Suehisa Takada

Infectivity of Cryptosporidium muris (strain RN 66) in various laboratory animals

The infectivity ofCryptosporidium muris (strain RN 66), originally isolated from the house rat (Iseki 1986), to various laboratory animals was studied by transmission experiments. After oral inoculation with 1×106 oocysts, mice, guinea pigs, rabbits, dogs, and cats all discharged endogenously produced oocysts in their feces. Among these host species, mice and cats were highly susceptible to the parasite. The prepatent period for six 3-week-old specific pathogen-free (SPF) mice was 5 days postinoculation (PI), the patent periods varied between 34 and 75 days for each mouse, and the number of oocysts discharged per individual per day (OPD) was 11–46×106 at the maximum on days 16–26 PI. The total number of oocysts discharged per mouse during the patent period was estimated to be 170–560×106. Three inoculated cats (1–2 months old) also discharged a large number of oocysts for a long period. Guinea pigs, rabbits, and dogs showed low susceptibility to this strain; the OPD was extremely small and the patent periods were less than 3 weeks. The entire endogenous development of this parasite occurred in the stomach and not in the small and large intestines of these experimental animals. Because of this lack of host specificity, it is suspected thatC. muris could be infective to humans, especially immunocompromised patients such as those with AIDS.

Ultrastructure of Cryptosporidium muris (strain RN 66) parasitizing the murine stomach.

The ultrastructure of Cryptosporidium muris, which parasitizes the stomach of mice, was studied by transmission electron microscopy. The entire development of the parasite occurred in the microvilli of the surface mucus cells in the gastric glands. The ultrastructural features of the attachment site of C. muris to the host cell differed remarkably from those of C. parvum and its closely related species, which parasitize the intestine of various animals. The size of C. muris was greater at almost every developmental stage than that of C. parvum. These findings confirmed that C. muris and C. parvum are distinct species. The mitochondria, subpellicular microtubules, and Golgi complex were demonstrated in detail. A small invagination in the meront and intravacuolar tubules were found in Cryptosporidium. The wall of each developing oocyst in the parasitophorous vacuole was composed of three layers: the outermost layer was considered to be a true oocyst wall, whereas the middle and innermost layers were assumed to develop into the sporocyst wall. The outermost layer was fragile and disintegrated as the oocyst matured. In excystation in vitro, a suture was seen in a thick layer of the two-layered sporocyst wall of an oocyst (sporocyst wall; see Discussion) that enveloped four sporozoites. The fine structure of the attachment site of the present species to the host cell appears to reveal a unique mode of hostparasite interaction in Cryptosporidium infection.

Karyological Analysis of 12 Species of Bats from Thailand

SUMMARYThe karyotypes of Rousettus leschenaulti, Cynopterus spinhx, Eonycteris spelaea, Scotophilus kuhlt, Tadarida plicata, Megaerops ecaudatus, Taphozous theobaldi, Rhinolophus acuminatus, Rhinolophus malayanus, Rhinolophus coelophylus, Hipposideros lekaguli and Hipposideros larvatus from Thailand are investigated. Karyotypes of 7 latter species are described for the first time. Comparison of karyotypic data of all related species and phylogenetic relationship had been discussed.

Karyological Studies of two Japanese Noctule Bats (Chiroptera)

SUMMARYKaryological investigations of two Japanese Nyctalus species were made based on G- and C-banding pattern analysis. The karyotype of N. furvus (2n = 44, FN = 50) was similar to the standard karyotype of Myotis species. On the other hand, the karyotype of N. lasiopterus aviator (2n = 42, FN = 50) was characterized by having an additional large metacentric pair. By comparison of the G-banding pattern between the two Nyctalus species, it is clear that the metacentric pair of N. lasiopterus aviator has derived from the Robertsonian fusion of the two pairs (nos. 8 and 10) of N. furvus. There was also a significant difference in amount of constitutive heterochromatin between the two Nyctalus species. In N. furvus the additional heterochromatin was observed on the majority of autosomes, while in N. lasiopterus aviator a small C-band was restricted to the centromeric area of each autosome. Thus, the C-band pattern of N. lasiopterus aviator would be interpreted by assuming the decrease of heterochromatin in ...

Toxoplasma gondii: penetration into differentiating Friend erythroleukemia cells.

The ability of Toxoplasma gondii tachyzoites to penetrate erythroid-differentiating Friend erythroleukemia cells (FL cells) was examined in vitro. The parasites were incubated for 4 hr with FL cells which had been induced to synthesize spectrin, a major erythrocyte membrane protein, or hemoglobin by culturing the cells in the presence of dimethylsulfoxide (DMSO) or sodium butyrate. The penetration rate, in terms of both the average number of T. gondii per cell and the percentage of cells containing parasities, observed in the DMSO-treated FL cells was depressed as compared with that found in untreated cells. However, this depression was not related to the presence of spectrin or hemoglobin. This conclusion was based on the fact that the penetration rate in the butyrate-treated cells was the same as that in untreated cells. These results suggest that it is not the presence of spectrin and hemoglobin that inhibits penetration by T. gondii. The failure of T. gondii to enter mammalian erythrocytes is discussed in relation to surface changes in FL cells undergoing erythroid differentiation.

Plasmodium berghei: Suppressed response of antibody-forming cells in infected mice

Abstract Mice experimentally infected with Plasmodium berghei NK65 were immunized with sheep red blood cells (SRBC) or polyvinylpyrrolidone (PVP), and the numbers of hemolytic plaque forming cells (PFC) produced in the spleen were measured. The antibody response showed two distinct phases. In the initial period of infection (Days 0–3), the PFC response to SRBC, a thymus-dependent antigen, was depressed, whereas the PFC response to PVP, a thymus-independent antigen, was normal. The PFC response to PVP was not depressed in infected athymic nude (nu/nu) mice, indicating that B cell function was not impaired at this stage of infection. Furthermore, spleen cells from malarial donor mice gave the same PFC response to SRBC when transferred to X-irradiated recipients, showing that neither B nor T cells are damaged at this stage. The suppressed immune response to SRBC was therefore attributed to dysfunction of the antigen-handling macrophages. When infection proceeded further (Days 5–7), the PFC response to SRBC was greatly depressed not only in the spleen but also in the popliteal lymph nodes, which had not shown suppressed responses in the earlier phase of infection. The response of spleen cells to PVP was also depressed at this time. The participation of suppressor cells in this immunosuppression was discounted, since spleen cells from malarial mice failed to suppress cells from normal animals when both types of cell were transferred simultaneously to X-irradiated recipients.

Penetration of Maturating Red Blood Cells by Toxoplasma gondii

Penetration of Toxoplasma gondii tachyzoites was studied in vitro using murine erythroid cells at different stages of development. Toxoplasma gondii penetrated nucleated erythroblasts and macroreticulocytes from foetal mouse liver and the circulating erythrocytes of foetal, neonatal or severely anaemic adult mice. Immature reticulocytes were more susceptible to penetration than mature ones, indicating that some change in their membrane properties occurred during maturation. The present results confirmed our previous finding that the major erythrocyte membrane-specific proteins do not prevent erythrocyte penetration since these proteins are known to be present in the reticulocyte membrane.

Karyotypes of seven species of bats from Thailand (Chiroptera, Mammalia)

Karyotypes ofMyotis siligorensis, Myotis mystacinus, Pipistrellus pulveratus, Tylonycteris robustula, Miniopterus schreibersi fuliginosus, Hipposideros fulvus andAselliscus stoliczkanus from Thailand are investigated.

Multiplication of Toxoplasma gondii in maturing erythroid cells.

Multiplication of Toxoplasma gondii was examined in vitro in murine erythroid cells at different stages of development. Toxoplasma gondii multiplied in nucleated erythroblasts and enucleated reticulocytes from the foetal liver, and in immature reticulocytes and yolk-sac derived erythrocytes from the foetal circulation. However, the rate of multiplication was lowered as erythroblasts matured, and multiplication was not detected in foetal erythrocytes. A decrease in the multiplication rate with maturation was also observed with yolk-sac erythrocytes.

Karyotypes of two species of Insectivora from Taiwan (Insectivora, Soricidae)

The karyotypes of two Insectivora species from Taiwan are described here for the first time.Soriculus caudatus fumidas has 2n=40 chromosomes, FN=52 andAnourosorex squamipes yamashinai has 2n=50 chromosomes, FN=96. ForA. s. yamashinai the G- and C-banding pattern are presented.