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1.
Prostaglandins and (PG) have been reported to be an important gastric acid suppressive factor. However, the mechanism underlying is yet to be clearly established. In vitro study with gastric microsomes in presence of both PGE2 and PGI2 shows a stimulation of gastric H+ K+-ATPase activity below 1X10−6M and 2.5X10−7M concentrations respectively. However, with further increase in concentrations of both PGE2 and PGI2, H+, K+-ATPase activity shows an inhibition but PGI2 completely obliterates the K+ stimulated part of H+, K+-ATPase activity at higher concentration. The H+-ion transport study using chambered frog gastric mucosa shows that both PGE2 and PGI2 inhibit H+-ion transport at 5X10−6 M and 10X10−6M concentrations respectively but the effect of PGI2 is reversible. These differential effects of PGE2 and PGI2 on microsomal H+, K+-ATPase and on H+ transport my be caused by the differential effects of these phospholipid mediators with the gastric mucosal cell membrane. This in vitro investigation shows the role of prostaglandin (s) as a physiological switch/regulator of gastric H+ ion transport leading to the cessation of gastric acid secretion.  相似文献   

2.
Understanding the mineralogy of the Earth''s interior is a prerequisite for unravelling the evolution and dynamics of our planet. Here, we conducted high pressure-temperature experiments mimicking the conditions of the deep lower mantle (DLM, 1800–2890 km in depth) and observed surprising mineralogical transformations in the presence of water. Ferropericlase, (Mg, Fe)O, which is the most abundant oxide mineral in Earth, reacts with H2O to form a previously unknown (Mg, Fe)O2Hx (x ≤ 1) phase. The (Mg, Fe)O2Hx has a pyrite structure and it coexists with the dominant silicate phases, bridgmanite and post-perovskite. Depending on Mg content and geotherm temperatures, the transformation may occur at 1800 km for (Mg0.6Fe0.4)O or beyond 2300 km for (Mg0.7Fe0.3)O. The (Mg, Fe)O2Hx is an oxygen excess phase that stores an excessive amount of oxygen beyond the charge balance of maximum cation valences (Mg2+, Fe3+ and H+). This important phase has a number of far-reaching implications including extreme redox inhomogeneity, deep-oxygen reservoirs in the DLM and an internal source for modulating oxygen in the atmosphere.  相似文献   

3.
The periodic differential equation (1+ε cos t)y&#x030B; + py = 0, hereby termed the Carson–Cambi equation, is the simplest second-order differential equation having a periodic coefficient associated with the second derivative. Provided |ε|<1, which is the case we examine, then the differential equation is a Hill's equation and thus possesses regions of stability and instability in the p–ε plane. Ordinary perturbation theory is employed to obtain the stable (periodic) solutions to ε3. Two-timing theory is employed to obtain solutions for values of k near the critical points k = ±12, ±32, ±52. Three-timing is employed to extend the solution near k = ±12. The solutions of the Carson–Cambi equation are compared with the solutions of the corresponding Mathieu equation.  相似文献   

4.
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5.
Obesity is one of the most important health problems, which many people suffer from it. As a chronic disease, it is a precipitating factor for many medical conditions like hypertension, diabetes mellitus, hyperlipidemia, coronary artery disease, sleep apnea syndrome and some malignancies (breast, uterus, prostate and colon carcinoma). With attention to this fact that obesity is an independent risk factor associated with significant increase in morbidity and mortality, treatment of overweight individuals is very important. One of the medications for short-term weight loss is fluoxetin. In this clinical trial study, fluoxetin effect on weight loss induction during 8 weeks was investigated. 201 cases with BMI between 25–42 were selected randomly (113 female and 88 male) and all received fluoxetine (40 mg daily) for 8 weeks. Measurement was carried out after the 4th and 8th week of administration and 4 weeks after end of treatment. Management of 9 cases (4 due to weight gain and 5 due to headache) were discontinued after 4 weeks of treatment. Data assessments were performed using t-test and SPSS program. Mean body weight at first visit was 89.32±13.30kg. At the 4th, 8th week of treatment and 4 weeks after study, the mean body weight of cases reached 86.09±13.27 (p=0.00), 82.69±11.31 (p=0.00) and 81.97±13.26 (p=0.00) respectively. Mean BMI at first visit was 34.90±5.20kg/m2. At 4th, 8th weeks of treatment it was 33.72±5.20kg/m2 and 32.40±5.18kg/m2 respectively. Mean weight loss at 4th and 8th weeks of treatment was 3.24kg and 6.67kg respectively without any weight gain at the end of the 4th week after discontinuation of the drug. Fluoxetine is an effective, well-tolerated and relatively safe drug for short-term treatment of obesity.  相似文献   

6.
BackgroundThe increasing rate of breast cancer globally requires extraordinary efforts to discover new effective sources of chemotherapy with fewer side effects. Glutaminase-free l-asparaginase is a vital chemotherapeutic agent for various tumor malignancies. Microorganisms from extreme sources, such as marine bacteria, might have high l-asparaginase productivity and efficiency with exceptional antitumor action toward breast cancer cell lines.Resultsl-Asparaginase-producing bacteria, Bacillus velezensis isolated from marine sediments, were identified by 16S rRNA sequencing. l-Asparaginase production by immobilized cells was 61.04% higher than that by free cells fermentation. The significant productivity of enzyme occurred at 72 h, pH 6.5, 37°C, 100 rpm. Optimum carbon and nitrogen sources for enzyme production were glucose and NH4Cl, respectively. l-Asparaginase was free from glutaminase activity, which was crucial medically in terms of their severe side effects. The molecular weight of the purified enzyme is 39.7 KDa by SDS-PAGE analysis and was ideally active at pH 7.5 and 37°C. Notwithstanding, the highest stability of the enzyme was found at pH 8.5 and 70°C for 1 h. The enzyme kinetic parameters displayed Vmax at 41.49 μmol/mL/min and a Km of 3.6 × 10−5 M, which serve as a proof of the affinity to its substrate. The anticancer activity of the enzyme against breast adenocarcinoma cell lines demonstrated significant activity toward MDA-MB-231 cells when compared with MCF-7 cells with IC50 values of 12.6 ± 1.2 μg/mL and 17.3 ± 2.8 μg/mL, respectively.ConclusionThis study provides the first potential of glutaminase-free l-asparaginase production from the marine bacterium Bacillus velezensis as a prospect anticancer pharmaceutical agent for two different breast cancer cell lines.How to cite: Mostafa Y, Alrumman S, Alamri S, et al. Enhanced production of glutaminase-free L-asparaginase by marine Bacillus velezensis and cytotoxic activity against breast cancer cell lines. Electron J Biotechnol 2019;42. https://doi.org/10.1016/j.ejbt.2019.10.001.  相似文献   

7.
BackgroundOleaginous yeasts can be grown on different carbon sources, including lignocellulosic hydrolysate containing a mixture of glucose and xylose. However, not all yeast strains can utilize both the sugars for lipogenesis. Therefore, in this study, efforts were made to isolate dual sugar-utilizing oleaginous yeasts from different sources.ResultsA total of eleven isolates were obtained, which were screened for their ability to utilize various carbohydrates for lipogenesis. One promising yeast isolate Trichosporon mycotoxinivorans S2 was selected based on its capability to use a mixture of glucose and xylose and produce 44.86 ± 4.03% lipids, as well as its tolerance to fermentation inhibitors. In order to identify an inexpensive source of sugars, nondetoxified paddy straw hydrolysate (saccharified with cellulase), supplemented with 0.05% yeast extract, 0.18% peptone, and 0.04% MgSO4 was used for growth of the yeast, resulting in a yield of 5.17 g L−1 lipids with conversion productivity of 0.06 g L−1 h−1. Optimization of the levels of yeast extract, peptone, and MgSO4 for maximizing lipid production using Box–Behnken design led to an increase in lipid yield by 41.59%. FAME analysis of single cell oil revealed oleic acid (30.84%), palmitic acid (18.28%), and stearic acid (17.64%) as the major fatty acids.ConclusionThe fatty acid profile illustrates the potential of T. mycotoxinivorans S2 to produce single cell oil as a feedstock for biodiesel. Therefore, the present study also indicated the potential of selected yeast to develop a zero-waste process for the complete valorization of paddy straw hydrolysate without detoxification.How to cite: Sagia S, Sharma A, Singh S, et al. Single cell oil production by a novel yeast Trichosporon mycotoxinivorans for complete and ecofriendly valorization of paddy straw. Electronic Journal of Biotechnology 2020;44. https://doi.org/10.1016/j.ejbt.2020.01.009.  相似文献   

8.
The rate of evaporation of electrons, νe, from a thoriated tungsten filament depends on the temperature T and on θ, the fraction of the surface covered by thorium atoms. The relation of νe to θ and T has been given by Brattain and Becker. From νe the change in contact potential V of the filament surface produced by the adsorbed thorium can be calculated by the Boltzmann equation. Knowing σ the number of thorium atoms per cm.3, the dipole moment M of each is given by V = 2τσM. By an equation already used for Cs films on tungsten, the 2-dimensional equation of state of the adsorbed film can be calculated from M. Then by Gibbs' adsorption equation the relation of the atom evaporation rate νa to θ and T can be determined. It is thus calculated that in the range from θ = 0.2 to θ = 0.6, νa varies in proportion to ?Hθ where H = 8.1 in good agreement with the value H = 7.8 given by Brattain and Becker's measurements. A recalculation of the data of numerous experiments in 1921–1923, using the new relations of νe to θ1 gives data on νa as a function of T and θ in good agreement with the values of νa calculated from νe.The diffusion coefficients of Th through tungsten crystals, along grain boundaries and over the free filament surface, are calculated. A theory is given for the cause of the variation in the surface diffusion coefficient with σ. The probable mechanism of the production of the metallic thorium within the filament is discussed. At 2400° the thorium which arrives at the surface along grain boundaries, for some unknown reason, does not spread out over the surface as it does at lower temperatures (1900–2100°).  相似文献   

9.
An Oxalate oxidase (Oxalate: O2 oxidoreductase, EC 1,2,3,4) has been purified to apparent homogeneity from leaves of 10-day old seedling plants of grain sorghum hybrid CSH-5. The enzyme exhibited maximum activity at pH 5.0 and 40°C. The rate of H2O2 formation was linear upto 2 min. The enzyme was strongly stimulated by Cu++. The enzyme has greater resistance towards various cations and anions found in urine, compared to moss, barley, banana peel and bleet stem oxalate oxidases. This improved characteristic of the enzyme make it better suited for its use in the determination of urinary oxalate. A simple method of measuring oxalate in urine using this enzyme preparation is described.  相似文献   

10.
BackgroundLXYL-P1-2 is the first reported glycoside hydrolase that can catalyze the transformation of 7-β-xylosyl-10-deacetyltaxol (XDT) to 10-deacetyltaxol (DT) by removing the d-xylosyl group at the C-7 position. Successful synthesis of paclitaxel by one-pot method combining the LXYL-P1-2 and 10-deacetylbaccatin III-10-β-O-acetyltransferase (DBAT) using XDT as a precursor, making LXYL-P1-2 a highly promising enzyme for the industrial production of paclitaxel. The aim of this study was to investigate the catalytic potential of LXYL-P1-2 stabilized on magnetic nanoparticles, the surface of which was modified by Ni2+-immobilized cross-linked Fe3O4@Histidine.ResultsThe diameter of matrix was 20–40 nm. The Km value of the immobilized LXYL-P1-2 catalyzing XDT (0.145 mM) was lower than that of the free enzyme (0.452 mM), and the kcat/Km value of immobilized enzyme (12.952 mM s−1) was higher than the free form (8.622 mM s−1). The immobilized form maintained 50% of its original activity after 15 cycles of reuse. In addition, the stability of immobilized LXYL-P1-2, maintained 84.67% of its initial activity, improved in comparison with free form after 30 d storage at 4°C.ConclusionsThis investigation not only provides an effective procedure for biocatalytic production of DT, but also gives an insight into the application of magnetic material immobilization technology.How to citeZou S, Chen TJ, Li DY, et al. LXYL-P1-2 immobilized on magnetic nanoparticles and its potential application in paclitaxel production. Electron J Biotechnol 2021;50.https://doi.org/10.1016/j.ejbt.2020.12.005  相似文献   

11.
The selective cell separation is a critical step in fundamental life sciences, translational medicine, biotechnology, and energy harvesting. Conventional cell separation methods are fluorescent activated cell sorting and magnetic-activated cell sorting based on fluorescent probes and magnetic particles on cell surfaces. Label-free cell separation methods such as Raman-activated cell sorting, electro-physiologically activated cell sorting, dielectric-activated cell sorting, or inertial microfluidic cell sorting are, however, limited when separating cells of the same kind or cells with similar sizes and dielectric properties, as well as similar electrophysiological phenotypes. Here we report a label-free density difference amplification-based cell sorting (dDACS) without using any external optical, magnetic, electrical forces, or fluidic activations. The conceptual microfluidic design consists of an inlet, hydraulic jump cavity, and multiple outlets. Incoming particles experience gravity, buoyancy, and drag forces in the separation chamber. The height and distance that each particle can reach in the chamber are different and depend on its density, thus allowing for the separation of particles into multiple outlets. The separation behavior of the particles, based on the ratio of the channel heights of the inlet and chamber and Reynolds number has been systematically studied. Numerical simulation reveals that the difference between the heights of only lighter particles with densities close to that of water increases with increasing the ratio of the channel heights, while decreasing Reynolds number can amplify the difference in the heights between the particles considered irrespective of their densities.Separating specific cells from heterogeneous or homogeneous mixtures has been considered as a key step in a wide variety of applications ranging from biomedicine to energy harvesting. For example, the separation and sorting of rare circulating tumor cells (CTCs) from whole blood has gained significant importance in the potential diagnosis and treatment of metastatic cancers.1,2 Similarly, malaria detection relies on the collection of infected red blood cells (RBCs) from whole blood.3,4 In addition, the selective separation of lipid-rich microalgae from homogeneous mixtures of microalgae is a promising technique in biomass conversion.5To date, conventional cell separation can be done by labelling cells with biomolecules to induce differences in physical properties. For instance, in a fluorescence-activated cell sorter (FACS), cells to be separated are labelled with antibodies or aptamers with fluorescent molecules, and then sorted by applying an electrical potential.6,7 Similarly, magnetic-activated cell sorter (MACS) uses magnetic.8,9 Alternatively, label-free cell separation methods have exploited inherent differences in the physical properties (e.g., size and dielectric properties) of different kinds of cells. For example, acoustophoresis forces particles larger than a desired size to move into the center of a fluidic channel by using ultrasonic standing waves.10–12 Inertial microfluidics takes advantage of curved fluidic channels in order to amplify the size differences between particles.13,14 Mass-dependent separation of particles based on gravity and hydrodynamic flow was also reported.15 Particles with different dielectric properties can also be sorted by dielectrophoresis which induces the movement of polarizable particles.16–18The disadvantage of these methods, however, is that they require external forces and labels that may cause unexpected damage to biological cells.19–21 More importantly, most methods are limited in separating cells of the same kind or cells with similar sizes and dielectric properties.Here we designed a novel, label-free density difference amplification-based cell sorting (dDACS) that allows the separation of particles with the same size and charge by exploiting subtle differences in density without the use of external forces. Figure 1(a) illustrates the proposed microfluidic model and its underlying mechanism. The conceptual microfluidic system consists of an inlet, a separation chamber (hydraulic jump cavity), and multiple outlets. Particles entering through the inlet experience gravity (FG), buoyancy (FB), and drag (FD) forces in the separation chamber. The net force acting on the particles can be described as F = FG + FB + FD.(1)As particles enter the separation chamber (i.e., hydraulic jump cavity), FD acting on the particles changes its direction along the streamline. The particles experience additional forces in the y direction due to large tangential angle (Fig. 1(b)). For lighter particles, whose densities are close to that of the surrounding water, FD becomes comparable to FG (i.e., in the y direction), while the net force for heavier particles is less affected by this additional contribution of FD due to a large FG. As a result, the height (H) and distance (D) that each particle can travel are different depending on its density. The difference in the maximum height (ΔHmax) between two particles with different density (ρp1 and ρp2) can be further approximated as ΔHmax∝(vyp0)2(vyf−vyp0), (ρp1−ρp2) ,(2)where vyp0 and vyf represent the velocity of particle and fluid along the y direction at the entrance of hydraulic jump cavity, respectively.Open in a separate windowFIG. 1.Schematic illustration of label-free density difference amplification-based cell sorting (dDACS), which exploits differences in the densities (ρ1 > ρ2) of particles with similar diameters (d) and charge. (a) The conceptual microfluidic design consists of an inlet, a separation chamber (hydraulic jump cavity), and multiple outlets. Incoming particles experience gravity (FG), buoyancy (FB), and drag (FD) forces in the separation chamber, and depending on their densities, the height (H) and distance (D) that each particle is able to reach will be different, allowing the particles to be separated into multiple outlets. (b) Possible microfluidic channel configurations for density-based separation: Uniform channel height (left), gradual channel expansion (middle), and hydraulic jump cavity with sudden channel expansion (right). The height difference between particles with different densities can be amplified by the sudden channel expansion compared to the other two cases due to the relatively large tangential angle, θ of FD. (|θ1|≪ |θ2|) (see Fig. S1 in the supplementary material22).In comparison with the other two cases (Fig. 1(b) uniform channel height and gradual channel expansion), the height difference between the particles with different densities can be amplified by the sudden channel expansion in the hydraulic jump cavity due to relatively large tangential angle (see supplementary material22). Therefore, the particles can be separated through the multiple outlets, depending on their height and distance.In order to analyze the separation behavior of particles in the chamber according to differences in their densities, H and D are systematically investigated. The numerical simulations are performed using a commercial CFD software (CFX 14.0; ANSYS 14.0; ANSYS, Inc.). Particles with the same density may have different trajectories in the separation chamber depending on their inlet positions (Fig. 2(a)). Prior to this investigation, the maximum height (Hmax) and distance (Dmax) for each particle are compared by examining H and D of 100 identical particles at different inlet positions since the inlet position of particles could be controlled.20 Fig. 2(b) shows Hmax and Dmax of particles with respect to density at a fixed Reynolds number (Re = 0.1). Note that Reynolds number is defined as Re = ρfvfDh/μ, where ρf, vf, Dh, μ are density of fluid, velocity of the fluid, hydraulic diameter of a channel, and dynamic viscosity of the fluid, respectively. The hydraulic diameter in the Reynolds number is determined with the inlet channel. Particle densities in the range of 1.1 to 2.0 g/cm3 are chosen with the increase of 0.1 g/cm3. These values are quite reasonable in that the densities of many microorganisms such as microalgae are typically within this range and their densities can be varied by 0.2 g/m3 depending on their cellular context.23 The lighter particles travel with a higher Hmax, and longer Dmax. With the separation chamber, the height difference between particles with densities of 1.1 and 1.2 g/cm3 can be amplified by about 10 times as compared to that in a channel without the chamber, judging from the position where the 1.1 g/cm3 particle reaches its Hmax.Open in a separate windowFIG. 2.Microfluidic particle separation with respect to Reynolds number (Re). (a) Trajectories in the separation chamber of a hundred particles with the same density starting from inlet positions chosen arbitrarily in order to investigate the effect of the inlet positions on the maxima of the height (Hmax) and distance (Dmax) prior to further simulation. (b) Representative trajectories of particles having different densities from 1.1 to 2.0 g/cm3. (c) The maximum height (Hmax) of each particle with respect to Re. (d) Representative maximum distance (Dmax) of each particle at Re = 0.1. (Left) Streamline of fluid and representative trajectories of particles with densities of 1.1 and 2.0 g/cm3 in the separation chamber at Re = 0.1 (right).In Fig. 2(c), the values for Hmax of particles with respect to Reynolds number (Re) are presented. Since in our study, the maximum height (Hmax) and distance (Dmax) for each particle were compared by examining H and D of 100 identical particles that are randomly distributed in the channel (throughout all figures), there is little variation in Hmax and Dmax between each simulation. However, the standard deviation between each simulation is quite small and can be negligible. The Hmax values particles at Re = 0.5 with densities of 1.1 g/cm3 and 1.2 g/cm3 are 2.21 × 103 μm and 2.17 × 103 μm, respectively. The difference between Hmax of different particles, ΔHmax, increases with decreasing Re. For example, ΔHmax between particles with densities of 1.1 and 2.0 g/cm3 becomes 0.26 × 103 μm at Re = 1.0, but increases to 1.38 × 103 μm as Re decreases to 0.1. As Re increases (velocity of fluid increases), the relative velocity in the y direction between the fluid and the particle increases resulting in increasing of FD in the y direction since the velocity of particle in the y direction is very small at the entrance of the separation chamber. Thus, contribution of FD becomes comparable to the net force in the y direction. As a result, most of the particles even in the case of heavier ones travel quite similarly with the streamline, and ΔHmax subsequently decreases. On the other hand, as Re decreases, the contribution of FG becomes dominant due to the decrease of FD in the y direction. Consequently, the particles start to cross downwards streamlines as the density of the particles increases and Hmax gradually decreases. In addition, irrespective of their densities, ΔHmax of the particles increases with decreasing Re.Fig. 2(d) shows Dmax with respect to the density of the particles (left). Different densities of particles show different trajectories due to the relative contribution of FD to the net force in the y direction depending on the particle density (right). At Re = 0.1, Dmax of particles with densities of 1.1 cm3 and 1.2 g/cm3 are 2.91 × 104 μm and 1.43 × 104 μm, respectively. As the density of a particle increases, its Dmax dramatically decreases. The difference in Dmax between particles with densities of 1.1 and 1.2 g/cm3 is 1.48 × 104 μm, and 0.0037 × 104 μm for particles with densities of 1.9 and 2.0 g/cm3. The effect of FD is stronger compared to that of FG on lighter particles. Thus, lighter particles travel quite similarly with the streamline and finally have a large Dmax. On the other hand, heavier particles where effect of FG is stronger compared to that of FD cross downwards streamlines and finally have a small Dmax.Next, in order to investigate the separation behavior of particles with respect to the geometry of the microfluidic device, the effect of the ratio of the height of the separation chamber (hc) to the inlet (hi) on Hmax is investigated as shown in Fig. ​Fig.3.3. Interestingly, Hmax of particles with density of 1.1 g/cm3 increases from 1.93 × 103 μm to 6.48 × 103 μm while that of particles with density of 1.9 g/cm3 slightly changes from 0.70 × 103 μm to 0.73 × 103 μm as hc/hi increases from 5 to 20.Open in a separate windowFIG. 3.Microfluidic particle separation with respect to the ratio of the height of the inlet (hi) to the separation chamber (hc).This result can be attributed to two effects: (1) the change in the streamline and (2) the relative contribution of drag force to the net force depending on the density. With increasing hc/hi, dramatic increase in Hmax for lighter particles is because the streamline for the lighter ones experiences more vertical displacement in the separation chamber and the contribution of FD to the net force acting on the lighter one is more significant (see Fig. S2 in the supplementary material22).Based on this approach, we propose a microfluidic device for the selective separation of the lightest particle. Fig. 4(a) shows one unit (with three outlets) of the proposed microfluidic device that can be connected in series. The ratio of channel heights (hc/hi) is set to 20, and the particle densities are in the range of 1.1 ∼ 1.5 g/m3. Fig. 4(b) shows the representative separation behavior of the particles. A portion of the lightest particles (1.1 g/cm3) is selectively separated into the upper and middle outlets, while remaining light particles together with four other heavier particles with densities in the range of 1.2 to 1.5 g/cm3 leave through the lowest outlet. With a single operation of this unit, 40% of the lightest particles are recovered. In addition, the yield increases with increasing number of cycles (Fig. 4(c)).Open in a separate windowFIG. 4.(a) One unit of the proposed microfluidic device for the selective separation of the lightest particle based on the simulation results. Particles are separated into two outlets based on differences in both the height and distance travelled stemming from differences in density. (b) Representative separation behavior of particles observed in the device. (c) The yield of the lightest particle (1.1 g/cm3) with the proposed microfluidic device according to the number of cycles (i.e., this unit is assumed to be connected in series).In summary, we have demonstrated a label-free microfluidic system for the separation of particles according to subtle differences in their densities without external forces. Our microfluidic design consists simply of an inlet, a separation chamber, and multiple outlets. When entering the separation chamber, the particles experience an additional drag force in the y direction, amplifying the difference in both the height and the distance that the particles with different densities can travel within the chamber. At a fixed Reynolds number, with increasing particle density, Hmax decreases monotonously, and Dmax decreases dramatically. On the other hand, as Reynolds number increases, the difference between the heights of particles with different densities is attenuated. In addition, the simulation reveals that increasing the ratio of the channel heights increases the difference between the heights of particles only when their densities are close to that of the surrounding water. Based on this approach, a microfluidic device for the separation of the lightest particles has been proposed. We expect that our density-based separation design can be beneficial to the selective separation of specific microorganisms such as lipid-rich microalgae for energy harvesting application.  相似文献   

12.
Oxygen derived free radicals have been implicated in a number of clinical disorders including atherosclerosis (1), ischemic heart disease (IHD) (2), post ischemic reperfusion injury (3) and respiratory distress syndrome (4). These radical are generated by sequential reduction of molecular oxygen; the primary product being superoxide anion (O2 .−) which is subsequently reduced to hydrogen peroxide (H2O2), hydroxy1 radical (OH.) and singlet oxygen (1O2). However the evidence for ODFR induced cell damage in various clinical disorders is still debated and rests largely on free radical scavenging studies, through electron paramagnetic resonance spectroscopic (EPRS) studies have provided direct evidence for ODFR generation following coronary artery ligation (5). By definition, a free radical is an atom, ion or molecule with one or more unpaired electrons (the presence of unpaired electron in a free radical being represented by a superscribed bold dot-R.) and may be formed as a result of homolytic fission of a covalent bond or by electron transfer reactions, and may have cationic (NH3 +), anionic (O2 .−) or neutral (NO) characteristics. The most important in vivo source for these radical species have been found to be univalent biochemical redox reactions involving oxygen. (a) A:B→A.+B. (b) A:+B→A.+B.  相似文献   

13.
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14.
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15.
Reactive oxygen species, as singlet oxygen (1O2), is continuously being generated by aerobic organisms, and react actively with biomolecules. At excessive amounts, 1O2 induces oxidative stress and shows carcinogenic and toxic effects due to oxidation of lipids, proteins and nucleic acids. In our study, immunoglobulin G (IgG) was modified by 1O2 generated by the ultraviolet (UV) irradiation of methylene blue. The modified IgG was characterized by UV spectroscopy, carbonyl content determination, thermal denaturation and electrophoretic study. Oxidation induced by modification of IgG by 1O2 also analyzed by scavenging studies. It was found that ultraviolet absorption spectra of modified IgG shows marked hyperchromicity. The carbonyl content was found to be high in modified IgG as compared to native IgG which confirms its oxidation. Thermal denaturation of modified protein sample shows decrease in Tm value by 3 °C and less intensity banding pattern on polyacrylamide gel electrophoresis. The quenching effect of sodium azide provides clue for modification of IgG by methylene blue, as it is known 1O2 scavenger. Hence, the IgG modified with 1O2 may be one of the etiological pathogenic factors for rheumatoid arthritis and diabetes.  相似文献   

16.
As the reaction product of subducted water and the iron core, FeO2 with more oxygen than hematite (Fe2O3) has been recently recognized as an important component in the D” layer just above the Earth''s core-mantle boundary. Here, we report a new oxygen-excess phase (Mg, Fe)2O3+δ (0 < δ < 1, denoted as ‘OE-phase’). It forms at pressures greater than 40 gigapascal when (Mg, Fe)-bearing hydrous materials are heated over 1500 kelvin. The OE-phase is fully recoverable to ambient conditions for ex situ investigation using transmission electron microscopy, which indicates that the OE-phase contains ferric iron (Fe3+) as in Fe2O3 but holds excess oxygen through interactions between oxygen atoms. The new OE-phase provides strong evidence that H2O has extraordinary oxidation power at high pressure. Unlike the formation of pyrite-type FeO2Hx which usually requires saturated water, the OE-phase can be formed with under-saturated water at mid-mantle conditions, and is expected to be more ubiquitous at depths greater than 1000 km in the Earth''s mantle. The emergence of oxygen-excess reservoirs out of primordial or subducted (Mg, Fe)-bearing hydrous materials may revise our view on the deep-mantle redox chemistry.  相似文献   

17.
Proposed international terminology1 used in the paper is as follows: pharos F = luminous flux (lumen), pharosage D - luminous flux density (lumen m?2, helios H = generalized brightness (pharosage per unit solid angle, expressed in blondels).  相似文献   

18.
Partial pressure of oxygen (PO2) was estimated at various intervals during conventional Acetate hemodialysis (A), Sequential haemodialysis (SHD) i.e. ultrafiltration followed by haemodialysis and Isolated ultrafiltration (IUF) on 35 patients. Study was extended for PO2 measurement one hour after termination of above treatment. There was a significant lowering of PO2 observed at 1 h. during ‘A’ (93.3±10.5 Pre to 78.8±4.2 post, P<0.01) during SHD, a significant fall was observed after the dialysate flow was started (81.1±11.5 Pre to 76.3±11.8, 2hr P<0.05) at second hour of the procedure. IUF showed significant increase (88.4±10.3 pre, to 100.4±12.4, post, P<0.01) at the end of treatment. A significant rebound increase was observed after one hour of termination of ‘A’. Changes observed after termination of ‘SHD’ and ‘IUF’ were not significant. The results suggest that, though dialyzer membrane lowers the PO2 level, major role is played by the dialysis fluid.  相似文献   

19.
Diabetes mellitus and thyroid disorders are common endocrinopathies, which often occur parallel. Dyslipidemia is very common in both of these conditions. The development of hypothyroidism is well-known in type 1 diabetics, but it was not distinctly understood in type 2 diabetics. Thus we tried to examine the association between type II deiodinase (D2 or DIO2) Thr92Ala single nucleotide gene polymorphism and thyroid function among type 2 diabetes mellitus patients. A total of 130 type 2 diabetics were screened and genotyped for DIO2 Thr92Ala polymorphism. Fasting plasma glucose, Glycosylated haemoglobin, lipid and thyroid profiles, malondialdehyde (MDA) and paraoxonase were estimated according to standard procedures. A significant altered level of thyroid hormones (TH’s) was found in Ala/Ala genotype when compared with Thr/Thr or Thr/Ala genotype. DIO2 and T3:T4 ratio significantly decreased, whereas total T4 and thyroid stimulating hormone levels significantly elevated among Ala/Ala genotype (131 ± 30 ng/ml; 0.12 ± 0.05; 7.17 ± 2.05 µg/dl; 4.77 ± 3.1 µIU/ml, respectively) when compared with Thr/Thr + Thr/Ala genotypes (176 ± 33 ng/ml; 0.21 ± 0.05; 5.21 ± 1.1 µg/dl; 2.59 ± 1.61 µIU/ml respectively). Moreover, D2 levels were significantly negatively correlated with TH’s levels except total T4 among Ala/Ala genotypes. All the patients were having a poor glycemic control, and their glycemic status was positively correlating with MDA levels. On the other hand, serum paraoxonase activity decreased among Ala/Ala genotype (104 ± 21 vs. 118 ± 18 nmol/min/ml). In conclusion, DIO2 Ala92 homozygous variant found to be associated with altered levels of DIO2, Thyroid profile and paraoxonase. Hence, we recommend to do detail study of genetic factors related to thyroid function and prevent additional diabetic complications.  相似文献   

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