In the present paper we describe changes of anatomical parameters in inbred Lewis strain rats, namely their body weight, body weight gain per week, absolute and relative heart, thyroid gland and skeletal muscle weights, that are assumed to reflect experimentally altered thyroid status. The hyperthyroid state was induced by DL-thyroxine or Na 3,3',5-triiodo-L-thyronine, while methimazole was employed for inducing hypothyroidism. We have found that when compared to euthyroid rats, hypothyroidism resulted in a significantly lower body weight gain, absolute and relative heart weight and, in contrast, in a significant increase of absolute and relative thyroid gland weight. On the other hand, hyperthyroidism led to a significant increase of absolute and relative heart weight and to a significant reduction of absolute and relative thyroid gland weight. However, the body mass was not significantly altered in hyperthyroidism as compared with euthyroid rats. We conclude that our protocol leads to chronic hyper- or hypothyroidism as demonstrated by body, heart and thyroid gland weight changes. These anatomical data can thus be utilized as supplemental criteria for the assessment of the thyroid state of experimental rats., T. Soukup, G. Zachařová, V. Smerdu, I. Jirmanová., and Obsahuje bibliografii
The cancerogen 1,2-dimethylhydrazine (DMH), widely used in the experimental animal model of carcinogenesis, affects various organs, but its effect on muscle fibers is unknown. To evaluate the effect of 15-week DMH treatment on the fiber size and myosin heavy chain (MyHC) isoforms, which substantially determine fiber types and their contractile characteristics, pure and hybrid fiber types were immunohistochemically determined according to the MyHC isoform expression in soleus, extensor digitorum longus, gastrocnemius medialis and lateralis muscles of DMH-treated and control male Wistar rats. Whereas the size of fibers was mostly unaffected, the MyHC isoform expression was partially affected in both gastrocnemius samples, but not in the soleus and extensor digitorum longus of DMH-treated rats. The lower proportions of hybrid fiber types and especially that of type 1/2x in most gastrocnemius samples of DMH-treated rats resulted in a shift towards a single MyHC isoform expression, but the extent and pattern of the MyHC isoform shift varied across the different gastrocnemius samples. Such variable response to DMH treatment across muscles indicates that each muscle possesses its own adaptive range. These findings are essential for an accurate evaluation of skeletal muscle characteristics in DMH animal model.
We examined the effects of the unilateral heterochronous isotransplantation on the fiber type composition and myosin heavy chain (MyHC) isoform content of unoperated slow soleus and fast extensor digitorum longus muscles of female inbred Lewis strain rats. Comparison was made between “control” unoperated muscles of experimental rats (after intramuscular transplantation surgery) with the corresponding muscles of completely naive (unoperated) rats of three age groups (5-, 8- and 14-month-old). This was done in order to ascertain whether these muscles can be used as reliable controls to the transplanted and host muscles for our ongoing grafting experiments. The fiber type composition was determined by assessing the histochemical reaction for myofibrillar adenosine triphosphatase, the MyHC isoform content was determined immunocytochemically using monoclonal antibodies specific to different MyHC isoforms and by sodium dodecyl sulphate polyacrylamide gel electrophoresis. Our experiments show that the heterochronous intramuscular isotransplantation procedure had no significant effect on the fiber type composition and MyHC isoform content of the “control” unoperated muscles of the experimental rats when compared to the corresponding muscles of the naive animals. Furthermore, the duration and type of isotransplantation did not also lead to differences among corresponding “control” muscles of experimental animals. We conclude that the unoperated muscles of the experimental rats can be used as controls in our current transplantation project dealing with long-term grafting experiments., T. Soukup, V. Smerdu, G. Zachařová., and Obsahuje seznam literatury
To reveal the effect of foreign innervation and altered thyroid status on fiber type composition and the myosin heavy chain (MyHC) isoform expression in the rat slow soleus (SOL) and fast extensor digitorum longus (EDL) muscles, a method of heterochronous isotransplantation was developed. In this experimental procedure, the SOL or EDL muscles of young inbred Lewis rats are grafted either into the host EDL or SOL muscles of adult rats of the same strain with normal or experimentally altered thyroid status. To estimate the extent of fiber type transitions in the transplanted muscles, the SOL and EDL muscle from the unoperated leg and unoperated muscles from the operated leg could be legitimately used as controls, but only when the experimental procedure itself does not affect these muscles. To verify this assumption, we have compared the fiber type composition and the MyHC isoform content of unoperated contralateral SOL and EDL muscles and ipsilateral unoperated SOL muscle of experimental rats after unilateral isotransplantation into the host EDL muscle with corresponding muscles of the naive rats of the same age and strain. We provide compelling evidence that the unilateral heterochronous isotransplantation has no significant effect on the fiber type composition and the MyHC isoform content of unoperated muscles of experimental animals. Hence, these muscles can be used as controls in our grafting experiments.