Increasing Exposure Time Research Articles

Experimental investigation on the post-fire mechanical properties and charring rate of inorganic-bonded bamboo composite exposed to fire

The fire resistance remains a challenging topic for engineered wood and bamboo structures due to the combustibility of wood and bamboo and the usage of organic adhesives, which are temperature-sensitive substance in fire. As an alternative solution, this paper investigated a novel bamboo-based composite prepared with magnesium oxysulfide inorganic adhesive (inorganic-bonded bamboo composite, InorgBam), and the fire tests were carried out to investigate the post-fire mechanical properties and charring behavior of InorgBam. The reduction effect of fire exposure on compressive or tensile strength parallel-to-grain was experimentally studied. The effects of fire exposure surface numbers, grain direction, geometric dimension and exposure time on charring rate were discussed. Results showed that the InorgBam can be maintained the post-fire strength under compressive or tensile loads parallel to grain without significant degradation when the exposure temperature below 250 °C. The temperature of the char front was determined to be approximate 350°C by using an interpolation method. The charring rate was mainly dominated by the exposure time and decreases nonlinearly with the increase of exposure time, and the charring rate with multi-sided fire exposure was approximately 1.1 times of that exposed to one-sided fire. Finally, a nonlinear model was proposed to predict the charring rate of InorgBam material, which provides a basic reference for understanding the fire resistance of InorgBam material exposed to fire.

Repeated release of cerium oxide nanoparticles altered algal responses: Growth, photosynthesis, and photosynthetic gene expression

The expanding production of engineered nanomaterials (ENMs) can eventually cause their increased release into and presence in aquatic ecosystems, potentially threatening the health of aquatic organisms and the stability of the ecological environment. Generally, ENMs are repeatedly released into real-world aquatic environments in relatively low concentrations, potentially affecting photosynthesis in primary producers such as algae. However, knowledge regarding the effects of repeated exposure to ENMs on algal photosynthesis is still lacking. Herein, the physiological responses of the freshwater algae Chlorella vulgaris following single and repeated exposures to cerium oxide nanoparticles (CeO2 NPs) were investigated at 10 mg/L, with a focus on photosynthesis. The results showed that repeated exposures triggered increased photosynthetic pigment contents, oxidative stress levels, decreased photosynthetic performance, and lower biomass in C. vulgaris compared to a single exposure. Photosynthesis-related genes (i.e., petA, petB, psaA, atpB, and rbcL) were found to be upregulated following repeated exposures. Particularly for petB, repeated rather than single exposure treatment significantly upregulated its expression levels by 2.92–10.24-fold compared to unexposed controls. Furthermore, increased exposure times could aggravate the interaction between CeO2 NPs and algae, elevating 8.13%, 12.13%, and 20.51% Ce distribution on the algal cell surface or intracellularly, compared to a single exposure. This study is the first to investigate the effects of ENM exposure times on algal photosynthesis, providing new insights into the assessment of the risks these materials pose to real-world aquatic environments.

Predicting corrosion for life estimation of ocean and coastal steel infrastructure

AbstractPhysical infrastructure in coastal and offshore locations often is constructed from mild and low alloy steels. These are prone to marine corrosion even with the application of protective coatings and cathodic protection. Particularly for high‐value assets such as energy facilities (wind farms, oil and gas production and subsea pipelines), the prediction of their safe and economic life is of much interest. Herein, a review is given of the modern development of models for the prediction of long‐term marine corrosion of steel exposed to various marine environments. These include immersion, tidal, splash and atmospheric zones and contact with sands and soils. The effects of temperature and water pollution are especially important, as is the ability of the steels or irons to form protective corrosion products. Comments are made also about other alloys such as copper‐nickels and aluminium. All show that corrosion, including pitting corrosion, develops with increased exposure time in a bimodal manner. The reasons for such behaviour are considered, together with the practical implications, important for containment structures such as pipelines, tanks and floating offshore energy platforms.

Evaluation of the abilities of atomic oxygen/ultraviolet resistance for the filled silicone rubber coating: Structures, properties, and aging mechanism

A series of experimental techniques were used to study the erosion-damage effect of a silica-filled silicone rubber coating exposed to simulated space environment (atomic oxygen and ultraviolet irradiation). The elastomer is known to be chemically and thermally stable, but there are insufficient data on its durability in the space environment. In the present work, atomic oxygen doses up to 3.8 × 1021 atoms·cm−2 and ultraviolet irradiation doses up to 360 equivalent sun-hours (ESH) were applied from Space Environment Simulation Measurement System, respectively. Since the aging and failure processes of the filled silicone rubber relate to different aspects of chemical structure and physics form, therefore, this study explored the use of chemical-mechanics methods to comprehensively evaluate the erosion-damage effect of materials. Morphology and chemical changes due to radiation were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), and nanoindentation test probed surface mechanical properties changed with exposure dose. Results demonstrated that, with increased exposure time and irradiation-induced free radicals，the aggregation state and molecular chain structure of the silica-filled silicone rubber have changed, which caused an increase in surface hardness and modulus. Taken together, the results indicated that oxidative cross-linking was the dominant degradation mechanism under the irradiation dose in this paper.

Corrosion performance and mechanisms of tantalum coatings on 316 stainless-steel in subcritical aqueous solutions of NaCl and NaBr

The corrosion behavior of 316 stainless-steel with a tantalum (Ta-316) coating deposited using PVD technology was investigated in subcritical environments containing Cl− and Br− at 290 °C and 6 MPa. The corrosion rate of Ta-316 continuously decreased with increasing exposure time, demonstrating its high corrosion resistance. A thin film, mainly composed of Ta2O5, formed on the surface of the tantalum coating, preventing the diffusion of substrate elements. The corrosion process and mechanism of Ta-316 were also examined.

Revealing the superior oxidation resistance of alloy 690 in deaerated supercritical water at 600 °C through advanced characterization

The corrosion behavior of a well-polished Alloy 690 in deaerated supercritical water at 600 °C was examined. The study found that the weight gain follows a near-cubic rate law. A key observation was that the direct external oxidation and the rapid transition from internal to external oxidation within the initial 24-h exposure are responsible for its superior oxidation resistance. As exposure time increases, the transformation of Cr-rich spinel oxides and Ni-rich networks in the internal oxidation zone into Cr2O3 leads to the expansion of the protective chromia layer, effectively slowing down the oxidation process. Conversely, the Cr2O3 layer at the grain boundaries (GBs) was less effective at preventing oxidation, resulting in a significantly faster oxidation rate in these areas compared to the bulk grains. The extensive GB oxidation exhibits little consequential correlation with carbides.

Folic acid supplementation improves seed germination, seedling growth and cadmium uptake in a mining ecotype of Solanum nigrum L.

Cadmium (Cd) contamination poses a significant threat to global agricultural production and hyperaccumulating plant species, such as Solanum nigrum (L.), face challenges in phytoremediation due to limited biomass production. Application of plant growth regulators such as, folic acid (FA) is a promising strategy to increase biomass production in these plant species. Therefore, a study was conducted to assess the interaction between FA and Cd in the mining ecotype of S. nigrum. The study involved two phases: germination and growth. In the first phase, seeds were exposed to different concentrations of CdCl2 (i.e. 0, 10, 25, 50, 100, 200, and 400 µM) in the presence (0, 25, 50 and 100 µM) or absence of FA for ten days. Results showed that FA enhanced seed germination under Cd stress and acted as an antioxidant and stimulated germination and emergence at moderate concentrations. At higher concentrations, it reduced germination percentage. The study also found significant variations (P <0.05) in growth attributes and Cd uptake in all FA concentrations. Cd was generally higher in shoots than roots, with the highest Cd concentration found in T6 (200 µmol Cd + 50 µmol/L FA) with a 170-fold difference (mean value: 1690 mg/kg) from control (10 mg/kg). Furthermore, an increase in exposure time led to a 2-fold increase in reduced glutathione (GSH) level in leaves at T3 (100 µmol/L Cd + 50 µmol/L FA).Therefore, we concluded that FA is a biostimulant that activates protective mechanism, alleviates oxidative stress and improves Cd uptake and accumulation in hyper-accumulating species.

Multi-azobenzene moieties on rigid cyclotriphosphazene core: Synthesis, structural characterization, electrochemistry, and photoisomerization study

Multi-azobenzene derivatives capable of showing multi-stimuli responsive material can exhibit superior performance in biomedicine, the dye industry, cosmetics, and photonics. Here, a nucleophilic substitution reaction was employed to assemble two (Az2CPZ(biph)2) or four (Az4CPZ(biph)) or six (Az6CPZ) units of azobenzene moieties on the cyclotriphosphazene (CPZ) core. We have observed that the color of each compound varied by changing the number of azobenzene moieties on the CPZ core. These compounds were characterized by elemental analysis, 1H, 13C{1H}, and 31P{1H} NMR techniques. Single crystal X-ray diffraction techniques ensure the trans conformation in the azobenzene for Az2CPZ(biph)2 and Az4CPZ(biph). Electronic spectroscopy forAz2CPZ(biph)2,Az4CPZ(biph), andAz6CPZhaving π-π* transition around 325 nm show a hypsochromic shift with ∼25 nm compared to the parent molecule, 4-hydroxyazobenzene AzH. As a result of the electronic spectroscopy, the cis isomer formation enhanced upon increasing the concentration ofAz2CPZ(biph)2/Az4CPZ(biph)/Az6CPZ in DCM/DMF. The photoisomerization study confirms that these molecules having at least one azo moiety can switch from trans to cis conformation upon exposure to 365 nm light. Interestingly, the thin-layer chromatography (TLC) corroborated the switch of trans to cis conformation occurs at room temperature in a solution state even without UV irradiation. The proton NMR integration providesthe generationofthe cis-azobenzene moiety is about 12–20 % inAz2CPZ(biph)2upon exposure to 365 nm light for 15 to 60 mins. Additionally, TLC verifies the generation of multiple isomers that confirm multi-functional switch behavior when the sample with UV exposure time increases. Owing to these molecules undergoing a isomerization process (trans-azo⇌cis-azo) even without UV, their fluorescence gets quenched in the solution state. Cyclic voltammetry confirms the quasi-reversible type redox behavior of all compounds in dry dichloromethane. We believe the results presented in this work will be significant for dye and biomedical applications.

Evaluation of Cytotoxicity of 4-Hydroxycinnamic Acid Using Tetrazolium Bromide Assay and Zebrafish Embryotoxicity: An In-Vitro Study.

Aim This study aimed to evaluate the cytotoxicity of a novel compound, 4-hydroxycinnamic acid (4-HCA), with the help of a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and zebrafish embryotoxicity. Materials and methods In this in vitro study, MTT fibroblast assays using dental pulp stem cells, which were cultured in Modified Eagle's Medium or Dulbecco's Modified Eagle Medium, and zebrafish cytotoxicity and embryotoxicity were done to evaluate the cytotoxicity of the novel compound 4-HCA. The data was analyzed by plotting cell number versus absorbance, allowing quantitation of changes in cell proliferation. Results 4-HCA (40 μl) showed acceptable levels of cell viability according to the American Society for Testing and Materials standards. Cell viability is reduced with increased exposure time and concentrations of 4-HCA. Similarly, the cytotoxicity assessment in zebrafish (Danio rerio) showed an acceptable range of toxicity levels in embryonic stagesused to evaluate the mortality rate of zebrafish embryos. Conclusion Considering the constraints of this research, it can be deduced that hydroxycinnamic acid at a concentration of 40 μl was non-toxic. The findings from the MTT assay indicated a correlation between the concentration and the toxicity of the compound. Likewise, the zebrafish test demonstrated minimal toxicological effects.

Spatiotemporal distribution, interactions and toxic effect of microorganisms and ARGs/MGEs from the bioreaction tank in hospital sewage treatment facility

Antibiotic resistance genes (ARGs) can be emitted from wastewater to ambient air and impose unignorable inhalable hazards, which could be exacerbated in antibiotic-concentrated hospital sewage. However, whether the ARG-carrying pathogens are more likely to infect cells remains largely unknown. Here, this study investigated and analyzed the spatiotemporal distribution, interaction, and toxicity of airborne microorganisms and their hosting ARGs in a hospital sewage treatment facility. The average concentration of ARGs/MGEs in sewage of bioreaction tank (BRT-W) was 2.27 × 104 gene copies/L. In the air of bioreaction tank (BRT-A), the average concentration of ARGs/MGEs was 15.86 gene copies/m3. In the four seasons, the ARGs concentration of sewage gradually decreased over time; The concentration of ARGs in the air first decreased and then increased. In spring, the concentration of ARGs/MGEs (qacedelta1-01) in BRT-W was highest (1.05 × 105 gene copies/L); The concentration of ARGs/MGEs (strB) in BRT-A in winter was higher than other seasons (26.18 gene copies/m3). Different from the past, this study also paid attention to the pathogenic potential of ARGs/MGEs in the air. The results of cell experiments showed that the cytotoxicity of drug-resistant Escherichia coli could reach Grade V. This suggested that the longer the drug-resistant E. coli were exposed to cells, the greater the cytotoxicity. Moreover, the cytotoxicity of bacteria increased with the increase in exposure time. In spring, the toxic effect of ARGs/MGEs in sewage of BRT-W was highest. Traceability analysis proved that BRT-W was an essential source of microorganisms and ARGs/MGEs in BRT-A. Furthermore, the combined risk of people exposed to the air of BRT in spring was higher than that in other seasons.

Ecotoxicity of perfluorooctanoic acid and perfluorooctane sulfonate on aquatic plant Vallisneria natans.

Perfluorinated compounds (PFCs) are persistent organic contaminants that are highly toxic to the environment and bioaccumulate, but their ecotoxic effects on aquatic plants remain unclear. In this study, the submerged plant Vallisneria natans was treated with short-term (7 days) and long-term (21 days) exposures to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at concentrations of 0, 0.01, 0.1, 1.0, 5.0, and 10 mg/L, respectively. The results showed that both high concentrations of PFOA and PFOS inhibited the growth of V. natans and triggered the increase in photosynthetic pigment content in leaves. The oxidative damage occurred mainly in leaves, but both leaves and roots gradually built up tolerance during the stress process without serious membrane damage. Both leaves and roots replied to short-term stress by activating superoxide dismutase (SOD), catalase (CAT) and polyphenol oxidase (PPO), while peroxidase (POD) was involved under high concentration stress with increasing exposure time. Leaves showed a dose-effect relationship in integrated biomarker response (IBR) values under short-term exposure, and the sensitivity of roots and leaves to PFOS was higher than that of PFOA. Our findings help to increase knowledge of the toxic effects of PFCs and have important reference value for risk assessment and environmental remediation of PFCs in the aquatic ecosystem.

In Vitro Risk Assessment of Dental Acid Erosion Caused by Long-Term Exposure to Oral Liquid Bandages.

Oral mucosa inflammation can cause severe pain and interfere with eating, reducing quality of life. However, few options for self-care are available. An oral liquid bandage forms a protective film over the affected area. We aimed to assess the acid erosion risk when a newly developed oral liquid bandage (ORAPLA) is accidentally deposited on teeth and to examine the relative acid erosion risk at multiple time points of the maximum recommended duration of continuous use. ORAPLA was applied to both enamel and dentin blocks from 45 bovine anterior mandibular teeth, and an acid challenge was performed in a simulated oral cavity with artificial saliva, with one exposure cycle lasting 6 h. The enamel showed substantial defects and a decrease in Vickers hardness after nine cycles, with no change in surface roughness. Dentin showed an increase in parenchymal defects and surface roughness and a trend toward decreased Vickers hardness with increasing exposure time. We found no significant acid corrosion in enamel after up to nine times the upper limit of normal use time or in dentin after up to six times the upper limit. We conclude that the acid erosion risk due to accidental attachment to teeth is low, and in the human oral cavity with salivary buffering and remineralization, likely even lower.

Seed thermo-priming accelerates the growth of Ceiba glaziovii (Kutze) K.Schum. seedlings

Background: Global climate changes have caused temperature increases that can harm plant development, especially the initial growth and establishment of seedlings for the recovery of degraded areas. However, there are species in which these losses are attenuated when the seeds are thermo-primed to sublethal temperatures. Therefore, the objective of the present study was to evaluate the influence of seed heat conditioning on germination and initial growth of Ceiba glaziovii (Kuntze) K. Schum seedlings, an endemic species occurring in seasonally tropical dry forest in Brazil. Methods: Seeds of C. glaziovii were exposed to 70 oC for 15, 30, 45, 60 and 90 minutes as pre-germination treatments. The control did not undergo heat treatment. Germination variables, vegetative growth, survival rate and normal leaves were evaluated. Results: Thermo-priming negatively affected the germination proportion of C. glaziovii seeds with increasing exposure time. However, it significantly enhanced vegetative growth and seedling survival rate of this species after transplanting, without impairing the formation of normal leaves. Conclusions: Thermo-priming of seeds was found to produce more vigorous seedlings of Ceiba glaziovii.

Sterilization of Human Amniotic Membrane Using an Ozone Hydrodynamic System.

Human amniotic membrane (hAM) is an important biomaterial for Tissue Engineering, due to its great regenerative properties and potential use as a scaffold. The most used procedure to sterilize biomaterials is gamma-irradiation, but this method can affect several properties, causing damage to the structure and reducing the growth factors. The present work evaluated the efficiency of a new method based on ozonated dynamic water for hAM sterilization. HAM fragments were experimentally contaminated with Staphylococcus aureus, Escherichia coli, Candida albicans, Staphylococcus epidermidis, and Clostridium sporogenes (106CFU/mL) and submitted to sterilization process for 5, 10 and 15min. The analyses did not reveal microbial activity after 10min for S. aureus and C. sporogenes and after 15min for E. coli and S. epidermidis. The microbial activity of C. albicans was reduced with the exposure time increase, but the evaluated time was insufficient for complete sterilization. The depyrogenation process was investigated for different ozonation times (15, 20, 25, 30, and 35min) to evaluate the ozone sterilization potential and presented promising results after 35min. The ozone effect on hAM structure was evaluated by histological analysis. A decrease in epithelium average thickness was observed with the exposure time increase. Furthermore, some damage in the epithelium was observed when hAM was exposed for 10 and 15min. It can indicate that ozone, besides being effective in sterilization, could promote the hAM sample's de-epithelization, becoming a possible new method for removing the epithelial layer to use hAM as a scaffold.

Adverse effects of 2,4-D dimethylammonium based-herbicide on Acetylcholinesterase expression in Nile tilapia (Oreochromis niloticus)

In this study, the evaluation of a 2,4-D dimethylammonium based-herbicide impacted on Nile tilapia was done. The effects focus on Acetylcholinesterase (AChE) expression in the brain, gill, muscle, and plasma using antibody techniques. Our findings revealed a decrease in AChE expression with prolonged exposure. For these, AChE was purified using hydroxyapatite column chromatography. Moreover, the isolated protein was characterized as AChE by Polyclonal Ab specific to AChE through the Western blot. For interpretation at the cellular and molecular level, we employed two analytical techniques, histology, and optical coherence tomography (OCT). Alterations in the gill, liver, and muscle were observed to increase with increased exposure time. Field study concludes that AChE could serve as a biomarker to detect herbicide contamination in water and its accumulation in aquatic animals. This study may aid in surveillance and strategy formulation for managing contamination from such substances in various water sources.

Chemical composition, toxicity, and repellency of some Myrtaceae plants essential oils against Tribolium castaneum (Herbst)

Essential oils (EOs) obtained from plants have the potential to be environment-friendly alternatives to synthetic insecticides in agriculture. Tribolium castaneum (Herbst) is a cosmopolitan pest that causes the loss of a major proportion of stored crops. Therefore, we studied the insecticidal and repellent effects of EOs derived from the plants viz. Eucalyptus rudis, Eucalyptus crebra, and Melaleuca genistifolia against larvae and adults of T. castaneum. Essential oils were derived from the leaves of each plant using hydro-distillation. Gas chromatography-mass spectrometry (GC-MS) of the extracted EOs revealed that eucalyptol, viridiflorol, α-terpineol, and eugenol methyl comprised the major components of the EOs. However, the composition and quantity of the compounds varied across EOs. Specifically, EOs derived from E. rudis exhibited the highest fumigation toxicity against adult and larval T. castaneum, followed by M. genistifolia and E. crebra. In the presence of wheat grains, fumigation toxicity against T. castaneum declined by nearly threefold. Contact toxicity assays revealed that EOs from E. rudis were overall the most effective against the pest (LC50: 0.392 μL/cm2 for adult; LC50: 0.471 μL/cm2 for larva) followed by M. genistifolia (LC50: 0.424 μL/cm2 for adult; LC50: 0.478 μL/cm2 for larva) and E. crebra (LC50: 0.471 μL/cm2 for adult; LC50: 0.515 μL/cm2 for larva). The LC50 value of each EO was up to five times lower in adults than in larvae. Melaleuca genistifolia was the most effective repellent against T. castaneum adults; however, its effectiveness decreased with increasing exposure time. In conclusion, the EOs of E. rudis, E. crebra, and M. genistifolia were all viable green biopesticide alternatives to synthetic insecticides.

UV-C pretreatment of wastewater-grown algal biomass for recover of biofuel precursors

In the present study, ultraviolet radiation C (UV-C) was used as a pretreatment tool for the optimal recovery of biofuel precursors from algae Chlorella vulgaris. The pretreatment efficiency of UV-C with fixed light intensity (1.173 mWcm−2) on 1.5 gL-1 algal biomass was observed at 0, 0.5, 1, 2, 5, 10, and 20 h of irradiation by measuring the released sugar content and soluble chemical oxygen demand (sCOD). The UV-C pretreated algal cells were also analyzed through impedance spectroscopy, fluorescence microscope, and digital images to assess the degree of cell wall disintegration. The released sugar content reached a maximum of 73.61 mg L-1 at 10 h of exposure, whereas the maximum sCOD of 190 mg L-1 was achieved at 20 h exposure. Image analysis indicated that the chlorophyll content declined exponentially from 7.21 to 0.14 µgmL-1 with UV-C exposure. An increase in UV-C exposure time resulted in decreased impedance and increased conductance. The SYTOX green fluorescence also increased with 10 h of exposure, followed by a decline. Therefore, the cell wall stability gets compromised and the permeability increases with increment in UV-C exposure. This triggers extensive release in cell wall sugar content with exposure. Further exposure destabilizes the cell wall leading to discreet breakage. This breakage disperses internal content to bulk liquid, causing elevated sCOD with reduced sugar content. The present study showed that UV-C to be a potential pretreatment strategy to release precursors to derive biofuels such as biohydrogen, bioethanol and others.

Response of the modified GAFCHROMIC EBT2 radiochromic film to DC glow discharge plasma

The response of the modified GAFCHROMIC EBT2 radiochromic film to DC Oxygen glow discharge plasma was investigated using a flatbed scanner and an UV–Vis spectrophotometer. The film was modified by removing the polyester overlaminate, adhesive, and topcoat layers with a total thickness of 80 µm, and is now referred to as EBT2-M. The EBT2-M films were exposed to DC Oxygen plasma for different durations: 0, 0.5, 1, 2, 3, 4, 7, and 10 min. The exposed films exhibit coloration homogeneity with an average variation of (1.6 ± 0.3) × 10−4 pixel values/µm, irrespective of the applied exposure time. The pixel values of the red-and-green channels and weighted grayscale images decreased exponentially with different sensitivity amounts to ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim$$\\end{document} 39.67, 49.69, and 42.11 min−1, respectively, as the exposure time increased. The two absorption peaks at 580 ± 4 nm and 632 ± 4 nm in the UV–Vis absorption spectra of the exposed GAFCHROMIC EBT2-M radiochromic films are increasing with increasing exposure time up to 4 min, thereafter saturated for prolonged exposure time. The integrated absorbance in the range from 400 to 700 nm is linearly correlated with the exposure time. The indirect and direct optical energy band gaps and Urbach energy of the modified GAFCHROMIC EBT2 film are weakly correlated with the exposure time. These findings suggest the utilization of the modified GAFCHROMIC EBT2 radiochromic film as a novel and simple technique for plasma diagnostics.

K2Cr2O7-induced DNA damage in HT1080 cells: Electrochemical signal response mechanism

The existing DNA damage detection technology cannot meet the current detection requirements. It is critical to build new methods and discover novel biomarkers. In this study, alkaline comet and 8-OHDG ELISA assays were used to identify DNA damage in HT-1080 cells exposed to K2Cr2O7, and electrochemical behaviors of HT-1080 cells with DNA damage was studied. With an increase in K2Cr2O7 exposure time, two electrochemical signals from HT-1080 cells at 0.69 and 1.01 V steadily grew before decreasing after reaching their highest values. The electrochemical signal's initial response time and peak time decreased as the concentration of K2Cr2O7 increased. The duration of the high dose group was 0.5 and 1 h, while the low dose group was 1.5 and 6 h. Western blotting analysis revealed that DNA damage increased the expression of proteins involved in catabolism and de novo purine synthesis, particularly de novo purine synthesis. Expressions of PRPP amidotransferase, IMPDH, and ADA were all higher than those of ADSS, XOD, and GDA, which resulted in larger concentrations of hypoxanthine, guanine, and xanthine, and in turn improved electrochemical signaling. These findings suggest that intracellular purine identified by linear scan voltammetry is predicted to evolve as a marker of early DNA damage.

Effects of cadmium exposure on haemocyte immune function of clam Ruditapes philippinarum at different temperatures

Haemocytes are crucial for the immune defence of mollusks. It is important to explore the immune performance of haemocytes of mollusks under the stress of heavy metals with global warming. In order to study the effects of cadmium (Cd) exposure and temperature stress on the haemocyte immune function of clam Ruditapes philippinarum, clams were exposed to different Cd concentrations (0.05, 0.10 and 0.25 mg/L) at 20 °C, 25 °C and 30 °C respectively. Haemocyte mortality, reactive oxygen species (ROS) and superoxide dismutase (SOD) activity were measured at day 1, day 3, day 5 and day 7. The results showed that the changes of the three indexes were not obvious when exposed to 0.05 mg/L of Cd at 20 °C, while significant differences were observed with the increase of temperature, Cd concentration and exposure time. Under a condition of relative high temperature coupling with high concentration of Cd, the clams were significantly influenced, showing an obvious synergistic effect. Selected indexes reflect the clam's response to the combined stress of temperature and Cd. Moreover, R. philippinarum might be an ideal biological index species to the Cd pollution.