Temperature-dependent insertion of prolipoprotein into Escherichia coli membrane vesicles and requirements for ATP, soluble factors, and functional SecY protein for the overall translocation process.

The requirements for the translocation of prolipoprotein into membrane vesicles were examined in an in vitro system. As measured by the eventual modification and processing of the prolipoprotein to form mature lipoprotein, the overall translocation process was found to require ATP hydrolysis, the presence of some heat-labile soluble cytoplasmic translocation factors, and the function of a cytoplasmic membrane protein, SecY/PrlA. However, the initial step of complete insertion of prolipoprotein into the membrane vesicles occurred without apparent requirements of a nucleotide, cytoplasmic translocation factors, or a functional SecY/PrlA membrane protein. Immunopurified prolipoprotein spontaneously inserted into membrane vesicles at elevated temperatures and required ATP and cytoplasmic translocation factors to form mature lipoprotein. The prolipoprotein inserted most efficiently into liposomes made of negatively charged phospholipids, indicating the importance of phospholipids in protein translocation. These results suggest that ATP hydrolysis and the actions of both cytoplasmic translocation factors and a functional SecY/PrlA membrane protein occur at a step(s) after the insertion of the precursors into membrane vesicles. The initial step of spontaneous insertion of prolipoprotein into membranes is in good agreement with membrane trigger hypothesis proposed by W. Wickner (Annu. Rev. Biochem. 48:23-45, 1979) and the helical hairpin hypothesis proposed by D. M. Engleman and T. A. Steitz (Cell 23:411-422, 1981).     

椭圆斜羽叶的解剖研究及斜羽叶的系统分类位置

本文根据对椭圆斜羽叶(Plagiozamites oblongifolius)钙质石化化石的研究,认为其主要特征如下:羽状复叶,叶肉无海绵组织和栅栏组织分化。羽片叶脉维管束外韧式,木质部外始式,与现代苏铁属叶脉特征相近。羽轴维管束为“U”形,外始式木质部、梯状纹孔管胞,与现代苏铁属的羽轴维管束相似。根据上述特征,目前可将斜羽叶属归入原始苏铁类植物。但是,如果斜羽叶的生殖器官同 Noeggerathia 一样,为异孢型孢子囊穗,则斜羽叶可能为一种与苏铁类起源有关的原裸子植物。     

Prostaglandin I2 and the constricted maternal ovine placenta: effects of local infusion and placental age

We have tested the hypotheses that systemic responses to the infusion of prostaglandin I2 may have masked the ability of this substance to dilate the maternal placenta and that the inability of prostaglandin I2 to dilate the maternal near-term placenta may be a function of placental age. Regional blood flows were measured with radioactive microspheres. In 8 near-term sheep the control flows were measured and angiotensin II (AII) infusion was begun at 5 micrograms/min and continued for the duration of the experiments. At t = 15 min, regional blood flows were again measured. Prostaglandin I2 was then infused via a retrograde uterine arterial catheter at 10 micrograms/min. At t = 30 min, the flows were again measured. At this time the infusion of prostaglandin I2 was stopped and at t = 45 min the blood flows were measured for the last time. AII increased the resistance of all tissues examined. The blood pressure increased with AII and did not change thereafter. The non-placental uterine tissue served by the retrograde catheter dilated with prostaglandin I2. The placental tissue had an initial resistance of 59 +/- 6 mmHg.ml-1.min.g which increased to 98 +/- 22 mmHg.ml-1.min.g with the infusion of AII (P less than 0.05). This resistance remained constant at 82 +/- 19 mmHg.ml-1.min.g with the administration of prostaglandin I2 and did not change after prostaglandin I2 was removed. The local application of prostaglandin I2 in the presence of AII induced vasoconstriction caused vasodilatation in the nonplacental vessels but could not change the AII induced constriction in the placental vasculature.(ABSTRACT TRUNCATED AT 250 WORDS)     

Signal transduction of gamma/delta T cell antigen receptor with a novel mitogenic anti-delta antibody

Human T lymphocytes express either alpha/beta- or gamma/delta-TCR in association with the CD3 complex. We have isolated a mAb, delta TCS1, that immunoprecipitated the gamma/delta-TCR heterodimer from cell lysates of Peer and Molt-13 leukemia cell lines. After dissociation of the gamma- and delta-chains of TCR by treatment with SDS, delta TCS1 specifically immunoprecipitated the delta-chain. This antibody bound to the surface of other gamma/delta-positive T cell lines and clones and was able to stimulate the proliferation of a minor cell population (0.9 to 4.0%) of resting human PBL. Upon binding to gamma/delta-TCR-bearing Molt-13 cells and PBL, delta TCS1 elicited a fura-2 Caa+ signal indicating that the gamma/delta-receptor is functionally similar to the alpha/beta-heterodimer. These data indicate that the delta TCS1 antibody recognizes an epitope on TCR delta-chain and its mitogenic activity should be useful in characterizing the functional properties of human gamma/delta-positive T lymphocytes.     

Protoplast isolation and callus production from leaves of tissue-cultured Vitis spp.

Protoplasts were isolated from mesophyll of axenic cultures of grape, Vitis rotundifolia cv. Summit and V. vinifera cv. Cabernet Sauvignon. Enzymes effective for protoplast isolation were Macerozyme R-10 (0.5% and 0.1%) and Cellulase Onozuka R-10 (1.0% and 0.5%) for V. rotundifolia and V. vinifera, respectively. Polyvinylpyrrolidone and 2-(N-morpholino)ethanesulfonic acid were essential in the isolation media. Protoplasts were purified using flotation/centrifugation. The protoplasts of V. rotundifolia cultured in Gamborg's B5 basal medium with 2.2 M 6-benzyladenine, 4.5 M 2,4-dichlorophenoxyacetic acid and 0.4% agarose gave the best plating efficiency of conditions tried in this study. Cell division occurred within 5 to 6 days and visible microcalli developed within one month. After 6 weeks in culture, microcalli transferred to liquid medium exhibited active callus growth. Protoplasts of V. vinifera cultured under these conditions had similar results.Abbreviations MES 2-(N-morpholino)ethanesulfonic acid monohydrate - PVP polyvinylpyrrolidone - PDS potassium dextran sulfate - BA 6-benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - FDA fluorescein diacetate     

Development of shoot inHydrangea macrophylla I. Terminal and axillary buds

The structure of shoots, in particular of winter buds, ofHydrangea macrophylla was examined. The non-flower-bearing shoot is usually composed of a lower and an upper part, between which a boundary is discernible by means of a distinctly short internode. This internode is the lowermost of the upper part, and it is usually shorter than the internodes immediately above and below, although the internodes tend to shorten successively from the proximal to the distal part of the shoot. Variations exist in the following characters among the terminal bud, the axillary bud on the lower part of the shoot and the axillary bud on the upper part: (1) length of bud; (2) character of the outermost pair of leaf primordia; (3) degree of development of secondary buds in the winter bud; and (4) the number of leaf primordia. Usually, the terminal bud contains several pairs of foliage leaf primordia with a primordial inflorescence at the terminal of the bud, but the axiallary bud contains only the primordia of foliage leaves in addition to a pair of bud scales.     

猪肺血管紧张素转换酶的提纯

本文报道了猪肺血管紧张素转换酶(ACE)的提纯方法及其鉴定,并讨论了方法的改进。肺匀浆经1.6—2.6mol/L硫酸铵沉淀,Sephadex G-200凝胶过滤,DEAE-Sephaeel及羟基磷灰石柱层析步骤,从168克肺中获得4.5毫克酶蛋白纯品。活力回收45.2％,比活力15.6单位/毫克蛋白;和匀浆上清比较,提纯390倍。经聚丙烯酰胺凝胶电泳(pH8.3)鉴定为一条带。按SDS聚丙烯酰胺凝胶电泳(SDS-PAGE)测得其分子量为132,000道尔顿。酶蛋白在-30℃貯存10月,比活力丢失30％。     

水生观赏植物的调查和研究

水生绿化观赏植物是美化园林水景的重要植物材料,作者通过几年的调查研究和引种栽培,提出了28种(其中荷花含18个品种,睡莲含20个品种)水生绿化观赏植物,同时介绍了20种(其中荷花含6个品种)观赏价值较高的水生绿化观赏植物。     

阔叶树的叶形曲线方程：—适于叶面积计算的数学模型

树木的叶形可以看作一个平面几何图形。这种几何图形可用解析方程给予表达,我们把这种解析方程称为叶形曲线方程。由于叶形是一个左右对称,而上下不对称的图形,也就是说叶的最宽处绝大多数不在叶的中部,少数在