Asymmetric modulation of cytosolic cAMP activity induces growth cone turning.

The possible role of cyclic nucleotides as second messengers mediating growth cone turning was studied by producing an asymmetric distribution of cyclic nucleotides across the growth cone. A repetitive pulse application method was developed to produce microscopic chemical gradients near the growth cone of embryonic Xenopus neurons in cell culture. When picoliters of a solution containing 20 mM dibutyryl cAMP (dB-cAMP), a membrane-permeable analog of cAMP, were repetitively ejected from a micropipette near the growth cone, neurite growth was consistently directed toward the pipette. Theoretical analysis of the diffusion gradient showed that the neurite is capable of detecting a 10% difference in dB-cAMP concentration across the growth cone. Similar responses were also observed using gradients of the phosphodiesterase inhibitor isobutylmethylxanthine, or of forskolin, which activates adenylate cyclase. Dibutyryl cGMP, however, produced no significant turning. These results suggest that a cytoplasmic gradient of cAMP across the growth cone is sufficient to initiate its turning response, and that cAMP in the growth cone could serve as a second messenger in mediating the action of extracellular guidance cues.     

Growth inhibitory effect of triple anti-tumor gene transfer using Semliki Forest virus vector in glioblastoma cells

The gene delivery of multiple tumor suppressors can provide an efficient tumor therapy in the case of malignant human glioblastomas containing multiple genetic alteration and inactivation. As such, the current study presents a new delivery system that can simultaneously express three anti-tumor genes using a Semliki Forest virus (SFV) vector in the expectation of combined or synergistic effects of angiogenesis inhibition by angiostatin and apoptosis induction by p53, PTEN and the rSFV particle itself. Recombinant SFV (rSFV) containing three anti-tumor genes (rSFV-Agt/p53/PTEN) were found to efficiently transduce and express each anti-tumor gene in glioblastoma cells. In addition, rSFV-Agt/p53/PTEN also resulted in a more effective induction of apoptosis in vitro and inhibition of tumor growth in nude mice when compared with other rSFVs containing only one or two anti-tumor genes. Accordingly, the current results demonstrate that a triple anti-tumor gene transfer using an rSFV vector would be a powerful strategy for regional cancer gene therapy.     

Pharmacokinetics of ruboxistaurin are significantly altered by rifampicin-mediated CYP3A4 induction

AIMS: The aim of this study was to evaluate the effect of rifampicin co-administration on the pharmacokinetics of ruboxistaurin and its active metabolite, N-desmethyl ruboxistaurin and, in addition, to compare the changes in pharmacokinetics of ruboxistaurin and N-desmethyl ruboxistaurin with the urinary 6beta-hydroxycortisol : cortisol ratio. Ruboxistaurin is a specific protein-kinase-C beta inhibitor in clinical development for the treatment of diabetic microvascular complications. METHODS: This was a two-period, one-sequence study. Sixteen healthy male subjects completed both study periods. In period one, a single 64 mg oral dose of ruboxistaurin was administered. In period two, 600 mg rifampicin was administered daily for 9 days, during which another single 64 mg ruboxistaurin dose was administered on day 7. Blood samples were collected and assayed for ruboxistaurin and N-desmethyl ruboxistaurin. CYP3A4 induction was assessed by ratios of urinary 6beta-hydroxycortisol : cortisol (6beta-OHC : C) obtained via 24 h and morning-spot sampling techniques. Results Following repeated doses of rifampicin, both the mean C(max) and AUC(0,infinity) of ruboxistaurin were significantly reduced by approximately 95% (P < or = 0.001). For the metabolite, the mean C(max) decreased by 68% (P < or = 0.001), and AUC(0,infinity) decreased by 77% (P < or = 0.001). The t(max) values did not appear affected. The 6beta-OHC : C ratios from both 24 h and morning spot methods increased significantly, consistent with CYP3A4 induction. CONCLUSIONS: The effect of rifampicin co-administration on the exposure of ruboxistaurin is consistent with ruboxistaurin being a substrate of CYP3A4. Therefore, co-administration with known CYP3A4 inducing agents (rifampicin, carbamazepine, phenobarbital, etc.) may decrease the concentrations of ruboxistaurin and N-desmethyl-ruboxistaurin. In this study, 6beta OHC : C ratios substantially underestimated the impact of rifampicin on ruboxistaurin.     

A p75(NTR) and Nogo receptor complex mediates repulsive signaling by myelin-associated glycoprotein

Myelin-associated glycoprotein (MAG), an inhibitor of axon regeneration, binds with high affinity to the Nogo-66 receptor (NgR). Here we report that the p75 neurotrophin receptor (p75(NTR)) is a co-receptor of NgR for MAG signaling. In cultured human embryonic kidney (HEK) cells expressing NgR, p75(NTR) was required for MAG-induced intracellular Ca2+ elevation. Co-immunoprecipitation showed an association of NgR with p75(NTR) that can be disrupted by an antibody against p75(NTR) (NGFR5), and extensive coexpression was observed in the developing rat nervous system. Furthermore, NGFR5 abolished MAG-induced repulsive turning of Xenopus axonal growth cones and Ca2+ elevation, both in neurons and in NgR/p75(NTR)-expressing HEK cells. Thus we conclude that p75(NTR) is a co-receptor of NgR for MAG signaling and a potential therapeutic target for promoting nerve regeneration.     

关于建设一流医科大学的战略思考

本文以美国和日本等发达国家大学建设的战略为例，就一流大学的界定、我国建设一流医科大学的战略思路和具体措施进行了探讨。     

Pharmacokinetics and Tolerability of Duloxetine following Oral Administration to Healthy Chinese Subjects

OBJECTIVES: The objectives of the study were to characterise the pharmacokinetics and assess the tolerability of duloxetine in healthy Chinese subjects after single and multiple oral 60 mg dosing. METHODS: This was a single-centre, double-blind, randomised, placebo-controlled, single-period study in healthy native Chinese subjects. A total of 32 subjects, 19 men (14 on duloxetine, 5 on placebo) and 13 women (10 on duloxetine, 3 on placebo) between the ages of 20 and 39 years, participated in the study. Duloxetine 60 mg (enteric-coated pellets in a capsule) was given orally once on day 1 and once daily on days 4 to 9. Sequential blood samples were collected over 72 hours after the dose on days 1 and 9, and a predose sample was obtained on days 7 and 8. Duloxetine concentrations in plasma were determined by a validated liquid chromatography-tandem mass spectrometry method. The tolerability evaluation included a physical examination, vital signs, adverse event monitoring and clinical laboratory evaluations. RESULTS: Duloxetine disposition on oral administration is characterised by a one-compartment pharmacokinetic model. Duloxetine is well absorbed, with a median time of maximum plasma concentration at 6 and 4 hours following single and multiple dosing, respectively. At steady state, the mean apparent oral clearance (CL(ss)/F), mean apparent volume of distribution (V(ss)/F) and mean terminal elimination half-life (t((1/2))) were 86.8 L/h, 1570L and 11 hours, respectively. CL/F and V(ss)/F on single dosing were not statistically significantly different (p > 0.05) compared with multiple dosing. The linearity index, calculated as the ratio of the area under the plasma concentration-time curve (AUC) during the dosing interval tau at steady state (AUC(tau)(,ss)) to the AUC from time zero to infinity after single dosing (AUC(infinity,single dose)) was 1.15 (coefficient of variation 35.7%). The accumulation in duloxetine exposure was estimated to be 50% on multiple dosing compared with single dosing, consistent with the t((1/2)) and dosing interval (24 hours). The pharmacokinetic parameters of duloxetine in Chinese subjects were not statistically significantly different from those reported previously in Caucasian and Japanese subjects. There were no clinically significant adverse events, abnormal safety laboratory data or vital sign changes reported. CONCLUSION: Duloxetine pharmacokinetics in healthy Chinese subjects given a 60 mg once-daily dosing regimen were well characterised and consistent with known duloxetine pharmacokinetics in healthy Caucasian and Japanese subjects. Both single dosing and multiple once-daily dosing of duloxetine 60 mg were well tolerated by healthy Chinese subjects in this study.     

Prognostic value of (13)C-phenylalanine breath test on predicting survival in patients with chronic liver failure

AIM: To evaluate the prognostic value of percentage of 13C-phenylalanine oxidation (13C-PheOx) obtained by 13C-phenylalanine breath test (13C-PheBT) on the survival of patients with chronic liver failure. METHODS: The hepatic function was determined by standard liver blood tests and the percentage of 13C-PheOx in 118 chronic liver failure patients. The follow-up period was of 64 mo. Survival analysis was performed by the Kaplan-Meier method and variables that were significant (P < 0.10) in univariate analysis and subsequently introduced in a multivariate analysis according to the hazard model proposed by Cox. RESULTS: Forty-one patients died due to progressive liver failure during the follow-up period. The probability of survival at 12, 24, 36, 48 and 64 mo was 0.88, 0.78, 0.66, 0.57 and 0.19, respectively. Multivariate analysis demonstrated that Child-Pugh classes, age, creatinine and the percentage of 13C-PheOx (HR 0.338, 95% CI: 0.150-0.762, P = 0.009) were independent predictors of survival. When Child-Pugh classes were replaced by all the parameters of the score, only albumin, bilirubin, creatinine, age and the percentage of 13C-PheOx (HR 0.449, 95% CI: 0.206-0.979, P = 0.034) were found to be independent predictors of survival.CONCLUSION: Percentage of 13C-PheOx obtained by 13C-PheBT is a strong predictor of survival in patients with chronic liver disease.