Chronotype ontogeny related to gender

Chronotype is an established concept designed to identify distinct phase relationships between the expression of circadian rhythms and external synchronizers in humans. Although it has been widely accepted that chronotype is subjected to ontogenetic modulation, there is no consensus on the interaction between age and gender. This study aimed to determine the relationship between age- and gender-related changes in the morningness-eveningness character in a large sample of people. A total of 14,650 volunteers were asked to complete the Brazilian version of the Horne and Östberg chronotype questionnaire. The data demonstrated that, on average, women were more morning-oriented than men until the age of 30 and there were no significant differences between men and women from 30 to 45 years of age. In contrast to the situation observed until the age of 30, women older than 45 years were more evening-oriented than men. These results suggest that the ontogenetic development of the circadian timekeeping system is more plastic in men, as represented by the larger amplitude of chronotype changes throughout their aging process. The phase delay of adolescence and phase advance of the elderly seem to be phenomena that are more markedly present in men than in women. Thus, our data, for the first time, provide support that sharply opposes the view that there is a single path toward morningness as a function of age, regardless of gender.

Effect of exercise on occurrence of diurnal rhythms of plasma ions and metabolites in Thoroughbred racehorses

Records of plasma calcium (Ca++), phosphorus (Pi), potassium (K+), sodium (Na+), chloride (Cl-), magnesium (Mg++), iron (Fe++), glucose, cholesterol, triglycerides and total protein levels were measured to determine the effects of exercise on occurrence of diurnal rhythms in Throughbred racehorses (n=7) under physical training. Physical activities consisted of gallop on the track and walking. Blood samples were collected from jugular vein every 4h over a 48h period. Plasma Ca++, K+, Mg++ and Na+ levels were obtained by flame photometry; and, Pi, Cl-, Fe++, glucose, cholesterol, triglycerides and total protein levels were measured by colorimetric tests using visible UV spectrophotometry. The data were analyzed using a 24h period to each exercise performed. Diurnal rhythm of Pi was observed when walking was the physical activity performed, and its acrophase occurred at the light period. Plasma triclycerides showed significant diurnal rhythms, with their acrophases occurring at the dark period, even when walking or gallop were performed. High intensity exercise (gallop) decreased triglycerides amplitude. No significant diurnal rhythms of other variables were found. Gallop, as physical activity, masked phosphorus diurnal rhythm. However, physical training did not influence triglycerides diurnal rhythm occurrence. High intensity exercise (gallop) just declined triglycerides amplitude

Mensuraram-se as concentrações plasmáticas de cálcio (Ca++), fósforo (Pi), potássio (K+), sódio (Na+), cloreto (Cl-), magnésio (Mg++), ferro (Fe++), glicose, colesterol, triglicerídeos e proteínas totais para determinar os efeitos do exercício sobre a ocorrência dos ritmos diários em cavalos de corrida da raça Puro Sangue Inglês (n=7), em treinamento. A atividade física consistiu de galope na raia e passo. Amostras de sangue foram coletadas da veia jugular a cada 4h durante um período de 48h. As concentrações plasmáticas de Ca++, K+, Mg++ e Na+ foram obtidas por espectrofotometria de absorção atômica com chama, e as concentrações de Pi, Cl-, Fe++, glicose, colesterol, triglicerídeos e proteína total foram mensuradas por testes colorimétricos utilizando-se a espectrometria de luz UV visível. Os dados foram analisados utilizando-se um período de 24h para cada tipo de exercício desenvolvido. Ritmo diário de Pi foi observado quando o passo foi a atividade física desenvolvida, apresentando sua acrofase no período diurno. A concentração plasmática de triglicerídeos mostrou significante ritmo diário com a acrofase ocorrendo no período noturno, independente se foi desenvolvido o galope ou passo. O exercício de alta intensidade (galope) diminuiu a amplitude dos triglicerídeos. Nenhum ritmo diurno foi achado nas outras variáveis. Estes resultados mostram que o galope como atividade física, mascara o ritmo diário do fósforo. Entretanto, o treinamento físico não apresentou nenhum efeito na ocorrência do ritmo diário de triglicerídeos, somente na sua amplitude

The brain decade in debate: VII. Neurobiology of sleep and dreams

This article is a transcription of an electronic symposium held on February 5, 2001 by the Brazilian Society of Neuroscience and Behavior (SBNeC) during which eight specialists involved in clinical and experimental research on sleep and dreaming exposed their personal experience and theoretical points of view concerning these highly polemic subjects. Unlike most other bodily functions, sleep and dreaming cannot, so far, be defined in terms of definitive functions that play an ascribable role in maintaining the organism as a whole. Such difficulties appear quite clearly all along the discussions. In this symposium, concepts on sleep function range from a protective behavior to an essential function for maturation of the nervous system. Kleitman's hypothesis [Journal of Nervous and Mental Disease (1974), 159: 293-294] was discussed, according to which the basal state is not the wakeful state but sleep, from which we awake to eat, to protect ourselves, to procreate, etc. Dreams, on the other hand, were widely discussed, being considered either as an important step in consolidation of learning or simply the conscious identification of functional patterns derived from the configuration of released or revoked memorized information

The brain decade in debate: IV. Chronobiology

The present article is the adapted version of an electronic symposium organized by the Brazilian Society of Neuroscience and Behavior (SBNeC) which took place on June 14, 2000. The text is divided into three sections: I. The main issues, II. Chronodrugs, and III. Methods. The first section is dedicated to the perspectives of chronobiology for the next decade, with opinions about the trends of future research being emitted and discussed. The second section deals mostly with drugs acting or potentially acting on the organism's timing systems. In the third section there are considerations about relevant methodological issues concerning data analysis

Human chronobiology

Brief introduction to Chronobiology, followed by considerations on the landmarks of this new field of biological science, focussed on its implications on human physiology, and behaviour, as well as its applications to medicine and social organization. Periodicals, Internet sites and relevant literature dedicated to Chronobiology are included to help newcomers.

Becoming circadian: a one-year study of the development of the sleep-wake cycle in children

Data on three children's sleep-wake behavior during the first year of life submitted to spectral analysis reveal the presence of several frequencies in the circadian and ultradian ranges. The changes in the resulting spectra as age progresses show both an increase in overall rhythmicity, i.e., more data are explained by regular oscillations, and irregular changes in the circadian component. This circadian component shows an increase in power which appears at different ages among the individuals studied.