[Surgical approach to radicular pain of the degenerative cervical spine]

Radicular pain is a common feature in day-to-day clinical practice. Only a small percentage of patients with persistent pain and/or neurological deficit need surgical decompression. Exact anatomical localization of the decompressive agent and the correlation of clinical symptoms and radiological findings are mandatory. In most cases, surgery is performed by an anterior approach; by which the causative agent is removed. In cases with narrowing of the neuroforamen total resection of the uncus is indicated. Additional fusion supports the physiological cervical lordosis.

[Surgical therapy in radicular symptoms of the degenerative cervical spine]

Radicular pain is a common feature in day-to-day clinical practice. Only a small percentage of patients with persistent pain and/ or neurological deficit need surgical decompression. Exact anatomical localization of the decompressive agent and the correlation of clinical symptoms and radiological findings are mandatory. In most cases, surgery is performed by an anterior approach; by which the causative agent is removed. In cases with narrowing of the neural foramen total resection of the uncus is indicated. Additional fusion supports the physiological cervical lordosis.

[Stenosis of the lumbar spine in elderly persons. Surgical decompression]

The degenerative changes in the lumbar vertebral spine frequently appear as encroachment of the lumbar spinal canal. Degenerative changes of the anatomical structures dictate the location of the stenosis, which are divided in central or lateral stenosis of the lumbar spinal canal. According to this localization, more radicular symptoms in a lateral stenosis might be prevalent in contrast to the mixed symptoms of a central stenosis. Operative decompression might be indicated in cases with correlation of clinical symptoms and radiological findings. The operative treatment aims at a satisfactory decompression without creating iatrogenic instability. An additional fusion might be avoided in cases without apparent instability. Adequate operative decompression is most efficient concerning reduction of pain and increasing of walking distance.

Case report: diclofenac-induced rhabdomyolysis

A case is described in which, after administration of diclofenac for 13 days for arthritis attributed to gout, the patient experienced erythema multiforme followed by muscle weakness, elevation of serum creatine phosphokinase (CPK) level from 101 to 83,770 U/L, 100% muscle isoenzyme, blood urea nitrogen (BUN) level from 15 to 87 mg/dL, creatinine level from 1.0 to 2.1 mg/dL and urine myoglobin level to 1,190 micrograms/dL (N < 1.2). The diagnosis was rhabdomyolysis due to diclofenac, with myoglobinuria resulting in mild renal failure. Treatment consisted of discontinuing diclofenac and administering sufficient fluids to prevent progression of myoglobinuric renal failure. Serum CPK level gradually returned to normal by day 50, BUN and creatinine levels by day 28, and muscle strength between day 90 and 180. Rhabdomyolysis due to diclofenac or to other nonsteroidal antiinflammatory drugs has not been reported.

Direct pediculo-body fixation in cases of spondylolisthesis with advanced intervertebral disc degeneration

In inveterate cases of grade 2-3 spondylolisthesis (degenerative or spondylolytic), segmental mobility may be reduced by radiologically confirmed disc resorption. Fusion may be indicated in patients with persistent pain. A simple technique for fusion without reduction of the spondylolisthesis is presented. Fixation of the segment is achieved by two cancellous bone screws inserted bilaterally through the pedicles of the lower vertebra into the body of the upper slipped, vertebra. The cases of 16 patients with an average follow-up of 31 months (range 24-27 months) treated with this direct pediculo-body fixation are presented. Clinical evaluation showed significant decrease in pain and, in patients with concomitant spinal stenosis, walking distance without pain improved from between 500 and 1000 m to more than 3000 m. Radiologically, fusion was observed in all cases. The presented technique of internal fixation of a slipped segment in the degenerative lumbar spine represents a simple minimally traumatic procedure with successful clinical and radiological outcome. Additional procedures, such as decompression of the spinal canal, may be performed.

The effectiveness of various cervical orthoses. An in vivo comparison of the mechanical stability provided by several widely used models

STUDY DESIGN

The amount of motion allowed by various cervical orthoses was compared with the amount of unrestricted neck motion in vivo.

OBJECTIVES

To determine how much mechanical stability commonly used cervical orthoses provide to the wearer.

SUMMARY OF BACKGROUND DATA

Few studies have compared quantitatively the restriction of motion from cervical orthoses that are commonly prescribed for patients. No studies have used methods allowing measurement of all three rotations throughout the range of motion in passive and active tests. Previous studies may have overstated the amount of restriction provided resulting from the methods used.

METHODS

Five subjects were tested for cervical range of motion in flexion-extension, axial, rotation, and lateral bending. Each was tested with no collar, with soft collar, with Philadelphia collar, with Philadelphia collar with thoracic extension, and with sterno-occipital mandibular immobilizer brace. Each test was conducted passively and actively. Measurements were taken with the CA-6000 Spine Motion Analyzer, a highly accurate and precise computerized linkage system that simultaneously records all three rotations in real time.

RESULTS

All orthoses restricted motion to some extent. Generally, the collars ranked (from least restrictive to most restrictive): soft, Philadelphia, Philadelphia with extension, and sterno-occipital mandibular immobilizer brace. However, the differences were not usually large, and the collars did not restrict motion as much as previously reported. No collar restricted the motion of any of the subjects to less than 19 degrees of flexion-extension, 46 degrees of axial rotation, or 45 degrees of lateral bending, and most subjects demonstrated significantly more motion.

CONCLUSIONS

Although cervical orthoses can be helpful for other reasons, they do not provide a high level of mechanical restriction of motion. Additionally, the restriction they do provide can vary widely between people. Prescribing physicians should consider the relative merits of the various orthoses before deciding whether they will meet a patient's needs. The differences between the collars tested may not be enough to justify one of the more expensive or less comfortable collars.

Foraminal changes with distraction and compression of the L4/5 and L5/S1 segments

The width of the foramen in the lumbar spine is directly related to the position of the vertebrae. In an MRI study the measurements of the cross-sectional area of the neuroforamen of L4/5 and L5/S1 in neutral position, segmental distraction and compression were calculated. Nine cadaver specimens were investigated and the foraminal width of L4/5 and L5/S1 was measured. In both segments of all specimens the foraminal space significantly enlarged under distraction and decreased under compression. In the L4/5 segment the average relative difference between distraction and compression was 27%.

Enzyme therapy of xeroderma pigmentosum: safety and efficacy testing of T4N5 liposome lotion containing a prokaryotic DNA repair enzyme

Xeroderma pigmentosum (XP) is a rare genetic disease in which patients are defective in DNA repair and are extremely sensitive to solar UV radiation exposure. A new treatment approach was tested in these patients, in which a prokaryotic DNA repair enzyme specific for UV-induced DNA damage was delivered into the skin by means of topically applied liposomes to supplement the deficient activity. Acute and chronic safety testing in both mice and humans showed neither adverse reactions nor significant changes in serum chemistry or in skin histology. The skin of XP patients treated with the DNA repair liposomes had fewer cyclobutylpyrimidine dimers in DNA and showed less erythema than did control sites. The results encourage further clinical testing of this new enzyme therapy approach.

Predictors of bad and good outcome of lumbar spine surgery. A prospective clinical study with 2 years' follow up

STUDY DESIGN

Based on prospective assessment, patients with lumbar disc surgery were examined to determine reliable predictors for clinical outcome.

OBJECTIVES

The prognostic value of a screening checklist developed in a previous study was evaluated in a 2-year follow-up.

SUMMARY OF BACKGROUND DATA

Outcome studies of lumbar disc surgery document a success rate between 49-90%. It has been shown that a number of medical history data and sociodemographic and psychodiagnostic findings are of prognostic value for the outcome of lumbar spine surgery.

METHODS

In addition to clinical and neuroradiologic examinations, 164 patients took part in a standardized interview. Eighty-two percent participated in a follow-up performed 2 years after the operation. Preoperative findings, outcome, and prediction of three diagnostic subgroups were compared. Eighty-three (51%) patients had disc herniation only, 29 (18%) had disc herniation and other relevant back diagnoses, and 51 (31%) had no disc herniation but had other relevant back diagnoses.

RESULTS

In patients with disc herniation only, good results were observed in 53%, moderate in 19%, and bad in 28%. The accuracy of prediction of the postoperative result was 75% for the patients with good outcome and 86% for those with bad outcome. In the group of patients with diagnoses other than disc herniation, the success rate of the operation was 38% good, 28% moderate, and 41% bad, but the predictor score was not as useful as for the other groups.

CONCLUSION

Patients with a high risk of a bad operation outcome after lumbar discectomy could be identified preoperatively. It is suggested that those patients take part in a pain management approach instead of or in addition to surgical intervention.

Production and role of cytokines in the CNS of mice with acute viral encephalomyelitis

Semliki Forest Virus (SFV) causes a more severe acute encephalomyelitis in B6 than in SJL mice despite similar T cell proliferation and antibody responses in these two strains. To determine the immunological mechanisms that may contribute to this difference, CNS tissues from SFV-infected B6 and SJL mice were analyzed for viral replication, inflammatory responses and cytokine production, by semiquantitative reverse transcriptase-PCR and immunohistochemistry. Although initially similar on day 2 p.i., SFV replicated to higher viral titers in B6 than SJL mice on days 4 and 7 p.i. Infectious virus was cleared from both strains by day 10 p.i. There were no differences in numbers of CD4+, CD8+ or MHC class I and II+ inflammatory cells at any time point. Higher levels of IL-4 mRNA, lower levels of TNF-alpha, IL-6, IL-1 beta and IL-2 mRNAs and lower IL-2+ and IFN-gamma+ cells were found in B6. These findings suggest that despite comparable immune responses, different patterns of cytokine production correlated with higher levels of virus in the brains and more severe clinical disease in B6, and more efficient clearance of virus and less severe disease in SJL mice.

Cotrel-Dubousset and Harrington Instrumentation in idiopathic scoliosis: a comparison of long-term results

Between 1968 and 1977, 72 patients with idiopathic scoliosis underwent Harrington Instrumentation (HI). Between 1985 and 1988, 21 patients with idiopathic scoliosis had posterior spinal fusion with Cotrel-Dubousset instrumentation (CDI). All patients were operated by the same orthopedic surgeon. None of the CDI patients had postoperative brace or cast protection, the HI group had on average 6 months' postoperative brace treatment. The two groups of patients were comparable in age, sex, and type of curves. The HI group and CDI group were reexamined with clinical and radiological assessment after mean periods of 148 months and 60 months respectively. The average preoperative Cobb angle in the CDI group was 59.9 degrees (HI group 67.8 degrees), which improved to 20.8 degrees (HI group 33 degrees) postoperatively--a correction of 66.3% (HI group 51.3%). The loss of correction on reassessment amounted to 5% in the CDI group and 20.7% in the HI group. In both groups, the mean rib hump height was reduced to 2.2 cm. In 40% of the Harrington patients, a flat back was found, but this was not related to clinical back pain. The rate of complications and reintervention was 9.5% in the CDI group and 8.3% in the HI group. There were no neurological complications. Subjectively, 86% of the Harrington patients and 95.2% of the CDI patients rated the results of their operation as "good" or "very good." The CDI group showed better results in correction of the Cobb angle and loss of correction, while saving one mobile lumbar segment. The correction of the rib hump showed the same results for both techniques. Blood loss and operation time was much lower in the HI group. However, the rate of complications was similar in both groups.

Rhabdomyolysis and myoglobinuric acute renal failure associated with classic heat stroke

Classic heat stroke is a disorder of thermal regulation that predominantly affects elderly patients during heat waves. In contrast to exertional heat stroke, rhabdomyolysis and myoglobinuric acute renal failure are considered to be unusual manifestations of classic heat stroke. We retrospectively reviewed the charts of seven patients admitted to Maimonides Medical Center with classic heat stroke over a 3-day period during a heat wave in July 1993. Three of these patients with classic heat stroke had rhabdomyolysis, but no renal failure; two completely recovered; and one had an ataxic gait disturbance. Three additional patients had rhabdomyolysis and myoglobinuric acute renal failure; one of them completely recovered, one survived with quadriplegia, and one died. Our findings suggest that rhabdomyolysis and myoglobinuric acute renal failure are common manifestations of classic heat stroke. Recognition of this complication warrants rigorous hydration and alkalinization of the urine to prevent or attenuate myoglobinuric acute renal failure.

Degenerative lumbar spinal stenosis. Decompression with and without arthrodesis

We prospectively evaluated the results of decompression of the spine, with and without arthrodesis, for the treatment of lumbar spinal stenosis without instability in forty-five patients (twenty-one men and twenty-four women) who had been managed between November 1989 and November 1990. The average age at the time of the operation was sixty-seven years (range, forty-eight to eighty-seven years). The patients were randomly assigned to one of three treatment groups (fifteen patients in each group) according to when they were admitted to the hospital. Group I was treated with decompression with laminotomy and medial facetectomy; Group II, with decompression and arthrodesis of the most stenotic segment; and Group III, with decompression and arthrodesis of all of the decompressed vertebral segments. All of the operations were performed by the same surgeon. The average duration of follow-up was twenty-eight months (range, twenty-four to thirty-two months). All three groups had a significant improvement in the distance that the patients were able to walk at the time of the latest follow-up examination compared with before the operation (p < 0.001 for Group I, p < 0.002 for Group II, and p < 0.005 for Group III). With the numbers available, there were no significant differences in the results among the three groups with regard to the relief of pain (p = 0.25 for Group I compared with Group II, p = 0.36 for Group II compared with Group III, and p = 0.92 for Group I compared with Group III).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of ethanol on function of the rat heart and skeletal muscles

The present study was undertaken to evaluate the acute effects of ethanol on responses of the rat heart and skeletal muscles both in vivo and in vitro. In the anesthetized rat, intravenous infusion of ethanol at 0.1-0.5 g/kg body weight (33-167 mM) decreased the breathing rate by 8-83%, heart rate by 4-52%, and QRS amplitude by 5-27%, and increased the P-R interval by 1-49%. In the anterior tibialis muscle subjected to repetitive nerve stimulation at 100 Hz for 0.5 sec, ethanol at 0.1 g/kg increased the amplitude of the muscle action potential (AP) by 7%, whereas at 0.5 g/kg it decreased the muscle AP by 32%. The nerve-evoked tetanic tension was reduced by 7-34% at 0.1-0.5 g/kg ethanol. In the isolated rat heart, perfusion of ethanol at 0.1-3.0% (22-651 mM) decreased the heart rate by 8-48% and QRS amplitude by 10-39%, and increased the P-R interval by 5-61%. Left ventricular pressure was increased by 10% at 0.1% ethanol, and decreased by 80% at 3.0% ethanol. In the isolated rat phrenic nerve-diaphragm muscle preparation subjected to repetitive nerve stimulation at 100 Hz for 0.5 sec, 0.1-3.0% ethanol decreased the amplitude of the nerve AP by 5-89%, nerve-evoked muscle AP by 2-96%, and peak tetanic tension by 1-87%. On repetitive direct muscle stimulation at 100 Hz for 0.5 sec, 0.1-3.0% ethanol decreased the amplitude of the muscle-evoked muscle AP by 8-65%, and muscle-evoked tetanic tension by 2-65%. These studies indicate that ethanol causes smaller reduction in responses of the heart and skeletal muscles at clinical concentrations, but marked reduction in these responses at higher concentrations due to direct action on excitability of these tissues. At higher concentrations, ethanol causes greater reduction in excitability of the skeletal muscle than of the heart.

The role of motor evoked potentials in psychogenic paralysis

STUDY DESIGN

This prospective clinical study identified patients in whom paralysis developed after lumbar surgery.

OBJECTIVE

To determine whether patients with psychogenic paralysis could be identified using noninvasive techniques.

SUMMARY OF BACKGROUND DATA

Before the advent of transcranial magnetic stimulation, no clinically applicable, noninvasive technique was available to confirm the integrity of the corticospinal tract.

METHODS

Patients with suspected postoperative psychogenic paralysis were evaluated by clinical examination and neurophysiologic work-up, including transcranial magnetic stimulation.

RESULTS

Six patients with psychogenic paralysis were identified in a 15-month period. In each case, motor evoked potentials could be demonstrated from the affected muscle(s), thus obviating the need for further invasive imaging or surgical exploration.

CONCLUSIONS

Transcranial magnetic stimulation is a reliable, painless, and noninvasive technique for demonstrating structural integrity of the corticospinal tracts.

Fiber composition and fiber transformations in neck muscles of patients with dysfunction of the cervical spine

Biopsies of ventral neck muscles (sternocleidomastoid, omohyoid, and longus colli) and dorsal neck muscles (rectus capitis posterior major, obliquus capitis inferior, splenius capitis, and trapezius) were taken from 64 patients who underwent spondylodesis for cervical dysfunction of different etiologies. The muscle fibers were classified histochemically as type I, IIA, IIB, or IIC (transitional or intermediate fibers) according to the pH lability of their myofibrillar ATPase. Signs of muscle fiber transformations were observed in all muscles investigated, as evidenced by an increased relative amount of type-IIC fibers. The transformations occurred independently of (a) the type of muscle (i.e., more "postural" or more "phasic"), (b) the sex and age of the patient, (c) the type of condition, and (d) the presence of additional neurological deficits. Thus, the same pattern of muscular reaction was found in patients with rheumatoid arthritis as in patients with soft-tissue injuries of the neck (e.g., "whiplash injury"). In the ventral muscles and the obliquus capitis inferior, the occurrence of transformations correlated strongly with the duration of symptoms; in the ventral muscles the vast majority of transformations were encountered in patients with a shorter history of symptoms, whereas in the obliquus capitis inferior the reverse occurred. In the other dorsal muscles, no correlation with the duration of symptoms was found. Muscles in which transformations had ceased displayed, on average, a significantly higher percentage of fast type-IIB fibers than were found in muscles with ongoing transformations. This strongly indicates that the transformations proceeded in the direction from "slow oxidative" to "fast glycolytic."

Normal motion of the lumbar spine as related to age and gender

The CA-6000 Spine Motion Analyzer was used to measure the lumbar spine's range of motion (ROM). One hundred and four asymptomatic volunteers were examined to obtain normal values for flexion/extension, lateral bending, and axial rotation. A detailed error analysis was conducted to investigate the inter- and intraobserver reliability of the measurement equipment, the differences between passive and active examination, the effects of stretching exercises before examination, and the diurnal changes related to lumbar spine ROM. Subjects were divided into groups by age and gender. Values for each group were compared with respect to age and gender. The measurements were found to be consistent and repeatable. Stretching exercises were observed to increase ROM. Passive examination was recommended to achieve maximum ROM. ROM was observed to increase during the course of the day. A normative database was established showing significantly decreased motion as age increased, but no gender differences were discovered. The validity of the axial rotation values due to fixation difficulties is questioned.

Treatment of myasthenia gravis by immunoadsorption of plasma

We treated 16 patients with moderately severe to severe generalized myasthenia gravis (MG) by immunoadsorption (perfusion through a resin that adsorbs proteins) of 2,500 ml plasma on each of four alternate days. Fourteen patients who completed treatment all had significant improvement in strength (6 excellent, 6 good, and 2 fair), which began a mean of 42 hours after the first immunoadsorption, reached a maximum 4 days after the fourth immunoadsorption (mean, 250% of baseline strength), and returned to baseline over a mean of 2 months. Thirty-seven grams of plasma proteins were removed during each immunoadsorption, which required no replacement, compared with 175 grams during plasma exchange, which requires replacement with albumin. Serum or plasma concentration of all proteins fell, more so for most of the larger proteins than for the smaller ones: acetylcholine receptor antibody (AChR Ab) fell to a mean of 23% of original level, fibrinogen to 26%, C4 to 29%, IgM to 33%, IgG to 35%, CH50 to 41%, C3 to 42%, IgA to 54%, and albumin to 76%. All proteins, including AChR Ab, returned to their original levels within 1 to 3 weeks after the last immunoadsorption, while improvement in strength lasted a mean of 6 weeks longer. One seronegative patient had excellent improvement lasting more than a month. Activated complement C5a and white blood cell count rose during each immunoadsorption, while activated complement C3a fell, and each returned to its original level within hours. Eight patients had transient symptomatic hypotension attributable to withdrawal of blood more rapidly than it was returned; this hypotension was prevented or ameliorated by intravenous saline.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of alcohol and electrical stimulation on leakage of creatine kinase from isolated fast and slow muscles of rat

Binge drinking of alcohol may lead to acute alcoholic myopathy with rhabdomyolysis, which is characterized by skeletal muscle damage, elevated serum creatine kinase (CK), and myoglobinuria. This study was undertaken to test whether alcohol acts directly on the skeletal muscles to enhance the leakage of CK, and to assess the influence of fiber-type composition and repetitive contractions of the muscle on the effect of alcohol. After 4 hr of incubation in normal physiological solution at 37 degrees C, mean leakage of CK was 0.7 units/mg from isolated rat extensor digitorum longus (EDL), which has more fast-twitch glycolytic muscle fibers, and 1.2 units/mg from the soleus, which has more slow-twitch oxidative muscle fibers. Ethanol at 0.1, 0.2, and 0.5% concentrations caused significantly greater increase in leakage of CK from soleus than from EDL. In normal physiological solution, electrical stimulation at 1 Hz for 4 hr increased the leakage of CK by about the same degree in both EDL and soleus. In the presence of 0.1 and 0.2% ethanol, electrical stimulation markedly potentiated the alcohol-induced leakage of CK from both soleus and EDL. These results indicate that alcohol increases the leakage of CK by acting directly on skeletal muscle fibers, especially of the slow-twitch oxidative type, and that repeated muscle contractions potentiate the alcohol effect. These studies suggest that exercise may increase the chances of rhabdomyolysis in the alcoholics.

On the understanding of clinical instability

STUDY DESIGN

Three-dimensional flexibility changes due to the application of an external fixator at C4-C5 were studied in cervical spine specimens.

OBJECTIVES

To evaluate the biomechanical effects of applying a cervical external fixator to a patient using an in vitro model.

SUMMARY OF BACKGROUND DATA

There is controversy regarding the relationship between the changes in spinal motion and clinical instability.

METHODS

Using fresh cadaveric C4-C7 specimens, multidirectional flexibility was measured at all vertebral levels, before and after the fixator application at C4-C5, C5-C6, and C4-C6.

RESULTS

The average ranges of motion for flexion, extension, lateral bending, and axial rotation were 8.3 degrees, 7.2 degrees, 5.3 degrees, and 5.6 degrees, which decreased by 40%, 27%, 32%, and 58%, respectively, because of the fixator application. The corresponding neutral zones were 3.4 degrees, 3.4 degrees, 3.0 degrees, and 2.0 degrees, which decreased by 76%, 76%, 54% and 69%, respectively. The decreases with the fixation at C4-C5 were similar to those for fixation at C5-C6.

CONCLUSIONS

This in vitro study documented that the application of an external fixator to the cervical spine decreases the intervertebral motion in general, and decreases flexion, extension and torsional neutral zones in particular. The findings help explain the clinical instability of the spine and support the hypothesis that the neutral zone is more closely associated with the clinical instability than is the range of motion.

The role of plate and screw fixation in occipitocervical fusion in rheumatoid arthritis

STUDY DESIGN

In a clinical retrospective study, the results of occipitocervical fusion in patients with rheumatoid arthritis were studied and analyzed.

OBJECTIVES

The results of two different operative techniques were compared. The advantages of screw fixation compared with wiring techniques in this population of patients were investigated.

SUMMARY OF BACKGROUND DATA

Numerous different implants have been presented in the literature for occipitocervical fusion in patients with rheumatoid arthritis. The use of wires being the standard fixation technique.

METHODS

Occipitocervical fusion was performed in patients with rheumatoid arthritis: 26 patients with the wiring technique and 33 patients with a new Y-plate fixation. The results were compared at a follow-up period of 24 months and 50 months, respectively. Clinical and radiologic results were investigated.

RESULTS

The atlantodental distance could be significantly better reduced in the group with the Y-plate fixation and the neurologic improvement in the wiring group was 40%, whereas in the Y-plate fixation 86% of neurologic improvement was observed. Pseudarthrosis was seen in 27% of the wiring technique and in 6% in the plate and screw fixation technique.

CONCLUSIONS

In occipitocervical fusion for patients with rheumatoid arthritis, the screw and plate fixation technique provides superior results than other techniques using wire fixations.

[The unstable spine--an "in vitro" and "in vivo study" on better understanding of clinical instability]

In cases of suspected painful instability of a cervical segment, temporary external fixation by means of external fixator was applied. The segmental immobilization caused immediate relief of pain. The pain reoccurred after removal of the immobilization. The effect of immobilization by external fixation was investigated in biomechanical tests using fresh cadaveric C4-7 specimens. Multidirectional flexibility was measured before and after application of the fixator at C4/C5, C5/C6 and C4-6. We measured the reduction in motion between the different segments. In every situation the neutral zone decreased more than the range of motion. The findings are helpful to understand the clinical instability of the spine and support the hypothesis that the neutral zone is more closely associated with clinical instability than range of motion. The combination of clinical application and biomechanical investigation allowed us to establish a direct correlation between instability and pain.

Immune responses, and autoimmune outcome, during virus infection of the central nervous system

A combined role of a virus infection of the central nervous system (CNS) and an autoimmune response to myelin basic protein (MBP), an autoantigen of the CNS, is suggested in the pathogenesis of multiple sclerosis (MS). SJL mice are highly susceptible while B6 mice are less susceptible to the induction of experimental autoimmune encephalomyelitis (EAE), the autoimmune model of MS. Peripheral inoculation of Semliki forest virus (SFV) into SJL and B6 mice resulted in: (1) Higher viral titers, more severe clinical disease, and hence a stronger nonspecific and SFV-specific lymphoproliferation, and production of IFN-gamma and TNF/LT was observed by splenocytes (SPL) of B6 than by those of SJL mice, on Day 7 postinfection. (2) Following viral clearance, however, proliferation to SFV, and to MBP, and the production of IFN-gamma and TNF/LT by SPL of SFV-infected SJL mice were significantly higher, while the production of TGF-beta was significantly lower than by those of B6 mice. In conclusion, the immune responses to SFV, and to MBP, which were triggered by SFV infection were significantly higher and more prolonged in the SPL of SJL mice, the EAE-susceptible mice, than by those of B6 mice after the infection was cleared.

Potassium and caffeine contractures of mouse muscles before and after fatiguing stimulation

To assess the impairment of muscle membrane excitation, excitation-contraction (E-C) coupling, and contractility during muscle fatigue, we monitored the contracture responses of resting and fatigued muscles on exposure to high potassium and caffeine. On exposure to 140 mmol/L potassium, mouse extensor digitorum longus (EDL) developed a contracture which was 15.7% of tetanic tension before fatigue and 31.7% after fatigue, while soleus developed 59.4% contracture before and 68.8% after fatigue. Potassium causes contractures by depolarizing the muscle fiber membrane. Hence, membrane excitation is reduced in fatigued EDL and soleus. On exposure to 32 mmol/L caffeine, the contracture was 7.1% in resting EDL, 8.5% in fatigued EDL, 50.1% in resting soleus, and 43.7% in fatigued soleus. On exposure to 1 mmol/L caffeine followed by rapid cooling, the contracture was 3.0% in resting EDL, 3.2% in fatigued EDL, 21.5% in resting soleus, and 10.3% in fatigued soleus. Caffeine causes contracture by releasing Ca++ from the sarcoplasmic reticulum. Our results indicate reduced E-C coupling attributable to reduced membrane excitation in fatigued EDL, and reduced contractility in fatigued soleus.

Production of anti-acetylcholine receptor-alpha antibody in vitro by peripheral blood lymphocytes of patients with myasthenia gravis: role of immunoregulatory T cells and monocytes

To study the role of T cells in T and B cell interaction resulting in production of antibody (Ab) to the alpha chain of acetylcholine receptor (anti-AChR-alpha Ab) in myasthenia gravis (MG), we cocultured peripheral blood-purified B and T cells of patients with MG and of control subjects with and without multiple sclerosis in the presence of AChR-alpha or pokeweed mitogen. Under these conditions, a high level of anti-AChR-alpha Ab was produced by cells of patients with MG but not of control subjects. Production of anti-AChR-alpha Ab by B cells was stimulated by autologous purified or cloned CD4+ T cells, whereas autologous CD8+ T cells had no effect. CD8+ T cells did not suppress anti-AChR-alpha Ab production when added to B cells cocultured with CD4+ T cell clones. Anti-AChR-alpha Ab production was inhibited by monoclonal antibodies against CD4 and class II major histocompatibility complex (MHC) antigens, indicating that these antigens are required for productive T-B cell interactions resulting in anti-AChR-alpha Ab synthesis. Anti-AChR-alpha Ab production by peripheral blood lymphocytes of patients with MG was significantly lower than that by their purified or cloned T cells cultured with B cells. Cell-mixing experiments indicated that anti-AChR-alpha Ab synthesis was inhibited by monocytes. The prostaglandin synthetase inhibitor, indomethacin, partially restored the suppressive effect of monocytes on anti-AChR-alpha Ab synthesis. These results indicate that induction of anti-AChR-alpha Ab production by CD4+ T cell clones requires CD4 and class II MHC antigens and is inhibited by suppressor macrophages and not by CD8+ T cells.