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.

Effects of the insecticide cypermethrin on plasma calcium and ultimobranchial gland of a teleost, Heteropneustes fossilis.

Heteropneustes fossilis were subjected to 5.76 and 1.44 microg/L of cypermethrin for short- and long-term experiments, respectively. Fish were sacrificed at 24, 48, 72, and 96 h in the short-term and 7, 14, 21, and 28 days in the long-term experiment. Plasma calcium levels were determined. Ultimobranchial glands were fixed for histological studies. Plasma calcium levels of fish exhibit a decrease after 48, 72, and 96 h. After 96 h a decrease in the staining response of the cytoplasm of ultimobranchial cells has been noticed. The nuclear volume of these cells undergoes a slight decrease. Chronically exposed fish exhibit a decrease in calcium level on day 7 which persists through 28 days. After 21 days, nuclear volume of the ultimobranchial cells undergoes a decrease and these cells exhibit a slight decrease in the staining response of the cytoplasm. Following 28 days exposure, the nuclear volume undergoes further decrease and degeneration and vacuolization sets in.

Molecular cloning of otoconin-22 complementary deoxyribonucleic acid in the bullfrog endolymphatic sac: effect of calcitonin on otoconin-22 messenger ribonucleic acid levels.

Anuran amphibians have a special organ called the endolymphatic sac (ELS), containing many calcium carbonate crystals, which is believed to have a calcium storage function. The major protein of aragonitic otoconia, otoconin-22, which is considered to be involved in the formation of calcium carbonate crystals, has been purified from the saccule of the Xenopus inner ear. In this study, we cloned a cDNA encoding otoconin-22 from the cDNA library constructed for the paravertebral lime sac (PVLS) of the bullfrog, Rana catesbeiana, and sequenced it. The bullfrog otoconin-22 encoded a protein consisting of 147 amino acids, including a signal peptide of 20 amino acids. The protein had cysteine residues identical in a number and position to those conserved among the secretory phospholipase A(2) family. The mRNA of bullfrog otoconin-22 was expressed in the ELS, including the PVLS and inner ear. This study also revealed the presence of calcitonin receptor-like protein in the ELS, with the putative seven-transmembrane domains of the G protein-coupled receptors. The ultimobranchialectomy induced a prominent decrease in the otoconin-22 mRNA levels of the bullfrog PVLS. Supplementation of the ultimobranchialectomized bullfrogs with synthetic salmon calcitonin elicited a significant increase in the mRNA levels of the sac. These findings suggest that calcitonin secreted from the ultimobranchial gland, regulates expression of bullfrog otoconin-22 mRNA via calcitonin receptor-like protein on the ELS, thereby stimulating the formation of calcium carbonate crystals in the lumen of the ELS.

Responses of the ultimobranchial gland to vitamin D3 treatment in freshwater mud eel, Amphipnous cuchia, kept in different calcium environments.

Freshwater mud eel, Amphipnous cuchia, were injected intraperitoneally daily with 100 ng of vitamin D3/100 g body weight and maintained in media containing either no calcium or different calcium concentrations. The eels were killed after 1, 3, 5, 10 and 15 days following the treatment and their serum calcium levels were measured. The ultimobranchial glands were fixed and processed using the routine paraffin method for histological studies. The results of the present study indicate that vitamin D3 can induce hypercalcaemia in eels kept in different calcium environments. Also, the ultimobranchial glands became hyperactive following vitamin D3 treatment. It is concluded that in mud eels, the gland has a calcium-regulating function.

Expression and development of the proenkephalin mRNA in the C cells of chicken ultimobranchial glands.

A large number of enkephalin-immunoreactive cells transiently appear in chick ultimobranchial glands during embryonic development. The expression and development of proenkephalin mRNA were examined in the ultimobranchial glands by in situ hybridization with digoxigenin (DIG)-labeled oligonucleotide probes, in comparison with those of calcitonin mRNA and enkephalin peptide. Proenkephalin mRNA, as well as calcitonin mRNA, appeared in some C cells at embryonal day 14 (E 14), and in many cells at E 16. Subsequently, there is a marked increase in the level of calcitonin mRNA around E 18-19; all C cells exhibited intense reaction for calcitonin mRNA. After hatching, intensity of calcitonin mRNA expression was more and more increased. Northern blot analysis with the calcitonin probe also indicated that calcitonin synthesis of the C cells progressively increased with developmental gradient, and reached to the adult level at 1 month after hatching. On the other hand, intensity of hybridization signal of proenkephalin mRNA was maintained moderately during development. In contrast to enkephalin immunoreactivity, which is markedly decreased after hatching, proenkephalin mRNA expression was consistently detected in many C cells of 1- and 2-month-old chickens. Reverse transcription-polymerase chain reaction (RT-PCR) analysis confirmed that proenkephalin mRNA was obtained in the ultimobranchial glands of not only embryos but also 1-day- and 1-month-old chickens. Furthermore, Northern blot analysis demonstrated that a single band for proenkephalin mRNA was obtained in the poly (A)+RNA isolated from the ultimobranchial gland of 1-day-old chicks. Thus, the present study evidences that proenkephalin mRNA is synthesized in almost all C cells of chicken ultimobranchial glands throughout life. Enkephalin may be essential for C cell function.

Morphological and functional aspects of reptilian ultimobranchial gland.

The intention of this review is to compare studies on the morphology and histology (light and electron microscopic) of ultimobranchial glands of various groups of reptiles. Moreover, experiments (including our investigations) on suppression or stimulation of the ultimobranchial gland are included. Adult reptiles possess one (on the left side) or two ultimobranchial glands (UBG). The UBG lie just anterior to the heart. Light as well as electron microscopically, the gland has been shown to contain follicles and cell cords (cell aggregates). The follicular epithelium is lined by simple cuboidal or pseudostratified columnar cells. Ciliated and goblet cells may be present in the follicular epithelia in some groups. The lumen may contain a colloid-like substance with desquamated cells or debris. The UBG of reptiles seem to be an active secretory organ with influence on calcium regulation. Other functions of calcitonin have also been suggested in reptiles for example in neurotransmission, in volume regulation, phosphate balance and promotion of bone calcification (at least in juveniles).

[C-cells in the thyroid gland and in the remainder of the ultimobranchial body of bison]. / C-Zellen in der Schilddrüse und in den Resten des Ultimobranchialkörpers des Wisents.

C cells of the thyroid gland of 85 European bison, 43 males and 42 females, of age ranging from 1 month to 25 years were examined. For the identification of the C cells by Grimelius silver impregnation, toluidine blue, pseudoisocyanin and azur A stainings were employed. In the thyroid of the bison the C cells in the central region were distributed denser than in the peripheral region. They may particularly appear in great numbers in the interior of ultimobranchial (UB) remnants; in these cases, however, a great variety of changes has been observed. In part of the adults animals individual differences of the hyperplasia C cells in the preserved UB structures were observed: C cells have not been detected in the internal parathyroid glands. In the discussion, the meaning of paracrine has been described in autoregulatory mechanisms controlling the thyroid activity.

Studies on the hypocalcemic actions of salmon calcitonin and ultimobranchial gland extracts in the freshwater teleost Cyprinus carpio.

A single injection of synthetic salmon calcitonin (sCT) or homologous ultimobranchial gland (UBG) extract caused a significant reduction in total and ultrafiltrable plasma Ca2+ in a freshwater teleost, Cyprinus carpio. A time-bound analysis on the effect of sCT or UBG extract caused a short-duration hypocalcemia and the response was more pronounced in fish kept in low-Ca2+ water. Sexually immature fish showed a greater response than did mature fish. In all the studies the protein-bound Ca2+ fraction remained unaffected. The observation thus indicate a potent hypocalcemic role of calcitonin or UBG in freshwater common carp under laboratory conditions.

Endocrinology of calcium metabolism in amphibians, with emphasis on the evolution of hypercalcemic regulation in tetrapods.

Amphibians are the most diverse group as regards the endocrinology of Ca homeostasis because in them only "true" parathyroid glands made first appearance but its involvement varies greatly according to their phyletic affinities and habitats. Presence of ultimobranchial gland, parathyroid and renal 25-hydroxyvitamin-D-1-hydroxylase enzyme in anurans represents their tetrapod pattern of Ca regulation. Among "higher" urodeles, both parathyroid and pituitary are involved in hypercalcemic regulation whereas in "lower" urodeles (some of them are "aparathyroid" too), pituitary alone appears to discharge this function. The latter situation is analogous to the fish. Apodans do possess ultimobranchial and parathyroid glands but the problem of their Ca metabolism has not yet been explored. This review deals exhaustively with the endocrinology of Ca metabolism in amphibians. Also, the evolution of hypercalcemic regulation in tetrapods will be discussed in the light of recent developments.

Circannual rhythms in the activity of the parathyroid gland and ultimobranchial body cells of the frog Rana temporaria (Anura, Amphibia).

The annual activity of the parathyroid gland cells and those of the ultimobranchial body cells of the frog Rana temporaria is quantitatively investigated by a morphometric study. A cosinor analysis shows a periodic succession of different parameters. The secretory activity of the parathyroid cells starts after a maximal value of external temperature in July. This activity is followed by an increase of plasma calcium which seems to induce the activity of the ultimobranchial cells.

Voltage-gated sodium and potassium currents and their variation in calcitonin-secreting cells of the chick.

1. The electrical properties of dissociated ultimobranchial cells from chick embryos (18-20 days after fertilization) were studied using whole-cell patch electrodes. Antibodies for immunohistological identification of calcitonin-secreting cells in the preparation were obtained by immunizing rabbits with a conjugated analogue of eel calcitonin. 2. In a proportion of cells, spike-like action potentials were generated in response to depolarization when cells were immersed in standard saline containing 140 mM-Na+ but no Ca2+. When the membrane potential was shifted from a holding potential (-83 - -103 mV) to a test depolarization (-50 mV or more positive) under voltage-clamp conditions, a transient inward current was produced which was followed by a slowly developing outward current. 3. The inward current was identified as a Na+-carried current, since (1) the kinetics of the current seemed fast and the amplitude consistently depended on the holding potential, (2) replacement of external Na+ with choline ions reversibly abolished the current, and (3) external application of tetrodotoxin (1 microM) abolished the current completely. The cells in which inward currents were detected showed intense to intermediate degrees of staining with anti-calcitonin antibodies. 4. In some other cells, no regenerative potentials were evoked even with intense depolarization, but a delayed decrease in membrane depolarization during the current pulse was observed. Voltage-clamp experiments in these cells revealed the existence of slowly developing outward currents, and the cells showed an intermediate degree of antibody staining. 5. The outward currents in both types of cells were selectively diminished in the presence of K+ channel blockers such as tetraethylammonium (1-10 mM) or 4-aminopyridine (1 mM). When the pipette contained 120 mM-CsCl, none of the dissociated cells exhibited any appreciable outward currents. Thus, the outward currents were most likely to be membrane potential-dependent K+ currents. The potential dependency of activation and inactivation of the currents were consistent with those of delayed K+ rectifier. 6. In the remaining cells, only passive responses of membrane potentials were observed with current injection. No discernible voltage-dependent inward or outward currents were detected under voltage-clamp conditions. Although these cells had a similar appearance to the two types of cells previously mentioned under phase-contrast microscopy, none of them showed significant antibody staining. These cells were presumed to represent non-secretory or supporting cells within the gland.(ABSTRACT TRUNCATED AT 400 WORDS)

Hypocalcemic potency of the ultimobranchial gland in some urodelan amphibians.

The hypocalcemic potencies of the ultimobranchial glands of two urodelans, Onychodactylus japonicus and Hynobius nigrescens, were studied; according to the rat bioassay, their calcitonin values (MRC) were 30 and 18 mU/kg body wt, respectively. Various organs other than the ultimobranchial gland were also assayed in rats to see whether they had any hypocalcemic potency. However, the ultimobranchial gland was the only organ examined with detectable hypocalcemic potencies in these urodelans. The hypocalcemic potencies of urodelan ultimobranchial glands are one order lower than those reported in the other vertebrate classes, contrasting with the potencies of anuran ultimobranchial glands. The biological significance of this low potency is discussed.

[Seasonal variations of the ultimobranchial body of the turtle (Pseudemys scripta)]. / Sulle modificazioni cicliche stagionali del corpo ultimobranchiale di tartaruga (Pseudemys scripta).

Ultrastructural seasonal cyclic aspects of ultimobranchial body (C.U.B.) in fresh turtles (Pseudemys scripta) are studied. The C.U.B. consists of follicles and cords. The cord cells are characterized by many secretory granules measuring approximately 180 nm with variable feature and electron density. These granules are localized in the cytoplasm close to basal laminae. The follicular cells, on the contrary, present few and large secretory granules, glycogen particles, bundle of filaments and a scarcely developing Golgi apparatus and granular endoplasmic reticulum. The apical and follicular cytoplasmatic membrane is provided with small number of cilia and short microvilli. Seasonal cellular variations are described clearly in the winter (february-march) specimens of ultimobranchial body, these are characterized by more cord aspects and few follicles. The only cord cells present significant ultrastructural changes, represented by more glycogen particles, middle and wide lipid droplets and poor presecretory granules in Golgi zone. These morphological elements orient to a parallelism with the C cells of hibernant animals (Azzali 1967, Frink and Coll.) and the chief cells of parathyroid gland of the self turtle species as by our previous study.