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Biomedical subjects

R Möllby

Publications and source records attributed to R Möllby.

At least 19 recordsLinked to original sources
PubMed1979

Classification of microbial, plant and animal cytolysins based on their membrane-damaging effects of human fibroblasts.

38 cytolytic agents of mainly microbial origin were investigated with respect to membrane-damaging activity on human diploid fibroblasts. Increased plasma membrane permeability was measured as leakage of three defined cytoplasmic markers of various sizes: alpha-aminoisobutyric acid, uridine nucleotides and ribosomal RNA. The relative leakages of these markers, caused by different concentrations of the various cytolysins, yielded a leakage pattern for each substance. Five distinct types of leakage patterns were obtained. These were transformed into numerical expressions by calculating the ratios between the amounts of cytolysin needed to release 50% of the nucleotide and ribosomal RNA markers and the amounts required to release 50% of the alpha-aminoisobutyric acid marker (ED50 ratios). A classification of the cytolysins into five groups was arrived at on the basis of the different types of leakage patterns with the aid of reference cytolysins with well-known mechanisms of membrane interaction. These groups comprised: (1) detergent-like agents, (2) agents interacting with only certain constituents of the cell membrane, (3) agents interacting with specific receptor molecules in the membrane, (4) agents inducing small functional holes of a definable size, and (5) agents inducing only a very limited increase in plasma membrane permeability. The system may be useful for characterization and differentiation of new cytolytic agents of various sources as it divides membrane-damaging agents into separate groups on the basis of their principal function on intact human cells.

Animals↗
PubMed1979

Enterotoxigenic enteric bacteria in foods and outbreaks of food-borne diseases in Sweden.

All of 86 food routinely examined for potentially pathogenic enteric bacteria were found to harbour one or more coliform species. None of the strains isolated produced heat-labile enterotoxin (LT) or showed invasive properties. The suckling mouse test indicated that one strain of Escherichia coli produced heat-stable enterotoxin (ST). Twelve incidents of suspected food poisoning were also investigated. In two of them the foods examined contained LT-producing strains of E. coli and in two there were LT-producing strains of Klebsiella pneumoniae. The counts of viable enterotoxigenic micro-organisms in these foods were 3000-30,000 E. coli/g and 50,000 to 1 million K. pneumoniae/g. The dominant symptom in all the incidents was watery diarrhoea. These seem to be the first reported cases of foodborne enterotoxigenic enteric bacteria in Europe. Though enterotoxigenic E. coli and related gram-negative enterotoxin-producing species are rare in correctly handled food in Sweden, these micro-organisms should be searched for when outbreaks of food poisoning are investigated.

Enterotoxins↗
PubMed1979

Enterotoxins, O-groups, and K88 antigen in Escherichia coli from neonatal piglets with and without diarrhea.

In a comparison between piglets (1-7 days old) with diarrhea and healthy piglets of the same age and 1 to 8 weeks old, 810 intestinal strains of Escherichia coli from 81 piglets from as many different herds in Sweden were investigated with regard to O-group, enterotoxicity, and possession of K88 antigen. A clear difference was found between the E. coli isolates from piglets with diarrhea and from representatives of healthy herds without diarrhea, with regard to (i) the homogeneity of strains in individual pigs and (ii) the distribution of O-groups, K88 antigen, and frequency of enterotoxicity. Strains from piglets with diarrhea showed a high frequency of O-group 149 (53%), enterotoxicity (61%), and K88 antigen (56%), while not more than 3% of the strains from healthy piglets of the same age harbored any of these characteristics. Of the isolates in O-groups 8, 64, and 115, 36% were enterotoxigenic. The corresponding data for O-group 149 and nontypable strains were 96 and 1%, respectively. Furthermore, K88 antigen was only found in O-groups 8 and 149. In O-group 149, 96% of the strains (n = 167) produced the K88 antigen as well as heat-labile enterotoxin. In contrast, strains producing heat-stable enterotoxin were mainly found in O-groups 8, 9, 64, 115, and 141. There was a significant difference in the frequencies of E. coli strains producing heat-labile enterotoxin between piglets with diarrhea and those without, whereas the pathogenic role of heat-stable enterotoxin-producing strains was less apparent.

Animals↗
PubMed1979

Evaluation of a ganglioside immunosorbent assay for detection of Escherichia coli heat-labile enterotoxin.

The GM1 ganglioside enzyme-linked immunosorbent assay (GM1-ELISA), an immunological method for detection of Escherichia coli heat-labile enterotoxin (LT), was quantitatively and qualitatively compared with the conventional adrenal cell test for the identification of LT-producing strains. A micromodification model of the assay was developed. Enterotoxin preparations from 120 E. coli isolates from individuals with diarrhea, which had been previously shown to be enterotoxigenic by the adrenal cell test, and from 44 control strains of E. coli were compared in parallel by the two methods. Quantitatively the covariation of the enterotoxin titers was highly significant (RS = 0.98, P less than 0.001), the GM1-ELISA being somewhat more sensitive than the adrenal cell test. The methodological error was less than 5% in both tests. Qualitatively the overall agreement for positive and negative reactions for the two methods was 89%. The GM1-ELISA is practical for routine use in the diagnosis of enterotoxigenic E. coli, especially in laboratories without facilities for cell culture.

Adrenal Glands↗
PubMed1978

Inhibition of noradrenaline-stimulated lipolysis and cyclic AMP accumulation in isolated rat adipocytes by purified phospholipase C and theta-toxin from Clostridium perfringens.

Purified phospholipae C (phosphatidylcholine cholinephosphohydrolase, EC 3.1.4.3) and theta-toxin from Clostridium perfringens both inhibited noradrenaline-stimulated lipolysis and cyclic AMP accumulation in isolated rat adipocytes in a dose-dependent manner. The action of phospholipase C was gradual in onset, while the effect of theta-toxin was almost immediate. Phospholipase C, but not theta-toxin, hydrolyzed membrane phospholipids and inhibited adenylate cyclase (EC 4.6.1.1) in a crude membrane fraction from fat cells. The inhibitory effects of phospholipase C were associated with morphological alterations detectable by electron microscopy, whereas effects of theta-toxin were observed at a time when no clearcut morphological alterations could be observed. It is concluded that the two purified principles from C. perfringens, which are both present in commercial preparations of phospholipase C, antagonize noradrenaline-stimulated cyclic AMP accumulation and lipolysis. Although their exact mechanisms of action have not been elucidated, phospholipase C and theta-toxin have different modes of attack.

Adenylyl Cyclases↗
PubMed1977

Cytopathogenic effects of atoxyl, an ototoxic compound, on human diploid fibroblasts in vitro.

Atoxyl, an arsenic compound, may cause degeneration in vivo of the inner ear including cells of the stria vascularis and hair cells. The mechanism behind the cytotoxic effect is not known. The effects of atoxyl at the subcellular level were investigated in this study using human diploid embryonic lung fibroblasts in monolayer cultures as an in vitro model system. Atoxyl caused a subtle but significant increase in the permeability of the fibroblast plasma membrane, as measured by release of a low molecular weight cytoplasmic marker (alpha-amino isobutyric acid). At higher concentrations or after longer incubation times, protein synthesis was impaired. This effect occurred in parallel with alterations in the cellular morphology as viewed by light microscopy. In the final stages of atoxyl intoxication the cells released also a higher molecular weight marker (nucleotide), indicating a further increased membrane permeability following the primary damage. It is concluded that atoxyl exerts a dual effect on the human fibroblasts, namely on membrane permeability and protein synthesis. Although the concentrations used were higher than those exerting the ototoxic effects in vivo, the prolonged exposure times to low concentrations obtained in whole animals may very well compensate for this fact. The effects observed in the in vitro fibroblast model system may thus be relevant to the mechanism of action of atoxyl during induction of ototoxic effects in vivo.

Aniline Compounds↗
PubMed1976

Production of phospholipase C (alpha-toxin), haemolysins and lethal toxins by Clostridium perfringens types A to D.

To obtain high yields of extracellular enzymes and toxins for immunological analysis, type culture collection strains of Clostridium perfringens types A to D and 28 fresh isolates of C. perfringens type A from humans were grown in fermenters under controlled conditions in a pre-reduced proteose peptone medium. The type culture collection strains all showed different characteristics with respect to growth rates and pH optima for growth. Production of phospholipase C (alpha-toxin), haemolysin and lethal activity varied considerably between the different types. Growth and extracellular protein production in fermenters with pH control and static or stirred cultures were compared. Production of all extracellular proteins measured was markedly improved by cultivation in fermenters with pH control. Strain ATCC13124 produced five times more phospholipase C than any of 28 freshly isolated strains of C. perfringens type A, grown under identical conditions. Haemolytic and lethal activities of the ATCC strain were equal or superior to the activities of any of the freshly isolated strains. There were no differences in the bacterial yields and in the production of extracellular toxins between type A strains isolated from clinical cases of gas gangrene and abdominal wounds, and those isolated from faecal samples from healthy persons.

Abdominal Injuries↗
PubMed1976

Enterotoxin-producing bacteria and parasites in stools of Ethiopian children with diarrhoeal disease.

Enterotoxinogenic bacteria were isolated from 131 (37%) of 354 Ethiopian infants and children with acute gastrointestinal symptoms. Only one of these isolates belonged to the classical enteropathogenic serotypes of Esch. coli. Two colonies from each patient were isolated and tested for production of enterotoxin by the rabbit ileal loop test, the rabbit skin test, and an adrenal cell assay. However, only 38% of the isolated enterotoxinogenic strains were Esch. coli; the others belonged to Klebsiella, Enterobacter, Proteus, Citrobacter, Serratia, and Aeromonas. In 18 patients both isolates were toxinogenic and belonged to different species. The incidence of intestinal parasites was 35% with no apparent correlation to the occurrence of toxinogenic bacteria in the stools.

Biological Assay↗