Batista E J, de Menezes Feitosa L F, de Souza W
Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio De Janeiro, Ilha do Fundão, Brazil.
Parasitol Res. 2000 Nov;86(11):881-90. doi: 10.1007/s004360000269.
We studied the endocytic pathway of Entamoeba histolytica using (a) confocal laser scanning microscopy to observe living cells labeled with fluorescent probes and (b) transmission electron microscopy of cells incubated in the presence of gold-labeled proteins or in a cytochemical medium designed for the localization of acid phosphatase activity. Images of acridine-orange-labeled cells showed that most of the intracellular vacuoles were acidic and were also labeled with Lucifer yellow, a fluorescent dye widely used for labeling of compartments of the endocytic pathway. A similar labeling pattern was observed when the cells were incubated in the present of fluorescein-labeled bovine albumin. However, no labeling was observed when fluorescein-labeled transferrin was used. Gold-labeled proteins (albumin, transferrin, horseradish peroxidase, and lactoferrin) were used for further characterization of the endocytic pathway. With the exception of transferrin, all the proteins bound to the protozoan surface and were subsequently internalized, appearing in small peripheral vesicles and some tubular structures. The ingested molecules accumulated in large vesicles located in the more central portion of the cell, which also presented acid phosphatase activity.
（a）共聚焦激光扫描显微镜观察用荧光探针标记的活细胞；（b）对在金标记蛋白存在下孵育的细胞或在用于定位酸性磷酸酶活性的细胞化学培养基中孵育的细胞进行透射电子显微镜观察。吖啶橙标记细胞的图像显示，大多数细胞内液泡呈酸性，并且也被广泛用于标记内吞途径区室的荧光染料路西法黄标记。当细胞在荧光素标记的牛血清白蛋白存在下孵育时，观察到类似的标记模式。然而，当使用荧光素标记的转铁蛋白时，未观察到标记。金标记蛋白（白蛋白、转铁蛋白、辣根过氧化物酶和乳铁蛋白）用于对内吞途径进行进一步表征。除转铁蛋白外，所有蛋白质都与原生动物表面结合，随后被内化，出现在小的外周囊泡和一些管状结构中。摄取的分子积聚在位于细胞更中心部分的大囊泡中，这些大囊泡也呈现酸性磷酸酶活性。
