G. Meola

S-100 Protein and laminin: immunocytochemical markers for human Schwann cells in vitro

Human fetal and adult Schwann cells, which had been maintained in culture for 5 weeks according to an explant-reexplantation technique, were labeled by immunoperoxidase using antibodies directed against S-100 protein and laminin in order to find specific antigenic markers. Immunocytochemical analysis of the distribution of both proteins showed that they were expressed in long-term cultures. The localization of S-100 protein and laminin in long-term cultures indicated that the expression of these proteins by human Schwann cells was not axon-dependent and also occurred in absence of myelin synthesis.

The syndrome of carnitine deficiency: morphological and metabolic correlations in two cases.

Two cases of systemic carnitine deficiency are described. In both patients, carnitine concentration was lower than normal in serum and muscle tissue. In the first case, the illness began at age 35; the clinical manifestations were only muscular. In the second case, the illness began in childhood; there were intermittent episodes of hepatic enlargement and coma. An excessive lipid content was present in muscle tissue, especially in type 1 fibers, of both cases, and in the liver of the second patient. Ultrastructural studies of muscle tissue revealed important changes of mitochondria. During muscular exercise, aerobic and anaerobic metabolism were investigated. For a given relative work intensity, these patients showed abnormally high blood lactic acid concentration and lactic acid/pyruvic acid ratios. These data, together with the morphological alterations observed in mitochondria, suggest an impaired function of the respiratory chain, leading to a shift of the red/ox potential of the tissue towards a non reduced state.

Kearns-Sayre syndrome: different amounts of deleted mitochondrial DNA are present in several autoptic tissues.

A population of deleted mitochondrial DNA (mtDNA) was found in different amounts in autoptic muscle, heart, cortex, cerebellum, liver and kidney of a patient who died of Kearn-Sayre Syndrome (KSS). The widespread occurrence of the deletion correlates with the multisystem nature of KSS and supports the hypothesis that this is a genetic disease due to an alteration of mtDNA presumably arising in the oocyte or early embryo.

Recessive carnitine palmityl transferase deficiency: biochemical studies in tissue cultures and platelets

SummaryIn a new case of carnitine palmityl transferase (CPT) deficiency the defect was documented in muscle and muscle cultures with an isotope exchange reaction, using different concentrations of palmityl-dl-carnitine and a forward reaction with and without albumin. The defect was expressed in cultured skin fibroblasts only by the “reverse” and “hydroxamate” reactions. The parents and the patients daughter had intermediate levels of the enzyme in platelets and fibroblasts, supporting the concept that CPT deficiency has an autosomal recessive pattern of inheritance. The growth pattern and development of muscle cultures in this CPT-deficient patient indicate that CPT activity may be sufficient to allow normal muscle differentiation in culture without lipid storage.

SCN4A mutation as modifying factor of myotonic dystrophy type 2 phenotype.

In myotonic dystrophy type 2 (DM2), an association has been reported between early and severe myotonia and recessive chloride channel (CLCN1) mutations. No DM2 cases have been described with sodium channel gene (SCN4A) mutations. The aim is to describe a DM2 patient with severe and early onset myotonia and co-occurrence of a novel missense mutation in SNC4A. A 26-year-old patient complaining of hand cramps and difficulty relaxing her hands after activity was evaluated at our department. Neurophysiology and genetic analysis for DM1, DM2, CLCN1 and SCN4A mutations were performed. Genetic testing was positive for DM2 (2650 CCTG repeat) and for a variant c.215C>T (p.Pro72Leu) in the SCN4A gene. The variation affects the cytoplasmic N terminus domain of Nav1.4, where mutations have never been reported. The biophysical properties of the mutant Nav1.4 channels were evaluated by whole-cell voltage-clamp analysis of heterologously expressed mutant channel in tsA201 cells. Electrophysiological studies of the P72L variant showed a hyperpolarizing shift (-5 mV) of the voltage dependence of activation that may increase cell excitability. This case suggests that SCN4A mutations may enhance the myotonic phenotype of DM2 patients and should be screened for atypical cases with severe myotonia.

Muscle phosphoglycerate mutase (PGAM) deficiency in the first Caucasian patient: biochemistry, muscle culture and31P-MR spectroscopy

Muscle phosphoglycerate mutase (PGAM) deficiency has been so far identified in only six patients, five of these being African Americans. We report the results of clinical, morphological, biochemical, muscle culture and31P-MR spectroscopy studies in the first Caucasian patient with muscle PGAM deficiency. A 23-year-old man had a 10-year history of cramps after physical exertion with one episode of pigmenturia. Neurological examination and EMG study were normal. ECG and echocardiography revealed hypertrophy of the interventricular septum and slight dilatation of the left chambers of the heart. Muscle biopsy revealed increased glycogen content and some accumulation of mitochondria. Muscle PGAM activity was markedly decreased (6.5% and 9.7% of control value in two different biopsies). Citrate synthase and other mitochondrial respiratory chain enzyme activities were much higher than normal. In contrast to the marked decrease of PGAM activity observed in muscle biopsy, total enzyme activity in the patients aneural muscle culture was normal, being represented exclusively by BB isoenzyme. The deficiency of PGAM-MM isoenzyme was reproduced in the patients innervated muscle culture. Muscle31P-MR spectroscopy showed accumulation of phosphomonoesters only on fast “glycolytic” exercise. On “aerobic” exercise, Vmax, calculated from the work-energy cost transfer function, showed an increase consistent with the morphological and biochemical evidence of mitochondrial proliferation. This might represent a sort of compensatory aerobic effort in an attempt to restore muscle power.

Physiological and histochemical changes of the extensor digitorum longus and soleus muscles after lateral cordotomy in the albino rat.

Abstract The physiological and histochemical effects of unilateral and bilateral cordotomy on the extensor digitorum longus and soleus muscles were studied in the albino rat. After unilateral cordotomy, the ipsilateral extensor digitorum longus and soleus muscles became slower and relatively faster, respectively, compared to the contralateral and normal muscles. No gross histological abnormalities were found, but changes in fiber diameter and typology were statistically significant in both muscle types compared to their contralateral muscles, and were in substantial agreement with the changes observed on the contractile force and kinetics of the isometric twitch. Bilateral cordotomy in adult animals, like unilateral cordotomy in immature animals, affected only the soleus muscle fiber types. The results have implications for the role of the upper motoneuron physiological and histochemical trophic influences in controlling slow and fast motor units.

Workshop Report: consensus on biomarkers of cerebral involvement in myotonic dystrophy, 2–3 December 2014, Milan, Italy

A workshop on the central nervous system involvement in myotonic dystrophy type 1 took place in Milan on 2nd and 3rd December 2014. Twenty-four clinicians, scientists and delegates from pharmaceutical industries convened to debate the most relevant issues on cognitive impairment and potential brain-related biomarkers in myotonic dystrophy. As Myotonic Dystrophy (DM) is a multisystemic disease, as explored previously during the Consensus conference [1], this workshop focused especially on cognitive dysfunction in DM patients, with the aim of establishing uniform guidelines for cognitive assessment. This Consensus confirmed the importance of a multidisciplinary approach, based on the collaboration among specialists that integrate data from neuroimaging, clinical evaluation, molecular studies on human models and mouse models, neuropathological results and neuropsychological assessments in order to enhance the understanding of CNS alteration in DM1 patients. This document reports on the major themes that were discussed during this two-day meeting, providing an overview of the latest achievements, new proposals and future goals of the investigation on CNS dysfunction in myotonic dystrophy.

A newly-described myotonic disorder (proximal myotonic myopathy — PROMM): personal experience and review of the literature

The aim of this study is to describe the essential characteristics of a family affected by the newly-described proximal myotonic myopathy (PROMM). The clinical, laboratory and genetic findings are described and compared with those reported in the literature, and the clinical spectrum of the manifestations that are similar to but distinct from myotonic dystrophy (MD) is also explored. This has practical implications because the cases so far described suggest that the long-term prognosis of patients with PROMM seems to be more favourable than that of patients with MD.SommarioLo scopo di questo lavoro è descrivere gli aspetti clinici, di laboratorio e biomolecolari di una famiglia affetta da un nuovo disordine miotonico chiamato PROMM (proximal myotonic myopathy). Oltre al confronto con i dati di altre famiglie PROMM descritte in letteratura, viene sottolineato lo spettro clinico di presentazione rispetto alla distrofia miotonica di Steinert, miopatia simile ma allo stesso tempo distinta sia clinicamente che geneticamente. Individuare questo nuovo disordine miotonico ha delle implicazioni cliniche pratiche in quanto, sulla base dei casi descritti finora, il fenotipo PROMM ha una prognosi a lungo termine migliore della distrofia miotonica di Steinert.

Cytogenetic analysis and muscle differentiation in a girl with severe muscular dystrophy.

SummaryThe uncommon case is described of a girl severely affected with Duchenne muscular dystrophy. Cytogenetic analysis revealed no numerical or structural abnormalities of the X-chromosome in any of the cells examined (leucocytes and myoblasts). No abnormality in morphology, growth pattern or differentiation was observed in the dystrophic muscle cultures as compared with control cultures.