Granisetron (Kytril) plus dexamethasone for antiemetic control in bone marrow transplant patients receiving highly emetogenic chemotherapy with or without total body irradiation

This prospective trial evaluated the efficacy and toxicity of granisetron for antiemetic control in patients receiving high-dose cyclophosphamide (CY)-containing regimens with/without TBI for bone marrow (BM) or peripheral blood stem cell (PBSC) transplantation or PBSC mobilization. Granisetron 1 mg i.v. plus dexamethasone 10 mg i. v. were administered daily 30 min before chemotherapy or radiation for a median of 5 days. Response was defined as the number of emetic episodes per 24 h: complete response, 0 and no emetic rescue; major response, 1-2; minor response, 3-5; failure, >5. One hundred patients were enrolled. Ninety-eight received CY-containing regimens and 26 of these additionally received TBI (12 Gy divided over 4 days). Response was complete on 216 (47%) of a total 456 patient days, major on 222 (49%), minor on 14 (3%), and failure on 4 (1%). Mean number of emetic episodes per patient per day and breakthrough medication required per patient per day was 0.24 (range 0-8) and 0. 40 (range 0-8), respectively. Adverse effects were minimal, with headache (20%) reported most frequently. Based on these results, granisetron plus dexamethasone is an effective and well-tolerated antiemetic regimen in BMT/PBSCT recipients conditioned with high-dose chemotherapy with/without TBI. Bone Marrow Transplantation (2000) 25, 1279-1283.

beta2-adrenergic receptor desensitization, internalization, and phosphorylation in response to full and partial agonists

Previous studies indicated that partial agonists cause less desensitization of the beta2-adrenergic receptor (betaAR) than full agonists; however, the molecular basis for this in intact cells has not been investigated. In the present work, we have determined the rates of desensitization, internalization, and phosphorylation caused by a series of betaAR agonists displaying a 95-fold range of coupling efficiencies. These studies were performed with HEK-293 cells overexpressing the betaAR with hemagglutinin and 6-histidine epitopes introduced into the N and C termini, respectively. This modified betaAR behaved identically to the wild type receptor with regard to agonist Kd, coupling efficiency, and desensitization. The coupling efficiencies for betaAR agonist activation of adenylyl cyclase relative to epinephrine (100%) were 42% for fenoterol, 4.9% for albuterol, 2.5% for dobutamine, and 1.1% for ephedrine. At concentrations of these agonists yielding >90% receptor occupancy, the rate and extent (0-30 min) of agonist-induced desensitization of betaAR activation of adenylyl cyclase followed the same order as coupling efficiency, i.e. epinephrine >/= fenoterol > albuterol > dobutamine > ephedrine. The rate of internalization of the betaAR with respect to these agonists also followed the same order as the desensitization and exhibited a slight lag. Like internalization and desensitization, betaAR phosphorylation exhibited a dependence on agonist strength. The two strongest agonists, epinephrine and fenoterol, provoked 11-13-fold increases in the level of betaAR phosphorylation after just 1 min, whereas the weak agonists dobutamine and ephedrine caused only 3-4-fold increases, similar to levels induced by cAMP-dependent protein kinase activation with forskolin. With longer treatment times, the level of betaAR phosphorylation declined with strong agonists, but it progressively increased with the weaker partial agonists, such that after 30 min the -fold elevation with epinephrine (6.2 +/- 0.82) was not appreciably different from ephedrine (5.0 +/- 0.96) and significantly less than that caused by albuterol (10.4 +/- 1.7). In summary, our results demonstrate an excellent proportionality between the agonist strength and agonist-induced desensitization, internalization, and the rapid initial phase of phosphorylation. The data support the hypothesis that increasing agonist-coupling efficiency primarily affects desensitization by increasing the rate of betaARK phosphorylation of the betaAR.

Identification of nearest-neighbor peptides in protease digests by mass spectrometry for construction of sequence-ordered tryptic maps

Continuous-flow fast atom bombardment mass spectrometry was used for the identification of the intermediates and end products of the tryptic digest of polypeptides throughout the time-course of the reactions. Precursor/product relationships for these peptides were determined with the aid of a simple personal computer program. The C-terminal tryptic peptides were identified by performing a tryptic digest in 50% 18O-enriched buffer which resulted in labeling of all non-C-terminal peptides with 18O. This information, along with the precursor/product correlations, was used to create a sequence-ordered tryptic map of the original polypeptide. Ion intensities of intermediate hydrolysis products are compared for enzyme to substrate ratios of 1:100 and 1:1000 (w/w) over the course of the reaction. Intermediates were found to have significantly longer lifetimes when lower levels of trypsin were present.