Fröhlich A, Meinertzhagen I A
J Neurocytol. 1982 Feb;11(1):159-80. doi: 10.1007/BF01258010.
The developmental transformation of the chief afferent class of fly photoreceptor synapse has been examined from serial electron micrographs of animals fixed at 74, 81, 94 and 100% pupal development (100% pupal development being defined by the time of normal adult eclosion). Animals were selected both by their age and the conformity of their eye coloration to standards for each stage. Two animals were analysed from each stage, one in greater detail than the other. For the first, the exact coordinates of the cartridges (the synaptic columns of the first optic neuropile) from which the analyses were made were mapped and selected to be within the same region of the eye field at all stages. From all animals a portion of one or two cartridges was analysed from series of up to 100 sections and the synapse populations (greater than 80) were analysed for their fine structure and postsynaptic composition. Adult synapses are confirmed as tetrads, with two of the four postsynaptic elements invariably from two monopolar interneurons L1 and L2, one from each. The two others are usually from alpha processes of the same amacrine cell. Synapses appear during the last half of pupal development, with no obvious asynchrony of ultrastructural maturation and in parallel with those of at least one of the other synaptic classes present (which were otherwise not studied). Many adult features of synaptic ultrastructure emerge late, only by 94% pupal development. These include adult numbers of synaptic vesicles, the complete form of the presynaptic ribbon with platform and the postsynaptic cisternae of L1/L2. Prior to 94% the synapses are smaller with postsynaptic elements having a less regular geometry and with postsynaptic densities which are subsequently lost (alpha processes) or replaced by cisternae (L1/L2). At the presynaptic sites of the younger animals (74%, 81%) dyads and triads of postsynaptic elements coexist with tetrads, those of older animals having, on average, more postsynaptic processes per synapse. It is suggested that individual synapses assemble piecemeal, element by element.
通过对处于蛹发育74%、81%、94%和100%阶段（100%蛹发育定义为正常成虫羽化时间）固定的动物的系列电子显微照片进行观察，研究了果蝇光感受器突触主要传入类别的发育转变。根据动物的年龄以及其眼睛颜色与各阶段标准的符合程度进行选择。每个阶段分析两只动物，其中一只分析得比另一只更详细。对于第一只动物，确定了进行分析的小室（第一视神经节的突触柱）的确切坐标，并选择在所有阶段都位于眼场的同一区域内。从所有动物中，从多达100个切片系列中分析一两个小室的一部分，并对突触群体（超过80个）的精细结构和突触后组成进行分析。成年突触被确认为四联突触，四个突触后元件中的两个总是来自两个单极中间神经元L1和L2，各一个。另外两个通常来自同一个无长突细胞的α突起。突触出现在蛹发育的后半期，超微结构成熟没有明显的异步性，并且与至少一种其他存在的突触类别（其他方面未进行研究）同步。突触超微结构的许多成年特征出现较晚，直到蛹发育94%时才出现。这些特征包括成年数量的突触小泡、带有平台的突触前带的完整形式以及L1/L2的突触后池。在94%之前，突触较小，突触后元件的几何形状不太规则，突触后密度随后会消失（α突起）或被池取代（L1/L2）。在较年轻动物（74%、81%）的突触前位点，二元和三元突触后元件与四联突触共存，较年长动物的突触平均每个突触有更多的突触后突起。有人提出，单个突触是逐个元件逐步组装而成的。
