Continuous inhibition of 11ß-hydroxysteroid dehydrogenase type I in adipose tissue leads to tachyphylaxis in humans and rats but not in mice.

BACKGROUND AND PURPOSE: 11ß-hydroxysteroid dehydrogenase type I (11ß-HSD1), a target for Type 2 diabetes mellitus, converts inactive glucocorticoids into bioactive forms, increasing tissue concentrations. We have compared the pharmacokinetic-pharmacodynamic (PK/PD) relationship of target inhibition after acute and repeat administration of inhibitors of 11ß-HSD1 activity in human, rat and mouse adipose tissue (AT). EXPERIMENTAL APPROACH: Studies included abdominally obese human volunteers, rats and mice. Two specific 11ß-HSD1 inhibitors (AZD8329 and COMPOUND-20) were administered as single oral doses or repeat daily doses for 7-9 days. 11ß-HSD1 activity in AT was measured ex vivo by conversion of (3) H-cortisone to (3) H-cortisol. KEY RESULTS: In human and rat AT, inhibition of 11ß-HSD1 activity was lost after repeat dosing of AZD8329, compared with acute administration. Similarly, in rat AT, there was loss of inhibition of 11ß-HSD1 activity after repeat dosing with COMPOUND-20 with continuous drug cover, but effects were substantially reduced if a 'drug holiday' period was maintained daily. Inhibition of 11ß-HSD1 activity was not lost in mouse AT after continuous cover with COMPOUND-20 for 7 days. CONCLUSIONS AND IMPLICATIONS: Human and rat AT, but not mouse AT, exhibited tachyphylaxis for inhibition of 11ß-HSD1 activity after repeat dosing. Translation of observed efficacy in murine disease models to human for 11ß-HSD1 inhibitors may be misleading. Investigators of the effects of 11ß-HSD1 inhibitors should confirm that desired levels of enzyme inhibition in AT can be maintained over time after repeat dosing and not rely on results following a single dose.

K-ras point mutation detection in lung cancer: comparison of two approaches to somatic mutation detection using ARMS allele-specific amplification.

BACKGROUND: The use of sensitive molecular techniques to detect rare cells in a population is of increasing interest to the molecular pathologist, but detection limits often are poorly defined in any given molecular assay. We combined the approaches of real-time quantitative PCR with ARMS(TM) allele-specific amplification in a novel assay for detecting mutant K-ras sequences in clinical samples. METHODS: ARMS reactions were used to detect seven commonly occurring mutations in the K-ras oncogene. These mutations produce amino acid changes in codon 12 (Gly to Ala, Arg, Asp, Cys, Ser, or Val) and codon 13 (Gly to Asp). A control reaction was used to measure the total amount of amplifiable K-ras sequence in a sample so that the ratio of mutant to wild-type sequence could be measured. Quantitative data were confirmed for a selection of samples by an independent cloning and sequencing method. The assay was used to analyze 82 lung tumor DNA samples. RESULTS: The assay detected K-ras mutations in 44% of adenocarcinomas, which is equivalent to frequencies reported in the literature using ultrasensitive techniques. Forty-six percent of squamous carcinomas were also positive. The ratio of mutant sequence in the tumor DNA samples was 0.04-100%. CONCLUSIONS: The assay is homogeneous, with addition of tumor DNA sample being the only step before results are generated. The quantitative nature of the assay can potentially be used to define the analytical sensitivity necessary for any specified diagnostic application of K-ras (or other) point mutation detection.

Rapid diagnosis of viral respiratory infections. Comparison between immunofluorescence on clinical samples and immunofluorescence on centrifuged cell cultures.

We compared the technique of immunofluorescence on clinical samples (IFCS) and immunofluorescence on centrifuged cell cultures (IFCC) for the detection of respiratory viruses, using monoclonal antibodies. Four hundred fourty five nasopharyngeal aspirates were tested prospectively for RSV, influenza- (A and B), parainfluenza viruses (1, 2, 3) and adenovirus. IFCS and IFCC detected 94% and 51% of RSV respectively, 78.5% and 82% of influenza viruses, 8.3% and 100% of parainfluenzaviruses and 0 and 100% of adenoviruses. We conclude that for routine rapid virus diagnosis the IFCS procedure is acceptable for RSV, that for influenza virus the IFCC procedure can be omitted for samples positive by IFCS, and that for the detection of parainfluenza and adenoviruses the IFCS procedure is too insensitive.

A study to evaluate the effect of ondansetron on psychomotor performance after repeated oral dosing in healthy subjects.

The aim of the study was to determine the effect of repeated oral administration of ondansetron, a 5-hydroxytryptamine type 3 (5-HT3) receptor antagonist, on psychomotor performance. The study was of a randomised, double-blind, four-way, cross-over design in 12 healthy subjects, with 1 mg and 8 mg ondansetron, placebo and 2 mg lorazepam evaluated. Each subject received five administrations per treatment period. Ondansetron, 1 mg and 8 mg, and placebo were given as twice daily dosing for 2 1/2 days. Lorazepam was administered as a 2 mg single oral dose which was taken as the fifth administration; placebo was given for the remaining four doses. Within each treatment period, subjects underwent a baseline (pre-dose) assessment of psychomotor performance using four commonly used and validated psychomotor tests, and were then re-assessed after the fifth and final dose over a 7-h, post-dose period. Following dosing with lorazepam, statistically significant changes were seen in five of the six test variables compared with placebo. Ondansetron, at both the 1 mg and the 8 mg doses, did not produce a statistically significant effect on any measure of psychomotor performance compared with placebo.