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Is methylmercury a new candidate obesogen?
- Gilles Tinant, Ineke Neefs, Jean-François Rees, Yvan Larondelle, Cathy Debier
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- Journal:
- Proceedings of the Nutrition Society / Volume 79 / Issue OCE2 / 2020
- Published online by Cambridge University Press:
- 10 June 2020, E280
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Recent studies suggest that environmental pollutants play a role in the continuous increase of the worldwide prevalence of obesity. To our knowledge, there is only one study investigating the impacts of methylmercury, a common and more toxic form of mercury, mainly present in fish and shellfish, on adipose tissue. It shows that methylmercury can cause changes in the structure and function of 3T3-L1 preadipocytes. In this context, we decided to study the effects of methylmercury on primary cultured adipocytes of rainbow trout. This species is a well-known model to study the impact of pollution. In addition, fish adipose tissue metabolism is close to the one of humans. Using an in vitro model allows us to focus on adipocyte differentiation and lipid metabolism.
Preadipocytes were obtained after isolating precursor cells from perivisceral adipose tissue by enzymatic digestion. Cells were cultured at 19°C until confluence before being incubated for 6 days in growth medium supplemented or not with a hormonal cocktail (insulin, dexamethasone, ciglitizone) enriched with 0, 0.3, 1.7 or 3.8 mM of methylmercury and lipid mixture. Cytotoxicity was evaluated every two days via LDH assay. At day 6, quantification of total mercury in cells was performed with Direct Mercury Analyser-80. Phospholipid and neutral lipid fractions were analyzed by gas chromatography and expression of adipocyte-related genes was evaluated by RT-PCR. Three biological replicates were carried out.
No cytotoxicity was observed during the methylmercury treatment. Methylmercury was partially accumulated but in a dose-dependent manner. At day 6, all fatty acids (FA) from neutral lipid fraction significantly increased at the highest methylmercury concentration. However, the rate of increase was different for each FA. In particular, n-3 polyunsaturated FA were preferentially accumulated. The total amount of phospholipids was not impacted by methylmercury but a decrease of n-6 polyunsaturated FA was observed. Surprisingly, methylmercury decreased the expression of three adipocyte markers, FA transport protein 1 and glycerol-3-phosphate dehydrogenase in presence or absence of hormonal cocktail, and CCAAT/enhancer binding protein delta in presence of hormonal cocktail. On the other hand, methylmercury increased the expression of FA synthase and perilipin.
As a conclusion, methylmercury appears to be a candidate obesogen as it increased the cellular lipid content in primary cultured trout adipocytes. Additional genes involved in adipogenesis, FA de novo synthesis and FA intracellular transport are being investigated. Further experiments currently conducted in our lab should allow us to better clarify the mechanisms involved.
Zeeman Doppler Imaging of Stars with the AAT
- Brad Carter, Steve Brown, Jean-François Donati, David Rees, Meir Semel
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- Journal:
- Publications of the Astronomical Society of Australia / Volume 13 / Issue 2 / May 1996
- Published online by Cambridge University Press:
- 25 April 2016, pp. 150-155
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Zeeman Doppler Imaging (ZDI) is a recent technique for measuring magnetic fields on rapidly rotating, active stars. ZDI employs spectropolarimetry taken at different rotational phases to derive information on the magnetic field distribution over the stellar surface. The Zeeman effect is used to identify the presence of a magnetic field, and variations in Doppler wavelength shifts across the rapidly rotating star allow fields to be resolved on different parts of the visible disk. Analysis of the spectra can be used to produce both thermal and surface magnetic images. ZDI requires very high S/N spectra to be acquired within a time interval short compared to the stellar rotation period. As a result, a large-aperture telescope is needed. Since an initial successful test in 1989, the 3·9 m Anglo-Australian Telescope has been used to obtain ZDI spectra of active stars of different evolutionary stages. The observations have concentrated on the K subgiant in the RSCVn system HR 1099 to monitor changes on this bright and active star. With the advent in 1991 of ZDI spectropolarimetry with the AAT échelle spectrograph, it has become possible to co-add the polarisation signature from the many magnetically sensitive lines recorded simultaneously. As a result, stellar magnetic field detections of unprecedented quality have been obtained. The aims of this paper are to briefly outline the principles of ZDI, describe the instrumental setup at the AAT and present some preliminary results from recent observations.
Effect of prooxidant agents added at the morula/blastocyst stage on bovine embryo development, cell death and glutathione content
- Jean-Magloire Feugang, Anne Van Langendonckt, Hichem Sayoud, Jean-François Rees, Serge Pampfer, André Moens, Franz Dessy, Isabelle Donnay
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Two prooxidant agents, 2,2′-azobis(2-amidinopropane)dihydrochloride (AAPH), a generator of free radicals in the culture medium, and buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, were used to reinforce from the morula stage (day 5 post-insemination, p.i.) the oxidative stress encountered by bovine embryos in culture. Exposure to increasing concentrations of both prooxidants from the morula stage did not affect blastocyst formation but some blastocysts were found degenerated on day 8 in a dose-dependent manner (0, 0.001, 0.01, 0.1 mM AAPH gave respectively 0, 10%, 32%, 48% degeneration, while 0, 0.1, 0.2, 0.4 mM BSO led respectively to 0, 14%, 30%, 41% degeneration). Hatching rates and cell numbers of surviving blastocysts were not affected. Morulae and early blastocysts exposed from day 5 to day 6 p.i. appeared more resistant than expanded blastocysts (75-80% survival vs 20-65%; p <0.05). Treatment with BSO significantly decreased the level of reduced glutathione in day 7 blastocysts (0.02 vs 0.42 pmol per embryo in the control) while AAPH had no effect (0.38 pmol per embryo). The proportion of cells showing membrane lesions was increased in degenerated blastocysts from day 7.5 p.i. In AAPH-treated, but not in BSO-treated embryos, cell membrane permeabilisation seems to occur before blastocyst degeneration. DNA fragmentation evaluated by the TUNEL technique was increased in day 7 blastocysts by both prooxidants (2.8 ± 0.4 in the control group vs 4.5 ± 0.4 and 6.0 ± 0.4 respectively in the AAPH- and BSO-treated groups). Addition of an inhibitor of caspase-3, DEVD-CHO, partially prevented DNA fragmentation, indicating that prooxidant treatment induced a caspase-dependent pathway of apoptosis.