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PubMed2000

Optimization of conditions for myofibril preparation from mechanically recovered chicken meat.

The influence of various conditions affecting the isolation of a myofibrillar preparation (MP) from chicken mechanically recovered meat (MRM), i.e. the time of additional chopping in a bowel chopper, washing time, the number of washings, and the water to MRM ratio, on the recovery of dry matter and myofibrillar protein, and fat content in the preparation was investigated. The following particular steps were determined to be the most desirable parameters: chopping MRM for 10 minutes, washing time of 15 minutes, 3 (or 2) consecutive washings, 3:1 water to MRM ratio (v/w). Under these conditions a significant decrease of fat content (93% on average) was found in comparison to the content in MRM. The removal of fat, sarcoplasmic protein and connective tissue increased the concentration of myofibrillar protein. The number of aqueous washings of MRM had the biggest influence on the protein and fat content in the concentrate. Electrophoretic analysis (SDS-PAGE) of protein in the preparation obtained under optimal conditions showed that myosin heavy chains (MHC) and actin constituted approximately 50% of all the proteins in the preparation.

Animals↗
PubMed2003

Temporal and topographic ultrastructural alterations of rat heart myofibrils caused by thyroid hormone.

In order to further our understanding regarding the temporal and topographic ultrastructural aspects of the myocardium under thyrotoxicosis, thyroxine (T4; 25 and 100 microg/100 g bw) was administered to young rats 24 hours after birth until 15 days. The animals were then sacrificed, the hearts excised and weighed, and the ventricle tissue samples were then processed for confocal and transmission electron microscopy. At 48/72 hours and 1 week after initiation of T4 treatment with 100 microg/100 g bw, numerous lamellar bodies (probably formed by phospholipids) progressively accumulated in the heart. These bodies were observed in the cytosol, inside mitochondria and in the extracellular matrix. At 2 weeks of T4 treatment with 100 microg/100 g bw, lamellar bodies were virtually absent. Changes in cell shape, disorganization of intercellular junctions, and substantial myofibrillar disarray were observed in many cardiomyocytes. A gradient of myofibrillar disarray, which increased in abundance and intensity from the endocardium to the epicardium, was also observed. Immunocytochemical staining for desmin showed that the arrangement of this protein was disorganized in many cells of T4-treated rats as compared with normal ones, confirming ultrastructural data. The predominant appearance of myofibrillar disarray, associated with disorganization of cytoskeletal proteins in the deep myocardium, may be due to higher mechanical wall stress and consequent higher metabolic demand. Alternatively, differential sensitivity of cardiomyocytes to thyroid hormone in different areas is also a possibility.

Animals↗
PubMed1978

Ultrastructural studies on the formation of myoflilaments and myofibrils in the human embryonic and adult hypertrophied heart.

The myofibrillogenesis in the human embryonic heart is described. The synthesis of thin filaments, which are the first to appear, takes place in close proximity to smooth surfaced SR tubules. Z-band material is closely related to the thin filaments and appears first as irregularly distributed patches in the filamenteous mass. Further cellular differentiation includes an organization of the thin filaments/Z-band material. The synthesis of thick filaments, which follows that of the thin filaments, takes place in ribosome rich areas of the cell. They are rapidly incorporated into the strings of organized thin filaments/Z-band material. The periodic binding sites on both kinds of filaments are believed to play an important role in the precise ordering of the filaments. The formation of myofilaments in the adult hypertrophied human heart is also described. The similarities between this process and that observed in the embryonic heart are striking, and we believe it to be the same process.

Adult↗