Only a few years ago, the poultry industry began to face a recent abnormality in breast meat, known as wooden breast, which frequently overlaps with white striping. This study aimed to assess the impact of wooden breast abnormality on quality traits of meat. For this purpose, 32 normal (NRM), 32 wooden (WB), and 32 wooden and white-striped (WB/WS) Pectoralis major muscles were selected from the same flock of heavy broilers (males, Ross 708, weighing around 3.7 kg) in the deboning area of a commercial processing plant at 3 h postmortem and used to assess histology, proximate (moisture, protein, fat, ash, and collagen) and mineral composition (Mg, K, P, Na and Ca), sarcoplasmic and myofibrillar protein patterns, and technological traits of breast meat. Compared to the normal group, WB/WS fillets showed more severe histological lesions characterized by fiber degeneration, fibrosis, and lipidosis, coupled with a significantly harder texture. With regard to proximate and mineral composition, abnormal samples exhibited significantly (P < 0.001) higher moisture, fat, and collagen contents coupled with lower (P < 0.001) amounts of protein and ash. Furthermore, increased calcium (131 vs. 84 mg kg(-1); P < 0.05) and sodium (741 vs. 393 mg kg(-1); P < 0.001) levels were found in WB/WS meat samples. The SDS-PAGE analysis revealed a significantly lower amount of calcium-ATPase (SERCA, 114 kDa), responsible for the translocation of Ca ions across the membrane, in normal breasts compared to abnormal ones. As for meat quality traits, fillets affected by wooden abnormality exhibited significantly (P < 0.001) higher ultimate pH and lower water-holding/water-binding capacity. In particular, compared to normal, abnormal samples showed reduced marinade uptake coupled with increased drip loss and cooking losses as well. In conclusion, this study revealed that meat affected by wooden breast or both wooden breast and white striping abnormalities exhibit poorer nutritional value, harder texture, and impaired water-holding capacity.
belong to the Deg/ENaC super family of ion channels (1). Members of this super gene family form Na ϩ -selective ion channels (P Na /P K , 8 -100) that can be blocked by amiloride (IC 50 , 0.2-20 M). All family members show some common hallmarks including two hydrophobic domains, short intracellular N and C termini, and a large extracellular loop containing conserved cysteines. Channels of this gene family probably form tetramers (2, 3).To date, six different members of the ASIC subfamily have been cloned (ASIC1a, ASIC1b, ASIC2a, ASIC2b, ASIC3, and ASIC4), which are encoded by four genes. ASIC1a and ASIC1b are alternative splice products of the ASIC1 gene (4, 5). Splicing exchanges approximately the first third of the protein, including the first transmembrane domain and the proximal part of the large ectodomain. In contrast, the C-terminal twothirds are identical. We will use the term ASIC1 when we do not refer to a specific splice variant. All ASICs with the exception of ASIC4 (6) are expressed in sensory neurons of the dorsal root ganglion. Proposed functions in sensory neurons include peripheral pain perception (1,7,8) and mechanotransduction (9, 10). Although some evidence suggests that some of the native H ϩ -gated currents in sensory neurons are mediated by heteromeric ASICs (11, 12), part of these currents are probably mediated by homomeric ASIC1 and ASIC3 (8, 11).ASIC1a is expressed in sensory neurons and throughout the brain (13), whereas ASIC1b is specifically expressed in sensory neurons (5). Both subunits are Na ϩ -selective (P Na /P K Ϸ 10 -15), and only ASIC1a has a low Ca 2ϩ permeability (P Na /P Ca Ϸ 15) (4). ASIC1a and ASIC1b form rapidly activating and completely desensitizing ion channels ( act , ϳ10 msec; desens , ϳ1 s) (4). The expression of ASIC1 in small diameter, capsaicinsensitive sensory neurons (5, 11, 14, 15) has led to the proposal that ASIC1a mediates excitation during tissue acidosis, which accompanies inflammation and ischemia. However, complete desensitization of ASIC1 makes it difficult to imagine how this channel can sense H ϩ signals during inflammation and ischemia when the pH persistently falls.Here we show that both ASIC1a and ASIC1b undergo steady-state inactivation. The steady-state inactivation curve for ASIC1b is shifted by 0.25 pH units to more acidic values as compared with ASIC1a, showing that ASIC1b can operate at a more acidic resting pH. pH activation is shifted by 0.7 pH units. Differences in the sensitivity of activation and inactivation by protons are intimately linked, as both are controlled by only two amino acids in the ectodomain. These two amino acids are exchanged by alternative splicing. Moreover, we show that Ca 2ϩ , Mg 2ϩ , and spermine, when applied during the steadystate, shift the steady-state inactivation curves of both ASIC1a and ASIC1b. This leads to a potentiation of the current. Modulation by di-and polyvalent cations may be a means to adapt ASIC1 activity to changes in the extracellular concentration of these ions. Our results show that ASIC1b...
A persistent puzzle in the field of biological electron transfer is the conserved iron-sulfur cluster motif in both high potential iron-sulfur protein (HiPIP) and ferredoxin (Fd) active sites. Despite this structural similarity, HiPIPs react oxidatively at physiological potentials, whereas Fds are reduced. Sulfur K-edge x-ray absorption spectroscopy uncovers the substantial influence of hydration on this variation in reactivity. Fe-S covalency is much lower in natively hydrated Fd active sites than in HiPIPs but increases upon water removal; similarly, HiPIP covalency decreases when unfolding exposes an otherwise hydrophobically shielded active site to water. Studies on model compounds and accompanying density functional theory calculations support a correlation of Fe-S covalency with ease of oxidation and therefore suggest that hydration accounts for most of the difference between Fd and HiPIP reduction potentials.
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