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Biomedical subjects

M Naka

Publications and source records attributed to M Naka.

At least 73 records · Page 4Linked to original sources
PubMed1992

7-[(1R,2S,3S,5R)-6,6-dimethyl-3-(4- iodobenzenesulfonylamino)bicyclo[3.1.1]hept-2-yl]-5(Z)-heptenoic acid: a novel high-affinity radiolabeled antagonist for platelet thromboxane A2/prostaglandin H2 receptors.

A high-affinity thromboxane (TX)A2/prostaglandin (PG) H2 receptor antagonist, I-SAP [7-[(1R,2S,3S,5R)-6,6-dimethyl-3-(4- iodobenzenesulfonylamino)bicyclo[3.1.1]hept-2-yl]-5(Z)-heptenoic acid] and its radiolabeled analog [125I]SAP (Mais et al., 1991) are characterized in the present study. I-SAP antagonized I-BOP ([1S-(1 alpha, 2 beta(5Z),3 alpha(1E,3R*),4 alpha)]-7-[3-(3-hydroxy-4- (4'-iodophenoxy)-1-butenyl)-7-oxabicyclo-[2.2.1]heptan-2y l]-5'heptenoic acid) and U46619 [15S-hydroxy-11 alpha,9 alpha-(epoxymethano)-prosta-5Z,13E-dienoic acid)], two different TXA2/PGH2 mimetics, induced aggregation of washed human platelets in a similar manner (pA2 of 8.11 +/- 0.09, Kd = 7.8 nM, n = 3; pA2 = 8.01 +/- 0.05, Kd = 9.7 nM, n = 8, respectively). I-SAP also had agonistic activity, producing platelet shape change (EC50 = 9.7 nM +/- 0.6 nM at pH 7.4, n = 3) which was blocked by pretreatment of platelets with SQ29548 ([1S-(1 alpha,2 beta(5Z),3 beta,4 alpha)]-7-[3-[[2- [(phenylamino)carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1]hept- 2-yl]-5-heptenoic acid), a TXA2/PGH2 receptor antagonist. Radioligand binding studies were performed with [125I]SAP using washed human platelets. Competition of three agonists and four antagonists for binding with [125I]SAP was determined. The compounds showed the appropriate rank order potencies, including stereoselective competition by a pair of stereoisomeric antagonists. In washed human platelets, the Kd for I-SAP was 468 +/- 49 pM and the maximum binding (Bmax) was 2057 +/- 156 sites/platelet at pH 7.4 (n = 6). The Bmax was significantly increased 49% to 3072 +/- 205 sites/platelet at pH 6.5 (P less than .01 but the Kd was unchanged (490 +/- 18 pM, n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)

Binding, Competitive↗
PubMed1992

[Platelet accumulation in abdominal aortic aneurysms and the effect of antiplatelet drugs: assessment by indium platelet scintigraphy].

A dual tracer technique using 111In labeled platelets and 99mTc labeled human serum albumin was applied to evaluate the in vivo thrombogenicity in 12 cases with abdominal aortic aneurysm (AAA) and the effect of antiplatelet drug on the thrombogenicity. The magnitude of platelet accumulation at AAA was expressed as the ratio of radioactivity of 111In platelets on the vascular wall to those in the blood pool (PAI; platelet accumulation index). Of the 12 patients with AAA, 11 had positive studies on baseline imaging and 1 had equivocally positive image. The PAI value (Mean +/- SD) over the AAA was 53.8 +/- 34.1% as compared to -8.6 +/- 4.4% in the control group (p less than 0.01). Seven patients with an AAA and positive baseline images were restudied during platelet active drug with 325 mg of aspirin. During treatment with aspirin, of 7 patients, 5 had positive images, of which 3 were decreased and others unchanged compared to baseline studies, 1 equivocally positive one and one negative one. The PAI value during treatment (21.9 +/- 18.6%) was significantly decreased compared to those in baseline study (52.1 +/- 23.9%). Our results suggest that the method used for platelet imaging in the present study may be useful for studying the in vivo thrombogenicity and the effect of platelet active drugs in AAA.

Aged↗
PubMed1991

Molecular cloning and expression of the cDNA coding for a new member of the S100 protein family from porcine cardiac muscle.

We isolated a new calcium-binding protein from porcine cardiac muscle by calcium-dependent hydrophobic and dye-affinity chromatography. It showed an apparent molecular weight of 11,000 on SDS-PAGE. Amino acid sequence determination revealed that the protein contained two calcium-binding domains of the EF-hand motif. The cDNA gene coding for this protein was cloned from the porcine lung cDNA library. Sequence analysis of the cloned cDNA showed that the protein was composed of 99 amino acid residues and its molecular weight was estimated to be 11,179. Immunological and functional characterization showed that the recombinant S100C protein expressed in Escherichia coli was identical to the natural protein. Homologies to calpactin light chain, S100 alpha and beta protein were 41.1%, 40.9% and 37.5%, respectively. The protein was expressed at high levels in lung and kidney, and low levels in liver and brain. The tissue distribution was apparently different from those of the other S100 protein family. These results indicate that this protein represents a new member of the S100 protein family, and thus we refer to it as S100C protein.

Amino Acid Sequence↗
PubMed1991

The catalytic subunit of cyclic AMP-dependent protein kinase directly inhibits sodium channel activities in guinea-pig ventricular myocytes.

We investigated the effects of the purified catalytic subunit (C subunit) of the cAMP-dependent protein kinase (A-kinase) on the cardiac Na+ channel currents. Single Na+ channel currents in guinea-pig ventricular myocytes were recorded using the patch clamp technique of the inside-out configuration. Application of C subunit decreased the peak average current and slowed the current decay, effects which were caused by decrease in the open probability of Na+ channels and increase in the first latency, whereas the unitary current amplitude and mean open times were not affected. We conclude that the cardiac Na+ channel is directly modulated by phosphorylation process through A-kinase.

Animals↗
PubMed1991

Memory psychophysics for areas: distortion in natural memory of a school campus.

As the perceived magnitude of a stimulus is related by power function t o the physical magnitude, the remembered visual areas and length are also related by power function to the actual areas and length. The main purpose of this study is to examine whether the power law is also applicable to remembered areas in natural environment, e.g., a school campus, and to its old memory. 31 junior high students and seven university undergraduates who graduated from the same junior high school seven years before were asked to draw a layout of the school campus. The areas of the school facilities and field, and other features of drawings such as the number of recalled facilities and objects, and direction of the sketch were assessed. Analysis showed that the areas remembered by the junior high subjects followed the power law while those remembered by the undergraduates did not. The divergence of exponents observed for undergraduates was accounted for by reconstruction by schema.

Adolescent↗
PubMed1990

Modulation of smooth muscle calponin by protein kinase C and calmodulin.

When smooth muscle calponin was incubated with protein kinase C, 1 mole of phosphate was incorporated per mole of calponin. The apparent Km value for calponin of the protein kinase was about 0.4 microM. The phosphorylation of calponin by protein kinase C was inhibited markedly by calmodulin in a calcium-dependent manner. Kinetic analysis of calmodulin-induced inhibition of calponin phosphorylation by protein kinase C revealed that calmodulin inhibited the phosphorylation in a noncompetitive fashion with calponin and the determined Ki value was 0.4 microM. These results suggest that interaction of calmodulin with calponin may play a regulatory role in the phosphorylation by protein kinase C and smooth muscle contraction.

Animals↗
PubMed1990

Effects of ruthenium red on activation of Ca2(+)-dependent cyclic nucleotide phosphodiesterase.

Ruthenium red inhibited Ca2(+)-dependent phosphodiesterase (Ca2(+)-PDE) selectively with an IC50 value of 15 microM. Increasing calmodulin concentration in the presence of both 100 microM and 4000 microM Ca2+ completely reversed the inhibition of Ca2(+)-PDE activity by ruthenium red. Ruthenium red-induced inhibition of Ca2(+)-PDE activity was also overcome by increasing the concentration of Ca2+ in the presence of both 200 ng and 2000 ng calmodulin, in sharp contrast to fluphenazine-induced inhibition of Ca2(+)-PDE. These results indicate that ruthenium red has distinct inhibitory mechanism which differs from that of calmodulin antagonists previously reported.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1990

A validation study on the reproducibility of transcranial Doppler velocimetry.

The transcranial Doppler method for the measurement of intracranial arterial blood flow velocity is a useful noninvasive technique with a number of applications. The present study validated the reproducibility of this method for repeated measurements of flow velocity in the middle cerebral and basilar arteries. Fifteen healthy volunteers were studied. Measurements were made twice by one examiner and once by another in a single day and again by the first examiner on another day. The reproducibility was evaluated by calculating the correlation coefficient (r) and the coefficient of variation (CV) of the difference between the values obtained from each pair of measurements. Although depending on the examiner, the time interval between the examinations and the vessels studied some differences were noted in the reproducibility, both the r (0.69-0.95) and CV (6.7%-19.5%) values in the whole study were good enough to warrant the applicability of this method for the repeated measurements of the intracranial arterial blood flow velocity in future studies.

Cerebral Arteries↗
PubMed1990

Effects of amrinone and enoximone on the subclasses of cyclic AMP phosphodiesterase from human heart and kidney.

We observed the intracellular localization of low-Km cyclic adenosine monophosphate (cAMP) phosphodiesterase (PDEIII) subclasses in human heart in comparison to that in human kidney by using comparable potencies of specific inhibitors. PDEIII was observed in not only soluble fraction but particulate fraction in human heart and kidney. Both soluble and particulate PDEIII from human heart selectively hydrolyzed cAMP with similar Km values of 0.36 and 0.40 microM, respectively. They were potently inhibited by amrinone, enoximone, and cyclic guanosine monophosphate (cGMP), but were weakly inhibited by rolipram with much the same IC50 values. Although several animals having soluble and particulate PDEIII possess two pharmacologically distinct subclasses of PDEIII, human heart has only one form, cGMP-sensitive PDEIII. In contrast to cardiac PDEIII, both soluble and particulate PDEIII from human kidney were not readily inhibited by amrinone, enoximone, and cGMP, but rather strongly inhibited by rolipram. Human kidney contains only cGMP-less sensitive form of PDEIII in soluble and particulate fractions. These results suggest that the intracellular distribution of PDEIII subclasses in human hearts are significantly different from those in the hearts of other animal species, and subclasses of PDEIII in humans hearts could not be distinguished by intracellular localization but by organ specificity.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1989

Effects of ONO-3708, an antagonist of the thromboxane A2/prostaglandin endoperoxide receptor, on platelet aggregation and thrombosis.

The beneficial effects of an antagonist of the thromboxane A2/prostaglandin endoperoxide receptor, 7-[2 alpha,4 alpha-(dimethylmethano)-6 beta-(2-cyclopentyl-2 beta- hydroxyacetamido)-1 alpha-cyclohexyl]-5(Z)-heptenoic acid (ONO-3708) on thrombosis were examined. ONO-3708 at 0.1-3 microM inhibited the human platelet aggregation induced by thromboxane A2, prostaglandin H2, collagen, ADP (secondary phase) and epinephrine (secondary phase) without affecting prostanoid synthesis and the content of cyclic AMP in platelets. The in vivo effects, on coronary thrombosis in this case, were examined in two canine models. ONO-3708, 3 to 300 micrograms/kg i.v., prevented dose dependently the coronary thrombosis induced by partial obstruction of the coronary artery. ONO-3708, 3 micrograms/kg per min i.v., significantly prevented electrically stimulated coronary thrombosis without affecting systemic blood pressure and heart rate. These results indicate that the thromboxane A2/prostaglandin endoperoxide receptor could play an important role in the pathogenesis of thrombosis and that ONO-3708 may have therapeutic advantages in preventing thrombosis.

Animals↗
PubMed1989

Echocardiographic studies on the relationship between atrial fibrillation and atrial enlargement in patients with hyperthyroidism of Graves' disease.

In order to study the relationship between the left atrial size and atrial fibrillation (AF) in patients with thyrotoxicosis, 92 patients with Graves' disease were examined. Out of 92 patients (23 men and 69 women, age 7-71 years), 21% had AF: 31% of the patients older than 40 years had AF whereas none of the patients younger than 40 years had AF. Echocardiography revealed that the left atrial enlargement (more than 40 mm) exist in 7% of patients younger than 40 years, in 2% of those older than 40 years without AF and 94% of those older than 40 years with AF. Serum T3 and T4 were higher in the patients with AF than in those without AF when patients older than 40 years were analyzed.

Adolescent↗