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Articles 36421 - 36450 of 39311
Full-Text Articles in Entire DC Network
Sulfur Accumulation In Xylem Tissue Of Forest Trees From Kentucky & Tennessee & Its Relation To Yearly Growth, Jennifer Sharp
Sulfur Accumulation In Xylem Tissue Of Forest Trees From Kentucky & Tennessee & Its Relation To Yearly Growth, Jennifer Sharp
Masters Theses & Specialist Projects
The levels of sulfur present in xylem tissue of Quercus alba (white oak) show a statistically significant increase from 1970 to 1983. This increase was found in trees from three different sites in Kentucky and Tennessee. The levels of sulfur present in Tsuga canadensis (hemlock) show a statistically significant increase from 1955 to 1970. Sensitivity, growth response to the tree's environment, decreased in oaks from 1933 to 1968 but increased slightly in hemlocks during the same time period. The data tend to support a direct relationship between increasing sulfur levels and a reduction in growth. Physiological and ecological studies of …
Intestinal Granules Found In The Parasitic Nematodes Ancylostoma Caninum, And Oesophagostomum Radiatum, Alan Joseph Gianotti
Intestinal Granules Found In The Parasitic Nematodes Ancylostoma Caninum, And Oesophagostomum Radiatum, Alan Joseph Gianotti
Dissertations and Theses
The parasitic nematodes Ancylostoma caninum and Oesophagostomum radiatum were collected and analyzed for intestinal inorganic granules. Three means of identification were utilized to determine the composition granules, including birefringence, x-ray diffraction and energy dispersive spectrometric (EDS) analysis. Initial x-ray diffraction results of the two worms showed a calcium sulfide presence within the worms. Closer examination of the granules within Ancylostoma caninum however, utilizing EDS analysis revealed their composition to be zinc sulfide. These results concur with those of Rogers (1940) and Clark (1956) who found zinc sulfide granules in several species of Strongylus. The ZnS granules seem to be …
Crystallization Of Trimeric Recombinant Human Tumor Necrosis Factor (Cachectin), M. J. Eck, B. Beutler, G. Kuo, J. P. Merryweather, S. R. Sprang
Crystallization Of Trimeric Recombinant Human Tumor Necrosis Factor (Cachectin), M. J. Eck, B. Beutler, G. Kuo, J. P. Merryweather, S. R. Sprang
Biological Sciences Faculty Publications
Crystals of tumor necrosis factor (TNF) have been obtained in two forms. Rhombohedral crystals grow in 1.8 to 2.0 M ammonium sulfite, pH 7.8 at 21°C, and tetragonal crystals grow in 2.6 M magnesium sulfate, pH 5.5 at 25°C. Analysis of TNF by isoelectric focusing under native and denaturing conditions indicates that TNF molecules exist as trimers in solution. The rhombohedral cachectin crystals belong to space group R3 and have unit cell constants a = b = c = 47.65 Å and α = β = γ = 88.1°. Density determinations and the space group indicate that the unit cell …
Sequence Of The Psba Gene From Wild Type Triazin-Resistant Nicotiana Plumbaginifolia, Anikó Páy, Marvin A. Smith, Ferenc Nagy, László Márton
Sequence Of The Psba Gene From Wild Type Triazin-Resistant Nicotiana Plumbaginifolia, Anikó Páy, Marvin A. Smith, Ferenc Nagy, László Márton
Faculty Publications
No abstract provided.
The Distribution Of Zooplankton In Selected Oregon Lakes, Mary Elizabeth Claska
The Distribution Of Zooplankton In Selected Oregon Lakes, Mary Elizabeth Claska
Dissertations and Theses
Zooplankton samples were collected from 166 Oregon lakes. The lakes included a wide range in size, trophic status, and water quality. Lakes were located throughout the state. Zooplankton were identified using standard taxonomic keys and counted. Seventy-four species were identified from the 200 total samples, including 32 species of cladocera, 22 copepods, and 11 rotifers. Two species of copepod were recorded for the first time in Oregon: Diaptomus mississippiensis and Diaptomus pallidus. Seven species had widespread distributions throughout most of the watersheds in the state. Seventeen other species had distributions restricted to eastern, central, or western Oregon. The remaining …
Anion-Exchange Chromatography Of The Murine Estrogen Receptor: Ionic Forms Of Receptor Under Different States Of Activation, Gregory Craft
Anion-Exchange Chromatography Of The Murine Estrogen Receptor: Ionic Forms Of Receptor Under Different States Of Activation, Gregory Craft
Morehead State Theses and Dissertations
A thesis presented to the faculty of the College of Arts and Sciences at Morehead State University in partial fulfillment of the requirements for the Degree of Master of Science by Gregory Craft on August 5, 1988.
Effects Of Indomethacin On Prostaglandin E2 In 7,12-Dimethybenz (A) Anthracene Induced Mammary Tumorigenisis In Rats Fed Different Levels Of Polyunsaturated Fat, Candace Sue Smith
Effects Of Indomethacin On Prostaglandin E2 In 7,12-Dimethybenz (A) Anthracene Induced Mammary Tumorigenisis In Rats Fed Different Levels Of Polyunsaturated Fat, Candace Sue Smith
Morehead State Theses and Dissertations
A thesis presented to the faculty of the School of Arts and Sciences at Morehead State University in partial fulfillment of the requirement for the Degree of Masters of Science in Biology by Candace Sue Smith on August 5, 1988.
A Reverse Genetics Approach For Studying Histone H4 Structure-Function Relationships In Yeast, Michael J. Bonaduce
A Reverse Genetics Approach For Studying Histone H4 Structure-Function Relationships In Yeast, Michael J. Bonaduce
Master's Theses
A previously constructed mutation of the histone H4 gene has been the subject of a detailed analysis. The mutation involves an H4 gene encoding two amino acid changes which substitute aspartic acid for glycine at positions 13 and 42 of the polypeptide. These substitutions result in a nonfunctional H4 protein when assayed in Saccharomyces cerevisiae. In contrast, an analysis of an amino terminal deletion of amino acids 3-26 results in a functional H4 protein. Physical biochemistry studies identify the sites of histone-histone interactions between residues 38-102 of histone H4, the same area in which position 42 resides. The question being …
A Rapid System For Analyzing Histone H4 Mutations In The Yeast Saccharomyces Cerevisiae, Edward Rex Lakey Harkrader
A Rapid System For Analyzing Histone H4 Mutations In The Yeast Saccharomyces Cerevisiae, Edward Rex Lakey Harkrader
Master's Theses
Genetically engineered, specific histone H4 mutations have been analyzed in yeast which lack normal H4 protein using the time consuming technique of tetrad dissection. The purpose of the present research project has been to develop a rapid new system for analyzing histone H4 mutations in yeast. The new system has made it possible to isolate quickly cells which are surviving on mutant H4 only. The system will make it possible to analyze more quickly large numbers of H4 mutations. It is termed a plasmid shuttle system because of the use of plasmid vectors for shuttling histone H4 alleles in and …
Sodium/Proton Exchange In The Gills Of Three Species Of Crabs : Libinia Dubia, Callinectes Sapidus, And Menippe Mercenaria, Nicholas J. Maiolo
Sodium/Proton Exchange In The Gills Of Three Species Of Crabs : Libinia Dubia, Callinectes Sapidus, And Menippe Mercenaria, Nicholas J. Maiolo
Master's Theses
Na+/H+ exchange was studied in plasma membrane vesicles from gills of three species of crabs: Callinectes sapidus (blue crab), Libinia dubia (spider crab), and Menippe mercenaria (stone crab). Spider crabs and stone crabs were acclimated to full (35ppt) seawater, while blue crabs were acclimated to both dilute (5ppt) and full strength seawater. Membrane vesicles were prepared by sucrose density centrifugation. Na+/H+ exchange was analyzed using acridine orange fluorescence. Male C. sapidus showed the most exchange activity (per g gill tissue), followed by M. mercenaria, female C. sapidus and Libinia dubia. No difference in exchange activity was evident when blue crabs …
Drosophila Has A Single Copy Of The Gene Encoding A Highly Conserved Histone H2a Variant Of The H2a.F/Z Type, Angela Van Daal, E White, M Gorovsky, Sarah C.R. Elgin
Drosophila Has A Single Copy Of The Gene Encoding A Highly Conserved Histone H2a Variant Of The H2a.F/Z Type, Angela Van Daal, E White, M Gorovsky, Sarah C.R. Elgin
Biology Faculty Research
The Tetrahymena histone H2A variant designated hv1 is localized exclusively in the transcriptionally active macronucleus and is absent from the quiescent micronucleus (1). A cDNA clone of the hv1 gene (2) was used to screen a Drosophila cDNA library. A cross-hybridizing clone was recovered and shown by sequence analysis to code for a protein homologous to hv1 as well as to the chicken H2A variant, H2A.F (3), the sea urchin H2A variant, H2A.F/Z (4) and the mammalian H2A variant H2A.Z (5). Southern analysis of Drosophila genomic DNA indicates that the H2AvD (H2A variant Drosophila) gene is present in one copy. …
Ultrastructural And Functional Effects Of Lipopolysaccharide And Interleukin-2 On Human Nk Cells, Yuan-Hsu Kang, Mitchell Carl, Lorrita P. Watson
Ultrastructural And Functional Effects Of Lipopolysaccharide And Interleukin-2 On Human Nk Cells, Yuan-Hsu Kang, Mitchell Carl, Lorrita P. Watson
Scanning Microscopy
Bacterial endotoxin (lipopolysaccharide, LPS) and interleukin-2 (IL-2) are known to stimulate NK cell mediated cytotoxicity against tumor cells. In the present report we sought to correlate the stimulatory effect of LPS and IL-2 on NK cell activity with ultrastructural changes which occurred as a result of such stimulation. Peripheral blood mononuclear cells (PBMC) were purified from healthy donors by a Ficoll-Hypaque density gradient technique. Leu-11a+ NK cells were isolated by flow microfluorometry using a monoclonal FITC conjugated anti-Leu-11a antibody and a FACS II cell sorter. The PBMC were incubated, respectively, with E. coli LPS or recombinant IL-2 (IL-2) for …
Crystal Associated Diseases: Role Of Scanning Electron Microscopy In Diagnosis, K. P. H. Pritzker, P. -T. Cheng, M. D. Grynpas, D. P. Holmyard
Crystal Associated Diseases: Role Of Scanning Electron Microscopy In Diagnosis, K. P. H. Pritzker, P. -T. Cheng, M. D. Grynpas, D. P. Holmyard
Scanning Microscopy
As crystals are important etiologic agents for disease, their accurate identification in tissues and body fluids is of utmost importance. This paper surveys the roles of crystals in disease process and outlines current analytical techniques for crystal detection and identification in bone tissues. The value of multiple correlated techniques is demonstrated including scanning electron microscopy, x-ray energy spectroscopy and powder diffraction analysis. The current feasibility of utilizing intermediate voltage scanning transmission analytical electron microscopy to integrate these analytical techniques on the same tissue sample is emphasized.
Clinical Applications Of Electron Microscopy In The Analysis Of Collagenous Biomaterials, Arthur J. Wasserman, Charles J. Doillon, Alvin I. Glasgold, Y. Pedro Kato, David Christiansen, Azam Rizvi, Eric Wong, Jack Goldstein, Frederick H. Silver
Clinical Applications Of Electron Microscopy In The Analysis Of Collagenous Biomaterials, Arthur J. Wasserman, Charles J. Doillon, Alvin I. Glasgold, Y. Pedro Kato, David Christiansen, Azam Rizvi, Eric Wong, Jack Goldstein, Frederick H. Silver
Scanning Microscopy
Scanning and transmission electron microscopy are of clinical value in assessing the interaction between biomaterials and ingrowing tissues. Ultrastructural information allows the clinician and biomaterials specialist to determine events occurring during wound healing and the biocompatibility of prosthetic devices. This paper reviews some of the experimental and clinical studies done in our laboratory on the use of natural and reconstituted collagen as replacements for connective tissues. Consideration is given to collagen flakes used for the treatment of dermal ulcers, a collagen fiber prosthesis used for tendon and ligament replacement, the effects of chemical preservatives on cartilage used for replacement of …
Scanning Tunneling Microscopy Methods For Spectroscopic Imaging Of Subsurface Interfaces, L. D. Bell, W. J. Kaiser
Scanning Tunneling Microscopy Methods For Spectroscopic Imaging Of Subsurface Interfaces, L. D. Bell, W. J. Kaiser
Scanning Microscopy
A new method for spatially-resolved, spectroscopic investigation of subsurface interface structure has been developed. The method, Ballistic Electron Emission Microscopy (BEEM), is based on Scanning Tunneling Microscopy (STM) techniques. BEEM combines STM vacuum tunneling with unique ballistic electron spectroscopy capabilities. BEEM enables, for the first time, direct imaging of subsurface interface electronic properties with nanometer spatial resolution. STM topographic images of surface structure and BEEM images of subsurface properties are obtained simultaneously. BEEM capabilities are demonstrated by investigation of important metal-semiconductor interfaces.
Effect Of Fluoride And Cobalt On Forming Enamel: Scanning Electron Microscope And X-Ray Microanalysis Study, S. H. Ashrafi, D. R. Eisenmann, A. E. Zaki, R. Liss
Effect Of Fluoride And Cobalt On Forming Enamel: Scanning Electron Microscope And X-Ray Microanalysis Study, S. H. Ashrafi, D. R. Eisenmann, A. E. Zaki, R. Liss
Scanning Microscopy
The forming surfaces of enamel of rat incisors were examined by scanning electron microscope one hour after injection of either 5 mg/100 g body weight of sodium fluoride or 12 mg/100 g body weight of cobalt chloride. The cell debris from the surfaces of the separated incisors was either gently wiped off with soft facial tissues or chemically removed by treating with NaOH, NaOCl or trypsin. Best results to remove cell debris were obtained from 0.25% trypsin treatment.
SEM studies revealed that the surface of the normal secretory enamel was characteristic in appearance with well-developed smooth prism outlines. In fluoride …
Detectors For Quantitative Electron Beam Voltage Measurements, A. R. Dinnis
Detectors For Quantitative Electron Beam Voltage Measurements, A. R. Dinnis
Scanning Microscopy
Qualitative voltage contrast is produced without difficulty in any SEM. Complete separation of the voltage contrast from other sources of contrast is not a straightforward matter because of the nonlinear relations between the phenomena causing contrast and the video signal.
Quantitative measurements depend on the availability of electron energy analysers which can detect accurately the shift in secondary electron energies due to potentials appearing on integrated circuit tracks, without being affected by transverse fields due to potentials on other conductors or insulators. The principles underlying existing detectors are explained, their effectiveness assessed, and a new form of electron detector is …
Double-Axis Rotary Shadowing For High-Resolution Scanning Electron Microscopy, R. Hermann, J. Pawley, T. Nagatani, M. Müller
Double-Axis Rotary Shadowing For High-Resolution Scanning Electron Microscopy, R. Hermann, J. Pawley, T. Nagatani, M. Müller
Scanning Microscopy
Thin continuous metal coatings and a scanning electron microscope-generated spot size in the range of the visualized particles, are necessary prerequisites if one hopes to extract high-resolution topographic information in the scanning electron microscope. Chemical fixation and dehydration in organic solvents at room temperature lead to severe ultrastructural artifacts which can be avoided by cryofixation and freeze-drying of the specimen. 0.9 to 2.7 nm thick homogeneous layers of chromium and germanium can be deposited onto the surface of cryofixed and freeze-dried specimens at high sub-zero temperatures by electron beam evaporation using "double-axis rotary shadowing". Theoretical calculations of the layer geometry …
Signal Of Backscattered Electrons From Multiple Marks In Dependence On Mark Profile, D. Kaczmarek, Z. Czyżewski
Signal Of Backscattered Electrons From Multiple Marks In Dependence On Mark Profile, D. Kaczmarek, Z. Czyżewski
Scanning Microscopy
The backscattered electron signal can be detected using a solid state detector system. Because this signal is affected by the surface topography it is necessary to determine the optimal detection condition for a registration mark detection in the electron-beam lithography and for an automatic topographical surface reconstruction.
The BSE signal from surface marks has been measured using semiconductor detectors with a small collection angle. Calculations of the BSE signal have been carried out by means of a simplified model of electron backscattering. The signal shape depends on some parameters of the mark profile, such as length, height and inclination angle …
Contribution Of Densely Distributed Electron Beam Induced Current Contrasts In Annealed Cz Silicon To Bulk Recombination, M. Kittler, W. Seifert
Contribution Of Densely Distributed Electron Beam Induced Current Contrasts In Annealed Cz Silicon To Bulk Recombination, M. Kittler, W. Seifert
Scanning Microscopy
The paper presents a detailed analysis of Electron Beam Induced Current (EBIC) diffusion-length and contrast data for samples containing defect accumulations. The formulae given allow one to estimate to which extent the average diffusion length is determined by recombination-active defects showing EBIC contrast.
This analysis may be used to identify essential sources of bulk recombination in annealed silicon. In the light of our results stacking faults are an essential source of bulk recombination in intrinsically gettered p-type Cz silicon.
Mounting Materials For Automated Image Analysis Of Coals Using Backscattered Electron Imaging, W. E. Straszheim, K. A. Younkin, R. T. Greer, R. Markuszewski
Mounting Materials For Automated Image Analysis Of Coals Using Backscattered Electron Imaging, W. E. Straszheim, K. A. Younkin, R. T. Greer, R. Markuszewski
Scanning Microscopy
In order to apply SEM-based automated image analysis (AIA) to the characterization of not only minerals in coal but to the coal itself, sample preparation methods need to be developed beyond common practice. A significant consideration is the degree of contrast achievable between the mount media chosen and the coal. Four low-atomic number materials (epoxy, polyethylene, polystyrene and carnauba wax) were compared for their potential as suitable mounting media for coal samples. Epoxy is satisfactory only for characterization of mineral particles since the contrast between epoxy and coal particles is negligible. Polyethylene or polystyrene have marginal application for use as …
The Use Of Backscattered Electron Imaging, X-Ray Microanalysis And X-Ray Microscopy In Demonstrating Physiological Cell Death, I. D. Bowen, N. A. Worrill, C. A. Winters, K. Mullarkey
The Use Of Backscattered Electron Imaging, X-Ray Microanalysis And X-Ray Microscopy In Demonstrating Physiological Cell Death, I. D. Bowen, N. A. Worrill, C. A. Winters, K. Mullarkey
Scanning Microscopy
The cytochemical localization of enzymatic activity by means of backscattered electron imaging (BEi) is reviewed and the application of BEI to changes in acid phosphatase and ATPase distribution during physiological (programmed) cell death in Heliothis midgut is explored. Programmed cell death entails the release of nascent free acid phosphatase as extracisternal hydrolase. This shift can readily be detected by means of the atomic number contrast imparted by BEI of the lead phosphatase reaction product, thus enabling the distribution of dying cells to be mapped. BEI is particularly useful in this context as it allows the examination of bulk specimens at …
Scanning Electron Microscopic Autoradiography Of Lung, K. E. Lauhala, C. L. Sanders, K. E. Mcdonald
Scanning Electron Microscopic Autoradiography Of Lung, K. E. Lauhala, C. L. Sanders, K. E. Mcdonald
Scanning Microscopy
Scanning electron microscopic (SEM) autoradiography of the lung is being used to determine the distribution of inhaled, alpha particle-emitting, plutonium dioxide particles. SEM autoradiography provides high visual impact views of alpha activity. Particles irradiating the bronchiolar epithelium were detected both on the bronchiolar surface and in peribronchiolar alveoli. The technique is being used to obtain quantitative data on the clearance rates of plutonium particles from bronchi and bronchioles.
The Influence Of Analyser Geometry Effects In Scanning Electron Microscope Voltage Contrast Measurements, Daniel S.H. Chan, Teck Seng Low, Wai Kin Chim, Jacob C. H. Phang
The Influence Of Analyser Geometry Effects In Scanning Electron Microscope Voltage Contrast Measurements, Daniel S.H. Chan, Teck Seng Low, Wai Kin Chim, Jacob C. H. Phang
Scanning Microscopy
A computer simulation model used to study specimen dependent and analyser geometry dependent effects is described in this paper. With this model, the influence of the specimen dependent effect on quantitative voltage contrast measurements can be isolated from the analyser geometry dependent effect. Linearization error voltages in quantitative voltage contrast measurements arising from the individual influences of the specimen dependent and analyser geometry dependent effects are presented. The results show that the error component due to very narrow analysers dominate the total linearization error. The same situation arises when the voltage measurement point on the specimen is very near to …
An Electron Microscopic Study Of Hemopoietic Tissues In The Course Of Lewis Lung Carcinoma, Cheryl Hardy, Yuzhi Wang, Bettye Collier, Mehdi Tavassoli
An Electron Microscopic Study Of Hemopoietic Tissues In The Course Of Lewis Lung Carcinoma, Cheryl Hardy, Yuzhi Wang, Bettye Collier, Mehdi Tavassoli
Scanning Microscopy
Lewis lung carcinoma of C57Bl/6 mice causes a progressive anemia with reticulocytosis and splenomegaly, metastasizes to lungs, liver, and kidneys but does not invade hemopoietic tissues. The cause of this anemia is uncertain. We studied the structure of spleen and bone marrow in these tumor hosts by light and electron microscopy. Splenic congestion of the red pulp with numerous erythropoietic islands and marrow hyperplasia characterized the hemopoietic tissues of these mice, which, when coupled with other hematological parameters suggested a hemolytic condition. However, the erythropoietic response appeared to be in part ineffective as evidenced by phagocytosis of immature as well …
Secondary Ion Mass Spectrometry Studies Of Isotope Effect In Diffusion, U. Södervall, H. Odelius, A. R. E. Lodding
Secondary Ion Mass Spectrometry Studies Of Isotope Effect In Diffusion, U. Södervall, H. Odelius, A. R. E. Lodding
Scanning Microscopy
The mass effect of diffusion is of interest in connection with interactions between defects and impurities and with the mechanisms of atomic displacements in the condensed states. The delineation entails the precise measurement of the isotope ratio as function of tracer concentration, varying within several orders of magnitude along the diffusion profile. The measurement by SIMS (secondary ion mass spectrometry), using stable isotopes, has proved to possess advantages compared to familiar techniques with radiotracers. However, the aims require the utmost counting economy and optimal precision available in SIMS, including the control of the mass fractionation and of some features peculiar …
Ua66/6/2 Bionews From The Hill, Wku Biology
Ua66/6/2 Bionews From The Hill, Wku Biology
WKU Administration Documents
Newsletter created by and about the WKU Biology department highlighting students, faculty and alumni activities.
Radar And Visual Observations Of Autumnal (Southward) Shorebird Migration On Guam, Timothy C. Williams , '64, J. M. Williams
Radar And Visual Observations Of Autumnal (Southward) Shorebird Migration On Guam, Timothy C. Williams , '64, J. M. Williams
Biology Faculty Works
Several species of shorebirds migrate between eastern Asia and the southern Pacific islands, Australia, and New Zealand. Observations made from Guam (13°25′N, 144°45′E) during autumn 1983 indicate that a significant number of birds take a direct route over the western Pacific Ocean. Radar observations and ground counts of migrants on Guam showed two periods of autumnal migratory activity. The first, largely adult birds, was in August and September. The second, largely juveniles, was in late September and October. Radar indicated that large numbers of birds passed over the island to the south with no evidence of compensation for drift by …
Comparative Analysis Of The Effects Of Visual And Auditory Stimuli On Avian Mobbing Behavior, C. Ray Chandler, Robert K. Rose
Comparative Analysis Of The Effects Of Visual And Auditory Stimuli On Avian Mobbing Behavior, C. Ray Chandler, Robert K. Rose
Biological Sciences Faculty Publications
Both visual and auditory stimuli elicit avian mobbing behavior, but there is little comparative information on their isolated and additive effects. Using three combinations of two experimental stimuli (mount and tape of an Eastern Screech-Owl, Otus asio) we tested the effects of stimuli on the frequency, intensity, and duration of avian mobbing behavior. Of 169 mount-only trials, only 11 (6.5%) were successful in attracting birds. Tape-only (n = 169) and mount-and-tape (n = 170) were equally successful in attracting birds (approximately 85% of all trials), but mount-and-tape trials were more likely to initiate mobbing behavior. Birds responding …
Basis Of The Structure And Development Of Mammalian Enamel As Seen By Scanning Electron Microscopy, A. Boyde, M. Fortelius, K. S. Lester, L. B. Martin
Basis Of The Structure And Development Of Mammalian Enamel As Seen By Scanning Electron Microscopy, A. Boyde, M. Fortelius, K. S. Lester, L. B. Martin
Scanning Microscopy
Mature enamel is the most mineralized of mammalian tissues, contains the least water and therefore does not present problems of shrinkage on preparation for SEM. However, the developing enamel is highly hydrated and presents severe problems in preparation.
The structure of enamel is determined by the activity of its individual formative cells and their group behaviour. The peculiar, unequal secretion of matrix at the distal pole of the ameloblast leads to the presence of characteristically shaped pits in the surface of the formative tissue. Crystals grow in a special relationship to this surface. Sharp changes in orientation of the surface …