Field-expedient screening and injury risk algorithm categories as predictors of noncontact lower extremity injury.

In athletics, efficient screening tools are sought to curb the rising number of noncontact injuries and associated health care costs. The authors hypothesized that an injury prediction algorithm that incorporates movement screening performance, demographic information, and injury history can accurately categorize risk of noncontact lower extremity (LE) injury. One hundred eighty-three collegiate athletes were screened during the preseason. The test scores and demographic information were entered into an injury prediction algorithm that weighted the evidence-based risk factors. Athletes were then prospectively followed for noncontact LE injury. Subsequent analysis collapsed the groupings into two risk categories: Low (normal and slight) and High (moderate and substantial). Using these groups and noncontact LE injuries, relative risk (RR), sensitivity, specificity, and likelihood ratios were calculated. Forty-two subjects sustained a noncontact LE injury over the course of the study. Athletes identified as High Risk (n = 63) were at a greater risk of noncontact LE injury (27/63) during the season [RR: 3.4 95% confidence interval 2.0 to 6.0]. These results suggest that an injury prediction algorithm composed of performance on efficient, low-cost, field-ready tests can help identify individuals at elevated risk of noncontact LE injury.

A fluorometric, high-performance liquid chromatographic assay for transglutaminase activity.

A fluorometric, high-performance liquid chromatographic assay for transglutaminase activity is described. The method uses the small synthetic peptide benzyloxycarbonyl-L-glutaminylglycine and the fluorescent amine monodansylcadaverine as substrates. Very small amounts of substrates and enzyme are required for this assay. The reaction product is separated from substrates on a reversed-phase, C-18 column, using an isocratic elution solvent consisting of 50% methanol in water, and is detected fluorometrically with didansylcadaverine as standard. A detection limit of 31 pmol of product per injection was measured. An apparent Km of 34.7 +/- 2.4 mM was determined for the peptide substrate with purified guinea pig liver enzyme. Using this assay, a series of alkyl aldehydes was shown to inhibit transglutaminase. Modification of this assay using either gradient or isocratic elution with various proportions of acetonitrile (0.1% trifluoroacetic acid)/water (0.1% trifluoroacetic acid) afforded assays for a series of glutamine-containing peptides including substance P, alpha-endorphin, and two small, synthetic peptides. The assay is suitable for measurement of transglutaminase activity with purified enzyme or with crude preparations. This method provides a sensitive, quantitative assay for the determination of substrate and inhibitor properties of small peptides toward transglutaminases.

gamma-Glutamylamine cyclotransferase. An enzyme involved in the catabolism of epsilon-(gamma-glutamyl)lysine and other gamma-glutamylamines.

gamma-Glutamylamine cyclotransferase, an enzyme found in a number of animal tissues and cells, catalyzes the conversion of epsilon-(L-gamma-glutamyl)-L-lysine to free lysine and 5-oxo-L-proline as well as the release of free amines and the formation of 5-oxo-L-proline from a variety of other L-gamma-glutamylamines. Among its substrates are both the mon- and di-gamma-glutamyl derivatives of putrescine, spermidine and spermine, and a derivative of epsilon-(L-gamma-glutamyl)-L-lysine in which both the alpha-amino group and the carboxyl group of the lysine moiety are blocked. The enzyme does not act on most gamma-glutamyl-alpha-amino acids, nor is it active toward the epsilon-lysyl derivatives of L-aspartic acid or D-glutamic acid. Derivatives of epsilon-(L-gamma-glutamyl)-L-lysine in which the alpha-amino or the alpha-carboxyl function of the glutamyl moiety is blocked also do not serve as substrates. The specificity of gamma-glutamylamine cyclotransferase is in accordance with the proposal that it functions biologically in the latter stages of the catabolism of products of the action of transglutaminases. Some suggestions as to the manner in which gamma-glutamylamine cyclotransferase serves this function are made based on present knowledge of protein degradation.

Importance of the amino acid in position 15 of VIP and secretin in influencing their interactions with membrane receptors on pancreatic acinar cells.

To explore the importance of the charge of the amino acid in position 15 in influencing the apparent affinities of VIP and secretin for their receptors on pancreatic acinar cells, we tested the synthetic C-terminal 23-peptide fragment of secretin (S5-27) and two analogues containing substitutions in position 15 for their abilities to interact with secretin-preferring and VIP-preferring receptors on pancreatic acinar cells. In inhibiting the increase in cyclic AMP caused by VIP acting through the VIP-preferring receptors, 15-Lys-S5-27 was equipotent with 15-Asn-S5-27, and these analogues were significantly more potent than S5-27. In inhibiting the increase in cyclic AMP caused by secretin acting through the secretin-preferring receptors, S5-27 was equipotent with 15-Asn-S5-27, and these peptides were significantly more potent than 15-Lys-S5-27. These findings indicate that the affinities of these 23-peptides for the VIP-preferring receptors and for the secretin-preferring receptors were influenced primarily by the absence of a particular charge in position 15 but not by the presence of the opposite charge.

gamma-Glutamylamine cyclotransferase: specificity toward epsilon-(L-gamma-glutamyl)-L-lysine and related compounds.

gamma-Glutamylamine cyclotransferase, an enzyme that catalyzes the conversion of L-gamma-glutamylamines to free amines and 5-oxo-L-proline, was found in rabbit kidney and in various other tissues. The specificity of this enzyme indicates that it functions in the metabolism of products of transglutaminase action; among its substrates are epsilon-(L-gamma-glutamyl)-L-lysine, a derivative of this peptide in which the alpha-amino and carboxyl groups of the lysine moiety are blocked, and L-gamma-glutamyl-polyamine derivatives.

Pancreatic secretory activity of secretin5-27 and substituted analogues.

The effect of secretin5-27 and four substituted analogues (9 Gln-secretin5-27, 15-Asn-secretin5-27, 9-Gln-15-Asn-secretin5-27, and 15-Lys-secretin5-27) on pancreatic secretion in the rat and guinea pig was examined. Secretin5-27 retained significant pancreatic secretory activity in both species. Its efficacy (intrinsic activity) relative to secretin was much higher in the rat (0.2) than in the guinea pig (0.03). The activity of secretin5-27 was not affected by a single or dual substitution of carboxylic acid residues by the corresponding carboxamides or by lysine despite a substantial decrease in the helical character of the peptide.

The role of some polar amino acid residues in secretin.

Three analogues of S5-27, the tricosapeptide with the carboxyl-terminal sequence of secretin, were studied. In the analogues, the acidic residues at positions 9 and 15 of S5-27 were replaced by the neutral residues glutamine and asparagine. These changes resulted in a decrease in immunoreactivity. Binding to an antibody against secretin could be correlated with the changes in the conformation of the synthetic analogues.

Interaction of peptides related to secretin with hormone receptors on pancreatic acinar cells.

Three analogues of the carboxyl-terminal tricosapeptide of secretin (S5-27), one with glutamine replacing glutamic acid in position 9 (9-Gln-S5-27), a second with asparagine substituted for aspartic acid in position 15 (15-Asn-S5-27), and a third with both replacements (9-Gln-15-Asn-S5-27) were tested for their ability to interact with hormone receptors on dispersed pancreatic acinar cells. Each of these analogues inhibited binding of 125I-labeled vasoactive intestinal peptide (VIP). None of the analogues increased cellular cyclic AMP but each inhibited the increase in cellular cyclic AMP produced by secretin or VIP. At the high affinity VIP receptor (the low affinity secretin receptor) each analogue had an apparent affinity which was greater than that for S5-27, whereas at he low affinity VIP receptor (the high affinity secretin receptor), each of the analogues had an apparent affinity which was the same as that for S5-27. Thus, in S5-27, substituting glutamine in position 9 or asparagine in position 15 makes the fragment more VIP-like but not less secretin-like. These results also provide additional evidence that the receptor having a low affinity for secretin and a high affinity for VIP is functionally distinct from the receptor having a high affinity for secretin and a low affinity for VIP.

A re-examination of the conformation of secretin in water.

An examination of a series of peptides corresponding to partial sequences of secretin and the application of empirical conformational parameters to the sequence has reopened the question about the position of the short helical stretch in the folded chain. In earlier studies, this was tentatively placed near the N-terminus, while newly accumulated evidence points to the C-terminal area. The possible role of ion pairs in the stabilization of the folding was investigated by the preparation and examination of synthetic analogues of the C-terminal tricosapeptide part of secretin. The carboxyl groups of glutamic acid (in position 9) and of aspartic acid (in position 15) were replaced by carboxamides. The 9-glutamine and the 15-asparagine analogues show a significant decrease in helical character. This loss of "structure" is even more pronounced in the 9-glutamine-15-asparagine tricosapeptide. Thus, ion-pair formation is indeed implicated as one of the forces which stabilize the folded conformation of the chain. Possible correlations between biological activity and secretin-like architecture were studied on several smooth muscle preparations.