RESUMO
To investigate reasons for the muscle increase observed when eggs are treated by IGF-1 and whether or not satellite cell activation is specific to different types of myofibers, duck eggs were administrated with IGF-1. After injection, during the neonatal stages, the duck breast muscle and leg muscle were isolated for analysis. The muscle weight, muscle fiber diameter (MFD), cross-sectional area (CSA), the number of myofibers per unit area (MFN) and frequency of satellite cell activation and mitosis at the embryo stage of 27 days (27E) and the postnatal stage of 2 days after hatching (P2D) were determined. In addition, expression of two important myogenic transcription factors MyoD and Myf5 were detected and compared in the two types of muscle tissues. Results indicated that IGF-1 administration increased the duck body weight, MFD, CSA, MFN, and quantity of activated satellite cells and mitotic nuclei in the two types of muscle tissues. The MyoD and Myf5 expressed at a higher level in IGF-1-treated muscle. IGF-1 stimulated muscle weight growth more in the leg muscle than in the breast muscle. These results indicate that in ovo feeding of IGF-1 can stimulate duck growth and, especially, lead to increased muscle hypertrophy. These increases appear to be mainly dependent on the activation of satellite cells, some of which proliferate and fuse to the myofiber, enabling increased muscle mass. IGF-1 can indirectly affect satellite cells by regulating the expression of two important myogenic transcription factors, MyoD and Myf5, which help activate satellite cells.
Assuntos
Patos/embriologia , Patos/crescimento & desenvolvimento , Fator de Crescimento Insulin-Like I/administração & dosagem , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/crescimento & desenvolvimento , Células Satélites de Músculo Esquelético/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Peso Corporal/efeitos dos fármacos , Patos/genética , Patos/metabolismo , Hipertrofia , Mitose/efeitos dos fármacos , Desenvolvimento Muscular/efeitos dos fármacos , Desenvolvimento Muscular/genética , Desenvolvimento Muscular/fisiologia , Fibras Musculares Esqueléticas/efeitos dos fármacos , Fibras Musculares Esqueléticas/patologia , Músculo Esquelético/embriologia , Músculo Esquelético/patologia , Proteína MyoD/genética , Proteína MyoD/metabolismo , Fator Regulador Miogênico 5/genética , Fator Regulador Miogênico 5/metabolismo , Proteínas Recombinantes/administração & dosagem , Células Satélites de Músculo Esquelético/patologiaRESUMO
Follistatin (FST) can inhibit the expression of myostatin, which is a predominant inhibitor of muscle development. The potential application of myostatin-based technology has been prompted in different ways in agriculture. We previously constructed an expression vector of duck FST and isolated the FST fusion protein. After the protein was purified and refolded, it was added to the medium of duck myoblasts cultured in vitro. The results show that the 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide value of the myoblasts in the duck FST treatment group is higher than that in the control group, which indicates that the duck FST fusion protein exhibits the biological activities that can accelerate myoblast proliferation. To further investigate the roles of duck FST on muscle development, we injected the protein into the duck muscle tissues in vivo. The results show that both the duck muscle fiber cross-sectional area and the satellite cell activation frequency are influenced more in the FST treatment group than they are in the control group. In addition to these phenomena, expression of MyoD and Myf5 were increased, and the expression of myostatin was decreased. Together, these results suggest the potential for using duck FST fusion protein to inhibit myostatin activity and subsequently to enhance muscle growth in vivo. The mechanism by which FST regulates muscle development in the duck is similar to that in mammals and fishes.
Assuntos
Proliferação de Células/efeitos dos fármacos , Folistatina/administração & dosagem , Folistatina/metabolismo , Hipertrofia/induzido quimicamente , Músculos/efeitos dos fármacos , Animais , Patos , Injeções Intramusculares , Miostatina/antagonistas & inibidores , Proteínas Recombinantes/administração & dosagem , Proteínas Recombinantes/metabolismoRESUMO
Cage-like nano-tetrapod ZnO is a novel structure, which was successfully synthesized by combustion oxidation at 850 degrees C. No catalyst or carrier gases were used. Thorough SEM and TEM analyses revealed that the linking legs of the tetrapod ZnO can have or not interface. The formation or not of an interface is discussed and it was attributed to different growth process of the cage-like ZnO nano-tetrapod. Enhanced UV emission peak at the wavelength of 375 nm, featuring high intensity and narrow width, indicates a highly crystalline structure. A green emission, recorded at 502 nm, was related to the defects of the surface of the branching configuration as well as to the ZnO nuclei of the cage-like nano-tetrapod ZnO.
Assuntos
Nanopartículas/química , Nanoestruturas/química , Nanotubos/química , Óxido de Zinco/química , Cristalografia por Raios X , Luz , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Nanotecnologia/métodos , Espectrofotometria Ultravioleta , Temperatura , Raios Ultravioleta , Difração de Raios XRESUMO
In this study, few-layered MoS2 nanosheets (MoS2-NS) were obtained via the top-down exfoliation method from bulk MoS2 (MoS2-Bulk), and the dielectric properties and microwave absorption performance of MoS2-NS were first reported. The dimension-dependent dielectric properties and microwave absorption performance of MoS2 were investigated by presenting a comparative study between MoS2-NS and MoS2-Bulk. Our results show that the imaginary permittivity (ε'') of MoS2-NS/wax is twice as large as that of MoS2-Bulk/wax. The minimum reflection loss (RL) value of MoS2-NS/wax with 60 wt% loading is -38.42 dB at a thickness of 2.4 mm, which is almost 4 times higher than that of MoS2-Bulk/wax, and the corresponding bandwidth with effective attenuation (<-10 dB) of MoS2-NS/wax is up to 4.1 GHz (9.6-13.76 GHz). The microwave absorption performance of MoS2-NS is comparable to those reported in carbon-related nanomaterials. The enhanced microwave absorption performance of MoS2-NS is attributed to the defect dipole polarization arising from Mo and S vacancies and its higher specific surface area. These results suggest that MoS2-NS is a promising candidate material not only in fundamental studies but also in practical microwave applications.
RESUMO
This study simulates thermal conductivity via a carrier scattering mechanism and the related parameters are obtained based on first principles for intrinsic and doped silicon carbide (SiC) over a temperature range of 300-1450 K. The theoretical analysis results show that the thermal conductivity decreases with increasing temperature along each orientation for both cubic SiC (3C-SiC) and doped SiC. Compared with traditional calculations, the thermal conductivity of doped SiC is larger than that of intrinsic SiC in the high-temperature region. In particular, the n-type thermal conductivity is higher than the p-type thermal conductivity because of the scattering probability between electrons and the ionization impurity increasing with the temperature. Our studies are important to a further understanding of thermal transportation.
RESUMO
Light-weight nanocomposites filled with carbon nanotubes (CNTs) are developed for their significant potentials in electromagnetic shielding and attenuation for wide applications in electronics, communication devices, and specific parts in aircrafts and vehicles. Specifically, the introduction of a second phase into/onto CNTs for achieving CNT-based heterostructures has been widely pursued due to the enhancement in either dielectric loss or magnetic loss. In this work, ferroferric oxide (Fe(3)O(4)) was selected as the phase in multiwalled carbon nanotube (MWCNT)-based composites for enhancing magnetic properties to obtain improved electromagnetic attenuation. A direct comparison between the two-phase heterostructures (Fe(3)O(4)/MWCNTs) and polyaniline (PANI) coated Fe(3)O(4)/MWCNTs, namely, three-phase heterostructures (PANI/Fe(3)O(4)/MWCNTs), was made to investigate the interface influences of Fe(3)O(4) and PANI on the complex permittivity and permeability separately. Compared to PANI/Fe(3)O(4)/MWCNTs, Fe(3)O(4)/MWCNTs exhibited enhanced magnetic properties coupled with increased dielectric properties. Interfaces between MWCNTs and heterostructures were found to play a role in the corresponding properties. The evaluation of microwave absorption of their wax composites was carried out, and the comparison between Fe(3)O(4)/MWCNTs and PANI/Fe(3)O(4)/MWCNTs with respect to highly efficient microwave absorption and effective absorption bandwidth was discussed.