Some factors involved in the dissolution of Autographa californica nuclear polyhedrosis virus polyhedra by digestive fluids of Trichoplusia ni larvae

Factors involved in the dissolution of polyhedra of Autographa californica nuclear polyhedrosis virus (AcNPV) by digestive fluid collected from fifth stage Trichoplusia ni larvae were studied in vitro. Observations were made at timed intervals using phase contrast microscopy and transmission electron microscopy. When digestive fluid was heated at 50°C proteases retained activity. Exposure of polyhedra to digestive fluid previously heated to 50°C resulted in polyhedral matrix dissolution and envelope disruption in a manner similar to that of unheated digestive fluid, only delayed slightly. After exposure of polyhedra for 3 min, only enveloped virons were observed. Heating the digestive fluid to 60° or higher inactivated the proteases and altered the effect on polyhedra. Dissolution of the occlusion body matrix occurred but the polyhedral envelope remained and only a few weakened areas were observed in its structure. Within the polyhedral envelope, enveloped virons were not observed, only nucleocapsids and capsids. Exposure of polyhedra to 0.1 m sodium carbonate buffer at pHs of 9.5 or higher had effects similar to those of the digestive fluid with heat (60°C)-inactivated proteases. The addition of trypsin and chymotrypsin to the 0.1 m sodium carbonate buffer had no effect, while the addition of a bacterial protease (Streptomyces griseus) at pHs of 9.5 or higher resulted in dissolution of the matrix and disruption of the polyhedral envelope like the digestive fluid. Material infectious to TN-368 cells was obtained by exposure of AcNPV to T. ni digestive fluid. Maximum infectivity resulted from a 5-min exposure to unheated digestive fluid, with a dramatic decrease in infectivity with longer exposure. Exposure to digestive fluid with heat (60°C)-inactivated proteases resulted in a slower release of infectious material from the occlusion body, with a steady increase in the level of infectivity throughout the 30-min digestion period.     

杨尺蠖核型多角体病毒蛋白质的特性

本文研究了杨尺蠖核型多角体病毒(AciNPV)蛋白质特性,用反复调等电点法,从AciNPV的多角体蛋白中分离到A,B两种蛋白,Sepharose 6B柱层析和超离心沉降分析表明,两者均为一个峰纯,沉降系数(S20w)分别为4.9和8.9,对A蛋白进行了16种氨基酸组成分析,Glu、Asp和Leu含量高于其它氨基酸,不含Cys,用SDS-聚丙烯酰胺凝胶电泳和免疫双扩散法分析表明,用两倍体积饱和硫酸铵沉淀法制备的多角体蛋白,与提纯的多角体A、B蛋白之间无差异,多角体蛋白结构多肽由6种组成,分子量在12500—54000道尔顿范围内,其中32000是多角体蛋白的主要多肽,病毒粒子结构多肽和核衣壳蛋白分别由19和7个多肽组成,分子量范围分别在89000～13000和34000～13000之间,间接试验结果表明,在AciNPV中有碱性蛋白酶活性存在。     

大尺蠖核多角体病毒DNA的限制性消化和物理图谱

用5种限制性核酸内切酶消化大尺蠖核多角体病毒(BsNPV)基因组DNA,所得片段数分别是:BamH Ⅰ,9;Bgl Ⅱ,7;Xho Ⅰ,10;HindⅢ 13;EcoR Ⅰ,12,从各个片段的累加测出BsNPV基因组的平均大小约为91,75kb;分子量约为59.60×10~6d。在单酶消化的基础上,用BamH Ⅰ/Bgl Ⅱ双酶消化得到16个片段(即9+7);大小为91,27kb,用、Bgl Ⅱ/Xho Ⅰ双酶消化产生7+10=17个片段,大小为90.04kb,由此组建了这三个酶在BsNPV基因组上的物理图谱。     

Involvement of colchicine-sensitive cytoplasmic element in premitotic nuclear positioning ofAdiantum protonemata

Summary When the red-light grown protonema ofAdiantum capillus-veneris was transferred to the dark, the nucleus ceased its migration ca. 5 hours before cell plate formation (Mineyuki andFuruya 1980). To see whether the nucleus was held by some cytoplasmic structure during nuclear positioning, protonemata were treated with various centrifugal forces at different stages of the cell cycle. Nuclei of G₁ phase were easily displaced by centrifugation at 360×g for 15 minutes, but those of G₂ or M phase were not displaced by it, suggesting that the nuclei were held by some cytoplasmic elements in G₂ or M phase. This nuclear anchoring was not detectable in protonemata that were treated with 5mM colchicine. With this treatment, the nucleus did not stop its migration at late G₂ and moved even in prophase. And the retardation of organelle movement which was observed in cytoplasm on the lateral side of the nucleus after the cessation of premitotic nuclear migration (Mineyuki andFuruya 1984) was not observed in the presence of colchicine. Thus the nuclei appear to be held by colchicine-sensitive structure in cytoplasm between the lateral surface of the nucleus and cell wall during the premitotic nuclear positioning. Electron micrographs showing cytoplasmic microtubules were consistent with the idea.Abbreviations PPN Premitotic positioning of the nucleus - L region Cytoplasm between the lateral surface of the nucleus and cell wall (seeMineyuki et al. 1984)     

Electrorotation of lymphocytes—The influence of membrane events and nucleus

Electrorotation—the spin of cells in rotating high frequency electric fields—has been used to investigate properties of human peripheral blood lymphocytes. The rotation spectra of lymphocytes deviate from those of single shell spheres. The deviations are caused by the electrical properties of the nucleus in the cell interior.Electrorotation allows the distinction between successfully stimulated lymphocytes and unstimulated cells after application of concanavalin A. Notwithstanding the fact that only a proportion of the cells will be mitogenically stimulated we detected an enhanced cell membrane conductivity for the whole cell population immediately after the addition of mitogen.     

Kinetics of 5-enolpyruvylshikimate-3-phosphate synthase inhibition by glyphosate

The herbicide glyphosate (N-phosphonomethyl glycine) is a potent reversible inhibitor of the 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase activity of the purified arom multienzyme complex from Neurospora crassa. Inhibition of the EPSP synthase reaction by glyphosate is competitive with respect to phosphoenolpyruvate, with K(i) 1.1 microM, and uncompetitive with respect to shikimate-3-phosphate. The kinetic patterns are consistent with a compulsory order sequential mechanism in which either PEP or glyphosate can bind to an enzyme: shikimate-3-phosphate complex.     

Aminoacyl-tRNA synthetases: inter-site interaction as a possible proofreading mechanism

Smooth muscle cell energetics of taenia caeci during relaxation, activity and maximal contraction were investigated using ³¹P-NMR. In relaxed muscle obtained in calcium-free medium, [ATP], [phosphocreatine] and [sugar phosphate] were 4.4 mM, 7.7 mM and 2.8 mM, respectively. There was only a small difference in the energetics of spontaneously active and maximally contracted muscles, but under both conditions substantial changes occurred as compared with relaxed muscles. The internal pH in relaxed muscle was found to be 7.05, which acidified to 6.5 during contraction. The level of sugar phosphates was found to be not a limiting factor in energetics.     

A Tipula paludosa population with a high incidence of two pathogens

The incidence of lethal parasites in the larvae of a Tipula paludosa population was monitored for two seasons. The proportions of larvae infected with Tipula iridescent virus (TIV) and a tachinid insect were similar to those in previously studied populations, whereas the proportions of larvae infected with Tipula nuclear polyhedrosis virus (NPV) and a spore-forming bacterium (SFB) were higher. Conservative estimates of mortality due to these four agents were 10.7% in 1977–1978 and 7.7% in 1978–1979. The mean population density and the proportion of SFB-infected larvae were lower in 1978–1979 than in 1977–1978, while the proportion of NPV-infected larvae was higher. In 1979 the proportion of NPV-infected larvae was positively correlated with population density, which was highest in the wettest part of the study area. In both seasons the proportion of SFB-infected larvae was negatively correlated with population density. Larvae infected with the NPV or the SFB became pallid at an advanced stage of infection, but, although infected larvae were found throughout the larval period, pallid larvae were only found in the later part. It is suggested that larvae become infected in an early instar, then the infections slowly develop throughout the remainder of the larval period. Five larvae were found with mixed infections; four were infected with the SFB and NPV, while the fifth was infected with the SFB and TIV.