Study on nucleotide, myofibrillar protein biochemical properties and microstructure of freeze-dried scallop striated muscle during storage and rehydration.

The biochemical properties and microstructural changes of freeze-dried Japanese scallop (Patinopecten yessoensis) striated muscle during room temperature storage and rehydration were investigated. The results showed that the content of ATP in freeze-dried scallop muscle remained stable with no significant difference (p > 0.05). However, ATP was rapidly decomposed and AMP accumulated within 1.5 min of rehydration, and HxR and Hx were gradually produced from AMP decomposition with the extension of rehydration time. Besides, the results of chymotryptic digestion patterns demonstrated that the rod of myosin was unstable after dehydration, reflecting lower salt solubility than that of frozen-thawed scallop. In contrast, the myosin subfragment-1 (S-1) was stable, as indicated by the constant of Ca2+-ATPase activity of freeze-dried scallops throughout the storage and rehydration (p > 0.05). Furthermore, the microstructural analysis revealed that the Z line of the freeze-dried scallop was broken after dehydration process. This study might be useful for developing high-quality dehydrated scallops in the future.

Characterization of myofibrils cold structural deformation degrees of frozen pork using hyperspectral imaging coupled with spectral angle mapping algorithm.

The study investigated the possibility of using hyperspectral imaging (HSI) in the spectral range of 1000-2200nm to characterize myofibrils cold structural deformation degrees of frozen pork samples. The HSI images of pork samples frozen under different freezing rates were acquired in the frozen state without thawing. The myofibrils cold structural deformation degrees were evaluated by surface hydrophobicity (S0ANS) and Ca2+-ATPase activity. Spectral angle mapping (SAM) algorithm was used for the first time to extract the spectral information for regression. Compared with the optimized partial least square regression (PLSR) models based on selected wavebands by successive projections algorithm (SPA), the optimized PLSR models developed based on the spectral angles calculated by the SAM algorithm achieved comparable or even better performance with R2P of 0.896 for S0ANS and 0.879 for Ca2+-ATPase activity, respectively. The implications of the frozen meat spectrum were also analyzed in the current study.

Effects of Four Interior-warming Drugs on the Tension of Ileum Smooth Muscle and Ca2+-ATPase in Rabbits / 医药导报

Objective To investigate the effects of four interior-warming drugs( galangal,cinnamon,evodia rutaecarpa,and dried ginger)on the tension of ileum smooth muscle and Ca2+-ATPase on the cell membrane in rabbits. Methods The effects of galangal,cinnamon,evodia rutaecarpa,and dried ginger were examined on normal ileum smooth muscle,in vitro intestinal muscle contraction caused by acetylcholine(ACh),barium chloride(BaCl2 )and histamine(His), and ACh-induced calcium release by using BL-420E+ biological signal collection and processing system.The average tension was measured within 1 min before delivery and within 3 minutes after the treatment,and the inhibition rate was calculated according to the average tension value.The effects of sera containing galangal,cinnamon,evodia rutaecarpa,and dried ginger on Ca2+-ATPase activity on the cell membrane of the intestinal smooth muscle were examined by phosphorus method. Results Galangal,cinnamon,evodia rutaecarpa,and dried ginger at high concentrations could restrain in vitro intestinal contraction in normal circumstances(P<0.05 or P<0.01).Significant inhibitory effects on intestinal contraction caused by ACh,His and BaCl2 were found in low,medium and high concentration groups(P<0.01).There was a dose-effectiveness relationship between the inhibition rate and final drug concentrations.The ACh-induced intracellular and extracellular calcium dependent contraction were significantly inhibited by the four interior-warming drugs( P < 0. 05 or P < 0. 01). The Ca2+-ATPase activities were( 0. 384 ± 0.070),(0.302±0.016),(0.307±0.016),(0.296±0.016),(0.313±0.003)U·mg-1 ,respectively,in intestinal smooth muscle in normal control group and high concentration groups of galangal,cinnamon,evodia rutaecarpa,and dried ginger(P<0.01). Conclusion Interior-warming drugs may relax intestinal smooth muscle by reducing the intracellular calcium release and the extracellular calcium inflow via receptor-controlled calcium channels,and inhibiting the Ca2+-ATPase activity in smooth muscle.

Role of protein phosphorylation in excitation-contraction coupling in taurine deficient hearts.

Taurine is a beta-amino acid found in very high concentration in the heart. Depletion of these intracellular stores results in the development of cardiomyopathy, thought to be mediated by abnormal sarcoplasmic reticular (SR) Ca(2+) transport. There is also evidence that taurine directly alters the Ca(2+) sensitivity of myofibrillar proteins. Major regulators of SR Ca(2+) ATPase (SERCA2a) are the phosphorylation status of a regulatory protein, phospholamban, and SERCA2a expression, which are diminished in the failing heart. The failing heart also exhibits reductions in myofibrillar Ca(2+) sensitivity, a property regulated by the phosphorylation of the muscle protein, troponin I. Therefore, we tested the hypothesis that taurine deficiency leads to alterations in SR Ca(2+) ATPase activity related to reduced phospholamban phosphorylation and expression of SERCA2a. We found that a sequence of events, which included elevated protein phosphatase 1 activity, reduced autophosphorylation of CaMKII, and reduced phospholamban phosphorylation, supports the reduction in SR Ca(2+) ATPase activity. However, the reduction in SR Ca(2+) ATPase activity was not caused by reduced SERCA2a expression. Taurine transporter knockout (TauTKO) hearts also exhibited a rightward shift in the Ca(2+) dependence of the myofibrillar Ca(2+) ATPase, a property that is associated with an elevation in phosphorylated troponin I. The findings support the observation that taurine deficient hearts develop systolic and diastolic defects related to reduced SR Ca(2+) ATPase activity, a change mediated in part by reduced phospholamban phosphorylation.

Temperature induced denaturation of myosin: evidence of structural alterations of myosin subfragment-1.

Denaturation of myofibrillar proteins in porcine longissimus thoracis et lumborum muscle was investigated after pre-rigor temperature incubation at 20, 30 and 40°C. At 24h myofibrils were isolated and myosin was further cleaved by chymotrypsin. High temperature pre-rigor induced release of myosin S1 (subfragment-1), less (P < 0.05) Ca(2+)-ATPase activity and structural alterations of the region of the myosin molecule that harbors S1. Surface hydrophobicity of myofibrils from the 40°C group increased (P<0.001), suggesting a temperature-induced structural rearrangement exposing hydrophobic groups on the surface of myofibrils which in turn may explain the reduced water-holding of PSE meat.

Protection of CCl4-Induced Liver and Kidney Damage by Phenolic Compounds in Leaf Extracts of Cnestis ferruginea (de Candolle).

BACKGROUND: The chemoprevention of chemically-induced hepatotoxicity is a crucial means of minimizing susceptibility to hepatic carcinogenesis and plants remain a rich source of anti-hepatotoxicants with antioxidant properties. OBJECTIVE: The protective role of defatted-methanol (MECF) and ethyl acetate fractions (EF), obtained from Leaves of Cnestis ferruginea in rats induced with carbon tetrachloride (CCl4) toxicity was investigated. MATERIALS AND METHODS: Adult male Wistar rats were orally administered MECF or EF (125 - 500 mg/kg bwt/5mL) or silymarin (25 mg/kg bwt/5 mL) separately for three days before intervention with an intraperitoneal dose of CCl4. Biomarkers of liver and kidney toxicity as well as Ca(2+) regulation were evaluated. RESULTS: Pre-treatment with MECF and EF significantly (P < 0.05) decreased the activities of serum alanine and aspartate aminotransferases, levels of urea, creatinine and cholesterol. A significantly (P < 0.05) enhanced Ca(2+) -ATPase activity and lowered levels of membrane cholesterol: Phospholipid ratio were observed in liver microsomes of pre-treated as compared to CCl4 -only treated rats. Rat liver superoxide dismutase activity was enhanced by 125 mg/kg and 250 mg/kg of EF and MECF, while decreases were observed at 500 mg/kg. MECF and EF, like silymarin, attenuated CCl4 -induced hepatotoxicity, microsomal membrane Ca(2+) -ATPase inactivation and renal dysfunction. Phytochemistry of MECF revealed the presence of anthraquinones, cardiac and flavone glycosides, tannins and trihydroxyl phenol. CONCLUSION: These findings suggest that the mechanism of hepatoprotection elicited by MECF and EF, involve its antioxidative properties and regulation of Ca(2+) homeostasis.

Antimalarial screening via large-scale purification of Plasmodium falciparum Ca2+-ATPase 6 and in vitro studies.

The most severe form of human malaria is caused by the parasite Plasmodium falciparum. Despite the current need, there is no effective vaccine and parasites are becoming resistant to most of the antimalarials available. Therefore, there is an urgent need to discover new drugs from targets that have not yet suffered from drug pressure with the aim of overcoming the problem of new emerging resistance. Membrane transporters, such as P. falciparum Ca(2+)-ATPase 6 (PfATP6), the P. falciparum sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA), have been proposed as potentially good antimalarial targets. The present investigation focuses on: (a) the large-scale purification of PfATP6 for maintenance of its enzymatic activity; (b) screening for PfATP6 inhibitors from a compound library; and (c) the selection of the best inhibitors for further tests on P. falciparum growth in vitro. We managed to heterologously express in yeast and purify an active form of PfATP6 as previously described, although in larger amounts. In addition to some classical SERCA inhibitors, a chemical library of 1680 molecules was screened. From these, we selected a pool of the 20 most potent inhibitors of PfATP6, presenting half maximal inhibitory concentration values in the range 1-9 µm. From these, eight were chosen for evaluation of their effect on P. falciparum growth in vitro, and the best compound presented a half maximal inhibitory concentration of ~ 2 µm. We verified the absence of an inhibitory effect of most of the compounds on mammalian SERCA1a, representing a potential advantage in terms of human toxicity. The present study describes a multidisciplinary approach allowing the selection of promising PfATP6-specific inhibitors with good antimalarial activity.

Suitability of chitosan as cryoprotectant on croaker fish (Johnius gangeticus) surimi during frozen storage.

Effect of chitosan on physicochemical attributes of croaker fish surimi during storage at -20 ± 2 °C for 180 days was evaluated. The quality of croaker surimi added with 1% (w/w) chitosan was examined in terms of muscle protein, thaw drip, gel strength and Ca(2+) ATPase activity comparing with those surimi samples added with 4% sucrose and 4% sorbitol. Surimi without any cryoprotectant was treated as control. Chitosan showed cryoprotective effect similar to commercial cryoprotectants as both of them minimized the negative effects of frozen storage on physico-chemical attributes of myofibrillar proteins. The residual Ca(2+) ATPase activity and gel strength of surimi with chitosan were higher than those of control throughout the storage period. Ca(2+) ATPase activity and gel strength had high positive correlation. It is concluded that chitosan was effective in preservation of croaker muscle protein native structure during 6 months of frozen storage and is comparable to other commercial cryoprotectants.

Preservation on calcium homeostasis is involved in mitochondrial protection of Limonium sinense against liver damage in mice.

Mechanisms underlying the mitochondrial protection of Limonium sinense extracts (LSE) was studied in lipopolysaccharide and D-galactosamine (LPS/D-GalN) intoxicated mice. It was found that increased activities of serum aspartate aminotransferase and alanine aminotransferase induced by LPS/D-GalN were significantly inhibited by pretreatment with LSE. The obvious disruption of membrane potential, intramitochondrial Ca (2+) overload and suppression in mitochondrial Ca (2+) -ATPase activity induced by LPS/D-GalN were significantly blocked by pretreatment with LSE. It was concluded that mechanisms underlying protection of LSE against liver mitochondria damage might be related to the preservation on mitochondrial Ca (2+) homeostasis through the preservation on mitochondrial Ca (2+) -ATPase activity.