Mechanical Tension Research Articles

Serotonin receptor and serotonin transporter expressions in the placental villous tree in gestational diabetes mellitus

BACKGROUND: The serotonergic system during pregnancy plays an important role not only in carbohydrate metabolism, but also in the laying and regulation of the fetoplacental complex, growth and development of the fetus. The study of the expression of placental serotonin 5-HT2A receptor and serotonin transporter (SERT) in gestational diabetes mellitus is foremost for scrutinizing the pathogenesis of perinatal complications, as it may allow for finding new opportunities for their prevention and correction.
 AIM: The aim of this study was to compare the expression patterns of the serotonin 5-HT2A receptor and SERT in placental tissue in gestational diabetes mellitus and in normal pregnancy.
 MATERIALS AND METHODS: This comparative cohort study included pregnant women with gestational diabetes mellitus (n = 6) and patients with normal pregnancy (n = 10). The expression of serotonin 5-HT2A receptor (Abcam, USA) and SERT (Bioss Antibodies, USA) was studied in placenta samples from the both study groups by immunohistochemical method. Morphometric analysis was performed using the VideoTest-Morphology 5.2 program (Videotest Ltd., Russia).
 RESULTS: The relative area of SERT expression in the placenta in gestational diabetes mellitus was higher compared to normal pregnancy (p 0.001). The relative areas of expression of the serotonin 5-HT2A receptor in the placenta did not differ between the study groups (p = 0.5).
 CONCLUSIONS: Higher SERT expression in the placentas of patients with gestational diabetes mellitus compared to those from women with normal pregnancies may reflect the level of tension of compensatory mechanisms in gestational diabetes mellitus and the effect of insulin therapy on these mechanisms.

Orthodontic tension promotes cementoblast mineralization by regulating autophagy

Background/purposeExternal root resorption is a main side effect of orthodontic treatment and is more likely to occur on the pression side than the tension side. To explore the potential protective mechanisms on the tension side, this study investigated the influence of mechanical tension on cementoblast mineralization and elucidated the role of autophagy in mediating this process. Materials and methodsMechanical tension was applied to cementoblasts using iStrain. The expression of mineralization-related and autophagy-related markers was detected by qRT-PCR, Western blot analysis, and immunofluorescence staining. RNA sequencing identified key regulators. Immunohistochemical staining assessed related markers expression in in vivo experiments. ResultsApplying tension to cementoblasts increased mineralization-related gene expression in a force-dependent and time-dependent manner. The immunohistochemical staining result of in vivo experiments supported these findings, demonstrating elevated expression of mineralization markers under tension. Mechanical tension also enhanced autophagic activity in cementoblasts, which was demonstrated by the results of qRT-PCR, Western blot analysis, immunofluorescence staining, and in vivo experiments. Suppression of autophagy with chloroquine attenuated the mineralization of cementoblasts induced by tension stimulus. RNA-seq identified Postn as a key regulator, and the knockdown of Postn impaired the mechanical tension-promoted mineralization of cementoblasts. ConclusionThis study proposed the tension-induced promotion in mineralization of cementoblasts and emphasized the mediating role of autophagy in this process. Postn, a mediator connecting autophagy and mineralization, was identified as a key regulator. These discoveries helped elucidate orthodontic-related microprocesses on tooth roots and offer potential targets for therapeutic interventions to prevent and restore external root resorption clinically.

The ability of the LIMD1 and TRIP6 LIM domains to bind strained f-actin is critical for their tension dependent localization to adherens junctions and association with the Hippo pathway kinase LATS1.

A key step in regulation of Hippo pathway signaling in response to mechanical tension is recruitment of the LIM domain proteins TRIP6 and LIMD1 to adherens junctions. Mechanical tension also triggers TRIP6 and LIMD1 to bind and inhibit the Hippo pathway kinase LATS1. How TRIP6 and LIMD1 are recruited to adherens junctions in response to tension is not clear, but previous studies suggested that they could be regulated by the known mechanosensory proteins α-catenin and vinculin at adherens junctions. We found that the three LIM domains of TRIP6 and LIMD1 are necessary and sufficient for tension-dependent localization to adherens junctions. The LIM domains of TRIP6, LIMD1, and certain other LIM domain proteins have been shown to bind to actin networks under strain/tension. Consistent with this, we show that TRIP6 and LIMD1 colocalize with the ends of actin fibers at adherens junctions. Point mutations in a key conserved residue in each LIM domain that are predicted to impair binding to f-actin under strain inhibits TRIP6 and LIMD1 localization to adherens junctions and their ability to bind to and recruit LATS1 to adherens junctions. Together these results show that the ability of TRIP6 and LIMD1 to bind to strained actin underlies their ability to localize to adherens junctions and regulate LATS1 in response to mechanical tension.

Microenvironment with NIR-Controlled ROS and Mechanical Tensions for Manipulating Cell Activities in Wound Healing.

The extracellular matrix (ECM) orchestrates cell behavior and tissue regeneration by modulating biochemical and mechanical signals. Manipulating cell-material interactions is crucial for leveraging biomaterials to regulate cell functions. Yet, integrating multiple cues in a single material remains a challenge. Here, near-infrared (NIR)-controlled multifunctional hydrogel platforms, named PIC/CM@NPs, are introduced to dictate fibroblast behavior during wound healing by tuning the matrix oxidative stress and mechanical tensions. PIC/CM@NPs are prepared through cell adhesion-medicated assembly of collagen-like polyisocyanide (PIC) polymers and cell-membrane-coated conjugated polymer nanoparticles (CM@NPs), which closely mimic the fibrous structure and nonlinear mechanics of ECM. Upon NIR stimulation, PIC/CM@NPs composites enhance fibroblast cell proliferation, migration, cytokine production, and myofibroblast activation, crucial for wound closure. Moreover, they exhibit effective and toxin removal antibacterial properties, reducing inflammation. This multifunctional approach accelerates healing by 95%, highlighting the importance of integrating biochemical and biophysical cues in the biomaterial design for advanced tissue regeneration.

The zonula adherens matura redefines the apical junction of intestinal epithelia

Cell-cell apical junctions of epithelia consist of multiprotein complexes that organize as belts regulating cell-cell adhesion, permeability, and mechanical tension: the tight junction (zonula occludens), the zonula adherens (ZA), and the macula adherens. The prevailing dogma is that at the ZA, E-cadherin and catenins are lined with F-actin bundles that support and transmit mechanical tension between cells. Using super-resolution microscopy on human intestinal biopsies and Caco-2 cells, we show that two distinct multiprotein belts are basal of the tight junctions as the intestinal epithelia mature. The most apical is populated with nectins/afadin and lined with F-actin; the second is populated with E-cad/catenins. We name this dual-belt architecture the zonula adherens matura. We find that the apical contraction apparatus and the dual-belt organization rely on afadin expression. Our study provides a revised description of epithelial cell-cell junctions and identifies a module regulating the mechanics of epithelia.

Evaluation of orange peel (Citrus sinensis) bioplastic through morphological and thermo-mechanical characteristics.

Objective: To evaluate the morphological and thermo-mechanical properties of a biofilm obtained from orange peel.
 Design/methodology/approach: Pectin, a polysaccharide obtained from orange peel, has the potential to be used as a raw material in the bioplastics industry. The samples obtained were characterized by the Scanning Electron Microscopy (SEM) technique, mechanical tension and by thermogravimetric analysis (TGA).
 Results: The elastic modulus was in the range of 7.7 to 29.9 MPa, depending on the plasticizer content. The thermogravimetric analysis showed a thermal decomposition between 134.42 to 153.98 °C depending on the plasticizer content and up to five events were identified.
 Limitations of the study/implications: During the process, a pectin yield of 75% of orange peel was obtained.
 Findings/conclusions: In developing countries such as Mexico, waste originating from agricultural and agro-industrial activities represents an important source of natural carbohydrate polymers that can be used to produce bioplastics, intended to replace petroleum-derived materials. In the case of orange peel, it can become a potential raw material to obtain value-added products in sectors of the food industry. These results indicated that our pectin has suitable properties to be used as raw material for the manufacture of bioplastics.

The Role of ZO-2 in Modulating JAM-A and γ-Actin Junctional Recruitment, Apical Membrane and Tight Junction Tension, and Cell Response to Substrate Stiffness and Topography.

This work analyzes the role of the tight junction (TJ) protein ZO-2 on mechanosensation. We found that the lack of ZO-2 reduced apical membrane rigidity measured with atomic force microscopy, inhibited the association of γ-actin and JAM-A to the cell border, and instead facilitated p114RhoGEF and afadin accumulation at the junction, leading to an enhanced mechanical tension at the TJ measured by FRET, with a ZO-1 tension probe, and increased tricellular TJ tension. Simultaneously, adherens junction tension measured with an E-cadherin probe was unaltered. The stability of JAM-A and ZO-2 binding was assessed by a collaborative in silico study. The absence of ZO-2 also impacted the cell response to the substrate, as monolayers plated in 20 kPa hydrogels developed holes not seen in parental cultures and displayed a retarded elongation and formation of cell aggregates. The absence of ZO-2 was sufficient to induce YAP and Snail nuclear accumulation in cells cultured over glass, but when ZO-2 KD cells were plated in nanostructured ridge arrays, they displayed an increased abundance of nuclear Snail and conspicuous internalization of claudin-4. These results indicate that the absence of ZO-2 also impairs the response of cells to substrate stiffness and exacerbates transformation triggered by substrate topography.

Mechanotransduction and epigenetic modulations of chromatin: Role of mechanical signals in gene regulation.

Mechanical forces may be generated within a cell due to tissue stiffness, cytoskeletal reorganization, and the changes (even subtle) in the cell's physical surroundings. These changes of forces impose a mechanical tension within the intracellular protein network (both cytosolic and nuclear). Mechanical tension could be released by a series of protein-protein interactions often facilitated by membrane lipids, lectins and sugar molecules and thus generate a type of signal to drive cellular processes, including cell differentiation, polarity, growth, adhesion, movement, and survival. Recent experimental data have accentuated the molecular mechanism of this mechanical signal transduction pathway, dubbed mechanotransduction. Mechanosensitive proteins in the cell's plasma membrane discern the physical forces and channel the information to the cell interior. Cells respond to the message by altering their cytoskeletal arrangement and directly transmitting the signal to the nucleus through the connection of the cytoskeleton and nucleoskeleton before the information despatched to the nucleus by biochemical signaling pathways. Nuclear transmission of the force leads to the activation of chromatin modifiers and modulation of the epigenetic landscape, inducing chromatin reorganizationand gene expression regulation; by the time chemical messengers (transcription factors) arrive into the nucleus. While significant research has been done on the role of mechanotransduction in tumor development and cancer progression/metastasis, the mechanistic basis of force-activated carcinogenesis is still enigmatic. Here, in this review, we have discussed the various cues and molecular connections to better comprehend the cellular mechanotransduction pathway, and we also explored the detailed role of some of the multiple players (proteins and macromolecular complexes) involved in mechanotransduction. Thus, we have described an avenue: how mechanical stress directs the epigenetic modifiers to modulate the epigenome of the cells and how aberrant stress leads to the cancer phenotype.

Photolipid excitation triggers depolarizing optocapacitive currents and action potentials

Optically-induced changes in membrane capacitance may regulate neuronal activity without requiring genetic modifications. Previously, they mainly relied on sudden temperature jumps due to light absorption by membrane-associated nanomaterials or water. Yet, nanomaterial targeting or the required high infrared light intensities obstruct broad applicability. Now, we propose a very versatile approach: photolipids (azobenzene-containing diacylglycerols) mediate light-triggered cellular de- or hyperpolarization. As planar bilayer experiments show, the respective currents emerge from millisecond-timescale changes in bilayer capacitance. UV light changes photolipid conformation, which awards embedding plasma membranes with increased capacitance and evokes depolarizing currents. They open voltage-gated sodium channels in cells, generating action potentials. Blue light reduces the area per photolipid, decreasing membrane capacitance and eliciting hyperpolarization. If present, mechanosensitive channels respond to the increased mechanical membrane tension, generating large depolarizing currents that elicit action potentials. Membrane self-insertion of administered photolipids and focused illumination allows cell excitation with high spatiotemporal control.

In Vivo Effects of Joint Movement on Nerve Mechanical Properties Assessed with Shear-Wave Elastography: A Systematic Review and Meta-Analysis

Peripheral nerves are subjected to mechanical tension during limb movements and body postures. Nerve response to tensile stress can be assessed in vivo with shear-wave elastography (SWE). Greater tensile loads can lead to greater stiffness, which can be quantified using SWE. Therefore, this study aimed to conduct a systematic review and meta-analysis to perform an overview of the effect of joint movements on nerve mechanical properties in healthy nerves. The initial search (July 2023) yielded 501 records from six databases (PubMed, Embase, Scopus, Web of Science, Cochrane, and Science Direct). A total of 16 studies were included and assessed with a modified version of the Downs and Black checklist. Our results suggest an overall tendency for stiffness increase according to a pattern of neural tensioning. The main findings from the meta-analysis showed a significant increase in nerve stiffness for the median nerve with wrist extension (SMD [95%CI]: 3.16 [1.20, 5.12]), the ulnar nerve with elbow flexion (SMD [95%CI]: 2.91 [1.88, 3.95]), the sciatic nerve with ankle dorsiflexion (SMD [95%CI]: 1.13 [0.79, 1.47]), and the tibial nerve with both hip flexion (SMD [95%CI]: 2.14 [1.76, 2.51]) and ankle dorsiflexion (SMD [95%CI]: 1.52 [1.02, 2.02]). The effect of joint movement on nerve stiffness also depends on the nerve segment, the amount of movement of the joint mobilized, and the position of other joints comprised in the entirety of the nerve length. However, due to the limited number of studies, many aspects of nerve behavior together with the effect of using different ultrasound equipment or transducers for nerve stiffness evaluation still need to be fully investigated.

Sustainable Polypropylene-Based Composites with Agro-Waste Fillers: Thermal, Morphological, Mechanical Properties and Dimensional Stability.

Natural fiber composites (NFC) are eco-friendly alternatives to synthetic polymers. However, some intrinsic natural fillers' properties hinder their widespread implementation as reinforcement in polymeric matrices and require further investigation. In the scope of this study, the thermal, rheologic, mechanical (tension and flexural modes), and morphological properties, as well as the water absorption and dimensional stability of the NF polypropylene (PP)-based injection molded composites reinforced with rice husk (rh) and olive pits (op) of 20 wt.% and 30% wt.%, respectively, were investigated. The results suggest that the higher content of the rice husk and olive pits led to a similar reduction in the melt flow index (MFI), independent of the additive type compared to virgin polypropylene (PPv). The melting and crystallization temperatures of the PPrh and PPop composites did not change with statistical significance. The composites are stiffer than the PP matrix by up to 49% and possess higher mechanical strength in the tension mode at the expense of decreased ductility. PPrh and PPop have a superior flexural modulus in the bending mode, while the flexural strength improvement was accomplished for the PP30%rh. The influence of the fibers' distribution in the bulk of the parts on their mechanical performance was confirmed based on a non-localized morphology evaluation, which constitutes a novelty of the presented research. The dimensional stability of the composites was improved as the linear shrinkage in the flow direction was decreased by 49% for PPrh and 30% for PPop, positively correlating with an increase in the filler content and stiffness. PPop was less susceptible to water sorption than PPrh due to fibers' composition and larger surface-to-area volume ratios.

Retracted: RNA-Sequence Reveals the Regulatory Mechanism of miR-149 on Osteoblast Skeleton under Mechanical Tension.

[This retracts the article DOI: 10.1155/2022/9640878.].

Elastic Contractile Stress in the Basement Membrane Generates Basal Tension in Epithelia

The shaping of epithelial tissues into functional organs often depends on dynamic changes of mechanical tension at the apical and basal sides of cells. While on the apical side, tension is known to be regulated by the apical actomyosin meshwork, basal tension regulation remains elusive due to the presence of a basal sheet of specialized extracellular matrix, the basement membrane. Here, we use atomic force microscopy to provide direct measurements of mechanical tension in the basal surface of the wing disk epithelium of in control and perturbed conditions. We find that next to actomyosin, the basement membrane is a key structure for the generation of basal tension. Furthermore, we show that the basement membrane is a solidlike sheet subject to an expansile stretch in epithelial homeostasis. Performing osmotic shocks and optogenetic actomyosin activation, we find evidence that basal stretch and tension can be generated by intracellular hydrostatic pressure and actomyosin tension in lateral cell faces of the epithelium. In conclusion, we propose that elastic contractile stress corresponding to the actomyosin-induced expansile stretch of the basement membrane generates a major contribution to basal tension. We thereby disclose fundamental differences in the mechanical regulation of apical and basal epithelial tension. Published by the American Physical Society 2024

Influence of 8-weeks of supervised static stretching or resistance training of pectoral major muscles on maximal strength, muscle thickness and range of motion.

Current research suggests static stretch-induced maximal strength increases and muscle hypertrophy with potential to substitute resistance-training routines. However, most studies investigated the plantar flexors. This study explored the effects of a static stretching program on maximal strength, hypertrophy and flexibility of the pectoralis major and compared the effects with those of traditional resistance training. Eighty-one (81) active participants were allocated to either a static stretching, strength-training or control group. Pectoralis stretching was applied 15min/day, 4days per week for 8weeks, while resistance training trained 3days per week, 5 × 12 repetitions. There was an increase in all parameters (strength: p < 0.001, ƞ2 = 0.313, muscle thickness: p < 0.001, ƞ2 = 0.157-0.264, flexibility: p < 0.001, ƞ2 = 0.316) and a time*group interaction (strength: p = 0.001, ƞ2 = 0.154, muscle thickness: p = 0.008-0.001, ƞ2 = 0.117-0.173, flexibility: p < 0.001, ƞ2 = 0.267). Post-hoc testing showed no difference between both intervention groups regarding maximal strength and muscle thickness (p = 0.905-0.983, d = 0.036-0.087), while flexibility increased in the stretching group (p = 0.001, d = 0.789). Stretching showed increases in maximal strength and hypertrophy, which were comparable with commonly used resistance training. Based on current literature, the influence of mechanical tension as the underlying mechanism is discussed. Furthermore, as equipment and comparatively long stretching durations are requested to induce meaningful strength increases in recreationally active participants, practical application seems limited to special circumstances.

Preparation of Fe7S8/C composite by one-step hydrothermal method for fast efficient lithium storage with long cycle life

High-capacity metal sulfide electrode materials for lithium storage have received extensive attention for the booming battery technology. However, metal sulfide electrodes have poor reaction kinetics in the light of capacity delivery and rate performance. To increase Li-ion storage, an easy one-pot hydrothermal method was presented to prepare a Fe7S8/C composite for lithium-ion batteries anode. The homogeneous doping of nitrogen in the carbon layer is beneficial to the rapid and uniform growth of Fe7S8 nanoparticles. The Fe7S8/C composite provides a strong honeycomb network with stable interfacial bonds by the strong chemical bonds between Fe7S8 and C, which can ease mechanical tension to ensure the stability of the structure during cycling. So the Fe7S8/C composite material has long-term stability (466.8 mAh g−1 at 2C after 2000 cycles). The impressive electrochemical behaviors can be ascribed to enhanced reaction kinetics, where unique carbon network matrix plays a dual role of conductive substrate and channels for electron and ion transport, respectively.

Analysis of the adaptation potential of the cardiovascular system of students studying in medical specialties

Relevance. Studying the adaptive potential of students is an important way to assess the level of health and early career guidance of future doctors.The purpose of the study is to study the adaptive potential of the cardiovascular system among second-year medical university students.Object and methods. The study involved 507 students of both sexes studying in their second year at Samara State Medical University. At the first stage of the study, anthropometric parameters were studied in all subjects. At the second stage, an analysis of the adaptive potential was carried out by calculating the following indicators: index of functional changes, adaptive potential according to the equation of L.A. Konevskikh, Robinson index.Conclusions. An analysis of the functional state of the cardiovascular system of medical university students revealed that the majority of students already in their second year have a disruption of adaptation processes, which is associated with low functional capabilities of the body, tension in adaptation mechanisms and disruption in the functioning of regulatory systems.

Mechanical, electrical and self-healing properties of carbon fibre-reinforced ultra-lightweight ECC

The hybrid mixes of carbon fibres (CF), fly ash cenosphere and polyethylene fibre could be used to develop smart ultra-lightweight engineered cementitious composites (ULW-ECCs). In this study, the effects of CF length (1, 3, 6, 9, 12, 15, 20 mm) with different volume fractions (0.0, 0.5 and 1.0 vol%) on the fundamental mechanical (compression, tension and flexure) and electrical properties of CF-reinforced ULW-ECCs were evaluated. Pseudo-strain-hardening indices, multiple micro-cracking behaviours and self-healing properties were also tested. The experimental results reveal that, except for the 1 mm particle CF, incorporating CF could improve the strength (compression, tension and flexure) of ULW-ECCs but decrease the strain ductility properties under tension; and CF lengths of 9- and 12-mm show better results. The electrical conductivity of ULW-ECCs was improved by CF, and the higher dosage further increased the conductivity. The conductivity increased first and then decreased with the increase in CF length and the 9 mm CF (1.0 vol%) shows higher conductivity. The conductive network was affected by the volume fraction, length, count under the same content, and possible fracture of CF. Long CFs work well at low content in forming conductive networks, while short CFs are more effective at high content. The conductivity decreased with the increase of curing age and reached a constant value after 90 d. Incorporating CF and increasing its length/content negatively impacted crack number and width. CF-reinforced ULW-ECCs exhibit excellent self-healing, with reduced ability as wet-dry cycles and curing age increase.

Mechanical Tensions Regulate Gene Expression in the Xenopus laevis Axial Tissues.

During gastrulation and neurulation, the chordamesoderm and overlying neuroectoderm of vertebrate embryos converge under the control of a specific genetic programme to the dorsal midline, simultaneously extending along it. However, whether mechanical tensions resulting from these morphogenetic movements play a role in long-range feedback signaling that in turn regulates gene expression in the chordamesoderm and neuroectoderm is unclear. In the present work, by using a model of artificially stretched explants of Xenopus midgastrula embryos and full-transcriptome sequencing, we identified genes with altered expression in response to external mechanical stretching. Importantly, mechanically activated genes appeared to be expressed during normal development in the trunk, i.e., in the stretched region only. By contrast, genes inhibited by mechanical stretching were normally expressed in the anterior neuroectoderm, where mechanical stress is low. These results indicate that mechanical tensions may play the role of a long-range signaling factor that regulates patterning of the embryo, serving as a link coupling morphogenesis and cell differentiation.

Research progress of non-coding RNA-mediated regulation of the osteogenesis of periodontal tissues when mechanical tension is applied

Research progress of non-coding RNA-mediated regulation of the osteogenesis of periodontal tissues when mechanical tension is applied

Determination of pore edge tension from the kinetics of rupture of giant unilamellar vesicles using the Arrhenius equation: effects of sugar concentration, surface charge and cholesterol.

The pore edge tension (Γ) of a membrane closely intertwines with membrane stability and plays a vital role in the mechanisms that facilitate membrane resealing following pore formation caused by electrical and mechanical tensions. We have explored a straightforward procedure to determine Γ by fitting the inverse of the tension-dependent logarithm of the rate constant of rupture of giant unilamellar vesicles (GUVs) using the Arrhenius equation. The GUVs were prepared using a combination of 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DOPG) and 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) in a physiological environment. The effects of sugar concentration, membrane surface charge density, and membrane cholesterol concentration on Γ have been investigated. The values of Γ increase with sugar concentration in the physiological buffer, measuring 9.6 ± 0.3, 10.4 ± 0.1, and 16.2 ± 0.1 pN for 40, 100, and 300 mM, respectively. A higher concentration of anionic lipids (70 mol% of DOPG) significantly reduces Γ. An increasing trend of Γ with cholesterol content was observed; specifically, the values of Γ were 11.9 ± 0.9, 13.9 ± 0.7, and 16.2 ± 0.4 pN for 15, 29, and 40 mol% cholesterol, respectively. Thus, the presence of higher anionic lipids in the bilayer led to a decrease in membrane stability. In contrast, the presence of higher sugar concentrations in the buffer and increased cholesterol concentration in the membranes enhanced membrane stability.