Donald G. Dusanic

Trypanosoma lewisi: termination of pregnancy in the infected rat.

Abstract Trypanosoma lewisi has previously been described as a nonpathogenic parasite of the rat, but these experiments demonstrate that both embryonal and maternal death may occur in the pregnant rat after infection with this parasite. Rats infected early in the first week of pregnancy resorbed their young with little apparent difficulty, and exhibited parasitemia curves typical of nonpregnant infected females of similar age. Rats infected late in the first week of pregnancy experienced greater difficulty resorbing the young, with half of the females dying shortly before parturition. The parasitemia counts were also similar to those of nonpregnant infected rats. The majority of rats infected during the midterm of pregnancy died at the time of parturition, without giving birth to their young. The number of parasites in these animals was abnormally high compared to nonpregnant infected females. Unusually large numbers of dividing trypanosomes were present in the placentae of these animals, many of them containing 8–16 nuclei and kinetoplasts. Animals infected during the last week of pregnancy gave birth to litters of normal size with little apparent difficulty, and had extremely low parasite counts. The hematocrits of all groups of infected animals showed a decrease at the time of peak parasitemia, and the hematocrits of all groups of pregnant rats showed a decrease at the time of birth, except for those infected when day 2 pregnant. These animals completely resorbed their young. The weight losses of rats infected on day 2 and day 6 of pregnancy reflected a termination of pregnancy.

Mechanisms of amino acid Transport in 'Trypanosoma lewisi.'

Abstract 1. 1. Mechanisms of amino acid transport have been studied in blood stream forms of Trypanosoma lewisi . 2. 2. The kinetic data indicate that valine and phenylalanine are transported by mediated processes through the same locus on the membrane as evidenced by complete inhibition of one by the other. 3. 3. The locus for arginine transport is different from valine and phenylalanine. Two modes of transport are observed with arginine. At low substrate concentrations T. lewisi absorbs arginine by a mediated process; at high substrate concentrations diffusion appears to be the main mode of entry. 4. 4. Aspartic acid is not taken up by these hemoflagellates during the time periods studied.

Respiratory activity of Trypanosoma lewisi during several phases of infection in the rat

Abstract Inhibition of reproduction of Trypanosoma lewisi by ablastin is accompanied by alterations in the physiology and biochemistry of the parasite. The respiration of 4-, 8-, and 12-day postinoculation cells with glucose and glutamine, as the substrates, was compared. Metabolic inhibitors indicated that reproducing trypanosomes have primarily a glycolytic pathway, shifting to dependence on the tricarboxylic acid cycle at 8-days postinoculation and possibly back to glycolysis at 12 days. The levels of inorganic phosphate and ATPases in the parasites corresponded to the changes in respiration. Postinoculation plasma affected the oxygen uptake and glucose consumption differentially of trypanosomes collected at various times after inoculation. The results may implicate factors, beside immunological ones, influencing the parasites metabolism. The data presented suggests differences in the biochemistry of 4-, 8-, and 12-day postinoculation trypanosomes. Eight-day parasites differed from 4- and 12-day parasites that may be similar in many respects to each other. These differences may be correlated with biochemical changes in the host. This approach to the study of T. lewisi , along with what is known about the immune response, may provide additional insights into the phenomenon of T. lewisi infections.

Transport of nucleosides in Trypanosoma lewisi.

Abstract 1. 1. Transport of nucleosides have been studied in blood stream forms of Trypanosoma lewisi. 2. 2. Thymidine and uridine are transported by a dual mechanism. Active transport is observed at low concentrations. At high concentrations, the nucleosides enter the cells by diffusion. Partially competitive inhibition of thymidine by uridine suggest specific as well as common sites for these nucleosides. 3. 3. The uptake of both thymidine and uridine increase in the presence of thymine.

Trypanosoma lewisi: creatine phosphokinase, ornithine carbamyl transferase, ATPases, Pi, and glucose levels in the rat host.

Abstract Studies on biochemical changes in sera from Trypanosoma lewisi infected rats were initiated to determine whether any correlation exists with metabolic changes reported to occur in the parasite. The levels of inorganic phosphate and ATP hydrolyzing enzymes in rat sera paralleled the parasitemia of T. lewisi throughout the infection. Creatine phosphokinase and ornithine carbamyl transferase activity were altered as a result of the infection. A hypoglycemic condition was observed during the time when the parasitemia was greatest in T. lewisi infected rats. The data indicate that metabolic changes in the rat occur concurrent with physiological and biochemical alterations in the parasites during infection. The interrelationships between the host and the parasite are discussed.

Comparative studies on blood-stream and culture forms of Trypanosoma lewisi— II. Biochemical composition☆

Abstract 1. 1. The non-protein nitrogen and RNA content per milligram dry weight and per trypanosome of both the blood-stream and culture forms is higher at 4 days than at any other time during cultivation or infection. 2. 2. The percentage protein per milligram of dry weight of the blood-stream forms increases during the course of the infection, but it decreases during the growth of the culture forms. 3. 3. The 4-day blood-stream form has a lower protein content per trypanosome than 7- and 12-day blood-stream or 4-, 6- and 10-day culture forms. 4. 4. Variation in the dry weight of trypanosomes occur both with the blood-stream and culture forms. 5. 5. Variations in neural lipid, phospholipid and cholesterol content per trypanosome appear to exist in both forms. 6. 6. The amounts of RNA and protein, but not DNA, per trypanosome for the culture forms of Trypanosoma lewisi and Trypanosoma cruzi are similar.

Cultivation of Trypanosoma lewisi in a dialysate medium—I. Amino acid alterations during growth

Abstract 1. 1. Culture forms of Trypanosoma lewisi were successfully grown in the liquid phase of a culture medium in which the blood agar components were placed inside of a double layer of dialysis tubing, autoclaved and immersed in Lockes solution. 2. 2. These culture forms have been transferred at weekly intervals for a total of seventy subcultures to date in this dialysate medium. 3. 3. When agar was omitted from the medium, the flagellates did not multiply. 4. 4. A single peptide was demonstrable by polyacrylamide gel electrophoresis in the liquid phase which did not precipitate upon the addition of 10% tricholoroacetic acid. 5. 5. The amino acids of the dialysate were determined qualitatively and quantitatively and changes during the growth of the culture forms were characterized.

Serologic and enzymatic investigations of Trichinella spiralis. I. Precipitin reactions and lactic dehydrogenase.

Abstract The numbers and physiochemical composition of the precipitating antigens of Trichinella spiralis have been determined although their biologic functions have not been ascertained. In infected rabbits there is a temporal sequence in the production of antibodies to the worms somatic constituents and to its secretion-excretion products (SEP). Alterations concurrent with the infection were demonstrated in serum proteins and lactic dehydrogenase (LDH) by polyacrylamide gel electrophoresis and biochemical assay. These assays showed that the LDH of the trichina larvae was inhibited by antisera from infected rabbits. Polyacrylamide gel electrophoresis demonstrated two isozymes of LDH in saline extracts of the parasites somatic constituents and one in the SEP. Immunoelectrophoresis and incubation in a buffered lactate-tetrazolium medium indicated that one to two of the resultant precipitin arcs were stained specifically for LDH. Somatic extract and isolated LDH isozymes of the larvae in polyacrylamide gel were used to immunize rabbits. Precipitin arcs formed by sera from those immunized animals and the somatic extract in immunoelectrophoretic analyses showed LDH activity. Larvae incubated in sera from infected or from immunized rabbits showed oral precipitates which, when washed and incubated in the buffered lactate-tetrazolium medium, stained for LDH. These studies suggest the LDH of the Trichinella larvae is secreted during the infection and stimulates the production of specific antibodies in the rabbit.

Comparative studies on blood stream and culture forms of Trypanosoma lewisi—I. Oxygen utilization, carbon dioxide production and glucose uptake

Abstract 1. 1. Glucose-stimulated oxygen uptake by the blood-stream forms of Trypanosoma lewisi was comparatively higher than the culture forms. 2. 2. Endogenous oxygen consumption by the culture forms was relatively higher than the blood-stream forms. 3. 3. Production of glucose-stimulated carbon dioxide was higher by the blood-stream forms than the culture forms. 4. 4. As the duration of growth of the culture forms was extended, glucose uptake by the organisms increased significantly, while the blood-stream form decreased slightly during the course of the infection. 5. 5. The μM O 2 /μM glucose ratio of the blood-stream form increased significantly from 4 to 7 days, while the ratio decreased during the growth of the culture-form trypanosomes.

Crossed-immunoelectrophoretic analyses of Trypanosoma cruzi epimastigote, metacyclic, and bloodstream forms.

Sonicated suspensions of epimastigote, metacyclic, or bloodstream forms of Trypanosoma cruzi were emulsified in Freunds complete adjuvant. Rabbits immunized with epimastigotes or metacyclics received five intramuscular (i.m.) injections of 1 x 10(9) sonicated trypanosomes at weekly intervals. Immunization with bloodstream forms included three i.m. injections of 5 x 10(7) and six injections of 2 x 10(8) sonicated trypanosomes. Selected antisera from these rabbits were employed in crossed immunoelectrophoretic studies against the homologous or heterologous extracts of sonicated trypanosomes. Extracts of epimastigote, metacyclic, and trypomastigotes produced 31, 29, and 11 precipitin peaks respectively against the homologous rabbit antisera. Tandem, crossed-immunoelectrophoresis of these extracts against antiepimastigote or antimetacyclic sera revealed that epimastigotes or metacyclics may each have at least four antigens that did not appear to be shared by the other, whereas each of these forms may have at least eight or nine antigens that were not detected with extracts from trypomastigotes. Cross-absorptions of antiepimastigote or antimetacyclic sera with live trypanosomes caused marked reductions in the numbers of precipitin peaks formed against the homologous extracts, but cross-absorptions with sonicated suspensions of epimastigotes or metacyclics showed that epimastigotes or metacyclics each have at least two antigens that were not detected in extracts of the other. Differentiation appeared to be accompanied by antigenic change. More antigens appear to be shared by epimastigotes and metacyclic forms than by trypomastigotes and epimastigotes or metacyclics.