Biology subjects

Semenov, Y. S.

Publications and source records attributed to Semenov, Y. S..

3 recordsLinked to original sources

bioRxiv2024

Respiration and gas exchange under negative pressure breathing during simulated microgravity

The research considers the effect of inspiratory negative pressure breathing (NPBin, -20 cmH2O relative to barometric pressure) on respiration and gas exchange in healthy humans under various conditions: in the sitting and supine positions as well as during simulating the physiological effects of a long stay in conditions of microgravity (dry immersion and head-down bed rest). Under NPBin, respiratory rate significantly decreased (by 7 min-1 on average, in some volunteers up to two or three cycles per minute), tidal volume increased (by an average of 0.3 l), while minute ventilation decreased (on average by 1.8 l/min), and respiratory exchange ratio increased (on average by 0.09). The response of respiratory and gas exchange parameters to NPBin in all the considered conditions was almost the same (there were no significant differences in parameters changes induced by NPBin between the conditions). Despite the decrease in minute ventilation, the results indicate CO2 washout from the body under NPBin.

physiology↗

bioRxiv2024

Human circulatory system response to changes in alveolar pressure and lung volume

The response of hemodynamic parameters in healthy volunteers to changes in alveolar pressure and lung volume was studied by noninvasive methods during respiratory maneuvers similar to Valsalva and Muller maneuvers (in a sitting position and lying on the back horizontally). The following lung volumes and values of pressure (relative to atmospheric pressure) were considered in various combinations: total lung capacity, functional residual capacity, residual volume, -30, -15, 0, +15, +30 mmHg. Changes in hemodynamic parameters averaged over the duration of a maneuver were studied (the duration of a maneuver was 30 s). Changes in alveolar and, accordingly, intrathoracic pressure influenced hemodynamic more strongly than changes in lung volume or body position. Stroke volume decreased with increasing alveolar pressure and increased with decreasing pressure regardless of lung volume and body position; changes ranged from -35 to +15 ml. The effect of changes in alveolar pressure was more pronounced in a sitting position. Heart rate increased with increasing alveolar pressure (up to +20 bpm) but changed little with decrease in pressure. Mean arterial pressure decreased with decreasing alveolar pressure regardless of lung volume and body position; with increasing alveolar pressure, the result depended on lung volume. When performing maneuvers at total lung capacity, mean arterial pressure remained below baseline values, in other cases it increased. Changes in mean arterial pressure were within {+/-}20 mmHg. Regardless of lung volume and body position, total peripheral resistance decreased with decreasing alveolar pressure and increased with increasing alveolar pressure; the range of changes in total peripheral resistance was -0.3 to +0.7 mmHg{middle dot}s/ml.

physiology↗

bioRxiv2023

luxA gene from Enhygromyxa salina encodes a functional homodimeric luciferase

Several clades of luminescent bacteria are known currently. They all contain similar lux operons, which include the genes luxA and luxB encoding a heterodimeric luciferase. The aldehyde oxygenation reaction is catalyzed by the subunit LuxA, while LuxB is inactive. Recently, genomic analysis identified a subset of bacterial species with rearranged lux operons lacking luxB. Here, we show that the product of the luxA gene from the reduced luxACDE operon of Enhygromyxa salina is luminescent upon addition of aldehydes both in vivo in Escherichia coli and in vitro. Overall, EsLuxA is less bright compared with luciferases from Aliivibrio fischeri (AfLuxAB) and Photorhabdus luminescens (PlLuxAB), and most active with medium-chain C4-C9 aldehydes. Crystal structure of EsLuxA determined at the resolution of 2.71 [A] reveals a classical monooxygenase fold, and the protein preferentially forms a dimer in solution. The mobile loop residues 264-293, which form a {beta}-hairpin or a coil in Vibrio harveyi LuxA, form -helices in EsLuxA. Phylogenetic analysis shows EsLuxA and related proteins may be bacterial protoluciferases that arose prior to duplication of the luxA gene and its speciation to luxA and luxB in the previously described luminescent bacteria. Our work paves the way for discovery of new luciferases that have an advantage of being encoded by a single gene.

biochemistry↗