Department of Anatomy and Cell Biology, University of Cantabria, Santander, Spain.
J Anat. 2008 Aug;213(2):106-19. doi: 10.1111/j.1469-7580.2008.00901.x.
This paper reports on the structure and ultrastructure of the ventricular myocardium of the African lungfish Protopterus dolloi in freshwater (FW), in aestivation (AE), and after the AE period. The myocardium shows a conventional myofibrillar structure. All the myocytes contain large intracytoplasmic spaces occupied by a pale material that could contain glycosaminoglycans and/or glycogen, which may be used as food and water reservoirs. In FW, the myocytes in the trabeculae associated with the free ventricular wall show structural signs of low transcriptional and metabolic activity (heterochromatin, mitochondria of the dense type). These signs are partially reversed during the AE period (euchromatin, mitochondria with a light matrix), with a return to the FW appearance after arousal. The myocytes in the septum show, in FW conditions, nuclear polymorphism (heterochromatin, euchromatin), and two types (colliquative and coagulative) of necrosis. In AE, all the septal myocytes show euchromatin, and the number of necrotic cells increases greatly. Cell necrosis appears to be related to the septal architecture. After arousal, the septal myocytes exhibit a heterochromatin pattern, the number of necrotic cells decreases, cell debris accumulates under the endocardium, and phagocytosis takes place. Despite being a morphologic continuum, the trabeculae associated with the free ventricular wall appear to constitute a different compartment from that formed by the trabeculae in the ventricular septum. Paradoxically, AE appears to trigger an increase in transcriptional and synthetic myocardial activities, especially at the level of the ventricular septum. This activity may be involved in mechanisms of autocrine/paracrine regulation. Aestivation cannot be regarded as the result of a general depression of all cellular and organic activities. Rather, it is a much more complex state in which the interplay between upregulation and downregulation of diverse cell activities appears to play a fundamental role.
本文报告了非洲肺鱼 Protopterus dolloi 在淡水中（FW）、夏眠（AE）和 AE 期后的心室心肌的结构和超微结构。心肌显示出常规的肌原纤维结构。所有的心肌细胞都含有大的胞质内空间，被淡色物质占据，这些物质可能含有糖胺聚糖和/或糖原，可作为食物和水的储存库。在 FW 中，与游离心室壁相关的小梁中的心肌细胞显示出低转录和代谢活性的结构特征（异染色质、致密型线粒体）。在 AE 期间，这些特征部分逆转（常染色质、浅色基质的线粒体），在唤醒后恢复到 FW 的外观。在 FW 条件下，隔肌中的心肌细胞表现出核多态性（异染色质、常染色质）和两种类型（液化和凝固）的坏死。在 AE 中，所有的隔肌心肌细胞都表现出常染色质，坏死细胞的数量大大增加。细胞坏死似乎与隔肌的结构有关。唤醒后，隔肌心肌细胞表现出异染色质模式，坏死细胞数量减少，细胞碎片在心内膜下积聚，并发生吞噬作用。尽管是形态上的连续体，但与游离心室壁相关的小梁似乎构成了与心室间隔中的小梁不同的隔室。矛盾的是，AE 似乎引发了转录和合成心肌活性的增加，尤其是在心室间隔水平。这种活性可能参与了自分泌/旁分泌调节的机制。夏眠不能被视为所有细胞和有机活动普遍抑制的结果。相反，它是一种更为复杂的状态，其中各种细胞活动的上调和下调之间的相互作用似乎起着至关重要的作用。
