Biology Commons^™

Tooth Enamel Structure In The Koala, Phascolarctos Cinereus: - Some Functional Interpretations, William G. Young, Maria Mcgowan, Terrence J. Daley

Scanning Microscopy

The purpose of this study is to determine whether the structural organization of Pattern 2 marsupial enamel in the Koala is disposed to resist wear on the sectorial crests of the molar teeth. The orientation of wear on the crests is uniformly delineated by parallel scratches on their polished surfaces. Twin blades, a leading and a trailing edge of enamel are formed on each crest by wear into dentine on which the differential wear at enamel to dentine interfaces indicates that the direction of wear is labial to lingual.

96 leading and trailing edges from 12 koala molars were examined …

Industrial Problem Solving With Microbeam Analysis, Klara Kiss

Scanning Microscopy

The objective of this paper is to provide an overview of the microbeam analytical techniques and to help select the appropriate one to solve complex problems often arising in today's high - tech industries. case histories are given to show how renowned analytical service laboratories and microbeam experts formulated their strategies to approach a real life problem, what type of conclusions were deduced from the data and, finally, how the problem was solved.

Numerical Approaches To Non-Destructive Depth Profiling By Variable Angle X-Ray Photoelectron Spectroscopy, P. C. Mccaslin, V. Young

Scanning Microscopy

Variable angle x-ray photoelectron spectroscopy (VAXPS), also known as angle-resolved x-ray photoelectron spectroscopy (ARXPS), is a method which can be used to depth profile the near surface region non-destructively. The intensity variation with angle of a given energy level in a sample contains the complete information about the concentration profile of the photoionized component in the depth probed. It has been shown that the intensity is the Laplace transform of the concentration profile. Theoretically it should be possible to uniquely determine the concentration profile as the inverse Laplace transform of the intensity data. After a brief background sketch, the numerical …

Interactions Between A Condensed Target And A Non-Equilibrium Plasma: Acid-Base Reactions At The Interface, J. Amouroux, J. L. Brisset, A. Doubla, A. Gicquel, A. Goldman, F. Rouzbehi

Scanning Microscopy

A new approach of plasma processes of industrial use is presented, with emphasis on the chemical properties of the plasma gas. Reactions occurring at the gas/target interface are for the first time interpreted in terms of acid-base reactions and pertinent examples are given of laboratory experiments and of industrial treatments (e. g., etching, plasma polymerization or surface modification processes). Proton exchanges between the plasma phase and an aqueous target gives evidence of Bronsted acid-base phenomena. Illustrations of Lewis acid-base characters are provided by the role of biradicals (e.g., halogenocarbenes, nitrenc) which are the main reacting species in etching or in …

Somites And Axon Guidance, Kathryn W. Tosney

Scanning Microscopy

The somites are arrayed in a repeating pattern along the longitudinal axis of the embryo, as are the developing sensory and sympathetic ganglia and the spinal nerves. This pattern is not a coincidence: the somite imposes a segmental pattern on the cells and axons that invade it. Both neural crest cells and axons prefer the anterior portion of the sclerotome (the ventral part of the somite) for outgrowth. What differences in anterior and posterior sclerotome are responsible? I used scanning electron microscopy to ask whether these populations differed on the tissue level in chick embryos. This study shows that differences …

Evolutionary Aspects Of Reptilian And Mammalian Enamel Structure, A. Sahni

Scanning Microscopy

The evolution of enamel structure is dealt with here on the basis of fossil reptiles and mammals ranging from the Triassic to the present. The evidence suggests that prismatic enamel had developed in some therapsid reptiles and the mammal, Eozostrodon about 180 million years ago. For the next 100 million years, mammalian evolutionary history is sparingly documented and this is reflected in the poor record of enamel evolution during this period. The few Jurassic reptiles and mammals studied suggest a pre-prismatic structure. In the Late Cretaceous (BO to 65 million years ago) when the fossil record improves, mammalian enamel investigated …

The Use Of Silver Nitrate Staining And Backscattered Electron Imaging To Visualize Nematode Sensory Structures, D. J. Vanderburgh, C. A. Ackerley, D. H. Lynn, R. C. Anderson

Scanning Microscopy

Parasitic nematodes of the species Cosmocercoides variabilis were stained with silver nitrate and examined with backscattered electron imaging (BEI). Sensory papillae were selectively highlighted in backscatter images. Silver stain deposited on papillae was located on the papillary surface as well as on the underlying dendritic process. Portions of the body cuticle were also stained. Some cuticular staining was attributed to non-specific deposition of silver but, consistent patterns of cuticular staining were noted in the anterior and posterior regions. This observation suggests that some staining of the cuticle was specific. Results of this preliminary work suggest that BEI is a technique …

Megakaryocyte Motility And Platelet Formation, Robert M. Leven

Scanning Microscopy

The mechanism of platelet formation is reviewed with special emphasis on the role of the cytoskeleton. The three major theories for platelet formation are by cytoplasmic budding, cytoplasmic dissolution or pseudopod formation. Most evidence indicates that platelets form as fragments of megakaryocyte pseudopodia. Pseudopodia formation is stimulated in vitro by thrombocytopenic rabbit plasma. It is inhibited by vincristine and altered by taxol. Cytochalasins cause pseudopodia to form in isolated megakaryocytes. Therefore, normal pseudopodia formation may depend on a combination of microfilament disorganization and microtubule elongation.

Optical Emission And Laser Spectroscopy In Studies Of Sputtering: Actual Research Activities And Recent Achievements, W. Husinsky, G. Betz

Scanning Microscopy

Laser Spectroscopy has been developed into a powerful tool for the detection and energy analysis of neutral particles. Laser Induced Fluorescence Spectroscopy (LIF) has yielded a wealth of information about sputtered neutral particles. In addition, Laser Ionization Spectroscopy has recently offered an increased detection sensitivity. In this paper a summary of recent results is given. By combining LIF with other methods capable of measuring densities and energy distributions of sputtered excited atoms in short lived states, new information about sputtering and excitation mechanisms have been recently obtained and will be summarized here.

Scanning Electron Microscopy Application In Clinical Research, R. Laschi, G. Pasquinelli, P. Versura

Scanning Microscopy

Our personal experience on the application of scanning electron microscopy in cardiology, gastroenterology and ophthalmology is reviewed.

SEM has not yet significantly contributed to myocardium pathology. However, in the near future, SEM could be a reliable technique to complete the information available from other sources. As to atherosclerosis, SEM allowed us to improve our knowledge of the early stages of the disease; some pathological features, not always detected by conventional morphological examinations, can be documented. An important contribution to gastrointestinal pathology was made by SEM investigations both in the staging of some important diseases (i.e., coeliac disease, peptic ulcer, Crohn's …

Proton Energy Loss Spectroscopy For Surface Monolayer Analysis, Noriaki Matsunami

Scanning Microscopy

A survey is given of recent advances in the use of high-energy proton backscattering spectroscopy or proton energy loss spectroscopy (PELS) under the glancing incidence geometry for monolayer-sensitive analysis. Two theories of the energy loss involved in the PELS are described, based on the continuous and impact parameter dependent slowing down models. The latter theory leads to the azimuthal angle dependence of the energy loss. It is also shown that this technique is applicable to underlayer composition analysis

The Normal Structure Of Regional Feline Gastric Mucosae: Scanning Electron Microscopic Study, M. Al-Tikriti, F. Al-Bagdadi, R. W. Henry, J. Hoskins, C. Titkemeyer, G. Strain

Scanning Microscopy

Regions of cat's stomach can be identified by looking at the surface epithelial cells by scanning electron microscopy (SEM). The luminal surface of cells of the cardiac region were elongated, of the fundus rounded, of the corpus polygonal shaped, and of the pyloric region diamond shaped. The quantity and distribution of microvilli covering the epithelial cells varies, being abundant and evenly distributed in the cardiac region and gradually decreasing in number toward the gastro-duodenal junction, where they were confined to cell perimeters. The colliculi varied in shape and distribution from few in the fundus and corpus to numerous in the …

Analysis Of Thick Targets By Proton-Induced X-Ray Emission, J. L. Campbell, A. Perujo, W. J. Teesdale, J. A. Maxwell

Scanning Microscopy

Most published PIXE (proton-induced X-ray emission) work concerns thin targets. Recently progress in improving both the fundamental data base and in developing a range of standardization techniques has propelled thick target analysis to the forefront of activity in the PIXE field. Limits of detection are a complex issue depending not only on the continuous background but also on the characteristic X-rays of the matrix; in favorable cases a few ppm may be reached in convenient analysis times. The unfolding of multi-element PIXE spectra is akin to the same problem in EPMA (electron probe microanalysis), and EPMA methodologies, especially as regards …

Microvascular Corrosion Casting Of The Lung. A State-Of-The-Art Review, Dean E. Schraufnagel

Scanning Microscopy

Corrosion casting and viewing of replicas with the scanning electron microscope is an excellent way to study the microvascular structure of the lung. This method can demonstrate aspects of the three-dimensional relationships, branching patterns, maximum diameters, arterio-venous connections, unusual sized and shaped capillaries, development and growth, neovascular structures and changes in development and disease better than any other means. Comparisons can be made in many experimental conditions and fundamental information obtained to answer physiologic questions. This paper reviews how the lung microvasculature has been studied by corrosion casting and scanning electron microscopy and indicates new areas where investigation might be …

Scanning Electron Microscopy Of Black Stain On Human Permanent Teeth, J. Theilade, K. M. Pang

Scanning Microscopy

Black stain may develop on the coronal surfaces of human teeth, and this type of stain is common in the Hong Kong Chinese population. The present study was undertaken to ascertain if the deposit conforms in composition to the black stain found elsewhere, and to describe its ultrastructure using the scanning electron microscope. Gram-stained smears were made from black stain on the teeth of 11 adult Hong Kong Chinese and studied microscopically. From another 15 persons extracted teeth exhibiting black stain were obtained and fixed. Two ground sections were made from each tooth, one was stained with toluidine blue, the …

Secretory Ameloblasts And Calcium Distribution During Normal And Experimentally Altered Mineralization, S. H. Ashrafi, Dale R. Eisenmann, A. E. Zaki

Scanning Microscopy

The distribution of calcium in relation to secretory ameloblasts of the rat incisor was studied. An experimental model system in which enamel mineralization was temporarily inhibited by injecting sodium fluoride and cobalt chloride was used. Potassium pyroantimonate (PPA) cytochemistry, electron energy loss spectroscopy (EELS), and energy dispersive X-ray spectrometry (EDS) were used to clarify the role of the ameloblast in controlling calcium distribution during normal and experimentally altered enamel mineralization.

Secretory ameloblasts chemically-preserved in glutaraldehyde either with or without PPA were analyzed for calcium; those preserved with PPA showed higher concentrations of calcium than did those preserved with glutaraldehyde only. …

Fictitious Calculi And Human Calculi With Foreign Nuclei, P.-T. Cheng, K. P. H. Pritzker, J. Richards, D. Holmyard

Scanning Microscopy

The correlative approach employing polarized light microscopy, x-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and energy dispersive x-ray microanalysis proves to be very useful in identifying fictitious calculi and genuine human calculi with foreign body nuclei. The common artifacts as reported in the literature and observed also by us were minerals, vegetable and plant seeds, cereals, sand grains and sea shell fragments.

Two interesting cases involving foreign body nuclei have been reported: one urinary calculus containing a piece of plastic-coated titanium foil in the center; one nasal calculus with a nut as a nucleus. …

Effects Of Fractionated Irradiation On The Esophageal Mucosa: A Scanning And Transmission Electron Microscopic Study, M. Albertsson, C-H Hakansson, C. Mercke, H. Morner

Scanning Microscopy

The mucosa of rabbit esophagus was irradiated with daily fractions of 2 Gy to an accumulated dose of 20 Gy. Specimens were taken for scanning electron microscopy, transmission electron microscopy and light microscopy investigations. Examination was made 1-10 days after each fractionation schedule. Light microscopy showed dose-dependent edema of the irradiated mucosa which also could be seen and scored from SEM pictures. SEM investigations showed that this was accompanied by loosening of microridges and a slightly increased cell loss. By SEM, a varying amount of bacteria could be seen which did not make intimate contact with the surface cells.

During …

Effects Of Cis-Dichlorodiammineplatinum Alone And In Combination With Ionizing Radiation On The Esophageal Mucosa: A Scanning And Transmission Electron Microscopic Study, M. Albertsson, C-H Hakansson, C. Mercke

Scanning Microscopy

Cis-dichlorodiammineplatinum (cis-DDP) has for more than 20 years been part of the therapeutic arsenal of oncology. Most of the knowledge about its biological action is based on clinical investigations and therefore an examination of the influence of cis-DDP at the cellular and sub-cellular level is necessary. Five mg of cis-DDP was given intraperitoneally (i.p.) to ten rabbits. Ultrastructural examinations were performed on the upper and lower parts of the esophagus each day after the injection on the following ten days. Another 50 rabbits were given 5 mg cis-DDP and were irradiated in an area just beneath the hypopharynx. They were …

Channel Plate Detection In Low Energy Scanning Electron Microscopy, H. F. Helbig, R. D. Rydgren, L. Kotorman

Scanning Microscopy

Microchannel plate (MCP) electron detectors compare favorably with the Everhart-Thornley detector for producing SEM images from both secondary and back-scattered electrons. The MCP is a compact array of 10⁵ - 10⁶ channel electron multipliers with a gain in excess of 10⁶ and the collective ability to count ~ 10⁸ electrons per second. The MCP can be mounted coaxially with the beam allowing un-tilted sample orientation and electron collection into a large, field-free solid angle. The speed and low noise of the MCP allow images to be made in less than one second at moderate beam currents …

Scanning Electron Microscopy Of Vertebrate Cerebellar Cortex, Orlando J. Castejón

Scanning Microscopy

In this study, the Golgi method for light microscopy, transmission and conventional scanning electron microscopy, the ethanol-cryofracturing technique, the freeze-fracture method for SEM, and the freeze-etching method have been used in conjunction to analyze the three-dimensional cytoarchitectonic arrangement and intracortical circuits of vertebrate cerebellar cortex. Approximately more than 100 specimens of mice, rat, teleost fishes and human cerebelli were processed by the above mentioned techniques. A chronological review of other methods for studying hidden surfaces of cerebellar nerve cell has been also described. The three-dimensional morphology, outer and inner surfaces of granule, Golgi, Purkinje and stellate cells were reviewed by …

Surface Roughening Studies By Field Emission, R. Gomer, Y. M. Gong

Scanning Microscopy

Measurements of surface self-diffusion by the field emission fluctuation method along the zones (011)-(112) and (011)-(001) of a tungsten emitter show both 2 and I dimensional diffusion, attributed to diffusion of W atoms on the terraces and of kinks along the edges of the stepped surfaces found in these zones. At 950 K -1000 K the steps along (011)-(112) disorder completely, as indicated by the merging of the two types of diffusion into a single, 2-dimensional regime. Along (011)-(001) definite transitions can only be seen on (023) and (017). The transition temperatures are much lower, ~750 K.

An Algorithm For On-Line Digital Image Processing For Assisting Automatic Focusing And Astigmatism Correction In Electron Microscopy, Norio Baba, Eisaku Oho, Koichi Kanaya

Scanning Microscopy

An algorithm for processing a diffractogram of an electron image input by an on-line system has been improved, with the aid of projection theory, so as to achieve real time operation. This algorithm can, therefore, automatically focus in scanning electron microscope, and correct for the astigmatic aberration of both transmission and scanning electron microscopes by analyzing the spectrum computed from the diffractogram. Experimental results show that this algorithm is effective for detecting the amount of defocus and astigmatism in both transmission and scanning electron microscopes.

Characteristics Of An Electric/Magnetic Quadrupole Detector For Low Voltage Scanning Electron Microscopy, M. Brunner, R. Schmid

Scanning Microscopy

The electric/magnetic quadrupole detector allow's efficient detection of secondary electrons in low voltage scanning electron microscopy without introducing disturbing aberrations. The original detector of this type was built in 1986; it has now been equipped with scintillator-photomultiplier assemblies on both positive electrodes. Their signals, A and B, can be combined to A+B or A-B, thus enhancing or suppressing different types of contrast. The aberration disc produced by the present design of detector was estimated to have a diameter of 10 nm. Experimentally, no deterioration of image resolution was observed. The collection efficiency was predicted to be 26% and can be …

An Electron Microscopic Study Of Microfibrils Of Bone Marrow, Ferrell R. Campbell

Scanning Microscopy

After fixation of bone marrow with glutaraldehyde, tannic acid and saponin, a delicate network of microfibrils (10 nm) was observed in the extracellular space. Masses of microfibrils were most frequently observed between the endothelial cells of the sinusoidal wall and adventitial reticular cells, but were also observed at other sites throughout the marrow stroma. Microfibrils are an important component of the extracellular material of bone marrow and appear to provide an anchoring substrate for the endothelium.

Quasi-Elastic Scattering Studies Of Water Diffusion, H. E. Rorschach, D. W. Bearden, C. F. Hazlewood, D. B. Heidorn, R. M. Nicklow

Scanning Microscopy

Quasi-elastic neutron scattering is a powerful method to study the dynamics of protons in biological systems. The technique has been used both for the study of water diffusion and protein motion. The neutron scattering measurements on water show that the translational and rotational diffusion coefficients in biological systems are reduced from bulk values. We review the measurements on water in frog muscle, cysts of artemia, and phycocyanin. Measurements on dry trypsin and trypsin-D₂O solutions over the temperature range 75-300K show that there is proton motion at the one angstrom level even in the dry or frozen state.

Ultrastructure Of Spermatozoa From Domesticated Birds: Comparative Study Of Turkey, Chicken And Guinea Fowl, R. J. Thurston, R. A. Hess

Scanning Microscopy

Typical for non-passerine birds, the spermatozoa of the turkey, chicken and guinea fowl were vermiform with a maximum width of 0.5-0. 7μm and lengths of 90μm for chicken sperm, and 75-80μm for those of the turkey and guinea. An acrosome, nucleus, midpiece and flagellum could be distinguished by SEM.

The acrosomal cap projected over a perforatorium surrounded by granular material. At its base, the cap encircled apical projections of the nucleus. The nucleus consisted of dense chromatin, and formed a concave implantation fossa where it joined the midpiece of the tail. For turkey and chicken spermatozoa, the neck region of …

Secondary Electron Emission Induced By Electron Bombardment Of Polycrystalline Metallic Targets, R. Bindi, H. Lanteri, P. Rostaing

Scanning Microscopy

The aim of the present paper is the analysis of the backward secondary electron emission phenomenon, under electron bombardment, on the basis of experimental and theoretical results. Among the theoretical models, we will mention the phenomenological models, those which use a Monte-Carlo type simulation method, and those based on the numerically solved Boltzmann transport equation.

To correlate experimental and theoretical results on all the data characterizing this phenomenon, it is necessary to use an appropriate description for the excitation process of the internal secondary electrons; it also needs a complete description of the transport process for the excited electrons, which …

External Shape Of Enamel Crystals, H. Warshawsky

Scanning Microscopy

Biological hydroxyapatite crystals are either small, as in bone and dentin, or large as in enamel. Enamel crystallites are unique since each is initiated and grows in length, thickness and width until the entire layer of enamel is secreted. In maturation, these extremely long crystallites grow only in thickness and width. Crystal growth in vitro follows physico-chemical principles, but lacks biological intelligence; in vivo this intelligence is contributed by protein templates. The location of the organic template in enamel is congruent with the crystallite, constituting the crystal ghost. Since crystals cannot accommodate proteins, the explanation is logically inconsistent. In sections, …

X-Ray Microanalysis Of Cells In Suspension And The Application Of This Technique To The Study Of The Thymus Gland, A. Warley

Scanning Microscopy

Although X-ray microanalysis has become a well established technique in the study of tissues there are still relatively few papers reporting results from cells in culture. Our early investigations on freshly isolated murine thymocytes reported higher than expected concentrations of Na and Cl in these cells but subsequent studies have shown that these high concentrations are artefactual. Rat thymocytes that have been isolated and incubated for a short time to allow them to recover from the isolation procedure have lower concentrations of Na and Cl. Sections prepared from pellets of cells which have been concentrated by centrifugation in a microhaematocrit …