Xanthophylls and abscisic Acid biosynthesis in water-stressed bean leaves

Experiments were designed to obtain evidence about the possible role of xanthophylls as abscisic acid (ABA) precursors in water-stressed leaves of Phaseolus vularis L. Leaves were exposed to ¹⁴CO₂ and the specific activities of several major leaf xanthophylls and stress-induced ABA were determined after a chase in ¹²CO₂ for varying periods of time. The ABA specific radioactivities were about 30 to 70% of that of lutein and violaxanthin regardless of the chase period. The specific activity of neoxanthin, however, was only about 15% of that of ABA. The effects of fluridone on xanthophyll and ABA levels and the extent of labeling of both from ¹⁴CO₂ were determined. Fluridone did not inhibit the accumulation of ABA when leaves were stressed once, although subsequent stresses in the presence of fluridone did lead to a reduced ABA accumulation. The incorporation of ¹⁴C from ¹⁴CO₂ into ABA and the xanthophylls was inhibited by fluridone and to about the same extent. The incorporation of ¹⁸O into ABA from violaxanthin which had been labeled in situ by means of the violaxanthin cycle was measured. The results indicated that a portion of the ABA accumulated during stress was formed from violaxanthin which had been labeled with ¹⁸O. The results of these experiments are consistent with a preformed xanthophyll(s) as the major ABA precursor in water-stressed bean leaves.     

Chromosome aberration and ploidy equilibrium of Vicia faba in tissue culture

Summary Different phytohormone concentrations induced different fequencies of various chromosome aberrations in calli of Vicia faba. NAA 10 ppm plus KT 2.5 ppm produced more haploids and NAA 30 ppm plus NAA 7.5 ppm produced more tetraploids and breakage. The relationship among the aberrations was analyzed. The hypothesis of ploidy equilibrium was established. The chromosome doubling rate and reduction rate of each treated group were calculated in relation to the observed data and the hypothesis. The frequency of tetraploids and breakage are correlated with each other. The frequency of total aberrations is linearly correlated with that of micronucleus formation. The regression equation is x=31.92+ 10.67 y.     

心不甘中甾体皂甙元的分离和结构鉴定(2)

自心不甘(Tupistra aurantiaca Wall et Backer)根的醋酸乙酯萃取物经硅胶柱层析分离除可得到1β、2β、3β、4β、5β、7α-hexahydroxyspirost-25(27)-en-6-one外,还得到7个游离的甾体皂甙元A—G,其中A及B分别为3-epiruscogenin及3-epi-neoruscogenin,F为△~(25(27))-pentrogenin(6)、C、D和E系新化合物,经IR、MS、~1H NMR及~(13)C NMR谱鉴定分别推定为ranmogenin A(3)、B(4)和C(5)(兰茂甙元甲、乙和丙)。     

心不甘中甾体皂甙元的分离和结构鉴定(3)

本文报告心不甘(Tupistra aurantiaca Wall et Backer)根的粗甙经盐酸水解后的总甙元中分离的甙元E和F的结构鉴定。甙元F经鉴定为△~(25(27))-pentrogenin(2)。甙元E(ranmo-genin D)为新化合物,其结构经IR、MS、~1H NMR和~(13)C NMR谱分析推定如(1)所示。     

不同海拔地区种植的水稻地上部干物质的生产和分配

根据1983—1985年“高原水稻高产栽培的生理生态规律研究”中低热的元江(海拔400米左右)、温凉的昆明(约1900米)和冷凉的丽江(约2400米)的资料,以六个处理、十八个小区、三年总平均值,比较了不同海拔地区种植的水稻中地上部干物质生产和分配的总趋势。主要结果如下: 1.全生育期总的干物质生产量以温凉地区最高,低热地区居中,冷凉地区最低。 2.抽穗前干物质生产速率和齐穗期干物重占黄熟期干物重的比例随海拔降低而增加;抽穗期至黄熟期干物质生产速率,以温凉地区最高,低热地区居中,冷凉地区最低,但低热地区低于前期,高海拔地区高于前期,不过冷凉的丽江增加的更多。 3.抽穗前(旗叶完全展开后)叶干重占当时植株总干重的比例,随海拔升高而降低。 4.抽穗期至黄熟期的次库(茎 叶鞘)干重的改变,不同海拔地区种植的水稻表现不同:低热地区减重,温凉地区稍增,冷凉地区明显增加。 5.与高海拔地区种植的水稻相比,在黄熟期低海拔地区的有较高的穗重/总重和穗增重/总增重的比例。另外低海拔地区的穗增重超过总增重。结实率和谷/草比例均随海拔增高而减低。     

High-performance liquid chromatography of type-III heptocarboxylic porphyrinogen isomers.

A reversed-phase h.p.l.c. system is described for the separation of the four type-III heptacarboxylic porphyrinogen isomers. The effects of buffer concentration, pH and type and proportion of organic modifier in the mobile phase on retention and resolution of isomers were studied. Optimum separation on an ODS-Hypersil column was by elution with a ternary mobile phase of acetonitrile, methanol and 1 M-ammonium acetate, pH 5.16 (7:3:90, by vol.). Isomer identification was based on a comparison of their retention times with those of authentic standards, and was further confirmed by h.p.l.c. analysis of the characteristic mixture of three pentacarboxylic porphyrins formed after partial decarboxylation of individual isomers in 0.3 M-HCl at 160 degrees C.     

Estrogen carcinogenesis in Syrian hamster tissues: role of metabolism

Evidence for a role of estrogen metabolism in hormonal carcinogenesis was obtained with the Syrian hamster as an in vivo model system. Both natural and synthetic estrogens are capable of inducing a high incidence of renal carcinomas in this species. A high incidence of hepatocellular carcinomas can also be induced in the hamster with synthetic estrogens such as ethinyl estradiol or diethylstilbestrol, provided alpha-naphthoflavone (ANF) is present in the diet. Although steroid receptor-mediated hormonal events appear to be intimately involved in the process of in vivo cell transformation of both tissues, certain observations strongly suggest that nonhormonal events are also important. Despite their potent estrogenic activity at the doses used, ethinyl estradiol and alpha-zearalanol induce relatively low renal tumor incidences after 9.0 and 10.0 months of continuous treatment, respectively. A role for the metabolism of estrogens to reactive intermediates is also suggested by studies showing estrogen-induced renal tumorigenesis can be partially inhibited by concomitant administration of ANF or ascorbic acid. Consistent with this is the general correlation between the amount of catechol estrogen formed by a compound, as mediated by estrogen 2-/4-hydroxylase, and renal carcinogenicity data. Recently, additional supporting evidence has been obtained from studies involving the irreversible binding of reactive metabolites of steroidal or stilbene estrogens to hamster liver microsomal proteins.     

NAD-linked aldehyde dehydrogenase for aerobic utilization of L-fucose and L-rhamnose by Escherichia coli.

Mutant analysis revealed that complete utilization of L-fucose and L-rhamnose by Escherichia coli requires the activity of a common NAD-linked aldehyde dehydrogenase which converts L-lactaldehyde to L-lactate. Mutations affecting this activity mapped to the ald locus at min 31, well apart from the fuc genes (min 60) encoding the trunk pathway for L-fucose dissimilation (as well as L-1,2-propanediol oxidoreductase) and the rha genes (min 88) encoding the trunk pathway for L-rhamnose dissimilation. Mutants that grow on L-1,2-propanediol as a carbon and energy source also depend on the ald gene product for the conversion of L-lactaldehyde to L-lactate.     

Comparison of the tissue-specific expression and developmental regulation of two closely linked rodent genes encoding cytosolic retinol-binding proteins

Cellular retinol-binding protein (CRBP) and cellular retinol-binding protein II (CRBP II) are two highly homologous cytoplasmic proteins that bind all-trans-retinol. We have recently demonstrated that the mouse genes encoding CRBP and CRBP II are closely linked on chromosome 9 and that both human genes are located on chromosome 3 (Demmer, L.A., Birkenmeier, E.H., Sweetser, D.A., Levin, M.S., Zollman, S., Sparkes, R.S., Mohandas, T., Lusis, A.J., and Gordon, J.I. (1987) J. Biol. Chem. 262, 2458-2467). We have now used RNA blot hybridization analysis to assess the degree to which these genes are coordinately expressed in fetal, suckling, weaning, and adult rat tissues. Both genes exhibit different developmental patterns of expression in liver, intestine, lung, kidney, testes, and placenta. In the intestine, CRBP mRNA was detected during the 16th day of gestation--prior to the development of a well-differentiated absorptive epithelium--and remained essentially unchanged throughout the peri- and postpartum periods. By contrast, the pattern of intestinal CRBP II mRNA accumulation closely parallels the times of first appearance, and subsequent proliferation, of the intestinal absorptive columnar epithelium, supporting the hypothesis that CRBP II is involved in the intestinal uptake or intracellular trafficking of this hydrophobic vitamin. In the fetal liver, both genes were expressed by gestational day 16. Whereas the concentration of hepatic CRBP mRNA increased markedly during the suckling and early weaning periods, CRBP II mRNA levels fell abruptly immediately after birth. These peripartum changes were not paralleled by remarkable alterations in the steady state levels of hepatic retinol. Marked changes in the expression of CRBP in the liver and of CRBP II in the intestine were also documented in pregnant and lactating female rats. These differences in CRBP/CRBP II gene expression strongly suggest that their proteins serve different physiological functions. The peripartum liver may provide a useful model for dissecting the relative roles played by these homologous proteins in retinoid metabolism as well as the factors which modulate activation and repression their genes.