The effect of photoperiod regimes on daily RNA:DNA ratio rhythms in Chinese soft-shelled turtles (Pelodiscus sinensis)

2017 ◽  
Vol 38 (2) ◽  
pp. 217-223
Author(s):  
Fangshuo Ji ◽  
Haiyan Liu ◽  
Chao Li ◽  
Zhencai Yang
Keyword(s):  
Daily Variation ◽  
Constant Darkness ◽  
Continuous Darkness ◽  
Pelodiscus Sinensis ◽  
Physiological Processes ◽  
Variable Environments ◽  
Environmental Variations ◽  
Animal Growth ◽  
Forelimb Muscles ◽  
Rna:Dna Ratio

The ratio of RNA to DNA is widely used to reflect instantaneous animal growth; however, little is known about its daily variation. Photoperiod can modify expression of internal clocks, providing animals with the flexibility to adapt to variable environments. This study focused on the influence of photoperiod regimes on the daily variation of RNA:DNA ratio in Pelodiscus sinensis. We randomly divided 260 turtles into four groups: constant dark (0L), 8 h light with 16 h dark (8L), 12 h light with 12 h dark (12L), and 16 h light with 8 h dark (16L). Turtles were housed under specific photoperiods for 15 days (fed for first 10 days then starved for 5 days), thereafter we sampled the tissues every 2 h for 24 h. We dissected forelimb muscles and measured the concentration of isolated RNA and DNA. There were rhythmic variations in the RNA:DNA ratio, even in turtles under continuous darkness, indicating that P. sinensis has circadian RNA:DNA ratio rhythms, and the rhythms were likely controlled by internal clocks. Additionally, the acrophase was advanced by two hours in constant darkness in contrast to the other three photoperiods, indicating that the photoperiod considerably modified the rhythm set by the internal clocks. Notably, the RNA:DNA ratio differed between photoperiod regimes, with 0L > 16L > 8L ≈ 12L, indicating the photoperiod may be a seasonal indicator for turtles to synchronize their physiological processes with environmental variations.

Altered circadian responses to light in streptozotocin-induced diabetic mice

1999 ◽  
Vol 277 (2) ◽  
pp. E232-E237 ◽  
Author(s):  
Etienne Challet ◽  
Olivier van Reeth ◽  
Fred W. Turek
Keyword(s):  
Daily Variation ◽  
Serum Glucose ◽  
Temporal Organization ◽  
Constant Darkness ◽  
Diurnal Changes ◽  
Ambient Light ◽  
Circadian Pacemaker ◽  
Diabetic Mice ◽  
Phase Resetting ◽  
Insulin Producing Cells

Diabetes mellitus affects the daily expression of many behavioral and metabolic processes. Recent studies indicate that changes in brain glucose metabolism alter the entraining effects of light of the circadian pacemaker. To test whether diabetes-associated diurnal changes are related to alterations in the responses of the circadian pacemaker to light, photic phase resetting of the circadian rhythm of locomotor activity was analyzed in diabetic mice housed in constant darkness. Multiple low doses of streptozotocin, which damages pancreatic β-insulin-producing cells, were used to render C57BL/6J mice mildly diabetic. In those mice treated with streptozotocin, serum glucose was increased by 25% and circadian responses to light either were increased by 40% for phase delays or were close to those observed in control animals for phase advances. Furthermore, insulin-induced hypoglycemia normalized light-induced phase delays in diabetic animals, without altering those in nondiabetic mice. These results show that abnormalities of daily temporal organization associated with diabetes can result from altered circadian responses to the daily variation in ambient light. Such alterations could be normalized with appropriate insulin therapy.

Factors affecting perithecial production in Gibberella (Fusarium) tricincta

1979 ◽  
Vol 57 (22) ◽  
pp. 2497-2500 ◽  
Author(s):  
N. E. El-Gholl ◽  
C. L. Schoulties ◽  
W. H. Ridings
Keyword(s):  
Mass Culture ◽  
Basal Medium ◽  
Continuous Light ◽  
Colony Growth ◽  
Constant Darkness ◽  
Continuous Darkness ◽  
Hedera Helix ◽  
Pigment Formation ◽  
Factors Affecting ◽  
Leaf Spots

Three pigmentation types (brown, red, and white) of Fusarium tricinctum (Corda) Sacc. were observed when an isolated mass culture from leaf spots on English ivy (Hedera helix L.) was single spored. Perithecia of the heterothallic fungus Gibberella tricincta El-Gholl were produced at 20 and 27 °C on stem pieces of Cynodon dactylan Pers. resting on water agar, under 12-h alternating light and dark when certain pigmentation types were paired. Pairing of red and brown pigmentation types yielded significantly (P < 0.05) more perithecia than red and white pairings at 20 and 27 °C. Perithecia were formed only in combinations of red with brown or white pigmentation types. In both sets of pairings, significantly (P < 0.05) more perithecia were produced at 27 than at 20 °C. No perithecia were formed in constant darkness. Occasionally, the red pigmentation type became white after subsequent transfers and never reverted to the red pigmentation on various media and failed to produce perithecia with any pigmentation type. Continuous darkness slightly favored red pigment formation over continuous light as detected by the Munsell color codes. Increasing temperatures from 20 to 32 °C decreased the colony growth diameter of the red-pigmented cultural type. At 32 °C a change in hue was noted with corresponding changes in color codes. Red mycelial pigmentation was intensified by the addition of copper, iron, manganese, and zinc to a basal medium. The addition of 0.1% yeast extract favored mycelial development and caused a more pronounced red mycelial pigmentation in the presence of heavy metals.

EFFECTS OF PINEALECTOMY AND CONSTANT LIGHT AND DARKNESS ON PROLACTIN LEVELS IN THE PITUITARY AND PLASMA AND ON PITUITARY ULTRASTRUCTURE OF THE RAT

1972 ◽  
Vol 54 (2) ◽  
pp. 263-NP ◽  
Author(s):  
R. RELKIN ◽  
M. ADACHI ◽  
S. A. KAHAN
Keyword(s):  
Plasma Concentrations ◽  
Virgin Female ◽  
Female Rats ◽  
Constant Light ◽  
Constant Darkness ◽  
Plasma Prolactin ◽  
Continuous Darkness ◽  
Prolactin Content ◽  
Intermediate Degree ◽  
Pituitary Prolactin

SUMMARY The effects of constant light, constant darkness and diurnal lighting, in combination with pinealectomy or sham-pinealectomy, on pituitary and plasma concentrations of radioimmunoassayable prolactin were investigated in 8-week-old male and virgin female rats. Two to three days after operation random groups of pinealectomized and sham-pinealectomized animals of the same sex were placed together in either continous light, continuous darkness or diurnal light, and killed 21 days later. Compared with sham-operated diurnally-illuminated controls, constant darkness caused a decrease in pituitary prolactin content and a rise in plasma prolactin levels. Pinealectomy or constant illumination reversed the effect of constant darkness, resulting in an increase in pituitary prolactin content and a fall in plasma prolactin levels when compared with sham-operated diurnally-illuminated controls. Electron microscopy of lactotrophic cells of the sham-pinealectomized animals exposed to constant darkness revealed few cytoplasmic granules, whereas these cells in the sham-pinealectomized animals exposed to constant light contained abundant granules; compared with the former groups, lactotrophic cells of sham-pinealectomized rats exposed to diurnal lighting revealed an intermediate degree of granulation.

Melatonin administration entrains female rat activity rhythms in constant darkness but not in constant light

1988 ◽  
Vol 255 (2) ◽  
pp. R237-R242
Author(s):  
E. M. Thomas ◽  
S. M. Armstrong
Keyword(s):  
Estrous Cycle ◽  
Activity Rhythm ◽  
Onset Time ◽  
Circadian System ◽  
Female Rats ◽  
Male Rats ◽  
Constant Darkness ◽  
Female Rat ◽  
Continuous Darkness ◽  
Activity Rhythms

In female rats the luteinizing hormone (LH) is timed by the circadian system and is followed by a display of intense, estrogen-induced running behavior. This proestrous running on the night of ovulation can be used as a marker of the estrous cycle. Entrainment of the mammalian circadian system by exogenous melatonin (MT) has been demonstrated only in the activity rhythms of male rats. The present experiments were designed to study the effect of daily MT injections on activity rhythms and proestrous running of female rats in 1) continuous dim white light (LL) and 2) continuous darkness (DD). In LL, MT injections (50 micrograms/kg or 1 mg/kg) had no discernible effect on activity rhythms. In DD, four of the six MT-treated rats (100 micrograms/kg) entrained to the injection, and a fifth animal showed phase advances in its activity rhythm when onset of activity passed through injection time. The sixth animal was not injected with MT at activity onset time. None of the six control animals showed either effect. MT had no effect on the length of the estrous cycle. Thus MT injections can entrain circadian rhythms of activity and proestrous running in female rats in DD but not in LL.

Germination strategies of annual forbs from south-eastern Australian semiarid grasslands

2012 ◽  
Vol 60 (4) ◽  
pp. 340 ◽  
Author(s):  
Andrew J. Scott ◽  
John W. Morgan
Keyword(s):  
Temperature Regime ◽  
Environmental Conditions ◽  
Seed Banks ◽  
Constant Darkness ◽  
Continuous Darkness ◽  
Soil Seed Banks ◽  
South Eastern ◽  
Single Temperature ◽  
Risk Spreading ◽  
Main Strategy

Germination is a key process driving the composition and dynamics of annual-forb communities and soil seed banks. We tested the germination biology of 20 annual forbs from semiarid grasslands in southern Australia, under a single temperature regime (20/10°C) in either constant darkness or 12-h diurnal light, to assess whether their laboratory germination responses are consistent with transient seed banks and rapid field emergence. Germination in the light was generally moderate to high, with most (70%) species achieving >35% final germination. Additionally, most (90%) species began germinating within 5 days, and all species achieved at least 50% of final germination within 10 days, suggesting that rapid and synchronous germination is the main strategy of annual forbs in this region. However, several species had seeds that continued to germinate for a prolonged period, and in most species, a fraction of seeds did not germinate, demonstrating risk-spreading strategies. Additionally, the germination of most (79%) species was significantly inhibited by continuous darkness. Despite the potential for the formation of large persistent seed banks through low germination in some species and dark inhibition in most, rapid germination and prevailing environmental conditions apparently prevent this in the field.

Retinomotor Rhythms in the Bluegill, Lepomis macrochirus

1968 ◽  
Vol 25 (2) ◽  
pp. 373-381 ◽  
Author(s):  
Kenneth R. John ◽  
David M. Gring
Keyword(s):  
Intermediate State ◽  
Lepomis Macrochirus ◽  
Constant Darkness ◽  
Artificial Light ◽  
Continuous Darkness ◽  
Free Running

Bluegills, Lepomis macrochirus, entrained to natural or artificial light–dark cycles, were confined to constant darkness for varying periods up to 42 hr at temperatures in the range 20–25 C. The retinomotor activities were determined from histological preparations. In the first night, the eyes became maximally dark-adapted within 1 or 2 hr. The pigment was contracted to a dense basal band, twin cones extended to the boundary of the pigment, and single cones extended into the pigment. After 2 or 3 hr in darkness, these components began a return toward their light-adapted positions, slowly for 5 or 6 hr, and then rapidly during the last 3 or 4 hr, and came to rest in an intermediate state of adaptation at subjective sunrise. In continuous darkness, the retina exhibited a rudimentary free-running rhythm, and there was some evidence of a 12-hr oscillation within the 24-hr period. The amplitudes of the rhythms ranged in decreasing order from twin cones to single cones to pigment and the extreme amplitudes occurred about 2 hr after sunset and at subjective sunrise. Single cones were always more extended than twin cones and only the rod-shaped particles, not the spheres, of pigment appeared to cycle. By the end of the experiment, the rhythms of cones were slightly damped and the rhythm of the pigment was greatly damped. Rods were not studied.

Performance Evaluation and Shelf Life of Onion Varieties in Western Tigray, Ethiopia

2020 ◽  
pp. 38-47
Author(s):  
Yirga Belay Kindeya ◽  
Shushay Chermet ◽  
Haile Zibelo ◽  
Asmelash Tuemay ◽  
Mehari Kassie ◽  
...  
Keyword(s):  
Shelf Life ◽  
Block Design ◽  
Environment Interaction ◽  
Stability Parameters ◽  
Variable Environments ◽  
Allium Cepa L ◽  
Stability Ranking ◽  
Irrigation Condition ◽  
Environmental Variations ◽  
The Stability

Onion (Allium cepa L.) is an important underground vegetable bulb crop of tropical and subtropical part of the world. The experiment was carried out in randomized complete block design (RCBD) with three replications and conducted during 2016 to 2018 under irrigation condition at three testing sites. The experiment was designed to select high yielding and good shelf life varieties with the following specific objectives (1) to evaluate and select high yielding onion varieties, (2) to select the adaptable onion varieties and (3) to evaluate and select onion varieties having long shelf life. The study result showed that different variations were observed among the varieties; (29.82%) by environments, (21.94%) Genotype x Environment Interaction and genotypes (6.6. The high environmental variations and differential response of genotypes to the variable environments leading to inconsistency ranking of genotypes across years and locations. The highest yield was obtained  from Bombey red (440.3 kgha-1), followed by Nafis(395 kgha-1), Shendi(391 kgha-1), Nasik red(373 kgha-1) and Adama red(387 kgha-1) respectively. The highest %yield loss recorded from Adama red (28.30%) followed by Nafis (23.23%), Nasik red (22.90) Bombey red (22.48%) and Shendi (5.67%) respectively. Even though, the stability ranking of the varieties were varied among the stability parameters.  Nafis and Bombey red were found the most stable. While Nasik red, Adama red and Shendi unstable across years and locations.  From each of the onion varieties 5 kg was stored for three months and shelf life data recorded and analyzed using R software. Based on the study Shendi can store more than six months without any problem will be recommended and promoted for commercial production. Therefore, the stable varieties recommended and promoted for wider areas.

Melatonin and activity rhythm responses to light pulses in mice with the Clock mutation

2003 ◽  
Vol 284 (5) ◽  
pp. R1231-R1240 ◽  
Author(s):  
David J. Kennaway ◽  
Athena Voultsios ◽  
Tamara J. Varcoe ◽  
Robert W. Moyer
Keyword(s):  
Wheel Running ◽  
Activity Rhythm ◽  
Mutant Mice ◽  
Constant Darkness ◽  
Wild Type ◽  
Continuous Darkness ◽  
Light Pulses ◽  
Essentially Normal ◽  
Running Activity ◽  
Wheel Running Activity

Melatonin and wheel-running rhythmicity and the effects of acute and chronic light pulses on these rhythms were studied in Clock Δ19 mutant mice selectively bred to synthesize melatonin. Homozygous melatonin-proficient Clock Δ19 mutant mice ( Clock Δ19/Δ19 -MEL) produced melatonin rhythmically, with peak production 2 h later than the wild-type controls (i.e., just before lights on). By contrast, the time of onset of wheel-running activity occurred within a 20-min period around lights off, irrespective of the genotype. Melatonin production in the mutants spontaneously decreased within 1 h of the expected time of lights on. On placement of the mice in continuous darkness, the melatonin rhythm persisted, and the peak occurred 2 h later in each cycle over the first two cycles, consistent with the endogenous period of the mutant. This contrasted with the onset of wheel-running activity, which did not shift for several days in constant darkness. A light pulse around the time of expected lights on followed by constant darkness reduced the expected 2-h delay of the melatonin peak of the mutants to ∼1 h and advanced the time of the melatonin peak in the wild-type mice. When the Clock Δ19/Δ19 -MEL mice were maintained in a skeleton photoperiod of daily 15-min light pulses, a higher proportion entrained to the schedule (57%) than melatonin-deficient mutants (9%). These results provide compelling evidence that mice with the Clock Δ19 mutation express essentially normal rhythmicity, albeit with an underlying endogenous period of 26–27 h, and they can be entrained by brief exposure to light. They also raise important questions about the role of Clock in rhythmicity and the usefulness of monitoring behavioral rhythms compared with hormonal rhythms.

scholarly journals Physical Dormancy Release in Medicago truncatula Seeds Is Related to Environmental Variations

Plants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 503 ◽  
Author(s):  
Juan Pablo Renzi ◽  
Martin Duchoslav ◽  
Jan Brus ◽  
Iveta Hradilová ◽  
Vilém Pechanec ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Seed Dormancy ◽  
Arid Environments ◽  
Dormancy Release ◽  
Hormone Regulation ◽  
Physical Dormancy ◽  
Variable Environments ◽  
Genome Wide ◽  
Environmental Variations ◽  
Metabolite Synthesis

Seed dormancy and timing of its release is an important developmental transition determining the survival of individuals, populations, and species in variable environments. Medicago truncatula was used as a model to study physical seed dormancy at the ecological and genetics level. The effect of alternating temperatures, as one of the causes releasing physical seed dormancy, was tested in 178 M. truncatula accessions over three years. Several coefficients of dormancy release were related to environmental variables. Dormancy varied greatly (4–100%) across accessions as well as year of experiment. We observed overall higher physical dormancy release under more alternating temperatures (35/15 °C) in comparison with less alternating ones (25/15 °C). Accessions from more arid climates released dormancy under higher experimental temperature alternations more than accessions originating from less arid environments. The plasticity of physical dormancy can probably distribute the germination through the year and act as a bet-hedging strategy in arid environments. On the other hand, a slight increase in physical dormancy was observed in accessions from environments with higher among-season temperature variation. Genome-wide association analysis identified 136 candidate genes related to secondary metabolite synthesis, hormone regulation, and modification of the cell wall. The activity of these genes might mediate seed coat permeability and, ultimately, imbibition and germination.

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