No abstract

The origin, course and mode of termination of the artery of the sinuatrial node was studied in 45 anatomic specimens by injection-dissection. It was solitary in 88.89% of the cases and double in 11.11%. It arose from the right coronary a. in 64.45% of cases, from the left coronary a. in 24.44%, and from both in 11.11%. The side of origin was not significantly influenced by the coronary dominance. When it arose from the right coronary a., the course of the sinuatrial a. varied greatly with its site of origin from the coronary vessel, either from an atrial a. or from one of its collateral branches, and also depended on its relations with the interatrial septum. When it arose from the left coronary a., its course was relatively uniform, except for arteries arising from the inferior atrial aa., which characteristically involve the posterior wall of the left atrium. Three modes of termination were found: precaval, retrocaval, and in a pericaval arterial circle. These observations made it possible to understand the possible origin of disorders of rhythm observed following disturbance of the arterial supply to the sinuatrial node during certain stages of cardiac surgery, particularly during atriotomies and the surgical correction of certain valvular disorders and congenital malformations, which expose the a. of the sinuatrial node.

Mesophyll cells of Nicotiana glutinosa exposed to starvation in the light after leaf excision showed the following major changes: vacuolation of the cytoplast; rearrangement of chloroplast and nuclear material; accumulation of cytoplasmic crystals and of starch; evagination and increased perforation of the nuclear membrane; and lysis of the tonoplast. Rearrangement of chloroplast material resulted in extended, 3-dimensional arrays (pseudocrystalline bodies), composed of electron-dense globules 85–100 Å in diameter. The ultrastructural degeneration of cells within a leaf was unsynchronized, and the sequence of degenerative intracellular events was not fixed. These observations are compatible with an unequal distribution of "essential" metabolites among those cells. Cells suffering from starvation stress showed ultrastructural changes not observed in cells of aging attached leaves and vice versa. Thus, starvation stress does not merely accelerate the process of cell-aging, as it operates in attached leaves.

The area of merger between head and stalk was found to be anatomically much more diverse and to extend much deeper into the head than was previously thought. Interior cells of this transition zone, which we call the "neck area," were closely apposed to elements of the parenchyma bell of the head, and they contained many plasmodesmata in their walls. These features suggest that metabolites transported from the head to the leaf via the stalk largely follow an "interior route," especially since the inner stalk cells have some characteristics of conductive elements.The distinct cuticle, which covers the entire tentacle, was found to contain many pores in the area of the outer gland cells, with diameters up to 318 mμ. Complex tubular structures were detected in the outer pericline and upper anticline walls of the same cells. Together with the cuticle pores they were believed to account for the extreme permeability of the head.Intercellular spaces were detected in the middle and lower tentacle stalk. Since these spaces were not randomly distributed and were sometimes partially or completely closed, they were considered to be functional in tentacle bending.

The origin and course of the artery of the atrioventricular node (AAVN) was studied in 45 anatomic specimens by the method of injection-dissection in 38 human hearts removed at medicolegal autopsies from black Senegalese subjects. Though sometimes double, the AAVN is classically solitary. Its coronary origin, which is always distal, occurred on the right side in the great majority of cases, at the level of the "U-turn of James", and on the left side at the level of the terminal portion of the circumflex a. At the level of Koch's triangle, its course is marked by a close relationship with the zone of attachment of the septal cusp of the right atrioventricular valve on the one hand, and with the orifice of the coronary sinus on the other. In cardiac surgery, respect for the area of Koch's triangle, the base of the interatrial septum and the region of the intersection of the cardiac sulci will reduce the risks of injury to the AAVN.