The present study investigated the potential role of the composition of dietary fatty acids in the regulation of biological rhythms, such as the sleep architecture, core body temperature and leukocyte clock gene expression, in subjects fed meals rich in palmitic acid (PA) or oleic acid (OA). Eleven males participated in two sessions of indirect calorimetry in a whole-room metabolic chamber. In each session, subjects consumed three meals rich in PA (44·3 % of total fat as PA and 42·3 % as OA) or OA (11·7 % of total fat as PA and 59·3 % as OA) in the metabolic chamber. The ratio of PA to OA in plasma was significantly lower and fat oxidation was significantly higher during 24 h of indirect calorimetry in the session with meals rich in OA than in that with meals rich in PA. The duration of slow wave sleep (SWS) was shorter, the latency of SWS was longer and the nadir of core body temperature after bedtime was later in the session with meals rich in PA than in that with meals rich in OA. The peak in CRY1 gene expression was earlier and its amplitude was higher in the session with meals rich in PA than in that with meals rich in OA. In healthy young males, meals rich in PA decreased fat oxidation and disrupted biological rhythms, particularly the sleep architecture and core body temperature during sleep, more than meals rich in OA.

A case is described where phototherapy rapidly restored sleep-wake disturbances and concurrent symptoms of delirium in a patient who did not respond to conventional treatment with haloperidol. In this case, the delirious state may have been caused by a change in metabolism as a result of sepsis. Exposition of the patient to 8,000 Lux during 1.5 h for 5 consecutive days was sufficient to suppress all delirious symptoms and to normalize sleep. This result may encourage the setup of systematic studies towards the extent of desynchronization between various rhythmic cycles in delirium and towards the value of phototherapy for the restoration of normal circadian rhythmicity.

5-methoxypsoralen (5-MOP) stimulates pineal melatonin secretion, and a decrease in dark phase melatonin levels has been described in major depression. As exogenous melatonin has shown synchronizer properties, authors hypothesized that giving 5-MOP would have antidepressant properties.

Twenty-six inpatients meeting the criteria of major depressive disorders were enrolled in a four-week, double blind trial of 5-MOP versus amitriptyline. Clinical improvement was identical in both treatment groups but biological changes were different in each group: 5-MOP patients showed an early nocturnal surge of melatonin levels that was maintained at the fourth treatment week, while melatonin levels remained unchanged in patients treated with amitriptyline.

Greenhouse and growth chamber studies were conducted to determine the cause of previously observed differences in the effectiveness of bentazon [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] when applied at various times of the day to velvetleaf (Abutilon theophrasti Medic). Leaves of velvetleaf moved rhythmically from a near horizontal day position to a near vertical night position with the tip of the blade pointed downward. Plants were sprayed with bentazon at various times of day. The amount of spray retained and the degree of control decreased as the leaves moved toward the vertical downward night position. This suggested that a major cause of the time-of-day effect with bentazon treatments on velvetleaf is variation in the amount of spray intercepted and retained as a function of varying leaf angles.

Time of day at which a herbicide is applied can affect efficacy, and variability may be attributed to leaf angles at application. Spray interception by hemp sesbania (Sesbania exaltata), sicklepod (Senna obtusifolia), and prickly sida (Sida spinosa) under day and night conditions was quantified by measuring interception of a 2-M potassium nitrate solution. Following the night application, interception by prickly sida, hemp sesbania, and sicklepod was reduced 17, 67, and 70%, respectively. In a second study in the greenhouse, glyphosate was applied to hemp sesbania, pitted morningglory (Ipomoea lacunosa), prickly sida, and sicklepod at 6:00 and 11:00 A.M. and 4:00 and 9:00 P.M. Control of all species was dependent on the time of day treated, with night applications generally being less effective.

Biological rhythms occur at different levels in the organism. In single cells, the celldivision cycle shows rhythmicity in the way its molecular regulators, the cyclin dependantkinases (CDKs), modulate their activity periodically to ensure a healthy progression. Intissues, cell proliferation is driven by the circadian clock, which modulates theprogression through the cell cycle along the day. The circadian clock shows endogenousrhythmicity through a robust network of transcription-translation feedback loops thatcreate sustained oscillations. Rhythmicity is preserved in cell populations by thecoordination of the clocks among cells, through rhythmic synchronization signals. Here wediscuss mechanisms for generating rhythmic activities in cell populations by reviewingsome of the mathematical models that deal with them. We discuss the implication ofbiological rhythms for tissue growth and the possible application to chronomodulatedcancer treatments.

Four experiments were serially carried out conducted to study foraging activity in the freshwater gastropod Lymnaea stagnalis in the absence and presence of predators (crayfish or fish) under daylight and in the dark. The snails were either parasitized by digenean trematodes (Diplostomum pseudospathaceum or Plagiorchis elegans) or remained unparasitized. The snails had an evident circadian foraging rhythm: they preferred diurnal foraging notwithstanding the predators and parasites. However, the snail's parasite status and the predation risk had an interaction effect on the number of feeding events per snail individual so that especially the snails parasitized by D. pseudospathaceum were more active in the presence of a fish predator than in the absence of predators. Some of the snails responded to cues from a crayfish predator by crawling out of the water. The results suggest that D. pseudospathaceum may be capable of manipulating the behaviour of its first intermediate snail host in ways that enhance its success of transmission to the parasite's second intermediate fish host. The results also indicate that the effects of biotic stressors, such as predation risk and parasitism, on the foraging pattern in the snails L. stagnalis may be interactive and highly specialized rather than generalized.

Bien que la maladie dépressive se manifeste par des troubles majeurs du sommeil, reposant sur une désorganisation architecturale assez spécifique, la privation totale du sommeil (DTS) d’une nuit apporte un allègement symptomatique notable le plus souvent immédiat, contemporain de la privation.

A la suite des observations fortuites de Schulte, des séries systématiques et contrôlées ont défini le cadre et les limites de l’efficacité de la PTS et diverses investigations biologiques ont cherché à identifier des variables prédictives de son activité.

La PTS apporte une amélioration dans environ 60% des cas, plus régulièrement dans les formes endogènes et lorsqu’il y a des variations diurnes de l’humeur. Cette amélioration est globale et elle apparaît le plus souvent aux heures de l’aube mais elle est transitoire, le bénéfice étant perdu au lendemain de la nuit de récupération d’où la nécessité de répéter la privation ou d’y associer une chimiothérapie antidépressive.

Les investigations neurobiologiques situent la réponse clinique en rapport avec diverses modifications sur les paramétres catécholaminergiques et neuro-endocriniens ainsi que sur la structuration du sommeil.

L’activation thymique se corrèle avec une facilité relative à maintenir l’éveil et se manifeste à un horaire particulier qui correspond à une époque circadienne critique. La PTS produirait une réorganisation des rapports entre la veille et le sommeil et parviendrait à rétablir les coïncidences de phases des rythmes biologiques. Ces données apportent une contribution nouvelle à la notion spécifique d’instabilité dépressive.