禿杉组织培养研究

本文详细报道了从秃杉(Taiwania flousiana Gaussen)离体胚诱导不定芽、不定根及从无菌苗茎端培养再生植株的过程。诱导不定芽要求较低的蔗糖浓度(以3％最好);同时BA是必须的,在附加0.1—3 mg/1 BA的White培养基上,从离体胚的子叶或胚轴上诱导了不定芽的发生(以1 mg/1最好);NAA与BA结合使用,对不定芽诱导无促进作用;适当提高光照有利于不定芽的诱导。在诱导不定芽的同时,在子叶表面还观察到有许多无结构的“不定突起”。不定芽起源于子叶表皮下1—2层细胞。IBA对诱导离体胚上产生不定根效果较好。在有或无生长素的培养基上,从生长1月龄的无菌苗茎端培养获得了不定根的产生,在加有细胞分裂索的培养基上,从无菌苗上产生了腋芽。     

3-磷酸甘油醛脱氢酶胍变性时的活力及构象变化

酵母3-磷酸甘油醛脱氢酶在盐酸胍溶液中的内源荧光及剩余活力的变化结果提示:apo酶及holo酶的活力在胍浓度为0.5M左右可完全丧失.同时伴有内源荧光强度的下降,光谱宽度的增加和335nm最大发射峰的红移(提示了色氨酸残基的暴露).与已经报导的肌肉酶(内源荧光强度在胍浓度为0.4—1.2M范围相对稳定)不同,酵母酶内源荧光在此浓度范围内表现为逐渐降低.在0.7M胍溶液中,内源荧光变化动力学过程只能测出一相,而酶失活动力学过程为快慢两相,快相动力学速度常数至少大于内源荧光降低速度常数三个数量级以上.以上结果提示:低浓度胍可引起该酶的完全失活,活性部位的空间构象比酶分子的构象更易受到变性剂的扰乱;有一个色氨酸残基位于或靠近酶的活性部位.     

cDNAs encoding members of a family of proteins related to human sterol carrier protein 2 and assignment of the gene to human chromosome 1 p21----pter.

Sterol carrier protein 2 (SCP2) is believed to play a key role in intracellular lipid movement. Here we report the cloning and nucleotide sequences of cDNAs encoding SCP2-related proteins of 58.85 kD and 30.8 kD and the assignment of the SCP2 gene to human chromosome 1 p21-pter. The SCP2-related proteins share common deduced carboxyl amino acid sequences with SCP2 and the cDNAs have a common 3' untranslated nucleotide sequence. The mRNAs encoding these proteins increased in a coordinate fashion as human placental cytotrophoblasts differentiated into syncytiotrophoblasts in culture. Our observations document the existence of a family of related proteins encoded by the human SCP2 gene.     

A comparison of neural networks and partial least squares for deconvoluting fluorescence spectra

This article compares backpropagation neural networks (BNN) with partial least squares (PLS) techniques in terms of their ability to deconvolute fluorescence spectra. Both actual experimental and simulated spectral data are studied for 2 binary systems. These systems consist of mixtures of tryptophan and tyrosine, and NADH and tryptophan over a total concentration range of 10(-7) to 10(-4) M. It is shown that BNN is superior to PLS for both systems.     

Enhanced Sensitivity to Ethylene in Nitrogen- or Phosphate-Starved Roots of Zea mays L. during Aerenchyma Formation

Adventitious roots of maize (Zea mays L. cv TX 5855), grown in a well-oxygenated nutrient solution, were induced to form cortical gas spaces (aerenchyma) by temporarily omitting nitrate and ammonium (-N), or phosphate (-P), from the solution. Previously this response was shown (MC Drew, CJ He, PW Morgan [1989] Plant Physiology 91: 266-271) to be associated with a slower rate of ethylene biosynthesis, contrasting with the induction of aerenchyma by hypoxia during which ethylene production is strongly stimulated. In the present paper, we show that aerenchyma formation induced by nutrient starvation was blocked, under noninjurious conditions, by addition of low concentrations of Ag⁺, an inhibitor of ethylene action, or of aminoethoxyvinyl glycine, an inhibitor of ethylene biosynthesis. When extending roots were exposed to low concentrations of ethylene in air sparged through the nutrient solution, N or P starvation enhanced the sensitivity to exogenous ethylene at concentrations as low as 0.05 microliters ethylene per liter air, promoting a more rapid and extensive formation of aerenchyma than in unstarved roots. We conclude that temporary deprivation of N or P enhances the sensitivity of ethylene-responsive cells of the root cortex, leading to cell lysis and aerenchyma.     

Molecular cloning and mapping of phenol degradation genes from Bacillus stearothermophilus FDTP-3 and their expression in Escherichia coli.

Two genes of the meta pathway of phenol degradation were cloned from a phenol-utilizing strain of Bacillus stearothermophilus and were mapped by subcloning and by use of a Tn5 insertion mutation. They code for phenol hydroxylase and catechol 2,3-dioxygenase, respectively. The gene encoding catechol 2,3-dioxygenase, which is more thermostable than catechol 2,3-dioxygenase encoded by the other gene, shares rather limited homology with that from Pseudomonas putida.     

眶脊巨蜂属一新种记述(膜翅目:姬蜂总科, 巨蜂科)

巨蜂科 Megalyridae 是姬蜂总科 Ichneumonoidea 的一个小科,主要分布于大洋洲及南非。寄生于树木的穿孔性昆虫幼虫,我国尚未见报道。眶脊巨蜂属 EttchellsiaCameron(1909)过去仅知2种,分别产于加里曼丹岛和菲律宾。该属的主要特征是:沿复眼上颊眶有一明显的脊(汉名即据此而拟),前缘脉和亚前缘分开;中胸盾片有一明显