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Biomedical subjects

A Tanini

Publications and source records attributed to A Tanini.

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

Effects of endothelin-1 on bovine parathyroid cells.

Endothelin-1 (ET-1) is synthesized and released by parathyroid epithelium. The effects of endothelin isopeptides were studied in clonal bovine parathyroid endothelial (BPE) cells. BPE cells did not produce ET-1, but showed ETA receptors (Kd = 0.1 +/- 0.02 nM, mean +/- SE). ET-1 (10(-8)10(-11)M) increased the intracellular calcium ion concentration ([Ca2+]i) in BPE cells, while endothelin-3 (ET-3) was ineffective. The increase in [Ca2+]i was less sustained in the absence of extracellular Ca2+ ions. Moreover ET-1 induced phospholipase C (PLC) activation, as demonstrated by the increase in inositol trisphosphate. Cell growth was not affected by ET-1 in a wide range of concentrations. The present findings demonstrate: 1) BPE cells possess ETA receptors; 2) the peptide activates PLC and increases cytosolic [Ca2+]i via both a release of Ca2+ ions from intracellular calcium pool(s) and an influx of the cation from the extracellular milieu. A possible role of ET-1 as a paracrine factor in parathyroid tissue can be hypothesized.

Animals↗
PubMed1993

Bone endothelial cells as estrogen targets.

In the present study, we investigated the effects of estrogens on bone endothelial cell metabolism and the presence of estrogen binding sites in the same cells. For these studies, we have used a continuous cell line of clonal bovine bone endothelial cells for evidence of a direct response to estrogens in vitro. Receptor analysis to intact viable cells was steroid specific and saturable, with an apparent dissociation constant of 17.2 nM and a Bmax of 3.2 x 10(4) sites/cell. Northern blot analysis revealed a 6.5-kilobase mRNA that hybridized with a cDNA to human estrogen receptor. The 6.5-kilobase size is in close agreement with the reported size of the human estrogen receptor mRNA. In vitro estrogen responses of bone endothelial cells included a stimulation of cell proliferation as well as an inhibition of parathyroid hormone responsiveness. These findings clearly demonstrate the presence of functional estrogen receptors in bone endothelial cells in vitro, suggesting a role of estrogens in bone angiogenesis and in the entire process of bone remodeling.

Animals↗
PubMed1993

Natriuretic hormone receptors and actions on bone endothelial cells.

[125I]Atrial natriuretic peptide (ANP) was used to identify ANP receptors on a clonal line of bovine bone endothelial (BBE) cells. Specific binding of [125I]ANP was saturable and of high affinity. Computer analysis of the equilibrium binding data indicated that the Scatchard plots are best fit by a straight line (Kd = 69.3 +/- 20.9 pM; binding capacity = 37.9 fmol/10(6) cells). The order of potency for competing with [125I]ANP binding was human ANP (hANP) > rat atriopeptin-1 (rAP-1) > porcine brain natriuretic peptide (pBNP) > porcine C-type natriuretic peptide. Affinity cross-linking studies indicated the presence of two major 130- and 70-kilodalton bands that specifically bound to hANP, rAP-1, pBNP, and porcine C-type natriuretic peptide. The binding of natriuretic peptides to BBE cells resulted in an increase in cGMP production and a significant decrease in Na+/K+/Cl- cotransport, without effects on cAMP intracellular accumulation. hANP, rAP-1, and pBNP at 100-nM concentrations, significantly inhibited PTH-induced cAMP production. Treatment with natriuretic hormones was also associated with an increase in 6-keto-prostaglandin F1 alpha levels in the culture medium of BBE cells and a higher cell growth rate. These studies demonstrate that bone endothelial cells bear receptors for natriuretic hormones associated with changes in PTH-induced cAMP production, prostaglandin production, and cell proliferation.

Animals↗
PubMed1992

Adhesion, growth, and matrix production by osteoblasts on collagen substrata.

A number of studies have demonstrated the pivotal role of collagen molecules in modulating cell growth and differentiation. In order to analyze the direct effects of collagen type I on the osteoblastic phenotype, we have devised an in vitro culture system for studying the interactions between bovine collagen type I and Saos-2 cells, a human osteoblastic cell line. Saos-2 cells were cultured both on top of collagen-coated culture dishes as well as inside a three-dimensional collagen network. Plating on dishes treated with collagen induced maximal adhesion of Saos-2 cells after 24-hour incubation. Cells cultured on collagen gel matrix expressed about 2.5-fold more alkaline phosphatase when compared with untreated plastic dishes. On collagen-coated dishes the responsiveness of Saos-2 cells to parathyroid hormone was decreased, whereas no modifications were observed in the effect of vasoactive intestinal peptide on these cells. Using a microfluorimetric measurement of DNA, an increase of proliferation was observed in Saos-2 cells cultured on collagen gel. Saos-2 cells were also able to colonize collagen sponges and in this three-dimensional network they were able to synthesize osteocalcin, as assessed both by immunocytochemistry and radioimmunoassay. In this study we have demonstrated that bovine collagen type I exhibits favorable effects on attachment and functional and growth activities of a human osteoblastic cell line, encouraging its use as a bone graft material.

Alkaline Phosphatase↗
PubMed1992

Phorbol ester induced osteoclast-like differentiation of a novel human leukemic cell line (FLG 29.1).

Studies on human osteoclast formation have been hampered by lack of a defined isolated progenitor cell population. We describe here the establishment of a human leukemic cell line (designated FLG 29.1) from bone marrow of a patient with acute monoblastic leukemia. The cultured cells are predominantly undifferentiated leukemic blasts, but addition of 12-o-tetradecanoylphorbol 13-acetate (TPA; 0.1 microM) induces irreversible differentiation into adherent, non-dividing, multinucleated cells. TPA-treated cells bear surface antigens typical of fetal osteoclasts, degrade 45Ca-labeled devitalized bone particles, display tartrate-resistant acid phosphatase in both mononuclear and multinuclear cells and receptors for calcitonin. Calcitonin increases intracellular cAMP accumulation in TPA-treated cells. TPA-treated cells show some ultrastructural features of osteoclasts as evidenced by transmission EM. These results indicate that FLG 29.1 cells may represent an osteoclast committed cell population, which upon induction with TPA acquire some morphological, phenotypical, and functional features of differentiated osteoclasts.

Antigens, CD↗
PubMed1991

Effects of ipriflavone and its metabolites on a clonal osteoblastic cell line.

Protective effects of ipriflavone, an isoflavone derivative, in osteoporosis are believed to be caused by the inhibitory action on bone resorption. A direct effect of ipriflavone on bone formation is as yet unknown. Ipriflavone and four of its metabolites (I, II, III, and V) were examined for their effects on parathyroid hormone response, collagen synthesis, alkaline phosphatase activity, and cell proliferation in a clonal cell population of rat osteoblastic cells. Pretreatment of osteoblasts with high concentrations of ipriflavone for 48 h significantly inhibited the cAMP response to parathyroid hormone, producing a shift in the dose-response curve; at lower concentrations metabolites II and III potentiated the cAMP accumulation induced by low doses of parathyroid hormone. The 48 h treatment with metabolite V at the 1 nM dose significantly stimulated collagen synthesis in osteoblastic cells. Ipriflavone and metabolite I showed a biphasic stimulatory action on the alkaline phosphatase activity of osteoblasts, with a maximal effect at the 0.1 and 1 nM doses, respectively. A similar biphasic response was observed with ipriflavone and metabolite I on osteoblastic cell growth, with a maximal effect at the 0.1 nM concentration. These results suggest a direct role of ipriflavone in modulating the synthetic and growth properties of osteoblast-like cells.

Alkaline Phosphatase↗
PubMed1989

Insulin-like growth factor-I: autocrine secretion by human thyroid follicular cells in primary culture.

Insulin-like growth factor-I (IGF-I) stimulates the growth of thyroid cells of different animal species. However, conflicting results have been reported as regards the function and mechanism of the action of IGF-I at the thyroid level. This study was designed to determine whether normal human thyroid cells have IGF-I receptors and whether IGF-I could act on such cells through an autocrine mechanism. Human thyroid follicular cells in primary culture, not contaminated by fibroblasts, were used. They had specific and saturable binding sites for IGF-I, as revealed by radiolabeled binding method, and displayed an average receptor number of 2000/cell. Under the same experimental conditions, insulin receptors were not detectable. Human thyroid follicular cells secreted IGF-I into the culture medium, as assessed by a specific chemiluminescent immunoassay. The IGF-I secretory process was detectable for at least 12 days of culture, but a high degree of variability has been found among individual samples. Acid-gel chromatography demonstrated that IGF-I and a higher mol wt IGF-I, most likely IGF-I bound to its binding protein, were secreted by human thyroid cells. TSH stimulated the secretion of the two molecules in normal human thyroid cells. The TSH effect on IGF-I secretion was concentration dependent between 0.1 nmol/L and 0.1 mumol/L. GH stimulated IGF-I synthesis by thyroid cells in a concentration range from 20-200 micrograms/mL. Since binding studies demonstrated the presence of IGF-I receptors on human thyroid cells, IGF-I probably regulates human thyroid function through an autocrine mechanism.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1987

Cholinergic control of cyclic nucleotide metabolism in human thyroid cells.

In the presence of Ro 20-1724, a selective inhibitor of cyclic nucleotide phosphodiesterase, carbamylcholine increases cAMP and cGMP levels in human thyroid cells in primary culture. The increase of cAMP exhibited at concentrations of carbamylcholine between 10 fM and 10 pM, is dose- and time-dependent, it is maximum after 30 min and is abolished after 60 min. At higher carbamylcholine concentration (10 microM), cAMP increases rapidly, becoming maximum after 15 min, but returns to unstimulated values after 30 min. The increase of cGMP is also dose-dependent (0.1 nM-10 microM); it reaches the maximum after 30 min and returns to unstimulated values after 120 min. A significant increase of phosphodiesterase activity is observed at 10 microM carbamylcholine. Atropine, a muscarinic receptor antagonist, blocks carbamylcholine effects on both cAMP and cGMP production without affecting the thyrotropin-induced cAMP accumulation. Hexamethonium, a nicotinic receptor antagonist does not affect the cholinergic effects. In the presence of Ro 20-1724, 10 microM carbamylcholine significantly inhibits the effect of thyrotropin on cAMP production, while the combined addition of low doses of carbamylcholine and thyrotropin (0.1 nM and 10 pM, respectively) results in an additive effect on cAMP levels. Inhibition of thyrotropin activity on cAMP production, similar to that exerted by 10 microM carbamylcholine is produced by increasing free intracellular calcium; this inhibition is relieved by using a calmodulin-sensitive phosphodiesterase inhibitor, M and B 22948 at 50 microM dose. High concentrations (10 microM) of carbamylcholine increase the adenylate cyclase activity, without any significant effect on the thyrotropin-induced activation of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗
PubMed1987

Insulin stimulates cell growth of a new strain of differentiated rat thyroid cells.

A new strain, named WRT cells, has been generated from primary cultures of rat thyroids. The primary culture was grown in Coon's modified Ham's F12 medium with 5% calf serum, insulin, hydrocortisone, transferrin, somatostatin, glycyl-L-histidyl-L-lysine and thyrotropin (TSH). On the basis of the following facts, the WRT cell strain, cloned from the primary culture, was considered 'normal': the cells are euploid, not carcinogenic, not able to grow in soft agar, and show contact inhibition. Their differentiated functions consist of the ability to synthesize thyroglobulin and to take up iodide, and they have a TSH-dependent adenylate cyclase system. TSH increases cellular adenosine 3',5'-cyclic monophosphate (cAMP) levels and [3H]thymidine incorporation in WRT cells from a concentration similar to that active on another clonal rat cell line (FRTL-5), even though the cell replication appears to be differently regulated in the two cell strains. In fact, the WRT cell doubling time is 42 h and they are also able to grow in the absence of TSH, though more slowly. In the same conditions, FRTL-5 cells have a population doubling time of 38 h, but they are not able to grow in the absence of TSH. When the effect of the other growth factors of the medium was studied, insulin appears to be a growth stimulus by itself, while it is only a facilitative step for TSH action in FRTL-5 cells. WRT cells, unlike FRTL-5 cells, can grow with a population doubling time of 80 h, when cultured for prolonged periods in a medium with a low serum concentration (0.5%), but containing insulin plus TSH. In conclusion, the WRT cell strain is a new and interesting experimental model for studying growth factors at the level of the thyroid, especially for their mechanism of action on the TSH receptor.

Animals↗
PubMed1986

Transient lack of response to TSH of human cultured thyroid cells obtained from hyperfunctioning tissue.

TSH-induced cAMP accumulation in cells obtained from normal and pathological thyroid tissue was studied during the first 12 days of primary culture. In normal thyroid tissue cultures (N = 7), the response of cAMP to TSH was present from the second day of culture and reached its maximum after 8 days. A similar behaviour was observed in cultures obtained from euthyroid sporadic goitres (N = 8), even if the rate of response was slightly lower than that of normal tissue. Similarly, cultured cells from euthyroid 'autonomous' nodules (N = 8) appeared to be responsive to TSH during the period of study, but the rate of response was also lower than in the controls. On the contrary, in cultures obtained from toxic adenomas (N = 5) and from diffuse toxic goitres (N = 5) the response to TSH was absent during the first 4 days of culture. The cells became sensitive to TSH from 6 and 6 day onwards, with the rate of response increasing progressively and reaching its maximum on day 12. Finally, in cultured cells obtained from different areas of multinodular toxic goitres (N = 4), the response to TSH was similar to that of euthyroid goitres in cells prepared from 'cold' areas, and to that of toxic adenomas in cells obtained from 'hot' areas. The present data demonstrate the existence of an inhibitory action of unknown factors, possibly iodothyronines or thyroglobulin, on the TSH effect in short-term cultures obtained from thyrotoxic tissues. A normal TSH responsiveness can be restored when the culture is prolonged.

Adenoma↗
PubMed1983

Noncovalent interactions of a 26,000-dalton peptide with 19 S human thyroglobulin.

Extensive succinylation of 19 S normal human thyroglobulin having a high iodine content results in the formation of a 26,000-Da peptide. One-half mole of the peptide is obtained from 1 mol of the high molecular weight glycoprotein. The dissociation of the peptide is accompanied by the appearance of an intense absorption band which has a maximum at 264 nm. The absorption band is associated exclusively with the 26,000-Da peptide. The amino acid composition of the peptide differs from 19 S thyroglobulin by having no cysteine and higher contents of serine, alanine, tyrosine, phenylalanine, lysine, glycine, isoleucine, and histidine. The peptide also has a high thyroxine content. There were no detectable carbohydrates in the peptide. The fluorescence spectrum of the 26,000-Da peptide shows an emission maximum at 405 nm which we have recently assigned to iodotyrosine-iodotyrosine interactions (Shifrin, S., Consiglio, E., and Kohn, L. D. (1983) J. Biol. Chem. 258, 3780-3786). A 26,000-Da peptide with the same physicochemical properties is found in extracts of normal human thyroid glands.

Amino Acids↗
PubMed1983

Specificity of thyroglobulin interactions with thyroid cells and membranes.

Homologous species specificity is demonstrated with bovine and human thyroglobulin in which the two terminal sugars of the B carbohydrate chain, sialic acid and galactose have been removed by enzymatic hydrolysis. The species specificity is demonstrated by measuring the ability of the deglycosylated thyroglobulin derivatives to inhibit thyrotropin-induced increases in cAMP in human, rat and bovine thyroid cells in culture. Thus human-human or bovine-bovine interactions have higher activity coefficients by at least an order of magnitude than their heterologous counterparts. The homologous interactions are confirmed in binding studies and shown to be associated with negligible degradation of the bound ligand over a 24 hour period.

Animals↗
PubMed1983

Evidence for alpha-adrenergic receptors acting through the guanylate cyclase system in human cultured thyroid cells.

In order to investigate the presence of alpha-adrenergic receptors in human thyroid, we have studied the effect of alpha-adrenergic agonists and antagonists on cGMP cellular content of human thyroid cells in primary culture. Epinephrine as well as TSH were not able to modify the cGMP cellular levels, while norepinephrine significantly increased cGMP accumulation already at 10 nM, a dose inactive on cAMP accumulation. A non selective alpha-adrenergic antagonist, phentolamine, significantly inhibited cGMP accumulation induced by norepinephrine. Norepinephrine-induced cGMP accumulation was unaffected by prazosin, an alpha 1-adrenergic antagonist, but was abolished by yohimbine, an alpha 2-adrenergic antagonist. Phenylephrine, an alpha-adrenergic agonist, produced an increase of cellular cGMP levels without modifying cAMP content. In the presence of TSH, the cGMP response to norepinephrine was not modified; however, the increase of cAMP levels was inhibited by norepinephrine at doses inactive on cAMP accumulation, but active on cGMP levels. The present results demonstrate the existence in human thyroid cells of alpha 2-adrenergic receptors, regulating the guanylate cyclase system. It may be postulated that the counter-regulation exerted by alpha-adrenergic agonists on the response to TSH operates on the TSH-dependent adenylate cyclase.

Adrenergic alpha-Agonists↗
PubMed1982

Effects of TSH on cAMP levels and thyroid hormone release in human thyroid 'autonomous' nodules: relationship with iodothyronine and iodine content in thyroglobulin.

The effect of TSH on the adenylate cyclase-cAMP system and in vitro iodothyronine release, together with the iodothyronine and iodine content of 19s thyroglobulin, were studied in seven clinically euthyroid patients with autonomous thyroid nodules. Basal cAMP and cGMP content together with phosphodiesterase and protein-kinase activities were normal in nodular, and suppressed in extranodular tissue. TSH-dependent cAMP accumulation was reduced in nodular tissue, but normal in the suppressed extranodular tissue. In vitro TSH-dependent iodothyronine release from nodular and extranodular tissue was absent. Thyroxine and iodine content of thyroglobulin extracted from nodular tissue was reduced, while triiodothyronine content was normal but with a low T4/T3 ratio. In extranodular tissue T3, T4 and iodine contents were reduced. In conclusion, autonomous thyroid nodules produced a poorly iodinated thyroglobulin leading to preferential T3 secretion with increased circulating free thyroid hormones even in clinically euthyroid patients.

Adult↗
PubMed1981

Dissociation in the response of the adenylate cyclase system to thyrotropin and prostaglandin E2 in human thyroid carcinoma tissue.

Because the existence of a damaged thyrotropin (TSH) receptor in thyroid tumors may be relevant in the perspective of a correct postsurgical therapy, the effect of TSH on cAMP intracellular accumulation in thyroid carcinoma (N = 16), follicular adenoma (N = 27) and normal tissue (N = 30) slices was studied and compared with that of nonspecific stimulus of thyroid adenylate cyclase-cAMP system, such as prostaglandin E2 (PGE2). While in all follicular adenomas a normal behavior of basal and post-TSH and -PGE2 stimulated cAMP accumulation was observed, basal cAMP levels were generally higher than in controls in 14 differentiated carcinomas, responses to TSH were reduced or absent, and response to PGE2 was close to normal. On the contrary, in two anaplastic carcinomas, both TSH and PGE2 produced a negligible modification of cAMP levels. Thus, in undifferentiated carcinomas, the adenylate cyclase-cAMP system seems to be altered; in differentiated carcinomas, the catalytic part of the system appears unaffected as it is PGE2-responsive. Therefore, some hypotheses are ruled out as an explanation for decreased sensitivity to TSH of differentiated carcinomatous cells.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1981

Prostacyclin stimulates the adenylate cyclase system of human thyroid tissue.

Since Prostacyclin (PGI2) is a major product of arachidonic acid metabolism in the human thyroid, we have studied the effects of PGI2 on cAMP accumulation in human thyroid slices and cultured thyrocytes. In both systems, PGI2 caused a dose- and time-dependent increase of cAMP accumulation with higher potency and efficacy than PGE2. Two optically active isomers of 5,6-dihydro-PGI2, i.e. stable synthetic analogs of PGI2, had qualitatively similar effects to PGI2. The relative potency ratio between the alpha- and beta- isomer as well as their potency compared to PGI2 were substantially similar to their potency in inhibiting human platelet aggregation. In thyroid slices, PGI2 and its stable analogs had a greater effect than TSH in causing cAMP accumulation; however, in contrast to TSH, this effect was not associated with increased iodothyronine release except at maximal PGI2 concentrations. TSH had no detectable effect on thyroidal PGI2 synthesis and release. In cultured thyrocytes the effects of PGI2 and its stable analogs were considerably less than those obtained with TSH and required higher concentrations. Such a discrepancy was not found in the case of PGE2. These findings suggest the existence of a specific PGI2-responsive adenylate cyclase system in human thyroid cells other than thyrocytes, of possible physiologic significance.

6-Ketoprostaglandin F1 alpha↗