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Biomedical subjects

D C Dixon

Publications and source records attributed to D C Dixon.

17 recordsLinked to original sources
PubMed1995

Radiographic diagnosis of temporomandibular disorders.

Although many of the disorders involving the temporomandibular joint and associated structures can be diagnosed clinically on the basis of the history and physical findings, there are others that require the use of various imaging techniques to make an accurate diagnosis or to determine the extent of involvement. To take maximum advantage of the benefits of these procedures, however, it is not only important for the clinician to be able to select the correct methods, but also to understand their limitations as well as their capabilities. In this article the various techniques used for imaging the hard and soft tissues of the temporomandibular joint are reviewed and recommendations are made regarding their appropriate applications.

Arthrography↗
PubMed1994

Production of active human interleukin-1 beta-converting enzyme in a baculovirus expression system.

The cDNA coding for the precursor form of human interleukin-1 beta-converting enzyme (proICE) was expressed in Spodoptera frugiperda (Sf9) insect cells using a baculovirus expression system. The 45-kDa recombinant protein was further processed to several smaller forms of 32, 24, 20, 13 and 10 kDa. Active recombinant ICE derived from the baculovirus expression system (bvICE) was found to be present in soluble lysates of insect cells as an associated heterodimer consisting of 10- and 20-kDa subunits. The activity of bvICE was determined by conversion of precursor interleukin-1 beta (preIL-1 beta) to the mature form (mIL-1 beta) and via site-specific cleavage of a decapeptide which spans the ICE cleavage site in preIL-1 beta. The bvICE system was inhibited by an ICE inhibitor to the same extent as native ICE from the monocytic cell line THP-1. Expression of an active-site mutant (Cys285 to Ser) of proICE in insect cells resulted in the accumulation of partially processed (32-kDa) ICE. The availability of a facile expression system will permit further characterization of the biochemical properties and processing pathway of this unique protease.

Animals↗
PubMed1994

Current status of diagnostic procedures for temporomandibular disorders.

Temporomandibular disorders encompass a group of musculoskeletal conditions that involve the joints, the masticatory musculature, or both. In any given patient, there may be several overlapping TM disorders, an orofacial pain condition mimicking a TM disorder or a concomitant TMD and non-TM disorder. The differential diagnosis becomes extremely important.

Arthrography↗
PubMed1993

Habit reversal treatment of temporomandibular disorders: a pilot investigation.

This study evaluated the use of behavior therapy to reduce teeth clenching and grinding as a treatment for temporomandibular disorders (TMD). Habit reversal was used to treat three adults with TMD using a multiple baseline across subjects design. The results indicated significant improvement for two of the three subjects including decreased self-reported pain, decreased pain upon muscle palpation, and increased maximum mandibular opening. However, temporomandibular joint sounds were increased. Habit reversal appears to be more effective in reducing the myofascial pain symptoms of TMD than in improving temporomandibular joint functioning.

Behavior Therapy↗
PubMed1993

Comparison of two scales in the assessment of muscle and joint palpation tenderness in chronic temporomandibular disorders.

Following the guidelines of the Craniomandibular Index, 23 chronic patients had 42 muscle and temporomandibular joint sites palpated. Two- and four-point scales were generated in response to the patient's reactions. After 6 weeks of treatment, patients measured with the 2-point scale showed 6.39% improvement in muscle tenderness and patients measured with the 4-point scale showed a 14.99% improvement. These changes were significantly different. Correlation between scales was r = .88 originally and increased to r = .91 after 6 weeks. Results showed that the 4-point scale is significantly more able to detect clinical changes in muscle and joint tenderness than is the 2-point scale.

Adult↗
PubMed1991

Differential targeting of the tobacco PR-1 pathogenesis-related proteins to the extracellular space and vacuoles of crystal idioblasts.

Several biochemical and localization studies have shown that the acidic isoforms of the tobacco pathogenesis-related (PR) proteins, PR-1a, -1b and -1c are secreted to the extracellular spaces of leaves in response to pathogen infection or chemical treatment. Here we report the differential accumulation of these proteins within the vacuoles of specialized cells known as crystal idioblasts. In situ hybridization analysis indicated that crystal idioblasts expressed the PR-1 genes at the mRNA level and suggested that PR-1 proteins were synthesized by these cells. Transgenic plants which constitutively express a chimeric gene encoding an acidic PR-1b isoform also accumulated PR-1 protein in the extracellular spaces and within crystal idioblast vacuoles. Analysis of mRNA derived from these transgenic plants indicated that expression of the introduced PR-1b gene was responsible for the accumulation of PR-1 protein in these two distinct locations. The synthesis and accumulation within crystal idioblasts of PR-1 proteins, which are secreted by other cell types, indicates that idioblasts sort these proteins in a unique manner. Moreover, this suggests that protein sorting in higher plants may be modulated in a cell specific manner.

Antibodies, Monoclonal↗
PubMed1991

Diagnostic imaging of the temporomandibular joint.

This article reviews the more commonly used imaging techniques for examining the temporomandibular joint. Emphasis is placed on assessment of their accuracy as diagnostic tests for pain, dysfunction, and intracapsular disease processes.

Arthrography↗
PubMed1989

A simplified psychologic questionnaire as a treatment planning aid for patients with temporomandibular joint disorders.

Psychologic factors are often believed to have a significant role in the etiology and maintenance of temporomandibular joint disorders. Anxiety and depression have received the greatest focus. Approximately 132 patients with temporomandibular joint disorders completed seven self-administered depression questionnaires and four anxiety questionnaires. Correlation among all 11 questionnaires was significant. Factor analysis was interpreted as indicating the 11 questionnaires were measuring a single factor. For preliminary screening diagnosis, two questions were suggested to be a good approximation of the total battery of questionnaires.

Adult↗
PubMed1989

Disease response to tobacco mosaic virus in transgenic tobacco plants that constitutively express the pathogenesis-related PR1b gene.

Correlation of the temporal and spacial pattern of induction of the pathogenesis-related (PR) genes PR1a, PR1b, and PR1c with viral infections in certain tobacco cultivars has implicated PR proteins in viral disease resistance. To test whether the PR1 proteins of tobacco are involved in viral resistance, transgenic Nicotiana tabacum plants were constructed which constitutively express the PR1b gene. This protein was secreted from cells of transgenic plants and accumulated in the extracellular space at levels equivalent to those found in nontransgenic plants in association with disease resistance. Transgenic plants derived from the cultivar (cv.) Xanthi (susceptible to tobacco mosaic virus [TMV] infection) exhibited no delayed onset or reduction in the severity of systemic symptoms after TMV infection. In transgenic plants derived from cv. Xanthi-nc (TMV resistant), the time of appearance, the size and general morphology, and the number of viral lesions produced were similar to the parental control plants after TMV infection. These data indicate that the PR1b protein of tobacco is not sufficient for TMV resistance, and imply that the PR1 proteins may not function as unique antiviral factors.

Cell Transformation, Viral↗
PubMed1987

Synthesis and localization of pathogenesis-related proteins in tobacco.

The PR1 family of pathogenesis-related proteins from tobacco (Nicotiana tabacum L.) leaves is induced by a variety of pathogenic and chemical agents and is associated with resistance to tobacco mosaic virus. The majority of the PR1 proteins did not copurify with mesophyll protoplasts (the major cell type of the leaf) isolated from tobacco mosaic virus-infected N. tabacum cv. Xanthi-nc leaves. However, these isolated protoplasts were capable of synthesizing and selectively secreting the PR1 proteins. Using monoclonal antibodies for immunofluorescence microscopy, we localized these proteins to the extracellular spaces predominantly in regions adjacent to viral lesions as well as in xylem elements of infected leaves.

Antibodies, Monoclonal↗
PubMed1985

Synthesis of pathogenesis-related proteins in tobacco is regulated at the level of mRNA accumulation and occurs on membrane-bound polysomes.

The pathogenesis-related (PR) proteins of tobacco plants are induced in response to a variety of pathogenic and chemical agents. Although the function of these proteins is unknown, they are associated with resistance to multiplication and/or spread of tobacco mosaic virus. We report that functional mRNAs encoding PR proteins are present only when synthesis of these proteins has been induced, suggesting that their synthesis is controlled in part at the level of mRNA accumulation. In addition PR proteins appear to be synthesized and processed in a manner analogous to proteins destined for the endoplasmic reticulum since (i) the in vitro translation products synthesized in the wheat-germ cell-free system are slightly larger than the in vivo products, (ii) translation of PR mRNAs in the rabbit reticulocyte lysate system is blocked unless that system is supplemented with dog pancreas microsomes, and (iii) mRNAs for PR proteins are associated predominantly with membrane-bound polysomes in vivo. This pathway of synthesis and posttranslational modification suggests possible sites of action of these proteins.

Journal Article↗
PubMed1984

The validity of transcranial radiography in diagnosing TMJ anterior disk displacement.

Two transcranial radiographic methods for determining anterior disk displacement in the TMJ were evaluated in comparison with results obtained from arthrography. Both transcranial radiographic methods could only accurately predict the presence of an anteriorly displaced disk in a range of 26% to 56% of the time (for example, the methods gave false-negative results 44% to 74% of the time). The methods were more valuable in correctly identifying joints that were free of disease, achieving this identification anywhere from 64% to 96% of the time. Although noninvasive, these two transcranial radiographic techniques produced results that lacked validity and, therefore, remain of questionable value to the clinician who is diagnosing anterior disk displacement.

Cartilage, Articular↗
PubMedDate not supplied

Rural health care: a case study in Maine.

Experience recommends a dual financial strategy--"hard" practice money and "soft" grant and contract money--as a flexible approach to rural healthcare problems.

Delivery of Health Care↗