Reduction In Maximum Velocity Research Articles

A Load-Velocity Relationship in Sprint?

The aims were to compare predicted maximal velocity from load-velocity relationships established with different resisted and assisted loads by different regression analyses to the measured maximal velocity during sprint running, and to compare maximal velocity measured between a robotic pulley system and laser gun. Sixteen experienced male sprinters performed regular 50 m sprints, a 50 m with 5-kilogram-assisted sprint, and 10, 20, 30, and 30 m resisted sprints with, respectively, 65, 50, 25, and 10% calculated reduction in maximal velocity. Maximal velocity obtained by laser gun during the regular sprint was compared with predicted maximal velocity calculated from four trendlines (linear and polynomial based upon four resisted loads, and linear and polynomial based upon four resisted and one assisted load). Main findings demonstrate that the robotic pulley system and laser measure similar maximal velocities at all loads except at the load of 10% velocity reduction. Theoretical maximal velocity based upon calculated predictions were underestimated by 0.62-0.22 m/s (2.2-0.78 km/h; 6.7-2.3%) compared to measured maximal velocity. It was concluded that different regression analyses underestimated measured maximal velocity in regular sprinting and polynomial regression analysis (with resisted and assisted loads) estimation was closest to measured velocity (2.3%).

An oxidoreductase enzyme, fungal laccase immobilized on zeolitic imidazolate frameworks for the biocatalytic degradation of an endocrine-disrupting chemical, dimethyl phthalate

This study investigated a facile one-pot synthesis procedure of zeolitic imidazolate frameworks (ZIF) and laccase immobilization for use in the biodegradation of an endocrine-disrupting chemical (EDC), dimethyl phthalate (DMP). The as-synthesized Lac-ZIF’s characterization results revealed preserved crystallinity of the ZIF particles and lightly enzyme-coated decahedral particles. The immobilized laccase demonstrated enhanced temperature and storage stabilities for up to 65 ℃ and 20 d, respectively, for the DMP removal. While a reduced maximum velocity (Vmax) after the laccase immobilization (0.651–0.238 mg L−1 h−1) was observed, the Lac-ZIF presented a higher DMP removal efficiency (90.1%) compared to the free laccase (53.2%) within 4 h of contact time. Additionally, after 5 cycles of reuse, the Lac-ZIF retained a remarkable 95.2% efficiency and improved effectiveness in DMP decontamination from river water samples than the free laccase. Furthermore, the resulting DMP degradation metabolites were studied and revealed the production of relatively less toxic compounds after probable complete microbial mineralization. The study, therefore, demonstrates that Lac-ZIF has an admirable performance in the effective removal of phthalates from wastewater, making it a promising candidate for environmental remediation.

Mind the GAP: Purification and characterization of urea resistant GAPDH during extreme dehydration.

The African clawed frog (Xenopus laevis) withstands prolonged periods of extreme whole-body dehydration that lead to impaired blood flow, global hypoxia, and ischemic stress. During dehydration, these frogs shift from oxidative metabolism to a reliance on anaerobic glycolysis. In this study, we purified the central glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) to electrophoretic homogeneity and investigated structural, kinetic, subcellular localization, and post-translational modification properties between control and 30% dehydrated X. laevis liver. GAPDH from dehydrated liver displayed a 25.4% reduction in maximal velocity and a 55.7% increase in its affinity for GAP, as compared to enzyme from hydrated frogs. Under dehydration mimicking conditions (150 mM urea and 1% PEG), GAP affinity was reduced with a Km value 53.8% higher than controls. Frog dehydration also induced a significant increase in serine phosphorylation, methylation, acetylation, beta-N-acetylglucosamination, and cysteine nitrosylation, post-translational modifications (PTMs). These modifications were bioinformatically predicted and experimentally validated to govern protein stability, enzymatic activity, and nuclear translocation, which increased during dehydration. These dehydration-responsive protein modifications, however, did not appear to affect enzymatic thermostability as GAPDH melting temperatures remained unchanged when tested with differential scanning fluorimetry. PTMs could promote extreme urea resistance in dehydrated GAPDH since the enzyme from dehydrated animals had a urea I50 of 7.3 M, while the I50 from the hydrated enzyme was 5.3 M. The physiological consequences of these dehydration-induced molecular modifications of GAPDH likely suppress GADPH glycolytic functions during the reduced circulation and global hypoxia experienced in dehydrated X. laevis.

Effects of windblown sand damage on desert highway guardrails

Barriers, which are normally used as highway safety instruments, cause adverse sand deposition damage to pavements along desert highways. To select a suitable barrier type for desert highways, this study conducted wind tunnel experiments and field test to measure the velocity field and sediment deposition morphology for different types of barriers. The results indicate that the velocity decreases in the foot of the subgrade, and the smooth air flow is maintained along the pavement. Wind velocity decreases slightly under the W-beam bottom, and the maximum velocity reduction is in the lee of the W-beam barrier. Wind velocity considerably decreases before and after the concrete barrier because of the dense structure of the barrier. Cable barriers slightly disturb the air flow and marginally decrease its velocity. Sediment deposition characteristic measurements demonstrate that for W-beam median barrier, sand is deposited on pavement in the lee of the barrier; further, for both W-beam roadside barrier and median barriers, sand is easy to be deposited in the front and back of the barrier, mainly on the windward pavement. For concrete barriers, considerable amount of sand is deposited in the front and back of the barriers, which induces the serious sand deposition damage on the pavement. The cable barrier causes minimal sand deposition, and it is a recommended structure for the barrier selection of desert highways. Further, small wind incidence angles are also favorable when designing desert highways.

Numerical simulation of nanofluid flow inside a root canal

ABSTRACTSilver nano particles have antimicrobial property which makes them appropriate for disinfection. Due to their antimicrobial feature, these particles are applicable for root canal irrigation. Fluid flow inside root canal and its appropriate circulation results in more efficient removal of microorganisms. Due to the very small dimensions of a root canal, performing experimental research is very difficult to identify the phenomena occurring in the root canal; therefore, numerical investigation will be very helpful to gain appropriate insight into the flow features of a root canal during irrigation for disinfection. Computation Fluid Dynamic (CFD) can be employed to numerically simulate the flow of irrigants inside the root canal. In the present study, the flow of Ag/water nanofluid in the root canal is numerically modeled. In order to evaluate the impact of height of injection and nanofluid concentration, two heights and concentrations are considered and compared. According to the results, lower injection height is more favorable due to better circulation of an irrigant in the root canal. Moreover, increase in the concentration of the nanofluid leads to reduction in maximum velocity of the fluid; which is attributed to higher increase in dynamic viscosity in comparison with the density. Velocity and wall shear stress contours in various cases are represented to gain better insight into the irrigant motion inside the canal. According to the results of simulation, wall shear stress of the root canal increases by increment in the concentration of the nanofluid and volumetric flow rate of the irrigants.

Using Sprint Velocity Decrement to Enhance Acute Sprint Performance.

Cochrane, DJ and Monaghan, D. Using sprint velocity decrement to enhance acute sprint performance. J Strength Cond Res 35(2): 442-448, 2021-Acute sled towing has the capability to elicit a potentiation. Currently, sled loading is determined from body mass (BM) percent. However, it may be more relevant to use a percentage of maximal sprint reduction to determine an individual's load. The purpose of this study was to determine if individualizing sled loads at 35 and 55% reduction in velocity would improve 20-m sprint performance. In addition, electromyography (EMG) was assessed to determine if any sprint-related improvements in velocity were due to changes in neural excitation. Twelve senior club male rugby union players performed familiarization and 2 sled towing sessions using a randomized, cross-over, and counterbalanced design. Testing sessions involved: baseline unresisted 20-m sprints, resisted sprint (35 and 55% reduction in velocity), and unresisted 20-m sprints at 2, 4, 6, 8, 12, and 16 minutes. The sled load to reduce maximal velocity by 35% significantly improved 20-m velocity (p <0.05, effect size [ES] = 0.21) compared with the heavier sled load (55% reduction in maximum velocity). A significant decline in sprint velocity occurred at 12 minutes (p < 0.01, ES = -0.61) and 16 minutes (p < 0.01, ES = -0.45) compared with baseline velocity. Other time intervals reported trivial small nonsignificant changes in sprint velocity (p >0.05). There was no significant change in EMG. Reducing sprint velocity provides an alternate method to determining sprint loading. Nonetheless, a greater range of reduced sprint velocity is required to assess if it is more effective than using BM percent procedure.

Influence of selected antithrombotic treatment on thromboelastometric results

Rotatory thromboelastometry (ROTEM®) is used for diagnosing and monitoring bleeding patients. Some of these patients receive antithrombotic treatment, thus having an increased risk of bleeding. Only sparse knowledge exists about whether the ROTEM® analysis is influenced by antithrombotic treatment. The objective of the present study was to examine if the ROTEM® results are affected in patients receiving antithrombotic treatment. This prospective observational study included patients receiving either vitamin K-antagonists (VKA), aspirin (ASA) or ASA combined with an adenosine diphosphate (ADP) receptor antagonist (ASA + ADP). ROTEM® analyses were performed using the standard assays EXTEM®, INTEM® and FIBTEM®. Furthermore, haemoglobin, platelet count, International Normalized Ratio (INR), activated partial thromboplastin time, fibrinogen (functional), creatinine, estimated glomerular filtration rate, and C-reactive protein were determined. The study included 231 patients receiving antithrombotic treatment and compared the results to ROTEM® previously collected data from 73 healthy subjects. The VKA (n = 73) patients had a consistently prolonged EXTEM clot initiation (p < .0001), which was significantly correlated to the INR (Spearman’s r = 0.53, p < .0001). Additionally, the VKA patients had significantly reduced clot propagation [reduced maximum velocity, maximum velocity (MaxVel) and increased time to maximum velocity (MaxVelt)]. ASA (n = 80) and ASA + ADP patients (n = 78) revealed a prolonged clot initiation. ASA patients had decreased clot propagation (increased MaxVelt), whereas ASA + ADP patients had an inconsistent change in clot propagation (increased MaxVel and MaxVelt). In conclusion, VKA treatment was revealed by the ROTEM® analysis. On the contrary, ASA and ASA + ADP treatment were not consistently revealed by the analysis.

Rock-weir fishway I: flow regimes and hydraulic characteristics

ABSTRACTIn recent years, ecologically oriented river engineering practices such as nature-like fishways have become a common solution to mitigate or compensate for negative environmental impacts. This study investigated the flow regimes and hydraulics of rock-weir-type nature-like fishways for different structure geometries (weir configurations, pool spacing and boulder diameter) and channel characteristics (bed slope and flow rate). A criterion was proposed to predict three distinct flow regimes (weir, transitional and streaming) based on quantitative thresholds associated with three dimensionless parameters for discharge, pool spacing and pool water depth. For the depth–discharge relationship, a new equation to predict the weir flow based on water depth, weir length and bed slope of the fishway was introduced. Finally, a maximum velocity reduction factor as a function of discharge was proposed to predict maximum weir velocity in rock-weir fishways. These results must be compared with the swimming ability of the fish that the fishway is being designed for to assess passability.

Rational and timely haemostatic interventions following cardiac surgery - coagulation factor concentrates or blood bank products

BackgroundCardiac surgery may cause a serious coagulopathy leading to increased risk of bleeding and transfusion demands. Blood bank products are commonly first line haemostatic intervention, but has been associated with hazardous side effect. Coagulation factor concentrates may be a more efficient, predictable, and potentially a safer treatment, although prospective clinical trials are needed to further explore these hypotheses. This study investigated the haemostatic potential of ex vivo supplementation of coagulation factor concentrates versus blood bank products on blood samples drawn from patients undergoing cardiac surgery. Methods30 adults were prospectively enrolled (mean age=63.9, females=27%). Ex vivo haemostatic interventions (monotherapy or combinations) were performed in whole blood taken immediately after surgery and two hours postoperatively. Fresh-frozen plasma, platelets, cryoprecipitate, fibrinogen concentrate, prothrombin complex concentrate (PCC), and recombinant FVIIa (rFVIIa) were investigated. The haemostatic effect was evaluated using whole blood thromboelastometry parameters, as well as by thrombin generation. ResultsImmediately after surgery the compromised maximum clot firmness was corrected by monotherapy with fibrinogen or platelets or combination therapy with fibrinogen. At two hours postoperatively the coagulation profile was further deranged as illustrated by a prolonged clotting time, a reduced maximum velocity and further diminished maximum clot firmness. The thrombin lagtime was progressively prolonged and both peak thrombin and endogenous thrombin potential were compromised. No monotherapy effectively corrected all haemostatic abnormalities. The most effective combinations were: fibrinogen+rFVIIa or fibrinogen+PCC. Blood bank products were not as effective in the correction of the coagulopathy. ConclusionCoagulation factor concentrates appear to provide a more optimal haemostasis profile following cardiac surgery compared to blood bank products.

Experimental study on a debris-flow drainage channel with different types of energy dissipation baffles

Debris-flow deceleration baffles can effectively reduce debris-flow velocity and hence reduce the impact of flowing debris on architectural structures in mountainous areas. In this study, baffles with three different shapes were developed to investigate the velocity reduction effect and energy dissipation characteristics in a 6-m-long flume. The influences of debris-flow density, baffle shape, and row spacing were investigated. The debris-flow velocity was measured to calculate the velocity reduction ratio, which was influenced by the above variables. Experimental results reveal that the arrangement consisting of three rows of staggered baffles can reduce the velocity by 27.30%–39.32% compared to velocity reduction ratio of the controlled trials, wherein the flume bottom is empty. The velocity reduction ratio increases with an increase in the density; increasing the density from 1200 to 2100kg/m3 can lead to a 20% increase in the velocity reduction ratio. The velocity reduction ratio is not proportional to the equivalent area of impact, and the maximum velocity reduction ratios for the cubic, trapezoidal, and triangular-prism-shaped baffles are 25.0%, 26.3%, and 23.5%, respectively, at the channel slope is 12°. Furthermore, the velocity reduction ratio is inversely proportional to the spacing between adjacent rows. Increasing the row spacing from 0.10 to 0.25m leads to a 22% decrease in the average velocity reduction ratio. The maximum average velocity reduction ratio reaches around 25%, when the row spacing reduces to zero, and the baffles lose their deceleration ability when the row spacing increases to 1.42m and the velocity reduction ratio is −13%. These experimental results can provide useful references for the design of large gradient drainage channels.

Numerical investigation of multiphase supersonic swirl flow inside convergent-divergent nozzle

Numerical study of multiphase swirl flow induced by helical insert inside the supersonic nozzle is investigated as applied in sandblasting systems. The finding of this research is crucial in improving the performance of abrasive blasting systems by reducing operation time and saving energy. Simulations are performed with Reynolds Stress Model turbulence modelling to capture anisotropy inside the flow. To simulate particles inside the nozzle, discrete phase model has been applied. The multiphase Eulerian method did not provide accurate results on modelling particles with small volume fraction ( &lt;10%), and also it was not capable of modelling particles interaction. The analyses are performed at three inlet pressures (2, 3 and 4 atm) with constant mass flow rate for particles. The results show that swirl effect increases the mixing feature of the flow, and therefore increases the cleaning area on a working surface. Furthermore, with swirl there was less reduction in maximum velocity compare with single phase simulations, hence particles will have greater speed at the exit of the nozzle.

Bio-inspired dewetted surfaces based on SiC/Si interlocked structures for enhanced-underwater stability and regenerative-drag reduction capability.

Drag reduction has become a serious issue in recent years in terms of energy conservation and environmental protection. Among diverse approaches for drag reduction, superhydrophobic surfaces have been mainly researched due to their high drag reducing efficiency. However, due to limited lifetime of plastron (i.e., air pockets) on superhydrophobic surfaces in underwater, the instability of dewetted surfaces has been a sticking point for practical applications. This work presents a breakthrough in improving the underwater stability of superhydrophobic surfaces by optimizing nanoscale surface structures using SiC/Si interlocked structures. These structures have an unequaled stability of underwater superhydrophobicity and enhance drag reduction capabilities,with a lifetime of plastron over 18 days and maximum velocity reduction ratio of 56%. Furthermore, through photoelectrochemical water splitting on a hierarchical SiC/Si nanostructure surface, the limited lifetime problem of air pockets was overcome by refilling the escaping gas layer, which also provides continuous drag reduction effects.

SEISMIC BASE ISOLATION IN STRENGTHENING AN EXISTING RETROFITTED MASONRY-REINFORCED CONCRETE BUILDING IN HUATING - CHINA

Seismic base isolation is a fast advancing technology in which the superstructure is isolated from the entire structure or from the substructure by means of rubber bearing isolators or frictional sliding isolators. The main aim of the base isolation technology is to isolate the structure from the harmful effects of the ground accelerations or earthquake excitations. In this paper, the procedure for the selection of the three ground motions is briefly explained and they are used in analyzing a masonry – reinforced concrete office building for the Internal Revenue Service in the Huating County of the Pingliang City in China. The structure is first analyzed with the PKPM software to ascertain the structural internal forces are within reasonable limits but because this software cannot be used to advance analysis in the area of base isolation, Sap 2000 is used to remodel the structure, analyze, then apply the seismic base isolation. This office building has been strengthened to be fortified against ultimate bearing capacity failure as it is an existing structure. The lead rubber bearing isolators, LRB 400, LRB 500 and LRB 600 are used to isolate the building model and results from the structural response are compared, first amongst the time histories and then between the enveloped time histories and the response spectrum. The floor joint accelerations are observed to be reduced and the joint velocities as well, whereas the floor joint displacements are increased. The response spectrum alone is seen to not be an enough ground acceleration parameter in a seismic analysis and design of this model; as such it is recommended to include time history analysis. The maximum percentage decrease in acceleration and velocity can be seen occurring in the response spectrum, namely, 85.82% and 59.76%, respectively. The maximum percentage increase in the displacement is also evident in the response spectrum, 57.59%. In the time histories, the maximum is seen in Ec County Y-direction for the acceleration reduction at a value of 60.57%; Delta artif records a maximum velocity reduction of 28.42% in the Y-direction and finally, the Delta artif X-direction also records a maximum displacement increment, at a value of 26.36%.

Sensorimotor restriction affects complex movement topography and reachable space in the rat motor cortex.

Long-duration intracortical microstimulation (ICMS) studies with 500 ms of current pulses suggest that the forelimb area of the motor cortex is organized into several spatially distinct functional zones that organize movements into complex sequences. Here we studied how sensorimotor restriction modifies the extent of functional zones, complex movements, and reachable space representation in the rat forelimb M1. Sensorimotor restriction was achieved by means of whole-forelimb casting of 30 days duration. Long-duration ICMS was carried out 12 h and 14 days after cast removal. Evoked movements were measured using a high-resolution 3D optical system. Long-term cast caused: (i) a reduction in the number of sites where complex forelimb movement could be evoked; (ii) a shrinkage of functional zones but no change in their center of gravity; (iii) a reduction in movement with proximal/distal coactivation; (iv) a reduction in maximal velocity, trajectory and vector length of movement, but no changes in latency or duration; (v) a large restriction of reachable space. Fourteen days of forelimb freedom after casting caused: (i) a recovery of the number of sites where complex forelimb movement could be evoked; (ii) a recovery of functional zone extent and movement with proximal/distal coactivation; (iii) an increase in movement kinematics, but only partial restoration of control rat values; (iv) a slight increase in reachability parameters, but these remained far below baseline values. We pose the hypothesis that specific aspects of complex movement may be stored within parallel motor cortex re-entrant systems.

Rock Damage Structure of the South Longmen‐Shan Fault in the 2008 M8 Wenchuan Earthquake Viewed with Fault‐Zone Trapped Waves and Scientific Drilling

Abstract:This article is to review results from scientific drilling and fault‐zone trapped waves (FZTWs) at the south Longman‐Shan fault (LSF) zone that ruptured in the 2008 May 12 M8 Wenchuan earthquake in Sichuan, China. Immediately after the mainshock, two Wenchuan Fault Scientific Drilling (WFSD) boreholes were drilled at WFSD‐1 and WFSD‐2 sites approximately 400 m and 1 km west of the surface rupture along the Yinxiu‐Beichuan fault (YBF), the middle fault strand of the south LSF zone. Two boreholes met the principal slip of Wenchuan earthquake along the YBF at depths of 589‐m and 1230‐m, respectively. The slip is accompanied with a 100–200‐m‐wide zone consisting of fault gouge, breccia, cataclasite and fractures. Close to WFSD‐1 site, the nearly‐vertical slip of ∼4.3t‐m with a 190‐m wide zone of highly fractured rocks restricted to the hanging wall of the YBF was found at the ground surface after the Wenchuan earthquake. A dense linear seismic array was deployed across the surface rupture at this venue to record FZTWs generated by aftershocks. Observations and 3‐D finite‐difference simulations of FZTWs recorded at this cross‐fault array and network stations close to the YBF show a distinct low‐velocity zone composed by severely damaged rocks along the south LSF at seismogenic depths. The zone is several hundred meters wide along the principal slip, within which seismic velocities are reduced by ∼30–55% from wall‐rock velocities and with the maximum velocity reduction in the ∼200‐m‐wide rupture core zone at shallow depth. The FZTW‐inferred geometry and physical properties of the south LSF rupture zone at shallow depth are in general consistent with the results from petrological and structural analyses of cores and well log at WFSD boreholes. We interpret this remarkable low‐velocity zone as being a break‐down zone during dynamic rupture in the 2008 M8 earthquake. We examined the FZTWS generated by similar earthquakes before and after the 2008 mainshock and observed that seismic velocities within fault core zone was reduced by ∼10% due to severe damage of fault rocks during the M8 mainshock Scientific drilling and locations of aftershocks generating prominent FZTWs also indicate rupture bifurcation along the YBF and the Anxian‐Guangxian fault (AGF), two strands of the south LSF at shallow depth. A combination of seismic, petrologic and geologic study at the south LSF leads to further understand the relationship between the fault‐zone structure and rupture dynamics, and the amplification of ground shaking strength along the low‐velocity fault zone due to its waveguide effect.

Rose hip alleviates pain and disease progression in rats with monoiodoacetate induced osteoarthritis

Although rose hip administration reduces pain and stiffness in patients with osteoarthritis, the mechanism of rose hip to alleviate primary symptoms has not been investigated. We examined how two types of Rosa canina, grown in Denmark (I-Flex) and Coesam in Chile, attenuate the osteoarthritis symptoms in male rats with osteoarthritis. Therefore pain-related behaviors were evaluated, and histological changes and cytokine expression in the articular cartilage of right knee induced osteoarthritis were assessed via intra-articular monoiodoacetate (MIA) injection. The right knee induced swollen knee, limping legs, and disproportional weight distribution into the right hind paw, and reduced maximum velocity to run on a treadmill from day 3 after MIA injection. The symptoms were exacerbated up to about 2 weeks and remained steady until day 21. Overall the osteoarthritis symptoms in MIA-injected control rats did not significantly change over the experimental period. After 21 days, bone mineral density in right leg and knee had greatly decreased in rats injected with MIA. These symptoms were related to increased expression of matrix metalloprotinase (MMP)-3 and MMP-13 in articular cartilage that degraded collage and elevated the production of TNF-α, IL-1β, and IL-6. However, both types of rose hip markedly attenuated all of the symptoms experienced by the control and overall symptoms from day 3 were improved at day 21. However, some symptoms of osteoarthrit remained and there was no difference between both rose hips for alleviating osteoarthritis symptoms. In conclusion, rose hips from Denmark and Coesam in Chile are potential therapeutic agents for the protection of articular cartilage against progression of osteoarthritis.

Effects of tacrolimus on action potential configuration and transmembrane ion currents in canine ventricular cells

Tacrolimus is a commonly used immunosuppressive agent which causes cardiovascular complications, e.g., hypertension and hypertrophic cardiomyopathy. In spite of it, there is little information on the cellular cardiac effects of the immunosuppressive agent tacrolimus in larger mammals. In the present study, therefore, the concentration-dependent effects of tacrolimus on action potential morphology and the underlying ion currents were studied in canine ventricular cardiomyocytes. Standard microelectrode, conventional whole cell patch clamp, and action potential voltage clamp techniques were applied in myocytes enzymatically dispersed from canine ventricular myocardium. Tacrolimus (3-30μM) caused a concentration-dependent reduction of maximum velocity of depolarization and repolarization, action potential amplitude, phase-1 repolarization, action potential duration, and plateau potential, while no significant change in the resting membrane potential was observed. Conventional voltage clamp experiments revealed that tacrolimus concentrations ≥3μM blocked a variety of ion currents, including I(Ca), I(to), I(K1), I(Kr), and I(Ks). Similar results were obtained under action potential voltage clamp conditions. These effects of tacrolimus developed rapidly and were fully reversible upon washout. The blockade of inward currents with the concomitant shortening of action potential duration in canine myocytes is the opposite of those observed previously with tacrolimus in small rodents. It is concluded that although tacrolimus blocks several ion channels at higher concentrations, there is no risk of direct interaction with cardiac ion channels when applying tacrolimus in therapeutic concentrations.

Shear wave velocity structure of the southern African upper mantle with implications for the uplift of southern Africa

SUMMARY Broad-band seismic data from the southern African seismic experiment and the AfricaArray network are used to investigate the seismic velocity structure of the upper mantle beneath southern Africa, and in particular beneath the Kaapvaal Craton. A two-plane approximation method that includes a finite frequency sensitivity kernel is employed to measure Rayleigh wave phase velocities, which are inverted to obtain a quasi-3-D shear wave velocity model of the upper mantle. We find phase velocities for the Kaapvaal Craton and surrounding mobile belts that are comparable to those reported by previous studies, and we find little evidence for variation from east to west across the Namaqua–Natal Belt, a region not well imaged in previous studies. A high-velocity upper-mantle lid is found beneath the Kaapvaal Craton and most of southern Africa. For the Kaapvaal Craton, the thickness of the lid (∼150–200 km) is consistent with the lid thicknesses reported in many previous studies. The cratonic lid is underlain by a ∼100-km thick low-velocity zone with a 3.9 per cent maximum velocity reduction. By comparing the velocity model to those published for other Archean cratons, we find few differences, and therefore conclude that there is little evidence in the shear wave velocity structure of the mantle to indicate that the southern African plateau is supported by an upper-mantle thermal anomaly.

Reduced Activity and Expression of Mitochondrial Citrate Carrier in Streptozotocin-Induced Diabetic Rats

Citrate carrier (CiC), an integral protein of the mitochondrial inner membrane, plays an important role in hepatic intermediary metabolism, supplying the cytosol with acetyl-coenzyme A for fatty acid and cholesterol synthesis. Here, the effect of streptozotocin-induced diabetes on CiC activity and expression in rat liver was investigated. The rate of citrate transport was reduced by about 35% in mitochondria from diabetic vs. control rats. Kinetic studies in mitochondria from diabetic rats showed a reduction in maximum velocity and almost unchanged Michaelis-Menten constant of the CiC protein. Mitochondrial phospholipid amount was not significantly affected, whereas an increase in the cholesterol content and in the cholesterol/phospholipid ratio was observed. To thoroughly investigate the mechanism responsible for the reduced CiC activity in the diabetic state, molecular studies were performed. Ribonuclease protection assays and Western blotting analysis indicated that both hepatic CiC mRNA accumulation and protein level decreased similarly to the CiC activity. The reduced mRNA level and the lower content of the mitochondrial CiC protein, might account for the decline of CiC activity in diabetic animals. To discriminate between the role played by hyperglycemia from that of hypoinsulinemia in the reduction of CiC activity and expression, studies were conducted administrating phlorizin or insulin to streptozotocin-diabetic rats. Our data indicated that both insulin and glucose affect CiC activity and expression in diabetic rats, although they act at different regulatory steps.

Aldehyde Dehydrogenase 2 Ameliorates Acute Cardiac Toxicity of Ethanol: Role of Protein Phosphatase and Forkhead Transcription Factor

This study was designed to evaluate the role of facilitated detoxification of acetaldehyde, the main metabolic product of ethanol, through systemic overexpression of mitochondrial aldehyde dehydrogenase-2 (ALDH2) on acute ethanol exposure-induced myocardial damage. Binge drinking may exert cardiac toxicity and interfere with heart function, manifested as impaired ventricular contractility, although the underlying mechanism remains poorly defined. ALDH2 transgenic mice were produced using the chicken beta-actin promoter. Wild-type FVB (friend virus B) and ALDH2 mice were challenged with ethanol (3 g/kg, intraperitoneally), and cardiac function was assessed 24 h later using the Langendroff and cardiomyocyte edge-detection systems. Western blot analysis was used to evaluate protein phosphatase 2A and 2C (PP2A and PP2C), phosphorylation of Akt, AMP-activated protein kinase (AMPK), and the transcription factors Foxo3 (Thr32 and Ser413). ALDH2 reduced ethanol-induced elevation in cardiac acetaldehyde levels. Acute ethanol challenge deteriorated myocardial and cardiomyocyte contractile function evidenced by reduction in maximal velocity of pressure development and decline (+/-dP/dt), left ventricular developed pressure, cell shortening, and prolonged relengthening duration, the effects of which were alleviated by ALDH2. Ethanol treatment dampened phosphorylation of Akt and AMPK associated with up-regulated PP2A and PP2C, which was abrogated by ALDH2. ALDH2 significantly attenuated ethanol-induced decrease in Akt- and AMPK-stimulated phosphorylation of Foxo3 at Thr32 and Ser413, respectively. Consistently, ALDH2 rescued ethanol-induced myocardial apoptosis, protein damage, and mitochondrial membrane potential depolarization. Our results suggest that ALDH2 is cardioprotective against acute ethanol toxicity, possibly through inhibition of protein phosphatases, leading to enhanced Akt and AMPK activation, and subsequently, inhibition of Foxo3, apoptosis, and mitochondrial dysfunction.