[Brain natriuretic peptide: physiological, biological and clinical aspects]

Brain natriuretic peptide is one member of the natriuretic peptide family, including also ANP, CNP, DNP and urodilatin. In human, brain natriuretic peptide is mainly secreted by the cardiac ventricles. BNP is synthetized as pre-proBNP form, secondary cleaved in proBNP, itself equimolarly cleaved in BNP and NT-proBNP. The biological action of BNP is mediated by the NPR-A receptor. This peptide is eliminated from the systemic circulation by a neutral endopeptidase and by a clearance receptor (NPR-C). The BNP and NT-proBNP concentrations are measured using automated rapid immunoassay techniques. Plasma concentrations of the two peptides physiologically increase with age and are found to be higher in women than in men. The action of BNP against fluid expansion is explained by its vascular (vasodilatation), renal (diuretic and natriuretic) and cerebral activities. The measurement of these two peptides contributes to the diagnosis of heart failure. These peptides are prognostic markers both in heart failure and in acute coronary syndromes. In renal insufficiency, the interpretation of the increase in these two peptide concentrations may be difficult, particularly with the NT-proBNP which is mainly excreted by the kidneys.

[Chemical and enzymatic degradation of Helminthosporium spiciferum cell walls. Protective role of pigments]

Cell walls of the fungus Helminthosporium spiciferum, prepared by mechanical grinding of the cells, were treated chemically and with helicase. The purified cell walls and the fractions were analyzed chemically and micromorphologically to localize the major cell-wall constituents and to determine the protective role of the pigments against degradative processes. The encrusting of the external area by the pigments associated with chitin formation leads to an increased resistance of this cell-wall area against the degradative processes.