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Biomedical subjects

N Yoshida

Publications and source records attributed to N Yoshida.

At least 649 records · Page 36Linked to original sources
PubMed1978

Abnormal plasminogen. A hereditary molecular abnormality found in a patient with recurrent thrombosis.

A patient who suffered a recurring thrombosis over the last 15 yr has been investigated. The only abnormality found in this patient was a significantly depressed level of plasminogen activity in plasma. In spite of the depressed plasminogen activity, the patient was found to have a normal level of plasminogen antigen concentration. It was calculated that the activity per milligram of plasminogen of the patient was approximately one-half the values of normal subjects. The same discrepancy between biological activity and antigen concentration was found in the other members of the kindred. A niece was found to have practically no plasminogen activity but possessed a normal concentration of plasminogen antigen. Both her parents were found to have approximately half the normal plasminogen activity and normal antigen levels. These studies suggested that the molecular abnormality was inherited as an autosomal characteristic, and the family members who had half the normal levels of activity with normal plasminogen antigen were heterozygotes whereas the one with practically no plasminogen activity was homozygote. Subsequent studies showed that the pattern of gel electrofocusing of purified plasminogen of the heterozygotes consisted of 10 normal bands and 10 additional abnormal bands, each of which had a slightly higher isoelectric point than each corresponding normal component. This indicates that plasminogen of the heterozygote is a mixture of normal and abnormal molecules in an approximately equal amount, which was substantiated by active site titration of purified plasminogen preparations obtained from the propositus and a normal individual. The gel electrofocusing pattern of the homozygote consisted of abnormal bands only. The defect is a hereditary abnormality of plasminogen.

Adult↗
PubMed1978

Biosynthetic pathways for corticoids and androgen formation in human fetal adrenal tissue in vitro.

Eleven incubations of minced human fetal adrenal tissue from two fetuses at midtrimester of pregnancy terminated for socio-economic reasons, were performed for different periods of time with labelled pregnenolone, progesterone, 17alpha-hydroxyprogesterone and deoxycorticosterone (DOC). The order of magnitudes of enzyme activity when progesterone was used as a substrate and incubated with midterm fetal adrenals was 17alpha-hydroxylase, 21-hydroxylase and 16alpha-hydroxylase. The activity of 3beta-hydroxysteroid dehydrogenase and delta5-4 isomerase was almost negligible as compared to other enzymic activities as mentioned above. Similar biosynthetic pathways for adrenal corticoids formation were observed in human fetal adrenals as reported in human adults and animals; once progesterone was converted into DOC, further 17alpha-hydroxylation did not take place.

Adrenal Cortex Hormones↗
PubMed1978

Inhibition of fetal adrenal 21-hydroxylase by naturally occurring steroids.

Inhibitory effects of naturally occurring steroids on 21-hydroxylase activity were determined by measuring the initial conversion rate of 17-hydroxyprogesterone (17alpha-hydroxy-4-pregnene-3, 20-dione) to 11-deoxycortisol (17alpha, 21-dihydroxy-4-pregnene-3, 20-dione) in incubation experiments with the microsomal fraction (10,000--105,000 X g percipitate) of the human fetal adrenal gland. The apparent Michaelis constant (Km) for conversion of 17-hydroxyprogesterone was 13.3 X 10(-6)M. Human fetal adrenal 21-hydroxylase was inhibited by some of the steroids produced in the feto-placental unit. The following steroids acted as competitive inhibitors of the reaction; progesterone (Ki = 20.0 X 10(-6)M), 11-deoxycortisol (Ki = 87.5 X 10(-6)M) and estradiol-17beta (Ki = 87.5 X 10(-6)M). The most potent inhibitor among the estrogens was estradiol-17beta.

Adrenal Glands↗
PubMed1978

Inhibition of platelet aggregation by protease inhibitors. Possible involvement of proteases in platelet aggregation.

The possible participation of proteases in human platelet aggregation was explored using various protease inhibitors and substrates. Protease inhibitors used included naturally occurring inhibitors of serine proteases and synthetic inhibitors that modify the active site of protease. Substrates used were synthetic substrates for the trypsin type as well as for the chymotrypsin type of protease. All these inhibitors and substrates inhibited platelet aggregation and serotonin release induced by ADP, collagen, epinephrine, or thrombin. In ADP- and epinephrine-induced platelet aggregation the second phase of aggregation was most efficiently inhibited. The inhibitors suppressed the formation of malondialdehyde during platelet aggregation. Release by aggregating agents of arachidonate and its metabolites from indomethacin-treated platelets as well as nontreated platelets was also inhibited. The inhibitors apperar to interact with stimulated platelets but not with unstimulated platelets. These observations suggest that the interaction of an aggregating agent with its platelet receptor activates a unique precursor serine protease that in turn activates platelet phospholipase to liberate arachidonic acid (the precursor of the potent platelet aggregating agent thromboxane A2) from platelet phospholipids.

Arachidonic Acids↗
PubMed1978

Release of arachidonic acid from human platelets. A key role for the potentiation of platelet aggregability in normal subjects as well as in those with nephrotic syndrome.

Low (nonaggregating) concentrations of collagen that potentiate platelet aggregation did not induce the formation of measurable amount of malondialdehyde (MDA) but released small but significant amounts of radioactivity from 14C-arachidonic acid-labeled platelets. A major portion of the radioactive compounds released by nonaggregating concentrations of collagen existed as arachidonic acid and a minor part as thromboxane B2. The nephrotic syndrome enhances platelet aggregability, and this effect is abolished by correcting hypoalbuminemia in vitro and in vivo by the addition of albumin, which is the main carrier for free fatty acids, including arachidonic acid. Human albumin (fatty acid free) inhibited collagen-induced aggregation, MDA formation, and release of the radioactivity from 14C-arachidonic acid-labeled platelets in normals as well as in those with nephrotic syndrome. These data support our hypothesis that the main mechanism responsible for the potentiation of platelet aggregation is the release of arachidonic acid from platelet membrane phospholipids via the activation of phospholipase A2. Furthermore, enhanced platelet aggregation in the nephrotic syndrome was at least partly attributable to an increased availability of arachidonic acid released secondary to hypoalbuminemia. Albumin inhibits aggregation probably by binding to released arachidonic acid preventing arachidonic acid from being metabolized to potent aggregating substances, endoperoxides and thromboxane A2. The mechanism of release of arachidonic acid may play a key role in the potentiation of platelet aggregability in normals as well as in pathologic conditions such as the nephrotic syndrome.

Albumins↗
PubMed1977

A semi-automated measurement of urinary catecholamines using high-speed ion-exchange column chromatography.

Semi-automated measurement of urinary catecholamines, specific for dopa, noradrenaline, adrenaline and dopamine and other metabolites has been developed. Steps included alumina extraction, separation by high-speed ion-exchange column chromatography and fluorescent development by trihydroxyindole (THI) method without interference by other fluorescent substances. Recovery, reproducibility and sensitivity were satisfactory. alpha-Methyldopa, a metabolite of alpha-methyldopa, and isoproterenol were separated completely without interfering with the measurement of noradrenaline, adrenaline and dopamine.

Adult↗
PubMed1977

Purification of angiotensin I-converting enzyme from human lung.

Angiotensin I-converting enzyme (peptidyl dipeptide hydrolase, EC 3.4.15.1) was solubilized from the membrane fraction of human lung using trypsin treatment and purfied using columns of DE 52-cellulose, hydroxyapatite and Sephadex G-200. The purified enzyme was shown to convert angiotensin I to angiotensin II and also to inactivate bradykinin. The specific activity of the enzyme was 9.5 units/mg protein for Hippuryl-His-Leu-OH and 0.665 mumol/min per mg protein for angiotensin I. The enzymic activity obtained after trypsin treatment (1 mg/200 mg protein) for 2 h could be divided into three components: (i) an enzyme of molecular weight 290 000 (peak I), (ii) an enzyme of molecular weight 180 000 (peak II) and (iii) an enzyme of molecular weight 98 000 (peak III), by columns of DE 52-cellulose and Sephadex G-200. Km values of peak I, II and III fraction for Hippuryl-His-Leu-OH were identical at 1.1 mM. pH optimum of the enzyme was 8.3 for Hippuryl-His-Leu-OH.

Angiotensin II↗