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The quality of fish gametes, both male and female, are determined by several factors (age, management, feeding, chemical and physical factors, water quality, etc.) that have an impact on the survivability of embryos, larvae and/or fry in the short or long term. One of the most important factors is gamete ageing, especially for those species that are unable to spawn naturally in hatcheries. The chemical and physical factors in hatcheries and the nutrition that they provide can significantly alter harvest quality, especially from females; as a rule, males are more tolerant of stress conditions produced by inadequate feeding, management and/or poor water conditions. The stress produced on broodstock by inadequate conditions in hatcheries can produce adverse effects on gamete quality, survival rates, and the embryonic eggs after hatching.

Covalent attachment of therapeutic proteins to polyethylene glycol (PEG) is widely used for the improvement of its pharmacokinetic and pharmacological properties, as well as the reduction in reactogenicity and related side effects. This technique named PEGylation has been successfully employed in several approved drugs to treat various diseases, even cancer. Some methods have been developed to obtain PEGylated proteins, both in multiple protein sites or in a selected amino acid residue. This review focuses mainly on traditional and novel examples of chemical and enzymatic methods for site-selective PEGylation, emphasizing in N-terminal PEGylation, that make it possible to obtain products with a high degree of homogeneity and preserve bioactivity. In addition, the main assay methods that can be applied for the characterization of PEGylated molecules in complex biological samples are also summarized in this paper.

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This work evaluated the incorporation of dimethyl sulphoxide (DMSO) into the medium used for storing rainbow trout semen at 4°C for 13 days. The treatments used were: fresh semen as control (C); semen stored without dilution (T1); semen diluted in saline solution (0.2% KCl and 0.7% NaCl) (T2); T2 + DMSO 1% (T3); T2 + DMSO 2.5% (T4) and T2 + DMSO 5% (T5). Sperm motility (level and duration) and fertility were evaluated in all the treatments. The results show that at day 3, all the treatments maintained level 3 motility. After 5 days in storage, only T4 and T5 fell to level 2 motility. The maximum duration of flagellar activity was in T3 with 70.0 AE 2.14 s, and the minimum in T4 with 51.73 AE 0.29 s. At day 7, the fertility of T3 and T4 was maintained with no statistically significant differences from T2 (96.6 AE 2.5%), however, the fertility of T5 was 53.2 AE 11.8%. At day 13 the fertility of T3, the only treatment which remained fertile, was 68.8 AE 5.09%. The results show that the sperm fertility of semen stored with a low concentration of 1% DMSO is prolonged significantly.