Electron Microscopy of Basophilic Structures of Some Invertebrate Oocytes

Abstract

Highly basophilic plate-shaped regions from oocytes of the surf clam have been examined with the electron microscope. The regions are composed of flat, hollow vesicles perforated by pores arranged, in surface view, in a hexagonal pattern. Cross-sections of this structure show a periodicity consisting of loops (cross-sections of the continuous space within the vesicle) alternating with spaces partly filled with dense material (pores). These structures are shown to resemble closely, the nuclear envelope. Similarities to and differences from basophilic regions of other cells are discussed and it is suggested that the small granules of Palade (38) are represented by granules composing the walls of the annuli of the nuclear envelope and assumed to be present in the annuli of the vesicles. Because of differences in the structure of these regions from basophilic regions of other cells, the name periodic lamellae is suggested since the structures show periodically repeating substructures (annuli) in both cross-sections and surface views.

The Fine Structure of Annulate Lamellae

“…Lamellae from salivary gland cells of Drosophila (2) and from frog oocytes (3) are possibly also annulate, but magnification is insufficient for an analysis of their structure. Annulate lamellae from oocytes of the clam Spisula and the snail Otala have previously been described from this laboratory (9,10). This paper supplements these previous observations, and demonstrates similar structures from acinar cells of amphibian pancreas, and from rat spermatids.…”

On the Interrelations between the Macronucleus and the Cytoplasm in the Gymnostome Ciliate <i>Chlamydodon pedarius</i>

“…The size and morphology of these aggregates are very similar to those of the nurse cells of Rhodnius mentioned above. , The ex tensions of the extruding materials from nucleus in echinoderm oocytes (Afzelius, 1955), in Spisula and Otala (Rebhun 1956) and in the growing oocytes of Rana pipiens (Kemp 1956) seem to be much smaller than those of the aggregates described just above, but they may correspond to the simple masses of granules on the outer surface of the macronucleus taken up in this study. The outpocketing of nuclear membrane in salivary gland cells of third instar larvae of Drosophila (Gay 1956), and in spermatid of crayfish (Moses 1956) may correspond to the blisters of the nuclear mem brane of the macronucleus.…”

“…The hypothesis that the nucleo-cytoplasmic interface is a region in which materials from both nucleus and cytoplasm are gathered and there organized into definite, cytoplasmic lamellate structures, has been presented by Rebhun (1956) in the electron microscopic studies of Otala and Spisula oocytes. On the other hand, Ornstein (1956) has presented the suggestive pictures of mito chondrial and nuclear interaction in an early oocyte of Rana clamitans, but he has not given any definite description to the pictures.…”

The Nuclear Envelope after KMnO4 Fixation

“…The first interpretation is compatible with the fact that KMnO,, generally speaking, preserves membranes better than other structures. The small granules associated with the endoplasmic reticulum are not present after KMnO4 (9), and this is a fact of particular interest since a relationship between these granules and the annuli has been suggested by several authors (7,10,12,13). However, thickened rims around the pores are occasionally seen after KMnO4, especially in regions which appear to have been stretched during preparation.…”

“…One can reconcile the differences between OsO4-and KMnO4-fixed material in basically two ways: (1) One can assume that an annulus is a short cylindrical tube (1,14) or a circlet of granules (7,10,13) fitted into or surrounding a pore. KMnOa fixation preserves the membranous parts of the envelope, but permits complete dissolution of the annuli, whereas OsO4 preserves both membranes and annuli.…”