Mirjana Kalafatić

Early toxic effects of fumonisin B1 in rat liver.

Mycotoxin fumonisin B1 (FB1) is hepatotoxic and carcinogenic in experimental animals. It is known that long-term exposure of experimental animals to FB1 causes apoptosis and lipid peroxidation. In this study, male adult Wistar rats were treated with single FB1 doses (5, 50, and 500 μg/kg b.w.) and sacrificed 4, 24, and 48 hours after treatment. Parameters of oxidative stress, histopathological changes, and DNA damage were monitored in the liver of treated and control animals. Parameters of oxidative stress were not affected by such treatment. A significant increase in apoptotic cells appeared in animals when 5 μg/kg b.w. dose was given and sacrificed after 24 hours with further increase at higher doses. In contrast to the number of mitotic figures and karyomegaly seen mostly at lower FB1 doses, necrosis was the prominent feature at higher doses. Significant increase in liver cells DNA mobility was observed 48 hours following treatment with 50 and 500 μg/kg b.w. as compared to control (tail length 15.2 ± 0.3, 16.4 ± 0.5, and 13.5 ± 0.1 μm, respectively). Tail intensity appeared to be more sensitive parameter for detecting DNA damage even at 5 μg/kg b.w. after 48 hours (1.69 ± 0.27% DNA; control 0.59 ± 0.11% DNA). This study proved that FB1-induced DNA damage is time- and dose-dependent, and that it could be caused in Wistar rats by a single dose.

Resistance of Two Planarian Species to UV-irradiation

The aim of this work was to determine the effects of 20, 25 and 30 minute UV-irradiation periods lambda = 253.5 nm to two planarian species Dugesia tigrina (Gir.) and Polycelis felina (Daly.). In vivo, UV light effects have been reported to affect intracellular receptors and disrupt simple behaviour. The effects of UV-rays on mortality and behavior as well as morphological, cytological and histological changes in the two planarian species were assessed, and the course and the dynamics of regenerative processes were compared between them. Experimental populations of Dugesia tigrina and Polycelis felina species were maintained in laboratory conditions at room temperature. Mortality, behavioral and morphological changes were monitored daily by means of a light stereomicroscope. For cytological and histopathological analysis, planarians were fixed in Bouine fixative on the first, second, third, fifth and seventh day after exposure to UV-irradiation, respectively. They were embedded in paraffin, cut on a microtome, stained with toluidin blue and embedded in Canada-balsam. UV-rays caused mortality, behavioral, morphological, cytological and histological changes in each planarian species. In regeneration of damaged body parts reticular cells and neoblasts played the main role. Neoblasts as totipotent cells extremely increased in number in the area of damaged tissue, immediately after UV-exposure. Dugesia tigrina was more sensitive to UV-rays than Polycelis felina due to possession of less pigmented cells. The course of regeneration in both species was similar. Most individuals of both species regenerated in 5 to 12 days after UV-irradiation.

Endosymbiotic alga from green hydra under the influence of cinoxacin

Cinoxacin (Cxn) showed a strong effect on the endosymbiotic algaChlorella; it was significantly damaged. Changes in algal color, position, structure and ultrastructure were found. In some algal cells ultrastructures were completely destroyed. The antichloroplastal and antimitochondrial effect was especially expressed. Damage to the thylakoid system of chloroplasts was more pronounced with increasing Cxn concentration. Some of the mitochondria were swollen and some of them were completely destroyed. From the evolutionary point of view, the correlation between antibacterial, and antichloroplastal and antimitochondrial effect of Cxn points to the evolutionary connection of chloroplasts and mitochondria with eubacteria.

Morphological features and isoenzyme characterization of endosymbiotic algae from green hydra

Symbiotic associations are of a wide significance in evolution and biodiversity. Green hydra is a typical example of endosymbiosis. In its gastrodermal myoepithelial cells, it harbors individuals of unicellular green algae. Morphological characteristics of isolated algae determined by light and electron microscopy are presented. Cytological morphometric parameters (cell area, cell radius, chloroplast area) of isolated algae from green hydra (Cx), as well as from reference species Chlorella kessleri (Ck) and Chlorella vulgaris (Cv), revealed similarity between the isolated endosymbiont and C. kessleri. Isoenzyme patterns of esterase (EST), peroxidase (POX), and catalase (CAT) were used for the investigation of genetic variability in endosymbiotic algae isolated from green hydra. Out of 14 EST isoenzymes observed in Cx species, 9 were expressed in the Cx sample. Results of the EST isoenzyme analysis indicated a higher degree of similarity between Cx and Cv than between Cx and Ck. Due to much higher heterogeneity, EST isoenzymes seem to be more suitable genetic markers for identification of different Chlorella species than CAT and POX isoenzymes. Results obtained suggest that symbiogenesis in green hydra has probably not been terminated yet.

POSTEMBRYONIC DEVELOPMENT OF DROSOPHILA MELANOGASTER MEIGEN, 1830 UNDER THE INFLUENCE OF QUERCETIN

ABSTRACT Quercetin is one of the best studied and most abundant flavonoid molecules in plants. Flavonoids are a large group of natural polyphenols that are almost ubiquitously present in the plants. The consumption of fruit and vegetables containing quercetin has been associated with several health benefits. In this study, we examined the impact of dietary quercetin (0, 0.005, 0.05, 0.5 and 1.75% quercetin by weight) on Drosophila melanogaster Meigen, 1830 postembryonic development and histological changes in larvae and females. A possible hormonmimetic (ecdysonergic) activity of quecetin was also studied on polytene chromosomes present in the larval salivary glands. We noticed a decrease in the duration of the larval period of flies raised on 1.75% quercetin diet. Quercetin-fed larvae entered metamorphosis sooner than the control ones. The most dramatic change was observed in larval fat body. Dark round structures were observed in fat body cells from larvae treated with quercetin.

Algal endosymbionts in European Hydra strains reflect multiple origins of the zoochlorella symbiosis

Symbiotic associations are of broad significance in evolution and biodiversity. Green Hydra is a classic example of endosymbiosis. In its gastrodermal myoepithelial cells it harbors endosymbiotic unicellular green algae, most commonly from the genus Chlorella. We reconstructed the phylogeny of cultured algal endosymbionts isolated and maintained in laboratory conditions for years from green Hydra strains collected from four different geographical sites within Croatia, one from Germany and one from Israel. Nuclear (18S rDNA, ITS region) and chloroplast markers (16S, rbcL) for maximum likelihood phylogenetic analyses were used. We focused on investigating the positions of these algal endosymbiotic strains within the chlorophyte lineage. Molecular analyses established that different genera and species of unicellular green algae are present as endosymbionts in green Hydra, showing that endosymbiotic algae growing within green Hydra sampled from four Croatian localities are not monophyletic. Our results indicate that the intracellular algal endosymbionts of green Hydra have become established several times independently in evolution.