bluuebunny/crossref_metadata_2025 huggingface dataset:
The variation of intermolecular contacts in helical aggregates of glutamine synthetase
Authors: Frey T.G. , Eisenberg D.S. , Smith P.R.
Published: June 2020

Glutamine synthetase from E. coli is a large (MW 600,000) oligomeric enzyme composed of twelve identical polypeptide chains of MW 50,000. These twelve subunits are arranged at the vertices of two eclipsed hexagons to produce a structure with symmetry 622 or D6 as shown by electron microscopy and X-ray diffraction. The dodecameric molecule has a hexagonal profile of approximately 140 Å diameter and a thickness of approximately 90 Å. When treated with divalent cations such as Co++, Zn++, Ni++ or Cu++, glutamine synthetase molecules aggregate along their six-fold axes to form long strands and these strands will often wrap around one another to form cables (Fig. 1). The aggregation is completely reversed by the addition of excess Mn++ resulting in regeneration of full enzymatic activjjy. The most regular helical aggregates are formed in the presence of 10 mM Co++ at pH 7.0, and we have used these helical cables to study the three dimensional structure and symmetry of the glutamine synthetase molecule and the types of protein-protein interactions involved in the formation of glutamine synthetase cables.
Contribution to the study of elastin ultrastructure
Authors: Pasquali Ronchetti I. , Fornieri C. , Mori G. , Baccarani Contri M.
Published: June 2020

Because of its peculiar elastic property, elastin has been studied by several authors in order to define whether or not it has to be considered an amorphous elastomer. Physical investigations showed that very likely eIastin has an anisotropic organization,that the molecule has regions of different mobiI ity and that the mechanism of deformation can be of entropic nature. Chemically, the elastin molecule exhibits more than 60% of the aminoacid residues having nonpolar side chains and Iysine-derivated desmosines provide strong crosslinks that tie the protein chains together. Ultrastructurally, after prolonged sonication and negative staining, elastin appears as 50 A° large filaments made up of subunits. Very similar results have been recently obtained with coacervates of syntheticpolypenta and polyhexapeptides. The main criticisms to the “filament” structure are that the prolonged sonication and/or the negative stains may have contributed to the final fiIamentous appearance of elastin.
Electron microscope autoradiography of isolated molecules
Authors: Bouteille M. , Delain E. , Angelier N.
Published: June 2020

The LIGOP method of electron microscope autoradiography which consists in a combination of coating Ilford emulsion with the loop technique and developing with gold latensification and phenidon has proved to provide small, compact developed silver grains with high efficiency.

This has made it possible to use this technique with very small materials such as isolated molecules of molecular complexes.

The method was assayed first with 3H-Thymidine labelled T7 phages DNA molecule with 630,000 cpm/μg specific activity (fig. 1). The molecules were spread using the adsorption technique constrasted by rotatory shadowing with platinum and then subjected to autoradiography. The Labelling was sufficient to obtain quantitative data in which the spread molecules were considered as a material comparable to a “hot line”. The efficiency (45%) and the HD value (1600 Å) were calculated.

The method was also applied to transcription units of pleurodeles oocytes nucleoli (fig. 2) labelled in vitro with 3H-Uridine.
The structure of pre-mRNA and mRNA from erythroid cells
Authors: Ladhoff A.-M. , Thiele B.J. , Coutelle Ch. , Rosenthal S.
Published: June 2020

The suggested precursor-product relationship between the nuclear pre-mRNA and the cytoplasmic mRNA has created increased interest also in the structure of these RNA species. Previously we have been published electron micrographs of individual pre-mRNA molecules from erythroid cells. An intersting observation was the appearance of a contour, probably corresponding to higher ordered structures, on one end of 10 % of the pre-mRNA molecules from erythroid rabbit bone marrow cells (Fig. 1A). A virtual similar contour was observed in molecules of 9S globin mRNA from rabbit reticulocytes (Fig. 1B). A structural transformation in a linear contour occurs if the RNA is heated for 10 min to 90°C in the presence of 80 % formamide. This structural transformation is reversible when the denatured RNA is precipitated and redissolved in 0.2 M ammonium acetate.
Structural similarity of ribosomes from E. coli and A. salina
Authors: Boublik M. , Wydro R.M. , Hellmann W. , Jenkins F.
Published: June 2020

Ribosomes are ribonucleoprotein particles necessary for processing the genetic information of mRNA into proteins. Analogy in composition and function of ribosomes from diverse species, established by biochemical and biological assays, implies their structural similarity. Direct evidence obtained by electron microscopy seems to be of increasing relevance in understanding the structure of ribosomes and the mechanism of their role in protein synthesis.

The extent of the structural homology between prokaryotic and eukaryotic ribosomes has been studied on ribosomes of Escherichia coli (E.c.) and Artemia salina (A.s.). Despite the established differences in size and in the amount and proportion of ribosomal proteins and RNAs both types of ribosomes show an overall similarity. The monosomes (stained with 0.5% aqueous uranyl acetate and deposited on a fine carbon support) appear in the electron micrographs as round particles with a diameter of approximately 225Å for the 70S E.c. (Fig. 1) and 260Å for the 80S A.s. monosome (Fig. 2).
Contributions to the mechanisms of mitosis and roles of cytoplasmic microtubules from ultrastructural analyses of fungi
Authors: Brent Heath I.
Published: June 2020

Detailed ultrastructural analysis of fungal mitotic systems and cytoplasmic microtubules might be expected to contribute to a number of areas of general interest in addition to the direct application to the organisms of study. These areas include possibly fundamental general mechanisms of mitosis; evolution of mitosis; phylogeny of organisms; mechanisms of organelle motility and positioning; characterization of cellular aspects of microtubule properties and polymerization control features. This communication is intended to outline our current research results relating to selected parts of the above questions.

Mitosis in the oomycetes Saprolegnia and Thraustotheca has been described previously. These papers described simple kinetochores and showed that the kineto- chores could probably be used as markers for the poorly defined chromosomes. Kineto- chore counts from serially sectioned prophase mitotic nuclei show that kinetochore replication precedes centriole replication to yield a single hemispherical array containing approximately the 4 n number of kinetochore microtubules diverging from the centriole associated "pocket" region of the nuclear envelope (Fig. 1).
Cell surface topography in adhesion and detachment
Authors: Allen T.D.
Published: June 2020

The effects of trypsin and EGTA were investigated in parallel on two epithelial cell lines: a normal rat-liver parenchyma line (Fig. 1) and a spontaneously transformed line which had been subcloned in soft agar. The basic ultrastructural differences between these two cell lines has already been reported; briefly, the transformed cells, although typically epithelial in morphology, lack the well ordered microtubular and microfilamentous organisation of the normal cells but exhibit a marked increase in the number of surface microvilli.

The reaction of each cell line to trypsination was broadly similar between the normal and transformed cell lines, with the transformed cells rounding up and detaching at a slightly quicker rate than the normals. In both cases the central region of the cell became domed with the peripheral cytoplasm being withdrawn in a thin sheet, some of which remained extended in short retraction fibrils (Fig. 2). Collection of the detached cells (after fixation in suspension) by aspiration onto silver filters showed the increased density of microvilli on the transformed cells to be maintained.
Surface charge and morphogenesis of regular arrays of macromolecules on bacterial cell walls
Authors: Sleytr U. B. , Friers G. P.
Published: June 2020

Regular arrays of macromolecules can be demonstrated on the surface of a wide range of bacteria by negative staining and freeze-etching techniques. The isolated subunits of the regular surface layers (S-layers) examined in this study have shown to consist of protein or glycoprotein and to possess the ability to assemble spontaneously under certain conditions to form regular arrays with the same dimensions as those seen on intact bacteria. In appropriate conditions the isolated subunits reattach to the cell wall from which they have been removed. Analysis of the orientation of the reconstituted S-layers have shown that the pattern of the regular arrays seem to be determined only by the directional bonds between the subunits and not by any order in the underlying (peptidoglycan) layer.
Type-C oncornavirus assembly in NIH/3T3 cells infected with Temperature-sensitive mutants of rauscher murine leukemia virus
Authors: Yeger H. , Kalnins V. I. , Stephenson J. R.
Published: June 2020

Selected conditional-lethal mutants of mammalian leukemia virus have been used in an ultrastructural study to investigate type-C virus assembly at the cell membrane. Several temperature-sensitive (ts) mutants of Rauscher murine leukemia virus (R-MuLV) have been previously isolated and characterized by biochemical methods and electron microscopy. Biochemical analysis of one particular class of these mutants, the Class II ts mutants, which are defective in late replication functions, indicates that they are defective in cleavage of the gag-gene coded polypeptide precursor, Pr65, of the viral structural proteins at the non-permissive temperature. Because of this defect, NIH/3T3 cells infected with the Class II mutants, ts24, ts25, and ts29 produce very low levels of virus at the non-permissive temperature as compared to wt infected cells.
Unique association of three new type B retrovirus isolates with kinetochores and centrioles of the host cell
Authors: Heine U. I. , Todaro G. J.
Published: June 2020

Three new virus isolates, M432, M832 and M960, obtained from the Southeast Asian mouse have been characterized morphologically in ultrathin sections and by negative staining with respect to their composition and intracellular assembly. The three isolates share certain morphological properties with the murine mammary tumor virus, a retrovirus of type B; yet previous investigations illustrated that they can readily be distinguished both from each other and from known retroviruses of the mouse, both of type B and C, by their RNA genome protein composition and reverse transcriptase activity.

As illustrated in ultrathin sections (Fig. 1), the mature virions of about 100-120 nm in diameter contain a centrally located, electron dense nucleoid, a thin intermediate shell and an enveloping membrane derived from the plasma membrane. In negatively stained preparations (Fig. 1), the virions exhibit on their surface spikes which are best resolved on the isolate M432 and resemble the spikes present on the surface of retroviruses of type B.
Herpes simplex virus induced alterations of membrane morphology and
permeability of cells
Authors: Schlehofer Jörg R. , Habermehl Karl-Otto
Published: June 2020

Infection of HEp-2 cells with HSV-1 results in an increased stability of the cell membrane in comparison to uninfected cells. This effect is characterized by a reduced release of 51Cr, by an increased resistance against the non-ionic detergent Triton-X-100 and by a protection from complement mediated immune cytolysis with anti-HSV-1 antibodies. Infection with other viruses however (Poliomyelitis type 1, Mouse Elberfeld, Coxsackie B 6, Vesicular stomatitis) leads to opposite results with an enhancement of the 51Cr-release. - Comparative experiments with 7 other cell lines (Chang liver, FL, BHK21, primary rabbit kidney, HeLa, KB, primary embryonic chick fibroblasts) confirmed the above mentioned HSV-induced stability of the cell membrane with one exception: in embryonic chick fibroblasts (ECF), HSV-1 infection leads to an enhanced release and uptake of 51Cr as well as to an increased sensitivity to Triton-X-100, and the complement mediated immune cytolysis clearly can be demonstrated (Table 1).
The plasma membrane of pityrosporum has natural markers to show how the cell grows
Authors: Takeo Kanji , Nakai Ei-Ichi
Published: June 2020

Pityrosporum is a lipophilic yeast containing the causative agent of tinea versicolor, and has spiral grooves on the inner surface of the cell wall and the plasma membrane. Detailed studies on the plasma membrane of this organism revealed the existence of asymmetry around the plasma membrane, peculiar mode of the growth of this organism, mode of spiral groove formation, and a possible mechanism of groove formation. One strain each of Pityrosporum orbiculare and P. pachydermatis and ten strains of P. ovale were grown on a potato yeast extract agar, supplemented with 1% olive oil at 27-37°C for 1-20 days. Cultures were directly transferred to the specimen holder of the freeze-etching apparatus without no pretreatment. 40% glycerol was added before cooling.

All the strains tested of the genus Pityrosporum had only left-handed spiral grooves of the plasma membrane. Left-handedness of the spiral grooves of Pityrosporum was confirmed by scanning electron microscopy which occasionally revealed left-handed spiral grooves on the outer surface of the wall.
Chloroplast ontogenesis in Lippia citriodora L
Authors: Casadoro G. , Rascio N.
Published: June 2020

In the last decade it has been reported more and more frequently the pre sence of particular, electron-dense, membrane-bound plastid inclusions which, mostly, have been related to the building up of thylakoid membranes. Recently, in some plants with such plastid inclusions, it has been possible to evidence particular patterns of chloroplast ontogenesis and we think that many plants do not possess the chloroplast ontogenesis in conformity with the classic ontogenetic model. In Lippia aitriodora L. we could evidence one of this cases following its chloroplast ontogenesis from the shoot apex to adult leaves. (The leaf tissues have been sampled in the basal zone of successively older leaves. All the samples have been fixed with glutaraldehyde and osmium tetroxide and stained with uranyl acetate and lead citrate). The proplastids of shoot apex meristems show both membrane profiles filled with electron-dense material and membrane profiles with electron-transparent contents (fig. 1); sometimes the latter outlines are seen in continuity with the inner membrane of the plastid envelope.
The use of ultracryotomy to localize sites of activity of endogenous and exogenous enzymes in plant cells
Authors: Vian B. , Roland J. C.
Published: June 2020

During the recent years ultracryotomy revealed as a technique suitable for the study of plant cells. The main advantages are that the tissues support the minimum of chemical modifications and that the sections retain enzymatic activities. On an other hand, since the sections are devoided of plastic embedding, problems of penetration are eliminated. The sections are hydrophilic and directly accessible to reactives Therefore it seems possible to perform a wide range of enzymatic attacks at this level.

Both aspects were investigated for different cases previously studied with conventional methods and for which some technical problems remained unsolved. For example, the attack of wall components is difficult to perform, even when the specimens are embedded in more or less hydrophilic resins.

Attempts were made on adult leaves of spinach and mung bean hypocotyls prepared for ultracryotomy according to Tokuyasu. The specimens were prefixed (lh, 4°C) in 1 - 3% glutaraldehyde, infused (10-20 min, 4°C) in 1. 5 M sucrose, frozen in liquid nitrogen or supercooled nitrogen and sectioned at - 80°C on a Sorvall MT2 microtome fitted with a cryokit FTS.
Electron microscopic study on the phagocytic lining cells in the cavernous body of the lamprey gill
Authors: Yamaguchi Kazuhito , Awaya Kazuhiko
Published: June 2020

The lining cells in the cavernous body, which is a branch of the afferent branchial artery, of lamprey gills were studied with transmission (TEM) and scanning electron microscope (SEM).

Adult and larval lampreys, Lampertra planeri, were used in this study. Lamprey gills removed after perfusion were fixed in 2 % glutaraldehyde/formaldehyde (pH 7. 4) for 1 hour and postfixed in 1 % osmic acid. For TEM, the gills were dehydrated in ethanol and embedded in epon 812. Ultrathin sections were doubly stained with uranyl acetate and lead citrate. For SEM, most of the gills were dehydrated in ethanol and isoamylacetate and cracked in liquid nitrogen. Some of the gills dehydrated were embedded in stylene monomer. Stylene embedded blocks were cracked with a hummer and dissolved in propylene oxide. All the specimens were dried in a critical point dryer and coated 100 Å thickness with gold-paladium.

The cavernous body is composed of trabeculae, between which are blood spaces, the lacunae.
Morphology of vascular smooth muscle cells and pericytes as revealed by transmission and scanning EM
Authors: Uehara Y. , Komuro T. , Desaki J.
Published: June 2020

Although subcellular organization of vascular smooth muscle cells and pericytes have been described by a number of authors, the precise overall structure of these cells has not been revealed at the fine structural level.

In order to extend our knowledge in understanding of vascular function, the present paper deals the three dimensional organization of these cells as studied with a transmission EM using serial sections and with a scanning EM using materials from which connective tissue elements are removed.

For the reconstruction study, arterioles ranging in diameter from l0um to 25um are selected from the hamster skeletal muscle and the rat pancreas.

Fig. 1. demonstrates an example of the reconstructed model of the arteriole smooth muscle cell. Here the muscle cell takes a spiral form which coils nearly twice around the endothelial column. The shape and disposition of the muscle cells gradually become to be irregular towards the capillary bed.
Hemoglobin crystals of the red blood cells in the human renal cortex: electron microscopic observations of the renal lithiasis
Authors: Ueda Kosuke , Washida Hiroto , Watari Nakazo
Published: June 2020

Introduction

Hemoglobin crystals in the red blood cells were electronmicroscopically reported by Fawcett in the cat myocardium. In the human, Lessin revealed crystal-containing cells in the periphral blood of hemoglobin C disease patients. We found the hemoglobin crystals and its agglutination in the erythrocytes in the renal cortex of the human renal lithiasis, and these patients had no hematological abnormalities or other diseases out of the renal lithiasis. Hemoglobin crystals in the human erythrocytes were confirmed to be the first case in the kidney.

Material and Methods

Ten cases of the human renal biopsies were performed on the operations of the seven pyelolithotomies and three ureterolithotomies. The each specimens were primarily fixed in cacodylate buffered 3. 0% glutaraldehyde and post fixed in osmic acid, dehydrated in graded concentrations of ethanol, and then embedded in Epon 812. Ultrathin sections, cut on LKB microtome, were doubly stained with uranyl acetate and lead citrate.
Ultrastructure and derivation of the alveolar brush cell
Authors: Hijiya Kazuyuki
Published: June 2020

In the alveolar lining layer of the rat lung, besides the well documented two types of alveolar epithelical cell (Types I and II), the third epithelial cell (alveolar brush cell or Type III cell) has been found by Meyrick. Fine structure of alveolar brush cell and its relationship with Type I and II cells were investigated using a transmission, and especially a scanning electron microscope (TEM, SEM).

Materials and Methods.

Ninety—five male rats of the Wistar strain were injected intraperitoneally with lOmg/kg/day body weight of Bleomycin sulfate for 31 successive days. Another sixty male rats of the same strain ranged from 1 week to 20 weeks in age were also used. The animals were sacrificed under deep Ketalar anesthesia chronologically after treatment. The preparation of the lung specimens for TEM and SEM was carried out in the same way as described previously. TEM observations were made with an Akashi S500 electron microscope, and SEM observations were made with a Hitachi HFS-2S field emission source scanning electron microscope.
Human fetal lung organotypic cultures preserved by lipid-carbohydrate retaining methods
Authors: Stratton C. J. , Douglas W. H. J. , McAteer J. A.
Published: June 2020

Surfactant studies in general, and particularly those on the type II cell are hindered by the intrinsic cellular heterogeneity and structural complexity of the lung. Indeed, electron microscopic investigations of the lung encounter problems with both non-uniform sampling, and the technical difficulty of preserving intra- and extracellular surfactant through the dehydration steps. Fetal lung organotypic cultures provide a highly enriched type II cell population in which the in vivo cellular relationship of an intact epithelial-mesenchymal interface is maintained. The new lipid-carbohydrate retaining electron microscopic procedures have been shown to preserve most of the structural components of biomembranes and carbohydrate gels, and thus retain the natural appearance of both intra- and extracellular surfactant.

Human fetal lung (18 and 18. 5 weeks gestational age) was: enzymatically dissociated (0. 1% trypsin, 0. 1% collagenase, 1. 0% chicken serum in Moscona's saline); filtered; centrifuged (160 x G for 6 minutes); incubated at 37°C for one hour; resuspended in culture medium (Ham's F12K + 10% FBS); and cultured on a Gelfoam collagen sponge.
A correlative histochemical and immunological electron microscopy of the alveolar lining layer of the lung
Authors: Katsuno Hiroshi , Iwabuchi Tsutomu , Matsumoto Keiko , Aihara Kaoru , Yajima Gompachi
Published: June 2020

Objective: The alveolar lining layer or film has attract the much attention of various physiologist and biochemist initially as is related with the interface action of the lung. von Neeargars is the first investigation who called an attention of the surfactant activity or surface tention in the lung. Since then various literature are accumulated on the biochemical or biophysical properties of the surfactant attention. From the ultrastructual point of view, Gil & Weibel and Dermer's described the methodological approaches to demonstrate the phospholipid (Dipalmitoyl lecithin). However, whether they represent the precised and critical surfactant materials are remaining still controversial. Kikkawa also described the method to purity the isolated type II cells which will give further informative basis of the biological action of the cells. The present investigation is performed to make a critical evaluation of the surfactant interacting patterns of the surfactant action, mucopolysaccharide and apoprotein layers from histochemical and immunochemical viewpoint.
Ultrastructural changes in the rat hepatocytes during azo dye carcinogenesis modified by furaciline
Authors: Pinchouk V. G. , Monastyrskaya B. D. , Andrianov V. M. , Nikitchenko V. V. , Bilitch K. M.
Published: June 2020

Nitrofuran derivatives have been known to have a strong inhibitory effect on azo dye hepatic carcinogenesis when they are fed to rats simultaneously with an azo dye (Miyaki et al., 1969; Miyaji, 1971; Akao et al., 1971). It is assumed that the nitrofurans retarded the induction of hepatomas because they stimulate RNA-polymerase activity of liver nuclei inhibited by azo dye feeding (Akao et al., 1972; 1974)

Male rats were fed a rice diet containing 0, 06% 4-dimethylamino- azobenzene (DAB) and 0, 2% furaciline /semicarbason-5-nitrofurfurole/ (F6) for 6 months. Their liver tissue was then examined by light and electron microscopy at different intervals for 14 months. Strong inhibitory effect of F6 on DAB-carcinogenesis was found.

The changes produced in hepatocytes by F6 included the hypertrophy of nucleolus, disorganization and slight reduction of granular endoplasmic reticulum (GER), moderate hyperplasia of agranular endoplasmic reticulum (AER), swelling of some mitochondria and diminition of glycogen content /Figs. 1-2/.
SEM study on gastrulation; internal structure at the stage of ventral blastoporal groove in bufo arenarum
Authors: Herkovits Jorge
Published: June 2020

SEM studies on amphibian gastrulation have shown the overall shape and arrangement of several cell types (e. g. bottle cells, mesodermal cells, ectodermal cells, etc. ) as well as the cellular activities in the blastocoel cavity during archenteron floor descent. The main purpose of the present communication is to show the internal structure of Bufo arenarum gastrula as viewed in sagittal dissection at the stage when the ventral blastoporal groove starts forming.

Material and Methods: Bufo arenarum gastrula were fixed in 2, 5% glutaraldehyde in phosphate buffer for 2, 5 hrs. After removing the vitelline membrane the embryos were fractured and then dissected near the mid-sagittal plane. The specimens were dehydrated through an acetone series, dried according to the critical point technique, coated with evaporated gold-platinum and observed in a Jeol JSM-U3 scanning electron microscope operated at 5-15 kW.

Observations: The internal structure of a Bufo arenarum gastrula at the ventral blastoporal groove stage is illustrated in Fig. 1. Blastocoel cavity (B), internal endodermal yolky cells (Y), prospective ectoderm (PE), archenteron (A), dorsal blastoporal lip (L), ventral blastoporal groove (V).
Formation and behavior of the nurse cell giant granules in the sea urchin ovary
Authors: Takashima Y. , Tominaga A. , Kume T.
Published: June 2020

The nurse cells in the sea urchin ovary indicate a peak of their development at the beginning of the breeding season. They contain giant granules (A-, B- and C-types) and glycogen particles in their cytoplasm as nutrient materials, which are taken into the growing oocytes during oogenesis (Fig. 1) The nurse cells indicate remarkable seasonal changes. As oogenesis proceeds the giant granules are broken down and materials in them are taken into the oocytes. Mature eggs contain cortical granules and yolk particles as the storage for nutrient materials. Nutrient intake of the oocyte from the nurse cells have been reported by us. The present report deals with the formation of the nurse cell giant granules and their behavior observed by the TEM, SEM and ultracytochemistry.

The ovaries of two Japanese sea urchin species, Hamicentrotus pulcherrimus and Anthocidalis crassispina, during and after the breeding season were fixed in glutaraldehyde and/or in osmium tetroxide and prepared for TEM (section and freeze-fracture replica) and SEM observations. Ultracytochemistry, mainly for mucopolysaccharide and the catalase activity demonstrated by 3, 3' -diaminobenzidine (DAB) method, was also performed.
The formation and function of the extraacrosomal layer and modification of the plasma membrane in spermiogenesis of Acrida lata motschulsky (Orthoptera)
Authors: Yasuzumi Gonpachiro , Asai Toshikatsu
Published: June 2020

Receptor-specific proteins are now being widely and usefully applied to the study of cell-surface topography. We have been actively interested in this field from the standpoint of spermiogenesis of the grasshopper. The surface of developing spermatids is in contact with other cells or with their environment, and in addition to carrying on metabolic processes necessary for maturation they must also exhibit the specificity that distinguishes cells from the same cell types from different individuales. The cell bodies of the grasshopper, Acrida lata Motschulsky, spermatids are spherical in the early stage of metamorphosis, but later they become conical and more and more elongate until they are long slender rods, rounded at the base and tapering at the tip to a sharp point. Concurrently with these changes in the spermatid cell bodies, the remarkable trans formation occurs in the fine structure of the cell-surface. In the early stage of maturation of spermatids, the cell-surface is smooth and consists of the unit membrane structure.
Fine structure of compound eyes of cicindela tranquebarica herbst (coleoptera: cicindelidae)
Authors: Kuster Janice E.
Published: June 2020

The fine structure of photopic eucone eyes of Cicindela tranquebarica adults was examined using cryofracture SEM, TEM, and freeze-etch techniques. A “subcorneal layer” can be distinguished between the corneal lens and crystalline cone. In surface view (Fig. 1) this layer consists of concave polygons (po). It has parabolic lamellae (lm) of endocuticle consisting of microfibrils (mf) having a chitin core with protein deposits along their lengths (Fig. 2). Two primary pigment cells (lp) are devoid of pigment granules, but are rich in rough endoplasmic reticulum (rer) and surround a crystalline thread (ct) (Fig. 3). Extensions of the crystalline thread form inter-retinular fibers (f) containing microtubules between retinula cells 1/2, 3/4, 5/6, and 7/1 (Figs. 4, 5).

Distal to each retinula cell nucleus are two basal bodies (bb), one perpendicular to the other (Fig. 4). The proximal body extends two fibrillar feet which fuse to form a horizontally banded ciliary rootlet which extends the retinula length peripheral to the rhabdom.
Organ culture of adult amphibian heart
Authors: Nag Asish C. , Healy Christopher J. , Cheng Mei
Published: June 2020

A long-term culture method of beating heart explants of adult newt has been developed recently in our laboratory. This method has enabled us to study the ultrastructure and contractile activities of beating adult heart explants at selected intervals. Adult newt heart ventricle was excised and washed with amphibian balanced salt solution and cut into several pieces of approximately 0. 5-1. 0 mm. Heart pieces were cultured for 2 months at 25°C in a medium containing 90% modified Leibovitz medium (L-15), 10% fetal calf serum and 1% penicillin-Streptomycin. In first week of culture, more than 37% of heart explants were attached to the substrate, and more than 33% established pulsation rates. Some explants had a rate of 3-12 beat/min., while others had a rate of 28-67 beat/min. A few cells migrated from the explants and were attached to the substrate around the explants. These migrated cells did not show pulsation.
Dendritic cells of the human epidermis: immuno-electron microscopic studies of la antigen reactivity
Authors: Rowden G. , Lewis M. G. , Phillips T. M.
Published: June 2020

Langerhans cells of mammalian stratified squamous epithelial have proven to be an enigma since their discovery in 1868. These dendritic suprabasal cells have been considered as related to melanocytes either as effete cells, or as post divisional products. Although grafting experiments seemed to demonstrate the independence of the cell types, much confusion still exists. The presence in the epidermis of a cell type with morphological features seemingly shared by melanocytes and Langerhans cells has been especially troublesome. This so called "indeterminate", or " -dendritic cell" lacks both Langerhans cells granules and melanosomes, yet it is clearly not a keratinocyte. Suggestions have been made that it is related to either Langerhans cells or melanocyte. Recent studies have unequivocally demonstrated that Langerhans cells are independent cells with immune function. They display Fc and C3 receptors on their surface as well as la (immune region associated) antigens.
Freeze-fracture study of mammalian skin: melanocyte-keratinocyte interactions
Authors: Garcia Raul I. , Flynn Evelyn A. , Szabo George
Published: June 2020

The interactions of epidermal melanocytes(M) and keratinocytes(K) involve the unique process of melanosome transfer, from the melanin-synthesizing cell to the recipient, desquamative K, and are responsible for the skin color of man and other mammals. M-K interactions have been well studied in mammalian skin using thin section analysis, and there have been several freeze-fracture studies of skin. This study represents the first application of freeze-fracture to the study of M-K interactions and melanosome transfer. Several mechanisms of melanosome transfer have been proposed to explain the varied observations made in vivo and in vitro: melanosomes migrate from the M perikaryon peripherally into M dendrites, followed by cytophagocytosis by the K of the M dendrite tip containing melanosomes, formation of intercellular communicating channels between M and K through localized fusion of cell membranes with melanosome entry into K through this passage, release of melanosomes from M into the extracellular space(ECS) by exocytosis with subsequent phagocytosis by the K. Our own EM work using lanthanum tracer in skin in vivo has produced evidence supporting the second mechanism while cell culture studies suggest that a different mechanism may operate in vitro.
Proteoglycan alterations in rheumatoid arthritis—a light and electron microscopy study
Authors: Mitchell Nelson S.
Published: June 2020

We have previously studied the ultramorphology oh cells in rheumatoid arthritis using conventional staining techniques. We have recently reported a technique for the precipitation and fixation of proteoglycan using Toluidine Blue 0 or Safranin 0 which permits simultaneous localization of proteoglycan using either light or electron microscopy in sections cut from the same block. This paper reports a study of rheumatoid arthritic cartilage using this technique.

Samples oh cartilage were removed from the femoral condyles of thirteen patients with classical rheumatoid arthritis who were having operations on the knee. Control samples were removed from the knees of eleven normal patients who were having surgery for recent trauma. In both Instances, the tissues were prepared with Toluidine Blue or Safranin 0 Introduced into the fixation process as will be described.

When fixed and stained by conventional methods, articular cartilage has been traditionally reported to consist ofi chondrocytes lying in a matrix of collagen and proteoglycan though separated from this matrix by a pericellular clear space, “halo” or “lacuna” of varying dimensions. This pericellular space was thought to contain only small amounts of collagen.
Electron microscopy of the microangiopathy and immunohistochemistry of the inflammatory infiltrate in eosinophilia-myalgia syndrome
Authors: Smith Stephen A.
Published: June 2020

The ingestion of L-tryptophan (LT) was linked with the eosinophilia-myalgia syndrome (EMS) in the fall of 1989. The pathology is a microangiopathy consisting of endothelial cell dysfunction and invasion of blood vessels by lymphocytes. Perimysial, fascial, and dermal perivascular lymphocytes and eosinophils are present. A contaminant in the manufacturing process of LT has been identified as the di-L-tryptophan aminal of acetaldehyde. This report describes the electron microscopic appearance of the microangiopathy and the phenotyping of the inflammatory infiltrate by immunohistochemistry.

Muscle, fascia, and skin biopsies from 21 affected individuals were rapidly frozen for light microscopy, histochemistry, and immunohistochemistry. For electron microscopy tissues were preserved in 4% formaldehyde-1% glutaraldehyde with post-fixation in osmium tetroxide. Thin sections were stained with uranyl acetate and lead citrate and examined in a JEOL 100CX electron microscope. Eight anlisera were used for the immunohistochemistry to identify lymphocyte subsets and macrophages. The markers were CD-2 (pan T), CD-3 (pan T), CD-4 (T helper), CD-5 (T helper), CD-8 (T suppressor), CD-19 (B cell), CD- 22 (B cell), and CD-68 (macrophage). Three high power fields were examined from the dermis, fascia, and muscle from eight biopsies counting the immunoperoxidase labelled cells for each marker.
Novel methods for demonstrating osseointegration of hydroxylapatite-coated titanium hip prostheses
Authors: Frayssinet P. , Hanker J. , Hardy D. , Giammara B.
Published: June 2020

Prostheses implanted in hard tissues cannot be processed for electron microscopic examination or microanalysis in the same way as those in other tissues. For these reasons, we have developed methods allowing light and electron microscopic studies as well as microanalysis of the interface between bone and a metal biomaterial coated by plasma-sprayed hydroxylapatite(HA) ceramic.

An HA-coated titanium hip prosthesis (Corail, Landos, France), which had been implanted for two years, was removed after death (unrelated to the orthopaedic problem). After fixation it was dehydrated in solutions of increasing ethanol concentration prior to embedment in polymethylmethacrylate(PMMA). Transverse femur sections were obtained with a diamond saw and the sections then carefully ground to a thickness of 200 microns. Plastic-embedded sections were stained for calcium with a silver methenamine modification of the von Kossa method for calcium staining and coated by carbon. They have been examined by back-scatter SEM on an ISI-SS60 operated at 25 KV. EDAX has been done on cellular inclusions and extracellular bone matrix.
Microstructural comparison of synthetic bioceramics with natural bioceramics
Authors: Wen Shulin , Feng Jingwei , Krajewski A. , Ravaglioli A.
Published: June 2020

Hydroxyapatite bioceramics has attracted many material scientists as it is the main constituent of the bone and the teeth in human body. The synthesis of the bioceramics has been performed for years. Nowadays, the synthetic work is not only focused on the hydroapatite but also on the fluorapatite and chlorapatite bioceramics since later materials have also biological compatibility with human tissues; and they may also be very promising for clinic purpose. However, in comparison of the synthetic bioceramics with natural one on microstructure, a great differences were observed according to our previous results. We have investigated these differences further in this work since they are very important to appraise the synthetic bioceramics for their clinic application.

The synthetic hydroxyapatite and chlorapatite were prepared according to A. Krajewski and A. Ravaglioli and their recent work. The briquettes from different hydroxyapatite or chlorapatite powders were fired in a laboratory furnace at the temperature of 900-1300°C. The samples of human enamel selected for the comparison with synthetic bioceramics were from Chinese adult teeth.
Quantitative geometric scanning electron microscopy
Authors: Bastacky Jacob , Hayes Thomas , Yager Deborah , Lee Charles
Published: June 2020

Quantitative SEM assessment of the geometry of biological specimens requires attention to 1) statistically valid sampling, 2) dimensional changes during fixation, dehydration, drying, and cutting, 3) artifacts produced by coating, 4) microscope raster and display system field distortion 5) magnification calibration 6) stage tilt calibration and hysteresis, and 7) counting protocols for selecting parts of the final images as data.

This analysis is necessary, for example, in measuring the thickness of the liquid layer lining the alveoli in lung from cross-fractured frozen hydrated pulmonary alveoli.

Adequate numbers of animals, with samples from each significant organ region must be studied. Sampling may be in a stratified random manner or by guided microdissection to preserve additional structural information.
High-pressure freezing/freeze substitution of plant cells
Authors: Kiss J.Z. , Staehelin L.A.
Published: June 2020

Electron microscopy of chemically fixed plant tissues has lead to important insights into the relationship between structure and function of plant cells. However, the slow rate of chemical fixation (seconds to minutes) potentially permits numerous artifacts to be induced. Most of these limitations ofs chemical fixatives can be overcome by the use of cryofixation techniques since cell structure is stabilized rapidly (milliseconds). Several types of cryofixation techniques have been developed such as cold metal block freezing and propane jet freezing. Although application of these techniques has yielded exciting new information, they are limiting in that specimens can be preserved only to a relatively shallow depth (approx. 40 μm). In contrast, under optimal conditions, high pressure freezing (HPF) at 2100 bar can produce excellent freezing of biological samples up to 600 μm in thickness. Since a commercial HPF apparatus has only recently become available, the number of systematic structural studies of biological samples utilizing HPF is still rather limited, and basic questions concerning specimen preparation and processing, HPF artifacts, and interpretation of images need to be addressed.
Some advantages and uses of cryopreservation techniques for ultrastructural studies in mycology
Authors: Edelmann Richard E. , Czymmek Kirk , Klomparens Karen L.
Published: June 2020

To date, only limited use has been made of the advanced techniques of cryopreservation for mycological samples, with the exception of the unofficial “lab rat” Saccharomyces cerevisae. However, cyropreservation can offer some distinct advantages over conventional chemical fixation, as well as unique solutions for specific mycological problems. This presentation specifically deals with the utilization of cryo-scanning electron microscopy (cryo-SEM), freeze substitution for transmission electron microscopy (TEM), freeze fracture and freeze etching of mycological samples. Due to the distinctive morphological and biochemical nature of fungi, as compared to plant and animal samples, some significant adaptations to existing published protocols have had to be devised and are presented here.
Preservation of the relationship of airway mucus and epithelium by slam freezing
Authors: Godleski John J. , Hastings Cindy L. , Katler Marshall , Sweeney Theresa D.
Published: June 2020

The anatomic relationships of airway mucus and ciliated cells has become increasingly important in understanding clearance of inhaled particles. In order to study the relationships between mucus, particles, and epithelium, it is critical to capture the mucus in place and maintain the anatomical position of all its constituents during subsequent processing. Also, to study how inhaled particles are coated by endogenous substances in situ requires fixation suitable for immunocytochemistry. Chemical fixation limits the possibility of some immunocytochemical studies and freeze substitution methods may remove important components of mucus, especially lipids. The purpose of this study is to develop a method to optimally preserve airway mucus in relationship to inhaled particles and cilia.
Transmission electron microscopic study of large myelinated fiber injury from percutaneous trigeminal ganglion compression for trigeminal neuralgia in a rabbit model
Authors: Hoeflinger B.F. , Gunning W.T. , Brown J.A. , Eckhardt A. , McDaniel M. , Weaver M.
Published: June 2020

Trigeminal neuralgia (TN) is a disorder characterized by paroxysmal, lancing facial pain confined to the distribution of trigeminal nerve fibers. A procedure to relieve this sensation, Percutaneous Trigeminal Ganglion Compression(PTGC), was introduced in 1983 and has been shown in clinical studies to be an effective treatment for TN. The effect of PTGC on the trigeminal system has not been adequately studied. In a previous study. New Zealand White rabbits were utilized in an attempt to evaluate the consequences of PTGC at the light microscopic level. This investigation revealed a differential demyelination and fragmentation of axons in the trigeminal(V) sensory root while trigeminal ganglion neurons were found to be preserved. Immunocytochemical stains of the spinal trigeminal tract showed no specific loss of fine caliber Ad and C-fibers. Degeneration of axon terminals was found in the deeper layers of the spinal trigeminal nucleus, the region corresponding to the termination of large myelinated axons suggesting a differential loss of these specific fibers.
Lymphocyte infiltration into sponge allografts
Authors: Suresh A. , Smith N. , Martinez O. , Nieto M.
Published: June 2020

A sponge matrix model utilized for the study of allograft (graft of tissue between genetically different members of the same species) provides sufficient cell numbers to characterize the cells which infiltrate an allograft in vivo. Circumstantial evidence supports the postulated role of specifically sensitized cytotoxic lymphocytes as the principle mediators of allograft rejection in vivo. The sponge matrix model showed that sponge allografts acquire alloantigenreactive T lymphocytes, whereas sponge isografts (grafts between genetically identical individuals) fail to do so, even though the T cells are continuously circulating in the peripheral blood. High endothelial venules (HEV) are present in the normal lymph nodes and they regulate lymphocyte extravasation from the blood. HEV-like vessels have been identified in the sponge allografts. A correlation has been shown between the formation of HEV-like vessels and the presence of alloantigen-reactive T cells in the sponge matrix. Sponges were examined with the scanning electron microscope (SEM) to study the infiltration of different cell types into the sponge allografts and the development of endothelial venules and neovascularization.
Effect of monocrotaline pyrrole on cultured cell cytoskeletons: An ultrastructural study
Authors: Wood J.I. , Klomparens K.L. , Hoorn C.M. , Roth R.A. , Reindel J.
Published: June 2020

The cytoskeleton (CS) is responsible for locomotion, intracellular motility and maintenance of cell structure. The system is composed of three major components: microfilaments, responsible for motility and cell structure, microtubules for organization and movement within the cell, and intermediate filaments, which may provide stability of intracellular contents.

Monocrotaline (MCT) is a pyrrolizidine alkaloid plant toxin. When administered to rats, MCT is metabolized to monocrotaline pyrrole (MCTP) which induces lung injury and pulmonary hypertension. When administered to cultured pulmonary artery endothelial cells, MCTP causes progressive detachment, release of LDH, inhibition of cell proliferation, and distorted and enlarged nuclei. MCTP is a bifunctional alkylating agent that can crosslink DNA. We speculate that MCTP may also affect the cytoskeleton, resulting in inhibition of cell division.
An ultrastructural study of endothelial cells in branched regions of rat artery
Authors: Yang V. C. , Kao C. H.
Published: June 2020

Endothelial injuries in artery have long been considered as the initial event of the intimal thickening in atherogenesis. It has been noted clinically that some lesions tend to be situated at regions with the greatest mechanical stresses. These regions include branchings, bends, and narrowings. Physiological evidences showed that patterns of blood flow and mural tensions in these regions were notably different from those in the unbranched vessels. However, there have been no morphological studies on the endothelium about the branches of the arteries. Our experiment was designed for a comparison between the ultrastructrue of endothelia at the branched and the unbranched areas of the arteries in rats. The specific intention was to apply morphological quantitative methods to investigate the transendothelial transport mechanisms.