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Mother sporocyst of Echinostoma caproni (3 days post-infection). Transmission electron microphotographs of sections through germinal cells
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The localisation and the composition of germinal material in miracidia and mother sporocysts of Echinostoma caproni were studied with the use of histological and electron microscopic methods. Germinal material in miracidia was localised in the posterior body half and was represented by 3–4 undifferentiated cells and 5–7 germinal cells. Taken togeth...
Citations
... This hypothesis was later renounced by Clark (1974) and Whitfield and Evans (1983), who suggested that sporocysts and rediae reproduced by budding and that their germinal cells were totipotent stem cells. Subsequent detailed histological (Dobrovolskij et al. 1983;Galaktionov and Dobrovolskij 2003;Dobrovolskij and Ataev 2003;Isakova 2011;Ataev 2017) and electron-microscopic (Podvyaznaya 2007;Podvyaznaya andGalaktionov 2014, 2018;Ataev and Tokmakova 2018;Podvyaznaya et al. 2020) studies of sporocysts and rediae in various digeneans showed that the germinal mass was a fully fledged organ of reproduction, consisting of cells of several types. Germinal cells were shown to have some ultrastructural features indicating that they were germ line cells (Klag et al. 1997;Podvyaznaya 2007;Podvyaznaya andGalaktionov 2014, 2018). ...
Embryonic development of reproductive organs in rediae of the digenean Bunocotyle progenetica was studied using transmission electron microscopy. The germinal primordium becomes morphologically distinct in early embryos as a weakly separated cell mass with a forming cavity. It consists of undifferentiated, differentiating, and supporting cells. As embryos develop, the supporting cells form a wall around the enlarging cavity. Other cells of the germinal primordium are incorporated into the wall as solitary cells or as small cell aggregations. Those situated posteriorly give rise to an incipient germinal mass functioning during postembryonic development. Undifferentiated and differentiating cells in the middle and the anterior part of the primordium ensure a considerable growth of the cavity wall, which incorporates solitary germinal cells. In advanced embryonic rediae, these cells mature, cleave, and give rise to germinal balls, which enter the forming brood cavity. In the most mature embryonic rediae, all these early cercarial embryos reside in a brood cavity, which is lined by that time with a syncytium continuous with the supporting tissue of the incipient germinal mass. Based on our results and the literature data, we suggest that the morphogenesis of the reproductive apparatus of the daughter parthenitae in hemiuroid digeneans may be characterized by (1) emergence of an incipient brood cavity within the germinal primordium, (2) formation of the cavity lining from the cells of the germinal primordium, (3) fragmentation and uneven distribution of the germinal material of the germinal primordium around the cavity, and (4) an anticipatory development of some of this germinal material.
... Both these cell types are located in the posterior half of the miracidial body and both have a vesicular nucleus surrounded by a fine layer of basophilic cytoplasm. It has been suggested that UC are smaller and less intensely stained and that their nuclei are characterised by a more condensed chromatin, which forms large clusters of heterochromatin in the centre of the nucleus and directly under the nuclear envelope (Dobrovolskij and Ataev 2003;Ataev and Tokmakova 2018). However, the size of GC may also vary. ...
... Assuming that the main morphological characteristics of GC in trematode parthenitae are universal, we decided to use the characters mentioned above for an analysis of the cell composition of miracidia. This approach has been successfully employed for the description of UC and GC in miracidia of Echinostoma caproni (Ataev et al. 2001;Ataev and Tokmakova 2018). The presence of two types of germinal elements in them suggests that GC multiplication in MS of this species proceeds by division of UC. ...
We performed histological and electron microscopic analysis of miracidia of Schistosoma mansoni in order to examine their germinal elements. In total, about 20 germinal cells at different stages of maturation were found. We described their ultrastructure and proposed a scheme of reproduction of mother sporocysts of S. mansoni based on our data and literature information. According to this scheme, the only germinal elements present in the miracidia are germinal cells (undifferentiated cells were not found). Regardless of their size and localisation, none of the germinal cells in the miracidia has undergone full differentiation. This process is completed after the metamorphosis of the larva into the sporocyst.
... Установлено, что для них характерно наличие округлого светлого ядра с равномерно расположенными небольшими скоплениями гетерохроматина и центрально расположенным ядрышком, большое количество полирибосом и обширное скопление митохондрий на одном из полюсов клетки. Отмеченные признаки ранее были описаны как особенности ГК партенит [7,8]. В свою очередь последние по размерам разделяются на три размерных класса, приуроченность к которым не зависит от локализации в мирацидии. ...
histological and electron microscopic investigations were performed of the development of generative elements of Schistosoma mansoni mother sporocysts (MS). On average 20 germinal cells (GC) are found in miracidium. After metamorphosis of miracidium into sporocysts GC grow and on the 3d day start to divide thus forming first embryos of daughter sporocysts. During the same time germinal masses start to form in the subtegumental body area of MS. At this point proliferation of undifferentiated cells (UC) occurs only in the germinal masses. Here also a part of UC differentiates into GC. These cells form sporocystoid embryos. Therefore, the formation of generative elements into S. mansoni MS occurs in two stages. The primaries GC are formed in the process of the miracidium development into the egg, but secondary GC forming into germinal masses of MS.
В учебном пособии рассматриваются основные принципы организации микро-
скопов разных типов, а также методы и способы обработки и анализа микро-
скопических изображений. Приводится краткий обзор физических свойств, вли-
яющих на создание микроскопического изображения, а также рассматриваются
наиболее распространённые оптические механизмы контрастирования и методы
микроскопии. Также приведена информация о факторах, определяющих разре-
шающую способность микроскопов: функция рассеяния точки, числовая апер-
тура, аберрации, глубина резкости и др. Рассмотрены основные типы световой
и электронной микроскопии, используемые для анализа биологических объектов,
специализированные системы микроскопии, применяемые в научных и клини-
ческих исследованиях, а также приведён краткий обзор программ для обработки
и анализа цифровых изображений.
Учебное пособие написано для студентов вузов, обучающихся по программам
бакалавриата и магистратуры биологических специальностей.
