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PubMed1987

Localization of calcium in roots and microsomal membranes of corn by direct pyroantimonate precipitation.

Many cell membrane systems, including microsomal vesicles of corn, are able to regulate calcium levels both in vivo and in vitro, often in an ATP-dependent, calmodulin-stimulated fashion. The purpose of this study was to determine calcium distribution in meristematic cells of intact tissue and microsomal vesicles from corn roots using direct pyroantimonate-osmium fixation. In root cells, precipitates were localized in mitochondria, plastids, the nucleus, endoplasmic reticulum, Golgi apparatus, and along the plasma membrane. Plasma membrane-enriched microsomal vesicles isolated from corn roots incubated in media to permit calcium transport before pyroantimonate-osmium fixation show internal precipitates associated with the membrane and in the lumen of the vesicles. De-staining of the sections with 1 mM EDTA or EGTA removed precipitate from the sections, confirming the presence of calcium in the antimonate precipitates. These data support biochemical data that this same membrane preparation exhibited ATP-dependent calcium sequestration that was stimulated by calmodulin, as measured by retention of 45Ca. This provides evidence that these membranes are responsible for ATP-requiring, calmodulin-stimulated calcium transport in the intact cell.

Antimony↗
PubMed1989

Synthesis of a more stable osmium ammine electron-dense DNA stain.

Specific DNA staining for electron microscopic observation is simplified by a shorter synthesis of the staining reagent. The new, more reliable reagent, osmium ammine-B, is stable for more than a year, dissolves completely in water, and does not require reoptimization of staining conditions for every batch, yet reproducibly gives strong contrast to DNA-containing structures.

Animals↗
PubMed1989

Techniques to preserve soluble surface components in birch pollen wall: a scanning and transmission electron microscopic study.

The exine of birch pollen was examined by scanning and transmission electron microscopy in the native state and after fixation in different aqueous fixatives: glutaraldehyde + OsO4; glutaraldehyde + cetylpyridinium chloride (CPC) + OsO4; glutaraldehyde + cuprolinic blue (CB); and periodate + lysine + paraformaldehyde (PLP). The native pollen exine showed a thin (3-5-nm) border of electron-dense material lining the tectum and electron-dense material within microchannels and bacula cavities. Fixation with the addition of CPC resulted in a voluminous surface coat surrounding the pollen grain, but empty microchannels and bacula cavities. After fixation with the addition of CB, there was a thin surface coat, whereas microchannels and bacula cavities were partially filled with electron-dense material. The other fixatives led to empty microchannels and bacula cavities. There was no surface coat on the pollen grain. However, after all fixation procedures, a thin electron-dense border of the tectum remained visible. Concerning the electron-dense material filling microchannels and bacula cavities in the native pollen grain, the results obtained in the present study suggest that it is either completely lost (after conventional and PLP fixation) or, after fixation with a precipitating additive, partially (CB) or completely (CPC) solubilized and precipitated on the surface of the pollen grain as a surface coat.

Cetylpyridinium↗
PubMed1990

Selective staining of nucleic acids by osmium-ammine complex in thin sections from lowicryl-embedded samples.

Osmium-ammine (OA)/SO2 selectively contrasted RNA- and DNA-containing structures in thin sections from Lowicryl-embedded samples. No cell structures were stained after Epon embedding. RNAse and DNAse digestion experiments demonstrated that only RNA and DNA were stained in Lowicryl thin sections. Protease digestion did not modify the staining reaction. The very fine end-reaction produced a very high resolution of the stained structures. The staining reaction was not due to the presence of SO2 but to the low pH of the solution (ranging from 1.5-2.2). OA in glycine buffer, pH 1.5, selectively contrasted nucleic acids. Electrostatic bonds between nucleic acids and OA complex were probably involved in the staining reaction. Increasing the pH value of the staining medium resulted in loss of OA specificity for nucleic acids. The high electrolyte concentration of the staining medium hindered the staining reaction.

Acrylic Resins↗
PubMed1993

Distribution of DNA in human Sertoli cell nucleoli.

For better understanding of nucleolar architecture, different techniques have been used to localize DNA within the dense fibrillar component (DF) or within the fibrillar centers (FC) by electron microscopy (EM). Since it still remains controversial which components contain DNA, we investigated the distribution of DNA in human Sertoli cells using various approaches. In situ hybridization (ISH) with human total genomic DNA as probe and the use of anti-DNA antibody were followed by immunogold detection. This allowed statistical evaluation of the signal density over individual components. The Feulgen-like osmium-ammine (OA) technique for the selective visualization of DNA was also applied. The anti-DNA antibodies detected DNA in mitochondria, in chromatin, and in the DF of the nucleolus. ISH using human total genomic DNA showed similar labeling patterns. The OA technique revealed DNA filaments in the FC and focal agglomerates of decondensed DNA within the DF. We conclude that (a) EM staining techniques that utilize colloidal gold appear to be less sensitive for DNA detection than the OA method, (b) the DF consists of different domains with different molecular composition, and (c) decondensed DNA is not necessarily confined to one particular nucleolar component.

Cell Nucleolus↗
PubMed1994

An alternative method for preparation of Schiff-like reagent from osmium-ammine complex for selective staining of DNA on thin Lowicryl sections.

Batches of osmium-ammine (OA) complex vary considerably in staining properties when used in a Feulgen-like reaction for selective staining of DNA-containing structures. An alternative procedure for preparation of Schiff-like reagent from OA complex is described. It is based on generation of H2SO3, respectively SO2, within the OA solution and ensures more favorable conditions for production of a Schiff-like stain than bubbling with SO2 does. The method is reproducible and yields high staining intensity. Data obtained suggest that the ability of OA complex to produce Feulgen-like staining is strongly influenced by variations in its chemical composition. Their unfavorable effect can be overcome by selecting suitable conditions for preparation of a Schiff-like reagent. Conditions for obtaining specific and sensitive Feulgen-like staining are determined.

Acrylic Resins↗
PubMed1992

Visualization of DNA within mitochondria by osmium-ammine staining of mouse duodenal crypt cells.

Previous investigators have examined mitochondrial DNA (mtDNA) in the electron microscope (EM) after extraction from mitochondria and rotary shadowing. We have observed mtDNA in situ by the osmiumammine procedure for specific staining of DNA in the EM. The procedure was modified to improve the regularity of the staining and then applied to the rapidly dividing cells present in mouse duodenal crypts. In the stained sections of these cells, 25% of the mitochondria exhibited discrete reactive filaments. The filaments, whether observed directly or in stereopairs, appeared either irregular or arranged into distinct patterns, some of which were similar to those previously described after rotary shadowing of duplicating mtDNA: namely, simple and double circular figures, displacement loops and supercoiled forms. The filaments could be traced in serial sections of the same mitochondria and, therefore, were not artifacts. Moreover, their disappearance after DNase digestion demonstrated that they were composed of DNA. It is concluded that mtDNA can be visualized by the modified osmium-ammine technique and may show patterns that can be interpreted as phases in its replication.

Animals↗
PubMed2001

Evaluation of osmium(II) complexes as electron transfer mediators accessible for amperometric glucose sensors.

In order to lower the redox potentials of Os(III/II) complexes, the mixed ligand complexes of Os(II) were synthesized. The redox potentials of Os(III/II) complexes could be lowered by the use of 4,4'-dimethyl-2,2'-bipyridine (dmbpy), imidazole (Him) or its derivatives, and chloride ion as ligands, e.g., values of the redox (formal) potentials of 628 mV vs. Ag/AgCl for [Os(bpy)3]3+/2+ (bpy: 2,2'-bipyridine) and -6 mV for [OsCl(Him)(dmbpy)2]2+/+ were given in deaerated 0.1 mol dm-3 phosphate buffer (pH 7.0). The evaluation of Os(II) complexes as electron transfer mediators accessible for amperometric glucose sensors was examined according to the determination of the redox potentials of Os(III/II) complexes and the second-order rate constants for electron transfer between glucose oxidase (GOx) in reduced form and the Os(III) complex. Although the Os(II) complexes with lower redox potentials tended to decrease the second-order rate constants ks, the ks values for the majority of Os(II) complexes synthesized in this study were greater than that for ferrocenecarboxylic acid. Acceleration of the electron-transfer reaction is attributable to the hydrogen bonding and/or the electrostatic interaction between the Os(II) complexes and GOx. It may be consequently concluded that the mixed ligand complexes of Os(II) with bpy (dmbpy), Him (its derivatives), and Cl- can act as more efficient electron transfer mediators for the fabrication of amperometric glucose sensors.

Biosensing Techniques↗
PubMed1990

Pseudomelanosis duodeni: a case report with electron-probe X-ray analysis.

Pseudomelanosis of the duodenum is rare. Only 17 cases have been documented in the world literature. A 59-year-old man presented to Bankstown Hospital, New South Wales with dysphagia. On endoscopy, he was found to have melanosis of the duodenum in addition to oesophageal ulceration. It has been previously suggested that the pigment ferrous sulphide is derived from gastro-intestinal bleeding and lodged in the macrophages. A detailed examination of the pigment, including X-ray probe micro-analysis at various levels of the intestinal epithelium as well as in macrophages is presented.

Calcium↗
PubMed1975

Ultrastructural histochemical alteration of the plasma membrane in chronic myelocytic leukemia.

Ultrastructural histochemical evaluation of the surface of normal human blood and bone marrow cells exposed to the pyroantimonate-osmium (PAO) reaction indicated the selective binding of pyroantimonate to certain cations (calcium, magnesium, and possibly sodium) associated with the plasma membrane of neutrophilic leukocytes and their developmental forms. Other leukocytes and their precursors did not exhibit plasma membrane PAO reactivity. The extent of surface binding was related to cell maturity, with maximal labeling evident in the mid and late promyelocytes; decreased binding occurred with subsequent maturation while myeloblasts were nonreactive. This study was initiated to ascertain if histochemical surface modifications of neutrophilic cells occur in certain myeloproliferative disorders. In this regard, we have been able to demonstrate a distinctive defect in the plasma membrane PAO binding characteristics of the leukemic cells in chronic myelocytic leukemia (CML). Limited binding of pyroantimonate to the plasma membrane of the leukemic cell series in four patients with CML contrasted with that of the normal granulocytic cell series and the neutrophilic cells seen in myelomonocytic leukemia (two patients), myelofibrosis (one patient), and acute myelocytic leukemia (three patients). Comparison of surface PAO reactivity of neutrophilic cells in all stages of maturation in two patients with CML in blast crisis revealed that, in the patient with 30% circulating blast cells, PAO reactivity was identical to that noted in CML, while in the patient with 80% circulating blast forms, the PAO reactivity of the maturing neutrophilic cells more nearly resembled that observed in neutrophilic cells from normal individuals. Many neutrophilic cells from patients with myelofibrosis and myelomonocytic leukemia and from one patient in severe blast crisis had large surface deposits of pyroantimonate considered to reflect increased membrane-associated reactive cation.

Antimony↗
PubMed1992

Pharmacomodulations on new organometallic complexes of Ir, Pt, Rh, Pd, Os: in vitro and in vivo trypanocidal study against Trypanosoma brucei brucei.

New organometallic complexes have been synthesized by association of an active organic molecule with a metallic element such as Pt, Rh, Ir, Pd, Os. Their trypanocidal activity was studied in vitro and in vivo against T. b. brucei. The more active compounds were pentamidine derivatives. The Ir- COD-pentamidine complex, and Iridium (I) cationic and organometallic complex showed and in vitro activity at 60 micrograms/l. Moreover, all infected mice were cured by this compound subcutaneously administered in a single dose at 0.5 mg/kg (0.317 mumol/kg). In the same conditions, pentamidine cured all the mice at 5 mumol/kg. Ir-COD-pentamidine (or P1995) was 16 fold more efficient than pentamidine. Since the chemotherapeutic index of this molecule was 7.5 fold higher than those of pentamidine, P1995 can be considered as a potential trypanocidal drug of the future.

Animals↗
PubMed2005

[Theoretical calculation of vibrational frequencies for clusters of (1,2-micro2-L1)(1,2-micro2-L2)-decacarbonyltriosmium [L1, L2=H, Cl, Br, I]].

Density functional theory (DFT) and ab initio method have been employed to optimize the molecular geometry of (1,2-micro2-H) (1, 2-micro2-L) Os3 (CO)10 (L: Cl, Br, I) at B3LYP/CEP-4G, B3LYP/LanL2DZ, RHF/CEP-4G and RHF/LanL2DZ levels, respectively. By using ab initio method, the authors have optimized the molecular geometry of (1,2-t12 -L)2 Os3 (CO)20 (L: H, Cl, Br, I). The calculations showed that the charge was translated from Os(CO)3 to Os(CO)4. Harmonic vibrational analysis was performed at the RHF/CEP-4G levels, and according to the frequencies and intensities of the equilibrium structure obtained by using ab initio method, the IR spectra of structure have been simulated. The calculated results were compared with each other and with available experimental data, and were discussed in detail.

Bromine↗
PubMedDate not supplied

[Enzymatic hydroxylation of ruthenocene and osmocene by liver microsomes].

In buffer solution (pH 7,4) ruthenocene and osmocene are far more stable than ferrocene. The metallocenes ruthenocene and osmocene are metabolized by microsomes of mouse liver in the presence of NADPH and O2. The Km-values are similar for both metallocenes, the rate of metabolism is higher for osmocene that for ruthenocene.

Animals↗
PubMed1995

Activation of osmium ammine by SO2-generating chemicals for EM Feulgen-type staining of DNA.

We present herein an improved method for the use of osmium ammine in a Feulgen-type reaction for specific staining of DNA at EM level and an analysis of its Schiff-type reagent behaviour. The activation of osmium ammine to a Schiff-type reagent (so far routinely performed by bubbling with gaseous SO2) can be accomplished by adding S0(2)-generating chemicals as for light microscopy. When used after HCI hydrolysis on epon or acrylate sections, activated osmium ammine behaves like a Schiff-type reagent, and the DNA staining can be selectively and completely abolished by aldehyde blocking agents. This preparation has the advantage of eliminating the use of gaseous SO2 thus rendering the technique more widely available to laboratories which cannot handle gas cylinders containing SO2. We recommend the use of osmium ammine in 8N acetic acid and 40mM sodium metabisulfite for 1 h at 37 degrees C for epon sections, and in 0.2N HCl and 0.2M metabisulfite for 30 min at room temperature for acrylate sections.

Adrenal Glands↗
PubMed1996

Osmium ammine: review of current applications to visualize DNA in electron microscopy.

This review has been collectively written. The contribution of the authors is mentioned for each part. References have been grouped at the end of the review. The objective of this review is to outline the principle of the method for electron microscopy, to emphasize the major applications and recent developments of this technique for DNA detection and finally to compare this technique with some other methods of DNA detection.

Coloring Agents↗