Heart muscle cells, or cardiomyocytes, exhibit intrinsic contractility in vitro. We found that commercially-available mammalian cardiomyocytes serve as an excellent model system for studying the cytoskeleton and cellular contractility, fundamental topics in undergraduate cell and molecular biology courses. Embryonic rat cardiomyocytes were plated on cell culture dishes or glass coverslips and visualized using an inverted phase-contrast microscope. The cardiomyocytes began contracting within 1–2 days after plating and continued to contract for many weeks, allowing their use in multiple laboratory sessions. Following background reading and instruction, students fixed and triple-stained the cardiomyocytes to examine the relative distributions of actin filaments and microtubules and the position of nuclei. Analysis and image capture with fluorescence microscopy provided striking examples of highly organized cytoskeletal elements. Students then designed experiments in which cardiomyocyte intrinsic contractility was explored. Changes in contraction rates were examined after treatment with signaling molecules, such as epinephrine. The addition of epinephrine to the culture medium, within a usable concentration window, increased the rate of contraction. These adaptable exercises provide undergraduate cell and molecular biology students with the exciting opportunity to study cardiomyocytes using standard cell culture and microscopy techniques.

中文翻译：

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跳动的心脏细胞：使用培养的心肌细胞研究实验室练习中的细胞结构和收缩性

心肌细胞或心肌细胞在体外表现出内在的收缩性。我们发现市售的哺乳动物心肌细胞是研究细胞骨架和细胞收缩性的优秀模型系统，这是本科细胞和分子生物学课程的基本主题。将胚胎大鼠心肌细胞铺板在细胞培养皿或玻璃盖玻片上，并使用倒置相差显微镜观察。心肌细胞在铺板后 1-2 天内开始收缩，并持续收缩数周，从而可以在多个实验室中使用。在背景阅读和指导之后，学生对心肌细胞进行固定和三重染色，以检查肌动蛋白丝和微管的相对分布以及细胞核的位置。荧光显微镜的分析和图像捕获提供了高度组织的细胞骨架元素的惊人例子。然后，学生们设计了探索心肌细胞内在收缩力的实验。在用肾上腺素等信号分子治疗后，检查了收缩率的变化。在可用浓度范围内向培养基中添加肾上腺素可增加收缩率。这些适应性练习为细胞和分子生物学本科生提供了使用标准细胞培养和显微镜技术研究心肌细胞的令人兴奋的机会。