Experimentally, primary amoebic meningoencephalitis (PAM) is induced by Naegleria fowleri in mouse and development of PAM may be influenced by the strain, weight and sex of mouse, and inoculum size of N. fowleri trophozoite. In this paper, the effect of these factors on PAM development of mouse was studied. N. fowleri trophozoites, strain 0359, were introduced into mouse intranasally under secobarbital anesthesia (0.05 mg/g). PAM was developed more frequently in BALB/c mouse than ICR mouse. The survival time of mouse with PAM was influenced by the weight, that is, it was shorter in 15 g mouse than in the heavier groups. No difference was observed on PAM development according to sex. In case of inoculated amoeba, PAM incidence of 0.5 x 10(4) was markedly decreased.
parasitology-protozoa ; Naegleria fowleri ; primary amoebic meningoencephalitis ; mouse

This study was to observe the changes of blastogenic responses of splenic lymphocytes to T-cell mitogens, N. fowleri lysate and concanavalin A, and serum antibody titer during the course of experimental PAM in mice. Naegleria fowleri, strain 0359, was cultured in the CGVS medium axenically and inoculated intranasally with 7 x 10(4) trophozoites for the development of experimental PAM in mice. The amoebae were subjected to ultrasonication and centrifuged at 20,000 g for 60 minutes, and filtered through 0.2 micro-m filter membrane. The supernatant, N. fowleri lysate, was used as T-cell mitogen, and antigen for ELISA. The serum antibody was examined by ELISA using peroxidase conjugate. Two hundred micro-l of 10(6) splenocytes in RPMI 1640 containing 10% fetal calf serum were added to each well of a microtiter plate. To each well was added T-cell mitogens, 100 micro-g/ml of N. fowleri lysate or 4 micro-g/ml of con. A, and the plates were incubated for 42 hours at 37 C in 5% CO(2) incubator. Cultures were pulsed with 1 micro-Ci of methyl-(3H)-thymidine 6 hour before harvesting. The mean blastogenic response of the splenocytes to N. fowleri lysate was reduced, whereas that to con. A was also reduced up to on day 11 after infection. Both of these results were statistically significant compared with those of uninfected control group. The serum antibody titers were increased gradually up to day 15. The results indicated that there was an impairment of the blastogenic response of splenocytes to N. fowleri lysate during the acute course of experimental PAM in mice.
parasitology-protozoa ; Naegleria fowleri ; primary amoebic meningoencephalitis ; immunology ; spleen ; lymphocyte ; mouse

Present study was undertaken to elucidate the changes of the ultrastructure of Naegleria fowleri trophozoite in brain tissue of mice and culture medium. Naegleria fowleri, 0359 strain, which used in this study was cultured in axenic liquid medium, CGVS medium. Each mouse was inoculated with 1 x 10(5) amoebas intranasally under secobarbital anesthesia, and sacrificed on 7th day after the infection. Comparative observation of the ultrastructure of the amoebas in axenic culture and experimentally infected mice brain was done with transmission electron microscope. The results are summarized as follows: The amoebas in mouse brain tissue were round in outline, whereas those of amoebas from axenic culture showed irregular appearance. Mitochondria in the amoebas from axenic culture was oval, round and cylindrical shape and darkly stained, whereas those of the amoebas from mouse brain tissue showed dumbbell shape together with above forms. The stain was not unique, but light and/or dark. Rough endoplasmic reticulum of amoebas in brain tissue was tubular, but from culture it was vesicular or tubular in shape. Empty vacuoles were demonstrated in amoebas from culture, while food vacuoles with myelinated structures were abundant in those from tissue, suggesting a strong phagocytic activity. Mouse brain tissue infected were extensively destroyed, and polymorphonuclear leukocytes were infiltrated predominantly with inflammatory lesion. Amoebas were observed in the vicinity of the capillary.
parasitology-protozoa ; Naegleria fowleri ; primary amoebic meningoencephalitis ; CGVS medium ; electron microscopy ; culture ; brain ; mouse

The pathogenicity of free-living amoeba, Naegleria fowleri, is influenced according to the strain, cultural condition and host (Culbertson et al., 1968; Carter, 1970; Wong et al., 1975). Phillips (1973) demonstrated that Entamoeba histolytica became avirulent after more than 2 year maintenance in axenic culture in vitro. This study was carried out to compare the difference in pathogenicity between two strains of N. fowleri, one of a prolonged maintenance in axenic medium and the other one obtained by serial brain passage in mice. The 0 strain was that N. fowleri had cultivated axenically more than 7 years in CGVS medium. The 2-1 strain was obtained from the brain of mouse inoculated intranasally with a strain, which was from the mouse brain infected with 0 strain, and cultured for 15 weeks until the beginning of this experiment. White male mice weighing 18-22 g were used. Mice were anesthetized by an intraperitoneal injection of about 1 mg secobarbital, and inoculated intranasally with 10 x 10(4) live N. fowleri trophozoites in a 5 microliter cell suspension. Sluggish behaviour, nervousness, rotation and leg paralysis were developed earlier and more frequently in the 2-1 experimental group than the control 0 group. Pathological changes such as inflammatory and necrotic lesion were observed in the olfactory and anterior portion of brain, and these changes were more extensive in the 2-1 group. The edematous and inflammatory changes in lung were demonstrated in mice died after 13th day post-inoculation. The experimental mice of 2-1 group began to die suddenly from 7th day post-inoculation, and the survival time in 2-1 group mice was shorter than 0 group mice. The typical primary amoebic meningoencephalitis was developed in the mice inoculated intranasally with N. fowleri. The prolonged maintenance of N. fowleri amoebae in axenic CGVS medium was observed to have lost their original pathogenicity for mice, but their pathogenicity was restored by serial brain passage in mice.
parasitology-protozoa ; Naegleria fowleri ; pathogenesis ; mouse ; brain ; primary amoebic meningoencephalitis ; secobarbital ; CGVS medium ; pathology ; nervousness ; leg paralysis