Histological alterations in the ultimobranchial gland of teleost Heteropneustes fossilis in response to chlorpyrifos treatment.

In this study, an experiment was performed on Heteropneustes fossilis for short-term (1.76 mg/L chlorpyrifos, i.e., 0.8 of 96-h LC50) and long-term (0.44 mg/L chlorpyrifos, i.e., 0.2 of 96-h LC50) exposure. The fish were sacrificed after 24, 48, 72 and 96 h in the short-term experiment and after 7, 14, 21 and 28 days in the long-term experiment. On these intervals, blood was collected and analysis of serum calcium was done. Ultimobranchial glands were also fixed for histological study. The serum calcium levels of H. fossilis exhibit a decline after 24 h following exposure to chlorpyrifos. This decrease continues until the end of the experiment (96 h). The serum calcium levels of chronically exposed fish exhibit a decrease on day 7. Thereafter, the levels continue to fall progressively until the end of the experiment (28 days). The ultimobranchial gland of chlorpyrifos treated fish exhibits no histological change up to 48 h. After 72 h, there is a decrease in the staining response of cytoplasm of the ultimobranchial cells. The nuclear volume of these cells is slightly decreased. After 96 h following chlorpyrifos exposure, these changes become exaggerated. In chlorpyrifos-treated fish there is no change in the histological structure of the ultimobranchial gland up to 14 days. After 21 days, the cytoplasm of ultimobranchial cells stain feebly and the nuclear volume of these cells exhibits a decrease. Following 28 days treatment, the nuclear volume of these cells records a further decrease and the gland depicts vacuolization and degeneration at certain areas.

Ultimobranchial gland of a freshwater teleost, Heteropneustes fossilis, in response to cadmium treatment.

Heteropneustes fossilis were subjected to 288 mg/L (0.8 of 96 h LC(50)) and 72 mg/L (0.2 of 96 h LC(50)) of cadmium chloride for short-term and long-term experiments, respectively. After sacrificing the fish, the blood was collected on 24, 48, 72, and 96 h in short-term and after 7, 14, 21, and 28 days in long-term experiment and analyzed for plasma calcium levels. Also, ultimobranchial glands were fixed on these intervals. The plasma calcium levels of short-term cadmium-exposed fish remain unchanged after 24 h. The levels exhibit a progressive decrease from 48 h onwards. The fish exposed to cadmium for 7 days exhibit a decrease in the plasma calcium level. Thereafter, the levels progressively decrease till the end of the experiment (28 days). Up to 72 h exposure of the fish to cadmium, the ultimobranchial gland exhibits no histological change. After 96 h, a decrease in the staining response of the cytoplasm of ultimobranchial cells has been noticed. The nuclear volume of these cells records a slight decrease. Up to 14 days of cadmium exposure, there is no change in the histological structure of ultimobranchial gland. After 21 days following the exposure, the ultimobranchial cells exhibit a slight decrease in the staining response of the cytoplasm and the nuclear volume of these cells records a decrease. Following 28 days cadmium exposure the nuclear volume exhibits a further decrease, and degeneration and vacuolization sets in.

Ultimobranchial gland respond in a different way in male and female fresh water teleost Mastacembelus armatus (Lacepede) during reproductive cycle.

The present study was carried out to analyze the differences in the activity of ultimobranchial gland (UBG) between male and female fresh water teleost Mastacembelus armatus during reproductive cycle. Considerable variations in the nuclear diameter of UBG cells and plasma calcitonin (CT) levels during different reproductive phases of testicular and ovarian cycle suggested that the activity of the UBG depends upon the sexual maturity of fishes. A positive correlation was observed between plasma CT and sex steroid levels and the gonadosomatic index in both sexes which further confirmed the involvement of UBG in the processes related to gonadal development in fishes irrespective of the sex. Sudden increase in the level of plasma CT and nuclear diameter of UBG cells after administration of 17 α-methyltestosterone in males and 17 ß-estradiol in females during resting phase of the reproductive cycle clearly showed that UBG becomes hyperactive with increases in the level of sex steroids. Plasma calcium level was also found to be positively correlated with gonadal maturation in females. However no such change in plasma calcium level in relation to testicular cycle was observed. Thus it can be concluded that UBG becomes hyperactive during gonadal maturation but its role differs between male and female fishes. In females it may involved in both gonadal maturation and plasma calcium regulation while in males its involvement in calcium regulation was not justified. Variations in the level of CT during various phases of testicular cycle evidenced its involvement in gonadal maturation only.

Calcitonin secretion in vitro. III. Synergistic secretory effects of enteric polypeptide hormones.

Crude and highly purified preparations of enteric peptide hormones were shown to stimulate trout calcitonin (tCT) secretion in vitro. Since the maximal stimulatory effects of crude pancreozymin/secretin preparations were seen to be greater than the secretory effects obtained with the individual purified enteric peptides, the current study has focused on the secretory effects of several combinations of enteric peptides. The additive and synergistic secretory effects of various specific peptide combinations are demonstrated. Marked (85-fold) stimulation tCT secretion occurs in response to combinations of synthetic secretin (5 X 10(-5)M) with pentagastrin (10(-6)M) or the carboxylterminal octapeptide of pancreozymin (10(-6)M). These findings have significance with regard to the potentiation of hormone action, and are preliminary evidence for the presence of separate receptors for various enteric peptide secretagogues on C-cells.

Dynamics of plasma Ca and calcitonin levels in stonefish (Inimicus japonicus) administered a high-Ca solution into the stomach.

In stonefish, changes in plasma total Ca and calcitonin levels were examined after administration of a high-Ca solution into the stomach. Blood was taken successively at 0, 1, 3, 9, 33, and 81 hr from a fine tube cannulated into the aortic bulb. Plasma Ca levels increased acutely at 1 hr and attained the peak after 3-9 hr of the administration. Although plasma calcitonin levels did not exhibit conspicuous changes for 1-3 hr, they began to rise significantly at 33 hr. The plasma Ca level began to decline significantly at 33 hr, although the level was still significantly higher than the initial level. At 33 hr, however, the plasma calcitonin level still continued to increase. At 81 hr, the plasma Ca level had returned to the initial level. At that time, the plasma calcitonin level was also significantly lower than that at 33 hr. These results suggest that, in stonefish, the ultimobranchial gland has the ability to respond physiologically to rises in plasma Ca levels, to secrete calcitonin, and to cease the secretion when the plasma Ca levels return to the initial level.

Direct raises in blood Ca levels by infusing a high-Ca solution into the blood stream accelerate the secretion of calcitonin from the ultimobranchial gland in eels.

In eels, a CaCl(2) solution was infused into the pneumatic duct vein. Plasma Ca levels were significantly increased during 3 hr and were followed by significant raises in plasma calcitonin levels. These results strongly suggest that, in eels, direct raises in blood Ca levels by infusion of a high-Ca solution via blood vessels can accelerate the secretion of calcitonin from the ultimobranchial gland.

Influence of prolactin administration on the ultimobranchial body and parathyroid glands of the freshwater snake, Natrix piscator.

The effects of ovine prolactin (10 I.U./100 g body wt) on the ultimobranchial body and parathyroid glands were investigated in Natrix piscator for 15 days. The ultimobranchial body of the prolactin treated specimens depicts signs of increased activity whereas the parathyroid glands exhibit reduced activity.