Fröhlich A, Meinertzhagen I A
Life Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada.
J Neurobiol. 1993 Dec;24(12):1642-54. doi: 10.1002/neu.480241208.
Houseflies (Musca domestica) were exposed to pulses of heat (1 h) or cold (several hours) during early pupal life, and the effects were investigated on the development of the first optic neuropile, or lamina, of the visual system. The treatments were designed to perturb the cellular organization of the cartridges, the unit synaptic structures of the lamina, so as to provide novel synaptic opportunities among the normally fixed composition of these modules, thereby testing the preferences of their component cells during synaptogenesis. Various abnormalities were identified, but these were not always consistent between flies: retinal abnormalities included the loss and fusion of rhabdomeres, especially of the central cells of the ommatidium, whereas in the lamina low frequencies of abnormal cartridges were found. These included seven that were studied with serial sections, which instead of the normal pair of L1 and L2 monopolar interneurons had supernumerary cells of this type. The normal pairing of L1 and L2 at postsynaptic sites of receptor terminal tetrad synapses was preserved in these cases, the cells eschewing pairings of homologous L1/L2 or L2/L2 partners. This meant that more than one L1 could pair with a single L2 and vice versa, even at the same terminal, and appeared to do so opportunistically on the basis of proximity, with cells closer to each other pairing more frequently. Thus the cells behave during synaptogenesis as if they recognize other cells only as cell types (receptor, L1 or L2) and not as individual cells.
在蛹发育早期，将家蝇（家蝇属）暴露于热脉冲（1小时）或冷脉冲（数小时）下，研究其对视觉系统首个视神经纤维层（即视叶）发育的影响。这些处理旨在扰乱视叶中突触小体（视叶的单位突触结构）的细胞组织，从而在这些模块通常固定的组成成分之间提供新的突触形成机会，进而测试它们的组成细胞在突触形成过程中的偏好。识别出了各种异常情况，但这些异常在不同的苍蝇个体之间并不总是一致的：视网膜异常包括视杆的缺失和融合，尤其是小眼中央细胞的视杆，而在视叶中发现异常突触小体的频率较低。其中有七个通过连续切片进行了研究，这些突触小体中，正常情况下一对L1和L2单极中间神经元被额外的此类细胞所取代。在这些情况下，受体终末四联突触的突触后位点上L1和L2的正常配对得以保留，细胞避开同源的L1/L2或L2/L2伙伴之间的配对。这意味着不止一个L1可以与单个L2配对，反之亦然，即使在同一个终末也是如此，而且似乎是根据距离机会性地进行配对，彼此距离更近的细胞配对更频繁。因此，细胞在突触形成过程中的行为就好像它们只将其他细胞识别为细胞类型（感受器、L1或L2），而不是个体细胞。
