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Biomedical subjects

T Akasaka

Publications and source records attributed to T Akasaka.

At least 271 records · Page 15Linked to original sources
PubMed1977

Total one-stage repair of interrupted aortic arch associated with aortic septal defect and patent ductus arteriosus.

Successful total repair in one stage was performed in a 3-year-old girl who had interrupted aortic arch associated with aortic septal defect and patent ductus arteriosus. Surface-induced deep hypothermia and interrupted perfusion were used. The results of postoperative catheterization and angiocardiographic studies are analyzed, and the literature and results of previous surgical attempts at correction are reviewed.

Adolescent↗
PubMedDate not supplied

Heat shock-induced homeotic transformations of the axial skeleton and associated shifts of Hox gene expression domains in mouse embryos.

Pregnant ICR mice were immersed in water at 42 degrees C for up to 15 min on Day 8.5 of gestation (plug day = Day 0), and their term fetuses were double stained with alcian blue and alizarin red S for skeletal examination. Heat exposure for 15 min induced homeotic vertebral transformations in more than one-third of the living fetuses, in which the morphologic identity of vertebrae (T6-S1) was shifted anteriorly by one or two segmental levels. The frequency of fetuses with vertebral transformations and the degree of the shift of vertebral identity were dependent on the length of heat exposure. The expression domains of Hoxa-7, Hoxc-8, and Hoxc-9 genes as examined by whole mount in situ hybridization were found to be shifted anteriorly in heated embryos. The heat-induced shifts of Hox gene expression domains were consistent with the observed vertebral transformations and suggested correlation or colinearity with the clustered organization of the Hox genes. The result of the present study indicates that a brief heat shock at a critical stage of differentiation can interfere with the normal establishment of Hox codes and subsequently, perturb the specification of vertebral identity.

Animals↗
PubMedDate not supplied

Estimation of severity of stenosis with a Doppler guide wire in the experimental models.

Application of the continuity equation to Doppler catheter measurement of quantitative coronary flow velocity has been reported recently to be one of the accurate methods to evaluate mild to moderate coronary stenosis. This method, however, has not been validated in moderate to severe coronary stenosis. Furthermore, the ratio of prestenotic velocity/stenotic velocity may be influenced by side branches proximal to moderate to severe stenosis. Therefore we designed this study to evaluate the accuracy of the continuity equation method in the assessment of moderate to severe stenosis by an 0.018-inch (0.46 mm) Doppler guide wire (12 MHz) and the influence of a side branch on estimation of stenotic severity. Doppler spectra were recorded in the straight rigid tubes (4 mm diameter) with different severities of stenosis (50%, 62.5%, and 75% diameter stenosis) without a side branch with a Doppler guide wire. By the continuity equation, percent diameter stenosis was calculated from the proximal/stenotic and distal/stenotic velocity ratios in each model at different flow rates. In the model of 75% diameter stenosis with a side branch (1 mm diameter) proximal to the stenosis and the model of 75% diameter stenosis with a side branch (1 mm diameter) distal to the stenosis, percent diameter stenosis was calculated by the same method. Percent diameter stenosis derived from the proximal/stenotic velocity ratio in each model was in agreement with the true severity of stenosis in each model without a side branch (48% +/- 1%, 62% +/- 1%, and 75% +/- 1%, respectively). Percent diameter stenosis from the distal/stenotic velocity ratio was also in agreement with the true severity of stenosis in each model without a side branch (48% +/- 3%, 61% +/- 1%, and 75% +/- 1% respectively). In the model of 75% diameter stenosis with a side branch proximal to the stenotic site, however, percent diameter stenosis derived from the proximal/stenotic velocity ratio was underestimated compared with the real stenosis and significantly smaller than that derived from the distal/stenotic velocity ratio (65% +/- 1% versus 74% +/- 1%; p < 0.001). On the other hand, in the model of 75% diameter stenosis with a side branch distal to the stenotic site, the percent diameter stenosis derived from both the proximal/stenotic and distal/stenotic velocity ratios was in agreement with that derived from the distal/stenotic velocity ratio (75% +/- 2% and 77% +/- 1%). In the experimental models the estimation of stenotic severity by a Doppler guide wire is accurate even in moderate to severe stenosis unless a side branch exists just proximal to the stenosis. However, the distal/stenotic velocity ratio is applicable even if a side branch exists. This suggests that severity of stenosis derived from the distal/stenotic velocity ratio may be more useful than that from the proximal stenotic velocity ratio in human coronary stenosis with side branches.

Algorithms↗
PubMedDate not supplied

Noninvasive measurement of left internal mammary artery bypass graft flow by duplex Doppler echocardiography from the supraclavicular fossa.

To test the ability of duplex Doppler echocardiography from the supraclavicular fossa in detecting the left internal mammary artery (LIMA) graft flow and to verify the flow velocity measurement with this method, we studied 12 consecutive patients who underwent coronary artery bypass graft surgery with the LIMA graft. Duplex Doppler echocardiography detected the LIMA graft flow in 11 (92%) of the 12 patients. In these patients, simultaneous supraclavicular duplex Doppler and Doppler catheter measurements of the LIMA graft flow were performed. There were significant correlations in systolic peak velocity (r = 0.84, p < 0.01) and diastolic peak velocity (r = 0.79, p < 0.01) between the supraclavicular and Doppler catheter methods. There were also significant correlations in the diastolic to systolic peak flow velocity ratio (r = 0.86, p < 0.01) and diastolic fraction (r = 0.90, p < 0.01) between the supraclavicular and Doppler catheter methods. Thus, duplex Doppler echocardiography from the supraclavicular fossa is useful in the detection of the LIMA graft flow and permits accurate noninvasive measurement of the LIMA graft flow.

Blood Flow Velocity↗