Early treatment with metformin induces resistance against tumor growth in adult rats

It is known that antidiabetic drug metformin, which is used worldwide, has anti-cancer effects and can be used to prevent cancer growth. We tested the hypothesis that tumor cell growth can be inhibited by early treatment with metformin. For this purpose, adult rats chronically treated with metformin in adolescence or in adulthood were inoculated with Walker 256 carcinoma cells. Adult rats that were treated with metformin during adolescence presented inhibition of tumor growth, and animals that were treated during adult life did not demonstrate any changes in tumor growth. Although we do not have data to disclose a molecular mechanism to the preventive metformin effect, we present, for the first time, results showing that cancer growth in adult life is dependent on early life intervention, thus supporting a new therapeutic prevention for cancer.     

Olfactory bulbs influence testosterone feedback on gonadotropin secretion in male hamsters on long or short photoperiod

Previous studies have shown that prepubertal olfactory bulbectomy will prevent the testicular regression associated with short photoperiod in golden hamsters. The gonadal regression which normally occurs in hamsters on short photoperiod is known to be due in part to an increased responsiveness of the reproductive neuroendocrine system to the negative feedback actions of testosterone on LH and FSH secretion. The present study tested whether the olfactory bulbs influence the feedback effects of testosterone on gonadotropin secretion. Twenty-four- to 26-day-old male golden hamsters were either olfactory-bulbectomized (BX) or sham-olfactory-bulbectomized. Eight weeks later, all hamsters were castrated, and one half of each group was placed in LD 10:14 (this was called week-8 of the study), while the other half was returned to long photoperiod (LD 14:10). Eight weeks following castration (week 0 of the study), all animals were implanted with silastic capsules containing 0, 4, 8 or 16 mm of testosterone. All hamsters were bled by cardiac puncture at -8, -4, 0, +2, +4, +6 and +8 weeks. The concentration of LH and FSH in these samples was then determined by RIA. BX completely prevented the negative feedback of testosterone on gonadotropin secretion in hamsters on either long or short photoperiod at all levels of testosterone tested in this study. In addition, there were seemingly steroid-independent effects of BX on gonadotropin levels in the castrated hamsters prior to testosterone replacement at weeks -4 and 0.(ABSTRACT TRUNCATED AT 250 WORDS)     

Outcome of AIDS-associated cryptococcal meningitis initially treated with 200 mg/day or 400 mg/day of fluconazole

Background  

AIDS-associated cryptococcal meningitis has a high mortality. Fluconazole was the only systemic antifungal therapy available in our centre. From 1999–2001 we used low-dose fluconazole (200 mg daily initially), and did not offer therapy to patients perceived to have poor prognoses. In 2001 donated fluconazole became available, allowing us to use standard doses (400 mg daily initially). Antiretroviral therapy was not available during the study period.     

The TRAPIST Study. A multicentre randomized placebo controlled clinical trial of trapidil for prevention of restenosis after coronary stenting, measured by 3-D intravascular ultrasound.

BACKGROUND: Studies have reported benefit of oral therapy with the phosphodiesterase inhibitor, trapidil, in reducing restenosis after coronary angioplasty. Coronary stenting is associated with improved late outcome compared with balloon angioplasty, but significant neointimal hyperplasia still occurs in a considerable proportion of patients. The aim of this study was to investigate the safety and efficacy of trapidil 200 mg in preventing in-stent restenosis. METHODS: Patients with a single native coronary lesion requiring revascularization were randomized to placebo or trapidil at least 1 h before, and continuing for 6 months after, successful implantation of a coronary Wallstent. The primary end-point was in-stent neointimal volume measured by three-dimensional reconstruction of intravascular ultrasound images recorded at the 6 month follow-up catheterization. RESULTS: Of 312 patients randomized at 21 centres in nine countries, 303 (148 trapidil, 155 placebo) underwent successful Wallstent implantation, and 139 patients (90%) in the placebo group and 130 (88%) in the trapidil group had repeat catheterization at 26+/-2 weeks. There was no significant difference between trapidil and placebo-treated patients regarding in-stent neointimal volume (108.6+/- 95.6 mm(3)vs 93.3+/-79.1 mm(3);P=0.16) or % obstruction volume (38+/-18% vs 36+/-21%;P=0.32), in angiographic minimal luminal diameter at follow-up (1.63+/-0.61 mm vs 1.74+/-0.69 mm;P=0.17), restenosis rate (31% vs 24%;P=0.24), cumulative incidence of major adverse cardiac events at 7 months (22% vs 20%;P=0.71) or anginal complaints (30% vs 24%;P=0.29). CONCLUSION: Oral trapidil 600 mg daily for 6 months did not reduce in-stent hyperplasia or improve clinical outcome after successful Wallstent implantation and is not indicated for this purpose.     

Impact of bleeding severity on clinical outcomes among patients with acute coronary syndromes

Bleeding is a complication of current therapies for acute coronary syndrome (ACS). No studies have examined the effect of bleeding events on clinical outcomes. We analyzed pooled data from 4 multicenter, randomized clinical trials of patients who had ACS (n = 26,452) to determine an association between bleeding severity as measured by the GUSTO scale and 30-day and 6-month mortality rates using Cox proportional hazards modeling that incorporated bleeding as a time-dependent covariate. The analysis was repeated to examine procedure- and non-procedure-related bleeding and after censoring at the time of coronary artery bypass grafting. Of all the patients included, 27.6% had > or =1 bleeding episode. Patients who bled were older and sicker at presentation than were those who did not bleed. Unadjusted rates of 30-day and 6-month mortality increased as bleeding severity increased. There were stepwise increases in the adjusted hazards of 30-day mortality (mild bleeding, hazard ratio [HR] 1.6, 95% confidence interval [CI] 1.3 to 1.9; moderate bleeding, HR 2.7, 95% CI l 2.3 to 3.4; severe bleeding, HR 10.6, 95% CI 8.3 to 13.6) and 6-month mortality (mild bleeding, HR 1.4, 95% CI 1.2 to 1.6; moderate bleeding, HR 2.1, 95% CI 1.8 to 2.4; severe bleeding, HR 7.5, 95% CI 6.1 to 9.3) as bleeding severity increased. Results were consistent after censoring for coronary artery bypass grafting and for procedure- and non-procedure-related bleeds. In conclusion, the GUSTO bleeding classification identifies patients who are at risk for short- and long-term adverse events. Therapies that minimize bleeding risk and maintain an anticoagulant effect may improve outcomes among patients who have ACS.     

Mechanism of cGMP-mediated protection in a cellular model of myocardial reperfusion injury

OBJECTIVE: Reperfusion injury of the myocardium is characterised by development of cardiomyocyte hypercontracture. Previous studies have shown that cGMP-mediated stimuli protect against reperfusion injury, but the cellular mechanism is still unknown. METHODS: To simulate ischemia/reperfusion, adult rat cardiomyocytes were incubated anoxically (pH(o) 6.4) and then reoxygenated (pH(o) 7.4). Cytosolic calcium [Ca(2+)](i) (fura-2 ratio), pH(i) (BCECF ratio), cell length, and phospholamban phosphorylation were analysed. Under simulated ischemia cardiomyocytes develop [Ca(2+)](i) overload. When reoxygenated they rapidly undergo hypercontracture, triggered by oscillations of [Ca(2+)](i). We investigated whether cGMP-mediated stimuli can modulate [Ca(2+)](i) or pH(i) recovery and whether this contributes to their protective effect. Membrane-permeable cGMP analogues, 8-bromo-cGMP (1 mmol/L) or 8-pCPT-cGMP (10 micrommol/L), or a receptor-mediated activator of particulate guanylyl cyclase, urodilatin (1 micromol/L), were applied. RESULTS: The investigated stimuli protect against reoxygenation-induced hypercontracture (cell length as percent of end-ischemic length; control: 68+/-1.6; 8-bromo-cGMP: 88+/-1.5*; 8-pCPT-cGMP: 84+/-2.9*; urodilatin: 87+/-1.1*; n=24; *p<0.05). Recovery from [Ca(2+)](i) overload after 2 min reoxygenation [fura-2 ratio (a.u.); control: 1.43+/-0.15; 8-bromo-cGMP: 1.86+/-0.15*; 8-pCPT-cGMP: 1.92+/-0.19*; urodilatin: 1.93+/-0.24*; n=25; *p<0.05] was accelerated, and the frequency of [Ca(2+)](i) oscillations (min(-1)) was significantly reduced (control: 49+/-5.0 min(-1); 8-bromo-cGMP: 18+/-3.5* min(-1); 8-pCPT-cGMP: 18+/-4.5* min(-1); urodilatin: 16+/-4.1* min(-1); n=24; *p<0.05). cGMP-mediated stimuli increased sarcoplasmic Ca(2+) sequestration (caffeine-releasable Ca(2+) pool: 2-3 fold increase vs. control). Inhibition of sarcoplasmic Ca(2+)-ATPase (SERCA) by thapsigargin (150 nmol/L) or of protein kinase G with KT-5823 (1 micromol/L) abolished the effect of these stimuli on [Ca(2+)](i) recovery. The investigated stimuli significantly enhanced phospholamban phosphorylation. CONCLUSIONS: We conclude that cGMP-dependent signals activate SERCA via a protein kinase G-dependent phosphorylation of phospholamban. The increase in SERCA activity seems to reduce peak [Ca(2+)](i) and [Ca(2+)](i) oscillation during reoxygenation and to attenuate the excessive activation of the contractile machinery that otherwise leads to the development of hypercontracture.