[Ultrastructure of the ovary of Viviparus contectus (Millet, 1813) (Gastropoda, Prosobranchia). II. Oocytes]

The annulate lamellae--from obscurity to spotlight

This review aims to provide a comprehensive and in-depth survey of a cell organelle, the annulate lamellae, that is widely distributed and especially prevalent in both female and male sex cells as well as tumor and cancer cells. The organelle is also present in many somatic cells and plant cells. Emphasis is placed on the contributions that electron microscopy and associated experimental approaches have made in providing information about the distribution, ultrastructure, morphogenesis and relationships of annulate lamellae to other cellular organelles, especially the nuclear envelope and endoplasmic reticulum, as well as cell product. An increasing number of experimental manipulations have recently been shown to alter, either increase or decrease, the amount of annulate lamellae and these studies are explored in depth. Information about the origin and morphogenesis of annulate lamellae in different cells is summarized and extensive coverage is given to several hypotheses about possible annulate lamellae function. A detailed bibliography provides a thorough compilation of research dealing with annulate lamellae. A major goal of this extensive review is to generate increased awareness of, and interest in, this cell organelle for students and investigators of the cell who, by bringing current techniques in cell and molecular biology to bear, might focus and intensify studies on the function of an organelle whose precise role in the cell is presently enigmatic.

The ultrastructural localization of lysosomal acid hydrolases in developing oocytes of the common marine mussel Mytilus edulis

Azo dye techniques were used to investigate the ultrastructural localization of lysosomal acid hydrolases in ovarian oocytes of the common marine mussel Mytilus edulis. The enzymes were arylsulphatase, beta-glucuronidase, nonspecific esterase, N-acetyl-beta-hexosaminidase and acid phosphatase. For arylsulphatase, the azo dye technique was compared with an alternative method using nitrocatechol sulphate as the substrate and barium as the capturing ion. Activity of all the enzymes was found to be associated with the yolk granules and with pinocytotic phenomena which were observed along the basal membrane of developing oocytes. Activity was also found to be associated with resorption of atretic oocytes.

Ultrastructural indications for autosynthetic proteinaceous yolk formation in amphibian oocytes

The formation of proteinaceous yolk is a main feature during amphibian oogenesis. The main bulk is built up by a process called heterosynthesis. The precursor complex vitellogenin is synthesized in the liver, transported by the bloodstream to the ovary, where the oocytes sequester the material by means of endocytosis. This pathway has been described in detail by many authors. The ultrastructural study of amphibian oocytes indicates on the other hand a small but distinct contribution of the oocyte itself towards yolk formation. This process has been called autosynthesis and starts before the onset of heterosynthetic activities. The cell organelles possibly involved in yolk-recursor and yolk-platelet formation are the nuclear envelope, annulate lamellae, endoplasmic reticulum, Golgi complex, GERL and mitochondria. The aim of this paper is to discuss the data, mainly of ultrastructural nature, so far accumulated during the study of autosynthesis. It is hoped to stimulate more biochemically orientated research in this field.

Ultrastructural evidence for both autosynthetic and heterosynthetic yolk formation in the oocytes of an annelid (Phragmatopoma lapidosa: Polychaeta)

The ovaries of the reef-building polychaete Phragmatopoma lapidosa are attached to the genital blood vessels on the caudal surface of the intersegmental septa of the abdominal segments. Oogenesis is not synchronized and vitellogenesis occurs before the oocytes are released from the ovary into the coelomic cavity. A portion of each developing oocyte rests on the basal lamina of the genital blood vessel while the remaining surface of the oocyte is covered by follicle cells. Two morphologically distinct types of yolk are formed during vitellogenesis: Type I, which may be formed autosynthetically by the conjoined efforts of the rough ER and Golgi systems; and Type II, which is presumably formed heterosynthetically from endocytosis of yolk precursors from the genital blood vessel. Heterosynthetic production of yolk in an annelid has not been reported previously.

Oocyte differentiation in Urechis caupo (Echiura): a fine structural study

The fine structure of oocytes of Urechis caupo is described for seven arbitrary stages ranging from the smallest oocytes (7 mum in diameter) in the coelom to the mature oocytes (115 mum in diameter) in the storage organs. Although most types of cytoplasmic organelles accumulate more or less continuously, yolk granules do not appear until oocytes reach a diameter of 35 mum, and there is stage-specific synthesis of cortical granules in 60-80 mum oocytes. In the nucleus a single nucleolus first appears when an oocyte is 15 mum in diameter. Then a nucleolus satellite, which is about 3 mum in diameter, forms in 30 mum oocytes; this nucleolus satellite later (60-70 mum oocytes) becomes surrounded by 750 nm dense spherical bodies. Large (2-4 mum in diameter) juxtachromosomal spherules occur only in the nuclei of mature oocytes. Microvilli become progressively more numerous and longer until the oocyte reaches a diameter of 90 mum; their tips project 1 mum beyond the fibrous surface coat, which is 2 mum thick when well developed. Near the end of oocyte growth, the microvilli retract into the surface coat leaving their pinched-off tips adhering to the outside of the coat.