Acute effect of heel-drop exercise with varying ranges of motion on the gastrocnemius aponeurosis-tendon’s mechanical properties

The objectives of this study was to investigate the acute effects of various magnitudes of tendon strain on the mechanical properties of the human medial gastrocnemius (MG) in vivo during controlled heel-drop exercises. Seven male and seven female volunteers performed two different exercises executed one month apart: one was a heel-drop exercise on a block (HDB), and the other was a heel-drop exercise on level floor (HDL). In each regimen, the subjects completed a session of 150 heel-drop exercises (15 repetitions × 10 sets; with a 30 s rest following each set). Before and immediately after the heel-drop exercise, the ankle plantar flexor torque and elongation of the MG were measured using a combined measurement system of dynamometry and ultrasonography and then the MG tendon strain and stiffness were evaluated in each subject. The tendon stiffness measured prior to the exercises was not significantly different between the two groups 23.7 ± 10.6 N/mm and 24.1 ± 10.0 N/mm for the HDB and HDL, respectively (p > .05). During the heel-drop exercise, it was found that the tendon strain during the heel-drop exercise on a block (8.4 ± 3.7%) was significantly higher than the strain measured on the level floor (5.4 ± 3.8%) (p < .05). In addition, the tendon stiffness following the heel-drop exercise on a block (32.3 ± 12.2 N/mm) was significantly greater than the tendon stiffness measured following the heel-drop exercise on the level floor (25.4 ± 11.4 N/mm) (p < .05). The results of this study suggest that tendon stiffness immediately following a heel-drop exercise depends on the magnitude of tendon strain.     

Suppression of MAPKAPK2 during mammalian hibernation

Metabolic signaling coordinates the transition by hibernating mammals from euthermia into profound torpor. Organ-specific responses by activated p38 mitogen activated protein kinase (MAPK) are known to contribute to this transition. Therefore, we hypothesized that the MAPK-activated protein kinase-2 (MAPKAPK2), a downstream target of p38 MAPK, would also be active in establishing the torpid state. Kinetic parameters of MAPKAPK2 from skeletal muscle of Richardson’s ground squirrels, Spermophilus richardsonii, were analyzed using a fluorescence assay. MAPKAPK2 activity was 27.4 ± 1.27 pmol/min/mg in muscle from euthermic squirrels and decreased by ∼63% during cold torpor, while total protein levels were unchanged (as assessed by immunoblotting). In vitro treatment of MAPKAPK2 via stimulation of endogenous phosphatases and addition of commercial alkaline phosphatase decreased enzyme activity to only ∼3–5% of its original value in muscle extracts from both euthermic and hibernating squirrels suggesting that posttranslational modification suppresses MAPKAPK2 during the transition from euthermic to torpid states. Enzyme S_0.5 and n_H values for ATP and peptide substrates changed significantly between euthermia and torpor, and also between assays at 22 versus 10 °C but, kinetic parameters were actually closely conserved when values for the euthermic enzyme at 22 °C were directly compared with the hibernator enzyme at 10 °C. Arrhenius plots showed significantly different activation energies of 40.8 ± 0.7 and 54.3 ± 2.7 kJ/mol for the muscle enzyme from euthermic versus torpid animals, respectively but MAPKAPK2 from the two physiological states showed no difference in sensitivity to urea denaturation. Overall, the results show that total activity of MAPKAPK2 is in fact reduced, despite previous findings of p38 MAPK activation, and kinetic parameters are altered when ground squirrels enter torpor but protein stability is not apparently changed. The data suggest that MAPKAPK2 suppression may have a significant role in the differential regulation of muscle target proteins when ground squirrels enter torpor.     

Effects of stress fiber contractility on uniaxial stretch guiding mitosis orientation and stress fiber alignment

It has been documented that mitosis orientation (MO) is guided by stress fibers (SFs), which are perpendicular to exogenous cyclic uniaxial stretch. However, the effect of mechanical forces on MO and the mechanism of stretch-induced SFs reorientation are not well elucidated to date. In the present study, we used murine 3T3 fibroblasts as a model, to investigate the effects of uniaxial stretch on SFO and MO utilizing custom-made stretch device. We found that cyclic uniaxial stretch induced both SFs and mitosis directions orienting perpendicularly to the stretch direction. The F-actin and myosin II blockages, which resulted in disoriented SFs and mitosis directions under uniaxial stretch, suggested a high correlation between SFO and MO. Y27632 (10 μM), ML7 (50 μM, or 75 μM), and blebbistatin (50 μM, or 75 μM) treatments resulted in SFO parallel to the principle stretch direction. Upon stimulating and inhibiting the phosphorylation of myosin light chain (p-MLC), we observed a monotonic proportion of SFO to the level of p-MLC. These results suggested that the level of cell contraction is crucial to the response of SFs, either perpendicular or parallel, to the external stretch. Showing the possible role of cell contractility in tuning SFO under external stretch, our experimental data are valuable to understand the predominant factor controlling SFO response to exogenous uniaxial stretch, and thus helpful for improving mechanical models.     

Influence of muscle activity on musculotendinous stiffness quantification in stunted,prepubertal children

The quick-release technique to estimate musculotendinous (MT) stiffness has been extensively used over the last years, in both animals and humans, to gain insights in the adaptive process of the series elastic component (SEC). Recently, MT stiffness quantification, i.e., SEC behavior, has been revisited for subjects not able to fully activate their muscles (effects of long-term spaceflight or non-mature muscles). Such a phenomenon can also be encountered in stunted children. So, the aim of the present study was to analyze the effect of stunting on MT stiffness taking into account possible defect in muscle activation. For this study, 20 eutrophic children (EU) with an average age of 9 years ± 4 months were compared to 11age matched stunted children (S) evaluated by the height-to-age index. The MT stiffness index was obtained with regard to stiffness–torque and stiffness–soleus EMG relationships. The children of the S group presented a significantly lower Maximal Voluntary Contraction (MVC) in plantar flexion in comparison with children of the EU group (?37.8%). The significantly lower MT stiffness index for S children (?42.6%) was evidenced only when quantified with regard to the stiffness–soleus EMG relationship (66.5 ± 42.8 vs. 38.2 ± 19.9 Nm rad^?1%^?1). Possible delay in fiber type differentiation or tendinous structure maturation can account for the lower MT stiffness index in S children. In conclusion, stunting during early childhood delays the differentiation and maturation processes of musculotendinous structures as shown by the lower MT stiffness quantified with regards to muscle activity, also altered for stunted prepubertal children.     

Mechanical properties of the patellar tendon in adults and children

It is not currently known how the mechanical properties of human tendons change with maturation in the two sexes. To address this, the stiffness and Young's modulus of the patellar tendon were measured in men, women, boys and girls (each group, n=10). Patellar tendon force (F_pt) was calculated from the measured joint moment during a ramped voluntary isometric knee extension contraction, the antagonist knee extensor muscle co-activation quantified from its electromyographical activity, and the patellar tendon moment arm measured from magnetic resonance images. Tendon elongation was imaged using the sagittal-plane ultrasound scans throughout the contraction. Tendon cross-sectional area was measured at rest from ultrasound scans in the transverse plane. Maximal F_pt and tendon elongation were (mean±SE) 5453±307 N and 5±0.5 mm for men, 3877±307 N and 4.9±0.6 mm for women, 2017±170 N and 6.2±0.5 mm for boys and 2169±182 N and 5.9±0.7 mm for girls. In all groups, tendon stiffness and Young's modulus were examined at the level that corresponded to the maximal 30% of the weakest participant's F_pt and stress, respectively; these were 925–1321 N and 11.5–16.5 MPa, respectively. Stiffness was 94% greater in men than boys and 84% greater in women than girls (p<0.01), with no differences between men and women, or boys and girls (men 1076±87 N/mm; women 1030±139 N/mm; boys 555±71 N/mm and girls 561.5±57.4 N/mm). Young's modulus was 99% greater in men than boys (p<0.01), and 66% greater in women than girls (p<0.05). There were no differences in modulus between men and women, or boys and girls (men 597±49 MPa; women 549±70 MPa; boys 255±42 MPa and girls 302±33 MPa). These findings indicate that the mechanical stiffness of tendon increases with maturation due to an increased Young's modulus and, in females due to a greater increase in tendon cross-sectional area than tendon length.     

Endothelial actin and cell stiffness is modulated by substrate stiffness in 2D and 3D

There is a growing appreciation of the profound effects that passive mechanical properties, especially the stiffness of the local environment, can have on cellular functions. Many experiments are conducted in a 2D geometry (i.e., cells grown on top of substrates of varying stiffness), which is a simplification of the 3D environment often experienced by cells in vivo. To determine how matrix dimensionality might modulate the effect of matrix stiffness on actin and cell stiffness, endothelial cells were cultured on top of and within substrates of various stiffnesses. Endothelial cells were cultured within compliant (1.0–1.5 mg/ml, 124±8 to 202±27 Pa) and stiff (3.0 mg/ml, 502±48 Pa) type-I collagen gels. Cells elongated and formed microvascular-like networks in both sets of gels as seen in previous studies. Cells in stiffer gels exhibited more pronounced stress fibers and ～1.5-fold greater staining for actin. As actin is a major determinant of a cell's mechanical properties, we hypothesized that cells in stiff gels will themselves be stiffer. To test this hypothesis, cells were isolated from the gels and their stiffness was assessed using micropipette aspiration. Cells isolated from relatively compliant gels were 1.9-fold more compliant than cells isolated from relatively stiff gels (p<0.05). Similarly, cells cultured on top of 1700 Pa polyacrylamide gels were 2.0-fold more compliant that those cultured on 9000 Pa (p<0.05). These data demonstrate that extracellular substrate stiffness regulates endothelial stiffness in both three- and two-dimensional environments, though the range of stiffnesses that cells respond to vary significantly in different environments.     

Volatile fatty acids accumulation and rhamnolipid generation in situ from waste activated sludge fermentation stimulated by external rhamnolipid addition

The solubilization and acidification of waste activated sludge (WAS) were apparently enhanced by external rhamnolipid (RL) addition. The maximum solute carbohydrate concentrations increased linearly from 48 ± 5 mg COD L⁻¹ in the un-pretreated WAS (blank) to 566 ± 19 mg COD L⁻¹, and protein increased from 1050 ± 8 to 3493 ± 16 mg COD L⁻¹ at RL dosage of 0.10 g g⁻¹ TSS. The highest VFAs concentration peaked at 3840 mg COD L⁻¹ at RL dosage of 0.04 g g⁻¹ TSS, which was 4.24-fold higher than the blank test. RL was generated in situ during WAS fermentation when external RL was added. It was detected that RL concentration was increased from initial 880 ± 92 mg L⁻¹ to 1312 ± 7 mg L⁻¹ at the end of 96 h with RL dosage of 0.04 g g⁻¹ TSS, which was increased to 1.49-fold. Meanwhile, methane production was notably reduced to a quite low level of 2.0 mL CH₄ g⁻¹ VSS, showing effective inhibition of methanogens by RL (58.8 mL CH₄ g⁻¹ VSS in the blank). In addition, the activity of hydrolytic enzymes (protease and α-glucosidase) was enhanced accordingly. VFAs accumulation and RL generation in situ demonstrated that the additional RL substantially performed enhanced biological effects for waste activated sludge fermentation.     

Biochemical changes in the follicular fluid of the dominant follicle of high producing dairy cows exposed to heat stress early post-partum

High yielding dairy cows experience a negative energy balance (NEB) early post-partum and it was hypothesized that this may be aggravated under summer heat stress (HS) conditions. In this study, which was performed in Egypt, 20 Holstein cows were followed during summer (n = 10) and winter (n = 10) seasons. All cows were multiparous and kept at the same herd. Blood was sampled from each cow starting 1 week before the expected calving date and then at 1-week intervals until week 6 post-partum. From week 2 to 6 post-partum follicular fluid was collected through transvaginal follicular fluid aspiration at 6 days intervals. Ambient air temperature (AT) and relative humidity (RH) were recorded and temperature–humidity index (THI) was calculated as well. Respiration rate (RR), rectal temperature (RT), and body condition score (BCS) were recorded for each cow at the time of blood sampling. Concentrations of glucose, insulin like growth factor-1 (IGF-1), non-esterified fatty acids (NEFA), urea and total cholesterol (TC) were measured in each blood and follicular fluid sample. All the cows showed a significantly higher RR and RT in summer (95.5 ± 1.1 and 39.88 ± 0.06, respectively) than in winter (43.89 ± 0.61 and 38.94 ± 0.07, respectively) (P < 0.001). Body condition score loss during the early post-partum period was higher in summer than in winter (1.1 ± 0.07 vs. 0.85 ± 0.06 point, respectively) (P < 0.001). The average dominant follicle diameter was significantly lower in summer than in winter during the period of negative energy balance (11.6 ± 0.7 mm vs. 15.3 ± 1.2 mm, respectively) (P < 0.01). Under summer heat stress, the concentrations of glucose (2.98 ± 0.07 and 2.19 ± 0.04 mmol/L), IGF-1 (106.7 ± 2.9 and 99.0 ± 3.4 ng/ml) and TC (137.3 ± 5.3 and 62.2 ± 5.1 mg/dl) in blood and FF, respectively, were significantly lower than winter concentrations by (0.17 ± 0.03 mmol/L, P < 0.001 and 0.26 ± 0.06 mmol/L, P < 0.001), (12.3 ± 3.6 ng/ml, P < 0.001 and 9.0 ± 2.7 ng/ml, P < 0.001) and (20.7 ± 1.8 mg/dl, P < 0.001 and 7.3 ± 1.1 mg/dl, P < 0.01), respectively. However, the concentrations of NEFA (0.68 ± 0.14 and 0.22 ± 0.02 mmol/L) and urea (9.27 ± 0.34 and 9.96 ± 0.25 mmol/L) in blood and FF, respectively, were significantly higher in summer compared to winter (0.50 ± 0.08 mmol/L, P < 0.001 and 0.20 ± 0.02 mmol/L, P < 0.001) and (8.77 ± 0.23 mmol/L, P < 0.05 and 8.96 ± 0.29 mmol/L, P < 0.001), respectively, throughout the experimental period. The results of the present study indicate that heat stress early post-partum aggravates NEB in high yielding dairy cows, reduces BCS, dominant follicle diameter and alters the biochemical concentrations in the follicular fluid of the dominant follicle which may result in inferior oocyte and granulosa cell quality and hence poorer fertility.     

Oxidative stress and DNA damage in relation to transition metals overload in Abu-Qir Bay,Egypt

The aim of the present study is to evaluate the transition metals overload in Abu-Qir Bay in Egypt, as compared to a less polluted area (reference area) through some biomarkers of oxidative stress. Catalase enzyme activity, malondialdehyde (MDA) concentration and DNA damage (number of apurinic/apyrimidinic sites) were the tested biomarkers. The levels of iron and copper in Mugil cephalus liver tissues were significantly higher in samples from the polluted area as compared to the reference area: Fe: 407 ± 38 vs. 216 ± 21 μg/g wet wt; p = 0.008, Cu: 54 ± 6 vs. 17.7 ± 4 μg/g wet wt; p = 0.0001. This could account for the observed increase in MDA concentration (15.7 ± 5.7 vs. 2.5 ± 0.5 U/g; p = 0.035), and the elevated number of AP sites (13.9 ± 2.6 vs. 0.37 ± 0.2 AP site/1 × 10⁵ bp; p = 0.0001). Similarly, the activity of catalase enzyme responsible for the cellular defense was significantly high (58.3 ± 12.2 vs. 28.4 ± 4.0 U/mg; p = 0.032). The present data indicated a clear relationship between the pollution degree of the above marine environment and both biochemical and molecular responses of the piscine system.     

Caulerpa taxifolia responses to hyposalinity stress

An investigation into salinity responses of Caulerpa taxifolia was undertaken in a series of laboratory trials to evaluate the use of hyposalinity stress as an eradication strategy. The effect of instantaneous (or shock) exposure to reduced salinity (10 ppt) on the effective quantum yield (EQY) of C. taxifolia for different incubation periods (15, 30, 45, 60, 90, 180, 360, 720 and 1440 min) indicated that 180 min or more at this salinity was required to kill the alga. Average EQY declined by 88.2 ± 4.6% (mean ± S.E.) of the pre-treatment level for the 180 min treatment but were as much as 96.6 ± 2.5% lower than pre-treatment EQY for the 1440 min exposure. Exposure for 90 min or less resulted in an intermediate response, whereas lesser exposures (60, 30 and 15 min) had no lasting effect on C. taxifolia health. The effect of gradual changes in salinity, as might be anticipated in an eradication scenario, on EQY of C. taxifolia was investigated through the dilution of seawater (35 ppt) over different time scales (5 h, 2, 4, 7 and 27 days). In all trials >5 h, the response to hyposalinity was the same regardless of the rate of change in salinity with all treatments resulting in a marked loss in EQY below ∼15 ppt. Declines in the average ratio of EQY after to EQY before for 4, 7 and 27 days treatments (85.2 ± 8.2%, 78.8 ± 9.05% and 77.3 ± 18.2% of pre-treatment levels, respectively), were significantly larger than the 5 h treatment (2.6 ± 4.4% of pre-treatment levels). The 2 days salinity reduction (48.5 ± 17.1%) resulted in an intermediate response. In the 5 h treatment, the exposure to salinities below 15 ppt was less than 3 h, which given the result of the preceding trial explains the lack of substantial EQY response as the minimum exposure period required to kill the alga at 10 ppt is ≥180 min. There is thus no evidence that C. taxifolia is capable of acclimation to gradual reductions in salinity. Consequently, hyposalinity is an effective means of killing the algae and may prove highly effective for populations in relatively small, contained water bodies.     

Water-use efficiency of tree species following calcium and phosphorus application on an abandoned pasture,central Amazonia,Brazil

This research represents one of the first studies in Amazonia to examine soil moisture and water-use efficiency (WUE) in secondary forest (SF) vegetation regrowing on abandoned pastures subjected to reduced nutrient constraints via a nutrient addition experiment. Extensive forested areas (about 80% of deforestation) have been converted to pastures in Amazonia, which were later abandoned following soil degradation and reduction in grass productivity. Colonization of these areas proceeds through species adapted to adverse edaphic conditions, such as low soil nutrients. Yet there is little data from such environments showing the interaction of soil nutrients and water availability on plant physiological processes. The objective of this study was to test whether three common SF tree species have positive physiological responses, e.g. increased photosynthesis and water-use efficiency, when nutrient limitations are relaxed through fertilization. The experiment was conducted on an abandoned pasture in central Amazonia with 6-year-old secondary vegetation following the application of four treatments: control; +phosphorus (P); +phosphorus and lime (P + Ca); and +phosphorus, lime and gypsum (P + Ca + G). The control had higher mean soil moisture at 140 and 180 cm depth at the end of the dry season, indicating that the treatment plots responded positively to fertilizer additions by taking up additional water. Trees of Vismia japurensis and Bellucia grossularioides growing on the fertilized plots had the highest net photosynthesis rates (A) (18.7 and 20.4 μmol m^?2 s^?1, respectively). The three species utilized different strategies with regard to physiological and nutritional response, with V. japurensis, regardless of treatment, using these limiting resources most efficiently to colonize abandoned pastures. Trees growing on the P + Ca but not +P alone plots increased A rates, indicating that Ca is an important limiting nutrient in post-pasture secondary succession. The addition of Ca as ash by burning primary and secondary vegetation could explain the rapid growth and dominance of V. japurensis in abandoned pasture areas in central Amazonia. The efficiency of Vismia to use limiting resources could lead to a restructuring of SF and altered rates of stand-level productivity.     

Does local immersion in thermo-neutral bath influence surface EMG measurements? Results of an experimental trial

This study investigated the effect of water immersion on surface electromyography (EMG) signals recorded from the brachioradial muscle of 11 healthy subjects, both in a dry environment and a thermo-neutral forearm bath (36 °C). EMG measurements were registered in a sitting position, using waterproof electrodes under 3 conditions: relaxed muscle, maximum voluntary isometric contraction (MVC, 1 s, grip test) and 70% of the MVC (5 s). In relaxed muscle, mean EMG values were significantly higher under immersion compared to the dry conditions (dry: 5.4 ± 3.6 μV; water: 19.5 ± 14.9 μV; p = 0.014). In maximum voluntary isometric contraction, there was a significant difference, though not in the same direction (dry: 145.9 ± 58.9 μV; water: 73.2 ± 35.0 μV; p = 0.003). Under 70% MVC, there was no difference between wet and dry conditions (dry: 102.4 ± 75.0 μV; water: 100.4 ± 65.3 μV; p = 0.951). Results suggest that dry and underwater conditions influence EMG readings; however, the results are inconsistent. These findings indicate additional influences on resting muscle activity, as well as MVC. Further measurements with other muscle groups and different types of immersion are needed to clarify conflicting observations.     

Validity of resting myotonometric assessment of lower extremity muscles in chronic stroke patients with limited hypertonia: A preliminary study

The aim of this preliminary study was to examine the validity of a recently-introduced tool (MyotonPRO) for the assessment of mechanical parameters of the main lower extremity muscles in patients with chronic stroke. Thigh and shank muscles of 20 stroke patients with limited hypertonia (11 men and 9 women; mean age: 52 ± 11 yrs) and 20 healthy controls (11 men and 9 women; mean age: 53 ± 10 yrs) were bilaterally evaluated with (i) MyotonPRO for muscle stiffness, tone and elasticity, (ii) ultrasonography for muscle and subcutaneous thickness, and (iii) dynamometry for isometric muscle strength. MyotonPRO parameters of stroke patients were reassessed a week later (inter-day test-retest design). For all the investigated muscles, MyotonPRO variables did not differ between the more affected and the less affected side of patients (P > 0.05 for main side effect), and neither differed between patients and controls (P > 0.05 for main group effect), except for gastrocnemius medialis stiffness that was higher in patients (300 ± 51 N/m) than in controls (281 ± 29 N/m; P < 0.05). Thigh muscle stiffness was negatively correlated to subcutaneous thickness (r = −0.84 for the vastus lateralis; P < 0.001), while only tibialis anterior stiffness and tone correlated positively with muscle thickness (both r = 0.46; P < 0.01). Test-retest reliability of MyotonPRO parameters was adequate, except for muscle elasticity. The validity of MyotonPRO for the evaluation of thigh muscles in chronic stroke patients is partially challenged by the poor discriminant ability and by the considerable impact of subcutaneous tissue thickness (sex-dependent) on mechanical parameters. The potential validity of MyotonPRO for the assessment of shank muscles requires further investigation.     

Performance evaluation of constructed wetlands in a tropical region

Five emergent plant species were compared for their effectiveness in treating contaminants in a wetland system constructed on a military base in El Salvador. The system consisted of the subsurface flow (SSF), open water (OW) and free surface flow (SF) wetlands with a combined flow capacity of up to 151.4 m³ d^?1. Reliability and consistent performance in extreme conditions, such as those occurring during the tropical dry or wet seasons were important evaluation criteria. The discontinuous flow patterns typical of tropical climates necessitated the use of water balance calculations using climatic data such as rainfall and evapotranspiration. System characterization was achieved by computation of daily input and output mass loading rates for each individual constituent. Results suggest that Phragmites and Brachiaria were the most effective plants in SSF wetland. Brachiaria provided the added benefit of serving as a source of fodder and proved proficient, with N and P uptakes of 1.5–3.14% and 0.17–0.25% per dry plants’ biomass, respectively. Typha yielded the highest dry season removal efficiency within the SF (BOD₅: 80.78 ± 9.35%, COD: 65.18 ± 19.6%, TN: 58.59 ± 19.3%, oil and grease: 78.34 ± 10.55%, total dissolved phosphorus: 66.5 ± 20.7%). Phragmites–Typha treatment subset performed better year-round than either Thalia–Thalia or Brachiaria–Cyperus. Evaluated plants were capable of surviving and proliferating in extreme tropical climates.     

Effect of induced high myopia on functional MRI signal changes

PurposeThe current study evaluated the effect of lens-induced high myopia (IHM) on the activity of the occipital visual cortex during two visual stimuli presentations to the subjects. This was done by measuring the Blood Oxygenation Level Dependent (BOLD) signal using functional MRI (fMRI).MethodsBOLD contrast fMRI was performed with a 1.5T MRI scanner on 12 emmetropic subjects (refractive error <±0.25Diopter) with no history of neurologic disorder. IHM conditions were applied to subjects by three convex lenses of +5D, +7D and +10D. Visual stimuli with 0.34 cpd and 1.84 cpd spatial frequencies (SF) were presented as a block paradigm to the participants in three IHM states and normal vision state during fMRI data acquisition. Resultant fMRI data were compared among different refractive states.ResultsData analysis showed that IHM did not cause a significant change in the visual cortex activity throughout the presentation of 0.34 cpd SF visual stimulus and BOLD signal intensity remained approximately constant (p = 0.17). Although, fMRI responses to visual stimuli with spatial frequency of 1.84 cpd demonstrated that visual cortex activity was significantly reduced in IHM states compared to normal vision (p = 0.01), the results showed no significant differences between three different values of IHM.ConclusionsThis study shows severe blurring caused by lens induced high myopia can decrease BOLD signal intensity depending on the visual stimulus pattern details. However in the low and moderate range of spatial frequencies, blur increment from +5D up to +10D is not associated with further reduction in the BOLD signal of the occipital visual cortex.     

Influence of ankle functional instability on the ankle electromyography during landing after volleyball blocking

The purpose of this study was to describe, interpret and compare the EMG activation patterns of ankle muscles – tibialis anterior (TA), peroneus longus (PL) and gastrocnemius lateralis (GL) – in volleyball players with and without ankle functional instability (FI) during landing after the blocking movement. Twenty-one players with FI (IG) and 19 controls (CG) were studied. The cycle of movement analyzed was the time period between 200 ms before and 200 ms after the time of impact determined by ground reaction forces. The variables were analyzed for two different phases: pre-landing (200 ms before impact) and post-landing (200 ms after impact). The RMS values and the timing of onset activity were calculated for the three studied muscles, in both periods and for both groups. The co-activation index for TA and PL, TA and GL were also calculated. Individuals with FI presented a lower RMS value pre-landing for PL (CG = 43.0 ± 22.0; IG = 26.2 ± 8.4, p < 0.05) and higher RMS value post-landing (CG = 47.5 ± 13.3; IG = 55.8 ± 21.6, p < 0.10). Besides that, in control group PL and GL activated first and simultaneously, and TA presented a later activation, while in subjects with FI all the three muscles activated simultaneously. There were no significant differences between groups for co-activation index. Thus, the rate of contraction between agonist and antagonist muscles is similar for subjects with and without FI but the activation individually was different. Volleyball players with functional instability of the ankle showed altered patterns of the muscles that play an important role in the stabilization of the foot–ankle complex during the performance of the blocking movement, to the detriment of the ligament complex, and this fact could explain the usual complaints in these subjects.     

Glabridin induces oxidative stress mediated apoptosis like cell death of malaria parasite Plasmodium falciparum

Plants are known as the source of novel agents for developing new antimalarial drugs. Glabridin is a polyphenolic flavonoid, a main constituent in the roots of Glycyrrhiza glabra possesses various biological activities. However, its anti-plasmodial activity is unexplored. In the present work, it is for the first time demonstrated that glabridin inhibits Plasmodium falciparum growth in vitro with an IC₅₀ 23.9 ± 0.43 μM. Glabridin showed poor cytotoxicity in vitro with an IC₅₀ 246.6 ± 0.88 μM against Vero cell line and good selectivity index (9.6). In erythrocytic cycle, trophozoite stage was found to be most sensitive to glabridin. In silico study showed that glabridin inhibits Pf LDH enzyme activity by acting on NADH binding site. Glabridin induced oxidative stress by the generation of reactive oxygen and nitrogen species. Glabridin could induce apoptosis in parasite as evidenced by the depolarization of mitochondrial membrane potential (Δψ_m), activation of caspase like proteases and DNA fragmentation. These results indicate that glabridin exhibits antiplasmodial activity and is suitable for developing antimalarial agent from a cheap and sustainable source.     

Muscular activation patterns during active prone hip extension exercises

BackgroundChanges in activation patterns of hip extensors and pelvic stabilizing muscles are recognized as factors that cause low back disorders and these disturbances could have an impact on the physiological loading and alter the direction and magnitude of joint reaction forces.ObjectiveTo investigate activation patterns of the gluteus maximus, semitendinosus and erector spinae muscles with healthy young individuals during four different modalities of therapeutic exercise.MethodsThirty-one volunteers were selected: (16 men and 15 women), age (24.5 ± 3.47 years), body mass of 66.89 ± 11.89 kg and a height of 1.70 ± 0.09 m). They performed four modalities of therapeutic exercise while the electromyographic activity of the investigated muscles was recorded to determine muscle pattern activation for each exercise.ResultsRepeated measure ANOVA revealed that muscle activation patterns were similar for the four analyzed exercises, starting with the semitendinosus, followed by the erector spinae, and then, the gluteus maximus. The gluteus maximus was the last activated muscle during hip extension associated with knee flexion (p < 0.0001), knee extension (p < 0.0001), and with lateral rotation and knee flexion (p < 0.05).ConclusionFindings of the present study suggested that despite individual variability, the muscle firing order was similar for the four therapeutic exercises.     

Redox potential-driven repeated batch ethanol fermentation under very-high-gravity conditions

When Saccharomyces cerevisiae was cultivated under ～200 g glucose/l condition, the time point at which glucose was completely utilized coincided with the moment at which the slope of a redox potential profile changed from negative or zero to positive. Based on this feature, a redox potential-driven glucose-feeding fermentation operation was developed, and resulted in a self-cycling period of 14.25 ± 0.4 h. The corresponding ethanol concentration was maintained at 88.4 ± 1.0 g/l with complete glucose conversion, and the cell viabilities increased from 80% in the transition period to 97.2 ± 1.1%, implying the occurrence of yeast acclimatization. In contrast, a pre-determined 36-h manually adjusted period was chosen to oscillate yeast cells under ～250 g glucose/l conditions, which resulted in 106.76 ± 0.7 g ethanol/l and 15.19 ± 1.3 g glucose/l remaining at the end of each cycle. Compared to the equivalent batch and continuous ethanol fermentation processes, the annual ethanol productivity of the reported fermentation operation is 2.4% and 13.2% greater, respectively in ～200 g feeding glucose/l conditions.