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Biomedical subjects

H Schwabl

Publications and source records attributed to H Schwabl.

30 records · Page 2Linked to original sources
PubMed1993

Twenty-four hour melatonin profiles in a nocturnally migrating bird during and between migratory seasons.

The garden warbler Sylvia borin is a long-distance migrating bird that travels exclusively at night. During the migratory seasons caged warblers develop intense nocturnal activity which may become even more intense than that during the day. It is demonstrated that in spite of dramatic seasonal changes in the 24-h pattern of locomotor activity measured in caged garden warblers, the corresponding pattern of plasma melatonin changed only very little. As in other species melatonin levels were generally low during the day (below 50 pg/ml) and high at night (350 to 650 pg/ml). A slight reduction in the nocturnal melatonin peak (from 650 pg/ml to between 350 and 400 pg/ml) observed during the autumn and spring migratory seasons, was possibly due to an increased light perception of the birds moving around while being exposed to dim night lights. In general the results show that the 24-h plasma melatonin profiles of these birds are rather robust and that locomotor activity does not depend in a simple and direct way on plasma melatonin levels.

Animals↗
PubMed1992

Antiphonal duetting and sex hormones in the tropical bush shrike Laniarius funebris (HARTLAUB).

We investigated changes in antiphonal duetting with phases of reproduction and circulating levels of luteinizing hormone, testosterone, and estradiol in slate-colored boubous (Laniarius funebris) breeding in aviaries. Frequency of overall male singing did not vary with reproductive phase while frequencies of female singing and female vocal responses to male song were reduced during incubation and feeding of nestlings. This resulted in significant changes in frequency of duetting. Males sang the sexual song type M1 more often during courtship and nest building than during the nestlings phase. Their territorial song types M2 and M4 did not vary with breeding phase. Females were less responsive to M1 during incubation and to M2 during the nest building and nestlings than during the courtship phase. Plasma levels of luteinizing hormone and testosterone increased in males from the prebreeding to the courtship phase. While testosterone decreased already during nest building and remained low during subsequent phases of reproduction, luteinizing hormone decreased during incubation and feeding of nestlings. Female luteinizing hormone levels were highest during nest building. Female estradiol levels decreased from nest building to incubation and increased again during subsequent nest building. Female testosterone levels were low but not basal and did not vary with phase. Neither the overall male and female singing frequencies nor the frequencies of male song types were correlated with hormonal state. However, female participation in territorial duets M4 correlated positively with their testosterone levels. It is suggested that in this monogamous, duetting species with prolonged pairbonds behavioral cues between the mates are more important than the hormonal state in control of male and female singing.

Animals↗
PubMed1991

Territorial aggression and song of male European robins (Erithacus rubecula) in autumn and spring: effects of antiandrogen treatment.

Male robins aggressively defending a feeding territory in winter have low levels of testosterone, while males defending a breeding territory in spring have elevated levels of testosterone. Song is an integrated part of territorial defense during both phases. We investigated whether testosterone is involved in the expression of these behaviors by treating free-living and captive male robins during both phases with the antiandrogen flutamide. Results suggest that, similar to species in which territoriality is restricted to the reproductive phase, aggressive defense of a breeding territory by male robins is facilitated by androgens. Territorial defense during the nonbreeding season, however, does not require androgenic activity. Singing frequency, on the other hand, was not significantly reduced during either phase by flutamide application. Since the quality of male song changes with season we suggest that the incorporation of sexual signals into male song during breeding depends on testosterone, but that the year-round production of territorial "keep out" signals is independent of testosterone.

Aggression↗
PubMed1991

Variation in hypothalamic gonadotrophin-releasing hormone content, plasma and pituitary LH, and in-vitro testosterone release in a long-distance migratory bird, the garden warbler (Sylvia borin), under constant photoperiods.

Changes in concentrations of hypothalamic gonadotrophin-releasing hormone (GnRH), pituitary and plasma LH, testicular mass, in-vitro release of testosterone, body mass and migratory activity were measured in male garden warblers (Sylvia borin) kept from November to June under a constant photo-period of 12.8 h. Under such conditions garden warblers gradually change from the photorefractory to the photosensitive state and gonadal recrudescence then occurs. Hypothalamic GnRH content was low from December to March, but increased in April to reach the highest levels in June. The spontaneous increase in GnRH was paralleled by increases in pituitary LH content, testicular mass and in-vitro testosterone release. Body mass decreased 1 month and nocturnal activity 2 months before the spontaneous increase in GnRH. Ovine LH increased in-vitro testosterone release over basal release at all times. The results suggest that in garden warblers (1) changes in hypothalamic GnRH content can occur under constant photoperiodic condition, (2) the gradual change from the photorefractory to the photosensitive state is not characterized by a gradual increase in hypothalamic content of GnRH (cf. starlings), and (3) Leydig cells are capable of testosterone release even during the photorefractory state.

Animals↗
PubMed1990

[Reproducibility of the bronchospasmolytic effect of anticholinergic drugs and beta-sympathomimetics].

The bronchodilator effect of an anticholinergic and beta-adrenergic drug in the same patient was tested at 3 different times to study the reproducibility. There is a good average reproducibility: the curves concerning the bronchodilation are nearly identical or parallel. On the other hand there is a greater difference in the individual curves at different times: the patients with the most severe airway obstruction show the greatest difference in the bronchodilator effect at different times.

Administration, Inhalation↗
PubMed1990

[The bronchospasmolytic test with anticholinergic drugs and sympathomimetics: differences between body plethysmography and spirometry measuring procedures].

The different bronchodilator effects after inhalation of anticholinergic and beta-adrenergic drugs due to the different methods of measurement (i.a. body plethysmography vs. spirometry) were studied in 43 patients with COLD and in 20 healthy subjects. The greatest changes occur when the body plethysmographic value Rt was chosen. The spirometric values FEV1 and PEF show the greatest bronchodilator effect. The patients with COLD have the best bronchodilation after inhalation of the beta-adrenergic drug, whereas the healthy subjects show the greatest effect after anticholinergic drugs.

Airway Resistance↗
PubMed1989

Hormonal patterns in breeding and nonbreeding kestrels, Falco tinnunculus: field and laboratory studies.

Plasma levels of luteinizing hormone (LH), androgens, and corticosterone (B) were measured in breeding and nonbreeding kestrels, both in the field and in captivity under different food conditions. LH levels in breeding males were elevated from courtship through incubation and androgen concentration peaked during courtship and laying. Seasonal changes in LH and androgens were similar in breeding and nonbreeding males, although androgens declined sharply after laying in breeding males. Egg laying was characterized by marked increases in both female body mass and plasma concentrations of LH and B. In both breeding and nonbreeding females LH and B increased during pair formation and courtship (March-April), although maximum levels were lower in nonbreeders. Two marked differences were found between free-living and captive (paired) birds. First, during winter plasma levels of LH were basal in free-living birds, while significantly elevated in both captive males and females. Second, during courtship androgen levels in breeding males were three-fold higher in the field than in captivity, probably as a result of intermale aggression under natural conditions. Females breeding early, late, or not at all had similar LH concentrations on arrival and during early courtship. Before breeding there were also no differences in LH (males and females) or in androgen levels (males) between pairs fed ad libitum and pairs temporary food rationed. However, captive females with experimentally reduced food intake showed low levels of B until their rations were increased. Nonbreeders showed hormonal changes similar to breeders, except for those changes in females that were associated with laying. These results suggest that at the start of the breeding season both nonbreeding and breeding kestrels have functional reproductive systems. That some breed early, late, or not at all is primarily an effect of food availability and is not due to hormonal modulation of the reproductive cycle.

Androgens↗
PubMed1988

Effects of ovariectomy on long-day-induced premigratory fat deposition, plasma levels of luteinizing hormone and prolactin, and molt in white-crowned sparrows, Zonotrichia leucophrys gambelii.

Long days initiate the hyperphagia, fat deposition, and nocturnal restlessness, characteristic of the vernal migratory state in white-crowned sparrows. Ovariectomy, when performed in November, but not when performed in January, prevented induction by long days (20L:4D) of vernal fat deposition, whereas autumnal fat deposition was not affected. This is consistent with results obtained previously with males. Very high plasma levels of luteinizing hormone (LH) after photostimulation of ovariectomized females did not interfere with fat deposition. During fat deposition, levels of prolactin were not different from short-day levels and similar in ovariectomized and control females. However, ovariectomy performed in November suppressed the maximum levels of prolactin produced by long-day stimulation and inhibited or disturbed postnuptial molt. These effects were absent when ovariectomy was performed in January. Long-day-induced prolactin levels were higher when birds were photostimulated during a later phase of the annual cycle. It is suggested that castration does not interfere with long-day-induced vernal fat deposition via reduced secretion of prolactin in the absence of ovarian hormones or via supernormal secretion of LH, but that vernal fat deposition, prolactin secretion, and postnuptial molt require the presence of ovarian hormones prior to photostimulation. Autumnal migratory fat deposition, which is part of the cluster of events associated with photorefractoriness, has no requirement for gonadal hormones.

Adipose Tissue↗
PubMed1988

Oral corticosteroids and histamine releasability of basophil granulocytes.

The influence of oral corticosteroid therapy (7.5 and 15 mg prednisolon/day for 8 days) on basophil releasability by antigens was investigated in a series of 16 patients with chronic obstructive airway disease. A significantly smaller histamine release was observed after the treatment. Different types of releasing curves were observed which mostly persisted after treatment.

Administration, Oral↗