Biomedical subjects
B Loughner
Publications and source records attributed to B Loughner.
The development of strains, forces and nociceptor activity in retrodiscal tissues of the temporomandibular joint of male and female goats.
Chronic pain in the temporomandibular (TM) joint is predominantly manifested in women. We examined biomechanical and neural factors that could contribute to this differential representation. Relationships between jaw rotation, soft tissue strains and soft tissue forces were examined in the goat TM joint. Strains were minimal until the jaw was rotated beyond the normal range of motion (7.25 deg). There were no significant differences in rotation-strain patterns in males and females. Stress developed as strains were introduced by jaw rotation. Gender differences were observed. Males manifested higher failure loads (15.94 +/- 1.98 and 11.37 +/- 2.02 N, for males and females respectively) and higher elastic stiffness than females (5.62 +/- 1.19 N/mm and 1.64 +/- 0.31 N/mm, for males and females respectively). Recordings were made from cell bodies in the trigeminal ganglion whose distal processes innervated the retrodiscal tissue of the temporomandibular joint of the goat (n = 48). Nociceptor reactivity was characterized with respect to the capacity to transduce mandibular rotation (rotation-interval functions; n = 29). On the basis of established relationships between rotation, strain and tissue forces, rotation-interval functions were transformed into strain-interval and force-interval functions. Comparisons were made between nociceptor properties grouped by gender. No differences in properties were observed when nociceptors were characterized with respect to jaw rotation; however, gender differences were obtained when nociceptor reactivity was characterized with respect to retrodiscal strains or forces. Consistent with smaller failure loads, nociceptors of retrodiscal tissues of females manifested a smaller range (1.12 vs 4.33 N), force to average (1.51 vs 4.64 N), force to minimum (0.95 vs 2.48 N) and force to asymptotic discharge (2.07 vs 6.81 N). Consistent with lower elastic stiffness, nociceptors of female tissues manifested higher average strain (54.4% vs 41.9%) and peak strain (74.0% vs 58.1%) to asymptotic discharge relative to those sampled from male tissues. The implications of these findings for TM joint injury and chronic pain are considered.
Parallels between properties of high-threshold mechanoreceptors of the goat oral mucosa and human pain report.
In the following experiments, we examined parallels between properties of A-delta high-threshold mechanoreceptors (HTMs; mechanonociceptors, MN, and intense pressure receptors, IPR) innervating the goat mucosa and human mucosal pain report. As suggested in previous studies, activation thresholds of afferents which are generally considered to be mechanical nociceptors are far below mechanical pain thresholds. It was determined that classification of nociceptors by frequency thresholds, i.e., the pressure at which HTMs maintained a minimum frequency (97 g/mm2 and 117 g/mm2 for IPRs and MNs respectively) brings afferent reactivity into alignment with perceptual events. The range of reactivity of the nociceptor pool paralleled pain report from "faint-weak" (142 g/mm2) to "strong-intense" (277 g/mm2). It is suggested that coding of intense mechanical pain from compressive forces is likely to arise from both individual afferents, whose reactivity spanned the range, and from recruitment of afferent populations with progressively higher thresholds.
Properties of high-threshold mechanoreceptors in the oral mucosa. I. Responses to dynamic and static pressure.
1. Mechanical response properties of high-threshold mechanoreceptors (HTMs) of the goat oral mucosa were determined by single-unit recording from the palatine and alveolar nerves and from the trigeminal ganglion. The following observations were made. 2. HTMs of the oral mucosa could be separated into two subgroups on the basis of their threshold to mechanical stimulation. Intense pressure receptors (IPRs) comprised a group of A-delta afferents with thresholds of 2-16 g. Mechanonociceptors (MNs) comprised a group of relatively slowly conducting afferents (A-delta and C-fibers) with a higher threshold range (16-300 g). 3. In most instances, MNs lacked pressure-transducing capacity. Tests of reactivity to dynamically or statically applied stimuli revealed that significant functions were rarely fit between MN activity and pressure (4/20 cases). 4. IPRs differed from MNs by their pressure-transducing properties. The afferent response interval was in inverse proportion to the applied pressure. Significant pressure interval functions were fit in 16/20 cases. The relationship between pressure and response interval was best described by power functions. 5. Tests of reactivity to dynamically or statically applied stimuli revealed that IPRs preferred static pressure. Tighter fits and steeper slopes were observed in power functions fit to data generated by statically applied stimuli (mean fitted function, dynamic test: LnISI = -0.97 LnP + 3.4; mean fitted function, static test: LnISI = -1.6 LnP + 4.71). 6. Pressures-frequency thresholds (PFTs), asymptotes (PFAs), and mean response intervals (MRIs) were determined for IPRs from the static test series. The first two values are the pressures that produce the lower and upper limits of response frequency of mucosal HTMs (mean PFT, 1.48 N/mm2; mean PFA, 3.34 N/mm2). The MRI (28 ms) is simply computed from the function. When PFTs and PFAs are combined with activation threshold and power functions, they provide a relatively complete description of the range and form of reactivity of the IPR of the oral mucosa.
Condylar movement recordings for analyzing TMJ derangements.
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