On the release of catecholamines and dopamine-beta-hydroxylase evoked by ouabain in the perfused cat adrenal gland

1 Secretion of catecholamines (CA) and dopamine-beta-hydroxylase (DBH) activity from the retrogradely perfused cat adrenal gland was studied following ouabain infusion. Perfusion with ouabain (10(-4) M) for 10 min caused a gradual release of CA in the effluent which reached its peak 30 min after the ouabain pulse, and was maintained constant for at least 1 h. The effect of ouabain seemed to be irreversible. 2 Mecamylamine, while blocking the CA secretory effects of acetylcholine (ACh) perfusion, did not affect the secretion of CA evoked by ouabain. In denervated adrenal glands, ouabain-induced CA secretion was similar to that in the contralateral, innervated gland. However, physostigmine perfusion potentiated the CA secretory effects of ouabain. 3 The release of CA evoked by ouabain was accompanied by a proportional release of DBH activity. The time course of appearance of DBH activity followed the pattern of CA release. 4 The CA and DBH outputs in response to a pulse of ouabain were suppressed in the absence of calcium. Calcium reintroduction to a calcium-free perfused, ouabain-treated gland not only restored but greatly potentiated the release of CA and DBH. The amplitude of the secretory response to calcium reintroduction in ouabain-treated glands was proportional to the extracellular calcium concentration, and was antagonized by an external sodium-deficient medium. 5 These data demonstrate that ouabain releases CA from the perfused cat adrenal gland by a calcium-dependent exocytotic mechanism. The secretory effect of ouabain is not secondary to the release of ACh from cholinergic nerve terminals present in the adrenal gland, but due to a direct action on the chromaffin cell itself. In addition, the results suggest that this action is exerted through redistribution of monovalent cations secondary to the inhibition by the glycoside of the sodium pump. Such monovalent cation redistribution may cause a rise of intracellular ionized calcium levels through the activation of an internal sodium-dependent calcium influx system probably located in the chromaffin cell membrane.

99mTc-PP and 67Ga imaging following insertion of orthopedic devices

Deposition of 67Ga in bone does not explicitly imply osteomyelitis. Osteomyelitis complicating insertion of orthopedic devices is manifested by lack of congruence in the distribution patterns of 99mTc-PP and 67Ga. Congruent patterns can reflect the increased bone reaction to implantation or loosening of the device, not necessarily osteomyelitis. Both (a) nonseptic synovitis secondary to reactive bursa formation and (b) cellulitis exhibit an affinity for 67Ga and virtually none for 99mTc-PP, whereas the reverse is true for heterotopic bone. Thus combined sequential 99mTc-PP/67Ga imaging is necessary for evaluation of complications associated with internal orthopedic devices.

Differential diagnosis of jaundice by 99mTc-IDA hepatobiliary imaging

The utility of 99mTc-IDA imaging in the differential diagnosis of jaundice was assessed. Although overall accuracy was 84%, this method is still inferior to the reported efficiency of ultrasonography and CT in making the correct diagnosis. Radionuclide imaging is a good alternative when these other modalities are not available and it functions well in an adjuvant capacity. The diagnostic limitations of 99mTc-dimethyl IDA imaging in cases of moderate to severe jaundice are largely overcome by the use of 99mTc-p-butyl IDA.

99mTc-IDA hepatobiliary imaging following upper abdominal surgery

Bile flow patterns were studied with serial 99mTc-IDA images in 19 patients with cholecysto- and choledochointestinal anastomoses, gastroenteric bypasses, and combinations of the two. Complications such as anastomotic, afferent, and efferent loop obstruction and bile leakage were readily detected even in the presence of jaundice. This noninvasive technique warrants further investigation to determine its indications and weaknesses.

[Treatment of chronic osteomyelitis]

Levels of Cephaloridine and Cefazoline were measured in serum, pus and bone in 20 patients with chronic osteomyelitis and the efficiency of these drugs in the treatment of osteomyelitis was evaluated.

The effect of sympathetic denervation on cerebral CO2 sensitivity

The responsiveness of cerebral blood flow to changes in arterial carbon dioxide tension was determined in six monkeys following bilateral superior cervical ganglionectomy. Experiments were conducted 10 to 14 days following the removal of both ganglions using phencyclidine hydrochloride as the anesthetic agent. Following the initial acute experiments, the animals were placed in a sealed environmental chamber for five days at an inspired carbon dioxide level of 6%. The responsiveness to carbon dioxide was repeated following the chronic exposure to carbon dioxide. The animal was killed immediately and the brain removed. The major vessels of the circle of Willis were examined histochemically for the presence of sympathetic nerve fibers. The results of the study demonstrated that: (1) autoregulation was still present, (2) acute exposure to increased levels of carbon dioxide increased flow, and (3) some adaptation of flow occurred following a chronic exposure to 6% carbon dioxide. The carbon dioxide sensitivity of this group of animals was found to be 0.37 cm per second mm Hg -1 as compared to a value of 0.94 cm per second mm Hg -1 for normal animals. The difference in these two values was significant. It is concluded that the sympathetic nervous system is necessary for the normal responsiveness to changes in arterial carbon dioxide.