Showing papers in "Journal of Parasitology in 1983"
333 citations
TL;DR: Replacement of the fetal calf serum with bovine serum albumin and Tween-80 increased the time of colony formation by 50% but did not affect the cloning efficiency.
Abstract: A simple technique, developed for the isolation of clones derived from single, promastigote cells of Leishmania donovani and Leishmania tropica, involved the use of semisolid agar. Both species of Leishmania promastigotes formed discrete colonies at high efficiency either in semidefined medium containing 10% fetal calf serum or in completely-defined medium lacking serum. Visible colonies appeared between 8 and 14 days in growth medium containing 10% fetal calf serum. Replacement of the fetal calf serum with bovine serum albumin and Tween-80 increased the time of colony formation by 50% but did not affect the cloning efficiency. Viability of colonies transferred from semisolid agar to liquid suspension culture was 100%.
142 citations
130 citations
TL;DR: Findings are the first to suggest antigenic differences between these two forms of Toxoplasma gondii, and suggest that antisera against the cystozoite reacted against both endozoite and cyStozoite.
Abstract: Antigenic differences between the cystozoite and endozoite of Toxoplasma gondii were found using fluorescent antibody staining. Antisera against the cystozoite reacted against only the cystozoite, whereas antisera against the endozoite reacted against both endozoite and cystozoite. Absorption of sera with endozoites removed only positive reactions with endozoites. These findings are the first to suggest antigenic differences between these two forms of Toxoplasma.
123 citations
117 citations
TL;DR: Significant differences in prevalence of mange across habitat variables of host age and sex, and across seasons were related to the juvenile/adult ratio in the coyote population at any particular time because the infection progressed more rapidly in juveniles.
Abstract: An epizootic of sarcoptic mange in coyotes from south Texas, Canis latrans , was studied over a 7-yr period, 1975 through 1981. From a four-county area centered in Webb County, Texas the epizootic radiated centrifugally to include a 27-county area. The disease progressed from initial, scabby encrustations on the ischium and fore and hind legs to severe, thickened, slate-gray hyperkeratotic lesions with almost complete alopecia. There were significant decreases in alpha-globulin and albumin, significant increases in gamma-globulin, and significant decreases in fat deposits and total body weight indicative of a chronic infection with establishment of a humoral antibody response as the infection progressed in severity. Significant differences in prevalence of mange across habitat variables of host age and sex, and across seasons were related to the juvenile/adult ratio in the coyote population at any particular time because the infection progressed more rapidly in juveniles. Population dynamics and abundance of coyotes were generally unaffected by the mange epizootic. Although higher mortality was associated with mange-infected animals, this had no effect on overall mortality in the coyote population.
111 citations
TL;DR: periods of reduced defensiveness corresponded with maximum mosquito engorgement and with periods of maximum gametocyte infectivity to mosquitoes, which may be important to the natural maintenance of these malaria parasites.
Abstract: Mice infected with Plasmodium berghei, P. chabaudi, or P. yoelii became lethargic and ceased to display normal antimosquito behavior. Periods of reduced defensiveness corresponded with maximum mosquito engorgement and with periods of maximum gametocyte infectivity to mosquitoes. Increased feeding success of mosquitoes during periods of peak gametocyte infectivity may be important to the natural maintenance of these malaria parasites.
98 citations
TL;DR: Because it was less pathogenic and did not require chemoprophylaxis, strain ts-4 best fulfilled the requirements for a good vaccine; its effect in hosts other than the mouse remains to be determined.
Abstract: Mice were immunized with live organisms of the different stages (i.e., tachyzoites, bradyzoites, or sporozoites) of Toxoplasma gondii, or with killed tachyzoites with or without adjuvants. The adjuvants used were liposomes, anhydrides of myristic or lauric acid, levamisole and Freund's complete or incomplete adjuvant. The following strains of T. gondii were used: RH, M-7741, the nonpersisting, temperature-sensitive mutants ts-1, ts-4, or ts-5, and the "back mutant" of ts-1 (Pfefferkorn and Pfefferkorn, 1976). The protection afforded was measured by challenge with the pathogenic M-7741 strain. Killed tachyzoites alone, or with adjuvants, offered only slight protection against challenge with M-7741 and no protection against challenge doses that were lethal to all control mice. Chronic infection and live nonpersisting vaccines conveyed a strong immunity to challenge, except strain ts-1. Because it was less pathogenic and did not require chemoprophylaxis, strain ts-4 best fulfilled the requirements for a good vaccine; its effect in hosts other than the mouse remains to be determined. The immunity induced by tachyzoites, bradyzoites, or sporozoites appeared equally strong when challenged with sporozoites.
95 citations
TL;DR: Gametocytogenesis of the malaria parasite Plasmodium falciparum was studied in monolayers of erythrocytes attached to tissue culture dishes and found that in those cells infected with two or more merozoites the formation of a gametocyte was usually associated with a block in the further development of other parasites.
Abstract: Gametocytogenesis of the malaria parasite Plasmodium falciparum was studied in monolayers of erythrocytes attached to tissue culture dishes. Merozoites produced by single schizonts in erythrocytes overlaying the monolayer infected the attached erythrocytes and produced clusters of progeny. Parasites in these readily indentifiable clusters then underwent either asexual growth or sexual differentiation. The progeny of most schizonts yielded no gametocytes. However, the progeny of those schizonts that did yield gametocytes showed a marked tendency to produce multiple gametocytes. Gametocytogenesis, therefore, was not random. Instead, the progeny of certain schizonts were committed to produce gametes. However, even those clusters containing several gametocytes also contained asexual forms. Therefore, not all merozoites of a single schizont were committed to gametocytogenesis. In those cells infected with two or more merozoites the formation of a gametocyte was usually associated with a block in the further development of other parasites.
85 citations
TL;DR: The results, in which Giardia isolated from different mammalian hosts share multiple isoenzymes, question the validity of the practice of assigningGiardia species names on the basis of the animal host from which the protozoan was obtained.
Abstract: The relative mobilities of six enzymes from the trophozoites of five axenically-cultured isolates of Giardia from human, cat, and guinea pig hosts were compared by starch and polyacrylamide gel electrophoresis. The six enzymes compared were malate dehydrogenase (NAD+) (MDH) (EC 1.1.1.37), malate dehydrogenase (decarboxylating) (ME) (EC 1.1.1.40), hexokinase (EC 2.7.1.1), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), glucose-6-phosphate dehydrogenase (G6P) (EC 1.1.1.49), and alpha-glycerophosphate dehydrogenase (EC 1.1.1.8). The latter three enzymes have not been previously reported in Giardia. On the basis of zymogram patterns, the five Giardia isolates were divided into three zymodemes. Zymodeme I comprised human-1/England, human-1/Bethesda, and cat-1/Portland, Zymodeme II the guinea pig-1/Portland isolate, and Zymodeme III the human-1/Portland isolate. These zymodemes were further substantiated when several physical and kinetic properties of three of the enzymes, MDH, ME, and G6P, were examined. Our results, in which Giardia isolated from different mammalian hosts share multiple isoenzymes, question the validity of the practice of assigning Giardia species names on the basis of the animal host from which the protozoan was obtained.
TL;DR: Polymorphonuclear leukocytes from normal blood donors phagocytosed P. falciparum-infected red blood cells (IRBC) to a greater extent than normal RBC under in vitro culture condition are suggested to be one of the mechanisms involved in the clearance in individuals living in areas endemic for malaria.
Abstract: Polymorphonuclear leukocytes (PMN) from normal blood donors phagocytosed P. falciparum-infected red blood cells (IRBC) to a greater extent than normal RBC under in vitro culture condition. The phagocytic activity of PMN was greatly increased by the addition of sera from individuals living in areas endemic for malaria (immune sera) but not by sera from individuals recovering from a first acute P. falciparum infection. The enhancement of the phagocytic activity was associated with the purified IgG fraction of immune sera and was lost after absorption of IgG on protein A sepharose column of preincubation of the immune sera with IRBC. These experiments suggest that opsonisation of IRBC and their subsequent phagocytosis may be one of the mechanisms involved in the clearance of P. falciparum infection in individuals living in areas endemic for malaria.
TL;DR: Modifications of existing continuous culture methods for P. falciparum allow the rapid, accurate and economical determination of drug effects directly against the human pathogen.
Abstract: Current models for antimalarial drug screening generally measure the survival of drug-treated rodents infected with Plasmodium berghei. Modifications of existing continuous culture methods for P. falciparum allow the rapid, accurate and economical determination of drug effects directly against the human pathogen. Parasite cultures can be maintained in RPMI 1640 medium supplemented with human or rabbit serum or with hypoxanthine-supplemented bovine serum. The antiparasite effects of four drugs, chloroquine, chloramphenicol, clindamycin, and halofuginone, are identical in these sera; drugs can be screened routinely against P. falciparum grown in bovine serum supplemented with hypoxanthine. Drug effects may be rapidly and accurately determined by monitoring the incorporation of 3H-hypoxanthine into parasite nucleic acids. Results obtained with this technique are highly correlated with those derived from visual counting of parasites in thin blood films. Compounds with antimalarial activity in culture may be further screened by measuring the effects of serum obtained from drug-treated rabbits on parasites in culture. The advantages of this system over models currently used for antimalarial screening are discussed.
TL;DR: The best evidence points to competition for limited space or nutrient resources within the intestine of mosquitofish as the most probable cause for decline in parasite density.
Abstract: Changes in mean infrapopulation densities of Bothriocephalus acheilognathi in Gambusia affinis followed a clear seasonal pattern in the ambient and thermally altered areas of Belews Lake, a North Carolina cooling reservoir that is devoid of piscivorous fish except in the headwaters. Highest infrapopulations occurred during fall and winter and lowest in mid to late summer. The composition of the infrapopulations varied seasonally. From late spring to late summer, the majority of worms were segmented (maturing) or gravid; this period coincided with time of recruitment. Beginning in October and continuing into May, nearly all (> 98%) of the worms were nonsegmented. The major shifts in composition occurred when surface water temperatures increased above 25 C in the spring and fell below 25 C in the fall. Laboratory studies showed conclusively that growth and development were stimulated at water temperatures above 25 C. Moreover, at temperatures above 25 C, mean infrapopulation densities declined significantly. It is suggested that the decline in mean infrapop- ulation densities could result from a temperature-dependent rejection response, selective mortality or an immune response. However, the best evidence points to competition for limited space or nutrient resources within the intestine of mosquitofish as the most probable cause for decline in parasite density. Egg maturation and hatching, and coracidium motility, were all found to be temperature dependent, with maximum activity occurring at 25 and 30 C; at 20 and 35 C, activity was depressed. The lower hatching success and briefer period of coracidium motility at 35 C may, in part, explain differences in the population biology of the cestode at the thermally altered and ambient temperature sites during part of the summer months.
TL;DR: These optimum ranges and metabolic rates can be used in the development of parasite culture techniques and exhibited significantly lower glycolysis per 10(9) parasitized RBC than cultures that were 0 to 25% ring forms after 24 hr.
Abstract: Yields of P. falciparum in intraerythrocytic in vitro cultures were maximized when extracellular pH was maintained between 7.2 and 7.45, and extracellular lactate was kept below 12 mM. Host erythrocytes metabolized 4.6 +/- 1.5 microM glucose/10(9) RBC/24 hr and produced 7.9 +/- 1.8 microM lactate/10(9) RBC/24 hr. Asynchronous parasite cultures used 122 +/- 34 microM glucose/10(9) parasitized RBC/24 hr and produced 143 +/- 47 microM lactate/10(9) parasitized RBC/24 hr. Synchronous cultures that were 80 to 100% ring forms after 24 hr in culture exhibited significantly lower glycolysis per 10(9) parasitized RBC than cultures that were 0 to 25% ring forms after 24 hr. The percent of glucose utilization accounted for by lactate production by parasites was significantly less than that of uninfected erythrocytes. These optimum ranges and metabolic rates can be used in the development of parasite culture techniques.
TL;DR: It was shown that an antibody response to the surface antigen of trypanosomes was necessary for rapid elimination of parasites after DFMO treatment, as effects of drug treatment were greatly reduced in immunosuppressed mice.
Abstract: The drug DL-alpha-difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase, was studied as an antitrypanosomal drug. We showed that an antibody response to the surface antigen of trypanosomes was necessary for rapid elimination of parasites after DFMO treatment, as effects of drug treatment were greatly reduced in immunosuppressed mice. Efficacy of the treatment also varied with the inherent ability of different mouse strains to mount antibody responses to trypanosomal surface antigen. Further, some trypanosomes were more resistant to the combined effects of drug and host immunity, as relapses occurred with certain parasite clones.
TL;DR: The potencies of 10 quinoline-containing antimalarials were determined in vitro against five strains of Plasmodium falciparum characterized in vivo and in vitro by various degrees of sensitivity to chloroquine, and showed little or no variation in potency among these strains.
Abstract: The potencies of 10 quinoline-containing antimalarials, including chloroquine, amodiaquine, CM-2,999-2K, quinine, mefloquine, SN-6911, SN-11875, SN-12108, SN-12308, and SN-12309, were determined in vitro against five strains of Plasmodium falciparum characterized in vivo and in vitro by various degrees of sensitivity to chloroquine. These strains included the chloroquine-sensitive strains Honduras and FCC1, and R1-resistant line FCR3TC, and the R3-resistant strains FCR1 and Viet Nam Smith (VNS). The potency of chloroquine varied 100-fold in these strains, with minimum inhibitory concentrations (MIC) ranging from 3.2 X 10(-9) M in FCC1 to 3.2 X 10(-7) M in FCR1. The other drugs had different patterns; SN-12108 had an MIC of 3.2 X 10(-9) M in FCC1, Honduras, and FCR1, and 3.2 X 10(-8) M in VNS. However, SN-6911 (3-methylchloroquine), amodiaquine, and mefloquine showed little or no variation in potency among these strains. There was no correlation between sensitivity to chloroquine and any other drug. This lack of cross-resistance in vitro must be taken into account in consideration of theories of chloroquine action in these parasites.
TL;DR: Serum AP values varied little in PR albino snails except for a significant increase at 2 wk PE, indicating a possible response to tissue damage resulting from migrating daughter sporocysts, and total hemocyte numbers in infected snails varied little.
Abstract: The distribution and abundance of the lysosomal enzyme markers, acid phosphatase (AP), perox- idase (PO), and nonspecific esterase (NE), within circulating blood cells (hemocytes) were examined in a schis- tosome-susceptible (PR albino M-line) and a resistant (10-R2) strain of Biomphalaria glabrata during the course of infection with Schistosoma mansoni. The dynamics of serum (cell-free hemolymph) AP activities and total hemocyte numbers in infected snails also were investigated. Hemocyte subpopulations, as determined by these enzyme markers, responded differently to parasite infection between snail strains. Generally, the hemocyte subpopulations within PR albino snails remained largely unchanged, whereas the same subpopulations in 10- R2 snails fluctuated considerably. The distribution of AP in the hemocytes of 10-R2 snails decreased by 1 hr postexposure (PE) to the parasite and remained low through 12 hr before increasing to control values at 24 hr and 2 wk PE. In comparison, PO activity increased by 1 hr PE and peaked at 12 hr before dropping to 0 hr values by 2 wk PE. The NE activity exhibited still another pattern with the percentage of NE-positive cells decreasing from 0 to 12 hr PE followed by a recovery to 0-hr values by 24 hr. The abundance of these hemocyte enzymes followed a similar pattern to that of their distribution, although some differences were observed. Serum AP values varied little in PR albino snails except for a significant increase at 2 wk PE, indicating a possible response to tissue damage resulting from migrating daughter sporocysts. In contrast, serum AP values in 10-R2 snails showed an increase for the first 24 hr of infection before decreasing to control values by 2 wk. The rapid alterations in both hemocyte and serum lysosomal enzymes may be associated with larval schistosome destruction in the 10-R2 strain. The PR albino snails exhibited an increase in hemocyte numbers by 1 hr PE and then a decrease to the control state by 12 hr in comparison to 10-R2 snails which showed a decrease in hemocyte number by 1 hr PE, followed by a gradual increase to the control state by 24 hr. The peak in the number of PR albino hemocytes probably represents a nonspecific response to external perturbation. The decrease in the number of 10-R2 hemocytes was correlated with sporocyst encapsulation reactions suggesting that blood cells may be removed from the circulation to participate in capsule formation. Results of this study clearly showed that S. mansoni evoked little enzymatic or leukocytic responses from susceptible PR albino snails whereas the parasite was apparently activating hemocytes in the resistant 10-R2 strain.
TL;DR: Certain temperature-sensitive mutants of the RH strain of Toxoplasma gondii and a "back mutant," all maintained in human fibroblasts, were studied in mice, and it appears that the limited persistence of ts-4 is related to the immunologic response.
Abstract: Certain temperature-sensitive mutants of the RH strain of Toxoplasma gondii and a "back mutant," all maintained in human fibroblasts, were studied in mice. Most mutants gave rise to acute, fatal infections, and after sulfonamide prophylaxis rarely persisted as chronic infections in mice. However, the ts-4 strain was nonfatal in doses up to 10(3) to 10(5) tachyzoites, elicited high titers of antibody, and did not persist beyond 2 mo. No Toxoplasma cysts were found. There was no evidence that a febrile reaction of the mice was restrictive, because the highest temperatures, 37.9 to 38.4 C, occurred 3 days after infection, whereas the organisms were recoverable for 16 to 32 days. Because doses of Toxoplasma, survived by 11 of 12 normal BALB/c mice, and by one of five thymic transplanted athymic mice, killed six of six athymic mice, it appears that the limited persistence of ts-4 is related to the immunologic response.
TL;DR: In this paper, the effect of syngeneic neonatal thymus grafts on recovery of worms at day 40 PI, and responses to Concanavalin A (Con A) were examined in reconstituted nudes.
Abstract: The dichotomy of resistance to Brugia pahangi (Nematoda: Filarioidea) between nonsusceptible, euthymic C3H/HeN mice, heterozygotic for the "nu" gene (+/nu), and susceptible, congenitally-athymic "nude" (nu/nu) C3H/HeN mice, suggests that resistance is thymus-dependent. To test this hypothesis, the effect of syngeneic neonatal thymus grafts and neonatal thymus cell suspensions on recovery of worms at day 40 PI, and responses to Concanavalin A (Con A) were examined in reconstituted nudes. Nude recipients of a thymus graft 7 or 14 wk before subcutaneous inoculation with 50 infective larvae (L3) yielded no worms and responded strongly to Con A. Serum from these mice reacted in two lines of identity with serum from similarly-infected heterozygotes by double radial immunodiffusion against an adult worm saline extract. Nude recipients of a thymus 2 days or 3 wk before inoculation harbored an average of three or two worms, respectively. Intravenous injection of nude recipients with 107 or 108 neonatal thymus cells seven weeks before inoculation was less effective in conferring resistance to B. pahangi and responsiveness to Con A. Complete resistance to B. pahangi could be adoptively transferred to nude mice by 108 spleen cells obtained from infection-primed heterozygotes and injected intravenously on the day of larval inoculation. The same numbers of unprimed spleen cells were less effective when injected 3 wk before inoculation, although numbers of worms were significantly reduced. Passive transfer of primed heterozygote serum, containing high titers of antibodies to adult worm and larval antigens, failed to protect nude recipients against a larval inoculum in the absence of cellular reconstitution. These results suggest that resistance to B. pahangi in mice is the consequence of complex thymus-dependent immune responses, and that the nude mouse-B. pahangi system will be a useful new model for the study of mechanisms of protective immunity to lymphatic filarial parasites.
TL;DR: Transmission and scanning electron microscopy showed many knobs on the erythrocytes infected with P. falciparum in human RBC's and the distribution pattern of the knobs was more easily detectable by scanning electron microscopeopy than by thin-section transmission electron microscope.
Abstract: Erythrocytes infected by certain species of malarial parasites show two types of alterations of erythrocyte membranes such as electron-dense protrusions called knobs and caveola-vesicle complexes (Aikawa et al., 1975, Am. J. Path. 79: 285; Aikawa, 1977, Bull. WHO 55:2). The knobs are found on the membrane of erythrocytes infected with falciparum-type malaria parasites. These knobs form focal junctions with the endothelial cell membranes or with the knobs of other erythrocytes, resulting in the sequestration of these infected erythrocytes along the vascular endothelium (Trager et al., 1966, Bull. WHO 35: 883; Luse and Miller, 1971, Am. J. Trop. Med. Hyg. 20: 655; Aikawa et al., 1972, Z. Zellforsch. 124: 72; Udeinya et al., 1981, Science 213: 555). The erythrocyte membrane covering the knobs is immunologically different from the rest of the erythrocyte membrane (Kilejian et al., 1977, Exp. Parasitol. 42: 157; Langreth et al., 1979, J. Exp. Med. 150:1241; Chulay et al., 1981, Am. J. Trop. Med. Hyg. 30: 12). The erythrocytes infected with small trophozoites show few knobs, but they increase in number as the parasite grows within the erythrocyte. Because the morphology of these knobs is still not fully understood, we have attempted to characterize them by transmission and scanning electron microscopy together with freeze-fracture and etch techniques. Plasmodiumfalciparum (Camp strain) in Aotus erythrocytes and P. falciparum (Thailand and Liberian strains) in human erythrocytes were obtained from culture (Udeinya et al., 1981, Science 213: 555). The infected erythrocytes were fixed in 2% glutaraldehyde in 0.1 M cacodylate buffer (pH 7.4) containing 4% sucrose, washed in 0.1 M cacodylate buffer and postfixed for 1 hr in 1% osmium tetroxide. After fixation, the samples were centrifuged and then processed for thin section transmission and scanning electron microscopy. Freeze-fracturing and etching were performed on P. falciparum in human RBC's. Fracturing was carried out at -120 C under a vacuum of 2 X 10-7 Torr. Etching was performed at -100 C, under a vacuum of 2 X 10-7 Torr for 2 min. The surfaces obtained were replicated with platinum and carbon. Replicas were cleaned as described previously (Aikawa et al., 1981, J. Cell Biol. 91: 55). Transmission electron microscopy was performed with a JEOL 100CX electron microscope. Scanning electron microscopy was performed with a JEOL 100CX electron microscope with a scanning unit at 20 kV. Thin-section electron microscopy showed many knobs on the erythrocytes infected with P. falciparum (Fig. 1). Each knob is a cone-shaped, electron-dense structure measuring 30 to 40 nm in height and 9 to 100 nm in width and is covered by the erythrocyte membrane. The base is not sharply demarcated, but gradually merges into the erythrocyte cytoplasm. Scanning electron microscopy showed numerous cone-shaped knobs evenly distributed over the entire erythrocyte surface (Fig. 2). The distribution pattern of the knobs was more easily detectable by scanning electron microscopy than by thin-section transmission electron microscopy. Therefore, scanning electron microscopy appears to be a useful and easy method for the study of knob distribution. Freeze-fracture and etching demonstrated that the knobs were protruded structures and were evenly distributed over the erythrocyte membrane. The P face of the infected, human RBC membrane showed evenly distributed intramembrane particles (IMP) and no aggregation or depletion of IMP could be observed over the erythrocyte membrane covering the knobs (Fig.
TL;DR: The results of this study demonstrated that the cidal effect of monensin on extracellular sporozoites was caused by the capability of the ionophore to act as a transmembrane sodium carrier.
Abstract: Extracellular Eimeria tenella sporozoites exposed to 1.0 ,ug/ml monensin at 40 C had an accelerated rate of sodium influx as well as an increased rubidium uptake that was inhibited by the cardiac glycoside, ouabain. These results suggested the presence of a functional (Na+-K+)-ATPase and its stimulation by monensin. Under the same conditions, sporozoite ATP concentrations declined, lactate production increased and the rate of amylopectin utilization was enhanced. Exposure to monensin also appeared to stimulate the rate of sporozoite glycolysis. The results of this study demonstrated that the cidal effect of monensin on extracellular sporozoites was caused by the capability of the ionophore to act as a transmembrane sodium carrier. The polyether, ionophorous antibiotic, mo- nensin, is an effective anticoccidial agent and has been used extensively for the control of coccid- iosis for more than a decade. Despite its wide use the precise anticoccidial mode of action of this drug is not understood. Smith and Strout (1979) provided evidence that the polyether ionophores are accumulated by free (extracellular) Eimeria tenella sporo- zoites. Later, Smith et al. (1981) demonstrated that this uptake may reduce the number of spo- rozoites capable of invading host cells and may deny the initiation of first generation schizogony for those that do penetrate. In this same study it was shown that monensin may also express a lethal activity against the extracellular sporo- zoite. More recently Long and Jeffers (1982) pre- sented evidence that the merozoites are subject to a similar fate. Thus it appears that the free, invasive stages of the coccidia are susceptible to an anticoccidial activity of monensin. These findings show the utility of a readily available model system, the free sporozoite, for the study of the specific anticoccidial mode of action of the ionophorous antibiotics. In the present study we examined the influence of monensin on sodium and rubidium (as a po-
TL;DR: The effect of cyclic AMP on asexual maturation and gametocyte formation of Plasmodium falciparum grown in vitro was examined over a wide range of concentrations.
Abstract: The effect of cyclic AMP on asexual maturation and gametocyte formation of Plasmodium falci- parum grown in vitro was examined over a wide range of concentrations. Cyclic AMP inhibited both processes in a stage-specific manner. Asexual maturation was inhibited from shortly after parasite entry into the red cell through the ring stage. However, trophozoites and schizonts matured normally in the presence of cyclic AMP and produced infectious merozoites. Gametocyte formation was inhibited by 95% when 1.0 mM cyclic AMP was added to synchronously growing parasites in the ring stage of development but was only inhibited by 15% when added in the trophozoite or schizont stages. Cyclic AMP was not found to increase gametocyte formation over a wide range of concentrations.
TL;DR: Results indicate that mucosal mast cells that accumulate in the small intestine in response to parasite infection may not be functionally involved in the rejection mechanism.
Abstract: The ability of congenitally mast cell-deficient W/Wv anemic mice and mast cell-reconstituted W/Wv mice to reject the intestinal parasite Nippostrongylus brasiliensis was examined. The W/Wv mice were deficient in connective tissue mast cells and mucosal mast cells and, unlike normal mice, did not accumulate intestinal mucosal mast cells in response to N. brasiliensis infection. They had higher peak egg counts than did normal littermates and were slower than littermates to reject the parasites. Reconstitution with bone marrow or spleen cells repaired both the connective tissue and mucosal mast cell defects in W/Wv mice but did not alter the time of parasite rejection or decrease the high peak egg counts. These results indicate that mucosal mast cells that accumulate in the small intestine in response to parasite infection may not be functionally involved in the rejection mechanism.
TL;DR: Fasciola hepatica infections of lambs were shown to alter the proliferative responses of peripheral blood lymphocytes (whole blood culture) to mitogens at specific times postinfection (PI).
Abstract: Fasciola hepatica infections of lambs (250 or 500 metacercariae) were shown to alter the proliferative responses of peripheral blood lymphocytes (whole blood culture) to mitogens at specific times postinfection (PI). Responses to concanavalin A (Con A) were significantly suppressed at weeks 4, 8, 10, and 11 PI whereas suppressed responses to phytohemagglutinin (PHA) occurred at weeks 4, 10, 11, and 16 PI. Only on weeks 4 and 6 PI were responses to pokeweed mitogen (PWM) suppressed. The fluke-induced modulation of responses appeared to be related more to specific phases of infection rather than to worm burdens. The modulation of host immune responses by parasites has been recently reviewed (Bloom, 1979; Capron and Camus, 1979). Most accounts of parasite-induced suppression of host immune responses have been described in the protozoan diseases trypanosomiasis and malaria and in the helminth diseases trichinellosis and schistoso- miasis. Conclusive evidence of host immuno- suppression by Fasciola hepatica has been lack-
TL;DR: The results indicate that except for these species of veterinary or medical significance, parasites of west central Wisconsin foxes are similar to those reported in other surveys of foxes in this geographical area.
Abstract: C. plica in the urinary bladder. Butterworth and Beverley-Burton reviewed the taxonomy of Capillaria spp. in carnivorous mammals in Canada (1980, Syst. Parasitol. 1: 211-236) and discussed prevalence and intensity of these species (1981, Proc. Helminthol. Soc. Wash. 48: 24-37). Notable by their absence in Wisconsin foxes were three helminth species of veterinary or medical importance: Dirofilaria immitis (Leidy, 1856), Trichinella spiralis (Owen, 1835), and Echinococcus multilocularis. Schlotthauer (1964, J. Parasitol. 50: 801-802) reported a low prevalence of D. immitis in Minnesota foxes compared with its occurrence in Canis familiaris. Extensive investigations of E. multilocularis by Leiby and his coworkers (Leiby, Carney, and Woods, 1970, J. Parasitol. 56: 1141-1150; Leiby and Kritsky, 1974, Amer. J. Trop. Med. Hyg. 23: 667-675) have provided ecological and epidemiological information for E. multilocularis, and these authors have described the southerly spread of this tapeworm from the boreal regions of North America into the northcentral United States. Recently, Ballard and Vande Vusse (1983, J. Parasitol. 69: 790-791) reported E. multilocularis from rodents and foxes in the prairie biome of southwestern Minnesota. Our results indicate that except for these species of veterinary or medical significance, parasites of west central Wisconsin foxes are similar to those reported in other surveys of foxes in this geographical area.
TL;DR: The Mongolian gerbil model could be useful in epidemiological studies for two reasons: it can be used for determination of cyst viability, and for the identification of the etiological agent.
Abstract: Mongolian gerbils (Meriones unguiculatus) were inoculated with known numbers of Giardia cysts isolated from humans, beavers and mice. The pattern of cyst release in the feces was studied for a period of 35 days. After a latent period of 5 days, animals infected with G. muris release cysts in their feces every day until day 14. Gerbils infected with human or beaver isolates released cysts in their feces intermittently for 30 days. These results indicated that the mode of cyst release in these animals was characteristic of the parasite, and was independent of the host. Mongolian gerbils acquire complete resistance upon homologous species challenge but demonstrate only partial protection when challenged with a different species of Giardia. We concluded that the Mongolian gerbil model could be useful in epidemiological studies for two reasons: it can be used for determination of cyst viability, and for the identification of the etiological agent.
TL;DR: The surface morphology of three subspecies of Trichinella spiralis was examined by SEM in an attempt to find characteristics useful for distinguishing the subspecies.
Abstract: The surface morphology of three subspecies of Trichinella spiralis was examined by SEM in an attempt to find characteristics useful for distinguishing the subspecies. The subspecies studied were T. spiralis spiralis, which had been maintained in swine and laboratory animals for about 50 yr; T. spiralis nativa collected from Ursus maritimus at 58 degrees N latitude and 95 degrees W longitude in 1976; and, T. spiralis pseudospiralis, which was derived from the original isolation of this subspecies from Procyon lotor at 43 degrees N latitude and 47 degrees 30'E longitude in 1972. All three subspecies were passed in CFW mice and adult worms were collected from the small intestine at 4, 5, 6, 7, 8, and 11 days PI. Characteristics examined included labial and cephalic papillae, cuticular ridges and folds, hypodermal gland cell pores, pseudobursal lobes, genital papillae, cloacal aperture, copulatory bell and vulval morphology. Previous reports of subspecies differences within Trichinella spiralis in the number and distribution of hypodermal gland cell pores, position of genital papillae, shape of the cloacal aperture and shape of pseudobursal lobes were not confirmed and are believed to have been in error resulting from artifacts of fixation and a lack of knowledge of variations within the subspecies caused by low numbers of samples. Differences in surface morphology were not found among the three subspecies. The available names of the recognized biological populations of Trichinella were used at the subspecies level rather than species level because this more clearly represents the state of our knowledge of the nematodes. The question of whether the epidemiology of trichinosis is complicated by the presence of more than one species has not been answered, and it is important that our nomenclature reflect this.