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Biomedical subjects

S D Campbell

Publications and source records attributed to S D Campbell.

At least 19 recordsLinked to original sources
PubMed2001

Surgeons and injury prevention: what you don't know can hurt you!

BACKGROUND: The most effective treatment for traumatic injuries is to prevent them from occurring. Currently, few surgeons receive any formal training in injury' control and prevention. This study was designed to test the knowledge of injury prevention principles among practicing surgeons, in order to identify areas in need of intensified educational efforts. STUDY DESIGN: Survey questions designed by members of the American College of Surgeons Committee on Trauma were programmed into a specialized touch-screen computer, which was displayed at four different surgery and trauma meetings, including the ACS Clinical Congress in 1999 and 2000. Participants were questioned about their knowledge of trauma epidemiology, bicycle helmet effectiveness, child safety seat usage, suicide, and domestic violence. RESULTS: Seventy-nine surveys were completed by surgeons, including 33 specializing in trauma care, and by 106 nurses attending trauma courses. Overall, the percentage of correct answers was 50%. There were no significant differences in survey scores between trauma surgeons and general surgeons, although both scored higher than trauma nurses. Areas where knowledge deficits were the most apparent included proper use of child safety seats, the effectiveness of airbags, the prevalence of suicide, and the annual cost of injury in America. CONCLUSIONS: The majority of practicing surgeons and nurses, including those working at trauma centers, are unaware of the basic concepts of injury prevention. Advancements in the field of injury control will require efforts to educate medical professionals and the public.

Accident Prevention↗
PubMed2001

Influence of core buildup material on the fatigue strength of an all-ceramic crown.

STATEMENT OF PROBLEM: Clinically relevant variables and testing methods have not been used to investigate the effects of core buildup materials on the strength of all-ceramic restorations. PURPOSE: The aim of this study was to evaluate the compressive strength of Optimal Pressable Ceramic (OPC) all-ceramic crowns supported by 1 of 3 different core materials and subjected to static or cyclic loading in air or water. MATERIAL AND METHODS: A total of 135 human extracted third molar teeth were divided into 3 equal groups, and cores of amalgam, composite, and dentin (control) were fabricated. Complete crown preparations with a circumferential 90 degrees shoulder margin 1 mm deep were prepared to support complete crown restorations. Testing in compression was performed at a loading rate of 2.0 mm/min. Sixty teeth (20 with each type of core) were subjected to static loading, with equal numbers tested in air and water. The remaining 75 teeth (25 with each type of core) were subjected to cyclic loading in water. The compressive and diametral tensile strengths of 6 x 12-mm OPC cylinders also were tested in both air and water. The data were analyzed with 1-way analysis of variance followed by the Tukey multiple means comparison test (P<.05). RESULTS: Analysis of the static fracture stress of OPC crowns indicated no significant differences among the core materials (values from testing in air and water, respectively: dentin core 22.7 +/- 4.5 MPa and 19.7 +/- 4.7 MPa; amalgam core 25.2 +/- 5.2 MPa and 21.6 +/- 6.3 MPa; and composite core 20.9 +/- 4.1 MPa and 18.7 +/- 4.9 MPa). Under wet conditions, static versus cyclic loading produced significantly different results for each of the core materials (dentin core 19.7 +/- 4.7 MPa vs. 9.5 +/- 1.5 MPa; amalgam core 21.6 +/- 6.3 MPa vs. 10.3 +/- 1.6 MPa; composite core 18.7 +/- 4.9 MPa vs. 13.3 +/- 3.2 MPa). A significant difference was observed for the solid compressive cylinders tested in water (793.8 +/- 280.1 MPa) versus in air (1473.6 +/- 527.4 MPa). CONCLUSION: Within the limitations of this study, the mean compressive strength of OPC crowns tested in water was significantly different under cyclic versus static loading. No significant difference among the 3 core materials was found with respect to crown compressive strength.

Analysis of Variance↗
PubMed2001

Effect of pH on endotoxin affinity for metal-ceramic alloys.

STATEMENT OF PROBLEM: Crevicular pH may modify bacterial endotoxin affinity for high-noble metal-ceramic alloys. PURPOSE: Porphyromonas gingivalis lipopolysaccharide (LPS) affinity for 3 metal-ceramic alloys at 3 different pH levels was compared in vitro by measuring adsorption to and release from the alloy surface. MATERIAL AND METHODS: Metallographically polished disks were fabricated from Pd-Ag-Sn, Au-Pd-Ag-Sn-In, and Au-Pd-In-Ga alloys. Clean disks were placed individually into 1 mL at pH 6.5, 7.0, or 7.5 phosphate-buffered saline solution containing 0.9 endotoxin units per square millimeter tritiated LPS (n = 3 disks per alloy-pH group). The disks were incubated for 24 hours at 37 degrees C before being transferred to LPS-free buffer and incubated, again for 24 hours at 37 degrees C, to evaluate elution. This transfer continued at 24-hour intervals up to 96 hours total elution incubation. Lipopolysaccharide adsorption to and elution from disks was determined through liquid scintillation spectrometry. Adsorption data were evaluated with a 2-way analysis of variance (alpha=.05) and the post hoc Tukey honestly significant difference test. RESULTS: Lipopolysaccharide adsorption values ranged from 0.48 +/- 0.04 EU/mm(2) for the Au-Pd-Ag-Sn-In alloy at pH 7.5 to 0.75 +/- 0.04 EU/mm(2) for the Pd-Ag-Sn alloy at pH 6.5. Alloy type (P=.0001) and environmental pH (P=.0001) significantly influenced adsorption. Adsorption to the Pd-Ag-Sn and Au-Pd-In-Ga alloys at pH 6.5, 7.0, and 7.5 were similar and decreased with increasing pH. In contrast, adsorption to the Au-Pd-Ag-Sn-In alloy was significantly less than to other alloys at pH 6.5 but did not differ at other pH levels. Lipopolysaccharide release from the alloy surface could not be detected. CONCLUSION: P. gingivalis LPS affinity for metal-ceramic alloys was modified by environmental pH. The degree of LPS adsorption depended on the composition and surface chemistry of each alloy.

Adsorption↗
PubMed2000

Domestic violence and the trauma surgeon: results of a study on knowledge and education.

BACKGROUND: Despite the frequency of domestic violence in trauma patients, little emphasis has been placed on this subject in the education of surgeons and emergency medicine physicians. The 1997 Advanced Trauma Life Support (ATLS) course included, for the first time, education about domestic violence. This study was done to test the hypothesis that baseline knowledge about domestic violence in trauma care providers is poor and is not improved by the 1997 ATLS course. STUDY DESIGN: A study on domestic violence was designed using attending general surgeons, general surgery and emergency medicine residents, and medical students as test subjects. An educational lecture and pre- and post-tests were developed using the Eastern Association for the Surgery of Trauma position paper on domestic violence and other peer-reviewed literature as information sources. Data collected included level of training, date ATLS course was taken, and pre- and post-test scores. Statistical analysis was performed with ANOVA, with significance attributed to p < 0.05. RESULTS: Ninety-two subjects attended the lecture and completed the pre- and post-tests. The overall mean pre-test score was 54 +/- 1. There was no difference in scores for the 1997 ATLS cohort (with domestic violence material) versus the group with earlier ATLS courses (52 +/- 2 versus 51 +/- 1). The group that had never taken ATLS scored significantly better on the pre-test than the other groups (58 +/- 2, p < 0.05). All groups had significantly increased scores on the post-test (mean 77 < 1, p < 0.001 versus pre-test). CONCLUSIONS: Baseline knowledge about domestic violence among surgeons and emergency medicine physicians was poor and was not improved by participation in the 1997 ATLS course. This study strongly supports the need for expanded domestic violence education for trauma care providers.

Adult↗
PubMed2000

Periodontal tissue responses after insertion of artificial crowns and fixed partial dentures.

PURPOSE: The purpose of this review was, first, to critically evaluate published evidence on the effects of artificial crowns and fixed partial dentures (FPDs) on adjacent periodontal tissue health, and second to synthesize this evidence into meaningful summaries. Restoration qualities that contribute to inflammatory responses were identified based on strength of evidence, and variables that should be controlled in future investigations were outlined. Such information is necessary to accurately predict the prognosis of periodontal tissues adjacent to crowns or FPDs. METHODS: Clinical trial and epidemiologic evidence published in English was collected. The effects of crowns or FPDs on gingival inflammation, probing depths, and bone loss were evaluated based on accuracy of measurement, reliability of measurement, and/or appropriateness of data analysis. RESULTS: Crowns and FPDs increased the incidence of advanced gingival inflammation adjacent to restorations, particularly if restorations had intracrevicular finish line placement, poor marginal adaptation, or rough surfaces. However, because of the limitation in the accuracy and reliability of probing depth measurements, reports of greater mean probing depths of crowned teeth, which tended to be less than 1 mm greater than control teeth, should be questioned. Finally, crowns and FPDs in general did not accelerate the rate of adjacent bone loss. CONCLUSION: Clinically deficient restorations, as well as clinically acceptable restorations, can contribute to gingival inflammation. However, with the limitations of the applied methods of measurement, current evidence has not shown an increased attachment loss adjacent to crowns or FPDs. Future trials should document periodontal health before therapy and periodically after restoration insertion so that each tooth serves as its own control. In future studies, the periodontal disease history of the patient, the influence of the restoration on plaque formation, and the composition of the crevicular microflora must be recorded.

Alveolar Bone Loss↗
PubMed2000

Drosophila wee1 has an essential role in the nuclear divisions of early embryogenesis.

In Drosophila, the maternally expressed mei-41 and grp genes are required for successful execution of the nuclear division cycles of early embryogenesis. In fission yeast, genes encoding similar kinases (rad3 and chk1, respectively) are components of a cell cycle checkpoint that delays mitosis by inhibitory phosphorylation of Cdk1. We have identified mutations in a gene encoding a Cdk1 inhibitory kinase, Drosophila wee1 (Dwee1). Like mei-41 and grp, Dwee1 is zygotically dispensable but is required maternally for completing the embryonic nuclear cycles. The arrest phenotype of Dwee1 mutants, as well as genetic interactions between Dwee1, grp, and mei-41 mutations, suggest that Dwee1 is functioning in the same regulatory pathway as these genes. These findings imply that inhibitory phosphorylation of Cdk1 by Dwee1 is required for proper regulation of the early syncytial cycles of embryogenesis.

Alleles↗
PubMed1999

The role of external loop regions in serotonin transport. Loop scanning mutagenesis of the serotonin transporter external domain.

Chimeric transporters were constructed in which the predicted external loops of the serotonin transporter (SERT) were replaced one at a time with a corresponding sequence from the norepinephrine transporter (NET). All of the chimeric transporters were expressed at levels equal to or greater than those of wild type SERT, but the transport and binding activity of the mutants varied greatly. In particular, mutants in which the NET sequence replaced external loops 4 or 6 of SERT had transport activity 5% or less than that of wild type, and the loop 5 replacement was essentially inactive. In some of these mutants, binding of a high affinity cocaine analog was less affected than transport, suggesting that the mutation had less effect on the initial binding steps in transport than on subsequent conformational changes. The more severely affected mutants also displayed an altered response to Na(+). In contrast to the dramatic reduction in transport and binding, the specificity of ligand binding was essentially unchanged. Chimeric transporters did not gain affinity for dopamine, a NET substrate, or desipramine, an inhibitor, at the expense of affinity for serotonin or paroxetine, a selective SERT inhibitor. The results suggest that external loops are not the primary determinants of substrate and inhibitor binding sites. However, they are not merely passive structures connecting transmembrane segments but rather active elements responsible for maintaining the stability and conformational flexibility of the transporter.

Base Sequence↗
PubMed1999

Drosophila grapes/CHK1 mutants are defective in cyclin proteolysis and coordination of mitotic events.

The Drosophila grapes (grp) gene, which encodes a homolog of the Schizosaccharomyces pombe Chk1 kinase, provides a cell-cycle checkpoint that delays mitosis in response to inhibition of DNA replication [1]. Grp is also required in the undisturbed early embryonic cycles: in its absence, mitotic abnormalities appear in cycle 12 and chromosomes fail to fully separate in subsequent cycles [2] [3]. In other systems, Chk1 kinase phosphorylates and suppresses the activity of Cdc25 phosphatase: the resulting failure to remove inhibitory phosphate from cyclin-dependent kinase 1 (Cdk1) prevents entry into mitosis [4] [5]. Because in Drosophila embryos Cdk1 lacks inhibitory phosphate during cycles 11-13 [6], it is not clear that known actions of Grp/Chk1 suffice in these cycles. We found that the loss of grp compromised cyclin A proteolysis and delayed mitotic disjunction of sister chromosomes. These defects occurred before previously reported grp phenotypes. We conclude that Grp activates cyclin A degradation, and functions to time the disjunction of chromosomes in the early embryo. As cyclin A destruction is required for sister chromosome separation [7], a failure in Grp-promoted cyclin destruction can also explain the mitotic phenotype. The mitotic failure described previously for cycle 12 grp embryos might be a more severe form of the phenotypes that we describe in earlier embryos and we suggest that the underlying defect is reduced degradation of cyclin A.

Anaphase↗
PubMed1998

Exit from mitosis in Drosophila syncytial embryos requires proteolysis and cyclin degradation, and is associated with localized dephosphorylation.

The cyclin proteolysis that accompanies the exit from mitosis in diverse systems appears to be essential for restoration of interphase. The early syncytial divisions of Drosophila embryos, however, occur without detectable oscillations in the total cyclin level or Cdk1 activity. Nonetheless, we found that injection of an established inhibitor of cyclin proteolysis, a cyclin B amino-terminal peptide, prevents exit from mitosis in syncytial embryos. Similarly, injection of a version of Drosophila cyclin B that is refractory to proteolysis results in mitotic arrest. We infer that proteolysis of cyclins is required for exit from syncytial mitoses. This inference can be reconciled with the failure to observe oscillations in total cyclin levels if only a small pool of cyclins is destroyed in each cycle. We find that antibody detection of histone H3 phosphorylation (PH3) acts as a reporter for Cdk1 activity. A gradient of PH3 along anaphase chromosomes suggests local Cdk1 inactivation near the spindle poles in syncytial embryos. This pattern of Cdk1 inactivation would be consistent with local cyclin destruction at centrosomes or kinetochores. The local loss of PH3 during anaphase is specific to the syncytial divisions and is not observed after cellularization. We suggest that exit from mitosis in syncytial cycles is modified to allow nuclear autonomy within a common cytoplasm.

Animals↗
PubMed1998

The cell cycle program in germ cells of the Drosophila embryo.

The germ cells of metazoans follow a program of proliferation that is distinct from proliferation programs of somatic cells. Despite their developmental importance, the cell proliferation program in the metazoan primordial germ cells is not well characterized and the regulatory controls are not understood. In Drosophila melanogaster, germ cell precursors (called pole cells) proliferate early in embryogenesis and then enter a prolonged quiescence. We found that polar nuclear divisions are asynchronous and lag behind somatic nuclear divisions during syncytial cycles 9 and 10. Thus, the polar division program deviates from the somatic division program when pole nuclei and somatic nuclei still share a common cytoplasm, earlier than previously thought. The lag in polar nuclear divisions is independent of grapes, which is required for lengthening somatic cell cycles 10-13. Mapping of the last S phase in pole cells and measurement of their DNA content indicate that pole cells become quiescent in G2 phase of the cell cycle. We were able to drive quiescent pole cells into mitosis by induction of either an activator of Cdc2 (Cdc25string phosphatase) or a mutant form of Cdc2 that cannot be inhibited by phosphorylation. In contrast, induction of wild-type Cdc2 with a mitotic cyclin did not induce mitosis in pole cells. We propose that inhibition of Cdc2 by phosphorylation contributes to G2 arrest in pole cells during embryogenesis. Furthermore, pole cells enter G1 following induced mitoses, indicating that entry into both mitosis and S phase is blocked in quiescent pole cells. These studies represent the first molecular characterization of proliferation in embryonic germ cells of Drosophila.

Animals↗
PubMed1997

The Drosophila grapes gene is related to checkpoint gene chk1/rad27 and is required for late syncytial division fidelity.

BACKGROUND: Cell cycle checkpoints maintain the fidelity of the somatic cell cycle by ensuring that one step in the cell cycle is not initiated until a previous step has been completed. The extent to which cell cycle checkpoints play a role in the initial rapid embryonic divisions of higher eukaryotes is unclear. The initial syncytial divisions of Drosophila embryogenesis provide an excellent opportunity to address this issue as they are amenable to both genetic and cellular analysis. In order to study the relevance of cell cycle checkpoints in early Drosophila embryogenesis, we have characterized the maternal-effect grapes (grp) mutation, which may affect feedback control during early syncytial divisions. RESULTS: The Drosophila grp gene encodes a predicted serine/threonine kinase and has significant homology to chk1/rad27, a gene required for a DNA damage checkpoint in Schizosaccharomyces pombe. Relative to normal embryos, embryos derived from grp-mutant mothers exhibit elevated levels of DNA damage. During nuclear cycles 12 and 13, alignment of the chromosomes on the metaphase plate was disrupted in grp-derived embryos, and the embryos underwent a progression of cytological events that were indistinguishable from those observed in normal syncytial embryos exposed to X-irradiation. The mutant embryos also failed to progress through a regulatory transition in Cdc2 activity that normally occurs during interphase of nuclear cycle 14. CONCLUSION: We propose that the primary defect in grp-derived embryos is a failure to replicate or repair DNA completely before mitotic entry during the late syncytial divisions. This suggests that wild-type grp functions in a developmentally regulated DNA replication/damage checkpoint operating during the late syncytial divisions. These results are discussed with respect to the proposed function of the chk1/rad27 gene.

Amino Acid Sequence↗
PubMed1997

A system for digital reconstruction of gypsum dental casts.

A range scanner is developed that can scan a gypsum dental cast and reconstruct the cast digitally for display and storage purposes. The scanner is based on subtractive light and computes the range values using optical triangulation. A fiducial marker is introduced that, when attached to a dental cast at the time of image acquisition, makes it possible to integrate multiview range images of the cast without image registration. A method for calibrating the scanner is described and experimental results showing the accuracy of the scanner are presented.

Algorithms↗
PubMed1996

Ceramics in dentistry: historical roots and current perspectives.

This article presents a brief history of dental ceramics and offers perspectives on recent research aimed at the further development of ceramics for clinical use, at their evaluation and selection, and very importantly, their clinical performance. Innovative ceramic materials and ceramics processing strategies that were introduced to restorative dentistry since the early 1980s are discussed. Notable research is highlighted regarding (1) wear of ceramics and opposing enamel, (2) polishability of porcelains, (3) influence of firing history on the thermal expansion of porcelains for metal ceramics, (4) machining and CAD/CAM as fabrication methods for clinical restorations, (5) fit of ceramic restorations, (6) clinical failure mechanisms of all-ceramic prostheses, (7) chemical and thermal strengthening of dental ceramics, (8) intraoral porcelain repair, and (9) criteria for selection of the various ceramics available. It is found that strong scientific and collaborative foundations exist for the continued understanding and improvement of dental ceramic systems.

Ceramics↗
PubMed1995

Effects of firing cycle and surface finishing on distortion of metal ceramic castings.

The "as-cast" fit of metal ceramic restorations has been reported to deteriorate during the high-temperature firing cycles used for application of porcelain veneer. In this study, thermocycling and surface finishing or cold working were examined for their effects on marginal adaptation of metal ceramic castings. Methods for minimizing the loss of marginal adaptation were evaluated, and casting variables were eliminated by construction of acrylic resin measuring dies directly in the restorations. Thermocycling of metal ceramic restorations resulted in increased marginal openings, and all of the loss of marginal fit occurred during the first thermocycling of the alloy. The restorations that were cold worked and then oxidized by conventional manipulation had substantially more marginal opening than any other group. A fourfold, statistically significant improvement (p < 0.001) in the marginal adaptation of a metal ceramic restoration was observed when the initial thermal cycle was completed before the specimens were finished.

Acrylic Resins↗
PubMed1995

A survey of temporomandibular disorder conducted by the Greater New York Academy of Prosthodontics.

The results of a temporomandibular joint survey sent to 167 members of the Greater New York Academy of Prosthodontics indicated a great variation in the diagnosis and treatment of patients with temporomandibular joint dysfunction. Although most indicated that their background in temporomandibular joint disorders was from clinical experience and/or textbooks and the dental literature, only 59% treated patients for these disorders. The most common diagnostic procedures were occlusal evaluation; joint evaluation for tenderness, crepitus, and click; evaluation of range of motion of the mandible; and a muscular evaluation. Only 35% used a formal temporomandibular joint dysfunction questionnaire. The percentage of complete denture patients with these symptoms was 5% or less. Thirty-three percent of clinicians sometimes treated asymptomatic patients who were without pain but had a click. Two thirds of the respondents believed that surgery was sometimes indicated for disk degeneration and displacement. More recent graduates are more likely to treat patients who have temporomandibular joint dysfunction than are older more experienced practitioners.

Attitude of Health Personnel↗
PubMed1995

Dimensional and formation analysis of a restorative ceramic and how it works.

In-Ceram ceramic appears to use conventional powder/liquid processing techniques to form the coping substructure; however, the process results in a near net-shape restoration with minimal sintering shrinkage. Scanning electron microscopy, Brunauer-Emmett-Teller analysis, particle size classification, and linear dimensional changes during sintering were used to analyze In-Ceram ceramic. In-Ceram ceramic had a minimal linear shrinkage of 0.21% after the sintering of the alumina powder. This shrinkage can be readily compensated for by the expansion of conventional gypsum products and should result in acceptable clinical fits for In-Ceram ceramic restorations. Theories and explanations were described to account for the near net-shape and high strength of In-Ceram. Continuous interpenetrating phase composite technologies were used to create a substantial increase in strength. Future applications of this technology are encouraging.

Aluminum Oxide↗
PubMed1995

Drosophila Wee1 kinase rescues fission yeast from mitotic catastrophe and phosphorylates Drosophila Cdc2 in vitro.

Cdc2 kinase activity is required for triggering entry into mitosis in all known eukaryotes. Elaborate mechanisms have evolved for regulating Cdc2 activity so that mitosis occurs in a timely manner, when preparations for its execution are complete. In Schizosaccharomyces pombe, Wee1 and a related Mik1 kinase are Cdc2-inhibitory kinases that are required for preventing premature activation of the mitotic program. To identify Cdc2-inhibitory kinases in Drosophila, we screened for cDNA clones that rescue S. pombe wee1- mik1- mutants from lethal mitotic catastrophe. One of the genes identified in this screen, Drosophila wee1 (Dwee1), encodes a new Wee1 homologue. Dwee1 kinase is closely related to human and Xenopus Wee1 homologues, and can inhibit Cdc2 activity by phosphorylating a critical tyrosine residue. Dwee1 mRNA is maternally provided to embryos, and is zygotically expressed during the postblastoderm divisions of embryogenesis. Expression remains high in the proliferating cells of the central nervous system well after cells in the rest of the embryo have ceased dividing. The loss of zygotically expressed Dwee1 does not lead to mitotic catastrophe during postblastoderm cycles 14 to 16. This result may indicate that maternally provided Dwee1 is sufficient for regulating Cdc2 during embryogenesis, or it may reflect the presence of a redundant Cdc2 inhibitory kinase, as in fission yeast.

Amino Acid Sequence↗