Development and innervation of the heart — A light microscopic study

81 DEVELOPMENT AND INNERVATION OF THE HEART - A LIGHT MICROSCOPIC STUDY. R. Prakash and S. Kumar. School of Biological Sciences, Phopal University, Bhopal, India. The development and innervation of the heart of Urodela (Amphibia) have been studied with the help of silver and dye staining techniques. The present investigation reveals that the formation of the Preendocardium and the development of the pericardial space become distinct at stages 25 - 27 and the preendocardium becomes distinct at stages 28 By stage 29 to 30 the endocardium cells begin to collect in large numbers and they rearrange to form a tubular structure. In the meantime the myocardium layer begins to surround the endocardium cells, which is completed between stages 34 - 35. The indication of doubling that results from the fusion of the two heart primordia occur in the posterior part of the endocardial tube close to the region of the sinus venosus. The nerve elements develop in the heart at 15 - 17 mm. C.R. length embryos. Two ganglion cells and a few medullated nerve fibres appear The Bidat the sinuatrial junction (primordium or Remak's ganglion). At 100 mm. C.R. der's ganglia develop at a later stage of development. length embryo the heart is profusely innervated by the sympathic, parasympathetic and postganglionic nerve fibre of the intracardiac ganglia. Very early development of nerve tissue observed for the first time in the heart of this amphibian suggests that the conducting tissue is neither exclusively myogenic nor neurogenic but is a related complex combination of the two.

INTRACELLULAR ELECTROLYTES OF HEARTDURINGEYPOTEERMIC CARDIACARREST USINGCARDIOPDLMONARY BY-PASS. K. Prasad, B. Bharadwaj and J.C. Khatter. Dept. of Physiology and Cardiovascular Surgery, University of Saskatchewan, Saskatoon, Sask., Canada. Stone heart during ischemic arrest in open heart surgery might result from an excess accumulation of cytoplasmic calcium causing a continued contractile state and/or a decreased amount of ATP required for muscle relaxation. This presentation deals with the study of intracellular electrolytes during hypothermic and anoxic cardiac arrest in dogs placed on total cardiopulmonary bypass. Anoxic arrest for 30 minutes produced no stone heart and also no intracellular electrolyte changes and the heart function returned to normal. Anoxic arrest for one hour invariably produced stone heart and the intracellular Ca* decreased si nificantly. During hypothermic arrest for one hour, the intracellular Also, there was no cardiac ccntracture Ca& did not change significantly. and the heart function returned to normal. These results suggest that the stone heart may not be due to an increased intracellular Ca*. (Supported by Saskatchewan Heart Foundation).