F.P.J.G. Lafeber

Studies on teleost corpuscles of Stannius : Physiological and biochemical aspects of synthesis and release of hypocalcin in trout, goldfish, and eel

Hypercalcemia (induced by CaCl2-injection or seawater exposure of the fish) reduced the hypocalcin content of corpuscles of Stannius (CS) in trout, goldfish and eel; concomitantly the synthetic activity of CS of hypercalcemic fish, as determinedin vitro, was enhanced. The monomeric forms of prohypocalcin and of hypocalcin of trout and goldfish are 32 and 28 kDA Mr glycoprotein species respectively; those of the eel are 2 kDa bigger,viz. 34 and 30 kDa respectively. Moreover, eel CS producein vitro an enigmatic 70 kDa glycoprotein with affinity for concanavalin-A. It is concluded that plasma calcium levels control storage and synthesis rates of hypocalcin in the CS.

Characterization of antisera raised against hypocalcin (teleocalcin) purified from corpuscles of stannius of rainbow trout, Salmo gairdneri

Highly specific antisera were raised against hypocalcin, a 54-kDa glycoprotein purified from the corpuscles of Stannius (CS) of rainbow trout, Salmo gairdneri. The specificity of the antisera was determined by using Ouchterlonys double immunodiffusion test, radioimmunoassay (RIA), enzyme-linked immunosorbent assay (ELISA), and immunocytochemistry. In the double immunodiffusion test, a single precipitin line was formed between the antisera and hypocalcin. Both RIA and ELISA studies showed that serial dilutions of hypocalcin, teleocalcin, and CS extracts produced dose-response curves, whereas rat FSH, chicken LH, bovine TSH, salmon calcitonin, bovine parathyroid hormone, and human angiotensins I and II failed to cross-react with the antiserum. Immunoreactive hypocalcin was demonstrated in the plasma of a teleost (flounder), but not of an elasmobranch (dogfish). In the immunocytochemistry, most of the gland cells showed strong immunoreaction with the antisera, whereas some cells displayed no immunoreactivity.

Immunocytochemical demonstration of a novel system of neuroendocrine peptidergic neurons in the pond snail Lymnaea stagnalis, with antisera to the teleostean hormone hypocalcin and mammalian parathyroid hormone

Immunocytochemical staining with antisera raised against trout hypocalcin, the hypocalcemic hormone of the Stannius corpuscles and against bovine parathyroid hormone (bPTH1-84), revealed a new system of neuroendocrine neurons in the pond snail Lymnaea stagnalis. The neurons are located in small groups or single cells in the visceral, parietal, and pedal ganglia of the central nervous system. The axons of these cells are running to the periphery of the pleuroparietal, visceroparietal, and pleuropedal connections, the dorsopedal commissure, and to several nerves originating in the visceral, parietal, and pedal ganglia. The axons are ending with characteristic axonal distensions in the periphery of these connectives, commissure, and nerves. These regions probably act as neurohaemal areas. The affinity of this neuroendocrine system for both the anti-hypocalcin and anti-PTH sera is another indication for a special relationship between hypocalcin and PTH, which possess some immunological resemblance and similar biological activities, although no similarity in primary structure.