scholarly journals FEATURES OF THE COURSE OF ENAMEL BIOMINERALIZATION PROCESSES IN VARIOUS ANATOMICAL AREAS OF THE TOOTH

2020 ◽  
Vol 73 (5) ◽  
pp. 864-867 ◽  
Author(s):  
Dmytro V. Kalashnikov ◽  
Petro A. Hasiuk ◽  
Anna B. Vorobets ◽  
Svitlana O. Rosolovska ◽  
Dmytro D. Kindiy ◽  
...  
Keyword(s):  
Calcium Ions ◽  
Continuous Process ◽  
Electron Microscopic Examination ◽  
Structural Features ◽  
Tooth Crown ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Mineralization Processes ◽  
Enamel Mineralization ◽  
Examination Methods

The aim: To establish the features of the structural organization of enamel in various anatomical areas of the tooth and determine their influence on the characteristics of the course of biomineralization processes. Materials and methods: The study of the structural features of enamel and dentin was performed on thin sections of various groups of teeth. Then morphological, histochemical and electron microscopic examination methods were used. Results: The study found that there are three structural and functional barriers to biomineralization of enamel, which are located in different anatomical areas of the tooth crown. Each of them has both general and specific features. Enamel biomineralization is a continuous process of exchange of calcium ions, donor of which is brushite. The stepwise process of biomineralization turns the latter into calcium octaphosphate, which then turns into hydroxyapatite. The latter, when destroyed by carbon dioxide, forms carboxyapatite. Conclusions: In the result of conducted study was established peculiarities of enamel mineralization processes in different anatomical parts of tooth.

Toxic effects of inhaled DMMP on the kidneys of Fischer-344 rats

1987 ◽  
Vol 45 ◽  
pp. 880-881
Author(s):  
D.R. Mattie ◽  
C.J. Hixson
Keyword(s):  
Left Kidney ◽  
Inhalation Exposure ◽  
Electron Microscopic Examination ◽  
Exposure Period ◽  
Male Rats ◽  
Continuous Exposure ◽  
Fischer 344 Rats ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Fischer 344

Dimethylmethylphosphonate (DMMP) is a simple organophosphate used industrially as a flame retardant and to lower viscosity in polyester and epoxy resins. The military considered the use of DMMP as a nerve gas simulant. Since military use of DMMP involved exposure by inhalation, there was a need for a subchronic inhalation exposure to DMMP to fully investigate its toxic potential.Male Fischer-344 rats were exposed to 25 ppm or 250 ppm DMMP vapor on a continuous basis for 90 days. An equal number of control rats were sham-exposed. Following the 90-day continuous exposure period, 15 male rats were sacrificed from each group. Two rats from each group had the left kidney perfused for electron microscopic examination. The kidneys were perfused from a height of 150 cm water with 1% glutaraldehyde in Sorensen's 0.1M phosphate buffer pH 7.2. An additional kidney was taken from a rat in each group and fixed by immersion in 2.5% glutaraldehyde and 2% paraformaldehyde in 0.1M cacodylate buffer pH 7.4. A portion of the 9 kidneys collected for electron microscopy were processed into Epon 812. Thin sections, stained with uranyl acetate and lead citrate, were examined with a JEOL 100B Transmission Electron Microscope. Microvilli height was measured on photographs of the cells of proximal tubules. This data, along with morphologic features of the cells, allows the proximal convoluted tubules (PCT) to be identified as being S1, S2, or S3 segment PCT.

Immunolocalization of a Schistosoma mansoni facilitated diffusion glucose transporter to the basal, but not the apical, membranes of the surface syncytium

Parasitology ◽  
1995 ◽  
Vol 110 (4) ◽  
pp. 383-394 ◽  
Author(s):  
C. Zhong ◽  
P. J. Skelly ◽  
D. Leaffer ◽  
R. G. Cohn ◽  
J. P. Caulfield ◽  
...  
Keyword(s):  
Schistosoma Mansoni ◽  
Glucose Transporter ◽  
Light And Electron Microscopy ◽  
Linear Structure ◽  
Electron Microscopic Examination ◽  
Cdna Clones ◽  
Facilitated Diffusion ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Internal Domain

SUMMARYAdult parasites of Schistosoma mansoni reside within vertebrate mesenteric veins where they consume immense quantities of host glucose after transporting the sugar through their surface syncytium or tegument. Previously we obtained cDNA clones encoding two functional facilitated diffusion glucose transporter proteins expressed by S. mansoni adult worms (Skelly et al. 1994). Antibodies specific for one transporter (SGTP1) have been generated against an extrafacial and an internal domain of the protein and used to localize the protein by light and electron microscopy. By light microscopy both antibodies stain a linear structure approximately 1–5 μm from the surface of the tegument of adult male and female schistosomes. Electron microscopic examination of frozen thin sections show binding of the antibodies to membranes in the base of the tegument and not to the membranes covering the outer surface or their invaginations. Analysis of the gold distribution suggests that the extrafacial domain is disposed toward the interstitial space beneath the tegument and the internal domain faces the syncytial plasm. The localization suggests that SGTP1 may function to transport free glucose from within the tegument and into the interstitial fluids that bathe the internal organs of these parasites.

Cation Content and Transport Characteristics of the Sickle-Cell Erythrocyte and their Relationship with Structural Changes in the Membrane

1974 ◽  
Vol 46 (6) ◽  
pp. 679-692 ◽  
Author(s):  
J. Kurantsin-Mills ◽  
M. Kudo ◽  
S. Kojo Addae
Keyword(s):  
Sickle Cell ◽  
Sodium Transport ◽  
Structural Changes ◽  
Electron Microscopic Examination ◽  
Active Sodium ◽  
Electron Microscopic ◽  
Potassium Efflux ◽  
Thin Sections ◽  
Sodium Efflux ◽  
Active Sodium Transport

1. The intra-erythrocytic concentrations of sodium and potassium and the water content have been determined for haemoglobin (Hb) SS cells and negroid Hb AA cells. 2. The erythrocyte concentration of sodium was 40% higher and potassium 10% lower in the Hb SS than in the Hb AA cells. The cell water expressed as % weight of cell (corrected for trapped plasma) was identical for both cell types. 3. Normal Caucasian erythrocytes with Hb AA contained 40–50% less sodium but about the same potassium concentration as negroid Hb AA cells. 4. Potassium efflux into buffered iso-osmotic sucrose medium was much faster in Hb SS than in negroid Hb AA cells; ouabain-sensitive active sodium transport was twice as fast in the sickle-cell erythrocytes. Passive sodium efflux of erythrocytes suspended in a physiological medium was similarly faster in Hb SS cells. 5. Under the conditions of the experiments not less than 85% of the Hb SS erythrocytes appeared biconcave. Electron-microscopic examination of ultra-thin sections of Hb SS cells revealed marked discontinuities in the membrane. This suggests definite membrane alterations, which have probably resulted from the sickling-unsickling cycles occurring during the life-span of the cells. 6. It is suggested that the enhanced active sodium transport in the Hb SS erythrocyte is secondary to the augmented passive cation efflux, which in turn results from the leakiness of the erythrocyte membrane produced by the sickling-unsickling process.

Effect of Streptozotocin-Induced Diabetes on Estradiol-Stimulated Changes in the Ultrastructure of the Rat Endometrium

1981 ◽  
Vol 39 ◽  
pp. 532-533
Author(s):  
G.T. Frederick ◽  
R.M. Gardner ◽  
J.M. Kirkland ◽  
G.M. Stancel
Keyword(s):  
Electron Microscopic Examination ◽  
Sprague Dawley ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Whole Cells ◽  
Glucose Levels ◽  
Blood Glucose Levels ◽  
Sprague Dawley Rats ◽  
Uterine Growth ◽  
Streptozotocin Induced Diabetes

Estradiol (E2)-stimulated uterine growth has been well characterized both biochemically and morphologically. Recent studies have shown that insulin plays an important role in the regulation of cellular development. This study examines the effect of streptozotocin-induced diabetes on E2-stimulated changes in the ultrastructure of the endometrium of the rat uterus.Sprague-Dawley rats were ovariectomized at 21 days of age. Diabetes, defined as blood glucose levels greater than 300mg%, was induced in half of these animals by the injection of 85mg streptozotocin/kg body weight.The remaining animals were classified as normal. Animals from both groups were injected with either 0.9% saline or 4μg E2/100gm body weight. At 18, 24, 36 and 48 hours post-injection of E2, uterine segments were collected from 8-10 animals in each experimental group and processed for electron microscopic examination. Uterine segments from saline-injected animals served as controls. Data summarized describe observations made from thin-sections and have not been extrapolated for whole cells.

Electron microscopic evidence for a double hair-like nap appearing at low frequency on Bacillus anthracis Sterne spores

1969 ◽  
Vol 15 (10) ◽  
pp. 1247-1248 ◽  
Author(s):  
M. J. Kramer ◽  
Ivan L. Roth
Keyword(s):  
Bacillus Anthracis ◽  
Microscopic Examination ◽  
Low Frequency ◽  
Electron Microscopic Examination ◽  
Uranyl Acetate ◽  
Spore Coat ◽  
Lead Citrate ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Very Low Frequency

Electron microscopic examination of thin sections of Bacillus anthracis Sterne spores triply poststained with KMnO4, uranyl acetate, and lead citrate has indicated an unusual morphological variant. These spores are seen at very low frequency and have, in addition to the hair-like nap normally associated with the exosporium a second hairy layer which appears to originate in the spore coat complex.

The influence of aluminium on iron oxides: IX. Dissolution of Al-goethites in 6 M HCl

Clay Minerals ◽  
1984 ◽  
Vol 19 (1) ◽  
pp. 9-19 ◽  
Author(s):  
U. Schwertmann
Keyword(s):  
Crystal Growth ◽  
Surface Area ◽  
Electron Microscopic Examination ◽  
Separate Experiment ◽  
Dissolution Time ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Al Substitution ◽  
Crystallite Dimension ◽  
Oriented Parallel

AbstractThe rate of dissolution of synthetic Al-goethites with 0–10 mole% Al in 6 m HCl at 24°C decreases markedly with increasing extent of Al substitution. Most of the dissolution-time curves are S-shaped, suggesting some increase in surface area during the initial stages of dissolution. Based on electron microscopic examination, the increase in surface area is explained by preferential dissolution of less ordered ‘interdomainic’ zones and the consequent production of isolated ‘domains’. Thin sections of crystals provided some support for defect zones oriented parallel to the crystallographic c-direction. Stepwise multiple correlation analysis employing various properties of the goethites was used to investigate the large variation in half-dissolution time (1–96 h). 94% of the variation could be explained by the variation of the mean crystallite dimension perpendicular to the planes (110) and (111) (MCD110, MCD111). Inclusion of Al-substitution increased R2 to only 97%. As shown in a separate experiment, increasing Al concentration in the system retarded crystal growth. It is therefore believed that Al affects the dissolution rate of goethites not directly, but indirectly, by influencing crystal growth rate which, in turn, affects crystal size and order as measured by MCD110 and MCD111.

scholarly journals STUDIES ON GONOCOCCUS INFECTION

1971 ◽  
Vol 134 (4) ◽  
pp. 886-906 ◽  
Author(s):  
John Swanson ◽  
Stephen J. Kraus ◽  
Emil C. Gotschlich
Keyword(s):  
Animal Cell ◽  
Electron Microscopic Examination ◽  
Electron Microscopic ◽  
Fluid Medium ◽  
Thin Sections ◽  
Outer Membranes ◽  
Different Strains ◽  
Type 3

The four colony types of several different strains of gonococci were isolated by selective transfers on agar. These colony variants differed in the degree of autoagglutination which occurred when they were grown in fluid medium. It was found that this clumping behavior was related to the colonial type, with type 2 isolates exhibiting the greatest autoagglutination followed by types 3, 1, and 4. Electron microscopic examination of thin sections indicated that the clumping in fluid medium was mediated by peculiar zones of adherence of the outer membranes of gonococci. These resembled the gap junctions seen in animal cell systems but differed in that the gonococcal membranes involved in the zone of adherence did not bear typical surface modifications. Electron microscopic study of negatively stained specimens of gonococci revealed that pili with a diameter of approximately 85 A and a length up to 4 µ were present on the surfaces of all type 1 and type 2 gonococci examined, and were not seen on any type 3 or 4 gonococci. The consistent presence of pili on type 1 and type 2 gonococci which are virulent colony forms and the lack of pili on avirulent colony types 3 and 4 suggests a relationship between the gonococcal pili and pathogenetic potential of the organisms.

Fine structure of sunflower crown gall tissue

1970 ◽  
Vol 48 (8) ◽  
pp. 1455-1458 ◽  
Author(s):  
M. S. Manocha
Keyword(s):  
Crown Gall ◽  
Electron Microscopic Examination ◽  
Mesophyll Cell ◽  
Ultrastructural Changes ◽  
Bacterial Inoculation ◽  
Electron Microscopic ◽  
Mesophyll Cells ◽  
Thin Sections ◽  
Gall Tissue ◽  
Crown Gall Tissue

Electron microscopic examination of thin sections from sunflower crown gall tissue, induced by Agrobacterium tumefaciens, revealed certain details about its intracellular organization not previously reported. Tumor tissue showed a marked increase in the number of ribosomes, endoplasmic reticulum, and Golgi dictyosomes, over that of normal mesophyll cells. Mitochondria and chloroplasts did not show any detectable change. Crystalline bodies, consisting of a lattice surrounded by a unit membrane, were frequently observed in tumorous cells. The nucleoli of tumor cells contained vacuoles and were clearly differentiated into two zones, pars amorpha and nucleolonema. The possible significance of these ultrastructural changes has been discussed. Small vesicle-like bodies were observed in the nuclei of mesophyll cells 4 days after bacterial inoculation. Whether or not these vesicle-like bodies are responsible for the transformation of a normal mesophyll cell to a fully autonomous tumor cell is not known, but the possibility is an intriguing one.

Electron-Microscopic Examination of the Surface Layer of Titanium Alloys OТ4 after Ion Implantation

2019 ◽  
Vol 973 ◽  
pp. 3-8
Author(s):  
Viktor V. Ovchinnikov ◽  
Nadezhda V. Uchevatkina ◽  
Elena V. Lukianenko ◽  
Irina A. Kurbatova ◽  
Svetlana Y. Yakutina
Keyword(s):  
Titanium Alloy ◽  
Surface Layer ◽  
Diffraction Analysis ◽  
Deformation Mechanism ◽  
Microscopic Examination ◽  
Electron Microscopic Examination ◽  
Structural Features ◽  
Internal Stresses ◽  
Electron Microscopic ◽  
Diffusion Relaxation

The electron microscopic and diffraction analysis presented in the article showed that the structure of the surface layer of the titanium alloy OT4 after implantation at an accelerating voltage of 30 kV from the cathode Cu-Pb-Bi has a different hierarchical character. As a result of investigations of each of the levels, it was determined experimentally that the deformation mechanism under the action of internal stresses, as well as diffusion-relaxation reactions, are the main reasons for their formation, leading to the appearance of structural features in the surface layer of the OT4 alloy. In this case, penetration of alloying components to a depth of 10-25 nm is observed.

Occurrence of virions in developing ovules and embryo sacs of barley in relation to the seed transmissibility of barley stripe mosaic virus

1976 ◽  
Vol 54 (21) ◽  
pp. 2497-2512 ◽  
Author(s):  
Thomas W. Carroll ◽  
Dennis E. Mayhew
Keyword(s):  
Mosaic Virus ◽  
Microscopic Examination ◽  
Embryo Sac ◽  
Electron Microscopic Examination ◽  
Barley Stripe Mosaic Virus ◽  
Ovule Development ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Seed Transmissibility ◽  
Spindle Microtubules

Electron microscopic examination revealed the occurrence of virions in thin sections of developing ovules and embryo sacs of Atlas barley infected with a seed-transmitted strain of barley stripe mosaic virus, MI-1. It appeared that the virus invaded the primaiy meristem early, then infected the megaspore mother cell. In later stages of ovule development, the virus was seen in megaspores and in the cells of the embryo sac, including the egg. Virions were commonly associated with wall, cytoplasmic, or spindle microtubules. By contrast, virions of the non-seed-transmitted strain of the virus (NSP) did not occur in developing ovules or embryo sacs. Ovule transmission was only demonstrated for MI-1.

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