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Biomedical subjects

Y Shomura

Publications and source records attributed to Y Shomura.

At least 19 recordsLinked to original sources
PubMed2006

Percutaneous transluminal cutting-balloon angioplasty for hemodialysis access stenoses resistant to conventional balloon angioplasty.

PURPOSE: To examine the value of cutting-balloon percutaneous transluminal angioplasty (PTA) for hemodialysis access with residual stenosis after conventional balloon PTA. MATERIAL AND METHODS: Angioplasty with conventional balloons was performed on 48 hemodialysis access stenoses in 28 patients. If the balloon waist still remained at the rated burst pressure, the balloon was reinflated up to three times. Fifteen of 48 stenoses had residual stenoses of more than 30% after conventional balloon PTA. In these 15 stenoses, additional cutting-balloon PTA was performed. RESULTS: The mean residual percent diameter stenoses before and after conventional balloon PTA were 77.6+/-3.4% and 48.6+/-8.5%, respectively. Additional cutting-balloon PTA decreased the mean residual percent diameter to 27.9+/-10.0%, and the cutting balloon was completely inflated without complication. In 12 patients, the 6-month primary patency rate (+/-SE) was 90.0% (9.5), and the 1-year primary patency rate (+/-SE) was 25.0% (14.8). CONCLUSION: Additional cutting-balloon PTA was found useful for reducing residual stenosis.

Adult↗
PubMed2005

Percutaneous vertebroplasty for compression fracture: analysis of vertebral body volume by CT volumetry.

PURPOSE: To evaluate the relationships between volume of vertebral bodies with compression fracture (measured by CT volumetry) before percutaneous vertebroplasty, the amount of bone cement injected, and the effect of treatment. MATERIAL AND METHODS: We examined 49 consecutive patients, with 104 vertebral body compression fractures, who underwent percutaneous injection of bone cement. Vertebral body volume was measured by CT volumetry. The patient's pain level was assessed using a visual analog scale (VAS) before and after the procedure. Improvement in VAS was defined as the decrease in VAS after the procedure. Relationships between vertebral body volume, the amount of bone cement, and the effect of treatment were evaluated using Pearson's correlation coefficient test. RESULTS: Average vertebral body volume was 26.3 +/- 8.1 cm3; average amount of bone cement was 3.2 +/- 1.1 ml; and average improvement in VAS was 4.9 +/- 2.7. The vertebral body volume was greater if a larger amount of bone cement was injected. There was a significant positive correlation between vertebral body volume and amount of bone cement (r = 0.44; P < 0.0001). However, there was no correlation between vertebral body volume and improvement in VAS, or between amount of bone cement and improvement in VAS. CONCLUSION: In percutaneous vertebroplasty for vertebral body compression fracture, there is a positive correlation between vertebral body volume and amount of bone cement, but improvement in VAS does not correlate with vertebral body volume or amount of bone cement.

Aged↗
PubMed2003

[A device to prevent an air-leakage after a thoracoscopic surgery for spontaneous pneumothorax].

PURPOSE: In a thoracoscopic surgery for the patient with spontaneous pneumothorax, an air-leakage from the staple-line is one of the most troublesome complications. Recently we have been using a polyglycolic acid (PGA) sleeve for staple-line reinforcement. The purpose of this study was to investigate an efficacy of staple-line reinforcement in the patients who underwent thoracoscopic lung resection using an automatic stapler. OBJECTS: Last 4 years, 55 patients with primary spontaneous pneumothorax underwent thoracoscopic surgery using an automatic stapler. PGA sleeve was used in 19 patients as PGA group, fibrin glue was applied to the staple-line in 6 patients as fibrin group and no staple-line reinforcement was applied in 30 patients as no-reinforce group. We investigated the efficacy of staple-line reinforcement according to the results after surgery in these 3 groups. RESULTS: Average drainage time in PGA group, fibrin group and no-reinforce group were 2.1, 2.2 and 2.8 days, respectively. In PGA group, the drainage time after surgery tended to be short term. The relapse of pneumothorax after surgery developed in 2 patients in PGA group (10.5%) and 8 patients in non-reinforce group (26.7%). In PGA group, the relapse after surgery tended to be low rate. CONCLUSIONS: Bioabsorbable PGA sleeve could be an useful device for a staple-line reinforcement in the patients who underwent lung resection using automatic stapler.

Adolescent↗
PubMed2002

Aortic and pulmonary root: are their dynamics similar?

OBJECTIVES: The long-term behavior of the pulmonary autograft in the aortic position (Ross procedure) remains uncertain. Using three-dimensional (3D) sonomicrometry (200 Hz) we compared the dynamics of the aortic and pulmonary roots. METHODS: Twenty-four crystals were implanted in each aortic (eight sheep) and pulmonary roots (six sheep) at: base (3 x 2), commissures (3 x 2), sinotubular junction (3 x 2), ascending aorta (3) and pulmonary trunk (3). Under stable hemodynamic conditions, geometric changes were time-related to left ventricular pressure (LV) and aortic pressure. RESULTS: The expansion of the aortic root is twice that of the pulmonary root. During the cardiac cycle, the aortic root volume increased by 37.7 +/- 2.7% (mean +/- SEM) versus 20.9 +/- 1.0% for the pulmonary root. Both were cone-shaped at end diastole. Because expansion at commissures was twice that of the base, both roots became more cylindrical during ejection. Although both roots started to expand prior to ejection and reached maximal expansion during the first third of ejection, the commissural and sinotubular junction dynamics were different in each root. While in the aortic root, expansion at commissural and sinotubular junction levels was significantly different (63.7 +/- 3.6% versus 37.0 +/- 2.1%), in the pulmonary root, they were similar (29.0 +/- 1.3% versus 27.7 +/- 1.4%). Expansion of the three sinuses was also different (P<0.001). In the aortic root: the right expanded more than the left and more than the non-coronary sinus. In the pulmonary root: the right sinus expanded more than the anterior more than the left. CONCLUSIONS: Dynamic differences might explain the global pulmonary root dilatation when subjected to systemic pressure, particularly at the level of the sinotubular junction which might result in the autograft failure. Differences in the asymmetrical expansion of the aortic and pulmonary roots should be considered for the implantation of the pulmonary autograft in the most physiological position.

Analysis of Variance↗
PubMed2002

A four-dimensional study of the aortic root dynamics.

OBJECTIVE: Although aortic root expansion has been well studied, its deformation and physiologic relevance remain controversial. Three-dimensional (3-D) sonomicrometry (200Hz) has made time-related 4-D study possible. METHODS: Fifteen sonomicrometric crystals were implanted into the aortic root of eight sheep at each base (three), commissures (three), sinuses of Valsalva (three), sinotubular junction (three), and ascending aorta (three). In this acute, open-chest model, the aortic root geometric deformations were time related to left ventricular and aortic pressures. RESULTS: During the cardiac cycle, aortic root volume increased by mean+/-1 standard error of the mean (SEM) 33.7+/-2.7%, with 36.7+/-3.3% occurring prior to ejection. Expansion started during isovolumic contraction at the base and commissures followed (after a delay) by the sinotubular junction. At the same time, ascending aorta area decreased (-2.6+/-0.4%). During the first third of ejection, the aortic root reached maximal expansion followed by a slow, then late rapid decrease in volume until mid-diastole. During end-diastole, the aortic root volume re-expanded by 11.3+/-2.4%, but with different dynamics at each area level. Although the base and commissural areas re-expanded, the sinotubular junction and ascending aorta areas kept decreasing. At end-diastole, the aortic root had a truncated cone shape (base area>commissures area by 51.6+/-2.0%). During systole, the root became more cylindrical (base area>commissures area by 39.2+/-2.5%) because most of the significant changes occurred at commissural level (63.7+/-3.6%). CONCLUSION: Aortic root expansion follows a precise chronology during systole and becomes more cylindrical - probably to maximize ejection. These findings might stimulate a more physiologic approach to aortic valve and aortic root surgical procedures.

Animals↗
PubMed2002

A new liquid embolic material for liver tumors.

PURPOSE: To evaluate the feasibility of a new liquid embolic material, Onyx, for treating liver tumors. MATERIAL AND METHODS: Onyx is a mixture of 6% (w/v) ethylene-vinyl-alcohol copolymer dissolved in anhydrous dimethyl sulfoxide (DMSO) with 28% (w/v) tantalum powder. In addition to 6% Onyx, we also tried 4%, 2% and 1% solutions, prepared by adjusting the amount of DMSO. We used 15 white rabbits with liver tumors created by percutaneous injection of VX2 tumor cells. In 4 groups with 3 rabbits in each, the liver arteries were embolized with 6%, 4%, 2% and 1% Onyx, respectively, and in 3 rabbits DMSO alone was injected. The injections were performed just proximal to the bifurcation of the proper hepatic artery, followed by celiac arteriography. Post mortem, the livers were examined by soft-tissue radiography, and liver-tissue section microscopy. RESULTS: The maximum number of arterial branching points passed by embolic material in either the right or left hepatic arteries was 11, 15 and 16, for 6%, 4% and 2% Onyx, respectively, but was non-measurable for 1% Onyx. Minimum diameters of arteries reached by 6%, 4%, 2% and 1% Onyx in tumorous areas were 40 microm, 35 microm, 20 microm and 10 microm, respectively, and in non-tumorous areas 35 microm, 5 microm, 5 microm and 5 microm, respectively. CONCLUSION: This study suggests that Onyx may be feasible for treatment of hepatic tumors.

Animals↗
PubMed2002

[Reoperation for metachronous pulmonary or tracheal lesions after pneumonectomy].

Although aggressive reoperation for metachronous multiple primary lung cancer or intrathoracic recurrence without distant metastases have been recommended to the patients of primary lung cancer and metastatic lung tumor, surgical indication after a previous pneumonectomy is restricted because of residual pulmonary function. We report about 3 reoperated cases for metachronous pulmonary or tracheal lesions after left pneumonectomy. Case 1: A 61-year old male who underwent left pneumonectomy for primary lung cancer was reoperated for tracheal cancer 41 months after the pneumonectomy. Case 2: A 61-year old male who underwent left pneumonectomy for primary lung cancer was reoperated for metachronous multiple primary lung cancer 59 months after the pneumonectomy. Case 3: A 59-year old male who underwent left pneumonectomy for metastatic lung tumor from rectal cancer was re-operated for intrathoracic recurrence 28 months after the pneumonectomy. All cases are alive without recurrence.

Humans↗
PubMed2001

Glycine at the 65th position plays an essential role in ATP-dependent protein folding by Archael group II chaperonin.

In the previous study, we have found that G65C and I125T double mutant of alpha chaperonin homo-oligomer from a hyperthermophilic archaeum, Thermococcus sp. strain KS-1, lacks ATP-dependent protein refolding activity despite showing ATPase activity and the ability to bind the denatured proteins. In this study, we have characterized several mutant Thermococcus chaperonin homo-oligomers with the amino acid substitutions of Gly-65 or Ile-125. The results showed that amino acid residue at 65th position should be a small amino acid such as glycine or alanine for the ATP-dependent refolding activity. The alpha chaperonin homo-oligomers with amino acid substitution of Gly-65 by amino acids whose side chains are larger than the methyl group did not have ATP-dependent protein refolding activity, but exhibited an increase of the binding affinity for unfolded proteins in the presence of ATP or AMP-PNP. (c)2001 Elsevier Science.

Adenosine Triphosphatases↗
PubMed2001

Hemodynamic evaluation of a new stentless autologous pericardial mitral valve.

BACKGROUND: There is no satisfactory mitral valve prosthesis. An ideal mitral valve substitute should be biologic, nonantigenic, and anatomically correct. METHODS: We developed a stentless, chordal-supported (including anterior basal stay chords) mitral valve made with glutaraldehyde-treated autologous pericardium. Eight such prostheses were implanted in sheep. RESULTS: Seven animals survived the operation and were studied postoperatively immediately, at 1 week, and at 1 month. Simultaneous left ventricular and left atrial pressures showed peak and mean transvalvular pressure gradients of 6+/-2 mm Hg and 1+/-1 mm Hg, respectively. Echocardiography performed intraoperatively and then 1 week and 1 month postoperatively showed normal valve leaflet movements. Color and pulsed Doppler echocardiography showed no sign of transvalvular stenosis or regurgitation. Effective orifice area was 5.39+/-0.35 cm2 at intraoperative, 5.51+/-0.29 cm2 1 week after operation (n = 5), and 5.51+/-.28 cm2 1 month after operation (n = 3). Three animals were sacrificed at 19 days and at 1 and 3 months. One animal is alive at 10 months. CONCLUSIONS: This new stentless pericardial mitral valve performed satisfactorily with low gradients and no regurgitation. Possible advantages of this pericardial valve are excellent hemodynamics, ease of construction and implantation, lack of immunogenicity, and low cost. Similarly designed valves but with a shorter nonglutaraldehyde treatment time have been used in 3 sheep monitored for more than 3 months.

Animals↗
PubMed2001

A new method for the preservation of aortic valve homografts.

BACKGROUND AND AIM OF THE STUDY: Aortic valve homografts were treated with 50% ethanol and glycerol followed by freeze-drying (D-Hydro). Comparative results of fresh versus D-Hydro-treated aortic roots implanted for up to nine months in the descending aorta of sheep with induced aortic regurgitation (AR) are reported. METHODS: Six fresh and six D-Hydro valves were implanted in 12 sheep for three, six and nine months, and echocardiography and pressures were taken at surgery and sacrifice. Tissue sections were stained with hematoxylin and eosin, von Kossa, Masson's trichrome, Movat's pentachrome, von Willebrand factor, CD3 (a T-cell marker) and smooth muscle alpha-actin. RESULTS: No grafts had increased gradients after implantation, or at sacrifice. At explantation, fresh homografts showed early pannus formation followed by thrombus, annular dilatation and wall calcification. Leaflets were thickened and progressively retracted. All had severe AR. The appearance of D-Hydro-treated homografts was normal, except for mild leaflet retraction in three, resulting in AR (in two animals the induced AR had healed). Histologically, a T-cell-mediated reaction was evident in the fresh homografts, and collagen distortion was noted. Calcification was present in all fresh specimens and was severe at nine months. D-Hydro roots showed only minor calcification in the six-month samples. Normal collagen, and a complete layer of von Willebrand factor-stained cells were present at three months. At nine months, cell rehabitation extended for two-thirds of the leaflets (alpha-actin +). The inflammatory reaction was very mild, with CD3+-stained cells absent in most samples. CONCLUSION: Aortic valve homografts treated with the D-Hydro freeze-drying method performed better than fresh homografts due to the absence of thrombus and annulus dilatation, limited calcification, and rehabitation of the aortic wall and parts of the leaflet by myofibroblasts, as well as the presence of a complete endothelial layer on the aortic wall and leaflet.

Animals↗
PubMed2000

A study of the junction between glutaraldehyde-treated allogeneic aorta and host aorta.

BACKGROUND AND AIM OF THE STUDY: Stentless aortic valve bioprostheses have become popular because of their superior hemodynamics and expected increased durability. However, the stentless bioprosthesis differs from stented valves in that glutaraldehyde (GA)-treated tissue is implanted in direct contact with the native aorta. The effect of GA-treated tissue on host tissue has not been reported. METHODS: In order to analyze the effect of GA in the healing process, sheep descending aortic conduits treated with 0.625% GA were inserted in the descending thoracic aorta of 10 adult sheep. The implants were removed after 4, 5, 10, 12, 15, 25, 30, 32, 60 and 120 days. The upstream and downstream junctions were evaluated macro- and microscopically, and by immunohistology for smooth muscle cell alpha-actin and von Willebrand factor. RESULTS: By day 60 of implantation, the GA-treated conduits were calcified. By days 60 and 120, the calcification had spread to the host aorta, and was seen as foci of calcification in the junctional area. Acellular areas were also seen in the host aorta near the anastomosis. A fibrotic layer spanning the abluminal aspect of the junction between the implant and host aorta was present at day 4 and continued through 120 days. This layer was characterized by a progressive increase in collagenous matrix and cellularity, as well as new blood vessel formation. The luminal aspect of the junction had a neointimal layer of variable thickness containing alpha-actin-expressing cells covered by a monolayer of von Willebrand factor-expressing cells, seen at 15-30 days and present through 120 days. CONCLUSION: In our model, implanting GA-fixed tissue in direct contact with living tissues resulted in cell death and calcification of host tissue within 60 days. The integrity of the junction did not appear to be compromised. This may be of interest in light of the increased popularity of the stentless aortic bioprosthesis.

Actins↗
PubMed2000

[Surgical results and perioperative complications in patients presenting lung cancer and cardiovascular diseases].

Among 525 patients with lung cancer who underwent an operation between 1985 and 1998, 24 patients who also had a cardiovascular disease, most commonly ischemic heart disease. We gave all of these patients a preoperative assessment for ischemic heart disease, done according to a diagnostic flow chart. Eighteen patients (3.4%) were found to have IHD. We performed myocardial revascularization before or simultaneously with an operation for lung cancer in patients who also have known IHD. None of these patients had major perioperative cardiac trouble. Inspite of our efforts, perioperative myocardial ischemic events occurred in 6 patients (1.2% of all patients) who were not detected by our preoperative IHD assessment. We conclude that this IHD assessment flow chart may be useful for proper perioperative management of patients undergoing lung surgery. However, more precise methods to detect patients with IHD will be necessary to improve their perioperative cardiac risk.

Aged↗
PubMed1999

Afferent and efferent nerve activity of arterial baroreceptor reflex under nonpulsatile systemic circulation.

We studied the changes in arterial baroreceptor reflex (ABR) afferent activity and efferent activity induced by nonpulsatile systemic circulation (NC) during total left heart bypass (TLHB) in rabbits. To evaluate the influence of the circuit priming fluid and exposure to NC, we directly measured aortic depressor nerve activity (ADNA) (n = 5) and renal sympathetic nerve activity (RSNA) (n = 5) before the start of partial left heart bypass (PLHB) (Before), after PHLB (After), and 5 min after the start of TLHB (During THLB) while maintaining the mean aortic pressure. The circuit priming fluid did not affect the ABR. ADNA exhibited periodic discharge at Before and After, but at During THLB, this periodic discharge transformed into a continuous discharge, and ADNA increased significantly. However, there were no significant differences in RSNA. Our results suggested that in the acute phase under NC, the ABR differed from that under natural circulation.

Adrenergic Agonists↗
PubMed1998

Arterial baroreceptor afferent activity in nonpulsatile systemic circulation.

We directly measured aortic depressor nerve activity (ADNA) in rabbits to investigate changes in arterial baroreceptor afferent activity (ABAA) in response to nonpulsatile systemic circulation (NC) during total left heart bypass (TLHB). ADNA was measured before and 5, 20, 30, 40, 50, and 60 min after the start of TLHB while maintaining the mean aortic pressure (MAP) at preestablished values (n=10). At 5 min, the ADNA was significantly increased compared to its baseline value. At 30 min, it was significantly decreased compared to its value at 5 min and thereafter remained the same. The ADNA was then measured before and 5 and 30 min after the start of TLHB under increased MAP (n=10). The results showed that the percentage changes in ADNA during TLHB were significantly less than that observed when the MAP was increased before TLHB. We conclude that ABAA acutely adapts to NC 30 min after its initiation, but changes in ABAA are depressed under NC combined with increased MAP.

Afferent Pathways↗
PubMed1997

Silicone-coated polypropylene hollow-fiber oxygenator: experimental evaluation and preliminary clinical use.

BACKGROUND: A membrane oxygenator consisting of a microporous polypropylene hollow fiber with a 0.2-microm ultrathin silicone layer (cyclosiloxane) was developed. Animal experimental and preliminary clinical studies evaluated its reliability in bypass procedures. METHODS: Five 24-hour venoarterial bypass periods were conducted on dogs using the oxygenator (group A). In 5 controls, bypass periods were conducted using the same oxygenator without silicone coating (group B). As a preliminary clinical study, 14 patients underwent cardiopulmonary bypass with the silicone-coated oxygenator. RESULTS: Eight to 16 hours (mean, 12.2 hours) after initiation of bypass, plasma leakage occurred in all group B animals, but none in group A. The O2 and CO2 transfer rates after 24 hours in group A were significantly higher than at termination of bypass in group B (p < 0.005 and p < 0.03, respectively). Scanning electron microscopy of silicone-coated fibers after 24 hours of bypass revealed no damage to the silicone coating of the polypropylene hollow fibers. In the clinical study, the oxygenator showed good gas transfer, acceptable pressure loss, low hemolysis, and good durability. CONCLUSIONS: This oxygenator is more durable and offers greater gas transfer capabilities than the previous generation of oxygenators.

Animals↗
PubMed1996

Clinical experience with the Nikkiso centrifugal pump.

The Nikkiso HPM-15 is a minimally sized centrifugal pump. Preliminary results regarding clinical use of this pump for cardiopulmonary bypass (CPB) procedures have been reported previously. Recently, we have managed some additional cases using a newly developed controller. This article reports our clinical experiences with the use of this pump. We have managed 23 cases with a Nikkiso centrifugal pump. Twenty-two patients underwent CPB and 1 patient with fulminant viral myocarditis underwent percutaneous cardiopulmonary support (PCPS). With this pump, the circuit was extremely easy to prepare and deaeration was achieved readily. Hemodynamics during CPB and PCPS were stable in all cases. The increase in serum-free hemoglobin levels during CPB with this pump was as low as that seen in preliminary tests. A decrease in the platelet count was observed after the initiation of CPB with this pump; however, platelet counts returned to preoperative values 7 days after surgery. Moreover, urine output during CPB with this pump was as high as that seen in preliminary tests. No abnormalities in renal or liver function occurred during CPB. It appears that this new centrifugal pump is safe and easy to operate, and we conclude that it is useful for CPB and PCPS.

Adult↗
PubMedDate not supplied

Experimental evaluation of a newly developed ultrathin silicone layer coated hollow fiber oxygenator.

The authors developed a new membrane oxygenator that consists of microporous polypropylene hollow fibers coated with a 0.2 micron ultrathin silicone layer. Five venoarterial bypasses were conducted on mongrel dogs for 24 hr using these new oxygenators. The blood flow rate was maintained at 750 ml/min, and the V/Q ratio was maintained at 1:1. As a control, three venoarterial bypasses were conducted under the same conditions using an oxygenator with the same design but without the silicone coating. Eight to 16 hr after the initiation of bypass, severe plasma leakage occurred in all control experiments, so the bypasses were terminated. However, plasma leakage did not occur throughout the 24 hr of any of the experiments using the new oxygenator. The O2 transfer rate of the new oxygenators after 24 hr of perfusion was 59.7 +/- 6.6 ml/min/m2, and the plasma free hemoglobin level 8 hr after the initiation of bypass was 41.4 +/- 40.2 mg/dl, compared with 145.3 +/- 189.6 mg/dl in the control group. Scanning electron microscopic examination of the silicone coated fibers after 24 hr of bypass revealed a few scattered platelet adherents and no damage to the silicone coated surface. These results suggest that this new oxygenator has satisfactory gas transfer and good durability.

Animals↗