Search tips
Search criteria

Results 1-8 (8)

Clipboard (0)

Select a Filter Below

Year of Publication
Document Types
1.  Tequila Regulates Insulin-Like Signaling and Extends Life Span in Drosophila melanogaster  
The aging process is a universal phenomenon shared by all living organisms. The identification of longevity genes is important in that the study of these genes is likely to yield significant insights into human senescence. In this study, we have identified Tequila as a novel candidate gene involved in the regulation of longevity in Drosophila melanogaster. We have found that a hypomorphic mutation of Tequila (Teq f01792), as well as cell-specific downregulation of Tequila in insulin-producing neurons of the fly, significantly extends life span. Tequila deficiency–induced life-span extension is likely to be associated with reduced insulin-like signaling, because Tequila mutant flies display several common phenotypes of insulin dysregulation, including reduced circulating Drosophila insulin-like peptide 2 (Dilp2), reduced Akt phosphorylation, reduced body size, and altered glucose homeostasis. These observations suggest that Tequila may confer life-span extension by acting as a modulator of Drosophila insulin-like signaling.
PMCID: PMC4675830  PMID: 26265729
Aging; Longevity; Neurotrypsin; Glucose homeostasis
2.  Reduced Gut Acidity Induces an Obese-Like Phenotype in Drosophila melanogaster and in Mice 
PLoS ONE  2015;10(10):e0139722.
In order to identify genes involved in stress and metabolic regulation, we carried out a Drosophila P-element-mediated mutagenesis screen for starvation resistance. We isolated a mutant, m2, that showed a 23% increase in survival time under starvation conditions. The P-element insertion was mapped to the region upstream of the vha16-1 gene, which encodes the c subunit of the vacuolar-type H+-ATPase. We found that vha16-1 is highly expressed in the fly midgut, and that m2 mutant flies are hypomorphic for vha16-1 and also exhibit reduced midgut acidity. This deficit is likely to induce altered metabolism and contribute to accelerated aging, since vha16-1 mutant flies are short-lived and display increases in body weight and lipid accumulation. Similar phenotypes were also induced by pharmacological treatment, through feeding normal flies and mice with a carbonic anhydrase inhibitor (acetazolamide) or proton pump inhibitor (PPI, lansoprazole) to suppress gut acid production. Our study may thus provide a useful model for investigating chronic acid suppression in patients.
PMCID: PMC4593636  PMID: 26436771
3.  Probing substrate influence on graphene by analyzing Raman lineshapes 
We provide a new approach to identify the substrate influence on graphene surface. Distinguishing the substrate influences or the doping effects of charged impurities on graphene can be realized by optically probing the graphene surfaces, included the suspended and supported graphene. In this work, the line scan of Raman spectroscopy was performed across the graphene surface on the ordered square hole. Then, the bandwidths of G-band and 2D-band were fitted into the Voigt profile, a convolution of Gaussian and Lorentzian profiles. The bandwidths of Lorentzian parts were kept as constant whether it is the suspended and supported graphene. For the Gaussian part, the suspended graphene exhibits much greater Gaussian bandwidths than those of the supported graphene. It reveals that the doping effect on supported graphene is stronger than that of suspended graphene. Compared with the previous studies, we also used the peak positions of G bands, and I2D/IG ratios to confirm that our method really works. For the suspended graphene, the peak positions of G band are downshifted with respect to supported graphene, and the I2D/IG ratios of suspended graphene are larger than those of supported graphene. With data fitting into Voigt profile, one can find out the information behind the lineshapes.
PMCID: PMC3924919  PMID: 24506825
Substrate influence; Graphene; Raman lineshapes; Voigt fitting
4.  Surface-enhanced Raman scattering of suspended monolayer graphene 
Nanoscale Research Letters  2013;8(1):480.
The interactions between phonons and electrons induced by the dopants or the substrate of graphene in spectroscopic investigation reveal a rich source of interesting physics. Raman spectra and surface-enhanced Raman spectra of supported and suspended monolayer graphenes were measured and analyzed systemically with different approaches. The weak Raman signals are greatly enhanced by the ability of surface-enhanced Raman spectroscopy which has attracted considerable interests. The technique is regarded as wonderful and useful tool, but the dopants that are produced by depositing metallic nanoparticles may affect the electron scattering processes of graphene. Therefore, the doping and substrate influences on graphene are also important issues to be investigated. In this work, the peak positions of G peak and 2D peak, the I2D/IG ratios, and enhancements of G and 2D bands with suspended and supported graphene flakes were measured and analyzed. The peak shifts of G and 2D bands between the Raman and SERS signals demonstrate the doping effect induced by silver nanoparticles by n-doping. The I2D/IG ratio can provide a more sensitive method to carry out the doping effect on the graphene surface than the peak shifts of G and 2D bands. The enhancements of 2D band of suspended and supported graphenes reached 138, and those of G band reached at least 169. Their good enhancements are helpful to measure the optical properties of graphene. The different substrates that covered the graphene surface with doping effect are more sensitive to the enhancements of G band with respect to 2D band. It provides us a new method to distinguish the substrate and doping effect on graphene.
78.67.Wj (optical properties of graphene); 74.25.nd (Raman and optical spectroscopy); 63.22.Rc (phonons in graphene)
PMCID: PMC3842687  PMID: 24229405
Suspended graphene; Raman spectroscopy; SERS
5.  BMP4 Is a Peripherally-Derived Factor for Motor Neurons and Attenuates Glutamate-Induced Excitotoxicity In Vitro 
PLoS ONE  2013;8(3):e58441.
Bone morphogenetic proteins (BMPs), members of the transforming growth factor-beta (TGF-β) superfamily, have been shown to play important roles in the nervous system, including neuronal survival and synaptogenesis. However, the physiological functions of BMP signaling in the mammalian neuromuscular system are not well understood. In this study, we found that proteins of the type II bone morphogenetic receptors (BMPRII) were detected at the neuromuscular junction (NMJ), and one of its ligands, BMP4, was expressed by Schwann cells and skeletal muscle fibers. In double-ligated nerves, BMP4 proteins accumulated at the proximal and distal portions of the axons, suggesting that Schwann cell- and muscle fiber-derived BMP4 proteins were anterogradely and retrogradely transported by motor neurons. Furthermore, BMP4 mRNA was down-regulated in nerves but up-regulated in skeletal muscles following nerve ligation. The motor neuron-muscle interactions were also demonstrated using differentiated C2C12 muscle cells and NG108-15 neurons in vitro. BMP4 mRNA and immunoreactivity were significantly up-regulated in differentiated C2C12 muscle cells when the motor neuron-derived factor, agrin, was present in the culture. Peripherally-derived BMP4, on the other hand, promotes embryonic motor neuron survival and protects NG108-15 neurons from glutamate-induced excitotoxicity. Together, these data suggest that BMP4 is a peripherally-derived factor that may regulate the survival of motor neurons.
PMCID: PMC3589418  PMID: 23472198
6.  Layer-dependent morphologies of silver on n-layer graphene 
Nanoscale Research Letters  2012;7(1):618.
The distributions of sizes of silver nanoparticles that were deposited on monolayer, bilayer, and trilayer graphene films were observed. Deposition was carried out by thermal evaporation and the graphene films, placed on SiO2/Si substrates, were obtained by the mechanical splitting of graphite. Before the deposition, optical microscopy and Raman spectroscopy were utilized to identify the number of the graphene layers. After the deposition, scanning electron microscopy was used to observe the morphologies of the particles. Systematic analysis revealed that the average sizes of the nanoparticles increased with the number of graphene layers. The density of nanoparticles decreased as the number of graphene layers increased, revealing a large variation in the surface diffusion strength of nanoparticles on the different substrates. The mechanisms of formation of these layer-dependent morphologies of silver on n-layer graphene are related to the surface free energy and surface diffusion of the n-layer graphene. The effect of the substrate such as SiO2/Si was investigated by fabricating suspended graphene, and the size and density were similar to those of supported graphene. Based on a comparison of the results, the different morphologies of the silver nanoparticles on different graphene layers were theorized to be caused only by the variation of the diffusion barriers with the number of layers of graphene.
PMCID: PMC3507757  PMID: 23140587
Graphene; Nanoparticle growth mechanisms; Diffusion difference barriers; 68.65.Pq (graphene films); 68.70.+w (whiskers and dendrites); 78.67.Wj (optical properties of graphene)
7.  Observation of strain effect on the suspended graphene by polarized Raman spectroscopy 
Nanoscale Research Letters  2012;7(1):533.
We report the strain effect of suspended graphene prepared by micromechanical method. Under a fixed measurement orientation of scattered light, the position of the 2D peaks changes with incident polarization directions. This phenomenon is explained by a proposed mode in which the peak is effectively contributed by an unstrained and two uniaxial-strained sub-areas. The two axes are tensile strain. Compared to the unstrained sub-mode frequency of 2,672 cm−1, the tension causes a red shift. The 2D peak variation originates in that the three effective sub-modes correlate with the light polarization through different relations. We develop a method to quantitatively analyze the positions, intensities, and polarization dependences of the three sub-peaks. The analysis reflects the local strain, which changes with detected area of the graphene film. The measurement can be extended to detect the strain distribution of the film and, thus, is a promising technology on graphene characterization.
PMCID: PMC3502527  PMID: 23013616
Graphene strain; Polarization Raman spectroscopy; suspended graphene; 78.67.Wj (optical properties of graphene); 74.25.nd (Raman and optical spectroscopy); 63.22.Rc (phonons in graphene)
8.  Autophagy-related gene 7 is downstream of heat shock protein 27 in the regulation of eye morphology, polyglutamine toxicity, and lifespan in Drosophila 
Autophagy and molecular chaperones both regulate protein homeostasis and maintain important physiological functions. Atg7 (autophagy-related gene 7) and Hsp27 (heat shock protein 27) are involved in the regulation of neurodegeneration and aging. However, the genetic connection between Atg7 and Hsp27 is not known.
The appearances of the fly eyes from the different genetic interactions with or without polyglutamine toxicity were examined by light microscopy and scanning electronic microscopy. Immunofluorescence was used to check the effect of Atg7 and Hsp27 knockdown on the formation of autophagosomes. The lifespan of altered expression of Hsp27 or Atg7 and that of the combination of the two different gene expression were measured.
We used the Drosophila eye as a model system to examine the epistatic relationship between Hsp27 and Atg7. We found that both genes are involved in normal eye development, and that overexpression of Atg7 could eliminate the need for Hsp27 but Hsp27 could not rescue Atg7 deficient phenotypes. Using a polyglutamine toxicity assay (41Q) to model neurodegeneration, we showed that both Atg7 and Hsp27 can suppress weak, toxic effect by 41Q, and that overexpression of Atg7 improves the worsened mosaic eyes by the knockdown of Hsp27 under 41Q. We also showed that overexpression of Atg7 extends lifespan and the knockdown of Atg7 or Hsp27 by RNAi reduces lifespan. RNAi-knockdown of Atg7 expression can block the extended lifespan phenotype by Hsp27 overexpression, and overexpression of Atg7 can extend lifespan even under Hsp27 knockdown by RNAi.
We propose that Atg7 acts downstream of Hsp27 in the regulation of eye morphology, polyglutamine toxicity, and lifespan in Drosophila.
PMCID: PMC3483682  PMID: 22621211
Atg7; Hsp27; Neurodegeneration; Lifespan; Drosophila

Results 1-8 (8)