Tanaka T, Yamaguchi H, Kishimoto Y, Gould R M
John F. Kennedy Institute, Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD.
Biochim Biophys Acta. 1987 Oct 31;922(1):85-94. doi: 10.1016/0005-2760(87)90248-7.
The purpose of this investigation was to compare the incorporation of radioactivity from various precursors into lipids of different regions of squid giant nerve fiber systems including axoplasm, axon sheath, giant fiber lobes which contain stellate ganglion cell bodies, and the remaining ganglion including giant synapses. To identify the labeled lipids, stellate ganglia including giant fiber lobes and the remaining tissue were first incubated separately with [14C]glucose, [32P]phosphate, [14C]serine, [14C]acetate and [3H]myristate. The radioactivity from glucose, after conversion to glycerol and fatty acids, was incorporated into most lipids, including triacylglycerol, free fatty acids, cardiolipin, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, phosphatidylinositol, phosphatidylserine, sphingomyelin and ceramide 2-aminoethylphosphanate [corrected]. The radioactivity from serine was largely incorporated into phosphatidylserine and, to a lesser extent, into other phospholipids, mainly as the base component. The sphingoid bases of ceramide and sphingomyelin were also significantly labeled. Saturated and monounsaturated and, to a lesser extent, polyunsaturated fatty acids of these lipids were synthesized from acetate, glucose and myristate. Among the major lipids, cholesterol was not labeled by any of the radioactive compounds used. Ganglion residues incorporated the most radioactivity in total lipids from either [14C]glucose or [14C]serine, followed by giant fiber lobes and then sheath. Axoplasm incorporated the least. Among various lipids, phosphatidylethanolamine with shorter saturated fatty acids and phosphatidylglycerol contained the most radioactivity from glucose in all regions. Axoplasm was characterized by a higher proportion of glucose radioactivity in ceramide, sphingomyelin and phosphatidylglycerol. Axoplasm and sheath contained a higher proportion of serine radioactivity than did the other two regions in ceramide. Essentially no radioactivity from [14C]galactose was incorporated in any region.
本研究的目的是比较各种前体的放射性掺入鱿鱼巨大神经纤维系统不同区域脂质中的情况，这些区域包括轴浆、轴鞘、含有星状神经节细胞体的巨大纤维叶以及包括巨大突触在内的其余神经节。为了鉴定标记的脂质，首先将包括巨大纤维叶的星状神经节和其余组织分别与[¹⁴C]葡萄糖、[³²P]磷酸盐、[¹⁴C]丝氨酸、[¹⁴C]乙酸盐和[³H]肉豆蔻酸盐一起孵育。葡萄糖转化为甘油和脂肪酸后的放射性被掺入大多数脂质中，包括三酰甘油、游离脂肪酸、心磷脂、磷脂酰乙醇胺、磷脂酰甘油、磷脂酰胆碱、磷脂酰肌醇、磷脂酰丝氨酸、鞘磷脂和2-氨基乙基磷酸神经酰胺[已校正]。丝氨酸的放射性主要掺入磷脂酰丝氨酸，在较小程度上掺入其他磷脂，主要作为碱基成分。神经酰胺和鞘磷脂的鞘氨醇碱基也有明显标记。这些脂质的饱和脂肪酸、单不饱和脂肪酸以及较小程度的多不饱和脂肪酸由乙酸盐、葡萄糖和肉豆蔻酸盐合成。在主要脂质中，胆固醇未被所用的任何放射性化合物标记。神经节残余物在来自[¹⁴C]葡萄糖或[¹⁴C]丝氨酸的总脂质中掺入的放射性最多，其次是巨大纤维叶，然后是轴鞘。轴浆掺入的最少。在所有区域中，具有较短饱和脂肪酸的磷脂酰乙醇胺和磷脂酰甘油在来自葡萄糖的放射性方面含量最高。轴浆的特征是神经酰胺、鞘磷脂和磷脂酰甘油中葡萄糖放射性的比例较高。轴浆和轴鞘在神经酰胺中含有的丝氨酸放射性比例高于其他两个区域。基本上没有[¹⁴C]半乳糖的放射性掺入任何区域。
