Li J, Ashton F T, Gamble H R, Schad G A
Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104, USA.
J Comp Neurol. 2000 Feb 14;417(3):299-314.
When infective larvae of Haemonchus contortus (a highly pathogenic, economically important, gastric parasite of ruminants) are ingested by grazing hosts, they are exposed to environmental changes in the rumen, which stimulate resumption of development. Presumably, resumption is controlled by sensory neurons in sensilla known as amphids. Neuronal function can be determined by ablation of specifically recognized neurons in hatchling larvae (L1) in which neuronal cell bodies are easily visualized using differential interference microscopy. Using three-dimensional reconstructions from electron micrographs of serial transverse sections, amphidial structure of the L1 is described. Each amphid of H. contortus is innervated by 12 neurons. The ciliated dendritic processes of 10 neurons lie in the amphidial channel. Three of these end in double processes, resulting in 13 sensory cilia in the channel. One process, that of the so-called finger cell, ends in a number of digitiform projections. Another specialized dendrite enters the amphidial channel, but leaves it to end within the sheath cell, a hollow, flask-shaped cell that forms the base of the amphidial channel. Although not flattened, this process is otherwise similar to the wing cells in Caenorhabditis elegans; we consider it AWC of this group. Two other neurons, ASA and ADB, appear to be homologs of wing cells AWA and AWB in C. elegans, although they end as ciliated processes in the amphidial channel, rather than as flattened endings seen in C. elegans. Each of the 12 amphidial neurons was traced to its cell body in the lateral ganglion, posterior to the worm's nerve ring. The positions of these bodies were similar to their counterparts in C. elegans; they were named accordingly. A map for identifying the amphidial cell bodies in the living L1 was prepared, so that laser microbeam ablation studies can be conducted. These will determine which neurons are involved in the infective process, as well as others important in establishing the host-parasite relationship.
当捻转血矛线虫（一种对反刍动物具有高度致病性且在经济上很重要的胃部寄生虫）的感染性幼虫被放牧宿主摄入时，它们会暴露于瘤胃中的环境变化中，这种变化会刺激发育的重新开始。据推测，这种重新开始是由被称为双感器的感觉器中的感觉神经元控制的。神经元功能可以通过对孵化幼虫（L1）中特定识别的神经元进行消融来确定，在这些幼虫中，使用微分干涉显微镜可以很容易地观察到神经元细胞体。利用连续横切面电子显微照片的三维重建，描述了L1的双感器结构。捻转血矛线虫的每个双感器由12个神经元支配。10个神经元的纤毛状树突过程位于双感器通道中。其中三个以双过程结束，导致通道中有13根感觉纤毛。一个过程，即所谓的指状细胞的过程，以许多指状突起结束。另一个特化的树突进入双感器通道，但离开通道后在鞘细胞内结束，鞘细胞是一个中空的烧瓶状细胞，构成双感器通道的基部。虽然这个过程没有变平，但在其他方面类似于秀丽隐杆线虫中的翼细胞；我们认为它是该组的AWC。另外两个神经元，ASA和ADB，似乎是秀丽隐杆线虫中翼细胞AWA和AWB的同源物，尽管它们在双感器通道中以纤毛状过程结束，而不是像秀丽隐杆线虫中那样以扁平末端结束。12个双感器神经元中的每一个都在虫体神经环后方的侧神经节中追踪到其细胞体。这些细胞体的位置与其在秀丽隐杆线虫中的对应物相似；因此对它们进行了命名。绘制了一张用于识别活的L1中双感器细胞体的图谱，以便能够进行激光微束消融研究。这些研究将确定哪些神经元参与感染过程，以及在建立宿主 - 寄生虫关系中其他重要的神经元。
