Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.

Ex Input:
Abstract: Surgically prepared cryptorchid mouse testes containing only type A spermatogonia were cultured with (Bu)2cAMP in combination with vitamin A (retinol). Treatment with (Bu)2cAMP and retinol for 12-24 h and with basal medium for an additional 8 days stimulated mitotic activity in type A spermatogonia and induced differentiation of germ cells. However, (Bu)2cAMP alone did not induce differentiation of type A spermatogonia. Moreover, when cryptorchid testes were treated with (Bu)2cAMP for longer than 3 days in the presence or absence of retinol, differentiation of type A spermatogonia did not take place; disintegration of the seminiferous tubules occurred instead. When the cryptorchid testes were cultured for 24 h in a medium containing a fixed concentration of retinol and varying concentrations of (Bu)2cAMP from 0.001-0.4 mM, there was a dose-dependent increase in the number of differentiated and mitotic germ cells and type A spermatogonia. Likewise, at a fixed dose of (Bu)2cAMP and increasing concentrations of retinol, a dose-dependent increase in the number of differentiated and mitotic germ cells occurred. However, the number of type A spermatogonia was decreased. The addition of puromycin, cycloheximide, and actinomycin D to the medium completely blocked retinol-(Bu)2cAMP-induced differentiation of the germ cells. The present results suggest that cAMP and retinol trigger biochemical events promoting the synthesis of specific macromolecules involved in the proliferation and differentiation of type A spermatogonia.

Ex Output:
Dibutyryl adenosine cyclic monophosphate regulates differentiation of type A spermatogonia with vitamin A in adult mouse cryptorchid testis in vitro.

Ex Input:
Abstract: To summarize the results: Bilirubin removal by hemoperfusion was successfully performed for the first time on a premature infant. The hemoperfusion caused no adverse effects on the clinical state of the infant. The bilirubin removed in 90 min--13 mg--indicates the existence of a large extravascular pool. Hemoperfusion is suggested for bilirubin removal from newborn babies, reducing the need for blood exchange with bank blood.

Ex Output:
Bilirubin removal from a jaundiced premature infant by resin hemoperfusion.

Ex Input:
Abstract: Twenty-five patients with fracture of the penis were treated surgically between 1968 and 1984. Long-term follow-up was obtained in 17. In no case were there any early post-operative complications. All patients stated that they were achieving normal, painless erections; two patients developed a slight penile curvature but this did not affect their sexual activities. We strongly recommend early surgical intervention because of these encouraging results. Urethral injury associated with the fracture did not occur in this series.

Ex Output:
Fracture of the penis and long-term results of surgical treatment.