Biomedical subjects

M Naka

Publications and source records attributed to M Naka.

At least 109 records · Page 6Linked to original sources

PubMed1986

[Coronary thrombolytic therapy in acute myocardial infarction: time dependence of beneficial effects assessed by two-dimensional echocardiography].

To elucidate the effects of coronary thrombolytic therapy in acute myocardial infarction, we observed serially the degree of left ventricular (LV) wall motion immediately after on day 1, and on days 7, 14, 21 and 28 after thrombolytic therapy, in 22 patients with acute anteroseptal myocardial infarction. Base-line coronary arteriography revealed significant lesions in the proximal portions of the left anterior descending artery of all the patients. The patients were categorized according to results of thrombolytic therapy as Group I-a: seven patients with spontaneous or successful recanalization within three hours of onset of chest pain; Group I-b: nine patients with successful recanalization between three and seven hours, with a mean of 4.8 hours from onset; and Group II: six patients in whom thrombolytic therapy was unsuccessful and infarct-related vessels remained totally occluded. The LV wall motion index (WMI) was defined as the sum of point scores for the degrees of regional wall motion at nine segments on serial two-dimensional echocardiograms, and used for quantitative assessments of LV function. Results were as follows: On day 1, immediately after thrombolytic therapy, the WMI of Group I-a was smaller than that of Group II. However, there was no significant difference between Groups I-a and I-b and between Groups I-b and II. These findings suggest that LV function cannot be recovered immediately after recanalization of occluded arteries unless recanalization occurs exceptionally early. Percent improvement of the WMI from days 1 to 28 in Group I-a, 65 +/- 14%, was significantly greater than that in Group I-b, 31 +/- 18%. However, Group II did not show significant improvement in the WMI. The WMI in Group I-a decreased significantly from days 1 to 7 (9.0 +/- 1.6 vs 7.1 +/- 1.8, p less than 0.05); whereas, the WMI in Group I-b showed no significant decrease until day 21. On day 1, the regional wall motion of the antero-apical wall was akinetic or dyskinetic in all patients studied. On day 28, it improved in six of seven patients in Group I-a, while it remained akinetic or dyskinetic in all patients in Groups I-b and II.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1985

Conformational studies of myosin phosphorylated by protein kinase C.

Smooth muscle myosin from chicken gizzard is phosphorylated by Ca2+-activated phospholipid-dependent protein kinase, protein kinase C, as well as by Ca2+/calmodulin-dependent kinase, myosin light chain kinase (Endo, T., Naka, M., and Hidaka, H. (1982) Biochem. Biophys. Res. Commun. 105, 942-948). We have now demonstrated the effect of phosphorylation by protein kinase C on the smooth muscle myosin molecule. In glycerol/urea polyacrylamide gel electrophoresis the 20,000-dalton light chain phosphorylated by protein kinase C co-migrated with that phosphorylated by myosin light chain kinase. Moreover, the light chain phosphorylated by both kinases migrated more rapidly than did the light chain phosphorylated by either myosin light chain kinase or protein kinase C alone. Myosin phosphorylated by protein kinase C formed a bent 10 S monomer while that phosphorylated by myosin light chain kinase was an unfolded and extended 6 S monomer in the presence of 0.2 M KCl. In addition, myosin phosphorylated by kinases had a sedimentation velocity of 7.3 S, thereby suggesting that the myosin was partially unfolded. The unfolded myosin was visualized electron microscopically. The fraction in the looped form was higher when for myosin phosphorylated by both kinases higher than for that phosphorylated by light chain kinase alone. Therefore, phosphorylation by protein kinase C does not lead to the change in myosin conformation seen with myosin light chain kinase.

Animals↗

PubMed1985

Imino acid and related alicyclic amine levels in biological fluids.

Imino acid and related alicyclic amine concentrations in blood and urine of mammals including humans were concurrently determined by a selected ion monitoring technique. Nanomole levels of proline and pipecolic acid, and pyrrolidine and piperidine as well, were found in human urine. Proline levels but not pipecolic acid levels were higher in blood of humans than in urine. Pyrrolidine and piperidine levels in blood of humans were picomole levels and much lower than those in urine. Similar tendencies were also recognized when these 4 compounds were analyzed using animal blood and urine, although the levels were generally higher in animals than in humans. Significantly high concentrations of the imino acids and the amines were found also in animal semen.

Amines↗

PubMed1985

Some properties of large and small granules of waxy barley (Hordeum vulgare L.) endosperm starch.

Large and small starch granules were isolated and characterized from mature barley kernels with waxy endosperms. The large granules of any given waxy cultivar contained more amylose than the small granules of the same cultivar. It was also found that large granules contained a greater amount of long amylopectin B chains and had a lower fraction III:fraction II ratio, one of the structural characteristics of amylopectin, than the small granules in the same cultivar. Small granules showed a wider range of gelatinization and smaller heat of gelatinization by differential scanning calorimetry.

Edible Grain↗

PubMed1985

[Continuous wave Doppler echocardiography as a noninvasive evaluation of aortic regurgitation].

Continuous wave Doppler echocardiography permits measurement of high blood flow velocity, which is not obtained by conventional pulsed Doppler echocardiography. In this study, continuous wave Doppler echocardiography was used to measure aortic regurgitant flow velocity, and the utility of this method in evaluating aortic regurgitation (AR) was examined. Continuous wave Doppler recordings of the left ventricular outflow were obtained with the guidance of the long-axis two-dimensional echocardiogram from the apex in 20 patients with AR and 10 without AR. In 18 of the 20 patients with AR, Doppler signals of regurgitant flow were successfully detected. The recorded regurgitant flow velocity pattern had characteristic contours: the regurgitant flow was greater than 1.8 m/sec in velocity immediately after aortic valve closure, and gradually decelerated until the next ventricular systole. The Doppler half time index, which was the time profile to decline to 0.5 of the peak velocity, was significantly shortened in accordance with the degree of AR (p less than 0.01). Thus, continuous wave Doppler echocardiography is a simple, useful method for the noninvasive evaluation of AR.

Adult↗

PubMed1985

The localization of a new antithrombotic agent, cilostazol, in CHO-K1 cells as demonstrated by autoradiography.

Cilostazol (6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy]-3,4-dihydro-2(1H)- qui nolinone, OPC-13013), a new antithrombotic agent, has a potent inhibitory action on platelet aggregation. The cellular and subcellular distribution of this compound was investigated. Autoradiographic studies using tritiated cilostazol showed that this compound penetrates the cell membrane of Chinese hamster ovary cells, clone K1 (CHO-K1 cells) and is distributed mainly in the cytoplasma. These results suggest that this compound exhibits its pharmacological action through specific inhibition of cytoplasmic cyclic AMP phosphodiesterase.

Animals↗

PubMed1984

Two types of thyroid function-blocking antibodies in autoimmune atrophic thyroiditis and transient neonatal hypothyroidism due to maternal IgG.

We examined the effects of IgG from four patients with autoimmune atrophic thyroiditis on cAMP responses and iodine metabolism (post-receptor processes), using cultured thyroid cells. We found two types of thyroid function-blocking antibodies: (1) one blocks TSH binding to its receptors and inhibits TSH-stimulated cAMP responses but does not block cAMP-stimulated iodine uptake and organification; (2) the other blocks TSH binding to its receptors, inhibits TSH-stimulated cAMP responses and does block cAMP-stimulated iodine uptake and organification (post-receptor processes). Among the four patients with autoimmune atrophic thyroiditis, three had TSH binding blocking antibodies only and one had antibodies which block post-receptor processes. These antibodies might be responsible for thyroid dysfunction in autoimmune atrophic thyroiditis. The daughter of one of the women with autoimmune atrophic thyroiditis had transient neonatal hypothyroidism and recovered spontaneously from the hypothyroid state with the disappearance of the maternal blocking antibodies.

Adult↗

PubMed1984

Age-related alterations of pituitary-thyroid function in normal female subjects and in female patients with simple goitre.

Age-related alterations in pituitary-thyroid function were studied in 173 female patients with simple goitre and in 70 normal female subjects. They were divided into 4 groups according to age: A group, less than 19 years; B group, 20 to 29 years; C group, 30 to 39 years; D group, 40 to 59 years. Serum triiodothyronine (T3) concentrations decreased progressively but insignificantly with age in female patients with simple goitre and in normal female subjects, whereas serum thyroxine (T4) concentrations remained constant throughout the studied age range. Only in female patients with simple goitre, did basal serum TSH concentrations show a tendency to increase with age. However, thyrotrophin-releasing hormone (TRH)-stimulated increase of serum TSH was progressively augmented with age both in female patients with simple goitre and in normal female subjects; the magnitude of change was greater in the former group. As reflected by acute increases of serum T3 and T4 concentrations, thyroidal responsiveness to endogenous TSH was progressively depressed with age in female patients with simple goitre and in normal female subjects. This age-related thyroidal refractoriness to TSH was more apparent when the changes were expressed as delta T3 (stimulated T3 - basal T3)/delta TSH (maximum TSH after TRH - basal TSH), and delta T4 (stimulated T4 - basal T4)/delta TSH. Delta T4/delta TSH was lower in female patients with simple goitre than in normal female subjects in all age groups. However, the difference was significant only for delta T4/delta TSH in group A. Thyroidal responsiveness to exogenous TSH also gradually declined with age in female patients with simple goitre.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1984

[Interaction of activations in a semantic network: an effect of presentation intervals between homographs and context words on recognition memory of homographs].

This study investigated the interactive activation process of homograph (H :e.g. "jam") and context word (c :e.g. "strawberry"). Subjects studied a list of H-C or C-H pairs, where presentation intervals between H and C were varied (0, 0.6, or 1.2 s). Then they were tested for the recognition memory of H in a changed context (e.g. "jam-traffic") in Exp. 1, or in the same context (e.g. "jam-raspberry") in Exp. 2. The recognition memory of H as a function of presentation interval was obtained. An interesting phenomenon was that the recognition memory of H in H-C pairs at the 1.2 s interval was poorer than that of the 0.6 s interval, when tested in a changed context, but better in the same context. This suggests that both meanings of H were activated at the 0.6 s interval, but one of them related to C was selected at the 1.2 s interval. Results were discussed in terms of the spreading activation model of semantic memory.

Adult↗

PubMed1983

Hydrophobic properties of Tetrahymena calmodulin related to the phosphodiesterase activity.

We have examined hydrophobic properties of Tetrahymena CaM using the uncharged probe, n-phenyl-1-naphthylamine (NPN) fluorescence. The maximal fluorescence intensity of Tetrahymena calmodulin (CaM) is less than 1/12 of that of the bovine brain CaM. In the phosphodiesterase activation, the potency of Tetrahymena CaM, which was represented by reciprocals of the quantity of CaM required for half-maximal activation of enzyme was 22.7% respectively, of that of the bovine brain CaM. Here, Tetrahymena CaM had less hydrophobic groups exposed in the presence of Ca2+. Then Ca2+-CaM dependent enzymes require much amount of Tetrahymena CaM, comparing with the bovine brain CaM.

1-Naphthylamine↗

PubMed1983

[Evaluation of myocardial ischemia in acute myocardial infarct by thallium scintigraphy and radioisotope angiography].

It is very important to evaluate the size of myocardial infarction and reversibility of ischemic myocardium in order to determine the severity and prognosis of patients with acute myocardial infarction. We performed thallium-201 redistribution myocardial scintigraphy and first pass radionuclide angiography in 12 patients with acute myocardial infarction. In eight cases, left ventricular wall motion was improved after nitroglycerin infusion (improved group), but in four cases it was unchanged (non-improved group). Six of the improved group showed a positive redistribution image, while in the non-improved group, no patient showed such an image. Ejection fraction increased after nitroglycerin infusion in the improved group, but unchanged in the non-improved group. There was no significant difference in hemodynamic parameters between the two groups at the time of admission, and after treatment hemodynamic parameters changed in the same way in both groups. In coronary angiography, three collateral channels were observed in the improved group, but none in the non-improved group. The severity of coronary artery stenosis in the two groups was almost identical. In eight patients, their regional ventricular wall motion improved after nitroglycerin administration, but there were four patients whose regional ventricular wall motion was unchanged. In both groups, hemodynamic and coronary angiographic findings were not different. But there were many positive redistribution images and collateral channels in the improved group. This result shows that reversible ischemia is indispensable for the improvement of regional wall motion. There was a case which showed a positive redistribution image on acute phase Tl-201 scintigraphy and a transient defect on the chronic phase exercise Tl-201 scintigraphy. But after the improvement of ischemia by aorto-coronary bypass operation, the defect on Tl-201 scintigraphy decreased and the wall motion improved. Neither redistribution on acute phase scintigraphy nor a transient defect on chronic phase exercise scintigraphy was observed in the non-improved group. From these data we conclude that the improvement of regional wall motion depends on reversible ischemia.

Adult↗

PubMed1982