S. Kobayashi

An evidence of the peroxidase-dependent oxygen transfer from hydrogen peroxide to sulfides

Horseradish- and chloro-peroxidase catalyzed oxidation of sulfides have been investigated. Thioanisoles were oxygenated to the corresponding sulfoxides by such peroxidases at the expense of H2O2. Dealkylation was observed only in the chloroperoxidase-dependent oxidations of p-methoxy- and p-iso-propoxy-thioanisoles. The experiments with 18O-labeled H2O2 indicated that an oxygen atom of H2O2 is incorporated into the sulfoxides. These research lead to the conclusion that compound I or II is capable of acting as an oxygen donor as well as an electron acceptor.

Contraction of the Canine Basilar Artery following Linoleic, Arachidonic, 13-Hydroperoxylinoleic, or 15-Hydroperoxyarachidonic Acid

Abstract The contractile activity of linoleic acid (LA), arachidonic acid (AA), 13l-hydroperoxy-cis-9-trans-11-octadecadienoic acid (13HPLA), or 15l-hydroperoxy-cis-5-cis-8-cis-11-trans-13-eicosatetraenoic acid (15HPAA) was tested on canine basilar artery segments in a small chamber, using serotonin as the reference vasoconstrictor. The cumulative dose–response contraction was approximately 400 times that of serotonin. On the other hand, either 15HPAA or 13HPLA at 10-6 M induced a contraction almost equal to the maximum attained with serotonin (1 × 10-6 M) contraction. The maximal artery response to each of the hydroperoxy fatty acids was almost 1.4 times stronger than that obtained with serotonin, LA, or AA.

Excitation of indole acetate in myeloperoxidase-H2O2 system: Possible formation of indole acetate cation radical

Abstract Myeloperoxidase-H 2 O 2 -indole acetate system at pH 7.4 emitted light in visible region. Luminescent spectrum showed a weak peak at or near 480 nm and prominent peaks at or near 550, 580, and 620 nm with deep troughs near 500 and 600 nm. In some cases, no definite peak emissions near 550 and 580 nm, but a prominent broad emission between 550 and 580 nm, is observed. Such spectral patterns in the region of 510 to 620 nm were quite similar to those report for the luminescence of photo-products formed from the indole analogs (tryptophan and indole) in 50% alcohol irradiated by U.V. (365 nm) at 77°K, assuming red shift (20–25 nm) by solvent effect. Possible formation of indole acetate cation radical (a precursor of excited indole acetate) was discussed.

Cyclo (His-Pro), a metabolite of thyrotropin-releasing hormone: specific binding to rat liver membranes.

[3H]cyclo(His-Pro) bound with high affinity (59 nM) to a single class of sites in rat liver plasma membranes, without significant tracer degradation during equilibration for 60 min at 0 degrees C. Binding was specific and saturable (3.9 pmol/mg protein), and were increased by the addition of K+, Mg++ and Na+ at optimal concentrations, but not of Ca++ at all concentrations tested. In vivo administration of cyclo(His-Pro), but not thyrotropin-releasing hormone, to rats caused the downregulation of cyclo(His-Pro)-binding sites with decreases in specific binding numbers but did not change binding affinity.

Stimulation by a TRH precursor, TRH-Gly, of TSH and PRL secretion in rats: Effect of starvation

The hypophysial activities of a possible direct precursor of thyrotropin (TSH)-releasing hormone (TRH), TRH-Gly, were evaluated in estrogen, progesterone-primed rats under urethane anesthesia. Intravenous administration of TRH-Gly in doses of 2-200 micrograms caused a significant and dose-dependent increase in blood TSH and prolactin (PRL). The stimulatory activity of TRH-Gly was 170 to 400-times less potent than that of TRH. The lower potency was confirmed by the action of TRH-Gly on the anterior pituitary cells in vitro. In starved rats, TRH-Gly apparently stimulated TSH and PRL secretion in a dose-dependent manner, and the stimulatory activity increased in starved rats as compared to normal controls. TRH-Gly did not affect [3H-MeHis]TRH binding in pituitary plasma membranes. These data imply that large amounts of TRH-Gly may have significant biological activities and these are potentiated in the starved condition.

Thyrotropin-releasing hormone stimulation of thyrotropin secretion is suppressed by calcium ion antagonists that block transmembrane influx and intracellular mobilization of calcium ion in human subjects

To evaluate whether extracellular and intracellular calcium ion may be involved in the regulation of TSH secretion in response to TRH in human subjects, the TSH blood level was determined in normal man before and after administration of two kinds of calcium ion antagonists, nifedipine that blocks transmembrane influx of calcium ion and nicorandil that inhibits mobilization of intracellular calcium ion. Administration of nifedipine and nicorandil significantly decreased the blood level of TSH stimulated by TRH, although calcium ion antagonistsdid not affect the basal level of TSH. The blood level of neither T4, T3, free T4, free T3, nor reverse T3 was altered by administration of calcium ion antagonists. The present study indicates that cytoplasmic calcium ion derived from the extracellular and intracellular sources plays a pivotal role in the controlling of TRH-stimulated TSH secretion in human subjects.

Central hypothyroidism due to isolated TRH deficiency in a depressive man

Abstract. A depressive man was evaluated for developing chronic fatigue and cold intolerance, in whom laboratory findings showed decreased thyroid hormone levels (T4, 2.7 μg dl−1; T3, 0.76 ng ml−1) with normal blood levels of TSH. A single bolus injection of TRH (500 μg) significantly stimulated prolactin secretion, but did not cause an increase in blood TSH levels (basal level, 1.2 μU ml−1 vs. 1.3 μU ml−1 30 min after injection). By contrast, TRH‐induced TSH stimulation occurred after repeated injection of TRH for 4 consecutive days (basal level, 1.5 μU ml−1 vs. 5.6 μU ml−1 30 min after injection). Blood thyroid hormone concentrations were restored to normal levels after long‐term administration of TRH. Other pituitary functions remained unchanged. A diagnosis of central hypothyroidism due to isolated TRH deficiency was made in this case, and the data presented here indicate that partial resistance of pituitary thyrotrophs to TRH may be associated with depression.

Involvement of interleukin-1 in the inhibition of in vivo insulin release: possible role of adrenal glands

The effect of recombinant human interleukin-1 beta (rhlL-1b) on in vivo insulin secretion was examined in intact and adrenalectomized (ADX) rats under conscious and pentobarbital anesthetized conditions. In conscious rats, rhlL-1b dosedependently decreased blood glucose levels at 2 h in both groups and significantly inhibited insulin release only at doses of 1 and 10 µg/kg in ADX rats. Under pentobarbital anesthesia, rhlL-1b administration decreased blood glucose levels 2 h later in both intact and ADX rats and resulted in severe hypoglycemia in ADX rats. At 2 h later, rhlL-1b significantly suppressed insulin release by pentobarbital injection in both intact and ADX rats. It is concluded that rhlL-1b suppresses in vivo insulin secretion in conscious ADX and anesthetized rats.

Recognition by anti-idiotypic anti-thyrotropin-releasing hormone (TRH) antibody of rat TRH receptors

We asked whether anti-idiotypic antibodies raised against anti-TRH antibody could bind to TRH receptors in the rat anterior pituitary and brain. Six rabbits were immunized with IgG from a rabbit anti-TRH antiserum. One anti-idiotypic antibody caused strong, dose-dependent inhibition in anti-TRH antibody-binding to [125]I-TRH. This inhibition was not observed after treatment with goat anti-rabbit IgG antibody. The anti-idiotypic anti-TRH antibody significantly immunoprecipitated digitonin-solubilized pituitary TRH receptors. When eluates of digitonin-solubilized membranes which were adsorbed by either an anti-idiotypic anti-TRH IgG-, normal rabbit IgG-linked affinity column or control column were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and visualized by silver stain, only the former eluate showed two bands under nonreducing conditions; one corresponded to a molecular weight marker of 200K, the other to 100K. Western blotting analysis with an anti-idiotypic anti-TRH antiserum showed a single band of molecular weight 56K under reducing conditions. The present study indicates that one can make anti-idiotypic antibodies that specifically recognize TRH receptors.

Diabetes insipidus with spontaneous remission

Pathogenesis of idiopathic diabetes insipidus is unknown and the clinical course of the disease is permanent. However, we observed one patient who was diagnosed of idiopathic diabetes insipidus spontaneously reverted after approximately 13 months. The cause and pathogenesis of the disease were not evident. However, some reversible abnormalities should have been encountered in the hypothalamic-neurohypophyseal system. It is suggested that some unknown reversible impairments of the supraopticohypophyseal tract can cause diabetes insipidus. This case represents a well-documented description of idiopathic diabetes insipidus with spontaneous remission.