scholarly journals Stress-induced glucocorticoids alter the rhythmic activity of Leydig cells depending on the circadian time

2021 ◽  
Author(s):  
Marija Lj Medar ◽  
Silvana A Andric ◽  
Tatjana S Kostic
Keyword(s):  
Leydig Cells ◽  
Glucocorticoid Receptors ◽  
Rhythmic Activity ◽  
Circadian System ◽  
Transcriptional Analysis ◽  
Dark Phase ◽  
Similar Response ◽  
Light Phase ◽  
Mediated Communication ◽  
Circadian Time

AbstractThe connection between two fundamental processes in cells, the stress response and circadian timekeeping, were analyzed on Leydig cells from stressed rats. Stress increased glucocorticoids and decreased testosterone blood level. Transcriptional analysis revealed different sensitivity to stress events depending on the circadian time: the majority of steroidogenesis-related genes (Lhcgr, Nr3c1, Cyp11a1, Cyp17a1, Hsd3b1/2) were down-regulated by stress in the inactive (light) phase, but in the active (dark) phase of the day, they were unchanged or even up-regulated. Stress potentiates the expression of clock elements Bmal1/BMAL1, Per1/2/PER1 and Rev-erba. Glucocorticoid-treated rats showed a similar response, likewise stress on the negative clock regulators (Rev-erba/b, Cry1/2, Per1/2), suggesting that stress-induced glucocorticoids regulate clock loops but also outside genes through E-/RORE-box. Blockade of intratesticular glucocorticoid receptors prevented stress-induced change in expression negative clock regulators. The results reveal glucocorticoid-mediated communication between the stress- and circadian-system resets the Leydig cell’s clock.

scholarly journals Impact of circadian time of dosing on cardiac-autonomous effects of glucocorticoids

2021 ◽  
Author(s):  
Michelle Wintzinger ◽  
Manoj Panta ◽  
Karen Miz ◽  
Ashok D.P. Pragasam ◽  
Michelle Sargent ◽  
...  
Keyword(s):  
Heart Failure ◽  
Energy Demand ◽  
Heart Function ◽  
Daily Intake ◽  
Metabolic Stress ◽  
Single Pulse ◽  
High Energy ◽  
Dark Phase ◽  
Light Phase ◽  
Circadian Time

Bioenergetic capacity is critical to adapt the high energy demand of the heart to circadian oscillations and diseased states. Glucocorticoids regulate the circadian cycle of energy metabolism, but little is known about how circadian timing of exogenous glucocorticoid dosing directly regulates cardiac bioenergetics through the primary receptor of these drugs, the glucocorticoid receptor (GR). While chronic once-daily intake of glucocorticoids promotes metabolic stress and heart failure, we recently discovered that intermittent once-weekly dosing of exogenous glucocorticoids promoted muscle metabolism and heart function in dystrophic mice. However, the effects of glucocorticoid intermittence on heart failure beyond muscular dystrophy remain unknown. Here we investigated the extent to which circadian time of dosing regulates the cardiac-autonomous effects of the glucocorticoid prednisone in conditions of single pulse or chronic intermittent dosing. In WT mice, we found that prednisone improved cardiac content of NAD+ and ATP with light-phase dosing (ZT0), while the effects were blocked by dark-phase dosing (ZT12). The effects on mitochondrial function were cardiomyocyte-autonomous, as shown by inducible cardiomyocyte-restricted GR ablation, and depended on an intact activating clock complex, as shown by hearts from BMAL1-KO mice. Conjugating time-of-dosing with chronic intermittence, we found that once-weekly light-phase prednisone improved metabolism and function in heart after myocardial injury. Our study identifies cardiac-autonomous mechanisms through which circadian time and chronic intermittence reconvert glucocorticoid drugs to bioenergetic boosters for the heart.

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.

Locomotor activity responses in juvenile sockeye salmon, Oncorhynchus nerka, to melatonin and serotonin

1970 ◽  
Vol 48 (6) ◽  
pp. 1425-1427 ◽  
Author(s):  
John E. Byrne
Keyword(s):  
Locomotor Activity ◽  
Sockeye Salmon ◽  
Oncorhynchus Nerka ◽  
Dark Phase ◽  
Light Phase ◽  
Selective Activity

Intraperitoneal injections administered for 3 consecutive days to juvenile sockeye salmon resulted in selective activity responses to either the light or the dark phase of the photoperiodic cycle. Serotonin increased locomotor activity only during the dark phase, while melatonin decreased locomotor activity only during the light phase.

scholarly journals Algae-Assisted Microbial Desalination Cell: Analysis of Cathode Performance and Desalination Efficiency Assessment

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2011
Author(s):  
David Ewusi-Mensah ◽  
Jingyu Huang ◽  
Laura Katherin Chaparro ◽  
Pau Rodenas ◽  
Marina Ramírez-Moreno ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Chlorella Vulgaris ◽  
Coulombic Efficiency ◽  
Geobacter Sulfurreducens ◽  
Dark Phase ◽  
Water Production ◽  
Light Phase ◽  
Experimental Conditions ◽  
Residual Concentration ◽  
Microbial Desalination Cell

Algae-assisted microbial desalination cells represent a sustainable technology for low-energy fresh water production in which microalgae culture is integrated into the system to enhance oxygen reduction reaction in the cathode chamber. However, the water production (desalination rate) is low compared to conventional technologies (i.e., reverse osmosis and/or electrodialysis), as biocathodes provide low current generation to sustain the desalination process. In this sense, more research efforts on this topic are necessary to address this bottleneck. Thus, this study provides analysis, from the electrochemical point of view, on the cathode performance of an algae-assisted microbial desalination cell (MDC) using Chlorella vulgaris. Firstly, the system was run with a pure culture of Chlorella vulgaris suspension in the cathode under conditions of an abiotic anode to assess the cathodic behavior (i.e., cathode polarization curves in light-dark conditions and oxygen depletion). Secondly, Geobacter sulfurreducens was inoculated in the anode compartment of the MDC, and the desalination cycle was carried out. The results showed that microalgae could generate an average of 9–11.5 mg/L of dissolved oxygen during the light phase, providing enough dissolved oxygen to drive the migration of ions (i.e., desalination) in the MDC system. Moreover, during the dark phase, a residual concentration of oxygen (ca. 5.5–8 mg/L) was measured, indicating that oxygen was not wholly depleted under our experimental conditions. Interestingly, the oxygen concentration was restored (after complete depletion of dissolved oxygen by flushing with N2) as soon as microalgae were exposed to the light phase again. After a 31 h desalination cycle, the cell generated a current density of 0.12 mA/cm2 at an efficiency of 60.15%, 77.37% salt was removed at a nominal desalination rate of 0.63 L/m2/h, coulombic efficiency was 9%, and 0.11 kWh/m3 of electric power was generated. The microalgae-assisted biocathode has an advantage over the air diffusion and bubbling as it can self-sustain a steady and higher concentration of oxygen, cost-effectively regenerate or recover from loss and sustainably retain the system’s performance under naturally occurring conditions. Thus, our study provides insights into implementing the algae-assisted cathode for sustainable desalination using MDC technology and subsequent optimization.

scholarly journals Aging Alters Daily and Regional Calretinin Neuronal Expression in the Rat Non-image Forming Visual Thalamus

2021 ◽  
Vol 13 ◽  
Author(s):  
Felipe P. Fiuza ◽  
José Pablo G. Queiroz ◽  
Antônio Carlos Q. Aquino ◽  
Diego A. Câmara ◽  
Luiz Eduardo M. Brandão ◽  
...  
Keyword(s):  
Calcium Binding ◽  
Brain Dysfunction ◽  
Dark Phase ◽  
Light Phase ◽  
Dark Light ◽  
Visual Thalamus ◽  
Age Related ◽  
Spatial Domains ◽  
Subcortical Regions ◽  
Daily Changes

Aging affects the overall physiology, including the image-forming and non-image forming visual systems. Among the components of the latter, the thalamic retinorecipient inter-geniculate leaflet (IGL) and ventral lateral geniculate (vLGN) nucleus conveys light information to subcortical regions, adjusting visuomotor, and circadian functions. It is noteworthy that several visual related cells, such as neuronal subpopulations in the IGL and vLGN are neurochemically characterized by the presence of calcium binding proteins. Calretinin (CR), a representative of such proteins, denotes region-specificity in a temporal manner by variable day–night expression. In parallel, age-related brain dysfunction and neurodegeneration are associated with abnormal intracellular concentrations of calcium. Here, we investigated whether daily changes in the number of CR neurons are a feature of the aged IGL and vLGN in rats. To this end, we perfused rats, ranging from 3 to 24 months of age, within distinct phases of the day, namely zeitgeber times (ZTs). Then, we evaluated CR immunolabeling through design-based stereological cell estimation. We observed distinct daily rhythms of CR expression in the IGL and in both the retinorecipient (vLGNe) and non-retinorecipient (vLGNi) portions of the vLGN. In the ZT 6, the middle of the light phase, the CR cells are reduced with aging in the IGL and vLGNe. In the ZT 12, the transition between light to dark, an age-related CR loss was found in all nuclei. While CR expression predominates in specific spatial domains of vLGN, age-related changes appear not to be restricted at particular portions. No alterations were found in the dark/light transition or in the middle of the dark phase, ZTs 0, and 18, respectively. These results are relevant in the understanding of how aging shifts the phenotype of visual related cells at topographically organized channels of visuomotor and circadian processing.

Adrenal corticoids in hamsters: role in circadian timing

1985 ◽  
Vol 248 (4) ◽  
pp. R434-R438 ◽  
Author(s):  
H. E. Albers ◽  
L. Yogev ◽  
R. B. Todd ◽  
B. D. Goldman
Keyword(s):  
Wheel Running ◽  
Sampling Period ◽  
Dark Phase ◽  
Cortisol Secretion ◽  
Experimental Protocol ◽  
Light Phase ◽  
Dark Cycle ◽  
Physiological Control ◽  
Circadian Organization

The 24-h patterns of circulating cortisol and corticosterone were determined in male hamsters housed under a 14:10 light-dark cycle. Corticoid levels varied significantly over the 24-h sampling period with peak levels of both hormones occurring near the onset of the daily dark phase. The ratio of cortisol to corticosterone changed dramatically during the day. Corticosterone levels were significantly higher than cortisol during the early part of the light phase; however, cortisol levels became significantly higher than corticosterone when both hormones began their daily rise. To examine whether the circadian rhythm of cortisol secretion could be involved in the physiological control of hamster circadian organization, cortisol was infused at approximately physiological levels into adrenalectomized hamsters either continuously or in a 24-h rhythm. No significant differences were observed in the timing of circadian wheel-running rhythms in hamsters housed in LD 16:8, LD 14:10, or LL when cortisol was infused continuously, in a 24-h rhythm that mimicked the cortisol rhythm of intact hamsters, or in a 24-h rhythm several hours out of phase with the rhythm of intact hamsters. Provision of cortisol in a 24-h rhythm appeared to promote the survival of adrenalectomized hamsters since hamsters receiving a 24-h pattern of cortisol survived the experimental protocol significantly longer than those receiving the same dose of cortisol continuously.

Diurnal potassium excretory cycles in the rat

1986 ◽  
Vol 250 (5) ◽  
pp. F930-F941 ◽  
Author(s):  
L. Rabinowitz ◽  
C. J. Wydner ◽  
K. M. Smith ◽  
H. Yamauchi
Keyword(s):  
Extracellular Fluid ◽  
Potassium Content ◽  
Extracellular Potassium ◽  
Dark Phase ◽  
Adrenal Steroids ◽  
Light Phase ◽  
High Potassium ◽  
Potassium Intake ◽  
Low Levels ◽  
Adrenalectomized Rats

Diurnal potassium cycles (DPC) were measured in unanesthetized undisturbed rats fed a liquid diet and maintained in a 12-h light-dark environment. A fourfold step increase in diet potassium content increased DPC amplitude without altering phase. After presentation of the high-potassium diet, the initial adaptive increase in excretion occurred within 1.5 h (diet given during dark phase) and within 6 h (diet given during light phase). On a day when food was withheld (no potassium intake), DPC were present but with a lowered amplitude. The amount of potassium excreted on a fasting day exceeded gut and extracellular fluid potassium content and was only modestly increased when rats were previously fed a high-potassium diet. In adrenalectomized rats that received no steroid replacement or received constant infusions of low levels of aldosterone, dexamethasone, or aldosterone plus dexamethasone, potassium balance and DPC were normal. It is concluded that the amplitude of DPC in the rat is determined in part by the availability of potassium from both intracellular and extracellular potassium pools; mechanisms independent of potassium intake can generate the DPC; and the presence or the cyclic secretion of adrenal steroids is not necessary for the generation of DPC in the rat.

scholarly journals Time matters: pathological effects of repeated psychosocial stress during the active, but not inactive, phase of male mice

2012 ◽  
Vol 215 (3) ◽  
pp. 425-437 ◽  
Author(s):  
Manuela S Bartlang ◽  
Inga D Neumann ◽  
David A Slattery ◽  
Nicole Uschold-Schmidt ◽  
Dominik Kraus ◽  
...  
Keyword(s):  
Social Preference ◽  
Active Phase ◽  
Time Of Day ◽  
Dark Phase ◽  
Light Phase ◽  
Immunological Parameters ◽  
Repeated Restraint Stress ◽  
Inactive Phase ◽  
Home Cage Activity

Recent findings in rats indicated that the physiological consequences of repeated restraint stress are dependent on the time of day of stressor exposure. To investigate whether this is also true for clinically more relevant psychosocial stressors and whether repeated stressor exposure during the light phase or dark phase is more detrimental for an organism, we exposed male C57BL/6 mice to social defeat (SD) across 19 days either in the light phase between Zeitgeber time (ZT)1 and ZT3 (SDL mice) or in the dark phase between ZT13 and ZT15 (SDD mice). While SDL mice showed a prolonged increase in adrenal weight and an attenuated adrenal responsiveness to ACTHin vitroafter stressor termination, SDD mice showed reduced dark phase home-cage activity on observation days 7, 14, and 20, flattening of the diurnal corticosterone rhythm, lack of social preference, and higherin vitroIFNγ secretion from mesenteric lymph node cells on day 20/21. Furthermore, the colitis-aggravating effect of SD was more pronounced in SDD than SDL mice following dextran sulfate sodium treatment. In conclusion, the present findings demonstrate that repeated SD effects on behavior, physiology, and immunology strongly depend on the time of day of stressor exposure. Whereas physiological parameters were more affected by SD during the light/inactive phase of mice, behavioral and immunological parameters were more affected by SD during the dark phase. Our results imply that repeated daily SD exposure has a more negative outcome when applied during the dark/active phase. By contrast, the minor physiological changes seen in SDL mice might represent beneficial adaptations preventing the formation of those maladaptive consequences.

Amiloride effect on diurnal cyclic Na and K excretion in rats

1989 ◽  
Vol 256 (2) ◽  
pp. R510-R517 ◽  
Author(s):  
P. L. Dalton ◽  
L. Rabinowitz
Keyword(s):  
Dark Phase ◽  
Transport Mechanisms ◽  
Light Phase ◽  
Diurnal Cycles ◽  
High K ◽  
K Secretion

Amiloride was administered to rats during the peak and minimum of Na and K diurnal rhythmic excretion (i.e., during early dark phase and early light phase). In rats receiving a normal-K diet (2.34 meq/day) amiloride decreased K excretion from 186 to 37 mueq/h (dark phase) and from 31 to 4 mueq/h (light phase). Amiloride increased Na excretion from 91 to 344 mueq/h (dark phase) and from 35 to 164 mueq/h (light phase). Rats receiving a high-K diet (10.4 meq/day) showed a higher diurnal peak and minimum for K excretion. During high-K intake, amiloride decreased K excretion from 787 to 191 mueq/h (dark phase) and from 197 to 40 mueq/h (light phase) and increased Na excretion from 237 to 891 mueq/h (dark phase) and from 31 to 222 mueq/h (light phase). Whenever given, amiloride reduced K excretion to approximately 20% of control excretion. It is concluded that rhythmic changes in amiloride-sensitive distal transport are largely, but not entirely, responsible for the diurnal K cycle, but do not cause the concurrent Na cycle. Thus the diurnal cycles in Na and K are expressed through changes in different transport mechanisms. In rats maintained on a high-K diet there is an increase in rhythmic K secretion and Na reabsorption by amiloride-sensitive transport. To maintain Na excretion unchanged, Na reabsorption must be correspondingly depressed at an amiloride-insensitive site.

scholarly journals Bright light during lactation alters the functioning of the circadian system of adult rats

2000 ◽  
Vol 278 (1) ◽  
pp. R201-R208 ◽  
Author(s):  
M. M. Canal-Corretger ◽  
T. Cambras ◽  
J. Vilaplana ◽  
A. Díez-Noguera
Keyword(s):  
Motor Activity ◽  
Activity Rhythm ◽  
Bright Light ◽  
Circadian System ◽  
Constant Darkness ◽  
Adult Rats ◽  
Light Pulses ◽  
Circadian Time ◽  
Role Of Light

To examine the role of light in the maturation of the circadian pacemaker, twelve groups of rats were raised in different conditions of exposure to constant bright light (LL) during lactation: both duration and timing of LL were varied. We studied the motor activity rhythm of the rats after weaning, first under LL and then under constant darkness (DD). In DD, two light pulses [at circadian time 15 (CT15) and CT22] were applied to test the response of the pacemaker. Greater exposure to LL days during lactation increased the number of rhythmic animals and the amplitude of their motor activity rhythm in the LL stage and decreased the phase delay due to the light pulse at CT15. The timing of LL during lactation affected these variables too. Because the response of the adult to light depended on both the number and timing of LL days during lactation, the exposure to light at early stages may influence the development of the circadian system by modifying it structurally or functionally.

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