Ferenc Mechler

Cerebral blood flow and glucose metabolism in mitochondrial disorders.

Objective: To investigate cerebral metabolism by 2-[18F]fluorodeoxy-d-glucose (FDG) uptake using PET and cerebrovascular reverse capacity by transcranial Doppler sonography (TCD) in different mitochondrial diseases (mitochondrial myopathy; mitochondrial encephalopathy, lactacidosis, and stroke-like episodes [MELAS]; and chronic external ophthalmoplegia). Background: Previous studies on individual patients with mitochondriopathies revealed abnormal accumulations of mitochondria in endothelium, smooth muscle cells, and pericytes of blood vessels in different parts of the nervous system (cerebrum, cerebellum, sural nerve) and skeletal muscle. On this basis, some investigators suggested a pathogenic role of vascular involvement in the MELAS syndrome and other encephalopathies. {smhd1} Design/Methods: The authors investigated neuronal metabolism and cerebrovascular involvement with PET in 5 cases and with TCD with acetazolamide stimulation in 15 cases. The patients were divided into three groups: 1) interictal MELAS (n = 4); 2) progressive external ophthalmoplegia (n = 6); and 3) pure mitochondrial myopathy and neuropathy (n = 5). The results were compared with those from matched normal control subjects. The diagnoses were based on clinical phenotype as well as histopathologic and molecular analysis. Results: Cerebral glucose uptake was impaired in all patients, both with and without CNS symptoms, particularly in the occipital and temporal lobes. The vasoreactivity of the small arterioles to acetazolamide did not differ significantly between the patients and healthy control subjects or between the different groups of mitochondrial disorders. Conclusions: MELAS does not appear to be a functional disturbance of arterioles leading to an ischemic vascular event. The clinical symptoms in MELAS are not the result of a mitochondrial angiopathy but are the consequences of a mitochondrial cytopathy affecting neurons or glia. There is no correlation between the decreased glucose metabolism and the duration of the disease.

Differential expressions of protein kinase C isozymes during proliferation and differentiation of human skeletal muscle cells in vitro.

Abstract The mechanism of skeletal muscle regeneration in vivo can be well modeled in vitro by culturing skeletal muscle cells. In these cultures mononuclear satellite cells fuse to form polynuclear myotubes by proliferation and differentiation. The aim of this study was to determine how the different protein kinase C (PKC) isozymes were expressed during differentiation of human skeletal muscle in vitro. The expressions of desmin, used as a muscle-specific intermediate filament protein marker of differentiation, and of different PKC isozymes were detected by single and double immunohistochemical labeling, and by Western blot analysis. In skeletal muscle cells we could identify five PKC isozymes (PKCα, -γ, -η, -θ and -ζ). The expressions of PKCα and -ζ did not change significantly during differentiation; their levels of expression were high in the early immature cells and remained unchanged in later phases. In contrast, the expression levels of PKCγ and -η increased with differentiation. Furthermore, the cellular localization of PKCγ markedly altered during differentiation, with a perinuclear-nuclear to cytoplasmic translocation. The change in the level of expression of PKCθ during differentiation showed different pattern; its expression was high during the early phases, but a decreased immunostaining was detected in the matured, well-differentiated myotubes. We conclude, therefore, that cultured human skeletal muscle cells possess a characteristic PKC isozyme pattern, and that the different phases of differentiation are accompanied by different expression patterns of the various isozymes. These data suggest the possible functional and differential roles of PKC isozymes in human skeletal muscle differentiation.

Inflammatory Changes in Facioscapulohumeral Muscular Dystrophy

SummaryFifteen patients (10 familial and 5 sporadic cases) with facioscapulohumeral dystrophy were studied with regard to the presence of inflammatory changes. Mononuclear infiltrations were not characteristic of any stage of the disease, but they may be present in differring degrees during the whole course of the process. However, their lack or presence was uniform in the affected families, suggesting that the appearance of infiltrations may be genetically determined. Parallel with the presence of cell infiltrations, the serum creatine kinase (CK) activity was moderately increased and the progress of the disease was slightly accelerated. The relation of these phenomena to polymyositis and the diagnostic difficulties are discussed.

Phorbol ester treatment inhibits proliferation and differentiation of cultured human skeletal muscle satellite cells by differentially acting on protein kinase C isoforms

Abstract. We have previously shown that cultured human skeletal muscle cells express five protein kinase C (PKC) isoforms (PKCα, -γ, -η, -θ, and -ζ) and that expression levels of various PKC isozymes differentially change during differentiation. In this study we investigated the effects of the PKC activator phorbol 12-myristate 13-acetate (PMA) on differentiation and on PKC isozymes of human skeletal muscle satellite cells. PMA inhibited the growth and fusion of cultured human myoblasts in a dose-dependent manner. In addition, prolonged treatment of cells with PMA suppressed the expression of the myogenic differentiation marker desmin showing similar dose-response characteristics. Furthermore, PMA also induced the intracellular translocation of PKCγ, -η, and -θ, whereas cellular localization of PKCα and -ζ were not altered. These changes in subcellular localization patterns were of great importance since only those PKC isoforms were translocated that possessed alterations in their expression levels during differentiation. Our findings, therefore, suggest that the PMA-induced inhibition of differentiation of human skeletal muscle cells is mediated by certain PKC isoforms. Moreover, these data strongly argue for differential and isozyme-specific roles of various PKC isoforms in these processes.

The significance of simultaneous estimation of serum creatine kinase and myoglobin in neuromuscular diseases

SummarySerum creatine kinase (CK) and myoglobin (Mb) levels were measured in patients with different neuromuscular diseases, carriers of X-linked Duchenne-type muscular dystrophy and normal volunteers. The highest levels were found in Duchenne dystrophy and both values decreased in parallel with age. In patients suffering from limb-girdle dystrophy the increases in CK activity and Mb concentration were also pronounced. However, there were families with normal and others with elevated CK and Mb levels in facioscapulohumeral dystrophy. In neurogenic atrophies both CK and Mb levels generally increased only slightly. Serum Mb and CK levels have similar values as indicators of muscle damage in primary and secondary skeletal muscle disorders. The serum Mb level helps in the detection of carriers but is not more sensitive than CK measurement.

Ion Concentrations in Serum and Cerebrospinal Fluid of Patients with Neuromuscular Diseases

SummaryThe Na+, K+, Ca2+, Mg2+, Cl−, and Pi concentrations in serum and lumbar CSF of 17 controls and 62 patients with neuromuscular diseases were determined and the values statistically evaluated. Although alterations in ion concentrations specifical to different groups were not observed in either of these biological fluids, the significant increase in serum Pi concentration in Duchenne muscular dystrophy seems to be remarkable. It is suggested that the possible alterations in the ion content of the serum and CSF may contribute additional data to the diagnosis of various neuromuscular diseases.ZusammenfassungBei 62 Patienten mit neuromuskulären Erkrankungen und bei 17 Kontrollpatienten wurde die Konzentration von Na+, K+, Ca2+, Mg2+, Cl− und anorganischem Phosphor (Pi) im Serum und im lumbalen Liquor vergleichend gemessen, und die Werte wurden statistisch bearbeitet. Obwohl keine für die verschiedenen Erkrankungstypen charakteristischen Veränderungen beobachtet werden konnten, ist die signifikante Erhöhung der Pi-Konzentration im Serum bei Duchenne-Dystrophie doch erwähnenswert. Die eventuellen Veränderungen der Ionenkonzentration im Serum und im Liquor können zur Diagnosestellung bei verschiedenen neuromuskulären Erkrankungen beitragen.

Lipid peroxidation and superoxide dismutase activity in muscle and erythrocytes in adult muscular dystrophies and neurogenic atrophies

SummaryLipid peroxidation (LP) and superoxide dismutase (SOD) activity were determined in erythrocytes and skeletal muscle obtained from patients with limb-girdle and facioscapulohumeral muscular dystrophies, neurogenic atrophies and from age-matched control subjects. Neither lipid peroxidation nor SOD activity in erythrocytes of patients differed from control values. SOD activity and LP in muscle specimens were also normal in types of neurogenic atrophy. Lipid peroxidation in the muscle from patients with adult types of muscular dystrophy had a tendency to be increased. The values were widely scattered, the highest being obtained in the older patients with long duration of disease.

Peripheral nerves are progressively involved in multiple sclerosis – A hypothesis from a pilot study of temperature sensitized electroneurographic screening

Multiple sclerosis (MS) is primarily a disease of the central nervous system. Although the involvement of the peripheral nervous system in MS was suggested over 100 years ago, the issue is still controversial, and it is generally accepted that except for the optic nerve the peripheral nerves are left unaffected by the disease. We hypothesize, that an electroneurographical study if thorough enough, may reveal differences in some nerve conduction parameters between MS patients and healthy subjects. Second, we assume that the sensitivity of nerve conduction measurements might be increased if performed at a range of temperatures, reflecting a differential effect of cooling and warming on the peripheral nerve conduction parameters in MS patients and controls. Finally, we expect that the differences in these parameters between controls and MS patients will increase with the progression of the disease. To test these hypotheses in a pilot study, we performed a detailed analysis of the motor and sensory nerve conduction features of the right median nerve in 13 MS patients and 13 controls at 5 degrees C increments between 20 and 40 degrees C, and repeated these measurements after 3 years. The motor latencies were 0.3-0.6 ms longer in MS patients compared to the controls both initially and 3 years later (0.058<p<0.09). The durations and areas of the compound motor action potential (CMAP) appeared more sensitive to changes in temperature in the MS group (0.057<p<0.1). The change in both distal motor latency and sensory latency per unit change in temperature decreased significantly in 3 years within the MS but not in the control group. These results suggest a mild and progressive involvement of the PNS in MS. Most differences in this pilot study were on the border of statistical significance therefore our hypotheses should be confirmed in studies with larger sample size.

Intellectual function in muscular dystrophies

SummaryIntellectual function was studied in 28 boys with Duchenne dystrophy, 12 patients with facioscapulohumeral-type and 10 patients with limb-girdle-type muscular dystrophy. A definite relationship between intelligence level and the type of muscle disease was found. The more severe the genetic damage manifested by the rapidity of progression of muscular dystrophy the more definite the affection of the CNS manifesting as mental deficit. The factors influencing the level and structure of intelligence seem to exert their effect before the manifestation of muscle lesions.

Decrease in the carbamylcholine-induced chemotaxis of monocytes in myasthenia gravis

SummaryThe carbamylcholine-induced chemotaxis of monocytes was decreased in patients with myasthenia gravis, whereas no change was found in the C5a-induced locomotion of these cells compared with that of the normal controls. The decrease in the chemotaxis induced by carbamylcholine correlated with the severity of clinical symptoms. The beneficial effect of themectomy was also reflected in the improvement of chemotaxis. The method is simple, not expensive and could be used in the diagnosis of myasthenia gravis.