Involvement of superoxide in malaoxon-induced toxicity in primary cultures of cortical neurons

Organophosphorus compounds (OP) represent a class of insecticides that are used most globally. The neurotoxic effects are attributed mainly to acetylcholinesterase (AChE) enzyme inhibition, which is responsible for cholinergic manifestations in individuals acutely exposed to OP. However, AChE inhibition alone cannot account for the wide range of symptoms that were reported following OP exposures. In agreement with this, evidence shows that non-cholinergic events may be mechanistically linked to OP-induced neurotoxicity. The aim of this study was to investigate the potential occurrence of oxidative stress as a critical step in the toxicity induced by the OP malaoxon(MAL) using primary cultures of mouse cortical neurons, as well as to distinguish MAL-induced oxidative stress and cell toxicity from an action on AChE blockade. Primary cultures of mouse cortical neurons were treated with MAL (0.01; 0.1; 1; 10; or 100 µM) at varying time points (1, 3, 6, 24, 48, or 144 hr) and the following biochemical parameters determined including cell viability, AChE activity, and superoxide production. MAL significantly reduced cell viability in a concentration- and time-dependent manner. Of note, 1 µM MAL significantly inhibited (approximately 75%) AChE activity after 48 hr incubation. Pralidoxime (PRAL) (600 µM), a classical AChE reactivator, significantly protected against MAL-induced AChE blockade; however, PRAL did not affect MAL-mediated fall in cellular viability, indicating that AChE inhibition is not necessarily correlated with insecticide-induced decrease in cell survival. MAL-induced diminished cell viability was preceded by a significant increase in superoxide anion production. The antioxidant agent ascorbic acid (AA) (200 µM), which significantly protected against MAL-induced superoxide anion production, did not alter MAL-induced AChE inhibition and significantly prevented insecticide-mediated fall in cell survival. Data show that increased superoxide anion production is an event that precedes MAL-induced cell toxicity in primary cultures of mouse cortical neurons. Based on the preventative effects of AA against MAL-mediated superoxide anion production and reduced cell viability, evidence indicates that oxidative stress represents an important step mediating MAL-induced toxicity in neurons and that AChE inhibition is not necessarily correlated with lowered cell survival noted in insecticide-exposed cells.

Localized iron accumulation precedes nucleation and growth of magnetite crystals in magnetotactic bacteria

Many magnetotactic bacteria (MTB) biomineralize magnetite crystals that nucleate and grow inside intracellular membranous vesicles that originate from invaginations of the cytoplasmic membrane. The crystals together with their surrounding membranes are referred to magnetosomes. Magnetosome magnetite crystals nucleate and grow using iron transported inside the vesicle by specific proteins. Here we address the question: can iron transported inside MTB for the production of magnetite crystals be spatially mapped using electron microscopy? Cultured and uncultured MTB from brackish and freshwater lagoons were studied using analytical transmission electron microscopy in an attempt to answer this question. Scanning transmission electron microscopy was used at sub-nanometric resolution to determine the distribution of elements by implementing high sensitivity energy dispersive X-ray (EDS) mapping and electron energy loss spectroscopy (EELS). EDS mapping showed that magnetosomes are enmeshed in a magnetosomal matrix in which iron accumulates close to the magnetosome forming a continuous layer visually appearing as a corona. EELS, obtained at high spatial resolution, confirmed that iron was present close to and inside the lipid bilayer magnetosome membrane. This study provides important clues to magnetite formation in MTB through the discovery of a mechanism where iron ions accumulate prior to magnetite biomineralization.

Biomineralization of calcium carbonate in the cell wall of Lithothamnion crispatum (Hapalidiales, Rhodophyta): correlation between the organic matrix and the mineral phase

Over the past few decades, progress has been made toward understanding the mechanisms of coralline algae mineralization. However, the relationship between the mineral phase and the organic matrix in coralline algae has not yet been thoroughly examined. The aim of this study was to describe the cell wall ultrastructure of Lithothamnion crispatum, a cosmopolitan rhodolith-forming coralline algal species collected near Salvador (Brazil), and examine the relationship between the organic matrix and the nucleation and growth/shape modulation of calcium carbonate crystals. A nanostructured pattern was observed in L. crispatum along the cell walls. At the nanoscale, the crystals from L. crispatum consisted of several single crystallites assembled and associated with organic material. The crystallites in the bulk of the cell wall had a high level of spatial organization. However, the crystals displayed cleavages in the (104) faces after ultrathin sectioning with a microtome. This organism is an important model for biomineralization studies as the crystallographic data do not fit in any of the general biomineralization processes described for other organisms. Biomineralization in L. crispatum is dependent on both the soluble and the insoluble organic matrix, which are involved in the control of mineral formation and organizational patterns through an organic matrix-mediated process. This knowledge concerning the mineral composition and organizational patterns of crystals within the cell walls should be taken into account in future studies of changing ocean conditions as they represent important factors influencing the physico-chemical interactions between rhodoliths and the environment in coralline reefs.

Strontium ranelate improves the interaction of osteoblastic cells with titanium substrates: Increase in cell proliferation, differentiation and matrix mineralization

We describe direct effects of strontium ranelate on the interaction of osteoblastic cells with different titanium substrates. Our goal was to better understand the potential of this drug for improving the efficacy of bone implants. Treatment was done with 0.12 and 0.5 mM Sr(2+) of strontium ranelate in cell culture. We analyzed cell response to the drug on titanium substrates with surface topographies obtained using acid etching, electro-erosion processing, sandblasting, and machine-tooling. Treatment preserved the initial cell adhesion to the substrates, cell shape parameters (area, aspect ratio, circularity, and solidity), and the orientation of cells on grooved surfaces. However, both concentrations of the drug increased cell proliferation in all substrates. Moreover, a dose-dependent increase in alkaline phosphatase activity and in the production of mineralized matrix with typical features of bone tissue was shown. The observed effects were similar in the different substrates. In conclusion, strontium ranelate improved the interaction of osteoblastic cells with titanium substrates, increasing cell proliferation and differentiation into mature osteoblasts and the production of bone-like mineralized matrix for all substrates. This study highlights a promising role of strontium ranelate on enhancing the clinical success of bone implants, particularly in patients with osteoporosis.

Rheological properties of cells measured by optical tweezers

BACKGROUND

The viscoelastic properties of cells have been investigated by a variety of techniques. However, the experimental data reported in literature for viscoelastic moduli differ by up to three orders of magnitude. This has been attributed to differences in techniques and models for cell response as well as to the natural variability of cells.

RESULTS

In this work we develop and apply a new methodology based on optical tweezers to investigate the rheological behavior of fibroblasts, neurons and astrocytes in the frequency range from 1Hz to 35Hz, determining the storage and loss moduli of their membrane-cortex complex. To avoid distortions associated with cell probing techniques, we use a previously developed method that takes into account the influence of under bead cell thickness and bead immersion. These two parameters were carefully measured for the three cell types used. Employing the soft glass rheology model, we obtain the scaling exponent and the Young's modulus for each cell type. The obtained viscoelastic moduli are in the order of Pa. Among the three cell types, astrocytes have the lowest elastic modulus, while neurons and fibroblasts exhibit a more solid-like behavior.

CONCLUSIONS

Although some discrepancies with previous results remain and may be inevitable in view of natural variability, the methodology developed in this work allows us to explore the viscoelastic behavior of the membrane-cortex complex of different cell types as well as to compare their viscous and elastic moduli, obtained under identical and well-defined experimental conditions, relating them to the cell functions.

Crystallographic orientation and concentric layers in spicules of calcareous sponges

In this work, the crystallography of calcareous sponges (Porifera) spicules and the organization pattern of the concentric layers present in their inner structure were investigated in 10 species of the subclass Calcaronea and three species of the subclass Calcinea. Polished spicules had specific concentric patterns that varied depending on the plane in which the spicules were sectioned. A 3D model of the concentric layers was created to interpret these patterns and the biomineralization process of the triactine spicules. The morphology of the spicules was compared with the crystallographic orientation of the calcite crystals by analyzing the Kikuchi diffraction patterns using a scanning electron microscope. Triactine spicules from the subclass Calcinea had actines (rays) elongated in the 〈210〉 direction, which is perpendicular to the c-axis. The scale spicules of the hypercalcified species Murrayona phanolepis presented the c-axis perpendicular to the plane of the scale, which is in accordance with the crystallography of all other Calcinea. The triactine spicules of the calcaronean species had approximately the same crystallographic orientation with the unpaired actine elongated in the ∼[211] direction. Only one Calcaronea species, whose triactine was regular, had a different orientation. Three different crystallographic orientations were found in diactines. Spicules with different morphologies, dimensions and positions in the sponge body had similar crystallographic directions suggesting that the crystallographic orientation of spicules in calcareous sponges is conserved through evolution.

Trojan-Like Internalization of Anatase Titanium Dioxide Nanoparticles by Human Osteoblast Cells

Dentistry and orthopedics are undergoing a revolution in order to provide more reliable, comfortable and long-lasting implants to patients. Titanium (Ti) and titanium alloys have been used in dental implants and total hip arthroplasty due to their excellent biocompatibility. However, Ti-based implants in human body suffer surface degradation (corrosion and wear) resulting in the release of metallic ions and solid wear debris (mainly titanium dioxide) leading to peri-implant inflammatory reactions. Unfortunately, our current understanding of the biological interactions with titanium dioxide nanoparticles is still very limited. Taking this into consideration, this study focuses on the internalization of titanium dioxide nanoparticles on primary bone cells, exploring the events occurring at the nano-bio interface. For the first time, we report the selective binding of calcium (Ca), phosphorous (P) and proteins from cell culture medium to anatase nanoparticles that are extremely important for nanoparticle internalization and bone cells survival. In the intricate biological environment, anatase nanoparticles form bio-complexes (mixture of proteins and ions) which act as a kind of ‘Trojan-horse’ internalization by cells. Furthermore, anatase nanoparticles-induced modifications on cell behavior (viability and internalization) could be understand in detail. The results presented in this report can inspire new strategies for the use of titanium dioxide nanoparticles in several regeneration therapies.

Yeast-derived biosynthesis of silver/silver chloride nanoparticles and their antiproliferative activity against bacteria

Here, we provided the first evidence of Ag/AgCl-nanoparticles production in yeast strains fromin vitrocultures.

129Xe NMR studies of morphology and accessibility in porous biochar from almond shells

¹²⁹Xe NMR EXSY plot demonstrating pore connectivity in sustainable almond shell biochar generated from anaerobic thermal activation and rainwater washing.

The effects of strontium on bone mineral: A review on current knowledge and microanalytical approaches

The interest in effects of strontium (Sr) on bone has greatly increased in the last decade due to the development of the promising drug strontium ranelate. This drug is used for treating osteoporosis, a major bone disease affecting hundreds of millions of people worldwide, especially postmenopausal women. The novelty of strontium ranelate compared to other treatments for osteoporosis is its unique effect on bone: it simultaneously promotes bone formation by osteoblasts and inhibits bone resorption by osteoclasts. Besides affecting bone cells, treatment with strontium ranelate also has a direct effect on the mineralized bone matrix. Due to the chemical similarities between Sr and Ca, a topic that has long been of particular interest is the incorporation of Sr into bones replacing Ca from the mineral phase, which is composed by carbonated hydroxyapatite nanocrystals. Several groups have analyzed the mineral produced during treatment; however, most analysis were done with relatively large samples containing numerous nanocrystals, resulting thus on data that represents an average of many crystalline domains. The nanoscale analysis of the bone apatite crystals containing Sr has only been described in a few studies. In this study, we review the current knowledge on the effects of Sr on bone mineral and discuss the methodological approaches that have been used in the field. In particular, we focus on the great potential that advanced microscopy and microanalytical techniques may have on the detailed analysis of the nanostructure and composition of bone apatite nanocrystals produced during treatment with strontium ranelate.

Platelet-rich plasma releasate differently stimulates cellular commitment toward the chondrogenic lineage according to concentration

Platelet-rich plasma has been used to treat articular cartilage defects, with the expectations of anabolic and anti-inflammatory effects. However, its role on cellular chondrogenic or fibrogenic commitment is still a controversy. Herein, the role of platelet-rich plasma releasate, the product obtained following platelet-rich plasma activation, on cellular commitment toward the chondrogenic lineage was evaluated in vitro. Human nasoseptal chondrogenic cells and human bone marrow mesenchymal stromal cells were used as cell types already committed to the chondrogenic lineage and undifferentiated cells, respectively, as different concentrations of platelet-rich plasma releasate were tested in comparison to commonly used fetal bovine serum. Low concentration of platelet-rich plasma releasate (2.5%) presented similar effects on cellular growth compared to 10% fetal bovine serum, for both cell types. In a three-dimensional culture system, platelet-rich plasma releasate alone did not induce full nasoseptal chondrogenic cells cartilage-like pellet formation. Nonetheless, platelet-rich plasma releasate played a significant role on cell commitment as high-passage nasoseptal chondrogenic cells only originated cartilage-like pellets when expanded in the presence of platelet-rich plasma releasate rather than fetal bovine serum. Histological analyses and measurements of pellet area demonstrated that even low concentrations of platelet-rich plasma releasate were enough to prevent nasoseptal chondrogenic cells from losing their chondrogenic potential due to in vitro expansion thereby promoting their recommitment. Low concentration of platelet-rich plasma releasate supplemented in chondrogenic medium also increased the chondrogenic potential of mesenchymal stromal cells seeded on collagen-hyaluronic acid scaffolds, as observed by an increase in chondrogenic-related gene expression, sulfated glycosaminoglycan production, and compressive modulus following in vitro culture. On the contrary, higher concentration of platelet-rich plasma releasate (10%) hampered some of these features. In conclusion, platelet-rich plasma releasate was able to prevent cellular chondrogenic capacity loss, inducing regain of their phenotype, and modulate cell commitment. Our data support the hypothesis of platelet-rich plasma chondrogenic potential, allowing fetal bovine serum substitution for platelet-rich plasma releasate at specific concentrations in culture medium when chondrogenic commitment is desired on specific cell types and moments of culture.

Peritoneal Submesothelial Stromal Cells Support Hematopoiesis and Differentiate into Osteogenic and Adipogenic Cell Lineages

The peritoneum is a thin membrane that covers most of the abdominal organs, composed of a monolayer of mesothelial cells and subjacent submesothelial loose connective tissue. Cells from the peritoneal wall are correlated with peritoneal fibrosis and epithelial-to-mesenchymal transition. However, the distinct involvement of mesothelial or submesothelial cells in such phenomena is still not clear. Here, we propose a new strategy to obtain stromal cells from anterior peritoneal wall explant cultures. These cells migrated from peritoneal tissues and proliferated in vitro for 4 weeks as adherent fibroblast-like cells. Optical and electronic microscopy analyses of the fragments revealed a significant submesothelial disorganization. The obtained cells were characterized as cytokeratin- vimentin+ laminin+ α-smooth muscle actin+, suggesting a connective tissue origin. Moreover, at the third passage, these stromal cells were CD90+CD73+CD29+Flk-1+CD45-, a phenotype normally attributed to cells of mesenchymal origin. These cells were able to support hematopoiesis, expressing genes involved in myelopoiesis (SCF, G-CSF, GM-CSF, IL-7 and CXCL-12), and differentiated into osteogenic and adipogenic cell lineages. The methodology demonstrated in this work can be considered an excellent experimental model to understand the physiology of the peritoneal wall in healthy and pathological processes. Moreover, this work shows for the first time that submesothelial stromal cells have properties similar to those of mesenchymal cells from other origins.