Characterization of Senescence in Lemna gibba G3: A Determinate Growth System

Frond senescence in Lemna gibba G3 was characterized, and itscontrol by light, ABA and kinetin investigated. The plant exhibitsa determinate growth pattern with a frond producing a set numberof daughter fronds before undergoing senescence and death regardlessof whether or not it flowers. When a frond was cut in half,the distal half (half frond) which lacks any meristem underwentrapid senescence as compared with intact fronds. In both intactand half fronds, the onset of senescence was accelerated byABA and retarded by kinetin. Continuous white light acceleratedsenescence in both intact and half fronds over the dark controls.Under different photoperiodic light regime, the pace of daughterfrond production is accelerated in proportion to the lengthof light period. In half fronds, however, very short photoperiodiclight treatments (e.g. 1L: 23D or 3L: 21D) rather delayed senescenceover the dark controls. Two separate light control systems operatingin opposite directions in Lemana senescence appear to exist. ¹Present address: Department of Biology, Yonsei University,Seoul 120-749, Korea ²Present address: U.S. Department of Agriculture, Aero SpaceBuilding, Rm. 323, 901 D Street, S.W., Washington, D.C. 20251-2200, U.S.A. (Received July 13, 1989; Accepted May 8, 1990)     

Molecular genetic study of human arginase deficiency

We have explored the molecular pathology in 28 individuals homozygous or heterozygous for liver arginase deficiency (hyperargininemia) by a combination of Southern analysis, western blotting, DNA sequencing, and PCR. This cohort represents the majority of arginase-deficient individuals worldwide. Only 2 of 15 homozygous patients on whom red blood cells were available had antigenically cross-reacting material as ascertained by western blot analysis using anti-liver arginase antibody. Southern blots of patient genomic DNAs, cut with a variety of restriction enzymes and probed with a near-full-length (1,450-bp) human liver arginase cDNA clone, detected no gross gene deletions. Loss of a TaqI cleavage site was identified in three individuals: in a homozygous state in a Saudi Arabian patient at one site, at a different site in homozygosity in a German patient, and in heterozygosity in a patient from Australia. The changes in the latter two were localized to exon 8, through amplification of this region by PCR and electrophoretic analysis of the amplified fragment after treatment with TaqI; the precise base changes (Arg291X and Thr290Ser) were confirmed by sequencing. It is interesting that the latter nucleotide variant (Thr290Ser) was found to lie adjacent to the TaqI site rather than within it, though whether such a conservative amino acid substitution represents a true pathologic mutation remains to be determined. We conclude that arginase deficiency, though rare, is a heterogeneous disorder at the genotypic level, generally encompassing a variety of point mutations rather than substantial structural gene deletions.     

Characterization of "depolarization"-induced calcium release from sarcoplasmic reticulum in vitro with the use of membrane potential probe.

In the triad, the complex of transverse (T) tubule and sarcoplasmic reticulum (SR) Ca2+ release is induced from SR by mediation of the T-tubule. We report here evidence that this Ca2+ release is produced by depolarization of the T-tubule moiety. Thus, we found that the amount of [14C]SCN- taken up by T-tubules and triads (but not that by SR) increased upon incubation with (K, Na) gluconate, Mg ATP, indicating that the T-tubule was polarized making the lumenal side (equivalent to the extracellular side of an intact muscle fiber) more positive. Upon mixing with choline chloride, the procedure to induce Ca2+ release, [14C]SCN- uptake decreased, indicating that the T-tubule became depolarized. Activation of the T-tubule polarization by Na+ and prevention of it by digoxin [inhibitor of the (Na+, K+) pump], respectively, led to activation and inhibition of choline chloride-induced SR Ca2+ release.     

Kinetics of producing pro-urokinase in perfusion cultivations

Summary Better production of pro-urokinase from human cell line was observed with 5% serum containing medium than 10% or serum free medium on Cytodex II under perfusion chemostat operations, showing 0.8×10^–5 (IU/daycell) of maximum productivity at 0.020 (l/h) of dilution rate in 5% serum medium, which corresponds to 800 IU/mL at this dilution rate. Conversion of pro-urokinase was reduced in the serum-containing media.     

泥鳅精子入卵的动力作用

在扫描电镜下,泥鳅成熟卵卵膜孔外围呈现完整的左涡旋状结构,受精时精子是顺着涡旋的流线进入卵膜孔。涡旋纹理接近对数螺线。本文分析了真骨鱼类的受精因素,除已知的化学因素外,还存在物理因素。也讨论了泥鳅成熟卵卵膜孔形态形成的必然性。     

黄皮种子发育过程中脱水敏感性与细胞膜透性的关系

黄皮（Ｃｌａｕｓｅｎａ ｌａｎｓｉｕｍ （Ｌｏｕｒ．） Ｓｋｅｅｌｓ）胚轴与完整种子的发育模式以及发育中电解质渗漏率变化有些不同． 种子生理成熟前、后的胚轴对脱水的反应也不同,前者经轻微脱水可提高萌发率和活力指数,后者不耐任何程度的脱水．活力指数的急剧下降伴随着电解质渗漏率的迅速上升．实验表明,黄皮种子在发育过程中没有形成耐脱水性． 细胞膜透性变化可反映脱水对种子的伤害程度     

露水草的光合特性及其生态学意义

用盆栽和遮阴试验研究了露水草（Ｃｙａｎｏｔｉｓ ａｒａｃｈｎｏｉｄｅａ Ｃｌａｒｋｅ） 的光合作用特征,比较了不同遮光水平对光合速率、光合器官特性及光合产量的影响。结果如下：１．露水草是一种耐阴偏阳的Ｃ３ 类草木植物,其光合作用的光饱和点约为６５０ μｍ ｏｌ·ｍ － ２·ｓ－ １,光补偿点约为１７ μｍ ｏｌ·ｍ － ２·ｓ－ １,且具有高达１３０×１０－ ６的ＣＯ２ 补偿点。２．露水草的最大净光合速率为１２．４５ μｍ ｏｌ·ｍ － ２·ｓ－ １。叶片净光合速率的日变化规律呈双峰曲线,主峰在１１～１２ 时,次峰在１５时左右。３．遮光２０％ ～５０％ 有利于露水草的生长。与对照相比,叶片中叶绿素ｂ 的含量增加了４７％ ～８３％ ,并且由于净光合速率（相对光合速率）的提高,使光合生产量增加了１２％ ～１８％ 。     

Production of a novel copolyester of 3-hydroxybutyric acid and medium-chain-length 3-hydroxyalkanoic acids by Pseudomonas sp. 61-3 from sugars

 Pseudomonas sp. 61-3 (isolated from soil) produced a polyester consisting of 3-hydroxybutyric acid (3HB) and of medium-chain-length 3-hydroxyalkanoic acids (3HA) of C₆, C₈, C₁₀ and C₁₂, when sugars of glucose, fructose and mannose were fed as the sole carbon source. The polyester produced was a blend of homopolymer and copolymer, which could be fractionated with boiling acetone. The acetone-insoluble fraction of the polyester was a homopolymer of 3-hydroxybutyrate units [poly (3HB)], while the acetone-soluble fraction was a copolymer [poly(3HB-co-3HA)] containing both short- and medium-chain-length 3-hydroxyalkanoate units ranging from C₄ to C₁₂:44 mol% 3-hydroxybutyrate, 5 mol% 3-hydroxyhexanoate, 21 mol% 3-hydroxyoctanoate, 25 mol% 3-hydroxydecanoate, 2 mol% 3-hydroxydodecanoate and 3 mol% 3-hydroxy-5-cis-dodecenoate. The copolyester was shown to be a random copolymer of 3-hydroxybutyrate and medium-chain-length 3-hydroxyalkanoate units by analysis of the ¹³C-NMR spectrum. The poly(3HB) homopolymer and poly (3HB-co-3HA) copolymer were produced simultaneously within cells from glucose in the absence of any nitrogen source, which suggests that Pseudomonas sp. 61-3 has two types of polyhydroxy-alkanoate syntheses with different substrate specificities. Received: 9 June 1995/Received last revision: 30 October 1995/Accepted: 6 November 1995     

Charactererization of novel non-toxic Bacillus thuringiensis isoloates from Korea

J.Y. ROH, H.W. PARK, B.R. JIN, H.S. KIM, Y.M. YU AND S.K. KANG. 1996. Four Bacillus thuringiensis isolates from soil samples produced parasporal inclusions which were non-toxic to insects. The isolates were named B. thuringiensis NTB-1, NTB-2, NTB-3 and NTB-4. The parasporal inclusions were shown to be ovoid by phase contrast and scanning electron microscopy. The serotypes of the four isolates were determined by agglutination using 33 antisera; NTB-1 and NTB-4 seemed to be subsp. isruelensis ,and NTB-2 seemed to be subsp. pondzcheriensis . NTB-3 did not react with the 33 antisera. However, comparison of parasporal protein and plasmid DNA patterns of the four isolates with those of 15 known non-toxic B. thuringiensis strains demonstrated that the four isolates are novel.     

Ras induces anchorage-independent growth by subverting multiple adhesion-regulated cell cycle events.

Anchorage-independent growth is a hallmark of transformed cells, but little is known of the molecular mechanisms that underlie this phenomenon. We describe here studies of cell cycle control of anchorage-independent growth induced by the ras oncogene, with the use of a somatic cell mutant fibroblast line (ER-1-2) that is specifically defective in oncogene-mediated, anchorage-independent growth. Control, nontransformed PKC3-F4 cells and ER-1-2 cells cannot proliferate in semisolid medium. Three important cell cycle events are dependent on adhesion of these cells to a substratum: phosphorylation of the retinoblastoma protein, pRB; cyclin E-dependent kinase activity; and cyclin A expression. PKC3-F4 cells that express ras (PKC3-F4/ras cells) proliferate in nonadherent cultures, and each of these three events occurs in the absence of adhesion in PKC3-F4/ras cells. Thus, ras can override the adhesion requirement of cellular functions that are necessary for cell cycle progression. ER-1-2 cells that express ras (ER-1-2/ras cells) possess hyperphosphorylated forms of pRB and cyclin E-dependent kinase activity in the absence of adhesion but remain adhesion dependent for expression of cyclin A. The adhesion dependence of pRB phosphorylation and cyclin E-dependent kinase activity is therefore dissociable from the adhesion dependence of cyclin A expression. Furthermore, ectopic expression of cyclin A is sufficient to rescue anchorage-independent growth of ER-1-2/ras cells but does not induce anchorage-independent growth of PKC3-F4 or ER-1-2 cells. However, like pRB phosphorylation and cyclin E-dependent kinase activity, the kinase activity associated with ectopically expressed cyclin A is dependent on cell adhesion, and this dependence is overcome by ras. Thus, the induction of anchorage-independent growth by ras may involve multiple signals that lead to both expression of cyclin A and activation of G1 cyclin-dependent kinase activities in the absence of cell adhesion.