Regional variation of series elasticity in canine arterial smooth muscles

1978 ◽  
Vol 234 (5) ◽  
pp. H542-H551 ◽  
Author(s):  
R. H. Cox

Segments of carotid, iliac, renal, mesenteric, coronary, and internal thoracic arteries were studied in vitro to correlate the mechanical properties of series (SE) and parallel (PE) elastic elements with connective tissue (CT) composition and with active responses to potassium activation. The PE properties were determined using pressure-diameter data with passive smooth muscle (SM). SE properties were determined from periodic incremental releases imposed during isometric responses to [K+]O at a diameter corresponding to Lmax, the optimum muscle length. Active stress responses and diameter responses were determined using pressure-diameter data for active and passive conditions. Collagen and elastin contents were determined for each sample. No correlation was found between CT content and PE or SE properties for the various sites. A close correlation was found to exist between SE and PE properties at each site, i.e., the sites with the stiffest PE also had the stiffest SE. SM, with stiffer SE, had a larger diameter response with the same active stress response and the same diameter response with a smaller active stress response, compared to SM with more compliant SE. This suggests that passive properties of SM can have a significant influence on the external manifestations of contractile element properties.

Cells ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 2478
Author(s):  
Xingwen Wu ◽  
Antony Bacic ◽  
Kim L. Johnson ◽  
John Humphries

The plant cell wall plays a critical role in signaling responses to environmental and developmental cues, acting as both the sensing interface and regulator of plant cell integrity. Wall-associated kinases (WAKs) are plant receptor-like kinases located at the wall—plasma membrane—cytoplasmic interface and implicated in cell wall integrity sensing. WAKs in Arabidopsis thaliana have been shown to bind pectins in different forms under various conditions, such as oligogalacturonides (OG)s in stress response, and native pectin during cell expansion. The mechanism(s) WAKs use for sensing in grasses, which contain relatively low amounts of pectin, remains unclear. WAK genes from the model monocot plant, Brachypodium distachyon were identified. Expression profiling during early seedling development and in response to sodium salicylate and salt treatment was undertaken to identify WAKs involved in cell expansion and response to external stimuli. The BdWAK2 gene displayed increased expression during cell expansion and stress response, in addition to playing a potential role in the hypersensitive response. In vitro binding assays with various forms of commercial polysaccharides (pectins, xylans, and mixed-linkage glucans) and wall-extracted fractions (pectic/hemicellulosic/cellulosic) from both Arabidopsis and Brachypodium leaf tissues provided new insights into the binding properties of BdWAK2 and other candidate BdWAKs in grasses. The BdWAKs displayed a specificity for the acidic pectins with similar binding characteristics to the AtWAKs.


2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Jialin He ◽  
Jianyang Liu ◽  
Yan Huang ◽  
Xiangqi Tang ◽  
Han Xiao ◽  
...  

The mechanism of Golgi apparatus (GA) stress responses mediated by GOLPH3 has been widely studied in ischemic stroke, and the neuroprotection effect of olfactory mucosa mesenchymal stem cells (OM-MSCs) against cerebral ischemia/reperfusion injury (IRI) has been preliminarily presented. However, the exact role of OM-MSCs in the GA stress response following cerebral IRI remains to be elucidated. In the present study, we used an oxygen-glucose deprivation/reoxygenation (OGD/R) model and reversible middle cerebral artery occlusion (MCAO) model to simulate cerebral IRI in vitro and in vivo. Our results showed that the level of GOLPH3 protein, reactive oxygen species (ROS), and Ca2+ was upregulated, SPCA1 level was downregulated, and GA fragmentation was increased in ischemic stroke models, and OM-MSC treatment clearly ameliorated these GA stress responses in vitro and in vivo. Subsequently, the knockdown of PEDF in OM-MSCs using PEDF-specific siRNA further demonstrated that secretion of PEDF in OM-MSCs protected OGD/R-treated N2a cells and MCAO rats from GA stress response. Additionally, rescue experiment using specific pathway inhibitors suggested that OM-MSCs could promote the phosphorylation of the PI3K/Akt/mTOR pathway, thereby mitigating OGD/R-induced GA stress response and excessive autophagy. In conclusion, OM-MSCs minimized the GA stress response following cerebral IRI, at least partially, through the PEDF-PI3K/Akt/mTOR pathway.


Author(s):  
А.А. Московцев ◽  
Д.В. Колесов ◽  
А.Н. Мыльникова ◽  
Д.М. Зайченко ◽  
А.А. Соколовская ◽  
...  

Эндотелиальные клетки, выстилающие стенки сосудов, являются одними из важнейших регуляторных элементов кровеносной системы. Непосредственно соприкасаясь с потоком крови, эти механочувствительные клетки способны детектировать свою деформацию через ее тангенциальный компонент (сдвиг) и составляющую, направленную по нормали к поверхности (растяжение). Деформация сдвига является ключевым индуктором комплекса сигнальных путей, опосредуемых тирозинкиназами, интегринами, ионными каналами, вовлекающих также мембранные липиды, гликокаликс и другие клеточные компоненты. На фоне достаточно большого количества данных о сигнальной трансдукции, в литературе меньше внимания уделено клеточной адаптации к сдвиговой деформации и сравнительно мало информации об участии генов стрессового ответа. Гидродинамические условия в определенных зонах сосудистой системы характеризуются значительной неоднородностью, что может приводить к ослаблению обратных связей, необходимых для поддержания гомеостаза в эндотелиальных клетках. Это может способствовать развитию заболеваний, например, таких, как атеросклероз. В обзоре обсуждаются новые аспекты и концепции, связанные с ответами эндотелиоцитов на сдвиговую деформацию и основные методы анализа эффектов сдвиговой деформации in vitro . Цель исследования. Обобщение современных данных о механизмах механочувствительности и механотрансдукции эндотелия. Результаты. В обзоре изложены основные механизмы механочувствительности клеток эндотелия, пути внутриклеточной передачи сигнала, рассмотрено вовлечение механизмов стрессового ответа клеток и адаптации. Обсуждаются эксперименты по изучению молекулярных основ механотрансдукции, в том числе белков и других молекул, вовлеченных в детектирование, передачу сигнала и клеточный ответ на сдвиговую деформацию. Endothelial cells lining the walls of blood vessels are one of the most important regulatory elements of the circulatory system. These mechanosensitive cells are in a direct contact with the flow of blood and able to detect deformation through its tangential component (shear) and the component directed along the normal to the surface (tension). Shear stress is the key inducer of the complex of signaling pathways mediated by tyrosine kinases, integrins, ion channels, involving also membrane lipids, glycocalyx and other cellular components. There are large amount of data on signal transduction in the literature, but less attention is paid to cellular adaptation to shear stress and there is relatively little information on the involvement of stress response genes in that process. Hydrodynamic conditions in certain zones of the vascular system are characterized by considerable heterogeneity, which can lead to weakening of feedbacks necessary for maintaining homeostasis in endothelial cells. This can contribute to the development of diseases such as atherosclerosis. This review presents new aspects and concepts related to the responses of endotheliocytes to shear stress and, in addition, highlights the basic methods of analyzing the effects of shear stress in vitro . Purpose of the study. Generalization of modern data on mechanisms of mechanosensitivity and mechanotransduction of the endothelium. Results. The review outlines the main mechanosensitivity mechanisms of endothelial cells, the pathways of intracellular signaling, the involvement of mechanisms of cellular stress response and adaptation. There are descriptions of experiments in which the molecular basis of mechanotransduction is identified, including the determination of proteins and other molecules involved in detection, signal transduction, and cellular response to shear stress.


2016 ◽  
Vol 2 (1) ◽  
pp. 263-266
Author(s):  
Robert Arnold ◽  
Anton J. Prassl ◽  
Ernst Hofer ◽  
Gernot Plank

AbstractComputer simulation turns out to be beneficial when clinical data lack spatio-temporal resolution or parameters cannot be measured at all. To derive trustworthy results, these in-silico models have to thoroughly parameterized and validated. In this work we present data from a simplified in-vitro setup for characterizing ventricular electromechanics. Right ventricular papillary muscles from New Zealand rabbits were isolated and stretched from slack length to lmax, i.e. the muscle length at maximum active force development. Active stress development showed an almost linear increase for moderate strain (90–100% of lmax) and a significant decrease for larger strain (100–105% of lmax). Passive strain development showed a nonlinear increase. Conduction velocity CV showed an increase of ≈10% between low and moderate strain and no significant decrease beyond. Fitting active active stress-strain relationship using a 5th-order polynomial yielded adequate results for moderate and high strain values, whereas fitting using a logistic function yielded more reasonable results for low strain values. Passive stress-strain relationship was satisfactorily fitted using an exponential function.


2007 ◽  
Vol 189 (11) ◽  
pp. 4204-4216 ◽  
Author(s):  
Laurent Sauviac ◽  
Heinui Philippe ◽  
Kounthéa Phok ◽  
Claude Bruand

ABSTRACT Sinorhizobium meliloti genes transcriptionally up-regulated after heat stress, as well as upon entry into stationary phase, were identified by microarray analyses. Sixty stress response genes were thus found to be up-regulated under both conditions. One of them, rpoE2 (smc01506), encodes a putative extracytoplasmic function (ECF) sigma factor. We showed that this sigma factor controls its own transcription and is activated by various stress conditions, including heat and salt, as well as entry into stationary phase after either carbon or nitrogen starvation. We also present evidence that the product of the gene cotranscribed with rpoE2 negatively regulates RpoE2 activity, and we therefore propose that it plays the function of anti-sigma factor. By combining transcriptomic, bioinformatic, and quantitative reverse transcription-PCR analyses, we identified 44 RpoE2-controlled genes and predicted the number of RpoE2 targets to be higher. Strikingly, more than one-third of the 60 stress response genes identified in this study are RpoE2 targets. Interestingly, two genes encoding proteins with known functions in stress responses, namely, katC and rpoH2, as well as a second ECF-encoding gene, rpoE5, were found to be RpoE2 regulated. Altogether, these data suggest that RpoE2 is a major global regulator of the general stress response in S. meliloti. Despite these observations, and although this sigma factor is well conserved among alphaproteobacteria, no in vitro nor in planta phenotypic difference from the wild-type strain could be detected for rpoE2 mutants. This therefore suggests that other important actors in the general stress response have still to be identified in S. meliloti.


1986 ◽  
Vol 250 (1) ◽  
pp. C146-C154 ◽  
Author(s):  
S. J. Gunst

The effects of shortening on force redevelopment were studied in canine tracheal smooth muscles that were tonically contracted with electrical stimulation or acetylcholine. Muscle strips were suspended in vitro so that muscle length, force, and rate of change of force could be continuously monitored. The strips were rapidly shortened from different initial lengths to the same final length, at which the effects of shortening distance on force redevelopment were evaluated. Both the rate and magnitude of force redevelopment declined as the shortening distance was increased. Decreasing the activation of the muscle or increasing the prerelease contraction time enhanced the depressive effect of shortening. The time course of the latter corresponded to a decline in the velocity of unloaded shortening. However, force redevelopment was also substantially decreased by releases performed before the onset of force development. The shortening process per se had a depressive effect on both the rate and magnitude of force redevelopment in contracted canine tracheal smooth muscle, and this effect was reduced as the activation of the muscle was increased.


1997 ◽  
Vol 83 (3) ◽  
pp. 731-738 ◽  
Author(s):  
X. Shen ◽  
M. F. Wu ◽  
R. S. Tepper ◽  
S. J. Gunst

Shen, X., M. F. Wu, R. S. Tepper, and S. J. Gunst. Mechanisms for the mechanical response of airway smooth muscle to length oscillation. J. Appl. Physiol. 83(3): 731–738, 1997.—Airway smooth muscle tone in vitro is profoundly affected by oscillations in muscle length, suggesting that the effects of lung volume changes on airway tone result from direct effects of stretch on the airway smooth muscle. We analyzed the effect of length oscillation on active force and length-force hysteresis in canine tracheal smooth muscle at different oscillation rates and amplitudes during contraction with acetylcholine. During the shortening phase of the length oscillation cycle, the active force generated by the smooth muscle decreased markedly below the isometric force but returned to isometric force as the muscle was lengthened. Results indicate that at rates comparable to those during tidal breathing, active shortening and yielding of contractile elements contributes to the modulation of force during length oscillation; however, the depression of force during shortening cannot be accounted for by cross-bridge properties, shortening-induced cross-bridge deactivation, or active relaxation. We conclude that the depression of contractility may be a function of the plasticity of the cellular organization of contractile filaments, which enables contractile element length to be reset in relation to smooth muscle cell length as a result of smooth muscle stretch.


1978 ◽  
Vol 234 (3) ◽  
pp. H280-H288 ◽  
Author(s):  
R. H. Cox ◽  
Pennsylvania. Bockus Institute, Philadelphia,

Cylindrical segments of carotid arteries from rat, rabbit, and dog were studied in vitro in order to compare active and passive mechanical properties, with gross morphology and composition. Pressure-diameter relations were determined under active (norepinephrine) and passive (2 mM EGTA) conditions, and were used to compute values of tangential wall stress, incremental elastic moduli, characteristic impedance, and active smooth muscle responses. The water and connective tissue contents of these segments were also determined. Significant differences were found in the passive mechanical properties of these arteries, with those of the rat being most compliant and those of the dog being the stiffest. These differences were consistent with the connective tissue content of these arteries. The ratio of collagen to elastin was smallest in the rat and largest in the canine carotids. Differences were also demonstrated in the responses to smooth muscle activation. The maximum value of active stress response was essentially the same in the canine and rabbit arteries, both of which were larger than that of the rat carotids. On the other hand, the rabbit vessels produced a larger maximum diameter response than either of the other arteries. Values of incremental elastic modulus were largest at specific values of transmural pressure for the rabbit vessels. This latter fact may make the contractile system more effective in reducing wall diameter in the rabbit arteries in spite of the fact that they did not have the capacity to generate a larger active stress response.


2020 ◽  
Vol 44 (6) ◽  
pp. 417-426
Author(s):  
Kaan ADACAN ◽  
Pınar OBAKAN YERLİKAYA

Epibrassinolide (EBR), a plant-derived polyhydroxylated derivative of 5α-cholestane, structurally shows similarities to animal steroid hormones. According to the present study, EBR treatment triggered a significant stress response via activating ER stress, autophagy, and apoptosis in cancer cells. EBR could also increase Akt phosphorylation in vitro. While the activation of Akt resulted in cellular metabolic activation in normal cells to proceed with cell survival, a rapid stress response was induced in cancer cells to reduce survival. Therefore, Akt as a mediator of cellular survival and death decision pathways is a crucial target in cancer cells. In this study, we determined that EBR induces stress responses through activating Akt, which reduced the mTOR complex I (mTORC1) activation in SW480 and DLD-1 colon cancer cells. As a consequence, EBR triggered macroautophagy and led to lipidation of LC3 most efficiently in SW480 cells. The cotreatment of spermidine (Spd) with EBR increased lipidation of LC3 synergistically in both cell lines. We also found that EBR promoted polyamine catabolism in SW480 cells. The retention of polyamine biosynthesis was remarkable following EBR treatment. We suggested that EBR-mediated Akt activation might determine the downstream cellular stress responses to induce autophagy related to polyamines.


2019 ◽  
Vol 476 (21) ◽  
pp. 3141-3159 ◽  
Author(s):  
Meiru Si ◽  
Can Chen ◽  
Zengfan Wei ◽  
Zhijin Gong ◽  
GuiZhi Li ◽  
...  

Abstract MarR (multiple antibiotic resistance regulator) proteins are a family of transcriptional regulators that is prevalent in Corynebacterium glutamicum. Understanding the physiological and biochemical function of MarR homologs in C. glutamicum has focused on cysteine oxidation-based redox-sensing and substrate metabolism-involving regulators. In this study, we characterized the stress-related ligand-binding functions of the C. glutamicum MarR-type regulator CarR (C. glutamicum antibiotic-responding regulator). We demonstrate that CarR negatively regulates the expression of the carR (ncgl2886)–uspA (ncgl2887) operon and the adjacent, oppositely oriented gene ncgl2885, encoding the hypothetical deacylase DecE. We also show that CarR directly activates transcription of the ncgl2882–ncgl2884 operon, encoding the peptidoglycan synthesis operon (PSO) located upstream of carR in the opposite orientation. The addition of stress-associated ligands such as penicillin and streptomycin induced carR, uspA, decE, and PSO expression in vivo, as well as attenuated binding of CarR to operator DNA in vitro. Importantly, stress response-induced up-regulation of carR, uspA, and PSO gene expression correlated with cell resistance to β-lactam antibiotics and aromatic compounds. Six highly conserved residues in CarR were found to strongly influence its ligand binding and transcriptional regulatory properties. Collectively, the results indicate that the ligand binding of CarR induces its dissociation from the carR–uspA promoter to derepress carR and uspA transcription. Ligand-free CarR also activates PSO expression, which in turn contributes to C. glutamicum stress resistance. The outcomes indicate that the stress response mechanism of CarR in C. glutamicum occurs via ligand-induced conformational changes to the protein, not via cysteine oxidation-based thiol modifications.


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