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The present study compared the performance of Ultra-high performance liquid chromatography (UHPLC) and UV-Vis spectrophotometry for the quantification of metformin hydrochloride in five commercially available metformin hydrochloride products with different strengths. The metformin hydrochloride was measured in the UHPLC with a mobile phase consisting of a mixture of 0.05 M phosphate buffer solution and methanol (35:65, v/v) with a pH of 3.6. Metformin hydrochloride was determined spectrophotometrically at 234 nm using a mixture of methanol and water as a blank. The methods' linearity for metformin hydrochloride was within the concentration range of (2.5-40 µg/ml) in both techniques. The validation process encompassed assessments of specificity, selectivity, linearity, accuracy, precision, the lower limit of quantification (LLOQ), the lower limit of detection (LLOD), robustness, and system suitability. For the UHPLC validation method, the repeatability and reproducibility (expressed as relative standard deviation) were less than 1.578 and 2.718 %, respectively. The LLOQ for metformin hydrochloride was 0.625 µg/ml, and the LLOD was 0.156 µg/ml. For the UV-Vis spectrophotometric validation method, the repeatability and reproducibility (stated as relative standard deviation) were less than 3.773 and 1.988 %, respectively. The percentage recovery results for the five brands of metformin hydrochloride tablets were (98-101 %) and (92-104 %) for the UHPLC and UV-Vis spectrophotometric methods, respectively. In conclusion, the described methodologies were successfully employed for the quantitative analysis of metformin hydrochloride in different pharmaceutical tablet products.

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Ruthenium chloride (RuCl3) is widely utilized for synthesis and catalysis of numerous compounds in academia and industry and is utilized as a key molecule in a variety of compounds with medical applications. Interestingly, RuCl3 has been demonstrated to modulate human plasmatic coagulation and serves as a constituent of a compounded inorganic antivenom that neutralizes the coagulopathic effects of snake venom in vitro and in vivo. Using thrombelastography, this investigation sought to determine if RuCl3 inhibition of the fibrinogenolytic effects of Crotalus atrox venom could be modulated by vehicle composition in human plasma. Venom was exposed to RuCl3 in 0.9% NaCl, phosphate-buffered saline (PBS), or 0.9% NaCl containing 1% dimethyl sulfoxide (DMSO). RuCl3 inhibited venom-mediated delay in the onset of thrombus formation, decreased clot growth velocity, and decreased clot strength. PBS and DMSO enhanced the effects of RuCl3. It is concluded that while a Ru-based cation is responsible for significant inhibition of venom activity, a combination of Ru-based ions containing phosphate and DMSO enhances RuCl3-mediated venom inhibition. Additional investigation is indicated to determine what specific Ru-containing molecules cause venom inhibition and what other combinations of inorganic/organic compounds may enhance the antivenom effects of RuCl3.

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BACKGROUND: Phosphate buffer is often used as a replacement for the physiological bicarbonate buffer in pharmaceutical dissolution testing, although there are some discrepancies in their properties making it complicated to extrapolate dissolution results in phosphate to the in vivo situation. This study aims to characterize these discrepancies regarding solubility and dissolution behavior of ionizable compounds. METHODS: The dissolution of an ibuprofen powder with a known particle size distribution was simulated in silico and verified experimentally in vitro at two different doses and in two different buffers (5 mM pH 6.8 bicarbonate and phosphate). RESULTS: The results showed that there is a solubility vs. dissolution mismatch in the two buffers. This was accurately predicted by the in-house simulations based on the reversible non-equilibrium (RNE) and the Mooney models. CONCLUSIONS: The results can be explained by the existence of a relatively large gap between the initial surface pH of the drug and the bulk pH at saturation in bicarbonate but not in phosphate, which is caused by not all the interfacial reactions reaching equilibrium in bicarbonate prior to bulk saturation. This means that slurry pH measurements, while providing surface pH estimates for buffers like phosphate, are poor indicators of surface pH in the intestinal bicarbonate buffer. In addition, it showcases the importance of accounting for the H2CO3-CO2 interconversion kinetics to achieve good predictions of intestinal drug dissolution.

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Maltose, cellobiose, and lactose dissolved in 0.01 mol/L arginine solution or 0.01 mol/L phosphate buffer (pH 7.0) at 0.2 mol/L were reacted batchwise at 110 °C. The yields of the corresponding keto-disaccharides were 23.4% and 17.6% for maltose, 19.3% and 13.0% for cellobiose, and 20.0% and 13.7% for lactose in arginine solution at 30 min and phosphate buffer at 150 min, respectively. All the disaccharides were hydrolyzed in the range of 0.5 to 3.5%, the degree of hydrolysis being greater in arginine solution than in phosphate buffer. The monosaccharides produced by hydrolysis were slightly isomerized to other monosaccharides. A decrease in pH and an increase in absorbance at 280 and 420 nm continued even at the almost constant yields of the main products. The browning was particularly pronounced in the latter half of the reaction, suggesting a change of the by-products to substances with high absorption coefficient.

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An alternative metric to account for particulate matter (PM) composition-based toxicity is the ability of PM-species to generate reactive oxygen species (ROS) and deplete antioxidants, the so-called oxidative potential (OP). Acellular OP assays are the most used worldwide, mainly those based on ascorbic acid (AA) and dithiothreitol (DTT) depletion; OP values are calculated from AA/DTT concentration over time kinetic curves. Since a great variability in OP-DTT and OP-AA values can be found in the literature, the understanding of those factors affecting the kinetic rate of AA and DTT oxidation in the presence of PM-bound species will improve the interpretation of OP values. In this work, a kinetic study of the oxidation rate of AA and DTT driven by species usually found in PM (transition metals and naphthoquinone (NQ)) was carried out. In particular, the influence of the concentration of Cu(II), Fe(II), Fe(III), Mn(II), Mn(III), and 1,4-NQ, and the type of fluid used in the assay (phosphate buffer (PB), phosphate buffer saline (PBS) and artificial lysosomal fluid (ALF)) is analysed and discussed. The reaction orders with respect to the AA/DTT and the active compound, and the kinetic rate constants were also determined. The results show great variability in OP values among the studied species depending on the fluid used; the OP values were mostly higher in PB0.05 M, followed by PBS1x and ALF. Moreover, different species concentration-responses for OP-DTT/OP-AA were obtained. These differences were explained by the different reaction orders and kinetic rate constants obtained for each active compound in each fluid.

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BACKGROUND: Human immunodeficiency virus (HIV) rapid diagnostic tests (RDTs) are widely used. However, buffer stockouts commonly lead to utilising non-approved liquids, resulting in errors. Our aim was to evaluate the diagnostic accuracy of an alternative buffer. METHODS: Paired Determine HIV-1/2 rapid tests with commercial buffer and locally produced 0.01M phosphate-buffered saline (PBS) were performed on consecutive consenting individuals requiring HIV testing. Serum samples were sent for confirmation through the local gold-standard algorithm (Murex HIV Ag/Ab, Hexagon HIV with/without Geenius HIV 1/2). Test accuracy, κ and exact McNemar's test were also carried out. RESULTS: Of 167 participants, 137 had confirmatory testing. The sensitivity of the Determine HIV-1/2 test using PBS compared with the gold standard was 100% (95% confidence interval [CI] 90.5 to 100) with a specificity of 98% (95% CI 92.9 to 99.8). The κ value was 0.94 compared with the gold standard and 0.92 compared with the Determine HIV-1/2 test using the commercial buffer. McNemar's test showed no evidence of differing sensitivities. Due to operational constraints, the study included 37 of the 49 positive cases as determined by the sample size calculation, resulting in an attained power of 80% instead of the intended 90%. CONCLUSIONS: These results suggest that 0.01M PBS is an alternative solution for Determine HIV-1/2 when buffer stockouts occur.

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Isomerization and epimerization of fructose to glucose, mannose, allulose, and allose were executed using a subcritical phosphate buffer solution to effectively produce useful monosaccharides. The conversion of the substrate and the yield of products were dependent on the reaction temperature, initial pH, initial substrate concentration, and buffer concentration. A high yield of mannose was achieved under the optimal reaction conditions we identified. We subsequently performed the kinetic analysis based on the proposed reaction network, and evaluated the effects of temperature and pH on the reactions. We then estimated the apparent activation energy values for each reaction.

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This present study investigated the effect of cold atmospheric plasma (CAP) pre-treatment on the quality of ready-to-eat drunken red shrimp (Solenocera crassicornis) during chilled storage. The shrimp were pre-treated with the CAP at 40 kV and 36 kH for 100 s in a plasma generating equipment before the drunken treatment and compared with an untreated control sample. The results showed that the CAP pre-treatment significantly inhibited the total viable count (TVC) values, total volatile basic nitrogen (TVB-N) content, and polyphenol oxidase (PPO) activity of the drunken shrimp compared to the control treatment. Furthermore, the CAP pre-treatment also significantly maintained the myofibrillar protein (MP) content, texture properties, and a more stable histological structure of muscle fibers compared to the control. High-throughput sequencing results confirmed that the CAP pre-treatment significantly reduced the diversity and abundance of several bacteria in the shrimp. Gas chromatography-ion mobility spectrometry (GC-IMS) analysis detected that the CAP pre-treatment effectively maintained the stability of volatile organic compounds (VOCs). These findings provide valuable theoretical support for the processing and storage of drunken shrimp.

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Microbial fuel cells are one of the alternative methods that generate green, renewable sources of energy from wastewater. In this study, a new bio-electrochemical system called the sulfide-oxidizing fuel cell (SOFC) is developed for the simultaneous removal of sulfide/sulfide and electricity generation. To improve the application capacity of the SOFC, a system combining sulfate-reducing and sulfide-oxidizing processes for sulfate/sulfide removal and electricity generation was designed. Key factors influencing the sulfide-removal efficiency and electricity-generation capacity of the SOFC are the anolytes and catholytes. The sulfide produced from the sulfate-reducing process is thought to play the key role of an electron mediator (anolyte), which transfers electrons to the electrode to produce electricity. Sulfide can be removed in the anodic chamber of the SOFC when it is oxidized to the element sulfur (S°) through the biochemical reaction at the anode. The performance of wastewater treatment for sulfate/sulfide removal and electricity generation was evaluated by using different catholytes (dissolved oxygen in deionized water, a phosphate buffer, and ferricyanide). The results showed that the sulfate-removal efficiency is 92 ± 1.2% during a 95-day operation. A high sulfide-removal efficiency of 93.5 ± 1.2 and 83.7 ± 2% and power density of 18.5 ± 1.1 and 15.2 ± 1.2 mW/m2 were obtained with ferricyanide and phosphate buffers as the catholyte, respectively, which is about 2.6 and 2.1 times higher than dissolved oxygen being used as a catholyte, respectively. These results indicated that cathode electron acceptors have a direct effect on the performance of the treatment system. The sulfide-removal efficiency and power density of the phosphate buffer SOFC were only slightly less than the ferricyanide SOFC. Therefore, a phosphate buffer could serve as a low-cost and effective pH buffer for practical applications, especially for wastewater treatment. The results presented in this study clearly revealed that the integrated treatment system can be effectively applied for sulfate/sulfide removal and electricity generation simultaneously.

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We present a novel and easy approach using a silicon-based impedance chip to determine the concentration of the given aqueous buffer solution. An accurate determination of the post-dilution concentration of the buffers is necessary for ensuring optimal buffer capacity, pH stability, and to assess solution reproducibility. In this study, we focused on phosphate buffer as the test liquid to achieve precise post-dilution concentration determinations. The impedance chip consisting of a top gold ring electrode, where a test volume of 20 µL to 30 µL of phosphate buffer was introduced for impedance measurements within the frequency range of 40 Hz to 1 MHz. For impedance investigation, we used phosphate buffers with three different pH values, and the impedance was measured after diluting the phosphate buffers to a concentration of 1.00 M, 0.75 M, 0.50 M, 0.25 M, 0.10 M, 0.05 M, and 0.01 M. In order to analyze the distinctive changes in the measured impedance, an equivalent circuit was proposed and modeled. From the impedance modeling, we report that the circuit parameter RAu/Si showed exponential dependence on the concentration of phosphate buffer and no dependence on the pH values of the phosphate buffer and on the added volume inside the ring electrode. The proposed silicon-based impedance chip is quick and uses reduced liquid volume for post-dilution concentration measurements of buffers and has perspective applications in the pharmaceutical and biological domains for regulating, monitoring, and quality control of the buffers.

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The electrochemical properties of as-cast Zr56Cu19Ni11Al9Nb5 metallic glass and samples annealed at different temperatures were investigated using potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) in phosphate buffer saline (PBS) solution. It was shown that passivation occurred for the as-cast sample and the samples annealed at 623-823 K, indicating good corrosion resistance. At higher annealing temperature, the corrosion resistance first increased, and then decreased. The sample annealed at 823 K exhibited the best corrosion resistance, with high spontaneous corrosion potential Ecorr at -0.045 VSCE, small corrosion current density icorr at 1.549 × 10-5 A·cm-2, high pitting potential Epit at 0.165 VSCE, the largest arc radius, and the largest sum of Rf and Rct at 5909 Ω·cm2. For the sample annealed at 923 K, passivation did not occur, with low Ecorr at -0.075 VSCE, large icorr at 1.879 × 10-5 A·cm-2, the smallest arc radius, and the smallest sum of Rf and Rct at 2173 Ω·cm2, which suggested the worst corrosion resistance. Proper annealing temperature led to improved corrosion resistance due to structural relaxation and better stability of the passivation film, however, if the annealing temperature was too high, the corrosion resistance deteriorated due to the chemical inhomogeneity between the crystals and the amorphous matrix. Optical microscopy and scanning electron microscopy (SEM) examinations indicated that localized corrosion occurred. Results of energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) illustrated that the main corrosion products were ZrO2, CuO, Cu2O, Ni(OH)2, Al2O3, and Nb2O5.

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Metals in particulate matter (PM) are hypothesized to have enhanced toxicity based on their ability to catalyze reactive oxygen species (ROS) formation. Acellular assays are used to measure the oxidative potential (OP) of PM and its individual components. Many OP assays, including the dithiothreitol (DTT) assay, use a phosphate buffer matrix to simulate biological conditions (pH 7.4 and 37 °C). Prior work from our group observed transition metal precipitation in the DTT assay, consistent with thermodynamic equilibria. In this study, we characterized the effects of metal precipitation on OP measured by the DTT assay. Metal precipitation was affected by aqueous metal concentrations, ionic strength, and phosphate concentrations in ambient PM sampled in Baltimore, MD and a standard PM sample (NIST SRM-1648a, Urban Particulate Matter). Critically, differences in metal precipitation induced differing OP responses of the DTT assay as a function of phosphate concentration in all PM samples analyzed. These results indicate that comparison of DTT assay results obtained at differing phosphate buffer concentrations is highly problematic. Further, these results have implications for other chemical and biological assays that use phosphate buffer for pH control and their use to infer PM toxicity.

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OBJECTIVES: This study aimed to analyse the effect of using phosphate buffer solution (PBS) on the solubility, pH changes, surface structure, and elemental composition of a new bioceramic Cerafill sealer compared with Endosequence sealer and AH26 resin-based sealer. METHODS: A fresh mixture of each sealer moistened with either deionised water or PBS was subjected to a setting time test. Set discs (n = 10) were submerged in either deionised water or PBS to evaluate pH changes and solubility at 1, 7, 14, 21, and 28 days. Surface characterisation of the sealers was done before and after solubility tests using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and Fourier transform infrared (FTIR) spectroscopy analyses. RESULTS: An analysis of variance revealed a significant delay in setting of BC-Endosequence (P < .001) with no significant difference when each sealer was moistened with deionised water or PBS (P > .05). Both bioceramic sealers exhibited highly alkaline pH (range, 9.47-10.72). When the sealer was submerged in deionised water, Endosequence exhibited significantly greater solubility, whilst Cerafill and AH26 gained weight. When the sealers were submerged in PBS, both bioceramic sealers gained more weight, with significantly greater values for Endosequence (P < .001). Hydroxyapatite formation was revealed by SEM/EDX and FTIR. CONCLUSIONS: PBS promoted the formation of hydroxyapatite crystals that protect the bioceramic sealers from dissolving.

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PURPOSE: New formulations of the glycopeptide drug dalbavancin containing 2-hydroxpropyl-ß-cyclodextrin (2HPßCD) with or without divalent metal ions in phosphate buffer (pH 7.0) were tested to evaluate whether these excipients influence the aqueous solution stability of dalbavancin. METHOD: Recovery of dalbavancin from phosphate buffered solutions at pH 7.0 with different concentrations of 2HPßCD and a divalent metal ion (Ca2+, Mg2+, or Zn2+) was evaluated by RP-HPLC and HP-SEC after four weeks of storage at 5°C and 55°C. A long-term study of formulations with 2HPßCD and Mg2+ was carried out over six months at 5°C, 25°C, and 40°C using RP-HPLC. RESULTS: Dalbavancin solutions with either 5.5 mM or 55 mM 2HPßCD were significantly more stable with Mg2+ than with the other divalent metal ions, both at 55°C for four weeks and at 40°C for six months. Dalbavancin was found to be more stable in aqueous solutions at a concentration of 1 mg/mL than at 20 mg/mL with 2HPßCD and Mg2+ at 40°C for six months. CONCLUSION: The results suggest that 2HPßCD forms an inclusion complex with dalbavancin that slows the formation of the major degradant, mannosyl aglycone (MAG). The effect of 2HPßCD is increased in the presence of Mg2+ and phosphate at pH 7.0, and the complex is more stable at a dalbavancin concentration of 1 mg/mL than at 20 mg/mL. These observations point towards the possibility of formulating a dalbavancin injection solution with a long shelf life at room temperature and physiological pH.

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The blending of natural polysaccharides with synthetic polymers has attracted much attention in drug delivery models owing to their remarkable biodegradable and biocompatible characteristics. This study focuses on the facile preparation of a sequence of composite films having Starch/Poly(allylamine hydrochloride) (ST/PAH) in different compositions to propose a novel drug delivery system (DDS). ST/PAH blend films were developed and characterized. FT-IR evaluation confirmed the involvement of intermolecular H-bonding between the ST and PAH counterparts in blended films. The water contact angle (WCA) ranged from 71° to 100° indicating that all the films were hydrophobic. TPH-1 (90 % ST and 10 % PAH) was evaluated for in vitro controlled drug release (CDR) at 37 ± 0.5 °C in a time-dependent fashion. CDR was recorded in phosphate buffer saline (PBS) and simulated gastric fluid (SGF). In the case of SGF (pH 1.2), the percentile drug release (DR) for TPH-1 was approximately 91 % in 110 min, while the maximum DR was 95 % in 80 min in PBS (pH 7.4) solution. Our results demonstrate that the fabricated biocompatible blend films can be a promising candidate for a sustained-release DDS for oral drug administration, tissue engineering, wound dressings, and other biomedical applications.

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Stereology and semiautomated binary image histomorphometry are two common methods used for morphometry of nerve fibres. Nucleator probe can be used for the estimation of morphometric parameters like diameter, perimeter, area and volume of a structure that is approximately either a circle or a sphere. In this study, we estimated these parameters with the help of ImageJ software on calibrated transmission electron micrographs. We procured samples of the cochlear nerve (CN) during winter months, within 6-12 hours of death, to reduce post-mortem autolytic changes. The temporal bones containing the CN were fixed by immersion in chilled paraformaldehyde. After dissecting out from the petrous part of the temporal bone, the CN were osmicated and processed for embedding in resin. From the resin blocks, silver coloured (70 nm) ultrathin sections were cut and picked on 300-mesh copper grids, stained with uranyl acetate and lead citrate and viewed under Tecnai G2-20 transmission electron microscope. The transmission electron micrographs had scale bars embedded into them by the software at the time of imaging, and the morphometric parameters of randomly selected nerve fibres were measured using the ImageJ software. The ImageJ software could become a low-cost and dependable tool for nerve fibre morphometry.•Nucleator probe is used for the estimation of morphometric parameters like diameter, perimeter, area or volume•Morphometric parameters were estimated by the ImageJ software on calibrated transmission electron micrographs•The ImageJ software could become a low-cost and dependable tool for nerve fibre morphometry.

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Heparin, a major anticoagulant drug, comprises a complex mixture of motifs. Heparin is isolated from natural sources while being subjected to a variety of conditions but the detailed effects of these on heparin structure have not been studied in depth. Therefore, the result of exposing heparin to a range of buffered environments, ranging pH values from 7 to 12, and temperatures of 40, 60 and 80 °C were examined. There was no evidence of significant N-desulfation or 6-O-desulfation in glucosamine residues, nor of chain scission, however, stereochemical re-arrangement of α-L-iduronate 2-O-sulfate to α-L-galacturonate residues occurred in 0.1 M phosphate buffer at pH 12/80 °C. The results confirm the relative stability of heparin in environments like those during extraction and purification processes; on the other hand, the sensitivity of heparin to pH 12 in buffered solution at high temperature is highlighted, providing an important insight for heparin manufacturers.

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Common treatments for the management of diabetes have limitations due to side effects, hence the need for continuous research to discover new remedies with better therapeutic efficacy. Previously, we have reported that the combination treatment of gallic acid (20 mg/kg) and andrographolide (10 mg/kg) for 15 days demonstrated synergistic hypoglycemic activity in the streptozotocin (STZ)-induced insulin-deficient diabetes rat model. Here, we attempt to further elucidate the effect of this combination therapy at the biochemical, histological and molecular levels. Our biochemical analyses showed that the combination treatment significantly increased the serum insulin level and decreased the total cholesterol and triglyceride level of the diabetic animals. Histological examinations of H&E stained pancreas, liver, kidney and adipose tissues of combination-treated diabetic animals showed restoration to the normalcy of the tissues. Besides, the combination treatment significantly enhanced the level of glucose transporter-4 (GLUT4) protein expression in the skeletal muscle of treated diabetic animals compared to single compound treated and untreated diabetic animals. The molecular docking analysis on the interaction of gallic acid and/or andrographolide with the adiponectin receptor 1 (AdipoR1), a key component in the regulation of pancreatic insulin secretion, revealed a greater binding affinity of AdipoR1 to both compounds compared to individual compounds. Taken together, these findings suggest the combination of gallic acid and andrographolide as a potent therapy for the management of diabetes mellitus.

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Antibody-based T cell-activating biologics are promising therapeutic medicines being developed for a number of indications, mainly in the oncology field. Among those, T cell bispecific antibodies are designed to bind one tumor-specific antigen and the T cell receptor at the same time, leading to a robust T cell response against the tumor. Although their unique format and the versatility of the CrossMab technology allows for the generation of safer molecules in an efficient manner, product-related variants cannot be completely avoided. Therefore, it is of extreme importance that both a manufacturing process that limits or depletes product-related impurities, as well as a thorough analytical characterization are in place, starting from the development of the manufacturing cell line until the assessment of potential toxicities. Here, we describe such an end-to-end approach to minimize, quantify and control impurities and -upon their functional characterization- derive specifications that allow for the release of clinical material.

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Global temperature is increasing due to anthropogenic activities and the effects of elevated temperature on DNA lesions are not well documented in marine organisms. The American oyster (Crassostrea virginica, an edible and commercially important marine mollusk) is an ideal shellfish species to study oxidative DNA lesions during heat stress. In this study, we examined the effects of elevated temperatures (24, 28, and 32 °C for one-week exposure) on heat shock protein-70 (HSP70, a biomarker of heat stress), 8­hydroxy-2'-deoxyguanosine (8-OHdG, a biomarker of pro-mutagenic DNA lesion), double-stranded DNA (dsDNA), γ-histone family member X (γH2AX, a molecular biomarker of DNA damage), caspase-3 (CAS-3, a key enzyme of apoptotic pathway) and Bcl-2-associated X (BAX, an apoptosis regulator) protein and/or mRNA expressions in the gills of American oysters. Immunohistochemical and qRT-PCR results showed that HSP70, 8-OHdG, dsDNA, and γH2AX expressions in gills were significantly increased at high temperatures (28 and 32 °C) compared with control (24°C). In situ TUNEL analysis showed that the apoptotic cells in gill tissues were increased in heat-exposed oysters. Interestingly, the enhanced apoptotic cells were associated with increased CAS-3 and BAX mRNA and/or protein expressions, along with 8-OHdG levels in gills after heat exposure. Moreover, the extrapallial (EP) fluid (i.e., extracellular body fluid) protein concentrations were lower; however, the EP glucose levels were higher in heat-exposed oysters. Taken together, these results suggest that heat shock-driven oxidative stress alters extracellular body fluid conditions and induces cellular apoptosis and DNA damage, which may lead to increased 8-OHdG levels in cells/tissues in oysters.