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Biomedical subjects

H Tamura

Publications and source records attributed to H Tamura.

At least 343 records · Page 19Linked to original sources
PubMed1990

[Evaluation of left ventricular mechanical energy efficiency and ventriculo-arterial coupling in humans using the conductance catheter technique].

To evaluate left ventricular mechanical energy efficiency and ventriculo-arterial coupling in humans, left ventricular pressure-volume relations were determined using the conductance catheter technique in 20 patients undergoing cardiac catheterization. The results were as follows: 1. A convex, curvilinear relationship was observed between end-systolic pressure-volume relations (Emax) and left ventricular ejection fraction (EF), as shown in the equation of EF = 28.5 x log (Emax) + 39.6 (r = 0.67, p less than 0.01, n = 20); EF remained nearly constant in the range of Emax greater than or equal to 4 mmHg/ml/m2, whereas, EF decreased markedly under the Emax of 4 mmHg/ml/m2. 2. A convex, curvilinear relationship was observed between Emax and mechanical energy efficiency (EW/PVA), as shown in the equation of EW/PVA = 30.5 x log (Emax) + 54.8 (r = 0.83, p less than 0.01, n = 16). 3. A concave, curvilinear relationship was observed between Emax and ventriculo-arterial coupling (Ea/Emax), as shown in the equation of Ea/Emax = -0.8 x (Emax)0.5 + 2.6 (r = -0.85, p less than 0.01, n = 16). Accordingly, EW/PVA was markedly decreased with changes in Emax in the range less than 4 mmHg/ml/m2, although it remained slightly increased above 4 mmHg/ml/m2. Ea/Emax was maintained constant (p less than 0.5) in the range of Emax above 4 mmHg/ml/m2 but was abruptly decreased when Emax was reduced below 4 mmHg/ml/m2. These results indicate that depressed left ventricle attempts to work effectively at the risk of mechanical energy efficiency and with suitable matching by aortic property. Application of pressure-volume relationships provides a new framework for evaluation and treatment of the failing heart.

Adolescent↗
PubMed1990

[Methodological and clinical evaluation of a microplate assay of endotoxin in whole blood sample].

We have developed a simple, rapid method for determining endotoxin in whole blood using a microtiter plate. The samples were pretreated with 0.66 mol/l nitric acid containing 0.25% Triton X-100; the supernatants were placed in a microtiter plate well, and incubated with endotoxin-specific chromogenic limulus test reagent (Endospecy; Seikagaku Corporation). The calibration curve was linear from 0 to 50 pg/ml of Escherichia coli 0111: B4 endotoxin with a variation coefficient less than 5%. The recovery of endotoxin added to human and experimental animals was about 100% without being affected by dilution. The normal endotoxin level in human whole blood was less than 10 pg/ml in reference to E. coli 0111: B4 endotoxin. The results in 120 patients with various diseases correlated well with those determined by a conventional method using plasma as a sample (r = 0.877; p less than 0.05). Whole blood sample has advantages over plasma in that it allows all endotoxin in a sample to be determined, requires a smaller amount of sample, and has less risk of contamination.

Animals↗
PubMed1990

[Grinding of titanium. 1. Commercial and experimental wheels made of silicon carbide abrasives].

Cast titanium was ground with commercial and experimental wheels made of silicon carbide abrasives, and their grinding performance was investigated. With the vitrified wheels made of the GC abrasive, at a higher the wheel circumferential speed and heavier the grinding pressure, the cutting rate was greater, accompanied by violent wear of the wheel. Being independent of the wheel speed, the grinding ratio reached about 1 under pressure heavier than 100 gf. The MgO-MgCl2-bonded wheels of the C abrasive exhibited a similar tendency. The manner in which the wheel was moved over the work during grinding proved to be very important, compared with the Ni-Cr alloy as reported previously. Only depression of the wheel against the work resulted in chemical attrition of the abrasive and discoloration of the work surface, or grinding burn, due to oxidation of titanium. Even when the wheel was moved over the work, chip-formation process of the cutting edge was far from ideal, and the work surface was contaminated due to reaction of titanium with the abrasive. At a higher wheel circumferential speed, more chips were loaded or built-up in the wheel and strongly rubbed the work surface, resulting in violent wear of the wheel; loading and dislodging of such chips were repeated.

Carbon↗
PubMed1990

[Grinding of titanium. 2. Commercial vitrified wheels made of alumina abrasives].

Cast titanium was ground with commercial vitrified wheels made of alumina abrasives, and their grinding performance was investigated. For cutting, the appropriate circumferential speed of the alumina wheels was about 700 m/min. A speed lower or higher than this yielded unfavorable grinding results, which were attributed to wheel loading or chemical attrition of the abrasive, respectively. The hard wheel made of the A abrasive was suitable for grinding of titanium, and moreover, the wheel of the WA abrasive was more suitable than that made of the A abrasive. Generally, the cutting rate of the alumina wheels was inferior to that of the silicon carbide ones investigated previously. Depression of the wheel against the work yielded unfavorable grinding results; the manner in which the wheel was moved over the work during grinding was very important, compared with the silicon carbide wheels. Although the wheel was moved over the work, the high circumferential speed of the wheel resulted in chemical attrition of the abrasive and discoloration of the work surface, or grinding burn. The grinding burn layer mainly consisted of a few microns-thick titanium oxide.

Aluminum Oxide↗
PubMed1990

[A case report of the reinforcing technique with collared prosthesis for the prosthetic valve endocarditis in mitral position].

A 58-year-old female was admitted to our hospital because of the prosthetic valve endocarditis in mitral position. In the past, this patient was undertaken double valve replacement in mitral and aortic position. Nevertheless, postoperative course was not in stable condition, showing persistent sign of the infection. The appearance of mitral regurgitant murmur and regurgitant signal by colour Doppler cardiography could make sure of the diagnosis for prosthetic valve endocarditis (PVE) in mitral position. The operation for PVE in mitral prosthesis was undertaken as follows. As there was extensive annular infection around the mitral valve, the new mitral prosthesis (Duromedics valve) with the Gore-tex flange, so called collared prosthesis, was revised. The collared prosthesis was implanted in the mitral annulus by using the suture ring of the Duromedics valve as well as possible, furthermore, the Gore-tex flange were sutured in the left atrial wall 2 cm above the mitral ring. Postoperatively, the infection sign and congestive heart failure were completely subsided. This patient has been in very healthy condition these days and restored to the daily life.

Endocarditis, Bacterial↗
PubMed1990

[Perioperative hemodynamic changes and management of hemodialysed patients].

Perioperative hemodynamic changes of hemodialysed patients were investigated and the changes of emergency cases (group E, n = 8) were compared with those of scheduled ones (group S, n = 13). By preoperative hemodialysis (HD), the values of blood urea nitrogen, serum creatinine, serum potassium, serum bicarbonate, and hematocrit were adjusted within normal range in group E, with no significant difference from those of group S. On the other hand, concerning the effect of preoperative removal of body water by HD, cardio-thoracic ratio (CTR, 53.6 +/- 3.1%) and pulmonary artery diastolic pressure (PADP, 11.6 +/- 5.0 mmHg) of group E were significantly higher than those of group S (CTR = 46.9 +/- 4.5%, PADP = 7.8 +/- 3.0 mmHg), indicating that the removal of body water by preoperative HD might be less in group E. However, group E patients required more administration of fluid and pressor agents in order to maintain their blood pressure and/or cardiac output during operation. Although with less water removal preoperatively and more fluid intraoperatively, postoperative PADP was significantly reduced (8.3 +/- 3.0 mmHg) in group E, suggesting that the requirement of perioperative water is more in group E. We conclude that the safe perioperative hemodynamic management for emergency surgery of hemodialysed patients requires following points; (1) The excessive removal of body water by preoperative HD should be avoided. (2) Intraoperative fluid infusion should be adequate so that they do not fall into hemodynamic collapse.

Adult↗
PubMed1990

[A case report of surgical treatment of prosthetic valve endocarditis in tricuspid position].

A case of right sided prosthetic valve endocarditis in tricuspid position was presented. This 38-year-old male underwent tricuspid valve replacement (TVR) with SJM (31 mm) prosthetic valve because of tricuspid valve endocarditis caused by staphylococcus epidermidis five years ago. At the beginning of this year, 1989, he was admitted with complain of high fever and bloody sputa. Doppler color imaging showed prosthetic valve was stenotic whose pressure gradient was 16 mmHg in peak pressure gradient, but vegetation was not identified. Following with gastrectomy perhaps due to AGML, re-TVR was done with Carpentier-Edwards vale (31 mm). He was discharged without any problems. It seems important to determine the timing of re-operation before leading any complications.

Adult↗
PubMed1990

[CT of gold pneumonitis].

We experienced five cases of gold pneumonitis. CT findings of four cases and pathological findings of an autopsy case were discussed. CT findings of gold pneumonitis could be classified as follow; (1) high density shadow of subpleural zone-BOOP suspected- (2) high density shadow along the broncho-vascular bundle (3) small cystic shadow of subpleural zone-UIP. Histological findings of an autopsy case revealed the fibrosis along the broncho-vascular bandle. A variety of radiologic and pathologic feature on the gold pneumonitis were seen.

Adult↗
PubMed1990

[A case of constrictive pericarditis due to traumatic pericardial hematoma].

Although the cause varies widely, we recently experienced a case of constrictive pericarditis of which cause seemed to be traumatic as described below. The patient was a 62-year-old man having a history of epigastric trauma about 20 years ago. Since then, palpitation appeared and he was recently hospitalized in our department for the purpose of receiving an operation under the diagnosis of constrictive pericarditis. At operation, a hematoma was found in the pericardial region, which was considered to have been caused by trauma in the past. Less reports have so far been available concerning trauma-induced constrictive pericarditis and this case thus seemed to be of rarity as well.

Constriction, Pathologic↗
PubMed1990

[Experimental evaluation for tricuspid annular constriction with the model of tricuspid annular dilatation].

We have obtained the good result about tricuspid annular constriction (TAC) for secondary tricuspid insufficiency. The purpose of this study is to investigate the effectiveness of TAC for the experimental model of tricuspid annular dilatation. First of all, tricuspid annular dilatation was made surgically in 8 mongrel dogs by placing 8 incisions to tricuspid annulus except septal cusp under the condition of heart-lung preparation. On clinical evaluation, septal annulus was kept to be intact in many cases compared with the two other areas. This experimental model of tricuspid annular dilatation was considered to be substituted to the clinical model of tricuspid annular dilatation. TAC suture was surrounded circumferentially around the dilated tricuspid annulus. And then, TAC suture was pulled out from the right atrial wall, and the circumferential length of tricuspid annulus was completely accommodated by pulling the TAC suture. The hemodynamic status was observed by right atrial pressure (V wave and mean) and right ventricular end-diastolic pressure (RVEDP). After heart resuscitation and gradual increase of preload, right atrial pressure was significantly elevated especially right atrial pressure (V wave) compared with control values. When 2 cm of circumferential length of tricuspid annulus on an average was constricted by shortening of TAC suture, right atrial pressure was significantly decreased, and then RVEDP tended to decrease. It was shown that TAC was an effective operative technique for the secondary tricuspid annular dilatation and tricuspid insufficiency from the standpoint of experimental aspect as well as clinical results.

Animals↗
PubMed1990

[A study of tricuspid-tailoring annular constriction in autopsy cases--cases which appear to embody limitation of tricuspid-tailoring annular constriction].

We our department have performed tricuspid-tailoring annular constriction (T-TAC) as salvage operation for secondary tricuspid regurgitation (TR) with gratifying results. Of those cases undergoing MVR and T-TAC for mitral valve regurgitation (MR) and secondary TR with an associated severe cardiac cachexia, 2 autopsy cases in which an associated severe cardiac cachexia, 2 autopsy cases in which residual tricuspid regurgitation culminated in patient's death long after operation were investigated. In Case 1, the patient was discharged asymptomatic 2 months after operation, but later developed severe left heart failure and marked tricuspid regurgitation as precipitated by upper respiratory tract infection and died from exacerbation of LOS before undergoing a scheduled reoperation. T-TAC was found successful on autopsy. In Case 2, the patient died of long-persisting left heart failure and severe residual tricuspid regurgitation after following a similar postoperative course to that in Case 1. On autopsy stitches made through the tricuspid anterior leaflet, septum and posterior leaflet were found untied and loosened and the tricuspid annulus diameter increased. In severe valvular heart disease, even if T-TAC has proven successful, aggravation of cardiac failure may lead to the development of TR. Because of the fragility of myocardial tissue due to severe myocardial damage in such compromised patients, sophisticated operative techniques need to be devised. Cases illustrative of a limited long-term success of T-TAC used alone are presented.

Constriction↗
PubMed1989

Micronucleus test with 1-beta-D-arabinofuranosylcytosine administered by intraperitoneal injection and oral gavage.

The effect of route of administration on the outcome of the micronucleus test was evaluated in 2 laboratories by administering the model chemical, 1-beta-D-arabinofuranosylcytosine (Ara-C), by intraperitoneal injection (i.p.) and oral gavage (p.o.) to 2 mouse strains, MS/Ae and CD-1. On the basis of a small-scale acute toxicity study and a pilot experiment for the micronucleus test, a full-scale test was performed with a 24-h sampling time at doses of 12.5, 25, 50, and 100 mg/kg i.p. and 25, 50, 100, and 200 mg/kg p.o. In both strains, MNPCEs were induced at lower dose levels by the i.p. treatment, as determined not only on the basis of mg/kg but also as a ratio of the LD50. When compared with other chemicals tested in this collaborative study, the effective dose levels of this chemical based on the LD50s were exceptionally low by both routes and in both strains, e.g., less than 0.3% of the LD50 by the i.p. treatment. The maximum frequencies of MNPCEs induced were, however, identical (MS/Ae) or even higher (CD-1) by the p.o. treatment.

Administration, Oral↗
PubMed1989

Endotoxin levels in milk and plasma of mastitis-affected cows measured with a chromogenic limulus test.

A chromogenic limulus test ("Toxicolor") was applied to cow's milk and plasma after treatment with perchloric acid to remove interfering factors. The endotoxin levels in normal cow's milk and plasma were all less than 10 pg ml-1. In acute mastitis, the milk endotoxin level averaged (1.1 +/- 0.7) X 10(3) pg ml-1 in the cases where Gram-negative bacteria were isolated, while the plasma endotoxin concentration was normal. The endotoxin levels in the quarters infected with Gram-positive bacteria were all normal, both in milk and plasma. In gangrenous mastitis due to Gram-negative bacteria, the endotoxin concentration was very high in both milk [(9.3 +/- 5.3) X 10(6) pg ml-1] and plasma (85.2 +/- 68.2 pg ml-1). In similar cases due to Gram-positive bacteria, endotoxin levels were all normal, both in milk and plasma, resembling the acute mastitis due to Gram-positive bacteria. The test was considered suitable for the diagnosis of mastitis due to Gram-negative organisms and the levels of endotoxin detected would aid in assessing the prognosis.

Animals↗
PubMed1989

Kinetic studies on the inhibition mechanism of diamine oxidase from porcine kidney by aminoguanidine.

The mechanism of inhibition of diamine oxidase [DAO, histaminase, amine: oxygen oxidoreductase (deaminating) (copper-containing), EC 1.4.3.6] by aminoguanidine was studied kinetically. The DAO reaction was carried out with putrescine as a substrate in the presence of o-aminobenzaldehyde and followed by the continuous increase in A430. An enzymatic reaction product, 4-aminobutyraldehyde, was spontaneously cyclized to delta 1-pyrroline, which coupled with o-aminobenzaldehyde to give rise to a yellow quinazolinium chromophore [Holmstedt et al. (1961) Biochim. Biophys. Acta 48, 182-186]. First, to measure the initial velocities as accurately as possible, the kinetic relationship between the oxidase reaction rate and the color development rate was formulated. The reaction proceeded linearly in the absence of aminoguanidine, but slowed down time-dependently in its presence. When the color development velocities in the presence of the inhibitor were plotted against time, the plot was nonlinear and there seemed to be at least two phases of the inhibition. Nonlinear least-squares analysis of the data dA430/dt showed that the simplest model that fitted best was a model composed of two species of enzyme-inhibitor complexes: E + I k+1 in equilibrium k-1 EI k+2 in equilibrium k-2 E'I where E is the enzyme, I is aminoguanidine (an inhibitor), and the ks are the rate constants.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldehydes↗