THE EFFECT OF CINCHONA ALKALOIDS ON PARASITES OF FROG

摘要

References(9) Our previous studies (1-4) of the experimental chemotherapy of malaria have been done by the use of Plasmodium cathemerium in canary birds. Not only is the Plasmodium cathemerium unsatisfactory as a test subject, but it is necessary to study plasmodia other than the human malaria plasmodium in various animals in investigations of the action of cinchona alkaloids. It is a well known fact that Plasmodium cathemerium, relictum, gallinaceum and lophurae of birds, Plasmodium cynomolgi of the monkey and Plasmodium berghei of the rat and mouse, which are .test subjects for experimental malaria, have different sensitivities for plasmodicidal agents. The effects of plasmodicidal agents on the parasites of the cold-blooded vertebrates have not been studied.Two different types of parasites exist in the peripheral blood of the frog (Rana esculenta). Their. development is not completely known. One is Lankestella minima (Chaussat). This was found by Labbe (1899) in the red blood cell of the frog, which was first seen by Chaussat (1850). This parasite has been studied chiefly by Noeller (5). It is a small vermicle, which may attain half the length of the corpuscle. Various observers have described the vermicle as becoming spherical and reproducing in the red cells by sehizogony, but Noeller believes the schizonts belong to Dactylosoma ranarum, which is another parasite in the frog's red cells. Infection of the frog is brought about by the leech, which introduces the sporozoites. They, then apparently enter the endothelial cells. Schizogony results in numerous merozoites, which bring about infection of further host cells. Ultimately macro- and micro-gametocytes are formed. The zygotes transform into oocysts in which a number of sporozoites develop. These sporozoites are set free upon disintegration of the oocyst wall in the plasma and enter the red cells. In the red cell of the frog another type of small parasite which is devoid of pigment and which multiplies by producing 4-16 merozoites was found by Kruse (1890). This is Dactylosoma ranarum (Kruse). Two years later Grassi and Feletti (6) described it under the name of Hoemogregarina ranarum and recognized it as having a close resemblance to human malaria parasites. According to Noeller (7) the asexual stage of the parasite. may be seen within the living red cell as hyaline masses of cytoplasm, either elongate or rounded. The schizonts have a diameter of 4 to 9 micra, while the number of merozoites produced is four to sixteen. When nuclear multiplication is completed, merozoite formation commences and this takes place frequently by the development, of buds on one side of the parasite only, producing eventually a fan-like appearance. The other type of merozoite, after entering another red cell, grows into a gametocyte instead of a schizont. They usually lie at one end of the red cell and the narrower end is often bent into a loop. In some of the gametocytes the nucleus, which is a spherical body, contains a small karyosome while in others there is a much larger one. The former may represent the male gametocytes and the latter the female.Since the specificity of drugs in the treatment of malaria depends upon the type of infecting parasite, it is of interest to know the difference in sensitivity to the cinchona alkaloids between the avian parasite and .frog's parasite.