Comparative ecotoxicity of single and binary mixtures exposures of cadmium and zinc on growth and biomarkers of Lemna gibba

In the present study, single and mixture effects of cadmium (Cd) and zinc (Zn) on Lemna gibba were analyzed and compared using growth parameters, based on frond number and fresh weight, and biochemical parameters, such as pigment, protein content and activity of antioxidant enzymes. Plants were exposed for 7 days to these metals in nutrient solution. Single and mixture exposures affected plant growth and the biomarkers of the antioxidant response. Considering the growth parameters, Cd was found to be much more toxic than Zn. IC50-7d, based on growth rate calculated on frond number, were 17.8 and 76.73 mg/L, and on fresh weight were 1.08 and 76.93 mg/L, for Cd and Zn respectively. For Cd, LOEC values were obtained at 2.06 and 1.03 mg/L, for frond number and fresh weight respectively; while for Zn, at 20.1 and 74.6 mg/L. A high toxicity effect, considering the same response variables, was observed in plants exposed to the mixtures. Three fixed ratios, based on toxic units (TU) were assayed, ratio 1: 2/3 Cd−1/3 Zn, ratio 2: 1/2 Cd−1/2 Zn and ratio 3: 1/3 Cd−2/3 Zn. Ratio 3 (where Zn was added in higher proportion) was the less toxic. All concentrations of Ratio 1 and 2 significantly inhibited plant growth, showing a 100% inhibition of growth rate at the highest concentrations when based on frond number. Catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APOX; EC 1.11.1.11) and guaiacol peroxidase (GPOX; EC 1.11.1.7) activities in single metals assays were higher than controls. In mixture tests, the activity of APOX and GPOX was significantly stimulated in plants exposed to all evaluated combinations, while CAT was mainly stimulated in Ratio 3. It was observed that the activity of the enzymes was increased in the mixtures compared with similar concentrations evaluated individually. APOX activity was observed to fit the CA model and following a concentration-response pattern. The response of this antioxidant enzyme could serve as a sensitive stressor biomarker for Cd–Zn interactions. Frond number in Cd–Zn mixtures was not well predicted from dissolved metal concentration in solution using concentration addition (CA) as reference model, as results showed that toxicity was more than additive, with an average of ΣTU = 0.75. This synergistic effect was observed up to 50 mg Zn/L in the mixture, but when it was present in higher concentrations a less than additive effect was observed, indicating a protective effect of Zn. A synergistic and dose-ratio deviations from CA model were also observed.     

Increased proliferation and apoptosis of colonic epithelial cells in dextran sulfate sodium-induced colitis in rats

We have evaluated morphologic alterations and epithelial cell apoptosis and proliferation of colonic mucosa in the acute and chronic phases of DSS-induced colitis. Colitis was induced in Sprague-Dawley rats by 7 days of 4% DSS oral administration followed by 7 days of tap water for one, two, and three cycles. Control rats receved tap water only. Morphological changes in colonic mucosa were evaluated and scored by light and scanning electron microscopy. Apoptosis was studied by TUNEL assay and cell proliferation by Ki-67 immunoreaction. The expression of both proapoptotic (Fas, FasL, Bax, p53) and antiapoptotic (Bcl2) cellular proteins was determined by immunohistochemistry. Morphologic assessment showed the most severe colonic epithelial lesions and inflammation in the distal colon with a trend to increasing severity from the first to the third DSS cycle. In DSS rats, the epithelial apoptotic index increased 20-fold after the first cycle and 120-fold after the second and third cycles compared with the controls; in the same way, the expression index of proapoptotic proteins (Fas, FasL, Bax, p53) dramatically increased. The proliferative index increased about 40 to 60-fold compared to controls, with no difference among the three DSS cycles. In conclusion, DSS-induced colitis in rats, which has many structural and ultrastructural features similar to those seen in human ulcerative colitis, is a suitable model for studying increased epithelial apoptosis and proliferation. Further studies employing this model will permitt two hypotheses to be tested. (1) Increased apoptosis may lead to a breakdown of the epithelial barrier function and facilitate the mucosal invasion of intraluminal microorganisms and/or antigens. (2) Abnormal and persistent epithelial hyperproliferation could be causally related to the development of colorectal cancers in the setting of chronic colonic inflammation.     

Solitary fibrous tumor of the liver

We report a new case of benign solitary fibrous tumor (SFT) of the liver. A 65‐year‐old man presented to our unit with upper right abdominal discomfort. On examination abdominal distension was present and palpation showed a large firm mass in the right hypochondrium and epigastrium. The patient's past medical history was not significant and laboratory tests were normal. Ultrasonography and computed tomography showed a large tumor, 20 cm in diameter, in the right lobe of the liver. An extended right hepatectomy was performed. The tumor measured 30 × 28 × 14 cm and weighed 4725 g. Microscopic evaluation showed a benign SFT of the liver with tumor cells typically positive for vimentin and CD34. The postoperative course was uneventful, and the patient is alive 30 months after surgery. This is a rare neoplasm of mesenchymal origin that occasionally involves the liver in adult patients. Most SFTs are benign, but some may have malignant histological features and recur locally or metastasize. Because of their rarity, overall experience has not been significant and little has been published concerning this tumor, Including the present one, 28 cases have been reported in the English literature. Surgery is the mainstay of treatment. Little can be said about the benefits of adjuvant radiochemotherapy in these patients. As SFT of the liver is often a benign neoplasm, chemotherapy or radiotherapy should not be necessary, and should be reserved for when resection is incomplete and/or histological examination reveals features of malignancy. Surgeons must be aware of SFT of the liver, and this neoplasm should be included in the differential diagnosis of a single large hepatic mass.