Egg hatching in 3 species of monocotylid monogenean parasites from the shovelnose ray Rhinobatos typus at Heron Island, Australia

Parasitology ◽  
2000 ◽  
Vol 121 (3) ◽  
pp. 303-313 ◽  
Author(s):  
L. A. CHISHOLM ◽  
I. D. WHITTINGTON
Keyword(s):  
Circadian Rhythms ◽  
Host Tissue ◽  
Adaptive Responses ◽  
Dark Cycle ◽  
Egg Hatching ◽  
Dark Light ◽  
Monogenean Species ◽  
Distinct Peak ◽  
Host Behaviour ◽  
Monocotylid Monogenean

Eggs of Neoheterocotyle rhinobatidis, Troglocephalus rhinobatidis and Merizocotyle icopae (Monogenea: Monocotylidae) from the shovelnose ray Rhinobatos typus (Rhinobatidae) have a distinct hatching pattern linked to light periodicity. Larvae of these 3 monogenean species emerge only during daylight when exposed to natural illumination or when incubated in alternating 12 h periods of light and dark (light on 06.00 h, light off 18.00 h). N. rhinobatidis larvae emerge with a distinct peak during the first 2 h of light; this peak is not as pronounced in T. rhinobatidis or M. icopae. Eggs of N. rhinobatidis incubated in a reverse light/dark cycle (light on 18.00 h, light off 06.00 h) hatched only during periods of illumination, again with a peak during the first 2 h of light. Evidence suggests that the hatching patterns observed in all 3 species represent true circadian rhythms because eggs incubated in 24 h light or 24 h dark conditions continued to hatch with a rhythm. Shadows, disturbance and host tissue did not promote hatching in N. rhinobatidis or T. rhinobatidis but there were indications that host tissue may promote hatching in M. icopae. The hatching patterns observed are discussed with respect to their adaptive responses to host behaviour and predation pressure.

scholarly journals Drugs of Abuse Can Entrain Circadian Rhythms

2007 ◽  
Vol 7 ◽  
pp. 203-212 ◽  
Author(s):  
Ann E. K. Kosobud ◽  
Andrea G. Gillman ◽  
Joseph K. Leffel ◽  
Norman C. Pecoraro ◽  
G. V. Rebec ◽  
...  
Keyword(s):  
Locomotor Activity ◽  
Circadian Rhythms ◽  
Drug Metabolism ◽  
Suprachiasmatic Nucleus ◽  
Drugs Of Abuse ◽  
Social Cues ◽  
Dark Cycle ◽  
Drug Reward ◽  
Locomotor Stimulation ◽  
Almost All

Circadian rhythms prepare organisms for predictable events during the Earth's 24-h day. These rhythms are entrained by a variety of stimuli. Light is the most ubiquitous and best known zeitgeber, but a number of others have been identified, including food, social cues, locomotor activity, and, most recently drugs of abuse. Given the diversity of zeitgebers, it is probably not surprising that genes capable of clock functions are located throughout almost all organs and tissues. Recent evidence suggests that drugs of abuse can directly entrain some circadian rhythms. We have report here that entrainment by drugs of abuse is independent of the suprachiasmatic nucleus and the light/dark cycle, is not dependent on direct locomotor stimulation, and is shared by a variety of classes of drugs of abuse. We suggest that drug-entrained rhythms reflect variations in underlying neurophysiological states. This could be the basis for known daily variations in drug metabolism, tolerance, and sensitivity to drug reward. These rhythms could also take the form of daily periods of increased motivation to seek and take drugs, and thus contribute to abuse, addiction and relapse.

Neuropeptide Y: Role in light-dark cycle entrainment of hamster circadian rhythms

1984 ◽  
Vol 50 (1-3) ◽  
pp. 163-168 ◽  
Author(s):  
H.Elliott Albers ◽  
Craig F. Ferris
Keyword(s):  
Circadian Rhythms ◽  
Neuropeptide Y ◽  
Dark Cycle

scholarly journals Photoperiodic modulation of circadian rhythms in the silk gland protein profiles of Bombyx mori and its influence on the silk productivity and quality

2010 ◽  
Vol 2 (1) ◽  
pp. 48-56 ◽  
Author(s):  
B. Sailaja ◽  
S. Sivaprasad
Keyword(s):  
Circadian Rhythms ◽  
Bombyx Mori ◽  
Continuous Light ◽  
Silk Gland ◽  
Protein Profiles ◽  
Dark Cycle ◽  
Response Curves ◽  
Silk Proteins ◽  
Free Running ◽  
Clock Shift

Circadian rhythms in the silk gland protein profiles of Bombyx mori were analyzed under 12 h light and 12 h dark cycle (LD), continuous light (LL) and continuous dark (DD) conditions. The phase response curves of protein rhythms indicate the prevalence of a series of silk cycles, each comprising three phases; transcription, translation and consolidation of silk proteins. In the 24h- protein rhythm, the silk cycle repeats every 3h, 42 m under LD, 2h, 36m under LL and 3h under DD. The light and dark conditions advanced the rhythm of each silk cycle by 48m and 24m respectively. As a result the silk gland completes 7 rounds of protein synthesis under LD, 9 rounds under LL and 8 rounds under DD during the 24h-free running time of the rhythm. The light-induced clock-shift in the protein rhythm caused significant gains in economic parameters of sericulture with positive signals for enhancing silk productivity and quality.

Advance shift of feeding circadian rhythm induced by obesity progression in Zucker rats

1992 ◽  
Vol 263 (6) ◽  
pp. R1169-R1175 ◽  
Author(s):  
K. Fukagawa ◽  
T. Sakata ◽  
H. Yoshimatsu ◽  
K. Fujimoto ◽  
K. Uchimura ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Circadian Rhythms ◽  
Least Squares ◽  
Developmental Stages ◽  
Ingestive Behavior ◽  
Zucker Rats ◽  
Circadian Cycle ◽  
Dark Cycle ◽  
Behavioral Measures ◽  
Obese Rats

To determine the relation between the circadian rhythm of ingestive behavior and the progression of obesity in Zucker rats, ingestion and ambulation were analyzed at four different developmental stages. The obese rats were disrupted gradually in nocturnal patterns of feeding, drinking, and ambulation with the progression of obesity, although the lean littermates maintained the patterns during whole test periods. Analysis of autocorrelogram revealed that circadian rhythms of those behaviors remained throughout the whole test periods. Least-squares spectrum ascertained the following. 1) The obese made advance shift of acrophases in feeding and drinking circadian cycles, but not in ambulation. 2) Amplitudes in those behavioral measures decreased with the progression of obesity. 3) Mesor in the obese feeding was not affected, although that in the lean feeding decreased. The findings indicate that disruption of the light-dark cycle in ingestion of the obese was not due to disappearance of circadian rhythm but to transformation by both decreased amplitude and advance shift of the circadian cycle.

Circadian rhythms of body temperature and activity levels during 63 h of hypoxia in the rat

2000 ◽  
Vol 279 (4) ◽  
pp. R1378-R1385 ◽  
Author(s):  
B. Bishop ◽  
G. Silva ◽  
J. Krasney ◽  
A. Salloum ◽  
A. Roberts ◽  
...  
Keyword(s):  
Circadian Rhythm ◽  
Body Temperature ◽  
Circadian Rhythms ◽  
Phase I ◽  
Phase Ii ◽  
Phase Iii ◽  
Hypoxic Exposure ◽  
Sprague Dawley ◽  
Dark Light ◽  
Hypothermic Response

The hypothermic response of rats to only brief (∼2 h) hypoxia has been described previously. The present study analyzes the hypothermic response in rats, as well as level of activity (La), to prolonged (63 h) hypoxia at rat thermoneutral temperature (29°C). Mini Mitter transmitters were implanted in the abdomens of 10 adult Sprague-Dawley rats to continuously record body temperature (Tb) and La. After habituation for 7 days to 29°C and 12:12-h dark-light cycles, 48 h of baseline data were acquired from six control and four experimental rats. The mean Tb for the group oscillated from a nocturnal peak of 38.4 ± 0.18°C (SD) to a diurnal nadir of 36.7 ± 0.15°C. Then the experimental group was switched to 10% O2 in N2. The immediate Tb response, phase I, was a disappearance of circadian rhythm and a fall in Tb to 36.3 ± 0.52°C. In phase II, Tb increased to a peak of 38.7 ± 0.64°C. In phase III, Tb gradually decreased. At reoxygenation at the end of the hypoxic period, phase IV, Tb increased 1.1 ± 0.25°C. Before hypoxia, La decreased 70% from its nocturnal peak to its diurnal nadir and was entrained with Tb. With hypoxia La decreased in phase I to essential quiescence by phase II. La had returned, but only to a low level in phase III, and was devoid of any circadian rhythm. La resumed its circadian rhythm on reoxygenation. We conclude that 63 h of sustained hypoxia 1) completely disrupts the circadian rhythms of both Tb and La throughout the hypoxic exposure, 2) the hypoxia-induced changes in Tb and La are independent of each other and of the circadian clock, and 3) the Tb response to hypoxia at thermoneutrality has several phases and includes both hypothermic and hyperthermic components.

Hatching rhythms in three species ofDiclidophora(Monogenea) with observations on host behaviour

Parasitology ◽  
1975 ◽  
Vol 71 (2) ◽  
pp. 211-228 ◽  
Author(s):  
Sheila Macdonald
Keyword(s):  
Host Tissue ◽  
Seasonal Difference ◽  
Specific Host ◽  
Mechanical Disturbance ◽  
Host Fishes ◽  
Host Behaviour ◽  
Larval Recovery

Eggs of three species ofDiclidophorawere incubated in alternating 12 h periods of light and darkness at 13°C. Eggs ofD. merlangicollected at Arbroath hatched during the illumination period with most larvae being recovered in the first 4–6 h; some evidence of a seasonal difference in hatching of these eggs was found. Eggs ofD. merlangicollected at Plymouth hatched with a peak of larval recovery in the 2 h period before the light came on. Eggs ofD. luscaehatched over ‘dusk’ while those ofD. denticulatahatched after the light was switched off. Neither mechanical disturbance nor the proximity of host tissue caused hatching inD. merlangiorD. luscae. Observations on the behaviour of the host fishes suggest that the hatching rhythms are adapted to specific host behaviour patterns.

Internal synchronization among several circadian rhythms in rats under constant light

1978 ◽  
Vol 235 (5) ◽  
pp. R243-R249 ◽  
Author(s):  
K. I. Honma ◽  
T. Hiroshige
Keyword(s):  
Locomotor Activity ◽  
Body Temperature ◽  
Circadian Rhythms ◽  
Continuous Light ◽  
Biological Rhythms ◽  
Plasma Corticosterone ◽  
Dark Cycle ◽  
Internal Oscillator ◽  
Free Running ◽  
Phase Angles

Three biological rhythms (locomotor activity, body temperature, and plasma corticosterone) were measured simultaneously in individual rats under light-dark cycles and continuous light. Spontaneous locomotor activity was recorded on an Animex and body temperature was telemetrically monitored throughout the experiments. Blood samples were obtained serially at 2-h intervals on the experimental days. Phase angles of these rhythms were calculated by a least-squares spectrum analysis. Under light-dark cycles, the acrophases of locomotor activity, body temperature, and plasma corticosterone were found at 0029, 0106, and 1940 h, respectively. When rats were exposed to 200 lx continuous light, locomotor activity and body temperature showed free-running rhythms with a period of 25.2 h on the average. Plasma corticosterone levels determined at 12 days after exposure to continuous light exhibited a circadian rhythm with the acrophase shifted to 0720. The acrophases of locomotor activity and body temperature, determined simultaneously on the same day, were found to be located at 1303 and 1358 h, respectively. Phase-angle differences among the three rhythms on the 12th day of continuous light were essentially the same with those under the light-dark cycle. These results suggest that circadian rhythms of locomotor activity, body temperature, and plasma corticosterone are most probably coupled to a common internal oscillator in the rat.

scholarly journals Physiology of Circadian Entrainment

2010 ◽  
Vol 90 (3) ◽  
pp. 1063-1102 ◽  
Author(s):  
Diego A. Golombek ◽  
Ruth E. Rosenstein
Keyword(s):  
Circadian Rhythms ◽  
Clock Gene ◽  
Retinal Diseases ◽  
Suprachiasmatic Nuclei ◽  
Circadian Variations ◽  
Dark Cycle ◽  
Clock Gene Expression ◽  
Biological Oscillators ◽  
Pituitary Adenylate Cyclase ◽  
Neurotransmitter Glutamate

Mammalian circadian rhythms are controlled by endogenous biological oscillators, including a master clock located in the hypothalamic suprachiasmatic nuclei (SCN). Since the period of this oscillation is of ∼24 h, to keep synchrony with the environment, circadian rhythms need to be entrained daily by means of Zeitgeber (“time giver”) signals, such as the light-dark cycle. Recent advances in the neurophysiology and molecular biology of circadian rhythmicity allow a better understanding of synchronization. In this review we cover several aspects of the mechanisms for photic entrainment of mammalian circadian rhythms, including retinal sensitivity to light by means of novel photopigments as well as circadian variations in the retina that contribute to the regulation of retinal physiology. Downstream from the retina, we examine retinohypothalamic communication through neurotransmitter (glutamate, aspartate, pituitary adenylate cyclase-activating polypeptide) interaction with SCN receptors and the resulting signal transduction pathways in suprachiasmatic neurons, as well as putative neuron-glia interactions. Finally, we describe and analyze clock gene expression and its importance in entrainment mechanisms, as well as circadian disorders or retinal diseases related to entrainment deficits, including experimental and clinical treatments.

The perception of light—dark transitions

1983 ◽  
Vol 303 (1116) ◽  
pp. 523-536 ◽  
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Laboratory Experiments ◽  
Light Quality ◽  
Accurate Method ◽  
Dark Light ◽  
Timing Mechanism ◽  
Rapid Formation ◽  
Special Case ◽  
Dark Transition

Transitions between light and darkness are particularly important where these serve as Zeitgebers to synchronize circadian rhythms. A special case is photoperiodism, which depends on the accurate detection of light—dark transitions and on the coupling of this information to a timing mechanism that appears to be based on the circadian clock. Results from laboratory experiments are considered in relation to the natural changes experienced at dawn and dusk, and evidence is presented that the light—dark transitions that couple to the timing mechanism in short-day plants are perceived through changes in irradiance rather than through changes in light quality. It has been generally accepted that the light—dark transition is sensed by a decrease of P fr levels in darkness, whereas dark—light is sensed by the rapid formation of P fr in the light. However, P fr in light-grown plants appears to be rather stable and so changes in P fr level after transfer to darkness may not be a sufficiently accurate method of detecting the light—dark transition in photoperiodism. The paper reviews some of the evidence from photoperiodic experiments and concludes that the plant may discriminate between light and darkness through the continuous or intermittent formation o f ‘new’ P fr .

scholarly journals The fish watch: Zebrafish: a clock in every cell

2005 ◽  
Vol 27 (6) ◽  
pp. 23-26
Author(s):  
Amanda-Jayne F. Carr ◽  
David Whitmore
Keyword(s):  
Circadian Rhythms ◽  
Danio Rerio ◽  
Biological Process ◽  
Genetic Model ◽  
Model System ◽  
Biological Processes ◽  
Powerful Method ◽  
Dark Cycle ◽  
Environmental Light ◽  
The One

The environmental light–dark cycle is one of the most reliable rhythmic signals, and many organisms have evolved a circadian (circa diem, ‘about a day’) system to co-ordinate biological processes with this predictable environmental change. These rhythms are endogenous and persist even in constant conditions, the light–dark cycle serving to synchronize these rhythms precisely to 24 hours. Genetic approaches have proved invaluable in increasing our understanding of the circadian clock. The ability to isolate a mutant with a defect in a rhythmic process is a very powerful method, which depends on no prior assumptions about the biological process under investigation. Consequently, Drosophila and the mouse have become the most powerful genetic models to study circadian rhythms in animals. The one alternative vertebrate genetic model system to the mouse is the zebrafish (Danio rerio).

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