Roles of PGC-1α/PPARs pathway in regulating insulin sensitivity in mouse skeletal muscle cells under prolonged hypoxia

Using the C2C12 mouse myoblast cell line, I investigated how prolonged hypoxia affected components of the insulin signalling and FAO/PGC-1α/PPARs pathways, as they might impact insulin sensitivity in skeletal muscle cells. Hypoxia resulted in lower p-Akt (Thr 308) and higher total cellular GLUT4 protein levels after 7 days of differentiation. This coincided with higher triglyceride content and alterations of the FAO/PGC-1α/PPARs components, both of which could contribute to the changes observed in the components of the insulin signalling pathway. Specifically, cells differentiating in 1% O2 had lower SIRT1, PPAR- α, FATP4 and MCAD mRNA; accompanied by lower SIRT1, PGC-1α and higher PPAR- γ protein following 7 days of differentiation. Additionally, cells in prolonged hypoxia had significantly higher phosphorylation of PGC-1α, AMPKα and ACC; concurrent with higher PGC-1α acetylation. However, none of these alterations above persisted following an additional 2-day re-oxygenation treatment (recovery). In conclusion, prolonged hypoxia impairs components of the insulin signalling and FAO/PGC-1α/PPARs pathways, although the degree of this impairment is reduced followed re-oxygenation. An altered FAO/PGC-1α/ PPARs interaction contributes to depress FAO, resulting in increased triglyceride content, which likely impairs insulin signaling, specifically Akt phosphorylation (Thr 308). It is important to note that the alterations of FAO/PGC-1α/ PPARs observed here are similar to those reported in insulin resistant adults. The changes obtained during hypoxia may partly explain the in utero factors contributing to decreased insulin sensitivity in intrauterine growth restriction offspring

Effect of estrogen application timing on adipose tissue revascularization and immune regulation in rats after autologous fat transplantation

Purpose: To study the effect of timing of estrogen application on adipose tissue revascularization and immune regulation in rats given autologous fat transplantation.Methods: Ninety (90) healthy rats were selected for use in this study. The rats were randomly divided into a study group (n = 45) and control group (n = 45). After ovariectomy, the study group was given estrogen replacement therapy before autologous fat transplantation, while the control group was given estrogen replacement therapy after autologous fat transplantation. The rats were observed for 6 weeks after transplantation. Micro-vessel density, wet weight of transplanted fat, VEGF expression level, levels of M1 and M2 in macrophages, and macrophage infiltration rate were determined 40 days postautologous fat transplantation.Results: Forty days after autologous fat transplantation, microvessel density, wet weight of transplanted fat, expression level of VEGF and levels of M1 and M2 in macrophages were significantly higher in study group rats than in controls (p < 0.05). There was 80 % macrophage infiltration in the study group rats, while the corresponding control value (61 %) was significantly lower (p < 0.05).Conclusion: Estrogen treatment before autologous fat transplantation in rats is helpful for the revascularization of adipose tissue, enhances vascular regeneration, promotes the survival of adipose tissue after transplantation, and activates immune cells. It also promotes the production of immune factors, and improves immunoregulation in adipose tissue. Thus, this therapeutic strategy may be useful in clinical practice, but further clinical trials are required

Polarization properties of Raman scattering by surface phonon polaritons in GaAsP nanowires

Strong resonant enhancement of Raman scattering on photonic resonance was observed in GaAsP semiconductor nanowires. The enhancement allowed for detailed studies of the surface phonon polariton (SPhP) scattering peak on individual nanowires. In particular, for the first time, the effect of the nanowire cross section shape on SPhP properties has been investigated. It was found that the cross section flattening induces a strong polarisation and a spectral shift of SPhPs supported by such nanowire. The assisting numerical simulations allowed to link the induced polarisation effect to a splitting of the resonant HE11 mode in the flattened nanowire. The observed spectral shift of SPhP has been also theoretically reproduced in elliptical approximation for the flattened cross section. The obtained results pave a ground for engineering of SPhP polarisation response and accurate spectral control of SPhPs in applications utilising the nanowire morphology

Resonant enhancement of Raman scattering by surface phonon polaritons in GaAs nanowires

Surface optical phonons are normally considered as subtle and poorly reproducible features in the Raman spectra of nanostructured semiconductors, from which little or no information about the sample can be extracted. The present study demonstrates the potential for changing this situation. For a common type of GaAs semiconductor nanowire (NW), we have shown that due to a combination of size-resonant light concentration, tapered shape and favourable scattering geometry, the surface phonon polariton (SPhP) Raman signal can be enhanced by orders of magnitude. The high signal gain enables routine detailed characterisation of the SPhP peak on an individual NW level, revealing its polarisation properties and spectral shift under variation of the dielectric environment. This detailed characterisation was conducted using very low excitation power density despite high absorption of the excitation light in the NW material. The findings provide an effective way to use SPhP Raman scattering in the characterisation of dielectric NWs and the prospect of developing novel surface sensors

Light-emitting GaAs nanowires on a flexible substrate

Semiconductor nanowire-based devices are among the most promising structures used to meet the current challenges of electronics, optics and photonics. Due to their high surface-to-volume ratio and excellent optical and electrical properties, devices with low power, high efficiency and high density can be created. This is of major importance for environmental issues and economic impact. Semiconductor nanowires have been used to fabricate high performance devices, including detectors, solar cells and transistors. Here, we demonstrate a technique for transferring large-area nanowire arrays to flexible substrates while retaining their excellent quantum efficiency in emission. Starting with a defect-free self-catalyzed molecular beam epitaxy (MBE) sample grown on a Si substrate, GaAs core–shell nanowires are embedded in a dielectric, removed by reactive ion etching and transferred to a plastic substrate. The original structural and optical properties, including the vertical orientation, of the nanowires are retained in the final plastic substrate structure. Nanowire emission is observed for all stages of the fabrication process, with a higher emission intensity observed for the final transferred structure, consistent with a reduction in nonradiative recombination via the modification of surface states. This transfer process could form the first critical step in the development of flexible nanowire-based light-emitting devices

Dosimetric comparison of intensity modulated radiotherapy and three-dimensional conformal radiotherapy in patients with gynecologic malignancies: a systematic review and meta-analysis

BACKGROUND: To quantitatively evaluate the safety and related-toxicities of intensity modulated radiotherapy (IMRT) dose–volume histograms (DVHs), as compared to the conventional three-dimensional conformal radiotherapy (3D-CRT), in gynecologic malignancy patients by systematic review of the related publications and meta-analysis. METHODS: Relevant articles were retrieved from the PubMed, Embase, and Cochrane Library databases up to August 2011. Two independent reviewers assessed the included studies and extracted data. Pooled average percent irradiated volumes of adjacent non-cancerous tissues were calculated and compared between IMRT and 3D-CRT for a range of common radiation doses (5-45Gy). RESULTS: In total, 13 articles comprised of 222 IMRT-treated and 233 3D-CRT-treated patients were included. For rectum receiving doses ≥30 Gy, the IMRT pooled average irradiated volumes were less than those from 3D-CRT by 26.40% (30 Gy, p = 0.004), 27.00% (35 Gy, p = 0.040), 37.30% (40 Gy, p = 0.006), and 39.50% (45 Gy, p = 0.002). Reduction in irradiated small bowel was also observed for IMRT-delivered 40 Gy and 45 Gy (by 17.80% (p = 0.043) and 17.30% (p = 0.012), respectively), as compared with 3D-CRT. However, there were no significant differences in the IMRT and 3D-CRT pooled average percent volumes of irradiated small bowel or rectum from lower doses, or in the bladder or bone marrow from any of the doses. IMRT-treated patients did not experience more severe acute or chronic toxicities than 3D-CRT-treated patients. CONCLUSIONS: IMRT-delivered high radiation dose produced significantly less average percent volumes of irradiated rectum and small bowel than 3D-CRT, but did not differentially affect the average percent volumes in the bladder and bone marrow

Ten-fold enhancement of InAs nanowire photoluminescence emission with an InP passivation layer

In this letter, we demonstrate that a significant improvement of optical performance of InAs nanowires can be achieved by capping the core InAs nanowires with a thin InP shell, which successfully passivates the surface states reducing the rate of non-radiative recombination. The improvements have been confirmed by detailed photoluminescence measurements, which showed up to ten-fold increase in the intensity of room-temperature photoluminescence from the capped InAs/InP nanowires compared to the sample with core-only InAs nanowires. Moreover, the nanowires exhibit high stability of total photoluminescence emission strength across temperature range from 10 to 300 K as a result of strong quantum confinement. These findings could be the key to successful implementation of InAs nanowires into optoelectronic devices

Nonradiative step facets in semiconductor nanowires

One of the main advantages of nanowires for functional applications is their high perfection, which results from surface image forces that act on line defects such as dislocations, rendering them unstable and driving them out of the crystal. Here we show that there is a class of step facets that are stable in nanowires, with no long-range strain field or dislocation character. In zinc-blende semiconductors, they take the form of Σ3 (112) facets with heights constrained to be a multiple of three {111} monolayers. Density functional theory calculations show that they act as nonradiative recombination centers and have deleterious effects on nanowire properties. We present experimental observations of these defects on twin boundaries and twins that terminate inside GaAsP nanowires and find that they are indeed always multiples of three monolayers in height. Strategies to use the three-monolayer rule during growth to prevent their formation are discussed