Application of the OECD 301F respirometric test for the biodegradability assessment of various potential endocrine disrupting chemicals

The biodegradability of several potential endocrine disrupting compounds, namely 4-n-nonylphenol (4-n-NP), nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO), bisphenol A (BPA), triclosan (TCS), di-(2-ethylhexyl)-phthalate (DEHP), perfluorooctanoate (PFOA) and perfluorononanoate (PFNA) was evaluated in this study, using OECD method 301F (manometric respirometry test) and activated sludge as inoculum. According to the results, 4-n-NP and BPA meet the strict definition of ready biodegradability and they are not expected to be persistent during the activated sludge process. Partial biodegradation was observed for DEHP (58.7+/-5.7%, n=3), TCS (52.1+/-8.5%, n=3) and NP1EO (25.9+/-8.1%, n=3), indicating their possible biodegradation in wastewater treatment systems, while no biodegradation was observed for NP2EO, PFOA and PFNA. Experiments in the co-presence of a readily biodegradable compound showed the absence of co-metabolic phenomena during 4-n-NP, BPA and TCS biodegradation. Using first order kinetics to describe biodegradation of the target compounds, half-lives of 4.3+/-0.6, 1.3+/-0.2, 1.8+/-0.5, 6.9+/-2.6 days were calculated for 4-n-NP, BPA, TCS and DEHP, respectively. Toxicity tests using marine bacterium Vibrio fischeri showed that biodegradation of 4-n-NP, NP1EO, BPA and TCS is a simultaneous detoxification process, while possible abiotic or biotic transformations of NP2EO, DEHP, PFOA and PFNA during respirometric test resulted to significant increase of their toxicities.     

Alternative photosynthetic electron flow to oxygen in marine Synechococcus

Cyanobacteria dominate the world's oceans where iron is often barely detectable. One manifestation of low iron adaptation in the oligotrophic marine environment is a decrease in levels of iron-rich photosynthetic components, including the reaction center of photosystem I and the cytochrome b₆f complex [R.F. Strzepek and P.J. Harrison, Photosynthetic architecture differs in coastal and oceanic diatoms, Nature 431 (2004) 689-692.]. These thylakoid membrane components have well characterised roles in linear and cyclic photosynthetic electron transport and their low abundance creates potential impediments to photosynthetic function. Here we show that the marine cyanobacterium Synechococcus WH8102 exhibits significant alternative electron flow to O₂, a potential adaptation to the low iron environment in oligotrophic oceans. This alternative electron flow appears to extract electrons from the intersystem electron transport chain, prior to photosystem I. Inhibitor studies demonstrate that a propyl gallate-sensitive oxidase mediates this flow of electrons to oxygen, which in turn alleviates excessive photosystem II excitation pressure that can often occur even at relatively low irradiance. These findings are also discussed in the context of satisfying the energetic requirements of the cell when photosystem I abundance is low.     

DNA ploidy and immunomarking of bladder urothelial tumors before and after intravesical bacillus Calmette-Guérin treatment

OBJECTIVE: To investigate DNA ploidy and immunoexpression of Ki-67 and p53 as predictivefactors in cases of superficial urothelial cell carcinoma (UCC) treated with bacillus Calmette-Guérin (BCG). STUDY DESIGN: Samples were obtained from 66 patients with UCC (pTa grade 3 or high grade and pT1 independent of grade or with concomitant carcinoma in situ) before and after intravesical BCG treatment. DNA ploidy analysis (ploidy balance, degree of hyperploidy and aneuploidy, proliferation index) was done by static cytometry. Ki-67 and p53 were analyzed immunohistochemically in paraffin-embedded tissue, and their quantification was carried out using an image analysis system. RESULTS: During a mean follow-up of 63.8 months, 31 of the 66 patients developed recurrent tumors (46.9%). DNA ploidy analysis showed that ploidy balance as well as degree of hyperploidy and aneuploidy were not statistically different between recurrent and nonrecurrent tumors. Only proliferation index was statistically significant between recurrent and nonrecurrent tumors. No statistically significant difference was observed in the percentage of Ki-67- and p53-positive cells between primary tumors that recurred and those that did not. CONCLUSION: These findings suggest that only proliferation index has predictive value for recurrence and progression in UCC treated with BCG.     

Cadherins mediate both the association between PS1 and beta-catenin and the effects of PS1 on beta-catenin stability

Presenilin1 (PS1), a protein involved in cellular development, forms functional complexes with beta-catenin, a regulator of Wnt signaling and cell-cell adhesion. In addition, both proteins have been shown to play important roles in disease including cancer and Alzheimer disease. Although PS1 and beta-catenin are found in the same complexes, it is not clear whether they bind directly to each other or a third complex component, like cadherin, may mediate their interactions. Here we show that PS1 and beta-catenin form no detectable complexes in cells that express no cadherin. In contrast, these complexes are readily found in E-cadherin containing cells. Furthermore, binding of both PS1 and beta-catenin to E-cadherin is necessary for the formation of PS1/beta-catenin complexes. Importantly, our data show that binding of PS1 to cadherin mediates the effects of PS1 on the phosphorylation, ubiquitination, and destabilization of beta-catenin. Thus, cadherins mediate both the association of PS1 and beta-catenin and the effects of PS1 on the cellular levels of beta-catenin.     

Characterization of human thioredoxin-like 2. A novel microtubule-binding thioredoxin expressed predominantly in the cilia of lung airway epithelium and spermatid manchette and axoneme

We describe here the cloning and characterization of a novel member of the thioredoxin family, thioredoxin-like protein 2 (Txl-2). The Txl-2 open reading frame codes for a protein of 330 amino acids consisting of two distinct domains: an N-terminal domain typical of thioredoxins and a C-terminal domain belonging to the nucleoside-diphosphate kinase family, separated by a small interface domain. The Txl-2 gene spans approximately 28 kb, is organized into 11 exons, and maps at locus 3q22.3-q23. A splicing variant lacking exon 5 (Delta 5Txl-2) has also been isolated. By quantitative real time PCR we demonstrate that Txl-2 mRNA is ubiquitously expressed, with testis and lung having the highest levels of expression. Unexpectedly, light and electron microscopy analyses show that the protein is associated with microtubular structures such as lung airway epithelium cilia and the manchette and axoneme of spermatids. Using in vitro translated proteins, we demonstrate that full-length Txl-2 weakly associates with microtubules. In contrast, Delta 5Txl-2 specifically binds with very high affinity brain microtubule preparations containing microtubule-binding proteins. Importantly, Delta 5Txl-2 also binds to pure microtubules, proving that it possesses intrinsic microtubule binding capability. Taken together, Delta 5Txl-2 is the first thioredoxin reported to bind microtubules and might therefore be a novel regulator of microtubule physiology.     

Probing green algal hydrogen production

The recently developed two-stage photosynthesis and H(2)-production protocol with green algae is further investigated in this work. The method employs S deprivation as a tool for the metabolic regulation of photosynthesis. In the presence of S, green algae perform normal photosynthesis, carbohydrate accumulation and oxygen production. In the absence of S, normal photosynthesis stops and the algae slip into the H(2)-production mode. For the first time, to our knowledge, significant amounts of H(2) gas were generated, essentially from sunlight and water. Rates of H(2) production could be sustained continuously for ca. 80 h in the light, but gradually declined thereafter. This work examines biochemical and physiological aspects of this process in the absence or presence of limiting amounts of S nutrients. Moreover, the effects of salinity and of uncouplers of phosphorylation are investigated. It is shown that limiting levels of S can sustain intermediate levels of oxygenic photosynthesis, in essence raising the prospect of a calibration of the rate of photosynthesis by the S content in the growth medium of the algae. It is concluded that careful titration of the supply of S nutrients in the green alga medium might permit the development of a continuous H(2)-production process.