Metabolic and endocrine effects of water and/or food deprivation in rats

Metabolic and endocrine effects of water and/or food deprivation in rats. We aim at studying the effect of water deprivation, food deprivation and their combination for three days on adrenal cortex, pituitary-thyroid axis and vasopressinergic system activity in rats. Corticosterone level was determined by fluorimetric method. The levels of free thyroxine (FT4) and thyroid stimulating hormone (TSH) were determined by immunoenzymatic assay and vasopressin (AVP) level was determined by radio-immunoassay. In all three groups, basal levels of plasma corticosterone were increased. A thyroid dysfunction was shown after water deprivation, food deprivation and their combination reflected by a significant decrease in FT4 levels. Paradoxically, a significant decrease in TSH level was observed in food-deprived rats and in rats subjected to simultaneous food and water deprivation, while a slight and not significant decrease in TSH level was shown in water-deprived rats. A significant increase in plasma AVP level was observed after water deprivation and simultaneous water and food deprivation, while no change was found after food deprivation. The data indicated that water deprivation, food deprivation and their combination stimulated the adrenal cortex, thereby suggesting a stress state. On the other hand, it seems that nutritional stress modifies the pituitary-thyroid axis through mechanisms different from those of osmotic stress. Moreover, it seems that food deprivation partially prevented the stimulatory effect of water deprivation on vasopressinergic system.     

Biochemical identification of proteasome-associated endonuclease activity in sunflower

Proteasomes have been purified from sunflower hypocotyles. They elute with a molecular mass of 600 kDa from gel filtration columns and two-dimensional gel electrophoresis indicates that the complex contains at least 20 different protein subunits. Peptide microsequencing revealed the presence of four subunits homologous to subunits Beta2, Beta6, Alpha5 and Alpha6 of plant proteasomes. These proteasomes have chymotrypsin-like activity and the highly purified fraction of this complex is associated with an endonuclease activity hydrolyzing Tobacco mosaic virus RNA and Lettuce mosaic virus RNA with a cleavage pattern showing fragments of well-defined size. This is the first evidence of a RNA endonuclease activity associated with plant proteasomes.     

Overexpression of the triose phosphate translocator (TPT) complements the abnormal metabolism and development of plastidial glycolytic glyceraldehyde‐3‐phosphate dehydrogenase mutants

The presence of two glycolytic pathways working in parallel in plastids and cytosol has complicated the understanding of this essential process in plant cells, especially the integration of the plastidial pathway into the metabolism of heterotrophic and autotrophic organs. It is assumed that this integration is achieved by transport systems, which exchange glycolytic intermediates across plastidial membranes. However, it is unknown whether plastidial and cytosolic pools of 3‐phosphoglycerate (3‐PGA) can equilibrate in non‐photosynthetic tissues. To resolve this question, we employed Arabidopsis mutants of the plastidial glycolytic isoforms of glyceraldehyde‐3‐phosphate dehydrogenase (GAPCp) that express the triose phosphate translocator (TPT) under the control of the 35S (35S:TPT) or the native GAPCp1 (GAPCp1:TPT) promoters. TPT expression under the control of both promoters complemented the vegetative developmental defects and metabolic disorders of the GAPCp double mutants (gapcp1gapcp2). However, as the 35S is poorly expressed in the tapetum, full vegetative and reproductive complementation of gapcp1gapcp2 was achieved only by transforming this mutant with the GAPCp1:TPT construct. Our results indicate that the main function of GAPCp is to supply 3‐PGA for anabolic pathways in plastids of heterotrophic cells and suggest that the plastidial glycolysis may contribute to fatty acid biosynthesis in seeds. They also suggest a 3‐PGA deficiency in the plastids of gapcp1gapcp2, and that 3‐PGA pools between cytosol and plastid do not equilibrate in heterotrophic cells.     

A Comparative Study of the Oxidative Profile in Graves’ Disease, Hashimoto’s Thyroiditis, and Papillary Thyroid Cancer

The aim of this study was to evaluate and compare the oxidative profiles of three thyroid disorders: Graves’ disease (GD), Hashimoto thyroiditis (HT), and papillary thyroid cancer (PTC). Malondialdehyde levels (MDA), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) activities were examined in the plasma of 52 patients (29 untreated HT, 16 untreated GD, and 7 PTC who underwent surgical therapy). Results were compared with those of 30 healthy controls and among the three groups of patients. The GD, HT, and PTC patients exhibited increased plasma MDA levels and SOD activities compared with the controls (p?<?0.05, p?<?0.05, and p?<?0.001, respectively). CAT activities significantly increased only for the PTC and HT patients (p?<?0.001 and p?<?0.05, respectively), whereas GPx activities significantly decreased only in the GD and PTC (p?<?0.05 and p?<?0.01, respectively). The comparison among the three groups of patients has shown increased MDA level and SOD activity for the PTC patients as compared to the GD patients (p?<?0.01 and p?<?0.001, respectively). Compared with HT, PTC patients exhibited significant higher MDA level, SOD, and CAT activities and a significant lower GPx activity (p?<?0.01, p?<?0.001, p?<?0.05, and p?<?0.05, respectively). No significant discrepancies were noted between the GD and HT patients. Our results have clearly shown an oxidative profile that is highly disturbed for the PTC patients as compared to those of autoimmune disorders. Future studies are needed to determine whether or not the oxidative stress has a prognostic value in this pathology.     

High Resolution Genome-Wide Analysis of Chromosomal Alterations in Burkitt's Lymphoma

Additional chromosomal abnormalities are currently detected in Burkitt''s lymphoma. They play major roles in the progression of BL and in prognosis. The genes involved remain elusive. A whole-genome oligonucleotide array CGH analysis correlated with karyotype and FISH was performed in a set of 27 Burkitt''s lymphoma-derived cell lines and primary tumors. More than half of the 145 CNAs<2 Mb were mapped to Mendelian CNVs, including GSTT1, glutathione s-transferase and BIRC6, an anti-apoptotic protein, possibly predisposing to some cancers. Somatic cell line-specific CNVs localized to the IG locus were consistently observed with the 244 K aCGH platform. Among 136 CNAs >2 Mb, gains were found in 1q (12/27), 13q (7/27), 7q (6/27), 8q(4/27), 2p (3/27), 11q (2/27) and 15q (2/27). Losses were found in 3p (5/27), 4p (4/27), 4q (4/27), 9p (4/27), 13q (4/27), 6p (3/27), 17p (3/27), 6q (2/27),11pterp13 (2/27) and 14q12q21.3 (2/27). Twenty one minimal critical regions (MCR), (range 0.04–71.36 Mb), were delineated in tumors and cell lines. Three MCRs were localized to 1q. The proximal one was mapped to 1q21.1q25.2 with a 6.3 Mb amplicon (1q21.1q21.3) harboring BCA2 and PIAS3. In the other 2 MCRs, 1q32.1 and 1q44, MDM4 and AKT3 appeared as possible drivers of these gains respectively. The 13q31.3q32.1 <89.58–96.81> MCR contained an amplicon and ABCC4 might be the driver of this amplicon. The 40 Kb 2p16.1 <60.96–61> MCR was the smallest gained MCR and specifically encompassed the REL oncogene which is already implicated in B cell lymphomas. The most frequently deleted MCR was 3p14.1 <60.43–60.53> that removed the fifth exon of FHIT. Further investigations which combined gene expression and functional studies are essential to understand the lymphomagenesis mechanism and for the development of more effective, targeted therapeutic strategies.     

Biochemical evaluation of hepatic damage in subchronic exposure to malathion in rats: effect on superoxide dismutase and catalase activities using native PAGE

The aim of this study was the evaluation of the hepatic damages following a subchronic exposure to malathion, an organophosphorus (OP) insecticide. Malathion was administered intragastrically in 1 ml corn oil containing 100 mg/kg Body Weight daily for 32 days. Malondialdehyde (MDA) concentration superoxide dismutase (SOD) and catalase (CAT) activities were analysed using a non-denaturing electrophoresis. The serum activities of Pseudocholinesterase (PchE), aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) were determined. Malathion exposure leads to a significant decrease in AchE activity, an increase in hepatic MDA, and in serum ASAT and ALAT activities. A positive correlation between serum transaminases levels and hepatic MDA was demonstrated. These results indicate that malathion exposure induced lipid peroxidation LPO, a process of degradation of membrane lipids, involving the deterioration of the cellular integrity. We have recorded a slight increase in antioxidant enzymes activities. This leads us to suggest an insufficient elimination of free radicals, causing cytotoxic effects. To cite this article: R. Rezg et al., C. R. Biologies 331 (2008).     

Substrate affinity and substrate specificity of proteasomes with RNase activity

We have partially reconstituted 20S proteasome/RNA complexes using oligonucleotides corresponding to ARE (adenosine- and uridine-rich element) (AUUUA)₄ and HIV-TAR (human immunodeficiency virus-Tat transactivation response element), a stem-loop structure in the 5 UTR (untranslated region) of HIV-mRNAs. We demonstrate that these RNAs which associate with proteasomes are degraded by proteasomal endonuclease activity. The formation of these 20S proteasome/RNA substrate complexes is rather specific since 20S proteasomes do not interfere with truncated TAR that is not cleaved by proteasomal endonuclease. In addition, affinity of proteasomes for (AUUUA)₄ is much stronger as it is for HIV-TAR. These results provide further arguments for our hypothesis that proteasomes could be involved in the destabilisation of cytokines mRNAs containing AUUUA sequences as well as viral mRNAs.