scholarly journals EVIDENCE FROM ELECTRON MICROGRAPHS FOR THE PASSAGE OF MATERIAL THROUGH PORES OF THE NUCLEAR MEMBRANE

1956 ◽  
Vol 2 (4) ◽  
pp. 439-444 ◽  
Author(s):  
Everett Anderson ◽  
H. W. Beams
Keyword(s):  
Electron Micrographs ◽  
Nuclear Membrane ◽  
Relative Size ◽  
Nurse Cells ◽  
Feulgen Reaction ◽  
Process Of Or ◽  
Show Evidence

1. The nurse cells of Rhodnius possess nucleoli that stain with Heidenhain's hematoxylin but give a negative Feulgen reaction. In localized positions adjacent to the nuclear membrane are seen masses of material both within the nucleus and the adjoining cytoplasm that stain with Heidenhain's hematoxylin, but, like the nucleolus, give a negative Feulgen reaction. 2. Electron micrographs of the nurse cells of Rhodnius reveal the nuclear membrane to contain pores approximately 400 A in diameter. 3. In electron micrographs the nucleolus is seen to be composed of a reticulum containing tightly packed granules. Between the centrally located nucleolus and the nuclear membrane are observed relatively small bunches of granules of the same relative size as those occurring in the nucleolus. Aggregated at certain positions adjacent to the nuclear membrane both within the nucleus and in the adjoining cytoplasm are irregularly shaped masses of granules. Certain of these masses within the nucleus are seen to be continuous with those in the cytoplasm through narrow isthmuses of material extending through pores of the nuclear membrane. Other masses of granules show evidence of preparing to enter the pores by projecting tongues of material toward and into them. In the adjacent cytoplasm pear-shaped masses of granules are seen in front of and in contact with the pores which suggests that they were fixed in the process of or just after completing passage through the pores.

Interpreting HVEM of muscle-cell impulse networks

1992 ◽  
Vol 50 (1) ◽  
pp. 126-127
Author(s):  
Paul DeCosta ◽  
Kyugon Cho ◽  
Stephen Shemlon ◽  
Heesung Jun ◽  
Stanley M. Dunn
Keyword(s):  
Structural Analysis ◽  
Muscle Cell ◽  
Electron Micrographs ◽  
Relative Size ◽  
Automatic Classification ◽  
Nerve Fibers ◽  
Analysis Algorithm ◽  
Structural Networks

Introduction: The analysis and interpretation of electron micrographs of cells and tissues, often requires the accurate extraction of structural networks, which either provide immediate 2D or 3D information, or from which the desired information can be inferred. The images of these structures contain lines and/or curves whose orientation, lengths, and intersections characterize the overall network.Some examples exist of studies that have been done in the analysis of networks of natural structures. In, Sebok and Roemer determine the complexity of nerve structures in an EM formed slide. Here the number of nodes that exist in the image describes how dense nerve fibers are in a particular region of the skin. Hildith proposes a network structural analysis algorithm for the automatic classification of chromosome spreads (type, relative size and orientation).

scholarly journals Geotropic Response of Wheat Coleoptiles in Absence of Amyloplast Starch

1966 ◽  
Vol 49 (5) ◽  
pp. 1065-1086 ◽  
Author(s):  
Barbara Gillespie Pickard ◽  
Kenneth V. Thimann
Keyword(s):  
Electron Micrographs ◽  
Triticum Durum ◽  
Asymmetric Distribution ◽  
Ordinary Sense ◽  
Starch Grains ◽  
Fixed Material ◽  
Show Evidence

Young coleoptiles of wheat (Triticum durum var. Henry), depleted of amyloplast starch by incubation at 30°C with gibberellin plus kinetin, retained their geotropic responsiveness. Depleted coleoptiles curved upward more slowly than controls, but this was commensurate with their slower growth. The ratio of curvature to growth was about 50° per mm of elongation in both cases. Newly excised coleoptiles, though containing much more starch than incubated controls, curved only about 25° per mm. The tissue treated in gibberellin plus kinetin appeared to contain no starch when examined (a) freshly squashed, (b) as fixed material sectioned thin and stained by the PAS procedure, and (c) as electron micrographs. Shrunken, starch-free amyloplasts could be identified in certain regions, but these did not show evidence of asymmetric distribution under the influence of gravity. The possibilities that other organelles function as statoliths are considered, and it is concluded not only that georeception is independent of starch grains, but further that it may not be due to statoliths at all in an ordinary sense.

scholarly journals CHROMOSOME-NUCLEAR MEMBRANE-CYTOPLASMIC INTERRELATIONS IN DROSOPHILA

1956 ◽  
Vol 2 (4) ◽  
pp. 407-414 ◽  
Author(s):  
Helen Gay
Keyword(s):  
Drosophila Melanogaster ◽  
Salivary Gland ◽  
Larval Development ◽  
Electron Micrographs ◽  
Nuclear Membrane ◽  
Membrane Structure ◽  
Deoxyribonucleic Acid ◽  
Cellular Function ◽  
Gland Cells ◽  
Salivary Gland Cells

The structural evidence for nucleocytoplasmic interrelationships observed in electron micrographs of salivary-gland cells of third instar larvae of Drosophila melanogaster has been reviewed. It has been found that the characteristic nuclear membrane outpocketings with their adjacent highly differentiated chromosomal materials occur at one stage of larval development at a time when a new cellular function is being initiated. Preliminary cytochemical studies to characterize the materials transferred from nucleus to cytoplasm indicate that deoxyribonucleic acid occurs within the blebs. Observations on chromosome and nuclear membrane structure are also presented.

scholarly journals STRUCTURE AND DEVELOPMENT OF VIRUSES OBSERVED IN THE ELECTRON MICROSCOPE

1956 ◽  
Vol 2 (3) ◽  
pp. 351-360 ◽  
Author(s):  
Councilman Morgan ◽  
Calderon Howe ◽  
Harry M. Rose ◽  
Dan H. Moore
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
Nuclear Membrane ◽  
Hela Cells ◽  
Light Microscope ◽  
Thin Sections ◽  
Viral Particles ◽  
Crystalline Aggregates ◽  
Internal Body

Representative viruses of the RI-APC group were observed with the electron microscope in thin sections of infected HeLa cells. The viral particles varied in density, were approximately 60 mµ in diameter and had a center to center spacing when close packed of about 65 mµ. Many of the less dense particles exhibited an internal body averaging 24 mµ in diameter. It was suggested that within the nucleus the virus differentiated from dense granular and reticular material and formed crystals. Disintegration of the crystals and disruption of the nuclear membrane with release of virus into the cytoplasm appeared to occur at any stage. No evidence to suggest development of the virus in the cytoplasm was obtained. It was possible to deduce the structure of the viral crystal from the electron micrographs. The viral particles are packed in a cubic body—centered lattice. Correlative histochemical observations in the light microscope which are now in progress revealed that the crystals and non-crystalline aggregates of virus were strongly Feulgen-positive.

The role of microfilaments in cytoplasmic streaming in Drosophila follicles

1986 ◽  
Vol 80 (1) ◽  
pp. 159-169 ◽  
Author(s):  
H.O. Gutzeit
Keyword(s):  
Cell Membrane ◽  
Nuclear Membrane ◽  
Actin Filaments ◽  
Cytoplasmic Streaming ◽  
Nurse Cell ◽  
Time Lapse ◽  
Nurse Cells ◽  
Cell Nuclei ◽  
Cell Cytoplasm

During the last phase of oogenesis in Drosophila, nurse cell cytoplasm can be seen to be streaming into the growing oocyte when visualized in time-lapse films. This process can be reversibly inhibited by cytochalasins. The distribution of F-actin filaments in the nurse cells has been studied by staining with rhodamine-conjugated phalloidin. At the beginning of cytoplasmic streaming (stage 10B) increasingly thick bundles of microfilaments formed, many of which spanned the nurse cell cytoplasm from the cell membrane to the nuclear membrane. The association of F-actin with the nuclear membrane persisted when nurse cell nuclei were isolated mechanically. The experimental evidence suggests that microfilament contraction in the nurse cells leads to cytoplasmic streaming by pressure flow.

Memoirs: The Rôles of the Nurse-cells, Oocytes and Follicle-cells in Tenthredinid Oogenesis

1928 ◽  
Vol s2-71 (284) ◽  
pp. 541-561
Author(s):  
A. D. PEACOCK ◽  
R.A. R. GRESSON
Keyword(s):  
Nuclear Membrane ◽  
Nurse Cell ◽  
Follicle Cell ◽  
Narrow Channel ◽  
Nuclear Material ◽  
Follicle Cells ◽  
Nurse Cells ◽  
Accessory Nuclei ◽  
Dark Staining ◽  
The Common

1. Ovary formation in Tenthredinidae follows the general hymenopterous plan. 2. Nurse-cell phenomena are as follows: the nuclei of the first nutritive chamber are surrounded by a chromatin cloud and many of them contain irregular darkly-staining masses of nuclear material, which masses may also be present in the riper chambers; the granules given off from the nuclei into the chromatin cloud eventually become surrounded by a vesicle and give rise to the ‘secondary’ or ‘accessory’ nuclei. 3. Oocyte nucleolar phenomena show the following: the nucleoli in Thrinax mixta and Platycampus luridiventris give rise to buds which become free; in one case buds were observed close to the inner surface of the nuclear membrane in Allantus (Emphytus) pallipes are shown what are apparently later stages of this process, viz. the passage of the buds through the nuclear membrane into the egg substance and their formation there into accessory nuclei. 4. The fate of the nurse-cells is shown in the older nutritive chambers and oocytes--the cell boundaries become indistinct and some of the cytoplasm, together with contained accessory nuclei, passes by a narrow channel into the oocyte. The cytoplasmic flow becomes more marked in the last chamber. In the final stages, shown in the last chamber, all the cells lose their boundaries and the common cytoplasm passes into the oocyte, carrying with it the free nuclei to their engulfment and absorption in the ooplasm. 5. Some of the follicle-cells surrounding the last oocyte in Pristiphora padi, and the fifth, sixth, and seventh of Thrinax mixta, contain granular dark-staining material which may completely fill the cell, these granules probably originating from the nucleus. They pass out of the follicle-cell into the egg where they become surrounded by vesicles, and, finally, present an appearance indistinguishable from that of accessory nuclei. 6. Secondary or accessory nuclei, therefore, have a threefold origin, namely, from the nuclei, of nurse-cells and oocytes and from follicle-cells, their source of derivation in the last being the follicular nuclei. 7. The follicle-cells of the distal pole of the last oocyte of one ovariole of Pristiphora padi have processes which insinuate themselves into the ooplasm. 8. The phenomena of oogenesis described in these four species of sawflies, while embracing certain which have not hitherto been recorded, conform, in essentials, with those already discovered for Hymenoptera generally.

scholarly journals ULTRASTRUCTURE OF DNA-CONTAINING AREAS IN THE CHLOROPLAST OF CHLAMYDOMONAS

1962 ◽  
Vol 13 (3) ◽  
pp. 383-391 ◽  
Author(s):  
Hans Ris ◽  
Walter Plaut
Keyword(s):  
Acridine Orange ◽  
Electron Micrographs ◽  
Genetic System ◽  
Feulgen Reaction ◽  
Electron Microscopic ◽  
Chlamydomonas Moewusii

The chloroplast of Chlamydomonas moewusii was examined by electron microscopic and cytochemical methods for the possible presence of DNA. Both the Feulgen reaction and acridine orange indicated the presence within the chloroplast of one or more irregularly shaped DNA-containing bodies generally in the vicinity of the pyrenoid. Electron micrographs revealed 25 A microfibrils in these areas which correspond to DNA macromolecules with respect to their location, morphology, and sensitivity to deoxyribonuclease digestion. The possibility that this material is the genetic system of the chloroplast and the hypothesis that the chloroplast represents an evolved endosymbiont are discussed.

Utilizing Dark Field Electron Microscopy to Produce Lantern Slides

1974 ◽  
Vol 32 ◽  
pp. 116-117
Author(s):  
J. N. Meador ◽  
C. N. Sun ◽  
H. J. White
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
Dark Field ◽  
Limiting Factor ◽  
Clinical Laboratories ◽  
Field Electron ◽  
Time Element ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Dark Field Micrographs

The electron microscope is being utilized more and more in clinical laboratories for pathologic diagnosis. One of the major problems in the utilization of the electron microscope for diagnostic purposes is the time element involved. Recent experimentation with rapid embedding has shown that this long phase of the process can be greatly shortened. In rush cases the making of projection slides can be eliminated by taking dark field electron micrographs which show up as a positive ready for use. The major limiting factor for use of dark field micrographs is resolution. However, for conference purposes electron micrographs are usually taken at 2.500X to 8.000X. At these low magnifications the resolution obtained is quite acceptable.

Light Optical Diffraction Studies of Macromolecular Ultrastructure

1970 ◽  
Vol 28 ◽  
pp. 258-259
Author(s):  
Glen B. Haydon
Keyword(s):  
High Resolution ◽  
Diffraction Analysis ◽  
Diffraction Pattern ◽  
Electron Micrographs ◽  
Optical Diffraction ◽  
Electron Micrograph ◽  
Its Analysis ◽  
Resolution Electron ◽  
Diffraction Patterns

Analysis of light optical diffraction patterns produced by electron micrographs can easily lead to much nonsense. Such diffraction patterns are referred to as optical transforms and are compared with transforms produced by a variety of mathematical manipulations. In the use of light optical diffraction patterns to study periodicities in macromolecular ultrastructures, a number of potential pitfalls have been rediscovered. The limitations apply to the formation of the electron micrograph as well as its analysis.(1) The high resolution electron micrograph is itself a complex diffraction pattern resulting from the specimen, its stain, and its supporting substrate. Cowley and Moodie (Proc. Phys. Soc. B, LXX 497, 1957) demonstrated changing image patterns with changes in focus. Similar defocus images have been subjected to further light optical diffraction analysis.

The Cellular Origin in Atheromatous Lesion

1970 ◽  
Vol 28 ◽  
pp. 202-203
Author(s):  
T. M. Murad ◽  
H. A. I. Newman ◽  
K. F. Kern
Keyword(s):  
Smooth Muscle ◽  
Smooth Muscle Cells ◽  
Rabbit Aorta ◽  
Mixed Population ◽  
The Other ◽  
Cellular Origin ◽  
Ultrastructural Studies ◽  
Atherosclerotic Lesions ◽  
Show Evidence ◽  
Early Lesion

The origin of lipid containing cells in atheromatous lesion has been disputed. Geer in his study on atheromatous lesions of rabbit aorta, suggested that the early lesion is composed mainly of lipid-laden macrophages and the later lesion has a mixed population of macrophages and smooth muscle cells. Parker on the other hand, was able to show evidence that the rabbit lesion is primarily composed of lipid-laden cells of smooth muscle origin. The above studies and many others were done on an intact lesion without any attempt of cellular isolation previous to their ultrastructural studies. Cell isolation procedures have been established for atherosclerotic lesions through collagenase and elastase digestion Therefore this procedure can be utilized to identify the cells involved in rabbit atheroma.

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