bluuebunny/crossref_metadata_2025 huggingface dataset:
Interleukin‐4 activates large‐conductance, calcium‐activated potassium (BKCa) channels in human airway smooth muscle cells
Authors: Martin Gilles , O'Connell Robert J. , Pietrzykowski Andrzej Z. , Treistman Steven N. , Ethier Michael F. , Madison J. Mark
Published: April 2008

Large‐conductance, calcium‐activated potassium (BKCa) channels are regulated by voltage and near‐membrane calcium concentrations and are determinants of membrane potential and excitability in airway smooth muscle cells. Since the T helper−2 (Th2) cytokine, interleukin (IL)‐4, is an important mediator of airway inflammation, we investigated whether IL‐4 rapidly regulated BKCa activity in normal airway smooth muscle cells. On‐cell voltage clamp recordings were made on subconfluent, cultured human bronchial smooth muscle cells (HBSMC). Interleukin‐4 (50 ng ml−1), IL‐13 (50 ng ml−1) or histamine (10 μm) was added to the bath during the recordings. Immunofluorescence studies with selective antibodies against the α and β1 subunits of BKCa were also performed. Both approaches demonstrated that HBSMC membranes contained large‐conductance channels (>200 pS) with both calcium and voltage sensitivity, all of which is characteristic of the BKCa channel. Histamine caused a rapid increase in channel activity, as expected. A new finding was that perfusion with IL‐4 stimulated rapid, large increases in BKCa channel activity (77.2 ± 63.3‐fold increase, P < 0.05, n= 18). This large potentiation depended on the presence of external calcium. In contrast, IL‐13 (50 ng ml−1) had little effect on BKCa channel activity, but inhibited the effect of IL‐4. Thus, HBSMC contain functional BKCa channels whose activity is rapidly potentiated by the cytokine, IL‐4, but not by IL‐13. These findings are consistent with a model in which IL‐4 rapidly increases near‐membrane calcium concentrations to regulate BKCa activity.
2‐Aminoethoxydiphenyl borate directly facilitates and indirectly inhibits STIM1‐dependent gating of CRAC channels
Authors: Peinelt Christine , Lis Annette , Beck Andreas , Fleig Andrea , Penner Reinhold
Published: April 2008

2‐Aminoethoxydiphenyl borate (2‐APB) has emerged as a useful pharmacological tool in the study of store‐operated Ca2+ entry (SOCE). It has been shown to potentiate store‐operated Ca2+ release‐activated Ca2+ (CRAC) currents at low micromolar concentrations and to inhibit them at higher concentrations. Initial experiments with the three CRAC channel subtypes CRACM1, CRACM2 and CRACM3 have indicated that they might be differentially affected by 2‐APB. We now present a thorough pharmacological profile of 2‐APB and report that it can activate CRACM3 channels in a store‐independent manner without the requirement of STIM1, whereas CRACM2 by itself is completely unresponsive to 2‐APB and CRACM1 is only very weakly activated. However, when coexpressed with STIM1 and activated via store depletion, CRACM1 and CRACM2 are facilitated at low 2‐APB concentrations and inhibited at higher concentrations, while CRACM3 only exhibits potentiated currents. Consistently, the 2‐APB‐induced CRAC currents exhibit altered selectivities that are characterized by a leftward shift in reversal potential and the emergence of large outward currents that are carried by normally impermeant monovalent cations such as Cs+ or K+. These results suggest that 2‐APB has agonistic and antagonistic modes of action on CRAC channels, acting at the channel level as a store‐independent and direct gating agonist for CRACM3 and a potentiating agonist for CRACM1 and CRACM2 following store‐operated and STIM1‐dependent activation. The inhibition of CRACM1 channels by high concentrations of 2‐APB appears to involve a direct block at the channel level and an additional uncoupling of STIM1 and CRACM1, since the compound reversed the store‐dependent multimerization of STIM1. Finally, we demonstrate that single‐point mutations of critical amino acids in the selectivity filter of the CRACM1 pore (E106D and E190A) enable 2‐APB to gate CRACM1 in a STIM1‐independent manner, suggesting that 2‐APB facilitates CRAC channels by altering the pore architecture.
The effects of experimental muscle and skin pain on the static stretch sensitivity of human muscle spindles in relaxed leg muscles
Authors: Birznieks Ingvars , Burton Alexander R. , Macefield Vaughan G.
Published: April 2008

Animal studies have shown that noxious inputs onto γ‐motoneurons can cause an increase in the activity of muscle spindles, and it has been proposed that this causes a fusimotor‐driven increase in muscle stiffness that is believed to underlie many chronic pain syndromes. To test whether experimental pain also acts on the fusimotor system in humans, unitary recordings were made from 19 spindle afferents (12 Ia, 7 II) located in the ankle and toe extensors or peronei muscles of awake human subjects. Muscle pain was induced by bolus intramuscular injection of 0.5 ml 5% hypertonic saline into tibialis anterior (TA); skin pain was induced by 0.2 ml injection into the overlying skin. Changes in fusimotor drive to the muscle spindles were inferred from changes in the mean discharge frequency and discharge variability of spindle endings in relaxed muscle. During muscle pain no afferents increased their discharge activity: seven afferents (5 Ia, 2 II) showed a decrease and six (4 Ia, 2 II) afferents were not affected. During skin pain of 13 afferents discharge rate increased in one (Ia) and decreased in two (1 Ia, 1 II). On average, the overall discharge rate decreased during muscle pain by 6.1% (P < 0.05; Wilcoxon), but remained essentially the same during skin pain. There was no detectable correlation between subjective pain level and the small change in discharge rate of muscle spindles. Irrespective of the type of pain, discharge variability parameters were not influenced (P > 0.05; Wilcoxon). We conclude that, contrary to the ‘vicious cycle’ hypothesis, acute activation of muscle or skin nociceptors does not cause a reflex increase in fusimotor drive in humans. Rather, our results are more aligned with the pain adaptation model, based on clinical studies predicting pain‐induced reductions of agonist muscle activity.
Interpolated twitches in fatiguing single mouse muscle fibres: implications for the assessment of central fatigue
Authors: Place Nicolas , Yamada Takashi , Bruton Joseph D. , Westerblad Håkan
Published: April 2008

An electrically evoked twitch during a maximal voluntary contraction (twitch interpolation) is frequently used to assess central fatigue. In this study we used intact single muscle fibres to determine if intramuscular mechanisms could affect the force increase with the twitch interpolation technique. Intact single fibres from flexor digitorum brevis of NMRI mice were dissected and mounted in a chamber equipped with a force transducer. Free myoplasmic [Ca2+] ([Ca2+]i) was measured with the fluorescent Ca2+ indicator indo‐1. Seven fibres were fatigued with repeated 70 Hz tetani until 40% initial force with an interpolated pulse evoked every fifth tetanus. Results showed that the force generated by the interpolated twitch increased throughout fatigue, being 9 ± 1% of tetanic force at the start and 19 ± 1% at the end (P < 0.001). This was not due to a larger increase in [Ca2+]i induced by the interpolated twitch during fatigue but rather to the fact that the force–[Ca2+]i relationship is sigmoidal and fibres entered a steeper part of the relationship during fatigue. In another set of experiments, we observed that repeated tetani evoked at 150 Hz resulted in more rapid fatigue development than at 70 Hz and there was a decrease in force (‘sag’) during contractions, which was not observed at 70 Hz. In conclusion, the extent of central fatigue is difficult to assess and it may be overestimated when using the twitch interpolation technique.
Electrostatic Spray Deposition of Nanostructured Hydroxyapatite Coating for Biomedical Applications
Authors: Jiang Wenping , Sun Li , Nyandoto Gilbert , Malshe Ajay P.
Published: April 2008

Hydroxyapatite, a calcium phosphate ceramic, is chemically similar to bone mineral and one of the few materials able to produce direct-bonding osteogenesis. Nanostructured hydroxyapatite coating has proved effective in promoting cell growth. However, synthesis of the coating on components of complex geometries with controlled phases is still a challenge. In this paper, we present the results from the exploration of electrostatic spray coating of hydroxyapatite nanoparticles and the interaction of particles with laser. The nanoparticles were deposited on commercial grade titanium alloy (Ti6Al4V) as a coating perform and bonded using a transient laser heating process. The coating was characterized for its surface morphology, particle size, and adhesion, and analyzed for its chemical compositions and phases. Results have shown the potential of this process to address some of the issues present in the current synthesis processes.
Numerical Study of Radiation Characteristics in a Dish Solar Collector System
Authors: Shuai Yong , Xia Xin-Lin , Tan He-Ping
Published: April 2008

This paper aims at predicting radiation characteristics of the solar collector system by the Monte Carlo method with respect to the corresponding optical properties. Several probability models were introduced to analyze the effects of sunshape and surface roughness. Directional characteristics of radiative flux in the focal region and flux distribution of the cavity receiver were considered. An equivalent radiation flux method is presented for designing the shape of the cavity receiver. Based on the relative numerical simulation results, a new shape cavity receiver called “upside-down tear drop” is proposed to meet an almost uniform radiation flux field. Radiation effects due to multiple reflections and thermal emission in the cavity are parametrized by using the radiative exchange factor. The calculation results can be a valuable reference for the design and assemblage of the dish solar collector system.
Buoyancy Effects on Thermal Behavior of a Flat-Plate Solar Collector
Authors: Fan Jianhua , Furbo Simon
Published: April 2008

Theoretical and experimental investigations of the flow and temperature distribution in a 12.53m2 solar collector panel with an absorber consisting of two vertical manifolds interconnected by 16 parallel horizontal fins have been carried out. The investigations are focused on overheating and boiling problems in the collector panel. Single-phase liquid flow and heat transfer in the collector panel are studied by means of computational fluid dynamics (CFD) calculations. Differently designed collectors are investigated with different collector fluid volume flow rates. The effect of friction and the influence of the buoyancy effects are considered in the investigations. Further, experimental investigations of the solar collector panel are carried out. The flow distribution through the absorber is evaluated by means of temperature measurements on the back of the absorber tubes. The measured temperatures are compared to the temperatures determined by the CFD model and there is a good agreement between the measured and calculated temperatures. Calculations with the CFD model elucidate the flow and temperature distribution in the collector. The influences of collector fluid flow rate and inlet temperature on the flow and temperature distribution are shown. The flow distribution through the absorber tubes is uniform if a high flow rate of 10.0l∕min is used. By decreased collector fluid flow rate and by increased collector fluid inlet temperature, the flow distribution gets less uniform due to the influence of buoyancy force. If the collector fluid flow rate is small and the collector fluid inlet temperature is high enough, severe nonuniform flow distribution may happen with a small flow rate or even zero or reverse flow in the upper horizontal strips, resulting in overheating or boiling problems in the strips. The CFD calculations elucidate the flow and temperature distribution in the collector panels of different designs. Based on the investigations, recommendations are given in order to avoid overheating or boiling problems in the solar collector panel.
A Feasibility Study of Using Solar Liquid-Desiccant Air Conditioner in Queensland, Australia
Authors: Alizadeh Shahab
Published: April 2008

A feasibility study of using solar liquid-desiccant air conditioner (LDAC) developed in Queensland has been undertaken. The system uses high effectiveness cross-flow polymer plate heat exchanger (PPHE), as the absorber unit. Outside air is dehumidified by strong liquid desiccant and indirectly cooled within the PPHE. The warm dry air is, subsequently, cooled and humidified through a direct evaporative cooler and supplied to the conditioned space. The weak desiccant solution from the absorber unit is concentrated in a scavenger air regenerator using hot water from flat plate solar collectors. The prototype of the absorber unit of the liquid-desiccant system has been tested under the summer conditions of Brisbane, using lithium chloride as the absorbent solution. The results of the experiments indicate that they are in good agreement with a previously developed model for the absorber unit. The tests further reveal that the unit has a satisfactory performance in controlling the air temperature and relative humidity when installed on a commercial site of 120m2 area in Brisbane. A commercialization strategy has been proposed in this study for a solar operated LDAC in Queensland and compared with the conventional direct expansion (DX) system. Based on the computer modeling results obtained from the system simulation for a building in Cairns, North Queensland, the operating costs of the LDAC are significantly lower than its conventional DX counterpart. This study further reveals that using the solar operated LDAC with a storage system will result in considerable savings in operating costs when compared with the equivalent gas-fired system. A simple payback of five years was determined for the solar components in this study.
Life Cycle Environmental Impacts of Electricity Production by Solarthermal Power Plants in Spain
Authors: Lechón Yolanda , de la Rúa Cristina , Sáez Rosa
Published: April 2008

The objectives of the analysis reported in this paper are to evaluate the environmental impacts of the electricity produced in a 17MW solar thermal plant with central tower technology and a 50MW solar thermal plant with parabolic trough technology, to identify the opportunities to improve the systems in order to reduce their environmental impacts, and to evaluate the environmental impact resulting from compliance with the solar thermal power objectives in Spain. The methodology chosen is the life cycle assessment (LCA), described in the international standard series ISO 14040-43. The functional unit has been defined as the production of 1kWh of electricity. Energy use needed to construct, operate, and dismantle the power plants is estimated. These results are used to calculate the “energy payback time” of these technologies. Results were around 1yr for both power plants. Environmental impacts analyzed include the global warming impacts along the whole life cycle of the power plants, which were around 200g∕kWh generated. Finally, the environmental impacts associated with the compliance of the solar thermal power objectives in Spain were computed. Those figures were then used to estimate the avoided environmental impacts including the potential CO2 emission savings that could be accomplished by these promotion policies. These savings amounted for 634kt of CO2 equiv./yr.
The Influence of Process Variation on a Cortical Bone Interference Fit Pin Connection
Authors: Mauntler Nathan A. , Schmitz Tony L. , Ziegert John C.
Published: April 2008

The interference fit is a common method for creating mechanical assemblies. When manufacturing the individual components to be assembled in this method, close dimensional control of the mating components is required in order to ensure that the amount of interference is sufficient to create a secure assembly, but not so great as to cause excessive stresses or failure of the individual components. In this work, we study interference fit connections in an assembly of human (cadaveric) cortical and cancellous bone, i.e., an allograft, used in spinal fusion surgeries. A difficulty encountered in this application is that, in addition to the machining steps, the assembly must go through subsequent sterilization and lyophilization, or freeze drying, processes that may affect the quality of the interference fit. This report examines the quality of the allograft interference fits using dimensional measurements of manufactured components at all stages of the manufacturing process, followed by examination for cracking and measurement of the pull-apart forces for assemblies. The experimental results are compared to finite element models of the interference fit and also to Monte Carlo models of the assembly using a simple thick-wall cylinder model. Experimental results show that the lyophilization process significantly affects the component dimensions, resulting in a much greater spread in interference values and likely leading to cracking and∕or loss of interference.
Low Plasticity Burnishing: An Innovative Manufacturing Method for Biomedical Applications
Authors: Seemikeri C. Y. , Brahmankar P. K. , Mahagaonkar S. B.
Published: April 2008

Biomedical manufacturing technologies are assuming highly visible position at the frontiers of manufacturing. A new field, “engineered surfaces,” is emerging as a more effective and economic route to successful manufacture. Low plasticity burnishing (LPB) is relatively a new method of surface enhancement, which raises the burnishing to the next level of sophistication. LPB can provide deep and stable surface compression for improved surface integrity characteristics. This technology could be applied to diversified biomedical applications, since it has the potential to improve many surface characteristics, such as low- and high-cycle fatigue strengths, surface finish, surface hardness, corrosion resistance, wear resistance, etc. The present study focuses on the surface roughness, microhardness, surface integrity, and fatigue life aspects of AISI 316L work material, which is most commonly used in prosthesis, using full factorial design of experiments. Favorable and optimum conditions could be predicted and tailored for different biomedical requirements and applications. The assessment of the surface integrity aspects on work material was done, in terms of identifying the predominant factors, their order of significance, evaluating the interaction effects of parameters, and setting the levels of the factors for minimizing surface roughness and∕or maximizing surface hardness and fatigue life. Regression models were developed for surface characteristics of importance as response variables. Subsurface microhardness studies were also done to assess the depth of compression, altered material zone, and correlate fatigue life with surface roughness and surface hardness. The process can be applied to critical components used in biomedical field, such as total hip prosthesis, invasive surgeries, or medical implants effectively, as the LPB process today has significant process cycle time advantages, lower capital cost, and adaptability to conventional machine shop environment.
Rheological Properties of Cell-Hydrogel Composites Extruding Through Small-Diameter Tips
Authors: Cheng Jie , Lin Feng , Liu Haixia , Yan Yongnian , Wang Xiaohong , Zhang Renji , Xiong Zhuo
Published: April 2008

To form 3D structures with composites of living cells and hydrogel is now becoming an attractive technology in both bioengineering and manufacturing areas. Variant processes have been presented, most of which are based on the cell composite extrusion and deposition technique. So, the design of cell extrusion nozzle turns into an important phase, and the rheological properties of cell-hydrogel composites act as a key parameter and must be well investigated. In this paper, an entrance pressure detection device and adaptor for small-diameter tips were developed. With the hypothesis of power law fluid type, the power law constant and coefficient were calculated. As derived from the experimental results, the cell-hydrogel composites (with the maximum cell concentration of 107∕ml) show no difference from hydrogel materials in rheological properties. Based on these, the manufacturability of cell-hydrogel composites was discussed. Also, the cell viability, which is another important issue in cell assembly technology, was discussed. The peak percentage (97%) was achieved at the flow rate of 0.5mm3∕s. The extruding duration and the maximum shear stress loaded on cells were considered as two influence mechanisms.
Fabrication of Cell-Encapsulated Alginate Microfiber Scaffold Using
Microfluidic Channel
Authors: Kim Byung , Kim Intae , Choi WooSeok , Kim Sung Won , Kim JooSung , Lim Geunbae
Published: April 2008

Traditional approaches in tissue engineering are limited in that cell seeding is inefficient and cells cannot be located on a scaffold precisely. Moreover, the traditional methods, which rely on a random and probabilistic process, produce scaffolds with low regularity in porosity, pore size, and interconnection of pores. In this research, we propose a novel method to fabricate a scaffold for tissue engineering, which can overcome the limitations of traditional approaches. Cell-encapsulated alginate solution and cross-linker solution were laminarly flowed into a microfluidic channel. Then, the alginate solution was gelled to form a cell-encapsulated alginate microfiber by the diffusion of gelation ion from the cross-linker solution and ejected from the outlet of channel to the reservoir. The diameter of the fabricated microfiber can be controlled by the flow rate ratio of the two solutions. Moreover, this method, which has no cell seeding step, eliminates the possibility of loss of cells and the problems related to distribution of cells. We also show the feasibility of the alginate microfiber as a scaffold, which can promote chondrogenesis. The chondrogenesis in the alginate microfiber was evaluated by both histological and biochemical analyses. The increase of major markers of chondrogenesis such as glycosaminoglycan and collagen shows the potential of alginate microfiber as a scaffold for cartilage.
Characterization of Cell Constructs Generated With Inkjet Printing Technology Using In Vivo Magnetic Resonance Imaging
Authors: Xu Tao , Olson John , Zhao Weixin , Atala Anthony , Zhu Jian-Ming , Yoo James J.
Published: April 2008

We report the use of a high resolution magnetic resonance (MR) imaging technique to monitor the development and maturation of tissue-printed constructs in vivo. Layer-by-layer inkjet printing technology was used to fabricate three different tissue constructs on alginate∕collagen gels: bovine aortic endothelial cell-printed (to represent soft tissue), human amniotic fluid-derived stem cell-printed (to represent hard tissue as they underwent osteogenic differentiation in vivo), and cell-free constructs (scaffold only). The constructs were subcutaneously implanted into athymic mice and regularly monitored using a 7T magnetic resonance imaging (MRI) scanner. The three tissue construct types showed distinct image contrast characteristics due to the different tissue microstructures and biochemical compositions at various time points. In addition, changes in tissue microvasculature were examined with dynamic perfusion MRI. These results indicate that high resolution MRI is a promising method for noninvasive, long-term monitoring of the status of cell-printed construct growth, differentiation, and vascularization.
Mutations in the Scaffoldin Gene,
cipA
, of
Clostridium thermocellum
with Impaired Cellulosome Formation and Cellulose Hydrolysis: Insertions of a New Transposable Element, IS
1447
, and Implications for Cellulase Synergism on Crystalline Cellulose
Authors: Zverlov Vladimir V. , Klupp Martina , Krauss Jan , Schwarz Wolfgang H.
Published: April 2008

Mutants of
Clostridium thermocellum
that had lost the ability to adhere to microcrystalline cellulose were isolated. Six of them that showed diminished ability to depolymerize crystalline cellulose were selected. Size exclusion chromatography of the proteins from the culture supernatant revealed the loss of the supramolecular enzyme complex, the cellulosome. However, denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis resulted in extracellular protein patterns comparable to those of isolated cellulosomes, except for a missing CipA band. Sequencing of the six mutant
cipA
genes revealed a new insertion (IS) element, IS
1447
, belonging to the IS
3
family. It was inserted into the
cipA
reading frame in four different locations: cohesin module 1, two different positions in the carbohydrate binding module, and cohesin module 3. The IS sequences were identical and consisted of a transposase gene and the inverted repeats IRR and IRS. The insertion resulted in an obviously nonspecific duplication of 3 base pairs within the target sequence. This lack of specificity allows transposition without the need of a defined target DNA sequence. Eighteen copies of IS
1447
were identified in the genomic sequence of
C. thermocellum
ATCC 27405. At least one of them can be activated for transposition. Compared to the wild type, the mutant culture supernatant, with a completely defective CipA protein, showed equal specific hydrolytic activity against soluble β-glucan but a 15-fold reduction in specific activity with crystalline cellulose. These results identify a genetic basis for the synergistic effect of complex formation on crystalline-cellulose degradation.
Muscle deoxygenation of upper-limb muscles during progressive arm-cranking exercise
Authors: Lusina Sarah-Jane C. , Warburton Darren E. R. , Hatfield Nicola G. , Sheel A. William
Published: April 2008

The purpose of this study was to determine which upper-limb muscle exhibits the greatest change in muscle deoxygenation during arm-cranking exercise (ACE). We hypothesized that the biceps brachii (BB) would show the greatest change in muscle deoxygenation during progressive ACE to exhaustion relative to triceps brachii (TR), brachioradialis (BR), and anterior deltoid (AD). Healthy young men (n = 11; age = 27 ± 1 y; mean ± SEM) performed an incremental ACE test to exhaustion. Near-infrared spectroscopy (NIRS) was used to monitor the relative concentration changes in oxy- (O2Hb), deoxy- (HHb), and total hemoglobin (Hbtot), as well as tissue oxygenation index (TOI) in each of the 4 muscles. During submaximal arm exercise, we found that changes to NIRS-derived measurements were not different between the 4 muscles studied (p > 0.05). At maximal exercise HHb was significantly higher in the BB compared with AD (p < 0.05). Relative to the other 3 muscles, BB exhibited the greatest decrease in O2Hb and TOI (p < 0.05). Our investigation provides two new and important findings: (i) during submaximal ACE the BB, TR, BR, and AD exhibit similar changes in muscle deoxygenation and (ii) during maximal ACE the BB exhibits the greatest change in intramuscular O2 status.
Chronic quercetin ingestion and exercise-induced oxidative damage and inflammation
Authors: McAnulty Steven R. , McAnulty Lisa S. , Nieman David C. , Quindry John C. , Hosick Peter A. , Hudson Matthew H. , Still Laura , Henson Dru A. , Milne Ginger L. , Morrow Jason D. , Dumke Charles L. , Utter Alan C. , Triplett Nan T. , Dibarnardi Adrianna
Published: April 2008

Quercetin is a flavonoid compound that has been demonstrated to be a potent antioxidant in vitro. The objective of this study was to evaluate if quercetin ingestion would increase plasma antioxidant measures and attenuate increases in exercise-induced oxidative damage. Forty athletes were recruited and randomized to quercetin or placebo. Subjects consumed 1000 mg quercetin or placebo each day for 6 weeks before and during 3 d of cycling at 57% work maximum for 3 h. Blood was collected before and immediately after exercise each day, and analyzed for F2-isoprostanes, nitrite, ferric-reducing ability of plasma, trolox equivalent antioxidant capacity, and C-reactive protein. Statistical analyses involved a 2 (treatment) × 6 (times) repeated measures analysis of variance to test main effects. F2-isoprostanes, nitrite, ferric-reducing ability of plasma, trolox equivalent antioxidant capacity, and C-reactive protein were significantly elevated as a result of exercise, but no group effects were found. Despite previous data demonstrating potent antioxidant actions of quercetin in vitro, this study indicates that this effect is absent in vivo and that chronic quercetin ingestion does not exert protection from exercise-induced oxidative stress and inflammation.
Association between dietary fat intake, liver fat, and insulin sensitivity in sedentary, abdominally obese, older men
Authors: Kuk Jennifer L. , Davidson Lance E. , Hudson Robert , Kilpatrick Katherine , Bacskai Kinga , Ross Robert
Published: April 2008

Whether dietary fat influences the interaction between liver fat, visceral adipose tissue (VAT), and metabolic risk is unclear. Thus, we sought to determine the independent associations between 1 and 10 d dietary fat intake, liver fat, and VAT on insulin sensitivity using a cross-sectional design. Liver fat score (LFS) was assessed by computed tomography and VAT by magnetic resonance imaging in 42 abdominally obese older men. Insulin sensitivity was measured by the hyperinsulinemic–euglycemic clamp technique. Diet composition was determined from self-recorded diet records for 1 and 10 d preceding the assessment of LFS. LFS was positively associated with the 10 d average fat and alcohol intake, but not with any 1 d average dietary variables. VAT (r = –0.36) and LFS (r = –0.32) were both negatively correlated with insulin sensitivity (p < 0.05). When LFS and VAT were entered in the same model, only VAT was an independent predictor of insulin sensitivity (p < 0.05). Control for the average 10 d alcohol consumption and fat intake improved the association between insulin sensitivity and LFS (from r = –0.32, p > 0.10 to r = –0.49, p < 0.05), but not VAT. In fact, after control for the 10 d dietary variables, both LFS and VAT were independent predictors of insulin sensitivity (p < 0.05). This was not true for any of the 1 d dietary intake variables. In conclusion, liver fat is associated with dietary fat intake and alcohol consumption over 10 d, but not 1 d. Furthermore, dietary habits may influence the relationship between liver fat and insulin sensitivity.
Influence of fiber-type composition on recovery from tourniquet-induced skeletal muscle ischemia–reperfusion injury
Authors: Walters Thomas J. , Kragh John F. , Baer David G.
Published: April 2008

This study was designed to determine if previously reported differences in the functional impairment of muscles composed of predominantly different fiber types occurs following extended periods of ischemia. We hypothesized that the soleus (Sol) muscle, a predominantly slow-twitch muscle, would be less vulnerable to tourniquet-induced ischemia–reperfusion than the plantaris (Plant), a predominantly fast-twitch muscle, as determined by the assessment of isometric contractile function. Male Sprague–Dawley rats were assigned to one of the following groups to undergo tourniquet application (TKA) (n = 6/group): 2 h TKA, 2 d recovery; 4 h TKA, 2 d recovery; 2 h TKA, 14 d recovery; or 4 h TKA, 14 d recovery. In situ isometric contractile properties were assessed in the predominantly slow-twitch Sol and the predominantly fast-twitch Plant; the contralateral muscle served as the internal control. At 2 d, muscle contraction could not be elicited via neural stimulation, but muscles did contract with direct stimulation, which indicates neural injury. This condition was resolved by day 14. At this time point, tetanic tension (Po) in the Plant was reduced by 45% and 69% in the 2 and 4 h groups, respectively. Po for the Sol was unaffected in the 2 h group, but was reduced by 30% in the 4 h group. The fatigue resistance of the Plant was increased 2 fold in the 4 h group and was unchanged in all other groups. These results demonstrate that vulnerability to tourniquet-induced ischemia–reperfusion injury is dramatically different with respect to muscle fiber-type composition.
Non-invasive methods in paediatric exercise physiology
Authors: Armstrong Neil , Fawkner Samantha G.
Published: April 2008

Oded Bar-Or’s hypothesis that children may be “metabolic non-specialists”, even when engaging in specialized sports, has stimulated the study of paediatric exercise metabolism since the publication of his classic text Pediatric sports medicine for the practitioner in 1983. Evidence drawn from several methodologies indicates an interplay of anaerobic and aerobic exercise metabolism in which children have a relatively higher metabolic contribution from oxidative energy pathways than adolescents or adults, whereas there is a progressive increase in glycolytic support of exercise with age, at least into adolescence and possibly into young adulthood. The picture is generally consistent but incomplete, as research with young people has been limited by both ethical and methodological constraints. The recent rigorous introduction of non-invasive techniques such as breath-by-breath respiratory gas analysis and magnetic resonance spectroscopy into paediatric exercise physiology promises to open up new avenues of research and generate unique insights into the metabolism of the exercising muscle during growth and maturation. It therefore appears that we might have available the tools necessary to answer some of the elegant questions raised by Professor Bar-Or over 25 years ago.
The time course of denervation-induced changes is similar in soleus muscles of adult and old rats
Authors: Degens Hans , Koşar Şükran Nazan , Hopman Maria T.E. , de Haan Arnold
Published: April 2008

Muscle denervation is accompanied by atrophy and a decline in oxidative capacity. We investigated whether the time course of adaptations following denervation of the soleus muscle differs in adult (5 months old) and older adult (25 months old) rats. We denervated the soleus muscle of the left leg, while the right leg served as an internal control. Two weeks after denervation, muscle mass was decreased both in adult and old animals to, respectively, 57% and 54% (p < 0.001) and capillary to fibre ratio (C:F) decreased to 51% and 50% (p < 0.01) of the control values. Yet, the capillary density was increased in older adult but not in adult muscles, indicating that the regression of the capillary bed during denervation lags behind the decrease in fibre size in the soleus muscle of the older rats. One week after denervation the optical density of sections stained for succinate dehydrogenase was 83% and 79% (p < 0.05) of control adult and older adult muscles, respectively, and then remained stable. This indicates that during the first week of denervation loss of oxidative capacity occurred at a relatively higher rate than that of muscle mass. No major changes occurred between 2 and 4 weeks of denervation, except for an increase in the proportion of hybrid (I/IIa) fibres in 4 week denervated muscles (adult 10% vs. 23%; old 1% vs. 13%; p < 0.05). Except for changes in capillarisation, the time course of atrophy and decrease in oxidative capacity following denervation was similar in soleus muscles from adult and old rats.
Metabolic syndrome in three ethnic groups using current definitions
Authors: Delisle Hélène , Désilets Marie-Claude , Vargas Estanislao Ramirez , Garrel Dominique
Published: April 2008

According to two current definitions, the prevalence of the metabolic syndrome (MetS) aamong black Haitians of Montreal was <20%, 30%–36% in Algonquin Indians of Quebec, and >45% in Mexicans of Oaxaca (all aged 35–60 y). Although phenotypes were different, high triglycerides and fasting dysglycemia were good predictors of MetS in all three groups using both definitions. The international cut-offs for abdominal obesity were not predictive of MetS in the Haitian subjects.
Sweat rate, salt loss, and fluid intake during an intense on-ice practice in elite Canadian male junior hockey players
Authors: Palmer Matthew S. , Spriet Lawrence L.
Published: April 2008

Previous research in many sports suggests that losing ~1%–2% body mass through sweating impairs athletic performance. Elite-level hockey involves high-intensity bursts of skating, arena temperatures are >10 °C, and players wear protective equipment, all of which promote sweating. This study examined the pre-practice hydration, on-ice fluid intake, and sweat and sodium losses of 44 candidates for Canada’s junior men’s hockey team (mean ± SE age, 18.4 ± 0.1 y; height, 184.8 ± 0.9 cm; mass, 89.9 ± 1.1 kg). Players were studied in groups of 10–12 during 4 intense 1 h practices (13.9 °C, 66% relative humidity) on 1 day. Hydration status was estimated by measuring urine specific gravity (USG). Sweat rate was calculated from body mass changes and fluid intake. Sweat sodium concentration ([Na]) was analyzed in forehead sweat patch samples and used with sweat rate to estimate sodium loss. Over 50% of players began practice mildly hypohydrated (USG > 1.020). Sweat rate during practice was 1.8 ± 0.1 L·h–1 and players replaced 58% (1.0 ± 0.1 L·h–1) of the sweat lost. Body mass loss averaged 0.8% ± 0.1%, but 1/3 of players lost more than 1%. Sweat [Na] was 54.2 ± 2.4 mmol·L–1 and sodium loss averaged 2.26 ± 0.17 g during practice. Players drank only water during practice and replaced no sodium. In summary, elite junior hockey players incurred large sweat and sodium losses during an intense practice, but 2/3 of players drank enough to minimize body mass loss. However, 1/3 of players lost more than 1% body mass despite ready access to fluid and numerous drinking opportunities from the coaches.
Recent developments in mass spectrometry-based quantitative phosphoproteomicsThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Systems and Chemical Biology, and has undergone the Journal's usual peer review process.
Authors: Smith Jeffrey C. , Figeys Daniel
Published: April 2008

Protein phosphorylation is a reversible post-translational modification that is involved in virtually all eukaryotic cellular processes and has been studied in great detail in recent years. Many developments in mass spectrometry (MS)-based proteomics have been successfully applied to study protein phosphorylation in highly complicated samples. Furthermore, the emergence of a variety of enrichment strategies has allowed some of the challenges associated with low phosphorylation stoichiometry and phosphopeptide copy number to be overcome. The dynamic nature of protein phosphorylation complicates its analysis; however, a number of methods have been developed to successfully quantitate phosphorylation changes in a variety of cellular systems. The following review details some of the most recent breakthroughs in the study of protein phosphorylation, or phosphoproteomics, using MS-based approaches. The majority of the focus is placed on detailing strategies that are currently used to conduct MS-based quantitative phosphoproteomics.
Ribosomal synthesis of nonstandard peptidesThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Systems and Chemical Biology, and has undergone the Journal's usual peer review process.
Authors: Kang Taek Jin , Suga Hiroaki
Published: April 2008

It is well known that standard peptides, which comprise proteinogenic amino acids, can act as specific chemical probes to target proteins with high affinity. Despite this fact, a number of peptide drug leads have been abandoned because of their poor cell permeability and protease instability. On the other hand, nonstandard peptides isolated as natural products often exhibit remarkable pharmaco-behavior and stability in vivo. Although it is likely that numerous nonstandard therapeutic peptides capable of recognizing various targets could have been synthesized, enzymes for nonribosomal peptide syntheses are complex; therefore, it is difficult to engineer such modular enzymes to build nonstandard peptide libraries. Here we describe an emerging technology for the synthesis of nonstandard peptides that employs an integrated system of reconstituted cell-free translation and flexizymes. We summarize the historical background of this technology and discuss its current and future applications to the synthesis of nonstandard peptides and drug discovery.
Solid-phase assays for small molecule screening using sol-gel entrapped proteinsThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Systems and Chemical Biology, and has undergone the Journal's usual peer review process.
Authors: Lebert Julie M. , Forsberg Erica M. , Brennan John D.
Published: April 2008

With compound libraries exceeding one million compounds, the ability to quickly and effectively screen these compounds against relevant pharmaceutical targets has become crucial. Solid-phase assays present several advantages over solution-based methods. For example, a higher degree of miniaturization can be achieved, functional- and affinity-based studies are possible, and a variety of detection methods can be used. Unfortunately, most protein immobilization methods are either too harsh or require recombinant proteins and thus are not amenable to delicate proteins such as kinases and membrane-bound receptors. Sol-gel encapsulation of proteins in an inorganic silica matrix has emerged as a novel solid-phase assay platform. In this minireview, we discuss the development of sol-gel derived protein microarrays and sol-gel based monolithic bioaffinity columns for the high-throughput screening of small molecule libraries and mixtures.
A closed-form solution for composite tunnel linings in a homogeneous infinite isotropic elastic medium
Authors: El Naggar Hany , Hinchberger Sean D. , Lo K. Y.
Published: April 2008

This paper presents a closed-form solution for composite tunnel linings in a homogeneous infinite isotropic elastic medium. The tunnel lining is treated as an inner thin-walled shell and an outer thick-walled cylinder embedded in linear elastic soil or rock. Solutions for moment and thrust have been derived for cases involving slip and no slip at the lining–ground interface and lining–lining interface. A case involving a composite tunnel lining is studied to illustrate the usefulness of the solution.
Hazard analysis of an active slide in the Thompson River Valley, Ashcroft, British Columbia, Canada
Authors: Eshraghian Arash , Martin C. Derek , Morgenstern Norbert R.
Published: April 2008

Current practice in landslide hazard analysis does not commonly address the potential for different rates of movement after failure. The movement rates of an active landslide may vary significantly; therefore, the consequences analysis for such a landslide requires the calculation of the probability of different post-failure movement rates. Slide CN50.9 near Ashcroft, B.C., is used to demonstrate the hazard analysis of active landslides that incorporates the probability of post-failure movement rate. After defining the characteristics of the slide and the movement trigger, a probabilistic slope stability analysis for a 100 year period is conducted that considers the material and trigger uncertainties in the analysis. Then the uncertainties in the groundwater condition and amount of toe erosion are added to the probabilistic slope stability results. A new method is introduced for incorporating the probability of the different movement rates of each translational block within the slide body in the hazard analysis. A relatively high probability (0.1) of rapid reactivation for the toe reactivation block is estimated. The probability of very rapid retrogression of the current main scarp within the next 100 year period is calculated to be relatively low (0.003). A detailed risk analysis based on this hazard analysis will be helpful for decision makers.
Resistivity measurements as a tool for outlining quick-clay extent and valley-fill stratigraphy: a feasibility study from Buvika, central Norway
Authors: Solberg Inger-Lise , Rønning Jan Steinar , Dalsegg Einar , Hansen Louise , Rokoengen Kåre , Sandven Rolf
Published: April 2008

Thick, marine clay deposits in valleys along the Norwegian coast are occasionally subjected to large landslides involving quick clay. Detailed mapping of the extent of quick clay is of great interest for planning and protection purposes, as the position of quick clay within slopes has a major impact on the landslide risk. Ground conditions in the small valley of Buvika, mid-Norway, are characterized by thick occurrences of quick clay, which are documented in numerous geotechnical investigations. The resistivity method is potentially well suited for outlining pockets of quick clay since quick clay has a slightly higher electric resistivity (10–80 Ωm) than intact unleached clay (1–10 Ωm). This is due to a higher salt content in the latter. These relations are supported in this study by pore-water salt content measurements. The acquired resistivity profiles are compared with other geophysical data and geotechnical drilling information. Results are promising, and acquired resistivity profiles are interpreted in terms of quick-clay extents, stratigraphy, bedrock influence, and groundwater drainage patterns. Mismatch between intersecting resistivity profiles may be an indication of local geological variations.
A coupled consolidation shear model for the process of formation of glaciated soils
Authors: Huang Bingquan , Sharma Jitendra S.
Published: April 2008

It has been generally observed that the measured preconsolidation pressure values for glaciated soils are not compatible with the measured effective pressure values at the bed of the glacier if one-dimensional consolidation alone is considered as the formation process for these soils. In this paper, a new model for the process of formation of glaciated soil, termed the coupled consolidation shear (CCS) model, is developed using the frameworks of critical state soil mechanics and small-strain consolidation theory. The CCS model includes simultaneous shearing and consolidation of subglacial sediments and is able to simulate profiles of preconsolidation pressure versus depth that closely resemble those observed in glaciated soils. The CCS model is validated by successfully simulating the profile of preconsolidation pressure versus depth for an 80 m deep Battleford till layer in Birsay, Saskatchewan, Canada. The CCS model suggests the existence of anisotropic yield strength and stiffness in glaciated soils as a consequence of coupling subglacial shear and consolidation.
Analysis of the annual thermal response of an earth dam for the assessment of the hydraulic conductivity of its compacted till core
Authors: Smith M. , Konrad J.-M.
Published: April 2008

Heat carried by the seepage water along hydraulic flow lines can serve as a natural tracer to help detect contrasting hydraulic conductivities in embankment dams. Thermal monitoring was realized on the 94.5 m high QA-01 embankment dam in northern Quebec to characterize the temperature distribution across its entire section. The analysis of the annual thermal response of the dam clearly showed a zone of higher seepage velocities in the compacted till core. Approximations concerning the increased hydraulic conductivity were made using a simple thermal model. Complementary numerical modelling provided a more rigorous quantitative assessment of the seepage patterns. The calculations have shown hydraulic conductivities that are 20 times larger than the expected values. Thermal monitoring can detect zones of increased seepage, which can be related to internal erosion or other factors, such as the variability of the soil properties due to construction practices. Temperature measurements alone are not adequate to determine the cause of a permeable zone in a dam or to predict its possible evolution.