Circulation and dioptric apparatus in the photophores of Euphausia pacifica: some ultrastructural observations

1977 ◽  
Vol 55 (5) ◽  
pp. 884-889 ◽  
Author(s):  
Brian J. Harvey
Keyword(s):  
Electron Micrographs ◽  
Circulatory System ◽  
Euphausia Pacifica ◽  
Capillary Bed ◽  
Dioptric Apparatus

The dioptric or light-directing apparatus of the abdominal photophores of Euphausia pacifica is briefly described. Electron micrographs of the lens, reflector, and lamellar ring are presented, with accompanying explanation concerning their probable optical role. Elements of the circulatory system are also discussed, and it is proposed that the 'rod mass' of classical cytologists is a highly ordered capillary bed.

Blood volume changes in rodents exposed to simulated high altitude

1961 ◽  
Vol 200 (3) ◽  
pp. 523-526 ◽  
Author(s):  
Adam Anthony ◽  
Judy Kreider
Keyword(s):  
Blood Volume ◽  
Plasma Volume ◽  
Circulatory System ◽  
Dilution Method ◽  
Total Blood Volume ◽  
Total Blood ◽  
Altitude Exposure ◽  
Volume Measurements ◽  
Capillary Bed ◽  
Rats And Mice

Blood volume measurements were made in rats and mice exposed to a simulated altitude of 20,000– 22,000 ft. for periods of 1–4 weeks. The noncapillary blood volume (which includes arteries, veins, arterioles and venules) was determined from plastic-corrosion preparations of the circulatory system. The plasma volume and total blood volume were measured using the T-1824 dye dilution method and capillary volume was calculated by subtracting noncapillary volume from total blood values. The increase in volume of the noncapillary vessels of rats and mice was about 1–2 ml/100 gm body weight after 1–4 weeks of altitude exposure. It was also shown that the total blood volume of acclimatized rats is about 40% greater than that of control animals whereas the plasma volume decreases by about 57%. It was concluded that altitude exposure resulted in a greater increase in the capacity of the noncapillary vessels ( ca. 60%) than in that of the capillary bed ( ca. 25%).

Utilizing Dark Field Electron Microscopy to Produce Lantern Slides

1974 ◽  
Vol 32 ◽  
pp. 116-117
Author(s):  
J. N. Meador ◽  
C. N. Sun ◽  
H. J. White
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
Dark Field ◽  
Limiting Factor ◽  
Clinical Laboratories ◽  
Field Electron ◽  
Time Element ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Dark Field Micrographs

The electron microscope is being utilized more and more in clinical laboratories for pathologic diagnosis. One of the major problems in the utilization of the electron microscope for diagnostic purposes is the time element involved. Recent experimentation with rapid embedding has shown that this long phase of the process can be greatly shortened. In rush cases the making of projection slides can be eliminated by taking dark field electron micrographs which show up as a positive ready for use. The major limiting factor for use of dark field micrographs is resolution. However, for conference purposes electron micrographs are usually taken at 2.500X to 8.000X. At these low magnifications the resolution obtained is quite acceptable.

Light Optical Diffraction Studies of Macromolecular Ultrastructure

1970 ◽  
Vol 28 ◽  
pp. 258-259
Author(s):  
Glen B. Haydon
Keyword(s):  
High Resolution ◽  
Diffraction Analysis ◽  
Diffraction Pattern ◽  
Electron Micrographs ◽  
Optical Diffraction ◽  
Electron Micrograph ◽  
Its Analysis ◽  
Resolution Electron ◽  
Diffraction Patterns

Analysis of light optical diffraction patterns produced by electron micrographs can easily lead to much nonsense. Such diffraction patterns are referred to as optical transforms and are compared with transforms produced by a variety of mathematical manipulations. In the use of light optical diffraction patterns to study periodicities in macromolecular ultrastructures, a number of potential pitfalls have been rediscovered. The limitations apply to the formation of the electron micrograph as well as its analysis.(1) The high resolution electron micrograph is itself a complex diffraction pattern resulting from the specimen, its stain, and its supporting substrate. Cowley and Moodie (Proc. Phys. Soc. B, LXX 497, 1957) demonstrated changing image patterns with changes in focus. Similar defocus images have been subjected to further light optical diffraction analysis.

On an Application of the Metallurgical Stage to Chromosome Morphology

1967 ◽  
Vol 25 ◽  
pp. 28-29
Author(s):  
Godfrey C. Hoskins
Keyword(s):  
Human Chromosome ◽  
Electron Micrographs ◽  
Chromosome Morphology ◽  
Electron Optics ◽  
Electron Micrograph ◽  
Photographic Evidence ◽  
Sophisticated Equipment ◽  
Periodic Arrangement

The first serious electron microscooic studies of chromosomes accompanied by pictures were by I. Elvers in 1941 and 1943. His prodigious study, from the manufacture of micronets to the development of procedures for interpreting electron micrographs has gone all but unnoticed. The application of todays sophisticated equipment confirms many of the findings he gleaned from interpretation of images distorted by the electron optics of that time. In his figure 18 he notes periodic arrangement of pepsin sensitive “prickles” now called secondary fibers. In his figure 66 precise regularity of arrangement of these fibers can be seen. In his figure 22 he reproduces Siegbahn's first stereoscopic electron micrograph of chromosomes.The two stereoscopic pairs of electron micrographs of a human chromosome presented here were taken with a metallurgical stage on a Phillips EM200. These views are interpreted as providing photographic evidence that primary fibers (1°F) about 1,200Å thick are surrounded by secondary fibers (2°F) arranged in regular intervals of about 2,800Å in this metanhase human chromosome. At the telomere the primary fibers bend back on themselves and entwine through the center of each of each chromatid. The secondary fibers are seen to continue to surround primary fibers at telomeres. Thus at telomeres, secondary fibers present a surface not unlike that of the side of the chromosome, and no more susceptible to the addition of broken elements from other chromosomes.

Criteria and Methods for Reliable Three-Dimensional Image Reconstruction

1974 ◽  
Vol 32 ◽  
pp. 330-331
Author(s):  
R. A. Crowther
Keyword(s):  
Image Reconstruction ◽  
Finite Number ◽  
Density Distribution ◽  
Electron Micrographs ◽  
Mathematical Problem ◽  
Three Dimensional ◽  
Ideal Case ◽  
Dimensional Image ◽  
General Object ◽  
The Ideal

The reconstruction of a three-dimensional image of a specimen from a set of electron micrographs reduces, under certain assumptions about the imaging process in the microscope, to the mathematical problem of reconstructing a density distribution from a set of its plane projections.In the absence of noise we can formulate a purely geometrical criterion, which, for a general object, fixes the resolution attainable from a given finite number of views in terms of the size of the object. For simplicity we take the ideal case of projections collected by a series of m equally spaced tilts about a single axis.

Some Structural Features of Metaphase Chromosomes of Mice and Men

1967 ◽  
Vol 25 ◽  
pp. 190-191
Author(s):  
Godfrey C. Hoskins ◽  
Betty B. Hoskins
Keyword(s):  
Electron Microscopy ◽  
Electron Micrographs ◽  
Structural Features ◽  
Metaphase Chromosomes ◽  
The Future ◽  
Of Mice And Men ◽  
Mouse Cells ◽  
Human And Mouse

Metaphase chromosomes from human and mouse cells in vitro are isolated by micrurgy, fixed, and placed on grids for electron microscopy. Interpretations of electron micrographs by current methods indicate the following structural features.Chromosomal spindle fibrils about 200Å thick form fascicles about 600Å thick, wrapped by dense spiraling fibrils (DSF) less than 100Å thick as they near the kinomere. Such a fascicle joins the future daughter kinomere of each metaphase chromatid with those of adjacent non-homologous chromatids to either side. Thus, four fascicles (SF, 1-4) attach to each metaphase kinomere (K). It is thought that fascicles extend from the kinomere poleward, fray out to let chromosomal fibrils act as traction fibrils against polar fibrils, then regroup to join the adjacent kinomere.

The structure of pre-mRNA and mRNA from erythroid cells

1978 ◽  
Vol 36 (2) ◽  
pp. 234-235
Author(s):  
A.-M. Ladhoff ◽  
B.J. Thiele ◽  
Ch. Coutelle ◽  
S. Rosenthal
Keyword(s):  
Bone Marrow ◽  
Structural Transformation ◽  
Electron Micrographs ◽  
Ammonium Acetate ◽  
Bone Marrow Cells ◽  
Erythroid Cells ◽  
Globin Mrna ◽  
Ordered Structures ◽  
Rabbit Bone ◽  
Rabbit Reticulocytes

The suggested precursor-product relationship between the nuclear pre-mRNA and the cytoplasmic mRNA has created increased interest also in the structure of these RNA species. Previously we have been published electron micrographs of individual pre-mRNA molecules from erythroid cells. An intersting observation was the appearance of a contour, probably corresponding to higher ordered structures, on one end of 10 % of the pre-mRNA molecules from erythroid rabbit bone marrow cells (Fig. 1A). A virtual similar contour was observed in molecules of 9S globin mRNA from rabbit reticulocytes (Fig. 1B). A structural transformation in a linear contour occurs if the RNA is heated for 10 min to 90°C in the presence of 80 % formamide. This structural transformation is reversible when the denatured RNA is precipitated and redissolved in 0.2 M ammonium acetate.

High Resolution Stereography of Complementary Freeze-Fracture Replicas Reveals the Presence of Depressions Opposite Membrane Associated Particles of Split Membranes

1971 ◽  
Vol 29 ◽  
pp. 442-443
Author(s):  
Russell L. Steere
Keyword(s):  
High Resolution ◽  
Cardiac Muscle ◽  
Electron Micrographs ◽  
Chromic Acid ◽  
Freeze Fracture ◽  
Distilled Water ◽  
Fine Scale ◽  
Acid Cleaning ◽  
Cleaning Solution

Complementary replicas have revealed the fact that the two common faces observed in electron micrographs of freeze-fracture and freeze-etch specimens are complementary to each other and are thus the new faces of a split membrane rather than the original inner and outer surfaces (1, 2 and personal observations). The big question raised by published electron micrographs is why do we not see depressions in the complementary face opposite membrane-associated particles? Reports have appeared indicating that some depressions do appear but complementarity on such a fine scale has yet to be shown.Dog cardiac muscle was perfused with glutaraldehyde, washed in distilled water, then transferred to 30% glycerol (material furnished by Dr. Joaquim Sommer, Duke Univ., and VA Hospital, Durham, N.C.). Small strips were freeze-fractured in a Denton Vacuum DFE-2 Freeze-Etch Unit with complementary replica tooling. Replicas were cleaned in chromic acid cleaning solution, then washed in 4 changes of distilled water and mounted on opposite sides of the center wire of a Formvar-coated grid.

Pinocytotic-Like Forms of Mitochondria From Rat Anterior Pituitary

1968 ◽  
Vol 26 ◽  
pp. 146-147
Author(s):  
Burton B. Silver
Keyword(s):  
Electron Micrographs ◽  
Conformational Changes ◽  
Anterior Pituitary ◽  
Dynamic State ◽  
Surrounding Cell ◽  
The Matrix ◽  
The Moment ◽  
Cell Medium ◽  
Sectioned Tissue ◽  
State Of Activity

Sectioned tissue rarely indicates evidence of what is probably a highly dynamic state of activity in mitochondria which have been reported to undergo a variety of movements such as streaming, divisions and coalescence. Recently, mitochondria from the rat anterior pituitary have been fixed in a variety of configurations which suggest that conformational changes were occurring at the moment of fixation. Pinocytotic-like vacuoles which may be taking in or expelling materials from the surrounding cell medium, appear to be forming in some of the mitochondria. In some cases, pores extend into the matrix of the mitochondria. In other forms, the remains of what seems to be pinched off vacuoles are evident in the mitochondrial interior. Dense materials, resembling secretory droplets, appear at the junction of the pores and the cytoplasm. The droplets are similar to the secretory materials commonly identified in electron micrographs of the anterior pituitary.

Simulated Dark-Field Electron Micrographs of Point Defects and Organometallics

1975 ◽  
Vol 33 ◽  
pp. 200-201
Author(s):  
William Krakow
Keyword(s):  
Electron Micrographs ◽  
Point Defects ◽  
Structure Determination ◽  
Atomic Structure ◽  
Image Interpretation ◽  
Dark Field ◽  
Field Electron ◽  
Dark Field Microscopy ◽  
Dark Field Electron

Tilted beam dark-field microscopy has been applied to atomic structure determination in perfect crystals, several synthesized molecules with heavy atcm markers and in the study of displaced atoms in crystals. Interpretation of this information in terms of atom positions and atom correlations is not straightforward. Therefore, calculated dark-field images can be an invaluable aid in image interpretation.

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