bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultracytochemical demonstration of sulfhydryl groups in the rabbit erythrocytic membrane
Authors: Ogawa Kazuo , Tanaka Teruo 
Published: June 2020

Elucidation of the macromolecular structure of the cellular membrane is one of the most current topics in cell biology. In relation to such study, development of the membrane ultracytochemistry, in particular ultracytochemistry of functional groups, is of great value in elucidation of the structure and function of the cell as well as in filling gap between the morphological findings and the physicochemical or biochemical findings on the cellular membrane. At first development of the methods for amino groups (NH2) was tried and then sulfhydryl groups (SH). In the present report recent findings on SH groups are presented.Formaldehyde-glutaraldehyde-fixed rabbit erythrocytes, intact or ghost, were used to demonstrate SH groups. SH groups were detected by 4 different ways. Fast blue BBN (FBBBN) method: Specimens were incubated in 0. 5% FBBBN in 0.1M cacodylate buffer, pH 7.4, for 40 to 45 min at 0-4°C, fixed in osmium tetroxide (OT) and processed for electron microscopy (EM).
Correlative LM, SEM and TEM of argentaffin cells
Authors: Frederickson R.G. , Spagnoli D.B. , DeNee P.B. 
Published: June 2020

The identification of small numbers of cells containing specific materials or having a particular location in a tissue can be observed cften in light microscopic (IM) sections by selective staining. In contrast, the same cells are often difficult to identify in alternate thin sections on grids by transmission electron microscopy (TEM). Grid bars produce periodic obstructions and consequently prevent the visualization of tissue continuity, making it difficult to identify landmarks. Also, the TEM image of a thin section of tissue does not correlate well with the thicker IM image. This is a matter of interpretation based on the different principles of image formation and the different levels of resolution.The purpose of this paper is to demonstrate a method which allows the same cells identified by IM to be more easily located in thin sections for TEM. This method combines the principles of backscattered electron imaging (BSI), secondary electron imaging (SEI) and heavy metal staining with scanning electron microscopy (SEM).
Direct observations of semithin sections by the use of TEM and STEM
Authors: Sakai Toshio 
Published: June 2020

It has been routin to cut semithin sections to look for desired areas before cutting ultrathin sections for electron microscope studies. A new method made it possible to observe larger semithin sections of epoxy resin-embedded tissue with both light microscope and two kinds of electron microscopes,: Transmission Electron Microscope and Scanning Transmission Electron Microscope.Samples obtained from kidneys of rats and mice were sliced to 0. 5.mm to 1 mm thickness. They were fixed for 4 hours in Sorensen phosphate buffer of pH 7.4, containing 2 % glutaraldehyde and 1.5 % paraformaldehyde, rinsed in plain buffer for 12 hours (overnight) and postfixed in 1 % osmium tetroxide buffered with phosphate for 90 minutes. The tissu blocks were then embedded in epoxy resin in a ratio of 6:4 or 5:5 by weight, based on the method of Luft.
Scanning transmission electron microscopy and X-ray microanalysis of unstained biological thin sections
Authors: Freeman R. , Griffiths G.W. , Jones A. V. , Leonard K.R. 
Published: June 2020

The scanning transmission electron microscope (STEM) has two distinct advantages over the conventional transmission electron microscope (CTEM) for the investigation of low contrast specimens such as unstained thin sections. These are the much higher collection efficiency for scattered electrons and the possibility of electronic enhancement of the image forming signal. The addition of an X-ray analysis system to STEM may also enable the identification of some of the elements contributing to the overall image contrast and to detect individual element concentrations in features of high contrast occurring in the specimens.Fresh tissue was fixed in 1-2.5% glutaraldehyde in PIPES buffer, quickly dehydrated in ethanol and embedded in epon. Thin (silver/grey) sections were collected on carbon coated copper or nylon grids and viewed in the STEM without further treatment. The microscope used was a Vacuum Generators HB5 STEM with field emission source operating at lOOkV with simultaneous bright field (BF) and dark field (DF) detection systems.
X-ray microanalysis of cryofixed skeletal muscle in culture
Authors: Zierold K. , Pietruschka F. , Schäfer D. 
Published: June 2020

X-ray microanalysis of electrolyte ions in cells and tissues involves the problem of preserving the distribution of diffusible substances throughout preparation and investigation in the scanning electron microscope. Cryofixation of objects thicker than about 200,um induces considerable freezing artifacts. The dissection of the specimen from the intact tissue also influences the distribution of diffusible ions. With respect to these problems, tissue culture cells seem advantageous, because they need not be dissected from their environment and are small enough to be frozen without ice crystal damage.Tissue cultures were grown from skeletal muscle of the hindleg of 20-day-old rat embryos on plastic coverslips. Small pieces of the specimens (diameter about 4 mm) were mounted on cupreous specimen stubs with conducting silver paint and frozen in liquid propane.
Quantitative X-ray microanalysis of a mouse cardiac muscle by means of the freeze substitution method
Authors: Mizuhira Vinci , Shiihashi Michiko 
Published: June 2020

"Analytical electron microscope": We have deviced a new analytical electron microscope in Japan for the detection of elemental localization in tissues and cells in 1973.Our analytical EM is basically composed of a JEM 100C transmission electron microscope fitted with a scanning device(ASID-4), a side-entry goniometer stage and an energy dispersive type X-ray microanalyzer unit(EDAX-707B) with an EDIT-Computer system.Freeze substitution method: We compared the results between the freeze dried and the freeze substituted sections of fresh mouse kidney before the cardiac muscle examination. The results were clear that the freeze substitution method with ether or acetone followed by vinylcyclohexane dioxide (ERL-4206) resin mixture seems superior both in the STEM-image and the X-ray microanalysis to that of the freeze dried method.Freshly prepared mouse heart muscle was cut in small pieces within a 3 mm3 in size, mounted on an alminum foil, and frozen with cooled methycyclohexane at the liquid nitrogen temperature, after acrolein vapor fixation for 3 min.
Replication of biological specimens at -150°c with an improved freezefracture apparatus
Authors: Pscheid P. , Müller W. 
Published: June 2020

It is advantageous to fracture at the lowest temperature possible to minimize the plastic deformation of the specimen. However, the contamination rate is in- versly proportional to the temperature. One way to avoid this problem is to decrease the pressure and therefore the contamination rate.The present paper describes inexpensive modifications of the Balzer freeze-etch machine (BA 360 M) which reduces the contamination rate of the specimen. This is done by an improvement of the vacuum and a modification in the specimen table.The vacuum can be improved in the following manner: by desorption of water from the surfaces of the vacuum chamber; by condensation of water in the residual gas mixture of the vacuum on cold surfaces; by minimizing frost build-up at the specimen surface during the transfer to the machine.
Immunoferritin localization of intracellular antigens in positively stained frozen sections
Authors: Tokuyasu K. T. 
Published: June 2020

During the past investigations of immunoferritin localization of intracellular antigens in ultrathin frozen sections, we found that the degree of negative staining required to delineate u1trastructural details was often too dense for the recognition of ferritin particles. The quality of positive staining of ultrathin frozen sections, on the other hand, has generally been far inferior to that attainable in conventional plastic embedded sections, particularly in the definition of membranes. As we discussed before, a main cause of this difficulty seemed to be the vulnerability of frozen sections to the damaging effects of air-water surface tension at the time of drying of the sections.Indeed, we found that the quality of positive staining is greatly improved when positively stained frozen sections are protected against the effects of surface tension by embedding them in thin layers of mechanically stable materials at the time of drying (unpublished).
Aggregation properties of electric eel acetylcholinesterase: a possible mechanism of enzyme association at the synapse
Authors: Cartaud J. , Bon S. , Massoulié J. 
Published: June 2020

Electrophorus acetylcholinesterase activity (E.C.3.1.1.7) is associated with several molecular forms (D = 18.5 S, M.W.= 1,150,000; C = 14.4 S, M.W.= 796,000; A = 9 S, M.W. = 410,000; G = 11.8 S, M.W.= 330,000; G' = 7.7 S, M.W.= 165,000 and G” = 5.3 S, M.W. = 70,000). All the lighter forms probably derive from the heaviest (D) which is an asymmetric assembly of three tetramers of catalytic subunits linked by a collagen-like filament or “tail”. The two lighter asymmetric forms, A and C, contain respectively one and two tetramers linked to a tail.When exposed to low ionic strength conditions, the asymmetric forms of the enzyme associate reversibly into fast sedimenting aggregates (70 S), the process not being correlated with any change in catalytic activity.
Cytochemical study of the plant interphase nucleolus
Authors: Luck B. , Lafontaine J.G. 
Published: June 2020

Under light microscopy, plant interphase nucleoli show a heterogeneous organization due to the presence of a coarse, contorted filamentous structure which, at high magnification, may be demonstrated to give rise to the fibrillar zones. This thread-like structure, or nucleolonema, is continuous with extranucleolar segments of chromosomes and corresponds, therefore, to the nucleolar organizer. It is observed that this filamentous structure gradually contracts during prophase and eventually forms a nucleolar secondary constriction. The latter chromosomal segment differentiates during telophase and is intimately involved in the process of nucleolar reformation.A still unresolved feature of the nucleolonema is the presence of a series of complexly organized lighter areas referred to as lacunae. A dense structure, or core, sometimes observed in the central portion of these lacunae is believed to consist of compact chromatin whereas the surrounding lighter material presumably represents diffuse chromatin. Digestion with deoxyribonuclease as well as high resolution radioautography indicate that DNA is indeed present within the nucleolonema.
Synaptonemal complexes in the mosquitoCulex quinquefasciatus
Authors: Fiil Annelise 
Published: June 2020

The presence of synaptonemal complexes between the paired homologous chromosomes at meiotic prophase is a prerequisite for meiotic crossing over, and it may be important for the regular disjunctions of the chromosomes at meiosis I (Moses, 1968; Westergaard and von Wettstein, 1972; Gillies, 1975). Reconstructions of nuclei during zygotene and pachytene have shown that the ends of the synaptonemal complexes in many organisms are attached to the nuclear membrane, often in a polarized fashion (Moens, 1969; Rasmussen, 1976); such a bouquet arrangement of the chromosomes is found in Culex.Materials and MethodsOvaries from Culex quinquefasciatus were fixed in glutaraldehyde, followed by 0s04, and embedded in Epon. The synaptonemal complexes were reconstructed from serial sections.Results and DiscussionCulex has 3 pairs of very long metacentric or slightly submetacentric chromosomes which during pachytene loop around the nucleus several times (Fig. 1). The centromeric regions are fused, and the synaptonemal complexes do not continue through the structure.
Centromeric heterochromatin in phyllotis darwini
Authors: Eduardo Couve M. 
Published: June 2020

Centric fusion plays an important role in karyotype evolution as a mechanism of chromosomal change. Centromeric Heterchromatic regions (CeHR) can be observed in optical and electron microscopes and their location during meiotic stages should be fundamental for the occurrence of centric fusion.This work is concerned with centromeric he terochromatin orientation and cytochemistry of this structure in meiotic male cells of Phyllotis darwini rupestris, obtained from their natural region. This is a Chilean species with diploid number 38, all chromosomes biarmed (meta- and submetacentric). Heterochromatin is always located in the centromere region, except the Y chromosome.Spreads for light microscopy were made from testicular tissues and stained with Arrighi and Hsu (1971) procedure. For electron microscope pieces of seminiferous tubules were fixed in glutaraldehyde 3% in 0.2M cacodylate buffer pH 7.2 and postfixed in osmium tetroxide 1%. Tissue was stained in block with 5% uranyl acetate, dehydrated in ethanol and embedded in Epon 812.
Mitochondrial changes related to yolk formation in oocytes of a viviparous teleost
Authors: Azevedo Carlos , Coimbra Antonio 
Published: June 2020

Mitochondria have been implicated in yolk formation in amphibians the oocytes of which were shown to contain intramitochondrial yolk crystals. We recently observed, however, in the viviparous teleost Xiphophorus helleri, that mitochondria seem to intervene in yolk accumulation in a different way by developing invaginations of their contour which enclose materials that are later incorporated into yolk globules. Ovaries were fixed in glutaraldehyde—osmium or osmium alone and epon embedded.In 15 day-old females, at leptotene, oocyte mitochondria appeared closely associated with granulo-fibrilar perinuclear masses identical to other masses situated on both sites of nuclear pores or near the nucleoli (Fig. 1). Granules in all these masses measured 12 nm in diameter and were similar to those forming the nucleolar pars granulosa. At dictyate, while nucleoli became vacuolated and ring-shaped, mitochondria surrounded the granulo-fibrilar masses (Fig. 2), though by the second half of this stage they appeared detached from those masses and showed constrictions and sinuous contours.
Mitochondria microcrystals deposition in some inherited diseases of lipid metabolism.
Authors: Laoussadi S. , Kahan A. , Aubouy G. , Delbarre F. 
Published: June 2020

Several patients with Fabry's, Gaucher's diseases and hyperlipoproteinemia type II and with arthropatic manifestations were observed.As no histological explanation for these symptoms was available,an ultrastructural study of synovial tissue was done to establish an anatomoclinical relation.Material and Methods :synovial membrane samples were obtained by needle biopsies of the knee from three patients with arthropatic manifestations of each disease.They were fixed in 5% glutaraldehyde, postfixed in 1% osmium tetraoxyde and embedded in Epon 812. Thin sections coloured by uranyl acetate and lead citrate were observed with an Elmiskop I Siemens electron microscope.Two important phenomena were observed in synovial tissue:Specific patterns of each lipid storage disease,which are now well known.In all the three metabolic diseases, hydroxyapatite-like crystals were found. They are characterized by their intramitochondrial localization, without any relation with cristae,an anarchic disposition and a mean size of 550 A.Crystals may be found also free in the cytoplasm of synoviocytes Some micrographs suggest an evolution in four steps :a. mitochondria with only a few microcrystalsb. mitochondria stuffed with these structuresc. disruption of mitochondria membranesd. microcrystals appear free in the cytoplasm
Thermotropic lipid clustering in endoplasmic reticulum membranes of tetrahymena
Authors: Wunderlich F. , Kreutz W. 
Published: June 2020

Freeze-etch electron microscopy detects lipid-protein-segregations in endoplasmic reticulum membranes directly within Tetrahymena cells. This manifests in the emergence of smooth areas on the fracture faces at ˜12°C upon cooling the cells from their suboptimal growth temperature of 18°C to 0°C (Figs.1,2). The membrane-intercalating-particles do not become laterally aggregated, but rather appear to be displaced perpendicularly to the membrane plane. Our previous studies using electron spin resonance, fluorescence spectroscopy, proton nuclear magnetic resonance, and differential thermal calorimetry have indicated that these lipid-protein-segregations are induced by a thermotropic lateral lipid clustering.In order to support this suggestion we have now analyzed the thermotropism of the lipids gxtracted from microsomal membranes isolated from cells grov/n at 18°C by wide- and small-angle X-ray diffraction. Our data show that total lipids undergo a broad thermotropic fluid→ ordered phase separation (Figs. 3-5).
Ultrastructure and raman spectra changes caused by uncouplers of oxidative phosphorylation in artificial membranes
Authors: Pasquali-Ronchetti I. , Ghisellini M. , De Alojsio G. , Fini G. 
Published: June 2020

Despite substantial evidence showed the existence of ultrastructural changes in uncoupled mitochondrial membranes, the precise mechanisms by which some chemicals uncouple oxidation from phosphorylation are still to be established.In the present study evidence is presented that some uncoupling agents at the same concentrations (related to lipid content) that uncouple phosphorylation from oxidation in isolated mitochondria, alter the lipid phase of artificial phospholipid membranes.Dipalmitoyl phosphatidyl choline dispersions in saline were studied by freeze-etching electron microscopy and Raman spectrometry and the changes caused by the uncoupling agents on the membrane structure were compared to those obtained by increasing the temperature of the system.
Types of cell contacts in different smooth muscles
Authors: Henderson Ruth M. 
Published: June 2020

It is generally agreed that, where present, gap junctions or nexuses provide low-resistance pathways for cell-to-cell coupling of activity. Though these contacts were first described in smooth muscle and occur widely there, some types of smooth muscle contain few or no gap junctions, and many contain other types of contacts.A variety of smooth muscles from several species was fixed with phosphate-buffered glutaraldehyde by intra-arterial perfusion or by immersion of small strips. Samples were prepared for electron microscopy by standard methods, using oriented embedding to view muscle in both longitudinal and cross sections.Four types of cell contacts were identified in various smooth muscles, which have been previously recognized. 1) The gap junction or nexus appears with the usual double staining as a five-layered contact, often with adjacent clear areas of cytoplasm (Fig. 1).
Role of spectrin in membrane fusion and in shape change of human erythrocyte ghost
Authors: Hayashi Hideo , Hirai Yoshikazu , Penniston John T. 
Published: June 2020

Spectrin is a membrane associated protein most of which properties have been tentatively elucidated. A main role of the protein has been assumed to give a supporting structure to inside of the membrane. As reported previously, however, the isolated spectrin molecule underwent self assemble to form such as fibrous, meshwork, dispersed or aggregated arrangements depending upon the buffer suspended and was suggested to play an active role in the membrane conformational changes. In this study, the role of spectrin and actin was examined in terms of the molecular arrangements on the erythrocyte membrane surface with correlation to the functional states of the ghosts.Human erythrocyte ghosts were prepared from either freshly drawn or stocked bank blood by the method of Dodge et al with a slight modification as described before. Anti-spectrin antibody was raised against rabbit by injection of purified spectrin and partially purified.
Preparation of the rigid layer (murein) of bacterial cell walls for high resolution electron microscopy
Authors: Formanek Helmut 
Published: June 2020

I. Preparation of murein Murein or peptidoglycan is responsible for the rigidity of the cell- walls of almost all bacteria. It is a network of polysaccharide chains crosslinked by short peptide chains (Fig. 1 and 2). Based on the known primary structure and on X-ray and IR data a three dimensional model of peptidoglycan could be derived by theoretical considerations (Fig. 3). Peptidoglycan was prepared from deep frozen cells of the Gram negative bacterium Spirillum serpens.The free aminogroups of peptidoglycan are brought to reaction with an excess of propylenesulfide in 1, 5 M K2HPO4, After removal of the excess of propylenesulfide by dialysis against water, the -SH groups incorporated into the peptidoglycan have been stained with equimolar amounts of the following heavy atom compounds: 2, 4, 6 Tri-acetoxymercuri-acet- aminotoluene or platinum blue Pt (CH3CONH)2. Since one free amino- group has been found per mesh of the murein network its periodicity has been marked with the single heavy atom molecules.
Reconstruction of the crystal-like particle arrangement within a bacterial membrane interlayer
Authors: Schiske P. , Reuber E. , Tesche B. , Wecke J. , Giesbrecht P. 
Published: June 2020

Recently the existence of crystal-like particle arrangements in the interlayer between cell wall and cytoplasmic membrane in Gram-positive bacteria could be demonstrated for the first time, Results so far show the crystal-like regions as networks of interlinked ring-shaped units.For further analysis of these structures, despite the limited extension of the ordered regions, digital image processing was attempted. For comparison of different preparation methods, specimens treated with freeze-etching and specimens treated with negative stain were used. The latter proved to be more amenable to reconstruction without separate correction of non-linear lattice distortion.The micrographs were scanned along a 24-micron square grid with an effective collecting aperture of 50 micron diameter. 256 x 256 point Fourier transform was used. The filter mask was built from Gaussian peaks of equal shape and magnitude. Fourier transform of this shape in direct space gives an estimate of the area contributing to a single point of the reconstructed image.
Tubuloreticular structures in rubella virus-infected human fetuses
Authors: Kistler Gonzague S. , Groscurth Peter 
Published: June 2020

Tubuloreticular structures (TRS) consisting of branching tubules of variable length and with a diameter of 18-30 nm have been described within dilated endoplasmic reticulum cisternae of endothelial and other cells in a variety of conditions. Thus, TRS have been observed in apparently normal human and animal cells, in cells of patients with auto-immune disease (e. g. systemic lupus erythematodes), with neoplasia (leukemias, carcinomas, sarcomas) as well as with a number of viral infections caused by both DNA or RNA viruses. Whereas earlier investigators regarded TRS as viral or virus-like in nature, it is now widely accepted that these structures represent focal proliferations of ER-membranes and that they reflect a cellular response to a broad range of stimuli. The biological significance of TRS has, however, not been resolved.In rubella-infected human embryos and fetuses, vascular lesions are the most frequently observed light microscopical findings.