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P Cochaux

Publications and source records attributed to P Cochaux.

At least 19 recordsLinked to original sources
PubMed1992

Identification of a minor Tg mRNA transcript in RNA from normal and goitrous thyroids.

Polymerase chain reaction (PCR) amplification of nt 4502 to nt 5184 of the thyroglobulin (Tg) mRNA from several patients, with or without elevated serum thyrotropin (TSH), showed a predominant fragment of the expected size (683 bp) and a minor fragment of 512 bp. The sequence of this minor fragment revealed that 171 bp were missing between position 4567 and 4737. It is highly probable that the deleted sequence corresponds to a complete exon, suggesting an alternative splicing as mechanism for the generation of the minor transcript.

Amino Acid Sequence↗
PubMed1992

Identification of a mutation in the coding sequence of the human thyroid peroxidase gene causing congenital goiter.

Thyroid peroxidase (TPO) is the key enzyme in the synthesis of thyroid hormones, and the TPO defects are believed to be the most prevalent causes of the inborn errors of thyroid metabolism. We investigated an adopted boy with iodide organification defect, who presented with florid hypothyroidism at the age of 4 mo, poorly complied with thyroxine treatment, and developed a compressive goiter necessitating partial resection at the age of 12 yr. Biochemical studies revealed the absence of TPO activity in the resected tissue. Genomic DNA studies identified a 4 base-pair insertion in the eighth exon of the TPO gene, and showed that the patient was homozygous for this frameshift mutation. The direct genetic diagnosis of this mutation can be made by digestion of polymerase chain reaction products with NaeI restriction enzyme. This will help assessing its prevalence among the heterogenous genetic group of TPO defects.

Amino Acid Sequence↗
PubMed1992

Leber's hereditary optic neuropathy: clinical and molecular genetic aspects. Preliminary results in our families.

Leber's hereditary optic neuropathy (LHON) is a genetic maternally transmitted disorder characterised by sudden bilateral loss of vision. The discovery of at least one mitochondrial DNA mutation associated with the disease has provided the basis for a molecular diagnosis in about 50% of families with LHON. We present a brief review of the clinical and molecular genetic aspects of LHON along with our results in 13 patients.

Adolescent↗
PubMed1991

A 3' splice site mutation in the thyroglobulin gene responsible for congenital goiter with hypothyroidism.

A case of congenital goiter with defective thyroglobulin synthesis has been studied in molecular terms. The patient is the fifth of a kindred of six, three of which have a goiter. The parents are first cousins. Segregation of thyroglobulin alleles in the family was studied by Southern blotting with a probe revealing a diallelic restriction fragment length polymorphism (RFLP). The results demonstrated that the three affected siblings were homozygous for the RFLP. Northern blotting analysis of the goiter RNA with a thyroglobulin probe suggested that thyroglobulin mRNA size was slightly reduced. Polymerase chain reaction amplification of the 8.5-kb thyroglobulin mRNA as overlapping cDNA fragments demonstrated that a 200-bp segment was missing from the 5' region of the goiter mRNA. Subcloning and sequencing of the cDNA fragments, and of the patient genomic DNA amplified from this region, revealed that exon 4 is missing from the major thyroglobulin transcript in the goiter, and that this aberrant splicing is due to a C to G transversion at position minus 3 in the acceptor splice site of intron 3. The presence in exon 4 of a putative donor tyrosine residue (Tyrosine nr 130) involved in thyroid hormone formation provides a coherent explanation to the hypothyroid status of the patient.

Adult↗
PubMed1990

CF screening.

Explore the source record for details and available documents.

Cystic Fibrosis↗
PubMed1990

Diadenosine 5',5'''-P1,P4-tetraphosphate (AP4A) levels under various proliferative and cytotoxic conditions in several mammalian cell types.

Diadenosine 5',5'''-P1,P4-tetraphosphate (Ap4A) has been proposed as an intracellular signal for growth. In order to test this hypothesis Ap4A levels were followed in several cell types under various conditions. Quiescent dog thyroid cells in a primary culture were induced to proliferate by addition of a mixture of epidermal growth factor, thyrotropin and foetal calf serum; V79 cells were synchronized by serum depletion then stimulated to proliferate by addition of foetal calf serum. Protein and DNA synthesis increased in both cases, although no significant changes in Ap4A levels per cell could be demonstrated. HeLa D98/AH2 and L929 cells were treated with human recombinant tumour necrosis factor alpha which caused marked cell death. This was measured by a decrease in DNA content and a release into extracellular medium of incorporated radioactive precursor. No concomitant variations in Ap4A concentrations could be observed under these conditions. The data from these various systems do not support the hypothesis that changes in Ap4A levels regulate cellular proliferation.

Animals↗
PubMed1990

[Chorionic villi sampling: experience of the initial 500 samples].

We report our experience in first trimester antenatal diagnosis since 1984. Transcervical chorionic villus sampling (CVS) was performed in 498 pregnancies. The rate of abnormal pregnancies was 6%, the rate of chromosomal abnormalities (trisomy) in the indication group "maternal age" was 2%. The fetal loss rate (until 28 weeks) was 3.4% (17 cases), the procedure related loss plus the background loss was 2.4% (12 cases). For 92.8% of the patients a diagnosis was available after 1 CVS procedure. Ultimately an antenatal diagnosis was given to 99% of the women through a second CVS procedure or an amniocentesis or a cordocentesis. No maternal complication was observed.

Chorionic Villi Sampling↗
PubMed1990

[Molecular and diagnostic genetics].

Using the recent developments of molecular biology techniques, our laboratory is offering carrier and prenatal diagnosis for a variety of genetic disorders including cystic fibrosis, phenylketonuria, thalassaemia alpha and beta, sickle cell anaemia, myotonic dystrophy, von Recklinghausen's disease, autosomal polycystic kidney disease, haemophilia A and B, Martin-Bell syndrome (fragile X), Becker and Duchenne muscular dystrophy, etc. It is likely that the rapid advances made in the establishment of the human genetic map will considerably expand the spectrum of diseases for which diagnosis by molecular genetics will become available.

Genetic Carrier Screening↗
PubMed1990

[Cordocentesis: experience in 391 initial samples].

The first diagnostic cordocentesis was performed in our unit in october 1985. Our 4-year experience is reported: 391 cordocentesis were performed in 360 patients during gestational weeks 14 to 42. The first attempt was successful in 90% of the procedures, 4 samplings failed, there were 4 fetal deaths within one week after diagnostic cordocentesis, one of them appears to be directly linked to the punction. A transient fetal bradycardia was observed in 9.9% of the cases, bleeding occurred in 19% of the cases. The indications for cordocentesis were: risk of fetal infection, karyotyping, hemopathy, search for paternity, assessment of fetal acid-base status, biochemical dosage. Our data confirm that cordocentesis is a safe and reliable diagnostic procedure providing guidelines for management of the pregnancy.

Chromosome Aberrations↗
PubMed1989

A pitfall in the computer-aided quantitation of autoradiograms.

Computer-aided quantitation of autoradiograms is now available as a result of recent developments in optical scanners and microcomputers. Data expressed as optical density values, however, are based on the unverified assumption that optical density and radioactivity density are linearly correlated. This article demonstrates the need to construct a calibration curve which should be used to calculate radioactivity density values more precisely.

Autoradiography↗
PubMed1988

Pathogenesis of autonomous thyroid nodules: in vitro study of iodine and adenosine 3',5'-monophosphate metabolism.

The in vitro characteristics of iodide and cAMP metabolism have been compared in tissues from autonomously functioning thyroid nodules and their quiescent counterpart to test the hypothesis that autonomy may result from constitutive activation of the tissue's TSH, cAMP, and protein phosphorylation regulatory axis, as in vivo nodular tissue took up more iodide. This effect was entirely due to increased transport capacity, the affinity of iodide transport, and the fractional binding of iodide to protein remaining unchanged. However, at high concentrations total iodide binding to protein was similar in quiescent and nodular tissue. In both tissues, this metabolic step was enhanced by phorbol esters and the ionophore A23187. As evaluated by autoradiography of two-dimensional gel protein electrophoregrams, no differences in the patterns of protein synthesis or phosphorylation between quiescent and nodular tissue were found. Basal cAMP levels were similar in quiescent and nodular tissue. The cAMP response to TSH was lower in nodular tissue, with no change in sensitivity or kinetics; both tissues responded to forskolin. No systematic suppression of iodide inhibition or abnormal responses to other hormones or neurotransmitters were found. Three proteins (24K-1, 24K-2, and 26K) were phosphorylated only in the presence of TSH or forskolin in both quiescent and nodular tissue. One protein substrate (20K) was phosphorylated in the presence of TSH in the quiescent, but not in the nodular, tissue. In conclusion, 1) slices from autonomous thyroid nodules reproduce the in vivo characteristics of the lesion and are, therefore, a suitable in vitro experimental model for biochemical studies; 2) taken together with data from transplantation experiments, the reproduction in vitro or its in vivo characteristics suggest an inherent defect in the nodule; 3) the homogeneity of biochemical findings within each nodule is compatible with the clonality of the lesion; 4) the autonomous nodule is a minimal deviation tumor; and 5) the characteristics of the TSH, cAMP, protein phosphorylation cascade are qualitatively normal, and autonomy does not result from constitutive activation of this system; and 6) a 20K protein, not phosphorylated in response to TSH in the nodule, could represent an absent negative controlling element.

Adult↗
PubMed1987

Iodide-induced inhibition of adenylate cyclase activity in horse and dog thyroid.

The characteristics of the iodide-induced inhibition of cyclic AMP accumulation in dog thyroid slices have been previously described [Van Sande, J., Cochaux, P. and Dumont, J. E. (1985) Mol. Cell. Endocrinol. 40, 181-192]. In the present study we investigated the characteristics of the iodide-induced inhibition of adenylate cyclase activity in dog and horse thyroid. The inhibition of cyclic AMP accumulation by iodide in stimulated horse thyroid slices was similar to that observed in dog thyroid slices. The inhibition was observed in slices stimulated by thyroid-stimulating hormone, cholera toxin and forskolin. Increasing the concentration of the stimulators did not overcome the iodide-induced inhibition. Adenylate cyclase activity, assayed in crude homogenates or in plasma-membrane-containing particulates (100,000 x g pellets), was lower in homogenates or in particulates prepared from iodide-treated slices than from control slices. This inhibition was observed on the cyclase activity stimulated by forskolin, fluoride or guanosine 5'-[beta, gamma-imino]triphosphate, but also on the basal activity. It was relieved when the homogenate was prepared from slices incubated with iodide and methimazole. Similar results were obtained with dog thyroid. The inhibition persisted when the particulate fraction was washed three times during 1 h at 100,000 x g, in the presence of bovine serum albumin or increasing concentration of KCl. It was similar whatever the duration of the cyclase assay, in a large range of protein concentration. These results indicate that a stable modification of adenylate cyclase activity, closely related to the plasma membrane, was induced when slices were incubated with iodide. Iodide inhibition did not modify the affinity of adenylate cyclase for its substrate (MgATP), but induced a decrease of the maximal velocity of the enzyme. The percentage inhibition was slightly decreased when Mg2+ concentration increased, and markedly decreased when Mn2+ concentration increased. A detectable adenylate cyclase activity was demonstrated when intact slices were incubated in the presence of [alpha-32P]ATP, probably because of the presence of broken cells produced during the slicing. Iodide had no direct effect on this cyclase system, which confirms that iodide needs the integrity of the cell to induce the inhibition and suggests that the inhibition is not transmitted between cells.

Adenylyl Cyclase Inhibitors↗
PubMed1986

The escape of cyclic AMP from dog thyroid slices exposed to positive and negative regulators.

Incubation of dog thyroid slices with 1 mU/ml TSH resulted in enhanced intracellular and extracellular cAMP accumulation. In the absence of TSH, the intra- and extracellular cAMP concentrations remained at a constant low level. The release of cAMP from TSH-stimulated slices was inhibited by 10 microM PGA1, 1 mM probenecid or 1 mM IBMX, which are known inhibitors of cAMP escape in several tissues. Negative controls of intracellular cAMP levels are exerted in the dog thyroid by 10 microM carbamylcholine (shown to activate a Ca++- calmodulin dependent phosphodiesterase), 100 microM norepinephrine and 100 microM iodide (both inhibiting adenylate cyclase activity). The purpose of the present study was to demonstrate that these three agents do not enhance cAMP escape. The results presented here show that these agents decrease both intracellular accumulation and escape in parallel. Moreover, the escape constants obtained by numerical simulation were not greater in the presence of inhibiting concentrations of carbamylcholine, norepinephrine or iodide. Thus the inhibition by these agents of cAMP accumulation in TSH-stimulated dog thyroid slices cannot be explained by a stimulation of cAMP escape from these cells.

1-Methyl-3-isobutylxanthine↗
PubMed1985

Islet-activating protein discriminates between different inhibitors of thyroidal cyclic AMP system.

TSH-induced cyclic AMP accumulation in dog thyroid slices is inhibited by norepinephrine through an alpha 2-adrenergic receptor, by carbamylcholine through a muscarinic cholinergic receptor, and by iodide. The inhibitory effect of iodide bears on the adenylate cyclase, but the exact mechanism of its action is still unknown. It is known that norepinephrine acts through activation of the Ni subunit of the cyclase, and that carbamylcholine, activating a phosphodiesterase, acts independently of Ni. IAP (islet-activating protein) has been shown to inactivate the Ni subunit. We studied the effect of IAP on the inhibitory action of iodide, norepinephrine, and carbamylcholine on cyclic AMP accumulation in TSH-stimulated thyroid slices. Incubations of 15 or 22 h, and relatively high concentrations of IAP (250 ng/ml) were necessary to demonstrate an effect of IAP on thyroid slices. We report here that, under those conditions, inhibition of cyclic AMP accumulation by norepinephrine, but not by carbamylcholine or iodide, was suppressed by IAP treatment. These results indicate that the cyclase inhibition by iodide, is either not mediated by Ni, or if mediated by Ni, involves a mode of regulation of this coupling protein that is different from that by which the other 'Ni-mediated' inhibitory hormones act on the enzyme.

Adenylate Cyclase Toxin↗