Simulated natural day lengths synchronize seasonal rhythms of asynchronously born male Siberian hamsters

2007 ◽  
Vol 293 (1) ◽  
pp. R402-R412 ◽  
Author(s):  
Matthew P. Butler ◽  
Kevin W. Turner ◽  
Jin Ho Park ◽  
James P. Butler ◽  
Justin J. Trumbull ◽  
...  
Keyword(s):  
Somatic Growth ◽  
Day Length ◽  
Delayed Puberty ◽  
Testicular Development ◽  
Early Puberty ◽  
Seasonal Rhythms ◽  
Siberian Hamsters ◽  
Natural Photoperiod ◽  
Timing Of Puberty ◽  
Short Days

Photoperiodism research has relied on static day lengths and abrupt transitions between long and short days to characterize the signals that drive seasonal rhythms. To identify ecologically relevant critical day lengths and to test the extent to which naturally changing day lengths synchronize important developmental events, we monitored nine cohorts of male Siberian hamsters ( Phodopus sungorus) born every 2 wk from 4 wk before to 12 wk after the summer solstice in a simulated natural photoperiod (SNP). SNP hamsters born from 4 wk before to 2 wk after the solstice underwent rapid somatic and gonadal growth; among those born 4–6 wk after the solstice, some delayed puberty by many weeks, whereas others manifested early puberty. Hamsters born eight or more weeks after the solstice failed to undergo early testicular development. The transition to delayed development occurred at long day lengths, which induce early puberty when presented as static photoperiods. The first animals to delay puberty may do so predominantly on the basis of postnatal decreases in day length, whereas in later cohorts, a comparison of postnatal day length to gestational day length may contribute to arrested development. Despite differences in timing of birth and timing of puberty, autumn gonadal regression and spring gonadal and somatic growth occurred at similar calendar dates in all cohorts. Incrementally changing photoperiods exert a strong organizing effect on seasonal rhythms by providing hamsters with a richer source of environmental timing cues than are available in simple static day lengths.

Timing of puberty and synchronization of seasonal rhythms by simulated natural photoperiods in female Siberian hamsters

2007 ◽  
Vol 293 (1) ◽  
pp. R413-R420 ◽  
Author(s):  
Matthew P. Butler ◽  
Justin J. Trumbull ◽  
Kevin W. Turner ◽  
Irving Zucker
Keyword(s):  
Pubertal Development ◽  
Somatic Growth ◽  
Life History Trait ◽  
Delayed Puberty ◽  
Summer Solstice ◽  
Early Puberty ◽  
Seasonal Rhythms ◽  
Siberian Hamsters ◽  
Natural Photoperiod ◽  
Timing Of Puberty

The timing of puberty is a critical life history trait of short-lived species; spring-born individuals mature rapidly and breed in the season of birth, whereas young born in mid- to late summer delay puberty until the next spring. The cues that govern the transition from rapid to delayed maturation in natural populations remain unknown. To identify ecologically relevant photoperiod cues that control timing of puberty, we monitored nine cohorts of female Siberian hamsters ( Phodopus sungorus) born every 2 wk from 4 wk before to 12 wk after the summer solstice in a simulated natural photoperiod (SNP). Hamsters born by the summer solstice underwent rapid somatic growth and achieved puberty that summer; among females born 2–4 wk after the solstice, some delayed puberty by many weeks, whereas others manifested early puberty. Hamsters born 6 or more weeks after the solstice generally delayed puberty until the following spring. The transition from accelerated to delayed pubertal development in the SNP occurred at day lengths that induce early puberty when presented as static photoperiods. Despite differences in timing of birth and timing of puberty, fall and subsequent spring seasonal events occurred at similar calendar dates in all cohorts. We found no evidence that prenatal photoperiod history influenced postnatal development of female hamsters. Considered together with a parallel study on males, the present findings point to sex differences in responsiveness to natural photoperiod variations. In both sexes, incrementally changing photoperiods exert a strong organizing effect on seasonal rhythms.

Perinatal photoperiod organizes adult immune responses in Siberian hamsters (Phodopus sungorus)

2006 ◽  
Vol 290 (6) ◽  
pp. R1714-R1719 ◽  
Author(s):  
Zachary M. Weil ◽  
Leah M. Pyter ◽  
Lynn B. Martin ◽  
Randy J. Nelson
Keyword(s):  
Immune System ◽  
Immune Function ◽  
Breeding Season ◽  
Somatic Growth ◽  
Developmental Trajectory ◽  
Day Length ◽  
Phodopus Sungorus ◽  
Siberian Hamsters ◽  
Time Of Year ◽  
Induced Changes

Individuals of many nontropical rodent species display reproductive, immunological, and somatic responses to day length. In general, short day (SD) lengths inhibit reproduction and enhance immune function in the laboratory when all other conditions are held constant. Most studies to date have focused on seasonal variation in immune function in adulthood. However, perinatal photoperiods also communicate critical day length information and serve to establish a developmental trajectory appropriate for the time of year. Nontropical rodents born early in the breeding season undergo rapid reproductive development, presumably to promote mating success during their first reproductive season. Rodents born late in the breeding season suspend somatic growth and puberty until the following vernal breeding season. We tested the hypothesis that perinatal day lengths have similar enduring effects on the immune system of rodents. Siberian hamsters ( Phodopus sungorus) were maintained prenatally and until weaning (21 days) in either SDs (8 h light:16 h dark) or long days (LD) (16 h light:8 h dark), then they were weaned into either the opposite photoperiod or maintained in their natal photoperiod, forming four groups (LD-LD, LD-SD, SD-LD, and SD-SD). After 8-wk in these conditions, cell-mediated immune activity was compared among groups. SD-SD hamsters of both sexes enhanced immune function relative to all other groups. The reproductive effects of perinatal photoperiod were not evident by the end of the experiment; circulating testosterone and cortisol sampled at the end of the experiment reflected the postweaning, but not the perinatal photoperiod. This experiment demonstrates long-lasting organizational effects of perinatal photoperiod on the rodent immune system and indicates that photoperiod-induced changes in the immune system are dissociable from changes in the reproductive system.

scholarly journals The Posterodorsal Medial Amygdala Regulates the Timing of Puberty Onset in Female Rats

Endocrinology ◽  
2015 ◽  
Vol 156 (10) ◽  
pp. 3725-3736 ◽  
Author(s):  
X. F. Li ◽  
M. H. Hu ◽  
B. P. Hanley ◽  
Y. S. Lin ◽  
L. Poston ◽  
...  
Keyword(s):  
Body Weight ◽  
Brain Region ◽  
Female Rats ◽  
Delayed Puberty ◽  
Calorie Intake ◽  
Medial Amygdala ◽  
Early Puberty ◽  
Receptor Antagonism ◽  
Play Fighting ◽  
Timing Of Puberty

Obesity is the major risk factor for early puberty, but emerging evidence indicates other factors including psychosocial stress. One key brain region notable for its role in controlling calorie intake, stress, and behavior is the amygdala. Early studies involving amygdala lesions that included the medial nucleus advanced puberty in rats. More recently it was shown that a critical site for lesion-induced hyperphagia and obesity is the posterodorsal subnucleus of the medial amygdala (MePD), which may explain the advancement of puberty. Glutamatergic activity also increases in the MePD during puberty without a corresponding γ-aminobutyric acid (GABA)ergic change, suggesting an overall activation of this brain region. In the present study, we report that neurotoxic lesioning of the MePD advances puberty and increases weight gain in female rats fed a normal diet. However, MePD lesioned rats fed a 25% nonnutritive bulk diet also showed the dramatic advancement of puberty but without the increase in body weight. In both dietary groups, MePD lesions resulted in an increase in socialization and a decrease in play fighting behavior. Chronic GABAA receptor antagonism in the MePD from postnatal day 21 for 14 days also advanced puberty, increased socialization, and decreased play fighting without altering body weight, whereas glutamate receptor antagonism delayed puberty and decreased socialization without affecting play fighting. In conclusion, our results suggest the MePD regulates the timing of puberty via a novel mechanism independent of change in body weight and caloric intake. MePD glutamatergic systems advance the timing of puberty whereas local GABAergic activation results in a delay.

scholarly journals Seasonal regulation of reproduction: altered role of melatonin under naturalistic conditions in hamsters

2010 ◽  
Vol 277 (1695) ◽  
pp. 2867-2874 ◽  
Author(s):  
Matthew P. Butler ◽  
Kevin W. Turner ◽  
Jin Ho Park ◽  
Elanor E. Schoomer ◽  
Irving Zucker ◽  
...  
Keyword(s):  
Body Weight ◽  
Day Length ◽  
Seasonal Transition ◽  
Siberian Hamsters ◽  
Long Day ◽  
Spring Equinox ◽  
Natural Photoperiod ◽  
History Of ◽  
Seasonal Regulation

The seasonal reproductive cycle of photoperiodic rodents is conceptualized as a series of discrete melatonin-dependent neuroendocrine transitions. Least understood is the springtime restoration of responsiveness to winter-like melatonin signals (breaking of refractoriness) that enables animals to once again respond appropriately to winter photoperiods the following year. This has been posited to require many weeks of long days based on studies employing static photoperiods instead of the annual pattern of continually changing photoperiods under which these mechanisms evolved. Maintaining Siberian hamsters under simulated natural photoperiods, we demonstrate that winter refractoriness is broken within six weeks after the spring equinox. We then test whether a history of natural photoperiod exposure can eliminate the requirement for long-day melatonin signalling. Hamsters pinealectomized at the spring equinox and challenged 10 weeks later with winter melatonin infusions exhibited gonadal regression, indicating that refractoriness was broken. A photostimulatory effect on body weight is first observed in the last four weeks of winter. Thus, the seasonal transition to the summer photosensitive phenotype is triggered prior to the equinox without exposure to long days and is thereafter melatonin-independent. Distinctions between photoperiodic and circannual seasonal organization erode with the incorporation in the laboratory of ecologically relevant day length conditions.

Gonadal hormone-dependent and -independent regulation of immune function by photoperiod in Siberian hamsters

2008 ◽  
Vol 294 (2) ◽  
pp. R384-R392 ◽  
Author(s):  
Brian J. Prendergast ◽  
Scott R. Baillie ◽  
Firdaus S. Dhabhar
Keyword(s):  
Immune Function ◽  
Gonadal Hormones ◽  
Day Length ◽  
Gonadal Hormone ◽  
Testosterone Secretion ◽  
Siberian Hamsters ◽  
Long Day ◽  
Sickness Behaviors ◽  
Immunological Effects ◽  
Short Days

Siberian hamsters ( Phodopus sungorus) exhibit changes in reproductive and immune function in response to seasonal variations in day length. Exposure to short days induces gonadal regression and inhibits testosterone secretion. In parallel, short days enhance immune function: increasing leukocyte numbers and attenuating cytokine and behavioral responses to infection. We examined whether photoperiodic changes in leukocyte phenotypes and sickness behaviors are dependent on concurrent photoperiodic changes in gonadal function. Male hamsters were gonadectomized or sham-gonadectomized and either exposed to short days (9 h light/day; SD) or kept in their natal long-day (15 h light/day; LD) photoperiod for 10–13 wk. Blood samples were obtained for leukocyte enumeration, and hamsters were challenged with bacterial LPS, which induced behavioral (anorexia, reductions in nest building) and somatic (weight loss) sickness responses. Among gonad-intact hamsters, exposure to SD increased total and CD62L+ lymphocytes and CD3+ T lymphocytes in blood and significantly attenuated LPS-induced sickness responses. Independent of photoperiod, castration alone increased total and CD62L+ lymphocyte and CD3+ T lymphocyte numbers and attenuated somatic and anorexic sickness responses. Among castrated hamsters, SD exposure increased lymphocyte numbers and suppressed sickness behaviors. In castrated hamsters, the magnitude of most immunological effects of SD were diminished relative to those evident in gonad-intact hamsters. The SD phenotype in several measures of immunity can be instated via elimination of gonadal hormones alone; however, photoperiodic effects on immune function persist even in castrated hamsters. Thus, photoperiod affects the immune system and neural-immune interactions underlying sickness behaviors via gonadal hormone-dependent and -independent mechanisms.

Photoperiod alters pain responsiveness via changes in pelage characteristics

2008 ◽  
Vol 86 (10) ◽  
pp. 1212-1216
Author(s):  
Zachary M. Weil ◽  
Michelle Gatien Hotchkiss ◽  
Randy J. Nelson
Keyword(s):  
Behavioral Plasticity ◽  
Pain Tolerance ◽  
Day Length ◽  
Hot Plate Test ◽  
Thermal Pain ◽  
Short Day ◽  
Siberian Hamsters ◽  
Nociceptive Responses ◽  
Short Days ◽  
Pain Responses

Small mammals use day length to adjust morphology and physiology to anticipate seasonal changes in environmental conditions. The canonical photoperiod-mediated annual adaptation is seasonal breeding. However, increasing evidence suggests that day-length information can induce plasticity in the nervous system, and thus provoke behavioral plasticity that can aid in winter survival. We hypothesized that low temperatures and reduced food availability in the winter would necessitate the evolution of increased pain tolerance mediated by short day lengths. Siberian hamsters ( Phodopus sungorus (Pallas, 1773)) housed in short days regressed their reproductive tracts and molted to winter pelage. Short-day hamsters also displayed elevated latencies of nociceptive responses in the hot-plate test, suggesting reduced pain responsivity. Prior to assessing potential neuronal or neuroendocrine mediators of altered pain responses, however, we investigated the possibility that changes in fur characteristics mediated photoperiod differences in pain responsivity. Removal of fur with a depilatory cream eliminated photoperiod differences in pain responsivity. Taken together, these data indicate that day length regulates thermal pain responses via changes in fur properties; also, changes in pelage properties have both thermoregulatory and thermal insulatory properties.

Postnatal growth rate and gonadal development in circadian tau mutant hamsters reared in constant dim red light

Reproduction ◽  
2000 ◽  
pp. 327-330 ◽  
Author(s):  
RJ Lucas ◽  
JA Stirland ◽  
YN Mohammad ◽  
AS Loudon
Keyword(s):  
Time Course ◽  
Red Light ◽  
Somatic Growth ◽  
Postnatal Growth ◽  
Gonadal Development ◽  
Testicular Development ◽  
Wild Type ◽  
Similar Time ◽  
Syrian Hamsters ◽  
Body Weights

The role of the circadian clock in the reproductive development of Syrian hamsters (Mesocricetus auratus was examined in wild type and circadian tau mutant hamsters reared from birth to 26 weeks of age under constant dim red light. Testis diameter and body weights were determined at weekly intervals in male hamsters from 4 weeks of age. In both genotypes, testicular development, subsequent regression and recrudescence exhibited a similar time course. The age at which animals displayed reproductive photosensitivity, as exhibited by testicular regression, was unrelated to circadian genotype (mean +/- SEM: 54 +/- 3 days for wild type and 59 +/- 5 days for tau mutants). In contrast, our studies revealed a significant impact of the mutation on somatic growth, such that tau mutants weighed 18% less than wild types at the end of the experiment. Our study reveals that the juvenile onset of reproductive photoperiodism in Syrian hamsters is not timed by the circadian system.

INFLUENCE OF PHOTOPERIOD ON THYROTROPIN RELEASING HORMONE-INDUCED PROLACTIN RELEASE IN EWES

1983 ◽  
Vol 63 (1) ◽  
pp. 67-73 ◽  
Author(s):  
B. E. HOWLAND ◽  
D. SONYA ◽  
L. M. SANFORD ◽  
W. M. PALMER
Keyword(s):  
Thyrotropin Releasing Hormone ◽  
Day Length ◽  
Constant Light ◽  
Serum Prolactin ◽  
Prolactin Release ◽  
Blood Samples ◽  
Releasing Hormone ◽  
Before And After ◽  
Release Curve ◽  
Short Days

The influence of photoperiod on serum prolactin levels and prolactin release induced by thyrotropin releasing hormone (TRH) was determined in ewes maintained under the following lighting regimes: Room 1, lighting mimicked natural changes in photoperiod; Room 2, annual photoperiod changes condensed into 6 mo with short days in June; Room 3, same as Room 2 except photoperiod changed abruptly from 16.5 to 8.0 h on 21 Mar. and back to 16.5 h on 21 June; Room 4, constant light. Weekly blood samples were obtained from February to August. Additionally, blood samples were collected before and after treatment with 10 μg TRH on 19 May, 13 June, 27 June and 19 July. Prolactin levels were elevated in ewes exposed to long days or constant light. The mean of all pre-TRH samples was significantly correlated with stress-induced elevations in prolactin (highest pre-TRH value) (r = 0.72) and area under the TRH-induced release curve (r = 0.56). The prolactin release in response to TRH was greatest in ewes exposed to long days or constant light. Abrupt increase of day length elevated pretreatment prolactin levels (P < 0.01) and increased area under the response curve (P < 0.05). Key words: Photoperiod, TRH, prolactin, ewes

scholarly journals Managing flowering time in Miscanthus and sugarcane to facilitate intra- and intergeneric crosses

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0240390
Author(s):  
Hongxu Dong ◽  
Lindsay V. Clark ◽  
Xiaoli Jin ◽  
Kossonou Anzoua ◽  
Larisa Bagmet ◽  
...  
Keyword(s):  
Flowering Time ◽  
High Latitude ◽  
Floral Induction ◽  
Day Treatment ◽  
Day Length ◽  
Close Relative ◽  
Short Day ◽  
Culm Length ◽  
Low Latitudes ◽  
Short Days

Miscanthus is a close relative of Saccharum and a potentially valuable genetic resource for improving sugarcane. Differences in flowering time within and between Miscanthus and Saccharum hinders intra- and interspecific hybridizations. A series of greenhouse experiments were conducted over three years to determine how to synchronize flowering time of Saccharum and Miscanthus genotypes. We found that day length was an important factor influencing when Miscanthus and Saccharum flowered. Sugarcane could be induced to flower in a central Illinois greenhouse using supplemental lighting to reduce the rate at which days shortened during the autumn and winter to 1 min d-1, which allowed us to synchronize the flowering of some sugarcane genotypes with Miscanthus genotypes primarily from low latitudes. In a complementary growth chamber experiment, we evaluated 33 Miscanthus genotypes, including 28 M. sinensis, 2 M. floridulus, and 3 M. ×giganteus collected from 20.9° S to 44.9° N for response to three day lengths (10 h, 12.5 h, and 15 h). High latitude-adapted M. sinensis flowered mainly under 15 h days, but unexpectedly, short days resulted in short, stocky plants that did not flower; in some cases, flag leaves developed under short days but heading did not occur. In contrast, for M. sinensis and M. floridulus from low latitudes, shorter day lengths typically resulted in earlier flowering, and for some low latitude genotypes, 15 h days resulted in no flowering. However, the highest ratio of reproductive shoots to total number of culms was typically observed for 12.5 h or 15 h days. Latitude of origin was significantly associated with culm length, and the shorter the days, the stronger the relationship. Nearly all entries achieved maximal culm length under the 15 h treatment, but the nearer to the equator an accession originated, the less of a difference in culm length between the short-day treatments and the 15 h day treatment. Under short days, short culms for high-latitude accessions was achieved by different physiological mechanisms for M. sinensis genetic groups from the mainland in comparison to those from Japan; for mainland accessions, the mechanism was reduced internode length, whereas for Japanese accessions the phyllochron under short days was greater than under long days. Thus, for M. sinensis, short days typically hastened floral induction, consistent with the expectations for a facultative short-day plant. However, for high latitude accessions of M. sinensis, days less than 12.5 h also signaled that plants should prepare for winter by producing many short culms with limited elongation and development; moreover, this response was also epistatic to flowering. Thus, to flower M. sinensis that originates from high latitudes synchronously with sugarcane, the former needs day lengths >12.5 h (perhaps as high as 15 h), whereas that the latter needs day lengths <12.5 h.

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