Stephanie A. Collins

Prospects of enhancing dietary zinc bioavailability with food-derived zinc-chelating peptides.

Zinc is an essential micronutrient that strongly influences human health and nutrition through its involvement in several biological processes. Zinc functions as structural and functional component of many transcription factors and enzymes that regulate cell growth, gene expression, and immune response, and its deficiency can lead to retarded growth and impaired immune functions. The physiological functions of zinc are dependent on its bioavailability in tissues, which in turn depends on intestinal absorption of dietary zinc. The presence of dietary fibre and phytates impedes intestinal zinc absorption, as they can form insoluble complexes with zinc, decreasing its bioavailability. Peptides derived from food proteins can enhance zinc absorption and bioavailability. Peptides that contain amino acid residues such as cysteine, histidine, serine, aspartate and glutamate can chelate divalent metals, including zinc, forming soluble metal coordinate complexes. The structure-function relationship of zinc-chelating peptides and the stability of the peptide-metal complexes to gastrointestinal digestion are critical to their relevance in human nutrition and health promotion.

The Development of Gaze Following in a Third-Party Context

Infants follow the gaze of an individual with whom they are directly interacting by the end of the first year. By 18 months infants are capable of learning novel words in observational (or third-party) contexts (Floor & Akhtar, 2006). To examine third-party gaze following in 12- and 18-month-olds, the parent and experimenter engaged in a conversation while the infant was present. For 8 trials approximately every 30 sec the experimenter would turn her head to the right or left to fixate on a toy placed on either side of the room with the parent following suit. In the first experiment, the parent was seated next to the infant and the experimenter opposite, whereas in the second experiment the positions of the adults were switched. In Experiment 1, 18-month-olds but not 12-month-olds followed gaze. In Experiment 2, 12-month-olds acquired a tendency to follow gaze during the experimental session. These results suggest that an incipient ability to follow third-party gaze is present by 12 months and that infants acquire a more reliable and general ability to follow the gaze of noninteractive others between 12 and 18 months.