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Biomedical subjects

Takahiro Kawai

Publications and source records attributed to Takahiro Kawai.

15 recordsLinked to original sources
PubMed2006

Removal of formaldehyde by hydroxyapatite layer biomimetically deposited on polyamide film.

Some harmful volatile organic compounds (VOCs), such as formaldehyde, are regulated atmospheric pollutants. Therefore, development of a material to remove these VOCs is required. We focused on hydroxyapatite, which had been biomimetically coated on a polyamide film, as an adsorbent and found that formaldehyde was successfully removed by this adsorbent. The amount of formaldehyde adsorbed increased with the area of the polyamide film occupied by hydroxyapatite. The amount of adsorbed formaldehyde and its rate of adsorption were larger for hydroxyapatite deposited on polyamide film than for the commercially available calcined hydroxyapatite powder. This high adsorption ability is achieved by the use of nanosized particles of hydroxyapatite with low crystallinity and containing a large number of active surface sites. Therefore, hydroxyapatite biomimetically coated on organic substrates can become a candidate material for removing harmful VOCs such as formaldehyde.

Adsorption↗
PubMed2006

Biventricular pacing 18 months after Batista operation.

We conducted biventricular pacing in a patient with dilated cardiomyopathy and complete left bundle branch block who had recurrent heart failure and mitral valve regurgitation 18 months after partial left ventriculectomy and mitral valve repair. An epicardial lead was fixed on the left ventricular free wall surgically through a thoracotomy, and the other two leads were implanted transvenously. Biventricular pacing restored contractile synchrony and led to more efficient left ventricular contraction and reductions in mitral regurgitation. Biventricular pacing may produce beneficial effects for patients with the recurrent intractable heart failure associated with cardiomyopathy and complete left bundle branch block after partial left ventriculectomy.

Bundle-Branch Block↗
PubMed2005

Development of gene delivery systems for the epsilon-poly-L-lysine producer, Streptomyces albulus.

Streptomyces albulus IFO14147 produces epsilon-poly-L-lysine (epsilon-PL), an amino acid homopolymer antibiotic that is used as a food preservative in many countries, including Japan, South Korea, and the United States. To construct an overproducer of the industrially important epsilon-PL and to develop a deeper understanding of its biosynthetic mechanism, we developed systems for DNA delivery into the S. albulus strain based on both polyethylene glycol-mediated protoplast transformation and intergeneric conjugation from Escherichia coli. The successes of these transformations in particular were accomplished by employing the new cryptic-plasmid-based shuttle vectors constructed in this study. The genetic systems developed here should facilitate a molecular genetic approach to S. albulus.

Drug Delivery Systems↗
PubMed2004

A novel covalently crosslinked gel of alginate and silane with the ability to form bone-like apatite.

Hybrids consisting of bone-like apatite and biodegradable polymers are attractive materials for bone repair. We have shown that an alginate gel crosslinked covalently with ethylenediamine (EDA) enhances the repair of skin and nerves. In this study, we report a novel method for fabrication of an apatite-alginate nanohybrid using a simulated body fluid (SBF). Alginate was reacted with 3-aminopropyltriethoxysilane (APES), which gives silanol groups after hydrolysis, and/or EDA, by dehydration condensation using water-soluble carbodiimide to form gels. Modification of alginate with APES alone also gave a gel, because the alginate could be crosslinked by dehydration of silanol groups derived from APES. The gels obtained were soaked in a 1 mol/L CaCl2 solution and subsequently soaked in SBF. Apatite was formed on and inside the alginate gels modified with APES, whereas it was not formed on the gels without APES. Modification of alginate with silanol groups induced not only gel formation but also the apatite-forming ability on and inside the alginate gel in SBF. Consequently, a hydroxyapatite-alginate hybrid can be produced by modification of alginate with silanol groups and subsequent soaking in CaCl2 solution and SBF. Such a material is expected to be useful in bone repair.

Alginates↗
PubMed2004

Coating of an apatite layer on polyamide films containing sulfonic groups by a biomimetic process.

Coating organic polymers with hydroxyapatite is an attractive method for the development of materials for medical applications, as it allows hydroxyapatite to show its unique biological properties such as its ability for bone bonding and protein adsorption. The biomimetic process focuses attention on fabricating such hydroxyapatite-polymer hybrids, where bone-like apatite is deposited on an organic polymer surface in solutions mimicking physiological conditions. In this process, a bone-like apatite layer can be coated onto organic substrates either by using a simulated body fluid (SBF), which has ion concentrations nearly equal to those of human extracellular fluid, or by using fluids that are supersaturated with respect to apatite at ambient conditions. We previously reported that apatite was deposited on polyamide films containing carboxyl groups in a solution mimicking body fluid, when they were incorporated with calcium salts. In the present study, to find an alternative functional group effective in apatite formation, we examined the apatite-forming ability of polyamide films containing sulfonic groups in the same solution. It was found that the polyamide film containing sulfonic groups could deposit apatite on its surface in the solution when the film was incorporated with calcium salts. These results show that the sulfonic group also acts as a functional group, and is as effective for apatite deposition in the body environment as the carboxyl group.

Biocompatible Materials↗
PubMed2004

Radionuclide study of mid-term left ventricular function after endoventricular circular patch plasty.

OBJECTIVE: Although the early result of endoventricular circular patch plasty (EVCPP) has been reported, few are seen about the long-term results. We studied left ventricular (LV) function in the early and mid-term periods after EVCPP with electrocardiographic-gated single photon emission computed tomography (Gated SPECT). METHODS: Consecutive 14 patients with LV asynergy after myocardial infarction, who had the EVCPP procedure, were studied by Gated SPECT. Mean age of patients was 67+/-10 years. Gated SPECT images were obtained and LV end-diastolic volume index (EDVI), LV end-systolic volume index (ESVI) and ejection fraction (EF) were studied with QGS(+) program. Gated SPECT study was performed before surgery, early (23 days) and mid-term periods (32 months) after surgery. RESULTS: EDVI changed significantly from preoperative value to early postoperative value (107+/-39 to 72+/-37 ml/m(2), P < 0.01). There was no significant difference between early and mid-term postoperative values. ESVI also changed significantly from preoperative value to early postoperative value, and from early value to mid-term postoperative value (78+/-37 to 51+/-34 to 47+/-35 ml/m(2), P < 0.05, respectively). EF increased significantly from preoperative value to early postoperative value, and from early value to mid-term postoperative value (30+/-10 to 35+/-13 to 45+/-18%, P < 0.05, respectively). CONCLUSIONS: Direct influence of EVCPP brought significant improvement of LV function in early period. Further decrease of ESVI and increase of EF were noticed from early period to mid-term period. This result suggest that the effect of EVCPP sustains long and yields reverse LV remodeling.

Aged↗
PubMed2004

SMXA-5 mouse as a diabetic model susceptible to feeding a high-fat diet.

The SMXA-5 strain, a new mouse model for type 2 diabetes, is a recombinant inbred strain derived from non-diabetic SM/J and A/J strains. As dietary fat is a key component in the development of diabetes, we compared the glucose tolerance and diabetes-related traits among the SMXA-5, SM/J, and A/J strains while feeding a high-fat diet for 10 weeks. SMXA-5 fed on a high-fat diet showed an increased serum insulin concentration. Judging from the hyperinsulinemia in SMXA-5, this strain showed insulin resistance, an inability of peripheral tissues to respond to insulin, which was strengthened by feeding with a high-fat diet. When fed on a high-fat diet for 5 weeks, the SMXA-5 mice showed severely impaired glucose tolerance. On the other hand, SM/J showed mildly impaired glucose tolerance, even when fed on a high-fat diet for 10 weeks. These results indicate that SMXA-5 would be available for use as a diabetic model susceptible to a high-fat diet.

Adipose Tissue↗
PubMed2003

Biosynthesis of epsilon-poly-L-lysine in a cell-free system of Streptomyces albulus.

epsilon-Poly-L-lysine (epsilon-PL) is a homo-poly-amino acid characterized by a peptide bond between carboxyl and epsilon-amino groups of L-lysine. Here we report the cell-free synthesis of epsilon-PL by a sensitive radioisotopic epsilon-PL assay system. In vitro epsilon-PL synthesis depended on ATP and was not affected by ribonuclease, kanamycin, or chloramphenicol. epsilon-PL synthesizing activity was detected in the membrane fraction. The reaction product, epsilon-PL, from L-lysine was identified by MALDI-TOF MS and the number of lysine residues of the epsilon-PL products was apparently 11-34. These results suggest that the biosynthesis of epsilon-PL is nonribosomal peptide synthesis and is catalyzed by membrane bound enzyme(s). The enzyme preparation showing the epsilon-PL synthesizing activity also catalyzed lysine-dependent AMP production and an ATP-PPi exchange reaction, suggesting that L-lysine is adenylated in the first step of epsilon-PL biosynthesis.

Adenosine Monophosphate↗
PubMed2002

Angiographic evaluation of the luminal changes in the radial artery graft in coronary artery bypass surgery: a concern over the long-term patency.

OBJECTIVE: The radial artery graft (RA) still involves two unsolved problems, namely, vasospasm and intimal hyperplasia, although satisfactory early and mid-term outcomes have been obtained recently. METHODS: Two hundred patients underwent coronary artery bypass surgery with RA between October,1996 and December,2000. We made a comparison of the luminal diameters at early and mid-term periods in 23 patients who underwent mid-term angiographies after a mean follow-up of 27 months. The proximal anastomoses of the RA were the ascending aorta in these patients. The G/N ratio was determined as a ratio of the luminal diameter of the graft to that of the revascularized coronary artery so as to evaluate the luminal discrepancy between the graft and the native artery. RESULTS: In the 122 patients who underwent angiographies about one month after the operation, the patency rate was 99% (144 of 145) in the RA, 97% (139 of 143) in the left internal thoracic artery graft (LITA), 96% (75 of 78) in the saphenous vein graft (SV). In the 23 patients who underwent mid-term angiographies, the patency rate was 91% (24 of 26) in the RA, 100% (23 of 23) in the LITA, and 83% (20 of 24) in the SV. The luminal diameters of the RA and LITA significantly increased from 2.15 to 2.52 mm, and from 1.75 to 1.97 mm, respectively. The luminal change from 3.78 to 3.33 mm in the SV was not significant. The G/N ratios changed from 1.10 to 1.31, from 1.01 to 1.13, and from 2.05 to 1.86 in the RA, LITA, and SV, respectively. The change of the RA alone was statistically significant. CONCLUSIONS: The angiographic early patency rate was almost the same in three kinds of graft material, but the mid-term patency rate of the RA was between those of the LITA and SV. The mid-term luminal dilatation of the RA could involve two conflicting characteristics, namely, a good intimal function and a propensity to increase in the luminal discrepancy. Therefore, a further observation is required to evaluate whether the clinical outcome of the RA could remain as good as that of the LITA in the long-term period.

Aged↗
PubMed2002

Long-term follow-up of cardiac valve replacement using bioprosthesis in patients 70 years old and older.

Good long-term results with the bioprosthetic valves for patients 70 years old and older have been reported. However, because the average lifespan is increasing, we aimed to clarify whether patients older than 70 may still be candidates for valve re-replacement. Seventy-one patients 70 years old and older, who received a total of 81 bioprosthetic valve replacements during 73 procedures between 1988 and 2000, were reviewed. There were 8 hospital and 7 late deaths. Ten-year actual survival after valve replacement was 73.5%, and 82.8% when hospital deaths were excluded. During the follow-up period, 2 patients received mitral valve re-replacement. Ten years of freedom from reoperation were found in 66.7% for all valves and in 50.0% for mitral valves. The average lifespan in Japan is currently 77.64 years for men and 84.62 years for women; therefore, valve degeneration in patients who receive bioprosthesis replacement in their early 70s should be anticipated.

Aged↗
PubMed2002

Endoventricular circular patch plasty with aortic valve replacement for post-infarction cardiac rupture complicated with aortic valve stenosis: case report.

Cardiac rupture after acute myocardial infarction (AMI) in patients with aortic valve stenosis (AS) is uncommon and only 2 survival cases after surgery have been reported to date. The present patient, a 69-year-old woman with aortic valve stenosis (AS), suffered an acute myocardial infarction and despite a successful baloon angioplasty to the proximal left anterior descending artery, the condition progressed into congestive heart failure. Echocardiography demonstrated AS with a valve area of 0.7 cm2 and a left ventricular aneurysm with a thin and dyskinetic anterior to apical wall. An urgent operation was performed and the opening of the pericardium revealed oozing rupture of the aneurysm. An endoventricular circular patch plasty combined with aortic valve replacement was successfully performed, and good results during 2-year follow-up were achieved. Physiological repair with exclusion of the infarcted area is essential to achieve a good long-term outcome in such a critical case. Special care should be taken with AMI in a patient with AS because of the possible occurrence of aneurysm and rupture of the left ventricle.

Aged↗
PubMedDate not supplied

Comparison of volume study by left ventriculography and gated SPECT in endoventricular circular patchplasty.

Although quantitative gated SPECT (QGS) is widely used for left ventricular (LV) volume study, its accuracy is not established for those who have a large myocardial infarction scar or who had endoventricular circular patch plasty (EVCPP). Therefore, we compared LV volumes and LVEF calculated by QGS and those calculated by left ventriculography (LVG) before and after EVCPP. Sixteen patients (13 men and 3 women, mean age 67 +/- 9.5 years) were treated with EVCPP for postinfarction LV dyskinetic and/or akinetic scar. All patients were evaluated with both QGS and LVG before and after surgery. QGS was performed using eight frames per cardiac cycle, 1 hour after 740 MBq (99 m)Tc-tetrofosimin was administered. LVG images were acquired at a frame rate of 30 frames per second in the right anterior oblique 30-degree projection. We compared LV end-diastolic volume (LVEDV), LV end-systolic volume (LVESV), and LV ejection fraction (LVEF) between QGS and LVG. There was an excellent linear correlation between QGS and LVG in LVEDV (preoperative; r = 0.87, postoperative; r = 0.94), LVESV (preoperative; r = 0.95, postoperative; r = 0.89), and LVEF (preoperative; r = 0.73, postoperative; r = 0.81) before and after EVCPP. However, both preoperative LV volumes and postoperative LVEF calculated from QGS gave a smaller value than those calculated from LVG. Postoperative volume data by QGS was much close to LVG. The present study indicated that volume study by QGS is very useful to evaluate the LV function after EVCPP. However, we should pay attention to those facts.

Aged↗
PubMedDate not supplied

Surgical treatment of multiple coronary artery fistulas with an associated small saccular aneurysm--a case report.

Coronary angiography (CAG) of a 57-year-old woman with anterior chest discomfort revealed no stenosis of the coronary arteries but multiple coronary artery fistulas (CAFs). The sites of origin for the CAFs were the right coronary artery, left main coronary artery, left anterior descending coronary artery, and ascending aorta. The only site for drainage was the main pulmonary artery. Furthermore, a small saccular aneurysmal formation was detected. Surgical treatment was considered better than conservative treatment or coil embolization, and ligation and division of the CAFs were performed during cardiopulmonary bypass. Using a Harmonic Scalpel to expose fistulous arteries was very effective. CAG performed immediately after surgery demonstrated that all CAFs were repaired. The postoperative course was uneventful.

Aorta↗