X-ray Diffraction Analysis to Explore Molecular Traces of Eccentric Contraction on Rat Skeletal Muscle Parallelly Evaluated with Signal Protein Phosphorylation Levels

We performed X-ray diffraction analyses on rat plantaris muscle to determine if there are strain-specific structural changes at the molecular level after eccentric contraction (ECC). ECC was elicited in situ by supramaximal electrical stimulation through the tibial nerve. One hour after a series of ECC sessions, the structural changes that remained in the sarcomere were evaluated using X-ray diffraction. Proteins involved in cell signaling pathways in the muscle were also examined. ECC elicited by 100, 75, and 50 Hz stimulation respectively developed peak tension of 1.34, 1.12 and 0.79 times the isometric maximal tetanus tension. The series of ECC sessions phosphorylated the forkhead box O proteins (FoxO) in a tension-time integral-dependent manner, as well as phosphorylated the mitogen-activated protein kinases (MAPK) and a protein in the mammalian target of rapamycin (mTOR) pathway in a maximal tension dependent manner. Compared to isometric contractions, ECC was more efficient in phosphorylating the signaling proteins. X-ray diffraction revealed that the myofilament lattice was preserved even after intense ECC stimulation at 100 Hz. Additionally, ECC < 75 Hz preserved the molecular alignment of myoproteins along the myofilaments, while 75-Hz stimulation induced a slight but significant decrease in the intensity of meridional troponin reflection at 1/38 nm−1, and of myosin reflection at 1/14.4 nm−1. These two reflections demonstrated no appreciable decrease with triple repetitions of the standard series of ECC sessions at 50 Hz, suggesting that the intensity decrease depended on the instantaneous maximal tension development rather than the total load of contraction, and was more likely linked with the phosphorylation of MAPK and mTOR signaling proteins.

The Musical Oeuvres of Rodion Shchedrin

The previous issues of the journal featured publications of lectures about such outstanding 20th century Russian composers as Sergei Rachmaninoff, Igor Stravinsky, Sergei Prokofi ev, Nikolai Myaskovsky, Dmitri Shostakovich, Aram Khachaturian and Georgy Sviridov. This series is continued with a lecture about the music of Rodion Shchedrin. Following the portions of the lecture which deal with the early and middle periods of the composer’s music, the drama and even the tragic quality of his world perception and their overcoming. the present situation acquired maximal tension upon Shchedrin’s turning to the most acute problem for the romantic consciousness — the problem of interactions of personality and its surroundings, especially in the event of their confrontation. During the lecture’s exposition fragments of musical compositions are offered with their recommended performances, in their sum providing a perception of the most substantial sides of Shchedrin’s musical legacy.

Cortical tension overrides geometrical cues to orient microtubules in confined protoplasts

In plant cells, cortical microtubules (CMTs) generally control morphogenesis by guiding cellulose synthesis. CMT alignment has been proposed to depend on geometrical cues, with microtubules aligning with the cell long axis in silico and in vitro. Yet, CMTs are usually transverse in vivo, i.e., along predicted maximal tension, which is transverse for cylindrical pressurized vessels. Here, we adapted a microwell setup to test these predictions in a single-cell system. We confined protoplasts laterally to impose a curvature ratio and modulated pressurization through osmotic changes. We find that CMTs can be longitudinal or transverse in wallless protoplasts and that the switch in CMT orientation depends on pressurization. In particular, longitudinal CMTs become transverse when cortical tension increases. This explains the dual behavior of CMTs in planta: CMTs become longitudinal when stress levels become low, while stable transverse CMT alignments in tissues result from their autonomous response to tensile stress fluctuations.

«Steppe eagle» a play by O. P. Chuhuy – a sample of drama portrait in the genre system of the author’s biographical creative work

Despite the fact, that literary work of O.P. Chuhuy has already become an object of scientific research by A. Novikov, T. Kononchuk, T. Virchenko and others, drama portrait still remains unnoticed by literary critics. The aim of the author’s research is an attempts to analyze the chosen type of biographical work which requires keeping a specific filling of measure while using actual material and fiction. The peculiarities of using biographical material in the literary work of O.P. Chuhuy, in particular when creating the images of H. Skovoroda, V. Karazin, O. Kurbas, V. Ivasuk and others are surveyed in the article. The main attention is concentrated on analyzing the bibliographical portrait of I.P. Kotlyarevskiy, the famous of the new Ukrainian literature, created by O.P. Chuhuy in his play “Steppe eagle” (which appeared in 2012), reflecting his versatile activity aimed of defending the rights of the Ukrainian people for their identity, realizing cultural and enlightment process in their native language. A high mastery of the author in plot creating, in building up characters, very often by just a few phrases, making up monologs and dialogues, independent of space and time, for that matter, in widely using folklore in confirmed. The important role of drama portrait for achieving of genre diversity of the authors plays is emphasized. The above works by O.P. Chuhuy testify to complete mastery of biographical genre in the process of drama reflection of the reality, great mastery of using techniques and means of poetics, in particular, when choosing conflicts and characters capable of fighting either to a complete victory or failure, achieving maximal tension, unity and concentration of action, expressive psychological characteristics. Thanks to these peculiarities of the play I.P. Kotlyarevskiy as a personality is shown multi-faceted and attractive way so typical of him, closely connected with social and political events of that time, in particular, with the desembrist community and national liberation movement. That is why, the drama portrait created by O.P. Chuhuy in “Steppe eagle” maybe used not only by the teachers of high and secondary schools but also by all admires and masters of literature, music and theatre and hence is worth of being staged by the talented servants of Melpomene.

A tension-adhesion feedback loop in plant epidermis

Mechanical forces have emerged as coordinating signals for most cell functions. Yet, because forces are invisible, mapping tensile stress patterns in tissues remains a major challenge in all kingdoms. Here we take advantage of the adhesion defects in the Arabidopsis mutant quasimodo1 (qua1) to deduce stress patterns in tissues. By reducing the water potential and epidermal tension in planta, we rescued the adhesion defects in qua1, formally associating gaping and tensile stress patterns in the mutant. Using suboptimal water potential conditions, we revealed the relative contributions of shape- and growth-derived stress in prescribing maximal tension directions in aerial tissues. Consistently, the tension patterns deduced from the gaping patterns in qua1 matched the pattern of cortical microtubules, which are thought to align with maximal tension, in wild-type organs. Conversely, loss of epidermis continuity in the qua1 mutant hampered supracellular microtubule alignments, revealing that coordination through tensile stress requires cell-cell adhesion.

Rein tension in novice riders when riding a horse simulator

This study reports tension in the left and right reins when riding a horse simulator that moved only in the sagittal plane. The objective was to determine whether asymmetries in rein tension of novice riders at the rising trot, canter, and halt were present, and if so, to investigate their relationship with the rider’s handedness. The experimental hypothesis was that rein tension would be higher on the side of the rider’s non-dominant hand. 22 novice riders (19 right-handed; 3 left-handed) rode a horse simulator at halt, rising trot and canter. Rein tension was recorded in both reins at a sampling rate of 1000 Hz for 8 s at each gait. The variables measured in rising trot and canter were minimal and maximal tension, the change between minimal and maximal values and mean tension per step at rising trot or per stride at canter. At halt only mean tension during the 8 s recording was measured. Comparisons between right and left reins and between right-handed and left-handed riders were made using mixed models. The results showed no asymmetries in mean tension at halt. In rising trot and canter all significant differences involved higher tension in the right rein regardless of handedness of the riders. During rising trot the minimum was higher in the right rein over all riders and both the mean and maximal values were higher in the right rein in left-handed riders. In canter left-handed riders had higher mean tension in the right rein. All recorded asymmetries had higher tension in the right rein compared with the left and they were more prevalent in left-handed riders which implies higher tension in the non-dominant hand. Rein tension patterns were not symmetrical on the left and right sides and asymmetries in left-handed riders were not mirrored in right-handed riders.

Cardiomyopathy-related mutation (A30V) in mouse cardiac troponin T divergently alters the magnitude of stretch activation in α- and β-myosin heavy chain fibers

The present study investigated the functional consequences of the human hypertrophic cardiomyopathy (HCM) mutation A28V in cardiac troponin T (TnT). The A28V mutation is located within the NH2 terminus of TnT, a region known to be important for full activation of cardiac thin filaments. The functional consequences of the A28V mutation in TnT remain unknown. Given how α- and β-myosin heavy chain (MHC) isoforms differently alter the functional effect of the NH2 terminus of TnT, we hypothesized that the A28V-induced effects would be differently modulated by α- and β-MHC isoforms. Recombinant wild-type mouse TnT (TnTWT) and the mouse equivalent of the human A28V mutation (TnTA30V) were reconstituted into detergent-skinned cardiac muscle fibers extracted from normal (α-MHC) and transgenic (β-MHC) mice. Dynamic and steady-state contractile parameters were measured in reconstituted muscle fibers. Step-like length perturbation experiments demonstrated that TnTA30V decreased the magnitude of the muscle length-mediated recruitment of new force-bearing cross bridges ( ER) by 30% in α-MHC fibers. In sharp contrast, TnTA30V increased ER by 55% in β-MHC fibers. Inferences drawn from other dynamic contractile parameters suggest that directional changes in ER in TnTA30V + α-MHC and TnTA30V + β-MHC fibers result from a divergent impact on cross bridge-regulatory unit (troponin-tropomyosin complex) cooperativity. TnTA30V-mediated effects on Ca2+-activated maximal tension and instantaneous muscle fiber stiffness ( ED) were also divergently affected by α- and β-MHC. Our study demonstrates that TnTA30V + α-MHC and TnTA30V + β-MHC fibers show contrasting contractile phenotypes; however, only the observations from β-MHC fibers are consistent with the clinical data for A28V in humans. NEW & NOTEWORTHY The differential impact of α- and β-myosin heavy chain (MHC) on contractile dynamics causes a mutant cardiac troponin T (TnTA30V) to differently modulate cardiac contractile function. TnTA30V attenuated Ca2+-activated maximal tension and length-mediated cross-bridge recruitment against α-MHC but augmented these parameters against β-MHC, suggesting divergent contractile phenotypes.

Cell division plane orientation based on tensile stress in Arabidopsis thaliana

Cell geometry has long been proposed to play a key role in the orientation of symmetric cell division planes. In particular, the recently proposed Besson–Dumais rule generalizes Errera’s rule and predicts that cells divide along one of the local minima of plane area. However, this rule has been tested only on tissues with rather local spherical shape and homogeneous growth. Here, we tested the application of the Besson–Dumais rule to the divisions occurring in the Arabidopsis shoot apex, which contains domains with anisotropic curvature and differential growth. We found that the Besson–Dumais rule works well in the central part of the apex, but fails to account for cell division planes in the saddle-shaped boundary region. Because curvature anisotropy and differential growth prescribe directional tensile stress in that region, we tested the putative contribution of anisotropic stress fields to cell division plane orientation at the shoot apex. To do so, we compared two division rules: geometrical (new plane along the shortest path) and mechanical (new plane along maximal tension). The mechanical division rule reproduced the enrichment of long planes observed in the boundary region. Experimental perturbation of mechanical stress pattern further supported a contribution of anisotropic tensile stress in division plane orientation. Importantly, simulations of tissues growing in an isotropic stress field, and dividing along maximal tension, provided division plane distributions comparable to those obtained with the geometrical rule. We thus propose that division plane orientation by tensile stress offers a general rule for symmetric cell division in plants.

Hypercapnia Attenuates the Hypoxia-Induced Blunting of the Reactivity in Chronically Hypoxic Rats

Chronic hypoxia causes oxidative injury of pulmonary vessels and attenuates their reactivity to different stimuli. When combined with hypercapnia, biochemical markers of this injury are reduced but the effect of concomitant hypoxia and hypercapnia on vascular reactivity is not fully understood. This study was therefore designed to test whether hypercapnia can prevent also the hypoxia-induced loss of reactivity of pulmonary vessels. The reactivity of vessels from rats exposed either to hypoxia or hypoxia combined with hypercapnia was tested using a small vessel myograph (M 500A, Linton, Norfolk, GB). The second and third intrapulmonary branches of pulmonary arteries were isolated under a dissecting microscope from lungs of 8 control rats (group N), 6 rats exposed to hypoxia for 5 days (isobaric, 10 % O2, group H) and 7 rats exposed to hypoxia combined with hypercapnia for 5 days (10 % O2, 5 % CO2, group H+CO2). The transmural pressure was set by automatic normalization to 30 mm Hg. The vessel size did not vary among the groups. After stabilization we challenged the vessels twice with KCl (80 mM) and once with PGF2α (0.1 mM). There were no significant differences in KCl induced contractions among the groups. The responses to PGF2α were expressed as a ratio to the maximal tension obtained by the exposure to 80 mM KCl. Contractions induced by PGF2α were markedly reduced in group H (0.07±0.02) and in group H+CO2 (0.26±0.03) in comparison with group N (0.83±0.07). The vessels of group H responded to PGF2α less than those of group H+CO2. However we observed the attenuated reactivity also in group H+CO2 in comparison with N. Hypercapnia therefore partially blunted the hypoxia-induced loss of reactivity in pulmonary arteries. This finding supports the hypothesis that hypercapnia significantly alters the nature of lung injury induced by chronic hypoxia.