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Biomedical subjects

G Karpati

Publications and source records attributed to G Karpati.

At least 163 records · Page 9Linked to original sources
PubMed1987

Combined central and peripheral myelinopathy.

We studied clinical, electrophysiologic, and nerve biopsy findings in two men with evidence of severe central and peripheral demyelinating disease. These patients may be rare examples of MS with associated severe, chronic, clinically evident peripheral demyelinating neuropathy. Alternatively, they may be cases of some other form of combined central-peripheral myelinopathy or fortuitous coincidence of MS with idiopathic inflammatory-demyelinating neuropathy. There have been only five other reports of clinically evident combined central-peripheral myelinopathy, but there have also been reports of only electrophysiologic or nerve biopsy evidence (without clinical manifestation) of peripheral neuropathy in MS patients.

Adult↗
PubMed1986

Small-caliber skeletal muscle fibers do not suffer deleterious consequences of dystrophic gene expression.

In Duchenne dystrophy and in the genetic dystrophies of CHF-147 hamsters and MDX mice, the fundamental deleterious consequence of dystrophic gene expression is segmental necrosis of skeletal muscle fibers. The nature of the gene defects and the pathogenesis of muscle fiber damage are not known. However, clinical and experimental evidence indicates that muscle fibers, whose girth is below a certain level (estimated at approximately 20-25 microns in diameter in dystrophic hamsters and MDX mice) are not susceptible to necrosis. This apparent "immunity" has been observed in muscle fibers that are naturally of small girth (such as those in extraocular muscles), and in fibers that were prevented from growing normally by experimental procedures (hamsters and mice) or by pathological processes (Duchenne patients). The cellular or molecular basis by which small-caliber muscle fibers are resistant to the necrotizing effect of the dystrophic gene expression remains unknown. In small-caliber muscle fibers, the normal contraction-related mechanical strains per unit surface area are relatively less than in larger fibers; this could explain their relative resistance to necrosis in some dystrophies.

Animals↗
PubMed1986

Myopathy caused by a deficiency of Ca2+-adenosine triphosphatase in sarcoplasmic reticulum (Brody's disease).

Four male patients from two families were first seen with impaired skeletal muscle relaxation that rapidly worsened during exercise. Muscle biopsies from 2 patients were examined by appropriate biochemical and microscopic immunocytochemical techniques. The adenosine triphosphate (ATP)-dependent Ca2+ transport rate was extremely low in a particulate membrane fraction of skeletal muscle, and there was also a marked reduction of the concentration of 100-kD phosphoprotein, corresponding to Ca2+-ATPase of sarcoplasmic reticulum, in muscle microsomes. The concentration of immunoreactive Ca2+-ATPase of sarcoplasmic reticulum was markedly reduced on immunoblots. Evaluation by microscopic immunocytochemical techniques, using one polyclonal and two monoclonal antibodies against sarcoplasmic reticulum Ca2+ transport protein, revealed that the severe reduction of immunoreactive Ca2+-ATPase was limited to the histochemical type 2 fibers. The deficiency of the Ca2+ transport protein in the sarcoplasmic reticulum of type 2 fibers, which may be the primary expression of a presumed gene defect, can explain the impaired muscle relaxation of the patients. This disease appears to be a clinically, electromyographically, and biochemically distinct metabolic myopathy.

Adult↗
PubMed1986

Calcium-induced damage of skeletal muscle fibers is markedly reduced by calcium channel blockers.

Vascular perfusion of rat hind limbs with a Ca2+-free physiological solution containing ethylenediaminetetraacetate, when followed by a physiological solution with normal concentration of Ca2+, caused a marked rise of creatine kinase (CK) in the venous effluent. When calcium channel blockers were present in the perfusing solutions, no rise of CK occurred. On histological sampling of perfused muscles, CK rise was roughly correlated with muscle fiber damage of the appropriate muscles. Removal of calcium from the plasmalemma of muscle fibers appears to prevent closure of calcium channels, making the muscle fibers susceptible to a deleterious influx of extracellular calcium. This influx can be prevented by the presence of calcium channel blockers in the perfusates.

Animals↗
PubMed1986

Skeletal muscle endurance: the effect of increased availability of endogenous long-chain fatty acid fuel.

A possible role of intramuscularly derived fatty acid fuel on muscle endurance was investigated in curarized diaphragms of fasted rats. These showed significantly improved endurance during 60 min of intermittent stimulation at 20 Hz in vitro compared with diaphragms of fed control animals. The improved endurance appeared to be related to an increased availability and utilization of fatty acid fuel derived from greatly increased numbers of lipid globules in muscle fibers of fasted animals. The pH of muscles with improved endurance (fasted rats) was not different from that of muscles from fed controls at rest. After 60 min of intermittent stimulation, the muscle pH diminished to the same extent in both groups. Diaphragms of fasted rats that were refed 12 h before testing did not show improved endurance. Epinephrine in the bath abolished the improved endurance of diaphragms of fasted rats. Diaphragms of fasted guinea pigs did not show significantly improved endurance (despite abundant intracellular lipid globules), possibly because of a reduced intracellular carnitine.

Animals↗
PubMed1986

Lysosomal storage in human skeletal muscle.

Skeletal muscle is involved symptomatically in two lysosomal storage diseases, acid maltase deficiency and a similar condition in which enzyme levels are normal. Asymptomatic storage in skeletal muscle cells is found in Batten-Kufs' disease (ceroid lipofuscinosis), Fabry's disease, and mannosidosis, as well as in rare patients with an unidentified storage disease. Other cell types (vascular endothelium, smooth muscle, fibroblasts, satellite cells) within the confines of the biopsy specimen may reveal storage in other diseases. The differential diagnosis involves predominantly both normal and abnormal conditions in which acid phosphatase activity is prominent in cells.

Biopsy↗
PubMed1985

Hexosaminidase-A deficiency presenting as atypical juvenile-onset spinal muscular atrophy.

Three patients from two families had an unusual phenotypical variant of late-onset hexosaminidase-A deficiency. The clinical picture was dominated by spinal motor neuron involvement mimicking juvenile-onset spinal muscular atrophy. Atypical features included prominent muscle cramps, postural and action tremor, recurrent psychosis, incoordination, corticospinal and corticobulbar involvement, and dysarthria. The presence of these atypical features in patients whose lower motor neuron involvement would otherwise be consistent with juvenile-onset spinal muscular atrophy should raise the suspicion of the presence of hexosaminidase-A deficiency and GM2 gangliosidosis that can be proved by appropriate enzyme assays.

Adult↗
PubMed1985

Hypophysectomy mitigates skeletal muscle fiber damage in hamster dystrophy.

Ablation of the pituitary gland by a radiofrequency lesion markedly retarded the musculoskeletal growth of young dystrophic hamsters. The prevalence of centronucleated muscle fibers, which is a reliable cumulative index of the microscopic pathological expression of dystrophy, was drastically reduced in quadriceps muscles of 35- and 45-day-old hypophysectomized dystrophic hamsters, compared with sham-operated controls. Mitigation of skeletal muscle fiber damage by musculoskeletal growth retardation may also occur in human dystrophy.

Animals↗
PubMed1985

New observations in reducing body myopathy.

Numerous autofluorescent reducing bodies were found in deltoid and biceps muscle biopsies of a 7-year-old girl with progressive, asymmetric muscle weakness. The structures were composed of tubular filaments as seen by electronmicroscopy. They seemed to have formed around nuclei. An excess of two unidentified proteins was found in muscle homogenates. This patient, like one previously reported, had high serum titers of antibodies to coxsackievirus, but her serum, when tested by indirect immunocytochemistry, did not react with the reducing bodies.

Animals↗
PubMed1984

Neurofilament subunit--related proteins in neuronal intranuclear inclusions.

Well-preserved nuclei were isolated from the brain of a patient with neuronal intranuclear inclusion disease ( NIID ). The inclusions in situ stained for proteins and, by immunohistochemical techniques, for the 200K and 68K components of the neurofilament protein triplet but were negative for the 145K neurofilament protein. At the electron microscopic level the inclusions were seen to consist of straight, randomly arranged tubular filaments 8.5 to 9.5 nm in diameter. They were resistant to extraction with hot buffer containing sodium dodecyl sulfate (SDS) and 2-mercaptoethanol, indicating that the proteins of NIID inclusions are probably cross-linked by covalent bonds other than disulfide. This feature is also exhibited by the paired helical filaments occurring in brain in Alzheimer's disease. No major differences were found in the polypeptide composition of nuclei in NIID and control nuclei resolved by SDS-polyacrylamide gel electrophoresis. The inclusions isolated from SDS-extracted nuclei were shown by immunohistochemical techniques to stain for all three neurofilament subunits, indicating that 145K -related antigenic sites were uncovered during the extraction procedure.

Aged↗
PubMed1983

Reinnervation is followed by necrosis in previously denervated skeletal muscles of dystrophic hamsters.

Hind leg muscles of dystrophic hamsters were continually denervated by multiple crushes of the sciatic nerve to as long as 93 days of age. In these muscles, the prevalence of centronucleated fibers which is a cumulative index of prior necrosis, remained very low. In control dystrophic muscles the prevalence of centronucleated fibers increased steadily to approximately 80% where it leveled off. By omitting further crushes in other groups of animals, previously denervated muscles became adequately reinnervated. In the reinnervated muscles the prevalence of centronucleated fibers steadily increased throughout the necrotic phase of dystrophy at a rate that was comparable to corresponding stages of the natural history of the disease. These experiments indicated that continued denervation was effective in negating skeletal muscle fiber necrosis throughout the necrotic phase and that the electromechanical activity of muscle fibers which allows muscle fiber necrosis was not a time-locked factor.

Animals↗
PubMed1982

Necrosis of capillaries in denervation atrophy of human skeletal muscle.

Gastrocnemius muscles from eight adults with moderate to severe denervation of various causes (excluding vascular diseases), along with biopsy specimens from seven controls, were studies in semithin epoxy resin sections and by electron microscopy. Morphometry showed diminution in the number of capillaries per muscle fiber roughly proportional to the degree of muscle fiber atrophy. The number of capillaries per transverse muscle fiber area tended to increase. By phase microscopy, destroyed capillaries were found in all denervated muscle specimens. Denervated muscle becomes relatively overvascularized, and probably as a result, some capillaries become necrotic. This tends to restore the normal equilibrium between muscle mass and blood supply. The capillary changes of denervation can be distinguished from those in dermatomyositis.

Adult↗
PubMed1981

Lectin histochemistry of human skeletal muscle.

Biotinyl derivatives of seven plant lectins-concanavalin A (Con A), peanut agglutinin (PNA), Ricinus communis agglutinin I (RCA I), Ulex europeus agglutinin I (UEA I), soybean agglutinin (SBA), Dolichos biflorus agglutinin (DBA), and wheat germ agglutinin (WGA)-were bound to cryostat sections of biopsied normal human muscle and visualized with avidin-horseradish peroxidase conjugates. A distinct staining pattern was observed with each lectin. The most general staining was observed with Con A, RCA I, and WGA, which permitted strong visualization of the plasmalemma-basement membrane unit, tubular profiles in the interior of muscle fibers, blood vessels, and connective tissue. PNA gave virtually no intracellular staining, while SBA and UEA I selectively stained blood vessels. DBA was unique in providing good visualization of myonuclei. In each case, lectin staining could be blocked by appropriate sugar inhibitors. Neuraminidase pretreatment of the cryostat sections altered the pattern of staining by all lectins except UEA I and Con A; staining with RCA I became stronger and that with WGA became less intense, while staining with PNA, SBA and DBA became stronger and more generalized, resembling that of RCA I. These effects of neuraminidase pretreatment are in conformity with the known structure of the oligosaccharide chains of membrane glycoproteins and specificities of the lectins involved.

Glycoproteins↗
PubMed1981

Sweat gland duct cells in Lafora disease: diagnosis by skin biopsy.

Skin biopsies of three patients with Lafora disease (clinically typical and proven by liver biopsy) showed PAS-positive inclusions in numerous peripheral cells of eccrine sweat ducts. By electronmicroscopy, the inclusions consisted of polyglucosan-type material; they were not bounded by a membrane. Skin biopsy should be a convenient method of diagnosing Lafora disease.

Adolescent↗