Changes Induced by Pre-Fixation in Polycation Bacteriolysis and Surface Alterations Matching the Model of Wall Picnosis in Cell Lysis

1980 ◽  
Vol 35 (9-10) ◽  
pp. 805-810
Author(s):  
Alexandru Popescu ◽  
Stefan Antohi ◽  
Stefan Trasculescu ◽  
Adriana Aurescu ◽  
Nicolae Manolescu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Osmium Tetroxide ◽  
Cell Lysis ◽  
Cell Sensitivity ◽  
Lytic Effect ◽  
Shape And Size ◽  
Scaning Electron Microscopy

Abstract Pretreatments of B. subtilis and S. aureus cells with lower concentrations of fixative agents, led to modifications in bacteriolytic effect exerted by polyarginine and protamine: Glutaraldehyde blocked polycation bacteriolysis while formaldehyde and osmium tetroxide (OSO4) having no influence on polyarginine action, increased constantly the cell sensitivity to protamine in lower doses otherwise nonlytic; the sensitizing action also resulted in the extension of protamine bacteriolytic pattern including several staphylococcal strains; higher bacteriolytic doses of protamine were contrastively unable to lyse OSO4 prefixed cells and gave an inconstant lytic value with formaldehyde treated bacteria. With higher concentrations, OSO4 preserved intactly its sensitizing action while formaldehyde displayed a decrease in its ability to sensitize B. subtilis cells to the lytic effect of protamine. Scaning electron microscopy of polycation treated cells showed prelytic lesions as surface granulations, shape and size modifications and cell splits. The interpretation of the results in terms of intra-and intermolecular adducts accompanied by con­ formational changes in surface macromolecules is discussed. It is concluded that the results match the model of polycation bacteriolysis by wall multizonal picnosis leading to surface splits and thereby triggering cell-lysis.

Spontaneous Cataract in Nude Athymic Mice

1977 ◽  
Vol 35 ◽  
pp. 512-513
Author(s):  
Ronald H. Bradley ◽  
R. S. Berk ◽  
L. D. Hazlett
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Nude Mouse ◽  
Cellular Immunity ◽  
Phosphate Buffer ◽  
Osmium Tetroxide ◽  
Athymic Mice ◽  
Transmission Microscopy ◽  
Mouse Lens ◽  
Scanning Electron

The nude mouse is a hairless mutant (homozygous for the mutation nude, nu/nu), which is born lacking a thymus and possesses a severe defect in cellular immunity. Spontaneous unilateral cataractous lesions were noted (during ocular examination using a stereomicroscope at 40X) in 14 of a series of 60 animals (20%). This transmission and scanning microscopic study characterizes the morphology of this cataract and contrasts these data with normal nude mouse lens.All animals were sacrificed by an ether overdose. Eyes were enucleated and immersed in a mixed fixative (1% osmium tetroxide and 6% glutaraldehyde in Sorenson's phosphate buffer pH 7.4 at 0-4°C) for 3 hours, dehydrated in graded ethanols and embedded in Epon-Araldite for transmission microscopy. Specimens for scanning electron microscopy were fixed similarly, dehydrated in graded ethanols, then to graded changes of Freon 113 and ethanol to 100% Freon 113 and critically point dried in a Bomar critical point dryer using Freon 13 as the transition fluid.

Scanning and Transmission Microscopy of Nematocyst Batteries in Epitheliomuscular Cells of Hydra

1971 ◽  
Vol 29 ◽  
pp. 410-411 ◽  
Author(s):  
Jane A. Westfall ◽  
S. Yamataka ◽  
Paul D. Enos
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Osmium Tetroxide ◽  
External Surface ◽  
Three Dimensional ◽  
Surface Structures ◽  
Transmission Microscopy ◽  
Transmission Electron ◽  
Freeze Dried ◽  
Scanning Electron

Scanning electron microscopy (SEM) provides three dimensional details of external surface structures and supplements ultrastructural information provided by transmission electron microscopy (TEM). Animals composed of watery jellylike tissues such as hydras and other coelenterates have not been considered suitable for SEM studies because of the difficulty in preserving such organisms in a normal state. This study demonstrates 1) the successful use of SEM on such tissue, and 2) the unique arrangement of batteries of nematocysts within large epitheliomuscular cells on tentacles of Hydra littoralis.Whole specimens of Hydra were prepared for SEM (Figs. 1 and 2) by the fix, freeze-dry, coat technique of Small and Màrszalek. The specimens were fixed in osmium tetroxide and mercuric chloride, freeze-dried in vacuo on a prechilled 1 Kg brass block, and coated with gold-palladium. Tissues for TEM (Figs. 3 and 4) were fixed in glutaraldehyde followed by osmium tetroxide. Scanning micrographs were taken on a Cambridge Stereoscan Mark II A microscope at 10 KV and transmission micrographs were taken on an RCA EMU 3G microscope (Fig. 3) or on a Hitachi HU 11B microscope (Fig. 4).

A Resorcinol-Formaldehyde Resin as an Embedding Material for Electron Microscopy of Membranes

1969 ◽  
Vol 27 ◽  
pp. 328-329 ◽  
Author(s):  
J. G. Robertson ◽  
D. F. Parsons
Keyword(s):  
Electron Microscopy ◽  
Osmium Tetroxide ◽  
Neutral Lipids ◽  
Lipid Extraction ◽  
Water Soluble ◽  
Formaldehyde Resin ◽  
Electron Microscope Autoradiography ◽  
Resorcinol Formaldehyde ◽  
Major Disadvantage ◽  
Cell Organization

The extraction of lipids from tissues during fixation and embedding for electron microscopy is widely recognized as a source of possible artifact, especially at the membrane level of cell organization. Lipid extraction is also a major disadvantage in electron microscope autoradiography of radioactive lipids, as in studies of the uptake of radioactive fatty acids by intestinal slices. Retention of lipids by fixation with osmium tetroxide is generally limited to glycolipids, phospholipids and highly unsaturated neutral lipids. Saturated neutral lipids and sterols tend to be easily extracted by organic dehydrating reagents prior to embedding. Retention of the more saturated lipids in embedded tissue might be achieved by developing new cross-linking reagents, by the use of highly water soluble embedding materials or by working at very low temperatures.

Effect of Acetone and Kerosene on Skin Ultrastructure

1972 ◽  
Vol 30 ◽  
pp. 92-93
Author(s):  
A. P. Lupulescu ◽  
H. Pinkus ◽  
D. J. Birmingham
Keyword(s):  
Electron Microscopy ◽  
Human Skin ◽  
Osmium Tetroxide ◽  
Human Epidermis ◽  
Ultrastructural Changes ◽  
Chemical Agents ◽  
Skin Ultrastructure ◽  
Volar Surface

Our laboratory is engaged in the study of the effect of different chemical agents on human skin, using electron microscopy. Previous investigations revealed that topical use of a strong alkali (NaOH 1N) or acid (HCl 1N), induces ultrastructural changes in the upper layers of human epidermis. In the current experiments, acetone and kerosene, which are primarily lipid solvents, were topically used on the volar surface of the forearm of Caucasian and Negro volunteers. Skin specimens were bioptically removed after 90 min. exposure and 72. hours later, fixed in 3% buffered glutaraldehyde, postfixed in 1% phosphate osmium tetroxide, then flat embedded in Epon.

The Current Situation in Chemical Stabilization of Biological Materials

1972 ◽  
Vol 30 ◽  
pp. 132-133
Author(s):  
John H. Luft
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Osmium Tetroxide ◽  
Molecular Level ◽  
Cross Linking ◽  
Chemical Stabilization ◽  
Specimen Preparation ◽  
Sufficient Condition ◽  
Radio Telescopes

With information processing devices such as radio telescopes, microscopes or hi-fi systems, the quality of the output often is limited by distortion or noise introduced at the input stage of the device. This analogy can be extended usefully to specimen preparation for the electron microscope; fixation, which initiates the processing sequence, is the single most important step and, unfortunately, is the least well understood. Although there is an abundance of fixation mixtures recommended in the light microscopy literature, osmium tetroxide and glutaraldehyde are favored for electron microscopy. These fixatives react vigorously with proteins at the molecular level. There is clear evidence for the cross-linking of proteins both by osmium tetroxide and glutaraldehyde and cross-linking may be a necessary if not sufficient condition to define fixatives as a class.

Application of ruthenium red/osmium tetroxide to bacteria, plant and animal tissue

1986 ◽  
Vol 44 ◽  
pp. 54-55
Author(s):  
R. L. Grayson ◽  
N. A. Rechcigl
Keyword(s):  
Electron Microscopy ◽  
Electron Density ◽  
Osmium Tetroxide ◽  
Biological Materials ◽  
Ruthenium Red ◽  
Animal Tissue

Ruthenium red (RR), an inorganic dye was found to be useful in electron microscopy where it can combine with osmium tetroxide (OsO4) to form a complex with attraction toward anionic substances. Although Martinez-Palomo et al. (1969) were one of the first investigators to use RR together with OsO4, our computor search has shown few applications of this combination in the intervening years. The purpose of this paper is to report the results of our investigations utilizing the RR/OsO4 combination to add electron density to various biological materials. The possible mechanisms by which this may come about has been well reviewed by previous investigators (1,3a,3b,4).

The External Morphology of the Eggs of Culex (Culex) saltanensis (Diptera: Culicidae) Under Scanning Electron Microscopy

2020 ◽  
Author(s):  
J R Santos-Mallet ◽  
T D Balthazar ◽  
A A Oliveira ◽  
W A Marques ◽  
A Q Bastos ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Optical Microscopy ◽  
Osmium Tetroxide ◽  
Neotropical Region ◽  
External Morphology ◽  
Metal Supports ◽  
Scanning Electron

Abstract The aim of the present study was to describe the morphology of the eggs of Culex (Culex) saltanensis Dyar that occurs in the Neotropical region. Eggs of the Cx. (Cux.) saltanensis were collected at the Mata Atlântica FIOCRUZ campus, fixed in 1% osmium tetroxide, prepared for mounting on metal supports, observed under a scanning electron microscope, and described morphologically. The eggs had a coniform shape with a length of approximately 0.5 mm (505–510 µm) and a width in the median portion of 117 µm (113–123 µm). Upper portion is lined with tubers of irregular shape and varying sizes (0.64–1.31 µm), located on a cross-linked matrix forming bands observed under optical microscopy. The micropyle is encased in a necklace of approximately 6.6-µm plates arranged in a flower-like shape. Comparing Cx. (Cux.) saltanensis eggs with several species of different genera, important divergent characteristics can be observed. However, this study points to the need for new descriptions of eggs of species belonging to the same subgenus in order to analyze if there will be differences between them. Culex (Cux.) saltanensis eggs have particular characteristics not observed in eggs of other Culicidae genera.

Relationships between Microstructure and Mechanical Properties of Polycristalline Alumina

2014 ◽  
Vol 625 ◽  
pp. 192-195
Author(s):  
Lillia Haddour ◽  
Mourad Keddam ◽  
Nadir Mesrati
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Alumina Ceramics ◽  
Intergranular Phase ◽  
Microstructural Parameters ◽  
Mechanical And Electrical Properties ◽  
Resistance Breakdown ◽  
Dielectrical Properties ◽  
Scaning Electron Microscopy ◽  
Fundamental Mechanism

Some low purity alumina ceramics with an alumina content ranging from 86% to 93% were investigated, in order to explore the effects of microstructural parameters (grain size, intergranular phase) on mechanical (wear) and dielectrical parameters. The microstructure and worn surfaces were analysed using scaning electron microscopy. The correlation between microstructural, dielectrical properties and wear is discussed. It has been proposed that mechanical and electrical properties are two aspects of the same fundamental mechanism. Key words: Al2O3, Microstructure final, Wear resistance, Breakdown.

scholarly journals FIXATION OF NEURAL TISSUES FOR ELECTRON MICROSCOPY BY PERFUSION WITH SOLUTIONS OF OSMIUM TETROXIDE

1962 ◽  
Vol 12 (2) ◽  
pp. 385-410 ◽  
Author(s):  
Sanford L. Palay ◽  
S. M. McGee-Russell ◽  
Spencer Gordon ◽  
Mary A. Grillo
Keyword(s):  
Electron Microscopy ◽  
Nervous System ◽  
Osmium Tetroxide ◽  
Microscopic Level ◽  
Electron Microscopic Level ◽  
Electron Microscopic ◽  
Vascular Perfusion ◽  
Neural Tissues ◽  
Structural Relations ◽  
Cellular Components

This paper describes in detail a method for obtaining nearly uniform fixation of the nervous system by vascular perfusion with solutions of osmium tetroxide. Criteria are given for evaluating the degree of success achieved in the preservation of all the cellular components of the nervous system. The method permits analysis of the structural relations between cells at the electron microscopic level to an extent that has not been possible heretofore.

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