Biology Commons^™

Heterogeneous Nucleation Of Calcium Oxalate Crystals In Mammalian Urine, Saeed R. Khan

Scanning Microscopy

It is generally recognized that calcium oxalate crystal formation in urine is induced by heterogeneous nucleation. However, there is no consensus as to the nature of the nucleation substrate. Evidence is provided in this paper that membranous cellular degradation products are the most likely candidates because they: (1) are ubiquitous in urine and urinary stones; (2) are found in close association with crystal deposits in the kidneys; and (3) can induce nucleation of crystals from a meta-stable solution of calcium oxalate in vitro and metastable urine in vivo.

Imaging Of The Cytoplasmic Leaflet Of The Plasma Membrane By Atomic Force Microscopy, C. Le Grimellec, E. Lesniewska, M. -C. Giocondi, C. Cachia, J. P. Schreiber, J. P. Goudonnet

Scanning Microscopy

The cytoplasmic face of ventral cell membranes of Madin-Darby canine kidney (MDCK) cells grown on glass coverslips was imaged by atomic force microscopy (AFM) in air and under aqueous medium, in "contact" mode. Micrometer range scans on air-dried samples revealed a heterogeneous structure with some filaments, likely corresponding to actin filaments that abut the inner leaflet of the membrane, and a few semi-organized lattice structures that might correspond to clathrin lattices. Experiments in phosphate-buffered saline confirmed the heterogeneity of the inner membrane surface with the presence of large (> 100 nm) globular structures emerging from the surface. Using sub-micrometer scan …

Heterogeneous Distribution Of Ecto-Ca-Atpases In Primary Cultures Of Human Adenohypophyseal Cells, A. Kittel, I. Miklos, E. Bacsy

Scanning Microscopy

The aim of this study was to investigate the localization of ecto-Ca-adenosine-triphosphatase (ecto-Ca-ATPase) in different parenchymal cells of the human pituitary in tissue culture. The distribution of ecto-ATPases on the surface membrane of a particular parenchymal cell varied with the type of cells in contact with this parenchymal cell; the membrane portions immediately exposed to the medium showed low if any ecto-ATPase activity. These results suggest that ecto-Ca-ATPases of the parenchymal cells may be involved in cell adhesion processes and may be of crucial importance in the organization (in vivo) and reorganization (in vitro) of human …

Scanning Electron Microscope Study Of The Healing Molar Tooth Extraction Socket In The Rat, M. D. Mcmillan

Scanning Microscopy

Healing molar tooth extraction wounds in rats were examined by scanning electron microscopy from 15 minutes to 40 days following tooth removal. The wound epithelium, which was derived mainly from the gingiva but also from the cheek and hard palate, migrated be-neath the superficial socket contents. The contents were lost between 5 to 11 days, thus leaving a central epithelial-lined depression. This decreased in width with time as the level of the wound epithelium approached that of the hard palate but was still present at 40 days. Between 5 and 7 days, the wound epithelium became more regular. However, from …

The Interaction Of Laser Energy With Ureter Tissues In A Long Term Investigation, U. Stratmann, K. Schaarschmidt, R. R. Lehmann, A. Heinze, G. H. Willital, E. Unsold

Scanning Microscopy

This study investigates tissue responses after laser irradiation of the rabbit ureter, which serves as an experimental model for rectourogenital fistulae of children. Twenty-five rabbit ureters were irradiated intraluminally by a Nd:YAG laser 1320 nm (2 Watt, 20 seconds and 3 Watt, 8 seconds) via an applicator with radialsymmetrical light distribution. Immediately, 2 weeks, 4 weeks, 8 weeks, and 16 weeks after irradiation, the ureters were X-rayed with contrast solution and prepared for light and transmission electron microscopy. For the parameters employed, no apparent morphological differences could be observed. Immediately, the central laser zone showed a transmural therrnonecrosis prevailed by …

Imaging Of Single Antigens, Antibodies, And Specific Immunocomplex Formation By Scanning Force Microscopy, Arjan P. Quist, Anna A. Bergman, Curt T. Reimann, Sven O. Oscarsson, Bo U. R. Sundqvist

Scanning Microscopy

The most sensitive analytical techniques available today for detecting immuno assay complexes are radio or enzyme immuno analytical techniques, by which quantities of 10⁷-10⁸ analyte molecules can be detected. With the introduction of scanning force microscopy, a new method for detecting biological processes became available. Here, we examine the feasibility of using scanning force microscopy as a biosensitive tool. We demonstrate that single or multiple rabbit anti-human serum albumin molecules form complexes with preadsorbed single human serum albumin molecules on mica. However, no interaction is observed between human immunoglobulin G molecules and preadsorbed single albumin molecules; only …

Simulation Of Electron Emission From Beryllium Under Electron And Ion Bombardments, Kaoru Ohya, Jun Kawata

Scanning Microscopy

A Monte Carlo simulation model of particle-induced electron emission from beryllium, a candidate material for use on the wall in thermonuclear fusion devices, is developed. Comparative studies between secondary electron emission by electron bombardment and kinetic electron emission by proton bombardment reveal some interesting similarities and differences. The kinetic emission of electrons under heavy-ion bombardment is simulated as well for analyzing the effect of the initial charge state and mass of projectile ions on the kinetic emission. Furthermore, the model is applied to bowl-and-ripple structures for the study of surface roughness effects on the energy and angular distributions of secondary …

Dynamics Of Vortices In Superconductors Observed By Electron Waves, Akira Tonomura

Scanning Microscopy

Although, in electron microscopy, an object is usually observed by using the intensity of an electron beam transmitted through it, the phase distribution of the electron beam also provides different information about the object. It has been difficult, however, to obtain the phase information because of the low coherence of an electron beam. Recent development of a "coherent" field emission electron beam and related techniques, such as electron holography, has provided a way to observe microscopic objects and fields by precisely measuring the phase information of an electron beam. It has, for example, become possible to observe the dynamics of …

Scanning Force Microscopy Of Chromatin, Wolfgang Fritzsche, James Vesenka, Eric Henderson

Scanning Microscopy

Scanning force microscopy (SFM) is a new method to obtain the topography of surfaces with nanometer-resolution. The ability to image under liquids makes the technique attractive for biological applications, especially for the determination of the ultrastructure of biomolecules under native conditions. One growing field of interest is the investigation of chromatin and chromatin-related structures. Different levels of chromatin condensation were the subject of several previous SFM investigations, from the nucleosomal chain, to the 30-nm fiber, ending with the metaphase chromosome. The SFM yielded new information on such fundamental problems as the core spacing of the nucleosomal chain, the internal structure …

The Ampullae Of The Inner Ear In The Lizard Podarcis S. Sicula. Ultrastructural Aspects, G. Balsamo, B. Avallone, D. Calabro, F. Marmo

Scanning Microscopy

The inner ear ampullae of the lizard Podarcis s. sicula were studied to determine better the ultrastructure of ampullar epithelial cells.

Our study confirmed that the ampullae of the membranous labyrinth of this lizard are similar to those of other vertebrates in their ultrastructural aspect.

Moreover, our observations revealed a special type of dark cells, restricted to a small area of the crista. They appeared similar to type II sensory cells and showed a dark, finely granular cytoplasm, containing numerous mitochondria and ribosomes, extensive Golgi apparatus and abundant glycogen.

The morphology of these cells suggests that they may be …

Scanning Tunneling Microscopy Studies Of Chloroplasts In Solution, Douglas C. Dahn, Katrina Cake, T. Lynn Macdonald, Lawrence R. Hale

Scanning Microscopy

Previous work has shown that it is possible to image whole uncoated chloroplasts using scanning tunneling microscopy (STM), provided this is done in solution using tunnelling currents below about 100 pA.

More recent images include some which suggest that the STM is sensitive to dynamic processes occurring on chloroplast surfaces. Current-versus-distance curves and dI/ds measurements are consistent with tunnelling between the tip and sample surface, and relatively small deformations of the sample surface due to tip-sample forces. Attempts to use the same imaging conditions on bacteria were unsuccessful.

Mammalian Enamel Prism Patterns And Enamel Deposition Rates, Elizabeth R. Dumont

Scanning Microscopy

Enamel prism patterns and enamel deposition rates were compared for specimens representing six mammalian orders. Enamel samples were characterized by either pattern 1 or pattern 3 prisms. Each prism pattern cate-gory contained prisms from at least two mammalian orders. Enamel deposition rate was estimated for each sample by measuring prism cross striation repeat intervals. Statistical analysis of cross striation repeat intervals illustrates significant differences in deposition rate between prism patterns 1 and 3. No statistically significant differences were found in deposition rate between the higher-level taxa represented within each prism pat-tern category. That enamel deposition rate is not taxon-specific reinforces …

Low Concentrations Of Mercury Induce Changes In Ion Composition Of Cultured Myoblasts, Joanna Wroblewski, Jan Ekstrand, Romuald Wroblewski

Scanning Microscopy

The effects of low concentrations (1 pM, 1 nM, 1 μM) of mercuric chloride on ion distribution in cultured myoblasts were analysed by energy dispersive X-ray microanalysis. An increase in intracellular sodium concentration was observed five minutes after addition of HgC12 to the culture medium. This increase was dose dependent and accompanied by a transient decrease in potassium concentration. Exposure to 1 nM and 1 μM HgC12 led to a two-fold increase in the cytoplasmic chlorine concentration. The higher HgC12 concentration (1 μM) induced morphological alterations in the form of cell membrane blebs, perforations and shrinkage or flattening of the …

Cross-Linking Of Cell Surface Receptors As A Trigger Of Cell Apoptosis And Proliferation, Yuri N. Korystov

Scanning Microscopy

A hypothesis of the mechanism by which the protein cross-linking agents trigger apoptosis of lymphoid cells and proliferation of other cell types is proposed. It is assumed that both effects are triggered by aggregation of receptors on cell surface, which results from their cross-linking. This idea is substantiated by the example of one of these agents, ionizing radiation. As in the case of physiological agents, such as, antigens and growth factors, the aggregation of receptors induced by radiation activates receptor protein tyrosine kinases from which the signal is transduced to genes through protein kinase C. The hypothesis is consistent with …

From Scattering And Recoiling Spectrometry To Scattering And Recoiling Imaging, M. M. Sung, V. Bykov, A. Al-Bayati, C. Kim, S. S. Todorov, J. W. Rabalais

Scanning Microscopy

A new ion scattering technique, called scattering and recoiling imaging spectrometry (SARIS), is being developed. The SARIS technique uses a large, position sensitive microchannel plate (MCP) and time-of-flight methods to capture images of scattered and recoiled particles from a pulsed ke V ion beam. These images combine the advantage of atomic scale microscopy and spatial averaging simultaneously since they are created from a macroscopic surface area but they are directly related to the atomic arrangement of the surface. This paper de-scribes the basis of the SARIS technique, the instrument which is under development, and the scattering and recoiling …

Vitamin E Deficiency As A Model Of Precocious Brain Aging: Assessment By X-Ray Microanalysis And Morphometry, Carlo Bertoni-Freddari, Patrizia Fattoretti, Ugo Caselli, Roberta Paoloni, William Meier-Ruge

Scanning Microscopy

Vitamin E (α-tocopherol) is a known biological antioxidant able to quench the lipid peroxidation chain and to protect the cellular structures (e.g., plasma membranes) from the attack of free radicals which are reported to play a primary role in aging. To assess whether the absence of α-tocopherol from the diet of young laboratory animals may be considered a reliable model of precocious brain aging, intracellular ionic content of brain cortex pyramidal cells, ultrastructural features of synaptic contact zones, synaptic mitochondria and perykarial mitochondria positive to the succlillc dehydrogenase (SDH) histochemical reaction with copper ferrocyanide have been investigated by X-ray microanalysis …

High Resolution Electron Microscopy Of The Interface Between Dental Calculus And Denture Resin, Yoshihiko Hayashi

Scanning Microscopy

Dental calculus may grow on the denture surface. In order to demonstrate the mechanism of deposition, the interface between calculus and denture resin was investigated using a high resolution electron microscope. Ultrathin sections were also used for electron diffraction of selected areas to reveal any mineral phase.

The mineral layers without mineralized bacteria adjacent to the denture surface revealed a marked variation in thickness and crystal shape. Three types of crystal shape were observed at the junction: needle-like, rod-like and plate-like crystals. High resolution electron microscopy (HREM) showed that both rod-like and plate-like crystals were an aggregation of fine crystallites. …

The Influence Of 5-Fluorouracil On The Endothelium In Small Arteries. An Electron Microscopic Study In Rabbits, M. Cwikiel, B. Zhang, J. Eskilsson, J. B. Wieslander, M. Albertsson

Scanning Microscopy

5-Fluorouracil (5-FU) is a widely used antineoplastic agent. 5-FU induced cardiotoxicity is a still relatively unknown side-effect of this drug. This phenomenon could be due to a direct cytotoxic effect on the endothelial cells. We tested this hypothesis in an experimental study in rabbits, by scanning or transmission electron microscopic evaluation of endothelium in small arteries (the central artery of the ear) after in vivo treatment with 5-FU. Both local and systemic effects of 5-FU on endothelium were studied 15, 30, 60 and 120 minutes after intra-arterial or intraperitoneal treatment. Perfusion fixation at physiological pressure and temperature was used in …

Cathodoluminescence Contrast Of Localized Defects Part I. Numerical Model For Simulation, K. L. Pey, D. S. H. Chan, J. C. H. Phang

Scanning Microscopy

A three-dimensional model has been developed for cathodoluminescence contrast of localized defects in semiconductors. The numerical model incorporates electron-solid interaction effects, charge transport phenomena and optical losses. Electron-solid interaction is modelled by a Monte Carlo method. Three-dimensional continuity equation and derivative boundary conditions are discretized by a central-difference quotients scheme. Localized defects are represented by regions of enhanced non-radiative recombination. The discretized linear difference equations of the boundary value problem are solved by the successive-over-relaxation method. A method for avoiding the divergence problem during the successive-over-relaxation calculation is illustrated. The solutions of the model are compared with the analytical results …

Cathodoluminescence Contrast Of Localized Defects Part Ii. Defect Investigation, K. L. Pey, J. C. H. Phang, D. S. H. Chan

Scanning Microscopy

Cathodoluminescence contrast from defects with different geometrical and electronic properties have been studied using the numerical model developed in Part I. The contrast of a localized subsurface defect exhibits a maxima at a specific beam energy E_max which corresponds to the depth of the defect. The contrast of a dis-location which intersects the top surface perpendicularly is a decreasing function of beam energy. The differences in the image profiles of the two different kinds of defects allow the two types of imperfections to be distinguished. In addition, the resolution of a subsurface defect at beam energies lower than E …

Apoptosis Induced By Microtubule Disrupting Drugs In Normal Murine Thymocytes In Vitro, Vladimir Bumbaširević, Andjelija Škaro-Milić, Aleksandar Mirčić, Bogdan Djuričić

Scanning Microscopy

Disruption of cytoplasmic and spindle microtubules by colchicine or nocodazole increases mitotic index, but it also enhances apoptosis in isolated mouse thymocytes; the apoptotic index exceeds 20% after 4 hours of incubation with either drug (5% in controls). Apoptosis was confirmed by DNA fragmentation, and was blocked by calcium chelators and inhibitors of protein synthesis. The apoptotic effect of microtubule disrupting drugs (MOD) was directed to interphase thymocytes and was independent on MOD action on mitotic cells. However, cell death of mitotically arrested cells showed ultrastructural changes similar in many aspects to apoptosis.

Optical Microscopy And Atomic Force Microscopy Imaging Of 2,4,6-Trinitrotoluene Droplets And Clusters On Mica, D. O. Henderson, M. A. George, A. Burger, R. Mu, Zhiyu Hu, G. C. Huston

Scanning Microscopy

Optical and atomic force microscopy (AFM) were used to image 2,4,6-trinitrotoluene (TNT) on a cleaved mica (001) surface. The vapor deposition of TNT resulted in ellipsoidal drop formation on the mica surface. The growth rate of the drop diameter was found to be linear with vapor dosing time while the drop density followed a 1/r² dependence, where r is the length of the major axis of the ellipsoid, for increasing dosing times. TNT platelets surrounded by a region depleted of drops were observed after 8 hours of dosing. The depleted region is attributed to a 10% shrinkage for liquid-solid …

The Effect Of Arf-Excimer Laser Irradiation Of The Human Enamel Surface On The Bond Strength Of Orthodontic Appliances, U. Stratmann, K. Schaarschmidt, M. Schürenberg, U. Ehmer

Scanning Microscopy

This study investigated enamel laser conditioning as an alternative to acid etching in bracket therapy. In preliminary experiments optimal laser parameters for achieving a bond strength of 6-10 N/mm² were defined. Enamel surface morphology was assessed and the ablation depth was measured on serial enamel sections. Thirty human molars were exposed to 193 nm ArF-excimer laser radiation (energy density: 260 mJ/cm²) by single pulse application of 23 nanoseconds. Thirty molars were etched with phosphoric acid (37%) for 60 seconds. The brackets from the treated molars and 30 untreated molars were debonded vertically for tensile bond strength measurement. …

Cell Death In The Embryonic Developing Limb, J. M. Hurle, M. A. Ros, V. Garcia-Martinez, D. Macias, Y. Ganan

Scanning Microscopy

In amniote vertebrates, the development of form and structure of the limb bud is accompanied by precise patterns of massive mesodermal cell death with morphological features of apoptosis. These areas of cell death appear to eliminate undifferentiated cells which are required only for a limited time period of limb development. Predictable skeletal and morphological anomalies of the limb occur when the pattern of cell death is modified in mutant species or under experimental conditions. Most evidence points to the occurrence of local triggering mechanisms to account for the establishment of the areas of cell death and the subsequent activation of …

Alterations In Mdck And Llc-Pk1 Cells Exposed To Oxalate And Calcium Oxalate Monohydrate Crystals, R. L. Hackett, P. N. Shevock, S. R. Khan

Scanning Microscopy

Structural analysis of human kidney stones reveals the presence of cellular membranes and other cell fragments. Experimentally, calcium oxalate crystallization is facilitated when an exogenous nephrotoxin is given with ethylene glycol, thus providing cellular degradation products to act as heterogenous nuclei. In this report, we tested whether oxalate alone could act as a cell toxin capable of producing damaged cells without the presence of an exogenous agent. Cultured LLC-PK₁ and MDCK cells, when exposed to 1.0 mmol KOx, a concentration at the limit of metastability for calcium oxalate nucleation, were severely damaged as measured by specific lactate dehydrogenase (LDH) …

Radiation Nephropathy: A Review, M. E. C. Robbins, S. M. Bonsib

Scanning Microscopy

The marked radiosensitivity of renal tissue represents a limitation on the total radiotherapeutic dose that safely can be applied to treatment volumes that include the kidneys. Radiation nephropathy is characterized by a progressive reduction in renal hemodynamics associated with a severe anemia. The latter is often normochromic normocytic in character, but can progress to a microangiopathic hemolytic anemia. The pathogenic mechanisms responsible for the development of radiation nephropathy remain ill-defined. Experimental studies which allow serial determinations of functional, morphologic, and cell kinetic radiation-induced changes indicate that primarily glomerular but also tubular alterations occur in the primary stages of radiation nephropathy. …

A New Scanning Electron Microscopy Approach To The Quantification Of Bone Mineral Distribution: Backscattered Electron Image Grey-Levels Correlated To Calcium Kα-Line Intensities, P. Roschger, H. Plenk Jr., K. Klaushofer, J. Eschberger

Scanning Microscopy

The introduction of backscattered electron (BSE) imaging in scanning electron microscopy (SEM) has led to new possibilities for the evaluation of mineral distributions in bone on a microscopic level. The different grey-levels seen in the BSE-images can be used as a measure for the local mineral content of bone. In order to calibrate these BSE-grey-levels (BSE-GL) and correlate them to mineral contents, various attempts, using reference samples with known weighted mean atomic number and/or using simulated bone tissues with known hydroxyapatite concentrations, have been made. In contrast, a new approach is presented here based on measurements of the X-ray intensities …

Gold Coating Of Respiratory Cilia For Scanning Electron Microscopy, E. Toskala, J. Nuutinen, M. Rautiainen, A. Pelttari

Scanning Microscopy

The optimal thickness of gold coating of cilia for scanning electron microscopy was studied using respiratory mucosa obtained from pigs. We tested 8 different coating times, from 10 seconds to 4 minutes, which resulted in gold layer thicknesses varying from 16 ± 1 nm to 100 ± 3 nm. The thickness of the gold layer with a coating time of 60 seconds and voltage of 2.5 kV was 43 ± 5 nm. This thickness of gold layer gave good image quality without causing any electric charging. With thinner gold films, the amount of electric charging increased. When the coating time …

Early Elemental And Ionic Changes In Cultured Cells After Stimulation With Epidermal Growth Factor, Julian E. Beesley, Simon R. Hall, Martin J. Page, Karen Affleck

Scanning Microscopy

Stimulation of A43 l cells (a human vulval epidermal cell line) with 50 ng/ml of epidermal growth factor (EGF) in the presence of 1. 7 mM extracellular calcium produced a sharp and sustained rise in intracellular ionic Ca2+, increased elemental Na, decreased K and a rise in Ca. In the absence of extracellular calcium, the initial Ca2+ rise remained but the sustained elevation of intracellular Ca2+ was abolished, Na and K fluxes were variable and the Ca did not change. Increased Na and decreased K was marked at 2 minutes and returned to the control value after 60 minutes. The …

Scanning Electron Microscopic Observation Of Dark Cells After Streptomycin Perfusion Of The Vestibule In Guinea Pigs, Xianxi Ge, John J. Shea Jr.

Scanning Microscopy

Hearing has been stabilized in the majority of patients studied in the treatment of Meniere's disease with streptomycin. This observation suggests that effects of streptomycin may ameliorate endolymphatic hydrops, possibly by attenuating the activity of secretory tissue. The purpose of this study is to observe the dark cells of the utricle in guinea pigs after streptomycin perfusion of the vestibule. Twelve pigmented guinea pigs weighing 250-350 grams were used in this study. The vestibules in five guinea pigs were perfused monolaterally with 150 μg of streptomycin in artificial perilymph and, in seven, the vestibules were perfused only with artificial perilymph …