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Biomedical subjects

N Yamazaki

Publications and source records attributed to N Yamazaki.

At least 199 records · Page 11Linked to original sources
PubMed1989

[Molecular composite resins reinforced with polyaramides (Part 1). Molecular interaction between N-Octylated-Poly-p-Phenylene Terephthalamide (PPTA) as core molecule and PMMA and Polystyrene (PS) as matrices].

Molecular composite PMMA resin (Oct-PPTA-PMMA) can be reinforced with poly-N-octyl-p-phenylene terephthalamide (Oct-PPTA) as rigid core molecule. Compounding 3 wt% of Oct-PPTA to PMMA increased compressive, diametral and bending strength by 10 to 15%. The molecular interaction between Oct-PPTA as the core molecule and PMMA as a polar matrix and polystyrene (PS) as a non-polar matrix was examined with respect to dynamic viscoelasticity. Compounding 3 wt% of Oct-PPTA (Oct-PPTA-PS) to PS decreased compressive, diametral and bending strength by 15 to 30%. The dynamic storage modulus (G') value of Oct-PPTA-PS is lower than G' of PS in the region from rubbery state to viscous flow state. These results reveal a significant effect of the polar groups on the molecular interaction between the core molecule and matrices in the molecular composites compounding Oct-PPTA as core molecule.

Chemical Phenomena↗
PubMed1989

[Experimental and clinical evaluations of flow cytometric DNA-aneuploidy for the determining malignancy of head and neck tumors].

Using flow cytometry, basic experiments and clinical trials to investigate DNA aneuploidy were performed. The site of the peak in the DNA histogram was found to be unstable in the flow cytometric assay. However, relatively stable DNA indices can be obtained if only internal standards, such as human lymphocytes, etc., are added to the samples, thus results in a more precise detection of aneuploidy. In 11 cases of head and neck tumors, DNA aneuploidy was observed in six out of seven cases that were histopathologically diagnosed as being malignant tumors, showing a correlation with the pathological studies as a whole. Further clinical studies may prove that the present method can be useful for the pathological, supplementary diagnostic and prognostic evaluations.

Aneuploidy↗
PubMed1989

Dual tracer autoradiographic study with thallium-201 and radioiodinated fatty acid in cardiomyopathic hamsters.

To investigate the usefulness of myocardial scintigraphy with radioiodinated 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) in cardiomyopathy, quantitative dual tracer autoradiographic study with 201Tl and [125I]BMIPP was performed in 27 cardiomyopathic Bio 14.6 Syrian hamsters and eight normal hamsters. Furthermore, 16 Bio 14.6 Syrian hamsters aged 21 days were divided into verapamil-treated (during 70 days) and control groups (respectively, n = 8), and autoradiography with 201Tl and [125I]BMIPP was performed. Quantitative autoradiography demonstrated an uncoupling of 201Tl and [125I]BMIPP distributions and a regional heterogeneity of [125I]BMIPP distribution in cardiomyopathic hamsters aged more than 2 mo, while normal hamsters showed only mild heterogeneity of [125I]BMIPP distribution without an uncoupling of tracers. Age-matched comparison between normal and cardiomyopathic hamsters (5-8 mo old) demonstrated that a difference between their [125I]BMIPP distributions are more marked than that between their 201Tl distributions. Furthermore, [125I]BMIPP visualized effects of verapamil on cardiomyopathy more distinctly than did 201Tl. In conclusion, myocardial imaging with [123I]BMIPP could be useful for investigating cardiomyopathy and evaluating the efficacy of therapeutic intervention in patients with cardiomyopathy.

Animals↗
PubMed1988

Relationship between smoking and fibrinolytic system with special reference to t-PA and PA inhibitor.

Recently tissue plasminogen activator (t-PA) has been clinically applied to the thrombolytic therapy of myocardial infarction. We investigated relationship between cigarette smoking and fibrinolytic system, namely the plasma level of t-PA antigen, plasminogen activator inhibitor (PAI), and PA activity. Nineteen healthy volunteers were asked to smoke for 10 min. The plasma levels of t-PA antigen, PAI activity, PA activity and catecholamine were measured together with measurement of blood pressure and heart rate before, soon after or 30 min after cigarette smoking. Plasma t-PA antigen after cigarette smoking increased to 8.83 +/- 3.11 ng per ml, significantly higher (p less than 0.005) than 6.35 +/- 1.7 ng/ml before cigarette smoking. Plasma PAI activity after cigarette smoking was 5.52 +/- 2.03 u/ml, significantly higher (p less than 0.05) than 4.18 +/- 1.06 u/ml before smoking. Plasma PA activity after smoking was 6.28 +/- 3.85 u/ml significantly higher (p less than 0.05) than 4. 49 +/- 2.74 u/ml. Furthermore, plasma epinephrine level after smoking increased to 59.1 +/- 52.4 pg/ml (p less than 0.1), compared with 36.2 +/- 22.5 pg/ml before smoking. There was a positive correlation between the rate of increase in plasma t-PA antigen and the rate of increase in plasma epinephrine after smoking. It is suggested that plasma epinephrine was related to the mechanism of increased plasma levels of t-PA in cigarette smoking.

Adult↗
PubMed1988

Technetium-99m pyrophosphate tomogram of nontransmural myocardial infarction: a case report.

Single-photon emission computed tomography (SPECT) with 99mTc-pyrophosphate (99mTc-PYP) has been reported to be useful in the detection and localization of acute nontransmural infarctions. Localized uptake of 99mTc-PYP has been shown in patients with nontransmural infarction in these studies. It is likely, however, that anatomically transmural infarctions could be mislabelled as nontransmural infarctions, since the absence of new abnormal Q waves has been used in differentiating between nontransmural and transmural infarctions. We report a case of relatively diffuse nontransmural infarction demonstrated by a semicircle of 99mTc-PYP activity which significantly overlapped 201Tl uptake on the SPECT study.

Aged↗
PubMed1988

Effect of a new anti-ulcer drug, (3-[p-(trans-4-aminomethylcyclohexylcarbonyl)-phenyl] propionic acid hydrochloride, TEI-5103) on prostaglandin (PG) levels in rat gastric mucosa.

1. Effect of TEI-5103 on the levels of various prostaglandins (PG's) in rat gastric mucosa was studied by HPLC and RIA methods. 2. When administrated in vivo, TEI-5103 significantly increased the level of prostaglandin E2 (PGE2) but only slightly increased that of prostaglandin I2 (PGI2) or thromboxane A2 (TXA2). 3. In the water-immersion stress model, the PGE2 level in control animals was increased immediately after stress and then decreased gradually to the initial level. Indomethacin (5 mg/kg, s.c.) sustained a lower PGE2 level during the experiment, as well as aggravated the lesions. 4. TEI-5103 (400 mg/kg, p.o.) increased the PGE2 level just before stress, and it resulted in the prevention of lesion formation. 5. TEI-5103 inhibited the activity of 15-OH-PG-dehydrogenase from guinea pig lungs, but did not affect the activity of phospholipase A2 from porcine pancreas.

Animals↗
PubMed1988

Role of alpha 1-adrenergic receptors and the effect of bunazosin on the histopathology of cardiomyopathic Syrian hamsters of strain BIO 14.6.

In order to clarify the pathological involvement of the sympathetic nervous system in the development of cardiomyopathy, a receptor-binding study was carried out on cardiomyopathic Syrian hamsters of strain BIO 14.6 (BIO) at 21 days (prenecrotic stage); 35-42 days (onset of cardiomyopathy); and 70-84 days of life (early cardiac hypertrophy). The newly developed alpha 1-blocker (bunazosin hydrochloride) was initially administered at doses of 100 micrograms/kg or 10 mg/kg to BIO hamsters at 21 days of life and continued for 70 days. At the onset of cardiomyopathy and early cardiac hypertrophy, there was an increase in the number of alpha 1-receptors in the BIO hamsters compared to controls, but there were no significant changes at the prenecrotic stage. On histopathological examination, 10 mg/kg bunazosin had a significant beneficial effect on cardiomyopathy [area of necrosis 1.38% in untreated vs 0.33% in treated animals; area of calcification 2.70% (untreated) vs 0.60% (treated); area of all myocardial injuries 6.97% (untreated) vs 3.19% (treated)]. However, 100 micrograms/kg bunazosin had no effect. It was concluded that the increase in the number of alpha 1-receptors may not be involved in the pathogenesis of cardiomyopathy but that alpha 1-receptors could be implicated in the later progression of the condition.

Adrenergic alpha-Antagonists↗
PubMed1988

Activities of aromatic L-amino acid decarboxylase with L-dopa as substrate in brush-border- and basolateral membranes and cytoplasm obtained from rat renal cortex.

Activities of aromatic L-amino acid decarboxylase (AADC) with L-dopa as its substrate were determined in the plasma membranes and other cellular components isolated from rat renal cortex. The cytoplasm contained a high level of AADC activity, but much lower levels were found in the brush-border- and basolateral membranes. The main site involved in the formation of dopamine from L-dopa was considered to be the cytoplasm, with participation of neither the brush-border- nor the basolateral membranes.

Animals↗
PubMed1988

Effects of procainamide and disopyramide on long chain acyl carnitine and long chain acyl CoA concentrations in the ischemic heart.

Though the efficacies of procainamide and disopyramide in treating arrhythmias are well established, their precise mechanisms of antiarrhythmic action remain unclear. Arrhythmias which occur during acute myocardial ischemia can be explained partly on a metabolic basis. The accumulation of intermediates subsequent to impaired beta-oxidation of free fatty acids has been suggested as a cause of serious arrhythmias. The purpose of this study was to investigate changes in free carnitine, long chain acyl carnitine and long chain acyl CoA concentrations in the ischemic canine heart following the administration of procainamide and disopyramide. The coronary artery was occluded for 40 min and myocardial samples were prepared from both nonischemic and ischemic areas. Procainamide and disopyramide prevented the accumulation of long chain acyl carnitine and long chain acyl CoA in the ischemic myocardium. The results showed that procainamide and disopyramide had beneficial effects on fatty acid metabolism. It was suggested that one of the antiarrhythmic mechanisms of these drugs might be the prevention of the accumulation of fatty acyl derivatives in the ischemic myocardium.

Acyl Coenzyme A↗
PubMed1988

Time-dependent changes in plasma levels of cationic electrolytes produced by hypertonic solutions of low potent substance intraperitoneally administered to rats.

In order to investigate interrelations of plasma levels of potassium with those of the other electrolytes in case of intraperitoneal administration of hypertonic solution consisting of low potent substance, each of the three hypertonic solutions (2,800 mOsm/L), i.e., 50% glucose, 8.12% sodium chloride, and 13.16% sodium sulphate, was intraperitoneally injected to rats in a dose of 3.5 ml/kg body weight. Blood was sampled from the femoral artery at 0, 5, 10, 20, 30 and 45 min after the administration and at the time-point of death. In all cases of the three administered groups, the plasma levels of magnesium was observed to start increasing from 5 min, and, then, the potassium levels from 10 min. The phosphorus levels did not show a significant increase until 20 min, showing later an abrupt increase until the death. Calcium, on the other hand, did not show any significant change in the plasma level until the death. These findings denote that a high osmotic pressure moves first intracellular water and magnesium ion to the outside of the cell, and , with a time delay, intracellular potassium ion is forced to move slowly to the outside. Finally, intracellular phosphorus seems to be released into the extracellular space as a result of damages by suppression of mitochondrial oxidative phosphorylation and by activation of phospholipase both of which were caused directly or indirectly by a critical osmotic force.

Animals↗
PubMed1987

Relationship between age and plasma t-PA, PA-inhibitor, and PA activity.

A positive correlation between age and the occurrence of thrombosis has been suggested. We studied the relationship between age and fibrinolytic activities; namely levels of tissue plasminogen activator (t-PA) antigen, plasminogen activator inhibitor (PA inhibitor) activity, and plasminogen activator activity (PA activity). A dramatic increase in both t-PA antigen and PA inhibitor was shown in persons with increasing age. PA activity decreased with age. Therefore it is suggested that the tendency of decreased PA activity with increasing age may be related to the high incidence of thrombosis in older persons.

Adolescent↗
PubMed1987

Effects of verapamil on experimental cardiomyopathy in the Bio 14.6 Syrian hamster.

The Bio 14.6 Syrian hamster provides a good model for experimental study of cardiomyopathy. Cardiac receptor binding sites (alpha-1-, beta- and calcium antagonists) were studied in early (21 days old) and late (70 days old) stages of cardiomyopathy. The effects of verapamil on histologic features and free radicals in the heart were studied. The number of alpha-1- and beta-cardiac receptor binding sites was significantly greater in the late stage of cardiomyopathy when compared with findings in normal golden hamsters used as controls. The calcium antagonist receptors were significantly increased in the early stage but alpha-1- and beta-receptors were not. Verapamil-treated hamsters received intraperitoneal injections of verapamil at a dose of 5 mg/kg per day for 70 days from age 20 days. The percent areas of fibrosis and calcification in the verapamil-treated group were significantly smaller than those in the control group. The concentrations of lipid peroxides in the whole heart and free radicals in the heart mitochondria were significantly higher in the cardiomyopathic hamsters, and verapamil inhibited the increase in free radical concentration in the hearts of these hamsters. This study confirms that the number of calcium channels is increased early in the course of cardiomyopathy in the Bio 14.6 Syrian hamster. A larger number of free radicals may participate in the accumulation of calcium and cell injury in the myocytes of these hamsters. Verapamil protects against myocardial damage and may do so by inhibiting voltage-dependent calcium uptake and by preventing cell injury from free radicals.

Age Factors↗