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M E Boyer

Publications and source records attributed to M E Boyer.

5 recordsLinked to original sources
PubMed1992

Knowledge, concepts, and inferences in childhood.

The role of knowledge in children's inferences was investigated in 3 experiments. Experiment 1 examined developmental changes in the role of categorical membership, perceptual appearance, and item complexity in inferences for natural kind and artifact concepts. Preschoolers (5-year-olds), second graders (8-year-olds), and fourth graders (10-year-olds) were taught novel properties about target concepts and asked whether each of 4 probes had those properties. Probes varied in category membership and perceptual appearance relative to the target item. Item complexity also varied. Experiments 2 and 3 examined inferences with known and unknown concepts for familiar and unfamiliar properties. Older children's knowledge led to differential weighting of categorical information over appearance but only for known concepts and/or familiar properties. Preschoolers made no distinction between category and appearance for either known or unknown concepts. Additionally, as target item complexity increased, older children made more inferences than preschoolers. No differences between inferences about natural kind and artifact concepts were found. The role of theories and knowledge in children's drawing of inferences is discussed.

Attention↗
PubMed1988

Minimal ligand analysis of gastrin releasing peptide. Receptor binding and mitogenesis.

Gastrin releasing peptide (GRP) is a peptide hormone containing 27 amino acids which is structurally analogous to the amphibian peptide bombesin. GRP serves a variety of physiological functions and has been implicated in the pathophysiology of small cell lung cancer. Previous work has demonstrated that the modified C terminus of GRP, N-acetyl-GRP-20-27, exerts full agonist activity in a variety of assay systems. However, no systematic comparison of binding of GRP fragments to its receptor and mitogenic potency has been reported. To investigate whether smaller GRP fragments could bind to the GRP receptor without stimulating mitogenesis, we performed binding inhibition and thymidine uptake assays with Swiss 3T3 fibroblasts. These studies were facilitated by the development of a novel tritiated GRP-based radioligand, [3H-Phe15] GRP-15-27, which exhibits enhanced chemical stability compared to iodinated GRP derivatives. We examined a series of C-terminal GRP fragments, from the pentapeptide to the octapeptide, with both N-acetyl and free amine moieties at the N terminus. N-Acetylated derivatives were more potent than their primary amine counterparts in both assays. Deletion of N-terminal residues from GRP-20-27 resulted in significant loss of potency in both assays: the EC50 values of N-acetyl-GRP-21-27 were 10(2)-fold higher than N-acetyl-GRP-20-27, those of N-acetyl-GRP-22-27 were 10(4)-fold higher, and N-acetyl-GRP-23-27 showed minimal activity at concentrations below 100 microM. These results suggest that 1) both His20 and Trp21 play an important role in binding of GRP to the receptor, and 2) for this series of N-terminal deletions, binding to the receptor and mitogenic activity are tightly coupled.

Amino Acid Sequence↗