Biomedical subjects

H Sako

Publications and source records attributed to H Sako.

At least 19 recordsLinked to original sources

PubMed2006

Leptonic and charged kaon decay modes of the phi meson measured in heavy-ion collisions at the CERN super proton synchrotron.

We report on results of a measurement of meson production in central Pb-Au collisions at E(lab) = 158A GeV. For the first time in the history of high energy heavy-ion collisions, phi mesons were reconstructed both in the K+K- and the dilepton decay channels in the same experiment. This measurement yields rapidity densities near midrapidity, from the two decay channels, of 2.05 +/- 0.14(stat) +/- 0.25(syst) and 2.04 +/- 0.49(stat) +/- 0.32(syst), respectively. The shape of the measured transverse momentum spectrum is also in close agreement in both decay channels. The data rule out a possible enhancement of the phi yield in the leptonic over the hadronic decay channel of a factor 1.6 or larger at the 95% C.L. This rules out the discrepancy reported in the literature between measurements of the hadronic and dimuon decay channels by two different experiments.

Journal Article↗

PubMed2004

Semihard scattering unraveled from collective dynamics by two-pion azimuthal correlations in 158A GeV/c Pb+Au collisions.

Elliptic flow and two-particle azimuthal correlations of charged hadrons and high-p(T) pions (p(T)>1 GeV/c) have been measured close to midrapidity in 158A GeV/c Pb+Au collisions by the CERES experiment. Elliptic flow (v(2)) rises linearly with p(T) to a value of about 10% at 2 GeV/c. Beyond p(T) approximately 1.5 GeV/c, the slope decreases considerably, possibly indicating a saturation of v(2) at high p(T). Two-pion azimuthal anisotropies for p(T)>1.2 GeV/c exceed the elliptic flow values by about 60% in midcentral collisions. These nonflow contributions are attributed to nearside and back-to-back jetlike correlations, the latter exhibiting centrality dependent broadening.

Journal Article↗

PubMed2003

Enhanced production of low-mass electron-positron pairs in 40-AGeV Pb-Au collisions at the CERN SPS.

We report on first measurements of low-mass electron-positron pairs in Pb-Au collisions at the CERN SPS beam energy of 40 AGeV. The observed pair yield integrated over the range of invariant masses 0.2 e(+)e(-) annihilation with a modified rho propagator. They may be linked to chiral symmetry restoration and support the notion that the in-medium modifications of the rho are more driven by baryon density than by temperature.

Journal Article↗

PubMed2003

Universal pion freeze-out in heavy-ion collisions.

Based on an evaluation of data on pion interferometry and on particle yields at midrapidity, we propose a universal condition for thermal freeze-out of pions in heavy-ion collisions. We show that freeze-out occurs when the mean free path of pions lambda(f) reaches a value of about 1 fm, which is much smaller than the spatial extent of the system at freeze-out. This critical mean free path is independent of the centrality of the collision and beam energy from the Alternating Gradient Synchrotron to the Relativistic Heavy Ion Collider.

Journal Article↗

PubMed2002

Tuberculous pseudoaneurysm of the ascending aorta associated with intracranial tuberculoma.

A tuberculous aneurysm is rare and fatal because it may lead to a rupture due to the forming of a pseudoaneurysm. A lesion is especially uncommon in the ascending aorta. We report an unusual case of tuberculous pseudoaneurysm of the ascending aorta which developed 7 months after the onset of multiple intracranial tuberculoma in a 59-year-old man. He was treated for multiple intracranial tuberculomas in another hospital because of headache and left homonymous hemianopia. The temporal intracranial tuberculomas were reduced after antituberculous drug administration. However, they enlarged again shortly thereafter. At that time, a pseudoaneurysm of the ascending aorta was found, so he was introduced to our department. Intensive antituberculous drugs were administered perioperatively and postoperatively. The intracranial tuberculoma was reduced preoperatively. After that, the ascending aorta was successfully replaced with a Dacron graft. A hole was noted in the back of the ascending aorta. Three years after the operation, no symptoms of recurrence have been recognized. A tuberculous pseudoaneurysm of the ascending aorta may easily cause systemic tuberculosis or rupture, therefore it should be treated as early as possible.

Aneurysm, False↗

PubMed2002

[Arch translocation method for an arch aneurysm with open stent grafting using a nephrostomy catheter].

An 81-year-old female found to have an aneurysm in the distal aortic arch was successfully treated with arch translocation method. Under selective cerebral perfusion, a stent graft bound to a nephrostomy balloon catheter with a chainstitch was inserted from the ascending aorta into the descending aorta and its proximal end was sutured together with the distal aortic stump. Then a 4-branched Dacron graft replaced the ascending aorta reconstructing cephalobracheal branches individually. Each proximal end of cephalobracheal branches was ligated. The patient had no neurological deficit except for recurrence nerve palsy that had already existed before the operation. Postoperative angiography revealed complete thrombocclusion of the aneurysm.

Aged↗

PubMed2001

Left ventricular free wall rupture possibly induced by coronary spasm. Surgical repair in the emergency room.

A 68-year-old woman complained of chest discomfort after a traffic accident in which she driving hit a child. At about twenty-five minutes later, she went into sudden cardiogenic shock due to acute myocardial infarction caused by non-occlusive intracoronary thrombosis without significant organic coronary stenosis and without any sign of extraluminal contrast pooling on coronary angiography. She was transported to our emergency room by ambulance because of cardiac tamponade caused by a left ventricular free wall rupture following the acute myocardial infarction. On arrival, she was near cardio-pulmonary arrest on intraaortic balloon pumping. We performed emergency open cardiac massage and pericardiotomy. The hairline perforation responsible for the blowout-type left ventricular free wall rupture was successfully closed with Teflon-reinforced sutures. In conclusion, it was strongly suspected that the present case of left ventricular free wall rupture was caused by acute myocardial infarction due to intracoronary thrombosis following coronary spasm without significant organic coronary stenosis or rupture of atheromatous plaque.

Aged↗

PubMed2001

Stented elephant trunk method for multiple thoracic aneurysms.

Stent-grafting and open graft replacement was introduced to reduce the complications of suture anastomosis in the descending aorta. We applied this technique in the treatment of a patient with multiple thoracic aneurysms. The elephant trunk procedure was used for thromboexclusion. A single branched graft was placed easily without twisting. In patients with aneurysms at both the proximal and distal thoracic aorta, combined stent-grafting and open graft replacement is an excellent approach.

Aged↗

PubMed2001

[A case report of Ebstein's anomaly treated with Hetzer's procedure].

A 27-year-old male who had been diagnosed with Ebstein's anomaly was admitted with uncontrollable congestive heart failure. The echocardiogram revealed severe tricuspid valve incompetence and the electrocardiogram showed atrial fibrillation. He underwent Hetzer's repair procedure for tricuspid valve incompetence and Minzioni's right atrial isolation technique to restore sinus rhythm. His congestive heart failure quickly disappeared and sinus rhythm was restored after operation. He was discharged 3 weeks postoperatively and remains well 22 months after his operation. Hetzer's technique for tricuspid valve repair in Ebstein's anomaly restructures the valve mechanism at the level of the true tricuspid anulus by using the most mobile leaflet for valve closure without plication of the atrialized chamber. We conclude that Hetzer's procedure is an effective operation for Ebstein's anomaly.

Adult↗

PubMed2001

Early and long-term results of cardiovascular surgery in octogenarians.

The purpose of this study was to evaluate characteristics and outcomes of octogenarians undergoing cardiovascular surgery with cardiopulmonary bypass in a Japanese population. Thirty-one consecutive patients over 80 years of age underwent coronary artery bypass grafting 19 (61%), combined coronary artery bypass grafting and ventricular septal perforation closure 1 (3%), valve replacement 3 (10%), and prosthetic graft replacement 8 (26%). The early mortality rate was 16.1%. Survival estimates were 74% after 1 year, 74% after 3 year, and 64% after 5 years. Emergency and urgent cases involved 16 (51.6%), and 2 patients (6.5%), respectively. Multivariate analyses revealed that predictors of early mortality was preoperative left ventricular ejection fraction. Predictors of hospital death (within 3 months after surgery) were preoperative renal dysfunction, intraaortic balloon pumping, and age. Predictors of late mortality were chronic lung disease and age. Twenty-one patients expected to have died before surgery were living at home, and 9 (40.9%) patients were completely autonomous. Multivariate analyses revealed diabetes mellitus and a small number of bypass grafts were predictive risk factors for postoperative autonomy. Thus, cardiovascular surgery can be performed in octogenarians under 85 years of age with a favorable long-term outcome, when appropriately applied in selective octogenarians without significant comorbidity. If patients are over 85 years of age or have significant comorbidity, clinical treatment recommendations should be individually tailored while evaluating the risk of having or not having surgery and their life expectancy. QOL of survivors was almost satisfactory and significantly improved compared with a preoperative state.

Age Factors↗

PubMed2000

Rescue of contractile parameters and myocyte hypertrophy in calsequestrin overexpressing myocardium by phospholamban ablation.

Cardiac-specific overexpression of murine cardiac calsequestrin results in depressed cardiac contractile parameters, low Ca(2+)-induced Ca(2+) release from sarcoplasmic reticulum (SR) and cardiac hypertrophy in transgenic mice. To test the hypothesis that inhibition of phospholamban activity may rescue some of these phenotypic alterations, the calsequestrin overexpressing mice were cross-bred with phospholamban-knockout mice. Phospholamban ablation in calsequestrin overexpressing mice led to reversal of the depressed cardiac contractile parameters in Langendorff-perfused hearts or in vivo. This was associated with increases of SR Ca(2+) storage, assessed by caffeine-induced Na(+)-Ca(2+) exchanger currents. The inactivation time of the L-type Ca(2+) current (I(Ca)), which has an inverse correlation with Ca(2+)-induced SR Ca(2+) release, and the relation between the peak current density and half-inactivation time were also normalized, indicating a restoration in the ability of I(Ca) to trigger SR Ca(2+) release. The prolonged action potentials in calsequestrin overexpressing cardiomyocytes also reversed to normal upon phospholamban ablation. Furthermore, ablation of phospholamban restored the expression levels of atrial natriuretic factor and alpha-skeletal actin mRNA as well as ventricular myocyte size. These results indicate that attenuation of phospholamban function may prevent or overcome functional and remodeling defects in hypertrophied hearts.

1-Methyl-3-isobutylxanthine↗

PubMed2000

Comparative evaluation of a 5-day Hershberger assay utilizing mature male rats and a pubertal male assay for detection of flutamide's antiandrogenic activity.

A 5-day Hershberger assay utilizing mature male rats and a pubertal male assay were evaluated for the ability to detect antiandrogenic compounds such as flutamide, an androgen receptor antagonist. Six days after the operation, implantation with two silicon capsules containing testosterone (T) (30 mg/capsule) in castrated rats provided the ventral prostate and seminal vesicle weights as well as serum T and luteinizing hormone (LH) levels equivalent to those of the controls (non-castrated, non-implanted rats). Castrated rats implanted with two T-capsules (6 rats/dose) were treated by gavage for 5 days with vehicle (0.5% carboxymethylcellulose) or flutamide (0.15, 0.6, 2.5, or 10 mg/kg/day). Flutamide produced significant decreases in weights of the seminal vesicles and the levator ani plus bulbocavernosus muscles (> or =0.6 mg/kg/day) and ventral prostate (> or =2.5 mg/kg/day), and an increase in serum LH levels (> or =2.5 mg/kg/day), but no changes in serum T levels. When age-matched intact male rats were treated with 10-mg/kg/day flutamide, a significant increase in serum T levels was observed concomitant with a tendency of increased LH. The organ weights were also decreased; however, the changes were less than those in the castrated, T-implanted rats. Immature intact male rats (10 rats/dose) were treated for 20 days with flutamide (0, 0.15, 0.6, 2.5, or 10 mg/kg/day). Flutamide produced significant decreases in weights of the seminal vesicles, ventral prostate, and levator ani plus bulbocavernosus muscles at 2.5 and 10 mg/kg/day. Serum LH levels, but not T levels, were increased at 10 mg/kg/day. Statistical significance of some of these changes was not observed in the 6 animals/dose examined. Our findings support that the Hershberger assay, in the current conditions, is the most sensitive among the assays examined and a useful short-term screening method for the detection of antiandrogenic compounds.

Androgen Antagonists↗

PubMed2000

Atherosclerotic aneurysm of the intrathoracic segment of the subclavian artery: a case report.

True aneurysms of the intrathoracic segment of the subclavian artery are extremely rare. Atherosclerosis is the most common etiology. The surgical approach and timing of repair remain controversial. We successfully treated a patient with a large proximal subclavian artery aneurysm which was secondary to atherosclerosis. The patient was asymptomatic for 30 years as the aneurysm enlarged. Three-dimensional computed tomography provided the most useful information regarding anatomy of the cervical vasculature. The patient underwent closure of the inlet port of the aneurysm and repair using a 6-mm Dacron bypass graft (Gelsoft , VASCTEK, Scotland) via a minimally invasive surgical approach.

Aged↗

PubMed2000

Ascending aortic infected pseudoaneurysm with aortic insufficiency following cardiac operation for infective endocarditis.

An infected pseudoaneurysm of the ascending aorta after heart surgery is a fatal disease due to its rapid progress, worsening of the systemic condition and a tendency of recurrence. We report a 53-year-old man with this condition who presented with fever and an aortic regurgitation due to compression of the ascending aortic root 2 months after mitral valve replacement for infective endocarditis. We performed an aneurysmectomy with a cardiopulmonary bypass using groin cannulation and moderate systemic hypothermia. A pseudoaneurysm developed 5 mm proximally of the previous aortotomy. There was no dehiscence of the former aortic suture line. After debridement of the ascending aorta involving the previous aortotomy and pseudoaneurysm, we elected to directly close the aortic defect using Teflon felt strips to avoid a prosthetic graft. The aortic valve had no infective endocarditis and other abnormality. Postoperatively, there was no aortic regurgitation, and the cause of the previous aortic regurgitation was believed to be due to a compression of the aortic root from outside. The postoperative course has been good.

Aneurysm, False↗

PubMed1999

Cardiac-specific overexpression of Galphaq alters excitation-contraction coupling in isolated cardiac myocytes.

Transgenic mice with cardiac-specific overexpression of G alpha q exhibit a biochemical and physiological phenotype of load-independent cardiac hypertrophy with contractile dysfunction. To elucidate the cellular basis for altered contractility, we measured cellular contraction, Ca(2+)transients, and l -type Ca(2+)channel currents (I(Ca)) in left ventricular (LV) myocytes isolated from non transgenic (NT) controls or G alpha q hearts. Although baseline contractile function (% shortening) and the amplitude of Ca(2+)transients in G alpha q myocytes were similar to NT myocytes, the rates of cellular shortening and relengthening and the duration of Ca(2+)transients were prolonged in G alpha q myocytes. Myocytes from G alpha q hearts had larger cell capacitance but no change in I(Ca)density, voltage-dependence of activation and inactivation. The responses of I(Ca)to dihydropyridine drugs and a membrane permeable cAMP analog, 8-(4-chlorophenylthio) cAMP, were not altered; however, the time course of I(Ca)inactivation was significantly slower in G alpha q myocytes compared to NT myocytes. The kinetic difference in inactivation was abolished when Ba(2+)was used as the charge carrier or when the sarcoplasmic reticulum (SR) Ca(2+)was depleted by ryanodine, suggesting that Ca(2+)-dependent inactivation is reduced in G alpha q myocytes due to altered SR Ca(2+)release. Consistent with this hypothesis, the function of SR as assessed by the maximal Ca(2+)uptake rates and the apparent affinity of SR Ca(2+)-ATPase for Ca(2+)was reduced in ventricles of G alpha q heart. These results suggest that the reduced SR function contributes to the depressed contractility associated with this form of cardiac hypertrophy.

Animals↗

PubMed1999

Surgical treatment of abdominal aortic aneurysms located close to the visceral arteries: report of three cases.

The standard surgical treatment for abdominal aortic aneurysms (AAA) is in situ replacement of the infrarenal aorta, which is associated with a low mortality rate. On the other hand, thoracoabdominal aortic aneurysms (TAA) remain a formidable challenge and the complications that can occur may be severe including neurologic dysfunction and renal failure. We report herein three cases of patients with AAA located very close to the visceral arteries, for which in situ replacement of the infrarenal aorta was not feasible due to severe inflammation and adhesion. Therefore, aortic stump closure and in situ bypass grafting was performed to avoid reconstruction of the visceral arteries. No major complications or operation-related deaths occurred. Thus, while in situ replacement is usually recommended over bypass grafting for patients whose aneurysms are located very close to the visceral arteries, aortic stump closure and in situ bypass grafting should be considered as a more effective surgical option.

Aged↗

PubMed1999

Familial hyperparathyroidism: report of a case.

We report herein a case of familial primary hyperparathyroidism diagnosed in a 23-year-old woman who presented with hypercalcemia and urolithiasis. The parathyroid gland was removed, and pathological examination revealed chief cell adenoma. The proband's younger sister had undergone surgery for parathyroid adenoma at the age of 19, and her aunt had a history of urolithiasis with a high level of serum parathyroid hormone. We have not yet found evidence of any other endocrine disorders suggesting multiple endocrine neoplasia (MEN) type 1 in this pedigree.

Adenoma↗

PubMed1998

Cardiac-specific overexpression of mouse cardiac calsequestrin is associated with depressed cardiovascular function and hypertrophy in transgenic mice.

Calsequestrin is a high capacity Ca2+-binding protein in the sarcoplasmic reticulum (SR) lumen. To elucidate the functional role of calsequestrin in vivo, transgenic mice were generated that overexpressed mouse cardiac calsequestrin in the heart. Overexpression (20-fold) of calsequestrin was associated with cardiac hypertrophy and induction of a fetal gene expression program. Isolated transgenic cardiomyocytes exhibited diminished shortening fraction (46%), shortening rate (60%), and relengthening rate (60%). The Ca2+ transient amplitude was also depressed (45%), although the SR Ca2+ storage capacity was augmented, as suggested by caffeine application studies. These alterations were associated with a decrease in L-type Ca2+ current density and prolongation of this channel's inactivation kinetics without changes in Na+-Ca2+ exchanger current density. Furthermore, there were increases in protein levels of SR Ca2+-ATPase, phospholamban, and calreticulin and decreases in FKBP12, without alterations in ryanodine receptor, junctin, and triadin levels in transgenic hearts. Left ventricular function analysis in Langendorff perfused hearts and closed-chest anesthetized mice also indicated depressed rates of contraction and relaxation of transgenic hearts. These findings suggest that calsequestrin overexpression is associated with increases in SR Ca2+ capacity, but decreases in Ca2+-induced SR Ca2+ release, leading to depressed contractility in the mammalian heart.

Amino Acid Sequence↗