[Microscopic analysis of the effect of mercuric salts on the parasite concentration in feces].

The fixation of mercuric ions on the uterin layer of the Ascaris lumbricoides egg wall is proved by light microscopic histochemical technics and electron microscopic microanalysis. These observations support the hypothesis of a possible reaction between the egg surface components and those of the dilution reagents. This reaction is used in the methods of concentration in coprology.

[Role of prolactin in changes of parasitism induced by lactation].

In order to establish the role played by prolactin in lactation during the evolution of Strongyloides ratti in the female rat, the authors tried to reproduce the effects of this physiological state by treatment with sulpiride (substituted benzamide), of which the prolactinogenic effect is intense in the female rat. Low doses partially reproduced the effects of lactation on parasitism by diminishing its intensity and delaying the onset of rejection, although without preventing it. The pharmacological action of sulpiride, which acts by blocking the dopamine receptors, explains why only low doses are active and why their action is limited to the onset of parasitism.

[The role of inflammation in the spontaneous elimination of Strongyloides ratti infestation].

In order to assess the role of inflammation and its components in spontaneous cure of Strongyloides ratti infestation, rats were treated with non-steroid anti-inflammatory agents (indometacin; sodium salicylate) or with antagonists of certain mediators (dexchlorpheniramin; cyproheptadin, promethazin). Results were compared with those obtained in similar treatments of rats infested by other Nematoda which also give rise to spontaneous cure: especially Trichinella spiralis, and Nippostrongylus brasiliensis. Coordinating the various findings made it possible to devise a pattern accounting for the chain of reactions that lead to rejection of the parasite.

[Course of blood corticosterone in trichinosis in rats; its relation with immunosuppression].

Beyond a certain level of parasite density, trichinellosis of the rat is accompanied by high plasma corticosterone, the intensity of which depends on that of the parasitism. It develops in two phases: a primary phase, starting early on (40 hours after infestation), is characterized by a more or less high degree of plasma corticosterone, varying according to parasite intensity. It stops around the fifteenth day.

[Inhibition of Plasmodium berghei in rats infested with Strongyloides ratti or Trichinella spiralis; role of high blood corticosterone in reaction to the development of helminths].

The plasma corticosterone induced in the rat by the development of Strongyloides ratti or Trichinella spiralis reaches a sufficient level of intensity to determine reticulocytopenia. The latter is linked chronologically to the inhibition of parasitemia in Plasmodium berghei, which occurs when this protozoa develops at the same time as the Nematodes, and seems to be the causal factor. This hypothesis may be verified by replacing the helminths with the corticotropic action of A.

[Relations between parasitism of the rat by Strongyloides ratti, female sex hormones and blood corticosterone].

Situated under strict conditions in order to try to limit experimental aggravation and to respect the accomplishment of an endocrine balance, the experiments carried out study the influence on parasitism by Strongyloides ratti of ovariectomie and the treatments, of female rats castrated or not, by oestradiol, hexoestrol, diethylstilboestrol, progesterone, mestranol, chlormadinone association. Similarly, adrenal cortex reactions (corticosterone) to the treatment and parasitism are recorded. The analysis of the results lead to the thought that the glucocorticosteroid function of adrenal cortex could be one of the relays between gonades and the development of parasitism (intensity, removal of parasites).

[Interactions of 2 associated parasitoses in the rat: Plasmodium berghei and Strongyloides ratti].

When Plasmodium berghei and Strongyloides ratti are associated, each one of these parasites can modify development of the other one. This repercussion is subordinated to the respective periods of contamination and strength of influential parasitism. It lies in an inhibition of Protozoosis or intensification of helminthiasis.

[Cortico-adrenal reaction in rats to attempts of reinfestation by Strongyloides ratti (author's transl)].

After spontaneous recovery from infestation by Strongyloides ratti, reinfestation by a new generation of adult parasites is not possible if the primary infestation was by 5,000 or 10,000 larvae administered in one or more contacts and if the secondary infestation takes place 3 weeks after. Reinfestation becomes possible again 51 days after recovery from a primary infestation by 15,000 larvae. However although the larvae do not reach the adult stage, they do begin their migration and cause hypersecretion of gluco-cortico-steroids.

[Parasitism and corticosteronemy in rats during repeated infestations with Strongyloides ratti].

The greater the number of larvae, the lower the possibilities of superinfestation when rats are repeated exposed to contact with Strongyloides ratti larvae, once a week or every two days for periods of up to twenty-four days: super-infestations occurs only on the 2nd day (10,000 larvae), the 4th day (5,000 larvae) and the 9th day (1,000 larvae). However, superinfestation continues throughout the entire duration of the experiment (46 days) when contamination is very low (10 larvae). Although there is now superinfestations, each new contact with larvae produces a hypercorticosteronemia reaction.

[Importance of the time of sample taking in order to follow the variations in corticosteronemy during parasitism of the rat by Stronglyoides ratti (author's transl)].

The variations in corticosteronemy induced by the development of Stronglyoides ratti in the Rat can be detected both in the afternoon, when corticosteronemy reaches its maximum, and in the morning when it is at its lowest rate. Nevertheless, hypercorticosteronemy, which is at its maximum 48 hours after infestation, is more sensible in the morning, whereas on the contrary hypocorticosteronemy is more significant in the afternoon and then shows a sudden and very important drop which seems to coincide with the beginning of the expulsion of the adult worms. According to previous results, inhibition of the secretion of gluco-cortico-steroids is caused by the worms; furthermore, Ogilvie and Jones show the determinant role of sensitized lymphocytes, for the expulsion of antibody-damaged worms, whereas some authors suggest that eosinophils act as cytotoxic cells on sensitized helminths; the hypothesis may therefore be put forward that hypocorticosteronemy liberates the intervention of active lymphocytes and eosinophils, triggering so the phenomenon of spontaneous deparasiting.

[Role of hypocorticosteronemy in the self cure mechanism in rats with Strongyloides ratti parasites (author's transl)].

Repeated injections of corticosterone acetate, physiological hormone of the Rat, in rats carrying Strongyloides ratti, oppose the deparasiting which normally takes place spontaneously. The secretion induced by this hormone by impregnating the organism through the corticotropic factor administered in the form of tetracosactide-zinc, achieves the same result. During all these treatments, an important hypercorticosteronemy is established.

[The effect of lactation on the parasitism of rats by Strongyloides ratti (author's transl)].

In lactating females of many animal species infested by Nematoda, the self-cure is, if not suppressed, at least very distinctly delayed. It does not appear that an immunological deficiency is the cause of this. We show that this phenomenon also exists in lactating female rats with Strongyloides ratti parasites.

[Mechanism of hyocorticosteronemia action of Strongyloides ratti in the rat].

In order to explain the hypocorticosteronemia which establishes itself in rats with Strongyloides ratti parasites, we are proceeding with a functional exploration of the hypothalamo-hypophyso-corticosurrenal axis in experimentally infested rodents. The adreno-cortico-tropic-hormone test (A.C.