bluuebunny/crossref_metadata_2025 huggingface dataset:
Scanning Electron Microscopy of an 8 μm Thick ZrO2 Film
Authors: Ploc R.A. , Miller M.A.
Published: June 2020

This abstract reports the occurrence of 'breakaway oxidation' for unalloyed zirconium in 300°C oxygen. An excellent review of zirconium and zirconium alloy oxidation can be found elsewhere (1).

Approximately one dozen crystal bar zirconium coupons were placed in a resistance wound furnace held at 300°C and through which oxygen (initially passed through a silica gel dessicant) was passed. Over a period of three years, the samples accumulated over 700 days of oxidation time. The kinetics followed a rate law between cubic and parabolic until achieving an oxide thickness approximately 350 nm at which point 'breakaway' occurred. For instance, in one year the film increased in thickness from 0.35 to more than 8 μm. These thick, post-transition oxides were examined in the SEM.

The samples were characterized by regions approximately 40 μm in diameter which spalled with a density of about 45 per cm2.
Dislocation Substructures Produced During Tensile, Creep, and Fatigue Deformation of Ti3Al at 700°C
Authors: Sastry S. M. L.
Published: June 2020

Ti3Al is an ordered intermetallic compound having the DO19-type superlattice structure. The compound exhibits very limited ductility in tension below 700°C because of a pronounced planarity of slip and the absence of a sufficient number of independent slip systems. Significant differences in slip behavior in the compound as a result of differences in strain rate and mode of deformation are reported here.

Figure 1 is a comparison of dislocation substructures in polycrystalline Ti3Al specimens deformed in tension, creep, and fatigue. Slip activity on both the basal and prism planes is observed for each mode of deformation. The dominant slip vector in unidirectional deformation is the a-type (b) = <1120>) (Fig. la). The dislocations are straight, occur for the most part in a screw orientation, and are arranged in planar bands. In contrast, the dislocation distribution in specimens crept at 700°C (Fig. lb) is characterized by a much reduced planarity of slip, a tangled dislocation arrangement instead of planar bands, and an increased incidence of nonbasal slip vectors.
Post Creep Microstructures of Ti-6A12Sn4Zrf3Mo Alloy
Authors: Fujishiro S. , Sommer A. W.
Published: June 2020

It has been reported (1,2) that in highly textured titanium alloys the secondary creep rate in the direction normal to major concentration of basal poles at elevated temperatures is much greater than that of the c-direction. This phenomenon can be attributed to two major reasons: the first is that Youngs Modulus in the c-direction is approximately 25% higher than in the a-direc- tion; the second is that if an alpha grain is oriented in the c-direction with respect to the applied stress, the Schmid factor for prismatic planes is zero, and thus the slip on the major slip systems is extremely restricted. In the present study, two sets of creep specimens have been prepared from a highly textured Ti-6A12Sn4Zr6Mo alloy plate; one set is parallel to the rolling direction and the other set is parallel to the long transverse direction (major concentration of c-poles).
Origin of Voids in Thin Films
Authors: Nakahara S.
Published: June 2020

A recent transmission-electron-microscope (TEM) study has shown, using the defocus contrast technique, that thin evaporated gold films contain a high density of small voids.

In this communication, we report a TEM study on the structure and distribution of voids in thin films prepared by evaporation, sputtering, and electrodeposition and discuss a possible mechanism, by which voids are generated during film growth.

In evaporation, sputtering, and electrodeposition processes, the entrapment of gaseous and/or organic impurities at growing film surface cannot be avoided due to their relatively unclean environment. Such impurity entrapment could take place conveniently at surface irregularities such as growth steps, grain boundaries and valleys between aggregates of crystallites. The incorporation of trapped impurities, therefore, results in the formation of voids at the above three sites. It can be easily seen that the spacial distribution of voids generated at grain boundaries should closely follow the grain structure of thin films.
Fine Microstructure of a Mechanically Alloyed Oxide Dispersion Strengthened Nickel-Base Superalloy
Authors: Marti Jordi , Howson Timothy E. , Kratz David , Tien John K.
Published: June 2020

The previous paper briefly described the fine microstructure of a mechanically alloyed oxide dispersion strengthened nickel-base solid solution. This note examines the fine microstructure of another mechanically alloyed system. This alloy differs from the one described previously in that it is more generously endowed with coherent precipitate γ forming elements A1 and Ti and it contains a higher volume fraction of the finely dispersed Y2O3 oxide. An interesting question to answer in the comparative study of the creep and stress rupture of these two ODS systems is the role of the precipitate γ' in the mechanisms of creep and stress rupture in alloys already containing oxide dispersoids.

The nominal chemical composition of this alloy is Ni - 20%Cr - 2.5%Ti - 1.5% A1 - 1.3%Y203 by weight. The system receives a three stage heat treatment-- the first designed to produce a coarse grain structure similar to the solid solution alloy but with a smaller grain aspect ratio of about ten.
Preparation of Titanium Microgrids for Scanning Transmission Electron Microscopy
Authors: Collins M.L. , Parker N.W.
Published: June 2020

The ideal supporting microgrid for high resolution scanning transmission electron microscopy should be: 1) made of material of low atomic number, 2) uniformly flat for ease in focusing, 3) resistant to any treatments necessary for cleaning and specimen preparation, and 4) a good electrical and thermal conductor. In the past, microgrid supports have been made of fenestrated plastic films strengthened by carbon or metal coatings. While adequate for most work, they cannot be baked at temperatures greater than 50°C. which may be necessary in some cases to completely eliminate contamination for single atom imaging using the STEM. To provide a reliably non-contaminating substrate support for high resolution scanning transmission microscopy, we have developed a simple technique for the preparation of microgrids of titanium metal. As can be seen in table 1, titanium posesses many attractive features.
A Scanning Electron Microscopy Study of the Attachment of a Thromboresistive Surface Coating to a Membrane Blood Oxygenator
Authors: Borovetz H. S. , Matta R. K. , Goitein K. J. , Hung T.-K. , Weissman M. H. , Hardesty R. L.
Published: June 2020

The need for systemic heparin anticoagulation during extended cardiopulmonary bypass (CPB) remains a serious impediment to clinical CPB support of circulatory and respiratory failures, especially in the newborn. Recent development of thromboresistive substrates which can be used to treat extracorporeal surfaces in contact with blood offers the potential for elimination of systemic blood heparinization. The present paper describes a scanning electron microscopy study of the attachment of one such substrate, tridodecyl- methylammonium chloride (TDMAC), to a novel micro-membrane oxygenator.

Figure 1 shows a cross-sectional image of the alternating pattern of microchannel conduits for blood flow through the oxygenator. The micro-channels were fabricated on thin metal sheets with an approximate semi-circular shape (150 + 25 microns in radius). The gas exchange to the blood flow in the channels was accomplished through a micro-porous membrane which was placed across the diametric plane of the channels (1).
Ultrastructure of Melanin Formation in Curvularia sp., Alternaria sp., and Drechslera Sorokiniana
Authors: Wheeler M. H. , Tolmsoff W. J. , Bell A. A.
Published: June 2020

(+)-Scytalone [3,4-dihydro-3,6,8-trihydroxy-l-(2Hj-naphthalenone] and 1,8-di- hydroxynaphthalene (DHN) have been proposed as intermediates of melanin synthesis in the fungiVerticillium dahliae(1, 2, 3, 4) andThielaviopsis basicola(4, 5). Scytalone is enzymatically dehydrated byV. dahliaeto 1,3,8-trihydroxynaphthalene which is then reduced to (-)-vermelone [(-)-3,4- dihydro-3,8-dihydroxy-1(2H)-naphthalenone]. Vermelone is subsequently dehydrated to DHN which is enzymatically polymerized to melanin.

Melanin formation inCurvulariasp.,Alternariasp., andDrechslera soro- kinianawas examined by light and electron-transmission microscopy. Wild-type isolates of each fungus were compared with albino mutants before and after treatment with 1 mM scytalone or 0.1 mM DHN in 50 mM potassium phosphate buffer, pH 7.0. Both chemicals were converted to dark pigments in the walls of hyphae and conidia of the albino mutants. The darkened cells were similar in appearance to corresponding cells of the wild types under the light microscope.
Intranuclear and Intramitochondrial Alterations in Heterologous Antibody-Treated HeLa Cells
Authors: Seman Gabriel , Walsh Patrick , Dmochowski Leon
Published: June 2020

Investigations on the effect of immune sera and complement on ultrastructure of human cells in vitro, whether tumor-derived such as HeLa (1) or normal (2), have been limited in the past to studies of immediate cellular damage caused by the cytotoxic or cytolytic effect of the sera. The biological behavior of HeLa cells surviving the lytic effect of immune sera or grown for several generations in the presence of heat-inactivated heterologous antiserum has been described (see 1), but fine structural changes occurring in such cells remained to be explored in detail. We have grown HeLa cells (450,000 per flask) for 7 days in the presence of final concentration of 0.005 to 0.02 percent rat or rabbit antiserum to the cells in 10 ml of Eagle's MEM and 10 percent fetal calf serum. Antisera were used unheated and without addition of complement.
Lipoproteins in Golgi Apparatus and GERL of Rat Hepatocytes: A CytoChemical Study
Authors: Novikoff P.M. , Yam A.
Published: June 2020

Our laboratory has recently reported that the marked fatty liver induced in rats by feeding a purine-free diet with 1% orotic acid (OA) can be reversed by addition of ethyl chlorophenoxyiso- butyrate (clofibrate or CPIB) to the OA diet (1). Hepatocyte ultrastructure returns to normal, as do the triacylglycerol levels in liver and serum. During reversal, GERL becomes prominent, distended with particles interpreted as lipoproteins undergoing degradation.

This communication reports cytochemical observations on such hepatocytes. Thiamine pyrophosphatase (TPPase) activity in hepatocytes, as in various cell types (2), is localized to the inner (trans) element of the Golgi apparatus (Figure 1). GERL, in contrast, shows no TPPase activity but displays acid phosphatase (AcPase) activity (Figure 2). Particles resembling very low density lipoproteins (VLDL) are found in both GERL and elements of the Golgi apparatus. The presence of both AcPase activity and VLDL-like particles strengthens our earlier suggestion that lipoproteins may undergo transformations in GERL.
High Resolution Histochemical Studies on the Surface of the External Vesicular Membrane of Cysticercus Cellulosae
Authors: Sosa A. , Alva S. , Girόn H. , Hohman W.
Published: June 2020

The external vesicular membrane of the bladder of Cysticercus cellulosae serves two essential purposes for the survival of this endoparasite: (1) the principal organ for transporting substances to and from the environment, and (2) the principal surface through which the host-parasite relationships are established. The first is important because C. cellulosae does not possess an alimentary tract and the external vesicular membrane performs the role of acquiring nutrients from the environment. The second is important because the morpho-physiological connections between the parasite and host tissues are formed and maintained by this surface. Therefore the study of the structure and function of this surface is important to elucidate both aspects of membrane transport and host-parasite interrelationships. The purpose of this study is to use alcian blue- lanthanum, concanavalin A (con-A) and colloidal iron hydroxide (CIH) methods to demonstrate the presence and distribution of carbohydrate components and charge density on the surface of the external vesicular membran of C. cellulosae, All cysticerci used were obtained from anconeous muscle of parasitized hogs in Mexico City.
The Demonstration of Calcium in Abacus Bodies and Secretory Granules of the Rat Odontoblast by Combined Histochemical and X-Ray Analysis
Authors: Reith E. J. , Bates S. R. , Johnson P. F. , Hren J. J.
Published: June 2020

Collagen precursor can be identified in the Golgi saccules of the rat odontoblast .1,2The Golgi saccules vary in size; the largest display spherical profiles, whereas somewhat smaller saccules display elongate or cylindrical profiles. Within the largest saccules, there are randomly disposed fine filaments and sometimes small dense particles. In the smaller cylindrical saccules, the filaments are disposed in a parallel manner and dense particles associated with the filaments are present as a regular feature. In favorable sections, many particles are seen to be in register along different loci on the filamentous component, giving the structure some resemblance to an abacus body.3The abacus bodies become still smaller and develop into secretory granules which migrate to the secretory pole of the cell. It is considered that the filamentous component represents collagen precursor.4
Scanning and Transmission Electron Microscopy of Isolated Cells from the Avian Salt Gland
Authors: Thompson Ian G.
Published: June 2020

With the advent of new techniques for isolating single cells for biochemical and physiological investigation, an important consideration is the morphological integrity of these cells after dissociation from the intact tissue. Do isolated cells retain the degree of structural differentiation that is apparent in vivo? The principal secretory cells of the avian salt gland are an example of cells that are highly differentiated in form under conditions of physiological stress. This report describes the ultrastructure of dissociated salt gland cells as visualized with the scanning and transmission electron microscope.

The dissociation procedure employed here was the same as that applied to the exocrine pancreas. For transmission electron microscopy the cell suspension was centrifuged and the resultant pellet prefixed in cacodylate buffered 3% glutaraldehyde- 1% paraformaldehyde, postfixed in unbuffered 1% osmium tetroxide, and embedded in epon-araldite. An assessment of the cell surface coat following enzymatic dissociation was facilitated by the inclusion of ruthenium red (500 ppm) in both the aldehyde and osmium fixation steps.
Banded Structure in a Hepatocellular Carcinoma
Authors: Chew E. C. , Chan W. C.
Published: June 2020

Extracellular banded structures were first reported by Luse (1) in a neural tumor and subsequently by others in many types of tissues. This subject was summerized in detail by Sun and White in 1975 (2). This communication reports observations of banded structures discovered by electron microscopy in the study of a human hepatocellular carcinoma. The tissue was fixed in 3% glutaraldehyde in 0.1 M cacodylate buffer and post-fixed in buffered osmium tetroxide. Sections were stained with uranyl acetate and lead citrate. Thick sections, about 1 - 2 μ, were stained with periodic acid-Schiff's reagent involving heating of the slides.

Banded structures are observed in the connective tissue area intermingled with collagen fibrils and are usually fusiform in shape (Fig. 1). The fusiform bodies average 0.5 μ in diameter and are outlined with periodicity of 800 to 1000 A°. Each period consists of a light and a dark band. Fine filaments of about 24 A° in thickness are present in the light bands (Fig. 2). They are also found to be periodic acid-Schiff positive (Fig. 3).
Ultrastructural Effects of Mercury on the Intact Proximal Tubule of the Euryhaline TeleostFundulus Heteroclitus
Authors: Wasserman Jay , Koepp Stephen J.
Published: June 2020

In vitro renal cytopathology has been reported for several fish species following acute exposure to mercury (1,2). Less is known about pathogenesis in kidney tissue from intact fish exposed to environmental levels of the toxicant. Prior toxicity (3) and pathological investigations (4) with the common mummi- chog (Fundulus heteroclitus) have indicated a particular susceptibility to mercury for this important estuarine inhabitant.

Male fish (3.5-4.5 g) were incubated in artificial seawater containing one of three toxicologically-significant concentrations of mercuric chloride (0.25, 0.75, and 1.50 ppm). Kidney tissue cubes of survivors at 12, 36, and 96-hours exposure for each test concentration (plus controls) were fixed in cold 4% phosphate-buffered glutaraldehyde, postfixed in 1% osmium tetroxide, and subsequently embedded in Epon 812. Thin sections were doubly-stained with uranyl acetate and lead citrate.

Exposure to the lowest mercury concentration (0.25 ppm) produced progressive dilatation of smooth endoplasmic reticulum and apical vesicles (Fig. 1).
Applications of X-Ray Microanalysis to Human and Experimental Pathology
Authors: Berezesky I.K. , Chang S.H. , Pendergrass R.E. , Bulger R.E. , Mergner W.J. , Trump B.F.
Published: June 2020

The fields of human and experimental pathology offer many areas where the application of x-ray microanalysis promises to increase our knowledge of diagnostic pathology and pathophysiology. We will present two examples recently being studied in our laboratory illustrating this method. One is an example of an insoluble precipitate which can be studied in Epon sections; the other, an example of localization of diffusible substances requiring ultrathin frozen sections. In all studies an AMR 1000 SEM equipped with a Kevex SiLi detector and a Northern NS 880 collection system were used. The first study involves the ccmposition of Fe deposits found in two types of Fe overload: thalassemia and sideroblastic anemia. In thalas semia, Fe overload occurs in lysosomes of several organ systems including liver, spleen, heart, and bone marrow and is associated with disability and death in these patients, presumably through membrane damage.
Small Round Cell Tumors
Authors: Mackay B. , Garza D.
Published: June 2020

The term "small round cell tumor" is used to designate a heterogenous group of neoplasms that have in common the fact that they are composed of small round, polygonal, or occasionally ovoid cells, compactly grouped with little or no evidence of architectural organization. Identification of tumors within this group by light microscopy can be difficult and is often not possible. Selection of a specific diagnosis by the pathologist is frequently influenced by the clinical behavior and location of the tumor, and by the age of the patient. For example, tumors with this morphology occurring in young children are usually assumed to be rhabdomyosarcoma, neuroblastoma, Ewing's sarcoma, or lymphoma.

By studying these neoplasms with the electron microscope and correlating the findings with the light microscopic and clinical data, it is possible to reach a specific diagnosis in most cases. Each tumor possesses distinctive ultrastructural features that serve to identify the cell type.
Reconstruction of Mammalian Heart Tissue from Isolated Embryonic Heart Cells
Authors: Nag Asish C. , Buszke Debra S.
Published: June 2020

Although monolayer cultures are useful in various cell studies, they are not always adequate for examining the nature of cellular interrelationships and interactions in the formation, differentiation, and function of tissues. The procedures of aggregation in vitro of dissociated cells (Moscona & Moscona, 1966) enable one to study in detail the formation of cell contacts, the assembly of cells into multicellular systems, and cell cooperation in forming organized and differentiating tissues. We adapted the techniques of cell aggregation by rotation to studies on embryonic mammalian heart cells. Cell suspensions from the 18-day-old embryonic rat were prepared by dissociation with 0. 5% trypsin. The cells were dispersed in a culture medium which consisted of Eagle's basal medium with 10% fetal bovine serum, 1% glutamine solution, and 1% penicillin-streptomycin mixture. Cultured in 25ml Erlenmeyer flasks on a gyratory shaker at 70 rpm at 37°C were 3ml aliquots of the cell suspensions.
Morphological Evidence for Reinnervation in the Adult Mammalian Central Nervous System
Authors: Seall R. H. , Kingsley R. E.
Published: June 2020

It has been shown that the adult mammalian CNS is capable of axonal sprouting and limited regeneration in response to injury, but this regeneration is interrupted by the scar produced in the lesioned area by proliferating glia. Experiments by Barnes and Worrall (1) demonstrated that the proximal stump of a ventral root when grafted to a ganglionectomized dorsal root is capable of reinnervating the spinal cord without interference by the glia, and is capable of forming new functional synapses within the spinal cord. In an effort to provide anatomical verification for this physiological study, we repeated their experimental procedure. A transmission electron microscopic investigation of the spinal cord where the dorsal roots terminate was undertaken in an attempt to identify these reinnervating axons and newly formed synapses. Regeneration time was varied from 8 to 16 weeks. In order to identify reinnervating from normal tissue, the graft was lesioned 3 or 4 days prior to preparation of the spinal cord for electron microscopy.
Ovarian Dysfunction in Fetally Irradiated Beagles
Authors: Seed T. M. , Sanderson M. H. , Gutzeit D. L. , Fritz T. E. , Tolle D. V. , Poole C. M. , Norris W. P.
Published: June 2020

The developing mammalian fetus is thought to be highly sensitive to ionizing radiation. However, dose, dose-rate relationships are not well established, especially the long term effects of protracted, low-dose exposure. A previous report (1) has indicated that bred beagle bitches exposed to daily doses of 5 to 35 R 60Co gamma rays throughout gestation can produce viable, seemingly normal offspring. Puppies irradiated in utero are distinguishable from controls only by their smaller size, dental abnormalities, and, in adulthood, by their inability to bear young.

We report here our preliminary microscopic evaluation of ovarian pathology in young pups continuously irradiated throughout gestation at daily (22 h/day) dose rates of either 0.4, 1.0, 2.5, or 5.0 R/day of gamma rays from an attenuated 60Co source. Pups from non-irradiated bitches served as controls. Experimental animals were evaluated clinically and hematologically (control + 5.0 R/day pups) at regular intervals.
Cytological Events Associated with the Secretory Process in the Desert Gerbil (Meriones Crassus) Oviduct
Authors: Nayak Ramesh K. , Marafi Enaam M.
Published: June 2020

The gerbil (Meriones Crassus) is the most abundant small mammal in Kuwait and information on reproduction of these rodents is scanty. The gerbil, M. crassus, belongs to the subfamily Gerbillinae of the family Cricetidae, Order Rodentia. Extensive light and electron microscopic studies of the oviduct of mouse, rat, rabbit, guinea pig, ruminants, and man have been reported by Nilsson and Reinius. To the best of our knowledge, no electron microscopic studies of the desert gerbil tubal epithelium during the estrous cycle have been reported. It has been shown that the secretion of the tubal epithelium is controlled by hormones and that secretion is necessary for the survival of the egg. Our knowledge of the fine structural changes which take place during secretion is incomplete. This report describes for the first time the fine structural features of the secretory process of the gerbil oviduct.
Two Investigations into Grain Boundary Structure
Authors: Humble P.
Published: June 2020

There has been sustained interest over the last few years into both the intrinsic (primary and secondary) structure of grain boundaries and the extrinsic structure e.g. the interaction of matrix dislocations with the boundary. Most of the investigations carried out by electron microscopy have involved only the use of information contained in the transmitted image (bright field, dark field, weak beam etc.). Whilst these imaging modes are appropriate to the cases of relatively coarse intrinsic or extrinsic grain boundary dislocation structures, it is apparent that in principle (and indeed in practice, e.g. (1)-(3)) the diffraction patterns from the boundary can give extra independent information about the fine scale periodic intrinsic structure of the boundary.

In this paper I shall describe one investigation into each type of structure using the appropriate method of obtaining the necessary information which has been carried out recently at Tribophysics.
Scanning transmission electron microscopy of biological macromolbcules
Authors: Tichelaar W. , Oostergetel G.T. , Haker J. , Bruggen E.F.J. Van.
Published: June 2020

Our aim is to use Scanning Transmission Electron Microscopy (STEM) for research on biological macromolecules. Preliminary experiments have been carried out on a Philips EM 300 (equipped with a high resolution stage and normal hairpin cathode) with a STEMattachment. The elastically scattered electrons were detected on an annular detector and the images were photographed from the monitor screen. The instrumental resolution was about 15Å. The biological macromolecules were mounted on a carbon film with a thickness of about 25Å supported by a holey film; in most cases the objects were lightly (negatively) stained with uranyl acetate (UAc).

Fig. 1 shows a STEM-dark field (df) image of lightly stained rooster liver (poly-) ribosomes. The mRNA can be seen; this is remarkable considering the instrumental resolution. The subunits cannot be seen; however we hope to succeed in visualizing the substructure of the ribosome by lightly negative staining.
Cryoultramicrotomy of plant protoplasts
Authors: Williamson Francis A.
Published: June 2020

Introduction

Naked plant cells (protoplasts) have been used for the study of lectin binding to the plasma membrane, and of the initial stages of cell wall formation (2,3 and refs, therein). In this paper, I describe methods for the cryoultramicrotomy of plant protoplasts and give a general description of their ultrastructure. In addition, labelled lectins have been applied to cryo-sections to locate intracellular binding sites, and the superior resolution of the negatively stained cryo-sections has been applied to a preliminary study of cell wall fibril formation.

Materials and Methods

Protoplasts were prepared from meristematic leaves of leek (Allium porrum) by enzymatic digestion (3). After washing, the cells were fixed in 1% glutaraldehyde in 0.55 M sorbitol and 1 mM CaCl2 buffered at pH 7.2 with 10 mM sodium cacodylate or HEPES. They were then washed (16 h) in 100 mM sodium cacodylate pH 7.2 and infused with 1 M sucrose in the same buffer for 3 h. A very concentrated suspension of the cells was mounted on a specimen holder and frozen in nitrogen slush (liquid nitrogen at its freezing point).
Etching of red blood cells by means of ion beam sputtering
Authors: Hojou Kiichi , Fujita Hiroshi , Ito Masamichi , Hirahata Tetsuyuki , Kanaya Koichi
Published: June 2020

Ion etching techniques have recently been utilized in attempts to reveal subsurface cell structure in the scanning electro microscope. There has, however,been some difficulties indistingushing infracellar structure from artifacts and comtamination produced by the ion etching process.

In order to avoid thermal defects caused by conventional etching processes of DC- or rf-sputtering ion beam etching can be used to study biological specimens. In this case, and in addition to using an ion beam which is well- collimated and highly accelerated, the specimen must be both cooled and rotated during processing. Using this procedure on red blood cells examined by SEM, details of their structure were revealed. However, the cone-like structures reported by several previous investigators were not consistantly observed.

It is concluded that this procedure for etching may be more informative than those obtained by other ion etching processes.
Tissue section lifting for electron microscopy
Authors: van Dellen Adrian F.
Published: June 2020

The morphologic pathologist may require information on the ultrastructure of a non-specific lesion seen under the light microscope before he can make a specific determination. Such lesions, when caused by infectious disease agents, may be sparsely distributed in any organ system. Tissue culture systems, too, may only have widely dispersed foci suitable for ultrastructural study. In these situations, when only a few, small foci in large tissue areas are useful for electron microscopy, it is advantageous to employ a methodology which rapidly selects a single tissue focus that is expected to yield beneficial ultrastructural data from amongst the surrounding tissue. This is in essence what "LIFTING" accomplishes. We have developed LIFTING to a high degree of accuracy and repeatability utilizing the Microlift (Fig 1), and have successfully applied it to tissue culture monolayers, histologic paraffin sections, and tissue blocks with large surface areas that had been initially fixed for either light or electron microscopy.
High resolution experiments with a cross-hair beam-stop
Authors: Tesche B.
Published: June 2020

Dupouy and collaborators achieved what is now known as a central beam stop with diaphragms which were partly covered by strips. The width and arrangement of these strips, however, excluded a substantial part of the Fourier spectrum, although the zero beam could readily be stopped.

We succeeded in arranging a cross-hair in the center of an aperture. The three-micron thick quartz fibers are made conductive by evaporating gold onto them and also in the thin layer aperture onto which they are mounted. By this means, charging of the cross-hair and contamination of the apertures are avoided. The thin diameter of the cross-hairs permits the exclusion of the zero beam as well, yet without any great loss of the Fourier spectrum. Furthermore, small shifts of the aperture permit partial exclusion of the zero beam, which leads to very interesting contrast phenomena. It must be emphasized that the optical quality of the microscope is not impaired by such small shifts of the aperture and that the cut-off frequency remains unchanged.
Metal measured in earthworm tissue by X-ray microanalysis
Authors: Gullvåg B.M.
Published: June 2020

Subcellular localization of polluting metals in organisms collected from the environment is an important step towards understanding the toxicological effects of environmental metal pollution.

Material and Methods

Lumbricid earthworms were collected from a rather trafficated road in the Trondheim area and from a supposed control area several miles from town with no traffic nearby. The earthworms were kept in a glass container for three days before fixation and given a diet of mixed cornflour and agar in order to eliminate all mineral particles from their intestine. The material which was to be used for X-ray analysis was fixed in glutaraldehyde (2.5%) for 4 hrs and no post-staining was used. Section thickness was 100 to 150 nm. Analyses were carried out with a JSTEM 200 C electron microscope combined with a side-entry goniometer and an energy dispersive X-ray spectrometer using spot size 500 Å.
Membrane alterations during thylakoid formation in rhodospirillum rubrum
Authors: Yokomura E. , Sugimoto M. , Gomi-Baba C
Published: June 2020

Thylakoid formation in RhodospiriHum rubrum is one of the model systems adequate for studying the differentiation of the biological membranes. It is well established that thylakoids are formed from the invaginations of cell membranes. This is based on electronmicroscopic observations and biochemical studies. However, the alterations in the architecture of the cell membranes during thylakoid- forming process is ambiguous. Therefore, in the present study, thylakoid formation in R.. rubrum was investigated with freeze-fracture technique and DAB-histochemistry.

For inducing thylakoid formation, the cells grown at 25° C in an aerobic-dark (AD) environment were transferred to an anaerobic-light (NL) environment. At various times after transferring from AD to NL, the cells were immersed in 30 % glycerol without any chemical prefixation and then immediately frozen in liquid Freon to be prepared for the freeze-fracture replicas. The materials were handled at 25° C throughout before freezing.
Observation of biological macromolecules using various electron microscopic methods
Authors: Ohtsuki Mitsuo , Sogard Michael
Published: June 2020

Structural investigations of biological macromolecules commonly employ CTEM with negative staining techniques. Difficulties in valid image interpretation arise, however, due to problems such as variability in thickness and degree of penetration of the staining agent, noise from the supporting film, and artifacts from defocus phase contrast effects. In order to determine the effects of these variables on biological structure, as seen by the electron microscope, negative stained macromolecules of high density lipoprotein-3 (HDL3) from human serum were analyzed with both CTEM and STEM, and results were then compared with CTEM micrographs of freeze-etched HDL3. In addition, we altered the structure of this molecule by digesting away its phospholipid component with phospholipase A2and look for consistent changes in structure.
Acetylcholine receptor protein structure
Authors: Brisson A.
Published: June 2020

The acetylcholine receptor protein plays a leading part in the synaptic transmission mechanism. The binding of the neurotransmitter, acetylcholine, to the protein triggers conformational changes, allowing the translocation of ions through the membrane. The structural relationships between the binding sites of the cholinergic ligands and the translocating part of the protein are still unknown, as the subunit composition is. A better knowledge of the structure of the acetylcholine receptor protein is the aim of the present study.

Negatively stained preparations of purified cholinergic receptor protein and of membrane fragments rich in acetylcholine receptor protein are characterized by the presence of particles having a diameter of 8-9 mm, and exhibiting a doughnut like structure, with a central pit filled with stain. The variability in the stain distribution on the particle surface did'nt allow to determine the subunit structure of the protein. In the case of crystalline biological specimens, methods of averaging have allowed to overcome this problem; then, we have tried to crystallize the membrane-bound cholinergic receptor protein.
Evaluation of the dark field method for large association of spread DNA
Authors: Barker Douglas C.
Published: June 2020

A number of satisfactory methods are available for the electron microscopy of nicleic acids. These methods concentrated on fragments of nuclear, viral and mitochondrial DNA less than 50 megadaltons, on denaturation and heteroduplex mapping (Davies et al 1971) or on the interaction between proteins and DNA (Brack and Delain 1975). Less attention has been paid to the experimental criteria necessary for spreading and visualisation by dark field electron microscopy of large intact issociations of DNA. This communication will report on those criteria in relation to the ultrastructure of the (approx. 1 x 10-14g) DNA component of the kinetoplast from Trypanosomes. An extraction method has been developed to eliminate native endonucleases and nuclear contamination and to isolate the kinetoplast DNA (KDNA) as a compact network of high molecular weight. In collaboration with Dr. Ch. Brack (Basel [nstitute of Immunology), we studied the conditions necessary to prepare this KDNA Tor dark field electron microscopy using the microdrop spreading technique.
Counting superhelical turns in electron micrographs of large plasmids
Authors: Klotz Günther , Kleinschmidt Albrecht K. , Goebel Werner
Published: June 2020

Dark-field electron microscopy allows high resolution imaging of super- coiled DNA. Plasmid molecules isolated from Halobacterium halobium were spread by basic monolayer techniques with cytochrome c. They were subsequently mounted onto thin indirectly deposited carbon films and positively stained with ethanolic uranyl salts. A Siemens Elmiskop 102 was operated at 10 000 and 40 000 times magnification using tilted and hollow cone dark-field illumination respectively. Micrographs obtained (Fig. 1) allowed contour length determination by tracing molecules and direct counting superhelical turns. This led to calculation of the superhelical density of large plasmids. The contour length of supercoiled and of relaxed circular molecules which were contained within the same spreading solution and thus photographed from the same grid were evaluated by projection of micrographs and tracing with a digitizer connected to a Wang 2200 calculator. The values obtained are (49.1 ± 2.5) μn and (52,7 ± 2.2) μm for superhelical and relaxed circles respectively.
Morphometric studies of chromatin structure and nuclear organization: hepatic polyploidy and mammalian erythropoiesis
Authors: Brasch Klaus
Published: June 2020

Morphometric techniques have seen only limited application in the establishment of quantitative parameters relating to chromatin structure and nuclear organization at the EM level. The usefulness of this approach, however, was recently demonstrated by studies on avian erythropoiesis, showing that contrary to subjective impression there is no progressive increase in the amount of condensed chromatin in developing erythrocyte nuclei. This report extends similar analysis to liver nuclei of different ploidy classes and to mammalian erythroid cells.

Materials and Methods

Rat liver and bone marrow from anemic rabbits were prepared for microscopy as described. Data for 2c and 4c liver nuclei were obtained using rats of appropriate ages: 28 days, >90% 2c; 400 days, >70% 4c; 8c nuclei are larger than 380 μm3. Mean nuclear volumes were calculated from the major and minor axes of at least 50 nuclei of each type measured with a micrometer using 2-3 μm thick sections. Nuclei were treated as prolate spheroids. Morphometric analysis was carried out as described, using the point counting stereological method.
Cytochemical study of nucleolar structure and formation inphysarum polycephalum
Authors: Lafontaine J.G. , Cadrin M.
Published: June 2020

Under appropriate culture conditions the slime mold, Physarum polycephalum, can be grown in the form of multinucleated plasmodia. In view of the fact that these numerous nuclei divide in perfect synchrony, this organism offers unique advantages for studying different aspects of the cell cycle.

As in other organisms studied so far, the interphase nucleolus consists of fibrillar regions surrounded by conspicuous granular zones. These fibrillar regions, however, are spherical in shape and are characterized by the presence of opaque particles. As the nucleolar mass disorganizes these spherical nucleolar portions persist in the form of bodies which migrate with the mitotic chromosomes to the nuclear poles. Prelabeling of G2nuclei with tritiated thymidine permits to demonstrate that these nucleolar remnants contain DNA and that this DNA is still present within their mass as they become integrated within the early interphase daughter nuclei. Since the G1period is lacking in this organism, both DNA and RNA synthesis are resumed soon after mitosis: the nucleus increases in size and the nucleolus is also reformed quite rap idly.
Mitochondrial DNA of acute myeloid leukemic cells
Authors: Paul Choudhury R. , Misra D. N. , Sadhukhan P.
Published: June 2020

Mitochondrial DNA (mtDNA) of non-malignant animal tissue ceils consists of a population of covalently closed double stranded duplex circular molecules with contour lengths varying between 4.5 and 6 μ. Majority of the circles are found to be highly twisted. If they are nicked during extraction process, some molecules are fully open (Swift and Wolstenholme; Choudhury and Sadhukhan). The purpose of this paper is to describe changes in molecular configurations of mtDNA molecules of malignant cells using a model system of human acute myeloid leukemia.

Peripheral blood was withdrawn aseptically from acute myeloid leukemic patients and collected in a test tube containing A.C.D. solution in the proportion of 5 : 1. The blood was allowed to settle at 4°C for 24 hr. At the end of this period buffy coat of white blood cells was drawn off and the contaminating red cells were removed by haemolysis with distilled water for 20 sec. The leukocytes were spun down at 1000g for 5 min at 4°C.
Lamella-particle complexes
Authors: Banfield William G. , Lee Cecil W.
Published: June 2020

Lamella-particle complexes are a distinct group of morphologic structures. They have been reported in a growing number of papers often without detailed description. This could be accounted for because of the paucity of occurrence in the tissue or cells examined, the limitations inherent in preparing the tissue for electron microscopy, or because the photographs were not at a high enough magnification. We will take a closer look at these complexes, adding new information on their morphology, make correlations overlooked or not possible when initial observations were published and dispel some erroneous impressions as to the degree of similarity between complexes of different origin. Standard methods of fixation, dehydration and epon embedding were used. Staining was with lead and uranyl acetate.

The lamella-particle complex is well illustrated in a lymphoma cell of the northern pike (Fig. 1). In cross section its wall is made up of a striated lamella associated with ribosome-like particles.
Formation and disintegration of lipid droplets associated with cell organelles, especially smooth-surfaced endoplasmic reticulum in the white adipose cell
Authors: Usuku G. , Iyama K. , Ohzono K. , Hirashima M.
Published: June 2020

Although a number of ultrastructural studies on the white adipose cell have been reported, not a few unsolved problems still remain on the morphological and functional relationships between formation or disintegration of lipid droplets and cell organelles in those cells. In order to re-examine such the points, we have made electron microscopical studies on the epididymal adipose cells from normal and starved Wistar adult rats, and on these cells from rats refed ordinary animal food or given only lipid without carbohydrate after a period of starvation. Additionally, for the same purpose we have observed the ultrastructure of developing and differentiating fat cells in the epididymal adipose tissue of rats ranging from newborn to 5 weeks old.

The adipose cell from normal adult rats shows that the peripheral cytoplasm which envelopes a central large lipid mass contains well-developed cell organelles and occasionally small lipid droplets. These lipid droplets have no limiting membrane, but are often observed to be closely encircled by fenestrated profiles of smooth-surfaced endoplasmic reticulum (SER) which connects with a part of rough-surfaced endoplasmic reticulum (RER) in places (Fig. 1).
Arrangement of microtubules and microfilaments during oriented secondary wall formation
Authors: Seagull R. W.
Published: June 2020

Introduction. Microtubules have long been hypothesized to function as track-like elements, directing cellular components (Hepler & Palevitz 1974). In higher plants, cortical microtubules (cmt) have been hypothesized to function in this manner in the orientation of secondary wall microfibrils (MF) (reviewed by Heath, 1974). Involvement in such a process requires that the cmt be close to the structures being moved, be parallel to the direction of orientation and be of sufficient length to function as guide elements. In radish root hairs, sub-pl cmt occur along the length of the hair, paralleling the secondary wall MF. Root hair elongation occurs via tip growth, which results in simultaneous deposition of primary, randomly arranged MF (first 25 μm of root hair) and secondary, oriented MF (distances greater than 25 μm, Fig. 1).

Results. Longitudinal serial sections show that cmt start and terminate randomly throughout the length of the hair, but are absent in the tip region (0-3 μm from tip). Microtubules are rarely found more than 500 nm from the pl. Bridges between cmts and the pl are evident, Fig. 4. In the region between 20 and 60 μm from the tip, 50% of the cmt are less than 1 μm long.
Orientation of the purple membrane using a new specimen preparation technique
Authors: Hayward S.B.
Published: June 2020

It is known that the purple membrane of Halobacterium halobium is asymmetric with respect to its function as a proton pump. It has also been shown that the structure of the membrane is asymmetric, both with respect to its profile, and with respect to its handedness when viewed from one side or the other. Recently, Henderson has determined which side of the molecular structure corresponds to the cytoplasmic side of the membrane. This paper reports the application of a new method of frozen-hydrated specimen preparation to this same question. This specimen preparation technique has made possible the recording of selected-area electron diffraction patterns from membranes that have been adsorbed to polylysine-coated grids. At pH 7.4 purple membranes have been shown to adsorb preferentially with the cytoplasmic side toward the polylysine. This orientation has been shown to reverse 2/3 of the time when membranes have been titrated to pH4 before adsorption.
Crystalline structure in the milk fat globule membrane (MFGM)
Authors: Wooding F.B.P.
Published: June 2020

The MFGM has been suggested (Patton and Keenan 1975) to be a very convenient and readily available source of plasma membrane from an active secretory cell. It can easily be isolated in pure form by churning or freeze thawing washed cream. However, there is also evidence (Wooding 1977) that the MFGM is not only a simple unit membrane structure such as is found for other isolated plasmalemmas. Characteristically, it has a coat of material 10-20 nm thick on one side which is derived from the cytoplasm of the mammary alveolar secretory cell.

The milk fat globule secreted from the mammary alveolar cell has a continuous unit membrane boundary with a thin but uniform zone of cytoplasmic material between this membrane and the fat droplet core (Fig 1, inset). Immediately after the release of the milk fat globule from the secretory cell this “initial” MFGM undergoes rapid changes which produce a stable inhomogeneous “secondary” milk fat globule boundary characteristic of the fat globules in the milk of any species.
Direct visualization of phase-separated domains in lipid membranes
Authors: Hui S. W. , Stewart T. P.
Published: June 2020

Direct electron microscopic study of biological molecules has been hampered by such factors as radiation damage, lack of contrast and vacuum drying. In certain cases, however, the difficulties may be overcome by using redundent structural information from repeating units and by various specimen preservation methods. With bilayers of phospholipids in which both the solid and fluid phases co-exist, the ordering of the hydrocarbon chains may be utilized to form diffraction contrast images. Domains of different molecular packings may be recgnizable by placing properly chosen filters in the diffraction plane. These domains would correspond to those observed by freeze fracture, if certain distinctive undulating patterns are associated with certain molecular packing, as suggested by X-ray diffraction studies. By using an environmental stage, we were able to directly observe these domains in bilayers of mixed phospholipids at various temperatures at which their phases change from misible to inmissible states.