- Email: [email protected]
Effect of glucocorticoids on peptide-chain initiation in heart and skeletal muscle
85 NEUROANATOMY OF THE CARIDAC CONDUCTION SYSTEM OF THE HEART OF THE COMMON MYNA, ACRIDOTHERES TRISTIS. H. A. Rahman. Department of Zoology, Saifia Postgraduate College, Bhopal, India. In the present investigation anatomy and innervation of the heart of common myna, Acridotheres tristis has been studied. The heart is typical ly avain comprising of two atria and two ventricles. The caridac conduction system is well developed and comprised of a sinuatrial node, atrioventricular node and the atrioventricular bundle. The sinuatrial node is slightly U-shaped and is placed close.to the openings of precavals into the right atrium. The atrioventricular node is situated at the ventrocaudal extremity of the interatrial septum. The atrioventricular bundle is well developed and is placed at the cephalic extremity of the interventricular septum. The heart is richly innervated as is evidenced by the presence of large number of nerve fibres and ganglion cells at the sulcus terminalis and atrioventricular sulcus. Nerve fibres have also been observed in the sinuatrial node, atrioventricular node and the atrioventricular bundle. In spite of careful observation nerve cells could not be observed in any of the components of the cardiac conduction system. Fine nerve fibres have been noted in both the atria, both the ventricles and interatrial and interventricular septa.
EFFECT OF GLUCOCORTICOIDS ON PEPTIDE-CHAIN INITIATION IN HEART AND SKELETAL MUSCLE. D. E. Rannels, S. R. Rannels, A. E. Pegg and L. S. Jefferson. Dept. Physiol., Hershey Med. Cntr., Hershey, PA, U.S.A. 17033 Treatment of normal rats with cortisone acetate for 5 days reduced the rate of synthesis of skeletal muscle protein 55% as measured in the perfused rat hemicorpus. Loss of tissue RNA accounted for 15% of this decrease; the remaining reduction resulted from a block in peptide-chain initiation which developed Protein synthesis in perfused heart --in vivo. muscle was not affected by steroid treatment --in vivo, nor were tissue RNA content or peptide-chain initiation altered. Activity of an eIF-2-like initiation factor (IF) in post-ribosomal supernatants from psoas was reduced 35% by cortisone treatment. This difference was not i lysis and was not due to accelerated rates of ~~f;;~~~~o~~t"$e~ or to changes in nucleotide levels during incubation. IF activity WHS unchanged in supernatants from hearts of cortisone-treated animals. Reduced RNA content in skeletal muscle, but not in heart, of hormone-treated rats suggested a relationship between IF activity and RNA content. In other experiments, ribosomal subunits accumulated in psoas muscles of rats treated 4 hours with dexamethasone; tissue RNA content and IF activity remained unchanged. Thus, adrenocortical steroids may reduce protein synthesis in psoas, but not in heart, in part by regulating the activity of factors involved in peptide initiation; factor activity may be linked to tissue RNA content. supported by NIH grants HL20388, AM15658 and CA18138 and by The American Diabetes Association.
EFFECT OF GLUCOCORTICOIDS ON PEPTIDE-CHAIN INITIATION IN HEART AND SKELETAL MUSCLE. D. E. Rannels, S. R. Rannels, A. E. Pegg and L. S. Jefferson. Dept. Physiol., Hershey Med. Cntr., Hershey, PA, U.S.A. 17033 Treatment of normal rats with cortisone acetate for 5 days reduced the rate of synthesis of skeletal muscle protein 55% as measured in the perfused rat hemicorpus. Loss of tissue RNA accounted for 15% of this decrease; the remaining reduction resulted from a block in peptide-chain initiation which developed Protein synthesis in perfused heart --in vivo. muscle was not affected by steroid treatment --in vivo, nor were tissue RNA content or peptide-chain initiation altered. Activity of an eIF-2-like initiation factor (IF) in post-ribosomal supernatants from psoas was reduced 35% by cortisone treatment. This difference was not i lysis and was not due to accelerated rates of ~~f;;~~~~o~~t"$e~ or to changes in nucleotide levels during incubation. IF activity WHS unchanged in supernatants from hearts of cortisone-treated animals. Reduced RNA content in skeletal muscle, but not in heart, of hormone-treated rats suggested a relationship between IF activity and RNA content. In other experiments, ribosomal subunits accumulated in psoas muscles of rats treated 4 hours with dexamethasone; tissue RNA content and IF activity remained unchanged. Thus, adrenocortical steroids may reduce protein synthesis in psoas, but not in heart, in part by regulating the activity of factors involved in peptide initiation; factor activity may be linked to tissue RNA content. supported by NIH grants HL20388, AM15658 and CA18138 and by The American Diabetes Association.