scholarly journals AN ELECTRON MICROSCOPE STUDY OF THE EARLY ASSOCIATION BETWEEN TWO MAMMALIAN VIRUSES AND THEIR HOSTS

1962 ◽  
Vol 13 (2) ◽  
pp. 303-322 ◽  
Author(s):  
Samuel Dales
Keyword(s):  
Electron Microscope ◽  
Hela Cells ◽  
Electron Microscope Study ◽  
The Other ◽  
Single Particles ◽  
Thin Sections ◽  
Infectious Process ◽  
Free Particles ◽  
Whole Mount ◽  
Early Interaction

Early interaction between two animal viruses, vaccinia and adenovirus 7, which multiply readily in L strain and HeLa cells, respectively, was examined in both whole mount preparations and in thin sections. To observe the association at the surface, cells carrying adsorbed virus were swelled under controlled conditions and then "stained" with neutral phosphotungstate. Each particle of both virus types becomes attached to the cell by several capsomeres and is then ingested by phagocytosis. Within the cell, near the surface, single particles or small clumps of adenovirus are lodged within vesicles. Deeper in the cytoplasm this virus is packed in large, numerous inclusions, whereas very close to the nuclear envelope only free particles are found. Vaccinia, on the other hand, either free or in vesicles, is always found in the cytoplasm, at some distance from the nucleus (11). Adsorption and intracellular disposition of these two viruses is discussed in relation to the infectious process.

Chromocentres and The Synaptinemal Complex

1970 ◽  
Vol 6 (3) ◽  
pp. 655-667
Author(s):  
L. F. LA COUR ◽  
B. WELLS
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
The Other ◽  
Near Surface ◽  
Thin Sections ◽  
Restricted Movement ◽  
Homologous Chromosomes ◽  
Synaptinemal Complex ◽  
Mother Cells ◽  
Fibrillar Network

The 1-4 chromocentres seen in nuclei of Fritillaria lanceolata, which derive from fusion of heterochromatic segments situated proximal to the centromere in all but two of the 24 chromosomes, were studied with the electron microscope in thin sections of pollen mother cells at zygotene and pachytene, in respect of the synaptinemal complex. Prophase stages of meiosis in two plants were also surveyed briefly with the light microscope. The latter observations revealed that the timing of the separation of heterochromatic segments from chromocentres is genetically controlled. In one plant the segments were still contained in chromocentres at pachytene, whereas in the other they were free at zygotene. At this time they could be identified by a near-surface position in the nucleus and an even condensation concomitant with an absence of chromomeres. In thin section, the fine structure of the chromocentres in zygotene nuclei was distinctive in that the chromatin fibrils were less condensed and more widely dispersed than those in euchromatic regions. The fibrillar network was also interspersed with ‘clear areas’ or channels. After further chromosome condensation, the condensation of fibrils in the chromocentres became equivalent at pachytene to those in euchromatic regions. Synaptinemal complexes were seen at zygotene and pachytene both in euchromatic regions and chromocentres. Their presence in the chromocentres signifies that homologous chromosomes must have been closely paired in regions extending from the centromeres to the distal ends of the heterochromatic segments already at telophase of the last pre-meiotic mitosis. Configurations involving entangled pairs of axial cores, peculiar to zygotene and chromocentres and parts of euchromatic regions proximal to them, are interpreted as resulting from restricted movement.

Reconstruction tridimensionnelle du chondriome de Ginkgo en culture tissulaire; étude au moyen de coupes épaisses et de coupes fines sériées

1979 ◽  
Vol 57 (4) ◽  
pp. 332-340 ◽  
Author(s):  
René Rohr
Keyword(s):  
Electron Microscope ◽  
Cultured Cells ◽  
Three Dimensional ◽  
The Other ◽  
Important Place ◽  
Thin Sections ◽  
Dimensional Models ◽  
Complete Cell ◽  
Three Dimensional Models

The observation of thick sections and serial thin sections with the electron microscope demonstrates a reticular organization of mitochondria in cultured cells from Ginkgo. Thick sections show that most of the mitochondria fuse either in loose networks made up of elongated elements or in dense clusters composed of globular units. Serial thin sections enable us to prove the true reticular nature of the mitochondrial organization; most of the mitochondrial profiles are part of highly fused and branched networks. These mitochondrial reticula (about two to three per cell) occupy an important place within the cell. Some mitochondria remain isolated or they fuse slightly. Two three-dimensional models have been built: the first one constructed with cardboard sheets is used to display the organization of a reticulum; the other of Plexiglas clearly indicates the relative positions and the form of mitochondria in a complete cell. The mitochondria, plastids, and vacuoles of this cell are also measured and enumerated.

AN ELECTRON MICROSCOPE STUDY OF THIN SECTIONS OF HAEMOPHILUS VAGINALIS (GARDNER AND DUKES) AND SOME POSSIBLY RELATED SPECIES

1966 ◽  
Vol 12 (6) ◽  
pp. 1125-1136 ◽  
Author(s):  
Alice Reyn ◽  
A. Birch-Andersen ◽  
S. P. Lapage
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
Electron Microscope ◽  
Lactobacillus Acidophilus ◽  
Related Species ◽  
Electron Microscope Study ◽  
Similar Degree ◽  
Gram Positive ◽  
Thin Sections

The line structure of Haemophilus vaginalis (Gardner and Dukes 1955) was compared with that of four, possibly related species (Butyribacterium rettgeri, Corynebacterium diphtheriae var. mitis, Lactobacillus acidophilus, Haemophilus influenzae) and an unrelated species, Neisseria haemolysans, which had shown a similar degree of Gram-variability as that of H. vaginalis. Although H. vaginalis was first described as a Gram-negative rod, its fine structure, particularly that of cell wall and septa, was more like that of Gram-positive organisms. Also N. haemolysans had a fine structure close to that of Gram-positive organisms, and its typical Gram-positive cell wall varied in. thickness from one cell to another.The study did not solve the problem of the classification of the so-called H. vaginalis, but the appearance of the few strains studied in the electron microscope suggests that it: should be included in Corynebacterium or Butyribacterium rather than in Lactobacillus.

scholarly journals An Electron Microscope Study of the Contractile Vacuole in Tokophrya infusionum

1958 ◽  
Vol 4 (2) ◽  
pp. 195-202 ◽  
Author(s):  
Maria A. Rudzinska
Keyword(s):  
Electron Microscope ◽  
Blood Cells ◽  
Microscope Study ◽  
Electron Microscope Study ◽  
Vacuolar Membrane ◽  
Contractile Vacuole ◽  
Thin Sections ◽  
Mode Of Operation ◽  
Contractile Vacuoles ◽  
Elaborate Structure

Contractile vacuoles are organelles that collect fluid from the cytoplasm and expel it to the outside. After each discharge (systole), they appear again and expand (diastole). They are widely distributed among Protozoa, and have been found also in some fresh water algae, sponges, and recently in some blood cells of the frog, guinea pig, and man. In spite of the extensive work on the contractile vacuole, very little is known concerning its mode of operation. An electron microscope study of a suctorian Tokophrya infusionum provided an opportunity to study thin sections of contractile vacuoles, and in these some structures were found which could be part of a mechanism for the systolic and diastolic motions the organelle displays. In Tokophrya, as in Suctoria and Ciliata in general, the contractile vacuole has a permanent canal connecting it with the outside. The canal appears to have a very elaborate structure and is composed of three parts: (1) a pore; (2) a channel; and (3) a narrow tubule located in a papilla protruding into the cavity of the contractile vacuole. Whereas the pore and channel have fixed dimensions and are permanently widely open, the tubule has a changeable diameter. At diastole it is so narrow (about 25 to 30 mµ in diameter) that it could be regarded as closed, while at systole it is widely open. It is assumed that the change in diameter is due to the contraction of numerous fine fibrils (about 180 A thick) which are radially disposed around the canal in form of a truncated cone, with its tip at the channel, and its base at the vacuolar membrane. It seems most probable that the broadening of the tubule results in discharge of the content of the contractile vacuole. In the vicinity of the very thin limiting vacuolar membrane, small vesicles and canaliculi of the endoplasmic reticulum, very small dense particles, and mitochondria may be found. In addition, rows of closely packed vesicles are present in this region, and in other parts of the cytoplasm. It is suggested that they might represent dictyosome-like bodies, responsible for withdrawing fluids from the cytoplasm and then conveying them to the contractile vacuole, contributing to its expansion at diastole.

scholarly journals OBSERVATIONS WITH THE ELECTRON MICROSCOPE ON THE FINE STRUCTURE OF THE NUCLEI OF TWO SPHERICAL BACTERIA

1961 ◽  
Vol 9 (1) ◽  
pp. 171-181 ◽  
Author(s):  
Woutera Van Iterson ◽  
C. F. Robinow
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Electron Micrographs ◽  
Growth Cycle ◽  
The Other ◽  
Low Density ◽  
Thin Sections ◽  
Dna Molecule

The nuclei of two spherical bacteria have been examined in electron micrographs of thin sections of specimens prepared by the method of Ryter and Kellenberger (1958). The nuclei appear to consist of the same fine fibers in a matrix of low density which have already been seen in many other bacteria prepared by the same procedure. They are worth a separate description because their constituent fibers are arranged in patterns of uncommon orderliness. In the nuclei of one of the two bacteria this is seen at all times, in the nuclei of the other one only at the beginning of the growth cycle. In some places the diameter of the nuclear fibers is close to that of the DNA molecule in the model of Watson and Crick (1953).

An electron microscope study of the internal structure of casein micelles

1964 ◽  
Vol 31 (1) ◽  
pp. 121-123 ◽  
Author(s):  
P. D. Shimmin ◽  
R. D. Hill
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Internal Structure ◽  
Microscope Study ◽  
Electron Microscope Study ◽  
Casein Micelles ◽  
Thin Sections

SummaryA study of casein micelles was made with the electron microscope, using very thin sections cut from micelles embedded in Araldite. The micelles appear to be built up of units that are approximately spherical, about 100 Å in diameter and of about 300000 molecular weight.

scholarly journals ELECTRON MICROSCOPE STUDIES ON BLUE-GREEN ALGAE

1961 ◽  
Vol 9 (1) ◽  
pp. 63-80 ◽  
Author(s):  
Hans Ris ◽  
R. N. Singh
Keyword(s):  
Electron Microscope ◽  
Green Algae ◽  
Animal Cell ◽  
General Pattern ◽  
The Other ◽  
Thin Sections ◽  
Double Membrane ◽  
Photosynthetic Membranes ◽  
Blue Green Algae ◽  
Developmental States

Several species of blue-green algae were studied in thin sections with the electron microscope. Our electron micrographs confirm the view that the cell of blue-green algae is different and simpler in organization than the typical plant or animal cell. On the other hand, the general pattern of ultrastructure is the same as that found in bacteria and Streptomyces. The cell boundary is formed by a double membrane which consists of two typical unit membranes. Situated in between these membranes is the dense inner investment or wall which continues uninterrupted into the cross-walls. The cells always contain photosynthetic lamellae, nucleoplasm with DNA, small granules resembling ribosomes, and often also a number of larger granules of various sorts. The photosynthetic membranes either form the boundary of vesicles or flattened sacs, or, when the lumen of the vesicles disappears and the vesicular surfaces of the membranes zip together, they appear as lamellae made of two closely applied unit membranes. These vesicles or lamellae are disposed irregularly through the cell or arranged in parallel stacks of two or more. A thin layer of cytoplasm always separates the lamellae. The nucleoplasm is composed of masses of fine fibrils about 25 A thick and is either dispersed through the cell or concentrated in polymorphous reticular structures near the center of the cell. The improved resolution of the electron microscope makes it obvious that the terms "chromatoplasm" and "centroplasm" commonly used in the description of blue-green algae are really misleading. There are not different kinds of cytoplasm, but the cell consists of various structural (and functional) units like the ones mentioned above, which are arranged in the cell in a number of ways characteristic for each species or for different physiological or developmental states.

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