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Biomedical subjects

F Lamy

Publications and source records attributed to F Lamy.

At least 37 records · Page 2Linked to original sources
PubMed1993

General inhibition by transforming growth factor beta 1 of thyrotropin and cAMP responses in human thyroid cells in primary culture.

Transforming growth factor beta 1 (TGF beta 1) mRNA has previously been identified in human thyroid cells and this agent has been shown to inhibit DNA synthesis in thyroid cells of some other species. In normal human thyroid cells in primary culture, TGF beta 1 inhibited inconstantly the low basal DNA synthesis and strongly the stimulation of DNA synthesis by epidermal growth factor (EGF) and serum, and by thyroid-stimulating hormone (TSH) acting through cAMP. This inhibition, by TGF beta 1, of the TSH and cAMP-dependent DNA synthesis was associated with an inhibition of PCNA (proliferating cell nuclear antigen) synthesis. TGF beta 1 almost completely abolished the cAMP induced stimulation of iodide uptake and thyroperoxidase synthesis. It thus, like EGF, also acts as a dedifferentiating agent. Investigation of the pattern of protein synthesis by two-dimensional gel electrophoresis revealed that while TGF beta 1, by itself, increased the synthesis of only one protein, a tropomyosin isoform, it inhibited most of the effects of cAMP on protein synthesis (35 out of 45 cAMP-regulated proteins were affected). It also reversed the effect of cAMP on the morphology of the thyrocytes. The fact that TGF beta 1 did not affect the increase in cAMP provoked by TSH in human thyroid cells while inhibiting most of the effects of dibutyryl cAMP in these cells suggests an action at a step distal to cAMP generation.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Physiological Phenomena↗
PubMed1993

Selenium and the thyroid: how the relationship was established.

Several hypotheses concerning consequences of selenium deficiency on iodine metabolism can be proposed on the basis of experimental studies in rats and from epidemiological and experimental studies in humans. By decreasing intracellular GSH peroxidase activity, selenium deficiency may increase hydrogen peroxide (H2O2) supply and lead over several weeks to the thyroid atrophy observed in myxoedematous cretins. By improving thyroid hormone synthesis and by decreasing peripheral thyroxin (T4) deiodination, selenium deficiency could protect fetal brain T4 supply and thus prevent neurologic cretinism. Selenium deficiency may protect against iodine deficiency by decreasing T4 metabolism--and thus iodide leakage and--perhaps also by increasing H2O2 supply and thyroid hormone synthesis and thus thyroid efficiency.

Animals↗
PubMed1991

Intermediate filaments in normal thyrocytes: modulation of vimentin expression in primary cultures.

In dog thyrocyte primary cultures, the antagonistic effects of thyrotropin (TSH) and epidermal growth factor (EGF) on differentiation expression were accompagnied by distinct long-term morphological changes: TSH-treated cells showed an epitheloid morphology; EGF reversibly induced a fusiform shape. Using indirect immunofluorescence microscopy and two-dimensional gel electrophoresis, we studied the modifications in the distribution and synthesis of the intermediate filament proteins of the cytoskeleton in response to TSH and EGF. These factors had little effect on the expression of cytokeratins 8 and 18, which were expressed in 98% of cells. However, TSH induced a profound redistribution of cytokeratins (and actin) with the appearance of a marked staining of cell junctions. Vimentin was coexpressed with cytokeratins in about 40% of cells from normal thyroid follicles freshly isolated by collagenase. During culture, immunostained vimentin network progressively developed in 90% of control and EGF-treated cells simultaneously with vimentin synthesis. In contrast, only 20% of TSH-treated cells reacted with vimentin antibody and we observed a marked decrease in vimentin synthesis in response to TSH. Therefore, vimentin synthesis, which should occur in at least some normal thyroid follicles in vivo, was inhibited in vitro by TSH which promotes differentiation expression. However, EGF-treated cells thereafter cultured with TSH regained an epitheloid morphology and differentiation in spite of the persistency of a complete network of vimentin.

Actins↗
PubMed1991

The TSH cyclic AMP cascade in the control of thyroid cell proliferation: the story of a concept.

Thyrotropin stimulates the growth and proliferation of thyroid cells in vivo. Starting in the 1970, we have progressively shown that these effects could be reproduced in vitro in dog thyroid cells in primary culture. They are accompanied by the expression of differentiation. All the effects of thyrotropin are mediated by the cyclic AMP cascade. The best argument that this concept applies in vivo is the generation of hyperfunctioning adenoma involving the whole gland in transgenic mice expressing the constitutively active adenosine A2 receptor in the thyroid.

Animals↗
PubMed1990

Control of protein synthesis by thyrotropin and epidermal growth factor in human thyrocytes: role of morphological changes.

UNLABELLED: The effect of thyrotropin (TSH) and epidermal growth factor (EGF) on the synthesis of proteins has been studied using two-dimensional gel electrophoresis in primary cultures of thyroid cells developing as a monolayer or that remained associated as dense aggregates. (1) A 4-day treatment of monolayer cells by TSH or dibutyryl cAMP enhanced the synthesis of 26 proteins and decreased that of 19 others. (2) The synthesis of 29 proteins was similarly modified by TSH and dibutyryl cAMP in both types of culture organizations. Both agents stimulated the synthesis of thyroperoxidase and of proliferating cell nuclear antigen (PCNA)/cyclin and decreased that of actin and of a high Mr isoform of tropomyosin. (3) TSH induced the retraction of monolayer cells. Its effect on the synthesis of many proteins was mimicked by culturing unstimulated cells as dense aggregates instead of monolayers which similarly affected cell morphology. (4) EGF alone had no effect on protein synthesis in monolayer cells but it inhibited both the morphological changes induced by TSH and dibutyryl cAMP and the effect of these agents on the synthesis of 23 proteins including thyroperoxidase. IN CONCLUSION: (1) TSH and cAMP induce both proliferation and the expression of differentiation in thyroid cells while EGF has a small mitogenic effect but a marked inhibitory action on differentiation expression; (2) many TSH (cAMP) and EGF effects on the pattern of protein synthesis might be related to morphological changes; (3) the expression of the differentiation marker thyroperoxidase and of the mitogenic marker PCNA/cyclin appears independent of cell configuration and morphology.

Biomarkers↗
PubMed1990

Detection of bovine leukemia virus antibodies in bulk tank milk using an ELISA test: improvement of the predictive value of results by repeated testing.

In 9457 dairy farms located in an area with low prevalence of bovine leukemia virus (BLV) infection, bulk tank milk was examined to detect for the presence of antibodies using an ELISA test. If the result was positive or doubtful, serum of all animals in the farm was tested and bulk tank milk was tested again five times every 8-12 days. The results were used to establish decision rules in the event of a positive or doubtful result during mass screening.

Animals↗
PubMed1990

Reduction of Ib autogenetic inhibition in motoneurons during contractions of an ankle extensor muscle in the cat.

1. Triceps surae and plantaris (Pl) motoneurons were recorded intracellularly in chloralose or pentobarbital sodium (Nembutal)-anesthetized cats during unfused tetanic contractions of gastrocnemius medialis muscle (GM) produced by stimulating either a cut branch of the GM nerve or the muscle directly. 2. In alpha-motoneurons, during a series of GM twitches at 10/s, contraction-induced inhibitory potentials, probably the result of input from Golgi tendon organs (autogenetic inhibition), rapidly subsided before the end of the series. In contrast, excitatory potentials, probably the result of the activation of spindle primary endings during relaxation from contraction, persisted. 3. In gastrocnemius lateralis-soleus (GL-S) and Pl motoneurons lacking an excitatory connection with Ia afferents from GM, the sustained contraction of this muscle also elicited a declining inhibition. Rapid reduction of contraction-induced autogenetic inhibition was also observed in homonymous gamma-motoneurons. During unfused tetanic contractions lasting 0.5-4s, inhibitory potentials quickly subsided, but an abrupt increase in contractile force elicited a new series of decreasing inhibitory potentials. 4. The assumption that the inhibition induced by GM unfused tetanic contractions was due to activation of homonymous Ib afferents was supported by observations of the effects of electrical stimulation of the GM nerve. In Pl motoneurons lacking an excitatory connection with Ia afferents from GM, repetitive trains applied to the GM nerve, at a strength just above threshold for group I fibers, elicited rapidly declining inhibitory potentials similar to those produced by GM contraction. It was verified that during such stimulation, the amplitude of the group I afferent volleys did not decrease. 5. Reduction of contraction-induced Ib inhibition during sustained GM contraction was still present after a low spinalization of the preparation. As GM tendon organ discharges were verified to persist throughout prolonged contractions, the observed decline of autogenetic inhibition is likely to depend on a spinal mechanism, possibly involving presynaptic inhibition of Ib afferents and/or mutual inhibition of Ib-inhibitory interneurons.

Animals↗
PubMed1989

Cloning and sequencing of a calcium-binding protein regulated by cyclic AMP in the thyroid.

p24 is a thyroid protein (Mr 24,000) identified by two-dimensional gel electrophoresis on the basis that its synthesis and phosphorylation are up-regulated by thyrotropin and cyclic AMP agonists. p24 cDNA was cloned from a lambda gt11 cDNA library using a polyclonal antibody raised against the protein recovered from a Western blot spot. The encoded polypeptide (189 residues) displays a putative target-site for phosphorylation by cyclic AMP-dependent protein kinase and belongs to the superfamily of proteins binding Ca2+ through 'EF hand' domains. It presents four such domains of which two agree closely with the consensus. The ability of p24 to bind Ca2+ has been directly confirmed on Western blots. p24 was detected in many tissues including the salivary glands, the lung and the brain. The ubiquitous nature of p24, together with its regulatory and sequence characteristics suggest that it constitutes an important target common to the cyclic AMP and Ca2+-phosphatidylinositol cascades.

Animals↗
PubMed1989

Protein synthesis during induction of DNA replication in thyroid epithelial cells: evidence for late markers of distinct mitogenic pathways.

The synthesis of specific protein has been investigated in primary cultures of dog thyroid epithelial cells, which can be induced to progress into G1 phase, in the presence of insulin, by different types of mitogens: thyrotropin (TSH) acting through cyclic adenosine monophosphate (cAMP), epidermal growth factor (EGF), 12-O-tetradecanoyl-phorbol-13-acetate (TPA), or 10% serum. EGF, TPA, or serum specifically induce [35S] methionine labeling of protein 1 (Mr approximately 80,000). The effect of EGF on protein 1 labeling and DNA replication is dependent on insulin. The level of protein 1 labeling as well as that of DNA synthesis is higher when TSH or TSH + serum are added together with EGF. It peaks in mid-G1. TSH alone, in the presence of insulin, stimulates DNA replication without inducing protein 1 synthesis, which thus represents a cell-cycle-dependent event that is not obligatory in mitogenic activation through cyclic AMP. Among the eight proteins whose synthesis is stimulated by TSH, only the labeling of protein 7, molecular weight ratio (Mr approximately 38,000), correlates with the DNA synthetic activity of the cells. The present authors identified protein 7 as cyclin/proliferating cell nuclear antigen (PCNA), the auxiliary protein of DNA polymerase-delta. The effect of TSH on cyclin synthesis is already detectable when most of the cells are in late G1, but its stimulation by EGF or EGF + serum is delayed and detected only after extending the labeling period to the S-phase. These data support the view that the cAMP-mediated mitogenic pathway remains partly distinct from the better known pathways induced by growth factors and tumor promoters, even at late stages of the G1-phase.

Animals↗
PubMed1989

Actin stress fiber disruption and tropomyosin isoform switching in normal thyroid epithelial cells stimulated by thyrotropin and phorbol esters.

Thyrotropin (TSH), through cyclic AMP, promotes both proliferation and differentiation expression in dog thyroid epithelial cells in primary culture, whereas the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) also stimulates proliferation but antagonizes differentiating effects of TSH. In this study, within 20 min both factors triggered the disruption of actin-containing stress fibers. This process preceded distinct morphological changes: cytoplasmic retraction and arborization in response to TSH and cyclic AMP, cell shape distortion, and increased motility in response to TPA and cyclic AMP, cell shape distortion, and increased motility in response to TPA and diacylglycerol. TSH and TPA also induced a marked decrease in the synthesis of three high Mr tropomyosin isoforms, which were not present in dog thyroid tissue but appeared in culture during cell spreading and stress fiber formation. In contrast, the synthesis of two low Mr forms of tropomyosin that were already present in thyroid tissue remained unchanged after treatment with TSH or TPA. Epidermal growth factor, another mitogenic and dedifferentiating factor for these cells, did not induce acute morphological changes, nor modification of tropomyosin synthesis. The tropomyosin isoform switching observed here closely resembled similar processes in various cells transformed by oncogenic viruses. However, it did not correlate with differentiation or mitogenic activation. Contrasting with current hypothesis on this process in transformed cells, tropomyosin isoform switching in normal thyroid cells was preceded and thus might be caused by early disruption of stress fibers.

Actin Cytoskeleton↗
PubMed1988

Degradation of Kraft Indulin Lignin by Streptomyces viridosporus and Streptomyces badius.

Crawford and collaborators have studied extensively the solubilization of lignocellulose by two Streptomyces species, S. badius and S. viridosporus. Using a condensed industrial lignin essentially devoid of carbohydrates, Indulin AT, as the sole source of carbon, similar results were obtained: (i) the growths of the bacteria were optimum at pH 7.5 to 8.5; (ii) yeast extract was a better source of nitrogen than NH(4)Cl; (iii) the products of the depolymerization of Indulin were soluble, acid-precipitable polymers. When d-glucose was added as a secondary carbon source, it was used preferentially and the production of acid-precipitable polymers began only after the complete depletion of the sugar. On the assumption that the degradation of Indulin was catalyzed by enzymes, proteins found in the culture media and soluble and insoluble intracellular proteins were incubated with Indulin at pH 7.0 at 37 degrees C. Proteins in all fractions from S. badius had ligninolytic activities which, with the exception of those in the intracellular soluble fraction, were increased in the presence of H(2)O(2). In S. viridosporus, both extra- and intracellular soluble activities were found which were not increased by H(2)O(2). The extracellular activity of S. viridosporus was not affected by heat, resisted partially an exposure to pH 1.0, and was completely destroyed by proteolysis.

Journal Article↗
PubMed1988

Differential protein phosphorylation in induction of thyroid cell proliferation by thyrotropin, epidermal growth factor, or phorbol ester.

Protein phosphorylation was studied in primary cultures of thyroid epithelial cells after the addition of different mitogens: thyrotropin (TSH) acting through cyclic AMP, epidermal growth factor (EGF), or 12-O-tetradecanoylphorbol-13-acetate (TPA). EGF or TPA increased the phosphorylation of five common polypeptides. Among these, two 42-kilodalton proteins contained phosphotyrosine and phosphoserine with or without phosphothreonine. Their characteristics suggested that they are similar to the two 42-kilodalton target proteins for tyrosine protein phosphorylation demonstrated in fibroblasts in response to mitogens. No common phosphorylated proteins were detected in TSH-treated cells and in EGF- or TPA-treated cells. The differences in the protein phosphorylation patterns in response to TSH, EGF, and TPA suggested that the newly emerging cyclic AMP-mediated mitogenic pathway is distinct from the better known growth factor- and tumor promoter-induced pathways.

Animals↗
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↗
PubMed1988

Effects of a selenium deficient diet on thyroid function of normal and perchlorate treated rats.

Pregnant rats were submitted to a selenium-deficient diet immediately after mating; it was continued for 4 weeks after delivery. The pups were sacrificed at 3 and 4 weeks of age. Perchlorate, an antithyroid agent inhibiting iodide trapping in the thyroid, was administered via the drinking water to half of the rats. Rats submitted to a normal laboratory diet and to the experimental diet supplemented with selenium were used as controls. The effects of selenium deficiency were an increase in the number of growth abnormalities, growth retardation, and decreased seleno-dependent glutathione peroxidase (GSH-Px) activity in plasma and in various organs. These effects were relieved by selenium supplementation in the diet. Perchlorate treatment induced the classic picture of primary hypothyroidism. Selenium deficiency increased thyroid hormone levels in perchlorate-treated rats and in controls drinking tap water. In the latter group, it also decreased TSH plasma concentration and thyroid weight. These effects were partially reversed by Se supplementation. In vitro experiments, performed on adult rats, revealed increased radioiodide uptake and organification in glands from the rats submitted to the selenium-free diet. Plasma T3 half-life was similar in control and Se-deficient rats. These data suggest a higher efficiency of thyroid hormone synthesis in the thyroids of selenium-deficient rats, despite a lower thyroid stimulation as evaluated by serum TSH. They are compatible with the hypothesis that decreased selenium supply, leading to a decreased GSH-Px in the thyroid, increases hydrogen peroxide steady state level and thus thyroid peroxidase activity and thyroid hormone synthesis.

Animals↗
PubMed1988

[Effects of partial unfused contractions of the gastrocnemius medialis muscle on homonymous and synergist motor neurons in cats].

Autogenetic inhibition of homonymous and synergist motoneurones can be elicited by very weak partial twitches of gastrocnemius medialis muscle, but during sustained contractions the amplitude of inhibitory post-synaptic potentials decreases quickly. A similar decrease also occurs during stronger contractions. The mechanism responsible for this decrease is still active in low spinal preparations. Pre-synaptic inhibition of Ib afferent fibres might contribute to this reduction of efficiency in the transmission of Ib afferent inputs to motoneurones.

Animals↗
PubMed1987

Use of electroblotting to detect and analyze phosphotyrosine containing peptides separated by two-dimensional gel electrophoresis.

A technique to detect and analyze phosphotyrosine containing peptides after separation of total cellular proteins by two-dimensional gel electrophoresis is described. This is achieved by electroblotting of proteins on nylon membranes followed by alkali treatment. In comparison with direct alkali treatment of the polyacrylamide gel, this procedure is easier to perform; avoids the diffusion of proteins out of the gel during alkali treatment; allows a more precise localization of phosphotyrosine containing peptides on the untreated membrane; and is less time consuming with respect to extraction of proteins for phosphoamino acid analysis.

Animals↗