this rare and isolated injury are discussed. The clinical symptoms are not clear. In diagnostics the arthrography of the upper ankle joint proves very good. For the protection of suture of the ligament the hook according to Engelbrecht seems to be superior to the positioning screw.

Adult↗
PubMed1990

[Electrophysiologic effects of penticainide in patients with supraventricular tachycardia].

The electrophysiologic effects of the new class-I antiarrhythmic drug pentisomide were investigated after intravenous (5 mg/kg) application in nine patients with atrioventricular nodal reentrant tachycardia and six patients with atrioventricular tachycardia. Pentisomide did not change sinus cycle length, effective refractory period of the right ventricle (ERP-RV), the AV-node (ERP-AVN) and QT interval. Intranodal (AH-interval) and infranodal conduction time (HV-interval), effective refractory period of the right atrium (ERP-A), QRS duration, antegrade effective refractory period of the accessory pathway (ERP-Kent), ventricular cycle length during atrial fibrillation and tachycardia cycle length were significantly (P less than 0.05) increased. Intravenous pentisomide prevented induction of the tachycardia in 5/9 patients with atrioventricular nodal tachycardia and in 2/6 patients with atrioventricular tachycardia. The electrophysiologic properties of pentisomide indicate that it might be a useful drug in the treatment of supraventricular tachycardia.

Adult↗
PubMed1990

[Electrophysiologic effects of the calcium antagonist isradipine, a double-blind placebo controlled study].

The electrophysiologic effects of the calcium channel antagonist isradipine (0.5 mg) in comparison to placebo were evaluated in a double blind study with nine patients in two groups. The patient groups were not different in respect to the underlying cardiac disease, electrophysiologic parameters at the baseline study, or in blood pressure. Isradipine significantly decreased the systolic (p less than 0.01) and diastolic (p less than 0.05) blood pressure, while sinus cycle length decreased significantly (p less than 0.05) in the placebo group and the isradipine group with no difference between the two study groups. The influence on sinus node recovery time, effective refractory period of the av-node, intranodal conduction time, and PR interval were not significant. In conclusion, isradipine significantly decreased systolic and diastolic blood pressure. The decrease in sinus cycle length after intravenous isradipine was not significantly different from the decrease seen in the placebo group. Atrioventricular conduction was not significantly affected.

Atrioventricular Node↗
PubMed1990

[Pulmonary metastasis with left intra-atrial extension of liposarcoma. Apropos of a case].

The direct extension of a neoplastic thrombus of the pulmonary veins into the left atrium is extremely rare. The authors report the case of a pulmonary metastasis from a liposarcoma of the thigh extending into the pulmonary veins and prolapsing into the left atrium. The patient was successfully treated by tumorectomy under cardiopulmonary bypass then by left upper lobectomy.

Adult↗