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Biomedical subjects

David Schultz

Publications and source records attributed to David Schultz.

12 recordsLinked to original sources
PubMed2006

Strategies for data collection and calibration with a pinhole-geometry SAXS instrument on a synchrotron beamline.

Undulator X-ray sources on third-generation synchrotrons have pushed small-angle X-ray scattering (SAXS) to the forefront of techniques in nanoscience and technology. With higher X-ray fluxes and improved focusing, it is usually the scattered intensity detector that places the most serious limitations on the overall capabilities of the instrument. Incorporating relatively simple components like point detectors, scattering standards, masking filters and in-line sample visualization into the flight tube of a pinhole-geometry SAXS camera can do much to mitigate these limitations. How these enhancements can be incorporated into routine data collection is demonstrated on the ChemMatCARS SAXS instrument, which utilizes pinhole geometry with an undulator insertion device at sector 15 of the Advanced Photon Source. In addition, with an X-ray energy range of 6-32 keV (2.0-0.4 A) and an energy resolution of 10(-4) DeltaE/E, this instrument can measure anomalous SAXS over a wide variety of atom species, with reliable normalization of scattered data.

Calibration↗
PubMed2006

Designing multistep transformations using the Hammett equation: imine exchange on a copper(I) template.

Herein, we quantify how imine exchange may be used to selectively transform one metallo-organic structure into another. A series of imine exchange reactions were studied, involving a set of 4-substituted anilines, their 2-pyridylimines and 1,10-phenanthrolyl-2,9-diimines, as well as the copper complexes of these imine ligands. Electron-rich anilines were found to displace electron-poor anilines in all cases. Linear free energy relationships (LFERs) were discovered connecting the electron-donating or -withdrawing character of the 4-substituent of an aniline, as measured by the Hammett sigma(para) parameter, to that aniline's ability to compete with unsubstituted aniline to form imines. The quality of these LFERs allowed for quantitative predictions: to obtain the desired degree of selectivity in an imine exchange between anilines A and B, the required sigma(para) differential could be predicted using a variant of the Hammett equation, log(K(AB)) = rho(sigma(A) - sigma(B)). We validated this methodology by designing and executing a three-step transformation of a series of copper(I)-containing structures. Each step proceeded in predictably high yield, as calculated from sigma differentials. At each step in the series of transformations, macrocyclic structures could be created or destroyed through the selection of mono- or di-amines as subcomponents. The same methodology could be used to predict the formation of a diverse dynamic library of helicates from a set of four aniline precursors, as well as the collapse of this library into one helicate upon the addition of a fifth aniline.

Journal Article↗
PubMed2006

Effective retention of primary survey skills by medical students after participation in an expanded Trauma Evaluation and Management course.

BACKGROUND: The Trauma Evaluation and Management (TEAM) module orients medical students to the initial assessment of an injured patient. At the Medical College of Wisconsin, a course based on expanded TEAM (eTEAM) was developed for junior medical students. This study determined whether eTEAM improved the ability to perform and retain primary survey skills. METHODS: Objective Structured Clinical Examination methodology was used to compare 2 groups of senior medical students 1 year after receiving either a 2-hour lecture or eTEAM. RESULTS: Students receiving eTEAM performed the primary survey much better than those receiving lecture alone. The overall Objective Structured Clinical Examination scores did not differ between groups. CONCLUSIONS: Medical students participating in eTEAM retained the ability to perform a primary survey in proper sequence 1 year later better than students receiving the information in lecture format only.

Curriculum↗
PubMed2005

Spatially and temporally controlled biomineralization is facilitated by interaction between self-assembled dentin matrix protein 1 and calcium phosphate nuclei in solution.

Bone and dentin biomineralization are well-regulated processes mediated by extracellular matrix proteins. It is widely believed that specific matrix proteins in these tissues modulate nucleation of apatite nanoparticles and their growth into micrometer-sized crystals via molecular recognition at the protein-mineral interface. However, this assumption has been supported only circumstantially, and the exact mechanism remains unknown. Dentin matrix protein 1 (DMP1) is an acidic matrix protein, present in the mineralized matrix of bone and dentin. In this study, we have demonstrated using synchrotron small-angle X-ray scattering that DMP1 in solution can undergo oligomerization and temporarily stabilize the newly formed calcium phosphate nanoparticle precursors by sequestering them and preventing their further aggregation and precipitation. The solution structure represents the first low-resolution structural information for DMP1. Atomic force microscopy and transmission electron microscopy studies further confirmed that the nascent calcium phosphate nuclei formed in solution were assembled into ordered protein-mineral complexes with the aid of oligomerized DMP1, recombinant and native. This study reveals a novel mechanism by which DMP1 might facilitate initiation of mineral nucleation at specific sites during bone and dentin mineralization and prevent spontaneous calcium phosphate precipitation in areas in which mineralization is not desirable.

Calcification, Physiologic↗
PubMed2005

Dynamic covalent and supramolecular direction of the synthesis and reassembly of copper(I) complexes.

The technique of subcomponent self-assembly has been applied to the preparation of a set of copper(I) complexes from diamines and aldehydes in aqueous solution. These complexes may be synthesized alongside one another in solution despite the chemical non-orthogonality of their respective starting materials; thermodynamic equilibration eliminates all mixed products. The reactivity of these complexes has been studied, revealing that in certain cases, the substitution of both ligands and ligand subcomponents could be independently carried out. In one particular case, a complex was shown to be inert to ligand substitution but readily underwent ligand subcomponent substitution, creating the possibility of a previously undocumented kind of cascade reaction: Once ligand subcomponent substitution had occurred, ligand exchange could then happen, allowing both reactions to be triggered by a single chemical event.

Copper↗
PubMed2005

Phosphorylation of phosphophoryn is crucial for its function as a mediator of biomineralization.

Phosphoproteins of the organic matrix of bone and dentin have been implicated as regulators of the nucleation and growth of the inorganic Ca-P crystals of vertebrate bones and teeth. One such protein identified in the dentin matrix is phosphophoryn (PP). It is highly acidic in nature because of a high content of aspartic acid and phosphate groups on serines. The 244-residue carboxyl-terminal domain of rat PP, predominantly containing the aspartic acid-serine repeats, has been cloned, and the corresponding protein has been expressed recombinantly in Escherichia coli. This portion of PP, named DMP2 (dentin matrix protein 2), is not phosphorylated by the bacteria and thus provided a means to study the function of the phosphate groups, the major post-translational modification of native PP. The recombinant DMP2 (rDMP2) possessed much lower calcium binding capacity than native PP. Small angle x-ray scattering experiments demonstrated that PP folds to a compact globular structure upon calcium binding, whereas rDMP2 maintained an unfolded structure. In vitro nucleation experiments showed that PP could nucleate plate-like apatite crystals in pseudophysiological buffer, whereas rDMP2 failed to mediate the transformation of amorphous calcium phosphate to apatite crystals under the same experimental conditions. Collagen binding experiments demonstrated that PP favors the formation of collagen aggregates, whereas in the presence of rDMP2 thin fibrils are formed. Overall these results suggested that the phosphate moieties in phosphophoryn are important for its function as a mediator of dentin biomineralization.

Amino Acid Sequence↗
PubMed2004

Selection rules for helicate ligand component self-assembly: steric, pH, charge, and solvent effects.

The reaction between 1,10-phenanthroline-2,9-dicarboxaldehyde, copper(I), and certain primary amines was found to give quantitatively a dicopper double-helicate product (two of which were crystallographically characterized) by imine self-assembly around Cu(I) templates. The parameters of this reaction were investigated, and important roles were found to be played by (i) the steric bulk of the amine, (ii) the charge of the amine, (iii) the solvent used, and (iv) the pH of the solution. Water was found to allow the broadest range of structures to form, and ligand-component exchange reactions (involving the substitution of an aromatic for an aliphatic amine) were demonstrated to proceed readily in this solvent.

Journal Article↗
PubMed2004

Children's emotion processing: relations to emotionality and aggression.

We examined the relations between emotionality, emotion processing, and aggression in 182 first- and second-grade children. Consistent with Tomkins' and Izard's theoretical predictions, emotionality correlated with emotion processing. In particular, the happiness component of emotionality correlated with emotion attribution accuracy and empathy, the anger component correlated with anger attribution bias and empathy, and the fear component correlated with fear attribution bias. Multiple emotion processing deficits--including emotion attribution accuracy, anger attribution bias, and self-report of empathy--placed children at risk for heightened levels of teacher-reported aggression. Mediational analyses revealed that an emotion processing risk index fit a model of significant partial mediation between happiness and aggression but not between anger and aggression. The results suggest the multifaceted manner in which children's emotion experiences may influence the development of aggressive tendencies.

Aggression↗
PubMed2002

Downregulation of ANG II receptor is associated with compensated pressure-overload hypertrophy in the young dog.

We studied the gradual onset of pressure overload (PO) induced by a mildly constricting aortic band in 8-wk-old puppies (n = 8) that increased to 98 +/- 11 mmHg at 9 mo. Left ventricular (LV) weight/body weight was increased in PO versus sham-operated littermate controls [8.11 +/- 0.60 (SE) vs. 4.46 +/- 0.38 g/kg, P < 0.001]. LV end-diastolic diameter, diastolic pressure, and fractional shortening did not differ in PO versus control dogs. There were no inducible arrhythmias in response to an aggressive electrophysiological stimulation protocol in PO dogs. Furthermore, isolated cardiomyocyte function did not differ between control and PO dogs. LV angiotensin II (ANG II) levels were increased (68 +/- 12 vs. 20 +/- 5 pg/g, P < 0.01) as steady-state ANG II type 1 (AT(1)) receptor mRNA was decreased 40% and endothelial nitric oxide synthase mRNA levels were increased 2.5-fold in PO versus control dogs (P < 0.05). Total ANG II receptor binding sites of freshly prepared cardiac membranes demonstrated no difference in the dissociation constant, but there was a 60% decrease in maximum binding (B(max)) in PO versus control dogs (P < 0.01). LV ANG II levels correlated negatively with AT(1) receptor mRNA levels (r = -0.75, P < 0.01) and total AT(1) receptor B(max) (r = -0.77, P < 0.02). These results suggest that LV ANG II negatively regulates AT(1) receptor expression and that this is an adaptive response to chronic PO before the onset of myocardial failure in the young dog.

Adaptation, Physiological↗
PubMed2002

Teaching clinical skills in musculoskeletal medicine: the use of structured clinical instruction modules.

OBJECTIVE: To assess student evaluation, satisfaction, and examination outcomes for a new method of teaching musculoskeletal (MSK) medicine clinical skills, structured clinical instruction modules (SCIM), and to compare with the outcomes of a traditional method of teaching clinical skills (small group bedside tutorials). METHODS: Year 2 students in a 4 year graduate medical school were taught using the method of bedside senior registrar teaching, supplemented by outpatient attendances in 1997 and by SCIM in 2000. All students in 1997 and 2000 were debriefed at the end of each unit of clinical skills teaching for student feedback on their teaching experience using a standardized questionnaire. At the end of the academic year, all students underwent an objective structured clinical examination (OSCE) in clinical skills that included rheumatology (hand examination) and orthopedic surgery (knee examination) stations. The effect of the method of teaching on the students' performance in the rheumatology (hand) and orthopedic surgery (knee) stations was analyzed. RESULTS: Sixty-seven students were taught clinical skills and completed the OSCE in 1997 and 78 students were taught clinical skills by SCIM and completed the OSCE in 2000. The teaching of orthopedics using traditional methods was poor, but there was no difference in satisfaction between traditional methods of teaching and SCIM for orthopedic surgery and rheumatology. There was no statistically significant difference in the performance of students in the hand OSCE stations in 2000 compared to the same station in 1997. There was a small but statistically significant difference in the performance of students in 1997 and 2000 in the knee station, the 1997 students performing better in this station. CONCLUSION: The SCIM is an effective method of teaching clinical skills in MSK medicine, comparable with patient partners and traditional registrar based bedside teaching methods, but it is less resource intensive.

Clinical Competence↗