Oxygen Pretreatment Research Articles

Combining oxygen plasma treatment with anchorage of cationized gelatin for enhancing cell affinity of poly(lactide- co-glycolide)

Surface characteristics greatly influence attachment and growth of cells on biomaterials. Although polylactone-type biodegradable polymers have been widely used as scaffold materials for tissue engineering, lack of cell recognition sites, poor hydrophilicity and low surface energy lead to a bad cell affinity of the polymers, which limit the usage of polymers as scaffolds in tissue engineering. In the present study, surface of poly ( l-lactide- co-glycolide) (PLGA) was modified by a method of combining oxygen plasma treatment with anchorage of cationized gelatin. Modification effect of the method was compared with other methods of oxygen plasma treatment, cationized gelatin or gelatin coating and combining oxygen plasma treatment with anchorage of gelatin. The change of surface property was compared by contact angles, surface energy, X-ray photoelectron spectra (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) measurement. The optimum oxygen pretreatment time determined by surface energy was 10 min when the power was 50 W and the oxygen pressure was 20 Pa. Analysis of the stability of gelatin and cationized gelatin anchored on PLGA by XPS, ATR-FTIR, contact angles and surface energy measurement indicated the cationized gelatin was more stable than gelatin. The result using mouse NIH 3T3 fibroblasts as model cells to evaluate cell affinity in vitro showed the cationized gelatin-anchored PLGA (OCG-PLGA) was more favorable for cell attachment and growth than oxygen plasma treated PLGA (O-PLGA) and gelatin-anchored PLGA (OG-PLGA). Moreover cell affinity of OCG-PLGA could match that of collagen-anchored PLGA (AC-PLGA). So the surface modification method combining oxygen plasma treatment with anchorage of cationized gelatin provides a universally effective way to enhance cell affinity of polylactone-type biodegradable polymers.

Hypoxia protects human corneal endothelium from tertiary butyl hydroperoxide and paraquat-induced cell death in vitro.

To develop new and safe approaches to protect and preserve the function of the human corneal endothelium (HCE), we have established an in vitro model of cell loss using an HCE cell line and have examined the potential for hypoxia conditioning to protect HCE from death induced by two ROS generating cytotoxins (tertiary butyl hydroperoxide [tBHP] and paraquat [PQ]). Cell death was assessed by flow cytometric analysis of Annexin-V (An) and propidium iodide (PI) double staining and oligonucleosome production. Mitochondrial membrane potential (MMP) was measured with JC-1 fluorescent dye to determine possible associations between MMP preservation and cell survival. PQ and tBHP both induced HCE cell death in a dose-dependent manner, with 48% and 32% of An(+) cells observed with 60 microM tBHP and 500 microM PQ, respectively. In addition, this level of tBHP and PQ resulted in 66% and 49% decreases in MMP, respectively. Hypoxia (0.6% +/- 0.1% oxygen) pretreatment (8 hrs) significantly reduced An(+) cells caused by 60 microM tBHP to 15%, whereas hypoxia had no effect on the decreased MMP. Hypoxia pretreatments (24 hrs) slightly reduced An(+) cells caused by 500 microM PQ to 25% and completely prevented the induced MMP reduction. Conversely, hypoxia posttreatment (24 hrs) resulted in a greater inhibition of cell death than pretreatment and yet failed to prevent the PQ-induced MMP collapse. In conclusion, these results suggest that hypoxia can sufficiently protect HCE cells against cell death caused by tBHP and PQ, although no direct link between hypoxia cell protection and MMP preservation was observed.

Isoflurane Produces Delayed Preconditioning against Spinal Cord Ischemic Injury via Release of Free Radicals in Rabbits

Whether isoflurane preconditioning produces delayed neuroprotection in the spinal cord is unclear. The authors tested the hypothesis that isoflurane produces delayed preconditioning against spinal cord ischemic injury and, further, that the beneficial effect is dependent on free radicals. In experiment 1, 63 rabbits were randomly assigned to seven groups (n = 9 each): Animals in the control group only underwent spinal cord ischemia without pretreatment; animals in the Iso24h, Iso48h, and Iso72h groups received 40 min of 1.0 minimum alveolar concentration isoflurane in 100% oxygen each day for 5 consecutive days, with the last pretreatment at 24, 48, and 72 h, respectively, before spinal cord ischemia; animals in the O2 24h, O2 48h, and O2 72h groups received 40 min of 100% oxygen each day for 5 consecutive days, with the last pretreatment at 24, 48, and 72 h, respectively, before spinal cord ischemia. In experiment 2, 48 rabbits were randomly assigned into four groups (n = 12 each): Animals in the O2 and Iso groups received 3 ml/kg saline intraperitoneally 1 h before each session of oxygen pretreatment and isoflurane pretreatment, respectively. In the DMTU+Iso and DMTU+O2 groups, 10% dimethylthiourea (DMTU, a potent free radical scavenger) dissolved in saline (3 ml/kg) was administered at the same time point. Twenty-four hours after the last pretreatment, animals were subjected to spinal cord ischemia. Spinal cord ischemia was induced by an infrarenal aorta clamping for 20 min. Forty-eight hours after reperfusion, neurologic function and histopathology of the spinal cord were examined. In experiment 1, the neurologic and histopathologic outcomes in the Iso24h and Iso48h groups were better than those in the control group (P < 0.005 for each comparison); the neurologic and histopathologic outcomes in the control group showed no significant differences in comparison with the O2 24h, O2 48h, O2 72h, and Iso72h groups (P > 0.05 for each comparison). In experiment 2, the neurologic and histopathologic outcomes in the Iso group were better than those in the DMTU+Iso, O2, and DMTU+O2 groups (P < 0.01 for each comparison); there were no significant differences in the neurologic and histopathologic outcomes among the DMTU+Iso, O2, and DMTU+O2 groups (P > 0.05 for each comparison). Isoflurane produces delayed preconditioning against spinal cord ischemic injury, and the beneficial effect may be dependent on the release of free radicals.

Effect of oxygen treatment on the catalytic activity of Au/SiO 2 catalysts

In this paper we investigated the effect of oxygen treatment on the catalytic performance of Au/SiO 2 catalysts towards CO oxidation. The Au/SiO 2 catalysts were prepared via the deposition–precipitation method. The as-prepared Au/SiO 2 catalyst behaves a poor catalytic activity, which is attributed to the relatively large size of Au particles. Treatment of the catalyst in O 2 at temperatures higher than 800 °C greatly enhances the catalytic activity. However, XRD results demonstrate that the oxygen treatment at temperatures above 800 °C leads to the agglomeration of Au particles. Meanwhile, TEM results reveal the co-existence of well-dispersed ultrafine Au particles on the surface. XPS results reveal that the Au 4f binding energy shifts to higher binding energy after the oxygen pretreatment at temperatures above 800 °C. Interestingly, treatment of the Au/SiO 2 catalyst in He at 800 °C also shows the similar geometric and electronic structure changes of Au particles and thus the enhancement effect as that in O 2, indicating that the Au–O 2 interactions at high temperatures do not contribute much to the improvement of catalytic activity. We propose an evaporation–deposition mechanism of gold particles treated at high temperatures, accounting for the formation of ultrafine Au particles, which are responsible for the enhancement of the catalytic activity.

HO-1 Mediates the Effects of HBO Pretreatment Against Sepsis

We have recently shown that attenuation of sepsis-induced lung injury by hyperbaric oxygen (HBO) pretreatment involves expression regulation of inducible nitric oxide synthase (iNOS) and heme oxygenase (HO)-1. This study was performed to determine the effects of HBO pretreatment on acute kidney and liver injuries in septic rats and the roles of iNOS and HO-1. One group of adult male rats (n = 48) were pretreated with HBO. The other group of rats (n = 48) breathed air at normal atmospheric pressure instead. Rats in each group were randomly allocated to receive injection of lipopolysaccharide (LPS), normal saline (N/S), LPS plus hemin (a HO-1 inducer), hemin, LPS plus SnPP (a HO-1 inhibitor), SnPP, LPS plus hemin plus SnPP, or hemin plus SnPP. Hemin and SnPP were injected at 1 h before HBO or air pretreatment. Rats were maintained for 6 h before sacrifice. LPS caused prominent kidney and liver injuries as well as iNOS and HO-1 expression in stimulated rats. HBO pretreatment significantly attenuated LPS-induced kidney but not liver injury. However, in conjunction with hemin (a HO-1 inducer), HBO pretreatment did attenuate LPS-induced liver injury. In addition, the inhibition of iNOS expression by HBO pretreatment was associated with "super-induction" (i.e., further enhancement) of LPS-induced HO-1 expression. Furthermore, the therapeutic effect of HBO could be counteracted by SnPP (a HO-1 inhibitor). HBO pretreatment significantly attenuates LPS-induced acute organ injuries in septic rats. The beneficial effect of HBO pretreatment against sepsis is mediated, at least in part, by "super-induction" of HO-1.

Effects of High O2 Pretreatment and Gibberellic Acid on Sensorial Quality and Storability of Table Grapes

Kyoho grapes ( Vitis vinifera X V. labrusca) were stored under three different treatments at 0°C in 95% relative humidity for 60 days. Grapes in the first treatment were stored in to air (control), in the second treatment the grapes were stored in 80% O2 for 15 days and then transferred into air for 45 days, and in the third treatment the grapes were sprayed with 100ppm of gibberellic acid (GA)3 containing 100ppm of Tween 20 and then kept in air. Compared with the air control, high oxygen pretreatment (HOP) and GA3 maintained higher fruit detachment force and membrane integrity, markedly reduced berry drop, rachis browning and decay and delayed the decrease of soluble solids content (SSC) and vitamin C. In addition, HOP and GA3 retarded the conversion of protopectin to water-soluble pectin and improved berry firmness. HOP resulted in a significantly firmer berry, less berry drop, and more soluble solids content, total acidity and protopectin than those treated with GA3, but did not markedly reduce rachis browning and membrane integrity loss. There were no significant differences in fruit detachment force and water-soluble pectin levels between HOP and GA3. In conclusion, high O2 pretreatment and GA3application retained effectively the quality of harvested grapes.

Restructuring and Redispersion of Silver on SiO2 under Oxidizing/Reducing Atmospheres and Its Activity toward CO Oxidation

The effects of oxygen-hydrogen pretreatments of nanosilver catalysts in cycle mode on the structure and particle size of silver particles, and subsequently the activity of the catalyst toward CO oxidation (or CO selective oxidation in the presence of H2), are reported in this paper. Ag/SiO2 catalyst with silver particle sizes of ca. 6 approximately 8 nm shows relatively high activity in the present reaction system. The adopting of a cycle of oxidation/reduction pretreatment has a marked influence on the activity of the catalyst. Oxygen pretreatment at 500 degrees C results in the formation of subsurface oxygen and activates the catalyst. As evidenced by in-situ XRD and TEM, the following H2 treatment at low temperatures (100 approximately 300 degrees C) causes surface faceting and redispersing of the silver particles without destroying the subsurface oxygen species. The subsequent in-situ FTIR and catalytic reaction results show that CO oxidation occurs at -75 degrees C and complete CO conversion can be obtained at 40 degrees C over such a nanosilver catalyst pretreated with oxygen at 500 degrees C followed by H2 at 100 degrees C. However, prolonged hydrogen treatment at high temperatures (>300 degrees C) after oxygen pretreatment at 500 degrees C induces the aggregation of silver particles and also depletes so much subsurface oxygen species that the pathway of CO oxidation by the subsurface oxygen species is inhibited. Meanwhile, the ability of the catalyst to adsorb reactants is greatly depressed, resulting in a 20 approximately 30% decrease in the activity toward CO oxidation. However, the activity of the catalyst pretreated with oxygen at 500 degrees C followed by hydrogen treatment at high temperatures (>300 degrees C) is still higher than that directly pretreated with H2. This kind of catalytic behavior of silver catalyst is associated with physical changes in the silver crystallites because of surface restructuring and crystallite redispersion during the course of oxygen-hydrogen pretreatment steps.

Low Oxygen Pretreatment for Reduction of Respiration and Delay in Ripening of Tomato Fruits Exposed to Hot Air

Low Oxygen Pretreatment for Reduction of Respiration and Delay in Ripening of Tomato Fruits Exposed to Hot Air

Formation of subsurface oxygen species and its high activity toward CO oxidation over silver catalysts

Silver is well known to show peculiar catalytic activities in several oxidation reactions. In the present paper, we investigate the catalytic activity of silver catalysts toward CO-selective oxidation in H 2. XRD, TEM, TPD, and in situ FTIR techniques were used to characterize the catalysts. The pretreatment of the catalysts was found to have great influence on their performance. The pretreatment in O 2 improves the activity of the silver catalyst, whereas He pretreatment at 700 °C or direct hydrogen pretreatment shows an inverse effect. Silver catalysts undergo massive structural change during oxygen pretreatment at high temperatures ( > 500 °C ), and there is solid evidence for the formation of subsurface oxygen species. The existence of this silver-subsurface oxygen structure facilitates the formation of active sites on silver catalysts for CO oxidation, which are related to the size, morphology, and exposed crystal planes of the silver particles. Its formation requires a certain temperature, and a higher pretreatment temperature with oxygen is required for the silver catalyst with a smaller particle size. It is observed, for the first time, that adsorbed CO on the surface of silver particles can directly react with subsurface oxygen species at low temperatures (e.g., RT), and the surface oxygen can migrate into and refill these subsurface sites after the consumption of subsurface oxygen by the reaction with CO. This finding provides a new reaction pathway for CO oxidation on silver catalyst.

Active sites in HZSM-5 with low Fe content for the formation of surface oxygen by decomposing N 2O: is every deposited oxygen active?

Surface-active centers were detected in HZSM-5 with a low content of iron (<1000 ppm) activated by steaming and high-temperature calcination in inert atmospheres (up to 1323 K). These centers lead to the formation of surface oxygen (O) ad species from N 2O and were characterized quantitatively by the transient response method. The total amount of active centers was proportional to the content of iron in the zeolites. Only a part of (O) ad deposited by decomposing N 2O was active in CO oxidation at 523 K and appeared as sharp O 2 peaks at 666 K during the TPD measurements. A binuclear Fe center is suggested featuring a “diamond core” structure, similar to that of the monooxygenase enzyme, as an active center. The active O atoms were assigned to the paired terminal oxygen atoms each bonded to one Fe site (ferryl groups) in the diferric [Fe 2O 2H] + cluster. Oxygen pretreatment at 823 K decreases somewhat the total amount of active sites but does not affect the ratio of active/inactive oxygen. Zeolite presaturated by water vapor at 473–523 K generates (O) ad species from N 2O completely inactive in the CO oxidation. Part of it appears as a broad peak at 940 K in the TPD profile. The total amount of the deposited oxygen corresponds to half of the stoichiometric amount of the surface Fe atoms and suggests that water blocks a half of the binuclear [Fe 2O 2H] + center, the remaining acting as a single Fe site.

Spiral waves and formation of low work function areas in catalytic NO reduction with hydrogen on a Rh(111) surface

The catalytic NO+H2 reaction on Rh(111) has been investigated in the 10−6–10−5 mbar range using photoelectron emission microscopy as spatially resolving method. Without extended oxygen pretreatment the system is excitable, i.e., one observes spiral waves and target patterns. In addition, irregular islands form. The existence range of the patterns has been mapped out for pNO=1×10−6 mbar. After extended oxygen treatments (pO2=2×10−4, T=770 K, tox&amp;gt;24 h) low work function (WF) areas develop upon the collision of pulses which are assigned to subsurface oxygen (sub-O). A WF decrease up to 0.8 eV below the level of the clean surface is found. The long range interaction of pulses leading to sub-O formation below a distance of ≈100–150 μm is attributed to diffusing atomic hydrogen.

Multiple stressors in Caenorhabditis elegans induce stress hormesis and extended longevity.

We demonstrate here that the nematode Caenorhabditis elegans displays broad hormetic abilities. Hormesis is the induction of beneficial effects by exposure to low doses of otherwise harmful chemical or physical agents. Heat as well as pretreatment with hyperbaric oxygen or juglone (a chemical that generates reactive oxygen species) significantly increased subsequent resistance to the same challenge. Cross-tolerance between juglone and oxygen was also observed. The same heat or oxygen pretreatment regimens that induced subsequent stress resistance also increased life expectancy and maximum life span of populations undergoing normal aging. Pretreatment with ultraviolet or ionizing radiation did not promote subsequent resistance or increased longevity. In dose-response studies, induced thermotolerance paralleled the induced increase in life expectancy, which is consistent with a common origin.

Preliminary studies on TCF bleaching of Pinus pinaster acetosolv pulps

Oxygen pre-treatment of Pinus pinaster acetosolv pulps has been studied as a first step towards TCF bleaching. Using a 2 3 factorial design, the influence of temperature (80–120 °C), time (1–2 h) and NaOH concentration (1.5–3%) on pulp yield in the oxygen stage, chemical composition and physical properties of the pulps obtained was studied. Pulps pre-bleached with oxygen in the conditions selected as optimal (80 °C, 1 h with 2.25% NaOH) have been bleached with TCF sequences which included stages with hydrogen peroxide or hydrogen peroxide–oxygen under pressure. Even if high degrees of delignification were reached, with a reduction in Kappa number up to 95% and without important loss of viscosity, the carbohydrates degradation, especially hemicelluloses in the acetic acid delignification, reduces the strength potential of the pulps.

The interaction of oxygen with alumina-supported palladium particles.

Utilizing a combination of molecular beam techniques and scanning tunneling microscopy (STM) under ultrahigh vacuum (UHV) conditions we have studied the interaction of oxygen with an alumina-supported Pd model catalyst as well as the influence of the oxygen pretreatment on the kinetics of the CO oxidation reaction. The Pd particles were deposited by metal evaporation in UHV onto a well-ordered alumina film prepared on a NiAl(110) single crystal. The particle density, morphology and structure are determined by STM both immediately after preparation and after oxygen adsorption and CO oxidation. The oxygen sticking coefficient and uptake in the temperature regime between 100 and 500 K and the kinetics of the CO oxidation reaction are quantitatively probed by molecular beam techniques. It is found that starting at temperatures below 300 K the Pd particles rapidly incorporate large amounts of oxygen, finally reaching stoichiometries of PdO>0.5. STM shows, that neither the overall particle shape nor the dispersion is affected by the oxygen and CO treatment. Only after saturation of the bulk oxygen reservoir are stable CO oxidation conditions obtained. In the low-temperature regime (<500 K), only the surface oxygen, but not the bulk and subsurface oxygen is susceptible to the CO oxidation. The activation energies for the Langmuir–Hinshelwood step of the CO oxidation reaction were determined both in the regime of high CO coverage and high surface oxygen coverage. A comparison shows that the values are consistent with previous Pd(111) single crystal results. Thus, we conclude that, at least for the particle size under consideration in this study (5.5 nm), the LH activation energies are neither affected by the reduced size nor by the oxygen pretreatment.

Negative electron affinity and electron emission at cesiated GaN and AlN surfaces

The electronic structure of GaN and AlN (0001) surfaces and modification by cesium (Cs) adsorption are investigated via ultra-violet and X-ray photoemission spectroscopy (UPS, XPS) and total yield spectroscopy. The electron affinity (EA) of the clean and ordered 1×1 surfaces is found to be equal to 3.3 and 1.9 eV for GaN and AlN, respectively. Cs adsorption (with the help of oxygen pre-treatment in the case of GaN) reduces EA on both surfaces by about 2.6–2.8 eV, leading to true negative electron affinity (NEA) in the case of AlN and effective NEA in the case of GaN. Total yield spectroscopy confirms NEA on both surfaces.

The Correlation of Subsurface Oxygen Diffusion with Variations of Silver Morphology in the Silver–Oxygen System

Silver undergoes pronounced morphological changes following high-temperature treatment in various gas atmospheres. SEM analysis shows that high-temperature treatment in oxygen leads to pronounced facetting of the silver surface.In situXRD shows a strong texturing of the polycrystalline bulk and an expansion of the unit cell resulting from the dissolution of oxygen. Two distinctly different forms of subsurface oxygen have been identified and the influence of morphological changes on the mechanism leading to their formation clarified. The first of these species is Oβ. It is bulk-dissolved oxygen which diffuses via an interstitial mechanism through low-resistance diffusion paths such as grain boundaries and open crystalline planes. Temperature programmed desorption spectroscopy analysis reveals that high-temperature oxygen pretreatment results in the formation of crystalline surfaces exhibiting different oxygen diffusion barriers. At elevated temperatures, pure thermal reordering dominates over oxygen-induced restructuring of the silver bulk and surface. The near-surface region is, therefore, comprised primarily of close-packed crystalline planes at elevated temperatures. The barrier for interstitialcy diffusion is overcome at temperatures in excess of 923 K, allowing bulk-dissolved, atomic oxygen to (Oβ) segregate into these low-indexed planes. This likely occurs via an interstitialcy diffusion mechanism where oxygen substitutes for silver atoms in the lattice. This oxygen species is referred to here as Oγ. Analysis of ISS depth profiling of silver foils treated under various conditions shows that the diffusion coefficient is a positive function of the oxygen concentration. This is a direct result of the oxygen-induced recrystallization of the silver resulting in a lowered barrier to diffusion.In situXRD shows that oxygen located in octahedral holes of silver preferentially diffuses in the [110] direction. This requires the anisotropic displacement of silver atoms. The resulting strain culminates in a slight expansion of the silver unit cell and the preferential growth of crystals in the shape of needles. STM imaging of the surface shows the macroscopic silver facets to be composed of smaller, columnar crystallites, thus confirming the validity of the model based on the XRD data.

Plasma-modified interfaces between polypropylene films and vacuum roll-to-roll coated thin barrier layers

Vacuum roll-to-roll coating is an important method to improve the functionality of polymer films , especially in flexible packaging applications. The most common coating material is Al, and oxides like SiO x or Al 2 O 3 are used less frequently. The final functionality — as the adhesion and permeation barrier — depends very much on the character or chemical composition of the interface between the substrate film and the coated barrier layer. For polypropylene films, this interface can be modified by different oxygen plasma pretreatments. In order to obtain the systematic correlations between the roll-to-roll pretreatment and the functionality of the roll-to-roll coated films: • plasma conditions were characterized by a quadrupole-type plasma monitor and a Langmuir probe , • untreated and pretreated films were analyzed by atomic force microscopy (AFM), contact angle measurements and X-ray photoelectron spectroscopy (XPS), • films were coated with Al, Al 2 O 3 and SiO x , and finally, • the functionality of the coated films was assessed by peel strength and O 2 permeability measurements. The results can be summarized as follows: • Smoothing of the polymer surface by plasma pretreatment before vacuum coating increases the oxygen barrier of the investigated types of vacuum coated films. • Oxygen plasmas improve the unpolar polypropylene surface by producing oxygen groups. These groups form chemical Al–O–C bonds to vacuum coated aluminum and improve the adhesion of aluminum barrier layers. The oxygen pretreatment does not increase the adhesion of layers from Al 2 O 3 and SiO x to polypropylene any further. • The electrons, ions and UV radiation also present in the oxygen plasma weaken the cohesive strength of the polymer by inner chain scissions . Therefore, the atomic oxygen of the plasma should dominate the pretreatment process.

Hyperbaric oxygen pretreatment attenuates hepatic reperfusion injury.

Microcirculatory derangement, energy depletion and lipid peroxidation have been related to development of ischemia-reperfusion injury in the liver. This study investigates the effects of hyperbaric oxygen (HBO) on hepatic ischemia-reperfusion injury. Adult, male Sprague-Dawley rats were used. Three groups were evaluated: 1) sham-operated control (laparotomy only, no ischemia, no HBO), n=8; 2) ischemia control (1-h ischemia, 2-h reperfusion, no HBO), n=8; and 3) HBO pretreatment (100%, oxygen, 2.5 atm absolute, 90 min) plus ischemia (1-h ischemia, 2-h reperfusion), n=8. An in vivo microscope was used to investigate hepatic microcirculation. Tissue malondialdehyde (MDA) and adenosine triphosphate (ATP) were determined. In comparison with the ischemia control group, HBO significantly improved harmful insults following ischemia-reperfusion. HBO lessened adherent leukocyte count (6.00+/-1.31 cells/200 microm vs 11.38+/-2.88 cells/200 microm), and improved flow velocity (1.72+/-0.26 mm/s vs 0.83+/-0.19 mm/s) in post-sinusoidal venules. HBO also reduced MDA (1.04+/-0.24 nmol/mg protein vs 2.24+/-0.49 micromol/g protein), and increased ATP (2.03+/-0.17 micromol/g wet wt vs 0.73+/-0.11 micromol/g wet wt) levels. This study demonstrates that HBO before ischemia may ameliorate the ischemia-reperfusion injury of the liver in the rat model.

Effect of cocaine, 95% oxygen and ellagic acid on the development and antioxidant status of cultured rat embryos

Prenatal exposure to cocaine has been associated with adverse developmental effects and current data suggest cocaine induced malformations are caused by ischemic-reperfusion injury. This study was undertaken to assess a new in vitro model which uses a routine rat whole embryo culture system that incorporates a change in oxygen status, and to examine the effects of altered oxygen status and pretreatment with ellagic acid (EA), an anti-oxidant, after cocaine exposure. Embryos were evaluated by determining a developmental score and by measuring tissue reduced glutathione (GSH) levels. Following re-oxygenation with 95% O 2 for the last 6 h of culture, embryos treated with cocaine had reduced developmental scores and GSH levels. Embryos treated with cocaine and not re-oxygenated with 95% O 2 did not have reduced developmental scores. EA blocked the effects of cocaine on developmental score and GSH level. These data support ischemia-reperfusion injury as the mechanism of cocaine developmental toxicity.

Infrared chemiluminescence study of the dynamics of steady-state CO oxidation on single-crystal Pd surfaces: effect of oxygen pretreatment

Infrared chemiluminescence has been applied to obtain information on the dynamics of steady-state CO oxidation over well-defined Pd(110) and Pd(111). The dynamics of the CO oxidation is structure sensitive, i.e., the internal energy states (vibration and rotation) of the product CO 2 depend on the surface structure of the reaction sites. Furthermore, the effect of exposures of Pd(110) to high-pressure O 2 (10 −2 Torr) on the internal energy states of the CO 2 was investigated, but the dynamics of CO 2 formation appeared to be the same between clean and oxidized Pd(110) surfaces.