bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intercellular junctions in thin sections of human senile cataracts
Authors: Costello M. J. , Oliver T. N. , Cobo L. M. 
Published: June 2020

The ultrastructural analysis of normal and cataractous lenses is often hindered by incomplete fixation especially of the centers of the lenses. To overcome this limitation, we have achieved good preservation by chemically fixing 50-200 um thick vibratome sections1 of six human senile cataractous lens nuclei obtained after extracapsular surgery. The remaining nuclear core of each lens was deep yellow to amber and contained central opacities. Fresh vibratome sections (15-30 per lens) were examined in the light microscope (FIG. 1) or were prepared for EM. Fixed and embedded whole vibratome sections were usually bisected and examined along a diameter by trimming successive plateaus (FIG. 2 inset) which gave us access to most regions within the lenses.Whole sections in the light microscope (FIG. 1) consistently showed rings of varying density. Undetectable in uncut lenses, the rings may represent slight discontinuities in composition, refractive index or adherence of layers of fiber cells. These rings roughly correspond to the location of cracks in sections which appear after EM processing (FIG.2 & 3). Fiber cells within these lenses generally displayed complex and irregular shapes, but the cells were well preserved with distinct cell boundaries. We emphasize here the common features of the nuclear cataracts which all contained severe enough opacities to warrant surgical removal but in which the cells appeared to remain intact. Adjacent cells interdigitate with irregular protrusions (FIG. 4). Differential cytoplasmic density between neighboring cells is suggestive of variations in refractive index which might cause excessive light scattering. In this same region in FIG. 4 we also note that dense staining material is present in the extracellular space appearing between the undulating membranes of adjacent cells (FIG. 4, inset). We know of no other report of such deposits in normal or abnormal lenses. The thickness of these deposits may also be sufficient to scatter light. A prominent feature of the lens preparations regardless of location is the presence of undulating membranes which are part of tongue-and-groove junctions (FIG. 5). It is noteworthy that the convex side of the curves is consistently well-preserved and is probably the crystalline array of protein noted in other studies, including in human autopsy lenses. It is not known whether cell communication occurs in the nucleus via gap junctions, but structures with the distinctive morphology of gap junctions are present even within senile cataracts (FIG. 5). FIG. 5 also shows a complex clustering of undulating junctions. The multilamellar membrane cluster in FIG.6, which is similar to structures reported in Emory mouse cataracts, is not commonly seen within the mass of lens tissue but is seen at cut surfaces and within cracks where cells are pulled apart.
Electron Microscopy in the diagnosis of lysosomal storage diseases
Authors: Vogler Carole , Rosenberg Harvey S. 
Published: June 2020

Diagnostic procedures for evaluation of patients with lysosomal storage diseases (LSD) seek to identify a deficiency of a responsible lysosomal enzyme or accumulation of a substance that requires the missing enzyme for degradation. Most patients with LSD have progressive neurological degeneration and may have a variety of musculoskeletal and visceral abnormalities. In the LSD, the abnormally diminished lysosomal enzyme results in accumulation of unmetabolized catabolites in distended lysosomes. Because of the subcellular morphology and size of lysosomes, electron microscopy is an ideal tool to study tissue from patients with suspected LSD. In patients with LSD all cells lack the specific lysosomal enzyme but the distribution of storage material is dependent on the extent of catabolism of the substrate in each cell type under normal circumstances. Lysosmal storages diseases affect many cell types and tissues. Storage material though does not accumulate in all tissues and cell types and may be different biochemically and morphologically in different tissues.Conjunctiva, skin, rectal mucosa and peripheral blood leukocytes may show ultrastructural evidence of lysosomal storage even in the absence of clinical findings and thus any of these tissues can be used for ultrastructural examination in the diagnostic evaluation of patients with suspected LSD. Biopsy of skin and conjunctiva are easily obtained and provide multiple cell types including endothelium, epithelium, fibroblasts and nerves for ultrastructural study. Fibroblasts from skin and conjunctiva can also be utilized for the initiation of tissue cultures for chemical assays. Brain biopsy has been largely replaced by biopsy of more readily obtained tissue and by biochemical assays. Such assays though may give equivical or nondiagnostic results and in some lysosomal storage diseases an enzyme defect has not yet been identified and diagnoses can be made only by ultrastructural examination.
Facilitated migration of cells from a transected peripheral nerve over collagen fibers: in vivo observations
Authors: Wasserman Arthur J. , Rizvi Azam , Zazanis George , Silver Frederick H. 
Published: June 2020

In cases of peripheral nerve damage the gap between proximal and distal stumps can be closed by suturing the ends together, using a nerve graft, or by nerve tubulization. Suturing allows regeneration but does not prevent formation of painful neuromas which adhere to adjacent tissues. Autografts are not reported to be as good as tubulization and require a second surgical site with additional risks and complications. Tubulization involves implanting a nerve guide tube that will provide a stable environment for axon proliferation while simultaneously preventing formation of fibrous scar tissue. Supplementing tubes with a collagen gel or collagen plus extracellular matrix factors is reported to increase axon proliferation when compared to controls. But there is no information regarding the use of collagen fibers to guide nerve cell migration through a tube. This communication reports ultrastructural observations on rat sciatic nerve regeneration through a silicone nerve stent containing crosslinked collagen fibers.Collagen fibers were prepared as described previously. The fibers were threaded through a silicone tube to form a central plug. One cm segments of sciatic nerve were excised from Sprague Dawley rats. A control group of rats received a silicone tube implant without collagen while an experimental group received the silicone tube containing a collagen fiber plug. At 4 and 6 weeks postoperatively, the implants were removed and fixed in 2.5% glutaraldehyde buffered by 0.1 M cacodylate containing 1.5 mM CaCl2and balanced by 0.1 M sucrose. The explants were post-fixed in 1% OSO4, block stained in 1% uranyl acetate, dehydrated and embedded in Epon. Axons were counted on montages prepared at a total magnification of 1700x. Montages were viewed through a dissecting microscope. Thin sections were sampled from the proximal, middle and distal regions of regenerating sciatic plugs.
Effects of sterilization modes on the mechanical strengths of plaster of paris implants
Authors: Cowden K. , Giammara B. , Devine T. , Hanker J. 
Published: June 2020

Plaster of Paris (calcium sulfate hemihydrate, CaSO4. ½ H2O) has been used as a biomedical implant material since 1892. One of the primary limiting factors of these implants is their mechanical properties. These materials have low compressive and tensile strengths when compared to normal bone. These are important limiting factors where large biomechanical forces exist. Previous work has suggested that sterilization techniques could affect the implant’s strength. A study of plaster of Paris implant mechanical and physical properties to find optimum sterilization techniques therefore, could lead to a significant increase in their application and promise for future use as hard tissue prosthetic materials.USG Medical Grade Calcium Sulfate Hemihydrate Types A, A-1 and B, were sterilized by dry heat and by gamma radiation. Types A and B were additionally sterilized with and without the setting agent potassium sulfate (K2SO4). The plaster mixtures were then moistened with a minimum amount of water and formed into disks (.339 in. diameter x .053 in. deep) in polyethylene molds with a microspatula. After drying, the disks were fractured with a Stokes Hardness Tester. The compressive strengths of the disks were obtained directly from the hardness tester. Values for the maximum tensile strengths σowere then calculated:where (P = applied compression, D = disk diameter, and t = disk thickness). Plaster disks (types A and B) that contained no setting agent showed a significant loss in strength with either dry heat or gamma radiation sterilization. Those that contained potassium sulfate (K2SO4) did not show a significant loss in strength with either sterilization technique. In all comparisons (with and without K2SO4and with either dry heat or gamma radiation sterilization) the type B plaster had higher compressive and tensile strengths than that of the type A plaster. The type A-1 plaster however, which is specially modified for accelerated setting, was comparable to that of type B with K2SO4in both compressive and tensile strength (Table 1).
Electron spectroscopy imaging cytochemistry : Use of boronated-protein A
Authors: Bendayan M. , Barth R.F. , Gingras D. , Londoño I. , Robinson P.T. , Alam F. , Adams D.M. , Mattiazzi L. 
Published: June 2020

The ultrastructural organization of the cell and the functional properties of its components have reached a high level of knowledge due to the development of electron microscopy and related cytochemical techniques. Colloidal gold particles having a size down to 3 to 5 nm provide the best resolution in cytochemistry. In order to improve this, one must look at tracers detectable at the molecular and atomic levels.Recent advances in analytical electron microscopy, including electron energy loss spectroscopy (EELS) and electron spectroscopy imaging (ESI) provide much higher levels of resolution. By choosing the appropriate edge of energy loss, ESI allows for the simultaneous detection and ultrastructural distribution of specific elements in ultrathin tissue sections, with a spatial resolution of 3 to 5 Å. We have recently tested this approach for the detection of an element, boron, introduced in the tissue as a cytochemical marker. Because of the advantages of protein A as a second reagent in indirect immunocytochemistry, we investigated the potential of boronated protein A (B-pA) for the detection of antigenic sites in tissue sections.
Immunogold labelling of neutral endopeptidase 24.11 (enkephalinase), on human neutrophils and neutrophil cytoplasts
Authors: Kriho V. , Wagner B. , Erdos E.G. , Becker R.P. 
Published: June 2020

We have documented the presence of neutral endopeptidase 24.11 (NEP), on the surface of human neutrophils (PMN) and PMN cytoplasts. Cytoplasts are whole cell preparations which contain cytomatrix, but lack internal membranes and organelles ,such as nuclei and lysosomal granules. These structures have been extracted mechanically, leaving the plasma membrane “outside-out” topology intact. Cytoplasts are very useful in correlative studies of cell surface structure and function. Biochemically, the membrane component of cytoplasts is predominantly plasma membrane; structurally, chemical activity may be localized to domains of the intact cell surface. NEP is a membrane-bound metalloendopeptidase present in human PMN' s. We have marked NEP on the plasma membranes of PMNs and PMN cytoplasts via pre-embedding iramunocytochemistry. We used scanning electron microscopy (SEM) with backscattered electron imaging (BEI) to visualize Au labelled anti-NEP on the surface of a large number of cells. Transmission electron microscopy (TEM) was used to confirm the presence of the enzyme on PMN's and PMN cytoplasts.Suspensions of PMN or PMN cytoplasts (2 x 106 cells/ml) were fixed for 8 min at room temp. in 0.25% glutaraldehyde in phosphate buffered saline (PBS) pH 7.2 rinsed in PBS, treated with 0.1% glycine in PBS for 10 rain and then incubated for 15 min in 5% normal goat serum (NGS) in 0.1% bovine serum albumin dissolved in PBS (BSA/PBS). Following this step, cells were incubated for 20 min in anti- NEP antibody, rinsed in BSA/PBS, incubated in goat anti-rabbit IgG coupled to 15nm colloidal Au particles (GARG15) for 1 h and again rinsed in PBS. Postfixation for 30 min in 2.5% glutaraldehyde and PBS rinsing followed. For SEM a drop of cell suspension was put on a polylysine- treated Formvar-carbon-coated Au grid and cells were allowed to settle and attach for 30 min. The grid was rinsed in water, dehydrated and critical point dried. Cells were coated with carbon before viewing by SEM. For TEM, following immunolabelling, cells were post-fixed in OsO4, rinsed, dehydrated and embedded in Epon for sectioning.
Microtubule number increases locally within regions of axonal compression
Authors: Price R.L. , Lasek R.J. , Katz M.J. 
Published: June 2020

Along the length of myelinated axons, stereotyped variations in the interaction with the enveloping Schwann cell produce different amounts of compressive force on the axon and its internal elements. Comparisons of histologically distinct axonal regions indicate that compression of the axon by the Schwann cell increases in the following order: internodal regions of compact myelin < Schmidt-Lanterman (S-L) clefts < nodes of Ranvier. Quantitative morphometry has shown that regions of greater Schwann cell compression are associated with regions of smaller axon diameter and greater neurofilament (NF) packing density. By locally decreasing axon diameter and increasing NF density, Schwann cell compression (especially at the node of Ranvier) may slow the transport of those axonal structures - such as microtubules (MTs) - that move by a polymer sliding mechanism. Under this hypothesis, a local slowing of MT transport should produce a local increase in MT number, and here we have studied whether such a local increase in MT number can be quantitatively documented.A twenty-eight day old chicken was perfused by cardiac puncture with 4 1 of fixative (4% paraformaldehyde, 2% glutaraldehyde, 0.005% CaCl2, in 0.1M cacodylate buffer, pH 7.4). The somatic motor branch of the oculomotor nerve was removed (noting the proximo-distal orientation) and fixed overnight at 4°C, followed by a buffer rinse in 0.1M cacodylate buffer at room temperature and postfixation in OSO4. The nerve was then dehydrated in a graded ethanol series and embedded in PolyBed/812. Starting at the proximal end of the nerve segment, l00nm sections were cut at consecutive 2-3 um intervals over a 225 um length of nerve, stained with an LKB Ultrostainer, and photographed on a JEOL 100CX microscope. We selected two axons with normal morphology, in which the cytoskeletal polymer profiles were consistently cross-sectioned and in which nodes were located approximately 120 um distal to the first section taken. All sections from these 2 axons were photographed, and MTs were counted on 58,000X micrographs.
A serial section analysis of rabbit foliate taste buds using the high voltage electron microscope
Authors: Royer S.M. , Kinnamon J. C. 
Published: June 2020

We have examined the foliate taste buds of the rabbit using a combination of serial section analysis and computer-assisted three-dimensional (3-D) reconstructions. Previous investigators of rabbit foliate taste buds have classified taste cells into types I, II, and III, basal cells, and peripheral cells. Based on the presence of synaptic contacts with nerve processes, only the type III cells have been considered to be taste receptor cells. Our goals were the elucidation of morphological details of the various cell types and the characterization and quantification of synaptic contacts between taste receptor cells and intragemmal nerve fibers.Adult white rabbits were perfused with a fixative containing 2.5% glutaraldehyde and 1% paraformaldehyde in 0.05 M cacodylate buffer at pH 7.3. The foliate papillae were excised fixed overnight in fresh fixative at 4°C, rinsed in buffer, postfixed with buffered 1% OsO4, washed, and stained en bloc in 5% uranyl acetate in 70% ethanol for 48 hours. The specimens were then dehydrated and embedded according to standard procedures. Serial 0.25 μm sections of the embedded tissue were cut with a Diatome Semi diamond knife using a Reichert Ultracut E ultramicrotome. Sections were mounted on Formvar-coated slot grids and poststained in triple lead stain and alcoholic uranyl acetate. After carbon coating, the sections were examined with a JEOL JEM-1000 high voltage electron microscope (HVEM) operated at 1 meV. Contours of interest were traced from micrographs onto a Summagraphics digitizing tablet and entered into an IBM-compatible PC, using programs developed by the authors.
Comparative fine structure of whole cells by High Voltage Electron Microscopy
Authors: Porter Keith R. , Anderson Karen , Peachey Lee D. 
Published: June 2020

When fish scales are isolated and treated with collagenase and hyaluronidase, populations of five different kinds of cells are obtained. These can be maintained in vitro for several days and even encouraged to proliferate by enriching the culture medium. As a model for studying comparative fine structure, the system is ideal. For example the isolated cells can be cultured directly on formvar- and carbon-coated gold grids. In preparation for microscopy they are all exposed to precisely the same conditions and receive identical treatment. It is important also that they are not embedded and sectioned but are on the grids as whole cells with organelles etc. in functional relation to one another and to the cytoplasmic matrix. Such differences as are shown by the cells can be regarded as native to the various types.These differences can be dramatic and extend from compact and thick iridophores to thinly spread epidermal units. It is essential for their successful study to use a high energy beam that can penetrate even the thickest cells or parts of cells. In this instance we have used a Zeiss 10 operated at 100 kV; a JEOL 400 kV (IVEM) and a JEOL 1000 kV (HVEM). As expected, penetration and resolution improve as the voltage is increased (Figs. 1-4) and so also does the information content of the micrographs. The cytoplasmic matrix heretofor poorly resolved and difficult to interpret, is seen as a 3D lattice of thin (50A) strands (microtrabeculae) that contains other components of the cytoskeleton as well as polysomes. The lattice varies strikingly in different kinds of cells found in these preparations. For example, in fibroblasts the cytomatrix is dense compared with the matrix in cytoplasm of similar depth in epidermal cells. In fibroblasts the microtrabeculae are shorter and thicker and the intertrabecular spaces are smaller. In a comparative examination of the cytoskeletons, it is possible to follow microtubules in a single cell from begining to end, a feat that is impossible in thin sections. All of these features of the matrix are under study using morphometric techniques to quantitate the differences. The structural dimensions of the lattice suggest it may be the intracellular equivalent of “plectin” isolated and characterized by Wiche and colleagues.
Cellulase-gold labelling of cellulose in forages
Authors: Woodward Janet H. 
Published: June 2020

Current fiber analyses provide information on the chemical and structural composition of the fiber as a whole. However, these techniques do not offer insight into the compositional and structural differences between specific fiber tissues which may affect digestibility. The purpose of this study was to: (1) ultrastructurally localize one cell wall constituent, cellulose, in four forages; and (2) apply this technique as a tool for the evaluation of biodegradation in forages.Insoluble fibers were prepared using a modified AOAC Total Dietary Fiber Technique. Two millimeter sections cut from leaflets of alfalfa (Medicago sativa L.) and 1-76 1espedeza [Sericea cuneata (Dumont)] and leaves of coastal bermudagrass (Cynodon dactylon L. Pers.) and orchardgrass (Dactylis glomerata L.) were incubated stepwise with: (1) α-amylase, pH 6.0 for ½ h at 100°C; (2) protease, pH 7.5 for ½ h at 60°C; (3) amyloglucosidase, pH 4.5 for ½ h at 60°C, and (4) 1% (w/v) cellulase in 0.05 M sodium acetate buffer, pH 5.0 for 24 h at 37°C.
Single molecule optical diffraction: A tool for understanding the structure of triple stranded left-hand helical cellulose
Authors: Ruben George C. , Krakow William 
Published: June 2020

Tobacco primary cell wall and normal bacterial Acetobacter xylinum cellulose formation produced a 36.8±3Å triple-stranded left-hand helical microfibril in freeze-dried Pt-C replicas and in negatively stained preparations for TEM. As three submicrofibril strands exit the wall of Axylinum , they twist together to form a left-hand helical microfibril. This process is driven by the left-hand helical structure of the submicrofibril and by cellulose synthesis. That is, as the submicrofibril is elongating at the wall, it is also being left-hand twisted and twisted together with two other submicrofibrils. The submicrofibril appears to have the dimensions of a nine (l-4)-ß-D-glucan parallel chain crystalline unit whose long, 23Å, and short, 19Å, diagonals form major and minor left-handed axial surface ridges every 36Å.The computer generated optical diffraction of this model and its corresponding image have been compared. The submicrofibril model was used to construct a microfibril model. This model and corresponding microfibril images have also been optically diffracted and comparedIn this paper we compare two less complex microfibril models. The first model (Fig. 1a) is constructed with cylindrical submicrofibrils. The second model (Fig. 2a) is also constructed with three submicrofibrils but with a single 23 Å diagonal, projecting from a rounded cross section and left-hand helically twisted, with a 36Å repeat, similar to the original model (45°±10° crossover angle). The submicrofibrils cross the microfibril axis at roughly a 45°±10° angle, the same crossover angle observed in microflbril TEM images. These models were constructed so that the maximum diameter of the submicrofibrils was 23Å and the overall microfibril diameters were similar to Pt-C coated image diameters of ∼50Å and not the actual diameter of 36.5Å. The methods for computing optical diffraction patterns have been published before.
Comparative ultrastructural study of lymphocystis disease virus and frog virus 3 by means of enzymatic digestions
Authors: Heppell J. , Berthiaume L. 
Published: June 2020

Fish lymphocystis disease is a common viral infection reported in over a hundred teleost species. The causative agent, Lymphocystis disease virus (LDV), has been classified in the Iridoviridae family. Though it has an icosahedral shape, its capsid is complex and still not very well characterized. However, several studies have been reported on the ultrastructure of Frog virus 3 (FV3), another iridovirus, showing outside protein units with an underlying lipidic layer, surrounding the viral core. In order to verify whether or not the structure of LDV particles correspond to that of FV3 , a comparative electron microscopic study was undertaken.LDV strain Leetown (ATCC VR-342) was propagated on BF-2 cells, and FV3 strain Granoff (ATCC VR-567) on FHM cells. Viral particles, concentrated and suspended in 0.1M Tris buffer (pH appropriate for the enzyme used), were adsorbed on formvar-coated grids prior to digestion with proteases (pronase E or proteinase K, 20 U/ml) and/or phospholipases (A2 or C, 15 U/ml) at 37°C for various incubation periods. Particles were negatively stained with 2% (w/v) phosphotungstic acid pH 6.0 before examination with a Philips 300 transmission electron microscope (TEM) at 80 kV.