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In this research study, the ability of a boron nitride nanocluster (hereafter B24N24 NC) to detect osmium tetroxide (hereafter OT) after the decoration of Ni into the B24N24 is investigated through the density functionals B3LYP, M06-2X and B97D. The results revealed that the interaction of the pure B24N24 was a physical adhesion or adsorption and the sensing response (SR) of B24N24 is approximately 5.2. The adsorption energy of OT becomes more negative by changing from −5.0 to −20.9 kcal mol−1 after the decoration of the Ni metal on the surface of B24N24, which also leads to a noticeable increase in the corresponding SR to 76.2, indicating that the sensitivity of Ni-decorated B24N24 (Ni@B24N24) is increased. Based on energy decomposition analysis, the nature of the interaction between OT and Ni@B24N24 is mostly an electrostatic cation–lone pair interaction. The theoretically obtained results further confirmed that Ni@BN-based nanostructures can be used for practical purposes. [ABSTRACT FROM AUTHOR]

Background. Today, acute pancreatitis is one of the most common and severe visceral disorders in patients worldwide. The aim of the work was to study the dynamics of ultrastructural changes of type II alveolocytes in the long-term periods of development of experimental acute pancreatitis. Material and methods. The experiments were carried out on 54 white Wistar male rats weighing 180-220 g. The animals were divided into three groups: first -- intact, second -- control, third -- experimental with a model of acute pancreatitis, which was reproduced by intraperitoneal administration of a 20% solution of L-arginine at a total dose of 5 g/kg at one-hour interval. The control group of animals was intraperitoneally injected with an equivalent dose of isotonic sodium chloride solution. All research were performed under sodium thiopental anesthesia at the rate of 60 mg/kg body weight. Lung tissue for electron microscopic examination was collected from the lower lobe of the left lung at 3-5 and 7 days. Pieces of lung tissue measuring 1×1×1 mm were fixed in a 2.5% glutaraldehyde solution, followed by additional fixation in a 1% osmium tetroxide solution. After dehydration, the material was poured into Epon-Araldite. Sections with a thickness of 20-50 nm obtained on "Tesla BS-490" ultramicrotome were studied in a PEM-125K electron microscope. Results. It was found that three days after the start of the study, along with dystrophic-destructive changes, type II alveolocytes in a state of increased functional activity were observed. Continuation of the experiment (5 days) leads to the progression of ultrastructural changes in type II alveolocytes are determined, which are most pronounced on the 7 day of the study. Conclusion. Acute experimental pancreatitis is accompanied by marked changes in the ultrastructural structure of type II alveolocytes. The nature and severity of structural changes of type II alveolocytes depends on the duration of the course of arginine-induced acute pancreatitis. [ABSTRACT FROM AUTHOR]

Background. Nowadays, acute pancreatitis continues to remain an actual problem both in surgery and in intensive care medicine. The aim of the work was to study the dynamics of ultrastructural changes of alveolar macrophages in the longterm development of experimental acute pancreatitis. Material and methods: The experiments were carried out on 62 white Wistar male rats weighing 180-220 g. The animals were divided into three groups: first -- intact, second -- control, third -- experimental with a model of acute pancreatitis, which was reproduced by intraperitoneal administration of a 20% solution of L-arginine in a total dose of 5 g/kg at one-hour interval. The control group of animals was intraperitoneally injected with an equivalent dose of isotonic sodium chloride solution. All research were performed under sodium thiopental anesthesia at the rate of 60 mg/kg body weight. Lung tissue for electron microscopic examination was collected from the lower lobe of the left lung at 3-5 and 7 days. Pieces of lung tissue measuring 1×1×1 mm were fixed in a 2.5% glutaraldehyde solution, followed by additional fixation in a 1% osmium tetroxide solution. After dehydration, the material was poured into Epon-Araldite. Sections with a thickness of 20-50 nm obtained on "Tesla BS-490" ultramicrotome were studied in a PEM-125K electron microscope. Results: It was found that three days after the start of the study, significant heterogeneity of alveolar macrophages was observed in the alveolar lumen. Next to active phagocytic macrophage elements with dystrophic-destructive changes are determined. Continuation of the experiment (5 days) leads to the progression of submicroscopic changes in alveolar macrophages, which are most pronounced on the7 day of the study. Conclusion. Acute experimental pancreatitis is accompanied by pronounced changes in the ultrastructural structure of alveolar macrophages. The features and severity of structural changes in alveolar macrophages depends on the duration of arginine-induced acute pancreatitis. [ABSTRACT FROM AUTHOR]

Serial block-face (SBF) scanning electron microscopy (SEM) is used for imaging the entire internal ultrastructure of cells, tissue samples or small organisms. Here, we present a workflow for SBF SEM of adherent cells, such as Giardia parasites and HeLa cells, attached to the surface of a plastic culture dish, which preserves the interface between cells and plastic substrate. Cells were embedded in situ on their substrate using silicone microwells and were mounted for cross-sectioning which allowed SBF imaging of large volumes and many cells. A standard sample preparation and embedding protocol for thin section electron microscopy provided already sufficient resolution and image quality to visualize larger structures. To improve resolution and image quality of SBF imaging, we stepwise tested modifications of the protocol, such as the moderate increase of the heavy metal content of the sample. Modifications of the embedding by either the reduction of the resin layer (minimal embedding) or the addition of silver colloid to the resin were evaluated at high and low vacuum imaging conditions. The optimized sample preparation protocol is very similar to the standard preparation protocol for thin section electron microscopy, so that the samples can also be used for this application. The protocol applies a higher concentration of osmium tetroxide, a higher temperature for heavy metal incubation and an additional lead en bloc staining. In summary, the presented workflow provides a generic and adaptable solution for studying adherent cells by SBF SEM. [ABSTRACT FROM AUTHOR]

Testing the hemocompatibility of medical devices after their interaction with blood entails the need to evaluate the activation of blood elements and the degree of their coagulation and adhesion to the device surface. One possible way to achieve this is to use scanning electron microscopy (SEM). The aim was to develop a novel SEM-based method to assess the thrombogenic potential of medical devices and their adhesiveness to blood cells. As a part of this task, also find a convenient procedure of efficient and non-destructive sample fixation for SEM while reducing the use of highly toxic substances and shortening the fixation time. A polymeric surgical mesh was exposed to blood so that blood elements adhered to its surface. Such prepared samples were then chemically fixed for a subsequent SEM measurement; a number of fixation procedures were tested to find the optimal one. The fixation results were evaluated from SEM images, and the degree of blood elements' adhesion was determined from the images using ImageJ software. The best fixation was achieved with the May–Grünwald solution, which is less toxic than chemicals traditionally used. Moreover, manipulation with highly toxic osmium tetroxide can be avoided in the proposed procedure. A convenient methodology for SEM image analysis has been developed too, enabling to quantitatively evaluate the interaction of blood with the surfaces of various medical devices. Our method replaces the subjective assessment of surface coverage with a better-defined procedure, thus offering more precise and reliable results. [ABSTRACT FROM AUTHOR]

Sharpless asymmetric dihydroxylation is an important reaction in the enantioselective synthesis of chiral vicinal diols that involves the treatment of alkene with osmium tetroxide along with optically active quinine ligand. Sharpless introduced this methodology after considering the importance of enantioselectivity in the total synthesis of medicinally important compounds. Vicinal diols, produced as a result of this reaction, act as intermediates in the synthesis of different naturally occurring compounds. Hence, Sharpless asymmetric dihydroxylation plays an important role in synthetic organic chemistry due to its undeniable contribution to the synthesis of biologically active organic compounds. This review emphasizes the significance of Sharpless asymmetric dihydroxylation in the total synthesis of various natural products, published since 2020. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to provide advanced insights into scanning electron microscopy (SEM) of adipose derived mesenchymal stem cells (oAD-MSCs). In this study after isolation and proliferation of ADMSCs, their cell surface markers characterized using antibodies RT-PCR. SEM was used to study of ultrastructure of oAD-MSCs. Adipose tissue was obtained from tail fat of sheep. Surface markers (CD44, CD90, CD34, CD31) evaluated by RT-PCR. RT-PCR was done for CD44, CD90, CD34 and CD31 to identify of cells. Morphological characterization was done by inverted microscope and SEM. Cells was prepared by glutaraldehyde for first fixation and tetroxide osmium for second fixation and dehydration with different percent of ethanol. Finally, cells coated with gold and observed in SEM. Adipose derived mesenchymal stem cells (AD-MSCs) were isolated and proliferated. They were positive for CD44 and CD90 markers and negative for CD31 and Cd34 markers in RT-PCR technique. AD-MSCs showed a fibroblast-like, spindleshaped morphology after they attached to the culture flasks observing in inverted microscope. Explanted specimens were imaged with scanning electron microscopy (SEM). SEM provides the main technology to visualize surface features. In SEM the outer surface of the mesenchymal cells could be observed; so, in this study, the pseudopods arising from each cell and extending through each other were clearly shown. [ABSTRACT FROM AUTHOR]

In-resin CLEM (Correlative Light and Electron Microscopy) of Epon-embedded cells involves correlating fluorescence microscopy with electron microscopy in the same Epon-embedded ultrathin section. This method offers the advantage of high positional accuracy compared to standard CLEM. However, it requires the expression of recombinant proteins. In order to detect the localization of endogenous target(s) and their localized ultrastructures of Epon-embedded samples using in-resin CLEM, we investigated whether immunological and affinity-labeling using fluorescent dyes applied to in-resin CLEM of Epon-embedded cells. The orange fluorescent (λem ∼550 nm) and far-red (λem ∼650 nm) fluorescent dyes examined maintained a sufficient level of fluorescent intensity after staining with osmium tetroxide and subsequent dehydration treatment with ethanol. Immunological in-resin CLEM of mitochondria and the Golgi apparatus was achieved using anti-TOM20, anti-GM130 antibodies, and fluorescent dyes. Two-color in-resin CLEM revealed that wheat germ agglutinin-puncta showed the ultrastructures of multivesicular body-like structures. Finally, taking the advantage of high positional accuracy, volume in-resin CLEM of mitochondria in the semi-thin section (2 μm thick) of Epon-embedded cells was performed by focused ion beam scanning electron microscopy. These results suggested that the application of immunological reaction and affinity-labeling with fluorescent dyes to in-resin CLEM of Epon-embedded cells is suitable for analyzing the localization of endogenous targets and their ultrastructures by scanning and transmission electron microscopy.

The article presents a study which showed that cystathione β-synthase (CBS), compared with cystathionine γ-lyase, is the major enzyme that synthesizes hydrogen sulfide in the pathogenic fungus Candida (C.) albicans. Topics include participation of both CBS and CSE in hydropersulfidation, deletion of CBS on mitochondrial dysfunction in C. albicans, and the crystal structure of C. albicans CBS.

Purpose: Spinal cord injury (SCI) causes various neurological consequences that disrupt the structure of axons. The C/EBP Homologous Protein (CHOP) acts in neuronal death by apoptosis has been demonstrated in experimental models. Rosmarinic acid (RA) is a phenolic compound used for therapeutic purposes in many diseases. In this study, we investigated the therapeutic effect of Rosmarinic acid application on inflammation and apoptotic development after spinal cord injury. Methods: Male Wistar albino rats (n: 24) were assigned to three group: control, SCI and SCI+ RA. All rats were fixed on the operating table after anesthesia, the skin of the thoracic region was opened with a midline incision and the paravertebral muscles were dissected and T10-T11 laminas were exposed. A cylindrical tube of 10 cm length was fixed to the area to be laminectomy. A metal weight of 15 grams was left down the tube. Spinal damage was created, skin incisions were sutured. 50 mg/kg rosmarinic acid was given orally for 7 days after the spinal injury. Spinal tissues were fixed in formaldehyde solution and processed for paraffin wax tissue protocol and 4-5 µm sections were taken with microtome for further immunohistochemical examination. Caspase-12 and CHOP antibodies were applied to sections. Remaining tissues were carried out in glutaraldehyde for the first fixation then in osmium tetroxide for the second. Tissues were kept in pure araldite and thin sections were taken for transmission electron microscope. Results: Values of malondialdehyde (MDA), myeloperoxidase (MPO), glutathione peroxidase (GSH), neuronal degeneration, vascular dilation, inflammation, CHOP and Caspase-12 expression were increased in SCI group compared to control group. Only glutathione peroxidase content was decreased in SCI group. In SCI group, disruption of basement membrane structure in canalis ependymalis, degeneration in structures of unipolar bipolar and multipolar neurons, and apoptotic changes were seen with increased inflammation in the piamater region and positive CHOP expression in vascular endothelial cells. In SCI+RA group, reorganization of basement membrane pill in canalis ependymalis were observed with mild Caspase-12 activity in some canalis ependymal and glial cells. Also, moderate CHOP expression in multipolar and bipolar neurons and glia cells were observed. Conclusions: The application of RA has a significant effect on preventing damage in SCI. It was thought that CHOP and Caspase-12 mediated oxidative stress could be a guide in showing the potential and therapeutic target to stop the apoptotic course after SCI injury. [ABSTRACT FROM AUTHOR]

Electron microscopy of biological tissue has recently seen an unprecedented increase in imaging throughput moving the ultrastructural analysis of large tissue blocks such as whole brains into the realm of the feasible. However, homogeneous, high-quality electron microscopy staining of large biological samples is still a major challenge. To date, assessing the staining quality in electron microscopy requires running a sample through the entire staining protocol end-to- end, which can take weeks or even months for large samples, rendering protocol optimization for such samples to be inefficient. Here, we present an in situ time-lapsed X-ray- assisted staining procedure that opens the ‘black box’ of electron microscopy staining and allows observation of individual staining steps in real time. Using this novel method, we measured the accumulation of heavy metals in large tissue samples immersed in different staining solutions. We show that the measured accumulation of osmium in fixed tissue obeys empirically a quadratic dependence between the incubation time and sample size. We found that potassium ferrocyanide, a classic reducing agent for osmium tetroxide, clears the tissue after osmium staining and that the tissue expands in osmium tetroxide solution, but shrinks in potassium ferrocyanide reduced osmium solution. X-ray- assisted staining gave access to the in situ staining kinetics and allowed us to develop a diffusion-reaction- advection model that accurately simulates the measured accumulation of osmium in tissue. These are first steps towards in silico staining experiments and simulation-guided optimization of staining protocols for large samples. Hence, X-ray- assisted staining will be a useful tool for the development of reliable staining procedures for large samples such as entire brains of mice, monkeys, or humans. [ABSTRACT FROM AUTHOR]

The article demonstrate the applicability of self-assembly dopamine-coated magnetite nanocrystals (MNcs) into microsized matrix-based magnetic particles (M3P) for ultrasensitive molecular imaging of inflammation in the brain, kidneys, and intestinal mucosa. Topics discussed include producing a microsized magnetic particle that is fully biodegradable and can be functionalized for molecular MRI, and synthesizing M3P, a new contrast agent for molecular MRI made of MNc embedded in a PDA matrix.

Biotin ligases have been developed as proximity biotinylation enzymes for analyses of the interactome. However, there has been no report on the application of proximity labeling for in-resin correlative light-electron microscopy of Epon-embedded cells. In this study, we established a proximity-labeled in-resin CLEM of Epon-embedded cells using miniTurbo, a biotin ligase. Biotinylation by miniTurbo was observed in cells within 10 min following the addition of biotin to the medium. Using fluorophore-conjugated streptavidin, intracellular biotinylated proteins were labeled after fixation of cells with a mixture of paraformaldehyde and glutaraldehyde. Fluorescence of these proteins was resistant to osmium tetroxide staining and was detected in 100-nm ultrathin sections of Epon-embedded cells. Ultrastructures of organelles were preserved well in the same sections. Fluorescence in sections was about 14-fold brighter than that in the sections of Epon-embedded cells expressing mCherry2 and was detectable for 14 days. When mitochondria-localized miniTurbo was expressed in the cells, mitochondria-like fluorescent signals were detected in the sections, and ultrastructures of mitochondria were observed as fluorescence-positive structures in the same sections by scanning electron microscopy. Proximity labeling using miniTurbo led to more stable and brighter fluorescent signals in the ultrathin sections of Epon-embedded cells, resulting in better performance of in-resin CLEM. [ABSTRACT FROM AUTHOR]

If fixation is not adequate, the other processes that follow such as dehydration, clearing, infiltration, embedding, microtomy and staining, will also be inadequate. A poorly processed tissue will make it difficult for the Pathologist/Histoscientist to render a proper diagnosis. This article is aimed at elucidating more on fixatives and fixation process in histopathology. The information presented in this review was gathered primarily from an extensive literature search on PubMed, Scopus and Textbooks. Fixatives in histopathology can be grouped into simple and compound fixatives. Simple fixative is a solution or gas which contains only one active ingredient or that has a singlechemical solution. Examples include; Formaldehyde, Glutaraldehyde, Mercuric Chloride, Potassium Dichromate, Picric Acid, Osmium Tetroxide, Acetic Acid, Ethanol, Acetone and Chromic Acid. When two or more simple fixatives are combined in a solution, the resulting solution is called a compound fixative. This can be further divided into Microanatomical and cytological fixatives. Examples of a micro-anatomical fixatives include; 10% formal-saline, Heidenhain's Susa, Boiun's fluid, Formol Sublimate. Cytological fixatives are grouped into cytoplasmic and nuclear fixatives. Fixation terminates any ongoing biochemical reactions, and also increases the mechanical strength or stability of the treated tissues. To accomplish this, tissue samples are usually immersed immediately in a fixative fluid. The fixatives employed prevent autolysis and putrefaction from taking place. Fixatives are integral substances used in histopathology to forestall the actions of autolysis and putrefaction in tissue samples. [ABSTRACT FROM AUTHOR]

The stereoselective total synthesis of (+)-casuarine has been achieved via a functionalized pyrrolidine obtained from a chiral 1,3-oxazine. The synthetic strategy includes a stereoselective dihydroxylation reaction using osmium tetroxide and stereoselective Grignard-type vinyl addition reaction as the key steps to generate the two new stereocenters. The dihydroxylation catalyzed by osmium tetroxide formed anti -amino alcohol, and the vinyl addition formed syn -alcohol. (+)-Casuarine was prepared from the functionalized pyrrolidine over 11 steps in an overall yield of 16%. [ABSTRACT FROM AUTHOR]

Research is conducted to determine the effect of production parameters on osmium extraction during leaching roasting cinders containing osmium and rhenium from copper production cakes with water, hydrogen peroxide and various oxidizing agents. The main goal is to maximize osmium extraction into the gas phase for subsequent conversion into osmium sulfide. Material leaching is performed within a unit assembled for this purpose. During leaching osmium is distributed among the leaching products: gas phase, leaching solutions, and leaching cakes. Results of the work and their novelty: the effect of temperature and duration on the extraction of osmium during water leaching of cinder is studied. The activity of 11 oxidizing agents during cinder leaching is investigated; an oxidizing agent close to the optimum is selected for transferring osmium tetroxide into the gas phase and its absorption by sodium alkali. Oxidizing agent consumption during cinder leaching in various regimes is determined. [ABSTRACT FROM AUTHOR]

High-pressure freezing followed by freeze-substitution is a valuable method for ultrastructural analyses of resin-embedded biological samples. The visualization of lipid membranes is one of the most critical aspects of any ultrastructural study and can be especially challenging in high-pressure frozen specimens. Historically, osmium tetroxide has been the preferred fixative and staining agent for lipid-containing structures in freeze-substitution solutions. However, osmium tetroxide is not only a rare and expensive material, but also volatile and toxic. Here, we introduce the use of a combination of potassium permanganate, uranyl acetate, and water in acetone as complementing reagents during the freeze-substitution process. This mix imparts an intense en bloc stain to cellular ultrastructure and membranes, which makes poststaining superfluous and is well suited for block-face imaging. Thus, potassium permanganate can effectively replace osmium tetroxide in the freeze-substitution solution without sacrificing the quality of ultrastructural preservation. [ABSTRACT FROM AUTHOR]

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Tensile tests of birch cork were performed in the tangential direction. Birch cork in the wet state showed significantly higher extensibility than those in the dried state. The histochemical structure of birch cork was investigated by microscopic observation and spectroscopic analysis. Birch cork cell walls showed a two-layered structure and the inner material bordering cell wall. In transmission electron micrographs, osmium tetroxide stained the outer layer and inner material, whereas potassium permanganate stained the inner layer and inner material. After removal of suberin and lignin, only inner layer remained and Fourier-transformed infrared spectra showed the cellulose I pattern. Polarizing light micrographs indicated that molecular chains in the outer layer and inner material were oriented perpendicular to suberin lamination, whereas those in the inner layer showed longitudinal orientation. These results suggested that the outer layer and inner material mainly consist of suberin, whereas the inner layer and compound middle lamella consist of lignin, cellulose, and other polysaccharides. We hypothesized a hierarchical model of the birch cork cell wall. The lignified cell wall with helical arrangement of cellulose microfibrils is sandwiched between suberized outer layer and inner material. Cellulose microfibrils in the inner layer bear tensile loads. In the wet state, water and cellulose transfer tensile stress. In the dried state, this stress-transferal system functions poorly and fewer cells bear stress. Suberin in the outer layer and inner material may prevent absolute drying to maintain mechanical properties of the bark and to bear tensile stress caused by trunk diameter growth. [ABSTRACT FROM AUTHOR]

The volatile synthetic products of photochemical vapor generation (PVG) of Os(IV) and W(VI) have been confirmed by GC-MS. Osmium tetroxide has been identified as the species generated from an oxidizing medium of dilute nitric acid, and tungsten hexacarbonyl is produced during PVG from a reducing medium of formic acid. Attempts to ascertain the PVG products of Os and Ru generated in high yield from reducing media (i.e., acetic and formic acids, respectively in the presence of metal sensitizers) were unsuccessful, possibly due to their instability or reactivity with the GC support, and thus remain to be identified using more direct approaches such as Direct Analysis in Real Time (DART)-MS. The mass spectra for OsO4 and W(CO)6, reported here for the first time, serve to aid the further development/refinement of mechanistic models for PVG. [ABSTRACT FROM AUTHOR]

Cyclohexane is selectively oxidized to cyclohexyl hydroperoxide (P) by the reaction with hydrogen peroxide (H2O2) in the presence of a catalytic amount of osmium tetroxide (OsO4). The product is converted to cyclohexanol (A) by the treatment with PPh3. The catalytic reactivity of OsO4 is enhanced by adding a coordinative anion such as benzoate anion. Encouraged by this result, we have developed an OsO4-immobilized heterogeneous catalyst using mesoporous silica (SBA-15) containing carboxylate groups on the surface. [ABSTRACT FROM AUTHOR]

Fosamprenavir calcium is an active pharmaceutical ingredient (API) in which trace elements must be monitored by ICH Q3D Guideline. It delivers appropriate method to ensure the quality of the product and its safe use. Elemental impurities in API are separated in three classes based on their toxicity and probability of their occurrence in the product. ICP-MS has proven to be a suitable technique with the appropriate sample preparation method. Due to the presence of oxidising agents in the sample preparation, determination of osmium is problematic. In the presence of oxidising nitric acid, a highly volatile and toxic osmium tetraoxide is formed. Due to its high volatility, the recovery of osmium has reached the value of 287 %, which exceeds recovery limit (70–150 %). However, osmium can be stabilised by complexation with thiourea in the hydrochloric acid solution (recovery = 87 %). In that way, the loss of osmium is reduced and good results are achieved in terms of usability, accuracy, and precision. A method with addition of thiourea has been successfully validated through main validation parameters: linearity, quantitation limit, selectivity, accuracy, precision (which included repeatability and intralaboratory reproducibility), and robustness. Each of these validation parameters met the acceptance criteria, and therefore it was concluded that the method is suitable for the determination of trace elements in fosamprenavir calcium by ICP-MS. [ABSTRACT FROM AUTHOR]

Osmium tetroxide is a strong oxidizing agent. After dermal exposure to osmium tetroxide, skin discoloration and red papules can occur. We describe a patient with skin discoloration due to osmium tetroxide. A 25-year-old postgraduate student unintentionally exposed his hand to osmium tetroxide while working in a laboratory setting. After immediate washing, he sought medical care due to left middle finger discoloration. He reported no discomfort in the affected area. Thorough water rinsing was continued, and corticosteroid ointment was applied. Our patient developed dark brown pigmentation on the ventral side of the left middle finger. The pigmentation disappeared one week later. Osmium tetroxide may induce dark brown skin discoloration. [ABSTRACT FROM AUTHOR]

This communication reports experimental and theoretical evidences of σ‐hole interactions in adducts between nitrogen or oxygen nucleophiles and tetroxides of osmium or other group 8 elements. Cocrystals between pyridine or pyridine N‐oxide derivatives and osmium tetroxide are characterized through various techniques and rationalized as σ‐hole interactions using DFT calculations and several other computational tools. We propose the term "osme bond" (OmB, Om=Fe, Ru, Os, (Hs)) for naming the noncovalent interactions wherein group 8 elements have the role of the electrophile. The word osme is the transcription of ὀσμή, the ancient Greek word for smell that was used to name the heaviest group 8 element in relation to the smoky odor of its tetroxide. [ABSTRACT FROM AUTHOR]

Aims: The objective of this study was to elucidate the early white matter changes in CADASIL small vessel disease. Methods: We used high‐pressure freezing and freeze substitution (HPF/FS) in combination with high‐resolution electron microscopy (EM), immunohistochemistry and confocal microscopy of brain specimens from control and CADASIL (TgNotch3R169C) mice aged 4–15 months to study white matter lesions in the corpus callosum. Results: We first optimised the HPF/FS protocol in which samples were chemically prefixed, frozen in a sample carrier filled with 20% polyvinylpyrrolidone and freeze‐substituted in a cocktail of tannic acid, osmium tetroxide and uranyl acetate dissolved in acetone. EM analysis showed that CADASIL mice exhibit significant splitting of myelin layers and enlargement of the inner tongue of small calibre axons from the age of 6 months, then vesiculation of the inner tongue and myelin sheath thinning at 15 months of age. Immunohistochemistry revealed an increased number of oligodendrocyte precursor cells, although only in older mice, but no reduction in the number of mature oligodendrocytes at any age. The number of Iba1 positive microglial cells was increased in older but not in younger CADASIL mice, but the number of activated microglial cells (Iba1 and CD68 positive) was unchanged at any age. Conclusion: We conclude that early WM lesions in CADASIL affect first and foremost the myelin sheath and the inner tongue, suggestive of a primary myelin injury. We propose that those defects are consistent with a hypoxic/ischaemic mechanism. [ABSTRACT FROM AUTHOR]

Immunogold labeling allows localization of proteins at the electron microscopy (EM) level of resolution, and quantification of signals. The present paper summarizes methodological issues and experiences gained from studies on the distribution of synaptic and other neuron-specific proteins in cell cultures and brain tissues via a pre-embedding method. An optimal protocol includes careful determination of a fixation condition for any particular antibody, a well-planned tissue processing procedure, and a strict evaluation of the credibility of the labeling. Here, tips and caveats on different steps of the sample preparation protocol are illustrated with examples. A good starting condition for EM-compatible fixation and permeabilization is 4% paraformaldehyde in PBS for 30 min at room temperature, followed by 30 min incubation with 0.1% saponin. An optimal condition can then be readjusted for each particular antibody. Each lot of the secondary antibody (conjugated with a 1.4 nm small gold particle) needs to be evaluated against known standards for labeling efficiency. Silver enhancement is required to make the small gold visible, and quality of the silver-enhanced signals can be affected by subsequent steps of osmium tetroxide treatment, uranyl acetate en bloc staining, and by detergent or ethanol used to clean the diamond knife for cutting thin sections. Most importantly, verification of signals requires understanding of the protein of interest in order to validate for correct localization of antibodies at expected epitopes on particular organelles, and quantification of signals needs to take into consideration the penetration gradient of reagents and clumping of secondary antibodies. [ABSTRACT FROM AUTHOR]

Lobomycosis is a skin infection produced by the fungus Lacazia loboi, which mainly affects some indigenous and afro‐descendant populations in Tropical America. We previously reported the comparative effect of osmium tetroxide (OsO4) and ruthenium tetroxide (RuO4) in the electron microscopy (EM) of other related microorganisms. The objective of this study is to compare the effect of postfixation with OsO4 and RuO4 in the ultrastructure of L. loboi yeasts. Skin biopsies on patients diagnosed with lobomycosis were fixed in glutaraldehyde at 3% and postfixed in the following solutions: (a) 1% OsO4, (b) 0.2% RuO4, and (c) OsO4 at 1% followed by RuO4 at 0.2%. They were then processed using the conventional method for EM. Unlike OsO4, the treatment with RuO4 revealed different shades of gray and electron dense bands in the cell wall and other cell components of L. loboi. The most notable finding was the presence of radial filamentous structures around the yeast, which made the image look like the sun. Postfixation with RuO4 revealed ultrastructural details that had not been previously reported for L loboi. The combined use of OsO4 and RuO4 in EM of microorganisms with cell walls can be useful to evaluate the effect of microbicide substances. [ABSTRACT FROM AUTHOR]

Researchers have used transmission electron microscopy (TEM) to make contributions to cell biology for well over 50 years, and TEM continues to be an important technology in our field. We briefly present for the neophyte the components of a TEM-based study, beginning with sample preparation through imaging of the samples. We point out the limitations of TEM and issues to be considered during experimental design. Advanced electron microscopy techniques are listed as well. Finally, we point potential new users of TEM to resources to help launch their project.

Introduction: the study examined the ultrastructural features of the palatine tonsils of local mixed breed of buffalo (Bubalus bubalis) using scanning and transmission electron-microscopy. Materials and methods: the tissue samples were collected from 6 heads of buffaloes killed by captive bolt stunning gun. The tissues for SEM were washed with chilled 0.1M phosphate buffer (pH 7.4) and fixed in 2% glutaraldehyde solution for 6-8 hours. The tissues were dehydrated using ascending grades of alcohol, critical point dried, mounted on stubs and sputter coated with gold, and viewed using a scanning electron-microscope. The tissue samples for TEM were primarily fixed in 2.5% glutaraldehyde for 6-8 hours and post-fixed in 2% osmium tetraoxide for 1 hour. The blocks were prepared using epoxy resins and thin sections of 1 µ were stained to select regions of interest. The ultrathin sections were stained and viewed with Technai G2. Results: the epithelium presented folded mucosa consisting of folds divided by shallow grooves. The surface had a squamous arrangement of cells. The squamous cells at higher magnification presented the microplicae which appeared as if filled with material. A few small ducts opening were irregularly placed throughout the mucosal surface. TEM described structural details of the distinct strata of the surface and reticular epithelia, the cell organelles as well as the lymphocytes migration across the high endothelial venules. The vesiculo-vacuolar organelle was also observed. Conclusion: the study provided detailed ultramicroscopic features of the palatine tonsil which might play a significant role in the induction of immunity against ingested antigens sampled at the mucosal surface. [ABSTRACT FROM AUTHOR]

The study of the localization of secondary metabolites in both plants and the cell cultures on the intravital sections is hampered by the difficulty of obtaining thin, correctly oriented sections. Techniques for fixing tissues in resins allow these difficulties to be overcome. Properly selected tissue fixation techniques allow using different dyes to identify the compound of interest. In addition, some components of tissue fixation can act as fixatives and as a dye for identifying secondary metabolites. For example, osmium tetroxide, which fixes lipids in tissues, stains phenolic compounds black. This paper describes methods for the detection of phenolic compounds in morphogenic callus culture of buckwheat using osmium tetroxide, Toluidine Blue O dye, and ferric chloride as dyes in epoxy resin-embedded cell culture with double fixation of the material and when material fixed in Karnovsky's fixative., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Epoxidation of olefinic heterocyclic amines and subsequent acid-catalyzed hydrolysis or alternatively the direct dihydroxylation with the help of osmium tetroxide led to diols, which underwent ring cleavage in the presence of lead tetraacetate to give 3-isopropyl-2,2,4,4-tetramethyl-3-azahexanedial and 3- tert -butyl-2,2,4,4-tetramethyl-3-azapentanedial. Whereas the former dialdehyde is a highly unstable model compound because of a rapid intramolecular aldol reaction, the latter product proves to be isolable at room temperature. Furthermore, this compound is the first open-chain tri- tert -alkylamine establishing in a new record of steric crowding in tertiary amines. Strong tendencies to a Hofmann-like elimination reaction or to ring-closing reactions were observed when the aldehyde units of 3- tert -butyl-2,2,4,4-tetramethyl-3-azapentanedial were transformed into other functionalities, since both types of reactions led to a significantly decrease of the steric stress. [ABSTRACT FROM AUTHOR]

Osmium tetroxide is a strong oxidizing agent used in electron microscopy. Eye exposure may cause severe burns, and after inhalation or ingestion damage to the respiratory or gastrointestinal tract occurs. Exposure to osmium and its compounds is extremely rare. We present a case of a 32‐year‐old female stained by 9 mL of 2% osmium tetroxide in acetone during an accident in the laboratory, with rare dermal and ocular findings. Due to lack of data in toxicological databases and the absence of antidote, the therapy was symptomatic. Osmium was detected in serum 19 hours later (0.22 μg/L) and in urine during the 15‐hour collection (three samples—7.05, 1.65 and 8.45 μg/L). In blood serum on admission, after 1 and 2 days after exposure, the levels of iron (28.2, 39.8 and 50.5 μmol/L; reference range 5.8‐34.5 μmol/L) and transferrin receptor/ferritine were elevated. To our knowledge, this is the first paper documenting a significant absorption from the skin and potentially from the eye conjunctiva, based on serum and urine analysis. The relationship between increased iron in blood and exposure has not been described yet, and the mechanism remains unknown. The patient is being followed up for the unknown long‐term effects. [ABSTRACT FROM AUTHOR]

Bird feather lipids are usually attributed to the oily secretion product of the uropygial (preen) gland. We have observed, however, that feathers exhibit a strong reaction with osmium tetroxide (OsO4), even after treatment with detergents. This leads us to postulate the existence of endogenous feather lipids distinct from preen gland lipids. In order to substantiate our hypothesis, we investigated down feathers from a 1-day-old chicken as their uropgygial gland is not functionally active. The results confirmed the osmiophilic reaction, which was concentrated in the center of barbs and strongly reduced after lipid extraction. In these lipid extracts, we identified using thin layer chromatography, cholesterol, various ceramides, glycolipids, phospholipids, and fatty acids, which closely resembled the lipid composition of the water barrier in the chicken-cornified epidermal envelope. This composition is clearly distinct from chicken uropygeal gland secretion (UGS) known to consist of fatty alcohols as part of aliphatic monoester waxes and of free, predominantly saturated, fatty acids. A filter assay showed a strong reactivity between OsO4 and the fatty acids C18:1 and C18:2 and with feather lipid extracts, but not with UGS. These observations were confirmed by gas chromatography detecting unsaturated fatty acids including C18:1 and C18:2 as well as cholesterol exclusively in chicken feathers. Our results indicate that (1) endogenous lipids are detectable in chicken feathers and distinct from UGS and (2) in analogy to the morphogenesis of the cornified envelope of chicken feather lipids that may have derived from cellular feather-precursors, apparently enduring the specific cell death during developmental feather cornification. [ABSTRACT FROM AUTHOR]

Fat embolism is the mechanical blockage of blood vessels by circulating fat particles. It is frequently related to traumas involving soft tissues and fat-containing bones. Different techniques have been used for decades to demonstrate histologically fat emboli, being the extremely toxic post-fixation with osmium tetroxide one of the most used techniques in the last decades. In the present study, the osmium tetroxide technique was compared qualitatively and quantitatively, for the first time, with chromic acid and Oil Red O frozen techniques for histological fat emboli detection in the lungs of eight sperm whales that died due to ship strikes. This was also the first time that chromic acid technique was tested in cetaceans. Results showed that the three techniques were valuable for the histological detection of fat embolism in cetaceans, even when tissues presented advanced autolysis and had been stored in formaldehyde for years. Although quantitative differences could not be established, the Oil Red O frozen technique showed the lowest quality for fat emboli staining. On the contrary, the chromic acid technique was proven to be a good alternative to osmium tetroxide due to its slightly lower toxicity, its equivalent or even superior capacity of fat emboli detection, and its significantly lower economic cost. [ABSTRACT FROM AUTHOR]

The kinetics and mechanism of the cis dihydroxylation of cis‐1,2‐dichloroethylene, trans‐1,2‐dichloroethylene, and trichloroethylene by osmium tetroxide was studied systematically in aqueous solution. The stoichiometry of the process was determined based on the principle of continuous variation of reactant ratios with spectrophotometric detection. The results always showed 1:1 stoichiometry, which is in agreement with dihydroxylation. All three reactions were found to proceed in two distinct steps. The first step occurred on a time scale of seconds and was associated with a minor change in absorbance and was identified as the formation of a 1:1 adduct between the two reagents, which is the osmium(VI) ester that plays a decisive role in catalytic applications. This species is formed in an equilibrium that is very much shifted toward the reactants, so the osmium(VI) complex is a short‐lived intermediate of the process, which is detected kinetically, but its concentration is never high enough for structural characterization. The second reaction is accompanied by major spectral changes; it involves the formation of the final products. Our results clearly show that it is possible to detect the intermediate of the process by careful kinetic studies. It is also possible that the same strategy might be successful in other OsO4‐dependent dihydroxylation processes. [ABSTRACT FROM AUTHOR]

The oxidative cyclization of amino alcohols by osmium tetroxide/NMO or tetrapropylammonium perruthenate (TPAP)/NMO was found to provide an N,O‐acetal moiety through the trapping of the resulting iminium ion by the alcohol. These two transformations were demonstrated in the synthesis of indolizidines (–)‐223AB and 3‐epi‐(–)‐223AB. [ABSTRACT FROM AUTHOR]

The views of A.B. Zezin and V.A. Kabanov on the structure of polyelectrolyte complexes of linear polymers are considered and confirmed by studying chitosan hydrogels with lambda-carrageenan formed by regulated gelation. The complexes are visualized by transmission electron microscopy using osmium tetroxide for staining. [ABSTRACT FROM AUTHOR]

Bacterial natural products containing heptosides such as septacidin represent interesting scaffolds for the development of drugs to combat antimicrobial resistance. However, very few synthetic strategies have been reported to grant access to these derivatives. Here, we have devised a synthetic pathway to l - glycero - l -glucoheptoside, a key building block en route to septacidin, directly from l -glucose. Importantly, we show that carbon homologation at C6, encompassing oxidation of the C6-OH followed by methylenation, is significantly influenced by the nature of the C4-moiety. In order to observe the effect of various patterns, namely azide (N 3), p -methoxybenzyloxy (OPMB), and benzyloxy (OBn), a thorough analysis was conducted on the corresponding l -glucosides. The results unveiled a distinct trend where the efficiency of methylenation followed the trend OBn > OPMB > N 3. Finally, the C6-alkene was dihydroxylated in the presence of osmium tetroxide to yield the expected l/d - glycero - l -glucoheptosides. The lead building block, which features a C-4 azide, was delivered as a phenyl thioglycoside. Added to the suitable masking of the 6,7-diol, this combination enables further functionalization to achieve versatile compounds of biological interest. The study insights into the interplay between substitution at C-4 and carbon homologation at C-6 provide valuable guidance for future endeavors in the synthesis of these carbohydrate molecules. [Display omitted] • We present a successful synthesis of l/d - glycero - l -glucoheptoside building blocks derived from l -glucose. • Key reaction steps involve carbon homologation, encompassing the oxidation of C6-OH, followed by methylenation wherein the C4-moiety exhibits notable influence. • Three distinct protecting groups were investigated and the order of methylenation yields was OBn > OPMB > N 3. [ABSTRACT FROM AUTHOR]

Biological nanoparticles, such as bacterial outer membrane vesicles (OMVs), are routinely characterized through transmission electron microscopy (TEM). In this study, we report a novel method to prepare OMVs for TEM imaging. To preserve vesicular shape and structure, we developed a dual fixation protocol involving osmium tetroxide incubation prior to negative staining with uranyl acetate. Combining osmium tetroxide with uranyl acetate resulted in preservation of sub-50 nm vesicles and improved morphological stability, enhancing characterization of lipid-based nanoparticles by TEM., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Correlative fluorescent and electron microscopic images of the same section of epoxy (or other polymer)-embedded samples, hereafter referred to as 'in-resin CLEM', have been developed to improve the positional accuracy and Z-axis resolution limitations of conventional correlative light and electron microscopy (CLEM). High-pressure freezing and quick-freezing substitution result in in-resin CLEM of acrylic-based resin-embedded cells expressing green fluorescent protein, yellow fluorescent protein, mVenus and mCherry, which are sensitive to osmium tetroxide. The identification of osmium-resistant fluorescent proteins leads to the development of in-resin CLEM of Epon-embedded cells. Using subtraction-based fluorescence microscopy with a photoconvertible fluorescent protein, mEosEM-E, its green fluorescence can be observed in thin sections of Epon-embedded cells, and two-color in-resin CLEM using mEosEM-E and mScarlet-H can be performed. Green fluorescent proteins, CoGFP variant 0 and mWasabi, and far-red fluorescent proteins, mCherry2 and mKate2, are available for in-resin CLEM of Epon-embedded cells using the standard procedure for Epon-embedding with additional incubation. Proximity labeling is applied to in-resin CLEM to overcome the limitations of fluorescent proteins in epoxy resin. These approaches will contribute significantly to the future of CLEM analysis., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

• An improved method to identify organic matter located within aggregate structure was developed. • Samples were prepared using liquid-state osmium-thiocarbohydrazide-osmium staining and resin-embedding techniques. • SEM/EDS analysis showed plant detritus that was enriched in Os and C. • Dual energy scanning by μCT identified Os-rich spots of roughly 5−50μm in size. • Advantages and cautions associated with current method were discussed. Organic matter (OM) in surface soil is largely present within porous mineral-dominant clusters called aggregates. Recent studies have shown the localization of OM within large macroaggregate structure based on synchrotron X-ray micro-computed tomography (μCT) coupled with a vapor-phase, osmium (Os)-staining pretreatment. Here we developed a new approach to identify OM locations within submillimeter-sized aggregates at higher spatial resolution and assessed its applicability using a well-characterized surface volcanic soil, an allophanic Andisol, under no-tillage with leaf compost addition. Water-stable aggregates (500–800 μm in diameter) were embedded in agarose, chemically fixed, and repeatedly stained by osmium tetroxide and thiocarbohydrazide, followed by gradual dehydration with ethanol and resin fixation. Scanning electron microscopy and μCT observation showed no signs of physical alteration during sample preparation. Energy-dispersive X-ray spectroscopy analysis of the microtome-cut surface of the aggregate identified plant detritus highly enriched in Os and much smaller amorphous OM (<10 μm) that were high in Fe, Al, and Si as well as Os. Synchrotron μCT imaging by photon energies above and below Os L 3 X-ray absorption edge (10.87 keV) and subsequent image calculation showed the distribution of Os-stained voxels down to micrometer scale. The improved resolution compared to previous studies was partly attributable to liquid-state staining and thiocarbohydrazide bridging. Other advantages and some cautions of the proposed method were discussed. [ABSTRACT FROM AUTHOR]

The article focuses on the total syntheses of natural and biologically important products employing an enantioselective metal-catalyzed domino reaction as a key step; and mentions many syntheses of natural and bioactive products include as key steps asymmetric domino processes.