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S Mallet

Publications and source records attributed to S Mallet.

28 records · Page 2Linked to original sources
PubMed1990

Effects of size of Trichostrongylus colubriformis infections on histopathology of the mucosa along the whole small intestine in rabbits.

The influence of population size of Trichostrongylus colubriformis on the structures of the small intestine, especially with regard to the development and origin of an intestinal adaptive response, was examined in experimentally infected rabbits. The effects of low (500 L3) and high (50,000 L3) infection on histological (villous length, mucosa to serosa ratio, crypt surface) and biochemical (protein content, alkaline phosphatase and leucine aminopeptidase activities) aspects of the mucosa were assessed along the whole small intestine. The presence of a small number of worms induced only minor mucosal changes, indicating a regenerative response of the intestinal epithelium. The role of a local small population of T. colubriformis in the development of a previously described adaptive response appeared thus to be limited. On the other hand, the 50,000 L3 inoculum was associated with severe lesions of villi, marked crypt hyperplasia and with a major reduction of enzyme activities. The changes were found along the whole length of the small intestine. These results suggest that the generally recognized dose-dependent pathogenicity of the intestinal nematode infections could be ascribed to two different processes: firstly, a greater severity of the lesions; secondly, more extensive damage leading to the disappearance of any adaptive intestinal region.

Alkaline Phosphatase↗
PubMed1988

Changes in enzyme activities in the small intestine of rabbits during early infection with Trichostrongylus colubriformis.

In rabbits experimentally infected by fourth and fifth stages (L4 and S5) of Trichostrongylus colubriformis, 16 enzymatic activities in the small intestine were compared to control values, by means of a modified Api Zym method. In the proximal part of the gut, the wide depletion in brush border enzyme activities previously recorded with presence of adult T colubriformis was also noticed with L4 and S5. Moreover, a 10 to 23% reduction was observed for enzyme activities linked to lysosomes and endoplasmic reticulum. In the distal region of the small intestine, no difference in enzymatic activities was present between infected and control animals, although an hyperplasia of villi has been previously described in this part of the parasitised gut. Referring to these enzymatic results for the whole small intestine, the hypothesis of a mechanical effect of worms on the intestinal epithelium and/or disturbance in the renewal of epithelial cells is discussed.

Animals↗
PubMed1987

Relationship between exsheathment and enzyme activity (alkaline phosphatase and leucine amino peptidase) during ageing of Trichostrongylus colubriformis infective larvae.

A stock of Trichostrongylus colubriformis infective larvae (L3) was stored for up to 15 weeks at 24 degrees C. At three weeks intervals, samples of L3 were taken to assess exsheathment rate and enzyme activity Leucine Amino Peptidase (LAP) and Alkaline Phosphatase (AP). From 0 to 9 weeks of storage, a decrease in enzyme activity was observed correlated with a decrease in exsheathment rate (percentage of L3 exsheathed in vitro after 20 min); the maximum percentage of exsheathed larvae (L3 exsheathed after 180 min) was then 75%. From 9 to 15 weeks of storage, both enzyme activity and exsheathment rate were low and constant; the maximum percentage of exsheathed larvae never exceeded 30%. The role of enzymes in the mechanism of exsheathment is discussed.

Alkaline Phosphatase↗
PubMed1987

Trichostrongylus colubriformis and Heligmosomoides polygyrus: relationship between infectivity and exsheathment during ageing of infective larvae.

Infective larvae of two trichostrongyle parasites of the small intestine were stored from 0 to 22 weeks at 24 degrees C for T colubriformis and from 0 to 82 weeks at 4 degrees C for H polygyrus. A loss in infectivity with ageing was observed in vivo as well as a decrease in the exsheathment potential (number of larvae exsheathed in vitro after 20 min of incubation). A linear regression was established between the number of larvae exsheathed in vitro within 20 min and the number of adult worms developed in vivo.

Animals↗
PubMed1986

Winter survival of third stage Trichostrongylus colubriformis larvae: effects on infectivity and fecundity of adult worms.

Two groups of six lambs were fed with grass cut from two plots which had been contaminated by spreading Trichostrongylus colubriformis larvae. One plot received larvae in December, the other in April. The post mortem examination results showed that the infectivity of overwintering larvae was significantly higher than that of fresh larvae. An inverse relationship was demonstrated between infectivity of larvae and egg production of adult worms developed from these larvae. The results are compared with those obtained under laboratory conditions.

Animals↗
PubMed1985

Trichostrongylus colubriformis: relationship between ageing of infective larvae, infectivity and egg production by adult female worms.

Relationships between egg production and infectivity were studied with infective larvae of Trichostrongylus colubriformis which had been stored for up to 22 weeks at 24 degrees C. After different storage times, larvae were administered to lambs and the number of parasites which reached the adult stage was counted five weeks after infection. Egg production was estimated for the same batches of animals by performing a quantitative coproscopic examination from the third week of infection onwards. Infectivity was maximum and constant during the first six weeks of storage and then decreased regularly from the 9th week to the end of the experiment. However, the number of eggs produced per female worm was constant during the first 6 weeks then doubled and remained constant from the 9th to the 22nd week of storage.

Aging↗
PubMedDate not supplied

Characterization of acetylcholinesterase secreted by the trichostrongyle nematode parasites of ruminants.

Acetylcholinesterase (AChE) secreted by seven different ruminant trichostrongyles was studied in vitro. AChE activity was particularly high (84 and 160 x 10(-3) M.g-1.min-1) in the excretion products of Nematodirus spathiger and N battus, moderate (3 and 5 x 10(-3) M.g-1.min-1) for Trichostrongylus colubriformis and T vitrinus and low (0.9 x 10(-3) M.g-1.min-1) for Teladorsagia circumcincta. No activity was observed with Haemonchus contortus and Cooperia curticei. At 4 degrees C, 80% of AChE activity was maintained over 72 h except for T circumcincta where a loss of 50% was observed after 24 h. At 37 degrees C, N spathiger and T colubriformis maintained an activity over 72 h, but for the other species, a loss of 50% was observed after 24 h. The molecular weights of the AChE from the different species, estimated by gel filtration (Sephadex S300HR), ranged between 64 and 150 kDa. The coefficients of sedimentation estimated by sucrose density gradient ranged between 4.8 S and 7.8 S and corresponded to a monomeric hydrophilic form (G1). For T vitrinus, an amphiphilic form was suspected.

Acetylcholinesterase↗