固氮酶铁钼辅因子FeMo-co在水与非水体系内重组活力与催化活力的比较研究

 本文提出一种测定FeMo-co催化活力的反应体系,用此反应体系,在测定FeMo-co催化活力的过程中,FeMo-co与变种UW45抽提液的重组活性始终保持不变。讨论了水含量、还原剂对FeMo-co催化活力和重组活力的影响。     

Size Effects on the Uptake of Particles by Populations of Tetrahymena pyriformis Cells

Flow cytometry has been used to make direct measurements of rates of uptake of latex microspheres from dilute, monodisperse suspensions by Tetrahymena pyriformis. Measurements were made for five different sizes of microspheres, ranging from 1.09 to 6.17 μm diameter. Fractions of cells in the population that did not ingest the microspheres offered were also determined. In addition, the size distributions, as indicated by the forward angle light scattering intensity which is measured by the instrument, were determined for the whole population and for the subpopulations of cells that did and did not ingest the particles, for each particle size used. It was found that the fraction of cells that did not ingest the particles was small and independent of particle size when this was less than about 2.7 μm, but increased with particle size when particle size was increased above this value. The so-called maximum clearance rate, which can be calculated from the data, was found to increase monotonically with particle size if it were based only on those cells which actually ingested the particles offered. However, a plot of maximum clearance rate vs. particle size exhibited a maximum if the clearance rate were based on all cells present in the population.     

A simple and reliable turbidimetric and kinetic assay for alpha-amylase that is readily applied to culture supernatants and cell extracts

Summary A simple, reliable and sensitive assay for alpha-amylase activity is reported, together with its theoretical derivation, that overcomes many of the problems encountered with other assays, especially when attempting to assay alpha-amylase activity in crude cell extracts or culture supernatants. The method relies on the reduction in turbidity that occurs upon digestion of a starch suspension with alpha-amylase. The initial rate of decrease in turbidity is shown to be proportional to a wide range of enzyme concentrations, permitting a rapid spectrophotometric and kinetic determination of alpha-amylase activity.     

Kinetic disposition of an aqueous formulation of alphacypermethrin applied to the dorsal mid-line of sheep with long wool and its effect on lice

A group of 5 adult Merino sheep with fleeces about 70 mm long (7-months growth of wool) was treated with a topical formulation of the synthetic pyrethroid insecticide, alphacypermethrin, applied to the dorsal mid-line. Insecticide concentrations at the tip, middle and base of wool staples collected from meridians along the back, upper and lower flanks were measured at intervals from 1 to 98 days after treatment. Some movement of the alphacypermethrin from the back to the lower body occurred within 24h after treatment, but despite careful application of the insecticide there was wide variation in the concentration between and within meridians. The majority of the alphacypermethrin remained close to the dorsal mid-line and near the tip of the staple. There were significant differences in the concentration between the tip, middle and base segments of the staples in the back and lower flank meridians (P < 0.05). Despite exposure of the sheep to normal weathering, there was no significant difference in the concentration of alphacypermethrin between samples collected at day 1 or day 98 after treatment (P > 0.05). Numbers of pyrethroid-susceptible lice surviving exposure in vitro for 20 h differed significantly between samples collected at different times after treatment (P < 0.05). The numbers of lice surviving in samples collected within 28 days after treatment tended to be lower than in those collected from 28 to 98 days but, in some samples, regardless of time after treatment, lice survived for 20 h in wool taken from parts of the fleece that contained high concentrations of alphacypermethrin.     

五种野生稻叶绿体DNA多态性研究

对野生稻 5个种的18个材料的叶绿体DNA(cpDNA)进行了EcoRI的RFLP分析。 结果显示,共有10种酶切模式,不同种野生稻的cpDNA的RFLP类型都不同,而且在其中一些 种内也有变化,尤以O.rufipogon的种内多态性最为显著,并主要与地理来源有关。本研究还在O.punctata的材料中发现一种以往的分析都不曾描述过的多态性模式。通过对结果的分析,探讨了不同种类野生稻的叶绿体基因组之间以及它们与核基因组之间的进化关系。 Abstract:The polymorphisms of chloroplast DNA from 18 materials of 5 wild rice species were investigated using RFLP analysis.10 restriction patterns were obtained from the analysis of these materials.Different species had different of its RFLP patterns chloroplast DNA,and the polymorphisms existed even with species,especially in O.rufipogon varieties of different geographical origins.In O.punctata a new type of rice chloroplast DNA restriction pattern was discovered which had not been reported before.According to the results obtained,the evolutionary relationships among chlorplast genomes,and between chloroplast and nuclear genomes in different wild rice are discussed.     

Membrane receptors for estrogen,progesterone, and testosterone in the rat brain: Fantasy or reality

Summary 1. There are numerous circumstantial evidence supporting the concept that steroid hormones control cellular function by means other than the nuclear receptor steroid binding mechanism. It is the intent of this report to present evidence indicating that steroids bind to specific sites in neuronal membranes.2. Some of the criteria to define steroid membrane receptors using steroid-BSA conjugates that can be radioiodinated to desired specific activity have been fulfilled for each of the three sex steroids using crude synaptosomal membrane preparations (P2 fractions) from the CNS of female and male rats. Ligand binding for each of the three steroids indicate high-affinity and high-capacity sites with distinct brain selectivity and stereospecificity. For example, 17-E-6-[¹²⁵I]BSA binds hypothalamic P2 fractions (HYP-P2) with an estimatedK _d of about 3±0.7 nM (X ± SE;n=3), whereas the cerebellum P2 (CB-P2) fractions bind the ligand with aK _d of 34±7 nM and, aB _max of 3 and 42 pmol/mg protein, respectively. Estrogen and testosterone binding fit best a one-single site, while progesterone binding sites can be best represented by a two-binding site, one high-affinity (K _d=1–2 nM) and one low affinity (K _d=62 nM), in CB-P2 fractions from intact adult female rat brain. Kinetics studies for T-3-[¹²⁵I]BSA indicate that the estimatedK _d of 30±2 nM for the olfactory bulb P2 fractions (OB-P2) from male rats is in good agreement withK _d values computed from Scatchard-derived data using the LIGAND algorithm.3. 17-E-6-[¹²⁵I]BSA binding sites are stereospecific and appears to be present as early as 5 days of age in both the OB- and the CB-P2 fractions without changes during development. In contrast, P-6-[¹²⁵I]BSA binding sites are practically absent during days 5 and 12 and appear by day 22.4. Finally, membrane receptor molecules for estrogen and progesterone have been isolated and purified by affinity chromatography and characterized by PAGE and Western blot. Microsequencing of one of the membrane estrogen binding proteins indicates that the high-affinity site corresponds to the OSCP subunit of the proton ATP synthase.5. It remains to be determined if P and T also bind to this complex enzyme or if they bind to other subunits of the family of proton ATPases. Overall the data indicate that steroid hormones conjugated to BSA are important tools to study the reality of membrane steroid receptors.     

Influx and efflux of inorganic carbon in Synechococcus UTEX625

The CO₂ and HCO₃^? fluxes in air-grown cells of Synechococcus UTEX 625 al pH 8-0 were measured during dark to light and light to dark transitions using a mass spectrometer and sampling of the reaction medium. The kinetic parameters for initial uptake of CO₂ and HCO₃^? were determined during the initial period of illumination. The development of the internal C_i pool was followed up to steady-state photosynthesis, which occurred when the size of the internal inorganic carbon pool remained apparently constant for a limited period. The experimental procedure confirmed that only CO₂ transport occurred with 100mmolm^?3 Na⁺ and that both CO₂ and HCO^?3 transport occurred with 25molm^?3 Na⁺. The K_1/2 values of initial CO₂ and HCO₃ uptake were 0.7 and 17.2 mmolm^?3respectively and agreed closely with the K_1/2 values of net CO₂ and HCO₃^? transport during steady-state photosynthesis, which were 0.66 and 17.1 mmolm^?3 respectively. Maximum rates of CO₂and HCO₃^? transport were 423 and 219mmolh^?1 g^?1 Chl. Maximum CO₂ efflux observed upon darkening was 118mmolh^?1 g^?1 Chl. A permeability coefficient of the cell for CO₂ of 3 × 10^?8 m s^?1 was determined from the dark CO₂ efflux assuming an internal pH of 7.2 in the dark. Following the initial CO₂ uptake in the light, the extracellular [CO₂] steadily declined when only CO₂ transport was allowed, but an increase in the extracellular [CO₂] when HCO₃^? transport was allowed to proceed suggested that an enhanced CO₂ efflux occurred as a result of the larger size of the intracellular C_i pool.     

Halcyon days with Bill Arnold

The circumstances that led to the discovery that plants luminesce after they are illuminated are described, as are other discoveries that would not have been possible were it not for the fortuitous association I had with my dear and most admirable friend, W.A. Arnold, to whom this special issue is dedicated.     

Isolation and promoter characterization of barley geneItr1 encoding trypsin inhibitor BTI-CMe: differential activity in wild-type and mutantlys3a endosperm

The geneItr1, encoding trypsin inhibitor BTI-CMe, has been obtained from a genomic library ofHordeum vulgare L. The gene has no introns and presents in its 5-upstream region 605 bp that are homologous to the long terminal repeats (LTR) of the copia-like retro-transposon Bare-1. Functional analysis of theItr1 promoter by transient expression in protoplasts derived from different barley tissues, has shown that in this system theItr1 promoter retains its endosperm specifity and thetrans-regulation mediated by theLys3a gene. The proximal promoter extending 343 bp upstream of the translation initiation ATG codon is sufficient to confer fullGUS expression and for endosperm specifity. In protoplasts derived from thelys3a mutant, Risø 1508,GUS activity was less than 5% of that obtained with the same constructs in the protoplasts of wild-type Bomi from which it derives. Gel retardation experiments, after incubation with proteins obtained from both types of endosperm nuclei, also show differential patterns. Possible reasons for these differences are discussed.Equal authours