1152 



SUBMAMMALIAN VERTEBRATES 



internal mechanism for the reguhition of 

 ovulation. It fails to account for the shift 

 in ovulation time by 12 hours when the time 

 of feeding is shifted 12 hours. A more serious 

 objection to the hyj^othesis is that release 

 of gonadotrophin from the pituitary, and 

 subsequent ovulation, can be induced by 

 progesterone injection, during the "re- 

 covery" period. In Nalbandov's hypothesis 

 one of the crucial points in the regulation 

 of timing is the slow recovery by the pitui- 

 tary, but the fact that the release of enough 

 gonadotrophin can be induced to stimulate 

 ovulation indicates that the pituitary is 

 competent, but that a stimulus is lacking or 

 that the threshold is too high for the stimu- 

 lus to be effective. 



In each of the hypotiieses, fluctuations in 

 threshold of the ovary to LH (Bastian and 

 Zarrow, 1953), neural threshold (Fraps, 

 1955b j, or pituitary recovery (Nalbandov, 

 1959c) are an essential part of the hyi)othe- 

 sis. Whether these changes actually occur 

 remains to be proven in each case, and, there- 

 fore, it seems that judgment as to the cor- 

 rectness of each hypothesis must be with- 

 held. Indirect evidence from other species 

 can often be marshalled, but applying data 

 obtained with one species to another si)ecies 

 is fraught with danger, especially in the 

 case of a species which has been as strongly 

 influenced by artificial selection as the 

 chicken. 



1. l^se of Birds in Bioassays 



Birds can be used in a variety of l)io- 

 assays that w^ill be described briefly in this 

 chapter. In several cases reference will be 

 made to reviews because they contain the 

 essential information on sensitivity and de- 

 tails of procedures. 



Gonadotrophin as.says. Total gonado- 

 trophins. 1. One-day-old cockerels are kept 

 in shipping boxes with food and water. In- 

 jections are made subcutaneously at 12- 

 hour intervals and the chicks are killed 12 

 hours after the last injection. Usually a 

 total of 5 injections is made (Breneman and 

 Mason, 1951). At autopsy the testes are re- 

 moved and weighed to the nearest 0.1 mg. 

 With this assay a minimal total dosage of 

 5.0 I.U. PMS, 5.0 ^ig. rSH, or 50 /.g. LH 

 give responses significantly different from 



water-injected controls. The index of pre- 

 cision for each of the three gonadotrophins 

 in this assay was 0.5734, 0.5766, and 0.4459, 

 respectively (Breneman, Zeller and Beek- 

 man, 1959). Each of the gonadotroj)hins 

 gave a linear log dose-response relationship. 

 No response was obtained with human 

 chorionic gonadotrophin nor was there evi- 

 dence of a FSH-LH synergism. Ten to fif- 

 teen chicks should be used for each point 

 on the regression. In this assay no reduc- 

 tion of error mean square was obtained by 

 adjusting testes weights for differences in 

 body weight of the chicks by the use of a 

 covariance analysis (Phillips, 1959). By 

 measuring P^- uptake by chick testes Flor- 

 sheim, VelcofT and Bodfish (1959) were able 

 to detect 0.1 I.U. of human chorionic gon- 

 adotrophin, 0.05 I.U. of PMS, and 0.5 to 

 1.0 |ug. of LH and FSH. 



2. Nall)andov and Baum (1948) proposed 

 the use of estrogen-inhibited roosters. Ac- 

 cording to their data, FSH would cause an 

 increase in testicular size and an increase 

 in tubule diameter, but no increase in comb 

 size, whereas LH would cause an apprecia- 

 ble increase in comb size, but only a small 

 increase in testicular size. By this method 

 an estimate of FSH and LH content could 

 be made in unpurified gonadotrojihin ex- 

 tracts. As far as the author is aware, no use 

 has been made of this method to make such 

 estimates. 



LH assay (Weaver-Finch test). In this 

 assay male, female, castrate, or noncastrate 

 Euplectes, Steganura, or Quelea are partially 

 deplumed and given a rest for 5 days. The 

 feather follicles reorganize and the tips of 

 new feathers are formed. The material is 

 injected subcutaneously in 1 or 2 doses. In a 

 positive reaction a colored bar is formed on 

 the new feather. The test is specific for LH 

 and human chorionic gonadotrophin (Wits- 

 chi, 1955; Segal, 1957). The response is not 

 affected l)y the presence of FSH, jirolactin, 

 ACTH, or TSH in the material to be tested, 

 and as little as 5 /*g. LH can be detected 

 (Witschi, 1955; Segal, 1957). 



Prolactin assay. Several methods for the 

 assay of prolactin on pigeons have been de- 

 scribed in a review by Meites and Turner 

 (1950). In each of the assays the stimula- 

 tion of the pigeon crop gland is measured. A 



