Inhibitory effect of quercetin on carrageenan-induced inflammation in rats

We examined the effect of quercetin on the inflammatory response induced by carrageenan in the rat. Air pouches were induced subcutaneously on the backs of rats and injected with carrageenan. The rats were treated with either vehicle or quercetin at a dose of 10 mg/kg one hour before carrageenan challenge. Fourty-eight hour after carrageenan challenge, the air pouches were removed and analyzed. The volume, protein amounts and cell counts in the exudation obtained from the quercetin-treated animals were significantly reduced compared to those from vehicle-treated animals. The contents of PGE(2), TNF-alpha, RANTES, MIP-2 and the mRNA for cyclooxygenase-2 were also suppressed in these rats. The histological examination displayed the suppression of the inflammatory response in the pouch tissues from quercetin-treated rats. As the anti-inflammatory effect of the flavonols was more or less at the similar level among the quercetin-, isoquercitrin- or rutin-treated rats, it appeared that the sugar parts did not influence on the anti-inflammatory effect.Our study indicated that the flavonols modulated the inflammatory response, at least in part, by modulating the prostanoid synthesis as well as cytokine production.     

The Arabidopsis sweetie mutant is affected in carbohydrate metabolism and defective in the control of growth, development and senescence

Sugars modulate many vital metabolic and developmental processes in plants, from seed germination to flowering, senescence and protection against diverse abiotic and biotic stresses. However, the exact mechanisms involved in morphogenesis, developmental signalling and stress tolerance remain largely unknown. Here we report the characterization of a novel Arabidopsis thaliana mutant, sweetie , with drastically altered morphogenesis, and a strongly modified carbohydrate metabolism leading to elevated levels of trehalose, trehalose-6-phosphate and starch. We additionally show that the disruption of SWEETIE causes significant growth and developmental alterations, such as severe dwarfism, lancet-shaped leaves, early senescence and flower sterility. Genes implicated in sugar metabolism, senescence, ethylene biosynthesis and abiotic stress were found to be upregulated in sweetie . Our physiological, biochemical, genetic and molecular data indicate that the mutation in sweetie was nuclear, single and recessive. The effects of metabolizable sugars and osmolytes on sweetie morphogenesis were distinct; in light, sweetie was hypersensitive to sucrose and glucose during vegetative growth and a partial phenotypic reversion took place in the presence of high sorbitol concentrations. However, SWEETIE encodes a protein that is unrelated to any known enzyme involved in sugar metabolism. We suggest that SWEETIE plays an important regulatory function that influences multiple metabolic, hormonal and stress-related pathways, leading to altered gene expression and pronounced changes in the accumulation of sugar, starch and ethylene.     

Inactivation and Phosphorylation of Kanamycin by Drug-resistant Staphylococcus aureus

The cell-free system of clinical isolates of drug-resistant Staphylococcus aureus inactivated kanamycin, and the inactivated product was identified with kanamycin-3′-phosphate, in which the C-3-OH of the 6-amino-6-deoxy-d-glucose moiety of kanamycin was phosphorylated.     

Method for mapping a partial lethal-factor locus on a molecular-marker linkage map of a backcross and doubled-haploid population

 Distorted segregation has been repeatedly observed in various plant species in molecular-marker linkage mapping where distant crosses were made. It may be caused by a partial lethal-factor acting in the filial generations. A method is presented for estimating the recombination values between a partial lethal-factor locus and a linked molecular marker and the relative viability or fertilization ability of zygotes or gametes, respectively affected by the partial lethal factor in backcross (BC) and doubled-haploid (DH) populations using the maximum-likelihood method associated with the expectation maximization (EM) algorithm. The method was applied to segregation data of molecular markers for a population of 150 DH lines developed from the ‘Steptoe’בMorex’ cross in barley. The presence of a partial lethal-factor locus, located on chromosome 4, causing partial selection was suggested. This locus was tightly linked to the ABG500B marker, and the chance of fertilization of female gametes possessing the partial lethal factor was, on average, 59.8% that of a normal one. Two additional partial lethal factors were found on chromosome 5. Received: 3 December 1997 / Accepted: 25 February 1998     

Visualization of site-specific recombination catalyzed by a recombinase from Zygosaccharomyces rouxii in Arabidopsis thaliana

Excision of a DNA segment can occur in Arabidopsis thaliana by reciprocal recombination between two specific recombination sites (RSs) when the recombinase gene (R) from Zygosaccharomyces rouxii is expressed in the plant. To monitor recombination events, we generated several lines of transgenic Arabidopsis plants that carried a cryptic β-glucuronidase (GUS) reporter gene which was designed in such a way that expression of the reporter gene could be induced by R gene-mediated recombination. We also made several transgenic lines with an R gene linked to the 35S promoter of cauliflower mosaic virus. Each transgenic line carrying the cryptic reporter gene was crossed with each line carrying the R gene. Activity of GUS in F₁ and F₂ progeny was examined histochemically and recombination between two RSs was analyzed by Southern blotting and the polymerase chain reaction. In seedlings and plantlets of F₁ progeny and most of the F₂ progeny, a variety of patterns of activity of GUS, including sectorial chimerism in leaves, was observed. A small percentage of F₂ individuals exhibited GUS activity in the entire plant. This pattern of expression was ascribed to germinal recombination in the F₁ generation on the basis of an analysis of DNA structure by Southern blotting. These results indicate that R gene-mediated recombination can be induced in both somatic and germ cells of A. thaliana by cross-pollination of parental transgenic lines.     

F9 Cells Can be Differentiated toward Two Distinct, Mutually Exclusive Pathways by Retinoic Acid and Sodium Butyrate

Both retinoic acid (RA) and sodium butyrate (NaB) induce differentiation in embryonal carcinoma F9 cells. Phenotypic changes caused by RA are irreversible, whereas those of NaB are rapid and reversible. In this study, we investigated the effects of combinations of these two agents on F9 cell differentiation and showed that RA had no effect on the cells induced to differentiate with NaB and vice versa. Thus, F9 cells are induced to differentiate along two distinct pathways which are mutually exclusive.     

Resistance to Active Oxygen Toxicity of Transgenic Nicotiana tabacum that Expresses the Gene for Glutathione Reductase from Escherichia coli

A chimeric gene consisting of a gene from Escherichia coli thatencodes glutathione reductase (GR), the 35S promoter of cauliflowermosaic virus and the terminator sequences of the gene for nopalinesynthase, was introduced into tobacco (Nicotiana tabacum SRI)cells via a Ti plasmid vector. Expression of the bacterial genein transformed plants and their descendants was confirmed byimmunochemical analysis. GR activity in leaf extracts variedamong transgenic plants, ranging from about 1.0 to 3.5 timesthe control level. These transgenic plants exhibited lower susceptibilityto paraquat than control plants in terms of the extent of visiblefoliar damage, a result that suggests that GR may play an importantrole in the detoxification of active oxygen in the cytoplasmicmatrix of plant cells. However, the transgenic plants were nomore resistant to ozone than were the controls, both in termsof the extent of visible foliar damage and with respect to photosyntheticactivity. (Received January 28, 1991; Accepted May 9, 1991)     

Development of visible markers for transgenic plants and their availability for environmental risk assessment

Monitoring of transgenic plants in the field is important, but risk assessment has entailed laborious use of invisible marker genes. Here, we assessed three easily visible marker transgenes--green fluorescent protein (GFP), R, and Nicotiana tabacum homeobox (NTH) 15 genes--for their potential use as marker genes for monitoring genetically modified plants. Transgenic Arabidopsis thaliana plants for each of these genes were visibly distinguished from wild-type plants. We determined the germination rate, 3-week fresh weight, time to first flowering, and seed weight of the transgenic plants to evaluate whether the expression of these marker genes affected the growth of the host. Introduction of GFP gene had no effect on the evaluated parameters, and we then used the GFP gene as a marker to assess the outcrossing frequency between transgenic and two Arabidopsis species. Our results showed that the hybridization frequency between transgenic plants and Arabidopsis thaliana was 0.24%, and between transformants and Arabidopsis lyrata it was 2.6% under experimental condition. Out-crossing frequency was decreased by extending the distance between two kinds of plants. Thus, the GFP gene is a useful marker for assessing the whereabouts of transgenes/transformants in the field. We also demonstrated that the GFP gene is possibly applicable as a selection marker in the process of generation of transgenic plants.     

Synthesis of a fluorogenic mucopolysaccharide by chondrocytes in cell culture with 4-methylumbelliferyl β-d-xyloside

Culture of chondrocytes in the presence of 4-methylumbelliferyl β-d-xyloside resulted in a synthesis of protein-free, fluorogenic chondroitin sulfate which was heterogeneous on DEAE-cellulose chromatography. Degradation of the major chromatographic fraction with chondroitinase-ABC yielded, in addition to a large quantity of Δ⁴-glucuronic acid-containing disaccharides, two flurogenic oligosaccharides of different size. Quantitative analysis showed that Δ⁴-glucuronic acid, galactose, xylose, and 4-methylumbelliferone were present in the small oligosaccharide fragment in a molar ratio of 1:2:1:1. Since these analytical data are analogous to those reported for glycopeptides derived from proteochondroitin sulfates, it may be suggested that 4-methylumbelliferyl β-d-xyloside replaces the need for xylosyl protein core in the normal synthesis of proteochondroitin sulfate with a resultant production of the unusual polysaccharide bearing the added xyloside at the reducing end.