Comparison of the pharmacokinetics of oxycodone and noroxycodone in male dark agouti and Sprague-Dawley rats: Influence of streptozotocin-induced diabetes

Purpose. The aims of this study are to evaluate whether cytochrome P450 (CYP)2D1/2D2-deficient dark agouti (DA) rats and/or CYP2D1/2D2-replete Sprague-Dawley (SD) rats are suitable preclinical models of the human, with respect to mirroring the very low plasma concentrations of metabolically derived oxymorphone seen in humans following oxycodone administration, and to examine the effects of streptozotocin-induced diabetes on the pharmacokinetics of oxycodone and its metabolites, noroxycodone and oxymorphone, in both rodent strains. Methods. High-performance liquid chromatography-electrospray ionization-tandem mass spectrometry was used to quantify the serum concentrations of oxycodone, noroxycodone, and oxymorphone following subcutaneous administration of bolus doses of oxycodone (2 mg/kg) to groups of nondiabetic and diabetic rats. Results. The mean (+/- SEM) areas under the serum concentration vs. time curves for oxycodone and noroxycodone were significantly higher in DA relative to SD rats (diabetic, p < 0.05; nondiabetic, p < 0.005). Serum concentrations of oxymorphone were very low (< 6.9 nM). Conclusions. Both DA and SD rats are suitable rodent models to study oxycodone's pharmacology, as their systemic exposure to metabolically derived oxymorphone (potent mu-opioid agonist) is very low, mirroring that seen in humans following oxycodone administration. Systemic exposure to oxycodone and noroxycodone was consistently higher for DA than for SD rats showing that strain differences predominated over diabetes status.

Silencing of the ACC synthase gene ACACS2 causes delayed flowering in pineapple [Ananas comosus (L.) Merr.]

Flowering is a crucial developmental stage in the plant life cycle. A number of different factors, from environmental to chemical, can trigger flowering. In pineapple, and other bromeliads, it has been proposed that flowering is triggered by a small burst of ethylene production in the meristem in response to environmental cues. A 1-amino-cyclopropane-1-carboxylate synthase (ACC synthase) gene has been cloned from pineapple (ACACS2), which is induced in the meristem under the same environmental conditions that induce flowering. Two transgenic pineapple lines have been produced containing co-suppression constructs designed to down-regulate the expression of the ACACS2 gene. Northern analysis revealed that the ACACS2 gene was silenced in a number of transgenic plants in both lines. Southern hybridization revealed clear differences in the methylation status of silenced versus non-silenced plants by the inability of a methylation-sensitive enzyme to digest within the ACACS2 DNA extracted from silenced plants, indicating that methylation is the cause of the observed co-suppression of the ACACS2 gene. Flowering characteristics of the transgenic plants were studied under field conditions in South East Queensland, Australia. Flowering dynamics studies revealed significant differences in flowering behaviour, with transgenic plants exhibiting silencing showing a marked delay in flowering when compared with non-silenced transgenic plants and control non-transformed plants. It is argued that the ACACS2 gene is one of the key contributors towards triggering 'natural flowering' in mature pineapples under commercial field conditions.

Heparin-induced thrombocytopenia: recent experience in a large teaching hospital

Background: Heparin-induced thrombocytopenia (HIT) is a potentially serious adverse reaction caused by platelet-activating antibodies. Aim: To describe experience with HIT. Methods: Twenty-two patients identified by laboratory records of heparin-associated antibodies with a 50% or greater decrease in platelet count were reviewed in our 600-bed metropolitan teaching hospital from 1999 to April 2005. Results: There was an increase in the frequency of HIT diagnosed during the review period, which was associated with a rise in the number of requests for HIT antibodies. Thrombotic complications were identified in 14 of 22 patients with HIT. Mean age was 65 years, and 11 patients were men. Seven patients died and HIT was considered contributory in four. One patient required mid-forearm amputation. Unfractionated heparin was used in all cases and five patients also received enoxaparin. Mean time to HIT screen, reflecting when the diagnosis was first suspected, was 14 days. Platelet nadir ranged from 6 x 10(9)/L to 88 x 10(9)/L, with a percentage drop in platelet count of 67-96%. Alternative anticoagulation (danaparoid) was not used in three patients, two of whom died. Conclusions: HIT is a potentially life-threatening complication of heparin therapy, associated with a fall in platelet count and a high incidence of thromboembolic complications. It is most frequently seen using unfractionated heparin therapy. The increase in frequency of HIT diagnosed in our hospital appears to be associated with a greater awareness of the entity, although detection is often delayed. Platelet count should be monitored in patients on heparin and the presence of antiplatelet antibodies determined if HIT is suspected. Treatment involves both discontinuation of heparin and the use of an alternative anticoagulant such as danaparoid because of the persisting risk of thrombosis.

Methyl jasmonate induced gene expression in wheat delays symptom development by the crown rot pathogen Fusarium pseudograminearum

The necrotrophic fungal pathogen Fusarium pseudograminearum (F. pseudograminearum) causes crown rot disease (CR) in wheat. This host-pathogen interaction has not been studied previously at the molecular level. In this study. using real-time quantitative PCR, the expression of 26 selected wheat genes was examined 1, 2 and 4 days after inoculation of wheat seedlings of the CR susceptible cultivar Kennedy and the partially field-resistant cultivar Sunco. Reproducible induction of eight defence genes consisting of PR1.1, PR2 (beta,1-3 glucanase), PR3 (chitinase), PR4 (wheativin), PR5 (thaumatin-like protein). TaPERO (peroxidase), PR10 and TaGLP2a (germin-like) was observed. These genes were induced in both cultivars, however. some genes were induced more rapidly in Sunco than in Kennedy. MJ treatment also induced the above pathogen responsive defence genes in both cultivars while benzo(1,2,3)thiadiazole-7-carbothionic acid S-methyl ester (BTH) treatment weakly induced them in Kennedy only. Similarly. treatment with MJ before inoculation significantly delayed the development of necrotic symptoms for 2 weeks in both wheat cultivars, while BTH pre-treatments delayed symptom development in Kennedy only. The chemically induced protection, therefore, correlated with induction of the F. pseudograminearum-responsive genes. These results support the emerging role of jasmonate signalling in defence against necrotrophic fungal pathogens in monocots and future manipulation of this pathway may improve CR resistance in wheat. (c) 2006 Elsevier Ltd. All rights reserved.