Search Results (40)

Background: Recent technological advances have sparked growing interest in high-power laser devices due to their capacity for energy delivery and therapeutic potential, especially in deeper tissues. This promising approach may be comparable to photobiomodulation for modulating inflammatory and redox processes in various tissues. However, to our knowledge, this is the first study to evaluate the safety profile and redox modulation capacity of high-power laser therapy in BV-2 microglial cells. Methods: This study investigated the cellular responses of BV-2 microglial cells exposed to three laser irradiation protocols using a high-power laser device (650/810/915/980 nm, 657 J total dose), applied at variable distances to simulate in vivo power attenuation. Cell viability, apoptosis, adenosine triphosphate(ATP) levels, mitochondrial membrane potential (MMP), reactive oxygen species (ROS), nitric oxide (NO), and intracellular calcium levels were assessed at multiple time points (5 min to 24 h). Results: Protocol-dependent effects were observed. Protocol A promoted early increases in cell viability and ATP levels, along with decreased apoptotic markers and ROS production, suggesting a protective bioenergetic response. In contrast, Protocol C showed transient increases in oxidative stress and reduced MMP, suggesting possible mitochondrial stress. A selective increase in NO levels under Protocol A also suggests modulation of inflammatory pathways without cytotoxicity. Conclusions: High-power laser therapy modulates redox balance, mitochondrial function, and inflammatory mediators (e.g., NO) in a dual-phase manner in BV-2 microglial cells. These findings contribute to defining safe and effective parameters for potential musculoskeletal and neurological applications. Full article

While calcium (Ca²⁺) is a universal cellular messenger, the ionic properties of magnesium (Mg²⁺) make it less suited for rapid signaling and more for structural integrity. Still, besides being a passive player, Mg²⁺ is the only active Ca²⁺ antagonist, essential for tuning the efficacy of Ca²⁺-dependent cardiac excitation–contraction coupling (ECC) and for ensuring cardiac function robustness and stability. This review aims to provide a comprehensive framework to link the structural and molecular mechanisms of Mg²⁺/Ca²⁺ antagonistic binding across key proteins of the cardiac ECC machinery to their physiopathological relevance. The pervasive “dampening” effect of Mg²⁺ on ECC activity is exerted across various players and mechanisms, and lies in the ions’ physiological competition for multiple, flexible binding protein motifs across multiple compartments. Mg²⁺ profoundly modulates the cardiac action potential waveform by inhibiting the L-type Ca²⁺ channel Cav1.2, i.e., the key trigger of cardiac ryanodine receptor (RyR2) opening. Cytosolic Mg²⁺ favors RyR2 closed or inactive conformations not only through physical binding at specific sites, but also indirectly through modulation of RyR2 phosphorylation by Camk2d and PKA. RyR2 is also potently inhibited by luminal Mg²⁺, a vital mechanism in the cardiac setting for preventing excessive Ca²⁺ release during diastole. This mechanism, able to distinguish between Ca²⁺ and Mg²⁺, is mediated by luminal partners Calsequestrin 2 (CASQ2) and Triadin (TRDN). In addition, Mg²⁺ favors a rearrangement of the RyR2 cluster configuration that is associated with lower Ca²⁺ spark frequencies. Full article

In this study, 3D Mg scaffolds were obtained by the spark plasma sintering (SPS), and a calcium phosphate coating was then obtained on the samples by the plasma electrolytic oxidation. A hybrid coating with vancomycin, zoledronic acid, and menaquinone MK-7 was formed to improve biocompatibility. The mechanical properties of the formed specimens were studied. According to XRD, XRF, SEM, EDS, and OSP studies obtained scaffolds have developed morphology and contain hydroxyapatite as well as bioactive substances. Formation of coatings improves the wettability of samples (contact angle decreases from 123.8 ± 3.1° to 26.9 ± 4.1°) and increases the surface roughness by more than 3 times. This makes them promising for use as a new generation of implantation materials. The results are important for the development of personalized implants with improved functional characteristics. Full article

Previous studies have observed alterations in excitation–contraction (EC) coupling during end-stage heart failure that include action potential and calcium (Ca²⁺) transient prolongation and a reduction of the Ca²⁺ transient amplitude. Underlying these phenomena are the downregulation of potassium (K⁺) currents, downregulation of the sarcoplasmic reticulum Ca²⁺ ATPase (SERCA), increase Ca²⁺ sensitivity of the ryanodine receptor, and the upregulation of the sodium–calcium (Na⁼-Ca²⁺) exchanger. However, in human heart failure (HF), debate continues about the relative contributions of the changes in calcium handling vs. the changes in the membrane currents. To understand the consequences of the above changes, they are incorporated into a computational human ventricular myocyte HF model that can explore the contributions of the spontaneous Ca²⁺ release from the sarcoplasmic reticulum (SR). The reduction of transient outward K⁺ current (I_to) is the main membrane current contributor to the decrease in RyR2 open probability and L-type calcium channel (LCC) density which emphasizes its importance to phase 1 of the action potential (AP) shape and duration (APD). During current-clamp conditions, RyR2 hyperphosphorylation exhibits the least amount of Ca²⁺ release from the SR into the cytosol and SR Ca²⁺ fractional release during a dynamic slow–rapid–slow (0.5–2.5–0.5 Hz) pacing, but it displays the most abundant and more lasting Ca²⁺ sparks two-fold longer than a normal cell. On the other hand, under voltage-clamp conditions, HF by decreased SERCA and upregulated I_NCX show the least SR Ca²⁺ uptake and EC coupling gain, as compared to HF by hyperphosphorylated RyR2s. Overall, this study demonstrates that the (a) combined effect of SERCA and NCX, and the (b) RyR2 dysfunction, along with the downregulation of the cardiomyocyte’s potassium currents, could substantially contribute to Ca²⁺ mishandling at the spark level that leads to heart failure. Full article

The machinability of steel is a crucial factor in manufacturing, influencing tool life, cutting forces, surface finish, and production costs. Traditional machinability assessments are labor-intensive and costly. This study presents a novel methodology to rapidly determine steel machinability using spark testing and convolutional neural networks (CNNs). We evaluated 45 steel samples, including various low-alloy and high-alloy steels, with most samples being calcium steels known for their superior machinability. Grinding experiments were conducted using a CNC machine with a ceramic grinding wheel under controlled conditions to ensure a constant cutting force. Spark images captured during grinding were analyzed using CNN models with the ResNet18 architecture to predict V15 values, which were measured using the standard ISO 3685 test. Our results demonstrate that the created prediction models achieved a mean absolute percentage error (MAPE) of 12.88%. While some samples exhibited high MAPE values, the method overall provided accurate machinability predictions. Compared to the standard ISO test, which takes several hours to complete, our method is significantly faster, taking only a few minutes. This study highlights the potential for a cost-effective and time-efficient alternative testing method, thereby supporting improved manufacturing processes. Full article

The pH- and thermo-responsive behavior of polymeric hydrogels $\left({\mathrm{M}}_{\mathrm{C}}-\mathrm{c}\mathrm{o}-{\mathrm{M}}_{\mathrm{A}}\right)$ have been studied in detail using dynamic light scattering $\left(\mathrm{D}\mathrm{L}\mathrm{S}\right)$, scanning electron microscopy$\left(\mathrm{S}\mathrm{E}\mathrm{M}\right)$, nuclear magnetic resonance (¹H NMR) and rheology to evaluate the conformational changes, swelling–shrinkage, stability, the ability to flow and the diffusion process of nanoparticles at several temperatures. Furthermore, polymeric systems functionalized with acrylic acid $\left({\mathrm{M}}_{\mathrm{C}}\right)$ and acrylamide $\left({\mathrm{M}}_{\mathrm{A}}\right)$ were subjected to a titration process with a calcium chloride $\left({\mathrm{C}\mathrm{a}\mathrm{C}\mathrm{l}}_2\right)$ solution to analyze its effect on the average particle diameter$\left({\mathrm{D}}_{\mathrm{z}}\right)$, polymer structure and the intra- and intermolecular interactions in order to provide a responsive polymer network that can be used as a possible nanocarrier for drug delivery with several benefits. The results confirmed that the structural changes in the sensitive hydrogels are highly dependent on the corresponding critical solution temperature $\left(\mathrm{C}\mathrm{S}\mathrm{T}\right)$ of the carboxylic (–COOH) and amide (–CONH₂) functional groups and the influence of calcium ions $\left({\mathrm{C}\mathrm{a}}^{2+}\right)$ on the formation or breaking of hydrogen bonds, as well as the decrease in electrostatic repulsions generated between the polymer chains contributing to a particle agglomeration phenomenon. The temperature leads to a re-arrangement of the polymer chains, affecting the viscoelastic properties of the hydrogels. In addition, the diffusion coefficients $\left(D\right)$ of nanoparticles were evaluated, showing a closeness among with the morphology, shape, size and temperature, resulting in slower diffusions for larger particles size and, conversely, the diffusion in the medium increasing as the polymer size is reduced. Therefore, the hydrogels exhibited a remarkable response to pH and temperature variations in the environment. During this research, the functionality and behavior of the polymeric nanoparticles were observed under different analysis conditions, which revealed notable structural changes and further demonstrated the nanoparticles promising high potential for drug delivery applications. Hence, these results have sparked significant interest in various scientific, industrial and technological fields. Full article

Managing mineral bone disease (MBD) could reduce cardiovascular risk and improve the survival of dialysis patients. Our study focuses on the impact of calcium bath exposure in dialysis patients by comparing peritoneal dialysis patients (PD, intervention group) and hemodialysis patients (HD, control group). We assessed various factors, including calcium, phosphorus, magnesium, PTH, vitamin D 25-OH, C-terminal telopeptide (CTX), and FGF-23 levels, as well as the calcium bath six hours before the blood sample and the length of daily calcium exposure. We enrolled 40 PD and 31 HD patients with a mean age of 68.7 ± 13.6 years. Our cohort had median PTH and FGF-23 levels of 194 ng/L (Interquartile range [IQR] 130-316) and 1296 pg/mL (IQR 396-2698), respectively. We identified the length of exposure to a 1.25 mmol/L calcium bath, phosphate levels, and CTX as independent predictors of PTH (OR 0.279, p = 0.011; OR 0.277, p = 0.012; OR 0.11, p = 0.01, respectively). In contrast, independent predictors of FGF-23 were phosphate levels (OR 0.48, p < 0.001) and serum calcium levels (OR 0.25, p = 0.015), which were affected by the calcium bath. These findings suggest that managing dialysate calcium baths impacts phosphaturic hormones and could be a critical factor in optimizing CKD-MBD treatment in PD patients, sparking a new avenue of research and potential interventions. Full article

Our objective is to achieve a new good-quality and mechanically durable high-transparency material that, when activated by rare earth ions, can be used as laser sources, scintillators, or phosphors. The best functional transparent ceramics are formed from high-symmetry systems, mainly cubic. Considering hexagonal hydroxyapatite, which shows anisotropy, the particle size of the initial powder is extremely important and should be of the order of several tens of nanometers. In this work, transparent micro-crystalline ceramics of non-cubic Ca₁₀(PO₄)₆(OH)₂ calcium phosphate were fabricated via Spark Plasma Sintering (SPS) from two types of nanopowders i.e., commercially available (COM. HA) and laboratory-made (LAB. HA) via the hydrothermal (HT) protocol. Our study centered on examining how the quality of sintered bodies is affected by the following parameters: the addition of LiF sintering agent, the temperature during the SPS process, and the quality of the starting nanopowders. The phase purity, microstructure, and optical transmittance of the ceramics were investigated to determine suitable sintering conditions. The best optical ceramics were obtained from LAB. HA nanopowder with the addition of 0.25 wt.% of LiF sintered at 1000 °C and 1050 °C. Full article

Coordinated events of calcium (Ca²⁺) released from the endoplasmic reticulum (ER) are key second messengers in excitable cells. In pain-sensing dorsal root ganglion (DRG) neurons, these events can be observed as Ca²⁺ sparks, produced by a combination of ryanodine receptors (RyR) and inositol 1,4,5-triphosphate receptors (IP3R1). These microscopic signals offer the neuronal cells with a possible means of modulating the subplasmalemmal Ca²⁺ handling, initiating vesicular exocytosis. With super-resolution dSTORM and expansion microscopies, we visualised the nanoscale distributions of both RyR and IP3R1 that featured loosely organised clusters in the subplasmalemmal regions of cultured rat DRG somata. We adapted a novel correlative microscopy protocol to examine the nanoscale patterns of RyR and IP3R1 in the locality of each Ca²⁺ spark. We found that most subplasmalemmal sparks correlated with relatively small groups of RyR whilst larger sparks were often associated with larger groups of IP3R1. These data also showed spontaneous Ca²⁺ sparks in <30% of the subplasmalemmal cell area but consisted of both these channel species at a 3.8–5 times higher density than in nonactive regions of the cell. Taken together, these observations reveal distinct patterns and length scales of RyR and IP3R1 co-clustering at contact sites between the ER and the surface plasmalemma that encode the positions and the quantity of Ca²⁺ released at each Ca²⁺ spark. Full article

This research introduces a method to enhance the biocompatibility of bioinert Al₂O₃-based ceramics by incorporating calcium phosphates (hydroxyapatite (HAp) and tricalcium phosphate (TCP)) into alumina via spark plasma sintering-reactive sintering (SPS-RS). TGA/DTG/DTA and XRD revealed phase formation of HAp and TCP and determined the main temperature points of solid-phase reactions occurring in situ during the sintering of the CaO-CaHPO₄ mixture within the volume of Al₂O₃ under SPS-RS conditions in the range of 900–1200 °C. SEM, EDX, low temperature, and nitrogen physisorption were used to monitor changes in the morphology, structure, and elemental composition of bioceramics. Structural meso- and macroporosity, with a mean mesopore size of 10 nm, were revealed in the ceramic volume, while sintering temperature was shown to play a destructive role towards the porous inorganic framework. The physico-chemical characterization demonstrated increased relative density (up to 95.1%), compressive strength (640 MPa and above), and Vickers microhardness (up to 700 HV) depending on the HAp and TCP content and sintering temperature. Four bioceramic samples with different contents of HAP (20 and 50 wt.%) were bio-tested in in vivo models. The samples were implanted into the soft tissues under the superficial fascia of the thorax of a laboratory animal (a New Zealand White rabbit, female) in the area of the trapezius muscle and the broadest muscle of the back. Based on the results of the assessment of the surrounding tissue reaction, the absence of specific inflammation, necrosis, and tumor formation in the tissues during the implantation period of 90 days was proven. Microbial tests and dynamics of Pseudomonas aeruginosa bacterial film formation on bioceramic surfaces were studied with respect to HAp content (20 and 50 wt.%) and holding time (18, 24, and 48 h) in the feed medium. Full article

Calcium (Ca²⁺) sparks are the elementary events of excitation–contraction coupling, yet they are not explicitly represented in human ventricular myocyte models. A stochastic ventricular cardiomyocyte human model that adapts to intracellular Ca²⁺ ([Ca²⁺]_i) dynamics, spark regulation, and frequency-dependent changes in the form of locally controlled Ca²⁺ release was developed. The 20,000 CRUs in this model are composed of 9 individual LCCs and 49 RyRs that function as couplons. The simulated action potential duration at 1 Hz steady-state pacing is ~0.280 s similar to human ventricular cell recordings. Rate-dependence experiments reveal that APD shortening mechanisms are largely contributed by the L-type calcium channel inactivation, RyR open fraction, and [Ca²⁺]_myo concentrations. The dynamic slow-rapid-slow pacing protocol shows that RyR open probability during high pacing frequency (2.5 Hz) switches to an adapted “nonconducting” form of Ca²⁺-dependent transition state. The predicted force was also observed to be increased in high pacing, but the SR Ca²⁺ fractional release was lower due to the smaller difference between diastolic and systolic [Ca²⁺]_SR. Restitution analysis through the S1S2 protocol and increased LCC Ca²⁺-dependent activation rate show that the duration of LCC opening helps modulate its effects on the APD restitution at different diastolic intervals. Ultimately, a longer duration of calcium sparks was observed in relation to the SR Ca²⁺ loading at high pacing rates. Overall, this study demonstrates the spontaneous Ca²⁺ release events and ion channel responses throughout various stimuli. Full article

Intracellular Ca²⁺ signals are key for the regulation of cellular processes ranging from myocyte contraction, hormonal secretion, neural transmission, cellular metabolism, transcriptional regulation, and cell proliferation. Measurement of cellular Ca²⁺ is routinely performed using fluorescence microscopy with biological indicators. Analysis of deterministic signals is reasonably straightforward as relevant data can be discriminated based on the timing of cellular responses. However, analysis of stochastic, slower oscillatory events, as well as rapid subcellular Ca²⁺ responses, takes considerable time and effort which often includes visual analysis by trained investigators, especially when studying signals arising from cells embedded in complex tissues. The purpose of the current study was to determine if full-frame time-series and line-scan image analysis workflow of Fluo-4 generated Ca²⁺ fluorescence data from vascular myocytes could be automated without introducing errors. This evaluation was addressed by re-analyzing a published “gold standard” full-frame time-series dataset through visual analysis of Ca²⁺ signals from recordings made in pulmonary arterial myocytes of en face arterial preparations. We applied a combination of data driven and statistical approaches with comparisons to our published data to assess the fidelity of the various approaches. Regions of interest with Ca²⁺ oscillations were detected automatically post hoc using the LCPro plug-in for ImageJ. Oscillatory signals were separated based on event durations between 4 and 40 s. These data were filtered based on cutoffs obtained from multiple methods and compared to the published manually curated “gold standard” dataset. Subcellular focal and rapid Ca²⁺ “spark” events from line-scan recordings were examined using SparkLab 5.8, which is a custom automated detection and analysis program. After filtering, the number of true positives, false positives, and false negatives were calculated through comparisons to visually derived “gold standard” datasets. Positive predictive value, sensitivity, and false discovery rates were calculated. There were very few significant differences between the automated and manually curated results with respect to quality of the oscillatory and Ca²⁺ spark events, and there were no systematic biases in the data curation or filtering techniques. The lack of statistical difference in event quality between manual data curation and statistically derived critical cutoff techniques leads us to believe that automated analysis techniques can be reliably used to analyze spatial and temporal aspects to Ca²⁺ imaging data, which will improve experiment workflow. Full article

Reconstructive and regenerative bone surgery is based on the use of high-tech biocompatible implants needed to restore the functions of the musculoskeletal system of patients. Ti6Al4V is one of the most widely used titanium alloys for a variety of applications where low density and excellent corrosion resistance are required, including biomechanical applications (implants and prostheses). Calcium silicate or wollastonite (CaSiO₃) and calcium hydroxyapatite (HAp) is a bioceramic material used in biomedicine due to its bioactive properties, which can potentially be used for bone repair. In this regard, the research investigates the possibility of using spark plasma sintering technology to obtain new CaSiO₃-HAp biocomposite ceramics reinforced with a Ti6Al4V titanium alloy matrix obtained by additive manufacturing. The phase and elemental compositions, structure, and morphology of the initial CaSiO₃-HAp powder and its ceramic metal biocomposite were studied by X-ray fluorescence, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller analysis methods. The spark plasma sintering technology was shown to be efficient for the consolidation of CaSiO₃-HAp powder in volume with a Ti6Al4V reinforcing matrix to obtain a ceramic metal biocomposite of an integral form. Vickers microhardness values were determined for the alloy and bioceramics (~500 and 560 HV, respectively), as well as for their interface area (~640 HV). An assessment of the critical stress intensity factor K_Ic (crack resistance) was performed. The research result is new and represents a prospect for the creation of high-tech implant products for regenerative bone surgery. Full article

The magnesium-based alloys produced by mechanical alloying (MA) are characterized by specific porosity, fine-grained structure, and isotropic properties. In addition, alloys containing magnesium, zinc, calcium, and the noble element gold are biocompatible, so they can be used for biomedical implants. The paper assesses selected mechanical properties and the structure of the Mg₆₃Zn₃₀Ca₄Au₃ as a potential biodegradable biomaterial. The alloy was produced by mechanical synthesis with a milling time of 13 h, and sintered via spark-plasma sintering (SPS) carried out at a temperature of 350 °C and a compaction pressure of 50 MPa, with a holding time of 4 min and a heating rate of 50 °C∙min⁻¹ to 300 °C and 25 °C∙min⁻¹ from 300 to 350 °C. The article presents the results of the X-ray diffraction (XRD) method, density, scanning electron microscopy (SEM), particle size distributions, and Vickers microhardness and electrochemical properties via electrochemical impedance spectroscopy (EIS) and potentiodynamic immersion testing. The obtained results reveal the compressive strength of 216 MPa and Young’s modulus of 2530 MPa. The structure comprises MgZn₂ and Mg₃Au phases formed during the mechanical synthesis, and Mg₇Zn₃ that has been formed during the sintering process. Although MgZn₂ and Mg₇Zn₃ improve the corrosion resistance of the Mg-based alloys, it has been revealed that the double layer formed because of contact with the Ringer’s solution is not an effective barrier; hence, more data and optimization are necessary. Full article

Increased adenosine A_2A receptor (A_2AR) expression and activation underlies a higher incidence of spontaneous calcium release in atrial fibrillation (AF). Adenosine A₃ receptors (A₃R) could counteract excessive A_2AR activation, but their functional role in the atrium remains elusive, and we therefore aimed to address the impact of A₃Rs on intracellular calcium homeostasis. For this purpose, we analyzed right atrial samples or myocytes from 53 patients without AF, using quantitative PCR, patch-clamp technique, immunofluorescent labeling or confocal calcium imaging. A₃R mRNA accounted for 9% and A_2AR mRNA for 32%. At baseline, A₃R inhibition increased the transient inward current (I_TI) frequency from 0.28 to 0.81 events/min (p < 0.05). Simultaneous stimulation of A_2ARs and A₃Rs increased the calcium spark frequency seven-fold (p < 0.001) and the I_TI frequency from 0.14 to 0.64 events/min (p < 0.05). Subsequent A₃R inhibition caused a strong additional increase in the I_TI frequency (to 2.04 events/min; p < 0.01) and increased phosphorylation at s2808 1.7-fold (p < 0.001). These pharmacological treatments had no significant effects on L-type calcium current density or sarcoplasmic reticulum calcium load. In conclusion, A₃Rs are expressed and blunt spontaneous calcium release at baseline and upon A_2AR-stimulation in human atrial myocytes, pointing to A₃R activation as a means to attenuate physiological and pathological elevations of spontaneous calcium release events. Full article