Diurnal Differences in the Innermost Surface of the S2 Layer in Differentiating Tracheids of Cryptomeria japonica Corresponding to a Light-Dark Cycle

Holzforschung ◽  
2003 ◽  
Vol 57 (6) ◽  
pp. 567-573 ◽  
Author(s):  
Y. Hosoo ◽  
M. Yoshida ◽  
T. Imai ◽  
T. Okuyama
Keyword(s):  
Cryptomeria Japonica ◽  
Dark Period ◽  
Amorphous Material ◽  
Light Period ◽  
Cellulose Microfibrils ◽  
Dark Phase ◽  
Diurnal Changes ◽  
Dark Cycle ◽  
Tangential Strain ◽  
S2 Layer

Summary This paper describes the effect of light on the diurnal change in the innermost surface of developing secondary walls. Cryptomeria japonica D. Don saplings were grown in two growth chambers, in which temperature and relative humidity were kept constant and the light-dark phase of the photoperiod varied. One chamber reproduced the natural light-dark phase, while the other reversed it. Samples of differentiating xylem were collected during the dark period when the tangential strain, used as an index of volumetric changes in differentiating cells, was high, and during the light period when the tangential strain was low. The innermost surface of developing secondary walls in differentiating tracheids was observed by field emission scanning electron microscopy. In the specimens collected during the dark period, amorphous material was observed and the cell wall surface was immunogold-labeled with an anti-glucomannan antiserum. In the specimens collected during the light period, cellulose microfibrils were clearly evident, and amorphous material and immunogold labeling were rarely observed. These results demonstrate that the diurnal changes in the innermost surface of developing secondary walls correspond to the light-dark cycle over 24 h.

Stimulation of Melatonin Receptors Decreases Calcium Levels in Xenopus Tectal Cells by Activating GABAC Receptors

2005 ◽  
Vol 94 (2) ◽  
pp. 968-978 ◽  
Author(s):  
Claudia Prada ◽  
Susan B. Udin ◽  
Allan F. Wiechmann ◽  
Irina V. Zhdanova
Keyword(s):  
Receptor Antagonist ◽  
Dark Period ◽  
Light Period ◽  
Melatonin Receptors ◽  
Receptor Activity ◽  
Calcium Dynamics ◽  
Rt Pcr ◽  
Dark Cycle ◽  
Bath Application ◽  
Stimulation Of

To investigate the physiological effects of melatonin receptors in the Xenopus tectum, we have used the fluorescent indicator Fluo-4 AM to monitor calcium dynamics of cells in tectal slices. Bath application of KCl elicited fluorescence increases that were reduced by melatonin. This effect was stronger at the end of the light period than at the end of the dark period. Melatonin increased γ-aminobutyric acid-C (GABAC)–receptor activity, as demonstrated by the ability of the GABAC-receptor antagonists, picrotoxin and TPMPA, to abolish the effects of melatonin. In contrast, neither the GABAA-receptor antagonist bicuculline nor the GABAB-receptor antagonist CGP 35348 diminished the effects of melatonin. RT-PCR analyses revealed expression of the 3 known melatonin receptors, MT1 (Mel1a), MT2 (Mel1b), and Mel1c. Because the effect of melatonin on tectal calcium increases was antagonized by an MT2-selective antagonist, 4-P-PDOT, we performed Western blot analyses with an antibody to the MT2 receptor; the data indicate that the MT2 receptor is expressed primarily as a dimeric complex and is glycosylated. The receptor is present in higher amounts at the end of the light period than at the end of the dark period, in a pattern complementary to the changes in melatonin levels, which are higher during the night than during the day. These results imply that melatonin, acting by MT2 receptors, modulates GABAC receptor activity in the optic tectum and that this effect is influenced by the light–dark cycle.

Monophasic and diphasic patterns of the circadian caecotrophy rhythm of rabbits

1982 ◽  
Vol 16 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Burghart Jilge
Keyword(s):  
Dark Period ◽  
Continuous Light ◽  
Light Period ◽  
Period Length ◽  
Rodent Species ◽  
Average Period ◽  
Dark Cycle

The circadian caecotrophy rhythm was synchronized with the light-dark cycle of 12 : 12 h. During this the rabbits practised caecotrophy regularly during the light period. While most rabbits manifested 1 caecotrophy per 24 h (monophasic caecotrophy), some had an additional caecotrophy during the dark period (diphasic caecotrophy). During continuous light the circadian caecotrophy rhythm ran free monophasically, even in those rabbits which were diphasic under the preceding 12 : 12 regime. The average period length amounted to 24·7 ± 0·3 h. Following restoration of the 12 : 12 routine animals reestablished their original caecotrophy pattern. In a further test the caecotrophy pattern remained constant during a constant 12 : 12 regimen, but changed in 7 of 16 animals when the photoperiod was reduced first to 60 min and then to 2 × 60 min light every 24 h. The reduction of the lit time resulted in an increased occurrence of diphasic animals. Details of synchronization of the caecotrophy rhythm with the different light-dark schedules are given. These results accord with data obtained in nocturnal rodent species.

scholarly journals Shifting eating to the circadian rest phase misaligns the peripheral clocks with the master SCN clock and leads to a metabolic syndrome

2015 ◽  
Vol 112 (48) ◽  
pp. E6691-E6698 ◽  
Author(s):  
Atish Mukherji ◽  
Ahmad Kobiita ◽  
Manohar Damara ◽  
Nisha Misra ◽  
Hamid Meziane ◽  
...  
Keyword(s):  
Metabolic Syndrome ◽  
Molecular Level ◽  
Dark Period ◽  
Active Phase ◽  
Light Period ◽  
Dark Cycle ◽  
Peripheral Clocks ◽  
Molecular Signals ◽  
Glucagon Receptors

The light-entrained master central circadian clock (CC) located in the suprachiasmatic nucleus (SCN) not only controls the diurnal alternance of the active phase (the light period of the human light-dark cycle, but the mouse dark period) and the rest phase (the human dark period, but the mouse light period), but also synchronizes the ubiquitous peripheral CCs (PCCs) with these phases to maintain homeostasis. We recently elucidated in mice the molecular signals through which metabolic alterations induced on an unusual feeding schedule, taking place during the rest phase [i.e., restricted feeding (RF)], creates a 12-h PCC shift. Importantly, a previous study showed that the SCN CC is unaltered during RF, which creates a misalignment between the RF-shifted PCCs and the SCN CC-controlled phases of activity and rest. However, the molecular basis of SCN CC insensitivity to RF and its possible pathological consequences are mostly unknown. Here we deciphered, at the molecular level, how RF creates this misalignment. We demonstrate that the PPARα and glucagon receptors, the two instrumental transducers in the RF-induced shift of PCCs, are not expressed in the SCN, thereby preventing on RF a shift of the master SCN CC and creating the misalignment. Most importantly, this RF-induced misalignment leads to a misexpression (with respect to their normal physiological phase of expression) of numerous CC-controlled homeostatic genes, which in the long term generates in RF mice a number of metabolic pathologies including diabetes, obesity, and metabolic syndrome, which have been reported in humans engaged in shift work schedules.

CYCLICAL CHANGES IN CONCENTRATIONS OF α-MELANOTROPHIN IN THE PLASMA OF MALE AND FEMALE RATS

1979 ◽  
Vol 82 (3) ◽  
pp. 361-366 ◽  
Author(s):  
J. F. WILSON ◽  
MERRILL A. MORGAN
Keyword(s):  
Time Series ◽  
Time Series Analysis ◽  
Diurnal Rhythm ◽  
Dark Period ◽  
Light Period ◽  
Female Rats ◽  
Male Rats ◽  
Dark Phase ◽  
Male And Female ◽  
Male And Female Rats

Radioimmunoassay measurements of α-melanotrophin in plasma have identified a diurnal rhythm in male rats. Animals maintained on a 12 h light: 12 h darkness photoperiod had raised levels of plasma α-melanotrophin during the dark phase. Time-series analysis gave a fitted mean level of α-melanotrophin of 52·4 pmol/l, an amplitude of 12·1 pmol/l and peak levels 2·2 h before dawn. Measurements throughout the oestrous cycle in female rats showed that similar variations between the dark and light phases occurred on the 2 days of dioestrus. The raised levels during the dark period were, however, absent on the nights of pro-oestrus and oestrus. During this pro-oestrous/oestrous period, plasma α-melanotrophin levels were below average but higher than the normal minimum levels found during the light period.

scholarly journals Resetting Process of Peripheral Circadian Gene Expression after the Combined Reversal of Feeding Schedule and Light/Dark Cycle Via a 24-h Light Period Transition in Rats

2010 ◽  
pp. 581-590
Author(s):  
T Wu ◽  
Y Ni ◽  
F Zhuge ◽  
Z Fu
Keyword(s):  
Time Course ◽  
Clock Genes ◽  
Dark Period ◽  
Light Period ◽  
Feeding Schedule ◽  
Circadian Gene ◽  
Dark Cycle ◽  
Peripheral Clocks ◽  
Effect Of Light

To investigate the effect of light cue on the resetting of the peripheral clocks, we examined the resetting processes of clock genes (Per1, Per2, Bmal1, Cry1, Dec1, and Rev-erbα) in the liver and heart of rats after the feeding and light-dark (LD) reversal via a 24-h light period transition. The liver clock was reset quickly within 3 days, while the heart clock needed a longer time course of 5-7 days to be completely re-entrained. Moreover, the reentrainment of Per1 and Per2 in the liver clock was more rapid than that of the other four clock genes, suggesting the important role of these two clock genes in initiating the circadian resetting of the hepatic clock. However, the resetting rates of these two clock genes were as similar as the others in the heart clock. Therefore, the resetting mechanisms underlining these two peripheral clocks may be totally distinct. Furthermore, the reentrainment of the liver and heart clocks were relatively lengthened after the feeding and LD reversal via a light period transition compared to a dark period transition, suggesting a simultaneous shift of feeding schedule and the LD cycle may facilitate the circadian resetting in rats.

Blockade of corticotropin-releasing hormone receptors reduces spontaneous waking in the rat

1998 ◽  
Vol 275 (3) ◽  
pp. R793-R802 ◽  
Author(s):  
Fang-Chia Chang ◽  
Mark R. Opp
Keyword(s):  
Hormone Receptors ◽  
Dark Period ◽  
Light Period ◽  
Corticotropin Releasing Hormone ◽  
Dark Cycle ◽  
Receptor Antagonists ◽  
Releasing Hormone ◽  
Waking And Sleep ◽  
Effective Doses ◽  
Time Courses

We have previously hypothesized that corticotropin-releasing hormone (CRH) is involved in the regulation of physiological waking. To further elucidate this role for CRH, we administered intracerebroventricularly into rats two specific CRH-receptor antagonists, α-helical CRH-(9—41) (α-hCRH) or astressin, and determined changes in electroencephalogram-defined waking and sleep. Our results indicate that both of these receptor antagonists reduce the amount of time spent awake in a dose-related manner when administered before the dark period of the light-dark cycle. However, the time courses for these effects differ between antagonists; effective doses of α-hCRH reduce waking during the first 2 h postinjection, whereas effective doses of astressin reduce waking during postinjection hours 7–12. In contrast to dark-onset administrations, the amount of waking is not altered by either CRH-receptor antagonist when administered before the light period. These results support our hypothesis that CRH contributes to the regulation of physiological waking, since interfering with the binding of CRH to its receptor reduces spontaneous waking.

scholarly journals Diurnal Regulation of Cellular Processes in the Cyanobacterium Synechocystis sp. Strain PCC 6803: Insights from Transcriptomic, Fluxomic, and Physiological Analyses

mBio ◽  
2016 ◽  
Vol 7 (3) ◽  
Author(s):  
Rajib Saha ◽  
Deng Liu ◽  
Allison Hoynes-O’Connor ◽  
Michelle Liberton ◽  
Jingjie Yu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dark Period ◽  
Expression Patterns ◽  
Light Period ◽  
Transcriptional Analysis ◽  
Transcriptional Networks ◽  
Diurnal Changes ◽  
Cellular Processes ◽  
Diurnal Behavior ◽  
Pcc 6803

ABSTRACT Synechocystis sp. strain PCC 6803 is the most widely studied model cyanobacterium, with a well-developed omics level knowledgebase. Like the lifestyles of other cyanobacteria, that of Synechocystis PCC 6803 is tuned to diurnal changes in light intensity. In this study, we analyzed the expression patterns of all of the genes of this cyanobacterium over two consecutive diurnal periods. Using stringent criteria, we determined that the transcript levels of nearly 40% of the genes in Synechocystis PCC 6803 show robust diurnal oscillating behavior, with a majority of the transcripts being upregulated during the early light period. Such transcripts corresponded to a wide array of cellular processes, such as light harvesting, photosynthetic light and dark reactions, and central carbon metabolism. In contrast, transcripts of membrane transporters for transition metals involved in the photosynthetic electron transport chain (e.g., iron, manganese, and copper) were significantly upregulated during the late dark period. Thus, the pattern of global gene expression led to the development of two distinct transcriptional networks of coregulated oscillatory genes. These networks help describe how Synechocystis PCC 6803 regulates its metabolism toward the end of the dark period in anticipation of efficient photosynthesis during the early light period. Furthermore, in silico flux prediction of important cellular processes and experimental measurements of cellular ATP, NADP(H), and glycogen levels showed how this diurnal behavior influences its metabolic characteristics. In particular, NADPH/NADP + showed a strong correlation with the majority of the genes whose expression peaks in the light. We conclude that this ratio is a key endogenous determinant of the diurnal behavior of this cyanobacterium. IMPORTANCE Cyanobacteria are photosynthetic microbes that use energy from sunlight and CO 2 as feedstock. Certain cyanobacterial strains are amenable to facile genetic manipulation, thus enabling synthetic biology and metabolic engineering applications. Such strains are being developed as a chassis for the sustainable production of food, feed, and fuel. To this end, a holistic knowledge of cyanobacterial physiology and its correlation with gene expression patterns under the diurnal cycle is warranted. In this report, a genomewide transcriptional analysis of Synechocystis PCC 6803, the most widely studied model cyanobacterium, sheds light on the global coordination of cellular processes during diurnal periods. Furthermore, we found that, in addition to light, the redox level of NADP(H) is an important endogenous regulator of diurnal entrainment of Synechocystis PCC 6803.

Diurnal variation of thermal resistance in rats

1980 ◽  
Vol 58 (10) ◽  
pp. 1174-1179 ◽  
Author(s):  
Y. Isobe ◽  
S. Takaba ◽  
K. Ohara
Keyword(s):  
Body Temperature ◽  
Heat Resistance ◽  
Time Of Day ◽  
Dark Phase ◽  
Diurnal Changes ◽  
Survival Times ◽  
Light Phase ◽  
Dark Cycle ◽  
Hot Environment ◽  
Normal Light

Effects of photoperiod on heat resistance were studied in 88 rats by observing their survival times in a hot environment (42.5 °C). Prior to the experiments individual rats were exposed to a given heat (42.5 °C) at a definite time of day and a "predicted survial time" in a given heat in individual rats was obtained. Rats were then divided into eight groups (with nine rats in each group) so as to ensure intergroup homogeneity regarding their predicted survival time and were exposed to heat at different times of day (every 3 h) until they were exhausted.It was found that the heat resistance varied with the time of day. In the eight groups kept under a normal light–dark cycle (L, 0700–1900; D, 1900–0700), heat resistances were observed to be significantly higher in the light phase than in the dark phase. Lethal body temperature was not correlated with the heat resistance. In two other groups (n = 8) kept under conditions reversed from the normal lighting cycle, resistance was higher in the nighttime (corresponding to the light phase when the rats were kept in the reversed lighting cycle) than in the morning (corresponding to the dark phase), these changes being accompanied by a phase shift of the diurnal changes in body temperature.

Immunocytochemical studies on the behavior of RuBisCO and LHCP II during the cell cycle of synchronized Euglena gracilis

1990 ◽  
Vol 48 (3) ◽  
pp. 662-663
Author(s):  
Tetsuaki Osafune ◽  
Shuji Sumida ◽  
Tomoko Ehara ◽  
Eiji Hase ◽  
Jerome A. Schiff
Keyword(s):  
Cell Cycle ◽  
Immunoelectron Microscopy ◽  
Growth Phase ◽  
Euglena Gracilis ◽  
Dark Period ◽  
Light Period ◽  
Carboxylase Activity ◽  
Immunocytochemical Studies ◽  
Lhcp Ii

Changes in the morphology of pyrenoid and the distribution of RuBisCO in the chloroplast of Euglena gracilis were followed by immunoelectron microscopy during the cell cycle in a light (14 h)- dark (10 h) synchronized culture under photoautotrophic conditions. The imrnunoreactive proteins wereconcentrated in the pyrenoid, and less densely distributed in the stroma during the light period (growth phase, Fig. 1-2), but the pyrenoid disappeared during the dark period (division phase), and RuBisCO was dispersed throughout the stroma. Toward the end of the division phase, the pyrenoid began to form in the center of the stroma, and RuBisCO is again concentrated in that pyrenoid region. From a comparison of photosynthetic CO2-fixation with the total carboxylase activity of RuBisCO extracted from Euglena cells in the growth phase, it is suggested that the carboxylase in the pyrenoid functions in CO2-fixation in photosynthesis.

scholarly journals Melatonin MT1 and MT2 Receptors Exhibit Distinct Effects in the Modulation of Body Temperature across the Light/Dark Cycle

2019 ◽  
Vol 20 (10) ◽  
pp. 2452 ◽  
Author(s):  
Martha López-Canul ◽  
Seung Hyun Min ◽  
Luca Posa ◽  
Danilo De Gregorio ◽  
Annalida Bedini ◽  
...  
Keyword(s):  
Body Temperature ◽  
Receptor Antagonist ◽  
Partial Agonist ◽  
Receptor Subtypes ◽  
Dark Phase ◽  
Light Phase ◽  
Dark Cycle ◽  
Simultaneous Activation ◽  
Type 3 ◽  
G Protein Coupled

Melatonin (MLT) is a neurohormone that regulates many physiological functions including sleep, pain, thermoregulation, and circadian rhythms. MLT acts mainly through two G-protein-coupled receptors named MT1 and MT2, but also through an MLT type-3 receptor (MT3). However, the role of MLT receptor subtypes in thermoregulation is still unknown. We have thus investigated the effects of selective and non-selective MLT receptor agonists/antagonists on body temperature (Tb) in rats across the 12/12-h light–dark cycle. Rectal temperature was measured every 15 min from 4:00 a.m. to 9:30 a.m. and from 4:00 p.m. to 9:30 p.m., following subcutaneous injection of each compound at either 5:00 a.m. or 5:00 p.m. MLT (40 mg/kg) had no effect when injected at 5 a.m., whereas it decreased Tb during the light phase only when injected at 5:00 p.m. This effect was blocked by the selective MT2 receptor antagonist 4P-PDOT and the non-selective MT1/MT2 receptor antagonist, luzindole, but not by the α1/MT3 receptors antagonist prazosin. However, unlike MLT, neither the selective MT1 receptor partial agonist UCM871 (14 mg/kg) nor the selective MT2 partial agonist UCM924 (40 mg/kg) altered Tb during the light phase. In contrast, UCM871 injected at 5:00 p.m. increased Tb at the beginning of the dark phase, whereas UCM924 injected at 5:00 a.m. decreased Tb at the end of the dark phase. These effects were blocked by luzindole and 4P-PDOT, respectively. The MT3 receptor agonist GR135531 (10 mg/kg) did not affect Tb. These data suggest that the simultaneous activation of both MT1 and MT2 receptors is necessary to regulate Tb during the light phase, whereas in a complex but yet unknown manner, they regulate Tb differently during the dark phase. Overall, MT1 and MT2 receptors display complementary but also distinct roles in modulating circadian fluctuations of Tb.

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