• Parasites, Hosts and Diseases
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• v.23 no.2
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• pp.293-299
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• 1985

This study is to verify the protective ability against experimental Naegleria meningoencephalitis by immunization with Naegleria fowleri in mice. Naegleria fewleri, strain 0359, and Naegleria gruberi, strain EGB, were used in this study, and cultured in CGVS medium akenically. Inbred BALB/C mice, weighing about 20g, were immunized by three intraperitoneal injection of $1{\times}10^6$ N. fowleri trophozoites at the interval of one week. This N. fowleri trophozoites antigen was fixed with 5% formaldehyde. N. fowleri trophozoites from culture were homogenized with soiicator at $4^{\circ}C$ as monitored by phase contrast microscopy, and their membrane and cell content preparations were made for the immunization of mice. Their inoculation dose in volume was equivalent to the $1{\times}10^6$ trophozoites in each injection for immunization. And N. gruberi trophosoites, whieh was fixed with 5% formaldehyde, were also used for immunisation. Mice were inoculated intranasally with $5{\times}10^4$ N. fowleri trophozoites in a 511 suspension under anesthesia by as intraperitoneal injection of about 1 mg secobarbiturate. Nervousness, rotation or sluggish behaviour were observed in the mice which were infected with N. fewleri. Necrotic lesion was demonstrated in the anterior portion of brain, especially in the olfactory lobe. The inflammatory cell infiltration with numerous H. fowleri trophozoites was noticed. This pathological changes were more extensive in the control than in the experimental groups. Mice were dead due to experimental primary amoebic meningoencephalitis that developed between 8 days and 23 days after inoculation. Mortality rate of the mice was low in the immunized experimental group. Mean survival time, which is the survival duration of mice from the infection to death, was prolonged significantly in the immunized mice except in the mice immunized with JV, fowleri membrane. Even in the mice immunized with N. gruberi, survival time was delayed. In summary, the effectiveness of immunization is demonstrated in terms of protective immunity against Naegleria meningoencephalitis in mice.

• Journal of Microbiology
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• v.33 no.3
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• pp.222-227
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• 1995

We have examined DNase I sensitivity of .betha.-tubulin and flagellar calmodulin genes which are transiently and coordinately activated differentiation of Naegleria gruberi amebae into flagellates. The DNase I sensitivity of .betha.-tubulin and flagellar calmodulin genes changed in parallel with the changes in transcriptional activity of the respective genes during differentiation. The two genes were resistant to DNase I inamebae stage when transcription of the two genes was inactive. Forthy minutes after initiation of differentiation, when the two genes were most actively being transcribed, the two genes showed the highest sensitsivity to DNase I. One hundred and twenty minutes after initiation, the differentiation was completed and transcriptional activity of the two genes decreased to a low level. At this stage, the two genes were resistant to DNase I treatment like the ones at the amebae stage. This change in the DNase I sensitivity of the two genes was not observed when transcription of the two genes was blocked by adding cycloheximide at the beginning of differentiation.

• Parasites, Hosts and Diseases
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• v.21 no.2
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• pp.234-240
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• 1983

The pathogenicity of free-living amoeba, Waegleria fcwleri, is influenced according to the strain, cultural condition and host (Culbertson et at., 1968; Carter, 1970; Wong et at., 1975), Phillips (1973) demonstrated that Entamoeba histolytica became avirulent after more than 2 year maintenance in axonic 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 arsenic 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{\times}$10^4 live N. fowleri trophoBoites in a $5{\;}{\mu}l$ 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 axonic CGVS medium was observed to have lost their original pathogenicity for mice, but their pathogenicity was restored by serial brain passage in mice.

• Korean Journal of Veterinary Service
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• v.42 no.4
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• pp.169-175
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• 2019

Naegleria fowleri, a pathogenic free-living amoeba, leads to a fatal infection known as primary amebic meningoencephalitis (PAM) in human and animals. PAM is an acute, fulminant, necrotizing, and hemorrhagic disease that leads to death in approximately seven days. In this study, we investigate the cytotoxicity of target cells and the secreted molecules of N. fowleri under the non-contact condition. The target cell (U87MG cell) treated with N. fowleri lysates showed no morphological changes and no cytotoxicity. By contrast, the U87MG cells co-cultured with N. fowleri trophozoites under the non-contact condition induced morphological changes and reduction in number. When U87MG cells were co-cultured with N. fowleri trophozoites under the non-contact condition for 30 min, 2 hr, and 4 hr, the levels of cytotoxicity of target cells were 32.3, 35.5, and 37.8%, respectively. Particularly, when the ratio of amoeba to target cells is 10 to 1, the level of cytotoxicity of target cells was 49.7% at 30 min. To show the proteins secreted from N. fowleri under the non-contact condition, we carried out 2D electrophoresis and observed 6 major proteins. Finally, these results suggest that the molecules released from N. fowleri under the non-contact condition induce the cell death and this process is an important step in pathogenesis of N. fowleri.

• Parasites, Hosts and Diseases
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• v.25 no.2
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• pp.195-198
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• 1987

In order to test the function of Iymphocytes in Naegleria fowleri-nniected mice, the in nitro blastogenic response of splenocyte cultures to non-specific mitogens was studied. Concanavalin A and lipopolysaccharide stimulation were used as tests of T cell and B cell function. For the first 14 days following N. fowleri infection, Iymphoblastic transformation induced by T-cell mitogen was markedly reduced in comparison to the uninfected control mice. The blastogenic response to B-cell mitogen remained depressed in the infected mice up to 14 days after infection. The fluorescent antibody titers of sera of N. fowleri infected mice were between 1 : 4 and 1 : 32. The results suggest that there is a suppression of cell mediated immunity during the acute course of experimental Naegleria meningoencephalitis in mice.

• Biomedical Science Letters
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• v.27 no.4
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• pp.323-328
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• 2021

Naegleria fowleri is a free-living amoeba causing primary amoebic encephalitis. In this study, we analyzed how the N-aceytlglucosamine (GlcNAc) and D-galactose affected the interaction between Naegleria fowleri and methicillin-resistant Staphylococcus aureus (MRSA) or Escherichia coli O157:H7, and the interaction with bacteria when monosaccharides were treated with N. fowleri for a longer pre-incubation time. When GlcNAc was treated with N. fowleri for 1 hr, the E. coli association was almost the same as that of the control not treated with GlcNAc until the concentration of GlcNAc was 25 mM. However, the E. coli association was reduced by approximately 91% with 100 mM GlcNAc. E. coli invasion into N. fowleri showed statistical significance only in the group treated with 100 mM GlcNAc. The interaction when treated with galactose showed a very different pattern in the 50 mM galactose group than when treated with GlcNAc. In the MRSA interaction, a statistically significant decrease in association (76.3% by GlcNAc and 88.7% by galactose) and invasion (3.6% by GlcNAc and 9.3% by galactose) was shown by the concentration of two 100 mM monosaccharides. The group treated with monosaccharides at the same time showed almost no difference in all interactions from the group treated with monosaccharides at the same time. Taken together, it suggested that the effect of monosaccharides on the interaction of several Gram-negative or positive bacteria and the evidence that the interaction could be enhanced by longer pre-incubation time.

• Journal of Microbiology
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• v.39 no.1
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• pp.42-48
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• 2001

The regulation of actin gene expression during the differentiation of Naegleria gruberi was examined. Actin mRNA concentration was maximal in amoebae and decreased rapidly after the initiation of differentiation. At 20 min after initiation, the concentration of actin mRNA decreased to 55% of the maximal value. The actin mRNA concentration decreased to the minimum at 80 min (15% of the maximum), and then began to increase slightly at the end of differentiation. This decrease of actin mRNA concentration was regulated by the repression of actin gene transcription based on nuclear run-on transcription experiments. The rates of transcription of actin gene in nuclei prepared at 40 and 80 min after the initiation of differentiation were 50 and 28% of that of nuclei prepared at the beginning of differentiation, respectively. The addition of cycloheximide at the initiation of differentiation inhibited both the rapid decrease in the concentration of actin mRNA and the repression of actin gene transcription. These results suggest that the rapid decrease in the concentration of actin mRNA during the differentiation of N. gruberi is accomplished by the repression of actin gene transcription and this transcriptional regulation requires continuous protein synthesis during the differentiation.

• Biomedical Science Letters
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• v.16 no.4
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• pp.221-227
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• 2010

To elucidate the invasion mechanism of pathogenic Naegleria fowleri, especially a receptor-ligand recognition, we investigated the in vitro cytotoxicity of pathogenic N. fowleri and nonpathogenic N. gruberi to murine macrophages, RAW 264.7, by adding four kinds of saccharides, ${\alpha}$-fucose, ${\beta}$-galactose, ${\alpha}$-D-mannopyranoside (${\alpha}$-mannose) and xylose. There was not enough of a difference in the cytotoxicity of N. fowleri treated with 10 mM of each saccharide. In particular, the cytotoxicity of N. fowleri was highly inhibited by 100 mM ${\alpha}$-mannose, which was 62.3% inhibition calculated by the analysis of lactate dehydrogenase (LDH) release assay. Although murine macrophages were not significantly destroyed by nonpathogenic N. gruberi under hematoxylin staining, the cytotoxicity of N. gruberi was inhibited from 31.5% to 14.5% (P<0.01) by 100 mM ${\alpha}$-mannose treatment. The binding of N. fowleri to macrophages was inhibited from 33% to 50% by 100 mM ${\alpha}$-mannose. Furthermore, as results of the adhesion assays which were performed to determine whether binding of Naegleria is mediated by saccharides-binding protein, the binding ability of N. fowleri as well as N. gruberi was inhibited by 100 mM ${\alpha}$-mannose.

• Parasites, Hosts and Diseases
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• v.51 no.2
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• pp.203-206
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• 2013

After bathing at a hot spring resort, a 75-year-old man presented to the emergency department because of seizure-like attack with loss of conscious. This is the first case of primary amebic meningoencephalitis (PAM) caused by Naegleria fowleri in Taiwan. PAM was diagnosed based on detection of actively motile trophozoites in cerebrospinal fluid using a wet-mount smear and the Liu's stain. The amoebae were further confirmed by PCR and gene sequencing. In spite of administering amphotericin B treatment, the patient died 25 days later.

• Parasites, Hosts and Diseases
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• v.22 no.2
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• pp.253-258
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• 1984

Experimentally, primary amoebic meningoencephalitis (PAM) is induced by Naegleria fowleri in mouse and development of PAM may be inauenced 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 (0.05mg/g). 1. PAM was developed more frequently in BALB/C mouse than ICR mouse. 2. 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. 3. No difEerence was observed on PAM development according to sect. 4. In case of inoculated amoeba, PAM incidence of $0.5{\times}10^4$ was markedly decreased.