Lower Swimming Research Articles

The interaction between predation risk and food ration on behavior and morphology of Eurasian perch.

The risk of both predation and food level has been shown to affect phenotypic development of organisms. However, these two factors also influence animal behavior that in turn may influence phenotypic development. Hence, it might be difficult to disentangle the behavioral effect from the predator or resource‐level effects. This is because the presence of predators and high resource levels usually results in a lower activity, which in turn affects energy expenditure that is used for development and growth. It is therefore necessary to study how behavior interacts with changes in body shape with regard to resource density and predators. Here, we use the classic predator‐induced morphological defense in fish to study the interaction between predator cues, resource availability, and behavioral activity with the aim to determine their relative contribution to changes in body shape. We show that all three variables, the presence of a predator, food level, and activity, both additively and interactively, affected the body shape of perch. In general, the presence of predators, lower swimming activity, and higher food levels induced a deep body shape, with predation and behavior having similar effect and food treatment the smallest effect. The shape changes seemed to be mediated by changes in growth rate as body condition showed a similar effect as shape with regard to food‐level and predator treatments. Our results suggests that shape changes in animals to one environmental factor, for example, predation risk, can be context dependent, and depend on food levels or behavioral responses. Theoretical and empirical studies should further explore how this context dependence affects fitness components such as resource gain and mortality and their implications for population dynamics.

Kinematics and Hydrodynamics of Mobuliform Swimming: Oscillatory Winged Propulsion by Large Pelagic Batoids

AbstractLarge, pelagic rays (family Myliobatidae) that swim by flapping movements of wing-like pectoral fins use the mobuliform mode of swimming. These rays have pectoral fins with a triangular planform and streamlined cross-sectional geometry that would minimize drag. Thrust is produced by vertical oscillations of the fins with spanwise and chordwise flexibility. The thrust is derived from lift generated by the fins. Speed is modulated by changes in oscillatory frequency, whereas the amplitude of heave remains relatively constant with speed. Mobuliform swimming is considered to be a highly efficient means of propulsion. The Strouhal number for different species of myliobatoid rays is within the optimal range for efficient propulsion, except at low swimming speeds. The design of the body, posture of the pectoral fins, and mode of swimming provide a stable platform to resist external and internal perturbations, while permitting maneuverability. The advantages of mobuliform swimming can be exploited through the biomimetic approach to develop a bioinspired autonomous underwater vehicle.

Low Reynolds number swimming of helical structures in circular channels

Rotating helical structures are very effective in low Reynolds number swimming and propulsion. Helical rods are extensively studied theoretically and computationally with asymptotical methods, but the effects of the geometric variables in full-scale and the performance of other helical structures, such as ribbons and Archimedean screws, are also important for the understanding of swimming in confinements and design of micro swimming robots. In this study, a CFD model is developed to study swimming of helical rods, ribbons, screws and filaments, in circular channels under constant angular velocity or constant external torque. Effects of geometric parameters and the confinement radius on the swimming velocity and efficiency are demonstrated. Wavelength and amplitude of the helical wave, filament radius, thickness and width of ribbons, and eccentricity of tails are studied. Swimming performance of magnetically coated ribbons is compared with the ribbons with magnetic heads. Theoretical results in literature are used to validate the CFD results and to identify the role of hydrodynamic interactions between helical body and the channel wall.

Prosecretory effect of loperamide in ileal and colonic mucosae of mice displaying high or low swim stress-induced analgesia associated with high and low endogenous opioid system activity.

Irritable bowel syndrome (IBS) is characterized by abdominal pain, bloating, and changes in bowel habit. The aim of this study was to characterize the effect of loperamide hydrochloride (LOP) and naloxone hydrochloride (NLX), an opioid agonist and antagonist, respectively, on electrolyte equilibrium in ileal and colonic mucosae and to estimate the possible influence of divergent activity of the endogenous opioid system (EOS) on IBS therapy. Two mouse lines bidirectionally selected for high (HA) and low (LA) swim stress-induced analgesia associated with high and low EOS activity were used in this study. To assess the effect of LOP and NLX on HA/LA lines in vivo, we used the castor oil-induced diarrhea model. Changes in electrolyte equilibrium were determined on the basis of short-circuit current (ΔIsc ) in isolated mouse ileum and colon exposed to LOP and NLX and stimulated by forskolin (FSK), veratridine (VER), and bethanechol (BET). In vivo, we found that LOP significantly prolonged time to appearance of diarrhea in HA and LA lines. In vitro, LOP and NLX increased ΔIsc in FSK- and VER-stimulated colonic tissue, respectively, in HA line. In the ileum, LOP increased ΔIsc in FSK- and VER-stimulated tissue and decreased ΔIsc in BET-stimulated tissues in HA line. Individual differences in EOS activity may play a crucial role in the response to the IBS-D therapy, thus some patients may be at an increased risk of side effects such as constipation or diarrhea.

Comparative phenotypic analysis of “Clostridium neonatale” and Clostridium butyricum isolates from neonates

“Clostridium neonatale” was recently described as a new species within the Cluster I of the Clostridium genus sensu stricto. In this study, we characterized “C. neonatale” isolates (n = 42) and compared their phenotypic properties with those of Clostridium butyricum (n = 26), a close related species. Strains isolated from fecal samples of healthy neonates were tested for different phenotypic characteristics. Compared to C. butyricum, “C. neonatale” showed a significant higher surface hydrophobicity (p = 0.0047), exopolysaccharide production (p = 0.0069), aero-tolerance (p = 0.0222) and viability at 30 °C (p = 0.0006). A lower swimming ability (p = 0.0146) and tolerance against bile (0.3%) (p = 0.0494), acid (pH 4.5) (p < 0.0001), osmolarity (NaCl 5%, p = 0.0188) and temperature at 50 °C (p = 0.0013) characterized “C. neonatale” strains. Our results showed that “C. neonatale” behaves very differently from C. butyricum and suggests specific responses to environmental changes. Besides it is the first study on clinical isolates for these two anaerobic members of the newborns' gut microbiota and broadens our knowledge about their phenotypic traits.

Corticosterone response to gestational stress and postpartum memory function in mice.

Maternal stress is a common adversity during pregnancy. Gestational corticosterone alternations are thought to contribute to the etiology of postpartum behavioral disturbances. However, the impact of stress during pregnancy, in particular noise exposure, on gestational corticosterone fluctuations and spatial cognition in postpartum mice has not been fully understood yet. We hypothesized that noise exposure during pregnancy negatively affects gestational corticosterone levels and postpartum memory function in the dams similar to the physical stressors. Pregnant C57BL/6 mice were randomly assigned to either one of two stress conditions or a control condition. The noise stress (NS) was induced by presenting a loud intermittent 3000 Hz frequency on gestational days (GDs) 12, 14, and 16 for 24 hours, whereas the physical stress (PS) consisted of restraint and exposure to an elevated platform on GDs 12–16. Plasma corticosterone level was collected on GDs 11 and 17, and Morris water task (MWT) was carried out 30 days after parturition. Compared to the control group, the level of corticosterone in the stressed groups was significantly increased on GD17 relative to GD11. Significantly longer swim time and lower swim speed were observed in both stressed groups relative to the control group. Probe time was significantly shorter in the NS group than the other groups. The delta corticosterone level was significantly correlated with the swim time as well as the probe time in the three groups. Given the results, the adverse effects of gestational noise exposure on the hypothalamic pituitary-adrenal (HPA) axis activation and postpartum spatial learning and memory function were as large as/ or a bit stronger than the physical stresses. The findings suggest the significance of conservation against loud noise exposure in daily living, as well as need to further notice to the different aspects of gestational stress in mothers’ behavior like offspring.

Enriched environment alters the behavioral profile of tenascin-C deficient mice

Tenascin-C (TnC) is an extracellular matrix glycoprotein implicated in a variety of processes ranging from brain development to synaptic plasticity in the adult vertebrates. Although the role of the TnC gene in regulation of behavior has been investigated, it remained elusive how TnC deficiency interacts with the environment in shaping the behavioral phenotype. To address this, 3-week-old TnC+/+ and TnC-/- male mice were housed over an 8-week period in standard conditions (SC), or enriched environment (EE). A comprehensive battery of tests was used in behavioral phenotyping. When housed in SC, TnC−/− mice showed spontaneous nocturnal hyperactivity, as well as poor sensorimotor coordination and low swimming velocity. However, housing of TnC−/− mice in EE abolished hyperlocomotion, led to faster habituation to novel environment, strengthened the grasp of fore limbs and partially improved movement coordination, while the swimming ability remained deficient. Conversely, TnC deficiency attenuated both the beneficial effects of EE on learning/memory capacity and the anxiolytic effect of EE in reducing the level of acrophobia. This study expands the existing knowledge about the phenotype associated with TnC deficiency, and reveals that the effect of genetic background on the behavioral response could be altered by post-weaning housing in a highly stimulating environment.

Divergence in physiological factors affecting swimming performance between anadromous and resident populations of brook charr Salvelinus fontinalis.

In this study, an anadromous strain (L) and a freshwater-resident (R) strain of brook charr Salvelinus fontinalis as well as their reciprocal hybrids, were reared in a common environment and submitted to swimming tests combined with salinity challenges. The critical swimming speeds (Ucrit ) of the different crosses were measured in both fresh (FW) and salt water (SW) and the variations in several physiological traits (osmotic, energetic and metabolic capacities) that are predicted to influence swimming performance were documented. Anadromous and resident fish reached the same Ucrit in both FW and SW, with Ucrit being 14% lower in SW compared with FW. The strains, however, seemed to use different underlying strategies: the anadromous strain relied on its streamlined body shape and higher osmoregulatory capacity, while the resident strain had greater citrate synthase (FW) and lactate dehydrogenase (FW, SW) capacity and either greater initial stores or more efficient use of liver (FW, SW) and muscle (FW) glycogen during exercise. Compared with R♀ L♂ hybrids, L♀ R♂ hybrids had a 20% lower swimming speed, which was associated with a 24% smaller cardio-somatic index and higher physiological costs. Thus swimming performance depends on cross direction (i.e. which parental line was used as dam or sire). The study thus suggests that divergent physiological factors between anadromous and resident S. fontinalis may result in similar swimming capacities that are adapted to their respective lifestyles.

Naloxone exacerbates memory impairments and depressive-like behavior after mild traumatic brain injury (mTBI) in mice with upregulated opioid system activity

The neuroprotective role of the endogenous opioid system in the pathophysiological sequelae of brain injury remains largely ambiguous. Noteworthy, almost no data is available on how its genetically determined activity influences the outcome of mild traumatic brain injury. Thus, the aim of our study was to examine the effect of opioid receptor blockage on cognitive impairments produced by mild traumatic brain injury in mice selectively bred for high (HA) and low (LA) swim-stress induced analgesia that show innate divergence in opioid system activity. Mild traumatic brain injury was induced with a weight-drop device on anaesthetized mice. Naloxone (5mg/kg) was intraperitoneally delivered twice a day for 7days to non-selectively block opioid receptors. Spatial memory performance and manifestations of depressive-like behavior were assessed using the Morris Water Maze and tail suspension tests, respectively. Mild traumatic brain injury resulted in a significant deterioration of spatial memory performance and severity of depressive-like behavior in the LA mouse line as opposed to HA mice. Opioid receptor blockage with naloxone unmasked cognitive deficits in HA mice but was without effect in the LA line. The results suggest a protective role of genetically predetermined enhanced opioid system activity in suppression of mild brain trauma-induced cognitive impairments. Mice selected for high and low swim stress-induced analgesia might therefore be a useful model to study the involvement of the opioid system in the pathophysiology and neurological outcome of traumatic brain injury.

Fitness component assessments of wild-type and growth hormone transgenic coho salmon reared in seawater mesocosms

Growth hormone (GH) transgenic fish have been proposed for use in aquaculture to enhance production efficiency. As part of a risk analysis for use of such fish, the influence of GH transgenesis on the potential to persist and succeed in natural ecosystems is being examined in confined laboratory conditions. GH transgenesis can greatly accelerate growth and, in culture conditions, is associated with secondary effects such as poor swimming capacity and spawning success. However, standard culture has also been shown to negatively affect fitness components of wild-type fish, raising the question of whether culture conditions influence fitness components of transgenic fish in a similar way. To examine factors influencing the phenotype of marine-stage GH transgenic salmon (T), and to determine if genotype-by-environment interactions exist at this life stage, we grew T and wild-type (NT) coho salmon (Oncorhynchus kisutch) over six cohort years in 350,000L seawater tanks (termed mesocosms) designed to minimize effects of standard culture conditions. Mesocosm rearing partially facilitated development of normal size and morphology of NT fish relative to nature-reared counterparts, but altered overall body shape, indicating mesocosm conditions do not fully mimic natural environmental effects on coho salmon phenotype. T fish reared in mesocosms had larger mass at maturity than mesocosm- or nature-reared NT fish, indicating GH transgenesis can alter maximum obtainable mass in salmon. Unlike NT, T fish obtained maximum size at maturity across environments, suggesting marine environmental conditions may affect T growth less than NT growth. Screening parents for a common disease agent (Renibacterium salmoninarum) improved seawater survival, and T fish had lower survival than NT fish when from unscreened parents and inconsistent relative survival when from screened parents, indicating GH transgenesis may constitute an advantage or disadvantage in terms of survival. Transgenic salmon had lower swimming capacity and aerobic scope, but similar routine metabolic rate and thermal tolerance, demonstrating transgenesis can have different influences depending on what phenotype is examined. Using an alternate strain of T fish in phenotypic comparisons did not greatly influence most fitness components, although had a strong effect on female fecundity. The inconsistent influence of GH transgenesis on different fitness components, and existence of genotype-by-environment interactions during the marine life stage, complicates extrapolation of laboratory data for transgenic fish to natural environments. However, current and previous data do not provide evidence that overall increased performance of GH transgenic salmon over wild-type fish would arise in the marine environment. Statement of relevanceRearing in seawater mesocosms demonstrate that growth hormone transgenesis has inconsistent effects on marine fitness components in coho salmon.

Seasonal, Diel, and Age Differences in Activity Budgets of a Group of Bottlenose Dolphins (Tursiops truncatus) Under Professional Care

Wild bottlenose dolphin (Tursiops truncatus) behavior is impacted by a number of factors including season, time of day, and age. However, less is known about how these factors may influence animals under professional care in zoos, aquariums and marine parks. Management practices such as scheduled feeding times, human interactions, lack of predators and show performances may also impact the activity budgets of dolphins. The current study examined the rest, swim and play behavior of seven dolphins (three adults, four calves) at one facility. Data were collected over the entire 24-hour day for a period of one year. Observed behaviors were recorded in mutually exclusive categories including rest, low intensity swim, high intensity swim, low intensity play, high intensity play and social play. Data were analyzed to determine how often dolphins engaged in particular behaviors and if activity budgets varied due to season, time of day and age. These dolphins spent the majority of their time in low intensity swim and low intensity play. The activity budget varied between observational periods. First, seasonal differences were found in low intensity swim, low intensity play, social play and high intensity play behaviors. In the comparison for time of day, differences were found in rest, low intensity swim, low intensity play and social play. Finally, no significant differences were found in age comparisons. Information gained from this study can help to better understand how different factors influence the behavior of bottlenose dolphins under professional care within zoos, aquariums and marine parks.

Biomechanics of diving: the influence of the swimming speed on the kinematics of lower limbs of professional divers.

The aim of this study is to evaluate the influence of the swimming speed during diving on the biomechanical parameters describing the movement of selected measurement points of the lower limb in professional divers. The study involved a group of 4 professional divers whose movement was recorded during underwater swimming at slow (approx. 0.4 m·s-1), medium (approx. 0.5 m·s-1), and fast (approx. 0.8 m·s-1) pace. During swimming at medium speed, the divers made a smaller displacement (along the axes Y) of the midpoint of fin than during swimming at fast speed. The range of motion in the ankle joint increased in fast speed in comparison with low and medium swimming speed. The same relationship was noted for the obtained velocity and angular acceleration in the hip, knee and ankle joints. The authors observed that during swimming at slow pace the divers choose movement ensuring high swimming comfort while the efficiency of motion is a secondary factor. On the other hand, during swimming at higher pace, the applied movement pattern ensures far greater efficiency rather than swimming comfort. The conducted analysis showed that divers adjust the movement of their lower limbs to the swimming pace.

Comparison of low temperature adaptation ability in three native and two hybrid strains of the rotifer Brachionus plicatilis species complex

The low temperature adaptation ability of five selected strains of the Brachionus plicatilis species complex, i.e., three native strains [ Japanese (NH1L), Australian, German] and two hybrid strains [♀NH1L and ♂Australian (N × A) and ♀NH1L and ♂German (N × G),was investigated in terms of life history traits, reproductive characteristics, and mobility under different thermal conditions (12 and 25 °C). The life history traits of these five strains included a longer lifespan, reproduction period and generation times at 12 °C than at 25 °C, combined with reduced lifetime egg and offspring production. At 12 °C, the intrinsic rate of natural increase was higher in NH1L and N × A strains. Reproductive characteristics determined at 12 °C by batch culture showed active population growth for NH1L and N × G strains, while no resting egg production was observed in all of the strains tested. The ratio of swimming rotifers at 12 °C was monitored every hour for 6 h (short term) and every day for 10 days (long term). In the short-term study there was a 81% ratio of swimming rotifers of the NH1L strain, while other strains exhibited low swimming ratios ( 75% swimming ratio from the initial day of the study. These results suggest that outcrossing of rotifer strains is useful to obtain live food resources for the larviculture of cold water fish.

Hyperbaric Oxygen Pretreatment Improves Cognition and Reduces Hippocampal Damage Via p38 Mitogen-Activated Protein Kinase in a Rat Model.

PurposeTo investigate the effects of hyperbaric oxygen (HBO) pretreatment on cognitive decline and neuronal damage in an Alzheimer’s disease (AD) rat model.Materials and MethodsRats were divided into three groups: normal saline (NS), AD, and HBO+AD. In the AD group, amyloid β peptide (Aβ)1-40 was injected into the hippocampal CA1 region of the brain. NS rats received NS injection. In the HBO+AD group, rats received 5 days of daily HBO therapy following Aβ1-40 injection. Learning and memory capabilities were examined using the Morris water maze task. Neuronal damage and astrocyte activation were evaluated by hematoxylin-eosin staining and immunohistochemistry, respectively. Dendritic spine density was determined by Golgi-Cox staining. Tumor necrosis factor-α, interleukin-1β, and interleukin-10 production was assessed by enzyme-linked immunosorbent assay. Neuron apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling. Protein expression was examined by western blotting.ResultsLearning and memory dysfunction was ameliorated in the HBO+AD group, as shown by significantly lower swimming distances and escape latency, compared to the AD group. Lower rates of neuronal damage, astrocyte activation, dendritic spine loss, and hippocampal neuron apoptosis were seen in the HBO+AD than in the AD group. A lower rate of hippocampal p38 mitogen-activated protein kinase (MAPK) phosphorylation was observed in the HBO+AD than in the AD group.ConclusionHBO pretreatment improves cognition and reduces hippocampal damage via p38 MAPK in AD rats.

The effects of nest incubation temperature on embryos and hatchlings of the loggerhead sea turtle: Implications of sex difference for survival rates during early life stages

In sea turtles, higher hatch and emergence successes, larger body size of hatchlings, and superior terrestrial and swimming locomotor performances are important to maximize survival rates. Here, the hatch and emergence successes, embryonic mortality rates, hatchling morphology, and terrestrial and swimming locomotor performances of the loggerhead sea turtle (Caretta caretta) from male and female producing nests were investigated. Mortality rates during the early embryonic stage in the male producing nests were significantly lower than those in the female producing nests. The hatchlings from male producing nests showed higher terrestrial locomotor performances than those from female producing nests. Furthermore, while the other factors did not show differences between the two nesting groups, the high incubation temperatures significantly affected the mortality rate of embryos and the swimming performance of hatchlings. The present study indicates that male hatchlings are likely to have higher survival rates than female hatchlings during the critical terrestrial period. In addition, the present study suggests that as global warming proceeds, female-fate embryos and/or female hatchlings are likely to face lower survival rates than males, owing to high mortality rate of embryos and low swimming performance of hatchlings.

Flow analysis of the low Reynolds number swimmerC. elegans

Swimming cells and microorganisms are a critical component of many biological processes. In order to better interpret experimental studies of low Reynolds number swimming, we combine experimental and numerical methods to perform an analysis of the flow-field around the swimming nematode Caenorhabditis elegans. We first use image processing and particle tracking velocimetry to extract the body shape, kinematics, and flow-fields around the nematode. We then construct a three-dimensional model using the experimental swimming kinematics and employ a boundary element method to simulate flow-fields, obtaining very good quantitative agreement with experiment. We use this numerical model to show that calculation of flow shear rates using purely planar data results in significant underestimates of the true three-dimensional value. Applying symmetry arguments, validated against numerics, we demonstrate that the out-of-plane contribution can be accounted for via incompressibility and therefore simply calculated from particle tracking velocimetry. Our results show how fundamental fluid mechanics considerations may be used to improve the accuracy of measurements in biofluiddynamics.

A Cryptic Marine Ciliate Feeds on Progametes of Noctiluca scintillans

The dinoflagellate Noctiluca scintillans (Noctiluca) has the ability to reproduce sexually, which may help to increase or restore its population size during periods of blooms or environmental stress. Here, we documented for the first time a marine ciliate Strombidium sp. that feeds on Noctiluca's progametes undergoing stages 5 to 9 of nuclear division. This ciliate frequently swam on or around gametogenic and some vegetative Noctiluca cells. The ciliates associated with gametogenic cells had significantly lower swimming speed and changed direction more frequently than those associated with vegetative cells, which overall increased their time spent around the food patches (progametes). This trophic interaction constitutes an upside-down predator-prey link, in which ciliates within the typical size range of Noctiluca prey, become the predators. Based on the phylogenetic tree (maximum-likelihood), there are 14 environmental clones similar to Strombidium sp. found in other coastal waters, where Noctiluca presence or blooms have been reported. This novel predator-prey relationship could therefore be common in other Noctiluca habitats. Additional studies are needed to assess the magnitude of its impacts on Noctiluca population dynamics and plankton bloom succession.

Self-propelled swimming simulations of bio-inspired smart structures

This paper presents self-propelled swimming simulations of a foldable structure, whose folded configuration is a box. For self-locomotion through water the structure unfolds and undulates. To guide the design of the structure and understand how it should undulate to achieve either highest speed or maximize efficiency during locomotion, several kinematic parameters were systematically varied in the simulations: the wave type (standing wave versus traveling wave), the smoothness of undulations (smooth undulations versus undulations of rigid links), the mode of undulations (carangiform: mackerel-like versus anguilliform: eel-like undulations), and the maximum amplitude of undulations. We show that the swimmers with standing wave are slow and inefficient because they are not able to produce thrust using the added-mass mechanism. Among the tested types of undulation at low Reynolds number (Re) regime of (Strouhal number of about 1.0), structures that employ carangiform undulations can swim faster, whereas anguilliform swimmers are more economic, i.e., using less power they can swim a longer distance. Another finding of our simulations is that structures which are made of rigid links are typically less efficient (lower propulsive and power efficiencies and also lower swimming speed) compared with smoothly undulating ones because a higher added-mass force is generated by smooth undulations. The wake of all the swimmers bifurcated at the low Re regime because of the higher lateral relative to the axial velocity (high Strouhal number) that advects the vortices laterally creating a double row of vortices in the wake. In addition, we show that the wake cannot be used to predict the performance of the swimmers because the net force in each cycle is zero for self-propelled bodies and the pressure term is not negligible compared to the other terms.

Analysis of free-surface effects on swimming by the application of the computational fluid dynamics method

In this study, free-surface effects on swimming are investigated by the application of the computational fluid dynamics method for the first time. The major goal of this study is to represent a new methodology to numerically investigate free-surface effects on swimming. Utilizing a two-dimensional solver with steady flow conditions, the numerical results for swimming at a fully submerged level are validated with the data presented by previous researchers. The validity of the results is also examined through the study of mesh independency and the control of a critical turbulence feature, entitled as non-dimensional wall distance (y+). Finally, for the analysis of swimming at the free-surface level, a two-dimensional time-dependent solver with a well-known multiphase mathematical model is implemented to simultaneously investigate two-phase flow interactions and wave propagation in the proximity of the swimmer’s body. The development of different flow topology features, including major vortex cores and secondary recirculation zones as well as turbulence mixing and flow updraft and downdraft, are investigated and used to compare free-surface swimming against fully submerged cases. While the drag coefficient continuously decreases for higher advance velocities for a fully submerged case, a gradual augmentation is observed for the drag coefficient at a free-surface swimming level. The obtained results suggest that while the proportion of wave drag is ignorable at low swimming speeds below 1 m/s, in the case of higher speeds, its amount enhances significantly and constitutes about 15% of the total drag. Moreover, the proposed methodology is demonstrated to be efficient in the simulation of flow characteristics and phase interactions in swimming at the free-surface level.

Physical Exercise versus Natural Estrogen Supplement in Treatment of Metabolic Syndrome in Aged Postmenopausal Wistar Rats

The present study was performed to evaluate the effects of either a low intensity swim- exercise program or low soybean flour supplementation on the different components of metabolic syndrome in aged postmenopausal rats.