Mammalian oocyte organelles with special reference to pleomorphic mitochondria and vacuole formation in marsupials

Abstract

Marsupial oocytes are larger and have a thinner zona than eutherian oocytes; and the ooplasm becomes almost completely filled with empty-looking vacuoles the contents of which have, so far, defied histochemical analysis. In the opossum, Monodelphis domestica, apart from orthodox mitochondria, a 'hooded' form is found occasionally in young primary oocytes, and a novel 'spiked' form-which is very elongate and has longitudinally-running filaments attached to the outer membrane--is found in mature oocytes. On the genesis of the ooplasmic vacuoles in mammals, information is available only for two marsupials. In Monodelphis, the vacuoles originate from endoplasmic, endocytotic and Golgi vesicles which generate multivesicular bodies; these give rise to the vacuoles. For the bandicoot, Isoodon macrourus, evidence is presented for the formation of the vacuoles from enlarged, transformed mitochondria which undergo a complex evolution during development. Primordial oocytes of Isoodon contain three ooplasmic localizations--a paranuclear complex, a vesicle microtubule complex and an aggregate of tubular cistenae-which have not been described for other mammalian oocytes. The origin, fate and function of these organelle localizations is unknown. In this paper, problems with respect to the definition of 'yolk' are described and the extent of our ignorance concerning oocyte organelles is discussed.

Mouse oocytes within germ cell cysts and primordial follicles contain a Balbiani body

“…However, subsequent studies failed to confirm these observations, and it is now widely accepted that mouse oocytes lack such mitochondrial aggregates (1,2). This situation is surprising, because Balbiani bodies have been found in marsupials (29) and many mammalian species including goat (21), rat (30,31), hamster (32), and humans (33)(34)(35), although the function of mammalian Balbiani bodies is unknown.…”

Oogenesis in the Marsupial Stripe-Faced Dunnart, <i>Sminthopsis macroura</i>

“…In Sminthopsis as well as in Monodelphis and many eutherians the close contact of mitochondria to the endoplasmic reticulum is very conspicuous. Mitochondria densely surrounded by microtubules, as depicted for ovulated oocytes of Monodelphis Ullmann and Butcher, 1996] and of T. vulpecula [Frankenberg and Selwood, 1998] could not be detected in preovulatory oocytes of Sminthopsis. Kress/Merry/Selwood form.…”

“…In no species has the ultrastructure of oocyte differentiation been correlated with a timetable of oogenesis and an analysis of oocyte growth. This is surprising considering the unusual growth pattern shown by some marsupial oocytes [Falconnier and Kress, 1992;Rodger et al, 1992] and the distinctive nature of marsupial oocytes, which develop prominent electronlucent vesicles during oogenesis [Breed et al, 1989;Breed and Leigh, 1990;Breed, 1996;Kress, 1996;Roberts and Breed, 1996;Ullmann and Butcher, 1996].…”

“…The grey shorttailed opossum (Monodelphis domestica), which reproduces readily under laboratory conditions, seems the best documented [Falconnier and Kress, 1992;Mate, 1996;Ullmann and Butcher, 1996]. In no species has the ultrastructure of oocyte differentiation been correlated with a timetable of oogenesis and an analysis of oocyte growth.…”

Analysis of Heterogeneous Mitochondria Distribution in Somatic Cell Nuclear Transfer Porcine Embryos

“…Mitochondrial morphologies vary to some extent in different mammalian species. Hooded mitochondria morphologies are more frequent in bovine embryos while fenestrated mitochondria have been reported for marsupials as well as bovine and pig embryos~Krause et al, 1992;Ullmann & Butcher, 1996; present report!, but the significance for these morphological specifications is not known. Vacuole formation had been reported for marsupials to be the result of mitochondrial restructuring~Ullmann & Butcher, 1996!, but no such vacuolization has been reported for pig oocytes, including the present report.…”