Hypoxic Regulation of the Large-Conductance, Calcium and Voltage-Activated Potassium Channel, BK

Hypoxia is a condition characterized by a reduction of cellular oxygen levels derived from alterations in oxygen balance. Hypoxic events trigger changes in cell-signaling cascades, oxidative stress, activation of pro-inflammatory molecules, and growth factors, influencing the activity of various ion channel families and leading to diverse cardiovascular diseases such as myocardial infarction, ischemic stroke, and hypertension. The large-conductance, calcium and voltage-activated potassium channel (BK) has a central role in the mechanism of oxygen (O2) sensing and its activity has been related to the hypoxic response. BK channels are ubiquitously expressed, and they are composed by the pore-forming α subunit and the regulatory subunits β (β1–β4), γ (γ1–γ4), and LINGO1. The modification of biophysical properties of BK channels by β subunits underly a myriad of physiological function of these proteins. Hypoxia induces tissue-specific modifications of BK channel α and β subunits expression. Moreover, hypoxia modifies channel activation kinetics and voltage and/or calcium dependence. The reported effects on the BK channel properties are associated with events such as the increase of reactive oxygen species (ROS) production, increases of intracellular Calcium ([Ca2+]i), the regulation by Hypoxia-inducible factor 1α (HIF-1α), and the interaction with hemeproteins. Bronchial asthma, chronic obstructive pulmonary diseases (COPD), and obstructive sleep apnea (OSA), among others, can provoke hypoxia. Untreated OSA patients showed a decrease in BK-β1 subunit mRNA levels and high arterial tension. Treatment with continuous positive airway pressure (CPAP) upregulated β1 subunit mRNA level, decreased arterial pressures, and improved endothelial function coupled with a reduction in morbidity and mortality associated with OSA. These reports suggest that the BK channel has a role in the response involved in hypoxia-associated hypertension derived from OSA. Thus, this review aims to describe the mechanisms involved in the BK channel activation after a hypoxic stimulus and their relationship with disorders like OSA. A deep understanding of the molecular mechanism involved in hypoxic response may help in the therapeutic approaches to treat the pathological processes associated with diseases involving cellular hypoxia.

EXPRESS METHOD FOR CALCULATING THE SPECIFIC HEAT OF EXPLOSIVE TRANSFORMATION OF CHNO CONDENSED EXPLOSIVES

Разработан экспресс-метод расчета теплоты взрыва СаHbNcOdконденсированных взрывчатых веществ с различным кислородным балансом от резко отрицательного до положительного. Предложенный метод использует минимальный набор входных данных, состоящих из элементного состава, плотности энтальпий образований исходного взрывчатого вещества и его продуктов детонации. Расчет теплоты взрыва основывается на корреляционной связи между минимальной и максимальной теплотами взрыва с плотностью высокоэнергетического соединения. В статье подробно приведены реакции разложения взрывчатых веществ для случаев с минимальной и максимальными теплотами взрыва. Проведены расчеты теплоты взрыва по новому способу и методу Пепекина по представленной в статье базы взрывчатых веществ, а также приведены результаты сравнения, которые показали большую точность (в 2,3 раза) предложенного метода. An express method has been developed for calculating the explosion heat of cahbncod condensed explosives with different oxygen balance from sharply negative to positive. The proposed method uses a minimal set of input data consisting of the elemental composition, enthalpy density of the formations of the initial explosive and its detonation products. The calculation of the heat of explosion is based on the correlation between the minimum and maximum heat of explosion with the density of a high-energy compound. The article describes in detail the decomposition reactions of explosives for cases with minimum and maximum explosion heats. Calculations of the heat of explosion according to the new method and the pepekin method are carried out according to the explosives database presented in the article, and comparison results are also presented, which showed a better accuracy (2.3 times) of the proposed method.

Control of HIF-1α Levels Potentially Promotes the Tissue Repair in Various Conditions Through Target Gene Expression

Hypoxia inducible factor-1 (HIF-1) is a transcription factor that plays an important role in maintaining oxygen balance at both the cellular and systemic levels, and is associated with various controls in the body. HIF-1 is a heterodimer of alpha and beta subunits. Alpha subunits are mostly dependent on oxygen levels in the body. In many cancers, excessive HIF-1α is thought to be involved in the promotion of tumor growth and metastasis. In addition, in the induction of systemic hypoxia, there is an increase of HIF-1α in the heart, brain, and even the kidneys as an adaptation response to hypoxia. Several studies regarding HIF-1a expression in traumatic brain injury, found that HIF-1a increased immediately after TBI, and decreased significantly after 24 hours. This can be used as a basis for further research on HIF-1a control as an effort to stop tissue damage or even help tissue repair.

ON CALCULATION OF OXYGEN BALANCE OF MULTICOMPONENT THERMOBARIC EXPLOSIVE SUBSTANCE

Most modern military confrontations take place near or directly in inhabited area. The use in such conditions of munition (warheads) which hit typical targets based on fragmentation (high-explosive) or cumulative action is impractical due to insufficient “selectivity” of hitting targets with such munition. At present, modern world tendency is the development of the latest munition (warheads) with increased properties of “destruction selectivity”. One of the directions is the development of munition based on thermobaric explosives. Such munitions can cause maximum damage due to high temperature and the impact of a shock wave with a low level of collateral damage, since thermobaric munition, especially in the open area, have a clearly defined or even limited area of effective damage, which determines the significance of their further development. Since modern thermobaric explosives include a large number of chemical elements (including chemically active metals), there is a need to calculate the physical balance of oxygen and oxygen coefficient to take into account the physical characteristics of modern multicomponent thermobaric explosives. The oxygen balance of multicomponent thermobaric explosives largely determines the nature of the reaction of its explosive transformation, i.e the composition of the explosive products and, consequently, the value of thermodynamic characteristics such as heat, temperature, volume and pressure of gas-like explosive products. The calculated ratio and coefficients for complex multicomponent thermobaric explosives should be calculated during the development of explosives, taking into account the composition of components and elements and their possible chemical reactions during the explosion. The abovementioned improved calculations of oxygen balance and oxygen coefficient of thermobaric explosives, which include aluminum, allows taking into account the physical characteristics of destruction of typical targets by thermobaric munitions.

Appearance of phenotypic plasticity of leaves in psammophyte Corynephorus canescens during flooding

The results of the study of the leaf structure in psammophyte Corynephorus canescens, which grew under controlled conditions and flooding using the methods of light microscopy, scanning electron microscopy, and laser confocal microscopy, are presented. This study revealed common and distinctive signs of morphological and anatomical parameters of C. canescens leaves in the phase of vegetative growth. Among the common features were the shape and size of the leaf laminas, hypostomatic type of the leaf, isolateral structure of the parenchyma, the thick-walled epidermis, and the bilayered hypodermis. Among the distinctive features were the signs of the destruction of cells in the photosynthetic parenchyma, change in their shape with the formation of protuberances at the cells’ poles, and almost doubling area of the aerenchyma in C. canescens leaves under flooding conditions. Scanning electron microscopy showed the similarity of ultrastructure and density of trichomes on the adaxial surface, excepting the formation of cuticular wax structures on the epidermal surface of the leaves in flooded plants. The subcellular localization of silicon inclusions was studied for the first time. The presence of amorphous and small crystalline silicon inclusions in the periclinal walls of the main epidermal cells and amorphous silicon inclusions in leaf trichomes was established. An increase in the relative silicon content along the trichomes in the leaves’ epidermis after flooding was revealed. It was assumed that the phenotypic plasticity of C. canescens, is realized through the increasing area of aerenchyma in leaves and increasing silicon content in trichomes. Such plasticity helps to optimize both the oxygen balance of plants and water balance in flooded plants, thus increasing the species’ resistance to prolonged flooding.

Effects on Cerebral Oxygen Balance in Coronary Artery Bypass Grafting: A Comparison of Conventional and Minimal Extracorporeal Circulation

Objective: To investigate the cerebral oxygen balance difference between minimal extracorporeal circulation (MECC) and conventional extracorporeal circulation (CECC) during coronary artery bypass grafting. Methods: 20 patients undergoing coronary artery bypass grafting with cardiopulmonary bypass (CPB) were divided into two groups, the CECC group (n=10) and the MECC group (n=10). Blood withdrawn from radial artery and right jugular vein were analyzed at the following timepoints: during the anesthesia induction (T1), before CPB (T2), the initiation of CPB (T3), aorta crossclamped (T4), after temperature decreased (T5), during stable hypothermia (T6), initiation of rewarming (T7), aorta unclamped (T8), after weaning of CPB (T9), end of the operation (T10).The artery oxygen content (CaO2 ) and cerebral oxygen extraction ratio (OER) were calculated. The mean artery pressure (MAP), hemoglobin (Hb), nasopharyngeal temperature (NPT), and pump perfusion flow were recorded during the operation. Results: (1) MAP and Hb of MECC group were significantly higher than those in the CECC group from T3 to T10 (P<0.05); perfusion flow in MECC group during CPB was significantly lower than those in CECC group (P<0.05); NPT in MECC group was significantly higher than those in CECC group (P<0.05). (2) During T3-T4 and T8-T9, jugular venous oxygen saturation in CECC group was significantly lower than those in MECC (P<0.05); OER in CECC group was significantly higher than those in MECC group (P<0.05). (3) The arterial lactic acid and venous lactic acid in these two groups were decreased gradually from T3 to T10. Thearteriovenous difference in lactic acid in CECC group were higher than those in MECC group during T3-T4 and T8-T9 (P<0.05). Conclusion: Patients undergoing coronary artery bypass grafting with MECC enjoy more stable blood pressure, less intense hemodilution and lighter temperature disturbance than those with CECC, which indicating a better cerebral oxygen balance in CABG.

Particulate Formation During High Explosive Detonations: How Oxygen Balance Drives Parameters Pertinent to Atmospheric Lofting

High explosive (HE) detonations reach pressures and temperatures that extend beyond normal environmental conditions, thereby permitting access to various carbon and metal allotropes of different morphologies, sizes and surface structures. The products of HE detonations are dependent on multiple parameters, including the chemical and physical properties of the starting material and atmospheric conditions (i.e. oxygen). One important factor is the HE oxygen balance, which is the extent to which the material can be oxidized. Insensitive HEs are designed to resist external stimuli that would cause detonation in conventional HEs. The insensitive HEs are negatively oxygen balanced and therefore produce not only gaseous species but solid carbon products during detonation. Insensitive HEs were studied, Composition B-3 and PBX 9501, with steady and overdriven geometries in an oxygen-free atmosphere that reached different pressure and temperature regimes. Small angle x-ray scattering provided the size and surface structure of the resulting particulates. Composition B-3 primary particles were 157.0 ± 0.3 Å and 199.5 ± 0.3 Å for steady and overdriven detonations; where PBX 9501 primary particles were larger than Composition B-3 at 300 ± 6 Å and 334.5 ± 0.3 Å for steady and overdriven detonations. The two compounds formed contrasting primary particles with different cluster structures, in the Composition B-3 steady detonation the particles were agglomerated into a surface fractal with rough surfaces where as the PBX 9501 was a mass fractal cluster with smooth surface primary particles. In the overdriven detonation the primary particles were reversed, Composition B-3 was agglomerated into a mass fractal structure with smooth surfaces and PBX 9501 had a surface fractal structure with a rough surface primary particles. Scanning electron microscopy provided a snapshot of the morphology of the materials on the micron length scale, supporting the observation of x-ray scattering that the Composition B-3 particulates/agglomerates are smaller than the PBX 9501. Raman spectroscopy provided information as to the carbon bonding of the detonation soot, showing significantly more product variation in Composition B-3 than PBX 9501, likely due the poor oxygen balance of Composition B-3 leading to more complex carbon bonding formations. Finally, x-ray photoelectron spectroscopy showed how the difference in the oxygen balance of the HE fuel directly relates to the amount of carbon-oxygen bonding that is present in the final products, where PBX 9501 had significantly more oxygen on the surface of the particulates. We used two HEs to understand the detonation pathways for both synthesis and atmospheric processes; where the chemical constituents of the particulates can promote processes such as self-lofting and aerosol-cloud interactions after the particles are launched into the troposphere or stratosphere during detonation.

Study on the Balance of Oxygen in Supply and Demand in Wastewater Treatment Plant

In order to accurately evaluate the comprehensive operation efficiency of aerobic biological treatment system in wastewater treatment plants (WWTPs), the process state aeration performance tester and the specific oxygen uptake rate online monitoring device were used to measure the oxygenation performance and the activated sludge performance in aeration tank, and the comprehensive operation efficiency of aerobic tank was evaluated by combining physical-chemical indexes and water quality analysis of the treatment system. The results showed that the oxygen transfer efficiency (OTE) of aerators under process state are reduced by 13.07% and 14.48% respectively compared with that in clean water in the No.3-tank and No.6-tank, and the aeration uniformity index (IAU) is 4.86 and 1.46 respectively. The oxygen uptake rate (OUR) in the third corridor decreased significantly, but dissolved oxygen (DO) was a high level. Oxygen in supply (Qs) was much greater than oxygen in demand (Cs), which have resulted a large waste of energy consumption. Finally, the subsection regulation strategy was proposed based on the principle of oxygen balance. The results of this study will not only help the WWTP to achieve energy-saving and consumption-reducing, but also stable operation.