From lysozyme digests of the N-acetylated cell walls of BacilZus cereus AHU 1356, a polysaccharide fraction and a teichoic acid fraction were isolated by ion-exchange chromatography and gel chromatography. The former fraction, accounting for 50 % of the walls, contained N-acetylglucosamine, N-acetylmannosamine, N-acetylgalactosamine and glucose in a molar ratio of 4: 1 : 1 : 1 together with a small amount of the peptidoglycan constituents. The latter fraction accounted for 5 % of the walls and was composed of N-acetylglucosamine, galactose, glycerol and phosphorus in a molar ratio of 1 :

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We investigated the electrophysiological alterations induced by the removal of sialic acid from the sarcolemma in canine Purkinje fibres. About 70% of total sialic acid content of Purkinje fibres was removed by 120 min of exposure to neuraminidase (1 U X ml-1). The treatment with neuraminidase did not change any of the action potential characteristics at normal Ca2+ concentration (2.7 mmol X litre-1). However, action potential duration and maximum upstroke velocity of phase zero of the action potential were reduced to a greater degree in neuraminidase-treated Purkinje fibres than in non-treated controls at high Ca2+ concentration (8.1 mmol X litre-1). At high Ca2+ concentration, delayed afterdepolarisations were induced in five out of nine neuraminidase-treated Purkinje fibres and triggered activity was observed in two, when driven in trains of 20 stimuli of different cycle length (1000 to 180 ms). No discernible delayed afterdepolarisations were observed in nine non-treated control Purkinje fibres. In addition, the amplitude of delayed afterdepolarisations induced by ouabain (0.2 mumol X litre-1) in neuraminidase-treated Purkinje fibres was larger than non-treated controls. These findings suggest that sialic acid residues of glycocalyx function as a kind of barrier to Ca2+ influx.

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