Dynamic simulation studies of structural formation and transition in electro-magneto-rheological fluids

The computer simulation method has been used to study the structural formation and transition of electro-magneto-rheological (EMR) fluids under compatible electric and magnetic fields. When the fields are applied simultaneously and perpendicularly to each other, the particles rapidly arrange into two-dimensional close-packed layer structures parallel to both fields. The layers then combine together to form thicker sheet-like structures, which finally relax into three-dimensional close-packed structures with the help of the thermal fluctuations. On the other hand, if the electric field is applied firstly to induce the body-centered tetragonal (BCT) columns in the system, and then the magnetic field is applied in the perpendicular direction. the BCT to face-centered cubic (FCC) structure transition is observed in very short time. Following that. the structure keeps on evolving due to the demagnetization effect and finally form the three-dimensional close-packed structures.

Many-body effect in electrorheological responses

The many-body effect in the kinetic responses of ER fluids is studied by a molecular-dynamic simulation method. The mutual polarization effects of the particles are considered by self-consistently calculating the dipole strength on each particle according to the external field and the dipole field due to all the other particles in the fluids. The many-body effect is found to increase with the enhancement of the particle concentration and the permittivity ratio between the solvent and the particles. The calculated response times are shorter than that predicted with the 'point-dipole' model and agree very well with experimental results. The many-body effect enhances the shear stresses of the fluids by several times. But they are not proportional to the many-body correction factor lambda as expected. This is due to the fact that larger interaction forces between the particles lead to coarsening of the fibers formed in the suspensions. The results show that the many-body and multipolar interaction between the particles must be treated comprehensively in the simulations in order to get more reliable results.

Regulation of cell migration in cancer: investigation into the regulation of cancer cell blebbing in the extracellular matrix

Cell migration is a highly coordinated process and any aberration in the regulatory mechanisms could result in pathological conditions such as cancer. The ability of cancer cells to disseminate to distant sites within the body has made it difficult to treat. Cancer cells also exhibit plasticity that makes them able to interconvert from an elongated, mesenchymal morphology to an amoeboid blebbing form under different physiological conditions. Blebs are spherical membrane protrusions formed by actomyosin-mediated contractility of cortical actin resulting in increased hydrostatic pressure and subsequent detachment of the membrane from the cortex. Tumour cells use blebbing as an alternative mode of migration by squeezing through preexisting gaps in the ECM, and bleb formation is believed to be mediated by the Rho-ROCK signaling pathway. However, the involvement of transmembrane water and ion channels in cell blebbing has not been examined. In the present study, the role of the transmembrane water channels, aquaporins, transmembrane ion transporters and lipid signaling enzymes in the regulation of blebbing was investigated. Using 3D matrigel matrix as an in vitro model to mimic normal extracellular matrix, and a combination of confocal and time-lapse microscopy, it was found that AQP1 knockdown by siRNA ablated blebbing of HT1080 and ACHN cells, and overexpression of AQP1-GFP not only significantly increased bleb size with a corresponding decrease in bleb numbers, but also induced bleb formation in non-blebbing cell lines. Importantly, AQP1 overexpression reduces bleb lifespan due to faster bleb retraction. This novel finding of AQP1-facilitated bleb retraction requires the activity of the Na+/H+ pump as inhibition of the ion transporter, which was found localized to intracellular vesicles, blocked bleb retraction in both cell lines. This study also demonstrated that a differential regulation of cell blebbing by AQP isoforms exists as knockdown of AQP5 had no effect on bleb formation. Data from this study also demonstrates that the lipid signaling PLD2 signals through PA in the LPA-LPAR-Rho-ROCK axis to positively regulate bleb formation in both cell lines. Taken together, this work provides a novel role of AQP1 and Na+/H+ pump in regulation of cell blebbing, and this could be exploited in the development of new therapy to treat cancer.

Adipocyte differentiation is inhibited by melatonin through the regulation of C/EBP beta transcriptional activity

Considering that melatonin has been implicated in body weight control, this work investigated whether this effect involves the regulation of adipogenesis. 3T3-L1 preadipocytes were induced to differentiate in the absence or presence of melatonin (10(-3) m). Swiss-3T3 cells ectopically and conditionally (Tet-off system) over-expressing the 34 kDa C/EBP beta isoform (Swiss-LAP cells) were employed as a tool to assess the mechanisms of action at the molecular level. Protein markers of the adipogenic phenotype were analyzed by Western blot. At 36 hr of differentiation of 3T3-L1 preadipocytes, a reduction of PPAR gamma expression was detected followed by a further reduction, at day 4, of perilipin, aP2 and adiponectin protein expression in melatonin-treated cells. Real-time PCR analysis also showed a decrease of PPAR gamma (60%), C/EBP alpha (75%), adiponectin (30%) and aP2 (40%) mRNA expression. Finally, we transfected Swiss LAP cells with a C/EBP alpha gene promoter/reporter construct in which luciferase expression is enhanced in response to C/EBP beta activity. Culture of such transfected cells in the absence of tetracycline led to a 2.5-fold activation of the C/EBP alpha promoter. However, when treated with melatonin, the level of C/EBP alpha promoter activation by C/EBP beta was reduced by 50% (P = 0.05, n = 6). In addition, this inhibitory effect of melatonin was also reflected in the phenotype of the cells, since their capacity to accumulate lipids droplets was reduced as confirmed by the poor staining with Oil Red O. In conclusion, melatonin at a concentration of 10(-3) m works as a negative regulator of adipogenesis acting in part by inhibiting the activity of a critical adipogenic transcription factor, C/EBP beta.

Effects of approach velocity and foot-target characteristics on the visual regulation of step length

Two questions emerge from the literature concerning the perceptual-motor processes underlying the visual regulation of step length. The first concerns the effects of velocity on the onset of visual control (VCO), when visual regulation of step length begins during goal-directed locomotion. The second concerns the effects of different obstacles such as a target or raised surface on step length regulation. In two separate experiments, participants (Experiment 1 & 2: n=12, 6 female, 6 male) walked, jogged, or sprinted towards an obstacle along a 10 m walkway, consisting of two marker-strips with alternating black and white 0.50 m markings. Each experiment consisted of three targeting or obstacle tasks with the requirement to both negotiate and continue moving (run-through) through the target. Five trials were conducted for each task and approach speed, with trials block randomised between the six participants of each gender. One 50 Hz video camera panned and filmed each trial from an elevated position, adjacent to the walkway. Video footage was digitized to deduce the gait characteristics. Results for the targeting tasks indicate a linear relationship between approach velocity and accuracy of final foot placement (r=0.89). When foot placement was highly constrained by the obstacle step length shortened during the entire approach. VCO was found to occur at an earlier tau-margin for lower approach velocities for both experiments, indicating that the optical variable ‘tau' is affected by approach velocity. A three-phase kinematic profile was found for all tasks, except for the take-off board condition when sprinting. Further research is needed to determine whether this velocity affect on VCO is due to ‘whole-body' approach velocity or whether it is a function of the differences between gait modes.

Exercise and myocyte enhancer factor 2 regulation in human skeletal muscle

Overexpression of GLUT4 in skeletal muscle enhances whole-body insulin action. Exercise increases GLUT4 gene and protein expression, and a binding site for the myocyte enhancer factor 2 (MEF-2) is required on the GLUT4 promoter for this response. However, the molecular mechanisms involved remain elusive. In various cell systems, MEF-2 regulation is a balance between transcriptional repression by histone deacetylases (HDACs) and transcriptional activation by the nuclear factor of activated T-cells (NFAT), peroxisome proliferator-activated receptor- coactivator 1 (PGC-1), and the p38 mitogen-activated protein kinase. The purpose of this study was to determine if these same mechanisms regulate MEF-2 in contracting human skeletal muscle. Seven subjects performed 60 min of cycling at 70% of Vo2peak. After exercise, HDAC5 was dissociated from MEF-2 and exported from the nucleus, whereas nuclear PGC-1 was associated with MEF-2. Exercise increased total and nuclear p38 phosphorylation and association with MEF-2, without changes in total or nuclear p38 protein abundance. This result was associated with p38 sequence-specific phosphorylation of MEF-2 and an increase in GLUT4 mRNA. Finally, we found no role for NFAT in MEF-2 regulation. From these data, it appears that HDAC5, PGC-1, and p38 regulate MEF-2 and could be potential targets for modulating GLUT4 expression.

Regulation of metabolic genes in human skeletal muscle by short-term exercise and diet manipulation

Changes in dietary macronutrient intake alter muscle and blood substrate availability and are important for regulating gene expression. However, few studies have examined the effects of diet manipulation on gene expression in human skeletal muscle. The aim of this study was to quantify the extent to which altering substrate availability impacts on subsequent mRNA abundance of a subset of carbohydrate (CHO)- and fat-related genes. Seven subjects consumed either a low- (LOW; 0.7 g/kg body mass CHO) or high- (HIGH; 10 g/kg body mass CHO) CHO diet for 48 h after performing an exhaustive exercise bout to deplete muscle glycogen stores. After intervention, resting muscle and blood samples were taken. Muscle was analyzed for the gene abundances of GLUT4, glycogenin, pyruvate dehydrogenase kinase-4 (PDK-4), fatty acid translocase (FAT/CD36), carnitine palmitoyltransferase I (CPT I), hormone-sensitive lipase (HSL), β-hydroxyacyl-CoA dehydrogenase (΄β-HAD), and uncoupling binding protein-3 (UCP3), and blood samples for glucose, insulin, and free fatty acid (FFA) concentrations. Glycogen-depleting exercise and HIGH-CHO resulted in a 300% increase in muscle glycogen content (P < 0.001) relative to the LOW-CHO condition. FFA concentrations were twofold higher after LOW- vs. HIGH-CHO (P < 0.05). The exercise-diet manipulation exerted a significant effect on transcription of all carbohydrate-related genes, with an increase in GLUT4 and glycogenin mRNA abundance and a reduction in PDK-4 transcription after HIGH-CHO (all P < 0.05). FAT/CD36 (P < 0.05) and UCP3 (P < 0.01) gene transcriptions were increased following LOW-CHO. We conclude that 1) there was a rapid capacity for a short-term exercise and diet intervention to exert coordinated changes in the mRNA transcription of metabolic related genes, and 2) genes involved in glucose regulation are increased following a high-carbohydrate diet.

St. Johns wort attenuates irinotecan-induced diarhea via down-regulation of intestinal pro-inflammatory cytokines and inhibition of intestinal epithelial apoptosis

Diarrhea is a common dose-limiting toxicity associated with cancer chemotherapy, in particular for drugs such as irinotecan (CPT-11), 5-fluouracil, oxaliplatin, capecitabine and raltitrexed. St. John's wort (Hypericum perforatum, SJW) has anti-inflammatory activity, and our preliminary study in the rat and a pilot study in cancer patients found that treatment of SJW alleviated irinotecan-induced diarrhea. In the present study, we investigated whether SJW modulated various pro-inflammatory cytokines including interleukins (IL-1β, IL-2, IL-6), interferon (IFN-γ) and tumor necrosis factor-α (TNF-α) and intestinal epithelium apoptosis in rats. The rats were treated with irinotecan at 60 mg/kg for 4 days in combination with oral SJW or SJW-free control vehicle at 400 mg/kg for 8 days. Diarrhea, tissue damage, body weight loss, various cytokines including IL-1β, IL-2, IL-6, IFN-γ and TNF-α and intestinal epithelial apoptosis were monitored over 11 days. Our studies demonstrated that combined SJW markedly reduced CPT-11-induced diarrhea and intestinal lesions. The production of pro-inflammatory cytokines such as IL-1β, IFN-γ and TNF-α was significantly up-regulated in intestine. In the mean time, combined SJW significantly suppressed the intestinal epithelial apoptosis induced by CPT-11 over days 5–11. In particular, combination of SJW significantly inhibited the expression of TNF-α mRNA in the intestine over days 5–11. In conclusion, inhibition of pro-inflammatory cytokines and intestinal epithelium apoptosis partly explained the protective effect of SJW against the intestinal toxicities induced by irinotecan. Further studies are warranted to explore the potential for STW as an agent in combination with chemotherapeutic drugs to lower their dose-limiting toxicities.

Historical dynamics of the fur seal population : evidence of regulation by man?

The Australian fur seal (Arctocephalus pusillus doriferus) was severely over-exploited in the 18th and 19th centuries and until relatively recently its population had remained steady at well below estimated presealing levels. However, the population is now increasing rapidly (6%–20% per annum) throughout its range and there is a need to understand its dynamics in order to assess the potential extent and impact of interactions with fisheries. Age distribution (n = 156) and pregnancy rate (n = 110) were determined for adult females collected at a breeding colony on Seal Rocks, southeast Australia, in 1971–1972. Mean ± SE and maximum observed ages were 9.37 ± 0.41 and 20 years (n = 1), respectively. A stochastic modelling approach was used to fit an age distribution to the observed age-structure data and calculate rates of recruitment and adult survival. Annual adult female survival and recruitment rates between 1954 and 1971 were 0.478 ± 0.029 (mean ± SE) and 0.121 ± 0.007, respectively, suggesting that the population was experiencing a decline during the 1960s. The pregnancy rate increased from 78% at 3 years of age to an average of 85% between 4–13 years of age before significantly decreasing in older females (the oldest was 19 years of age). There was no significant effect of body mass or condition on the probability of a female being pregnant (P > 0.5 in both cases) and the nutritional burden of lactation did not appear to affect pregnancy rates or gestational performance. These findings suggest that the low survivorship was due to density-independent effects such as mortality resulting from interactions with fishers, which are known to have been common at the time. The recent increase in the population is consistent with anecdotal evidence that such interactions have decreased as fishing practices have changed.

The struggle for the body, mind and soul of AFL footballers

"The book discusses the profound, often troubling, always complex struggles for the body, mind and soul of elite performers in contemporary sports entertainment environments. This struggle is shaped by two powerful processes. On the one hand we witness the translation and application of a range of rationalities and knowledges from fields such as psychology, sport science and medicine, dietetics, education and management. All of which have the consequence of subjecting elite performers to often intrusive regimes of measurement, testing, medical intervention, surveillance, education and regulation in the pursuit of performance and success. At the same time we can identify ways in which the commodification of sports/games, the drive to develop and grow as a sports entertainment business and the pursuit and maintenance of a media presence and profile on which brand relationships can be established and grown has the consequence of transforming elite performers into highly paid sports celebrities whose image, persona and brand is positioned in a crowded, highly competitive marketplace to be scrutinised, judged and consumed.
[The] struggle that takes on new dimensions in the evolution of sports/games into global sports entertainment industries and businesses....The book reveals new insights into the tensions that emerge between different levels of the AFL sports entertainment industry about what it means to be a professional footballer at the start of the 21st century. The book analyses aspects of this struggle for the body, mind and soul at different stages in a playing career."--Media release.

Offender emotion and self-regulation : implications for offender rehabilitation programming

Despite a growing body of evidence pointing to the central role of negative emotional states in the offence process, there has been relatively little work, either theoretical or applied, investigating this area. This paper offers a review of the literature that has sought to investigate the association between negative emotion and offending. It is concluded that there are grounds to consider negative emotional states as important dynamic risk factors that should be addressed as part of any psychological intervention to reduce the risk of re-offending amongst forensic clients.

Central regulation of energy balance in Psammomys obesus

This body of work focussed on the central regulation of energy balance in a polygenic animal model of obesity and type II diabetes, the Israeli Sand Rat. These studies investigated the role of a number of hypothalamic neuropeptides in the development of obesity, and highlighted the complex nature of this disease.

Professional identity in the global sports entertainment industry : regulating the body, mind and soul of Australian Football League footballers

In this article we discuss the ways in which the professional identity of Australian Football League (AFL) footballers — in a physical, high body contact sport — is shaped by concerns to develop different aspects of the body, mind and soul of the young men who want to become AFL footballers. Drawing on Michel Foucault’s later work on the care of the self we argue that narratives of identity necessarily involve a struggle for the body, mind and soul of these young men. Foucault’s work enables us to identify and analyse how relations of power, forms of regulation and arts of governing interact in ongoing attempts to develop the professional footballer. The article explores these issues via an analysis of the rationalities and techniques that inform talent identification and player management practices; and risk management in relation to these practices and processes in the AFL.

Dietary omega-3 fatty acids modify body fluid and cardiovascular homeostasis

Dietary omega-3 fatty acids are important for optimal nutrition. This research demonstrated the significant beneficial effects of these fatty acids on body fluid balance in aging and the regulation of blood pressure. A significant findng was that omega-3 fatty acids reduce neuro-inflammation (inflammation in the brain)

Behaviour and buoyancy regulation in the deepest-diving reptile : the leatherback turtle

In the face of the physical and physiological challenges of performing breath-hold deep dives, marine vertebrates have evolved different strategies. Although behavioural strategies in marine mammals and seabirds have been investigated in detail, little is known about the deepest-diving reptile – the leatherback turtle (Dermochelys coriacea). Here, we deployed tri-axial accelerometers on female leatherbacks nesting on St Croix, US Virgin Islands, to explore their diving strategy. Our results show a consistent behavioural pattern within dives among individuals, with an initial period of active swimming at relatively steep descent angles (∼–40 deg), with a stroke frequency of 0.32 Hz, followed by a gliding phase. The depth at which the gliding phase began increased with the maximum depth of the dives. In addition, descent body angles and vertical velocities were higher during deeper dives. Leatherbacks might thus regulate their inspired air-volume according to the intended dive depth, similar to hard-shelled turtles and penguins. During the ascent, turtles actively swam with a stroke frequency of 0.30 Hz but with a low vertical velocity (∼0.40 ms–1) and a low pitch angle (∼+26 deg). Turtles might avoid succumbing to decompression sickness (‘the bends’) by ascending slowly to the surface. In addition, we suggest that the low body temperature of this marine ectotherm compared with that of endotherms might help reduce the risk of bubble formation by increasing the solubility of nitrogen in the blood. This physiological advantage, coupled with several behavioural and physical adaptations, might explain the particular ecological niche the leatherback turtle occupies among marine reptiles.