Search PubMed⌕ Search

Biomedical subjects

Keiichi Tambara

Publications and source records attributed to Keiichi Tambara.

30 records · Page 2Linked to original sources
PubMed2003

Intramyocardial sustained delivery of basic fibroblast growth factor improves angiogenesis and ventricular function in a rat infarct model.

Recently we have demonstrated that the release of basic fibroblast growth factor (bFGF) from a biodegradable gelatin hydrogel carrier depends on the degradation of hydrogel in vivo. The purpose of our study was to assess whether bFGF-incorporating gelatin hydrogels induce myocardial angiogenesis and improve left ventricular function in the infarcted myocardium of rats. Studies were conducted in 22 Lewis rats after a 4-week ligation of the proximal left anterior descending coronary artery. The rats were randomized into the following two groups: the control group (n = 11) had an intramyocardial injection of saline alone, and the FGF group (n = 11) had gelatin hydrogel microspheres containing 100 microg of bFGF injected into the border zone of the infarct area after the repeat left thoracotomy. For visualization of the regional myocardial blood flow in the rat heart, (201)Tl images were taken just before and 4 weeks after the treatment using a 4-head single photon emission computed tomography scanner with pinhole collimators. Left ventricular function was also assessed with echocardiography and a micromanometer-tipped catheter. Finally, the extent of myocardial angiogenesis was evaluated quantitatively in the postmortem analysis. The (201)Tl defect score in the control group remained unchanged before and after the treatment, whereas it decreased significantly in the FGF group. Both regional and global left ventricular function was significantly better in the FGF group compared with the control group. The vascular density in the border zone of the infarct in the FGF group was significantly higher than that in the control group. In conclusion, intramyocardial injection of bFGF-impregnated gelatin hydrogels induces functionally significant angiogenesis and improves left ventricular systolic and diastolic function in the infarcted myocardium of rats.

Animals↗
PubMed2003

A pig model of chronic heart failure by intracoronary embolization with gelatin sponge.

BACKGROUND: We produced a large-animal model of left ventricular (LV) failure induced by transcatheter embolization of the left coronary artery using a gelatin sponge. METHODS: Fourteen male pigs underwent transcatheter embolization of the left anterior descending artery (LAD) using gelatin sponge to produce anteroapical myocardial infarction. Coronary angiography was performed 1 week after the coronary embolization. The animals were followed up with echocardiography and LV pressure-volume study for the subsequent 8 weeks, and the data were compared with those of the control group (n = 13). RESULTS: The procedure mortality was 2 of 14 (14%). Coronary angiography revealed the occluded LAD was recanalized with poor run-off. The LV end-diastolic dimension progressively increased (control versus myocardial infarction: 39 +/- 2 mm versus 49 +/- 4 mm, p < 0.001 at week 4; and 40 +/- 2 mm versus 57 +/- 6 mm, p < 0.001 at week 8). Fractional area change decreased over 8 weeks (77% +/- 10% versus 43% +/- 6%, p < 0.001 at week 4; and 77% +/- 10% versus 40% +/- 8%, p < 0.001 at week 8). End-systolic elastance progressively decreased over 8 weeks (3.04 +/- 0.73 mm Hg/mL versus 1.54 +/- 0.51 mm Hg/mL, p < 0.0001 at week 4; and 2.88 +/- 0.44 mm Hg/mL versus 1.05 +/- 0.21 mm Hg/mL, p < 0.001 at week 8). The plasma levels of brain natriuretic peptide were significantly higher in the study group (543 +/- 131 pg/mL versus 1,321 +/- 364 pg/mL, p < 0.001 at week 4; and 610 +/- 152 pg/mL versus 1,523 +/- 232 pg/mL, p < 0.001 at week 8). CONCLUSIONS: This pig model of chronic heart failure is reliable, reproducible, and amenable to investigate other surgical procedures.

Animals↗
PubMed2003

Toward surgical angiogenesis using slow-released basic fibroblast growth factor.

OBJECTIVE: Therapeutic angiogenesis using basic fibroblast growth factor (bFGF) in coronary artery disease has been documented in a number of papers. However, the effectiveness is discrepant among documents. In this study, we evaluated the distribution of bFGF in the rat heart by different administration methods, and investigated the efficacy of slow-released administration of bFGF using biodegradable hydrogel microspheres (bFGF microspheres) in a pig infarction model toward an enhanced coronary bypass surgery. METHODS: Heart failure due to myocardial infarction was induced in rats and pigs. In the rat study, free form of bFGF (central venous injection, intracoronary injection, and intramyocardial administration) and bFGF microspheres (intramyocardial administration) were given 4 weeks later. The remaining radioactivity of bFGF in the hearts was estimated 1, 24, and 72 h later. On the other hand, the pigs were randomized into two groups 4 weeks after myocardial infarction. While the control group (n=8) had gelatin hydrogel microspheres with saline, the FGF group (n=8) received bFGF microspheres in the left ventricular (LV) wall. RESULTS: In the rat study, after intramyocardial administration of bFGF microspheres, more bFGF remained in the rat heart 72 h later compared with the other methods (P<0.0001). In the pig study, 4 weeks after the treatment, the FGF group had smaller LV diastolic diameter (48.7+/-5.3 vs. 56.7+/-5.2 mm, P<0.01) than the control group. LV end-systolic elastance was higher in the FGF group (2.96+/-1.2 vs. 1.06+/-0.3 mmHg/ml, P<0.01). In microscopic examinations, many neovessels were found in and around the scar tissue, and the vascular density in the FGF group was significantly higher (61.5+/-18.3 vs. 153.0+/-29.0/mm2, P<0.01). In addition, the infarcted LV walls were less expanded and more thickened in the FGF group. CONCLUSIONS: Biodegradable hydrogel microspheres with bFGF improved LV function and inhibited LV remodeling by angiogenesis in pigs with chronic myocardial infarction. bFGF microspheres into ischemic myocardium may revascularize small ungraftable vessels and may potentially increase distal run-off when applied in coronary bypass surgery.

Animals↗
PubMed2002

Combined procedure of surgical repair and cell transplantation for left ventricular aneurysm: an experimental study.

BACKGROUND: This study was designed to investigate the efficacy of the combined procedure of left ventricular (LV) repair and fetal cardiomyocyte transplantation (CM-TX) in a rat myocardial infarction model. METHODS AND RESULTS: A moderate-sized LV aneurysm was created by proximal ligation of the left coronary artery in 47 Lewis rats. Four weeks later, they were underwent another operation and received culture medium injection (n=10; group I), fetal CM-TX (n=10; group II), purse-string LV repair with culture medium injection (n=14; group III), or LV repair with fetal CM-TX (n=13; group IV). They were echocardiographically followed-up during the subsequent 4 weeks, and cardiac catheterization was performed in the final week. In the late period, LV dimension in group IV was smaller than that in group III (end-diastolic dimension, 0.92+/-0.02 versus 1.01+/-0.03 cm, P=0.0090; end-systolic dimension, 0.62+/-0.02 versus 0.74+/-0.04 cm, P=0.0093; at the fourth week), although they initially showed similar decreases in both groups. At the final week, end-systolic elastance was higher in group IV than in groups I, II, or III (0.61+/-0.10 versus 0.19+/-0.03, 0.30+/-0.09, 0.33+/-0.07 mm Hg/ micro L, P=0.0002, 0.0037, and 0.0042, respectively). CONCLUSIONS: Fetal CM-TX exerted preventive effects against late LV dilation and dysfunction after LV repair in the rat model. The results suggest that repair surgery combined with fetal CM-TX may enhance the surgical benefits for patients with LV aneurysm in the long term.

Animals↗
PubMed2002

Cardiomyocyte transplantation does not reverse cardiac remodeling in rats with chronic myocardial infarction.

BACKGROUND: Several reports have documented the potential benefits of cell transplantation as an alternative to cardiac transplantation. This study was designed to investigate whether cardiomyocyte transplantation is effective in rats with chronic myocardial infarction. METHODS: Syngeneic Lewis rats were used in this study. Chronic myocardial infarction was induced in rats by ligating the left anterior descending artery. Four weeks later, after left ventricular (LV) dysfunction with akinetic regions was confirmed by echocardiography, the rats were randomized into two groups: a group that received fetal cardiomyocyte transplantation (TX group; n = 11); and a group that received an intramyocardial injection of culture medium only (control group; n = 12). RESULTS: Four weeks after treatment, the TX group had smaller end-systolic dimension (LVDs) (7.5 +/- 0.9 vs 8.9 +/- 0.8 mm, p < 0.01) and better fractional shortening (FS) (26.2 +/- 5.9 vs 17.7% +/- 5.1%, p < 0.01) than the control group. However, there were no differences in LV end-diastolic dimension, LVDs, and FS between baseline and post-treatment values in the TX group. In addition, plasma levels of atrial natriuretic peptide were not significantly different between the two groups 4 weeks after treatment. In microscopic examination, small amounts of transplanted cardiomyocytes were found only in the periinfarct area, not in the center of scar area, and a thicker ventricular wall in the infarct area was detected in the TX group. CONCLUSIONS: Fetal cardiomyocyte transplantation prevented, but did not reverse, cardiac remodeling that was accompanied with heart failure in myocardial infarction rats. Further investigation is warranted for optimal clinical application to the failing heart.

Animals↗
PubMed2002

Composite arterial Y graft has less coronary flow reserve than independent grafts.

BACKGROUND: It is not known whether a composite Y graft of the left internal thoracic artery can provide sufficient blood flow to the whole left coronary system. The aim of this study was to compare regional myocardial blood flow (MBF) and coronary flow reserve after coronary artery bypass grafting using arterial composite Y graft or independent arterial grafts. METHODS: Positron emission tomography was performed at rest and after dipyridamole infusion using oxygen-15-labeled water 2 weeks after coronary artery bypass grafting. Regional MBF was calculated in seven segments of the left ventricle. Coronary flow reserve was defined as the ratio of MBF after dipyridamole infusion to MBF at rest. In the Y graft group (n = 22), a free arterial graft to obtuse marginal arteries was anastomosed to the proximal side of in situ left internal thoracic artery, which was anastomosed to the left anterior descending artery. In the independent graft group (n = 13), left anterior descending and obtuse marginal arteries were independently revascularized using in situ left internal thoracic artery and a free arterial graft. RESULTS: There was no difference between the groups in MBF at rest. Coronary flow reserve in the Y graft group was lower than that in the independent group in the anterobasal (1.43 +/- 0.07 versus 1.90 +/- 0.13, p = 0.038), apical (1.24 +/- 0.06 versus 1.64 +/- 0.12, p = 0.003), septal (1.34 +/- 0.05 versus 1.75 +/- 0.13, p = 0.023), and lateral regions (1.19 +/- 0.04 versus 1.66 +/- 0.09, p = 0.001). CONCLUSIONS: Although arterial composite Y graft improved MBF at rest, it was not as effective as independent grafts for improving coronary flow reserve soon after coronary artery bypass grafting.

Aged↗
PubMed2002

Double-breasted repair of the posterior mitral valve leaflet.

The double-breasted repair of the posterior leaflet of the mitral valve is an alternative technique for correction of mitral regurgitation in selected patients. This new technique has the advantage of avoiding distortion of the posterior annulus and simplifies the repair, especially in complex posterior leaflet prolapse.

Cardiac Surgical Procedures↗
PubMed2002

Trepopnea in patients with chronic heart failure.

This article will review the recumbent positions of patients with chronic congestive heart failure. The time for the right lateral decubitus position was two-fold longer than that for the supine and left lateral decubitus positions. Sympathetic nervous modulation was most attenuated and parasympathetic tone was most augmented in the right lateral decubitus position. The underlying mechanisms why heart failure patients prefer this position will be discussed. In conclusion, the right lateral decubitus position preferred by patients with chronic congestive heart failure may be a self-protecting mechanism to augment cardiac output and to attenuate the imbalance of cardiac autonomic nervous activity.

Chronic Disease↗
PubMed2002

Prevascularization with gelatin microspheres containing basic fibroblast growth factor enhances the benefits of cardiomyocyte transplantation.

OBJECTIVE: The effects of cell transplantation on the ischemic failing heart have already been documented. However, the area in and around infarct regions is not a good environment for cells to survive in because they are exposed to poor conditions in which certain requirements cannot be adequately supplied. We therefore designed a study to investigate the efficacy of prevascularization in ischemic regions before cell transplantation. METHODS: Rats with myocardial infarction were randomized into 4 groups: 11 rats received a culture medium injection to the left ventricular wall (control group), 11 received fetal cardiomyocyte transplantation (TX group), 11 received gelatin hydrogel microspheres incorporating basic fibroblast growth factor (FGF group), and 11 received basic fibroblast growth factor pretreatment sequentially, followed by cardiomyocyte transplantation (FGF-TX group). Four weeks later, left ventricular function was assessed by means of echocardiography and cardiac catheterization. RESULTS: In the FGF and FGF-TX groups neovascularization was found in the scar tissue 1 week later. The TX, FGF, and FGF-TX groups showed better fractional shortening than the control group (TX, FGF, FGF-TX, and control: 28% +/- 4.4%, 24% +/- 8.6%, 27% +/- 7.3%, and 17% +/- 4.6%, respectively; P <.01). Left ventricular maximum time-varying elastance was higher in the FGF-TX group than in the TX and FGF groups (FGF-TX, TX, and FGF: 0.52 +/- 0.23, 0.30 +/- 0.08, and 0.27 +/- 0.20 mm Hg/microL, respectively; P <.01). Histologically, more transplanted cells survived in the FGF-TX group than in the TX group. CONCLUSIONS: Prevascularization with basic fibroblast growth factor-incorporated microspheres enhances the benefits of cardiomyocyte transplantation. We expect that this system will contribute to regeneration medicine through its extensive application to other growth factors.

Animals↗
PubMedDate not supplied

Primary cardiac lymphoma demonstrated by delayed contrast-enhanced magnetic resonance imaging.

Delayed contrast-enhanced magnetic resonance (MR) imaging that nullifies the signal of normal myocardium produces great differences in myocardial signal intensity between normal and infarcted myocardium. A case of primary cardiac lymphoma is presented in which delayed contrast-enhanced MR imaging clearly identified the localization and extension of a lymphoma infiltrating the myocardium.

Contrast Media↗