Biomedical subjects

J Uberos Fernández

Publications and source records attributed to J Uberos Fernández.

3 recordsLinked to original sources

PubMed2002

[Puberty and melatonin].

BACKGROUND: Melatonin is the main hormone secreted by the pineal gland and secretion is maximal at night. Although researchers disagree, numerous data suggest that elevated melatonin levels during the prepubertal age maintain the hypothalamic-pituitary-gonadal axis in quiescence, thus exerting an inhibitory effect on pubertal development. The decrease in serum melatonin with advancing age activates hypothalamic pulsatile secretion of gonadotropin-releasing hormone and consequently the reproductive axis, which results in the onset of puberty. OBJECTIVE: To evaluate urinary melatonin levels in children of different ages and the characteristics of its rhythmic excretion and to determine whether puberty is associated with a significant reduction in urinary melatonin levels. MATERIAL AND METHODS: Thirty-two children were studied (17 boys and 15 girls). Concentrations of 24-h urinary melatonin were quantified by radioimmunoassay in daytime samples (collected between 9.00 and 21.00) and nighttime samples (collected between 21.00 and 9.00 on the following day). Blood levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol, testosterone and dehydroepiandrosterone sulfate (DHEAS) were calculated. Circadian rhythms and melatonin secretion in the various Tanner stages were assessed (ANOVA). RESULTS: No significant differences were found between day- and nighttime secretion of melatonin among boys (daytime melatonin: 1.38 0.52 pg/ml; nighttime melatonin: 6.92 2.06 pg/ml) and girls (daytime melatonin: 1.15 0.43 pg/ml; nighttime melatonin: 11.41 4.32 pg/ml). Highly significant differences were found (p < 0.001) between the day and night rates of melatonin secretion in both genders. Highly significant differences (p < 0.001) were also found in day-, nighttime and total secretion among the different Tanner stages. Comparison among groups revealed a significant decrease in secretion rates in stages I and II in both boys and girls. Melatonin significantly decreased with age in both sexes (lineal relationship). This decrease was greater at night. No relationship was found between the secretion of melatonin and estradiol, testosterone, LH, FSH and DHEAS. CONCLUSIONS: Melatonin secretion follows a circadian pattern, with greater secretion at night. The change in this rhythm was significantly greater in girls, due to greater nighttime secretion. Secretion significantly decreases in Tanner stages I and II with subsequent decreases in the later stages.

Adolescent↗

PubMed2000

[Evaluation of the antipyretic safety and accuracy of two pediatric ibuprofen formulations].

AIM: To compare the efficacy and to evaluate the clinical bioequivalence of two different formulations of ibuprofen (suspension and effervescent granules) in febrile children. METHODS: An open, randomized, multicenter study. Febrile children (axillary temperature 38 degrees C) weighing more than 25 kg, admitted into the emergency departments of the participating hospitals were randomly assigned to either of the two treatment groups: ibuprofen suspension (7 mg/kg) or effervescent granules at the following dosages: 200 mg in children weighing 2540 kg or 400mg in children weighing 3540 kg and with an axillary temperature above 39 degrees C. This latter dose of 400 mg was also given to children weighing more than 40 kg.The investigators took axillary temperature before treatment and 30, 60, 90, 120, 180 and 240 min after administration of the corresponding dose. Possible adverse events were noted. RESULTS: A total of 103 patients were included in the study; 51 received the effervescent granules and 52 received the suspension formulation. The mean temperature was reduced in both groups during the study (p < 0.005). No differences were found between the formulations. The mean differences of temperatures at each point of the study were within the clinical bioequivalence interval (+/-0.5 degrees C). Only one patient had an axillary temperature of 35.9 degrees C. This was the only adverse event recorded in the study. CONCLUSIONS: Both ibuprofen formulations were effective in reducing fever and may be considered clinically bioequivalent.

Adolescent↗

PubMed1996

[Pineal functioning (melatonin levels) in healthy children of different ages. An update and the value of pineal gland study in pediatrics].

BACKGROUND: Classically, the function of the pineal gland involved the regulation of several endocrine and non-endocrine functions, such as seasonal breeding, biological rhythm synchronization and the sleep/wake cycle. The study of the pineal gland has not a new increasing interest due to the recent discovery that melatonin is the most potent antioxidant compound known to date. MATERIAL AND METHODS: We present here the data of aMT levels (mean +/- SD, pg/ml) measured by RIA in healthy children grouped by age and time of sample extraction. The group differences are evaluated by a mean comparison test. RESULTS: The results showed that plasma levels of aMT in cord blood reflect both the aMT levels and their circadian rhythm seen in the mother, without significant differences between umbilical artery and vein. In children between 18 months and 6 years of age, aMT concentrations at 09.00 reaches a maximum of 60.8 +/- 100.58. This value significantly decreased in children between 6-8 years old (35.54 +/- 9.17, p < 0.001), with a more significant decrease in children 8-13 years old (25.28 +/- 7.16, p < 0.01). However, in children 13-15 years of age, aMT concentrations increased to 31.14 +/- 8.29 pg/ml (p < 0.01). CONCLUSION: Our data support the existence of a functional pineal gland during the neonatal period, although it lacks the rhythmic secretion of aMT. From the preschool stage, children show a significant decrease in aMT concentration, except during the pubertal period when there is a small increase in aMT levels. In this paper we also review the available information about pineal function, specifically in regards to the relationship between pineal-melatonin and CURRENT PEDIATRICS in order to better understand the infant physiology and physiopathology related to this area.

Adolescent↗