Effects Of Short Photoperiod Research Articles

Effect of Short Photoperiod on Behavior and Brain Plasticity in Mice Differing in Predisposition to Catalepsy: The Role of BDNF and Serotonin System.

Seasonal affective disorder is characterized by depression during fall/winter as a result of shorter daylight. Catalepsy is a syndrome of some grave mental diseases. Both the neurotransmitter serotonin (5-HT) and brain-derived neurotrophic factor (BDNF) are involved in the pathophysiological mechanisms underlying catalepsy and depressive disorders. The aim was to compare the response of behavior and brain plasticity to photoperiod alterations in catalepsy-resistant C57BL/6J and catalepsy-prone CBA/Lac male mice. Mice of both strains were exposed for six weeks to standard-day (14 h light/10 h darkness) or short-day (4 h light/20 h darkness) conditions. Short photoperiod increased depressive-like behavior in both strains. Only treated CBA/Lac mice demonstrated increased cataleptic immobility, decreased brain 5-HT level, and the expression of Tph2 gene encoding the key enzyme for 5-HT biosynthesis. Mice of both strains maintained under short-day conditions, compared to those under standard-day conditions, showed a region-specific decrease in the brain transcription of the Htr1a, Htr4, and Htr7 genes. After a short photoperiod exposure, the mRNA levels of the BDNF-related genes were reduced in CBA/Lac mice and were increased in the C57BL/6J mice. Thus, the predisposition to catalepsy considerably influences the photoperiodic changes in neuroplasticity, wherein both C57BL/6J and CBA/Lac mice can serve as a powerful tool for investigating the link between seasons and mood.

SAD rats: Effects of short photoperiod and carbohydrate consumption on sleep, liver steatosis, and the gut microbiome in diurnal grass rats

ABSTRACT Seasonal affective disorder (SAD) is a recurrent depression triggered by exposure to short photoperiods, with a subset of patients reporting hypersomnia, increased appetite, and carbohydrate craving. Dysfunction of the microbiota – gut – brain axis is frequently associated with depressive disorders, but its role in SAD is unknown. Nile grass rats (Arvicanthis niloticus) are potentially useful for exploring the pathophysiology of SAD, as they are diurnal and have been found to exhibit anhedonia and affective-like behavior in response to short photoperiods. Further, given grass rats have been found to spontaneously develop metabolic syndrome, they may be particularly susceptible to environmental triggers of metabolic dysbiosis. We conducted a 2 × 2 factorial design experiment to test the effects of short photoperiod (4 h:20 h Light:Dark (LD) vs. neutral 12:12 LD), access to a high concentration (8%) sucrose solution, and the interaction between the two, on activity, sleep, liver steatosis, and the gut microbiome of grass rats. We found that animals on short photoperiods maintained robust diel rhythms and similar subjective day lengths as controls in neutral photoperiods but showed disrupted activity and sleep patterns (i.e. a return to sleep after an initial bout of activity that occurs ~ 13 h before lights off). We found no evidence that photoperiod influenced sucrose consumption. By the end of the experiment, some grass rats were overweight and exhibited signs of non-alcoholic fatty liver disease (NAFLD) with micro- and macro-steatosis. However, neither photoperiod nor access to sucrose solution significantly affected the degree of liver steatosis. The gut microbiome of grass rats varied substantially among individuals, but most variation was attributable to parental effects and the microbiome was unaffected by photoperiod or access to sucrose. Our study indicates short photoperiod leads to disrupted activity and sleep in grass rats but does not impact sucrose consumption or exacerbate metabolic dysbiosis and NAFLD.

Effects of short photoperiod on cashmere growth, hormone concentrations and hair follicle development-related gene expression in cashmere goats

ABSTRACT Shanbei White Cashmere goat is a typical goat species, the growth of cashmere is affected by photoperiod. To further investigate the effects of short photoperiod treatment on cashmere growth, hormone concentrations and hair follicle development-related gene expression in cashmere goats, twenty Shannbei white cashmere goats were selected and randomly divided into long-day photoperiod treatment group and short-day photoperiod treatment group. The results revealed the cashmere on short-day photoperiod treatment began to develop earlier, and its length and growth rate increased dramatically (P < 0.05). The short-day photoperiod treatment increased the concentration of serum Melatonin, reduced the concentration of serum prolactin, decreased the expression of estrogen receptor alpha and raised the expression of hair follicle development-related genes [catenin beta-1, Bone morphogenetic protein 2, Fibroblast growth factor 5 and platelet-derived growth factor subunit A] (P < 0.05), thereby accelerating the reconstruction of the secondary follicle, increasing the density of the secondary follicle (P < 0.05) and triggering the growth of cashmere goats. The present study provides new insights into the dynamic changes in cashmere growth, hormone concentrations and hair follicle development-related gene expression in cashmere goats under short photoperiod, and is expected to be useful for future studies on intensive feeding research.

Photoperiod affects female life history traits in temperate populations of Aedes aegypti from South America

Abstract In many insects, short photoperiods induce females to lay diapausing eggs, which are associated with a reduction in female fecundity, and/or with an increase in their growth rate, allowing for a larger size at adulthood. The effects of short photoperiods may also differ among populations, depending on the different selection pressures imposed by the winter conditions. Thus, this study aimed to experimentally assess the effects of short photoperiods on Aedes aegypti, an invasive mosquito species that also vectors several viral diseases. We compared life history parameters of the females reared from the first larval instar under contrasting photoperiods, in two populations from the temperate region of Argentina, one with a milder winter (BA) and the other with a harsher winter (SB). The results showed a significant increase in the time to oviposition, a trend to a larger size of females (significant only for SB) and higher inhibition of egg hatching (more pronounced in SB), in response to short photoperiods. No differences in fecundity were detected among treatments. The different reaction norms of the populations in female body size and egg hatching response suggest an adaptation to local conditions, which might favour a further expansion of A. aegypti towards colder climates.

Effect of Short Photoperiod on the Behavior and Brain Serotonin System in Zebrafish Danio rerio.

Reduced daylight duration causes the development of seasonal affective disorder (SAD; depression-like disorders characterized by depressed mood, apathy, bulimia, and weight gain) in sensitive individuals. Neurotransmitter serotonin (5-HT) is involved in the mechanism of SAD. Zebrafish (D. rerio) is a promising model for translational studies. We studied changes in the behavior, content of 5-HT and its major metabolite 5-hydroxyindoleacetic acid (5-HIAA), and the expression of genes encoding the key enzymes of 5-HT metabolism, tryptophan hydroxylases TPH1A, TPH1B, TPH2, monoamine oxidase (MAO), 5-HT transporter, and 5-HT1A and 5-HT2A receptors in the brain of zebrafish reared for 60 days under short (04:20 h) compared to those reared at normal (12:12 h) photoperiod. Exposure to short photoperiod decreased locomotor activity in the novel tank diving test, increased the level 5-HIAA, and reduced the level of Mao gene mRNA, but did not affect the level of 5-HT and expression of Tph1a, Tph1b, Tph2, Slc6a4a (transporter), Htr1aa, and Htr2aa (receptors) genes. Thus, zebrafish can be used as a promising model to study the involvement of 5-HT in the SAD mechanism.

Temperature is an important driver for cold acclimation in garden roses

Low non-freezing temperatures and short days are two main environmental factors that can independently or collectively initiate cold acclimation in temperate perennials. Freezing temperatures are required for the full development of mid-winter cold hardiness. In the present study, six rose genotypes with different cold hardiness levels were selected to investigate cold acclimation under both long and short photoperiods to reveal the role of temperature and day length on cold acclimation of roses. A five-week short-day treatment at 20/18 °C did not induce cold acclimation in any of the genotypes. Cold hardiness levels (LT50 values) increased significantly at low non-freezing temperatures (2 °C) and freezing temperatures (-5 °C) irrespective of the photoperiod for all genotypes. The more cold-hardy ‘Dagmar Hastrup’ and ‘John Cabot’ responded strongly, achieving lower LT50 values under low non-freezing temperatures. Low non-freezing temperatures/freezing temperatures but not short days promoted the degradation of starch and the accumulation in sucrose, hexoses, and raffinose. Short days alone induced RhDHN5 in ‘Yesterday’, ‘Abraham Darby’, and Rosa wichurana. However, the expression of RhDHN5 was up-regulated significantly by low non-freezing temperatures in all genotypes. The up-regulation of RhBAM3 by lowering the temperature (low non-freezing temperatures and/or freezing temperatures) is genotype-independent. Freezing temperatures had a prominent role in accelerating the expression of RhGolS2 in all genotypes. The up-regulation of RhRS2 and RhRS6 is mainly induced by low non-freezing temperatures and freezing temperatures, respectively, but transcript levels for both were less pronounced than those for RhGolS2. Stem dehydration during cold acclimation was only found for ‘Chandos Beauty’ under long days and R. wichurana under short day length. R. wichurana was insufficiently acclimated to withstand freezing temperatures under short day length. This study clearly shows that the main factors triggering cold acclimation in roses in 5 rose genotypes are low non-freezing temperatures or freezing temperatures, but a synergistic effect of short photoperiod and low non-freezing temperatures was found for R. wichurana.

The effect of short photoperiod on behavior, brain-derived neurotrophic factor and brain serotonin system in tumour necrosis factor knockout mice

The effect of short photoperiod on behavior, brain-derived neurotrophic factor and brain serotonin system in tumour necrosis factor knockout mice

Architecture and Florogenesis in Female Cannabis sativa Plants.

The inflorescence is the main product of medical cannabis. Hundreds of specialized metabolites with potential bioactivity are produced and accumulated in the glandular trichomes that are highly abundant mainly on female inflorescences. Understanding the morphophysiological and genetic mechanisms governing flower and inflorescence development is therefore of high scientific and practical importance. However, in-depth investigations of cannabis florogenesis are limited. Cannabis producers and researchers consider long photoperiod to be “non-inductive” or “vegetative,” but under these growth conditions, the development of solitary flowers and bracts in shoot internodes clearly indicates that the plant cannot be defined as vegetative or non-inductive in the classical sense. Most probably, induction of solitary flowers is age-dependent and controlled by internal signals, but not by photoperiod. Short photoperiod induces intense branching, which results in the development of a compound raceme. Each inflorescence consists of condensed branchlets with the same phytomer structure as that of the larger phytomers developed under long day. Each phytomer consists of reduced leaves, bracts, one or two solitary flowers, and an axillary shoot (or inflorescence). Therefore, the effect of short photoperiod on cannabis florogenesis is not flower induction, but rather a dramatic change in shoot apex architecture to form a compound racemose inflorescence structure. An understanding of the morphophysiological characteristics of cannabis inflorescence will lay the foundation for biotechnological and physiological applications to modify architecture and to maximize plant productivity and uniformity in medical Cannabis.

The Effect of Temperature and Photoperiod on Diapause Induction in Pupae of Scrobipalpa ocellatella (Lepidoptera: Gelechiidae).

Scrobipalpa ocellatella (Boyd) (Lepidoptera: Gelechiidae) is one of the most important pests of sugar beet that causes quantitative and qualitative yield loss in the late summer. To locate the position for diapause induction, combinations of constant temperatures at 15, 18, 20, and 25°C and day lengths of 8, 10, 12, 14, 16, and 24 h were studied from egg to adult emergence. The incidence of diapause peaked at 15 and 18°C, with the day lengths of 12 and 11 h, whereas low temperatures did not improve the effects of short photoperiods (day lengths of 8 and 10 h) in diapause induction. The results showed that the critical day length for diapause induction was 12.8 h at overall 15 and 18°C. It was observed that the third instar larvae were the most sensitive stage to the inductive photoperiod (12:12 [L:D] h). The non-24-h light-dark experiment showed that the nigh length is more important than the day lengths measurement. In a set of 24-h light-dark cycles at 2:12 (L:D) h, a 1-h light pulse declined diapause induction markedly 1 h after scotophase. Field monitoring of the S. ocellatella for 2 yr (2015 and 2016) showed that the 50% of larvae enter winter pupal diapause in early September and this proportion increases in response to a decrease in the day lengths and temperature. From this study, it was concluded that low temperature acts in conjunction with short-day photoperiod in diapause induction of S. ocellatella.

Body Temperature Patterns in Captive Barbary Striped Grass Mousse (Lemniscomysbarbarus): Influence of Photoperiod and Sex Steroids

This study use miniature temperature-sensitive data loggers to record core body temperature (Tb) in Lemniscomysbarbarus, a diurnal Muridae rodent living in Africa. The work shows the existence of a strong and bimodal daily Tb rhythm in this species whose external synchronizer is the light-dark cycle; it’s also confirmed the diurnal and photoperiodic character of this animal. The highest values of Tb were registered during the light-phase in anti-phase with the nocturnal species. In the experimental conditions of this work Lemniscomysbarbarus do not express the phenomenon of diurnal torpor. Nevertheless, this characteristic mechanism of energy saving in small-sized mammals could be appearing by the association of the combined effects of short photoperiod, low ambient temperature and limited food supply.

Research of oat lines differing for genes of photoperiodic sensitivity

Oat lines (A. sativa) are studied in long and short photoperiods. Fast-ripening low-sensitive and late-ripening sensitive forms of this culture, differing for photoperiodic sensitivity genes, were selected from the hybrid population. The effect of short photoperiods on economically valuable traits is established. The long flag leaf sheath and high relative content of chlorophyll contributed to increased panicle productivity in oat lines.

Differential effects of photoperiod length on depression- and anxiety-like behavior in female and male diurnal spiny mice

The relationships between biological rhythms and affective disorders are known but their underlying biology not clear. There is difficulty in studying circadian rhythms in humans and appropriate animal models are hard to identify or develop. Some studies show that diurnal rodents can be advantageous model animals for the study of interactions between biological rhythms and affective disorders but previous studies did not include females whereas in humans there are sex differences in affective disorders. The present study tested the effects of short photoperiods in both males and females of the diurnal golden spiny mouse (Acomys russatus).Adult, female and male spiny mice were housed in either neutral photoperiod (12:12 light/dark; NP), or short photoperiod (5:19 light/dark; SP) conditions. After 3weeks acclimatization, animals were tested for spontaneous activity in an open field, elevated plus maze (EPM), sweet solution preference (SSP) and the forced swim test (FST).Both sexes responded to the SP, but while SP males showed increased anxiety-like behavior in the EPM and depression-like behavior in the FST, females showed increased activity, reduced anxiety-like behavior in the EPM, depression-like response in the SSP and no effect in the FST.Differences between sexes were previously demonstrated in behavioral tests that followed a variety of manipulations, and were usually explained in the context of sex hormones. Yet, the current results cannot be compared with previous data from diurnal rodents and further testing of females from other diurnal rodents are needed to explore whether these differences are a general phenomenon or possibly unique to golden spiny mice.

Plasma Melatonin and Progesterone Profiles of Suffolk and Romney Marsh Ewes Implanted with Melatonin during Anoestrus Season at Lower Latitudes in Southern Hemisphere

Background: The subcutaneous implants of melatonin are stimulatory and mimic the positive effects of short photoperiod on reproduction in small ruminants. This study investigated the daily plasma melatonin profiles in ewes treated with melatonin implants and kept under natural photoperiod in Southeastern Brazil. The plasma progesterone concentrations were also investigated before and after melatonin implantation.Materials, Methods &amp; Results: Romney Marsh (n = 11) and Suffolk (n = 10) ewes, which had been isolated from rams for at least 2 months prior to the beginning of the trial, were randomly allocated in two groups based on melatonin implant treatment (with or without melatonin implant). For plasma melatonin concentration, 43 days after melatonin implantation and 3 days before the ram introduction blood samples were collected every 2 hours during 24 hours. For plasma progesterone concentrations, blood samples were collected every once to twice a week for 2 different periods: prior to melatonin implantation and 46 days after the melatonin implantation and at the same day of the introduction of rams. The hormonal concentrations were determined by the radioimmunoassay method (RIA). The data were analyzed according to MIXED procedure (SAS) as repeated measurements for random animal effects. The effect of melatonin treatment on plasma melatonin 24-h period varied according to the breed. At the dark-phase, there were no plasma melatonin differences (P &gt; 0.05) between implanted and no-implanted (228.02 ± 58.39 vs. 169.59 ± 48.39) Romney Marsh ewes whereas for Suffolk ewes the plasma melatonin levels were higher in implanted (305.61 ± 68.39 pg/mL) than no-implanted (151.26 ± 38.35 pg/mL) ones. At the light-phase, melatonin treatment effects could be evidenced and these differences (P &lt; 0.01) consisted of higher melatonin values for implanted ewes and basal values for no-implanted ones in both breed groups. Before the melatonin implantation, the plasma progesterone levels were ˂ 1 ng/mL for Romney Marsh (0.41 ± 0.02 ng/mL) and Suffolk (0.47 ± 0.02 ng/mL) ewes. During the ram introduction period, no melatonin treatment effect was observed on plasma progesterone concentrations in both breed groups, but 2 days after ram introduction the plasma progesterone concentrations increased the mean values &gt; than 1 ng/mL in implanted and no-implanted Suffolk ewes. In implanted Romney Marsh ewes the elevation of progesterone mean values was weak whereas in no-implanted Romney Marsh ewes the progesterone levels were maintained ˂ 1 ng/mL during all the blood sample collection times.Discussion: The melatonin treatment also produced a similar model of daily melatonin levels as reported previously by others, which is characterized by high plasma melatonin concentrations during the light phase of the day. The effect of melatonin implants on plasma melatonin profiles interacted with breed confirming an individual response to melatonin implantation which is proportional to genetic individual variation pattern of melatonin secretion. Before the melatonin implantation all Romney Marsh and Suffolk ewes were judged to be in non-ovulatory period (anoestrus) with plasma progesterone mean values lower than 1 ng/mL. The melatonin treatment helped to induce the ovulatory activity in most of the ewes that were in anestrous at the time of melatonin implantation and the efficacy of this treatment depends on the individual variation in ovulatory response to ram introduction. In Southeastern Brazil., melatonin implant altered the daily plasma melatonin profiles of Suffolk and Romney Marsh ewes by increasing the melatonin levels during the light-phase of the day. Melatonin implant also induced an ovulatory response in Suffolk and Romney Marsh after the introduction of the rams. For no-implanted Suffolk ewes, the male effect is sufficient to provoke an ovulatory response.

Short day photoperiod protects against acetaminophen-induced heptotoxicity in rats

This study investigated the effect of different photoperiods on acetaminophen-induced hepatotoxicity in rats. Twenty four adult male rats (average weight = 160±7g) were conditioned to different photoperiod regimens for 6 weeks. At the end of the 6-week period, rats exposed to normal, short and long photoperiods received oral acetaminophen (2g/kg body weight) while in the control group, exposed to normal photoperiod, received oral saline. Rats were sacrificed 24 h after acetaminophen administration by cervical dislocation and blood was collected by cardiac puncture for the estimation of liver enzymes activities. Liver tissues were excised and homogenized for estimation of liver malondialdehyde (MDA) concentration. Elevation of serum levels of alanine and aspartate transaminases and alkaline phosphatase caused by acetaminophen intoxication were not affected in rats subjected to long photoperiod while these parameters were significantly (P<0.05) reduced in rats subjected to short photoperiod. However, alteration of photoperiod resulted in significantly (P<0.05) lower serum gamma glutamate transpeptidase and total protein in acetaminophentreated rats. All groups of rats had similar serum albumin while serum malondialdehyde concentration was significantly lower in rats subjected to short photoperiod. This study revealed the protective effects of short photoperiod against acetaminophen-induced hepatotoxicity and lipid peroxidation in rats. Key words : Acetaminophen, photoperiod, lipid peroxidation, Hepatotoxicity

Effects of short photoperiod on energy intake, thermogenesis, and reproduction in desert hamsters (Phodopus roborovskii).

Desert hamsters (Phodopus roborovskii) are the least known species in the genus Phodopus with respect to ecology and physiology, and deserve scientific attention, particularly because of their small body size. Here, the responses of energy metabolism and reproductive function to short photoperiods in desert hamsters were investigated. Male and female desert hamsters were acclimated to either long day (LD) (L:D 16:8 h) or short day (SD) photoperiods (L:D 8:16 h) for three months, and then the females were transferred back to an LD photoperiod for a further five months, while at the end of the SD acclimation the males were killed and measurements were taken for serum leptin as well as molecular markers for thermogenesis. We found that like the other two species from the genus Phodopus, the desert hamsters under SD decreased body mass, increased adaptive thermogenesis as indicated by elevated mitochondrial protein content and uncoupling protein-1 content in brown adipose tissue, and suppressed reproduction compared to those under LD. However, different from the other two species, desert hamsters did not show any differences in energy intake or serum leptin concentration between LD and SD. These data suggest that different species from the same genus respond in different ways to the environmental signals, and the desert adapted species are not as sensitive to change in photoperiod as the other two species.

Temporal dynamic of adrenocortical and gonadal photo-responsiveness in male Japanese quail exposed to short days

The study evaluated whether different short-term endocrine testicular and adrenocortical responses to short photoperiod exposure can persist over time and particularly when birds exhibit spontaneous cloacal gland recovery. At 11 wk of age, 33 male Japanese quail exposed to long photoperiod were switched to short photoperiod (8L:16D). Another group of males was kept under long photoperiod (n = 11; LD quail). After 5 wk of short photoperiod exposure, quail were classified as nonresponsive or responsive to short photoperiod, depending on whether the cloacal gland volume was above or below 1,000 mm3 and with or without foam production, respectively. Since 11 wk of age and during a 20-wk period, droppings of all quail were collected to determine corticosterone and androgen metabolites (AM) by enzyme immunoassays. Cloacal gland volume was also determined weekly. Both short photoperiod nonresponsive (SD-NR) and responsive quail showed overall significantly lower (P < 0.01) AM values (518.8 ± 11.9 and 248.6 ± 17.1 ng/g, respectively) than quail that remained under long photoperiod (814.3 ± 24.1 ng/g). However, nonresponsive quail showed a significantly smaller reduction in their AM levels than their responsive counterparts. During the first 6 wk of short photoperiod exposure, SD-NR quail showed similar corticosterone metabolites values than LD quail. Corticosterone metabolite profiles changed from 7 wk of short photoperiod exposure onward, with photoperiodic differences (P < 0.01) persisting up to the end of study (LD: 228.9 ± 22.4 > SD-NR: 133.1 ± 15.5 > short photoperiod responsive: 61.6 ± 17.9 ng/g, respectively). Testicular and adrenocortical glands showed different degrees of activity associated with cloacal gland photoresponsiveness to short photoperiod manipulation. Our findings suggest long-term effects of short photoperiod, both in the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenocortical axis activity of quail, including males that exhibited spontaneous cloacal gland recovery.

Effects of Short Photoperiod on Codling Moth Diapause and Survival

The potential presence of codling moth, Cydia pomonella L., in apples shipped to countries within the 30th latitudes has raised concerns that this pest could establish and spread in these countries. Previous research demonstrated that codling moth in apples handled under simulated commercial cold storage conditions and held under short day lengths could not break diapause and emerge in sufficient numbers to establish a minimum viable population. This study expands the in-fruit work by examining the ability of codling moth to establish a laboratory population under a short photoperiod of 12:12 (L:D) h, as compared with a long photoperiod of 16:8 (L:D) h. Codling moth larvae were collected from field infested fruits in 2010 and 2011. Moths were collected from the infested fruits and separated into two groups representing the two daylength conditions. In total, 1,004 larvae were monitored for adult emergence and ability to generate a subsequent population. Larvae held under the photoperiod of 12:12 (L:D) h generated only one moth in the 2 yr period, whereas larvae held under the photoperiod of 16:8 (L:D) h generated 186 females and 179 males, that sustained subsequent generations on artificial diet under laboratory conditions. These results indicate that under controlled environmental conditions, codling moth cannot complete diapause and emerge in sufficient numbers to sustain a viable population when held under a short photoperiod.

The thermogenic and metabolic responses to photoperiod manipulations in Apodemus chevrieri

Environmental cues play important roles in the regulation of an animal’s physiology and behavior. In the present study, we examined the effects of short photoperiod on body weight as well as on several physiological, hormonal, and biochemical measures indicative of thermogenic capacity to test our hypothesis that short photoperiod stimulates increases in thermogenesis without cold stress in Apodemus chevrieri. A. chevrieri were randomly assigned to either a long or short photoperiod for 4 weeks at constant temperature. The short photoperiod group of A. chevrieri showed increases in resting metabolic rate and nonshivering thermogenesis during the 4-week photoperiod acclimation. At the end, A. chevrieri at short photoperiod had lower body weights, higher levels of mitochondrial protein content and cytochrome C oxidase activity in liver and brown adipose tissues, and had higher levels of mitochondrial uncoupling protein-1 contents in brown adipose tissues. No difference in serum leptin levels were found between short and long photoperiod groups, but serum leptin levels were positively correlated with body mass and body fat mass, and negatively correlated with energy intake and uncoupling protein-1 content in brown adipose tissues, respectively. All results suggest that the short photoperiod may induce an increased thermogenesis capacity in A. chevrieri and that leptin is potentially involved in the photoperiod induced body mass regulation and thermogenesis in A. chevrieri.

Sprague Dawley Ratlarda Kısaltılmış Işık Süresinin Bazı Büyüme Özelliklerine Etkisi

Summary The effect of short photoperiod on some growth traits in outbred Sprague Dawley rats was examined. The pups were assigned to two photoperiod groups: long/routin (12 h light/dark: control) and short (9 h light/15 h dark: experiment) lighting, since, in nature, photoperiod may decrease to 9 hours in winters, in subtropical regions. At 15 weeks of ages, body weight, weight of heart, liver, spleen, lungs, kidneys, gastear, adrenal glands, testis and ovaries of the rats from experimental group were compared to those in control group. Body growth, weight of heart, liver and spleen and large intestine length in control and experimental rats were not significantly different (P>0.05). No differences were observed in testis and ovary weights between control and experiment groups, statistically. Rats exposed to short photoperiod had lower lung, kidney, gastear, adrenal gland and intestine weight than those of control rats (P<0.01 and P<0.05). In outbred Sprague Dawley rats, short photoperiod had no effect on body growth and reproduction organs and it is concluded that, there may be a chance for some strains of outbred Sprague Dawley rats to be kept under short photoperiod conditions, without reducing body weight and reproductive organ growth.

Role of photoperiod on hormone concentrations and adaptive capacity in tree shrews, Tupaia belangeri

Environmental factors, such as photoperiod and temperature, play an important role in the regulation of an animal's physiology and behavior. In the present study, we examined the effects of short photoperiod (SD, 8L:16D) on body mass as well as on several physiological, hormonal, and biochemical measures indicative of thermogenic capacity, to test our hypothesis that short photoperiod stimulates increases thermogenic capacity and energy intake in tree shrews. At the end, these tree shrews (SD) had a significant higher body mass, energy intake, cytochrome C oxidase (COX) activity and uncoupling protein-1 (UCP1) content, serum tri-iodothyronine (T3) and thyroxine (T4) compared to LD (16L:8D) tree shrews. However, there were no significant differences in serum leptin and melatonin between the two groups. Together, these data suggest tree shrews employ a strategy of maximizing body growth and increasing energy intake in response to cues associated with short photoperiod.