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Biomedical subjects

E ANDERSON

Publications and source records attributed to E ANDERSON.

At least 19 recordsLinked to original sources
PubMed1964

OOCYTE DIFFERENTIATION AND VITELLOGENESIS IN THE ROACH PERIPLANETA AMERICANA.

The ovary of the roach Periplaneta americana has been studied by techniques of light and electron microscopy. Each ovariole (panoistic type) contains a linear array of oocytes in varying stages of development. Newly formed oocytes become encased by a layer of follicle cells and begin pinocytosis. All subsequent growth stages of the oocytes are dependent, in part, on this phenomenon. All of the pinocytotic caveolae show an unique surface modification; i.e., on their internal surface they have an amorphous or filamentous substance and their external surface is studded with many fine radially oriented spike-like projections. The pinosomes of early oocytes do not contain a demonstrable internal structure; they are thought to contain nutritive substances for the developing oocytes rather than yolk precursors. When the oocyte enters its last stage of growth, characterized by yolk deposition, the caveolae become filled with a dense material which is thought to be the precursors of yolk. Hence the conclusion is drawn that yolk formation is independent of any cytoplasmic organelle system of the oocyte and that the precursors of this deutoplasmic substance are manufactured outside the ovary and are internalized by the process of pinocytosis. Under the phase-contrast microscope the nucleoli of early oocytes are large irregular masses and show the phenomenon of nucleolar emission (fragmentation). These "emissions" become randomly dispersed in the nucleoplasm and some of them come to be intimately associated with the fenestrated nuclear envelope. After this process ceases, the main nucleolar mass becomes vacuolated. Electron micrographs suggest that the constituent particles of the nucleolar emissions migrate from the nucleus through patent pores of the nuclear envelope.

Animals↗
PubMed1960

Studies on the fine structure of ultracentrifuged spinal ganglion cells.

THE FOLLOWING STRUCTURES WERE OBSERVED IN ELECTRON MICROGRAPHS OF THE MOUSE SPINAL GANGLION CELLS: Nissl bodies composed of both aggregated rough-type, largely oriented, membranes of the endoplasmic reticulum and discrete particles; short rodlike mitochondria with well-developed transverse, obliquely or longitudinally arranged cristae, and a relatively typical Golgi complex. The components of ultracentrifuged ganglion cells (400,000 times gravity for 20 minutes) are stratified, the layers appearing in the order of their decreasing density as follows: (1) A microsomal or ergastoplasmic layer which may be further divided into three sublayers without sharp boundaries, namely, a discrete particle layer, a layer of discrete particles and highly distorted membranes of the endoplasmic reticulum, and a layer composed of relatively intact, but stretched membranes of the endoplasmic reticulum and discrete particles. (2) Mitochondria constitute a relatively broad layer. They are sometimes stretched; however, they retain most of their fine structure. The stratified nucleus is found within the mitochondrial layer. (3) A relatively wide layer of tightly packed vesicles. (4) At the centripetal end, resting against the cell membrane, are a few lipid vacuoles. A comparison is made between the ultrastructure of the stratified layers in situ and those described by others in differentially ultracentrifuged homogenates.

Animals↗
PubMed1958

Electron microscopic observations on spinal ganglion cells of Rana pipiens after injection of malononitrile.

Spinal ganglionic cells of Rana pipiens were studied with light and electron microscopes in normal animals and in animals which had received graded dosages of malononitrile intraperitoneally. After treatment no increase in the intensity of staining was noted in the Nissl substance when spinal ganglion cells were examined with the light microscope. The electron micrographs demonstrated the following in malononitrile-treated animals: 1. The cisternae of the endoplasmic reticulum composing the Nissl bodies appeared to fragment and lose their parallel orientation. 2. The microvesicular components of the Golgi complex appeared to increase in number, and the increase was apparently due to fragmentation of the membrane system of the Golgi complex. 3. The mitochondria enlarged and became pleomorphic, but displayed no alterations of internal structure. The morphological changes may be interpreted as reflections of biochemical alterations.

Animals↗