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At least 145 records · Page 8Linked to original sources
PubMed1993

The thyroid and photoperiodic control of seasonal reproduction in American tree sparrows (Spizella arborea).

To explore the role of the thyroid gland in the control of seasonal reproduction in obligately photoperiodic American tree sparrows (Spizella arborea), the effects of (1) thyroxine administered in drinking water to thyroid-intact photosensitive or photorefractory birds, and (2) radiothyroidectomy before and after photostimulation and during photorefractoriness were examined. Chronic administration of pharmacological doses of thyroxine induced testicular growth and usually regression in initially photosensitive birds held on short or intermediate daylengths. Some thyroxine-treated birds with regressed testes were absolutely photorefractory, but most remained photosensitive. Exogenous thyroxine never induced testicular growth in photorefractory birds moved to short days, though it often impeded, and sometimes even blocked, the recovery of photosensitivity. Although circumstantial, these effects of exogenous thyroxine are consistent with an hypothesis that assigns to thyroid hormones two roles--one stimulatory and the other inhibitory--in the control of seasonal reproduction. Radiothyroidectomy before photostimulation inhibited (but did not prevent) photoinduced testicular growth, blocked spontaneous testicular regression, suppressed molt, and prevented photorefractoriness. Moreover, as demonstrated by testicular growth after thyroxine replacement therapy, radiothyroidectomy during photorefractoriness later restored photosensitivity despite continued photostimulation. Thus, euthyroidism is an essential condition for maximizing (but not for initiating) photoinduced testicular growth and for triggering and maintaining photorefractoriness in photostimulated tree sparrows. However, when performed early during photostimulation, radiothyroidectomy neither immediately induced nor later blocked spontaneous testicular regression. Thus, endogenous thyroid hormones and long days may interact during a critical period to program a sequence of physiological events that plays out as photorefractoriness in chronically photostimulated birds. Such an organizational event cannot be permanent, for seasonal reproduction is episodic and its control mechanism necessarily cyclic. Because thyroidectomy simulated the well-known restorative effect of short days (and exogenous thyroxine impeded it), short days may dissipate photorefractoriness by creating a milieu wherein thyroid hormones are deficient or inactive.

Animals↗
PubMed1988

Contributions of the kidneys and intestines to water conservation, and plasma levels of antidiuretic hormone, during dehydration in house sparrows (Passer domesticus).

The contributions of the kidneys, the small intestine and the lower intestine (rectum plus cloaca) to water conservation during dehydration in unanaesthetized, unrestrained house sparrows (Passer domesticus) were assessed. Thirty hours of acute dehydration resulted in a 12% loss in body mass and a significant increase in plasma osmolality. Glomerular filtration rate declined by 55%, from 7.7 to 3.5 ml/h, and urine flow rate delined by more than 80%, from 0.2 to 0.03 ml/h. These changes are likely attributable to a large increase in plasma levels of arginine vasotocin during dehydration, from less than 26 pg/ml in hydrated birds to greater than 200 pg/ml after 30 h dehydration. Flow of water from the ileum to the lower intestine was reduced during dehydration, primarily because of a reduced flow of dry matter (with no significant reduction in water content). The rate of water loss in the excreta declined from 0.2 ml/h in hydrated birds to 0.04 ml/h in dehydrated birds. The rate of water reabsorption in the lower intestine (equal to the rate of water loss in the excreta minus the combined rates of inflow into the lower intestine from the urine and the ileal contents) slightly exceeded the rate of water flow from the ileum in both hydrated and dehydrated birds. We suggest that much of the water reabsorbed in the lower intestine of hydrated birds derives from the urine, but that primarily water from ileal contents is reabsorbed in dehydrated birds. That is, urine undergoes significant post-renal modification in hydrated but not dehydrated house sparrows.

Animals↗
PubMed1975

Natural and experimental infections of Japanese tree sparrows with Japanese encephalitis virus.

20 to 37 per cent of wild Japanese tree sparrows had neutralizing antibodies to Japanese encephalitis virus (JEV). Sparrows free of antibodies were inoculated with 10,000 plaque-forming units of JEV. None of the birds became clinically ill. Virus could be detected in blood plasma during the first 3 days after inoculation but not thereafter. Neutralizing antibodies started to appear at 4 days after inoculation and the response was of variable duration, in some cases extending up to 200 days after inoculation.

Animals↗
PubMed1999

Hippocampal lesions do not impair the geomagnetic orientation of migratory savannah sparrows.

The avian hippocampal formation is known to participate in naturally occurring spatial behavior such as homing in pigeons and cache recovery in food storing passerines, but its participation in the often spectacular migrations of birds remains uncertain. As a first investigation into the possible role of hippocampal formation in migration, the effect of hippocampal formation lesions on the geomagnetic migratory orientation of Savannah sparrows was examined. When tested indoors, hippocampal formation-lesioned sparrows were able to orient in an appropriate migratory direction indicating no necessary role for hippocampal formation in geomagnetic migratory orientation. However, hippocampal formation-lesioned birds displayed significantly less migratory (nocturnal) activity, a result that inspires further study.

Animals↗
PubMed2002

Simple roost nests confer large energetic savings for sparrow-weavers.

White-browed sparrow-weavers (Plocepasser mahali, body mass 40 g) are group-living passerines adapted to the semi-arid environment of north-eastern and south-western Africa. During winter, the nocturnal ambient temperature of these regions often falls below 0 degrees C. imposing conditions demanding an increase in thermoregulatory heat production. Individuals roost throughout the year in inverted U-shaped roost nests. We investigated the energetic advantages of roosting by measuring nest and ambient temperatures in the field, as well as the resting metabolic rate (RMR) of the birds. The sparrow-weavers exhibited a wide thermoneutral zone (13 degrees C - 32 degrees C). Although RMR at thermoneutrality (40.2 J g.h(-1)) conforms with those of other passerines. the value at 0 degrees C (74.8 J g.h(-1)) is significantly lower than expected. The slope of the line below the lower critical temperature is unexpectedly steep, however, and appears to cause the physiological requirement for nest roosting due to a high cost of thermoregulation at low temperatures, perhaps due to shivering or non-shivering thermogenesis. The nest temperature at 0 degrees C ambient is 5 degrees C. resulting in a saving of some 7% in the energy spent during winter nights when food resources are in short supply compared with the rest of the year.

Acclimatization↗
PubMed2003

Intestinal passive absorption of water-soluble compounds by sparrows: effect of molecular size and luminal nutrients.

We tested predictions that: (1) absorption of water-soluble probes decreases with increasing molecular size, consistent with movement through effective pores in epithelia, and (2) absorption of probes is enhanced when measured in the presence of luminal nutrients, as predicted for paracellular solvent drag. Probes (L-arabinose, L-rhamnose, perseitol, lactulose; MW 150.1-342.3 Da) were gavaged in nonanesthetized House sparrows ( Passer domesticus), or injected into the pectoralis, and serially measured in plasma. Bioavailability was calculated as F=AUC by gavage/AUC by injection, where AUC is the area under the curve of plasma probe concentration vs. time. Consistent with predictions, F declined with probe size by 75% from the smallest to the largest probe, and absorption of probes increased by 40% in the presence of luminal glucose or food compared to a mannitol control. Absorption of water-soluble probes by sparrows is much higher than in humans, which is much higher than in rats. These differences seem mainly attributable to differences in paracellular solvent flux and less to differences in effective paracellular pore size.

Absorption↗
PubMed2003

L-glucose absorption in house sparrows (Passer domesticus) is nonmediated.

We previously demonstrated in intact house sparrows substantial absorption in vivo of L-glucose, the stereoisomer of D-glucose that is assumed not to interact with the intestine's D-glucose transporter. Results of some studies challenge this assumption for other species. Therefore, we tested it in vitro and in vivo, based on the principle that if absorption of a compound (L-glucose) is mediated, then absorption of its tracer will be competitively inhibited by high concentrations of either the compound itself or other compounds (e.g., D-glucose) whose absorption is mediated by the same mechanism. An alternative hypothesis that L-glucose absorption is primarily paracellular predicts that its absorption in vivo will be increased (not decreased) in the presence of D-glucose, because the permeability of this pathway is supposedly enhanced when Na(+)-coupled glucose absorption occurs. First, using intact tissue in vitro, we found that uptake of tracer-radiolabeled L-glucose was not significantly inhibited by high concentrations (100 mM) of either L-glucose or 3-O-methyl-D-glucose, a non-metabolizable but actively transported D-glucose analogue. Second, using intact house sparrows, we found that fractional absorption of the L-glucose tracer was significantly increased, not reduced, when gavaged along with 200 mM 3-O-methyl-D-glucose. This result was confirmed in another experiment where L-glucose fractional absorption was significantly higher in the presence vs. absence of food in the gut. The greater absorption was apparently not due simply to longer retention time of digesta, because no significant difference was found among retention times. Our results are consistent with the idea that L-glucose is absorbed in a non-mediated fashion, largely via the paracellular pathway in vivo.

3-O-Methylglucose↗
PubMed2001

Daily and photoperiod variations of basal and stress-induced corticosterone concentrations in house sparrows (Passer domesticus).

Corticosterone concentrations were measured in captive house sparrows (Passer domesticus) and found to vary both daily and with different photoperiods. Basal corticosterone was highest during the dark hours of the daily cycle and lowest during the light hours. This trend remained constant when the birds were held on short-day and long-day light cycles, and while the birds were undergoing a prebasic molt. At all times, corticosterone concentrations significantly increased in response to the stress of handling and restraint. Stress-induced corticosterone concentrations, however, only reflected a daily rhythm when the birds were held on short-days. Furthermore, even though mean basal corticosterone concentrations were equivalent over the short-day, long-day, and molt, total corticosterone output in response to stress was lower in molting birds, especially at night. Therefore, these data indicate that captive house sparrows modulate corticosterone in daily cycles that change in response to photoperiod.

Animals↗
PubMed2003

Schizogonic stages of Haemoproteus from Wenyon's Baghdad sparrows are also found in Passer domesticus biblicus in Israel.

Schizont bodies reminiscent of those described by Wenyon from Baghdad sparrows were found in the liver and lungs of an Israeli house sparrow ( Passer domesticus biblicusHartert 1904) infected with Haemoproteus passeris Kruse, 1890. All observed schizonts were composed of packed assemblages of walled compartments, each holding a differentiating schizogonic body. The schizogonic bodies in the various compartments demonstrated sequential stages in the differentiation process from a compact multinucleate cytoplasmic mass to massive formation of multiple merozoites. Young non-differentiated schizont assemblages reached 0.2 x 0.25 mm in size and the fully differentiated ones, containing merozoites, were double or triple that. Among species of Haemopterus, division to compartmented and single-plasmodium schizonts could not be associated with any recognized generic or infrageneric division. Moreover, in some species of Haemoproteus, both types of schizogony co-existed.

Animals↗
PubMed1994

Comparison of circadian oscillation of melatonin release in pineal cells of house sparrow, pigeon and Japanese quail, using cell perfusion systems.

We compared the circadian oscillation of melatonin release from cultured pineal cells in Japanese quail, pigeon and house sparrow, to determine whether the pineal gland of these species retains the circadian oscillator function in vitro. After dissociated pineal cells have been cultured for 4 days under 12 h: 12 h light-dark (LD) cycle, they were perfused at a flow rate of 0.25 ml/h for 6-7 days under LD or constant darkness (DD). Melatonin release increased during the dark period and low during the light period in all pineal cell cultures. Under DD conditions, the circadian rhythm of melatonin release persisted for up to 3-4 cycles in pigeon and house sparrow pineal cells, but the amplitude of the rhythm decreased gradually. However, in Japanese quail pineal cell culture the circadian oscillation of melatonin release was weak or abolished under DD conditions. These results strengthen the argument that the avian pineal gland's role in circadian organization differs between species. The direct demonstration of species-specific differences in the mechanism of the circadian oscillation of melatonin release from pineal cells should provide a useful model for the analysis of the pineal's circadian system at the cellular level.

Animals↗
PubMed1984

Environmental and endocrine control of reproduction in the song sparrow, Melospiza melodia. II. Agonistic interactions as environmental information stimulating secretion of testosterone.

A group of eight free-living adult male song sparrows, selected at random, were given subcutaneous implants of testosterone (T) in Silastic tubing. In a separate area, 1 km distant, a second group of eight free-living males were given empty implants as controls. All implants were administered in late March and early April and in the experimental group maintained plasma levels of T at the springtime peak. To test whether prolonged high levels of T maintained aggressive territorial behavior at the springtime maximum, each bird was "challenged" by stimulating a territorial intrusion achieved by playing tape-recorded conspecific songs on their territories. Sparrows with T implants were more aggressive than controls in accordance with other studies showing that T increases frequency and intensity of aggression. Blood samples were collected from all implanted birds, and their untreated neighbors, at intervals throughout the breeding season, and plasma levels of luteinizing hormone (LH) and T were measured. Circulating T levels in males with territories next to control males show declines in T levels in April, increase again in May, and are low during the parental phase in June and July. However, the decline of T in males with territories next to males implanted with T did not occur, and levels remained significantly higher than those of males in the control area. Plasma T levels did decrease in May, however, but rose again in June, and in July were significantly higher than controls. Curiously, plasma levels of luteinizing hormone did not differ between controls and experimentals.

Aggression↗
PubMed1985

Absence of gonadal-hormone feedback on luteinizing hormone in both photorefractory and photosensitive white-crowned sparrows (Zonotrichia leucophrys gambelii).

Elimination of gonadal-hormone feedback by castration from photorefractory male White-crowned sparrows in mid-July or early October, and from photosensitive males in early December, had no significant effect on plasma levels of LH. Photorefractory birds held on natural daylengths regained photosensitivity in the absence of gonadal-hormone feedback with no increase in plasma levels of LH. Implants of testosterone propionate into castrated males during November and December had no effect on plasma LH levels. These results indicate that gonadal-hormone feedback is not responsible for the very low levels of LH secretion in either the photorefractory or the photosensitive male White-crowned sparrow.

Animals↗
PubMed1988

Identity of gonadotropin-releasing hormone in passerine birds: comparison of GnRH in song sparrow (Melospiza melodia) and starling (Sturnus vulgaris) with five vertebrate GnRHs.

Gonadotropin-releasing hormone (GnRH) was detected in the brains of passerine birds, a recently evolved and diverse avian group. The molecular forms of GnRH in two species of birds under breeding conditions were deduced using methods of HPLC and immunology. The brain extracts of song sparrows (Melospiza melodia) contained a form of GnRH identified as chicken I GnRH-like peptide by its HPLC elution pattern and cross-reactivity with four antisera. In contrast, starling (Sturnus vulgaris) brain extracts showed molecular heterogeneity of GnRH forms; equal amounts of chicken I and chicken II GnRH-like peptides were present. Neither bird contained GnRH that could be identified as mammalian, salmon, or lamprey GnRH. Chicken II GnRH-like peptide may not have evolved after the separation of the song sparrow and starling as both peptides are found in chicken, a more primitive bird. The possibility remains that different stages of the life cycle are associated with the expression of these GnRH-like peptides or their ratio. Only determination of the primary structure will establish whether our chromatographic and immunological evidence is correct that chicken I and II GnRH are present in passerine birds and have been conserved in representatives throughout the reptiles and birds. Starlings can be added now to the growing list of submammalian species that express multiple forms of GnRH in their brains.

Animals↗
PubMed1992

Photorefractory Harris' sparrows (Zonotrichia querula) exposed to a winter-like daylength gradually regain photosensitivity after a lag.

The time course of regaining photosensitivity was monitored in intact and in castrated Harris' sparrows (Zonotrichia querula) held on short days. Measured endpoints, assumed to be equivalent indicators of the photosensitive state, were photoinduced testicular growth in intact males and a photoinduced elevation in plasma LH (luteinizing hormone) concentration in castrated males. Intact males were initially photorefractory when they were moved from long days to short days, and they remained so for at least 3 weeks thereafter. Photosensitivity was partially restored between Weeks 3 and 5 on short days and then gradually increased to a maximum by Week 13. No further change was detected through Week 25 on short days, when the experiment ended. Castrated males, also photorefractory when moved from long days to short days, regained photosensitivity as early as Week 7 on short days, but not uniformly until Week 16. As reflected by linear regression analysis, recovery of photosensitivity was a gradual process through Week 22 on short days, when the experiment ended. Discrepancies between intact and castrated males raise the possibility that the measured endpoints are not equivalent indicators of the photosensitive state. In accordance with an earlier report (Wilson, 1990), recovery of photosensitivity in castrated Harris' sparrows held on short days was not signaled by a spontaneous increase in plasma LH concentration. Indeed, plasma LH concentrations of castrated males remained suppressed even after photosensitivity had been fully restored in intact males.

Animals↗
PubMed1983

Evidence for androgen independence of male mounting behavior in white-crowned sparrows (Zonotrichia leucophrys gambelii).

Previous experiments have shown that expression of mounting behavior in sexually inexperienced, adult male white-crowned sparrows does not require elevated plasma levels of androgen; adult males maintained on nonstimulatory short days mount sexually receptive females. The experiments reported here demonstrate that (1) sexually inexperienced, prepubertal males maintained on nonstimulatory short days show very low mounting rates in response to female sexual displays; (2) these males exhibit high mounting rates when exposed to stimulatory long days but androgen treatment on short days is ineffective in stimulating high mounting rates; and (3) prepubertal castration has no effect on the expression of mounting behavior by photostimulated adult males. Thus, there is no evidence that mounting behavior of adult male white-crowned sparrows depends on androgen.

Animals↗
PubMed1986

Effects of corticosterone on territorial behavior of free-living male song sparrows Melospiza melodia.

A group of 10 territorial male song sparrows, Melospiza melodia, were given subcutaneous implants of corticosterone in Silastic tubing. A second group of 10 territorial males were given empty implants as controls. After 18-24 hr all males were then subjected to a simulated territorial intrusion (STI) by placing a caged male song sparrow in the center of the subject's territory, and playing tape recorded songs through a speaker placed alongside. Significantly fewer males with corticosterone implants responded to STI than to controls, and the latency to respond was longer. Of the 3 experimental males that did respond to STI, all had a lower frequency of songs and did not approach the simulated intruder as closely as controls. Many males were captured 2-7 days after implantation and blood samples collected for measurement of circulating hormone levels. As expected, plasma levels of corticosterone were high in the group given corticosterone implants. However, plasma levels of luteinizing hormone (LH) were not affected by treatment with corticosterone, and although circulating levels of testosterone were depressed slightly compared with controls, they were within the normal range for territorial and breeding males. There were no differences in body mass despite greatly increased fat depots in males treated with corticosterone. These data suggest that high levels of corticosterone, similar to those measured during stressful episodes both in the laboratory and field, may suppress territorial behavior independently of the adenohypophysial-gonad axis. Since plasma levels of LH and testosterone are not depressed markedly, thus maintaining the gonads in a near functional state, renesting can begin as soon as environmental conditions ameliorate. Such mechanisms could potentially increase the probability of raising viable young after unpredictable, severe weather resulted in failure of the previous breeding attempt.

Animals↗
PubMed1986

Behavioral and endocrine correlates of multiple brooding in the semicolonial house sparrow Passer domesticus. I. Males.

Behavioral and endocrine changes associated with reproductive events were studied in free-living male house sparrows (Passer domesticus). Circulating levels of luteinizing hormone (LH), testosterone (T), and dihydrotestosterone (DHT) were maximal during egg-laying and declined during incubation and the first 2/3 of the nestling stage. As the young approached fledging, levels of LH and T rose to levels similar to those of the first egg-laying stage. This pattern was repeated three to five times during the prolonged breeding season of this species. Multivariate statistical analysis demonstrated that elevated levels of LH and androgens during egg-laying stages were associated with high rates of intrusion at nests by conspecifics, especially other adult males, and elevated levels of agonistic activity, nest defense, and mate-guarding behavior by breeding males. Feeding rates of males declined significantly as plasma levels of T began to rise. Concentrations of corticosterone (B) were high during each egg-laying and nestling stage and were correlated with high or rising levels of reproductive hormones. This suggests that reproductive activity, while energetically demanding, was not overly stressful to these birds. Body mass and fat depots were lowest during the final brood of the season. We suggest that the temporal pattern of circulating levels of T in male house sparrows is an adaptation which compromises between two conflicting selective pressures: a high level of male-male competition for limiting nesting sites in a semicolonial setting, and a strong demand for parental care associated with large broods of altricial young.

Androgens↗
PubMed1986

Behavioral and endocrine correlates of multiple brooding in the semicolonial house sparrow Passer domesticus. II. Females.

Behavioral and endocrine changes associated with reproductive events were studied in free-living female house sparrows (Passer domesticus). Circulating levels of luteinizing hormone (LH) and estradiol (E2) were maximal during egg-laying, declined during incubation, and began to rise during the nestling stage. This pattern was repeated three to five times during the prolonged breeding season of this species. Multivariate statistical analysis demonstrated that elevated levels of LH and E2 were associated with maximal sexual activity, high rates of intrusion at nests by conspecifics, and elevated rates of agonistic activity. Patterns of sexual activity varied during the season and perhaps reflected differing strategies for protecting paternity adopted by the male. Curiously, elevated levels of testosterone (T) and dihydrotestosterone (DHT) were not associated with high levels of intrusion or agonistic response, but rather were associated with incubation stages. As in males, concentrations of corticosterone (B) were high during each egg-laying and nestling stage and were associated with high or rising levels of reproductive hormones, suggesting that reproductive activity was not overly stressful to these birds. Body mass and fat depots declined during the season and may regulate termination of reproduction. It appears that access to abundant food resources found in association with human dwellings allows house sparrows to maintain reproductive activity longer than most other temperate-zone dwelling bird species.

Animals↗