치은아메바(entamoeba gingivalis)의 미세구조에 관한 연구

Abstract

[한글]

Fine structure of Entomoeba gingivalis in culture and in oral cavity

Joung-Kang Yang, D.D.S.

Department of Medical Science The Graduate School, Yonsei University

(Directors: Professor Chin-Thack Soh, M.D. Professor Man-Su Kim, D.D.S.)

Entamoeba gingivalis was first described by Gros in 1849. It inhabits the mouth

under unhygienic conditions, especially in one with a periodontal disease, though

it may also be found in healthy and clean mouths.

Jhee (1962) reported an incidence of E. gingivalis among dental patients in

Severance Hospital up to 38.4 per cent, though the pathogenicity was not

identified. According to microscopic studies the morphology of E. gingivalis

resembles closely that of E. histolytica, with the exception of the contents of

vacuoles and the characteristics of peripheral chromatin and karyosome.

Keller et al. (1967) described the fine structure of E. gingivatis in culture.

But no attempt was made to correlate those observations with the appearance of

trophozoites collected from the oral cavity. The present study was designed to

observe the structural characteristics of E. gingivalis in culture and in oral

cavities, and to discuss those structures and compare them with the fine structures

of another species of amoeba.

For the electron microscopic study of E. gingivalis, a cultured form of YG

210-strain was used. The strain was isolated from the gingival crevice of a

periodontitis patient, a 38 year-old man, in March of 1971 and was maintained on a

diphasic medium overlayed with egg-yolk fluid media(pH 7.5) containing unidentified

oral flora. Meanwhile the trophozoites were collected directly from the oral cavity

of two periodontal disease patients, a 53 and a 55 year-old man. The sediments from

cultures (48 hour-old) or scrapings in 1 ml of phosphate buffered saline (pH 7.5),

were centrifuged at 500 rpm and were solidified by adding a few drops of warm agar.

They were cut into 1 mm cubes and the cubes were fixed with 3% glutaraldehyde and

1% osmium tetroxide. Further steps were followed by standard techniques for

electron microscopic studies.

The results were summarized as follows.

A. E. gingivalis in culture

1. The trophozoites were oval or irregular in shape. Pseudopodia, ectoplasm and

endoplasm were clearly indentified in oval shaped amoeba, and a big sized

cytoplasmic projection was observed in an irregular shaped amoeba. The two layered

plasma membrane of the amoeba had a lamella structure in general, but was thickened

at the portions of pseudopodia or at the tip of cytoplasmic projections. Some

portions of plasmalemma were invaginated, and contained bacteria and particles of

rice starch.

2. Vacuoles in the cytoplasm varied in number, size and shape, and contained

ingested rice starch, bacteria or membrane whorls. The basic matrix of the

cytoplasm contained widely scattered fine dense granules, short filaments,

rosette-like particles and dense granules. Endoplasmic reticulum were sparse.

Mitochondria and Golgi-complex were not observed.

3. The nuclei varied from oval to irregular in shape. The nuclear envelope was

composed of a double membrane, and distinct nuclear pores were rarely observed.

Medium sized electorn-dense granules were confluently accumulated beneath the

nuclear membrane.

B. E. gingivalis in oral eavity

1. The trophozoites were generally irregular in shape, and a number of smaller

cytoplasmic projections were observed around the cytoplasm. In some amoeba,

collections of extracellular vacuoles, vesicles and cellular debris were observed

close to the plasmalemma, which resembled the "uroid" described by Zaman(1961).

2. Vacuoles in the cytoplasm contained ingested cellular fragments, bacteria and

membrane whorls. Nuclear substances of other cells were observed in some vacuoles.

Dense pigment rods were distributed throughout the cytoplasm. Some of the rods

appeared in groups but central clusters of fine granules were not observed. Other

structures of the cytoplasm were similar to the amoeba in culture.

3. The nucleus was oval in shape. There were regularly spaced pores in the

nuclear envelope. Electron-dense patches of chromatin lined the inner boundary of

nuclei at regular intervals. In one nucleus, a single dense mass of granules

observed close to the karyosome.

The above findings indicated somewhat interesting differenes between the E.

gingivalis from culture media and those from the oral cavity.

In summary, the pigment rod in the cytoplasm and "uroid" like structure close to

the plasmalemma were present in oral cavity but not present in cultured form.

[영문]

Entamoeba gingivalis was first described by Gros in 1849. It inhabits the mouth under unhygienic conditions, especially in one with a periodontal disease, though it may also be found in healthy and clean mouths.

Jhee (1962) reported an incidence of E. gingivalis among dental patients in Severance Hospital up to 38.4 per cent, though the pathogenicity was not identified. According to microscopic studies the morphology of E. gingivalis resembles closely that of E. histolytica, with the exception of the contents of vacuoles and the characteristics of peripheral chromatin and karyosome.

Keller et al. (1967) described the fine structure of E. gingivatis in culture. But no attempt was made to correlate those observations with the appearance of trophozoites collected from the oral cavity. The present study was designed to observe the structural characteristics of E. gingivalis in culture and in oral cavities, and to discuss those structures and compare them with the fine structures of another species of amoeba.

For the electron microscopic study of E. gingivalis, a cultured form of YG 210-strain was used. The strain was isolated from the gingival crevice of a periodontitis patient, a 38 year-old man, in March of 1971 and was maintained on a diphasic medium overlayed with egg-yolk fluid media(pH 7.5) containing unidentified oral flora. Meanwhile the trophozoites were collected directly from the oral cavity of two periodontal disease patients, a 53 and a 55 year-old man. The sediments from

cultures (48 hour-old) or scrapings in 1 ml of phosphate buffered saline (pH 7.5), were centrifuged at 500 rpm and were solidified by adding a few drops of warm agar. They were cut into 1 mm cubes and the cubes were fixed with 3% glutaraldehyde and 1% osmium tetroxide. Further steps were followed by standard techniques for

electron microscopic studies.

The results were summarized as follows.

A. E. gingivalis in culture

1. The trophozoites were oval or irregular in shape. Pseudopodia, ectoplasm and endoplasm were clearly indentified in oval shaped amoeba, and a big sized cytoplasmic projection was observed in an irregular shaped amoeba. The two layered plasma membrane of the amoeba had a lamella structure in general, but was thickened at the portions of pseudopodia or at the tip of cytoplasmic projections. Some portions of plasmalemma were invaginated, and contained bacteria and particles of rice starch.

2. Vacuoles in the cytoplasm varied in number, size and shape, and contained ingested rice starch, bacteria or membrane whorls. The basic matrix of the cytoplasm contained widely scattered fine dense granules, short filaments, rosette-like particles and dense granules. Endoplasmic reticulum were sparse.

Mitochondria and Golgi-complex were not observed.

3. The nuclei varied from oval to irregular in shape. The nuclear envelope was composed of a double membrane, and distinct nuclear pores were rarely observed. Medium sized electorn-dense granules were confluently accumulated beneath the nuclear membrane.

B. E. gingivalis in oral eavity

1. The trophozoites were generally irregular in shape, and a number of smaller cytoplasmic projections were observed around the cytoplasm. In some amoeba, collections of extracellular vacuoles, vesicles and cellular debris were observed close to the plasmalemma, which resembled the "uroid" described by Zaman(1961).

2. Vacuoles in the cytoplasm contained ingested cellular fragments, bacteria and membrane whorls. Nuclear substances of other cells were observed in some vacuoles. Dense pigment rods were distributed throughout the cytoplasm. Some of the rods

appeared in groups but central clusters of fine granules were not observed. Other structures of the cytoplasm were similar to the amoeba in culture.

3. The nucleus was oval in shape. There were regularly spaced pores in the nuclear envelope. Electron-dense patches of chromatin lined the inner boundary of nuclei at regular intervals. In one nucleus, a single dense mass of granules

observed close to the karyosome.

The above findings indicated somewhat interesting differenes between the E. gingivalis from culture media and those from the oral cavity.

In summary, the pigment rod in the cytoplasm and "uroid" like structure close to the plasmalemma were present in oral cavity but not present in cultured form.