Torque Curve Optimization of Ankle Push-Off in Walking Bipedal Robots Using Genetic Algorithm.

Ankle push-off occurs when muscle-tendon units about the ankle joint generate a burst of positive power at the end of stance phase in human walking. Ankle push-off mainly contributes to both leg swing and center of mass (CoM) acceleration. Humans use the amount of ankle push-off to induce speed changes. Thus, this study focuses on determining the faster walking speed and the lowest energy efficiency of biped robots by using ankle push-off. The real-time-space trajectory method is used to provide reference positions for the hip and knee joints. The torque curve during ankle push-off, composed of three quintic polynomial curves, is applied to the ankle joint. With the walking distance and the mechanical cost of transport (MCOT) as the optimization goals, the genetic algorithm (GA) is used to obtain the optimal torque curve during ankle push-off. The results show that the biped robot achieved a maximum speed of 1.3 m/s, and the ankle push-off occurs at 41.27-48.34% of the gait cycle. The MCOT of the bipedal robot corresponding to the high economy gait is 0.70, and the walking speed is 0.54 m/s. This study may further prompt the design of the ankle joint and identify the important implications of ankle push-off for biped robots.

Simulation Analysis of Impulsive Ankle Push-Off on the Walking Speed of a Planar Biped Robot.

Ankle push-off generates more than 80% positive power at the end of the stance phase during human walking. In this paper, the influence of impulsive ankle push-off on the walking speed of a biped robot is studied by simulation. When the push-off height of the ankle joint is 13 cm based on the ground (the height of the ankle joint of the swing leg) and the ankle push-off torque increases from 17 to 20.8 N·m, the duration of the swinging leg actually decreases from 50 to 30% of the gait cycle, the fluctuation amplitude of the COM (center of mass) instantaneous speed of the robot decreases from 95 to 35% of the maximum speed, and the walking speed increases from 0.51 to 1.14 m/s. The results demonstrate that impulsive ankle push-off can effectively increase the walking speed of the planar biped robot by accelerating the swing leg and reducing the fluctuation of the COM instantaneous speed. Finally, a comparison of the joint kinematics of the simulation robot and the human at a normal walking speed shows similar motion patterns.

Phalangeal joints kinematics in ostrich (Struthio camelus) locomotion on sand.

In ostriches, the toes are the only body parts that contact loose sand surfaces. Thus, toe interphalangeal joint motions may play vital biomechanical roles. However, there is little research on ostrich phalangeal joint movements while walking or running on sand. The results from the three-dimensional motion track analysis system Simi Motion show that gait pattern has no significant effect on the key indicators (angles at touch-down, mid-stance, lift-off and range of motion) of the toe joint angles. The motion of the toe phalanges when walking and running on sand is basically the same. The ground medium is the key factor that changes the toe postures adopted by ostriches during the stance phase in slow to fast locomotion. The 3rd toe and the 4th toe are connected by the interphalangeal ligament, and the motions of the MTP3 and MTP4 joints are highly synchronized on a loose sand substrate. The 3rd toe and 4th toe are coupled to maintain static balance in slow locomotion and dynamic balance in fast locomotion. In addition, the gait pattern has a marked effect on the range of forward displacement of the toenail (YTN). The ostrich toenail plays an important role in preventing slip and provides traction at push-off in a sandy environment. The metatarsophalangeal joint plays an important role in energy saving during fast locomotion on loose sand substrates. Simulation reveals that the particle velocity field, particle force field and sand particle disturbance in the running gait are denser than those in the walking gait.

Macroscopic and microscopic analyses in flexor tendons of the tarsometatarso-phalangeal joint of ostrich (Struthio camelus) foot with energy storage and shock absorption.

Flexor tendons function as energy storage and shock absorption structures in the tarsometatarso-phalangeal joint (TMTPJ) of ostrich feet during high-speed and heavy-load locomotion. In this study, mechanisms underlying the energy storage and shock absorption of three flexor tendons of the third toe were studied using histology and scanning electron microscopy (SEM). Macroscopic and microscopic structures of the flexor tendons in different positions of TMTPJ were analyzed. Histological slices showed collagen fiber bundles of all flexor tendons in the middle TMTPJ were arranged in a linear-type, but in the proximal and distal TMTPJ, a wavy-type arrangement was found in the tendon of the M. flexor digitorum longus and tendon of the M. flexor perforans et perforatus digiti III, while no regular-type was found in the tendon of the M. flexor perforatus digiti III. SEM showed that the collagen fiber bundles of flexor tendons were arranged in a hierarchically staggered way (horizontally linear-type and vertically linear-type). Linear-type and wavy-type both existed in the proximal TMTPJ for the collagen fiber bundles of the tendon of the M. flexor perforatus digiti III, but only the linear-type was found in the distal TMTPJ. A number of fibrils were distributed among the collagen fiber bundles, which were likely effective in connection, force transmission and other functions. The morphology and arrangement of collagen fiber bundles were closely related to the tendon functions. We present interpretations of the biological functions in different positions and types of the tendons in the TMTPJ of the ostrich feet.

Plantar pressure distribution of ostrich during locomotion on loose sand and solid ground.

BACKGROUND: The ostrich is a cursorial bird with extraordinary speed and endurance, especially in the desert, and thus is an ideal large-scale animal model for mechanic study of locomotion on granular substrate. METHODS: The plantar pressure distributions of ostriches walking/running on loose sand/solid ground were recorded using a dynamic pressure plate. RESULTS: The center of pressure (COP) on loose sand mostly originated from the middle of the 3rd toe, which differed from the J-shaped COP trajectory on solid ground. At mid-stance, a high-pressure region was observed in the middle of the 3rd toe on loose sand, but three high-pressure regions were found on solid ground. The gait mode significantly affected the peak pressures of the 3rd and 4th toes (p = 1.5 × 10-6 and 2.39 × 10-8, respectively), but not that of the claw (p = 0.041). The effects of substrate were similar to those of the gait mode. DISCUSSION: Ground reaction force trials of each functional part showed the 3rd toe bore more body loads and the 4th toe undertook less loads. The pressure distributions suggest balance maintenance on loose sand was provided by the 3rd and 4th toes and the angle between their length axes. On loose sand, the middle of the 3rd toe was the first to touch the sand with a smaller attack angle to maximize the ground reaction force, but on solid ground, the lateral part was the first to touch the ground to minimize the transient loading. At push-off, the ostrich used solidification properties of granular sand under the compression of the 3rd toe to generate sufficient traction.

Phalangeal joints kinematics during ostrich (Struthio camelus) locomotion.

The ostrich is a highly cursorial bipedal land animal with a permanently elevated metatarsophalangeal joint supported by only two toes. Although locomotor kinematics in walking and running ostriches have been examined, these studies have been largely limited to above the metatarsophalangeal joint. In this study, kinematic data of all major toe joints were collected from gaits with double support (slow walking) to running during stance period in a semi-natural setup with two selected cooperative ostriches. Statistical analyses were conducted to investigate the effect of locomotor gait on toe joint kinematics. The MTP3 and MTP4 joints exhibit the largest range of motion whereas the first phalangeal joint of the 4th toe shows the largest motion variability. The interphalangeal joints of the 3rd and 4th toes present very similar motion patterns over stance phases of slow walking and running. However, the motion patterns of the MTP3 and MTP4 joints and the vertical displacement of the metatarsophalangeal joint are significantly different during running and slow walking. Because of the biomechanical requirements, osctriches are likely to select the inverted pendulum gait at low speeds and the bouncing gait at high speeds to improve movement performance and energy economy. Interestingly, the motions of the MTP3 and MTP4 joints are highly synchronized from slow to fast locomotion. This strongly suggests that the 3rd and 4th toes really work as an "integrated system" with the 3rd toe as the main load bearing element whilst the 4th toe as the complementary load sharing element with a primary role to ensure the lateral stability of the permanently elevated metatarsophalangeal joint.

Macro-microscopic Research in Reideer (Rangifer Tarandus) Hoof Suitable for Efficient Locomotion on Complex Grounds.

INTRODUCTION: Reindeer are adapted to long distance migration. This species can cope with variations in substrate, especially in ice and snow environment. However, few detailed studies about reindeer hoof are available. Thus this article describes the results of studies on macro- and micro-structures of reindeer hoof. MATERIAL AND METHODS: The gross anatomy of the reindeer hooves was examined. Stereo microscope (SM) and a scanning electron microscope (SEM) were used to observe four key selected positions of reindeer hooves. Moreover, element contents of the three selected positions of reindeer hooves were analysed using the SEM equipped with energy dispersive spectroscope. RESULTS: Hoof bone structures were similar to other artiodactyl animals. In the microscopic analysis, the surfaces of the ungula sphere and ungula sole presented irregular laminated structure. Ungula edge surfaces were smooth and ungula cusp surfaces had unique features. Aside from C, O, and N, reindeer hooves contained such elements as S, Si, Fe, Al, and Ca. The content of the elements in different parts varied. Ti was the particular element in the ungula sole, and ungula edge lacked Mg and S which other parts contained. CONCLUSION: The macro- and micro-structures of the reindeer hooves showed high performance of skid and abrasion resistance. It is most probably essential to the long distance migration for the animals.

Protective effects of paeoniflorin against cobalt chloride-induced apoptosis of endothelial cells via HIF-1α pathway.

Accumulating evidence has suggested the importance of hypoxia in the initiation and development of atherosclerotic lesion, and hypoxia has a profound impact on endothelial cell properties during cardiovascular disease processes. Paeoniflorin, isolated from the root of Paeonia lactiflora pall, can protect endothelial cells from hypoxic damage in a variety of ways, such as by enhancing the production of nitric oxide (NO) and decreasing the expressions of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). This study evaluated the protective effects of paeoniflorin against cobalt chloride (CoCl2, a hypoxia-mimicking agent)-induced apoptosis of endothelial cells (CRL-1730) and the underlying mechanisms in vitro. Endothelial cells were exposed to CoCl2 with or without pre-treatment with different concentrations of paeoniflorin. After treated with 0.6mM CoCl2 for 24 h, endothelial cells showed significant decrease in cell viability and increased apoptosis rate, which could be reversed by pre-treatment with paeoniflorin. Similarly, pre-treatment with paeoniflorin could prevent CoCl2-induced hypoxia-induced factor-1α (HIF-1α) accumulation and down-regulate the expressions of p53 and Bcl-2/adenovirus E1B 19kDa interacting protein 3 (BNIP3). These findings indicate that paeoniflorin had effective protection against hypoxia-induced apoptosis of endothelial cells and that HIF-1α, p53 and BNIP3 might be involved in this process.

The roles of buyang huanwu decoction in anti-inflammation, antioxidation and regulation of lipid metabolism in rats with myocardial ischemia.

Buyang Huanwu Decoction (BYHWD) is a well-known Chinese medicine formula. Recent studies have reported that BYHWD can be used to treat ischemic heart disease. This study investigated the potential mechanism underlying the roles of BYHWD in alleviating the myocardial ischemia induced by isoproterenol (ISO) in rats. Different doses of BYHWD (25.68, 12.84 and 6.42 g kg(-1)) were lavaged to rats, respectively. Then the expression of the cluster of differentiation 40 (CD40) in the mononuclear cells was measured using flow cytometry, and the expressions of CD40 and its ligand (CD40L) in myocardial tissues were determined by western blotting. The serum biochemical values of superoxide dismutase (SOD) activity, the malondialdehyde (MDA) level and the free fatty acid (FFA) content were measured. The results showed that the SOD activities of BYHWD groups were significantly higher than that of the ISO group, while the MDA levels and FFA contents of all BYHWD groups were lower than that of the ISO group. BYHWD could decrease the expression of CD40 in the mononuclear cells and the CD40 and CD40L expressions in myocardial tissues. Our data suggest that the roles of BYHWD are not only related to its antioxidative action and regulation of lipid metabolisms, but also to the inhibition of inflammatory pathway by the decreased CD40 and CD40L expressions in rats with myocardial ischemia.

Effect of exercise training on renal function and renal aquaporin-2 expression in rats with chronic heart failure.

1. Chronic heart failure (CHF) is often accompanied by renal dysfunction. Exercise training may relieve the symptomatic burden and improve the overall prognosis of CHF. In the present study, the effects of exercise training on renal function and renal aquaporin (AQP)-2 expression in CHF rats were examined to determine whether exercise training could relieve renal dysfunction in CHF rats. 2. Male Sprague-Dawley rats were divided into three groups: sham, sedentary CHF (Sed-CHF) and exercise training CHF (Ex-CHF) groups. Cardiorenal function was assessed in each group by haemodynamic measurement and ultraviolet spectrophotometry. Pathological changes in cardiac and renal tissues were evaluated histologically and the collagen volume fraction (CVF) was calculated. The expressions of AQP-2 and ß-tubulin were determined by western blotting and immunohistochemistry. 3. The Sed-CHF rats were found to have increased left ventricular end-diastolic pressure (LVEDP) and CVF in the heart compared with sham rats. Exercise training decreased LVEDP and CVF values in Ex-CHF rats. The Sed-CHF rats were found to have increased serum levels of creatinine (sCr), blood urea nitrogen (BUN) and arginine vasopressin (AVP), as well as increased CVF in the kidney, compared with sham rats. Exercise training decreased levels of sCr, BUN, AVP and CVF in Ex-CHF rats. Moreover, exercise training decreased AQP-2 and ß-tubulin protein expression in the kidney of CHF rats. 4. The results suggest that exercise training can significantly improve the renal dysfunction in CHF rats and that the underlying mechanism may be related to water reabsorption and preventing changes to the cytoskeleton.

Protective effects of chinese traditional medicine buyang huanwu decoction on myocardial injury.

Many clinical studies have reported that Buyang Huanwu Decoction (BYHWD) has a protective effect on ischemic heart disease (IHD). In the present study, the protective effect of BYHWD on myocardial ischemia was investigated. Different doses of BYHWD and Compound Danshen Dropping Pills (CDDP) were lavaged to rats, respectively, isoproterenol (ISO) was intraperitoneally injected in to all animals to induce myocardial ischemia except the control group. Electrocardiogram (ECG) of each animal was recorded; activities of lactate dehydrogenase (LDH), creatine kinase (CK) and aspartate aminotransferase (AST) in serum were detected. As the results of ECG showed, pre-treatment with BYHWD inhibited ischemic myocardial injury, and the activities of LDH, CK and AST were lower than those in the myocardial ischemia model group, which suggests that BYHWD rescues the myocardium from ischemia status. To research the potential mechanism, the level of nitric oxide (NO), nitric oxide syntheses (NOS) and inducible nitric oxide syntheses (iNOS), the expression of iNOS and ligand of cluster of differentiation 40 (CD40L) were detected. The results revealed that BYHWD significantly decreased the level of NO, NOS and iNOS in serum. Moreover, BYHWD decreased the expression of iNOS and CD40L in myocardial tissues. These results indicate that the protective effect of BYHWD on myocardial ischemia and mechanism are associated with inhibition of iNOS and CD40L expression.

Participation of lipid transport and fatty acid metabolism in valproate sodium-induced hepatotoxicity in HepG2 cells.

The hepatotoxicity induced by valproic acid (VPA) has been described in many clinical studies and the related mechanism has been partly elucidated. The objective of this study is to investigate the hepatotoxicity and its underlying mechanism of valproic acid on human hepatoma carcinoma cell line HepG2. The cell viability was evaluated by 3-(4,5-dimethyltyiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) in the medium were detected using spectrophotometry. The gene expressions of cytochrome P450 1 A1 (CYP1A1), ATP-binding cassette transporter G1 (ABCG1) and carnitine palmitoyltransferase 1 (CPT1A), related to lipid transport and fatty acid metabolism, were measured by quantitative real-time reverse transcriptase-PCR. Treatment with valproate sodium obviously decreased the viability of HepG2 cells, accompanied by the increased leakages of ALT, AST and LDH in a dose-dependent manner. Furthermore, the gene expressions of CYP1A1, ABCG1 and CPT1A were almost up-regulated in the treated groups. In conclusion, these data suggest that VPA-induced hepatotoxicity was critically enhanced with the elevation of valproate sodium, which may be correlated with up-regulated gene expressions of CYP1A1, ABCG1 and CPT1A.

Buyang Huanwu decoction ameliorates coronary heart disease with Qi deficiency and blood stasis syndrome by reducing CRP and CD40 in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Qi deficiency and blood stasis is traditional Chinese medicine (TCM) syndrome. It leads to many diseases including coronary heart diseases (CHD) and cerebrovascular diseases (CVD). Inflammatory biomarkers and many endothelium-derived vasoactive factors are considered to play pivotal roles in CHD. Buyang Huanwu decoction (BYHWD), a TCM formula, has been recognized as a treatment for CHD with Qi deficiency and blood stasis syndrome and CVD in clinic. The mechanisms of BYHWD effect on CHD with Qi deficiency and blood stasis syndrome are unclear. AIM OF THE STUDY: The aim is to investigate whether the effects of BYHWD on CHD with Qi deficiency and blood stasis syndrome in rats are associated with the inhibition of CRP, CD40 and vascular endothelial regulators. MATERIALS AND METHODS: The treated groups were lavaged with 25.68, 12.84 and 6.42 g/kg BYHWD respectively once a day for 21 days. The level of C-reactive protein (CRP) in serum and the expression of cluster of differentiation 40 (CD40) in the heart and aorta of rats were detected. Moreover, the levels of thromboxaneA(2) (TXA(2)) and prostacyclin (PGI(2)) in plasma were measured and the levels of inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) in serum were detected. RESULTS: BYHWD (25.68 g/kg) significantly decreased the level of CRP in serum and BYHWD (25.68 and 12.84 g/kg) decreased the expression of CD40 in the heart and aorta (P<0.01). The results also revealed that BYHWD (25.68 g/kg) inhibited the levels of iNOS in serum and TXA(2) in plasma and increased the levels of eNOS in serum and PGI(2) in plasma (P<0.01). CONCLUSION: The study shows that the ameliorative effects of BYHWD on CHD with Qi deficiency and blood stasis syndrome in rats are associated with the inhibition of CRP and CD40 and the regulation of endothelium-derived vasoactive factors.

DNA binding and aggregation by carbon nanoparticles.

Significant environmental and health risks due to the increasing applications of engineered nanoparticles in medical and industrial activities have been concerned by many communities. The interactions between nanomaterials and genomes have been poorly studied so far. This study examined interactions of DNA with carbon nanoparticles (CNP) using atomic force microscopy (AFM). We experimentally assessed how CNP affect DNA molecule and bacterial growth of Escherichia coli. We found that CNP were bound to the DNA molecules during the DNA replication in vivo. The results revealed that the interaction of DNA with CNP resulted in DNA molecule binding and aggregation both in vivo and in vitro in a dose-dependent manner, and consequently inhabiting the E. coli growth. While this was a preliminary study, our results showed that this nanoparticle may have a significant impact on genomic activities.

NanoPCR observation: different levels of DNA replication fidelity in nanoparticle-enhanced polymerase chain reactions.

Nanoparticle-assisted PCR (polymerase chain reaction) technology is getting more and more attention recently. It is believed that some of the DNA recombinant technologies will be upgraded by nanotechnology in the near future, among which DNA replication is one of the core manipulation techniques. So whether or not the DNA replication fidelity is compromised in nanoparticle-assisted PCR is a question. In this study, a total of 16 different metallic and non-metallic nanoparticles (NPs) were tested for their effects on DNA replication fidelity in vitro and in vivo. Sixteen types of nanomaterials were distinctly different in enhancing the PCR efficiency, and their relative capacity to retain DNA replication fidelity was largely different from each other based on rpsL gene mutation assay. Generally speaking, metallic nanoparticles induced larger error rates in DNA replication fidelity than non-metallic nanoparticles, and non-metallic nanomaterials such as carbon nanopowder or nanotubes were still safe as PCR enhancers because they did not compromise the DNA replication fidelity in the Taq DNA polymerase-based PCR system.

[Protective effect of Buyanghuanwu Decoction on myocardial ischemia induced by isoproterenol in rats].

OBJECTIVE: To study the protective effect of Buyanghuanwu Decoction on myocardial ischemia induced by isoproterenol in rats. METHODS: Buyanghuanwu Decoction was given in different dose and the rat model of myocardial ischemia was established by peritoneal injection of isoproterenol. The expression of CD40 in whole blood was detected by flow cytometry,and the expression of CD40L in myocardial tissues was detected by immunohistochemistry. The activities of lactate dehydrogenase (LDH), creatine kinase (CK) and aspartate aminotransferase (AST) in blood serum were detected by biochemistry detector. RESULTS: Compared with the model group, Buyanghuanwu Decoction in high and middle dose significantly inhibited the expression of CD40 in blood serum and CD40L in myocardial tissues (P < 0.01), and obviously decreased the activities of LDH, CK and AST in blood serum (P < 0.01). CONCLUSION: Buyanghuanwu Decoction has a protective effect on myocardial ischemia induced by isoproterenol in rats, and it may be relevant to the decrease of the expression of CD40-CD40L and the activities of myocardial enzymes.

Food storage material silver nanoparticles interfere with DNA replication fidelity and bind with DNA.

Nanosilver is increasingly used in the food industry and biomedical applications. A lot of studies have been done to investigate the potential toxicity of nanosilver. But information on whether or how nanosilver particles bring changes in genetic materials remains scant. In this study, the replication fidelity of the rpsL gene was quantified when nanosilver particles were present in polymerase chain reactions (PCRs) or cell cultures of E. coli transformed with the wild-type rpsL gene. Three types of nanosilver (silver nanopowder, SN; silver-copper nanopowder, SCN; and colloidal silver, CS) were tested. The results showed that the replication fidelity of the rpsL gene was differentially compromised by all three kinds of nanosilver particle compared with that without nanosilver. This assay could be expanded and applied to any other materials to preliminarily assess their potential long-term toxicity as a food additive or biomedical reagent. Moreover, we found that nanosilver materials bind with genomic DNA under atomic force microscopy, and this might be an explanation for the compromised DNA replication fidelity.

Down-regulation of CD40 gene expression and inhibition of apoptosis with Danshensu in endothelial cells.

Danshen is commonly used in China for the treatment of atherosclerosis-related disorders such as cardiovascular and cerebrovascular diseases. Research shows that it also has immunostimulation properties. The present study evaluates the protective effect of danshensu, an active water-extractable component isolated from danshen, on an endothelial cell line (CRL-1730) treated with hydrogen peroxide (H(2)O(2)). Danshensu significantly inhibited endothelial cell viability induced by H(2)O(2). The treatment of endothelial cells with danshensu resulted in most cells being arrested in the S and G(2)/M phases of the cell cycle. The fraction of cells in G(0)/G(1) phase was markedly decreased by danshensu treatment compared to the control groups. The apoptosis was also markedly decreased after danshensu treatment. Additionally, danshensu restrains decreased nitric oxide level, increased the release of lactate dehydrogenase and expression of cluster of differentiation 40 (CD40) significantly. These results suggest that danshensu protects endothelial cells from the damage induced by H(2)O(2) through its CD40 anti-inflammatory approach and cell apoptosis inhibition.