家猫的胚胎工程

家猫是惟一一种没有被列为珍稀或濒危的猫科动物。通过家猫的胚胎工程研究,对保护其它濒危猫科物种有重要的借鉴意义。本文描述了家猫的一般生殖特点,着床前的胚胎在体内的发育概况;综述了近年来对家猫的超数排卵,卵母细胞的体外成熟,体外受精,胚胎的体外培养,胚胎移植,冷冻保存和胚胎克隆等方面的研究进展。     

Zebrafish IGF Genes: Gene Duplication,Conservation and Divergence,and Novel Roles in Midline and Notochord Development

Insulin-like growth factors (IGFs) are key regulators of development, growth, and longevity. In most vertebrate species including humans, there is one IGF-1 gene and one IGF-2 gene. Here we report the identification and functional characterization of 4 distinct IGF genes (termed as igf-1a, -1b, -2a, and -2b) in zebrafish. These genes encode 4 structurally distinct and functional IGF peptides. IGF-1a and IGF-2a mRNAs were detected in multiple tissues in adult fish. IGF-1b mRNA was detected only in the gonad and IGF-2b mRNA only in the liver. Functional analysis showed that all 4 IGFs caused similar developmental defects but with different potencies. Many of these embryos had fully or partially duplicated notochords, suggesting that an excess of IGF signaling causes defects in the midline formation and an expansion of the notochord. IGF-2a, the most potent IGF, was analyzed in depth. IGF-2a expression caused defects in the midline formation and expansion of the notochord but it did not alter the anterior neural patterning. These results not only provide new insights into the functional conservation and divergence of the multiple igf genes but also reveal a novel role of IGF signaling in midline formation and notochord development in a vertebrate model.     

Reflection coefficients in pulsatile flow through converging junctions and the pressure distribution in a simple loop

Analytical expressions for the reflection coefficients in pulsatile flow through converging junctions are derived by two independent methods and are used to study the effects of wave reflections on the pressure distribution in a simple vascular loop. A simulated physiological situation is used as an example in which the loop is formed by the combination of a bypass and a bypassed vessel, the relative diameter of the latter being varied in order to simulate a narrowing. The results demonstrate how, in the case of a converging junction, the effects of wave reflections on the pressure distribution in one vessel depend on conditions within the vessel itself as well as in the other. The new reflection coefficients take into account this interdependence of flow in the two vessels forming a converging junction, and are shown to be consistent with reflection coefficients commonly used in diverging junctions.     

Ribosome engineering and fermentation optimization leads to overproduction of tiancimycin A,a new enediyne natural product from <Emphasis Type="Italic">Streptomyces</Emphasis> sp. CB03234

Tiancimycin (TNM) A, a recently discovered enediyne natural product from Streptomyces sp. CB03234, showed rapid and complete killing of cancer cells and could be used as a payload in antibody drug conjugates. The low yield of TNM A in the wild-type strain promoted us to use ribosome engineering and fermentation optimization for its yield improvement. The Streptomyces sp. CB03234-R-16 mutant strain with a L422P mutation in RpoB, the RNA polymerase β-subunit, was obtained from the rifamycin-resistant screening. After fermentation optimization, the titers of TNM A in Streptomyces sp. CB03234-R-16 reached to 22.5 ± 3.1 mg L^?1 in shaking flasks, and 13 ± 1 mg L^?1 in 15 L fermentors, which were at least 40-fold higher than that in the wild-type strain (~ 0.3 mg L^?1). Quantitative real-time RT-PCR revealed markedly enhanced expression of key genes encoding TNM A biosynthetic enzymes and regulators in Streptomyces sp. CB03234-R-16. Our study should greatly facilitate the future efforts to develop TNM A into a clinical anticancer drug.     

Conversion of a rice CMS maintainer into a photo- or thermo-sensitive genetic male sterile line

A maintainer line of 3-line hybrid rice commonly presents a certain genetic distance to a 2-line restorer line, but in many cases, 2-line restorer lines present defects upon recovery of the object cytoplasmic male sterile (CMS) line of the maintainer line, which impedes the utilization of their heterosis. Here, we report a strategy and an example of converting a maintainer into a photoperiod/temperature-sensitive genic male sterile (P/TGMS) line with an almost identical genetic background, thus maximizing the heterosis. Firstly, through treatment of maintainer line T98B with ⁶⁰C_O-γ irradiation, we identified the TGMS line T98S, which is sterile at higher temperatures and fertile at lower temperatures. Secondly, the T98S line was proven to be identical to T98B with regard to genetic background via an examination of 48 parental polymorphous SSR markers and exhibited excellent blossom traits similar to those of T98B, with an extensive forenoon flowering rate of 75.92% and a high exertion rate of 64.59%. Thirdly, in a combination test, three out of six hybrids from T98S crossed with 2-line restorer lines showed a yield increase of 6.70–15.69% for 2 consecutive years. These results demonstrated that the strategy can generate a new P/TGMS line with strong general combining ability (converted from a maintainer line), thus helping to increase the genetic diversity of male sterile heterotic groups.     

Optical and Thermal Enhancement of Plasmonic Nanofluid Based on Core/Shell Nanoparticles

The plasmonic effect is introduced in solar thermal areas to enhance light harvest and absorption. The optical properties of plasmonic nanofluid are simulated by finite difference time domain (FDTD) method. Due to the excitation of localized surface plasmon resonance (LSPR) effect, an intensive absorption peak is observed at 0.5 μm. The absorption characteristics are sensitive to particle size and concentration. As the particle size increases, the absorption peak is broadened and shifted to longer wavelength. The absorption of SiO₂/Ag plasmonic nanofluid is improved gradually as the volume concentration increases, especially in the UV region. The absorption edge is shifted from 0.6 to 1.0 μm as the volume concentration increases from 0.001 to 0.01. The thermal simulation of suspended SiO₂/Ag nanoparticle shows a uniform temperature rise of 17.91 K under solar irradiation (AM 1.5), while under the same condition, the temperature rises in Ag nanoparticle and Al nanoparticle are 11.12 and 5.39 K, respectively. The core/shell plasmonic nanofluid exhibits a higher photothermal performance, which has a potential application in photothermal areas. A higher temperature rise can be obtained by improving the incident light intensity or optical absorption properties of nanoparticles.     

Strong Coupling in the Structure of Single Metallic Nanoparticle Partially Buried in Molecular J-Aggregates

We investigate the strong coupling phenomenon in the structure of metallic nanoparticle partially buried in molecular J-aggregates. The wave vector and the polarization of incident light impact on the strong coupling phenomenon. With the wave vector and the polarization of incident light in the plane of the interface between the air and molecular J-aggregates, the detuning energies δ reach to the largest. Incident light being injected normally from the air to molecular J-aggregates or from molecular J-aggregates to the air does not influence on δ, but influences on the intensities of the scattering spectra. Our structure has a great help in fabricating the structure which is used to generate the strong coupling phenomenon and also has potential applications in quantum networks, single-atom lasers, quantum information processing, and so on.