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Biomedical subjects

E Griffiths

Publications and source records attributed to E Griffiths.

At least 91 records · Page 5Linked to original sources
PubMed1978

Alterations in tRNAs containing 2-methylthio-N6-(delta2-isopentenyl)-adenosine during growth of enteropathogenic Escherichia coli in the presence of iron-binding proteins.

Escherichia coli grown in chemically produced iron-deficient media have well characterized alterations in the chromatographic properties of tRNAs containing the modified nucleoside 2-methylthio-N6-(delta2-isopentenyl) adenosine. The present report shows that similar tRNA alterations occur in enteropathogenic E. coli inhibited by human milk and bovine colostrum, the inhibited bacteria containing 10% or less of the normal tRNA species. Adding sufficient iron to saturate the iron-binding capacity of the lactoferrin present in milk and colostrum reversed these changes which are probably due to a failure to methylthiolate the isopentenyladenosine. Although adding iron led to a rapid replacement of abnormal tRNA by the chromatographically normal species, and to a resumption of multiplication, the tRNA alterations are not directly related to the inhibition of growth. Strains of E. coli which grew normally in milk, colostrum and in defined media containing the iron-binding protein transferrin or ovotransferrin also contained about 90% of the abnormal species. Rapid conversion of abnormal tRNA to normal tRNA occurred on adding iron and in the absence of RNA synthesis. The tRNA changes are discussed in relation to their possible connection with both the adaptation of E. coli to growth under the iron-restricted conditions imposed by iron-binding proteins in tissue fluids and with bacterial pathogenicity.

Adenosine↗
PubMed1978

Alterations in the tRNA's of Escherichia coli recovered from lethally infected animals.

Escherichia coli grown in chemically defined iron-deficient media or in fluids containing the iron-binding proteins transferrin, lactoferrin, or ovotransferrin have well-characterized alterations in the chromatographic properties of tRNA's containing the modified nucleoside 2-methylthio-N6-(delta2-isopentenyl)-adenosine. The present work shows that similar tRNA alterations occur in E. coli O111 recovered from the peritoneal cavities of lethally infected guinea pigs and rabbits. Adding iron to these in vivo-grown bacteria resulted in the rapid conversion of chromatographically abnormal tRNA's to the normal species. The work strongly suggests that host iron-binding proteins, present in mucosal and other secretions, can affect the metabolism of invading organisms. The idea that the tRNA alterations are connected with the adaptation of E. coli to growth under the iron restricted conditions imposed by iron-binding proteins in tissue fluids, and thus with bacterial pathogenicity, is therefore made particularly attractive.

Animals↗
PubMed1977

Bacteriostatic effect of human milk and bovine colostrum on Escherichia coli: importance of bicarbonate.

At pH 7.4 and in the presence of NaHCO3, human milk and bovine colostrum inhibited the growth of Escherichia coli O111. Adding sufficient iron to saturate the iron-binding capacity of the lactoferrin present in the milk or colostrum prevented bacteriostasis. At pH 6.8 neither molk nor colostrum inhibited E. coli 0111. Adjusting the pH to 7.4 with NaHCO3 resulted in the development of bacteriostatic activity. Adjusting the pH to 7.4 with NaOH was ineffective. Dialyzed colostrum and milk inhibited bacterial growth at pH 6.8 in the absence of added NaHCO3; addition of citrate or iron abolished bacteriostasis. The chromatographic elution profile of tyrosyl-transfer ribonucleic acid (tRNA) from iron-replete E. coli differs significantly from that of tyrosyl-tRNA from iron-deficient organisms. Examination of the elution profile tyrosyl-tRNA from E. coli 0111 growing in colostrum without added NaHCO3 showed that such bacteria were fully replete in iron. The nature of the elution profile of tyrosyl-tRNA also showed that iron was freely available to the bacteria when citrate was added to dialyzed colostrum but not available in its absence, even at pH 6.8. Results support the idea that the bacteriostatic action of milk and colostrum, due to the combined action of antibody and lactoferrin, depends on the addition of bicarbonate to counteract the iron-mobilizing effect of the citrate normally present in these secretions.

Animals↗
PubMed1976

The effect of antipolymorphonuclear leucocyte serum on Pseudomonas aeruginosa infection in rabbits.

Studies were made on the rate of phagocytosis and killing of Pseudomonas aeruginosa by phagocytic cells in the peritoneal cavity of rabbits. In sublethal and lethal infections the phagocytosed bacteria were killed very quickly. In antibody-protected animals, the polymorphs became loaded with liveing bacteria, but this had little effect on the decline in infection. In sublethal infections and in protected animals theproportion of intracellular bacteria labelled with 32O or [14C]uracil was high and antibody greatly enhanced phagocytosis. In lethal infections the rate of phagocytosis was insufficient to prevent the development of a fatal septicaemia. Antipolymorphonuclear leucocyte serum (APS) completely suppressed the normal polymorph response to infection and greatly reduced resistance. The macrophages in the peritoneum, which were not affected by APS, delayed bacterial growth for several hours but were eventually unable to control bacterial mutiplication. The outcome of infection appeared to depend almost entirely on the ratio of bacterial to phagocytes and the presence of antibody. Iron-binding proteins probably make a significant contribution to resistance by reducing the rate of multiplication of extracellular bacteria.

Animals↗
PubMed1975

Effect of pH and haem compounds on the killing of Pasteurella septica by specific antiserum.

The killing of Pasteurella septica by horse antiserum has features not previously associated with serum bactericidal reactions. The present work showed that lowering the pH from 7-4 to 6-8 abolished the action of antiserum. The bactericidal effect and the degradation of RNA seen when antiserum is added to P. septica growing in horse serum, were abolished at pH 6-8 in much the same way as when haem compounds were added to the system. Addition of chloramphenicol, rifampicin or puromycin to P. septica growing apparently normally in antiserum at pH 6-8 or in antiserum containing haem compounds led to rapid killing of the bacteria and to degration of their RNA. Addition of these antibiotics to P. septica growing in normal serum produced only bacteriostasis and did not induce RNA breakdown. In contrast, nalidixic acid, although inhibiting growth, did not induce rapid killing and RNA breakdown under the same conditions. These findings were unexpected and led to a reassessment of ideas concerning the mechanism of action of specific antiserum to P. septica. Although iron compounds clearly abolish the bactericidal based simply on an interference with bacterial iron supply is no longer sufficient. The process is more complex and must involve other factors.

Antibodies, Bacterial↗