Y. Zhai

Downregulation of Nrf2 promotes autophagy-dependent osteoblastic differentiation of adipose-derived mesenchymal stem cells

Adipose derived stem cells (ADSCs) are an important source of stem cells for tissue repair and regeneration; therefore, understanding the mechanisms that regulate stem cell differentiation into a specific lineage is critical. The NF-E2-related factor 2 (Nrf2) pathway and autophagy promote cell survival in response to oxidative stress. However, the roles of Nrf2 and autophagy in bone metabolism under oxidative stress are controversial. Here, we explored the involvement of Nrf2 signaling and autophagy on the differentiation of ADSCs under conditions of oxidative stress. Exposure of ADSCs to H2O2 promoted reactive oxygen species (ROS) accumulation concomitant with the reduction of cell viability, upregulation of Nrf2, the induction of apoptosis and autophagy, and the promotion of osteogenesis. Suppression of autophagic activity at particular stages resulted in the activation of the Nrf2 pathway, whereas osteoblastic differentiation of ADSCs was inhibited upon ROS stimulation. Silencing of Nrf2 promoted autophagy and osteoblastic differentiation upon ROS stimulation in vitro, and this effect was confirmed in vivo in a mouse model, in which bone formation was enhanced in mice receiving Nrf2-knockdown ADSCs. Taken together, these findings indicate that a negative interaction between the Nrf2 pathway and autophagy may modulate oxidative stress-induced ADSC osteogenesis, and suggest that Nrf2 is a potential target to regulate the differentiation of ADSCs into a specific lineage.

Is Willems method universal for age estimation: A systematic review and meta-analysis

Dental age (DA) has been widely accepted as a way to evaluate chronological age (CA) in recent years. However, the applicability of Willems method, as one of the most popular radiographic ways, still remains controversial in different areas. The aim of this study is to assess the difference between DA and CA with Willems method. Relevant studies published up to February 28th, 2017 were selected via PubMed, Embase, the Cochrane Library, CNKI, CBM and manual search. Studies that examined Willems dental age and chronological age were selected. 11 articles with 9347 individuals whose age ranged from 3.0 to 18.9 years old were ultimately included in this study. The general polled data indicated that Willems method overestimated CA by 0.18 years and 0.06 years for males and females respectively. Subgroup analysis for ethnicity showed significant difference for different ethnicities. Our aggregated data demonstrated that Willems method may not be an overall applicable tool to estimate chronological age for the reason of the difference of ethnicity and rational validity is suggested when necessary.

β decay of 32Cl: Precision γ-ray spectroscopy and a measurement of isospin-symmetry breaking

Background: Models to calculate small isospin-symmetry-breaking effects in superallowed Fermi decays have been placed under scrutiny in recent years. A stringent test of these models is to measure transitions for which the correction is predicted to be large. The decay of 32Cl decay provides such a test case. Purpose: To improve the gamma yields following the beta decay of 32Cl and to determine the ft values of the the beta branches, particularly the one to the isobaric-analogue state in 32S. Method: Reaction-produced and recoil-spectrometer-separated 32Cl is collected in tape and transported to a counting location where beta-gamma coincidences are measured with a precisely-calibrated HPGe detector. Results: The precision on the gamma yields for most of the known beta branches has been improved by about an order of magnitude, and many new transitions have been observed. We have determined 32Cl-decay transition strengths extending up to E_x~11 MeV. The ft value for the decay to the isobaric-analogue state in 32S has been measured. A comparison to a shell-model calculation shows good agreement. CONCLUSIONS: We have experimentally determined the isospin-symmetry-breaking correction to the superallowed transition of this decay to be (\delta_C-\delta_NS)_exp=5.4(9)%, significantly larger than for any other known superallowed Fermi transition. This correction agrees with a shell-model calculation, which yields \delta_C-\delta_NS=4.8(5)%. Our results also provide a way to improve the measured ft values for the beta decay of 32Ar.

Circadian Rhythm Regulates Development of Enamel in Mouse Mandibular First Molar.

Rhythmic incremental growth lines and the presence of melatonin receptors were discovered in tooth enamel, suggesting possible role of circadian rhythm. We therefore hypothesized that circadian rhythm may regulate enamel formation through melatonin receptors. To test this hypothesis, we examined expression of melatonin receptors (MTs) and amelogenin (AMELX), a maker of enamel formation, during tooth germ development in mouse. Using qRT-PCR and immunocytochemistry, we found that mRNA and protein levels of both MTs and AMELX in normal mandibular first molar tooth germs increased gradually after birth, peaked at 3 or 4 day postnatal, and then decreased. Expression of MTs and AMELX by immunocytochemistry was significantly delayed in neonatal mice raised in all-dark or all-light environment as well as the enamel development. Furthermore, development of tooth enamel was also delayed showing significant immature histology in those animals, especially for newborn mice raised in all daylight condition. Interestingly, disruption in circadian rhythm in pregnant mice also resulted in delayed enamel development in their babies. Treatment with melatonin receptor antagonist 4P-PDOT in pregnant mice caused underexpression of MTs and AMELX associated with long-lasting deficiency in baby enamel tissue. Electromicroscopic evidence demonstrated increased necrosis and poor enamel mineralization in ameloblasts. The above results suggest that circadian rhythm is important for normal enamel development at both pre- and postnatal stages. Melatonin receptors were partly responsible for the regulation.

Astrophysical S factor for the radiative capture (12)N(p,gamma)(13)O determined from the (14)N((12)N,(13)O)(13)C proton transfer reaction

The cross section of the radiative proton capture reaction on the drip line nucleus 12 N was investigated using the asymptotic normalization coefficient (ANC) method. We have used the 14 N( 12 N, 13 O) 13 C proton transfer reaction at 12 MeV/nucleon to extract the ANC for 13 O → 12 N + p and calculate from it the direct component of the astrophysical S factor of the 12 N(p, γ) 13 O reaction. The optical potentials used and the distorted-wave Bom approximation analysis of the proton transfer reaction are discussed. For the entrance channel, the optical potential was inferred from an elastic scattering measurement carried out at the same time as the transfer measurement. From the transfer, we determined the square of the ANC, C 2 P1/2 ( 13 O g.s. ) = 2.53 ± 0.30 fm -1 , and hence a value of 0.33(4) keV b was obtained for the direct astrophysical S factor at zero energy. Constructive interference at low energies between the direct and resonant captures leads to an enhancement of S total (0) = 0.42(6) keV b. The 12 N(p, γ) 13 O reaction was investigated in relation to the evolution of hydrogen-rich massive Population III stars, for the role that it may play in the hot pp-chain nuclear burning processes, possibly occurring in such objects.

Astrophysical S factor for the radiative capture 12N(p, γ)13O determined from the 14N(12N, 13O)13C proton transfer reaction

The cross section of the radiative proton capture reaction on the drip line nucleus 12 N was investigated using the asymptotic normalization coefficient (ANC) method. We have used the 14 N( 12 N, 13 O) 13 C proton transfer reaction at 12 MeV/nucleon to extract the ANC for 13 O → 12 N + p and calculate from it the direct component of the astrophysical S factor of the 12 N(p, γ) 13 O reaction. The optical potentials used and the distorted-wave Bom approximation analysis of the proton transfer reaction are discussed. For the entrance channel, the optical potential was inferred from an elastic scattering measurement carried out at the same time as the transfer measurement. From the transfer, we determined the square of the ANC, C 2 P1/2 ( 13 O g.s. ) = 2.53 ± 0.30 fm -1 , and hence a value of 0.33(4) keV b was obtained for the direct astrophysical S factor at zero energy. Constructive interference at low energies between the direct and resonant captures leads to an enhancement of S total (0) = 0.42(6) keV b. The 12 N(p, γ) 13 O reaction was investigated in relation to the evolution of hydrogen-rich massive Population III stars, for the role that it may play in the hot pp-chain nuclear burning processes, possibly occurring in such objects.

AstrophysicalSfactor for the radiative captureN12(p,γ)O13determined from theN14(N12,O13)C13proton transfer reaction

The cross section of the radiative proton capture reaction on the drip line nucleus 12 N was investigated using the asymptotic normalization coefficient (ANC) method. We have used the 14 N( 12 N, 13 O) 13 C proton transfer reaction at 12 MeV/nucleon to extract the ANC for 13 O → 12 N + p and calculate from it the direct component of the astrophysical S factor of the 12 N(p, γ) 13 O reaction. The optical potentials used and the distorted-wave Bom approximation analysis of the proton transfer reaction are discussed. For the entrance channel, the optical potential was inferred from an elastic scattering measurement carried out at the same time as the transfer measurement. From the transfer, we determined the square of the ANC, C 2 P1/2 ( 13 O g.s. ) = 2.53 ± 0.30 fm -1 , and hence a value of 0.33(4) keV b was obtained for the direct astrophysical S factor at zero energy. Constructive interference at low energies between the direct and resonant captures leads to an enhancement of S total (0) = 0.42(6) keV b. The 12 N(p, γ) 13 O reaction was investigated in relation to the evolution of hydrogen-rich massive Population III stars, for the role that it may play in the hot pp-chain nuclear burning processes, possibly occurring in such objects.