Department of Chemistry and Chemical Biology, Wyss Institute for Biologically Inspired Engineering, Harvard University, Cambridge, Massachusetts, United States of America.
PLoS One. 2013 Jul 29;8(7):e69651. doi: 10.1371/journal.pone.0069651. Print 2013.
Although the starvation response of the model multicellular organism Caenorhabditis elegans is a subject of much research, there is no convenient phenotypic readout of caloric restriction that can be applicable to large numbers of worms. This paper describes the distribution of mass densities of populations of C. elegans, from larval stages up to day one of adulthood, using isopycnic centrifugation, and finds that density is a convenient, if complex, phenotypic readout in C. elegans. The density of worms in synchronized populations of wildtype N2 C. elegans grown under standard solid-phase culture conditions was normally distributed, with distributions peaked sharply at a mean of 1.091 g/cm(3) for L1, L2 and L3 larvae, 1.087 g/cm(3) for L4 larvae, 1.081 g/cm(3) for newly molted adults, and 1.074 g/cm(3) at 24 hours of adulthood. The density of adult worms under starvation stress fell well outside this range, falling to a mean value of 1.054 g/cm(3) after eight hours of starvation. This decrease in density correlated with the consumption of stored glycogen in the food-deprived worms. The density of the worms increased when deprived of food for longer durations, corresponding to a shift in the response of the worms: worms sacrifice their bodies by retaining larvae, which consume the adults from within. Density-based screens with the drug Ivermectin on worms cultured on single plates resulted in a clear bimodal (double-peaked) distribution of densities corresponding to drug exposed and non-exposed worms. Thus, measurements of changes in density could be used to conduct screens on the effects of drugs on several populations of worms cultured on single plates.
尽管模式多细胞生物秀丽隐杆线虫的饥饿反应是许多研究的主题，但目前还没有一种方便的热量限制表型读数方法，适用于大量的线虫。本文描述了使用等密度离心法对线虫种群的质量密度分布的研究，这些线虫种群从幼虫阶段到成虫期第一天不等，发现密度是秀丽隐杆线虫中一种方便的（如果复杂的话）表型读数。在标准固相培养条件下生长的野生型 N2 秀丽隐杆线虫同步化群体中，线虫的密度呈正态分布，分布峰值尖锐，L1、L2 和 L3 幼虫的平均密度为 1.091 g/cm(3)，L4 幼虫的平均密度为 1.087 g/cm(3)，刚蜕皮的成虫的平均密度为 1.081 g/cm(3)，24 小时成虫的平均密度为 1.074 g/cm(3)。饥饿应激下的成虫密度明显低于此范围，饥饿 8 小时后降至 1.054 g/cm(3)的平均值。这种密度的降低与食物剥夺线虫中储存糖原的消耗有关。当线虫被剥夺食物更长时间时，密度会增加，这对应着线虫反应的转变：线虫通过保留幼虫来牺牲自己，幼虫从内部消耗成虫。在用伊维菌素对单板培养的线虫进行基于密度的筛选时，会导致密度出现明显的双峰（双峰）分布，对应于暴露和未暴露药物的线虫。因此，密度变化的测量可用于对单板培养的几批线虫进行药物作用的筛选。
