An interspecific somatic hybrid between Actinidia chinensis and Actinidia kolomikta and its chilling tolerance

Protoplasts isolated from cotyledon-derived callus of Actinidia chinensisPlanch. var. chinensis (2N=2x=58) were fused with mesophyll protoplasts of Actiniadia kolomikta(Maxim. et Rupr.) Maxim (2N=2x=58) using a PEG method. Plantlets were regenerated from the fusion product clone 11. RAPD analyses, chromosome numbers of root tip cells and fluorescence peak position of leaf nuclei confirmed that clone 11 was an interspecific somatic hybrid (2N=4x=116) between A. chinensis and A. kolomikta. The chilling tolerance of the somatic hybrid was tested with in vitro leaves at low temperatures. Based on data of leaf thickness, electroconductivity, proline levels, malondialdehyde content and activity of superoxide dismutase, dendrogram cluster analysis suggested that the interspecific somatic hybrid was similar to A. kolomikta, and might have a higher capacity of cold resistance than A. chinensis.     

固定化酶的微环境效应—载体离子基团性质的影响

作者合成了阴离子型和阳离子型葡聚糖,以此为载体,用CNBr活化其剩余羟基,固定化了葡萄糖淀粉酶和葡萄糖异构酶。就离子型载体对固定化酶的蛋白载量、最适pH和热稳定性等的影响做了考察。发现固定化酶的蛋白载量不仅与载体的电性质有关,也与酶分子自身的电性质有关。当载体电性质与酶蛋白电性质相反时,固定化酶的蛋白载量增加,热稳定性提高、载体电性质与酶蛋白电性质相同时,固定化酶的蛋白载量不变或下降,其热稳定性不变。作者还发现当离子型载体孔度和体系缓冲液浓度一定时,酶分子能否进入多孔性载体内部,对其最适pH是否变化影响极大。若酶分子仅被连接在载体的外表层,其最适pH不发生变化,反之亦然。作者还观察到当多糖类载体引入氨基或羧基后,大大增强了其抵抗微生物侵蚀的能力。     

Stereospecificity for nicotinamide nucleotides in enzymatic and chemical hydride transfer reactions

The pyridine nucleotide (NAD and NADP)-linked enzymes are a large class of enzymes constituting approximately 17% of all classified enzymes. When these enzymes catalyze their reactions, the hydride transfer between the substrate and the reaction site (i.e., C-4 of the nicotinamide/dihydronicotinamide ring) of the coenzyme takes place in a stereospecific manner. Thus, in the reaction of oxidation of the reduced coenzyme, one group of enzymes catalyzes the extraction of only the hydrogen having the R configuration at the No. 4 carbon, while the other group catalyzes the removal of only that with the S configuration. Because this aspect of enzyme stereospecificity provides essential information for a given enzyme's reaction mechanism, active site structure, and evolutionary relationship with other enzymes, intensive effort has been made to establish the stereospecificities of as many enzymes as possible. This review presents the compilation of the stereospecificities of these enzymes. Some empirical rules, which are useful but not definitive, in predicting a given enzyme's stereospecificity are also described. In addition, the stereospecificity in enzymatic reactions is compared to the stereo-preference in chemical oxidoreduction of the coenzyme. In order to elucidate the mechanism for the enzyme stereospecificity, the conformations of the coenzyme in free-state and enzyme-bound state are extensively discussed here.     

Stimulation of arachidonic acid metabolism: differences in potencies of recombinant human interleukin-1 alpha and interleukin-1 beta on two cell types

Recombinant human interleukin-l (rIL-1) alpha and beta, which have 26% homology in their amino acid sequence, stimulated arachidonic acid metabolism by squirrel monkey smooth muscle cells and rat liver cells; their relative effectiveness, however, varied with the two cells. Recombinant IL-1 alpha was 3 times more effective than rIL-1 beta at stimulating arachidonic acid metabolism by the primate smooth muscle cells. Recombinant IL-1 alpha was 3 times less effective than rIL-1 beta when measured by their capacity to synergistically stimulate arachidonic acid metabolism of rat liver cells in the presence of palytoxin and anti-diuretic hormone (ADH). The rIL-1 alpha and rIL-1 beta also stimulated the release of radiolabelled arachidonic acid from the smooth muscle cells prelabelled with [3H]arachidonic acid. The two recombinant IL-1s have different heat stabilities, again when measured by their capacity to stimulate arachidonic acid metabolism; IL-1 alpha was more heat stable than IL-1 beta.     

Elongation factor 1α genes of the red alga Porphyra purpurea include a novel, developmentally specialized variant

The life cycle of the red alga Porphyra purpurea alternates between two morphologically distinct phases: a shell-boring, filamentous sporophyte and a free-living, foliose gametophyte. From a subtracted cDNA library enriched for sporophyte-specific sequences, we isolated a cDNA encoding an unusual elongation factor 1 (EF-1) that is expressed only in the sporophyte. A second EF-1 gene that is expressed equally in the sporophyte and the gametophyte was isolated from a genomic library. These are the only EF-1 genes detectable in P. purpurea. The constitutively expressed gene encodes and EF-1 very similar to those of most eukaryotes. However, the sporophyte-specific EF-1 is one of the most divergent yet described, with nine insertions or deletions ranging in size from 1 to 26 amino acids. This is the first report of a developmental stage-specific EF-1 outside of the animal kingdom and suggests a fundamental role for EF-1 in the developmental process.     

汉防己甲素及克矽平对矽肺大鼠Ⅰ型和Ⅲ型胶原mRNA的影响

汉防己甲素（汉甲）及克矽平（Ｐｏｌｙｖｉｎｙｌｐｙｒｉｄｉｎｅ－Ｎ－Ｏｘｉｄｅ,ＰＶＮＯ）是目前较为有效的抑制矽肺纤维化的药物。本文研究了其对胶原ｍＲＮＡ水平的影响．斑点杂交实验表明大鼠接尘６０天和１２０天后α１（Ⅰ）及α１（Ⅲ）ｍＲＮＡ水平明显上升,经汉甲或克矽平治疗１个月或３个月后,胶原ｍＲＮＡ水平明显下降。原位杂交结果表明胶原ｍＲ－ＮＡ银颗粒与细胞性结节和增厚的肺泡壁的成纤维细胞分布重合。汉甲或克矽平治疗后银颗粒数下降。提示汉甲及克矽平对矽肺进程中的胶原基因表达增强有抑制作用。