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Biomedical subjects

K Teraoka

Publications and source records attributed to K Teraoka.

At least 73 records · Page 4Linked to original sources
PubMed1989

Effect of lithium carbonate administration singly or in combination with some psychotropic drugs on the radioiodide uptake by mouse thyroid.

The present study dealt with two objects; the first object was to examine whether or not lithium uptake in thyroid is modified by the thyroid state and how the intrathyroidal Li affects iodide uptake by the thyroid. Male and female mice were given lithium carbonate (Li) with propylthiouracil (PTU) or thyroxine (T4). Li was measured by a flameless atomic absorption spectrometry. The total Li content in thyroid was unaffected with PTU or T4, however, Li concentration per unit mass was reduced by PTU but unaffected by T4. The thyroid: serum ratio (T/S) of 125I resulted that the T/S became higher when Li concentration per unit mass was lower and vice versa, suggesting that Li uptake is controlled by thyroid states and Li in the gland interferes with the iodide uptake. Serum triiodothyronine (T3) and T4 by radioimmunoassay showed that PTU alone and in combination with Li lowered serum T4, while a high level of T4 by its supplement was suppressed by co-administration of Li. T3 level was lowered by Li alone, but not severely affected by other drugs. The results suggest that Li enhances T4 clearance without T4-T3 conversion. The second object was to examine the effect of combined psychotropic drugs on thyroid function. Carbamazepine (CBZ), haloperidol (HLP) and imipramine (IPA) were given singly or in combination with Li to examine their effects on the T/S of 125I. Only CBZ reduced the T/S but CBZ plus Li had no summative effect. Neither HLP nor IPA affected the T/S, singly or in combination with Li, suggesting that HLP or IPA does not interfere with an iodide pumping machinery. No distinct sex difference was observed in drug effects.

Animals↗
PubMed1989

Cross-linking and stereospecific structure of collagen in mineralized and nonmineralized skeletal tissues.

Molecular distributions of the intermolecular cross-links in fetal bovine bone type I collagen fibrils were quantitatively determined and compared with those of periodontal ligament. Results indicated that Hyl and Lys residues in the COOH-terminal nonhelical peptide portions (residues 16C) of both alpha 1 chains were quantitatively converted to aldehydes. These in turn stoichiometrically formed cross-links with residues Hyl-87 on both alpha 1 and alpha 2 chains of neighboring molecules. The ratio of cross-linked alpha 1 to alpha 2 chains was 3.5 to 1 indicating a stereospecific packing of collagen molecules in the fibrils similar manner to periodontal ligament collagen. It was found that there were few aldehyde derived cross-links in the NH2-terminal nonhelical portions of the bone type I collagen. The relative paucity of the cross-links in NH2-terminal region of bone collagens may favor mineralization.

Animals↗
PubMed1989

Effects of cytoskeleton-disrupting agents on tyrosine transport into cultured bovine adrenal chromaffin cells.

The effects of various cytoskeleton-disrupting agents on tyrosine transport into chromaffin cells were examined to assess the possibility of cytoskeleton involvement in the regulation of precursor supply for catecholamine synthesis. Tyrosine transport was markedly increased by cytochalasin B. Vinblastine also stimulated tyrosine transport, although its effect was less pronounced than that of cytochalasin B. While colchicine failed to cause any significant increase in the transport under the same conditions. These results therefore suggest a possible role of microfilaments as a factor regulating tyrosine transport into chromaffin cells.

Adrenal Medulla↗
PubMed1987

Interaction of cytoplasmic tyrosine hydroxylase with chromaffin granule. In vitro studies on association of soluble enzyme with granule membranes and alteration in enzyme activity.

The interaction of soluble tyrosine hydroxylase with isolated chromaffin granule membranes was studied. The incubation of the granule membranes with the soluble fraction in the mixture that may approximate the intracellular environment of the resting cell resulted in a marked increase in the enzyme activity recovered in the membrane fraction, and enzyme activity precipitated with the granule membranes was increased according to incubation time and dependent on amounts of both the granule membranes and soluble fraction. The association of the soluble enzyme with the granule membranes was reversible and specific, whereas a decrease in activity of the soluble enzyme was observed when the soluble fraction was incubated with the granule membranes in the mixture in which association of the soluble enzyme with the granule membranes might occur. These results seem to indicate that activity of the soluble enzyme is presumably modulated by the granule through association of the soluble enzyme with the surface of the granule, thus suggesting that interaction between tyrosine hydroxylase and the chromaffin granule may play a possible role in regulation of catecholamine biosynthesis as a consequence of modulating activity of the rate-limiting enzyme within the cell.

Adrenal Medulla↗
PubMed1987

X-ray photoelectron spectroscopic studies of the adsorption of salivary constituents on enamel.

Time-dependent change of adsorption of salivary components on the outermost surface layer of enamel was studied by x-ray photoelectron spectroscopy. Adsorption of proteinaceous components, as monitored in terms of the relative mass of nitrogen, was detected within 30 min, increased with time, and reached a plateau at 90 min. Thus, the ratio of nitrogen to calcium in the two-hour sample increased to about 240 times that in the control sample. The ratio of carbon to nitrogen on the surface decreased to about one-half of that in the control sample. The data established the time required for equilibrium between the proteinaceous component in saliva and the amount of material adsorbed onto the tooth surface.

Adsorption↗
PubMed1986

Modulation by basic polypeptides of ATP-induced activation of tyrosine hydroxylase prepared from bovine adrenal medulla.

The effects of basic polypeptides on the activation of adrenal tyrosine hydroxylase by ATP were investigated to show a possible involvement of macromolecular cell components in the regulation of the enzyme activity. Basic polypeptides caused an enhancement of the activation of tyrosine hydroxylase by low concentrations of ATP, and the potentiating effects of these polypeptides were observed to be dependent on their concentrations. Kinetic studies showed that basic polypeptides caused an increase in the Vmax of the ATP-activated enzyme for the cofactor without any change in the Km. These results suggest that basic polypeptides convert the enzyme from a nonsusceptible form to a form susceptible to ATP, thus resulting in the potentiation of the ATP-induced activation. Furthermore, the activation by ATP of tyrosine hydroxylase was not observed after treatment of the enzyme preparation with CM-cellulose, and the responsiveness of the enzyme treated with CM-cellulose to ATP was partially restored by addition of basic polypeptides. These observations suggest the possibility that macromolecular cell components, presumably basic proteins, may be involved in the regulation of the activity of tyrosine hydroxylase through their modulating effects on the sensitivity of the enzyme to ATP within the cell.

Adenosine Triphosphate↗
PubMed1986

Inositol phospholipids cause the activation of adrenal tyrosine hydroxylase through their electrostatic action on the enzyme.

The effects of inositol phospholipids on adrenal tyrosine hydroxylase (TH) were studied. Phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2) caused a rapid and concentration-dependent activation of TH in vitro. The potency of this activation was dependent on the number of phosphate groups in the lipid molecule, and the activation was completely suppressed by increasing the concentrations of salts in the reaction mixture. These results seem to indicate that the activation of TH by inositol phospholipids may be due to their electrostatic action, and suggest a possible involvement of inositol phospholipids in the regulation of TH activity in vivo.

Adrenal Medulla↗
PubMed1986

Sex differences in appetitive learning of mice.

Learning abilities of male and female ddY mice were compared in two appetitive tasks (a lever-press task and an 8-arm radial maze task), and two avoidance tasks (a shuttle box task and a light-dark discrimination T-maze task). In the two types of appetitive learning, male mice were significantly superior to female mice. Sex differences were particularly apparent in the acquisition process. In contrast, there was no significant sex difference in learning of the two avoidance tasks. A sex difference in appetitive learning was not found in juvenile mice prior to sexual maturation, and the mice which had established a lever-press response as juveniles did not show any significant difference in the performance level when tested as adults. Thus, a sex difference appeared only in the acquisition stage of adult mice. These results suggest that there exists a sex difference in motivation level for hunting food but not for feeding, and that it causes a sex difference in appetitive learning.

Aging↗