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M F Cheng

Publications and source records attributed to M F Cheng.

At least 73 records · Page 4Linked to original sources
PubMed1981

Hormonal control of the gonadal regression and recovery observed in short days in male and female doves.

Sexually mature ring doves (Streptopelia risoria) maintained from hatch on a photoperiod of 14 h light : 10 h darkness (14L : 10D) and kept in isolation were transferred to 8L : 16D. This treatment resulted in a partial regression of the ovaries and testes and a fall in the concentration of plasma LH but not of plasma FSH. After 2--3 months exposure to 8L : 16D, the gonads regrew to their original size: this regrowth was accompanied by a parallel increase in the concentration of plasma LH. The responsiveness of the pituitary gland to LH releasing hormone in both sexes after 5 weeks of exposure to 8L : 16D (when the gonads were partially regressed) was similar to the response observed after 15 weeks exposure to this lighting schedule (when the gonads had regrown). It was concluded that the spontaneous recovery of gonadal size in ring doves exposed to 8L : 16D is controlled by the hypothalamus and does not involve changes in the functional capacity of the pituitary gland or of the gonads.

Animals↗
PubMed1980

Hormones modulate the concentration of cytoplasmic progestin receptors in the brain of male ring doves (Streptopelia risoria).

A cytoplasmic progestin receptor has been characterized in the brain of castrated ring doves using an in-vitro assay that measures the binding of a synthetic progestin, [3H]17 alpha,21-dimethyl-19-nor-pregna-4,9-diene-3,20-dione(promegestone; R5020). The affinity of the receptor was similar in both the hyperstriatum and the hypothalamus (Kd approximately equal to 4 X 10(-10) mol/l). Its concentration was higher in the anterior hypothalamus-preoptic area (63 +/- 4 fmol/mg (S.E.M.) protein) than in other brain regions (posterior hypothalamus, 33 +/- 5; hyperstriatum, 28 +/- 3; midbrain, 17 +/- 4 fmol/mg protein; n = 7). Progesterone and R5020 competed well for binding but oestradiol and 5 beta-dihydrotestosterone did not. Corticosterone and, to a lesser extent, testosterone and 5 alpha-dihydrotestosterone completed for binding but much higher concentrations were required than for progestins. Injections of testosterone (200 micrograms testosterone propionate daily for 7 days) significantly increased the concentration of progestin receptors in the anterior and posterior hypothalamus without having any significant effect on other brain areas. Shorter treatment, lasting for 2 days, with testosterone propionate (200 micrograms daily), 5 alpha-dihydrotestosterone (200 micrograms daily) or oestradiol benzoate (50 micrograms daily) did not always cause this increase but seven injections of oestradiol benzoate (50 micrograms daily for 7 days) were even more effective than seven injections of testosterone propionate (200 micrograms daily for 7 days). These data suggested that the sensitivity to progesterone of the brain of the bird changes as a consequence of increases in the level of testosterone in the circulation.

Animals↗
PubMed1977

Role of gonadotrophin releasing hormones in the reproductive behaviour of female ring doves (Streptopelia risoria).

This work was carried out to determine whether gonadotrophin releasing hormone(s) (GnRH) plays a role in the courtship behaviour of female ring doves. In particular, it tests the hypothesis that a high dose of oestrogen suppresses the synergistic action of GnRH with oestrogen which is required to elicit courtship behaviour. The hypothesis was formulated to provide an explanation for a finding in a previous study that ovariectomized ring doves treated with a high dose of oestrogen, paradoxically, failed to show courtship behaviour. In the present study, treatment with synthetic LH releasing hormone (RH) enabled such birds to show typical female behaviour, thus supporting the hypothesis. This LH-RH effect was not apparently mediated by LH or progesterone since treatment with LH or progesterone failed to induce courtship behaviour. In addition, LH-RH can synergise with sub-threshold doses of oestrogen to induce both nest-soliciting and squatting behaviour. This portion of the LH-RH effect complements similar results reported for the rat. Finally, the results of thyrotrophin releasing hormone point to the specificity of LH-RH and the results of an anti-ovulation LH-RH analogue agree with the LH-RH effect.

Animals↗
PubMed1975

Estrogen-progesterone regulation of nest-building and incubation behavior in ovariectomized ring doves (Streptopelia risoria).

The role of ovarian hormones in the induction of nest-building (tucking) and incubation behavior in female doves (Streptopelia risoria) was determined by systemic injections of estrogen, or progesterione, or estrogen combined with progesterone, or oil in reproductively experienced ovariectomized females. Combined estrogen and progesterone treatment was the most effective hormone regimen for eliciting both behavior patterns in females and also facilitated these behaviors in their untreated mates. Differences in role of the gonadal progesterone in male and female doves were discussed.

Animals↗
PubMed1975

Induction of incubation behaviour in male ring doves (Streptopelia risoria): a behavioural analysis.

Male ring doves (Streptopelia risoria) were treated with either progesterone or dexamethasone (a powerful ACTH inhibitor) and tested for incubation behaviour. Progesterone treatments shortened the latency of incubation response by facilitating nest-related pre-incubation behaviour patterns in the nest bowl and components of incubation behaviour. The accumulated rather than the daily dose level of progesterone injections appeared to be the determinant factor in mediating behavioural effects. Dexamethasone treatment at the dosage of 100 mug/day for 7 days inhibited the overall expression of male courtship behaviour. None of the dexamethasone-treated ring doves "sat" in 2 weeks. It is suggested that the hormonal and situational (non-hormonal) cues are not only important contributory factors but also complement one another in the induction of incubation behaviour.

Animals↗