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MANNFRED A. HOLLINGER

Summary.

Mitochondrial fraction from rat testes was found to metabolize ATP at a faster rate and to a more complete extent than mitochondria from liver or kidney. Catabolism of ATP by rat testis mitochondria is essentially complete by 30 min. Both ADP and AMP are formed in equal amounts.

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MANNFRED A. HOLLINGER and JOSEPH R. DAVIS

Summary.

The catabolic fate of [U-14C]d-glucose has been studied under aerobic conditions of incubation in slices of mature scrotal, immature abdominal and experimentally-induced cryptorchid testes of the rat. In comparison with the mature scrotal testis, CO2 production in the cryptorchid and the immature testis was found to be decreased by 45 and 55%, respectively. In contrast, protein labelling from radio-active glucose was found to be increased in the cryptorchid and the immature testis by a factor of 4·6 and 13·4, respectively. Successive ion-exchange chromatography of the perchloric acid-soluble fraction of the mature scrotal testis resulted in the elution of thirteen peaks of radio-activity from an anionic resin and five peaks of radio-activity from a cationic resin. The major catabolites occurring in slices of the mature scrotal testis were lactate, aspartate, glutamate, glutamine and α-ketoglutarate, accounting for 93% of the total perchloric acid-soluble radio-activity of glucose. Lactic acid accounted for 45·5, 36·9 and 15·9% in the mature scrotal, cryptorchid and immature testis, respectively. An additional unknown peak of radio-activity not found in samples of the mature scrotal testis was eluted from samples of both the immature abdominal and the experimentally-induced cryptorchid testis. It is suggested that of the cells of the seminiferous germinal epithelium, the maturing spermatids are characterized by the highest rate of glucose utilization into acid-soluble catabolites with a marked reduction in glucose catabolism occurring in the spermatogonia and primary spermatocytes.

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MANNFRED A. HOLLINGER and JOSEPH R. DAVIS

Summary.

The in vitro incorporation of [2-14C]thymidine and [2-14C]uridine into DNA and RNA respectively, has been studied in slices of immature, mature, cryptorchid, and contralateral-scrotal testes of the rat. The results demonstrate that DNA and RNA labelling are both enhanced in the cryptorchid testis following 30 days in the abdominal cavity. Of the four tissues studied, the immature testis possessed the highest in vitro rate of DNA and RNA labelling. In addition, uptake of [2-14C]uridine into RNA of the contralateral-scrotal testis of cryptorchid rats is elevated.

It is suggested that the enhanced nucleic acid labelling observed in the cryptorchid testis may be related to the predominance of those cells which normally synthesize nucleic acids during the cycle of the seminiferous epithelium, in association with compensatory gonadotrophin stimulation. Similarly, the increase in RNA labelling present in the contralateral scrotal testis may represent a compensatory `feed-back' mechanism from the pituitary by virtue of decreased testosterone production in the cryptorchid testis. Increased gonadotrophin output in cases of cryptorchidism may be a complicating factor in the increased tendency of abdominal testes to undergo neoplastic change.

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JOSEPH R. DAVIS, ROBERT N. MORRIS and MANNFRED A. HOLLINGER

Summary.

Unilateral cryptorchidism has been produced in prepubertal rats by abdominal fixation of an undescended testis and in adult rats by transplantation of a previously descended testis from the scrotal sac into the abdominal cavity. The incorporation of l-lysine-U-14C into protein of slices of both types of experimentally induced cryptorchid testes 30 days following the surgical procedure has been found to be markedly greater than that observed for slices of contralateral, scrotal testes of the same animal.