Cardioprotective Properties of Mannitol—Involvement of Mitochondrial Potassium Channels

Cardiac preconditioning (PC) and postconditioning (PoC) are powerful measures against the consequences of myocardial ischemia and reperfusion (I/R) injury. Mannitol—a hyperosmolar solution—is clinically used for treatment of intracranial and intraocular pressure or promotion of diuresis in renal failure. Next to these clinical indications, different organ-protective properties—e.g., perioperative neuroprotection—are described. However, whether Mannitol also confers cardioprotection via a pre- and/or postconditioning stimulus, possibly reducing consequences of I/R injury, remains to be seen. Therefore, in the present study we investigated whether (1) Mannitol-induced pre- and/or postconditioning induces myocardial infarct size reduction and (2) activation of mitochondrial ATP-sensitive potassium (mK_ATP) channels is involved in cardioprotection by Mannitol. Experiments were performed on isolated hearts of male Wistar rats via a pressure controlled Langendorff system, randomized into 7 groups. Each heart underwent 33 min of global ischemia and 60 min of reperfusion. Control hearts (Con) received Krebs–Henseleit buffer as vehicle only. Pre- and postconditioning was achieved by administration of 11 mmol/L Mannitol for 10 min before ischemia (Man-PC) or immediately at the onset of reperfusion (Man-PoC), respectively. In further groups, the mK_ATP channel blocker 5HD, was applied with and without Mannitol, to determine the potential underlying cardioprotective mechanisms. Primary endpoint was infarct size, determined by triphenyltetrazolium chloride staining. Mannitol significantly reduced infarct size both as a pre- (Man-PC) and postconditioning (Man-PoC) stimulus compared to control hearts (Man-PC: 31 ± 4%; Man-PoC: 35 ± 6%, each p < 0.05 vs. Con: 57 ± 9%). The mK_ATP channel inhibitor completely abrogated the cardioprotective effect of Mannitol-induced pre- (5HD-PC-Man-PC: 59 ± 8%, p < 0.05 vs. Man-PC) and postconditioning (5HD-PoC-Man-PoC: 59 ± 10% vs. p < 0.05 Man-PoC). Infarct size was not influenced by 5HD itself (5HD-PC: 60 ± 14%; 5HD-PoC: 54 ± 14%, each ns vs. Con). This study demonstrates that Mannitol (1) induces myocardial pre- and postconditioning and (2) confers cardioprotection via activation of mK_ATP channels.     

Optimization of activated carbon‐based decontamination of fish oil by response surface methodology

The effect of activated carbon (AC) adsorption on the reduction of persistent organic pollutants (POP) in fish oil was studied based on response surface methodology at a 5‐g/kg AC inclusion level. Pretreatment of the oil by alkali refining and bleaching increased the POP levels. The tested process variables (contact time and temperature) affected the AC adsorption rate and significant first‐ and second‐order response models could be established. Polychlorinated dibenzo‐p‐dioxins and dibenzofurans (PCDD/F) showed a very rapid adsorption behavior and the concentration and toxic equivalent (TEQ) level could be reduced by 99%. Adsorption of dioxin‐like polychlorinated biphenyls (DL‐PCB) was less effective and depended on ortho substitution, i.e. non‐ortho PCB were adsorbed more effectively than mono‐ortho PCB with a maximum of 87 and 21% reduction, respectively, corresponding to a DL‐PCB‐TEQ reduction of 73%. A common optimum for both PCDD/F and DL‐PCB adsorption could not be identified. AC treatment had no effect on the level of polybrominated diphenyl ether flame retardants. The differences in adsorption patterns may be explained based on molecular conformation. No change in oil quality could be observed based on oxidation parameters. Compliance with present PCDD/F and DL‐PCB legislation levels in fish oil can be achieved based on AC adsorption.     

Rheology of thermo-reversible fish protein isolate gels

Fish protein isolates (FPI) from cod muscle were studied at pH 9 and 11. Thermo-reversible gels, stable at and below room temperature could be produced at both pH values. Application of low shear stress to the gels led to an initial elastic response followed by a power-law deformation (creep) at both pH. Above a critical shear stress gels fractured and flowed regularly with a viscosity of about 0.05 Pa s.Strain–stress curves were recorded using both flow and oscillatory measurements. For all systems strain-hardening was observed followed by fracture. Fracture occurred at approximately the same deformation, but the amplitude of strain-hardening and the yield stress decreased with decreasing rate of the stress ramp. Results obtained from oscillatory shear at 1 or 0.1 Hz were close to those obtained with continuous shear during the fastest stress ramps.The structure of the gels was investigated using confocal laser scanning microscopy and turbidity measurements.     

A consumer preference study of raw Norwegian rainbow trout (Oncorhynchus mykiss) as sashimi with focus on young adults in Japan

This study was the first consumer study done in Japan, which investigated consumer preferences of raw Norwegian rainbow trout with the use of an experimental design. A full factorial design with three variables (body part, body weight and freshness) was applied at two levels. The results showed that the variation in body part had the greatest effect on the expected and experienced eating quality of raw rainbow trout among seventy-five young adult consumers. The effect was negative and it is possible that the high fat level observed in the belly region does not always lead to better overall likings. The high fat content could also result in the intense fishy odour distinctive to raw salmonidae at consumption and influence the perception of other quality attributes. The present study provides a new way of offering more practical and applicable suggestions to the fish farming industry.     

pKa-Values of Guaiacyl and Syringyl Phenols Related to Lignin

Abstract

The literature relating to the pK_a -values of guaiacyl- and syringyl-derived phenols has been thoroughly surveyed and summarized. In addition, the pK_a -values of a number of guaiacyl, syringyl and other phenols related to lignin have been determined using a spectrophotometric method combined with multivariate evaluation. Differences and similarities between the acidities of a number of substances are extensively discussed. The pK_a -value strongly affects the delignification during pulping, bleaching and leaching of lignin during pulp washing.     

Classification of fresh Atlantic salmon (Salmo salar L.) fillets stored under different atmospheres by hyperspectral imaging

Hyperspectral imaging (HSI) was used to investigate spectroscopic changes in fresh salmon stored under different atmospheres (air, 60% CO₂/40% N₂ and 90% vacuum) and to determine whether HSI can classify fillets by the type of packaging. Hyperspectral images of samples kept at 4 °C were acquired and bacterial growth and lipid oxidation were measured. Principal component analysis was applied to study spectral development of samples during storage and K nearest-neighbour classifier was used for the classification of fillets by packaging type. Partial least squares regression was run to reduce the number of wavelengths included in the classification model. The results demonstrated that spectral variations could be observed in the different packaging atmospheres primarily at the wavelengths 606 and 636 nm. Using HSI, successful classification of fillets according to the packaging used (>88%) was achieved and this was largely dependent on spectral characteristics at the wavelengths 606 and 636 nm, possibly due to the different oxidation states of the haem proteins in the muscles.     

Partial characterisation of gelatinolytic activities in herring (Clupea harengus) and sardine (Sardina pilchardus) possibly involved in post-mortem autolysis of ventral muscle

The present work aims at identifying enzymatic activities that may contribute to the post-mortem autolysis of the ventral muscle, known as belly bursting, in herring (Clupea harengus). Gelatinolytic proteases extracted from several herring tissues and also from a sardine (Sardina pilchardus) tissue were partially characterised using gelatin zymography, inhibitor analysis, immunodetection with anti-trypsin antibody and MALDI-TOF/TOF peptide sequencing. The results indicate the presence of gelatinolytic trypsin-like serine proteases and metalloproteases in several samples including the ventral muscle of herring. MS/MS analysis gave partial sequences of peptides from some of the proteases, and these were identified as elastase, trypsin and aspartyl aminopeptidase. It is likely that belly bursting in herring is caused by leakage of enzyme-rich fluids from the intestine and/or pyloric caeca which may also contain exogenous proteases from the digestive systems of the prey.