bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron Microscopy of the Camel Oviductal Epithelium During Early Pregnancy
Authors: Nayak Ramesh K. , Zein Anwar 
Published: June 2020

The function of the oviduct is essential to the reproductive process of mammals since it allows the meeting of gametes and the beginning of embryonic development. A detailed account on the fine structural changes of the porcine oviductal epithelium during pregnancy has been published. Scanning electron microscopic features of the oviduct from estrus camels have been recently described. To the best of our knowledge, no transmission electron microscopic studies of the camel oviductal epithelium during pregnancy have been reported. The purpose of this study was to identify some of the fine structural changes occurring in the tubal epithelium during early pregnancy and to establish a basis for subsequent physiological and pathological studies.Specimens from the infundibulum region of the oviduct were obtained from 10 pregnant camels. In the present study, it was not possible to determine the exact stage of pregnancy.
Low dose electron diffraction of wet protein crystals
Authors: Chang B.B. , Parsons D.F. 
Published: June 2020

High resolution electron diffraction patterns from wet unstained protein-crystals have been successfully obtained by using very low electron dose (∽10-2 e/Å2, much smaller dose than used by Unwin and Henderson (1975) for electron diffraction of their crystals). This enabled us to follow the radiation damage of the protein crystal due to increasing dosage by recording successive diffraction patterns given by the same crystal. Changes in intensities of both the high and the low order reflections can be studied. Another important consequence is that very low dose electron diffraction can be obtained from the same crystal and iterative procedures such as Gerchberg and Saxton's technique can be applied.The electron diffraction work with very low dose was performed at 200 kV using the environmental chamber in the Jeolco 200. To achieve best electron diffraction conditions with the specimen in the hydration chamber, the objective and intermediate lens currents have been changed.
A quantitative EM study op the packing and shape of the protein subunits organized in contractile sheaths
Authors: Cremers A.P.M. , Krijgsman P.C.J. 
Published: June 2020

Phages for example from the T-even family have a complex structure. They consist of a head in which the DNA is packaged, a contractile sheath and a complex structure with which the phage attaches itself to the membrane of the host cell.We are studying the structural mechanism by which the sheath transmits the DNA in the recipient cell by electron microscopy and image analysis techniques. The contractile sheath of these types of phages consists of a large number of identical protein subunits which are arranged in a regular way.To study the arrangement of the subunits in five PBS X-like defective phages, from B.subtilis and B.licheniformis, negatively stained specimens were imaged by electron microscopy and the images were subjected to optical diffraction and digital analysis. The extended and contracted sheath configuration of the five defective phages were found to be similar and differed from the known cases of T4 and Mu.
Topography of s bacterial membrane: the HPI-layer of M.radiodurans
Authors: Kübler O. , Hahn M. , Baumeister W. 
Published: June 2020

The cell wall of Micrococcus radlodurans has multilayered structure, which is quite untypical for grain-positive bacteria. The HPI-layer is a membraneous sheet containing lipids, carotenoids, carbohydrates and protein and covers the outer surface of the murein sacculus.HPI-layers isolated from Micrococcus radiodurans have been studied by electron microscopy employing negative as well as positive staining and subsequent digital image processing. The protein complexes in these layers form regular periodic arrays comprising up to about 3000 unit cells. The subunits making up the HPI-layer are arranged in almost perfect hexagonal symmetry (L1, L2 ∽16.9 nm; φ = 120. 12 ± 4.2°).The projected structure of negatively stained HPI-layers has been determined at a resolution of 3 nm. From the averaged images the topography of the protein and lipid components, the arrangement of the major subunits within each protein complex as well as the connections between these complexes in the lattice can be derived.
Incorporation of computer-assisted analytical diagnostic electron microscopy in clinical pathology—a critical technical assessment
Authors: Hirohata Yasuhisa , Aihara Kaoru , Suzuki Katsuya , Hata Toshio , Kurokawa Taneomi , Son Teijun 
Published: June 2020

Purpose: It is generally accepted that the incorporation of the transmi ssion and scanning electron microscopy is very virsatile in giving informations for diagnostic and therapeutic purposes.However,in the view point that the electron microscopy usually require very pain taking procedures for tissue preparation and limitation in the sizes of observation, there are admittingly existing some controversy if this could stand for the standard technology in medical investigative methods. In this sense, lack of quantitative or culumative electron microscopic methodology should be responsible to some extent. For establishing the standarized methodology for diagnostic biological electron microscopy, the laboratories has been undertaken an extensive survey for analytical diagnostic electron microscopy in virtue of the computer-assisted statistical methodology. The present investigation is dealing with the trial technological assessment of this systematized methodology.Materials and methods:The materials: Various types of the biopsied materials of kidney, liver and inherited metabolic diseases or tumorous conditions have been used for the investigation. However, for simplication and modulation or simulated study only the kidney diseases are discussed in this series of investigation.
Deposition and fabrication of specimen by means of ion beam sputtering
Authors: Hojou Kiichi , Kimura Toshiaki , Adachi Koichi , Kishi Shinichi , Arakawa Noboru , Kanaya Koichi 
Published: June 2020

The apparatus used in the experiment consists of a modified duoplasma- tron source in which the ion beam with 1-20 kV is collimated and focused by an electrostatic lens onto the target.For deposition purposes as when shadowing or coating a specimen, the beam of atoms emerging from the target with about 10 eV energy, is collimated by means of 0.5-1.0 mm slit in a metal shield placed close to the specimen. The shadowing angle ø can be varied from about 10-90° with the vacuum chamber at 10-6 Torr. Secondary electrons emitted from the target are trapped by a potential applied to the collimating slit. Usually the target is cooled by water.
Cis-dichloro-diammine platinum (II): a stain for electron microscopic preparations
Authors: Heinen Ernst 
Published: June 2020

We have previously reported that cis-dichloro-diammine platinum (II) (cis-Pt), an antimitotic agent discovered by Rosenberg and coworkers, can be used to contrast ultrathin sections. It was interesting to tend to increase the contrast given by this cis-Pt staining and to establish to which radicals cis-Pt binds in the cell.We have analysed various cell types (fibroblasts and Ehrlich tumour cells cultivated in vitro or various tissues : liver, pancreas, heart muscle, epididyme, intestine, etc.) fixed in glutaraldehyde, embedded in Epon and stained by immersion in a cis-Pt solution (1 mg/ml, 37°C, 2 or 3 days, in darkness).In all cases chromatin, especially heterochromatin, presents a very high contrast after cis-Pt staining and can easily be distinguished from the nucleolus (fig.). In the cytoplasm only ribosomes are well contrasted. The other organites are generally poorly stained, in some mitochondria, dense granules or filaments are apparent. Secretory granules containing proteins or mucopolysaccharides (basigranular or goblet cells of the intestine, mastocytes, pancreatic cells, etc.) are faintly stained by cis-Pt. In the heart muscle actin and myosin are only poorly contrasted. Cis-Pt suits thus for contrasting nucleic acids especially for differentiating DNA from RNA containing structures.
Ultrastructural details as revealed by stereo transmission electron microscopy of high resolution, pre-shadowed surface snd freeze-etch replicas: sample— the drosophila eye
Authors: Steere Russell L. 
Published: June 2020

Whereas SEM is useful for studying the surface of objects such as an insect eye at relatively low magnifications, TEM of pre-shadowed replicas has advantages for visualization of the ultrastructural details of surfaces, and freeze-fractured, or freeze-etched specimens.For surface replica studies, fruit flies (Drosophila melanogaster) were glued with glycerol onto a solid copper cap which was then placed on the stage of the Denton freezeetch module. Specimens were frozen by flowing liquid nitrogen into the specimen tube. When specimen temperature reached -105°C, the chamber was evacuated and the shroud cooled to -196°C. With a vacuum of 5 x 10-6 mm Hg, the specimen was warmed to -95°C for 3 to 5 minutes to allow sublimation of any ice which might have condensed on its surface. Specimen temperature was then lowered to -150°C and specimen was shadowed with Pt and coated with carbon.
Structural organization of escherichia coli ribosomes as determined by immuno electron microscopy
Authors: Stöffler G. , Bald R.W. , Dieckhoff J. , Eckhard H. , Lührmann R. , Tesche B. , Tischendorf G.W. 
Published: June 2020

A central step towards an understanding of the structure and function of the Escherichia coli ribosome, a large multicomponent assembly, is the elucidation of the spatial arrangement of its 54 proteins and its three rRNA molecules. The structural organization of ribosomal components has been investigated by a number of experimental approaches. Specific antibodies directed against each of the 54 ribosomal proteins of Escherichia coli have been performed to examine antibody-subunit complexes by electron microscopy. The position of the bound antibody, specific for a particular protein, can be determined; it indicates the location of the corresponding protein on the ribosomal surface.The three-dimensional distribution of each of the 21 small subunit proteins on the ribosomal surface has been determined by immuno electron microscopy: the 21 proteins have been found exposed with altogether 43 antibody binding sites. Each one of 12 proteins showed antibody binding at remote positions on the subunit surface, indicating highly extended conformations of the proteins concerned within the 30S ribosomal subunit; the remaining proteins are, however, not necessarily globular in shape (Fig. 1).
Molecular weight and ultrastructure of an oligomeric and a small monomeric protein molecule determined in the stem
Authors: Engel A. , van Driel R. 
Published: June 2020

We have used our STEM (Vacuum Generators HB-5) and digital data acquisition and display system to explore the experimental limits of electron microscopic MW determination of macromolecules. Two proteins have been used as test objects: (i) protein P23, which is the major structural protein of the phage T4 head precursor and has a MW of 58k daltons. P23 has been isolated as described elsewhere. Over a broad range of conditions P23 occurs in an oligomeric state, sedimenting at 11 S (van Driel, unpublished). (ii) Herring sperm protamine (protamine sulfate from Mann Res. Lab., New York), which has previously been used for exploring the limits of conventional and scanning darkfield electron microscopy on biological specimens; it has a MW of 4.2k daltons.P23 oligomers (0.3 mg/ml) in 0.1 M phosphate, pH7, were fixed in glutaraldehyde and dialized against distilled water. Protamine sulfate (0.1 mg/ml) was dissolved in distilled water. The proteins were absorbed on hydrophilic 2 nm thin carbon films.
Protamine-DNA interaction
Authors: Bazett-Jones D.P. , Ottensmeyer F.P. 
Published: June 2020

Dark field electron microscopy has been used for the study of the structure of individual macromolecules with a resolution to at least the 5Å level. The use of this technique has been extended to the investigation of structure of interacting molecules, particularly the interaction between DNA and fish protamine, a class of basic nuclear proteins of molecular weight 4,000 daltons.Protamine, which is synthesized during spermatogenesis, binds to chromatin, displaces the somatic histones and wraps up the DNA to fit into the small volume of the sperm head. It has been proposed that protamine, existing as an extended polypeptide, winds around the minor groove of the DNA double helix, with protamine's positively-charged arginines lining up with the negatively-charged phosphates of DNA. However, viewing protamine as an extended protein is inconsistent with the results obtained in our laboratory.
Visualization of native chromatin fibers in different embedding media
Authors: Muñoz-Guerra Sebastian , Subirana Juan A. 
Published: June 2020

The influence of the embedding medium is of critical importance in the observation of nucleoprotein structures in thin sections. The use of conventional epoxi media requires dehydratation, impregnation and subsequent polymerization, which may produce drastic alterations in the fine structure of chromatin. The use of water soluble embedding media may lead to improvements in the preservation of ultrastructure. In this paper we explore the differences which may be detected in nucleohistone fibers embedded in different media.Spermatozoa from Holothuria polii were subjected to moderate lysis in either 0.15M NaCl, ImM Tris-HCl, 0.4mM CaCl2, pH 8.0 (a) or 0.25M sucrose, 0.4mM CaCl2 (b) and then fixed by addition of 2 % glutaralde- hyde. Embedding was carried out as described in the literature in the following media: araldite-epon mixture (AREPO), glycol methacrylate (GMA, 1), hydroxipropyl methacrylate (HPMA, 2) and bovine serum albumin (BSA, 3) or histones.
Observation of DNA by negative staining: phage t7 DNA-capsid complexes
Authors: Serwer Philip 
Published: June 2020

A technique has been developed for observing extended nucleic acids in specimens negatively stained with uranyl acetate. This technique has been used to characterize bacteriophage T7 DNA-capsid complexes obtained by: a) disruption of T7 phage using glutaraldehyde treatment; b) isolation from Xysates of bacteriophage T7-infected E. coli. The latter complexes may be in the DNA packaging pathway of T7.A sample of circular, duplex bacteriophage ØX174 DNA (.2 μg/ml) in. 1 M NaCl,
.01 M Tris-Cl,. 001 M EDTA, pH 7.4, was mixed with an equal volume of cytochrome c (200 μg/ml) and was incubated for five minutes. This mixture was incubated with a carbon-coated grid for one minute; the grid was washed and was negatively stained with 1% uranyl acetate. An accumulation of negative stain around the DNA-bound cytochrome c reveals the presence of DNA circles (Figure 1). The cytochrome c bound to DNA is observed as an electron transparent region, 40-65 Å in diameter, within the negative stain.
Microtubules in optic nerves of temperature acclimated goldfish
Authors: Matheson D.F. , Diocee M.S. , Hussain S.T. , Roots B.I. 
Published: June 2020

The phenomenon of “fast axonal transport” whereby macromolecules and other material are transported rapidly down the axon has been extensively documented. Structural candidates which have been considered to be responsible for facilitating this fast axonal transport include mitochondria, microtubules and possibly neurofilaments. Few attempts have been made to define these structural entities quantitatively. This is particularly true for the goldfish optic system, a system for which much biochemical data on axonal transport exists.Goldfish were acclimated to 5° and 25°C for one month on a 12 h dark 12 h light photoperiod. Optic nerves were fixed in situ with 4% glutaraldehyde in either EGTA and PIPES or Millonig's phosphate buffer for 2 min, excised and immersed in fresh fixative for 24 h. They were post-fixed in 1% osmium tetroxide in the appropriate buffer for 1 1/2 h, dehydrated with ethanol and embedded in Spurr's medium.
Detection of glycoconjugates by lectins and glycosylated ferritin in the ciliary membrane of the quail oviduct
Authors: Sandoz Daniel , Boisvieux-Ulrich Emmanuelle , Chailley Bernadette 
Published: June 2020

The freeze-fractures of ciliary membrane show very few intramembrane particles except'for the ciliary necklace, located at the base of the organelle, which is composed of several sinuous arrays of particles (Fig.a). In the quail oviduct, it is also possible to distinguish these particles in thin sections, they appear as beads on the external surface of the ciliary membrane (Fig.b).Glycosylated ferritin allows the detection with a good resolution of the lectin binding sites of the plasma membrane.Pieces of quail oviduct (magnum) were incubated, after glutaralde- hyde fixation,either with Concanavaline A (major affinity : mannosyl or glucosyl residues), or wheat germ lectin (WGA)(major affinity : N-acetyl- glucosamine or N-acety1-neuraminic acid residues). The bound Con A molecules were visualized by Mannosyl-Ferritin. Control specimens were incubated directly with Mannosyl-Ferritin without prior incubation with Con A or with Con A in presence of 0-methyl-α -D-mannosyl-pyranoside.
Tight junction assembly in human adenocarcinoma cell line: relations to cytoskeletal elements
Authors: Polak-Charcon Sylvie , Ben-Shaul Yehuda 
Published: June 2020

Human colon adenocarcinoma cell line HT29 was found to be a favorable system for the study of junctions assembly. Using scanning electron microscopy (SEM), thin sectioning (TEM) and freeze fracturing, we were able to demonstrate that HT29 cells grown to confluency have desmosomes but clearly lack tight or gap junctions. When treated with trypsin, cells were rounded up, made contacts, and within 15 min formed tight and gap junctions. The desmosomes, however, were split to hemi-desmosomes. These findings agree with results obtained for other experimental systems.In this work we have used cytochalasin B (CB), colchicine (C) and CB + C, drugs known to interfere with microfilaments and microtubules, in order to determine to what extent these structures are involved with the assembly of tight junctions in HT29 cells treated with trypsin. The drugs were added to confluent monolayered cells (CB:20 μg/ml - 1 h; C: 10-4 M - 3 h; CB:20 μg/ml + C: 10-4 M/ml - 3 h), then trypsin was added to a final concentration of 0. 25% for 15 min.
Structure of the macromolecular surface arrays on the bacteriumsporosarcina urea: isolation, purification, and reassembly
Authors: Beveridge T. J. 
Published: June 2020

Sporosarcina ureais a unique bacterium that grows under alkaline conditions which would normally limit bacterial viability. It possesses a gram-positive wall which contains little phosphate, suggestive that teichoic polymers are absent, and a surface layer (Fig. 1A) which exhibited a predilection for heavy metal stains in thin section (Fig. 1B). Negative stains (Fig. 2) and freeze-etchings of this layer demonstrated it to be composed of a macromolecular tetragonal array (C-C = 120Å) and when these images were subjected to optical diffraction, substructure at ca. 15 Å was revealed (Fig. 3). This layer was sensitive to more acid conditions (pH ⋜6. 0) which negated the use of high contrasting agents such as uranyl acetate.Isolation of this regularly structured (RS) layer was accomplished by shearing a suspension of the bacteria (in 0. 05 M HEPES buffer pH 8. 2) in a French pressure cell and harvesting the wall fragments by centrifugation. Sequential treatment with 2% Triton X - 100 and 100 μg lysozyme per ml resulted in the solubilization of adherent plasma membrane and digestion of the wall proper.
Chemical modification of the bacterial wall to determine sites of metal deposition
Authors: Beveridge T. J. 
Published: June 2020

The Bacillus subtilis cell wall provides a protective sacculus about the vital constituents of the bacterium and consists of a collection of anionic hetero- and homopolymers which are mainly polysaccharidic. We recently demonstrated that unfixed walls were able to trap and retain substantial amounts of metal when suspended in aqueous metal salt solutions. These walls were briefly mixed with low concentration metal solutions (5mM for 10 min at 22°C), were well washed with deionized distilled water, and the quantity of metal uptake (atomic absorption and X-ray fluorescence), the type of staining response (electron scattering profile of thin-sections), and the crystallinity of the deposition product (X-ray diffraction of embedded specimens) determined.Since most biological material possesses little electron scattering ability electron microscopists have been forced to depend on heavy metal impregnation of the specimen before obtaining thin-section data. Our experience with these walls suggested that they may provide a suitable model system with which to study the sites of reaction for this metal deposition.
Ultrastructural studies of an aquatic bacterium, seliberia stellata
Authors: Swafford J. R. , Schmidt J. M. 
Published: June 2020

Seliberia stellata is a bacterium first isolated from tundra soil and described as a spirally twisted rod having one subpolar flagellum and reproducing by fission or budding. The cells stick at their poles forming a rosette or star form. Although this procaryotic organism has been noted in aquatic environments such as fresh water ponds and laboratory distilled water, strains from these habitats have apparently not been obtained in pure culture. We have isolated the bacteria from two fresh water sources and maintained them as pure cultures in dilute peptone-yeast extract broth or 1% agar media.Isolation of two strains of these organisms was achieved by enriching water samples with 0. 005% peptone. Enrichment culture surfaces were evaluated for the presence of bacteria by placing carbon-stabilized formvar grids onto the unbroken surface film followed by immediate removal and staining with 0. 25 or 0. 5% potassium phosphotungstate for TEM. The occurrence of Seliberia-like cells in these enrichments was rare (approximately 1/1000).
An ultrastructural study of vegetative incompatibility in plants
Authors: Moore Randy 
Published: June 2020

Cell and tissue interactions are a basic aspect of eukaryotic growth and development. While cell-to-cell interactions involving recognition and incompatibility have been studied extensively in animals, there is no known antigen-antibody reaction in plants and the recognition mechanisms operating in plant grafts have been virtually neglected.An ultrastructural study of the Sedum telephoides/Solanum pennellii graft was undertaken to define possible mechanisms of plant graft incompatibility. Grafts were surgically dissected from greenhouse grown plants at various times over 1-4 weeks and prepared for EM employing variations in the standard fixation and embedding procedure. Stock and scion adhere within 6 days after grafting. Following progressive cell senescence in both Sedum and Solanum, the graft interface appears as a band of 8-11 crushed cells after 2 weeks (Fig. 1, I). Trapped between the buckled cell walls are densely staining cytoplasmic remnants and residual starch grains, an initial product of wound reactions in plants.