Freeze-etch studies of the granular and vacuolated forms of Blastocystis hominis

Tan, Hak Koon; Harrison, Maria; Zierdt, Charles H.

doi:10.1007/bf00366110

Cited by 12 publications

(7 citation statements)

References 9 publications

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“…With regard to the central vacuole, additional differences between our observations and those reported by Tan et al (9,10) became apparent. They stated that the central vacuole was the site of the appearance of small granules which grew in size and gradually increased in number, possibly by division.…”

Section: Discussioncontrasting

confidence: 88%

“…The freezefracture method, on the other hand, has the advantage ofmaking it possible to examine the inner and outer membrane halves in replicas (1). To date, however, there is only one report describing the ultrastructure of B. hominis by this method (10). In the present study, we describe the fine structure of B. horninis as revealed by the freeze-fracture method.…”

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confidence: 83%

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Freeze‐Fracture Study of Blastocystis hominis¹

Yoshikawa

Yamada

Yoshida

1988

The Journal of Protozoology

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The ultrastructure of Blastocystis hominis was investigated by the freeze-fracture method. Freeze-fracture replicas of the membranes of B. hominis and its organelles were studied with special regard to the density and distribution of the intramembranous particles (IMP's). On all membrane replicas, the concentration of IMP's on the protoplasmic face (P face) invariably was greater than on the exoplasmic face (E face). On the P face, IMP's were heterogeneously distributed in dense aggregates, alternating with particle-free, smooth surface areas. Occasionally, small depressions and protrusions were observed in these areas. On the membrane of the central vacuole, invaginations into the vacuole were frequently observed within the smooth surface regions. Since most of the granules in the central vacuoles had no IMP's, it seems likely that the intervacuolar granules were formed from these invaginations of the vacuole membrane. The width of the intermembrane space between the inner and outer membranes of the nuclear envelope was uneven, with regions of relative narrowness interspersed with regions of expansion. Nuclear pores were localized within the narrow portions of this space. A nucleus, apparently in the process of dividing, was observed enclosed within an intact outer membrane. Division of the outer membrane would then result in the formation of two discrete nuclei.

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Section: Discussioncontrasting

confidence: 88%

mentioning

confidence: 83%

Freeze‐Fracture Study of Blastocystis hominis¹

Yoshikawa

Yamada

Yoshida

1988

The Journal of Protozoology

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“…Morphologically, the Blastocystis cell shows protistan features: it contains one or more nuclei, smooth and rough endoplasmic reticulum, Golgi complex, and mitochondrion-like organelles (23,49,191,192,215,224,228,231). A number of morphologically distinct forms of the organism have been described (22,23,49,179,192,228,231).…”

Section: Taxonomymentioning

confidence: 99%

Blastocystis hominis revisited

1996

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Blastocystis hominis is a unicellular organism found commonly in the intestinal tract of humans and many other animals. Very little is known of the basic biology of the organism, and controversy surrounds its taxonomy and pathogenicity. There morphological forms (vacuolar, granular, and ameboid) have been recognized, but recent studies have revealed several additional forms (cyst, avacuolar, and multivacuolar). The biochemistry of the organism has not been studied to any extent, and organelles and structures of unknown function and composition are present in the cells. Several life cycles have been proposed but not experimentally validated. The form used for transmission has not been defined. Infections with the organism are worldwide and appear in both immunocompetent and immunodeficient individuals. Symptoms generally attributed to B. hominis infection are nonspecific, and the need for treatment is debated. If treatment appears warranted, metronidazole is suggested as the drug of choice, although failures of this drug in eradicating the organism have been reported. Infection is diagnosed by light microscopic examination of stained smears or wet mounts of fecal material. Most laboratories identify B. hominis by observing the vacuolar form, although morphological studies indicate that other forms, such as the cyst form and multivacuolar form, also should be sought for diagnosis.

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“…This step initiates fixation and kills the B. hominis cells so that the compact growth sediment can be transferred to another tube of 4% glutaraldehyde in cacodylate buffer (72,73). After 1 h, the suspension is centrifuged at 500 x g for 10 min, decanted, resuspended in 1% glutaraldehyde buffer, and stored at 4°C.…”

Section: Temmentioning

confidence: 99%

Blastocystis hominis--past and future

1991

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The history of B. hominis is unique. Few infectious agents have provoked the many misconceptions that plague this enigmatic parasitic ameba. Conflicting descriptions of its nature and pathogenesis have continued throughout the 20th century. As seen by the greatly expanded number of reports in recent years, B. hominis is now a major subject of study, particularly for evidence of disease causation. Physicians are treating patients with intestinal disease caused by B. hominis. Many mild cases resolve in about 3 days without treatment, but others are acute and chronic disease is common. As with E. histolytica, the carrier state is often seen without symptoms. Treatment is usually with metronidazole, but emetine (for refractory infections), trimethoprim-sulfamethoxazole, and pentamidine are also effective. In fecal samples, this complex protozoan appears in a variety of cell forms which makes microscopic diagnosis difficult. As yet, no specific fluorescent-antibody test is available for diagnosis. A culture method to demonstrate the more easily recognized CB form is available, but probably not feasible for most diagnostic laboratories. The common cell forms are the CB form, the granular (mitochondria) form, and the ameba form. The unexpected size range of these forms in clinical material, from yeast size (ca. 7 microns) to giant cells of 20 to 40 microns, makes diagnosis difficult Pseudopodia may be demonstrated by the ameba form in heated microscope stage culture chambers. The anaerobic B. hominis has no cyst form. Its mitochondria are uniquely anaerobic and have no cytochrome protein or oxidative mitochondrial enzymes. Because of its many cell forms and anaerobic mitochondria, B. hominis is an organism of great interest for morphologic and biochemical study. Reproduction is asexual, usually by binary fission. Shizogony occurs in cultured cells. The CB appears to be an organelle whose specific purpose is for reproduction by shizogony. From 2 to 30 progeny are derived from schizogony. The ameba form reproduces by plasmotomy; it has no CB. The pathology of B. hominis infections has been studied in gnotobiotic guinea pigs in which inflammation of the intestinal mucosa and invasion of the superficial layers were seen. Only limited studies of human pathology are available. Those who have studied mucosal histopathology report inflammation and cellular changes that resolve after treatment. More study in this area is strongly indicated (32, 44, 57, 62, 67, 75). Ultrastructural details of B. hominis major forms, except for the schizont, are complete. The organism has no cell wall. The concentric CB takes up as much as 95% of the cell. The major organelles, which include multiple nuclei, Golgi apparatus, mitochondria, endoplasmic reticulum, fat, and other inclusions, are confined in two or four opposed pods in a thin band of peripheral cytoplasm between the spherical entire plasma membrane and the CB membrane. The pods buldge the CB membrane inward. There is evidence of a bacteroid endosymbiont. Education about B. hominis is needed. Entry of recent findings into new textbooks is imperative for its understanding among medical practitioners. Laboratory workers need to be aware of it for many reasons. The College of American Pathologists includes B. hominis in its proficiency testing samples and requires that it be reported from clinical samples.

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Freeze-etch studies of the granular and vacuolated forms of Blastocystis hominis

Cited by 12 publications

References 9 publications

Freeze‐Fracture Study of Blastocystis hominis¹

Freeze‐Fracture Study of Blastocystis hominis¹

Blastocystis hominis revisited

Blastocystis hominis--past and future

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Freeze-etch studies of the granular and vacuolated forms of Blastocystis hominis

Cited by 12 publications

References 9 publications

Freeze‐Fracture Study of Blastocystis hominis1

Freeze‐Fracture Study of Blastocystis hominis1

Blastocystis hominis revisited

Blastocystis hominis--past and future

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Freeze‐Fracture Study of Blastocystis hominis¹

Freeze‐Fracture Study of Blastocystis hominis¹