bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of hydrographic structure and seasonal run timing on genetic diversity and isolation-by-distance in chum salmon (Oncorhynchus keta)
Authors: Olsen Jeffrey B. , Flannery Blair G. , Beacham Terry D. , Bromaghin Jeffrey F. , Crane Penelope A. , Lean Charles F. , Dunmall Karen M. , Wenburg John K.
Published: September 2008

We used 20 microsatellite loci to compare genetic diversity and patterns of isolation-by-distance among three groups of chum salmon ( Oncorhynchus keta ) from two physically distinct watersheds in western Alaska, USA. The results were consistent with the hypothesis that gene flow decreases as the complexity of the hydrographic system increases. Specifically, higher gene flow was inferred among 11 populations from a nonhierarchical collection of short coastal rivers in Norton Sound compared with 29 populations from a complex hierarchical network of inland tributaries of the Yukon River. Within the Yukon River, inferred gene flow was highest among 15 summer-run populations that spawn in the lower drainage, compared with 14 fall-run populations that spawn in the upper drainage. The results suggest that the complexity of the hydrographic system may influence population connectivity and hence the level of genetic diversity of western Alaska chum salmon. Finally, evidence of isolation-by-time, when controlling for geographic distance, supported the hypothesis that genetic divergence in Yukon River chum salmon is influenced by seasonal run timing. However, evidence of isolation-by-distance, when controlling for season run timing, indicated the populations are not sufficiently isolated, spatially or temporally, to prevent gene flow. Dispersal among summer- and fall-run populations may play a role in maintaining genetic diversity.
Influence of origin on migration and survival of Atlantic salmon (Salmo salar) in the Bay of Fundy, Canada
Authors: Lacroix Gilles L.
Published: September 2008

Atlantic salmon ( Salmo salar ) smolts of wild and hatchery origins (n = 522) were tagged with ultrasonic transmitters and monitored at successive arrays of submerged receivers during migration from five watersheds in three regions of the Bay of Fundy (BoF), Canada. Two of the regions had endangered inner BoF salmon populations. Migration success of postsmolts leaving the BoF varied widely among 13 groups monitored (3%−70%) and was influenced by behaviour and passage time. Region of origin was the key variable in habitat-specific survival models selected using the Akaike information criterion. Rearing origin, migration and release timing, and smolt size were important variables in some habitats. Estimated survival rates (overall and habitat specific) differed markedly among salmon populations of different regions. Mediocre estuarine survival of smolts (0.54) from the outer BoF region affected overall survival (0.66). Poor survival (0.21) in coastal areas of the distant inner BoF region and mediocre survival in other habitats resulted in low overall survival (0.06) that severely limited the potential for population recovery. Potential predators were abundant in habitats where survival was lowest. High survival of salmon from the intermediate inner BoF region in all habitats (0.81–0.93) was not responsible for their failure to return.
Wildfire impacts on nitrogen concentration and production from headwater streams in southern Alberta’s Rocky Mountains
Authors: Bladon Kevin D. , Silins Uldis , Wagner Michael J. , Stone Micheal , Emelko Monica B. , Mendoza Carl A. , Devito Kevin J. , Boon Sarah
Published: September 2008

The objective of this study was to examine initial effects of the 2003 Lost Creek wildfire (southwestern Rocky Mountains of Alberta) on concentrations and production (yield and total export) of several nitrogen (N) forms, and to explore initial recovery of these effects within the first 3 years after the fire. During the first postfire year, nitrate (NO3–), dissolved organic nitrogen (DON), and total nitrogen (TN) concentrations in severely burned watershed streams were 6.5, 4.1, and 5.3 times greater, respectively, than those in reference streams. Weaker effects were evident for concentrations of ammonium (NH4+; 1.5 times) and total particulate nitrogen (TPN; 3.0 times). A rapid decline in mean watershed concentrations and production of NO3–, DON, total dissolved nitrogen (TDN), and TN was observed from burned watersheds over the three seasons after the fire. However, elevated NO3–, TDN, and TN concentrations and production were still evident during the snowmelt freshet and following precipitation events after 3 years. Effects of the burn were strongly influenced by the regional flow regime, with the most elevated N concentrations and production occurring during higher discharge periods (snowmelt freshet and storm flows).
Invasive forest pest surveillance: survey development and reliability
Authors: Coulston John W. , Koch Frank H. , Smith William D. , Sapio Frank J.
Published: September 2008

Worldwide, a large number of potential pest species are introduced to locations outside their native ranges; under the best possible prevention scheme, some are likely to establish one or more localized populations. A comprehensive early detection and rapid-response protocol calls for surveillance to determine if a pest has invaded additional locations outside its original area of introduction. In this manuscript, we adapt and spatially extend a two-stage sampling technique to determine the required sample size to substantiate freedom from an invasive pest with a known level of certainty. The technique, derived from methods for sampling livestock herds for disease presence, accounts for the fact that pest activity may be low at a coarse spatial scale (i.e., among forested landscapes) but high at a fine scale (i.e., within a given forested landscape). We illustrate the utility of the approach by generating a national-scale survey based on a risk map for a hypothetical forest pest species threatening the United States. These techniques provide a repeatable, cost-effective, practical framework for developing broad-scale surveys to substantiate freedom from non-native invasive forest pests with known statistical power.
The influence of fuelbed properties on moisture drying rates and timelags of longleaf pine litter
Authors: Nelson Ralph M. , Hiers J. Kevin
Published: September 2008

Fire managers often model pine needles as 1 h timelag fuels, but fuelbed properties may significantly change the rate at which needles exchange moisture with the atmosphere. The problem of determining whether moisture loss from fine fuels is being controlled by individual particles or by the fuelbed remains unresolved. Results from this laboratory experiment indicate that first-period timelags of longleaf pine ( Pinus palustris Mill.) needles are altered by fuelbed loading and needle arrangement. Timelags of individual needles ranged from 3.3 to 5.3 h; timelags of beds of vertically oriented needles (4.4 to 8.6 h) approximated those of individual particles, but were slightly influenced by loading. Beds of horizontal needles dried with load-dependent timelags that varied from 6.5 to 31.6 h. Fuel loads ranged from 0.04 (for individual particles) to 1.07 kg·m–2. We report a new metric, the area drying rate, which is analogous to a unit-area burning rate. For beds of flat needles, plots of the area drying rate versus fuel load illustrate a transition from control by individual particles to control by the bed structure when fuel loading is approximately 0.33 kg·m–2. Beds of vertical needles were particle controlled. Results should be useful to fire managers when modeling fire behavior.
Pathogen attack and spatial patterns of juvenile mortality and growth in a temperate tree, Prunus grayana
Authors: Seiwa Kenji , Miwa Yoshiko , Sahashi Norio , Kanno Hiroshi , Tomita Mizuki , Ueno Naoto , Yamazaki Miki
Published: September 2008

To examine whether the Janzen–Connell hypothesis is valid in temperate forests, we investigated the density, growth, mortality, and agents of mortality of seedlings and the density, size, and age of saplings of Prunus grayana Maxim. at three distances (0–3, 6–10, and 16–26 m) from conspecific adults in a temperate forest in Japan. An inoculation experiment was also conducted to test the host range of a leaf pathogen. The probability of mortality was highest at 0–3 m during the first 2 years of growth. Mortality mainly resulted from distance-dependent attack by two types of pathogen that caused damping-off epidemics and spot symptoms on leaves. The leaf pathogen was identified as Phaeoisariopsis pruni-grayanae Sawada, which infected many more seedlings of Prunus grayana than of the two other tree species tested in an inoculation experiment. The vertical and diameter growth was lowest at 0–3 m and highest at 16–26 m in both seedlings and saplings. As a result, the greatest number of large and older saplings was observed at 16–26 m. Our results demonstrate that the Janzen–Connell mechanism operates in a beech-dominated forest in the temperate region of Japan.
Genetic variation in direct and indirect measures of wood stiffness in coastal Douglas-fir
Authors: Cherry Marilyn L. , Vikram Vikas , Briggs David , Cress Daniel W. , Howe Glenn T.
Published: September 2008

We studied wood stiffness (estimated by modulus of elasticity, MOE), wood density, wood moisture content, and growth in a progeny test (50–130 families per trait; 1–3 sites) of coastal Douglas-fir ( Pseudotsuga menziesii var. menziesii (Mirb.) Franco). We measured MOE directly using lumber bending tests (MOEbl) and indirectly using tools (HM200 and ST300) that can be used to measure acoustic velocity in logs (VelHM) or standing trees (VelST). Acoustic MOEs in logs and standing trees (MOEHM and MOEST) were obtained from the velocities and green wood density. For backward selection, we estimated genetic gains in MOEbl of 8.6%–12.3%. Relative efficiencies (REs), the relative gains in MOEbl expected from indirect selection for correlated traits, were 78%–93% for the HM200 traits, 57%–58% for the ST300 traits, 38% for the basic wood density of basal discs (Denbd), and 98% for the oven-dry density of logs estimated from the lumber (Denol). The HM200 is an efficient tool for improving MOEbl, but gains will be lower using the ST300 on standing trees. Indirect selection on Denbd should be used with caution because the RE was low and Denbd was negatively correlated with growth (–0.49 to –0.73).
Inverse relationship between understory light and foliar nitrogen along productivity gradients of boreal forests
Authors: Kranabetter J. M. , Simard S. W.
Published: September 2008

The constraints of light and N on sapling growth in forest understories can covary with site productivity, but this reciprocal relationship is not always recognized when describing stand dynamics. To facilitate this, we examined light availability and foliar N status of understory subalpine fir ( Abies lasiocarpa (Hook.) Nutt.) along natural productivity gradients of old-growth boreal forests in British Columbia, Canada. Understory light declined with soil fertility, from a high of 30% of full sun on poor sites to as low as 15% on very rich sites. In contrast, understory foliar N concentration (N%) of subalpine fir increased with soil fertility (ranging from 9.3 to 14.2 g·kg–1) and paralleled asymptotic stand height, despite growing in the shade. Trends in foliar N% of the understory were comparable with overstory subalpine fir, and both increased in foliar N% with soil fertility more so than lodgepole pine ( Pinus contorta Dougl. ex Loud.). Foliar N per unit leaf area of the suppressed understory was fairly consistent and relatively low (approximately 2.0 g N·m–2), suggesting no net change in the resource constraints to growth along the productivity gradient. The inherent linkages between soil fertility, light attenuation, and species N nutrition provides a useful framework for understanding regeneration dynamics over a full range of site potential.
Growth, aerobic metabolism, and dissolved oxygen requirements of embryos and alevins of steelhead, Salmo gairdneri
Authors: Rombough Peter J.
Published: September 2008

Indirect calorimetry was used to estimate metabolic rates and critical dissolved oxygen concentrations for steelhead (Salmo gairdneri) at intervals between fertilization and complete yolk exhaustion at 6, 9, 12, and 15 °C. As well, tissue growth and yolk utilization were monitored. Energy budgets were constructed and the total amount of energy expended on respiration at each temperature estimated. On average, respiration accounted for 43.2% of the energy mobilized up to 90% yolk utilization. Absolute values agreed well with those estimated by integrating measured metabolic rates over the same period, confirming that measured metabolic rates and critical levels were representative of routine metabolism. Equations predicting metabolic rate and tissue mass as functions of time and temperature are given. Metabolic rate increased in virtually direct proportion to increases in tissue mass as indicated by a mean metabolic mass exponent of 1.05. Metabolic intensities averaged 200, 311, 405, and 548 μg O2∙ g wet tissue−1∙ h−1 at 6, 9, 12, and 15 °C, respectively. Critical oxygen concentrations increased continuously during embryonic development. Levels rose from <1 mg∙ L−1 shortly after fertilization to 7.5–9.7 mg∙ L−1, depending on temperature, just before hatch. Levels abruptly dropped by 2–3 mg∙L−1 at hatch and then declined gradually to reach stable levels of 2.3–4.8 mg∙L−1, depending on temperature, midway through the alevin period. Critical levels at all stages increased with increasing temperature as a direct reflection of increased metabolic demand. It is proposed that maximum critical levels (i.e., those just before hatch) be used to define dissolved oxygen criteria for steelhead in natural waters.
Helminth parasites of native frogs (Leiopelmatidae) from New Zealand
Authors: Baker Michael R. , Green David M.
Published: September 2008

The three native frog species of New Zealand were examined for gastrointestinal helminth parasites. Leiopelma hamiltoni was uninfected. Leiopelma hochstetteri was parasitized by the nematodes Aplectana novaezelandiae n.sp. and Cosmocerca australis n.sp. (both Cosmocercidae: Cosmocercinae), and the digenean Dolichosaccus (Lecithopyge) novaezealandiae Prudhoe, 1972 (Telorchiidae: Opisthoglyphinae). Leiopelma archeyi was infected with Cosmocerca archeyi n.sp. The three new cosmocercid species are differentiated readily from congenerics in other parts of the world by caudal features of the males and the shape of the female tail. Cosmocerca archeyi differs from C. australis in the shape of the tail in both males and females, the lack of rosette caudal papillae in males, and the possession of an unusually robust ventral somatic musculature in females. Since the native frogs from New Zealand are believed to have been isolated since the Mesozoic, the presence in them of cosmocercids that fall readily into well-established genera confirms the antiquity of the subfamily Cosmocercinae.
A new genus of neanurid Collembola from continental Southeast Asia
Authors: Deharveng Louis
Published: September 2008

Rambutanura n.gen. is proposed to include the new species Rambutanura yoshiiana n.sp. from Thailand and two other species previously described as Acanthanura dawydoffi Denis, 1934 (from Vietnam) and Womersleya malayana Yosii, 1976 (from Malaysia). The new genus belongs to the subfamily Neanurinae, but it displays a set of atypical characters, such as the differentiation of long tegumentary digitations and strong antennal plurichaetosis. In addition, R. yoshiiana has very large salivary glands in which each lobe gp2 and gp3 contains about 100 cells with highly polytenic nuclei.
Food availability for forest birds: effects of prey distribution and abundance on bird foraging
Authors: Holmes Richard T. , Schultz Jack C.
Published: September 2008

To evaluate availability of food for passerine birds in a northern hardwood forest, we measured the abundance and distribution of Lepidoptera larvae, a major food type, on the foliage of the dominant tree species and the foraging behaviour used by birds to capture prey from foliage substrates. Larval abundances averaged 2.1 per 400-leaf sample, and differed significantly among tree species and strata and within and between years. Although American beech had significantly higher larval densities, yellow birch hosted a greater proportion of free-living larvae, which were more readily available to foraging birds. Most larvae (78–91%) were found on leaf blades, with 62–75% on leaf undersurfaces. Bird species differed significantly in the frequencies at which they attacked prey on different foliage substrates (upper or lower leaf surfaces, petioles, twigs) and tree species. Several changed their foraging patterns from one tree species to another. Six of the 10 bird species directed attacks to substrates in proportion to the abundance of larvae there; the other 4 deviated from this pattern because of preferences for other kinds of prey or because of different abilities to perceive and capture prey from trees with differing foliage structures. Our results suggest that availability of food for forest birds is a function of (i) the types and abundances of prey present, which vary among tree species, (ii) the foliage structure and characteristics of the trees, which influence prey detectability and accessibility, and (iii) the morphological and behavioural abilities of each bird species to perceive and capture those prey. Food availability therefore cannot be assessed by simply measuring prey abundance alone and must essentially be determined separately for each bird species. Since each tree species provides a differing set of foraging opportunities for birds, the mix of tree species at a site, coupled with the arthropod resources they support, will influence which bird species can successfully exploit that habitat and hence will affect bird community structure.
A NEW CNN OSCILLATOR MODEL FOR PARALLEL IMAGE SEGMENTATION
Authors: STRZELECKI MICHAŁ , KOWALSKI JACEK , KIM HYONGSUK , KO SOOHONG
Published: September 2008

Segmentation of the textured images into disjoint homogeneous regions is a very important aspect of visual perception. The texture represents properties of visualized objects; it may provide information about their structure. One of the recently developed tools used for texture segmentation is a network of synchronized oscillators. A parallel network operation is based on a "temporary correlation" theory, which attempts to explain scene recognition as performed by the human brain. This theory states that the synchronized oscillations of neuron groups attract attention if it is focused on a coherent stimulus (image object). For more than one perceived stimulus, these synchronized patterns switch in time between different neuron groups, thus forming temporal maps coding several features of the analyzed scene. Consequently, to implement this theory, a new oscillator network was proposed for image segmentation. The segmentation is obtained due to local interactions among neighboring cells. Such a network was successfully used for segmentation of the wide range of different images, including textured and biomedical ones. The network is very suitable for a hardware realization owing to its parallel structure. The realization provides a much faster image segmentation when compared to computer simulation techniques.

The paper presents a new mathematical oscillator model suitable to be implemented in a CNN network chip. The model was used to design and simulate a CMOS oscillator circuit, which enables parallel network operation. The proposed oscillator model was analyzed and discussed from the point of view of its computer simulations. Furthermore, it was demonstrated that the oscillator network which implements the presented model is able to perform segmentation of the sample textured images. Oscillator circuit and block diagram of the proposed network chip were also presented and discussed.
SYNCHRONIZATION IN LINEARLY COUPLED DYNAMICAL NETWORKS WITH DISTRIBUTED TIME DELAYS
Authors: LI CHUN-HSIEN , YANG SUH-YUH
Published: September 2008

In this paper, we investigate the global exponential synchronization of linearly coupled dynamical networks with time delays. The time delay considered is of the distributed type and the outer-coupling matrix is not assumed to be symmetric. Employing the Lyapunov functional and matrix inequality techniques, we propose a sufficient condition for the occurrence of global exponential synchronization. Two illustrative examples, the coupled Chua's circuits and the coupled Hindmarsh–Rose neurons, and their numerical simulation results are presented to demonstrate the theoretical analyses.
SECURE DATA TRANSMISSION BASED ON MULTI-INPUT MULTI-OUTPUT DELAYED CHAOTIC SYSTEM
Authors: ZHENG G. , BOUTAT D. , FLOQUET T. , BARBOT J.-P.
Published: September 2008

This paper deals with the problem of secure data transmission based on multi-input multi-output delayed chaotic systems. A new multi-input secure data transmission scheme is proposed. Moreover, in order to increase again the robustness of secure data transmission, delays are introduced as a second firewall against known plain-text attack. With this method, the parameters used as secret keys of the system are not identifiable and, as a result, the proposed scheme is robust to known plain-text attacks.
APPLYING BIFURCATION ANALYSIS TO DETERMINE OPTIMAL PLACEMENTS OF MEASUREMENT DEVICES FOR POWER SYSTEM LOAD MODELING
Authors: LI YINHONG , CHIANG HSIAO-DONG , LI HUA , CHEN YUNG-TIEN , HUANG DER-HUA
Published: September 2008

Load modeling is well known to have a significant impact on power system analysis. The task of load modeling, however, is time-consuming and expensive. Accurate load models should be developed for loads at critical locations. In this paper, applying bifurcation analysis, the problem of optimal placements of measurement devices for load model development from the viewpoint of voltage stability analysis is investigated. Voltage instability/collapse is modeled using bifurcation theory first. An optimal placement problem is formulated. An optimal placement identification scheme is proposed and applied to Taiwan power system. Optimal placements of measurement devices are identified. Validation of the selected optimal placements is performed. The robustness of optimal placements under different power transfer patterns is also examined.
MICHELL TRUSSES AND LINES OF PRINCIPAL ACTION
Authors: BOUCHITTÉ GUY , GANGBO WILFRID , SEPPECHER PIERRE
Published: September 2008

We study the problem of Michell trusses when the system of applied equilibrated forces is a vector measure with compact support. We introduce a class of stress tensors which can be written as a superposition of rank-one tensors carried by curves (lines of principal strains). Optimality conditions are given for such families showing in particular that optimal stress tensors are carried by mutually orthogonal families of curves. The method is illustrated on a specific example where uniqueness can be proved by studying an unusual system of hyperbolic PDEs. The questions we address here are of interest in elasticity theory, optimal designs, as well as in functional analysis.
FLUID DYNAMIC LIMITS FOR GAS MIXTURE I: FORMAL DERIVATIONS
Authors: DOGBE CHRISTIAN
Published: September 2008

A macroscopic limit for a binary gas mixture in terms of the Boltzmann system with three small parameters: the Knudsen number, the Mach number and the diameter of particles, is considered in the whole physical space. When the small positive parameter ∊ goes to zero, it is shown that the Boltzmann system results in the compressible Euler equations decoupled with Navier–Stokes equations. In this first part of our paper, the results are of a conditional (formal) nature: both existence of a solution and existence of appropriate limits are assumed.
DISCRETE-MATURITY STRUCTURED MODEL OF CELL DIFFERENTIATION WITH APPLICATIONS TO ACUTE MYELOGENOUS LEUKEMIA
Authors: ADIMY MOSTAFA , CRAUSTE FABIEN , EL ABDLLAOUI ABDERRAHIM
Published: September 2008

We propose and analyze a mathematical model of hematopoietic stem cell dynamics, that takes two cell populations into account, an immature and a mature one. All cells are able to self-renew, and immature cells can be either in a proliferating or in a resting compartment. The resulting model is a system of age-structured partial differential equations, that reduces to a system of delay differential equations, with several distributed delays. We investigate the existence of positive and axial steady states for this system, and we obtain conditions for their stability. Numerically, we concentrate on the influence of variations in differentiation coefficients on the behavior of the system. In particular, we focus on applications to acute myelogenous leukemia, a cancer of white cells characterized by a quick proliferation of immature cells that invade the circulating blood. We show that a blocking of differentiation at an early stage of immature cell development can result in the over-expression of very immature cells, with respect to the mature cell population.
GENERAL DUALITY FOR PERPETUAL AMERICAN OPTIONS
Authors: ALFONSI AURÉLIEN , JOURDAIN BENJAMIN
Published: September 2008

In this paper, we investigate the generalization of the Call-Put duality equality obtained in Alfonsi and Jourdain (preprint, 2006, available at ) for perpetual American options when the Call-Put payoff (y - x)+ is replaced by ϕ(x,y). It turns out that the duality still holds under monotonicity and concavity assumptions on ϕ. The specific analytical form of the Call-Put payoff only makes calculations easier but is not crucial unlike in the derivation of the Call-Put duality equality for European options. Last, we give some examples for which the optimal strategy is known explicitly.
A HYBRID-FORM MODEL FOR THE PREPAYMENT-RISK-NEUTRAL VALUATION OF MORTGAGE-BACKED SECURITIES
Authors: KOLBE ANDREAS , ZAGST RUDI
Published: September 2008

In this paper we present a prepayment-risk-neutral valuation model for fixed-rate Mortgage-Backed Securities. Our model is based on intensity models as used in credit-risk modeling and extends existing models for individual mortgage contracts in a proportional hazard framework. The general economic environment is explicitly accounted for in the prepayment process by an additional factor which we fit to the quarterly GDP growth rate in the US. In our risk-neutral setting we account for both the fears of refinancing understatement and turnover overstatement which sometimes result in higher option-adjusted spreads (OAS) for premiums and discounts respectively. We apply our prepayment-risk-neutral pricing approach to a sample of generic 30yr GNMA MBS pass-throughs from 1996 to 2006. Our empirical results indicate that the GDP growth factor adds explanatory power to the model.
ON CONVOLUTION FOR WAVELET TRANSFORM
Authors: PATHAK R. S. , PATHAK ASHISH
Published: September 2008

A basic function D(x,y,z) associated with the general wavelet transform is defined and its properties are investigated. Using D(x,y,z) associated with the wavelet transform, translation and convolution for this transform are defined and certain existence theorems are proved. An approximation theorem involving wavelet convolution is also proved.
Role of Vector Control in the Global Program to Eliminate Lymphatic Filariasis
Authors: Bockarie Moses J. , Pedersen Erling M. , White Graham B. , Michael Edwin
Published: September 2008

Lymphatic filariasis (LF) is a major cause of acute and chronic morbidity in the tropical and subtropical parts of the world. The availability of safe, single-dose, drug treatment regimens capable of suppressing microfilaremia to very low levels, along with improvements in techniques for diagnosing infection, has resulted in the targeting of this major mosquito-borne disease for global elimination. The Global Program to Eliminate Lymphatic Filariasis (GPELF) was launched in 2000 with the principal objective of breaking the cycles of transmission of Wuchereria bancrofti and Brugia spp. through the application of annual mass drug administrations (MDAs) to entire at-risk populations. Although significant progress in initiating MDA programs in endemic countries has been made, emerging challenges to this approach have raised questions regarding the effectiveness of using MDA alone to eliminate LF without the inclusion of supplementary vector control. Here, we review advances in knowledge of vector ecology, vector-parasite relationships, and both empirical and theoretical evidence regarding vector management to assess the feasibility and strategic value of including vector control in the GPELF initiative to achieve the global elimination of LF.
Dietary resistant starch upregulates total GLP-1 and PYY in a sustained day-long manner through fermentation in rodents
Authors: Zhou June , Martin Roy J. , Tulley Richard T. , Raggio Anne M. , McCutcheon Kathleen L. , Shen Li , Danna Samuel Colby , Tripathy Sasmita , Hegsted Maren , Keenan Michael J.
Published: September 2008

Glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) are anti-diabetes/obesity hormones secreted from the gut after meal ingestion. We have shown that dietary-resistant starch (RS) increased GLP-1 and PYY secretion, but the mechanism remains unknown. RS is a fermentable fiber that lowers the glycemic index of the diet and liberates short-chain fatty acids (SCFAs) through fermentation in the gut. This study investigates the two possible mechanisms by which RS stimulates GLP-1 and PYY secretion: the effect of a meal or glycemic index, and the effect of fermentation. Because GLP-1 and PYY secretions are stimulated by nutrient availability in the gut, the timing of blood sample collections could influence the outcome when two diets with different glycemic indexes are compared. Thus we examined GLP-1 and PYY plasma levels at various time points over a 24-h period in RS-fed rats. In addition, we tested proglucagon (a precursor to GLP-1) and PYY gene expression patterns in specific areas of the gut of RS-fed rats and in an enteroendocrine cell line following exposure to SCFAs in vitro. Our findings are as follows. 1) RS stimulates GLP-1 and PYY secretion in a substantial day-long manner, independent of meal effect or changes in dietary glycemia. 2) Fermentation and the liberation of SCFAs in the lower gut are associated with increased proglucagon and PYY gene expression. 3) Glucose tolerance, an indicator of increased active forms of GLP-1 and PYY, was improved in RS-fed diabetic mice. We conclude that fermentation of RS is most likely the primary mechanism for increased endogenous secretions of total GLP-1 and PYY in rodents. Thus any factor that affects fermentation should be considered when dietary fermentable fiber is used to stimulate GLP-1 and PYY secretion.
Clcn2encodes the hyperpolarization-activated chloride channel in the ducts of mouse salivary glands
Authors: Romanenko Victor G. , Nakamoto Tetsuji , Catalán Marcelo A. , Gonzalez-Begne Mireya , Schwartz George J. , Jaramillo Yasna , Sepúlveda Francisco V. , Figueroa Carlos D. , Melvin James E.
Published: September 2008

Transepithelial Cl−transport in salivary gland ducts is a major component of the ion reabsorption process, the final stage of saliva production. It was previously demonstrated that a Cl−current with the biophysical properties of ClC-2 channels dominates the Cl−conductance of unstimulated granular duct cells in the mouse submandibular gland. This inward-rectifying Cl−current is activated by hyperpolarization and elevated intracellular Cl−concentration. Here we show that ClC-2 immunolocalized to the basolateral region of acinar and duct cells in mouse salivary glands, whereas its expression was most robust in granular and striated duct cells. Consistent with this observation, nearly 10-fold larger ClC-2-like currents were observed in granular duct cells than the acinar cells obtained from submandibular glands. The loss of inward-rectifying Cl−current in cells from Clcn2−/−mice confirmed the molecular identity of the channel responsible for these currents as ClC-2. Nevertheless, both in vivo and ex vivo fluid secretion assays failed to identify significant changes in the ion composition, osmolality, or salivary flow rate of Clcn2−/−mice. Additionally, neither a compensatory increase in Cftr Cl−channel protein expression nor in Cftr-like Cl−currents were detected in Clcn2 null mice, nor did it appear that ClC-2 was important for blood-organ barrier function. We conclude that ClC-2 is the inward-rectifying Cl−channel in duct cells, but its expression is not apparently required for the ion reabsorption or the barrier function of salivary ductal epithelium.
Whole tissue hydrogen sulfide concentrations are orders of magnitude lower than presently accepted values
Authors: Furne Julie , Saeed Aalia , Levitt Michael D.
Published: September 2008

Hydrogen sulfide is gaining acceptance as an endogenously produced modulator of tissue function. The present paradigm of H2S (diprotonated, gaseous form of hydrogen sulfide) as a tissue messenger consists of H2S being released from the desulfhydration of l-cysteine at a rate sufficient to maintain whole tissue hydrogen sulfide concentrations of 30 μM to >100 μM, and these tissue concentrations serve a messenger function. Utilizing physiological concentrations of l-cysteine and aerobic conditions, we found that catabolism of hydrogen sulfide by mouse liver and brain homogenates exceeded the rate of enzymatic release of this compound such that measureable hydrogen sulfide release was less with tissue-containing vs. tissue-free buffers. Analyses of the gas space over rapidly homogenized mouse brain and liver indicated that in situ tissue hydrogen sulfide concentrations were only about 15 nM. Human alveolar air measurements indicated negligible free H2S concentrations in blood. We conclude rapid tissue catabolism of hydrogen sulfide maintains whole tissue brain and liver concentrations of free hydrogen sulfide that are three orders of magnitude less than conventionally accepted values and only 1/5,000 of the hydrogen sulfide concentration (100 μM) required to alter cellular function in vitro. For hydrogen sulfide to serve as an endogenously produced messenger, tissue production and catabolism must result in intracellular microenvironments with a sufficiently high hydrogen sulfide concentration to activate a local signaling mechanism, while whole tissue concentrations remain very low.
Na+/H+exchanger-1 inhibitors decrease myocardial superoxide production via direct mitochondrial action
Authors: Garciarena Carolina D. , Caldiz Claudia I. , Correa María V. , Schinella Guillermo R. , Mosca Susana M. , Chiappe de Cingolani Gladys E. , Cingolani Horacio E. , Ennis Irene L.
Published: September 2008

The possibility of a direct mitochondrial action of Na+/H+exchanger-1 (NHE-1) inhibitors decreasing reactive oxygen species (ROS) production was assessed in cat myocardium. Angiotensin II and endothelin-1 induced an NADPH oxidase (NOX)-dependent increase in anion superoxide (O2−) production detected by chemiluminescence. Three different NHE-1 inhibitors [cariporide, BIIB-723, and EMD-87580] with no ROS scavenger activity prevented this increase. The mitochondria appeared to be the source of the NOX-dependent ROS released by the “ROS-induced ROS release mechanism” that was blunted by the mitochondrial ATP-sensitive potassium channel blockers 5-hydroxydecanoate and glibenclamide, inhibition of complex I of the electron transport chain with rotenone, and inhibition of the permeability transition pore (MPTP) by cyclosporin A. Cariporide also prevented O2−production induced by the opening of mKATPwith diazoxide. Ca2+-induced swelling was evaluated in isolated mitochondria as an indicator of MPTP formation. Cariporide decreased mitochondrial swelling to the same extent as cyclosporin A and bongkrekic acid, confirming its direct mitochondrial action. Increased O2−production, as expected, stimulated ERK1/2 and p90 ribosomal S6 kinase phosphorylation. This was also prevented by cariporide, giving additional support to the existence of a direct mitochondrial action of NHE-1 inhibitors in preventing ROS release. In conclusion, we report a mitochondrial action of NHE-1 inhibitors that should lead us to revisit or reinterpret previous landmark observations about their beneficial effect in several cardiac diseases, such as ischemia-reperfusion injury and cardiac hypertrophy and failure. Further studies are needed to clarify the precise mechanism and site of action of these drugs in blunting MPTP formation and ROS release.
Anti-TNF treatment reduces rat skeletal muscle wasting in monocrotaline-induced cardiac cachexia
Authors: Steffen Brian T. , Lees Simon J. , Booth Frank W.
Published: September 2008

The aim was to explore efficacy of tumor necrosis factor (TNF) inhibitors in attenuating increases in anorexia and ubiquitin proteasome pathway transcripts in cardiac cachexia, a potentially lethal condition that responds poorly to current treatments. Cardiac cachexia was rapidly induced with monocrotaline in Sprague-Dawley rats. Either soluble TNF receptor-1 or the general inhibitor of TNF production, pentoxifylline, was given to diminish TNF action on the first indication of cachexia. Animals were anesthetized with a ketamine-xylazine-acepromazine cocktail, and then skeletal muscles were removed for subsequent measurements including ubiquitin proteasome pathway transcripts and Western blots. Both soluble TNF receptor-1 and pentoxifylline attenuated losses in both body and skeletal muscle masses and also reduced increases in selected ubiquitin proteasome pathway transcripts. The action of soluble TNF receptor-1 was partly through reversal of reduced food consumption, while the effects of pentoxifylline were independent of food intake. Here we demonstrate, for the first time, that attenuation of anorexia by soluble TNF receptor-1 treatment in monocrotaline-induced cardiac cachexia is responsible for attenuating increases in some ubiquitin proteasome pathway transcripts as well as preserving body mass and attenuating loss of skeletal muscle mass.
Selective vulnerability of the inner ear to decompression sickness in divers with right-to-left shunt: the role of tissue gas supersaturation
Authors: Mitchell Simon J. , Doolette David J.
Published: September 2008

Inner ear decompression sickness has been strongly associated with the presence of right-to-left shunts. The implied involvement of intravascular bubbles shunted from venous to arterial circulations is inconsistent with the frequent absence of cerebral symptoms in these cases. If arterial bubbles reach the labyrinthine artery, they must also be distributing widely in the brain. This discrepancy could be explained by slower inert gas washout from the inner ear after diving and the consequent tendency for arterial bubbles entering this supersaturated territory to grow because of inward diffusion of gas. Published models for inner ear and brain inert gas kinetics were used to predict tissue gas tensions after an air dive to 4 atm absolute for 25 min. The models predict half-times for nitrogen washout of 8.8 min and 1.2 min for the inner ear and brain, respectively. The inner ear remains supersaturated with nitrogen for longer after diving than the brain, and in the simulated dive, for a period that corresponds with the latency of typical cases. It is therefore plausible that prolonged inner ear inert gas supersaturation contributes to the selective vulnerability of the inner ear to short latency decompression sickness in divers with right-to-left shunt.
Evidence of skeletal muscle damage following electrically stimulated isometric muscle contractions in humans
Authors: Mackey Abigail L. , Bojsen-Moller Jens , Qvortrup Klaus , Langberg Henning , Suetta Charlotte , Kalliokoski Kari K. , Kjaer Michael , Magnusson S. Peter
Published: September 2008

It is unknown whether muscle damage at the level of the sarcomere can be induced without lengthening contractions. To investigate this, we designed a study where seven young, healthy men underwent 30 min of repeated electrical stimulated contraction of m. gastrocnemius medialis, with the ankle and leg locked in a fixed position. Two muscle biopsies were collected 48 h later: one from the stimulated muscle and one from the contralateral leg as a control. The biopsies were analyzed immunohistochemically for inflammatory cell infiltration and intermediate filament disruption. Ultrastructural changes at the level of the z-lines were investigated by transmission electron microscopy. Blood samples were collected for measurement of creatine kinase activity, and muscle soreness was assessed in the days following stimulation. The biopsies from the stimulated muscle revealed macrophage infiltration and desmin-negative staining in a small percentage of myofibers in five and four individuals, respectively. z-Line disruption was evident at varying magnitudes in all subjects and displayed a trend toward a positive correlation ( r = 0.73, P = 0.0663) with the force produced by stimulation. Increased muscle soreness in all subjects, combined with a significant increase in creatine kinase activity ( P < 0.05), is indirectly suggestive of muscle damage, and the novel findings of the present study, i.e., 1) macrophages infiltration, 2) lack of desmin staining, and 3) z-line disruption, provide direct evidence of damage at the myofiber and sarcomere levels. These data support the hypothesis that muscle damage at the level of the sarcomere can be induced without lengthening muscle contractions.
Molecular Mechanisms of Atherosclerosis in Metabolic Syndrome
Authors: González-Navarro Herminia , Vinué Ángela , Vila-Caballer Marian , Fortuño Ana , Beloqui Oscar , Zalba Guillermo , Burks Deborah , Díez Javier , Andrés Vicente
Published: September 2008

Objective—

The mechanisms underlying accelerated atherosclerosis in metabolic syndrome (MetS) patients remain poorly defined. In the mouse, complete disruption of insulin receptor substrate-2 (
Irs2
) causes insulin resistance, MetS-like manifestations, and accelerates atherosclerosis. Here, we performed human, mouse, and cell culture studies to gain insight into the contribution of defective
Irs2
signaling to MetS-associated alterations.

Methods and Results—

In circulating leukocytes from insulin-resistant MetS patients,
Irs2
and
Akt2
mRNA levels inversely correlate with plasma insulin levels and HOMA index and are reduced compared to insulin-sensitive MetS patients. Notably, a moderate reduction in
Irs2
expression in fat-fed
apolipoprotein E-null
mice lacking one allele of
Irs2
(
apoE
−/−
Irs2
+/−
) accelerates atherosclerosis compared to
apoE-null
controls, without affecting plaque composition. Partial
Irs2
inactivation also increases CD36 and SRA scavenger receptor expression and modified LDL uptake in macrophages, diminishes
Akt2
and
Ras
expression in aorta, and enhances expression of the proatherogenic cytokine MCP1 in aorta and primary vascular smooth muscle cells (VSMCs) and macrophages. Inhibition of AKT or ERK1/2, a downstream target of RAS, upregulates
Mcp1
in VSMCs.

Conclusions—

Enhanced levels of MCP1 resulting from reduced IRS2 expression and accompanying defects in AKT2 and Ras/ERK1/2 signaling pathways may contribute to accelerated atherosclerosis in MetS states.
Differential Role of von Willebrand Factor and P-Selectin on Microvascular Thrombosis in Endotoxemia
Authors: Patel Kavita N. , Soubra Said H. , Bellera Ricardo V. , Dong Jing-Fei , McMullen Colleen A. , Burns Alan R. , Rumbaut Rolando E.
Published: September 2008

Objective—

Endotoxin (lipopolysaccharide [LPS]) enhances microvascular thrombosis in mouse cremaster venules. Because von Willebrand factor (vWF) and P-selectin are suggested to mediate LPS-induced platelet–microvessel interactions, we determined whether vWF and P-selectin contribute to microvascular thrombosis in endotoxemia.

Methods and Results—

A light/dye-induced thrombosis model was used in cremaster microvessels of saline or LPS-injected mice (wild-type, P-selectin–deficient, vWF-deficient, or littermate controls). In each strain except vWF-deficient mice, LPS enhanced thrombosis in venules, resulting in ≈30% to 55% reduction in times to thrombotic occlusion. LPS had no effect on thrombosis in vWF-deficient mice, although these mice had similar systemic responses to LPS (tachycardia, thrombocytopenia, and plasma coagulation markers). vWF-deficient mice demonstrated prolonged times to thrombotic occlusion relative to littermates. LPS increased plasma vWF in each strain studied. While immunofluorescence in wild-type mice failed to detect LPS-induced differences in microvascular vWF expression, it revealed markedly higher vWF expression in venules relative to arterioles.

Conclusions—

vWF mediates light/dye-induced microvascular thrombosis and endotoxin-induced enhancement of thrombosis in mouse cremaster venules; P-selectin is not required for enhanced thrombosis in response to endotoxin. Enhanced vWF expression in venules relative to arterioles has potential implications for the differences in thrombotic responses among these microvessels.
Contribution of Bone Marrow–Derived Cells Associated With Brain Angiogenesis Is Primarily Through CD69
+
Authors: Hao Qi , Liu Jianrong , Pappu Rajita , Su Hua , Rola Radoslaw , Gabriel Rodney A. , Lee Chanhung Z. , Young William L. , Yang Guo-Yuan
Published: September 2008

Objective—

We investigated the role of bone marrow–derived cells (BMDCs) in an angiogenic focus, induced by VEGF stimulation.

Methods and Results—

BM from GFP donor mice was isolated and transplanted into lethally irradiated recipients. Four weeks after transplantation, groups of mice received adeno-associated viral vector (AAV)-VEGF or AAV-lacZ gene (control) injection and were euthanized at 1 to 24 weeks. BMDCs were characterized by double-labeled immunostaining. The function of BMDCs was further examined through matrix metalloproteinase (MMP)-2 and -9 activity. We found that capillary density increased after 2 weeks, peaked at 4 weeks (
P
<0.01), and sustained up to 24 weeks after gene transfer. GFP-positive BMDCs infiltration in the angiogenic focus began at 1 week, peaked at 2 weeks, and decreased thereafter. The GFP-positive BMDCs were colocalized with CD45 (94%), CD68 (71%), 5% Vimentin (5%), CD31/von Willebrand factor (vWF) (1%), and α-smooth muscle actin (α -SMA, 0.5%). Infiltrated BMDCs expressed MMP-9. MMP-9 KO mice confirmed the dependence of the angiogenic response on MMP-9 availability.

Conclusions—

Nearly all BMDCs in the angiogenic focus showed expression for leukocytes, indicating that BMDCs minimally incorporated into the neovasculature. Colocalization of MMPs with GFP suggests that BMDCs play a critical role in VEGF-induced angiogenic response through up-regulation of MMPs.