Adaptative Response (adaptative + response)

Distribution by Scientific Domains

Selected Abstracts

Adaptative response of antioxidant enzymes in different areas of rat brain after repeated d -amphetamine administration

Félix Carvalho
d-Amphetamine has been shown to be a potential brain neurotoxic agent, particularly to dopaminergic neurones. Reactive oxygen species indirectly generated by this drug have been indicated as an important factor in the appearance of neuronal damage but little is known about the adaptations of brain antioxidant systems to its chronic administration. In this study, the activities of several antioxidant enzymes in different areas of rat brain were measured after repeated administration of d-amphetamine sulphate (sc, 20 mg/kg/day, for 14 days), namely glutathione-S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GRed), catalase, and superoxide dismutase (SOD). When compared to a pair-fed control group, d-amphetamine treatment enhanced the activity of GST in hypothalamus to 167%, GPx in striatum to 127%, in nucleus accumbens to 192%, and in medial prefrontal cortex to 139%, GRed in hypothalamus to 139%, as well as catalase in medial prefrontal cortex to 153%. However, the same comparison revealed a decrease in the activity of GRed in medial pre-frontal cortex by 35%. Food restriction itself reduced GRed activity by 49% and enhanced catalase activity to 271% in nucleus accumbens. The modifications observed for the measured antioxidant enzymes reveal that oxidative stress probably plays a role in the deleterious effects of this drug in CNS and that, in general, the brain areas studied underwent adaptations which provided protection against the continuous administration of the drug. [source]

Hepcidin , central regulator of iron metabolism

Valeriu Atanasiu
Abstract The knowledge about mammalian iron metabolism has advanced dramatically over the past decades. Studies of genetics, biochemistry and molecular biology allowed us the identification and characterization of many of the molecules involved in regulation of iron homeostasis. Important progresses were made after the discovery in 2000 of a small peptide , hepcidin , that has been proved to play a central role in orchestration on iron metabolism also providing a link between iron metabolism and inflammation and innate immunity. Hepcidin directly interacts with ferroportin (FPN), the only known mammalian iron exporter, which is expressed by enterocytes, macrophages and hepatocytes. The direct hepcidin,FPN interaction allows an adaptative response from the body in situations that alter normal iron homeostasis (hypoxia, anemia, iron deficiency, iron overload, and inflammation). [source]

Pyruvate reduces DNA damage during hypoxia and after reoxygenation in hepatocellular carcinoma cells

FEBS JOURNAL, Issue 19 2007
Emilie Roudier
Pyruvate is located at a crucial crossroad of cellular metabolism between the aerobic and anaerobic pathways. Modulation of the fate of pyruvate, in one direction or another, can be important for adaptative response to hypoxia followed by reoxygenation. This could alter functioning of the antioxidant system and have protective effects against DNA damage induced by such stress. Transient hypoxia and alterations of pyruvate metabolism are observed in tumors. This could be advantageous for cancer cells in such stressful conditions. However, the effect of pyruvate in tumor cells is poorly documented during hypoxia/reoxygenation. In this study, we showed that cells had a greater need for pyruvate during hypoxia. Pyruvate decreased the number of DNA breaks, and might favor DNA repair. We demonstrated that pyruvate was a precursor for the biosynthesis of glutathione through oxidative metabolism in HepG2 cells. Therefore, glutathione decreased during hypoxia, but was restored after reoxygenation. Pyruvate had beneficial effects on glutathione depletion and DNA breaks induced after reoxygenation. Our results provide more evidence that the ,-keto acid promotes the adaptive response to hypoxia followed by reoxygenation. Pyruvate might thus help to protect cancer cells under such stressful conditions, which might be harmful for patients with tumors. [source]

The epigenetic calnexin-independent state is induced in response to environmental changes

Renée Guérin
Abstract Yeasts have evolved numerous responsive pathways to survive in fluctuating and stressful environments. The endoplasmic reticulum (ER) is sensitive to adverse conditions, which are detected by response pathways to ensure correct protein folding. Calnexin is an ER transmembrane chaperone acting in both quality control of folding and response to persistent stress. Calnexin is a key protein required for viability in certain organisms such as mammals and the fission yeast Schizosaccharomyces pombe. Nevertheless, S. pombe calnexin-independent (Cin) cells were obtained after transient expression of a particular calnexin mutant. The Cin state is dominant, is stably propagated by an epigenetic mechanism and segregates in a non-Mendelian fashion to the meiotic progeny. The nucleolar protein Cif1p was identified as an inducer of the Cin state in a previous genetic screen. Here, we report the identification of novel inducers isolated in an overexpression genetic screen: pyruvate kinase (Pyk1p) and phosphoglycerate kinase (Pgk1p). Addition of pyruvate, the end product of pyruvate kinase and glycolysis, also induced calnexin independence in a dose-dependent manner. Remarkably, growth in respiration media or cold temperatures induced the appearance of Cin cells at high frequencies. Taken together, our results indicate that the Cin state can be triggered by extracellular changes, suggesting that this state represents an epigenetic adaptative response to environmental modifications. [source]

Review: low caloric intake and gall-bladder motor function

D. Festi
Summary Cholelithiasis is the primary expression of obesity in the hepatobiliary system. In obese subjects the risk of developing gallstones is increased due to a higher cholesterol saturation of gall-bladder bile. During weight reduction with very low calorie diets (VLCD) the incidence of gallstones increases, but the mechanism for gallstone formation is not completely understood and several pathogenetic mechanisms have been suggested: increased saturation of bile, increased gall-bladder secretion of mucin and calcium, increased presence of prostaglandins and arachidonic acid. Alterations in gall-bladder motility may contribute to gallstone formation, but few studies have addressed the issue of gall-bladder motility during rapid weight loss and its possible role in gallstone formation. VLCD have been associated with a gall-bladder stasis, as a consequence of reduced gall-bladder stimulation by low fat content of the diets. A threshold quantity of fat (10 g) has been documented to obtain efficient gall-bladder emptying. Ursodeoxycholic acid administered during VLCD seems to have a protective role in developing a biliary cholesterol crystals. Gall-bladder emptying was lower in response to low fat meals with respect to relative higher fat meals, before as well as during the VLCD. This may account the possibility of an adaptative response of the gall-bladder motility to a given diet regimen. Adequate fat content of the VLCD may prevent gallstone formation, maintaining adequate gall-bladder motility and may be more economic and physiologically acceptable than administration of a pharmacological agent. [source]

A study of Streptococcus thermophilus proteome by integrated analytical procedures and differential expression investigations

Simona Arena
Abstract Streptococcus thermophilus is a Gram-positive bacterium belonging to the group of lactic acid bacteria, among which several genera play an essential role in manufacture of food products. Recently, a genomic consortium sequenced and annotated its entire genome, which has been demonstrated to contain 1900 coding sequences. In this study, we have revealed the expression products of almost 200 different genes using a proteomic strategy combining 2-DE plus MALDI-TOF PMF and differential 1-DE plus ,LC-ESI-IT-MS/MS. Thus, a number of cellular pathways related to important physiological processes were described at the proteomic level. Almost 50 genes were related to multiple electrophoretic species, whose heterogeneity was mainly due to variability in pI values. A 2-DE reference map obtained for lactose-grown cells was compared with those obtained after heat, cold, acid, oxidative and starvation stresses. Protein up/down-regulation measurements demonstrated that adaptation to different environmental challenges may involve the contribution of unique as well as combined physiological mechanisms. Common regulatory sites in the promoter region of genes whose expression was induced after stress were identified. These results provide a better comprehension of biochemical processes related to stress resistance in S. thermophilus, allowing defining the molecular bases of adaptative responses or markers for the identification of strains with potential industrial applications. [source]