Feit I N
Department of Biology, Franklin and Marshall College, Lancaster, Pennsylvania 17601.
Dev Biol. 1994 Aug;164(2):345-60. doi: 10.1006/dbio.1994.1205.
A substance or mixture of substances that stains positively with Nessler's reagent is localized above the surface layer of cells of the migrating slug of Dictyostelium discoideum, possibly incorporated into the slime sheath and coating its surface as well. The substance is manifested as outlines ("cell prints") conforming to the profiles of the surface cells and as small globules over the external face of these surface cells. The entire circumference of the slug is covered by the Nessler-positive cell print substance, which is present from the slug tip to the rear of the slug; presumably all cells at the surface of the slug produce the substance. Cell prints are also present on the surface of the culminating slug as well as on the stalk sheath. No cell prints are seen on the slime sheath or in the slime trail, the collapsed sheath behind the slug. Either the Nessler-positive substance is not incorporated into the sheath or it is uniformly smeared into the sheath as the slug migrates through it. Analysis of size and orientation of cell prints reveals characteristic regional differences that correlate with the prestalk/prespore boundary but not with the location of "zones of adhesion." These patterns of cell prints are compared with some current models of slug cell patterns and movements. Nessler's reagent, a sensitive detector of free ammonia, is shown to react with the amino acids asparagine and glutamine as well as with peptides containing these amino acids. Nessler's reactivity to N-acetylglucosamine suggests that polysaccharides containing this amino sugar also react with Nessler's reagent. Several matrix proteins and polysaccharides are enriched in asparagine, and sheath polysaccharides contain N-acetylglucosamine. It is likely that Nessler's reagent is reacting with such matrix proteins and polysaccharides when cell prints are visualized. The possibility is raised of an interaction between such molecules and the ammonia concentration and flux at the slug surface.
用奈斯勒试剂呈阳性染色的一种物质或物质混合物，位于盘基网柄菌迁移蛞蝓细胞表层上方，可能被并入黏液鞘并覆盖其表面。该物质表现为与表面细胞轮廓相符的轮廓（“细胞印记”）以及这些表面细胞外表面上的小球体。蛞蝓的整个圆周都被奈斯勒阳性细胞印记物质覆盖，从蛞蝓头部到尾部都有；推测蛞蝓表面的所有细胞都产生这种物质。细胞印记也存在于正在形成子实体的蛞蝓表面以及柄鞘上。在黏液鞘或蛞蝓后面塌陷的鞘形成的黏液痕迹中没有看到细胞印记。要么奈斯勒阳性物质没有并入鞘中，要么当蛞蝓穿过它时它均匀地涂抹在鞘中。对细胞印记大小和方向的分析揭示了与前柄/前孢子边界相关但与“黏附区”位置无关的特征性区域差异。将这些细胞印记模式与一些当前的蛞蝓细胞模式和运动模型进行了比较。奈斯勒试剂是游离氨的灵敏检测器，已证明它能与天冬酰胺和谷氨酰胺以及含有这些氨基酸的肽发生反应。奈斯勒试剂对N - 乙酰葡糖胺的反应性表明，含有这种氨基糖的多糖也能与奈斯勒试剂发生反应。几种基质蛋白和多糖富含天冬酰胺，鞘多糖含有N - 乙酰葡糖胺。当观察到细胞印记时，很可能奈斯勒试剂正在与这类基质蛋白和多糖发生反应。由此提出了这类分子与蛞蝓表面氨浓度和通量之间相互作用的可能性。
