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Chemistry (Weinheim An Der Bergstrasse,... Aug 2023Systematic investigations on the reactions between cis-[M(dppm) Cl ] (M=Ru/Os; dppm=1,1-bis(diphenylphosphino)methane) and pyridine/quinoline substituted homopropargylic...
Systematic investigations on the reactions between cis-[M(dppm) Cl ] (M=Ru/Os; dppm=1,1-bis(diphenylphosphino)methane) and pyridine/quinoline substituted homopropargylic alcohols uncovered the diverse Ru(II)/Os(II)-induced alkyne activation pathways. The alkynes underwent cyclization on M via a "non-vinylidene" pathway at lower temperatures, resulting in alkenyl intermediates which might further metallacyclize to give metallapyrroloindolizines. Conversely, reactions at higher temperatures induced alkyne cyclization on M via a "vinylidene" pathway, affording cyclic oxacarbene complexes. Additionally, a rare decyclization mechanism was observed during the transformation of a metallacyclization-resistant alkenyl complex into a cyclic oxacarbene complex. DFT calculations were employed to validate the experimental findings. Overall, these results not only provide insights into controlling alkyne activation pathways, but also offer new strategies for preparing metalated heterocyclic and metallacyclic complexes.
PubMed: 37198720
DOI: 10.1002/chem.202301292 -
Endocrine Jan 2024Accumulation of bone marrow adipose tissue (BMAT) is always seen in osteoporosis induced by estrogen deficiency. Herein, we aimed to investigate the mechanisms and...
BACKGROUND
Accumulation of bone marrow adipose tissue (BMAT) is always seen in osteoporosis induced by estrogen deficiency. Herein, we aimed to investigate the mechanisms and consequences of this phenomenon by establishing a mouse model of osteoporosis caused by ovariectomy (OVX)-mimicked estrogen deficiency.
METHODS
Micro-CT, osmium tetroxide staining, and histological analyses were performed to examine the changes in bone microstructure, BMAT and white adipose tissue (WAT) in OVX mice compared to sham mice. The osteogenesis and adipogenesis of primary bone marrow stromal cells (BMSCs) isolated from sham and OVX mice were compared in vitro. The molecular phenotypes of BMAT and WAT were determined and compared by quantitative PCR (qPCR). Bone marrow adipocyte-conditioned medium (BMA CM) was prepared from sham or OVX mice for coculture assays, and BMSCs or bone marrow monocytes/macrophages (BMMs) were isolated and subjected to osteoblast and osteoclast differentiation, respectively. Cell staining and qPCR were used to assess the effects of BMAT on bone metabolism.
RESULTS
OVX-induced estrogen deficiency induced reductions in both cortical and trabecular bone mass along with an expansion of BMAT volume. At the cellular level, loss of estrogen inhibited BMSC osteogenesis and promoted BMSC adipogenesis, whereas addition of estradiol exerted the opposite effects. In response to estrogen deficiency, despite the common proinflammatory molecular phenotype observed in both fat depots, BMAT, unlike WAT, unexpectedly exhibited an increase in adipocyte differentiation and lipolytic activity as well as the maintenance of insulin sensitivity. Importantly, BMAT, but not WAT, presented increased mRNA levels of both BMP receptor inhibitors (Grem1, Chrdl1) and Rankl following OVX. In addition, treatment with BMA CM, especially from OVX mice, suppressed the osteoblast differentiation of BMSCs while favoring the osteoclast differentiation of BMMs.
CONCLUSION
Our study illustrates that OVX-induced estrogen deficiency results in bone loss and BMAT expansion by triggering imbalance between the osteogenesis and adipogenesis of BMSCs. Furthermore, expanded BMAT, unlike typical WAT, may negatively regulate bone homeostasis through paracrine inhibition of osteoblast-mediated bone formation and promotion of osteoclast-mediated bone resorption.
Topics: Female; Mice; Animals; Humans; Bone Marrow; Adipose Tissue; Osteoporosis; Osteogenesis; Cell Differentiation; Estrogens; Ovariectomy; Eye Proteins; Nerve Tissue Proteins
PubMed: 37682419
DOI: 10.1007/s12020-023-03504-6 -
Microscopy (Oxford, England) Jun 2024The two-dimensional observation of ultrathin sections from resin-embedded specimens provides an insufficient understanding of the three-dimensional (3D) morphological... (Review)
Review
The two-dimensional observation of ultrathin sections from resin-embedded specimens provides an insufficient understanding of the three-dimensional (3D) morphological information of membranous organelles. The osmium maceration method, developed by Professor Tanaka's group >40 years ago, is the only technique that allows direct observation of the 3D ultrastructure of membrane systems using scanning electron microscopy (SEM), without the need for any reconstruction process. With this method, the soluble cytoplasmic proteins are removed from the freeze-cracked surface of cells while preserving the integrity of membranous organelles, achieved by immersing tissues in a diluted osmium solution for several days. By employing the maceration method, researchers using SEM have revealed the 3D ultrastructure of organelles such as the Golgi apparatus, mitochondria and endoplasmic reticulum in various cell types. Recently, we have developed new SEM techniques based on the maceration method to explore further possibilities of this method. These include: (i) a rapid osmium maceration method that reduces the reaction duration of the procedure, (ii) a combination method that combines agarose embedding with osmium maceration to elucidate the 3D ultrastructure of organelles in free and cultured cells and (iii) a correlative immunofluorescence and SEM technique that combines cryosectioning with the osmium maceration method, enabling the correlation of the immunocytochemical localization of molecules with the 3D ultrastructure of organelles. In this paper, we review the novel osmium maceration methods described earlier and discuss their potential and future directions in the field of biology and biomedical research.
Topics: Microscopy, Electron, Scanning; Imaging, Three-Dimensional; Organelles; Animals; Osmium; Golgi Apparatus; Humans; Endoplasmic Reticulum
PubMed: 37930813
DOI: 10.1093/jmicro/dfad050 -
Biosensors & Bioelectronics Oct 2023Viruses have unique coat proteins that are genetically modifiable. Their surface can serve as a nano-template on which electroactive molecules are immobilized. In this...
Viruses have unique coat proteins that are genetically modifiable. Their surface can serve as a nano-template on which electroactive molecules are immobilized. In this study, we report filamentous bacteriophage as a backbone to which redox mediators are covalently and densely tethered, constructing redox nanowire, i.e. an electron conducting biomaterial. The highly ordered coat proteins of a filamentous bacteriophage provide flexible and biocompatible platform to constitute a biohybrid redox nanowire. Incorporating bacteriophage and redox molecules form an entangled assembly of nanowires enabling facile electron transfer. Electron transfer among the molecular mediators in the entangled assembly originates apparent electron diffusion of which the electron transfer rate is comparable to that observed in conventional redox polymers. Programming peptide terminals suggests further enhancement in electron mediation by increasing redox species mobility. In addition, the redox nanowire film functions as a favorable matrix for enzyme encapsulation. The stability of the enzymes entrapped in this unique matrix is substantially improved.
Topics: Nanowires; Biosensing Techniques; Oxidation-Reduction; Electron Transport; Bacteriophages; Electrodes
PubMed: 37442029
DOI: 10.1016/j.bios.2023.115518 -
Journal of Medical Imaging (Bellingham,... Sep 2023X-ray phase-contrast tomography (XPCT) is a non-destructive, three-dimensional imaging modality that provides higher contrast in soft tissue than absorption-based CT and...
PURPOSE
X-ray phase-contrast tomography (XPCT) is a non-destructive, three-dimensional imaging modality that provides higher contrast in soft tissue than absorption-based CT and allows one to cover the cytoarchitecture from the centi- and millimeter scale down to the nanoscale. To further increase contrast and resolution of XPCT, for example, in view of addressing connectivity issues in the central nervous system (CNS), metal staining is indispensable. However, currently used protocols, for example, based on osmium and/or uranium are less suited for XPCT, due to an excessive -ratio. In this work, we explore the suitability of different staining agents for XPCT. Particularly, neodymium(III)-acetate (NdAc), which has recently been proposed as a non-toxic, non-radioactive easy to use alternative contrast agent for uranyl acetate (UAc) in electron microscopy, is investigated. Due to its vertical proximity to UAc in the periodic table, similar chemical but better suited optical properties for phase contrast can be expected.
APPROACH
Differently stained whole eye samples of wild type mouse and tissues of the CNS are embedded into EPON epoxy resin and scanned using synchrotron as well as with laboratory radiation. Phase retrieval is performed on the projection images, followed by tomographic reconstruction, which enables a quantitative analysis based on the reconstructed electron densities. Segmentation techniques and rendering software is used to visualize structures of interest in the sample.
RESULTS
We show that staining neuronal samples with NdAc enhances contrast, in particular for laboratory scans, allowing high-resolution imaging of biological soft tissue in-house. For the example of murine retina, specifically rods and cones as well as the sclera and the Ganglion cell layer seem to be targeted by the stain. A comparison of electron density by the evaluation of histograms allowed to determine quantitative measures to describe the difference between the examined stains.
CONCLUSION
The results suggest NdAc to be an effective stain for XPCT, with a preferential binding to anionic groups, such as phosphate and carboxyl groups at cell surfaces, targeting certain layers of the retina with a stronger selectivity compared to other staining agents. Due to the advantageous X-ray optical properties, the stain seems particularly well-suited for phase contrast, with a comparably small number density and an overall superior image quality at laboratory sources.
PubMed: 37885921
DOI: 10.1117/1.JMI.10.5.056001 -
Journal of Visualized Experiments : JoVE Jan 2024Correlative light and electron microscopy (CLEM) is a comprehensive microscopy that combines the localization information provided by fluorescence microscopy (FM) and...
Correlative light and electron microscopy (CLEM) is a comprehensive microscopy that combines the localization information provided by fluorescence microscopy (FM) and the context of cellular ultrastructure acquired by electron microscopy (EM). CLEM is a trade-off between fluorescence and ultrastructure, and usually, ultrastructure compromises fluorescence. Compared with other hydrophilic embedding resins, such as glycidyl methacrylate, HM20, or K4M, Epon is superior in ultrastructure preservation and sectioning properties. Previously, we had demonstrated that mEosEM can survive osmium tetroxide fixation and Epon embedding. Using mEosEM, we achieved, for the first time, Epon post embedding CLEM, which maintains the fluorescence and the ultrastructure simultaneously. Here, we provide step-by-step details about the EM sample preparation, the FM imaging, the EM imaging, and the image alignment. We also improve the procedures for identifying the same cell imaged by FM imaging during the EM imaging and detail the registration between the FM and EM images. We believe one can easily achieve Epon post embedding correlative light and electron microscopy following this new protocol in traditional EM facilities.
Topics: Microscopy, Electron; Microscopy, Fluorescence
PubMed: 38284521
DOI: 10.3791/66141 -
Microscopy (Oxford, England) Oct 2023Correlative fluorescent and electron microscopic images of the same section of epoxy (or other polymer)-embedded samples, hereafter referred to as 'in-resin CLEM', have...
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.
Topics: Humans; Epoxy Resins; Microscopy, Electron; Microscopy, Fluorescence; Green Fluorescent Proteins; HeLa Cells
PubMed: 37217182
DOI: 10.1093/jmicro/dfad028 -
Molecules (Basel, Switzerland) Feb 2024A series of new chelating bidentate (SS) alkylimidazole-2-thione-Ru(II)/Os(II) complexes (, , , /, , ), and the tridentate (SNS)...
A series of new chelating bidentate (SS) alkylimidazole-2-thione-Ru(II)/Os(II) complexes (, , , /, , ), and the tridentate (SNS) pyridine-2,6-diylimidazole-2-thione-Ru(II)/Os(II) complexes (, /, , ) in the forms [M(cym)(L)Cl]PF and [M(cym)(L)]PF (M = Ru or Os, cym = η--cymene, and L = heterocyclic derivatives of thiourea) respectively, were successfully synthesized. Spectroscopic and analytical methods were used to characterize the complexes and their ligands. Solid-state single-crystal X-ray diffraction analyses revealed a "piano-stool" geometry around the Ru(II) or Os(II) centers in the respective complexes. The complexes were investigated for in vitro chemotherapeutic activities against human cervical carcinoma (HeLa) and the non-cancerous cell line (Hek293) using the MTT assay. The compounds , , , , , , and the reference drug, 5-fluorouracil were found to be selective toward the tumor cells; the compounds , , , , , and , which were found not to be selective between normal and tumor cell lines. The IC value of the tridentate half-sandwich complex (86 ± 9 μM) showed comparable anti-proliferative activity with the referenced commercial anti-cancer drug, 5-fluorouracil (87 ± 15 μM). The pincer (SNS) osmium complexes (36 ± 10 μM) and (40 ± 4 μM) were twice as effective as the reference drug 5-fluorouracil at the respective dose concentrations. However, the analogous pincer (SNS) ruthenium complex was ineffective and did not show anti-proliferative activity, even at a higher concentration of 147 ± 1 μM. These findings imply that the higher stability of the chelating (SS) and the pincer (SNS) ligand architectures in the complexes improves the biological (anti-proliferative) activity of the complexes by reducing the chance of ligand dissociation under physiological conditions. In general, the pincer (SNS) osmium complexes were found to be more cytotoxic than their ruthenium analogues, suggesting that the anti-proliferative activity of the imidazole-2-thione-Ru/Os complexes depends on the ligand's spatial coordination, the nature of the metal center, and the charge of the metal complex ions.
Topics: Humans; Ruthenium; Osmium; Ligands; HEK293 Cells; Thiones; Chelating Agents; Antineoplastic Agents; Coordination Complexes; Cell Line, Tumor; Fluorouracil; Cymenes
PubMed: 38474456
DOI: 10.3390/molecules29050944 -
Bioelectrochemistry (Amsterdam,... Oct 2023We investigated the bioelectrochemical properties of an FAD-dependent glucose dehydrogenase from Trichoderma virens (TvGDH) and its electrochemical behaviour when...
We investigated the bioelectrochemical properties of an FAD-dependent glucose dehydrogenase from Trichoderma virens (TvGDH) and its electrochemical behaviour when immobilized on a graphite electrode. TvGDH was recently shown to have an unusual substrate spectrum and to prefer maltose over glucose as substrate, and hence could be of interest as recognition element in a maltose sensor. In this study, we determined the redox potential of TvGDH, which is -0.268 ± 0.007 V vs. SHE, and advantageously low to be used with many redox mediators or redox polymers. The enzyme was entrapped in, and wired by an osmium redox polymer (poly(1-vinylimidazole-co-allylamine)-{[Os(2,2'-bipyridine)Cl]Cl}) with formal redox potential of +0.275 V vs. Ag|AgCl via poly(ethylene glycol) diglycidyl ether crosslinking onto a graphite electrode. When the TvGDH-based biosensor was tested with maltose it showed a sensitivity of 1.7 μA mMcm, a linear range of 0.5-15 mM, and a detection limit of 0.45 mM. Furthermore, it gave the lowest apparent Michaelis-Menten constant (K) of 19.2 ± 1.5 mM towards maltose when compared to other sugars. The biosensor is also able to detect other saccharides including glucose, maltotriose and galactose, these however also interfere with maltose sensing.
Topics: Glucose 1-Dehydrogenase; Hypocrea; Graphite; Maltose; Glucose; Biosensing Techniques; Electrodes; Oxidation-Reduction; Polymers; Enzymes, Immobilized
PubMed: 37269684
DOI: 10.1016/j.bioelechem.2023.108480 -
Chemistry (Weinheim An Der Bergstrasse,... Feb 2024Macrocyclic and medium-sized ring ketones, lactones and lactams can all be made from common acryloyl imide starting materials through divergent, one-pot cascade...
Macrocyclic and medium-sized ring ketones, lactones and lactams can all be made from common acryloyl imide starting materials through divergent, one-pot cascade ring-expansion reactions. Following either conjugate addition with an amine or nitromethane, or osmium(VIII)-catalysed dihydoxylation, rearrangement through a four-atom ring expansion takes place spontaneously to form the ring expanded products. A second ring expansion can also be performed following a second iteration of imide formation and alkene functionalisation/ring expansion. In the dihydroxylation series, three- or four-atom ring expansion can be performed selectively, depending on whether the reaction is under kinetic or thermodynamic control.
PubMed: 37987097
DOI: 10.1002/chem.202303270