Effects of agmatine on the escalation of intravenous cocaine and fentanyl self-administration in rats

Escalation of drug intake reliably occurs when animals are allowed extended self-administration access. As a form of plasticity, escalation of drug intake may be accompanied by neuroadaptive changes that are related to the transition from controlled use to addiction. The purpose of the present experiment was to examine the effects of agmatine (decarboxylated L-arginine) on the escalation of intravenous (iv) fentanyl and cocaine self-administration in rats. Subjects were allowed 12 h of daily access to fentanyl (2.5 microg/kg) or cocaine (0.2 mg/kg) under a fixed-ratio (FR) 1 schedule of reinforcement for 30 days. Animals self-administering fentanyl were distributed into three groups: (1) low-dose agmatine (10 mg/kg) throughout self-administration; (2) high-dose agmatine (30 mg/kg) throughout self-administration; and (3) high-dose agmatine after significant escalation (Day 18) of drug intake had occurred. Animals in a fourth group were pretreated with a high dose of agmatine throughout 30 days of cocaine self-administration. Both doses of agmatine, when given throughout self-administration, significantly decreased the escalation of responding that occurred for fentanyl but not cocaine. In the group that received agmatine after significant escalation had occurred, fentanyl-maintained responding was not significantly altered. These data indicate that agmatine attenuates the escalation of fentanyl self-administration if administered before the escalation begins and may mediate neuroadaptive events related to chronic opioid self-administration.     

Value of the identification of microsatellite instability in colorectal cancer

Objective  Recent studies defend a possible prognostic and therapeutic value of the identification of microsatellite instability (MSI) in colorectal cancer. This work tries to assess the impact that the identification of MSI tumours can have in clinical practice. Material and methods  We recovered tumour samples from 92 of the 143 patients operated on for colorectal cancer in our institution between 1995 and 2000. Five MSI markers (BAT 25, BAT 26, D2S123, D5S346 and D17S250) were studied on them. The rate and clinicopathologic characteristics of MSI tumours were investigated along with their impact on the global and disease-free survival as compared with microsatellite stable (MSS) tumours. Results  All 5 microsatellite markers’ status were established in 73 patients (79.3% of the samples). Among them, 7 tumours showed instability in just one marker (low microsatellite instability [MSI-L]) whereas 5 tumours had mutations in 2 or more markers (high microsatellite instability [MSI-H]), for a total 15.4% rate of MSI tumours. All MSI-H tumours were located in the right colon. We could not find any impact from MSI detection on global or disease-free survival. Conclusions  MSI determination did not identify groups of patients with a different prognosis. Moreover, with such low incidence its determination can only be justified in those cases that fulfill Bethesda’s criteria to identify families with Lynch’s syndrome.     

Preliminary study on the effect of miniaturisation and use of volatile mobile phases in LC for the on-line LC-MS analysis of basic pharmaceuticals

To enhance to compatibility of the on-line coupling of liquid chromatography (LC) with mass spectrometry (MS) for the analysis of basic pharmaceuticals, the use of volatile mobile phase systems in combination with miniaturised LC was investigated. Multifactor analysis of variance (MANOVA) was used to evaluate the data obtained for the various variables (modifier, stationary phase, buffer, buffer pH and buffer concentration) on the resolution, peak symmetry and retention of four basic compounds analysed using LC columns with internal diameters (I.D.) of 0.3, 1.0 and 4.6 mm (conventional). Preliminary results obtained with the investigated micro and conventional columns showed similar behaviour with respect to ruggedness. The various investigated variables showed that miniaturisation by simply downscaling dimensions can result in varying selectivity and peak shapes for basic compounds. When comparing volatile mobile phases (containing ammonium acetate or ammonium citrate) and a conventional non-volatile mobile phase (containing sodium phosphate) under pH 3 conditions, similar separation performances were observed. In the present study, ammonium citrate as the buffering salt, a high buffer concentration and methanol as the modifier showed the best peak symmetry.     

Local interleukin‐12 gene transfer promotes conversion of an acute arthritis to a chronic destructive arthritis

Objective

To determine whether local overexpression of interleukin‐12 (IL‐12), a pleiotropic cytokine that promotes the development of naive T cells into Th1 cells, could aggravate murine streptococcal cell wall (SCW)‐induced arthritis, a model of acute arthritis.

Methods

C57BL/6 mice were injected intraarticularly with saline or with 10⁷ plaque‐forming units of control vector (Ad5del70‐3) or IL‐12 vector (AdmIL‐12.1) into the right knee joint 1 day before intraarticular injection of 25 μg of SCW fragments. The development of joint swelling, changes in chondrocyte proteoglycan (PG) synthesis, and joint destruction were examined thereafter.

Results

In normal joints, high levels of IL‐12 (20 ng/ml on day 1) could be detected after application of the AdmIL‐12.1 vector. After 14 days, expression of IL‐12 was still found locally, but IL‐12 alone did not induce protracted inflammation. Local expression of IL‐12, in combination with SCW, markedly aggravated SCW‐induced arthritis, as determined by enhanced joint swelling and prolonged inhibition of chondrocyte PG synthesis. Histologic examination on day 21 showed a chronic inflammatory process, with persistent cartilage PG depletion, cartilage erosion, and VDIPEN neoepitope expression (indicative of metalloproteinase activation). The mixture of IL‐12 with SCW fragments did not lead to a chronic destructive process in mice deficient for recombination‐activating gene 2, indicating the involvement of lymphocytes. In addition, systemic flare of smoldering SCW arthritis, produced by intravenous injection of SCW fragments, was only seen in the AdmIL‐12/SCW group.

Conclusion

These results indicate that local overexpression of IL‐12 promotes conversion of an acute arthritis to a chronic destructive immune‐mediated process, which is more susceptible to flares.