The slug Arion subfuscus produces a tough, highly adhesive defensive secretion. This secretion is a flexible hydrogel that is toughened by a double network mechanism. While synthetic double network gels typically require extensive time to prepare, this slug creates a tough gel in seconds. To gain insight into how the glue forms a double-network hydrogel so rapidly, the secretory apparatus of this slug was analyzed. The goal was to determine how the major components of the glue were distributed and mixed. Most of the glue comes from two types of large unicellular glands; one secretes polyanionic polysaccharides in small, membrane-bound packets, the other secretes proteins that appear to form a cross-linked network. The latter gland shows distinct regions where cross-linking appears to be occurring. These regions are darker, more homogeneous and appear more solid than the rest of the secretory material. The enzyme catalase is highly abundant in these regions, as are basic proteins. These results suggest that a rapid oxidation event occurs in this protein-containing gland, triggering cross-linking before the glue is released. The cross-linked microgels would then join together after secretion to form a granular hydrogel. The polysaccharide-filled packets would be mixed and interspersed among these microgels and may contribute to joining them together. This is an unexpected and highly effective way to form a tough gel rapidly.

中文翻译：

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Arion subfuscus 的粘附分泌细胞分析：深入了解微凝胶在坚韧、快速凝固的水凝胶中的作用

蛞蝓Arion subfuscus产生坚韧、高粘性的防御性分泌物。这种分泌物是一种柔性水凝胶，通过双网络机制增韧。虽然合成双网络凝胶通常需要大量时间来准备，但这种小块可以在几秒钟内形成坚韧的凝胶。为了深入了解胶水如何如此迅速地形成双网络水凝胶，对这种蛞蝓的分泌装置进行了分析。目标是确定胶水的主要成分是如何分布和混合的。大部分胶水来自两种大型单细胞腺体；一种分泌小分子膜结合的聚阴离子多糖，另一种分泌似乎形成交联网络的蛋白质。后一个腺体显示出似乎发生交联的不同区域。这些区域比分泌物质的其余部分更暗、更均匀并且看起来更坚实。过氧化氢酶在这些区域非常丰富，碱性蛋白质也是如此。这些结果表明，在这种含蛋白质的腺体中发生了快速氧化事件，在胶水释放之前触发了交联。交联的微凝胶在分泌后会结合在一起形成颗粒状水凝胶。充满多糖的包将混合并散布在这些微凝胶中，并可能有助于将它们连接在一起。这是一种意想不到的、高效的快速形成坚韧凝胶的方法。