Increased Oxygen Levels Research Articles

ROS sensitive collagen fibers with gradient concentration of MnO2 nanoparticles inhibit annulus fibrosus cell apoptosis.

Event Abstract Back to Event ROS sensitive collagen fibers with gradient concentration of MnO2 nanoparticles inhibit annulus fibrosus cell apoptosis. Christos Tapeinos1, Akshay Srivastava1, Sahana Ganesh1 and Abhay Pandit1 1 National University of Ireland Galway, Center for Research in Medical Devices, Ireland Introduction: The term inflammation is used to characterize a number of biological processes that take place when natural (tissue injury) or pathogenic (microbes, bacteria) factors attack the human body. Inflammation can occur in any tissue and one of the main characteristics of these inflamed tissues is the low levels of oxygen. The hypoxic microenvironment that is created around these inflamed tissues is one of the reasons responsible for the production of ROS. We hypothesize that collagen fibers with concentration gradients of manganese dioxide (MnO2) nanoparticles (NPs) can increase oxygen levels in a control manner through the reaction of MnO2 NPs with hydrogen peroxide (H2O2) resulting in attenuated hypoxia in inflamed tissues. Hence, our specific objective in this study is to fabricate collagen fibers embedded with MnO2 NPs (Fig. 1), with controlled degradability that are able to scavenge H2O2 and generate O2 to inhibit Annulus Fibrosus (AF) cell apoptosis under inflamed condition. Materials and Methods: MnO2 NPs were synthesized using a previously described method[1],[2]. The NPs were characterized structurally (XRD & IR) and morphologically (TEM) and their charge was measured with DLS. The same characterizations applied also on the fibers embedded with the NPs. An oxygen sensor was used to measure the increase in oxygen levels after the reaction of the NPs with various H2O2 concentrations. The NPs were mixed with Type I bovine collagen (3.5 mg/ml) in various concentrations and fibers were synthesized by the fiber extrusion method (Fig. 1A). The degradation profile as well as oxygen levels after reaction with H2O2 were assessed. Cytotoxicity of the NPs and of the fibers embedded with NPs was carried out on 3T3 fibroblast and IL-1β induced inflamed AF cells (Fig. 2D). Changes in the apoptosis rate and intracellular ROS levels in cultured inflamed AF cells were measured by flow cytometry. Results and Discussion: MnO2 NPs were successfully fabricated and embedded inside the collagen fibers in different concentrations creating a gradient along the fibers. Oxygen was generated following the reaction of the NPs with H2O2 (Fig. 2B) and the increase in oxygen was found to be proportional to the nanoparticles’ concentration. In vitro studies on 3T3 fibroblast cells after treatment with H2O2 before and after treatment with MnO2 NPs demonstrated that cells’ metabolic activity is higher after reaction with MnO2, indicating the scavenging effect of the NPs (Fig. 2C). Flow cytometry results showed that MnO2 loaded collagen fibers exhibit increased cell viability, decreased ROS formation and significantly reduced apoptosis. Conclusions: Modified collagen-MnO2 fibers with controlled degradation rates were successfully fabricated. These fibers were able to generate oxygen after treatment with various concentrations of H2O2. In vitro studies demonstrated a subsequent reduction in ROS levels and inflamed AF cell apoptosis after treatment with the modified fibers. Future studieds will involve measuring altered mitochondrial membrane potential of AF cells and molecular markers involved in extracellular matrix production. This publication has emanated from research supported in part by a research grant from Science Foundation Ireland (SFI) and is co-funded under the European Regional Development Fund under Grant Number 13/RC/2073; This material is based upon works supported by the European Union funding under the 7th Framework Programme under Grant Agreement Number 317304

TERAPI OKSIGEN HIPERBARIK SEBAGAI TERAPI TAMBAHAN UNTUK LUKA KAKI DIABET

Gangrenous wounds is one of the chronic complications of diabetes that most feared by every diabetic patient (Tjokroprawiro, 2007). Gangrenous wounds is a condition that begins from the tissue hypoxia where oxygen is reduced, it will affect the activity of vascular and cellular networks, which results in tissue damage (Guyton, 2006). TOHB (Hyperbaric Oxygen Therapy) or Hyperbaric Oxygen Therapy or HBO therapy (Hyperbaric Oxygen) is a way to increase tissue oxygen levels, by reducing the swelling caused by vasoconstriction of blood vessels. At the same time, TOHB also increases oxygen levels in the blood (Neubauer, 1998). Oxygen is expected to penetrate through to the peripheral tissues are deprived of oxygen, so that the supply of nutrients and oxygen are met, so that the network can do metabolism and function (Smeltzer, 2002). Review was conducted at 10 research/article. Search strategy articles by using two ways: manual and online libraries. This search is getting 113 articles, but the total articles reviewed were the 10 articles. 1 studies are case reports and 9 research is experimental research with 5 studies using random techniques. TOHB with adequate doses can have a positive effect on wound healing and reduce the risk of amputation. TOHB beneficial to improve peripheral perfusion and decrease the incidence of major amputation. However, there has been no research on the psychology of the patient.

The importance of integrated solutions to flooding and water quality problems in the tropical megacity of Jakarta

Rapid urbanisation is transforming many urban rivers by affecting their hydraulic conditions and water quality. This process is particularly intense in some areas of the planet, where migratory phenomena and the associated urbanisation pace and conurbation are extreme. In these cases, the lack of water supply and sewerage infrastructures can lead to enormous pressure on urban river corridors, which often implies irreversible pollution of surface waters and shallow aquifers. In this article we address the problem of how integrated planning of urban river corridor management is essential to achieve sustainable solutions and how modern simulation tools can contribute to this effect. This is done by reporting about an exemplary case study, the Ciliwung River flowing through Jakarta, which is highly polluted and floods frequently large areas of the city. Indonesian authorities’ highest priority is to reduce the flood problem but without a clear integrated rehabilitation strategy that accounts for water quality issues. Through field campaigns and model simulations we demonstrate how measures to solve the flood problem can further deplete water quality if the pollution load is not reduced. Results suggest that the current hydraulic river regime produces a benefit for the river health by increasing oxygen levels, natural degradation processes and dilution. A reduction in the average discharge by means of dam construction, as currently considered by the authorities, is likely to increase contamination levels of surface water and shallow aquifer, which is recharged by the river.

Analisis Penentuan Kandungan Gas Oksigen (O2) Fotosintesis Tanaman Gelombang Cinta (Anthuriumsp) Pada Variasi Daya Lampu

Fotositesis research has been done using a light source at the plant by analyzing the oxygen gas is produced. This study aims to determine the effective power light on the photosynthesis of plants. Gas levels of oxygen as a result of photosynthesis can be seen by using a tool-assisted oxygen sensor logger software pro. Plant sample used was a wave of love (Anthurium sp), aged approximately 5 months the number of leaves 4-5 pieces inserted in a tube or jar is closed. Variations lamp power used is 33 watts, 60 watts and 100 watts. Data were collected for 600 seconds for each lamp power. The resulting oxygen levels on photosynthesis recorded using Pro logger software then exported to Microsoft Excel for graphed. The curve is formed can be used to analyze the relationship between oxygen levels with time at each power lights are used. After curve fitting the data to form done by creating a line equation and R2 to analyze the most effective lamp power to increase the rate of photosynthesis. In this study showed that the greater the power of the lamp, the oxygen levels increased. Increased levels of oxygen means that the amount of oxygen produced during photosynthesis is greater than the amount of oxygen used for respiration. From the comparison of the three lights that have different power and graphed equation of the line, turns on the use lamps with power 66 watt and 100 watt having the largest gradient is 0.001. Mean increase in oxygen levels on both the power of this light is very large, while the gradient equation of a line on the lights with 33 watt power is the same, namely 0.0001. Comparison between the use of power 66 watt lamp has a gradient of 0.001, while the 100-watt power gradient 0.0011 has so increased oxygen levels is the most effective at 100 watts of power. R2 at 66 watts power is 100 watts of power 0.9535 while 0.9899. The conclusion for this study were 1) the greater power of the lights then the higher the rate of photosynthesis, and effective lamp power is 100 watts.

Analisis Penentuan Kandungan Gas Oksigen (O2) Fotosintesis Tanaman Gelombang Cinta (Anthuriumsp) Pada Variasi Daya Lampu

Fotositesis research has been done using a light source at the plant by analyzing the oxygen gas is produced. This study aims to determine the effective power light on the photosynthesis of plants. Gas levels of oxygen as a result of photosynthesis can be seen by using a tool-assisted oxygen sensor logger software pro.Plant sample used was a wave of love (Anthurium sp), aged approximately 5 months the number of leaves 4-5 pieces inserted in a tube or jar is closed. Variations lamp power used is 33 watts, 60 watts and 100 watts. Data were collected for 600 seconds for each lamp power. The resulting oxygen levels on photosynthesis recorded using Pro logger software then exported to Microsoft Excel for graphed. The curve is formed can be used to analyze the relationship between oxygen levels with time at each power lights are used. After curve fitting the data to form done by creating a line equation and R2 to analyze the most effective lamp power to increase the rate of photosynthesis.In this study showed that the greater the power of the lamp, the oxygen levels increased. Increased levels of oxygen means that the amount of oxygen produced during photosynthesis is greater than the amount of oxygen used for respiration. From the comparison of the three lights that have different power and graphed equation of the line, turns on the use lamps with power 66 watt and 100 watt having the largest gradient is 0.001. Mean increase in oxygen levels on both the power of this light is very large, while the gradient equation of a line on the lights with 33 watt power is the same, namely 0.0001. Comparison between the use of power 66 watt lamp has a gradient of 0.001, while the 100-watt power gradient 0.0011 has so increased oxygen levels is the most effective at 100 watts of power. R2 at 66 watts power is 100 watts of power 0.9535 while 0.9899. The conclusion for this study were 1) the greater power of the lights then the higher the rate of photosynthesis, and effective lamp power is 100 watts.

Using live algae at the anode of a microbial fuel cell to generate electricity.

Live green microalgae Chlorella pyrenoidosa was introduced in the anode of a microbial fuel cell (MFC) to act as an electron donor. By controlling the oxygen content, light intensity, and algal cell density at the anode, microalgae would generate electricity without requiring externally added substrates. Two models of algal microbial fuel cells (MFCs) were constructed with graphite/carbon electrodes and no mediator. Model 1 algal MFC has live microalgae grown at the anode and potassium ferricyanide at the cathode, while model 2 algal MFC had live microalgae in both the anode and cathode in different growth conditions. Results indicated that a higher current produced in model 1 algal MFC was obtained at low light intensity of 2500 lx and algal cell density of 5 × 10(6) cells/ml, in which high algal density would limit the electricity generation, probably by increasing oxygen level and mass transfer problem. The maximum power density per unit anode volume obtained in model 1 algal MFC was relatively high at 6030 mW/m(2), while the maximum power density at 30.15 mW/m(2) was comparable with that of previous reported bacteria-driven MFC with graphite/carbon electrodes. A much smaller power density at 2.5 mW/m(2) was observed in model 2 algal MFC. Increasing the algal cell permeability by 4-nitroaniline would increase the open circuit voltage, while the mitochondrial acting and proton leak promoting agents resveratrol and 2,4-dinitrophenol would increase the electric current production in algal MFC.

Telemetry‐based Recording of Renal Cortex Oxygenation During Endogenous RAS Activation: Preliminary Observations

Upon feeding of the food additive indole‐3‐carbinol (I3C) the liver of Cyp1A1Ren2 transgenic rats produces high levels of renin which leads to hypertension and tissue damage in the kidney. We hypothesized that endogenous RAS activation in this model would be associated with renal hypoxia. Using a new technology that enables the telemetric recording of intra‐renal tissue oxygen pressure (PO2) in conscious, free roaming animals, we here report preliminary observations on renal cortical PO2 changes during endogenous RAS activation. 1 week after implantation of the electrodes the relative change in renal cortex PO2 during bouts of 3 days of endogenous activation of RAS by feeding an 0.3% or 0.6% I3C containing diet (n=5) were recorded. 3±2 days after start of the 0.6% I3C diet, s.c. bolus infusions of valsartan/losartan (20/30 mg/kg) were administered. During 0.3% and 0.6% I3C feeding, renal PO2 levels fell to 75±7 and 63±13% from baseline values (mean±SD), with a nadir after 25±5 hours. Exogenous blockade of the angiotensin‐II receptor increased oxygen levels within 14±3 min to 98±38% of baseline values (mean±SD). These data suggest that oxygen levels in the renal cortex decrease rapidly during the onset of endogenous RAS hyperactivation. The effect is mediated by AT1‐receptor activation and may precede the known development of systemic hypertension and renal injury in this model.

Deep-tissue oxygen monitoring in the brain of rabbits for stroke research.

The primary event in the ischemic stroke is a rapid decline in the oxygen levels after the loss of blood flow in specific areas of the brain. Subsequent pathological processes results in a central core area of severely ischemic tissue surrounded by a region of moderate ischemic tissue (penumbra) with a preserved cellular metabolism. The outcome of an ischemic stroke depends on the size of the infarct core and the potential to salvage the cells in the penumbra, which is hypoperfused, and therefore, at risk of infarction but still viable. Such viable penumbral tissue can be rescued by quick interventions that can increase oxygen levels or slow metabolism in the ischemic area to minimize oxidative injury on reperfusion. Several strategies have been investigated to rescue ischemic tissue using experimental models, especially rodents, but largely failed in subsequent clinical trials. The rabbit model of ischemic stroke using embolic clot is a promising model for developing effective strategies. This model first led to the prediction of the clinical response of recombinant tissue-type plasminogen activator to restore blood flow in patients.1 The drug is currently recommended for administration within 3 hours for best outcomes and has also shown modest benefit when administered within 4.5 to 6 hours of clinical onset.2 The rabbit model of embolic clot is now considered as a pertinent model for translational research by the Stroke Therapy Academic Industry Roundtable recommendations.3 To rationally develop effectual therapies, it is important to understand the effect of ischemic stroke on oxygen levels (partial pressure of oxygen [pO2]) in the regions directly affected by the pathology, as well as contralateral regions of the rabbit brain. The potential changes in tissue po2 of contralateral regions may provide crucial information on adaptive response, if any, of the brain …

Captive rearing of the deep-sea coral Eguchipsammia fistula from the Red Sea demonstrates remarkable physiological plasticity.

The presence of the cosmopolitan deep-sea coral Eguchipsammia fistula has recently been documented in the Red Sea, occurring in warm (>20 °C), oxygen- and nutrient-limited habitats. We collected colonies of this species from the central Red Sea that successfully resided in aquaria for more than one year. During this period the corals were exposed to increased oxygen levels and nutrition ad libitum unlike in their natural habitat. Specimens of long-term reared E. fistula colonies were incubated for 24 h and calcification (G) as well as respiration rates (R) were measured. In comparison to on-board measurements of G and R rates on freshly collected specimens, we found that G was increased while R was decreased. E. fistula shows extensive tissue growth and polyp proliferation in aquaculture and can be kept at conditions that notably differ from its natural habitat. Its ability to cope with rapid and prolonged changes in regard to prevailing environmental conditions indicates a wide physiological plasticity. This may explain in part the cosmopolitan distribution of this species and emphasizes its value as a deep-sea coral model to study mechanisms of acclimation and adaptation.

Real-time effects of insulin-induced hypoglycaemia on hippocampal glucose and oxygen

The hippocampus plays a vital role in learning and memory and is susceptible to damage following hypoglycaemic shock. The effect of an acute administration of insulin on hippocampal function has been described in terms of behavioural deficits but its effect on hippocampal oxygen and glucose is unclear. Glucose oxidase biosensors (detecting glucose) and carbon paste electrodes (detecting oxygen) were implanted into the hippocampus of Sprague Dawley rats. Animals were allowed to recover and real-time recordings were made in order to determine the effects of fasting, insulin administration (15U/kg; i.p.) and reintroduction of food on hippocampal oxygen and glucose. Fasting caused a significant decrease in hippocampal glucose over the course of 24h. Insulin administration produced a significant decrease in hippocampal glucose along with a significant increase in hippocampal oxygen. Finally, the reintroduction of food resulted in glucose levels significantly increasing along with a transient but significant increase in oxygen levels. The findings presented here suggest that even a single acute period of hypoglycaemia may substantially disrupt hippocampal oxygen and glucose and therefore affect hippocampal function.

An Investigation into Improving the Germination Rates of Aloe Polyphylla Schönland Ex Pillans

A germination technique trial was carried out to improve the germination of Aloe polyphylla Schönland ex Pillans (common name spiral aloe). These germination trials involved different media and temperatures, increased oxygen levels, and light and dark environments. The best results (90% germination) were obtained by vernalising the seeds for two weeks and then placing them in a sunny, but not bright, area with varying temperatures on a water-based medium of either 10% recommended fertiliser solution or in distilled water.The germination of Aloe polyphylla was also compared to three other species in the genus: A. branddraaiensis Groenew, A. castanea Schönl and A. elegans Tod.. The results from this trial showed that, like A. polyphylla, these species can also germinate in water-based media.The success of finding the key requirements for germination show that techniques of this type are important methods for conserving this threatened species and can also be a useful propagation tool for the horticulture industry. The lack of research on this plant highlights the importance of this work for conserving this spectacular species which is listed as Vulnerable in the International Union for Conservation of Nature (IUCN) Plant Red Data list and is registered on the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

Effects of ecological engineered oxygenation on the bacterial community structure in an anoxic fjord in western Sweden.

Oxygen-depleted bodies of water are becoming increasingly common in marine ecosystems. Solutions to reverse this trend are needed and under development, for example, by the Baltic deep-water OXygenation (BOX) project. In the framework of this project, the Swedish Byfjord was chosen for a pilot study, investigating the effects of an engineered oxygenation on long-term anoxic bottom waters. The strong stratification of the water column of the Byfjord was broken up by pumping surface water into the deeper layers, triggering several inflows of oxygen-rich water and increasing oxygen levels in the lower water column and the benthic zone up to 110 μmol l(-1).We used molecular ecologic methods to study changes in bacterial community structure in response to the oxygenation in the Byfjord. Water column samples from before, during and after the oxygenation as well as from two nearby control fjords were analyzed. Our results showed a strong shift in bacterial community composition when the bottom water in the Byfjord became oxic. Initially dominant indicator species for oxygen minimum zones such as members of the SUP05 clade declined in abundance during the oxygenation event and nearly vanished after the oxygenation was accomplished. In contrast, aerobic species like SAR11 that initially were restricted to surface waters could later be detected deep into the water column. Overall, the bacterial community in the formerly anoxic bottom waters changed to a community structure similar to those found in oxic waters, showing that an engineered oxygenation of a large body of anoxic marine water is possible and emulates that of a natural oxygenation event.

On interlayer stability and high-cycle simulator performance of diamond-like carbon layers for articulating joint replacements.

Diamond like carbon (DLC) coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the orthopaedic field, layer performance, stability and adhesion in physiologically relevant setups are crucial and not consistently investigated. In vitro wear testing as well as adequate corrosion tests of interfaces and interlayers are of great importance to verify the long term stability of DLC coated load bearing implants in the human body. DLC coatings were deposited on articulating lumbar spinal disks made of CoCr28Mo6 biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD) process. As an adhesion promoting interlayer, tantalum films were deposited by magnetron sputtering. Wear tests of coated and uncoated implants were performed in physiological solution up to a maximum of 101 million articulation cycles with an amplitude of ±2° and −3/+6° in successive intervals at a preload of 1200 N. The implants were characterized by gravimetry, inductively coupled plasma optical emission spectrometry (ICP-OES) and cross section scanning electron microscopy (SEM) analysis. It is shown that DLC coated surfaces with uncontaminated tantalum interlayers perform very well and no corrosive or mechanical failure could be observed. This also holds true in tests featuring overload and third-body wear by cortical bone chips present in the bearing pairs. Regarding the interlayer tolerance towards interlayer contamination (oxygen), limits for initiation of potential failure modes were established. It was found that mechanical failure is the most critical aspect and this mode is hypothetically linked to the α-β tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD). It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs. ceramic.

The Cenomanian–Turonian Eagle Ford Group of South Texas: Insights on timing and paleoceanographic conditions from geochemistry and micropaleontologic analyses

The interbedded organic-rich marls and limestones of the Eagle Ford Group of South Texas were deposited on the shelf of the Central Texas Platform during the upper Cenomanian through the Turonian. Micropaleontological analyses of thin-sections and residue samples from subsurface cores taken in Atascosa and Karnes counties yielded 13 biostratigraphic datums, which were integrated with calcareous nannofossil datums, stable carbon isotopic and bulk inorganic geochemical analysis to gain an understanding of the paleoceanographic conditions of the study area and their relationship to regional and global events. The paired thin-section/residue sampling was necessitated by poor recovery of planktonic foraminifera in washed samples, which were, however, abundant in most thin-sections. Lower Eagle Ford marls were deposited under euxinic conditions produced by a stratified water column. Periodic enhanced water column mixing increased oxygen levels and surface-water primary productivity, which promoted calcite diagenesis and generation of limestones containing calcispheres and radiolaria. An oxygenated bottom water mass entered the basin in the uppermost Cenomanian prior to the onset of Oceanic Anoxic Event (OAE) 2, causing a spike in benthic foraminiferal diversity and decreasing preservation of organic matter. Although the lower portion of the upper Eagle Ford is age-equivalent to OAE2 as indicated by positive shift in δ13Corg, it contains less organic matter and evidence of more oxygen than the lower Eagle Ford, so deposition of the Eagle Ford black shales is not contemporaneous to OAE2.

SU‐E‐I‐84: MRI Relaxation Properties of a Pre‐Clinical Hypoxia‐Sensitive MRI Contrast Agent

Purpose:A possible hypoxia‐sensitive MRI agent, hexamethyldisiloxane (HMDSO), has been tried to image oxygen level in proton‐based MRI (Kodibagkar et al, NMR Biomed, 2008). The induced changes of T1 (or R1) value by the HMDSO as the oxygenation level changes are the principle that the hypoxia agent is based on: the R1 increases as the oxygen level increases. However, as reported previously, the range of R1 values (0.1–0.3 s‐1, corresponding to 3–10 s of T1) is not in the range where a regular MRI technique can easily detect the change. In order for this agent to be widely applied in an MRI environment, more relaxation properties of this agent, including T1 in the rotating frame (T1rho) and T2, need to be explored. Here, the relaxation properties of this agent are explored.Methods:A phantom was made with HMDSO, water and mineral oil, each of which was prepared with oxygen and nitrogen, and was imaged in a 3T MRI system. The T1 properties were explored by the inversion recovery (TR=3000ms, TE=65ms) while varying the inversion time (TI), and also by the fast‐field‐echo (TR=2 ms, TE=2.8ms) while varying the flip angle (FA). T1rho was explored with a 5‐pulse spin‐locking technique (TR=5000ms, TE=10ms, spin‐lock field=500Hz) while varying the spin‐lock duration. T2 was explored with multi‐shot TSE (TR=2500ms) while varying TE.Results:With the variable FA and TI, the signals of HMDSO with oxygen and nitrogen change in a similar way and do not respond well by the change of oxygen level, which confirms the large T1 value of HMDSO. The T1rho and T2, however, have a better sensitivity.Conclusion:For the possible pre‐clinical hypoxia MRI agent (HMDSO), the detection of T1 (or R1) changes may be more challenging than the detection of other relaxation properties, particularly T2, as the oxygen level changes.

Preserve the (intraocular) environment: the importance of maintaining normal oxygen gradients in the eye

Oxygen levels in the eye are generally low and tightly regulated. Oxygen enters the eye largely by diffusion from retinal arterioles and through the cornea. In intact eyes, oxygen from the retinal arterioles diffuses into the vitreous body. There is a decreasing oxygen gradient from the retina to the lens, established by oxygen consumption by ascorbate in the vitreous fluid and lens metabolism. Age-related degeneration of the vitreous body or removal during vitrectomy exposes the posterior of the lens to increased oxygen, causing nuclear sclerotic cataracts. Lowering oxygen in the vitreous, as occurs in patients with ischemic diabetic retinopathy, protects against cataracts after vitrectomy. Vitrectomy and cataract surgery increase oxygen levels at the trabecular meshwork and with it the risk of open angle glaucoma. Two additional risk factors for glaucoma, African heritage and having a thinner cornea, are also associated with increased oxygen in the anterior chamber angle. Preservation of the vitreous body and the lens, two important oxygen consumers, would protect against nuclear sclerotic cataracts and open angle glaucoma. Delaying removal of the lens for as long as possible after vitrectomy would be an important step in delaying ocular hypertension and glaucoma progression.

Isotope evolution in the HIMU reservoir beneath St. Helena: Implications for the mantle recycling of U and Th

HIMU (high-μ; 238U/204Pb) is a mantle reservoir that has been thought to form by subduction and subsequent storage of ancient oceanic crust and lithosphere in the mantle. In order to constrain the processes that acted on subducted materials over several billion years, we present precise Pb–Sr–Nd–Hf–He isotopic data together with 40Ar/39Ar and K/Ar ages of HIMU lavas from St. Helena in the Atlantic. Clinopyroxene separates were analyzed together with whole-rock samples to better describe the geochemical characteristics of the HIMU component. Although isotopic variations are small in the St. Helena lavas (20.6–21.0 for 206Pb/204Pb) between 12 and 8Ma, the younger lavas have more HIMU-like isotopic compositions than the older lavas. The mixing arrays defined by these lavas are remarkably similar to those observed in HIMU lavas from Austral Islands in the Pacific, suggesting that the two HIMU reservoirs located in different mantle domains are characterized by similar isotopic compositions with radiogenic 206Pb/204Pb and 208Pb/204Pb, enriched Nd and Hf isotopes, depleted Sr isotopes, and radiogenic 3He/4He. However, there is a significant difference between the St. Helena and Austral Islands lavas in 207Pb/204Pb. The St. Helena lavas show systematically higher 207Pb/204Pb for a given 206Pb/204Pb. Lead isotope evolution models suggest that both HIMU reservoirs formed around 2Ga; however, the HIMU reservoir for St. Helena is about 0.3Ga older than that for Austral Islands. The relation between 206Pb/204Pb and 208Pb/204Pb could reflect the time-integrated κ (232Th/238U) in the components. The HIMU components for St. Helena and Austral Islands have κ values between 3.3 and 3.7, which are intermediate between the present-day fresh mid-ocean ridge basalts (MORB; 2.6–3.2) and the chondritic silicate Earth (∼4). This is consistent with the model that the HIMU precursor is subducted oceanic crust created around 2Ga from depleted upper mantle, in which κ monotonously decreased from the chondritic to the present-day values since late Archean or early Proterozoic, because of enhanced U recycling from the Earth’s surface back to the mantle in response to the increasing oxygen levels in the hydrosphere. Moreover, the fact that the HIMU components have much higher κ than the present-day hydrothermally altered MORB (0.2–2) suggests that either the HIMU precursor was an unaltered ancient oceanic crust, or more likely, an altered oceanic crust with minimal U enrichment by hydrothermal fluids in the less oxic marine environment of the late Archean or early Proterozoic. The unradiogenic 87Sr/86Sr of the HIMU components also suggests formation of ancient oceanic crust altered with hydrothermal fluids having much lower 87Sr/86Sr in that eon than at present, followed by removal of Rb from it by subduction dehydration.

Aeration remediation of a polluted waterway increases near-surface coarse and culturable microbial aerosols

Aeration remediation is currently used in polluted urban waterways to increase oxygen levels in the water column. Recent studies have provided increasing evidence that the bursting of bubbles at water surfaces introduced by aeration, or other surface disturbances, can transfer viable bacteria to the air. In heavily sewage-polluted waterways these water-originated bacterial aerosols may pose as a health risk to recreators in small boats or residents inhabiting the shoreline. Nonetheless, few studies have explored aerosols above active aeration remediation projects in waterways or investigated how bacterial aerosols change with vertical distance from aeration activities. This study, conducted at the Newtown Creek superfund site in Brooklyn, NY, USA, measured coarse aerosol particles and culturable bacteria in near-surface air above waters undergoing aeration remediation. Regardless of aeration operation culturable bacterial fallout was greater near-surface (0.6m above water) than previously-reported measurements made at 2.5m. Molecular analysis of the 16S rRNA gene sequences from isolated bacteria demonstrates that water and air shared a large number of bacterial genera and that the genera present in the near-surface aerosols (0.6m) contained water-associated Vibrio and Caulobacter, which were not present at 2.5m, despite the smaller sequence library size from the near-surface. Also, the near-surface microbial assemblage had significantly greater association with sequences detected previously in aquatic environments compared to the 2.5m library. We found compelling evidence that aeration activity contributed to this vertical gradient in bacterial aerosol concentrations and identity. Similar to results from 2.5m, concentrations of near-surface respirable coarse aerosols (<10 um) increased significantly when aeration was occurring. Culturable bacterial aerosol fallout was also greater near-surface when the aerator was on compared to simultaneous measurements made at 2.5m. Furthermore, when the aerator was operating, the near-surface bacterial aerosol assemblage was statistically more similar to water assemblages than when the aerator was off. These findings highlight the potential for aeration remediation to increase exposure to viable bacterial aerosols in recreators (e.g. kayakers), a problem of greater concern where surface water is heavily polluted with sewage, as in Newtown Creek.

Causes and consequences of the Cambrian explosion

The Cambrian explosion has long been a basic research frontier that concerns many scientific fields. Here we discuss the cause-effect links of the Cambrian explosion on the basis of first appearances of animal phyla in the fossil record, divergence time, environmental changes, Gene Regulatory Networks, and ecological feedbacks. The first appearances of phyla in the fossil record are obviously diachronous but relatively abrupt, concentrated in the first three stages of the Cambrian period (541–514 Ma). The actual divergence time may be deep or shallow. Since the gene regulatory networks (GRNs) that control the development of metazoans were in place before the divergence, the establishment of GRNs is necessary but insufficient for the Cambrian explosion. Thus the Cambrian explosion required environmental triggers. Nutrient availability, oxygenation, and change of seawater composition were potential environmental triggers. The nutrient input, e.g., the phosphorus enrichment in the environment, would cause excess primary production, but it is not directly linked with diversity or disparity. Further increase of oxygen level and change of seawater composition during the Ediacaran-Cambrian transition were probably crucial environmental factors that caused the Cambrian explosion, but more detailed geochemical data are required. Many researchers prefer that the Cambrian explosion is an ecological phenomenon, that is, the unprecedented ecological success of metazoans during the Early Cambrian, but ecological effects need diverse and abundant animals. Therefore, the establishment of the ecological complexity among animals, and between animals and environments, is a consequence rather than a cause of the Cambrian explosion. It is no doubt that positive ecological feedbacks could facilitate the increase of biodiversity. In a word, the Cambrian explosion happened when environmental changes crossed critical thresholds, led to the initial formation of the metazoan-dominated ecosystem through a series of knock-on ecological processes, i.e., “ecological snowball” effects.

The medical use of oxygen: a time for critical reappraisal

Oxygen treatment has been a cornerstone of acute medical care for numerous pathological states. Initially, this was supported by the assumed need to avoid hypoxaemia and tissue hypoxia. Most acute treatment algorithms, therefore, recommended the liberal use of a high fraction of inspired oxygen, often without first confirming the presence of a hypoxic insult. However, recent physiological research has underlined the vasoconstrictor effects of hyperoxia on normal vasculature and, consequently, the risk of significant blood flow reduction to the at-risk tissue. Positive effects may be claimed simply by relief of an assumed local tissue hypoxia, such as in acute cardiovascular disease, brain ischaemia due to, for example, stroke or shock or carbon monoxide intoxication. However, in most situations, a generalized hypoxia is not the problem and a risk of negative hyperoxaemia-induced local vasoconstriction effects may instead be the reality. In preclinical studies, many important positive anti-inflammatory effects of both normobaric and hyperbaric oxygen have been repeatedly shown, often as surrogate end-points such as increases in gluthatione levels, reduced lipid peroxidation and neutrophil activation thus modifying ischaemia-reperfusion injury and also causing anti-apoptotic effects. However, in parallel, toxic effects of oxygen are also well known, including induced mucosal inflammation, pneumonitis and retrolental fibroplasia. Examining the available 'strong' clinical evidence, such as usually claimed for randomized controlled trials, few positive studies stand up to scrutiny and a number of trials have shown no effect or even been terminated early due to worse outcomes in the oxygen treatment arm. Recently, this has led to less aggressive approaches, even to not providing any supplemental oxygen, in several acute care settings, such as resuscitation of asphyxiated newborns, during acute myocardial infarction or after stroke or cardiac arrest. The safety of more advanced attempts to deliver increased oxygen levels to hypoxic or ischaemic tissues, such as with hyperbaric oxygen therapy, is therefore also being questioned. Here, we provide an overview of the present knowledge of the physiological effects of oxygen in relation to its therapeutic potential for different medical conditions, as well as considering the potential for harm. We conclude that the medical use of oxygen needs to be further examined in search of solid evidence of benefit in many of the current clinical settings in which it is routinely used.