Spurr's Epoxy Research Articles

Ultrastructural and immunohistochemical study of the effect of sodium alendronate in the progression of experimental periodontitis in rats.

The aim of the present research was to investigate the ultrastructural aspects and the immunoexpression of receptor activator of NFκB ligand (RANKL) and osteoprotegerin (OPG) on experimental periodontal disease of alendronate (ALN)-treated rats. Male Wistar rats received daily injections of 2.5 mg/kg body weight of ALN during 7 days previously and 7, 14, and 21 days after the insertion of a 4.0 silk suture into the gingival sulcus around the right upper second molar. Specimens were fixed in 0.1% glutaraldehyde + 4% formaldehyde under microwave irradiation, decalcified in 4.13% EDTA and paraffin embedded for TRAP histochemistry and immunohistochemistry for RANKL and OPG, or embedded in Spurr epoxy resin for TEM analysis. ALN reduced the activity of osteoclasts and significantly decreased the resorption of the alveolar crest. In the control group the alveolar crest appeared resorbed by TRAP-positive osteoclasts, which presented ultrastructural features of activated cells. The immunoexpression of RANKL was not inhibited by the drug; however, the expression of OPG was increased in the treated animals. The alveolar crest of ALN-treated specimens at 21 days showed signs of osteonecrosis, like empty osteocyte lacunae, the exposed bone regions and bacterial infection. The results showed that ALN treatment in individuals with periodontal disease represents a risk of osteonecrosis because of the reduced activity of osteoclasts resultant of the increased immunoexpression of OPG.

Myocilin Mediates Myelination in the Peripheral Nervous System through ErbB2/3 Signaling

The glaucoma-associated gene, myocilin, is expressed in ocular and non-ocular tissues including the peripheral nervous system, but its functions in these tissues remain poorly understood. We demonstrate that in sciatic nerve, myocilin is expressed in Schwann cells with high concentrations at the nodes of Ranvier. There, myocilin interacts with gliomedin, neurofascin, and NrCAM, which are essential for node formation and function. Treatment of isolated dorsal root ganglion cultures with myocilin stimulates clustering of the nodal proteins neurofascin and sodium channel Nav1.2. Sciatic nerves of myocilin null mice express reduced levels of several myelin-associated and basal membrane proteins compared with those of wild-type littermates. They also demonstrate reduced myelin sheath thickness and partial disorganization of the nodes. Myocilin signaling through ErbB2/3 receptors may contribute to these observed effects. Myocilin binds to ErbB2/ErbB3, activates these receptors, and affects the downstream PI3K-AKT signaling pathway. These data implicate a role for myocilin in the development and/or maintenance of myelination and nodes of Ranvier in sciatic nerve.

Ultrastructural and immunohistochemical study of early repair of alveolar sockets after the extraction of molars from alendronate‐treated rats

The aim of the present research was to analyze ultrastructural and immunohistochemical aspects of the alveolar repair after the extraction of molars of alendronate (ALN)-treated rats. Wistar rats received 2.5mg/kg body wt/day of ALN during 14 days previously and 7, 14 and 21 days after the extraction of the second mandibular molar. Specimens were fixed in 2% glutaraldehyde + 2.5% formaldehyde under microwave irradiation, decalcified in 4.13% EDTA and paraffin embedded for TRAP histochemistry and immunohistochemistry for OPN, BSP and endoglin, or embedded in Spurr epoxy resin for TEM analysis. Additional specimens had their soft tissues removed and were processed for scanning electron microscopy. The ALN group presented latent TRAP-positive osteoclasts and nonresorbed alveolar crests with bacterial infection. Mild bone necrosis signs were observed at all time points studied. Ultrastructurally, empty osteocyte lacunae were observed and bone trabeculae surface presented hyalinized aspect. A significant delay in alveolar repair occurred, as well as decreased angiogenesis. ALN treatment provoked mild signs of bone necrosis, despite the high dose employed. The present findings add new information about the ultrastructural aspect of the early repair of rats under ALN treatment and highlight for giving attention when oral surgeries are performed in patients using this drug.

Maternal corticosterone regulates nutrient allocation to fetal growth in mice

Stresses during pregnancy that increase maternal glucocorticoids reduce birth weight in several species. However, the role of natural glucocorticoids in the mother in fetal acquisition of nutrients for growth remains unknown. This study aimed to determine whether fetal growth was reduced as a consequence of altered amino acid supply when mice were given corticosterone in their drinking water for 5 day periods in mid to late pregnancy (day, D, 11-16 or D14-19). Compared to controls drinking tap water, fetal weight was always reduced by corticosterone. At D16, corticosterone had no effect on materno-fetal transfer of [(14)C]methylaminoisobutyric acid (MeAIB), although placental MeAIB accumulation and expression of the Slc38a1 and Slc38a2 transporters were increased. However, at D19, 3 days after treatment ended, materno-fetal transfer of MeAIB was increased by 37% (P < 0.04). During treatment at D19, placental accumulation and materno-fetal transfer of MeAIB were reduced by 40% (P < 0.01), although expression of Slc38a1 was again elevated. Permanent reductions in placental vascularity occurred during the earlier but not the later period of treatment. Placental Hsd11b2 expression, which regulates feto-placental glucocorticoid bioavailability, was also affected by treatment at D19 only. Maternal corticosterone concentrations inversely correlated with materno-fetal MeAIB clearance and fetal weight at D19 but not D16. On D19, weight gain of the maternal carcass was normal during corticosterone treatment but reduced in those mice treated from D11 to D16, in which corticosterone levels were lowest. Maternal corticosterone is, therefore, a physiological regulator of the amino acid supply for fetal growth via actions on placental phenotype.

Dendritic Cells Are Central Coordinators of the Host Immune Response to Staphylococcus aureus Bloodstream Infection

Dendritic cells (DCs) play an important role in integration of the immune responses induced by pathogens. The purpose of this study was to determine the importance of DCs in host defense against Staphylococcus aureus bacteremia. Using a murine infection model, we demonstrated that DCs are rapidly recruited into infected tissue after intravenous inoculation with S. aureus. The recruited DCs were fully functional and in a more advanced stage of maturation than those isolated from uninfected mice. Depletion of DCs in CD11c-DTR transgenic mice resulted in substantial worsening of infection, as indicated by increased bacterial loads in kidneys and lungs, accelerated mortality, and more severe pathology. Furthermore, DC depletion completely abolished IL-12 production in response to infection. The beneficial effect afforded by DCs during S. aureus infection was not mediated by their contribution to direct bacterial killing, nor by increased neutrophil recruitment. Instead, neutrophil influx (along with expression of CXC chemokines) was significantly enhanced in infected tissue after depletion of DCs. We also found that the bactericidal capacity of the recruited neutrophils was significantly impaired in DC-depleted mice. More importantly, the detrimental effect of DC depletion was practically reversed by treatment with exogenous recombinant mouse IL-12. Our results demonstrated that DCs, probably through their production of IL-12, play an important role in coordinating the inflammatory response during S. aureus infection.

Self-Assembly of Monolayer-Thick Alumina Particle−Epoxy Composite Films

Monolayer-thick composite films composed of alpha-alumina and Spurr's epoxy were prepared via a self-assembly process known as fluid forming. The process makes use of a high-spreading-tension fluid composed of volatile and nonvolatile components to propel particles across the air-water interface within a water bath. Continuous addition of the particle suspension builds a 2D particle film at the air-water interface. The spreading fluid compresses the film into a densely packed array against a submerged substrate. The assembled monolayer is deposited onto the substrate by removing the substrate from the bath. A dispersion containing a narrow size distribution, 10 microm alpha-alumina particles, light mineral oil, and 2-propanol was spread at the air-water interface and the alumina particles were assembled into densely packed arrays with an aerial packing fraction (APF) of 0.88. However, when mineral oil was replaced by Spurr's epoxy nonuniform films with low packing density resulted. It was found that replacing 2-propanol with a mixture of 2-propanol and 1-butanol with a volume ratio of 4:1 produced uniform, densely packed alumina/epoxy composite films. The role of the solvent mixture will be discussed.

Dielectric, Magnetic and Magnetoelectric Properties of a Laminated Composite with 1-3 Connection

A two-phase laminated composite was prepared by stacking one layer of thicknesspolarized 1−3 piezoelectric composite (PECP) plate between two layers of length-magnetized 1−3 magnetostrictive composite (MSCP) plates in the thickness direction. The PECP plate consisted of 0.68 volume-fraction PZT bars embedded in Spurr epoxy matrix, while the MSCP plates comprised 0.51 volume-fraction Terfenol-D particles embedded and magnetically aligned in Spurr epoxy matrix. The dielectric, magnetic and magnetoelectric properties of the laminate were measured as a function of both frequency and magnetic bias field. A giant magnetoelectric voltage coefficient ( αE) of 15.4 V/cm·Oe was observed at the resonance frequency of ~59 kHz under a relatively low bias field of 0.75 kOe. This resonance αE was ~30 times larger than its non-resonance values, showing promising application of the proposed laminate in magnetoelectric conversion devices.

Dynamic magnetoelastic properties of epoxy-bonded terfenol-D particulate composite with a preferred [112] crystallographic orientation

The dynamic magnetoelastic properties of a [112]-oriented magnetostrictive composite comprising 0.49 volume fraction of needle-shaped, [112]-oriented Terfenol-D particles and Spurr epoxy were investigated as a function of magnetic bias field. These properties included elastic moduli (E/sub 3//sup H/ and E/sub 3//sup B/), dynamic strain coefficient (d/sub 33/), and magnetoelastic coupling coefficient (k/sub 33/). A randomly oriented composite with 0.51 volume fraction of irregular-shaped, ball-milled Terfenol-D particles was also prepared and characterized for comparison. It was found that the [112] preferential particulate orientation increases non-180/spl deg/ domain-wall motion in the [112]-oriented composite, resulting in maximum negative-/spl Delta/E,d/sub 33/, and k/sub 33/ values of about 10%, 5.5 nm/A, and 0.34, respectively. These are the largest property values reported as yet for magnetostrictive particulate composites, being up to 67% larger than the randomly oriented composite and approach to 65% of the monolithic Terfenol-D.

RAPID METHOD OF CHEESE PROCESSING FOR MICROFLORA AND MICROSTRUCTURAL STUDIES BY ELECTRON MICROSCOPY 1

ABSTRACTPrevious methods for cheese sample processing for electron microscopy involves several days. Our objective was to identify a suitable yet rapid method. The rapid method involved an initial fixation of cheese in a solution of 2% glutaraldehyde and 1% OsO4 in 0.05M cacodylate buffer for 10 min. This was followed by a second fixation in 2 % glutaraldehyde and 2 % OsO4 in 0.05M buffer for an additional 20 min. Sample fixation by the rapid method was attained in a total of 30 min compared to 17 h in the control, i.e., the previous method, which required 15 h (overnight) fixation in 1% glutaraldehyde and 2 h fixation in 1 % OsO4. After fixation, en block staining with aqueous uranyl acetate was conducted for 30 min. This was followed by ethanol dehydration and infiltration in resin. Additionally, the rapid method was conducted with LR White resin compared to Spurr's epoxy resin in the control. The culture bacteria, protein matrix and dispersed fat globules were clearly visible and were unaltered by the rapid method.

A descriptive and quantitative study of the keratocytes of the corneal stroma of albino rabbits using transmission electron microscopy

The present morphometric study was designed to assess the dimensions and shape of keratocytes and their nuclei by transmission electron microscopy, and to assess these features in relation to the stromal lamellae. Corneas from 10 albino rabbits were fixed in 2% glutaraldehyde in cacodylate buffer (pH 7.4, 300mOsm/kg) and embedded in Spurr's epoxy resin. Both transverse and coronal thin sections through the corneal stroma were prepared. The stromal lamellae had an average thickness of 2.45 ± 1.15μm. The average cell thickness of the keratocytes was 1.34 ± 0.46μm (range 0.49–4.76μm), with the apparent cell thickness being related to the average anterior–posterior thickness of the adjacent lamellae (r= 0.424, P= 0.001)). The relative length and thickness of the cell nucleus, in transverse section, was measured to be 0.65 ± 0.13 and 0.76 ± 0.10 of the cell body section respectively. As assessed by planimetry, the area of the keratocyte cell body viewed in coronal section was 292 ± 118μm2, with a nucleus-to-cytoplasm ratio of 0.437 ± 0.295. The electron micrographs confirmed the presence of gap junctions between keratocyte cell processes, and the occasional presence of centrioles in the cells. Some keratocyte processes were observed to extend from one face of the lamellae to the other, suggesting anterior-to-posterior cell communication. These studies indicate that the keratocyte cell thickness is influenced by the physical pressure exerted by adjacent stromal lamellae. The cell nucleus, while a dominant feature in transverse section, has a normal size in relation to the cell cytoplasm when viewed in coronal section.

Blister Artifact Formation Due to Organic Solvent Effects on Spurr's Epoxy Resin

Wrinkles and air bubble artifacts may occur when preparing slides of semithin sections (0.5 μm) from blocks embedded in different resins. More than aesthetically annoying, wrinkles and air bubble artifacts may prohibit study of small structures. Present observations suggest that organic solvent based mounting media may interact with the resin of the section. This sometimes causes wrinkles and air bubble artifacts in the sections that degrade the quality of light microscope images. We compared the quality of semithin sections of several tissues in different resins using various types of mounting media. We observed that sections from Spurr's resin have many more artifacts. In particular, small, 2–10 μm round or oblong blister-like artifacts often plague our Spurr's resin sections. We demonstrate that Spurr's resin sections react with toluene and xylene in organic solvent based mounting media forming blisters, while sections from Araldite and L. R. White do not. We suggest combinations of embedding and mounting media for successful preparation of semithin sections for light microscopy without wrinkles, blisters, or air bubble artifacts.

Axially distorted 3-3 piezoelectric composites for hydrophone applications

Abstract Application of reticulated ceramic technology to the fabrication of 3–3 lead zirconate-titanate (PZT)/Spurr epoxy composites has been investigated. Use of this technology provides a substantial improvement in manufacturability over other methods. Directional distortion of the ceramic structure to enhance the composite's hydrostatic response is also possible. Composite fabrication is described and the effects of distortion on the piezoelectric properties are presented. The results for K33 and g33 are found to be comparable to other 3–3 PZT/epoxy composites while d33 and hydrostatic gh are reduced with density.

Corneal ultrastructure after excimer laser keratectomy

The Argon fluoride excimer laser emits light at 193nm. At a fluence of 500mJ/CM2, one micron of organic tissue should be removed. This removal occurs by the disruption of chemical bonds rather than the normal heat vaporization seen with other types of lasers. These characteristics should allow the use of this laser in performing precise removal of superficial corneal scars and opacities as well as inducing changes in corneal curvature for refractive corrections. In our studies we will report the ultrastructural changes induced in both primates and man following excimer laser treatment.Following excimer laser treatment, the primates were followed for two years and the corneas removed for morphological studies. The human specimens were taken at various times after excimer treatment for clinical reasons, all having to do with unfavorable outcomes. All human specimens were taken at the time of transplantation of a new cornea to these eyes. The specimens were fixed with 2% paraformaldehyde and 2% gluderaldehyde in cacodylate buffer at pH 7.3. After fixation, these specimens were dehydrated, imbedded in Spurr epoxy resin, then sectioned and examined ultrastructurally.

Container medium characterization by scanning electron microscopy and comparison with a Monte Carlo computer simulated medium

Abstract A 1:1 by volume pine bark and sand containermedium was embedded with Spurr's epoxy resin and cross‐sectioned for SEM characterization of particle distribution. A Monte Carlo computer simulated medium was built with spheres of the same particle size distribution as the pine bark and sand grains used in the experiment. Cross‐sections from the simulated systems were compared with actual experimental data and good agreement was obtained. SEM makes it possible to analyze particle and pore distribution of container media. Computer simulation provides a good approximation of container medium structure and may prove useful in estimating properties of container medium mixtures.

High-spatial-resolution maps of sulphur from human hair sections: an EELS study.

High-resolution sulphur maps have been acquired from human hair using a Zeiss CEM 902A transmission electron microscope equipped with an energy filter. Analysis by electron energy-loss spectroscopy (EELS) was performed on ultrathin sections of hair shafts embedded in three different types of resin: Nanoplast (water-soluble), Spurr (epoxy) and Lowicryl (low-temperature resin). Good-quality energy-loss images have been obtained with the three resins, although it was found that Nanoplast gave the best image contrast. For the first time, the results obtained for the detection of sulphur by silver staining of hair sections, which until now has been the only way to map sulphur at the electron microscopic level, have been confirmed. The results are compared with local sulphur concentrations from bulk analysis.

In vitro differentiation and ultrastructure of human extravillous trophoblast (EVT) cells

Tissue explants of anchoring villi from the first trimester placentae cultured on extracellular matrix (Matrigel) give rise to EVT cells in vitro. This study was designed to address two issues important for further application of the described in vitro model: first, were the observed EVT cells derived by cell proliferation in vitro and second, what is the degree of homology between the in vivo and the in vitro differentiated EVT cells. The cultures (tissue and matrix) were prepared for light and electron microscopic (EM) examinations. Semi-thin sections from Spurr epoxy resin-embedded tissue were used to 'pop-off' the selected area for EM examination. Cell proliferation in vitro was assessed immunohistochemically using proliferative cell nuclear antigen (PCNA) antibodies. Since positive hPL immunostaining has been consistently demonstrated in the invasive subpopulation of EVT cells from placental bed in situ, hPL staining was used as a marker of EVT cell differentiation in vitro. It has been demonstrated that PCNA antibodies immunostained nuclei of cytotrophoblast cells from cell column at the base of the anchoring villi, indicating that these cells expressed proliferative activity in vitro. Cytotrophoblast proliferation resulted in the formation of the flattened zone of cell outgrowths at the tip of anchoring villi. Cells from the distal layer of the cell column detached gradually and migrated into the surrounding matrix. These cells appeared as individual, round-shaped EVT cells with smooth surface cell membrane. Their cytoplasm was rich in glycogen and contained large lipid droplets and flattened cisternae of the RER. Positive PCNA immunostaining, along with the presence of mitotic figures, indicated that EVT cells in vitro retained the ability for cell proliferation. As a result of cell proliferation and migration, the number of EVT cells increased during the culture period of 4 days. EVT cell glycogen content and lipid stores decreased progressively as they migrated into the matrix. Individual EVT cells, as well as EVT cell clusters, became surrounded by the clear zone of digested matrix. Some cells started to express strong positive staining with hPL antibodies as soon as they had migrated outside the villous explant. By day 4 of culture, a small percentage of EVT cells (about 5-10%) ceased to migrate, firmly attached to the substratum and appeared as irregular shaped cells with filopodia-like projections. Their cytoplasm contained dilated cisternae of RER, a small number of glycogen granules and bundles of actin-like filaments located in the cytoplasm inside the plasma membrane.(ABSTRACT TRUNCATED AT 400 WORDS)

Micro-PIXE analyses of thick frozen lenses with cataracts

The microprobe of 27 MeV α particles has been utilized for the study of a possible role of ions in causing hereditary cataracts of mice. The distributions of S to Ca in lenses were determined at a resolution around 50 μm. In order to obtain the elemental concentrations on wet weight basis, thick frozen hydrated specimens were analyzed. The sample preparation method and the experimental setup developed to minimize redistributions of diffusible elements as well as dehydration of specimens are described. The ratio of the X-ray peak intensity to the continuum background intensity was used for quantification. The accuracy of this P/B method used for PIXE analyses of thick soft tissues was examined both by computer calculations and by experiments with biological standards such as Spurr's epoxy resins and NBS SRMs. The elemental distributions in cataractous lenses were obtained for two different types of hereditary cataract: Nakano mice and its congenic strain. The features of distributions and quantitative concentrations of S, Cl, K and Ca were compared.

Resins, Anyone???

Abstract The epoxy resins, especially Spurr's epoxy resin, are time consuming to prepare and dangerous to work with. In an effort to minimize contact time with the resin and to conserve components, we prepare one large batch of resin (minus catalyst) that is then dispensed into glass scintillation vials that are tagged to give the exact weight of resin in the vial, The resins are stored in the freezer (preferably -70° C) until needed at which time they are thawed and the appropriate amount of catalyst added. After mixing by gentle inversions and stirring, the resins are dispensed as needed using widebore pipettes. .Any resin remaining in the vial may be refrozen several times after adding a puff of Freon or dry air to the via!. When the resin becomes too depleted or too old to refreeze, the vial is placed into a 60° C oven and the contents polymerized. The vial may then bs discarded or recycled (i.e., reused) untii the space in the vial is diminished to an unacceptable level.

Leghemoglobin in Lupin Plants (Lupinus albus cv Multolupa)

Leghemoglobin was localized by immunogold techniques in nodules of Lupinus albus cv Multolupa inoculated with Bradyrhizobium sp. (Lupinus) strain ISLU 16. The protein localization was performed in nodules embedded in Spurr's and Araldite epoxy resins and Lowycryl K4M. A very good preservation of both the ultrastructure and antigenicity was obtained with the tissues embedded in Araldite following glutaraldehyde fixation and unpostfixed in osmium tetroxide. Lupin leghemoglobin is a stable and abundant protein which allows a conventional method to be safely used for localization of leghemoglobin. Labeling of leghemoglobin was specifically confined to the cytosol matrix and nuclei. Gold particles were never observed in the peribacteroidal spaces nor in the cytoplasmic organelles of the infected cells. Decrease of leghemoglobin was observed when the plants were grown with 10.7 micromolar and 21.4 micromolar of nitrate.

Anatomy and ultrastructure of Colocasia esculenta (L.) Schott (Araceae)

Taro, Colocasia esculenta (L.) Schott (Araceae), is a staple crop grown in much of the tropics and subtropics. The plant consists of an underground stem, the corm, which is the harvestable portion, and aerial leaves. Most production is by subsistance farmers and the plant is an important part of the culture of these people.Only a few studies have been done on the plant and its anatomy. In addition, much of the previous work on monocot anatomy has been done on the Poaceae. To establish a baseline for non-symptomatic plants for the study of diseases and physiology of taro and to expand the knowledge of the anatomy of monocotyledons, taro was examined ultrastructurally.Leaf tissues for TEM were fixed in glutaraldehyde, postfixed in osmium tetroxide, dehydrated in acetone, infiltrated and embedded in Spurr's epoxy. Blocks were sectioned on a LKB Ultramicrotome III.