The effects of photoperiod on androgen-induced reproductive behavior in male ring doves, Streptopelia risoria

The effect of photoperiod on reproductive behavior in male ring doves (Streptopelia risoria) was studied in androgen-injected castrates maintained under long (16L:8D) or short (86:16D) photoperiods. Behavioral recordings were made over a 2-week period during which each male was paired with a female for 6.5 hr/day. There was some indication that males held on long days display higher levels of courtship activity during the initial period following pairing, but the evidence was not conclusive. Day length had no effect upon copulatory behavior. Long-day males exhibited consistently higher levels of nest building than short-day males, indicating that photoperiod affects building through some mechanism other than changes in endogenous androgen levels.     

Oviposition of fertile eggs and postponement of subsequent egg laying in ring doves (Streptopelia risoria).

Within the 45 days after an oviposition, fewer female doves which had laid fertile eggs laid a subsequent clutch than did females which had laid infertile eggs. During incubation the fertile eggs were replaced by infertile ones; therefore, this difference was not a result of raising squabs.     

Changes in aromatase activity in the brain of the male ring dove (Streptopelia risoria) during the breeding cycle

Aromatase activity was measured in striatal and hypothalamic regions of the brain of the male ring dove throughout its breeding cycle. The enzyme activity in the anterior hypothalamus and hyperstriatum was significantly reduced in broody birds. A reduction in plasma LH and the number of spermatogonia per tubule cross-section were also observed at this time. The results support the view that testosterone is involved in the control of aromatase activity in the anterior hypothalamus and hyperstriatum. The enzyme activity in the posterior hypothalamus, paleostriatum and archistriatum showed no changes throughout the breeding cycle, indicating that other factors in addition to testosterone are involved in controlling the enzyme in these tissues.     

Hypothalamic monoamine turnover in ring doves (streptopelia risoria), courting,incubating and brooding young

1. The turnovers of hypothalamic 5-hydroxytryptamine (5HT), dopamine (DA) and noradrenaline (NE) were measured in male and female ring doves (Streptopelia risoria) at three stages of the breeding cycle: courtship, 3 days after pairing; early incubation, 1–2 days after egg laying; and brooding, 1–3 days after the squabs had hatched.2. In both sexes plasma LH decreased progressively from courtship through incubation to brooding young. Crop sacs were fully developed in doves brooding young but not at other stages of the reproductive cycle, indicating increased concentrations of plasma prolactin.3. The turnovers of 5HT and DA in both sexes were significantly higher (P<0.001) in doves brooding young than in birds incubating eggs or nest building. The turnover of DA was higher in females than in males at the onset of incubation. The turnover of NE was lower (P > 0.01) in females at the onset of incubation than during courtship or brooding.4. Increased turnover of hypothalamic DA may be more closely related to brooding behaviour than to changes in prolactin or LH secretion.5. Increased hypothalamic 5HT turnover in brooding doves appears to be more directly related to crop sac development, and by inference increased prolactin secretion, than to depressed plasma LH concentrations.     

Role of vocalizations in the reproductive cycle of ring doves (Streptopelia risoria): effects of hypoglossal nerve section on the reproductive behavior and physiology of the female

The role of vocalizations in the reproductive cycle of female ring doves was investigated. Two-stage bilateral hypoglossal nerve section (HNS) was performed on adult females to alter their cooing and they were observed for courtship behavior with the same stimulus males used in preoperation behavioral tests. The HNS females showed a reduction in both the vocalization and wing flipping components of nest-coos but no changes in other female courtship behaviors. In addition, the HNS females failed to show the typical male courtship-induced follicular growth observed in sham-operated females. The behavior of stimulus males did not differ between groups and therefore could not account for the failure of follicular growth in the HNS females. These data suggest that the female's performance of nest-coos, or factors associated with it, may stimulate her own follicular growth.     

Melatonin, lipid peroxidation, and age in heterophils from the ring dove (Streptopelia risoria)

Numerous recent studies have shown the ability of physiological as well as all pharmacological concentrations of melatonin to prevent oxidative stress. We have found that incubating avian heterophils from young birds with a pharmacological concentration of 100 μM (23 × 10⁶ pg/ml) melatonin reduced superoxide anion levels by modulating the activity of superoxide dismutase while also enhancing phagocytosis. There was also a decline in lipid peroxidation levels with both physiological and pharmacological concentrations of this indolamine.

In the present work, we evaluated malonaldehyde (MDA) levels as an indicator of lipid peroxidation (both basal and antigen-induced) in young and old animals (ring doves) at different times of day (16:00 and 00:00) and with two incubation times (15 and 60 min). The lipid peroxidation was also measured in heterophils from old animals, incubated with the physiological concentrations of melatonin measured in young animals (50 and 300 pg/ml, diurnal and nocturnal, respectively). The results, expressed as nmol MDA/mg protein, show that MDA levels were higher in heterophils of old animals than in the young birds in all the experimental groups studied at both 16:00 and 00:00 (00:00 is the time at which the lowest peroxidation levels were obtained). Incubation with melatonin was found to reduce MDA levels, with the maximum reduction being after the 60 min incubation time and the nocturnal melatonin concentration. At both concentrations (diurnal and nocturnal), melatonin also counteracted the enhancement of MDA levels caused by latex beads, with the effect being greater at the longer incubation time. In conclusion, the results are further evidence of the antioxidant effect of melatonin even at physiological concentrations, and suggest its utility as a therapeutic agent in some pathological processes associated with age.     

Changes in the immune response of the ring dove (Streptopelia risoria) during incubation

Changes in immune parameters following antigen administration were evaluated in non-breeding and incubating, male and female ring doves. The time course in the changes in immune parameters in response to antigen agrees closely with earlier studies on the domestic fowl. Incubating doves possessed phagocytes with increased activity, although there was no increase in cell number. These results suggest that in the incubating bird, with high levels of plasma prolactin, there is an antigen-independent increase in immune cell activity but no antigen-dependent action on cell number. The biological significance of the changes in the immune system during incubation awaits further study.     

Effect of exogenous melatonin on viability, ingestion capacity, and free-radical scavenging in heterophils from young and old ringdoves (Streptopelia risoria)

The decrease of melatonin production with aging contributes to the decline in immune function as organisms age. Treatment with the exogenously administered indoleamine restores the reduced immunological functions. Therefore, we investigated the effect of melatonin on viability, phagocyte ingestion capacity, and free radical generation levels of heterophils from young and old ringdove (Streptopelia risoria) aged 3–4 and 11–13 years, respectively. Animals received a single oral dose of melatonin 1 h before lights off for three consecutive days. Experiments were performed at the acrophases and nadirs of melatonin. Melatonin treatment significantly increased serum melatonin levels at the acrophases, but not at the nadirs of the two age groups. In both young and old animals there was increased heterophil viability at acrophases with respect to nadirs, and also increased cell resistance to oxidative stress in the old animals after the melatonin treatment. At acrophases, the index, percentage and efficiency of phagocytosis all increased significantly, and superoxide anion levels decreased significantly with respect to the nadir values of vehicle and melatonin-treated animals, the effect being greater in young than in old ringdoves. At the nadirs, no change was observed in any parameter analyzed. In both young and old animals, phagocytosis and melatonin were positively correlated, while superoxide anion levels and melatonin were negatively correlated. In conclusion, exogenous melatonin enhanced heterophil viability in old animals as well as increasing phagocytosis and free-radical scavenging in both age groups during the nocturnal period, accompanied by an increase in the levels of the indoleamine.     

Melatonin and tryptophan as therapeutic agents against the impairment of the sleep-wake cycle and immunosenescence due to aging in Streptopelia risoria

All organisms present circadian rhythm in most of their physiological functions, and among them there stand out sleep, motor activity, immune function, the secretion of melatonin, and the production and release of numerous neurotransmitters, in particular of serotonin because of its relationship with the aforementioned factors. Aging changes these rhythms, altering sleep quality and contributing to immunosenescence. Treatment with exogenously administered melatonin or tryptophan may restore these impaired functions due to aging. In our animal model (Streptopelia risoria), both the hormone and the amino acid acted on the activity-rest rhythms, modulating the circulating levels of melatonin and serotonin, and increased the cell viability and resistance to induced oxidative stress of blood heterophils, at the same time as enhancing the phagocytic function and neutralizing the superoxide anions deriving from this immune function. Also, in the old individuals, the treatments with melatonin and tryptophan at the concentrations and times of administration considered suitable improved nocturnal rest besides reverting the immunosuppressory and oxidative effects accompanying phagocytosis at these advanced ages.     

The influence of flock size and geometry on the scanning behaviour of spotted turtle doves,Streptopelia chinensis

Abstract The negative correlation between the time individuals spend scanning the environment for predators and group size is usually explained by the benefit of corporate vigilance. However, this negative correlation may be explained additionally in terms of the ‘dilution effect’ and ‘selfish herd geometry’. Our experimental investigation of the scanning behaviour of free-living spotted turtle doves foraging at different shaped feeders revealed that flock geometry influenced individual scanning rates. The time spent scanning declined with group size less rapidly among birds foraging in linear flocks than among those foraging in more two-dimensional flocks. These results were not confounded by aggressive behaviour, and indicate that the benefits of foraging in groups include the so-called selfish herd geometry.     

Temporal changes in the migration phenology of turtle doves Streptopelia turtur in Britain, based on sightings from coastal bird observatories

Using daily counts of birds seen at six coastal bird observatories in southern and eastern England, we explored the migration phenology of turtle doves during the period 1963 to 2000. Annual totals increased threefold up to the late 1970s then decreased again, in accordance with the BTO Common Birds Census (CBC) index of abundance. Median annual spring arrival and autumn departure dates of turtle doves were not related to abundance (CBC index) or mean temperature in spring or summer respectively. Although median annual spring arrival date has not altered over the 38-year period, median annual autumn departure date has become earlier by 8 days. This has resulted in a shortening of the breeding season by 12 days, which ties in with a reduction in average number of nesting attempts per pair observed by a recent autecological study. It is possible that breeding turtle doves are now out of phase with peaks in food availability. This may have resulted in reduced breeding performance and earlier termination of the breeding season, and may have partly contributed to the decline of the species.     

Biochemistry and physiology of monoamine oxidase (MAO) activity in the ring dove (Streptopelia risoria). II. Distribution of MAO in different tissues

Monoamine oxidase (MAO) activity was measured fluorometrically in liver, kidney, intestine and brain of adult male and female ring doves. Liver MAO was inhibited in a concentration-related fashion by clorgyline and harmaline (MAO type A inhibitors) where a plateau in the inhibition curve occurred with about 15% activity remaining, and also by the type B inhibitor deprenyl, which produced a plateau when about 85% activity remained. Kidney, intestine and brain MAO were inhibited in a biphasic manner by harmaline. Results with inhibitors suggest that 85% of liver MAO, 86% of kidney MAO, 88% of intestine and 75% of brain MAO is type A. Using 10(-6) M harmaline to differentiate between MAO-A and MAO-B type activities, the apparent maximal velocities (Vmax) and Michaelis constants (Km) were determined in different tissues. Most activity occurred in the intestine, with proportionally lesser amounts of kidney, liver and brain. The majority of MAO present was in the A form. Except for kidney, Km of MAO-B was higher than that of MAO-A. Both MAO-A and -B activities were higher in the intestines of male birds, although sex differences in content and type of MAO activity were not observed in other tissues of the ring dove.     

Biochemistry and physiology of monoamine oxidase (MAO) activity in the ring dove (Streptopelia risoria). I. Characteristics of MAO activity in vitro

Monoamine oxidase (MAO) activity was measured in ring dove (Streptopelia risoria) tissues using a fluorometric assay with kynuramine as substrate. Harmaline inhibited MAO activity in a time-dependent manner, and preincubation of enzyme with the drug did not affect its activity. Pargyline produced a slow-onsetting inhibition of activity which was enhanced by preincubation of enzyme and inhibitor. Harmaline displayed reversible non-competitive inhibition of MAO activity. Oxygen is also a substrate for dove MAO, and the reaction apparently involves "ping-pong", double-displacement kinetics. Dove MAO activity is temperature-dependent, with an activation energy of 13.1 kcal/mole.     

Comparative study of the activity/rest rhythms in young and old ringdove (Streptopelia risoria): correlation with serum levels of melatonin and serotonin

Aging is characterized by changes in the circadian rhythms of melatonin, serotonin, and sleep/wakefulness, alterations that affect sleep quality. The authors studied the circadian rhythms of serotonin and melatonin in young and old ringdoves (Streptopelia risoria) (2-3 and 10-12 yrs old, respectively), animals that are characterized by being monophasic and active by day, like humans. The aim was to correlate the indole rhythms with the animals' activity/rest periods. The animals were kept under a 12:12 h light/dark cycle, fed ad libitum, and housed in separate cages equipped for activity recording. Activity pulses were recorded with one actometer per animal (two perpendicular infrared transmitters) and were logged every 15 min by a computer program (DAS 16) throughout the experiment. Melatonin was measured by radioimmunoassay and serotonin by ELISA at intervals of 3 h (from 09:00 to 18:00 h) and 1 h (from 21:00 to 06:00 h), respectively. The results showed a reduction in nocturnal vs. diurnal activity of 89% and 61% in the young and old animals, respectively, with 100% considered to be the diurnal activity of each group. The amplitude of a cosine function fit to the melatonin concentrations of the old animals was half that of the young birds. The acrophase and nadir were at 02:00 and 14:00 h in the young and 01:00 and 13:00 h in the old animals, respectively. The amplitude of the corresponding cosine function fit to the serotonin concentrations in the old birds was one-third that of the young animals. The acrophase and nadir were at 15:00 and 03:00 h in the young and 16:00 and 04:00 h in the old animals, respectively. For both melatonin and serotonin, the concentrations in the young animals were significantly higher than in the old at most of the measurement times. There was a clear negative correlation between the circadian rhythms of activity and the serum melatonin levels in both young and old animals. The equivalent correlation for serotonin was positive, and stronger in the case of the young animals. The results suggest a possible relationship between the observed decline in the amplitude of the old animals' melatonin and serotonin rhythms and the lower percentage reduction in their nocturnal relative to diurnal activity pulses compared to the young animals. In conclusion, the circadian rhythms of melatonin and serotonin undergo alterations with age that could be involved in the changes in age-associated sleep.     

Diversity of feeding habitats and diet composition in the turtle doves Streptopelia turtur to buffer loss and modification of natural habitats during breeding season

The approach of the birds to use physical and alimentary resources in degraded and modified natural habitats is an important aspect of their adaptation. This study was undertaken during 2016-2017 at forty habitats in the Moulouya plain, Morocco to examine behavioral diet, habitat use and foraging ecology of turtle dove, Streptopelia turtur. We monitored turtle doves in four major plots namely cereal plots, lucerne farms, apple orchards, and stations in the Ansgmir River covering 40 habitats. Digestive tract contents were also identified and evaluated for 68 Turtle Doves shot by hunters during two consecutive years. The results showed that the turtle doves use a variability of feeding habitats. The cereal cultivation seemed to be more preferable habitat for feeding especially in the month of May, the first breeding phase of the year. But, during the months of August and July, the riverbanks were the preferred habitat for turtle doves. The diet of this species is polyphagous and diverse with a granivorous tendency. Diet analysis showed that soft wheat and barley seeds constituted 44.53% and 38.74% respectively followed by barley seeds with 38.74% and sand stones (9.16%) of the seeds eaten by Turtle Doves. However, moderate proportion of elements (7.32%) remained undefined. All these aspects, including the variability of feeding habitats and the wide diet seem to be an adaptive strategy followed by turtle dove to counter the degradation and the modification of its natural feeding habitats.     

On the transition from the meiotic to mitotic cell cycle during early mouse development

Here, we outline the mechanisms involved in the regulation of cell divisions during oocyte maturation and early cleavages of the mouse embryo. Our interest is focused on the regulation of meiotic M-phases and the first embryonic mitoses that are differently tuned and are characterized by specifically modified mechanisms, some of which have been recently identified. The transitions between the M-phases during this period of development, as well as associated changes in their regulation, are of key importance for both the meiotic maturation of oocytes and the further development of the mammalian embryo. The mouse is an excellent model for studies of the cell cycle during oogenesis and early development. Nevertheless, a number of molecular mechanisms described here were discovered or confirmed during the study of other species and apply also to other mammals including humans.     

Effects of stimuli emanating from the nest on the reproductive cycle in the ring dove. II: building during the pre-laying period.

The nest is a major focal point of the reproductive cycle in the ring dove (Streptopelia risoria). This study shows that the state of the nest is an important determinant of the type of nest-building exhibited. For example, birds faced with an empty nest bowl every day removed more material from dispensers and built more actively than did those allowed to construct nests normally. Conversely, those given completed nests were not very active, but were more efficient in using the little they removed from the dispensers and showed a reversal of sex roles in building. The relations between nest-building and egg-laying, and between male and the female are discussed.     

T-antigen interactions with chromatin and p53 during the cell cycle in extracts from xenopus eggs.

The role of SV40 large tumor T-antigen in replication of viral DNA is well established, but it is still unclear how T-antigen triggers cellular replication and cell transformation in non-permissive cells. Here, we used Xenopus egg extracts which reproduce most nuclear events linked to the cell cycle in vitro to analyze its interaction with genomic chromatin during the cell cycle. We show that T-antigen associates with chromatin before the nuclear membrane formation, and further demonstrate that the nuclear membrane is not necessary for its import into the nucleus. We show that the interaction of T-antigen with the endogenous chromatin does not occur at replication foci nor at RPA pre-replication centers. Immunoprecipitations as well as sucrose gradient experiments, indicate that the endogenous pool of p53 interacts with T-antigen. In addition, a transient association of both proteins with the nuclear matrix is observed during the ongoing DNA synthesis. These data are discussed in view of the T-antigen and p53 activity during the cell cycle.     

Comparative study of the heterophil phagocytic function in young and old ring doves (<Emphasis Type="Italic">Streptopelia risoria</Emphasis>) and its relationship with melatonin levels

A functional connection between the pineal gland (via the hormone melatonin) and the immune system has been suggested. In our previous results in the ring dove, we observed diurnal oscillations in the levels of this neurohormone in young animals and a decline in its plasma levels with advancing age (which is accompanied by the absence of diurnal rhythm). We also noted enhanced phagocytic activity of heterophils from old animals after in vitro incubation with both physiological and pharmacological doses of melatonin. Here, we evaluate the functional capacity of ring dove (Streptopelia risoria) heterophils in young (2 years of age) and old (8 years and more) animals at different times of day (0:00, 10:00 and 16:00, the times when the maximum, minimum, and mean values, respectively, of melatonin levels are observed in young animals). The phagocytic capacities for the ingestion of latex beads and Candida albicans were evaluated, as well as the oxidative metabolism which accompanies phagocytosis. At all three times of day studied, the heterophil phagocytic function with both latex and C. albicans was significantly greater in the young than in the old animals, and in the young animal cells it was significantly higher at 0:00. In addition, in the presence of latex beads, there was a significant decline at 10:00 and 0:00 of superoxide anion levels in the young animals relative to the old. In the young animals, there was a decline at 0:00 in comparison with both 10:00 and 16:00, and in the old animals there was a decline at both 0:00 and 16:00 compared with 10:00. These results could be due, at least in part, to the absence of a diurnal rhythm of melatonin in old animals, and to an enhancing effect of that hormone on young animals heterophil phagocytic function, which would also neutralize the oxidative stress deriving from this immune function.Abbreviations PBS phosphate-buffered saline - MIF macrophage migration-inhibition factor - PI phagocytosis index - PP phagocytosis percentage - PE phagocytosis efficiencyCommunicated by G. Heldmaier