Yoshihiro Arakawa

Adenoviral gene transfer of GDNF, BDNF and TGFβ2, but not CNTF, cardiotrophin-1 or IGF1, protects injured adult motoneurons after facial nerve avulsion

We examined neuroprotective effects of recombinant adenoviral vectors encoding glial cell line‐derived neurotrophic factor (GDNF), brain‐derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), cardiotrophin‐1 (CT1), insulin‐like growth factor‐1 (IGF1), and transforming growth factor‐β2 (TGFβ2) on lesioned adult rat facial motoneurons. The right facial nerves of adult Fischer 344 male rats were avulsed and removed from the stylomastoid foramen, and adenoviral vectors were injected into the facial canal. Animals avulsed and treated with adenovirus encoding GDNF, BDNF, CNTF, CT1, IGF1 and TGFβ2 showed intense immunolabeling for these factors in lesioned facial motoneurons, respectively, indicating adenoviral induction of the neurotrophic factors in these neurons. The treatment with adenovirus encoding GDNF, BDNF, or TGFβ2 after avulsion significantly prevented the loss of lesioned facial motoneurons, improved choline acetyltransferase immunoreactivity and prevented the induction of nitric oxide synthase activity in these neurons. The treatment with adenovirus encoding CNTF, CT1 or IGF1, however, failed to protect these neurons after avulsion. These results indicate that the gene transfer of GDNF and BDNF and TGFβ2 but not CNTF, CT1 or IGF1 may prevent the degeneration of motoneurons in adult humans with motoneuron injury and motor neuron diseases.

Smad4-independent regulation of p21/WAF1 by transforming growth factor- β

The transforming growth factor-β (TGF-β)–Smad signaling pathway inhibits the growth of human epithelial cells and plays a role in tumor suppression. The Smad4 gene is mutated or deleted in 50% of pancreatic cancers. In this study, the Smad4-null pancreatic cancer cell line BxPC-3 was transfected with either the Smad4 expression vector or the empty vector and incubated in the presence or absence of TGF-β. The cells were analysed using a cDNA microarray, which included 2280 named genes to screen for target genes regulated by TGF-β in either a Smad4-dependent or -independent manner. The microarray and subsequent quantitative RT–PCR analysis demonstrated that the Smad4-independent and -dependent signaling pathways driven by TGF-β upregulated only one of the 2280 genes, respectively, suggesting that Smad4-independent signaling downstream of TGF-β might be as widespread as Smad4-dependent signaling. In this study, we demonstrated that the cyclin-dependent kinase inhibitor p21/WAF1, which has been considered the major effector of the Smad-dependent growth inhibitory signal of TGF-β, is upregulated in a Smad4-independent manner. The upregulation occurs through Smad2/3-dependent transcriptional activation of the p21/WAF1 promoter region. These results suggest a novel mechanism of gene regulation, that is, a novel signal mediator other than Smad4.

Smad4 silencing in pancreatic cancer cell lines using stable RNA interference and gene expression profiles induced by transforming growth factor-beta.

The transforming growth factor-β (TGF-β)-Smad signaling pathway inhibits the growth of human epithelial cells and plays a role in tumor suppression. The Smad4 gene is mutated or deleted in 50% of pancreatic cancers. In this study, we succeeded in establishing Smad4 knockdown (S4KD) pancreatic cancer cell lines using the stable RNA interference (RNAi) method. Smad4 protein expression was reduced dramatically and TGF-β-Smad signaling was markedly inhibited in the S4KD cell lines. The S4KD and control cells were stimulated with TGF-β and analysed using a cDNA microarray that contained 3756 genes, in order to screen for target molecules downstream of TGF-β. The microarray analysis revealed that 187 S4KD genes and 155 genes in the control cells were regulated immediately upon TGF-β stimulation. Quantitative RT–PCR analysis on several of these genes produced results that corroborated the outcome of the microarray analysis. Most of the genes in the S4KD and control cells identified by the array differed, which suggests signaling pathways that differ according to Smad4 status. Of the identified genes, 246 have not been reported previously as genes that lie downstream of TGF-β. Genes that are involved in cell proliferation, adhesion, and motility were found to be regulated differentially with respect to S4KD and control cells. Cell migration induced by TGF-β was inhibited in the S4KD cells, which might be associated with a different regulation of integrin β7. The knock down of a specific gene using stable RNAi appears to be a promising tool for analysing endogenous gene function.

Development of thrust stand for low impulse measurement from microthrusters

A thrust stand has been developed to accurately measure thrust produced by two types of microthrusters—a liquid propellant pulsed plasma thruster (LP-PPT) and a diode laser ablation microthruster. The impulse of LP-PPT ranged from 20 to 80 μNs. The diode laser microthruster, which is a new type of microthruster, produces much lower impulse range of 1–10 μNs for about 1 s. The mechanical noise induced from the background vibrations becomes a crucial problem for precise estimate of thrust particularly in low impulse measurements. A data analysis method to reduce the effect of mechanical noise is proposed by introducing an additional term in a fitting function. It was verified that the analysis method used in our experimental conditions reduced variance caused by noise down to one-third that of a normal fitting method. The accuracy of the thrust stand is 2.1 μNs in the case of the LP-PPT and 0.7 μNs in the case of the diode laser microthruster.

Discharge Current Oscillation in Hall Thrusters

The discharge current oscillation at a frequency range of 10-100 kHz in Hall thrusters was investigated with the objective of extending their stable operational range. The amplitude of oscillation was measured using two types of Hall thrusters-the anode layer type and the magnetic layer type. The oscillation amplitude was found to be sensitive to the applied magnetic flux density, and this result indicated that the oscillation was affected by electron mobility. An oscillation model was proposed based on the experimental results, and the predicted frequency and stable operational range were found to agree qualitatively agreed with the experimental results. This model shows that the momentum transfer corresponding to plasma fluctuation, that is, the viscosity effect, is crucial to achieving stability. Thus, the oscillation amplitude for various acceleration channel configurations-divergent, parallel, and convergent-was measured because the momentum transfer could be affected by the channel configuration. The stable operational range was successfully extended by the adoption of the convergent configuration in each type of Hall thruster, as shown by this model.

Energy transfer from a laser pulse to a blast wave in reduced-pressure air atmospheres

Focusing a transversely excited atmospheric CO2 laser beam in air atmospheres induced a blast wave. The kinetic energy of a laser-induced blast wave was determined from shadowgraph images of shock wave expansion. Results showed that the fraction of input laser energy that is converted into the blast wave energy decreased from 0.45 to 0.2 concomitant with the decrease in ambient pressure from 100 to 10 kPa. Also, it was insensitive to input laser energy from 4 to 13 J.

Electromagnetic effects in an applied-field magnetoplasmadynamic thruster

Experimental and analytical studies have been conducted on the performance and thrust production mechanisms of an applied-field magnetoplasmadynamic thruster. The thruster was able to run with a high-thruster performance due to large electromagnetic effects related to the applied magnetic field. Using hydrogen, helium, and argon as the propellant, over 20 percent thrust efficiency was obtained over a wide specific impulse range from 1000 to 7000 s at input power levels between 2.2 and 15.9 kW. From the measurements of performance characteristics and current densities in the acceleration region, and by a theoretical analysis, it is found that the thruster operation is characterized by a parameter, B-squared/m (B: applied magnetic field strength, m: propellant mass flow rate). 9 refs.

Anti-albuminuric effect of the aldosterone blocker eplerenone in non-diabetic hypertensive patients with albuminuria: a double-blind, randomised, placebo-controlled trial

BACKGROUND Renin-angiotensin system inhibitors have renoprotective effects in patients with chronic kidney disease, but most patients treated with these drugs have residual urinary albumin excretion. Some small clinical studies show that mineralocorticoid receptor blockade reduces albuminuria. Our study aimed to examine the beneficial effects of addition of a selective aldosterone antagonist, eplerenone, to renin-angiotensin system inhibitors in hypertensive patients with non-diabetic chronic kidney disease. METHODS In this double-blind, randomised, placebo-controlled trial, we enrolled hypertensive patients, aged 20–79 years, with albuminuria (urinary albumin-to-creatinine ratio [UACR] in the first morning void urine of 30–599 mg/g), an estimated glomerular filtration rate of 50 mL/min per 1·73 m2 or more, and who had received an angiotensin-converting enzyme inhibitor, an angiotensin receptor blocker, or both, for at least 8 weeks. Participants were from 59 clinics and hospitals in Japan. Eligible patients were randomly assigned (1:1), stratified by baseline characteristics, to either low-dose eplerenone (50 mg/day) or placebo, with continuation of standard antihypertensive treatment to attain therapeutic goals (<130/80 mm Hg) for 52 weeks. We assessed efficacy in all patients who received allocated treatment, provided a baseline and post-treatment urine sample, and remained in follow-up. We assessed safety in all patients who received allocated treatment. The primary efficacy measure was percent change in UACR in the first morning void urine at week 52 from baseline. The trial is registered at the clinical trials registry of University Hospital Medical Information Network (UMIN), trial identification number UMIN000001803. FINDINGS Between April 1, 2009, and March 31, 2012, we randomly allocated 170 patients to the eplerenone group and 166 patients to the placebo group. In the primary efficacy analysis, mean percent change in UACR from baseline was −17·3% (95% CI −33·65 to −0·94) for 158 patients in the eplerenone group compared with 10·3% (−6·75 to 22·3) for 146 patients in the placebo group (absolute difference −27·6% [–51·15 to −3·96]; p=0·0222). In the safety analyses, 53 (31%) of 169 patients in the eplerenone group had adverse events (five serious), as did 49 (30%) of 163 in the placebo group (seven serious). Although mean serum potassium concentration was higher in the eplerenone group than the placebo group, severe hyperkalaemia (>5·5 mmol/L) was not recorded in either group. INTERPRETATION Addition of low-dose eplerenone to renin-angiotensin system inhibitors might have renoprotective effects through reduction of albuminuria in hypertensive patients with non-diabetic chronic kidney disease, without serious safety concerns. FUNDING Pfizer.

Survival activity of troglitazone in rat motoneurones

Troglitazone (TGZ), an antidiabetic drug that improves insulin‐resistance in the peripheral tissues, was tested for neurotrophic activity in motoneurones and other neurones in culture. In rat motoneurones, TGZ had a remarkable effect on survival, which was comparable or superior to that of brain‐derived neurotrophic factor, a known potent neurotrophic factor for rat motoneurones. However, TGZ did not promote the survival of sensory, sympathetic, septal or hippocampal neurones. The effect of TGZ on motoneurones was additive to that of insulin‐like growth factor‐I and both activities were inhibited by phosphatidylinositol 3‐kinase (PI3‐kinase) inhibitors, wortmannin and LY294002, suggesting the involvement of the activation of PI3‐kinase in the activity of TGZ. Pioglitazone, another antidiabetic drug structurally similar to TGZ, did not show any activity, indicating that the agonistic activity of TGZ for peroxisome proliferator‐activated receptor‐γ is not involved in the survival activity. Chromanol, an antioxidant moiety of TGZ, showed little or no survival activity. These results indicate specific neurotrophic activity of TGZ for motoneurones through the activation of PI3‐kinase and support the applicability of TGZ for the treatment of motor neurone diseases such as amyotrophic lateral sclerosis.

Influence of the focusing f number on the heating regime transition in laser absorption waves

Laser plasma was produced in air atmosphere using a transversely excited atmospheric CO2 pulse laser; the influence of the focusing f number (≡ focal length/laser beam diameter) on the threshold of a heating regime transition in laser absorption waves was then investigated. As a result, when the laser energy was 10 J/pulse, the transition threshold was 2.6±0.4 MW/cm2 with f=1.1 optics and 3.7±0.4 MW/cm2 with f=2.2. The difference was explained in terms of the front area and absorption layer thickness in the laser supported detonation regime.