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Biomedical subjects

M Leduc

Publications and source records attributed to M Leduc.

At least 37 records · Page 2Linked to original sources
PubMed1981

A latent thiol proteinase from ascitic fluid of patients with neoplasia.

Pepsin treatment of ascitic fluid from patients with neoplasia generated a cysteine (thiol) proteinase activity which resembles cathepsin B (EC 3.4.22.1) in its requirements for thiol activators, susceptibility to inhibitors and specificity for synthetic substrates. As judged by gel filtration, pepsin reduced the molecular size of the latent enzyme from an Mr of 41,000 to 33,000 after activation. Both forms are larger than human liver cathepsin B. In addition to its presence in ascitic fluid, the pepsin-activated species was found in the medium of ascites cells maintained in culture. The latent enzyme may be an enzyme-inhibitor complex or an inactive precursor of a cathepsin B-like proteinase.

Ascites↗
PubMed1980

Autolysis of Escherichia coli.

Autolysis of unwashed exponential-phase Escherichia coli cells was efficiently promoted by first submitting them to a quick downshock with distilled water before an upshock with 0.5 M sodium acetate, pH 6.5. The association of these two osmotic shocks had a remarkable synergistic effect and led to significant decreases in turbidity and viability. Different factors influencing the rate of cell lysis were examined. A close correlation was established between autolysis and the degradation of peptidoglycan. Both phenomena were induced by the same shock treatment, followed similar kinetics, and were efficiently blocked by addition of divalent cations. Cell lysis was also inducible by a shock treatment with 10(-3) M ethylenediaminetetraacetic acid or ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid and blocked by the addition of divalent cations.

Bacteriolysis↗
PubMed1977

Structure of the cell wall of Bacillus species C.I.P. 76-111.

An unusual type of bacterial cell wall was encountered in a Bacillus strain referred to as Bacillus sp. C.I.P. 76-111. The major constituent of this cell wall is a high-molecular-weight anionic protein non-covalently associated to a peptidoglycan-polysaccharide complex. The cell wall appeared as a multilayered structure when sections of whole cells or of isolated cell walls fixed with glutaraldehyde and postfixed with osmium tetroxide were examined by electron microscopy. The correlation between the observed morphological features and the biochemical data suggested that a thin central electron-dense layer identifiable with the peptidoglycan-polysaccharide complex is located between two similar thick layers of protein. Furthermore, negative staining of isolated cell walls revealed that the outer protein layer has a regular surface array of subunits with hexagonal symmetry. Several structural properties of the cell wall peptidoglycan were investigated and were found to resemble those of other bacilli. Further characterization of the autolytic system showed that an N-acetylmuramyl-L-alanine amidase and a glycosidase, presumably a N-acetylmuramidase, were associated with the peptidoglycan-polysaccharide complex. It was also established that this strain is devoid of membrane teichoic acid.

Bacillus↗