The sialic acid and galactose concentrations in erythrocyte membranes in patients with myotonic dystrophy, limb-girdle and facioscapulohumeral dystrophy

Anemia amelioration by lactose infusion during trypanosomosis could be associated with erythrocytes membrane de-galactosylation

African trypanosomosis is a potentially fatal disease that is caused by extracellular parasitic protists known as African trypanosomes. These parasites inhabit the blood stream of their mammalian hosts and produce a number of pathological features, amongst which is anemia. Etiology of the anemia has been partly attributed to an autoimmunity-like mediated erythrophagocytosis of de-sialylated red blood cells (dsRBCs) by macrophages. Lactose infusion to infected animals has proven effective at delaying progression of the anemia. However, the mechanism of this anemia prevention is yet to be well characterized. Here, the hypothesis of a likely induced further modification of the dsRBCs was investigated. RBC membrane galactose (RBC m-GAL) and packed cell volume (PCV) were measured during the course of experimental trypanosomosis in mice infected with Trypanosoma congolense (stb 212). Intriguingly, while the membrane galactose on the RBCs of infected and lactose-treated mice (group D) decreased as a function of parasitemia, that of the lactose-untreated infected group (group C) remained relatively constant, as was recorded for the uninfected lactose-treated control (group B) animals. At the peak of infection, the respective cumulative percent decrease in PCV and membrane galactose were 30 and 185 for group D, and 84 and 13 for group C. From this observed inverse relationship between RBCs membrane galactose and PCV, it is logical to rationalize that the delay of anemia progression during trypanosomosis produced by lactose might have resulted from an induction of galactose depletion from dsRBCs, thereby preventing their recognition by the macrophages.

Intracellular elemental composition of single muscle fibres in muscular dystrophy and dystrophia myotonica

Seven patients with myotonic muscle dystrophy (MD), 6 with muscle dystrophy without myotonia (limb-girdle and facio-scapulo-humeral dystrophy) and 6 healthy volunteers were subjected to biopsy from the anterior tibial muscle (TA). Light microscopic examination of cryostat sections revealed pathological changes of different kind and degree--the occurrence of ring fibres and multiple central nuclei was the most consistent in advanced MD. X-ray microanalysis (XRMA) of single muscle fibres demonstrated the intracellular content of such elements as Na, Cl, K, Mg, S and P. The most conspicuous finding was the increase in Na and Cl and decrease in K demonstrated in MD. The highest levels of Na and Cl were found in ring fibres. Decrease in K was as high in structurally normal fibres of MD biopsies as in ring fibres and was also found in the muscle dystrophies without myotonia, but to a lesser degree than in MD. Thus, the decrease in K was not correlated to increase in Na and Cl. These changes in muscle fibre elemental content are discussed in relation to plasma membrane changes of erythrocytes in MD and especially the indications of disturbed anion channels.

Sialic acid content in serum IgG from patients with myotonic dystrophy compared with healthy controls

One of the determinants of the lifetime of circulating glycoproteins is their content of the terminal carbohydrate sialic acid. In order to elucidate a possible mechanism behind reduced concentration of IgG in patients with myotonic dystrophy, serum IgG was isolated by affinity chromatography and its content of sialic acid determined. No difference between patients and healthy controls was found. The results provide further support to the idea that a host factor rather than an abnormality of the IgG molecule itself is responsible for the low concentration of serum IgG in this disease.

The physical state of the erythrocyte membrane in myotonic dystrophy

The molecular pathology of myotonic dystrophy is believed to be expressed at the plasma membrane level. Previous assessments of membrane fluidity, a marker of the biochemical state of the membrane, have yielded conflicting results. In this study, erythrocyte membrane fluidity was reevaluated using highly sensitive fluorescence probe techniques. Steady-state anisotropy was measured with diphenylhexatriene (DPH), trimethylaminophenyl-hexatriene (TMA-DPH) and phenylhexatrienylphenylpropionic acid, probing different regions of the membrane. In the patients, significantly increased steady-state anisotropy was obtained with DPH, probing the hydrophobic core of the membrane, while slightly reduced anisotropy was found with TMA-DPH. The dynamic properties of the membrane lipids were further examined by means of time-resolved measurements with DPH. The excited state decay kinetics could best be described by a bi-exponential decay model. A large redistribution of the probe populations and a reduction of the average order parameter were found in the patients indicating a less ordered or more fluid lipid matrix. These perturbations might be induced by a protein abnormality and altered protein-lipid interaction within the erythrocyte membrane.

Sialyltransferase activity in erythrocyte membranes and serum in patients with myotonic dystrophy

Sialyltransferase activity was measured in erythrocyte membranes and in serum in patients with myotonic dystrophy and in matched healthy controls. The reason for assaying this enzyme was to study a possible mechanism behind a previously reported deficiency of glycoprotein-bound sialic acid in the erythrocyte membrane in patients with this disease. No significant differences in sialyltransferase activity with endogenous or different exogenous glycoprotein acceptors were found.

Sialic acid concentration in erythrocyte membrane subfractions in patients with myotonic dystrophy and healthy controls

Previous studies have shown a selective reduction of the sialic acid concentration in erythrocyte membranes in patients with myotonic dystrophy. In order to locate this deficiency, chloroform/methanol/H2O extractions of erythrocyte membranes were analyzed in patients with myotonic dystrophy and in matched healthy reference individuals. In the patients, significant reductions of the sialic acid concentration were found in the aqueous phase (p = 0.03) containing mainly glycophorin A as well as in the band-3-containing interphase (p less than 0.005). These findings may be related to certain previously reported membrane abnormalities in myotonic dystrophy.

Carbohydrate composition of erythrocyte membranes and glycosidase activities in serum in patients with myotonic dystrophy, limb-girdle dystrophy and congenital myotonia

A number of abnormalities in cell membrane function, including cells other than muscle cells, have been described in patients with inherited muscular diseases such as myotonic dystrophy and congenital myotonia. The basic molecular defects are, however, still unknown. The complex carbohydrates of membrane-bound glycoconjugates are of vital importance for the normal performance of the cell membrane. In this study the concentrations of the three major carbohydrates (sialic acid, galactose and hexosamines) of the erythrocyte membrane were therefore determined in patients with myotonic dystrophy, limb-girdle dystrophy and congenital myotonia. The activities of relevant glycosidases in serum were also assayed. In each of the three diseases pertinent changes of the carbohydrate pattern were found. In patients with myotonic dystrophy the sialic acid and in patients with limb-girdle dystrophy the hexosamine concentration was significantly reduced (P less than 0.0005). The sialic acid, galactose and hexosamine concentrations were all significantly increased in patients with congenital myotonia. No increase of the neuraminidase (sialidase) activity was found in sera from patients with myotonic dystrophy. In patients with limb-girdle dystrophy, the activities of serum hexosaminidases were normal. These results support the contention that certain inherited muscular diseases may represent generalized membrane disorders, and suggests that disturbances of membrane-bound glycoproteins and/or glycolipids might be of importance in the pathogenesis of some of these disorders.

Increased fragility of erythrocytes from amyotrophic lateral sclerosis (ALS) patients provoked by mechanical stress

Erythrocytes from patients with amyotrophic lateral sclerosis (ALS) and controls were suspended in an electrolyte-substrate medium and subjected to mechanical stress by centrifugation under standardized conditions. Subsequent spectrophotometric analysis of the medium disclosed a significantly higher degree of haemolysis in samples from ALS-patients than from controls. The observation gives further evidence for the existence of an abnormality of the red cells in the disease. The nature and possible significance of this abnormality in relation to the pathogenesis of ALS is as yet unknown, but notably there was no significant correlation between the degree of cell abnormality as manifested by haemolysis and the duration of the disease in the individual patient.