Infectious bronchitis virus in testicles and venereal transmission.

Even though males represent only 8%-12% of the birds of a breeder flock, their role in infectious bronchitis virus (IBV) dissemination is largely unknown. We first assessed the effect of IBV replication in the chicken testes. Ten-week-old males were inoculated with Arkansas (Ark) or Massachusetts (Mass) IBV virulent strains. Seven days postinoculation (DPI) IBV RNA was detected in testicles of 100% of M41- and in 96% of Ark-infected males. Marginal nonsynonymous variation was detected in spike (S) gene of the predominant population of IBV replicating in the testes compared to the S gene of the predominant population of viruses prior to inoculation. IBV M41 and Ark were detected in spermatogonia and Sertoli cells of testicles of infected roosters by immunofluorescence, without evident histopathological changes. We next assessed venereal transmission of IBV by artificially inseminating 54-wk-old hens either with semen from IBV-infected roosters or with IBV suspended in naïve semen. IBV RNA was detected in the trachea of all hens inseminated with IBV-spiked semen and in 50% of hens inseminated with semen from IBV-infected males. The egg internal and external quality was negatively affected in hens inseminated with semen containing IBV. These results provide experimental evidence for IBV venereal transmission.

A pilot study of ovarian cancer chemoprevention using medroxyprogesterone acetate in an avian model of spontaneous ovarian carcinogenesis.

OBJECTIVE: Our previous studies have documented the feasibility of using the laying hen, Gallus domesticus, as a model of spontaneous ovarian carcinogenesis. This study was performed to determine the ability of medroxyprogesterone acetate (Depo-Provera) to reduce the frequency of spontaneously developing reproductive tract adenocarcinoma in the avian model. METHOD: Four hundred 3-year-old hens were in a two-arm trial designed to determine the frequency of epithelial reproductive tract adenocarcinomas. Animals were designated to receive three injections of 100 mg Depo-Provera versus no injection over a 16-month period. Both groups were subjected to two induced molts 12 months apart. Egg counts were obtained and decreased egg production was documented in the treated hens due to Depo-Provera. At the end of 16 months surviving animals were sacrificed and the frequency of reproductive tract adenocarcinoma was determined histologicically. RESULTS: Histologic information was obtained from the 293 hens that completed the full prescribed course of study. At the time of necropsy, multiple hens had evidence of carcinomatosis and massive ascites consistent with metastatic reproductive tract adenocarcinomas. Of the tissues examined from the informative cases gathered at the time of sacrifice, there was evidence of a reduction of reproductive tract adenocarcinoma observed in the Depo-Provera group (45/127-35%) when compared to the control group (69/166-42%). A risk reduction of 15% is observed in the treatment group (risk ratio 0.85: 95% confidence interval 0.63-1.15). CONCLUSION: The high rate of reproductive tract adenocarcinoma observed in this study supports the avian hen as a valid model of spontaneous ovarian carcinogenesis in which to test chemoprevention strategies and provides a unique opportunity for investigating the pathogenesis of ovarian carcinoma. The current histologic findings are consistent with the theory that a reduction of ovulatory events may prevent the development of ovarian adenocarcinoma.

Lead attenuation of episodic growth hormone secretion in male rats.

The purpose of this study was to characterize the effects of chronic lead exposure on growth hormone and insulin-like growth factor-1 status in growing male rats. Pituitary growth hormone content, episodic growth hormone release, plasma insulin-like growth factor-1 levels, and growth hormone response to exogenous growth hormone-releasing factor were quantified in young rats given lead nitrate. Twenty male Sprague-Dawley weanling rats were given lead nitrate (1000 ppm lead) in drinking water for a period of 6 weeks. Lead treatment significantly reduced body weight gain. Pituitary growth hormone content was not altered by lead treatment. Mean plasma growth hormone levels were reduced 44.6% by lead treatment (46.41 +/- 6.2 ng/ml; p = .003) as compared to controls (83.82 +/- 10 ng/ml). Lead treatment reduced mean growth hormone peak amplitude by 37.5%, mean nadir concentration by 60%, and growth hormone peak area by 35%. These findings are consistent with decreased hypothalamic growth hormone-releasing factor secretion or reduced somatotrope responsiveness. Exogenous growth hormone-releasing factor increased plasma growth hormone in lead-treated and control rats. However, this response was blunted by the lead treatment (lead treated: 485.6 +/- 57.8 vs. controls: 870.2 +/- 127 ng/ml; p = .03). Plasma insulin-like growth factor-1 concentration was not significantly affected by lead treatment. These results demonstrate that lead intoxication attenuates growth hormone release without abolishing the hypothalamic endocrine mechanisms driving growth hormone pulsatility. This suggests that lead acts at the level of the pituitary somatotroph rather than at the level of the hypothalamus.