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Identification Of The Physical Modification Threshold Of Dentin Induced By Neodymium And Holmium Yag Lasers Using Scanning Electron Microscopy, J. M. White, H. E. Goodis, G. W. Marshall Jr., S. J. Marshall

Scanning Microscopy

Laser application to dentin has been advocated to modify the dentin substrate for restorative procedures. We examined the minimum energy density required to physically modify the dentin surface using 1.06 μm and 1.32 μm Neodymium:Yttrium-Aluminum-Garnet (Nd: YAG) and 2.10 μm Holmium-YAG (Ho: YAG) lasers. Three millimeter thick dentin sections from the middle occlusal third of crowns of third molars were used. To determine the effect of surface preparation, the sections were ground to 240, 320, 400, 600 grit or polished to 0.5 μm. Smear layer was removed using 0.5 M EDTA for 2 minutes. Five single pulse repetitions at each …

Vascular Remodeling In Hypertension, Gary L. Baumbach, Shams Ghoneim

Scanning Microscopy

Cerebral arterioles in stroke-prone spontaneously hypertensive rats (SHRSP) paradoxically become more distensible, despite hypertrophy of the vessel wall. Cerebral arterioles in SHRSP also undergo remodeling with a reduction in external diameter. Based on these findings, we have proposed the concept that remodeling of cerebral arterioles may be an important mechanism, in addition to hypertrophy, for encroachment on the vascular lumen in SHRSP. The purpose of this review is threefold. First, consequences of vascular hypertrophy that have been proposed previously are reviewed with an emphasis on the hypothesis that encroachment on the vascular lumen by hypertrophy is an important mechanism …

Environmental Scanning Electron Microscope: Some Critical Issues, G. D. Danilatos

Scanning Microscopy

In the environmental scanning electron microscope (ESEM), the gas flow around the main pressure limiting aperture establishes a density gradient through which the electron beam passes. Electron beam losses occur in this transition region and in the uniform gas layer above the specimen surface. In the oligo-scattering regime, the electron distribution consists of a widely scattered fraction of electrons surrounding an intact focussed probe. Secondary electrons are multiplied by means of gaseous ionization and detected both by the ionization current and the accompanying gaseous scintillation. The distribution of secondary electrons is governed by the applied external electric and magnetic fields …

Physico-Chemical Changes Occurring In Gamma Irradiated Flours Studied By Small-Angle X-Ray Scattering, K. Ciesla, T. Zoltowski, R. Diduszko

Food Structure

Commercial samples of wheat, rye and potato flour and flaked oats, as well as ground flaked oats and fresh potatoes were gamma-irradiated (20 or 30 kGy dose). The products and appropriate control samples were inves tigated by small-angle X-ray scattering (SAXS) in the range of 28 from 0.357 to 6.46 degree (CuKa radiation). The results were compared with those obta ined for pure potato starch. Effects of grinding and heating at 100° Con SAXS results were also examined.

Different scattering curves were obtained for various unirradiated products. Refl ect ions derived from starch were de tected for some uni rradiated …

Liquid Holding Capacity And Structural Changes During Heating Of Fish Muscle: Cod (Gadus Morhua L.) And Salmon (Salmo Salar), Ragni Ofstad, Siw Kidman, Reidar Myklebust, Anne-Marie Hermansson

Food Structure

The loss of water and fat in cod and salmon muscle was studied as a function of heating temperature from 5-70 C. The liquid-holding capacity was measured by a low speed centrifugation net test leading to the separation of released liquid. To obtain a better understanding of the liquid-holding properties, the microscopic changes of the samples were evaluated by light microscopy. Two different preparation techniques were used . Cod lost twice as much water as salmon upon beating. After an initial delay , the water loss increased at 20-35°C, attained a maximum at 45-50°C, and thereafter decreased in both fish …

Identification Of Radiation Treatment Of Mineral-Enriched Milk Protein Concentrate By Complex Test Protocols. A Comparison Of Thermoluminescence, Electron Spin Resonance And Rheological Investigations, J. Kispeter, L. I. Horvath, K. Bajusz-Kabok, L. I. Kiss, P. Zahonyi-Racs

Food Structure

The combined application of thermoluminescence and electron spin resonance spectroscopy in conjunction with dynamic viscosity measurements provides a rather informative picture of radiation-induced processes. Spectroscopic techniques focus on the primary energy distribution following the absorption of high-energy γ-photons and the concomitant free radical formation. Such measurements, for methodological reasons, on milk protein concentrate samples allow the quantitative identification of radiation treatment for a limited period of 2-3 weeks following the radiation treatment. Rheological measurements on suspensions of milk protein concentrate, on the other hand, can reveal accumulating longterm modifications. The effects of chelated iron and selenium complexes added as food …

Interfacial Viscoelasticity In Emulsions And Foams, E. H. Lucassen-Reynders

Food Structure

Both the generation and the stability of emulsions and foams depend on interfacial properties induced by adsorbed surfactants. The essential function of surfactants during emulsification and foaming is not that they reduce the equilibrium interfacial tension, but they impart specific dynamic properties to the interface. A surfactant- covered interface behaves as a two-dimensional body with its own elasticity and viscosity, which a re related to the non-equilibrium values of the interfacial tension. Such viscoelasticity is a significant factor in any liquid flow near the interface, and in the stability of the thin films separating emulsion drops or foam bubbles. Numerically …

Heating Of Calcium Phosphate Crystals: Morphological Consequences And Biological Implications, W. Bohne, J. A. Pouezat, L. Peru, G. Daculsi

Cells and Materials

Sintering hydroxyapatite (HA) and ß-tricalcium phosphate (ß-TCP) affects the chemical composition, the crystallinity, and the morphological features as demonstrated by means of X-ray diffraction (XRD) , infrared spectroscopy (IR), and scanning electron microscopy (SEM). When heated to 1230°C, 16.7% of HA had decomposed to ß-TCP. SEM investigations showed homogeneous, sharp angular polyhedric blocks of 30 to 50 µm with rare surface pores. On heating at 1230°C, ß-TCP had entirely transformed to a-TCP. During sintering, the size of the powder grains increased and progressive bridging between the grains was observed. At 1230°C, a network within round-shaped polyhedric blocks of 50 to …

Surface Chemical Reactions At The Atomic Scale: Gas Reactions With Semiconductors Studied With Scanning Tunneling Microscopy, R. S. Becker, Y. J. Chabal, G. S. Higashi, A. J. Becker

Scanning Microscopy

The vacuum tunneling microscope has been extensively utilized in the study of the surface atomic configuration of conducting materials. Analysis of features in both the tunneling images and in the tunnel junction I-V characteristic yields insight into a wide variety of processes occurring at surfaces. In the last few years, elementary chemical reactions occurring at surfaces have been examined in this manner, principally adsorption of simple gas species such as H₂, O₂, and NH₃ on semiconductors and metals. Adsorption sites have been deduced from changes brought about in surface configuration subsequent to gas exposure. The …

Bone Growth On Sol-Gel Calcium Phosphate Thin Films In Vitro, Q. Qiu, P. Vincent, B. Lowenberg, M. Sayer, J. E. Davies

Cells and Materials

Thin, sub-micron, films of calcium phosphate were fabricated on either glass or quartz supports by a colloidal suspension sol-gel method. These films, which varied in both surface chemistry and topography were then employed as culture substrata for osteogenic rat bone marrow cells. During an 18 day culture period, the cells elaborated a morphologically distinguishable bone matrix on all substrata which was similar to that reported earlier on tissue culture polystyrene. Selected samples of the culture substrata were fractured, critical point dried, and observed by scanning electron microscopy. Particular attention was paid to the morphologies of the interface between the so1-gellayer …

High-Resolution Scanning Electron Microscopy Of Milk Products: A New Sample Preparation Procedure, William R. Mcmanus, Donald J. Mcmahon, Craig J. Oberg

Food Structure

A metal-impregnation technique (tannin-ferrocyanide- osmium tetroxide) and thin metal coating imparted excellent preservation , and electric and thermal properties to milk products for scanning electron microscopy, resulting in high- resolution images. Three nanometer resolution was obtained, with minimal edge effects, charging , thermal drift, and decoration. Samples were fixed in 2% gluta raldehyde, cryoprotected in 70% ethanol, and cryofractured, exposing internal structure. Fat was extracted with Freon 113 and the sample were metal -impregnated with 1.0% osmium tetroxide and 1.5% potassium ferrocyanide, reduced with 1% hydroquinone, dried using !he critical-point drying melhod , and ion beam sputter-coated with 2-5 nm …

Recent Developments In Multichannel Raman Microprobing, J. Barbillat, M. Delhaye, E. Da Silva

Scanning Microscopy

This paper reviews the capabilities of multichannel Raman microprobing instruments with emphasis on some major innovative progress recently proposed which looks promising for the development of new fields of application. This new progress includes: confocal Raman microanalysis that provides better spatial resolution and background rejection, confocal Raman mapping that revitalizes the field of Raman imaging pioneered by us 20 years ago, the coupling of molecular Raman microanalysis to elemental electron microprobe, and finally, Raman spectroscopy with near-infrared excitation which permits avoiding the fluorescence limitation of visible Raman spectroscopy.

Mineralized Matrix Synthesis By Isolated Mouse Odontoblast-Like Cells In Vitro, P. B. Andrews, A. R. Ten Cate, J. E. Davies

Cells and Materials

First mandibular molar tooth germs were dissected from 17 day mouse embryos. The dental papilla was isolated using both mechanical separation and enzymatic digestion. The cells of the papilla were then enzymatically disaggregated and cultured in 35 mm polystyrene dishes containing alpha minimum essential medium supplemented with 15 % fetal calf serum, 50 μglml ascorbic acid, 1 o-8 M dexamethasone and 10 mM Na-13-glycerophosphate. The cultures were maintained for 23 days. The cultured cells initially appeared as large flat cells having numerous cell processes. Multilayered cell nodules, distributed randomly in the cultures, were apparent after 5 days. Matrix was visible …

Ultrastructural, Cytochemical, And Immunocytochemical Studies On Bone And Its Interfaces, M. D. Mckee, A. Nanci

Cells and Materials

Bone cells possess the ability to synthesize, secrete and direct the assembly and maintenance of extracellular matrix to form a functionally rigid and/or weight-bearing mineralized tissue complex, the skeleton. The skeleton not only supports and protects the organs and tissues of the body, but also acts as a mineral ion reservoir for maintaining systemic calcium balance (calcium homeostasis). The remarkable biological precision necessary for the formation, turnover and constant adaptation of bone to external mechanical forces is a dynamic process requiring a coordinated cellular effort relying on a variety of cell-cell and cell-matrix/mineral interactions. Indeed, cell-matrix interfaces found in a …

Multinucleated Giant Cells-Hydroxyapatite Interactions: A Time-Related Quantitative Study In A Rat Skull Defect, J. M. Dersot, A. Llorens, J. L. Saffar

Cells and Materials

The implantation of calcium phosphate ceramics in the bone environment elicits the differentiation of multinucleated giant cells (MNGCs). MNGC interactions with both crushed and standard hydroxyapatite (HA, Bioapatite ®) particles (cHA and sHA) were studied in rat skull defects. Light microscopy (LM) of undemineralized material after 21 and 42 days of implantation showed that the number of particles in the defect significantly decreased (about SO%) with the two HA forms. Concomitantly, average cHA particle size increased significantly due to the elimination of the smallest particles by the MNGCs. The number of MNGCs per mm2 of defect decreased significantly between 21 …

A Comparison Of The Effects Of Oven Roasting And Oil Cooking On The Microstructure Of Peanut (Arachis Hypogaea L. Cv. Florigiant) Cotyledon, Clyde T. Young, William E. Schadel

Food Structure

Peanut (Arachis hypogaea L. cv. Florigiant) cotyledon microstructure after oven roasting and oil cooking at 160 C was documented with scanning electron microscopy, light microscopy and transmission electron microscopy . Changes in peanut cotyledon microstructure were compared as thermal processing time at 160°C was increased for both oven roasting and oil cooking. The purpose was to evaluate thermal modifications in the cytoplasmic network, protein bodies and cell-to-cell junctions as thermal processing time in creased for each heating method. Principal findings included differences in the times at which these modifications occurred during the two thermal processes. Oven roasting a t 160 …

Three-Dimensional Molecular Modeling Of Bovine Caseins, Harold M. Farrell Jr., Eleanor M. Brown, Thomas F. Kumosinski

Food Structure

Three-dimensional (3 -D) structures derived from X-ray crystallography are important in elucidating structure- function relationships for many proteins. However, not all food proteins can be crystallized. The casei ns of bovine milk are one class of non-crysta11izable proteins (a, 1-, K-, and /3-). The complete primary and partial secondary structures of these proteins are known, but homologous proteins of known crystallographic structure cannot be found. Therefore , sequence based predictions of secondary structure were made and adjusted to conform with data from Raman and Fourier-transformed infra- red spectroscopy. With this information, 3-D structures for these caseins were built using the …

Microstructure Of Black, Green And Red Gram, Enamuthu Joseph, Shelly G. Crites, Barry G. Swanson

Food Structure

The three most commonly consumed legumes (grams or pulses) in India, black gram (Vigna mungo (L.) Hepper), or urd , green gram (Vigna radiata (L.) Wilczek) or mung, and red gram (Cajanus cajan (L.) Millsp.) or tur, were examined by scanning electron microscopy . Seed coat and internal features were examined to differentiate these legumes from common beans (Phaseolus vulgaris) , adzuki beans (Vigna angu/aris) and lentils (Lens culinaris). Cross-sections of the seed coats of black, green and red gram contained single layers of columnar palisade cells extending as double palisade layers at the hilum regions. The funiculi located above …

Evaluation Of Drug Delivery Systems By Electron Microscopy Techniques, Y. V. Pathak, V. D. Labhashetwar

Cells and Materials

This review covers the applications of electron microscopic techniques to the characterization and evaluation of drug delivery systems. Various electron microscopic (EM) related techniques such as transmission electron microscopy, scanning electron microscopy (SEM), SEM with energy dispersive X-ray microanalysis, and freeze-fracture electron microscopy are extensively used for this purpose. Microcapsules, microspheres, nanocapsules, liposomes , polymeric carriers and other drug delivery systems are characterized using EM related techniques for their surface topography, size and shape analysis, biodegradation, in vitro - in vivo evaluation and drug excipient interactions and characterization. Electron microscopy methods are very useful in understanding the mechanism of drug …

A Comparative Study Of The Interactions Of Two Calcium Phosphates, Peo/Pbt Copolymer (Polyactive) And A Silicone Rubber With Bone And Fibrous Tissue, C. A. Van Blitterswijk, J. R. De Wijn, H. Leenders, J. V.D. Brink, S. C. Hesseling, D. Bakker

Cells and Materials

In this study, hydroxyapatite, tetracalcium phosphate, HPEO/PBT 55145 copolymer, PEO/PBT 55!45 copolymer (Polyactive) and silicone rubber were implanted as dense blocks, subcutaneously and. into the tibia of rats. Biocompatibility and degradation were investigated but most attention was directed to .the bone/biomaterial interactions. None of the materials showed any significant adverse tissue reactions. With exception of the silicone rubber, all materials sho~ed bone bonding phenomena based on both morphological and mechanical evaluations. (H)PEO/PBT 55145 copolymer is the first polymer reported to be bonded by bone and thus widens the spectrum of bone bonding materials with a low modulus, degradable, elastomer in …

Immunohistochemical Investigation Of Tracks Left By The Migration Of Fibroblasts On Titanium Surfaces, Y. Abiko, D. M. Brunette

Cells and Materials

Fibronectin, a major attachment protein, has been thought to be involved in pathway guidance, a process in which cells migrate along specific pathways within a tissue during development. Fibroblasts exhibit the phenomenon of contact guidance, the tendency of cells to be guided in their direction of migration by the shape of the substratum. The purpose of our study was to test the hypothesis that fibronectin tracks are deposited by fibroblasts moving on smooth and grooved titanium surfaces.

The study was carried out on human gingival fibroblasts which were plated onto both smooth and grooved titanium substrata using medium containing either …

Experimental Induction Of Odontoblast Differentiation And Stimulation During Preparative Processes, H. Lesot, C. Begue-Kirn, M. D. Kubler, J. M. Meyer, A. J. Smith, N. Cassidy, J. V. Ruch

Cells and Materials

In vivo implantation experiments have shown that ethylenediaminetetraaceticacid(EDTA)-soluble frac tions of dentin stimulate reparative dentinogenesis . When isolated embryonic dental papillae were cultured in the presence of these dentin constituents, odontoblast cytological and functional differentiation could be initiated and maintained in the absence of an enamel organ. These effects were attributed to the presence of TGF-/1- related molecules [TGF-/11 or bone morphogenetic protein -2a (BMP-2a)] which had to be used in combination with an EDT A-soluble fraction of dentin in order to specifically affect competent preodontoblasts . These EDT A-soluble constituents present in dentin could be replaced by heparin or …

Lysine Effect On Ruthenium Red And Alcian Blue Preservation And Staining Of The Staphylococcal Glycocalyx, Theresa A. Fassel, James R. Sanger, Charles E. Edmiston

Cells and Materials

The effect of lysine on ruthenium red (RR) and alcian blue (AB) preservation arid/or staining for transmission electron microscopy of glycocalyces was evaluated for three species of the gram-positive, coagulase-negative staphylococci. A RR and an AB procedure were compared with and without lysine included in the glutaraldehyde prefixation. Minimal or no glycocalyx was preserved or stained by glutaraldehyde fixation only. For all species, the inclusion of lysine increased visualization of fibrous material. RR treatment without lysine, results in sparse or limited fibrous material or artifactual condensations which contrasts with enhanced fibrous material seen when lysine is included with RR. The …

Are Long Term Cryopreservation And Patency Of Vein Allograft Truly Achievable?, G. Pasquinelli, G. L. Faggioli, P. Preda, M. Vici, G. N. Martinelli, R. Giardino, M. D'Addato, J. J. Ricotta

Cells and Materials

Despite extensive experimental work, neither the effect of long term cryopreservation on vein graft architecture nor the failure of alloveins due to graft rejection have yet been investigated. Herein, we investigated ultrastructurally: a) the integrity of rabbit jugular veins following 1, 2 and 3 months of cryopreservation; b) the outcome of the three-month cryopreserved vein auto- and allografts after 1 month of implantation in the rabbit carotid artery; and c) the immunologic response to cryopreserved vein allografts with and without seeded autologous endothelium. Prior to implantation, the cryopreserved rabbit veins were well-maintained except for endothelial cell damage. Following implantation, the …

Influence Of Crystal Structure On The Establishment Of The Bone-Calcium Phosphate Interface In Vitro, J. D. De Bruijn, C. P. A. T. Klein, K. De Groot, C. A. Van Blitterswijk

Cells and Materials

An in vitro rat bone marrow cell system was used to examine the interfacial ultrastructure established between various calcium phosphates and mineralized tissue. The investigated calcium phosphates comprised hydroxyapatite (HA), fluorapatite (FA), tricalcium phosphate (TCP), tetracalcium phosphate (TECP) and magnesium whitlockite (MWL). Both scanning and transmission electron microscopy were used to examine the elaborated interface. The time in which a mineralized extracellular matrix was formed on the various materials differed from 2 weeks on HA, TCP and TECP, to 8 weeks on FA. It was only occasionally observed in some areas on MWL, which might have been due to aluminum …

Degradation Of Polymeric Biomaterials, Shalaby W. Shalaby, Russell A. Johnson, Meng Deng

Cells and Materials

Environmental and processing factors affecting the biostability of medical devices made from traditionally "stable" polymers, such as isotactic polypropylene (PP) and ultrahigh molecular weight polyethylene (UHMW-PE) , were analyzed and their undesirable degradation was related to performance of typical medical devices. Among the critical phenomena determining the biological performance of UHMW-PE and PP devices are oxidation during melt-processing and the propensity of the polymer chains to radiolyse and radio-oxidize. Polyesters and their biomedical devices , which can be designed to degrade predictably, are addressed with some focus on the less obvious determinants of performance.

Osteoclastic Resorption Of Calcium Phosphate Ceramic Thin Films, J. E. Davies, G. Shapiro, B. F. Lowenberg

Cells and Materials

Sub-micron calcium phosphate ceramic thin films were formed by vertically dipping transparent quartz plates in a particulate sol-gel suspension. Primary adult rat bone marrow cell populations were cultured on the ceramic thin films in conditions known to allow the differentiation of cells of the osteoclast lineage. Monitoring the cultures for periods of 11 to 28 days revealed the creation of resorption lacunae in the thin films by multinucleate cells. Some cultures were heated at 42 °C overnight to remove adherent cells; using bright field light microscopy (LM), after staining with silver nitrate, the degree of resorption could be easily assessed. …

Anisotropic Secondary Electron Emission From Si(100) Surface Observed By Ultrahigh Vacuum Scanning Electron Microscopy, Yoshikazu Homma

Scanning Microscopy

The effect of surface atomic structure on secondary electron (SE) emission from a Si(100)2 X 1 surface is studied using an ultrahigh vacuum scanning electron microscope with an SE detector having angular resolvability. The double domain structure, alternate 2 X 1 and 1 X 2 domains, can be clearly imaged by SEs, indicating that the SE emission varies with the orientation of dimer rows on Si(100) surface: higher intensity in the direction parallel to the dimer rows and lower intensity in the perpendicular direction. The present results demonstrate that the SE emission is greatly influenced by the atomic configuration in …

Transmission Electron Microscopy And Nanoprobe Analysis Of Ferroelectric Thin Films, Maria Huffman, Mowafak M. Al-Jassim, Chuck Echer

Scanning Microscopy

Thin-film ceramic materials have a variety of electronic applications. Several deposition techniques are currently being used to produce such films with specific properties. For example, rf-sputtered ferroelectric perovskite films, with total thicknesses less than 0.5 μ.m, are being integrated with semiconductor devices as elements for non-volatile memories. Since there is a definite need to characterize these thin films after deposition, electron microscopy has been utilized as one of the most powerful techniques available for examining their morphology and microstructure. Transmission electron microscopy (TEM) examination of these oxides proved difficult. New TEM sample preparation techniques had to be developed in order …

X-Ray Topography, A. Zarka

Scanning Microscopy

The purpose of this paper is to discuss some elements of dynamical theory and to introduce some basic ideas on defect image formation in X-ray topographs. After some explanations of the basic principles of dynamical theory of X-rays, examples of defect contrast are given. Two examples of studies of quartz single crystals by X-ray topography are developed. First, the analysis of the X-ray spherical wave topographs of various Y-cut plates of synthetic quartz crystals show that the coherence of the lattice between the seed and the grown crystal is directly related to the density of the dislocations present in the …