A revision of trypanosoma (schizotrypanum) cruzi strains from British Honduras, and the importance of strain characteristics in experimental chemotherapy of Chagas' disease

The characteristics of 10 strains of Trypanosoma cruzi from British Honduras are reviewed and discussed. The strains were isolated from the faeces of wild-caught Triatoma dimidiata and all proved to be highly pathogenic to white mice and rats and to certain species of wild rodents. All the strains were characterized by a high cardiotropism, which did not diminish even after prolonged passage in further animals. A variable degree of neurotropism, characterized by parlysis of the limbs, produced by the strains was observed in many laboratory animal as well as in some of the experimentally infected wild rodents. Histological studies of organs from several of the paralized animals failed to provide definitive clues as to the origin of the paralysis. A wide range of dimorphism was observed in the blood-forms of T. cruzi from each of the isolated strains; this dimorphism and the mean nuclear index number changed during each passage. The morphogenisis of the parasites in tissues, in the insect vector, and in NNN culture medium, was found to include amastigote, sphaeromastigote, epimastigote and transitional trypomastigote forms, all leading to the formation of the infective trypanosome form. The importance of co-ordinated studies on the biological and physiological characteristics of T. cruzi strains from man, animal reservoirs, and triatomine insect vectors, from the regions where Chagas' disease is endemic, is emphasized as one of the fundamental requirements for the experimental chemotherapy of Chagas' disease (AU)

American trypanosomiasis in British Honduras: VIII. The morphogenesis of Trypanosoma (Schizotrypanum) cruzi in the tissues of animals experimentally infected with British Honduras strains of the parasite

The cycle is described of the intracellular development of British Honduras strains of Trypanosoma (Schizotrypanum) cruzi in the tissues of experimentally infected animals. From studies and observations on a considerable amount of material it is concluded that the morphogenesis of T. cruzi in tissues includes the amastigote, sphaeromastigote, epimastigote and transitional trypomastigote forms, leading to the formation of the bloodtype trypnosome. It is suggested that, in order to clarify the long-standing controversy on the morphogenesis of the parasite, more detailed studies are required on the characteristics and variations of T. cruzi strains from other geographical localities where Chagas' disease is epidemic.(Summary)

The role of mitosis in the post-natal morphogenesis of the basal synchondroses of the skull

In the study factors which influence the growth of any tissue, a distinction must be made between determination, the decision as to which of the inherent genetic potentialities a given tissue will realize, and differentiation, the realization of expression of a specific potentiality. In the two tissue systems that are involved in the morphogenesis of the skull namely, synchondroses and syndesmoses, mitosis seems to have an essential place in between the act of determination and the process of differentiation. Mitosis is the first visible sign that a determination has occurred, and it precedes the final differentiation which results in deposition of bone or hypertrophy of cartilage. We have been using tritiated thymidine autoradiography to label pre-mitotic cells in the periodontal ligament (a syndesmosis) and in the spheno-occipital synchondrosis in the rat. In the case of the synchondrosis, growth of the adjacent basal bones can be directly related to mitosis within the cartilage between 40 and 80 days of age by calculations comparable to those of Kember. However, between 1 and 40 days, there is more growth than can be accounted for on the basis of mitoses detected within the cartilage. On the other hand, if one calculates the portion of growth due to endochondral replacement alone, interstitial mitoses in the cartilage are found to be adequate. Perichondral apposition of cartilage cells need not be postulated. The remaining portion of the total growth of the bones is accounted for by apposition of bone from the periosteum (AU)