Goran Kovačević

Quercetin vs chrysin: effect on liver histopathology in diabetic mice.

Effects of flavonoids quercetin and chrysin on lipid peroxidation and histopathological changes in liver of diabetic mice were studied and compared with the antioxidant and reducing ability of quercetin and chrysin and their ability to chelate Fe2+ ions in vitro. Diabetes was induced in Swiss albino mice with a single intravenous injection of alloxan (75 mg kg−1). Two days after alloxan injection, flavonoid preparations (50 mg kg−1 per day) were given intraperitoneally for 7 days in diabetic mice. The lipid peroxidation was evaluated by measuring the malondialdehyde production using the 2-thiobarbituric acid test. Administration of quercetin and chrysin to diabetic mice resulted in a significant decrease in lipid peroxidation level in liver tissue. Treatment of diabetic mice with flavonoids solutions results in decreased number of vacuolated cells and degree of vacuolization of the liver tissue. The protective role of flavonoids against the reactive oxygen species–induced damages in diabetic mice gives a hope that they may exert similar protective action in humans.

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.

The effects of CaCl2 and CaBr2 on the reproduction of Daphnia magna Straus.

Abstract Concentrated CaCl2 and CaBr2 salt solutions of densities up to 2.3 kg L-1 are regularly used to control hydrostatic pressure in oil wells during special operations in the exploration and production of natural gas and crude oil. Various concentrations of high density salts are frequently left in mud pits near the drilling site as waste, polluting fresh and ground waters by spillage and drainage. The toxic effects of these salts have already been observed. This study investigated the effects of CaCl2 and CaBr2 on water flea Daphnia magna Straus in a 21-day reproduction test. The three tested concentrations of CaCl2 (240, 481, and 1925 mg L-1) caused a significant dose-response decrease of reproduction (p<0.001). With CaBr2 (533 and 1066 mg L-1), only aborted eggs were produced, demonstrating the embryotoxicity of the substance. The results suggest that high concentrations of the tested chemicals are harmful to Daphnia’s reproduction and could reduce its abundance. Koncentrirane otopine soli CaCl2 i CaBr2 gustoće do 2,3 kg L-1 redovito se koriste za kontrolu hidrostatskoga tlaka u bušotinama tijekom posebnih operacija u istraživanju i proizvodnji prirodnoga plina i sirove nafte. Različite koncentracije soli visoke gustoće često su bile ostavljene u isplačnim jamama u blizini područja bušenja te su prelijevajući se ili ocjeđujući u podzemlje zagađivale slatke i podzemne vode. Iako je dosad već provedeno nekoliko istraživanja toksičnoga učinka koncentriranih otopina soli CaCl2 i CaBr2, u ovom radu istraživan je učinak CaCl2 i CaBr2 na vodenbuhu Daphnia magna u dvadesetjednodnevnom testu reprodukcije. Tri ispitane koncentracije CaCl2 (1925, 481 i 240 mg L-1) prouzročile su značajan, o dozi ovisan pad reprodukcije (p<0,001). U otopinama CaBr2 (533 i 1066 mg L-1) proizvedena su samo abortirana jaja, što pokazuje embriotoksičnost te tvari. Rezultati upućuju na to da su visoke koncentracije ispitivanih tvari štetne za razmnožavanje vodenbuhe te mogu smanjiti brojnost tih organizama.

Importance of an appropriate visual presentation for avoiding a misconception of the menstrual cycle

Abstract Family planning, the prevention of unwanted pregnancy, and women’s reproductive health are topics that have received close attention for decades. It would therefore be fair to assume that there exists a good knowledge of the menstrual cycle. However, it is clear that many people have various misconceptions about the menstrual cycle and fertile days or ovulation, and that this process is still largely taught with the aid of materials and images that have not changed for many years. We investigated the effect of moving away from the usual teaching practice of using a 28-day diagram showing ovulation on the 14th day. A total of 184 students from three different high schools, aged between 17 and 18, participated in this research. The students who were taught using three diagrams showing different durations of the menstrual cycle showed a significantly better adoption of the facts and concepts compared to the students who were taught using a diagram of the average 28-day cycle. Our results confirmed that it is highly important to use appropriate visual displays in the teaching of the menstrual cycle and that it is essential to enhance the visual literacy of students and teachers.

A comparison of hemocytes in Phasmatodea and Blattodea species

ABSTRACT: The aim of this study was to characterize and quantify hemocyte types in the Indian stick insect Carausius morosus (Phasmatidae) and in the tropical cockroaches Blaberus craniifer and Archimandrita tessellata (Blaberidae) cultivated in an insectary. Plasmatocytes, prohemocytes, granulocytes, coagulocytes and spherulocytes were found in the cockroaches. Of the mentioned cells, the Indian stick insect lacks spherulocytes. C. morosus had the lowest total hemocyte count (THC) and B. craniifer had the highest THC. However, the number of plasmatocytes was high in all the insects, but was more pronounced in C. morosus. In cockroaches, as expected, the differential hemocyte count (DHC) was similar, and contained a high number of spherulocytes. The number of coagulocytes was relatively low in all species. Our results contribute to insect hemocyte data and confirm the need for further intensive research into the function of hemocytes and into evolutionary ecology.

Impact of water level fluctuation in shaping of zooplankton assemblage in shallow lake

Abstract Shallow lakes are strongly affected by global climate changes reflected in significant parameters of ecosystem deterioration, i.e. biodiversity decrease, and water turbidity. Zooplankton research in Škrčev kut oxbow lake (Krapina River watershed, NW Croatia, Europe) was conducted during the summer of 2012 and 2013 with the aim to determine the effect of inter-annual, short-timescale changes of hydrological regime on environmental conditions, macrophytes, zooplankton and fish assemblage within an oxbow lake in the temperate region. Within one-year period the water level increased by 2 meters. This caused a significant reduction of floating-leaved macrophytes (i.e. Nuphar lutea), while turbidity, ortho-phosphate and chlorophyll a concentrations increased. These altered ecological conditions were reflected in the shift from floating-leaved macrophytes at the lower water level to phytoplankton-dominated lake at the higher water level. Zooplankton underwent significant alteration in assemblage. The results suggest that fish preference suppressed cladocerans and enhanced the rotifer and copepod abundance. Our results indicate that even in a short-timescale zooplankton assemblage mediates in the modification of ecosystem functioning.