Search results for "mechanical stre"
showing 10 items of 28 documents
A versatile bioreactor for dynamic suspension cell culture. Application to the culture of cancer cell spheroids.
2016
A versatile bioreactor suitable for dynamic suspension cell culture under tunable shear stress conditions has been developed and preliminarily tested culturing cancer cell spheroids. By adopting simple technological solutions and avoiding rotating components, the bioreactor exploits the laminar hydrodynamics establishing within the culture chamber enabling dynamic cell suspension in an environment favourable to mass transport, under a wide range of tunable shear stress conditions. The design phase of the device has been supported by multiphysics modelling and has provided a comprehensive analysis of the operating principles of the bioreactor. Moreover, an explanatory example is herein prese…
Visualizing the spatiotemporal map of Rac activation in bovine aortic endothelial cells under laminar and disturbed flows.
2017
Disturbed flow can eliminate the alignment of endothelial cells in the direction of laminar flow, and significantly impacts on atherosclerosis in collateral arteries near the bifurcation and high curvature regions. While shear stress induced Rac polarity has been shown to play crucial roles in cell polarity and migration, little is known about the spatiotemporal map of Rac under disturbed flow, and the mechanism of flow-induced cell polarity still needs to be elucidated. In this paper, disturbed flow or laminar flow with 15 dyn/cm2 of average shear stress was applied on bovine aortic endothelial cells (BAECs) for 30 minutes. A genetically-encoded PAK-PBD-GFP reporter was transfected into BA…
Ranolazine-Mediated Attenuation of Mechanoelectric Feedback in Atrial Myocyte Monolayers.
2020
[EN] Background Mechanical stretch increases Na(+)inflow into myocytes, related to mechanisms including stretch-activated channels or Na+/H(+)exchanger activation, involving Ca(2+)increase that leads to changes in electrophysiological properties favoring arrhythmia induction. Ranolazine is an antianginal drug with confirmed beneficial effects against cardiac arrhythmias associated with the augmentation ofI(NaL)current and Ca(2+)overload. Objective This study investigates the effects of mechanical stretch on activation patterns in atrial cell monolayers and its pharmacological response to ranolazine. Methods Confluent HL-1 cells were cultured in silicone membrane plates and were stretched to…
Regulation of Autophagic Signaling by Mechanical Loading and Inflammation in Human PDL Fibroblasts
2020
Autophagy (cellular self-consumption) is a crucial adaptation mechanism during cellular stress conditions. This study aimed to examine how this important process is regulated in human periodontal ligament (PDL) fibroblasts by mechanical and inflammatory stress conditions and whether the mammalian target of rapamycin (mTOR) signaling pathway is involved. Autophagy was quantified by flow cytometry. Qualitative protein phosphorylation profiling of the mTOR pathway was carried out. Effects of mTOR regulation were assessed by quantification of important synthesis product collagen 1, cell proliferation and cell death with real-time PCR and flow cytometry. Autophagy as a response to mechanical or …
Mineral mass, size, and estimated mechanical strength of triple jumpers’ lower limb
2001
This study was designed to examine the anticipated strong influence of extreme impact loading on the mineral mass, size, and gross structural properties of triple jumpers' lower limb bones. We compared the bone data obtained with peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA) from 8 Finnish triple jumpers with corresponding data from gender-, age-, height-, and weight-matched nonathletic peers. The volumetric (trabecular) density was significantly higher in the jumpers than in controls (from an average 18% difference at the distal tibia to a 41% difference at the proximal tibia), whereas the cortical density did not differ between groups. The D…
Constitutive modeling of ascending thoracic aortic aneurysms using microstructural parameters.
2016
Ascending thoracic aortic aneurysm (ATAA) has been associated with diminished biomechanical strength and disruption in the collagen fiber microarchitecture. Additionally, the congenital bicuspid aortic valve (BAV) leads to a distinct extracellular matrix structure that may be related to ATAA development at an earlier age than degenerative aneurysms arising in patients with the morphological normal tricuspid aortic valve (TAV). The purpose of this study was to model the fiber-reinforced mechanical response of ATAA specimens from patients with either BAV or TAV. This was achieved by combining image-analysis derived parameters of collagen fiber dispersion and alignment with tensile testing dat…
Strength of pre-Roman amphorae: Comparison of the different types
2015
Abstract Given that amphorae were used for storage or for long and/or short distance transport, they must have been able to retain their content and, at the same time, be able to resist important load during transport. This paper concerns aspects of the techno-functionality of pre-Roman Iberian amphorae. The basic performance requirement concerned here is the mechanical strength (transverse rupture strength: TRS). Strength is related to the adequacy for storage or short and/or long distance transport that, up to now, is only assessed by typological identification or archaeological evidence. Experimental implementation on actual archaeological material has confirmed that strength increased w…
Do More Highly Organized Collagen Fibrils Increase Bone Mechanical Strength in Loss of Mineral Density After One-Year Running Training?
1999
The aim of this study was to evaluate the effects of long-term running training on the structural properties of bone. Ten beagle dogs ran according to a strenuous progressive program (up to 40 km/day) for 1 year. At the end of the training program, there was a significant reduction in bone mineral density (up to 9.7%) in the vertebrae of the runner dogs as compared with 10 sedentary control dogs. Polarized light microscopy of the vertebral trabecular bone, however, displayed proportionally higher retardation values of the collagen network of the runner dogs than of the sedentary dogs, suggesting a reorganization in a more parallel manner in the collagen fibrils. The concentration and cross-…
Conversion of furfural to 2-methylfuran over CuNi catalysts supported on biobased carbon foams
2021
In this study, carbon foams prepared from the by-products of the Finnish forest industry, such as tannic acid and pine bark extracts, were examined as supports for 5/5% Cu/Ni catalysts in the hydrotreatment of furfural to 2-methylfuran (MF). Experiments were conducted in a batch reactor at 503 K and 40 bar H2. Prior to metal impregnation, the carbon foam from tannic acid was activated with steam (S1), and the carbon foam from pine bark extracts was activated with ZnCl2 (S2) and washed with acids (HNO3 or H2SO4). For comparison, a spruce-based activated carbon (AC) catalyst and two commercial AC catalysts as references were investigated. Compressive strength of the foam S2 was 30 times great…
Emotion regulation strategies modulate the effect of adverse childhood experiences on perceived chronic stress with implications for cognitive flexib…
2020
Exposure to early life adversity is associated with chronic stress and a range of stress-related health problems in adulthood. Since chronic stress debilitates activity in the prefrontal cortex (pFC), maladaptive regulatory strategies in response to stress have been proposed as one explanation for the impact of early life adversity on health outcomes in adulthood. We conducted a study to examine the impact of adverse childhood experiences (ACEs) on cognitive flexibility, a key executive function implicated in activity in the pFC, in a sample of adults (N = 486). Additionally, we investigated whether perceptions of chronic stress in adulthood would mediate the influence of ACEs on cognitive …