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Biomedical subjects

J G Marshall

Publications and source records attributed to J G Marshall.

At least 19 recordsLinked to original sources
PubMed2000

Role of TNF-alpha in myocardial dysfunction after hemorrhagic shock and lower-torso ischemia.

Ruptured abdominal aortic aneurysm (RAAA) repair, a combination of hemorrhagic shock and lower-torso ischemia, is associated with a 50-70% mortality. Myocardial dysfunction may contribute to the high rate of mortality after aneurysm repair. We attempted to determine whether RAAA repair results in cardiac dysfunction mediated by tumor necrosis factor-alpha (TNF-alpha). We modeled aortic rupture and repair in the rat by inducing hemorrhagic shock to a mean blood pressure of 50 mmHg for 1 h, followed by supramesenteric clamping of the aorta for 45 min. After 90 min of reperfusion, cardiac contractile function was assessed with a Langendorff preparation. Myocardial TNF-alpha, ATP and creatine phosphate (CP) levels, and markers of oxidant stress (F(2)-isoprostanes) were measured. Cardiac function in the combined shock and clamp rats was significantly depressed compared with sham-operated control rats but was similar to that noted in animals subjected to shock alone. Myocardial TNF-alpha concentrations increased 10-fold in the combined shock and clamp rats compared with sham rats, although there was no difference in myocardial ATP, CP, or F(2)-isoprostanes. TNF-alpha neutralization improved cardiac function by 50% in the combined shock and clamp rats. Hemorrhagic shock is the primary insult inducing cardiac dysfunction in this model of RAAA repair. An improvement in cardiac contractile function after immunoneutralization of TNF-alpha indicates that TNF-alpha mediates a significant portion of the myocardial dysfunction in this model.

Adenosine Triphosphate↗
PubMed1999

Synthesis and oxidative insolubilization of cell-wall proteins during osmotic stress.

The cell walls in the new white roots of jack pine (Pinus banksiana Lamb.) were observed to constrict around the shrinking protoplast of osmotically stressed roots, and pressure was maintained via an apparent adjustment of cell-wall size and elasticity. These elastic alterations of the cell wall permitted the root cells to maintain full turgor despite the loss of most of the water in the tissue. The constriction of the root cell wall around the dehydrating protoplasts to maintain turgor may reflect changes in cell wall structure. We found that these shrinking root cells synthesize and secrete into the intercellular fluid a set of proteins. These proteins become tightly associated (i.e. guanidine HCl- and sodium dodecyl sulfate-insoluble) with the cell wall but can be released from the matrix, after briefly boiling in 0.1% sodium dodecyl sulfate, by the combination of guanidine HCl, CaCl2 and dithiothreitol. However, these cell-wall proteins became insoluble with time. The proteins could subsequently be destructively extracted from the wall with acid NaClO2 treatments. After these proteins were incorporated into the cell walls, the roots adopted a new, smaller maximal tissue volume and elastic coefficients returned to normal levels.

Amino Acid Sequence↗
PubMed1999

Evaluation of diamond-coated ultrasonic instruments for root-end preparation.

Ultrasonic instrumentation has been associated with cracking of the dentin in the area of the root-end preparation. The purpose of this study was to evaluate root-end preparations for cracking and to describe cavosurface morphology after the use of diamond-coated instruments. Forty teeth were inspected for intradentin cracks, incomplete canal cracks, and complete canal cracks before and after preparation with a stainless steel CT-5 ultrasonic instrument and again after root-end preparation with an S12D/90 degrees diamond-coated instrument. Six teeth had polyvinylsiloxane impressions taken of the root ends after preparation with the CT-5 and again after preparation with the diamond-coated instrument. Replicas were made, split, sputter-coated, and inspected using the scanning electron microscope. This study indicates that use of the diamond-coated instrument for root-end preparation does not result in significant root-end cracking and that it can remove cracks created by a prior instrument's use. The use of the diamond-coated instrument resulted in a heavily abraded, debris-covered cavosurface that may affect the apical seal.

Analysis of Variance↗
PubMed1999

A scanning electron microscopic study of in vivo ultrasonic root-end preparations.

The purpose of this in vivo study was to evaluate root-ends for cracks after root resection and again after ultrasonic root-end preparation in patients undergoing endodontic surgery. Endodontic surgery was performed on 25 roots from 20 patients. In vivo vinyl polysiloxane impressions were made after root resection and again after ultrasonic root-end preparations. Epoxy resin casts were made from the impressions and scanning electron micrographic examination of the root-end replicas was performed. There was no evidence of cracks after root resection. One incomplete canal crack was evident after ultrasonic root-end preparation.

Apicoectomy↗
PubMed1998

The topography of root ends resected with fissure burs and refined with two types of finishing burs.

OBJECTIVES: This study compared the surface topography of roots resected with #57, Lindeman, and Multi-purpose burs. Further comparisons were made after refinements with either a multifluted carbide or an ultrafine diamond finishing bur. STUDY DESIGN: Three groups of single-rooted human teeth were resected with each resection bur, and resin replicas of the root ends were made. Root ends from each resection bur group were finished with either a multifluted carbide or an ultrafine diamond finishing bur, and the root ends were replicated. All replicas were evaluated at a magnification of x20 for smoothness and surface irregularities. Data analysis was done with the Wilcoxon signed rank test and the chi-square test at a significance level of p < 0.05. RESULTS: The Multi-purpose bur produced a smoother and more uniplanar surface than the #57 bur and caused less damage to the root than either the #57 or the Lindeman bur. The multifluted carbide finishing bur tended to improve the smoothness of the root end, while the ultrafine diamond tended to roughen the surface. CONCLUSIONS: The Multi-purpose bur produced the smoothest and most uniplanar resected root-end surface with the least root shattering. The multifluted carbide finishing bur produced a smoother surface than the ultrafine diamond bur.

Apicoectomy↗
PubMed1997

Comparison of ultrasonic and high-speed-bur root-end preparations using bilaterally matched teeth.

The purpose of this study was to compare ultrasonic and high-speed-bur root-end preparations. Seventy-six roots from 29 bilaterally matched pairs of human teeth in cadavers were used in this study. In group 1 ultrasonic preparations were made in 38 roots and filled with amalgam. In group 2 high-speed bur preparations were made in 38 roots and filled with amalgam. The size of the bony crypt was measured and the teeth were extracted and radiographed mesial-distally and buccal-lingually. None of the root-end preparations resulted in root perforation. The mean mesial-distal minimum depth of ultrasonic and high-speed bur preparations were 2.11 mm and 1.39 mm, respectively. The mean buccal-lingual minimum depth of preparation was 2.51 mm for the ultrasonic and 2.05 mm for the high-speed bur preparations. The depth of the ultrasonic preparations was significantly greater for both measurements. A significantly greater bevel angle was associated with the bur preparations, 35.1 degrees versus 16.0 degrees for the ultrasonic preparations. The incidence of ultrasonic root-end preparations deviating from the uninstrumented canal spaces was found to be 2.6%. All bur root-end preparations were at an acute angle to the long axis of the root. The bony crypt size for bur preparations was significantly greater than that for ultrasonic preparations.

Cadaver↗
PubMed1997

Evaluation for cracks associated with ultrasonic root-end preparation of gutta-percha filled canals.

Many clinicians use ultrasonics for root-end preparations. The purpose of this study was to evaluate resected root-end surfaces of bilaterally matched human teeth for cracks before and after ultrasonic root-end preparation. Twenty matched pairs of extracted single rooted teeth were divided into two experimental groups. In group 1, root-end resection was performed on uninstrumented teeth. In group 2, root-end resection was performed after the canals were instrumented and filled with gutta-percha. All teeth in both groups received root-end preparations using ultrasonic instrumentation at low power. Two examiners evaluated the root-ends after root-end resection and again after root-end preparation using zoom magnification of 20x to 63x. The number, types, and location of cracks were mapped. There were no significant differences when gutta-percha filled roots were compared to uninstrumented roots with regard to the number or type of cracks after root-end resection or root-end preparation. In addition, there were no significant differences in the number or type of cracks following root resection and ultrasonic root-end preparation when compared to teeth with root resection alone.

Analysis of Variance↗
PubMed1996

Evaluation of cracks associated with ultrasonic root-end preparation.

The purpose of this study was to evaluate the integrity of resected root-end surfaces of extracted human teeth after using ultrasonic tips at low or high frequencies for root-end preparation. Thirty bilaterally matched pairs of single-rooted human teeth had root-end resections using a low-speed diamond saw and were examined for root-end cracks. The matched pairs of teeth were then divided into two experimental groups, with one member of each pair being placed in each group. In group 1, root-end preparations were made with an ultrasonic tip on the lowest frequency setting. The preparations in group 2 were done on the highest power setting. Two investigators again examined the resected root-ends using a stereomicroscope at x20 to x63 and recorded the numbers, types, and location of the cracks. Three types of cracks were observed: canal cracks, intradentin cracks, and cemental cracks. There were significantly more root-ends with cracks after ultrasonic root-end preparation than after root-end resection only. In root-ends that had any cracks, significantly more canal cracks per root occurred when the ultrasonic tip was used on the high-frequency setting for root-end preparation than when the ultrasonic tip was used on the low power setting.

Apicoectomy↗
PubMed1996

Benchmarking reference services: step by step.

This article is a companion to an introductory article on benchmarking published in an earlier issue of Medical Reference Services Quarterly. Librarians interested in benchmarking often ask the following questions: How do I determine what to benchmark; how do I form a benchmarking team; how do I identify benchmarking partners; what's the best way to collect and analyze benchmarking information; and what will I do with the data? Careful planning is a critical success factor of any benchmarking project, and these questions must be answered before embarking on a benchmarking study. This article summarizes the steps necessary to conduct benchmarking research. Relevant examples of each benchmarking step are provided.

Data Collection↗
PubMed1995

A comparison of four instrumentation techniques on apical canal transportation.

The ability of four instrumentation techniques to enlarge and maintain the central axis of 51 curved canals was evaluated radiographically. Curved canals in extracted human teeth were instrumented using a step-back preparation with K-files, crowndown preparation with K-files, sonic instrumentation with Shaper-Sonic files, and the NiTiMatic preparation system. Following coronal preflaring, each canal was instrumented to a #35 file 1 mm from the anatomic foramen. Radiographs were taken with mercury filling the canal system using a specially designed model that allowed for the pre- and postinstrumentation canal to be viewed on the same radiograph. Canal enlargement and apical transportation resulting from the various instrumentation techniques were evaluated using computer analysis. No statistically significant differences were found for canal transportation. Sonic instrumentation significantly increased coronal flaring. The crown-down and sonic techniques produced more ledges. Elbow formation was associated with all instrumentation techniques. The model system developed for this study provided an accurate method of assessing the preparation techniques and the instrument effects on the canal walls.

Analysis of Variance↗
PubMed1995

Evaluation of root thickness in curved canals after flaring.

Root thickness in the mesial canals of lower first and second molars was compared before and after flaring by using a muffle system. Gates Glidden burs or M-Series Canal Openers were used with either a straight up-and-down motion or with an anticurvature motion. It was found that Gates Glidden burs used straight up and down removed statistically more dentin at the level of the furcation than Canal Openers used straight up and down or in an anticurvature fashion. At a level 2 mm apical to the furcation, Gates Glidden burs used in an anticurvature fashion removed statistically more dentin than any other method tested.

Analysis of Variance↗
PubMed1995

Using scientific evidence to improve information practice.

The recent policy statement of the Medical Library Association (MLA) takes the position that scientific evidence is the basis for improving the quality of library and information sciences now and in the future. Research activity is seen as the foundation of an evolving knowledge base for the profession--a knowledge base that will set health sciences librarians apart from others in an increasingly competitive world of information service providers. The statement represents the culmination of many years of activity by association members, during which the role of research in health information practice has been debated. Over a similar time period, the quality movement, with its increasing demand for the collection and use of data, has been growing. Developments such as total quality management (TQM) and continuous quality improvement (CQI) reinforce the centrality of research with its increasing demand for the collection and use of data, has been growing. Developments such as total quality management (TQM) and continuous quality improvement (CQI) reinforce the centrality of research and its relationship to efficient and effective information practice as envisioned in the MLA policy statement.

Artificial Intelligence↗
PubMed1995

Using evaluation research methods to improve quality.

The idea of evaluation, or the measurement of a person, a service or a programme against some type of yardstick, has been around for a long time. In everyday language, the term evaluation is used to refer to everything from employee performance appraisal, to informal opinions about whether a particular service appears to be working well, to carefully planned and executed programmes of evaluation. In the past, librarians have tended to rely on their own professional judgement as a primary means of informal evaluation, and as long as the librarian was considered competent by others in the organization, this method seemed to work reasonably well. In the rapidly changing fiscal climate of the 1990s, greater demands for accountability are altering the standards of evaluation, and informal methods based on professional judgement are less and less likely to be seen as adequate. Formal evaluation is becoming even more important as management strategies, such as total quality management (TQM) and continuous quality improvement (CQI), are adopted--strategies that rely on gathering and using data for measuring service quality. Although programme jargon such as TQM and CQI may change in the future, it is likely that the evaluation process inherent in these approaches will continue to be an important management tool for deciding on the allocation of scarce resources.

Canada↗
PubMed1995

Benchmarking reference services: an introduction.

Benchmarking is based on the common sense idea that someone else, either inside or outside of libraries, has found a better way of doing certain things and that your own library's performance can be improved by finding out how others do things and adopting the best practices you find. Benchmarking is one of the tools used for achieving continuous improvement in Total Quality Management (TQM) programs. Although benchmarking can be done on an informal basis, TQM puts considerable emphasis on formal data collection and performance measurement. Used to its full potential, benchmarking can provide a common measuring stick to evaluate process performance. This article introduces the general concept of benchmarking, linking it whenever possible to reference services in health sciences libraries. Data collection instruments that have potential application in benchmarking studies are discussed and the need to develop common measurement tools to facilitate benchmarking is emphasized.

Efficiency, Organizational↗
PubMed1993

Effect of variable doses of dexamethasone on posttreatment endodontic pain.

One hundred six patients with pretreatment pain presenting for endodontic treatment participated in a controlled double blind study. After root canal therapy, the patients were given an intraoral intramuscular injection of either a saline placebo or various dosages of dexamethasone. Posttreatment pain incidence and severity were evaluated at 4, 8, 24, 48, and 72 h. Injection of the various dosages of dexamethasone, taken as a group, was shown to significantly reduce the severity of pain at 4 and 8 h, and 0.07 to 0.09 mg/kg dosage alone significantly reduced pain at 8 h. Patients who received dexamethasone took significantly fewer posttreatment pain medications than those who received the placebo. Although there was a trend toward a reduction in the incidence of posttreatment pain for patients who received dexamethasone, the difference was not statistically significant.

Analysis of Variance↗
PubMed1993

Factors associated with endodontic posttreatment pain.

One hundred six patients with pretreatment pain presenting for endodontic treatment participated in a controlled double-blind study of dexamethasone use. Endodontic therapy was performed and, after controlling for use of nonuse of dexamethasone, patient variables and treatment factors were evaluated for their effects on endodontic posttreatment pain. Patients with no radiographic periapical lesions had significantly more pain than patients with periapical lesions at 8-, 24-, 48-, and 72-h posttreatment regardless of whether they received placebo or dexamethasone. No other patient or treatment factors correlated with posttreatment pain. Twenty-two patients in the subgroup receiving placebo reported an 81% incidence of posttreatment pain, 73% of them required posttreatment pain medications. By 72-h posttreatment, the incidence and severity of pain in the placebo group was minimal.

Adult↗
PubMed1993

A study of library use in problem-based and traditional medical curricula.

A key question for librarians and medical educators who are planning for curriculum change is whether students and faculty in problem-based learning (PBL) programs use the library and its resources differently than do participants in traditional programs. During 1991, this research question was explored at three medical schools in the province of Ontario, Canada. At the time of the study, McMaster University medical school was totally problem-based, the University of Western Ontario had one PBL day each week for first-year medical students, and the University of Toronto, although planning for medical curriculum change, had not yet initiated PBL. Data collected in the study suggest that more medical students in the problem-based curriculum than in the more traditional programs use the library and that, when the PBL students use the library, they do so more frequently, for longer periods of time, and as a source of a greater proportion of their study materials. PBL students also use the library more than their counterparts as a place to study and meet other students. Students in the problem-based curriculum use the following resources more extensively: end-user MEDLINE searching, library journals, reserve or short-term loan materials, photocopy services, and audiovisual materials. PBL students also report purchasing more textbooks. In contrast to the differences found among medical students, however, patterns of library and resource use by medical faculty at the three schools were quite similar.

Computer-Assisted Instruction↗