Search PubMed⌕ Search

Biomedical subjects

N Takasu

Publications and source records attributed to N Takasu.

At least 145 records · Page 8Linked to original sources
PubMed1988

Cytoplasmic pH in the action of epidermal growth factor (EGF) in cultured porcine thyroid cells.

We demonstrate measurement of cytoplasmic pH (pHi), using 2',7'-bis(2-carboxyethyl)-5 (and 6-) carboxyfluorescein (BCECF), and internalized fluorescent pHi indicator, in thyroid cells. Using cultured porcine thyroid cells, we studied the effects of epidermal growth factor (EGF) on pHi and [3H] thymidine incorporation; 10 nM EGF alkalinizes thyroid cells and stimulates thymidine incorporation. The results indicate that Na+/H+ exchange or cell alkalinization may function as a transmembrane signal transducer in the action of EGF in the thyroid cells.

Animals↗
PubMed1988

Hydrogen peroxide generation in whole rat pancreatic islets; synergistic regulation by cytoplasmic free calcium and protein kinase-C.

This is the first report to show that pancreatic islet cells generate H2O2 and this H2O2 generation is regulated synergistically by cytoplasmic free calcium ([Ca2+]i) and protein kinase-C. Effects of calcium ionophore A23187 and 12-O-tetradecanoylphorbol 13-acetate (TPA), a tumor promoter, on H2O2 generation were studied in whole pancreatic islets obtained from male Wistar rats. We employed A23187 to elevate cytoplasmic free calcium, and TPA to activate protein kinase-C and monitored continuously their effects on H2O2 generation, measured using homovanillic acid and horseradish peroxidase. A23187 stimulates H2O2 generation. TPA, which activates protein kinase-C, augments this A23187-stimulated H2O2 generation. H2O2 generation is stimulated by an increase in [Ca2+]i and regulated synergistically by [Ca2+]i and protein kinase-C.

Animals↗
PubMed1988

Morphological identification of an interneuron in the hypoglossal nucleus of the rat: a combined Golgi-electron microscopic study.

Hypoglossal small neurons of adult and juvenile (10-15-day-old) rats were examined by a combined Golgi-electron microscopic technique. In adult rats, Golgi-impregnated neurons were fusiform or ovoid (17 X 12 micron) and emitted a few primary dendrites with few branches and few spines and an axon mainly from the proximal portion of the primary dendrite. At the ultrastructural level, the soma displayed an invaginated nucleus with a conspicuous nucleolus and a relatively scanty cytoplasm in which cisternae of rough endoplasmic reticulum were not organized into extensive lamellar arrays. A moderate number of axon terminals, which contained spherical clear or pleomorphic vesicles approximately 25-40 nm in diameter, formed symmetric or asymmetric synapses on the soma, the dendrites, the axon hillock, and the initial segment. In a preparation from the juvenile rat, we could trace a full axon trajectory of the small neuron. In this sample, in which a small neuron and a motoneuron were simultaneously impregnated, the axon of the small neuron was found to receive an axoaxonic symmetric synapse with pleomorphic vesicles on a varicosity and to contact the motoneuron dendrites by means of another varicosity of the main axon and of two boutons from an axon collateral. The varicosity and the boutons contained pleomorphic synaptic vesicles and synapsed symmetrically with the motoneuron dendrites. We identified the small neuron in the rat hypoglossal nucleus morphologicaly as a Golgi type II interneuron. We discuss its function in relation to the GABAergic nature of small neurons (Takasu et al.: J. Comp. Neurol. 263:42-53, '87).

Age Factors↗
PubMed1988

Epidermal growth factor (EGF) produces inositol phosphates and increases cytoplasmic free calcium in cultured porcine thyroid cells.

The initial signal for thyroid cell proliferation is unknown. This is the first report to show that epidermal growth factor (EGF) produces inositol phosphates and increases cytoplasmic free calcium ([Ca2+]i) in the thyroid gland. In cultured porcine thyroid cells, 10 nM EGF produces a breakdown of phosphatidylinositol and stimulates inositol phosphate production. Ten nM EGF increases [Ca2+]i, measured using fura-2, a fluorescent Ca2+ indicator; the EGF-induced [Ca2+]i response occurs immediately, reaches a maximum within several seconds, and then slowly declines. EGF stimulates production of inositol phosphates, which seem to increase [Ca2+]i. Inositol phosphate production and an increase in [Ca2+]i after EGF-stimulation may function as an initial signal for thyroid cell proliferation.

Animals↗
PubMed1988

Polarized thyroid cells in monolayers cultured on collagen gel: their cytoskeleton organization, iodine uptake, and resting membrane potentials.

Porcine thyroid cells were cultured on collagen gel-coated cover glasses. They were reorganized into polarized monolayer cells; the basal cell membranes were in contact with the collagen gel, and the apical ones faced the culture medium. We studied cytoskeleton organization, resting membrane potentials, and iodine uptake of these cells. The quick-freezing and deep-etching replica method provided three-dimensional images of the cytoskeleton organization. Networks of microfilaments were observed under the apical cell membrane. In the deep cytoplasm and near the basal cell membranes, intermediate filaments predominated and were interlinked with the microfilaments. When the cells were cultured in the presence of TSH, TSH induced the formation of microvilli at the apical cell membranes and the accumulation of microfilaments under these membranes; in the deep cytoplasm, the intermediate filaments were more closely interlinked with the microfilaments. The microfilaments were immunostained with antiactin antibody. Thus, collagen is a factor in determining the cell polarity, and TSH further augments polarization through reorganizing the cytoskeletons. Electrophysiological study revealed that the resting membrane potential of cells cultured in the absence of TSH was -46 mV, and that of cells cultured in the presence of TSH was -58 mV. TSH hyperpolarized resting membrane potentials. These cells took up iodine. TSH in the medium augmented this uptake. TSH augments thyroid cell polarization through reorganizing the cytoskeletons and hyperpolarizing the resting membrane potentials and enhances iodine uptake by the cells.

Animals↗
PubMed1988

Thyrotrophin and prostaglandin E2 increase calmodulin levels and cyclic AMP phosphodiesterase activity in cultured porcine thyroid cells.

Thyrotrophin (TSH) and prostaglandin E2 (PGE2) increased cellular cyclic AMP (cAMP), calmodulin levels and cAMP phosphodiesterase activity in cultured porcine thyroid cells. Dibutyryl cAMP (dbcAMP), a stable analogue of cAMP, increased calmodulin levels and cAMP phosphodiesterase activity. These results indicate that TSH- and PGE2-stimulated increases in calmodulin are mediated by cAMP. This increased concentration of calmodulin in turn stimulates cAMP phosphodiesterase. Double reciprocal plots of cAMP hydrolysis yielded two apparent Michaelis constants (Km); the lower in the 1 mumol/l and the higher in the 10 mumol/l range. Thyrotrophin, PGE2 and dbcAMP increased the values of maximal velocity without changing the Km values.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1987

Epidermal growth factor (EGF), tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) and calcium ionophore A23187 increase cytoplasmic free calcium and stimulate arachidonic acid release and PGE2/6-keto PGF1 alpha production in cultured porcine thyroid cells.

Epidermal growth factor (EGF), 12-O-tetradecanoylphorbol 13-acetate (TPA) and calcium ionophore A23187 increase cytoplasmic free calcium ([Ca2+]i) and stimulate arachidonic acid release and production of PGE2 and 6-keto PGF1 alpha, an end metabolite of PGI2, in cultured porcine thyroid cells. Addition of EGF, TPA or A23187 to the cells loaded with fura-2, a fluorescent Ca2+ indicator, causes an immediate increase in [Ca2+]i, which is the earliest event after mitogen stimulation. This [Ca2+]i response occurs immediately, reaching a maximum within several seconds. EGF, TPA and A23187 stimulate arachidonic acid release and PGE2 and 6-keto PGF1 alpha production; the maximum effects are obtained after 2-4 h incubation. EGF, TPA and A23187 increase [Ca2+]i and then stimulate arachidonic acid release and PG production.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Generation of H2O2 is regulated by cytoplasmic free calcium in cultured porcine thyroid cells.

Effects of calcium ionophore A23187 and BAY-K-8644, a calcium channel agonist, on cytoplasmic free calcium ([Ca2+]i) and H2O2 generation were studied in cultured porcine thyroid cells. We monitored continuously the effects of A23187 and BAY-K-8644 on [Ca2+]i and H2O2 generation, using the intracellularly trapped fluorescent Ca2+ indicator, fura-2, and homovanillic acid, respectively. A23187 and BAY-K-8644 induce an immediate increase in [Ca2+]i and H2O2 generation. The A23187- and BAY-K-8644-induced [Ca2+]i responses and H2O2 generation occur immediately, reach a maximum within several seconds, and then slowly decline. The minimum doses of A23187 or BAY-K-8644 to increase [Ca2+]i stimulate H2O2 generation. H2O2 generation is regulated by [Ca2+]i.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1987

Immunocytochemical localization of gamma-aminobutyric acid in the hypoglossal nucleus of the macaque monkey, Macaca fuscata: a light and electron microscopic study.

The hypoglossal nucleus of the macaque monkey Macaca fuscata was investigated with light and electron microscopic immunocytochemistry with an antibody directed against gamma-aminobutyric acid (GABA). At the light microscopic level, GABA immunoreactivity was present in small neurons, punctate structures, and thin, fiberlike structures. These GABA-positive elements were distributed throughout the hypoglossal nucleus at rostrocaudal levels. There was no immunoreactivity in the hypoglossal motoneurons. The GABA-positive small neurons were fusiform or ovoid (15 X 9 micron) and extended a few proximal dendrites from both poles. At the ultrastructural level, these small neurons were characterized by a markedly invaginated nucleus and a scanty cytoplasm in which cisternae of rough endoplasmic reticulum were not organized into extensive lamellar arrays as seen in the motorneurons. The GABA-positive punctate structures at the light microscopic level were identified as vesicle-containing axon boutons at the electron microscopic level. These GABA-positive axon terminals made synaptic contacts mainly with the dendrites of the motoneurons and infrequently with the somata. The majority of them made symmetric synapses and they contained pleomorphic synaptic vesicles. However, a small number of GABA-positive terminals (7%) formed asymmetric synapses with the dendrites of motoneurons, and these contacts exhibited postsynaptic dense bars or Taxi bodies lying beneath the postsynaptic membranes. There were no GABA-positive boutons that contacted the cell bodies of the small neurons. Although GABA-positive myelinated and unmyelinated axons were seen as thin, fiberlike structures, these myelinated and unmyelinated axons rarely gave rise to boutons on the motoneurons. The present study suggests that GABAergic inhibition in the monkey hypoglossal nucleus occurs mainly on the dendrites of the motoneurons and to some extent on the somata.

Animals↗
PubMed1987

Epidermal growth factor (EGF) and tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulate PG synthesis and thymidine incorporation in cultured porcine thyroid cells.

This is the first report to show that epidermal growth factor (EGF) and 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulate the production of PGE2 and 6-keto PGF1 alpha, an end metabolite of PGI2, in the thyroid gland. In cultured porcine thyroid cells, EGF and TPA stimulate PGE2 and 6-keto PGF1 alpha production; the maximum PG levels were obtained after 3-4 h incubation with EGF or TPA; the addition of as little as 10(-11) M EGF or 5 X 10(-11) M TPA resulted in increases in PGE2 and 6-keto PGF1 alpha, and the maximum levels were obtained with 10(-8)-10(-7) M EGF or TPA. This report also shows that EGF and TPA stimulate [3H] thymidine incorporation.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

BAY-K-8644, a calcium channel agonist, induces a rise in cytoplasmic free calcium and iodide discharge in thyroid cells.

BAY-K-8644, a calcium channel agonist, induces a rise in cytoplasmic free calcium and iodide discharge in cultured porcine thyroid cells. The cytoplasmic free calcium concentration, [Ca2+]i, was measured using aequorin, a calcium-sensitive photoprotein. BAY-K-8644, a dihydropyridine derivative, acts as a Ca channel agonist and induces a rise in [Ca2+]i and iodide discharge; 0.5 nM BAY-K-8644 is a minimal dose to effect a rise in [Ca2+]i and iodide discharge and 50 nM BAY-K-8644 produces the maximal effect. The data indicate that BAY-K-8644-induced iodide discharge is mediated by a rise in [Ca2+]i.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1987

Evidence for thyrotropin (TSH)-blocking activity in goitrous Hashimoto's thyroiditis with assays measuring inhibition of TSH receptor binding and TSH-stimulated thyroid adenosine 3',5'-monophosphate responses/cell growth by immunoglobulins.

There are two forms of autoimmune thyroiditis that may cause hypothyroidism: autoimmune atrophic thyroiditis (primary idiopathic hypothyroidism or primary myxedema) and autoimmune goitrous thyroiditis (Hashimoto's disease). Patients with the former have impalpable thyroid glands, and those with the latter have goiters. We studied TSH binding inhibitory immunoglobulins (TBII), TSH-stimulated cAMP response inhibitory immunoglobulins (TSII), and TSH-stimulated cell growth inhibitory immunoglobulins (TGII) in 42 patients with the former (group 1) and 115 patients with the latter (group 2). Porcine thyroid cells in primary culture and rat thyroid cells in continuous culture (FRTL-5 cells) were used to study TSII and TGII activities, respectively; TSII was expressed as percent inhibition of 0.1 mU/ml TSH-stimulated cAMP response by the patient's immunoglobulin (IgG; 1 mg/ml) during 2-h incubation, and TGII was expressed as percent inhibition of 10 mU/ml TSH-stimulated [14C]thymidine incorporation by the patient's IgG (1 mg/ml) during 24-h incubation. The new findings in this report are: some patients in both groups had TBII, TSII, and/or TGII; the frequency of the presence of TBII, TSII, and TGII in the patients with autoimmune atrophic thyroiditis was higher than that in the patients with autoimmune goitrous thyroiditis, and TSII and TGII were significantly associated with autoimmune atrophic thyroiditis; no correlation was found between goiter size and TBII, TSII, or TGII activity; and there were good correlations between TBII, TSII, and TGII activities. We also found that TSH-stimulated thymidine incorporation was through cAMP production and that the inhibitory IgGs inhibited TSH-stimulated thymidine incorporation by decreasing cAMP production in FRTL-5 cells, but not in porcine or human thyroid cells.

Adult↗
PubMed1987

Presence of antideoxyribonucleic acid antibody in patients with hyperthyroidism of Graves' disease.

In 16 untreated patients with hyperthyroidism due to Graves' disease, serum antidouble stranded DNA antibody, measured by RIA, was positive (greater than 20 U/ml) in 14. In methimazole-treated patients with T3-suppressible thyroid uptake, anti-DNA antibody was found in 9% (3 of 35). The frequency of positive tests in methimazole-treated patients with T3-nonsuppressible thyroid uptake and in surgically treated patients was 24% (5 of 21) and 57% (4 of 7), respectively. Among anti-DNA antibody-negative (less than 9 U/ml) and weakly positive (10-19 U/ml) patients, those with T3-suppressible thyroid uptake had lower anti-DNA antibody titers than those with T3-nonsuppressible thyroid uptake. Among 32 patients with Hashimoto's thyroiditis, anti-DNA antibody was positive in 7. None of the patients with simple goiter had positive or weakly positive anti-DNA antibody results. Although the quantity of antibodies did not correlate well in individual patients, the rates of positive TSH binding-inhibiting immunoglobulin and anti-DNA antibody tests were roughly comparable in these patient groups. None of these patients with thyroid disease associated with anti-DNA antibody had clinical or other serological evidence suggestive of systemic lupus erythematosus or related collagen vascular disorders. The finding of anti-DNA antibody provides a new aspect of immunological abnormality associated with hyperthyroidism of Graves' disease.

Antibodies, Antinuclear↗
PubMed1987

Tumour promoter 12-O-tetradecanoylphorbol 13-acetate and epidermal growth factor stimulate proliferation and inhibit differentiation of porcine thyroid cells in primary culture.

12-O-Tetradecanoylphorbol 13-acetate (TPA) is a potent tumour promoter and shows several biological activities of epidermal growth factor (EGF). EGF and TPA stimulated proliferation and inhibited differentiation of porcine thyroid cells in primary culture. They also stimulated [3H]thymidine incorporation and inhibited an early step in thyroid hormone synthesis (iodine organification). The results indicate that EGF and TPA switch the developmental course of porcine thyroid cells from differentiation to proliferation.

Animals↗
PubMed1987

Ca2+ ionophore A23187-induced rise in cytoplasmic free calcium and iodide discharge in porcine thyroid cells: measurement of cytoplasmic free calcium by aequorin.

The cytoplasmic concentration of free calcium was measured using aequorin, a calcium-sensitive photoprotein. The Ca2+ ionophore A23187 induced a rise in cytoplasmic free calcium and iodide discharge in cultured porcine thyroid cells. The minimum dose of A23187 effecting an increase in cytoplasmic free calcium induced iodide discharge. The A23187-induced rise in cytoplasmic free calcium was followed by iodide discharge. The results indicate that A23187-induced iodide discharge is mediated by a rise in the cytoplasmic concentration of free calcium.

Aequorin↗
PubMed1986

TSH-stimulated increases in calcium uptake and calmodulin levels in thyroid cells.

This is the first report to show that polypeptide hormone increases cellular calmodulin contents. In cultured porcine thyroid cells, 6 days' exposure to TSH (above 0.02 mU/ml) increased cellular calmodulin contents. Six days' exposure to TSH also increased calcium uptake in thyroid cells. This TSH-stimulated increase in calcium uptake was partly due to the increase in cellular calmodulin contents.

Animals↗
PubMed1986

Changes in left ventricular preload and contractility following severe burns in the dog.

To examine the effects of severe burns on preload and left ventricular (LV) contractility, we continuously measured LV pressures and dimensions in severely burned dogs throughout the early part of the postburn period. Hemodynamic parameters, including cardiac output (CO), mean aortic pressure (MAP), heart rate (HR), LV pressures and their first derivatives (dP/dt), and the LV regional dimension, were measured and compared before and every 30 min after burns were produced (up to 360 min) in four groups: group A (n = 7), dogs with sham burns; group B (n = 5), dogs with nonresuscitated full-thickness burns involving 50% of the total body surface area; group C (n = 6), dogs with burns resuscitated with lactated Ringer's solution at 4 ml X kg X % burn/24 h; and group D (n = 6), dogs with burns resuscitated with 1.5% dextran in lactated Ringer's solution at 2 ml X kg X % burn/24 h. From these measurements, we obtained the LV end-diastolic segment length (EDL) as an index of preload and three indices of cardiac contractility, i.e., peak dP/dt, the percentage of shortening (% delta L), and mean Vcf. Our results showed that CO, MAP, and preload (i.e., EDL) decreased significantly more in the three burn groups (groups B, C, and D) than in the sham burn group, but that there were no significant differences in CO, MAP, and EDL among the three burn groups. The three indices of contractility also decreased significantly more in the three burn groups than in the sham burn group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗