The Experts below are selected from a list of 48 Experts worldwide ranked by ideXlab platform

R B Wilcox - One of the best experts on this subject based on the ideXlab platform.

  • effects of exogenous Monoiodotyrosine on the serum levels of anterior pituitary hormones
    European Journal of Endocrinology, 1991
    Co-Authors: J E Lewis, L S Berk, R B Wilcox
    Abstract:

    : Monoiodotyrosine is a tyrosine hydroxylase inhibitor. Ingestion of one gram Monoiodotyrosine caused a 10,000-fold increase of serum Monoiodotyrosine from basal levels of 0.69 +/- 0.20 nmol/l to a peak of 10.6 +/- 1.7 mumol/l in women and 7.1 +/- 2.3 mumol/l in men 30 min later, and the t1/2 was 45 min. Monoiodotyrosine stimulated PRL to a peak of 170 +/- 51 micrograms/l in women and 90 +/- 6 micrograms/l in men 30 min after the Monoiodotyrosine peak, or 60 min after the ingestion. Other anterior pituitary hormones were unchanged. Dopamine infusion or L-dopa pretreatment attenuated the Monoiodotyrosine effect. TRH exaggerated the PRL peak, and chlorpromazine did not increase but prolonged the hyperprolactinemia. These results suggest that dopamine synthesis inhibition may be the mechanism of PRL stimulation.

  • extrathyroidal physiology of Monoiodotyrosine in humans
    Clinical physiology and biochemistry, 1990
    Co-Authors: J E Lewis, L S Berk, R B Wilcox
    Abstract:

    : Normal serum Monoiodotyrosine (MIT) levels (n = 152) were 0.69 +/- 0.20 nmol/l. There was wide variation of MIT levels in a 24-hour period without diurnal pattern, and there was no change throughout the menstrual cycle. MIT levels declined upon aging, but levels in hypo- and hyperthyroidism were not significantly different. MIT levels were detected in athyrotic patients (0.32 +/- 0.08 nmol/l). Desiccated thyroid raised the athyrotic MIT levels to the normal range, while levothyroxine did not. Diiodotyrosine (DIT) infusion caused an MIT rise which paralleled but lagged 1 h behind the DIT rise. These data suggest thyroidal as well as nonthyroidal sources of MIT, one of which is deiodination of DIT. Ingestion of 1 g MIT increased serum MIT to 10.6 +/- 1.7 mumol/l in women, and 7.1 +/- 2.3 mumol/l in men 30 min after ingestion; the serum half-life was 45 min.

William A Gahl - One of the best experts on this subject based on the ideXlab platform.

  • characterization of lysosomal Monoiodotyrosine transport in rat thyroid cells evidence for transport by system h
    Journal of Biological Chemistry, 1990
    Co-Authors: Hans C Andersson, L D Kohn, Isa Bernardini, Henk J Blom, F Tietze, William A Gahl
    Abstract:

    Abstract Lysosomal transport of Monoiodotyrosine was characterized in countertransport experiments using rat FRTL-5 thyroid cell lysosomes. Monoiodotyrosine carrier activity was temperature-dependent (Ea = 11.65 kcal/mol) and had a pH optimum of 7.5. Carrier activity was minimally inhibited by KCl and NaCl, but unaffected by the presence of other ions or ATP. Monoiodotyrosine transport was unaffected by the presence of carbonyl cyanide m-chlorophenylhydrazone, nigericin, or ammonium chloride, indicating that a proton or K+ gradient is not necessary for Monoiodotyrosine transport across the lysosomal membrane. Monoiodotyrosine countertransport showed a 6-fold increase in lysosomes from FRTL-5 cells grown in medium containing thyrotropin by comparison to cells grown without this hormone. Thyrotropin responsiveness raised the possibility that Monoiodotyrosine was transported by system h, the only known lysosomal carrier whose activity is enhanced by thyrotropin. Consistent with this, Monoiodotyrosine-loaded lysosomes exhibited countertransport of [3H]tyrosine, [3H]phenylalanine, and [3H]leucine, three system h ligands, but not [3H]cystine, a nonsystem h ligand. Unlabeled tyrosine, phenylalanine, and leucine, but not cystine or proline, inhibited [125I]Monoiodotyrosine countertransport, and leucine inhibition of [3H]tyrosine countertransport and [125I]Monoiodotyrosine countertransport yielded virtually identical KI values, 3.5 and 3.2 microM, respectively. Competition studies with Monoiodotyrosine analogues showed that system h recognizes a broad range of ligands with an alpha-amino acid configuration at one end and a hydrophobic region at the other. Ring-substituted halogens, regardless of mass or ring position, but not amino, nitro, hydroxy, or methoxy groups, enhanced carrier recognition of system h analogues. It appears that a single system effects the transport of iodinated (e.g. Monoiodotyrosine) and noniodinated (e.g. tyrosine) thyroglobulin catabolites into the cytosol for salvage and reutilization by FRTL-5 thyroid cells.

  • characterization of lysosomal Monoiodotyrosine transport in rat thyroid cells
    1990
    Co-Authors: Hans C Andersson, Leonard D Kohnn, Isa Bernardinis, Henk J Bloms, Frank Tietzell, William A Gahl
    Abstract:

    Lysosomal transport of Monoiodotyrosine was characterized in countertransport experiments using rat FRTL-5 thyroid cell lysosomes. Monoiodotyrosine carrier activity was temperature-dependent (I$, = 11.65 kcal/mol) and had a pH optimum of 7.5. Carrier activity was minimally inhibited by KC1 and NaCl, but unaffected by the presence of other ions or ATP. Monoiodotyrosine transport was unaffected by the presence of carbonyl cyanide m-chlorophenylhydrazone, nigericin, or ammonium chloride, indicating that a proton or K+ gradient is not necessary for Monoiodotyrosine transport across the lysosomal membrane. Monoiodotyrosine countertransport showed a 6-fold increase in lysosomes from FRTL-5 cells grown in medium containing thyrotropin by comparison to cells grown without this hormone. Thyrotropin responsiveness raised the possibility that Monoiodotyrosine was transported by system h, the only known lysosomal carrier whose activity is enhanced by thyrotropin. Consistent with this, Monoiodotyrosine-loaded

J E Lewis - One of the best experts on this subject based on the ideXlab platform.

  • effects of exogenous Monoiodotyrosine on the serum levels of anterior pituitary hormones
    European Journal of Endocrinology, 1991
    Co-Authors: J E Lewis, L S Berk, R B Wilcox
    Abstract:

    : Monoiodotyrosine is a tyrosine hydroxylase inhibitor. Ingestion of one gram Monoiodotyrosine caused a 10,000-fold increase of serum Monoiodotyrosine from basal levels of 0.69 +/- 0.20 nmol/l to a peak of 10.6 +/- 1.7 mumol/l in women and 7.1 +/- 2.3 mumol/l in men 30 min later, and the t1/2 was 45 min. Monoiodotyrosine stimulated PRL to a peak of 170 +/- 51 micrograms/l in women and 90 +/- 6 micrograms/l in men 30 min after the Monoiodotyrosine peak, or 60 min after the ingestion. Other anterior pituitary hormones were unchanged. Dopamine infusion or L-dopa pretreatment attenuated the Monoiodotyrosine effect. TRH exaggerated the PRL peak, and chlorpromazine did not increase but prolonged the hyperprolactinemia. These results suggest that dopamine synthesis inhibition may be the mechanism of PRL stimulation.

  • extrathyroidal physiology of Monoiodotyrosine in humans
    Clinical physiology and biochemistry, 1990
    Co-Authors: J E Lewis, L S Berk, R B Wilcox
    Abstract:

    : Normal serum Monoiodotyrosine (MIT) levels (n = 152) were 0.69 +/- 0.20 nmol/l. There was wide variation of MIT levels in a 24-hour period without diurnal pattern, and there was no change throughout the menstrual cycle. MIT levels declined upon aging, but levels in hypo- and hyperthyroidism were not significantly different. MIT levels were detected in athyrotic patients (0.32 +/- 0.08 nmol/l). Desiccated thyroid raised the athyrotic MIT levels to the normal range, while levothyroxine did not. Diiodotyrosine (DIT) infusion caused an MIT rise which paralleled but lagged 1 h behind the DIT rise. These data suggest thyroidal as well as nonthyroidal sources of MIT, one of which is deiodination of DIT. Ingestion of 1 g MIT increased serum MIT to 10.6 +/- 1.7 mumol/l in women, and 7.1 +/- 2.3 mumol/l in men 30 min after ingestion; the serum half-life was 45 min.

L S Berk - One of the best experts on this subject based on the ideXlab platform.

  • effects of exogenous Monoiodotyrosine on the serum levels of anterior pituitary hormones
    European Journal of Endocrinology, 1991
    Co-Authors: J E Lewis, L S Berk, R B Wilcox
    Abstract:

    : Monoiodotyrosine is a tyrosine hydroxylase inhibitor. Ingestion of one gram Monoiodotyrosine caused a 10,000-fold increase of serum Monoiodotyrosine from basal levels of 0.69 +/- 0.20 nmol/l to a peak of 10.6 +/- 1.7 mumol/l in women and 7.1 +/- 2.3 mumol/l in men 30 min later, and the t1/2 was 45 min. Monoiodotyrosine stimulated PRL to a peak of 170 +/- 51 micrograms/l in women and 90 +/- 6 micrograms/l in men 30 min after the Monoiodotyrosine peak, or 60 min after the ingestion. Other anterior pituitary hormones were unchanged. Dopamine infusion or L-dopa pretreatment attenuated the Monoiodotyrosine effect. TRH exaggerated the PRL peak, and chlorpromazine did not increase but prolonged the hyperprolactinemia. These results suggest that dopamine synthesis inhibition may be the mechanism of PRL stimulation.

  • extrathyroidal physiology of Monoiodotyrosine in humans
    Clinical physiology and biochemistry, 1990
    Co-Authors: J E Lewis, L S Berk, R B Wilcox
    Abstract:

    : Normal serum Monoiodotyrosine (MIT) levels (n = 152) were 0.69 +/- 0.20 nmol/l. There was wide variation of MIT levels in a 24-hour period without diurnal pattern, and there was no change throughout the menstrual cycle. MIT levels declined upon aging, but levels in hypo- and hyperthyroidism were not significantly different. MIT levels were detected in athyrotic patients (0.32 +/- 0.08 nmol/l). Desiccated thyroid raised the athyrotic MIT levels to the normal range, while levothyroxine did not. Diiodotyrosine (DIT) infusion caused an MIT rise which paralleled but lagged 1 h behind the DIT rise. These data suggest thyroidal as well as nonthyroidal sources of MIT, one of which is deiodination of DIT. Ingestion of 1 g MIT increased serum MIT to 10.6 +/- 1.7 mumol/l in women, and 7.1 +/- 2.3 mumol/l in men 30 min after ingestion; the serum half-life was 45 min.

Hans C Andersson - One of the best experts on this subject based on the ideXlab platform.

  • characterization of lysosomal Monoiodotyrosine transport in rat thyroid cells evidence for transport by system h
    Journal of Biological Chemistry, 1990
    Co-Authors: Hans C Andersson, L D Kohn, Isa Bernardini, Henk J Blom, F Tietze, William A Gahl
    Abstract:

    Abstract Lysosomal transport of Monoiodotyrosine was characterized in countertransport experiments using rat FRTL-5 thyroid cell lysosomes. Monoiodotyrosine carrier activity was temperature-dependent (Ea = 11.65 kcal/mol) and had a pH optimum of 7.5. Carrier activity was minimally inhibited by KCl and NaCl, but unaffected by the presence of other ions or ATP. Monoiodotyrosine transport was unaffected by the presence of carbonyl cyanide m-chlorophenylhydrazone, nigericin, or ammonium chloride, indicating that a proton or K+ gradient is not necessary for Monoiodotyrosine transport across the lysosomal membrane. Monoiodotyrosine countertransport showed a 6-fold increase in lysosomes from FRTL-5 cells grown in medium containing thyrotropin by comparison to cells grown without this hormone. Thyrotropin responsiveness raised the possibility that Monoiodotyrosine was transported by system h, the only known lysosomal carrier whose activity is enhanced by thyrotropin. Consistent with this, Monoiodotyrosine-loaded lysosomes exhibited countertransport of [3H]tyrosine, [3H]phenylalanine, and [3H]leucine, three system h ligands, but not [3H]cystine, a nonsystem h ligand. Unlabeled tyrosine, phenylalanine, and leucine, but not cystine or proline, inhibited [125I]Monoiodotyrosine countertransport, and leucine inhibition of [3H]tyrosine countertransport and [125I]Monoiodotyrosine countertransport yielded virtually identical KI values, 3.5 and 3.2 microM, respectively. Competition studies with Monoiodotyrosine analogues showed that system h recognizes a broad range of ligands with an alpha-amino acid configuration at one end and a hydrophobic region at the other. Ring-substituted halogens, regardless of mass or ring position, but not amino, nitro, hydroxy, or methoxy groups, enhanced carrier recognition of system h analogues. It appears that a single system effects the transport of iodinated (e.g. Monoiodotyrosine) and noniodinated (e.g. tyrosine) thyroglobulin catabolites into the cytosol for salvage and reutilization by FRTL-5 thyroid cells.

  • characterization of lysosomal Monoiodotyrosine transport in rat thyroid cells
    1990
    Co-Authors: Hans C Andersson, Leonard D Kohnn, Isa Bernardinis, Henk J Bloms, Frank Tietzell, William A Gahl
    Abstract:

    Lysosomal transport of Monoiodotyrosine was characterized in countertransport experiments using rat FRTL-5 thyroid cell lysosomes. Monoiodotyrosine carrier activity was temperature-dependent (I$, = 11.65 kcal/mol) and had a pH optimum of 7.5. Carrier activity was minimally inhibited by KC1 and NaCl, but unaffected by the presence of other ions or ATP. Monoiodotyrosine transport was unaffected by the presence of carbonyl cyanide m-chlorophenylhydrazone, nigericin, or ammonium chloride, indicating that a proton or K+ gradient is not necessary for Monoiodotyrosine transport across the lysosomal membrane. Monoiodotyrosine countertransport showed a 6-fold increase in lysosomes from FRTL-5 cells grown in medium containing thyrotropin by comparison to cells grown without this hormone. Thyrotropin responsiveness raised the possibility that Monoiodotyrosine was transported by system h, the only known lysosomal carrier whose activity is enhanced by thyrotropin. Consistent with this, Monoiodotyrosine-loaded