Influence of two pedalling rate conditions on mechanical output and physiological responses during all-out intermittent exercise

The purpose of this study was to investigate the effect of two cycling velocities on power output and concomitant metabolic and cardiorespiratory responses to repeated all-out exercises. Mean power output (P _m), total work (W _tot), total oxygen consumption (VO_2tot) and blood lactate accumulation (Δ[La]_b) were evaluated in 13 male subjects who performed two series of twelve 5-s bouts of sprint cycling. Recovery periods of 45-s were allowed between trials. One series was executed at optimal velocity (V _opt: velocity for greatest power) and the other one at 50% V _opt (0.5V _opt). Velocities obtained in these conditions were V_opt=116.6 (4.7) rpm; 0.5V_opt=60.6 (4.9) rpm. After a phase of adaptation in oxygen uptake in the first part of the series, the data from the 6th to the 12th sprint were as follows: P _m, 924.6 (73.9) versus 689.2 (61.8) W; W _tot, 29.95 (4.14) versus 22.04 (3.17) kJ; VO_2tot, 12.80 (1.36) versus 10.58 (1.37) l; Δ[La]_b, 2.72 (1.22) versus 0.64 (0.79) mmol.l⁻¹, respectively (P<0.001). Both W _tot and VO_2tot were consistently higher at optimal velocity (+21 and +35.8%, respectively). The present findings demonstrate that during intermittent short-term all-out exercise requiring maximal activation, the energy turnover is not necessarily maximal. It depends on muscle contraction velocity. The increase, lower than expected, in metabolic response from 0.5V _opt to V _opt suggests also that mechanical efficiency is higher at V _opt. Electronic Publication     

A quantitative investigation of immunocytochemically stained blood vessels in normal,benign, premalignant and malignant human oral cheek epithelium

The present study was designed to determine whether increased vascularity occurs during malignant transformation of human oral cheek epithelium. Nine normal (N) samples were taken from the resection margins of benign lesions; the pathological lesions were classified as chronic inflammation (CI; n=11), fibrous hyperplasia (FH; n=12), lichen planus (LIP; n=8), dysplasia (DYS; n=5), squamous cell carcinoma (SCC; n=25; well differentiated [SCCWD]; n=10; moderately to poorly differentiated [SCCMPD]; n=15) and epithelium adjacent to carcinomas (EAC; n=6). Sections were stained with monoclonal antibody (mAb) against vimentin using an ABC immunoperoxidase technique. All blood vessels present within a depth of 0.9 mm of lamina propria were quantified irrespective of their morphology. The blood vessel parameters quantified were volume density (V_{VBV, CT}), number per unit area (N_{ABV, CT}), length per unit volume (L_{VBV, CT}) and mean transverse sectional area (A_BV). V_{VBV, CT} increased significantly between normal and all pathological groups. Amongst the pathological groups, statistical differences were detected between CI and SCC, CI and EAC, FH and SCCWD, FH and EAC, LIP and SCC, LIP and EAC, DYS and SCCWD and DYS and EAC. The EAC group had the highest V_{VBV, CT} and the values of N_{ABV, CT} and L_{VBV, CT} were significantly higher in all the pathological groups when compared with the normal group. No significant differences were detected between any of the pathological group. The parameter A_BV increased significantly between normal and DYS, FH, SCC, EAC, FH and EAC, FH and SCC, CI and EAC, CI and SCC, LIP and EAC and LIP and SCC. Spearman rank correlations detected a positive correlation between the severity of oral lesions and all of the blood vessel parameters. We conclude that a mAb against vimentin improved the identification of smaller blood vessels and the blood vessel data suggest that angiogenesis occurs in premalignant and malignant lesions of human oral cheek epithelium. Angiogenesis seems to play an essential role in sustaining the actively growing and transforming cells.     

Metabolic consequences of reduced frequency breathing during submaximal exercise at moderate altitude

Summary The intention of this study was to determine the metabolic consequences of reduced frequency breathing (RFB) at total lung capacity (TLC) in competitive cyclists during submaximal exercise at moderate altitude (1520 m; barometric pressure, P _B=84.6 kPa; 635 mm Hg). Nine trained males performed an RFB exercise test (10 breaths · min ^–1) and a normal breathing exercise test at 75–85% of the ventilatory threshold intensity for 6 min on separate days. RFB exercise induced significant (P<0.05) decreases in ventilation (V _E), carbon dioxide production (VCO₂), respiratory exchange ratio. (RER), ventilatory equivalent for O₂ consumption (V _E/VO₂), arterial O₂ saturation and increases in heart rate and venous lactate concentration, while maintaining a similar OZ consumption (VO₂). During recovery from RFB exercise (spontaneous breathing) a significant (P< 0.05) decrease in blood pH was detected along with increases in V _E, VO₂, VCO₂, RER, and venous partial pressure of carbon dioxide. The results indicate that voluntary hypoventilation at TLC, during submaximal cycling exercise at moderate altitude, elicits systemic hypercapnia, arterial hypoxemia, tissue hypoxia and acidosis. These data suggest that RFB exercise at moderate altitude causes an increase in energy production from glycolytic pathways above that which occurs with normal breathing.     

Influence of anthropometric characteristics on changes in maximal exercise ventilation and breathing pattern during growth in boys

Summary The aim of this study was to investigate the effect of growth on ventilation and breathing pattern during maximal exercise oxygen consumption (VO_2max and their relationships with anthropometric characteristics. Seventy six untrained schoolboys, aged 10.5–15.5 years, participated in this study. Anthropometric measurements made included body mass, height, armspan, lean body mass, and body surface area. During an incremental exercise test, maximal ventilation (V_Emax), tidal volume (V _Tmax), breathing frequency (f _max), inspiratory and expiratory times (t _Imax and t _Emax), total duration of respiratory cycle (t _TOTmax), mean inspiratory flow (V _T/t _Imax), and inspiration fraction (t _I/t _TOTmax) were measured at VO_2max. A power function was calculated between anthropometric characteristics and ventilatory variables to determine the allometric constants. The results showed firstly, that V_Emax, V _Tmax, t _Imax, t _Emax, t _TOTmax, and V _T/t _Imax increased with age and anthropometric characteristics (P<0.001), f _max decreased (P<0.001), and t _I/t _TOTmax remained constant during growth; secondly that lean body mass explained the greatest percentage of variance of V_Emax (62.1%), V _Tmax (76.8%), and V _T/t _Imax (70.6%), while anthropometric characteristics explained a slight percentage of variance of f _max and timing; and thirdly that V_Emax, V _Tmax, and V _T/t _Imax normalized by lean body mass did not change significantly with age. We concluded that at VO_2max there were marked changes in ventilation and breathing pattern with growth. The changes in V_Emax, V _Tmax, and V _T/t _Imax were strongly related to the changes in lean body mass.     

Physiological differences between black and white runners during a treadmill marathon

Summary To determine why black distance runners currently out-perform white distance runners in South Africa, we measured maximum oxygen consumption (V _{O 2max}), maximum workload during a V _{O 2max} test (L _max), ventilation threshold (V _Thr), running economy, inspiratory ventilation (V _I), tidal volume (V _T), breathing frequency (f) and respiratory exchange ratio (RER) in sub-elite black and white runners matched for best standard 42.2 km marathon times. During maximal treadmill testing, the black runners achieved a significantly lower (P<0.05) L _max (17 km h^–1, 2% grade, vs 17 km h^–1, 4% grade) and V _I max (6.21 vs 6.821 kg^–2/3 min^–1), which was the result of a lower V _T (101 vs 119 ml kg^–2/3 breath^–1) as f _max was the same in both groups. The lower V _T in the black runners was probably due to their smaller body size. The V _Thr occurred at a higher percentage V _{O 2max} in black than in white runners (82.7%, SD 7.7% vs 75.6%, SD 6.2% respectively) but there were no differences in the V _{O 2max}. However, during a 42.2-km marathon run on a treadmill, the black athletes ran at the higher percentage V _{O 2max} (76%, SD 7.9% vs 68%, SD 5.3%), RER (0.96, SD 0.07 vs 0.91, SD 0.04) and f (56 breaths min^–1, SD 11 vs 47 breaths min^–1, SD 10), and at lower V _T (78 ml kg^–2/3 breath^–1, SD 15 vs 85 ml kg^–2/3 breath^–1, SD 19). The combination of higher f and lower V _T resulted in an identical V _I. Blood lactate levels were lower in black than in white runners (1.3 mmol l^–1, SD 0.6 vs 1.59 mmol l^–1, SD 0.2 respectively). It appeared that the only physiological difference that may account for the superior performance of the black runners was their ability to run at a higher percentage V _{O 2max} max during competition than white runners.     

The effects of rational and irrational self-verbalizations on performance efficiency and levels of anxiety

Investigated the effects of rational vs. irrational belief systems (as measured by the Ellis Irrational Values Scale) and rational vs. irrational self-verbalizations on levels of anxiety and persistence on a performance task. Ss (N = 40) were instructed to assemble a virtually insolvable task call Soma. The variables of interest were how long each S would persist on this task and how much anxiety (as measured by the A-State portion of the State-Trait Anxiety Inventory) was aroused in working on this task. Following a baseline trial trying to solve Soma, Ss were assigned to either a rational or irrational self-talk condition and were led to believe that such self-talk would help in a second attempt to solve Soma. In line with cognitive models of psychology, it was found that rational self-talk Ss showed a significant decrease in levels of state anxiety compared to irrational self-talk Ss in attempting to solve Soma in the second trial. Contrary to cognitive models of psychology, scores obtained from the EIVS and the A-Trait portion of the STAI were not found to be related to persistence.     

Aerobic capacity and skeletal muscle properties of normoxic and hypoxic rats in response to training

The aim of this study was to determine, in the rat, the effects of chronic exposure (7–9 weeks) to normobaric hypoxia (FIO₂ = 0.13, equivalent to 3700 m altitude) on cardiac and skeletal muscle properties, on maximal oxygen uptake (VO_2max), and endurance time to exhaustion (ETE). In addition, we evaluated the impact of endurance training (90 min of treadmill running per day, 5 days per week, for 9 weeks) on these parameters. The results were compared to normoxic rats fed ad libitum (N_AL) and to normoxic pair-weight (N_PW) animals in order to take into account the influence of hypoxia on growth rate. It was found that, in sedentary rats, hypoxia results in stunted growth, adrenal atrophy, a significant reduction of cross-sectional area of fast-twitch (type II) fibres, a reduced capillary-to-fibre ratio (C/F), and a reduced oxidative capacity (decreases in citrate synthase and 3-hydroxy-Acyl CoA dehydrogenase activities) of the plantaris muscle. These effects are mainly related to the anorexic effects of prolonged exposure to hypoxia. Nevertheless, hypoxic (H) rats displayed higher VO_2max and ETE values when compared either to N_AL or to N_PW animals. Endurance training resulted, in all groups (H, N_AL, N_PW), in a significant change of the fibre type distribution of the plantaris which displayed an increased number of type IIA fibres and a decreased proportion of type IIB fibres. In addition, the C/F ratio and cross-sectional area of fast-twitch fibres were normalized by superimposition of training on hypoxia. Both VO_2max and ETE were significantly higher in trained H rats than in N_AL, but these improvements were mainly related to the reduced body weight induced by hypoxia. These data suggest that the greater aerobic capacity and tolerance for prolonged exercise induced by chronic exposure to hypoxia can be mainly accounted for by the anorexic effects of hypoxia, although other factors (e.g. increase in oxygen carrying capacity induced by hypoxia acclimatization) may play a significant role in some circumstances (e.g. in sedentary rats). Received: 30 March 1995/Received after revision: 30 August 1995/Accepted: 4 September 1995     

Chest wall kinematics, respiratory muscle action and dyspnoea during arm vs. leg exercise in humans

Aim: We hypothesize that different patterns of chest wall (CW) kinematics and respiratory muscle coordination contribute to sensation of dyspnoea during unsupported arm exercise (UAE) and leg exercise (LE). Methods: In six volunteer healthy subjects, we evaluated the volumes of chest wall (V_cw) and its compartments, the pulmonary apposed rib cage (V_rc,p), the diaphragm‐abdomen apposed rib cage (V_rc,a) and the abdomen (V_ab), by optoelectronic plethysmography. Oesophageal, gastric and trans‐diaphragmatic pressures were simultaneously measured. Chest wall relaxation line allowed the measure of peak rib cage inspiratory muscle, expiratory muscle and abdominal muscle pressures. The loop V_rc,p/V_rc,a allowed the calculation of rib cage distortion. Dyspnoea was assessed by a modified Borg scale. Results: There were some differences and similarities between UAE and LE. Unlike LE with UAE: (i) V_cw and V_rc,p at end inspiration did not increase, whereas a decrease in V_rc,p contributed to decreasing CW end expiratory volume; (ii) pressure production of inspiratory rib cage muscles did not significantly increase from quiet breathing. Not unlike LE, the diaphragm limited its inspiratory contribution to ventilation with UAE with no consistent difference in rib cage distortion between UAE and LE. Finally, changes in abdominal muscle pressure, and inspiratory rib cage muscle pressure predicted 62% and 41.4% of the variability in Borg score with UAE and LE, respectively (P < 0.01). Conclusion: Leg exercise and UAE are associated with different patterns of CW kinematics, respiratory muscle coordination, and production of dyspnoea.     

Performance changes in world-class kayakers following two different training periodization models

This study was undertaken to compare training-induced changes in selected physiological, body composition and performance variables following two training periodization models: traditional (TP) versus block periodization (BP). Ten world-class kayakers were assessed four times during a training cycle over two consecutive seasons. On each occasion, subjects completed an incremental test to exhaustion on the kayak ergometer to determine peak oxygen uptake (VO_2peak), VO₂ at second ventilatory threshold (VO₂ VT2), peak blood lactate, paddling speed at VO_2peak (PS_peak) and VT2 (PS _VT2), power output at VO_2peak (Pw_peak) and VT2 (Pw _VT2), stroke rate at VO_2peak (SR_peak) and VT2 (SR _VT2) as well as heart rate at VO_2peak and VT2. Volume and exercise intensity were quantified for each endurance training session. Both TP and BP cycles resulted in similar gains in VO_2peak (11 and 8.1%) and VO₂ VT2 (9.8 and 9.4%), even though the TP cycle was 10 weeks and 120 training hours longer than the BP cycle. Following BP paddlers experienced larger gains in PS_peak, Pw_peak and SR_peak than those observed with TP. These findings suggest that BP may be more effective than TP for improving the performance of highly trained top-level kayakers. Although both models allowed significant improvements of selected physiological and kayaking performance variables, the BP program achieved similar results with half the endurance training volume used in the TP model. A BP design could be a more useful strategy than TP to maintain the residual training effects as well as to achieve greater improvements in certain variables related to kayaking performance.     

Olfactory and non-olfactory epithelia in the nasal cavity of the mouse,Peromyscus

The nasal cavities of 14 deer mice, Peromyscus maniculatus, were examined histologically to determine the variability in surface area of the olfactory epithelium and its correlation with nasal cavity volume, area of non-olfactory epithelial surface, and body size. Forty-four per cent of the nasal cavity surface of P. maniculatus is covered by a non-olfactory epithelium with an area of 129.8 mm²; the epithelial surface consists of gradations in type from keratinized stratified squamous rostrally to ciliated pseudostratified columnar caudally. An extensive portion of this epithelium is non-ciliated and devoid of goblet cells. Situated dorsocaudal to the non-olfactory epithelium is the olfactory epithelial surface measuring 166.8 mm² in area. The areas of total, non-olfactory and olfactory epithelial surfaces are highly variable in a sample of mice containing two subspecies, both sexes and various ages. Surface area measurements of non-olfactory and olfactory epithelia are correlated significantly with body length, body weight and volume of the nasal cavity. A relatively constant epithelial area to volume ratio is present in the nasal cavity of P. maniculatus. It is surmised that a stable ratio of molecules in the air to epithelial area may occur within a species.     

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Aim: To investigate the hypothesis that mitochondrial efficiency (i.e. P/O ratio) is higher in type I than in type II fibres during submaximal rates of respiration. Methods: Mitochondria were isolated from rat soleus and extensor digitorum longus (EDL) muscles, representing type I and type II fibres, respectively. Mitochondrial efficiency (P/O ratio) was determined with pyruvate (Pyr) or palmitoyl‐l ‐carnitine (PC) during submaximal (constant rate of adenosine diphosphate infusion) and maximal (V_max, state 3) rates of respiration and fitted to monoexponential functions. Results: There was no difference in V_max between PC and Pyr in soleus but in EDL V_max with PC was only 58% of that with Pyr. The activity of 3‐hydroxyacyl‐CoA dehydrogenase was threefold higher in soleus than in EDL. P/O ratio at V_max was 8–9% lower with PC [2.33 ± 0.02 (soleus) and 2.30 ± 0.02 (EDL)] than with Pyr [2.52 ± 0.03 (soleus) and 2.54 ± 0.03 (EDL)] but not different between the two muscles (P > 0.05). P/O ratio was low at low rates of respiration and increased exponentially when the rate of respiration increased. The asymptotes of the curves were similar to P/O ratio at V_max. P/O ratio at submaximal respirations was not different between soleus and EDL neither with Pyr nor with PC. Conclusion: Mitochondrial efficiency, as determined in vitro, was not significantly different in the two fibre types neither at V_max nor at submaximal rates of respiration. The low V_max for PC oxidation in EDL may relate to low activity of β‐oxidation.     

Interleukin-1 receptor antagonist restores homeostatic function and limits multiorgan damage in heatstroke

We measured diffusing capacity (DLCO), alveolar membrane properties (D _m), capillary lung volume (V _c), and alveolar volume (V _A ) in 20 healthy subjects (12 males; age 32.4 ± 13 (SD); BMI 21.7 ± 3; non smokers) at total lung capacity (TLC) and at ∼80, 60, and 40% TLC. In all subjects, D _m increased with lung volume, the increase being significantly greater for higher values of D _m(TLC): the inter-individual differences can be interpreted by a greater number of alveolar units coupled to a lower thickness of the air–blood barrier (thus a higher alveolar surface to thickness ratio S _A/τ). On the average, the volume-dependent increase of D _m from ∼40 to 100% TLC is less than expected based on geometrical increase of S _A /τ. In fact, up to ∼80% TLC, the increase in D _m closely reflects only the increase of S _A, suggesting “unfolding” of the septa with no appreciable decrease in τ. Conversely, above 80% TLC, the decrease in τ due to parenchymal stretching becomes the main factor affecting D _m. In all subjects, V _c decreased with increasing lung volume, in line with an increase in parenchymal stretching; the decrease was significantly larger for higher values of V _c (40% TLC). Possibly reflecting differences in alveolar capillary density. No correlation was found between D _m(TLC) and V _c(40%TLC). The individual specificity in the lung volume dependence of V _c and D _m can be reasonably described by evaluating the V _c/D _m ratio at TLC and at ∼40%TLC.     

Effects of stretch-shortening cycle training on mechanical properties and fibre type transition in the rat soleus muscle

The effects of exercise training on mechanical properties and fibre type transitions have been investigated in rat soleus muscle. The exercise was a repetition of stretch-shortening cycles. A method of dual controlled releases was applied to obtain tension/extension curves, which characterize the elastic behaviour of the series elastic component (SEC), and the force/velocity relationship characterizing the contractile elements. Other contractile measurements included: contraction time (t _c), half-relaxation time (t _1/2) and twitch/tetanus ratio (P _t/P _o). Additionally, the muscle fibre type composition was determined by a classical histochemical method. A 12-week period of training induced a significantly higher percentage of fast-twitch fibres and a lower percentage of slow-twitch fibres (P<0.01). This fibre adaptation led to a significant (P<0.01) decrease in t _c and an increase in maximum shortening velocity (V _max). An increase in compliance of the SEC was also observed. This elastic adaptation is interpreted in terms of modification of the active components of the SEC. All the histochemical and mechanical data presented in this study show that rat soleus muscles trained by stretch-shortening cycles acquired faster characteristics. Thus the results confirm that a slow-twitch to a fast-twitch fibre transition is obtainable in mature rats.     

The role of cytosolic Ca2+ in the secretion of NaCl in isolated in vitro perfused rectal gland tubules of Squalus acanthias

 In many exocrine glands cytosolic Ca²⁺ ([Ca²⁺]_i) plays a pivotal role in stimulation-secretion coupling. In the rectal gland of the dogfish Squalus acanthias this appears not to be the case and it is believed that secretion is mainly controlled by the Cl^– conductance of the luminal membrane. We have examined this question in a study of isolated in vitro perfused rectal gland tubules (RGT). Three types of measurements were performed: (1) measurements of [Ca²⁺]_i by the fura-2 technique; (2) measurements of transepithelial electrical parameters, i.e. transepithelial voltage (V _te), transepithelial resistance (R _te), the equivalent short-circuit current (I _sc) and the voltage across the basolateral membrane (V _bl), and (3) whole-cell patch-clamp measurements of cellular voltage (V _m), conductance (G _m) and membrane capacitance (C _m). The data indicates that carbachol (CCH) increases [Ca²⁺]_i by increasing store release and Ca²⁺ influx. Other agonists, producing cytosolic cAMP, also increased [Ca²⁺] by enhancing Ca²⁺ influx. CCH hyperpolarized these cells and enhanced G _m significantly. The effect of CCH on V _te and I _sc was most marked under control conditions and disappeared in RGT otherwise stimulated by agonists that lead to cAMP production. It is concluded that [Ca²⁺]_i plays a major role in the stimulation of NaCl secretion in RGT by enhancing the basolateral K⁺ conductance. cAMP-producing agonists enhance [Ca²⁺]_i by increased Ca²⁺ influx. CCH releases Ca²⁺ from respective stores. CCH, unlike the cAMP-producing agonists, only increases basolateral K⁺ conductance. It modulates secretion especially under conditions in which the cAMP pathway is not fully activated. Received: 25 November 1997 / Received after revision: 19 January 1998 / Accepted: 21 January 1998     

Ultrastructure of Skeletal Muscles in Mice Lacking Muscle‐Specific VEGF Expression

Vascular endothelial growth factor‐A (VEGF) influences several physiological processes including endothelial cell function, angiogenesis and maintenance of organ/tissue capillarity. While the functional aspects of VEGF were vigorously investigated, only little detail is known on structural integrity of skeletal muscle fibers and capillaries in mice lacking VEGF expression in their muscles. Therefore, we assessed systematically the architecture of the glycolytic plantaris and the oxidative soleus muscles obtained from muscle‐specific VEGF knockout (mVEGF‐KO, n = 7) mice and their wild‐type (WT, n = 7) littermates by morphometry after transmission electron microscopy. The capillary/fiber ratio was lower (plantaris: ?63.5%; soleus: ?54.8%; P ≤ 0.05) in mVEGF‐KO mice than in WT mice. In plantaris, quantification of volume density (Vv) of compartments revealed higher Vv of total mitochondria (+56.5%, P ≤ 0.05) as well as higher Vv‐values for both intrafibrillar (+39%; P ≤ 0.05) and subsarcolemmal (+220%; P ≤ 0.05) mitochondrial pools in mVEGF‐KO mice than WT mice. The capillary phenotype also differed (P ≤ 0.05) between the two mouse‐strains: Vv (–17.4%), absolute area size (–19.1%) and thickness (–19.6%) of the endothelium layer were lower and Vv of capillary lumen (+15.1%) was higher in mVEGF‐KO mice than in WT littermates. In soleus, mitochondrial Vv in fibers and the structural indicators specific to the capillary phenotype exhibited the same tendency in differences between the mouse strains without reaching statistical significance. Our morphometric analysis demonstrates that the lower capillary supply in plantaris of mVEGF‐KO mice is accompanied by higher mitochondrial Vv in muscle fibers as well as lumen dilation and endothelium thinning of capillaries. These structural alterations were more pronounced in a glycolytic than an oxidative muscle. Anat Rec, 300:2239–2249, 2017. © 2017 Wiley Periodicals, Inc.     

Walk–run transition in young and older adults: with special reference to the cardio-respiratory responses

Cardio-respiratory responses of young and older subjects performing walking and running protocols at the walk–run transition speed (WRT) were compared. A total of 26 volunteers assigned to younger (YG, 24 ± 3 years) and older (OG, 64 ± 6 years) groups underwent a protocol to determine the WRT used in 6-min walking and running protocols. Oxygen uptake (VO₂), ventilation (V _E), expired carbon dioxide (VCO₂), heart rate (HR) and perceived exertion (RPE) were assessed. Oxygen pulse (O₂ pulse) and respiratory exchange ratio (RER) were calculated. The WRT was not different between groups (OG: 6.84 ± 0.69 km h⁻¹ vs. YG: 7.04 ± 0.77 km h⁻¹, P = 0.62). No between-group differences were found within a given gait pattern for VO₂ (P = 0.061) and VCO₂ (P = 0.076). However, VO₂ (P = 0.0022) and VCO₂ (P = 0.0041) increased in OG when running, remaining stable in YG (VO₂: P = 0.622; VCO₂: P = 0.412). The VE was higher in OG compared to YG in walking (P = 0.030) and running (P = 0.004) protocols. No age-related (P = 0.180) or locomotion (P = 0.407) effects were found for RER. The HR increased in OG and between-group difference was detected while running (P = 0.003). No within- (P = 0.447) or between-group (P = 0.851) difference was found for O₂ pulse. The net VO₂ increased from walking to running in OG (P < 0.0001) but not in YG (P = 0.53), while RPE was lower in YG (P = 0.041) but stable in OG (P = 0.654). In conclusion, the WRT speed was similar across the age groups. However, the VO₂ and VCO₂ increase from walking to running was larger for OG than YG. The HR, VE and RPE were also higher when running in OG compared to YG. Therefore, the locomotion strategy had different impacts on the metabolic demand of older and younger subjects.     

Development of Fe3O4/Ag core/shell-based multifunctional immunomagnetic nanoparticles for isolation and detection of CD34+ stem cells

Fe₃O₄/Ag core/shell nanoparticles functionalized with the free amino (NH₂) functional groups (Fe₃O₄/Ag-NH₂) were conjugated with fluorescent electron coupled dye (ECD)-antiCD34 antibody using the 1-ethyl-3-(3′-dimethyl-aminopropyl) carbodiimide (EDC) catalyst (ECD – Electron Coupled Dye or R Phycoerythrin-Texas Red is a fluorescent organic dye attached to the antibody). The characteristic fluorescence of ECD in the antibody was investigated and was used as a good indicator for estimating the percentage of the antibodies that were successfully conjugated with the nanoparticles. The conjugation efficiency was found to increase depending on the V_NP:V_AB ratio, where V_NP and V_AB are the volumes of the nanoparticle solution (concentration of 50 ppm) and the as-purchased antibody solution, respectively. The conjugation efficiency rapidly increased from approximately 18% to approximately 70% when V_NP:V_AB was increased from 2:1 to 100:1, and it gradually reached the saturated state at an efficiency of 95%, as the V_NP:V_AB was equal to 300:1. The bioactivity of the abovementioned conjugation product (denoted by Fe₃O₄/Ag-antiCD34) was evaluated in an experiment for the collection of stem cells from bone marrow samples.     

Cloning and characterization of voltage‐gated calcium channel alpha1 subunits in Xenopus laevis during development

Voltage‐gated calcium channels play a critical role in regulating the Ca²⁺ activity that mediates many aspects of neural development, including neural induction, neurotransmitter phenotype specification, and neurite outgrowth. Using Xenopus laevis embryos, we describe the spatial and temporal expression patterns during development of the 10 pore‐forming alpha1 subunits that define the channels' kinetic properties. In situ hybridization indicates that Ca_V1.2, Ca_V2.1, Ca_V2.2, and Ca_V3.2 are expressed during neurula stages throughout the neural tube. These, along with Ca_V1.3 and Ca_V2.3, beginning at early tail bud stages, and Ca_V3.1 at late tail bud stages, are detected in complex patterns within the brain and spinal cord through swimming tadpole stages. Additional expression of various alpha1 subunits was observed in the cranial ganglia, retina, olfactory epithelium, pineal gland, and heart. The unique expression patterns for the different alpha1 subunits suggests they are under precise spatial and temporal regulation and are serving specific functions during embryonic development. Developmental Dynamics 238:2891–2902, 2009. © 2009 Wiley‐Liss, Inc.     

The dynamics of cross-bridge movement in vascular smooth muscle estimated from a single isometric contraction of the portal vein: The influence of temperature and calcium

The velocity of the contractile elementV _CE of the rat portal vein during a single isometric twitch was calculated from the ratio of the rate of tension increase (dT/dt) to the stiffness (dT/dL) of the series elastic element. This stiffness was considered as a linear function of tension (dT/dL=k · T), and thus the respective term wasV _CE=(dT/dt)/(kT). A polynome of the 10th order was fitted to the time course of tension change within the first seconds of stimulation. From this function, the instantaneous values of forceT, rate of tension increasedT/dt, as well as the ratio(dT/dt)/T were computed. The series elasticity was treated as the respective stiffness factor k.V _max isV _CE extrapolated to zero load, and this value gives an index of the turnover rate of the myosin cross-bridges. The experiments were carried out at different temperatures (37° C, 30° C, and 25° C) as well as at different intracellular calcium levels occurring as a staircase phenomenon in the first contractions after a period of non-stimulation of 20 min.With increasing temperature,T remained constant but there was an increase inV _max (Q ₁₀=1.9), peakV _CE (Q ₁₀=1.8) and in (dT/dt)_max (Q ₁₀=1.8). Furthermore, this so-called tachytropic effect of temperature showed a reduction of the time to the maximumdT/dt (Q ₁₀=1.4), and to the peakV _CE (Q ₁₀=1.2).During a staircase cycle the parameters describing the contractile state, i.e. theV _max, the time to maximumdT/dt, and the time to peakV _CE remained constant.T, maximumdT/dt and peakV _CE were, however, considerably increased. These results are typical of the socalled polytropic effect of calcium.The experimental results obtained from the isometric force-velocity relation were compared with those calculated by means of isotonic contractions in previous experiments. There were similar changes in the dynamics of contraction, irrespective of the method used for calculation ofV _max; this was the case in experiments with varied temperatures and calcium levels. Therefore the determination ofV _max from a single isometric contraction seems to be a suitable method of describing the elementary process of contraction in vascular smooth muscle. This method showed a higher time resolution as compared with other methods using isotonic contractions.