Low Oxygen Pressure Research Articles

Role of endothelial cells in the regulation of mechanical microenvironment on tumor progression

Majority of cancer patients die from cancer metastases. The physical stimulation produced by microenvironment regulates invasive behavior of cancer cells. Blood vessel is one of the “pathways” for cancer to metastasize, in which tumor cells need to cross the endothelial barrier for intravasation and extravasation. Tumor vessels are arranged in untraditional hierarchies and characterized with rupture, bend, swell and high permeability that are beneficial to intravasation of cancer cell. Abnormal vessels are accompanied with uneven blood flow, increased compression and interstitial fluid pressure. Meanwhile, excessive proliferation of tumor leads to low oxygen pressure in solid tumor. The aberrant tumor mechanical microenvironment changes the biochemical and mechanical signal transduction of endothelial cells and participates in tumor progression. Many current researches focus on how chemical signals regulate endothelial cell function while the role of physical cues is unclear. In this review, the role of endothelial cells in the regulation of shear stress, intercellular force, extracellular matrix and pressure on tumor progression is summarized.

High-Quality β-Ga2O3 Films with Influence of Growth Temperature by Pulsed Laser Deposition for Solar-Blind Photodetectors

High-quality β-Ga2O3 films were grown on (0001) sapphire substrates at various substrate temperature by pulsed laser deposition (PLD) in a high vacuum chamber. Low pressure (1.6 mPa) and high reactivity oxygen plasma was introduced as reaction gas. The films were used to fabricate metal–semiconductor–metal (MSM) solar-blind photodetectors by electron-beam evaporation. The β-Ga2O3 -based photodetector exhibited high performance with a low dark current (about 40 pA), fast response speed (τrise: 0.17 s, τdecay: 0.03 s) and high responsivity (0.35 A/W). These results represent the high quality of β-Ga2O3 films and excellent performance for PLD-grown β-Ga2O3 -based MSM solar-blind photodetectors.

Metabolic Signatures of Cryptosporidium parvum-Infected HCT-8 Cells and Impact of Selected Metabolic Inhibitors on C. parvum Infection under Physioxia and Hyperoxia

Simple SummaryCryptosporidium parvum is one of the causal agents of cryptosporidiosis. This water-borne disease is responsible for around one million human deaths every year and the only approved anti-cryptosporidial drug for humans, i.e., nitazoxanide, lacks efficacy in immunocompromised patients. We here present, to the best of our knowledge, the first analyses of C. parvum impact on the metabolism of its host-cells under physiological oxygen conditions. Moreover, based on the here presented metabolic evidence, we blocked specific metabolic pathways in order to find new anti-cryptosporidial targets. Our findings besides confirming glycolysis as anti-cryptosporidial target prove glutaminolysis and lactate release as necessary for parasite replication.Cryptosporidium parvum is an apicomplexan zoonotic parasite recognized as the second leading-cause of diarrhoea-induced mortality in children. In contrast to other apicomplexans, C. parvum has minimalistic metabolic capacities which are almost exclusively based on glycolysis. Consequently, C. parvum is highly dependent on its host cell metabolism. In vivo (within the intestine) infected epithelial host cells are typically exposed to low oxygen pressure (1–11% O2, termed physioxia). Here, we comparatively analyzed the metabolic signatures of C. parvum-infected HCT-8 cells cultured under both, hyperoxia (21% O2), representing the standard oxygen condition used in most experimental settings, and physioxia (5% O2), to be closer to the in vivo situation. The most pronounced effect of C. parvum infection on host cell metabolism was, on one side, an increase in glucose and glutamine uptake, and on the other side, an increase in lactate release. When cultured in a glutamine-deficient medium, C. parvum infection led to a massive increase in glucose consumption and lactate production. Together, these results point to the important role of both glycolysis and glutaminolysis during C. parvum intracellular replication. Referring to obtained metabolic signatures, we targeted glycolysis as well as glutaminolysis in C. parvum-infected host cells by using the inhibitors lonidamine [inhibitor of hexokinase, mitochondrial carrier protein (MCP) and monocarboxylate transporters (MCT) 1, 2, 4], galloflavin (lactate dehydrogenase inhibitor), syrosingopine (MCT1- and MCT4 inhibitor) and compound 968 (glutaminase inhibitor) under hyperoxic and physioxic conditions. In line with metabolic signatures, all inhibitors significantly reduced parasite replication under both oxygen conditions, thereby proving both energy-related metabolic pathways, glycolysis and glutaminolysis, but also lactate export mechanisms via MCTs as pivotal for C. parvum under in vivo physioxic conditions of mammals.

Gene Expression Effect of Plant Seeds Irradiated by Low Pressure Oxygen Plasma

Gene Expression Effect of Plant Seeds Irradiated by Low Pressure Oxygen Plasma

Plasma-assisted oxidation of Cu(100) and Cu(111).

Oxidized copper surfaces have attracted significant attention in recent years due to their unique catalytic properties, including their enhanced hydrocarbon selectivity during the electrochemical reduction of CO2. Although oxygen plasma has been used to create highly active copper oxide electrodes for CO2RR, how such treatment alters the copper surface is still poorly understood. Here, we study the oxidation of Cu(100) and Cu(111) surfaces by sequential exposure to a low-pressure oxygen plasma at room temperature. We used scanning tunnelling microscopy (STM), low energy electron microscopy (LEEM), X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption fine structure spectroscopy (NEXAFS) and low energy electron diffraction (LEED) for the comprehensive characterization of the resulting oxide films. O2-plasma exposure initially induces the growth of 3-dimensional oxide islands surrounded by an O-covered Cu surface. With ongoing plasma exposure, the islands coalesce and form a closed oxide film. Utilizing spectroscopy, we traced the evolution of metallic Cu, Cu2O and CuO species upon oxygen plasma exposure and found a dependence of the surface structure and chemical state on the substrate's orientation. On Cu(100) the oxide islands grow with a lower rate than on the (111) surface. Furthermore, while on Cu(100) only Cu2O is formed during the initial growth phase, both Cu2O and CuO species are simultaneously generated on Cu(111). Finally, prolonged oxygen plasma exposure results in a sandwiched film structure with CuO at the surface and Cu2O at the interface to the metallic support. A stable CuO(111) surface orientation is identified in both cases, aligned to the Cu(111) support, but with two coexisting rotational domains on Cu(100). These findings illustrate the possibility of tailoring the oxidation state, structure and morphology of metallic surfaces for a wide range of applications through oxygen plasma treatments.

Base-Free, Vanadium-Catalyzed Conversion of Chitin into Acetic Acid under Low Oxygen Pressure

The “shell biorefinery” has been proposed and developed rapidly in recent years, which valorizes the underestimated chitin biopolymer from oceanic waste to complement the lignocellulosic biomass fo...

Moderating oxygen deficiency induced better thermochromic properties of monoclinic vanadium dioxide thin films

Monoclinic vanadium dioxide (M-VO2) is a kind of typical thermal phase change materials, but its relatively high phase transition temperature (68 °C) and low solar modulation efficiency greatly hinder the applications as energy materials. In this work, well-crystalline M-VO2 were prepared by pulsed laser deposition (PLD) under the adjustable oxygen pressure range. By fine adjusting the low oxygen pressure (0.1–0.9 Pa), VO2 maintain the monoclinic crystal and excellent photoelectrical properties, even if oxygen deficiency and other defects exist. Results indicate that the phase-transition temperature (Tc) decreases with the decrease of oxygen pressures while the solar modulation efficiency (ΔTsol) increases with the decrease of oxygen pressures. Moreover, the M-VO2 thin films prepared with 0.3 Pa oxygen pressure showed the best photoelectric performance, in which the sheet resistance changes up to three orders of magnitude, the phase-transition temperature is 61 °C and the ΔTsol is as high as 8.3%. This work has demonstrated the role of moderate oxygen defects in optimizing the photoelectric properties of M-VO2, also provided a feasibility study on how to deposit pure M-VO2 by PLD.

Laser synthesis of non-volatile memristor structures based on tantalum oxide thin films

The amorphous thin TaOx films (x ≤ 5) of different thicknesses with different levels of oxygen vacancy content, which are promising for use as an active region of non-volatile memristors, were fabricated by the pulsed laser deposition in a drop-free mode on the c-sapphire substrates. The films were obtained from tantalum metal targets at substrate temperatures of 25 °C and 350 °C in the oxygen pressure range from 0.5 to 50 mTorr. The relationship between the partial oxygen pressure and the optical, electrical, and chemical properties of the films was studied. It was found that the amorphous TaOx phase, which is a source of defects associated with oxygen deficiency, required for the creation of memristors, appears only at low oxygen pressures in the chamber (~ 5 × 10−4 Torr), this leads to low values resistivity in the films (~ 10−3 Ohm · cm). Memristor structures Ag(Pt)/TaOx/TaOy/Ta/c-Al2O3 (x > y) in cross-bar geometry have been created that do not require electroforming, due to the choice of design and deposition conditions. Memristor using two mechanisms of resistive switching based on oxygen vacancies and silver cations showed very reliable RS performance with memory window performance RON/ROFF ~ 103 and RESET operating voltage ~ 1 V.

Hesperidin ameliorates hypobaric hypoxia-induced retinal impairment through activation of Nrf2/HO-1 pathway and inhibition of apoptosis

High-altitude retinopathy is initiated by hypobaric hypoxia and characterized by retinal functional changes, but the precise cellular and molecular mechanisms that mediate this dysfunction remain unclear. The aim of our investigation is to determine the protective efficacy of hesperidin (HSD) on the hypobaric hypoxia-induced damage to the retina. Experiment rats were randomly grouped as the control, hypobaric hypoxia group and HSD intervention group. The hypobaric hypoxia and the HSD intervention groups were maintained in a low-pressure oxygen cabin. We found that hypobaric hypoxia dramatically reduced nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1(HO-1) levels, induced an elevation in immunostaining of TUNEL-positive cells. Hypobaric hypoxia exposure resulted in the increase of Bcl-2, decrease of caspase3 and caspase9 expression as well as Bax level. HSD protected the retina from hypobaric hypoxia-caused impairment by enhancing Nrf2 and HO-1 activation, attenuating apoptotic caspases levels, and reducing Bax and preserving Bcl-2 expression. Additionally, oxidative stress increased poly (ADP-ribose) polymerase 1 (PARP1) and suppressed ciliary neurotrophic factor (CNTF) level, HSD treatment reverted this effect by down-regulation of PARP1 and up-regulation of CNTF expression. Taken together, our findings implicate that HSD exerts a protective role in response to hypobaric hypoxia stress by activating Nrf2/HO-1 pathway and inhibiting apoptosis.

Mass transfer and reaction characteristics of homogeneously catalyzed aerobic oxidation of 5-hydroxymethylfurfural in slug flow microreactors

Oxidation of 5-hydroxymethylfurfural (HMF) using air or pure oxygen was performed in polytetrafluoroethylene capillary microreactors under gas–liquid slug flow, with Co/Mn/Br as the homogeneous catalyst in the acetic acid solvent. The temperature was varied from 90 to 165 °C at a pressure of 1 or 5 bar. At atmospheric pressure conditions (and 90 °C), acetaldehyde was further added as a co-oxidant to accelerate the reaction. At 150 °C, 5 bar oxygen and a residence time of 2.73 min, an HMF conversion of 99.2% was obtained, with the yields of 2,5-diformylfuran (DFF), 5-formylfurancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA) being 22.9%, 46.7%, and 23.8%, respectively. By operation under wetted slug flows and elevated partial oxygen pressures, mass transfer limitations and oxygen depletion in the microreactor could be eliminated. This allowed to run the microreactor under kinetically controlled conditions, where both the HMF consumption and DFF formation were found zero order in partial oxygen pressure and roughly first order in HMF. The total selectivity towards DFF/FFCA/FDCA was ca. 40% at low partial oxygen pressures due to the dominant occurrence of side reactions. By using pure oxygen at 5 bar the total selectivity was improved to 60–94%. The space time yields of DFF and FFCA in the microreactor exceeded those obtained in conventional (semi-)batch reactors at slightly elevated temperatures and pressures, due to the superior mass transfer and higher initial HMF concentrations in the microreactor. For highly efficient FDCA synthesis, more dedicated microreactor operations are needed to tackle its precipitation.

Mode transition in an oxygen low-pressure, very high frequency (162 MHz), multi-tile electrode capacitively coupled plasma

An experimental investigation of electrode voltage/discharge current, plasma density, including negative ions and ion flux, and ion energy distributions (IEDs) is performed in a low-pressure oxygen discharge excited by a multi-tile electrode, very high frequency (162 MHz) capacitively coupled plasma system. The results show a mode transition vs RF power. An inflection point is observed in the measured electrode voltage and current near to the mode transition. The negative ion density inferred from the measured electron density and ion flux using resonance hairpin probe and planar probe, respectively, shows an initial increase and then decrease after mode transition. The IED shows a symmetric narrow distribution and the mean energy first increases up to the transition point and then decreases with further increase in RF power. A change in the current coupling mechanism and variation in the discharge impedance due to the presence of negative ions are responsible for the observed mode transition.

Tribbles Homolog 3-Mediated Vascular Insulin Resistance Contributes to Hypoxic Pulmonary Hypertension in Intermittent Hypoxia Rat Model.

This study aimed to investigate the role of vascular insulin resistance (VIR) and Tribbles homolog 3 (TRIB3) in the pathogenesis of hypoxia-induced pulmonary hypertension (HPH). Rats were subjected to low air pressure and low oxygen intermittently for 4 weeks to induce HPH. The mean right ventricular pressure (mRVP), mean pulmonary arterial pressure (mPAP), and right ventricular index (RVI) were significantly increased in HPH rats. Pulmonary arteries from HPH rats showed VIR with reduced vasodilating effect of insulin. The protein levels of peroxisome proliferator-activated receptor gamma (PPARγ), phosphoinositide 3-kinase (PI3K), phosphorylations of Akt, and endothelial nitric oxide (NO) synthase (eNOS) were decreased, and TRIB3 and phosphorylated extracellular signal-regulated protein kinases (ERK1/2) were increased in pulmonary arteries of HPH rats. Early treatment of pioglitazone (PIO) partially reversed the development of HPH, improved insulin-induced vasodilation, and alleviated the imbalance of the insulin signaling. The overexpression of TRIB3 in rat pulmonary arterial endothelial cells (PAECs) reduced the levels of PPARγ, PI3K, phosphorylated Akt (p-Akt), and phosphorylated eNOS (p-eNOS) and increased p-ERK1/2 and the synthesis of endothelin-1 (ET-1), which were further intensified under hypoxic conditions. Moreover, TRIB3 knockdown caused significant improvement in Akt and eNOS phosphorylations and, otherwise, a reduction of ERK1/2 activation in PAECs after hypoxia. In conclusion, impaired insulin-induced pulmonary vasodilation and the imbalance of insulin-induced signaling mediated by TRIB3 upregulation in the endothelium contribute to the development of HPH. Early PIO treatment improves vascular insulin sensitivity that may help to limit the progression of hypoxic pulmonary hypertension.

MODIFICATION OF DIAMOND SURFACE DURING PHOTOLITHOGRAPHY, PLASMA-CHEMICAL CLEANING, AND MAGNETRON DEPOSITION

An influence of the conventional planar technology of the semiconductor surface treatment operations (photolithography, plasma-chemical surface cleaning in radio frequency low-pressure oxygen discharge, and thin metal films growth) on monocrystalline diamond surface topography and roughness is investigated. It is preliminary shown that photolithography without the plasma cleaning and magnetron deposition of an aluminum film do not induce any diamond surface changes which could be found by the optical profilometry, electron and optical microscopy. However, as a result of the lithography some organic contaminants can decrease the adhesion of the aluminum film and have to remove from the surface. Further, the influence of the above-listed surface treatment operations separately and in combinations on the synthetic diamond surface is investigated. It is found that an even short oxygen plasma cleaning during 5 min with a low bias power of 20 W leads to etching the grooves on the diamond surface The depth of the etching grooves varies by more than an order of magnitude in different experiments (0.3 - 19 nm), and by 10-20% within the same substrate under the influence of the poorly controlled external factors. Also, oxygen plasma treatment changes its secondary electron emission coefficient. Deposition of aluminum film after plasma cleaning does not induce noticeable changes in the diamond surface topography. The quality of diamond surface polishing (in “hard” of “soft” direction), the diamond’s type (IIa or IIb) as well as producing method (HPHT or homoepitaxial CVD) do not affect the result of grooves formation.

Effects of hypoxic acclimation on contractile properties of the spongy and compact ventricular myocardium of steelhead trout (Oncorhynchus mykiss).

The trout ventricle has an outer compact layer supplied with well-oxygenated arterial blood from the coronary circulation, and an inner spongy myocardium supplied with oxygen poor venous blood. It was hypothesized that: (1) the spongy myocardium of steelhead trout (Oncorhynchus mykiss), given its routine exposure to low partial pressures of oxygen (PO2), would be better able to maintain contractile performance (work) when exposed to acute hypoxia (100 to 10% air saturation) relative to the compact myocardium, and would show little benefit from hypoxic acclimation; and (2) the compact myocardium from hypoxia-acclimated (40% air saturation) fish would be better able to maintain work during acute exposure to hypoxia relative to normoxia-acclimated individuals. Consistent with our expectations, when PO2 was acutely lowered, net work from the compact myocardium of normoxia-acclimated fish declined more (by ~ 73%) than the spongy myocardium (~ 50%), and more than the compact myocardium of hypoxia-acclimated fish (~ 55%), and hypoxic acclimation did not benefit the spongy myocardium in the face of reduced PO2. Further, while hypoxic acclimation resulted in a 25% (but not significant) decrease in net work of the spongy myocardium, the performance of the compact myocardium almost doubled. This research suggests that, in contrast to the spongy myocardium, performance of the compact myocardium is improved by hypoxic acclimation; and supports previous research suggesting that the decreased contractile performance of the myocardium upon exposure to lowered PO2 may be adaptive and mediated by mechanisms within the muscle itself.

Nitrogen Assimilation and Transport by Ex Planta Nitrogen-Fixing Bradyrhizobium diazoefficiens Bacteroids Is Modulated by Oxygen, Bacteroid Density and l-Malate.

Symbiotic nitrogen fixation requires the transfer of fixed organic nitrogen compounds from the symbiotic bacteria to a host plant, yet the chemical nature of the compounds is in question. Bradyrhizobium diazoefficiens bacteroids were isolated anaerobically from soybean nodules and assayed at varying densities, varying partial pressures of oxygen, and varying levels of l-malate. Ammonium was released at low bacteroid densities and high partial pressures of oxygen, but was apparently taken up at high bacteroid densities and low partial pressures of oxygen in the presence of l-malate; these later conditions were optimal for amino acid excretion. The ratio of partial pressure of oxygen/bacteroid density of apparent ammonium uptake and of alanine excretion displayed an inverse relationship. Ammonium uptake, alanine and branch chain amino acid release were all dependent on the concentration of l-malate displaying similar K0.5 values of 0.5 mM demonstrating concerted regulation. The hyperbolic kinetics of ammonium uptake and amino acid excretion suggests transport via a membrane carrier and also suggested that transport was rate limiting. Glutamate uptake displayed exponential kinetics implying transport via a channel. The chemical nature of the compounds released were dependent upon bacteroid density, partial pressure of oxygen and concentration of l-malate demonstrating an integrated metabolism.

Polymer Electret Improves the Performance of the Oxygen-Doped Organic Field-Effect Transistors

Chemical doping is widely used in the electronic devices. In p-type semiconductor thin films, oxygen doping fills the hole traps and increases hole concentrations, improving the performance of the organic field-effect transistors (OFETs). Due to the low ionization potential for p-type semiconductors, the superfluous holes induced by the oxygen doping degrades the OFETs off-state leakage performance. On the other hand, for p-type semiconductors with high ionization potential (up to 5.5-6.0 eV), the limited oxidation of oxygen is hard to achieve satisfactory doping concentrations to fill the trap states. This refers to the well-known intrinsic incompatibility between the oxygen doping and high-performance OFETs. Herein, a novel strategy is introduced to overcome the incompatibility and achieve high-performance OFETs by using the structural polymer electret. That is, moderate hole concentrations induced by low-pressure (30 Pa) oxygen plasma fill the hole traps within semiconductor. And the built-in field resulted from polymer electret accumulates the holes inside semiconductor near the semiconductor/electret interface, thus improving the OFETs performance. Using a model organic semiconductor with high ionization potential-2,7-didodecyl[1]benzothieno [3,2-b][1]benzothiophene (C12-BTBT) as an example, the high-performance OFETs with field-effect mobility ( $\mu _{FET}$ ) of 3.5 cm2V−1 s−1, subthreshold-swing ( SS ) of 110 mV decade−1, on-off ratio of 104, and widely-tunable threshold voltage ( ${V} _{t}$ ) are realized at a low voltage below 2 V in the open air.

Hypoxia-mediated regulation of mitochondrial transcription factors in renal epithelial cells: implications for hypertensive renal physiology.

Kidneys have a high resting metabolic rate and low partial pressure of oxygen due to enhanced mitochondrial oxygen consumption and ATP production needed for active solute transport. Heightened mitochondrial activity leads to progressively increasing hypoxia from the renal cortex to the renal medulla. Renal hypoxia is prominent in hypertensive rats due to increased sodium reabsorption within the nephrons, which demands higher energy production by oxidative phosphorylation (OXPHOS). Consequently, spontaneously hypertensive rats (SHR) display greater oxygen deficiency (hypoxia) than normotensive Wistar Kyoto rats (WKY). Here, we sought to investigate the expression of key proteins for mitochondrial biogenesis in SHR and WKY, and study the regulation of mitochondrial transcription factors (mtTFs) under in vitro hypoxic conditions in renal epithelial cells. We report that renal expressions of hypoxia-inducible factor-1-alpha (HIF-1α), peroxisome proliferator-activated receptor-gamma coactivator-1-alpha (PGC-1α), mtTFs, and OXPHOS proteins are elevated in SHR compared to WKY. In addition, our experiments in cultured kidney cells demonstrate that acute hypoxia augments the expression of these genes. Furthermore, we show that the transcripts of HIF-1α and mtTFs are positively correlated in various human tissues. We reveal, for the first time to our knowledge, that HIF-1α transactivates mtTF genes by direct interaction with their promoters in rat kidney epithelial cells (NRK-52E) under acute hypoxia. Concomitant increases in the mitochondrial DNA and RNA, and OXPHOS proteins are observed. Taken together, this study suggests that hypoxia within the renal epithelial cells may enhance mitochondrial function to meet the energy demand in proximal tubular cells during prehypertensive stages in kidneys of young SHR.

Control of phase formation of (AlxGa1 − x)2O3 thin films on c-plane Al2O3

In this paper, the growth of orthorhombic and monoclinic (AlxGa1 − x)2O3 thin films on (00.1) Al2O3 by tin-assisted pulsed laser deposition is investigated as a function of oxygen pressure p(O2) and substrate temperature . For certain growth conditions, defined by ≥ 580°C and p(O2) ≤ 0.016 mbar, the orthorhombic κ-polymorph is stabilized. For = 540°C and p(O2) ≤ 0.016 mbar, the κ-, and the β-, as well as the spinel γ-polymorph coexist, as illustrated by XRD 2θ-ω-scans. Further employed growth parameters result in thin films with a monoclinic β-gallia structure. For all polymorphs, p(O2) and affect the formation and desorption of volatile suboxides, and thereby the growth rate and the cation composition. For example, low oxygen pressures lead to low growth rates and enhanced Al incorporation. This facilitates the structural engineering of polymorphic, ternary (Al,Ga)2O3 via selection of the relevant process parameters. Transmission electron microscopy (TEM) studies of a κ - (Al0.13Ga0.87)2O3 thin film reveal a more complex picture compared to that derived from x-ray diffraction measurements. Furthermore, this study presents the possibility of controlling the phase formation, as well as the Al-content, of thin films based on the choice of their growth conditions.

The Effects of High-Altitude Environment on Brain Function in a Seizure Model of Young-Aged Rats.

In this study, we examined the effects of high-altitude environment on the brain function of a young-rat seizure model. Two-hundred healthy, 3-week old, male rats were selected and equally divided into the plateau and plain groups. The plateau group was preconditioned in a simulated 5,000-m altitude (barometric pressure [PB], 405 mmHg; partial pressure of oxygen [PO2], 84 mmHg) for 6 h/day for 7 days, while the plain group was kept in the ordinary atmospheric environment (PB, 760 mmHg; PO2, 157 mmHg) for 7 days. After preconditioning, rats were administered pentylenetetrazol (PTZ) to generate level-4 or stronger seizures. Electroencephalogram (EEG) signals were recorded (16 rats/group); the histology and apoptosis of hippocampal tissue were evaluated (6 rats/group); and spatial learning and memory were examined in the Morris water maze (12 rats/group; 6-weeks old). To induce a level 4 or stronger seizure successfully, a significantly higher PTZ dose was used in the plateau (81.32 ± 21.57 mg/kg) than in the plain group (63.41 ± 19.77 mg/kg, p < 0.01); however, the plateau group survival rate was significantly lower than that of the plain group (26.2 vs. 42.9%, p < 0.05). EEG parameters did not differ between the two groups. Histological analysis revealed that in the plateau group, more neurons were observed (p < 0.001), especially in DG and CA1 areas, and less apoptotic cells were found in DG areas (p = 0.035), comparing with the plain group. No differences were found between the two groups in any of the parameters examined in the Morris water maze. Our results show that the disease outcome caused by low pressure and low oxygen environment in the plateau group was different to that in the plain group. The high drug dosage to induce seizures in the plateau group, accompanied by increased mortality rates after seizures, indicates that the seizure threshold may be higher in the plateau than in the plain group. Moreover, based on the histological findings, the plateau environment seems to exert a protective effect on brain development after seizures only for survived individuals with mild conditions.

Oxygen plasma surface treatment of polymer films—Pellethane 55DE and EPR-g-VTMS

A systematic study using a central composite design of experiments (DoE) was performed on the oxygen plasma surface modifications of two different polymers—Pellethane 2363-55DE, which is a polyurethane, and vinyltrimethoxysilane-grafted ethylene-propylene (EPR-g-VTMS), a cross-linked ethylene-propylene rubber. The impacts of four parameters—gas pressure, generator power, treatment duration, and process temperature—were assessed, with static contact angles and calculated surface free energies (SFEs) as the main responses in the DoE. The plasma effects on the surface roughness and chemistry were determined using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Through the sufficiently accurate DoE model evaluation, oxygen gas pressure was established as the most impactful factor, with the surface energy and polarity rising with falling oxygen pressure. Both polymers, though different in composition, exhibited similar modification trends in surface energy rise in the studied system. The SEM images showed a rougher surface topography after low pressure plasma treatments. XPS and subsequent multivariate data analysis of the spectra established that higher oxidized species were formed with plasma treatments at low oxygen pressures of 0.2 mbar.