Biomaterial Database

The mitochondrial cloud of Xenopus oocytes: the source of germinal granule material. 1984

J Heasman, and J Quarmby, and C C Wylie

The mitochondrial cloud is a prominent mass in the cytoplasm of previtellogenic oocytes of Xenopus laevis. It is shown here that the cloud contains both mitochondria and electron-dense granulofibrillar material (GFM). Using a combination of light microscopical, fluorescence, time-lapse filming, and electron microscopical techniques, the ontogeny of these components is reported and their fate is studied. It was found that the cloud is stationary in previtellogenic stages and fragments into islands of mitochondria and GFM during stage II (using the staging system of J. N. Dumont [1972) J. Morphol. 136, 153-180). These islands become localized in the peripheral cytoplasm at one pole of the stage III oocyte. By studying successive stages, GFM was followed through oogenesis and it was found localized only at the vegetal pole of stage IV and V oocytes. Furthermore, it was found that it bears a striking resemblance in position, appearance, and associations with mitochondria to the "germinal granules" of unfertilized eggs. Germinal granules have been shown by others to become incorporated into germ-line cells. It is concluded that the GFM is the precursor of this material and that the mitochondrial cloud is the site of its accumulation and localization in the previtellogenic oocyte.

UI	MeSH Term	Description	Entries
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
D008928	Mitochondria	Semiautonomous, self-reproducing organelles that occur in the cytoplasm of all cells of most, but not all, eukaryotes. Each mitochondrion is surrounded by a double limiting membrane. The inner membrane is highly invaginated, and its projections are called cristae. Mitochondria are the sites of the reactions of oxidative phosphorylation, which result in the formation of ATP. They contain distinctive RIBOSOMES, transfer RNAs (RNA, TRANSFER); AMINO ACYL T RNA SYNTHETASES; and elongation and termination factors. Mitochondria depend upon genes within the nucleus of the cells in which they reside for many essential messenger RNAs (RNA, MESSENGER). Mitochondria are believed to have arisen from aerobic bacteria that established a symbiotic relationship with primitive protoeukaryotes. (King & Stansfield, A Dictionary of Genetics, 4th ed)	Mitochondrial Contraction,Mitochondrion,Contraction, Mitochondrial,Contractions, Mitochondrial,Mitochondrial Contractions
D009865	Oocytes	Female germ cells derived from OOGONIA and termed OOCYTES when they enter MEIOSIS. The primary oocytes begin meiosis but are arrested at the diplotene state until OVULATION at PUBERTY to give rise to haploid secondary oocytes or ova (OVUM).	Ovocytes,Oocyte,Ovocyte
D003594	Cytoplasmic Granules	Condensed areas of cellular material that may be bounded by a membrane.	Cytoplasmic Granule,Granule, Cytoplasmic,Granules, Cytoplasmic
D003599	Cytoskeleton	The network of filaments, tubules, and interconnecting filamentous bridges which give shape, structure, and organization to the cytoplasm.	Cytoplasmic Filaments,Cytoskeletal Filaments,Microtrabecular Lattice,Cytoplasmic Filament,Cytoskeletal Filament,Cytoskeletons,Filament, Cytoplasmic,Filament, Cytoskeletal,Filaments, Cytoplasmic,Filaments, Cytoskeletal,Lattice, Microtrabecular,Lattices, Microtrabecular,Microtrabecular Lattices
D005260	Female		Females
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D014981	Xenopus	An aquatic genus of the family, Pipidae, occurring in Africa and distinguished by having black horny claws on three inner hind toes.