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Biomedical subjects

A Jullienne

Publications and source records attributed to A Jullienne.

At least 55 records · Page 3Linked to original sources
PubMed1992

Transforming growth factor-beta enhances calcitonin-induced cyclic AMP production and the number of calcitonin receptors in long-term cultures of human umbilical cord blood monocytes in the presence of 1,25-dihydroxycholecalciferol.

Transforming growth factor-beta (TGF-beta) is a multifunctional polypeptide, abundant in bone, that regulates both proliferation and differentiation of a wide variety of cells, but its role in osteoclast differentiation remains controversial. We have recently shown that long-term cultures of human cord blood monocytes, in the presence of 1,25 dihydroxycholecalciferol (1,25-(OH)2D3), give rise to cells that express two markers of the osteoclast phenotype, namely, the vitronectin receptor (VNR) and the calcitonin receptor (CTR). TGF-beta enhanced the proportion of cells expressing the VNR. In the present study, we investigated the effect of TGF-beta on the expression of CTR in cord blood monocytes cultured during 3 weeks in the presence of 1,25-(OH)2D3. When added within the first 2 weeks of culture, TGF-beta (500 pg/ml) significantly decreased the cell protein content. TGF-beta alone did not stimulate basal cAMP production. The 10 nM-sCT-stimulated cAMP production was enhanced by increasing TGF-beta concentrations from 50 pg/ml to 1,000 pg/ml: for 500 pg/ml TGF-beta, it was 294 +/- 28% vs. 140 +/- 25% for control cultures (p less than 0.01). The sCT dose-response curves showed a higher cAMP production from 10(-9) M to 10(-7) M of sCT in the presence of 500 pg/ml TGF-beta than in control cultures. The increase was 325 +/- 36% in the presence of TGF-beta and 195 +/- 13% in the absence of TGF-beta, for 10(-7) M sCT (p less than 0.01). This effect of TGF-beta on cAMP production was not observed either when it was added to monocyte cultures the last day or 2 hours before the end of the culture or in MCF7, a human breast cancer cell line that expresses CTR. [125I]-sCT binding studies performed on confluent cells showed similar Kd in control and TGF-beta-treated cells. By contrast, the CTR number was significantly increased in the presence of TGF-beta: 6.1 +/- 2 x 10(4) receptors per cell in control cultures and 28.8 +/- 8.1 x 10(4) receptors per cell in TGF-beta-treated cultures (p less than 0.05). It is thus suggested that TGF-beta increases the number of CTR of these cells that have other features of preosteoclasts. The role of this cytokine on the process of osteoclast differentiation and in bone resorption is thus emphasized.

Autoradiography↗
PubMed1991

A novel calcitonin carboxyl-terminal peptide produced in medullary thyroid carcinoma by alternative RNA processing of the calcitonin/calcitonin gene-related peptide gene.

The calcitonin/calcitonin gene-related peptide gene expresses two different mRNAs by tissue-specific alternative processing. The calcitonin mRNA is produced in thyroid C cells by splicing of the first three exons to the fourth polyadenylated exon. It encodes a protein precursor containing an amino-terminal peptide, calcitonin, and a carboxyl-terminal peptide (CCP I). Calcitonin gene-related peptide (CGRP) mRNA is produced in neuronal cells by splicing of the three common exons to the fifth exon and the polyadenylated sixth exon, leading to the production of a CGRP precursor. Our studies concerning the expression of the calcitonin/CGRP gene in human medullary thyroid carcinoma revealed the presence of a new RNA transcript. Amplification by polymerase chain reaction and direct sequencing showed that the novel transcript is composed of exons 1, 2, and 3, part of exon 4, exon 5, and a polyadenylated exon 6. This transcript contains an open reading frame coding for the known amino-terminal and calcitonin peptides, as well as for a novel calcitonin carboxyl-terminal peptide, CCP II. This third alternative pathway utilizes an internal donor site within the exon coding for calcitonin. The presence of CCP II was demonstrated in plasma and thyroidal tissues of medullary thyroid carcinoma patients, implying that this novel mRNA is actively translated in medullary thyroid carcinoma.

Amino Acid Sequence↗
PubMed1991

Binding sites of calcitonin gene related peptide (CGRP) to trout tissues.

We localized specific binding sites for human calcitonin gene related peptide (hCGRP) in different organs of the trout using labelled human CGRP. Maximal binding was observed in gill and spleen membranes. The binding of 125I-hCGRP was time and temperature dependent. Scatchard analysis of binding data for the spleen and the gills disclosed two binding sites. The constants for the site of high affinity and low capacity (KAM-1 and Bmax (fmol/mg of proteins] were 2.9 x 10(9) for the spleen and 70 and 3.5 x 10(9) for the gill. Salmon calcitonin (sCT) inhibited the binding of 125I-hCGRP to spleen membranes with the same order of potency as hCGRP. In contrast sCT was less effective than hCGRP in suppressing the specific binding of 125I-hCGRP to gill membranes.

Animals↗
PubMed1991

Human umbilical cord blood monocytes express calcitonin receptors in culture in the presence of 1,25 dihydroxyvitamin D.

Calcitonin (CT) is a potent inhibitor of bone resorption and there are abundant CT receptors on mature osteoclasts. The relationship between osteoclast precursors and monocyte lineage is far from clear. We recently showed that human cord monocytes in culture, by contrast to adult monocytes, develop some features of osteoclast precursors. We therefore assessed the presence of CT receptors on monocytes. We could not demonstrate any CT receptors on adult monocytes. By contrast, we observed in cultured cord monocytes increased cAMP production in presence of CT. This cAMP response was observed after a 2-week culture and only in the presence of 10(-9) M 1,25-dihydroxyvitamin D. After a 3-week culture, CT 10(-9) to 10(-6) M increased cAMP production dose dependently from 10(-9) M; however the curve was shallower than the one observed in a control CT receptor positive tumoral cell line, MCF7. 125I sCT bound specifically to cord monocytes cultured during 3 weeks; apparent dissociation constant (Kd) was 3.3 +/- 2.2 10(-10) M and average receptor number was 5.1 +/- 0.4 10(4)/cell. On autoradiography all the cells, whether mono or multinucleated, were labeled with 125sCT. One or 2-h exposure to salmon CT did not induce cell contraction. In conclusion, CT receptors can be induced on newborn cord monocytes in the presence of 1,25-dihydroxyvitamin D. This observation shows that osteoclasts and fetal monocytes share a common membrane determinant.

Calcitonin↗
PubMed1991

Parathyroid hormone related protein (PTHrP) and breast cancer.

PTHrP, a newly characterized peptide is responsible for humoral hypercalcemia of malignancy in squamous cancers. It is also expressed by a variety of normal tissue and might have growth factor propriety. It is expressed by lactating breast and is frequently present in breast cancer. Although it is responsible for humoral hypercalcemia in an animal model of breast cancer its role in breast cancer hypercalcemia is still putative. The possibility that it might be one of the autocrine growth factors implicated in breast cancer cell proliferation has been suggested.

Animals↗
PubMed1990

Expression of the calcitonin gene during migration of the Pacific salmon, Oncorhynchus gorbuscha.

Plasma calcitonin levels increase during reproduction in female salmon. Whether these changes in circulating levels of the hormone are due to increased secretion and or increased biosynthesis is not established. We measured total and poly A+ RNAs and calcitonin content of ultimobranchial bodies of male and female pink salmon during the different stages of the reproductive cycle. Calcitonin mRNAs were analysed by hybridization of northern and dot blots with a specific probe for salmon calcitonin. Dot blot autoradiography indicated that female animals had higher levels of CT mRNA than males and these values were correlated with plasma calcitonin levels. In conclusion, sexual hormones still to be identified, are probably implicated in the expression of the calcitonin gene in females during the reproductive cycle.

Animals↗
PubMed1990

Predicted structure of rabbit N-terminal, calcitonin and katacalcin peptides.

Poly A rich RNA was extracted from rabbit thyroid and cDNA obtained by the action of reverse transcriptase. The cDNA was used to construct a library in lambda GT 11. Screening of the library with a radio-labelled probe specific for human calcitonin allowed the isolation of a clone containing an open reading frame with a high homology with human and murine exon 4 of calcitonin/calcitonin gene-related peptide gene. This sequence codes for a typical calcitonin precursor. We deduced the amino acid sequence of rabbit N-terminal peptide, calcitonin and katacalcin.

Amino Acid Sequence↗
PubMed1989

Identification and measurement of calcitonin precursors in serum of patients with malignant diseases.

Previous studies have suggested that molecular species larger than the mature calcitonin (CT) are produced by tumors of different origin. In order to study these species, we developed a monoclonal immunoradiometric assay for calcitonin precursors (CT-pr). This assay was based on both monoclonal antibody KC01 directed to the 1-11 region of katacalcin and monoclonal antibody CT08 directed to the 11-17 portion of CT. The sensitivity of this monoclonal immunoradiometric assay for CT-pr was less than 100 pg/ml. Only one of 131 healthy subjects had CT-pr serum levels greater than 100 pg/ml; this value was therefore selected as the standard serum value in healthy individuals. CT-pr was present in the serum of seven of ten patients with advanced renal failure and in that of 21 of 52 patients (40%) with benign liver disease but was undetectable in sera of patients with other benign diseases. The serum CT-pr level was correlated with that of mature CT in patients with medullary carcinoma of the thyroid. In contrast, the serum CT-pr level was frequently elevated in the absence of a detectable CT level in patients with various malignant tumors and, particularly, in those with either tumors of the neuroendocrine system (60%) or hepatocellular carcinomas (62%). CT-pr was detected in tumor extract from a patient with a hepatocellular carcinoma. Moreover, hybridization experiments with total RNA extracted from this tumor demonstrated the presence of RNAs hybridizing with complementary DNA encoding for common region, calcitonin, and katacalcin sequences. These results show that CT precursors are excreted by numerous cancers and might well be useful biological markers for the follow-up of productive tumors.

Antibodies, Monoclonal↗
PubMed1989

Actinomycin D inhibits the rapid increase in translatable calcitonin mRNA provoked by acute calcium stimulation.

Calcium, injected to rats, elicits a rapid increase in translatable calcitonin mRNA, by acting probably at the post-transcriptional level, as no change in calcitonin mRNA could be detected by hybridization assay. In this study we have measured calcitonin mRNA extracted from rats subjected or not to acute hypercalcemia and pretreated or not with actinomycin D. Calcitonin mRNA was quantified by its ability to direct the synthesis of calcitonin (CT) precursors in a cell free system and by hybridization to a 32P cDNA probe specific for CT mRNA. Actinomycin D, injected 5 hours before calcium administration, decreased the incorporation of 3H adenine in liver and thyroid, but did not inhibit the rise in plasma levels of calcium and CT (measured by radioimmunoassay). The antibiotic was able to inhibit the eightfold increase in translatable mRNA elicited by calcium administration in the control animals. Hybridizable CT mRNA levels were not modified by the treatments. Thus the increase in translatable CT mRNA after calcium stimulation is independent of CT secretion and is probably due to post-transcriptional modifications involving the expression of other gene(s).

Animals↗
PubMed1988

Potassium administration and calcitonin mRNA level in the rat.

We have investigated the acute effects of elevated plasma potassium concentrations on the calcitonin (CT) mRNA level measured by dot-blot hybridization. Plasma CT levels were significantly increased (X2) 30 min after potassium administration (1.2 mmol, KCl/100 g body weight) in adult female rats; a trend towards increased values was observed 10 min after treatment. No change in plasma calcium concentration was induced by the elevated extracellular potassium levels. The amount of CT mRNA measured by dot-blot hybridization was statistically significantly increased 10 min and 30 min (around 47-55%) after potassium treatment. This finding was confirmed by a Northern blot analysis. It is suggested for the first time that the potassium-induced CT release is associated with a slight increase in CT mRNA level. The increased CT secretion was probably mediated through a rise in the ionized calcium concentration of the C-cell.

Animals↗
PubMed1988

Calcitonin-like immunoreactivity and calcitonin gene expression in the placenta and in the mammary gland of the rat.

Recently, the presence of monomeric CT in plasma and milk was reported by others in a lactating woman surgically thyroidectomized. Similarly, the placenta was thought to be a possible source of CT. Since such findings were based exclusively on immunological arguments, we have investigated the CT gene expression in these rat tissues. CT mRNAs were detected by dot-blot hybridization of total RNAs extracted from rat tissues with a 32P-labelled human CT cDNA probe. Subcellular fractions of each tissue were screened for CT-like immunoreactivity using two different antibodies. With one antibody, extracts of the mammary gland and placenta both produced full displacement of labelled human CT from the antiserum and serial dilutions of the extracts gave displacement curves parallel to that of synthetic human CT, which suggests immunological similarity. However, dilution curves were not parallel for the second antibody, and for both antisera, CT-like immunoreactivity was found in all subsellular fractions from nuclei to cytosols. Immunoprecipitation of translation products from poly (A)+RNAs of placenta showed two major bands around 30 kD. Under stringent conditions, the weak hybridization of placental RNAs seen by dot-blot under less stringent conditions disappeared. Northern analyses of total RNAs from the placenta failed to detect mRNA of 1 k base size like in thyroid glands, but hybridization under weak stringent conditions occurred with larger mRNAs (around 4.4 and 2.4 k bases). Immunoprecipitation of translation products from mRNAs of rat mammary glands showed three major bands around 46, 30 and 20 kD. Dot-blot hybridization of total RNAs extracted from mammary glands was also negative.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Sequence and expression of the chicken calcitonin gene.

The avian calcitonin gene was isolated and sequenced; two mRNAs are expressed by tissue-specific alternate splicing. The peptides encoded by the mRNAs are the protein precursors of either calcitonin or calcitonin gene-related peptide (CGRP). Calcitonin is expressed predominantly in ultimobranchial bodies and CGRP in brain.

Amino Acid Sequence↗
PubMed1986

Isolation and partial characterization of the calcitonin gene in a lower vertebrate. Predicted structure of avian calcitonin gene-related peptide.

The gene coding for calcitonin was isolated and characterized in a non-mammalian vertebrate, chicken. Sequencing of the 3'-end of this gene revealed after the calcitonin coding exon, an intron followed by an exon coding for a calcitonin gene-related peptide, which displays significant amino acid sequence homology with mammalian CGRPs so far sequenced.

Amino Acid Sequence↗
PubMed1986

Calcitonin mRNA activity in genetically obese rats.

The etiology of the alterations in calcitonin (CT) secretion and plasma calcium of genetically obese (fa/fa) rats is unknown. In this study, we tested the postulate that there is an early occurrence of abnormalities in CT biosynthesis by thyroid glands of these rodents. Male genetically obese Zucker (fa/fa) rats and their lean littermates were therefore studied from 30 days to 10 months of age. Obese animals were characterized by hypercalcemia (delta approximately equal to 1 mg/dl), already present at 30 days of age. Increased thyroidal CT stores began at 6 weeks of age in fatty rats. Plasma CT levels were decreased in obese animals from 30 days to 10 weeks of age and were not different in leans and fatties 2 weeks later, but were higher at 10 months in fatty rats. Poly A + RNA were extracted from thyroid glands and subjected to translation assays. After SDS-PAGE, specific immunoprecipitates were autoradiographed and quantified by integration. A similar translation product with an apparent mol wt of 15,000 was specifically immunoprecipitated with CT antisera in obese (fa/fa) and lean Zucker rats at different ages. In 30-day-old fatty rats, a 50% decrease in translatable CT mRNA was observed in association with decreased plasma CT levels. In 12-week-old fatty rats, the translatable CT mRNA activity was unchanged or higher when compared to lean littermates, and clearly higher in 10-month-old fatty rats. The CT mRNA levels measured by dot-blot or northern blot hybridization paralleled at each stage studied the CT mRNA activity, determined by translation. It was concluded that in basal conditions, plasma CT level variations during development reflect the biosynthetic activity of C cells in genetically obese rats. The data presented in this study strengthen the point of an early occurrence of abnormalities in CT mRNA activity and in plasma calcium of fa/fa rats.

Aging↗
PubMed1985

Increased level of calcitonin mRNA after 1,25-dihydroxyvitamin D3 injection in the rat.

Vitamin D metabolites are able to change plasma calcitonin (CT) levels, but nothing is known about a possible effect at the CT gene level. Here we have investigated the acute effects of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) on the CT biosynthetic activity of thyroid glands from adult rats. Plasma CT levels were significantly increased (X2) 1 and 2 h after 1,25-(OH)2D3 injection in the face of unchanged plasma calcium values. The thyroidal CT content also was unchanged. A 2-fold increase in CT mRNA level measured by dot-blot hybridization occurred 1 and 2 h after 1,25-(OH)2D3 administration. Expression of CT gene products was examined in the rabbit reticulocyte lysate cell-free translation assay. After polyacrylamide gel electrophoresis, specific immunoprecipitates were autoradiographed and quantified by integration. A single precursor of Mr approximately equal to 15 000 could be specifically immunoprecipitated with CT antisera. A 3-4-fold rise in translatable CT mRNA activity was observed 1 and 2 h after 1,25-(OH)2D3 injection. Thus, parallel changes in CT mRNA level, CT mRNA activity and plasma CT levels were observed in adult female rats after administration of 1,25-(OH)2D3. These findings demonstrate for the first time that 1,25-(OH)2D3 enhanced CT gene expression in the face of unchanged plasma calcium levels.

Animals↗
PubMed1985

Elucidation of the nucleotide sequence of chicken calcitonin mRNA: direct evidence for the expression of a lower vertebrate calcitonin-like gene in man and rat.

Calcitonin shows considerable divergence in amino acid sequence between lower vertebrates and higher vertebrates. Immunoreactive salmon-like calcitonin molecules are present in the thyroid of man and rat. Elucidation of the almost complete sequence of chicken calcitonin mRNA revealed that the calcitonin precursor in chickens had the same organisation as in higher vertebrates (man and rat) but showed considerable differences in amino acid sequence. cDNA probes specific for chicken calcitonin mRNA hybridized to poly(A)-rich RNA extracted from a case of medullary carcinoma of the thyroid and from murine thyroid. These results suggest the expression in man and rat of a gene coding for an avian calcitonin-like precursor.

Amino Acid Sequence↗