Feeble Weekly Rhythmicity in Hematological,Cardiovascular, and Thermal Parameters in the Horse

The homeostatic control of physiological processes is affected by a variety of temporal programs, such as circadian rhythms, estrous cycles, and circannual rhythms. The existence of circaseptan rhythms (endogenous rhythms with the duration of a week) has been postulated but not properly verified. In this study, we compared plasma concentration of lactic acid, systolic and diastolic blood pressure, and rectal temperature in athletic horses (maintained under a weekly training schedule) with those in sedentary horses (maintained under a constant schedule throughout the week). Although exercise had robust acute effects on the measured parameters, measurements conducted early in the morning or in the evening showed significant weekly rhythmicity only in one of the parameters (plasma concentration of lactic acid) in a few animals. This rhythmicity was feeble, was present only in athletic horses, and vanished if rigorous statistical criteria were applied. In contrast, 24 h rhythmicity was significant in all parameters in all horses. We conclude that the overall 7-day pattern in physiological parameters of the horse is feeble and is caused by the weekly schedule of activity. The available evidence does not support the notion of endogenous, circaseptan rhythms.     

Feeble Weekly Rhythmicity in Hematological, Cardiovascular, and Thermal Parameters in the Horse

The homeostatic control of physiological processes is affected by a variety of temporal programs, such as circadian rhythms, estrous cycles, and circannual rhythms. The existence of circaseptan rhythms (endogenous rhythms with the duration of a week) has been postulated but not properly verified. In this study, we compared plasma concentration of lactic acid, systolic and diastolic blood pressure, and rectal temperature in athletic horses (maintained under a weekly training schedule) with those in sedentary horses (maintained under a constant schedule throughout the week). Although exercise had robust acute effects on the measured parameters, measurements conducted early in the morning or in the evening showed significant weekly rhythmicity only in one of the parameters (plasma concentration of lactic acid) in a few animals. This rhythmicity was feeble, was present only in athletic horses, and vanished if rigorous statistical criteria were applied. In contrast, 24 h rhythmicity was significant in all parameters in all horses. We conclude that the overall 7-day pattern in physiological parameters of the horse is feeble and is caused by the weekly schedule of activity. The available evidence does not support the notion of endogenous, circaseptan rhythms.     

Circadian rhythm of active amino acid transport in rat liver

Abstract

The circadian change of the encephalic photosensitivity of quail has been demonstrated. In this study the diurnal variation of the retinal photosensitivity was investigated by the electroretinogram (ERG) to explore the phase relation between the retinal and encephalic systems. The b‐wave, a major component of the ERG, was used as a measure of retinal photosensitivity.

1. In the bird maintained in LD12:12 the b‐wave amplitude of the ERG stayed at a high level for the first 10 h of the light period, and decreased abruptly around the time of light‐off. The decreased level continued until midnight. Thenceforth the b‐wave amplitude recovered progressively to the daytime level before the time of next light on.

2. In the bird maintained in LD16:8, the decrease of the retinal sensitivity in the light phase was initiated prior to the time of expected light‐off, and the onset time of decreasing tendency was advanced by 2 h, with dark adaptation for 30 min given immediately before the ERG measurement. Upon continuous light exposure, the b‐wave amplitude always remained at low level.

3. Periodic changes in retinal sensitivity persisted when the environmental dark phase was temporarily extended for 19 to 30 h.

These observations suggest that the diurnal rhythm of the neural retina in quail might be generated endogenously and appears to control the encephalic photosensitive system.     

Oviposition rhythm in Drosophila melanogaster is influenced by acetic acid

Fermenting fruit can contain acetic acid, a known attractant for fruit flies. Vinegar food induces a bimodal oviposition rhythm in Drosophila melanogaster, however non-vinegar (control) food induces a unimodal rhythm. The bimodal rhythm has a broad day mode showing variability in onset or pattern and a sharp dusk peak. The day mode may not be coupled to the dusk peak or to the 12L : 12D cycle because some flies show oviposition drifting. The day mode augments at the expense of the dusk mode, the latter diminishing within a few days. The unimodal expression on control food is a single dusk peak. Anticipation in the form of oviposition onset is shown by a few flies several hours before the light-off signal. On control food, a pulse of acetic acid fumes can induce a daytime oviposition. When pulsed twice in the day several hours apart two daytime modes are produced, thus leaving few eggs in the dusk mode. The experiments suggest that the fly is attracted to fruit by odours and oviposit rhythmically of a biological clock. If acetic acid is present in fermenting fruit oviposition is induced, thus overriding the clock.     

Field Chronobiology of a Molluscan Bivalve: How the Moon and Sun Cycles Interact to Drive Oyster Activity Rhythms

The present study reports new insights into the complexity of environmental drivers in aquatic animals. The focus of this study was to determine the main forces that drive mollusc bivalve behavior in situ. To answer this question, the authors continuously studied the valve movements of permanently immersed oysters, Crassostrea gigas, during a 1-year-long in situ study. Valve behavior was monitored with a specially build valvometer, which allows continuously recording of up to 16 bivalves at high frequency (10?Hz). The results highlight a strong relationship between the rhythms of valve behavior and the complex association of the sun-earth-moon orbital positions. Permanently immersed C. gigas follows a robust and strong behavior primarily driven by the tidal cycle. The intensity of this tidal driving force is modulated by the neap-spring tides (i.e., synodic moon cycle), which themselves depend of the earth–moon distance (i.e., anomalistic moon cycle). Light is a significant driver of the oysters' biological rhythm, although its power is limited by the tides, which remain the predominant driver. More globally, depending where in the world the bivalves reside, the results suggest their biological rhythms should vary according to the relative importance of the solar cycle and different lunar cycles associated with tide generation. These results highlight the high plasticity of these oysters to adapt to their changing environment. (Author correspondence: d.tran@epoc.u-bordeaux1.fr)     

生长猪结肠乳酸菌菌群的昼夜节律性变化

【目的】本文旨在研究生长猪在24 h内结肠乳酸菌的多样性变化、丰富度变化与节律性变化。【方法】选取6头装有结肠瘘管的“杜×长×大”三元杂交生长猪,于清晨6:00开始,每隔3 h连续采集一天内生长猪的结肠食糜,提取DNA,用乳酸菌特异性引物进行高通量测序,在属和种水平上分析结肠乳酸菌菌群丰度与节律性变化。【结果】生长猪结肠乳酸菌在24 h内Chao1和Simpson指数发生显著性变化(P<0.05);属水平上Lactobacillus相对丰度最高,一天内在6:00时相对丰度最低,为94.15%,18:00时相对丰度最高,为97.46%;种水平上Lactobacillus johnsonii相对丰度最高,一天内在3:00时相对丰度最低,为47.66%,18:00时相对丰度最高,为71.59%,Lactobacillus reuteri丰度次之。生长猪结肠乳酸菌中46个核心OTU具有节律性,均为Lactobacillus;而在种水平上Lactobacillus gasseri、Lactobacillus johnsonii、Lactobacillus sp. KC45a和Lactobacillus reuteri显现出节律性(P<0.05)。【结论】生长猪结肠乳酸菌在24 h内多样性发生显著性变化,在种水平上显现出节律性,丰富了我们对猪肠道微生物昼夜节律的了解。     

A simple method for separating cells of Microcystis aeruginosa for counting

Heat was used to break up the mucilage-bound colonies of the blue-green alga, Microcystis aeruginosa Kütz. emend. Elenkin, for cell counting. Samples were heated in a water bath at 80°C for 5–10 min, then agitated in a Vortex mixer for 30–60 s. The treatment separated cells completely and reaggregation of cells did not occur. There was no evidence that heating distintegrated the cells.     

Development and relationships of locomotor, feeding, and oxygen consumption rhythms in house crickets

ABSTRACT. Locomotor, feeding, drinking, and oxygen consumption rhythms in adult virgin Acheta domesticus L. all appear to peak in the first half of the scotophase, be entrained cophasically by a LD 14:10 h cycle, have a lights-off Zeitgeber and persist in LL with a π c. 25 h for the locomotor rhythm and c. 23 h for the oxygen consumption rhythm. There is no evidence of these rhythms in last instar larvae. The onset of the locomotor rhythm requires 3 days at 30°C but 5–7 days at 25–28°C after the final ecdysis in virgins, indicating a temperature related development of the locomotor rhythm. Oxygen consumption rhythms are lacking in 2-day-old virgins but present in 8-day-old virgins. Feeding rhythms can be recorded in virgins as young as 2 days (before locomotor rhythm developed). Both oxygen consumption and locomotor rhythms persist during starvation. The results suggest that a central brain oscillator drives both feeding and locomotor rhythms independently, but that the oxygen consumption rhythm is derived from the metabolic demands associated with the other rhythms.     

Plasma hyaluronan concentration: no circadian rhythm but large effect of food intake in humans

This study was designed to determine if a circadian rhythm in plasma hyaluronan concentration [HA] exists in the absence of physical activity, and if plasma [HA] is associated with feeding in human subjects. Five persons were studied under standardized conditions, blood samples being taken between 0600 and 2200 hours at 30-min intervals. Any orthostatic challenge and muscle activity was abolished by immobilization by a 6° head-down bed-rest, and the effect of a quasi-continuous ingestion of energy compared a normal, three-portion diet of equivalent energy content or to fasting. Reproducibility of HA profiles on two consecutive half-days was also studied. A highly sensitive immunoassay was used to determine plasma [HA]. The data indicated that without physical activity and without food ingestion, [HA] was unchanged and displayed no diurnal rhythm. In addition, we observed that [HA] increased after the first food intake, peaking after 60 min, and concluded from our results that without ingestion of a larger meal, and sessions of postural or muscle activity, no circadian plasma [HA] rhythm exists. Accepted: 10 June 1998     

Circadian rhythm of activity and sleep‐wakefulness in elderly institutionalized persons

Abstract

The circadian rhythms of blood pressure (BP) and heart rate (HR) were documented in 30 patients for a 24‐hour period before and during the 24 hours that included unilateral surgery for senile cataract or retinal detachment. The patients were premedicated with diazepam. Anaesthesia was induced at a fixed time (09.00) in all patients with thiopentone, and muscle relaxation was with pancuronium. Maintenance was with enflurane in 15 patients and with fentanyl and droperidol in the rest. Though the intraoperative changes in haemodynamic parameters were dissimilar with the two types of maintenance agents, but both types had a similar effect on the circadian rhythms of blood pressure and heart rate. Whereas preoperatively the BP and HR circadian rhythms were nearly in phase, with their peaks in the late morning to early afternoon, the postoperative rhythms underwent a dissociation to a phase shift in the BP 24‐h pattern. The phase effect may be hypothetically attributed to direct pharmacological actions or to masking effects.     

Dynamic oral administration of uridine affects the diurnal rhythm of bile acid and cholesterol metabolism-related genes in mice

Bile acids and cholesterol metabolism exhibits distinct daily rhythms and uridine closely associated with bile acids has been well documented. However, how dynamic oral administration of uridine affects bile acid and cholesterol metabolism has not been studied. We conducted the present study to investigate effects of oral administration of uridine in the daytime and nighttime (D-UR and N-UR) on bile acid and cholesterol metabolism-related genes expression in liver and ileum of mice. The results showed that oral administration of uridine in the nighttime (N-UR) reduced serum CHOL and ALT levels at Zeitgeber time (ZT) 4, ZT22, respectively. Compared with D-UR group, the mRNA expression of FXR and SHP genes of liver decreased in N-UR group at ZT10, ZT16, respectively. In addition, oral administration of uridine in the nighttime rhythmically increased the mRNA expression of bile acid transport, cholesterol excretion and decreased the mRNA expression of cholesterol absorption in ileum. Moreover, the expression of nucleotide transport and synthesis genes were also explored in duodenum. Oral administration of uridine in the nighttime rhythmically up-regulated nucleotide transport and synthesis genes expression. In conclusion, these results indicated dynamic oral administration of uridine has effects on the rhythmic fluctuation of cholesterol, bile acid and nucleotide metabolism-related genes. These findings have important physiological and pathophysiological implications, since bile acid and cholesterol metabolism are essential for cell function and closely involved in the development of metabolic syndrome.     

Behaviors and nutritional importance of coprophagy in captive adult and young nutrias (Myocastor coypus)

To estimate the contribution of coprophagy to protein intake, we observed the behavior, particularly that associated with coprophagy, in adult and young captive nutrias (experiment 1), and analyzed chemical composition and amino acid composition, including diaminopimeric acid (DAP), an indication of bacterial-deprived protein, of soft feces, entire hard feces, and the black part and green part of hard feces (experiment 2). Nutrias practiced coprophagy 48 times per 24 h in adults, and 28 times in young animals, which not only had a 24-h rhythm but also had 1-h or 2-h short-term rhythms. Nutrias ingested food and drank water vigorously after sunset, following which they practiced coprophagy from midnight to morning, before lying down for much of the day. When coprophagy was prevented we sampled soft feces, produced from midnight to noon, which had high (P < 0.05) concentration of crude protein (CP), DAP on a dry matter (DM) basis and 13 amino acids on a 16 g N basis than hard feces, and had a low (P < 0.05) content of acid detergent fiber (ADF). CP was greater in the black part than the green part of hard feces (P < 0.05) although ADF was less (P < 0.05). The chemical composition of the black part of hard feces was not significantly different from that of soft feces. The dry weight of soft feces excreted in experiment 1 was 34.5 g and 9.7 g DM per 24 h in adult and young animals, respectively. Using this value, the contribution of soft feces to CP intake in adult nutrias was estimated as 16%, superior to that obtained in rabbits for a diet with similar ADF concentration. To Met and Lys intake the contribution of soft feces was 26% and 19%, respectively in adult animals. These results suggest that coprophagy is quite an effective manner for nutrias to ingest extra protein. Accepted: 10 January 1991     

Circadian changes in endogenous concentrations of indole-3-acetic acid,melatonin, serotonin,abscisic acid and jasmonic acid in Characeae (Chara australis Brown)

Giant-celled Characeae (Chara australis Brown), grown for 4 months on 12/12 hr day/night cycle and summer/autumn temperatures, exhibited distinct concentration maxima in auxin (indole-3-acetic acid; IAA), melatonin and serotonin about 4 hr after subjective daybreak. These concentration peaks persisted after 3 day pretreatment in continuous darkness: confirming a circadian rhythm, rather than a response to “light on.” The plants pretreated for 3 d in continuous light exhibited several large IAA concentration maxima throughout the 24 hr. The melatonin and serotonin concentrations decreased and were less synchronized with IAA. Chara plants grown on 9/15 hr day/night cycle for 4 months and winter/spring temperatures contained much smaller concentrations of IAA, melatonin and serotonin. The IAA concentration maxima were observed in subjective dark phase. Serotonin concentration peaks were weakly correlated with those of IAA. Melatonin concentration was low and mostly independent of circadian cycle. The “dark” IAA concentration peaks persisted in plants treated for 3 d in the dark. The plants pretreated for 3 d in the light again developed more IAA concentration peaks. In this case the concentration maxima in melatonin and serotonin became more synchronous with those in IAA. The abscisic acid (ABA) and jasmonic acid (JA) concentrations were also measured in plants on winter regime. The ABA concentration did not exhibit circadian pattern, while JA concentration peaks were out of phase with those of IAA. The data are discussed in terms of crosstalk between metabolic pathways.     

A Diurnal Settling Rhythm in Platymonas subcordiformis Hazen*

SYNOPSIS. In cultures of Platymonas subcordiformis Hazen, grown in appropriate light-dark cycles, as many as 75% of the cells adhered to the surface of the glass culture vessel toward the end of the light period of each day. Cell division occurred primarily while the cells were attached. Subsequently, motile daughter cells were released into the growth medium by the rupture of the mother cell theca. The settling behavior appears to be an integral part of the life cycle being synchronized to the same extent as cell division.     

Altered Circadian Relationship Between Serum Nitric Oxide, Carbon Dioxide, and Uric Acid in Multiple Sclerosis

The free radical nitric oxide (NO^·) is involved in a variety of diverse biological processes from acting as a vasodilator in the cardiovascular system to being the rate-limiting component in the production of peroxynitrite (ONOO^-), a contributor to neurodegenerative disorders such as multiple sclerosis (MS). Uric acid (UA), the end product of purine metabolism in humans and a selective inhibitor of toxic reactions attributed to radicals formed by the interaction of ONOO^- and CO₂, is generally low in MS patients. We investigated the relationship between serum ONOO^-, CO₂, and UA in MS patients and normal controls by comparing the circadian characteristics of the NO^· metabolites nitrite/nitrate (NO), CO₂, and UA. In this preliminary study, we found the functional relationship ascribed to the circadian timing of the peak and trough levels of NO, CO₂, and UA in healthy subjects to be clearly altered in MS patients. These findings suggest that alterations in the temporal relationship between the 24 h pattern in serum ONOO^- formation and UA may either contribute to or reflect the disease processes in MS.     

Altered Circadian Relationship Between Serum Nitric Oxide,Carbon Dioxide,and Uric Acid in Multiple Sclerosis

The free radical nitric oxide (NO^·) is involved in a variety of diverse biological processes from acting as a vasodilator in the cardiovascular system to being the rate-limiting component in the production of peroxynitrite (ONOO^?), a contributor to neurodegenerative disorders such as multiple sclerosis (MS). Uric acid (UA), the end product of purine metabolism in humans and a selective inhibitor of toxic reactions attributed to radicals formed by the interaction of ONOO^? and CO₂, is generally low in MS patients. We investigated the relationship between serum ONOO^?, CO₂, and UA in MS patients and normal controls by comparing the circadian characteristics of the NO^· metabolites nitrite/nitrate (NO), CO₂, and UA. In this preliminary study, we found the functional relationship ascribed to the circadian timing of the peak and trough levels of NO, CO₂, and UA in healthy subjects to be clearly altered in MS patients. These findings suggest that alterations in the temporal relationship between the 24 h pattern in serum ONOO^? formation and UA may either contribute to or reflect the disease processes in MS.