A prospective randomized trial of four three-drug regimens in the treatment of disseminated Mycobacterium avium complex disease in AIDS patients: excess mortality associated with high-dose clarithromycin. Terry Beirn Community Programs for Clinical Research on AIDS

The optimal regimen for treatment of Mycobacterium avium complex (MAC) disease has not been established. Eighty-five AIDS patients with disseminated MAC disease were randomized to receive a three-drug regimen of clarithromycin, rifabutin or clofazimine, and ethambutol. Two dosages of clarithromycin, 500 or 1,000 mg twice daily (b.i.d.), were compared. The Data and Safety Monitoring Board recommended discontinuation of the clarithromycin dosage comparison and continuation of the rifabutin vs. clofazimine comparison. After a mean follow-up of 4.5 months, 10 (22%) of 45 patients receiving clarithromycin at 500 mg b.i.d. had died (70 deaths per 100 person-years) compared with 17 (43%) of 40 patients receiving clarithromycin at 1,000 mg b.i.d. (158 deaths per 100 person-years) (relative risk, 2.43; 95% confidence interval, 1.11-5.34; P = .02). After 10.4 months, 20 (49%) of 41 patients receiving rifabutin had died (81 deaths per 100 person-years) compared with 23 (52%) of 44 patients receiving clofazimine (94 deaths per 100 person-years) (relative risk, 1.20; 95% confidence interval, 0.65-2.19; P = .56). Bacteriologic outcomes were similar among treatment groups. In treating MAC disease in AIDS patients, the maximum dose of clarithromycin should be 500 mg b.i.d.

Binding sites for calcitonin gene-related peptide in distinct areas of rat brain

Calcitonin gene-related peptide (CGRP) binding sites were localized in rat brain and spinal cord by an in vitro labeling light microscopic technique using [125I]rCGRP as radioligand. Specific rCGRP binding with a dissociation constant (Kd) of 0.53 nM to membrane preparations from rat brain cortex was characterized. The presence and the selective distribution of specific high affinity CGRP binding sites in the central nervous system suggest a role for this recently predicted peptide as a neurotransmitter.

Receptor for calcitonin gene-related peptide: binding to exocrine pancreas mediates biological actions

In the present study we demonstrate by immunohistochemical techniques that calcitonin gene-related peptide (CGRP) is present in nerve terminals in the islets of Langerhans. Furthermore, binding studies with 125I-CGRP indicate that dispersed acini from guinea pig pancreas contain a single class of high-affinity binding sites for CGRP with an apparent dissociation constant of 18 nM. Vasoactive intestinal peptide (VIP), rat growth hormone-releasing factor (rGRF), cholecystokinin octapeptide (CCK-OP), and bombesin do not interact with these receptors. Interaction of CGRP with these receptors leads to release of amylase from the acinar cells. Amylase release is half maximal at 0.3 nM CGRP and maximal at 3 nM CGRP. Maximal amylase release with CGRP is one-third of that observed with VIP. CGRP-induced amylase release is dependent on theophylline in the incubation medium. CGRP potentiates the amylase release stimulated by bombesin and CCK-OP but has no effect on amylase release stimulated by VIP, rGRF, and natural glucagon. CGRP stimulates a 25% increase in basal cellular cAMP. These results indicate that guinea pig pancreatic acinar cells contain a novel receptor for CGRP and that interaction of CGRP with this receptor leads to digestive enzyme secretion through a cAMP-mediated pathway. The presence of CGRP in the islets of Langerhans suggests a pathway for CGRP to reach the exocrine pancreas through an insuloacinar portal system.