bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamics of dendrite development visualized by time-lapse confocal imaging in brain slices
Authors: Dailey M.E. , Smith S.J. 
Published: June 2020

In the mammalian CNS, dendritic neuronal branches typically are studded with numerous short (<3μm), lateral protrusions called “spines”. Such spines are the primary sites of excitatory synaptic input, and changes in spine morphology are thought to play important roles in plasticity of synaptic function in both the developing and adult animal. However, dynamic changes in spine number and structure are not easily determined by electron microscopy, and the small size of spines has made them difficult to study by conventional light microscopy. Recent advances in vital fluorescent staining and high resolution confocal imaging in tissue slices now afford the possibility of assessing changes in morphology of individual spines on single dendrite branches over time.To investigate the dynamics and plasticity of dendritic structure during development, vital fluorescent staining and time-lapse confocal imaging methods were applied to preparations of live brain slices from developing rat. Tissue slices were prepared from hippocampus of neonatal rat (postnatal day 2-7) and cultured for variable periods of time (hours to weeks).
Comparison of 13Å helical and 7Å crystallographic projection maps of frozen, hydrated acrosomal bundle from limulus sperm
Authors: Schmid Michael F. , Jakana Joanita , Matsudaira Paul , Chiu Wah 
Published: June 2020

Actin associates with crosslinking proteins to form bundles and networks. These assemblies can provide a scaffold to anchor organelles, a support for the cell membrane or can attach the cell to the extracellular matrix or to other cells. Each crosslinker must have at least two actin binding sites, one for each actin filament. Scruin, in the Limulus acrosomal bundle, shows no homology with other actin cross-linking proteins. However, it has two homologous domains also found in the sequence encoded by kelch, a gene in Drosophila that is important in nutrient transport into the oocyte, and in MIPP, a mouse placental protein.We have determined a 13Å helical 3-dimensional structure of the actin-scruin complex, which is the basic repeat unit of the acrosomal bundle in Limulus sperm and have fitted the F-actin filament of Holmes. Each scruin binds to two adjacent actin molecules along a single F-actin filament helix. In the present investigation, we used our high resolution (7Å) spot scan electron images of ice-embedded acrosomal bundles for further analysis of the actin atomic map and scruin-scruin contacts. Spot-scan images were obtained from the frozen, hydrated acrosomal bundles in a 400 kV electron cryomicroscope.
Glucuronyl 3-sulfate occurs exclusively on distal unmyelinated terminals of selected sensory neurons in the peripheral nervous system
Authors: Spicer S.S. , Schulte B.A. 
Published: June 2020

Generation of monoclonal antibodies (MAbs) against tissue antigens has yielded several (VC1.1, HNK- 1, L2, 4F4 and anti-leu 7) which recognize the unique sugar epitope, glucuronyl 3-sulfate (Glc A3- SO4). In the central nervous system, these MAbs have demonstrated Glc A3-SO4at the surface of neurons in the cerebral cortex, the cerebellum, the retina and other widespread regions of the brain.Here we describe the distribution of Glc A3-SO4in the peripheral nervous system as determined by immunostaining with a MAb (VC 1.1) developed against antigen in the cat visual cortex. Outside the central nervous system, immunoreactivity was observed only in peripheral terminals of selected sensory nerves conducting transduction signals for touch, hearing, balance and taste. On the glassy membrane of the sinus hair in murine nasal skin, just deep to the ringwurt, VC 1.1 delineated an intensely stained, plaque-like area (Fig. 1). This previously unrecognized structure of the nasal vibrissae presumably serves as a tactile end organ and to our knowledge is not demonstrable by means other than its selective immunopositivity with VC1.1 and its appearance as a densely fibrillar area in H&E stained sections.
DNA nick end labeling: a reliable marker for apoptosis?
Authors: Bushnell Anne F. , Webster Sarah , Perlmutter Lynn S. 
Published: June 2020

Apoptosis, or programmed cell death, is an important mechanism in development and in diverse disease states. The morphological characteristics of apoptosis were first identified using the electron microscope. Since then, DNA laddering on agarose gels was found to correlate well with apoptotic cell death in cultured cells of dissimilar origins. Recently numerous DNA nick end labeling methods have been developed in an attempt to visualize, at the light microscopic level, the apoptotic cells responsible for DNA laddering.The present studies were designed to compare various tissue processing techniques and staining methods to assess the occurrence of apoptosis in post mortem tissue from Alzheimer's diseased (AD) and control human brains by DNA nick end labeling methods. Three tissue preparation methods and two commercial DNA nick end labeling kits were evaluated: the Apoptag kit from Oncor and the Biotin-21 dUTP 3' end labeling kit from Clontech. The detection methods of the two kits differed in that the Oncor kit used digoxigenin dUTP and anti-digoxigenin-peroxidase and the Clontech used biotinylated dUTP and avidinperoxidase. Both used 3-3' diaminobenzidine (DAB) for final color development.
Microscopic studies of Procamallanus elatensis, a parasite in siganids, Red Sea fish in Egypt
Authors: Abdou N. , Heckmann R. A. , Gardner J. S. , Ashour A. A. 
Published: June 2020

Camallanidae is a common nematode family found in a variety of Red Sea fish. Procamallanids were found to be specific to Siganus luridus and S. rivulatus which are considered to be commercially important fish. Procamallanus elatensis collected from Siganids in the northern Gulf of Elat were first described by Fusco and Overstreet using light microscopy, This report includes the first SEM description of Camallanid nematodes.The parasites were washed in 7% saline and saved in 7% formalin until brought to Brigham Young University.They were washed with sodium cacodylate buffer (pH. 7.2), fixed in OSO4 for 12 hr, washed in cacodylate buffer, immersed into 2% tannic acid for 8 hr, washed in buffer, fixed again in OSO4 for 2 hr, washed in buffer, dehydrated with critical point drying and coated with gold.Adult worms were long, slender, and reddish in color. At the anterior end the mouth was round and surrounded by the cephalic plate.
Immunoelectron microscopic studies of the muscle protein titin
Authors: Fassel Theresa A. , Greaser Marion L. 
Published: June 2020

Titin, a skeletal and cardiac muscle protein, is almost 3 million daltons in mass and about 1μm in length. It extends approximately parallel to the long axis of the sarcomere from the Z line to the M line. A series of monoclonal anti-titin antibodies and a polyclonal anti-titin antibody were used to localize several titin epitope positions. A pre-embedding approach was used in which primary and secondary antibody incubations preceded chemical fixation, ethanol dehydration and LR White (room temperature infiltration, heat polymerization) or LR Gold (low temperature infiltration, ultraviolet light polymerization) processing for transmission electron microscopy. A post-embedding step provided a third layer of colloidal gold label. Monoclonal antibody incubations were followed by treatment with sheep anti-mouse IgG and finally with donkey anti-sheep IgG conjugated to 15 nm colloidal gold. Polyclonal antibody incubations were followed by biotinylated anti-chicken and streptavidin-gold (15 nm).Rabbit psoas bundles were tied to glass capillaries in relaxing solution and incubated in a skinning solution for 6 hours at 4°C.
Benzyldimethylamine(BDMA) and dimethylaminoethanol as the catalysts of choice for epoxy resin embedding media
Authors: Mascorro J.A. , Kirby G.S. 
Published: June 2020

INTRODUCTION: By long held tradition, many epoxy resin embedding media are catalyzed with 2,4,6-Tri(dimethylaminomethyl)phenol (DMP-30). Embedding media polymerized in this manner are widely-used and produce acceptable results, nevertheless they show high viscosity, a rapid loss in fluidity, and ultimately a shortened useful pot-life necessary for complete specimen infiltration. Perhaps using less viscous catalysts, such as Benzyldimethylamine (BDMA) or Dimethylaminoethanol (DMAE), would yield embedding media with lowered viscosity and prolonged fluidity, both very important characteristics that would ensure complete infiltration and strengthening of tissues subsequent to microtomy and ultrastructural study.MATERIALS & METHODS: The amine catalysts BDMA, DMAE, and DMP-30 were tested for Average Flow Time (AFT) and Volume Flow Rate (VFR) by recording the time necessary for 9 ml of each component to flow from a vertically oriented viscosimeter. Viscosity (cp), which is a relative measure of fluidity and a real correlate of AFT/VFR, then was calculated with the Hagen-Poiseville relation for laminar flow as applied to fluids. Embed 812 and LX112 media were prepared and catalyzed either with BDMA, DMAE, or DMP-30 and their AFT, VFR, and cp similarly determined @ 5, 30, and 60 minute intervals after initial mixing.
Cell monolayer technique using sectionable culture beads
Authors: Hogan Margaret E. 
Published: June 2020

The use of tissue culture, as an experimental model, has gained high regard in the study of organism function and control. For this reason the ability to observe these cells has become quite important in both transmission(TEM) and scanning electron microscopy(SEM).Most monolayers of cells have been grown on flat substrates (culture plates and flasks), and have required involved manipulation to prove the desired plane of sectioning. With the use of culture beads much of the handling is eliminated, in fact the procedure is really no different than preparing whole tissue for electron microscopy. Along with the ease of preparation, the beads provide increased tissue per section, and therefore a more broad sampling of the specimens.
Ruthenium tetroxide fixation comparison of bacterial surface ultrastructure
Authors: Caughey R. C. , Miller M. A. 
Published: June 2020

Ruthenium tetroxide is known to improve overall contrast and preservation of membranes. It is a cationic dye which has an affinity for strongly positive anionic polymers and thus more effectively preserves exopolysaccharide materials such as glycocalyx on bacterial membrane surfaces. This study was undertaken to determine the usefulness of this technique over conventional fixation procedures in the study of bacterial surface structures that are important in pathogenicity.Different strains of pathogenic bacteria (possessing various surface structures) were routinely fixed in 2.5% glutareldehyde and 1% osmium tetroxide, dehydrated in a graded series of ethanols, and embedded in Epon 812 epoxy resin. Half of each sample was fixed in 0.05% ruthenium tetroxide (pH7.1) instead of osmium tetroxide, and then dehydrated and embedded as above. All of the samples were sectioned and post stained in uranyl acetate/lead citrate.
TEM study of dislocation array/high angle grain boundary interaction in type 304 stainless steel
Authors: Wise Cynthia M. 
Published: June 2020

The interaction of dislocations with grain boundaries is considered a controlling process for many of the mechanical properties, including strength in a metal. The grain boundary acts as a barrier to impede the motion of dislocations, and strengthens the material because of the increased stress necessary to induce slip propagation.TEM samples were prepared from type 304 stainless steel which was solution treated, lightly deformed, electropolished using standard techniques, and examined in a JEOL 200CX TEM operating at 200KeV, using a double-tilt goniometer stage.
The twin lens system - A high resolution objective lens at 300 kV
Authors: Bormans B. , Hagemann P. 
Published: June 2020

Point resolution of better than 0.2 nm is today achievable in medium voltage electron microscopes. Crucial for this achievement is the objective lens design which has to provide sufficiently low spherical and chromatic aberration figures. In addition to the lens itself, its integration into the overall microscope optics has to ensure a reproducible and accurate alignment.Cleaver has shown that symmetrical lenses have lower aberrations than their asymmetrical counterparts by a factor of 1.5 or 2. Theoretical optimization of this lens at 300 kV can be carried out using a first-order finite element program, as developed by Munro. The symmetrical single-field condenser objective with saturated pole-piece tips produces particularly good values with Cs = 1.0 mm and Cc = 1.4 mm at 300 kV. In this lens the specimen is placed in the centre of the magnetic field.
Linewidth measurement using the low voltage SEM
Authors: Rosenfield M.G. 
Published: June 2020

Minimum feature sizes in experimental integrated circuits are approaching 0.5 μm and below. During the fabrication process it is usually necessary to be able to non-destructively measure the critical dimensions in resist and after the various process steps. This can be accomplished using the low voltage SEM. Submicron linewidth measurement is typically done by manually measuring the SEM micrographs. Since it is desirable to make as many measurements as possible in the shortest period of time, it is important that this technique be automated.Linewidth measurement using the scanning electron microscope is not well understood. The basic intent is to measure the size of a structure from the secondary electron signal generated by that structure. Thus, it is important to understand how the actual dimension of the line being measured relates to the secondary electron signal. Since different features generate different signals, the same method of relating linewidth to signal cannot be used. For example, the peak to peak method may be used to accurately measure the linewidth of an isolated resist line; but, a threshold technique may be required for an isolated space in resist.
Particulate carbon at the cretaceous-tertiary boundary
Authors: Mu Chongjun , Wolbach Wendy S. 
Published: June 2020

A worldwide Ir layer occurs at the Cretaceous-Tertiary (K-T) boundary, apparently from the impact of a 10 km meteorite that caused the mass extinctions at that time. The same boundary layer also is enriched in carbon showing the characteristic morphology of soot [grape-like, "aciniform" clusters of 0.03 μm spheroids]. Presumably this carbon came from major fires of forests or fossil carbon that were ignited by the impact.Extending the earlier SEM study, we have examined several samples by TEM. All samples were isolated by dissolving inorganic minerals with HCI and HF and removing extractable organics and most of the kerogen with organic solvents and NaOH. Fig. 1 shows a sample from the K-T boundary at Woodside Creek, New Zealand. The aciniform carbon is still covered with films of kerogen. Further extractions eventually yield the material in Fig. 2, which is free of kerogen, and shows the delicate, welded structure of soot
Crystallography of self-implanted and laser pulse-annealed silicon
Authors: McClure D.L. , Carpenter R.W. , Barry J.C. , Lowndes D.H. 
Published: June 2020

Results of a HREM investigation of the structure of the amorphous silicon (aSi) surface layers and the subsequent polycrystalline microstructure after laser pulse annealing are presented here. Amorphous silicon melts at about 200K less than the crystalline phase, resulting in undercooled liquid silicon as the driving force for crystallization.Surface layers of aSi ∽400nm thick were prepared by self ion implantation on <100> substrates at 77K. Annealing was done with an excimer laser (KrF, 248nm) of 35nsec pulse duration at 0.4, 0.7, 0.8 J/cm2 energy densities. Melt depth penetration into the aSi layer is proportional to laser pulse energy magnitude. Cross section HREM was done in <110>, perpendicular to the implant direction with a JEOL 4000EX, 200CX, Philips EM400 FEG, and EM400T.
Micrograph image processing system
Authors: Mittleman R. K. , Parker N. W. 
Published: June 2020

We have developed a computer-driven image processing system for the analysis of STEM micrographs. Modern computer and data storage devices give the researcher the ability to record and store large numbers of images. Our system was designed to allow rapid viewing and to facilitate the measurement process. Making use of an IBM 4381-2 mainframe computer and a high resolution (1024 x 1280 pixels) Metheus Omega 500 display system, we have written a flexible, interactive system to display and process data from our electron microscopes. The system is menu-driven from a mouse and can call subroutines from fortran, pascal or APL.APL is an interpreted, interactive language that is particularly well suited to real time image processing. Algebraic manipulations can be performed with equal ease on arrays of any rank and the user can affect many complex operations on dataarrays, usually with a single line of code (e.g., gray scale expansion, zoom, inner and outer product, etc.).
Electron microscope of the 21st century
Authors: Crewe A.V. 
Published: June 2020

I have been asked to talk about the future of the electron microscope by the Chairman and cannot refuse because he was one of my students. On the other hand, I do not feel comfortable with the position because there is a very poor history in science on the matter of making predictions; they are always wrong.After giving it some thought, it would seem that the best thing that I can do is to discuss some of the problems that I can see with the instruments and suggest that the solutions to these problems will slide into the next century. That puts me on safe ground and perhaps may allow me to suggest some solutions myself.To start with, one can say that the business shows every sign of being, or becoming, a mature industry. The instruments become more and more expensive every year. They become generally larger, and there is more attention given to appearances. This is very similar to the automobile industry and is at gross variance with the computer industry where the functionality increases and the cost decreases every year. In the present climate of financial support (or the lack of it), this means that fewer instruments are sold every year, and this increases the price of those that are sold.
Altered renal proximal tubule cell ion homeostasis during diabetes
Authors: Freudenrich Craig C. , Hockett Daniel , Kirk Benjamin , Gilliland Kurt , Scherer Brian , Winter Kerri , Ingram Peter , LeFurgey Ann 
Published: June 2020

A major characteristic of human and experimental diabetes mellitus is enhanced urinary excretion of electrolytes (e.g. Na, K, Mg, Ca). The increased urinary electrolyte excretion can lead to low serum electrolyte concentrations (e.g. hypomagnesemia, hyponatremia, hypocalcemia, hypokalemia), although this issue remains controversial. Ultimately, elevated urinary electrolyte excretion can result in mineral deficiencies which have important consequences such as retinopathies, convulsions, osteoporosis, arrhythmias, and sudden death ischemia. The increased urinary electrolyte excretion could be due to osmotic diuresis and/or altered renal tubule cell ion homeostasis; however, few studies have addressed whether diabetes alters specific tubule cell ion homeostasis. In this study, we used electron probe x-ray microanalysis (EPXMA) to obtain quantitative microchemical images of proximal tubule cells from diabetic rats so that we could define how subcellular ion homeostasis is altered during diabetes.Adult male Sprague-Dawley rats were housed in individual metabolic cages and urine output was measured daily; peri-orbital plasma samples were collected every 3 days. Urine and plasma ion concentrations (Na, K, Ca, Mg) were assayed by atomic absorption spectroscopy, blood glucose was measured with a commercial glucometer, and urine glucose and ketones were detected with commercial strips.
Plant anatomy, histochemistry, and gene expression as visualized by tissue printing
Authors: Reid Philip D. , Bickar David 
Published: June 2020

Tissue printing on nitrocellulose membranes followed by localization with appropriate probes has been used to study the distribution of protein and mRNA as well as the timing of gene expression in a variety of plant tissues. Included in these studies are cell wall proteins in soybean and cellulase activity in relation to abscission in kidney bean. Our recent studies have focused on the distribution of enzymes involved in crassulacean acid metabolism in the leaves of various species of Peperomia, the localization of ubiquitinated protein in various plant tissues, and the development of a stain for total protein transferred to nitrocellulose by tissue printing.Tissue prints made on dry nitrocellulose membranes (0.45μm pore size) and viewed with side illumination at low (10X) magnification show the characteristic morphology and anatomical organization of the printed tissue (Figs. 1 and 2). Treatment of the membranes with 12 mM HC1 followed by a two minute incubation in an acidic 0.05% solution of copper phthalocyanine 3,4',4'',4'''-tetrasulfonic acid tetrasodium salt (CPTS) (Figs. 3 and 4) shows the distribution of total protein transferred to the membrane.
Imaging in 5 dimensions: Quantitative measurement of membrane potential from single mitochondria in living cells
Authors: Loew Leslie M. , Tuft Richard A. , Carrington Walter , Fay Fredric S. 
Published: June 2020

The energy released during the oxidation reactions in the mitochondrial respiratory chain is stored as an electrochemical potential consisting of a transmembrane electrical potential (Vmit) of about −180 mV and a proton gradient of about 1 pH unit; this drives the synthesis of the ATP required to fuel the cell’s energy-dependent processes. This key cellular system has been the subject of thousands of studies. However, data on how it is regulated by the physiological state of the cell has only been gathered via indirect studies on isolated mitochondrial suspensions; quantitative studies on individual mitochondria in situ have been precluded by their small size, their high motility, and the absence of appropriate methodologies.An approach toward a more quantitative assessment of Vmit within intact cells was based on the development of the potentiometric fluorescent dyes TMRE and TMRM, which rapidly equilibrate across membranes in accord with the Nernst equation.
Three-dimensional reconstruction of the golgi complex and trans-golgi network: A HVEM tomographic study
Authors: Ladinsky Mark S. , Kremer James R. , Furcinitti Paul S. , Richard McIntosh J. , Howell Kathryn E. 
Published: June 2020

The Golgi complex is the central organelle in the secretory pathway of eukaryotic cells. It is composed of multiple cisternae that contain various enzymes involved in posttranslational modification of newly synthesized proteins. The cisternae are connected to a reticular lattice, the trans-Golgi Network (TGN), which is responsible for sorting and targeting proteins and lipids to other cellular locations. Transport between the Golgi cisternae is thought to occur largely via carrier vesicles, but recent studies suggest that some transport may be via tubules which link the cisternae and TGN. Although the Golgi complex has been well characterized biochemically, only a few studies have addressed its 3-D fine structure.Specific staining, high voltage electron microscopy (HVEM), and computer axial tomography were used to visualize the structure of the Golgi cisternae and the TGN in 3-D. A technique developed by R. E. Pagano was used to facilitate the visualization of the TGN and trans-most cisternae: Normal rat kidney (NRK) cells are treated with a fluorescent analog of ceramide (BODIPY-cer) which is internalized and metabolized in the Golgi complex (Fig. 1a).