scholarly journals CYTOPLASMIC FILAMENTS OF AMOEBA PROTEUS

1970 ◽  
Vol 46 (2) ◽  
pp. 267-289 ◽  
Author(s):  
Thomas D. Pollard ◽  
Susumu Ito
Keyword(s):  
Electron Microscopy ◽  
Normal Structure ◽  
Amoeba Proteus ◽  
Second Phase ◽  
Polarization Microscopy ◽  
Electron Microscopic ◽  
Thin Filaments ◽  
Cytoplasmic Filaments ◽  
Two Phases ◽  
Birefringent Fibrils

The role of filaments in consistency changes and movement in a motile cytoplasmic extract of Amoeba proteus was investigated by correlating light and electron microscopic observations with viscosity measurements. The extract is prepared by the method of Thompson and Wolpert (1963). At 0°C, this extract is nonmotile and similar in structure to ameba cytoplasm, consisting of groundplasm, vesicles, mitochondria, and a few 160 A filaments. The extract undergoes striking ATP-stimulated streaming when warmed to 22°C. Two phases of movement are distinguished. During the first phase, the apparent viscosity usually increases and numerous 50–70 A filaments appear in samples of the extract prepared for electron microscopy, suggesting that the increase in viscosity in caused, at least in part, by the formation of these thin filaments. During this initial phase of ATP-stimulated movement, these thin filaments are not detectable by phase-contrast or polarization microscopy, but later, in the second phase of movement, 70 A filaments aggregate to form birefringent microscopic fibrils. A preparation of pure groundplasm with no 160 A filaments or membranous organelles exhibits little or no ATP-stimulated movement, but 50–70 A filaments form and aggregate into birefringent fibrils. This observation and the structural relationship of the 70 A and the 160 A filaments in the motile extract suggest that both types of filaments may be required for movement. These two types of filaments, 50–70 A and 160 A, are also present in the cytoplasm of intact amebas. Fixed cells could not be used to study the distribution of these filaments during natural ameboid movement because of difficulties in preserving the normal structure of the ameba during preparation for electron microscopy.

scholarly journals HYDROLYTIC ENZYMES DURING SPERMATOGENESIS IN RAT AN ELECTRON MICROSCOPIC AND HISTOCHEMICAL STUDY

1968 ◽  
Vol 16 (4) ◽  
pp. 249-262 ◽  
Author(s):  
ZOLTAN POSALAKI ◽  
DEZSÖ SZABÓ ◽  
ERNÖ BÁCSI ◽  
ISTVÁN ÖKRÖS
Keyword(s):  
Endoplasmic Reticulum ◽  
Enzyme Activity ◽  
Acid Phosphatase ◽  
Sertoli Cells ◽  
Hydrolytic Enzymes ◽  
Appreciable Amount ◽  
Second Phase ◽  
Nonspecific Esterase ◽  
Electron Microscopic ◽  
Two Phases

The localization of lipids and the activities of nonspecific esterase, aryl sulfatase and acid phosphatase were studied in different stages of spermatogenesis in rats. In addition, the distribution of acid phosphatase activity was demonstrated electron histochemically. The spermatogenetic cycle was divided into two phases—corresponding to the first and the last four stages of Roosen-Runge-Giesel (RG) classification. Spermatids in the first phase contained abundant endoplasmic reticulum with rosette formation and well developed Golgi apparatus with numerous vesicles. They displayed high activity of hydrolytic enzymes but contained no appreciable amount of lipids. The Sertoli cells contained large lipid granules but showed minimal enzyme activity. During the second phase reduction of the cytoplasm of spermatids with fragmentation of the endoplasmic reticulum and Golgi lamellae, accumulation of lipids, aggregation of ribonucleo-protein particles, formation of residual bodies and marked decrease of enzyme activity were seen. The Sertoli cells contained large mitochondria, well developed endoplasmic reticulum and numerous dense bodies and revealed high activities of hydrolytic enzymes and rapid depletion of lipids. These ultrastructural and histochemical findings suggested an interaction between the Sertoli cells and the developing spermatids which probably contributed to the regulation of spermatogenesis.

scholarly journals Underwater Shock Response of Circular HSLA Steel Plates

2000 ◽  
Vol 7 (4) ◽  
pp. 251-262 ◽  
Author(s):  
R. Rajendran ◽  
K. Narasimhan
Keyword(s):  
Hsla Steel ◽  
Underwater Explosion ◽  
High Strength ◽  
Steel Plates ◽  
Analytical Models ◽  
Second Phase ◽  
Electron Microscopic ◽  
Shock Response ◽  
Slant Fracture ◽  
Two Phases

Studies on shock response of circular plates subjected to underwater explosion is of interest to ship designers. Non-contact underwater explosion experiments were carried out on air backed circular High Strength Low Alloy (HSLA) steel plates of 4 mm thickness and 290 mm diameter. The experiments were carried out in two phases. In the first phase, strain gauges were fixed at intervals of 30 mm from the centre of the plate and strains were recorded for the shock intensity gradually increasing to yielding. Semi-analytical models were derived for the elastic strain prediction which showed good agreement with the experiments. Dynamic yield stress and the shock factor for yielding were established. In the second phase, individual plates were subjected to increasing shock severity until fracture and the apex bulge depth and the thickness strains were measured. Empirical models were derived to predict the plastic deformation which were validated through a fresh set of experiments. Analysis of the fractured surface by visual examination showed that there was slant fracture indicating ductile mode of failure and the same was corroborated by Scanning Electron Microscopic (SEM) examination.

An electron microscopic study of Amoeba proteus

1959 ◽  
Vol 150 (939) ◽  
pp. 216-232 ◽  
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Microscopic Study ◽  
Electron Microscopic Study ◽  
Amoeba Proteus ◽  
Contractile Vacuole ◽  
Electron Microscopic ◽  
Functional Implications ◽  
Food Vacuoles

Methods of fixing, embedding and sectioning of Amoeba proteus for electron microscopy are described. The fine structure of the various organelles: nucleus, mitochondria, food vacuoles; and the contractile vacuole, is discussed in detail. A number of minor unidentified objects has also been found. The functional implications of the structural findings are considered.

scholarly journals FINE STRUCTURAL DEMONSTRATION OF ORDERED ARRAYS OF CYTOPLASMIC FILAMENTS IN VERTEBRATE IRIDOPHORES

1974 ◽  
Vol 62 (2) ◽  
pp. 295-304 ◽  
Author(s):  
Susannah T. Rohrlich
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Vertebrate Species ◽  
Thin Filaments ◽  
Ordered Arrays ◽  
Cytoplasmic Filaments

Thin and thick sections of both physiologically active and physiologically passive iridophores from a range of vertebrate species have been examined by electron microscopy at 60 kV and at 1,000 kV. All iridophores studied have been found to contain 65-Å filaments linking successive crystals in their parallel stacks; their orientation in the cell is shown in stereo pairs of 0.25-µm sections obtained from high voltage microscopy. In addition, several of the physiologically passive iridophores contain 100-Å filaments in varying numbers. It is suggested that the thin filaments might be iridophore actin and play a role in the movement of iridophore components, and that the 100-Å filaments might play a cytoskeletal role in the iridophores in which they occur.

The Structure and Properties of MoSi2-Mo5Si3 Composites

1992 ◽  
Vol 273 ◽  
Author(s):  
H. Kung ◽  
D. P. Mason ◽  
A. Basu ◽  
H. Chang ◽  
D. C. Van Aken ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Second Phase ◽  
Structure And Properties ◽  
Transmission Electron ◽  
Interfacial Structures ◽  
Two Phases ◽  
Hardness Values

ABSTRACTThe addition of Mo5Si3 as a reinforcing second phase in a MoSi2 matrix has been investigated for possible high temperature strengthening effects. MoSi2 with up to 45 vol % Mo5Si3 was fabricated using powder metallurgy (PM) and arc-casting (AC) techniques. Effects of processing routes, which result in different microstructures, on their mechanical properties are given. PM composites, which have an equiaxed microstructure, exhibit a limited increase in hardness. Higher hardnesses are observed in script-structured AC eutectics and Er-modifiedeutectics throughout the temperatures studied (25–1300°C). Crack propagation paths induced by indentation show long transphase cracks in the AC materials vs short intergranular and interphase cracks in the PM composites at high temperatures.Transmission electron microscopy discloses that the interface in the AC composites has a low-index orientation relationship between the two phases and shows regularly faceted interfacial structures, while planar interfaces are found in the PM composites. These observations suggest the interface is stronger and lower in energy in the AC composites, which is consistent with the higher hardness values and long transphase cracks observed.Dislocation analysis shows the presence of ordinary dislocations (<100>, <110> and 1/2<111>) in MoSi2 in the as-fabricated composites. These types of dislocation are also responsible for the high temperature plastic deformation in compression in both the monolithic MoSi2 and the composites. <331> types of dislocation are only found in MoSi2 either near the interface of the AC composites or in materials deformed below 1000°C.

Temporal deposition and spatial distribution of cytoskeletal proteins in the sperm head of an Australian rodent

2009 ◽  
Vol 21 (3) ◽  
pp. 428 ◽  
Author(s):  
William G. Breed ◽  
Dina Idriss ◽  
Christopher M. Leigh ◽  
Richard J. Oko
Keyword(s):  
Electron Microscopy ◽  
Spatial Distribution ◽  
Light And Electron Microscopy ◽  
Sperm Head ◽  
Cytoskeletal Proteins ◽  
Concave Surface ◽  
Second Phase ◽  
Protein Deposition ◽  
Murine Rodent ◽  
Two Phases

The Australian murine rodent, the plains mouse (Pseudomys australis), possesses a highly complex sperm head, in which there are, in addition to an apical hook, two ventral processes that extend from its upper concave surface. The present study set out to determine the temporal deposition and distribution of the proteins within these structures during late spermiogenesis by light and electron microscopy using various antibodies to bull and laboratory rat sperm-head cytoskeletal proteins. The findings show that there are two phases of protein deposition. In the first phase, perinuclear theca proteins are deposited at the base of the ventral processes around the acrosomal extensions of the developing spermatids. In the second phase, as the ventral processes expand, actin and then perforatorial proteins are laid down during which time the processes become progressively more bilaterally flattened. These various proteins are moulded together to give rise to the two very large cytoskeletal structures that extend from the upper concave surface of the sperm head. They may be involved in binding the spermatozoon to the outer surface of the zona pellucida and/or in aiding the spermatozoon in zona penetration at the time of fertilisation.

Localization of immunolabels by electron microscopy and image averaging

1983 ◽  
Vol 41 ◽  
pp. 282-283
Author(s):  
J. Frank ◽  
P.-Y. Sizaret ◽  
A. Verschoor ◽  
J. Lamy
Keyword(s):  
Electron Microscopy ◽  
Single Particle ◽  
Attachment Site ◽  
Uranyl Acetate ◽  
Limulus Polyphemus ◽  
Resolution Limit ◽  
Electron Microscopic ◽  
Image Averaging ◽  
Top View ◽  
Better Than

The accuracy with which the attachment site of immunolabels bound to macromolecules may be localized in electron microscopic images can be considerably improved by using single particle averaging. The example studied in this work showed that the accuracy may be better than the resolution limit imposed by negative staining (∽2nm).The structure used for this demonstration was a halfmolecule of Limulus polyphemus (LP) hemocyanin, consisting of 24 subunits grouped into four hexamers. The top view of this structure was previously studied by image averaging and correspondence analysis. It was found to vary according to the flip or flop position of the molecule, and to the stain imbalance between diagonally opposed hexamers (“rocking effect”). These findings have recently been incorporated into a model of the full 8 × 6 molecule.LP hemocyanin contains eight different polypeptides, and antibodies specific for one, LP II, were used. Uranyl acetate was used as stain. A total of 58 molecule images (29 unlabelled, 29 labelled with antl-LPII Fab) showing the top view were digitized in the microdensitometer with a sampling distance of 50μ corresponding to 6.25nm.

Immunocytochemistry. A Review of Methodology for Electron Microscopic Applicaiton

1974 ◽  
Vol 32 ◽  
pp. 328-329
Author(s):  
Joseph E. Mazurkiewicz
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Ultrastructural Level ◽  
Electron Microscopic ◽  
Biological Interest ◽  
Investigative Approach ◽  
Immunologic Activity ◽  
Dense Label

Immunocytochemistry is a powerful investigative approach in which one of the most exacting examples of specificity, that of the reaction of an antibody with its antigen, isused to localize tissue and cell specific molecules in situ. Following the introduction of fluorescent labeled antibodies in T950, a large number of molecules of biological interest had been studied with light microscopy, especially antigens involved in the pathogenesis of some diseases. However, with advances in electron microscopy, newer methods were needed which could reveal these reactions at the ultrastructural level. An electron dense label that could be coupled to an antibody without the loss of immunologic activity was desired.

An Electron Microscopic Study of an Avian Reovirus that Causes Arthritis

1971 ◽  
Vol 29 ◽  
pp. 254-255
Author(s):  
E, R. Walker ◽  
N. O. Olson ◽  
M. H. Friedman
Keyword(s):  
Electron Microscopy ◽  
Viral Genome ◽  
Inner Core ◽  
Avian Reovirus ◽  
Electron Microscopic ◽  
Outer Coat ◽  
Acid Type ◽  
Chicken Eggs ◽  
Icosahedral Particle ◽  
Mature Virus

An unidentified virus, responsible for an arthritic-like condition in chickens was studied by electron microscopy and other methods of viral investigation. It was characterized in chorio-allantoic membrane (CAM) lesions of embryonating chicken eggs and in tissue culture as to: 1) particle size; 2) structure; 3) mode of replication in the cell; and 4) nucleic acid type.The inoculated virus, coated and uncoated, is first seen in lysosomal-like inclusions near the nucleus; the virions appear to be uncoated in these electron dense inclusions (Figure 1), Although transfer of the viral genome from these inclusions is not observable, replicating virus and mature virus crystals are seen in the cytoplasm subsequent to the uncoating of the virions.The crystals are formed in association with a mass of fibrils 50 to 80 angstroms in diameter and a ribosome-studded structure that appears to be granular endoplasmic reticulum adapted to virus replication (Figure 2). The mature virion (Figure 3) is an icosahedral particle approximately 75 millimicrons in diameter. The inner core is 45 millimicrons, the outer coat 15 millimicrons, and the virion has no envelope.

A Comparative Study of Fractographic Replicas

1974 ◽  
Vol 32 ◽  
pp. 566-567
Author(s):  
Loren Anderson ◽  
Pat Pizzo ◽  
Glen Haydon
Keyword(s):  
Electron Microscopy ◽  
Electron Microscopic Examination ◽  
Direct Examination ◽  
Electron Microscopic ◽  
Reliable Technique ◽  
Service Failures ◽  
Transmission Electron ◽  
Mode Of Failure ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

Transmission electron microscopy of replicas has long been used to study the fracture surfaces of components which fail in service. Recently, the scanning electron microscope (SEM) has gained popularity because it allows direct examination of the fracture surface. However, the somewhat lower resolution of the SEM coupled with a restriction on the sample size has served to limit the use of this instrument in investigating in-service failures. It is the intent of this paper to show that scanning electron microscopic examination of conventional negative replicas can be a convenient and reliable technique for determining mode of failure.

Sign in / Sign up

Export Citation Format

Share Document