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Biomedical subjects

F Dorner

Publications and source records attributed to F Dorner.

At least 109 records · Page 6Linked to original sources
PubMed1985

Heat-labile enterotoxin of Escherichia coli. Characterization of different crystal forms.

Heat-labile enterotoxin (LT) was obtained in large quantities (several-gram amounts) and great purity from Escherichia coli C600 carrying the LT-coding multicopy plasmid EWD299. By growing this strain on a medium that allows high cell densities in the early stationary phase, we increased the net LT production per milliliter by a factor of 200, compared to natural porcine enterotoxigenic E. coli. Adsorption and redesorption on Controlled-Pore Glass usually resulted in a 50-100-fold purification of LT in one simple step, which was followed by established purification procedures. LT shows a natural tendency to form large crystals, which, however, are disordered. After numerous trials, conditions were found which virtually eliminated the disorder. Much better crystals were obtained by employing CdCl2 and KF as coprecipitating agents. CdCl2 yielded crystals which did not contain A subunits as judged by electrophoresis of dissolved crystals. Adding KF results in beautifully shaped crystals which diffracted beyond 2 A and are suitable for a high resolution structure determination.

Bacterial Toxins↗
PubMed1985

Bacterial toxin vaccines.

A rebirth of interest and activity in vaccine development has occurred in recent years which is probably due to the persistence of threat to health by infectious diseases, as well as technological advances which have made possible new approaches to solve old problems. Most work being done today with vaccine development against diseases caused entirely or in part by bacterial toxins falls into the categories of, attenuated organisms (whether by classical means or application of newly developed genetic technologies), and/or toxin subunits (derived by genetic manipulations, peptide synthesis, or chemical modification of toxins). This review discusses some of these new approaches in general as well as specific examples of their application to several bacterial diseases whose pathologies involve toxins.

Animals↗
PubMed1982

Protection against colibacillosis in neonatal piglets by immunization of dams with procholeragenoid.

Protection against colibacillosis in neonatal piglets was obtained by immunization of pregnant dams with procholeragenoid. Procholeragenoid is a stable high-molecular-weight aggregate of cholera toxin formed during the heating of cholera toxin. Procholeragenoid retained approximately 1% of the toxicity of native toxin as determined in the rabbit ileal loop and Y-1 adrenal cell assays and 5% of the activity in the rabbit skin assay. Immunization of pregnant dams with 50 micrograms of procholeragenoid 5 and 2 weeks before the expected delivery date elicited high titers of antitoxic immunoglobulin G and toxin-neutralizing antibody in both the colostrum and serum. In three independent field trials, immunization with procholeragenoid resulted in a substantial decrease in diarrhea (73% in controls versus 11% in immunized) and death (4.7% in controls versus 0.77% in immunized) in neonatal piglets. The protection rate in the immunized population was approximately 85% for both diarrhea and death. In the following gestation period, reimmunization of dams with a single dose of procholeragenoid (50 micrograms) 2 weeks before delivery elicited titers of antitoxic immunoglobulin G and toxin-neutralizing antibody comparable to those obtained during the primary immunization. The death rate in neonatal piglets (0.86%) was comparable to that seen after immunization during the first gestation period (0.77%). These results indicate that substantial protection of neonatal piglets against colibacillosis can be obtained by immunization of dams with procholeragenoid. Protection was found to be based solely on antitoxic immunity.

Animals↗
PubMed1980

[Developments in the serological diagnosis of malignant diseases].

The present study gives an evaluation of carcinoembryonic antigen (CEA), macrophage electrophoretic mobility test (MEM), sialyltransferase, galactosyltransferase isoenzyme (SGT), ribonuclease and reverse transcriptase as diagnostic aids in malignant diseases. CEA and sialyltransferase are of certain value in the monitoring of cancer, as their values in the serum may rise before progression of disease or relapse. Both tests are not reliable parameters in the early diagnosis of malignancy. Our results with regard to the MEM test have not proved in any way useful in the diagnosis of cancer. Our preliminary results appear to indicate that, provided further simplification of the method can be achieved, SGT isoenzyme determination seems to be a better means of diagnosing cancer. In view of inherent-methodological difficulties reverse transcriptase has, at present, no clinical application in the diagnosis of cancer.

Carcinoembryonic Antigen↗
PubMed1980

[Familial distribution of cholesterolemia, arterial blood pressure and relative weight].

The "Sion" study, a part of the Swiss National Research Program on Cardiovascular diseases, investigated the relationships between parents' and children's cholesterolemia, blood pressure and relative weight. After a health control at school 101 fathers and 108 mothers of ten year old children have been examined. The representativeness of these parents was studied using twice as many adults of the same age from Nyon and from Aarau. Direct significant statistical associations are then demonstrated between fathers' and children's blood pressure, cholesterolemia and relative weight. Analogous associations were found out for the last two variables only between mothers and children. Available data suggest that environmental determinants of risk factor exposure are more likely to explain these relationships. It then appears that the family represents a proper setting for primary prevention.

Adult↗
PubMed1980

[The relationship of Coli strains and hemolysis in diarrhea].

In the majority of diarrheal diseases no causative bacterial organism can be identified. Enteropathogenic E.-Coli-Strains were incriminated as causative agents in gastroenteritis on a epidemiologic basis, no pathogenetic mechanisms could be attributed. Cholera research initiated a new understanding of the pathogenesis of E. coli diarrheas: An enterotoxin was found which stimulated fluid and electrolyte secretion in the intestine. We were able to grow E.-Coli-Strains with hemolysis in a number of infants with severe, longstanding diarrheas. As the plasmids for hemolysis, enterotoxin production and adhesiveness of organisms on the intestinal mucosa is frequently transmitted simultaneously, we expected to find the majority of enterotoxic strains in the group of E. coli with hemolysis. 12 out of 100 strains E. coli with hemolysis isolated from diarrheal stools were enterotoxin producing strains. Enterotoxic strains were found almost exclusively in infants under one year of age with intractable diarrhea. We conclude therefore that enterotoxic E.-Coli-Strains are real causes of diarrhea also in our region and not as usually assumed only in the tropics. Furthermore, enterotoxic E.-Coli-Strains are found predominantly in the group of E. coli with hemolysis. Other biochemical and serological tests offer no additional possibilities for identification. Possibly also other pathogenetic mechanisms for E. coli with hemolysis might exist for acute diarrheas, however they are not sufficiently investigated yet.

Child, Preschool↗
PubMed1979

Escherichia coli heat-labile enterotoxin: DNA-directed in vitro synthesis and structure.

Escherichia coli heat-labile enterotoxin was synthesized in a cell-free system directed by DNA of the plasmid P307. Synthesis of the toxin, assayed by the elongation induced in Chinese hamster ovary cells, was strongly stimulated by cyclic AMP and occurred at physiological levels of Mg2+ only when the polyamine spermidine was present. Activity was abolished by heat and antisera prepared against the enterotoxins of both E. coli P263 and Vibrio cholera. Tritium-labeled enterotoxin was purified by immunoprecipitation and examined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. When gel slices were assayed for the ability to stimulate adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] activity in erythrocyte ghosts, two peaks were found, one at Mr 26,000 and frequently, but not always, another at Mr 23,000. Detection of radiolabeled protein by fluorography and scintillation counting of gel slices revealed three prominent polypeptides, two corresponding to the peaks having adenylate cyclase-stimulating activity and a further one of Mr 11,500, identical to that of the cholera subunit B. The data suggest that the E. coli heat-labile enterotoxin synthesized in the cell-free system has a subunit structure.

Animals↗
PubMed1976

Escherichia coli enterotoxin: purification, partial characterization, and immunological observations.

Enterotoxin, a diarrhea-inducing protein elaborated by pathogenic Escherichia coli strains, was isolated from the supernate of fermenter cultures of E. coli strain P263, a porcine enteropathogen. Purification involved chromatography and preparative isotachophoresis. The resulting product appeared to be pure according to immunoelectrophoretic, disc electrophoretic, ultracentrifugal, and immunologic criteria. The enterotoxin had an apparent molecular weight of 102,000 daltons, and its isoelectric point was 6.90. The isolated product was active in inducing experimental diarrhea in adult rabbits and piglets. In small dosage it also elicited a drastic increase in adenylate cyclase activity in broken-cell preparations of cat heart tissue. The enterotoxin activity was acid labile and was destroyed by heat (65 C for 30 min). It is suggested that the heat-stable enterotoxin was derived from heat-labile enterotoxin by complexing with endotoxin or with capsular material in the culture supernatant. The antigenic relations between the heat-labile enterotoxins of enteropathogenic E. coli strains of different serological types and different host adaptations, as well as between the E. coli enterotoxin and that of Vibrio cholerae, were investigated.

Animals↗
PubMed1975

Escherichia coli enterotoxin. Purification and partial characterization.

Enterotoxin, a diarrheagenic protein elaborated by pathogenic Escherichia coli strains has been isolated from the supernatant of fermenter cultures of E. coli strain P263, a porcine enteropathogen. Purification steps involving Bio-Gel agarose A-5m, Sephadex G-75 chromatography, and preparative isotachophoresis were used in the isolation. The resulting product appears to be pure according to immunoelectrophoretic, disc electrophoretic, ultracentrifugal, and immunologic criteria. The entertoxin has an apparent molecular weight of 102,000 as judged by gel filtration and sodium dodecyl sulfate polyacrylamide gel electrophoresis, and its isoelectric point is 6.90. The isolated product is highly active in inducing experimental diarrhea in adult rabbits and piglets. It also elicits, in small dosage, a marked increase in adenylate cyclase activity in broken cell preparations of cat heart tissue. The enterotoxin activity is acid-labile and is destroyed by heating at 65 degrees for 30 min. It is suggested that the heat-stable enterotoxin material is derived from heat-labile enterotoxin by forming a complex with endotoxin or capsular material present in the culture supernatant.

Adenylyl Cyclases↗
PubMed1975

Purification of arginases from human-leukemic lymphocytes and granulocytes: study of their physicochemical and kinetic properties.

Arginase has been isolated from granulocytes of a patient with chronic myelocytic leukemia and from lymphocytes of a patient with chronic lymphocytic leukemia and both enzymes have been purified to apparent homogeneity. The purification procedure employed acetone extraction, ammonium sulfate precipitation, DEAE-cellulose and CM-Sephadex chromatography and gel filtration on Bio-Gel A 1.5m. Both enzymes appear to be metalloenzymes, and to have molecular weights of about 120 000. Studies with the dissociated enzymes suggest that the subunit molecular weight is about 37 000, in agreement with a tetrameric aggregate structure of the native enzymes. Human leukemic granulocyte and lymphocyte arginases are strongly basic proteins with pI values between 9.25 and 9.35. Their free -SH groups enabled them to be linked to organomercurial-agarose. The kinetic properties estimated for both enzymes showed an optimum pH of 8.5, and an optimal MnCl2 concentration of 0.01 M. The Km for L-arginine is 2.7-3.1 mM and L-ornithine exhibits a mixed type of inhibition, with a Ki of 15.5-15.7 mM.

Arginase↗