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The 13th Symposium on Polar Science/Ordinary sessions [OM] Polar meteorology and glaciology, Wed. 16 Nov.

The Karoonda CK4 chondrite exhibits pronounced silicate darkening of matrix and chondrule mesostases. Our scanning electron microscope study showed that the Karoonda matrix contains unusual olivine, with a high density of vesicles and inclusions of mainly magnetite and pentlandite, all between 0.1 and 3 μm in diameter. The vesicular and nonvesicular olivines occur as an intermixture, and vesicularity is particularly abundant in regions that exhibit a high degree of silicate darkening. Our transmission electron microscope study revealed that the vesicular olivine is entirely crystalline and contains a high density of much smaller (< 10 to 100 nm) vesicles and inclusions of mostly pentlandite. In contrast, nonvesicular olivine contains no such inclusions. The observations indicate that the silicate darkening is caused by the dispersion of not only opaque mineral inclusions but also vesicles, and the microinclusion-rich vesicular olivine is the principal cause of the silicate darkening. The texture and mineralogy of the vesicular olivine suggest that it was formed by crystallization of melt that was produced from nonvesicular olivine by shock at a high temperature.

The ultrastructure of the parathyroid glands of adult Japanese lizards (Takydromus tachydromoides) in the spring and summer season was examined. The parenchyma of the gland consists of chief cells arranged in cords or solid masses. Many chief cells contain numerous free ribosomes and mitochondria, well-developed Golgi complexes, a few lysosome-like bodies, some multivesicular bodies and relatively numerous lipid droplets. The endoplasmic reticulum is mainly smooth-surfaced. Cisternae of the rough endoplasmic reticulum are distributed randomly in the cytoplasm. Small coated vesicles of 700-800 Å in diameter are found occasionally in the cytoplasm, especially in the Golgi region. The chief cells contain occasional secretory granules of 150-300 nm in diameter that are distributed randomly in the cytoplasm and lie close to the plasma membrane. Electron dense material similar to the contents of the secretory granules is observed in the enlarged intercellular space. These findings suggest that the secretory granules may be discharged into the intercellular space by an eruptocrine type of secretion. Coated vesicles (invaginations) connected to the plasma membrane and smooth vesicles arranged in a row near the plasma membrane are observed. It is suggested that such coated vesicles may take up extracellular proteins. The accumulation of microfilaments is sometimes recognized. Morphological evidence of synthetic and secretory activities in the chief cells suggests active parathyroid function in the Japanese lizard during the spring and summer season.

Electron-microscopic studies were made on the parathyroid gland of cadmiumtreated mice. Most chief cells in treated mice were rich in free ribosomes and secretory granules compared to the control mice. In the parathyroid gland after 3 and 4 weeks of administration of cadmium, interdigitations between adjacent chief cells became more complex than in the control mice. In most chief cells of the parathyroid gland after 2, 3 and 4 weeks of administration of cadmium, the Golgi complexes associated with numerous prosecretory granules were better developed than in the control mice. These ultrastructural appearances suggest that parathyroid gland cellular activity was stimulated in response to cadmium treatment.

The immunocytochemical localization of parathyroid hormone was examined in the hamster parathyroid gland by using the protein A-gold technique. Protein A-gold particles were concentratedover secretory granules, large secretory granules thought to be storage granules and Golgi vacuoles. No protein A-gold particles were detected over large vacuolar bodies and cisternae of the granular endoplasmic reticulum.

The frequency of lipid droplets in the parathyroid glands of young, adult and senile golden hamsters after starvation was investigated. In the parathyroid glands of the young and senile golden hamsters, the number of lipid droplets increased to reach a peak by 2 days, then decreased slowly by 5 days after starvation, and decreased rapidly after refeeding. In the glands of adult animals it increased to reach a peak by 5 days after starvation and decreased rapidly after refeeding.These findings suggest that in the fasting condition there is a relationship between the number of lipid droplets and aging.

The fine structure of the parathyroid glands of propranolol-treated hamsters subjected to 5 × gravity environment was studied. In the parathyroid glands of the propranolol-treated hamsters exposed to hypergravity environment, the volume density occupied by the Golgi complexes and cisternae of the granular endoplasmic reticulum was increased as compared to that of propranolol-treated hamsters and was decreased as compared to that of hamsters exposed to a hypergravity environment but was almost similar to that of control hamsters. In addition, many chief cells contained rich free ribosomes, abundant mitochondria and some secretory granules located in the peripheral cytoplasm. These findings suggest that the parathyroid gland which may be suppressed by treatment of propranolol and stimulated in response to a hypergravity environment indicates the secretory activity of the control parathyroid gland.

Ultrastructural aspects of the parathyroid glands of acetazolamide-treated mice were examined. Many chief cells of the treated mice are deficient in free ribosomes compared with the control mice. Most Golgi complexes are poorly developed and associated with a few prosecretory granules. However, relatively numerous secretory granules are observed in the cytoplasm, and a few secretory granules are present in the peripheral cytoplasm. Large secretory granules (storage granules), homogeneously dense bodies with a low electron density, heterogeneously dense bodies containing osmiophilic substance and/or lipid-like material, multivesicular bodies and lipid droplets have apparently increased in number in many chief cells of the experimental mice. Many transitional forms are recognized between each of the large secretory granules and the bodies mentioned above. These ultrastructural features suggest that parathyroid gland cellular activity is suppressed in response to acetazolamide treatment. In addition, correlations of the occurrence of large secretory granules and various bodies are discussed.

Ultrastructural changes in the parathyroid glands of dexamethasone-treated mice were examined. Many chief cells of the treated mice contained a decreased number of prosecretory granules, secretory granules and storage granules, and an increased number of lipid droplets, compared with the control mice. In addition, myelin-like structures associated with cisternae of the granular endoplasmic reticulum were observed in the parathyroid glands of the treated mice. These findings suggest that cellular activity of the parathyroid gland may be suppressed by dexamethasone.

Ultrastructural changes of the parathyroid glands of isoproterenol-treated golden hamsters were investigated. Many chief cells in the parathyroid glands after 5 and 10 minutes of administration of isoproterenol contain well-developed Golgi complexes and granular endoplasmic reticulum, numerous prosecretory granules, and many secretory granules in the peripheral cytoplasm as compared with the control animals. Many chief cells in the parathyroid glands after 1,3,6 and 12 hours of administration have poorly-developed Golgi complexes, granular endoplasmic reticulum, many secretory granules and numerous lipid droplets as compared with the control animals. The morphology of the parathyroid gland after 30 minutes and 24 hours of administration resembles that of the control animals. It is considered that isoproterenol affects the secretory activity of the parathyroid gland.

Immunocytochemical localization of parathyroid hormone was examined in the rabbit parathyroid gland by means of protein A-gold technique. Protein A-gold particles were observed on the secretory granules and the large secretory granules thought to be storage granules. No protein A-gold particles were observed on cisternae of the endoplasmic reticulum and the Golgi apparatus

The cells of origin of nerve fibers innervating the parathyroid gland were studied in the rabbit using the HRP-retrograde transport method. Numerous labeled neurons were observed in the caudal half of the ipsilateral superior cervical ganglion following HRP injection into the parathyroid gland. Furthermore, in the medulla oblongata, labeled neurons were found in the dorsal nucleus of the vagus and many of them were distributed caudal to the level of the obex.

A small granular cell tumor (GCT) of the esophagus, which developed in a 44-year-old Japanese man and was removed by endoscopic polypectomy, is presented. Histopathologically, the tumor, located in the submucosa, was composed of uniform neoplastic cells with nuclei and abundant round or oval cytoplasm containing eosinophilic granules. An immunohistochemical examination showed positive reactions with S-100 protein, especially the beta subunit, and neuron specific enolase in the neoplastic cells. Electron microscopic observation revealed abundant electron-dense or light granules and myelin-like structures in the cytoplasm. These findings support the concept that esophageal GCT is derived from Schwann cells.

The fine structure of the parathyroid glands of golden hamsters exposed to 2, 5 or 10 g environment for 5 h was studied. In the centrifuged hamsters, many secretory granules are located in a peripheral position just beneath the plasma membrane of chief cells, and the Golgi complexes and cisternae of the granular endoplasmic reticulum are significantly increased compared with those of control animals. There are no significant differences between the control and centrifuged animals with regard to secretory granules, large secretory granules, lysosomes, vacuolar bodies and lipid droplets. These findings suggest that the secretory activity of the parathyroid gland may be stimulated in response to hypergravity environment.

The effect of polyamines on ribonucleases in the presence of various inhibitors (poly(G), heparin, and rat liver RNase inhibitor) has been studied. Bovine pancreatic RNas A and a ribonuclease from horse submaxillary gland (RNase HS) were inhibited by the inhibitors, but RNase T1 and RNase M were not inhibited. Polyamines were found to restore the activites of RNase A and RNase HS inhibited by poly(G) or heparin but not those activities inhibited by rat liver RNase inhibitor. When poly(U) and poly(C) were used as substrates, the inhibitory effects of poly(G) and heparin were greater with poly(U) than poly(C) as a substrate. However, when poly(C) was used as a substrate in the presence of either of the above inhibitors, the restoration of RNase activity by sperimine was more efficient. In fact, a stimulatory effect was observed. From the double-reciprocal plots, it was concluded that polyamines restored the activiities of RNases by increasing the availability of the substrate and enzyme to each other. The restoration of enzyme activity by polyamines occurred through the binding of the polyamines to the inhibitor and the subsequent release of enzyme from the inhibitor.

Ultrastructural changes of the parathyroid glands of ovariectomized golden hamsters were investigated. In the parathyroid glands there is a decrease in the area of each cell occupied by the Golgi complex, in the number of prosecretory granules and in the tortuosity of plasma membrane as compared with those of the control golden hamsters. In addition, the area occupied by lipid droplets appears to be increased and the number of secretory granules in the peripheral cytoplasm and large vacuolar body appears to be decreased compared to those of the control animals. These features suggest that the synthesis and release of parathyroid hormone may be suppressed in many chief cells of the ovariectomized golden hamsters.

Ultrastructural changes of the parathyroid glands of starved mice were examined. The parathyroid glands of the starved mice showed a decrease in the volume of Golgi complexes and storage granules and an increase in the volume of lipid droplets, and contained more heterogeneously dense bodies and multivesicular bodies compared with that of the control mice. In addition, the volume of mitochondria, cisternae of granular endoplasmic reticulum and secretory granules and the number of prosecretory granules appeared to be decreased compared to those of the control mice. Myelin-like structures were observed in the parathyroid glands of the starved mice. The results of our study provide support for the hypothesis that starvation exerts an inhibitory influence not only on the synthesis but also on release of parathyroid hormone.

The ultrastructure of the parathyroid glands of hamsters subjected to 5 g environment after an intra-peritoneal injection of isoproterenol was studied. In the isoproterenol-treated hamsters exposed to hypergravity environment, the Golgi complexes, cisternae of the granular endoplasmic reticulum and lipid droplets were significantly increased and secretory granules were significantly decreased compared with those of the control group. In addition, many chief cells contained numerous prosecretory granules in the Golgi areas and several secretory granules were situated close to the plasma membrane of the chief cells. These results suggest that the synthesis and release of parathyroid hormone may be markedly stimulated in the parathyroid glands of the isoproterenol-treated hamsters exposed to hypergravity environment.

Ultrastructural changes of the parathyroid glands of 18-day-old mouse fetuses after administration of calcium chloride (calcium) or ethylenediaminetetraacetic acid (EDTA) were examined. Many chief cells in the parathyroid glands of the calcium-treated mouse fetuses contained poorly developed Golgi complexes and cisternae of the granular endoplasmic reticulum and many secretory granules as compared with those of the control fetuses. Many chief cells in the glands of the EDTA-treated mouse fetuses contained well-developed Golgi complexes and cisternae of the granular endoplasmic reticulum and many prosecretory granules as compared with those of the control fetuses. These findings suggest that calcium or EDTA affects the secretory activity of the parathyroid gland of the mouse fetus.

The ultrastructure of the parathyroid glands of calcium-treated golden hamsters subjected to 5 gravity environment was studied. In the calcium-treated animals exposed to hypergravity environment, the Golgi complexes and cisternae of the granular endoplasmic reticulum were significantly decreased compared with those of the animals exposed to hypergravity environment only and appeared to increase compared with those of the calcium-treated animals, but were almost similar to those of the control animals. In addition, many chief cells contained some prosecretory granules in the Golgi areas, some secretory granules situated close to the plasma membrane and many lysosomes. The morphology of the parathyroid glands in the calcium-treated animals exposed to hypergravity environment resembled that of the control animals. These results suggest that the parathyroid glands suppressed by treatment of calcium and stimulated in response to hypergravity environment may indicate the secretory activity of the parathyroid glands of the control animals.