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Biomedical subjects

E H Lambert

Publications and source records attributed to E H Lambert.

At least 37 records · Page 2Linked to original sources
PubMed1987

Definition of myasthenogenic sites of the human acetylcholine receptor using synthetic peptides.

Experimental autoimmune myasthenia gravis (EAMG) and antibodies that modulate AChRs from cultured human muscle are induced by a disulfide-looped peptide comprising the human acetylcholine receptor (AChR) alpha-subunit residues 125-147 (H alpha 125-147). To delineate the essential antigenic requirements for induction of EAMG by this peptide, a series of peptides was synthesized: (a) a nonlooped analog (Cys 128 replaced by Ser) stimulated modulating autoantibodies, induced EAMG, and bound antibodies induced by native AChR; (b) H alpha 131-147, a heptadecylpeptide shorter by 6 N-terminal residues, induced modulating antibodies, EAMG, and T cells that responded to H alpha 125-147, but not to H alpha 137-147; (c) H alpha 137-147, an undecapeptide shorter than H alpha 125-147 by 12 N-terminal residues, did not stimulate T cells or induce antibody production, but it bound antibodies generated by the longer peptides. Thus, when coupled to an epitope that could stimulate helper T cells, the region 137-147 was able to stimulate B cells. This study has defined a myasthenogenic region of the human AChR's alpha-subunit, 17 amino acids long, that contains several distinct epitopes, including at least one N-terminal site inducing T-cell responses (region 131-136) and two possibly overlapping sites that induce antibodies (regions 131-136 and 137-147). Further definition of antigenic sites inducing helper and suppressor T-cell responses and stimulating production of autoantibodies to AChR is essential to the goal of antigen-specific immunotherapy for myasthenia gravis.

Action Potentials↗
PubMed1987

Synaptic vesicle abnormality in familial infantile myasthenia.

In familial infantile myasthenia (FIM) the miniature end-plate potential (MEPP) amplitude is normal in rested muscle, but stimulation in vitro at 10 Hz decreases it abnormally, and neuromuscular transmission fails in a few minutes. In search of a morphologic correlate of the transmission failure, we analyzed the densities and diameters of synaptic vesicles in deep and superficial regions of nerve terminals in external intercostal muscles of three FIM patients and three nonweak controls before and after 10-Hz stimulation for 10 minutes. The densities of superficial or deep synaptic vesicles before or after stimulation in FIM were not significantly different from the corresponding control values. The diameters of superficial and deep synaptic vesicles before stimulation were significantly smaller in the three FIM patients than in the three controls. Stimulation in the FIM patients reduced the MEPP amplitude by 51 to 75%, but increased the vesicle diameter in two patients and did not change the vesicle diameter in one patient. Stimulation in the controls reduced the MEPP amplitude by only 16 to 34%, decreased the vesicle diameter in two, and did not change the vesicle diameter in one. Stimulation after treatment with 1 mg/dl hemicholinium markedly reduced the MEPP amplitude in the controls, had no further effect on the transmission defect in FIM, and had no consistent effect on vesicle diameter in FIM or controls. We conclude that synaptic vesicles are abnormally small in rested muscle in FIM, but vesicle size cannot be reliably correlated with the MEPP amplitude in FIM or controls.

Adult↗
PubMed1986

The exercise test in periodic paralysis.

Of 21 patients with clinically definite hypokalemic, hyperkalemic, or normokalemic periodic paralysis, 15 (71%) had a greater than normal increase in compound muscle action potential amplitude during 2-5 minutes of intermittent strong voluntary contraction of the muscle. This increase was followed by a progressive decline in amplitude, which was greater than in a control population and which was most rapid during the first 20 minutes after exercise. The amplitude often decreased to a level below the preexercise level. A similar response was seen in six of nine patients with periodic paralysis secondary to disorders such as thyrotoxicosis. This test may have value in the identification of patients with periodic paralysis.

Action Potentials↗
PubMed1985

Region of peptide 125-147 of acetylcholine receptor alpha subunit is exposed at neuromuscular junction and induces experimental autoimmune myasthenia gravis, T-cell immunity, and modulating autoantibodies.

A major antigenic region of native nicotinic acetylcholine receptors (AcChoR) has been identified by using a synthetic disulfide-looped peptide corresponding to alpha-subunit residues 125-147 of Torpedo electric organ AcChoR: Lys-Ser-Tyr-Cys-Glu-Ile-Ile-Val-Thr-His-Phe- Pro-Phe-Asp-Gln-Gln-Asn-Cys-Thr-Met-Lys-Leu-Gly. The peptide bound 26-56% of polyclonal antibodies induced in rat, rabbit, and dog by immunization with native AcChoR. Rats inoculated with 50 micrograms of unconjugated peptide developed helper T-cell responses, delayed hypersensitivity, and antibodies to native AcChoR. Anti-peptide antibodies were more reactive with native than denatured AcChoR and bound to the alpha subunit. Some reacted exclusively with mammalian muscle AcChoR, some induced modulation of AcChoR on cultured myotubes, but none inhibited binding of alpha-bungarotoxin to solubilized or membrane-associated AcChoR. Repeated immunization induced experimental autoimmune myasthenia gravis: clinical signs in one rat and electrophysiologic and/or biochemical signs in 10 of 11 rats. Thus, at least part of the corresponding region of the mammalian AcChoR alpha subunit is extracellular at the neuromuscular junction and a potential target for pathogenic autoantibodies in patients with acquired myasthenia gravis.

Amino Acid Sequence↗
PubMed1985

Acetylcholine receptors in small cell carcinomas.

The presence of muscarinic and nicotinic acetylcholine receptors (m- and nAChR, respectively) in small cell carcinomas (SCC) of the lung was assessed by measurement of specific binding of (-)[3H]quinuclidinyl benzilate ([3H]QNB) and 125I-alpha-bungarotoxin, respectively. Of five SCC studied, four were originally derived from patients with the Lambert-Eaton myasthenic syndrome, an autoimmune disease of neuromuscular transmission, and one was from a patient without evidence of neurological disease. There was no evidence of nAChR, but all tumors bound (-)[3H]QNB in a saturable and specific manner. Dissociation constants derived from saturation isotherms ranged between 35.4 and 181.7 fmol/mg protein (mean values for the five SCC). Competition studies revealed a pharmacological profile consistent with previous descriptions of mAChR. Competition by pirenzepine revealed only one class of binding sites, that with a relatively low affinity for pirenzepine. In the presence of the guanine nucleotide analogue 5'-guanylyl imidodiphosphate, a decrease in affinity of the mAChR of SCC for oxotremorine was observed, with an increase in the pseudo-Hill coefficient, but there was no change in the binding of atropine. The expression on SCC of mAChR, apparently of the M2 subclass, represents yet another neural differentiation marker of SCC. It is noteworthy that the expression of this marker is not restricted to patients with an autoimmune paraneoplastic syndrome involving cholinergic neurons.

Animals↗
PubMed1984

Hereditary form of sustained muscle activity of peripheral nerve origin causing generalized myokymia and muscle stiffness.

Six patients in two unrelated families had a hereditary form of sustained muscle activity of peripheral nerve origin. Although varying in severity among affected family members, the disease was manifested clinically as generalized myokymia and muscle stiffness. Motor and sensory nerve conduction velocities and results of nerve biopsy were normal. Repetitive after-discharges followed each motor nerve stimulus. Needle electrode examination demonstrated spontaneous recurrent bursts of motor unit activity. The burst activity of a motor unit occurred rhythmically (0.5 to 4 bursts per second) and independently of the activity of other units. Within a burst, the firing rate was high (150 to 300 Hz). The clinical and electromyographic abnormalities improved considerably after treatment with carbamazepine or phenytoin.

Adolescent↗
PubMed1983

Congenital myasthenia gravis in 13 smooth fox terriers.

In 13 Smooth Fox Terriers with a congenital form of myasthenia gravis, clinical signs included intermittent, progressive muscle weakness that became more pronounced with exercise; muscle wasting; megaesophagus; and aspiration pneumonia. Neurologic abnormalities were apparent only during periods of weakness and included inability to retract the fore- and hindlimbs from painful stimuli. A decrement of the compound muscle action potential was evident during repetitive supramaximal nerve stimulation. Intravenous injection of a short-acting cholinesterase inhibitor evoked immediate improvement of clinical and electromyographic signs. Intracellular microelectrode studies of a biopsied external intercostal muscle revealed reduced amplitude of miniature end-plate potentials, as occurs in acquired myasthenia gravis. However, in contrast to acquired myasthenia gravis, antibodies directed against acetylcholine receptors were not demonstrable in serum and were not bound to acetylcholine receptors in muscle. Despite lack of complexing with immunoglobulin, the amount of acetylcholine receptor protein in biopsied external intercostal muscles from 9 affected pups was less than 25% of the amount in 5 unaffected littermates. The latter finding accounted for the reduction in amplitude of miniature end-plate potential and the failure of neuromuscular transmission. Treatment with a long-acting cholinesterase inhibitor in 6 cases resulted in temporary improvement in muscle strength.

Animals↗
PubMed1983

Myasthenia gravis in two cats.

A case of the autoimmune form of myasthenia gravis and a case of what is probably a congenital form of myasthenia gravis were diagnosed in 2 unrelated cats. Neuromuscular weakness exacerbated by exercise was a prominent feature in both cats. Weakness was eliminated temporarily by administration of anticholinesterase drugs. Serum autoantibodies to acetylcholine receptors of skeletal muscle were present in the 1st cat and were not detected in the 2nd cat. A characteristic decrement in the amplitude of the compound muscle action potential during repetitive stimulation of the motor nerve was elicited in the 2nd cat. There was marked electromyographic improvement in response to anticholinesterase drugs. Electromyography was not performed in the 1st cat.

Animals↗
PubMed1983

Acute panautonomic neuropathy.

Two patients with acute panautonomic neuropathy had severe impairment of sympathetic and parasympathetic function of acute onset. Autonomic tests suggesting a postganglionic lesion and direct evidence of loss of unmyelinated and small myelinated fibers on nerve biopsy were found in Patient 1. There was a selective loss of small myelinated and unmyelinated nerve fibers; C potential was absent in the in vitro compound action potential; dopamine-beta-hydroxylase activity was unmeasurable. No definite abnormalities were found on the nerve biopsy of Patient 2. The acute panautonomic neuropathies appear to comprise a spectrum of somatic and autonomic involvement.

Acute Disease↗
PubMed1983

Failure to induce malignant hyperthermia in myotonic goats.

Six goats with myotonia congenita were exposed for 1 h to 1% halothane and a single injection of suxamethonium i.v. in an attempt to induce malignant hyperthermia. No evidence of malignant hyperthermia occurred. Suxamethonium did produce a myotonic response in each goat, lasting 10-20s, which was accompanied by a transient increase in aerobic metabolism as indicated by a decrease in PvO2 from 6.6 to 5.7 kPa, an increase in PaCO2 from 5.1 to 6.1 kPa and an increase in PVCO2 from 5.5 to 6.3 kPa. There was no evidence of any metabolic acidosis since the transient changes in pH and buffer base were consistent with the increase in carbon dioxide tension. It is concluded that in goats myotonia congenita does not predispose to susceptibility to malignant hyperthermia.

Animals↗
PubMed1983

Not 'indifference to pain' but varieties of hereditary sensory and autonomic neuropathy.

Three children, from different kinships, with generalized insensitivity to pain, showed unusual manifestations of congenital, presumably inherited, sensory and autonomic neuropathy. The first child appeared to have a syndrome resembling those previously described as congenital indifference to pain, congenital universal loss of pain sensation from infancy without other apparent neurological deficit. Unlike most types of hereditary sensory and autonomic neuropathies (types I, II, III), but like type IV, she had normal sensory nerve action potentials. Abnormalities of sudomotor function and of somatosensory evoked potentials were demonstrated. A severe decrease in the number of sural nerve A delta fibres and a small reduction in C fibres were demonstrated morphometrically. An abnormality of C fibres was confirmed by a marked reduction in nerve dopamine-beta-hydroxylase activity. The plasma and CSF concentrations of beta endorphins, substance P and several other neuropeptides and hormones were normal. Unequivocal evidence of a neuropathic lesion is provided by this patient; her disorder may be identified as the fifth type of hereditary sensory and autonomic neuropathy. The second patient had a congenital pansensory neuropathy and progressive retinitis pigmentosa. Whether the disorder is inherited and, if so, whether the retinitis pigmentosa results from the same or from a second genetic abnormality, is unclear. The third case has, in addition to what is usually seen in hereditary sensory and autonomic neuropathy, type II, an unusually severe kinaesthetic difficulty in oral food handling. The sural nerves of the second and third patients had fibre composition characteristic of hereditary sensory and autonomic neuropathy, type II, few or no myelinated fibres and reduced numbers of unmyelinated fibres.

Autonomic Nervous System Diseases↗
PubMed1983

Linkage evidence for genetic heterogeneity among kinships with hereditary motor and sensory neuropathy, type I.

Previous reports have shown linkage of hereditary motor and sensory neuropathy, type I (HMSN I), a dominantly inherited hypertrophic neuropathy, to the locus for the Duffy blood group on the long arm of chromosome 1. Two kinships that were extensively studied and reported almost 20 years ago and used to show heterogeneity among kinships with peroneal muscular atrophy and to characterize HMSN I were investigated for linkage to various blood erythrocyte and lymphocyte (HLA) antigens. Strong evidence against linkage to the Duffy blood group locus was found for one kinship, whereas suggestive evidence for linkage was found for the other. These data imply that HMSN I is heterogeneous--that is, caused by different genetic mechanisms. The HMSN I that is not linked to the Duffy locus might be identified as HMSN IA, and the HMSN I that is linked to the Duffy locus might be designated as HMSN IB. HMSN IA was not linked to other blood types or HLA antigens. In addition, no evidence for linkage to blood types and HLA was found for spastic paraplegia with peroneal muscular atrophy and sensory loss (HMSN V).

Adolescent↗
PubMed1982

A newly recognized congenital myasthenic syndrome attributed to a prolonged open time of the acetylcholine-induced ion channel.

Five familial cases (in two families) and one sporadic case of a new congenital myasthenic syndrome were investigated. Symptoms arise in infancy or later life. Typically, one finds selective involvement of cervical, scapular, and finger extensor muscles, ophthalmoparesis, and variable involvement of other muscles. There is a repetitive muscle action potential to single nerve stimulus in all muscles and a decremental response at 2 to 3 Hz stimulation in clinical affected muscles. Microelectrode studies reveal markedly prolonged end-plate potential (epp), miniature end-plate potential (mepp), and miniature end-plate current; normal quantum content of the epp; and a smaller than normal or low-normal mepp amplitude. Light microscopy demonstrates predominance of type I fibers, small groups of atrophic fibers, tubular aggregates and vacuoles near end-plates, abnormal end-plate configuration, and nonspecific myopathic changes. Abundant acetylcholinesterase activity is present at all end-plates, and the activity and kinetic properties of this enzyme in muscle are normal. Calcium accumulated at the end-plate in one patient. Quantitative electron microscopy shows decrease in the size of nerve terminals, increase in the density of synaptic vesicles, and reduction in the length of postsynaptic membranes. There is focal degeneration of junctional folds with corresponding loss of acetylcholine receptor, most marked in cases with the lowest mepp amplitude. There are no immune complexes at the end-plate. Fiber regions near end-plates display dilation, proliferation, and degeneration of the sarcoplasmic reticulum; nuclear, mitochondrial, and myofibrillar degeneration; and vacuoles resembling those found in periodic paralysis. A prolonged open time of the acetylcholine-induced ion channel is considered to be the basic abnormality and may account for the physiological, morphological, and clinical alterations.

Acetylcholine↗
PubMed1982

Autoimmunity in the Lambert-Eaton myasthenic syndrome.

Sera from 64 patients with the Lambert-Eaton myasthenic syndrome (LES) were tested for evidence of autoimmunity to a variety of tissue antigens. One or more organ-specific autoantibodies (thyroid, gastric, and/or skeletal muscle) were found in 29 patients (45%). Of 46 patients without evidence of tumor, autoantibodies were found in 24 (52%), and of 18 patients with tumor, autoantibodies were found in 5 (28%). In an age-matched group of 40 patients with miscellaneous neurologic diseases, 7 (17%) had one or more organ-specific autoantibodies, and in a control group of 47 patients with myasthenia gravis the combined prevalence of thyroid and gastric antibodies was 47%, comparable to that found in LES patients. The prevalence of non-organ-specific autoantibodies (for example, rheumatoid factor and/or antinuclear antibodies) was not significantly elevated in LES. These data clearly justify consideration of LES without tumor as an organ-specific autoimmune disease. If LES with tumor does prove to have an autoimmune basis, the mechanism may involve an antigen common to cholinergic neurons and oat cell carcinoma, both of which are neuroectoderm derivatives.

Adenocarcinoma↗
PubMed1982

Neuromuscular transmission in nude mice bearing oat cell tumors from Lambert-Eaton myasthenic syndrome.

Metastatic oat cell tumors from 3 patients with the Lambert-Eaton myasthenic syndrome were successfully transplanted to athymic nude mice, and serially passaged by subcutaneous inoculation. Mice bearing large tumors which maintained the characteristics of each patient's tumor had no evidence of muscle weakness. Intracellular microelectrode studies of end-plate potentials in the diaphragms of the mice revealed no evidence of a defect of neuromuscular transmission.

Aged↗
PubMed1982

Prednisone-responsive hereditary motor and sensory neuropathy.

Neurologic improvement with use of prednisone, in some cases on several occasions, was demonstrated in seven patients who had a chronic progressive polyradiculoneuropathy with nerve conduction velocity and electromyographic findings consistent with segmental demyelination and axonal degeneration and increases protein concentration in the cerebrospinal fluid. These patients seemed to have the progressive form of chronic inflammatory-demyelinating polyradiculoneuropathy and, in addition, had clinical features of hereditary motor and sensory neuropathy including pes cavus and hammer toes. On systematic examination, bony abnormalities or asymptomatic neuropathy typical of subclinical inherited neuropathy was discovered among their kin. There patients might therefore be identified as having inflammatory-demyelinating hereditary motor and sensory neuropathy. These cases may represent a chance association of chronic inflammatory-demyelinating polyradiculoneuropathy and hereditary motor and sensory neuropathy, a causally linked association of these disorders, or a prednisone-responsive inherited neuropathy only. We wish to draw attention to this treatable neuropathy and to raise the question of whether environmental factors play role in the expression of dominantly inherited mutant genes.

Adolescent↗