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Biomedical subjects

H Vernon

Publications and source records attributed to H Vernon.

At least 19 recordsLinked to original sources
PubMed1996

Involvement of NMDA receptor mechanisms in jaw electromyographic activity and plasma extravasation induced by inflammatory irritant application to temporomandibular joint region of rats.

The aim of this study was to examine the possible role of N-methyl-D-aspartate (NMDA) receptor mechanisms in responses induced by the small-fibre excitant and inflammatory irritant mustard oil injected into the temporomandibular joint (TMJ) region of rats. The effects of the non-competitive NMDA antagonist MK-801 were tested on the mustard oil-evoked increases in electromyographic (EMG) activity of the masseter and digastric muscles and Evans Blue plasma extravasation. Five minutes before the mustard oil injection, MK-801 or its vehicle was administered systemically (i.v.), into the third ventricle (i.c.v.), or locally into the TMJ region. Compared with control animals receiving vehicle, the rats receiving MK-801 at an i.v. dose of 0.5 mg/kg (n = 5) showed a significant reduction in the incidence and magnitude of EMG responses as well as in the plasma extravasation evoked by mustard oil; MK-801 at an i.v. dose of 0.1 mg/kg (n = 5) had no significant effect on plasma extravasation or on the incidence and magnitude of EMG responses but did significantly increase the latency of EMG responses. An i.c.v. dose of 0.1 mg/kg (n = 5) or 0.01 mg/kg (n = 5) had no significant effect on plasma extravasation or incidence of EMG responses but did significantly reduce the magnitudes of the masseter EMG response; the 0.01 mg/kg dose also significantly increased the latency of the digastric EMG response. The magnitudes of both the masseter and digastric EMG responses were also significantly reduced by MK-801 administered into the TMJ region at a dose of 0.1 mg/kg (n = 5) but not by 0.01 mg/kg (n = 5); neither dose significantly affected the incidence of EMG responses or the plasma extravasation. These data suggest that both central and peripheral NMDA receptor mechanisms may play an important role in EMG responses evoked by the small-fibre excitant and inflammatory irritant mustard oil, but that different neurochemical mechanisms may be involved in the plasma extravasation induced by mustard oil.

Animals↗
PubMed1996

Opioid involvement in electromyographic (EMG) responses induced by injection of inflammatory irritant into deep neck tissues.

Previously, we have demonstrated (Hu et al., 1993) that injection of the small-fiber excitant and inflammatory irritant mustard oil (MO) into deep paraspinal tissues surrounding C1-C2 vertebrae can evoke a sustained and reversible increase of electromyographic (EMG) activity of neck and jaw muscles, and can also produce an acute inflammatory response. This increased EMG activity lasts up to 20 min; within 30 min following MO injection, the activity returns to preinjection levels. The aim of our present study was to determine whether an opioid suppressive mechanism may be involved in limiting the increased EMG activity, despite the presence of an ongoing inflammatory response. Three doses (0.6 mg/kg, 1.2 mg/kg, and 2.5 mg/kg) of the opioid antagonist naloxone, along with vehicle (saline), were administered intravenously to determine whether naloxone is capable of inducing a significant recurrence ("rekindling" effect) of EMG activity. A dose-dependent process in the naloxone-induced rekindling effect was demonstrated for the area under the curve of rectified and integrated EMG activity. At the highest dose (2.5 mg/kg), the relative area of naloxone-evoked EMG activity increases reached 83% of the original MO-induced EMG activity level. These results suggest that a central opioid suppressive mechanism is activated by the MO-induced small-afferent barrage, and that this may limit the duration and magnitude of the evoked EMG changes.

Afferent Pathways↗
PubMed1995

Effects of inflammatory irritant application to the rat temporomandibular joint on jaw and neck muscle activity.

An electromyographic (EMG) study was carried out in 40 anaesthetized rats to determine if the activity of jaw and neck muscles could be influenced by injection of the small-fibre excitant and inflammatory irritant mustard oil into the region of the temporomandibular joint (TMJ). Injection of a vehicle (mineral oil, 20 microliters) did not produce any significant change in EMG activity. In contrast, injection of mustard oil (20 microliters, 20%) evoked increases in EMG activity in the jaw muscles but not in the neck muscles. The increased EMG activity evoked by mustard oil was reflected in 1 or 2 phases of increased activity. The early EMG increase occurred soon after the mustard oil injection (mean latency +/- SD: 3.5 +/- 2.3 sec), peaked within 1 min, and then subsided (mean duration: 7.5 +/- 5.2 min). The later EMG increase occurred at 14.6 +/- 10.0 min after the mustard oil injection and lasted 14.3 +/- 12.3 min. These excitatory effects of mustard oil on the EMG activity of jaw muscles appear to have a reflex basis since they could be abolished by pre-administration of local anaesthetic into the TMJ region. These results document that TMJ injection of mustard oil results in a sustained and reversible activation of jaw muscles that may be related to the reported clinical occurrence of increased muscle activity associated with trauma to the TMJ.

Animals↗
PubMed1994

Administration of opiate antagonist naloxone induces recurrence of increased jaw muscle activities related to inflammatory irritant application to rat temporomandibular joint region.

1. Our recent studies in rats have demonstrated that the small-fiber excitant and inflammatory irritant mustard oil injected into the temporomandibular joint (TMJ) region can evoke a sustained and reversible increase of electromyographic (EMG) activity in jaw muscles and an acute inflammatory response. The aim of the present study was to test if opioid mechanisms are involved in modulating the EMG increase evoked by mustard oil. 2. Mustard oil injected into the rat TMJ region evoked significant increases of jaw muscle EMG activity; the vehicle mineral oil had no such effect. The increased EMG activity lasted up to 20 min, and by 30 min after the mustard oil injection had returned to control (preinjection) levels, at which time administration of the opiate antagonist naloxone (1.3 mg/kg i.v.) induced a significant recurrence of the increase in EMG activity. This "rekindling" of EMG activity appeared at 5 to 10 min after the naloxone administration and lasted for 10 to 20 min. In contrast, naloxone administration in the animals receiving mineral oil injection into the TMJ region did not "rekindle" the EMG activity, nor did the administration of the peripherally acting opiate antagonist methylnaloxone or the vehicle of naloxone. 3. These findings reveal that the application of the opiate antagonist naloxone produces a recurrence of increased jaw muscle activity reflexively evoked by mustard oil injection into the rat TMJ region. They suggest that central opioid depressive mechanisms activated by the mustard oil-induced afferent barrage limit the duration of the evoked EMG changes.

Afferent Pathways↗
PubMed1993

Excitatory effects on neck and jaw muscle activity of inflammatory irritant applied to cervical paraspinal tissues.

A study was carried out in 19 anaesthetized rats to determine if the electromyographic (EMG) activity of jaw and neck muscles could be influenced by injection of the inflammatory irritant mustard oil into deep paraspinal tissues surrounding the C1-3 vertebrae. The EMG activity was recorded ipsilaterally in the digastric, masseter and trapezius muscles and bilaterally in deep neck muscles (rectus capitis posterior). In comparison with control (vehicle) injections, mustard oil (20 microliters, 20%) injected into the deep paraspinal tissues induced significant increases in EMG activity in the neck muscles in all the animals and in the jaw muscles in the majority of the animals; the effects of mustard oil were more prominent in the former. The EMG response evoked by mustard oil injection was frequently reflected in two phases of enhanced activity. The early phase of the increase in EMG activity was usually initiated immediately following mustard oil injection (mean latency: 20.4 +/- 17.7 sec) and lasted 1.6 +/- 1.1 min. The second phase occurred 11.3 +/- 7.6 min later and lasted 11.0 +/- 8.1 min. Evans Blue extravasation was apparent in the deep paraspinal tissues surrounding the C1-3 vertebrae after mustard oil injection, and histological examination showed that mustard oil injection induced an inflammatory reaction in the rectus capitis posterior muscle. These results document that injection of the inflammatory irritant mustard oil into deep paraspinal tissues results in a sustained and reversible activation of both jaw and neck muscles. Such effects may be related to the reported clinical occurrence of increased muscle activity associated with trauma to deep tissues.

Animals↗
PubMed1992

Congenital neonatal herpes simplex virus infection.

Intrauterine-acquired neonatal herpes simplex virus infection is a severe, often life-threatening infection that has a wide spectrum of clinical presentations. We describe a 31-week-gestation male who had a rarely reported epidermolysis bullosa-like clinical presentation. He acquired herpes simplex virus type II in utero secondary to a primary maternal infection that occurred on the knee. A review of the infection, the need for early therapy, and the prognosis are presented.

Female↗
PubMed1992

Cervicogenic dysfunction in muscle contraction headache and migraine: a descriptive study.

OBJECTIVE: The prevalence and nature of findings of cervicogenic dysfunction is explored in subjects with muscle contraction/tension-type (MCH) headache and common migraine without aura (CM). DESIGN: Descriptive survey. SETTING: Chiropractic outpatient research clinic. PATIENTS: Forty-seven (47) subjects, aged 18-55 with two categories of benign headache, were studied: MCH (tension-type) n = 19 (6 males, 13 females) and CM (without aura), n = 28 (3 males, 25 females). Subjects were recruited as part of an intervention trial and, thus, form a consecutive sample of patients. The present findings were elicited as part of the initial assessment. INTERVENTION: No therapeutic intervention is reported. MAIN OUTCOME MEASURES: Standardized headache history; plain film and dynamic spinal X rays; motion palpation; and pressure algometry. RESULTS: For CM, the most prevalent headache locations were frontal (81%) and occipital (78%). Neck pain and upper back pain accompanied headache in 90% and 41% of subjects, respectively. For MCH, the most prevalent headache locations were occipital (87%) and frontal (81%). Neck and upper back pain accompanied headache in 100% and 27%, respectively, of all subjects. For the total group, 77% of all subjects and 89% of females exhibited a marked reduction, absence or reversal of the normal cervical lordosis. Ninety-seven percent of all subjects exhibited, on dynamic X-ray studies, at least one significant abnormality of segmental mobility from C1 to C7, while 43% exhibited abnormalities at four or more segments. Segmental motion at C0-C1 was reduced in 90% of subjects in flexion and 70% of subjects in extension. On motion palpation, 84% of CM and MCH subjects were found to have at least two major fixations from C0 to C2. On pressure algometry, 92% of CM and 85% of MCH had at least one verifiable tender point (TP) in the upper cervical region. The most common locations for TPs were mid-cervical (C2-C3), lateral occipital and suboccipital. CONCLUSIONS: Both MCH and CM subjects demonstrate high occurrences of: a) occipital and neck pain during headaches; b) tender points in the upper cervical region; c) greatly reduced or absent cervical curve; and d) X-ray evidence of joint dysfunction in the upper and lower cervical spine. These findings support the premise that the neck plays an important, but largely ignored role in the manifestation of adult benign headaches. A case-control study should be conducted to confirm the greater prevalence of cervicogenic dysfunction in headache as compared to nonheadache subjects.

Adolescent↗
PubMed1991

The Neck Disability Index: a study of reliability and validity.

Injuries to the cervical spine, especially those involving the soft tissues, represent a significant source of chronic disability. Methods of assessment for such disability, especially those targeted at activities of daily living which are most affected by neck pain, are few in number. A modification of the Oswestry Low Back Pain Index was conducted producing a 10-item scaled questionnaire entitled the Neck Disability Index (NDI). Face validity was ensured through peer-review and patient feedback sessions. Test-retest reliability was conducted on an initial sample of 17 consecutive "whiplash"-injured patients in an outpatient clinic, resulting in good statistical significance (Pearson's r = 0.89, p less than or equal to .05). The alpha coefficients were calculated from a pool of questionnaires completed by 52 such subjects resulting in a total index alpha of 0.80, with all items having individual alpha scores above 0.75. Concurrent validity was assessed in two ways. First, on a smaller subset of 10 patients who completed a course of conservative care, the percentage of change on NDI scores before and after treatment was compared to visual analogue scale scores of percent of perceived improvement in activity levels. These scores correlated at 0.60. Secondly, in a larger subset of 30 subjects, NDI scores were compared to scores on the McGill Pain Questionnaire, with similar moderately high correlations (0.69-0.70). While the sample size of some of the analyses is somewhat small, this study demonstrated that the NDI achieved a high degree of reliability and internal consistency.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Chiropractic management of spondylolisthesis with spondylolysis of the pars interarticularis: an example of the single-case study experimental design.

Case records permeating the chiropractic literature, although claiming success utilizing conservative therapies, often are founded on isolated circumstances rather than scientific data. A detailed examination of such reports reveals a void with respect to definitive and specific approaches for the diagnosis and clinical management of disorders synonymous with chiropractic clinical practice. At best, therefore, such reports are fraught with empiricism, illustrating only the experiences of individual clinicians. The underlying difficulty encountered in reporting information on purely didactic grounds is likely due to the absence of a mechanism by which improvement in biomechanical function may be precisely and adequately quantified. In direct contrast, controlled clinical trials, as in medical research, offer the luxury of statistical clarity as to the selection of one treatment regimen over another. Researchers have indicated that the single-case study experimental design may be of value in chiropractic clinical practice, allowing for the formulation of deductive conclusions derived from each case. To facilitate the process, implementation of both retrospective and prospective aspects are proposed modifications to the general scheme. It is the purpose of this article to employ the concept of the single-case study experimental design, illustrating a condition commonly encountered in chiropractic clinical practice, that of spondylolisthesis. In so doing, we attempt to adhere to the prescribed format, while outlining both the retrospective and prospective aspects, commensurate with such a problem within the clinical setting.

Adult↗
PubMed1988

Making claims.

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Chiropractic↗
PubMed1984

Manipulation and pain tolerance. A controlled study of the effect of spinal manipulation on paraspinal cutaneous pain tolerance levels.

The response of paraspinal cutaneous pain tolerance levels to spinal manipulation has not been studied in an experimental model. This paper proposes such a model of pain tolerance measurement and describes the results of a controlled study of 50 assymptomatic subjects. The group receiving a spinal manipulation demonstrated a 140% increase in local cutaneous pain tolerance levels which was statistically significant (p less than 0.05). This is consistent with previous hypotheses regarding the mode of action of manipulation in the relief of spinal pain.

Adult↗
PubMed1984

The four quadrant weight scale: a technical and procedural review.

A discussion is presented of the four-quadrant weight scale; a postural analysis unit developed by the chiropractic profession to evaluate weight-bearing in the sagittal and frontal body planes. This report summarizes the technical description of the apparatus and attempts to establish a standardized procedural protocol. The normal and several aberrant weight-bearing patterns, and their clinical implications are discussed. Possible research applications for the future are suggested.

Biometry↗