Denervation alterations in surface membrane glycoprotein glycosyltransferases of mammalian skeletal muscle.

Plasma membrane fractions isolated from rat skeletal muscle demonstrate an increased carbohydrate composition after 7 days of denervation. Total hexose content increased 3.5-fold (from 278 to 985 nmol/mg protein), hexosamine increased 1.7-fold (from 30 to 52 nmol/mg protein), and sialic acid increased 2.5-fold (from 17 to 43 nmol/mg protein). The cytidine monophosphate (CMP) sialic acid-sialyl transferase and uridine diphosphate (UDP) galactose-galactosyl transferase activities localized in the enriched skeletal muscle plasma membrane fraction were also found to increase with denervation. Sialyl transferase activity increased from 27 to 50 pmol sialic acid transferred/mg protein/h using the acceptor asialo-fetuin. The galactosyl transferase activity increased from 21 to 44 pmol galactose transferred/mg protein/h using the acceptor asialo-agalacto-fetuin. These alterations in composition and transferase activities may help explain the renewed capacity for cell-cell interactions associated with denervation.     

Erythrocyte membrane lipids in Friedreich's ataxia.

In a study of the lipid composition of erythrocyte membranes in Friedreich's ataxia, the concentration of the major membrane components (phospholipids, cholesterol and protein) in ataxic patients, family members, and control subjects were found to be the same. The total fatty acid distribution was also normal. However, an altered distribution of phospholipid classes in erythrocytes was noted (an increase of PI + PS and a decrease of PE in Friedreich's ataxia patients).     

Erythrocyte plasma membrane fluidity in avian muscular dystrophy.

Erythrocytes from closely related dystrophic and normal adult chickens showed no differences in either membrane fluidity or polarity at 25°C, measured by electron paramagnetic resonance spectroscopy of fatty acid spin labels. The effects of temperature and spin label concentration on order parameters were identical for erythrocytes from dystrophic and normal birds. Similarly, erythrocyte ghosts from dystrophic and normal chickens showed identical spectral properties.     

Erythrocyte membrane studies in familial hypokalemic periodic paralysis.

A study of RBC membrane functions was performed in four patients suffering from familial hypokalemic periodic paralysis who had permanent muscular weakness. Electrophoretograms of membrane proteins, cell deformability, calcium-promoted potassium efflux, calcium-ATPase activity, and endogeneous phosphorylation of membrane proteins were all within the normal range. These results are compared with similar studies performed in myotonic and Duchenne-type dystrophies, in which abnormalities in the RBC membrane have been described. The results do not support the theory of RBC involvement in hypokalemic periodic paralysis. However, this does not imply that the muscle cell membrane is not involved in the underlying pathological processes in this disorder.     

Erythrocyte membrane abnormalities in human myotonic dystrophy

Membrane-bound enzyme activities and cardiac glycoside binding were determined in red blood cell membrane preparations from patients with myotonic dystrophy and in age matched controls. Na⁺-K⁺-activated ATPase activity was signficantly increased in myotonic patients. [³H]Ouabain binding to erythrocyte membranes was also significantly increased in myotonic dystrophy patients. The Mg²⁺-ATPase (ouabain-insensitive) was, however, unchanged. The K⁺-stimulated paranitrophenyl phosphatase (KPNPPase) activity was markedly enhanced in myotonic patients as compared to controls. The kinetic analysis showed a marked change in V_max of Na⁺-K⁺ ATPase with respect to the activation by Na⁺, K⁺ and ATP. However, the K_m values were the same in control as well as in myotonic groups. The increased erythrocyte membrane Na⁺-K⁺-ATPase activity, KPNPPase and [³H]ouabain binding in myotonic patients supports the hypothesis that generalized membrane abnormality may be involved in pathogenesis of the human myotonic dystrophy.     

Erythrocyte membrane lysophospholipase activity in muscular dystrophy

The membrane lysophospholipase activity of erythrocytes obtained from Duchenne muscular dystrophy patients was lower than that of erythrocytes from age-matched normal boys. On the other hand, the membrane enzyme activity of erythrocytes from myotonic dystrophy patients was not different from that of their age- and sex-matched controls. Dipyridamole (0.1 mM) and glycerol 3-phosphorylcholine (2 mM) had no significant effect on these enzyme activities. These results suggest that membrane lysophospholipid metabolism may be altered in Duchenne muscular dystrophy but not in myotonic dystrophy.     

Erythrocyte membrane abnormalities in patients with amyotrophic chorea with acanthocythosis. Part 2. Abnormal degradation of membrane proteins

Bands 2.1, 3 and 4.2 of the erythrocyte membrane proteins in chorea-acanthocytosis are self-digested faster than those in normal controls. The junction between spectrin and band 3 protein at the cytoplasmic side of the patients' erythrocyte membranes may have some conformational defects. The conformational defects of the proteins may be responsible for the low fluidity in the interior of the patients' erythrocyte membranes. These basic molecular defects may be widespread in other extraneural cell membranes as well as in neuronal cell membranes.     

Myotonic muscular dystrophy. Time-dependent alterations in erythrocyte membrane fluidity

The muscle cell membrane may be the site of the basic molecular defect in myotonic muscular dystrophy. Many laboratories, including our own, have suggested that this defect may also be manifested in membrane of extraneural tissue. In previous studies, we found that electron spin resonance results suggested an increased membrane fluidity in erythrocyte membranes that had aged two days in buffer, but we and others could find no such changes in fresh erythrocyte membranes. To investigate these findings further, the results of an initial study of the time course of the membrane fluidity changes in erythrocytes in myotonic muscular dystrophy are given in the present report. They suggested that increased membrane fluidity changes in erythrocytes in myotonic muscular dystrophy are given in the present report. They suggested that increased membrane fluidity in myotonic dystrophy is manifested after two days of in vivo ageing and confirm our original findings. These results are discussed in relation to possible effects of metabolic deprivation or of protein-lipid alterations in erythrocytes.     

Erythrocyte membrane cation-stimulated ATPase activities in myotonic muscular dystrophy

The cation-stimulated ATPase activities of erythrocyte membranes from patients with myotonic muscular dystrophy (MyD) were compared with the activities in age- and sex-matched controls. The enzymes included ouabain-sensitive ATPase, Mg2+-ATPase and Ca2+ + Mg2+-ATPase. Sampling and processing of the materials from patients with MyD and controls were simultaneously done in each experiment. The enzyme activities were varied with or without EGTA in the reaction medium, or with different temperatures for membrane storage, but no significant differences between MyD and control were observed in any conditions. The present study indicates no specific abnormality of the cation-stimulated ATPase activities of erythrocyte membranes in MyD.     

Erythrocyte lithium transport in bipolar affective disorders. The effect of membrane transport inhibitors

Erythrocyte lithium influx and efflux were investigated in vitro in patients with bipolar affective disorders and in age- and sex-matched healthy controls. To explore the components of lithium influx and efflux five selected inhibitors (ouabain, phloretin, p-chloromercury benzene sulfonate [PCMBS], 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene, and lanthanium chloride) were employed. The mean values of lithium influx were similar in both populations of erythrocytes. The addition of ouabain and phloretin reduced lithium influx, but this effect was comparable in both patients and controls. PCMBS had an accelerating effect, and this was more pronounced in patients. Total erythrocyte lithium efflux from lithium-containing erythrocytes was comparable in both patients and controls. The addition of phloretin reduced RBC lithium efflux, the magnitude of this parameter, however, was similar in patients and controls. Erythrocyte lithium efflux was accelerated in the presence of PCMBS, and this effect was greater in patients. The relevance of these findings to the postulated cell membrane defect in affective disorders is evaluated.     

Erythrocyte membrane sodium-potassium and magnesium ATPase in primary affective disorder

Erythrocyte membrane Mg2+ ATPase and Na+-K+ ATPase were measured in patients with affective disorder, their well relatives, and normal controls during euthymic moods. On the average, the Mg2+ ATPase activity was high in subjects belonging to affective disorder families. However, the difference between normal and affective disordered individuals was not statistically significant. Only the well individuals from affective disorder pedigrees as a group had significantly higher than normal Mg2+ ATPase activity (p less than 0.05). The Na+-K+ ATPase activity was similar for all the groups, including normal, bipolar manic-depressive (with or without lithium), unipolar depressive, and well individuals. Lithium treatment did not seem to have any effect on Mg2+ ATPase. Even though the values of Na+-K+ ATPase in the lithium-treated group were high, it is not certain that this was due to lithium per se.     

Erythrocyte membrane transports of monoamine precursor amino acids in schizophrenia

We have determined the erythrocyte membrane uptake of the monoamine precursors L-tyrosine (L-TYR) and L-tryptophane (L-TRYP) in 72 patients with schizophrenia: 21 without neuroleptic treatment and not depressed, 15 with neuroleptic treatment and depressed, 33 without neuroleptic treatment, 27 depressed, compared to: 59 control subjects, and 54 depressed patients. We found that the ratio of L-TYR facilitated membrane diffusion to that of L-TRYP is: decreased when the patients are depressed, increased when they are untreated. When untreated patients receive neuroleptics and are depressed, the ratio tends to equal that of depressed patients'. The meaning of these anomalies is analysed, using our up-to-date knowledge of the erythrocytes's role in uptaking and dispatching the human body amino-acids, and of the role of these uptakes in regulating the functional monoamine balance. We postulate that in depressions, Parkinson's disease and schizophrenia, a change of membrane fluidity occurs, being decreased in depressions and Parkinsons's disease, and increased in schizophrenia.     

Erythrocyte membrane in myotonic dystrophy: A study with acetylcholinesterase

Erythrocyte membrane in myotonic dystrophy (MyD) was studied with respect to acetylcholinesterase (AchE), an enzyme localized on the external surface of the membrane. The activity was determined over the temperature range of 7–41 °C (in hemolysates) and 25–41 °C (in ghosts). The activity, the transition temperature in the Arrhenius plots, and the activation energy either above or below the transition temperature did not differ between MyD and controls. The Hill coefficient for the inhibition by fluoride was approximately 1 in MyD and in controls at 13, 25 and 37°C. The dose of fluoride for 50% inhibition of the enzyme activity differed between different temperatures but not between MyD and controls. There seems to be no gross abnormality in AchE or its environment in erythrocyte membrane in MyD.     

Erythrocyte membrane transport of L-tyrosine and L-tryptophan in 66 patients with depressive syndromes. Preliminary results

The transport of Tyrosine and Tryptophan by the membrane of red blood cells has been studied in a group of 66 depressed patients (DSM-III: 27 major depressions, single episode or recurrent; 17 bipolar disorders, depressed; 22 dysthymic disorders). Anomalies were observed: tyrosine transport was decreased in the bipolar disorders and in the major depressions; tryptophan transport was increased in the major depressions and in the dysthymic disorders. These results suggest that membrane transports are disturbed in depressed syndromes, and may be related to dysfunction in the monoaminergic balance.     

Piracetam reverses hippocampal membrane alterations in Alzheimer's disease

Summary. The in vitro effects of piracetam treatment on the fluidity of membranes from the hippocampus of Alzheimer's Disease patients (AD) and non-demented controls were studied. Hippocampal membranes of AD patients showed a significant lower hydrocarbon core fluidity compared with membranes from elderly non-demented controls. Preincubation with piracetam enhanced the hydrocarbon core fluidity of hippocampal membranes from AD-patients as well as elderly controls in a concentration depending fashion, although the effect was more pronounced for the AD membranes. In the presence of piracetam, the difference of the membrane fluidity between AD and control membranes was not longer apparent. Received January 18, 1999; accepted April 13, 1999     

Erythrocyte membrane sodium — potassium adenosine triphosphatase activity in affective disorders

Summary Erythrocyte membrane Na⁺,K⁺-ATPase activity was studied in drug naive patients with bipolar (BP) mania (n=62) and unipolar (UP) depression (n=60) and normal controls (n=66). Compared to controls there was a significantly decreased Na⁺,K⁺-ATPase activity in UP depressives but no change in BP manics. However, lithium treatment caused a significant increase in Na⁺,K⁺-ATPase activity although there was no correlation between plasma lithium levels and enzyme activity. Plasma cortisol correlated inversely with Na⁺,K⁺-ATPase in UP depressives. Interestingly, the lithium responders [<50% Beck Rafaelson's Mania Rating Scale (BRMS) score] showed a significant increase in Na⁺,K⁺-ATPase activity compared to lithium nonresponders (>50% BRMS score). These observations indicate that monitoring of Na⁺,K⁺-ATPase activity during lithium therapy is useful to predict a therapeutic response.     

Cerebral endothelial plasma membrane alterations in acute hypertension

Summary This study was undertaken to localize oligosaccharide residues on the endothelial luminal plasma membrane of cerebral vessels of normotensive animals and vessels permeable to horseradish peroxidase (HRP) in angiotensin-induced acute hypertension. Wistar-Furth rats were injected with HRP intravenously and hypertension was induced by an intravenous infusion of angiotensin amide. Animals were fixed 2.5, 10 and 15 min later and the HRP reaction product was demonstrated in brain slices, followed by lectin localization using the avidin-biotinperoxidase method. Oligosaccharide residues demonstrable on the luminal plasma membrane of cerebral endothelium of normotensive controls and both permeable and nonpermeable vessels of hypertensive animals were: -d-mannosyl, -d-glucosyl, -N-acetylglucosaminyl, sialyl, -d-galactosyl, -l-fucosyl and -N-acetyl-d-galactosaminyl groups. Peanut agglutinin did not bind to the endothelium of normotensive controls or of nonpermeable vessels in hypertensive animals, but did bind to endothelium of vessels permeable to HRP 2.5 min after the onset of hypertension. At 10 min, the luminal plasma membrane of vessels regained their normal characteristics and peanut agglutinin binding was no longer demonstrable. Our studies suggest that increased cerebrovascular permeability to protein in acute hypertension is associated with loss of the terminal sialic acid groups on the luminal plasma membrane of permeable vessels. This results in the observed reduction of charge on the endothelium and an exposure of -d-gal-(1,3)-d-gal N-acetyl groups leads to binding of peanut agglutinin. Both alterations are rapidly reversible and no longer demonstrable 10 min after the onset of hypertension, when blood pressures reach resting levels and the blood-brain barrier is restored.Supported by Heart and Stroke Foundation of Ontario Grant 2-6