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J C Stevens

Publications and source records attributed to J C Stevens.

At least 109 records · Page 6Linked to original sources
PubMed1988

Click-evoked oto-acoustic emissions in normal and hearing-impaired adults.

Click-evoked oto-acoustic emissions have been recorded in 18 normal subjects and 19 hearing-impaired subjects taken from an ENT outpatient clinic. An emission could be recorded in all but 1 ear of those subjects where the psychoacoustic threshold to the click stimulus was 13 dB nHL or lower. No emission could be recorded in all subjects where this threshold was 18 dB nHL or higher. The level of stimulus required to obtain a recordable emission was found to be correlated with the psycho-acoustical threshold of the click stimuli but not to a high enough level to make this a useful measure of hearing loss.

Acoustic Impedance Tests↗
PubMed1988

Selective inactivation of four rat liver microsomal androstenedione hydroxylases by chloramphenicol analogs.

The steroid androstenedione has been shown to be a valuable tool for the study of the selective inactivation of cytochrome P-450 isozymes in intact rat liver microsomes. The validity of this approach was investigated using microsomes, purified cytochrome P-450 isozymes, antibodies to particular cytochromes P-450, and the known mechanism-based inactivator chloramphenicol. Enzyme inactivation and antibody inhibition studies show that microsomes from both phenobarbital- and non-phenobarbital-treated rats are needed to accurately monitor the inactivation of the major phenobarbital-inducible cytochrome P-450 isozyme (PB-B) and of the major constitutive androstenedione 16 alpha-hydroxylase (UT-A). Similar experiments indicate that, although isozyme P-450g does catalyze the 6 beta-hydroxylation of androstenedione in a reconstituted system, this cytochrome appears to make only a minimal contribution to microsomal 6 beta-hydroxylase activity, which reflects instead the activity of pregnenolone-16 alpha-carbonitrile-induced isozymes. With these parameters investigated, initial enzyme inactivation studies showed that the antibiotic chloramphenicol caused different rates of NADPH-dependent enzyme inactivation among the four androstenedione hydroxylases monitored (16 beta greater than 6 beta greater than 16 alpha greater than 7 alpha). Based on these data, 12 chloramphenicol analogs were examined, and the results with these compounds show that their selectivity as cytochrome P-450 inactivators is a function of at least three structural features: 1) the number of halogen atoms, 2) the presence of a para-nitro group on the phenyl ring, and 3) substitutions on the ethyl side chain. For example, the compound N-(2-phenethyl)dichloroacetamide was shown to reversibly inhibit but not inactivate the cytochrome(s) P-450 responsible for androstenedione 6 beta-hydroxylase activity, whereas N-(2-p-nitrophenethyl) and N-(1,2-diphenethyl)dichloroacetamide rapidly inactivated the 6 beta-hydroxylase. The ability to monitor the activity of multiple isozymes with a single substrate should allow the development of a systematic approach to the design of selective inactivators of rat liver cytochromes P-450.

Androstenedione↗
PubMed1987

AAEE minimonograph #26: The electrodiagnosis of carpal tunnel syndrome.

The electrodiagnosis of carpal tunnel syndrome is reviewed, including discussions of old and new techniques of motor and sensory nerve conduction, anomalous innervation, needle electrode examination, and one method of examining a patient with suspected carpal tunnel syndrome. The results of electromyographic testing of 505 patients with carpal tunnel syndrome in Rochester, Minnesota, from 1961 to 1980 are compared with results from previous studies. In the appendixes, a method of performing median motor and sensory nerve conduction studies and Mayo Clinic normal values are provided.

Carpal Tunnel Syndrome↗
PubMed1987

Syringomyelia: electrophysiologic aspects.

The clinical and EMG findings in 44 patients with syringomyelia who were seen at the Mayo Clinic between 1976 and 1985 are presented. In 10 of the patients, somatosensory evoked potentials (SEPs) of the upper and lower extremities were obtained. All 44 patients had radiographic or surgical evidence of a cervical syrinx. The most common abnormality on nerve conduction studies was a reduced hypothenar compound muscle action potential amplitude (23 patients). Abnormal findings on needle electromyography were present in 33 patients and included sparse fibrillation potentials, reduced motor unit potential (MUP) recruitment, and chronic neurogenic MUP changes in muscles innervated by the C-5, T-1 roots, with the most pronounced changes in small hand muscles. Ulnar and median nerve SEPs were usually normal in the presence of a dissociated sensory loss and were usually abnormal when all sensory modalities were impaired. Abnormalities of tibial nerve SEPs were frequent and were related to impaired proprioceptive sensation in the lower extremities.

Electromyography↗
PubMed1987

Assessment of nerve damage in the feet of long-distance runners.

To answer the question, "Does long-distance running injure nerves of the feet and legs?" we invited the 25 members of the Rochester Track Club who had run the greatest number of miles in their lifetime to participate in a study that involved neurologic examination, determination of detection thresholds of touch-pressure, vibratory, and cooling sensations of the foot, and evaluation of nerve conduction. None of the runners had clinical symptoms or signs of peripheral neuropathy. Most of them reported having had toe and foot injuries, sometimes associated with short-lived sensory symptoms. A computer-assisted sensory evaluation of the detection threshold for vibratory sensation of the toe revealed slightly, but significantly, higher values in the runners in comparison with age- and sex-matched control subjects. Similarly, small, but statistically significant, differences were also observed for some attributes of nerve conduction in the leg and foot nerves of the runners. These results suggest that long-distance running causes multiple small injuries to the toes and feet, which lead to measurable differences in the detection threshold for vibratory sensation and in nerve conduction but not to overt neuropathy. The trivial subclinical neuropathic deficits we noted are readily offset by the assumed health and recreational benefits of running.

Adolescent↗
PubMed1987

Nasal resistance to airflow (its measurement, reproducibility and normal parameters).

A method of rhinomanometry is described for use in clinical research work. The statistical distribution of nasal resistance values is studied in a sample of 59 normal individuals. The variation of nasal resistance within two individuals is studied over a period of 7 hours. The choice of appropriate statistical tests to be used when comparing nasal resistance values is discussed. The reproducibility of nasal resistance measurements is assessed in 47 normal individuals. The results were used to define a normal range of values for total nasal resistance to airflow.

Adolescent↗
PubMed1987

Old-age deficits in the sense of smell as gauged by thresholds, magnitude matching, and odor identification.

Twenty elderly subjects (70-90 years old) and 20 young control subjects (18-24 years old) underwent three kinds of olfactory testing: absolute thresholds to three odorants (d-limonene, iso-amyl butyrate, benzaldehyde), magnitude matching of these odorants to salt tastes, and odor identification of 30 common substances. For all three odorants elderly subjects' mean threshold significantly exceeded that of the young by about ninefold for d-limonene, about threefold for benzaldehyde, and about twofold for iso-amyl butyrate. These threshold differences predict approximate concentration differences necessary to arouse the same estimated odor strength above the threshold for the elderly and the young. Young subjects also scored better than the elderly in odor identification, even when subjects were given four alternatives from which to select the correct label. Unimpaired olfactory functioning is uncommon in the elderly; correlational tests show that as a group the young have better olfactory ability and show more interindividual uniformity.

Adolescent↗
PubMed1987

A comparison of oto-acoustic emissions and brain stem electric response audiometry in the normal newborn and babies admitted to a special care baby unit.

Brainstem auditory evoked potentials and oto-acoustic emissions have been recorded in 30 normal newborns and in 112 infants admitted to a special care baby unit as part of a study to determine whether these tests can be used to detect the hearing impaired infant. All the ears tested in the normal newborns, where the infant was quiet enough to complete the test, produced a brain stem electric response at a stimulus level less than or equal to 53 dB nHL (dB relative to normal hearing) and 96% produced an oto-acoustic emission at the highest level tested of 41 dB nHL. The mean threshold of the oto-acoustic emission in the normal newborns was 17.7 dB lower than the mean brain stem electric response threshold. The range of thresholds were similar. In the special care infants 84% of ears produced a brain stem electric response at a screening level of 43 dB nHL and 81% of ears produced an oto-acoustic emission at a screening level of 31 dB nHL.

Acoustic Stimulation↗
PubMed1987

Nonsystemic vasculitic neuropathy.

Among 65 patients with necrotizing vasculitis, 45 had systemic and 20 had nonsystemic vasculitic neuropathy. In nonsystemic vasculitic neuropathy, clinically only nerves are affected; there are no, or few, constitutional symptoms or serological abnormalities. The clinical and pathological features are those of an ischaemic neuropathy caused by a necrotizing vasculitis of small arterioles. These 20 patients had neuropathic symptoms for a median time of 11.5 yrs (range 1-35 yrs). The clinical pattern of neuropathy was that of multiple mononeuropathy in 13, asymmetric neuropathy in 4, distal polyneuropathy in 3, and sensory polyneuropathy in 1. As compared with their initial evaluation, 8 are now worse, 5 are better, 4 are approximately the same, and 3 are dead from unrelated causes. Prednisone was thought to prevent the development of new lesions in some cases. By contrast, of the 41 patients with systemic necrotizing vasculitis whose outcome is known, 12 are dead (median time, 1.5 yrs, range 3 months-8 yrs) and 29 are alive (median time, 6 yrs, range 6 months-22 yrs).

Adult↗
PubMed1987

Rhinomanometry: do the anterior and posterior methods give equivalent results?

Nasal resistance to airflow was measured by both anterior and posterior rhinomanometry in 15 healthy volunteers. It was found that the posterior method gave values on average 16% higher than the anterior method. This difference was statistically significant. We propose that this is due to posterior rhinomanometry measuring the resistance of the nasopharynx as well as the resistance of the nose. In the past a discrepancy between the 2 methods has been claimed to be due to an error in the standard form of the parallel resistance equation. This hypothesis was tested by measuring total nasal resistance by posterior rhinomanometry and comparing this with a total nasal resistance value derived from posterior rhinomanometric measurements of the resistance of the individual nasal cavities. The standard form of the parallel resistance formula was used to derive the total nasal resistance. There was no significant difference between the 2 values for total nasal resistance. We conclude that if measurements are made at the same pressure gradient then the use of this equation is valid.

Adult↗
PubMed1987

Magnetic resonance imaging in multiple sclerosis: analysis of correlations to peripheral blood and spinal fluid abnormalities.

MRI of the brain, peripheral blood (PB) T cell subsets and B cells, CSF T cell subsets, CSF IgG concentration and incidence of CSF oligoclonal bands (OB), and plasma cells were studied in 32 clinically suspected MS patients. The CSF in MS patients with MRI lesions showed increased IgG concentration and higher incidence of plasma cells and OB compared with those without MRI lesions. In PB, the percentage of kappa light-chain positive B cells was significantly increased in patients with abnormal MRI as compared with controls. The correlation of MRI of the head and immunologic studies in MS will be helpful in better understanding the pathogenesis and dynamics of the disease.

Adult↗
PubMed1987

Cranial neuralgias.

Explore the source record for details and available documents.

Glossopharyngeal Nerve↗
PubMed1986

Magnetic resonance imaging. Clinical correlation in 64 patients with multiple sclerosis.

Sixty-four patients with possible, probable, or definite multiple sclerosis (McAlpine criteria) were clinically evaluated using the expanded disability status scale (EDSS) and Scripps neurologic rating scale (NRS). All were examined with a 0.15T magnetic resonance scanner using T2- and T1-weighted images. Correlations between EDSS and NRS scores and severity of disease detected on magnetic resonance imaging were determined. Significant correlations existed between EDSS and NRS with magnetic resonance ratings. Moderate correlations were observed in the motor, cerebellar, and brainstem subgroups of the clinical scales. Significant low correlations existed in the mood/mentation, vision (optic nerves), and bowel/bladder subgroups. Clinical and neuroimaging limitations may account for the lack of higher correlations. Significant correlations suggest the utility of magnetic resonance imaging in monitoring disease progression, and it may prove to be the technique of choice in following up patients with multiple sclerosis.

Adolescent↗
PubMed1986

Superficial peroneal nerve conduction studies for electromyographic diagnosis.

A new standardized surface technique for conduction studies of the superficial peroneal nerve was developed and applied to 35 normal subjects and 63 patients with peroneal mononeuropathies, lumbar radiculopathies, sciatic neuropathies, lumbosacral plexopathies, or peripheral neuropathies. The response amplitude was greater than 5 microV and the response peak latency was less than 4.1 msec in all normal subjects; however, 8.6% of normal subjects had at least one unelicitable superficial peroneal nerve response (6% of all limbs tested). These data were compared with those of previous studies. Although this technique did not improve the diagnosis of peroneal neuropathy, it did distinguish lumbosacral plexopathy and sciatic neuropathy from L5 radiculopathy and served as a second, easily approachable, sensory conduction study of the leg.

Action Potentials↗
PubMed1986

Aging and the perception of nasal irritation.

Three types of measurement were employed to assess the effects of aging on nasal irritation (common chemical sense). These were measurement of detection threshold of CO2 mixed with air, measurement of the threshold concentration of CO2 that causes a transient reflex apnea, and measurement of the suprathreshold perceived strength of five levels of CO2 by the method of magnitude matching. Ancillary measurements included nasal airflow resistance and magnitude matching of an odorant (1-butanol). Twenty elderly (67 to 93) and twenty young persons (19 to 31) served as subjects. The young and elderly gave no evidence of average difference in detection threshold. In contrast, the elderly group showed a strong elevation of the threshold of apnea and a marked weakening of perceived CO2 suprathreshold strength. CO2 and butanol approximated power functions of concentration level, functions for the elderly being depressed relative to those for the young. Although the elderly had on the average slightly higher nasal resistance than the young, the differences played at most a minor role in the perception of nasal stimuli.

1-Butanol↗
PubMed1986

Multiple sclerosis: magnetic resonance imaging, evoked responses, and spinal fluid electrophoresis.

Magnetic resonance images (MRI), evoked responses (ER), and CSF findings were compared in 39 patients with possible, probable, or definite MS. MRI disclosed multiple lesions (72%) more often than ERs (55%) in the total group of patients. In possible MS, MRI showed multiple lesions in 71%, and ER abnormalities were found in 41%. MRI is the preferred test for patients with suspected MS, but ERs are useful when MRI is normal and in the evaluation of optic nerve or spinal cord lesions.

Adult↗
PubMed1986

Multiple sclerosis: MRI and clinical correlation.

Fifty-three consecutive patients with suspected multiple sclerosis were studied to determine if the extent of disease apparent on MRI correlated with the clinical severity of the disease. MRI images were evaluated and compared with an assessment of the patient's disability using three neurologic rating scales. The severity of the disease seen on MRI showed a strong statistically significant correlation (p = 0.0001) with two of the three methods of clinical evaluation and a significant correlation (p less than 0.01) with the third rating scale. The severity of disease shown on MRI correlated only weakly (p = 0.05) with the length of time the patients had been symptomatic. Normal controls did not show any abnormality characteristic of multiple sclerosis on MRI or on neurologic exam.

Brain↗