Presumptive synchronized nuclear divisions without cytokinesis in the Rhinosporidium seeberi parasitic life cycle.

Despite numerous studies of the Rhinosporidum seeberi parasitic phase, the stages of its nuclear cycle leading to the formation of endoconidia have yet to be properly described. R. seeberi resists culture and can only be investigated on histological preparations. We have evaluated tissue sections collected from 35 host species with rhinosporidosis searching for the presence of mitotic figures during sporangia development. This study found that soon after endoconidia release, the prominent reddish vesicles typical of this stage vanished leading to the development of juvenile sporangia (JS) 12-70 µm in diameter. This stage possesses granular cytoplasm, a thick cell wall, and a central reddish nucleus with a conspicuous nucleolus. The first nuclear division takes place in the JS. It is a rarely encountered event characterized by the development of a distorted nucleus leading to the formation of two nuclei without cytokinesis. The finding of multiple nuclear divisions at prophase-, metaphase- and telophase-like stages without cytokinesis was detected in intermediate sporangia (IS). IS with multiple dividing nuclei seem to be at the same stage of nuclear partitioning, suggesting synchronized nuclear division. In these sporangia, the nuclei continue divisions without cytokinesis until the sporangia reach ≥300 µm in diameter. The last nuclear division prior to cytokinesis appears to take place in very large sporangia with thousands of nuclei. The build-up of cytoplasm around each nucleus and the formation of a thin cell wall lead to the formation of endoconidia. This study revealed the presence of several mechanisms of pathogenesis in R. seeberi that deserved further investigation.

Rhinosporidiosis in Delhi, north India: case series from a non-endemic area and mini-review.

We report three cases of rhinosporidiosis from migrant population of Delhi. Three male patients had sino-nasopharyngeal, nasopharyngeal and nasal rhinosporidiosis, respectively. One patient gave a history of bathing in stagnant water. The diagnosis was made by clinical presentation and microscopic observation of characteristic sporangia of Rhinosporidium seebri in mycological and histopathological investigations. All the patients were successfully treated with complete surgical excision of lesions and cauterization of base. There were no recurrences.

Primary cutaneous rhinosporidiosis diagnosed on FNAC: a case report with review of literature.

Rhinosporidium seeberi causes granulomatous inflammation of mucocutaneous sites, presenting most frequently as polypoidal lesions in the nose. Sites like the conjunctiva, trachea, nasopharnyx, skin, and genitourinary tract are less frequently involved. Primary cutaneous lesion is extremely rare. We report the fine needle aspiration cytology (FNAC) of rhinosporidiosis occurring as a primary cutaneous lesion. FNAC of polypoidal and warty skin growths on leg in a 28-year-old male revealed numerous sporangia and spores of R. seeberi. There were no mucocutaneous lesions. Histopathologic examination confirmed the diagnosis. Globular bodies in endospores of R. seeberi are specific; their demonstration confirms diagnosis of rhinosporidiosis. FNAC or scrape cytology is economical and reliable in preoperative diagnosis of suspected and unsuspected cutaneous lesions of R. seeberi.

Recovery of growth of Hyphochytrium catenoides after exposure to environmental stress.

The survival of an isolate of Hyphochytrium catenoides collected from soil in the Blue Mountains in eastern New South Wales, Australia, was tested under extreme conditions in the laboratory. This isolate recovered growth after being subjected to drying on filter paper, to heat while desiccated, to hypersalinity, to strict anaerobic conditions, to freezing temperatures, and to a short period in solutions at pH 2.8-11.2. The capacity to survive under these conditions in the laboratory suggests adaptation to fluctuating conditions in the soil. The partial DNA sequence of the 28S ribosomal RNA gene in the isolate from New South Wales was 98% similar to that in an isolate from Arizona with a similar morphology.

Rhinosporidiosis in Raipur, Chhattisgarh: a report of 462 cases.

Rhinosporidiosis is endemic in the state of Chhattisgarh. 462 cases were encountered during the period of 12 years from January 1994 to December 2005. Maximum incidence was seen in men in the age group of 21-30 years. Nose and nasopharynx were the commonest site (81.1%), followed by ocular tissue (14.2%). Many rare sites of involvement were encountered. Seven cases of generalized rhinosporidiosis were seen. Rhinosporidium seeberi could be easily identified in Haematoxylin and eosin stained sections. Sporangias and spores are better delineated by periodic Acid Schiff, Mayer's mucicarmine, Verhoff's vonGieson and Grocott Gomori methamine silver stain.

Nature and significance of the electron-dense bodies of the endospores of rhinosporidium seeberi: their reactions with MTT (3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide) and TMRE (tetramethyl-rhodamine ethyl ester).

The most conspicuous internal structures of the endospore of Rhinosporidium seeberi are the 10-16 spherical, 1.0-1.5-microm bodies that have been termed electron-dense bodies (EDB) or lipid bodies (LB); some authors have regarded them as nutritive stores of lipid or protein while others have regarded them as DNA-containing, ultimate generative units of R. seeberi. The literature is reviewed as supporting either view. We report, for the first time, (i) reactions of the endospores with the salt MTT (3-[4,5-dimethyl-2-thiazolyl]-2,5-diphenyl-2H-tetrazolium bromide) and (ii) ultrastructural appearances; and suggest that both views on the nature of spherical bodies are valid (i.e. the endospore contains both EDB, and lipid or protein bodies). Well-marked reduction of the MTT with the production of deep-purple staining was seen in a proportion of the spherical bodies, probably the EDB, suggesting that they are actively metabolizing, viable elements with dehydrogenase activity, and that these bodies are the thick-walled electron-dense bodies described as EDB and visualized in the transmission electron microphotograph illustrated in this paper. The spherical bodies showed fluorescent labeling with acridine orange and with ethidium bromide supporting the idea that they contained nucleic acids. TMRE (tetramethyl rhodamine ethyl ester), a mitochondrion-specific dye, also labeled the intra-endosporial spherical bodies. Other bodies (LB) of a similar size that were MTT-non-reducing, electron lucent, and have no organized structure, are probably the lipid or protein containing, inert, nutritive storage bodies suggested by previous authors.

In vitro studies on the mechanisms of endospore release by Rhinosporidium seeberi.

Studies of Rhinosporidium seeberi have demonstrated that this organism has a complex life cycle in infected tissues. Its in vivo life cycle is initiated with the release of endospores into a host's tissues from its spherical sporangia. However, little is known about the mechanisms of sporangium formation and endospore release since this pathogen is intractable to culture. We have studied the in vitro mechanisms of endospore release from viable R. seeberi's sporangia. It was found that watery substances visibly stimulates the mature sporangia of R. seeberi to the point of endospore discharge. The internal rearrangement of the endospores within the mature sporangia, the opening of an apical pore in R. seeberi's cell wall, and the active release of the endospores were the main features of this process. Only one pore per sporangium was observed. The finding of early stages of pore development in juvenile and intermediate sporangia suggested that its formation is genetically programmed and that it is not a random process. The stimulation of R. seeberi's sporangia by water supports the epidemiological studies that had linked this pathogen with wet environments. It also explains, in part, its affinities for mucous membranes in infected hosts. The microscopic features of endospore discharge suggest a connection with organisms classified in the Kingdom Protoctista. This study strongly supports a recent finding that placed R. seeberi with organisms in the protoctistan Mesomycetozoa clade.

Rhinosporidiosis in Europe.

Rhinosporidiosis is an inflammatory disease of the nasal mucosa caused by Rhinosporidium seeberi. The disease is endemic in India but very rare in Europe or other continents. The literature concerning aetiology, clinical appearance, morphology and treatment is reviewed. All reported European cases are summarized.

Rhinosporidium seeberi: light, phase contrast, fluorescent and scanning electron microscopic study.

Phase contrast microscopic study indicated the multilayered structure of the sporangial wall of R. seeberi while the scanning electronmicroscopic study revealed a trilaminated wall compared to a thick double walled light microscopic structure. The scanning electronmicroscopy revealed the spores of varying sizes which were found either discretely or in groups interconnected and seen attached to the inner aspect of the sporangial wall. Autofluorescence of sporangia and spores was observed under microscope. Acridine orange staining revealed the presence of DNA materials in the spore and sporangia.

Rhinosporidiosis at King Edward VIII Hospital, Durban--1976-1985. A report of 6 cases.

Six cases of the fungal infection, rhinosporidiosis, are documented. Clinical, light microscopic and electron microscopic features of the causative organism (Rhinosporidium seeberi) are presented.