Response of calcitonin cells, parathyroid, serum calcium and serum inorganic phosphorus during glucagon-induced hypocalcemia in the house shrew, Suncus murinus.
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Biomedical subjects
Publications and source records attributed to K Swarup.
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The administration of calcitonin (4 MRC units injected intraperitoneally daily for 42 days) caused hypocalcaemia, hypophosphataemia and a decrease in the serum acid phosphatase level in adult Indian palm squirrels, Funambulus pennanti. Hypocalcaemia and the decrease in the serum acid phosphatase level persisted up to 21 days but the hypophosphataemic effect continued throughout the experiment. The serum calcium level increased from day 28 up to day 35 and the serum acid phosphatase level reached the control level at 28 days. At the close of the experiment (42 days), both serum calcium and acid phosphatase levels were again decreased. Calcitonin-induced hypocalcaemia resulted in hypertrophy of calcitonin cells which were densely packed with secretory granules up to day 21 of the treatment. Thereafter they displayed both hypertrophy and hyperplasia till the end of the experiment. Some calcitonin cells showed degranulation after 35 and 42 days of treatment. Few lead-haematoxylin-positive calcitonin cells with collapsed membranes and pyknotic nuclei were also seen in the lumina of the thyroid follicles toweards the close of the experiment. Parathyroid chief cells showed hypertrophy from 21 to 35 days of the treatment. From day 28 to the close of the experiment they released their secretory product. After 42 days of experimental treatment a growth-promoting effect of calcitonin was observed (increase in body weight and femur weight.
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Hypercalcaemia (induced by calcium-rich environment and vitamin D2 treatment) activates the ultimobranchial body of Rana cyanophlyctis. This is expressed by hyperplasia of follicular cells, formation of secondary follicles and increased vascular supply to the UBB. This activity of the gland is to counteract hypercalcaemia.
Jackal (Canis aureus) puppies (10) were subjected to hypocalcaemia by a single intravenous injection of crystalline porcine glucagon (Eli Lilly and Co.) in a dosage of 0.2 mg/kg body weight. Fasting blood samples from each specimen were collected 30 minutes before injection. Then again after an interval of 15, 30, 60, 90, 120, 150, 180, 210, 240, 270 and 300 minutes blood samples were taken. For histological study animals were killed after 30, 90, 120, 240 and 300 minutes of the injection. The mean serum calcium level records a fall upto 90 minutes but it tends to return to normal and at 300 minutes it returns to the preinjection level. The mean serum inorganic phosphate level records a fall upto 180 minutes and therafter the value increases approaching the preinjection levles after 300 minutes. Specific stains were used for staining the calcitonin cells. Animals killed 30 minutes after the injection exhibit beginning of degranulation of secretory granules in their C cells, while those killed after 300 minutes show marked degranulation. A progressive degranulation of calcitonin cells at the various stages of experimentation displays correspondingly poorer response to the staining reaction. There is no change in the histological picture of the parathyroid.
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The UBB of Notopterus notopterus is a paired structure situated between the oesophagus and sinus venosus. Both right and left lobes of the gland are enveloped by a common thick connective tissue which gets constricted between the lobes and separates them. Numerous follicles of varying sizes are encountered in each gland. In N. notopterus the effects of hypercalcaemia (caused by keeping the specimens in 0.5% of CaCl2 solution and by injecting 4000 I.U. of vitamin D2 on alternate days) on UBB has been observed. The effects of NaCl rich environment (created by keeping the fish in 0.5% NaCl solution) on this gland has also been studied. In the UBB of N. notopterus the activity of the gland is observed in terms of: 1. increase in the blood supply of the gland and the dilation of the blood vessel, 2. increase in the height of the follicular epithelium, 3. cytoplasmic hypertrophy resulting in the increase in secretory processes, 4. appearance of pseudostratified epithelium in place of single layered cuboidal follicular epithelium and 5. nuclear and cellular hypertrophy. According to these characteristics it is evident that the gland from group II shows gradual activity from the 2nd day onwards and is maximum on the 6th day. From 8th day to the close of the experiment gradual inactivity of the gland is discerned--follicles get atrophied and the cells appear in clumps. The gland from group III shows a good response to its environment and is more hypertrophied as compared to that of group II. The activity of the gland closely parallels serum sodium levels which increase up to the 8th day when UBB shows the maximum activity. The serum sodium level rises from a normal of 110 m eq/l to a peak of 180 m eq/l on 8th day. After 10 days onwards the gland shows gradual inactivity and degeneration. The serum sodium level is 130 m eq/l on 12th day. These observations support the view that the main role of UBB in N. notopterus lies in sodium metabolism and it is only partially responsible for calcium regulation.
1. Hypercalcemia was induced in S. murinus by alternate day intramuscular injections of vitamin D (25 000 IU) and by providing them 1% CaCl2 solution (prepared in tap water) for drinking. 2. After such a treatment the serum calcium values recorded a rise as compared to those of the control specimens. 3. The histological picture of the thyroid of the treated specimens reveals increased number of calcitonin cells. This observation is supported by the occurrence of mitotic figures among them. 4. Perpetual calcium challenge results in degranulation of the secretory material (calcitonin) among these cells (at 26th and 30th day of treatment). 5. It also results in degenerative changes in certain number of C cells. 6. The blood capillaries around these cells get dilated and secretory granules of C cells tend to gather at the periphery of cytoplasm and towards vascular pole. 7. The parathyroid shows atrophic changes.
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A chronic hypercalcaemia was induced in Suncus murinus by the daily subcutaneous injections of parathormone for 15 days. Serum calcium increased 4 hours after the first injection (+ 0.88 mg/100 ml), it reached its highest value on day 10 (+ 2.18 mg/100 ml), and then decreased slightly at the end of the experiment (day 15). The serum phosphate level in treated animals showed a progressive fall throughout the experiment. Serial sections of thyroid-parathyroid complex were subjected to selective staining for C cells identification. The chronic hypercalcaemia increased the number of C cells. This was supported by the presence of mitotic figures. Degranulation of the secretory material was observed as the result of the chronic hypercalcaemia; degenerative changes were found in some C cells. The chronic hypercalcaemia also inhibited the activity of parathyroid "Chief-Cells" which ultimately degenerated.
The present report deals with the occurrence of calcitonin cells (C cells) and cysts in the parathyroid IV of Suncus murinus. Histological preparations of the thyro-parathyroid complex reveal that (i) the parathyroid IV exhibits C cells either solitarily or in small groups (compact or follicular arrangement); (ii) the parathyroid IV also exhibits cysts (similar to those of the thyroid), the lining of these may contain either few C cells or it may be a continuous lining of C cells; (iii) the lumina of these cysts are filled with debris and desquamated cells with pycnotic nuclei, and (iv) sometimes few C cells are encountered hanging from the epithelial lining inside the lumen of the cyst.
Long term hypercalcaemia was induced in F. pennanti by alternate day intramuscular injections of 50,000 IU of vitamin D2 and by giving them 1% CaCl2 solution prepared in tap water to drink. The controls were not injected with vitamin D2 and were given tap water. The serum calcium levels at various stages of the experiment (1-29 days) show increased values as compared with those of control animals. The calcitonin cells in the treated animals generally exhibit an increase in their number up to the 15th day. Mitotic figures are also encountered between the 7th and the 15th day of treatment. This exhibits the increase in the number of C cells. Constant calcium challenge results in increased quantities of secretory granules among these cells up to the 15th day and in degranulation from the 17th day onwards. It also causes degenerative changes in a certain number of C cells. The parathyroids exhibit atrophic changes (25 days onwards) due to chronic hypercalcaemia. For short term hypercalcaemia, animals were injected intravenously with 1 ml of 10% solution of calcium gluconate. The calcitonin cells do not exhibit any change during the first half hour but thereafter they exhibit progressive degranulation, resulting in marked degranulation after 5 hours of the injection. The parathyroids remain unaffected throughout the experiment and show no histological change.
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1. The thyroid gland of 4 month old Wistar rats (both sexes) were made into serial sections and investigated by means of haematoxylin-eosin, PAS-haematoxylin, Davenport's silver impregnation and lead haematoxylin stainings. Calcitonln (C) cells are easily discernible by these techniques. 2. These cells are unevenly distributed and randomly concentrated in the thyroid. They are completely absent from cephalic and caudal poles of thyroid and are generally present in its middle region. They are scare in peripheral follicles and plentiful among central follicles. 3. The isthmus and the parathyroid are completely devoid of C cells. 4. Secretory granules in these cells have a tendency to concentrate towards vascular pole. 5. The unusual follicle is lined by squamous cells and filled with desquamated cells. C cells are completely absent from its epithelial lining.
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