bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of the Performance of a Custom Program for Image Processing of Pressure Sensitive Film
Authors: Muriuki Muturi G. , Gilbertson Lars G. , Harner Christopher D.
Published: November 2008

A custom program for the processing of pressure sensitive (Fuji) film data is presented and validated in this paper. Some of the shortcomings of previous descriptions of similar programs in literature are addressed. These shortcomings include incomplete descriptions of scan resolution, processing technique, and accuracy of results. Of these, the accuracy of results is the most important and is addressed in this study by using Fuji film calibration data. In Fuji film calibration, known loads are applied to forms with known area. The accuracy of this program and that of the two commercially available image processing programs were determined. The results of the custom program are found to be within 10% of the results from the commercial programs and from experimental data. This level of accuracy is the same reported level of accuracy of Fuji film, verifying the custom program for use in Fuji film contact pressure and area measurements.
Improving Net Joint Torque Calculations Through a Two-Step Optimization Method for Estimating Body Segment Parameters
Authors: Riemer Raziel , Hsiao-Wecksler Elizabeth T.
Published: November 2008

Two main sources of error in inverse dynamics based calculations of net joint torques are inaccuracies in segmental motions and estimates of anthropometric body segment parameters (BSPs). Methods for estimating BSP (i.e., segmental moment of inertia, mass, and center of mass location) have been previously proposed; however, these methods are limited due to low accuracies, cumbersome use, need for expensive medical equipment, and∕or sensitivity of performance. This paper proposes a method for improving the accuracy of calculated net joint torques by optimizing for subject-specific BSP in the presence of characteristic and random errors in motion data measurements. A two-step optimization approach based on solving constrained nonlinear optimization problems was used. This approach minimized the differences between known ground reaction forces (GRFs), such as those measured by a force plate, and the GRF calculated via a top-down inverse dynamics approach. In step 1, a series of short calibration motions was used to compute first approximations of optimized segment motions and BSP for each motion. In step 2, refined optimal BSPs were derived from a combination of these motion profiles. We assessed the efficacy of this approach using a set of reference motions in which the true values for the BSP, segment motion, GRF, and net joint torques were known. To imitate real-world data, we introduced various noise conditions on the true motion and BSP data. We compared the root mean squared errors in calculated net joint torques relative to the true values due to the optimal BSP versus traditionally-derived BSP (from anthropometric tables derived from regression equations) and found that the optimized BSP reduced the error by 77%. These results suggest that errors in calculated net joint torques due to traditionally-derived BSP estimates could be reduced substantially using this optimization approach.
Matrix Metalloproteinase-2 and -9 Are Associated With High Stresses Predicted Using a Nonlinear Heterogeneous Model of Arteries
Authors: Kim Yu Shin , Galis Zorina S. , Rachev Alexander , Han Hai-Chao , Vito Raymond P.
Published: November 2008

Arteries adapt to their mechanical environment by undergoing remodeling of the structural scaffold via the action of matrix metalloproteinases (MMPs). Cell culture studies have shown that stretching vascular smooth muscle cells (VSMCs) positively correlates to the production of MMP-2 and -9. In tissue level studies, the expressions and activations of MMP-2 and -9 are generally higher in the outer media. However, homogeneous mechanical models of arteries predict lower stress and strain in the outer media, which appear inconsistent with experimental findings. The effects of heterogeneity may be important to our understanding of VSMC function since arteries exhibit structural heterogeneity across the wall. We hypothesized that local stresses, computed using a heterogeneous mechanical model of arteries, positively correlate to the levels of MMP-2 and -9 in situ. We developed a model of the arterial wall accounting for nonlinearity, residual strain, anisotropy, and structural heterogeneity. The distributions of elastin and collagen fibers in situ, measured in the media of porcine carotid arteries, showed significant nonuniformities. Anisotropy was represented by the direction of collagen fibers measured by the helical angle of VSMC nuclei. The points at which the collagen fibers became load bearing were computed, assuming a uniform fiber strain and orientation under physiological loading conditions, an assumption motivated by morphological measurements. The distributions of circumferential stresses, computed using both heterogeneous and homogeneous models, were correlated to the distributions of expressions and activations of MMP-2 and -9 in porcine common carotid arteries incubated in an ex vivo perfusion organ culture system under physiological conditions for 48h. While strains computed using incompressibility were identical in both models, the heterogeneous model, unlike the homogeneous model, predicted higher circumferential stresses in the outer layer correlated to the expressions and activations of MMP-2 and -9. This implies that localized remodeling occurs in the areas of high stress and agrees with results from cell culture studies. The results support the role of mechanical stress in vascular remodeling and the importance of structural heterogeneity in understanding mechanobiological responses.
Dynamics of Voluntary Cough Maneuvers: A Theoretical Model
Authors: Naire Shailesh
Published: November 2008

Voluntary cough maneuvers are characterized by transient peak expiratory flows (PEFs) exceeding the maximum expiratory flow-volume (MEFV) curve. In some cases, these flows can be well in excess of the MEFV, generally referred to as supramaximal flows. Understanding the flow-structure interaction involved in these maneuvers is the main goal of this study. We present a simple theoretical model for investigating the dynamics of voluntary cough and forced expiratory maneuvers. The core modeling idea is based on a 1D model of high Reynolds number flow through flexible-walled tubes. The model incorporates key ingredients involved in these maneuvers: the expiratory effort generated by the abdominal and expiratory muscles, the glottis, and the flexibility and compliance of the lung airways. Variations in these allow investigation of the expiratory flows generated by a variety of single cough maneuvers. The model successfully reproduces the transient PEFs, reported in cough studies. The amplitude of the PEFs is shown to depend on the cough generation protocol, the glottis reopening time, and the compliance of the airways. The particular highlight is in simulating supramaximal PEFs for very compliant tubes. The flow-structure interaction mechanisms behind these are discussed. The wave-speed theory of flow limitation is used to characterize the PEFs. Existing hypotheses of the origin of PEFs, from cough and forced expiration experiments, are also tested using this model. This modeling framework could be a first step toward more sophisticated cough models as well as in developing ideas for new bench-top experiments.
Poroviscoelastic Cartilage Properties in the Mouse From Indentation
Authors: Chiravarambath Sidharth , Simha Narendra K. , Namani Ravi , Lewis Jack L.
Published: November 2008

A method for fitting parameters in a poroviscoelastic (PVE) model of articular cartilage in the mouse is presented. Indentation is performed using two different sized indenters and then these data are fitted using a PVE finite element program and parameter extraction algorithm. Data from a smaller indenter, a 15μm diameter flat-ended 60deg cone, is first used to fit the viscoelastic (VE) parameters, on the basis that for this tip size the gel diffusion time (approximate time constant of the poroelastic (PE) response) is of the order of 0.1s, so that the PE response is negligible. These parameters are then used to fit the data from a second 170μm diameter flat-ended 60deg cone for the PE parameters, using the VE parameters extracted from the data from the 15μm tip. Data from tests on five different mouse tibial plateaus are presented and fitted. Parameter variation studies for the larger indenter show that for this case the VE and PE time responses overlap in time, necessitating the use of both models.
Séparation des populations de hareng de l'Atlantique (Clupea harengus harengus) de l'estuaire du Saint-Laurent et de la péninsule gaspésienne
Authors: Côté G. , Lamoureux P. , Boulva J. , Lacroix G.
Published: November 2008

Examination of morphometric and meristic characteristics of Atlantic herring (Clupea harengus harengus) caught during spawning along the Gaspé coast and the St. Lawrence Estuary lead to the conclusion of the existence of at least three herring populations in that area. The first one occurs in the St. Lawrence Estuary, spawns in the spring and is characterized by smaller length-at-age values than the two other populations which are comprised respectively of spring-spawners and autumn-spawners that are fished off the Gaspé peninsula.Key words: Atlantic herring, St. Lawrence Estuary, Gaspé peninsula, morphometric characteristics, meristic characteristics
Oxygen Depletion in Lake Erie: Has There Been Any Change?
Authors: Charlton M. N.
Published: November 2008

A new analysis of hypolimnetic oxygen in Central Lake Erie indicates that historic increases in the apparent depletion were not as great as formerly believed. The differences that did occur were mostly related to variations in hypolimnion thickness. Changes, if any, in the oxygen depletion rate due to eutrophication are as yet too small to be recognized. Present-day oxygen depletion rates, when corrected for the relatively high temperatures in Lake Erie, are within the range thought to be indicative of mesotrophy in small lakes. The general level of oxygen depletion observed in the Central Basin of Lake Erie is expected on the basis of morphology alone.Key words: Lake Erie, oxygen, hypolimnion, oxygen depletion, trend
Role of Gut Flora in the Transfer of Amino Acids Through a Marine Food Chain
Authors: Fong W. , Mann K. H.
Published: November 2008

The gut of the sea urchin Strongylocentrotus droebachiensis has between 2 × 108 and 6 × 109 bacteria/mL of gut contents. When these bacteria are present, radioactive carbon fed to the urchins as either glucose or cellulose appears in all of the protein amino acids of the gonads. However, when the gut flora is suppressed by a mixture of antibiotics, injection of the sea urchins with radioactive glucose results in the labeling of some of the amino acids (nonessential amino acids) but not others (essential amino acids). These results imply that: (a) sea urchins have the ability to digest cellulose, probably with the aid of the gut flora; (b) intestinal microorganisms can synthesize essential amino acids; and (c) amino acids of microbial origin are available to the sea urchins. The amino acid compositions of (i) kelp (Laminaria longicruris), (ii) sea urchin intestinal microflora, and (iii) sea urchins, were determined over a yearly cycle. The amino acid composition of kelp and microbes were compared as a source of nutrient for the sea urchins, using as indications: overall similarity in compositions, essential amino acid index, and percentage of total amino acid that is essential. All three comparative methods show that the microbial protein is of higher nutritive value than the kelp protein.Key words: amino acids, nitrogen, bacteria, kelp, Laminaria longicruris, sea urchin, Strongylocentrotus droebachiensis
A Simple Reflectance Method for the Measurement of Particulate Pigment in Lake Water and its Application to Phosphorus–Chlorophyll–Seston Relationships
Authors: Bergmann Martin , Peters Robert Henry
Published: November 2008

This paper describes a new method to measure total sestonic pigment based on the reduction in the amount of light reflected from a membrane filter after a given volume of lake water has passed through the filter. For a sample of 30 lakes, this index of "reflectance" gave a better regression on total phosphorus than did chlorophyll which suggests that part of the variation in published phosphorus–chlorophyll relationships results from the association of phosphorus with pigments other than chlorophyll. But the residual variation suggests both that the amount of pigment developed per unit of phosphorus varies among lakes and that the index does not completely represent the seston. Relationships between reflectance and concentration of chlorophyll, phosphorus, and seston are good enough to suggest that this rapid, easy analysis may find application as an adjunct to more traditional analyses whereever membrane filters are routinely used in the analysis of lake water.Key words: Total pigment analysis, seston, phosphorus–chlorophyll
A Motion for the Retirement of the Von Bertalanffy Function
Authors: Roff Derek A.
Published: November 2008

The reasons for the continued use of the von Bertalanffy equation are examined. It is suggested that these reasons are insufficient to overcome the drawbacks of this function and alternative procedures are recommended.Key words: von Bertalanffy, growth, yield per recruit
The River Continuum Concept
Authors: Vannote Robin L. , Minshall G. Wayne , Cummins Kenneth W. , Sedell James R. , Cushing Colbert E.
Published: November 2008

From headwaters to mouth, the physical variables within a river system present a continuous gradient of physical conditions. This gradient should elicit a series of responses within the constituent populations resulting in a continuum of biotic adjustments and consistent patterns of loading, transport, utilization, and storage of organic matter along the length of a river. Based on the energy equilibrium theory of fluvial geomorphologists, we hypothesize that the structural and functional characteristics of stream communities are adapted to conform to the most probable position or mean state of the physical system. We reason that producer and consumer communities characteristic of a given river reach become established in harmony with the dynamic physical conditions of the channel. In natural stream systems, biological communities can be characterized as forming a temporal continuum of synchronized species replacements. This continuous replacement functions to distribute the utilization of energy inputs over time. Thus, the biological system moves towards a balance between a tendency for efficient use of energy inputs through resource partitioning (food, substrate, etc.) and an opposing tendency for a uniform rate of energy processing throughout the year. We theorize that biological communities developed in natural streams assume processing strategies involving minimum energy loss. Downstream communities are fashioned to capitalize on upstream processing inefficiencies. Both the upstream inefficiency (leakage) and the downstream adjustments seem predictable. We propose that this River Continuum Concept provides a framework for integrating predictable and observable biological features of lotic systems. Implications of the concept in the areas of structure, function, and stability of riverine ecosystems are discussed.Key words: river continuum; stream ecosystems; ecosystem structure, function; resource partitioning; ecosystem stability; community succession; river zonation; stream geomorphology
A General Theory for Analysis of Catch and Effort Data
Authors: Schnute Jon
Published: November 2008

This paper presents a general theory for analysis of catch and effort data from a fishery. Almost all previous methods are shown to be special cases, including those of Schaefer, Pella and Tomlinson, Schnute, and Deriso, as well as the stock reduction analysis technique of Kimura and Tagart and Kimura, Balsiger, and Ito. Like that of Deriso, the theory here is based on natural equations for an age structured population. However, instead of a fixed single model, this paper gives a general model that can be tailored to any particular fishery. The problem of determining the appropriate special case is conceptually identical to the model identification problem described by Box and Jenkins in the context of time series analysis, Identification necessarily begins with a suitable class of models. This paper defines such a class, unique to fisheries, complete with mathematical proofs and biological explanations of all important equations.
Discrimination d'un stock de poisson, l'anguille (Anguilla rostrata), basée sur la présence d'un produit chimique de synthèse, le mirex
Authors: Dutil J.-D. , Légaré B. , Desjardins C.
Published: November 2008

Mirex concentrations were measured in eels (Anguilla rostrata) from eastern Canada to determine the contribution of Lake Ontario eels to the Saint Lawrence commercial fishery. Mirex could be detected in all eels (50 specimens) collected in Lake Ontario (0.18 ± 0.11 μg∙g−1). Most sedentary eels collected from the Saint Lawrence commercial fishery and both the migratory and sedentary eels collected from the Saint Lawrence tributaries and the Maritimes had no mirex. Of the migrating eels collected in the Saint Lawrence 74% contained mirex (0.17 ± 0.19 μg∙g−1). These results show that stocks can be discriminated on the basis of the presence of synthetic chemical products such as pesticides and other contaminants that are distributed heterogeneously in the environment. Based on a presence–absence criterion, this method for stock discrimination has the distinct advantage that it is more accurate and less time consuming than similar methods based on the presence of natural chemical products.
Estimation of Harp Seal (Phoca groenlandica) Pup Production from Age Samples
Authors: Cooke Justin G.
Published: November 2008

A simple numerical example shows that previously used procedures such as the "survival index" method for estimating the pup production in populations of harp seals (Phoca groenlandica) from samples of aged adults are unreliable because of their poor mathematical formulation. A corrected formulation, based on a maximum likelihood criterion, performed well in simulations tests. This was applied to age data from the Northwest Atlantic harp seal stock to obtain revised pup production estimates. A method to correct for the effects of errors in ageing also performed favourably in simulation trials.
Water Circulation in Small Arctic Lakes in Winter
Authors: Welch Harold E. , Bergmann Martin A.
Published: November 2008

Dye experiments and detailed measurements of conductance and temperature in small lakes at Saqvaqjuac (63°39′N, 90°39′W), showed how water circulated in midwinter. Stored heat returning from the sediments warms adjacent water, which then sinks downslope. Water immediately beneath the ice moves laterally shoreward, picking up cryoconcentrated salts and sinking downslope. Displacement of deep waters upward at the lake center is postulated as completing the circulation. Rates of water movement are on the order of 10 m∙d−1 in 2- to 10-ha lakes. This type of winter circulation is expected to be ubiquitous throughout the arctic.
Winter Respiration of Lakes at Saqvaqjuac, N.W.T.
Authors: Welch Harold E. , Bergmann Martin A.
Published: November 2008

Winter oxygen consumption rates at64°N latitude were measured for 11 lake years. They ranged from 0.131 to 0.306 g O2∙m−2∙d−1. They were not correlated with lake depth, in contrast with the winter respiration rates of temperate lakes. We suggest that this difference results from lower summer temperatures and a lower proportion of planktonic respiration in arctic as compared with temperate lakes. C estimates of annual photosynthesis were generally lower than estimated annual respiration, and the 14C-measured photosynthesis beneath the ice in late winter was generally too low to account for the actual amounts of oxygen evolved by photosynthesis. In one lake, a 50% increase in annual production resulted in an increase of only 19% in winter respiration, suggesting that lake respiration is an integrative process that averages out production over a period of years. Addition of methane gas to simulate a gas pipeline break to a lake resulted in an immediate 67% increase in lake respiration rate.
Rates of Food Exploitation by Littoral Fishes in a Mesotrophic North-Temperate Lake
Authors: Boisclair D. , Leggett W. C.
Published: November 2008

The relationship between the biomass of food consumed by the littoral zone fish community of Lake Memphremagog, Quebec, and the total biomass of littoral zone food present was estimated on a daily and annual basis. The dominant food consumed were benthic invertebrates followed by forage fishes and plankton. The daily geometric mean exploitation rate was 0.55% of the total dry weight food biomass in the littoral zone. The corresponding annual rate was 72%. Energy equivalents were 0.81% (daily) and 105% (annual). When benthic invertebrate biomass values were adjusted to more accurately reflect availability (on the basis of depth distribution in the sediments and size) the geometric mean dry weight exploitation rates were 0.80% (daily) and 104% (annual). Corresponding energy rates were 1.15% (daily) and 150% (annual). These rates are significantly lower than reported benthic P/B ratios for 21 north-temperate lakes. These data indicate that littoral zone fishes crop only a very small fraction of the food biomass in the littoral zone. We conclude that the behaviors of both predator and prey act to limit the available fraction of the total food biomass and predict that the ratio of available to total food biomass in the littoral zone of north-temperate lakes will approximate 1%. This is consistent with existing empirical models linking fish production/biomass with biomass at lower trophic levels.
Water Temperature as the Primary Influence on Timing of Seaward Migrations of Atlantic Salmon (Salmo salar) Smolts
Authors: Jonsson Bror , Ruud-Hansen Jan
Published: November 2008

Using multiple regression models we tested if water temperature, water flow, cloudiness, and lunar cycle were significantly correlated with the timing of the yearly descent of Atlantic salmon (Salmo salar) smolts in the Norwegian Imsa River, 1976–83. Water temperature between 9 April and 16 May explained 91, 95, and 89% of the yearly variation in date of 25, 50, and 75% cumulative smolt descent, respectively. The regression models were not very sensitive to variations of which date we started and stopped recording the temperature. The start of the yearly smolt run was not triggered by a specific water temperature or a specific number of degree-days, but was controlled by a combination of temperature increase and temperature level in the river during spring. There was no significant correlation between smolt descent and any of the other environmental variables tested.
Breeding Tubercles in Three Species of Gadus (Cods)
Authors: Vladykov Vadim D. , Renaud Claude B. , Laframboise Sylvie
Published: November 2008

Breeding tubercles in Gadus are described for the first time. Each of the three known species of Gadus displays specific peculiarities: in G. ogac, tubercles are numerous, long, and club-shaped; in G. morhua, tubercles are numerous, medium in length, and horn-shaped; and in G. macrocephalus, tubercles are few and very small. These breeding tubercles may be used for taxonomic purposes. It is probable that the tubercles may serve to maintain contact during the reproductive period.
Temps d'ajustement de la flottabilité des saumons atlantiques (Salmo salar) d'élevage et flottabilité comparée de saumons atlantiques d'élevage et sauvages
Authors: Legault Michel , Lalancette Louis-Marie
Published: November 2008

We determined the time of adjustment of buoyancy of juvenile hatchery-reared Atlantic salmon (Salmo salar) and investigated whether if their higher position off the substratum, compared with wild fish, might better result from a higher buoyancy. In flowing water, hatchery-reared Atlantic salmon adjust their buoyancy within 24 h. No difference in buoyancy exists between juvenile hatchery-reared and wild Atlantic salmon in still water. However, juvenile hatchery-reared Atlantic salmon are more buoyant in flowing water than wild Atlantic salmon. Even after 3 mo in a stream, the buoyancy of juvenile hatchery-reared Atlantic salmon did not change. Acquired hatchery behaviour appears to be responsible for their difference in buoyancy.
Phosphate Uptake Rates of Phytoplankton Assemblages Grown at Different Dilution Rates in Semicontinuous Culture
Authors: Suttle C. A. , Harrison P. J.
Published: November 2008

We studied the effects of pulsed nutrient supplies on the physiology of natural phytoplankton assemblages. A natural phytoplankton community, from an oligotrophic lake, was grown at several dilution rates from 0.1 to 1.5∙d−1in P-limited semicontinuous cultures. Particulate C:P and N:P ratios (by atoms) were approximately 300:1 and 50:1, respectively, at the lowest dilution rate and 40:1 and 7:1, respectively, at the highest dilution rate. This demonstrates that a range of P-limited conditions can be established using the semicontinuous culturing technique. The time-course of uptake, in response to a saturating addition of phosphate, revealed that there was a short lag before maximum rates of uptake were observed at all but the highest dilution rate, and that maximum uptake rates over the first 30 min of incubation were higher at intermediate dilution rates. Subsequent to the maximum uptake rate occurring, the relationship between uptake rate and time was species dependent. In Oscillatoria sp. dominated cultures the uptake rates declined with increasing cellular P, and the rates of these declines increased with dilution rate; in Synechococcus sp. dominated cultures the uptake rates remained constant and were independent of cellular P.
Does Orthophosphate Uptake Supply Sufficient Phosphorus to Phytoplankton to Sustain Their Growth?
Authors: Currie David J.
Published: November 2008

It is generally supposed that phytoplankton obtain their P predominantly from orthophosphate uptake. Yet, phytoplankton are often observed to be responsible for only a very small fraction of the total planktonic community uptake of orthophosphate. Is this uptake of orthophosphate by algae nonetheless sufficient to meet their metabolic needs? To answer this question, I have compared the specific doubling rates of C and of P through orthophosphate uptake in the phytoplankton community of Lake Memphremagog. Orthophosphate uptake during the growing season supplied only a very small portion of the P required to support algal growth. Presumably, the phytoplankton obtained their P from some source other than orthophosphate uptake. Similar patterns of orthophosphate uptake in other P-limited lakes suggest that this phenomenon may be widespread.
Effects of pH on the Toxicities of Cadmium, Copper, and Zinc to Steelhead Trout (Salmo gairdneri)
Authors: Cusimano Robert F. , Brakke David F. , Chapman Gary A.
Published: November 2008

Increased metal concentrations have been associated with freshwater acidification. Continuous-flow acute toxicity tests were conducted in soft water to determine the effect of pH on the toxicity of cadmium, copper, and zinc to small (1–6 g) steelhead trout (Salmo gairdneri). LC50 values were calculated for 96- and 168-h exposure periods in waters of pH 4.7, 5.7, and 7.0. Test fish were significantly more tolerant of the metals at the lowest pH value than at higher pH's. The 96-h LC50 values at pH 4.7, 5.7, and 7.0 were 671, 97, and 66 μg∙L−1 for zinc, 66.0, 4.2, and 2.8 μg∙L−1 for copper, and 28.0, 0.7, and < 0.5 μg∙L−1 for cadmium, respectively. The 168-h results were similar to the 96-h values. These results indicate that for the metals tested, toxicity is ameliorated in depressed pH waters over short exposure periods, such as may occur during snowmelt runoff. The possibility of hydrogen ion interference with metal uptake is postulated.
Loss of Lampricides by Adsorption on Bottom Sediments
Authors: Dawson V. K. , Johnson D. A. , Allen J. L.
Published: November 2008

Problems have been encountered in maintaining effective concentrations of the lampricides 3-trifluoromethyl-4-nitrophenol (TFM) and 5,2′-dichloro-4′-nitrosalicylanilide (Bayer 73) during treatments of certain Great Lakes tributaries. Concentrations of Bayer 73 decreased by more than 80% in a portion of the Ford River, Michigan, during treatment in 1980. Adsorption of Bayer 73 on sediments was hypothesized as the primary mechanism of this excessive loss. Subsequent laboratory studies demonstrated that lampricides are adsorbed by silt-type sediments that are high in organic content, including those collected from the treated portion of the Ford River. Un-ionized lampricides (acidic solution) were more readily adsorbed than ionized forms (basic solution). Adsorption onto sediments was proportionally greater, and desorption proportionally less, for Bayer 73 than for TFM. When Ford River sediments were mixed with lampricide-free water, less than 10% of the adsorbed Bayer 73, but more than 60% of the TFM, was released. The extensive adsorption of the lampricides (especially Bayer 73) from solution by silt-type sediments explains much of the loss of effective concentrations in certain streams.
Locomotor Activity and Blood Plasma Parameters of Acid-Exposed Lake Whitefish, Coregonus clupeaformis
Authors: Scherer E. , Harrison S. E. , Brown S. B.
Published: November 2008

In laboratory experiments, lake whitefish (Coregonus clupeaformis) were exposed to acidified water of pH 5.0 4.7, 4.4, and 4.1 for 2 wk; controls were held at pH 7.6. Continuous recordings of locomotor activity over 4 days and nights at the end of each treatment showed a consistent trend towards reduced daytime activity and loss of diel rhythmicity with increasing ambient acidity. Feeding was observed to decrease at pH 4.7, and to cease at pH 4.4 and 4.1. Associated with these behavioral effects were changes of blood plasma variables. Plasma cortisol and glucose levels increased with lowered pH; sodium, chloride, and their fractional contribution to osmolality decreased.
Trophic Relationships in Freshwater Pelagic Ecosystems
Authors: McQueen Donald J. , Post John R. , Mills Edward L.
Published: November 2008

Relative impacts of bottom-up (producer controlled) and top-down (consumer controlled) forces on the biomass and size structure of five major components of freshwater pelagic systems (piscivores, planktivores, zooplankton, phytoplankton, and total phosphorus availability) were estimated. Predictions that emerge are (1) maximum biomass at each trophic level is controlled from below (bottom-up) by nutrient availability, (2) this bottom-up regulation is strongest at the bottom of the food web (i.e. phosphorus → phytoplankton) and weakens by a factor of 2 with each succeeding step up the food web, (3) as energy moves up a food web, the predictability of bottom-up interactions decreases, (4) near the top of the food web, top-down (predator mediated) interactions are strong and have low coefficients of variation, but weaken with every step down the food web, (5) variability around the bottom-up regressions can always be explained by top-down forces, and (6) interplay between top-down and bottom-up effects changes with the trophic status of lakes. In eutrophic lakes, top-down effects are strong for piscivore → zooplankton, weaker for planktivore → zooplankton, and have little impact for zooplankton → phytoplankton. For oligotrophic lakes, the model predicts that top-down effects are not strongly buffered, so that zooplankton → phytoplankton interactions are significant.
Fecundity and Egg Retention of Some Sockeye Salmon (Oncorhynchus nerka) Stocks in British Columbia
Authors: Manzer J. I. , Miki I.
Published: November 2008

The fecundity and egg retention of anadromous female sockeye salmon (Oncorhynchus nerka) collected during 1971–82 from several stocks in British Columbia undergoing controlled fertilization to enhance adult sockeye production were examined. The relationship between egg number and postorbital–hypural length based on 863 females representing 14 stocks was not consistent between all age-types, stocks, and years, probably because of inadequate sample size in some instances. Combined samples, however, revealed a significant positive relationship between postorbital–hypural length and egg number for age 1.2, 1.3, and 2.2 females. Mean absolute fecundity for the respective age-types was 3218, 4125, and 3544 eggs. For samples of 10 or more females, significant stock and annual differences were detected when individual mean absolute fecundity was adjusted to a postorbital–hypural length of 447 mm, but not for females of different age. A comparison of mean fecundities for coastal stocks with historical data for interior British Columbia stocks suggests that coastal stocks are 18% more fecund than interior stocks. Possible causal mechanisms for this regional difference are hypothesized. Examination of 796 carcasses (representing five stocks) for egg retention revealed a range from totally spawned to totally unspawned females, with 56% of the carcasses containing 20 eggs or less and 68% containing 50 eggs or less. The mean egg retention based on all samples combined was estimated to be 6.5% of the mean individual fecundity. This value was reduced to 3.9% when stock means were averaged.
Trypsin from Two Strains of Rainbow Trout, Salmo gairdneri, is Influenced Differently by Assay and Acclimation Temperature
Authors: McLeese J. M. , Stevens E. Don
Published: November 2008

Specific activity and kinetic constants of trypsin from the pyloric caeca of two strains of rainbow trout, Salmo gairdneri, were measured using α-N-benzoyl-DL-arginine-ρ-nitroaniline∙HCl No increase in activity was observed with cold acclimation, suggesting that cold acclimation induces no increase in trypsin concentration. The apparent Km for the substrate was independent of assay temperature over the physiological range in both strains, probably to maintain high rates of catalysis at higher temperatures when nutrient requirements are high. Strain A trout produced a trypsin with lower affinity on cold acclimation, but Strain B trout did not. The two strains differed in intestinal morphology as well as in the characteristics of their trypsins.
Susceptibility of Brook Trout (Salvelinus fontinalis) Fry to a Liquid Formulation of Bacillus thuringiensis serovar. israelensis (Teknar®) Used for Blackfly Control
Authors: Fortin C. , Lapointe D. , Charpentier G.
Published: November 2008

Exposure of brook trout (Salvelinus fontinalis) fry to 4500 and 6000 mg Teknar®∙L−1 for 45 min resulted in 20 and 86.4% mortality, respectively. At concentrations of 3000 mg∙L−1 and higher, fish became motionless and exhibited variable recovery within 2 h following contact, depending on concentration. Fish exposed to 6000 mg freeze-dried Teknar∙L−1, were not affected. Forty-eight hours of static exposure resulted in 1.33% mortality at 60 mg∙L−1, no mortality at 300 mg∙L−1, and 8% mortality for the controls; degradation of water quality may explain this response. Gas chromatographic analysis revealed the presence of 2% xylene in the formulation. Fish fed with chow contaminated with 30% (w/w) Teknar did not show any response. Considering the recovery and the absence of effects in 48-h static tests, the feeding test, and exposure to the freeze-dried formulation, we attribute the observed response to the effect of xylene a preservative agent of the formulation tested.
ALGEBRAIC STRUCTURE OF A MASTER EQUATION WITH GENERALIZED LINDBLAD FORM
Authors: FUJII KAZUYUKI
Published: November 2008

The quantum damped harmonic oscillator is described by the master equation with usual Lindblad form. The equation has been solved completely by us in arXiv: 0710.2724 [quant-ph]. To construct the general solution a few facts of representation theory based on the Lie algebra su(1,1) were used.

In this paper we treat a general model described by a master equation with generalized Lindblad form. Then we examine the algebraic structure related to some Lie algebras and construct the interesting approximate solution.
INTEGRABLE SYSTEMS DETERMINED BY DIFFERENTIAL FORMS FOR MOVING FRAMES ON IMMERSED SUBMANIFOLDS
Authors: BRACKEN PAUL
Published: November 2008

It is shown how a system of differential forms can reproduce the complete set of differential equations generated by an SO(m) matrix Lax pair. By selecting the elements in the given matrices appropriately, examples of integrable nonlinear equations can be produced. The SO(3) case is discussed in detail, then extended to an m - 1 dimensional manifold immersed in Euclidean space.
ON A SYSTEMATIC APPROACH TO DEFECTS IN CLASSICAL INTEGRABLE FIELD THEORIES
Authors: CAUDRELIER V.
Published: November 2008

We present an inverse scattering approach to defects in classical integrable field theories. Integrability is proved systematically by constructing the generating function of the infinite set of modified integrals of motion. The contribution of the defect to all orders is explicitely identified in terms of a defect matrix. The underlying geometric picture is that those defects correspond to Bäcklund transformations localized at a given point. A classification of defect matrices as well as the corresponding defect conditions is performed. The method is applied to a collection of well-known integrable models and previous results are recovered (and extended) directly as special cases. Finally, a brief discussion of the classical r-matrix approach in this context shows the relation to inhomogeneous lattice models and the need to resort to lattice regularizations of integrable field theories with defects.
EXTENDED ABSOLUTE PARALLELISM GEOMETRY
Authors: YOUSSEF NABIL. L. , SID-AHMED A. M.
Published: November 2008

In this paper, we study Absolute Parallelism (AP-) geometry on the tangent bundle TM of a manifold M. Accordingly, all geometric objects defined in this geometry are not only functions of the positional argument x, but also depend on the directional argument y. Moreover, many new geometric objects, which have no counterpart in the classical AP-geometry, emerge in this different framework. We refer to such a geometry as an Extended Absolute Parallelism (EAP-) geometry.

The building blocks of the EAP-geometry are a nonlinear connection (assumed given a priori) and 2n linearly independent vector fields (of special form) defined globally on TM defining the parallelization. Four different d-connections are used to explore the properties of this geometry. Simple and compact formulae for the curvature tensors and the W-tensors of the four defined d-connections are obtained, expressed in terms of the torsion and the contortion tensors of the EAP-space.

Further conditions are imposed on the canonical d-connection assuming that it is of Cartan type (resp. Berwald type). Important consequences of these assumptions are investigated. Finally, a special form of the canonical d-connection is studied under which the classical AP-geometry is recovered naturally from the EAP-geometry. Physical aspects of some of the geometric objects investigated are pointed out and possible physical implications of the EAP-space are discussed, including an outline of a generalized field theory on the tangent bundle TM of M.
Depot-specific adipocyte cell lines reveal differential drug-induced responses of white adipocytes—relevance for partial lipodystrophy
Authors: Kovsan Julia , Osnis Alexander , Maissel Adva , Mazor Livnat , Tarnovscki Tanya , Hollander Liat , Ovadia Shira , Meier Britta , Klein Johannes , Bashan Nava , Rudich Assaf
Published: November 2008

Intra-abdominal (IA) fat functionally differs from subcutaneous (SC) adipose tissue, likely contributing to its stronger association with obesity-induced morbidity and to differential response to medications. Drug-induced partial lipodystrophy, like in response to antiretroviral agents, is an extreme manifestation of the different response of different fat depots, with loss of SC but not IA. Investigating depot-specific adipocyte differences is limited by the low accessibility to IA fat and by the heterogenous cell population comprising adipose tissue. Here, we aimed at utilizing immortalized preadipocyte cell lines from IA (epididymal) or SC (inguinal) fat to investigate whether they differentially respond to the HIV protease inhibitor nelfinavir. Preadipocytes were readily amenable to adipogenesis, as evidenced by lipid accumulation, expression of adipose-specific genes, measurable lipolysis, and insulin responsiveness. Leptin secretion was higher by the SC line, consistent with known differences between IA and SC fat. As previously reported, nelfinavir inhibited adipogenesis downstream of C/EBPβ, but similarly in both cell lines. In contrast, nelfinavir's capacity to diminish insulin signaling, decrease leptin secretion, enhance basal lipolysis, and decrease expression of the lipid droplet-associated protein perilipin occurred more robustly and/or at lower nelfinavir concentrations in the SC line. This was despite similar intracellular concentrations of nelfinavir (23.8 ± 5.6 and 33.6 ± 12.2 μg/mg protein for inguinal and epididymal adipocytes, respectively, P = 0.46). The cell lines recapitulated depot-differential effects of nelfinavir observed in differentiated primary preadipocytes and with whole tissue explants. Thus, we report the use of fat depot-specific adipocyte cell lines for unraveling depot-differential responses to a drug causing partial lipodystrophy.
Cortisol infusion in late-gestation hypothalamo-pituitary disconnected sheep fetus restores pituitary cell responsiveness to arginine vasopressin
Authors: Carey Luke C. , Tatter Stephen B. , Rose James C.
Published: November 2008

Corticotrophs in the fetal sheep become increasingly responsive to arginine vasopressin (AVP) in late gestation. We previously reported that this may be due in part to corresponding increases in signal transduction (inositol 1,4,5-trisphosphate, IP3). These ontogenic changes are prevented by hypothalamo-pituitary disconnection (HPD), which also prevents fetal plasma cortisol concentrations from increasing in late gestation. This led us to hypothesize that cortisol is involved in mediating the changes in pituitary responsiveness. HPD was performed on fetal sheep at 120 days gestational age (dGA). Half of the HPD fetuses were infused with cortisol for 3 days beginning at 135–137 dGA (HPD+C). The remaining HPD fetuses and a group of sham-operated control fetuses were infused with saline. Pituitary cells were isolated and cultured. After 48 h, a subset of cells was stimulated with 100 nM AVP for 2 h, and the medium was collected for ACTH analysis. Another subset of cells was stimulated with 100 nM AVP for 30 min, and the formation of IP3was determined. Plasma cortisol concentrations increased rapidly within the first 6 h after infusion (5.2 ± 1.9 to 29.7 ± 4.9 ng/ml) but did not increase thereafter. Cells from HPD+C and sham-operated fetuses secreted significantly more ACTH than those from HPD fetuses (% increase from control: 33.0 ± 8.8%, 47.9 ± 10.6%, and 11.9 ± 2.4%, respectively). IP3formation was significantly increased in cells from HPD+C and sham-operated compared with HPD fetuses (% increase from control: 17.7 ± 4.4%, 18.9 ± 4.3%, and 4.6 ± 1.5%, respectively). These findings support the idea that cortisol plays a role in mediating the increase in pituitary responsiveness to AVP in the late-gestation fetal sheep.
Postnatal ontogeny of intestinal GCPII and the RFC in pig
Authors: Shafizadeh Tracy B. , Halsted Charles H.
Published: November 2008

In humans and pigs, hydrolysis of dietary polyglutamyl folates is carried out by intestinal brush border folate hydrolase [glutamate carboxypeptidase II (GCPII)], whereas the transport of the monoglutamyl folate derivatives occurs via the intestinal brush border reduced folate carrier (RFC). The study objective was to measure the expression of intestinal GCPII and RFC during postnatal development of pigs and their effects on plasma and liver folate concentrations. Duodenum, jejunum, ileum, liver, and plasma samples were collected from female Yorkshire pigs at birth, 24 h, 1 wk, 3 wk, and 6 mo ( n = 6 at each time point). GCPII mRNA transcripts and protein (normalized using β-actin), and enzyme activity (normalized per mg mucosal protein) were highest in all segments of small intestine at birth and were undetectable in ileum after 1 wk, whereas jejunal protein and activity predominated at 6 mo. RFC mRNA transcripts were present in all segments of small intestine at birth and declined significantly throughout development to 6 mo. Conversely, RFC protein increased twofold during the first 24 h and remained constant throughout development in all segments of small intestine. Liver RFC mRNA transcripts were detected at birth but were reduced by 6 mo. Liver folate concentration increased throughout postnatal development, whereas plasma folate levels increased during the first 24 h but decreased over time, reflecting the pattern of RFC expression in small intestine. These findings show that intestinal GCPII and intestinal and hepatic RFC all exhibit ontogenic changes in the pig that are reflected in postnatal folate status.
Uremia induces proximal tubular cytoresistance and heme oxygenase-1 expression in the absence of acute kidney injury
Authors: Zager Richard A.
Published: November 2008

Acute kidney injury (AKI) induces adaptive responses within proximal tubular (PT) cells that serve to protect them from further ischemic or toxic damage. However, it is not known whether uremia, a potential consequence of AKI, independently alters susceptibility to tubular injury. To address this issue, we subjected CD-1 mice to bilateral ureteral transection (BUTx), which produces uremia (blood urea nitrogen ∼150 mg/dl) in the absence of direct renal damage. PT segments were then isolated from BUTx and control mice and subjected to in vitro hypoxic injury. Additionally, “in vitro uremia” was modeled in isolated tubules or in cultured PT (HK-2) cells by addition of 1) peritoneal dialysate (obtained from mice with bilateral ureteral obstruction), 2) peritoneal fluid (from BUTx mice), or 3) normal human urine (pH 7.4, with and without boiling). Effects on injury severity (lactate dehydrogenase release) were assessed. Finally, because uremia is a prooxidant state, it was hypothesized that BUTx would increase renal lipid peroxidation (malondialdehyde) and induce heme oxygenase-1 (HO-1), a redox-sensitive cytoprotective protein. BUTx conferred striking protection against hypoxic damage. This could be partially modeled in tubules and HK-2 cells by induction of in vitro uremia. Urine's protective action was heat labile (largely destroyed by boiling). BUTx caused a tripling of renal malondialdehyde and HO-1 protein levels. Increased HO-1 transcription was likely involved, as indicated by a tripling of HO-1 mRNA and RNA polymerase II binding along the HO-1 gene (chromatin immunoprecipitation assay). “Gene-activating” histone modifications [H3K4 trimethylation (H3K4m3) and histone 2 variant (H2A.Z)] at HO-1 gene loci were also observed. Uremia, per se, can contribute to the AKI-induced cytoresistance. Low-molecular-weight, heat-labile, cytoprotective factor(s) and uremia-induced renal stress responses (e.g., HO-1 gene activation) are likely involved. Finally, renal HO-1 induction following AKI may reflect direct cell injury effects and adaptations to uremia.