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971.
972.
Hwa-Ja Ryu Doman Kim Do-Won Kim You-Youn Moon John F. Robyt 《Biotechnology letters》2000,22(5):421-425
Dextransucrase (FMCMDS) from Leuconostoc mesenteroides B-512FMCM, a dextransucrase constitutive and hyper-producing strain, catalyzes the synthesis of dextran from sucrose. The coding region for fmcmds was isolated and sequenced. It consisted of an open reading frame (ORF) of 4699 bp, coding for a 1527 amino acid protein with a molecular mass of 170 kDa. However, it showed a dextransucrase activity band at 180 kDa in SDS-PAGE. Only one nucleotide changed in the promoter site and two amino acid residues were changed in the structural gene from that of the parent L. mesenteroides NRRL B-512F dsrS; an inducible dextransucrase gene of low productivity. 相似文献
973.
Anuran (Rana) and urodele (Ambystoma) amphibian eggs were subjected to prolonged unnatural orientations in relation to gravity. In some cases eggs were rotated 90°, while in other instances eggs were rotated 180° (complete inversion). Alterations in the pigmentation pattern, cleavage pattern, and site of involution were observed. Despite these unnatural orientations to gravity, the morphogenesis of axial structures was frequently normal. Reorganization of the egg cytoplasm apparently takes place after the unnatural orientation. Rather than being localized in a fixed position in the egg (e.g., the egg cortex), the determinants for the pattern of early embryogenesis are probably located in that portion of the cytoplasm (e.g., “internal” cytoplasm) that orients to gravity. 相似文献
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975.
976.
Lateral root development in onion is accompanied by a variety of anatomical and permeability changes in some cells of the adventitious root. The endodermal Casparian band of the parent root is disrupted early in the development of the lateral but later extends so as to be continuous with the developing Casparian band of the new root. The lateral root emerges through a longitudinal split in the adventitious root exodermis and epidermis. Following this, the cell walls and intercellular air spaces adjacent to the lateral become incrusted with suberin and a small amount of lignin, forming a collar of modified tissue around the lateral. Subsequent radial expansion of the lateral distorts the adjacent cells of the adventitious root and forces a tight association between it and the lateral. The apoplastic permeability of lateral/parent root junctions was tested using Cellufluor, an apoplastic fluorescent dye which binds to cellulose. Prior to lateral root emergence, no dye enters the parent root cortex due to the Casparian band of the exodermis. Immediately after emergence, dye often penetrates through the break in the exodermal Casparian band and diffuses into the first cortical cell layer. However, when the collar of suberized cells develops (two days after lateral root emergence), movement of the dye into an undisturbed adventitious root is usually prevented (i.e., in 77% of the cases examined). In contrast, only 17% of the root systems which were transplanted just prior to treatment excluded the dye. This indicates that the apoplastic seals around the laterals are sensitive to movement and we recommend that only undisturbed root systems be used for permeability studies. 相似文献
977.
978.
Prostaglandin F (PGF) levels in endometriotic tissue in vitro have been shown to be higher than the levels in healthy ovarian tissue and uterine endometrium. The results of a study of nine women with endometriosis support this finding and suggest that prostaglandins have an important role in the pathogenesis of the symptoms and infertility in such women. 相似文献
979.
980.
Isolation and characterization of cDNA clones for chicken major histocompatibility complex class II molecules 总被引:2,自引:0,他引:2
The chicken major histocompatibility complex (MHC), the B complex, is being intensively analysed at the DNA level. To further probe the molecular structure of chicken MHC class II genes, cDNA clones coding for chicken MHC class II (B-L) p chain molecules were isolated from an inbred G-B2 Leghorn chicken spleen and liver. Twenty-nine cDNA clones were isolated from the spleen and eight cDNA clones were isolated from the liver. Based on restriction maps, most clones could be clustered into one family of genes. Four cDNA clones were sequenced (S7, S10 and S19 from the spleen and L1, which was identical to S19, from the liver). Complete amino acid sequences of B-Lβ chain molecules were predicted from the nucleotide sequences of the cDNA clones. Although both the nature and the location of the conserved residues were similar in chicken and mammalian sequences, some species-specific differences were found, suggesting that the structures of the B-L molecules of this haplotype are similar, but not identical, to their mammalian counterparts. 相似文献