Morphological and functional characterization of beige mouse adrenomedullary secretory vesicles.

We tested whether the giant secretory granules observed in the mast cells of the naturally occurring mutant beige mouse (BM) (C57BL/6N-bg) were also present in the adrenal chromaffin cells. The presence of large chromaffin granules (CG) would be a valuable tool for the study of exocytosis in neuronal tissues. Conversely, the observation of large vesicles within chromaffin cells that are different from CG could indicate that CG are of a different origin than granules of mast cells. Ultrastructural analysis demonstrated the presence of large lysososmal-like vesicles in the BM, and also a discrete increase in the number of CG with diameters larger than 240 nm but not of giant CG. In addition, amperometric measurements of single-event exocytosis, using carbon fiber microelectrodes, showed no differences between the quantal size of secretory events from BM and wildtype or bovine chromaffin cells. Minor but significant differences were found between the kinetics of exocytosis in BM cells andwild-type mouse cells. We conclude that CG, but not the abnormal-sized vesicles found in BM chromaffin cells contribute to the catecholamine secretion and that abnormal secretory granules are not present in adrenergic cell lineage.

Calcium channel subtypes and exocytosis in chromaffin cells: a different view from the intact rat adrenal.

In the intact rat adrenal gland perfused with an oxygenated Krebs-bicarbonate solution at 37 degrees C, the electrical field stimulation of splanchnic nerves (100 V, 0.5 ms duration, 10 Hz during 10 s) produced transient catecholamine release peaks that were reproduced in subsequent stimuli, applied at 8-min intervals. Omega-Conotoxin GVIA (0.3 microM) caused only a modest inhibition of the secretory response, suggesting that the N-subtype of voltage-dependent Ca2+ channels are scarcely involved in such a response. Both omega-conotoxin MVIIC (1 microM) and furnidipine (1 microM) halved the secretion, suggesting that the L- and P/Q-types of Ca2+ channels were involved. N-type Ca2+ channels appear to be involved in the maintenance of secretion in response to sustained stimulus since omega-conotoxin GVIA (0.3 microM) reduced the catecholamine output to 28%. When secretion was elicited by acetylcholine (10 microM), furnidipine reduced the catecholamine release by 50% and omega-conotoxin MVIIC by 40%, whereas omega-conotoxin GVIA did not modify the response. The K+-induced secretory responses (23.6 mM K+, 15 s) were reduced 75% by furnidipine and 45% by omega-conotoxin MVIIC, indicating that this type of stimulation preferentially recruited L-type channels. These data show that electrical stimulation recruits Ca2+ channel subtypes different from those recruited by direct depolarization of chromaffin cells.

Replacement of the common carotid artery by a plastic prosthesis. Report of a case with forty years of follow-up.

An 18-year-old man suffered a 38 caliber gunshot wound to the right side of the neck on 25 September 1957. On 16 October 1957, a traumatic arteriovenous aneurysm between the common carotid artery and the internal jugular vein was resected. The jugular vein was ligated and the common carotid was replaced by a nylon prosthesis. On 16 October 1960. the dilated nylon graft was replaced by a dacron prosthesis. The patient has been followed-up during more than 40 years and his condition is normal. To the best of our knowledge, this operation was the first of its kind performed in the world and has the longest follow-up.

Aorto-left atrial fistula.

The authors present a case of fistula between the ascending aorta and the left atrium, with four large aneurysmal sacs and marked enlargement of the left atrium. The 10-year-old patient was treated by closing the fistula with a Dacron patch. The results were satisfactory in this extremely rare case of a congenital cardiac lesion.

Effects of ketamine on canine cardiovascular function.

Left ventricular contractility was assessed before and during the peak effect of ketamine in eight canine right heart bypass preparations. Myocardial contractility was defined in terms of maximum left ventricular dp/dt, the ejection fraction, and left ventricular end-diastolic and left atrial pressures at constant heart rate and cardiac inflow. Ketamine produced significant decreases in contractility and there were some indications of a dose-response pattern. The action of ketamine was dependent partly on changes in arterial pressure, as the drug caused a mild but sustained vasodilatation which was not dose-dependent. These data offer further evidence of a small and transient negative inotropic effect of ketamine.

Ascending aorta-right pulmonary artery anastomosis in children with complex cardiac malformations. Long-term results in 30 cases.

In this report, we shall analyze the results obtained with palliative treatment in 30 patients with congenital heart disease who were operated upon at the University Hospital of Caracas during the period 1968 to 1972. In all cases, an ascending aorta-right pulmonary artery anastomosis was performed. Although we believe that the Blalock-Taussig and Potts shunt are satisfactory operations in some cases, at the present time we prefer the aorta-right pulmonary branch anastomosis in Fallots tetralogy and other congenital heart diseases such as single ventricle. In Fallot's tetralogy, particularly, this procedure provides better results, because the anastomosis can be closed through the aorta when these patients are later subjected to total correction with extracorporeal circulation.