Role of prolactin in the photoperiodic control of moulting in the mink (Mustela vison)

1984 ◽  
Vol 103 (1) ◽  
pp. 9-15 ◽  
Author(s):  
L. Martinet ◽  
D. Allain ◽  
C. Weiner
Keyword(s):  
Physiological Role ◽  
Plasma Prolactin ◽  
Summer Solstice ◽  
Natural Lighting ◽  
Short Day ◽  
Lighting Conditions ◽  
Natural Photoperiod ◽  
Moulting Cycle ◽  
Short Days

ABSTRACT Beginning at the summer solstice adult female mink were maintained in long- or short-day photoperiods and treated with bromocriptine or prolactin. In control females kept under natural lighting conditions the moult coincided with the seasonal decrease in prolactin and resulted in the growth of a dense winter coat which was completed by the end of November. Long days, which slowed the decrease in plasma prolactin relative to animals in the natural photoperiod, induced a more or less complete moult followed by growth of a thin summer coat. On the contrary we observed an accelerated decrease in plasma prolactin concentrations followed by an early and brief moult in females kept under long days but treated with bromocriptine and in females under short days. The growth of a dense winter coat was completed by the end of September in all the females of the short-day group and in six of eleven females treated with bromocriptine. In the other five females, moult was followed by the growth of a summer coat. These results may suggest that the decline of prolactin after the summer solstice is responsible for the onset of the autumn moult, but the early, abbreviated moult and the growth of a winter coat observed in females kept under short days and treated with prolactin do not seem to support this hypothesis. However, the huge non-physiological levels of prolactin measured in the plasma of these females and the appearance of abnormal white under-hairs might suggest that the hormonal balance in this group was completely disturbed by the treatment. The physiological role of prolactin in the seasonal moulting cycle in mink is discussed. J. Endocr. (1984) 103,9–15

Flowering of Stylosanthes guianensis in controlled temperatures under natural photoperiod

1984 ◽  
Vol 35 (2) ◽  
pp. 219 ◽  
Author(s):  
RL Ison ◽  
LR Humphreys
Keyword(s):  
Floral Initiation ◽  
Minimum Duration ◽  
Stylosanthes Guianensis ◽  
Short Day ◽  
Long Day ◽  
Natural Photoperiod ◽  
Low Levels ◽  
Short Days

Seedlings of Stylosanthes guianensis var. guianensis cv. Cook and cv. Endeavour were grown in naturally lit glasshouses at Brisbane (lat. 27� 30' S.) at 35/30, 30/25 and 25/20�C (day/night), and were sown so as to emerge at 18-day intervals from 18 January to 11 June. Cook behaved as a long day-short day plant, with seedlings emerging after 5 February flowering incompletely or remaining vegetative until the experiment was terminated in mid-October. In the 25/20�C regimen flowering was incomplete in Cook; in Endeavour flowering was delayed but a conventional short-day response was observed. At 35/30�C Endeavour flowering was inhibited in the shortest days of mid-winter, suggesting a stenophotoperiodic response, but short days were confounded with low levels of irradiance. Minimum duration of the phase from emergence to floral initiation was c. 66-70 days in Cook and c. 40-45 days in Endeavour; the duration of the phase floral initiation to flower appearance was linearly and negatively related to temperature.

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.

Seasonal changes in concentrations of plasma hormones in the male ring dove (Streptopelia risoria)

1986 ◽  
Vol 108 (3) ◽  
pp. 385-391 ◽  
Author(s):  
R. W. Lea ◽  
P. J. Sharp ◽  
H. Klandorf ◽  
S. Harvey ◽  
I. C. Dunn ◽  
...  
Keyword(s):  
Seasonal Changes ◽  
Plasma Corticosterone ◽  
Early Spring ◽  
Energy Requirements ◽  
Breeding Cycle ◽  
Plasma Prolactin ◽  
Winter Solstice ◽  
Natural Lighting ◽  
Short Day ◽  
Ring Dove

ABSTRACT Seasonal changes in concentrations of plasma LH, prolactin, thyroxine (T4), GH and corticosterone were measured in captive male ring doves exposed to natural lighting at latitude 56 °N. Plasma LH levels decreased steeply in autumn when the daylength fell below about 12·5 h but increased in November as the birds became short-day refractory. In comparison with plasma LH concentrations in a group of short-day refractory birds exposed to 6 h light/day from the winter solstice, plasma LH levels in birds exposed to natural lighting increased further in spring after the natural daylength reached about 12·5 h. There were no seasonal changes in plasma prolactin concentrations and plasma T4 concentrations were at their highest during December, January and February, the coldest months of the year. The seasonal fall in plasma LH levels in September was associated with a transitory increase in plasma T4, a transitory decrease in plasma corticosterone and a sustained increase in plasma GH. It is suggested that in the ring dove, short-day refractoriness develops rapidly in November to allow the bird to breed when the opportunity arises, during the winter and early spring. The annual breeding cycle is synchronized by a short-day induced regression of the reproductive system in the autumn, the primary function of which may be to enable the birds to meet the energy requirements for the annual moult. The changes in plasma T4, corticosterone and especially of GH at this time of year are probably concerned with the control of moult or the associated changes in energy requirements. J. Endocr. (1986) 108, 385–391

The role of prolactin in the reactivation of hair follicles in relation to moulting in cashmere goats

1994 ◽  
Vol 143 (3) ◽  
pp. 441-448 ◽  
Author(s):  
P Dicks ◽  
A J F Russel ◽  
G A Lincoln
Keyword(s):  
Prolactin Secretion ◽  
Hair Follicles ◽  
Plasma Prolactin ◽  
Dose Rates ◽  
Significant Difference ◽  
Natural Photoperiod ◽  
Cashmere Goats ◽  
Ovine Prolactin ◽  
Voluntary Food Intake

Abstract The effects of the suppression or elevation of plasma prolactin concentrations in spring on the timing of the reactivation of the hair follicles and the timing of the spring moult were investigated in cashmere goats. Thirty eight adult female goats, housed under conditions of natural photoperiod at 55°55′N from mid-December until May, were allocated to four groups starting on 5 January: ten served as untreated controls, eight received 2 mg ovine prolactin subcutaneously every 12 h for 7 weeks (PRL), twelve received 35 mg bromocriptine intramuscularly every 14 days for 17 weeks (BCR) and eight received injections of both ovine prolactin and bromocriptine at the above dose rates for 7 weeks (PRL+BCR). In the PRL group there was an earlier reactivation of the secondary hair follicles (PRL vs control, proportion of secondary follicles in anagen, weeks 1–5, P<0·01) associated with an earlier moult of secondary fibres (cashmere) but no significant difference in the activity of the primary hair follicles. In the BCR group there was a delay in the reactivation of both the secondary and primary hair follicles (BCR vs control, proportion of secondary and primary hair follicles in anagen, weeks 5–13, P<0·01) and a delay in the moult. In the PRL+BCR group there was an early reactivation and moult similar to the PRL group. Voluntary food intake (VFI) and liveweight were also measured. Only in the BCR group was there a decrease in VFI compared with the controls but with no effect on liveweight. It was concluded that the seasonal increase in prolactin secretion which normally occurs in spring is causally involved in the reactivation of primary and secondary hair follicles and moulting in cashmere goats. Journal of Endocrinology (1994) 143, 441–448

scholarly journals Environmental Regulation of a 25 kDa Dehydrin in Relation to Rhododendron Cold Acclimation

2004 ◽  
Vol 129 (3) ◽  
pp. 354-359 ◽  
Author(s):  
Calin O. Marian ◽  
Atilla Eris ◽  
Stephen L. Krebs ◽  
Rajeev Arora
Keyword(s):  
Cold Acclimation ◽  
Cold Hardiness ◽  
Leaf Water Content ◽  
Short Day ◽  
Cellular Dehydration ◽  
Third Stage ◽  
Natural Photoperiod ◽  
Molecular Masses ◽  
Winter Cold ◽  
Short Days

The influence of photoperiod and temperature on the seasonal (fall to winter) cold acclimation and accumulation of a 25 kDa dehydrin in Rhododendron `Chionoides' was studied by exposing two groups of plants each in the greenhouse or outdoors to either a natural photoperiod (or short days) or an extended photoperiod (or long days) regime. Results suggest that the shortening daylength alone is sufficient to trigger both the first stage of cold acclimation and concomitant 25 kDa dehydrin induction. Exposure of the plants to natural photoperiod and temperatures induced the greatest cold hardiness and 25 kDa accumulation, while exposure to extended photoperiods (long days) and warmer temperatures (in the greenhouse) failed to induce any significant freezing tolerance in leaves. Whereas short days trigger the cold acclimation process initially, low inductive temperatures can eventually replace the photoperiod stimulus. Seasonal accumulation of 25 kDa dehydrin, on the other hand, appears to be predominantly effected by short photoperiods. Data indicated that the leaf water content of outdoor plants maintained under natural photoperiod was lower than that of plants grown under extended photoperiod. This was also true for the greenhouse plants at the first (September) and the last (January) sampling. It is hypothesized that early 25 kDa dehydrin accumulation may be due to short-day-induced cellular dehydration. Accumulation of two other dehydrins of 26 kDa and 32 kDa molecular masses does not appear to be associated with short day (SD)-induced first stage of cold acclimation. Results show that their accumulation may be regulated by low, subfreezing temperatures and may be associated with the second and/or third stage of cold acclimation of `Chionoides' rhododendron leaves.

Effects of photoperiod on the reproductive physiology of male flying foxes, Pteropus poliocephalus

1992 ◽  
Vol 4 (1) ◽  
pp. 43 ◽  
Author(s):  
MA McGuckin ◽  
AW Blackshaw
Keyword(s):  
Reproductive Physiology ◽  
Adult Males ◽  
Progressive Decrease ◽  
Natural Conditions ◽  
Timing Of Reproduction ◽  
Pteropus Poliocephalus ◽  
Natural Photoperiod ◽  
Short Days ◽  
Photoperiod Manipulation

Melatonion concentrations were determined in plasma pools obtained from adult male Pteropus poliocephalus (autumn mating season) at four times of the year. Melatonin levels increased within 3 h of sunset and remained elevated for the duration of the scotophase at all times of the year. Two photoperiod manipulation experiments were performed to examine the role of daylength in the regulation of the timing of the breeding season of this species. In Experiment 1, three adult males were transferred from natural short days to 16L:8D for 137 days and then photoperiod was progressively decreased over 120 days to 9L:15D; this photoperiod was then maintained for 350 days. Testicular volume (TV) peaked during decreasing photoperiod well before the time of maximal size in natural conditions. During the period in extended short photoperiod these bats showed several cycles of TV change with a progressively decreasing interval between cycles. In Experiment 2, nine adult males were exposed to the same shift to 16L:8D as in Experiment 1, but were subsequently split into three groups: 8L:16D, progressive decrease to 8L:16D and maintenance in 16L:8D. The 8L:16D and decreasing photoperiod groups showed coincident premature increases in TV, as in Experiment 1, whereas in the 16L:8D group TV increased at about the same time as in animals in natural photoperiod. Melatonin determination in the different experimental groups showed that duration of secretion was related to the length of the scotophase in all cases. These experiments demonstrate that regulation of the timing of reproduction in males of this species is influenced by changes in daylength.

Inhibitory effect of increased photoperiod on wool follicle growth

1996 ◽  
Vol 148 (1) ◽  
pp. 157-166 ◽  
Author(s):  
A J Pearson ◽  
A L Parry ◽  
M G Ashby ◽  
V J Choy ◽  
J E Wildermoth ◽  
...  
Keyword(s):  
Day Treatment ◽  
Inhibitory Effect ◽  
Plasma Prolactin ◽  
Follicle Growth ◽  
Primary Follicle ◽  
Winter Solstice ◽  
Natural Photoperiod ◽  
Wool Follicle ◽  
Plasma Prl ◽  
Short Days

Abstract The relationships between circulating prolactin (PRL), wool follicle growth and daylength were investigated in 24 New Zealand Wiltshire ewes housed indoors from September 1989 to May 1991. Twelve control (C) ewes were maintained under natural photoperiod. Two other groups were held in short days (SD; 8 h light:16 h darkness) commencing from the winter solstice (22 June 1990) for either three (group SD3, n=7) or six (group SD6, n=5) months before reversion to natural daylength. Skin was sampled at one- to four-week intervals for histological determination of percentages of growing primary and secondary follicles. Hourly blood samples over 24 h were collected via jugular cannulae from C sheep in March and July and then monthly from all animals until December 1990 for estimation of mean monthly PRL concentrations for each treatment group. Between autumn (March 1990) and winter (July) primary follicle activity (PFA) and secondary follicle activity (SFA) declined in C ewes (PFA: 97 to 43%, SFA: 100 to 57%). Follicle regrowth during July and August in eight C ewes preceded the initial rise in plasma PRL from the winter minimum (1·6 ng/ml). Across the three groups, four instances of decreased follicle activity were observed, closely following or concurrent with increases in plasma PRL concentrations. The resumption of spring growth in four C sheep was temporarily checked by falls in follicle activities during September and October as PRL concentrations began to increase (3·4 to 8·9 ng/ml). Follicle activity also declined in November and December in eight C sheep, coincident with the rapid rise in PRL to a seasonal maximum in late November (165·4 ng/ml). The increase in SD3 follicle activity over spring was not delayed by short days but during October, after release from treatment, PRL concentrations rose (1·8 to 12·0 ng/ml) and follicle activity declined (PFA: 65 to 38%, SFA: 68 to 43%). In SD6 ewes, PRL concentrations were suppressed (2·1 ng/ml) and relatively constant levels of follicle activity (PFA: 73%, SFA: 95%) were maintained throughout short-day treatment. Release of SD6 ewes into summer photoperiod in January 1991 temporarily interrupted follicle growth (PFA: 68 to 17%, SFA: 96 to 19%) and caused out-ofseason shedding in March and April. Contemporary C follicle activities were high (PFA: 95%, SFA: 98%). These data suggest that natural and experimental increases in daylength have a short-term inhibitory effect on growing wool follicles which could be mediated through rising concentrations of plasma prolactin. Journal of Endocrinology (1996) 148, 157–166

Rate of reproductive involution following either exposure to short days or daily administration of melatonin is faster in inbred than in random-bred female Syrian hamsters

1989 ◽  
Vol 120 (3) ◽  
pp. 489-496 ◽  
Author(s):  
R. J. Reiter ◽  
I. Sabry ◽  
M. Nordio ◽  
M. K. Vaughan ◽  
S. Migliaccio
Keyword(s):  
Day Treatment ◽  
Plasma Concentrations ◽  
The Other ◽  
Plasma Prolactin ◽  
Hormonal Changes ◽  
Syrian Hamsters ◽  
Short Day ◽  
Melatonin Administration ◽  
Short Days ◽  
Marked Drop

ABSTRACT The onset of cessation of oestrous cyclicity and associated organ and hormonal changes were compared in random-bred (RB) and inbred (IB) female Syrian hamsters kept either under short days (8 h light:16 h darkness; 8L:16D) or long days (14L:10D) and given daily afternoon injections of 25 μg melatonin. In response to short-day treatment, 100% of the IB hamsters exhibited vaginal acyclicity within 35 days; by comparison, none of the RB animals were acyclic at this time. The IB hamsters also exhibited other changes associated with exposure to short days, including increased body weight, enlarged ovaries, regressed uteri, elevated pituitary concentrations of FSH, and depressed pituitary and plasma concentrations of prolactin. At this time, only the pituitary FSH levels were increased in the RB animals kept under the same short-day conditions. In a second experiment, RB and IB female Syrian hamsters were maintained under long days (14L:10D) and the rate of reproductive regression in response to daily afternoon injections of melatonin was compared. After 8 weeks of melatonin injections, 80% of the IB females were anoestrous, while all RB hamsters were still exhibiting 4-day oestrous cycles. Other changes associated with melatonin administration in the IB females included a marked drop in uterine weight and a depression in pituitary and plasma prolactin levels. The RB hamsters, although they were all still cyclic after 8 weeks, had increased body and ovarian weights, increased pituitary concentrations of FSH, and lower pituitary and plasma prolactin levels. The results show that the IB strain of Syrian hamster, compared with the RB strain, responded more quickly with vaginal acyclicity to both exposure to short days and daily injections of melatonin. On the other hand, the IB hamsters responded more slowly in terms of oestrous acyclicity to melatonin injections than to treatment with short photoperiod. Journal of Endocrinology (1989) 120, 489–496

Violation of the conditions of the insolution regime in trends of modern construction

2020 ◽  
pp. 80-85
Author(s):  
Myroslava Schevchuk ◽  
Svitlana Verkalets ◽  
Serhiy Schevchuk ◽  
Mykola Danylyshyn
Keyword(s):  
Residential Buildings ◽  
Light Conditions ◽  
Regulatory Requirements ◽  
Natural Health ◽  
Natural Lighting ◽  
Lighting Conditions ◽  
Building Insulation ◽  
Holding Back ◽  
The Impact

Purpose. The purpose of the work is analysis of violations of natural lighting conditions (insolation) in residential buildings, because in the modern conditions of construction the role of direct sunlight as a natural health factor has increased significantly, multi-storied buildings in cities are becoming increasingly detached from natural conditions. Method. The methodology is based on a comprehensive and objective analysis of the SSTC-R B normative document R.2.2-27: 2010 “Guidance on the Calculation of Civilian Object Insolation”. Results. It has been investigated during the process of analysis that the regulation and calculation of insolation is the most acute economic and social-legal problem. With the transition of land usage and construction to the market basis, building insulation rates have become a major factor in holding back investors, landlords and tenants from seeking to redevelop urban development in order to maximize profits. Scientific novelty. Imperfect normalization was found under the current conditions in the course of the research, which can lead to serious errors in the design and evaluation of the insulation regime of the apartment and the house as a whole. The maximum shade mask of a new home shall correspond to the maximum possible height of the projected house or to the combination of the maximum heights of each individual section at which the insolation regime in the premises of the existing house or in the surrounding area shall meet the regulatory requirements or shall not deteriorate during the normalized period of insolation. If the insolation is interrupted more than once, then for the estimated duration of the insolation, the sum of the duration of the two largest insolation periods should be taken. Practical meaning. The results of the study may be useful in further studies of violation of natural light conditions, as well as the impact of residential development on insolation processes.

Role of area postrema in control of torpor in Siberian hamsters

2000 ◽  
Vol 279 (2) ◽  
pp. R591-R598 ◽  
Author(s):  
Helen H. Bae ◽  
Juliet L. Stamper ◽  
Eric C. Heydorn ◽  
Irving Zucker ◽  
John Dark
Keyword(s):  
Food Intake ◽  
Food Restriction ◽  
Area Postrema ◽  
Solitary Tract ◽  
Metabolic Fuel ◽  
Short Day ◽  
Siberian Hamsters ◽  
Metabolic Challenge ◽  
Short Days

Siberian hamsters undergo torpor during the short days of winter and in response to glucoprivation or food restriction. We tested whether the area postrema and the adjacent nucleus of the solitary tract (hereafter the AP), which monitor metabolic fuel availability, also control the onset of torpor. Siberian hamsters that had manifested torpor spontaneously or had entered torpor in response to 2-deoxy-d-glucose (2-DG) treatment were subjected to area postrema ablations (APx). Hamsters continued to display torpor postoperatively; most features of torpor were unaffected by APx. The AP is not necessary for expression of torpor elicited by short day lengths or metabolic challenge. In contrast, decreases in food intake manifested by hamsters treated with 2-DG were counteracted by APx. In Siberian hamsters, the AP appears to mediate effects of 2-DG on food intake but not torpor.

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