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PubMed1984

Repair of the mouse synovial membrane after chemical synovectomy with osmium tetroxide.

Repair of the synovium of the mouse knee joint following intra-articular injection with osmium tetroxide has been studied by light and electron microscopy. Within a first few days after osmium tetroxide injection complete necrosis of the synovial intima and inflammatory response in the subintimal connective tissue occurred. The resurfacing of the denuded synovium was performed by proliferation of immature synovioblasts which appeared to be derived from mesenchymal cells in the transition zone. The synovial intima completely restored the original structure, while repair of the subintimal tissue was accomplished by a scarring.

Animals↗
PubMed1982

Binding of an inert, cationic osmium probe to walls of Bacillus subtilis.

X-ray fluorescence spectroscopy and electron microscopy of unstained specimens have been used to study the binding of chloropentaammineosmium(III) chloride to isolated walls of Bacillus subtilis. Native walls bound 0.220 mumol of the osmium probe per mg (dry weight) of walls, whereas walls which were chemically treated to neutralize the available carboxylate groups of the peptidoglycan bound only 0.040 mumol. Teichoic acid-depleted walls bound 0.210 mumol. Thin sections of all wall types showed the osmium probe to be scattered throughout the wall matrix as a small staining deposit. The results support the idea that the metal ion-binding capacity of these walls is mediated by the available carboxylate groups in the wall fabric.

Bacillus subtilis↗
PubMed1985

Very small fat cell populations determined by a modified osmium tetroxide-urea method.

To facilitate investigations on very small fat cell (VSFC) populations in adipose tissue, an alternate method of preparing fat tissue samples was explored. The osmium tetroxide-8M urea method, modified by addition of a 95% ethanol step in tissue processing, centrifugation between steps, and final resuspension in 55% glycerol in 0.01% Triton-saline, was compared with the collagenase method for determination of VSFC populations in Fischer 344 epididymal and Sprague-Dawley retroperitoneal adipose depots. For each method and in both depots, the average histogram of 300 adipocyte diameters, measured by microscopy, was bimodal with the nadir between 30 and 40 micron diameter. The average histogram of fat cells less than 35 micron in diameter showed a separate population of VSFC existed in each depot. The modified osmium-urea method gave better results and was easier to perform than the collagenase method. It has confirmed our earlier results and raises anew questions concerning a role for the natural existence of a VSFC population in the adipose depot.

Adipose Tissue↗
PubMed1979

A chemical mechanism for tissue staining by osmium tetroxide-ferrocyanide mixtures.

The presence of Fe(CN)6(-4) provides sequential, one-electron reduction pathways for OSO4. An equilibrium is established containing OSO4, Fe(CN)6(-4), Fe(CN)6(-3), OSO2(OH)4(-4), and labile cyano-bridged OS-Fe species containing Os in nominal oxidation states of VIII, VII, and VI. These osmium complexes are chelated by appropriately placed donor atoms in the macromolecular tissue matrix, and chelation facilitates the reduction of osmium in situ to lower oxidation states (predominantly IV) that are relatively nonlabile. The greater reactivity and concentration of the Os(VII and VI) intermediates in this system leads to more Os deposition than OsO4 alone; the chelation is responsible for the immobilization of Os and the observed staining pattern in electron micrographs. Chemical data from model systems and electron micrographs of tissue are presented in support of this mechanism.

Animals↗
PubMed1984

Block-staining tissues with potassium ferrocyanide-reduced osmium tetroxide and lead aspartate for electron microscopic radioautography.

In the hope of devising a method for prestaining tissues en bloc for electron microscopic radioautography, pieces of radioiodine-labeled liver were taken through various combinations of ferrocyanide-reduced osmium tetroxide, lead aspartate, and aqueous uranyl acetate at room temperature or at 60 degrees C. Following the tests, the method adopted for routine use was to block-stain tissues for 2 hr in potassium ferrocyanide-reduced osmium tetroxide at 4 degrees C followed by 1 hr in Walton's lead aspartate at room temperature. This simple method, which requires no manipulation before or after emulsion coating and development of the radioautographs, provides adequate contrast without inducing background fog or artifacts.

Animals↗
PubMedDate not supplied

Differential effects of primary fixation with glutaraldehyde and osmium upon the membranous systems of the strial and external sulcus cells.

Ultrastructural preservation of the lateral cochlear wall differs between primary osmium fixation and primary glutaraldehyde fixation. Of significance in this study was the fact that whereas glutaraldehyde fixation preserves the parallel plasma membranes of interdigitations of the strial and external sulcus cells, fixation with osmium occasionally produces a breakdown of selected areas of membranes into apparent vesicles. The occurrence of these membrane artifacts was more common within the external sulcus cells. Reasons for the differential effects of the fixatives may include their differing modes of action. Care should be taken when evaluating unusual ultrastructure, since the type of fixative employed may be causal.

Aldehydes↗
PubMed1982

The use of osmium tetroxide-potassium ferrocyanide as an extracellular tracer in electron microscopy.

Secondary treatment of glutaraldehyde fixed liver samples with long term stored solutions of osmium tetroxide and potassium ferrocyanide (Os-Fe) results in tracing of the extracellular spaces of the tissue with an electron opaque substance. This substance does not diffuse across cell membranes, its formation probably being related to the progressive reduction of the OsO4 molecule by potassium ferrocyanide. The application of the present method in electron microscopy may be useful in overcoming the artifacts often induced by other tracing techniques such as vascular perfusion with peroxidase or immersion in lanthanum. Although the period of storage of the Os-Fe solution is a clear disadvantage of the method, it seems plausible to anticipate that further studies on the chemical interaction between osmium tetroxide and potassium ferrocyanide will provide us with a Os-Fe mixture having an immediate tracer effect.

Animals↗
PubMed1987

Osmium tetroxide recognized structural distortions at junctions between right- and left-handed DNA in a bacterial cell.

It was shown for the first time that the structural distortions at the junctions between contiguous right-handed and left-handed Z-DNA segments can be recognized in bacterial cells. E. coli containing recombinant plasmid pPK1 (a derivative of pUC19 containing (dC-dG)13 and (dC-dG)16 blocks) were treated with osmium tetroxide, 2.2'-bipyridine (Os,bipy); after this treatment pPK1 DNA was isolated by the boiling method. pPK1 DNA was then cleaved with BglI, and inhibition of BamHI (with its recognition sequence GGATCC lying on the boundary between the (dC-dG)n segments and the pUC19 nucleotide sequence) cleavage was tested. Treatment of cells with 2 mmol/l Os,bipy resulted in a strong inhibition of BamHI cleavage at both restriction sites showing a site-specific osmium modification at the B--Z junction. About the same inhibition of BamHI cleavage was observed after treatment of isolated pPK1 DNA with 0.2 mmol/l Os,bipy.

DNA Restriction Enzymes↗
PubMed1981

An electron microscopic and X-ray diffraction study of osmium localization in membrane structures after fixation with OsO4 introduced to native and freeze-dried specimens.

Ultrathin sections of the sciatic nerve myelin fibres of the frog Rana temporaria and liquid crystals of egg lecithin fixed in OsO4 have been treated by 4% or 30% acetic acid. Following uranyl acetate contrasting of thus treated sections the myelin structure and that of lecithin crystals completely recover. However, in the case of preliminary treatment of the sections with lead tetraacetate the subsequent contrasting fails to recover lamellar structures. The data obtained how that during the fixation of myelin sheath and lecithin crystals with osmium tetroxide, the whole amount of osmium locates in charged regions. The data on the X-ray analysis of myelin with OsO4 introduced before or after freeze-drying are in agreement with these results. It is assumed that the stabilization of fatty acid tails of the membrane lipid molecules is accomplished via formation of hydrogen links induced by glycol hydroxyl groups.

Animals↗
PubMed2002

Increasing membrane contrast by means of imidazole-osmium post-fixation as exemplified by skeletal muscle fiber.

Until now, the interpretation of findings derived from investigations on membrane structures (T tubules, sarcoplasmic reticulum, the Golgi apparatus) in thick sections of mammalian muscle tissue has been limited in TEM due to the lack of sharp resolution of the membrane contours. This article shows how the imidazol-osmium post-fixation of tissue blocks can be used to achieve well-contrasted, sharply defined membrane contours. Therefore, unstained sections from imidazol-osmium post-fixed tissue can be examined immediately. But protein structures (e.g., ribosomes) remain uncontrasted with this technique. If needed, it is possible to visualize the protein structures by conventional section staining with uranyl acetate and lead citrate. This method is suitable for both ultrathin and thick sections (>150 nm).

Animals↗
PubMed2003

Shape and position of the sarcoplasmic reticulum and the Golgi apparatus in the sole plate and remaining subsarcolemmal muscle region of the mouse using imidazole-osmium staining.

By means of thin (< or =150 nm) and thick (>150 nm) sections, the shape and position of the sarcoplasmic reticulum and of the Golgi apparatus in the sole plate and in the remaining subsarcolemmal sarcoplasmic region were investigated. For this purpose the membranes were stained by means of imidazole-osmium postfixation and unstained sections analyzed under the electron microscope. Both in the sarcoplasma of the sole plate and around the muscle fiber nuclei, a network of tubules is visible after imidazole-osmium staining which can be identified as the sarcoplasmic reticulum solely on the basis of its contacts with the perinuclear cistern and the cisterns of the triads. Findings in literature on the position of the Golgi apparatus are confirmed and similar spatial relationships and vesiculations between the perinuclear cisterns and the Golgi apparatus of the sole plate nuclei and the other subsarcolemmal fiber nuclei are also demonstrated using this new staining method.

Animals↗
PubMed1989

Improved chondrocyte morphology and glycogen retention in the secondary center of ossification following osmium-potassium ferrocyanide fixation.

The use of osmium-potassium ferrocyanide as the secondary fixative greatly improved chondrocyte preservation and stabilized the cartilage matrix proteoglycan. The proteoglycan was similar in appearance to that seen following fixation in the presence of cationic dyes. Extensive glycogen preservation was noted in these cells, occupying the area prior to and during the formation of the secondary center of ossification. The volume and organization of the glycogen within the cell cytoplasm were greater than that following buffered osmium fixation, and the cellular vacuoles within were greatly reduced. The cells forming the secondary center prior to the onset of mineralization were of greatest interest, because other studies compared them with the primary growth plate and described them as showing signs of hypertrophy as early as 5 days postnatally, as is found in the primary growth plate. Our observations indicate that glycogen is present in these cells, and cellular enlargement was not present. The cells do not resemble the hypertrophic chondrocytes of the primary growth plate, as far as cytoplasmic content is concerned, and we suggest that they may contribute to the development of the secondary center in a different fashion.

Animals↗
PubMed1992

Chemical extraction of the cytosol using osmium tetroxide for high resolution scanning electron microscopy.

Detailed examination of subcellular structures in three dimensions (3D) by high resolution scanning electron microscopy (HRSEM) is now possible due to improvements in the design of the scanning electron microscope and the introduction of methods of specimen preparation using chemical removal of the cytosol and cytoskeleton by dilute osmium tetroxide. Cells which have been fixed, frozen, cleaved, thawed, and subjected to cytosol extraction display intact intracellular structures in 3D including nuclear chromatin, endoplasmic reticulum, mitochondria, and the Golgi complex at a resolution close to that of conventional biological transmission electron microscopy (TEM). Small changes in the 3D structure of subcellular components can be conveniently examined in this way in development, in a variety of physiological processes and in disease. Broad areas of the specimen can be quickly surveyed by HRSEM since sectioning is not required and specimens of comparatively large size (up to 5 mm3) can be placed in the microscope. Extraction of the cytosol with dilute osmium tetroxide (OsO4) exposes subcellular structures in relief, permitting their examination in 3D from several aspects. However, the OsO4 extraction technique is limited, since significant intracellular structures, such as the cytoskeleton, vesicles, and antibody binding sites can be removed or inactivated during the cytosol removal steps.

Animals↗
PubMed1994

Improved ultrastructural preservation of rat ciliary body after high pressure freezing and freeze substitution: a perspective view based upon comparison with tissue processed according to a conventional protocol or by osmium tetroxide/microwave fixation.

Conventional fixation of the delicate, highly folded rat ciliary body and its iridial extension, as well as of vitreal structures, is associated with the induction of a number of artifacts, thus limiting the reliability of morphological interpretations. Improved ultrastructural preservation may be achieved by microwave heating in combination with osmium tetroxide fixation. This protocol, although simple and cheap, yields results, particularly with respect to the extracellular matrix compartment between inner and outer ciliary epithelial cells, which are not greatly inferior to those obtained by implementing the sophisticated high pressure freezing and freeze substitution technique. The latter affords good to very good ultrastructural preservation of epithelium and stromal components, such as blood vessels, neural elements, smooth muscle cells, fibrocytes, and free cells, up to a depth of 50-100 microns from the tissue surface. Its superiority over osmium tetroxide/microwave fixation is revealed in the cytoplasmic, intraorganellar, and vitreal matrix compartments, which incur no obvious losses.

Animals↗
PubMed1983

Sarcoplasmic reticulum and intermediate filament organization in cultured neonatal cardiac muscle cells. Studies with reduced osmium ferrocyanide.

Cardiac muscle cells from 3-day-old rat neonates were cultured for periods of 2 to 56 days. In order to facilitate ultrastructural studies on the organization of the sarcoplasmic reticulum, the cells were prepared for transmission electron microscopy according to a regimen including postfixation in reduced osmium ferrocyanide. The nonjunctional sarcoplasmic reticulum (NJSR) was organized as a loose, fenestrated sleeve around the exterior of bundles of myofilaments and was particularly prominent at the level of the Z line. The only recognizable junctional elements of the sarcoplasmic reticulum were in a peripheral location. Reduced osmium ferrocyanide was also useful in distinguishing intermediate (10 nm) filaments, since it understained Z substance, which often obscured these structures. Intermediate filaments were arranged both at the Z line and the intercalated disc, in parallel strands, approximately at right angles to the myofilaments.

Animals↗
PubMed1975

The demonstration of arylsulfatases with 4-nitro-1,2-benzenediol mono(hydrogen sulfate) by the formation of osmium blacks at the sites of copper capture.

A new method is described for the direct cytochemical demonstration of lysosomal arylsulfatases utilizing a synthetic substrate, 4-nitro-1,2-benzenediol mono(hydrogen sulfate), and a copper capture reaction. A small amount of Hatchett's brown (cupric ferrocyanide, Cu2Fe(CN)6-7 H2O) formed at the subcellular sites of copper capture is then utilized as a heterogeneous catalyst to effect the oxidative polymerization of 3,3'-diaminobenzidine which results in the formation of an insoluble, highly colored osmiophilic indamine polymer at the sites of enzymatic activity. The reaction product even at this stage prior to osmication is highly visible. It is readily seen with a light microscope in 50 mum sections of fixed tissues prepared with a mechanical chopper or in 10 micron cryostat sections treated for arylsulfatase activity. Upon osmication, an electron-opaque osmium black is formed which is much less soluble than the products of either the lead or barium capture reactions currently used for the demonstration of arylsulfatase with the electron microscope. The selection of areas of plastic-embedded tissues for ultrathin sectioning is facilitated by the ready visibility of these osmium black end products on 1-2 mum plastic sections which can be studied with the light microscope. This method gives permanent specimens demonstrating arylsulfatases A or B in lysosomes and autophagic vacuoles. In addition, enzyme activity is seen occasionally in the Golgi region or lamellae of certain cells believed to be elaborating sulfated products. In these instances, it may be demonstrating sulfotransferase activity.

Animals↗
PubMed1981

Staining of oral epithelium with the zinc iodide-osmium reaction.

Some of the parameters affecting the staining of keratinized oral epithelium with the zinc iodide-osmium reaction were examined using light and electron microscopy and electron probe microanalysis. Factors examined were block size, incubation temperature and the effect of aldehyde prefixation. Large blocks (4 mm cube) were subdivided after incubation and the staining of the centre and edge compared. Generally the reaction was more variable at the edge than in the centre. Small block (1 mm cube) showed a more intense reaction when incubated at 24 degrees C than at 4 degrees C. In all these preparations, final reaction product was seen over Golgi systems, lysosome-like bodies, membrane-coating granules and, in the more intensely stained regions, over endoplasmic reticulum and nuclear membranes as well. In prefixed material, mitochondria were frequently stained in addition to the other organelles. Energy dispersive analysis showed the reaction product to be similar in all preparations and to contain high levels of zinc and osmium but not iodine.

Animals↗
PubMed1976

The crystal and molecular structure of an osmium bispyridine adduct of thymine.

The bispyridine osmium adduct of thymine has been crystallised and subjected to an X-ray diffraction analysis. It crystallises in the triclinic space group P1, with cell dimensions a equals 7.975(3), b equals 10.381(3), c equals 11.036(3) A, alpha equals 82.73(2)degrees, beta equals 77.22(3) degrees, gamma equals 101.75(3), and with two molecules in the unit cell. The analysis has shown that the osmium reagent has added cis across the 5,6 thymine bond.

Binding Sites↗