bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Silver Carp Hypophthalmichthys molitrix and Freshwater Mussel Elliptio complanata Filtration on the Phytoplankton Community of Partitioned Aquaculture System Units
Authors: Mueller Christopher R. , Eversole Arnold G. , Turker Hakan , Brune David E.
Published: April 2007

Growers produce over 2.8 million kg of catfish (over $350 million wholesale revenue) annually in the United States. The microbiology of the phytoplankton community in culture water affects the growth and flavor of the catfish and is a consideration for growers. Filter feeders, like silver carp and freshwater mussels, in controlled growth systems are used to adjust the phytoplankton species. Our goal was to successfully control the algal populations with filter feeders in catfish production. We used silver carp Hypophthalmichthys molitrix as a filter feeder in Partitioned Aquaculture System (PAS) water. Silver carp completely eliminated the cyanobacteria Microcystis by size and biovolume reduction. This created the desired effect of small green algae dominating the algal community. A significant but opposite change was observed when freshwater mussels Elliptio complanata filtered PAS water resulting in Microcystis biovolume and size dominance in the PAS; a less desirable algal community. This study also showed an immediate shift in the phytoplankton community when silver carp and mussels were interchanged between PAS waters. The size‐selective filtration by the two filter‐feeding taxa was important in determining the composition of the PAS phytoplankton community, and it was apparent that filtration with silver carp successfully depleted undesirable algae.
Ionic Supplementation of Pond Waters for Inland Culture of Marine Shrimp
Authors: McNevin Aaron A. , Boyd Claude E. , Silapajarn Orawan , Silapajarn Kom
Published: April 2007

Saline well water used to fill ponds for inland culture of marine shrimp in Alabama often have low concentrations of potassium and magnesium. In 2002, pond waters on a shrimp farm were treated with enough muriate of potash and potassium‐magnesium sulfate (K‐Mag) to increase potassium concentration from 6.2 mg/L to about 40 mg/L and magnesium concentrations from 4.6 mg/L to about 20 mg/L. Salinity in ponds averaged 2.6 ppt at the time of mineral salt additions. The concentrations of potassium and magnesium remained fairly constant throughout the growing season without further applications of salts, and salinity increased to about 4 ppt mainly as a result of concentration through evaporation. Survival and production on the farm averaged 19% and 595 kg/ha, respectively, in 2001. In 2002, average survival improved to 67% and average production was 4,068 kg/ha. Ponds were stocked at similar rates and managed by similar procedures both years. Magnesium concentration was very low related to the concentration expected in normal seawater diluted to the same salinity as the pond water, while potassium was near the expected concentration. Thus, increased potassium concentration is thought to have influenced production much more than did the increase in magnesium concentration. K‐Mag does not dissolve as readily as muriate of potash. Thus, K‐Mag should not be dumped in shallow water areas of ponds to dissolve as can be done with muriate of potash. It should be broadcast over the pond surface, predissolved and splashed over the pond surface, or placed in porous bags suspended in front of aerators. Although a single application of mineral salts was effective, 2002 was a dry year. On a wet year, ions may be diluted or flushed out in overflow and more than one treatment with mineral salts might be necessary during the growing season.
Effects of Dietary Protein and Feeding Rate on Channel Catfish Ictalurus punctatus Production, Composition of Gain, Processing Yield, and Water Quality
Authors: Robinson Edwin H. , Li Menghe H. , Manning Bruce B. , Mischke Charles C. , Bosworth Brian G.
Published: April 2007

A 2 ± 4 factorial experiment was conducted to examine effects of dietary protein level (28, 32, 36, and 40%) and feeding rate (satiation or ± 90 kg/ha per d) on production characteristics, processing yield, body composition, and water quality for pond‐raised channel catfish Ictalurus punctatus. Fingerling channel catfish with a mean weight of 64 g/fish were stocked into 40 0.04‐ha ponds at a rate of 17,290 fish/ha. Fish were fed once daily to apparent satiation or at a rate of ± 90 kg/ha per d for 134 d during the growing season. Dietary protein concentration had no effect on feed consumption, weight gain, feed conversion, survival, aeration time, or on fillet moisture, protein, and fat levels. Fish fed to satiation consumed more feed, gained more weight, had a higher feed conversion, and required more aeration time than fish fed a restricted ration. Visceral fat decreased, and fillet yield increased as dietary protein concentration increased to 36%. Carcass yield was lower for fish fed a diet containing 28% protein. Increasing feeding rate increased visceral fat but had no major effect on carcass, fillet, and nugget yields. Fish fed to satiation contained less moisture and more fat in the fillets that those fed a restricted ration. Nitrogenous waste compounds were generally higher where the fish were fed the higher protein diets. Although there was a significant interaction in pond water chemical oxygen demand between dietary protein and feeding rate, generally ponds in the satiation feeding group had higher chemical oxygen demand than ponds in the restricted feeding group. There was a trend that pond water total phosphorus levels were slightly elevated in the satiation feeding group compared to the restricted feeding group. However, pond water soluble reactive phosphorus and chlorophyll‐a were not affected by either diet or feeding rate. Results from the present study indicate that a 28% protein diet provides the same level of channel catfish production as a 40% protein diet even when diet is restricted to 90 kg/ha per d. Although there was an increase in nitrogenous wastes in ponds where fish were fed high protein diets, there was little effect on fish production. The long term effects of using high protein diets on water quality are still unclear. Feeding to less than satiety may be beneficial in improving feed efficiency and water quality.
Laboratory Determination of a Phosphorus Leaching Rate from‘Trout (Onchorhynchus mykiss) Feces
Authors: McIntosh Dennis , Ryder Erin , Dickenson Gary , Fitzsimmons Kevin
Published: April 2007

In order to reduce the impact that trout farm effluent can have on receiving water, it imperative to reduce the overall phosphorus (P) loading of these effluents. In response, the United States Environmental Protection Agency (US EPA) is issuing new effluent regulations for aquaculture. Therefore, efficient removal of P from effluent water is becoming increasingly important. The goal of this project was to determine the leaching rate of total and reactive P from trout feces under different water temperatures and water velocities immediately after evacuation. Scatter plots of the P load in the experimental containers over time were created for each fish/fecal sample and regression analysis was used to determine P leaching rates. Results from this study suggest that reactive phosphorus leaching rates are not affected by water velocities between 0.027 and 0.134 m/sec. However, at higher temperatures, reactive P leaches 1.92‐mg PO4/hr per g feces faster (F1.52= 4.6445, P= 0.0358) than at lower temperatures. Mean reactive phosphorus leaching rates were 2.88 ± 0.704 and 0.96 ± 0.581mg PO4/hr/g feces, for the high and low temperatures, respectively. On the other hand, total P does not appear to be affected by either water velocity or temperature. Mean total P leaching rate is 4.50 ± 1.053 mg PO4/hr per g feces. This study suggests that removal time of feces from the system is critical in reducing the overall P load in effluent.
Cryopreservation of YamúBrycon siebenthalae Milt
Authors: Cruz‐Casallas Pablo E. , Pardo‐Carrasco Sandra C. , Arias‐Castellanos José A. , Lombo‐Castellanos Pedro E. , Lombo‐Rodríguez Dora A. , Pardo‐Mariño Jaime E.
Published: April 2007

The yamúBrycon siebenthalae is an endemic fish of the Orinoco river basin, but wild stocks are decreasing because of the disruption of their habitat. We evaluated a protocol for the cryopreservation of yamú sperm to contribute to the preservation of this endangered genetic resource. Milt was mixed with a cryoprotectant medium (5.5% glucose, 12% egg yolk, and 5%, 10%, or 15% dimethyl sulfoxide ‐ DMSO) in a ratio 1:4 (milt:medium), stored in 0.5‐mL French straws, frozen in nitrogen liquid vapor (‐76 C), then immersed and stored in liquid nitrogen for 10 d or 12 mo. Motility of thawed spermatozoa was higher (P < 0.001) in 10% DMSO medium than 5% DMSO or 15% DMSO mediums; but lower than the control (P < 0.001). With sperm cryopreserved, the highest level of fertilization was achieved with 10% DMSO (P < 0.001) after 10 d or 12 mo of cryopreservation. Fertilization of eggs inseminated with 6.4 × 109 spermatozoa per g of eggs was higher (P <0.05) than with 1.6 × 109 spermatozoa per g of eggs. There was no difference (P > 0.05) in fertilization between insemination doses of 3.2 × 109 and 6.4 × 109 spermatozoa per g of eggs. Cryopreservation of yamu milt can be performed successfully with a simple medium combined with 10% of DMSO as cryoprotectant. The highest level of fertility was achieved using between 3 × 109 and 6 × 109 spermatozoa per g of fresh eggs.
Growth of Stocker Channel Catfish to Large Market Size in Single‐Batch Culture
Authors: Green Bartholomew W. , Engle Carole R.
Published: April 2007

Catfish farmers increasingly are producing fish larger than the traditional size of 0.45‐0.57 kg/fish in order to meet processing plant requirements for larger fish. Production of larger channel catfish Ictalurus punctatus in multiple‐batch culture has been investigated in a few studies, but the impact of understocked fingerlings on growth of carry‐over fish is unknown. The present study was conducted to quantify growth, feed conversion ratio, net daily yield, and net and total yield of stocker channel catfish grown in single‐batch, one‐season culture to mean individual weights of 0.60, 0.72, 0.91, or 1.17 kg/fish. Channel catfish (mean weight = 0.26 kg/fish) were stocked into 12 0.1‐ha ponds at 11,115 fish/ha. Fish were fed a 32% crude protein floating extruded feed once daily to apparent satiation. When the average weight of the fish population reached the target weight, three randomly selected ponds were harvested. Fish growth was linear in all treatments. Growth rates were similar for fish grown to 0.60, 0.72, and 0.91 kg/fish, and significantly lower (P < 0.05) than for fish grown to 1.17 kg. Variation in individual fish weight increased linearly with increased duration of culture period. Feed conversion ratio averaged 1.9 and did not differ significantly among treatments. The percentage of the fish population at harvest that fell within the 0.57 to 2.04 kg‐size range preferred by processing plants increased from 56.6 to 98‐5% as the mean weight at harvest increased from 0.60 to 1.17 kg/fish.
Effect of Stocking Weight and Stocking Density on Production of Hybrid Striped Bass (Sunshine) in Earthen Ponds in the Second Phase of a 2‐Phase System
Authors: D'Abramo Louis R. , Ohs Cortney L. , Hanson Terrill R.
Published: April 2007

Sunshine bass from Phase I or pond production were graded into two weight classes, 3 and 5 g, and stocked into experimental earthen ponds at a density of either 8,649/ha or 11,120/ ha in a 2 × 2 factorial design. After stocking, the fish were fed a commercially manufactured feed (43.0‐45.5% crude protein) twice daily to satiation for 17 mo. At harvest, mean survival ranged from 67.4 to 84.8% but was highest for the fish stocked at 5g. Average production Tor ponds stocked at 8,649/ha and 11,120/ha, regardless of stocking weight, was 4,506 kg/ha and 5350 kg/ha, respectively. Production and percentages of assigned weight classes were not significantly different among treatments as a result of wide variation among replicates. Using size‐dependent market prices assigned to the different harvest size groups, an economic analysis revealed gross receipts, variable costs, and total costs for the 11,120/ha 5‐g treatment. Net returns were not significantly different among the four treatments due to large variation among replicates per treatment. These results confirm that the traditional phase II of pond production can be eliminated in favor of a direct stocking of phase I fish into a single production phase and economically competes very well with traditional three‐phase growout management. The potential reduction in turnover time of production units achieved through the direct stock practice is an efficiency trait that should translate into significantly higher returns and a greater profit over the long term. Further reduction of stocking density combined with a stocking weight greater than 5 g should translate into greater proportion of larger, higher valued fish at harvest and a growout period of 18‐20 mo, rather than the 24‐30 mo traditionally needed for the combined phase II and phase III of production.
Artificial Propagation and Induction of Triploidy in Largemouth Bass Micropterus salmoides and Ploidy Discrimination using Erythrocyte Length
Authors: Neal J. Wesley , Neal Diana M. , Noble Richard L. , McGee Michael V.
Published: April 2007

We describe an artificial propagation procedure and simple ploidy discrimination techniques using erythrocyte major axis length for largemouth bass Micropterus salmoides. Hormonal treatments of 5 mg/kg of carp pituitary and 50 μg/kg of leutinizing hormone‐releasing hormone (LHRH) produced viable gametes in 21‐24 h, and triploidy was induced using a pressure treatment of 563 kg/cm2 on embryos for a 1‐min duration exactly 5 min following fertilization. We produced about 500 fingerling triploids and about 500 diploid controls, and verified genetic status of a subset of each group using flow cytometry. Erythrocyte length was measured for 10 known diploid and 10 known triploid individuals. Remaining fish were internally microtagged with group‐specific tags and mixed to test the model. We developed ploidy discrimination intervals based on the 99% confidence limits of mean erythrocyte length (MEL, N= 25 erythrocytes) for individual fish, which were 14.43‐16.66 μ.m for triploids, and 10.23‐13.62 μm for diploids. Logistic regression provided the discrimination model: Ploidy status (±) = ‐196.16 + 13.97 x MEL, with positive (+) outcomes considered triploid. Both discrimination techniques were 100% effective at differentiating ploidy of the 22 microtagged largemouth bass recollected from the mixed population. We did not observe a significant change in erythrocyte length as fish size increased, indicating that erythrocyte length is an accurate predictor of ploidy for all sizes of largemouth bass.
Genetic Effects for Response to Live Edwardsiella ictaluri, Killed E. ictaluri, and Stress in Juveniles from All Crosses Among USDA 103, USDA 102, and Norris Channel Catfish Ictalurus punctatus Strains
Authors: Bosworth Brian G. , Wolters William R. , Wise David J. , KLESIUS P. H.
Published: April 2007

Juveniles from all possible crosses among USDA 102. USDA 103, and Norris channel catfish Ictalurus punctatus strains were compared for: 1) survival and mix‐Edwardsiella ictaluri antibody after exposure to live E. ictaluri bacterium (isolate 597‐458); 2) antibody level after injection with formalin‐killed E. ictaluri (597‐458); and 3) pre‐stress. post‐stress, and stress‐recovery serum Cortisol levels. Purebred and crossbred USDA 102 strain fish had higher survival (mean of five genetic groups = 87%) and lower anti‐ E.ictaluri antibody (mean optical density (OD) of five genetic groups = 0.167) 30 d after live E. ictaluri challenge than purebred Norris and USDA 103 strains and their crosses (means of four genetic groups = 60% survival and 0.210 OD antibody level). Significant general combining ability, line effects, and heterosis indicated that the USDA 102 strain contributed additive and dominance genetic effects for increased survival and lower antibody level after live E. ictaluri challenge. Antibody response to formalin‐killed, intra‐peritoneally injected E. ictaluri was not different among genetic groups (overall mean = 0.198 OD). Serum Cortisol was measured prior to (pre‐stress), immediately after (post‐stress), and 2 h after (stress‐recovery) a standard stressor. Serum Cortisol level was highest in post‐stress fish (35.8 ng/mL), intermediate in stress‐recovery fish (10.9 ng/mL), and lowest in pre‐stress fish (6.5 ng/mL), but was not different among genetic groups within a stress time period. Results indicate diat differences exist among genetic groups of channel catfish for survival and antibody production after live E. ictaluri challenge, but these differences were not related to antibody response to killed E. ictaluri or serum Cortisol levels.
A Comparative Study of the Dietary Lysine Requirement of Juvenile Striped bassMorone saxatilisand Sunshine bassM. chrysops x M. saxatilis
Authors: Brougher Daniel S. , Douglass Larry W. , Soares Joseph H.
Published: April 2007

Previous reports have indicated there are significant differences in both the dietary lysine requirement and the metabolic rate of striped bass and its hybrids. However, there is very little directly comparative data to confirm these suggestions. A series of experiments was conducted to comparatively assess efficiency of protein and energy retention between striped bassMorone saxatilisand sunshine bassM. chrysops♀×M. saxatilis♂ grown under identical culture conditions. In experiment one, a dose response study was conducted using digestible energy (DE) levels of 3,200 kcal/kg and 3,600 kcal/kg. At each level of DE, six levels of dietary lysine were fed to striped bass and sunshine bass. Ten sunshine bass weighing 3.48 ± 0.08 g or six striped bass weighing 3.23 ± 0.14 g were stocked into 15‐L tanks supplied with single‐pass flow‐through fresh water. After 12 wk on the experimental regime, feed conversion ratios (FCR), weight gain, and % nitrogen (N) retention were determined. Nonlinear regression analysis indicated that the dietary lysine requirement of both bass groups was similar. The dietary lysine requirement was determined to be 2.0 ± 0.08% of dry diet (or 6.0 ± 0.26 g lysine/1,000 kcal DE), and 1.7 ± 0.08% of dry diet (or 4.7 ± 0.22 g lysine/1,000 kcal DE), for the 3,200 and 3,600 kcal DE/kg diets, respectively. A second experiment comparatively assessed growth, metabolism, and energy partitioning between striped bass and sunshine bass. Two diets were formulated to be isonitrogenous and isocaloric with a calculated DE level of 3462 kcal/kg and contained lysine concentrations approximating the published dietary requirements of sunshine bass (low lysine = LL diet) and striped bass (high lysine = HL diet). The diets were fed at an average rate of 2% of body weight/d to 25 juvenile striped bass or hybrid bass held separately in eight 2000‐L single‐pass flow‐through tanks supplied with freshwater. In general, growth performance of sunshine bass was superior to striped bass. Both bass groups performed better when fed the HL diet. Mean FCRs were 1.19 ± 0.12 and 1.94 ± 0.29, respectively, for hybrids and striped bass fed the LL diet(P= 0.066); and 1.17 ± 0.07, and 1‐58 ± 0.08, respectively, for hybrids and striped bass fed the HL diet(P =0.011). Mean % gain/d values were significantly higher(P= 0.001) for hybrids (2.77 ± 0.85) than for striped bass (1‐30 ± 0.27) when fed the LL diet. When fed the HL diet, mean % gain/d was significantly higher(P =0.003) for sunshine bass (2.72 ± 0.83) compared to striped bass (1.51 ± 0.25). Additionally, when fed the HL diet, sunshine bass had significantly higher percent nitrogen(P= 0.006) and energy retention(P= 0.014) when compared to striped bass. These results further document that sunshine bass are more efficient at protein and energy retention compared to striped bass in freshwater.
Sperm Quality Over Consecutive Spermatophore Regenerations in the Pacific White Shrimp Litopenaeus vannamei
Authors: Ceballos‐Vázquez Bertha P. , Aparicio‐Simón Benjamin , Palacios Elena , Racotta Ilie S.
Published: April 2007

The reproductive potential of males plays an important role in the productivity of captive penaeids. Males present a large variability in their reproductive potential, and thus the selection of appropriate males for reproduction is highly desirable. The present study compares sperm quality at the beginning of the experiment (baseline values) with variations in sperm quality as a result of consecutive spermatophore regenerations. This was done to evaluate possible predictive criteria for optimal sperm quality based on morphological and biochemical criteria in pond‐reared Pacific white shrimp Litopenaeus vannamei males. Sperm quality was similar between left and right spermatophore. Sperm count and proportion of normal sperm increased by 86 and 65% (P < 0.05) respectively, from baseline values to third spermatophore regeneration. Proportion of dead sperm progressively decreased with consecutive regenerations, attaining values 33% lower by the third regeneration, compared to baseline values. This indicates that no decrease in sperm quality occurs in L. vannamei during consecutive regenerations and that the existing spermatophores at stocking of males should be expelled to have higher sperm quality in regenerated spermatophores. Furthermore, this procedure allows selecting individuals with high baseline sperm quality based on significant correlations between baseline and regenerated sperm quality observed in the present work. Baseline values of glucose concentration in the hemolymph were positively correlated to baseline values of sperm count (r = 03, P < 0.05). In contrast, baseline values of several lipids in the hemolymph were negatively correlated to several traits of sperm quality at first sampling (baseline values) or at first regeneration. These results are discussed in terms of nutritional requirements of males and of possible predictive criteria of sperm quality.
Evaluation of Five Microalgae Diets for Juvenile Pen Shells Atrina maura
Authors: Lora‐Vilchis Maria Concepción , Ruiz‐Velasco‐Cruz Esperanza , Reynoso‐Granados Teodoro , Voltolina Domenico
Published: April 2007

–Juvenile pen shells Atrina maura were fed for 21 d with equal daily rations, equivalent to 6.5% of their live weight, of monoalgal cultures of Tetraselmis suecica, Isochrysis galbana, Chaetoceros muelleri, Chaetoceros calcitrans, and Thalassiosira pseudonana. Pen shell survival was 100% in all cases. All microalgae diets produced shell growth, and live and ash‐free dry weight increases. However, the two Chaetoceros strains gave significantly better results, with shell height increases of 4.7 to 2.9 mm, live weight gains of 0.5 to 0.3 g, and final ash‐free dry weights of 0.16 to 0.14 g after 3 wk. These results are not related to the algae gross biochemical composition, suggesting that other factors are involved in their nutritional value for this mollusc species.
Deposition of Particles on Ocular Tissues and Formation of Krukenberg Spindle, Hyphema, and Hypopyon
Authors: Kumar Satish , Acharya Sumanta , Beuerman Roger
Published: April 2007

Eye diseases, such as Krukenberg’s spindle, hyphema, and hypopyon, are related to the deposition of specific particles such as pigmentary cells, leukocytes, and erythrocytes. These particles are circulated by the aqueous humor (AH) and tend to deposit in regions of low velocities or high resistance. In the present paper, numerical simulations are reported of the AH flow and particle transport, and the particle concentration predictions are qualitatively compared to clinical images. The particle concentration distributions provide an understanding of the likely sources of deposition and the origin of the deposited particles. Pigmentary cells are seen to concentrate in a vertical band on the corneal surface consistent with clinical observations of Krukenberg’s spindle. Leukocytes and erythrocytes are seen to collect at the bottom of the anterior chamber similar to the observations made for hypopyon and hyphema. These results confirm the potential of using numerical calculations in order to obtain a better understanding of the particle transport and deposition patterns in the anterior chamber of the eye.
A Bimodular Polyconvex Anisotropic Strain Energy Function for Articular Cartilage
Authors: Klisch Stephen M.
Published: April 2007

A strain energy function for finite deformations is developed that has the capability to describe the nonlinear, anisotropic, and asymmetric mechanical response that is typical of articular cartilage. In particular, the bimodular feature is employed by including strain energy terms that are only mechanically active when the corresponding fiber directions are in tension. Furthermore, the strain energy function is a polyconvex function of the deformation gradient tensor so that it meets material stability criteria. A novel feature of the model is the use of bimodular and polyconvex “strong interaction terms” for the strain invariants of orthotropic materials. Several regression analyses are performed using a hypothetical experimental dataset that captures the anisotropic and asymmetric behavior of articular cartilage. The results suggest that the main advantage of a model employing the strong interaction terms is to provide the capability for modeling anisotropic and asymmetric Poisson’s ratios, as well as axial stress–axial strain responses, in tension and compression for finite deformations.
Elasticity Imaging of Polymeric Media
Authors: Sridhar Mallika , Liu Jie , Insana Michael F.
Published: April 2007

Viscoelastic properties of soft tissues and hydropolymers depend on the strength of molecular bonding forces connecting the polymer matrix and surrounding fluids. The basis for diagnostic imaging is that disease processes alter molecular-scale bonding in ways that vary the measurable stiffness and viscosity of the tissues. This paper reviews linear viscoelastic theory as applied to gelatin hydrogels for the purpose of formulating approaches to molecular-scale interpretation of elasticity imaging in soft biological tissues. Comparing measurements acquired under different geometries, we investigate the limitations of viscoelastic parameters acquired under various imaging conditions. Quasi-static (step-and-hold and low-frequency harmonic) stimuli applied to gels during creep and stress relaxation experiments in confined and unconfined geometries reveal continuous, bimodal distributions of respondance times. Within the linear range of responses, gelatin will behave more like a solid or fluid depending on the stimulus magnitude. Gelatin can be described statistically from a few parameters of low-order rheological models that form the basis of viscoelastic imaging. Unbiased estimates of imaging parameters are obtained only if creep data are acquired for greater than twice the highest retardance time constant and any steady-state viscous response has been eliminated. Elastic strain and retardance time images are found to provide the best combination of contrast and signal strength in gelatin. Retardance times indicate average behavior of fast (1–10s) fluid flows and slow (50–400s) matrix restructuring in response to the mechanical stimulus. Insofar as gelatin mimics other polymers, such as soft biological tissues, elasticity imaging can provide unique insights into complex structural and biochemical features of connectives tissues affected by disease.
On the Relative Importance of Rheology for Image-Based CFD Models of the Carotid Bifurcation
Authors: Lee Sang-Wook , Steinman David A.
Published: April 2007

Background: Patient-specific computational fluid dynamics (CFD) models derived from medical images often require simplifying assumptions to render the simulations conceptually or computationally tractable. In this study, we investigated the sensitivity of image-based CFD models of the carotid bifurcation to assumptions regarding the blood rheology. Method of Approach: CFD simulations of three different patient-specific models were carried out assuming: a reference high-shear Newtonian viscosity, two different non-Newtonian (shear-thinning) rheology models, and Newtonian viscosities based on characteristic shear rates or, equivalently, assumed hematocrits. Sensitivity of wall shear stress (WSS) and oscillatory shear index (OSI) were contextualized with respect to the reproducibility of the reconstructed geometry, and to assumptions regarding the inlet boundary conditions. Results: Sensitivity of WSS to the various rheological assumptions was roughly 1.0dyn∕cm2 or 8%, nearly seven times less than that due to geometric uncertainty (6.7dyn∕cm2 or 47%), and on the order of that due to inlet boundary condition assumptions. Similar trends were observed regarding OSI sensitivity. Rescaling the Newtonian viscosity based on time-averaged inlet shear rate served to approximate reasonably, if overestimate slightly, non-Newtonian behavior. Conclusions: For image-based CFD simulations of the normal carotid bifurcation, the assumption of constant viscosity at a nominal hematocrit is reasonable in light of currently available levels of geometric precision, thus serving to obviate the need to acquire patient-specific rheological data.
A Computationally Efficient Optimization Kernel for Material Parameter Estimation Procedures
Authors: Schmid H. , Nash M. P. , Young A. A. , Röhrle O. , Hunter P. J.
Published: April 2007

Estimating material parameters is an important part in the study of soft tissue mechanics. Computational time can easily run to days, especially when all available experimental data are taken into account. The material parameter estimation procedure is examplified on a set of homogeneous simple shear experiments to estimate the orthotropic constitutive parameters of myocardium. The modification consists of changing the traditional least-squares approach to a weighted least-squares. This objective function resembles a L2-norm type integral which is approximated using Gaussian quadrature. This reduces the computational time of the material parameter estimation by two orders of magnitude.
Cortical Screw Pullout Strength and Effective Shear Stress in Synthetic Third Generation Composite Femurs
Authors: Zdero Radovan , Rose Shaun , Schemitsch Emil H. , Papini Marcello
Published: April 2007

Background: The use of artificial bone analogs in biomechanical testing of orthopaedic fracture fixation devices has increased, particularly due to the recent development of commercially available femurs such as the third generation composite femur that closely reproduce the bulk mechanical behavior of human cadaveric and∕or fresh whole bone. The purpose of this investigation was to measure bone screw pullout forces in composite femurs and determine whether results are comparable to cadaver data from previous literature. Method of Approach: The pullout strengths of 3.5 and 4.5mm standard bicortical screws inserted into synthetic third generation composite femurs were measured and compared to existing adult human cadaveric and animal data from the literature. Results: For 3.5mm screws, the measured extraction shear stress in synthetic femurs (23.70-33.99MPa) was in the range of adult human femurs and tibias (24.4-38.8MPa). For 4.5mm screws, the measured values in synthetic femurs (26.04-34.76MPa) were also similar to adult human specimens (15.9-38.9MPa). Synthetic femur results for extraction stress showed no statistically significant site-to-site effect for 3.5 and 4.5mm screws, with one exception. Overall, the 4.5mm screws showed statistically higher stress required for extraction than 3.5mm screws. Conclusions: The third generation composite femurs provide a satisfactory biomechanical analog to human long-bones at the screw-bone interface. However, it is not known whether these femurs perform similarly to human bone during physiological screw “toggling.”
Stepwise Exposure of
Staphylococcus aureus
to Pleuromutilins Is Associated with Stepwise Acquisition of Mutations in
rplC
and Minimally Affects Susceptibility to Retapamulin
Authors: Gentry Daniel R. , Rittenhouse Stephen F. , McCloskey Lynn , Holmes David J.
Published: April 2007

To assess their effects on susceptibility to retapamulin in
Staphylococcus aureus
, first-, second-, and third-step mutants with elevated MICs to tiamulin and other investigational pleuromutilin compounds were isolated and characterized through exposure to high drug concentrations. All first- and second-step mutations were in
rplC
, encoding ribosomal protein L3. Most third-step mutants acquired a third mutation in
rplC
. While first- and second-step mutations did cause an elevation in tiamulin and retapamulin MICs, a significant decrease in activity was not seen until a third mutation was acquired. All third-step mutants exhibited severe growth defects, and faster-growing variants arose at a high frequency from most isolates. These faster-growing variants were found to be more susceptible to pleuromutilins. In the case of a mutant with three alterations in
rplC
, the fast-growing variants acquired an additional mutation in
rplC
. In the case of fast-growing variants of isolates with two mutations in
rplC
and at least one mutation at an unmapped locus, one of the two
rplC
mutations reverted to wild type. These data indicate that mutations in
rplC
that lead to pleuromutilin resistance have a direct, negative effect on fitness. While reduction in activity of retapamulin against
S. aureus
can be seen through mutations in
rplC
, it is likely that target-specific resistance to retapamulin will be slow to emerge due to the need for three mutations for a significant effect on activity and the fitness cost of each mutational step.
Effects of Piperaquine, Chloroquine, and Amodiaquine on Drug Uptake and of These in Combination with Dihydroartemisinin against Drug-Sensitive and -Resistant
Plasmodium falciparum
Strains
Authors: Fivelman Quinton L. , Adagu Ipemida S. , Warhurst David C.
Published: April 2007

Piperaquine is being developed as a long-acting component in artemisinin combination therapies. It was highly active in vitro and drug interaction studies showed that dihydroartemisinin combinations with piperaquine, chloroquine, and amodiaquine were indifferent tending toward antagonism. Competitive uptake of radiolabeled chloroquine and dihydroartemisinin in combination with other antimalarials was observed.
The Type IV Pilin ofBurkholderia malleiIs Highly Immunogenic but Fails To Protect against Lethal Aerosol Challenge in a Murine Model
Authors: Fernandes Paula J. , Guo Qin , Waag David M. , Donnenberg Michael S.
Published: April 2007

Burkholderia malleiis the cause of glanders and a proven biological weapon. We identified and purified the type IV pilin protein of this organism to study its potential as a subunit vaccine. We found that purified pilin was highly immunogenic. Furthermore, mice infected via sublethal aerosol challenge developed significant increases in titers of antibody against the pilin, suggesting that it is expressed in vivo. Nevertheless, we found no evidence that high-titer antipilin antisera provided passive protection against a sublethal or lethal aerosol challenge and no evidence of protection afforded by active immunization with purified pilin. These results contrast with the utility of type IV pilin subunit vaccines against other infectious diseases and highlight the need for further efforts to identify protective responses against this pathogen.
Systemic CD8 T-Cell Memory Response to aSalmonellaPathogenicity Island 2 Effector Is Restricted toSalmonella entericaEncountered in the Gastrointestinal Mucosa
Authors: Jones-Carson Jessica , McCollister Bruce D. , Clambey Eric T. , Vázquez-Torres Andrés
Published: April 2007

To better understand the evolution of a systemic memory response to a mucosal pathogen, we monitored antigen-specific OT1 CD8 T-cell responses to a fusion of the SspH2 protein and the peptide SIINFEKL stably expressed from the chromosome ofSalmonella entericaand loaded into the class I pathway of antigen presentation of professional phagocytes through theSalmonellapathogenicity island 2 type III secretion system (TTSS). This strategy has revealed that effector memory CD8 T cells with low levels of CD62L expression (CD62Llow) are maintained in systemic sites months after vaccination in response to low-grade infections withSalmonella. However, the CD8 T-cell pool eventually declines. Low numbers of central memory cells surviving after prolonged resting from an antigen encounter can nevertheless reconstitute the systemic effector memory pool in a route-specific recall response to cognate antigens encountered in the gut. Accordingly, populations of CD62Lhighinterleukin-7 receptor-positive progenitor central memory cells grafted into naïve mice expand in response to orally administeredSalmonellaexpressing the chromosomal translational fusion ofsspH2and the sequence encoding the SIINFEKL peptide but fail to proliferate following systemic stimulation. Moreover, populations of systemic memory CD8 T cells restricted toSalmonellain oral vaccines selectively expand in response to cognate antigens presented by cells isolated from mesenteric lymph nodes (MLN). Together, these findings have revealed the imprinting of systemic CD8 central memory T-cell recall responses against enteropathogens by MLN. MLN restriction represents a novel mechanism by which systemic CD8 T-cell immunity is confined to periods of high risk for extraintestinal dissemination.
CD4+Lymphocytes and Gamma Interferon Predominate in Local Immune Responses in Early Experimental Syphilis
Authors: Leader Brandon T. , Godornes Charmie , VanVoorhis Wesley C. , Lukehart Sheila A.
Published: April 2007

The clearance ofTreponema pallidumsubsp.pallidumfrom early syphilis lesions involves infiltration of a large number of mononuclear cells and is characteristic of a cell-mediated immune response. In the present study, we sought to determine the relative abundance of different T-lymphocyte populations and Th1/Th2-associated cytokines present in testicular lesions following experimental infection with the Chicago strain ofT. pallidum. Using flow cytometry, we examined the proportion of CD4+and CD8+T cells present throughout the progression and resolution of primary syphilis in the rabbit model. We related these findings to the results of real-time reverse transcription-PCR quantification of treponemal and cytokine mRNA levels. Treponemal mRNA levels reached peak values on day 18 postinfection, coincident with an initial peak in the level of T cells, which were primarily CD4+T cells. T-cell levels increased again during resolution of orchitis, and there was an increased proportion of CD8+T cells. The maximum gamma interferon (IFN-γ) and interleukin-10 (IL-10) mRNA levels were observed on days 11 and 18, respectively, while only negligible amounts of IL-4 and IL-2 were detected throughout the infection. In addition to showing the temporal relationship between treponemal burden and T-cell responses during lesion progression, our results also demonstrate that the composition of the T-cell population changes during lesion resolution. The presence of the mRNA for IFN-γ, but not IL-4, is consistent with cytokine expression in human syphilis and provides further support for the hypothesis that there is a Th1 predominance during the early immune response toT. pallidum.
Human papilloma virus in squamous carcinoma of the head and neck: a study of cases in south east Scotland
Authors: Anderson C E , McLaren K M , Rae F , Sanderson R J , Cuschieri K S
Published: April 2007

Several studies have found human papillomavirus virus (HPV) in tissue from head and neck squamous cell carcinomas (HNSCCs), although the number of positive cases varies greatly from study to study. The extent and molecular epidemiology of HPV in HNSCC were assessed within cases drawn from southeast Scotland by performing broad-spectrum, real-time HPV polymerase chain reaction (PCR) on DNA extracted from 100 cases of HNSCC in formalin-fixed, paraffin wax-embedded material. All HPV-positive specimens were genotyped and sampled by laser capture microdissection. Pure samples of tumour, and, where possible, dysplastic and normal epithelium were then submitted for further HPV PCR and genotyping to investigate the sensitivity of the technique in small tissue samples. 10 of 100 cases tested positive for HPV, with 8 of these being derived from Waldeyer’s ring. HPV DNA was found in adjacent epithelium in two of four cases where this was available. These findings confirm that HPV is likely to be involved in a subset of HNSCC in this population and that successful amplification of HPV nucleic acid is possible even using small amounts of paraffin wax-embedded tissue.
A distinctive vulval fibroma of so-called prepubertal type in a postmenopausal patient
Authors: Ajibona O O , Richards C J , Davies Q
Published: April 2007

The case of a 65-year-old female patient who has had a large right vulval mass for over 30 years is reported here. The mass was excised, but the hypocellular mesenchymal tumour was difficult to classify histologically. On further specialist assessment, it was found to be identical to the recently recognised distinctive prepubertal vulval fibroma. These are very rarely reported in children, and till now, has never been reported in an adult.
The regulation of FSHβ transcription by gonadal steroids: testosterone and estradiol modulation of the activin intracellular signaling pathway
Authors: Burger Laura L. , Haisenleder Daniel J. , Wotton Gordon M. , Aylor Kevin W. , Dalkin Alan C. , Marshall John C.
Published: April 2007

Recent reports suggest that androgens increase FSHβ transcription directly via the androgen receptor and by modulating activin signaling. Estrogens may also regulate FSHβ transcription in part through the activin system. Activin signaling can be regulated extracellularly via activin, inhibin, or follistatin (FS) or intracellularly via the Smad proteins. We determined the effects of androgen and estrogen on FSHβ primary transcript (PT) concentrations in male and female rats, and we correlated those changes with pituitary: activin βB mRNA, FS mRNA, the mRNAs for Smads2, -3, -4, and -7, and the phosphorylation (p) status of Smad2 and -3 proteins. In males, testosterone (T) increased FSHβ PT two- to threefold between 3 and 24 h and was correlated with reduced FS mRNA, transient increases in Smad2, -4, and -7 mRNAs, and a six- to 10-fold increase in pSmad2, and activin βB mRNA was unchanged. In females, T also increased FSHβ PT twofold and pSmad2 threefold but had no effect on activin βB, FS, or the Smad mRNAs. Androgen also increased Smad2 phosphorylation in gonadotrope-derived αT3 cells. In contrast, estradiol had no effect on FSHβ PT but transiently increased activin βB mRNA and suppressed FS mRNA before increasing FS mRNA at 24 h and increased Smads2, -3, and -7 mRNAs and pSmad2 threefold. In conclusion, T acts on the pituitary to increase FSHβ PT in both sexes and modulates FS mRNA, Smad mRNAs, and/or Smad2 phosphorylation. These findings suggest that T regulates FSHβ transcription, in part, through modulation of various components of the activin-signaling system.
Caffeine-induced Ca2+ release increases AMPK-dependent glucose uptake in rodent soleus muscle
Authors: Jensen Thomas E. , Rose Adam J. , Hellsten Ylva , Wojtaszewski Jørgen F. P. , Richter Erik A.
Published: April 2007

Previous studies have proposed that caffeine-induced activation of glucose transport in skeletal muscle is independent of AMP-activated protein kinase (AMPK) because α-AMPK Thr172 phosphorylation was not increased by caffeine. However, our previous studies, as well as the present, show that AMPK phosphorylation measured in whole muscle lysate is not a good indicator of AMPK activation in rodent skeletal muscle. In lysates from incubated rat soleus muscle, a predominant model in previous caffeine-studies, both acetyl-CoA carboxylase-β (ACCβ) Ser221 and immunoprecipitated α1-AMPK activity increased with caffeine incubation, without changes in AMPK phosphorylation or immunoprecipitated α2-AMPK activity. This pattern was also observed in mouse soleus muscle, where only ACCβ and α1-AMPK phosphorylation were increased following caffeine treatment. Preincubation with the selective CaMKK inhibitor STO-609 (5 μM), the CaM-competitive inhibitor KN-93 (10 μM), or the SR Ca2+ release blocking agent dantrolene (10 μM) all inhibited ACCβ phosphorylation and α1-AMPK phosphorylation, suggesting that SR Ca2+ release may work through a CaMKK-AMPK pathway. Caffeine-stimulated 2-deoxyglucose (2DG) uptake reflected the AMPK activation pattern, being increased with caffeine and inhibited by STO-609, KN-93, or dantrolene. The inhibition of 2DG uptake is likely causally linked to AMPK activation, since muscle-specific expression of a kinase-dead AMPK construct greatly reduced caffeine-stimulated 2DG uptake in mouse soleus. We conclude that a SR Ca2+-activated CaMKK may control α1-AMPK activation and be necessary for caffeine-stimulated glucose uptake in mouse soleus muscle.
Protective Role of Endogenous Erythropoietin System in Nonhematopoietic Cells Against Pressure Overload–Induced Left Ventricular Dysfunction in Mice
Authors: Asaumi Yasuhide , Kagaya Yutaka , Takeda Morihiko , Yamaguchi Nobuhiro , Tada Hiroko , Ito Kenta , Ohta Jun , Shiroto Takashi , Shirato Kunio , Minegishi Naoko , Shimokawa Hiroaki
Published: April 2007

Background—

Erythropoietin (Epo) receptors (EpoRs) are expressed in the heart. We have recently demonstrated that the endogenous Epo-EpoR system plays an important protective role in myocardial ischemia in mice and humans. In the present study, we tested our hypothesis that the endogenous Epo-EpoR system in nonhematopoietic cells also plays a protective role against pressure overload–induced cardiac dysfunction in vivo.

Methods and Results—

Transgene-rescued EpoR-null mutant mice (
EpoR
−/−
rescued
) that express EpoR exclusively in the hematopoietic cells were subjected to transverse aortic constriction (TAC). At 1 week after TAC, left ventricular weight and lung weight were significantly increased in
EpoR
−/−
rescued
mice compared with wild-type mice, although the fibrotic area was comparably increased after TAC in the 2 genotypes. In the
EpoR
−/−
rescued
mice with TAC, left ventricular end-diastolic diameter was significantly increased, left ventricular fractional shortening was significantly decreased, and survival rate was significantly decreased compared with wild-type mice with TAC. Phosphorylation of STAT3 at 5 hours and 1 week after TAC and that of p38 at 5 hours after TAC were significantly increased in wild-type mice but not in
EpoR
−/−
rescued
mice. Vascular endothelial growth factor protein expression and capillary density in left ventricular myocardium were significantly decreased in
EpoR
−/−
rescued
mice with TAC compared with wild-type mice with TAC.

Conclusions—

These results suggest that the endogenous Epo-EpoR system in the nonhematopoietic cells plays an important protective role against pressure overload–induced cardiac dysfunction in vivo.