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PubMed2001

Neuropathy and IgM M-proteins: prognostic value of antibodies to MAG, SGPG, and sulfatide.

BACKGROUND: In polyneuropathy associated with immunoglobulin M (IgM) monoclonal gammopathy, antibodies to myelin-associated glycoprotein (MAG), sulfoglucuronyl paragloboside (SGPG), and sulfatide have been associated with specific clinical and electrophysiologic features. However, it is not known whether the results of antibody tests provide additional information for the individual patient (and the neurologist) in terms of future neurologic deficit or outcome. OBJECTIVE: To study the independent contribution of potential prognostic factors to the prediction of outcome of neuropathy associated with IgM monoclonal gammopathy. METHODS: In accordance with the chronology in which prognostic factors are available in clinical practice, the association between prognostic factors and outcome was evaluated by univariate and multivariate logistic regression analysis in 65 patients with polyneuropathy and IgM monoclonal gammopathy. RESULTS: In univariate analysis, the initial symptoms, the IgM light chain type, electrophysiologic and pathologic studies, the presence of sural nerve IgM deposition, and anti-MAG or anti-SGPG antibodies were significantly associated with outcome. However, multivariate analysis showed that only initial symptoms and electrophysiologic studies are independent prognostic factors: initial sensory symptoms of the feet are prognostic for a slowly progressive disease course and less disability at 4 years, and evidence for demyelination on electrophysiologic examination is prognostic for development of weakness and symptoms of the upper extremities at 4 years. Addition of anti-MAG or anti-SGPG antibody tests did not yield any additional prediction of outcome. CONCLUSION: These results indicate that in clinical practice, antibody tests in polyneuropathy associated with IgM monoclonal gammopathy do not have a prognostic value in terms of future neurologic deficit or outcome.

Globosides↗
PubMedDate not supplied

Myelin modifications in 8 cases of peripheral neuropathy with Waldenström's macroglobulinemia and anti-MAG activity.

Characteristic myelin modifications in patients with IgM monoclonal gammopathy and anti-MAG activity have mainly been studied in cases of undetermined significance, but also exist in cases with indolent Waldenström's macroglobulinemia, i.e., when lymphoplasmocytic infiltration in bone marrow is 15% or more, without any visceral involvement. Since 1983, the authors have examined nerve biopsies from 8 cases with Waldenström's macroglobulinelia by direct immunofluorescence examination on frozen sections and ultrastructural examination. At direct immunofluorescence, fixation of anti-IgM serum on myelinated fibers was present in 7 cases. At ultrastructural examination, a widening of some myelin lamellae at the periphery of a few fibers was visible in 8 cases. A few fibers with hypermyelination were present in 5 cases. In 2 of these 5 cases widening of some myelin lamellae was present in numerous fibers, 88% in one of them. Frequently, there was a major widening of some myelin lamellae with dilated lamellae present in the inner part of the myelin sheath. Certain lamellae were more dilated, up to 50 nm. Occasionally, enlarged lamellae were not compacted with each other. The authors also examined nerve biopsies from 36 patients with IgM monoclonal gammopathy of undetermined significance and anti-MAG activity, but found only one case with major widening of some myelin lamellae. Five other cases with major widening of some myelin lamellae, 4 Waldenström's macroglobulinemia and 1 IgM monoclonal gammopathy of undetermined significance, have been reported. Given that demyelinating neuropathies are far more numerous in cases with IgM monoclonal gammopathy of undetermined significance, it is likely that cases of indolent Waldenström's macroglobulinemia are prone to develop major myelin modifications, possibly due to another mechanism, added to the classic anti-MAG activity.

Aged↗
PubMed1997

Sodium channel distribution in axons of hypomyelinated and MAG null mutant mice.

Na+ channel organization was studied with immunofluorescence in the peripheral nervous system of mice genetically altered to produce abnormal myelin. In two of these strains, transcription of inserted transgenes was targeted to myelinating Schwann cells through linkage to a promoter for the myelin protein P0. Adults of both of these strains had hindlimb paralysis and a tremor on lifting by the tail. In one case, Schwann cells were eliminated via expression of the diphtheria toxin A chain (DT-A). During postnatal days 3-7, Na+ channel clustering at forming nodes was dramatically reduced compared with that of normal animals. At 1-3 months of age, Na+ channel immunofluorescence was often found spread over long stretches of the axolemma, instead of being confined to nodal gaps. In the second P0-linked transgenic model, Schwann cell expression of the large T antigen tsA-1609 resulted in cell cycle dysfunction. Adult axons had regions of diffuse Na+ channel labeling. Focal clusters were rare within these zones, which were characterized by a series of cells of myelinating phenotype tightly apposed to the axon. Previous studies suggested that Schwann cells had to reach the stage of ensheathment characterized by periaxonal myelin associated glycoprotein (MAG) expression in order to induce Na+ channel clustering. However, in MAG-deficient mice, Na+ channel labeling patterns within sciatic nerves were normal.

Aging↗
PubMed2001

Fluorescent detection of cyanobacterial DNA using bacterial magnetic particles on a MAG-microarray.

Bacterial magnetic particles (BMPs) were used for the identification of cyanobacterial DNA. Genus-specific oligonucleotide probes for the detection of Anabaena spp., Microcystis spp., Nostoc spp., Oscillatoria spp., and Synechococcus spp. were designed from the variable region of the cyanobacterial 16S rDNA of 148 strains. These oligonucleotide probes were immobilized on BMPs via streptavidin-biotin conjugation and employed for magnetic-capture hybridization against digoxigenin-labeled cyanobacterial 16S rDNA. Bacterial magnetic particles were magnetically concentrated, spotted in 100-microm-size microwell on MAG-microarray, and the fluorescent detection was performed. This work details the development of an automated technique for the magnetic isolation, the concentration of hybridized DNA, and the detection of specific target DNA on MAG-microarray. The entire process of hybridization and detection was automatically performed using a magnetic-separation robot and all five cyanobacterial genera were successfully discriminated.

Base Sequence↗
PubMed1992

Vasculitic neuropathy in a patient with cryoglobulinemia and anti-MAG IGM monoclonal gammopathy.

A patient with sensorimotor mononeuritis multiplex had a type II cryoglobulin with an IgM kappa M-protein that appeared to contain monoclonal anti-MAG antibodies of the same isotype. A sural nerve biopsy demonstrated necrotizing arteritis and features of both axonal degeneration and demyelination. IgM kappa and C3 deposits were present on the myelin sheath of some residual nerve fibers. The findings suggest that the anti-MAG antibodies contributed to the myelin damage, while cryoprecipitates may have caused the vasculitis and axonal degeneration.

Aged↗
PubMed1995

Sialoadhesin (Sn) maps to mouse chromosome 2 and human chromosome 20 and is not linked to the other members of the sialoadhesin family, CD22, MAG, and CD33.

Sialoadhesin is a cell-cell interaction molecule expressed by subpopulations of tissue macrophages. It contains 17 immunoglobulin (Ig)-like domains and is structurally related to CD22, MAG, and CD33. These molecules establish a distinct family of sialic acid-dependent adhesion molecules, the sialoadhesin family. We have mapped the rodent sialoadhesin gene, Sn, to chromosome 2F-H1 by in situ hybridization (ISH) and shown linkage to Il1b and four other markers by backcross linkage analysis. We have also used ISH and a human-mouse somatic cell hybrid panel to localize the human sialoadhesin gene, SN, to the conserved syntenic region on human chromosome 20p13. This demonstrates that the sialoadhesin gene is not linked to the other members of the Sialoadhesin family, CD22, MAG, and CD33, which have been independently mapped to the distal region of mouse chromosome 7 and to human chromosome 19q13.1-3.

Animals↗
PubMed1993

Measurement of free Zn2+ ion concentration with the fluorescent probe mag-fura-2 (furaptra).

The fluorescent probe mag-fura-2, previously used to measure [Mg2+], can also be used to measure [Zn2+]. The peak in the excitation spectrum occurs at 323 nm for Zn2+, compared with 335 nm for Ca2+ and Mg2+. This allows simultaneous measurements of [Zn2+] and either [Ca2+] or [Mg2+], by using 3 excitation wavelengths. The dissociation constant for Zn2+ is 20 nM at pH 7.0-7.8, ionic strength 0.15 and 37 degrees C. This allows [Zn2+] to be measured in the range from 0.5 nM to 1 microM. Mag-fura-2 was used to measure [Zn2+] in Zn2+/albumin and Zn2+/histidine mixtures in a physiological buffer at 37 degrees C and pH 7.4. The data obtained enable one to formulate Zn(2+)-buffers for the 1 to 100 nM Zn2+ range.

Animals↗
PubMed1986

Failure to detect anti-MAG antibodies by RIA in CSF of patients with multiple sclerosis.

Using a sensitive double-antibody radioimmunoassay (RIA) we measured IgG antibodies to the myelin-associated glycoprotein (MAG) in cerebrospinal fluid (CSF) of patients with active multiple sclerosis (MS) and with other neurological diseases (OND). Comparable levels of precipitation of radiolabeled MAG were obtained with CSF from the patients of the two groups.

Animals↗
PubMed1988

NK cells in patients with peripheral neuropathy and IgM monoclonal protein reacting with the myelin-associated glycoprotein (MAG).

We studied Leu 7+ cell distribution and natural killer (NK) activity in the peripheral blood of six patients who had peripheral neuropathy and monoclonal IgM protein directed against myelin-associated glycoprotein (anti-MAG IgM). We did not find any difference between patients and control subjects (healthy or polyneuropathic, some with IgM monoclonal paraprotein but without anti-MAG activity). The presence of autologous sera did not interfere with these results. We noted an increase in Leu 11+ cell percentages after pre-incubation of the patient cells with autologous sera but the phenotypes of cells from control subjects did not change after incubation with autologous or patient sera.

Aged↗
PubMed1994

Somatically mutated member of the human V lambda VIII gene family encodes anti-myelin-associated glycoprotein (MAG) activity.

A highly conserved small family of human V lambda genes was identified by DNA homology to a V lambda gene isolated from a patient with demyelinating peripheral neuropathy, and which encodes an autoantibody with anti-MAG activity. Comparison of the genes indicates that the patient V lambda gene was derived from one of the germline genes. Together with published analyses of other anti-MAG IgM antibodies, which also appear to be mutated in comparison to known germline V genes, these results suggest that development of these pathogenic antibodies may reflect an antigen-driven, T cell-dependent process.

Autoantibodies↗
PubMed1993

Clearance and distribution parameters of 99mTc-EHIDA, -DTPA and -MAG-3 by dynamic liver/kidney scintigraphy.

The radiopharmaceuticals (RF) EHIDA, DTPA and MAG-3 (labeled by 99mTc), commonly used in dynamic liver/kidney scintigraphy, are distributed in intravascular (i.v.) and extravascular (e.v.) spaces, as they are simultaneously cleared from the blood passing through their target organ (liver/kidney). The drop in concentration of these RF in blood is therefore determined by distribution as well as by clearance up to the time of equilibrium. From that time only the rate of decrease of RF in blood expresses the "true" (liver/kidney) clearance and this clearance parameter is a clinically reliable index of the function of the target organ. (A) The method of analysis of the clearance curve obtained from the heart region has been reported; the method is based on a physiological approach with respect to the distribution processes of the RF in the organism. Apart from the main important parameter, T (clear) (half-time of the "pure" clearance of the resp. RF from its distribution space), two further parameters are obtained: T (distr.) (half-time of the e.v. distribution of the RF) and END (distr.) (end of this distribution). (B) The results of 218 patients examined using 99mTc-EHIDA, 192 using DTPA and 65 using MAG-3 have been statistically processed. The mutual correlation of all parameters [T (distr.), END (distr.), T (clear)] within each group of patients as well as the differences of corresponding parameters between the groups of patients are studied. The main purpose of the work was to obtain the reliable clearance parameters of the RF with extravascular distribution for routine clinical practice.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed2004

Fluorescence measurements of free [Mg2+] by use of mag-fura 2 in Salmonella enterica.

The Mg2+ fluorescent dye mag-fura 2, entrapped in cells or organelles, has frequently been used for dual excitation ratio-metric determinations of free ionic Mg2+ concentrations in eukaryotic, mostly mammalian cells. Here we report its successful application to measure free Mg2+ concentrations ([Mg2+]i) in Salmonella enterica cells. When kept in nominally Mg2+ free buffer (resting conditions), the [Mg2+]i of wild-type cells has been determined to be 0.9 mM. An increase in the external Mg2+ concentration ([Mg2+]e) resulted in a rapid increase of [Mg2+]i, saturating within a few seconds at about 1.5 mM with [Mg2+]e of 20 mM. In contrast, cells lacking the Mg2+ transport proteins CorA, MgtA, MgtB failed to show this rapid increase. Instead, their [Mg2+]i increased steadily over extended periods of time and saturated at concentrations below those of wild-type cells. Mg2+ uptake rates increased more than 15-fold when corA was overexpressed in these mutant cells. Uptake of Mg2+ into corA expressing cells was strongly stimulated by nigericin, which increased the membrane potential DeltaPsi at the expense of DeltapH, and drastically reduced by valinomycin, which decreased the membrane potential DeltaPsi. These results reveal mag-fura 2 as a useful indicator to measure steady-state [Mg2+]i values in resting bacterial cells and to determine Mg2+ uptake rates. They confirm the role of CorA as the major Mg2+ transport protein and reveal the membrane potential as driving force for Mg2+ uptake into S. enterica cells.

Adenosine Triphosphatases↗
PubMed2005

MAG induces regulated intramembrane proteolysis of the p75 neurotrophin receptor to inhibit neurite outgrowth.

The three known inhibitors of axonal regeneration present in myelin--MAG, Nogo, and OMgp--all interact with the same receptor complex to effect inhibition via protein kinase C (PKC)-dependent activation of the small GTPase Rho. The transducing component of this receptor complex is the p75 neurotrophin receptor. Here we show that MAG binding to cerebellar neurons induces alpha- and then gamma-secretase proteolytic cleavage of p75, in a protein kinase C-dependent manner, and that this cleavage is necessary for both activation of Rho and inhibition of neurite outgrowth.

Amyloid Precursor Protein Secretases↗
PubMed1998

Measurements of intracellular Mg2+ concentration in mouse skeletal muscle fibers with the fluorescent indicator mag-indo-1.

Measurements of intracellular free magnesium concentration ([Mg2+]i) were performed on enzymatically isolated skeletal muscle fibers from mice, using the fluorescent ratiometric indicator mag-indo-1. An original procedure was developed to calibrate the dye response within the fibers: fibers were first permeabilized with saponin in the presence of a given extracellular magnesium concentration and were then embedded in silicone grease. The dye was then pressure microinjected into the saponin-permeabilized silicone-embedded fibers, and fluorescence was measured. The results show that for all tested [Mg2+], the value of the measured fluorescence ratio was higher than that found in aqueous solutions. Furthermore, the apparent binding curve that could be fit to the in vivo ratio data was shifted toward higher [Mg2+] by a factor of approximately 2. Using the in vivo calibration parameters, the mean resting [Mg2+]i was found to be 1.53 +/- 0.16 mM (n = 7). In an attempt to gain insight into the myoplasmic magnesium buffering capacity, we measured, together with mag-indo-1 fluorescence, the current elicited by the application of carbamylcholine (CCh) to the endplate of isolated fibers, in the presence of a high extracellular magnesium concentration. The results show that, under these conditions, a change in [Mg2+]i displaying a time course and amplitude qualitatively consistent with the CCh-induced inward current can be measured.

Animals↗
PubMed2003

Systematic synthesis and MAG-binding activity of novel sulfated GM1b analogues as mimics of Chol-1 (alpha-series) gangliosides: highly active ligands for neural siglecs.

Systematic synthesis and myelin-associated glycoprotein (MAG)-binding activity of novel sulfated GM1b analogues structurally related to Chol-1 (alpha-series) gangliosides, high-affinity ligands for neural siglecs, are described. The suitably protected gangliotriose derivatives, 2-(trimethylsilyl)ethyl 2-acetamido-2-deoxy-6-O-levulinoyl-beta-D-galactopyranosyl-(1-->4)-2,3,6-tri-O-benzyl-beta-D-galactopyranosyl-(1-->4)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside and 2-(trimethylsilyl)ethyl 2-acetamido-2-deoxy-6-O-levulinoyl-beta-D-galactopyranosyl-(1-->4)-2,6-di-O-benzyl-3-O-levulinoyl-beta-D-galactopyranosyl-(1-->4)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside were each glycosylated with alpha-NeuAc-(2-->3)-galactose donor to give the corresponding pentasaccharides in 94% (beta1,3 glycoside only) and 90% (beta1,3:beta1,4 = 2:1), respectively. After proper manipulation of the protecting groups, the pentasaccharides were converted into three novel sulfated GM1b gangliosides by the successive introduction of the ceramide and sulfo groups, followed by complete deprotection. Among the synthetic gangliosides, GSC-338 (II3III6-disulfate of iso-GM1b) was surprisingly found to be the most potent MAG binding structure tested to date.

Animals↗
PubMed1999

Ganglioside GD1 alpha analogues as high-affinity ligands for myelin-associated glycoprotein (MAG).

The first systematic synthesis of ganglioside GD1 alpha analogues carrying N-acetyldeoxyneuraminic acids linked to C-6 of the GalNAc residue was accomplished. The suitably protected GM1b pentasaccharide derivative was regioselectively glycosylated with the phenyl 2-thioglycosides of 7-deoxy, 8-deoxy, and 9-deoxy-N-acetylneuraminic acid promoted by N-iodosuccinimide (NIS)-trifluoromethanesulfonic acid (TfOH) in acetonitrile, and the resulting hexasaccharides were converted to the target GD1 alpha analogues. All of the analogues retained excellent efficiency in supporting the adhesion to myelin-associated glycoprotein (MAG), raising the possibility that the internal sialic acid linked to the GalNAc residue may be replaced by other anionic substituents, in contrast to the terminal sialic acid, which is essential for MAG binding.

Animals↗
PubMed1996

High cytoplasmic Ca2+ levels reached during Ca(2+)-induced Ca2+ release in single smooth muscle cell as reported by a low affinity Ca2+ indicator Mag-Indo-1.

The low-affinity Ca2+ indicator Mag-Indo-1 was used to measure increments of ionised Ca2+ concentration in the cytoplasm of single smooth muscle cells isolated from guinea-pig urinary bladder. With 3.6 mM [Ca2+]o, depolarization steps to 0 mV were associated with a transient increase of fluorescence ratio (F410/F470) only when Ica triggered a Ca(2+)-induced Ca2+ release (CICR). [Ca2+]i transiently peaked to 3-5 microM and despite continuous Ca2+ influx the [Ca2+]i signal fell close to the baseline. Rapidly applied caffeine (10 mM) increased [Ca2+]l by 16 microM, the response was completely blocked by intracellular ryanodine (20 microM). With ryanodine intracellularly, Ica produced very small [Ca2+]i signals unless it was augmented by elevation of [Ca2+]0 to 10 mM and addition of 1 microM Bay K8644. Under these conditions, [Ca2+]l responded with a tonic elevation lasting as long as the depolarizing pulse. It is concluded that the low-affinity indicator Mag-Indo-1 reports predominantly Ca2+ release from SR in cytoplasm.

Animals↗
PubMed1999

Prior exposure to neurotrophins blocks inhibition of axonal regeneration by MAG and myelin via a cAMP-dependent mechanism.

MAG is a potent inhibitor of axonal regeneration. Here, inhibition by MAG, and myelin in general, is blocked if neurons are exposed to neurotrophins before encountering the inhibitor; priming cerebellar neurons with BDNF or GDNF, but not NGF, or priming DRG neurons with any of these neurotrophins blocks inhibition by MAG/myelin. Dibutyryl cAMP also overcomes inhibition by MAG/myelin, and cAMP is elevated by neurotrophins. A PKA inhibitor present during priming abrogates the block of inhibition. Finally, if neurons are exposed to MAG/myelin and neurotrophins simultaneously, but with the Gi protein inhibitor, inhibition is blocked. We suggest that priming neurons with particular neurotrophins elevates cAMP and activates PKA, which blocks subsequent inhibition of regeneration and that priming is required because MAG/myelin activates a Gi protein, which blocks increases in cAMP. This is important for encouraging axons to regrow in vivo.

Animals↗