Overactivated transport in the localized phase of the superconductor-insulator transition.

Beyond a critical disorder, two-dimensional (2D) superconductors become insulating. In this Superconductor-Insulator Transition (SIT), the nature of the insulator is still controversial. Here, we present an extensive experimental study on insulating NbxSi1-x close to the SIT, as well as corresponding numerical simulations of the electrical conductivity. At low temperatures, we show that electronic transport is activated and dominated by charging energies. The sample thickness variation results in a large spread of activation temperatures, fine-tuned via disorder. We show numerically and experimentally that this originates from the localization length varying exponentially with thickness. At the lowest temperatures, there is an increase in activation energy related to the temperature at which this overactivated regime is observed. This relation, observed in many 2D systems shows that conduction is dominated by single charges that have to overcome the gap when entering superconducting grains.

Dissipative phases across the superconductor-to-insulator transition.

Competing phenomena in low dimensional systems can generate exotic electronic phases, either through symmetry breaking or a non-trivial topology. In two-dimensional (2D) systems, the interplay between superfluidity, disorder and repulsive interactions is especially fruitful in this respect although both the exact nature of the phases and the microscopic processes at play are still open questions. In particular, in 2D, once superconductivity is destroyed by disorder, an insulating ground state is expected to emerge, as a result of a direct superconductor-to-insulator quantum phase transition. In such systems, no metallic state is theoretically expected to survive to the slightest disorder. Here we map out the phase diagram of amorphous NbSi thin films as functions of disorder and film thickness, with two metallic phases in between the superconducting and insulating ones. These two dissipative states, defined by a resistance which extrapolates to a finite value in the zero temperature limit, each bear a specific dependence on disorder. We argue that they originate from an inhomogeneous destruction of superconductivity, even if the system is morphologically homogeneous. Our results suggest that superconducting fluctuations can favor metallic states that would not otherwise exist.

Anaesthetics as cardioprotectants: translatability and mechanism.

The pharmacological conditioning of the heart with anaesthetics, such as volatile anaesthetics or opioids, is a phenomenon whereby a transient exposure to an anaesthetic agent protects the heart from the harmful consequences of myocardial ischaemia and reperfusion injury. The cellular and molecular mechanisms of anaesthetic conditioning appear largely to mimic those of ischaemic pre- and post-conditioning. Progress has been made on the understanding of the underlying mechanisms although the order of events and the specific targets of anaesthetics that trigger protection are not always clear. In the laboratory, the protection afforded by certain anaesthetics against cardiac ischaemia and reperfusion injury is powerful and reproducible but this has not necessarily translated into similarly robust clinical benefits. Indeed, clinical studies and meta-analyses delivered variable results when comparing in the laboratory setting protective and non-protective anaesthetics. Reasons for this include underlying conditions such as age, obesity and diabetes. Animal models for disease or ageing, human cardiomyocytes derived from stem cells of patients and further clinical studies are employed to better understand the underlying causes that prevent a more robust protection in patients.

Point-contact transport properties of strongly correlated electrons on liquid helium.

We present transport measurements of a nondegenerate two-dimensional electron system on the surface of liquid helium at a point constriction. The constriction is formed in a microchannel by a split gate beneath the helium surface. The electrostatic energy of the electron system, which depends in part on the electron density, determines the split-gate voltage threshold of current flow through the constriction. Steplike increases in conductance are observed as the confinement strength is reduced. As the Coulomb interaction between electrons is strong, we attribute this effect to the increase in the number of electrons that can pass simultaneously through the constriction. Close to the threshold, single-electron transport is observed.

[Clinical evaluation of landiolol hydrochloride, an ultra short-acting beta-blocker].

Postoperative supraventricular tachyarrhythmia (SVT) remains the most common complication of cardiovascular surgery. Current guidelines recommend treatment with beta-blockers in prevention and management of postoperative atrial fibrillation after cardiac surgery. Landiolol hydrochloride is a newly developed ultra short-acting selective beta1-blocker with a half-life of approximately 4 minutes. We investigated its effects on the cardiac function as well as on postoperative SVT. Landiolol hydrochloride had a sufficient therapeutic effect without apparent side effect. After its administration cardiac index decreased, whereas stroke volume increased. Pulmonary artery wedge pressure, pulmonary artery pressure, and central venous pressure remained unchanged. Its main effect proved to be decrease in heart rate.

[Off-pump versus conventional coronary artery bypass grafting in octogenarians].

Coronary artery bypass grafting (CABG) in elderly patients is becoming increasingly common. From January 1996 to February 2002, 836 patients underwent CABG in our hospital, of whom 33 patients (3.9%) were aged 80 years or older. We evaluated the clinical and short-term results of 7 cases of off-pump CABG (OPCAB) and 26 cases of conventional CABG (C-CABG). Mean patient age and preoperative risk factors were similar in both groups. The OPCAB group had significantly decreased operation time (218 versus 281 minutes, p<0.05), and the number of distal anastomoses was significantly fewer in the OPCAB group than in the C-CABG group (1.9 versus 3.8, p<0.05). The frequency of complete revascularization in C-CABG was significantly higher than that of the OPCAB group (84.6% versus 42.9%, p<0.05), and there were no differences in the incidence of major postoperative complications between the groups. There was no hospital death in either group. Cumulative cardiac event free rates were 75% at 1 year and 75% at 3 years in the OPCAB group and 100% at 1 year and 84.6% at 3 years in the C-CABG group (p<0.05). In conclusion, CABG is safe and effective for myocardial revascularization in octogenarians. Except for high-risk cases, complete revascularization with OPCAB or C-CABG should be performed, because favorable outcomes can be expected even in the elderly patients.

Reconstruction of the left ventricle in a patient with cardiac hemangioma at the apex.

Cardiac hemangiomas in the left ventricle are extremely rare. A 34-year-old woman, without symptoms, with a diagnosis of cardiac tumor at the apex of the left ventricle was referred to us. The tumor was surgically resected, and the diagnosis was hemangioma. The Jatene technique, originally introduced for left ventricular aneurysmectomy was excellent for repair after resection of a cardiac tumor at the apex.

[Case report of a malfunctioning SJM 19 A aortic valve prosthesis requiring reoperation].

The patient was a 56-year-old female diagnosed with poor lung function who had undergone an aortic valve replacement 10 years ago, receiving an SJM 19 A prosthetic valve. She suffered from dyspnea and chest pain with postural change. Her anticoagulation level was maintained therapeutic. A cinefluoroscopy showed that one of the leaflets in the prosthetic valve was not moving. The aortic peak pressure gradient was calculated to be 68 mmHg using Doppler echocardiography. The patient's clinical condition improved after thrombolytic therapy with urokinase, but a complete normalization of her prosthetic discs was not obtained, so the patient was treated surgically. After an aortotomy, a pannus formation covering the entire SJM 19 A valve was observed. The aortic annulus was estimated to be 16 mm in diameter after the excision of the SJM 19 A valve and required before a larger prosthesis could be inserted. A SJM 19 HP valve was then anchored to the enlarged annulus. Her postoperative course was uneventful. We report a case requiring reoperation after a small aortic mechanical valve prosthesis implanted 10 years previously was damaged by thrombosis and pannus. Pannus formation on small aortic prosthesis easily caused hemodynamic obstructions and mechanical failure. Intensive evaluation with Doppler echocardiography and cinefluoroscopy is required for such patients.

Use of arterial grafts for coronary revascularization. Experience of 2987 anastomoses.

OBJECTIVES: The aim of this study was to evaluate the performance and the quality of arterial grafts for coronary artery bypass grafting at The Heart Institute of Japan, Tokyo Women's Medical University. PATIENTS AND METHODS: From January 1970 to March 1998, 2987 arterial grafts, including left and right internal thoracic arteries, gastroepiploic artery, radial artery and inferior epigastric artery, were used in 1673 patients. In the same period, 1225 saphenous vein grafts were used. Early graft patency was angiographically determined. Also, histological evaluation of operative specimens and preoperative angiographic evaluation of arterial grafts were performed. RESULTS: The total number of hospital deaths was 38 (2.3%). Of 4212 grafts, 3919 grafts (93%) were evaluated angiographically and 3714 of 3919 grafts were patent (94.8%). The patency rate of internal thoracic artery was better than that of gastroepiploic artery (p < 0.0001), radial artery (p = 0.0005) and saphenous vein grafts (p < 0.0001). However, the patency rate of gastroepiploic artery was better than that of saphenous vein grafts (p = 0.04), while no significant difference was detected between gastroepiploic artery and rdial artery. Only one internal thoracic artery specimen obtained at surgery showed atherosclerotic change, but all gastroepiploic artery specimens had moderate to severe atherosclerotic changes with CD68-positive cell infiltration. Only one patient's left internal thoracic artery out of 200 was not angiographically useable as a conduit, while multiple stenotic lesions in gastroepiploic artery were observed. CONCLUSIONS: In the graft selection for CABG, the primary choice is internal thoracic artery and the secondary choice is right internal thoracic artery, from the standpoint of histological and angiographic evaluation, gastroepiploic artery and/or radial artery, depending on the target anastomotic site, degree of stenosis, and in situ or free use is the third choice.

Evidence for association between the class I subset of the insulin gene minisatellite (IDDM2 locus) and IDDM in the Japanese population.

Although the shortest (class I) minisatellite (i.e., variable number of tandem repeats [VNTR]) alleles in the 5' region of the insulin gene are positively associated with IDDM in Caucasians, the majority of Japanese are homozygous for class I alleles. Here, we determined the exact length, in number of repeat units (RUs), of class I alleles in Japanese subjects. The distribution of class I alleles in Japanese was trimodal, with peaks located at 32/33, 41, and 44 RUs. The shortest component (i.e., 1S [25-38 RUs]) alleles were significantly increased in the IDDM group compared with the control group (54 vs. 46%; P = 0.040). The 1S/1S genotype was significantly increased in the IDDM patients (34 vs. 20%; P = 0.005; relative risk 2.1). Furthermore, the transmission disequilibrium test of Japanese families with 1S/1M or 1S/1L heterozygous parents confirmed the association of 1S alleles; 17 alleles of 1S and 6 alleles of 1M (39-41 RUs) or 1L (42-44 RUs) were transmitted to affected offspring (P = 0.022). In addition, we found tight linkage of 1S with allele 9 of the tyrosine hydroxylase gene microsatellite and allele (-) of the IGF-II gene Apa I polymorphism, but neither 9 nor (-) alleles were significantly associated with IDDM. The present study suggests that a class I subset may have a role in IDDM susceptibility in Japan. It was revealed that the difference between 1S alleles and 1M or 1L alleles is almost consistently characterized by a sequence variation generated by deletion of two copies of an ACAGGGGTCC CGGGG repeat element, implying that sequence variation of class I alleles may influence disease susceptibility.

Significant left ventricular unloading with transaortic catheter venting during venoarterial bypass.

Insufficient unloading of the left ventricle with blood stagnation is a main cause of unsuccessful left ventricular (LV) recovery during percutaneous cardiopulmonary support (PCPS). The purpose of this investigation was to evaluate the effectiveness of transaortic catheter venting (TACV) for LV unloading. Six adult mongrel dogs (mean weight 16.3 kg, range 14-20 kg) underwent venoarterial bypass (VAB) with TACV. Bypass flow ranged from 0.8-1.2 L/min, and TACV flow ranged from 160-240 ml/min. In addition to monitoring the standard hemodynamic parameters, the slope of the LV end-systolic pressure-volume relation (Emax) during transient occlusion of the inferior vena cava, the slope of the LV end-systolic pressure-stroke-volume relation (Ea), the stroke work (SW), the LV pressure-volume area (PVA), and the slope of the SW end-diastolic volume relation, the preload recruitable stroke work (PRSW) were assessed by means of a microtip manometer and a conductance catheter. The LV contractility (Emax) and aortic elastance (Ea) were equivalent in the 2 groups with or without TACV (7.7 +/- 1.1 versus 8.4 +/- 1.5 mm Hg/ml and 8.2 +/- 1.4 versus 7.6 +/- 1.3 mm Hg/ml). Comparing the measurements for the baseline to those for VAB with TACV, the SW was significantly reduced, and the PVA/SW was increased by TACV (1,685 +/- 309 versus 867 +/- 188 x 10(-4) J, p < 0.05 and 1.32 +/- 0.03 versus 1.58 +/- 0.11, p < 0.05, respectively). Furthermore, the PRSW was gradually decreased from the baseline value to the value resulting from VAB with TACV (75 +/- 8 versus 44 +/- 3 x 10(-4) J/ml, p < 0.01). In comparison, the percent reduction of SW between VAB and VAB with TACV tended to be increased by TACV (23.2 +/- 7.2% versus 46.9 +/- 7.7%, p = 0.05). These results suggest that TACV might reduce LV work (SW and PRSW) and might increase the LV energetic charge. In conclusion, TACV would be an adjunctive technique to VAB or PCPS for patients with LV failure.

LDL apheresis reduces the susceptibility of LDL to in vitro oxidation in a diabetic patient with hemodialysis treatment.

OBJECTIVE: We studied whether LDL apheresis would alter the susceptibility of LDL to in vitro oxidative modification induced by copper ion in a diabetic patient undergoing hemodialysis treatment. RESEARCH DESIGN AND METHODS: Isolated LDL was dialyzed against phosphate-buffered saline and resuspended at a concentration of 0.3 mg cholesterol mass/ml buffer LDL oxidation was then initiated by addition of 1.66 mumol/l CuSO4, and the formation of conjugated dienes was continuously monitored spectrophotometrically at 234 nm. RESULTS: The duration of the lag phase of LDL obtained after LDL apheresis was markedly longer than that of LDL obtained before LDL apheresis. The propagation rate and the maximum conjugated diene formation of LDL oxidation were not changed after LDL apheresis. CONCLUSIONS: A LDL subfraction that was susceptible to oxidation was removed by LDL apheresis, resulting in reduction of susceptibility of LDL to in vitro oxidation remaining in plasma. LDL apheresis may be of clinical importance for preventing atherosclerotic disease in diabetic patients undergoing hemodialysis.

[A case of extra anatomical bypass grafting for coarctation of aorta associated with Turner's syndrome].

A 24-year-old woman with manifestations of Turner's syndrome was referred for detail examinations and treatment of right subclavian tumor on chest X-ray. She was short and obese (147 cm tall and weigh 65 kg). And she had hypertension at upper extremities (160/100 mmHg). Chest enhanced CT revealed right subclavian arterial aneurysm and coarctation of aorta. Aortography showed interrupted descending thoracic aorta with short atretic segment followed by distal descending aorta, aneurysmal collateral artery from right subclavian artery to abdominal aorta and other small collateral arteries. Left lateral thoracotomy was thought to have a high risk for bleeding in the short and obese patient with ample collateral arteries. Therefore, extra anatomical bypass grafting from ascending aorta to abdominal aorta was performed through median sternotomy and laparotomy. After operation recovery was uneventful without residual hypertension. In this report, we discuss about the operation of adult coarctation of aorta and usefulness of extraanatomical bypass grafting.

Clinical implications of renal cyst in primary aldosteronism.

The present study surveyed 69 patients with aldosteronoma to study the clinical implications of renal cysts demonstrated in computed tomography. Patients who had cysts (n = 16, 23.2%) were older and had a longer duration of hypertension and more severe hypokalemia than those without cysts (n = 53). Patients with cysts therefore had longer-term, more severe hypokalemia than those without cysts. Endogeneous creatinine clearance (Ccr), measured in 61 patients, was significantly lower in patients with cysts (58.4 +/- 7.1 ml/min, n = 16) than in those without cysts (77.3 +/- 7.1 ml/min, n = 45, P = 0.0039). This significant difference was observed even after adjusting for covariables (age, duration of hypertension, and serum potassium) between the two groups by analysis of covariance (ANCOVA). No significant difference was observed in gender, blood pressure, serum creatinine, plasma aldosterone, or PRA. Age, serum potassium levels, and systolic and diastolic blood pressure were the significant determinants in predicting Ccr in a backward stepwise multiple regression analysis (r = 0.505, n = 61, P = 0.0025). Cysts were graded into four classes on the basis of number and size. Cyst grading correlated negatively with Ccr at a Spearman rank correlation (rho = -0.33, n = 61, P = 0.0103). The incidence of chronic renal failure was significantly higher in patients with cysts (18.8%) than in patients without (0%) in a Fischer's exact probability test (P = 0.0107). Thus, both renal cysts and dysfunction arose and/or developed from common roots, i.e., the duration and severity of hypokalemia, in primary aldosteronism. In addition, we surveyed 27 patients with pheochromocytoma. Patients with renal cysts (n = 8) had a significantly longer duration of hypertension than those without cysts. No significant difference was observed in Ccr between patients with and those without cysts. Thus, a significant link between renal cysts and Ccr was a specific feature of primary aldosteronism, but not of pheochromocytoma. In summary, the renal cysts in primary aldosteronism should be recognized as a significant complication representing the extent of renal injury and dysfunction.

Metformin decreases blood pressure and obesity in OLETF rats via improvement of insulin resistance.

To determine whether improvement of insulin resistance decreases blood pressure as well as obesity, metformin (100 mg/kg/d) or vehicle was administered for 20 weeks to 12-week-old male Otsuka Long-Evans Tokushima Fatty (OLETF) rats (n = 10 each), a newly developed animal model of non-insulin-dependent diabetes mellitus (NIDDM) with mild obesity, hyperinsulinemia, and hypertriglyceridemia. Oral administration of metformin ameliorated glucose intolerance and attenuated the insulin response to glucose loading (2 g/kg, i.p.), as evidenced by a decrease in the area under the curve for glucose and insulin at 24 weeks by 19% and 37%, respectively. At 21 weeks, systolic blood pressure was significantly lower in the metformin group than in controls (130 +/- 1.9 vs. 143 +/- 2.7 mmHg, p < 0.01), despite no difference in body weight. Subsequently, blood pressure tended to be slightly but insignificantly lower in the metformin group, and body weight was significantly lower in the metformin group (532 +/- 9.8 vs. 587 +/- 10.3 g at 31 weeks, p < 0.01). Metformin treatment also lowered the level of serum triglycerides (9.4 +/- 0.6 vs. 13.2 +/- 0.5 mmol/l, p < 0.01) and the plasma norepinephrine concentration (4,222 +/- 373 vs. 7,548 +/- 1,058 pg/ml, p < 0.01). These results suggest that metformin-induced improvement of insulin resistance in obese rats with NIDDM may lower blood pressure, as well as decrease sympathetic activity and reduce body weight.

LH and testosterone modulate mercuric chloride-induced acute renal failure in male rats: the implication of stress-induced hypogonadism.

The significance of stress-induced hypogonadism remains unclear. Since plasma testosterone and LH have renotropic activity that is other than reproductive, we hypothesize that stress-induced hypogonadism is an adaptive response to protect the kidney. To examine this hypothesis, we prepared hypogonadal male rats with different levels of LH and testosterone through orchiectomy (castration), through chronic treatment with a slowly secreted form of gonadotropin-releasing hormone agonist (GnRHA; GnRHA pretreatment), or through both treatments concomitantly (castration with GnRHA pretreatment). Castrated rats had undetectable plasma testosterone and high plasma LH. GnRHA-pretreated rats had low plasma testosterone and normal plasma LH. Castrated rats with GnRHA pretreatment had undetectable plasma testosterone and normal plasma LH. We compared their sensitivity to HgCl2 nephrotoxicity and found that, when a low dose of HgCl2 (1.5 mg/kg body weight (BW)) was injected s.c. to induce acute renal failure, endogenous creatinine clearance (Ccr) decreased from 390 +/- 30 to 94 +/- 17 ml/h per kg BW in intact (unpretreated) rats. Such a decrease in Ccr was completely prevented in castrated rats (388 +/- 30 ml/h per kg BW) and partially prevented in GnRHA-pretreated rats (216 +/- 40 ml/h per kg BW). When a high dose of HgCl2 (2.25 mg/kg BW) was injected, half of the eight intact rats died but castrated rats and GnRHA-pretreated rats survived (P < 0.05). The elevated resistance in castrated rats was reduced when plasma LH was reduced with GnRHA pretreatment, but was restored by additional pretreatment with ovine LH (40 micrograms/day), as evidenced by changes in Ccr. Elevated resistance in castrated rats was also reduced by the administration of testosterone propionate. In conclusion, hypogonadism activated the preventive and defensive mechanisms that protect the kidney through both decreased plasma testosterone and high or even normal plasma LH.

Characteristics of aldosterone-producing adenoma responsive to upright posture.

A small subgroup of primary aldosteronism due to aldosteronoma, named aldosterone-producing renin-responsive adenoma (AP-RA), has been reported to masquerade as idiopathic hyperaldosteronism (IHA) because of the responsiveness of the plasma aldosterone concentration (PAC) to upright posture (UP). We found two patients with AP-RA in 19 patients with aldosteronoma who were examined by UP stimulation and were treated surgically. In 17 patients with typical aldosterone-producing adenoma (APA), PAC decreased or increased only slightly (less than 200% of the basal level); in contrast, it increased to over 300% of the basal level in two patients with AP-RA. The two groups were comparatively studied as to their hormonal levels, adrenal computed tomography (CT) scan and histological findings in order to clarify the characteristics of AP-RA. Basal PAC was within the normal range (11.1 and 13.0 ng/dl) in AP-RA but in APA it ranged from 14.8 to 58.1 ng/dl with a mean of 32.3 +/- 2.7 ng/dl. The diameters of the adenoma in AP-RA were apparently smaller (6 and 9 mm) than those in APA ranged from 10 to 25 mm with a mean of 15.5 +/- 1.1 mm. After a contrast medium was injected at CT scan, the density of the normal adrenal gland adjacent to the adenoma increased but that of the adenoma did not in APA, making a clear distinction between the adenoma and the gland. On the other hand, the density of the adenoma and gland increased to almost the same degree in AP-RA.(ABSTRACT TRUNCATED AT 250 WORDS)

[The experience of mitral valve repair for valve regurgitation].

Between November 1993 and March 1995, 10 patients underwent mitral valve repair. Six of them were performed with McGoon's procedure for prolapsed posterior leaflet. Two of them were performed chodal reconstruction with PTFE sutures for prolapsed anterior leaflet. A patient received McGoon's procedure of posterior leaflet and chodal reconstruction of anterior leaflet. A patient of ischemic mitral regurgitation underwent mitral annuloplasty. There were no operative and late deaths. The MR disappeared or improved to grade I in 9 patients. A patient with McGoon's procedure had hemolytic anemia and required reoperation.