A number of fish species have been used for studies on endocrine disrupting chemicals (EDCs). However, despite the widespread use of oviparous fish, relatively little attention has been given to viviparous species. This study investigated the effects of EDCs in a viviparous fish and examined the possible usefulness of the fish as an alternative model for the studies on EDCs. Swordtails (Xiphophorus helleri) were exposed to nonylphenol (NP), bisphenol A (BPA), and their mixture. Both short-term (3-d) and relatively long-term (60-d) exposures were carried out using adult male and 30-d-old juvenile fish, respectively. Following the short-term exposure, both NP and BPA caused vitellogenin mRNA expression. Flow cytometric analysis and terminal deoxynucleotidyl transferase assay on the testes of treated fish indicated reproductive damage. Histopathological analysis found degenerative and necrotic cells in seminiferous tubules following the exposure to 100 ppb NP. The testes with lesions were also associated with highly suppressed spermatogenesis. Following the long-term exposure, both NP and BPA exposures significantly affected the growth of swordtails. In all cases, the results showed that the mixture was always more potent than a single chemical and that swordtail fish can be a useful model for the study of endocrine disruptors.

A number of fish species have been used for studies on endocrine disrupting chemicals (EDCs). However, despite the widespread use of oviparous fish, relatively little attention has been given to viviparous species. This study investigated the effects of EDCs in a viviparous fish and examined the possible usefulness of the fish as an alternative model for the studies on EDCs. Swordtails (Xiphophorus helleri) were exposed to nonylphenol (NP), bisphenol A (BPA), and their mixture. Both short-term (3-d) and relatively long-term (60-d) exposures were carried out using adult male and 30-d-old juvenile fish, respectively. Following the short-term exposure, both NP and BPA caused vitellogenin mRNA expression. Flow cytometric analysis and terminal deoxynucleotidyl transferase assay on the testes of treated fish indicated reproductive damage. Histopathological analysis found degenerative and necrotic cells in seminiferous tubules following the exposure to 100 ppb NP. The testes with lesions were also associated with highly suppressed spermatogenesis. Following the long-term exposure, both NP and BPA exposures significantly affected the growth of swordtails. In all cases, the results showed that the mixture was always more potent than a single chemical and that swordtail fish can be a useful model for the study of endocrine disruptors.

ABSTRACT. At present, the effect of cyclin D2 implicated in cell cycle regulation, differentiation, and oncogenic transformation is not fully confirmed. To better elucidate the role of cyclin D2 in controling the cell proliferation, cyclin D2 expression level was determined at the early initiation and promotion stages during the in vitro two-stage transformation process of Balb/3T3 A31 cells. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced G2/M-arrested cells expressed low level of cyclin D2 mRNA, while the contact-inhibited nonproliferating cells expressed high level of cyclin D2 mRNA. In the transformed proliferating cells at the promotion stage, cyclin D2 mRNA was not expressed. These data suggest that cyclin D2 expression may be associated with the type of growth arrest and nonproliferating state, but not with the cell proliferation and transformation.KEY WORDS: cyclin D2, G2/M arrest, transformation.J. Vet. Med. Sci. 64(3): 201-205, 2002 The D-type cyclins synthesized during the early G1 phase consist of three family members, cyclins D1, D2, and D3. Cyclin D1, encoded by bcl-1/PRAD1 oncogene, is an important cell cycle positive regulator facilitating the G1 progression toward the S phase similar to cyclin E and PCNA [23]. Cyclins D2 and D3 were cloned as a consequence of their homologies to cyclin D1 [10,15,23], and cyclin D2 was also independently identified to be encoded by a gene mutated with proviral insertion [8]. Aberrant expression of cyclin D2 has been linked to the human male germ cell tumorigenesis [9]. Moreover, overexpression of the cyclin D2 has been determined in chronic B-cell malignancies [5] and is known to be closely correlated with the gastric cancer progression and prognosis [19,20]. Cyclin D2 was expressed highly in transformed cells as well [6]. In addition, this cyclin has been linked to the differentiation of neural cell populations [16,17] and the activation of macrophage [21]. Furthermore, coexpression of cyclin D2 and Ha-Ras under low-serum conditions can induce a senescence-like phenotype [12]. However, several papers also reported that cyclin D2 was overexpressed in various nonproliferating states [11,14,18]. These results suggest that cyclin D2 may have different roles depending on its levels of expression and cell type. Therefore, to further understand the role of cyclin D2 on the cell proliferation, we determined the cyclin D2 mRNA expression level in G2/M-arrested cells initiated by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), contact-inhibited cells, and proliferating cells during the in vitro two-stage transformation process of Balb/ 3T3 A31 cells. MATERIALS AND METHODSChemicals: MNNG, cadmium chloride (CdCl 2 ), Tri reagent, and other commonly used chemicals were purchased from Sigma (St. Louis, MO, U.S.A.). Dulbecco's modified Eagle's medium (DMEM), DMEM/F12 medium and bovine calf serum (BCS) were obtained from GIBCO-BRL (Gaithesburg, MD, U.S.A.). Digoxigenin (DIG)-RNA labeling and detection kit, and β-actin plasmid cDNA were purchased from Boehringer Mannheim (Ma...

SummaryFive moldy corn samples were analyzed for Fusarium mycotoxins including 8-ketotrichothecenes, zeralenone (ZEA), and fumonisins and found to be heavily contaminated with these toxins. Among 8-ketotrichothecenes, deoxynivalenol (DON), 15-acetyl-DON, and nivalenol (NIV) were the major toxins rather than 3-acetyl-DON and 4-acetyl-NIV.In addition, one moldy corn sample was contaminated with iso-DON, which has the same molecular weight of DON. This is the first report iso-DON and DON as well as other Fusarium mycotoxins were occurred in moldy corn from Korea.