Light promotion of hypocotyl gravitropism of a starch-deficient tobacco mutant correlates with plastid enlargement and sedimentation

Dark-grown hypocotyls of a starch-deficient mutant (NS458) of tobacco (Nicotiana sylvestris) lack amyloplasts and plastid sedimentation, and have severely reduced gravitropism. However, gravitropism improved dramatically when NS458 seedlings were grown in the light. To determine the extent of this improvement and whether mutant hypocotyls contain sedimented amyloplasts, gravitropic sensitivity (induction time and intermittent stimulation) and plastid size and position in the endodermis were measured in seedlings grown for 8 d in the light. Light-grown NS458 hypocotyls were gravitropic but were less sensitive than the wild type (WT). Starch occupied 10% of the volume of NS458 plastids grown in both the light and the dark, whereas WT plastids were essentially filled with starch in both treatments. Light increased plastid size twice as much in the mutant as in the WT. Plastids in light-grown NS458 were sedimented, presumably because of their larger size and greater total starch content. The induction by light of plastid sedimentation in NS458 provides new evidence for the role of plastid mass and sedimentation in stem gravitropic sensing. Because the mutant is not as sensitive as the WT, NS458 plastids may not have sufficient mass to provide full gravitropic sensitivity.     

Formation of a novel enzymatic metabolite of leukotriene A4 in tissues of Xenopus laevis

Leukotriene-A4, hydrolase catalyzes the final step in the biosynthesis of the potent proinflammatory mediator leukotriene B4. Previously, leukotriene-A4 hydrolase has been characterized from human, mouse and rat sources, i.e. only from mammalian species. In the present investigation, expression of leukotriene-A4, hydrolase was studied in organs of Xenopus laevis. Enzyme activity was found in all nine organs tested with the highest levels in the intestine and the reproductive organs, i.e. oocytes and testes, previously unrecognized rich sources of the enzyme. No immunoreactive leukotriene-A4 hydrolase was detected in Western blots of 10000Xg supernatants of X. laevis organ homogenates, using a polyclonal antiserum raised against human leukotriene-A4 hydrolase. Likewise, Northern blot analysis of liver total RNA did not detect Xenopus leukotriene-A4 hydrolase mRNA using a human CDNA probe. These results indicate significant structural differences between the human and toad enzymes. Incubations of 10000Xg supernatants of organ homogenates with leukotriene A4 revealed the formation of a novel metabolite, denoted compound X. Conversion of leukotriene A4 into compound X was due to an enzymatic activity as judged by its protein dependence, heat sensitivity, and resistance to ultrafiltration, and this activity appeared to be linked, directly or indirectly,, to leukotriene A4 hydrolase. From data obtained by ultraviolet spectrophotometry, gas chromatography coupled to mass spectrometry, ultraviolet-induced isomerization, and comparison with a synthetic standard, compound X was assigned the structure 5S,12R-dihydroxy-6,10-trans-8,14-cis-eicosatetraenoic acid. Finally, compound X was found to exhibit contractile activity in guinea-pig lung parenchyma, apparently elicited via a leukotriene B receptor.     

Thrombopoietin: a potential T-helper lymphocyte stimulator. Change in T-lymphocyte composition and blood cytokine levels in thrombopoietin cDNA transferred mice

The aim of this study was to evaluate the effect of thrombopoietin (TPO) on T lymphocyte in Balb/c mice delivered hTPO cDNA with plasmid vector. Both mature and immature T lymphocytes in central organs increased, but only the CD4+ subset was preferably proliferated in circulation. High serum IFN-gamma was coinciding with the declination of platelet counts, but TNF-alpha was positively associated with the platelet count, while high IL-2 level was similar to the course of TPO expression. Our data suggested that TPO is a stimulator for T lymphocytes, especially the CD4+ subset.     

多孔泡沫金属研究现状及分析

多孔泡沫金属是一种新型多用途材料 ,在一般工业领域 ,特别是高技术领域受到越来越广泛的重视 ,为此近年来已引起了国内外研究者的研究兴趣 .笔者对多孔泡沫金属的研究现状进行了归纳和分析 ,提出了现存的问题和今后研究的几点建议 ,以求拓宽多孔泡沫金属的研究领域及在国民经济中的应用范围     

Quantification of compaction-induced crystallinity reduction of a pharmaceutical solid using 19F solid-state NMR and powder X-ray diffraction

¹⁹F solid-state nuclear magnetic resonance (NMR) was investigated as an analytical technique to quantify the amorphous phase in a fluorine-containing pharmaceutical candidate. The crystallinity of Compound 1 was calculated using two ¹⁹F T₁ relaxation-based methods. The first method employs both the pure amorphous and the crystalline reference standards while the second method is model independent and utilizes a single standard. The ¹⁹F solid-state NMR results were confirmed with powder X-ray diffraction methods. From X-ray diffraction data, two linear calibration curves were obtained from blends of crystalline and amorphous Compound 1: one is based on the total integrated intensity of selected diffraction peaks and the other on the total intensity of the amorphous halo at 2θ positions that have no interference from crystalline diffraction peaks. The crystallinity of Compound 1 after compaction calculated by both ¹⁹F solid-state NMR methods was in excellent agreement with the results from the X-ray calibration curves. ¹⁹F solid-state NMR was shown to be a powerful technique in determining the amount of amorphous phase present in a pharmaceutical solid.     

Role of lipid modifications in targeting proteins to detergent-resistant membrane rafts. Many raft proteins are acylated, while few are prenylated

Sphingolipid and cholesterol-rich Triton X-100-insoluble membrane fragments (detergent-resistant membranes, DRMs) containing lipids in a state similar to the liquid-ordered phase can be isolated from mammalian cells, and probably exist as discrete domains or rafts in intact membranes. We postulated that proteins with a high affinity for such an ordered lipid environment might be targeted to rafts. Saturated acyl chains should prefer an extended conformation that would fit well in rafts. In contrast, prenyl groups, which are as hydrophobic as acyl chains but have a branched and bulky structure, should be excluded from rafts. Here, we showed that at least half of the proteins in Madin-Darby canine kidney cell DRMs (other than cytoskeletal contaminants) could be labeled with [3H]palmitate. Association of influenza hemagglutinin with DRMs required all three of its palmitoylated Cys residues. Prenylated proteins, detected by [3H]mevalonate labeling or by blotting for Rap1, Rab5, Gbeta, or Ras, were excluded from DRMs. Rab5 and H-Ras each contain more than one lipid group, showing that hydrophobicity alone does not target multiply lipid-modified proteins to DRMs. Partitioning of covalently linked saturated acyl chains into liquid-ordered phase domains is likely to be an important mechanism for targeting proteins to DRMs.     

Polymerase chain reaction-based strain characterization of noncapsulate Haemophilus influenzae

A polymerase chain reaction-based typing method for noncapsulate Haemophilus influenzae was developed. Randomly amplified polymorphic DNA fingerprints were generated from boiled supernatants prepared directly from bacterial colonies without the need for DNA extraction. The technique was applied to isolates obtained during putative outbreaks of chest infection and validated by comparison with sodium dodecyl sulfatepolyacrylamide gel electrophoresis analysis of outer membrane protein-enriched preparations and rRNA gene restriction analysis. There was complete concordance between the three techniques. The results show that randomly amplified polymorphic DNA analysis provides a highly discriminatory method of characterizing strains of noncapsulate H. influenzae which is eminently suitable as an epidemiological tool for the rapid investigation of outbreaks of infection.