scholarly journals Photoperiod-Induced Neuroplasticity in the Circadian System

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Alessandra Porcu ◽  
Malini Riddle ◽  
Davide Dulcis ◽  
David K. Welsh
Keyword(s):  
Seasonal Changes ◽  
Phase Distribution ◽  
Light Exposure ◽  
Brain Regions ◽  
Day Length ◽  
Light Conditions ◽  
Seasonal Adaptation ◽  
Circadian Oscillators ◽  
Plastic Changes ◽  
Mood And Cognition

Seasonal changes in light exposure have profound effects on behavioral and physiological functions in many species, including effects on mood and cognitive function in humans. The mammalian brain’s master circadian clock, the suprachiasmatic nucleus (SCN), transmits information about external light conditions to other brain regions, including some implicated in mood and cognition. Although the detailed mechanisms are not yet known, the SCN undergoes highly plastic changes at the cellular and network levels under different light conditions. We therefore propose that the SCN may be an essential mediator of the effects of seasonal changes of day length on mental health. In this review, we explore various forms of neuroplasticity that occur in the SCN and other brain regions to facilitate seasonal adaptation, particularly altered phase distribution of cellular circadian oscillators in the SCN and changes in hypothalamic neurotransmitter expression.

scholarly journals Hybrid tea-roses under controlled light conditions. I. The effect of the level of irradiance on the growth and development of seedlings.

1978 ◽  
Vol 26 (1) ◽  
pp. 119-127
Author(s):  
D.P. de Vries ◽  
L. Smeets
Keyword(s):  
Light Intensity ◽  
Leaf Area ◽  
Growth And Development ◽  
Day Length ◽  
Light Conditions ◽  
Flower Bud ◽  
Juvenile Period ◽  
Low Light ◽  
Bud Formation ◽  
Flower Bud Abortion

As a basis for breeding cvs adapted to flowering in winter light conditions, the growth of hybrid tea rose seedlings under controlled conditions was studied. Irradiance varied from 4-24 W/m2, day length was 8 h, temperature 21 deg C. Like cvs, the seedlings sometimes aborted the flower bud at low light intensity. With increasing irradiances, the following phenomena were observed: the juvenile period of the seedlings shortened; plants were longer at bud formation, at first flowering and at flower bud abortion; leaf area and the number of petals increased. Leaf number was constant at all irradiances. Flowering seedlings were smaller at bud formation, but taller at actual flowering than blind ones. Blind seedlings had fewer leaves with a smaller area. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Reproductive management of the transitional mare

UK-Vet Equine ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 42-47
Author(s):  
Camilla Scott
Keyword(s):  
Light Exposure ◽  
Hormone Secretion ◽  
Light Therapy ◽  
Day Length ◽  
Reproductive Management ◽  
Incandescent Bulb ◽  
The Hours ◽  
Artificial Photoperiod ◽  
Lighting Regimen ◽  
Stimulating Hormone

The mare is a seasonally polyoestrous long-day breeder with a physiological breeding season lasting from April–October in the Northern Hemisphere. The hypothalamic-pituitary-gonadal axis in the mare is subject to a circannual endogenous rhythm that is primarily regulated by day length. Increasing ambient photoperiod in the spring alters the pattern of melatonin secretion. The resulting stimulation of hypothalamic gonadotropin-releasing hormone secretion triggers pituitary follicular stimulating hormone release and follicular growth. Exposure of mares in deep anoestrus to a stimulatory photoperiod remains the most successful method of advancing the first ovulation of the season. The most commonly used lighting regimen is providing a fixed length of 15–16 hours of light exposure and 8–9 hours of dark, with a minimum light intensity in a stable of 100-lux (100–200 watt incandescent bulb). Other methods include using an additional 2.5 hours of light beginning at sunset and a pulse lighting system, providing 1 hour of light, 9.5–10.5 hours after the onset of darkness, during the photosensitive phase. Alternatively, the EquilumeTM light masks provide a unilateral LED light source emitting 50 lux of blue-light directly to the eye during the hours after dusk (until 11 pm). Mares that have not been maintained under lights, or that have been exposed to ineffective light therapy, may require therapeutic hormonal intervention to advance the onset of the first ovulation of the season. Many hormone protocols involving progestins, GnRH, dopamine agonists and recombinant luteinising hormone/follicle stimulating hormone have been studied with variable results. Therapy is typically more effective when started either in late transitional mares or following a period of stimulatory artificial photoperiod.

Molecular Cloning, Characterisation, Tissue Distribution, and mRNA Expression Changes under Different Light Regimes of Brain and Muscle Arnt-Like Protein-1 (BMAL1) in Columba Livia

2017 ◽  
Vol 10 (3) ◽  
pp. 156-163 ◽  
Author(s):  
Y. Wang ◽  
H.M. Yang ◽  
Y.B. Li ◽  
W. Cao
Keyword(s):  
Circadian Rhythm ◽  
Light Exposure ◽  
Columba Livia ◽  
Full Length ◽  
Day Length ◽  
Mrna Levels ◽  
Tyto Alba ◽  
Full Length Cdna ◽  
Light Regimes ◽  
Significant Difference

Brain and muscle Arnt-like protein-1 (BMAL1) plays an important role in circadian rhythm, which is involved in daily behaviours and physiological activities. However, little is known about the molecular function of BMAL1 in the Pigeon ( Columba livia). In our study, the full-length cDNA of Bmal1 was cloned and sequenced from the Pigeon for the first time, and submitted to the GenBank to obtain the accession number (KF906247). The full-length cDNA of Bmal1 consists of 2,488 nucleotides, and encodes 634 amino acids. Phylogenetic analysis showed that it bore the greatest similarity to Bmal1 from the Chicken ( Gallus gallus) and Barn Owl ( Tyto alba). The amino acid sequence of the Pigeon BMAL1 contained a HLH domain and two PAS domains, which are involved in forming hetero-homodimers with the CLOCK as the positive element of the circadian rhythm. The results of real-time quantitative PCR of Bmal1 under different light regimes showed that the amplitude and expression pattern of Bmal1 were strongly affected by day length. Bmal1 was most highly expressed in the pancreas. Relative to Bmal1 expression level under 12 h of light exposure, it was increased significantly in the pituitary gland, ovary and uterus under 15 h of light exposure ( P < 0.05). However, other tissues, including the hypothalamus, heart, liver, spleen, kidney, intestines, crureus, and pectorals exhibited no significant difference ( P < 0.05) under the two light regimes. This is the first study to investigate Bmal1 mRNA levels in various tissues under different light cycles, and thereby provide data for further study of the molecular and regulatory mechanisms of Bmal1 and circadian clock genes of the Pigeon.

Temperature modulation of photoperiodism and the timing of late-season changes in life history for an aphid, Acyrthosiphon pisum

2011 ◽  
Vol 143 (1) ◽  
pp. 56-71 ◽  
Author(s):  
M.A.H. Smith ◽  
P.A. MacKay ◽  
R.J. Lamb
Keyword(s):  
Sexual Reproduction ◽  
Seasonal Changes ◽  
Acyrthosiphon Pisum ◽  
Late Summer ◽  
Day Length ◽  
Temperature Modulation ◽  
Four Seasons ◽  
Aphid Clone ◽  
Photoperiodic Responses

AbstractWhere winters are severe, aphids reproduce parthenogenetically and viviparously in summer, switch to sexual reproduction in late summer, and produce winter-hardy eggs by the end of the season. The role of day length and temperature in initiating seasonal changes from parthenogenetic to sexual reproduction by pea aphids, Acyrthosiphon pisum (Harris) (Hemiptera: Aphididae), are described and the selection pressures that affect the timing of this transition are investigated. Over four seasons, a pea aphid clone was sampled from field cages through late summer in southern Manitoba, Canada, and reared in the laboratory to determine the phenotypes of progeny produced as the season progressed. The timing of transitions from one phenotype to another under natural day length and temperature, and the critical day lengths that caused the transitions, coincided with expectations from laboratory studies of photoperiodic responses. Males and mating females appeared later when the weather in August was warm than when it was cool. The timing of seasonal changes was adapted to minimize the physiological time to the end of the season, which maximized the number of asexual summer generations. Ambient temperature modulated the response to day length and fine-tuned the timing of sexual reproduction to adapt for annual variation in autumn weather.

scholarly journals GABA-mediated repulsive coupling between circadian clock neurons in the SCN encodes seasonal time

2015 ◽  
Vol 112 (29) ◽  
pp. E3920-E3929 ◽  
Author(s):  
Jihwan Myung ◽  
Sungho Hong ◽  
Daniel DeWoskin ◽  
Erik De Schutter ◽  
Daniel B. Forger ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Synaptic Input ◽  
Chloride Concentration ◽  
Phase Relationship ◽  
Day Length ◽  
Intracellular Chloride ◽  
Circadian Oscillators ◽  
Length Changes ◽  
Excitatory Gaba ◽  
Intracellular Chloride Concentration

The mammalian suprachiasmatic nucleus (SCN) forms not only the master circadian clock but also a seasonal clock. This neural network of ∼10,000 circadian oscillators encodes season-dependent day-length changes through a largely unknown mechanism. We show that region-intrinsic changes in the SCN fine-tune the degree of network synchrony and reorganize the phase relationship among circadian oscillators to represent day length. We measure oscillations of the clock gene Bmal1, at single-cell and regional levels in cultured SCN explanted from animals raised under short or long days. Coupling estimation using the Kuramoto framework reveals that the network has couplings that can be both phase-attractive (synchronizing) and -repulsive (desynchronizing). The phase gap between the dorsal and ventral regions increases and the overall period of the SCN shortens with longer day length. We find that one of the underlying physiological mechanisms is the modulation of the intracellular chloride concentration, which can adjust the strength and polarity of the ionotropic GABAA-mediated synaptic input. We show that increasing day-length changes the pattern of chloride transporter expression, yielding more excitatory GABA synaptic input, and that blocking GABAA signaling or the chloride transporter disrupts the unique phase and period organization induced by the day length. We test the consequences of this tunable GABA coupling in the context of excitation–inhibition balance through detailed realistic modeling. These results indicate that the network encoding of seasonal time is controlled by modulation of intracellular chloride, which determines the phase relationship among and period difference between the dorsal and ventral SCN.

scholarly journals Photoperiodic regulation of prolactin secretion: changes in intra-pituitary signalling and lactotroph heterogeneity

2004 ◽  
Vol 180 (3) ◽  
pp. 351-356 ◽  
Author(s):  
JD Johnston
Keyword(s):  
Environmental Conditions ◽  
Seasonal Changes ◽  
Mammalian Species ◽  
Prolactin Secretion ◽  
Day Length ◽  
Pars Tuberalis ◽  
Photoperiodic Regulation ◽  
Pituitary Lactotroph

Many mammalian species utilise day-length (photoperiod) to adapt their physiology to seasonal changes in environmental conditions, via secretion of pineal melatonin. Photoperiodic regulation of prolactin secretion is believed to occur via melatonin-mediated changes in the secretion of a putative prolactin secretagogue, tuberalin, from the pituitary pars tuberalis. Despite the in vivo and in vitro evidence in support of this intra-pituitary signalling mechanism, the identity of tuberalin has yet to be elucidated. This paper reviews recent advances in the characterisation of tuberalin and the regulation of its secretion. Furthermore, the hypothesis that pituitary lactotroph cells display heterogeneity in their response to changing photoperiod and tuberalin secretion is examined.

scholarly journals Sustainable Illumination for Baroque Paintings with Historical Context Considerations

2020 ◽  
Vol 12 (20) ◽  
pp. 8705
Author(s):  
Pedro Luengo
Keyword(s):  
Eighteenth Century ◽  
Seasonal Changes ◽  
Light Exposure ◽  
Historical Context ◽  
Zero Energy ◽  
Museum Displays ◽  
Zero Energy Building ◽  
Sustainable Conservation ◽  
Scholarly Attention ◽  
Selection Of

The topic of museum illumination and conservation has been richly developed in recent years to take steps toward a zero-energy building concept. Most artworks preserved in museums’ expositions were designed for specifically defined light contexts, wherein daylight and seasonal changes were part of the artistic effect, an issue which has received little scholarly attention. From this premise, this paper aims to prove that defining the original illuminative context of artworks is required for a sustainable conservation, perception, and ultimate interpretation. To do this, a selection of seventeenth and eighteenth century churches and palaces from Europe, the Americas, and Asia will be presented using modern conservation frameworks for artworks. The results demonstrate that both aspects, chosen materials and light exposure, were connected, allowing the spaces to be effective without consuming too much electric lighting. This leads to a discussion about if museum displays should incorporate this context, if it is a more sustainable solution, and if it presents the artworks more accurately to visitors, even as other problems may arise.

Reproductive management of the transitional mare

Equine Health ◽  
2020 ◽  
Vol 2020 (2) ◽  
pp. 42-47
Author(s):  
Camilla Scott
Keyword(s):  
Light Exposure ◽  
Hormone Secretion ◽  
Light Therapy ◽  
Day Length ◽  
Reproductive Management ◽  
Incandescent Bulb ◽  
The Hours ◽  
Artificial Photoperiod ◽  
Lighting Regimen ◽  
Stimulating Hormone

The mare is a seasonally polyoestrous long-day breeder with a physiological breeding season lasting from April–October in the Northern Hemisphere. The hypothalamic-pituitary-gonadal axis in the mare is subject to a circannual endogenous rhythm that is primarily regulated by day length. Increasing ambient photoperiod in the spring alters the pattern of melatonin secretion. The resulting stimulation of hypothalamic gonadotropin-releasing hormone secretion triggers pituitary follicular stimulating hormone release and follicular growth. Exposure of mares in deep anoestrus to a stimulatory photoperiod remains the most successful method of advancing the first ovulation of the season. The most commonly used lighting regimen is providing a fixed length of 15–16 hours of light exposure and 8–9 hours of dark, with a minimum light intensity in a stable of 100-lux (100–200 watt incandescent bulb). Other methods include using an additional 2.5 hours of light beginning at sunset and a pulse lighting system, providing 1 hour of light, 9.5–10.5 hours after the onset of darkness, during the photosensitive phase. Alternatively, the EquilumeTM light masks provide a unilateral LED light source emitting 50 lux of blue-light directly to the eye during the hours after dusk (until 11 pm). Mares that have not been maintained under lights, or that have been exposed to ineffective light therapy, may require therapeutic hormonal intervention to advance the onset of the first ovulation of the season. Many hormone protocols involving progestins, GnRH, dopamine agonists and recombinant luteinising hormone/follicle stimulating hormone have been studied with variable results. Therapy is typically more effective when started either in late transitional mares or following a period of stimulatory artificial photoperiod.

Croissance et tubérisation du radis (Raphanus sativus) selon la durée d'éclairement

1988 ◽  
Vol 66 (9) ◽  
pp. 1834-1840 ◽  
Author(s):  
L. Combe ◽  
Ph. Quetin ◽  
G. Decoux
Keyword(s):  
Leaf Area ◽  
Raphanus Sativus ◽  
Dry Matter ◽  
Light Exposure ◽  
Day Length ◽  
Controlled Environment ◽  
Main Criterion ◽  
Tuber Dry Matter ◽  
Light Duration ◽  
Trophic Action

Radish tuberization was studied with plants grown in a controlled-environment room at 19 °C day and night, with a daily light duration (radiant flux density, 600 μmol m−2 s−1 photosynthetically active radiations (PAR)) varying from 4 to 24 h at 2 h intervals. Day length did not seem to play a role in the initiation of tuberization: tuber thickening began after about 50 h of cumulative light exposure for all treatments. Moreover, two light treatments with the same daily photosynthetic balance, 8 h a day at high saturating irradiance (600 μmol m−2 s−1 PAR) and 16 h a day at low irradiance (200 μmol m−2 s−1 PAR), resulted in the same growth and tuberization regardless of day length. When the photoperiod is shorter than 7 h, it can modify leaf area, but for longer photoperiods, age is the main criterion determining foliage area. Cumulative light exposure determines the tuber dry matter to foliage dry matter ratio (tuberization index) if the day length is shorter than 16 h; if it is not, plant age alone determines the tuberization index. Day length has an effect on radish tuberization essentially because of its trophic action by photo-synthetic assimilate allocation to tuber thickening.

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