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Search for other papers by D. M. VOWLES in
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Search for other papers by D. HARWOOD in
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SUMMARY
The aggressive and defensive behaviour of the ring dove was studied in response to a model predator and to another member of the same species. During a single breeding cycle defensive behaviour increased rapidly just before laying, reached a second peak at the time of hatching, and declined as the squabs became independent. Cocks showed aggressive behaviour to other doves throughout the cycle, but this response reached a peak soon after laying, and declined at the time of hatching.
The effects of seven daily injections of oestrogen, progesterone, progesterone plus oestrogen, testosterone, and prolactin were studied. In both sexes prolactin and progesterone (with and without oestrogen) increased defensive behaviour towards a predator; in hens these hormones also increased defensive behaviour towards other birds. In cocks, however, prolactin had no effect on the response to other doves; progesterone (with and without oestrogen) increased aggressiveness, and oestrogen increased nest-cooing.
Single injections of the same hormones produced similar effects, with the exception that testosterone and oestrogen in hens caused a temporary (1–5 hr.) increase in defensive behaviour. The latency of most hormonal effects was 30 min. to 2 hr., although the injections were intramuscular. This suggests a direct effect on central nervous mechanisms. Progesterone had a latency of 12–18 hr., suggesting an indirect effect.
Search for other papers by I. D. HERRIMAN in
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Search for other papers by D. J. HARWOOD in
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Search for other papers by C. B. MALLINSON in
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Search for other papers by R. J. HEITZMAN in
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Measurements were made of the plasma concentrations of testosterone, progesterone and oestradiol-17β during the oestrous cycle of the ewe, and of the plasma concentrations of testosterone and progesterone during the oestrous cycle of the heifer. The maximum concentration of progesterone in the heifer was nearly twice that in the ewe. The maximum concentration of testosterone was similar in both species and occurred at the onset of luteolysis; in the ewe the peak concentration of 19·5 pg/ml plasma was significantly greater (P < 0·05) than the concentrations of testosterone measured during the remainder of the oestrous cycle.
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Search for other papers by Harwood HJ Jr in
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Search for other papers by D Rozman in
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Lanosterol 14alpha-demethylase (CYP51) is a cytochrome P450 enzyme involved primarily in cholesterol biosynthesis. CYP51 in the presence of NADPH-cytochrome P450 reductase converts lanosterol to follicular fluid meiosis activating sterol (FF-MAS), an intermediate of cholesterol biosynthesis which accumulates in gonads and has an additional function as oocyte meiosis-activating substance. This work shows for the first time that cholesterogenic enzymes are highly expressed only in distinct stages of spermatogenesis. CYP51, NADPH-P450 reductase (the electron transferring enzyme needed for CYP51 activity) and squalene synthase (an enzyme preceding CYP51 in the pathway) proteins have been studied. CYP51 was detected in step 3-19 spermatids, with large amounts in the cytoplasm/residual bodies of step 19 spermatids, where P450 reductase was also observed. Squalene synthase was immunodetected in step 2-15 spermatids of the rat, indicating that squalene synthase and CYP51 proteins are not equally expressed in same stages of spermatogenesis. Discordant expression of cholesterogenic genes may be a more general mechanism leading to transient accumulation of pathway intermediates in spermatogenesis. This study provides the first evidence that step 19 spermatids and residual bodies of the rat testis have the capacity to produce MAS sterols in situ.
