PubMed Health⌕ Search

Biomedical subjects

L Klapper

Publications and source records attributed to L Klapper.

14 recordsLinked to original sources
PubMed1996

Diversification of Neu differentiation factor and epidermal growth factor signaling by combinatorial receptor interactions.

The ErbB family includes two receptors, ErbB-1 and ErbB-3, that respectively bind to epidermal growth factor and Neu differentiation factor, and an orphan receptor, ErbB-2. Unlike ErbB-1 and ErbB-2, the intrinsic tyrosine kinase of ErbB-3 is catalytically impaired. By using interleukin-3-dependent cells that ectopically express the three ErbB proteins or their combinations, we found that ErbB-3 is devoid of any biological activity but both ErbB-1 and ErbB-2 can reconstitute its extremely potent mitogenic activity. Transactivation of ErbB-3 correlates with heterodimer formation and is reflected in receptor phosphorylation and the transregulation of ligand affinity. Inter-receptor interactions enable graded proliferative and survival signals: heterodimers are more potent than homodimers, and ErbB-3-containing complexes, especially the ErbB-2/ErbB-3 heterodimer, are more active than ErbB-1 complexes. Nevertheless, ErbB-1 signaling displays dominance over ErbB-3 when the two receptors are coexpressed. Although all receptor combinations activate the mitogen-activated protein kinases ERK and c-Jun kinase, they differ in their rate of endocytosis and in coupling to intervening signaling proteins. It is conceivable that combinatorial receptor interactions diversify signal transduction and confer double regulation, in cis and in trans, of the superior mitogenic activity of the kinase-defective ErbB-3.

Animals↗
PubMed1996

Thrombin stimulates atrial natriuretic peptide secretion from rat cardiac atrium.

Atrial natriuretic peptide (ANP) is a hormone secreted predominantly by atrial myocytes. Although atrial distension is the primary stimulus of ANP secretion, several hormones have also been implicated in the regulation of ANP secretion. alpha-Thrombin, a serine protease participating in the blood coagulation system, has additional hormone-like effects in several cell types, apparently via interaction with specific cell surface receptors. Here we report that alpha-thrombin enhanced ANP secretion from isolated rat atrium within 10 min, in a concentration-dependent manner. The protease also significantly increased ANP release from cultured atrial myocytes, in a concentration-dependent manner. The alpha-thrombin-induced release of ANP from cultured atrial myocytes was completely abolished by hirudin, a specific alpha-thrombin protease inhibitor. Furthermore, synthetic peptides, identical in their amino acid sequence to the N-terminal segment of the proteolytically cleaved thrombin receptor, enhanced ANP release from adult rat cultured atrial myocytes. Our data suggest that thrombin may regulate ANP release from the cardiac atrium. This action involves activation of thrombin receptors in atrial myocytes.

Animals↗
PubMed1992

Variations in bracket placement in the preadjusted orthodontic appliance.

This study was conducted to determine the accuracy of bracket placement with the direct bonded technique. Ten orthodontic faculty members bonded a preadjusted orthodontic appliance on models of five cases of malocclusion in a simulated clinical situation (mannequin). A total of 50 sets of models served as the population of the study. Photographs of the models were measured to determine vertical and angular discrepancies in position between adjacent bracket pairs from a constructed reference line. Variations are evaluated with respect to the classification of malocclusion, specific tooth type, and intra/inter operator differences. A mean of 0.34 mm for the vertical discrepancies and a mean of 5.54 degrees for the angular discrepancies are found in placement of the orthodontic brackets.

Analysis of Variance↗
PubMed1992

The influence of extraction and nonextraction orthodontic treatment on brachyfacial and dolichofacial growth patterns.

The effects of extraction and nonextraction orthodontic treatment mechanics on patients with dolichofacial and brachyfacial growth patterns between one and two standard deviations were studied. Groups underwent treatment of either nonextraction or extraction of four premolars with the appropriate mechanics for the facial type. Changes in the facial axis and correlation between maxillary molar movement and facial axis change were measured. A positive correlation was found between the amount of anteroposterior movement of the upper molar and change in the facial axis in brachyfacial and dolichofacial patients undergoing nonextraction treatment. A weak correlation was found in the extraction treatment groups. No statistically significant difference was found in the facial axis change among any of the groups studied, regardless of facial type or plan of treatment. There were indications of a more severe opening of the facial axis (Ba-Na plane to constructed gnathion) with greater degrees of maxillary molar distal movement in both facial patterns studied.

Adolescent↗
PubMed1989

A cephalometric study of Korean adults.

A cephalometric study of 18-year-old Korean subjects with acceptable profile and occlusion was carried out by means of the Downs, Steiner, Ricketts, and vertical analyses. The subjects in the study sample consisted of 35 men and 45 women. Means and standard deviations of the Korean subjects were established. Statistical analyses were performed to compare Koreans to Caucasians.

Adolescent↗
PubMed1988

Expansion of the lower arch concurrent with rapid maxillary expansion.

The effect of rapid maxillary expansion on the mandibular intercanine and intermolar widths during treatment and its stability after retention was studied. In addition, the relationships between the interarch change and the facial types and ages of the subjects of the sample were evaluated. The sample consisted of 17 cases for the study of intercanine width, and 22 nonextraction cases for the study of the intermolar width. Initial, final, at least 2-years postretention models, and initial lateral cephalograms were analyzed. Treatment and postretention changes for the intercanine width and the mesial and distal intermolar widths were calculated and tested for significance. Mean expansions of the intercanine width of 1.1 mm and of the intermolar width of 2.8 mm postretention were found to be statistically significant. There were no correlations found between the amount of increase in arch width and the facial types and ages of the subjects.

Adolescent↗
PubMed1984

Force measurement and design of a torquing high-pull headgear.

The dynamic extraoral force analyzer (DEFA) was found to be capable of measuring linear deflection as a function of force created by a headgear. Ten standard nontorqued face-bows with a cervical and a high-pull direction were tested to determine the reliability of the DEFA. Statistical analysis showed the DEFA to be reliable and accurate in differentiating various directions and deflections of maxillary molars. Doubled-over distal ends of the inner bow with 0 degree of torque and a parietal direction of pull were used as controls. The same face-bows with 9 degrees of buccal root torque were tested on the DEFA. These face-bows were tested to determine whether transverse translation without buccal crown tipping of the maxillary first molar will occur. Statistical analysis showed that transverse translation occurred at a force of 200 to 347 gm.

Dental Stress Analysis↗
PubMed1982

Rotation of rectangular wire in rectangular molar tubes. Part II. Pretorqued molar tubes.

Buccal tubes from five manufactures producing the new generation of preadjusted (straight wire type) appliances were tested to determine the amount of rotation various-sized rectangular wires produced prior to binding within the tube. This rotation reflected the amount of torquing force dissipated because of the interaction of the wires and tube. In addition, it indicated the degree of compensatory third-order bends needed in the wire to deliver the desired torque force to the tooth. Wire and tube dimensions were measured and compared to manufacturers' stated specifications. The amount of rotation for each manufacturer's tube was compared to the theoretical values based on calculations. Theoretical calculations and published charts of deflection angles based on these calculations give a false impression in that they do not revealed a true expression of the amount of torque dissipated through rotation of the rectangular wire in that tube. There is variation between the manufacturer's stated lumen dimension and the actual lumen size, even beyond the manufacturer's stated tolerances. Rectangular wire will rotate within a rectangular buccal tube to varying degrees, depending upon the size of the wire used and the manufacturer of the appliance. This means that additional torsion or angulation may need to be placed in the wire prior to application intraorally. The amount of this additional torquing of the arch wire will depend upon the manufacturer of the appliance used and will vary from tube to tube of the same manufacturer.

Equipment Design↗
PubMed1981

Rotation of rectangular wire in rectangular molar tubes. Part I.

The degree of angular rotation of rectangular orthodontic wires in rectangular molar tubes was measured using a rotatable mechanical stage on a Unitron metallograph and compared to theoretical data. It was found that square 0.016 inch wire did not bind in 0.018 by 0.022 inch or larger mandrel- or inconel-formed tubes, whereas rotations of 11 to 23 degrees were noted in cast tubes of this dimension. Although 0.016 by 0.022 inch wire did bind in these tubes, the degree of rotation was far greater than expected on the basis of theoretical calculations or clinical expectations. The results indicated that it was unrealistic to expect fine control of a few degrees of torque to occur as expected for delicate clinical control.

Dental Equipment↗