The exudate of Cistus ladanifer L. consists mainly of two families of secondary metabolites: flavonoids and diterpenes. The amount of flavonoids present in the leaves has a marked seasonal variation, being maximum in summer and minimum in winter. In the present study, we demonstrate that the amount of diterpenes varies seasonally, but with a different pattern: maximum concentration in winter an...

Recent evidence suggests that yawning is a thermoregulatory behavior. To explore this possibility further, the frequency of contagious yawning in humans was measured while outdoors in a desert climate in the United States during two distinct temperature ranges and seasons (winter: 22°C; early summer: 37°C). As predicted, the proportion of pedestrians who yawned in response to seeing pictures of...

Blood pressure measurements recorded during the medical Research Council's treatment trial for mild hypertension have been analysed according to the calendar month in which the readings were made. For each age, sex, and treatment group systolic and diastolic pressures were higher in winter than in summer. The seasonal variation in blood pressure was greater in older than in younger subjects and...

BACKGROUND It has been postulated that developmental dysplasia of the hip (DDH) is more frequent in infants born in the winter months. It was the purpose of this study to ascertain if there was any seasonal variation in DDH at the author's institution and compare/contrast our results with those in the literature using rigorous mathematical fitting. METHODS All children with DDH treated at the...

Naturalized populations of buffelgrass (Cencchrus ciliaris L.) grow wild in some range areas and around farms in the Kingdom of Saudi Arabia. However, no attempt was made to study forage yield potential of these populations for use in range improvement or as a forage crop with low water requirement. This study was conducted to evaluate 24 seed sources collected from different places in the Riya...

The influence of weather on deep venous thrombosis (DVT) incidence remains controversial. We aimed to characterize the temporal association between DVT and meteorological variables including atmospheric pressure. Data relating to hospital admissions with DVT in Scotland were collected retrospectively for a 20 year period for which corresponding meteorological recordings were available. Weather ...

BACKGROUND Although seasonal variation in tuberculosis (TB) incidence has been described in many countries, it remains unknown in China. METHODS A time series decomposition analysis (X-12-ARIMA) was performed to examine the seasonal variation in active TB cases nationwide from 2005 through 2012 in China. Seasonal amplitude was calculated for the evaluation of TB seasonal variation. RESULTS ...

Seasonal polyphenisms are widespread in nature, yet the selective pressures responsible for their evolution remain poorly understood. Previous work has largely focussed either on the developmental regulation of seasonal polyphenisms or putative 'top-down' selective pressures such as predation that may have acted to drive phenotypic divergence. Much less is known about the influence of seasonal ...

OBJECTIVES This study was done to determine whether seasonal variation exists in hospitalizations and deaths due to heart failure (HF) and to examine possible contributors to such variability. BACKGROUND Although seasonal variation in the incidence of acute myocardial infarction and sudden death is well recognized, it is less well documented in HF. METHODS We used the linked Scottish Morbid...