The Origin and Fate of Annulate Lamellae in Maturing Sand Dollar Eggs

Abstract

Electron micrograph evidence is presented that the nuclear envelope of the mature ovum of Dendraster excentricus is implicated in a proliferation of what appear as nuclear envelope replicas in the cytoplasm. The proliferation is associated with intranuclear vesicles which apparently coalesce to form comparatively simple replicas of the nuclear envelope closely applied to the inside of the nuclear envelope. The envelope itself may become disorganized at the time when fully formed annulate lamellae appear on the cytoplasmic side and parallel with it.The concept of interconvertibility of general cytoplasmic vesicles with most of the membrane systems of the cytoplasm is presented.The structure of the annuli in the annulate lamel]ae is shown to include small spheres or vesicles of variable size embedded in a dense matrix.Dense particles which are about 150 A in diameter are often found closely associated with annulate lamellae in the cytoplasm. Similar structures in other echinoderm eggs are basophilic. In this species, unlike other published examples, the association apparently takes place in the cytoplasm only after the lamellae have separated from the nucleus. If 150 A particles are synthesized by annulate lamellae, as their close physical relationship suggests, then in this species at least the necessary synthetic mechanisms and specificity must reside in the structure of annulate lamellae.

Annulate lamellae‐soleplate nuclei associations in skeletal muscle fibers of rats during chronic high‐dose exposure to neostigmine

“…A third possibility is that the noninvaginated nuclear envelope has a main role in AL formation. The frequent observation of the AL-nucleus association is consistent with the view that the AL may originate from the nuclear envelope by delamination (Afzelius, 1955;Merriam, 1959). A freeze-fracture study of the Drosophia embryos has revealed that pores form a particular packing configuration on the nuclear envelope in the form of hexagonal arrays; the profiles of these pores are indistinguishable from those of the cytoplasmic AL (Stafstrom and Staehelin, 1984).…”

Some Dynamic Aspects of the Nuclear Envelope

“…They are confined to the membrane at the nuclear surface or to membranes probably formed originally at that surface (see e.g. 16,29). It is also noteworthy that while "pores" are present in the membrane on the nuclear surface, extensions of the membrane into the cytoplasm do not show them (see e.g.…”

“…Concentric arrays of membranes, for example, may be seen after virus infection (12) or during certain stages of oogenesis (16,24,29). Similarly, images showing blebbing of the membranous elements of the envelope into the cytoplasm (6,11,30,32) have sometimes (e.g.…”

Intranuclear Annulate Lamellae in Ascidian Embryos

“…However, similar structures have been observed in the pronucleus of the unfertilized sand dollar egg (Merriam, 1959), as well as in the pronuclei of penetrated ova of several mammalian species including man , the hamster FIGURE 1 Nucleus (N) and paranuclear structures. An intranuclear annulate lamella (IAL) is seen near a patch of condensed chromatin (CC).…”