动物细胞在鼓泡式生物反应器中的死亡速率

通过实验测定,证明生物反应器中细胞死亡速率与气体鼓泡速率成正比而与反应器体积成反比。实验发现气泡大小对细胞死亡速率具有两种作用,一种作用在于影响气泡表面积生成速率;另一种作用则在于影响细胞在气泡表面的吸附程度,其最佳直径为5mm左右。血清和Pluronic F68能显著降低细胞死亡速率,当Pluronic F68浓度达到0．1％时,kd趋于零。所有这些实验结果均与前文提出的生物反应器设计模型具有很好的一致性。     

C4 Photosynthesis (The Effects of Leaf Development on the CO2-Concentrating Mechanism and Photorespiration in Maize)

The effect of O2 on photosynthesis was determined in maize (Zea mays) leaves at different developmental stages. The optimum level of O2 for maximum photosynthetic rates was lower in young and senescing tissues (2-5 kPa) than in mature tissue (9 kPa). Inhibition of photosynthesis by suboptimal levels of O2 may be due to a requirement for functional mitochondria or to cyclic/pseudocyclic photophosphorylation in chloroplasts; inhibition by supraoptimal levels of O2 is considered to be due to photorespiration. Analysis of a range of developmental stages (along the leaf blade and at different leaf ages and positions) showed that the degree of inhibition of photosynthesis by supraoptimal levels of O2 increased rapidly once the ribulose-1,5-bisphosphate carboxylase/oxygenase and chlorophyll contents were below a critical level and was similar to that of C3 plants. Tissue having a high sensitivity of photosynthesis to O2 may be less effective in concentrating CO2 in the bundle sheath cells due either to limited function of the C4 cycle or to higher bundle sheath conductance to CO2. An analysis based on the kinetic properties of ribulose-1,5-bisphosphate carboxylase/oxygenase was used to predict the maximum CO2 level concentrated in bundle sheath cells at a given degree of inhibition of photosynthesis by supraoptimal levels of O2.     

常用食品防腐剂抗菌作用的研究

采用杯碟法和琼脂平板点种法分别测定２０种常用食品防腐剂对３０株菌的抑菌圈直径和最低抑菌浓度,借此判断药剂抗菌力的大小。实验结果表明,在所测２０种防腐剂中,对细菌抑制力最强者是乙酸,对霉菌和酵母菌抑制力最强者是富马酸二甲酯。     

Mechanical properties of neuronal growth cone membranes studied by tether formation with laser optical tweezers.

Many cell phenomena involve major morphological changes, particularly in mitosis and the process of cell migration. For cells or neuronal growth cones to migrate, they must extend the leading edge of the plasma membrane as a lamellipodium or filopodium. During extension of filopodia, membrane must move across the surface creating shear and flow. Intracellular biochemical processes driving extension must work against the membrane mechanical properties, but the forces required to extend growth cones have not been measured. In this paper, laser optical tweezers and a nanometer-level analysis system were used to measure the neuronal growth cone membrane mechanical properties through the extension of filopodia-like tethers with IgG-coated beads. Although the probability of a bead attaching to the membrane was constant irrespective of treatment; the probability of forming a tether with a constant force increased dramatically with cytochalasin B or D and dimethylsulfoxide (DMSO). These are treatments that alter the organization of the actin cytoskeleton. The force required to hold a tether at zero velocity (F0) was greater than forces generated by single molecular motors, kinesin and myosin; and F0 decreased with cytochalasin B or D and DMSO in correlation with the changes in the probability of tether formation. The force of the tether on the bead increased linearly with the velocity of tether elongation. From the dependency of tether force on velocity of tether formation, we calculated a parameter related to membrane viscosity, which decreased with cytochalasin B or D, ATP depletion, nocodazole, and DMSO.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased potency of vanadium using organic ligands

Thein vivo glucose lowering effect of orally administered inorganic vanadium compounds in diabetes was first reported in our laboratory in 1985. While both vanadate and vanadyl forms of vanadium are orally active, they are still not well absorbed. We have synthesized several organic vanadium compounds and one compound, bis(maltolato)oxovanadium(IV) or BMOV, has been extensively investigated. BMOV proved effective in lowering plasma glucose and lipids in STZ-diabetic rats when administered in drinking water over a 25 week period. The maintenance dose (0.18 mmol/kg/day) was approximately 50% of that required for vanadyl sulfate (VS). Secondary complications of diabetes were prevented by BMOV and no marked toxicity was noted. Oral gavage of STZ-diabetic rats with BMOV also reduced blood glucose levels. The ED₅₀ for BMOV was 0.5 mmol/kg, while for VS the estimated ED₅₀ was 0.9 mmol/kg. BMOV was also effective by the intraperitoneal route in STZ-diabetic rats. The ED₅₀ was 0.08 mmol/kg compared to 0.22 mmol/kg for VS. Some animals treated p.o. or i.p. remained euglycemic for up to 14 weeks. An i.v. infusion of BMOV of 0.05 mmol/kg over a 30 min period reduced plasma glucose levels by 50% while VS was not effective.     

发根农杆菌介导的菠菜毛状根遗传转化体系的建立

发根农杆菌(Agrobacterium rhizogenes)侵染植物后可诱导植物产生毛状根。菠菜(Spinacia oleracea)是常见的食用蔬菜, 目前尚未见菠菜毛状根的研究报道。经筛选得到适合诱导菠菜毛状根的发根农杆菌菌株LBA9402, LBA9402侵染菠菜外植体茎后, 毛状根的诱导率最高可达16%。菠菜毛状根呈白色, 具有丰富的根毛, 能在无外源激素的固体培养基上快速增殖生长。通过诱导菠菜毛状根产生愈伤组织并进行分化, 获得了菠菜毛状根的再生植株, 再生率为8%。此外, LBA9402可将含有Ri质粒的T-DNA和携带外源GFP基因的Ti质粒T-DNA共同导入外植体中。PCR检测和荧光显微观察结果显示, rolB及GFP基因在菠菜毛状根基因组中稳定表达, 共转化频率为50%。     

恒河猴心房利钠多肽的分离、纯化及活性研究

<正> 1983年以来,人们相继从人和大鼠等动物的心房中分离到心房利钠多肽(ANP)。但对非人灵长类动物——恒河猴的ANP了解甚少。由于ANP对机体循环系统的调节起着重要作用,其强大的降压、利钠、利尿的生理功能,在心血管疾病的防治方面具有重要意义。我们曾报导过恒河猴心房肌细胞中存在着大量的ANP样物质,随后对此物质进行了分离、纯化及活性检测,现简报如下。     

寡聚脱氧核苷酸d(G-C)_3的激光喇曼谱及其分析

用改进的固相磷酰三酯法合成了oligo-d(G-C)_3。以氩离子激光为激发光源,波长488nm.,在室温条件下,分别测定了纯化后的oligo-d(G-C)_3和其组分单体5’-dGMP和5’-dCMP的激光喇曼谱。观察到被测定的物质在300-2500cm~(-1)频率区间,各自都有其特征的谱形和喇曼峰。5’-dGMP和5’-dCMP谱中大多数特征峰在寡聚体的谱中消失,而在oligo-d(G-C)_3谱中出现了几处新的喇曼峰。经查证,峰832,851和899cm~(-1)系糖-磷酸主链的特征喇曼峰,另外几处峰与DNA的构象有关。实验结果表明oligo-d(G-C)_3在水溶液中(室温)主要以B-构象存在。     

Crystallization and preliminary X-ray analysis of phenylalanine hydroxylase from rat liver

Phenylalanine hydroxylase from rat liver has been crystallized from polyethylene glycol 4500 with sodium formate. The crystals are tetragonal rods and belong to space group P4(1)22 or P4(3)22 with unit cell dimensions a = b = 57.6 A and c = 304.1 A. They diffract to at least 2.4 A resolution and have one molecule per asymmetric unit.     

江苏菜豆同工凝集素的分离纯化及性质研究

江苏菜豆经酸水(PH2.0)抽提,硫酸铵分级沉淀,分离植物血球凝集素(PHA-P),分子量为128000的糖蛋白,活性回收率在80％以上,PHA-P经SP-sephadexc-50离子交换层析,分成L_4,L_3E_1,L_2E_2,L_1E_3,和E_4同工凝集素。 L_4和E_4等电点为5.4和6.5。亚基分子量分别是31000和33000,并有类似的氨基酸组成。PAGE分析为单一蛋白带。红细胞凝集活性随电泳迁移速度的加快而增强,促淋性细胞分裂活性则减弱。E_4血凝活性受CalNAc,EDTA抑制和Zn~(++)的促进。