The effect of urea on various ornithine cycle enzymes has been investigated. It was demonstrated that argininosuccinate lyase was the only ornithine cycle enzyme inhibited by urea in a competitive manner. Based on the data presented the possible role of urea in maintaining a physiological range of intracellular and extracellular urea concentration by controlling hepatic ureogenesis was discussed.

Process and efficacy of hemodialysis can be readily monitored by continuous measurement and registration of transmittance at 254 nm of the dialysate. An additional advantage of the method is that it can be easily automatized.

The role of basic amino acids in male infertility is discussed. The changes in the arginine, ornithine and total amino acid concentrations of the seminal plasma in various types of pathospermia are commented upon in the light of published evidence and of the authors' own observations. A recent procedure (CV-technique) introduced by the authors into the routine investigation scheme of infertility is reported. The method detects the arginine-deficient type of pathospermia, thus contributing to the possibility of its selective correction.