Howard R J, Seeley D C, Kao V, Wember M, Schauer R
Parasitology. 1986 Jun;92 ( Pt 3):545-57. doi: 10.1017/s0031182000065434.
Schizont-infected red blood cells (SI-RBC) from Plasmodium berghei-infected mice contain between 2 and 10 times as much sialic acid as uninfected RBC from the same blood (99-550 micrograms/10(10) RBC versus 33-65 micrograms/10(10) RBC). Total RBC samples from infected animals containing up to 63% ring- and trophozoite-infected cells had identical sialic acid contents to purified RBC samples (of less than 3% parasitaemia) from the same blood (52-64 micrograms/10(10) RBC). We conclude that RBC containing immature parasites have the same sialic acid content as uninfected RBC from infected blood and that total cellular sialic acid increases during maturation to the schizont stage. Uninfected RBC from infected blood had 25-50% as much sialic acid as normal mouse RBC (33-65 micrograms/10(10) RBC versus 126 micrograms/10(10) RBC). There were no qualitative changes in RBC sialic acids, all RBC samples having 60-70% N-acetylneuraminic acid, 30-40% N-acetyl-9-O-acetylneuraminic acid and 5-10% N-glycolylneuraminic acid. The quantitative changes we observed during infection must reflect changes in murine sialoglycoconjugates, as we have shown elsewhere that Plasmodia do not synthesize or contain sialic acids. Since the sialic acid composition of mouse serum glycoconjugates is quite different to that of the RBC fractions studied here, the quantitative data suggest that part of the sialic acids of the uninfected RBC has been transferred to SI-RBC. With higher molar ratios of periodate to substrate than generally used, we were able to radio-isotopically label normal murine sialoglycoproteins on SI-RBC and purified uninfected RBC from infected blood by the periodate/NaB3H4 method. Several new proteins were then tritiated with SI-RBC but these proteins may be intracellular and could even lack sialic acid.
来自感染伯氏疟原虫小鼠的裂殖体感染红细胞（SI-RBC）所含唾液酸是同一血液中未感染红细胞的2至10倍（99 - 550微克/10¹⁰个红细胞，而未感染红细胞为33 - 65微克/10¹⁰个红细胞）。感染动物的全红细胞样本中含有高达63%的环状体和滋养体感染细胞，其唾液酸含量与来自同一血液的纯化红细胞样本（寄生虫血症低于3%）相同（52 - 64微克/10¹⁰个红细胞）。我们得出结论，含有未成熟寄生虫的红细胞与感染血液中未感染的红细胞具有相同的唾液酸含量，并且在发育至裂殖体阶段的过程中，细胞总唾液酸含量会增加。感染血液中未感染的红细胞所含唾液酸是正常小鼠红细胞的25 - 50%（33 - 65微克/10¹⁰个红细胞对126微克/10¹⁰个红细胞）。红细胞唾液酸没有质的变化，所有红细胞样本中N - 乙酰神经氨酸占60 - 70%，N - 乙酰 - 9 - O - 乙酰神经氨酸占30 - 40%，N - 糖基神经氨酸占5 - 10%。我们在感染过程中观察到的定量变化必定反映了鼠类唾液糖缀合物的变化，因为我们在其他地方已经表明疟原虫不合成或含有唾液酸。由于小鼠血清糖缀合物的唾液酸组成与我们在此研究的红细胞部分有很大不同，定量数据表明未感染红细胞的部分唾液酸已转移至SI-RBC。使用比通常更高的高碘酸盐与底物摩尔比，我们能够通过高碘酸盐/硼氢化钠³H4方法对感染血液中的SI-RBC和纯化未感染红细胞上的正常鼠类唾液糖蛋白进行放射性同位素标记。然后用SI-RBC对几种新蛋白质进行了氚标记，但这些蛋白质可能是细胞内的，甚至可能缺乏唾液酸。
