1、MCB 细胞衰老与死亡 练习题 1 一问答题 1. Look carefully at the electron micrographs in Figure 10-1. Describe the differences between the cell that died by necrosis and the one that died by apoptosis. How do the pictures confirm the differences between the two processes? Explain your answer. (A) By necrosis: The pl
2、asma membrane of the cell that died by necrosis is ruptured; several clear breaks are visible, at 8, 9, and 12 oclock. The cells contents, mostly membranous and cytoskeletal debris, are seen spilling into the surrounding. The cytosol stains lightly, as most soluble components had been lost before th
3、e cell was fixed. (B) By apoptosis: An intact membrane surrounds the cell that underwent apoptosis, and its cytosol is densely stained, indicating a normal concentration of cellular components. The large blobs extrude from the nucleus, probably as the result of the breakdown of the nuclear lamina. T
4、he cytosol also contains many large, round membrane-enclosed vesicles. Summary: The pictures visually confirm the notion that necrosis involves cell lysis, whereas cells undergoing apoptosis remain relatively intact until they are engulfed and digested inside a normal cell. Cell death. (A) By necros
5、is. (B) By apoptosis. MCB 细胞衰老与死亡 练习题 2 2. Mice that are defective for Apaf-1 (Apaf1-/-) or for caspase-9 (Casp9-/-) die around the time of birth and exhibit a characteristic set of abnormalities, including brain overgrowth and cranial protrusions. Why do you suppose such abnormalities arise in thes
6、e deficient mice. Mice that are deficient for Apaf-1 or caspase-9 are defective for cytochrome c-dependent apoptosis. Apoptosis is a critical event in development, allowing excess brain cells to be weeded out. The extent of brain overgrowth and size of the cranial protrusions indicate that this weeding out process in the developing brain must be massive. The dramatic effects of the deficiencies of Apaf-1 and caspase-9 suggest that the cytochrome c-dependent apoptotic pathway must be critically important in brain development.
