. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MYOGENIC PRECURSOR CELLS IN SNAIL HEART 107 .* • • v -*A ** / m* / / >,J. Figure 2. Electron micrograph ot mature cardiomyocytes (m) of Achatina. Nerve ending In) with glio- interstitial cell (arrow) and endothelial cell (e) adjoin the luminal surface of the cardiomyocyte. hi. heart lumen. Scale bar = 2 ;um. Figure 3. Electron micrograph show ing a primitive intercalated disc between cardiomyocytes. Scale bar = I Figure 4. Electron micrograph of an undifferentiated cell (uc) adjoining cardiomyocytes (m) in the Achat
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MYOGENIC PRECURSOR CELLS IN SNAIL HEART 107 .* • • v -*A ** / m* / / >,J. Figure 2. Electron micrograph ot mature cardiomyocytes (m) of Achatina. Nerve ending In) with glio- interstitial cell (arrow) and endothelial cell (e) adjoin the luminal surface of the cardiomyocyte. hi. heart lumen. Scale bar = 2 ;um. Figure 3. Electron micrograph show ing a primitive intercalated disc between cardiomyocytes. Scale bar = I Figure 4. Electron micrograph of an undifferentiated cell (uc) adjoining cardiomyocytes (m) in the Achatina myocardium. Scale bar = 2 jam. Inset: a spot desmosome (arrow) between the undifferentiated cell (at the upper pan of the figure) and a mature cardiomyocyte (at the lower part of the figure). Scale bar = ;um. Figure 5. Electron micrograph of a cardiomyocyte at the early stage of myodifferentiation. A few myo- filaments embedded in an amorphous material (arrow) can be seen. Scale bar = 2 ^m. heart are myogenic. The autoradiographic experiments sup- ported this view. As evident from test I with a short [3H]Tdr-pulse, UCs are capable of DNA synthesis, but muscle cells, including those at the earliest stages of myo- differentiation. are not. The appearance of labeled myonu- clei in test II with a delayed fixation indicates that UCs underwent mitosis and myodifferentiation within the first several hours after [3H]Tdr injection. Furthermore, the la- beled UCs were also present in the heart tissue fixed 14 days after isotope injection. Since [?H]Tdr was available in he- molymph for only 2 h. it may be that not all UCs differen- tiated into myocytes after DNA synthesis and mitosis: that some daughter UCs might remain undifferentiated and com- pose a defined population. Thus, in the snail heart. UCs could produce a renewable population and eventually func- tion not only as a reserve but also as stem cells for the myocytes. The counts of labeled nuclei showed that their numbe
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
