Effect of actinomycin D on the structure of the chromatoid body in the rat spermatids

The effect of actinomycin D on the chromadoid body of rat spermatids has been studied by light and electron microscopy, high resolution autoradiography and biochemical methods. Actinomycin D caused structural changes in the chromatoid body of young round nucleated spermatids. The normal irregularily lobulated chromatoid body acquired a ring-like configuration 12 h after an intratesticular injection of 2 microgram of the drug. The labelling of the chromatoid body with 3H-uridine which can normally be seen after 12 h was also abolished by actinomycin D. These observations lead to the suggestion that the chromatoid body contains a store of long-lived mRNA molecules that are activated later during spermiogenesis when transcription in the spermatid nucleus has ceased but a high level of protein synthesis still persists.

RNA synthesis in different stages of rat seminiferous epithelial cycle

In vitro RNA synthesis has been analyzed using autoradiographic and electrophoretic methods in isolated 1-2 mm segments of rat seminiferous tubules. The cellular composition of each segment was accurately identified using microscopic analysis of the transillumination pattern of the freshly isolated, unstained, seminiferous tubules combined with phase-contrast microscopy of the living spermatogenic cells. The RNA synthesized in the seminiferous tubules was found to be mostly heterogenous nuclear RNA (HnRNA), which appeared to have a long lifetime. It was most actively formed in the stages which contain mid-pachytene spermatocytes. Formation of rRNA was slow in all stages and it was first observed when a 2-h pulse with [3H]uridine was followed by a 6-h chase. A very low RNA synthetic rate was observed in the stage containing the meiotic reduction divisions. The function of the meiotic RNA in regulation of spermiogenesis is discussed.

Incorporation of (3H)uridine by the chromatoid body during rat spermatogenesis

The in vitro incorporation of tritiated uridine into RNA by the spermatogenic cells of the rat has been analyzed by high-resolution autoradiography. Special attention has been focused on the unique cytoplasmic organelle, the chromatoid body. After a short labeling time (2 h), this organelle remains unlabeled in the vast majority of the early spermatids although the nuclei are labeled. When the 2-h incubation with (3H)uridine is followed by a 14-h chase, the chromatoid body is seen distinctly labeled in all spermatids during early spermiogenesis from step 1 to step 8. Very few grains are seen elsewhere in the cytoplasm of these cells. When RNA synthesis in the spermatid ceases, the chromatoid body also remains unlabeled. It is likely that the chromatoid body contains RNA which is synthesized in the nuclei of the spermatids. The function of this RNA as a stable messenger RNA needed for the regulation of late spermiogenesis is discussed.

Transport of material between the nucleus, the chromatoid body and the Golgi complex in the early spermatids of the rat

The movement and transport of material between intranuclear dense particles, the chromatoid body and the Golgi complex have been studied in early spermatids of the rat. The analyses involved observation of living accurately identified cells, time-lapse cinemicrography and electron microscopy. The chromatoid body establishes transient contacts with intranuclear material during early spermiogenesis. The chromatoid body also makes contacts with the Golgi complex. It is suggested that the chromatoid body receives material from the nucleus during the postmeiotic period and particites in the early formation of the acrosomic system.

Control of the mitotic activity in the rat seminal vesicle by "chalone"

One month after castration male rats were injected daily with 2 X 50 mug of testosterone. Starting before the highest mitotic activity of seminal vesicles, 3 injections of normal seminal vesicle extract were given into the lumen at 3 h intervals. The contralateral seminal vesicle was injected with rat liver extract. Tritiated thymidine was given intravenously. The labelling index of the seminal vesicles was determined by means of radioautography. The crude supernatant of seminal vesicle was the most effective to inhibit the mitotic activity of the seminal vesicles. The decrease was on an average 34 per cent. The liver extract did not influence the mitotic activity. When the seminal vesicle extract was fractionated by Sephadex G-25, the largest fraction (M. W. greater than 3000) showed the highest inhibitory activity, whereas the smallest fraction (M. W. less than 1000) was ineffective. The inhibition of mitosis can also be induced by an unspecific factor, since pronase showed slight inhibitory action on seminal vesicle mitosis. However, the seminal vesicle extract had no inhibitory action on the epidermal mitotic activity.

Weight gain and (3H)thymidine incorporation in accessory sex glands of castrated male rats after physiological doses of testosterone

One month after castration male rats were injected daily with a physiological dose (2 × 50 μg) of testosterone for 10 days. At certain time intervals a pair of rats were injected with [3H]thymidine and killed one hour later. The accessory sex organs were weighed and processed for radioautography.

The ventral prostate, dorsal prostate, seminal vesicle and coagulating gland showed a 2.5–4 fold increase in weight during treatment for 10 days with testosterone, whereas the weight of the preputial gland remained unchanged.

The daily physiological dose of testosterone clearly increased the [3H] thymidine incorporation in all the accessory sex glands except the preputial gland where only a slight initial peak was observed. The labelling index showed a peak value 42–90 hours after the start of the testosterone treatment. After the peak the labelling index showed some fluctuation and then decreased to a steady state level, which was of the same magnitude as the control level in uncastrated rats. This study shows that the 42–90 hour peak in the labelling index is dose-dependent whereas the steady state labelling index is independent of the testosterone dose. The refractory time to the initial peak of the labelling index is also independent of the testosterone dose.