Effects of genotype and environment on free amino acid levels in wheat grain: implications for acrylamide formation during processing

Acrylamide forms from free asparagine and reducing sugars during cooking, with asparagine concentration being the key parameter determining the formation in foods produced from wheat flour. In this study free amino acid concentrations were measured in the grain of varieties Spark and Rialto and four doubled haploid lines from a Spark x Rialto mapping population. The parental and doubled haploid lines had differing levels of total free amino acids and free asparagine in the grain, with one line consistently being lower than either parent for both of these factors. Sulfur deprivation led to huge increases in the concentrations of free asparagine and glutamine, and canonical variate analysis showed clear separation of the grain samples as a result of treatment (environment, E) and genotype (G) and provided evidence of G x E interactions. Low grain sulfur and high free asparagine concentration were closely associated with increased risk of acrylamide formation. G, E, and G x E effects were also evident in grain from six varieties of wheat grown at field locations around the United Kingdom in 2006 and 2007. The data indicate that progress in reducing the risk of acrylamide formation in processed wheat products could be made immediately through the selection and cultivation of low grain asparagme varieties and that further genetically driven improvements should be achievable. However, genotypes that are selected should also be tested under a range of environmental conditions.

Kinetic modeling of the generation of 2-and 3-methylbutanal in a heated extract of beef liver

Quantitative control of aroma generation during the Maillard reaction presents great scientific and industrial interest. Although there have been many studies conducted in simplified model systems, the results are difficult to apply to complex food systems, where the presence of other components can have a significant impact. In this work, an aqueous extract of defatted beef liver was chosen as a simplified food matrix for studying the kinetics of the Mallard reaction. Aliquots of the extract were heated under different time and temperature conditions and analyzed for sugars, amino acids, and methylbutanals, which are important Maillard-derived aroma compounds formed in cooked meat. Multiresponse kinetic modeling, based on a simplified mechanistic pathway, gave a good fit with the experimental data, but only when additional steps were introduced to take into account the interactions of glucose and glucose-derived intermediates with protein and other amino compounds. This emphasizes the significant role of the food matrix in controlling the Maillard reaction.

Expression and activities of cyclins and cyclin-dependent kinases in developing rat ventricular myocytes

The molecular mechanisms responsible for the alterations in proliferative capacity of cardiac myocytes during development remain unknown; however, cell cycle dependent molecules may be involved. We have determined the expression of cyclins A, D1–3and E, and cyclin-dependent kinases (CDKs) 2, 4, 5 and 6 and cdc2 in freshly isolated rat cardiac myocytes from fetal (18 days gestation), neonatal (2 days post-natal) and adult animals by immunoblotting. Our results show a dramatic decrease in expression of these proteins during normal cardiac development, such that levels are highest in fetal myocytes but are significantly down-regulated in adult cells (P<0.05, in each case). We also have determined thein vitrokinase activities of cdc2, CDK2, CDK4, CDK5 and CDK6 immunocomplexes in fetal, neonatal and adult myocytes. There was a consistent and significant loss of cdc2, CDK2, CDK4 and CDK6 kinase activities in adult cardiac cell lysates (5.3-, 10.6-, 1.5- and 1.9-fold decreases, respectively) when compared to neonatal samples (P<0.05); CDK5 activity showed a similar trend but failed to reach significance. In conclusion, our results show that the expression and activities of various positive regulators of the cell cycle are down-regulated significantly during development of the cardiac myocyte, concomitant with the loss of proliferative capacity in adult myocytes. Down-regulation of these proteins may be pivotal in the withdrawal of the cardiac myocyte from the cell cycle.