渗透胁迫下稻苗中铁催化的膜脂过氧化作用

在－０．７ＭＰａ渗透胁迫下,水稻幼苗体内和Ｈ２Ｏ２大量产生,Ｆｅ２＋积累,膜脂过氧化作用加剧。水稻幼苗体内Ｆｅ２＋含量与膜脂过氧化产物ＭＤＡ含量呈极显著的正相关。外源Ｆｅ２＋、Ｆｅ３＋、Ｈ２Ｏ２、Ｆｅ２＋＋Ｈ２Ｏ２、ＤＤＴＣ均能刺激膜脂过氧化作用,而铁离子的螯合剂ＤＴＰＡ则有缓解作用。ＯＨ的清除剂苯甲酸钠和甘露醇能明显地抑制渗透胁迫下Ｆｅ２＋催化的膜脂过氧化作用。这都表明渗透胁迫下水稻幼苗体内铁诱导的膜脂过氧化作用主要是由于其催化Ｆｅｎｔｏｎ型Ｈａｂｅｒ－Ｗｅｉｓｓ反应形成ＯＨ所致。     

Screening and production of erythritol by newly isolated osmophilic yeast-like fungi

Twenty-eight erythritol-producing strains were isolated from pollen, honey and high sugar food samples collected in Taiwan. Amongst these, six strains (166-2, 262-1, 278-3, 440, 441 and 442) were high erythritol-producers with a yield higher than 30% for 30% glucose. The erythritol productivity of these strains ranged from 90.9 to 116.4 g l⁻¹. ¹H- and ¹³C-NMR analyses confirmed that the fermentation product was erythritol. The results of morphological and physiological studies indicate that strains 166-2, 262-1, 278-3, 440, and 442 may be members of the genus Moniliella. More studies are required to determine the taxonomic position of strain 441. The use of a medium containing 30% glucose and 1% yeast extract gave the highest erythritol productivity. On batch fermentation in a 5-l fermentor using strain 166-2, a maximal erythritol productivity of 111.0 g l⁻¹ was obtained after cultivation for 144 h.     

高动态光学血管造影成像

我们提出一种高动态光学血管造影成像(HDOA)方法来实现活体生物样本血管造影成像.该方法通过设置高动态范围曝光时间,依据动态积分效应和吸收效应以实现高动态积分时间调制.通过该方法,不仅能够同时获得各级血管清晰的造影图像,还能消除样品厚度不均、吸收系数不同对成像造成的影响.论文以仿体和活体金鱼为样品,通过实验验证了HDOA方法根据动态积分调制效应和吸收效应,能有效实现各级血管同时成像.     

葛藤节肢动物类群结构动态

本文利用群落结构的有关指数(物种数S、丰富度指数R、多样性指数H、H'、D和DMc、均匀性指数J'、优势度指数d和优势集中性指数C)分析了葛藤节肢动物类群结构变化动态.结果表明,葛藤节肢动物类群丰富度和多样性一年中出现两个高峰,一个在五月下旬,一个在十一月上中旬,在第一个峰期,S,R,D,H',H和DMc的值依次为38.00,6.0205,0.9056,4.0205,3.8560和0.7207,在第二个峰期,上述指数依次为34.00,6.6661,0.9245,4.2124,3.6779和0.7808;均匀性在一至四月变化较剧烈,最大值0.8899出现在1月中旬,最小值0.5765出现在二月下旬,其它时间较为平稳;优势集中性和优势度指数的变化趋势一致,其高峰值出现在二月下旬至三月上旬.分析表明,多样性和优势集中性变化趋势往往相反,即物种越丰富,多样性越大,相应的优势集中性就越小,反之就大;均匀性与多样性关系密切,即群落多样性较高时均匀度变化较为平稳,反之,就剧烈.     

Pleiotropic mutants of NIH 3T3 cells with altered regulation in the expression of both type I collagen and fibronectin

Transformation of NIH 3T3 fibroblasts by v-mos causes a decrease in the levels of type I collagen RNA. In NIH 3T3 cells that have been made resistant to G418 by transfection with a plasmid in which the mouse alpha 2(I) collagen promoter is linked to the neo gene, subsequent v-mos transformation causes a loss of G418 resistance. After mutagenesis of these v-mos-transformed cells, G418-resistant colonies were selected. Two of these G418-resistant mutants showed an increased expression of the neo gene and of the endogenous type I collagen and fibronectin genes, without changes in their levels of v-mos RNA or in their ability to induce tumors. The mutations might alter cellular trans-acting factors that either directly or indirectly control the expression of the type I collagen and fibronectin genes in transformed cells.     

Malignant transformation and tumor promoter treatment increase levels of a transcript for a secreted glycoprotein.

The major excreted protein of transformed mouse fibroblasts, a secreted, mannose 6-phosphate-containing glycoprotein, is induced in nontransformed cells by a variety of transforming agents, by phorbol esters, and by platelet-derived growth factor. We report here the molecular cloning of the cDNA encoding this protein and demonstrate that its induction is a consequence of enhanced mRNA levels for major excreted protein in both tetradecanoyl phorbol acetate-treated 3T3 cells and 3T3 cells transformed by a variety of retroviruses or retroviral oncogenes. These results indicate that tumor promoters and retroviral transformation might share a common pathway of action in cultured cells and that major excreted protein is a molecular marker for the growth response of cells to these agents.     

Diverse roles of SERK family genes in plant growth,development and defense response

Plant receptor-like protein kinases (RLKs) are transmembrane proteins with an extracellular domain and an intracellular kinase domain, which enable plant perceiving diverse extracellular stimuli to trigger the intracellular signal transduction. The somatic embryogenesis receptor kinases (SERKs) code the leucine-rich-repeat receptor-like kinase (LRR-RLK), and have been demonstrated to associate with multiple ligand-binding receptors to regulate plant growth, root development, male fertility, stomatal development and movement, and immune responses. Here, we focus on the progress made in recent years in understanding the versatile functions of Arabidopsis SERK proteins, and review SERK proteins as co-receptor to perceive different endogenous and environmental cues in different signaling pathway, and discuss how the kinase activity of SERKs is regulated by various modification.     

In vitro acylation of rat gastric mucus glycoprotein with [3H]palmitic acid

The incorporation of fatty acids into gastric mucus glycoproteins was studied by incubating rat gastric mucosal cell suspensions with [9,10-3H]palmitic acid and [3H]proline. The mucus glycoprotein polymer, secreted into the growth medium (extracellular) and that contained within the cells (intracellular), was purified from the other components of the secretion, thoroughly delipidated, and then analyzed for the radiolabeled tracers. Both pools of mucus glycoprotein, incubated in the presence of [3H]palmitic acid, contained radioactive label which could not be removed by gel filtration, CsCl density gradient centrifugation, sodium dodecyl sulfate-gel electrophoresis, or lipid extraction. Treatment of the purified mucus glycoprotein with 1 M hydroxylamine or 0.3 M methanolic KOH released the radioactivity, thus indicating that [3H]palmitic acid was covalently bound by ester linkage to the glycoprotein. The released radioactivity was associated mainly (87%) with palmitic acid. The incorporation ratio of [3H]proline to [3H]palmitic acid was 0.12:1.0 in the extracellular glycoprotein and 1.38:1.0 in the intracellular glycoprotein, which suggested that acylation of mucus glycoprotein occurs in the intracellular compartment after completion of its polypeptide core. The fact that incorporation of [3H]palmitic acid was greater in the glycoprotein subunits than in the glycoprotein polymer indicates that acylation takes place near the end of subunit processing but before their assembly into the high molecular weight mucus glycoprotein polymer.     

Enzymatic sulfation of mucus glycoprotein in gastric mucosa. Effect of ethanol

A sulfotransferase activity that catalyzes the transfer of sulfate ester group from 3'-phosphoadenosine 5'-phosphosulfate to carbohydrate chains of gastric mucus glycoprotein has been demonstrated in the antral and body mucosa of rat stomach. Subcellular fractionation studies revealed that the enzyme is associated with Golgi-rich membrane fraction. The sulfotransferase activity of this fraction in antral mucosa was about 35% lower than that in the body. Optimum enzyme activity was obtained with 0.5% Triton X-100 and 30 mM NaF at a pH of 6.8 using desulfated mucus glycoprotein substrate. The enzyme was equally capable of sulfation of the proteolytically degraded and reduced forms of the desulfated glycoprotein, but the acceptor capacity of the intact mucus glycoprotein was about 60% lower than that of the desulfated preparation. The enzyme preparation also catalyzed the transfer of sulfate to galactosylceramide. The sulfation of mucus glycoprotein, however, was not affected by the presence of this glycolipid, suggesting that the sulfotransferase involved in mucus glycoprotein sulfation is different from that responsible for the synthesis of sulfatoglycosphingolipid. The mucus glycoprotein sulfotransferase activity was inhibited by ethanol. The rate of inhibition was proportional to the concentration of ethanol up to 0.3 M and was of the competitive type. The apparent Km value of the enzyme for mucus glycoprotein was 10.5 X 10(-6) M (21 mg/ml), and the KI in the presence of ethanol was 4.7 x 10(-1) M. The 35S-labeled mucus glycoprotein product of the enzyme reaction gave in CsCl density gradient a band in which the 35S label coincided with the glycoprotein. Alkaline borohydride reductive cleavage of this glycoprotein led to the liberation of the label into reduced acidic oligo-saccharide fraction. Most of the label was found incorporated in three oligosaccharides. These were identified as tri-, tetra-, and pentasaccharides, each carrying a labeled sulfate ester group on the terminal N-acetyl-glucosamine residue. Based on the results of structural analyses, the most abundant oligosaccharide was characterized as SO3H----6GlcNAc beta 1----3Gal beta 1----3GalNAc-ol.     

Angiogenesis in Differentiated Placental Multipotent Mesenchymal Stromal Cells Is Dependent on Integrin α5β1

Human placental multipotent mesenchymal stromal cells (hPMSCs) can be isolated from term placenta, but their angiogenic ability and the regulatory pathways involved are not known. hPMSCs were shown to express integrins α_v, α₄, α₅, β₁, β₃, and β₅ and could be induced to differentiate into cells expressing endothelial markers. Increases in cell surface integrins α₅ and β₁, but not α₄, α_vβ₃, or α_vβ₅, accompanied endothelial differentiation. Vascular endothelial growth factor-A augmented the effect of fibronectin in enhancing adhesion and migration of differentiated hPMSC through integrin α₅β₁, but not α_vβ₃ or α_vβ₅. Formation of capillary-like structures in vitro from differentiated cells was inhibited by pre-treatment with function-blocking antibodies to integrins α₅ and β₁. When hPMSCs were seeded onto chick chorioallantoic membranes (CAM), human von Willebrand factor-positive cells were observed to engraft in the chick endothelium. CAMs transplanted with differentiated hPMSCs had a greater number of vessels containing human cells and more incorporated cells per vessel compared to CAMs transplanted with undifferentiated hPMSCs, and overall angiogenesis was enhanced more by the differentiated cells. Function-blocking antibodies to integrins α₅ and β₁ inhibited angiogenesis in the CAM assay. These results suggest that differentiated hPMSCs may contribute to blood vessel formation, and this activity depends on integrin α₅β₁.