bluuebunny/crossref_metadata_2025 huggingface dataset:
Isolation and Characterization of a Generalized Transducing Phage for
Pseudomonas aeruginosa
Strains PAO1 and PA14
Authors: Budzik Jonathan M. , Rosche William A. , Rietsch Arne , O'Toole George A.
Published: May 2004

A temperate, type IV pilus-dependent, double-stranded DNA bacteriophage named DMS3 was isolated from a clinical strain of
Pseudomonas aeruginosa
. A clear-plaque variant of this bacteriophage was isolated. DMS3 is capable of mediating generalized transduction within and between
P. aeruginosa
strains PA14 and PAO1, thus providing a useful tool for the genetic analysis of
P. aeruginosa
.
−1 Frameshifting at a CGA AAG Hexanucleotide Site Is Required for Transposition of Insertion Sequence IS
1222
Authors: Mejlhede Nina , Licznar Patricia , Prère Marie-Françoise , Wills Norma M. , Gesteland Raymond F. , Atkins John F. , Fayet Olivier
Published: May 2004

The discovery of programmed −1 frameshifting at the hexanucleotide shift site CGA_AAG, in addition to the classical X_XXY_YYZ heptanucleotide shift sequences, prompted a search for instances among eubacterial insertion sequence elements. IS
1222
has a CGA_AAG shift site. A genetic analysis revealed that frameshifting at this site is required for transposition.
Using a large-angle gauge to select trees for measurement in variable plot sampling
Authors: Marshall David D , Iles Kim , Bell John F
Published: May 2004

Variable plot sampling has been widely used for many years. It was recognized, early in its application, that the process of getting stand volume could be divided into two components, counting trees to get basal area per unit area and measuring trees to get volume/basal area ratios (VBARs). It was further recognized that these two components had different amounts of variation and therefore should be sampled at different intensities. The fact that basal area per unit area is almost always more variable than the VBARs of individual trees has led to the widespread practice of counting trees on all plots and subsampling trees for VBAR measurements, typically by measuring all the trees on every third or fourth plot. This article presents an alternative, the "big BAF method," which uses a larger basal-area-factor angle gauge to do a second sweep of each plot to select the trees to be measured for VBAR. This procedure spreads the tree measurements throughout the stand and is thus more statistically efficient. The method is simple to apply, requires no additional computations, and is easy to audit. Two case-study examples are used to demonstrate the method.
Decay and nutrient dynamics of coarse woody debris in northern coniferous forests: a synthesis
Authors: Laiho Raija , Prescott Cindy E
Published: May 2004

We synthesize current information on input, accumulation, and decay of coarse woody debris (CWD) compared with other aboveground litter to assess the role of CWD in the nutrient cycles of northern coniferous forests. CWD contributes between 3% and 73% of aboveground litter input, but <20% of N, P, K, and Ca. Although CWD accounts for up to 54% of accumulated organic matter (including forest floor and soil), it contributes <5% of the N, <10% of the P, and <25% of the K, Ca, and Mg. Decay rates of CWD in northern forests range from 0.0025 to 0.071 year-1. Nitrogen or P concentrations in CWD increase during decay, depending on the initial N/P ratio, which eventually converges at about 20. CWD is initially a sink for N and (or) P, whichever is least available, but becomes a source later in decay. CWD contributes <5% of the N released annually. There is little evidence that CWD retains significant amounts of excess N following disturbance. We conclude that CWD is of minor importance in the nutrient cycles of northern coniferous forests, and that guidelines for CWD retention should be based on other perceived benefits of CWD.
Ten-year postharvest effects of silviculture systems on soil-resource availability and conifer nutrition in a northern temperate forest
Authors: Kranabetter J M , Coates K D
Published: May 2004

Silviculture systems (clear-cut, partial-cut, and unharvested forest) were compared 910 years after harvesting to determine their effects on conifer nutrition and the availability of soil resources, especially nitrogen. These results were used to discuss the effects of silviculture systems on tree growth in relation to the more commonly described effects of light. Differences in soil properties across the silviculture treatments were most apparent in the forest floor. Depth and C/N ratio of the forest floor had decreased slightly in clearcuts, and forest-floor moisture was highest under partial-cut forest. Despite these differences in soil chemistry and soil moisture, no differences were detected in mineralizable N (anaerobic incubation) or in situ net N mineralization among treatments. Height growth and foliar mass were reduced under the low-light conditions of the partial-cut forest, but there were no differences in foliar N concentrations of hybrid white spruce (Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carrière), western redcedar (Thuja plicata Dougl. ex D. Don), or western hemlock (Tsuga heterophylla (Raf.) Sarg.) saplings. Mature western hemlock trees in partial-cut forest also had concentrations of foliar N equal to that of mature trees in the unharvested forest. Overall, we detected only minor effects of silviculture systems on soils after 10 years, and we conclude that light availability is likely more responsible for the current differences in tree growth.
Measuring leakage from carbon projects in open economies: a stop timber harvesting project in Bolivia as a case study
Authors: Sohngen Brent , Brown Sandra
Published: May 2004

This paper develops methods for estimating leakage from forest-based carbon projects that seek to reduce carbon emissions from timber harvesting in tropical forests. A theoretical framework is presented in which a specific country, in this case Bolivia, is treated as a supplier to the global timber market. Leakage is measured, over a 30- to 50-year time period, as the difference in net national carbon emissions from timber harvesting between the baseline case and a scenario in which some of the land is removed from the concession base. Estimates of timber leakage are made for several different assumptions about future global sequestration policies, capital constraints, demand elasticity, and deadwood decomposition rates. The results suggest that leakage could range from 5% to 42% without discounting carbon, and from 2% to 38% when carbon is discounted. Demand elasticity and wood decomposition rates have the largest effects on the leakage calculation. Leakage is lowest when demand is more elastic and wood decomposition rates are faster, and vice-versa when these conditions are reversed. Leakage appears to be sensitive to capital constraints only when project benefits are measured over a shorter time period.
MAIDEN: a model for analyzing ecosystem processes in dendroecology
Authors: Misson Laurent
Published: May 2004

Ecophysiological and dendroecological data from a temperate sessile oak (Quercus petraea (Matt.) Liebl.) stand in Belgium were used to develop and parameterize a dendroecological process-based model. The purpose of this model is to serve as a tool for exploring the relationship between climate variability and tree growth based on dendro ecological data. When parameterized, the model was able to correctly simulate measurements of bud-burst date, through fall (r2 = 0.95), soil water content (r2 = 0.81), transpiration (r2 = 0.80), and ring-width series from 1960 to 1999 (r2 = 0.46). Model sensitivity analysis showed that atmospheric vapor pressure deficit is the major controlling factor of transpiration in this type of ecosystem. The model shows that bole increment is principally controlled by temperature because it affects the phenological process of bud burst and thus the growing season length. Precipitation variability does not affect variation of transpiration rate and bole increment because calculated soil water stress is negligible during the simulation period. Discrepancies between observed and simulated bole increment may be a consequence of stand density variations and worm defoliation in the spring. The MAIDEN model is particularly suited for dendreocological analysis because it takes simple species, site condition, and climatic variables as input.
Dendroecological analysis of climatic effects onQuercus petraeaandPinus halepensisradial growth using the process-based MAIDEN model
Authors: Misson Laurent , Rathgeber Cyrille , Guiot Joël
Published: May 2004

A process-based model (MAIDEN, modeling and analysis in dendroecology) is compared with statistical response functions to analyze the climategrowth relationship for two different species (sessile oak (Quercus petraea (Matt.) Liebl.) and Aleppo pine (Pinus halepensis Mill.)) growing in contrasting climates (temperate and Mediterranean). Growth data were obtained using dendroecological sampling procedures. Results obtained with both methods are consistent, but the MAIDEN model provides a more explanatory analysis than classical statistical tools. Analyses with MAIDEN indicate that oak stomatal conductance is sensitive to atmospheric vapor deficit, whereas precipitation and soil water deficit are not limiting factors in the study area. In contrast, the soil water regime is the major controlling factor of bole growth variability for Aleppo pine. The model shows that remobilization of the carbohydrate reserves in spring is of major importance for leaf and root expansion, and it affects the subsequent bole increment of oak. Because the amount of carbon that can be mobilized in spring is linked to carbon stored the previous year, these processes explain how the growth of oak trees is linked in this way from one year to the next. In contrast, the MAIDEN model shows that carbohydrate-reserve dynamics, phenology, and bole growth are less connected for Aleppo pine trees.
Effects of two silvicultural practices on ground beetles (Coleoptera: Carabidae) in a northern hardwood forest, Quebec, Canada
Authors: Moore Jean-David , Ouimet Rock , Houle Daniel , Camiré Claude
Published: May 2004

The impact of selective cutting (6 and 8 years after treatment) and strip clear-cutting (12 and 13 years after treatment) on abundance and diversity of carabid beetles was evaluated in a northern hardwood forest of Quebec, Canada. A total of 1078 individuals belonging to 14 species were captured with pitfall traps from June to September 1996 during 2568 day-trap. Abundance of Synuchus impunctatus Say was significantly higher in clear-cut compared with uncut control strips. There were no within-species differences between selectively cut and uncut plots. None of these two silvicultural systems had any significant impacts on species diversity and richness 613 years after treatment. Although we observed an effect of strip clear-cutting on the abundance of S. impunctatus in this northern hardwood forest, the discrepancy between the response of carabids to forest disturbance in this study compared with other studies in different ecological regions suggests that the same carabid beetle species cannot be used as an indicator of forest disturbance over a large region. Our results suggest the use of carabid beetles as a disturbance indicator at the ecological-type scale (relatively similar soil and forest type) in a given region.
AUTOMATIC SCHEDULING OF HYPERMEDIA DOCUMENTS WITH ELASTIC TIMES
Authors: MEDINA MAIRA T. , RIBEIRO CELSO C. , SOARES LUIZ F. G.
Published: April 2004

The problem of automatic scheduling hypermedia documents consists in finding the optimal starting times and durations of objects to be presented, to ensure spatial and temporal consistency of a presentation while respecting limits on shrinking and stretching the ideal duration of each object. The combinatorial nature of the minimization of the number of objects whose duration is modified makes it the most difficult objective to be tackled by optimization algorithms. We formulate this scheduling problem as a mixed integer programming problem and report some preliminary investigations. We propose an original approach to the minimization of the number of objects which are shrinked or stretched. A simple primal heuristic based on variable fixations along the solution of a sequence of linear relaxations of the mixed integer programming formulation is described. Computational experiments on realistic size problems are reported. The effectiveness of the heuristic in finding good approximate solutions within very small processing times makes of it a quite promising approach to be integrated within existing document formatters to perform compile time scheduling or even run time adjustments. We also discuss results obtained by Lagrangean relaxation and propose a dual heuristic using the modified costs, which consistently improves the solutions found by the primal heuristic.
Optimal Diffusion Schemes and Load Balancing on Product Graphs
Authors: ELSÄSSER ROBERT , MONIEN BURKHARD , PREIS ROBERT , FROMMER ANDREAS
Published: April 2004

We discuss nearest neighbor load balancing schemes on processor networks which are represented by a cartesian product of graphs and present a new optimal diffusion scheme for general graphs. In the first part of the paper, we introduce the Alternating-Direction load balancing scheme, which reduces the number of load balance iterations by a factor of 2 for cartesian products of graphs. The resulting flow is theoretically analyzed and can be very high for certain cases. Therefore, we further present the Mixed-Direction scheme which needs the same number of iterations but computes in most cases a much smaller flow. In the second part of the paper, we present a simple optimal diffusion scheme for general graphs, calculating a balancing flow which is minimal in the l2 norm. It is based on the spectra of the graph representing the network and needs only m-1 iterations to balance the load with m being the number of distinct eigenvalues. Known optimal diffusion schemes have the same performance, however the optimal scheme presented in this paper can be implemented in a very simple manner. The number of iterations of optimal diffusion schemes is independent of the load scenario and, thus, they are practical for networks which represent graphs with known spectra. Finally, our experiments exhibit that the new optimal scheme can successfully be combined with the Alternating-Direction and Mixed-Direction schemes for efficient load balancing on product graphs.
Parallel Algorithms for Recognizing P5-free and ${\bar P}_5$-free Weakly Chordal Graphs
Authors: Nikolopoulos Stavros D. , Palios Leonidas
Published: April 2004

We prove algorithmic characterizations of weakly chordal graphs, which lead to efficient parallel algorithms for recognizing P5-free and [Formula: see text]-free weakly chordal graphs. For an input graph on n vertices and m edges, our algorithms run in O( log 2n) time and require O(m2/ log n) processors on the EREW PRAM model of computation. The proposed recognition algorithms efficiently detect P5 s and [Formula: see text] in weakly chordal graphs in O( log n) time with O(m2/ log n) processors on the EREW PRAM. Additionally, we show how the algorithms can be augmented to provide a certificate for the existence of a P5 (or a [Formula: see text]) in case the input graph is not P5-free (respectively, [Formula: see text]-free) weakly chordal.
ESTIMATION OF MASS AND CENTER OF MASS OF UNKNOWN AND GRASPLESS CYLINDER-LIKE OBJECT
Authors: YU YONG , KIYOKAWA TAKASHI , TSUJIO SHOWZOW
Published: April 2004

In manipulating an object stably and accurately by a robot, the mass and the center of mass of the object is often required. For cases when the weight or shape of an object is over the grasp capacity of a robot's hand, a technique that can estimate the mass and center of mass of a graspless unknown object, which has curved surfaces and a base plane is proposed in this paper. A line called Passing-C.M. Line which contains the center of mass, is defined. For estimating the passing-C.M. line, we proposed the Tip Operation by a robot finger, which tips the object slowly and repeatedly in a parallel motion with a vertical operation plane. Using the fingertip position and force information measured from tip operations, an algorithm to estimate the passing-C.M. line is described. Then an algorithm to estimate the mass and center of mass of the object is given by estimating the intersecting point of several differently oriented passing-C.M. lines.
Coordinate downregulation of CaM kinase II and phospholamban accompanies contractile phenotype transition in the hyperthyroid rabbit soleus
Authors: Jiang M. , Xu A. , Jones D.L. , Narayanan N.
Published: May 2004

This study investigated the effects of l-thyroxine-induced hyperthyroidism on Ca2+/calmodulin (CaM)-dependent protein kinase (CaM kinase II)-mediated sarcoplasmic reticulum (SR) protein phosphorylation, SR Ca2+ pump (Ca2+-ATPase) activity, and contraction duration in slow-twitch soleus muscle of the rabbit. Phosphorylation of Ca2+-ATPase and phospholamban (PLN) by endogenous CaM kinase II was found to be significantly lower (30–50%) in soleus of the hyperthyroid compared with euthyroid rabbit. Western blotting analysis revealed higher levels of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) 1 (∼150%) Ca2+ pump isoform, unaltered levels of SERCA2 Ca2+ pump isoform, and lower levels of PLN (∼50%) and δ-, β-, and γ-CaM kinase II (40 ∼ 70%) in soleus of the hyperthyroid rabbit. SR vesicles from hyperthyroid rabbit soleus displayed approximately twofold higher ATP-energized Ca2+ uptake and Ca2+-stimulated ATPase activities compared with that from euthyroid control. The Vmax of Ca2+ uptake (in nmol Ca2+·mg SR protein−1·min−1: euthyroid, 818 ± 73; hyperthyroid, 1,649 ± 90) but not the apparent affinity of the Ca2+-ATPase for Ca2+ (euthyroid, 0.97 ± 0.02 μM, hyperthyroid, 1.09 ± 0.04 μM) differed significantly between the two groups. CaM kinase II-mediated stimulation of Ca2+ uptake by soleus muscle SR was ∼60% lower in the hyperthyroid compared with euthyroid. Isometric twitch force of soleus measured in situ was significantly greater (∼36%), and the time to peak force and relaxation time were significantly lower (∼30–40%), in the hyperthyroid. These results demonstrate that thyroid hormone-induced transition in contractile properties of the rabbit soleus is associated with coordinate downregulation of the expression and function of PLN and CaM kinase II and selective upregulation of the expression and function of SERCA1, but not SERCA2, isoform of the SR Ca2+ pump.
Functional characterization of an insulin-responsive glucose transporter (GLUT4) from fish adipose tissue
Authors: Capilla Encarnación , Díaz Mònica , Albalat Amaya , Navarro Isabel , Pessin Jeffrey E. , Keller Konrad , Planas Josep V.
Published: May 2004

Glucose transport across the plasma membrane is mediated by a family of glucose transporter proteins (GLUTs), several of which have been identified in mammalian, avian, and, more recently, in fish species. Here, we report on the cloning of a salmon GLUT from adipose tissue with a high sequence homology to mammalian GLUT4 that has been named okGLUT4. Kinetic analysis of glucose transport following expression in Xenopus laevis oocytes demonstrated a 7.6 ± 1.4 mM Kmfor 2-deoxyglucose (2-DG) transport measured under zero- trans conditions and 14.4 ± 1.5 mM by equilibrium exchange of 3- O-methylglucose. Transport of 2-DG by okGLUT4-injected oocytes was stereospecific and was competed by d-glucose, d-mannose, and, to a lesser extent, d-galactose and d-fructose. In addition, 2-DG uptake was inhibited by cytochalasin B and ethylidene glucose. Moreover, insulin stimulated glucose uptake in Xenopus oocytes expressing okGLUT4 and in isolated trout adipocytes, which contain the native form of okGLUT4. Despite differences in protein motifs important for insulin-stimulated translocation of mammalian GLUT4, okGLUT4 was able to translocate to the plasma membrane from intracellular localization sites in response to insulin when expressed in 3T3-L1 adipocytes. These data demonstrate that okGLUT4 is a structural and functional fish homolog of mammalian GLUT4 but with a lower affinity for glucose, which could in part explain the lower ability of fish to clear a glucose load.
PKC-δ and -ε regulate NF-κB activation induced by cholecystokinin and TNF-α in pancreatic acinar cells
Authors: Satoh Akihiko , Gukovskaya Anna S. , Nieto Jose M. , Cheng Jason H. , Gukovsky Ilya , Reeve Joseph R. , Shimosegawa Tooru , Pandol Stephen J.
Published: May 2004

Although NF-κB plays an important role in pancreatitis, mechanisms underlying its activation remain unclear. We investigated the signaling pathways mediating NF-κB activation in pancreatic acinar cells induced by high-dose cholecystokinin-8 (CCK-8), which causes pancreatitis in rodent models, and TNF-α, which contributes to inflammatory responses of pancreatitis, especially the role of PKC isoforms. We determined subcellular distribution and kinase activities of PKC isoforms and NF-κB activation in dispersed rat pancreatic acini. We applied isoform-specific, cell-permeable peptide inhibitors to assess the role of individual PKC isoforms in NF-κB activation. Both CCK-8 and TNF-α activated the novel isoforms PKC-δ and -ε and the atypical isoform PKC-ζ but not the conventional isoform PKC-α. Inhibition of the novel PKC isoforms but not the conventional or the atypical isoform resulted in the prevention of NF-κB activation induced by CCK-8 and TNF-α. NF-κB activation by CCK-8 and TNF-α required translocation but not tyrosine phosphorylation of PKC-δ. Activation of PKC-δ, PKC-ε, and NF-κB with CCK-8 involved both phosphatidylinositol-specific PLC and phosphatidylcholine (PC)-specific PLC, whereas with TNF-α they only required PC-specific PLC for activation. Results indicate that CCK-8 and TNF-α initiate NF-κB activation by different PLC pathways that converge at the novel PKCs (δ and ε) to mediate NF-κB activation in pancreatic acinar cells. These findings suggest a key role for the novel PKCs in pancreatitis.
Influence of structural geometry on the severity of bicuspid aortic stenosis
Authors: Richards Kathryn E. , Deserranno Dimitri , Donal Erwan , Greenberg Neil L. , Thomas James D. , Garcia Mario J.
Published: May 2004

Doppler-derived gradients may overestimate total pressure loss in degenerative and prosthetic aortic valve stenosis (AS) due to unaccounted pressure recovery distal to the orifice. However, in congenitally bicuspid valves, jet eccentricity may result in a higher anatomic-to-effective orifice contraction ratio, resulting in an increased pressure loss at the valve and a reduced pressure recovery distal to the orifice leading to greater functional severity. The objective of our study was to determine the impact of local geometry on the total versus Doppler-derived pressure loss and therefore the assessed severity of the stenosis in bicuspid valves. On the basis of clinically obtained measurements, two- and three-dimensional computer simulations were created with various local geometries by altering the diameters of the left ventricular outflow tract (LVOT; 1.8–3.0 cm), orifice diameter (OD; 0.8–1.6 cm), and aortic root diameter (AR; 3.0–5.4 cm). Jet eccentricity was altered in the models from 0 to 25°. Simulations were performed under steady-flow conditions. Axisymmetric simulations indicate that the overall differences in pressure recovery were minor for variations in LVOT diameter (<3%). However, both OD and AR had a significant impact on pressure recovery (6–20%), with greatest recovery being the larger OD and the smaller recovery being the AR. In addition, three-dimensional data illustrate a greater pressure loss for eccentric jets with the same orifice area, thus increasing functional severity. In conclusion, jet eccentricity results in greater pressure loss in bicuspid valve AS due to reduced effective orifice area. Functional severity may also be enhanced by larger aortic roots, commonly occurring in these patients, leading to reduced pressure recovery. Thus, for the same anatomic orifice area, functional severity is greater in bicuspid than in degenerative tricuspid AS.
Influenza virus inhibits ENaC and lung fluid clearance
Authors: Chen Xi-Juan , Seth Shaguna , Yue Gang , Kamat Pradip , Compans Richard W. , Guidot David , Brown Lou Ann , Eaton Douglas C. , Jain Lucky
Published: May 2004

Fluid-free alveolar space is critical for normal gas exchange. Influenza virus alters fluid transport across respiratory epithelia producing rhinorrhea, middle ear effusions, and alveolar flooding. However, the mechanism of fluid retention remains unclear. We investigated influenza virus strain A/PR/8/34, which can attach and enter mammalian cells but is incapable of viral replication and productive infection in mammalian epithelia, on epithelial sodium channels (ENaC) in rat alveolar type II (ATII) cells. In parallel, we determined the effects of virus on amiloride-sensitive (i.e., ENaC-mediated) fluid clearance in rat lungs in vivo. Although influenza virus did not change the inulin permeability of ATII monolayers, it rapidly reduced the net volume transport across monolayers. Virus reduced the open probability of single ENaC channels in apical cell-attached patches. U-73122, a phospholipase C (PLC) inhibitor, and PP2, a Src inhibitor, blocked the effect of virus on ENaC. GF-109203X, a protein kinase C (PKC) inhibitor, also blocked the effect, suggesting a PKC-mediated mechanism. In parallel, intratracheal administration of influenza virus produced a rapid inhibition of amiloride-sensitive (i.e., ENaC-dependent) lung fluid transport. Together, these results show that influenza virus rapidly inhibits ENaC in ATII cells via a PLC- and Src-mediated activation of PKC but does not increase epithelial permeability in this same rapid time course. We speculate that this rapid inhibition of ENaC and formation of edema when the virus first attaches to the alveolar epithelium might facilitate subsequent influenza infection and may exacerbate influenza-mediated alveolar flooding that can lead to acute respiratory failure and death.
H2O2inhibits alveolar epithelial wound repair in vitro by induction of apoptosis
Authors: Geiser Thomas , Ishigaki Masanobu , van Leer Coretta , Matthay Michael A. , Broaddus V. Courtney
Published: May 2004

Reactive oxygen species (ROS) are released into the alveolar space and contribute to alveolar epithelial damage in patients with acute lung injury. However, the role of ROS in alveolar repair is not known. We studied the effect of ROS in our in vitro wound healing model using either human A549 alveolar epithelial cells or primary distal lung epithelial cells. We found that H2O2inhibited alveolar epithelial repair in a concentration-dependent manner. At similar concentrations, H2O2also induced apoptosis, an effect seen particularly at the edge of the wound, leading us to hypothesize that apoptosis contributes to H2O2-induced inhibition of wound repair. To learn the role of apoptosis, we blocked caspases with the pan-caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp (zVAD). In the presence of H2O2, zVAD inhibited apoptosis, particularly at the wound edge and, most importantly, maintained alveolar epithelial wound repair. In H2O2-exposed cells, zVAD also maintained cell viability as judged by improved cell spreading and/or migration at the wound edge and by a more normal mitochondrial potential difference compared with cells not treated with zVAD. In conclusion, H2O2inhibits alveolar epithelial wound repair in large part by induction of apoptosis. Inhibition of apoptosis can maintain wound repair and cell viability in the face of ROS. Inhibiting apoptosis may be a promising new approach to improve repair of the alveolar epithelium in patients with acute lung injury.
Endotoxin responsiveness of human airway epithelia is limited by low expression of MD-2
Authors: Jia Hong Peng , Kline Joel N. , Penisten Andrea , Apicella Michael A. , Gioannini Theresa L. , Weiss Jerrold , McCray Paul B.
Published: May 2004

The expression of inducible antimicrobial peptides, such as human β-defensin-2 (HBD-2) by epithelia, comprises a component of innate pulmonary defenses. We hypothesized that HBD-2 induction in airway epithelia is linked to pattern recognition receptors such as the Toll-like receptors (TLRs). We found that primary cultures of well-differentiated human airway epithelia express the mRNA for TLR-4, but little or no MD-2 mRNA, and display little HBD-2 expression in response to treatment with purified endotoxin ± LPS binding protein (LBP) and soluble CD14. Expression of endogenous MD-2 by transduction of airway epithelial cells with an adenoviral vector encoding MD-2 or extracellular addition of recombinant MD-2 both increased the responses of airway epithelia to endotoxin + LBP and sCD14 by >100-fold, as measured by NF-κB-luciferase activity and HBD-2 mRNA expression. MD-2 mRNA could be induced in airway epithelia by exposure of these cells to specific bacterial or host products (e.g., killed Haemophilus influenzae, the P6 outer membrane protein from H. influenzae, or TNF-α + IFN-γ). These findings suggest that MD-2, either coexpressed with TLR-4 or secreted when produced in excess of TLR-4 from neighboring cells, is required for airway epithelia to respond sensitively to endotoxin. The regulation of MD-2 expression in airway epithelia and pulmonary macrophages may serve as a means to modify endotoxin responsiveness in the airway.
Effect of neonatal dexamethasone exposure on growth and neurological development in the adult rat
Authors: Neal Charles R. , Weidemann Gabrielle , Kabbaj Mohamed , Vázquez Delia M.
Published: May 2004

Until recently, the synthetic glucocorticoid dexamethasone was commonly used to lessen the morbidity of chronic lung disease in premature infants. This practice diminished as dexamethasone use was linked to an increased incidence of cerebral palsy and short-term neurodevelopmental delay. Of more concern is the fact that we know little regarding dexamethasone effects on long-term neurodevelopment. To study the effects of neonatal dexamethasone exposure on long-term neurodevelopment, we have developed a rat model where newborn pups are exposed to tapering doses of dexamethasone at time points corresponding to the neurodevelopmental age when human infants are traditionally exposed to this drug in the neonatal intensive care unit. Using a within-litter design, pups were assigned to one of three groups on postnatal day 2 (P2): handled controls, saline-injected controls, and animals receiving intramuscular dexamethasone between P3 and P6. Somatic growth was decreased in dexamethasone-treated animals. Dexamethasone-treated animals demonstrated slight delays in indexes of neurodevelopment and physical maturation at P7 and P14, but not P20. In adolescence (P45), there was no difference between groups in an open field test. However, as adult dexamethasone-treated animals were less active in the open field and spent more time in closed arms of the elevated plus maze. The serum corticosterone response to crowding stress in dexamethasone-treated animals was no different from controls, but they demonstrate a delay in return of corticosterone levels to baseline. These differences in behavior and hormonal stress responsiveness suggest that neonatal dexamethasone exposure may permanently alter function of the neuroendocrine stress axis.
Effect of acute exercise and exercise training on VEGF splice variants in human skeletal muscle
Authors: Jensen Lotte , Pilegaard Henriette , Neufer P. Darrell , Hellsten Ylva
Published: May 2004

The present study investigated the effect of an acute exercise bout on the mRNA response of vascular endothelial growth factor (VEGF) splice variants in untrained and trained human skeletal muscle. Seven habitually active young men performed one-legged knee-extensor exercise training at an intensity corresponding to ∼70% of the maximal workload in an incremental test five times/week for 4 wk. Biopsies were obtained from the vastus lateralis muscle of the trained and untrained leg 40 h after the last training session. The subjects then performed 3 h of two-legged knee-extensor exercise, and biopsies were obtained from both legs after 0, 2, 6, and 24 h of recovery. Real-time PCR was used to examine the expression of VEGF mRNA containing exon 1 and 2 (all VEGF isoforms), exon 6 or exon 7, and VEGF165mRNA. Acute exercise induced an increase ( P < 0.05) in total VEGF mRNA levels as well as VEGF165and VEGF splice variants containing exon 7 at 0, 2, and 6 h of recovery. The increase in VEGF mRNA was higher in the untrained than in the trained leg ( P < 0.05). The results suggest that in human skeletal muscle, acute exercise increases total VEGF mRNA, an increase that appears to be explained mainly by an increase in VEGF165mRNA. Furthermore, 4 wk of training attenuated the exercise-induced response in skeletal muscle VEGF165mRNA.
Spontaneous beat-by-beat fluctuations of total peripheral and cerebrovascular resistance in response to tilt
Authors: O'Leary Deborah D. , Shoemaker J. Kevin , Edwards Michael R. , Hughson Richard L.
Published: May 2004

Beat-by-beat estimates of total peripheral resistance (TPR) can be obtained from continuous measurements of cardiac output by using Doppler ultrasound and noninvasive mean arterial blood pressure (MAP). We employed transfer function analysis to study the heart rate (HR) and vascular response to spontaneous changes in blood pressure from the relationships of systolic blood pressure (SBP) to HR (SBP→HR), MAP to total peripheral resistance (TPR) and cerebrovascular resistance index (CVRi) (MAP→TPR and MAP→CVRi), as well as stroke volume (SV) to TPR in nine healthy subjects in supine and 45° head-up tilt positions. The gain of the SBP→HR transfer function was reduced with tilt in both the low- (0.03–0.15 Hz) and high-frequency (0.15–0.35 Hz) regions. In contrast, MAP→TPR transfer function gain was not affected by head-up tilt, but it did increase from low- to high-frequency regions. The phase relationships between MAP→TPR were unaffected by head-up tilt, but, consistent with an autoregulatory system, changes in MAP were followed by directionally similar changes in TPR, just as observed for the MAP→CVRi. The SV→TPR had high coherence with a constant phase of 150–160°. Together, these data that showed changes in MAP preceded changes in TPR, as well as a possible link between SV and TPR, are consistent with complex interactions between the vascular component of the arterial and cardiopulmonary baroreflexes and intrinsic properties such as the myogenic response of the resistance arteries.
Novel method for measuring effects of gas compression on expiratory flow
Authors: Sharafkhaneh Amir , Officer Todd M. , Goodnight-White Sheila , Rodarte Joseph R. , Boriek Aladin M.
Published: May 2004

During forced vital capacity maneuvers in subjects with expiratory flow limitation, lung volume decreases during expiration both by air flowing out of the lung (i.e., exhaled volume) and by compression of gas within the thorax. As a result, a flow-volume loop generated by using exhaled volume is not representative of the actual flow-volume relationship. We present a novel method to take into account the effects of gas compression on flow and volume in the first second of a forced expiratory maneuver (FEV1). In addition to oral and esophageal pressures, we measured flow and volume simultaneously using a volume-displacement plethysmograph and a pneumotachograph in normal subjects and patients with expiratory flow limitation. Expiratory flow vs. plethysmograph volume signals was used to generate a flow-volume loop. Specialized software was developed to estimate FEV1corrected for gas compression (NFEV1). We measured reproducibility of NFEV1in repeated maneuvers within the same session and over a 6-mo interval in patients with chronic obstructive pulmonary disease. Our results demonstrate that NFEV1significantly correlated with FEV1, peak expiratory flow, lung expiratory resistance, and total lung capacity. During intrasession, maneuvers with the highest and lowest FEV1showed significant statistical difference in mean FEV1( P < 0.005), whereas NFEV1from the same maneuvers were not significantly different from each other ( P > 0.05). Furthermore, variability of NFEV1measurements over 6 mo was <5%. We concluded that our method reliably measures the effect of gas compression on expiratory flow.
Maturation of the Na+/H+antiporter (NHE3) in the proximal tubule of the hypothyroid adrenalectomized rat
Authors: Gupta Neena , Dwarakanath Vangipuram , Baum Michel
Published: May 2004

In previous studies examining the role of glucocorticoids and thyroid hormone on the maturation of the Na+/H+antiporter (NHE3), we found attenuation in the maturational increase in proximal tubule apical Na+/H+antiporter activity but no change in NHE3 mRNA abundance in either glucocorticoid-deficient or hypothyroid rats. In addition, prevention of the maturational increase in either hormone failed to totally prevent the maturational increase in Na+/H+antiporter activity. We hypothesized that one hormone played a compensatory role when the other was deficient. The present study examined whether combined deficiency of thyroid and glucocorticoid hormones would completely prevent the maturation of the Na+/H+antiporter. Adrenalectomy was performed in 9-day-old hypothyroid Sprague-Dawley rats, a time before the normal postnatal maturational increase in these hormones occurs. Nine- and 30-day-old adrenalectomized (ADX), hypothyroid rats had comparable NHE3 mRNA abundance, which was 5- to 10-fold less than 30-day-old ADX, hypothyroid rats that received corticosterone-thyroxine replacement and 30-day-old sham control rats ( P < 0.05). Brush-border membrane NHE3 protein abundance was comparable in 9- and 30-day-old ADX, hypothyroid groups and ∼20-fold lower than both the 30-day replacement and 30-day sham groups ( P < 0.05). Similarly, the replacement and sham groups had higher sodium-dependent proton secretion than 9- and 30-day-old ADX, hypothyroid groups ( P < 0.05). We conclude that combined deficiency of both hormones totally prevents the maturational increase in NHE3 mRNA and protein abundance and Na+/H+antiporter activity.
The role of bladder-to-urethral reflexes in urinary continence mechanisms in rats
Authors: Kamo Izumi , Cannon Tracy W. , Conway Deirdre A. , Torimoto Kazumasa , Chancellor Michael B. , de Groat William C. , Yoshimura Naoki
Published: May 2004

Urethral closure mechanisms during passive increments in intravesicular pressure (Pves) were investigated using microtip transducer catheters in urethane-anesthetized female rats. After a block of reflex bladder contractions by spinal cord transection at T8-T9, abruptly raising Pves to 20, 40, or 60 cmH2O for 2 min induced a bladder pressure-dependent contractile response in a restricted portion of the middle urethra (12.5–15 mm from the urethral orifice) that was abolished by cutting the pelvic nerves bilaterally. In pelvic nerve-intact rats, the bilateral transection of either the pudendal nerves, the nerves to the iliococcygeous/pubococcygeous muscles, or the hypogastric nerves significantly reduced (49–74%) the urethral reflex response induced by passive Pves increases, and combined transection of these three sets of nerves totally abolished the urethra-closing responses. In spinal cord-intact rats, similar urethral contractile responses were elicited during Pves elevation (20 or 40 cmH2O) and were also eliminated by bilateral pelvic nerve transection. After spinal cord and pelvic nerve transection, leak point pressures, defined as the pressure inducing fluid leakage from the urethral orifice during passive Pves elevation by either bladder pressure clamping in 2.5-cmH2O steps or direct compression of the bladder, were significantly lowered by 30–35% compared with sham-operated (spinal cord-transected and pelvic nerve-intact) rats. These results indicate that 1) passive elevation of Pves can elicit pelvic afferent nerve-mediated contractile reflexes in the restricted portion of the urethra mediated by activation of sympathetic and somatic nerves and 2) bladder-to-urethral reflexes induced by passive Pves elevation significantly contribute to the prevention of stress urinary incontinence.
Short-term peaks in glucose promote renal fibrogenesis independently of total glucose exposure
Authors: Polhill T. S. , Saad S. , Poronnik P. , Fulcher G. R. , Pollock C. A.
Published: May 2004

Postprandial hyperglycemia is implicated as a risk factor predisposing to vascular complications. This study was designed to assess recurrent short-term increases in glucose on markers of renal fibrogenesis. Human renal cortical fibroblasts were exposed to fluctuating short-term (2 h) increases to 15 mM d-glucose, three times a day over 72 h, on a background of 5 mM d-glucose. To determine whether observed changes were due to fluctuating osmolality, identical experiments were undertaken with cells exposed to l-glucose. Parallel experiments were performed in cells exposed to 5 mM d-glucose and constant exposure to either 15 or 7.5 mM d-glucose. Fluctuating d-glucose increased extracellular matrix, as measured by proline incorporation ( P < 0.05), collagen IV ( P < 0.005), and fibronectin production ( P < 0.001), in association with increased tissue inhibitor of matrix metalloproteinase (MMP) ( P < 0.05). Sustained exposure to 15 mM d-glucose increased fibronectin ( P < 0.001), in association with increased MMP-2 ( P = 0.01) and MMP-9 activity ( P < 0.05), suggestive of a protective effect on collagen matrix accumulation. Transforming growth factor-β1 (TGF-β1) mRNA was increased after short-term (90 min) exposure to 15 mM glucose ( P < 0.05) and after 24-h exposure to 7.5 mM ? ( P < 0.05). Normalization of TGF-β1 secretion occurred within 48 h of constant exposure to an elevated glucose. Fluctuating l-glucose also induced TGF-β1 mRNA and a profibrotic profile, however, to a lesser extent than observed with exposure to fluctuating d-glucose. The results suggest that exposure to fluctuating glucose concentrations increases renal interstitial fibrosis compared with stable elevations in d-glucose. The effects are, in part, due to the inherent osmotic changes.
Adriamycin impairs the contraction of mesangial cells through the inhibition of protein kinase C and intracellular calcium
Authors: Jin Jong-Shiaw , Yao Chen-Wen , Chin Ting-Yu , Chueh Sheau-Huei , Lee Wei-Hwa , Chen Ann
Published: May 2004

The effects of adriamycin on the contractile function of cultured mesangial cells were measured by the changes in planar surface area in response to treatment with agonists. Incubation of mesangial cells with adriamycin (0.2 μg/ml) for 24 h significantly decreased the contractile responses to the calcium channel activator BAY K 8644 (1 μM) and to the PKC activator PMA (1 μM). Intracellular calcium concentration ([Ca2+]i), measured by changes in fura 2 levels in response to ATP (0.1 mM), was significantly inhibited in adriamycin-treated mesangial cells compared with control cells. In the absence of extracellular calcium, treatment with ionomycin (0.1 mM) or thapsigargin (10 μM) resulted in a significantly smaller increase in [Ca2+]iin adriamycin-treated mesangial cells compared with control, suggesting an important role of the endoplasmic reticulum in the effects of adriamycin. Using PKC-specific antibodies, adriamycin significantly decreased the cytosolic and membranous fractions of PKC-α in mesangial cells to 75 ± 6 and 70 ± 12% of control, respectively. The PKC activity of mesangial cells was also significantly inhibited after incubation with adriamycin for 24 h. In conclusion, adriamycin induces hypocontractility of mesangial cells, which may mediate this effect by inhibiting PKC-α and [Ca2+]i.
Satellite cell regulation of muscle mass is altered at old age
Authors: Gallegly Jason C. , Turesky Nicole A. , Strotman Beau A. , Gurley Cathy M. , Peterson Charlotte A. , Dupont-Versteegden Esther E.
Published: May 2004

Muscle mass is decreased with advancing age, likely due to altered regulation of muscle fiber size. This study was designed to investigate cellular mechanisms contributing to this process. Analysis of male Fischer 344 X Brown Norway rats at 6, 20, and 32 mo of age demonstrated that, even though significant atrophy had occurred in soleus muscle by old age, myofiber nuclear number did not change, resulting in a decreased myonuclear domain. Also, the number of centrally located nuclei was significantly elevated in soleus muscle of 32-mo-old rats, correlating with an increase in gene expression of MyoD and myogenin. Whereas total 5′-bromo-2′deoxyuridine (BrdU)-positive nuclei were decreased at older ages, BrdU-positive myofiber nuclei were increased. These results suggest that, with age, loss of muscle mass is accompanied by increased myofiber nuclear density that involves fusion of proliferative satellite cells, resembling ongoing regeneration. Interestingly, centrally located myofiber nuclei were not BrdU labeled. Rats were subjected to hindlimb suspension (HS) for 7 or 14 days and intermittent reloading during HS for 1 h each day (IR) to investigate how aging affects the response of soleus muscle to disuse and an atrophy-reducing intervention. After 14 days of HS, soleus muscle size was decreased to a similar extent at all three ages. However, myofiber nuclear number and the total number of BrdU-positive nuclei decreased with HS only in the young rats. IR was associated with an attenuation of atrophy in soleus muscles of 6- and 20- but not 32-mo-old rats. Furthermore, IR was associated with an increase in BrdU-positive myofiber nuclei only in young rats. These data indicate that altered satellite cell function with age contributes to the impaired response of soleus muscle to an intervention that attenuates muscle atrophy in young animals during imposed disuse.
MCT1 confirmed in rat striated muscle mitochondria
Authors: Butz C. Eric , McClelland Grant B. , Brooks George A.
Published: May 2004

We sought to test the hypothesis that monocarboxylate transporter isoform 1 (MCT1) is the inner mitochondrial membrane lactate/pyruvate transporter, and, as such, contributes to functioning of the intracellular lactate shuttle. However, presence of a mammalian mitochondrially localized MCT1 (mMCT1) has been contested. We sought to confirm by Western blotting the mitochondrial localization of MCT1 in rat cardiac, soleus, and extensor digitorum longus muscles utilizing three different cell fractionation methods and three different antibodies. We performed Western blotting using antibodies to cell membrane glucose transporter isoform GLUT1, inner mitochondrial constituent cytochrome oxidase, the monocarboxylate transporter protein chaperone CD147, as well as custom and commercially available MCT1 antibodies. Western blots demonstrated similar results with each MCT1 antibody and two of three methods of fractionation. MCT1 was found in the mitochondria, as well as in the sarcolemmal membrane and whole muscle homogenates. Probing with GLUT1 and CD147 demonstrated that mitochondrial fractions were not contaminated with sarcolemmal remnants. Probing with cytochrome oxidase showed mitochondrial localization of MCT1. Comparison of these results to the findings of others indicates that the most likely source of discrepancy is the cell fractionation procedure utilized.