abnormality was more marked in bilateral cryptorchidism than in unilateral cryptorchidism and, in the case of bilateral cryptorchidism, the anomaly was more severe in the right side than in the left side. The number of seminiferous tubules was significantly lower than in the scrotal testes of the healthy boars (P < 0.01); moreover, the seminiferous tubules showed a significant decrease in diameter (P < 0.01). The seminiferous epithelium was constituted by either immature Sertoli cells and few

more »

... ermatogonia or only immature Sertoli cells; in the bilateral disease, immature Sertoli cells showed a degenerative pattern. The alteration in germ cell number was more critical in bilateral cryptorchidism, especially in the right testis. Seminiferous tubules of abdominal testes also displayed a great thickening and collagenization of the lamina propria. The interstitial tissue exhibited significant development (P < 0.01), but abnormal appearance; the Leydig cell population showed a notable regression and the fibrous connective tissue became more developed. In the postpubertal boars, unilateral abdominal cryptorchidism on the right side provoked a significant increase of the weight and volume of the scrotal testis (P < 0.01). However, the scrotal testes of the unilateral cryptorchid boars displayed a significantly reduced number of seminiferous tubules (P < 0.01) associated with a major development of the interstitial tissue; the tubular diameter did not differ from the scrotal testes of the healthy boars (P > 0.01). The seminiferous epithelium showed normal appearance, but anomalies in the spermatid maturation were observed. Conclusion: The alterations of abdominal testes were more severe in bilateral cryptorchidism than in unilateral cryptorchidism; in the bilateral cryptorchidism abnormalities were more critical in the right side than in the left side. In both unilateral and bilateral cryptorchid boars, the alterations of abdominal testes were attributed to defective proliferation and differentation of Sertoli cells and Leydig cells during the prepubertal period. Differences in the structural appearance of immature Sertoli cells between unilateral and bilateral cryptorchidism indicated that testicular degeneration initiated earlier in the bilateral disease. In the scrotal testis of the unilateral abdominal cryptorchid boars, the increase of weight and volume was related to a compensatory hypertrophy. Decreased numbers of seminiferous tubules were attributed to anomalies in Sertoli cell proliferation during the prepubertal period; moreover, abnormal spermatid maturation indicated disturbances in the Sertoli cell activity.