Response of six neutron survey meters in mixed fields of fast and thermal neutrons

Calibration neutron fields have been developed at KAERI (Korea Atomic Energy Research Institute) to study the responses of commonly used neutron survey meters in the presence of fast neutrons of energy around 10 MeV. The neutron fields were produced by using neutrons from the (241)Am-Be sources held in a graphite pile and a DT neutron generator. The spectral details and the ambient dose equivalent rates of the calibration fields were established, and the responses of six neutron survey meters were evaluated. Four single-moderator-based survey meters exhibited an under-responses ranging from ∼9 to 55 %. DINEUTRUN, commonly used in fields around nuclear reactors, exhibited an over-response by a factor of three in the thermal neutron field and an under-response of ∼85 % in the mixed fields. REM-500 (tissue-equivalent proportional counter) exhibited a response close to 1.0 in the fast neutron fields and an under-response of ∼50 % in the thermal neutron field.

Characterization of side populations in HNSCC: highly invasive, chemoresistant and abnormal Wnt signaling

Side Population (SP) cells, a subset of Hoechst-low cells, are enriched with stem cells. Originally, SP cells were isolated from bone marrow but recently have been found in various solid tumors and cancer cell lines that are clonogenic in vitro and tumorigenic in vivo. In this study, SP cells from lymph node metastatic head and neck squamous cell carcinoma (HNSCC) cell lines were examined using flow cytometry and Hoechst 3342 efflux assay. We found that highly metastatic HNSCC cell lines M3a2 and M4e contained more SP cells compared to the low metastatic parental HNSCC cell line 686LN. SP cells in HNSCC were highly invasive in vitro and tumorigenic in vivo compared to non-SP cells. Furthermore, SP cells highly expressed ABCG2 and were chemoresistant to Bortezomib and etoposide. Importantly, we found that SP cells in HNSCC had abnormal activation of Wnt/beta-catenin signaling as compared to non-SP cells. Together, these findings indicate that SP cells might be a major driving force of head and neck tumor formation and metastasis. The Wnt/beta-catenin signaling pathway may be an important target for eliminating cancer stem cells in HNSCC.

PS-341 and histone deacetylase inhibitor synergistically induce apoptosis in head and neck squamous cell carcinoma cells

Proteasome inhibitor PS-341 (also known as bortezomib) and histone deacetylase (HDAC) inhibitors have emerged as novel therapeutic agents for a variety of malignancies. In this study, we examined whether PS-341 and the HDAC inhibitor trichostatin A (TSA) induced apoptosis in head and neck squamous cell carcinoma (HNSCC), a common and lethal malignancy. We found that, although TSA treatment alone did not induce apoptosis in HNSCC cells, it significantly enhanced PS-341-induced apoptosis in HNSCC cells in vitro. Consistently, TSA significantly improved PS-341-mediated inhibition of HNSCC tumor growth in nude mice. Mechanistically, we found that TSA increased PS-341-induced Noxa expression and caspase activation in HNSCC cells. The knockdown of Noxa significantly reduced apoptosis induced by cotreatment of PS-341 and TSA. Taken together, our results provide new insight into the mechanisms of synergistic antitumor activity of the PS-341 and HDAC inhibitor regimen, offering a new therapeutic strategy for HNSCC patients.

The effects of paroxetine on the pharmacokinetics of paliperidone extended-release tablets

INTRODUCTION

Co-morbid medical and psychiatric conditions are common in individuals with schizophrenia. As such, selecting antipsychotic medications with a low potential for drug-drug interactions (DDIs) is crucial, as many are extensively metabolized by hepatic cytochrome P450 (CYP) isozymes.

METHODS

This randomized, crossover study examined the effects of paroxetine (a potent CYP2D6 inhibitor) on the pharmacokinetic parameters of a single dose of the novel antipsychotic agent, paliperidone extended-release tablets (paliperidone ER), in healthy subjects.

RESULTS

The mean C (max) and AUC of paliperidone were slightly higher and paliperidone clearance was slightly lower following co-administration of paliperidone ER with paroxetine. There was a ratio of geometric treatment means of 116.48% for AUC (infinity) [90% CI: 104.49-129.84]. However, the increase in total exposure to paliperidone was not considered clinically relevant. The incidence of adverse events was lower when subjects received the combination of paliperidone ER and paroxetine compared with paroxetine alone.

DISCUSSION

Results suggest that no clinically relevant pharmacokinetic interaction occurs when paroxetine and paliperidone ER are co-administered and, therefore, initiation or discontinuation of concomitant treatment with CYP2D6-inhibiting drugs does not appear to warrant an adjustment in paliperidone ER dosage.

Addition of vildagliptin to insulin improves glycaemic control in type 2 diabetes

AIMS/HYPOTHESIS

Type 2 diabetes is difficult to manage in patients with a long history of disease requiring insulin therapy. Moreover, addition of most currently available oral antidiabetic agents increases the risk of hypoglycaemia. Vildagliptin is a dipeptidyl peptidase-IV inhibitor, which improves glycaemic control by increasing pancreatic beta cell responsiveness to glucose and suppressing inappropriate glucagon secretion. This study assessed the efficacy and tolerability of vildagliptin added to insulin therapy in patients with type 2 diabetes.

MATERIALS AND METHODS

This was a multicentre, 24-week, double-blind, randomised, placebo-controlled, parallel-group study in patients with type 2 diabetes that was inadequately controlled (HbA(1c) = 7.5-11%) by insulin. Patients received vildagliptin (n = 144; 50 mg twice daily) or placebo (n = 152) while continuing insulin therapy.

RESULTS

Baseline HbA(1c) averaged 8.4 +/- 0.1% in both groups. The adjusted mean change from baseline to endpoint (AMDelta) in HbA(1c) was -0.5 +/- 0.1% and -0.2 +/- 0.1% in patients receiving vildagliptin or placebo, respectively, with a significant between-treatment difference (p = 0.01). In patients aged >/=65 years, the AMDelta HbA(1c) was -0.7 +/- 0.1% in the vildagliptin group vs -0.1 +/- 0.1% in the placebo group (p < 0.001). The incidence of adverse events was similar in the vildagliptin (81.3%) and placebo (82.9%) groups. However, hypoglycaemic events were less common (p < 0.001) and less severe (p < 0.05) in patients receiving vildagliptin than in those receiving placebo.

CONCLUSIONS/INTERPRETATION

Vildagliptin decreases HbA(1c) in patients whose type 2 diabetes is poorly controlled with high doses of insulin. Addition of vildagliptin to insulin therapy is also associated with reduced confirmed and severe hypoglycaemia. ClinicalTrials.gov ID no.: NCT 00099931.

Effect of PK11195, a peripheral benzodiazepine receptor agonist, on insulinoma cell death and insulin secretion

Functional role of peripheral benzodiazepine receptor on mitochondrial membrane in apoptosis and insulin secretion from insulinoma cells was studied. A prototypic peripheral benzodiazepine receptor agonist PK11195 induced insulinoma cell apoptosis, while a central benzodiazepine receptor agonist did not. Death of insulinoma cells by PK11195 was inhibited by cyclosporin A, a blocker of mitochondrial permeability transition pore. Caspase inhibitors further inhibited MIN6N8 cell death. PK11195 induced dissipation of mitochondrial potential and cytochrome c translocation to cytoplasm. PK11195 induced an increase in cytoplasmic [Ca(2+)], which was reversed by cyclosporin A. Rhod-2 staining showed decreased mitochondrial [Ca(2+)] after PK11195 treatment. PK11195 potentiated glucose-induced insulin secretion probably due to the increased cytoplasmic [Ca(2+)]. Calpain was activated following Ca(2+) release, and calpain inhibitors attenuated death of insulinoma cells by PK11195. These results suggest that PK11195 induces mitochondrial potential loss, cytochrome c translocation, increased insulin secretion in conjunction with an increase in cytoplasmic [Ca(2+)] and calpain activation, which collectively leads to apoptosis of insulinoma cells.