Ultrastructural studies of early stages of oogenesis in a trichuroid nematode,<i>Trichuris muris</i>

Preston, Christine; Jenkins, Trisha A.

doi:10.1080/01651269.1983.10510027

Cited by 7 publications

(9 citation statements)

References 20 publications

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“…muris has two ovaries; that is, it is of the monodelphic type according to the nomenclature of Seurat (1920). In accordance with a report by Preston and Jenkins (1982), the organization of the genital tube was found to be hologonic. In T. muris, the vagina opens in the pharyngeal-intestinal transition zone.…”

Section: Morphology Of the Adult Wormssupporting

confidence: 73%

Light and electron microscopic studies on two nematodes, Angiostrongylus cantonensis and Trichuris muris, differing in their mode of nutrition

2007

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The morphological characteristics of the adult heteroxenous blood nematode Angiostrongylus cantonensis and the adult monoxenous intestinal nematode Trichuris muris were compared with special regard to the ultrastructure of their digestive systems. The small circular mouth of A. cantonensis appears sucker like. The very narrow mouth of T. muris is surrounded by three lips covered by the cuticle that extends into the buccal space. In the buccal cavity of A. cantonensis, a single tooth occurs opposite to a cutting plate, while no teeth are present in T. muris. The lumen of the well-developed muscular pharynx of A. cantonensis shows a trifurcated star-like cross-section. The anterior segment of the bipartite pharynx presumably functions as a pump. The lumen of the bipartite pharynx and esophagus of T. muris exhibits a very narrow oval cross-section and possesses no musculature. It is composed of a long column of stichosome cells. The esophagus region is lined inside by bands of bacillary cells as well as outside by two longitudinal rows of funnel-like papillae. These structures may be involved in the uptake of nutrients by T. muris. The gland cells might excrete digestive exoenzymes, while the bacillary cells take up the predigested nutrients. The presence of many vesicles suggests a vesicular transport of the material into the pharynx. The intestinal epithelium of A. cantonensis is densely covered with short microvilli. The lumen itself is filled with red blood cells originating from host blood. The intestine of T. muris has a thick epithelium being placed on a basal lamina and shows long thin microvilli. The intestinal lumen is very narrow and free from particles or granules. This again suggests that T. muris lives on low molecular nutrients resorbed from the environment. The epithelium cells of the intestine of T. muris contain glycogen and electron light granules but are lacking mitochondria. This finding may indicate that the epithelium cells have an anaerobic energy metabolism. This statement fits with the fact that the habitat of the worm, the cecum, is largely anaerobic.

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Section: Morphology Of the Adult Wormssupporting

confidence: 73%

Light and electron microscopic studies on two nematodes, Angiostrongylus cantonensis and Trichuris muris, differing in their mode of nutrition

2007

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“…A similar thickening of this membrane has been reported from Trichuris muris (see Preston and Jenkins, 1983) Aspiculuris tetraptera (see Anya, 1964), and Dipetalonema viteae (see McLaren, 1973) but the function of this coat in nematodes is not known.…”

Section: Electron Microscopymentioning

confidence: 64%

“…The granular nucleolus within the nucleus and the presence of numerous ribosomes in the cytoplasm of these cells indicates an active nucleus-to-cytoplasm transport of ribosomal precursors. Numerous authors report large amounts of ribosomes in oogonia or early oocytes in nematodes (Foor, 1967;Yuen, 1971;McLaren, 1973;Abirached and Brun, 1978;Herbaut et al, 1980;Preston and Jenkins, 1983) indicating similar metabolic activity early in development, which perhaps accounts in part for the rapidity with which nematode oogenesis proceeds. Dubinsky and Rybos (1980) report an increase in RNA (probably mRNA and rRNA) in oocytes of A. suum and Kaulenas and Fairbairn (1968) suggest that RNA in oocytes is primarily for the production of yolk.…”

Section: Electron Microscopymentioning

confidence: 96%

An Ultrastructural and Histochemical Study of Oogenesis in the Trichostrongylid Nematode Heligmosomoides polygyrus

MacKinnon¹

1987

The Journal of Parasitology

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Oogenesis in trichostrongylids has been examined for the first time in a light and electron microscopic investigation of Heligmosomoides polygyrus. The female reproductive tract is a single straight tube containing small oogonia (6 micron in diameter), which are arranged in a rosette pattern around a central rachis at the anterior end of the tract. Developing oocytes separate from the rachis and pass posteriorly in single file down the growth zone. Oocytes increase rapidly in volume due to the accumulation of cytoplasmic inclusion granules. These granules are of 3 types. Type 1 granules are amorphous and probably consist primarily of lipoprotein. Type 2 granules are large lipid inclusions and type 3 granules are electron-dense lipoprotein yolk bodies, which are probably used for energy reserves in the developing embryo. Histochemical studies show a more intense reaction for DNA in the nuclei of oogonia than in the nuclei of oocytes. There is a strong reaction for RNA in the nucleoli and in the cytoplasm of oogonia and oocytes. Ultrastructural studies indicate that this RNA is probably in the form of rRNA in the abundant ribosomes. Mature oocytes are cylindrical (60 X 70 micron), have a distinct nucleus with nuclear pores, and the cytoplasm is filled with inclusion granules and ribosomes but contains only small amounts of glycogen. Prior to fertilization the plasma membrane of oocytes acquires a flocculent coat. These oocytes contain 6 distinct bivalent chromosomes in diakinesis. Thus the major changes that occur in developing germ cells are 2-fold: nuclear changes that prepare the chromosomes for fertilization by initiating reduction division, and cytoplasmic changes that involve the synthesis and storage of inclusion granules.

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“…We have shown previously that oocytes within the ovary and oviduct of T. muris contain 2 types of granular cytoplasmic inclusions (Preston & Jenkins, 1983), and that both granule types are distributed throughout the ooplasm during the passage of the oocyte along the ovary and oviduct. We also recorded the gradual acquisition of a unit membrane-like vitelline layer external to the oolemma as the oocyte progressed along the oviduct.…”

Section: Observationsmentioning

confidence: 93%

“…Specimens for histological observations were processed as described previously (Preston & Jenkins, 1983).…”

Section: Methodsmentioning

confidence: 99%

Trichuris muris: structure and formation of the egg-shell

Preston

Jenkins

1984

Parasitology

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SummaryThe development of the egg-shell of the trichuroid nematode, Trichuris muris, was observed by light and electron microscopy. Initial stages of shell formation occurred immediately following sperm entry into the oocyte in the spermatheca of the female worm. The external vitelline layer separated from the oolemma, reticulate oocyte granules were discharged into the resultant perivitelline space and stored glycogen contributed to the formation of the chitinous shell. A lipid layer developed between the inner surface of the chitinous layer and the oolemma. The fully formed egg-shell thus comprised an external vitelline layer, a middle chitinous layer and an inner lipid layer. The outer vitelline layer resembled a unit membrane with strands of particulate material attached to its outer surface. The middle chitinous layer was composed of chitin microfibrils encased in a protein coat; the sheets of microfibrils were arranged as parallel lamellae forming a helicoidal architecture. The inner lipid layer contained a variable number of loosely arranged strands of electron-opaque and less-opaque material.

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Ultrastructural studies of early stages of oogenesis in a trichuroid nematode,Trichuris muris

Cited by 7 publications

References 20 publications

Light and electron microscopic studies on two nematodes, Angiostrongylus cantonensis and Trichuris muris, differing in their mode of nutrition

Light and electron microscopic studies on two nematodes, Angiostrongylus cantonensis and Trichuris muris, differing in their mode of nutrition

An Ultrastructural and Histochemical Study of Oogenesis in the Trichostrongylid Nematode Heligmosomoides polygyrus

Trichuris muris: structure and formation of the egg-shell

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