Sant S. Sekhon

Morphological studies on secretion in the silk glands of the caddis fly larvae, Platyphylax designatus Walker.

SummaryActively secreting silk gland cells of caddis fly larvae show the following fine structure: a well developed rough-surfaced endoplasmic reticulum, continuity between roughsurfaced and smooth-surfaced endoplasmic reticulum adjacent to the Golgi saccules, dense material (secretion) in the margins of the Golgi saccules, some of which appear in the form of blebs and discrete membane bounded secretion granules; the latter seem to coalesce and migrate to the surface of the cell where they are discharged. Intracisternal granules appear in glands where the secretion cycle has apparently been interrupted. These observations suggest a secretion cycle for the silk glands comparable to that demonstrated by both morphological and experimental methods in certain other protein secreting cells: namely, synthesis by the ribosomes, transport to the Golgi complex through the cisternae of the endoplasmic reticulum, concentration by the Golgi complex and movement of the secretion granules through the cytoplasm to the surface of the cell where they are discharged.

Fine structure of the body wall and cells in the pseudocoelom of the nematode Rhabditis pellio

Electron microscope studies have revealed the detailed structure of the layers in the body wall of Rhabditis pellio; namely, cuticle, hypodermis, and muscular layer. The pseudocoelom contains the intestine, gonads, and groups of cells thought to be glandular and components of the ill-defined excretory or coelomocyte systems. The gland-like cells are differentiated into an apical region including the surface, nucleus, and mitochondria and a basal region composed of a dense homogeneous cytoplasm free of cellular components. These cells possess numerous surface pores that are continuous with microvilli-lined surface membrane-invaginated pockets. Cells not in contact with the surface through the pore show vesicles, presumably secretory, located opposite and in apparent continuity with the pore. This type of surface architecture differs somewhat from that previously reported, but undoubtedly performs a similar function; namely, the increase in surface area and hence, the functional efficiency of these cells.

Fine structure of the nucleolus in the young oocyte of a centipede

SummaryThe young oocyte of the centipede Scutigera forceps possesses numerous nucleoli which vary considerably in size. The electron microscope reveals them to be composed of small ribosome-like granules (probably RNP), relatively dense matrix, and, in some cases, a poorly defined nucleolonema.The appearance of lamellae at the surface of the nucleoli is of special interest. These consist of nucleolar material, are about 70 mμ in thickness, and of much greater width. They encircle the nucleolus, forming a relatively large concentric body, and in some instances probably extend from one nucleolus to another. In that case, the lamellae may represent a means of transfer from one nucleolus to another.

Further studies on the fine structure of Lophomonas blattarum with special reference to the so-called calyx, axial filament, and parabasal body.

The calyx in Lophomonas blattarum is composed of longitudinally arranged lamellae, each consisting of a single row of microtubules. Small tubules 2–3 μ in length radiate from the nucleus. They appear continuous with the outer membrane of the nuclear envelope and they may be divided into two segments: proximal ones covered with ribosomes (rough-surfaced) and distal ones which are agranular (smooth-surfaced). The latter are surrounded by numerous granules considered to be glycogen, a circumstance which supports the view that the agranular segments of the tubules, like the agranular endoplasmic reticulum are involved in glycogen storage. It is suggested that both the rough- and smooth-surfaced segments of the perinuclear tubules are equal to the rough- and smooth-surfaced endoplasmic reticulum of other cells. Inside the nucleus and adjacent to its envelope is a well developed fibrous lamina.