Progressive myoclonus epilepsy with polyglucosans (Lafora disease): evidence for a third locus.

Lafora disease (LD) is the most common teenage-onset progressive myoclonus epilepsy. It is caused by recessive mutations in the EPM2A or EPM2B genes. The authors describe a family with three affected members with no mutations in either gene. Linkage and haplotype analyses exclude both loci from causative involvement in this family. Therefore, a third LD locus is predicted. Its identification will be a crucial element in the understanding of the biochemical pathway underlying the generation of Lafora bodies and LD.

Genetic mapping of a new Lafora progressive myoclonus epilepsy locus (EPM2B) on 6p22.

BACKGROUND: Lafora disease is a progressive myoclonus epilepsy with polyglucosan accumulations and a peculiar neurodegeneration with generalised organellar disintegration. It causes severe seizures, leading to dementia and eventually death in early adulthood. METHODS: One Lafora disease gene, EPM2A, has been identified on chromosome 6q24. Locus heterogeneity led us to search for a second gene using a genome wide linkage scan in French-Canadian families. RESULTS: We mapped a second Lafora disease locus, EPM2B, to a 2.2 Mb region at 6p22, a region known to code for several proteins, including kinesins. Kinesins are microtubule dependent motor proteins that are involved in transporting cellular components. In neurones, they play a major role in axonal and dendritic transport. CONCLUSION: Analysis of the present locus in other non-EPM2A families will reveal whether there is further locus heterogeneity. Identification of the disease gene will be of major importance towards our understanding of the pathogenesis of Lafora disease.

Tissue-specific regulatory elements in the human alcohol dehydrogenase 6 gene.

The human alcohol dehydrogenase gene ADH6 is expressed at the highest levels in fetal and adult liver. We have mapped cis-acting elements that affect its expression. The sequence from bp -34 to -62 (site C) that includes the TATA box was strongly bound by nuclear proteins from liver, hepatoma cells, and fibroblasts. A truncation that removed the upstream part of site C but left the TATA homology intact dramatically reduced transcription; altering 5 bp in this region had much less effect. Part of site C can be bound by C/EBPalpha, but cotransfection with C/EBPalpha or C/EBPbeta did not stimulate transcription. The proximal region did not display tissue specificity, so we cloned the upstream region to search for additional regulatory sequences. The region between -1.6 and -2.3 kb stimulated transcription in hepatoma cells and inhibited it in fibroblasts. We identified two sites in this region that affect transcription independently of their orientation. Site 1 was a negative regulatory element in fibroblasts but had no effect in hepatoma cells. Site 2 was a positive regulatory element in hepatoma cells but had no effect in fibroblasts. This combination of positive and negative regulatory elements can play a significant role in the tissue-specific expression of ADH6.

Effects of doxorubicin, 4'-epirubicin, and antioxidant enzymes on the contractility of isolated cardiomyocytes.

The purpose of this study was to determine the acute effects of doxorubicin and its less cardiotoxic epimer, 4'-epirubicin, on the contractile response of isolated myocytes, and to assess similarities or differences with respect to active oxygen-derived mechanisms. Calcium-tolerant myocytes from rat ventricle were field stimulated at 1.0 Hz, and the maximum extent of cell shortening, peak shortening velocity, and peak relaxation velocity of single twitches were measured by video edge detection. The contractile responses of the myocytes to the two anthracyclines were approximately equal. Exposure of the cells to 10 microM of either anthracycline for 20 min decreased all indices of contractility by 28% (p < 0.05). The active oxygen scavengers, superoxide dismutase and catalase, distinguished the extent to which active oxygen was involved in modifying cellular contractility. Paradoxically, superoxide dismutase alone (10 U/mL) decreased contractility by 21%. Nevertheless, superoxide dismutase (10 U/mL) prevented the decreases in contractility produced by doxorubicin. In contrast, superoxide dismutase only mildly (32%) protected against 4'-epirubicin. Catalase (10 U/mL), however, provided substantial (82-93%) protection against both anthracyclines. Hydrogen peroxide therefore, and presumably hydroxyl radicals, were involved in mediating the decreases in contractility from both doxorubicin and 4'-epirubicin. These results show that an acute exposure to clinically relevant concentrations of these anthracyclines significantly depresses myocyte contractility and that, in this respect, 4'-epirubicin is as potentially cardiotoxic as doxorubicin. The results with antioxidant enzymes also strongly support a free radical mechanism for the toxicity of doxorubicin and 4'-epirubicin to cardiomyocytes.

Relationship between asymmetries in striatal dopamine release and the direction of amphetamine-induced rotation during the first week following a unilateral 6-OHDA lesion of the substantia nigra.

In animals with a large unilateral 6-hydroxydopamine (6-OHDA) lesion of the nigrostriatal dopamine (DA) system the traditional "rotational behavior model" states that amphetamine will induce circling behavior towards the denervated striatum (ipsiversive), that is, away from the side where there is greater amphetamine-stimulated DA release and greater DA receptor stimulation. It is puzzling, therefore, why amphetamine induces contraversive rotation in rats tested 4 days after a unilateral 6-OHDA lesion, despite a 90-95% loss of the dopaminergic input to the striatum by this time. Rats reverse their direction of amphetamine-induced rotation by 8 days post-lesion and turn in the ipsiversive direction thereafter. To try and resolve this paradox, bilateral striatal microdialysis was used to estimate the effects of amphetamine on DA neurotransmission on Day 4 and Day 8 following a large unilateral 6-OHDA lesion of the substantia nigra. On Day 4 post-lesion, amphetamine produced a moderate (around 50% of control) increase in the extracellular concentration of DA in the denervated striatum. This amphetamine-releasable pool of DA was exhausted by a single amphetamine-challenge, because a second injection of amphetamine given 3 h after the first did not produce a comparable increase in DA. It is suggested that on Day 4 post-lesion the amount of DA released by amphetamine in the denervated striatum is sufficient to produce greater DA receptor stimulation on that side, because of DA receptor supersensitivity, and this leads to contraversive rotation. On Day 8 post-lesion, amphetamine induced DA release in the intact striatum but had no effect on extracellular DA in the denervated striatum (DA was nondetectable). On Day 8, therefore, DA receptor stimulation would be greatest in the intact striatum, leading to ipsiversive rotation. In conclusion, it is suggested that the seemingly paradoxical reversal in the direction of amphetamine-induced rotation that occurs over the first week following a unilateral 6-OHDA lesion is consistent with the traditional rotational model, and is due to time-dependent changes in the ability of amphetamine to release DA in the denervated striatum.

Distribution of morphine in body fluids and tissues in fatal overdose.

Two cases of fatal overdose with morphine are presented. Large amounts of the drug were involved in both cases, one by oral ingestion, the other by intravenous injection. Morphine concentrations in various body fluids and tissues are compared to those in the literature.

Screening for acidic and neutral drugs by high performance liquid chromatography in post-mortem blood.

A procedure for screening acidic and neutral drugs in post-mortem blood is presented. The procedure, which is sensitive and specific, employs high performance liquid chromatography with a reversed-phase column and an ultraviolet detector. The volume of specimen used is 1 mL. Over 40 drugs are identifiable by this technique, including analgesics, anti-inflammatory agents, barbiturates and other hypnotic-sedatives, and anti-epileptic drugs. To date, over 500 post-mortem blood specimens have been analyzed by the authors.

Iodo-bis(quaternary ammonium) salts. Potential cartilage-selective x-ray contrast agents.

Bis(quaternary ammonium) compounds in which one or both quaternary nitrogens bear iodinated benzyl moieties and the charged centers are separated by 2, 4, 6, or 10 methylene units have been synthesized and evaluted for (a) binding to cartilaginous material, (b) radiocontrast characteristics, and (c) in vitro pharmacological effects. Also prepared was 1,5-diiodo-2,4-bis(beta-trimethylammonioethyl)benzene diiodide, an analogue in which the iodinated aryl group lies between the charged nitrogen centers. Biological studies show that these compounds bind to cartilage but at relatively slow rates and with low persistence, resulting in low and transient levels of radiopacity. In common with simpler bisquaternary compounds, these compounds block synaptic transmission.

Binding of d-tubocurarine di (methyl-14C) ether iodide and other amines to cartilage, chondroitin sulfate and human plasma proteins.

The binding of d-tubocurarine di [methyl-14C] ether iodide (d-TCE) and other amines to bovine nasal septum, chondroitin sulfate (CS) and human plasma proteins was examined by equilibrium dialysis. Bovine nasal septum and CS bound d-TCE to a greater extent than they did morphine, d-methadone (d-ME) and l-methadone (l-ME). Cartilage, relative to an equal weight of pure CS, bound slightly more d-TCE, 50% more d-ME and l-ME, and the same amount of morphine. The amount of d-TCE bound to pure CS was similar to that of decamethonium [methyl-14C] dibromide but less than that of two new iodinated bisquaternary compounds: 1,6-bis(N,N-dimethyl-3-iodobenzylamino)hexane dichloride and 1,6-bis[dimethyl-(3-amino-4,6-diiodo-benzyl)amino]hexane dichloride. The binding of d-TCE is greater for pure CS than for impure CS which contains 26% protein, and binding to either preparation was inversely related to sodium ion concentration. In the drug concentration range explored, 30 to 40% of d-TCE is bound to plasma proteins, which is twice that of decamethonium binding but equivalent to the binding of morphine and about one-half the binding of d-ME and l-ME. In this same drug concentration range, each gram of cartilage (dry weight) can bind about 10(-7) mol of d-TCE. This study suggests that the binding of d-TCE to cartilage is an ionic type bonding to the anionic sites of the ester sulfates and glucuronate moieties of CS and that the binding of d-TCE to the protein fraction of cartilage is probably equal to, or less than, its binding to the CS fraction. It is concluded that cartilage may represent a measurable distribution pool for d-tubocurarine.