Photoinactivation of cellular catalase by ultraviolet radiation

Summary

Photoinactivation of catalase is found to be similar in solution and in human normal skin fibroblasts exposed to ultraviolet B, ultraviolet A and near visible light, and the kinetics of such photoinactivation obey first order processes. The action spectrum, measured for the first time in cells, suggests that catalase photoinactivation in solution and in cells proceeds via similar routes. In both systems, no protective effect was observed with diethyldithiocarbamate, a superoxide dismutase inhibitor, with desferrioxamine, an iron chelator which impedes the production of hydroxyl radical via the Fenton reaction, and with vitamin E which scavenges peroxyl radical to protect against membrane peroxidative process. While the absence of protection by these inhibitors may be anticipated for the photoinactivation of catalase in solution, the lack of effect in cells suggests that reactive oxygen species produced by endogenous photosensitization are not responsible for the enzyme inactivation. Moreover, the already established protective effect of ethanol in solution is also observed in cells, supporting the view that photoinactivation in solution and in cells is due to the same primary events.     

Analysis of chromatin and DNA during chromosome endoreduplication in the endosperm ofTriticum durum Desf.

Summary Chromatin structure was studied in nuclei of the endosperm of durum wheat (Triticum durum Desf., cv. Creso), where a large number of cells undergo chromosome endoreduplication during caryopsis development. Optical density profiles of interphase nuclei at different ploidy levels after Feulgen staining were determined cytophotometrically. It was observed that, within each development stage, polyploid nuclei (6–12C and 12–24C) show more condensed chromatin than euploid nuclei (3–6C): this should indicate that endoreduplication is accompanied by some reduction of nuclear activity. Within the same ploidy level, 3–6C and 6–12C nuclei become increasingly condensed with development (except for the last stage), while 12-24C nuclei are identical at all stages. DNA methylation at different stages of caryopsis development was then analyzed in genomic DNA, highly repeated sequences and ribosomal DNA, by digestion with cytosine-methylation-sensitive restriction enzymes. We observed that (i), depending on the enzyme, DNA from caryopses may show higher mean length than DNA from shoot apices and variations occur during endosperm development; (ii) highly repeated DNA sequences also show some variation in base methylation between apices and endosperms and among endosperm development stages, even though to a lesser extent than genomic DNA; (iii) rDNA shows variations only between endosperm and apices while no variation was observed among endosperm development stages in relation to chromosome endoreduplication. Our data may be explained by assuming the occurrence, during endosperm development, of processes of chromatin condensation possibly involved in silencing the activity of extra copies of DNA resulting from chromosome endoreduplication. At least in part, DNA methylation is involved in the process of chromatin condensation. rDNA shows no variation during endosperm development: this suggests that rDNA copies are actively transcribed in both triploid and endoreduplicated nuclei.     

Evidence for genomic changes in transgenic rice (Oryza sativa L.) recovered from protoplasts

The occurrence of genomic modifications in transgenic rice plants recovered from protoplasts and their transmission to the self-pollination progeny has been verfied with the random amplified polymorphic DNA (RAPD) approach. The plant was the Indica-type rice (Oryza sativa L.) cultivar Chinsurah Boro II. The analysed material was: (1) microspore-derived embryogenic rice cells grown in suspension culture, (2) transgenic plants recovered from protoplasts produced from the cultured cells and (3) the self-pollination progeny (two successive generations) of the transgenic plants. DNA purified from samples of these materials was PCR-amplified with different random oligonucleotide primers and the amplification products were analysed by agarose gel electrophoresis. Band polymorphism was scored and used in band-sharing analyses to produce a similarity matrix. Relationships among the analysed genomes were expressed in a dendrogram.The extensive DNA changes evidenced in cultured cells demonstrate the occurrence of somaclonal variation in the material used to produce protoplasts for gene transfer. Quantitatively reduced DNA changes were also found in the resulting transgenic plants and i their self-pollination progenies.While confirming the stability of the foreign gene in transgenic plants, this work gives molecular evidence for the occurrence of stable genomic changes in transgenic plants and points toin vitro cell culture as the causative agent. RAPDs are shown to be a convenient tool to detect and estimate the phenomenon at the molecular level. The methodology is also proposed as a fast tool to select those transgenic individuals that retain the most balanced genomic structure and to control the result of back-crosses planned to restore the original genome.     

Effect of sediment elutriate on the growth of Gymnodinium sp. (Dinophyceae). I.

Abstract

Sediments from the Emilia Romagna coast, an area periodically subjected to eutrophication, were investigated to determine the organic carbon and nitrogen content from the solid phase and organic and inorganic phosphorus, nitrogen and N/P ratio from a liquid elutriate from these sediments. The elutriates were tested for growth using a bioassay with a Gymnodinium sp. which previously caused extensive blooms in the Adriatic. Cultures were grown in the elutriates either enriched or unenriched with F/2 medium. Comparisons with controls were made on the basis of the maximum standing stock. The results obtained with the unenriched elutriates demonstrated the primary role of phosphate, while enriched elutriates produced slighter enhancement than the control. In most cases, the chemical composition of the elutriate was characterized by a negligible phosphate concentration, with respect to ammonium: the nutrient balance did not agree with the nutritional algal requirement. However, all the elutriates showed large quantities of inorganic and organic nitrogen. This finding could indicate that sediment-bound nitrogen may be a ready source of nitrogen for algal growth.     

Two wheat decapeptides prevent gliadin-dependent maturation of human dendritic cells

Celiac disease (CD) is a small intestinal enteropathy, triggered in susceptible individuals by the ingestion of dietary gluten.     

Larval feeding behaviour of Tetanocera elata (Diptera: Sciomyzidae): potential biocontrol agent of pestiferous slugs

Examining predatory behaviour is useful for determining the potential of novel biocontrol agents. We investigated the predatory behaviour of Tetanocera elata (Fabricius) larvae on the pestiferous slug Deroceras reticulatum (Müller). Results indicate three prey-finding strategies, including the predator reaching its prey without previous contact with it or its mucus trail.