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A. STEINBERGER and E. STEINBERGER

Summary.

In-vitro differentiation of germinal epithelium from testes of adult and 12-day rats was studied with the aid of radioautography. Following a single injection of tritiated thymidine, the animals were killed and the testes grown as organ cultures. Tissue samples fixed prior to cultivation and after various time intervals of in-vitro growth, were processed for radioautography. Localization of the label in relation to the germ cell types was determined. In tissues obtained from animals 3 hr after isotope injection, the most advanced labelled germinal cells were spermatogonia and resting primary spermatocytes. Following 3 to 7 days of cultivation, the label was present in the zygotene and leptotene stages of the meiotic prophase and after 2 to 3 weeks of cultivation, in the pachytene stage of primary spermatocytes. No labelled spermatids were found in the cultivated tissues.

Appearance of labelled pachytene spermatocytes in cultures of testicular tissue containing only labelled spermatogonia and resting spermatocytes prior to cultivation constitutes evidence that progressive, although limited, differentiation of germinal epithelium from adult and puberal rats, can take place in vitro.

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E. STEINBERGER

Summary.

The testicular germinal epithelium in rats treated with triethylenemelamine (tem) was subjected to a quantitative analysis. The analysis revealed that tem, at a dose level of 0·2 mg/kg, has a specific effect on the early generations of Type A spermatogonia. The disappearance of the more mature type of cells was shown to be largely due to a maturation-depletion process. A minimal effect on the primary spermatocytes was observed after repeated administration of tem. Evidence was presented that this could be a result of a cumulative action of the drug. In no instance, however, was an effect observed on the synchronicity of the spermatogenic process. The data support the hypothesis that the response of the germinal epithelium to noxious stimuli is a precisely defined process confined to one or more types of the germinal epithelium cells.

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A. K. CHOWDHURY and E. STEINBERGER

Summary.

The influence of a cryptorchid milieu on the initiation of spermatogenesis was studied, utilizing the technique of transplantation of newborn rat testes into cryptorchid testes of adult hosts. The histological changes in the host and the transplanted testes were evaluated at various periods after transplantation. The transplant showed progressive growth and differentiation of the germ cells up to mid-pachytene stage within 30 days of transplantation into the cryptorchid testes. Thereafter, further progression of spermatogenesis did not occur and the germ cells gradually degenerated. Within 60 days, the seminiferous tubules in the transplant were lined by a layer of Sertoli cells and were comparable in appearance to the host tissue. In another group of animals where the cryptorchid testis was returned to the scrotum at the time of transplantation, both initiation and completion of spermatogenesis were observed. The results indicate that a cryptorchid milieu does not interfere with the initiation of spermatogenesis, but prevents its progression and maintenance.

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D. Y. TJIOE and E. STEINBERGER

Summary.

A quantitative analysis of the germinal epithelium cells in rat testes rendered ischaemic for a period of 100 min was performed. This period of ischaemia produces a reversible damage to the process of spermatogenesis.

Analysis of the testes at 2-, 7-, 14- and 28-day intervals after ischaemia, revealed damage to type A spermatogonia in stages XII and XIV, intermediate type A spermatogonia, type B spermatogonia and resting primary spermatocytes. The decrease in numbers, or absence of other cell types at the various time intervals after ischaemia was shown to be due to a maturation depletion process. In view of the fact that only cells undergoing mitosis or in the DNA-synthesizing period of meiosis were affected, it is suggested that germinal epithelium cells are most susceptible to ischaemia during this DNA-synthesis period.

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A. K. CHOWDHURY and E. STEINBERGER

Summary.

Changes in the seminiferous epithelium of the rat testis occurring within 24 hr after exposure to 43° C for 15 min were investigated using a quantitative technique. The earliest cytochemical or morphological changes were detected in the pachytene spermatocytes in stages IX to XII, the diakinetic and dividing spermatocytes in stages XIII and XIV and the young spermatids at stage I of spermatogenesis within 1 hr after exposure. The spermatocytes showed changes in the cytoplasm and the spermatids, in the nucleus.

The number of abnormal spermatocytes increased progressively with time after the exposure and the damage was detectable in more stages at later time intervals. Within 4 hr after exposure, the damage could also be detected in pachytene spermatocytes at stages VII and VIII, as well as through all the stages up to XIV. The pachytene, diakinetic and dividing spermatocytes from stages IX to XIV were essentially absent 24 hr after the exposure, and those at stages VII and VIII showed a drastic reduction in count. Similarly, a progressive increase in the number of abnormal spermatids was noted, associated with an intensification of the morphological changes in the nucleus characterized by typical ring formation pyknosis and chromatolysis. The sequence of degenerative changes varied considerably between spermatids and spermatocytes—the former showing the earliest changes in the nucleus, and the latter in the cytoplasm.

These findings extend and confirm earlier observations on the specific susceptibility of testicular germinal cells to heat. The pachytene, dia-kinetic and dividing spermatocytes at stages IX to XIV and the young step-1 spermatids are most susceptible to heat under the described experimental conditions.