Variability of Behavioral Chronotypes of 16 Mammalian Species Under Controlled Conditions

Human chronotypes (differences in preference for early or late rising each day) have been extensively studied in recent years, but no attempt has been made to compare human chronotypes with the chronotypes of other animal species. We evaluated behavioral chronotypes in 16 mammalian species along a body size gradient of five orders of magnitude (from mice to cattle). Individuals of all species were studied under a 12L:12D photoperiod in a thermoneutral environment with food and water available at all times. Rhythms of locomotor activity were analyzed for onset time, acrophase, and robustness. Neither of these rhythmic parameters was significantly related to body size, but onset time and acrophase varied considerably from species to species, thus characterizing diurnal and nocturnal species. Chronotype spreads ranged from less than an hour in sheep to almost 24 hours in cats, thus extending both below and above the human chronotype spread of 6 hours. The variability of chronotype (as quantified by the standard deviation of group means) was much larger between species than within species and also larger between individuals of a species than within individuals on consecutive days. These results help situate the matter of human chronotypes within the broader context of variability in the phase angle of entrainment of circadian rhythms in animals

Daily Activity Patterns of 2,316 Men and Women from Five Countries Differing in Socioeconomic Development

Daily rhythmicity in the locomotor activity of laboratory animals has been studied in great detail for many decades, but the daily pattern of locomotor activity has not received as much attention in humans. We collected waist-worn accelerometer data from more than 2,000 individuals from five countries differing in socioeconomic development and conducted a detailed analysis of human locomotor activity. Body mass index was computed from height and weight. Individual activity records lasting 7 days were subjected to cosinor analysis to determine the parameters of the daily activity rhythm: mesor (mean level), amplitude (half the range of excursion), acrophase (time of the peak), and robustness (rhythm strength). The activity records of all individual participants exhibited statistically significant 24-hour rhythmicity, with activity increasing noticeably a few hours after sunrise and dropping off around the time of sunset, with a peak at 1:42 pm on average. The acrophase of the daily rhythm was comparable in men and women in each country but varied by as much as 3 h from country to country. Quantification of the socioeconomic stages of the five countries yielded suggestive evidence that more developed countries have more obese residents, who are less active, and who are active later in the day than residents from less developed countries. These results provide a detailed characterization of the daily activity pattern of individual human beings and reveal similarities and differences among people from five countries differing in socioeconomic development

Dosing-Time Dependent Effects of Sodium Nitroprusside on Cerebral, Renal, and Hepatic Catalase Activity in Mice

To investigate the time dependence of sodium nitroprusside- (NPS-) induced oxidative effects, the authors study the variation of the antioxidant enzyme CAT activity in various tissues after the administration of a single 2.5mg/kg dose of SNP or sodium chloride (NaCl 0.9%). For each of the two dosing times (1 and 13 hours after light onset, HALO, which correspond to the beginning of diurnal rest span and of nocturnal activity span of mice, resp.), brain, kidney, and liver tissues were excised from animals at 0, 1, 3, 6, 9, 12, 24, and 36 h following the drug administration and CAT activity was assayed.The results suggest that SNP-induced stimulation of CAT activity is greater in all three tissues when the drug is administered at 1 HALO than at 13 HALO. Two-way ANOVA revealed that CAT activity significantly (P \u3c 0.004) varied as a function of the sampling time but not of the treatment in all three tissues. Moreover, a statistically significant (P \u3c 0.004) interaction between the organ sampling-time and the SNP treatment was revealed in kidney regardless of the dosing time, whereas a highly significant (P \u3c 0.0002) interaction was validated in liver only in animals injected at 13 HALO

Western Diet Affects the Murine Circadian System Possibly Through the Gastrointestinal Microbiota

Consumption of a high-fat diet characteristic of human Western diet has been shown to affect the circadian system of laboratory rodents. The present study confirms an effect of Western diet on the circadian system of mice, specifically a shortening of the free-running circadian period of running-wheel activity, in addition to increased weight gain. Decimation of the gut microbiota by broad spectrum antibiotic treatment reversed the effect of Western-diet feeding on the free-running period, which suggests that the effect of Western-diet feeding on the circadian system is mediated by the gastrointestinal microbiota. This finding is particularly relevant in view of recent studies describing a relationship between gut microbes, circadian clock function, and obesity

Parameters of photic resetting of the circadian system of a durnal rodent, the nile grass rat

Research on circadian rhythms has been hampered by the lack of a suitable rodent model with diurnal habits. The goal of this study was to characterize the parameters of photic entrainment of the circadian system of the Nile grass rat, a small rodent that can potentially serve as a model for the study of circadian rhythms in diurnal animals. The state of the circadian system was accessed through the rhythm of running-wheel activity and manipulated by photic stimulation (white light). The results indicated that the grass rat exhibits a robust rhythm of running-wheel activity with a mean free-running period of 23.9 hours (range: 23.6 to 24.3 hours). The animal is clearly diurnal and starts activity daily approximately 50 minutes before lights-on under an L12:D12 light-dark cycle. Its photic phase-response curve shows a dead zone during most of subjective day, a phase delay region during early subjective night (maximal delay: 1.5 hours), and a phase advance region during late subjective night (maximal advance: 2.2 hours). When exposed to constant illumination, the grass rat exhibits longer circadian periods as the intensity of illumination increases, with a ceiling between 100 and 1,000 lux. Finally, its range of entrainment extends from at least 23.0 to 25.0 hours (from 22.0 to 25.5 in some animals)

Política urbana e acesso à habitação social em regiões metropolitanas da América Latina e Europa

O texto é uma reflexão produzida a partir de diversos estudos desenvolvidos pela equipe do Laboratório de Habitação e Assentamentos Humanos da Faculdade de Arquitetura e Urbanismo da Universidade de São Paulo – LABHAB FAUUSP. Seu principal conteúdo e dados utilizados advêm de trabalho sobre as cidades de São Paulo (Br), Rosário (Ar), Barcelona (Es), Florença (It), realizado no âmbito do Programa URB-AL, que consiste em síntese produzida pela equipe, de diagnósticos locais de cada cidade e da análise comparativa, por continente e geral. Abrange as condições de carência habitacional ou dificuldade de acesso à moradia e a um lugar na cidade, bem como as políticas públicas aplicadas para enfrentar a questão. Considera aspectos institucionais, financiamento, marco legal e organização social presente em cada país e relaciona, na América Latina, a implementação de projetos e ações não só a diretrizes e programas nacionais, mas também ao projeto político-ideológico dos governos municipais.El presente texto es una reflexión producida a partir de diversos estudios desarrollados por el equipo del Laboratório de Habitação e Assentamentos Humanos da Faculdade de Arquitetura e Urbanismo da Universidade de São Paulo – LABHAB FAUUSP. Su contenido principal y los datos utilizados provienen del trabajo realizado, en el ámbito del Programa URB-AL, sobre las ciudades de São Paulo (Br), Rosario (Ar), Barcelona (España) y Florencia (IT). Consiste en una síntesis, un análisis comparativo por continente y a nivel general producida por el equipo de diagnóstico local de cada ciudad. La investigación abarca las condiciones de carencia habitacional, o dificultad de acceso a la vivienda y a un lugar en la ciudad, tanto como a las políticas públicas aplicadas para enfrentar esta cuestión. Considera aspectos institucionales, financiamiento, marco legal y de organización social presente en cada país y relaciona, en América Latina, la implementación de proyectos y acciones no sólo en las directrices y programas nacionales, sino también en el proyecto político-ideológico de los gobiernos municipales.Peer Reviewe

Time for sex: nycthemeral distribution of human sexual behavior

BACKGROUND: Nycthemeral (daily) oscillation has been documented in a variety of physiological and behavioral processes. The present study was carried out to evaluate the existence of a nycthemeral rhythm of human sexual behavior and to identify environmental factors responsible for the rhythmic pattern. METHODS: Non-traditional university students (ages 18 to 51 years) recorded the times of day when they went to sleep, when they woke up, and when they had sex for 3 consecutive weeks. They also answered a questionnaire designed to identify the causes of their selection of time for sex. RESULTS: The majority of sexual encounters took place at bedtime (11 pm to 1 am). The most common explanations for this temporal pattern were the rigidity of the professional work schedule and family obligations and the availability of the partner, which reduced the opportunity for sexual encounters at other times of the day. CONCLUSION: Most sexual encounters take place around bedtime. Although the presence of an endogenous component responsible for this temporal pattern cannot be excluded, the evidence indicates strong environmental forcing, particularly from the work/family schedule of the individuals and from partner availability

Daily Rhythms of Physiological Parameters in the Dromedary Camel Under Natural and Laboratory Conditions

Camels are well adapted to hot arid environments and can contribute significantly to the economy of developing countries in arid regions of the world. Full understanding of the physiology of camels requires understanding of the internal temporal order of the body, as reflected in daily or circadian rhythms. In the current study, we investigated the daily rhythmicity of 20 physiological variables in camels exposed to natural oscillations of ambient temperature in a desert environment and compared the daily temporal courses of the variables. We also studied the rhythm of core body temperature under experimental conditions with constant ambient temperature in the presence and absence of a light-dark cycle. The obtained results indicated that different physiological variables exhibit different degrees of daily rhythmicity and reach their daily peaks at different times of the day, starting with plasma cholesterol, which peaks 24 minutes after midnight, and ending with plasma calcium, which peaks 3 hours before midnight. Furthermore, the rhythm of core body temperature persisted in the absence of environmental rhythmicity, thus confirming its endogenous nature. The observed delay in the acrophase of core body temperature rhythm under constant conditions suggests that the circadian period is longer than 24 hours. Further studies with more refined experimental manipulation of different variables are needed to fully elucidate the causal network of circadian rhythms in dromedary camels

Ethnic differences in calcium, phosphate and bone metabolism

The prevalence of osteoporosis and the incidence of age-related fragility fracture vary by ethnicity. There is greater than 10-fold variation in fracture probabilities between countries across the world. Mineral and bone metabolism are intimately interlinked, and both are known to exhibit patterns of daily variation, known as the diurnal rhythm (DR). Ethnic differences are described for Ca and P metabolism. The importance of these differences is described in detail between select ethnic groups, within the USA between African-Americans and White-Americans, between the Gambia and the UK and between China and the UK. Dietary Ca intake is higher in White-Americans compared with African-Americans, and is higher in White-British compared with Gambian and Chinese adults. Differences are observed also for plasma 25-hydroxy vitamin D, related to lifestyle differences, skin pigmentation and skin exposure to UVB-containing sunshine. Higher plasma 1,25-dihydroxy vitamin D and parathyroid hormone are observed in African-American compared with White-American adults. Plasma parathyroid hormone is also higher in Gambian adults and, in winter, in Chinese compared with White-British adults. There may be ethnic differences in the bone resorptive effects of parathyroid hormone, with a relative skeletal resistance to parathyroid hormone observed in some, but not all ethnic groups. Renal mineral excretion is also influenced by ethnicity; urinary Ca (uCa) and urinary P (uP) excretions are lower in African-Americans compared with White-Americans, and in Gambians compared with their White-British counterparts. Little is known about ethnic differences in the DR of Ca and P metabolism, but differences may be expected due to known differences in lifestyle factors, such as dietary intake and sleep/wake pattern. The ethnic-specific DR of Ca and P metabolism may influence the net balance of Ca and P conservation and bone remodelling. These ethnic differences in Ca, P and the bone metabolism may be important factors in the variation in skeletal health