Endocrine responses of protein-malnourished rats infected with Nippostrongylus brasiliensis (Nematoda)

Fluctuations in rat liver alanine-amino-transferase activity during experimental nippostrongylosis

The activity of the gluconeogenic enzyme, alanine-amino-transferase (ALT), in a preparation from the liver of rats was studied by means of an in vitro assay throughout the course of a primary infection of Nippostrongylus brasiliensis, established by a subcutaneous injection of approximately 4000 3rd-stage larvae. The activity was measured on days 1-14 p.i. in both uninfected and infected rats and a marked pattern in the enzyme's activity was observed. In infected rats, the activity increased from 1.46 +/- 0.19 U/g liver on day 1 p.i. to a peak on day 4 p.i. of 10.75 +/- 1.62 U/g liver, then decreased to a trough of 0.44 +/- 0.18 U/g liver on day 10 p.i. before returning to original levels by day 14 p.i., by which time the infection had been largely eliminated. In uninfected rats the activity of the liver enzyme remained constant throughout this period with a value of 2.54 +/- 0.12 U/g liver. The activity of the enzyme in vitro was found to be related to the size of the inoculum on days 4 and 10 p.i. It was proposed that these observations could be due to either (1) a direct effect of the parasite, or (2) a consequence of the host immune response to the infection. In order to investigate the second proposition more fully, liver ALT activity was investigated by in vitro assay on selected days p.i. in rats experiencing a secondary N. brasiliensis infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparisons of Heligmosomoides polygyrus primary infection in protein-deficient and well-nourished mice

Primary infections of Heligmosomoides polygyrus were studied in adult male CD1 mice fed on isoenergetic synthetic diets containing either 2% or 20% protein (casein). A slight reduction in food intake was observed during infection, and this was unaffected by diet. Protein deficiency was also found to have no effect upon worm establishment. Evidence was found, though, to suggest that the worms have a more severe effect upon the host in protein-deficient mice. Hypoalbuminaemia was observed due to diet and also infection, and this was synergistic. There was an increase in non-albumin plasma protein during infection which was not effected by diet. The circulating urea concentration was reduced during protein deficiency, as was the level of essential amino acids, but non-essential amino acid levels were raised. An increase in the levels of urea and essential amino acids was observed at day 4 of infection in mice on the 20% diet, but not on the 2% diet. Splenic atrophy occurred during infection, but the splanomegaly that occurred early during infection was proportionally greater in protein-deficient mice. These results are discussed in terms of the pathophysiology of both protein deficiency and infection, and comparisons are made with human malnutrition syndromes.

Nippostrongylus brasiliensis: physiological and metabolic responses of rats to primary infection

Primary infection of rats with Nippostrongylus brasiliensis was associated with alterations in host protein, carbohydrate and lipid metabolism. Infected rats fed ad libitum were compared with uninfected, weight matched, pair fed rats. Metabolic changes detected were related to the level of infection (larvae/g body weight) and also the time course of development of the parasite. The intestinal stage of the infection was associated with marked catabolism of skeletal muscle which did not appear to be mediated by increased secretion of corticosteroids. Plasma concentrations of protein in infected rats were altered even at the lowest dose (27 l/g), and in a biphasic manner corresponding to larval and adult stages of the parasite. Plasma globulin concentrations were increased on Day 2 after infection while from Days 5-10 after infection, plasma concentrations of both globulin and albumin were much reduced. Hypoglycemia developed on Days 8-9 after infection in rats given a dose of greater than or equal to 39 l/g. Infected rats had increased plasma concentrations of non-esterified fatty acids and in marked contrast with their pair fed partners, plasma triglyceride concentration increased dramatically with both the dose of parasites given and the duration of infection. The responses of the rat to infection with N. brasiliensis are compared with host responses to other helminths and microorganisms, and suggestions are made as to their possible functions and significance.

Nutritional aspects of infection

Current knowledge is examined about the means whereby ascariasis, hookworm disease, strongyloidiasis and trichuriasis may contribute to the aetiology of human malnutrition. Results from experiments with related parasites in the laboratory have demonstrated the role of gastrointestinal helminthiases in animal malnutrition. Some evidence shows that in children, infection with the intestinal stages of Ascaris lumbricoides is associated with reduced growth rate, disturbed nitrogen balance, malabsorption of vitamin A, abnormal fat digestion, lactose maldigestion and an increased intestinal transit time. The main impact of hookworm infection is its relationship with iron-deficiency anaemia which may have effects at the community level as regards work and productivity in adults and learning and school performance in children. More research is needed to extend knowledge of the nutritional impact of ascariasis and hookworm disease in order to establish their public health significance. Research is needed also to identify the range of nutritional effects on man that occur as a result of trichuriasis and strongyloidiasis. The significance of less prevalent and more localized gastrointestinal helminthiases should not be ignored.