Functionality of glycomacropeptide glycated with lactose and maltodextrin.

The Maillard reaction (MR), under proper environmental conditions, has been used to improve protein functionality. In the present work, 2 high temperatures (50-80°C) and water activity (Aw; 0.45-0.67) were used to promote exogenous glycosylation of glycomacropeptide (GMP) while minimizing processing times (0, 8, 24, 48, and 96 h at 50°C; 0, 2, 4, 8, and 24 h at 80°C). Maltodextrin, a polysaccharide commonly used in the food industry as a functional ingredient, was used as a reducing sugar, and compared with lactose, a native milk sugar. The progression of MR was evaluated by tracking changes in molecular weight using SDS-PAGE, the formation of Amadori compounds, and browning. Aqueous glycosylated GMP solutions (5 to 20% wt/vol) were tested for solubility, rheological properties, and foam formation. As expected, MR progression was faster with Aw = 0.67 and 80°C. Glycosylated GMP powders showed no change in their solubility after MR. However, the apparent viscosity (γ˙=30s-1) of the 20% wt/vol suspensions exhibited a slight increase when GMP was glycosylated with maltodextrin for 24 h at 80°C, and a 2-log increase when GMP was glycosylated with lactose, with a high browning development in both cases. The foam expansion index of the resuspended glycosylated powders was increased by between 25 and 66% compared with the nonglycosylated powders. Better foam stability (approximately 2 h) and no browning development were observed for GMP glycosylated with maltodextrin for 2 h at Aw = 0.67 and 80°C. The results show that GMP has undergone further glycosylation by means of controlled MR, which improves viscosity and foaming index without negatively affecting solubility. These preliminary studies provide a basis for the future creation of a new ingredient with GMP and reducing sugars.

Expression of dmrt1 and sox9 during gonadal development in the Siberian sturgeon (Acipenser baerii).

The sex differentiation period of the Siberian sturgeon was investigated through expression profiling of two testicular markers (dmrt1 and sox9). At the molecular level, a clear sexual dimorphism of dmrt1 and sox9 was observed in 3-year-old fish with immature gonads, in which males showed higher expression of these genes. Among 16-month-old sturgeons cultured in Uruguay, gonad morphology analyses showed one group of fish with undifferentiated gonads and a second group which had started their histological differentiation into ovaries or testes. dmrt1 showed a significantly higher expression in testes of recently differentiated fish, but this was not the case for sox9. In undifferentiated fish, we observed two clearly different groups in terms of expression: one group of fish over-expressing male markers (dmrt1, sox9) and another group of fish showing very low expression of these genes. This suggests that fish undergoing male differentiation can be identified by their profiles of gene expression before they undergo morphological differentiation.

Expression and phylogeny of candidate genes for sex differentiation in a primitive fish species, the Siberian sturgeon, Acipenser baerii.

The molecular mechanisms underlying testis differentiation in basal actinopterygian fish remains poorly understood. The sex differentiation period was investigated in the Siberian sturgeon, Acipenser baerii, by expression profiling of Sertoli cell transcription factors (dmrt1, sox9) that control testis differentiation in vertebrates; Leydig cell factors (cyp17a1, star) affecting androgen production; the androgen receptor (ar); a growth factor controlling testis development (igf1); and a gene coding for a gonadotropin hormone (lh). Two genes were characterised for the first time in the Siberian sturgeon (dmrt1, cyp17a1), while the others came from public databases. Sturgeon gonad development is very slow, with a late sexual differentiation time during their juvenile stage, and are still immature at 3 years of age. Immature fish showed a sex-dimorphic pattern; all the genes studied displayed a higher expression level in male gonads. We took advantage of the presence of juvenile fish with pre- and post-differentiated gonads (16 and 18 months old) to characterise them at the molecular level. The post-differentiated fish displayed a sex dimorphism of gene expression in their gonads for all genes studied, with the exception of sox9. The trends in undifferentiated fish lead us to propose that sturgeons undergoing male differentiation express high levels of Sertoli cell factors (dmrt1, sox9) and of genes involved in the production and receptivity of androgens (cyp17a1, star and ar) together with lh. Expression profiles and phylogenetic studies suggest that these genes are potential regulators of testis development in the Siberian sturgeon.