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PubMed2001

[(99m)Tc]MAG(3)-mannosyl-dextran: a receptor-binding radiopharmaceutical for sentinel node detection.

Technetium-99m-labeled benzoyl-mercaptoacetylglycylglycyl-glycine-mannosyl-dextran ([(99m)Tc]MAG(3)-mannosyl-dextran) is a receptor-binding radiotracer that binds to mannose-binding protein, a receptor expressed by recticuloendothelial tissue. This agent is composed of a 10.5-kilodalton molecule of dextran and multiple units of mannose, and benzoyl-mercaptoacetylglycylglycyl-glycine (BzMAG(3)). The tetraflorophenol-activated ester of BzMAG(3) and the imidate of thiomannose were used to covalently attach BzMAG(3) and mannose to an amino-terminated conjugate of dextran. This yielded a 19-kilodalton macromolecule consisting of 3 BzMAG(3) and 21 mannose units per dextran. Dynamic light scattering was used to measure a mean diameter of 5.5 nanometers for BzMAG(3)-mannosyl-dextran and 0.28 microns for filtered Tc-99m sulfur colloid. A preliminary sentinel node detection study employing right fore and hind footpad injections of [(99m)Tc]MAG(3)-mannosyl-dextran and left fore and hind footpad injections of filtered Tc-99m sulfur colloid demonstrated greater sentinel lymph node uptake by the receptor-binding agent.

Animals↗
PubMed1998

Characterization of myelin-associated glycoprotein (MAG) proteolysis in the human central nervous system.

Purified human central nervous system myelin contains an endogenous cysteine protease which degrades the 100-kDa myelin-associated glycoprotein into a slightly smaller 90-kDa derivative called dMAG, and which has been implicated in demyelinating diseases. The native proteolytic site in human MAG was determined in order to characterize this cysteine protease in humans further. This was accomplished by identifying the carboxy-terminus of purified dMAG. The results of these experiments, in conjunction with peptidolysis assays of myelin, demonstrated that the enzyme which proteolyses MAG is extracellular and has cathepsin L-like specificity. Furthermore, it was shown that this cathepsin L-like activity potentially was regulated by the endogenous extracellular inhibitor cystatin C.

Amino Acid Sequence↗
PubMed2002

Characterization of human nerve basal lamina for their binding properties of anti-MAG antibodies.

The functional importance of the basal lamina in Schwann cell development and in adult peripheral nerve fibers is well known. We have demonstrated previously by confocal microscopy that IgM deposits are present on the basal lamina of myelinating Schwann cells of nerve biopsies from patients with an anti-MAG IgM neuropathy. Therefore, the basal lamina was postulated to represent an early target for the uptake of autoantibodies on the surface of myelinated nerve fibers. In this study, the preparation of cell- and myelin-free basal lamina from human peripheral nerves, using a detergent-dependent method is described and characterized by immunohistochemical and biochemical analysis. Using these methods we demonstrated that an enrichment of basal lamina components of Schwann cells with extraction of myelin could be achieved. Western blot analysis and immunohistochemical characterization showed that anti-MAG IgM antibodies did not recognize an epitope on the basal lamina of normal nerves. The established method will allow in situ investigations of basal lamina components from human peripheral nerves in health and in disease, e.g. peripheral neuropathies of infectious or inflammatory origin.

Aged↗
PubMed2000

Native fluorescence and mag-indo-1-protein interaction as tools for probing unfolding and refolding sequences of the bovine serum albumin subdomain in the presence of guanidine hydrochloride.

Changes in the fluorescence spectrum of tryptophans Trp 134 and Trp 212 in bovine serum albumin (BSA) and of Trp 214 of human serum albumin in the presence of the chaotropic agent guanidine hydrochloride (Gnd) were studied. A detailed analysis of the fluorescence spectrum of native BSA yielded the fluorescence spectrum for each tryptophan of BSA. Modifications in the binding of Mag-indo-1 to BSA, which results in a specific quenching of the fluorescence spectrum of Trp 134 associated with an energy transfer from Trp 134 to the protein-bound Mag-indo-1, were also investigated. Changes occurring when the Gnd concentration is decreased stepwise cover a larger concentration scale of Gnd than the reverse protocol, allowing one to suggest that the resulting conformational changes in the subdomain IA of BSA involve at least three different steps.

Animals↗
PubMed2004

The SOGS-RA vs. the MAGS-7: prevalence estimates and classification congruence.

The purpose of this study was to compare the prevalence rate estimates and congruence in classification status derived from two popular measures of adolescent gambling (SOGS-RA and MAGS-7). Adolescents from three states (Alabama, Mississippi, and Oregon) completed an anonymous questionnaire ( n =1846 high school students total). Results indicate that the prevalence of probable adolescent pathological gambling varied both as a function of instrument and cut-off point utilized for classification (range 1.7%-8.2%). Classification groups (non-problem, at-risk, and problem gamblers) generated by both instruments were found to be associated with reports of gambling frequency, amount of money lost in one gambling occasion, and parental gambling problems. However, concern was raised because the MAGS-7 and the SOGS-RA had little congruence in their three-group classification decisions for specific individuals (e.g., only 20.5% agreement for problem gamblers). To improve clinical utility, an empirical case was made for using the SOGS-RA to generate a fourth group of adolescent gamblers, which we labeled "probable pathological gamblers" (SOGS-RA > or = 6). This group was differentiated from the remaining gambling groups on all the validity indices. The implications and limitations of these findings, as well as future directions, are discussed.

Adolescent↗
PubMed1995

Intrasynaptosomal free Mg2+ concentration measured with the fluorescent indicator mag-fura-2: modulation by Na+ gradient and by extrasynaptosomal ATP.

Synaptosomes can be loaded with mag-fura-2 without significant perturbation of their ATP content by incubation for 10 min at 37 degrees C with 10 microM mag-fura-2 acetoxymethyl ester in Hanks'-HEPES buffer (pH 7.45). The intrasynaptosomal free Mg2+ concentration ([Mg2+]i) was found to be dependent on external Mg2+ concentration, increasing from 0.8 to 1.25 mM when the concentration of Mg2+ in the incubation medium increased from 1 to 8 mM. Dissipation of the Na+ gradient across the plasma membrane of synaptosomes by treatment with the Na+ ionophore monensin (0.2 mM) or with veratridine (0.2 mM) and ouabain (0.6 mM) produced a moderate increase of [Mg2+]i, from 1.0 to 1.2-1.3 mM in an incubation medium containing 5 mM Mg2+. Plasma membrane depolarization by incubation of synaptosomes in a medium containing 68 mM KCl and 68 mM NaCl had no effect on [Mg2+]i. Reversal of the Na+ gradient by incubation of synaptosomes in a medium in which external Na+ was replaced by choline increased [Mg2+]i up to 1.6 and 2.2 mM for extrasynaptosomal Mg2+ concentrations of 1 and 8 mM, respectively. We conclude that a Na+/Mg2+ exchange operates in the plasma membrane of synaptosomes. In the presence of Mg2+ in the incubation medium, extrasynaptosomal ATP, but not ADP or adenosine, increased [Mg2+]i from 1.1 +/- 0.1 up to 1.6 +/- 0.1 mM. The nonhydrolyzable ATP analogue adenosine 5'-(beta gamma-imido)triphosphate antagonized the effect of ATP, but had no effect by itself on [Mg2+]i. It is concluded that Mg2+ transport across the plasma membrane of synaptosomes is modulated by the activity of an ecto-ATPase or an ecto-protein kinase.

Adenosine Triphosphate↗
PubMed2003

Degraded myelin-associated glycoprotein (dMAG) formation from pure human brain myelin-associated glycoprotein (MAG) is not mediated by calpain or cathepsin L-like activities.

The myelin-associated glycoprotein (MAG) is a transmembrane cell adhesion molecule participating in myelin formation and maintenance. Calcium-activated/-dependent proteolysis of myelin-associated glycoprotein by calpain and cathepsin L-like activities has already been detected in purified myelin fractions, producing a soluble fragment, called degraded (d)MAG, characterized by the loss of the transmembrane and cytoplasmic domains. Here, we demonstrate and analyze dMAG formation from pure human brain myelin-associated glycoprotein. The activity never exhibited the high rate previously reported in human myelin fractions. Degradation is time-, temperature-, buffer- and structure-dependent, is inhibited at 4 degrees C and by denaturation of the sample, and is mediated by a trans-acting factor. There is no strict pH dependency of the proteolysis. Degradation was inhibited by excess aprotinin, but not by 1-10 micro g/mL aprotinin and was not eliminated by the use of an aprotinin-sepharose matrix during the purification. dMAG formation was not enhanced by calcium, nor inhibited by a wide variety of protease inhibitors, including specific calpain and cathepsin L inhibitors. Therefore, while cysteine proteases may be present in human myelin membrane fractions, they are not involved in dMAG formation from highly purified human brain myelin-associated glycoprotein preparations.

Aged↗
PubMed2001

Focal myelin swellings and tomacula in anti-MAG IgM paraproteinaemic neuropathy: novel teased nerve fiber studies.

Focal myelin swellings and tomacula in teased nerve fibers from a case of IgM anti-myelin-associated glycoprotein (MAG) paraproteinaemic neuropathy were examined using a novel technique. Five different morphologic abnormalities were identified--myelin sheath outfolding, myelin sheath infolding, enlargement of the adaxonal space, myelin degeneration, multiple increased concentric loops--and a combination of these structural abnormalities often occur in association with myelin degeneration. Similar structural changes were found in externally normal segments of teased fibers without evidence of myelin swelling or tomacula from the same case. These structural abnormalities are consistent with a disturbance of the normal adhesion functions of MAG in the maintenance of axon-myelin relationships.

Aged↗
PubMed2000

Ionic selectivity of low-affinity ratiometric calcium indicators: mag-Fura-2, Fura-2FF and BTC.

Accurate measurement of elevated intracellular calcium levels requires indicators with low calcium affinity and high selectivity. We examined fluorescence spectral properties and ionic specificity of three low-affinity, ratiometric indicators structurally related to Fura-2: mag-Fura-2 (furaptra), Fura-2FF, and BTC. The indicators differed in respect to their excitation wavelengths, affinity for Ca2+ (Kd approximately 20 microM, 6 microM and 12 microM respectively) and selectivity over Mg2+ (Kd approximately 2 mM for mag-Fura-2, > 10 mM for Fura-2FF and BTC). Among the tested indicators, BTC was limited by a modest dynamic range upon Ca2+ binding, susceptibility to photodamage, and sensitivity to alterations in pH. All three indicators bound other metal ions including Zn2+, Cd2+ and Gd3+. Interestingly, only in the case of BTC were spectral differences apparent between Ca2+ and other metal ions. For example, the presence of Zn2+ increased BTC fluorescence 6-fold at the Ca2+ isosbestic point, suggesting that this dye may be used as a fluorescent Zn2+ indicator. Fura-2FF has high specificity, wide dynamic range, and low pH sensitivity, and is an optimal low-affinity Ca2+ indicator for most imaging applications. BTC may be useful if experimental conditions require visible wavelength excitation or sensitivity to other metal ions including Zn2+.

Animals↗
PubMed1993

Technique for in situ measurement of calcium in intracellular inositol 1,4,5-trisphosphate-sensitive stores using the fluorescent indicator mag-fura-2.

Stimulation of cells with calcium-mobilizing agonists frequently results in inositol 1,4,5-trisphosphate (InsP3)-mediated discharge of Ca from an internal store. We report here a technique for directly monitoring Ca within this and other stores in gastric epithelial cells. This technique takes advantage of the propensity of the acetoxymethyl ester derivative of the fluorescent dye mag-fura-2 (which is sensitive to Ca concentrations above 5 microM) to accumulate in subcellular compartments where it can report changes in the free Ca concentration. Intact dye-loaded cells responded to cholinergic stimulation with a decrease in the 350 nm/385 nm excitation ratio, as measured in individual cells with a digital imaging microscope, consistent with reduced Ca concentration in one or more cellular compartments. When cells were permeabilized with digitonin and incubated in an "intracellular buffer," the cytoplasmic dye was released, leaving the mag-fura-2 in the internal store. InsP3 caused the ratio from the trapped indicator to decrease (i.e., Ca was released) in a dose-dependent manner, and this effect was blocked by the InsP3 receptor antagonist heparin. Ca sequestration into the internal store was ATP-dependent, and reuptake into the InsP3-sensitive pool was blocked by thapsigargin, a specific inhibitor of the Ca-ATPase of the internal store. We used this technique to investigate the role of Cl on the release and reloading of the InsP3-sensitive internal store and found that Ca uptake was reduced in Cl-free solutions, suggesting an important function for Cl in the refilling of this pool.

Animals↗
PubMed1992

Wounds caused by contact with muzzle-lift relief ports (Mag-Na-Port).

Fan-shaped stippled burns were produced on the skin when a revolver whose barrel had been modified by the Mag-Na-Port process was fired twice with the side of the muzzle in contact. A grazing wound was produced by one bullet, and an oblique entry was produced by the other. The characteristics of Mag-Na-Port wounds and test shots are described, and these are compared with test shots from two other higher power revolvers.

Firearms↗
PubMed1991

A new approach in radionuclide imaging to ureteric peristalsis using 99Tcm-MAG 3 and condensed images.

A new method for the evaluation of ureteric peristalsis is described. Standard, dynamic renal scintigraphy was carried out using 99Tcm-MAG 3 in 59 patients. Time-activity curves and condensed images over the ureter area were created simultaneously. A six-grade scale (O-V) was chosen for the classification of ureteral function. The results obtained were compared with parameters of renographic curves and other clinical findings. In a group of 13 patients, two different renal radiopharmaceuticals were used: 131I-OIH and 99Tcm-DTPA. The results show that the new method is suitable for the assessment of ureteral disorders, and has some advantages compared with previously described methods. 99Tcm-MAG 3, with a better target-to-background ratio compared to 131I-OIH and 99Tcm-DTPA, is the most suitable radiopharmaceutical for this purpose.

Adult↗
PubMed1998

Intracellular Mg2+ regulation in voltage-clamped Helix aspersa neurones measured with mag-fura-2 and Mg(2+)-sensitive microelectrodes.

The extrusion mechanism for intracellular Mg2+ was investigated in voltage-clamped snail neurones using Mg(2+)-sensitive microelectrodes and mag-fura-2. The intracellular free magnesium ion concentration ([Mg2+]1) of snail neurones voltage clamped to -60 mV was estimated to be 0.57 +/- 0.06 mM (mean +/- S.E.M.; n = 12) using Mg(2+)-sensitive microelectrodes and 0.62 +/- 0.05 mM (n = 15) using mag-fura-2. Raising extracellular MgCl2 from 5 to 20 mM caused an average increase in [Mg2+]1 of 0.25 +/- 0.04 mM (n = 7). In three experiments, removing extracellular Mg Cl2 caused an average decrease in [Mg2+]1 of 0.1 mM. Replacing extracellular Na+ with N-methyl-D-glucamine (NMDG) caused a rise in [Mg2+]1 of 1.8 +/- 0.5 mM (n = 7); [Mg2+]1 recovered to resting levels when extracellular Na+ was restored. Iontophoretic injections of MgCl2 were used to raise [Mg2+]1. The rate of recovery from such increases in [Mg2+]1 ¿calculated from the slope of the recovery was inhibited by 85-100% (n = 5) in the absence of extracellular Na2+ compared with control conditions. Raising extracellular Ca2+ from 7 to 35 mM caused a reversible rise in [Mg 2+]1 of 0.4 +/- 0.05 mM (mean +/- S.E.M., n = 7). It was concluded that in snail neurones the main mechanism for [Mg2+]1 extrusion is a Na(+)-Mg2+ exchanger which may be partially inhibited be high extracellular Ca2+ concentrations.

Animals↗
PubMed2003

The MPN mag: introducing a critical area mediating pheromonal and hormonal regulation of male sexual behavior.

Mating behavior in male hamsters is regulated by a chemosensory pathway that converges on the bed nucleus of the stria terminalis (BST) and the medial nucleus of the amygdala (Me). Both the BST and the Me project to the lateral part of the medial preoptic area. Lesion studies have identified a small group of large cells referred to as the magnocellular medial preoptic nucleus (MPN mag) whose integrity is required for normal mating behavior. Our data, summarized within, indicate that the MPN mag is a sexually differentiated nucleus in a large steroid-responsive network that relays pheromonal signals from the sensory systems to the motor areas to affect behavior.

Animals↗
PubMed2006

High-dose rituximab and anti-MAG-associated polyneuropathy.

Rituximab has been administered successfully in patients with polyneuropathy associated with antibodies to myelin-associated glycoprotein (anti-MAG). The authors present a follow-up study with high-dose rituximab. Increase of rituximab from 375 mg/m2 to a dose of 750 mg/m2 was well tolerated and led to clinical improvement in four of eight patients, along with improvement of nerve conduction velocities and a reduction of anti-MAG antibody titers.

Aged↗
PubMed1987

Experimental demyelination of nerve induced by serum of patients with neuropathy and an anti-MAG IgM M-protein.

Demyelination of feline sciatic nerve was induced by intraneural injection of serum from three patients with neuropathy and an IgM M-protein that reacted with myelin-associated glycoprotein (MAG). Demyelination exceeded that induced by serum from 18 other individuals, including six IgM M-proteins unreactive with MAG. The myelinolytic effect required active human complement and was abolished by exposure of serum to homogenate of human peripheral nerve that removed 90% of the M-protein. Immunofluorescence studies demonstrated deposition of the injected M-protein and complement on the surface of myelin sheaths, implying that the M-protein reacted with epitopes of myelin exposed to the extracellular space.

Animals↗
PubMed1986

Chronic T cell leukemia with a NK phenotype reacting with anti-myelin-associated glycoprotein (MAG) mouse monoclonal antibody.

We describe a patient demonstrating chronic T cell leukemia with a natural killer (NK) phenotype. The leukemic cells could be stained by OKT 3 (T cells), anti-Leu-7 and anti-myelin-associated glycoprotein (MAG) (NK cells) but not anti-Leu-11 monoclonal mouse antibody (activated NK cells). Fresh mononuclear cells showed a very low NK activity, although this activity returned to normal levels after 18 days incubation with interleukin-2 and some stimulants. It was not known why the NK activity of fresh mononuclear cells was low. This report is the first on leukemia characterized by anti-MAG monoclonal antibody.

Antibodies, Monoclonal↗
PubMed2002

[Level of total and ionized magnesium fraction based on biochemical analysis of blood and hair and effect of supplemented magnesium (Slow Mag B6) on selected parameters in hypertension of patients treated with various groups of drugs].

The aim of this work was to determine the concentration of total and ionized magnesium in hair and blood of patients with primary hypertension and the influence of oral magnesium supplementation (Slow-Mag B6) on clinical parameters and blood pressure values. 92 patients were recruited from the Family Care Unit, Pomeranian Academy of Medicine in Szczecin. Each patient was treated during at least 6 months preceding the study with a single antihypertensive agent from one of the following groups: ACE inhibitors, beta-receptor inhibitors, Ca channel blockers, diuretics. The control group included patients with hypertension not treated pharmacologically. Changes in ionized magnesium concentration before and after oral magnesium supplementation were studied in relation to total cholesterol, triglycerides, and other parameters of importance in hypertension. Significantly lower total magnesium concentrations were demonstrated in hair of patients receiving ACE inhibitors and diuretics in comparison to controls. Ionized magnesium concentrations in serum of hypertensive patients were significantly reduced as compared with controls. A highly significant increase in these levels was noted after magnesium supplementation. Blood pressure values after magnesium supplementation were reduced in the study group by an average of 15-20 mmHg for systolic and 5-9 mmHg for diastolic blood pressure. Correlations between ionized magnesium and triglyceride concentrations in patients treated with Ca channel blockers before oral Mg supplementation were found. Patients treated with diuretics demonstrated correlations between total magnesium and total cholesterol concentrations. Following oral magnesium supplementation with Slow-Mag B6 at 320 mg/day, the frequency of complaints reported by patients, including irregular heart beat, pricking heart pain, nervousness, sleep disorders, irritability/tearfulness was reduced. There was no effect on other complaints, such as mental and physical fatigue, constipation/diarrhea, and anxiety.

Administration, Oral↗