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Biomedical subjects

H Miyano

Publications and source records attributed to H Miyano.

At least 55 records · Page 3Linked to original sources
PubMed1995

Relation of saphenous vein graft obstruction to serum cholesterol levels.

OBJECTIVES: To determine the potential of lipid-lowering therapy to reduce saphenous vein graft obstruction, we retrospectively studied the association between graft obstruction and serum cholesterol levels. BACKGROUND: Atherosclerosis is the major cause of vein graft obstruction. Approximately 50% of grafts are occluded by 10 years after operation. It remains to be established whether lipid control affects long-term graft survival. METHODS: We carried out a retrospective review of all 284 patients who had undergone coronary artery bypass graft surgery at Juntendo University Hospital between 1976 and 1991 and met the following additional criteria: at least one saphenous vein graft, repeat coronary arteriography at some point after coronary artery bypass graft surgery and a serum cholesterol level > or = 200 mg/dl before operation. Saphenous vein graft obstruction rates were compared among three groups classified by serum cholesterol levels at follow-up arteriography: group I < 200 mg/dl; group II 200 to 239 mg/dl; group III > or = 240 mg/dl. A vein graft was considered obstructed if it was narrowed by > or = 70%. RESULTS: In group I, 88% of grafts were not obstructed 7 years after operation. The respective rates were 61% in group II and 57% in group III (p < 0.005). This relation was true for vein grafts to the left anterior descending and other coronary arteries. CONCLUSIONS: Lower serum cholesterol levels are associated with lower rates of vein graft obstruction for up to 7 years. This suggests that cholesterol-lowering therapy may improve long-term saphenous vein graft survival after coronary artery bypass surgery.

Aged↗
PubMed1995

Effects of replacement of Lys25 with Gln on the conformation of ribonuclease T1: sequence-specific 1H NMR resonance assignments of Gln25 ribonuclease T1 by two-dimensional NMR spectroscopy.

Two isozymes of ribonuclease (RNase) T1 exist in nature, i.e. Gln25 RNase T1 and Lys25 RNase T1. Gln25 RNase T1 is less stable than Lys25 RNase T1, although the enzymatic activity is not distinguishable between these two isozymes. To elucidate the effects of the replacement of Lys25 with Gln on the conformation and microenvironments of RNase T1 in detail, two-dimensional NMR spectra were measured, sequence-specific 1H NMR resonance assignments of Gln25 RNase T1 were performed, and then the determined parameters and microenvironments of Gln25 RNase T1 were compared with those of Lys25 isozyme [Hoffmann, E. and Rüterjans, H. (1988) Eur. J. Biochem. 177, 539-560]. The main chain protons were assigned for 101 out of the total of 104 amino acid residues. Secondary structure elements were identified from analysis of characteristic NOE patterns, interstrand NOE connectivities, and hydrogen-deuterium exchange rates of main chain amide protons. The results indicated that Gln25 RNase T1 contains a single alpha-helix and seven beta-strands. The secondary structure of Gln25 RNase T1 is, thus, essentially the same as that of Lys25 RNase T1. On the other hand, comparison of the conformation-dependent shifts of Gln25 RNase T1 with these of Lys25 RNase T1 showed that the replacement of Lys25 with Gln has significant effects on the C-terminal part of the alpha-helix region and the base-binding site. These results may indicate that the base-binding site is relatively flexible in the RNase T1 molecule. Among the residues of the C-terminal part of the alpha-helix region, the protons of Asp29 were most affected in terms of their chemical shifts, which may indicate that the side chain carboxylate anion of Asp29 is the counterpart of the electrostatic interaction of Lys25 in Lys25 RNase T1. The Gln25 of Gln25 RNase T1 may have little or no interaction with Asp29, and this may be the reason why Gln25 RNase T1 is less stable than the Lys25 isozyme.

Amino Acid Sequence↗
PubMed1994

Thermal stabilization of ribonuclease T1 by carboxymethylation at Glu-58 as revealed by 1H nuclear magnetic resonance spectroscopy.

Ribonuclease T1 (RNase T1) carboxymethylated at the gamma-carboxyl group of Glu-58 with iodoacetic acid is known to be completely inactive while it retains an almost full substrate-binding ability. In order to further clarify the effects of the carboxymethylation, the thermal stabilities of intact and Glu-58-carboxymethylated (CM-) RNase T1 were compared by measuring 1H NMR spectra at various temperatures. The transition curves of unfolding were obtained by plotting, as a function of temperature, the peak areas for the alpha and delta protons of Asn-81 and Ile-90, respectively, which are well apart from each other in the three-dimensional structure of the enzyme. For each of intact and CM-RNase T1, the transition curve of the Asn-81 alpha proton was identical with that of the Ile-90 delta methyl protons, suggesting that the thermal unfolding occurred simultaneously in every part of the molecule of CM-RNase T1 as well as of intact RNase T1. The midpoint of unfolding was 52 degrees C for intact RNase T1, and was increased by 9 degrees C upon carboxymethylation at Glu-58. This marked stabilization by carboxymethylation is thought to be due to formation of a salt bridge between the introduced carboxymethyl group and the neighboring guanidium group of Arg-77.

Enzyme Stability↗
PubMed1994

Effectiveness of LDL-apheresis in preventing restenosis after percutaneous transluminal coronary angioplasty (PTCA): LDL-apheresis angioplasty restenosis trial (L-ART).

To investigate the efficacy of reducing plasma lipoprotein(a) (Lp(a)) as well as low density lipoprotein cholesterol (LDL-C) levels on the prevention of restenosis after PTCA, LDL-apheresis was attempted on a total of 54 patients at six institutions. LDL-apheresis using a dextran sulfate cellulose column has been proven to be an effective method for reducing both plasma Lp(a) and LDL-C levels. As a subgroup (apheresis-drug combined group), 29 of the 54 patients were given Pravastatin (HMG CoA reductase inhibitor) and Niceritrol (Nicotinic Acid) in addition to LDL-apheresis to maintain low plasma levels of both Lp(a) and LDL-C through the follow-up period of 5 months after PTCA. Patients whose plasma Lp(a) levels were reduced by more than 50% showed a lower restenosis rate than those whose plasma Lp(a) levels were reduced by less than 50% (21.2% vs. 52.4%, P = 0.0179), especially in patients with high plasma Lp(a) levels above 30 mg/dl where a much lower restenosis rate (15.0%) was observed. Furthermore, in the apheresis-drug combined group, the restenosis rate was 11.8% regardless of baseline plasma Lp(a) levels, including even those below 30 mg/dl. In conclusion, in patients with high plasma Lp(a) levels, a greater than 50% reduction in Lp(a) levels by LDL-apheresis is effective in preventing restenosis after PTCA. If the plasma Lp(a) reduction rate is greater than 50%, LDL-apheresis combined with lipid-lowering drugs such as niceritrol and pravastatin seems to be more effective, even in patients with low plasma Lp(a) levels.

Aged↗
PubMed1993

Endothelin-3-induced relaxation of rat thoracic aorta: a role for nitric oxide formation.

1. Endothelin-3 (ET-3) at concentrations below those which caused contraction (30 nM) elicited endothelium-dependent relaxation followed by rebound contraction in rat isolated thoracic aorta. 2. Endothelin-1 also relaxed the rat aorta with a similar potency. 3. The nitric oxide (NO) synthase inhibitor, NG-nitro L-arginine, the radical scavenger, haemoglobin and the soluble guanylate cyclase inhibitor, methylene blue, each inhibited the ET-3-induced relaxation. 4. The calmodulin inhibitor, calmidazolium, considerably attenuated the relaxation caused by ET-3 without affecting that to nitroprusside. 5. Concentrations of ET-3 that were necessary to induce the relaxation also caused concentration-dependent elevation of guanosine 3':5'-cyclic monophosphate (cyclic GMP) levels. 6. NG-nitro L-arginine, haemoglobin, methylene blue, calmidazolium and removal of the endothelium completely abolished ET-3-stimulated cyclic GMP production. 7. These results suggest that ET-3 triggers NO formation possibly via ETB receptors on the endothelium to activate soluble guanylate cyclase, which in turn stimulates cyclic GMP production and smooth muscle relaxation. The enzyme contributing to the NO formation may be of the calcium/calmodulin-dependent, constitutive type.

Acetylcholine↗
PubMed1992

Involvement of nitric oxide pathway in the PAF-induced relaxation of rat thoracic aorta.

1. The mechanism of the vasorelaxant effect of platelet activating factor (PAF) on rat thoracic aorta and the effect of aging on the PAF-induced relaxation were investigated. 2. PAF at concentrations causing relaxation induced marked increases in guanosine 3':5'-cyclic monophosphate (cyclic GMP) production, but did not induce an increase in adenosine 3':5'-cyclic monophosphate (cyclic AMP). 3. Removal of the endothelium by mechanical rubbing, and treatment with the PAF antagonists CV-3988, CV-6209 and FR-900452, the nitric oxide biosynthesis inhibitor, NG-nitro L-arginine, the radical scavenger, haemoglobin, and the soluble guanylate cyclase inhibitor, methylene blue, inhibited PAF-induced relaxation and abolished or attenuated PAF-stimulated cyclic GMP production. 4. The relaxation was greatest in arteries from rats aged 4 weeks. With an increase in age, the response of the arteries to PAF was attenuated. 5. Endothelium-dependent cyclic GMP production also decreased with increase in age of the rats. 6. These results suggest that PAF stimulates production of nitric oxide from L-arginine by acting on the PAF receptors in the endothelium, which in turn stimulates soluble guanylate cyclase in the smooth muscle cells, and so increases production of cyclic GMP, thus relaxing the arteries. Age-associated decrease in PAF-induced relaxation may result from a reduction of cyclic GMP formation.

Aging↗
PubMed1991

Effects of injection site on the accuracy of thermal washout right ventricular ejection fraction measurements in clinical and model investigations.

The purpose of this investigation was to improve the accuracy of measurement of thermal right ventricular ejection fraction (RVEF) using the modified Swan-Ganz catheter. Three serial ejection fractions (EFs) (EF1, 2, 3) and the mean were calculated, based on Holt's theory. RVEFs were compared between right ventricular (RV) and atrial (RA) injection in ten intensive care unit (ICU) patients using a modified catheter having RV and RA orifices (15 cm and 30 cm from the distal end, respectively), and paired duplicate (two patients) or triplicate (eight patients) measurements were performed. To determine what factors interfere with RVEF, a model heart (with diastolic volume of 150 ml) was constructed, in which model injection of cold water to the direct inflow tract (RA), to the direct mixing chamber (RV), or through the catheter running in the inflow tract were compared. When EFs were compared between RV and RA injection, those for the former were greater (RV vs RA in EF1 and EFmean: 0.46 +/- 0.15 vs 0.23 +/- 0.11 in EF1, and 0.45 +/- 0.13 vs 0.28 +/- 0.11 in EFmean, mean +/- SD, p less than 0.01). When the serial EFs were compared in each injection type, in the RV injection EF3 was the smallest as was EF1 in the RA injection. The same phenomenon was observed in the model as in the patients, and moreover when cold water was injected in RA through a catheter running through the circuit, EFs were greatly underestimated (EF1 = 0.29 +/- 0.02 at preset EF = 0.4). We conclude that these phenomena were caused by sluggish movement of the cold indicator from RA to RV when injected into RA, and by interference with the cooled cardiac chamber and catheter. Consequently, the first or second EFs obtained from RV injection might be closest to the actual values because of the least interference with those factors.

Adult↗
PubMed1991

[ARDS-like reactive respiratory failure after radical operation for esophageal cancer--with reference to PMN elastase and anaphylatoxin].

In a study undertaken to elucidate the pathophysiology underlying reactive respiratory failure following surgery for esophageal cancer, postoperative esophageal cancer patients were divided into 2 groups, i.e. one with respiratory failure (defined as impairment of oxygenating capacity with a respiratory index (RI) value of 1.5 or above, lasting from more than 5 days after surgery) and the other without it, and between-group comparisons were made of respiratory & circulatory dynamics and biologic response system components, e.g., complement, anaphylatoxins and polymorphonuclear granulocytes (PMN) elastase. There were no differences between the two groups in patient's age at operation and pulmonary function test. The mean duration of endotracheal control was 5.1 days for the respiratory failure (+) group against 3.7 days for the respiratory failure (-) group. Assessments of respiratory & circulatory dynamics showed that the RI was significantly increase early in the postoperative course in the respiratory failure (+) group as compared with the respiratory failure (-) group, while the hydrostatic pressure of pulmonary circulation (pulmonary microvascular pressure (Pmv)-plasma colloid-osmotic pressure (COP] and pulmonary shunting rate (Qs/Qt) were also elevated in the former group. Among biologic response parameters, the leukocyte count, platelet count, CH5, C3, and C5 showed long-sustained decreases from the postoperative day 1 on in the repertory failure (+) group as compared to the respiratory failure (-) while PMN elastase activity and anaphylatoxin C3a were elevated from the postoperative day 1 on in the former group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Exacerbation of hypercapnia and acidosis of central venous blood and tissue following administration of sodium bicarbonate during cardiopulmonary resuscitation.

Administration of sodium bicarbonate during cardiopulmonary resuscitation (CPR) is controversial, and our aim was to elucidate whether or not its administration is beneficial by analyzing the acid-base status and the level of carbon dioxide in central venous blood during CPR, and their changes following administration of sodium bicarbonate. Six patients were studied. They had all been admitted to the intensive care unit (ICU), had already had pulmonary arterial or central venous catheters inserted, and had acute episodes of circulatory collapse during their stay in the ICU. The following phenomena were observed: 1) hypercapnia and acidosis of central venous blood were prominent during both cardiogenic shock and CPR, although arterial hypocapnia was maintained by hyperventilation; 2) administration of sodium bicarbonate during cardiogenic shock and CPR induced exacerbation of hypercapnia and acidosis of central venous blood; 3) when arterial hypercapnia was present due to disturbed ventilation, administration of sodium bicarbonate exacerbated hypercapnia and acidosis of both arterial and central venous blood; 4) administration of sodium bicarbonate did not induce hypercapnia of central venous blood in a septic shock patient in whom the septic hyperdynamic state was prevalent in spite of low systemic perfusion pressure. It was concluded that hypercapnia and acidosis of the central venous blood and tissues were exacerbated by administration of sodium bicarbonate during CPR, and that such an effect might be dependent on the severity of the decrease in tissue perfusion.

Acid-Base Equilibrium↗
PubMed1987

Micro-scale sequence analysis from the N-terminus of peptides using the fluorogenic Edman reagent 4-N,N-dimethylamino-1-naphthyl isothiocyanate.

The fluorogenic Edman reagent 4-N,N-dimethylamino-1-naphthyl isothiocyanate (DNTC) was reacted with amino acids and peptides, cyclized by acid and the liberated 4-N,N-dimethylamino-1-naphthyl thiohydantoin (DNTH) amino acids were then separated and detected by HPLC. The fluorescence intensities of DNTH-amino acids except DNTH-proline and -serine were dramatically increased in the alkaline solution and organic solvent. Thus, the postcolumn reaction with alkaline acetonitrile solution was adopted in HPLC. The polar and aromatic amino acids afforded two DNTH-amino acids on derivatization with DNTC and cyclization with acids. These were suggested to be stereoisomers of DNTH-amino acids. The sequence analysis of 0.5 nmol Leu-enkephalin was achieved by the double coupling method with DNTC and phenyl isothiocyanate followed by the proposed HPLC system.

1-Naphthylisothiocyanate↗
PubMed1986

Amino acid composition analysis of minute amounts of cysteine-containing proteins using 4-(aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole and 4-fluoro-7-nitro-2,1,3-benzoxadiazole in combination with HPLC.

The simultaneous determination of amino acid composition including cysteine of egg albumin, a model protein containing a/s cysteine residue, is reported. All the thiol groups of the cysteine residue(s) of egg albumin were labelled with 4-(aminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole, a fluorogenic reagent for thiol groups. The labeled egg albumin was hydrolyzed in 6N HCl at 110 degrees C for 24 h. The hydrolysate was lyophilized, derivatized with 4-fluoro-7-nitro-2,1,3-benzoxadiazole, a fluorogenic reagent for amines, and subjected to HPLC. 18 derivatized amino acids including double labelled cysteine were separated within 90 min on a Nucleosil ODS column (150 mm X 4.6 mm i.d.; 5 microns), and detected at 530 nm (ex. 470 nm) in a range from 90 fmol (aspartic acid) to 1.3 pmol (cysteine) (S/N = 3). Composition ratios of amino acids of egg albumin were similar to theoretical values except for methionine, which would be destroyed under the present acid hydrolysis condition. Analytical methods for cysteine residues are reviewed, and the availability of fluorogenic reagents having the benzofurazan structure is also discussed.

4-Chloro-7-nitrobenzofurazan↗
PubMed1985

Influences of metal ions on the reaction of amino and imino acids with fluorogenic reagents.

When a twofold excess of metal ions (Cu2+, Ni2+, Zn2+, Mg2+, Ca2+, Fe3+, and Al3+) was added to a reaction medium of amino acids (1-50 microM each) with the fluorogenic reagents NBD-F (4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole), DNS-Cl (5-N,N-dimethylaminonaphthalenesulfonyl chloride), OPA (o-phthalaldehyde), and fluorescamine (4-phenylspiro[furan-2(3H),1'-phthalan]-3,3'-dione), a reduction of derivatization was observed. The effect was especially marked on the reaction with NBD-F. The derivatization of His and Asp with DNS-Cl and fluorescamine and of His with OPA was suppressed by Cu2+ and/or Ni2+. The suppression by the metal ions can be overcome by the addition of EDTA to the reaction medium. For determination of a small amount of amino and imino acids (less than microM) the addition of a chelating reagent to biological samples is recommended before derivatization with these electrophilic reagents.

4-Chloro-7-nitrobenzofurazan↗
PubMed1985

A surface electrode array for detecting action potential trains of single motor units.

Action potentials of single motor units were detected by a linear surface electrode array placed perpendicular to the longitudinal axis of the biceps brachii. Twelve myoelectric signals were derived simultaneously from a voluntarily contracting muscle. Using a visual feedback control, 3 subjects produced spike trains of single motor unit action potentials (MUAPs) at a weak contraction. When the myoelectric signals showed an interference pattern at a moderate contraction, several MUAPs were isolated by a visual analysis. MUAPs occurring at about fixed intervals with constant amplitudes and with identical wave forms were presumed to be the action potential trains of single motor units. Reliable estimates of single MUAP wave forms were obtained by averaging and superimposing the detected signals at a timing of characteristic potential peaks. Then not only the firing rate of the spikes but also the territory and the wave form of single MUAPs were investigated. Most MUAPs had a sharp and symmetrical distribution of potentials on a skin surface along the muscle circumference, while some MUAPs showed complex wave forms with some separate potential peaks. The possible arrangement of muscle fibers belonging to the motor units was estimated from the MUAP wave forms.

Action Potentials↗
PubMed1983

The distribution of myoneural junctions in the biceps brachii investigated by surface electromyography.

The location of the myoneural junction was investigated by a surface electromyogram. During a voluntary muscular contraction, an electrode array was placed on the skin overlying the muscle to detect myoelectric potentials propagating in both proximal and distal directions along the muscle fibers. The source of the propagating waves was presumed to mark the location of the myoneural junctions. The recordings were repeated to cover the whole muscle surface and the distribution of myoneural junctions was determined. Myoneural junctions in the biceps brachii were located nearly at the middle length of the muscle and were distributed in a zone across the muscle. The distribution showed differences in 3 subjects examined. In 1 subject, myoneural junctions occupied a single zone, while the other 2 subjects had 2 parallel zones separated by 10-20 mm. This information about the location of myoneural junctions is important for determining the electrode position in an electromyogram study.

Adult↗
PubMed1983

The propagation of motor unit action potential and the location of neuromuscular junction investigated by surface electrode arrays.

A myoelectric signal was recorded from the biceps brachii muscle using surface electrode arrays which consisted of 15 pieces of stainless steel wire placed parallel to each other with 5 mm interelectrode spacing. The electrode assembly was positioned parallel to the underlying muscle fibers and amplifiers were connected bipolarly to 11 pairs of adjacent electrodes. In the chart of recorded signals a propagation of the action potential was observed, originating from a neuromuscular junction and traveling both in the proximal and distal directions. In one recording under an isotonic and isometric contraction condition, two neuromuscular junctions were found to be active. One was located approximately at the center of the muscle and the other was 15 mm distal from it. It was found that the amplitude of the myoelectric potential originating from the distal neuromuscular junction increased gradually during a 1 min heavy muscular loading (50% maximum voluntary contraction).

Action Potentials↗