Comparative Ultrastructure of Freeze-Cleaved and Thin-Sectioned Membranes

1969 ◽  
Vol 27 ◽  
pp. 324-325
Author(s):  
Ronald S. Weinstein ◽  
N. Scott McNutt
Keyword(s):  
The Other ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Minor Degree ◽  
Technical Artifacts ◽  
A Minor ◽  
True Structure ◽  
Shed Light ◽  
Comparative Ultrastructure ◽  
Degree Of Overlap

The structure of biomembranes may now be studied at relatively high resolution using two vastly different electron microscopic preparative techniques. One utilizes thin sections of chemically fixed, dehydrated, and plastic embedded tissue while the other, freeze-cleaving, allows for the examination of partially hydrated tissues which are physically fixed by freezing. Each technique introduces certain artifacts, some of which have been investigated and others that are ill-defined. Although there is a minor degree of overlap between the artifacts of the two techniques, most of the artifacts are unique to one technique or the other. Therefore, comparison of the electron microscopic images of membranes produced with the two techniques may shed light on both technical artifacts and on the true structure of membranes. We have carried out comparative studies on a number of different kinds of membranes, two examples of which are briefly described.

Platelet Incorporation of Labelled Adenosine and Adenosine Diphosphate

1969 ◽  
Vol 22 (02) ◽  
pp. 304-315 ◽  
Author(s):  
E. W Salzman ◽  
T. P Ashford ◽  
D. A Chambers ◽  
Lena L. Neri
Keyword(s):  
Platelet Rich Plasma ◽  
Adenosine Diphosphate ◽  
Platelet Inhibition ◽  
Electron Microscopic ◽  
Platelet Binding ◽  
Minor Degree ◽  
A Minor ◽  
Plasma Marker ◽  
Electron Microscopic Radioautography ◽  
Simultaneous Assessment

SummaryAfter incubation of platelet-rich plasma with labelled adenosine or ADP, platelet incorporation of radioactivity was assessed. Platelets were rapidly separated for counting by filtration through cellulose acetate Millipore. Inulin-H3 served as a plasma marker, and triple isotope techniques permitted simultaneous assessment of the behavior of the adenine and phosphate moieties of ADP without washing of platelets. In other experiments, electron microscopic radioautography was employed to trace the label after platelet incorporation.The results were consistent with previous reports that ADP is dephosphorylated in plasma and is incorporated by platelets only as a dephosphorylated residue, probably adenosine. The label crossed the platelet membrane and entered the platelet, where it was distributed in platelet granules and the agranular cell sap. Concentration within granules occurred to a minor degree.The results support the hypothesis that platelet aggregation by ADP occurs without a persistent bond of ADP to the platelet. Inhibition of aggregation by adenosine probably depends on a metabolic or transport process rather than on competition between adenosine and ADP for platelet binding sites.

A unified theory of surface roughness

1984 ◽  
Vol 393 (1804) ◽  
pp. 133-157 ◽  
Keyword(s):  
Surface Roughness ◽  
Rough Surface ◽  
Random Noise ◽  
Sampling Interval ◽  
The Other ◽  
Real Surface ◽  
Unified Theory ◽  
Two Dimensional ◽  
Minor Degree ◽  
A Minor

The properties of the peaks and summits of a rough surface are predicted on the assumption that the surface is two-dimensional random noise. The important result is that, in non-dimensional form, the answers depend only to a minor degree on the parameters describing the surface or on the sampling interval used: on the other hand the absolute values are strongly dependent on the sampling interval. Experimental results on a real surface agree remarkably well with the predictions.

Comparative ultrastructure of methanogenic bacteria

1975 ◽  
Vol 21 (2) ◽  
pp. 121-129 ◽  
Author(s):  
J. G. Zeikus ◽  
V. G. Bowen
Keyword(s):  
Morphological Characteristics ◽  
Cell Types ◽  
Methanogenic Bacteria ◽  
Diverse Group ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Intracytoplasmic Membranes ◽  
Microscopic Studies ◽  
Different Cell Types ◽  
Comparative Ultrastructure

Electron-microscopic studies using thin sections revealed that methane-producing bacteria were an ultrastructurally diverse group. Fine structure and morphological characteristics separated these bacteria into four discrete cell types. Methanogenic bacteria displayed a gram-positive cell wall that varied considerably among different cell types. Differences in granular inclusions, reserve materials, and intracytoplasmic membranes were observed. Unique ultrastructural features were not shared by all methanogenic species studied.

The fine structure of some strains of Humicola Traaen

1974 ◽  
Vol 20 (2) ◽  
pp. 237-239 ◽  
Author(s):  
M. de Bertoldi ◽  
F. Mariotti ◽  
C. Filippi
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
Cell Surface ◽  
Outer Wall ◽  
Wall Layer ◽  
The Other ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Different Types ◽  
Microscopic Studies

The fine structure of three unclassified strains of Humicola and of H. grisea has been investigated. The hyphae of all the strains show septa with Woronin bodies of the ascomycetous type. The cytoplasm contains many nuclei per cell, mitochondria, ribosomes, and endoplasmic vesicles, all typical of fungal cells. Electron-microscopic studies of thin sections of mature aleuriospores reveal a thick multilayered cell wall and an accumulation, inside the spore, of β-hydroxybutyrate granules. Aleuriospores exhibit different types of cell surface; the outer wall layer of two strains is smooth, while the outer layer of the other strains is rough because of the presence of melanizing bodies on the cell wall matrix. The fine structure of phialospores and microconidia is also described. Differences in the fine structure among the strains studied are reported.

Colloquial Expressions in Euripides

1937 ◽  
Vol 31 (3-4) ◽  
pp. 182-191 ◽  
Author(s):  
P. T. Stevens
Keyword(s):  
Greek Tragedy ◽  
Marked Change ◽  
The Other ◽  
Greek Literature ◽  
Poetic Tradition ◽  
Other Hand ◽  
Frequent Use ◽  
Minor Degree ◽  
Ordinary Conversation ◽  
A Minor

The language of Greek Tragedy can be considered as a whole by virtue of the characteristics which distinguish it from that of other branches of Greek literature, and the resemblance between the three tragedians in this respect is more noticeable than the differences. Still, if we compare Aeschylus and Euripides it is impossible not to feel a marked change of tone, in λ⋯ξις as in δι⋯νοια and ἤθη. As in E. the familiar legends are frequently set in a more everyday atmosphere and the characters cast in a less heroic mould, it is natural that the tone of the language should be lowered, partly by the frequent use of distinctively prosaic expressions and partly by the introduction of what appear to be colloquialisms. This change of tone in language was at once noted by Aristophanes and is referred to by Aristotle as an innovation of E. On the other hand E.'s style presents a certain anomaly, since while deliberately securing a closer approximation to the language of prose and ordinary conversation he also shows a poetic and archaizing tendency in the use of Aeschylean and Homeric words and forms not found in Sophocles. This may be due to a reluctance to depart too far from the poetic tradition of Greek tragedy, and possibly to a scholar's interest in the language of Aeschylus and Homer, in a minor degree a foreshadowing of the learned archaism of the Alexandrian poets.

Symptomatic syringomyelia following surgery to treat retethering of lipomyelomeningoceles

1995 ◽  
Vol 82 (5) ◽  
pp. 752-755 ◽  
Author(s):  
Paul H. Chapman ◽  
David M. Frim
Keyword(s):  
De Novo ◽  
Early Recognition ◽  
Central Canal ◽  
Conus Medullaris ◽  
The Other ◽  
Neurological Deficits ◽  
Content Type ◽  
Minor Degree ◽  
Previously Treated ◽  
A Minor

✓ The authors report the cases of three children in whom symptomatic syringomyelia occurredde novo following an operation to relieve retethering of a previously treated lipomyelomeningocele. No patient had a Chiari malformation. In two cases, magnetic resonance imaging performed before the first operation did not show a syrinx. At the time of surgery to relieve retethering, it was discovered that one of these patients had a minor degree of terminal hydromyelia and the other had a prominent central canal within the conus medullaris. The third patient was initially studied by means of myelography, which gave no indication of a syrinx, and one was not found at the time of the surgery to release the retethering. Neurological deficits appeared abruptly within several months of operation in two children, and insidiously after 12 to 18 months in the other symptomatic individual. In all three cases, the syrinx involved the distal spinal cord adjacent to the site of the lipoma. Treatment consisted of syringosubarachnoid shunting, which arrested the progression of deficits but only partially reversed them. The details of each case are presented and the possible mechanism of syrinx formation discussed. Early recognition and treatment of this unusual but important problem are emphasized.

Scanning Electron Microscopic Study of the Cell Surface

1969 ◽  
Vol 27 ◽  
pp. 36-37 ◽  
Author(s):  
Toichiro Kuwabara
Keyword(s):  
Tissue Fluid ◽  
Biological Application ◽  
Biological Structure ◽  
Electron Microscopic ◽  
Surface Appearance ◽  
Minute Amount ◽  
Scanning Electron Microscopic Study ◽  
Scanning Electron Microscopic ◽  
True Structure ◽  
Scanning Electron

Although scanning electron microscopy has a great potential in biological application, there are certain limitations in visualization of the biological structure. Satisfactory techniques to demonstrate natural surfaces of the tissue and the cell have been reported by several investigators. However, it is commonly found that the surface cell membrane is covered with a minute amount of mucin, secretory substance or tissue fluid as physiological, pathological or artefactual condition. These substances give a false surface appearance, especially when the tissue is fixed with strong fixatives. It seems important to remove these coating substances from the surface of the cell for demonstration of the true structure.

The Immuno-Electron Microscopic Localization of the Mo-Fe Protein Component of Nitrogenase in Cells of Azotobacter Vinelandii

1973 ◽  
Vol 31 ◽  
pp. 574-575
Author(s):  
J. T. Stasny ◽  
R. C. Burns ◽  
R. W. F. Hardy
Keyword(s):  
Cellular Localization ◽  
Direct Evidence ◽  
Azotobacter Vinelandii ◽  
Intracellular Localization ◽  
Protein Component ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Fe Protein ◽  
Intracytoplasmic Membranes

Structure-functlon studies of biological N2-fixation have correlated the presence of the enzyme nitrogenase with increased numbers of intracytoplasmic membranes in Azotobacter. However no direct evidence has been provided for the internal cellular localization of any nitrogenase. Recent advances concerned with the crystallizatiorTand the electron microscopic characterization of the Mo-Fe protein component of Azotobacter nitrogenase, prompted the use of this purified protein to obtain antibodies (Ab) to be conjugated to electron dense markers for the intracellular localization of the protein by electron microscopy. The present study describes the use of ferritin conjugated to goat antitMo-Fe protein immunoglobulin (IgG) and the observations following its topical application to thin sections of N2-grown Azotobacter.

The High Resolution Appearance of Biological Substrates

1969 ◽  
Vol 27 ◽  
pp. 416-417
Author(s):  
Glen B. Haydon
Keyword(s):  
High Resolution ◽  
Phase Image ◽  
Biological Structure ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Resolution Electron ◽  
Discrete Structures ◽  
Large Phase ◽  
Biological Substrates ◽  
High Resolution Electron Micrographs

High resolution electron microscopic study of negatively stained macromolecules and thin sections of tissue embedded in a variety of media are difficult to interpret because of the superimposed phase image granularity. Although all of the information concerning the biological structure of interest may be present in a defocused electron micrograph, the high contrast of large phase image granules produced by the substrate makes it impossible to distinguish the phase ‘points’ from discrete structures of the same dimensions. Theory predicts the findings; however, it does not allow an appreciation of the actual appearance of the image under various conditions. Therefore, though perhaps trivial, training of the cheapest computer produced by mass labor has been undertaken in order to learn to appreciate the factors which affect the appearance of the background in high resolution electron micrographs.

Determination of the phase structure of polymerblends by electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 492-493
Author(s):  
Dr. G. Kaemof
Keyword(s):  
Screw Extruder ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Single Screw Extruder ◽  
Transmission Electron ◽  
The Matrix ◽  
Twin Screw ◽  
Special Case ◽  
Microscopic Investigations

A mixture of polycarbonate (PC) and styrene-acrylonitrile-copolymer (SAN) represents a very good example for the efficiency of electron microscopic investigations concerning the determination of optimum production procedures for high grade product properties.The following parameters have been varied:components of charge (PC : SAN 50 : 50, 60 : 40, 70 : 30), kind of compounding machine (single screw extruder, twin screw extruder, discontinuous kneader), mass-temperature (lowest and highest possible temperature).The transmission electron microscopic investigations (TEM) were carried out on ultra thin sections, the PC-phase of which was selectively etched by triethylamine.The phase transition (matrix to disperse phase) does not occur - as might be expected - at a PC to SAN ratio of 50 : 50, but at a ratio of 65 : 35. Our results show that the matrix is preferably formed by the components with the lower melting viscosity (in this special case SAN), even at concentrations of less than 50 %.

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