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T Akasaka

Publications and source records attributed to T Akasaka.

At least 199 records · Page 11Linked to original sources
PubMed1992

Intravascular ultrasound imaging--in vitro and vivo validation.

Intravascular ultrasound imaging is a new technique for visualizing arterial structures. The purpose of this study was twofold; first, to assess the ability of this intravascular ultrasound catheter to generate cross-sectional images of human artery segments in vitro and second, to determine the reliability of intravascular ultrasound technique in the evaluation of human arteries in vivo. For the vitro study, ultrasound images of the arteries were presented as a two-dimensional, 360 degrees display of vessel cross-section perpendicular to the long-axis of the probe. The ultrasound scanning provided an accurate description with high resolution of lumen structure and lumen-intima interface in all vessel specimens. There was a good correlation between the planimetric luminal area on the ultrasound images and the area obtained from histologic images (r = 0.92). There was also a good correlation in the plaque thickness between ultrasound and histological examination (r = 0.88). In the in vivo study, the ultrasound catheter was easily introduced, readily manipulated, and images were successfully obtained in all patients. No untoward effects were noted during manipulation of the catheter. There was a good correlation in the arterial dimension between ultrasound and angiographic measurements (r = 0.93). Thus, intravascular ultrasound imaging appears to be useful for characterizing and quantitating arterial lesions.

Carotid Arteries↗
PubMed1991

Metal-tetracycline/H+ antiporter of Escherichia coli encoded by a transposon Tn10. Histidine 257 plays an essential role in H+ translocation.

The transposon Tn10-encoded tetA gene product is a metal-tetracycline/proton antiporter (Yamaguchi, A., Udagawa, T., and Sawai, T. (1990) J. Biol. Chem. 265, 4809-4813). Its tetracycline transport activity was inhibited by a histidine-specific reagent, diethyl pyrocarbonate. Among five histidine residues in this antiporter, only His257 is located in the putative transmembrane helices. Thus, His257 was replaced by Glu or Asp. Inverted vesicles containing the Glu257 and Asp257 mutant proteins showed only 20 and 10% of the tetracycline uptake of wild-type vesicles, respectively. In contrast to wild-type vesicles, the mutant vesicles showed no tetracycline-dependent proton translocation, indicating that the mutant proteins had lost the tetracycline/H+ antiport activity. The significant 60Co2+ uptake without proton translocation by the mutant vesicles also confirmed that the mutant carriers act as uniporters of a metal-tetracycline complex. The metal-tetracycline uniport by the mutant proteins was not inhibited by diethyl pyrocarbonate, indicating that His257 is the only histidine residue essential for proton translocation. These mutant proteins conferred about half-level resistance to tetracycline, probably due to their catalyzing downhill efflux of a metal-tetracycline complex out of the cells.

Amino Acid Sequence↗
PubMed1991

Assessment of aortic regurgitation by the acceleration flow signal void proximal to the leaking orifice in cinemagnetic resonance imaging.

BACKGROUND: The proximal acceleration flow region is a laminar flow field that is located immediately upstream from the leaking orifice. The purpose of this study was to evaluate whether cinemagnetic resonance imaging can provide information regarding the proximal acceleration flow region in patients with aortic regurgitation and to analyze the relation between the area of the proximal acceleration flow delineated by cinemagnetic resonance imaging and the severity of aortic regurgitation delineated by angiography. METHODS AND RESULTS: Thirty-eight consecutive patients who underwent aortography were examined by cinemagnetic resonance imaging. The region of proximal flow acceleration was identified as a semicircular-shaped signal void in the aorta during diastole. Cinemagnetic resonance imaging detected the proximal acceleration flow region in 26 of the 30 patients who were proved to have this lesion (sensitivity, 87%). In eight patients without aortic regurgitation according to aortography, no proximal acceleration flow region was detected (specificity, 100%). The area of the acceleration flow signal void from the long-axis view was well correlated with angiographic degree of aortic regurgitation. CONCLUSIONS: Cinemagnetic resonance imaging is useful in detecting the proximal acceleration flow region and permits noninvasive assessment of the severity of aortic regurgitation.

Adult↗
PubMed1991

Infective endocarditis--analysis of 116 surgically and 26 medically treated patients.

We have reviewed 116 cases of bacterial endocarditis treated surgically and 26 cases treated medically since 1973. There were 123 patients with native valve endocarditis and 19 patients with prosthetic valve endocarditis. Overall, the left-sided valves were infected most frequently. There were 10 cases with right-sided valves involved. Multiple valves were infected in 6 patients. There were 6 perioperative deaths in the surgical group. The most common cause of death was multi-organ failure associated with uncontrollable sepsis. The overall operative mortality for active endocarditis was 7.7% (4/55), and for healed endocarditis, 3.3% (2/61). For active native valve endocarditis, the mortality was 4.2% (2/48), for healed native valve endocarditis, 3.6% (2/55), for active prosthetic valve endocarditis, 28.6% (2/7), and for healed prosthetic valve endocarditis, 0%. There was no difference in the operative mortality between active native valve endocarditis and healed native valve endocarditis. The mortality of active prosthetic valve endocarditis was significantly higher than that of active native valve endocarditis (p less than 0.01). Of the 26 patients treated medically, 7 died during the initial hospitalization. The major factor related to mortality in the medically treated patients was persistent sepsis (four patients), and congestive heart failure (three patients). The overall mortality of the medical group for active valve endocarditis was 15% (3/20), and for active prosthetic valve endocarditis, 67% (4/6). We conclude that patients with infective endocarditis with significant valve lesions who are unresponsive to medical therapy should be considered for urgent surgery.

Aortic Valve↗
PubMed1991

[A double blind study of the effectiveness of ketotifen in preventing the development of asthma in atopic dermatitis patients].

Many asthmatic children have experienced atopic dermatitis in their younger days. As it is very difficult to cure childhood asthma we attempted to determine the anti-allergic drug effects in preventing the development of asthma by using ketotifen on atopic dermatitis patients. The study was designed as a placebo controlled double blind trial of 128 atopic dermatitis patients aged from 2-34 months. 91 patients were given complete analysis in the study, 33 patients were given only a safety rate and 4 patients were dropped. The 91 patients were followed for 52 weeks. Our primary finding was that the development of bronchial asthma was inhibited in the ketotifen group compared to the placebo controlled group with a statistically significant degree (p less than 0.001). We also found that clinical symptoms of atopic dermatitis were significantly improved in the ketotifen group (p less than 0.001). Only 5 patients complained of mild side effects.

Age Factors↗
PubMed1990

Metal-tetracycline/H+ antiporter of Escherichia coli encoded by a transposon, Tn10. The role of the conserved dipeptide, Ser65-Asp66, in tetracycline transport.

The transposon Tn10-encoded tetracycline resistance protein functions as a metal-tetracycline/H+ antiporter (Yamaguchi, A., Udagawa, T., and Sawai, T. (1990) J. Biol. Chem. 265, 4809-4813). The Ser65-Asp66 dipeptide is conserved in all known tetracycline antiporter proteins and is an important target for site-directed mutagenesis. When Asp66 was replaced by Asn, the transport activity was completely lost, whereas when it was replaced by Glu, the activity was reduced to 10% of the wild-type level, indicating that a negative charge at position 66 is essential for tetracycline transport. Replacement of Ser65 by Cys or Ala, in contrast, caused only a minor change in tetracycline transport activity. However, the Cys65 mutant antiporter was sensitive to sulfhydryl reagents. Complete inactivation of the Cys65 antiporter by N-ethylmaleimide was not prevented by the substrate. A less bulky reagent, methyl methanethiosulfonate, caused partial inactivation of the Cys65 antiporter without changing its affinity to the substrate. These results indicate that a region including the dipeptide plays an important role in metal-tetracycline transport except for substrate binding. It may act as a gate which opens on the charge-charge interaction between Asp66 and the metal-tetracycline.

Amino Acid Sequence↗
PubMed1990

Valvular regurgitation in heart-lung transplant recipients: a Doppler color flow study.

To assess the frequency and degree of valvular regurgitation in combined heart and lung transplant recipients, 50 patients were investigated using Doppler color flow echocardiography 20 to 909 days (mean 369) after heart-lung transplantation. The mean age (+/- SD) of the patients was 25 +/- 9 years. No patient had evidence of rejection at the time of the study. Fifty normal volunteers acted as control subjects. Tricuspid, mitral and pulmonary regurgitation were commonly observed in the patients undergoing heart-lung transplantation (78%, 52% and 68%, respectively), but were not significantly more frequent than in the normal subjects (68%, 42% and 70%, respectively). Aortic regurgitation was uncommon in both groups (4% and 2%, respectively). However, tricuspid and mitral regurgitant jet areas were significantly greater (p less than 0.01) in heart-lung transplant recipients than in normal subjects (156 +/- 120 and 84 +/- 52 mm2 compared with 40 +/- 38 and 28 +/- 26 mm2, respectively); pulmonary regurgitant jet area was not significantly different in the two groups (32 +/- 26 and 28 +/- 26 mm2, respectively). Regurgitant jet area was not significantly correlated with patient or donor age, donor organ total ischemic time, time after operation, use of steroids for immunosuppression or total number of rejection episodes. These results show that valvular regurgitation is not significantly more frequent after heart-lung transplantation than in normal subjects, but atrioventricular (AV) valve regurgitation, when present, is significantly greater in degree. This suggests that the degree but not the frequency of AV valve regurgitation is related to transplantation.

Adolescent↗
PubMed1990

Effect of ketotifen on antigen-induced interleukin 2 (IL-2) responsiveness in lymphocytes from patients with atopic dermatitis and/or bronchial asthma.

We tested the effect of Ketotifen (4-(1-methyl-4-piperidylidene)-4H- benzo[4,5] cyclohepta[1,2-b]thiophen-10(9H)-one hydrogen (fumarate) on the induction of allergen-induced IL-2 responsiveness in lymphocytes from patients with atopic dermatitis and/or bronchial asthma. Ovalbumin (OVA)- and/or Dermatophagoides farinae(Df)-induced IL-2 responsiveness was increased in almost all patients (1-15 years old) before Ketotifen treatment. Two to 12 months administration of Ketotifen (0.06 mg/kg/day) decreased activity of the response in 7 out of 9 cases corresponding to improvement of clinical symptoms. In in-vitro studies, antigen presenting cells (adherent cells) from the patient pretreated with 5, 50 and 500 ng/ml doses of Ketotifen for 12 h failed to present OVA or Df antigen to T-cells for induction of IL-2 responsiveness. Antigen-pulsed adherent cells also failed to induce the response of the T-cells pretreated with 50 and 500 ng/ml doses of Ketotifen but not with a 5 ng/ml dose. A 50 ng/ml dose of Ketotifen did not affect T-cells for induction of the response. In contrast, the treated adherent cells are capable of presenting PPD antigen or Con A for the induced response. The combined data indicate that induction of IL-2 responsiveness of peripheral blood lymphocytes on stimulation with nominal antigen may reflect an immune response to allergen in patients with allergy and a weak immunosuppressive effect of Ketotifen seems to block the response in the pathogenic process of allergic diseases.

Adolescent↗
PubMed1990

Direct visualization of ruptured chordae tendineae by transesophageal two-dimensional echocardiography.

To determine the value of transesophageal echocardiography in the detection of ruptured chordae tendineae, 28 patients who had surgical therapy for pure mitral regurgitation were evaluated prospectively by conventional transthoracic and transesophageal two-dimensional echocardiography. Seventeen patients (Group I) had ruptured chordae tendineae and 11 (Group II) had intact chordae tendineae. Transthoracic echocardiography detected ruptured chordae tendineae in 6 patients from Group I (sensitivity 35%) and flail leaflets in 11 patients from Group I (sensitivity 65%). Transesophageal echocardiography disclosed ruptured chordae tendineae in all 17 Group I patients (sensitivity 100%); the sensitivity was significantly higher than that of transthoracic echocardiography. No abnormal chordal echoes were visualized in any patient from Group II by either transthoracic or transesophageal echocardiography (specificity 100%). Transesophageal echocardiography is a highly sensitive method for detecting ruptured chordae tendineae and is superior to transthoracic echocardiography in establishing its diagnosis.

Chordae Tendineae↗
PubMed1990

Value of acceleration flows and regurgitant jet direction by color Doppler flow mapping in the evaluation of mitral valve prolapse.

To clarify the role of color Doppler echocardiography in the evaluation of mitral valve prolapse, we studied 49 consecutive patients in whom the sites of mitral valve prolapse were confirmed at the time of operation. The study group consisted of 22 patients with anterior leaflet prolapse, 24 patients with posterior leaflet prolapse, and three patients with multiple scallop prolapse (one patient with both anterior leaflet and middle scallop prolapse, and two patients with both medial and lateral scallop prolapse). Two-dimensional echocardiographic diagnosis of anterior leaflet prolapse was correct in all patients. The diagnosis of posterior leaflet prolapse by two-dimensional echocardiography, however, was mistaken as anterior leaflet prolapse in 16 (13 patients with medial scallop prolapse and three patients with lateral scallop prolapse) of the 24 patients according to current diagnostic criteria for mitral valve prolapse. Eight patients with middle scallop prolapse were diagnosed correctly by two-dimensional echocardiography. Acceleration flows in the left ventricle were observed by color Doppler echocardiography in all 49 patients. The sites of acceleration flows detected by color Doppler echocardiography coincided with those of prolapse confirmed in all at the time of operation. There was a significant correlation between the maximum area of acceleration flow signals and severity of mitral regurgitation estimated by angiography. In the 13 patients with medial scallop prolapse and the three patients with lateral scallop prolapse, a regurgitant jet originated from a bulged portion of the posterior leaflet and was directed toward the opposite left atrial cavity to the bulged portion by short-axis images of color Doppler echocardiography.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1990

Detection of left main coronary artery stenosis by transesophageal color Doppler and two-dimensional echocardiography.

Although transthoracic two-dimensional echocardiography can detect dilation of the coronary arteries, the reliability of this technique in the detection of coronary artery stenosis is still doubtful. The purpose of this study was to test the ability of newly developed biplane transesophageal color Doppler and two-dimensional echocardiography in the detection of left main coronary artery stenosis. Blood flow in the left main coronary artery was detected in 57 of 67 (85%) patients by transesophageal color Doppler flow imaging. Using transesophageal two-dimensional echocardiography, adequate images of the full length of the left main coronary artery and identification of the bifurcation were obtained in 60 of 67 (90%) patients. Transesophageal echocardiography clearly showed significant (greater than or equal to 50%) narrowing of the coronary lumen in 10 of 11 patients (sensitivity, 91%) and insignificant narrowing or no abnormalities of the coronary lumen in the other 49 patients (specificity, 100%). The positive predictive accuracy for left main coronary artery disease was 100%, and the negative predictive accuracy was 98%. This preliminary study suggests that biplane transesophageal color Doppler and two-dimensional echocardiography appears to be a feasible noninvasive technique for imaging the left main coronary artery and detecting hemodynamically significant luminal obstruction.

Adult↗
PubMed1990

Assessment of mitral regurgitation by biplane transesophageal color Doppler flow mapping.

To test the role of recently developed biplane transesophageal color Doppler echocardiography in the assessment of severity of mitral regurgitation, we examined 51 patients undergoing cardiac catheterization and left ventriculography. Transesophageal color Doppler flow imaging detected mitral regurgitation in all 32 patients proved to have this lesion. In 10 of 16 patients without mitral regurgitation by angiography, mitral regurgitation signals were detected by transesophageal color Doppler flow imaging. Thus, the sensitivity and specificity of transesophageal color Doppler echocardiography for the detection of mitral regurgitation were 100% and 38%, respectively. There was some correlation between the regurgitant jet area from the longitudinal plane and angiographic grading. An improved angiographic correlation was achieved with the regurgitant jet area from the transverse plane. The best correlation with angiography was obtained when the maximum regurgitant jet area from two planes (the greater of the two measurements, each from a different plane) was considered. There was a significant difference in the maximum regurgitant jet area between none and mild (p less than 0.01), mild and moderate (p less than 0.001), and moderate and severe (p less than 0.01) mitral regurgitation. The maximum regurgitant jet area of less than 1.5 cm2 predicted the angiographic grading as none with a sensitivity and specificity of 88% and 94%, respectively. The maximum regurgitant jet of between 1.5 and 4 cm2 predicted the angiographic grading as mild with a sensitivity and specificity of 82% and 95%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Value of transesophageal color Doppler echocardiography in the evaluation of coronary artery anatomy and blood flow.

The purpose of this study was to test the efficacy of newly developed biplane transesophageal color Doppler and two-dimensional echocardiography in the evaluation of coronary artery anatomy and blood flow. Using these two techniques, high quality images of the entire main left coronary artery (from the left coronary ostium to the bifurcation of the left anterior descending and circumflex coronary arteries), adequate for assessment of luminal diameter and percent stenosis, were obtained in 34 (89%) out of 38 patients. Transesophageal color Doppler echocardiography visualized coronary blood flow in 32 (84%) of the 38 patients. Transesophageal two-dimensional echocardiography clearly showed significant (50% of greater) narrowing of the coronary lumen in 10 out of 12 patients (sensitivity; 83%) and insignificant narrowing or no abnormalities of the coronary lumen in 23 of 26 normal individuals (specificity; 88%). This preliminary study suggests that biplane transesophageal color Doppler and two-dimensional echocardiography are feasible, noninvasive techniques for imaging the main left coronary artery and blood flow.

Adult↗
PubMed1990

[Long-term follow-up studies of bronchial asthma in children. I. Prognosis and risk factors].

A questionnaire on the prognosis of bronchial asthma was sent in 1988 to 1,592 patients (1,038 males, 554 females) averaging 20 years of age after 12 years' follow up. The results were as follows: 75.6% in remission, 18.2% improved, 4.0% unchanged, 0.9% worse and 1.3% dead from asthma. The average age of onset was 2.7 years, about 1 year earlier than that in our report of 1965. The average age of remission (growing out of asthma) was 13.0 years for males and 12.3 years for females. The prognosis was significantly poorer among asthmatics with an onset age of under 2 years, with a 10-year history of asthma before the first visit to our hospital, with severe attack at the initial visit, a history of admissions for the attacks and food allergy. The asthmatic children with food allergy had a 1-year earlier onset of attack, a more severe attack at the initial visit, more eczema in infancy, and 2 or more other allergic complications than children without food allergy. We have to closely follow and care for those asthmatic children with high risk factors for an extended period.

Adolescent↗
PubMed1990

[A successful surgical case report of subaortic stenosis due to accessory mitral valve tissue associated with partial ventricular septal hypertrophy].

One-year- and ten-month-old male infant with subaortic stenosis due to the accessory mitral valve tissue associated with asymmetrical myocardial hypertrophy was treated successfully with surgery. Preoperative diagnosis of "discrete subaortic stenosis" was achieved by echocardiography and angiography. A 70 mmHg of preoperative pressure gradient from left ventricle through ascending aorta could be reduced to 25 mmHg by the operative excision of this accessory mitral valve tissue and partial resection of this septal hypertrophy. This patient was supposed to be complicated with the ventricular septal aneurysm according to the angiographic study, even though this aneurysm was not visualized at the time of the operation. According to our knowledge, only fifteen cases of stenosis due to accessory mitral valve tissue was reported. The pathological findings of the excised specimens of these anomalous tissue were presented and developmental genesis of this intracardiac anomalous tissues, perhaps based on the developmental anomaly of the primitive organ of the endocardial cushion, was discussed in this report.

Aortic Valve Stenosis↗
PubMed1990

[Long-term follow up studies of bronchial asthma in children. II. Prognosis and complications, treatment and allergic evaluations].

A questionnaire on the prognosis of bronchial asthma was sent in 1988 to 1592 patients (1038 males, 554 females) averaging 20 years of age after 12 years' follow up. We reported on the prognosis and risk factors associated with asthmatic children in part I. The relation between prognosis and other allergic complications, treatment and laboratory data were investigated in this study. Eosinophil counts of more than 1000/mm3 and/or total serum IgE levels of more than 500 IU/ml (100 IU/ml in infants) indicated poor prognosis. However, the prognosis was not affected either by the allergens themselves or by the number of allergens determined by skin test and RAST. The prognosis was worse for patients with multiple allergic complications than for those without complications. Treatment may after the natural course of childhood asthma, but it has been difficult to evaluate the effect of each regimen over a long period. We compared the effect of hyposensitization (specific immunization) and non-bronchodilator antiasthmatic drugs (NBAAD), and found that hyposensitization alone gave better results than NBAAD and its combination. We had better results from hyposensitization over a period of 1 to 5 years than for less than 1 year or more than 5 years. We conclude that asthmatic children with risk factors should be kept under strict environmental control and given suitable therapeutic regimens to avoid the development of allergic diseases, the slow down of "allergic march", and to avoid intractable asthma.

Asthma↗