Biomedical subjects

N De Pedro

Publications and source records attributed to N De Pedro.

11 recordsLinked to original sources

PubMed2006

Feeding entrainment of locomotor activity rhythms, digestive enzymes and neuroendocrine factors in goldfish.

The existence of food anticipatory activity (FAA) in animals subjected to daily feeding schedules seems to be mediated by a feeding-entrainable oscillator (FEO). Such an FEO may help in anticipating meal time and so optimizing food acquisition and nutrient utilization. In this study we investigated the existence of FAA and whether digestive enzymes, plasma cortisol, hypothalamic NPY and gastrointestinal tract (GIT) and plasma melatonin were entrained by periodic feeding in goldfish. We observed that periodically fed goldfish showed FAA in locomotor activity as well as in amylase and NPY. Alkaline protease and GIT melatonin were higher after feeding, whereas plasma cortisol levels were reduced. Plasma melatonin remained unmodified before and after meal time. These results suggested that scheduled feeding entrained both behavioral and certain physiological patterns in goldfish, FAA being of adaptive value to anticipate a meal and prepare the digestive physiology of fish.

Activity Cycles↗

PubMed2005

The endocannabinoid system in the brain of Carassius auratus and its possible role in the control of food intake.

Cannabinoid receptors and the endocannabinoids anandamide and 2-arachidonoylglycerol have been suggested to regulate food intake in several animal phyla. Orthologs of the mammalian cannabinoid CB(1) and CB(2) receptors have been identified in fish. We investigated the presence of this endocannabinoid system in the brain of the goldfish Carassius auratus and its role in food consumption. CB(1)-like immunoreactivity was distributed throughout the goldfish brain. The prosencephalon showed strong CB(1)-like immunoreactivity in the telencephalon and the inferior lobes of the posterior hypothalamus. Endocannabinoids were detected in all brain regions of C. auratus and an anandamide-hydrolysing enzymatic activity with features similar to those of mammalian fatty acid amide hydrolase was found. Food deprivation for 24 h was accompanied by a significant increase of anandamide, but not 2-arachidonoylglycerol, levels only in the telencephalon. Anandamide caused a dose-dependent effect on food intake within 2 h of intraperitoneal administration to satiated fish and significantly enhanced or reduced food intake at low (1 pg/g body weight) or intermediate (10 pg/g) doses, respectively, the highest dose tested (100 pg/g) being inactive. We suggest that endocannabinoids might variously contribute to adaptive responses to food shortage in fish.

Amidohydrolases↗

PubMed2003

Changes in glucose, glycogen, thyroid activity and hypothalamic catecholamines in tench by starvation and refeeding.

The effects of short-term food deprivation (7 days) and refeeding (2 days) on different biochemical and neuroendocrine parameters were studied in tench. A 7-days fast resulted in a significant reduction of plasma glucose and glycogen hepatic content, supporting the key role of liver glycogen as energy depot for being consumed during fasting. The rapid recovery of normal values of blood glucose and glycogen stores by refeeding indicates a rapid replenishment of liver glycogen stores. The short-term starvation decreased circulating thyroid hormones (both T3 and T4) and T4 release from thyroid, supporting an interaction between nutritional state and thyroid function in tench. All these metabolic and hormonal changes were partial or totally reversed under refeeding conditions. An increase in hypothalamic content of norepinephrine and dopamine was found in fasted fish. This result might be a consequence of stress induced by starvation.

Analysis of Variance↗

PubMed2002

Comparison of genotypic and phenotypic techniques for assessing the variability of the fungus Epicoccum nigrum.

AIMS: The diversity within a collection of worldwide isolates of Epicoccum nigrum has been studied using several phenotypic approaches. In addition, the abilities of phenotypic and genotypic techniques for the differentiation of a set of isolates are compared. METHODS AND RESULTS: The methodology used include the study of isozymes (acetyl esterase and alkaline phosphatase), HPLC profile of metabolites and antibiotic activities against a panel of bacteria, yeasts and filamentous fungi, and cytotoxicity against three mammalian cell lines. Two procedures for assessing the relationships within a collection of isolates, using a combination of the techniques, were evaluated, comparing the advantages and disadvantages of each method. CONCLUSIONS: The results showed that each individual technique allows differentiation of the isolates studied to some degree and that the information provided by each technique could be considered as complementary. Genotypic techniques were more powerful than the phenotypic ones to discriminate among the strains. SIGNIFICANCE AND IMPACT OF THE STUDY: This work evaluates the predictive value of several phenotypic techniques on a collection of fungal isolates, and compares the results obtained with genotypic techniques performed on the same strains.

Acetylesterase↗

PubMed2001

Day/night variations of dopamine ocular content during Xenopus laevis ontogeny.

Concentration of dopamine (DA) and its metabolite, 3,4-dihydroxyphenylacetic acid is quantified by high-pressure liquid chromatography with a coulometric detection system in the eye of Xenopus laevis through ontogeny and in adults at two times during photocycle (midday and midnight). Ocular dopaminergic activity remains low during pre- and prometamorphosis and significantly rises in postmetamorphic froglets. This increase is more pronounced at midnight than at midday. The dualism of DA content versus DA release in Xenopus ocular tissue is studied in an eyecup culture system. On a 24-h cycle of DA release from adult Xenopus eyecups the highest DA release by eyecups is produced during daytime, and significantly decreases in darkness. From these results it can be concluded that in spite of the early development of the retinal dopaminergic system in the ontogeny of Xenopus, the final maturation must occur during the metamorphic climax. Endogenous DA release is significantly inhibited by light offset, which explains the higher ocular DA content found at midnight as compared to midday in postmetamorphic froglets and adults.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2001

Food intake inhibition by melatonin in goldfish (Carassius auratus).

Feeding regulation by monoamines, neuropeptides and certain hormones has been studied in fish, but a possible role of melatonin is unknown. The purpose of the present study was to investigate the effects of melatonin on food intake in goldfish. Fishes were housed in 12L:12D and injected with different doses of either melatonin or 2-iodomelatonin. Two routes of administration, intracerebroventricular and intraperitoneal injections, and two times of the daily photocycle, midday and midnight, were tested. Food intake was measured at 2, 5 and 8 h postinjection. Melatonin and its analog, 2-iodomelatonin intracerebroventricularly injected had no effect on food intake at any time. However, intraperitoneal injections of both indoleamines significantly reduced food intake at different postinjection times. The inhibitory effect of melatonin was blocked by intraperitoneal administration of its antagonist, luzindole. These results demonstrate the in vivo efficiency of luzindole as melatonin antagonist, and thus provide a useful experimental tool to investigate melatonin functions. In conclusion, both melatonin and its agonist 2-iodomelatonin administered peripherally, inhibit food intake in goldfish, and this inhibitory effect appears to be mediated via luzindole-sensitive melatonin receptors. Our results strongly suggest that melatonin is involved in the peripheral satiety mechanisms in goldfish.

Animals↗

PubMed1998

Inhibitory effect of serotonin on feeding behavior in goldfish: involvement of CRF.

The possible action of 5-HT on feeding behavior in goldfish has been studied. Food intake was significantly reduced by intracerebroventricular (ICV) injection of serotonin (5-HT, 10 microg) at 2 h postinjection. After peripheral (intraperitoneal) administration of 5-HT (1 and 10 microg/g bw), no significant modifications in food intake were detected. Thus, it can be concluded that there is a central anoretic action of 5-HT in teleost fish. Taking in mind the inhibitory effect of corticotropin releasing factor (CRF) on feeding in teleosts and the interactions between 5-HT and CRF described in mammals, we investigated the possible involvement of CRF as mediator of the 5-HT anoretic action in goldfish. The ICV pretreatment with alpha-Helical CRF[9-41](20 microg) partially blocked the inhibitory effect of 5-HT on food consumption in goldfish. These results show that CRF mediates, at least in part, the 5-HT-induced feeding inhibition in goldfish. On the other hand, the alterations in hypothalamic indoleamines content evoked by ICV treatments would suggest that the activation of CRF neurons by 5-HT appears to inhibit hypothalamic serotoninergic transmission, supporting the intermediate role of this neuropeptide in the central anoretic effect of 5-HT in goldfish.

Animals↗

PubMed1995

CRF effect on thyroid function is not mediated by feeding behavior in goldfish.

In the present study we examined the effects of acute corticotropin-releasing factor (CRF) administration and refeeding treatment on glucose levels and thyroid hormones (plasma levels and thyroid contents) in 48-h food-deprived goldfish. Central CRF administration (2 micrograms) decreased food intake and the thyroid T3 free fraction, without significantly modifying either thyroid hormones bound fractions (T3 and T4) or plasma glucose levels. Subsequently, we tested whether CRF affects thyroid activity by itself, or whether this effect is mediated by CRF-induced feeding reduction. CRF treatment in fasted fish reduced thyroid-free T3 and increased thyroid-free T4, which could be mediated by a decreased intrathyroidal 5'-monodeiodinase activity. These data suggest a CRF effect upon thyroid activity independent of feeding reduction. On the other hand, refeeding after 48-h fasting caused a significant increase in thyroid free T4 content and plasma thyroid hormone levels. Thus, a relationship between nutritional status and thyroid function, which could overlap with CRF effects, cannot be discarded. Plasma glucose levels were only significantly modified by refeeding, which seems to be the signal triggering the increase in glucose titers. Our results support the existence of both CRF-thyroid activity and nutritional status-thyroid function interactions in goldfish.

Animals↗

PubMed1994

Ontogeny of ocular serotonin N-acetyltransferase activity daily rhythm in four anuran species.

The profile of daily ocular serotonin N-acetyltransferase (NAT) rhythm has been examined during the development of four anuran amphibians in different environments and of varying phylogenetic origins: Xenopus laevis, Discoglossus pictus, Rana perezi, and Bufo calamita. A significant day/night rhythm of ocular NAT with the acrophase at midnight was first detected at stages 43/44 and 25 in X. laevis and R. perezi, respectively. Total enzymatic activity increased with body weight throughout development, although both mean levels and amplitudes of NAT activity per milligram of protein significantly decreased; this attentuation of rhythm was more significant in postmetamorphic froglets, and the acrophase was delayed about 1 hr. There were no significant differences in daily NAT profiles before and after metamorphosis in D. pictus and B. calamita. The amplitude of the NAT rhythm was maximal (> 10-fold nocturnal values) in Xenopus compared with other species (2- to 3-fold).

Animals↗

PubMed1994

Serotonin N-acetyltransferase activity as a target for temperature in the regulation of melatonin production by frog retina.

The adaptive mechanisms of serotonin N-acetyltransferase (NAT) activity in the regulation of melatonin synthesis in frog retina in the face of chronic and acute temperature changes have been investigated. We performed thermal acclimation experiments to test different environmental temperatures at two seasons of the year (summer and winter), followed by the set-up of an eyecup culture system to investigate the acute effects of temperature on NAT activity and melatonin production daily rhythms. Low temperature induced a significant increase in NAT activity, independent of both the time of the photocycle (midday or midnight) and the season of the year (winter or summer). Acute cold-induced stimulation of NAT activity may be associated with lower decreases in the enzyme synthesis rate, rather than decreases in the degradation rate. In contrast, acclimation to warm temperature (25 degrees C) stimulated ocular melatonin production. Nocturnal melatonin production in eyecups cultured at 25 degrees C was significantly higher than in eyecups cultured at 5 degrees C. We suggest that this discrepancy in thermal regulation of melatonin synthesis can be justified by a seasonal variation in serotonin content within the photoreceptor cells, which determines the thermal response of melatonin production through changes in NAT kinetics.

Acclimatization↗

PubMed1993

Role of corticotropin-releasing factor (CRF) as a food intake regulator in goldfish.

The effect of intraperitoneal or intracerebroventricular corticotropin-releasing factor (CRF) administration on food intake has been studied in goldfish after 24 h of food deprivation. Food intake was evaluated at different time periods after injection, 0-2, 2-8, and 0-8 h. The 1 and 2 micrograms doses of CRF intracerebroventricularly administered induced a reduction in food intake during the first 2 h, although an increased feeding was observed in the next 6 h. The higher dose of CRF used in this study (3.3 micrograms) increased cumulative food intake at 8 h postinjection. However, intraperitoneal injection of 1 microgram CRF did not modify food intake in any of the studied intervals. These results suggest that CRF may play a role in central regulation of feeding behavior intake in goldfish, and show that CRF effects are time- and dose-dependent.

Animals↗