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Biomedical subjects

T Onaya

Publications and source records attributed to T Onaya.

At least 163 records · Page 9Linked to original sources
PubMed1988

Immunohistochemical localization of parvalbumin in rat and monkey autonomic ganglia.

The cellular distribution of parvalbumin-like immunoreactivity in autonomic ganglia such as superior cervical sympathetic ganglia, paravertebral sympathetic chain ganglia (T6), ciliary ganglia and enteric ganglia was investigated by immunohistochemical peroxidase-antiperoxidase methods using an antiserum against rat skeletal muscle parvalbumin. We detected parvalbumin-like immunoreactivity in almost all neurons of rat superior cervical sympathetic ganglia and other paravertebral sympathetic chain ganglia, where the antigen was located in the cytoplasm but the nuclei were not labelled. No neurons positive for parvalbumin-like immunoreactivity were observed in rat ciliary ganglia or enteric ganglia. In monkey, almost all neurons of the superior cervical sympathetic ganglia contained parvalbumin-like immunoreactivity, but none of the neurons of the ciliary ganglia were labelled with the antiserum to parvalbumin. These results suggest that parvalbumin-like immunoreactivity exists in a specific subpopulation of the neurons of the autonomic nervous system.

Animals↗
PubMed1988

Increased production of prostacyclin (PGI2) by vascular intimal smooth muscle cells from atherosclerotic rabbit aorta.

In vitro PGI2 synthesis by aortic strips obtained from thoracic aorta of rabbits fed a high cholesterol diet was examined and compared with that of control rabbits fed a normal diet. In this report, the amounts of PGI2 produced were shown as 6-keto-PGF1 alpha per microgram of aortic tissue DNA instead of per mg wet weight. We also investigated PGI2 synthesis by cultured smooth muscle cells (SMC) obtained from atherosclerotic intima. Basal PGI2 production by aortic strips from atherosclerotic rabbit aorta was significantly augmented compared with that of controls. Arachidonic acid (AA)-induced PGI2 production by atherosclerotic aorta was also significantly higher than that of controls. PGI2 producing capacities of intimal and medial layers, separated from atherosclerotic aorta, were examined and the intimal layer was found to elicit a significantly greater PGI2 production than the medial layer. Furthermore, cultured intimal SMC obtained from atherosclerotic rabbit aorta produced a greater amount of PGI2 than medial SMC from normal rabbit aorta at various cultured conditions. These results suggest that the possibility of enhanced PGI2 production by atherosclerotic aorta may well be considered as a defence mechanism of the vessel wall against damaging stimuli.

Animals↗
PubMed1988

Evidence for a preferential iodination site within the thyroglobulin molecule.

Mouse 330 kDa thyroglobulin labeled in vivo was analyzed using a tryptic peptide mapping technique and high performance liquid chromatography (HPLC). 30 min after Na125I injection, one peptide spot (spot 7) on a silica gel plate was the only prominent labeled peptide, followed by other labeled peptide spots after 1 h. HPLC showed that spot 7 was rich in monoiodotyrosine. The ratios between the iodoamino acids were strictly maintained from 1 to 6 h after Na125I injection. Spot 7 was again the first spot that appeared from the samples of iodine-deficient mice. These data indicate that there is some preferential iodination site(s) within the thyroglobulin molecule and also that their iodoamino acid composition is predetermined.

Amino Acids↗
PubMed1988

Postmortem changes in the level of calcium pumping adenosine triphosphatase in rat heart sarcoplasmic reticulum.

The activity of calcium pumping adenosine triphosphatase (Ca2+-ATPase) in cardiac sarcoplasmic reticulum plays a pivotal role in myocardiac contraction-relaxation. The Ca2+-ATPase activity is controlled by phosphorylation and dephosphorylation of a sarcoplasmic reticulum protein "phospholamban" in response to neurotransmitters and drugs. To clarify the role of Ca2+-ATPase in the development of cardiac rigor mortis, we examined the changes of cardiac rigidity and cardiac sarcoplasmic reticulum Ca2+-ATPase activity up to 5 h after the decapitation of rats. Fifteen minutes after decapitation, the rats showed a cardiac rigidity on left ventricles. After 30 min, rigidity was obvious over the whole heart. After 1 h, the rigidity reached a high degree which was maintained for the rest of the observation period. On the other hand, the Ca2+-ATPase activity controlled by phosphorylation and dephosphorylation of phospholamban did not change for the whole observation period (5 h). Another Ca2+-ATPase activity representing the total amount of Ca2+-ATPase in sarcoplasmic reticulum gradually decreased. The data suggest that no significant phosphorylation or dephosphorylation of phospholamban occurs for a short time, at least for 5 h, after death and that the Ca2+-ATPase tends to relax the myocardium against the development of cardiac rigor mortis.

Animals↗
PubMed1988

Phagocytotic activities of latex beads by FRTL cell: possible interaction of cell surface glycoprotein.

We investigated the phagocytic activity of cultured rat thyroid cells (FRTL) by using latex beads. FRTL cells ingested many carboxylate-modified polystyrene latex beads (c-latex beads), which had carboxyl residues on the surface, whereas they ingested few polystyrene latex beads (p-latex beads), which had no electrostatic charge. Phagocytotic activity of c-latex beads was stimulated by TSH in a dose-related manner. Dibutyryl, 8-bromo-cAMP, and forskolin also stimulated this process. Tunicamycin significantly inhibited dibutyryl cAMP-stimulated phagocytotic activity of c-latex beads by FRTL cells. N-acetylglucosaminidase also inhibited dibutyryl cAMP-stimulated phagocytosis. These results suggest that the interaction between negative surface charge of c-latex beads and positive surface charge probably induced by N-acetylglucosamine in the cell surface glycoprotein, might play an important role in the phagocytosis of FRTL cells.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1988

Effects of somatostatin and serotonin on calcitonin secretion from cultured rat parafollicular cells.

A primary culture of mammalian parafollicular cells was established from rat thyroid glands in order to investigate the effects of serotonin and somatostatin on calcitonin secretion. Minced rat thyroid glands were dissociated with collagenase and cultured in a Ham's F-12K medium supplemented with calf serum (5%), insulin (1.3 X 10(-6) mol/l), hydrocortisone (10(-8) mol/l), transferrin (6.1 X 10(-9) mol/l), and glycyl-L-histidyl-L-lysin (2.5 X 10(-8) mol/l). Immunohistochemical peroxidase-antiperoxidase method revealed that the cultured parafollicular cells were immunopositive for human calcitonin, and electron microscopy demonstrated the existence of dense secretory granules in the cultured parafollicular cells. Addition of the Ca2+ to the culture medium stimulated calcitonin secretion from the cells dose-dependently as measured by radioimmunoassay. Pre-incubation of serotonin with the cells produced higher calcitonin levels in a dose-dependent manner. On the other hand, pre-incubation of somatostatin with the cells significantly inhibited calcitonin secretion.

Animals↗
PubMed1987

Reevaluation of circulating prostacyclin and thromboxane in diabetes.

Although several investigators have attempted to measure the plasma levels of prostacyclin (PGI2) and thromboxane A2 (TXA2) in diabetes and normal subjects, their results have been controversial. In this study, we measured plasma PGI2 and TXA2 levels in diabetic patients and normal subjects. The plasma PGI2 and TXA2 were determined by RIA as 6-keto-PGF1 alpha and TXB2, respectively. The plasma levels of 6-keto-PGF1 alpha were significantly reduced in diabetics with microangiopathy (52.5 +/- 18.9 pg/ml, mean +/- SE, p less than 0.05) compared with those of normal subjects. Diabetics as a whole also showed lower levels of 6-keto-PGF1 alpha than normal subjects (57.8 +/- 26.1 vs. 70.2 +/- 20.7 pg/ml), though this was not significant statistically. The plasma 6-keto-PGF1 alpha levels did not significantly correlate with either age of the patients or duration of diabetes in diabetics. Interestingly, however, hemoglobin A1c significantly correlated inversely with 6-keto-PGF1 alpha levels in diabetics without microangiopathy (r = -0.60, p less than 0.05). The plasma levels of TXB2 in diabetics were significantly higher than those of normal subjects (155.2 +/- 69.5 vs. 108.0 +/- 30.0 pg/ml, p less than 0.05). These data suggest that an imbalance of circulating PGI2 and TXA2 may contribute to the development of diabetic microangiopathy.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Circulating prostacyclin and thromboxane in patients with Graves' disease.

We measured plasma levels of PGI2 as 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane A2 (TXA2) as thromboxane B2 (TXB2) in patients with Graves' disease and in normal subjects. The levels of plasma 6-keto-PGF1 alpha were significantly elevated and correlated with those of serum T4 and T3, respectively, in hyperthyroid patients with Graves' disease. Significant reduction of 6-keto-PGF1 alpha levels was observed after antithyroid drug therapy. In contrast, the levels of plasma TXB2 were significantly lower in untreated patients with Graves' disease than in normal subjects. These data suggest that an elevation of plasma 6-keto-PGF1 alpha may play some additional role in pathophysiology of Graves' disease.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Demonstration of calcium-dependent proteases (calpains) and thyroglobulin proteolysis in hog thyroid cytosol.

Ca2+-dependent neutral proteases in hog thyroid cytosol were found to digest thyroglobulin. The protease activity was divided into two peaks by DEAE-cellulose column chromatography. Peak I was eluted at 0.2 M NaCl and required only a micromolar range of Ca2+ for its 50% activation, while peak II, which was eluted at about 0.4 M NaCl, displayed little activity until the Ca2+ concentration was increased at more than 10(-4) M. Among various inhibitors used, thiol protease inhibitors (leupeptin, E-64 and monoiodoacetic acid) were the most effective, whereas a calmodulin antagonist (trifluoperazine) and serine protease inhibitors (phenylmethyl-sulfony-fluoride and pepstatin A) were not effective, indicating that these Ca2+-dependent proteases corresponded to calpains 1 and 2. Among the substrates tested, casein was the best and thyroglobulin was also a good for calpain 2. By using immunoblotting procedure with anti-thyroglobulin antibody, it has been found that calpain 2 degrades thyroglobulin to yield 67 K and 46 K thyroglobulin and further that it also degrades 40 K thyroglobulin.

Animals↗
PubMed1987

The inhibitory effects of calmodulin antagonists on TSH-stimulated thyroid hormone release by mouse thyroid lobes.

Calcium ions have been shown to play a mojor regulatory role in the release of various hormones from a wide variety of endocrine organs. More recently, in vitro evidence suggests that a calcium-binding protein, calmodulin, is also involved in the release of many hormones. So we examined the effects of several types of calmodulin antagonists on TSH-stimulated thyroid hormone release in vitro. Mouse thyroid lobes (one thyro-tracheal unit/tube) were incubated in Krebs-Ringer bicarbonate buffer at 37 degrees C for 4h. Free thyroxine (fT4) released in the incubation medium, thyroidal cAMP and calmodulin content were measured by RIA. TSH (5 mU/ml) and dibutyryl cAMP (DBC) (200 micrograms/ml) caused a 2-4 fold increase in thyroidal release of fT4. The stimulatory effects of TSH on fT4 release were significantly inhibited by trifluoprazine and prenylamine lactate at the concentration of 5 X 10(-5) M. More specific calmodulin antagonists, W-7 and W-13, were also shown to inhibit TSH stimulation of fT4 release at the concentration of 5 X 10(-5) M. In contrast, TSH stimulation of fT4 release was not depressed by non-specific antagonists, W-5 or W-12, at the same concentration as 5 X 10(-5) M. Further, W-13 also markedly inhibited DBC-stimulated fT4 release. Neither TSH nor PGI2 altered the thyroidal calmodulin content, dissociating with a marked increase in the cAMP concentration. These results suggest that calmodulin plays an important role in TSH-stimulated thyroid hormone release and further that this mechanism exists, at least in part, at the site subsequent to the generation of cAMP.

Animals↗
PubMed1986

Immunocytochemical and biochemical localization of parvalbumin in the retina.

The cellular distribution of parvalbumin-like immunoreactivity (PA-LI) in normal retina of rat, monkey, and human was investigated by immunohistochemical peroxidase-antiperoxidase methods, and the levels of PA-LI in normal rat retina and brain were measured by radioimmunoassay. The antibody, raised in rabbits using rat skeletal muscle parvalbumin, did not cross-react with other Ca2+-binding proteins such as calmodulin or S-100 proteins. In rat retina, PA-LI-containing cells are located in the proximal inner nuclear layer and send processes to the external half of the internal plexiform layer, suggesting that they are amacrine cells. In monkey and human retina, PA-LI-positive cells exist in the outermost sublayer of inner nuclear layer, and PA-LI-containing fibers that extend horizontally are found in the internal zone of outer plexiform layer. The radioimmunoassay revealed that the rat retina contained 1710 +/- 91 ng PA-LI/mg protein, the levels of which were higher than that of brain (881 +/- 165 ng PA-LI/mg protein). These results show an additional location for PA-LI outside skeletal muscle and brain, and also provide information on the function of interneurons of retina, which are still poorly understood.

Animals↗
PubMed1986

Immunochemical and immunohistochemical localization of parvalbumin in rat nervous tissues.

The contents of parvalbumin in various nervous tissues of the rat were measured by radioimmunoassay (RIA) and its cellular distribution was immunohistochemically examined by peroxidase-antiperoxidase methods. The antibody, raised in rabbits using rat skeletal muscle parvalbumin, did not cross-react with other Ca2+-binding proteins such as calmodulin or S-100 proteins. The RIA demonstrated the wide distribution of the antigen, with very high levels in the cerebellum (3,217 +/- 519 ng/mg protein). The immunohistochemical description by Celio and Heizmann [Nature 293, 300-302 (1981)] was confirmed concerning the existence of the antigen in Purkinje cells of the cerebellum; nonpyramidal neurons of the cerebral cortex; and medium-sized cells of the olfactory bulb, hippocampus, and reticular nucleus of the thalamus. In addition to these neurons, we found the parvalbumin-like immunoreactivity in the large neurons of the superior vestibular nucleus and the neurons of the medial superior olive nucleus. In the gamma-aminobutyric acid (GABA)-containing nuclei such as substantia nigra, caudatoputamen, and globus pallidus, parvalbumin-positive cells and fibers were rare. In the medial lemniscus of the midbrain which contains no GABA, parvalbumin-immunoreactive fibers were prominent. The possibility was discussed that parvalbumin exists in a specific population of neurons that differ from those containing GABA.

Animals↗
PubMed1986

Parvalbumin is reduced in the peripheral nerves of diabetic rats.

Parvalbumin (PA), one of the Ca2+-binding neuronal marker proteins, has been revealed to exist in the myelinated axons of the posterior root of the spinal cord and the peripheral nerve of rats. To investigate the role of PA for the genesis of diabetic neuropathy, the levels of PA in the sciatic nerve of normal and streptozotocin-induced diabetic rats were measured by radioimmunoassay (RIA) for PA. The immunohistochemical distribution of PA in the sciatic nerve from both groups was also studied. The RIA for PA revealed that the levels of PA in the sciatic nerve of diabetic rats were significantly decreased when compared with those of normal rats. However, the contents of S-100 protein, another type of Ca2+-binding glial marker protein, did not show any significant difference in the sciatic nerve from both groups. Immunohistochemically, the amount of PA containing myelinated axons of the diabetic nerve was markedly decreased when compared with nondiabetic subjects. These results suggest that the decreased level of PA in the peripheral nerve might contribute to the genesis of diabetic neuropathy.

Animals↗
PubMed1986

Iodide-induced hypothyroidism in a patient with anorexia nervosa.

A 39-year-old woman who had been suffering from anorexia nervosa was found to have hypothyroidism. Serum T4, free T4, T3, free T3 and TSH were 3.19 micrograms/dl, 0.5 ng/dl, 15.3 ng/dl, 1.2 pg/ml and 162.1 microU/ml, respectively. On careful questioning, she was found to have taken an iodine-rich diet. The serum iodine concentration was 122 micrograms/dl (normal: 4-9 micrograms/dl) and urinary iodide excretion was 13.05 mg/day (normal: less than 2 mg). After withdrawal of the iodine-rich diet, her serum T4 gradually increased and TSH returned to the normal range. She was diagnosed as having iodide-induced hypothyroidism. However, no significant elevation of serum T3 or free T3 was observed. Serum T4, free T4, T3, free T3 and TSH were 7.85 micrograms/dl, 0.8 ng/dl, 13.6 ng/dl, 4.3 pg/ml and 6.02 microU/ml, respectively. The iodide-perchlorate discharge test result was negative. These findings suggest that there exists some unknown mechanism by which a patient with anorexia nervosa may be sensitive to excess iodide. Furthermore, it is of interest to note that in a recovery phase from the hypothyroid state, normalization of serum T4 rather than T3 is well-correlated to TSH secretion.

Adult↗
PubMed1986

Effects of phorbol esters on protein phosphorylation and free T3 release by mouse thyroid lobes.

Phorbols stimulated 32P incorporation into several proteins in mouse thyroid lobes. Phosphoproteins (34 K and 23 K) were detected by SDS-polyacrylamide gel electrophoresis and autoradiography. Among phorbols tested, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) was the strongest stimulator of protein phosphorylation. On the other hand, TPA at 50-200 ng/ml significantly stimulated free T3 release by mouse thyroid lobes. The stimulatory effect of TPA was not additive to that of TPA or dibutyryl cAMP. TSH stimulation of free T3 release by mouse thyroid lobes, however, was significantly inhibited by H-7 (an inhibitor of protein kinase C) at a concentration of 50 microM. These results suggest that protein kinase C may play some role in thyroid hormone secretion by phosphorylating the endogenous substrates.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗