Muscle fibre conduction velocity and cardiorespiratory response during incremental cycling exercise in young and older individuals with different training status

We investigated the effect of ageing and training on muscle fibre conduction velocity (MFCV) and cardiorespiratory response during incremental cycling exercise. Eight young (YT; 24 ± 5 yrs) and eight older (OT; 64 ± 3 yrs) cyclists, together with eight young (YU; 27 ± 4 yrs) and eight older (OU; 63 ± 2 yrs) untrained individuals underwent to an incremental maximal test on a cycle ergometer. Ventilatory threshold (VT), respiratory compensation point (RCP) and maximal oxygen uptake (VO₂max) were identified and MFCV recorded from the vastus lateralis muscle using surface electromyography with linear arrays electrodes.In YT MFCV increased with the exercise intensity, reaching a peak of 4.99 ± 1.02 [m/s] at VT. Thereafter, and up to VO₂max, MFCV declined. In YU MFCV showed a similar trend although the peak [4.55 ± 0.53 m/s] was observed, at 75% of VO₂max an intensity higher than VT (66% of VO₂max). In both YT and YU MFCV did not decline until RPC, which occurred at 78% VO₂max in YU and at 92% VO₂max (P < 0.01) in YT. Differently from young individuals, MFCV in older subjects did not increase with exercise intensity. Moreover, maximal MFCV in OU was significantly lower [3.53 ± 0.40 m/s;] than that of YT (P < 0.005) and YU (P < 0.05).The present study shows that, especially in young individuals, MFCV reflects cardiorespiratory response during incremental dynamic cyclic exercise and hence can be used to investigate motor unit recruitment strategies.     

Non-invasive assessment of muscle fiber conduction velocity during an incremental maximal cycling test

Muscle fiber conduction velocity (MFCV) gives critical information on neuromuscular control and can be considered a size principle parameter, being suggestive of motor unit recruitment strategies. MFCV has been recently measured during constant-load sub-maximal cycling exercise and was found to correlate positively with percentage of type I myosin heavy chain.The aim of this study was to test the hypothesis that MFCV measured during an incremental cycling test using surface electromyography (sEMG), can be sensitive to the different metabolic requests elicited by the exercise. In particular, the relationship between ventilatory threshold (T-vent), V^′O_2max and MFCV was explored.Eleven male physically active subjects (age 30 ± 9 years) undertook a 1-min incremental cycling test to exhaustion. T-vent and V^′O_2max were measured using an open circuit breath by breath gas analyzer. The sEMG was recorded from the vastus lateralis muscle with an adhesive 4-electrodes array, and the MFCV was computed on each sEMG burst over the last 30-s of each step.The mean V^′O_2max obtained during the maximal test was 53.32 ± 2.33 ml kg^?1 min^?1, and the T-vent was reached at 80.77 ± 3.49% of V^′O_2max. In all subjects reliable measures of MFCV were obtained at every exercise intensity (cross correlation values >0.8). MFCV increased linearly with the mechanical load, reaching a maximum value of 4.28 ± 0.67 m s^?1 at an intensity corresponding to the T-vent. Thereafter, MFCV declined until maximal work intensities. This study demonstrates that MFCV can be used as non-invasive tool to infer MUs recruitment/derecruitment strategies even during dynamic exercise from low to maximal intensities.     

Aerobic Fitness and Glycemic Variability in Adolescents with Type 1 Diabetes

ObjectiveThis study examines the association of fitness on glycemic variability (GV) in adolescents with type 1 diabetes mellitus (T1DM). GV has been associated with high frequency of hyper-and hypoglycemia.MethodsNineteen adolescents with T1DM, ages 14 to 19 years, underwent aerobic fitness testing to determine their maximal aerobic capacity (VO₂ max). A continuous glucose monitoring (CGM) device was placed on each subject and worn for 3 to 5 days until a return visit when the subjects underwent a 1-hour treadmill exercise session. Mean amplitude of glycemic excursion (MAGE) was calculated from the CGM data collected between the 2 study visits. Metabolic equivalent (MET), a measure of accumulated metabolic workload during the exercise session, was also calculated.ResultsMean VO₂ max was 46.6 ± 6.8 mL/kg/min, with a range of 34.8 to 57.0 mL/kg/min. Mean MET during the exercise session was 577.2 ± 102.4 and ranged from 354.3 to 716.2 METs. There was an inverse association between VO₂ max and MAGE (r = − 0.46; 95% confidence interval [CI], − 0.01 to − 0.76; P = .048). MET load and MAGE also had an inverse relationship (r = − 0.48; 95% CI, − 0.03 to − 0.77; P = .037).ConclusionGV is inversely associated with fitness and MET load. Aerobic fitness should be promoted in adolescents with T1DM not only because of its multiple beneficial effects but also due to a possible association with GV, leading to fewer extremes in hypo-and hyperglycemia. (Endocr Pract. 2014;20:566-570)     

Human mitochondrial haplogroup H: The highest VO2max consumer – Is it a paradox?

Mitochondrial background has been demonstrated to influence maximal oxygen uptake (VO_2max, in mL kg^?1 min^?1), but this genetic influence can be compensated for by regular exercise. A positive correlation among electron transport chain (ETC) coupling, ATP and reactive oxygen species (ROS) production has been established, and mitochondrial variants have been reported to show differences in their ETC performance. In this study, we examined in detail the VO_2max differences found among mitochondrial haplogroups. We recruited 81 healthy male Spanish Caucasian individuals and determined their mitochondrial haplogroup. Their VO_2max was determined using incremental cycling exercise (ICE). VO_2max was lower in J than in non-J haplogroup individuals (P = 0.04). The H haplogroup was responsible for this difference (VO_2max; J vs. H; P = 0.008) and this group also had significantly higher mitochondrial oxidative damage (mtOD) than the J haplogroup (P = 0.04). In agreement with these results, VO_2max and mtOD were positively correlated (P = 0.01). Given that ROS production is the major contributor to mtOD and consumes four times more oxygen per electron than the ETC, our results strongly suggest that ROS production is responsible for the higher VO_2max found in the H variant. These findings not only contribute to a better understanding of the mechanisms underneath VO_2max, but also help to explain some reported associations between mitochondrial haplogroups and mtOD with longevity, sperm motility, premature aging and susceptibility to different pathologies.     

Local muscle cooling does not impact expression of mitochondrial-related genes

Recovery that takes place in a cold environment after endurance exercise elevates PGC-1α mRNA whereas ERRα and NRF2 mRNA expression are inhibited. However, the effect of local skeletal muscle cooling on mitochondrial-related gene expression is unknown.PurposeTo determine the impact of local skeletal muscle cooling during recovery from an acute bout of exercise on mitochondrial-related gene expression.MethodsRecreationally-trained male cyclists (n=8, age 25±3 y, height 181±6 cm, weight 79±8 kg, 12.8±3.6% body fat, VO_2peak 4.52±0.88 L·min⁻¹ protocol) completed a 90-min variable intensity cycling protocol followed by 4 h of recovery. During recovery, ice was applied intermittently to one leg (ICE) while the other leg served as a control (CON). Intramuscular temperature was recorded continuously. Muscle biopsies were taken from each vastus lateralis at 4 h post-exercise for the analysis of mitochondrial-related gene expression.ResultsIntramuscular temperature was colder in ICE (26.7±1.1 °C) than CON (35.5±0.1 °C) throughout the 4 h recovery period (p<0.001). There were no differences in expression of PGC-1α, TFAM, NRF1, NRF2, or ERRα mRNA between ICE and CON after the 4 h recovery period.ConclusionLocal muscle cooling after exercise does not impact the expression of mitochondrial biogenesis-related genes compared to recovery from exercise in control conditions. When these data are considered with previous research, the stimuli for cold-induced gene expression alterations may be related to factors other than local muscle temperature. Additionally, different intramuscular temperatures should be examined to determine dose-response of mitochondrial-related gene expression.     

Cocontraction and economy of triathletes and cyclists at different cadences during cycling motion

The purpose of this study was to compare the cycling technique of triathletes and cyclists on the basis of the cocontraction of selected muscles of the lower limbs and economy at different cadences. The economy (EC) and percent cocontraction from nine triathletes and eight cyclists were compared at 60, 75, 90 and 105 rpm cadences. Tests were performed on two separate days. The maximal oxygen uptake was measured and the second ventilatory threshold (VO_2VT) was estimated on the first day using a stationary bicycle. On the second day the four different cadences were tested at approximately 5% below the VO_2VT. The EMG activity of the rectus femoris (RF), biceps femoris (BF) and vastus lateralis (VL) was recorded and the EMG signal was normalized using the 60 rpm dynamic contraction. The percent cocontractions were calculated from RF/BF and VL/BF muscles. The EC was also calculated. The results showed that cyclists were significantly more economic, indicating that they exerted more power with less VO₂, and presented significantly lower percent cocontraction than triathletes (p < 0.05). Thus, the results suggest that the cyclists had a better technique than the triathletes. The simultaneous use of the percent cocontraction and economy seems to be a good performance indicator for cyclists and triathletes.     

Differential contributions of ankle plantarflexors during submaximal isometric muscle action: A PET and EMG study

The objective of this study was to investigate the relative contributions of superficial and deep ankle plantarflexors during repetitive submaximal isometric contractions using surface electromyography (SEMG) and positron emission tomography (PET). Myoelectric signals were obtained from twelve healthy volunteers (27.3 ± 4.2 yrs). A tracer ([¹⁸F]-FDG) was injected during the exercise and PET scanning was done immediately afterwards. The examined muscles included soleus (Sol), medial gastrocnemius (MG), lateral gastrocnemius (LG), and flexor hallucis longus (FHL). It was found that isometric maximal voluntary contraction (MVC) force, muscle glucose uptake (GU) rate, and SEMG of various plantarflexors were comparable bilaterally. In terms of %EMG MVC, FHL and MG displayed the highest activity (∼34%), while LG (∼21%) had the lowest activity. Cumulative SEMG from all parts of the triceps surae (TS) muscle accounted for ∼70% of the combined EMG signal of all four plantarflexors. As for GU, the highest quantity was observed in MG (2.4 ± 0.8 μmol * 100 g⁻¹ * min⁻¹), whereas FHL (1.8 ± 0.6 μmol * 100 g⁻¹ * min⁻¹) had the lowest uptake. Cumulative GU of TS constituted nearly 80% of the combined GU. The findings of this study provide valuable reference for studies where individual muscle contributions are estimated using models and simulations.     

Muscle fiber conduction velocity in different gait phases of early and late-stage diabetic neuropathy

We investigated the muscle fiber conduction velocity (MFCV) during gait phases of the lower limb muscles in individuals with various degrees of diabetic peripheral neuropathy (DPN). Forty-five patients were classified into severity degrees of DPN by a fuzzy model. The stages were absent (n = 11), mild (n = 14), moderate (n = 11) and severe (n = 9), with 10 matched healthy controls. While walking, all subjects had their sEMG (4 linear electrode arrays) recorded for tibialis anterior (TA), gastrocnemius medialis (GM), vastus lateralis (VL) and biceps femoris (BF). MFCV was calculated using a maximum likelihood algorithm with 30 ms standard deviation Gaussian windows. In general, individuals in the earlier stages of DPN showed lower MFCV of TA, GM and BF, whilst individuals with severe DPN presented higher MFCV of the same muscles. We observed that mild patients already showed lower MFCV of TA at early stance and swing, and lower MFCV of BF at swing. All diabetic groups showed a markedly reduction in MFCV of VL, irrespective of DPN. Severe patients presented higher MFCV mainly in distal muscles, TA at early and swing phases and GM at propulsion and midstance. The absent group already showed MFCV of VL and GM reductions at the propulsion phase and of VL at early stance. Although MFCV changes were not as progressive as the DPN was, we clearly distinguished diabetic patients from controls, and severe patients from all others.     

Redox-Optimized ROS Balance and the relationship between mitochondrial respiration and ROS

The Redox-Optimized ROS Balance [R-ORB] hypothesis postulates that the redox environment [RE] is the main intermediary between mitochondrial respiration and reactive oxygen species [ROS]. According to R-ORB, ROS emission levels will attain a minimum vs. RE when respiratory rate (VO₂) reaches a maximum following ADP stimulation, a tenet that we test herein in isolated heart mitochondria under forward electron transport [FET]. ROS emission increased two-fold as a function of changes in the RE (~ 400 to ~ 900 mV·mM) in state 4 respiration elicited by increasing glutamate/malate (G/M). In G/M energized mitochondria, ROS emission decreases two-fold for RE ~ 500 to ~ 300 mV·mM in state 3 respiration at increasing ADP. Stressed mitochondria released higher ROS, that was only weakly dependent on RE under state 3. As a function of VO₂, the ROS dependence on RE was strong between ~ 550 and ~ 350 mV·mM, when VO₂ is maximal, primarily due to changes in glutathione redox potential. A similar dependence was observed with stressed mitochondria, but over a significantly more oxidized RE and ~ 3-fold higher ROS emission overall, as compared with non-stressed controls. We conclude that under non-stressful conditions mitochondrial ROS efflux decreases when the RE becomes less reduced within a range in which VO₂ is maximal. These results agree with the R-ORB postulate that mitochondria minimize ROS emission as they maximize VO₂ and ATP synthesis. This relationship is altered quantitatively, but not qualitatively, by oxidative stress although stressed mitochondria exhibit diminished energetic performance and increased ROS release.     

Acute effects of incremental inspiratory loads on compartmental chest wall volume and predominant activity frequency of inspiratory muscle

AimThis research aims to analyze the acute effect of incremental inspiratory loads on respiratory pattern and on the predominant activity frequency of inspiratory muscle, taking into account differences in gender responses. Optoelectronic Plethysmography was performed during loads in 39 healthy subjects (20 women), placing 89 markers on the thoracic-abdominal wall to obtain total and regional volumes. Surface electromyography (SEMG) was taken simultaneously on the Sternocleidomastoid and Diaphragm muscles, to calculate the predominant muscle activity frequency through wavelet analysis. Inspiratory loads were performed using Threshold® with 2 min of breathing at different levels, ranging from a load of 10 cmH₂O plus 5 cmH₂O to 40 cmH₂O or fatigue.ResultsInspiratory Time increased during loads. Total and compartmental volumes increased with different regions, changing at different loads. These changes in volume occur earlier in women (20 cmH₂O) than in men (30 cmH₂O). The predominant activity frequency of Sternocleidmastoid muscle decreased at 30 cmH₂O, while Diaphragm activity decreased at 40 cmH₂O.ConclusionThe acute effects of incremental inspiratory loads are increases of total and regional volumes and inspiratory time. As for muscle activity, the predominant activity frequency declined in Sternocleidomastoid and Diaphragm muscles, but at different loads. Such respiratory and SEMG patterns and gender differences should be considered when clinical interventions are performed.     

Mensurations échographiques de la thyroïde chez des enfants de zéro à 15 ans de la ville de Ouagadougou

Among the methods used to carry out measurements of thyroid, echography is the best because it is noninvasive and more specific. The goals of this study were to determine the normal thyroid volume of the Burkinabe child; to study the parameters which induce a variation of thyroid volume and to compare our values with those from other localities. Through a cross-sectional study, 240 children from the town of Ouagadougou benefited from a thyroid echography. Thus the height (h), the transverse diameter (dt) and the thickness (e) were measured. Volume (vl) of each lobe was estimated by: vl = h × dt × e × 3.14/6. The total volume (VT) is the sum of the volumes of each lobe, the isthmus being neglected. A correlation set at the threshold p < 0.001 has been carried out between VT and some anthropometric parameters. The following averages were observed: before one year, the average volume is of 0.51 L ± 0.21; from one to three years, it is of 0.95 mL ± 0.33; from four to six years, the average volume is of 1.35 mL ± 0.43; from seven to nine years, it is of 1.95 mL ± 0.62. From 10 to 12 years, the average volume is of 3.01 mL ± 1.08 and it is of 5.32 mL ± 2.07 from 13 to 15 years. It stands out that the VT is positively associated with the age (r = 0.82), with the size (r = 0.73), with the weight (r = 0.81) and with body surface (r = 0.78). Moreover, the VT is higher among boys than in girls beyond one year of age. This parameter varies according to the area of origin. Lastly, compared with the American, European and Asian averages, our values are smaller. This study enabled us to establish our own standards which we will be able from now on to use in daily practice. However, multicentric studies associated with thyroid and sexual hormones blood levels measurements must be undertaken to ascertain these data.     

Effect of electrocardiographic contamination on surface electromyography assessment of back muscles

The purpose of this study was to demonstrate the relative effect of electrocardiography (ECG) on back muscle surface electromyography (SEMG) parameters and their corresponding sensitivity in low back pain (LBP) assessment.Back muscle SEMG activities were recorded from 17 healthy subjects and 18 chronic LBP patients under static postures (straight sitting and upright standing), and dynamic action (flexion–extension). ECG cancellation based on independent component analysis (ICA) method was performed. Root mean square (RMS) and median frequency (MF) of raw and denoised SEMG data were computed respectively. Multiple comparisons were then performed.A consistent trend of change (increased MF and decreased RMS) followed ECG removal was noticed. In particular, in SEMG measurements under static postures, a significant decrease in RMS (p < 0.05) and increase in MF (p < 0.05) were found in all recording muscle groups. Level of corruption by ECG artifacts on SEMG measurements was found to be more serious and prominent in static postures than that in dynamic action. After ECG removal, significant improvements in the ability of SEMG to discriminate LBP patients from healthy subjects were seen in RMS amplitude recorded while standing (p < 0.05) and MF in all measuring conditions (p < 0.05).This study provides a more complete understanding on the relative effect of ECG contamination on back muscles SEMG parameters and LBP assessment.     

An investigation of the simultaneously recorded occlusal contact and surface electromyographic activity of jaw-closing muscles for patients with temporomandibular disorders and a scissors-bite relationship

Surface electromyographic (SEMG) activity of the masseter and anterior temporalis (TA) muscles has been reported to be associated with occlusion and orofacial pain. However, our recent report did not reveal an association between the side of orofacial pain and the side showing higher or lower level of SEMG activity of masseter or TA. The present purpose was to re-test this association in patients who had unilateral scissors-bite relationship. Thirty-two unilateral scissors-bite femalepatients complaining of unilateral orofacial pain (n = 15) or TMJ sounds (n = 17) were enrolled to simultaneously record contacts, force distribution of occlusion, and SEMG activity of masseter and TA during centric maximal voluntary clenching (MVC). The results indicated that neither orofacial pain nor the TMJ sounds had an association with the masseter’s SEMG values, while scissors-bite had (P < 0.05). A lower SEMG value for masseter was found on the scissors-bite side where there was a smaller number of contacts and a lower biting force distribution (P < 0.05). No such association was revealed in TA. In conclusion, in patients with unilateral TMD symptom(s) and scissors-bite, the jawclosing muscles’ SEMG activity during centric MVC was associated with the scissors-bite rather than the symptoms of orofacial pain or TMJ sounds.     

Sodium orthovanadate associated with pharmacological doses of ascorbate causes an increased generation of ROS in tumor cells that inhibits proliferation and triggers apoptosis

Pharmacological doses of ascorbate were evaluated for its ability to potentiate the toxicity of sodium orthovanadate (Na₃VO₄) in tumor cells. Cytotoxicity, inhibition of cell proliferation, generation of ROS and DNA fragmentation were assessed in T24 cells. Na₃VO₄ was cytotoxic against T24 cells (EC₅₀ = 5.8 μM at 24 h), but in the presence of ascorbate (100 μM) the EC₅₀ fell to 3.3 μM. Na₃VO₄ plus ascorbate caused a strong inhibition of cell proliferation (up to 20%) and increased the generation of ROS (4-fold). Na₃VO₄ did not directly cleave plasmid DNA, at this aspect no synergism was found occurring between Na₃VO₄ and ascorbate once the resulting action of the combination was no greater than that of both substances administered separately. Cells from Ehrlich ascites carcinoma-bearing mice were used to determine the activity of antioxidant enzymes, the extent of the oxidative damage and the type of cell death. Na₃VO₄ alone, or combined with ascorbate, increased catalase activity, but only Na₃VO₄ plus ascorbate increased superoxide dismutase activity (up to 4-fold). Oxidative damage on proteins and lipids was higher due to the treatment done with Na₃VO₄ plus ascorbate (2–3-fold). Ascorbate potentiated apoptosis in tumor cells from mice treated with Na₃VO₄. The results indicate that pharmacological doses of ascorbate enhance the generation of ROS induced by Na₃VO₄ in tumor cells causing inhibition of proliferation and apoptosis. Apoptosis induced by orthovanadate and ascorbate is closer related to inhibition on Bcl-xL and activation of Bax. Our data apparently rule out a mechanism of cell demise p53-dependent or related to Cdk2 impairment.     

The cost of ventilation in birds measured via unidirectional artificial ventilation

The highly derived mechanism birds use to ventilate their lungs relies on dorsoventral excursions of their heavily muscled sternum and abdominal viscera. Our expectation of the level of mechanical work involved in this mechanism led us to hypothesize that the metabolic cost of breathing is higher in birds than in other tetrapods. To test this theory, we used unidirectional artificial ventilation (UDV) to stop normal ventilatory movements in guinea fowl (Numida meleagris L.) at rest and during treadmill locomotion at three speeds. Oxygen consumption was measured during normal breathing and UDV, and the difference was used to approximate the cost of ventilation. Contrary to our prediction, metabolism increased when ventilatory movements ceased during UDV at rest. Although we do not understand why this occurred we suspect that UDV induced a homeostatic mechanism to counteract the loss of carbon dioxide. Nevertheless, across all running speeds, metabolism decreased significantly with UDV, indicating a minimum cost of ventilation during running of 1.43 ± 0.62% of total running metabolism or 0.48 ± 0.21 mL O₂ (L ventilated)^? 1. These results suggest that the metabolic cost of ventilation is low in birds and that it is within the range of costs reported previously for other amniotes.     

The effect of time left alone at home on dog welfare

The aim of this study was to investigate the effect of time left alone on dog behaviour and cardiac activity. Twelve privately owned dogs, with no history of separation related behaviour problems, were video-recorded on three different occasions when left alone in their home environment. The treatments lasted for 0.5 h (T_0.5); 2 h (T₂) and 4 h (T₄). Video-recording started 10 min before the owner left the house and continued until 10 min after the owner returned, so that interactions between dog and owner as well as behaviour during separation could be studied. Data on heart rate (HR) and heart rate variability (HRV) were collected within the same time period in each treatment. In addition to analysing behaviours separately, behaviours were also grouped together and defined as new variables; physically active, attentive behaviour, vocal, interaction initiated by owner and interaction initiated by dog. There were no differences in behaviour between treatments at equivalent time intervals until the owner returned, although a number of differences were observed at reunion with the owner. Dogs showed a higher frequency of physical activity (P < 0.05) and attentive behaviour (P < 0.01) in T₂ (0.37 ± 0.07; 0.52 ± 0.08, mean frequency of occurrence/15 s ± SE) and T₄ (0.48 ± 0.08; 0.48 ± 0.07) compared to T_0.5 (0.20 ± 0.07; 0.21 ± 0.05). They also showed more tail wagging (P < 0.01) and interacted more with their owners (P < 0.01) in T₂ (0.27 ± 0.08; 0.47 ± 0.09) and T₄ (0.26 ± 0.04; 0.42 ± 0.09) compared to T_0.5 (0.09 ± 0.04; 0.14 ± 0.03). After a longer time of separation, the dogs also showed higher frequencies of lip licking (P < 0.05) and body shaking (P < 0.05) at the owner's return (T_0.5 = 0.09 ± 0.05; T₂ = 0.24 ± 0.08; T₄ = 0.27 ± 0.06 and T_0.5 = 0.03 ± 0.01; T₂ = 0.08 ± 0.03; T₄ = 0.07 ± 0.01, respectively). There was a tendency for higher HR (P < 0.1) during the first and second minute after reunion in T₂ (127.6 ± 1.25, mean bpm ± SE; 111.3 ± 1.24) compared to T_0.5 (106.2 ± 1.06; 87.5 ± 1.02). According to the results of this study, the effect of time left alone was shown by a more intense greeting behaviour by the dog towards their owner as well as by a higher frequency of physical activity and attentive behaviour when the owner returned, already after 2 h of separation. Although this study cannot distinguish between whether dogs were aware of the length of time they were alone (but did not signal it) or whether they were unaware until reminded of it by the return of their owner, it does confirm that dogs are affected by the duration of time at home alone.     

Design,synthesis and evaluation of novel metalloproteinase inhibitors based on l-tyrosine scaffold

A series of novel l-tyrosine derivatives were designed, synthesized and assayed for their inhibitory activities on matrix metalloproteinase 2 (MMP-2) and histone deacetylase 8 (HDAC-8). The results showed that these l-tyrosine derivatives exhibited inhibitory profiles against MMP-2 and HDAC-8. The compounds 6h (IC₅₀ = 0.013 ± 0.001 μM) and 6j (IC₅₀ = 0.017 ± 0.001 μM) were equal potent MMP-2 inhibitors to the positive control NNGH (IC₅₀ = 0.014 ± 0.001 μM). As for HDAC-8 inhibition, some of the hydroxamate compounds, such as 6d (IC₅₀ = 3.6 ± 0.2 μM) and 6c (IC₅₀ = 5.8 ± 0.5 μM), were equal potent to the positive control SAHA (IC₅₀ = 1.6 ± 0.1 μM). Structure–activity relationships were also briefly discussed.     

Synthesis of 6-chloro-2-Aryl-1H-imidazo[4,5-b]pyridine derivatives: Antidiabetic,antioxidant, β-glucuronidase inhibiton and their molecular docking studies

6-Chloro-2-Aryl-1H-imidazo[4,5-b]pyridine derivatives 1–26 were synthesized and characterized by various spectroscopic techniques. All these derivatives were evaluated for their antiglycation, antioxidant and β-glucuronidase potential followed their docking studies. In antiglycation assay, compound 2 (IC₅₀ = 240.10 ± 2.50 μM) and 4 (IC₅₀ = 240.30 ± 2.90 μM) was found to be most active compound of this series, while compounds 3 (IC₅₀ = 260.10 ± 2.50 μM), 6 (IC₅₀ = 290.60 ± 3.60 μM), 13 (IC₅₀ = 288.20 ± 3.00 μM) and 26 (IC₅₀ = 292.10 ± 3.20 μM) also showed better activities than the standard rutin (IC₅₀ = 294.50 ± 1.50 μM). In antioxidant assay, compound 1 (IC₅₀ = 69.45 ± 0.25 μM), 2 (IC₅₀ = 58.10 ± 2.50 μM), 3 (IC₅₀ = 74.25 ± 1.10 μM), and 4 (IC₅₀ = 72.50 ± 3.30 μM) showed good activities. In β-glucuronidase activity, compounds 3 (IC₅₀ = 29.25 ± 0.50 μM), compound 1 (IC₅₀ = 30.10 ± 0.60 μM) and compound 4 (IC₅₀ = 46.10 ± 1.10 μM) showed a significant activity as compared to than standard D-Saccharic acid 1,4-lactonec (IC₅₀ = 48.50 ± 1.25 μM) and their interaction with the enzyme was confirm by docking studies.     

Asociación de la fuerza muscular con marcadores tempranos de riesgo cardiovascular en adultos sedentarios

ObjectiveTo assess the association between muscle strength and early cardiovascular risk (CVR) markers in sedentary adults.Materials and methodsA total of 176 sedentary subjects aged 18-30 years were enrolled. Body mass index and fat percentage were calculated, and waist circumference, grip strength by dynamometry, systolic blood pressure, diastolic blood pressure, mean arterial pressure, and maximal oxygen uptake by VO_2max were measured as CVR markers. A multivariate logistic regression analysis was used to assess associations between muscle strength and CVR markers.ResultsInverse correlations were found between muscle strength and adiposity (r = -.317; P = .001), waist circumference (r = -.309; P = .001), systolic blood pressure (r = -.401; P = .001), and mean arterial pressure (r = -.256; P = .001). Subjects with lower levels of muscle strength had a 5.79-fold (95% CI 1.57 to 9.34; P = .008) risk of having higher adiposity levels (≥ 25%) and a 9.67-fold (95% CI = 3.86 to 19.22; P < .001) risk of having lower physical capacity values for VO_2max (≤ 31.5 mL/kg/min^-1).ConclusionsIn sedentary adults, muscle strength is associated to early manifestations of CVR. It is suggested that muscle strength testing is added to routine measurement of VO_2max and traditional risk factors for prevention and treatment of cardiovascular risk.     

Nonlinear analysis of gait kinematics to track changes in oxygen consumption in prolonged load carriage walking: A pilot study

Linking human mechanical work to physiological work for the purpose of developing a model of physical fatigue is a complex problem that cannot be solved easily by conventional biomechanical analysis. The purpose of the study was to determine if two nonlinear analysis methods can address the fundamental issue of utilizing kinematic data to track oxygen consumption from a prolonged walking trial: we evaluated the effectiveness of dynamical systems and fractal analysis in this study. Further, we selected, oxygen consumption as a measure to represent the underlying physiological measure of fatigue. Three male US Army Soldier volunteers (means: 23.3 yr; 1.80 m; 77.3 kg) walked for 120 min at 1.34 m/s with a 40-kg load on a level treadmill. Gait kinematic data and oxygen consumption (VO₂) data were collected over the 120-min period. For the fractal analysis, utilizing stride interval data, we calculated fractal dimension. For the dynamical systems analysis, kinematic angle time series were used to estimate phase space warping based features at uniform time intervals: smooth orthogonal decomposition (SOD) was used to extract slowly time-varying trends from these features. Estimated fractal dimensions showed no apparent trend or correlation with independently measured VO₂. While inter-individual difference did exist in the VO₂ data, dominant SOD time trends tracked and correlated with the VO₂ for all volunteers. Thus, dynamical systems analysis using gait kinematics may be suitable to develop a model to predict physiologic fatigue based on biomechanical work.