Ronald R. Watson

Influence of malnutrition on the concentration of IgA, lysozyme, amylase and aminopeptidase in children's tears.

Summary Sixty-four pre-school-age children from a poor urban population in Colombia were studied to determine the influence of moderate to severe malnutrition on several proteins in the serum and tears. Secretory IgA, lysozyme, and amylase were found in significantly reduced concentrations in the tears of malnourished children. No influence of nutritional status on total proteins, albumin, and aminopeptidase was observed in this secretion. In the serum, IgA concentrations were significantly higher in the most malnourished group, while total proteins and albumin were reduced. These data suggest that increased susceptibility to infections of mucosal surfaces in malnourished children may be due to reduced concentrations of protective substances such as IgA and lysozyme in secretions.

Chapter I Substrate Specificities of Aminopeptidases: A Specific Method for Microbial Differentiation

Publisher Summary The substrate specificities of aminopeptidases in various species of bacteria, parasites, and fungi have been shown to be radically different. These differences have been used to distinguish closely related species and even strains of the same species. The aminopeptidase (arylamidase) procedure is based upon the enzymatic liberation of fluorescent β-naphthylamine (βNA) from a nonfluorescent L-amino-acid-β-naphthylamide. This allows quantitative and qualitative measurements as fluorescence is linear. Bacteria, fungi, and parasites are differentiated on their ability to enzymatically hydrolyze a series of L-amino-acid-βNAs producing a specific, characteristic profile. Differentiation by substrate specificity of the aminopeptidases complements and sometimes supercedes morphological and cultural identification techniques. It does not suffer from data interpretational difficulties that are sometimes caused by interfering chemical constituents in electrophoretic, chromatographic, serological, or phosphorescent techniques. The chapter presents preparation of cell-free aminopeptidases from Enterobacteriaceae and profile determination with cell-free aminopeptidases. The use of cell-free aminopeptidases in place of an in vivo cellular source of the enzymes, although somewhat more cumbersome, it has the advantage of giving a more complete profile. Some amino-acid-βNAs are not transported into the cell for hydrolysis. Both methods produce different, although completely reproducible profiles.

Effect of moderate malnutrition on immediate hypersensitivity and immunoglobulin E levels in asthmatic children

Dermal reactions and IgE levels were compared in 51 asthmatic Colombian children identified on the basis of anthropometric measurements as nutritionally normal (25) or mildly (16) or moderately (10) undernourished. Twenty-five nonatopic children served as controls. Total serum IgE concentrations were significantly elevated in the asthmatic group as a whole. Moderately malnourished (grade II) asthmatic children had more than twice as much serum IgE as normal or mildly malnourished (grade I) asthmatic subjects and seven times more than nonatopic children. Intestinal parasitism did not appear to contribute to these differences in IgE levels. Serum levels of IgA and IgD were similarly elevated in grade II asthmatics. Concentrations of serum IgG, IgM, and C3 and C4 complement were unaffected by nutritional or allergic status. Eosinophilia in nasal mucus was significantly reduced in grade I and grade II malnourished asthmatic children. Among asthmatics, the most frequent dermal reactions were to mite antigens (96%), house dust (67%), and grass pollens (35%). Significant levels of specific IgE were detected by the RAST to two species of mites in nearly all atopic children. There was no apparent influence of nutritional status on the distribution of reactivity or specific IgE assay. The clinical significance of hyperimmunoglobulin E in atopic, moderately malnourished children remains to be elucidated.