bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of a Calcium Channel Agonist on Renin Release from Perfused Rat Kidneys
Authors: Dietz John R.
Published: November 2008

The effects of a calcium channel agonist, BAY K-8644, on renin release and renal function were examined in perfused rat kidneys. BAY K-8644 increased renal vascular resistance and reduced glomerular filtration rate, sodium excretion und urine flow in a dose-dependent manner. These actions were prevented by the calcium channel blocker nifedipine. BAY K-8644 had no significant effect on basal renin secretion and failed to prevent renin stimulation by low-perfusion pressure or isoproterenol. The inhibitory effect of high-perfusion pressure on renin secretion was attenuated by the calcium entry blocker verapamil but not by nifedipine. Thus, if voltage-dependent calcium channels in the juxtaglomerular cell membrane participate in the regulation of renin release then these channels appear to be very insensitive to blockade or augmentation by 1,4-dihydropyridines.
Whole Kidney Response to Reduced Arterial Pressure during Converting Enzyme Inhibition in the Rat
Authors: Göransson Ann , Isaksson Britta , Sjöquist Mats
Published: November 2008

Autoregulatory efficiency of renal blood flow (RBF) and glomerular filtration rate (GFR) was evaluated in male Sprague-Dawley rats during interference with the renin-angiotensin system by a converting enzyme inhibitor (CEI), captopril (3 mg · h-1 · kg-1 BW). RBF and GFR were approximately 25 (p < 0.01) and 20% (p < 0.02) higher, respectively, in rats infused with CEI than in control rats at spontaneous renal arterial pressure (RAP). A reduction of RAP to 100 mm Hg (within the autoregulatory range) resulted in effective autoregulation of GFR and RBF in control rats. In rats given CEI, however, the autoregulation of GFR was markedly impaired. GFR decreased by 35% (p < 0.001), while RBF remained relatively unchanged. This caused the filtration fraction to decrease from 0.33 ± 0.01 to 0.29 ± 0.01 (p < 0.001). RAP had a consistent effect on the urine flow rate, even though both GFR and RBF were well autoregulated in control rats. No significant decrease in electrolyte excretion was detected within the autoregulatory range in control rats, but during converting enzyme blockade this excretion decreased progressively as RAP was reduced, and the decrease correlated well to the reduction in GFR. In summary, these results suggest that the renin-angiotensin system plays an important intrarenal role in the autoregulation of GFR, probably through an efferent arteriolar mechanism. Furthermore, it is demonstrated that the contra-lateral kidney efficiently compensates in urinary electrolyte excretion for an acute unilateral reduction of RAP, both under control conditions when the perfusion pressure to the contra-lateral kidney increased and during blockade of the renin-angiotensin system when the increase in perfusion pressure was inhibited.
Functional and Histopathological Changes in Dog Kidneys after Administration of Cisplatin
Authors: Daugaard Gedske , Abildgaard Ulrik , Larsen Svend , Holstein-Rathlou Niels-Henrik , Amtorp Ole , Olesen H.P. , Leyssac P.P.
Published: November 2008

The nephrotoxic effect of cisplatin (5 mg/kg i.v.) was evaluated in 8 dogs 48–72 h after administration. The lithium clearance method was used for assessing the absolute and fractional reabsorption rates of sodium and water in proximal as well as in more distal segments of the total nephron population, before and during saline loading (infusion of 5 ml/kg of isotonic saline i.v.). Histological examinations of the kidney biopsies were used to evaluate the degree of renal tissue injury. During 48–72 h after administration of cisplatin blood urea nitrogen and plasma creatinine increased significantly from 3.9 ± 0.2 to 11.7 ± 1.4 mmol/l and 96 ± 3 to 178 ± 10 µmol/l, respectively. Mean values of renal blood flow, glomerular filtration rate, filtration fraction and lithium clearance in cisplatin-treated animals (143 ± 14 ml/min, 10.7 ± 1.1. ml/min, 0.14 ± 0.01 and 6.3 ± 0.6 ml/min, respectively) were significantly lower than in 6 control animals (212 ± 8 ml/min, 49.0 ± 2.0 ml/min, 0.36 ± 0.01 and 10.1 ± 1.3 ml/min, respectively). In contrast, urinary excretion rates of sodium, potassium and water were significantly higher, while fractional as well as absolute proximal and distal reabsorption rates were significantly lower in cisplatin-treated animals compared to controls. Saline loading caused an increase in the output of tubular fluid from the proximal tubules (lithium clearance) in the cisplatin-treated animals, while the fractional distal reabsorption rate of sodium decreased significantly. The histological changes are in agreement with the physiological data which point to the proximal tubules as the more severely damaged segment. In conclusion, the depressed renal function 48–72 h after administration of cisplatin can be attributed to impairment of proximal as well as distal tubular reabsorptive capacities associated with increased renal vascular resistance. The polyuria seems to be due to impaired reabsorption rates in the distal nephron segments, which will affect the concentration mechanism.
Decreased Lithium Clearance due to Distal Tubular Lithium Reabsorption in Sodium-Depleted Dogs
Authors: Boer W.H. , Joles J.A. , Koomans H.A. , Mees Dorhout
Published: November 2008

Lithium clearances were performed in conscious dogs on varying sodium intakes. Fractional lithium excretion (FE-Li) was 22.6 ± 2.2% in sodium-replete dogs (fractional sodium excretion, FE-Na > 0.4%, n=ll) but only 6.9 ± 2.3% in sodium-depleted dogs (FE-Na < 0.4%, n=25). In 4 markedly sodium-depleted dogs (FE-Na 0.03 ± 0.02%) the distally acting diuretic amiloride caused an 8-fold increase in FE-Li (from 1.5 ± 1.0 to 11.6 ± 2.0%). Our data suggest that tubular reabsorption of lithium in sodium-depleted dogs is not restricted to the proximal tubules but also occurs in the distal nephron. Therefore the lithium clearance cannot be used as an index of sodium and filtrate delivery from the proximal tubules in sodium-depleted dogs.
Marginal Effect of Changes in Acid-Base Status in vitro on Rheogenic H+ and HCO-3 Secretion in Turtle Urinary Bladder
Authors: Adrogué Horacio J. , Tasby Jerry , Ulate Guido
Published: November 2008

This study systematically evaluates the effect of changes in the acid-base composition of the incubation media on the electrogenic H+ and HCO-3 secretion (voltage clamp method and serosal ouabain) in the isolated turtle urinary bladder. Since the various cell types would change their acidity in a similar direction but to a variable degree, measured mean cell pH values (5, 5-dimethyl-2,3-oxazolidinedione method) were used for an overall assessment of the changes in the acid-base status of the acid-transporting cells. Although addition of exogenous CO2 (0.7–3%) increased H+ secretion (JH+) 2- to 4-fold from a CCVfree control period, a further increase in the percent of CO2 did not enhance JH+ demonstrating a permissive but not a stimulatory role of CO2. Cyclic AMP plus 3-isobutyl-l-methylxanthine-induced electrogenic HCO3 secretion (JHCO-3) remained unaltered at 10% CO2 from a 5% CO2 control period. Cell acidosis resulting from either alterations in the PCO2/HCO-3 levels or from NH4CI in the bathing solution did not enhance JH+; by contrast maximal levels of acidification were found at cell pH values of about 7.40 and comparable effects on JH+ were found with a variety of PCO2/HCO-3 combinations that led to a similar intracellular acidity.
Superiority of Tetraethylammonium to p-Aminohippurate as a Marker for Renal Plasma Flow during Furosemide Diuresis
Authors: Petersen Jørgen S. , Christensen Sten
Published: November 2008

The renal clearances (C) of p-aminohippurate (PAH) and tetraethylammonium (TEA) as markers for renal plasma flow (RPF) were compared in rats under different experimental conditions. Ctea and CpAH were of the same magnitude and varied synchronously during volume expansion and anesthesia. The renal extractions of the two substances were closely correlated and averaged 85.9% for PAH and 88.7% for TEA (p < 0.01). High doses of furosemide (120mg/kg as intravenous bolus) reversibly decreased the CPAH/CTEA ratio, suggesting that furosemide may compete for PAH secretion in the proximal tubule. A similar effect was observedv after administration of probenecid. The results indicate that TEA is a more reliable indicator of RPF than PAH in studies involving accumulation of endogenous or exogenous organic anions.
Changes in Lysosome Populations in the Rat Kidney Cortex Induced by Passive Heymann Glomerulonephritis
Authors: Haga Hans-Jacob , Andersen Knut-Jan , Iversen Bjarne M. , Ofstad Jarle , Dobrota Miloslav , Matre Roald
Published: November 2008

Acute passive Heymann glomerulonephritis in rats induced heavy proteinuria and highly increased urinary activity of N-acetyl-β-D-glucosaminidase, acid β-galactosidase and acid phosphatase. The cortical activity of these acid hydrolases was increased essentially in the large lysosomes as demonstrated by subfractionation of the lysosome-rich mitochondrial-lysosomal fraction, by rate zonal centrifugation. Banding density of small lysosomes shifted or reduced to slightly lower value (1.225 g/ml), which is between the banding densities of small ‘light’ (1.20 g/ml) and small ‘dense’ lysosomes (1.235 g/ml) in normal rat kidney cortex. Labelled protein reabsorbed in the proximal tubule is recovered in these populations of small lysosomes as well as in the large lysosomes or ‘protein droplets’. Glomerulonephritis also induced a new population of small ‘light’ lysosomes (density 1.185–1.195 g/ml) enriched in cathepsin D. The previously demonstrated morphological, biochemical, and physiological heterogeneity of renal lysosomes was confirmed and emphasized in the kidney cortex of glomerulonephritic rats. The main changes in the lysosomal populations appear to reflect the increased protein reabsorption as confirmed by the proteinuria.
Vasopressin Stimulates Urinary Kallikrein Excretion in the Isolated Erythrocyte-Perfused Rat Kidney
Authors: Stephens Gregory W. , Lieberthal Wilfred , Oza Narendra B. , Valeri Robert , Levinsky Norman G.
Published: November 2008

We have found that arginine vasopressin (AVP) (10 pg/ml) stimulates urinary kallikrein in the isolated erythrocyte perfused rat kidney. (In this model, perfusate flow rate approximates blood flow rates in vivo and morphology is normal.) Urinary kallikrein excretion rose from 6.9 ± 0.8 to 14.9 ± 2.4 ng/min 20 min after the addition of AVP to the perfusate, and then fell towards baseline levels over the next 30 min. 1-Desamino-8-D-AVP (8 pg/ml) caused a comparable increase in kallikrein excretion. Prostaglandin synthesis inhibition with indomethacin did not alter the stimulatory effect of AVP on kallikrein excretion. Parathyroid hormone 1–34 (144 ng/ml) and calcitonin (102 ng/ml) also increased urinary kallikrein. Kallikrein excretion rose from 9.1 ± 2.0 to 24 ± 4.5 ng/min in response to calcitonin and from 8.3 ± 1.6 to 43.7 ± 3.4 ng/min following the addition of parathyroid hormone to the perfusate. Kallikrein was found to accumulate in the perfusate in a linear fashion. Based on the slope of the relationship between perfusate kallikrein and time, the rate of release of kallikrein into the perfusate was estimated to be 0.79 ng/min in control kidneys. The rate of release of kallikrein into the perfusate in kidneys treated with AVP was the same (0.74 ng/min). Thus while kallikrein is released into the perfusate, this process is not influenced by AVP. In conclusion, AVP stimulates release of kallikrein into the urine (but not the perfusate) independently of systemic events. The effect of AVP is not mediated by prostaglandins. This effect of AVP is mediated via stimulation of the V2 receptor and also occurs in response to two other hormones (calcitonin and parathyroid hormone) that are known to stimulate adenyl cyclase in the rat distal nephron.
Ischemia in the Isolated Erythrocyte-Perfused Rat Kidney
Authors: Lieberthal Wilfred , Rennke Helmut G. , Sandock Kristina M. , Valeri Robert , Levinsky Norman G.
Published: November 2008

We have examined the effects of 25 min of ischemia in the isolated erythrocyte-perfused rat kidney (IEPK). We have previously shown that, in this model, perfusate flow rate is close to blood flow rates in vivo and morphology is normal. The functional and morphological consequences of both warm ischemia (at 37°C) and ischemia induced during mild hypothermia (27°C) were compared. (1) Warm ischemia resulted in a 51% increase in renal vascular resistance (RVR) during the reflow period, while glomerular filtration rate (GFR) was reduced to 24% of control levels. (2) Kidneys subjected to warm ischemia showed marked morphological damage localized to the proximal tubule. There was dilatation of the proximal segments and widespread loss of the proximal brush border due both to shedding into the lumen and interiorization into the cell. In contrast to the proximal tubular damage, the cells of the medullary thick ascending limb segments were intact. However, the lumena of many of these segements were filled with cytoplasmic blebs and necrotic cell debris. There was also pronounced vascular congestion of the capillary plexus in the inner stripe of the outer medulla. (3) Hypothermia to 27°C resulted in almost complete protection against ischemic injury: RVR and GFR were not different from control values. Also, kidneys subjected to cold ischemia showed only isolated areas of mild brush border damage; no evidence of tubular obstruction or vascular congestion was present. (4) Thus, warm ischemia in the IEPK results in functional and morphological effects comparable to those found in vivo. Post-ischemic vasoconstriction as well as medullary congestion occur in the absence of systemic hormones and renal nerves. These consequences of ischemia are prevented by modest hypothermia.
Increased Ca++ or Mg++ Concentration Reduces Relative Tight-Junction Permeability to Na+ in the Cortical Thick Ascending Limb of Henle’s Loop of Rabbit Kidney
Authors: Di Stefano A. , Wittner M. , Gebler B. , Greger R.
Published: November 2008

We have tested whether increased Ca++ and Mg++ concentrations have an effect on transepithelial voltage (PDte) and transepithelial resistance (Rte) in isolated perfused cortical thick ascending limbs (cTAL) of rabbit kidney. The divalent cations added at 2.5, 5.0 and 10.0 mmol · 1-1 to the lumen or peritubular bath perfusate led to a concentration-dependent increase in Rte. The maximal response in Rte was observed between 5 and 10 mmol · 1-1. No significant change in active transepithelial potential difference (PDte) was observed. The increase in Rte still occurred when the transcellular current was reduced by Ba++ (3 mmol · 1-1) added to the lumen perfusate. This suggests that the increase in Rte caused by Ca++ and Mg++ is due to a modification of the paracellular shunt pathway. In the absence of active transport, i.e. when furosemide (5 · 10-5 mol · 1-1) was added to the lumen perfusate, Ca++ and Mg++ reduced the transepithelial diffusion potential generated by a NaCl gradient established across the epithelium, and thus produced a reduction of the relative permeability for Na+ over Cl- (PNa+/Pcr) of the paracellular shunt pathway. This indicates that divalent cations increase Rte by reducing the sodium permeability of the tight junctions. The observed Ca++ and Mg++ induced reduction of the sodium permeability of the paracellular pathway corresponds to a decrease in net Na+ reabsorption by 5–10%. Since it has been demonstrated that peptide hormones such as parathyrin (PTH) modulate divalent cation and NaCl reabsorptions, in a second series of experiments we tested the effects of PTH (2–20 USP · 1-1) and dbcAMP (10-3 mol · 1-1) on PDte and Rte of isolated perfused cTAL segments of rabbit nephron. Neither Rte nor PDte were affected by PTH or dbcAMP.
Principles of Cell Volume Regulation
Authors: Macknight Anthony D.C.
Published: November 2008

Cell volume is determined by the content of osmotically active solute (cell osmoles) and the osmolarity of the extracellular fluid. Cell osmoles consist of non-diffusible and diffusible solutes. A large fraction of the diffusible cation content balances negative charges on the non-diffusible solutes. The content of diffusible solutes is determined by the electrochemical gradients driving them across the plasma membrane and the availability and activity of transport pathways in the membrane. The classical view that the sodium pump offsets passive leaks must be modified to accomodate the contributions of a number of secondary active transport processes, as well as to allow for changes in cell nondiffusible osmoles and in their net negative charge. The behaviour of cells in anisosmotic media is often different from that predicted for a perfect osmometer. In many cases this is a consequence of changes in cell osmole content. However, caution is required in extrapolating from in vitro responses of isolated cells to large, acutely induced changes in medium osmolality to the responses of tissues in vivo to more subtle changes in extracellular osmolality.
Cell Volume Regulation in Liver
Authors: Graf J. , Haddad P. , Haeussinger D. , Lang F.
Published: November 2008

The maintenance of liver cell volume in isotonic extracellular fluid requires the continuous supply of energy: sodium is extruded in exchange for potassium by the sodium/potassium ATPase, conductive potassium efflux creates a cell-negative membrane potential, which expelles chloride through conductive pathways. Thus, the various organic substances accumulated within the cell are osmotically counterbalanced in large part by the large difference of chloride concentration across the cell membrane. Impairment of energy supply leads to dissipation of ion gradients, depolarization and cell swelling. However, even in the presence of ouabain the liver cell can extrude ions by furosemide-sensitive transport in intracellular vesicles and subsequent exocytosis. In isotonic extracellular fluid cell swelling may follow an increase in extracellular potassium concentration, which impairs potassium efflux and depolarizes the cell membrane leading to chloride accumulation. Replacement of extracellular chloride with impermeable anions leads to cell shrinkage. During excessive sodium-coupled entry of amino acids and subsequent stimulation of sodium/potassium-ATPase by increase in intracellular sodium activity, an increase in cell volume is blunted by activation of potassium channels, which maintain cell membrane potential and allow for loss of cellular potassium. Cell swelling induced by exposure of liver cells to hypotonic extracellular fluid is followed by regulatory volume decrease (RVD), cell shrinkage induced by reexposure to isotonic perfusate is followed by regulatory volume increase (RVI). Available evidence suggests that RVD is accomplished by activation of potassium channels, hyperpolarization and subsequent extrusion of chloride along with potassium, and that RVI depends on the activation of sodium hydrogen ion exchange with subsequent activation of sodium/potassium-ATPase leading to the respective accumulation of potassium and bicarbonate. In addition, exposure of liver to anisotonic perfusates alters glycogen degradation, glycolysis and probably urea formation, which are enhanced by exposure to hypertonic perfusates and depressed by hypotonic perfusates.
Mechanisms in Volume Regulation in Ehrlich Ascites Tumor Cells
Authors: Hoffmann Else K. , Lambert Ian Henry , Simonsen Lars Ole
Published: November 2008

The Ehrlich ascites tumor cell has been used as a model of an unspecialized mammalian cell, in an attempt to disclose the mechanisms involved in the regulation of cellular water and salt content. In hypotonic medium Ehrlich cells initially swell as nearly perfect osmometers, but subsequently recover their volume within about 10 min with an associated net loss of KC1, amino acids, taurine and cell water. The net loss of KCl takes place mainly via separate, conductive K+ and Cl- transport pathways, and the net loss of taurine through a passive leak pathway. Ca2+ and calmodulin appear to be involved in the activation of the K+ and Cl- channels, as well as the taurine leak pathway. In hypertonic medium Ehrlich cells initially shrink as osmometers, but subsequently recover their volume with an associated net uptake of KCl and water. In this case, the net uptake of KC1 is the result of the activation of an electroneutral, Na+- and Cl-dependent cotransport system with subsequent replacement of cellular Na+ by extracellular K+ via the Na+/K+ pump. In the present review we describe the ion and taurine transporting systems which have been identified in the plasma membrane of the Ehrlich ascites tumor cell. We have emphasized the selectivity of these transport pathways and their activation mechanisms. Finally, we propose a model for the activation of the conductive K+ and Cl- transport pathways in Ehrlich cells which includes Ca2+, leukotrienes, and inositol phosphate as intracellular second messengers.
Cell Volume Regulation in Lymphocytes
Authors: Deutsch Carol , Lee Sherwin C.
Published: November 2008

This article reviews what is known about the volume regulatory responses of lymphocytes. We present a discussion of recent data and hypotheses pertaining to the underlying mechanisms in regulatory volume increase (RVI) and regulatory volume decrease (RVD). New results from our laboratory are included to demonstrate that RVD is modulated by both temperature and pH, and that RVD occurs in proliferating as well as quiescent lymphocytes. This information is considered in the context of a model that includes the dynamics of membrane potential, K+ conductance, Cl- conductance, a proposed stretch-activated conductance, gating mechanisms, and equilibrium potentials, as RVD progresses. The physiological relevance of volume homeostasis in lymphocyte function, in particular, and in cell growth and proliferation, in general, is discussed.
Does Hemispheric Lateralization Influence Functional and Cardiovascular Outcomes After Stroke?
Authors: Fink John N. , Frampton Christopher M. , Lyden Patrick , Lees Kennedy R.
Published: November 2008

Background and Purpose—

The influence of stroke lateralization on functional and cardiovascular outcome after stroke is not well established. We evaluated the influence of hemispheric lateralization among patients enrolled in prospective acute stroke trials.

Methods—

We obtained data from the VISTA database for acute stroke trials which reported lateralization. Baseline data, cardiac adverse events, and 90-day outcomes were compared between right and left hemisphere stroke patients. A “hemisphere unbiased” subscore of the NIHSS which omitted items strongly associated with lateralized cognitive deficits was also compared for trials which reported individual NIHSS item scores. A multivariable analysis of outcome predictors was performed.

Results—

Three acute stroke trials met the prespecified inclusion criteria. 1644 placebo-treated patients with documented hemispheric lateralization were included in the analysis. Baseline NIHSS was higher for left hemisphere patients (mean 16.2, versus 12.8 right,
P
<0.001); there was no difference in the “hemisphere unbiased” NIHSS subscore (10.88 left, 11.08 right, n=687,
P
=0.49). There was no difference between hemispheres in 90-day modified Rankin Score (3.43 left, 3.29 right,
P
=0.13), mortality (22.1% left, 19.5% right,
P
=0.20), or cardiac adverse events (
P
=0.71). Hemispheric lateralization was not an independent predictor of outcome in the multivariable analysis after controlling for the hemispheric bias intrinsic to the NIHSS.

Conclusions—

There is no difference in functional outcome between patients with right or left hemisphere stroke. Use of the baseline NIHSS score to predict stroke outcome must take hemispheric lateralization into account. Stroke lateralization is not an important predictor of cardiac adverse events or 90-day mortality.
The Relationship Between Baseline Blood Pressure and Computed Tomography Findings in Acute Stroke
Authors: Sare Gillian M. , Bath Philip M.W. , Gray Laura J. , Moulin Thierry , Woimant France , England Timothy , Geeganage Chamila , Christensen Hanne , De Deyn Peter Paul , Leys Didier , O'Neill Desmond , Ringelstein E. Bernd
Published: November 2008

Background and Purpose—

High blood pressure (BP) is present in ≈80% of patients with acute ischemic stroke and is independently associated with poor outcome. There are few data examining the relationship between admission BP and acute CT findings.

Methods—

TAIST was a randomized controlled trial assessing 10 days of treatment with tinzaparin versus aspirin in 1489 patients with acute ischemic stroke (<48 hr) with admission BP of ≤220/120 mmHg. CT brain scans were performed before randomization and after 10 days. The relationships between baseline BP and adjudicated CT findings were assessed. Odds ratios per 10 mmHg change in BP were calculated.

Results—

Higher systolic BP (SBP) was associated with abnormal CT scans because of independent associations with chronic changes of leukoariosis (OR, 1.12; 95% CI, 1.05–1.17) and old infarction (OR, 1.12; 95% CI, 1.06–1.17) at baseline, and signs of visible infarction at day 10 (OR, 1.06; 95% CI, 1.00–1.13). A lower SBP was associated with signs of acute infarction (OR, 0.94; 95% CI, 0.89–0.99). Hemorrhagic transformation, dense middle cerebral artery sign, mass effect, and cerebral edema at day 10 were not independently associated with baseline BP.

Conclusion—

Although high baseline BP is independently associated with a poor outcome after stroke, this was not shown to be through an association with increased hemorrhagic transformation, cerebral edema, or mass effect; trial design may be suboptimal to detect this. Higher SBP is associated with visible infarction on day 10 scans. The influence of changing BP in acute stroke on CT findings is still to be ascertained.
The Biography of the Sample: Notes on the Hidden Contexts of Acousmatic Art
Authors: Milutis Joe
Published: November 2008

Acousmatic sound art production has as its goal a transformation of recognizable recorded sound samples into new relations, effectively hiding the origin of the raw material so as to focus on an experience of pure sound. The author defines the “live” as the “life” from which these samples are pulled, and considers the ways in which the biography of the sample troubles acousmatic art.
Effects of defects on helical two-stage gear system behaviour
Authors: Driss Y. , Walha L. , Fakhfakh T. , Haddar M.
Published: November 2008

This paper presents a three-dimensional model of a helical two-stage gear system. Excitation is induced by periodic variation of the mesh stiffness. This case describes the real working of the gearing. The mesh phasing variation is related to the number of teeth and also to the location of the gears. First, dynamic response is calculated using Newmark's step-by-step time integration method. The numerical results are presented in both the frequency and time domains. The dynamic behaviour of a defect-free gear system and a defective one are compared in both the time domain and frequency domain. Two types of defect are considered: a cracked tooth and misalignment. The cracked tooth produces an amplitude modulation with the mesh frequency and its first harmonics on the dynamic response. An amplitude modulation also occurs when a misalignment is introduced. The Wigner–Ville distribution method is used to show the dynamic behaviour in the joint time–frequency domain and to localise the cracked teeth.
Extended finite-element analysis of fractures in concrete
Authors: Fang X.-J. , Jin F. , Yang Q.-D.
Published: November 2008

In this paper an extended finite-element method (X-FEM) that is fully compatible with standard FE program has been formulated based on a virtual node technique. A cohesive crack model that is appropriate for concrete fracture under mixed-mode loading has been integrated into the formulation. The proposed method was implemented into a commercial FE program as a user subroutine, and two benchmark experimental tests were successfully modelled. The numerical robustness and predictive power of the proposed method have been demonstrated by its excellent predictions on arbitrary crack evolution and the associated load–displacement curves. Detailed numerical investigation of the crack wake shielding effects on the fracture loading curves showed that: (a) crack wake shear shielding has little effect on the peak fracture load and its immediate neighbouring softening phase; (b) the initial shear cohesive stiffness has a significant influence on the descending slope of the softening part of the load–CMSD curve; and (c) the shear cohesive strength appears to make the softening phase more stable and to delay the abrupt fracture point.
Revisiting Canada's Brain Drain: Evidence from the 2000 Cohort of Canadian University Graduates
Authors: Zarifa David , Walters David
Published: November 2008

Les études déjà réalisées sur l’exode des cerveaux au Canada ont établi l’importance des revenus accrus en tant que facteur qui motive des individus à aller s’établir aux États-Unis. Toutefois, ces travaux n’ont pas mesuré, de façon précise et pour les individus ayant récemment obtenu un diplôme d’études secondaires, cet écart de revenus, ni indiqué si l’écart varie selon les champs d’études le plus touchés. Dans cette recherche, réalisée à partir des plus récentes données de l’Enquête nationale auprès des diplômés, nous comparons les revenus obtenus à l’entrée sur le marché du travail de deux groupes d’étudiants ayant obtenu un diplôme universitaire en 2000: ceux qui sont restés au Canada et ceux qui sont allés travailler aux États-Unis. Nos résultats indiquent qu’un faible pourcentage de ces diplômés ont émigré aux États-Unis; toutefois, dans le cas de la grande majorité de ceux qui l’ont fait, les emplois obtenus sont concentrés dans quelques secteurs seulement de l’économie du savoir. Par ailleurs, les revenus annuels de tous individus ayant émigré aux États-Unis sont plus élevés que ceux qui ont choisi de rester au Canada. De plus, l’écart est plus marqué chez les individus ayant un diplôme de premier cycle en génie ou en informatique.
Lyapunov‐based model predictive control of nonlinear systems subject to time‐varying measurement delays
Authors: Liu Jinfeng , Muñoz de la Peña David , Christofides Panagiotis D. , Davis James F.
Published: November 2008

In this work, we focus on model predictive control of nonlinear systems subject to time‐varying measurement delays. The motivation for studying this control problem is provided by networked control problems and the presence of time‐varying delays in measurement sampling in chemical processes. We propose a Lyapunov‐based model predictive controller that is designed taking time‐varying measurement delays explicitly into account, both in the optimization problem formulation and in the controller implementation. The proposed predictive controller allows for an explicit characterization of the stability region and guarantees that the closed‐loop system in the presence of time‐varying measurement delays is ultimately bounded in a region that contains the origin if the maximum delay is smaller than a constant that depends on the parameters of the system and the Lyapunov‐based controller that is used to formulate the optimization problem. The application of the proposed Lyapunov‐based model predictive control method is illustrated using a nonlinear chemical process example with asynchronous, delayed measurements and its stability and performance properties are illustrated to be superior to the ones of two existing Lyapunov‐based model predictive controllers. Copyright © 2008 John Wiley & Sons, Ltd.
Risk variants for atrial fibrillation on chromosome 4q25 associate with ischemic stroke
Authors: Gretarsdottir Solveig , Thorleifsson Gudmar , Manolescu Andrei , Styrkarsdottir Unnur , Helgadottir Anna , Gschwendtner Andreas , Kostulas Konstantinos , Kuhlenbäumer Gregor , Bevan Steve , Jonsdottir Thorbjorg , Bjarnason Hjordis , Saemundsdottir Jona , Palsson Stefan , Arnar David O. , Holm Hilma , Thorgeirsson Gudmundur , Valdimarsson Einar Mar , Sveinbjörnsdottir Sigurlaug , Gieger Christian , Berger Klaus , Wichmann H‐Erich , Hillert Jan , Markus Hugh , Gulcher Jeffrey Robert , Ringelstein E. Bernd , Kong Augustine , Dichgans Martin , Gudbjartsson Daniel Fannar , Thorsteinsdottir Unnur , Stefansson Kari
Published: November 2008

Objective

To find sequence variants that associate with the risk for ischemic stroke (IS), we performed a genome‐wide association study.

Methods

We genotyped 1,661 Icelandic IS patients and 10,815 control subjects using the Infinium HumanHap300 chip (Illumina, San Diego, CA). A total of 310,881 single nucleotide polymorphisms (SNPs) were tested for association with IS, and the most significant signals were replicated in two large European IS sample sets (2,224 cases/2,583 control subjects). Two SNPs, rs2200733 and rs10033464, were tested further in additional European IS samples (2,327 patients and 16,760 control subjects).

Results

In the Icelandic samples and the two replication sets combined, rs2200733 associated significantly with cardioembolic stroke (CES) (odds ratio [OR], 1.54; p = 8.05 × 10−9). No other variants associated with IS or any of its subtypes. rs2200733 associated significantly with IS in all sample sets combined (OR, 1.26; p = 2.18 × 10−10), and both rs2200733 and its neighbour, rs10033464 associated strongly with CES (rs2200733: OR, 1.52; p = 5.8 × 10−12; rs10033464: OR, 1.27; p = 6.1 × 10−4). Interestingly, rs2200733 also showed significant association to IS not classified as CES.

Interpretation

We discovered that variants previously shown to associate with atrial fibrillation (AF), rs2200733 and rs10033464, significantly associated with IS, with the strongest risk for CES. The association with noncardiogenic stroke is intriguing and suggests that atrial fibrillation may be underdiagnosed in patients presenting with stroke. This discovery may have implications for workup and treatment of IS. Ann Neurol 2008;64:402–409
ChemInform Abstract: Recent Progress in Oxide Thermoelectric Materials: p‐Type Ca3Co4O9 and n‐Type SrTiO3‐
Authors: Ohta Hiromichi , Sugiura Kenji , Koumoto Kunhito
Published: November 2008

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
TCR‐β chains derived from peripheral γδ T cells can take part in αβ T‐cell development
Authors: Bosco Nabil , Engdahl Corinne , Bénard Angèle , Rolink Johanna , Ceredig Rhodri , Rolink Antonius G.
Published: November 2008

Between 10 and 20% of the peripheral γδ T cells express cytoplasmic TCR‐β proteins, but whether such TCR‐β chains can partake in αβ T‐cell development has never been systematically investigated. Therefore, we reconstituted the T‐cell compartment of CD3ε‐deficient mice with Pax5‐TCR‐β deficient proB cells expressing, via a retroviral vector, TCR‐β chains from either peripheral γδ or αβ T cells. Recipient thymi reconstituted with proB cells containing empty vector were small (<15×106 cells), contained few γδ T but no αβ T cells. In contrast, thymi from mice receiving proB cells containing γδ or αβ T‐cell‐derived TCR‐β chains contained 80–130×106 cells, and showed a normal CD4, CD8 and αβ TCR expression pattern. However, regardless of the source of TCR‐β chain, reconstituted mice rapidly showed signs of autoimmunity dying 5–15 wk following reconstitution. Autoimmune disease induction could be prevented by co‐transfer of Treg cells thereby allowing the functionality of the generated T cells to be assessed. Results obtained show that TCR‐β chains from γδ T cells can efficiently take part in αβ T‐cell development. The implications of these findings for γδ T‐cell development will be discussed.
Diurnal evolutions of nitrogen oxides (NOx), ozone (O3), and PM10particles at a busy traffic cross‐road in the city of Tunis
Authors: Azri Chafai , Mabrouk Chaabane , Medhioub Khaled
Published: November 2008

This study reports on an air quality investigation carried out in the city of Tunis (a North African coastal town) during the period starting in October 2003 and ending in December 2003. It investigates the diurnal gaseous and particulate pollution in the vicinity of “Bab Saadoun,” one of the most heavily trafficked cross‐roads in the city of Tunis. The average concentrations under investigation exhibited some peculiarities stemming mainly from the general customs of the local population and from specific meteorological situations (anticyclones, cyclones with deep movement) pertaining to ozone levels. These peculiarities were taken into consideration and are elaborated on the present article. © 2008 American Institute of Chemical Engineers Environ Prog, 2009
Estradiol downregulation of the tumor suppressor gene BTG2 requires estrogen receptor‐α and the REA corepressor
Authors: Karmakar Sudipan , Foster Estrella A. , Smith Carolyn L.
Published: November 2008

B‐cell Translocation Gene 2 (BTG2/TIS21/PC3) is an anti‐proliferative tumor suppressor gene whose expression is significantly reduced in breast carcinomas, and in MCF‐7 and T‐47D breast cancer cell lines treated with estradiol (E2). In this study the mechanisms involved in E2 down regulation of BTG2 gene expression were examined. Depletion of ERα by siRNA indicated that the receptor is required for E2 down regulation of BTG2 mRNA levels, and cycloheximide experiments indicated that the effect of E2 on BTG2 expression was independent of intermediary protein synthesis. Chromatin immunoprecipitation analyses revealed that ERα interacts with the BTG2 promoter in a ligand‐independent fashion whereas transfection experiments indicated that ERα's DNA and ligand binding domains are required for E2 repression of BTG promoter activity. Surprisingly, histone deacetylase (HDACs) activity is essential for basal expression as evidenced by trichostatin A inhibition of BTG2 mRNA levels. Estradiol treatment did not alter histone H3 acetylation although it did induce displacement of RNA polymerase II from the BTG2 gene. Depletion of the ER specific corepressor REA (Repressor of Estrogen Receptor Activity) significantly abrogated E2‐mediated BTG2 repression. Taken together, our results reveal a requirement of HDAC activity for basal BTG2 expression and the ERα‐REA interaction for estrogen repression of the BTG2 gene. The ability of E2‐bound ERα and REA to suppress BTG2 expression indicates a positive role for this corepressor in regulation of breast cancer cell proliferation. © 2008 Wiley‐Liss, Inc.
Covalently‐linked hyaluronan promotes bone formation around Ti implants in a rabbit model
Authors: Morra Marco , Cassinelli Clara , Cascardo Giovanna , Fini Milena , Giavaresi Gianluca , Giardino Roberto
Published: November 2008

The goal of this study was the in vivo evaluation of nanoporous titanium (Ti) implants bearing a covalently linked surface hyaluronan (HA) layer. Implant surface topography and surface chemistry were previously evaluated by scanning electron micorscopy and X‐ray photoelectron spectroscopy. Results showed that the surface modification process did not affect surface topography, yielding a homogeneously HA‐coated nanotextured implant surface. In vivo evaluation of implants in both cortical and trabecular bone of rabbit femurs showed a significant improvement of both bone‐to‐implant contact and bone ingrowth at HA‐bearing implant interfaces at 4 weeks. The improvement in osteointegration rate was particularly evident in the marrow‐rich trabecular bone (bone‐to‐implant contact: control 22.5%; HA‐coated 69.0%, p < 0.01). Mechanical testing (push‐out test) and evaluation of interfacial bone microhardness confirmed a faster bone maturation around HA‐coated implants (Bone Maturation Index: control 79.1%; HA‐coated 90.6%, p < 0.05). Suggestions based on the biochemical role of HA are presented to account for the observed behavior. Published by Wiley Periodicals, Inc. J Orthop Res 27: 657–663, 2009
Structural determination of atricins A and B, new triterpenes from Perovskia atriplicifolia, by 1D and 2D NMR spectroscopy
Authors: Perveen Shagufta , Malik Abdul , Bakhsh Tareen Rasool
Published: November 2008

Atricins A (1) and B (2), two new oleanane‐type triterpenes have been isolated from the chloroform‐soluble fractions of Perovskia atriplicifolia and their structures assigned from 1H and 13C‐NMR spectra, Distortion Enhancement by Polarization Trasfer (DEPT) and by 2D‐COSY, HMQC, Nuclear Overhauser Enhancement Spectroscopy (NOESY) and Hetronuclear mutiple‐bond correlation (HMBC) experiments. Copyright © 2008 John Wiley & Sons, Ltd.
Critical micelle concentrations of block and gradient copolymers in homopolymer: Effects of sequence distribution, composition, and molecular weight
Authors: Sandoval Robert W. , Williams Daniel E. , Kim Jungki , Roth Connie B. , Torkelson John M.
Published: November 2008

The critical micelle concentrations (CMCs) of styrene–methyl methacrylate (S‐MMA) block and gradient copolymers present in a homopolymer poly(methyl methacrylate) (PMMA) matrix were determined using an intrinsic fluorescence technique based on the ratio of excimer to monomer fluorescence from styrene repeat units. The homopolymer molecular weight (MW) and copolymer MW, composition, and sequence distribution were varied to determine their effects on the CMC, and comparisons were made to theory. Although the effects of these parameters on micelle formation have been the focus of significant theoretical study, few experimental studies have addressed these issues. The MW of the S block (forming the micelle core) has a strong effect on the CMC. For example, an order of magnitude reduction in the CMC (from ∼ 1 to ∼ 0.1 wt %) is observed when the S block MW is increased from 51 to 147 kg/mol while maintaining the MMA block and PMMA MWs at 48–55 kg/mol. Increasing the PMMA matrix MW also has a strong an effect on the CMC, with the CMC for a nearly symmetric S‐MMA block copolymer with each block MW equal to 48–51 kg/mol decreasing by a factor of 5 and by several orders of magnitude when the matrix MW is increased from 55 to 106 kg/mol and 255 kg/mol, respectively. In contrast, similar changes in the MMA block MW have little effect on the CMC. Finally, when present in a 55 kg/mol PMMA matrix, a 55 kg/mol S‐MMA gradient copolymer with a styrene mole fraction of 0.51 exhibits a factor of 6 larger CMC than a block copolymer of similar MW and composition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2672–2682, 2008
Nitrogen incorporation in homoepitaxial ZnO CVD epilayers
Authors: Lautenschlaeger Stefan , Eisermann Sebastian , Meyer Bruno K. , Callison Gordon , Wagner Markus R. , Hoffmann Axel
Published: November 2008

ZnO:N thin films have been deposited on oxygen and zinc terminated polar surfaces of ZnO. The nitrogen incorporation in the epilayers, using NH3 as doping source, was investigated as a function of the growth temperature in the range between 380 °C and 580 °C. We used Raman spectroscopy and low temperature photoluminescence to investigate the doping properties. It turned out that the nitrogen incorporation strongly depends on both, the surface polarity of the epitaxial films and the applied growth temperatures. In our CVD process low growth temperatures and Zn‐terminated substrate surfaces clearly favour the nitrogen incorporation in the ZnO thin films. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonparametric comparison of two survival functions with dependent censoring via nonparametric multiple imputation
Authors: Hsu Chiu‐Hsieh , Taylor Jeremy M. G.
Published: November 2008

When the event time of interest depends on the censoring time, conventional two‐sample test methods, such as the log‐rank and Wilcoxon tests, can produce an invalid test result. We extend our previous work on estimation using auxiliary variables to adjust for dependent censoring via multiple imputation, to the comparison of two survival distributions. To conduct the imputation, we use two working models to define a set of similar observations called the imputing risk set. One model is for the event times and the other for the censoring times. Based on the imputing risk set, a nonparametric multiple imputation method, Kaplan–Meier imputation, is used to impute a future event or censoring time for each censored observation. After imputation, the conventional nonparametric two‐sample tests can be easily implemented on the augmented data sets. Simulation studies show that the sizes of the log‐rank and Wilcoxon tests constructed on the imputed data sets are comparable to the nominal level and the powers are much higher compared with the tests based on the unimputed data in the presence of dependent censoring if either one of the two working models is correctly specified. The method is illustrated using AIDS clinical trial data comparing ZDV and placebo, in which CD4 count is the time‐dependent auxiliary variable. Copyright © 2008 John Wiley & Sons, Ltd.
The Racketeer Menace and Antiunionism in the Mid-Twentieth Century US
Authors: Witwer David
Published: November 2008

In the postwar era, conservatives manipulated concerns about union corruption and organized crime in order to score political points against New Deal Democrats and to win new legal restrictions on union power. The resulting racketeer menace had much in common with the contemporary red scare. Antiunion conservatives framed the issue of labor racketeering in terms that resembled the language then being mobilized against internal communist espionage and subversion. This rhetoric proliferated in the congressional debates of the postwar era. Proponents of the Taft-Hartley Act invoked the racketeer menace in 1946 and 1947. They depicted the law as an effort to curb racketeering and thus protect workers and the general public by restricting abusive union power. In the years that followed, a series of congressional hearings into union corruption kept attention focused on the issue of racketeering. For the Eisenhower Administration this campaign against labor racketeering offered a chance to peel the working-class vote away from the Democratic Party by politically dividing union members from their leadership. The culmination of this trend came at the end of the 1950s during the McClellan Committee hearings, which was the largest congressional investigation up to that time. Those hearings transformed Teamsters President James R. Hoffa into a potent symbol of the danger posed by labor racketeering. The committee's revelations and the publicity they received undercut the labor movement. Polls showed growing public skepticism toward unions, and especially union leaders. Such attitudes helped conservatives win a new round of legislative restrictions on organized labor in the form of the Landrum-Griffin Act (1959).