• Journal of The Korean Society of Clinical Toxicology
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• v.4 no.2
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• pp.131-136
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• 2006

Metronidazole is an antimicrobial drug widely used against various types of infectious agents, including protozoa, amoeba, Helicobacter pylori, and anaerobes. Metronidazole may produce some adverse effects on hematologic, immunologic, neurologic and other systems. We report a case of reversible metronidazole-induced encephalopathy. The toxic dose of metronidazole and the onset of encephalopathy were variable. Two patients showed abnormally high signal intensity in the bilateral dentate nucleus of cerebellum, and characteristic abnormalities were detected by brain magnetic resonance imaging (MRI) and T2-weighted images, fluid-attenuated inversion recovery images and/or diffusion weighted imaging (DWI). Discontinuation of metronidazole resulted in the improvement of the neurologic symptoms over a period of two to three weeks. We followed up the brain MRI with DWI in one case following obvious clinical improvement, and the previously detected lesion had disappeared.

• 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.

• The Korean Journal of Applied Statistics
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• v.22 no.3
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• pp.569-584
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• 2009

Edge detection in images has been widely used in image processing system and computer vision. Morphological edge detection has used structuring elements with fixed shapes. This paper presents morphological operators with non-fixed shape kernels, or amoebas, which take into account the image contour variations to adapt their shape. Experimental results are analyzed in both qualitative analysis through visual inspection and quantitative analysis with PFOM and ROC curves. The Experiments demonstrate that these novel operators outperform classical morphological operations with a fixed, space-invariant structuring elements for edge detection applications.

• Parasites, Hosts and Diseases
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• v.43 no.1 s.133
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• pp.7-13
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• 2005

The taxonomy of Acanthamoeba spp., an amphizoic amoeba which causes granulomatous amoebic encephalitis and chronic amoebic keratitis, has been revised many times. The taxonomic validity of some species has yet to be assessed. In this paper, we analyzed the morphological characteristics, nuclear 18s rDNA and mitochondrial 16s rDNA sequences and the Mt DNA RFLP of the type strains of four Acanthamoeba species, which had been previously designated as A. divionensis, A. parasidionensis, A. mauritaniensis, and A. rhysodes. The four isolates revealed characteristic group II morphology. They exhibited 18S rDNA sequence differences of $0.2-1.1\%$ with each other, but more than $2\%$ difference from the other compared reference strains. Four isolates formed a different clade from that of A. castellanii Castellani and the other strains in morphological group lion the phylogenetic tree. In light of these results, A. paradivionensis, A. divionensis, and A. mauritaniensis should be regarded as synonyms for A. rhysodes.

• Korean Journal of Microbiology
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• v.32 no.4
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• pp.280-284
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• 1994

Lack of lysosomal fusion with symbiosomes in symbiont-bearing Amoeba proteus may be due either to the presence of a component in the symbiosome membrane or to the absence of a component needed in the fusion process. Using monoclonal antibody as a probe, lipopolysaccharides were identified as symbiosome-membrane components contributed by symbionts and were found to be exposed on the cytoplasmic side of the membrane. In order to test whether lipopolysaccharides may play a role in the prevention of lysosome-symbiosome fusion, the antilipopolysaccharides antibody was microinjected and processed for double immunostaining in conjuction with anti-lysosome antibody as a lysosome-fusion indicator. Microinjection of the anti-LPS antibody caused symbiosomes to fuse with lysosomes, suggesting that X-bacterial lipopolysaccharides could be 'fusion-preventing' factors.

• Parasites, Hosts and Diseases
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• v.59 no.5
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• pp.501-505
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• 2021

The pathogenic free-living amoeba Naegleria fowleri causes primary amoebic meningoencephalitis, a fatal infection, by penetrating the nasal mucosa and migrating to the brain via the olfactory nerves. N. fowleri can induce host cell death via lytic necrosis. Similar to phosphorylation, O-linked β-N-acetylglucosamine (O-GlcNAc) glycosylation (O-GlcNAcylation) is involved in various cell-signaling processes, including apoptosis and proliferation, with O-GlcNAc addition and removal regulated by O-GlcNAc transferase and O-GlcNAcase (OGA), respectively. However, the detailed mechanism of host cell death induced by N. fowleri is unknown. In this study, we investigated whether N. fowleri can induce the modulation of O-GlcNAcylated proteins during cell death in Jurkat T cells. Co-incubation with live N. fowleri trophozoites increased DNA fragmentation. In addition, incubation with N. fowleri induced a dramatic reduction in O-GlcNAcylated protein levels in 30 min. Moreover, pretreatment of Jurkat T cells with the OGA inhibitor PUGNAc prevented N. fowleri-induced O-deGlcNAcylation and DNA fragmentation. These results suggest that O-deGlcNAcylation is an important signaling process that occurs during Jurkat T cell death induced by N. fowleri.

• Parasites, Hosts and Diseases
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• v.57 no.3
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• pp.291-294
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• 2019

Primary amebic encephalitis (PAM) is a devastating central nervous system infection caused by Naegleria fowleri, a free-living amoeba, which can survive in soil and warm fresh water. Here, a 43-year-old healthy male was exposed to warm freshwater 5 days before the symptom onset. He rapidly developed severe cerebral edema before the diagnosis of PAM and was treated with intravenous conventional amphotericin B while died of terminal cerebral hernia finally. Comparing the patients with PAM who has similar clinical symptoms to those with other common types of meningoencephalitis, this infection is probably curable if treated early and aggressively. PAM should be considered in the differential diagnosis of purulent meningoencephalitis, especially in patients with recent freshwater-related activities during the hot season.

• Biomedical Science Letters
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• v.24 no.4
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• pp.435-438
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• 2018

Acanthamoeba culbertsoni is the causative agent of granulomatous amoebic encephalitis (GAE), a condition that predominantly occurs in immunocompromised individuals and which is typically fatal. A mannose-binding protein (MBP) among lectins was shown to have strong A. castellanii pathogenic potential when correlated with major virulence proteins. In this study, protective effects were analyzed using the monoclonal antibody to A. culbertsoni MBP by quantification and were also compared with other free-living amoebae. For the amoebial cytotoxicity to the target cell, amoeba trophozoites were incubated with Chinese hamster ovary (CHO) cells. For the protective effects of antibodies, amoebae were pre-incubated with them for 4 h and then added to the target cells. After 24 h, the supernatants were collected and examined for host cell cytotoxicity by measuring lactate dehydrogenase (LDH) release. The cytotoxicity of A. culbertsoni to the CHO cells showed about 87.4%. When the monoclonal antibody was pre-incubated with A. culbertsoni, the amoebial cytotoxicity was remarkably decreased as shown at LDH release (1.858 absorbance), which was represented with about 49.9%. Taken together, it suggested that the monoclonal antibody against MBP be important to inhibit the cytotoxicity of A. culbertsoni trophozoites to the target cell. The antibody will be applied into an in vivo functional analysis, which would help to develop therapeutics.

• Journal of Microbiology and Biotechnology
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• v.29 no.5
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• pp.713-720
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• 2019

Acanthamoeba castellanii belonging to the T4 genotype may cause a fatal brain infection known as granulomatous amoebic encephalitis, and the vision-threatening eye infection Acanthamoeba keratitis. The aim of this study was to evaluate the antiamoebic effects of three clinically available antidiabetic drugs, Glimepiride, Vildagliptin and Repaglinide, against A. castellanii belonging to the T4 genotype. Furthermore, we attempted to conjugate these drugs with silver nanoparticles (AgNPs) to enhance their antiamoebic effects. Amoebicidal, encystation, excystation, and host cell cytotoxicity assays were performed to unravel any antiacanthamoebic effects. Vildagliptin conjugated silver nanoparticles (Vgt-AgNPs) characterized by spectroscopic techniques and atomic force microscopy were synthesized. All three drugs showed antiamoebic effects against A. castellanii and significantly blocked the encystation. These drugs also showed significant cysticidal effects and reduced host cell cytotoxicity caused by A. castellanii. Moreover, Vildagliptin-coated silver nanoparticles were successfully synthesized and are shown to enhance its antiacanthamoebic potency at significantly reduced concentration. The repurposed application of the tested antidiabetic drugs and their nanoparticles against free-living amoeba such as Acanthamoeba castellanii described here is a novel outcome that holds tremendous potential for future applications against devastating infection.

• Parasites, Hosts and Diseases
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• v.61 no.4
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• pp.388-396
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• 2023

Entamoeba histolytica is an enteric tissue-invasive protozoan parasite causing amoebic colitis and liver abscesses in humans. Amoebic contact with host cells activates intracellular signaling pathways that lead to host cell death via generation of caspase-3, calpain, Ca²⁺ elevation, and reactive oxygen species (ROS). We previously reported that various NADPH oxidases (NOXs) are responsible for ROS-dependent death of various host cells induced by amoeba. In the present study, we investigated the specific NOX isoform involved in ROS-dependent death of hepatocytes induced by amoebas. Co-incubation of hepatoma HepG2 cells with live amoebic trophozoites resulted in remarkably increased DNA fragmentation compared to cells incubated with medium alone. HepG2 cells that adhered to amoebic trophozoites showed strong dichlorodihydrofluorescein diacetate (DCF-DA) fluorescence, suggesting intracellular ROS accumulation within host cells stimulated by amoebic trophozoites. Pretreatment of HepG2 cells with the general NOX inhibitor DPI or NOX2-specific inhibitor GSK 2795039 reduced Entamoeba-induced ROS generation. Similarly, Entamoeba-induced LDH release from HepG2 cells was effectively inhibited by pretreatment with DPI or GSK 2795039. In NOX2-silenced HepG2 cells, Entamoeba-induced LDH release was also significantly inhibited compared with controls. Taken together, the results support an important role of NOX2-derived ROS in hepatocyte death induced by E. histolytica.