Continuous-flow pump model study: the effect on pump performance of pump characteristics and cardiovascular conditions

This model study evaluates the effect of pump characteristics and cardiovascular data on hemodynamics in atrio–aortic VAD assistance. The model includes a computational circulatory sub-model and an electrical sub-model representing two rotary blood pumps through their pressure–flow characteristics. The first is close to a pressure generator—PG (average flow sensitivity to pressure variations, ?0.047 l mmHg^?1); the second is closer to a flow generator—FG (average flow sensitivity to pressure variations, ?0.0097 l mmHg^?1). Interaction with VAD was achieved by means of two interfaces, behaving as impedance transformers. The model was verified by use of literature data and VAD onset conditions were used as a control for the experiments. Tests compared the two pumps, at constant pump speed, in different ventricular and circulatory conditions: maximum ventricular elastance (0.44–0.9 mmHg cm^?3), systemic peripheral resistance (781–1200 g cm^?4 s^?1), ventricular diastolic compliance C _p (5–10–50 cm³ mmHg^?1), systemic arterial compliance (0.9–1.8 cm³ mmHg^?1). Analyzed variables were: arterial and venous pressures, flows, ventricular volume, external work, and surplus hemodynamic energy (SHE). The PG pump generated the highest SHE under almost all conditions, in particular for higher C _p (+50 %). PG pump flow is also the most sensitive to E _max and C _p changes (?26 and ?33 %, respectively). The FG pump generally guarantees higher external work reduction (54 %) and flow less dependent on circulatory and ventricular conditions. The results are evidence of the importance of pump speed regulation with changing ventricular conditions. The computational sub-model will be part of a hydro-numerical model, including autonomic controls, designed to test different VADs.     

Treatment of exertional heat stress developed during low or moderate physical work

Purpose

We examined whether treatment for exertional heat stress via ice water immersion (IWI) or natural recovery is affected by the intensity of physical work performed and, thus, the time taken to reach hyperthermia.

Methods

Nine adults (18–45 years; 17.9 ± 2.8 percent body fat; 57.0 ± 2.0 mL kg^?1 min^?1 peak oxygen uptake) completed four conditions incorporating either walking or jogging at 40 °C (20 % relative humidity) while wearing a non-permeable rain poncho. Upon reaching 39.5 °C rectal temperature (T _re), participants recovered either via IWI in 2 °C water or via natural recovery (seated in a ~29 °C environment) until T _re returned to 38 °C.

Results

Cooling rates were greater in the IWI [T _re: 0.24 °C min^?1; esophageal temperature (T _es): 0.24 °C min^?1] than the natural recovery (T _re and T _es: 0.03 °C min^?1) conditions (p < 0.001) with no differences between the two moderate and the two low intensity conditions (p > 0.05). Cooling rates for T _re and T _es were greater in the 39.0–38.5 °C (T _re: 0.19 °C min^?1; T _es: 0.31 °C min^?1) compared with the 39.5–39.0 °C (T _re: 0.11 °C min^?1; T _es: 0.13 °C min^?1) period across conditions (p < 0.05). Similar reductions in heart rate and mean arterial pressure were observed during recovery across conditions (p > 0.05), albeit occurred faster during IWI. Percent change in plasma volume at the end of natural recovery and IWI was 5.96 and 9.58 %, respectively (p < 0.001).

Conclusion

The intensity of physical work performed and, thus, the time taken to reach hyperthermia does not affect the effectiveness of either IWI treatment or natural recovery. Therefore, while the path to hyperthermia may be different for each patient, the path to recovery must always be immediate IWI treatment.     

Aortic distensibility is reduced during intense lower body negative pressure and is related to low frequency power of systolic blood pressure

As sympathetic activity approximately doubles during intense lower body negative pressure (LBNP) of ?60 mmHg or greater, we examined the relationship between surrogate markers of sympathetic activation and central arterial distensibility during severe LBNP. Eight participants were exposed to progressive 8-min stages of LBNP of increasing intensity (?20, ?40, ?60, and ?80 mmHg), while recording carotid-femoral pulse wave velocity (cPWV), stroke volume (SV), heart rate, and beat-by-beat blood pressure. The spectral power of low frequency oscillations in SBP (SBP_LF) was used as a surrogate indicator of sympathetically modulated vasomotor modulation. Total arterial compliance (C) was calculated as C = SV/pulse pressure. Both cPWV and C were compared between baseline, 50 % of the maximally tolerated LBNP stage (LBNP₅₀), and the maximum fully tolerated stage of LBNP (LBNP_max). No change in mean arterial pressure (MAP) occurred over LBNP. An increase in cPWV (6.5 ± 2.2; 7.2 ± 1.4; 9.0 ± 2.5 m/s; P = 0.004) occurred during LBNP_max. Over progressive LBNP, SBP_LF increased (8.5 ± 4.6; 9.3 ± 5.8; 16.1 ± 12.9 mmHg²; P = 0.04) and C decreased significantly (18.3 ± 6.8; 14.3 ± 4.1; 11.6 ± 4.8 ml/mmHg × 10; P = 0.03). The mean correlation (r) between cPWV and SBP_LF was 0.9 ± 0.03 (95 % CI 0.79–0.99). Severe LBNP increased central stiffness and reduced total arterial compliance. It appears that increased sympathetic vasomotor tone during LBNP is associated with reduced aortic distensibility in the absence of changes in MAP.     

Validity of bioelectrical impedance and ultrasonographic methods for estimating the muscle volume of the upper arm

The present study aimed to investigate the validity of bioelectrical impedance and ultrasonographic methods for predicting the muscle volume of the upper arm. Bioelectrical impedance of the right upper arm and the thickness of elbow flexor and extensor muscles were measured from 26 healthy young adult men using a specially designed bioelectrical impedance data acquisition system and brightness-mode ultrasound apparatus, respectively. As reference data, the muscle volume (MV_MRI) of the right upper arm was determined using a magnetic resonance imaging method. The impedance index was calculated as L ²/Z, where L is the upper arm length and Z is the impedance of the shoulder to the elbow. The muscle volume (MV_ULT) was calculated as π·(d/2)²·L, where d is muscle thickness. L ²/Z and MV_ULT were significantly correlated with MV_MRI with correlation coefficients of 0.971 and 0.962, respectively. In these relationships, the standard errors of estimation were 44.2 cm³ (6.3%) for L ²/Z and 50.7 cm³ (7.2%) for MV_ULT. There was no significant difference between the absolute errors of muscle volumes estimated by L ²/Z and MV_ULT: 36.2 (4.8, SEM) cm³ for L ²/Z versus 40.3 (5.8) cm³ for MV_ULT. The present results suggest that both bioelectrical impedance and ultrasonographic methods may be useful for predicting the muscle volume of the upper arm. Accepted: 7 March 2000     

Quantification of head sweating during rest and exercise in the heat

The head’s capacity for evaporative heat loss is important for design of protective helmets for use in hot environments. This study quantified head sweating rate (m _sw) in eight males during rest and exercise at three metabolic rates (338 ± 36, 481 ± 24, 622 ± 28 W) in hot-dry (HD: 45 °C, 21 % RH) and hot-wet (HW: 35 °C, 69 % RH) conditions (matched at 31.6 °C WBGT), which were counterbalanced. Heads were shaved, and surface area was (458 ± 61 cm²) measured by 3D scanner. For measurement of head m _sw, dry air was passed through a sealed helmet, whereas for forearm m _sw a capsule (15.9 cm²) was ventilated with ambient air. Evaporation rate was determined from the increase in vapor pressure in the exiting air. Whole-body sweat loss was calculated from the change in nude weight plus fluid intake and corrected for respiratory fluid losses. Head m _sw increased (p = 0.001) with metabolic rate, and was lower (p = 0.018) in HD (0.4 ± 0.2 mg cm^?2 min^?1 at rest to 1.1 ± 0.6 mg cm^?2 min^?1 at 622 W), compared to HW (0.5 ± 0.3–1.4 ± 0.8 mg cm^?2 min^?1). Forearm m _sw increased (p < 0.001) with metabolic rate, but was higher (p = 0.002) in HD (0.4 ± 0.3–1.4 ± 0.7 mg cm^?2 min^?1) than HW (0.1 ± 0.1–1.1 ± 0.3 mg cm^?2 min^?1). Whole-body sweat loss was not significantly different (p = 0.06) between HD (647 ± 139 g m^?2 h^?1) and HW (528 ± 189 g m^?2 h^?1). This study demonstrates the importance of the head for evaporative heat loss, particularly for populations who wear protective clothing which can impair vapor transfer from the skin.     

39K and 23Na relaxation times and MRI of rat head at 21.1 T

At ultrahigh magnetic field strengths (B₀ ≥ 7.0 T), potassium (³⁹K) MRI might evolve into an interesting tool for biomedical research. However, ³⁹K MRI is still challenging because of the low NMR sensitivity and short relaxation times. In this work, we demonstrated the feasibility of ³⁹K MRI at 21.1 T, determined in vivo relaxation times of the rat head at 21.1 T, and compared ³⁹K and sodium (²³Na) relaxation times of model solutions containing different agarose gel concentrations at 7.0 and 21.1 T. ³⁹K relaxation times were markedly shorter than those of ²³Na. Compared with the lower field strength, ³⁹K relaxation times were up to 1.9‐ (T₁), 1.4‐ (T_2S) and 1.9‐fold (T_2L) longer at 21.1 T. The increase in the ²³Na relaxation times was less pronounced (up to 1.2‐fold). Mono‐exponential fits of the ³⁹K longitudinal relaxation time at 21.1 T revealed T₁ = 14.2 ± 0.1 ms for the healthy rat head. The ³⁹K transverse relaxation times were 1.8 ± 0.2 ms and 14.3 ± 0.3 ms for the short (T_2S) and long (T_2L) components, respectively. ²³Na relaxation times were markedly longer (T₁ = 41.6 ± 0.4 ms; T_2S = 4.9 ± 0.2 ms; T_2L = 33.2 ± 0.2 ms). ³⁹K MRI of the healthy rat head could be performed with a nominal spatial resolution of 1 × 1 × 1 mm³ within an acquisition time of 75 min. The increase in the relaxation times with magnetic field strength is beneficial for ²³Na and ³⁹K MRI at ultrahigh magnetic field strength. Our results demonstrate that ³⁹K MRI at 21.1 T enables acceptable image quality for preclinical research. Copyright © 2016 John Wiley & Sons, Ltd.     

The influence of exercise training status on antigen-stimulated IL-10 production in whole blood culture and numbers of circulating regulatory T cells

Highly trained athletes are associated with high resting antigen-stimulated whole blood culture interleukin (IL)-10 production. The purpose of the present study was to examine the effects of training status on resting circulating T regulatory (T_reg) cell counts and antigen-stimulated IL-10 production and the effect of acute bout of exercise on the T_reg response. Forty participants volunteered to participate and were assigned to one of the four groups: sedentary (SED), recreationally active (REC), sprint-trained athletes and endurance-trained athletes (END). From the resting blood sample, CD4⁺CD25⁺CD127^low/? T_reg cells and in vitro antigen-stimulated IL-10 production were assessed. Ten REC subjects performed 60 min cycling at 70 % of maximal oxygen uptake and blood samples for T_reg analysis were collected post- and 1 h post-exercise. IL-10 production was greater in END compared with the other groups (P < 0.05). END had a higher T_reg percentage of total lymphocyte count compared with SED (P < 0.05). A smaller proportion of T_reg CD4⁺ cells were observed in SED compared with all other groups (P < 0.05). IL-10 production significantly correlated with the proportion of T_regs within the total lymphocyte population (r _s  = 0.51, P = 0.001). No effect of acute exercise was evident for T_reg cell counts in the REC subjects (P > 0.05). Our results demonstrate that high training loads in END are associated with greater resting IL-10 production and T_reg cell count and suggest a possible mechanism for depression of immunity commonly reported in athletes engaged in high training loads.     

Do greater rates of body heat storage precede the accelerated reduction of self-paced exercise intensity in the heat?

Aim

To reevaluate the previous hypothesis that greater reductions in self-paced exercise intensity in the heat are mediated by early differences in the rate of body heat storage (S).

Methods

Eight trained volunteers cycled in 19 °C/1.8 kPa (COOL), 25 °C/1.2 kPa (NORM), and 34 °C/1.6 kPa (HOT), while maintaining an RPE of 16. Potential differences in S following the onset of exercise were assessed by comparing rates of esophageal temperature change (ΔT _es/Δt); and estimated S values using a traditional two-compartment thermometric model (S _therm) of changes in rectal (T _re) and skin (T _sk) temperature, and partitional calorimetry (S _cal).

Results

After 15 min of exercise, workload decreased more in HOT vs. COOL (P = 0.03), resulting in a shorter time (HOT: 40.7 ± 14.9 min; COOL: 53.5 ± 18.7 min; P = 0.04) to 70 % of initial workload. However, there were no preceding differences in ΔT _es/Δt between conditions (P = 0.18). S _therm values were different between HOT and COOL during the first 5 min of exercise (P < 0.05), primarily due to negative S _therm values (?32 ± 15 kJ min^?1) in COOL, which according to partitional calorimetric measurements, required improbably high (~56 kJ min^?1) rates of evaporation when no sweating on the back and thigh was observed until after 7.6 ± 1.5 min and 4.8 ± 1.7 min of exercise, respectively. S _cal values in the first 5 min of exercise confirmed S was actually positive in COOL (+21 ± 8 kJ min^?1) and not negative. Different S _therm values following the onset of exercise at different environmental temperatures are simply due to transient differences in the rate of change in T _sk.

Conclusion

Reductions in self-paced exercise intensity in the heat are not mediated by early differences in S following the onset of exercise.     

Assessing neonatal heat balance and physiological strain in newborn infants nursed under radiant warmers in intensive care with fentanyl sedation

Purpose

To assess heat balance status of newborn infants nursed under radiant warmers (RWs) during intensive care.

Methods

Heat balance, thermal status and primary indicators of physiological strain were concurrently measured in 14 newborns nursed under RWs for 105 min. Metabolic heat production (M), evaporative heat loss (E), convective (C) and conductive heat flow (K), rectal temperature (T _re) and mean skin temperatures (T _sk) were measured continuously. The rate of radiant heat required for heat balance (R _req) and the rate of radiant heat provided (R _prov) were derived. The rate of body heat storage (S) was calculated using a two-compartment model of ‘core’ (T _re) and ‘shell’ (T _sk) temperatures.

Results

Mean M, E, C and K were 10.5 ± 2.7 W, 5.8 ± 1.1 W, 6.2 ± 0.8 W and 0.1 ± 0.1 W, respectively. Mean R _prov (1.7 ± 2.6 W) and R _req (1.7 ± 2.7 W) were similar (p > 0.05). However, while the resultant mean change in body heat content after 105 min was negligible (–0.1 ± 3.7 kJ), acute time-dependent changes in S were evidenced by a mean positive heat storage component of +6.4 ± 2.6 kJ and a mean negative heat storage component of –6.5 ± 3.7 kJ. Accordingly, large fluctuations in both T _re and T _sk occurred that were actively induced by changes in RW output. Nonetheless, no active physiological responses (heart rate, breathing frequency and mean arterial pressure) to these bouts of heating and cooling were observed.

Conclusions

RWs maintain net heat balance over a prolonged period, but actively induce acute bouts of heat imbalance that cause rapid changes in T _re and T _sk. Transient bouts of heat storage do not exacerbate physiological strain, but could in the longer term.     

Screening of plant extracts for anthelmintic activity against Dactylogyrus intermedius (Monogenea) in goldfish (Carassius auratus)

With the aim of finding natural anthelmintic agents against Dactylogyrus intermedius (Monogenea) in goldfish (Carassius auratus), 26 plants were screened for antiparasitic properties using in vivo anthelmintic efficacy assay. The results showed that Caesalpinia sappan, Lysima chiachristinae, Cuscuta chinensis, Artemisia argyi, and Eupatorium fortunei were found to have 100 % anthelmintic efficacy at 125, 150, 225, 300, and 500 mg L^?1 after 48 h of exposure. Crude extract of the five plants were further partitioned with petroleum ether, chloroform, ethyl acetate, methanol, and water to obtain anthelmintically active fractions with various polarity. Among these fractions tested, the ethyl acetate extract of L. chiachristinae was found to be the most effective with a 50 % effective concentration (EC₅₀) value of 5.1 mg/L after 48 h of exposure. This was followed by ethyl acetate extract of C. chinensis (48 h-EC₅₀?=?8.5 mg L^?1), chloroform extracts of C. sappan (48 h-EC₅₀?=?15.6 mg L^?1), methanol extract of C. chinensis (48 h-EC₅₀?=?15.9 mg L^?1), and chloroform and petroleum ether extract of L. chiachristinae (EC₅₀ values of 17.2 and 21.1 mg/L, respectively), suggesting that these plants, as well as the active fractions, provide potential sources of botanic drugs for the control of D. intermedius in aquaculture.     

Assessment of methodologies to calculate intraventricular pressure differences in computational models and patients

Intraventricular pressure differences (IVPDs) govern left ventricular (LV) efficient filling and are a significant determinant of LV diastolic function. Our primary aim is to assess the performance of available methods (color M-mode (CMM) and 1D/2D MRI-based methods) to determine IVPDs from intracardiac flow measurements. Performance of three methods to calculate IVPDs was first investigated via an LV computational fluid dynamics (CFD) model. CFD velocity data were derived along a modifiable scan line, mimicking ultrasound/MRI acquisition of 1D (IVPD_CMM/IVPD_{1D MRI}) and 2D (IVPD_{2D MRI}) velocity-based IVPD information. CFD pressure data (IVPD_CFD) was used as a ground truth. Methods were also compared in a small cohort (n = 13) of patients with heart failure with preserved ejection fraction (HFpEF). In silico data showed a better performance of the IVPD_{2D MRI} approach: RMSE values for a well-aligned scan line were 0.2550 mmHg (IVPD_{1D MRI}), 0.0798 mmHg (IVPD_{2D MRI}), and 0.2633 mmHg (IVPD_CMM). In vivo data exhibited moderate correlation between techniques. Considerable differences found may be attributable to different timing of measurements and/or integration path. CFD modeling demonstrated an advantage using 2D velocity information to compute IVPDs, and therefore, a 2D MRI-based method should be favored. However, further studies are needed to support the clinical significance of MRI-based computation of IVPDs over CMM.     

Relationship between core temperature, skin temperature, and heat flux during exercise in heat

Purpose

This paper investigates the relationship between core temperature (T _c), skin temperature (T _s) and heat flux (HF) during exercise in hot conditions.

Method

Nine test volunteers, wearing an Army Combat Uniform and body armor, participated in three sessions at 25 °C/50 % relative humidity (RH); 35 °C/70 % RH; and 42 °C/20 % RH. Each session consisted of two 1-h treadmill walks at ~350 W and ~540 W intensity. T _s and HF from six sites on the forehead, sternum, pectoralis, left rib cage, left scapula, and left thigh, and T _c (i.e., core temperature pill used as a suppository) were measured. Multiple linear regressions were conducted to derive algorithms that estimate T _c from T _s and HF at each site. A simple model was developed to simulate influences of thermal conductivity and thickness of the local body tissues on the relationship between T _c, T _s, and HF.

Results

Coefficient of determination (R ²) ranged from 0.30 to 0.88, varying with locations and conditions. Good sites for T _c measurement at surface were the sternum, and a combination of the sternum, scapula, and rib sites. The combination of T _s and HF measured at the sternum explained ~75 % or more of variance in observed T _c in hot environments. The forehead was found unsuitable for exercise in heat due to sweating and evaporative heat loss. The derived algorithms are likely applicable only for the same ensemble or ensembles with similar thermal and vapor resistances.

Conclusion

Algorithms for T _c measurement are location-specific and their accuracy is dependent, to a large degree, on sensor placement.     

Evaluation of sperm characteristics and plasma testosterone in the goldfish (Carassius auratus) during four consecutive seasons

The overall objective of the study was to investigate changes in quantitative parameters of goldfish (Carassius auratus) semen, testosterone (T), and gonadosomatic index (GSI) during the four seasons of the year (spring, summer, autumn, and winter). Simple environmental and hormonal treatments were used to induce out-of-season spawning in goldfish. The semen was taken from goldfish in different periods during the four seasons, and the characteristics of sperm and pH were analyzed. Plasma levels of T, GSI, and histological studies of the testes, as well as a range of indices of ovarian development, were measured. No significant differences were observed between volumes of semen which can be extracted per fish, in the four seasons (P?>?0.05). Significant differences were found between sperm motility at different seasons (P?<?0.05), as the maximum total duration of motility was observed in autumn (109.25?±?14.00 s). Sperm density showed a higher value during summer (57.30?±?10.41?spermatozoa (spz)?ml^?1) and winter (65.09?±?80.40 spz ml^?1) than values that were obtained from spring (48.00?±?7.08 spz ml^?1) and autumn (40.42?±?16.54?×?10⁹ spz ml^?1) (P?<?0.05). However, spermatocrit (in percent) was higher in winter (39.90?±?4.74) compared with other seasons (P?<?0.05). Values of pH were higher in autumn (7.87?±?0.05) and in winter (7.83?±?0.03) than values that were obtained from other seasons. The peaks of T and GSI during spermiation in spring (T, 21.08 ng/ml, and GSI?=?5.21 %) and in summer (T, 23.32 ng/ml, and GSI?=?6.10 %), when most gonadal development took place, were statistically significantly higher than the levels observed during autumn (T, 15.08 ng/ml, and GSI?=?3.21 %) and winter (T, 22.18 ng/ml, and GSI?=?2.78 %) (P?<?0.05). Our results provided the statistically significant evidence of seasonal variation in sperm characteristics, T and GSI, for goldfish. These findings may be used to: (1) optimize semen collection for hatchery production and (2) characterize the potential impact of seasons on sperm quality and plasma androgen levels.     

Vitamin D supplementation does not improve human skeletal muscle contractile properties in insufficient young males

Purpose

Vitamin D may be a regulator of skeletal muscle function, although human trials investigating this hypothesis are limited to predominantly elderly populations. We aimed to assess the effect of oral vitamin D₃ in healthy young males upon skeletal muscle function.

Methods

Participants (n = 29) received an oral dose of 10,000 IU day^?1 vitamin D₃ (VITD) or a visually identical placebo (PLB) for 3 months. Serum 25[OH]D and intact parathyroid hormone (iPTH) were measured at baseline and at week 4, 8 and 12. Muscle function was assessed in n = 22 participants by isokinetic dynamometry and percutaneous isometric electromyostimulation at baseline and at week 6 and 12.

Results

Baseline mean total serum 25[OH]D was 40 ± 17 and 41 ± 20 nmol L^?1 for PLB and VITD, respectively. VITD showed a significant improvement in total 25[OH]D at week 4 (150 ± 31 nmol L^?1) that remained elevated throughout the trial (P < 0.005). Contrastingly, PLB showed a significant decrease in 25[OH]D at week 12 (25 ± 15 nmol L^?1) compared with baseline. Despite marked increases in total serum 25[OH]D in VITD and a decrease in PLB, there were no significant changes in any of the muscle function outcome measures at week 6 or 12 for either group (P > 0.05).

Conclusions

Elevating total serum 25[OH]D to concentrations > 120 nmol L^?1 has no effect on skeletal muscle function. We postulate that skeletal muscle function is only perturbed in conditions of severe deficiency (<12.5 nmol L^?1).     

Anti-parasitic activities of specific bacterial extracellular products of Streptomyces griseus SDX-4 against Ichthyophthirius multifiliis

The ciliate Ichthyophthirius multifiliis is one of the most pathogenic parasites of fish maintained in captivity. In this study, effects of bacterial extracellular products of Streptomyces griseus SDX-4 against I. multifiliis were determined. The fermentation liquor of S. griseus was extracted successively in a separating funnel with petroleum ether, ethyl acetate, and n-butanol. In vitro assays revealed that the n-butanol extracts (NBu-E) and ethyl acetate extracts (Eto-E) of S. griseus were observed to be more effective against theronts than the other extracts with median effective concentration (EC₅₀) values of 0.86 and 12.5 mg L^?1, respectively, and significantly reduced the survival of the tomonts and the total number of theronts released by the tomonts (P?<?0.05). All encysted tomonts were killed when the concentration of NBu-E was 30.0 mg L^?1. Results of in vivo test demonstrated that the number of I. multifiliis trophonts on the grass carp treated with NBu-E was markedly lower compared to the control group at 11 days after exposed to theronts (P?<?0.05). In the control group, 100 % mortality was observed owing to heavy I. multifiliis infection at 11 days after the exposure. On the other hand, only 9.5 % mortality owing to parasite infection was recorded in the groups treated with the NBu-E (30 mg L^?1). The median lethal dose (LD₅₀) of NBu-E for grass carp was 152.4 mg L^?1. Our results indicate that n-butanol extract of S. griseus will be useful in aquaculture for controlling I. multifiliis infections.     

The effects of aerobic exercise training at two different intensities in obesity and type 2 diabetes: implications for oxidative stress, low-grade inflammation and nitric oxide production

Aims

To investigate the effect of 16 weeks of aerobic training performed at two different intensities on nitric oxide (tNOx) availability and iNOS/nNOS expression, oxidative stress (OS) and inflammation in obese humans with or without type 2 diabetes mellitus (T2DM).

Methods

Twenty-five sedentary, obese (BMI > 30 kg/m²) males (52.8 ± 7.2 years); 12 controls versus 13 T2DM were randomly allocated to four groups that exercised for 30 min, three times per week either at low (Fat-Max; 30–40 % VO_2max) or moderate (T _vent; 55–65 % VO_2max) intensity. Before and after training, blood and muscle samples (v. lateralis) were collected.

Results

Baseline erythrocyte glutathione was lower (21.8 ± 2.8 vs. 32.7 ± 4.4 nmol/ml) and plasma protein oxidative damage and IL-6 were higher in T2DM (141.7 ± 52.1 vs. 75.5 ± 41.6 nmol/ml). Plasma catalase increased in T2DM after T _vent training (from 0.98 ± 0.22 to 1.96 ± 0.3 nmol/min/ml). T2DM groups demonstrated evidence of oxidative damage in response to training (elevated protein carbonyls). Baseline serum tNOx were higher in controls than T2DM (18.68 ± 2.78 vs. 12.34 ± 3.56 μmol/l). Training at T _vent increased muscle nNOS and tNOx in the control group only. Pre-training muscle nNOS was higher in controls than in T2DMs, while the opposite was found for iNOS. No differences were found after training for plasma inflammatory markers.

Conclusion

Exercise training did not change body composition or aerobic fitness, but improved OS markers, especially when performed at T _vent. Non-diabetics responded to T _vent training by increasing muscle nNOS expression and tNOx levels in skeletal muscle while these parameters did not change in T2DM, perhaps due to higher insulin resistance (unchanged after intervention).     

External muscle heating during warm-up does not provide added performance benefit above external heating in the recovery period alone

Purpose

Having previously shown the use of passive external heating between warm-up completion and sprint cycling to have had a positive effect on muscle temperature (T _m) and maximal sprint performance, we sought to determine whether adding passive heating during active warm up was of further benefit.

Methods

Ten trained male cyclists completed a standardised 15 min sprint based warm-up on a cycle ergometer, followed by 30 min passive recovery before completing a 30 s maximal sprint test. Warm up was completed either with or without additional external passive heating. During recovery, external passive leg heating was used in both standard warm-up (CONHOT) and heated warm-up (HOTHOT) conditions, for control, a standard tracksuit was worn (CON).

Results

T _m declined exponentially during CON, CONHOT and HOTHOT reduced the exponential decline during recovery. Peak (11.1 %, 1561 ± 258 W and 1542 ± 223 W), relative (10.6 % 21.0 ± 2.2 W kg^–1 and 20.9 ± 1.8 W kg^–1) and mean (4.1 %, 734 ± 126 W and 729 ± 125 W) power were all improved with CONHOT and HOTHOT, respectively compared to CON (1,397 ± 239 W; 18.9 ± 3.0 W kg^–1 and 701 ± 109 W). There was no additional benefit of HOTHOT on T _m or sprint performance compared to CONHOT.

Conclusion

External heating during an active warm up does not provide additional physiological or performance benefit. As noted previously, external heating is capable of reducing the rate of decline in T _m after an active warm-up, improving subsequent sprint cycling performance.     

Haemodynamic responses to dehydration in the resting and exercising human leg

Dehydration and hyperthermia reduces leg blood flow (LBF), cardiac output ( $ \dot{Q} $ ) and arterial pressure during whole-body exercise. It is unknown whether the reductions in blood flow are associated with dehydration-induced alterations in arterial blood oxygen content (C _aO₂) and O₂-dependent signalling. This study investigated the impact of dehydration and concomitant alterations in C _aO₂ upon LBF and $ \dot{Q} $ . Haemodynamics, arterial and femoral venous blood parameters and plasma [ATP] were measured at rest and during one-legged knee-extensor exercise in 7 males in four conditions: (1) control, (2) mild dehydration, (3) moderate dehydration, and (4) rehydration. Relative to control, C _aO₂ and LBF increased with dehydration at rest and during exercise (C _aO₂: from 199 ± 1 to 208 ± 2, and 202 ± 2 to 210 ± 2 ml L^?1 and LBF: from 0.38 ± 0.04 to 0.77 ± 0.09, and 1.64 ± 0.09 to 1.88 ± 0.1 L min^?1, respectively). Similarly, $ \dot{Q} $ was unchanged or increased with dehydration at rest and during exercise, whereas arterial and leg perfusion pressures declined. Following rehydration, C _aO₂ declined (to 193 ± 2 mL L^?1) but LBF remained elevated. Alterations in LBF were unrelated to C _aO₂ (r ² = 0.13–0.27, P = 0.48–0.64) and plasma [ATP]. These findings suggest dehydration and concomitant alterations in C _aO₂ do not compromise LBF despite reductions in plasma [ATP]. While an additive or synergistic effect cannot be excluded, reductions in LBF during exercise with dehydration may not necessarily be associated with alterations in C _aO₂ and/or intravascular [ATP].     

Short-term high-intensity interval and continuous moderate-intensity training improve maximal aerobic power and diastolic filling during exercise

Purpose

This study examined the effects of short-term high-intensity interval training (HIT) and continuous moderate-intensity training (CMT) on cardiac function in young, healthy men.

Methods

Sixteen previously untrained men (mean age of 25.1 ± 4.1 years) were randomly assigned to HIT and CMT (n = 8 each) and assessed before and after six sessions over a 12-day training period. HIT consisted of 8–12 intervals of cycling for 60 s at 95–100 % of pre-training maximal aerobic power ( $\dot{V}$ O_2max), interspersed by 75 s of cycling at 10 % $\dot{V}$ O_2max. CMT involved 90–120 min of cycling at 65 % pre-training $\dot{V}$ O_2max. Left ventricular (LV) function was determined at rest and during submaximal exercise (heart rate ~105 bpm) using two-dimensional and Doppler echocardiography.

Results

Training resulted in increased calculated plasma volume (PV) in both groups, accompanied by improved $\dot{V}$ O_2max in HIT (HIT: from 39.5 ± 7.1 to 43.9 ± 5.5 mL kg^?1 min^?1; CMT: from 39.9 ± 5.9 to 41.7 ± 5.3 mL kg^?1 min^?1; P < 0.001). Resting LV function was not altered. However, increased exercise stroke volume (P = 0.02) and cardiac output (P = 0.02) were observed, secondary to increases in end-diastolic volume (P < 0.001). Numerous Doppler and speckle tracking indices of diastolic function were similarly enhanced during exercise in both training groups and were related to changes in PV.

Conclusion

Short-term HIT and CMT elicit rapid improvements in $\dot{V}$ O_2max and LV filling without global changes in cardiac performance at rest.     

Biophysical and biochemical characterization of virus-like particles containing a high molecular weight ds-RNA from Helminthosporium maydis.

Spherical virus-like particles (VLPs_ isolated from Helminthosporium maydis ATCC 32450 are 48 in diameter and have three serologically identical components which have the following properties: s_20,w = 152, 212, and 283; ? (in CsCl) = 1.298, 1.378, and 1.438 g cm^?3; percentage of RNA = 0, 17, and 32; and molecular weight = 14, 17, and 21 × 10⁶. The nucleic acid of the fastest sedimenting component is double-stranded and has the following properties: s_20,w = 20.69; T_m = 79.6°; ? (in Cs₂SO₄) = 1.6062 g cm^?3.; molecular weight = 6.3 ± 0.5 × 10⁶.