Contact angle,protein adsorption and osteoblast precursor cell attachment to chitosan coatings bonded to titanium

Chitosan, a derivative of the bio-polysaccharide chitin, has shown promise as a bioactive material for implant, tissue engineering and drug-delivery applications. The aim of this study was to evaluate the contact angle, protein adsorption and osteoblast precursor cell attachment to chitosan coatings bonded to titanium. Rough ground titanium (Ti) coupons were solution cast and bonded to 91.2% de-acetylated chitosan (1 wt% chitosan in 0.2% acetic acid) coatings via silane reactions. Non-coated Ti was used as controls. Samples were sterilized by ethylene oxide gas prior to experiments. Contact angles on all surfaces were measured using water. 5 × 10⁴ cells/ml of ATCC CRL 1486 human embryonic palatal mesenchyme (HEPM) cells, an osteoblast precursor cell line, were used for the cell attachment study. SEM evaluations were performed on cells attached to all surfaces. Contact angles and cell attachment on all surfaces were statistically analyzed using ANOVA. The chitosan-coated surfaces (76.4 ± 5.1°) exhibited a significantly greater contact angle compared to control Ti surfaces (32.2±6.1°). Similarly, chitosan-coated surfaces exhibited significantly greater (P < 0.001) albumin adsorption, fibronectin adsorption and cell attachment, as compared to the control Ti surfaces. Coating chitosan on Ti surfaces decreased the wettability of the Ti, but increased protein adsorption and cell attachment. Increased protein absorption and cell attachment on the chitosan-coated Ti may be of benefit in enhancing osseointegration of implant devices.     

Contact angle, protein adsorption and osteoblast precursor cell attachment to chitosan coatings bonded to titanium

Chitosan, a derivative of the bio-polysaccharide chitin, has shown promise as a bioactive material for implant, tissue engineering and drug-delivery applications. The aim of this study was to evaluate the contact angle, protein adsorption and osteoblast precursor cell attachment to chitosan coatings bonded to titanium. Rough ground titanium (Ti) coupons were solution cast and bonded to 91.2% de-acetylated chitosan (1 wt% chitosan in 0.2% acetic acid) coatings via silane reactions. Non-coated Ti was used as controls. Samples were sterilized by ethylene oxide gas prior to experiments. Contact angles on all surfaces were measured using water. 5 x 10(4) cells/ml of ATCC CRL 1486 human embryonic palatal mesenchyme (HEPM) cells, an osteoblast precursor cell line, were used for the cell attachment study. SEM evaluations were performed on cells attached to all surfaces. Contact angles and cell attachment on all surfaces were statistically analyzed using ANOVA. The chitosan-coated surfaces (76.4 +/- 5.1 degrees) exhibited a significantly greater contact angle compared to control Ti surfaces (32.2 +/- 6.1 degrees). Similarly, chitosan-coated surfaces exhibited significantly greater (P < 0.001) albumin adsorption, fibronectin adsorption and cell attachment, as compared to the control Ti surfaces. Coating chitosan on Ti surfaces decreased the wettability of the Ti, but increased protein adsorption and cell attachment. Increased protein absorption and cell attachment on the chitosan-coated Ti may be of benefit in enhancing osseointegration of implant devices.     

Venous blood lactate increase after vertical jumping in volleyball athletes

The aim of this study was to test the hypothesis that venous blood lactate concentrations ([La^–]) would vary from the beginning of brief exercise. Maximal vertical jumping was used as a model of brief intense exercise. Eleven healthy male volleyball players, aged [mean (SE)] 18.5 (0.7) years, performed three exercise tests with different protocols, each separated by quiet seated recovery periods of 45 min. After the first test, consisting of a single maximal jump [lasting ≅0.6 s for the pushing phase, and in which the subjects jumped 64 (2.2) cm], forearm venous [La^–] increased significantly with respect to rest at 1 min (t ₁), 3 min (t ₃), and 5 min (t ₅) of recovery. The second test, comprising six maximal jumps, each separated by 20-s recovery periods, resulted in an unchanged [La^–] with respect to the baseline value. After the third test [i.e., six consecutive maximal jumps that lasted a total of 7.36 (0.33) s], [La^–] increased significantly at t ₃ and t ₅ with respect to the pre-test value (F=10.3, P<0.001). We conclude that a significant venous [La^–] increase occurs after vertical jumping. This result may be explained by the activation of lactic anaerobic metabolism at the very onset of exercise, which participates in energy production and/or in the resynthesis of the phosphocreatine that was used during such brief exercise. Electronic Publication     

Osteoblast Interactions Within a Biomimetic Apatite Microenvironment

Numerous reports have shown that accelerated apatites can mediate osteoblastic differentiation in vitro and bone formation in vivo. However, how cells interact within the apatite microenvironment remains largely unclear, despite the vast literature available today. In response, this study evaluates the in vitro interactions of a well-characterized osteoblast cell line (MC3T3-E1) with the apatite microenvironment. Specifically, cell attachment, spreading, and viability were evaluated in the presence and absence of serum proteins. Proteins were found to be critical in the mediation of cell–apatite interactions, as adherence of MC3T3-E1 cells to apatite surfaces without protein coatings resulted in significant levels of cell death within 24 h in serum-free media. In the absence of protein–apatite interaction, cell viability could be “rescued” upon treatment of MC3T3-E1 cells with inhibitors to phosphate (PO₄ ³⁻) transport, suggesting that PO₄ ³⁻ uptake may play a role in viability. In contrast, rescue was not observed upon treatment with calcium (Ca²⁺) channel inhibitors. Interestingly, a rapid “pull-down” of extracellular Ca²⁺ and PO₄ ³⁻ ions onto the apatite surface could be measured upon the incubation of apatites with α-MEM, suggesting that cells may be subject to changing levels of Ca²⁺ and PO₄ ³⁻ within their microenvironment. Therefore, the biomimetic apatite surface may significantly alter the microenvironment of adherent osteoblasts and, as such, be capable of affecting both cell survival and differentiation.     

Insight in Human Skin Microcirculation Using In Vivo Reflectance-Mode Confocal Laser Scanning Microscopy

Reflectance-mode confocal laser scanning microscopy allows in vivo imaging of the human skin. We hypothesized that this high-resolution technique enables observation of dynamic changes of the cutaneous microcirculation. Twenty-two volunteers were randomly divided in two groups. Group 1 was exposed to local heating and group 2 to local cold stress. Confocal microscopy was performed prior t ₀ (control), directly t ₁ and 5 min t ₂ after local temperature changes to evaluate quantitative blood cell flow, capillary loop diameter, and density of dermal capillaries. In group 1, blood flow increased at t ₁ (75.82 ± 2.86/min) and further at t ₂ (84.09 ± 3.39/min) compared to the control (61.09 ± 3.21/min). The control capillary size was 9.59 ± 0.25 μm, increased to 11.16 ± 0.21 μm (t ₁) and 11.57 ± 0.24 μm (t ₂). The dermal capillary density increased in t ₁ (7.26 ± 0.76/mm²) and t ₂ (8.16 ± 0.52/mm²), compared to the control (7.04 ± 0.62/mm²). In group 2, blood flow decreased at t ₁ (41.73 ± 2.61/min) and increased at t ₂ (83.27 ± 3.29/min) compared to the control (60.73 ± 2.90/min). The control capillary size was 9.55 ± 0.25 μm, decreased at t ₁ (7.78 ± 0.26 μm) and increased at t ₂ (11.38 ± 0.26 μm). Capillary density decreased at t ₁ (5.01 ± 0.49/mm²) and increased at t ₂ (7.28 ± 0.53/mm²) compared to the control (7.01 ± 0.52/mm²). Confocal microscopy is a sensitive and noninvasive imaging tool for characterizing and quantifying dynamic changes of cutaneous microcirculation on a histomorphological level.     

A comparison of modelling procedures used to estimate the power–exhaustion time relationship

This study aimed to test the consistency of using the power required to elicit maximal oxygen uptake during incremental test (P _t) to demarcate the range of power intensity in the modelling of the power–exhaustion time relationship. Different mathematical procedures were tested using data from ten subjects exercising on a cycle ergometer. After the determination of P _t and the power at the ventilatory threshold, the subjects did six tests at constant power to exhaustion within 2–15 min. Estimates were obtained from a segmented model using two distinct equations of the anaerobic contribution to power below and above P _t, respectively. This model fit the overall data with a better adequacy than the simple hyperbolic model (standard error of 29.2 ± 25.2 vs. 42.3 ± 25.2 s). The power asymptotes were 225.7 ± 27.3 W from the segmented model, 226.2 ± 27.3 and 283.3 ± 20.5 W from the simple model applied to data below and above P _t, respectively. The estimates from the segmented model were strongly correlated with their analogues from the simple model applied only to data below P _t (R = 1.00 for power asymptote and curvature coefficient). They were not correlated with their analogues from the simple model applied only to data above P _t. These discrepancies between modelling procedures could arise from the method used to determine P _t and the oversimplification of the oxygen uptake kinetics. These limitations could lead the segmented model to an overestimation of the anaerobic contribution which was around 15% of total energy expended at P _t.     

Relationship between the curvature constant parameter of the power-duration curve and muscle cross-sectional area of the thigh for cycle ergometry in humans

For high-intensity cycle ergometer exercise, the relationship between power output (P) and its tolerable duration (t) has been well characterized by the hyperbolic relationship: (P–θ _F)·t=W′, where θ_F has been termed the "critical power" or "fatigue threshold". The curvature constant (W′) reflects a constant amount of work which can be performed above θ_F, and it may be regarded as a muscle energy store. The relationship of this energy store to muscle mass is not known. Therefore, the purpose of this study was to determine the relationships among W′, accumulated peak oxygen deficit (accumulated peak O₂-deficit), and muscle cross-sectional area (CSA) of the thigh for high-intensity cycle ergometry in humans. A group of 17 healthy male subjects (aged 21–41 years) participated in this study. The θ_F and W′ of the P-t hyperbolic relationship and the accumulated peak O₂-deficit was calculated by standard procedures. The CSA of muscle, fat and bone in the right thigh were measured using ultrasonography. The mean (SD) of θ_F, W′, accumulated peak O₂-deficit, and muscle CSA of the thigh were 200.0 (17.8) W, 12.60 (2.94) kJ, 2.29 (0.41) l, and 185.3 (22.6) cm², respectively. The muscle CSA of the thigh was positively correlated with W′ (r=0.59, P<0.01) and with accumulated peak O₂-deficit (r=0.54, P<0.05). The relationship between W′ and accumulated peak O₂-deficit also showed a positive correlation (r=0.63, P<0.005). Our results indicated that W′ derived from the P-t hyperbolic curve as anaerobic working capacity is related to the CSA of muscle. Electronic Publication     

How the vestibular system modulates tactile perception in normal subjects: a behavioural and physiological study

Caloric vestibular stimulation (CVS) is a physiological technique demonstrated to transiently improve hemianaesthesia in right brain-damaged patients (Bottini et al. in Exp Brain Res 99(1):164–169, 1994, Nature 376:778–781, 1995, Neurology 65(8):1278–1283, 2005). Recent studies suggest that these effects are based on the anatomical overlapping between vestibular and tactile projections (Bottini et al. in Nature 376:778–781, 1995) in the human brain. However, much less is known about behavioural effects of this manipulation on normal subjects. We aimed to explore tactile perception during left ear CVS in normal subjects. We administered seventeen right-handed normal subjects with different types of tactile stimuli (above and below threshold) during left ear CVS. To further ensure standardized procedure, tactile stimulation was delivered through a tool-developed ad hoc for the experiment. The experiment was divided in 3 conditions: (1) Baseline, (2) PostCVS and (3) Delayed CVS. We found a main effect of stimulus type (F _(2,32) = 907.712; P = 0.000) and condition (F _(2,32) = 55.505; P = 0.000). Moreover, post hoc comparisons revealed that below threshold stimuli are most affected by CVS (t ₍₁₆₎ = −11.213; P = 0.000). Left ear CVS modulates tactile perception also in normal subjects. Moreover, this modulation seems to be selective for below threshold stimuli and not caused by attentive processes. A multisensory phenomenon is possibly the best explanation for this interaction between touch and vestibular systems, corroborated also by the anatomical evidence and by the previous knowledge about interaction with the environment.     

Validity of the two-parameter model in estimating the anaerobic work capacity

The curvature of the power–time (P–t) relationship (W′) has been suggested to be constant when exercising above critical power (CP) and to represent the anaerobic work capacity (AWC). The aim of this study was to compare W′ to (1) the total amount of work performed above CP (W _90s′) and (2) the AWC, both determined from a 90s all-out fixed cadence test. Fourteen participants (age 30.5±6.5 years; body mass 67.8±10.3 kg), following an incremental VO_2max ramp protocol, performed three constant load exhaustion tests set at 103±3, 97±3 and 90±2% P-VO_2max to calculate W′ from the P–t relationship. Two 90s all-out efforts were also undertaken to determine W _90s′ (power output—time integral above CP) and AWC (power output—time integral above the power output expected from the measured VO₂). W′ (13.6±1.3 kJ) and W _90s′ (13.9±1.1 kJ; P=0.96) were not significantly different but were lower than AWC (15.9±1.2 kJ) by 24% (P=0.03) and 17%, respectively (P=0.04). All these variables were correlated (P<0.001) but great extents of disagreement were reported (0.2±6.4 kJ between W′ and W _90s′, 2.3±7.2 kJ between W′ and AWC, and 2.1±4.3 kJ between W _90s′ and AWC). The underestimation of AWC from both W′ and W _90s′ can be explained by the aerobic inertia not taking into consideration when determining the two latter variables. The low extents of agreement between W′, W _90s′ and AWC mean the terms should not be used interchangeably.     

An improved isolated, left ventricular ejecting, murine heart model

 An improved, isolated, left ventricular-ejecting, murine heart model is described and evaluated. Special attention was paid to the design and impedance characteristics of the artificial aortic outflow tract and perfusate composition, which contained glucose (10 mM plus insulin) and pyruvate (1.5 mM) as substrates. Temperature of the isolated perfused hearts was maintained at 38.5 °C. During antegrade perfusion (preload 10 mm Hg, afterload 50 mm Hg, 2.5 mM Ca²⁺) proper design of the aortic outflow tract provided baseline values for cardiac output (CO), left ventricular developed pressure (LVDP) and the maximum first derivative of left ventricular pressure (LV dP/dt _max) of 11.1±1.7 ml min^–1, 83±5 mm Hg and 6283±552 mm Hg s^–1, respectively, resembling findings in the intact mouse. During 100 min normoxic antegrade perfusion CO declined non-significantly by less than 10%. Varying pre- and afterloads resulted in typical Frank-Starling relationships with maximal CO values of 18.6±1.8 ml min^–1 at pre- and afterload pressures of 25 and 50 mm Hg, respectively. Left ventricular function curves were constructed at free [Ca²⁺] of 1.5 and 2.5 mM in the perfusion medium. Significantly higher values for CO, LVDP and LV dP/dt _max and LV dP/dt _min were obtained at 2.5 mM Ca²⁺ at all loading conditions investigated. Phosphocreatine and creatine levels remained stable throughout the perfusion period. Despite a small but significant decline in tissue ATP content, the sum of adenine nucleotides did not change during the normoxic perfusion period. The tissue content of glycogen increased significantly. Received: 28 April 1998 / Received after revision and accepted: 10 September 1998     

A diazo-2 study of relaxation mechanisms in frog and barnacle muscle fibres: effects of pH, MgADP, and inorganic phosphate

 The aim of this study was to compare the effects of increased concentrations of MgADP, inorganic phosphate (P_i) and H⁺ ([MgADP], [Pi] and [H⁺], respectively) on the rate of relaxation in two different muscle types: skinned muscle fibres from the frog Rana temporaria and myofibrillar bundles from the giant Pacific acorn barnacle Balanus nubilus. Relaxation transients are produced by the photolysis of diazo-2 and are well fitted with a double exponential curve, giving two rate constants: k₁ [5.6±0.1 s^–1 for barnacle, n=30; 26.3±0.7 s^–1 for frog, n=14 (mean±SEM)] and k₂ [0.6±0.1 s^–1 in barnacle, n=30; 10.4±1.0 s^–1 in frog, n=14 (mean±SEM)], at 10°C. Decreasing the pH by 0.5 pH units did not significantly affect k₁ for barnacle relaxation [5.6±0.1 s^–1 (mean±SEM), n=15] compared to the decrease in k₁ of 40% seen in frog. Use of the Ca²⁺-sensitive fluorescent label acrylodan on barnacle wild-type troponin C demonstrated that decreasing the pH from 7.0 to 6.6 only alters the pCa₅₀ value by 0.23 in the cuvette, while stopped-flow experiments with acrylodan revealed no significant change in k_off from the labelled protein [322±32 s^–1 at pH 7.0 and 381±24 s^–1 (mean±SEM) at pH 6.6]. Increasing [MgADP] by 20 μM (50 μM added ADP) from control values of 50 μM in frog decreased k₁ to 12.3±0.4 s^–1 (mean±SEM, n=8), and at 400 μM MgADP, k₁=9.6±0.1 s^–1 (mean±SEM, n=12). In barnacle, 500 μM MgADP had a much smaller effect on k₁ (4.0±0.9 s^–1, mean±SEM, n=8). Increasing the free [P_i] from the contaminant level of 0.36 mM to 1.9 mM slowed k₁ by ≈15% in barnacle [4.8±0.8 s^–1, mean±SEM, n=7], compared to a ≈30% reduction seen in frog. We conclude that the differences between barnacle and frog seen here are most probably due to different isomers of the contractile proteins, and that events underlying the crossbridge cycle are the same or similar. We interpret our results according to a model of crossbridge transitions during relaxation. Received: 18 May 1998 / Received after revision and accepted: / 1 September 1998     

Prior sprint cycling did not enhance training adaptation,but resting salivary hormones were related to workout power and strength

This study examined the effect of cycle sprints as a potentiating stimulus for power and strength adaptation in semi-elite athletes. Eighteen rugby players were assigned into training groups that completed either a 40-s cycle sprint (T_SPRINT) or rested (T_CONTROL) before each workout (n = 6–8) of a 4-week programme. Squat jump (SJ) peak power (PP) and mean power (MP), and box squat (BS) one repetition maximum (1RM) strength were assessed every workout. Saliva was collected across each workout and assayed for testosterone (Sal-T) and cortisol (Sal-C). The T_SPRINT and T_CONTROL groups both showed significant improvements in SJ PP (8.2 ± 2.9 vs. 11.9 ± 3.6%), SJ MP (11.8 ± 2.6 vs. 18.6 ± 4.8%) and BS 1RM (20.5 ± 2.6 vs. 23.2 ± 1.3%), respectively. However, there were no group differences in training adaptation, workout performance or the workout hormonal responses. As a combined group (all players), significant relationships were demonstrated between resting Sal-T and/or Sal-C concentrations and absolute SJ power (r = 0.20–0.30) and BS strength (r = 0.36–0.44) across all workouts. For individual players, the respective relationships with SJ power (r = 0.22–0.42) and BS strength (r = 0.41–0.49) were, on average, found to be stronger. In conclusion, leg workouts performed with or without prior cycle sprints can produce similar power and strength improvements in semi-elite rugby players. Resting salivary hormone concentrations appear important for workout performance, especially for individuals, thereby potentially moderating training adaptation.     

A comparative kinetic study of doramectin and moxidectin in zebu Gobra cattle (Bos indicus)

The plasma kinetics of doramectin and moxidectin were evaluated in zebu Gobra under field conditions after subcutaneous administration of 0.2 mg kg⁻¹ of commercially available formulations for cattle. The results indicate that the absorption of moxidectin from the site of injection was significantly faster (absorption half-life [t _1/2ab] = 0.7 day) than that of doramectin (t _1/2ab = 3.1 days). Moxidectin peak plasma concentration (C _max) was reached significantly earlier (t _max = 0.4 day) compared with that of doramectin (t _max = 5.3 days). No differences in C _max values were observed; the area under the concentration–time curve was higher for doramectin (475 ng day ml⁻¹) compared with moxidectin (198 ng day ml⁻¹), while the mean residence time was longer for moxidectin (13.4 days) compared with doramectin (9.4 days). These results obtained give interesting information on doramectin and moxidectin pharmacokinetics in zebu Gobra, which show a similar pharmacokinetic profile as in other cattle.     

Influence of prolonged intermittent high-intensity exercise on knee flexor strength in male and female soccer players

This study investigated the effect of an acute, prolonged, intermittent, high-intensity single-leg pedalling exercise task (PIHIET) on the isokinetic leg strength of the knee flexors in six male and seven female collegiate soccer players. Following determination of single-leg V˙O_2peak, subjects completed a PIHIET designed to simulate the energetics of soccer match play (~90 min in total; ~70% single-leg V˙O_2peak). Pre-, mid- and post-PIHIET gravity-corrected indices of knee flexion peak torque (PT) and range of motion-relativised torque at 15% of knee flexion (RRT_15%; 0% = full knee extension) were assessed at a lever-arm angular velocity of 1.05 rad·s⁻¹ for intervention and control limbs using an isokinetic dynamometer. Repeated measures ANOVAs revealed significant condition (PIHIET, control) × time (pre-, mid-, post-PIHIET) interactions for knee flexion PT (F _[2,22]=26.2; P<0.001) and RRT_15% (F _[2,22]=20.1; P<0.001). Flexion PT and RRT_15% were observed to decrease, pre- to post-intervention, from 92.8 (28.7) N·m to 72.1 (28.0) N·m and from 63.8 (17.5) N·m to 47.9 (18.4) N·m respectively, for the intervention limb alone. These data corresponded to 22.3% and 24.9% mean reductions pre–post intervention in PT and RRT_15%. Exploratory post hoc analysis of the pattern of the relative deterioration (%) of PT and RRT_15%, for the intervention limb alone, revealed a three-way interaction [group (male, female) x parameter (PT, RRT_15%) x assessment phase (pre- to mid-PIHIET, mid- to post-PIHIET)] (F _1,11=5.2; P<0.05). This interaction characterised a greater deterioration of strength performance during the mid- to post-PIHIET assessment phase, at the extremes of range of motion (RRT_15%) for the female group. The greater percentage of mid–post phase strength loss observed in women near the end-range extension may potentially be implicated in the higher incidence of knee injury reported in female soccer players. Electronic Publication     

Effects of phosphoric acid treatment of titanium surfaces on surface properties,osteoblast response and removal of torque forces

This study investigated the surface characteristics and biocompatibility of phosphate ion (P)-incorporated titanium (Ti) surfaces hydrothermally treated with various concentrations of phosphoric acid (H₃PO₄). The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy, optical profilometry, contact angle and surface energy measurement and inductively coupled plasma mass spectroscopy (ICP-MS). MC3T3-E1 cell attachment, spreading, proliferation and osteoblastic gene expression on different surfaces were evaluated. The degree of bony integration was biomechanically evaluated by removal torque testing after 4 weeks of healing in rabbit tibiae. The H₃PO₄ treatment produced micro-rough Ti surfaces with crystalline P-incorporated Ti oxide layers. High concentration H₃PO₄ treatment (1% and 2%) produced significantly higher hydrophilic surfaces compared with low H₃PO₄ treatment (0.5%) and untreated surfaces (P < 0.01). ICP-MS analysis showed P ions were released from P-incorporated surfaces. Significant increased cell attachment (P < 0.05) and notably higher mRNA expressions of Runx2, alkaline phosphatase, osteopontin and osteocalcin were observed in cells grown on P-incorporated surfaces compared with cells on untreated machined surfaces. P-incorporated surfaces showed significantly higher removal torque forces compared with untreated machined implants (P < 0.05). Ti surfaces treated with 2% H₃PO₄ showed increasing tendencies in osteoblastic gene expression and removal torque forces compared with those treated with lower H₃PO₄ concentrations or untreated surfaces. These results demonstrate that H₃PO₄ treatment may improve the biocompatibility of Ti implants by enhancing osteoblast attachment, differentiation and biomechanical anchorage.     

Physical fitness factors to predict male Olympic wrestling performance

To determine differences in maximal strength and muscle power output of the arm and leg extensor muscles, peak and mean power during a modified standing crank-arm Wingate test, running speed, muscle extensibility, and anthropometric markers between elite and amateurs wrestlers according to the weight classes system; 92 male wrestlers were assigned into 6 groups according to their body mass (light, middle and heavy weight) and their competitive level (elite and amateur): Light Weight (body mass ranged between 55 and 68 kg) in elite (LW_E, n = 18) and amateur (LW_A, n = 15) level; Middle Weight (body mass ranged between 68 and 84 kg) in elite (MW_E, n = 18) and amateur (MW_A, n = 19) level; and Heavy Weight (body mass ranged between 84 and 100 kg) in elite (HW_E, n = 10) and amateur (HW_A, n = 12) level. Elite wrestlers were older (8–12%), had more training experience (25–37%), fat-free mass (3–5%), maximal strength in absolute and relative terms (8–25%), muscle power (14–30%), mean and peak power during crank-arm Wingate testing in absolute and relative terms (13–22%), jumping height (8–17%) as well as grip (6–19%) and back strength (7–20%) compared to amateur wrestlers. However, no differences were observed between elite and amateur groups in height, body mass index, percentage of body fat, hamstring extensibility and running speed. The present results suggest that the higher absolute and relative values of maximal strength, muscle power, and anaerobic metabolism, explained in part by the differences in lean mass and neural activation patterns, will give elite wrestlers a clear advantage during the most frequently used techniques in Olympic wrestling.     

The effect of age on the power/duration relationship and the intensity-domain limits in sedentary men

The time to fatigue (t) in response to high-intensity constant-load exercise decreases hyperbolically with increasing power (W˙), at least in active and younger individuals [i.e. (W˙−θ_F)t=W′, where θ_F is the critical power asymptote and W′ is the curvature constant]. Little is known, however, about the combined effects of age and sedetarity on these parameters. We therefore evaluated 17 non-trained males (9 aged 60–75 years and 8 aged below 30 years) who underwent ramp-incremental cycle ergometry and, on different days, 4 high-intensity constant-load tests to t. Compared to their younger counterparts, the older subjects presented significantly lower maximum oxygen uptake (i.e. the maximum value of oxygen uptake attained at the end of a progressive exercise with the subject exerting a presumably maximal effort, μV˙O₂), estimated lactate threshold (V˙O₂θ_L), V˙O₂θ_F, and W′ (P < 0.05). Interestingly, however, both V˙O₂θ_L and V˙O₂θ_F, when expressed as a percentage of μV˙O₂, were higher in older than in younger men [61.8 (6.2)% versus 45.4 (4.6)% and 87.8 (7.3)% versus 79.0 (8.2)%, P < 0.05, respectively]. Therefore, age was associated with an increase in the relative magnitude of the “moderate”, sub-θ_L exercise-intensity domain (+30.4%), mainly at the expense of the “very-heavy”, supra-θ_F domain (−56%). Our results demonstrate that age and sedentarity are associated with: (1) marked reductions in both the aerobic (θ_F) and anaerobic (W′) determinants of the W˙/t relationship, and (2) changes in either the absolute or relative magnitudes of the exercise-intensity domains. These findings are consistent with the notion that endurance-related parameters are less diminished with ageing than the maximal capacity, thereby mitigating the deleterious effects of senescence in the functional capacity. Accepted: 5 April 2000     

Ultrastructural Study of Chitosan Effects on Klebsiella and Staphylococci

Antibacterial effect of chitosan on the morphofunctional organization of clinical strains of Klebsiella pneumoniae and Staphylococcus aureus was studied by transmission electron microscopy. Chitosan promoted aggregation of bacterial cells and disorganization of bacterial cell wall and cytoplasmic membrane, which leads to the release of bacterial contents into the environment. These structural changes result in bacterial death. __________ Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 140, No. 9, pp. 343–347, September, 2005     

Thermal face protection delays finger cooling and improves thermal comfort during cold air exposure

When people dress for cold weather, the face often remains exposed. Facial cooling can decrease finger blood flow, reducing finger temperature (T _f). This study examined whether thermal face protection limits finger cooling and thereby improves thermal comfort and manual dexterity during prolonged cold exposure. T _f was measured in ten volunteers dressed in cold-weather clothing as they stood for 60 min facing the wind (−15°C, 3 m s⁻¹), once while wearing a balaclava and goggles (BAL), and once with the balaclava pulled down and without goggles (CON). Subjects removed mitts, wearing only thin gloves to perform Purdue Pegboard (PP) tests at 15 and 50 min, and Minnesota Rate of Manipulation (MRM) tests at 30 and 55 min. Subjects rated their thermal sensation and comfort just before the dexterity tests. T _f decreased (p < 0.05 for time × trial interaction) by 15 min of cold exposure during CON (33.6 ± 1.4–28.7 ± 2.0°C), but not during BAL (33.2 ± 1.4–30.6 ± 3.2°C); and after 30 min T _f remained warmer during BAL (23.3 ± 5.9°C) than CON (19.2 ± 3.5); however, by 50 min, T _f was no different between trials (14.1 ± 2.7°C). Performance on PP fell (p < 0.05) by 25% after 50 min in both trials; MRM performance was not altered by cold on either trial. Subjects felt colder (p < 0.05) and more uncomfortable (p < 0.05) during CON, compared to BAL. Thermal face protection was effective for maintaining warmer T _f and thermal comfort during cold exposure; however, local cooling of the hands during manual dexterity tests reduced this physiological advantage, and performance was not improved.     

Aerobic power and peak power of elite America’s Cup sailors

Big-boat yacht racing is one of the only able bodied sporting activities where standing arm-cranking (‘grinding’) is the primary physical activity. However, the physiological capabilities of elite sailors for standing arm-cranking have been largely unreported. The purpose of the study was to assess aerobic parameters, VO_2peak and onset of blood lactate (OBLA), and anaerobic performance, torque–crank velocity and power–crank velocity relationships and therefore peak power (P _max) and optimum crank-velocity (ω_opt), of America’s Cup sailors during standing arm-cranking. Thirty-three elite professional sailors performed a step test to exhaustion, and a subset of ten grinders performed maximal 7 s isokinetic sprints at different crank velocities, using a standing arm-crank ergometer. VO_2peak was 4.7 ± 0.5 L/min (range 3.6–5.5 L/min) at a power output of 332 ± 44 W (range 235–425 W). OBLA occurred at a power output of 202 ± 31 W (61% of W_max) and VO₂ of 3.3 ± 0.4 L/min (71% of VO_2peak). The torque–crank velocity relationship was linear for all participants (r = 0.9 ± 0.1). P _max was 1,420 ± 37 W (range 1,192–1,617 W), and ω_opt was 125 ± 6 rpm. These data are among the highest upper-body anaerobic and aerobic power values reported. The unique nature of these athletes, with their high fat-free mass and specific selection and training for standing arm cranking, likely accounts for the high values. The influence of crank velocity on peak power implies that power production during on-board ‘grinding’ may be optimised through the use of appropriate gear-ratios and the development of efficient gear change mechanisms.