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C Doyon

Publications and source records attributed to C Doyon.

5 recordsLinked to original sources
PubMed2005

Stress elevates corticotropin-releasing factor (CRF) and CRF-binding protein mRNA levels in rainbow trout (Oncorhynchus mykiss).

The objectives of this study were to characterize rainbow trout (Oncorhynchus mykiss) corticotropin-releasing factor (CRF)-binding protein (CRF-BP) cDNA and to examine the variations in CRF-BP and CRF mRNA levels in response to different intensities of stress. Trout were physically disturbed by a single or three consecutive periods of chasing until exhaustion followed by 2 h of recovery. The pituitary CRF-BP and preoptic area CRF1 mRNA contents were significantly increased only after repeated chasing events. Physical disturbance increased plasma cortisol levels with the largest change occurring in the group of trout that were exposed to repeated chasing events. Trout were also individually isolated in 120 l tanks or confined to 1.5 l boxes for 4, 24 or 72 h. CRF-BP mRNA levels in confined fish were greater than those of isolated fish at 72 h although there were no differences compared with the control group. CRF1 mRNA levels in the preoptic area were greater and remained elevated for a longer period in confined compared with isolated trout. Isolation led to a transient increase in plasma cortisol levels, but the higher cortisol values developed in the confined fish suggest that this treatment was more stressful than isolation. These results demonstrate that the intensity and duration of stress are important factors regulating CRF and CRF-BP mRNA levels in rainbow trout. We hypothesize that pituitary CRF-BP is involved in regulating the activity of the stress axis, possibly by reducing access to CRF1 receptors in the corticotropes.

Animals↗
PubMed2003

Corticotropin-releasing factor and neuropeptide Y mRNA levels are elevated in the preoptic area of socially subordinate rainbow trout.

The objectives of this study were to characterize rainbow trout (Oncorhynchus mykiss) corticotropin-releasing factor (CRF) and neuropeptide Y (NPY) cDNAs and to determine their mRNA levels in response to social stress. Standard cloning techniques were used to obtain cDNAs, sequences for trout NPY and two CRF isoforms. At the predicted amino acid level, our NPY sequence differs from the trout amino acid sequence reported by. A phylogenetic analysis suggests that the two CRF isoforms result from a gene duplication that occurred in a common ancestor of salmonids. A tissue distribution demonstrated that the mRNAs of both CRF isoforms are predominantly present in the preoptic area of the trout brain, whereas NPY mRNA is more abundant in the telencephalon. Pairs of sized-matched juvenile female trout were allowed to interact for 72 h and social ranks were assigned on the basis of behavioural observations. Mean plasma cortisol levels were 13-fold higher in subordinate than in dominant trout. As measured by ribonuclease protection assay, CRF1 and NPY mRNA levels were respectively 51 and 32% higher in the preoptic area of subordinate trout; in addition, CRF1 and NPY mRNA levels were positively correlated (R2=0.44). These results suggest that subordinate rainbow trout chronically maintain high levels of CRF mRNA during social stress and that NPY may be involved in the control of the stress axis in trout.

Animals↗
PubMed2001

Molecular evolution of leptin.

Leptin, a hormone produced mainly by adipocytes, is involved in the regulation of food intake, metabolism, and reproduction. The objective of this study was to determine the evolutionary relationships of leptin genes. Partial nucleotide sequences of leptin were cloned and sequenced from six mammalian species: large hairy armadillo (Chaetophractus villosus), rabbit (Oryctolagus cuniculus), big brown bat (Eptesicus fuscus) [corrected], striped skunk (Mephitis mephitis), raccoon (Procyon lotor), and beluga whale (Delphinapterus leucas). The PUZZLE program was used to construct maximum-likelihood trees. Our phylogenetic analysis shows that the grouping of these new mammalian sequences with those currently available in GenBank respect the evolutionary relationships generally accepted for mammals. However, when leptin sequences for chicken and turkey are included in the analysis, these are found to group with mouse and rat leptins. Chicken and mouse leptins are 95% identical. However, when mouse is compared with closer relatives, such as rabbit or bat, identities are approximately 80%. A comparison of extant and ancestral leptin sequences suggests that convergent or parallel evolution is the most plausible hypothesis to explain the similarity between bird and rodent leptins.

Adipose Tissue↗
PubMedDate not supplied

Cytochrome P-450 measurement in rat liver homogenate and microsomes. Its use for correction of microsomal losses incurred by differential centrifugation.

Cytochrome P-450 was assayed in rat liver homogenates and microsomes in order to calculate microsomal recoveries and correct for losses during ultracentrifugation or sedimentation in presence of CaCl2. The values obtained for corrected microsomal protein in untreated female Sprague-Dawley rats were between 40 and 50 mg/g of liver. The assay of cytochrome P-450 in liver homogenate is accurate enough to calculate a reproducible recovery factor. The value of the method lies in its rapidity, its capacity to correct over a wide range of losses, and its capacity to yield reliable values of the total microsomal protein mass. The limits of this method include overestimation of homogenate cytochrome P-450 and inability to correct for nonmicrosomal protein contamination. Overestimation of cytochrome P-450 can be corrected by measuring the difference in absorbance between 450 and 510 nm with the extinction coefficient of 100 mM-1cm-1. To be accurate, cytochrome P-450 determination on microsomes must be done at protein concentrations of about 3 mg/ml. The error inherent to the method may be kept constant and minimal. The use of correction for microsomal losses is recommended in order to obtain uniformity between results from various laboratories and adequate correlation with in vivo studies of microsomal functions.

Acid Phosphatase↗