Hypothalamic expression of GnRH-I and GnIH in the Eurasian tree sparrow over a single long day.

Seasonal reproductive cycles of most birds are regulated by photoperiod via neuroendocrine control. The present study aims to investigate the role of a single long day in triggering hypothalamic expressions of GnRH-I and GnIH in the Eurasian tree sparrow (Passer montanus). Sparrows were divided into two groups (n = 24 each) and pre-treated under short days (9L: 15D) for 4 days. On the fifth day, one group was exposed to long day (14L: 10D), while other was continued under short day for another 1 day. Birds of both the groups were sacrificed and perfused on fifth day at different time points, i.e., ZT 14, ZT 16 and ZT 18 and the expressions of GnRH-I and GnIH mRNAs and peptides were studied using real-time PCR and immunohistochemistry, respectively. In addition, testicular size was measured to know testicular development. Observations revealed that birds exposed to a single long day (14L: 10D) showed an increase in hypothalamic expressions of GnRH-I mRNA and peptide and decrease in levels of GnIH mRNA only at ZT 16 and ZT 18 with no significant change in GnIH peptide. However, no significant change in GnRH-I or GnIH expression was observed at any time point under short day and birds maintained high and low expression levels of GnIH and GnRH-I, respectively. Our results clearly indicate that the photoperiodic response system of sparrow is highly sensitive to light and responds even to single long day. Furthermore, they suggest that the GnRH-I and GnIH are expressed in the hypothalamus of tree sparrow in an anti-phasic manner and switching over of their expression occurs at late hours of exposure of birds to single long day.

Morphological and Ultrastructural Studies of Pecten in the Eurasian Tree Sparrow.

We studied the fine histological structures of pecten oculi of the Eurasian tree sparrow using various microscopy techniques. The pecten of the tree sparrow was found to be of a pleated type comprising of pleats, bridges, and base. The light microscopic study revealed further that the pleats consist of capillaries of varying sizes, blood vessels, and numerous pigmented cells that give them a black color. Histochemical studies of pecten showed a large deposition of lipid droplets, which were more abundant in the basal area. The transmission electron microscopy displayed capillaries and blood vessels that remain surrounded by a thick fibrous basal membrane. They are formed of endothelial cells having a large lumen and abluminal area with microfolds. Interstitial spaces were found filled with rounded melanocytes, electron-dense pigment granules, and mitochondria. Observations under the scanning electron microscope revealed the presence of a dense vascular network of capillaries and vessels. In addition, large hyalocytes were also observed on the surface of the pleats. The above observations suggest that the histological structure of the pecten of the tree sparrow resembles those present in the pecten of other diurnal birds. However, further investigation is required to ascertain its functional role in birds.

Circadian rhythm in photoperiodic expressions of GnRH-I and GnIH regulating seasonal reproduction in the Eurasian tree sparrow, Passer montanus.

The present study investigates the involvement of circadian rhythm in photoperiodic expressions of GnRH-I and GnIH in the hypothalamus controlling seasonal reproduction in the Eurasian tree sparrow (Passer montanus). Groups of photosensitive birds were exposed for four weeks to resonance light dark cycles comprising of a light phase of 6 h (L) combined with dark phase of different durations (D) such that the period of LD cycles varied by 12 h increments viz. 12- (6 L/6D), 24- (6 L/18D), 36- (6 L/30D), 48- (6 L/42D), 60- (6 L/54D) and 72- (6 L/66D)h. In addition, a control group (C) was maintained under long day length (14 L/10D). Observations, recorded at the beginning and end of experiment, revealed significant testicular growth with corresponding increase in the hypothalamic expression of GnRH-I peptide but low levels of GnIH mRNA and peptide in the birds exposed to resonance cycles of 12, 36 and 60 h which were read as long days. On the other hand, birds experiencing resonance cycles of 24, 48 and 72 h read them as short days wherein they maintained their quiescent gonads and low levels of GnRH-I peptide but exhibited significant increase in GnIH mRNA and peptide expressions. Thus, sparrows responded to resonance light dark cycles differently despite the fact that each of them contained only 6 h of light. These findings suggest that an endogenous circadian rhythm is involved in photoperiodic expressions of above molecules and indicate a shift in their expressions depending upon whether the light falls in the photoinducible or non-photoinducible phase of an endogenous circadian rhythm.

Circadian versus circannual rhythm in the photoperiodic programming of seasonal responses in Eurasian tree sparrow (Passer montanus).

Experiments were performed on the subtropical tree sparrow (Passer montanus) to investigate whether day length, as a proximate factor, involves circadian rhythm in timing seasonal responses or these events are programmed by the mediation of an endogenous circannual rhythm. The experiments began from the two equinoxes, i.e. March and September, and continued for about 18 months. In each equinox, one group of wild birds of both sex was exposed to near simulated day length as it varies in nature at Shillong (Latitude 25°34'N, Longitude 91°53'E), and the other group was given a photoperiodic treatment in the reverse order corresponding to natural variation in day length from the other equinox. The birds exposed to near simulated day lengths in March and September showed gonadal, bill colour and molting responses, as observed in the wild birds in nature. Moreover, when photosensitive birds of March were given photoperiodic treatment in the reverse order (i.e., natural variation in day lengths beginning from September), they maintained their photosensitivity and responded only when they received increasing day length in the following September. However, when the photorefractory birds of September were exposed to reverse photoperiodic treatment (i.e. natural day length as it varies from March), they terminated their photorefractoriness after receiving decreasing day length in March the next year and responded when they again received increasing day length in the following September. These results strongly suggest that photoperiodic regulation of seasonal responses in the tree sparrow involves an endogenous circadian rhythm and exclude the possibility of circannual rhythm generation.

Photoperiodic control of GnRH-I expression in seasonal reproduction of the Eurasian tree sparrow.

Day length has been shown to be a major source of temporal information regulating seasonal reproduction in the Eurasian tree sparrow (Passer montanus). The present study aims to investigate the photoperiodic expression of gonadotropin-releasing hormone-I (GnRH-I), and how it mediates seasonal reproduction in male tree sparrows. In different experiments, we studied photoperiod-induced changes in GnRH-I expressing neurons in the hypothalamic preoptic area (POA), together with changes in testicular size under both natural and artificial photoperiodic conditions. Experiment 1, which involved studying changes in GnRH-I expression and testicular volume during different phases of the annual reproductive cycle under natural day length (NDL), revealed that sparrows possess a definite seasonal cycle of GnRH-I peptide expression that runs parallel to testicular size. Birds showed significantly higher levels of GnRH-I expression in the breeding phase when compared to the non-breeding phase. In experiment 2, photosensitive birds were exposed to artificial short (SD: 9L/15D) and long (LD: 14L/10D) day lengths for 240 days to investigate the photoperiodic regulation of GnRH-I expression. They exhibited a significant increase followed by a decrease in GnRH-I expression and testicular size under LD but not SD, suggesting photoperiodic regulation. In experiment 3, when photosensitive birds were exposed to increasing photoperiods (9L/15D, 10L/14D, 10.5L/13.5D, 11L/13D, 12L/12D) for 30 days to find out the critical photoperiod for GnRH-I expression, they responded only when the daily photoperiod was 11 h or more. These results clearly indicate that tree sparrows are capable of fine discrimination of photoperiodic information and use day length for GnRH-I expression to control their seasonal reproduction.

Temperature modulates photoperiodic seasonal responses in the subtropical tree sparrow, Passer montanus.

We studied the effects of temperature on the photoperiodic regulation of seasonal reproduction and related events in the subtropical tree sparrow at Shillong, India. In the first experiment, one group of birds was maintained in an outdoor open aviary receiving natural photoperiod and temperature conditions, while the other group was exposed to natural photoperiod and constant temperature of 17 ± 2 °C in an outdoor closed aviary for 12 months. Although both sexes achieved peak gonadal growth at the same time (May) under the two conditions, gonadal regression and feathers molt were delayed under the temperature controlled condition. In the second experiment, the groups of birds were exposed to three different temperatures (17, 25 and 30 °C) under both long (LD-14L:10D) and short (SD-9L:15D) day lengths for 7 months. Birds showed relatively small but significant gonadal growth, darkening of bill color and feathers molt only at 30 °C under SD. However, they behaved as though they were under natural conditions and exhibited the above responses significantly at all temperatures under LD. There was delayed gonadal regression at the lower temperature (17 °C), while feathers molt delayed with increasing temperature (25, 30 °C) under LD. These results clearly indicate that temperature modulates photoperiodic seasonal responses in the tree sparrow.

Role of GnIH in photoperiodic regulation of seasonal reproduction in the Eurasian tree sparrow.

Seasonal reproductive cycles of most birds are regulated by photoperiod via neuroendocrine control. Gonadotropin-inhibitory hormone (GnIH) in the hypothalamus has been reported to act as neuroendocrine integrator of photoperiodic cues. In this study, both captive and field investigations were carried out to understand the effects of photoperiod and seasonality on GnIH expression in subtropical tree sparrows. Monthly observations of GnIH mRNA and peptide expression in wild birds over a year revealed a significant increase in GnIH mRNA level and number of GnIH-ir neurons during the non-breeding season when compared with their expression in the breeding season. GnIH-ir neurons were found primarily in the paraventricular nucleus (PVN) with their fibers projecting into the median eminence and some other areas of the brain. In an 8 month-long experiment, birds exposed to short days had higher GnIH expression compared with birds exposed to long days regardless of sampling month. Long-day birds with regressed testes had similar GnIH levels to short-day birds. Though the number of GnIH peptide-expressing neurons ran almost parallel to the levels of GnIH mRNA, they were inversely related to gonadal size in both sexes under natural and artificial photoperiodic conditions. These results clearly indicate an inhibitory role of GnIH in photoperiodic regulation of seasonal reproduction in the tree sparrow.

Photoperiodic time measurement and photoentrainment of a circadian locomotor activity rhythm in subtropical tree sparrows.

Experiments were performed on the subtropical tree sparrow (Passer montanus) to investigate the involvement of an endogenous circadian rhythm in photoperiodic time measurement during the initiation of gonadal growth and functions and also to study the photic entrainment of the circadian activity rhythm. Groups of photosensitive birds of both sexes were exposed to different "night-interruption" light-dark regimes of 24 h duration viz., G1 - 6L/5D/1L/12D, G2 - 6L/6D/1L/11D, G3 - 6L/7D/1L/10D, G4 - 6L/8D/1L/9D, G5 - 6L/10D/1L/7D, G6 - 6L/12D/1L/5D, G7 - 6L/14D/1L/3D and G8 - 6L/16D/1L/1D for 30 days in which 17 h long nights were interrupted by 1 h light pulse falling at different ZTs (i.e., 11, 12, 13, 14, 16, 18, 20 and 22). A control group, for each sex, was maintained under 7L/17D. The birds of all groups behaved as though they had been exposed to a stimulatory photoperiod except those of G1, G8 and the control. Furthermore, the serum levels of testosterone in males and estradiol-17ß in females ran almost parallel to changes in the gonadal size. Birds, when exposed to 12L/12D, showed entrainment of their locomotor activity rhythm with the activity confined mainly during the light phase. However, various characteristics of the activity rhythm differed significantly upon transfer of birds to various night interruption regimes. These results suggest the involvement of the endogenous circadian rhythm in photoperiodic time measurement during the induction of gonadal growth and functions in the tree sparrow. Also, there is photic entrainment of the locomotor activity rhythm that shows variations in various circadian characteristics under different night interruption cycles suggesting that the photoinducible phase is differentially sensitive to light.

Seasonality in circadian locomotor activity and serum testosterone level in the subtropical tree sparrow (Passer montanus).

Seasonality in daily locomotor activity pattern was investigated in the subtropical tree sparrow by exposing a group of birds to natural day lengths (NDL) for 30days and another group to 12L/12D for 14days followed by transfer to constant dim light (LLdim) for another 15days in four different seasons of the year. Serum testosterone levels were also measured during different seasons. Sparrows, under NDL, exhibited distinct circadian rhythmicity in their locomotor activity with almost similar general pattern in different seasons that restricted mainly to the light hours. However, they showed season-dependent differences in the characteristics of circadian locomotor activity rhythm. Birds, when exposed to 12L/12D, showed entrainment of their locomotor activity rhythm with the activity confined mainly during the light phase. Though, tau (τ) under free run conditions did not show any significant difference, the activity period varied significantly in different seasons. The highest level of testosterone was recorded in the spring season that corresponded with the maximum locomotor activity in spring months. The seasonality in daily locomotor activity correlates with the seasonal changes in testosterone levels suggesting the influence of gonadal steroids on endogenous circadian system which is indicative of adaptation of tree sparrow to local photoperiodic conditions.

A comparative study on photoperiodic control of seasonal cycles in the females of migratory yellow breasted bunting and the resident tree sparrow.

We studied the detailed pattern of seasonality in reproduction and the associated functions in the females of migratory yellow breasted bunting (Emberiza aureola) and resident tree sparrow (Passer montanus) under natural and artificial photoperiods. They exhibited seasonal cycles of ovarian development, moult and bill colour under natural photoperiods which were found linked to the annual solar cycle. Photosensitive birds of both the species, when exposed to 9L/15D, 12L/12D and 14L/10D for 18 months, showed follicular growth followed by regression and development of photorefractoriness only under artificial long photoperiods (12L/12D and 14L/10D). Fattening and body weight increase were noticed only in bunting exposed to long natural and artificial photoperiods. Both species exhibited complete postnuptial moult of body and primary feathers under long natural and artificial photoperiods (except primaries moult under 12L/12D in bunting) that progressed with gonadal regression suggesting their photoperiodic control. In addition, bunting also showed an incomplete prenuptial moult of body feathers during gonadal stimulation. Thus, the moult and body weight responses of bunting differed significantly when compared with those of sparrows. Exposure of photosensitive birds to 24 h light-dark cycles with increasing photophase suggested that the threshold photoperiods of about 12 h in bunting and about 11 h in sparrow initiate follicular growth exceeding which the rate of growth increases with increasing photoperiods. However, the threshold photoperiod was found to be response specific in bunting.

Photoperiodic control of testicular growth, histomorphology and serum testosterone levels in the male Eurasian tree sparrow: involvement of circadian rhythm.

Experiments were performed on the subtropical population of male Eurasian tree sparrow (Passer montanus) to examine the mediation of the circadian rhythms in photoperiodic regulation of reproductive responses. In the first experiment, photosensitive sparrows were exposed to different resonance light dark cycles viz. 6L/6D, 6L/18D, 6L/30D, 6L/42D, 6L/54D and 6L/66D along with a control group under long day length (14L/10D) for 35days. The birds read the cycles of 6L/6D, 6L/30D and 6L/54D as long day and exhibited significant testicular growth and increased testosterone levels while the cycles of 6L/18D, 6L/42D and 6L/66D were read as short day with no testicular response. In the second experiment, groups of photosensitive birds were subjected to various intermittent light dark cycles of 2L/2D, 3L/3D, 4L/4D, 6L/6D, 8L/8D and 12L/12D with two control groups kept under 9L/15D and 14L/10D for 35days. The birds held under the light/dark cycles of 2L/2D, 3L/3D, 4L/4D, 6L/6D and 12L/12D showed testicular growth and increased serum levels of testosterone while those exposed to 8L/8D did not. The responses were significantly higher in the birds exposed to 2L/2D, 3L/3D, 4L/4D and 6L/6D when compared to 12L/12D. Histomorphology of testes revealed different stages of spermatogenesis only under gonadostimulatory light regimes. The germinative epithelium thickness and diameter of seminiferous tubules increase while the thickness of testicular wall and area of interstitial space decrease with the increase in testicular volume. The above results indicate the involvement of an endogenous circadian rhythm in photoperiodic induction of testicular growth and functions.

Morphology and ultrastructural studies of pineal organ of the tree sparrow (Passer montanus).

We studied fine structures of the pineal organ of the tree sparrow, Passer montanus under the light, scanner electron and transmission electron microscopes. The pineal gland of the sparrow was found comprising of a pea-shaped epiphysis cerebri and a long tube-like pineal stalk that connects with the choroid plexus. Histological preparations of the pineal organ revealed that it contains follicles having pinealocytes of uniform size. The enlarged images of the gland using the SEM showed distinct granular structures or cells protruding from the surface of the epiphysis cerebri. The choroid plexus possessed varying numbers of irregular ridges and furrows. The observation under TEM revealed rounded nucleus and mitochondria in the pinealocytes. Groups of small size vesicles were also seen scattered throughout the perinuclear cytoplasm. Numbers of microtubules were found running parallel to each other. Blood capillaries that supply blood to the pineal organ were also visible in the sections. The morphology of the pineal organ of tree sparrow showed similarity with those of the other birds in possessing elongated epiphysis cerebri which remains connected to choroid plexus through a stalk. The tree sparrow resembled with some passerine birds in possessing saccular type of pineal organ having elongated tubular structure with a central lumen and a thick follicular wall. The pineal organ of the tree sparrow, thus, differed from those reported in non-passerine birds with tubulo-follicular or solid type of pineal organ. The presence of saccular pineal organ in the subtropical tree sparrow, as reported in other passerine birds elsewhere indicates the conservation of the structural organization of the pineal organ in passerine birds.

Photoperiodic regulation of seasonal reproduction, molt and body weight in the migratory male yellow-breasted bunting (Emberiza aureola).

Photoperiod has been shown to be a major source of temporal information regulating reproduction and associated functions in a number of avian species. We studied seasonal cycles of testicular volume, molt and body weight in natural and temperature-controlled conditions and under different artificial photoperiods in the yellow-breasted buntings. Buntings posses seasonal cycles of testicular volume, molt, body weight and fattening with no major difference between natural and temperature-controlled conditions. These cycles follow an annual solar cycle suggesting the possibility of their photoperiodic control. To confirm this, photosensitive birds were studied under 9L/15D (close to shortest day length), 12L/12D (equinox day length) and 14L/10D (close to longest day length) for 18 months. Buntings showed testicular growth followed by regression and development of photorefractoriness; molt and body weight change only under 12L/12D and 14L/10D but not under 9L/15D. Reinitiation of above responses did not occur following initial cycles under stimulatory photoperiods precluding the possibility of circannual rhythm involvement. Birds exhibited an incomplete prenuptial molt of body feathers during gonadal stimulation under long days followed by complete postnuptial molt of body and primary feathers that progressed with gonadal regression. Exposure of photosensitive birds to light-dark cycles constituting 9-16h of light/day suggested that daily photoperiod of about 12h or more is essential in inducing testicular growth and function. These results clearly indicate that buntings are capable of fine discrimination of photoperiodic information and use annual changes in day length as an environmental factor to time their seasonal responses.

Seasonal variation in sensitivity of the photoperiodic response system in the subtropical tree sparrow (Passer montanus).

We investigated seasonal variations in response to photoperiods in subtropical tree sparrow (Passer montanus), by examining the effects of long and short days on stimulation of response and termination of refractoriness, respectively. We also assessed whether photoperiodic effects were sex dependent. In one study, wild sparrows were transferred in each month of the year to artificial long days (14L/10D) for 12 weeks. Birds transferred from November to March (female) or April (male) showed gradual increase in gonadal growth and darkening of bill color, while those transferred from April (female) or May (male) to July underwent gradual regression in the above responses. Moult in the wing primaries and body feathers progressed with gonadal regression and the birds transferred from April/May to October exhibited gradual increase and decrease in feathers moult. In another study, 6 weeks of short day (9L/15D) exposure could recover responsivity to long days in refractory birds. Male and female birds responded almost in similar fashion with some variations. Overall, our results show a gradual change over seasons in responsiveness of the endogenous response system to stimulatory effects of long day length. They suggest roles of both long and short day lengths in regulation of seasonal cycles in subtropical tree sparrows.

Photoperiod as a proximate factor in control of seasonality in the subtropical male Tree Sparrow, Passer montanus.

BACKGROUND: Most species of birds exhibit well-defined seasonality in their various physiological and behavioral functions like reproduction, molt, bill color etc. such that they occur at the most appropriate time of the year. Day length has been shown to be a major source of temporal information regulating seasonal reproduction and associated events in a number of avian species. The present study aims to investigate the role of photoperiod in control of seasonal cycles in the subtropical male tree sparrow (Passer montanus) and to compare its responses at Shillong (Latitude 25°34'N, Longitude 91°53'E) with those exhibited by its conspecifics and related species at other latitudes. RESULTS: Initial experiment involving study of seasonal cycles revealed that the wild tree sparrows posses definite seasonal cycles of testicular volume, molt and bill color. These cycles were found remarkably linked to annual solar cycle suggesting the possibility of their photoperiodic control. To confirm this possibility in the next experiment, the photosensitive birds were exposed to three different light-dark regimes that were close to what they experience at this latitude: 9L/15D (close to shortest day length), 12L/12D (equinox day length) and 14L/10D (close to longest day length) for 18 months. Tree sparrows showed testicular growth followed by regression and development of photorefractoriness, molting and bill color changes only under long daily photoperiods (12 L and 14 L) but not under short daily photoperiod (9 L). Birds, under stimulatory photoperiods, did not show reinitiation of the above responses after the completion of initiation regression cycle even after their exposure to these photoperiods for 18 months. This precludes the possibility of circannual rhythm generation and suggests the involvement of photoperiodic mechanism in control of their seasonal cycles. Further, replacement of body and primary feathers progressed with gonadal regression only under long days suggesting that the two high energy demanding events of reproduction and molt are phased at two different times in the annual cycle of the bird and are photoperiodically regulated. Results of the final experiment involving exposure of photosensitive birds to a variety of photoperiodic treatments (9L/15D, 10L/14D, 11L/13D, 12L/12D, 14L/10D and 16L/8D) for 30 days suggested that the light falling for 11 h or more is important in inducing testicular growth and function in this species. CONCLUSION: These results clearly indicate that despite of small photofluctuation, subtropical tree sparrows are capable of fine discrimination of photoperiodic information and use day length as a proximate environmental factor to time their seasonal responses similar to their conspecifics and related species at other latitudes suggesting the conservation of photoperiodic control mechanism in them.

Methysergide-induced valvular heart disease: a report of 2 cases.

Methysergide is a serotonin antagonist and is used as a long-term prophylactic treatment for migraine. Although many patients experience adequate control of migraine episodes, methysergide has been reported to cause retroperitoneal and pleuropulmonary fibrosis. Cardiovascular side effects mainly in the form of valvular fibrosis have been less recognized. We report 2 cases of methysergide-related mitral valve fibrosis.

Infective aortitis associated with the nonpatent remnant of a ductus arteriosus.

Infective aortitis is a rare condition, which occurs most commonly in association with some form of structural abnormality of the heart or vessel wall. We describe the successful excision of an infected, nonpatent remnant of the ductus arteriosus.