scholarly journals ELECTRON MICROSCOPIC STUDIES OF MITOSIS IN AMEBAE

1962 ◽  
Vol 12 (1) ◽  
pp. 57-78 ◽  
Author(s):  
L. E. Roth ◽  
E. W. Daniels
Keyword(s):  
Calcium Ions ◽  
Osmium Tetroxide ◽  
Interphase Nucleus ◽  
Divalent Cations ◽  
Divalent Ions ◽  
Electron Microscopic ◽  
Oriented Molecules ◽  
Protein Molecules ◽  
Microscopic Studies ◽  
Calcium Magnesium

Dividing nuclei from the giant ameba Pelomyxa carolinensis were fixed in osmium tetroxide solutions buffered with veronal acetate to pH 8.0. If divalent cations (0.002 M calcium, magnesium, or strontium as chlorides) were added to the fixation solution, fibrils that are 14 mµ in diameter and have a dense cortex are observed in the spindle. If the divalent ions were omitted, oriented particles of smaller size are present and fibrils are not obvious. The stages of mitosis were observed and spindle components compared. Fibrils fixed in the presence of calcium ions are not so well defined in early metaphase as later, but otherwise have the same diameter in the late metaphase, anaphase, and early telophase. Fibrils are surrounded by clouds of fine material except in early telophase, when they are formed into tight bundles lying in the cytoplasm unattached to nuclei. Metaphase and anaphase fibrils fixed without calcium ions are less well defined and are not observably different from each other. The observations are consistent with the concept that spindle fibrils are composed of polymerized, oriented protein molecules that are in equilibrium with and bathed in non-oriented molecules of the same protein. Partially formed spindle fibrils and ribosome-like particles were observed in the mixoplasm when the nuclear envelope had only small discontinuities. Remnants of the envelope are visible throughout division and are probably incorporated into the new envelope in the telophase. Ribosome-like particles are numerous in the metaphase and anaphase spindle but are not seen in the telophase nucleus, once the envelope is reestablished, or in the interphase nucleus.

Effects of Mg2+ on Chromatic Structure in Isolated Chicken Liver Nuclei

1990 ◽  
Vol 48 (3) ◽  
pp. 130-131
Author(s):  
Soichiro Arai ◽  
Yuh H. Nakanishi
Keyword(s):  
Chromatin Structure ◽  
Room Temperature ◽  
Osmium Tetroxide ◽  
Divalent Cations ◽  
Chromatin Condensation ◽  
Chicken Liver ◽  
Electron Microscopic ◽  
Razor Blade ◽  
Microscopic Studies ◽  
Liver Nuclei

Although many electron microscopic studies on extracted chromatin have provided considerable information on chromatin condensation induced by divalent cations, there is only a little literature available on the effects of divalent cations on chromatin structure in intact nuclei. In the present study, the effects of Mg2+ on chromatin structure in isolated chicken liver nuclei were examined over a wide concentration range of Mg2+ by scanning electron microscopy.Nuclei were prepared from chicken liver by the method of Chauveau et al. with some modifications. The nuclei were suspended in 25 mM triethanolamine chloride buffer (pH7.4) with 1 mM EDTA or in the buffer with concentrations of MgCl2 varying from 1 to 50 mM. After incubation for 1 min at 0°C, glutaraldehyde was added to 1.8% and the nuclei were fixed for 1 h at 4°C. The fixed nuclei were mixed with 15% gelatin solution warmed at about 40°C, and kept at room temperature until the mixture set. The gelatin containing the nuclei was fixed with 2% glutaraldehyde for 2-4 h, and cut into small blocks. The gelatin blocks were conductive-stained with 2% tannic acid and 2% osmium tetroxide, dehydrated in a graded series of ethanol, and freeze-cracked with a razor blade in liquid nitrogen.

Cytoplasmic Invaginations in Trophoblasts and Epithelial Cells of Rat

1971 ◽  
Vol 29 ◽  
pp. 524-525
Author(s):  
Iracema M. Baccarini
Keyword(s):  
Osmium Tetroxide ◽  
Uranyl Acetate ◽  
Nuclear Inclusions ◽  
Mucous Cells ◽  
Electron Microscopic ◽  
Cervical Epithelium ◽  
Intact Membrane ◽  
Microscopic Studies ◽  
Abnormal Cells ◽  
Nuclear Features

Some morphological nuclear features (invaginations) in normal and abnormal cells have been described in several electron microscopic studies. They have been referred to by others as blebs, loops, pockets, sheets, bodies, nuclear inclusions and cytoplasmic invaginations. Identical appearing structures were found in cells of the uterine cervical epithelium, in trophoblasts of blastocysts and in trophoblasts of rat placenta.Methods. Uterine cervix (normal rats), rat placenta (9-10 days gestation) and blastocyst were placed in 3% glutarahdehyde for 3 hours. The tissue was washed in phosphate buffer for 24 hours, postfixed in 1%. buffered osmium tetroxide for 1-2 hours and embedded in epon araldite. Sections were double stained with uranyl acetate and lead citrate and viewed in E. M. Siemens 200.Observations. Nuclear invaginations were found in basal, parabasal and mucous cells of the cervix epithelium, in trophoblasts of blastocyst and in trophoblasts of placenta. An oval, round or elongated invagination contained heterogenously cytoplasm surrounded by a double intact membrane; usually several invaginations were found in the same nucleus.

scholarly journals Effect of divalent ions on cariogenic biofilm formation

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Elena Laura Steiger ◽  
Julia Rahel Muelli ◽  
Olivier Braissant ◽  
Tuomas Waltimo ◽  
Monika Astasov-Frauenhoffer
Keyword(s):  
Biofilm Formation ◽  
Growth Parameters ◽  
Divalent Cations ◽  
Self Regulation ◽  
Antimicrobial Properties ◽  
Mutans Streptococci ◽  
Tooth Surface ◽  
Divalent Ions ◽  
Dental Biofilm ◽  
Calcium Magnesium

Abstract Background Divalent cations are able to interact with exopolysaccharides (EPS) and thus are capable to modify the structure and composition of dental biofilm. At the moment, little is known about the adsorption of metals by cariogenic EPS; thus, the aim of the present study was to evaluate the effect of divalent ions (calcium, magnesium, and zinc) on the growth and biofilm formation of mutans streptococci and on the dissolution of hydroxyapatite as well as to investigate their binding to the bacterial EPS. Results S. mutans strains used in this study show the highest tolerance towards calcium of the ions tested. Growth parameters showed no differences to control condition for both strains up to 100 mM; revealing natural tolerance to higher concentration of calcium in the surroundings. Although excessive levels of calcium did not impair the growth parameters, it also did not have a positive effect on biofilm formation or its binding affinity to EPS. Magnesium-saturated environment proved to be counterproductive as strains were able to dissolve more Ca2+ from the tooth surface in the presence of magnesium, therefore releasing excessive amounts of Ca2+ in the environment and leading to the progression of the disease. Thus, this supports the idea of self-regulation, when more Ca2+ is released, more calcium is bound to the biofilm strengthening its structure and however, also less is left for remineralization. Zinc inhibited bacterial adhesion already at low concentrations and had a strong antibacterial effect on the strains as well as on calcium dissolution; leading to less biofilm and less EPS. Additionally, Zn2+ had almost always the lowest affinity to all EPS; thus, the unbound zinc could also still remain in the surrounding environment and keep its antimicrobial properties. Conclusion It is important to maintain a stable relationship between calcium, magnesium and zinc as excessive concentrations of one can easily destroy the balance between the three in cariogenic environment and lead to progression of the disease.

Electrical stability of erythrocytes in the presence of divalent cations

1988 ◽  
Vol 8 (5) ◽  
pp. 421-426 ◽  
Author(s):  
T. Ch. Tomov ◽  
I. Ch. Tsoneva ◽  
J. Ch. Doncheva
Keyword(s):  
Ionic Strength ◽  
Divalent Cations ◽  
Protective Action ◽  
Electrical Pulse ◽  
Electrostatic Repulsion ◽  
Electrical Stability ◽  
Divalent Ions ◽  
Protein Molecules ◽  
Low Ionic Strength

Erythrocytes suspended in a medium of low ionic strength lyse under the effect of an exponential electrical pulse. The percentage of haemolysed cells decreases several-fold in the presence of divalent cations. The protective action of the ions studied increases in the following order: Ca++, Mg++, Zn++. It is assumed that divalent ions bind to the negative charges of the lipid and protein molecules and reduce their electrostatic repulsion, which results in stabilization of the membranes.

scholarly journals ELECTRON MICROSCOPIC STUDIES OF MITOSIS IN AMEBAE

1960 ◽  
Vol 8 (1) ◽  
pp. 207-220 ◽  
Author(s):  
L. E. Roth ◽  
S. W. Obetz ◽  
E. W. Daniels
Keyword(s):  
Electron Microscope ◽  
Nuclear Envelope ◽  
Osmium Tetroxide ◽  
Thin Sheet ◽  
Amoeba Proteus ◽  
Electron Microscopic ◽  
Interphase Nuclei ◽  
Nucleolar Material ◽  
Microscopic Studies ◽  
Early Reconstruction

Individual organisms of Amoeba proteus have been fixed in buffered osmium tetroxide in either 0.9 per cent NaCl or 0.01 per cent CaCl2, sectioned, and studied in the electron microscope in interphase and in several stages of mitosis. The helices typical of interphase nuclei do not coexist with condensed chromatin and thus either represent a DNA configuration unique to interphase or are not DNA at all. The membranes of the complex nuclear envelope are present in all stages observed but are discontinuous in metaphase. The inner, thick, honeycomb layer of the nuclear envelope disappears during prophase, reappearing after telophase when nuclear reconstruction is in progress. Nucleoli decrease in size and number during prophase and re-form during telophase in association with the chromatin network. In the early reconstruction nucleus, the nucleolar material forms into thin, sheet-like configurations which are closely associated with small amounts of chromatin and are closely applied to the inner, partially formed layer of the nuclear envelope. It is proposed that nucleolar material is implicated in the formation of the inner layer of the envelope and that there is a configuration of nucleolar material peculiar to this time. The plasmalemma is partially denuded of its fringe-like material during division.

scholarly journals Zonal heterogeneity of calcium distribution in rat hepatocytes: an electron microscopic study with a combined glutaraldehyde-osmium-pyroantimonate technique.

1994 ◽  
Vol 42 (5) ◽  
pp. 593-598 ◽  
Author(s):  
S Angermüller ◽  
R Juchem ◽  
K Beier ◽  
T Konrad ◽  
K Kusterer
Keyword(s):  
Calcium Ions ◽  
Osmium Tetroxide ◽  
Calcium Concentration ◽  
Rat Hepatocytes ◽  
Potassium Ions ◽  
Electron Spectroscopic Imaging ◽  
Electron Microscopic ◽  
Calcium Distribution ◽  
Pericentral Area ◽  
Potassium Pyroantimonate

Potassium pyroantimonate in combination with osmium tetroxide is an excellent technique for investigation of the subcellular distribution of calcium ions in glutaraldehyde-fixed liver tissue. Under appropriate incubation conditions potassium ions are replaced by calcium ions to form an insoluble electron-dense calcium antimonate precipitate. The presence of calcium within this antimonate precipitate is confirmed by the electron spectroscopic imaging (ESI) technique. Chelator treatment with EGTA [ethylene glycol-bis-(beta-amino-ethyl ether) N',N',N'-tetraacetic acid] is usually used as a control, preventing the precipitation of calcium. In our investigation, computerized image analysis revealed a gradient of the calcium distribution from the periportal to the pericentral area. A finely dispersed precipitate was found in the mitochondrial matrix and in the euchromatin of the nuclei of the periportal hepatocytes, and in the organelles of the pericentral area a coarser deposit in lower concentration was recognized. Our findings indicate that periportal and pericentral hepatocytes retain their zonal characteristics also with respect to calcium concentration in mitochondria and nuclei.

scholarly journals EVIDENCE FOR CHANGES IN PROTEIN POLYSACCHARIDE ASSOCIATED WITH THE ONSET OF CALCIFICATION IN CARTILAGE

1968 ◽  
Vol 39 (1) ◽  
pp. 43-48 ◽  
Author(s):  
Victor J. Matukas ◽  
George A. Krikos
Keyword(s):  
Electron Microscopy ◽  
Osmium Tetroxide ◽  
Marked Decrease ◽  
Uranyl Acetate ◽  
Lead Citrate ◽  
Electron Microscopic ◽  
Calcified Cartilage ◽  
The Matrix ◽  
Microscopic Studies ◽  
Matrix Components

Past work has suggested that protein polysaccharide may play a role in the calcification of cartilage. Recent electron microscopic studies on noncalcified cartilage have indicated that protein polysaccharide in cartilage matrix is represented by granules associated with collagen fibers. The present work has been designed for comparison of the matrix of noncalcified cartilage to that of calcified cartilage, with particular reference to these granules. Small blocks of tibia from 16-day embryos were fixed in cacodylate-buffered glutaraldehyde and postfixed in either phosphate- or Veronal-buffered osmium tetroxide. Special care was taken to maintain the pH above 7.0 at all times. For electron microscopy the tissues were dehydrated, embedded in Epon 812, sectioned, and stained with uranyl acetate or lead citrate. A marked decrease in the size of granules in the matrix of calcified cartilage compared to noncalcified cartilage was noted. Associated with the decrease in the size of granules was a condensation of matrix components and the presence of an amorphous electron-opaque material that was not seen in noncalcified areas. These results are interpreted to represent either a drop in concentration or a change in state of protein polysaccharide with the onset of calcification in cartilage.

scholarly journals WOUND HEALING AND COLLAGEN FORMATION

1962 ◽  
Vol 15 (1) ◽  
pp. 99-108 ◽  
Author(s):  
Russell Ross ◽  
Earl P. Benditt
Keyword(s):  
Osmium Tetroxide ◽  
Unit Area ◽  
Modified Technique ◽  
Electron Microscopic ◽  
Collagen Formation ◽  
Fibrillar Material ◽  
Nuclear Track Emulsion ◽  
Microscopic Studies ◽  
Healing Wounds ◽  
Collagenous Material

The sequence of incorporation and utilization of tritium-labeled proline has been examined in healing wounds from normal and scorbutic guinea pigs. Linear incisions in the skin of the animals were allowed to heal for 7 days. Each animal was given proline-H3, and the wounds were excised 30 minutes, 1 and 4 hours, 1, 3 and 7 days after proline administration. The tissues were fixed in osmium tetroxide, fixed again in neutral buffered formalin, embedded in epoxy resin, and sectioned at 1 micron thickness. The sections were coated with nuclear track emulsion, exposed, developed, and stained. The results of grain counts were quantitated as the number of counts per unit area overlying cells, fibers, etc. In both groups the proline reaches a maximum over the fibroblasts within 4 hours and subsequently disappears from the cells. Concomitantly, the proline reaches a maximum over the collagen (in normal animals) and extracellular fibrillar material (in scorbutic animals) by 4 hours, where it remains. The modified technique of radioautography used in this study allows not only resolution of approximately 1 micron, but also minimal background, decreased artifact, and a clear separation of the randomly situated elements within the wounds so that grain counting is facilitated. The results correlated with previous electron microscopic studies are consistent with the utilization of proline by the fibroblasts and its incorporation into collagen (in normal animals) and into the extracellular, fibrillar, non-collagenous material seen in scorbutic animals.

Transmission and Scanning Electron Microscopy of the Follicle in the Human Ovary

1974 ◽  
Vol 32 ◽  
pp. 142-143
Author(s):  
I. M. Baccarini
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Granulosa Cells ◽  
Osmium Tetroxide ◽  
Human Ovary ◽  
Scanning Microscope ◽  
Electron Microscopic ◽  
Ultrastructural Studies ◽  
Microscopic Studies ◽  
Scanning Electron

Several ultrastructural studies demonstrated that the granulosa cells changed the structure since their differentiation, maturation and degeneration. However, little is known about the organization of the granulosa cells in the follicle for instance, the connection between the cells and cellular interchanges.Fragments of ovary obtained from the surgery room were fixed in 3% buffered glutaraldehyde for scanning microscope and post-fixed in 1% buffered osmium tetroxide for electron microscopic studies.

scholarly journals ELECTRON MICROSCOPIC OBSERVATIONS ON THE ACCUMULATION OF DIVALENT CATIONS IN INTRAMITOCHONDRIAL GRANULES

1964 ◽  
Vol 20 (1) ◽  
pp. 95-111 ◽  
Author(s):  
Lee D. Peachey
Keyword(s):  
Divalent Cations ◽  
Rat Kidney ◽  
Toad Urinary Bladder ◽  
Mitochondrial Matrix ◽  
Divalent Ions ◽  
Electron Microscopic ◽  
Whole Cells ◽  
Kidney Mitochondria ◽  
Isolated Mitochondria

Electron microscopic evidence is presented, from mitochondria in whole cells of toad urinary bladder and from isolated rat kidney mitochondria, indicating that the divalent cations calcium, strontium, and barium are accumulated in granules localized in the mitochondrial matrix. This accumulation occurs under conditions in which divalent ions are present in the medium bathing either whole cells or isolated mitochondria. The evidence indicates that the divalent ions are deposited on, or in a pre-existing granule, possibly in exchange for other ions. It suggests a possible role of the intramitochondrial granules in the regulation of the internal ionic environment of the mitochondrion. Certain biochemical and physiological implications of this phenomenon are discussed.

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