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G Milhaud

Publications and source records attributed to G Milhaud.

At least 19 recordsLinked to original sources
PubMed1995

Calcitonin secretion, C cell differentiation and proliferation during the spontaneous development of murine medullary thyroid carcinoma.

Medullary thyroid carcinoma (MTC), a C cell neoplasm, synthesizes large amounts of calcitonin (CT), its biological marker. However, in some cases with a poor prognosis, MTC is associated with low basal CT levels owing to a decrease in the thyroid CT content. Using a murine model of human MTC, we studied the relationships between CT biosynthesis, C cell proliferation, and the circulating CT level during MTC progression. Cell proliferation was revealed by autoradiography of radioactive thymidine incorporation in dividing nuclei, after CT or CT mRNA detection by immunocytochemistry (ICC) or in situ hybridization (ISH). All rat thyroids showed a severe hyperplasia of C cells containing significant amounts of CT and CT mRNA, and a very low mitotic index. Tumours were found in 68% of the thyroids. In the strongly immunoreactive small nodules (ICC+), many labelled nuclei were observed. Subsequently some nodular cells, still containing detectable CT mRNA (ISH+), were not detected by immunocytochemistry (ICC-) owing to a dramatic decrease in secretory granules. Their mitotic index increased, and a rise of the basal CT plasma level was noted. These ISH+, ICC- tumour MTC cells represent a modified aggressive tumour C cell population exhibiting an increased ability to proliferate and were detected by the rise in the basal circulating CT level.

Animals↗
PubMed1995

Pharmacokinetics of cadmium following intravenous and oral administration to non-lactating ewes.

In a preliminary study, ewes received daily oral cadmium chloride administrations and cadmium concentration was measured in blood and tissues. A pharmacokinetic analysis of cadmium disposition was then carried out in ewes administered cadmium chloride iv and, 21 months later, orally in the same ewes. Pharmacokinetic parameters were analysed using a 3-compartment open model. The systemic availability was 0.15-0.5%, the half-life of elimination was 100-150 d, the blood clearance was 0.12-0.16 l.kg-1.d-1 and the steady-state volume of distribution was 17-35 l/kg. Following iv administration cadmium was found in tissues about 2 years later.

Administration, Oral↗
PubMed1994

Production of salmon calcitonin I in Oncorhynchus gorbuscha by alternative polyadenylation of two RNA species.

RNAs of ultimobranchial bodies (U.B.) from the pink salmon, Oncorhynchus gorbuscha, were studied using the polymerase chain reaction (PCR) with specific oligodeoxyribonucleotides (oligos) of the salmon calcitonin (sCT) mRNA selected in exon 2 or 3 and a poly(T) oligo. We observed two amplified DNA fragments, differing by 200 bp which hybridized with a specific exon 4 probe. Sequence analysis indicated that they both encoded exon 4, but differed in the length of their 3' non-coding regions by use of a putative polyadenylation signal situated 200 bp upstream from the established polyadenylation site. These two polyadenylation signals very likely were regulated differently, as the larger expressed transcript was predominant. To date, such use of an alternative polyadenylation signal in a CT mRNA has not been described in other vertebrates, and only the chicken CT mRNA possesses a second classical polyadenylation signal which is not known to be used. This characteristic of sCT biosynthesis appears to be typical in lower vertebrates and is of phylogenic interest. Moreover, it engenders a hypothesis of a relationship between the high concentration of the peptide observed in females of this species and their capacity to produce sCT by different biosynthetic pathways.

Alternative Splicing↗
PubMed1992

CCP II: a novel calcitonin carboxy terminal peptide is expressed in normal thyroid tissue.

We have recently identified in medullary thyroid carcinoma the existence of a second calcitonin messenger, generated by a splicing between the 3' coding region of exon 4 and exon 5 of Calc I gene. It differs from the first one in its 3' coding sequence and codes for a calcitonin precursor which generates the same N terminal peptide, calcitonin and a specific 21 amino acid carboxy terminal peptide differing from Katacalcin by its 8 last amino acids. We searched for the expression of this new messenger in normal human thyroid tissue by Northern and by polymerase chain reaction techniques. This second calcitonin messenger was expressed in 4/4 normal thyroids and 4/5 medullary thyroid carcinoma tissue samples. The expression of this second messenger is apparently a common occurrence in C cells whether normal or tumoral.

Amino Acid Sequence↗
PubMed1992

T-lymphocyte control of HLA-DR blood monocyte differentiation into neo-fibroblasts. Further evidence of pluripotential secreting functions of HLA-DR monocytes, involving not only collagen but also uromodulin, amyloid-beta peptide, alpha-fetoprotein and carcinoembryonic antigen.

Previous studies led us to demonstrate in pathological situations that the fibroblast, not the macrophage, was the terminal maturation step of the HLA-DR monocyte and that the entire process came under T-lymphocyte control. Fibrosis which developed under immunosuppressive treatment (cyclosporin) after organ transplantation is an illustration of these in vitro observations. The present in vitro study was undertaken in order to investigate whether or not this transformation process takes place under physiological conditions and if so, the nature of the T-lymphocyte control. We report that normal HLA-DR monocytes/macrophages are able to secrete type 1 collagen and to differentiate into neo-fibroblasts. However, contrarily to what happened in pathology, only a few neo-fibroblasts developed transiently. The addition of conditioned medium (CM) from activated T-lymphocytes greatly enhanced the transformation process. Counteracting this CM effect, cell-to-cell contact between neo-fibroblasts and T-cells resulted in the loss of fibroblastic shape. The 'end-result' macrophage engulfed numerous lymphocytes giving rise to a multinucleated cell. This giant cell no longer adhered to the slide and died. The question is raised as to whether the process observed in vitro is involved in vivo in tissue repair. We also report that HLA-DR monocytes and the neo-fibroblasts which derive from them are able to secrete, in addition to type 1 collagen, a variety of proteins such as uromodulin, amyloid-beta peptide, alpha-fetoprotein and carcinoembryonic antigen. In cystic fibrosis we previously reported a high level of uromodulin production by HLA-DR monocytes differentiating towards the fibroblastic phenotype. Pathologies characterized by excessive production of either alpha-feto-protein, carcinoembryonic antigen, beta-amyloid protein (Alzheimer's disease) should be investigated, taking into account the involvement of HLA-DR monocytes and their possible uncontrolled differentiation into neo-fibroblasts.

Amyloid beta-Peptides↗
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

Fluoride-induced bone changes in lambs during and after exposure to sodium fluoride.

The evolution of bone changes induced by fluoride after the end of exposure was investigated in lambs. Sodium fluoride (NaF) was given orally at a dose of 3.5 mg/kg per day to 14 animals for 120 days. A group of 7 control and 7 treated lambs was slaughtered at the end of NaF administration (T120) and another group 120 days after the end of NaF exposure (T240). At T120, the bone fluoride content (BFC) was very significantly increased in treated animals. The histomorphometric analysis confirmed that fluoride induces an increase in bone formation (the osteoid perimeter and area were 3-fold and 4.5-fold higher respectively in treated than in control animals). The number of osteoblasts was significantly augmented. Serum osteocalcin level was twice as high in treated animals compared with controls. The bone formation rate at the tissue level (BFR) doubled after treatment, but the apposition rate (Aj.AR) was half that in the control group. The mineralization lag time (Mlt) was 120 days in treated animals compared with 42 days in controls. At T240, BFC had decreased by 50% compared with the level at T120, but it was still significantly higher than in controls. The osteoid and osteoblastic parameters were 2 and 1.3 times higher than in control animals. BFR remained significantly increased in treated animals, but Aj.AR and Mlt were similar in control and treated animals. In conclusion, after 4 months of NaF exposure fluoride induced an increase in osteoblast natality and bone formation at the tissue level, associated with a toxic effect at the individual cell level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Calcitonin gene-related peptide immunoreactivity in a crustacean Nephrops norvegicus and correlation with calcitonin.

Immunoreactive calcitonin-gene-related peptide (ir-CGRP) was detected in the crustacean Nephrops norvegicus. High levels of ir-CGRP were present in the foregut and hepatopancreas (3 +/- 0.7 and 4.6 +/- 1.0 micrograms eq per 100 mg of fresh organ, respectively). Molecular sieving of acidic extracts of anterior gut of Nephrops norvegicus showed a high molecular weight immunoreactive peptide in the range 15,000 to 25,000 Da. Immunoreactivity related to salmon calcitonin was present in the high molecular weight fraction.

Animals↗
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

Cystic fibrosis: production of high levels of uromodulin-like protein by HLA-DR blood monocytes differentiating towards a fibroblastic phenotype.

We report here the spontaneous in vitro transformation of blood monocytes into fibroblasts, in a patient suffering from cystic fibrosis (CF). The blood monocytes with this capacity express HLA-DR specificity. Monocytes were identified by non-specific esterase activity and by immunofluorescence using monoclonal antibodies against monocytes/macrophages antigens. Neo-fibroblasts were identified by electron microscopy and immunofluorescence using monoclonal antibodies against a cytoplasmic enzyme specifically involved in the synthesis of collagen. The secretion of collagen was evidenced using antibodies against type I collagen. Both monocytes/macrophages and neo-fibroblasts express the monocytic and the fibroblastic markers and synthesize type I collagen. This transformation observed in vitro might mimick the process of fibrosis development which takes place in vivo, particularly in pancreatic acini, lungs and intestine of patients with CF. Interestingly, the whole process in vitro is inhibited when T lymphocytes are properly stimulated by IL2. In addition, both monocytes and neo-fibroblasts secrete high quantities of uromodulin-like glycoprotein. The significance of this finding is discussed in relation to the thick mucus secretion which characterizes the disease. In addition, from a fundamental point of view, it confirmed in a large series of patients that this observation may have significant implications, since CF mutation impairs the gene coding for cAMP-regulated Cl- channel and that it has been proposed that uromodulin might be implicated in Cl- transport. Therefore the question of the relationships between uromodulin and the cAMP-regulated Cl- channel arises.

Adolescent↗
PubMed1991

The lesson of the Chernobyl disaster.

On April 26, 1986 a major nuclear disaster took place at 1 h 24 min local time, destroying the fourth reactor of the Chernobyl plant. Five years later the consequences of the disaster are still not fully known. Nevertheless the long term future of nuclear energy in the world is uncertain. Questions need to be answered by observing hard facts if emotional attitudes are not to prevail over reality. The reactor and its core were destroyed by an explosion, causing two radioactive jet emissions of iodine 131, followed by caesium 137. Both elements are mainly incorporated in the body via food. The Chernobyl disaster was a consequence of inadequate safety regulations and human error. Enforcement of strict regulations are likely to be highly effective in preventing a further catastrophe. However, governments should consider another possibility. What would be the consequences for public health if a terroristic act deliberately destroyed a nuclear power station?

Accidents↗
PubMed1991

Monocytic origin of fibroblasts: spontaneous transformation of blood monocytes into neo-fibroblastic structures in osteomyelosclerosis and Engelmann's disease.

We describe here two pathological situations, osteomyelosclerosis and Engelmann's disease, in which HLA-DR blood monocytes modulate to the fibroblastic class, in long-term culture. Monocytes/macrophages were identified by immunofluorescence, using monoclonal antibodies against surface markers (Leu M3, CD 68, and HLA-DR) and the neo-fibroblasts by electron microscopy and immunofluorescence using monoclonal antibodies against a cytoplasmic enzyme specifically involved in the synthesis of collagen (5B5). Macrophages makers were found on the neo-fibroblasts, whereas HLA-DR macrophages expressed the cytoplasmic marker 5B5. Since osteoblasts are classically derived from fibroblasts, the significance of the in vitro differentiation of monocytes/macrophages into fibroblasts to the in vivo mechanism leading to excessive osteoblastic proliferation in both osteomyelosclerosis and Engelmann's disease, is discussed. The possible involvement of this pathway leading from monocytes to fibroblasts and osteoblasts in the normal process of bone modeling and remodeling in questioned.

Camurati-Engelmann Syndrome↗
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

PCR amplification of CGRP II mRNA. Variable expression in tumoral and non-tumoral human thyroid.

Two genes code for calcitonin gene-related peptides (CGRPs). One expresses by tissue-specific alternate splicing calcitonin and CGRP I mRNAs, the other CGRP II mRNA. Calcitonin is the marker of sporadic or hereditary human medullary thyroid carcinoma (MTC). CGRP II expression is not well established in normal or tumoral thyroid. After amplification by polymerase chain reaction, CGRP I and II mRNAs were detected in six cases of MTC associated with other endocrine neoplasia (MEN IIa) and in two cases of isolated MTC. CGRP I was detected in all non-C cell tumoral thyroids (6 samples), CGRP II was barely detectable in three out of six cases. CGRP II could be a specific tumoral marker of MTC.

Base Sequence↗
PubMed1990

Calcitonin gene-related peptide stimulates adenylate cyclase activity in trout gill cell membranes.

The physiological significance of calcitonin gene-related peptide (CGRP) was investigated by assessing the CGRP stimulated adenylate cyclase activity in various tissues of trout. The highest enzyme concentration was found in gill and stomach membranes. The maximal activity (190% of the basal value) was observed for a concentration of 53.3 nM CGRP I or II. In the presence of 58 nM sCT, the maximal enzyme activity represented 120% of the basal value. No additive effect was observed; this suggests that both CGRP and sCT activities are mediated through the same receptor. The present data are in favour of a role for this neuropeptide operating in branchial cell functions such as calcium transfer from the external to the internal milieu.

Adenylyl Cyclases↗
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↗
PubMed1990

Increase in calcitonin mRNA levels in rats at high risk of C cell tumours is genetically determined.

C-cells tumours are frequent (50%) in old WAG/Rij rats. In comparison to the original Wistar strain, three month old WAG/Rij rats are characterized by higher calcitonin synthesis and secretion, in addition to a genetically transmitted loss of calcitonin binding sites in the outer renal medulla. In order to determine if the increase of calcitonin gene expression is also of genetic origin, we quantified calcitonin and its specific messenger in the thyroid glands of second generation (Wistar x WAG/Rij) hybrids. These parameters ranged from low Wistar like to higher WAG/Rij like values. The amount of calcitonin messenger in the thyroid was highly correlated to the release of the hormone in plasma elicited by a calcium challenge and inversely correlated with the number of its binding sites in the kidney. Our results suggest that an enhanced expression of the calcitonin gene is genetically transmitted, probably as a consequence of the mutation involved in the loss of renal calcitonin binding sites. It may represent the first event leading to malignancy.

Animals↗