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Biomedical subjects

J Azuma

Publications and source records attributed to J Azuma.

At least 73 records · Page 4Linked to original sources
PubMed1981

Trapidil stimulation of slow Ca2+ current in cardiac muscle.

The effect of trapidil, a coronary vasodilator and positive inotropic agent (associated with elevated tissue cyclic AMP levels due to phosphodiesterase inhibition), was examined on the electrophysiological properties of cardiac muscle. Specifically, the trapidil was tested for its ability to induce slow action potentials (APs), and to affect the maximum upstroke velocity (+Vmax) of the slow APs in the ventricular myocardial cells of isolated perfused chick hearts. The effect of trapidil on the contractions accompanying the slow APs and on the tissue cyclic AMP levels was also examined. To study the slow channels exclusively, the fast Na+ channels were voltage-inactivated by elevated (25 mM) K+. In this condition of functional removal of the fast channels, the hearts could not be excited even by intense electrical stimulation. It was found that trapidil (10(-4)--10(-3) M) induced slow APs accompanied by contractions. Elevation of the trapidil concentration produced dose-dependent increases in +Vmax, dT/dt (first derivative of developed tension) and cyclic AMP. These effects of trapidil were not affected by propranolol, suggesting that they were not mediated by beta-adrenergic receptors. These results support the hypothesis that intracellular cyclic AMP levels regulate the number of available slow channels, thereby controlling contractile force in the heart muscle via the Ca2+ influx mediated by slow channels.

Action Potentials↗
PubMed1980

Process of attachment of phi X174 parental DNA to the host cell membrane.

The phi X174-DNA membrane complex was isolated from Escherichia coli infected with phi X174 am3 by isopycnic sucrose gradient centrifugation followed by zone electrophoresis. The phi X174 DNA-membrane complex banded at two positions, intermediate density membrane fraction and cytoplasmic membrane fraction, having bouyant densities of 1.195 and 1.150 g/ml, respectively. Immediately after infection with phi X147, replicating DNA was pulse-labeled and then the incorporated label was chased. The radioactivity initially recovered in the intermediate density membrane fraction migrated to the cytoplasmic membrane fraction. The DNAs from both complexes sedimented mainly at the position of parental replicative form I (RFI). The phi X174 DNA-membrane complex contained a speficic membrane-bound protein having a molecular weigth of 80,000 which is accumulated in the host DNA-membrane complex. These results suggest that when phi X174 DNA penetrated into cells in the early phase of infection, single-stranded circular DNA was converted to parental RFI at a wall/membrane adhesion region and migrated to the cytoplasmic membrane fraction, where the parental RF could serve as a template in the replication of progeny RF.

Bacteriophage phi X 174↗
PubMed1980

Clinicopathological correlations in patients who received an isolated model 104 Beall mitral valve.

Following reports of accelerated wear in the model 104 Beall prosthetic valve, the authors initiated a recall and prospective follow-up study of patients who received Beall valves. In the 3 years of the follow-up program, 12 patients who had an isolated Beall mitral valve implanted have had elective replacement of the prosthesis. Cinefluoroscopy was the most accurate preoperative method of predicting the degree of pathologic wear. The serum lactic dehydrogenase value was the next most helpful measurement. Change in functional class, mitral regurgitation murmur, hemodynamic status, echocardiography and the duration of the valve in situ were not sensitive indicators.

Adult↗
PubMed1978

Yohimbine blockade of ionic channels in myocardial cells.

The effects of yohimbine, an alkaloid shown to have local anesthetic properties on nerve, were determined in isolated perfused chick embryonic (19--21-day-old) hearts. Effects on the fast Na+ channels were studied in hearts perfused with normal Ringer solution by using the maximal upstroke velocity (+Vmax) as an index of the inward current flowing during the rising phase of the normal action potential. Yohimbine (10(-5)--10(-4) M) depressed +Vmax and overshoot and prolonged the action potential. At 5 x 10(-4) M, yohimbine completely blocked the fast Na+ channels, since this dose abolished the action potential when Mn2+ (2 mM) was present to eliminate the slow Ca2+ current. Effects on the slow channels were studied in hearts in which the fast Na+ channels were voltage-inactivated by partial depolarization to about--40 mV with an elevated (25 mM) K+-Ringer solution or blocked by tetrodotoxin (TTX), resulting in loss of excitability. Isoproterenol (10(-6) M) restored excitability by inducing a slowly rising overshooting electrical response (the "slow response") that was accompanied by contractions. At low concentrations (10(-5)--10(-4) M), yohimbine enhanced the isoproterenol-induced slow response; yohimbine induced the slow response in the absence of isoproterenol, even in the presence of a beta-adrenergic blocker. In contrast, at high concentrations (10(-3) M), yohimbine markedly depressed or blocked the slow response. Consistent with this dual action, yohimbine exerted a small positive inotropic action at low doses in hearts perfused with normal Ringer solution and exerted a considerable negative inotropic action at high doses, causing complete blockade of the contractions within 20 min. Cultured reaggregated cells obtained from chick embryo (15--17 day-old) ventricles showed a similar response to yohimbine in that both the normal action potentials and the slow responses were abolished. It is concluded that yohimbine exerts a local anesthetic-like action on myocardial cells, since both fast and slow channels were blocked, but the fast channels were more sensitive to yohimbine.

Action Potentials↗
PubMed1978

Studies on pig serum lipoproteins. V. Optical properties of low density lipoproteins.

The circular dichroism (CD), optical rotatory dispersion (ORD), and fluorescence emission spectra of two subfractions of pig serum low density lipoproteins (LDL1 and LDL2) were compared. The contribution of the carbohydrate moiety to the CD and ORD spectra was estimated on the basis of data obtained from isolated glycopeptides and the constituent monosaccharides. The carbohydrate moiety had no effect on the conformation of the protein moieties of LDL1 and LDL2 (apoLDL1 and apoLDL2). However, the intensities of the observed extrema in the CD and ORD spectra of the glycopeptides were greater than those expected from the monosaccharide composition. This suggests the existence of secondary structure in the carbohydrate moiety. In contrast to the carbohydrate moiety, the contribution of the lipid moiety to the CD and ORD spectra could not be neglected. When the effect of the lipid moiety was subtrated from the CD and ORD spectra, the spectra due to apoLDL1 and apoLDL2 were quite similar. Delipidation in the presence of sodium dodecyl sulfate (SDS) induced an increase in the content of disordered structure and alpha-helix accompanied by a decrease in the beta-structure. In the presence of SDS, marked quenching occurred in the fluorescence emission spectra with a blue shift of the maximum emission wavelength from 332 to 326 nm. ApoLDL1 and apoLDL2 showed quite similar SDS-induced conformational transitions. The secondary structures of apoLDL1 and apoLDL2 in the native lipoproteins were stable to changes of pH and temperature. However, this stability was lost in the presence of SDS. These results suggest the importance of the lipid moiety in maintaining the native secondary structures of LDL1 and LDL2. From the overall similarity of the optical properties of apoLDL1 and apoLDL2, we conclude that the secondary structures of apoLDL1 and apoLDL2 are identical.

Animals↗
PubMed1978

Levels of the glutamic oxaloacetic transaminase of erythrocytes of pregnant women and of cord bloods of newborn infants.

The mean basal specific activity (S.A.) of the glutamic oxaloacetic transaminase of erythrocytes (EGOT) for a group of 64 pregnant women was lower (p less than 0.001) than the value for the cord bloods of newborn infants, and lower (p less than 0.001) than the value for adults who had a top limit of S.A. of EGOT. In establishing the top limit of the S.A., it is important that the mean basal S.A. of the cord bloods from 49 newborn infants was identical to the mean basal S.A. of adults who had an adequate supplement of pyridoxine. There were no differences in the mean basal S.A.'s of the cord bloods between asymptomatic mothers and mothers who had anemia, edema, hypertension, proteinuria and glucosuria. An infant may be born with a top limit of S.A. which is non-deficient in pyridoxal 5'-phosphate, but a mother can have a low level of the transaminase, and which is deficient in the coenzyme.

Aspartate Aminotransferases↗
PubMed1977

Studies on pig serum lipoproteins. IV. Isolation and characterization of glycopeptides from pig serum low density lipoprotein.

Three glycopeptides were isolated from the pronase digest of the protein moiety of pig serum low density lipoprotein. The isolation procedure consisted of pronase digestion, gel filtration on Sephadex G-25 and G-50 columns, paper chromatography and DEAE-Sephadex A-50 column chromatography. Based on the carbohydrate analysis, the isolated glycopeptides were classified into two types. One type (GDI) consisted of mannose and N-acetylglucosamine residues in the molar ratio of 6:2 and had a molecular weight of about 2,300. The other type (GDII and GDIII) consisted of sialic acid, mannose, galactose, fucose, and N-acetylglucosamine residues in the molar ratio of 1:4:2:1:3 and 2:4:3:1:3, respectively. The molecular weights of GDII and GDIII were about 2,100 and 3,100, respectively. The results on the strong alkaline treatment of these glycopeptides suggested that all carbohydrate chains were linked to the peptide chains through N-acetylglucosaminyl-asparagine linkages. Of these glycopeptides and pig serum lipoproteins, only glycopeptide GDI and native LDL strongly interacted with concanavalin A.

Amino Acids↗
PubMed1977

A correlative study on the changes of cardiac dynamics and myocardial energy liberation in blood-let dogs.

Blood-letting of 450 to 1,000 ml with or without saline infusion was performed in dogs. In some dogs, right atrial pacing was carried out during blood-letting. Heart rate and isometric time-tension index were measured as the indicators of chronotropism and inotropism, respectively. After 60 min of blood-letting, dogs were sacrificed and mitochondria were isolated from the left ventricular myocardium. Mitochondrial respiration was measured polarographically and respiratory control index was calculated. As blood-letting advanced, the hearts revealed negative chronotropism with negative inotropism. Mitochondrial respiration was suppressed. When heart rate was forced to increase with atrial pacing, the hearts showed positive chronotropism with negative inotropism. Respiratory control index of mitochondria was deteriorated, showing uncoupling of oxidative phosphorylation. In consideration with our previous study on the ischemic heart, it is concluded that uncoupling of oxidative phosphorylation appeared in hypoxic myocardium when cardiac dynamics shifted to positive chronotropism with negative inotropism, though suppression of mitochondrial respiration was revealed when cardiac dynamics altered to negative chronotropism with negative inotropism.

Animals↗
PubMed1976

Vitamin B6 deficiency in patients with a clinical syndrome including the carpal tunnel defect. Biochemical and clinical response to therapy with pyridoxine.

Ten individuals having a severe clinical status associated with the carpal tunnel syndrome were selected for treatment with pyridoxine. The status of vitamin B6, as pyridoxal phosphate, was determined by the specific activities of the glutamic oxaloacetic transaminase of the erythrocytes (EGOT). Before treatment, the patients showed a deficiency of vitamin B6 as determined by 1) a comparison of the specific activities of EGOT with those of a control group (P less than 0.001); and 2) a differential assay based upon the principle of unsaturation and saturation of a Coenzyme-Apoenzyme System (CAS), as applied to EGOT. These patients were treated with pyridoxine, and the specific activities of EGOT were determined after 2 and 4 weeks. Not only was there a disappearance of the deficiency of pyridoxal phosphate, but the level of EGOT activity increased 55-68% during 2-4 weeks, respectively. More apoenzyme was apparently biosynthesized, because the specific activities were significantly higher than before therapy (P less than 0.001/4 wks). Clinical evaluation showed a great improvement in their status, and anticipated surgery for some of the patients became unnecessary. It is concluded that patients with a severe syndrome including the carpal tunnel defect have a deficiency of vitamin B6, and that both the syndrome and the deficiency are relived by therapy with pyridoxine.

Adult↗