谷子和狗尾草核型分析

作者研究了我国谷子(Setaria italica Beauv.)和狗尾草的核型与Giemsa带,两者核型基本相同,均为2n=18=14m+2sm+2st(SAT)。带型亦相近,另外在谷子和狗尾草中都发现有四倍体。     

新疆绿蟾蜍的染色体组型初步研究

近年来,有关两栖类的染色体组型已有不少报道。无尾两栖类中蜍蟾属(Bufo)的染色体数目分为两类:2n=22和2n=20(Blain,1972)。我们对采自新疆4个地区的绿蟾蜍进行了染色体组型分析,发现其二倍体细胞染色体数均为44,是四倍体。现将我们的初步研究报道如下。     

Cardenolides from Asclepias asperula subsp. Capricornu and A. Viridis

6′-O-(E-4-hydroxycinnamoyl) Desglucouzarin, the first cardenolide containing a cinnamoyl ester moiety, has been isolated from the ethanolic extract of the milkweed, Asclepias asperula. In addition, five known cardenolides were isolated and identified from A. asperula and A. viridis.     

Model studies of low-temperature optical transitions of photosynthetic reaction centers A-, LD-, CD-, ADMR- and LD-ADMR-spectra for Rhodopseudomonas viridis

The optical spectra of the reaction center (RC) of Rhodopseudomonas viridis including absorption (A), linear dichrosism (LD), circular dichroism (CD), absorption-detected magnetic resonance (ADMR) and its linear dichroism (LD-ADMR) are simulated by an exciton model. It involves the Q_y transitions of six prosthetic groups: four (bacteriochlorophyll-b molecules, two bacteriopheophytin-b molecules and the Soret bands B_y of the special-pair pigments, which couple most strongly with the corresponding Q_y transitions. For the ADMR-spectra additional excitations of the special-pair triplet are introduced. While interactions between the Q_y transitions and the B_y transitions are in principle determined from the structural arrangement of the pigments, the interactions to the other states are adjusted to fit the spectral features for the various transitions. The interaction of the newly introduced states are interpreted in terms of a simple model.     

Intertidal distribution of infauna in a central California lagoon: the role of seasonal blooms of macroalgae

This study examined the roles of seasonal blooms of green algae, Ulva expansa (Setchell) Setchell et Gardner, and biotic disturbance by burrowing ghost shrimp, Callianassa gigas Dana, and foraging rays, on the intertidal distributions of a phoronid, Phoronopsis viridis Hilton, and a tellinid bivalve, Macoma nasuta (Conrad). Algal removal experiments in 1984 and 1986 demonstrated that heavy seasonal algal cover in the lower zone significantly reduced the abundances of both Phoronopsis and Macoma. Growth of Macoma transplanted into the algal zone was significantly lower in plots with algal cover than in plots regularly cleared of algae. Algal cover did not significantly affect early recruitment of either Phoronopsis or Macoma. Neither ghost shrimp nor rays appeared to reduce the abundances of phoronids or clams, although ray disturbance did result in a significant increase in the proportion of phoronids regenerating dorsal body parts. These results indicate that seasonal algal blooms are capable of producing discrete patterns of infaunal distribution in intertidal sedimentary habitats.     

Construction of RFLP-based maps of foxtail millet, Setaria italica (L.) P. Beauv.

 An RFLP-based map consisting of 160 loci was constructed in an intervarietal cross of foxtail millet [Setaria italica (L.) P. Beauv.], Longgu 25×Pagoda Flower Green. The map comprises nine linkage groups, which were aligned with the nine foxtail millet chromosomes using trisomic lines, and spans 964 cM. The intraspecific map was compared to an interspecific map, constructed in a S. italica×S. viridis cross. Both the order of the markers and the genetic distances between the loci were highly conserved. Deviations from the expected 1 : 2 : 1 Mendelian segregation ratios were observed in both the intra- and inter-specific populations. The segregation data indicate that chromosome VIII in the Longgu 25×Pagoda Flower Green cross carries a gene that strongly affects gamete fertility. Received: 18 December 1996 / Accepted: 4 August 1997     

Functional analysis of plasma prophenoloxidase system in the marine mussel Perna viridis

The role of prophenoloxidase (proPO) system in recognition and phagocytosis of yeast cells by hemocytes was examined in vitro using whole plasma and proPO system isolated from the plasma of the marine mussel, Perna viridis. The proPO was isolated from the plasma by ammonium sulphate precipitation and gel filtration. The final proPO preparation was homogeneous in native PAGE, and could be activated by trypsin, α-chymotrypsin and pronase-E. Laminarin (a polymer of β-1, 3-glucan) and lipopolysaccharides (LPS) from diverse bacterial species effectively activated the isolated proPO, demonstrating the ability of this proenzyme to interact directly with microbial surface components. The susceptibility of proPO activation to inhibition by serine protease inhibitors such as soybean trypsin inhibitor (STI) or p-nitrophenyl-p′-guanidinobenzoate (p-NPGB), indicates that the isolated fraction may contain an integral serine protease domain in an inactive state. The presence of laminarin- or LPS-activated whole plasma of P. viridis facilitated adherence of yeast cells to hemocyte surface as well as eventually stimulated phagocytic uptake of the target cells by hemocytes, and no such hemocytic response was recorded with STI controls. This and other results strongly suggest that the intermediary factors generated during activation of plasma proPO system by non-self molecules play a key role in recognition and opsono-phagocytosis by hemocytes. However, the proPO system isolated from P. viridis plasma, after activation with microbial surface components, failed to show an opsonic effect.     

Time-resolved electron transfer at the donor side of Rhodopseudomonas viridis photosynthetic reaction centers in whole cells

We have studied the electron transfer reactions from the tetraheme cytochrome of Rhodopseudomonas viridis to the oxidized primary donor in whole cells with a new high sensitivity spectrophotometer. In this apparatus the monochromatic detecting flashes are provided by a YAG pumped Optical Parametric Oscillator, allowing a 10 ns time resolution. When four hemes are reduced the observed electron transfer reaction sequence is the following: first the low-potential c552 heme (the number refers to the maximum absorption wavelength in the alpha-band region) is oxidized with a half time of 130 ns, in agreement with previous reports of measurements performed with purified reaction centers. Then, the electron hole is transferred to the low potential c554 heme with a half time of 2.6 µs. When only the two high potential hemes are reduced the observed electron transfer sequence is the following: oxidation of the high potential c559 heme in the hundreds of ns time range (410 ns), reduction of this heme by the high potential c556 heme in the µs time range (2.7 µs). This confirms the first steps of electron transfer observed in isolated reaction centers. However, in the microsecond time domain, the overall amount of oxidized hemes increases suggesting that, in vivo, the equilibrium constant between the P⁺/P and the c559^ox/c559^red couples is significantly lower than expected from the difference in their midpoint potentials.     

绿色糖单孢菌木聚糖酶的分离纯化与酶学性质研究

木聚糖酶是一种重要的具有工业应用前景的木聚糖降解酶,在充分利用自然资源、保护生态环境等方面具有十分重要的意义.通过硫酸铵分级沉淀及Sephadex G-100凝胶柱层析方法从一株中度耐热耐碱放线菌—绿色糖单孢菌的胞外酶中纯化得到单一的木聚糖酶,相对分子质量为51 kD,酶纯度提高了13.01倍.纯酶最适反应温度为60℃,最适反应pH值为7.0;75℃以下该酶具有良好的热稳定性,在pH 7～10范围内具有较强的耐受力.金属离子Ca2+、Fe2+、Zn2+对该酶具有明显促进作用,Cu2+、Mn2+、Al3+和SDS具有抑制作用而K+,Na+,Mg2+没有明显的作用.该酶为大分子质量的糖基化蛋白,含糖量为21.96%.