Breaking Osteoclast-Acid Vicious Cycle to Rescue Osteoporosis via an Acid Responsive Organic Framework-Based Neutralizing and Gene Editing Platform.

In the osteoporotic microenvironment, the acidic microenvironment generated by excessive osteoclasts not only causes irreversible bone mineral dissolution, but also promotes reactive oxygen species (ROS) production to induce osteoblast senescence and excessive receptor activator of nuclear factor kappa-B ligand (RANKL) production, which help to generate more osteoclasts. Hence, targeting the acidic microenvironment and RANKL production may break this vicious cycle to rescue osteoporosis. To achieve this, an acid-responsive and neutralizing system with high in vivo gene editing capacity is developed by loading sodium bicarbonate (NaHCO3) and RANKL-CRISPR/Cas9 (RC) plasmid in a metal-organic framework. This results showed ZIF8-NaHCO3@Cas9 (ZNC) effective neutralized acidic microenvironment and inhibited ROS production . Surprisingly, nanoparticles loaded with NaHCO3 and plasmids show higher transfection efficiency in the acidic environments as compared to the ones loaded with plasmid only. Finally, micro-CT proves complete reversal of bone volume in ovariectomized mice after ZNC injection into the bone remodeling site. Overall, the newly developed nanoparticles show strong effect in neutralizing the acidic microenvironment to achieve bone protection through promoting osteogenesis and inhibiting osteolysis in a bidirectional manner. This study provides new insights into the treatment of osteoporosis for biomedical and clinical therapies.

Analysing the effect of sodium bicarbonate and glycine air polishing on tooth surfaces with two different imaging methods.

The aim of this study was to compare two different imaging methods by assessing changes caused by sodium bicarbonate and glycine air polishing on the tooth surfaces. Fourteen single root teeth with exposed root surfaces were included into the study. The teeth were randomly divided into two groups: sodium bicarbonate and glycine group. Samples were scanned in a micro-computed tomography (micro-CT) and CAD/CAM (computer-aided design/computer-aided manufacturing) at baseline and then after air-polishing powder applications, the defect volume values were evaluated. There was a statistically significant difference between mean defect volume values that occurred after glycine and sodium bicarbonate air polishing evaluated with micro-CT and CAD/CAM (p < 0.05). After sodium bicarbonate air polishing, defect volume on enamel surface at maximum power and defect volume on the exposed root surface at medium power values calculated with CAD/CAM were higher. After glycine air polishing, defect volume values on both surfaces at medium power setting calculated with CAD/CAM were lower. Defect volume values on enamel surface at maximum power setting calculated with CAD/CAM were higher than calculated with micro-CT. We concluded that CAD/CAM cannot provide as accurate results as micro-CT. Glycine-based powder is less abrasive than sodium bicarbonate, especially on enamel surface. Lay Description: Micro-CT is a non-destructive imaging method with high resolution and allows to examine all tooth structures individually. CAD/CAM are systems that are widely used in dentistry today. Access to the device is easier than micro-CT. Intraoral scanners in CAD/CAM systems also provide non-destructive image scanning. The aim of this study was to compare two different imaging methods by assessing changes caused by sodium bicarbonate and glycine air polishing on the tooth surfaces. The results showed that because of the analyses made with CAD/CAM, similar results could not be obtained with micro-CT and cannot be used to evaluate the changes that occur after air polishing.

Instant tough bioadhesive with triggerable benign detachment.

Bioadhesives such as tissue adhesives, hemostatic agents, and tissue sealants have potential advantages over sutures and staples for wound closure, hemostasis, and integration of implantable devices onto wet tissues. However, existing bioadhesives display several limitations including slow adhesion formation, weak bonding, low biocompatibility, poor mechanical match with tissues, and/or lack of triggerable benign detachment. Here, we report a bioadhesive that can form instant tough adhesion on various wet dynamic tissues and can be benignly detached from the adhered tissues on demand with a biocompatible triggering solution. The adhesion of the bioadhesive relies on the removal of interfacial water from the tissue surface, followed by physical and covalent cross-linking with the tissue surface. The triggerable detachment of the bioadhesive results from the cleavage of bioadhesive's cross-links with the tissue surface by the triggering solution. After it is adhered to wet tissues, the bioadhesive becomes a tough hydrogel with mechanical compliance and stretchability comparable with those of soft tissues. We validate in vivo biocompatibility of the bioadhesive and the triggering solution in a rat model and demonstrate potential applications of the bioadhesive with triggerable benign detachment in ex vivo porcine models.

High-throughput metabolomics method based on liquid chromatography-mass spectrometry: Insights into the underlying mechanisms of salinity-alkalinity exposure-induced metabolites changes in Barbus capito.

It is critical to investigate the adaptive development and the physiological mechanism of fish in external stimulation. In this study, the response of Barbus capito to salinity-alkalinity exposure was explored by high-throughput nontargeted and liquid chromatography-mass spectrometry-based metabolomics to investigate metabolic biomarker and pathway changes. Meanwhile, the biochemical indexes of Barbus capito were measured to discover the chronic impairment response to salinity-alkalinity exposures. A total of 29 tissue metabolites were determined to deciphering the endogenous metabolic changes of fishes during the different concentration salinity-alkalinity exposures environment, which were mainly involved in the key metabolism including the phenylalanine, tyrosine, and tryptophan biosynthesis, arachidonic acid metabolism, pyruvate metabolism, citrate cycle, and glycerophospholipid metabolism. Finally, we found the amino acid metabolism as key target was associated with the endogenous metabolites and metabolic pathways of Barbus capito to salinity-alkalinity exposures. In conclusion, metabolomics is a potentially powerful tool to reveal the mechanism information of fish in various exposure environments.

The implications of variations in nasal irrigation recipes in the United Kingdom.

OBJECTIVE: This study aims to investigate the variations in publicly available nasal irrigation recipes published in the United Kingdom (UK). DESIGN: Internet searches used to identify eligible nasal irrigation recipes. These were then examined for their physical and biochemical properties, through theoretical calculations and experimental measurement. SETTING: Recipes produced by healthcare providers or official national bodies in the UK. PARTICIPANTS: No human participants. MAIN OUTCOME MEASURES: Solution osmolality (classified into hypo-, iso- and hypertonic), acidity (pH) and specific gravity. RESULTS: Thirteen unique recipes were identified from 17 sources. Osmolality ranged from 166.2 to 1492.2 mosmol/kg in volumes ranging from 142 to 1136 mLs (isotonic range 275-295 mosmol/kg). Specific gravity ranged from 1.006 to 1.034. pH ranged from 7.74 to 8.11. No recipe produced a solution with isotonic properties. The majority produced hypertonic irrigations. CONCLUSIONS: Most publicly available nasal irrigation recipes produce hypertonic solutions but there is great variability in the osmolality and volume. UK organisations should take action to review published recipes to bring these into alignment with latest guidelines (recommending against hypertonic saline use) and reduce variability in patient interpretations.

Smart Nanosacrificial Layer on the Bone Surface Prevents Osteoporosis through Acid-Base Neutralization Regulated Biocascade Effects.

Osteoporosis is a global chronic disease characterized by severe bone loss and high susceptibility to fragile fracture. It is widely accepted that the origin acidified microenvironment created by excessive osteoclasts causes irreversible bone mineral dissolution and organic degradation during osteoclastic resorption. However, current clinically available approaches are mainly developed from the perspective of osteoclast biology rather than the critical acidified niche. Here, we developed a smart "nanosacrificial layer" consisting of sodium bicarbonate (NaHCO3)-containing and tetracycline-functionalized nanoliposomes (NaHCO3-TNLs) that can target bone surfaces and respond to external secreted acidification from osteoclasts, preventing osteoporosis. In vitro and in vivo results prove that this nanosacrificial layer precisely inhibits the initial acidification of osteoclasts and initiates a chemically regulated biocascade to remodel the bone microenvironment and realize bone protection: extracellular acid-base neutralization first inhibits osteoclast function and also promotes its apoptosis, in which the apoptosis-derived extracellular vesicles containing RANK (receptor activator of nuclear factor-κ B) further consume RANKL (RANK ligand) in serum, achieving comprehensive osteoclast inhibition. Our therapeutic strategy for osteoporosis is based on original and precise acid-base neutralization, aiming to reestablish bone homeostasis by using a smart nanosacrificial layer that is able to induce chemically regulated biocascade effects. This study also provides a novel understanding of osteoporosis therapy in biomedicine and clinical treatments.

Generation of High Dose Inhalable Effervescent Dispersions against Pseudomonas aeruginosa Biofilms.

PURPOSE: Novel particle engineering approach was used in this study to generate high dose inhalable effervescent particles with synergistic effects against Pseudomonas aeruginosa biofilms. METHODS: Spray dried co-amorphous salt of ciprofloxacin (CFX) and tartaric acid (TA) was prepared and coated with external layer of sodium bicarbonate and silica coated silver nanobeads. Design of experiments (DOE) was used to optimize physicochemical properties of particles for enhanced lung deposition. RESULTS: Generated particles were co-amorphous CFX/TA showing that CFX lost its zwitterionic form and exhibiting distinct properties to CFX/HCl as assessed by FTIR and thermal analysis. Particles exhibited mass mean aerodynamic diameter (MMAD) of 3.3 µm, emitted dose of 78% and fine particle dose of 85%. Particles were further evaluated via antimicrobial assessment of minimum inhibitory concentrations (MIC) and minimum biofilm eradication concentration (MBEC). MIC and MBEC results showed that the hybrid particles were around 3-5 times more effective when compared to CFX signifying that synergistic effect was achieved. Diffusing wave spectroscopy results showed that the silver containing particles had a disruptive effect on rheological properties as opposed to silver free particles. CONCLUSIONS: Overall, these results showed the potential to use particle engineering to generate particles that are highly disruptive of bacterial biofilms.

An effective method to produce 7-epitaxol from taxol in HCO3.

It is known that 7-epitaxol has much stronger cytotoxicity than taxol does. However, the content of 7-epitaxol in yew is much less than taxol, which makes it more costly to obtain. We describe here a method to effectively convert taxol to 7-epitaxol. The key condition for reaction needs NaHCO3 in solvent acetonitrile (ACN). The conversion rate can be over 82%.

The effect of concentration, reconstitution solution and pH on the stability of a remifentanil hydrochloride and propofol admixture for simultaneous co-infusion.

BACKGROUND: There are scenarios where pre-mixing and infusing analgesic and anaesthetic agents as a single intravenous (IV) solution is highly desirable; however, it is important to ensure the agents are compatible when mixed. As such, the long-term stability of a remifentanil-propofol mixture, and means of improving this, were assessed across a range of remifentanil concentrations, diluents, and time points. METHODS: Remifentanil was reconstituted with ultrapure water, 0.9% saline, 20% saline, or 8.4% sodium bicarbonate solution (the latter two chosen for their pH characteristics, rather than their use in pharmaceutical reconstitution) and then mixed with propofol (1%) or further diluted with water to derive concentrations of 10-50 µg mL- 1. Remifentanil and propofol concentrations were determined initially and then periodically for up to 24 h using high performance liquid chromatography (HPLC). Mass spectrometry (MS) was used to detect degradation products in solutions containing 30 µg mL- 1 of remifentanil. Statistical analysis was performed using ANOVA and Student's t-test, with a significance value of 0.05. RESULTS: Isolated remifentanil (pH < 4) and propofol (pH 7.35) did not degrade significantly when reconstituted with water or saline solution over 24 h, while remifentanil reconstituted with sodium bicarbonate degraded significantly (P < 0.001, pH 8.65). Mixing with propofol substantially increased the pH of the mixture and resulted in significant remifentanil degradation for all reconstitution solutions used, while propofol remained stable (pH 6.50). The amount of degradation product detected in samples containing isolated remifentanil and a mixture of the drugs was proportional to the remifentanil degradation observed. CONCLUSIONS: Remifentanil stability is affected by both the reconstitution solution used and when mixed with propofol, with pH appearing to be a contributing factor to degradation. If the pH of the solution and concentration of remifentanil are correctly controlled, e.g. through the use of a more acidic diluent, an admixture of remifentanil and propofol may be useful clinically.

Comparison on Reduction of VOCs Emissions from Radiata Pine (Pinus Radiata D. Don) between Sodium Bicarbonate and Ozone Treatments.

Volatile organic compounds (VOCs) in wood furniture are an important factor that affects indoor air quality. In this study, radiata pine (Pinus radiata D. Don) was treated with sodium bicarbonate and ozone aqueous solution to reduce the VOC contents without sacrificing mechanical properties. The VOCs of radiata pine were identified by gas chromatography-mass spectrometry (GC-MS), and the functional group changes of wood samples were characterized by Fourier-transform infrared spectroscopy (FTIR). The results showed that the main VOCs of radiata pine include alkenes, aldehydes, and esters. The sodium bicarbonate and ozone treatments almost eliminated the VOC contents of radiata pine. The two treatments mentioned above had little effect on compressive strength and surface color of radiata pine.

Effect of air-polishing on surface roughness of composite dental restorative material - comparison of three different air-polishing powders.

BACKGROUND: Increased composite roughness enhances bacterial adhesion and discoloration, thus increasing the risk of gingival inflammation and secondary caries. Concerns about detrimental effects of sodium bicarbonate on surface roughness influenced the development of less abrasive powders: a glycine-based powder and an erythritol-based powder, additionally - sodium bicarbonate-based powder of reduced grain size. However, there is limited evidence on effects of these materials on the surface of dental fillings. The aim of the present study was to compare the effects of three air-polishing powders (of a reduced abrasiveness) on surface roughness of microhybrid restorative composite material. MATERIAL AND METHODS: Microhybrid light-cure resin composite samples were placed on 64 plaster cubes and light-cured through polyester strips. Surface roughness was measured using laser confocal microscope (magnification 2160x). The specimens were randomly divided into three groups (n = 20, 20 and 24) and air-polished with: sodium bicarbonate (40 µm), glycine (25 µm) and erythritol (14 µm), respectively. Then surface roughness was remeasured, keeping the same field of observation. Specialized 3D analysis software was used for data processing. Parameters according to ISO 25178: Sa, Sq, Sku, Sp, Sv, Sz, Ssk were used to describe surface roughness. RESULTS: Sa, Sq, Sp, Sv, Sz increased significantly following air polishing. Ssk was significantly higher, whereas Sku was significantly lower in sodium bicarbonate and erythritol groups than before air polishing. Comparison between the three powders revealed that Sa was significantly higher in sodium bicarbonate group than in glycine group. Sku was significantly higher in glycine and erythritol groups than in sodium bicarbonate group. CONCLUSIONS: Sodium bicarbonate has a stronger detrimental effect on composite surface than glycine or erythritol. No advantage of erythritol comparing to glycine could be found.

Is ancestry, not natron, an explanation for fair haired children in Greco-Roman Egypt?

In an examination of three unwrapped mummified children from the Graeco-Roman Period of ancient Egypt there was an unexpected finding of fair hair. In the majority of unwrapped ancient Egyptian mummified bodies the hair was not fair but rather dark brown or black. To determine if exposure to natron during the mummification process was responsible for the fair hair color an experiment was carried out to partially replicate the environment in which bodies were desiccated. Fourteen samples of modern hair from various age groups, sex and ethnicity were subjected to synthetic natron for a period of 40 days to replicate the time taken to mummify a body. Macroscopic and microscopic examinations of samples were employed to ascertain any significant changes in hair color after treatment. Ancient wigs were studied for evidence of post mortem changes to hair color since construction over 2,000 years ago. Results of the study showed no significant lightening of hair color and in several samples the hair significantly darkened as the result of exposure to the natron. There was not any evidence that hair lightened as the result of natural post mortem changes and this was confirmed by the study of the natural hair wigs that had not changed color post mortem. This study concluded that the fair hair observed in the three child mummies was not the result of exposure to natron or post mortem changes but rather it was probably due to ancestry because of the presence of diverse genomes that were introduced into ancient Egypt during the Greco-Roman Period.

Effect of MnO2 Crystal Structure on Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid.

Aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) as a bioplastics monomer is efficiently promoted by a simple system based on a nonprecious-metal catalyst of MnO2 and NaHCO3. Kinetic studies indicate that the oxidation of 5-formyl-2-furancarboxylic acid (FFCA) to FDCA is the slowest step for the aerobic oxidation of HMF to FDCA over activated MnO2. We demonstrate through combined computational and experimental studies that HMF oxidation to FDCA is largely dependent on the MnO2 crystal structure. Density functional theory (DFT) calculations reveal that vacancy formation energies at the planar oxygen sites in α- and γ-MnO2 are higher than those at the bent oxygen sites. ß- and λ-MnO2 consist of only planar and bent oxygen sites, respectively, with lower vacancy formation energies. Consequently, ß- and λ-MnO2 are likely to be good candidates as oxidation catalysts. On the other hand, experimental studies reveal that the reaction rates per surface area for the slowest step (FFCA oxidation to FDCA) decrease in the order of ß-MnO2 > λ-MnO2 > γ-MnO2 ≈ α-MnO2 > δ-MnO2 > ε-MnO2; the catalytic activity of ß-MnO2 exceeds that of the previously reported activated MnO2 by three times. The order is in good agreement not only with the DFT calculation results, but also with the reduction rates per surface area determined by the H2-temperature-programmed reduction measurements for MnO2 catalysts. The successful synthesis of high-surface-area ß-MnO2 significantly improves the catalytic activity for the aerobic oxidation of HMF to FDCA.

Suicide by plastic bag suffocation combined with the mixture of citric acid and baking soda in an adolescent.

We describe a case of suicidal asphyxiation using a plastic bag combined with carbon dioxide (CO2) gas. A 20-year-old male, whose head was covered with a plastic bag, was found dead in his room. In the plastic bag, there were two glass-made cups containing liquid-like substance. Through crime scene investigation by police staffs, a bottle of citric acid and a box of baking soda were also discovered in his room. The forensic autopsy revealed that there were neither lesions nor injuries in all of the organs. Moreover, any drugs and poisons could not be detected in blood samples. Based on autopsy findings and crime scene investigation, the cause of death was diagnosed as acute asphyxia due to CO2 intoxication by the mixture of citric acid with baking soda in the plastic bag. To the best of our knowledge, there are no medical literatures describing plastic bag suffocation combined with CO2 gas generated from citric acid and baking soda, which has been widely distributed as suicidal means through websites. This case report promotes forensic pathologists and medical coroners to emphasize that the Internet has a crucial role on a source of suicidal information or a promoter of suicide all over the world.

Stability studies of two compounded solutions potentially used in tumor lysis syndrome.

OBJECTIVE: The aim of the study was to determine the stability of two non-commercially produced solutions: 1.68% sodium bicarbonate in 5% glucose (BIC solution) and 1.6% calcium chloride in 0.9% sodium chloride (CAL solution), which can be used to treat tumor lysis syndrome. One of the ways to treat the tumor lysis syndrome is to irrigate patients, alkalinize the urine through the supply of BIC solution or continuous hemodialysis with regional citrate anticoagulation, using a CAL solution. METHOD: The study took place in two independent hospital pharmacies. Fifty samples of each solution were prepared under aseptic conditions, then the concentration of sodium and calcium ions was determined and microbiological purity tests were carried out. The tests were performed on the day of sample preparation and after seven days of storage at 4 ± 1℃. RESULTS: The obtained results showed that applied preparation method was precise and accuracy. The average concentration of sodium ions in BIC solutions ranged from 187.7 to 185.26 mmol/L on 1st and 7th day, respectively. The average concentration of calcium ions in CAL solution ranged from 68.92 to 68.80 mmol/L on 1st and 7th day, respectively. None of the samples were microbiologically contaminated. CONCLUSION: Studied solutions for infusion were characterized by good chemical and microbiological stability when prepared in a clean room and stored at 4 ± 1℃.

Formulation, optimization, and evaluation of raft-forming formulations containing Nizatidine.

OBJECTIVE: The main objective of this research is to formulate, optimize, and evaluate raft-forming chewable tablets of Nizatidine. Various raft-forming agents were used in preliminary screening. Sodium alginate showed maximum raft strength, so tablets were prepared using sodium alginate as the raft forming agent, along with calcium carbonate (CaCO3) as antacid and raft strengthening agent, and sodium bicarbonate (NaHCO3) as a gas generating agent. RESEARCH DESIGN AND METHODS: Raft forming chewable tablets containing Nizatidine were prepared by direct compression and wet granulation methods, and evaluated for drug content, acid neutralization capacity, raft strength, and in-vitro drug release in 0.1 N HCl. Box-Behnken design was used for optimization. RESULTS: Two optimized formulations were predicted from the design space. The first optimized recommended concentrations of the independent variables were predicted to be X1 = 275.92 mg, X2 = 28.60 mg, and X3 = 202.14 mg for direct compression technique and the second optimized recommended concentrations were predicted to be X1 = 253.62 mg, X2 = 24.60 mg, and X3 = 201.77 mg for wet granulation technique. Optimized formulations were stable at accelerated environmental testing for six months at 35 °C and 45 °C with 75% relative humidity. X-Ray showed that the raft floated immediately after ingestion and remained intact for ∼3 h. CONCLUSION: Raft was successfully formed and optimized. Upon chewing tablets, a raft is formed on stomach content. That results in rapid relief of acid burning symptoms and delivering the drug into systemic circulation with enhanced bioavailability.

Correlations of Ion Composition and Power Efficiency in a Reverse Electrodialysis Heat Engine.

The main objective of this study is to explore the influence of ion composition on the trans-membrane potential across the ion exchange membrane (IEM), and thus offers a reference for the deep insight of "reverse electrodialysis heat engine" running in the composite systems. In comparison to the natural system (river water | seawater), the performance of the reverse electrodialysis (RED) stack was examined using NaHCO3, Na2CO3, and NH4Cl as the supporting electrolyte in the corresponding compartment. The effect of flow rates and the concentration ratio in the high salt concentration compartment (HCC)/low salt concentration compartment (LCC) on energy generation was investigated in terms of the open-circuit voltage (OCV) and power density per membrane area. It was found that the new system (0.49 M NaCl + 0.01 M NaHCO3|0.01 M NaHCO3) output a relatively stable power density (0.174 W·m-2), with the open-circuit voltage 2.95 V under the low flow rate of 0.22 cm/s. Meanwhile, the simulated natural system (0.5 M NaCl|0.01 M NaCl) output the power density 0.168 W·m-2, with the open-circuit voltage 2.86 V under the low flow rate of 0.22 cm/s. The findings in this work further confirm the excellent potential of RED for the recovery of salinity gradient energy (SGP) that is reserved in artificially-induced systems (wastewaters).

Acidulant effect on greening, reducing capacity, and tryptophan fluorescence of sunflower butter cookie dough during refrigerated storage.

BACKGROUND: Sunflower seed derived butter can be a source of protein and phenolic antioxidants in refrigerated dough. Chlorogenic quinone-amino acid induced greening can however occur at alkaline pH, which could result in less bioavailable conjugated phenol-amino acids. Acidulants were tested as potential anti-greening ingredients in refrigerated chemically leavened cookie dough. Effect of refrigerated storage time, leavening agents and acidulants on tryptophan fluorescence (λex = 280 nm, λem = 300-500 nm), color (hunter L*, a*, b* color scale), reducing capacity [1,1'-diphenyl-2-picryl-hydrazyl (DPPH) and Folin-Ciocalteu reducing capacity (FCRC)], and hydroxycinnamic acids were measured. RESULTS: The pH range of acidified doughs was 4.83-6.98 compared to 7.65-9.18 in non-acidified leavened doughs after 24 days. Greening was higher in baking soda dough control (a* = -0.54) than baking powder dough control (a* = 2.98) after 24 days, attributed to higher pH (9.18) of the former compared to pH 7.14 in the later. Tryptophan fluorescence intensity in baking soda dough decreased in the order: control > glucono-delta lactone ≈ citric acid after 24 days. The DPPH and FCRC of acidified doughs were greater than corresponding control doughs. CONCLUSION: The use of acidulants would prevent greening in sunflower dough without lowering its phenolic concentration, making use of sunflower butter in refrigerated dough for baked goods feasible. © 2018 Society of Chemical Industry.

Thermodynamics of NaHCO3 decomposition during Na2CO3-based CO2 capture.

Amine-basedcarbon-capture technologies have been shown to be energetically expensive and to cause significant environmental and epidemiological impacts due to their volatility. Bicarbonate formation from carbon dioxide's reaction with water has been suggested as an effective alternative for capturing CO2; however, the thermodynamics of this reaction are not well understood. This study experimentally determined the equilibrium constant of sodium bicarbonate (NaHCO3) decomposition to sodium, water, and carbon dioxide; the study also compared the equilibrium constant to theoretical calculations. Using a combination of experimentation and thermodynamic relationships, the unitless equilibrium constants of the forward and reverse reactions were calculated accurately (error <±9% and <±4%, respectively). Equilibrium data were calculated using enthalpy and entropy values of each component of NaHCO3 decomposition at temperatures ranging from 25 to 155°C respectively. These results offer more data essential to optimizing NaHCO3 use in environmentally friendly next-generation CO2-capture technologies.

Carbonic anhydrase expression in the branchial ionocytes of rainbow trout.

Rainbow trout (Oncorhynchus mykiss) exposed to acid-base challenges activate branchial mechanisms for the excretion of acid-base equivalents. Current models of branchial acid-base excretion in freshwater rainbow trout propose two main ionocyte types: the peanut lectin agglutinin-positive (PNA+) mitochondrion-rich cell or ionocyte is believed to secrete HCO3- in exchange for Cl-, whereas H+ secretion is thought to occur across PNA- ionocytes in exchange for Na+ Both HCO3- and H+ are supplied by intracellular hydration of CO2 catalysed by cytosolic carbonic anhydrase (CAc). Immunohistochemical approaches revealed that under control conditions, CAc was detectable in 92.3±1.0% (N=11) of PNA- ionocytes, and the abundance of PNA- ionocytes increased in response to systemic acidosis elicited by 72 h exposure to water of low pH (nominally pH 4.5), hypercapnia (1% CO2, nominally 7.6 Torr) or hyperoxia (achieved by gassing water with pure O2), as did the abundance of PNA- ionocytes that exhibited immunofluorescence for CAc. However, just 4.3±0.6% (N=11) of PNA+ ionocytes expressed detectable CAc under control conditions. Marked increases in the abundance of CAc-positive PNA+ ionocytes were detected following exposure of trout to a base load via recovery from hypercapnia or base infusion (72 h infusion with 140 mmol l-1 NaHCO3). The percentage of CAc-positive PNA+ ionocytes also was increased in trout treated with cortisol (10 mg kg-1 hydrocortisone 21-hemisuccinate daily for 7 days). These results suggest that regulation of CA within PNA+ ionocytes and/or the abundance of CAc-positive PNA+ ionocytes plays a role in activating base secretion in response to systemic alkalosis.