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Companion animals, including bitches, may be exposed to zearalenone (ZEN) toxins that are often present in feed, and ZEN intoxication may lead to ovarian dysfunction. This study involved evaluation of the degree of ZEN-induced hypo stimulation of ovary by determination of proliferative and apoptotic indices and description of the ultra-structural organization of ovarian follicles in pre-pubertal bitches subjected to experimental, long-term exposure to low-dose ZEN mycotoxicosis. The experiment involved 30 clinically healthy, immature Beagle bitches aged approximately 70 days with initial average body weight of 8 kg, randomly divided into three groups of 10 animals each: two experimental groups (EI and EII) and a control group (C). Over a period of 42 days, ZEN was administered per os to EI animals at a dose of 50 μg/kg BW, and to EII bitches at a dose of 75 μg/kg BW. Control group animals were fed placebo containing no ZEN for 42 days. Analytical samples of the mycotoxin were administered daily in gelatin capsules before morning feeding. All the bitches were subjected to ovario-hysterectomy at the end of the experiment. Proliferation index (PCNA method) and apoptotic index (TUNEL test) values were determined by immune-histological analyses. The median for apoptotic index was determined at 13.45 for group EI, 17.84 for group EII, and 8.59 for group C. The median for proliferation index was determined at 35.25 for group EII, 42.44 for group EI, and 70.60 for group C. The results of ultra-structural examinations of the ovaries revealed that experimental, ZEN-induced hyperestrogenism enhanced apoptosis and lowered the proliferative ability of follicular cells what contributed to organelle destruction in pre-pubertal bitches. The changes observed were particularly advanced in EII animals, which were administered a higher dose of ZEN.
Zearalenone is an estrogenic mycotoxin that often contaminates plant material used in the production of feeds for companion animals. Small daily doses of ingested zearalenone - a competitive substrate modulating the activity of enzymes participating in estrogen biosynthesis at the pre-receptor level - can induce subclinical symptoms of hyperestrogenism in bitches. The objective of this study was to determine the effects of low zearalenone doses on the presence of estrogen receptors in the ovaries of pre-pubertal Beagle bitches. The bitches were divided into three groups of 10 animals each: experimental group I - 50 μg zearalenone/kg body weight administered once daily per os; experimental group II - 75 μg zearalenone/kg body weight administered once daily per os; control group - placebo containing no ZEN administered per os. The animals were ovariorectomized at the end of the experiment, at 112 days of age. Estrogen receptors were detected in ovarian specimens by immunohistochemical methods. The results revealed an absence of estrogen receptors alpha in all groups. In both experimental groups a decrease in the positive response of estrogen receptors beta in specified structures of ovaries was observed. Very low α-zearalenol levels probably attested to the slowing down (hypostimulation) of the biotransformation process. Overall, zearalenone intoxication led to hyperestrogenism during a specific developmental stage of pre-pubertal bitches. As regards hormesis, the threshold dose of zearalenone (adaptive capability) was exceeded in the ovaries of experimental group II animals. The results obtained in both experimental groups suggest that long-term exposure to low-dose zearalenone intoxication decreased the degree of estrogen receptors beta staining in particular structures of ovaries in the experimental bitches, which initiated epigenetic modification mechanisms that inhibited ovarian development.
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Zwierzęta mogą być narażone na działanie mikotoksyn w łańcuchu paszowym. Miko-toksyny występują głównie, jako zanieczyszczenia w paszy i mogą być wydalane w płynach biologicznych, takich jak mocz lub w mleku zwierząt lub ludzi, jako substancja macierzysta lub jako metabolit. Wiele prób dotyczących obecności mikotoksyn zostało przeprowadzonych na całym świecie i z badań tych wynika, że ma miejsce współwy-stępowanie mikotoksyn w materiałach paszowych i żywności. W rzeczywistości, wyni-ki sugerują, że w pewnych sytuacjach nawet 50% produktów mleczarskich może być zanieczyszczone przez mikotoksyny. Jednak opierając się na danych analitycznych w celu określenia stopnia ekspozycji mikotoksynami zwierząt i ludzi wyniki są słabo obiecujące ze względu na niejednorodny rozkład mikotoksyn w materiałach paszo-wych i produktach spożywczych, odstępu czasu pomiędzy pobraniem mikotoksyn, rozwojem choroby przewlekłej i niedokładności dietetycznych podczas określania danych w paszy i żywności. Jednak w porównaniu do innych płynów ustrojowych, takich jak krew, osocze czy mocz, to poziom wielu mikotoksyn w mleku zwierząt i ludzi jest raczej mały. Mleko matki jest istotnym źródłem mikotoksyn dla noworod-ków zwierząt i ludzi, ponieważ ich obecność została udokumentowana w próbkach pobranych w kilku krajach europejskich. Dlatego obecność mikotoksyny w mleku krów może być ważnym i poważnym problemem.
The objective of this study was to determine the effect of 42-day ZEN intoxication on the presence of Ca2+ in selected ovarian cells from beagle bitches, using the potassium pyroantimonate (PPA) method. Samples were collected from 30 clinically healthy, pre-pubertal, genetically homogeneous animals. The bitches were divided into three groups of 10 animals each: experimental group I - 50 μg ZEN/kg BW (100% NOAEL) administered once daily per os; experimental group II - 75 μg ZEN/kg BW (150% NOAEL) administered once daily per os; control group - placebo containing no ZEN administered per os. An electron microscopic analysis revealed that cells died due to apoptosis, depending on the ZEN dose and the type of cells exposed to intoxication. Lower ZEN doses led to apoptosis-like changes in the cells. Cell death was a consequence of excess Ca2+ accumulation in the mitochondria, followed by cell dysfunction and a decrease in or the absence of mitochondrial metabolic activity in oocytes, follicle cells and interstitial cells in experimental bitches.
Companion animals, including bitches, are exposed to intoxication with zearalenone (ZEN) present in feed, and the above may lead to reproductive disorders which are often noted in veterinary practice. The aim of this study was to determine the effect of long-term and low-dose ZEN intoxication on the immunoexpression (optical density) of 3ß-hydroxysteroid dehydrogenase (3ß-HSD) and 17ß-hydroxysteroid dehydrogenase (17ß-HSD) in the ovaries of pre-pubertal bitches. The experiment involved 30 clinically healthy, immature Beagle bitches aged approximately 70 days with initial average body weight of 8 kg. The animals were randomly divided into two experimental groups (EI and Ell) and a control group (C; n=10 in all groups). Group EI was administered 50 |ig ZEN/kg BWper os over a period of 42 days, group Ell received 75 |ig ZEN/kg BW per os for 42 days, and group C was administered placebo per os over a period of 42 days. Weighed amounts of the analyzed mycotoxin were administered every morning in gel capsules before feeding. The animals were subjected to ovariohysterectomy at the end of the experiment. Immunocytochemical analyses were performed to localize 3ß-HSD and 17ß-HSD enzymes and determine their optical density. The results revealed that changes in the immunoexpression of the above enzymes were inversely proportional to the applied dose of ZEN substrate.
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