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Biomedical subjects

R F Mayer

Publications and source records attributed to R F Mayer.

At least 37 records · Page 2Linked to original sources
PubMed1992

Central motor conductivity in aged people.

The conductivity of motor neurons in 26 aged females (mean age 79 years) was analyzed by the conventional conduction method and by pulsed magnetic stimulation and compared with that in 14 younger controls. In aged people, slow motor conduction velocities were found in peripheral nerves. Central motor conduction time (CMCT) in relaxed muscle was shorter in the aged people, although CMCT was normal in mildly contracted muscle. These findings coincide with the results studied in Parkinson's disease, although these subjects were not diagnosed as having Parkinson's disease. Aged people generally have an anteflexed posture, slow movements, and poor postural reflexes, and have been reported to have a decrease in the dopamine level which is relatively earlier than that of other transmitters in the basal ganglia. This may account for the present finding that aged people have neurophysiological abnormalities in CNS which are similar to those in Parkinson's disease.

Adult↗
PubMed1991

Kinetics of anti-peripheral nerve myelin antibody in patients with Guillain-Barré syndrome treated and not treated with plasmapheresis.

Serial anti-peripheral nerve myelin antibody titers were determined in 28 consecutive patients with Guillain-Barré syndrome during the course of their illness. Eighteen patients were treated with plasmapheresis and 10 were not. Anti-peripheral nerve myelin antibody titers in the group treated with plasmapheresis declined significantly more rapidly than in the group not treated with plasmapheresis. Five patients treated with plasmapheresis who showed initial clinical improvement, with a concurrent decline in anti-peripheral nerve myelin antibody titer, had one or two recurrences of clinical symptoms during a 2- to 8-week period associated with an increase in anti-peripheral nerve myelin antibody titer. Recurrent weakness was severe enough to prompt additional courses of plasmapheresis. The data suggest that serial determinations of antiperipheral nerve myelin antibody in patients with Guillain-Barré syndrome may identify patients with antibody rebound associated with recurrence of clinical symptoms and prolonged recovery in whom further plasmapheresis should be considered.

Adolescent↗
PubMed1988

Autonomic dysfunction in Lambert-Eaton myasthenic syndrome.

Autonomic symptoms were observed in 6 patients with clinically and electrophysiologically documented Lambert-Eaton myasthenic syndrome (LEMS). Of the 6 patients, 2 were extensively investigated in the laboratory. In contrast to previous reports which recognized only cholinergic dysautonomia, abnormalities of sympathetic as well as parasympathetic function were evident. Of the 6 patients, 4 had small cell lung cancer (SCLC). In one male patient, chemotherapy for SCLC resulted in an early improvement of autonomic dysfunction and the electrophysiological defect, documenting simultaneous regression of dysautonomia and LEMS. In addition, the patients with SCLC and LEMS had a survival thus far of 3-13 years suggesting that a subgroup of SCLC patients have a better prognosis.

Adult↗
PubMed1988

Thoracoabdominal radiculopathy.

Thoracic nerve root dysfunction (TNRD) manifested as abdominal pain is an infrequently reported condition. We present data on six patients who had chronic intermittent thoracoabdominal pain originating in the back. Diabetes and osteoarthritis of the spine were the chief causes of these symptoms. The electromyogram in all patients showed changes consistent with an acute radiculopathy. All patients responded to anti-inflammatory therapy in combination with phenytoin, carbamazepine, amitriptyline, or local nerve block. TNRD is a condition that may be diagnosed earlier if clinical suspicion is increased, thus sparing patients excessive testing and surgery, and affording quicker relief.

Abdomen, Acute↗
PubMed1987

Conduction block in hereditary neuropathy with susceptibility to pressure palsies.

Slow nerve conduction velocities, temporal dispersion of action potentials and conduction block occur in polyneuropathies with segmental demyelination. Conduction block has been reported in focal compressive neuropathies and in acute and chronic autoimmune polyneuropathy but not in hereditary motor and sensory demyelinating neuropathy. We report conduction block in five nerves of four patients from two families with a hereditary neuropathy with susceptibility to pressure palsies and pathologic changes of segmental demyelination and tomaculous swellings. Conduction block that may be long lasting is a feature of this type of hereditary neuropathy, which should be considered in the differential diagnosis of this electrophysiologic finding.

Action Potentials↗
PubMed1987

[Conventional and analytic morphometry using the IBAS-1 computer in experimental Trypanosoma b. brucei infection].

A comparative morphometrical study of the experimental infection with T. b. brucei was realized using the conventional method and the IBAS-1 analytic computer. The studied strain of T. b. brucei was preserved during 10 years in laboratory conditions, through inoculations from mice to mice. The effect of a low dose of suramin upon the percentage of different morphological forms of the parasite was analysed and compared with the untreated lots. Certain differences could be appreciated in the results of the two methods of morphometrical studies. The presence of posteronuclear, multinuclear and "stumpy" dividing forms was confirmed in our study. The administration of low doses of suramin produces a serious increase of the number of the dividing, multinuclear and "stumpy" forms.

Animals↗
PubMed1986

Clinical correlation with anti-peripheral-nerve myelin antibodies in Guillain-Barré syndrome.

Anti-peripheral-nerve myelin antibodies (anti-PNM Ab) can be detected in the serum of all patients with acute-phase Guillain-Barré syndrome (GBS) thus far tested. Correlation of the titer of this antibody with the clinical course would help to establish a role for the humoral immune system in the pathophysiology of GBS. In this study, anti-PNM Ab levels were measured in serial serum samples of 7 patients with GBS with an assay that detects antibodies bound to peripheral nerve myelin antigens by fixation of the first component of complement. Although the titers of anti-PNM Ab detected in these patients varied between 0 and 256 U/ml, the antibody titer was always highest on admission (35 to 256 U/ml) and rapidly declined during a one-to-three-week period. Disappearance of antibodies or very low levels of them correlated with cessation of progression and considerable clinical improvement as documented by increased pulmonary vital capacity and muscular strength. Low but measurable antibody titers (5 to 12 U/ml) were frequently found up to four months following the acute neurological deficit. The close temporal relationship between anti-PNM Ab titer and the clinical course in GBS suggests that antibody most likely participates through complement activation in peripheral nerve demyelination.

Adolescent↗
PubMed1986

Caveolae preservation in the characterization of human neuromuscular disease.

We have examined freeze-fracture replicas and conventional thin-section images of rat myofibers prepared by perfusion and by conventional immersion fixation protocols, and myofibers of normal and dystrophic human myofibers prepared by similar immersion fixation methods. In both rat and human myofibers, the size and distribution of caveolae was found to differ substantially according to the method of glutaraldehyde exposure, the depth of the myofiber from the surface exposed to the fixative, and if surgically bisected, the distance from the cut end of the myofiber. Conventional immersion fixation resulted in unavoidable but predictable alterations in sarcolemmal caveolae. These reproducible artifacts of fixation technique substantially complicate the use of caveolae as reliable markers for the characterization of human neuromuscular disease.

Adult↗
PubMed1986

Nerve conduction studies in the Twitcher mouse (murine globoid cell leukodystrophy).

Progression of the neuropathy in the Twitcher mouse (twi-C57BL/6J), an animal model of globoid cell leukodystrophy, was assessed with serial motor nerve conduction studies from just after birth until near death (day 45) and after hematopoietic cell transplantation (HCT). Under ether anesthesia, the tibial nerve was stimulated percutaneously at the sacral notch and at the ankle, and recordings were made from plantar foot muscles. Motor conduction velocity (MCV), distal latency, amplitude, duration and number of phases of compound muscle action potentials on proximal (pCMAP) and distal (dCMAP) stimulation were measured. In 15-19 day-old Twitcher, despite the absence of motor signs, MCV was significantly reduced, 12.8 +/- 2.8 (10) m/s (M +/- SD, No. of recordings), compared with unaffected siblings, 18.1 +/- 2.6 (21) m/s (P less than 0.01). The ratio of pCMAP to dCMAP amplitudes was reduced in the Twitcher, 0.39 +/- 0.13 (10), compared with controls 0.72 +/- 0.17 (21) and the ratio of pCMAP to dCMAP phases was increased (2.8 +/- 0.8 (10) vs 1.0 +/- 0.2 (21), P less than 0.01 for all). As neurologic signs progressed by 35-39 days, MCV became slower, 5.8 +/- 1.0 (11) m/s, pCMAP and dCMAP became smaller, but the ratio of pCMAP to dCMAP amplitudes in the Twitcher (0.55 +/- 0.36, 11) was similar to controls (0.71 +/- 1.0, 20) as was the ratio of pCMAP to dCMAP phases (1.0 +/- 0.4 vs 1.0 +/- 0.1). These results suggest that there is diffuse non-uniform slowing of nerve conduction with block especially in proximal nerve fibers initially. With HCT, mean MCV remained slow (6.7 +/- 1.2 (18) m/s, vs 34.5 +/- 3.9 (12) m/s) but motor function persisted.

Age Factors↗
PubMed1985

Effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on the contractile properties of reinnervated rat skeletal muscle.

2,4-Dichlorophenoxyacetic acid (2,4-D), a common herbicide, was administered to rats (100 mg/kg, i.p.) during 24 days to determine whether or not it is toxic to regenerating peripheral nerve and reinnervating muscle. The peroneal nerve was crushed 1 cm proximal to the extensor digitorum longus muscle and recordings made in vivo after 1 to 24 days. Functional reinnervation was observed by day 10 and recovery was similar in rats receiving 2,4-D or vehicle. Distal motor latencies and muscle action potentials returned toward normal during the 24 days in a similar manner in 2,4-D and controls. Isometric twitch tensions per muscle weight on indirect stimulation returned to intact values by 17 days, but in the 2,4-D animals they became larger (P less than 0.01) than controls by day 24. The twitch:tetanus ratios were increased at day 10 and returned toward normal values in the controls but remained increased (P less than 0.01) in the 2,4-D animals at 24 days. Similar results were obtained on direct muscle stimulation. The data suggest that 2,4-D is not toxic to nerve during regeneration or muscle reinnervation in the rat, but that it does affect both twitch and tetanus tensions suggesting proliferation as well as disruption of myofibrils.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1985

2,4-Dichlorophenoxyacetic acid (2,4-D) reduces acetylcholinesterase activity in rat muscle.

A single dose (200 mg/kg body weight, i.p.) of 2,4-dichlorophenoxyacetic acid (2,4-D), commonly used as a herbicide, caused significant decreases in acetylcholinesterase (AChE) activity in diaphragm and other muscles of the rat. The 4S, 10S, and 16S forms of AChE were affected. The effect was maximal 15 to 24 h after injection. Choline acetyltransferase (CAT) activity was not affected. Neither AChE nor CAT activities changed in sciatic nerve from 2,4-D-treated animals. Spontaneous locomotor activity decreased dramatically 4 h after 2,4-D treatment. Myotonia that was present 1.5 h after 2,4-D injection became maximal at 2 to 6 h. Twenty-four hours after drug injection, when animals were recovering from myotonia, spontaneous locomotor activity was still depressed to 50% of control values. Prolonged distal motor latencies were observed 15 to 24 h after drug administration. AChE activity and spontaneous locomotor activity returned to control values at 48 h. Thus, 2,4-D causes a decrement of end-plate AChE, as well as behavioral and electrophysiologic changes. Decreased activity of AChE may be an early step in development of the myopathy that occurs after large dose 2,4-D.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1985

2,4-Dichlorophenoxyacetic acid (2,4-D) does not cause polyneuropathy in the rat.

2,4-Dichlorophenoxyacetic acid (2,4-D), a component of Agent Orange, was injected intraperitoneally into adult male Fisher rats for 3-12 weeks. During the period of study gait and toe-spreading reflexes remained normal and distal motor latencies, motor and mixed nerve conduction velocities and amplitudes remained similar (P greater than 0.05) in animals receiving 2,4-D or vehicle. This study suggests that 2,4-D is not toxic to peripheral nerves in the rat.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1985

[Persistence of pleomorphism and the presence of multinuclear forms in experimental infection with T.b. brucei].

Thirty white male mice SWISS ICO NMRI (IOPS) were inoculated intraperitoneally with blood-forms of T.b. brucei of a strain belonging to the Laboratory of Parasitology of the Medicine Faculty of the U.A.M. (Autonom University of Madrid). This strain was preserved during 8 years through inoculation from mice to mice. This strain was received from the Pasteur Institute from Paris. Once infected the mice were submitted to a controle through GIEMSA coloured smears. The various blood-forms registered during the experimental infection were carefully measured and also their proportional presence during the observation. We could appreciate an augment of the Slender forms following the progress of the infection and the apparition of the Stumpy at 48 hours after the inoculation as well as the multinucleate forms. Stumpy forms in division were also observed.

Animals↗
PubMed1985

Thymectomy for myasthenia gravis: 14-year experience.

Forty-eight consecutive patients with myasthenia gravis (MG) attended by generalized weakness were treated by complete thymectomy, performed transsternally in 46 patients and through a left thoracotomy in two with thymomas. There were no operative deaths. A 12-year-old child with fulminating MG died of acute pneumonia shortly after hospital discharge. Of the remaining 47 evaluable patients, thymectomy resulted in complete remission in six, marked improvement with a reduced need for medication in 20, and mild improvement on the same dosage of medication in 18. Neither the age of the patient, nor the histopathology of the excised thymus, nor the postoperative change in acetylcholine receptor antibody titer were found to have a significant influence on the response to thymectomy. If the ten patients who were 20 years of age or younger were excluded, the patients with a shorter duration of MG achieved a better response to operation. The authors conclude that thymectomy is effective treatment for MG, regardless of the age of the patient or the type of thymic pathology.

Adolescent↗
PubMed1985

Treatment of myasthenic crisis in late life.

In 32 patients with the onset of myasthenia gravis after age 50, myasthenic crisis occurred in 53% and persisted for a mean of 33 days (range six to 84 days). Three of the patients had a second crisis. Precipitating factors were found in 60% of the episodes. Treatment of 20 episodes of crisis resulted in excellent recovery. No patient died in crisis. All regained enough function to return home. Those patients (50%) who had no medical complications recovered most rapidly. The most common medical complications were aspiration and bacterial pneumonia, cardiac arrhythmias, and congestive heart failure. Large doses of prednisone in combination with serial plasma exchanges was the most effective therapy. This group of patients had the fewest medical complications (29%) and the fastest recovery.

Adult↗
PubMed1985

Weakness and 'tiredness': when to suspect myasthenia gravis.

Initial complaints of bulbar paresis may be problems with chewing and swallowing. Patients often choose to eat soft puddings and cereals rather than meats or hard fruits because of the fatigue associated with chewing. Immunosuppressive therapy with prednisone can result in a long-lasting remission, and is recommended especially for those patients who are older or are medically unable to tolerate surgical treatment.

Aged↗
PubMed1984

The effect of spinal cord transection on motor units in cat medial gastrocnemius muscles.

We studied the properties of whole medial gastrocnemius (MG) and soleus muscles, and of 74 individual MG motor units in three cats with long-term complete low thoracic spinal transection (TS). All animals remained paraplegic and there was considerable atrophy of MG and soleus muscles. Motor units in the MG pool were readily classified into the same groups, types FF, F(int), FR, and S, found in normal MG, but tetanic force outputs and mean fiber areas for the corresponding muscle fiber types were decreased in all unit types as were isometric twitch contraction times. The proportion of type F(int) motor units was greater (19.0%) than expected from normal samples (5.8%) and this was also true of the corresponding type 2AB muscle fibers (6.9% in TS vs 3.3% in controls). In addition, FR and S units were less numerous (17.5% each) than in control muscles (23.0% and 25.2%, respectively), and histochemical examination revealed a similar decrease in the percentage of type 2A (11.6%) and 1 (16.4%) fibers compared with controls (20.0% and 30.5%, respectively). The changes found in chronic paraplegic atrophy were different in some details from those found after chronic simple limb immobilization.

Animals↗