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BackgroundAn important variability of contractile and metabolic properties between muscles has been highlighted. In the literature, the majority of studies on beef sensorial quality concerns M. longissimus thoracis. M. rectus abdominis (RA) is easy to sample without huge carcass depreciation and may appear as an alternative to M. longissimus thoracis for fast and routine physicochemical analysis. It was considered interesting to assess the muscle fibres of M. rectus abdominis in comparison with M. longissimus thoracis (LT) and M. triceps brachii (TB) on the basis of metabolic and contractile properties, area and myosin heavy chain isoforms (MyHC) proportions. Immuno-histochemical, histochemical, histological and enzymological techniques were used. This research concerned two populations of Charolais cattle: RA was compared to TB in a population of 19 steers while RA was compared to LT in a population of 153 heifers.ResultsRA muscle had higher mean fibre areas (3350 μm2 vs 2142 to 2639 μm2) than the two other muscles. In RA muscle, the slow-oxidative fibres were the largest (3957 μm2) and the fast-glycolytic the smallest (2868 μm2). The reverse was observed in TB muscle (1725 and 2436 μm2 respectively). In RA muscle, the distinction between fast-oxidative-glycolytic and fast-glycolytic fibres appeared difficult or impossible to establish, unlike in the other muscles. Consequently the classification based on ATPase and SDH activities seemed inappropriate, since the FOG fibres presented rather low SDH activity in this muscle in comparison to the other muscles of the carcass. RA muscle had a higher proportion of I fibres than TB and LT muscles, balanced by a lower proportion either of IIX fibres (in comparison to TB muscle) or of IIA fibres (in comparison to LT muscle). However, both oxidative and glycolytic enzyme activities were lower in RA than in TB muscle, although the LDH/ICDH ratio was higher in RA muscle (522 vs 340). Oxidative enzyme activities were higher in RA than in LT muscle, whereas glycolytic enzyme activity was lower. In RA muscle, contractile and metabolic properties appeared to be less well-correlated than in the two other muscles.ConclusionsRA muscle has some particularities in comparison to the LT and TB muscles, especially concerning the unusual large cross-section surface of SO fibres and the very low oxidative activity of intermediate IIA fibres.

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La tendreté est un paramètre important dans l’évaluation de la qualité de la viande bovine. Elle est sous la dépendance d’une combinaison complexe de paramètres, parmi lesquelles les facteurs technologiques jouent un rôle essentiel. Cependant, lorsque l’environnement péri-abattage est maîtrisé, il demeure une variabilité de la tendreté des viandes, mal perçue par le consommateur, et qui peut être attribuée aux facteurs d’élevage. Au sein d’une même race, le type morphologique n’a pas d’impact sur la tendreté des viandes et la force de cisaillement des muscles. La tendreté et la force de cisaillement de la viande de bœuf et de taurillon n’évoluent pas avant l’âge de 2 ans. Avant 35 mois, elles n’évoluent que très rarement chez la femelle mais au-delà, un effet négatif de l’âge peut parfois être mis en évidence. Parmi les facteurs liés au mode de conduite, il apparaît que la gestation et le vêlage ne détériorent pas la tendreté de la viande et que l’activité physique est favorable à la tendreté des muscles locomoteurs sans influencer celle des muscles non locomoteurs. Concernant la conduite alimentaire, il faut retenir que la croissance compensatrice, l’augmentation du niveau alimentaire et de la durée de finition peuvent influencer favorablement la tendreté de la viande, mais ces effets positifs restent à confirmer. La nature de l’alimentation a également des effets limités sur la tendreté de la viande, variables selon les aliments étudiés et les conditions d’expérimentation.

Flow DNA analysis was performed on samples from 71 surgically removed lung cancers and from 145 patients undergoing bronchoscopy. Abnormal DNA stem lines, characterized by their DNA index (DI), were frequently observed in operated lung carcinomas (87%). Two or three abnormal DNA stem lines were discovered simultaneously in 10% of the samples. The mean DI of all abnormal tumor stem lines was lowest for rare tumor cell types and highest for adenocarcinomas. Intermediate mean DI values were found for epidermoid and small cell carcinomas, which were among the most proliferative tumors. The high rate of false negative results suggests poor diagnostic reliability of flow DNA analysis on bronchoscopic samples. However, the method appears to provide a promising objective tool capable of evaluating tumor behavior and prognosis.

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