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

Example Input: Abstract: Methods for endoscopic retrograde cholangiography (ERC) and endoscopic papillotomy (EPT) in patients with Billroth-II operations are described, and experience with their use during the last four years (since 1980) is presented. Endoscopic retrograde cholangiopancreatography was successful in 134 of 147 patients (92%) and endoscopic papillotomy was successful in 46 of 50 patients. The described methods were used in two different hospitals by two different endoscopists and there was no difference in the results. We conclude that patients with a Billroth-II operation may undergo endoscopic diagnostic as well as therapeutic procedures with a high rate of success, with similar results as in ordinary patients and with no greater risk of complications.
Example Output: Endoscopic retrograde cholangiography and endoscopic papillotomy in patients with a previous Billroth-II resection.

Example Input: Abstract: During the 17 years preceding March 1985, 140 patients sustained lightning injuries caused by 44 thunderbolts. Fifty patients showed evidence of current flow through their bodies. These 50 victims were classified into two groups, the first consisting of 9 victims who showed rupture of their clothes or linear superficial dermal burns along their whole bodies from head to feet, indicating the occurrence of surface flashovers. The remaining 41 patients showed no evidence of this flash effect. It is noteworthy that in the first group 5 of the 9 survived, whereas in the second group only 6 among 41 survived. The result indicates that when a flashover occurs along the whole body, the probability of survival is higher than 50 per cent. The conditions which determine death or survival were investigated experimentally, imposing artificial lightning voltage impulses on rats and developing flashovers on them. The rats survived when the voltage drop caused by flashover occurred immediately after the peak point, and the current waveform exhibited a sharp peak. In contrast, the rats were killed when the voltage drop caused by flashover was delayed by more than 20 microseconds, and the current waveform showed a blunt cone shape. It has been concluded that a fast flashover appreciably diminishes the energy dissipation within the body and consequently results in survival.
Example Output: Lightning injury caused by discharges accompanying flashovers--a clinical and experimental study of death and survival.

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