淡水魚類肝細胞,細胞形質の超微細構造に関する観察
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概要
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Studies were made on the liver cell of the crucian carp (Carassius auratus), freshwater fish found in this country, with electron microscope. The following observations were made: 1. There were scattered in the cytoplasm of a liver cell an innumerable microsome granules, which were divided into the following two kinds: the C-microsome, about 5 mμ in size, with high electron density, and the S-microsome, approximately 30 mμ in size, having low electron density. These microsome granules were connected with one another with threadlike structures, i. e. Morita's A-substance (1958). 2. Studies of the liver cell taken from the fish living in a normal environment during the summer revealed that the structures connecting these microsome granules often formed a close network, with a great number of enlarged vesicular granules inside it, which frequently presented the appearance of a mass of granules. It seemed that each these vesicular granules, which were considered to have grown out of the microsome granules, would further develop to become the endoplasmic reticulum. 3. The limiting membrane of an endoplasmic reticulum was composed of the A-substance as well as a great number of C-microsomes and S-microsomes. This is what Morita (1958) called the "Am-membrane." 4. The endoplasmic reticulum of the cytoplasm of the liver cell taken from the fish living in a normal condition during the winter was mostly vesicular in form. There was no evidence that it was of a large sac form. No endoplasmic reticulum was found in some of the cells. In appearance, the endoplasmic reticulum of the liver cell at this time of year bore a close resemblance to that of the liver cell of the fish undergoing hunger tests for a long period. This would indicate that the crucian carp passes the winter in a state of hunger, tantamount to hibernation. The mitochondria, which were greatly reduced in number, presented semicircular or oval, and rarely rod-shaped, appearance at this time of year.The mitochondria of round shape were observed in the cytoplasm of the liver cell of the fish undergoing 3-month hunger tests during the winter. 5. The endoplasmic reticulum of the cytoplasm of the liver cell of the fish living in a normal environment during the spawning season was well developed, but had no vesicular granules which were gathering together to form masses. 6. Conglomerations of vesicular granules were scattered in the periphery of the cytoplasm of the liver cell of the fish after 2-week hunger tests. There were also the vesicular granules which were scattered independently of each other. In the fish after 3-month hunger tests during the same season, these vesicular granules, which had similarity to the endo-plasmic reticula, were scattered in the cytoplasm in an orderly manner. 7. It seemed that the Cristae mitochondriales came into being through fusion of the S-microsomes which had grown in size and had come to present the appearance of a chain in the mitochondria. These Christae mitochondriales were seen sometimes to have a communication, through the limiting membrane of the mitochondria, with the threadlike structures connecting the microsome granules, 8. The cytoplasm had well; developed intracellular bile canaliculi, which seemed to be the tree-shaped ramification of an intercellular canaliculus extending into the cytoplasm. There are two kinds of intracellular bile canaliculi: one kind having the microvilli in the free surface of the lumen was called by the author the "primary intracellular canaliculiculus", and the other which is a branch and has no microvilli was called the "secondary intracellular bile canaliculus". Near the end of the secondary canaliculi, there often were the vesicular bodies which, being blind, were considered to be a reservoir of secretion. 9. The vesicular structures located near the end of the intracellular bile canaliculi seemed to grow into slightly larger vacuolar structures through fusion, which in turn would become the secondary intracellular bile canaliculi.These vesicular structures were named the "secretory vesicles". 10. The substance which makes up the microvilli of the intracellular bile canaliculi is not homogeneous, but has different structures. The so-called chains of microsome granules were seen in some of the microvilli. 11. The mechanism of the secretion and flow of the bile in the liver cell of the crucian carp would seem to be roughly as follows: the bile is secreted by the secretory vesicles which have developed from the microsomes, and flow into the slightly larger secretory vacuoles which have arose from the secretory vesicles through fusion. It then flows into the intracellular bile canaliculi, and finally into the intercellular bile canaliculi. 12. The Golgi apparatus is sometimes found in the cytoplasm around any primary intracellular canaliculus. There sometimes is a communication between the Golgi membrane and the limiting membrane of the mitochondria. This seems to suggest that there is an affinity between the two from the developmental viewpoint. It would seem that the vesicles, one of the constituent elements of the Golgi apparatus, arise from the so-called spindle vesicles.
- 千葉大学の論文