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Biomedical subjects

B Lang

Publications and source records attributed to B Lang.

At least 181 records · Page 10Linked to original sources
PubMed1989

Lambert-Eaton myasthenic syndrome: immunoglobulin G inhibition of Ca2+ flux in tumor cells correlates with disease severity.

We compared the effects of Lambert-Eaton myasthenic syndrome (LEMS) immunoglobulin G (IgG) obtained from patients with and without small-cell lung carcinoma (SCLC) on voltage-gated (K+-stimulated) 45Ca2+ flux in cell lines derived from a human SCLC (MAR10) and from a rat pheochromocytoma (PC12) and related these to electromyographic indexes of clinical severity. Control IgG was obtained from patients with other neurological disorders or healthy individuals. Inhibition of Ca2+ flux by LEMS IgG was time and dose dependent. The flux was significantly reduced in MAR10 cells grown in either SCLC-LEMS IgG (0.38 nmol/10(6) cells; p less than 0.001) or non-SCLC-LEMS IgG (0.35 nmol/10(6) cells; p less than 0.001), compared with that in MAR10 cells grown in control IgG (0.7 nmol/10(6) cells). Similar significant reductions were also observed in PC12 cells. The reduction in amplitude of the resting compound muscle action potential in the LEMS patients correlated positively (r = 0.70; p = 0.007) with the inhibition of Ca2+ flux in MAR10 cells by their IgG. These results strongly support the view that IgG autoantibodies that can inhibit Ca2+ flux in SCLC cells are responsible for the disorder of transmitter release at motor nerves in SCLC-associated LEMS.

Action Potentials↗
PubMed1989

Association of class I, II, and III MHC gene products with systemic lupus erythematosus. Results of a Central European multicenter study.

Class I, II, and III MHC gene products were examined in 248 Central European SLE patients. The previously reported association with HLA-A1, -B8 and -DR3, and C4AQ0 alleles was confirmed. The frequency of HLA-DR2 was also slightly elevated in SLE patients, while no increase in C4BQ0 alleles was observed. Additional findings were a significantly increased frequency of HLA-B13 and a significant decrease of HLA-B44.

Alleles↗
PubMed1989

Effects of botulinum neurotoxin and Lambert-Eaton myasthenic syndrome IgG at mouse nerve terminals.

The interaction between two presynaptically acting agents, Lambert-Eaton myasthenic syndrome (LEMS) immunoglobulin G (IgG) and purified botulinum neurotoxin (BoNT) type A, was studied. Intracellular microelectrode recordings were carried out on mouse muscles after injection with LEMS IgG. BoNT was either injected before recordings were made or applied in vitro. The time course of the in vitro actions of BoNT on miniature end-plate potential and end-plate potential parameters were not affected by pretreatment with LEMS IgG. After in vivo injection of BoNT, end-plate potential quantal content was reduced to less than 2% of control values, whether or not LEMS IgG had also been previously given. Quantitative electron-microscope autoradiographical analysis showed that neither the binding of 125I-BoNT to acceptors on the nerve terminal membrane nor the pattern of its internalisation were affected by pretreatment with LEMS IgG. We conclude that the effects of BoNT are not affected by LEMS IgG, suggesting different presynaptic binding sites for the two agents.

Action Potentials↗
PubMed1989

Autoimmunity to the voltage-gated calcium channel underlies the Lambert-Eaton myasthenic syndrome, a paraneoplastic disorder.

The Lambert-Eaton myasthenic syndrome (LEMS) is a disorder of neuromuscular transmission, often associated with small cell lung carcinoma (SCLC), and characterized by reduced quantal release of acetylcholine from the motor nerve terminals. Another neuromuscular transmission disorder, myasthenia gravis, has a well-understood autoimmunological cause. This review discusses the evidence for a similar autoimmunological effect in the development of LEMS. Injection of LEMS IgG into mice passively transfers the physiological and morphological abnormalities, which include paucity and disorganized arrangement of active zone particles believed to represent the voltage-gated calcium channels (VGCCs). Calcium influx via VGCCs into SCLC cells is reduced by LEMS IgG suggesting that in SCLC-associated LEMS, antibodies may be triggered by VGCCs expressed on these cells; this immunological cross-reactivity may lead to the neurological abnormality. Similar VGCCs on neuronally derived cells may trigger the disorder in those without a tumour. The disorder provides another example of the complicated relationships between the nervous and immune systems and tumorigenic processes.

Autoimmune Diseases↗
PubMed1988

The effect of Lambert-Eaton myasthenic syndrome antibody on slow action potentials in mouse cardiac ventricle.

Immunoglobulin G (IgG) from Lambert-Eaton myasthenic syndrome (LEMS) patients acts at motor nerve terminal Ca2+ channels. It was injected into mice to investigate effects on cardiac Ca2+ channels. Intracellular recordings were made of slow action potentials in right ventricular muscle cells in the presence of high K+ concentrations and isoprenaline (1 microM). Reduction in Ca2+ concentration reduced the rate of rise and amplitude, but not the duration, of slow action potentials whereas verapamil (1 microM) blocked them. They were not blocked by tetrodotoxin (10 microM), and 4-aminopyridine (1 mM) prolonged the decay phase without affecting the rate of rise and amplitude. The rate of rise, amplitude and duration of slow action potentials were not affected by LEMS IgG. These results show that LEMS IgG does not act on Ca2+ channel currents that underlie slow action potentials in mouse ventricles, suggesting antigenic differences between Ca2+ channels at motor nerve terminals and heart.

4-Aminopyridine↗
PubMed1988

Stimulation of the conjugation of lipid dienes in hepatic microsomes by 3,3'-dichlorobenzidine.

Pretreatment of male rats with 3,3'-dichlorobenzidine (DCB) resulted in the accumulation of conjugated dienes in lipids from hepatic microsomes. In vitro, these microsomes had 2-fold the NADPH-dependent malondialdehyde (MDA)-forming capacity of microsomes from untreated rats. To determine the mechanisms of the DCB-induced accumulation of diene conjugation, the effects of added DCB on NADPH- or iron + ascorbic acid- (Fe2+-ascorbate-) dependent diene conjugation, oxygen uptake and MDA formation were examined in microsomes from untreated rats in vitro. In the presence of NADPH, added DCB stimulated diene conjugation in microsomal lipids as did in vivo DCB pretreatment but inhibited the uptake of oxygen and the formation of MDA. When Fe2+-ascorbate was substituted for NADPH, the formation of diene conjugation, oxygen uptake, and MDA formation were inhibited by added DCB. The DCB-induced stimulation of diene conjugation, in addition to being strictly NADPH dependent, was carbon monoxide sensitive and was concomitant with the binding of added DCB to microsomal lipids. It is postulated that a metabolite of DCB generated by cytochrome P-450 reacts with membrane lipids both in vivo and in vitro in a manner analogous to the initiation of lipid peroxidation but at the same time prevents the autocatalytic decomposition of the lipids. The DCB-induced diene conjugation is interpreted as predisposing to deleterious changes in microsomes.

3,3'-Dichlorobenzidine↗
PubMed1988

Lambert-Eaton myasthenic syndrome IgG depletes presynaptic membrane active zone particles by antigenic modulation.

The Lambert-Eaton myasthenic syndrome (LEMS) is an autoimmune disease that can be transmitted from human to mouse with immunoglobulin G (IgG). Electrophysiological studies indicate that LEMS IgG acts on presynaptic voltage-sensitive calcium channels, probably reducing their number, and freeze-fracture electron microscopy demonstrates that LEMS IgG has an effect on the presynaptic active zone particles, which represent putative voltage-sensitive calcium channels. The active zone particles, normally arranged in double parallel rows, move closer together, form clusters, and are reduced in number. The morphological data suggest modulation of the active zone particles crosslinked by LEMS IgG. If this were the case, then only divalent LEMS IgG and F(ab')2 should alter the deployment of active zone particles and monovalent Fab should be without effect. To test this hypothesis, mouse diaphragms were exposed to control and LEMS IgG and IgG fragments in organ culture for 24 hours and then studied by quantitative freeze-fracture electron microscopy. Divalent LEMS IgG and F(ab')2 aggregated and depleted the active zone particles, whereas monovalent Fab had no effect. The findings reconfirm that the active zone particles are targets of LEMS IgG and are direct evidence for modulation of the particles by LEMS IgG. The findings are in harmony with parallel electrophysiological studies of the effects of LEMS IgG fragments on transmitter release in the same diaphragm muscles (Lang et al, J Physiol 1987;390:173P).

Animals↗
PubMed1988

Plasma from myasthenia gravis patients reduces acetylcholine receptor agonist-induced Na+ flux into TE671 cell line.

Plasma from myasthenia gravis patients was tested for its ability to inhibit agonist-induced 22Na+ influx into the TE671 cell line that expresses human acetylcholine receptors. Reduced 22Na+ influx correlated weakly with the total anti-acetylcholine receptor antibody level in the plasma, and was also related to the presence of antibody directed against the agonist binding site, as detected by inhibition of 125I-alpha-bungarotoxin binding. However, in some cases there was inhibition of 22Na+ flux without evident anti-alpha-bungarotoxin binding site antibody. We conclude that in most patients antibodies that interfere with 22Na+ influx do so by blocking the agonist binding site. However, in some cases antibodies may be directed at the Na+ ion channel or some important functional determinant.

Adult↗
PubMed1988

Lambert-Eaton syndrome antibodies: reaction with membranes from a small cell lung cancer xenograft.

Lambert-Eaton myasthenic syndrome (LEMS) is a paraneoplastic autoimmune disorder caused by an IgG-mediated reduction in number of presynaptic voltage-gated calcium channels (VGCC) at the neuromuscular junction. In at least 50% of cases, the stimulus for antibody production may be VGCC on small cell lung cancer (SCLC). In this study membranes isolated from a human small cell lung cancer xenograft (Mar), that bound [3H]PN200-110, a VGCC antagonist, were subjected to Western blotting using plasma from 12 LEMS patients and eight controls. Although one band recognised by 3/12 LEMS IgGs might be associated with the VGCC, a number of other proteins were recognised both by LEMS plasma, and by plasma from patients with other disorders. The results illustrate the difficulties found using Western blotting with autoimmune plasma to identify specific polypeptides in a crude antigen preparation.

Adult↗
PubMed1988

HLA-Dw14 and HLA-DR3 haplotypes share a functional determinant recognized by a human alloreactive T-cell clone.

In the process of studying the fine specificity of HLA class II molecules, we identified an alloreactive T-cell clone raised to a HLA-Dw14 homozygous cell line that was specifically stimulated by Dw14+ homozygous typing cells but negatively with cells expressing the HLA-Dw4,-Dw10, -Dw13, and -Dw15 subspecificities of DR4. Of interest, this clone was also equivalently activated by stimulation with all DR3 cells and cell lines tested. Negative responses were obtained using a panel of 87 non-DR3 and non-Dw14 cells, including cell lines of the Tenth Histocompatibility Workshop. A monoclonal antibody inhibition study revealed the relevant stimulating determinant to be on HLA-DR molecules in both Dw14- and DR3-positive cells. A comparison of the DR beta 1-chain-inferred amino acid sequences suggests that formation of a topologically equivalent stimulating determinant would involve the participation of two noncontiguous regions of the third diversity region of DR beta 1. The putative recognition conformation detected by the clone is most probably specified by the presence of a valine at position 86 and a nonnegatively charged residue at positions 70, 71, and 74, since these are the only residues where DR3 and Dw14 are distinguishable from all other HLA-DR types. These findings illustrate that the functional ability of class II molecules is not necessarily either illustrated or predicted by serologic typing or by simple considerations of amino acid sequence.

Amino Acid Sequence↗
PubMed1988

Metabolism of 3,3'-dichlorobenzidine by horseradish peroxidase.

1. The peroxidatic oxidation of 3,3'-dichlorobenzidine by horseradish peroxidase in the presence of H2O2 was examined spectrophotometrically and the reactivity of the spectral species were compared to those formed from the peroxidative oxidation of benzidine. 2. The horseradish peroxidase-catalyzed oxidation of 3,3'-dichlorobenzidine yielded two transient and one stable spectral species with absorption maxima at 630 nm, 370 nm and 410 nm, respectively, whereas that of benzidine yielded three stable spectral species with absorption maxima at 610 nm, 425 nm and 370 nm, respectively. 3. The 425 nm species from benzidine, but not the 410 nm species from 3,3'-dichlorobenzidine was scavenged by butylated hydroxyanisole, glutathione, N-acetylcysteine or 2-deoxyguanosine. 4. H.p.l.c. mass spectrometric analysis, and comparative studies with potassium dichromate oxidation of 3,3'-dichlorobenzidine, indicated that the major product from the horseradish peroxidase-catalyzed oxidation of 3,3'-dichlorobenzidine is azo-3,3'-dichlorobenzidine. 5. None of the products from enzymic or chemical oxidation of either 3,3'-dichlorobenzidine or benzidine was directly mutagenic to S. typhimurium TA98 in the Ames test; however the chemically oxidized and enzymic products from 3,3'-dichlorobenzidine were mutagenic in the presence of H2O2. 6. The data indicate that despite apparent structural similarities between the intermediates formed during the peroxidatic oxidation of all benzidines, the intermediates and products of peroxidatic oxidation of dichlorobenzidine have reactivities and stabilities different from those of other benzidines.

3,3'-Dichlorobenzidine↗
PubMed1987

Lambert-Eaton myasthenic syndrome: I. Early morphological effects of IgG on the presynaptic membrane active zones.

In the freeze-fractured presynaptic membrane of the motor end-plate, the active zones consist of two parallel arrays and each array contains 10- to 12-nm particles arranged in two rows. In the Lambert-Eaton myasthenic syndrome (LEMS) and in mice treated with 10 mg/day of LEMS IgG, administered intraperitoneally for several weeks, there was a paucity and disorganization of the active zones, and clusters of 10- to 12-nm particles appeared. To further define the changes in the active zones, mice were studied that had been treated over 2 days with 104 to 180 mg of IgG. Treatment transferred the physiological defect of LEMS. Control mice received normal human IgG or no IgG. The spacing and density (number/unit area) of active-zone particles were evaluated in presynaptic membrane P-faces using computer-assisted stereometry. In the normal active zone, the distance between particles in a given row and between adjacent rows of an array was less than, but the distance between the two arrays was greater than, the distance between the two antigen-binding sites on human IgG. In mice treated with LEMS IgG, the initial alteration in the active zone was a decrease in the distance between particles in a given row and between adjacent rows of an array; the distance between the two arrays remained unaltered. In more affected active zones, the parallel orientation of the rows was disturbed and the arrays became clusters. There was a significantly reduced density of active zones and of large-membrane particles associated with all active zones and clusters.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Lambert-Eaton myasthenic syndrome: II. Immunoelectron microscopy localization of IgG at the mouse motor end-plate.

The autoimmune origin of the Lambert-Eaton myasthenic syndrome (LEMS) was documented by passive transfer of its electrophysiological features from humans to mice with IgG. Freeze-fracture electron microscopy has demonstrated a loss of active-zone particles in human LEMS and in its mouse passive transfer model. These data imply that the active zones are targets of the pathogenic LEMS autoantibodies. Immunolocalization of the antibodies has been hindered, however, by a paucity of active-zone particles (about 50/micron2 normally and still lower in LEMS) and by diffusion artifacts in the immunoperoxidase method. To obviate these problems, we employed sensitive avidin-biotin detection systems, both peroxidase and ferritin labels, and quantitative immunoelectron microscopy and end-plate morphometry. We compared mice treated with LEMS IgG, control IgG, and no IgG. In all mice, nonspecific background staining was found in the basal lamina covering the muscle fibers and Schwann cells. When a single 10-mg dose of IgG was injected intravenously, IgG samples from 12 patients produced significant immunostaining of the mouse active zones; from 7 patients they did not. Higher doses of intraperitoneally injected IgG (20 mg, three times a day for 2 days, or 10 mg/day for 15 days) from each of 4 patients (3 of whose IgG previously transferred LEMS to mice) caused significant immunostaining of mouse active zones: (1) the mean density (no./micron presynaptic membrane length) of positive active zones was 0.91 in the immunoferritin study and 0.72 in the immunoperoxidase study (control values, 0.12 and 0.02); and (2) 43% of the ferritin particles in the primary cleft were concentrated at the active zones and the rest were scattered randomly (control value, 5.3%). The findings indicate that LEMS IgG binds to the active zones of the presynaptic membrane.

Animals↗