太空诱变玉米核不育材料花粉败育的细胞学观察(简报)

玉米是最早利用雄性不育系生产杂交种的作物之一。在玉米T型细胞质雄性不育杂交种遭受毁灭性病害侵袭之后,科学家认识到利用细胞质雄性不育制种存在潜在的遗传脆弱性,从此试图通过多种途径来创造新的雄性不育．并对雄性不育材料的遗传多样性进行研究。空间诱变育种是80年代于我国发展起来的新技术,在农作物品种改良和种质创新上已初见成效。[第一段]     

Pollen-Ovule Ratio and Gamete Investment in Pedicularis （Orobanchaceae）

The Pedicularis species provides ideal materials to study floral evolution because of their substantial flower variation based on a narrow genetic basis, even though they are almost exclusively pollinated by bumblebee. These traits allow us to detect the evolutionary trends of floral parameters without considering genetic background and the difference of pollination vectors. The pollen-ovule ratio is widely used to estimate the pattern of resource investment in two sexual functions in flowering plants. Forty species representing all of the corolla types in Pedicularls were used to study pollen-ovule ratio, gamete investment, and their correlations. Results show that pollen-ovule ratio does not differ among both different corolla types and taxonomic groups. It is therefore suggested that pollen-ovule ratio should be a parallel evolution. The correlations between pollen-ovule ratio and pollen size （-）, and ovule size （＋） can be successfully explained in terms of sex allocation theory. The biological significance of such relationships was also discussed. Additionally, we analyzed the pattern of resource investment into female gamete, which has been somewhat neglected, and found that plants have different patterns of gamete investment between the two sexual functions.     

Effects of Acetylcholine, Cytochalasin B and Amiprophosmethyl on Phloem Transport in Radish （Raphanus sativas）

We investigated the role of the ＂sieve tube-companion cell complex＂ lining the tube periphery, particularly the microfilament and microtubule, in assisting the pushing of phloem sap flow. We made a simple phloem transport system with a living radish plant, in which the conducting channel was exposed for local treatment with chemicals that are effective in modulating protoplasmic movement （acetylcholine, （ACh） a neurotransmitter in animals and insects; cytochalasin B, （CB） a specific inhibitor of many cellular responses that are mediated by microfilament systems and amiprophos-methyl, （APM） a specific inhibitor of many cellular responses that are mediated by microtubule systems）. Their effects on phloem transport were estimated by two experimental devices： （i） a comparison of changes in the amount of assimilates in terms of carbohydrates and ^14C-labeled photosynthetic production that is left in the leaf blade of treated plants; and （ii） distribution patterns of ^14C-labeled leaf assimilates in the phloem transport system. The results indicate that CB and APM markedly inhibited the transfer of photosynthetic product from leaf to root via the leaf vein, while ACh enhanced the transfer of photosynthetic product in low concentrations （5.0×10^-4 mol/L） but inhibited it in higher concentrations （2.0×10^-3 mol/L） from leaf to root via the leaf vein. Autoradiograph imaging clearly reveals that ACh treatment is more effective than the control, and both CB and APM treatments effectively inhibit the passage of radioactive assimilates. All of the results support the postulation that the peripheral protoplasm in the sieve tube serves not only as a passive semi-permeable membrane, but is also directly involved in phloem transport.     

Changes of Photosystem Ⅱ Electron Transport in the ChlorophyⅡ-deficient Oilseed Rape Mutant Studied by ChlorophyⅡ Fluorescence and Thermoluminescence

The photosystem Ⅱ （PSII） complex of photosynthetic membranes comprises a number of chlorophyll-binding proteins that are important to the electron flow. Here we report that the chlorophyll b-deficient mutant has decreased the amount of light-harvesting complexes with an increased amount of some core polypeptldes of PSII, including CP43 and CP47. By means of chlorophyll fluorescence and thermolumlnescence, we found that the ratio of Fv/Fm, qP and electron transport rate in the chlorophyll b-deficient mutant was higher compared to the wild type. In the chlorophyll lPdeflclent mutant, the decay of the primary electron acceptor quinones （QA-） reoxidation was decreased, measured by the fluorescence. Furthermore, the thermoluminescence studies in the chlorophyll bdeficient mutant showed that the B band （S2/S3QB-） decreased slightly and shifted up towards higher temperatures. In the presence of dlchlorophenyl-dlmethylurea, which is inhibited in the electron flow to the second electron acceptor quinines （QB） at the PSll acceptor side, the maximum of the Q band （S2QA-） was decreased slightly and shifted down to lower temperatures, compared to the wild type. Thus, the electron flow within PSll of the chlorophyⅡ b-deficient mutant was down-regulated and characterized by faster oxidation of the primary electron acceptor quinine QA-via forward electron flow and slower reduction of the oxidation S states.     

Synthesis, characterization, and biodegradation of novel poly(ether ester amide)s based on L-phenylalanine and oligoethylene glycol

A new family of novel biodegradable poly(ether ester amide)s (PEEAs) consisting of three building blocks (L-phenylalanine, oligoethylene glycol, and aliphatic acid dichloride) were synthesized by solution polycondensation. Using N,N-dimethylacetamide as the solvent, these PEEA polymers were obtained with fairly good yields with reduced viscosity (eta(red)) ranging from 0.13 to 0.61 dL/g. The chemical structures of the PEEAs were confirmed by IR, NMR spectra, and elemental analysis. The PEEAs had Tg values lower than that of the saturated poly(ester amide)s (PEAs) of similar structures due to the incorporation of ether bonds in the backbones. An increase in the number of ether bonds in PEEA resulted in a lower Tg value. The solubility of the PEEA polymers in a wide range of common organic solvents was significantly improved when compared with unsaturated PEAs. The preliminary in vitro biodegradation behaviors of PEEA polymers were investigated in both pure PBS buffer and alpha-chymotrypsin solution of different concentrations. The polymers showed a significantly faster weight loss in an enzyme solution (alpha-chymotrypsin) but a very slow biodegradation rate in pure PBS buffer. The enzymatic hydrolysis rates of PEEAs (in terms of weight loss) were found to be much faster than those of saturated and unsaturated polyesteramides reported in previous studies. The zero-order-like biodegradation kinetics and molecular weight data also suggested surface erosion biodegradation mechanisms for these PEEAs.     

Establishment of the active catalytic domain of human PDGFRbeta tyrosine kinase-based ELISA assay for inhibitor screening

Tyrosine kinases are emerging as frequent targets of primary oncogenic events and therefore represent an optimal focus of therapeutic intervention. In an effort towards therapeutic PDGFR inactivation, we expressed the catalytic domain of PDGFRbeta as a soluble active kinase using Bac-to-Bac expression system, and studied the correlations between PDGFRbeta activity and enzyme concentration, ATP concentration, substrate concentration and divalent cation type. And a convenient, effective and non-radioactive ELISA screening model is then established for identification of the potential inhibitors targeting PDGFRbeta kinase. Of 500 RTK target-based compounds, TKI-30 was identified as a small molecule potential inhibitor of PDGFRbeta (IC(50)=0.34 microM). Further studies indicated that TKI-30 blocked PDGF-BB-induced autophosphorylation of PDGFRbeta in a dose-dependent manner in Swiss 3T3 cells and human umbilical vein smooth muscle cells (HUVSMCs). Moreover, it dose-dependently suppressed the PDGF-BB-induced proliferation in HUVSMCs and tube formation of HUVEC. Our data collectively indicated that PDGFRbeta-based ELISA assay is a new method available for screening inhibitors targeting PDGFRbeta kinase and TKI-30 is a potential novel anti-cancer agent worthy of being further investigated.     

Functional and crystal structure analysis of active site adaptations of a potent anti-angiogenic human tRNA synthetase

Higher eukaryote tRNA synthetases have expanded functions that come from enlarged, more differentiated structures that were adapted to fit aminoacylation function. How those adaptations affect catalytic mechanisms is not known. Presented here is the structure of a catalytically active natural splice variant of human tryptophanyl-tRNA synthetase (TrpRS) that is a potent angiostatic factor. This and related structures suggest that a eukaryote-specific N-terminal extension of the core enzyme changed substrate recognition by forming an active site cap. At the junction of the extension and core catalytic unit, an arginine is recruited to replace a missing landmark lysine almost 200 residues away. Mutagenesis, rapid kinetic, and substrate binding studies support the functional significance of the cap and arginine recruitment. Thus, the enzyme function of human TrpRS has switched more to the N terminus of the sequence. This switch has the effect of creating selective pressure to retain the N-terminal extension for functional expansion.     

Brief small intestinal ischemia lessens renal ischemia-reperfusion injury in rats

Ischemic preconditioning (IPC) not only reduces local tissue injury caused by subsequent ischemia-reperfusion (IR) but may also have a beneficial effect on IR injury of tissues remote from those undergoing preconditioning. In this study, we investigated the effect of small intestinal IPC on renal IR injury in rats. Renal IR injury was induced by a 45-min renal artery occlusion and reperfusion for 2 or 24 h in rats with a previous contralateral nephrectomy, and ischemic preconditioning was induced by 3 cycles of 8-min ischemia and 5-min reperfusion of the small intestine. We then measured the concentrations of plasma creatinine (Cr) and blood urine nitrogen (BUN) and the level of malondialdehyde (MDA) and activities of superoxide dismutase (SOD) and catalase (CAT) in the renal cortex. Renal histopathology also was evaluated. Pretreatment with intestinal ischemic preconditioning significantly alleviated renal IR injury, as shown by decreases in the levels of Cr, BUN, and MDA, decreased renal morphologic change, and improved preservation of SOD and CAT activities. These results suggest that remote ischemic preconditioning of the small intestine protects against renal IR injury by inhibition of lipid peroxidation and preservation of antioxidant enzyme activities.     

Effects of caveolin-1 on the 17beta-estradiol-mediated inhibition of VSMC proliferation induced by vascular injury

Estrogen has a protective effect on the cardiovascular system. Yet the mechanism of how estrogen inhibits vascular smooth muscle cell (VSMC) proliferation after vascular injury and the role of caveolin-1 in this process are not clear. To understand the protection effect of estrogen and caveolin-1, we employed a vascular balloon-injury model. Sixteen New Zealand White rabbits with or without estrogen were tested. 17beta-estradiol is able to inhibit VSMC proliferation in a range from 10(-10)-10(-5) mol/L, with an optimal concentration of 10(-8) mol/L. Estrogen exerted its effect through suppressing the activity of p42/44 MAPK, which can be blocked by tamoxifen. Moreover, in estrogen pretreated cells as well as in common carotid arteries of the balloon injury model, expression of caveolin-1 is enhanced compared to the estrogen-deficient group, as assessed by both western blotting and RT-PCR and morphological studies. Our results showed that the inhibition effect of estrogen in VSMCs is mediated by p42/44 MAPK. Caveolin-1 plays an important role in this protective process.     

ompC突变造成大肠杆菌在碱性条件下对渗透压敏感

大肠杆菌DH42突变株碱性条件下对高渗透压敏感。采用mini-Tn5转座突变质粒,同源重组构建突变菌株和DNA片段亚克隆等技术确定了造成大肠杆菌DH42在碱性条件下,对高渗透压敏感的原因是ompC基因突变。通过P1转导,构建了大肠杆菌D9（W3110 ompC：：kan）菌株。比较D9菌株和DH42菌株在不同pH和不同盐浓度条件下的生长,发现大肠杆菌ompC基因是大肠杆菌在碱性条件下应对高渗透压环境胁迫的必须基因。