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J Taboulet

Publications and source records attributed to J Taboulet.

32 records · Page 2Linked to original sources
PubMed1986

Purification and characterization of calcitonin receptors in rat kidney membranes by covalent cross-linking techniques.

We have characterized the binding parameters of renal receptors (Scatchard analysis revealed the presence of two binding sites: site I, Ka1 = 1.29 X 10(9) M-1, number of binding sites = 9.9 X 10(6)/micrograms protein; site II, Ka2 = 0.93 X 10(8) M-1, number of binding sites = 4.27 X 10(8)/micrograms protein) and studied the effect of solubilization. The high-affinity sites are preserved during affinity chromatography and the process results in a 6080-fold purification of those sites. The lower-affinity sites are also preserved but the overall purification factor is about 40% lower than that obtained using molecular sieving. The purification of the renal calcitonin receptor by molecular sieving (Sephacryl S-200) is accompanied by total loss of the high-affinity site; however, the low-affinity site is enriched over 1642-fold. Binding parameters were obtained for the purified fractions. Synthetic salmon calcitonin was also bound to renal membranes using the bifunctional reagent disuccinimidyl suberate and photo-affinity cross-linking using hydroxysuccinimidyl azidobenzonate reagent. Cross-linked receptor eluted in the same volume as solubilized membranes specifically binding salmon calcitonin (S-200 chromatography). Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis of purified fractions showed several protein bands with apparent molecular masses ranging from 18 000 Da to 100 000 Da in the presence or absence of a reducing agent (2-mercaptoethanol). Autoradiography of polyacrylamide gels of cross-linked calcitonin receptor showed only three protein bands specifically binding salmon calcitonin. Their molecular masses were 70 000 Da, 40 000 Da and 33 000 Da respectively. The 40 000-Da molecule represents a major band (47% total binding species). This suggests that these three proteins are the principal components of the calcitonin receptor and that S-S bonds are not involved in the assembly of the receptor subunits.

Animals↗
PubMed1984

Ultimobranchial gland of the domestic fowl. Two types of secretory cells involved in calcitonin metabolism.

The ultimobranchial gland (UBG) of birds is particularly rich in calcitonin, the hypocalcaemic hypophosphataemic hormone, that is secreted by the C-cells of the mammalian thyroid. The principal cells of the UBG have a striking resemblance with the mammalian C-cells, i.e., they possess small intracytoplasmic dense-core secretory granules, 150-300 nm in diameter. The gland also contains a second, morphologically distinct, endocrine cell type with larger granules, 500-800 nm in diameter. A sensitive immunocytochemical reaction was developed with the use of antibodies against salmon calcitonin. By means of this technique the presence of calcitonin-immunoreactive molecules was demonstrated in both secretory cell types of the UB gland of the chicken. This gland can thus be considered as a homogeneous calcitonin-producing tissue. Whether the secretory products are identical is discussed and differences in the secretory pathways are suggested.

Animals↗
PubMed1983

Calcium regulating hormones during the estrous cycle of the rat.

Plasma levels of calcium (Ca), phosphate (P), calcitonin (CT), parathyroid hormone (PTH), and prolactin (PRL) were measured at 8, 13, and 17 hr during the 4-day estrous cycle of the rat. Ca levels fell throughout the day during proestrus (PE) and estrus (E). In contrast Ca rose transiently during diestrus (D1, D2). P levels fluctuated inconsistently at all stages of the cycle with the exception of E where P levels were significantly higher at 13 hr. CT levels showed an increase during D1 and D2 and fell to their lowest values during E, at 13 hr. Daily fluctuations in each stage were also recorded. Variations of PTH levels during the estrous cycle were minor. PRL levels increased sharply during PE. No direct relationship between PRL secretion and CT secretion could be established. These results indicate that CT but not PTH varies specifically in relation to the estrous cycle. They suggest that there is a link between sexual hormones and CT, apparently independent of plasma calcium levels.

Animals↗
PubMed1981

Influences of fixatives on the immunodetection of calcitonin in mouse "C" cells during pre- and post- natal development.

The presence of calcitonin in fetal and postnatal mouse "C" cell was demonstrated by radioimmunoassays of fetal and adult thyroid extracts and by immunohistochemistry following the use of Bouin's fixative from 18 days postcoitum onwards. However, after fixation with formaldehyde no calcitonin could be detected in fetal or early postnatal samples, although it was still easily detectable in adult tissues treated with this fixative, raising the possibility that there may be age-dependent differences in the chemistry or physiological state of intracellular calcitonin. Experiments conducted with several other fixatives and the results of the radioimmunoassays suggest that the loss of calcitonin reactivity is not due to differences in the anti-genic sites of the molecule at the two stages in development. Neither can the positive detection of fetal material treated with Bouin's fixative be due to any action of this liquid. However, the inhibiting action of the aldehydes could be related to the preservation of the granule membranes in the fetal "C" cells: our ultrastructural studies show that the granules can be morphologically classified in dense-core and homogeneous matrix. Such granule membranes are abundant in the young and adult "C" cell and would be reactive, while the small dense-core granules are prevalent in the fetus and would be unreactive, confirming the hypothesis of a difference of structure of the granule membrane and not of calcitonin between fetal and late postnatal "C" cells.

Acetates↗
PubMed1979

[Immunohistochemical demonstration of calcitonin cells in the fetal thyroid of mice].

Calcitonin was revealed by means of an indirect immunohistochemical method using a serum against synthetic human calcitonin. After the use of the Bouin-Hollande fixative liquid, the hormone was detected in cells located in the central part of the thyroïdian wings. They are few at the 18th day of fetal life, their number increases regularly until reaching ten times the initial number at birth. The immunological reaction is negative if only aldehyde fixatives are used.

Animals↗
PubMed1975

[Tests of stimulation of calcitonin secretion. Value in medullary cancer of the thyroid].

The detection of high circulating levels of calcitonin is a most valuable procedure to diagnose advanced cases of medullary carcinoma of the thyroid. However, the diagnosis of a primitive tumor in the early stages of development (as in cases of the familial form of the disease) or of a metastasis following ablation of the tumor is more difficult. In the latter cases, the levels of circulating calcitonin may be within normal limits, and for diagnosis one must then resort to tests to stimulate the secretion of calcitonin. We are reporting from our personal experiences the advantages, disadvantages and inconveniences of the three most well-known tests. All patients responded positively to administration of calcium or pentagastrin. The alcohol test, however, produced inconsistent results.

Adult↗
PubMed1975

[Heterogeneity of human calcitonin].

Chromatographic analysis of plasma, urine and tumour tissues extracted from medullary cancer patients demonstrates the existence of immunoreactive calcitonins with higher molecular weight than that of the monomer hormone.

Calcitonin↗
PubMed1975

[Heterogeneity of immunoreactive calcitonin in the plasma of patients with bone marrow cancer].

Plasma from patients with medullary carcinoma containing very high levels of immunoreactive calcitonin were fractionated by filtration on Sephadex gel. In all cases the elution gave four immunoreactive fractions. Two of these fractions correspond to the volume of elution of the monomere and of the dimere of human calcitonin. The two other fractions emerge at an elution volume corresponding to much higher molecular weights. After stimulation of calcitonin secretion in vivo, by dynamic tests, the fractions corresponding to the monomere and dimere increase more strongly than the two other fractions. Preliminary studies of secretion, in vitro, of calcitonin by medullary carcinoma tissue, show the presence in the incubate of four immunoreactive forms having the same elution characteristics as those found in the plasma. The significance of these results is discussed.

Bone Marrow Diseases↗
PubMedDate not supplied

Expression of CGRP mRNAs in the pink salmon, Oncorhynchus gorbuscha.

We report the isolation of calcitonin gene-related peptide (CGRP) mRNAs and expression of these RNAs in different tissues in the pink salmon, Oncorhynchus gorbuscha. Hybridization of poly(A+) RNAs indicated a mature CGRP RNA of 1.1 kb. The CGRP-like immunoreactivity occurring in tissues and plasma had the same relative molecular weight as the synthetic molecule. Variations in CGRP plasma levels were observed during migration, spawning, and postspawning states. These data suggest that CGRP may play an important role during the reproductive cycle of salmon.

Animals↗
PubMedDate not supplied

Calcitonin secretion during the estrous cycle of the rat.

Plasma levels of calcitonin (CT), parathyroid hormone (PTH), and estradiol (E2) were measured in the rat during the estrous cycle. Changes in the circulating levels of CT were observed, in particular a significant fall during estrus. No significant changes in PTH levels were recorded using a N terminal assay. E2 levels were not correlated with CT or PTH levels.

Animals↗