[Microscopic analysis of the effect of mercuric salts on the parasite concentration in feces]. / Analyse microscopique de l'action des sels mercuriques sur la concentration parasitaire en coprologie.

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. In the case of mercuric salts, the free thiol components which are missing in all the Ascaris egg wall layers are not the factors of the reaction.

[Role of prolactin in changes of parasitism induced by lactation]. / Rôle de la prolactine dans les modifications du parasitisme induites par la 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. This experiment lends weight to the hypothesis that prolactin plays a fundamental role in modifications of the evolution of Strongyloides ratti during lactation.

[The role of inflammation in the spontaneous elimination of Strongyloides ratti infestation]. / Role de l'inflammation dans le déparasitage spontané de Strongyloides ratti.

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.

[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]. / Inhibition de Plasmodium berghei chez des rats infestes par Strongyloides ratti ou par Trichinella spiralis; rôle de l'hypercorticostéronémie réactionnelle à l'évolution des helminthes.

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.C.T.H. which causes a decrease in the number of reticulocytes.

[Course of blood corticosterone in trichinosis in rats; its relation with immunosuppression]. / Evolution de la corticostéronémie au cours de la trichinose du rat; ses relations avec l'immunodépression.

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. The second phase develops from approximately the third week onwards, and can last five or six months; it occurs even when the primary phase is not pronounced. The discussion points to parallel between this reaction and the characteristic immunodepression of trichinellosis, with respect to kinetic and physio-pathological parameters. A fundamental role in immunodepression may therefore be attributed to plasma corticosterone.

[Relations between parasitism of the rat by Strongyloides ratti, female sex hormones and blood corticosterone]. / Relations entre le parasitisme du rat par Strongyloides ratti, les hormones sexuelles femelles et la corticostéronémie.

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]. / Interactions de deux parasitoses associées chez le rat: Plasmodium berghei et 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. When severe, palustral infection releases two hypercosticosteronemy phases; the more important one is situated at the peak of the parasitemia. These hypercorticosteronemiae reactions to a severe malaria enable the interpretation of the variations of an associateds trongyloïdiasis. They may be regarded as one of the inducer elements of immunological depression which takes place in the course of malaria in rodents.

[Parasitism and corticosteronemy in rats during repeated infestations with Strongyloides ratti]. / Evolution du parasitisme et de la corticostéronémie lors d'infestations répétées des rats par 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. Thus, the immunity acquired, although it is rapidly capable of preventing the larvae from reaching adulthood, does not prevent the larvae from beginning their migration and triggering the reaction. Progressively and slowly, this cortico-adrenal reaction decreases. It no longer takes place after 3 weeks of weekly infection by 10,000 larvae of after 2 weeks of bi-daily infection by 10,000 or 5,000 larvae. The reactional hypercorticosteronemia which follows an infestation does not intensify after repeated infections, whatever their frequency or intensity.

[Cortico-adrenal reaction in rats to attempts of reinfestation by Strongyloides ratti (author's transl)]. / La réaction corticosurrénale lors d'une tentative de réinfestation des rats par Strongyloides ratti.

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. There is thus a contrast between the ease with which the organism rapidly and lastingly prevents the transformation of larvae into adults and the difficulty in neutralising the larvae and preventing them from triggering a stress.

[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)]. / Importance de l'heure du prélèvement pour suivre les variations de la corticostéronémie au cours du parasitisme du rat par Stronglyoïdes ratti.

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)]. / Rôle de l'hypocorticostéronémie dans le mécanisme de la "self-cure" des rats, parasités par Strongyloides ratti

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. Stopping the injections is quickly followed by the worms-being rejected and the corticosteronemy returning to normal. The relations between the corticosteronemy and the parasitism are analysed and lead to the conclusion that the parasite induces an aspecific hypocorticosteronemiant reaction which, through its aspecific and specific repercussions, participates in the self-cure phenomenon.

[The effect of lactation on the parasitism of rats by Strongyloides ratti (author's transl)]. / Action de la lactation sur le parasitisme des rats par Strongyloides ratti

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. In fact, for Strongyloides ratti, the maintenance of the worms is not the only notable modification determined by lactation; much more important is the decrease in the intensity of the parasitism. This aspect is not mentioned by writers who have only studied the different parasitic states in their final phase. Parallel to these alterations in the parasitism, the evolution of the corticosteronemy differs, from two points of view, from that described in infested virgin rats: --Suppression of the hypercorticosteronemy which normally appears 48 hours after infestation; --Attenuation of the hypocorticosteronemy which usually sets in from the tenth day of infestation. This opposition of lactation to the variations in the corticosteronemy induced by the worms is explained by the effect of lactation on the secretion of gluco-cortico-steroids, described under the term of "buffer effect of lactation". The decrease in the intensity of the parasitism may be explained by the fact that lactation, by preventing the hypercorticosteronemy normally caused by larval migration, permits the intervention of aspecific defences. As for the prolongation of the parasitism, it would seem to result on one hand, from a reduced solicitation of the means of defence owing to a smaller number of worms and, on another hand, from the slowing down of the hypocorticosteronemy through the buffer effect of lactation with all the consequences flowing from this at the level of the specific and aspecific defence reactions.

[Mechanism of hyocorticosteronemia action of Strongyloides ratti in the rat]. / Mécanisme de l'action hypocorticostéronémiante de Strongyloides ratti chez le 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.T.H.), stress to ether and the Lysin-8-Vasopressin and Metopirone tests lead to concordant results: -- the hypothalamo-pituitary-corticosurrenal present a functional integrity which allows it to react normally to direct stimulation or to feed-back; -- the deficiency seems to relate to the hypothalamic secretion of the cortico-releasing factor; -- the cause would stem from an inhibition of the nervous mechanism which regulates this neurosecretion.