Seasonal variations in hair zinc concentrations in Canadian and African children

Proximal occipital scalp hair samples were collected during three survey periods from 30 omniverous Canadian boys aged 75.6 +/- 10.4 months (mean +/- SD) and 66 rural Malawian children (37 M; 29 F) aged 62 +/- 10 months (mean +/- SD) consuming predominantly plant-based diets. Hair samples were washed and then analyzed for zinc and copper using instrumental neutron activation analysis. Selected anthropometric measurements were also taken and dietary intakes calculated from weighed dietary records. A marked seasonal variation in hair zinc concentrations occurred in both groups; levels were highest in the season with shortest daylight hours (i.e. December /January in Canada vs July/August in Malawi). A similar trend was not observed for hair copper concentrations. Changes in hair zinc were not associated with changes in growth indices; age; socio-economic group; method of infant feeding; in either group; but were related to intakes of protein (per 1000 kcal) (p = 0.02; r = -0.36); zinc (mg day-1) (p = 0.01; r = -0.39); and dietary fiber (g day-1) (p = 0.04; r = 0.28); in the Malawian children during the second survey period. The seasonal effect on hair zinc concentrations must always be considered when interpreting hair zinc concentrations in children; its etiology remains unclear

Antimycoplasmal activities of the pseudomonic acids and structure-activity relationships of monic acid A derivatives.

The antimycoplasmal activities of the pseudomonic acids isolated from Pseudomonas fluorescens NCIB 10586 are reported. Structure-activity relationships of a variety of ester, amide and thiol ester derivatives of the nucleus, monic acid A, are described. Enhanced antimycoplasmal activity is reported for a number of monic acid A esters and the most potent derivative, m-nitrobenzyl monate A, is a 100-fold more active against Mycoplasma hyopneumoniae than pseudomonic acid A.

Reproducible pneumonia in gnotobiotic piglets induced with broth cultures of Mycoplasma hyopneumoniae and the effect of animal passage on virulence.

The virulence of a laboratory adapted culture of Mycoplasma hyopneumoniae strain NB12 was determined in three- to five-day-old gnotobiotic piglets. Intranasal inoculation or exposure to an aerosol of the culture caused low incidences of pneumonia in the piglets. Passage of M hyopneumoniae strain NB12 in gnotobiotic piglets resulted in a rapid increase in virulence. After only three in vivo passages, severe pneumonia involving most lobes of the lung developed in all inoculated piglets within three and a half weeks. All 49 piglets inoculated with the piglet-passaged NB12 strain in nine subsequent experiments developed pneumonia but the extent of the pneumonic lesions varied considerably from piglet to piglet. The histopathology of the lung lesions was similar to that reported as being induced by other strains of M hyopneumoniae in gnotobiotic piglets and resembled that seen previously in conventionally reared neonatal piglets inoculated with homogenised lung from pigs with enzootic pneumonia. Aspiration pneumonia caused by milk inhalation occurred in some piglets. The pneumonia induced with the piglet-passaged NB12 strain was judged to be suitable for the study of porcine enzootic pneumonia or for the evaluation of chemotherapeutic agents.

Fructosyltransferase activity of a glucan-binding protein from Streptococcus mutans.

Streptococcus mutans serotype c produces several extracellular proteins which bind to affinity columns of immobilized glucans. The proteins are three distinct glucosyltransferases and another glucan-binding protein (molecular weight 74000) which is now shown to be a fructosyltransferase. This enzyme is antigenically distinct and genetically independent of two other fructosyltransferases produced by the same organism. A mutant is described which lacks the glucan binding fructosyltransferase and has defective ability to form adherent colonies in the presence of sucrose. Although the production of glucans from sucrose results in the glucan binding protein becoming bound to the bacterial surface, and hence perhaps contributing to adherence, the fructans synthesized by the enzyme do not appear to contribute to this phenomenon.