Heat-induced gelation of myosin in a low ionic strength solution containing L-histidine.

Binding properties are important for meat products and are substantially derived from the heat-induced gelation of myosin. We have shown that myosin is solubilized in a low ionic strength solution containing L-histidine. To clarify its processing characteristics, we investigated properties and structures of heat-induced gels of myosin solubilized in a low ionic strength solution containing L-histidine. Myosin in a low ionic strength solution formed transparent gels at 40-50°C, while myosin in a high ionic strength solution formed opaque gels at 60-70°C. The gel of myosin in a low ionic strength solution with L-histidine showed a fine network consisting of thin strands and its viscosity was lower than that of myosin in a high ionic strength solution at 40-50°C. The rheological properties of heat-induced gels of myosin at low ionic strength are different from those at high ionic strength. This difference might be caused by structural changes in the rod region of myosin in a low ionic strength solution containing L-histidine.

Myosin filament depolymerizes in a low ionic strength solution containing L-histidine.

Myosin, one of the major myofibrillar proteins, forms a filamentous polymer and is insoluble in physiological and low ionic strength solutions. We have shown that myosin is soluble in a low ionic strength solution containing L-histidine. In this study, to clarify the role of L-histidine in the solubilization of myosin, we investigated effects of L-histidine on the filament formation and the morphology of myosin at a low ionic strength. In the presence of L-histidine, myosin formed a filamentous polymer in a physiological ionic strength solution and dispersed in a low ionic strength solution. Transmission electron microscopy showed that light meromyosin (LMM), the rod region of myosin, in a low ionic strength solution containing L-histidine was longer than that in a high ionic strength solution without L-histidine. L-histidine causes the elongation of LMM region of myosin contributing to the weakening of the myosin filament and the dissociation of myosin in a low ionic strength solution.

Myosin is solubilized in a neutral and low ionic strength solution containing l-histidine.

Myosin, one of the major myofibrillar proteins, is insoluble at low and physiological ionic strength and soluble at high ionic strength. In this study, the behavior and morphology of myosin solubilized in a low ionic strength solution containing l-histidine (l-His) was investigated. More than 80% of myosin was solubilized in a low ionic strength solution with dialysis against a solution containing 1mM KCl and 5mM l-His. Transmission electron microscopy with rotary shadowing demonstrated that the rod of myosin in a low ionic strength solution containing l-His is longer than that of myosin in a high ionic strength solution. The elongation of the myosin rod in a low ionic strength solution containing l-His would inhibit the formation of a filament, resulting in the solubilization of myosin.

Observation of the distribution of Zn protoporphyrin IX (ZPP) in Parma ham by using purple LED and image analysis.

We investigated the distribution of Zn protoporphyrin IX (ZPP) in Parma ham by using purple LED light and image analysis in order to elucidate the mechanism of ZPP formation. Autofluorescence spectra of Parma ham revealed that ZPP was present in both lean meat and fat, while red emission other than that of ZPP was hardly detected. Although ZPP was found to be distributed widely in Parma ham, it was more abundant in intermuscular fat and subcutaneous fat than in lean meat. The intensity of red emission was weak in muscles that were exposed during the processing. ZPP in both lean meat and subcutaneous fat tended to be more abundant in the inner region than in the outer region. It was thought that ZPP is transferred from lean meat to fat tissue during the processing, resulting in the small amount of ZPP in the lean meat adjacent to subcutaneous fat. Our results led to a completely new hypothesis that ZPP is formed in lean meat and transferred to fat tissue.

A Zn-porphyrin complex contributes to bright red color in Parma ham.

The Italian traditional dry-cured ham (Parma ham) shows a stable bright red color that is achieved without the use of nitrite and/or nitrate. In this study we examined the pigment spectroscopically, fluoroscopically and by using HPLC and ESI-HR-MASS analysis. Porphyrin derivative other than acid hematin were contained in the HCl-containing acetone extract from Parma ham. A strong fluorescence peak at 588 nm and a weak fluorescence peak at 641 nm were observed. By HPLC analysis the acetone extract of Parma ham was observed at the single peak, which eluted at the same time as Zn-protoporphyrin IX and emitted fluorescence. The results of ESI-HR-MS analysis showed both agreement with the molecular weight of Zn-protoporphyrin IX and the characteristic isotope pattern caused by Zn isotopes. These results suggest that the bright red color in Parma ham is caused by Zn-protoporphyrin IX.

Establishment of a model experiment system to elucidate the mechanism by which Zn-protoporphyrin IX is formed in nitrite-free dry-cured ham.

The aim of this study was to establish a model experiment system to elucidate the mechanism by which Zn-protoporphyrin IX (ZPP) is formed in Parma ham. The established model consisted of myoglobin, meat and antibiotics, and incubation under anaerobic conditions resulted in a greater yield of ZPP. Formation of ZPP was observed even in the presence of various antiseptics. The amount of ZPP formed increased as the period of incubation increased. ZPP formation was inhibited by heating meat homogenate depending on the heating temperature. Our results show that anaerobic conditions are suitable for the formation of ZPP in meat products without nitrate or nitrite and that endogenous enzymes as well as microorganisms may be involved in ZPP formation.

A novel 550-kDa protein in skeletal muscle of chick embryo: purification and localization.

We have found a novel protein with a molecular mass of 550 kDa on SDS-polyacrylamide gels, which is abundant in skeletal muscle tissues at an early stage of chick embryonic development. The 550-kDa protein decreased with the progress of development, and only a slight amount of the protein was present in adult chicken skeletal muscle. The 550-kDa protein was purified from the cytoplasm of 18 day embryos by a procedure including ultracentrifugation and gel filtration. The purified 550-kDa protein was essentially free of contaminants as judged by SDS-PAGE. By immunofluorescence and immunoelectron microscopy using the antibody raised against the 550-kDa protein, this protein was shown to be localized in the peripheries of adult muscle fibers and at the Z-disks of isolated myofibrils. These findings have led us to conclude that the 550-kDa protein is a novel myofibrillar protein in chicken skeletal muscle.

Characterization of a novel 550-kDa protein in skeletal muscle of chick embryo.

Some characteristics of a novel 550-kDa protein which is abundant in skeletal muscle tissues at an early stage of the chick embryo, and localized in the peripheries of adult muscle fibers and at the Z-disks of isolated myofibrils, was investigated. A cosedimentation experiment and solid phase immunoabsorbent assay showed that the 550-kDa protein binds directly to F-actin. Therefore, it is concluded that the 550-kDa protein is a novel actin-binding protein. The 550-kDa protein was also interacted with alpha-actinin, laminin, fibronectin and Type IV collagen. Reactions with several kinds of lectin revealed that the 550-kDa protein is a glycoprotein containing oligosaccharides. Electron microscopic observation of negatively stained 550-kDa protein showed that native 550-kDa protein molecules are particles with an average diameter of 26.5 nm, but those particles treated with ethanol/ether are filamentous structures. These results suggest that the 550-kDa protein in the cytoplasma of unorganized skeletal muscle tissues exists as lipid-protein complex. Consequently, the 550-kDa protein may play an important role in the binding of myofibrils to the basal lamina by interaction with F-actin, alpha-actinin, laminin, fibronectin or Type IV collagen.

[Diagnosis of cancer with magnetic resonance imaging (MRI)].

Following a brief review of the history of magnetic resonance imaging (MRI), advantages and disadvantages of MRI are discussed in the diagnosis of malignant tumors of the various parts of the body. The advantages include high contrast resolution, no artifacts from the bones, and arbitrary imaging planes obtainable in multiple slices, whereas disadvantages include no signals from calcifications and prolonged imaging time. The roles of MRI were discussed in relation to detection of early cancers, extent of the lesions, histologic diagnosis and monitoring of treatments. Early diagnosis of tumors is successful in the central nervous system, whereas it is not accomplished in other parts of the body. Extent of the tumors or staging of the tumors can be accomplished to excellent advantage, but signal intensity is often not useful for differential diagnosis.