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Biomedical subjects

J G Quinlan

Publications and source records attributed to J G Quinlan.

16 recordsLinked to original sources
PubMed2001

Long-term evaluation of extended thymectomy with anterior mediastinal dissection for myasthenia gravis.

BACKGROUND: Thymectomy for the treatment of myasthenia gravis (MG) is well established. The extent of resection, however, remains a source for debate. Outcomes for newer surgical techniques need to be compared to more extensive procedures. METHODS: A retrospective review was done of 64 consecutive patients who underwent transsternal thymectomy with extended anterior mediastinal dissection for MG between 1979 and 2000 and who were operated on by a single surgeon. RESULTS: Fifty-six patient charts were available, providing 58 operative procedures. Three patients had died of unrelated causes. The mean age of symptom onset was 36.0 +/- 2.5 years, with a mean duration of 3.3 +/- 0.5 years until surgery was undertaken. The mean length of follow-up was 6.8 +/- 0.8 years. Operative procedures were associated with a 10.3% major morbidity rate and no mortality. Drug-free remission was achieved in 50.0% of the patients, and symptoms were absent or improved in 76.8% of the patients. Patients followed up long-term (>10 years) achieved the greatest remission rate (71.4%) and symptomatic improvement (85.7%). After thymectomy, the mean dosages of prednisone and Mestinon decreased by 69.3% and 58.8%, respectively. CONCLUSIONS: Extended thymectomy provides excellent overall symptom improvement, which is enhanced over time. This review provides a basis for long-term comparison with other less invasive and perhaps less extensive procedures.

Adolescent↗
PubMed1997

Regeneration-blocked mdx muscle: in vivo model for testing treatments.

We have refined the mdx mouse as a clinical model for Duchenne dystrophy. Our power estimates, primary measures, regular sacrifice intervals, and quality checks constitute a high-speed, low-cost system for preclinically testing therapies designed to slow muscle destruction in Duchenne dystrophy. Irradiated (18 Gy) and contralateral shielded anterior tibial muscles were studied in 21-day-old mdx and normal mice at the time of irradiation and 4, 8, 12, 16, and 20 weeks thereafter. Regeneration-blocked mdx (irradiated) muscle expressed muscular dystrophy as progressive wasting after a brief (4 week) period of growth. Regeneration-blocked normal muscle showed stunted growth but neither progressive wasting nor microscopic pathological changes.

Animals↗
PubMed1996

Dystrophinopathies: clarification and complication.

The purpose of this review is to analyze the clinical applications of a remarkable series of advances made in molecular genetics, primarily with regard to Becker muscular dystrophy. A new classification is required to clarify such syndromes as Duchenne and Becker muscular dystrophy. Dystrophinopathies can be seen in patients with early onset and a severe course (Duchenne muscular dystrophy), patients with later onset and milder weakness (Becker muscular dystrophy), patients with myalgia and cramp syndrome, and patients with dilated cardiomyopathies. Dystrophin testing in muscle is the most sensitive test for identification of dystrophinopathy patients, although gene deletion studies can make the diagnosis in most cases.

Adolescent↗
PubMed1996

Myalgia and cramps: dystrophinopathy with wide-ranging laboratory findings.

We present 12 cases of males with myalgia and cramps and a normal muscle strength examination. All the patients had muscle dystrophin values consistent with Becker muscular dystrophy. Five of the patients had a normal electromyogram, and five had normal light microscopic muscle biopsy results. Of particular note, four of the 12 patients had normal serum creatine kinase levels, and four others had only mild elevations (less than twice the upper limit of normal). These patients establish an identifiable dystrophinopathy of adolescent boys and young men that can present with muscle pain and, in some cases, normal routine laboratory evaluations.

Adolescent↗
PubMed1995

Radiation inhibition of mdx mouse muscle regeneration: dose and age factors.

A single hind limb was irradiated with 12, 18, 24, or 30 Gy in mdx and C57 mice aged 12, 21, or 42 days to determine regeneration inhibition dose-response curves in different aged dystrophic mice and to characterize radiation side-effects in normal mice. The anterior tibial muscle mass (8 weeks postirradiation) and percent central nucleated (i.e., regenerated) muscle fibers were measures of regeneration inhibition. Twenty-one-day-old mdx mice irradiated with 18 Gy had complete inhibition of muscle regeneration, but 30 Gy only partially blocked regeneration in mdx mice irradiated at 12 and 42 days in age. In working to produce a clinically relevant model for Duchenne dystrophy, it is crucial to regard mouse age as a major factor in determining radiation effects on mdx muscle regeneration.

Aging↗
PubMed1995

Clinical effects of intravenously administered dantrolene.

OBJECTIVE: To compare side effects after intravenous administration of dantrolene sodium in subjects susceptible to and those nonsusceptible to malignant hyperthermia (MHS and MHN, respectively). DESIGN: We studied two groups, six patients thought to be MHS and six assumed MHN subjects, and analyzed their responses to intravenously administered dantrolene. MATERIAL AND METHODS: Dantrolene (3 mg/kg) was administered slowly into an antecubital vein, and blood samples were withdrawn from the other arm at 5 and 25 minutes after infusion. Shortly thereafter, all subjects underwent a clinical neurologic assessment, and side effects were graded subjectively by the study participants. RESULTS: Side effects occurred in all subjects. Visual symptoms occurred more commonly in MHN than in MHS subjects. Subjective muscle weakness of the extremities, dizziness, and fatigue occurred more commonly and were more severe in MHS patients than in MHN subjects. CONCLUSION: In patients recovering from an episode of malignant hyperthermia for which dantrolene has been administered, these side effects should be considered. Although the presence of side effects does not outweigh the usefulness of this drug in treating malignant hyperthermia, it may be a consideration in deciding whether to administer dantrolene prophylactically before surgical procedures in known or suspected MHS patients.

Adult↗
PubMed1992

Twitch and tetanus in mdx mouse muscle.

We compared mdx and C57BL10 anterior tibial muscle force in situ (single pulse, multiple pulse, staircase, posttetanic potentiation, and fatiguing stimulation patterns) to define muscle strength, physiology, and fatigue resistance. The relatively hypertrophied mdx muscle showed: reduced strength (N/cm2), an increased twitch-tetanus ratio, and resistance to post-fatigue twitch slowing. These differences implicate altered mdx calcium regulation, and emphasize the importance of measuring both muscle function and morphology in mdx treatment trials.

Animals↗
PubMed1992

Management of myasthenia gravis by extended thymectomy with anterior mediastinal dissection.

BACKGROUND: Thymectomy has continued to gain acceptance as definitive treatment for myasthenia gravis. Because of the nature of thymic embryology with scattered rests throughout the anterior mediastinum, we advocate a transsternal thymectomy with extended anterior mediastinal dissection. METHODS: A series of 48 patients with myasthenia gravis treated by thymectomy between 1979 and 1991 were reviewed. RESULTS: The mean length of duration of disease from onset to operation was 48.7 +/- 11.3 months, and the mean length of follow-up was 51.6 +/- 6.5 months. The operation was associated with a 21% morbidity rate (4% major morbidity) with no deaths. Forty-five patients (94%) have improved, requiring decreased medication. The overall drug-free remission rate was 42%. Of the 20 patients in remission, three had thymomas and four had hyperplastic glands. All of the patients who achieved drug-free remission were classified as Osserman's I or II. CONCLUSIONS: An aggressive surgical approach to myasthenia gravis can result in a high percentage of overall improvements and drug-free remissions. The best results are achieved in patients with lower-stage disease. Therefore transsternal extended thymectomy for myasthenia gravis appears to be the procedure of choice and should be advocated as soon as the diagnosis is made and the patient stabilized.

Adult↗
PubMed1990

Twitch response in a myopathy with impaired relaxation but no myotonia.

A patient with slow muscle relaxation but without accompanying motor unit or myotonic electrical activity had a unique staircase twitch response to repeated nerve stimulation. During 1-Hz stimulation, twitches recorded by measurement of the ankle dorsiflexor group displayed progressively increasing relaxation times with successive stimuli (37% increase) unlike the progressively decreasing relaxation time of the normal response (12-37% decrease). The response may be diagnostic of this unusual myopathy; the test methods are noninvasive and easily tolerated.

Action Potentials↗
PubMed1990

Multiple-pulse stimulation and dantrolene in malignant hyperthermia.

A potentially fatal condition, yet preventable, malignant hyperthermia (MH) lacks a satisfactory noninvasive diagnostic test. Studying the effects of intravenous dantrolene (3 mg/kg) on electrically stimulated skeletal muscle, we found that this approach does not conclusively distinguish between normal humans and those susceptible to malignant hyperthermia but nonetheless yielded important information about the action of dantrolene in man and in MH. Supramaximal single- and multiple-pulse stimulation of the common peroneal nerve produced stable torque responses of the dorsiflexor muscles (monitored in vivo), which dantrolene suppressed. With the multiple-pulse stimulation (5-6 pulses) this torque suppression was significantly less in MH-susceptible subjects than in control subjects. This distinction, also observed in MH swine, confirms this animal as a good model for human MH. That dantrolene's effect in MH can be more completely reversed with high frequency stimulation is intriguing; presumably, excitation-contraction coupling differs in MH and normal muscle.

Adult↗
PubMed1990

Interictal spike detection comparing subdural and depth electrodes during electrocorticography.

We compared the ability of subdural and depth electrodes to detect and localize interictal epileptiform discharges (IEDs) in the temporal lobe. Sixteen patients had simultaneous intraoperative recordings with depth and subdural electrodes while undergoing anterior temporal lobe resections under local anesthesia for medically intractable seizures. IEDs that were focal (detected at just 1 or 2 electrode contacts) typically registered at the nearest contact, regardless of type. IEDs that were regional (engaging more than 2 electrode contacts) typically appeared simultaneously at both electrode types. Neither method was better able to indicate whether an IED was mesial or lateral, posterior or anterior. Subdural and depth electrodes seem to provide complementary information on the location of IEDs within the temporal lobe.

Electrodes, Implanted↗
PubMed1989

Ankle dorsiflexor twitch properties in malignant hyperthermia.

A noninvasive method to diagnose malignant hyperthermia (MH) was sought. To this end, in vivo isometric twitch properties of the ankle dorsiflexor muscles were studied in three groups: (1) MH-susceptible patients (n = 12), (2) relatives (n = 12) of MH-susceptible patients who were judged to be MH resistant, and (3) a group of normal volunteers (n = 42) chosen from the community. Twitch properties were studied under resting state conditions and with 1 or 2 Hz stimulation to produce the negative staircase twitch response. There was a high degree of overlap between the ranges of the measured twitch parameters of all groups. Thus, the techniques presented in this study have no value in diagnosing susceptibility to MH. Several physiological features of human isometric twitch properties were demonstrated: (1) slowing of twitch speed with advancing age, (2) strong positive correlation between body weight and twitch torque, and (3) a negative staircase response typical of that described in other mammalian twitch studies.

Adolescent↗
PubMed1987

Allopurinol and oxypurinol are hydroxyl radical scavengers.

Allopurinol is a scavenger of the highly reactive hydroxyl radical (k2 approx. 10(9) M-1 X s-1). One product of attack of hydroxyl radical upon allopurinol is oxypurinol, which is a major metabolite of allopurinol. Oxypurinol is a better hydroxyl radical scavenger than is allopurinol (k2 approx. 4 X 10(9) M-1 X s-1) and it also reacts with the myeloperoxidase-derived oxidant hypochlorous acid. Hence the protective actions of allopurinol against reperfusion damage after hypoxia need not be entirely due to xanthine oxidase inhibition.

Allopurinol↗
PubMed1986

Use of dantrolene plus multiple pulses to detect stress-susceptible porcine muscle.

Twitch characteristics of tibialis anterior muscles in situ were examined in stress-susceptible and normal swine. Three groups of pigs were studied: (1) purebred Pietrain stress-susceptible, (2) purebred Yorkshire normal, and (3) a crossbred (Pietrain-Yorkshire) litter containing both stress-susceptible and normal animals. Purebred and crossbred stress-susceptible pigs provided qualitatively similar results, as did purebred and crossbred normal pigs. Single stimuli produced greater than normal peak tensions and faster rates of tension development in stress-susceptible animals. Multiple stimuli (2-6 pulses at 5-ms intervals) increased peak tensions and rates of tension development, but did not augment differences between normal and stress-susceptible pigs. Intravenous administration of dantrolene reduced peak tensions and rates of tension development in all groups for single and multiple stimuli. However, the reduction was significantly less (P less than 0.01) for stress-susceptible pigs. Multiple stimuli (4-6 pulses) plus dantrolene amplified differences (P less than 0.01) in contractile properties between normal and stress-susceptible skeletal muscles, with stress-susceptible muscles obtaining larger peak tensions and faster rates of tension development. Normal and stress-susceptible pigs may, therefore, be distinguished by these procedures.

Animals↗