Several small (<25aa) peptides have been designed based on the sequence of the dentin phosphoprotein, one of the major noncollagenous proteins thought to be involved in the mineralization of the dentin extracellular matrix during tooth development. These peptides, consisting of multiple repeats of the tripeptide aspartate-serine-serine (DSS), bind with high affinity to calcium phosphate compounds and, when immobilized, can recruit calcium phosphate to peptide-derivatized polystyrene beads or to demineralized human dentin surfaces. The affinity of binding to hydroxyapatite surfaces increases with the number of (DSS)n repeats, and though similar repeated sequences—(NTT)n, (DTT)n, (ETT)n, (NSS)n, (ESS)n, (DAA)n, (ASS)n, and (NAA)n—also showed HA binding activity, it was generally not at the same level as the natural sequence. Binding of the (DSS)n peptides to sectioned human teeth was shown to be tissue-specific, with high levels of binding to the mantle dentin, lower levels of binding to the circumpulpal dentin, and little or no binding to healthy enamel. Phosphorylation of the serines of these peptides was found to affect the avidity, but not the affinity, of binding. The potential utility of these peptides in the detection of carious lesions, the delivery of therapeutic compounds to mineralized tissues, and the modulation of remineralization is discussed.

In spite of differing mechanisms of injury, the PHI group's discourse performance was consistent with what has been reported for individuals with CHI. The model tested represents a preliminary step toward understanding discourse production following traumatic brain injury.

Background: Story grammar is a super-structural measure of discourse performance that has shown to be sensitive to the deficits seen following traumatic brain injury (TBI). Narrative organisation and identification of logical relationships between events and characters are key components of story grammar. Reports of significant correlations for measures of story grammar and scores from various tests of executive functioning for individuals with TBI are thought to reflect executive control of cognitive and linguistic organisational processes. Aims: The purpose of the present study was to re-examine the relationship between story grammar and executive functions (EF) in a large group of participants with severe TBI secondary to diverse penetrating head wounds. It was hypothesised that participants with TBI would have significantly lower story grammar scores than a comparison group without TBI, and that story grammar performance of the group with TBI would be significantly correlated with their EF scores. Methods & Procedures:A total of 167 participants with TBI and a comparison group of 46 adults without TBI were asked to retell a 16-frame story. Transcripts of each story retelling were broken into T-units and were analysed for story grammar. Outcomes & Results: Results of MANOVA showed significant effect of group on the discourse measures. Univariate tests showed significant differences between the group with TBI and the comparison group for each of the story grammar measures. Story grammar measures were significantly correlated with executive function (EF) scores. Conclusions: Results indicated that the participants with TBI demonstrated significantly poorer performance on measures of story grammar abilities, lending support to earlier reports of story grammar impairments resulting from closed head injury (CHI). The present study also found significant correlations for measures of story grammar and the Sorting Test. Cognitive skills such as mental flexibility, required for successful performance on this card sorting task are likely the same as those required for episode generation. These findings have clinical implications for the management of cognitive-communication disorders in individuals with TBI. First, story grammar warrants inclusion in analyses of discourse. Second, discourse deficits following brain injury do not resolve spontaneously and persist as social barriers.

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