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Biomedical subjects

K Kamijo

Publications and source records attributed to K Kamijo.

At least 91 records · Page 5Linked to original sources
PubMed1981

Studies on beta-phenylethylamine deamination by human placental monoamine oxidase.

Kinetical properties of human placental monoamine oxidase (MAO) were investigated in studies on inhibitors and mixed substrates. MAO activity was determined by a radioisotopic assay. Lineweaver-Burk plots were linear at higher and lower concentrations of PEA, whereas at intermediate substrate concentrations, a downward curving plot was obtained. The Km values of the low- and high-affinity sites for PEA deamination were estimated. Studies with mixed substrates showed that 5-HT was a competitive inhibitor and tyramine a mixed-type inhibitor of deamination at high concentrations of PEA, whereas both were non-competitive inhibitors at lower concentrations of PEA. After pre-incubation of human placental mitochondrial preparations with deprenyl, Lineweaver-Burk plots were completely linear, and the Km value was the same as that obtained at low concentrations of PEA in the absence of deprenyl. Tyramine and 5-HT were competitive inhibitors of PEA deamination by deprenyl-treated MAO. From these results it is concluded that there are two kinds of MAO with high- and low-affinity sites for PEA in mitochondria of human placenta, corresponding to type B and A Mao, and that tyramine, 5-HT and PEA share a substrate-binding site on type A Mao, while tyramine and 5-HT bind to a site on type B MAO that is different from the PEA binding site.

Deamination↗
PubMed1981

Effect of tris (hydroxymethyl) aminomethane on amine oxidase activity in dog brain, liver and serum and in human placenta.

The effect of Tris (hydroxymethyl) aminomethane on mitochondrial monoamine oxidase (MAO) activity in dog brain and liver and in human placenta was studied and the results obtained were compared with results on dog serum amine oxidase. With benzylamine as substrate, Tris did not inhibit mitochondrial MAO activity in these preparations, whereas inhibited mitochondrial MAO activity in these preparations, whereas it inhibited amine oxidase activity in a serum preparation. However, with tyramine, 5-hydroxytryptamine or beta-phenylethylamine as substrate, Tris inhibited MAO activity in all these preparations and its mode of inhibition was found to be non-competitive and reversible. The inhibition of Tris of MAO activity in these preparations was not due to decrease in the extent of extraction of aldehydes produced during the enzyme reaction. Moreover, increase in the oxygen tension did not change the extent of inhibition of MAO activity by Tris. From these results, it is concluded that with benzylamine as substrate, there is a remarkable difference in the effects of Tris on amine oxidase activity in mitochondrial and serum preparations. This difference in the inhibitions of mitochondria and serum is discussed.

Animals↗
PubMed1981

Evidence of sex difference in dopaminergic modulation of serum TSH secretion in primary hypothyroidism.

We have demonstrated the sex difference with respect to the dopaminergic modulation of serum TSH secretion in patients with primary hypothyroidism. Ten patients, 4 men and 6 women, with hypothyroidism were given 10 mg of Domperidone (Domp) iv, a very potent and specific dopamine receptor blocking agent, which could not readily cross the blood brain barrier. There was a significant rise in the TSH level after Domp iv in female patients with primary hypothyroidism, from basal values at zero time at 74.4 +/- 33.8 (M +/- SE) microU/ml to 171.2 +/- 94.9 at 30 min (p less than 0.001), 159.6 +/- 100.5 at 60 min (p less than 0.001). In contrast, no significant change in serum TSH values after Domp iv occurred in male patients with primary hypothyroidism, from basal values at zero time of 181.1 +/- 39.9 microU/ml to 171.4 +/- 31.1 at 30 min, 180.7 +/- 33.2 at 60 min and 172.7 /+- 31.0 at 90 min. After thyroid hormone therapy, max delta TSH values and the change from basal to peak values were significantly related to basal TSH values in female patients with primary hypothyroidism (r = +0.93, p less than 0.001), while max delta TSH in male patients was inversely related to basal TSH values within the limited concentrations (r - =0.78, p less than 0.02). It was conjectured from our results that maximum TSH responses to intravenous administration of domperidone in male and female hypothyroid patients were observed in respectively different basal TSH values, that is, less than 100 microU/ml in males and more than 100 microU/ml in females. Our findings provided evidence of sex difference in dopaminergic modulation of TSH secretion in primary hypothyroidism.

Adult↗
PubMed1980

Growth hormone response to thyrotropin-releasing hormone in cancer patients.

Plasma GH responses to TRH were investigated in 50 cancer patients. Out of 50 cancer patients, 33 were found to be responders. At 15, 30 and 60 min after TRH injection, the mean values GH for cancer patients was significantly higher than the corresponding value for normal controls and the base-line level following saline injection in cancer patients (p < 0.001). Our results suggests that a possible alteration of hypothalamic-pituitary function regulating GH secretion may occur in patients with cancer.

Adult↗
PubMed1980

[Effects of cysteine compounds on antibiotics I. Effects of L-cysteine and its derivatives on the potency of antibiotics (author's transl)].

Various derivatives of L-cysteine obtained by conversion to an -S-S- bond in the mucoprotein by means of -SH in the chemical structure are widely used as expectorants because they show mucous dissolving action. Recently, there have been reports that L-cysteine derivatives lower the potencies of various antibiotics. Various types of antibiotics and cysteine-type expectorants are often used concomitantly for the treatment of bacterial infections in respiratory tract diseases, and any decrease in the antibiotic potency presents a major therapeutic problem. We investigated the effects of four cysteine derivatives on 12 antibiotics, ampicillin (ABPC), amoxicillin (AMPC), sulbenicillin (SBPC), cefazolin (CEZ), cephalexin (CEX), cephalothin (CET), oxytetracycline (OTC), doxycycline (DOTC), minocycline (MINO), erythromycin (EM), ribostamycin (VSM) and lincomycin (LCM), widely used clinically in vitro with the minimum inhibitory concentration (MIc) obtained by the liquid dilution method as an index. L-Cysteine, acetylcysteine, ethylcysteine and mecysteine lowered the potencies of almost all of the antibiotics at high concentrations (500 mcg/ml), but at low concentrations (12.5 mcg/ml), mecysteine lowered the potencies of only three antibiotics and L-cysteine those of only four antibiotics, while acetylcysteine decreased the potencies of six and ethylcysteine those of seven antibiotics.

Anti-Bacterial Agents↗