Hypoxic cells in tumors are proposed to consist of at least 2 types, depending on whether they remain hypoxic for long (chronic hypoxia) or short (acute hypoxia) periods. Experimental evidence of the possible presence ofacutely-hypoxic cells in one type of murine tumour is presented. Finally, the possible implications for radiotherapy and chemotherapy of the presence of acutely-hypoxic cells in human tumors is discussed briefly.
A settlement of Temiars, an aboriginal tribe residing in the north-eastern jungles of the Malay Peninsula, was selected for a study of their cardiorespiratory fitness. A step-test was used to elicit the Vo2max, V E max and HR max in a group of 19 boys aged 12 to 18 years and 6 men aged 19 - 40 years. The mean VO2max of the boys was found to be 45.9 +/- 6.9 ml-kg-1-min-1 compared with 45.6 +/- 5.4 ml-kg-1-min-1 for the men. The mean V E max, HR max and blood lactate levels were found to be 65.5 +/- 11.31/min and 69.2 +/- 23.71/min; 194 +/- 8 beats/min and 186 +/- 10 beats/min; and 79.8 +/- 13.4 mg% and 97.7 +/- 33.4 mg% respectively. These results are comparable to those obtained in urban populations as well as those found in other primitive communities. Telemetric monitoring of the routine daily physical activity of the men revealed that these jungle dwellers rarely tax their oxygen transport systems in their daily living and their cardiorespiratory functions were similar to communities who do not specifically train for physical fitness.
Campylobacter jejuni survival in aerobic environments has been suggested to be mediated by biofilm formation. Biofilm formation by eight C. jejuni strains under both aerobic and microaerobic conditions in different broths (Mueller-Hinton (MH), Bolton and Brucella) was quantified. The dissolved oxygen (DO) content of the broths under both incubation atmospheres was determined. Biofilm formation for all strains was highest in MH broth under both incubation atmospheres. Four strains had lower biofilm formation in MH under aerobic as compared to microaerobic incubation, while biofilm formation by the other four strains did not differ under the 2 atm. Two strains had higher biofilm formation under aerobic as compared to microaerobic atmospheres in Bolton broth. Biofilm formation by all other strains in Bolton, and all strains in Brucella broth, did not differ under the 2 atm. Under aerobic incubation DO levels in MH > Brucella > Bolton broth. Under microaerobic conditions levels in MH = Brucella > Bolton broth. Levels of DO in MH and Brucella broth were lower under microaerobic conditions but those of Bolton did not differ under the 2 atm. Experimental conditions and especially the DO of broth media confound previous conclusions drawn about aerobic biofilm formation by C. jejuni.
Palm oil-based Trimethylolpropane ester (TMP ester), with an iodine value of 66.4 g/100g, was epoxidizedto produce epoxidized TMP esters. In situ epoxidation method was used with peracetic acid to eliminatefatty acid double bonds in palm oil-based TMP ester and change it into oxirane ring. This was done toimprove the oxidative stability of trimethylolpropane ester which is a key concern limiting the usefulservice life in lubricants. The epoxidation was performed by reacting acetic acid as active oxygen carrierwith concentrated hydrogen peroxide as oxygen donor and a small amount of homogeneous catalyst(sulphuric acid). The effects of various parameters on the rate of epoxidation (such as the ratio of moleacetic acid to ethylenic unsaturation, hydrogen peroxide to ethylenic unsaturation and acetic acid moleratio, and amount of catalyst) were studied. The rate of oxidation was investigated by the percentageof oxirane oxygen analysis and iodine value.
Matched MeSH terms: Oxygen; Reactive Oxygen Species
Throughout the cryopreservation process, plants were exposed to a series of
abiotic stresses such as desiccation and osmotic pressure due to highly concentrated
vitrification solution. Abiotic stress stimulates the production of reactive oxygen species
(ROS) which include hydrogen peroxide, superoxide radicals, and singlet oxygen. Higher
production of ROS may lead to oxidative stress which contributes to the major injuries in
cryopreserved explants. Antioxidant enzymes in plant such as ascorbate peroxidase
(APX) can protect plants from cell damage by scavenging the free radicals. This study was
determined based on APX enzyme activity of Aranda Broga Blue orchid’s protocorm-like
bodies (PLBs) in response to PVS2 (Plant Vitrification Solution 2) cryopreservation
treatments at different stages. PLBs that were precultured at 0.25 M sucrose for 3 days
were subjected to vitrification cryopreservation method. Results obtained showed that the
highest APX activity was achieved at PVS2 cryoprotectant treatment prior liquid nitrogen
(LN) storage. This phenomenon indicating that accumulation of osmotic and dehydrating
stress throughout the cryopreservation treatment resulted in oxidative burst which in turn
leads to higher APX activity in order to control the excess production of ROS. To
conclude, PVS2 treatment was revealed as the most detrimental step throughout
cryopreservation treatment. Thus, this research also suggested that exogenous
antioxidant such as ascorbic acid can be added throughout cryopreservation procedure
especially at PVS2 treatment in the future experiments to aid in regrowth of cryopreserved
explants by reducing oxidative stress.
Matched MeSH terms: Reactive Oxygen Species; Singlet Oxygen
The performance of modified anaerobic inclining-baffled reactor (MAI-BR) treating recycled paper mill effluent (RPME) was investigated by varying the influent chemical oxygen demand (CODin) concentration from 1000 to 4000 mg/L, and the hydraulic retention time (HRT) from 3 to 1 day, corresponding to an organic loading rate increase from 0.33 to 4 g COD/L day. Throughout 126 days of operation, a maximum removal efficiency of up to 96% of chemical oxygen demand (COD) and 99% of biological oxygen demand, methane (CH4) yield of 0.259 L CH4/g COD, and a stable effluent pH of 6.5 were achieved. Furthermore, the compartmental performance showed that most of the organic substrates were removed in the initial two compartments, resulting in low pH and alkalinity levels and a high concentration of volatile fatty acids. Overall, the results showed that the MAI-BR successfully treated RPME, and the performance was affected by the variation of HRT more than the CODin.
Sabah in Malaysian Borneo is among the Malaysian states which reported a high number of detected COVID-19 cases during the current pandemic. Due to geographical challenges and limited resources, clinicians developed novel strategies for managing patients. The use of a dual oxygen concentrator system for mechanical ventilation is one of the innovations developed by retrieval team members from the Emergency Department (ED) of the Sabah Women and Children's Hospital. Due to conditions requiring isolation of patients suspected of or positive for COVID-19, high-risk patients were treated in an ED extension area that lacked central wall oxygen. Direct access to oxygen tanks became the only viable option, but ensuring a continuous supply was laborious. The novel setup described within this paper has been used on intubated patients in the ED extension area with moderate to high ventilator settings successfully. This simple setup, designed to meet the limited resources within a pandemic environment, needed only a turbine-driven ventilator, two oxygen concentrators, a 3-way connector, and three oxygen tubing. The application of this setup could potentially save more critically ill patients who are being managed in resource-limited conditions such as in smaller district hospitals or out in the field.
Training at high altitude for prolonged periods can cause low oxygen tension which can developed complication of hypoxia. Hypoxia is a cascade activity from a level of down regulation and function of cell’s nucleus. Early detection of biomarker and physiological changes are important in prevent the hypoxia at high altitude. Hyperbaric medicine is a new treatment that were used an oxygen therapy to treat hypoxic and inflammatory driven conditions which patients are treated with 100% oxygen at pressure greater than atmospheric pressure. The review discusses physiological changes associated with hypoxia, the response of biomarker hypoxia changes in high altitude and the role of hyperbaric oxygen therapy can play as part of the treatment for pilots and athletes training at high altitudes that suffering from disease with underlying hypoxia.
Hemodynamic monitoring provides us with refined details about the cardiovascular system. In spite of increased availability of the monitoring process and monitoring equipment, hemodynamic monitoring has not significantly improved survival outcome. Care providers should be cognizant of the role of the cardiovascular system and its importance in oxygen delivery to the cells in order to sustain life. Effective hemodynamic monitoring should be able to delineate how well the system is performing in carrying out this role. Different hemodynamic monitors serve in this role to a different extent; some provide very little information on this. The cardiovascular system is only one of the many systems that need to function optimally for survival; others of equal importance include the integrity of the airway, the breathing process, the adequacy of hemoglobin level, and the health of the tissue bed, especially in the brain and the heart. Advances in hemodynamic monitoring with focus on oxygen delivery at the cellular level may ultimately provide the edge to effective monitoring that can impact outcome.
A study has been carried out to define the effect of drastic temperature changes on the performance of lab-scale hollow-fibre MBR in treating municipal wastewater at a flux of 10 L m(-2) h(-1) (LMH). The objectives of the study were to estimate the activated sludge properties, the removal efficiencies of COD and NH(3)-N and the membrane fouling tendency under critical conditions of drastic temperature changes (23, 33, 42 & 33 °C) and MLSS concentration ranged between 6,382 and 8,680 mg/L. The study exhibited that the biomass reduction, the low sludge settleability and the supernatant turbidity were results of temperature increase. The temperature increase led to increase in SMP carbohydrate and protein, and to decrease in EPS carbohydrate and protein. The BRE of COD dropped from 80% at 23 °C to 47% at 42 °C, while the FRE was relatively constant at about 90%. Both removal efficiencies of NH(3)-N trended from about 100% at 33 °C to less than 50% at 42 °C. TMP and BWP ascended critically with temperature increase up to 336 and 304 mbar respectively by the end of the experiment. The values of suspended solids (SS) and the turbidity in the final effluent were negligible. The DO in the mixed liquor was varying with temperature change, while the pH was within the range of 6.7-8.3.
Glycolipids form materials of considerable potential for a wide range of surfactant and thin film applications. Understanding the effect of glycolipid covalent structure on the properties of their thermotropic and lyotropic assemblies is a key step toward rational design of new glycolipid-based materials. Here, we perform molecular dynamics simulations of anhydrous bilayers of dodecyl β-maltoside, dodecyl β-cellobioside, dodecyl β-isomaltoside, and a C(12)C(10) branched β-maltoside. Specifically, we examine the consequences of chain branching and headgroup identity on the structure and dynamics of the lamellar assemblies. Chain branching of the glycolipid leads to measurable differences in the dimensions and interactions of the lamellar assembly, as well as a more fluid-like hydrophobic chain region. Substitution of the maltosyl headgroup of βMal-C(12) by an isomaltosyl moiety leads to a significant decrease in bilayer spacing as well as a markedly altered pattern of inter-headgroup hydrogen bonding. The distinctive simulated structures of the two regioisomers provide insight into the difference of ~90 °C in their observed clearing temperatures. For all four simulated glycolipid systems, with the exception of the sn-2 chain of the branched maltoside, the alkyl chains are ordered and exhibit a distinct tilt, consistent with recent crystallographic analysis of a branched chain Guerbet glycoside. These insights into structure-property relationships from simulation provide an important molecular basis for future design of synthetic glycolipid materials.
Biochemical oxygen demand (BOD) of the leachates originally from the different types of landfill sites was studied based on the data measured using the two manometric methods. The measurements of BOD using the dilution method were carried out to assess the typical physicochemical and biological characteristics of the leachates together with some other parameters. The linear regression analysis was used to predict rate constants for biochemical reactions and ultimate BOD values of the different leachates. The rate of a biochemical reaction implicated in microbial biodegradation of pollutants depends on the leachate characteristics, mass of contaminant in the leachate, and nature of the leachate. Character of leachate samples for BOD analysis of using the different methods may differ significantly during the experimental period, resulting in different BOD values. This work intends to verify effect of the different dilutions for the manometric method tests on the BOD concentrations of the leachate samples to contribute to the assessment of reaction rate and microbial consumption of oxygen.
Emerging evidence suggests that reactive oxygen (ROS) and nitrogen (RNS) species can contribute to diverse signalling pathways of inflammatory and tumour cells. Cucurbitacins are a group of highly oxygenated triterpenes. Many plants used in folk medicine to treat cancer have been found to contain cucurbitacins displaying potentially important anti-inflammatory actions. The current study was designed to investigate the anti-ROS and -RNS effects of cucurbitacin L 2-O-β-glucoside (CLG) and the role of these signaling factors in the apoptogenic effects of CLG on human colon cancer cells (HT-29). This natural cucurbitacin was isolated purely from Citrullus lanatus var. citroides (Cucurbitaceae). The results revealed that CLG was cytotoxic to HT-29. CLG increased significantly (P < 0.05) RNA and protein levels of caspase-3 in HT-29 cells when verified using a colorimetric assay and realtime qPCR, respectively. The results showed that lipopolysaccharide/interferon-gamma (LPS/INF-γ) increased nitrous oxide (NO) production inR AW264.7macrophages, whereas N(G)-nitro-L-argininemethyl ester (L-NAME) and CLG curtailed it. This compound did not reveal any cytotoxicity on RAW264.7 macrophages and human normal liver cells (WRL-68) when tested using the MTT assay. Findings of ferric reducing antioxidant power (FRAP) and oxygen radical absorption capacity (ORAC) assays demonstrate the antioxidant properties of CLG. The apoptogenic property of CLG on HT-29 cells is thus related to inhibition of reactive nitrogen and oxygen reactive species and the triggering of caspase-3-regulated apoptosis.
Matched MeSH terms: Oxygen; Reactive Oxygen Species
Influences of river hydrodynamic behaviours on hydrochemistry (salinity, pH, dissolved oxygen saturations and dissolved phosphorus) were evaluated through high spatial and temporal resolution study of a sandbar-regulated coastal river. River hydrodynamic during sandbar-closed event was characterized by minor dependency on tidal fluctuations, very gradual increase of water level and continual low flow velocity. These hydrodynamic behaviours established a hydrochemistry equilibrium, in which water properties generally were characterized by virtual absence of horizontal gradients while vertical stratifications were significant. In addition, the river was in high trophic status as algae blooms were visible. Conversely, river hydrodynamic in sandbar-opened event was tidal-controlled and showed higher flow velocity. Horizontal gradients of water properties became significant while vertically more homogenised and with lower trophic status. In essence, this study reveals that estuarine sandbar directly regulates river hydrodynamic behaviours which in turn influences river hydrochemistry.
A fed-batch strategy was established based on the maximum substrate uptake rate (MSUR) of Pseudomonas aeruginosa USM-AR2 grown in diesel to produce rhamnolipid. This strategy matches the substrate feed rates with the substrate demand based on the real-time measurements of dissolved oxygen (DO). The MSUR was estimated by determining the time required for consumption of a known amount of diesel. The MSUR trend paralleled the biomass profile of Ps. aeruginosa USM-AR2, where the MSUR increased throughout the exponential phase indicating active substrate utilization and then decreased when cells entered stationary phase. Rhamnolipid yield on diesel was enhanced from 0·047 (g/g) in batch to 0·110 (g/g) in pulse-pause fed-batch and 0·123 (g/g) in MSUR fed-batch. Rhamnolipid yield on biomass was also improved from 0·421 (g/g) in batch, 3·098 (g/g) in pulse-pause fed-batch to 3·471 (g/g) using MSUR-based strategy. Volumetric productivity increased from 0·029 g l(-1) h(-1) in batch, 0·054 g l(-1) h(-1) in pulse-pause fed-batch to 0·076 g l(-1) h(-1) in MSUR fed-batch.
Physiological and ecological constraints that cause the slow growth and depleted production of crops have raised a major concern in the agriculture industry as they represent a possible threat of short food supply in the future. The key feature that regulates the stress signaling pathway is always related to the reactive oxygen species (ROS). The accumulation of ROS in plant cells would leave traces of biomarkers at the genome, proteome, and metabolome levels, which could be identified with the recent technological breakthrough coupled with improved performance of bioinformatics. This review highlights the recent breakthrough in molecular strategies (comprising transcriptomics, proteomics, and metabolomics) in identifying oxidative stress biomarkers and the arising opportunities and obstacles observed in research on biomarkers in rice. The major issue in incorporating bioinformatics to validate the biomarkers from different omic platforms for the use of rice-breeding programs is also discussed. The development of powerful techniques for identification of oxidative stress-related biomarkers and the integration of data from different disciplines shed light on the oxidative response pathways in plants.
Shrimps have been a popular raw material for the burgeoning marine and food industry contributing to increasing marine waste. Shrimp waste, which is rich in organic compounds is an abundant source of chitin, a natural polymer of N-acetyl-D-glucosamine (GluNac), a reducing sugar. For this respect, chitinase-producing fungi have been extensively studied as biocontrol agents. Locally isolated Trichoderma virens UKM1 was used in this study. The effect of agitation and aeration rates using colloidal chitin as control substrate in a 2-l stirred tank reactor gave the best agitation and aeration rates at 200 rpm and 0.33 vvm with 4.1 U/l per hour and 5.97 U/l per hour of maximum volumetric chitinase activity obtained, respectively. Microscopic observations showed shear sensitivity at higher agitation rate of the above system. The oxygen uptake rate during the highest chitinase productivity obtained using sun-dried ground shrimp waste of 1.74 mg of dissolved oxygen per gram of fungal biomass per hour at the kappaL a of 8.34 per hour.
A one-dimensional biofilm model was developed based on the basic principle of conservation of mass. Three simple, generic processes were combined in the model which includes microbial growth, diffusive and convective mass transport. The final model could generate a quantitative description of the relationship between the microbial growth and the consumption of substrate (oxygen) within the fixed biofilm thickness. Mass transfer resistance contributes large influence on the substrates and microbial concentration across the biofilm thickness due to the effect of biofilm structure.
The bioregeneration efficiencies of powdered activated carbon (PAC) and pyrolyzed rice husk loaded with phenol and p-nitrophenol were quantified by oxygen uptake measurements using the respirometry technique in two approaches: (i) simultaneous adsorption and biodegradation and (ii) sequential adsorption and biodegradation. It was found that the applicability of the simultaneous adsorption and biodegradation approach was constrained by the requirement of adsorption preceding biodegradation in order to determine the initial adsorbent loading accurately. The sequential adsorption and biodegradation approach provides a good estimate of the upper limit of the bioregeneration efficiency for the loaded adsorbent in the simultaneous adsorption and biodegradation processes. The results showed that the mean bioregeneration efficiencies for PAC loaded with phenol and p-nitrophenol, respectively, obtained using the two approaches were in good agreement.
Photo fermentation is a biological process that can be applied for hydrogen production. The process is environmental friendly which is operated under mild conditions using renewable resources. In order to increase yield of H2 produced by Rhodobacter sphaeroides, some experimental factors that may enhance H2 production were studied. The effect of operating parameters including agitation, aeration and light on hydrogen production using R. sphaeroides NCIMB 8253 was investigated. Rhodobacter sphaeroides NCIMB 8253 was grown in 100 mL serum bottle containing growth medium with maliec acid as the sole organic carbon source. The cultures were incubated anaerobically at 30 degrees C with tungsten lamp (100 W) as the light source (3.8 klux) and argon gas was purged for maintaining anaerobic condition. The results show that maximum hydrogen produced was higher (54.37 mL) in static culture with 69.98% of H2 in the total gas compared with shake culture (11.57 mL) with 57.86% of H2. By using static culture, H2 produced was five times higher compared with non-static in both aerobic and anaerobic condition. It was found that growth and H2 production with fluorescent lamp showed better results than growth and H2 production with tungsten light.