bluuebunny/crossref_metadata_2025 huggingface dataset:
Tract tracing, neuronal morphology and ultrastructural studies in human postmortem brain
Authors: Roberts Rosalinda C. , Vogel Michael W. , de Rijk Maarten , Peretti Frank J. , Conley Robert R. , Francis Sarah M.N.
Published: June 2020

Classical and modern neuroanatomical techniques are applied to an analysis of the neuroanatomical basis of schizophrenia using postmortem brain tissue from the Maryland Brain Collection. Techniques for Golgi staining of cell bodies and dendritic arbors, axonal tract tracing with the carbocyanine dye, DiI and ultrastructural analyses will be used to study brain tissue with postmortem times of less than 6 hours. Although these techniques are routinely used in animal models, they are rarely used for studying human brain tissue. These techniques will allow us to characterize neuronal architecture in normal and diseased brains.
Cellular and molecular mechanisms of proliferating and migrating neurons
Authors: Fishell Gord , Hatten Mary E.
Published: June 2020

In the developing CNS, neurogenesis is restricted to discrete zones, the ventricular zones and the External Germinal Layer (EGL) of the cerebellar cortex. At early postnatal periods, in the mouse, the cerebellar EGL contains two discrete zones, a superficial layer, one-two cells thick containing mitotic figures and an underlying zone of postmitotic cells. It is in this lower zone where the first visible evidence of neural differentiation can be seen (RamonyCajal, 1911), the extension of granule cell axons, the parallel fibers, and the inward migration of the cell soma of immature granule cells along the radially aligned processes of the Bergmann glial cells (Rakic, 1971). To provide an experimental analysis of the molecular components of granule cell neurogenesis and migration, we have developedin vitromodel system using purified EGL precursor cells.
The normal human hippocampus and that of Alzheimer’s patients contain filopodia like those of octopus neuropils and nerve growth cones
Authors: Robertson J. David , Lee Psyche
Published: June 2020

New synapses are generally formed in long-term learning [See (3) for references], but it is believed that short-term learning involves only alterations in synaptic efficacy with activity (1). We have studied this problem extensively in Octopus vulgaris (2-5). Electron Microscopic (EM) studies of serial sections reveal that filopodia like those in nerve growth cones occur in its touch learning neuropils (2). They increase in numbers transiently during learning and some form new synapses, while others retract. Calcium influx into neurites during activity triggers actin polymerization and related filopodial extension. This, by interpolation of new membranes, results in separation of interactive membranes, formerly in contact. An alteration in the total electrochemical interactions of the membranes results that alters the summation of interactions between all the membranes and changes the overall integrated output. This can be defined as learning and one of us has advanced a filopodial theory of learning based on these ideas (5). Accordingly, there is a localized reactivation of growth processes normally only operating during development to bring about structural alterations beginning with short-term learning. If correct, leaning should be blocked by cytochalasins B (CB) and D (CD) that interfere with actin polymerization and it should be stimulated by nerve growth factor (NGF). We have good evidence that CB and CD block touch learning reversibly in Octopus (2-5) and recently that NGF stimulates touch learning.
Progress in ultrastructural and molecular analysis of the nuclear matrix
Authors: Fey Edward G.
Published: June 2020

In the past few years, considerable advances have been made regarding the structure and function of the nuclear matrix. In the first half of this presentation, the field of nuclear matrix research will be summarized. Emphasis will be placed on those studies where molecular interactions are demonstrated in situ utilizing high resolution light and/or electron microscopy. Studies demonstrating the role of the nuclear matrix in DNA synthesis and replication, RNA transcription and processing, and the binding of matrix attachment regions to specific nuclear matrix proteins will be summarized.
Cryo-electron microscopy of two-dimensional crystals of reduced type B botulinum neurotoxin
Authors: Flicker P. F. , Kulkarni V.S. , Robinson J. P. , Stubbs G. , DasGupta B. R.
Published: June 2020

Botulinum toxin is a potent neurotoxin produced byClostridium botulinum. The toxin inhibits release of neurotransmitter, causing muscle paralysis. There are several serotypes, A to G, all of molecular weight about 150,000. The protein exists as a single chain or or as two chains, with two disulfide linkages. In a recent investigation on intracellular action of neurotoxins it was reported that type B neurotoxin can inhibit the release of Ca++-activated [3H] norepinephrine only if the disulfide bonds are reduced. In order to investigate possible structural changes in the toxin upon reduction of the disulfide bonds, we have prepared two-dimensional crystals of reduced type B neurotoxin. These two-dimensional crystals will be compared with those of the native (unreduced) type B toxin.
Z-band cross sections in rigor skeletal muscle have similar detailed structures as in tetanized muscle
Authors: Goldstein M. A. , Schroeter J. P. , Edwards R. J.
Published: June 2020

We have previously shown that two structural states of the Z-band in muscle cross-sections are related to the contractile state of the muscle. In skeletal muscle at rest, the z-band is in the small square (ss) form, but tetanized muscle exhibits the basket weave (bw) form. Recently, we have shown that skeletal muscle in rigor also exhibits the bw form and dimensions.

We have used two dimensional computer enhancement techniques on digitized electron micrographs to compare the detailed structure of the tetanized and rigor Z-band lattices. Both lattice averaging and Fourier filtering techniques were used, with enhanced images displayed as grey-scale projections, as contour maps, and in false color. There is only a slight difference between the lattices produced by the two different enhancement techniques. Thus, information in the enhanced images is not likely to be an artifact of the enhancement algorithm.
Self-organizing cytoplasmic microtubule networks in foraminiferan pseudopodia
Authors: Welnhofer Elizabeth Patterer , Orokos Donald , Rupp Gerald , Travis Jeffrey L.
Published: June 2020

The foraminifera (i.e. “forams”), like all Granuloreticulose protists, produce extensive networks of pseudopodia that are supported and powered by an elaborate cytoskeleton of motile microtubules (MT). These pseudopodia may reach lengths nearly 100X the diameter of the cell body, which is the synthetic center of the cell, and the network is continuously remodelled as pseudopodia form, extend, retract, branch and fuse. The fact that these morphogenetic processes occur in even the most remotely located regions of the network suggests there is considerable local autonomy in the assembly, disassembly, and organization of the MT cytoskeleton.
3-D reconstruction and analysis of mammalian mitotic spindle structure
Authors: McDonald Kent , Mastronarde David , Ding Rubai , O'Toole Eileen , McIntosh J. Richard
Published: June 2020

Mammalian spindles are generally large and may contain over a thousand microtubules (MTs). For this reason they are difficult to reconstruct in three dimensions and many researchers have chosen to study the smaller and simpler spindles of lower eukaryotes. Nevertheless, the mammalian spindle is used for many experimental studies and it would be useful to know its detailed structure.

We have been using serial cross sections and computer reconstruction methods to analyze MT distributions in mitotic spindles of PtK cells, a mammalian tissue culture line. Images from EM negatives are digtized on a light box by a Dage MTI video camera containing a black and white Saticon tube. The signal is digitized by a Parallax 1280 graphics device in a MicroVax III computer. Microtubules are digitized at a magnification such that each is 10-12 pixels in diameter.
A study of the mineralization of bone by high voltage EM tomography
Authors: Arena James , McEwen Bruce F. , Song Min Ja , Landis William J.
Published: June 2020

Complete characterization of the inorganic and organic interaction in calcifying tissues is fundamental to understanding their structure-function relations. In this context, high resolution tomographic three-dimensional (3D) reconstruction of normally calcifying avian tendon imaged by high voltage electron microscopy has recently been used to determine specific structural features of hydroxyapatite crystals associated with collagen fibrils in this vertebrate model of biological mineralization. The present work is an extension of these previous investigations, now applied to bone for the first time.
Pronuclear migration, maturation and fusion: A confocal light microscopy study of fertilization in Drosophila
Authors: Karr Timothy L.
Published: June 2020

Most of what we know about fertilization in animals comes from studies of the interactions at the surface, or near the surface of sperm and egg. Examples include the acrosome reaction, cortical exocytosis and the formation of the fertilization envelope. One area in particular where our knowledge is limited are those events that occur inside the egg following sperm penetration. These include pronuclear maturation, pronuclear migration and pronuclear fusion. Molecular studies have also suffered from the lack of a genetically tractable system that would allow function to be assigned to the individual molecules associated with fertilization.
Ultrastructural study of experimental duodenal ulcer in a new animal model
Authors: Bui H.X. , delRosario A. , Abdulla M. , Ballouk F. , Bajakian V. , Lee C.Y. , Ross J.S.
Published: June 2020

Various animal models have often been utilized as the basis of studies of the pathophysiology of peptic ulcer disease, however the ultrastructural changes in the evolution of duodenal ulcers produced in experimental animals have not been well elucidated. Utilizing a surgical method developed for the study of gastric ulcers we have established an experimental duodenal ulcer production technique in the rat which is highly reproducible and readily standardized. In the following time sequence study of experimental duodenal ulcers we present the ultrastructural features of ulcer induction and evolution.

Duodenal ulcers were produced in 150-200 gram male Sprague Dawley rats by application of 50% acetic acid for 30 seconds through a 3 mm polyethylene tube to the serosa 1.0-1.5 cm distal to the pyloric sphincter. Routine transmission and scanning electron microscopy were performed on duodenal specimens at specific time points subsequent to surgical ulcer generation. Thin sections were stained with uranyl acetate and lead citrate and examined with a Phillip's EM 300 transmission electron microscope. For SEM, specimens were post-fixed in 2% osmium for two days, coated with gold/palladium and examined with JEOL JSM-6100 scanning electron microscope (JEOL, Inc., Peabody, MA).
Immunotactoid glomerulopathy: Recurrence of disease in renal transplant
Authors: Price George , Moses Gregory , Holcomb Allen , Cerezo Lizardo
Published: June 2020

Immunotactoid glomerulopathy (ITG) is a disease of the kidney, first described 1980. It is characterized by the specific deposition of immunoglobulin in the renal glomeruli, producing diffuse mesangial expansion similar to that commonly noted in the sclerosing process of amyloidosis. However, these patients do not exhibit the clinical symptoms of patients with extra renal, or systemic disease, and therefore have a better prognosis. The demonstration by electron miscroscopy of fibrillar deposits that are thicker than that of amyloid is crucial to the diagnosis.

The association of this disease to an autoimmune response is demonstrated by the immunofluorescent staining of antihuman IgG and C3 to the affected glomeruli. Other immunoglob ins may be implicated, but are not as common.
Optimization of diagnostic EM for enteric viruses
Authors: Humphrey C. D. , Huang H.H. , Tanaka H.
Published: June 2020

Virus identification by negative stain electron microscopy (EM) is one of the most versatile and sensitive assays for rapid viral diagnosis. Electron microscopy is particularly important for the study of enteric viruses because they are difficult to cultivate and characterize. The gastroenteritis viruses most frequently identified include rotavirus (Fig. 1), enteric adenovirus (Fig. 2), enteric coronavirus (Fig. 3), calicivirus (Fig. 4), Norwalk agent, and astrovirus (Fig. 6). In addition, there are several unclassified viruses categorized as either small round structured viruses (Fig. 5) or small round viruses (Fig. 7).
Phase behavior of cationic and anionic surfactants at low concentrations
Authors: Naranjo E.
Published: June 2020

Equilibrium vesicles, those which are the stable form of aggregation and form spontaneously on mixing surfactant with water, have never been demonstrated in single component bilayers and only rarely in lipid or surfactant mixtures. Designing a simple and general method for producing spontaneous and stable vesicles depends on a better understanding of the thermodynamics of aggregation, the interplay of intermolecular forces in surfactants, and an efficient way of doing structural characterization in dynamic systems.
Confocal laser scanning microscopical investigation of epithelial membrane polarity in 3-dimensional MDCK multicellular cysts
Authors: Wang Allan Z. , Wang Jane C. , Diamond Herbert S.
Published: June 2020

We have previously described the process ol membrane polarity formation and reversal in MDCK epithelial cysts (Fig.1) using immunofluorescent staining on frozen sections. Apical surface of polarized epithelial cells faced the growth media and basl surface faced the cyst lumen by locating membrane domain-specific proteins (Fig.2). Polarity reversal was demonstrated by showing that polarized distribution of membrane proteins were reversed after the suspension-cultured cysts were transferred into collagen I gel embedding (Fig.3). There was loss of endogeneous basal membrane protein and appearance of apical membrane protein at the lumenal surface, indicating a novel mechanism for de novo formation of apical domain in the multicellular cysts.
Fish kidney cell line in response to heat shock
Authors: Tung Li-Chu , Chen Yung-Reui , Chen Shiu-Nan , Kuo Guang-Hsiung
Published: June 2020

In the present study, the ultrastructural changes of BPK cells, a fibroblast-like cell line, derived from the kidney of juvenile black porgy Acanthopagrus schlegeli, under heat shock treatment are described.

The BPK cells were maintained in L-15 medium supplemented with 10% fetal calf serum and 0.15 M NaCl at 28|C2. The heating was carried out in precalibrated water baths. Monolayers of cells, grown on coverslips in parafilm-sealed petri dishes were submerged under water for 30 min at 40|C treatments. Cells were fixed in 2.5% glutaraldehyde in 0.1 M cacodylate buffer supplemented with 6.6% sucrose, postfixed in 1% OsO4 and flat embedded in Spurr’s resin. Silver section were cut parallel to the substratum, stained with uranyl acetate and Reynold’s lead citrate, and examined in a Hitachi H-600 electron microscope at 75 KV.
Gap junctions in the prothoracic glands of the tobacco hornworm, Manduca sexta
Authors: Dai Ji-da , Costello M. Joseph , Gilbert Lawrence I.
Published: June 2020

Insect molting and metamorphosis are elicited by a class of polyhydroxylated steroids, ecdysteroids, that originate in the prothoracic glands (PGs). Prothoracicotropic hormone stimulation of steroidogenesis by the PGs at the cellular level involves both calcium and cAMP. Cell-to-cell communication mediated by gap junctions may play a key role in regulating signal transduction by controlling the transmission of small molecules and ions between adjacent cells. This is the first report of gap junctions in the PGs, the evidence obtained by means of SEM, thin sections and freeze-fracture replicas.
Low-angle shadowing and colloidal gold-labeling of liposome interaction with the eosinophil major basic protein
Authors: Hukee Margaret J. , Abu-Ghazaleh Randa I. , Prendergast Franklyn G.
Published: June 2020

The eosinophil major basic protein (MBP) has been localized in the crystalloid core of the specific eosinophil granule. High levels of MBP are present in sputa and at sites of epithelial damage in patients with brochial asthma suggesting that MBP is released from the eosinophil. In vitro, the toxicity of MBP to mammalian cells, helminths, protozoa, and bacteria, has been demonstrated. MBP also induced the degranulation of platelets, basophils, and mast cells. Since these events involve extracellular MBP and rupture of plasma membranes, the mechanism of toxicity may be due to a direct interaction between MBP and biological membranes. Fluorescence spectroscopy studies using synthetic lipid bilayers (liposomes) showed the ability of MBP to induce disorder, fusion and lysis of those membranes. In this report, structural evidence is presented for liposome aggregation and possible lysis in the presence of MBP.
Immunogold localization of intrinsic factor in rat and human stomach
Authors: Becich Michael J. , Misra Dhirendra N. , Howard Tamara , Alpers David H.
Published: June 2020

There are several proteins that mediate uptake and transport of dietary cobalamin (vitamin B12). The gastric intrinsic factor (IF) is one of these which binds cobalamin in the gut lumen and allows for efficient intestinal absorption of the ingested vitamin. The IF has a rather novel and complicated secretory pathway and precise knowledge of the expression and cellular distribution will help us to understand the recognized defects in vitamin B12 absorption and metabolism. Earlier studies using autoradiographic and immunocytochemical methods have identified different IF production sites for various animals: gastric chief cells in rodents; antropyloric cells in the hog; parietal cells in humans and most other species. In the present work, we have used immunogold electron microscopy for cellular and subcellular localization of IF.
Elemental distribution in trace metal-treated Pisolithus tinctorius prepared by propane jet and high pressure freezing methods
Authors: McQuattie C.J. , Klomparens K.L. , Wood J.I. , Heckman J.W.
Published: June 2020

Localization of trace metals on or within mycorrhizal (M) fungi may serve a protective function for roots of forest trees growing in soils containing high concentrations of metals such as Pb and Al. The presence of both Pb and Al have been demonstrated in the M fungus Pisolithus tinctorius after preparation by propane jet (PJ) freezing and freeze substitution. High pressure freezing (HPF) is an alternative method of cryopreparation that has demonstrated excellent ultrastructural preservation in studies of developing ascospores. The purpose of this study was to compare ultrastructural preservation and trace metal localization in P. tinctorius using PJ freezing and HPF methods.
How to sample the entire length of a single muscle fiber quick-frozen after electrical point stimulation for high resolution EM
Authors: Sommer Joachim R. , High Teresa , Scherer Betty , Taylor Isaiah , Nassar Rashid
Published: June 2020

We have developed a model that allows the quick-freezing at known time intervals following electrical field stimulation of a single, intact frog skeletal muscle fiber isolated by sharp dissection. The preparation is used for studying high resolution morphology by freeze-substitution and freeze-fracture and for electron probe x-ray microanlysis of sudden calcium displacement from intracellular stores in freeze-dried cryosections, all in the same fiber. We now show the feasibility and instrumentation of new methodology for stimulating a single, intact skeletal muscle fiber at a point resulting in the propagation of an action potential, followed by quick-freezing with sub-millisecond temporal resolution after electrical stimulation, followed by multiple sampling of the frozen muscle fiber for freeze-substitution, freeze-fracture (not shown) and cryosectionmg. This model, at once serving as its own control and obviating consideration of variances between different fibers, frogs etc., is useful to investigate structural and topochemical alterations occurring in the wake of an action potential.
Structure of emulsified and unemulsified lipid-protein food systems revealed by SEM and laser scanning confocal microscopy
Authors: Lamarche François , Montpetit Diane
Published: June 2020

Lipids and proteins are major constituents of numerous food systems where they contribute significantly to the kinesthetic and organoleptic properties. Physical (creaming, coalescence, flocculation) and chemical deterioration (lipolysis, fat oxydation, fat soluble vitamins) are also prevented by lipid-protein interactions. Scanning electron microscopy (SEM) and con focal scanning laser microscopy (CSLM) were used to visualise emulsified and unemulsified lipid-protein model systems.
Enhanced information from biological materials through technological improvements in cryo-electron microscopy
Authors: de Jong Marc J.C. , Busing Wim M. , Otten Max T.
Published: June 2020

Biological materials damage rapidly in the electron beam, limiting the amount of information that can be obtained in the transmission electron microscope. The discovery that observation at cryo temperatures strongly reduces beam damage (in addition to making it unnecessaiy to use chemical fixatives, dehydration agents and stains, which introduce artefacts) has given an important step forward to preserving the ‘live’ situation and makes it possible to study the relation between function, chemical composition and morphology.

Among the many cryo-applications, the most challenging is perhaps the determination of the atomic structure. Henderson and co-workers were able to determine the structure of the purple membrane by electron crystallography, providing an understanding of the membrane's working as a proton pump. As far as understood at present, the main stumbling block in achieving high resolution appears to be a random movement of atoms or molecules in the specimen within a fraction of a second after exposure to the electron beam, which destroys the highest-resolution detail sought.
Cytochemical localization of glycogen synthase activity in rat liver
Authors: Michaels John E. , Cardell Robert R.
Published: June 2020

Glycogen synthase (GS) is the rate limiting enzyme for liver glycogen synthesis and its activity varies with the phosphorylation state of the enzyme. The current study focused on changes in the intralobular patterns of distribution of cytochemically localized GS activity during glycogen synthesis.

Normal and adrenalectomized (ADX) rats were fasted overnight to reduce liver glycogen to minimal levels. Fasted ADX rats received 2 mg dexamethasone (DEX) 0-8 h prior to sacrifice to stimulate glycogen synthesis. Liver was removed, rapidly frozen in isopentane cooled in liquid nitrogen, then cryostat sectioned. GS activity was localized histochemically by 3 h incubation in medium containing both UDP-glucose and glucose 6-phosphate. Glycogen was formed as reaction product. Control incubations omitted the substrate. Two stains were used to identify glycogen: 1) iodine staining of the incubated sections was rather specific for the newly formed glycogen (Figs. 1-6), whereas 2) periodic acid-Schiff (PAS) stained both native and nascent glycogen.
Plasminogen activator inhibitor 1 (PAI-1): Immunogold localization within platelet-fibrin thrombi
Authors: Lewis J.C. , Hantgan R.R. , Jerome W.G. , Grant K.G. , Dekker A. , Handt S. , Kirkpatrick C.J.
Published: June 2020

Thrombosis, the major clinical sequelae to atherosclerosis, is complex and encompasses a multiplicity of interactions among plasma proteins, platelets and other blood cells, and vascular endothelial cells. Thrombolysis, in a fashion paralleling thrombus progression, is also influenced by a multiplicity of interactions, and recent evidence has suggested that both platelets and endothelial cells play a role in prolonging the lytic process. This prolongation is detrimental to prognosis following vascular occlusion. We have previously reported that thrombin-stimulated platelets will prolong clot lysis when included in an in-vitro assay comprised of tissue-type plasminogen activator, plasminogen, and fibrin(ogen). This observation has been expanded in the present study to included TNF stimulated human umbilical vein endothelial cells, and our data document the association of platelet and EC derived PAI-1 with the fibrin network. HUVEC grown on carbon-stabilized, formvar-coated gold grids for whole mount IVEM were stimulated with tumor necrosis factor, prior to clot initiation and subsequent lysis, by addition to the cultures of fibrinogen, t-PA, plasminogen and thrombin-stimulated platelets. At selected times of lysis following polymerization, based upon laser light scattering kinetic studies, the samples were fixed and processed for PAI-1 localization using the immunogold technique. When observed by SEM, the partially lysed thrombi consisted of an anastomosing fibrin network that extended from endothelial cell surfaces (Figure 1). Within the thrombus, the delicate, branching fibrin strands often were focused at points containing the activated platelets. The interaction of fibrin with endothelial cells was evidenced by IVEM as a delicate extracellular array extending between and among adjacent cells (Figure 2 a,b). Immunogold probes, documenting PAI-1, were distributed in clusters along the fibrin (Figures lb,c). PA1-1, although cellular in origin, was not associated with the surfaces of either platelets or endothelial cells. The specificity of PAI-1 localization was verified through inclusion of a non-related immunogold probe which bound in substantially lower concentration and without site selectivity (Figure 2c). We conclude that HUVEC and platelets modulate thrombolysis through the release of PAI-1 which binds to fibrin and retards plasminogen activation.
An immunoelectron microscopy investigation of simian immunodeficiency virus (SIV) infected AA2 cells
Authors: Norton W.N. , Brown C.R. , Rippy M.K. , Lewis M. , Zack P.M.
Published: June 2020

Human immunodeficiency virus (HIV), the causative agent of AIDS, and simian immunodeficiency virus (SIV) are both retroviruses and members of the lentivirus family. The initial step leading to infection for HIV and SIV involves the binding of a viral envelope protein, GP120, to a specific surface determinate, CD4, which serves as a receptor site. The clinical manifestations of SIV infection in the Asian macaque, an important primate host of the virus, are similar to those detected in humans diagnosed with AIDS. Consequently, SIV and its host represent a potentially valuable system in which drugs and vaccines focused against HIV can be subjected to testing.
Ca++-ATPase activity in the hindgut epithelial cells ofOniscus asellus
Authors: Vernon G.M. , Pierre A. Jean , Witkus R.
Published: June 2020

Specialized junctional complexes and the ultrastructural morphology of the hindgut epithelial cells indicate that the terrestrial isopod hindgut epithelium functions in transport. The hindgut is divided into an anterior hindgut (typhlosole region), a posterior hindgut (papillate region) and a rectum. Using mitochondrial morphometry as an indicator of cell transport activity, Coruzzi et al. demonstrated that the posterior hindgut ofArniadillidium vulgareis active in osmoregulation to a greater degree thanO. asellus. A study was undertaken to determine if this difference is reflected in the CA++-ATPase activity of the hindgut epithelial cells ofO. asellus.
The application of environmental SEM to marine biology
Authors: Ray Richard
Published: June 2020

Preparation of marine biological material for standard scanning electron microscopy (SEM) requires extensive manipulation, including fixation, removal of salts, dehydration, and either air drying or critical-point drying because the SEM operates at high vacuum. Non-conducting samples including biological material must be coated with a conductive film of metal before the specimen can be imaged.

The Electroscan Corporation (Wilmington, MA) recently introduced a new development in SEM technology—the environmental scanning electron microscope (ESEM). This instrument uses a unique secondary electron detector capable of forming high resolution images at pressures in the range of 0.1 to 20 torr. If water vapor is used as the specimen environment, wet samples including wet biofilms can be observed directly. This paper illustrates the use of the ESEM to view bacteria, dinoflagellates, and diatoms on surfaces.
TEM analysis of basidiosporogenesis in Panellus stypticus
Authors: Lingle Wilma L. , Clay Ronald P. , Porter David
Published: June 2020

Panellus stypticus is a white-rot basidiomycete of world-wide distribution. The 0.5 cm to 2.5 cm diameter gilled basidiocarps are evident from late summer through winter, usually on dead hardwood limbs. Basidiocarps can revive from desiccation when moistened, often generating more basidiospores. Basidiospores are thin-walled, hyaline and amyloid (i.e., they stain with Melzer’s iodine solution). In the present study the ultrastructure of events in basidiosporogenesis in P. stypticus was investigated using transmission electron microscopy (TEM). Conventional fixation (CF), using aqueous-based fixatives, and plunge freezing followed by freeze substitution (FS) fixation procedures were employed. Gold-tagged wheat germ agglutinin (WGA), Riccinis communis agglutinin (RcA) and α-amylase were used to investigate the composition of cytoplasmic and extra-cytoplasmic polysaccharides and cell walls, and to localize polysaccharides which may be involved in the ability to revive from desiccation.
Electron microscopy of Malacosoma disstria (Lepidoptera: Lasiocampidae) nuclear polyhedrosis virus in hemocyte cultures
Authors: Brownwright A.J. , MacDonald J.A. , Sohi S.S.
Published: June 2020

The forest tent caterpillar, Malacosoma disstria, is a significant pest of hardwoods in Canada and the United States. Periodic heavy outbreaks of this insect cause appreciable losses in tree growth and fiber production in aspen stands and reductions in the yield of maple syrup and syrup products. Furthermore, large numbers of migrating larvae can have adverse effect on tourism and recreation. The Forest Pest Management Institute is trying to develop biorational control agents for this pest. A nuclear polyhedrosis virus (NPV) of this insect has shown promise as an insecticide, and has been successfully used in field trials. At present the virus can be produced only in the host larvae. However, continuous cell lines, IPRI-MD-66 and IPRI-MD-108, have been established from the hemocytes of this insect to develop an alternative method of virus production.
The innervation of toad lymph hearts: An ultrastructural study
Authors: Pucci A.M. , Fruschelli C. , Rebuffat A. , Guarna M. , Alessandrini C. , Fruschelli M.
Published: June 2020

Amphibians have paired muscular pump organs, called “lymph heart”, which rhythmically pump back the lymph from the large subcutaneous lymph sacs into the veins. The structure and ultrastructure of these organs is well known but to date there is a lack of information about the innervation of lymph hearts. Therefore has been carried out an ultrastructural study in order to study the distribution of the nerve fibers, and the morphology of the neuromuscular junctions in the lymph heart wall.
Elaborate hull cupules of chiton eggs focus the sperm: A Scanning Electron Microscope study
Authors: Buckland-Nicks John
Published: June 2020

The outer hull of most chiton (Mollusca: Polyplacophora) eggs is elaborated into complex spines or cupules that project, from the surface effectively increasing egg diameter. Cupules are either open or closed in free-spawning species but are reduced to flat plates in brooding forms. In open cupule species such as Mopaliaciliata (Fig. 1) invariably sperm swim inside the cupules and become segregated into one of seven internal channels. This was first demonstrated by rolling eggs on sticky tape to remove cupules prior to sputter coating (Fig. 2). Sperm penetrate the thin hull at the base of each cupule during the first stage of fertilization (Figs.3, 4) . One can slice the egg in half using a Keisei microknife (Japan) and examine sperm penetration at the cut surface (Fig. 3).
Innervation of endoneurial microvessels in human sural nerve
Authors: Beggs John L. , Johnson Peter C. , Olafsen Astrid G. , Watkins C. Jane
Published: June 2020

The blood supply (vasa nervorum) to peripheral nerves is composed of an interconnected dual circulation. The endoneurium of nerve fascicles is maintained by the intrinsic circulation which is composed of microvessels primarily of capillary caliber. Transperineurial arterioles link the intrinsic circulation with the extrinsic arterial supply located in the epineurium. Blood flow in the vasa nervorum is neurogenically influenced (1,2). Although a recent hypothesis proposes that endoneurial blood flow is controlled by the action of autonomic nerve fibers associated with epineurial arterioles (2), our recent studies (3) show that in addition to epineurial arterioles other segments of the vasa nervorum are also innervated. In this study, we examine blood vessels of the endoneurium for possible innervation.
Ultrastructure of gypsy moth (Lymantria dispar) nephrocytes
Authors: Shields Kathleen S.
Published: June 2020

Nephrocytes are endocytotic cells that exist in distinct groups at fixed sites within the body cavity of arthropods. They can be identified by their uptake of the vital dye, Trypan blue. The only types of nephrocyte that have been described in the insect order Lepidoptera are the pericardial cells, which have been described in many species, and the cells of the unusual “organe rameux” of Bombyx mori.
Overcoming beam-induced specimen motion: A major advance in improving image contrast for organic specimens
Authors: Downing Kenneth H.
Published: June 2020

Electron microscopists have for some time been progressing toward the goal of atomic resolution of the structure of several proteins; these are proteins that are available in thin crystals that can produce electron diffraction patterns extending beyond 3 Å. The diffraction patterns demonstrate that the specimens themselves should be amenable to high resolution studies. Progress in the solution of these structures has been limited, however, because it has not yet been possible to obtain images of the crystals which have the same quality as the diffraction patterns. Fourier transforms of the images show diffraction spots which decrease in intensity with increasing resolution much faster than do the corresponding electron diffraction patterns, recorded under essentially the same conditions.

The source of this limitation in image quality is clearly not the electron microscope. Materials scientists routinely achieve the resolution which structural biologists still strive for.
Information and estimation in image processing
Authors: Roy Frieden B.
Published: June 2020

Despite the skill and determination of electro-optical system designers, the images acquired using their best designs often suffer from blur and noise. The aim of an “image enhancer” such as myself is to improve these poor images, usually by digital means, such that they better resemble the true, “optical object,” input to the system. This problem is notoriously “ill-posed,” i.e. any direct approach at inversion of the image data suffers strongly from the presence of even a small amount of noise in the data. In fact, the fluctuations engendered in neighboring output values tend to be strongly negative-correlated, so that the output spatially oscillates up and down, with large amplitude, about the true object. What can be done about this situation? As we shall see, various concepts taken from statistical communication theory have proven to be of real use in attacking this problem. We offer below a brief summary of these concepts.
Simulation and information assessment of TEM and STEM images
Authors: Fan Gary
Published: June 2020

Small and moderate digital systems, especially those with computer-microscope interface capabilities and possibly equipped with image frame stores, are being commonly employed in electron microscopy laboratories. The complexity of such systems varies greatly, ranging from those composed of simply a personal computer with minimum interfacing hardwares such as digital to analog converters(DACs) and pulse counters (or ADCs), compact enough to be fitted into a small cart and transported from room to room, to those consisting of image processing systems controlled by mini- or super mini-computers with system-bus interface for massive data transfer, array processors for fast online data handling. Be it simple or complex, such a system allows signals from various sources to be collected and stored in digital form for on-line or off-line manipulation. Fig.1 is a highly schematic diagram of the system currently working in ASU HREM laboratory, on which this work was done.
A new background extrapolation procedure for quantification in EELS
Authors: Liu D.-R. , Williams D. B.
Published: June 2020

The background fitting to the region before the ionization edge is very important especially for quantification of a small amount of one element in a matrix of another. Theoretically the background can be approximated by the AE-r inverse power law. A commonly employed approach is that one first takes a logrithmic transformation of the recorded spectrum and then performs a conventional linear least squares fit (LLSF). This scheme generally gives reasonable results, but is not satisfactory when the spectrum is noisy or a small elemental amount is to be quantified. Over the past few years, this problem has lead to the development of various schemes, such as the two region approach, the polynomial function method and the ravine-search method.
Inner-shell energy loss spectroscopy under reflection-microscopy condition
Authors: Wang Z.L. , Rez P.
Published: June 2020

Electron energy loss spectroscopy(EELS) of the inner shells of atoms is now a well established technique for determination of specimen composition, especially for the light elements. In recent years there has been a revival interest in reflection electron microscopy(REM) as a method for examining surface morphology. It would be useful if the techniques of bulk microanalysis could also be applied in reflection mode. The first electron microscope reflection energy loss measurement were due to Krivanek et al. They successfully showed the enhancement of the surface plasmon in silicon but the Si L edge at 100eV could only be seen as a change in spectrum shape. This is a characteristic of multiple scattering and it is hardly surprising that it should be more important in REM. Multiple scattering in TEM limits energy loss to relatively thin regions, but even under conditions in which multiple scattering has eliminated a low energy edge (such as Si L) the edge of a deep inner shell with binding energy greater than 1 kV can still be clearly seen, though sometimes distorted in shape.
Parameterization of the mean free path for inelastic scattering of fast electrons
Authors: Egerton R. F. , Cheng S. C. , Malis T.
Published: June 2020

The areas, Iz and It, under the zero-loss peak and under the entire energy-loss spectrum (of a sample of thickness t) are related by the formula:

t/ƛ(β) = ln (It/Iz) (1)

where ƛ(β) is the inelastic mean free path for all energy losses and for scattering into the collection aperture, of semiangle β. We have used Eq.(l) to experimentally determine ƛ(β) by electron energy-loss spectroscopy of specimens of known composition and thickness. In the case of crystalline samples, the local thickness t was measured by convergent-beam diffraction. In the case of evaporated thin-film specimens, the average thickness was obtained by accurately weighing the substrate before and after deposition. The energy-loss spectroscopy was carried out in CTEM mode with incident energies Eo between 20keV and 120keV, and with collection semiangles in the range 0.2 mrad to 100 mrad.
The electron energy loss near edge structure of MGO: Theory and experiment
Authors: Neumann K.D. , Spence J.C.H.
Published: June 2020

A similiarity between theoretical calculations of the differential scattering cross section for electron energy-loss near edge structure (ELNES) and the cross section for x-ray absorption near edge structure (XANES) has been demonstrated by several workers (see, e.g. Leapman et al). Since theoretical XANES calculations using band structure methods have often given impressive agreement with experimental results, it is expected hat these same methods can be used under certain experimental conditions to fit ELNES theory to experimental data. The interpretation of ELNES may however, be subject to additional complications involving the multiple scattering of both the beam electron and the ejected core electron. Band structure calculations and multiple scattering techniques have also been used to interpret the ELNES of the carbon K-edge in Be2C. MgO has also been studied using the K.K.R. or Green's function method by Lindner et al. Here we report a further comparison of theoretical and experimental ELNES for MgO.
The dependences of the surface plasmon frequencies on the supported metal particle sizes and shapes
Authors: Wang Z.L. , Cowley J.M.
Published: June 2020

I. Theoretical and experimental studies of supported spherical metal particles show that the existence of the support introduce some new surface plasmon modes. As a continuation of our previous work, hydrodynamics theory is used to calculate the plasmon frequencies of the half-embedded spherical particles as a function of the particle sizes. In this study, the spatial dispersion effects of the particle sizes are illustrated. The predicted surface plasmons ⍵h and ⍵LO, as in Fig. 1(A), and ⍵1 to ⍵4 as in Fig. 1(B) are for the cases of a metal A1 particle covered with thin Al2O3 layer sitting on (A) a dielectric insulator AlF3 and (B) a metallic AI plate, respectively. The detailed model description is given in, The dotted solid curves in Fig. 1 are plots of the surface plasmon frequencies for an isolated metal particle. It is clearly seen that the appearance of ⍵LO and ⍵1, ⍵2, and ⍵4, for the two different supporting cases, are due to the existence of the support. It shows that the effect of the support on the metal particle properties must be considered in the practical experiments.
A TEM study of electron tunneling in biological macromolecules
Authors: Panitz J. A.
Published: June 2020

Tunneling is a ubiquitous phenomenon. Alpha particle disintegration, the Stark effect, superconductivity in thin films, field-emission, and field-ionization are examples of electron tunneling phenomena. In the scanning tunneling microscope (STM) electron tunneling is used as an imaging modality. STM images of flat surfaces show structure at the atomic level. However, STM images of large biological species deposited onto flat surfaces are disappointing. For example, unstained virus particles imaged in the STM do not resemble their TEM counterparts.

It is not clear how an STM image of a biological species is formed. Most biological species are large compared to the nominal electrode separation of ∼ 1nm that is required for electron tunneling. To form an image of a biological species, the tunneling electrodes must be separated by a distance that would normally be too large for a tunneling current to be observed.
Characterization of potassium aluminates in an α-Al2O3 matrix
Authors: Susnitzky D.W. , McKeman S. , Carter C.B.
Published: June 2020

Potassium-rich aluminates have been observed along the grain boundaries of many commercial aluminas. The presence of alkali aluminates can seriously limit the operation lifetime of sodium vapor lamp tubing by increasing the rate of sodium leakage out of the tube. As part of an investigation into phase and interface structure within the K2O-Al2O3 system, high-purity α-Al2O3, seeded with small granules of potassium carbonate, was studied. In samples which were vacuum hot-pressed within a graphite die at 1400°C for 30min, the potassium (K) doping resulted in the precipitation of a spatially inhomogeneous array of K-rich aluminates. It has since been determined that the precipitation phenomenon was due to insufficient mixing of the starting powders. The potassium carbonate was therefore not originally distributed uniformly within the compacts and locally high K concentrations thus resulted.
Twin boundaries in hausmannite (α-Mn3O4)
Authors: Tietz L. A. , Dieckmann R. , Carter C. B.
Published: June 2020

The manganese oxides hausmannite (Mn3-δ O4) and manganosite (Mn1-△O) have recently been characterized by Keller and Dieckmann in terms of their point defect structures and transport properties and a phase diagram has been compiled for the Mn1-△O-Mn3-δO4 portion of the Mn-O system. As might be expected, the manganese oxides bear a strong resemblence to the iron oxides. Both Fe1-△O and Mn1-△O (a=4.44Å) have the NaCl-type structure and are highly non-stoichiometnc, the major point defects being cation vacancies. In Mn1-△O, △ is of the order of 0.1 at 1400 °C and high oxygen activities. Likewise, Mn3-δO4, is the crystallographic analog of Fe3-δO4 (magnetite) but with one major difference; although both compounds have the spinel-type crystal structure, Mn3-δO4 is cubic only above 1150 °C with aα=8.42Å. Below this temperature, it transforms to a tetragonally distorted spinel structure with aα=8.14 Å, cα=9.47 Å, and c/a=1.16. This distortion has been attributed to the Jahn-Teller effect of Mn+3 cations in the octahedral sites of the spinel structure. The purpose of this study is to describe the crystallography of transformations around the Mn1-△O-Mn3-δO4 equilibrium.
A TEM investigation of silicon nitride whiskers
Authors: Roy Tapan
Published: June 2020

Ceramic fibers are being used to improve the mechanical properties of metal matrix and ceramic matrix composites. This paper reports a study of the structural and other microstructural characteristics of silicon nitride whiskers using both conventional TEM and high resolution electron microscopy.

The whiskers were grown by T. E. Scott of Michigan Technological University, by passing nitrogen over molten silicon in the presence of a catalyst. The whiskers were ultrasonically dispersed in chloroform and picked up on holey carbon grids. The diameter of some whiskers (<70nm) was small enough to allow direct observation without thinning. Conventional TEM was performed on a Philips EM400T while high resolution imaging was done on a JEOL 200CX microscope with a point to point resolution of 0.23nm.
Electron beam radiation effects on NiO crystals
Authors: Liu J. , Cowley J. M.
Published: June 2020

It is well known that various electron beam induced effects can occur under high energy electron beam irradiation on the studied material in an electron microscope. It has been reported that under electron beam irradiation small metallic Ni particles can be reduced from the bulk NiO crystals and these Ni crystals are always in epitaxial relationship with the NiO substrate. These Ni particles may be formed by the preferential knock-out of oxygen atoms by the incident electrons and the subsequent aggregation of Ni atoms to form the nucleii. These nuclei will grow with further electron beam irradiation, forming the small Ni islands on the surface of the NiO crystals. Recently, we observed that not only does the reduction process occur on the NiO surface but also other kinds of interactions occur at the same time. First, large NiO crystals can be melted and flow away from the radiated area in an electron microscope. The process is radiation dose dependent.