bluuebunny/crossref_metadata_2025 huggingface dataset:
An Age- and Temperature-Mediated Growth Model for Cod (Gadus morhua) and Haddock (Melanogrammus aeglefinus) Larvae in the Gulf of Maine
Authors: Campana Steven E. , Hurley Peter C. F.
Published: June 2009

While field studies of larval fish growth require an easily parameterized growth model, simple relationships between size and age are seldom applicable to other populations and/or environments. The model presented here attempts to bridge the gap between simple age–length regressions and more sophisticated experiment-based models by incorporating a temperature term as a function of absolute growth rate. Growth is assumed to be logistic, with temperature influencing growth rate parabolically on a daily basis. The integrated form of the model provides an estimate of length-at-age of the larva. When fitted to a variety of independent cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) data sets collected in the Gulf of Maine, the model performed with minimal bias despite the absence of a food availability term. Larval age data were generated through validated otolith microstructure examinations, although the resolution limits of light microscopy introduced a small degree of bias (2–3 d) into the estimates. The daily temperature record was generated from a sinusoidal model using monthly mean temperatures. Since otolith microstructure examination and remote sensing of temperature are established techniques, this model may prove useful in other larval studies.
Biological Model of Fisheries Production Based on Physiological and Ecological Scalings of Body Size
Authors: Boudreau P. R. , Dickie L. M.
Published: June 2009

Earlier ecological studies showing regularity in the relationship of certain indices of production to body size are used to develop a predictive equation of fish production on a year to year basis, with biomass and body size as independent stock variables. The prediction system makes use of the observed regular adjustments of local biomass density with body size and the parallelism of the functional relationships of production and biomass with body size both between and within stock cohorts. The method obviates the need to invoke assumptions of population equilibrium. The model is applied to three data series for individual species exploited by commercial fisheries on the Scotian Shelf. The results suggest that despite the vagaries of population sampling, ecological information can provide practical estimates of the production potential of fish stocks.
Biologically Available Phosphorus: Estimation and Prediction Using an Anion-Exchange Resin
Authors: Hanna Micheline
Published: June 2009

The suitability of ion-exchange resin extraction for assessing biologically available P (phosphorus) concentrations was evaluated in a wide range of water samples of different origins (natural waters, wastewater treatment plant effluents, and industrial effluents). A recycling system was specifically designed to enhance P adsorption by the resin by maintaining a steep P gradient. Resin extractable P compared favorably with total P, total soluble P, and soluble reactive P, as a predictor of bioassay available P (BAP). Biologically available P was generally greater than soluble reactive P and less than total soluble P. Over the diverse water samples tested, the best model for predicting BAP used resin extractable P and soluble reactive P.
Predicting Winter Flounder (Pseudopleuronectes americanus) Catches by Time Series Analysis
Authors: Jeffries Perry , Keller Aimee , Hale Stephen
Published: June 2009

Long-term changes in catches of winter flounder (Pseudopleuronectes americanus) were compared at five locations within Narragansett Bay, Rhode Island, USA and in three areas directly offshore. In the lower Bay, relative abundance decreased 86% during warming in the early 1970's, recovered briefly, and then declined to an all-time low in 1986. Time-series analysis successfully predicted a recovery in 1987. Year ahead predictions, based on annual models, had a maximum error of 14% (1986); monthly forecasts explained 62–72% of catch variation during the entire investigation; cumulative monthly error (forecast compared with actual over an annual cycle) was 11% in the Bay and 21% offshore. Commercial offshore catch and the fish retained on power plant intake screens in two major rivers showed the same 11-yr pattern of population fall and recovery detected in the lower Bay. Coherent behavior was also demonstrated by the similarity of random processes which generated the time-series data. Thus a single time-series model for southern New England winter flounder seems feasible.
Feeding Flexibility in Northern Pike (Esox lucius): Fish versus Invertebrate Prey
Authors: Chapman Lauren J. , Mackay William C. , Wilkinson Craig W.
Published: June 2009

We describe the frequency of occurrence of fish and invertebrates in the stomach contents of northern pike (Esox lucius) from eight populations in Alberta and the Northwest Territories. Lakes were sampled one to eight times between 1979 and 1985, and a total of 899 pike were examined (mean standard length = 44 ± 8 cm, SD). Although northern pike are widely considered to be top aquatic piscivores, we found that the frequency of occurrence of invertebrates was high, at least on a seasonal basis, in some systems. In all of the lakes considered, the frequency of occurrence of fish (expressed as a percentage of non-empty stomachs) was 88% or greater in one or more of the sample periods. However, diets where the frequency of occurrence of invertebrates was greater than 90% occurred in three of the populations in one or more of the sample periods. The frequency of occurrence of invertebrates was negatively correlated with the percentage of empty stomachs, while the frequency of occurrence of fish was positively related to the percentage of empty stomachs. Invertebrate feeding was not limited exclusively to smaller pike; invertebrates were found in the stomachs of pike 24 to 60 cm long (standard length).
Optimal Environmental Window and Pelagic Fish Recruitment Success in Upwelling Areas
Authors: Cury Philippe , Roy Claude
Published: June 2009

Food availability and physical constraints such as turbulence are now considered as important factors that affect larval survival and pelagic fish recruitment. In Ekman-type upwelling, vertical advection, new inputs of nutrients and turbulence are linked to wind speed. According to the literature, food availability for larvae is related to biological dynamics (primary production) up to a point where the biological processes are disturbed by physical processes (turbulence generated by wind mixing). This limitation does not exist for non Ekman-type upwelling where upwelling intensity is not correlated with wind speed. We hypothesize that relations between annual recruitments and upwelling intensity are dome shaped in Ekman-type upwellings and linear for non Ekman-type upwellings. A statistical method is used to analyse the form of the relationships between recruitments and upwelling indices or wind mixing. The recruitment of the Peruvian anchoveta (Engraulis ringens), of the Pacific sardine (Sardinops sagax caerulea) and of the West African sardines and sardinellas are thereby examined. Results show that for Ekman-type upwelling the annual recruitment increases with upwelling intensity until wind speed reaches a value of roughly 5–6 m∙s−1 and decreases for higher values. For a non Ekman-type upwelling the relationship between recruitment and upwelling intensity is linear. These results confirm the existence of an optimal environmental window for recruitment.
Effects of Forest Harvesting on Spawning Gravel and Incubation Survival of Chum (Oncorhynchus keta) and Coho Salmon (O. kisutch) in Carnation Creek, British Columbia
Authors: Scrivener J. C. , Brownlee M. J.
Published: June 2009

Following logging, pea gravel and sand (i.e. fines) in the stream bed of Carnation Creek, British Columbia increased 4.6 and 5.7%, respectively. The quantity of fines was greater in the bottom layer, while the frequency and magnitude of changes in composition were greater in the top layer of streambed cores. Changes in streambed fines depended on the timing and type of streamside logging and on the timing of large freshets. Accumulating fines appeared to originate from erosion of streambanks or from upstream storage areas and they were transported as bedload. Suspended sediment (11.4–44.5 t∙km−2∙yr−1) did not increase after road construction or logging. Deposition and scour rates of pea gravel and sand in the streambed were inversely related to particle size, and to their depth in the bed. Following logging, survival to emergence declined from 29.1 to 16.4% for coho salmon (Oncorhynchus kisutch) and from 22.2 to 11.5% for chum salmon (O. keta). Annual mean survival to emergence and size of fry of both species were positively related to two indices of substrate composition. Annual changes in substrate composition and peak flows explained 60 and 73% of the variability in survival to emergence for chum and coho salmon, respectively.
Rapid Branchial Excretion of Dietary Quinoline by Rainbow Trout (Salmo gairdneri)
Authors: Dauble D. D. , Curtis L. R.
Published: June 2009

Excretion of the nitrogen heterocycle14C-quinoline was characterized in rainbow trout (Salmo gairdneri) following its ingestion with food. Quinoline-derived radioactivity was readily absorbed from the stomach as shown by peak serum levels that occurred 4–8 h after feeding. Pharmacokinetics were described using a two-compartment body model with first-order absorption and disposition; estimated half-lives for the α and β phase were 4.1 and 54.1 h, respectively. About 98% of the ingested dose was absorbed by gut epithelium before fecal excretion. Depending on dose, 71–83% of the ingested radioactivity was excreted during the first 24 h after feeding. Branchial elimination was the primary route of excretion since all other routes (fecal, biliary, urinary, and dermal) contributed < 5% of the eliminated dose within 48 h after ingestion. There was evidence for saturation of minor excretory pathways as the dose was increased from 1 to 100 mg quinoline∙kg−1body weight. Apparent spillover occurred into the branchial route at the 100 mg∙kg−1dose. Dietary quinoline was eliminated across the gills as parent compound, independent of the dose.
Imprinting and Homing of Atlantic Salmon (Salmo salar) Kelts
Authors: Foster J. R. , Schom C. B.
Published: June 2009

Experiments were conducted to determine if a process similar to imprinting occurs during each seaward migration of Atlantic Salmon (Salmo salar). Displaced Atlantic salmon kelts homed to the site from which they had previously emigrated to sea as smolts (Big Salmon River, New Brunswick, Canada) and did not home to their release sites, or their overwintering sites 150 km away. Delaying release of kelts past the time of normal seaward migration did not cause the behavioral changes associated with interference of the imprinting process described for smolts. Delayed release kelts did not remain near their seawater or estuarine release sites, home to their release sites, or non-selectively home to suitable spawning streams near their release sites. Delayed released kelts travelled away from the release site faster than kelts released during their normal time of seaward migration, but they did not return either to Passamaquoddy Bay or their natal stream in the calendar year of their release (the normal time for this stock) or in subsequent years.
Housing Supply
Authors: Gyourko Joseph
Published: June 2009

Research on housing supply has grown owing to improved data combined with heightened interest in policies such as local land use regulations. Heterogeneity in supply conditions across markets is shown to be essential to understanding the growing price dispersion across metropolitan areas, as well as to understanding whether positive growth shocks to a metropolitan area manifest themselves more in terms of expanding population and homebuilding or in terms of higher wages and house prices. The nature of supply obviously also influences local housing-market dynamics. Recent research has shown that differences in the elasticity of housing supply can account for the wide variation in new construction volatility (but not price volatility) across markets over time. The extraordinary nature of the recent boom only increases the need to understand how housing-market fundamentals and supply and demand affect the functioning of this huge asset market.
The Economic Consequences of the International Migration of Labor
Authors: Hanson Gordon H.
Published: June 2009

In this paper, I selectively discuss recent empirical work on the consequences of global labor mobility. I examine how international migration affects the incomes of individuals in sending and receiving countries and of migrants themselves. Were a social planner to choose the migration policies that would maximize global welfare, she would need to know, among other values, the elasticities of wages, prices, taxes, and government transfers with respect to national labor supplies as well as how these parameters vary across countries. My goal is to evaluate the progress of the literature in terms of providing these inputs.
Racial Profiling? Detecting Bias Using Statistical Evidence
Authors: Persico Nicola
Published: June 2009

We review the economics literature that deals with identifying bias, or taste for discrimination, using statistical evidence. A unified model is developed that encompasses several different strategies studied in the literature. We also discuss certain more theoretical questions concerning the proper objective of discrimination law.
Role of Ca2+ in injury-induced changes in sodium current in rat skeletal muscle
Authors: Filatov Gregory N. , Pinter Martin J. , Rich Mark M.
Published: June 2009

Characteristics of voltage-dependent sodium current recorded from adult rat muscle fibers in loose patch mode were rapidly altered following nearby impalement with a microelectrode. Hyperpolarized shifts in the voltage dependence of activation and fast inactivation occurred within minutes. In addition, the amplitude of the maximal sodium current decreased within 30 min of impalement. Impalement triggered a sustained elevation of intracellular Ca2+. However, buffering Ca2+ by loading fibers with AM-BAPTA did not affect the hyperpolarized shifts in activation and inactivation, although it did prevent the reduction in current amplitude. Surprisingly, the rise in intracellular Ca2+ occurred even in the absence of extracellular Ca2+. This result indicated that the injury-induced Ca2+ increase came from an intracellular source, but it was not blocked by an inhibitor of release from the sarcoplasmic reticulum, which suggested involvement of mitochondria. Ca2+ release from mitochondria triggered by carbonyl cyanide 3-chlorophenylhydrazone was sufficient to cause a reduction in sodium current amplitude but had little effect of the voltage dependence of activation and fast inactivation. Our data suggest the effects of muscle injury can be separated into a Ca2+-dependent reduction in amplitude and a largely Ca2+-independent shift in activation and fast inactivation. Together, the impalement-induced changes in sodium current reduce the number of sodium channels available to open at the resting potential and may limit further depolarization and thus promote survival of muscle fibers following injury.
Cdc42GAP, reactive oxygen species, and the vimentin network
Authors: Li Qing-Fen , Spinelli Amy M. , Tang Dale D.
Published: June 2009

Cdc42GAP (GTPase-activating protein) has been implicated in the regulation of cell motility, adhesion, proliferation, and apoptosis. In this study, Cdc42GAP was cloned from smooth muscle tissues. Cdc42GAP, but not inactive R282A Cdc42GAP (alanine substitution at arginine-282), enhanced the GTP hydrolysis of Cdc42 in an in vitro assay. Furthermore, we developed an assay to evaluate the activity of Cdc42GAP in vivo. Stimulation of smooth muscle cells with 5-hydroxytryptamine (5-HT) resulted in the decrease in Cdc42GAP activity. The agonist-induced GAP suppression was reversed by reactive oxygen species inhibitors. Treatment with hydrogen peroxide also inhibited GAP activity in smooth muscle cells. Because the vimentin cytoskeleton undergoes dynamic changes in response to contractile activation, we evaluated the role of Cdc42GAP in regulating vimentin filaments. Smooth muscle cells were infected with retroviruses encoding wild-type Cdc42GAP or its R282A mutant. Expression of wild-type Cdc42GAP, but not mutant R282A GAP, inhibited the increase in the activation of Cdc42 upon agonist stimulation. Phosphorylation of p21-activated kinase (PAK) at Thr-423 (an indication of PAK activation), vimentin phosphorylation (Ser-56), partial disassembly and spatial remodeling, and contraction were also attenuated in smooth muscle cells expressing Cdc42GAP. Our results suggest that the activity of Cdc42GAP is regulated upon contractile activation, which is mediated by intracellular ROS. Cdc42GAP regulates the vimentin network through the Cdc42-PAK pathway in smooth muscle cells during 5-HT stimulation.
Extracellular ATP dissociates nonmuscle myosin from P2X7 complex: this dissociation regulates P2X7 pore formation
Authors: Gu Ben J. , Rathsam Catherine , Stokes Leanne , McGeachie Andrew B. , Wiley James S.
Published: June 2009

The P2X7 receptor is a ligand-gated cation channel that is highly expressed on monocyte-macrophages and that mediates the pro-inflammatory effects of extracellular ATP. Dilation of the P2X7 channel and massive K+ efflux follows initial channel opening, but the mechanism of secondary pore formation is unclear. The proteins associated with P2X7 were isolated by using anti-P2X7 monoclonal antibody-coated Dynabeads from both interferon-γ plus LPS-stimulated monocytic THP-1 cells and P2X7-transfected HEK-293 cells. Two nonmuscle myosins, NMMHC-IIA and myosin Va, were found to associate with P2X7 in THP-1 cells and HEK-293 cells, respectively. Activation of the P2X7 receptor by ATP caused dissociation of P2X7 from nonmuscle myosin in both cell types. The interaction of P2X7 and NMMHC-IIA molecules was confirmed by fluorescent life time measurements and fluorescent resonance of energy transfer-based time-resolved flow cytometry assay. Reducing the expression of NMMHC-IIA or myosin Va by small interfering RNA or short hairpin RNA led to a significant increase of P2X7 pore function without any increase in surface expression or ion channel function of P2X7 receptors. S- l-blebbistatin, a specific inhibitor of NMMHC-IIA ATPase, inhibited both ATP-induced ethidium uptake and ATP-induced dissociation of P2X7-NMMHC-IIA complex. In both cell types nonmuscle myosin closely interacts with P2X7 and is dissociated from the complex by extracellular ATP. Dissociation of this anchoring protein may be required for the transition of P2X7 channel to a pore.
ROS and PDFG-β receptors are critically involved in indoxyl sulfate actions that promote vascular smooth muscle cell proliferation and migration
Authors: Shimizu Hidehisa , Hirose Yuichi , Nishijima Fuyuhiko , Tsubakihara Yoshiharu , Miyazaki Hitoshi
Published: June 2009

Patients with chronic renal failure are at greater risk of developing atherosclerosis than healthy individuals, and recent data suggest that the putative uremic toxin indoxyl sulfate (IS) promotes the pathogenesis of atherosclerosis. The present study examined the effects of IS on vascular smooth muscle cells (VSMCs) with respect to reactive oxygen species (ROS), platelet-derived growth factor (PDGF) receptors, and mitogen-activated protein kinases (MAPKs). IS induced the migration and proliferation of VSMCs and synergistically enhanced their PDGF-induced migration as well as proliferation. The effects of PDGF were promoted after a 24-h incubation with IS despite the absence of IS during PDGF stimulation. Intracellular ROS levels were increased in the presence of IS, and PDGF-dependent ROS production was augmented by a prior 24-h incubation with IS even in the absence of IS during PDGF stimulation. These data suggest that IS increases the sensitivity of VSMCs to PDGF. IS also phosphorylated PDGF-β-receptors and upregulated PDGF-β receptor but not α-receptor protein expression in the absence of exogenous PDGF. The NADPH oxidase inhibitor diphenylene iodonium blocked IS-dependent increase in receptor expression. Administration of IS to nephrectomized rats also elevated receptor protein expression in arterial VSMCs. Inhibitors of NADPH oxidase, PDGF-β receptors, extracellular-regulated protein kinase (ERK), and p38 MAPK all inhibited IS-induced VSMCs migration and proliferation. Taken together, these findings indicate that IS induces the migration as well as proliferation of VSMCs through PDGF-β receptors and that ROS generation is critically involved in this process, which promotes the development of atherosclerosis.
Myoferlin is critical for endocytosis in endothelial cells
Authors: Bernatchez Pascal N. , Sharma Arpeeta , Kodaman Pinar , Sessa William C.
Published: June 2009

Myoferlin is a member of the ferlin family of proteins that promotes endomembrane fusion with the plasma membrane in muscle cells and endothelial cells. In addition, myoferlin is necessary for the surface expression of vascular endothelial growth factor receptor 2 through the formation of a protein complex with dynamin-2 (Dyn-2). Since Dyn-2 is necessary for the fission of endocytic vesicles from the plasma membrane, we tested the hypothesis that myoferlin may regulates aspects of receptor-dependent endocytosis. Here we show that myoferlin gene silencing decreases both clathrin and caveolae/raft-dependent endocytosis, whereas ectopic myoferlin expression in COS-7 cells increases endocytosis by up to 125%. Interestingly, we have observed that inhibition of Dyn-2 activity or caveolin-1 (Cav-1) expression impairs endocytosis as well as membrane resealing after injury, indicating that Dyn-2 and Cav-1 also participate in both membrane fission and fusion processes. Mechanistically, myoferlin partially colocalizes with Dyn-2 and Cav-1 and forms a protein complex with Cav-1 solubilized from tissue extracts. Together, these data describe a new role for myoferlin in receptor-dependent endocytosis and an overlapping role for myoferlin-Dyn-2-Cav-1 protein complexes in membrane fusion and fission events.
Prolactin regulates ZNT2 expression through the JAK2/STAT5 signaling pathway in mammary cells
Authors: Qian Linxi , Lopez Veronica , Seo Young Ah , Kelleher Shannon L.
Published: June 2009

The zinc transporter ZnT2 ( SLC30A2) plays an important role in zinc secretion into milk during lactation. The physiological process of mammary gland secretion is regulated through complex integration of multiple lactogenic hormones. Prolactin plays a primary role in this regulation through the activation of various signaling cascades including Jak2/STAT5, mitogen-activated protein kinase (MAPK), p38, and phosphatidylinositol 3-kinase (PI3K). The precise mechanisms that regulate the transfer of specific nutrients such as zinc into milk are not well understood. Herein we report that prolactin increased ZnT2 abundance transcriptionally in cultured mammary epithelial (HC11) cells. To delineate the responsible mechanisms, we first determined that prolactin-mediated ZnT2 induction was inhibited by pretreatment with the Jak2 inhibitor AG490 but not by the MAPK inhibitor PD-98059. Using a luciferase reporter assay, we demonstrated that ZnT2 promoter activity was increased by prolactin treatment, which was subsequently abolished by expression of a dominant-negative STAT5 construct, implicating the Jak2/STAT5 signaling pathway in the transcriptional regulation of ZnT2. Two putative consensus STAT5 binding sequences in the ZnT2 promoter were identified (GAS1:−674 to −665 and GAS2:−377 to −368). Mutagenesis of the proximal GAS2 element resulted in complete abrogation of PRL-induced ZnT2 promoter activity. The promoter incorporating the distal GAS1 mutation was only able to respond to very high PRL concentrations. Results from both the mutagenesis and gel shift assays indicated that a cooperative relationship exists between GAS1 and GAS2 for PRL-induced activation; however, the proximal GAS2 plays a more critical role in STAT5-mediated signal transduction compared with the GAS1 element. Finally, chromosome immunoprecipition assay further confirmed that prolactin activates STAT5 binding to the ZnT2 promoter in vivo. Taken together, these results illustrate that prolactin regulates the transcription of ZnT2 through activation of the Jak2/STAT5 signaling pathway to assist in providing optimal zinc for secretion into milk during lactation.
Impaired acclimatization to chronic hypoxia in adult male and female rats following neonatal hypoxia
Authors: Lumbroso Delphine , Joseph Vincent
Published: June 2009

We tested the hypothesis that neonatal exposure to hypoxia alters acclimatization to chronic hypoxia later in life. Rat pups were exposed to normobaric hypoxia (12% O2; nHx group) in a sealed chamber, or to normoxia (21% O2; nNx group) from the day before birth to postnatal day 10. The animals were then raised in normal conditions until reaching 12 wk of age. At this age, we assessed ventilatory and hematological acclimatization to chronic hypoxia by exposing male and female nHx and nNx rats for 2 wk to 10% O2. Minute ventilation, metabolic rate, hypoxic ventilatory response, hematocrit, and hemoglobin levels were measured both before and after acclimatization. We also quantified right ventricular hypertrophy as an index of pulmonary hypertension both before and after acclimatization. There was a significant effect of neonatal hypoxia that decreases ventilatory response (relative to metabolic rate, V̇e/V̇co2) to acute hypoxia before acclimatization in males but not in females. nHx rats had an impaired acclimatization to chronic hypoxia characterized by altered respiratory pattern and elevated hematocrit and hemoglobin levels after acclimatization, in both males and females. Right ventricular hypertrophy was present before and after acclimatization in nHx rats, indicating that neonatal hypoxia results in pulmonary hypertension in adults. We conclude that neonatal hypoxia impairs acclimatization to chronic hypoxia in adults and may be a factor contributing to the establishment of chronic mountain sickness in humans living at high altitude.
Hyperaldosteronism, hypervolemia, and increased blood pressure in mice expressing defective APC
Authors: Bhandaru Madhuri , Kempe Daniela S. , Rotte Anand , Rexhepaj Rexhep , Kuhl Dietmar , Lang Florian
Published: June 2009

Adenomatous polyposis coli (APC) fosters degradation of β-catenin, a multifunctional protein upregulating the serum- and glucocorticoid-inducible kinase (SGK1). SGK1 regulates a wide variety of renal transport processes. The present study explored the possibility that APC influences renal function. To this end, metabolic cage experiments were performed in mice carrying a loss-of-function mutation in the APC gene ( apcMin/+), their wild-type littermates ( apc+/+), and apcMin/+mice lacking functional SGK1 ( apcMin/+/sgk1−/−). As a result, mean body weight, food intake, fluid intake, salt appetite, urinary flow, as well as plasma Na+and K+concentrations were similar in apcMin/+mice, apc+/+mice, and apcMin/+/sgk1−/−mice. Glomerular filtration rate and absolute renal Na+excretion were decreased, and fractional urinary K+excretion was enhanced in apcMin/+mice. The antinatriuresis, but not the hypofiltration and kaliuresis was partially reversed by additional lack of SGK1. Plasma corticosterone and aldosterone concentrations were significantly enhanced in apcMin/+mice. While the plasma corticosterone concentration was similar in apc+/+mice and apcMin/+/sgk1−/−mice, plasma aldosterone was even higher in apcMin/+/sgk1−/−mice than in apcMin/+mice. The hyperaldosteronism of apcMin/+mice was paralleled by significantly elevated plasma volume and blood pressure. The experiments reveal an influence of defective APC on adrenal hormone release and renal function, effects partially but not completely explained by APC dependence of SGK1 expression.
Acetazolamide suppresses the prevalence of augmented breaths during exposure to hypoxia
Authors: Bell Harold J. , Haouzi Philippe
Published: June 2009

Augmented breaths, or “sighs,” commonly destabilize respiratory rhythm, precipitating apneas and variability in the depth and rate of breathing, which may then exacerbate sleep-disordered breathing in vulnerable individuals. We previously demonstrated that hypocapnia is a unique condition associated with a high prevalence of augmented breaths during exposure to hypoxia; the prevalence of augmented breaths during hypoxia can be returned to normal simply by the addition of CO2to the inspired air. We hypothesized that counteracting the effect of respiratory alkalosis during hypocapnic hypoxia by blocking carbonic anhydrase would yield a similar effect. We, therefore, investigated the effect of acetazolamide on the prevalence of augmented breaths in the resting breathing cycle in five awake, adult male rats. We found a 475% increase in the prevalence of augmented breaths in animals exposed to hypocapnic hypoxia compared with room air. Acetazolamide treatment (100 mg/kg ip bid) for 3 days resulted in a rapid and potent suppression of the generation of augmented breaths during hypoxia. Within 90 min of the first dose of acetazolamide, the prevalence of augmented breaths in hypoxia fell to levels that were no greater than those observed in room air. On cessation of treatment, exposure to hypocapnic hypoxia once again caused a large increase in the prevalence of augmented breaths. These results reveal a novel means by which acetazolamide acts to stabilize breathing and may help explain the beneficial effects of the drug on breathing stability at altitude and in patients with central forms of sleep-disordered breathing.
Dynamic characterization and hemodynamic effects of pulmonary waves in fetal lambs using cardiac extrasystoles and beat-by-beat wave intensity analysis
Authors: Smolich Joseph J. , Mynard Jonathan P. , Penny Daniel J.
Published: June 2009

Steady-state wave intensity ( WI) analysis indicates that characteristic midsystolic falls in fetal pulmonary trunk (PT) and artery (PA) blood flow are due to an extremely large backward-running compression wave (BCWms) that 1) originates from the pulmonary microvasculature by a combination of cyclical pulmonary vasoconstriction and vascular reflection of the forward-running compression wave (FCWis) associated with impulsive right ventricular ejection, and 2) is transmitted into the PT. However, no information is available about the dynamic properties of PA BCWms and its contribution to beat-to-beat regulation of pulmonary hemodynamics. Accordingly, beat-by-beat WI analysis was performed during brief increases in ventricular contractility accompanying an extrasystole (ES) in nine anesthetized late-gestation fetal sheep instrumented with PT and left PA micromanometer catheters to measure pressure (P) and transit-time flow probes to obtain blood velocity ( U). WI was calculated as the product of P and U rates of change. At steady state, the magnitude of PA BCWms, and its associated P and U changes (ΔP and Δ U, respectively), were similar to those of FCWis. The PA FCWis and BCWms, and their accompanying ΔP and Δ U, were all transiently potentiated after an ES. Beat-by-beat PA FCWis-BCWms wave area, ΔP and Δ U relationships were highly linear ( R2 ≥ 0.91) with slopes of 1.36–1.47 ( P < 0.001), consistent with the presence of a vasoconstrictor component in PA BCWms. PA-PT BCWms area and ΔP and Δ U relationships were also linear ( R2 ≥ 0.77) with slopes of 0.23–0.64 ( P < 0.001). These results indicate that the fetal PA BCWms contributes to beat-to-beat regulation of not only PA but also PT hemodynamics.
Adaptation of exercise ventilation during an actively-induced hyperthermia following passive heat acclimation
Authors: Beaudin Andrew E. , Clegg Miriam E. , Walsh Michael L. , White Matthew D.
Published: June 2009

Hyperthermia-induced hyperventilation has been proposed to be a human thermolytic thermoregulatory response and to contribute to the disproportionate increase in exercise ventilation (V̇e) relative to metabolic needs during high-intensity exercise. In this study it was hypothesized that V̇e would adapt similar to human eccrine sweating (ĖSW) following a passive heat acclimation (HA). All participants performed an incremental exercise test on a cycle ergometer from rest to exhaustion before and after a 10-day passive exposure for 2 h/day to either 50°C and 20% relative humidity (RH) ( n = 8, Acclimation group) or 24°C and 32% RH ( n = 4, Control group). Attainment of HA was confirmed by a significant decrease ( P = 0.025) of the esophageal temperature (Tes) threshold for the onset of ĖSW and a significantly elevated ĖSW ( P ≤ 0.040) during the post-HA exercise tests. HA also gave a significant decrease in resting Tes ( P = 0.006) and a significant increase in plasma volume ( P = 0.005). Ventilatory adaptations during exercise tests following HA included significantly decreased Tes thresholds ( P ≤ 0.005) for the onset of increases in the ventilatory equivalents for O2 (V̇e/V̇o2) and CO2 (V̇e/V̇co2) and a significantly increased V̇e ( P ≤ 0.017) at all levels of Tes. Elevated V̇e was a function of a significantly greater tidal volume ( P = 0.003) at lower Tes and of breathing frequency ( P ≤ 0.005) at higher Tes. Following HA, the ventilatory threshold was uninfluenced and the relationships between V̇o2 and either V̇e/V̇o2 or V̇e/V̇co2 did not explain the resulting hyperventilation. In conclusion, the results support that exercise V̇e following passive HA responds similarly to ĖSW, and the mechanism accounting for this adaptation is independent of changes of the ventilatory threshold or relationships between V̇o2 with each of V̇e/V̇o2 and V̇e/V̇co2.
Dissecting the genetic basis of kidney tubule response to hyperoxaluria using chromosome substitution strains
Authors: Wiessner John H. , Garrett Michael R. , Roman Richard J. , Mandel Neil S.
Published: June 2009

Whether genetics may play a role in the pathophysiologic response of kidney tubules to oxalate exposure remains unexplored despite that as many as 15% of the U.S. population annually will experience a kidney stone composed of calcium oxalate. To explore this issue, we utilized a panel of chromosome substitution strains in which one chromosome at a time was transferred from the Brown Norway (BN) rat onto the Dahl salt-sensitive (SS) genetic background. Hyperoxaluria was induced by adding hydroxyproline (HP) to the drinking water. A dose-response (0–2% HP) study found that both SS and BN exhibited the same level of oxalate excretion as HP concentration increased, but only the BN exhibited changes in urothelial pathology and demonstrated crystal deposition at sites of urothelial injury as a function of dose (at 1.5–2.0%). The consomic panel was treated with 2.0% HP and evaluated for hyperoxaluria, renal injury, and crystal deposition. Tubular injury (% Area) and crystal deposition (% Area) were similar between the resistant SS and SS-4, -6, -7, -8, -9, -11, -16, and -20BN consomic rats. However, tubular injury was significantly increased in SS-2BN compared with the SS parental (9.8 ± 1.56 and 4.2 ± 1.09%, respectively). Crystal deposition was observed in SS-2BN and SS-18BN (4.7 ± 0.70 and 3.5 ± 1.3%, respectively) to the same extent as seen in the susceptible BN (3.2 ± 0.44%). The fact that crystal deposition was observed in SS-18BN without extensive overall tubule injury, compared with the more severe widespread tubular injury seen in SS-2BN, suggests that the underlying mechanism of each locus is different. In conclusion, these studies establish that BN rats demonstrate oxalate-associated pathology and they retain calcium oxalate crystals coincident with urothelial injury but SS rats do not. These observations establish that BN rat chromosome 2 and 18 harbor genes that contribute to these processes.
Dose-dependent effects of dihydrotestosterone in the streptozotocin-induced diabetic rat kidney
Authors: Xu Qin , Prabhu Anjali , Xu Shujing , Manigrasso Michaele B. , Maric Christine
Published: June 2009

We recently reported that castration exacerbates albuminuria, glomerulosclerosis, and tubulointerstitial fibrosis associated with diabetic renal disease. The aim of the present study was to examine whether these effects of castration can be attenuated with dihydrotestosterone (DHT) supplementation. The study was performed in castrated male Sprague-Dawley, streptozotocin-induced diabetic rats treated with 0 mg/day DHT (DHT0), 0.75 mg/day DHT (DHT0.75), or 2.0 mg/day DHT (DHT2.0) for 14 wk. Treatment with 0.75 mg/day DHT attenuated castration-associated increases in urine albumin excretion (DHT0, 81.2 ± 18.1; DHT0.75, 26.57 ± 5.8 mg/day; P < 0.05), glomerulosclerosis (DHT0, 1.1 ± 0.79; DHT0.75, 0.43 ± 0.043 arbitrary units; P < 0.001), tubulointerstitial fibrosis (DHT0, 1.3 ± 0.12; DHT0.75, 1.1 ± 0.096 AU; P < 0.05), collagen type IV [DHT0, 3.2 ± 0.11; DHT0.75, 2.1 ± 0.070 relative optical density (ROD); P < 0.01], transforming growth factor-β (DHT0, 3.2 ± 0.16; DHT0.75, 2.1 ± 0.060 ROD; P < 0.01), IL-6 (DHT0, 0.37 ± 0.011; DHT0.75, 0.27 ± 0.014 ROD; P < 0.05), and protein expression and reduced CD68-positive cell abundance (DHT0, 17 ± 0.86; DHT0.75, 4.4 ± 0.55 cells/mm2; P < 0.001). In contrast, treatment with 2.0 mg/day DHT exacerbated all these parameters. These data suggest that the detrimental effects of castration in the diabetic kidney can be attenuated with low doses of DHT, whereas high doses augment the adverse effects of castration, and these effects appear to be influenced by estradiol. We conclude that the effects of DHT are dose dependent but caution should be taken when DHT supplementation is considered in the treatment of diabetic renal disease.
Modulation of GABAergic Transmission by Muscarinic Receptors in the Entorhinal Cortex of Juvenile Rats
Authors: Xiao Zhaoyang , Deng Pan-Yue , Yang Chuanxiu , Lei Saobo
Published: June 2009

Whereas the entorhinal cortex (EC) receives profuse cholinergic innervations from the basal forebrain and activation of cholinergic receptors has been shown to modulate the activities of the principal neurons and promote the intrinsic oscillations in the EC, the effects of cholinergic receptor activation on GABAergic transmission in this brain region have not been determined. We examined the effects of muscarinic receptor activation on GABAAreceptor-mediated synaptic transmission in the superficial layers of the EC. Application of muscarine dose-dependently increased the frequency and amplitude of spontaneous inhibitory postsynaptic currents (IPSCs) recorded from the principal neurons in layer II/III via activation of M3muscarinic receptors. Muscarine slightly reduced the frequency but had no effects on the amplitude of miniature IPSCs recorded in the presence of tetrodotoxin. Muscarine reduced the amplitude of IPSCs evoked by extracellular field stimulation and by depolarization of GABAergic interneurons in synaptically connected interneuron and pyramidal neuron pairs. Application of muscarine generated membrane depolarization and increased action potential firing frequency but reduced the amplitude of action potentials in GABAergic interneurons. Muscarine-induced depolarization of GABAergic interneurons was mediated by inhibition of background K+channels and independent of phospholipase C, intracellular Ca2+release, and protein kinase C. Our results demonstrate that activation of muscarinic receptors exerts diverse effects on GABAergic transmission in the EC.
Recovery of Slow Potentials in AC-Coupled Electrocorticography: Application to Spreading Depolarizations in Rat and Human Cerebral Cortex
Authors: Hartings Jed A. , Watanabe Tomas , Dreier Jens P. , Major Sebastian , Vendelbo Leif , Fabricius Martin
Published: June 2009

Cortical spreading depolarizations (spreading depressions and peri-infarct depolarizations) are a pathology intrinsic to acute brain injury, generating large negative extracellular slow potential changes (SPCs) that, lasting on the order of minutes, are studied with DC-coupled recordings in animals. The spreading SPCs of depolarization waves are observed in human cortex with AC-coupled electrocorticography (ECoG), although SPC morphology is distorted by the high-pass filter stage of the amplifiers. Here, we present a signal processing method to reverse these distortions and recover approximate full-band waveforms from AC-coupled recordings. We constructed digital filters that reproduced the phase and amplitude distortions introduced by specific AC-coupled amplifiers and, based on this characterization, derived digital inverse filters to remove these distortions from ECoG recordings. Performance of the inverse filter was validated by its ability to recover both simulated and real low-frequency input test signals. The inverse filter was then applied to AC-coupled ECoG recordings from five patients who underwent invasive monitoring after aneurysmal subarachnoid hemorrhage. For 117 SPCs, the inverse filter recovered full-band waveforms with morphologic characteristics typical of the negative DC shifts recorded in animals. Compared with those recorded in the rat cortex with the same analog and digital methods, the negative DC shifts of human depolarizations had significantly greater durations (1:47 vs. 0:45 min:sec) and peak-to-peak amplitudes (10.1 vs. 4.2 mV). The inverse filter thus permits the study of spreading depolarizations in humans, using the same assessment of full-band DC potentials as that in animals, and suggests a particular solution for recovery of biosignals recorded with frequency-limited amplifiers.
Microprisms for In Vivo Multilayer Cortical Imaging
Authors: Chia Thomas H. , Levene Michael J.
Published: June 2009

Cortical slices allow for simultaneous imaging of multiple cortical layers. However, slices lack native physiological inputs and outputs. Although in vivo, two-photon imaging preserves the native context, it is typically limited to a depth of <500 μm. In addition, simultaneous imaging of multiple cortical layers is difficult due to the stratified organization of the cortex. We demonstrate the use of 1-mm microprisms for in vivo, two-photon neocortical imaging. These prisms enable simultaneous imaging of multiple cortical layers, including layer V, at an angle typical of slice preparations. Images were collected from the mouse motor and somatosensory cortex and show a nearly 900-μm-wide field of view. At high-magnification imaging using an objective with 1-mm of coverglass correction, resolution is sufficient to resolve dendritic spines on layer V neurons. Images collected using the microprism are comparable to images collected from a traditional slice preparation. Functional imaging of blood flow at various neocortical depths is also presented, allowing for quantification of red blood cell flux and velocity. H&E staining shows the surrounding tissue remains in its native, stratified organization. Estimation of neuronal damage using propidium iodide and a fluorescent Nissl stain reveals cell damage is limited to <100 μm from the tissue–glass interface. Microprisms are a straightforward tool offering numerous advantages for INTO NEOCORTICAL STISSUE.
Fully Connected PLL Networks: How Filter Determines the Number of Nodes
Authors: Bueno Átila Madureira , Ferreira André Alves , Piqueira José Roberto C.
Published: June 2009

Synchronization plays an important role in telecommunication systems,
integrated circuits, and automation systems. Formerly, the masterslave synchronization strategy was used in the great majority of cases due to its reliability and simplicity. Recently, with the wireless networks development, and with the increase of the operation frequency of integrated circuits, the decentralized clock distribution strategies are gaining importance. Consequently, fully connected clock distribution systems with nodes composed of phase‐locked loops (PLLs) appear as a convenient engineering solution. In this work, the stability of the synchronous state of these networks is studied in two relevant situations:
when the node filters are first‐order lag‐lead low‐pass or when the node filters are second‐order low‐pass. For first‐ order filters, the synchronous state of the network shows to be stable for any number of nodes. For second‐order filter, there is a superior limit for the number of nodes, depending on the PLL parameters.
Stability Results of a Class of Hybrid Systems under Switched Continuous‐Time and Discrete‐Time Control
Authors: De la Sen M. , Ibeas A.
Published: June 2009

This paper investigates the stability properties of a class of switched systems possessing several linear time‐invariant parameterizations (or configurations) which are governed by a switching law. It is assumed that the parameterizations are stabilized individually via an appropriate linear state or output feedback stabilizing controller whose existence is first discussed. A main novelty with respect to previous research is that the various individual parameterizations might be continuous‐time, discrete‐time, or mixed so that the whole switched system is a hybrid continuous/discrete dynamic system. The switching rule governs the choice of the parameterization which is active at each time interval in the switched system. Global asymptotic stability of the switched system is guaranteed for the case when a common Lyapunov function exists for all the individual parameterizations and the sampling period of the eventual discretized parameterizations taking part of the switched system is small enough. Some extensions are also investigated for controlled systems under decentralized or mixed centralized/decentralized control laws which stabilize each individual active parameterization.
Fragility of Bioprotectant Glass-Forming Systems in Extremophiles
Authors: Magazù S. , Migliardo F.
Published: June 2009

A central issue in the adaptation of proteins and enzymes to extreme conditions is the conservation of their functional state, which is characterized by a well-balanced compromise of stability and flexibility.
In this review work an overview of elastic neutron scattering (ENS) findings on a class of bioprotectant glass-forming systems, such as trehalose and its homologous (maltose and sucrose) water mixtures, is presented as a function of temperature and concentration. ENS, in fact, allows to determine some remarkable quantities in order to characterize the correlation among dynamical properties, the flexibility and fragility of biomolecules. The experimental results have pointed out a dynamical transition, which shows a crossover in molecular fluctuations between harmonic and anharmonic dynamical regimes. The ENS findings allow to characterize both the trehalose rigidity and flexibility, which are strictly connected to its superior bioprotective effectiveness. In this frame the lowest flexibility and fragility character of trehalose/H2O mixture with respect to maltose and sucrose/H2O mixtures indicate a better attitude to encapsulate biostructures in more rigid and temperature insensitive structures in approaching the glass transition.
A Discrete Heterogeneous‐Group Economic Growth Model with Endogenous Leisure Time
Authors: Zhang Wei-Bin
Published: June 2009

This paper proposes a one‐sector multigroup growth model with endogenous labor supply in discrete time. Proposing an alternative approach to behavior of households, we examine the dynamics of wealth and income distribution in a competitive economy with capital accumulation as the main engine of economic growth. We show how human capital levels, preferences, and labor force of heterogeneous households determine the national economic growth, wealth, and income distribution and time allocation of the groups. By simulation we demonstrate, for instance, that in the three‐group economy when the rich group′s human capital is improved, all the groups will economically benefit, and the leisure times of all the groups are reduced but when any other group′s human capital is improved, the group will economically benefit, the other two groups economically lose, and the leisure times of all the groups are increased.