Freeze fracture and scanning electron microscope studies on the nuclear envelope and perinuclear cytomembranes (parabasal apparatus) in the protozoan, Lophomonas blattarum.

Phase contrast, scanning electron microscope (SEM), and freeze fracture studies on the parasitic flagellate, Lophomonas blattarum, have demonstrated that the endomembrane system (parabasal apparatus) is highly ordered, restricted in position to a perinuclear zone at the anterior end of the organism, and is supported in this localized cytoplasmic region by overlapping sheets or plates of microtubules, previously called the calyx and axial filament, which may participate in supporting the nucleus-endomembrane system in a restricted region of the cell. Light microscope observations, SEM and freeze fracture data provide support to previous views that the rough- and smooth-surfaced endoplasmic reticulum are interconnected and attached to the outer layer of the nuclear envelope. The continuity of these membrane systems provides an orderly and restricted packing in the perinuclear cytoplasm since other areas of the cell may become filled with yeast.

Is the nuclear envelope a 'generator' of membrane? Developmental sequences in cytomembrane elaboration.

Early diplotene oocytes from Necturus maculosus ranging from approximately 0.2 to 0.5 mm in diameter were examined by electron microscopy.

The presence and distribution of gap junctions in the oocyte-follicle cell complex of the zebrafish, Brachydanio rerio.

Membranes of teleost female gametes and investing layer of follicle cells characteristically exhibit a prolonged, close spatial relationship. This relationship is manifested, in part, by numerous folds of the plasma membrane of both oocyte and follicle cells that extend through channels called pore canals within a thick, laminated extracellular coat, the vitelline membrane. During oogenesis the folded oocyte processes, or microvilli, increase in number and length, but decrease in width.

Relationships between annulate lamellae and filament bundles in oocytes of the zebrafish, Brachydanio rerio.

Bundles of filaments have been observed in the vitellogenic oocyte of the zebrafish, Brachydanio rerio; and these filaments illustrate a close spatial and structural relationship to annulate lamellae. The filaments range from 6-8 nm in diameter, and the annulate lamellae may cap both rounded ends of the bundle as well as extend parallel to the surface of the filament bundles. The ends of the filaments can be observed to exhibit an apparent termination in close relation to pore margins of the annulate lamellae, the membrane of the interpore regions of the annulate lamellae, as well as many nearby polyribosomes.

Intracisternal tubules and intramitochondrial filaments in cells of a snail, Limnaea.

Epithelial and peritubular cells associated with the reproductive tract of the snail, Limnaea stagnalis, contain an extensive system of endoplasmic reticulum that is often dilated with many closely packed intracisternal tubules. The intracisternal tubules are approximately 24-28 nm in diameter and they are often hexagonally packed. They have a two-layered wall, possess fine interconnections, and extend linearly for considerable distances, but angular bends in the tubules also occur.

Cytodifferentiation and vitellogenesis during oogenesis in arachnida: Cytological studies on developing oocytes of a harvestman.

Light and electron microscope studies were made on harvestman oocytes during the course of their origin, differentiation, and vitellogenesis. The germ cells appear to originate from the ovarian epithelium. They subsequently migrate to the outer surface of the epithelium, where they remain attached often by means of stalk cells which suspend them in the hemocoel during oogenesis.

Annulate lamellae and "yolk nuclei" in oocytes of the dragonfly, Libellula pulchella.

Annulated membranes in the form of single and short lamellae are present adjacent to and parallel to the nuclear envelope in oogonia and early oocyte (synaptene) stages of the dragonfly, Libellula pulchella. These solitary and short annulate lamellae are usually continuous with long, part rough- and part smooth-surfaced cisternae which extend into more distal areas of the oogonial ooplasm. These particular annulate lamellae then either disappear or decrease in number to be replaced by a much more extensive system of annulate lamellae in the cortical ooplasm of previtellogenic oocytes.