Oat leaf base: tissue with an efficient regeneration capacity

Summary An efficient short term regeneration system using seedling derived oat (Avena sativa) leaf tissue has been developed. Callus derived from the leaf base showed a higher response of plant regeneration than callus initiated from mesocotyls and more mature parts of the leaves. A correlation between the nuclear DNA content of the donor material, as analysed with flow cytometry, and its ability to form callus was observed. Somatic embryogenesis was histologically recognised from callus derived from tissue close to the apical meristem. Plant regeneration media with various concentrations of auxin were tested. Callus from three different cultivars had a similar regeneration potential with an optimal regeneration frequency of 60%. About 2 months after inoculation regenerated plantlets could be moved to a greenhouse for cultivation.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - DAPI 6-diamidino-2-phenylindole - IAA indole-3-acetic acid - KT kinetin - MS Murashige and Skoog's medium - NAA naphthalene acetic acid     

Oxytocin induced a biphasic increase in the intracellular Ca2+ concentration of porcine myometrial cells: Participation of a pertussis toxin—insensitive G-protein,inositol 1,4,5-trisphosphate—sensitive Ca2+ pool,and Ca2+ channels

This study investigated the underlying mechanisms of oxytocin (OT)-induced increases in intracellular Ca²⁺ concentrations ([Ca²⁺]_i) in acutely dispersed myometrial cells from prepartum sows. A dosedependent increase in [Ca²⁺]_i was induced by OT (0.1 nM to 1 μM) in the presence and absence of extracellular Ca²⁺ ([Ca²⁺]_e). [Ca²⁺]_i was elevated by OT in a biphasic pattern, with a spike followed by a sustained plateau in the presence of [Ca²⁺]_e. However, in the absence of [Ca²⁺]_e, the [Ca²⁺]_i response to OT became monophasic with a lower amplitude and no plateau, and this monophasic increase was abolished by pretreatment with ionomycin, a Ca²⁺ ionophore. Administration of OT (1 μM) for 15 sec increased inositol 1,4,5-trisphosphate (IP₃) formation by 61%. Pretreatment with pertussis toxin (PTX, 1 μg/ml) for 2 hr failed to alter the OT-induced increase in [Ca²⁺]_i and IP₃ formation. U-73122 (30 nM to 3 μM), a phospholipase C (PLC) inhibitor, depressed the rise in [Ca²⁺]_i by OT dose dependently. U-73122 (3 μM) also abolished the OT-induced IP₃ formation. Thapsigargin (2 μM), an inhibitor of Ca²⁺-ATPase in the endoplasmic reticulum, did not increase [Ca²⁺]_i. However, it did time-dependently inhibit the OT-induced increase in [Ca²⁺]_i. Nimodipine (1 μM), a Voltage-dependent Ca²⁺ channel (VDCC) blocker, inhibited the OT-induced plateau by 26%. La³⁺ (1 μM), a nonspecific Ca²⁺ channel blocker, abrogated the OT-induced plateau. In whole-cell patch-clamp studies used to evaluate VDCC activities, OT (0.1 μM) increased Ca²⁺ Current (I_ca) by 40% with no apparent changes in the current-voltage relationship. The OT-induced increase in I_ca reached the maximum in 5 min, and the increase was abolished by nimodipine (1 μM). These results suggested that (1) activation of OT receptors in porcine myometrium evokes a cascade in the PTX-insensitive G-protein–PLC-IP₃ signal transduction, resulting in an increase in [Ca²⁺]_i; (2) the OT-induced increase in [Ca²⁺]_i is characterized by a biphasic pattern, in which the spike is predominately contributed by the intracellular Ca²⁺ release from the IP₃-sensitive pool, and to a lesser extent by Ca²⁺ influx, whereas the plateau is from increased Ca²⁺ influx; and (3) the influx is via VDCC and receptor-operated Ca²⁺ channels. © 1995 Wiley-Liss, Inc.     

人肝刺激因子对大鼠实验性慢性肝损伤的保护作用

从健康孕妇水囊引产４─６个月龄的胎儿取肝,采用ＬａＢｒｅｃｑｕｅ方法提取人肝刺激因子（ｈＨＳＳ）。经３Ｈ－胸腺嘧啶核苷参入肝ＤＮＡ法测定其生物活性。表明此ｈＨＳＳ可刺激肝细胞ＤＮＡ合成。采用皮下注射ＣＣｌ４和饮用１０％乙醇来制备慢性肝损伤动物模型,观察了ｈＨＳＳ的保护肝脏作用。结果表明：ｈＨＳＳ可使ＣＣｌ４－乙醇所致慢性肝损伤大鼠的死亡率、血清谷丙转氨酶水平、肝组织中羟脯氨酸含量的升高以及肝组织中丙二醛的含量降低。肝组织切片表明：ｈＨＳＳ能减轻肝组织的损伤程度,促进肝细胞再生,并能明显防止肝纤维化的形成和发展。可见,ｈＨＳＳ对ＣＣｌ４－乙醇所致的慢性肝损伤大鼠有明显的保护作用,其机制可能与促进肝细胞再生及抑制肝细胞膜的脂质过氧化有关。     

动物鸣叫声计算机分析

动物鸣叫声计算机分析姜仕仁,丁平,施青松诸葛阳（杭州大学生物科学与技术系３１００１２）ＣｏｍｐｕｔｅｒＡｎａｌｙｓｉｓｏｆＡｎｉｍａｌ’ｓＣａｌｌｉｎｇＳｏｕｎｄ￥ＪｉａｎｇＳｈｉｒｅｎ,Ｄｉｎｇ,Ｐｉｎｇ,ＳｈｉＱｉｎｇｓｏｎｇ,ＺｈｕｇｅＹａｎｇ...     

High-level SUMO-mediated fusion expression of ABP-dHC-cecropin A from multiple joined genes in Escherichia coli

The antimicrobial peptide ABP-dHC-cecropin A is a small cationic peptide with potent activity against a wide range of bacterial species. Evidence of antifungal activity has also been suggested; however, evaluation of this peptide has been limited due to the low expression of cecropin proteins in Escherichia coli. To improve the expression level of ABP-dHC-cecropin A in E. coli, tandem repeats of the ABP-dHC-cecropin A gene were constructed and expressed as fusion proteins (SUMO-nABP-dHC-cecropin, n = 1, 2, 3, 4) via pSUMO-nABP-dHC-cecropin A vectors (n = 1, 2, 3, 4). Comparison of the expression levels of soluble SUMO-nABP-dHC-cecropin A fusion proteins (n = 1, 2, 3, 4) suggested that BL21 (DE3)/pSUMO-3ABP-dHC-cecropin A is an ideal recombinant strain for ABP-dHC-cecropin A production. Under the selected conditions of cultivation and isopropylthiogalactoside (IPTG) induction, the expression level of ABP-dHC-cecropin A was as high as 65 mg/L, with ∼21.3% of the fusion protein in soluble form. By large-scale fermentation, protein production reached nearly 300 mg/L, which is the highest yield of ABP-dHC-cecropin A reported to date. In antibacterial experiments, the efficacy was approximately the same as that of synthetic ABP-dHC-cecropin A. This method provides a novel and effective means of producing large amounts of ABP-dHC-cecropin A.     

工业酵母抗逆机理研究进展

工业酵母利用木质纤维素等生物质资源发酵生产醇、酮、醛、酸等各种化合物,是解决人类面临的不可再生资源和能源危机的重要途径,这激发了人们对木质纤维素水解液为原料和环保节能型浓醪发酵技术的极度关注。然而高浓度底物、产物、渗透压、木质纤维素水解液中抑制性物质、发酵过程温度的提高均会抑制微生物生长代谢及发酵性能,这是发酵行业"瓶颈"问题。本文简述了渗透压、温度及抑制性物质对酵母细胞生长的危害,并从胞内稳态平衡、分子水平等方面着重叙述工业酵母对渗透压、温度及抑制性物质的抗逆机制研究进展。     

不同发酵条件下产甘油假丝酵母有机酸代谢的研究

产甘油假丝酵母 (Candidaglycerolgenesis)发酵产生的有机酸对丙三醇产品质量和产率均有影响。发现在发酵其它条件恒定 ,装液比和玉米浆浓度增加时 ,发酵液总酸是递增的。在装液比为 0 2和玉米浆浓度为 8g L时 ,丙酮酸和乳酸在细胞生长期可分别积累达 4 1g L和 1 0g L ,比正常发酵时增加 2倍以上 ,丙三醇产率也低 ;然而 ,装液比为 0 0 8和玉米浆浓度为 4g L时 ,丙酮酸和乳酸产生较低 ,丙三醇产率较高 ,但乙酸积累比供氧不足时高 ,可达 2 6g L。发酵过程中有机酸被细胞代谢 ,含量逐渐下降 ,如在初糖浓度为 1 0 0g L时 ,有机酸在细胞生长期积累至高峰后 ,丙三醇和有机酸随之均降低至较低含量 ,并且丙酮酸或乳酸可以转化为乙酸。此外 ,在外加一些添加剂时对其产生有机酸也有影响 ,如添加 1 %油酸和VB1时可以降低乙酸的积累 ,同时增加丙酮酸的含量 ,丙三醇产量也有所增加 ;而丙酮酸结构类似物氟代丙酮酸和亚硫酸盐促进乙酸的产生 ,使酮戊二酸合成减少 ,丙三醇产量约增加 2 0 %。     

Cloning and over-expression of an alkaline protease from Bacillus licheniformis

The alkaline protease gene, apr, from Bacillus licheniformis 2709 was cloned into a Bacillus shuttle expression vector, pHL, to yield the recombinant plasmid pHL-apr. The pHL-apr was expressed in Bacillus subtilis WB600, yielding a high expression strain BW-016. The amount of alkaline protease produced in the recombinant increased by 65% relative to the original strain. SDS-PAGE analysis indicated a Mr of 30.5 kDa. The amino acid sequence deduced from the DNA sequence analysis revealed a 98% identity to that of Bacillus licheniformis 6816.