Summary Fibre characteristics and enzyme activities were determined for the gluteus, semitendinosus, vastus lateralis and triceps brachil muscles of 55 Standardbred trotters of different ages. Four fibre types (I, IIA, IIB, IIC) were demonstrated by histochemical staining of myofibrillar adenosine triphosphatase after preincubation at different pH values. Type II fibres predominated in all the muscles and the type IIA/IIB ratio was higher in horses over 5 years than in younger horses, except in the vastus in which the IIA/IIB ratio did not change with age. The vastus had the highest proportion of type IIA fibres and the semitendinosus the highest proportion of type IIB fibres. Histochemical demonstration of NADH dehydrogenase disclosed that almost 100 per cent of the type IIA and many of the type I and IIB fibres were medium‐stained; the remaining type I fibres were darkly stained and the type IIB fibres lightly stained. In older horses more fibres were stained for NADH dehydrogenase. The activity of triosephosphate dehydrogenase decreased and that of 3‐hydroxy‐acyl‐coA dehydrogenase and citrate synthase increased in all the muscles except the vastus with increasing age. The greatest increase in oxidative capacity occurred in the gluteus and triceps. Training, rather than age, was regarded as the factor inducing these changes. The results emphasise that histochemical data are only semiquantitative, and there are apparent discrepancies in the intensities of histochemical staining and the biochemical evaluation of various enzymes. Résumé Les caractéristiques des fibres et les activités enzymatiques ont été déterminées pour les muscles glutéal, semi tendineux, long vaste et triceps brachial chez 55 trotteurs de race standardbred, d'âges différents. Quatre types de fibres (I, IIA, IIB, IIC) ont été identifiés par coloration histochimique de la triphosphatase adénosique myofibrillaire, après incubation à des pH variables. Les fibres de type II étaient les plus nombreuses dans tous les muscles, et le rapport entre les fibres IIA/IIB a été trouve plus élevé chez les chevaux agés de plus de 5 ans, à l'exclusion du long vaste où ce rapport n'a pas varié avec l'âge. Le long vaste avait la proportion la plus élevée de type, IIA, le semi tendineux la proportion la plus élevée de type IIB. La mise en évidence histochimique de NADH déshydrogénase a révélé que presque 100% des fibres de type IIA, et beaucoup des fibres de type I et IIB étaient colorées modérément. Les fibres de type I restant étaient fortement colorées et celles du type IIB légèrement colorées. Chez les chevaux les plus âgés, les fibres à NDH déshydrogénase étaient plus nombreuses. L'activité de la triosephosphate déshydrogénase diminuait, l'activité de 3‐hydroxyacyl‐coA‐déshydrogénase et de la citrase synthase augmentait dans tous les muscles sauf le long vaste, quand l'âge augmentait. La plus grande augmentation du pouvoir d'oxydation se produisit dans les muscles glutéal et triceps. C'est l'entraînement, plus que l'âge, qui est tenu pour responsable de ces c...
Matrix metalloproteinases (MMPs) are a family of enzymes implicated in the degradation and remodeling of extracellular matrix and in vascularization. They are also involved in pathologic processes such as tumor invasion and metastasis in experimental cancer models and in human malignancies. We used gelatin zymography and immunohistochemistry to determine whether MMP-2 and MMP-9 are present in canine tumors and normal tissues and whether MMP production correlates with clinicopathologic parameters of prognostic importance. High levels of pro-MMP-9, pro-MMP-2, and active MMP-2 were detected in most canine tumors. Significantly higher MMP levels were measured in canine tumors than in nontumors, malignancies had higher MMP levels than benign tumors, and sarcomas had higher active MMP-2 than carcinomas. Cartilaginous tumors produced higher MMP levels than did nonsarcomatous malignancies, benign tumors, and normal tissues, and significantly greater MMP-2 than osteosarcomas and fibrosarcomas. Pro-MMP-9 production correlated with the histologic grade of osteosarcomas. The 62-kd form of active MMP-2 was detected only in high-grade, p53-positive, metastatic malignancies. Zymography proved to be a sensitive and quantitative technique for the assessment of MMP presence but has the limitation of requiring fresh tissue; immunohistochemistry is qualitative and comparatively insensitive but could be of value in archival studies. MMP presence was shown in a range of canine tumors, and their link to tumor type and grade was demonstrated for the first time. This study will allow a substantially improved evaluation of veterinary cancer patients and provides baseline information necessary for the design of clinical trials targeting MMPs.
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