A short red light pulse during dark phase of LD-cycle perturbs the hamster's circadian clock

1995 ◽  
Vol 177 (6) ◽  
Author(s):  
G. Klante ◽  
S. Steinlechner
Keyword(s):  
Circadian Clock ◽  
Light Pulse ◽  
Red Light ◽  
Dark Phase

scholarly journals Daily Fasting Blood Glucose Rhythm in Male Mice: A Role of the Circadian Clock in the Liver

Endocrinology ◽  
2015 ◽  
Vol 157 (2) ◽  
pp. 463-469 ◽  
Author(s):  
Hitoshi Ando ◽  
Kentaro Ushijima ◽  
Shigeki Shimba ◽  
Akio Fujimura
Keyword(s):  
Blood Glucose ◽  
Circadian Clock ◽  
Mrna Expression ◽  
Hepatic Glucose Production ◽  
Critical Role ◽  
Fasting Blood Glucose ◽  
Glucose Production ◽  
Diabetic Patients ◽  
Dark Phase ◽  
Dawn Phenomenon

Abstract Fasting blood glucose (FBG) and hepatic glucose production are regulated according to a circadian rhythm. An early morning increase in FBG levels, which is pronounced among diabetic patients, is known as the dawn phenomenon. Although the intracellular circadian clock generates various molecular rhythms, whether the hepatic clock is involved in FBG rhythm remains unclear. To address this issue, we investigated the effects of phase shift and disruption of the hepatic clock on the FBG rhythm. In both C57BL/6J and diabetic ob/ob mice, FBG exhibited significant daily rhythms with a peak at the beginning of the dark phase. Light-phase restricted feeding altered the phase of FBG rhythm mildly in C57BL/6J mice and greatly in ob/ob mice, in concert with the phase shifts of mRNA expression rhythms of the clock and glucose production–related genes in the liver. Moreover, the rhythmicity of FBG and Glut2 expression was not detected in liver-specific Bmal1-deficient mice. Furthermore, treatment with octreotide suppressed the plasma growth hormone concentration but did not affect the hepatic mRNA expression of the clock genes or the rise in FBG during the latter half of the resting phase in C57BL/6J mice. These results suggest that the hepatic circadian clock plays a critical role in regulating the daily FBG rhythm, including the dawn phenomenon.

scholarly journals The counteracting effect of potassium cyanide in sodium azide-inhibited germination of Paulownia tomentosa  Steud. seeds

2005 ◽  
Vol 57 (1) ◽  
pp. 29-34 ◽  
Author(s):  
Suzana Zivkovic ◽  
Dragoljub Grubisic ◽  
Zlatko Giba ◽  
Radomir Konjevic
Keyword(s):  
Seed Germination ◽  
Light Pulse ◽  
Sodium Azide ◽  
Incubation Medium ◽  
Red Light ◽  
Potassium Cyanide ◽  
Inhibitory Effect ◽  
Escape Time ◽  
Paulownia Tomentosa ◽  
Respiratory Inhibitors

The effect of some respiratory inhibitors on light-induced Paulownia tomentosa Steud. seed germination was studied. Millimolar solution of sodium azide was sufficient to completely prevent germination induced by a 5-min red light pulse. The inhibitory effect of azide was absent if seeds were rinsed before phytochrome activation by light. Sodium azide was effective only if present in the period of Pfr activity. The escape time from azide inhibition compared to the escape from far-red light action, was delayed for about 24 hours. When azide was applied after phytochrome activation, its effect depended on how long it was present in the incubation medium. The removal of azide allowed full restoration of germination by another red light pulse and the far-red escape time did not differ from the escape of untreated, i.e. water-imbibed seeds. Potassium cyanide alone did not produce any effect in light-stimulated germination of these seeds. However, it counteracted the inhibitory effect of azide in light-stimulated germination, if applied simultaneously at a concentration three times higher.

Circadian Rhythm of Output from Neurones in the Eye of Aplysia: III. Effects of Light on Clock and Receptor Output Measured in the Optic Nerve

1977 ◽  
Vol 70 (1) ◽  
pp. 183-194
Author(s):  
JACK A. BENSON ◽  
JON W. JACKLET
Keyword(s):  
Circadian Rhythm ◽  
Optic Nerve ◽  
Circadian Clock ◽  
Light Pulse ◽  
Temperature Sensitivity ◽  
Phase Point ◽  
Light Onset ◽  
Constant Illumination ◽  
Light Pulses ◽  
East West

1. The circadian rhythm of CAP frequency recorded from the optic nerve of isolated eyes at 15 °C was damped out by constant illumination (1100 lux) after several cycles of the rhythm. During illumination (LL) the rhythm was skewed with a rapid rising phase and slow falling phase, and the period was decreased by about 1 h. It is postulated that the circadian clock was stopped by LL at its lowest phase point, and that following cessation of LL, the rhythm was reinitiated from this phase point after a latency of 6-8 h. 2. For light pulses of 80 lux and 1100 lux, the photoresponse of the dark-adapted eye to 20 min light pulses applied beginning at 2 h intervals was not influenced by the circadian clock. At 5 lux there was a periodicity in the magnitude of the photoresponse, in phase with the circadian rhythm of spontaneous CAP production. 3. Small CAPs of non-circadian frequency were recorded together with normal CAPs in about 10% of records of output from isolated eyes. The cells producing the small CAPs had a different temperature sensitivity from those producing normal CAPs. The response of these cells to short light pulses consisted of a phasic burst of activity at light onset, followed by silence during the remainder of the short light pulse, and for 1 or 2 min following cessation of illumination. These small CAPs may be the activity either of H-type receptors or of secondary cells desynchronized from the major population. Note: Laboratory of Sensory Sciences, University of Hawaii at Manoa, 1993 East-West Road, Honolulu, Hawaii 96822, U.S.A.

Circadian rhythm and response to light of extracellular glutamate and aspartate in rat suprachiasmatic nucleus

1996 ◽  
Vol 271 (3) ◽  
pp. R579-R585 ◽  
Author(s):  
S. Honma ◽  
Y. Katsuno ◽  
K. Shinohara ◽  
H. Abe ◽  
K. Honma
Keyword(s):  
Circadian Rhythm ◽  
Suprachiasmatic Nucleus ◽  
Light Pulse ◽  
Continuous Light ◽  
In Vivo Microdialysis ◽  
Dark Phase ◽  
Dark Cycle ◽  
Complete Darkness ◽  
Endogenous Circadian Rhythm

Extracellular concentrations of glutamate and aspartate were measured in the vicinity of rat suprachiasmatic nucleus (SCN) by means of in vivo microdialysis. The concentrations of both excitatory amino acids (EAAs) were higher during the dark phase than during the light under the light-dark cycle, showing pulsatile fluctuations throughout the day. When rats were released into the complete darkness, the 24-h pattern in the aspartate continued for at least one cycle, whereas that in the glutamate disappeared. The nocturnal increases in the EAA levels were not due to the increase of locomotor activity during the nighttime, because the 24-h rhythms were also detected in animals under urethan anesthesia. The patterns of extracellular EAA levels were changed when rats were released into the continuous light. Circadian rhythm was not detected in the glutamate, whereas the 24-h pattern was maintained in the aspartate with the levels increased to various extents. A 30-min light pulse given either at zeitgber time (ZT) 1 or ZT 13 elevated the EAA levels during the latter half of the light pulse, except glutamate by a pulse at ZT 1. The extracellular EAA levels in the vicinity of the rat SCN showed the circadian rhythm with a nocturnal peak and increased in response to the continuous light and a brief light pulse. The aspartate level is considered to be regulated by the endogenous circadian rhythm, but the glutamate levels seems to be modified by the light-dark cycle.

Reversion of the apical hook of pea in the dark and its promotion by a red light pulse.

1990 ◽  
Vol 78 (1) ◽  
pp. 75-78
Author(s):  
Toshihiro Takagi ◽  
Seiji Tsurumi ◽  
Tohru Hashimoto
Keyword(s):  
Light Pulse ◽  
Red Light ◽  
Apical Hook

scholarly journals Sympathetic Activation Induces Skeletal Fgf23 Expression in a Circadian Rhythm-dependent Manner

2013 ◽  
Vol 289 (3) ◽  
pp. 1457-1466 ◽  
Author(s):  
Masanobu Kawai ◽  
Saori Kinoshita ◽  
Shigeki Shimba ◽  
Keiichi Ozono ◽  
Toshimi Michigami
Keyword(s):  
Food Intake ◽  
Circadian Clock ◽  
Sympathetic Tone ◽  
Dark Phase ◽  
Dependent Manner ◽  
Phosphate Metabolism ◽  
Sympathetic Activation ◽  
Clock Network

The circadian clock network is well known to link food intake and metabolic outputs. Phosphorus is a pivotal nutritional factor involved in energy and skeletal metabolisms and possesses a circadian profile in the circulation; however, the precise mechanisms whereby phosphate metabolism is regulated by the circadian clock network remain largely unknown. Because sympathetic tone, which displays a circadian profile, is activated by food intake, we tested the hypothesis that phosphate metabolism was regulated by the circadian clock network through the modification of food intake-associated sympathetic activation. Skeletal Fgf23 expression showed higher expression during the dark phase (DP) associated with elevated circulating FGF23 levels and enhanced phosphate excretion in the urine. The peaks in skeletal Fgf23 expression and urine epinephrine levels, a marker for sympathetic tone, shifted from DP to the light phase (LP) when mice were fed during LP. Interestingly, β-adrenergic agonist, isoproterenol (ISO), induced skeletal Fgf23 expression when administered at ZT12, but this was not observed in Bmal1-deficient mice. In vitro reporter assays revealed that ISO trans-activated Fgf23 promoter through a cAMP responsive element in osteoblastic UMR-106 cells. The mechanism of circadian regulation of Fgf23 induction by ISO in vivo was partly explained by the suppressive effect of Cryptochrome1 (Cry1) on ISO signaling. These results indicate that the regulation of skeletal Fgf23 expression by sympathetic activity is dependent on the circadian clock system and may shed light on new regulatory networks of FGF23 that could be important for understanding the physiology of phosphate metabolism.

Dormancy breakage and germination are tightly controlled by hypoxic submergence water on Echinochloa crus-galli seeds from an accession resistant to anaerobic germination

2020 ◽  
pp. 1-6 ◽  
Author(s):  
Juliana Echeverry Holguín ◽  
María Crepy ◽  
Gustavo G. Striker ◽  
Federico P.O. Mollard
Keyword(s):  
Light Pulse ◽  
Seedling Establishment ◽  
Inhibitory Action ◽  
Seedling Emergence ◽  
Red Light ◽  
Functional Trait ◽  
Dormancy Breaking ◽  
Temporal Window ◽  
Resistant Accession ◽  
Anaerobic Germination

Abstract In wetlands, dormancy may be a key functional trait enabling seeds to avoid underwater germination, which could be lethal for seedling establishment. Our objectives were to find out (i) if shallow dormant (i.e. conditionally dormant) Echinochloa crus-galli seeds from an anaerobic germination resistant accession can break dormancy under hypoxic submergence and (ii) if underwater germination can be restored in scarified, non-dormant seeds. Shallow dormant E. crus-galli seeds perceived diurnally alternating temperatures (AT) and red light (R) pulses (i.e. dormancy-breaking cues) under hypoxic submergence; however, an inhibitory far-red light pulse given at the end of the 4-d inundation period demonstrated that most of the seeds (85%) were unable to break dormancy. Scarified E. crus-galli seeds, which did not express dormancy under drained conditions, were unable to germinate under hypoxic submergence, despite being exposed to dormancy-breaking cues (AT + R). Lastly, the temporal window for germination sensitivity to the inhibitory action of hypoxia, once dormancy-breaking signals have been applied, is progressively lost and bounded to approximately 18 h for half of the seed lot. These results highlight the importance of dormancy as a trait enabling E. crus-galli seeds to avoid underwater germination, a risky scenario for seedling emergence and establishment in this facultative hydrophyte.

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