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.

scholarly journals ELECTRON MICROSCOPE STUDIES ON THE DICTYOSOMES AND ACROBLASTS IN THE MALE GERM CELLS OF THE CRICKET

1956 ◽  
Vol 2 (4) ◽  
pp. 123-128 ◽  
Author(s):  
H. W. Beams ◽  
T. N. Tahmisian ◽  
R. L. Devine ◽  
Everett Anderson
Keyword(s):  
Electron Microscope ◽  
Golgi Apparatus ◽  
Electron Micrographs ◽  
Germ Cells ◽  
Light Microscope ◽  
Golgi Body ◽  
Duplex Structure ◽  
Male Germ Cells ◽  
Secondary Spermatocyte ◽  
A Chain

The dictyosome (Golgi body) in the secondary spermatocyte of the cricket appears in electron micrographs as a duplex structure composed of (a) a group of parallel double-membraned lamellae and (b) a group of associated vacuoles arranged along the compact lamellae in a chain-like fashion. This arrangement of ultramicroscopic structure for the dictyosomes is strikingly comparable to that described for the Golgi apparatus of vertebrates. Accordingly, the two are considered homologous structures. Associated with the duplex structure of the dictyosomes is a differentiated region composed of small vacuoles. This is thought to represent the pro-acrosome region described in light microscope preparations. In the spermatid the dictyosomes fuse, giving rise to the acroblast. Like the dictyosomes, the acroblasts are made up of double-membraned lamellae and associated vacuoles. In addition, a differentiated acrosome region is present which, in some preparations, may display the acrosome vacuole and granule. Both the dictyosomes and acroblasts are distinct from mitochondria.

The Ultra-fine Structure of Lipid Globules in the Neurones of Helix aspersa

1958 ◽  
Vol s3-99 (46) ◽  
pp. 279-284
Author(s):  
J.T. Y. CHOU ◽  
G. A. MEEK
Keyword(s):  
Methylene Blue ◽  
Fine Structure ◽  
Electron Microscope ◽  
Electron Micrographs ◽  
Light Microscope ◽  
Helix Aspersa

The three kinds of lipid globules recognizable in the living neurones of Helix aspersa have been examined under the electron microscope. The globules of the kind that can be stained blue with methylene blue during life are seen in electron micrographs as spheres or spheroids, with concentric lamination, after calcium-osmium fixation. After fixation with sucrose-osmium laminated crescentic bodies are seen instead; these appear to be formed by distortion of the ‘blue’ globules. The yellow globules contain electrondense material, and sometimes appear reticular. It is possible that the yellow globules may originate by transformation of some of the ‘blue’ globules. The colourless globules generally appear as crenated objects; this appearance may be a shrinkage artifact. Apart from the mitochondria and the three kinds of lipid globules described, no other object large enough to be identified with the light microscope has been seen in the cytoplasm.

scholarly journals An Effective Method of Preparing Sections of Bacillus polymyxa Sporangia and Spores for Electron Microscopy

1960 ◽  
Vol 7 (2) ◽  
pp. 373-376 ◽  
Author(s):  
Pauline E. Holbert
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Electron Micrographs ◽  
Epoxy Resins ◽  
Bacillus Polymyxa ◽  
Thin Sections ◽  
Similar Images ◽  
Embedding Medium ◽  
First Time ◽  
Diamond Knife

Bacillus polymyxa sporangia and spores were prepared for examination in the electron microscope by methods whose critical features were apparently: judicious use of vacuum, to encourage complete penetration of the embedding medium; the use of epoxy resins as embedding media; and cutting of the thin sections with a diamond knife. Electron micrographs of material prepared in this manner exhibit undeformed sporangial sections. Some of the structures revealed have been shown before, though perhaps less distinctly; other structures are revealed here for the first time. While this single study does not pretend to elucidate all the complexities of sporulation in bacteria, these and similar images should make this possible, and some mention of the preparatory techniques that lead to them seems advisable at this time.

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.

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).

scholarly journals STUDIES ON INFLAMMATION

1961 ◽  
Vol 11 (3) ◽  
pp. 571-605 ◽  
Author(s):  
G. Majno ◽  
G. E. Palade
Keyword(s):  
Endothelial Cells ◽  
Electron Microscope ◽  
Basement Membrane ◽  
Blood Vessels ◽  
Electron Micrographs ◽  
Light Microscope ◽  
Intercellular Junctions ◽  
Supporting Evidence ◽  
Electron Microscopic ◽  
Tracer Particles

The mechanism, whereby histamine and serotonin increase the permeability of blood vessels, was studied in the rat by means of the electron microscope. The drugs were injected subcutaneously into the scrotum, whence they diffused into the underlying (striated) cremaster muscle. An intravenous injection of colloidal HgS was also given, in order to facilitate the identification of leaks by means of visible tracer particles. After intervals varying from 1 minute to 57 days the animals were killed; the cremaster was fixed, embedded in methacrylate, and examined with the electron microscope. One to 12 minutes after the injection, the blood vessels of the smallest caliber (3 to 5 micra as measured on electron micrographs) appeared intact. Numerous endothelial openings were present in blood vessels with a diameter of 7 to 8 micra or more. These gaps were 0.1 to 0.8 micra in width; portions of intercellular junctions were often present in one or both of the margins. The underlying basement membrane was morphologically intact. An accumulation of tracer particles and chylomicra against the basement membrane indicated that the latter behaved as a filter, allowing fluid to escape but retaining and concentrating suspended particulate matter of the size used. Uptake of tracer particles by endothelial vesicles was minimal. Phagocytosis by endothelial cells became more prominent at 3 hours, but as a secondary occurrence; the pericytes were actively phagocytic at all stages. At the 3-hour stage no leaks were found. The changes induced by histamine and serotonin were indistinguishable, except that the latter was more potent on a mole-to-mole basis. In control animals only small accumulations of tracer particles were found in the wall of a number of blood vessels. With regard to the pathogenesis of the endothelial leaks, the electron microscopic findings suggested that the endothelial cells become partially disconnected along the intercellular junctions. Supporting evidence was provided at the level of the light microscope, by demonstrating—in the same preparation—the leaks with appropriate tracer particles1, and the intercellular junctions by the silver nitrate method. The lipid nature of the chylomicron deposits observed in electron micrographs was also confirmed at the level of the light microscope, using cremasters fixed in formalin and stained in toto with sudan red.

The effects of oestradiol and relaxin on extensibility and collagen organisation of the pregnant rat cervix

1995 ◽  
Vol 146 (2) ◽  
pp. 331-337 ◽  
Author(s):  
S H Cheah ◽  
K H Ng ◽  
V T Johgalingam ◽  
M Ragavan
Keyword(s):  
Electron Microscope ◽  
Light Microscope ◽  
Late Pregnancy ◽  
Collagen Fibres ◽  
Thin Sections ◽  
Pregnant Rat ◽  
And Control ◽  
Collagen Organisation

Abstract The effects of exogenously introduced oestradiol-17β (E) and relaxin (RLX) on cervical extensibility and collagen organisation were tested in rats ovariectomised in late pregnancy. When the cervices were stretched in vitro by 1 mm increments, it was found that those from rats given E alone generated significantly higher tensions than those from control rats, while cervices from rats given both E and RLX had tensions similar to controls. Examination of cervical sections under the light microscope and ultra-thin sections under the electron microscope showed that the collagen fibres in the cervices from E-treated rats were highly organised, whereas those from animals given E+RLX and control animals were disorganised and dispersed. It was concluded that E decreased cervical extensibility, while RLX counteracted the effect of E to maintain a soft and easily extensible cervix. Journal of Endocrinology (1995) 146, 331–337

scholarly journals STUDIES ON THE FINE STRUCTURE OF THE MAMMALIAN TESTIS

1955 ◽  
Vol 1 (4) ◽  
pp. 287-300 ◽  
Author(s):  
Mario H. Burgos ◽  
Don W. Fawcett
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Golgi Complex ◽  
Nuclear Membrane ◽  
Posterior Margin ◽  
Frequent Occurrence ◽  
Thin Sections ◽  
Acrosomal Vesicle ◽  
Mammalian Testis

The differentiation of cat spermatids was studied in thin sections examined with the electron microscope. The Golgi complex of the spermatid consists of a central aggregation of minute vacuoles, partially surrounded by a lamellar arrangement of flattened vesicles. In the formation of the acrosome, one or more moderately dense homogeneous granules arise within vacuoles of the Golgi complex. The coalescence of these vacuoles and their contained granules gives rise to a single acrosomal granule within a sizable membrane-limited vacuole, termed the acrosomal vesicle. This adheres to the nuclear membrane and later becomes closely applied to the anterior two-thirds of the elongating nucleus to form a closed bilaminar head cap. The substance of the acrosomal granule occupies the narrow cleft between the membranous layers of the cap. The caudal sheath is comprised of many straight filaments extending backward from a ring which encircles the nucleus at the posterior margin of the head cap. Attention is directed to the frequent occurrence of pairs of spermatids joined by a protoplasmic bridge and the origin and possible significance of this relationship are discussed.

The structure of the nematocyst thread and the geometry of discharge in Corynactis viridis Allman

1965 ◽  
Vol 250 (764) ◽  
pp. 131-164 ◽  
Keyword(s):  
Electron Microscope ◽  
Surface Area ◽  
Water Vapour ◽  
Electron Micrographs ◽  
Light Microscope ◽  
Hexagonal Array ◽  
Capsule Wall ◽  
Compact Mass ◽  
Screw Surface ◽  
Flocculent Material

Electron microscope studies reveal that the undischarged nematocyst thread is not (as the light microscope image suggests) a cylinder containing a compact mass of barbs, but a screw, as first shown in the electron micrographs of Bretschneider (1949). In the process of discharge, the screw surface is converted to a cylinder without significant change in surface area. This transformation is markedly anisometric, the length of the thread increasing almost threefold, while the overall increase in diameter is less than 50 %. The screw shape of the undischarged thread is due to the presence of three helical pleats in the membrane; and discharge results in the smoothing out of these. The cavity of the thread is smaller in the undischarged condition—because of the presence of pleats—and is largely filled by the whorls of asymmetrical barbs (three to a whorl); the tips of the barbs are pressed closely together, while their spatulate bases are distributed in open hexagonal array over the pleated surface of the thread. Barbs readily become detached from the surface of the discharged thread, leaving a complex, striated scar. The discharged thread is a slightly tapering tube in holotrichous isorhizas, and the barbs show systematic changes in size and proportions with taper. Electron micrographs show that the cavity of the undischarged thread is filled with a flocculent material, as is the space between the capsule wall and the thread. This material is presumably the highly hygroscopic proteinaceous working substance responsible for the increase in volume of the capsular fluid—at least up to 200 %—on hydration. The undischarged thread and its contents, isolated under anhydrous conditions, are conspicuously hygroscopic and perform movements of elongation and rotation as water vapour is admitted to or removed from the system. The transformation of a membrane in the form of a screw surface to a cylinder, such as occurs in the discharge of the nematocyst thread, is only possible if portions of the membrane in the trough of the screw increase in area, or portions of the pleats decrease in area. The apparent constancy of the area of the thread throughout discharge suggests that both processes may occur.

scholarly journals An Electron Microscopic Study of the Changes in Platelets during Viscous Metamorphosis

Blood ◽  
1962 ◽  
Vol 20 (5) ◽  
pp. 566-580 ◽  
Author(s):  
P. A. CASTALDI ◽  
B. G. FIRKIN ◽  
P. M. BLACKWELL ◽  
K. I. CLIFFORD
Keyword(s):  
Electron Microscope ◽  
Microscopic Study ◽  
Electron Microscopic Study ◽  
Light Microscope ◽  
Phase Contrast ◽  
Intact Cell ◽  
Complete Loss ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Sectioned Material

Abstract Viscous metamorphosis of platelets has been studied with the light microscope, and ultra-thin sections have been prepared at progressive stages for examination in the electron microscope. The phase contrast light microscope reveals rapid aggregation and distortion of platelets and gives the impression of their fusion into structureless aggregates during viscous metamorphosis. Sectioned material collected during viscous metamorphosis of platelets and examined in the electron microscope reveals a remarkable degree of retention of structure in a majority of the platelets. All become deficient in granules and devoid of vesicular spaces, but most retain intact cell membranes, and the structureless masses seen with the light microscope are found to consist of densely aggregated platelets. Fusion and complete loss of identity occurs in the minority. The retracted clot was found to contain densely aggregated, distorted and elongated platelets, empty of granules and intimately related to fibrin particles.

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