Fontan''s procedure in two stages

Abdominal (truncal) fat distribution reflected by an elevated waist to hip ratio (WHR) predicts metabolic abnormalities such as diabetes and dyslipidemia as well as hypertension and stroke, all of which are associated with obesity. The pathogenesis is not known, although elevated splanchnic serum free fatty acid levels and reduced hepatic insulin clearance have been implicated. WHR and body fat (BF) by 40K-counting and 3H2O were measured before liver biopsy during antiobesity surgery in 68 severely obese women (body mass index [BMI], 48.9 +/- 1.1 SEM) and 15 men (BMI, 49.0 +/- 3.1) without histories of liver disease, diabetes, or hepatotoxic exposure. Biopsies were graded for fat content semiquantitatively (0 to 4+) by the hepatologist who was blinded to the patients' clinical characteristics. All 15 men had fatty infiltration (score, 2.5 +/- 0.3 v 1.4 +/- 0.1 in women; P < .001). The correlation between WHR and liver fat was .44 (P < .0005), while BF (-.16), weight (.15), or BMI (.04) did not correlate significantly with steatosis (all NS). As expected, percentage body fat (BF%) was greater in women than in men (40.3 +/- 0.8 kg v 33.9 +/- 2.0, P < .007), and accordingly liver fat was inversely related to BF% (r = -.32, P < .002). Steatosis was significantly greater in 14 men (2.5 +/- 0.3) than in 20 women (1.7 +/- 0.3, P < .04) matched for BF%. In multiple regression analysis R2 = .49, P < .0001), WHR and sex accounted for the variance in liver fat content without any further contribution from weight, BMI, BF, or BF%.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regulation of phosphatidate phosphatase activity from the yeast Saccharomyces cerevisiae by sphingoid bases

The regulation of Saccharomyces cerevisiae membrane-associated phosphatidate phosphatase (3-sn-phosphatidate phosphohydrolase, EC 3.1.3.4) activity by sphingoid bases was examined using Triton X-100/lipid-mixed micelles. Sphingosine, phytosphingosine, and sphinganine inhibited purified preparations of the 104- and 45-kDa forms of phosphatidate phosphatase in a dose-dependent manner. The structural requirements for the sphingoid base inhibition of phosphatidate phosphatase activity were a free amino group and a long chain hydrocarbon. A detailed kinetic analysis was performed to determine the mechanism of phosphatidate phosphatase inhibition by sphingoid bases. The phosphatidate phosphatase dependence on phosphatidate was cooperative (Hill numbers of approximately 2) in the absence and presence of sphingoid bases. Sphingosine, phytosphingosine, and sphinganine were parabolic competitive inhibitors of phosphatidate phosphatase activity. This indicated that more than one inhibitor molecule contributed to the exclusion of phosphatidate from the enzyme. The aKi values (inhibitor constants) for sphingosine, phytosphingosine, and sphinganine were 1.5, 0.4, and 0.2 mol %, respectively, and the Km value for phosphatidate was 2.2 mol %. The cellular concentrations of free phytosphingosine and sphinganine were 0.16 and 0.53 mol %, respectively, relative to the total phospholipids in S. cerevisiae. The cellular concentrations of phytosphingosine and sphinganine were in the range of the aKi values for these sphingoid bases. These results raised the suggestion that phosphatidate phosphatase activity may be regulated in vivo by sphingoid bases.     

Refractory period prolongation by biphasic defibrillator waveformsis associated with enhanced sodium current in a computer model of theventricular action potential

Mechanisms through which biphasic waveforms lower defibrillation threshold are unknown. Previous work showed that low-intensity biphasic shocks (BS2), delivered during the refractory period of a control action potential (S1), produced significantly longer responses than monophasic shocks (MS2). To test the hypothesis that longer responses are due to hyperpolarization-induced excitation channel recovery during the first portion of the biphasic waveform, the authors used the Beeler-Reuter ventricular action potential computer model with the Drouhard-Roberge (BRDR) modification to study refractory period stimulation with MS2 (10 msec) and symmetrical BS2 (10 msec each pulse). At 1.5 times diastolic threshold, BS2 prolonged action potential duration when delivered 50 msec into the S1 refractory period, and produced a maximum BS2 versus MS2 response duration difference of 62 msec. Longer BS2 responses corresponded to enhanced BS2-induced sodium current compared to MS2. Maximum BS2 vs MS2 sodium current difference was 400 uA/cm². These results show that, in a computer model of the ventricular action potential, hyperpolarization by the first phase of a biphasic waveform enhances S2 sodium current and prolongs duration of refractory-period responses. This effectively shortens the cellular refractory period. Prolonged refractory period responses, produced by biphasic defibrillator waveforms, may underlie enhanced defibrillating efficacy at low shock intensities     

Basal nitric oxide synthesis in essential hypertension

BACKGROUND: There is indirect evidence that nitric oxide (NO) synthesis in vascular endothelium of patients with hypertension is altered. The aim of this study was to estimate more directly NO production in patients with untreated essential hypertension by measurement of synthesis of inorganic nitrate, which is the end product of NO oxidation in humans. Two separate studies were undertaken in patients with hypertension and appropriate healthy controls. METHODS: In the first study, ten patients and 13 controls were given a diet containing 82 mumoles nitrate per day for 2 days, with urinary and plasma nitrate measurement and 24 h ambulatory blood pressure monitoring on the 2nd day. In the second study, 11 patients and 11 controls were studied in the postabsorptive state; a bolus of 200 mg L[15N]2 arginine was administered intravenously over 10 min. 24 h ambulatory blood pressure monitoring was done and complete urine collections were made for the next 36 h. FINDINGS: In the first study, 24 h urinary nitrate excretion was lower in the hypertensive patients than in the control group (mean 450 [SEM 37] vs 760 mumoles [77] per 24 h; p < 0.001). There was an inverse correlation between average mean daytime ambulatory blood pressure and nitrate excretion (p = 0.007; r2 = -0.73). In the second study, mean 36 h urinary 15N nitrate excretion was significantly lower in the hypertensive than in the control group (1313 [50] vs 2133 [142] pmoles; p < 0.001). There was an inverse correlation also between average mean daytime ambulatory blood pressure and 24 h urinary 15N nitrate excretion expressed per mmole of creatinine (p = 0.002, r2 = -0.59). In addition, total urinary 15N nitrate excretion in the hypertensive group was significantly higher in women than in men (285 [16] vs 198 [14] micrograms 15N nitrate per kg; p = 0.026). INTERPRETATION: These data suggest that whole-body NO production in patients with essential hypertension is diminished under basal conditions. The origin of the NO we measured is not known, and we cannot tell whether the impaired synthesis is primary or secondary to a rise in blood pressure.     

Modelling internal migration in Kenya: an econometric analysis with limited data

"In this paper the determinants of internal migration in Kenya are analyzed on the basis of a human capital model. Explanatory variables included in the specification are both economic (wage rates and employment rates) and noneconomic (for example, population density and educational attainment). Also incorporated are variables which reflect intervening opportunities.... The econometric results show that destination variables are important determinants of internal migration, as is distance between the districts. Further, the variables for the intervening opportunities add significantly to the explanatory power of the model."     

A study of the effects of process variables on the properties of PZT films produced by a single-layer sol-gel technique

Thin films of PbZr_0.53 Ti_0.47O₃ have been prepared from diol-based sols. Films up to 1 μ thick could be produced by applying a single coating on to platinized silicon substrates. A number of processing variables ranging from sol composition through to firing conditions have been examined, and their effects on film microstructure and electrical properties evaluated. Control of the lead stoichiometry was found to be of critical importance in determining dielectric and ferroelectric parameters. Values of remanent polarization and coercive field of 22–27 μC cm ⁻² and 40–45 kV cm ⁻¹, respectively, could be obtained by compensating for PbO lost by volatilization during firing; corresponding relative permittivity values were 800–1000.     

High throughput nanofabrication of silicon nanowire and carbon nanotube tips on AFM probes by stencil-deposited catalysts

A new and versatile technique for the wafer scale nanofabrication of silicon nanowire (SiNW) and multiwalled carbon nanotube (MWNT) tips on atomic force microscope (AFM) probes is presented. Catalyst material for the SiNW and MWNT growth was deposited on prefabricated AFM probes using aligned wafer scale nanostencil lithography. Individual vertical SiNWs were grown epitaxially by a catalytic vapor-liquid-solid (VLS) process and MWNTs were grown by a plasma-enhanced chemical vapor (PECVD) process on the AFM probes. The AFM probes were tested for imaging micrometers-deep trenches, where they demonstrated a significantly better performance than commercial high aspect ratio tips. Our method demonstrates a reliable and cost-efficient route toward wafer scale manufacturing of SiNW and MWNT AFM probes.     

MARTENSITIC AND R PHASE TRANSFOR MATIONS IN NiTiand NiTiHf

１　ＩＮＴＯＤＵＣＴＩＯＮＳｈａｐｅｍｅｍｏｒｙａｌｌｏｙｓ（ＳＭＡｓ）ａｒｅｅｘｃｅｌｌｅｎｔｃａｎｄｉｄａｔｅｓｆｏｒｃｏｎｔｒｏｌｓｙｓｔｅｍｓａｎｄａｒｅｃｏｍｍｏｎｌｙｒｅｆｅｒｒｅｄｔｏａｓ“ｓｍａｒｔ”ｍａｔｅｒｉａｌｓｄｕｅｔｏｔｈｅｉｒａｂｉｌｉｔｙｔｏｃｈａｎｇｅｓｈａｐｅｗｉｔｈｔｅｍｐｅｒａｔｕｒｅ．Ｔｈｅｓｅａｌｌｏｙｓｃａｎａｌｓｏｇｅｎｅｒａｔｅｓｉｇｎｉｆｉｃａｎｔａｍｏｕｎｔｓｏｆｓｔｒａｉｎ（ａｎｄｓｔｒｅｓｓ）ａｎｄａｒｅｉｄｅａｌｆｏｒｕｓｅｉｎａｃｔ…