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.

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.

Photoperiod modulates the effects of norepinephrine on lymphocyte proliferation in Siberian hamsters

2003 ◽  
Vol 285 (4) ◽  
pp. R873-R879 ◽  
Author(s):  
Gregory E. Demas ◽  
Timothy J. Bartness ◽  
Randy J. Nelson ◽  
Deborah L. Drazen
Keyword(s):  
Lymphocyte Proliferation ◽  
Splenic Tissue ◽  
Splenocyte Proliferation ◽  
Short Day ◽  
Siberian Hamsters ◽  
Long Day ◽  
Β Adrenergic Receptors ◽  
Short Days

Siberian hamsters ( Phodopus sungorus) rely on photoperiod to coordinate seasonally appropriate changes in physiology, including immune function. Immunity is regulated, in part, by the sympathetic nervous system (SNS), although the precise role of the SNS in regulating photoperiodic changes in immunity remains unspecified. The goal of the present study was to examine the contributions of norepinephrine (NE), the predominant neurotransmitter of the SNS, to photoperiodic changes in lymphocyte proliferation. In experiment 1, animals were maintained in long [16:8-h light-dark cycle (16:8 LD)] or short days (8:16 LD) for 10 wk, and splenic NE content was determined. In experiment 2, in vitro splenocyte proliferation in response to mitogenic stimulation (concanavalin A) was assessed in spleen cell suspensions taken from long- or short-day hamsters in which varying concentrations of NE were added to the cultures. In experiment 3, splenocyte proliferation was examined in the presence of NE and selective α- and β-noradrenergic receptor antagonists (phenoxybenzamine and propranolol, respectively) in vitro. Short-day animals had increased splenic NE content compared with long-day animals. Long-day animals had higher proliferation compared with short-day animals independent of NE. NE (1 μM) further suppressed splenocyte proliferation in short but not long days. Last, NE-induced suppression of proliferation in short-day hamsters was blocked by propranolol but not phenoxybenzamine. The present results suggest that NE plays a role in photoperiodic changes in lymphocyte proliferation. Additionally, the data suggest that the effects of NE on proliferation are specific to activation of β-adrenergic receptors located on splenic tissue. Collectively, these results provide further support that photoperiodic changes in immunity are influenced by changes in SNS activity.

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.

scholarly journals Day-Length Control of Inflorescence Initiation in the Grass Rottboellia Exaltata L.F.

1962 ◽  
Vol 15 (2) ◽  
pp. 291 ◽  
Author(s):  
LT Evans
Keyword(s):  
Day Length ◽  
Inflorescence Development ◽  
Short Day ◽  
Critical Photoperiod ◽  
The One ◽  
Short Days

R. exaltata is a strict short�day plant with a critical photoperiod of about 13 hr. The number of short days required for inflorescence initiation varies with age, being 6 with plants 5 weeks old. Exposure to additional short days increases the rate of inflorescence development. The expanding leaf is the one most sensitive to short.day induction and removal of the leaves below it accelerates inflorescence development.

Daily torpor in the absence of the suprachiasmatic nucleus in Siberian hamsters

1992 ◽  
Vol 263 (2) ◽  
pp. R353-R362 ◽  
Author(s):  
N. F. Ruby ◽  
I. Zucker
Keyword(s):  
Suprachiasmatic Nucleus ◽  
Food Restriction ◽  
Temporal Organization ◽  
Daily Torpor ◽  
Short Day ◽  
Siberian Hamsters ◽  
Random Fashion ◽  
Before And After ◽  
Ad Libitum ◽  
Short Days

Siberian hamsters express torpor spontaneously after several weeks of exposure to short days. In long days, torpor is expressed only when food intake is restricted. Hamsters maintained in a long photoperiod (16 h light/day) at 15 degrees C expressed daily torpor during food restriction both before and after bilateral ablation of the suprachiasmatic nucleus (SCN). Hamsters housed in short days (8 h light/day, ambient temperature 15 degrees C) and fed ad libitum displayed torpor before, but not after, ablation of the SCN (SCNX). Torpor was reinstated in all short-day SCNX hamsters during postoperative food restriction and persisted in several animals even after ad libitum feeding was reinstated. Torpor was entrained to the light-dark cycle in both long- and short-day hamsters preoperatively but appeared to occur in a temporally random fashion in SCNX animals. SCNX hamsters, unlike control animals, displayed multiple torpor bouts per 24 h. The SCN is not essential for the expression of torpor but plays a crucial role in its temporal organization.

scholarly journals Photoperiod-dependent modulation of anti-Müllerian hormone in female Siberian hamsters, Phodopus sungorus

Reproduction ◽  
2008 ◽  
Vol 135 (3) ◽  
pp. 335-342 ◽  
Author(s):  
Esther W Kabithe ◽  
Ned J Place
Keyword(s):  
Granulosa Cells ◽  
Expression Patterns ◽  
Follicular Development ◽  
Day Length ◽  
Phodopus Sungorus ◽  
Reproductive Aging ◽  
Primordial Follicles ◽  
Short Day ◽  
Siberian Hamsters ◽  
Secondary Stage

Fertility and fecundity decline with advancing age in female mammals, but reproductive aging was decelerated in Siberian hamsters (Phodopus sungorus) raised in a short-day (SD) photoperiod. Litter success was significantly improved in older hamsters when reared in SD and the number of primordial follicles was twice that of females held in long days (LD). Because anti-Müllerian hormone (AMH) appears to inhibit the recruitment of primordial follicles in mice, we sought to determine whether the expression patterns of AMH differ in the ovaries and serum of hamsters raised in SD versus LD. Ovaries of SD female hamsters are characterized by a paucity of follicular development beyond the secondary stage and are endowed with an abundance of large eosinophilic cells, which may derive from granulosa cells of oocyte-depleted follicles. In ovaries from 10-week-old SD hamsters, we found that the so-called ‘hypertrophied granulosa cells’ were immunoreactive for AMH, as were granulosa cells within healthy-appearing primary and secondary follicles. Conversely, ovaries from age-matched LD animals lack the highly eosinophilic cells present in SD ovaries. Therefore, AMH staining in LD was limited to primary and secondary follicles that are comparable in number to those found in SD ovaries. The substantially greater AMH expression in SD ovaries probably reflects the abundance of hypertrophied granulosa cells in SD ovaries and their relative absence in LD ovaries. The modulation of ovarian AMH by day length is a strong mechanistic candidate for the preservation of primordial follicles in female hamsters raised in a SD photoperiod.

Latitude affects photoperiod-induced changes in immune response in meadow voles (Microtus pennsylvanicus)

2005 ◽  
Vol 83 (10) ◽  
pp. 1271-1278 ◽  
Author(s):  
L M Pyter ◽  
Z M Weil ◽  
R J Nelson
Keyword(s):  
Immune Responses ◽  
Microtus Pennsylvanicus ◽  
Day Length ◽  
Delayed Type Hypersensitivity ◽  
Deer Mice ◽  
Meadow Voles ◽  
Short Day ◽  
Long Day ◽  
Induced Changes ◽  
Short Days

Animals use day length (photoperiod) to time seasonal adaptations to annual changes in their environment. Reproductive adjustments in deer mice (Peromyscus maniculatus (Wagner, 1845)) from high latitudes are more extensive in response to short days than in deer mice from low latitudes. These adjustments may permit individuals to survive the severe seasonal changes (e.g., temperature and food abundance) in high-latitude environments. Immune function is also affected by photoperiod. Short days were predicted to result in elevated immune and reproductive responses in meadow voles (Microtus pennsylvanicus (Ord, 1815)) from the Northwest Territories (NWT), Canada (~62°N), compared with voles from Ohio (OH), USA (~39°N). Male voles from both latitudes were maintained in long or short days for 10 weeks prior to a delayed-type hypersensitivity (DTH) immune challenge. Both populations displayed similar testicular regression and reduction of testosterone concentrations in short days. DTH immune responses, however, diverged between the two populations. DTH immune responses were enhanced in long-day NWT voles and short-day OH voles, but decreased in short-day NWT voles and long-day OH voles. Total and free corticosterone concentrations did not explain the latitudinal differences in immune responses. These results suggest that photoperiod affects reproductive and immune systems differently and that immune responses may reflect other environmental factors.

Exogenous T3 mimics long day lengths in Siberian hamsters

2007 ◽  
Vol 292 (6) ◽  
pp. R2368-R2372 ◽  
Author(s):  
David A. Freeman ◽  
Brett J. W. Teubner ◽  
Carlesia D. Smith ◽  
Brian J. Prendergast
Keyword(s):  
Gonadal Development ◽  
Day Length ◽  
Intermediate Step ◽  
Iodothyronine Deiodinase ◽  
Short Day ◽  
Siberian Hamsters ◽  
Long Day ◽  
Long Duration ◽  
Reproductive Response

Siberian hamsters ( Phodopus sungorus) exhibit seasonal cycles of reproduction driven by changes in day length. Day length is encoded endogenously by the duration of nocturnal melatonin (Mel) secretion from the pineal gland. Short-duration Mel signals stimulate reproduction and long-duration signals inhibit reproduction. The mechanism by which Mel signals are decoded at the level of neural target tissues remains uncharacterized. In Siberian hamsters, exposure to short day lengths or injections of Mel in long days results in a decrease in hypothalamic expression of type 2 iodothyronine deiodinase (Dio2) mRNA. Dio2 catalyzes the conversion of the thyroid hormone thyroxine to triiodothyronine (T3). Thus exposure to short and long day lengths should decrease and increase hypothalamic T3 concentrations, respectively. We tested the hypothesis that exogenous T3 administered to short-day hamsters would mimic exposure to long day lengths with respect to gonadal stimulation. Hamsters gestated and raised in short day lengths that exhibited photoinhibition of the testes were given daily subutaneous injections of T3 or saline vehicle for 4 wk beginning at week 12 of life. The results indicate that exogenous T3 induced gonadal growth in short-day hamsters and delayed spontaneous gonadal development by an interval equal to the number of weeks during which T3 was administered. T3 injections delayed gonadal regression if given coincident with the transfer of hamsters from long to short day lengths. These results suggest that T3 mimics long day exposure in Siberian hamsters and may serve as an intermediate step between the Mel rhythm and the reproductive response.

Suprachiasmatic and paraventricular control of photoperiodism in Siberian hamsters

1991 ◽  
Vol 260 (1) ◽  
pp. R90-R101 ◽  
Author(s):  
E. L. Bittman ◽  
T. J. Bartness ◽  
B. D. Goldman ◽  
G. J. DeVries
Keyword(s):  
Food Intake ◽  
Lateral Septum ◽  
Day Length ◽  
Serum Prolactin ◽  
Stria Terminalis ◽  
Bed Nucleus ◽  
Beta Endorphin ◽  
Short Day ◽  
Siberian Hamsters ◽  
Photoperiodic Responses

The effects of lesions of the suprachiasmatic (SCN) and paraventricular nuclei (PVN) of the hypothalamus on photoperiodic responses were examined in adult Siberian hamsters. SCN lesions reduced nocturnal water intake in long days, whereas PVN lesions increased body weight and food intake in both short and long days. SCN or PVN lesions blocked short-day-induced decreases in body, fat pad, and testes weights and in food intake. Serum prolactin (PRL), but not follicle-stimulating hormone, levels were increased. The distribution of immunostained neurons and fibers for gonadotropin-releasing hormone (GnRH), beta-endorphin, arginine vasopressin (AVP), and vasoactive intestinal polypeptide (VIP) resembled that of other rodent species. Short-day exposure reduced AVP staining in lateral septum, medial amygdala, and bed nucleus of the stria terminalis but not in the PVN of the thalamus or the SCN. Short-day-exposed hamsters had fewer beta-endorphin-positive arcuate nucleus cells and tended to have fewer GnRH-positive preoptic cells than long-day controls. VIP staining was unaffected by photoperiod. Most day length effects on immunostaining were eliminated by either lesion. These results establish the importance of the SCN and PVN in the photoperiodic control of several seasonal responses in Siberian hamsters.

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.

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