Biomedical subjects

R L Boyd

Publications and source records attributed to R L Boyd.

At least 55 records · Page 3Linked to original sources

PubMed1996

Analysis of the initiation period of spontaneous autoimmune thyroiditis (SAT) in obese strain (OS) of chickens.

The early, predictable, onset of spontaneous autoimmune thyroiditis (SAT) in Obese strain (OS) chickens provides a unique opportunity to analyse the mechanisms initiating autoimmunity which is virtually impossible to obtain in humans. In this study we focused on the respective roles of viruses and macrophages in the initiation of SAT. To analyse viruses, leukosis virus-free OS chickens were bred over three generations and reared under gnotobiotic conditions. By 2 weeks of age there were no differences in the levels of thyroid mononuclear cell infiltration between these and control animals. The role of mononuclear phagocytes in SAT was determined by their depletion via injecting newborn OS chicks with silica or carrageenan and dichloro-methylene diphosphonate encapsulated into liposomes. Although this treatment did not substantially change the amount of macrophages in primary lymphoid organs or blood, there was destruction of splenic architecture and, most importantly, mononuclear cell infiltration of the thyroids was significantly lower compared to controls. The role of activated macrophages in SAT is discussed.

Animals↗

PubMed1996

Characterization of the AKR thymic microenvironment and its influence on thymocyte differentiation and lymphoma development.

The thymic stroma has long been implicated in AKR thymic leukaemia. In this study an extensive panel of monoclonal antibodies was used to investigate changes in the AKR thymic microenvironment, in parallel with thymocyte differentiation of normal (2 month), preleukaemic (5-7 month) and leukaemic (> 7 month) mice. We found select alterations in the thymic stroma, including a loss of isolated medullary antigens and changes in MTS 32, a mAb detecting an antigen on both thymocytes and stroma in the thymic cortex. Stromal alterations were accompanied by shifts in thymocyte differentiation and the appearance of the leukaemogenic mink cell focus-forming (MCF) murine leukaemia virus.

Analysis of Variance↗

PubMed1996

Ossification of the distal phalanx of the first digit as a maturity indicator for initiation of orthodontic treatment of Class III malocclusion in Japanese women.

The influence of mandibular growth on the stability of orthodontic treatment has been well established. A particular problem is late mandibular growth in patients with Class III malocclusions, because of skeletal jaw discrepancies that may influence the timing and course of treatment, as well as the stability of posttreatment. We have used the ossification of the distal phalanx of the first digit as an indicator of the skeletal maturity of the patient and of their potential for further growth. Our previous studies have shown that fusion of the epiphysis and the diaphysis of the distal phalanx of the first digit occurs from 1 to 3 years after the pubertal growth maximum in Japanese women. In these case reports, the orthodontic treatment of two female patients with mild Class III skeletal malocclusions is presented to show the possible clinical application of the ossification of the first digit as an indicator of the completion or near cessation of mandibular growth in the timing of treatment of Class III malocclusions. The case reports show that, although both patients experienced some mild degree of mandibular growth after treatment, this method can be helpful in determining residual mandibular growth potential in Japanese female patients with Class III malocclusions and mild skeletal discrepancies.

Age Determination by Skeleton↗

PubMed1996

The decision to extract: part II. Analysis of clinicians' stated reasons for extraction.

In a recently reported study, the pretreatment records of each subject in a randomized clinical trial of 148 patients with Class I and Class II malocclusions presenting for orthodontic treatment were evaluated independently by five experienced clinicians (drawn from a panel of 14). The clinicians displayed a higher incidence of agreement with each other than had been expected with respect to the decision as to whether extraction was indicated in each specific case. To improve our understanding of how clinicians made their decisions on whether to extract or not, the records of a subset of 72 subjects randomly selected from the full sample of 148, have now been examined in greater detail. In 21 of these cases, all five clinicians decided to treat without extraction. Among the remaining 51 cases, there were 202 decisions to extract (31 unanimous decision cases and 20 split decision cases). The clinicians cited a total of 469 reasons to support these decisions. Crowding was cited as the first reason in 49% of decisions to extract, followed by incisor protrusion (14%), need for profile correction (8%), Class II severity (5%), and achievement of a stable result (5%). When all the reasons for extraction in each clinician's decision were considered as a group, crowding was cited in 73% of decisions, incisor protrusion in 35%, need for profile correction in 27%, Class II severity in 15% and posttreatment stability in 9%. Tooth size anomalies, midline deviations, reduced growth potential, severity of overjet, maintenance of existing profile, desire to close the bite, periodontal problems, and anticipation of poor cooperation accounted collectively for 12% of the first reasons and were mentioned in 54% of the decisions, implying that these considerations play a consequential, if secondary, role in the decision-making process. All other reasons taken together were mentioned in fewer than 20% of cases. In this sample at least, clinicians focused heavily on appearance-related factors that are qualitatively determinable by physical examination of the surface structures of the face and teeth. They appear to have made primary use of indicators available on study casts and facial photographs and relatively little use of information that is available only on cephalograms or that involves the application of specialized orthodontic theories.

Adolescent↗

PubMed1996

The decision to extract: Part 1--Interclinician agreement.

As part of an ongoing prospective clinical trial of conventional orthodontic treatment, the decision making patterns of a representative group of orthodontic clinicians were examined. Data were available for 148 subjects (100 adolescents and 48 adults) who had presented at the University of California San Francisco Graduate Orthodontic Clinic requesting treatment for correction of a Class I or Class II malocclusion. The records for each subject were evaluated independently by each of five members of the clinical faculty, making available a total of 740 independent patient evaluations. With regard to the primary decision as to whether extraction or nonextraction treatment was to be preferred, agreement among clinicians was higher than had been anticipated. In almost two thirds of the cases, the decisions of all five clinicians were in agreement as to whether extraction or nonextraction was the preferred treatment modality. (This figure included 59 cases of complete agreement for extraction therapy (40%) and 38 cases of complete agreement for nonextraction therapy (26%)). In only 51 cases (34%), did the reviewing clinicians disagree as to whether extraction or nonextraction was the preferred modality of treatment. The clinicians were also asked to indicate their opinions as to whether orthognathic surgery was likely to be a part of the ultimate treatment course for each individual subject. Nine percent of the 740 patient evaluations contained a clinician judgement that surgery would be a probable or definite component of the orthodontic treatment plan. For 29% of the adult subjects (14 cases) and 23% of the adolescent subjects (23 cases), one or more of the five examining clinicians believed that adjunctive surgical intervention would probably or definitely be appropriate. These high values were unexpected, particularly because the sample had been prescreened by a single clinician to exclude subjects who might require orthognathic surgery. Clinician agreement of Angle classification was also evaluated. Disagreements were observed in 14 adult subjects (29%) and 27 adolescent subjects (27%). Little association was observed between clinician agreement on Angle classification and clinician agreement on whether or not to extract.

Adolescent↗

PubMed1996

Apical root resorption in orthodontically treated adults.

This study analyzed the relationship in orthodontically treated adults between upper central incisor displacement measured on lateral cephalograms and apical root resorption measured on anterior periapical x-ray films. A multiple linear regression examined incisor displacements in four directions (retraction, advancement, intrusion, and extrusion) as independent variables, attempting to account for observed differences in the dependent variable, resorption. Mean apical resorption was 1.36 mm (sd +/- 1.46, n = 73). Mean horizontal displacement of the apex was -0.83 mm (sd +/- 1.74, n = 67); mean vertical displacement was 0.19 mm (sd +/- 1.48, n = 67). The regression coefficients for the intercept and for retraction were highly significant; those for extrusion, intrusion, and advancement were not. At the 95% confidence level, an average of 0.99 mm (se = +/- 0.34) of resorption was implied in the absence of root displacement and an average of 0.49 mm (se = +/- 0.14) of resorption was implied per millimeter of retraction. R2 for all four directional displacement variables (DDVs) taken together was only 0.20, which implied that only a relatively small portion of the observed apical resorption could be accounted for by tooth displacement alone. In a secondary set of univariate analyses, the associations between apical resorption and each of 14 additional treatment-related variables were examined. Only Gender, Elapsed Time, and Total Apical Displacement displayed statistically significant associations with apical resorption. Additional multiple regressions were then performed in which the data for each of these three statistically significant variables were considered separately, with the data for the four directional displacement variables. The addition of information on Elapsed Time or Total Apical Displacement did not explain a significant additional portion of the variability in apical resorption. On the other hand, the addition of information on Gender to the information on the four directional displacement variables yielded an R2 value of 0.35, which indicated that these variables taken together could account for approximately a third of the observed variability in apical resorption in this sample.

Adult↗

PubMed1996

Thymic medulla epithelial cells acquire specific markers by post-mitotic maturation.

The development of thymocyte subsets and of the thymic epithelium in SCID and RAG-2/-mice was monitored after normal bone-marrow-cell transfer. The kinetics of thymic reconstitution and their relationships with cell proliferation were investigated by using bromodeoxyuridine to detect DNA-synthesizing cells among lymphoid cells by 3-color flow cytometry, and in epithelial compartments by staining frozen sections. Thymocytes started to express CD8 and CD4 10 days after transfer, simultaneously with extensive proliferation. The first mature CD4+ single-positive cells were generated, from resting CD4+CD8+ cells after day 15. During this day 10-15 period, many epithelial cells positive for cortex-specific or panepithelial markers were labeled with BrdUrd after pulse-injection. Organized medullary epithelium also developed after day 15, that is, synchronously with the appearance of mature thymocytes, but medullary cells were never found BrdUrd+. These results suggest that, in these models, the reconstitution of the thymic epithelial network proceeds through expansion of preexisting cortical or undifferentiated cells and by later maturation (acquisition of specific markers) of medullary cells. This last process is dependent of the presence of mature thymocytes.

Animals↗

PubMed1995

Thymic epithelial cell abnormalities in (NZB x H-2u)F1 mice.

Thymic maturation processes including MHC restriction and self-recognition require intimate association of thymocytes and stromal cells. Compared to the thymic architecture of various "normal" control strains of mice, defects in the thymic microenvironment have been demonstrated in New Zealand black (NZB) mice. Moreover, it is well known that NZB(H-dd) mice, when crossed with NZW(H-2u) mice, (NZB x NZW)F1, display a unique spectrum of autoimmune disease manifestations, including murine SLE. Using an extensive panel of monoclonal antibodies that define the thymic microenvironment, we examined two additional strains of (NZB x H-2u)F1 mice: (NZB x C57BL/10.PL)F1 and (NZB x PL/J)F1 mice to investigate the contributions of the H-2 and non-H-2 loci to the thymic abnormalities previously documented to occur in murine lupus. NZB, NZW, and (NZB x NZW)F1 mice were studied concurrently as were two additional control strains C57BL/6 and C57BL/10Sn. NZW mice had a normal thymic architecture as did the other H-2u mice and the control strains. In contrast, (NZB x NZW)F1 mice had a significantly altered thymic microenvironment; mild thymic abnormalities were also found in (NZB x PL/J)F1 but not in (NZB x C57BL/10.PL)F1. As expected, (NZB x NZW)F1 mice developed elevated titers of autoantibodies to DNA, proteinuria, and decreased life span. Interestingly, only (NZB x PL/J)F1 mice had increased levels of IgM antibodies to dsDNA, but did not manifest IgG anti-DNA or reduced survival. Defects in thymic stromal cells are associated directly to autoimmunity and their origin appears to be determined by non-H-2 loci.

Animals↗

PubMed1995

Thymic microenvironment and lymphoid responses to sublethal irradiation.

Sublethal irradiation of the murine thymus has been a useful tool for depleting the thymus of dividing immature thymocyte subsets, to sequence thymocyte differentiation events occurring from radiation-resistant precursors. This massive reduction in thymocytes also represents a model in which the bidirectional interplay between the thymic stromal cells and lymphocytes can be investigated. The purpose of this study was thus twofold: to precisely map the initiation of thymopoiesis as a prelude to assessing the effects of injected mAb to novel thymic antigens; and to use a panel of mAbs to determine the alterations in the thymic stroma during the T-cell depletion and reconstitution phases. The striking finding from this study was that following T-cell depletion, there was a marked upregulation of specific stromal antigens, which retracted with the reappearance of T cells. Thus, following sublethal irradiation, there are modifications in the thymic microenvironment that may by necessary to support renewed thymopoiesis and the complete restoration of the thymus involved the synchronous development of both the stromal and lymphocytic components.

Animals↗

PubMed1995

Mononuclear cells isolated from fibrotic skin lesions in avian scleroderma constitutively produce fibroblast-activating cytokines and immunoglobulin M.

University of California, Davis line 200 and 206 chickens develop an inherited autoimmune fibrotic disease associated with autoantibodies and other features similar to human scleroderma. Early in life, line 200/206 chickens develop mononuclear cell (MNC) infiltrates in the skin, followed by severe dermal fibrosis and vascular occlusions. Cultured fibroblasts derived from fibrotic skin lesions of line 200/206 chickens display an activated phenotype producing elevated quantities of collagen and glycosaminoglycan (GAG) compared to fibroblasts derived from normal chicken skin. To demonstrate a link between skin mononuclear cell infiltration and fibroblast activation, we cultured MNC isolated from developing fibrotic skin lesions, normal appearing skin, and peripheral blood of line 206 chickens for 24-72 h. Subsequent assay of MNC culture supernatants for effect on the collagen and GAG production of normal chicken skin fibroblasts demonstrated that only fibrotic lesion MNC supernatants contained significant collagen and GAG synthesis stimulatory activity. Both stimulatory activities were constitutively produced, undialyzable, heat and protease sensitive, and coeluted on gel filtration with a M(r) of 24-32 kD. Gel filtration also revealed that fibrotic lesion MNC secrete a protein > 250 kD, which we have identified as immunoglobulin (Ig) M by Western blot analysis. These results demonstrate that skin infiltrating MNC secrete both fibroblast-activating cytokines and IgM and thus they likely play an important role as effector cells in the development of dermal fibrosis and autoantibodies in this avian model of scleroderma.

Animals↗

PubMed1994

MTS-32 monoclonal antibody defines CD4+8- thymocyte subsets that differ in their maturation level, lymphokine secretion, and selection patterns.

We have previously described MTS-32 as identifying an Ag on both thymic stromal cells and thymocytes. In contrast with CD4+8+ and CD4-8+ thymocytes, of which the vast majority are MTS-32+, a notable subset of CD4+8- thymocytes is MTS-32-. Here we show that with regard to heat-stable Ags, Qa-2, and CD69 expression CD4+8- MTS-32- thymocytes are phenotypically enriched in mature cells when compared with their MTS-32+ counterparts. Moreover, sorted CD4+8- MTS-32+ thymocytes are unable to respond to anti-CD3 cross-linking, whereas MTS-32- CD4+8- thymocytes respond to the same stimulus by producing IL-4, IL-5, IL-10, IFN-gamma, and trace amounts of IL-2. In addition, MTS-32- CD4+8- and CD4-8- TCR-alpha beta+ thymocytes differ in their TCR V beta repertoire on a Mls-1a selecting background. We therefore suggest that the MTS-32 ligand is involved in signals consecutive with TCR recognition in the thymus, i.e., selection, activation, and lymphokine production.

Animals↗

PubMed1994

Evidence for a selective and multi-step model of T cell differentiation: CD4+CD8low thymocytes selected by a transgenic T cell receptor on major histocompatibility complex class I molecules.

We have characterized a prominent (15-20%) thymocyte population expressing CD4 at a high and CD8 at a low level (CD4+8lo) in mice transgenic for a T cell receptor (TCR) restricted by major histocompatibility complex (MHC) class I molecules. The results demonstrate that the CD4+8lo population is an intermediate stage between immature CD4+8+ and end-stage CD4+8- thymocytes and that the survival of these cells crucially depends on the successful interaction of the transgenic TCR with self MHC class I molecules. In addition we demonstrate that the avidity of the interaction between TCR and self MHC class I molecules determines whether CD4+8lo thymocytes are found in significant numbers in this transgenic model. Our findings support a selective and multi-step model of T cell differentiation in the thymus.

Animals↗

PubMed1994

Effect of rotary electric toothbrush versus manual toothbrush on decalcification during orthodontic treatment.

The purpose of this study was to determine whether daily use of a rotary electric toothbrush (Rota-dent, Prodentec Corp., Batesville, Ark.) and a 0.05% sodium fluoride (NaF) rinse would significantly reduce decalcification when compared with manual toothbrushing only (control group) or manual toothbrushing and daily use of a NaF rinse (rinse group). All three groups used a standard fluoride toothpaste. Ninety consecutive adolescent patients who were to receive orthodontic treatment were placed into one of three groups according to age and sex criteria. Decalcification was evaluated single blind by two calibrated examiners on the facial surfaces of all permanent teeth before appliances were placed (baseline) and 3 months after appliances were removed (posttreatment). Data were analyzed by analysis of covariance with the dependent variable derived by subtracting the baseline decalcification scores from the posttreatment scores and using the baseline scores as the covariate. The results showed that although there were no significant differences between the three groups at baseline, the Rota-dent group showed significantly (p < 0.05) less posttreatment decalcification than either the control or rinse groups. In a separate analysis of first molars, the Rota-dent group again showed the least decalcification and the control group showed the most. These data suggest that twice daily use of the Rota-dent electric toothbrush with a standard fluoride toothpaste and once daily use of a 0.05% NaF rinse is more effective for preventing decalcification in adolescents during orthodontic treatment with fixed appliances than either conventional toothbrushing with a fluoride toothpaste, or similar toothbrushing and toothpaste with a once daily NaF rinse.

Adolescent↗

PubMed1994

Eighteen-month evaluation of the effects of a 0.4% stannous fluoride gel on gingivitis in orthodontic patients.

The purpose of this study was to determine whether conventional toothbrushing and twice daily use of a brush-on 0.4% stannous fluoride (SnF2) gel containing more than 90% available Sn2+ would be more effective for controlling plaque accumulation and gingivitis in the presence of orthodontic appliances than conventional toothbrushing alone. Consecutively treated adolescents who were to receive full-mouth fixed orthodontic appliances were assigned to one of two groups according to age and sex criteria. The first group (control, n = 35) used toothbrushing with a standard fluoride toothpaste, whereas the second group (treatment, n = 30) used toothbrushing supplemented with a 0.4% SnF2 gel used twice daily for the entire 18-month study period. Clinical assessments (Plaque Index, Gingival Index, bleeding tendency, and coronal staining) were made single blind before appliances were placed and 1, 3, 6, 9, 12, and 18 months after appliances were placed. Complete data were obtained for 32 control and 23 SnF2 gel subjects. The results indicated that the SnF2 gel group had significantly lower scores for plaque index (p < 0.01), gingival index (p < 0.001), and bleeding tendency (p < 0.001) at all examinations than did the control group. In the SnF2 group, one subject developed mild coronal staining, and two subjects developed moderate staining. We conclude that the use of a 0.4% SnF2 gel containing more than 90% available Sn2+ is an effective adjunct to mechanical tooth cleaning in preventing gingivitis in adolescents undergoing orthodontic treatment with fixed appliances.

Adolescent↗

PubMed1994

Long-term followup of orthodontic treatment of a patient with maxillary protrusion, severe deep overbite and thumb-sucking.

Oral habits should be of primary clinical concern to orthodontists because they may cause malocclusion, and/or interfere with treatment progress. Generally habit control should be achieved prior to correction of the malocclusion in an effort to remove any etiological factors in development and maintenance of the malocclusion. It is also important for the clinician to understand that habit-breaking treatment may require an extended treatment time because habits may have been present for long periods of time and may be related to underlying psychological problems. The present report documents the treatment of maxillary protrusion in a patient in which a thumb-sucking habit had persisted from infancy until almost age 12. Elimination of the habit was accomplished prior to correcting the malocclusion and for stability of the result. Orthodontic treatment consisted of extracting two maxillary premolars followed by full treatment with fixed appliances. Long-term postretention records show good stability of the corrected malocclusion.

Child↗

PubMed1994

Case report: nonsurgical treatment of an adult with severe anterior open bite.

A malocclusion characterized by open bite and vertical maxillary excess can be one of the most difficult problems to correct through orthodontic treatment because of the difficulty in permanently changing the morphological disharmony and/or functional disorder associated with open bite. However, in some patients with less severe skeletal impairment it may be possible to orthodontically correct the occlusal disharmony so that the new relationship of the dental arches becomes compatible with normal function of the oral environment. Stability may be enhanced if mechanics are used which do not extrude posterior teeth.

Activator Appliances↗

PubMed1994

Flow cytometric analysis reveals unexpected shared antigens between histologically defined populations of thymic stromal cells.

Utilizing flow cytometry, the expression of antigens recognized by six thymic stromal cell (TSC) reactive mAbs was investigated on fresh TSCs and TSC lines. It was found that some thymic epithelial cells and dendritic cells share antigenic phenotypes, and that most TSC reactive mAbs have a more extensive distribution than would have been predicted from immunohistology. While these findings illustrate the higher sensitivity of flow cytometric analysis, they more importantly emphasize the great complexity of TSC that direct T cell development. In order to identify the molecular parameters that define the various steps involved in T cell differentiation, TSC antigens (non-TCR/MHC/co-receptor) that are functional will have to be identified. This study represents the initial steps in characterizing such antigens.

Animals↗

PubMed1994

Long-term evaluation of a SnF2 gel for control of gingivitis and decalcification in adolescent orthodontic patients.

The purpose of this paper is to review two recently reported, long-term studies of several chemical methods to control gingivitis and decalcification in in adolescent orthodontic patients. The first study (gingivitis study) was designed to determine whether conventional toothbrushing and twice daily use of a brush-on 0.4 per cent SnF2 gel containing more than 90 per cent available Sn2+ would be more effective for controlling plaque accumulation and gingivitis in the presence of orthodontic appliances than conventional toothbrushing alone. The second study (decalcification study) was designed to compare the effectiveness of controlling decalcification in orthodontic patients with either a 1100 ppm F toothpaste used alone, this same toothpaste and a 0.05 per cent NaF rinse or this toothpaste and a 0.4 per cent SnF2 gel. In the gingivitis study, sixty-five consecutively treated adolescents who were to receive full-mouth fixed orthodontic appliances were assigned to two groups according to age and sex criteria. In the decalcification study an additional 30 subjects (95 total) were similarly assigned to a third group. The first group (control, n = 35) used only toothbrushing with a standard fluoride (1100 ppm F) toothpaste. The second group used toothbrushing with a similar dentifrice supplemented with a 0.4 per cent SnF2 gel (SnF2 gel group, n = 30) used twice daily for the entire 18-month study period. The third group (in the decalcification study only) used a similar toothpaste and 0.05 per cent NaF rinse (NaF rinse group, n = 30). Clinical assessments of plaque accumulation using the Plaque Index, gingival inflammation using the Gingival Index, and coronal staining were completed single-blind before appliances were placed and 1, 3, 6, 9, 12 and 18 months after appliances were placed. Decalcification was assessed single blind on all labial surfaces of all erupted teeth before appliances were placed and 3 months after appliances were removed. The results of the gingivitis study indicated that the SnF2 gel group had significantly lower scores for the Plaque Index (p < 0.01) and the Gingival Index (p < 0.001) at all examinations during orthodontic treatment than did the control group. In the SnF2 gel group, one subject developed mild coronal staining and two subjects developed moderate staining. In the decalcification study, when pre-treatment levels of decalcification were subtracted from post-treatment values, significantly lower decalcification scores (p < 0.05) were found for both whole mouth and first molars in the NaF rinse and gel groups as compared with the control group (toothpaste alone).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗