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Biomedical subjects

M Oka

Publications and source records attributed to M Oka.

At least 631 records · Page 35Linked to original sources
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

Serum ferritin and free erythrocyte protoporphyrin in rheumatoid arthritis.

In this prospective study 20 newly diagnosed patients with definite or classical rheumatoid arthritis were followed with serial measurements of serum ferritin and erythrocyte-free protoporphyrin at the beginning of the trial and at 3 and 6 months. The values were correlated with clinical disease activity ad with various laboratory parameters. It was shown that free erythrocyte protoporphyrin has a constant negative correlation with erythrocyte haemoglobin concentration independent of disease activity, while serum ferritin behaves like an acute phase protein. Initial serum ferritin or free erythrocyte protoporphyrin values or their early changes appeared to have no prognostic value as evaluated by the development of new erosions or by the response of the patient to the therapy.

Adult↗
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

Inhibitory action of hydralazine on catecholamine secretion from cultured bovine adrenal chromaffin cells.

Hydralazine caused a concentration-dependent inhibition of the secretion of catecholamines induced by carbamylcholine or high K+ from cultured bovine adrenal chromaffin cells, and also caused the significant inhibition of radioactive calcium uptake induced by carbamylcholine into the cells. However, hydralazine failed to inhibit the secretion of catecholamines evoked by the calcium-ionophore, A23187. The inhibitory action of hydralazine on catecholamine secretion induced by carbamylcholine was not affected by increasing the concentration of calcium ion in the reaction mixture. These observations therefore seem to indicate that the inhibitory action of hydralazine is not due to either the blocking of receptors for carbamylcholine or the disruption of the secretory machinery, and suggest that the drug may cause the inhibition of catecholamine secretion through its blocking action on calcium influx into the cells.

Adrenal Glands↗
PubMed1986

Response of isolated guinea pig myocardium to insulin therapy during normothermia and graded hypothermia.

The discovery of insulin in 1922 aroused immediate clinical interest in its use in heart disease. In severe heart failure, insulin release is suppressed by the combined effect of poor pancreatic perfusion and by increased sympathetic activity. In these circumstances, myocardial metabolism of glucose may break down through the deficiency of insulin. Because of this, glucose, insulin and potassium solution (GIK solution) has been used in cardiopulmonary resuscitation. However, its mechanism is not yet fully known. This study was designed to determine the effect of insulin on cardiac muscle at various temperatures. The mechanical response of papillary muscle isolated from guinea pig ventricle was observed under various thermal conditions (23-37 degrees C). Twitch tension was increased by the administration of 0.2 I.U./ml insulin under each thermal condition. In all circumstances, the increase in contractile force was noted about 2 min after the administration of insulin. The effect of insulin on 20 preparations demonstrated the mean maximum contractile force was 226% ( +/- 34 S.D., n = 5) in 37 degrees C, 194% ( +/- 36 S.D., n = 5) in 30 degrees C, 190% ( +/- 30 S.D., n = 5) in 27 degrees C and 200% ( +/- 36 S.D., n = 5) in in 23 degrees C. The differences between different temperatures was not significant. The effect of insulin during depression Na-K pump by high concentration of ouabain (g-strophanthin, 10(-5) M) was also observed. Insulin (0.2 I.U./ml) was administered when the papillary muscle showed no response to electrical stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Lymphoepithelial (branchial) cyst and amylase.

A case of a branchial cyst with a high amylase activity of the cyst fluid was found in a 58-year-old female. The literature on branchial cysts with high amylase activity is reviewed. Amylase that showed high activity in the cystic fluid was revealed to be due to the salivary isoenzymes (S3 and S4) which migrated more to the anodic side on electrophoresis.

Amylases↗
PubMed1986

Inhibitory action of hydralazine on catecholamine-synthesizing enzymes prepared from bovine adrenal medulla.

The direct effect of hydralazine on catecholamine-synthesizing enzymes was investigated. Hydralazine caused a concentration-dependent inhibition of tyrosine hydroxylase (TH) prepared from bovine adrenal medulla, and a more pronounced effect was obtained by incubating the enzyme with the drug prior to the enzyme assay. Kinetic studies showed that hydralazine increased the apparent Km value of the enzyme for tyrosine and cofactor, 6,7-dimethyl-5,6,7,8-tetrahydropterin (DMPH4), without any change in the Vmax. The inhibitory effect of the drug was irreversible, and an excess amount of FeSO4 failed to restore the enzyme activity inhibited by this drug. Furthermore, hydralazine also inhibited the dopamine beta-hydroxylase (DBH) in chromaffin granule membranes. Hydralazine increased the apparent Km value of DBH for ascorbic acid without any change in the Vmax, and it decreased the Vmax of the enzyme for tyramine with no change in the apparent Km value. The observations described here suggest the possibility that hydralazine presumably causes the inhibition of catecholamine-synthesizing enzymes as a result of allosteric alterations in the molecular structures of these enzymes. It thus seems unlikely that the inhibitory action of hydralazine on these enzymes may totally be based on its metal-chelating activity.

Adrenal Medulla↗
PubMed1986

Participation of opiate and serotonergic systems in brain conditioning stimulatory inhibition of the potentials evoked by tooth pulp stimulation in the pars caudalis of the trigeminal sensory nucleus of the rat.

Effects of conditioning stimulations of the nucleus raphe magnus (NRM), nucleus reticularis paragigantocellularis (NRPG), mesencephalic periaqueductal central gray (PAG), nucleus dorsomedialis hypothalami (DMH), corpus striatum (CP), sensory cortex (SCT) and visual cortex (VCT) and actions of morphine, naloxone and metergoline on the potentials recorded from the pars caudalis of the trigeminal sensory nucleus evoked by the electrical stimulation of rat incisor pulps were examined. The spinal potentials evoked by electrical stimulation of the pulp consisted of 3 components. Component 2 was mainly inhibited by morphine and antagonized by naloxone. Conditioning stimulation of NRM, NRPG, PAG, CP, SCT and DMH strongly inhibited component 2. VCT did not show any inhibition. 33-67% of antagonism was observed by naloxone in the NRM, NRPG, PAG, CP, SCT and DMH. On the other hand, 27-44% of antagonism was observed by metergoline, and the antagonism was not enhanced by the additional administration of naloxone. These results conclusively show that the endorphin system as well as the serotonergic system is in the series involved in the descending inhibition for nociception in the trigeminal sensory nucleus.

Animals↗
PubMed1986

Urinary neopterin index as a measure of rheumatoid activity.

The urinary neopterin index (U-NEOPT-I), expressed as micro-moles of neopterin/moles of creatinine) of 67 patients with definite or classical rheumatoid arthritis was significantly higher than that of sex- and age-matched persons or of 24 non-matched patients suffering from osteoarthrosis or arthralgia (2p less than 0.001). Furthermore, the patients with active disease had statistically significantly increased U-NEOPT-I when compared with patients with a clinically less active disease. In this study, the U-NEOPT-I value was the equal of CRP as a measure of rheumatoid activity. We suggest that neopterin might be involved in the pathogenesis of rheumatoid arthritis.

Adult↗
PubMed1986

[Sensitivity of esophageal cancer to anticancer agents and supplementary chemotherapy combined with surgical treatment].

The authors examined the sensitivities of esophageal cancer to Bleomycin (BLM), Peplomycin (PEP), Cisplatin (CDDP) and 5-FU by the INAS method using 3H-thymidine or 14C-formate as labeled precursors, and determined the concentrations of anticancer agents in cancer lesions by the Band Culture method. On the other hand, the authors investigated the superiority or inferiority of various methods of BLM administration by observing the prevention effect of BLM on the development of experimental esophageal cancer in rats. Forty-three cases out of 76, 57%, showed a sensitivity to BLM, 60% to PEP, 38% to CDDP and 56% to 5-FU. As to the types of roentgenological findings, the superficial and tumorous types showed a high sensitivity rate. As to the types of macroscopical findings, the protruded and superficial types showed a high sensitivity rate. As to the types of histological findings, well differentiated squamous cell carcinoma showed a high sensitivity rate. Sensitivity was higher in metastatic lymph nodes than in main cancer lesions. Tumor tissues which had undergone previous hyperthermic management (at 42 degrees C) showed a higher sensitivity than those which had not. PEP at a half dose brought about the same grade of anticancer effect as BLM. The sensitivities of esophageal cancer to various anticancer agents showed individual differences among clinical cases. Therefore, combination chemotherapy for esophageal cancer was thought to be an effective administration method. The divided administration of small doses of BLM was thought to be more superior than the one-shot administration of a large dose for esophageal cancer. The results of the INAS sensitivity test were perfectly coincident with the effects of chemotherapy in clinical cases of esophageal cancer.

Animals↗
PubMed1986

Evidence against a possible involvement of the serine, and thiol proteases in the exocytotic mechanism of catecholamine secretion in cultured bovine adrenal medullary cells.

The effects of protease inhibitors on the secretion of catecholamines were studied in cultured bovine adrenal medullary cells. Although the inhibitors of serine proteases could inhibit the carbamylcholine-induced secretion, they failed to inhibit the secretion evoked by either high K+ or A23187. The thiol protease inhibitor had no effect on the secretion. These results therefore seem to indicate that the serine protease inhibitors may inhibit the receptor-mediated secretion probably through their effects on the plasma membrane, thus suggesting that a possible involvement of the serine, and thiol proteases in exocytosis may be unlikely.

Adrenal Medulla↗
PubMed1986

General pharmacology of the novel angiotensin converting enzyme inhibitor alacepril. 2nd communication: Effects on central nervous and sensory systems and on the other functions.

The effects of 1-[(S)-3-acetylthio-2-methylpropanoyl]-L-prolyl-L-phenylalanine (alacepril, DU-1219), an orally active angiotensin converting enzyme inhibitor, on the central nervous and sensory systems and on several other functions were compared with those of captopril in the experimental animals. Alacepril at the high oral dose of 600 mg/kg prolonged the hexobarbital sleeping time and potentiated the reserpine-induced hypothermia in mice. However, alacepril at the same dose did not affect the general behavior, convulsions induced by maximal electroshock, pentetrazol and strychnine, active avoidance in mice and body temperature in rats. In addition, alacepril (200 mg/kg i.v.) has little effect on general behavior in mice. Captopril at over 107 mg/kg p.o. produced eyelid closure and at 320 mg/kg prolonged the hexobarbital sleeping time. A metabolite of alacepril, desacetylalacepril (DU-1227) (200 mg/kg i.v.), caused salivation in mice. Alacepril and DU-1227 at 60 mg/kg i.v. were without effect on flexor reflex and spontaneous electroencephalogram (EEG) in cats, while captopril at the equimolar dose depressed the flexor reflex and showed a tendency to increase the beta 2-band relative power of the cortical EEG. Alacepril and captopril neither affected the writhing syndrome induced by acetic acid nor that by phenylquinone in mice. Local anesthetic and irritant activities in rabbits and effect on neuromuscular junction in anesthetized rats were not observed with the two compounds. Alacepril at the oral dose of 0.1 mg/kg potentiated the carrageenin-induced edema in rats. However, the effect was one third that of captopril. Alacepril and captopril did not affect the increased vascular permeability by acetic acid in mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗