Biomedical subjects

T Boswell

Publications and source records attributed to T Boswell.

26 records · Page 2Linked to original sources

PubMed1995

NPY increases food intake in white-crowned sparrows: effect in short and long photoperiods.

To determine if altered sensitivity to neuropeptide Y (NPY) underlies premigratory fattening, white-crowned sparrows held on short day length (9:15-h light-dark) received injections into the third ventricle (ivt) of saline or several doses of NPY. An inverted-U function occurred with food intake increasing 30 and 60 min after doses of 1.0 and 2.0 micrograms NPY. When photostimulated (20:4-h light-dark), birds increased daily caloric intake and gained weight rapidly. Birds maintained on long day lengths significantly increased food intake after 0.25 and 0.5 micrograms of NPY and did not respond to higher doses. The effective dose range for NPY to increase food intake moved to the left, suggesting an increase in sensitivity to the peptide on long day lengths. In summary, white-crowned sparrows consume more food when administered NPY ivt and have increased sensitivity when photostimulated and gaining weight. Hence NPY may be a natural stimulator of food intake in this species.

Animals↗

PubMed1995

Regulation of food intake by metabolic fuels in white-crowned sparrows.

Migratory birds rely on increased fat storage and fatty acid utilization to meet seasonal changes of energy expenditure and as a result increase food intake and fat stores before migration. To determine whether their feeding behavior is sensitive to carbohydrate and/or fatty acid utilization, white-crowned sparrows maintained on short daylength (9L15D) were injected intraperitoneally with 2-deoxy-D-glucose (2-DG) or 2,5-anhydro-D-mannitol (2,5-AM). Low doses of 2-DG (25 or 50 mg/kg) had no effect on food intake, and higher doses (100 or 300 mg/kg) significantly suppressed feeding after 1 and 2 h. No dose of 2-DG increased meal size. Similarly, low doses of 2,5-AM (25, 50, or 100 mg/kg) had no effect on food intake, and higher doses (300 and 600 mg/kg) significantly suppressed intake. These data suggest that decreased carbohydrate metabolism does not elicit feeding in this species. Importantly, these drugs, as well as insulin and glucagon, were demonstrated to increase plasma fatty acids as well as to decrease feeding. Injections of tributyrin (100, 300, 600, or 2,000 mg/kg i.p.) or glycerol (300, 450, and 600 mg/kg) also significantly suppressed 60-min and 120-min food intake dose dependently in these birds, and equimolar glucose (1,200 mg/kg) had no effect. We conclude that feeding by the white-crowned sparrow is unresponsive to manipulations of carbohydrate metabolism and is decreased after manipulations that increase plasma lipids.

Animals↗

PubMed1995

Migratory fat deposition in European quail: a role for prolactin?

The present study addresses the role of prolactin as a regulator of migratory fattening in European quail (Coturnix coturnix). Plasma prolactin levels in captive birds undergoing migratory fattening in an outdoor aviary and in the laboratory were measured by radioimmunoassay with an antibody raised against recombinant-derived chicken prolactin. No strong association between prolactin and migratory fattening was apparent, and prolactin levels were more closely related to daylength, with the highest concentrations being reached on long days. Plasma prolactin profiles were similar in intact and castrated male quail. Prolactin was secreted in a daily rhythm, with the highest concentrations occurring early in the photophase. However, when birds were food-restricted for 50 days during a migratory phase, there was no difference in fat deposition between birds food-deprived for the first half of the daily photophase compared with those deprived for the second half. Fattening was reduced in the food-restricted birds relative to ad libitum-fed controls, but there was no difference in plasma prolactin levels between the groups. Injections of ovine prolactin (4 mg/kg) significantly increased food intake and body mass of birds maintained on long days, but there were no differences in fattening between birds injected in the morning compared with those injected in the afternoon. Collectively, these results do not support a major role for prolactin in the regulation of migratory fat deposition in European quail.

Adaptation, Physiological↗

PubMed1994

Seasonal changes in body mass, insulin, and glucocorticoids of free-living golden-mantled ground squirrels.

The aim of the present study was to determine the relationship between seasonal variation in levels of insulin, cortisol, and corticosterone and body mass in a natural population of golden-mantled ground squirrels (Spermophilus saturatus) over the active season, from April to August. The body mass of females is at an active season minimum on emergence from hibernation, increases during pregnancy and lactation, and shows a further rise during fattening, reaching a peak in August. Males are heavier than females on emergence from hibernation, lose mass during the mating period, then gradually increase to a maximum in August. Plasma insulin titers generally reflected these patterns of change in body mass. Levels in males were almost double those of females on emergence, then decreased as body mass was lost during mating. Male values increased in July and peaked in August, coincident with the body mass maximum. Females, in contrast, showed very low insulin levels in April on emergence and increased levels during lactation, continuing high into the fattening period. Corticosterone levels were low in both sexes at the beginning of the season and rose throughout most of the active season; female levels exceeded those of males during the lactation phase. Cortisol titers gradually decreased over the first half of the active season in both sexes, but later increased to a seasonal maximum at the end of the season, coincident with the peak in body mass.(ABSTRACT TRUNCATED AT 250 WORDS)

11-Hydroxycorticosteroids↗

PubMed1993

A method for third ventricular cannulation of small passerine birds.

This paper describes a method for chronically cannulating the third ventricle of the white-crowned sparrow, a small passerine bird, without damaging the midsagittal sinus. The method is reliable and chronic over at least 1 month. The technique was verified by assessing the effects of angiotensin II (ANG II) on inducing drinking behavior. All birds rapidly recovered from the surgery and tolerated repeated injections spaced over 1 month. Animals were injected with saline or 0.01, 0.5, 1.0, and 10.0 micrograms of ANG II, respectively. The intermediate dose of 1.0 microgram was maximally effective and caused a significant increase of water intake over the test hour. Lower and higher doses were less effective. This method for cannulating the third ventricle of small passerine birds should prove beneficial in future neurobiological applications.

Angiotensin II↗

PubMed1993

NPY and galanin in a hibernator: hypothalamic gene expression and effects on feeding.

Neuropeptides such as neuropeptide Y (NPY) and galanin may play a role in regulating the pronounced seasonal changes in food intake shown by golden-mantled ground squirrels (Spermophilus saturatus). We used in situ hybridization histochemistry to localize the expression of NPY and galanin mRNA in the hypothalamus of normally feeding animals. NPY mRNA was abundantly expressed in the arcuate nucleus, while galanin mRNA was concentrated in both the arcuate nucleus and the dorsomedial nuclei. When NPY (0.1, 0.5, 2, and 8 micrograms) or galanin (0.1, 0.5, 2, and 8 micrograms) were injected into the third cerebral ventricle, food intake was significantly and dose-dependently increased over the subsequent 30 min. NPY stimulated significant increases in food intake for up to 2 h whereas galanin's effect did not extend beyond 30 min. Our results suggest that hibernating and nonhibernating rodents share common neural substrates for the regulation of food intake. Seasonal modulation of these neural pathways may contribute to annual cycles of food intake in hibernating mammals.

Analysis of Variance↗

PubMed1993

Cholecystokinin octapeptide decreases food intake in white-crowned sparrows.

White-crowned sparrows maintained on short days (9:15-h light-dark cycle) were peripherally injected with 1.0, 4.0, and 16 micrograms/kg ip of cholecystokinin octapeptide (CCK-8). Meal size over the subsequent 30 min was significantly depressed in a dose-dependent fashion. Water intake was not affected. The anorexic effect caused by 4.0 micrograms/kg was attenuated by 100 micrograms/kg of the type-A CCK receptor antagonist MK-329 but not by 300 micrograms/kg of the type-B CCK receptor antagonist L 365,260, suggesting that CCK-induced suppression of food intake in this species is mediated by a CCK-A receptor. Administration of both CCK-A and CCK-B receptor antagonists alone resulted in no change in meal size. These experiments suggest that white-crowned sparrows, when weight stable, respond to CCK-8 in a manner comparable with several mammalian species.

Animals↗

PubMedDate not supplied

Intracerebroventricular corticotropin-releasing factor decreases food intake in white-crowned sparrows.

Neuropeptides such as corticotropin-releasing factor (CRF) may play a role in regulating the pronounced seasonal changes in food intake shown by white-crowned sparrows (Zonotrichia leucophrys gambelii). White-crowned sparrows held on short day length received injections into the third ventricle (icv) of saline or 5.0, 15.0, and 30 microg/kg. Meal size over the subsequent 180 min was significantly depressed in a dose-dependent fashion. Other non-specific behaviors such as preening, hopping, and immobile behaviors appeared to not be affected by a dose that suppressed food intake. This experiment suggests that white-crowned sparrows, when weight-stable, respond to CRF in a manner comparable with several mammalian species.

Animals↗