Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Brazil.
Microsc Res Tech. 2011 Sep;74(9):812-8. doi: 10.1002/jemt.20960. Epub 2010 Nov 17.
Rhoptries are organelles that have important, complex roles in Apicomplexa biology. During Toxoplasma gondii infection, these organelles take part in several essential and complex processes that include host cell entry and parasite development. Using different electron microscopy techniques, we characterized the fine morphology of the rhoptries of two of the most important life stages of T. gondii: the tachyzoite and the bradyzoite forms. The observed tachyzoite and bradyzoite rhoptries had delimited regions characterized by a dark and electron-dense neck, an amorphous and less electron-dense bulb, and a region of intermediate electron density, which connects the bulb to the neck. Metal replicas of frozen-fractured tachyzoites showed intramembranous particles of different densities and sizes on the fractured faces of rhoptry membranes. Both in tachyzoites and bradyzoites, the intramembranous particles were arranged in distinctive parallel arrays that decorated most part of these organelles. Tubulo-vesicular subcompartments and free particles within the rhoptry lumen were observed on freeze-fractured replicas. Cryo-fixed, deep-etched samples showed several pore-like structures localized in the bulb portion. No obvious evidence was found of a possible connection between rhoptries and micronemes.
顶复器是一类在顶复门生物中具有重要且复杂功能的细胞器。在刚地弓形虫感染过程中，这些细胞器参与了宿主细胞入侵和寄生虫发育等多个关键且复杂的过程。本研究利用不同的电子显微镜技术，对刚地弓形虫两个重要生活阶段（速殖子和缓殖子）的顶复器的精细形态进行了研究。观察到的速殖子和缓殖子顶复器具有不同的限定区域，特征是暗且电子致密的颈、无定形且电子密度较低的球、以及连接球和颈的中等电子密度区域。冷冻断裂速殖子的金属复制品显示，在顶复器膜的断裂面上存在不同密度和大小的膜内颗粒。在速殖子和缓殖子中，膜内颗粒排列成独特的平行排列，装饰着这些细胞器的大部分区域。在冷冻断裂复制品中观察到顶复器腔中的管状囊泡亚区室和游离颗粒。在深蚀刻的冷冻固定样本中，在球部发现了几个类似孔的结构。没有明显的证据表明顶复器和微线体之间可能存在连接。
