scholarly journals LOW TEMPERATURE ULTRAMICROINCINERATION OF THIN-SECTIONED TISSUE

1972 ◽  
Vol 55 (2) ◽  
pp. 328-354 ◽  
Author(s):  
Wayne Hohman ◽  
Harald Schraer
Keyword(s):  
Low Temperature ◽  
Metallic Elements ◽  
Fixed Tissue ◽  
Technical Problems ◽  
Thin Sections ◽  
Ultrastructural Studies ◽  
Fine Resolution ◽  
Excited Oxygen ◽  
Sectioned Tissue

Low temperature ultramicroincineration was employed to determine the morphological localization of "structure-bound" mineral and/or metallic elements within biological cells at the electron microscope level. This technique chemically removes organic material from thin sections of tissues with reactive, excited oxygen instead of heat as used in a furnace. The remaining ash representing the mineral/metallic ultrastructure of cells is advantageous for ultrastructural studies because incineration without applying heat is less destructive than the burning associated with high temperatures. This low temperature incineration method was applied to thin-sectioned avian shell gland mucosa, a calcium transporting system, as a sample tissue. The results include: recognition of many subcellular organelles in the ash patterns, identification of dense, ash-containing granules (possibly organic-metallic complexes) in epithelial cells which may be involved in calcium transport, description of ashed erythrocytes and collagen, comparison of ashed glutaraldehyde fixed tissue with and without osmium postfixation, description of lead-stained cells after ashing, demonstration that ash preservation is dependent upon section thickness, illustration of the fine resolution obtainable because the ash residues remain relatively near their in situ origins, discussion of technical problems in this relatively new field, and demonstration of the presence of Ca and P in the ash with electron microprobe X-ray analysis.

A comparison of isolated and in situ thick filaments from smooth muscle

1986 ◽  
Vol 44 ◽  
pp. 156-157
Author(s):  
E.L. Buhle ◽  
A.V. Somlyo ◽  
A.P. Somlyo
Keyword(s):  
Smooth Muscle ◽  
Actin Filaments ◽  
Muscle Actin ◽  
Thin Sections ◽  
Ultrastructural Studies ◽  
Thick Filaments ◽  
Myosin Filaments ◽  
Rabbit Portal Vein ◽  
Stable Structures

Early ultrastructural studies of smooth muscle are consistent with the sliding filament mechanism of contraction. Myosin filaments are stable structures in situ and can be found in both relaxed and contracted muscle. Actin filaments can be decorated with SI subfragments of myosin to show a polarity similar to the Z-lines of skeletal muscle. The work presented here is a comparison of isolated thick filaments from relaxed chick amnion with thick filaments obtained in situ from longitudinal thin sections (∽50nm thick) of rabbit portal vein in rigor.

The Mechanism of the Low-Temperature Oxidation of Coal by O2: Observation and Separation of Simultaneous Reactions Using In Situ FT-IR Difference Spectroscopy

1987 ◽  
Vol 41 (1) ◽  
pp. 50-63 ◽  
Author(s):  
Jon S. Gethner
Keyword(s):  
Low Temperature ◽  
Reactive Species ◽  
Spontaneous Ignition ◽  
Difference Spectroscopy ◽  
Low Temperature Oxidation ◽  
Experimental Conditions ◽  
Temperature Oxidation ◽  
Thin Sections ◽  
Ft Ir

Coal is complex, predominantly organic-containing porous solid which is important both as an energy and a chemical source material. The physical and chemical properties of most coals are extremely sensitive to air oxidation. There is no generally accepted mechanism for the oxidation process, in spite of past interest. Using in situ FT-IR difference spectroscopy of 0.4 μm thin sections of coal, we have examined the mechanism of the low-temperature oxidation of Illinois No. 6 bituminous coal by O2. The overall oxidation with O2 is found to be comprised of three separate chemical reactions. Two of the reactions involve O2 addition to reactive species in the coal. One is predominant at temperatures close to or slightly above room temperature and apparently involves the reversible binding of O2 to a free radical site, followed by reaction. The other oxidation is predominant by 100°C and proceeds by the formation and subsequent decomposition of hydroperoxides. The third reaction is a thermolysis which is important at temperatures between 25°C and 100°C and is competitive with the lower-temperature oxidation. It results in a partial decarbonylation and decarboxylation of the coal. Since three separate reactions contribute to the overall oxidation, the chemical and physical changes resulting from oxidation are dependent upon the oxidation conditions. Control of experimental conditions is critical in order for one to obtain reproducible results. Some of the possible implications of these results on the technologically important process of spontaneous ignition of coal are discussed. Results of previous oxidation studies are discussed in view of the present results. The large variations reported in oxidation studies are likely to be the consequence of ill-defined or poorly controlled experiments. We interpret the correlation between the present study and number of other studies to indicate that oxidation chemistry is the same in most coals, with the principal differences between coals being due to the different relative proportions of the reactive species in the starting coal.

Ultrastructural studies of Chondromyces crocatus vegetative cells

1975 ◽  
Vol 21 (11) ◽  
pp. 1815-1826 ◽  
Author(s):  
Thomas H. MacRae ◽  
Howard D. McCurdy
Keyword(s):  
Electron Microscopy ◽  
Cell Envelope ◽  
Thin Sections ◽  
Gram Negative ◽  
Ultrastructural Studies ◽  
Negative Cell ◽  
Slime Layer ◽  
Movement Characteristic ◽  
Gliding Movement

Electron microscopy of sectioned, chemically fixed Chondromyces crocatus revealed a microorganism with a typical gram-negative cell envelope. The cytoplasm contained, in addition to tubules and two types of granules, a membrane-associated structure (MAS) that, although less extensive, bears some resemblance to polar membranes observed in flagellated bacteria. Examination of swarming cells negatively stained in situ, as well as thin sections, established that cell division occurs by septum formation and that well-defined mesosomes are associated with the process. Polar pili and a compact, amorphous slime layer surrounding the cells were evident in shadowed preparations of in situ cells. The slime layer and pili, by providing cell-to-cell interconnections, may influence the organized gliding movement characteristic of C. crocatus and other myxobacteria.

Ultrastructural studies on the bacterium associated with the ratoon stunting disease of sugarcane

1977 ◽  
Vol 28 (5) ◽  
pp. 843 ◽  
Author(s):  
L Weaver ◽  
DS Teakle ◽  
AC Hayward
Keyword(s):  
Cell Wall ◽  
Sugar Cane ◽  
Gram Positive ◽  
Thin Sections ◽  
Positive Type ◽  
Ratoon Stunting Disease ◽  
Coryneform Bacteria ◽  
Ultrastructural Studies ◽  
Xylem Cell

The bacterium associated with ratoon stunting disease of sugar-cane was studied in thin sections of agar-embedded pellets of fibrovascular extracts, and in situ in the xylem of sugar-cane. The bacterium often possessed a single large lamellar mesosome, and the cell wall was smooth in outline and of the Gram-positive type. It lacked the acidic mucopolysaccharide capsule which was observed in several species of plant pathogenic coryneform bacteria. The bacterium was seen in the lumen and the pits of the xylem vessels and sometimes appeared to be in the xylem cell wall.

Probing the ultrastructure of the mitotic and meiotic spindle in eggs: An expeditious approach based on semi-thin (0.25 μm) serial sections

1983 ◽  
Vol 41 ◽  
pp. 552-555
Author(s):  
Conly L. Rieder ◽  
S. Bowser ◽  
R. Nowogrodzki ◽  
K. Ross ◽  
G. Sluder
Keyword(s):  
Small Sample Size ◽  
Small Sample ◽  
Meiotic Spindle ◽  
Serial Sections ◽  
Mitotic Apparatus ◽  
Thin Sections ◽  
Cell Cycles ◽  
Ultrastructural Studies

Eggs have long been a favorite material for studying the mechanism of karyokinesis in-vivo and in-vitro. They can be obtained in great numbers and, when fertilized, divide synchronously over many cell cycles. However, they are not considered to be a practical system for ultrastructural studies on the mitotic apparatus (MA) for several reasons, the most obvious of which is that sectioning them is a formidable task: over 1000 ultra-thin sections need to be cut from a single 80-100 μm diameter egg and of these sections only a small percentage will contain the area or structure of interest. Thus it is difficult and time consuming to obtain reliable ultrastructural data concerning the MA of eggs; and when it is obtained it is necessarily based on a small sample size.We have recently developed a procedure which will facilitate many studies concerned with the ultrastructure of the MA in eggs. It is based on the availability of biological HVEM's and on the observation that 0.25 μm thick serial sections can be screened at high resolution for content (after mounting on slot grids and staining with uranyl and lead) by phase contrast light microscopy (LM; Figs 1-2).

On the High Voltage Electron Microscopy (1 MeV) of Biological Thick Sections

1972 ◽  
Vol 30 ◽  
pp. 464-465
Author(s):  
William H. Massover
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Present Report ◽  
Biological Tissues ◽  
Specimen Preparation ◽  
Technical Problems ◽  
High Voltage Electron Microscopy ◽  
Thin Sections ◽  
Voltage Electron ◽  
High Voltage Electron

Stereoscopic examination of thick sections of fixed and embedded biological tissues by high voltage electron microscopy has been shown to allow direct visualization of three-dimensional fine structure. The present report will consider the occurrence of some new technical problems in specimen preparation and Image interpretation that are not common during lower voltage studies of thin sections.Thick Sectioning and Tissue Coloration - Epon sections of 0.5 μm or more that are cut with glass knives do not have a uniform thickness as Judged by their interference colors; these colors change with time during their flotation on the knife bath, and again when drying onto the specimen support. Quoted thicknesses thus must be considered only as rough estimates unless measured in specific regions by other methods. Chloroform vapors do not always result in good spreading of thick sections; however, they will spread spontaneously to large degrees after resting on the flotation bath for several minutes. Ribbons of thick sections have been almost impossible to obtain.

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

Role of boundaries in the crystallization of amorphous films

1988 ◽  
Vol 46 ◽  
pp. 626-627
Author(s):  
D. A. Smith
Keyword(s):  
Low Temperature ◽  
Amorphous State ◽  
Nucleation And Growth ◽  
Amorphous Films ◽  
Island Nucleation ◽  
Surface Steps ◽  
Transmission Electron ◽  
Component Systems ◽  
Temperature Deposition

The nucleation and growth processes which lead to the formation of a thin film are particularly amenable to investigation by transmission electron microscopy either in situ or subsequent to deposition. In situ studies have enabled the observation of island nucleation and growth, together with addition of atoms to surface steps. This paper is concerned with post-deposition crystallization of amorphous alloys. It will be argued that the processes occurring during low temperature deposition of one component systems are related but the evidence is mainly indirect. Amorphous films result when the deposition conditions such as low temperature or the presence of impurities (intentional or unintentional) preclude the atomic mobility necessary for crystallization. Representative examples of this behavior are CVD silicon grown below about 670°C, metalloids, such as antimony deposited at room temperature, binary alloys or compounds such as Cu-Ag or Cr O2, respectively. Elemental metals are not stable in the amorphous state.

A TEM study of the microstructure of avian eggshells

1992 ◽  
Vol 50 (2) ◽  
pp. 1102-1103
Author(s):  
S. Q. Xiao ◽  
S. Baden ◽  
A. H. Heuer
Keyword(s):  
Electron Microscope ◽  
Calcium Carbonate ◽  
Nucleation And Growth ◽  
Growth Mechanisms ◽  
Shell Surface ◽  
Thin Sections ◽  
Polycrystalline Metals ◽  
Transmission Electron ◽  
Nucleation And Growth Mechanisms

The avian eggshell is one of the most rapidly mineralizing biological systems known. In situ, 5g of calcium carbonate are crystallized in less than 20 hrs to fabricate the shell. Although there have been much work about the formation of eggshells, controversy about the nucleation and growth mechanisms of the calcite crystals, and their texture in the eggshell, still remain unclear. In this report the microstructure and microchemistry of avian eggshells have been analyzed using transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS).Fresh white and dry brown eggshells were broken and fixed in Karnosky's fixative (kaltitanden) for 2 hrs, then rinsed in distilled H2O. Small speckles of the eggshells were embedded in Spurr medium and thin sections were made ultramicrotome.The crystalline part of eggshells are composed of many small plate-like calcite grains, whose plate normals are approximately parallel to the shell surface. The sizes of the grains are about 0.3×0.3×1 μm3 (Fig.l). These grains are not as closely packed as man-made polycrystalline metals and ceramics, and small gaps between adjacent grains are visible indicating the absence of conventional grain boundaries.

Differentiation Processes of the Ocellar Retina of the Honeybee (Apis Mellifera L.)

1990 ◽  
Vol 48 (3) ◽  
pp. 430-431
Author(s):  
Maria Anna Pabst
Keyword(s):  
Apis Mellifera ◽  
Distal Part ◽  
Cell Layer ◽  
Single Layer ◽  
Photoreceptor Cells ◽  
Distal Segment ◽  
Compound Eyes ◽  
Thin Sections ◽  
Ultrastructural Studies ◽  
Adult Worker

In addition to the compound eyes, honeybees have three dorsal ocelli on the vertex of the head. Each ocellus has about 800 elongated photoreceptor cells. They are paired and the distal segment of each pair bears densely packed microvilli forming together a platelike fused rhabdom. Beneath a common cuticular lens a single layer of corneagenous cells is present.Ultrastructural studies were made of the retina of praepupae, different pupal stages and adult worker bees by thin sections and freeze-etch preparations. In praepupae the ocellar anlage consists of a conical group of epidermal cells that differentiate to photoreceptor cells, glial cells and corneagenous cells. Some photoreceptor cells are already paired and show disarrayed microvilli with circularly ordered filaments inside. In ocelli of 2-day-old pupae, when a retinogenous and a lentinogenous cell layer can be clearly distinguished, cell membranes of the distal part of two photoreceptor cells begin to interdigitate with each other and so start to form the definitive microvilli. At the beginning the microvilli often occupy the whole width of the developing rhabdom (Fig. 1).

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