Sperm selection with density gradient centrifugation and swim up: effect on DNA fragmentation in viable spermatozoa.

Subjects increasing sperm DNA fragmentation (sDF) during Density Gradient Centrifugation (DGC), a common sperm selection procedure in Assisted Reproduction Techniques (ARTs), experience a 50% lower probability of pregnancy. Hence, identification of these subjects is of clinical importance. Here, we investigated whether such subjects are identified with higher accuracy detecting DNA fragmentation in viable (viable sDF) instead of total spermatozoa (total sDF) and whether swim up, an alternative procedure to DGC, does not increase sDF. With DGC, we identified 10/20 subjects increasing total sDF, and 2 more subjects using viable sDF. With swim up, we identified 8/40 subjects increasing total sDF, and 8 more subjects using viable sDF. In addition, viable sDF reveals more accurately the increase of the damage when it occurs. Finally, a multivariate analysis demonstrated that the proportional increase of sDF was higher after DGC respect to swim up. In conclusion, viable sDF is a more accurate parameter to reveal the increase of the damage by selection both with swim up and DGC. Swim up increases sDF in some samples, although at a lesser extent than DGC, suggesting that it should be used to select spermatozoa for ARTs when possible.

Exo-enzymatic activities and dissolved organic pools in relation with mucilage development in the Northern Adriatic Sea.

We tested the hypothesis that the appearance of mucilage in the Northern Adriatic Sea was related with the accumulation of dissolved organic compounds released by intensive enzymatic activities and not utilized as direct substrate for microbial growth. To do this enzymatic activities and dissolved organic and inorganic pools in periods characterized by the presence of mucilage and in the same seasons but in absence of mucilage were compared. Extracellular enzymatic activities (aminopeptidase, beta-glucosidase and alkaline phosphatase), nutrient pool concentrations (total dissolved nitrogen, dissolved organic nitrogen, total dissolved phosphorus, dissolved organic phosphorus) and the biochemical composition of particulate and dissolved organic matter (in terms of proteins and carbohydrates) were determined on a monthly basis over a period of 3 years. Aminopeptidase and alkaline phosphatase activities displayed higher values in springs preceding the appearance of mucilage than in spring when no mucilage was observed. Beta-Glucosidase activity showed significantly higher values in summer periods characterized by the massive production of mucilage than in summers without mucilage events. The months preceding mucilage events were also characterized by an increase of the alkaline phosphatase to aminopeptidase activity ratio and by a significant accumulation of dissolved proteins. These findings, together with the significant increase of the DON/DOP ratio, suggest that mucilage formation is favoured by the deficiency of organic P. The present study provides compelling evidences that mucilage formation is favoured by the unbalance between organic matter mobilization by enzymatic activities and the accumulation of labile dissolved organic-N compounds.