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.     

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.     

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.     

Climatic and intertrophic effects detected in 10-year population dynamics of biological control of the arrowhead scale by two parasitoids in southwestern Japan

Relative effects of weather and three-trophic interactions were studied for a classical biological control system consisting of the arrowhead scale Unaspis yanonensis, known formerly as a serious pest of the Satsuma mandarin orange Citrus unshiu, and its two introduced parasitoids, Coccobius fulvus and Aphytis yanonensis. Yearly population responses of the three insect species on a per-tree basis for up to 10 years at two orange groves were analyzed by general linear models, with a backward stepwise procedure, to select among abiotic (summer/winter temperature and rainfall) and biotic (densities of the three insect species and orange bearing in the previous years) independent variables. Temperature positively affected the arrowhead scale and the two parasitoids. A negative correlation of rainfall was detected for all three insect species. Mandarin fruiting showed negative delayed density dependence, thereby supporting the observed alternate bearing phenomenon in mandarins, presumably due to physiological imbalance triggered by climatic factors. The arrowhead scale was negatively correlated with fruit production in the preceding years, possibly due to reduced resistance in subsequent years of mast fruiting. We found a negative correlation of the arrowhead scale with Coccobius only in a single grove and none with Aphytis. Thus, it appears that bottom-up forces may be more important than top-down control by the parasitoids in the post-transient phase of this system.