Genetic resistance of chickens to coccidiosis has been investigated for several decades. Many authors have paid attention to relationship between the resistance and alloantigen systems. Among 12 alloantigen systems of chicken blood types, the contribution of A, B, C, E, and I systems to susceptibility or resistance to coccidiosis have been studied. The B system, which is the major histocompatibility complex (MHC) of chickens, has been identified as contributing largely to susceptibility to coccidiosis of chickens, partially in collaboration with background genes, but several authors claimed that its contribution was less than background genes. Differences extent in the contributions of B system to resistance in embryos and that in chickens was observed. Possibility of contribution of alloantigen genes, e.g. A, E, C and I, other than B genes to the resistance of chickens to coccidiosis was also suggested. Alloantigen genes may work in collaboration with background genes in expressing susceptibility or resistance to coccidiosis in chickens.

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To determine the growth and morphogenesis of Trypanosoma cruzi in mammalian host cells, we have examined the conditions for in vitro propagation of amastigotes and trypomastigotes of T. cruzi in HeLa cells. Within one day after the infection, the developmental stage of parasites changed from the trypomastigote form to amastigote form in the host cells. The rate of infection by T. cruzi of the host cells increased in an inoculum-and time-dependent manner. The amastigotes proliferated rapidly by binary fission, reaching a peak of the average number of about 20 amastigotes per infected HeLa cell on day 6 after infection. Simultaneously, the alteration of morphology from amastigotes to trypomastigotes also took place within the host cells, the latter disrupting the host cells and again appearing in the culture medium. On day 8, the number of amastigotes decreased and that of trypomastigotes increased, inside and outside of HeLa cells, respectively. The system established in this study may facilitate 1) the quantitative propagation of amastigotes and trypomastigotes and 2) the study of molecular and cellular mechanisms that underlie stage-specific transformation of T. cruzi.

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An NADP-linked glutamate dehydrogenase (L-Glutamate dehydrogenase NADP-oxidoreductase, EC 1.4.1.4.) was purified 181 folds from Plasmodium knowlesi (simian malaria parasite) by ammonium sulfate fractionation, gel filtration and hydroxylapatite column chromato-graphy. The molecular weight of the enzyme was found to be 295,000 as determined by gel filtration. The enzyme appeared to be heat stable (4h at 56℃) and activated about 39% and 14% by KCl and NaCl respectively. It catalysed the amination of α-ketoglutarate and the deamination of glutamate with optimum activity at pH 7.4 and 8.6 respectively. Hyperbolic kinetics were observed for the substrates and cofactors yielding Km values of 0.25±0.02ｍM for α-ketoglutarate, 1.3±0.2mM for ammonium acetate, 0.011±0.001mM for NADPH, 1.8±0.1mM for glutamate and 0.050±0.002mM for NADP. The amination reaction was about 10 times more active as compared to the deamination reaction. Purine nucleotides did not show any effect on enzyme activity. These results suggest that the amination reaction may predominate in P. knowlesi parasites.

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Biochemical and restriction enzyme analysis were carried out to compare two Indian and one Portland (USA) isolate of Giardia lamblia. Electrophoretic isoenzyme patterns of four enzymes namely, Acid phosphatase (ACP), Alkaline phosphatase (ALP), Isocitrate dehydrogenase (ICDH), and Phospho glucomutase (PGM) revealed three different zymodemes amongst three isolates in 5% polyacrylamide gel. Each isolate differs from the other in two or more enzymes out of four enzymes studied. Significant differences were observed within the two Indian isolates in ICDH and ALP enzymes. Differences were also noticed between the Indian and Portland isolates in the electrophoretic migration patterns in PGM and ICDH enzyme systems. Heterogeneity among G. lamblia isolates is, therefore, postulated within the same area and in different geographical locations based on the isoenzyme studies. ICDH and ALP enzymes were used for first time in the study and found useful in differentiation of G. lamblia isolates. The restriction enzyme digestion pattern of DNA from the isolates showed no marked differences, thereby suggesting the development of gene specific probe for such studies.

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Restriction digestion pattern analysis has emerged as a useful tool in assessing strain variation at the genetic level. The present study was aimed at exploring its utility in assessing strain variation in Trichomonas vaginalis and correlating these with the clinical presentation. Vaginal swabs and urine specimens obtained from 500 women were processed for isolation of T. vaginalis by wet smear examination and culture technique. Twenty seven (5.4 percent) specimens were found to be positive for T. vaginalis. Twelve strains could be axenised out of 19 isolated by culture technique. Parasite DNA was extracted in both early and late stage culture of strains both from symptomatic and asymptomatic subjects. Parasite DNA was isolated by three different methods. Proteinase K digestion was found to be the most suitable method compared to the methods using guanidinium isothiocyanate or diethylpyrocarbonate. Different strains of T. vaginalis could not be differentiated by banding patterns following restriction endonuclease digestion. Although the study did not reveal any genotypic variation among different strains, the pathogenic potential of the parasite might parallel the phenotypic variation as a result of differences in the expression of various genes. It may well be that host factors might be playing a critical role in the pathogenesis of trichomoniasis.

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