几种真菌诱导子对云南红豆杉细胞产生紫杉醇的影响

自１９９３年以来,紫杉醇（Ｔａｘｏｌ）已成为临床上治疗乳腺癌和卵巢癌的重要药物。由于其药源植物—红豆杉属植物（ＴａｘｕｓＬ．）生长非常缓慢,体内紫杉醇含量很低,且资源有限,所以人们一直在寻找解决紫杉醇药源短缺的方法。用红豆杉属植物组织培养技术生产紫杉醇被认为是一种有潜力的方法之一,受到人们的高度重视。虽然有关这方面的报道较多［１］,但该研究仍处在试验阶段,还未见用此方法商业化生产紫杉醇的报道。其重要原因是目前红豆杉属植物离体细胞的紫杉醇产量还比较低,而且不稳。人们仍在继续寻找提高紫杉醇产量的方法…     

Methyl transfer in chemotaxis toward sugars by Bacillus subtilis.

Like amino acids, the sugars glucose and the nonmetabolizable 2-deoxyglucose caused a turnover of methyl groups on the methyl-accepting chemotaxis proteins. These sugars also caused methanol formation on addition. Thus, in contrast to chemotaxis in Escherichia coli, taxis to phosphotransferase sugars by Bacillus subtilis utilizes the methyl-accepting chemotaxis proteins.     

Early Gravi-Electrical Responses in Bean Epicotyls

The relationship between gravitropism and surface electrical potentials was studied using etiolated epicotyls of adzuki bean (Phaseolus angularis). Early downward curvature (or transient positive gravitropic response) was observed about 1 min after gravistimulation. The downward curvature was closely related to the speed of the subsequent upward curvature. Surface electrical potentials decreased cooperatively in a limited region on the upper side within only 0.5 to 2 min. This is the earliest event found so far to follow gravistimulation of intact epicotyls. The rapid change in the potential had a high correlation with the early downward curvature and also the subsequent negative gravitropism. It is suggested that the rapid potential change plays an important role in gravity perception.     

Protein Kinase Inhibitor H-7 Differentially Affects Early and Delayed Nerve Growth Factor Responses in PC12 Cells

Abstract: The effects of the protein kinase inhibitor H-7 on early and delayed responses to nerve growth factor (NGF) were investigated in PC12 cells. H-7 reduced the NGF-induced expression of c-Fos in a dose-dependent manner without affecting the time course of c-Fos appearance. Conversely, H-7 potentiated delayed NGF effects, i.e., neurite outgrowth and Ca²⁺/phospholipid-dependent protein kinase (PKC) induction, but not choline acetyltransferase induction. Long-term treatment with NGF resulted in an increase of at least four tyrosine-phosphorylated protein bands with molecular masses between 39 and 48 kDa, which was also potentiated by H-7. In the absence of NGF, H-7 had no significant effect on c-Fos expression, tyrosine phosphorylation of the 45 kDa protein, or choline acetyltransferase activity. However, 4 days of exposure to H-7 alone induced PKC activity and tyrosine phosphorylation of the 39-kDa protein. The action of H-7 derivatives on neurite outgrowth did not correlate with their inhibition profile of cyclic nucleotide-dependent protein kinases. Down-regulation of PKC activity by prolonged exposure to phorbol ester did not completely abolish the effects of NGF and H-7 on induction of c-Fos, choline acetyltransferase activity, and neurite outgrowth, indicating that PKC-independent pathways contribute to these actions. These results suggest that additional pathway(s) sensitive to H-7 may exist, which induce immediate early gene expression and suppress neuronal differentiation of PC12 cells.     

Methyl Jasmonate Primed Defense Responses Against Penicillium expansum in Sweet Cherry Fruit

Plant Molecular Biology Reporter - The effect of methyl jasmonate (MeJA) treatment on controlling blue mold decay caused by Penicillium expansum in sweet cherry fruit and the possible mechanisms...     

Metabolomic Responses of Guard Cells and Mesophyll Cells to Bicarbonate

Anthropogenic CO₂ presently at 400 ppm is expected to reach 550 ppm in 2050, an increment expected to affect plant growth and productivity. Paired stomatal guard cells (GCs) are the gate-way for water, CO₂, and pathogen, while mesophyll cells (MCs) represent the bulk cell-type of green leaves mainly for photosynthesis. We used the two different cell types, i.e., GCs and MCs from canola (Brassica napus) to profile metabolomic changes upon increased CO₂ through supplementation with bicarbonate (HCO₃ ^-). Two metabolomics platforms enabled quantification of 268 metabolites in a time-course study to reveal short-term responses. The HCO₃ ^- responsive metabolomes of the cell types differed in their responsiveness. The MCs demonstrated increased amino acids, phenylpropanoids, redox metabolites, auxins and cytokinins, all of which were decreased in GCs in response to HCO₃ ^-. In addition, the GCs showed differential increases of primary C-metabolites, N-metabolites (e.g., purines and amino acids), and defense-responsive pathways (e.g., alkaloids, phenolics, and flavonoids) as compared to the MCs, indicating differential C/N homeostasis in the cell-types. The metabolomics results provide insights into plant responses and crop productivity under future climatic changes where elevated CO₂ conditions are to take center-stage.     

Tim-3 Is Upregulated in NK Cells during Early Pregnancy and Inhibits NK Cytotoxicity toward Trophoblast in Galectin-9 Dependent Pathway

NK cells accumulate at the maternal-fetal interface (MFI) and play essential roles in maintaining immune tolerance during pregnancy. The mechanisms that facilitate NK cells tolerance to fetal tissue are largely unknown. T cell Ig and mucin domain-containing protein 3 (Tim-3) is a newly defined molecule with essential immunological function in many physiological and pathological processes. Recent study showed that Tim-3 was involved in the regulation of immune tolerance at MFI. However, whether Tim-3 regulates NK cells cytotoxicity toward trophoblasts is unclear. Here, we showed Tim-3 was mainly expressed by decidual NK cells (dNK) and Tim-3 level in dNK was higher than peripheral NK cells (pNK). Tim-3⁺ dNK expressed more levels of mature markers CD94 and CD69 than Tim-3^- dNK cells and blocking Tim-3 significantly inhibited dNK IFN-γ and TNF-α secretion. Furthermore, we found TGF-β1 may contribute to such up-regulation of Tim-3 in NK cells. Interestingly, blocking Tim-3 enhanced NK cytotoxicity toward trophoblast cell line HTR-8 but not K562. We found HTR-8 expressed Tim-3 ligand Galectin-9, in contrast K562 did not. Small interfering RNA-mediated silencing of Galectin-9 expression enhanced NK cytotoxicity toward HTR-8. We further showed Tim-3/Galecin-9 inhibited NK cytotoxicity toward trophoblast partially via impairing the degranulation process. In addition, clinical data showed that abnormal Tim-3 level on pNK might be associated with recurrent spontaneous abortion (RSA). Thus, our data demonstrate Tim-3/Galectin-9 pathway maintains local tolerance by suppressing NK cytotoxicity toward trophoblasts which may represent a new immunologic tolerance mechanism at MFI.     

Diverse Routes toward Early Somites in the Mouse Embryo

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