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Abstract: We reported the growth and its electrical properties of [100]-oriented diamond film using alcohol and hydrogen by HFCVD. SEM and Raman measurements indicated that high quality polycrystalline diamond films with [100]-faced structure were obtained. Dark current–voltage (I–V), capacitance–frequency (C–F), capacitance–voltage (C–V) and photocurrent under steady-state 55Fe 5.9keV X-ray excitation of freestanding diamond film were investigated at room temperature. Results indicated that after post-annealing for [100]-oriented diamond films dark current was in the order of 10−10 A and the photocurrent was of in the order 10−8 A by X-ray irradiation with the applied voltage of 40V, capacitance and dielectric loss were very small with the value of 2pF and 2×10−3 with the bias voltage of 0.05V, respectively, and almost had no variation with the change of frequency in high frequencies from 100kHz to 10MHz. [Copyright &y& Elsevier]

Serine racemase (SR) synthesizes l-type serine to its enantimor, d -serine which participates in physiological processes and in pathological conditions. In the central nervous system, SR is highly expressed in neurons and astrocytes but expressed at relatively lower amount in microglia. However, the mechanism by which SR is highly expessed in neurons is hitherto unknown. We report that the SR mRNA and protein levels in Neuro-2a were increased by valproic acid (VPA), a neuron differentiation stimulator as well as a histone deacetylase inhibitor. SR proximal promoter contained nine putative Sp-binding elements and in the exon 1, three putative anti-oxidant elements (AREs) were conservative among human, rat, and mouse genome. The promoter constructs including 5′-, 3′-fragment, and full length fragment from mouse were individually cloned into a luciferase reporter. Using dual-luciferase assay, the promoter harboring 3′-fragment contained much lower activity than the construct containing 5′-fragment which was though resistant to VPA induction, relative to 3′-fragment. Overexpression of Sp4 or Nrf2 increased whereas knockdown of either decreased Srr mRNA and SR protein. Using site-directed mutagenesis, mutation of Sp-binding elements or AREs in the constructs significantly decreased luciferase activity of the corresponding promoter construct. With chromatin immunoprecipitation, Sp4 was demonstrated to interact directly with the Sp-binding elements whereas Nrf2 bound AREs in Srr mRNA promoter. Altogether, our study highlights that Sp4 controls constitutive expression of SR in neuron and VPA mediates SR expression in N2A cells which is associated with its effect on neuron differentiation, that is, the effect is mediated via Nrf2. • VPA increased Srr mRNA and SR protein levels due to its effect on neuron differentiation. • Sp4 maintained high level of Srr transcription in N2A cells. • Nrf2-ARE mediated elevation of SR in response to VPA induction. [ABSTRACT FROM AUTHOR]

Regulation of serine racemase (SR) occurs at transcriptional and translational levels; post-translational modification, cytosolic distribution as well as allosteric effect regulate SR activity. In this study, we report a new route of SR regulation, i.e. oxidative stress and hypermethylation of the srr (gene of SR) promoter correlate with its reduced transcription in aging rat cerebella. We first showed that the mRNA and protein level of srr were decreased in the homogenates of rat cerebellum at age 12 months compared with the counterparts from age 20 days. The reduction of SR protein level in aging cerebella was evidenced by decreased immunostaining observed in the cell body of granule cells or Purkinje cells. Staining for 8-hydroxy-2′-deoxyguanosine (8-OHdG), a marker for oxidative stress to DNA, was much stronger in granule cell or Purkinje cell nuclei from rat cerebella at 12 months compared with staining at 20 days. We further detected srr promoter hypermethylation at 12 months compared with that at 20 days by use of bisulfite sequencing PCR, coinciding with elevated protein levels of DNA methyltransferase 1 (DNMT1) in homogenates of aging cerebella. In vitro, we demonstrated that chronic treatment with the oxidant, menadione (VK3), reduced srr mRNA levels, which was reversed by the DNA demethylating agent 5-Aza-dC-2′-deoxycytidine (5-Aza-dC) in primary cerebellar granule cell cultures. Together, the in vivo and ex vivo results suggest that oxidative DNA stress and srr promoter hypermethylation are associated with reduced srr gene transcription and corresponding reduced protein expression in aging cerebella. [ABSTRACT FROM AUTHOR]