bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlation averaging of sickle cell hemoglobin fibers
Authors: Crepeau R.H. , Edelstein S.J.
Published: June 2020

Deoxyhemoglobin S fibers, responsible for the erythrocyte deformation characteristic of sickle cell anemia, have been studied by applying correlation techniques to negatively stained images. The objectives of this study are to provide higher resolution three-dimensional reconstructions than previously obtained. Earlier studies in this laboratory required a combined real space - Fourier space analysis (REFORM) to determine the fourteen strand morphology of the cross-section and the approximate tetramer packing arrangement to about 30 Å resolution. That work provided the basis for preliminary molecular model building efforts, but higher resolution will be necessary to establish the orientation of individual tetramers. An absolute directionality in the fibers, implied by the presence of an odd number of pairs of filaments in the fourteen strand model, is demonstrated by the real space correlation method described here.

Correlation methods have been used for locating equivalent copies of a reference particle in either randomly ordered two-dimensional particles (projection) or imperfectly ordered flat sheets.
Ultrastructure in pituitary gonadotrophs and Leydig cells of sterile male mice
Authors: Andrews Annette M. , Hoage Terrell R. , Turner Jack , Bishop Jack B.
Published: June 2020

Mouse systems are used as models to test for chromosome translocations and other damage caused by exposure to environmental chemicals. To evaluate mutagenic activity of triethylenemelamine (TEM), 397 male offspring with chromosome translocations were produced from TEM-treated CD1males and F1(C57BL/6J x BALB/c) females. Breeding tests showed 26 to be sterile but cytogenetic examination by hemiorchiectomy at 11-13 months was inconclusive because of reduced meiotic activity. Radioimmunoassay for serum testosterone showed a range from 0.96 ± 0.41ng/ml to 10.55 ± 1.65ng/ml in sterile males while fertile translocation and control animals showed 3.17 ± 0.53 ng/ml. This study used 2-3 animals per group, selected from a non-treated control group and from groups with high serum testosterone (HT), medial serum testosterone (MT) and low serum testosterone (LT).

Pituitary and testes were removed from ether-anesthetized animals, immediately fixed in 4% gl utaraldehyde, post-fixed in 1% OsO4, dehydrated in ethanol, and embedded in Epon-araldite resin. Thin sections (l00nm) were stained with uranyl acetate and lead citrate then examined at 60kV in a Philips 201 electron microscope.
Emigration of neutrophils in the central nervous system
Authors: L.Beggs John , Waggener John D. , Miller Wanda , Watkins Jane
Published: June 2020

Studies using mesenteric and ear chamber preparations have shown that interendothelial junctions provide the route for neutrophil emigration during inflammation. The term emigration refers to the passage of white blood cells across the endothelium from the vascular lumen. Although the precise pathway of transendo- thelial emigration in the central nervous system (CNS) has not been resolved, the presence of different physiological and morphological (tight junctions) properties of CNS endothelium may dictate alternate emigration pathways.

To study neutrophil emigration in the CNS, we induced meningitis in guinea pigs by intracisternal injection of E. coli bacteria.

In this model, leptomeningeal inflammation is well developed by 3 hr. After 3 1/2 hr, animals were sacrificed by arterial perfusion with 3% phosphate buffered glutaraldehyde. Tissues from brain and spinal cord were post-fixed in 1% osmium tetroxide, dehydrated in alcohols and propylene oxide, and embedded in Epon. Thin serial sections were cut with diamond knives and examined in a Philips 300 electron microscope.
Dissolution of eosinophil granules in bronchial lavage obtained from allergic asthmatics during bronchoprovocation and seasonal exposure
Authors: Worden K. A. , Metzger W. J. , Kopp W. , Richerson H. B. , Hunninghake G.
Published: June 2020

Bronchial lavage was used to assess changes in cell populations from the airways of allergic asthmatic patients who were exposed seasonally to allergens or challenged with aerosolized allergen. Bronchoprovocation (BPC) was used to elicit early and late asthmatic responses (LAR), and bronchial lavage was performed at baseline out of season or at either 2, 6, or 24 hours after challenge, and during the season in five mildly symptomatic patients. Four normal subjects were challenged with allergen and lavaged either 2 or 6 hours later.

Bronchial lavage fluid and cells from subsegmental bronchi were immediately passed through 2 layers of gauze and cells were washed once with Hank's buffered salt solution and gently centrifuged. Cyto-preps of lavage cells were prepared and examined by light, microscopy with a Wright-Giemsa stain. These cells were then mixed with 50% Percoll and centrifuged at 1500 RPM for 20 minutes. This procedure was adopted to concentrate small numbers of cells such as eosinophils and mast cells into a pellet which contained relatively few macrophages.
Dynamical Aspects of Electron Diffraction
Authors: Humphreys C. J.
Published: June 2020

In this year of the 50th Anniversary of Electron Diffraction it seems particularly appropriate that a significant amount of the current work in dynamical electron diffraction is devoted to taking a second look at some of the more fundamental aspects of the subject. In 1927 electron diffraction was demonstrated experimentally and in 1928 the first formulation of the theory was given. The next thirty years saw the gradual development of the electron microscope and of diffraction theories applied to perfect crystals (for example, 4 to 7). In the last twenty years an enormous expansion of the theory and the practice of electron diffraction and microscopy has occurred in materials science, largely stemming from the discovery that dislocations could be imaged in the electron microscope (8,9). Most of this work has been concerned with studying the distribution and the nature of defects in crystalline materials.
Solute Segregation in Stainless Steel under Irradiation
Authors: Kenik Edward A.
Published: June 2020

Solute element additions can significantly influence the behavior of an alloy under irradiation. The aggregation of irradiation-induced vacancies into three-dimensional clusters, voids, and the volume expansion, swelling, associated with void formation is of prime concern in the design of nuclear reactors. A modified type 316 stainless steel, LS1A, has been developed which exhibits high resistance to swelling. This alloy, containing ˜1.0 wt % silicon and 0. 15 wt % titanium, swells 30 times less under nickel ion irradiation than a nominal type 316 stainless steel.

In addition to the observation of swelling resistance in LS1A, it was observed that the evolution of dislocation portions of the damage structure was modified by the silicon and titanium additions. Specifically, the stability of faulted dislocation loops in LS1A is quite high and the growth of large loops is severely curtailed. At higher doses, radiation-induced precipitates of the same size and shape as the dislocation loops were observed.
Stability of Chemical Order in Ni4Mo Alloy under Fast Electron Irradiation
Authors: Carpenter R. W. , Kenik E. A.
Published: June 2020

Short-range order (SRO) or clustering strongly influences swelling in alloys. For example, Al-Cu alloys containing G-P zones, Cu-Ti alloys containing modulated structures, and Ni-Mo alloys containing various degrees of chemical order are all resistant to void swelling caused by displacive irradiation at elevated temperature. Conversely, displacive particle irradiations may change the configuration of local composition variations. When aluminum-copper alloys containing G-P zones are irradiated with 1 MeV electrons a transformation to 'θ' occurs, and the usually observed θ” state is not observed. This paper presents the results of an experimental investigation of order stability in Ni—20 at. % Mo alloys during irradiation with 1 MeV electrons. This alloy is especially useful for studying the stability of order during irradiation because the symmetry of the intensity distribution in reciprocal space corresponding to SRO is quite different from that corresponding to the Dla long-range order (LRO) observed at thermal equilibrium in this alloy.
The Use of a Lanthanum Hexaboride Filament in a Transmission Electron Microscope - The Philips EM-400
Authors: Mumaw V. R. , Munger B. L.
Published: June 2020

The use of lanthanum hexaboride (LaBg) as an electron source in scanning electron microscopes equipped with an ion pumped emission chamber at less than 10~6 torr, has proven to be very advantageous. It was not until the introduction of the Philips EM-400 that a standard commercially available transmission electron microscope was differentially pumped between the emission chamber and the viewing chamber and capable of achieving a vacuum suitable for utilizing this type of electron source.

Only minor modifications were necessary to use the LaBg filament (Kimbal Physics, Wilton, N.H.) in the Philips EM-400 electron microscope. The Wehnelt cap was modified so that the Wehnelt aperture can be removed without disassembly of the cap (Fig. 1). The Wehnelt aperture is 0.7 mm in diameter. A simple spanner wrench is used to remove the Wehnelt aperture. Rough centering of the filament was quite easy using a Zeiss operating stereomicroscope at 25X with the Wehnelt aperture removed.
Vacuum System to Minimize the Specimen Contamination of High-Performance EM
Authors: Yoshimura N. , Shirota K. , Etoh T.
Published: June 2020

One of the most important requirements for a high-performance EM, especially an analytical EM using a fine beam probe, is to prevent specimen contamination by providing a clean high vacuum in the vicinity of the specimen. However, in almost all commercial EMs, the pressure in the vicinity of the specimen under observation is usually more than ten times higher than the pressure measured at the punping line. The EM column inevitably requires the use of greased Viton O-rings for fine movement, and specimens and films need to be exchanged frequently and several attachments may also be exchanged. For these reasons, a high speed pumping system, as well as a clean vacuum system, is now required. A newly developed electron microscope, the JEM-100CX features clean high vacuum in the vicinity of the specimen, realized by the use of a CASCADE type diffusion pump system which has been essentially improved over its predeces- sorD employed on the JEM-100C.
Observation of Atom Rows in Thorium Pyromellitate Using a Field Emission STEM
Authors: Todokoro H. , Nomura S. , Komoda T.
Published: June 2020

It is interesting to observe polymers at atomic size resolution. Some works have been reported for thorium pyromellitate by using a STEM (1), or a CTEM (2,3). The results showed that this polymer forms a chain in which thorium atoms are arranged. However, the distance between adjacent thorium atoms varies over a wide range (0.4-1.3nm) according to the different authors.

The present authors have also observed thorium pyromellitate specimens by means of a field emission STEM, described in reference 4. The specimen was prepared by placing a drop of thorium pyromellitate in 10-3CH3OH solution onto an amorphous carbon film about 2nm thick. The dark field image is shown in Fig. 1A. Thorium atoms are clearly observed as regular atom rows having a spacing of 0.85nm. This lattice gradually deteriorated by successive observations. The image changed to granular structures, as shown in Fig. 1B, which was taken after four scanning frames.
An Electron Microscope for High Quality Low Magnification with a Wide Field
Authors: Kubozoe M. , Sato H. , Kasai S. , Ozasa S.
Published: June 2020

A permanent magnet which is a combination of cobalt and some rare earth metal is recently being utilized. HICOREX is a commercial product of this magnet. Its maximum BH is several times larger than that of an ordinary Alnico magnet, providing a value of 10 n* 26 MGOe. When this permanent magnet is used for an electron lens (called HICOREX lens), not only does it offer a very strong lens but it can be made extremely small, and a new facility can be devised using this feature.

A triple pole piece lens which is made by combining two HICOREX magnets enables relatively easy compensation of magnification distortion and spiral distortion, and its effective radius of field is about twice that of an ordinary lens excited with an electromagnetic coil. This HICOREX lens has a diameter of 16 mm and height of about 10 mm. Despite being so tiny its focal length is about 3 mm at 75 kV accelerating voltage (refer to Fig. 2).
Measurement of the Displacement Across a Coincidence Grain Boundary
Authors: Matthews J. W. , Stobbs W. M.
Published: June 2020

Many high-angle grain boundaries in cubic crystals are thought to be either coincidence boundaries (1) or coincidence boundaries to which grain boundary dislocations have been added (1,2). Calculations of the arrangement of atoms inside coincidence boundaries suggest that the coincidence lattice will usually not be continuous across a coincidence boundary (3). There will usually be a rigid displacement of the lattice on one side of the boundary relative to that on the other. This displacement gives rise to a stacking fault in the coincidence lattice.

Recently, Pond (4) and Smith (5) have measured the lattice displacement at coincidence boundaries in aluminum. We have developed (6) an alternative to the measuring technique used by them, and have used it to find two of the three components of the displacement at {112} lateral twin boundaries in gold. This paper describes our method and presents a brief account of the results we have obtained.
Metallurgical Effects of Grain Boundary Ledges
Authors: Murr L.E.
Published: June 2020

Ledges in grain boundaries can be identified by their characteristic contrast features (straight, black-white lines) distinct from those of lattice dislocations, for example1,2[see Fig. 1(a) and (b)]. Simple contrast rules as pointed out by Murr and Venkatesh2, can be established so that ledges may be recognized with come confidence, and the number of ledges per unit length of grain boundary (referred to as the ledge density, m) measured by direct observations in the transmission electron microscope. Such measurements can then give rise to quantitative data which can be used to provide evidence for the influence of ledges on the physical and mechanical properties of materials.

It has been shown that ledge density can be systematically altered in some metals by thermo-mechanical treatment3,4.
Microscopical Detection Of Fiber-Finish Interaction Sites
Authors: Goynes W. R. , Carra J. H. , Timpa J. D.
Published: June 2020

In the chemical finishing of textile products, final location of the chemical agent is affected by several factors. Finish location can be critical to production of a desired effect, especially when more than one finish is used on a fabric blended of different fibers. To predetermine location sites, it is first necessary to be able to detect areas of chemical interaction and to determine under what conditions a given location is attained. Microscopical methods show the presence of chemical finishing agents in various sites of the morphological structure of a fabric.

Tetramethylol 2,4-diamino-6(3,3,3-tribromopropyl)triazine (TM-DABT) is an effective, durable flame retardant for all-cotton fabrics. Solubility studies of cross sections from TM-DABT-finished cotton fibers indicated that the chemical had penetrated the fiber and insolubilized it to the cellulose solvent cupriethylenediamine hydroxide (cuene).
Quantitative Stereology and Image Analysis
Authors: Underwood Ervin E.
Published: June 2020

Stereology is the study of the three-dimensional structure of materials from two-dimensional sections or projections. By suitable statistical measurements on the test plane or projection plane, and by utilizing the basic equations of stereology, the true three-dimensional quantities can be calculated. Such attributes of the structure as points P, lines L, surfaces S, volumes V, numbers N, as well as spacings, sizes, curvatures, etc. can be obtained without a priori assumptions.

In this review, the basic relationships of quantitative stereology are summarized, both for opaque and transparent materials. Thus the image to be analyzed may derive from a photograph of a metallic polished surface or from an electron transmission micrograph obtained from a biological slice or replica. The complete quantitative characterization of the microstructure involves data obtained from both reflected images and transmitted (or projected) images. We will discuss the relationships applicable to each type of image, then show their interrelationships.
A Method Of Interfacing A Transmission Electron Microscope (Tem) With An Automatic Image Analysis System (AIA)
Authors: Echelmeier R. H.
Published: June 2020

To interface a TEM with an AIA, I replaced the 70mm. camera mounting on the TEM with a fixture incorporating a fluorescent screen and a leaded glass X-ray shield. The phosphor I chose for the screen, “P-12”, is highly efficient and exhibits a spectral peak at the same wavelength as the television tube selected for the job. This tube is a Type 4532 silicon-intensified target (SIT) tube supplied by COHU, Inc. as part of their Type 4250 low-light-level television camera (LLLTV). The composite video signal from this camera is transmitted by cable to the AIA system where it is processed and displayed on a monitor along with information regarding the processing. A second cable returns this processed video signal to the TEM where another monitor allows the microscope operator to see the results. The processing of the signal includes detection of features in the field of view using a grey-level threshold set by the AIA operator, and selection of the desired features thus detected by means of size and shape parameters also supplied by the operator.
Data Analysis In Electron Energy Loss Spectroscopy
Authors: Spence J.C.H.
Published: June 2020

The sensitivity of the shape of K shell excitation differential energy loss peaks to the atomic environment suggests that this technique may be useful in determining the chemical state, amount, type and distribution of small quantities of light elements embedded in a host matrix (1,2). In order to extract useful information about, say, the bonding of atoms from K-shell spectra it is important to ensure that satellite peaks arising from multiple scattering are not allowed to mask genuine features which reflect the final density of states for a particular transition. In addition, for the rapid identification of several species, the vast multitude of closely spaced K, L, M and N losses possible from a specimen of unknown composition containing many elements together with their associated plasmon satellites makes it imperative that a systematic method of background subtraction be used which eliminates both multiple scattering and the effects of instrumental broadening. An asymmetric spectrometer energy loss impulse response may also lead to the appearance of spurious peaks in a spectrum.
The Uses of Electron Energy Loss Spectrometry in Biology
Authors: Johnson D. E.
Published: June 2020

The uses of electron energy loss spectrometry in biological microscopy range from the simple filtering of energy loss electrons to remove their degrading effect in conventional transmission microscopes, to the detailed use of the information carried by energy loss electrons in determining molecular and elemental composition on a microscopic level. The electron energy loss spectrum, to the extent that it is characteristic of the specimen, reflects the atomic and molecular energy levels of the specimen. In considering the uses of electron energy loss spectrometry in biology it is convenient to separate the energy loss events into two groups, those characteristic of the molecules present and those characteristic of the elements present.

The energy loss spectrum of organic materials in the region below ∽10ev energy loss reflects the same molecular transitions as ultraviolet and vacuum ultraviolet absorption spectra in this energy region and is equally characteristic of the molecules present.

In the region from ∽10ev to 50ev are energy loss events resulting from additional single electron excitations and ionizations modified by collective effects in the solid.
Cross-Sections for K-Shell Excitation by Fast Electrons
Authors: Egerton R. F. , Joy D. C.
Published: June 2020

The cross-section for excitation of an electron from the innermost shell of a given atom can be determined directly by measuring the proportion of fast incident electrons which have suffered an appropriate energy loss, or (if the X-ray or Auger yields are known) from the number of X-ray quanta or Auger electrons emitted as a result of de-excitation.

In the direct method, this cross-section is obtained as a function of α, the maximum scattering angle allowed into the detector, and for a thin specimen it is given by:

where n is the number of atoms per unit volume of specimen, t is the specimen thickness, Ik(α) represents the number of K-loss electrons reaching the detector and Itrepresents the total number of fast electrons entering the detector,1for the same value of α. Equation (1) can also be used12for microanalysis of low-atomic-number elements in order to measure n or nt if σK(α) is known.
Transmission Electron Microscopy Study of Precipitation in a Nickel-Beryllium Alloy
Authors: Hills C. R. , Nordstrom T. V.
Published: June 2020

The aging sequence in precipitation hardening Ni-2 w/o Be has been studied by transmission electron microscopy as a function of time at temperatures of 400°C, 565°C, 650°C and 750°C. The microstructural changes at different stages in the aging sequence were analyzed by a combination of electron diffraction and dark field microscopy. Prior to aging, the alloy was solution annealed at 1100°C for 6 hrs. Subsequent examination of the solution annealed material showed no evidence of either continuous or discontinuous precipitation.

The precipitation sequence following aging at 400°C and 565 °C was found to be:

This is analogous to that reported for the widely studied copper-beryllium1 and copper-zinc-beryllium2 systems. Precipitation commences with the nucleation of coherent platlet G. P. zones parallel to {001} matrix planes. As aging proceeds, the intermediate semicoherent γ precipitate is formed continuously from the G. P. zones.
“Black Hole” Scanning Electron Microscopy
Authors: Barish L.
Published: June 2020

In conventional photography two rules generally followed in portraying an isolated subject are first, the maintenance of an unobtrusive background and second, the maximization of contrast in shade between the subject and background. In SEM these rules are often difficult to obey. An isolated subject mounted over an ordinary stud can reveal all sorts of disturbing backgrounds, including, for example, a sea of lathe marks (Fig. 1). By mounting the subject over a highly polished stud or over a glass cover slip, a featureless background can result; however, it is often a shade of grey, insufficient in shade contrast against the subject. These problems can be overcome by a simple technique which renders the background in SEM perfectly black, merely by incorporating a deep guarded void beneath the subject. A portion of primary beam not striking the subject continues to the base of the void. The secondary electrons emanating from the base of the void are sufficiently remote from the scintillator that they have great difficulty reaching it; thus, a negligible signal results and the background is black.
TEM Specimen Preparation from Micro-Areas of Metallurgical Interest
Authors: Koch Edward F.
Published: June 2020

Most metallurgical phenomena of industrial interest can trace their origin to specific regions in operating components. Determining the microstructural changes that accompany the origins of these metallurgical phenomena helps considerably in their overall understanding. Examples include studies of microstructural changes at crack tips, surface oxidation effects on base material, and narrow reaction zones in suitably heat treated material. For such microareas, only a single region of interest is usually available for microstructural examination, making TEM specimen preparation procedures extremely critical.

304 austenitic steel is susceptible to intergranular stress corrosion cracking when subjected to a corrosive environment in the presence of stress and a sensitized microstructure. The latter is characterized by chromium carbide, Cr23C6, at the grain boundaries. Confirmation of the presence of these carbides at the tip of an intergranular crack created in an environment can be provided by TEM examination. The microarea of interest can be pinpointed by using selective platinum washers during electropolishing, yielding electron-transparent regions of the type shown in figure 1.
An Apparatus for Chemical Jet-Thinning
Authors: Russell Robert R.
Published: June 2020

A simple, inexpensive and safe apparatus has been constructed to chemically jet-thin silicon samples for transmission electron microscopy. The thinning apparatus, constructed from chemically resistant materials, is designed to quickly and reproducibly thin samples without subjecting the operator to hazards from highly corrosive polishing solutions. Polishing action is accomplished from one side of the sample while the obverse surface is protected from attack, thus allowing TEM studies of very shallow-surface effects.

Jet-thinning devices for producing electron transparent samples, particularly from silicon and germanium, have been previously reported (1, 2, 3, 4, 5). All of these devices accomplish essentially the same task. Most, however, have one or more of the following disadvantages: (a) they are cumbersome to use, requiring several steps of sample preparation prior to final thinning; (b) they are fairly complex mechanisms, expensive to construct, and often contain components susceptible to corrosion from polishing solutions, and (c) they are often hazardous to use, providing little protection to the user from highly caustic chemical polishes.
Void and Bubble Size Measurement: The Effect of Focus Condition
Authors: Sprague J. A.
Published: June 2020

In quantitative TEM of voids and bubbles in irradiated metals, the volume fraction of the specimen occupied by the cavities is often the final quantity of interest. This implies that linear sizes (diameters or edge lengths) must be determined very accurately, since, for example, a 15% overestimate of cavity size will cause a 52% overestimate of volume. The most commonly-used method for imaging voids is to orient the specimen away from strong Bragg reflections and focus the objective lens to produce the sharpest void images. This condition, with the objective lens underfocused by approximately one micron, normally produces images consisting of a bright central area surrounded by a dark ring, as shown in Fig. la. Although the contrast of cavities has been investigated by a number of authors, most recently Ruhle and Wilkens (1), the question of whether the edge of a void corresponds to the inside or the outside of the dark ring has not been fully resolved.
Origins of Vesicles in the Cells of Saccharomyces Cerevesiae
Authors: Gallili Gilad E. , Lai Margaret H. , Ghosh B. K.
Published: June 2020

It is a general characteristic of the fungal organism that they contain many vesicles. These vesicles are frequently associated to growth zone of the cells; e.g., growing hyphal tip (1) or the region of bud formation (2). They also have been located at the region where degradation of intracellular material takes place (3). It appears that these are transport vesicles which carry enzymes, wall material or other constituents needed in a high concentration in specific location of a cell. In Saccharomyces cerevesiae those vesicles have been suggested (2) to have originated from endoplasmic reticulum (ER). It is implied in this suggestion that secretory products are transported from the site of synthesis (i.e., ER) by a mechanism comparable to that established in mammalian or higher plant cells (4). Although this appears to be highly probable, the results presented in this paper offers the following cytological evidence which contradicts this view.
X-Ray Microanalysis of Enzyme Activity: Transport Atpase
Authors: Rosen S. , Beeuvkes R.
Published: June 2020

Although electron prohe analysis is considered useful for detection of constituent elements in biological studies, only a few investigations, basically concerned with elemental identification, have been made to explore its potential in histoehemical studies of enzymes. The methods available for the cytochemical study of sodium-potassium activated adenosine triphosphatase (transport ATPase) all contain probe detectable elements, but a recent technique dependent on the closely associated K+ dependent-ouabain sensitive phosphatase activity provides appropriate circumstances for both detection and quantitation of enzyme reaction product (l). Because it measures the immediate product of enzyme hydrolysis, this method parallels conventional biochemical methods. The resolution of the probe allows activity to be determined at the cellular level.

To perform probe analysis of enzyme activity in tissue sections, conditions must be found that result in the stabilization of enzyme product at the reaction site. For measurement of transport ATPase, the technique is based on the ouabain-sensitive, K-dependent phosphatase hydrolysis of p-nitrophenol phosphate in alkaline media containing dimethylsulfoxide.
Simultaneous Electron Microscopic Autoradiographic and Immunocytochemical Localization of H-l Parvovirus DNA Synthesis and Protein Accumulation in Human NB Cells
Authors: Singer Irwin I. , Rhode Solon L.
Published: June 2020

Fine structural and immunocytochemical experiments have indicated that two distinct categories of H-l viral proteins exhibit different sites of accumu- lation within infected human NB cell nuclei: A), assembled capsids (either “empty” or “full”) are associated with euchromatic fibers; B). unassembled viral proteins accumulate upon heterochromatin (HC) and nucleolar associated chromatin (NAC) (1,2). Since H-l progeny ss DNA synthesis requires viral protein synthesis (3), and presumably host cell enzymes as well, we attempted to localize it with respect to the above sites using electron microscopic autoradiography (EMARG). We studied infections induced by wt H-l, or ts-1 H-l, a conditional mutant defective in progeny ss DNA synthesis at the re- strictive temperature (3). Parasynchronous NB cultures were obtained by methotrexate treatment, infected with wt H-l (at,37°C), or ts-1 H-l (at 39.5°C), and pulsed with high specific activity H-thymidine (100 Ci/mmol) for either 2, 5, 10 or 60 min.
A Differential Centrifugation Procedure for Obtaining Unstretched Metaphase Chromosomes from Higher Plants for Transmission Electron Microscopy
Authors: Woods Philip S. , Van't Hof Jack , Ledbetter Myron C.
Published: June 2020

Metaphase chromosomes prepared as whole mounts for transmission electron microscopy have been studied by many workers using a variety of methods(1,2,3, 4). While satisfactory for some purposes these methods usually result in distortions which complicate interpretation of chromosome fine structure. In addition, most procedures were adapted for animal chromosomes and were inappropriate for plants in which cell walls present a barrier to isolation. Recently, Wolfe and Martin(5) used a pressing procedure devised by McLeish(6) to obtain plant root tip chromosomes and used this in combination with the water spreading method of Gall(3). Their electron micrographs, though unique in showing plant chromosomes essentially for the first time, nevertheless showed chromosomal distortions typical of water spreading. Chromosomes in the nearly natural state can be obtained by modifying Wolfe and Martin's procedure to the extent of replacing surface spreading with differential centrifugation of the broken-cell suspension.
Developmental Distribution of Microperoxisomes in the Rat Submandibular Gland
Authors: Mooradian B.A. , Cutler L.S.
Published: June 2020

In the mature rat submandibular gland (SMG) microperoxisomes have been identified in both acinar secretory cells and ductal cells. The present study was undertaken to investigate the size, number and distribution of microperoxisomes during the pre and postnatal development of the SMG in order to determine if there were changes in cellular microperoxisomes during the functional differentiation of the various cell types.
Ultrastructural Localization of Acetylcholinesterase in the Arcuate Nucleus and Median Eminence of the Rat
Authors: Carson K.A. , Nemeroff C.B. , Rone M.S. , Kizer J.S. , Hanker J.S.
Published: June 2020

Biochemical, physiological, pharmacological, and more recently enzyme histo- chemical data have indicated that cholinergic circuits exist in the hypothalamus. Ultrastructural correlates of these pathways such as acetylcholinesterase (AchE) positive neurons in the arcuate nucleus (ARC) and stained terminals in the median eminence (ME) have yet to be described. Initial studies in our laboratories utilizing chemical lesioning and microdissection techniques coupled with microchemical and light microscopic enzyme histo- chemical studies suggested the existence of cholinergic neurons in the ARC which project to the ME (1). Furthermore, in adult male rats with Halasz deafferentations (hypothalamic islands composed primarily of the isolated ARC and the ME) choline acetyltransferase (ChAc) activity, a good marker for cholinergic neurons, was not significantly reduced in the ME and was only somewhat reduced in the ARC (2). Treatment of neonatal rats with high doses of monosodium 1-glutamate (MSG) results in a lesion largely restricted to the neurons of the ARC.
Ultrastructural Localization of Cellulase in Diplodia Maydis and in D. Maydis-Infected Com Stalk Tissue
Authors: Murphy Judith A. , Thompson Mary R. , Pappelis A.J.
Published: June 2020

BeMiller et.al.(l) found that D. maydis did not have the solubilizing enzyme C1. They reported that D- maydis exhibited cellulolytic activity constitutively, and hypothesized that the cellulolytic enzymes were attached to fungal hyphal surfaces because they found cellulase released to the culture medium only after the growth period, when available cellulose had been used up.

The purpose of this study was to determine the location of cellulolytic enzymes (EC 3.2.1.4; beta-1,4-glucan glucanohydrolase) in D. maydis and D. maydis-infected corn tissue at the ultrastructural level.

Cellulase activity produces glucose as an end product which will reduce cupric oxide and can be visualized with an EM because it is electron dense and the Cu component can be verified with x-ray analysis(Figs.l,2). After thorough washing, samples fixed in aldehydes are incubated in a substrate mixture at a low pH. The enzyme is activated and reducing sugar is released. The sample is then reacted with Benedict's solution at a high temperature, allowing CuO crystals to be deposited at the site of reaction.
Membrane Changes in Polymorphonuclear Leukocytes During Ionophore (A23187) - Induced Lysosomal Release
Authors: Moore P.L. , Sannes P.L. , Bank H.L. , Spicer S.S.
Published: June 2020

It is thought that calcium and/or magnesium may play important roles in polymorphonuclear (PMN) leukocyte functions such as chemotaxis, adhesion and phagocytosis. Yet, a clear understanding of the biological roles of these ions has awaited the development of techniques which permit a selective alteration of intracellular ion concentrations. Recently, treatment of cells with the ionophore A23187 has been used to alter intracellular divalent cation concentrations. This ionophore is a lipid soluble antibiotic produced by Streptomyces chartreusensis that complexes with both calcium and magnesium (3) and is believed to carry these ions across biological membranes (4). Biochemical investigations of human PMN leukocytes demonstrate that cells treated with A23187 and extracellular calcium release their lysosomal enzymes into the extracellular medium without rupturing and releasing their soluble cytoplasmic enzymes (5,6). The aim of the present study and and a companion report (7) was to investigate the structural changes that occur in leukocytes during ionophore-induced lysosomal enzyme release.
SEM of the Hydatid Cyst of Echinococcus Granulosus
Authors: Behbehani Kazem , Hassounah Osama , Nayak Ramesh
Published: June 2020

The infection of cattle with the larval stage of Echinococcus granulosus in the State of Kuwait has been reported by several investigators. Both fertile and infertile cysts were present in the infected animals. Previous study revealed an infection rate of 40.2% in 881 Somalian cattle and 32.5% in 43 native cattle. The home slaughtered sheep appeared to play an important role in the dissemination of the parasite and the life of Echinococcus granulosus in the State of Kuwait was assumed to be sheep - dog - sheep. The fine structure of the hydatid cyst and protoscolex of Echinococcus granulosus has been studied by light and transmission electron microscopy. The three dimensional surface features of the hydatid cyst germinative membrane and the brood capsules have not been reported. The purpose of this study was to determine the three dimensional surface topographic features of the germinative membrane of the cyst and the brood capsule.
Temperature Dependence of Beam Induced Mass Loss of Phenylalanine
Authors: Ramamurti K.
Published: June 2020

We have previously reported the results of electron beam-induced mass loss of L-phenylalanine at 7°K (1,2). We are currently in the process of measuring the mass loss as a function of temperature.

As reported earlier, we found negligible mass loss at 7°K. Reference 2 discussed in detail the precautions to be taken to ensure that the measurements are meaningful. In the current series of measurements, the specimen thickness is measured directly as a function of dose rather than measuring the thickness of an irradiated area relative to a reference area. This is done by recording the energy loss spectrum in the range 0-150 Volts with a multichannel analyzer. The number of unscattered and inelastically scattered electrons are found by summing over the respective regions in the spectrum.

Corrections have been made to take into account 1) inclusion of a finite range of energy loss in the spectrum; 2) geometric collection efficiency of the aperture in the spectrometer; and 3) effects due to multiple scattering.
Ultra-Rapid Freezing of Isolated Skeletal Muscle Fibers
Authors: Sommer Joachim R. , Wallace Nancy R.
Published: June 2020

After Howell (1) had shown that ruthenium red treatment of fixed frog skeletal muscle caused collapse of the intermediate cisternae of the sarcoplasmic reticulum (SR), forming a pentalaminate structure by obi iterating the SR lumen, we demonstrated that the phenomenon involves the entire SR including the nuclear envelope and that it also occurs after treatment with other cations, including calcium (2,3,4).

From these observations we have formulated a hypothesis which states that intracellular calcium taken up by the SR at the end of contraction causes the M rete to collapse at a certain threshold concentration as the first step in a subsequent centrifugal zippering of the free SR toward the junctional SR (JSR). This would cause a) bulk transport of SR contents, such as calcium and granular material (4) into the JSR and, b) electrical isolation of the free SR from the JSR.
Quantitative Freeze Fracture Studies of Hepatoma Plasma Membranes
Authors: Stewart T.P. , Kowalak T.M. , Corwin S.P. , Hui S.W.
Published: June 2020

The intramembranous particles (IMP's) seen in most freeze fractured membranes are generally regarded as “randomly” distributed in the plane of the membrane. In certain cases, the distributions of IMP's are apparently non-random. These nonrandom distributions have been described qualitatively as patching, aggregation or domain formation. These characteristics have been used to distinguish transformed cell membranes from their normal parental cells.1

We attempted to quantitate the density and distribution of IMP's in the plasma membrane of (control) rat hepatocytes and in the plasma membranes of moderately slow-growing Reuber H-35 hepatomas. Because of the difficulty in obtaining a sufficiently large fractured surface area from the highly invaginated plasma membranes of these cells, the purified plasma membrane fraction was used for this study. The purified fraction2 consists mostly of right-side-out membrane vesicles.3 The purity of the membrane fraction was checked by thin section and marker enzyme assay.2
Electron Microscopy of the Camel Oviductal Epithelium During Early Pregnancy
Authors: Nayak Ramesh K. , Zein Anwar
Published: June 2020

The function of the oviduct is essential to the reproductive process of mammals since it allows the meeting of gametes and the beginning of embryonic development. A detailed account on the fine structural changes of the porcine oviductal epithelium during pregnancy has been published. Scanning electron microscopic features of the oviduct from estrus camels have been recently described. To the best of our knowledge, no transmission electron microscopic studies of the camel oviductal epithelium during pregnancy have been reported. The purpose of this study was to identify some of the fine structural changes occurring in the tubal epithelium during early pregnancy and to establish a basis for subsequent physiological and pathological studies.

Specimens from the infundibulum region of the oviduct were obtained from 10 pregnant camels. In the present study, it was not possible to determine the exact stage of pregnancy.
Quantitation of Secretion at the Membrane Level
Authors: Satir Birgit H.
Published: June 2020

In the ciliated protozoan Tetrahymena thermophila specific intramembrane particle arrays, called the fusion rosettes, have been shown to mark the site within the cell membrane towards which the secretory organelles of this cell migrate and dock prior to membrane fusion and release of product. Similarly, an annulus of particles is formed at the anterior end of the secretory organelle when it is docked in place below the rosette (1, 2). A single rosette consists of a small ring of 11 (PF + EF) particles with a large center particle (15nm diameter) approximately twice the size of the other particles. The outer diameter of the small ring is 60nm. Earlier studies have shown that, during the fusion of the two partner membranes, the rosette particles do not remain together as a stable unit, but the individual particles of the rosette spread out and become dispersed among the other particles present in the cell membrane.
Preirradiation and minimum beam microscopy of periodic biological specimens
Authors: Baker Timothy S.
Published: June 2020

Minimum beam microscopy, whereby a specimen receives little or no irradiation prior to recording the photographic image, is a useful technique for minimizing radiation damage to biological specimens. Dubochet showed that initial exposure to low beam intensity may somehow reduce specimen "burning" at high beam intensity. Recently, Johansen described a preirradiation method in which the specimen is first given a small dose (∽1 e/Å2), after which it is claimed that subsequent steps may be carried out by standard bright field techniques without loss of fine structural details. This would allow the microscopist more time to select specimen areas, correct for astigmatism, and focus. Preirradiation is said to favor cross-linking reactions over mass-loss, and thus stabilize the fragile biological molecules.
Low dose electron diffraction of wet protein crystals
Authors: Chang B.B. , Parsons D.F.
Published: June 2020

High resolution electron diffraction patterns from wet unstained protein-crystals have been successfully obtained by using very low electron dose (∽10-2 e/Å2, much smaller dose than used by Unwin and Henderson (1975) for electron diffraction of their crystals). This enabled us to follow the radiation damage of the protein crystal due to increasing dosage by recording successive diffraction patterns given by the same crystal. Changes in intensities of both the high and the low order reflections can be studied. Another important consequence is that very low dose electron diffraction can be obtained from the same crystal and iterative procedures such as Gerchberg and Saxton's technique can be applied.

The electron diffraction work with very low dose was performed at 200 kV using the environmental chamber in the Jeolco 200. To achieve best electron diffraction conditions with the specimen in the hydration chamber, the objective and intermediate lens currents have been changed.
A quantitative EM study op the packing and shape of the protein subunits organized in contractile sheaths
Authors: Cremers A.P.M. , Krijgsman P.C.J.
Published: June 2020

Phages for example from the T-even family have a complex structure. They consist of a head in which the DNA is packaged, a contractile sheath and a complex structure with which the phage attaches itself to the membrane of the host cell.

We are studying the structural mechanism by which the sheath transmits the DNA in the recipient cell by electron microscopy and image analysis techniques. The contractile sheath of these types of phages consists of a large number of identical protein subunits which are arranged in a regular way.

To study the arrangement of the subunits in five PBS X-like defective phages, from B.subtilis and B.licheniformis, negatively stained specimens were imaged by electron microscopy and the images were subjected to optical diffraction and digital analysis. The extended and contracted sheath configuration of the five defective phages were found to be similar and differed from the known cases of T4 and Mu.
Topography of s bacterial membrane: the HPI-layer of M.radiodurans
Authors: Kübler O. , Hahn M. , Baumeister W.
Published: June 2020

The cell wall of Micrococcus radlodurans has multilayered structure, which is quite untypical for grain-positive bacteria. The HPI-layer is a membraneous sheet containing lipids, carotenoids, carbohydrates and protein and covers the outer surface of the murein sacculus.

HPI-layers isolated from Micrococcus radiodurans have been studied by electron microscopy employing negative as well as positive staining and subsequent digital image processing. The protein complexes in these layers form regular periodic arrays comprising up to about 3000 unit cells. The subunits making up the HPI-layer are arranged in almost perfect hexagonal symmetry (L1, L2 ∽16.9 nm; φ = 120. 12 ± 4.2°).

The projected structure of negatively stained HPI-layers has been determined at a resolution of 3 nm. From the averaged images the topography of the protein and lipid components, the arrangement of the major subunits within each protein complex as well as the connections between these complexes in the lattice can be derived.