Effects of Cold Water Immersion and Active Recovery on Post-Exercise Heart Rate Variability

The aim of the present study was to investigate the potential benefits of cold water immersion (CWI) and active recovery (AR) on blood lactate concentration ([Lac]) and heart rate variability (HRV) indices following high-intensity exercise. 20 male subjects were recruited. on the first visit, an incremental test was performed to determine maximal oxygen consumption and the associated speed (MAS). The remaining 3 visits for the performance of constant velocity exhaustive tests at MAS and different recovery methods (6 min) were separated by 7-day intervals [randomized: CWI, AR or passive recovery (PR)]. The CWI and AR lowered [Lac] (p < 0.05) at 11, 13 and 15 min after exercise cessation in comparison to PR. There was a 'time' and 'recovery mode' interaction for 2 HRV indices: standard deviation of normal R-R intervals (SDNN) (partial eta squared = 0.114) and natural log of low-frequency power density (lnLF) (partial eta squared = 0.090). CWI presented significantly higher SDNN compared to PR at 15 min of recovery (p < 0.05). In addition, greater SDNN values were found in CWI vs. AR during the application of recovery interventions, and at 30 and 75 min post-exercise (p < 0.05 for all differences). The lnLF during the recovery interventions and at 75 min post-exercise was greater using CWI compared with AR (p < 0.05). For square root of the mean of the sum of the squares of differences between adjacent R-R intervals (RMSSD) and natural log of high-frequency power density (lnHF), a moderate effect size was found between CWI and PR during the recovery interventions and at 15 min post-exercise. Our findings show that AR and CWI offer benefits regarding the removal of [Lac] following high-intensity exercise. While limited, CWI results in some improvement in post-exercise cardiac autonomic regulation compared to AR and PR. Further, AR is not recommended if the aim is to accelerate the parasympathetic reactivation.

Energy Expenditure and Oxygen Consumption as Novel Biomarkers of Obesity-induced Cardiac Disease in Rats

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Oxygen consumption of the amphibious snail Pomacea lineata; Influence of weight, sex and environments

1. 1. Under normoxic conditions at 25°C Pomacea lineata, free to move into or out of water, showed an increase in O2 consumption with increase in body size (dry wt), the slope of the log-log plot of these two parameters being b = 0.76. 2. 2. The metabolic rate decreased with weight. 3. 3. Males and females in a sexually receptive state did not exhibit significantly different QO2 values. 4. 4. The metabolic rates of animals when under water using ctenidium did not differ significantly from when out of water using the lung. © 1981.

The respiratory responses of an amphibious snail Pomacea lineata (spix, 1827), to temperature and oxygen tension variations

1. 1. The respiratory responses of Pomacea lineata to short-term (or acute) exposure to temperature and oxygen tension variations were investigated in animals acclimated to 25°C. 2. 2. The respiratory rates increased with rising temperatures; this increase was sharper between 15 and 25°C than at any other temperature interval; a tendency to a plateau in the RT curve was recorded between 25 and 35°C. 3. 3. All animals survived well to 1 hr exposure to the extreme temperatures used (5 and 40°C). 4. 4. In two different experimental approaches, the animals showed ability to regulate the respiratory rate in declining oxygen tensions, at least down to 10% (70.8 mmHg) oxygen. 5. 5. After 1 hr exposure to hypoxic conditions, P. lineata exhibited the pattern of underpayment of the oxygen debt acquired. 6. 6. Six out of ten animals survived after 40 days in anoxia (100% nitrogen). © 1987.

Protective effect of nickel chloride on superoxide damage: enhancement of CuZn superoxide dismutase affinity to the oxygen free radical.

The effect of nickel from soluble NiCl2 on Cu-Zn superoxide dismutase (SOD) activity, as well as on rate of nitro blue tetrazolium reduction, was studied in vitro since lipid peroxidation has been implicated in cell damage by nickel insoluble compounds, whose toxicity and carcinogenicity are well established. The physical and chemical nature of nickel compounds is one of the key determinations of its toxicity. Soluble nickel freely enter cells, but is just as readily excreted reducing the opportunity for production of lipid damage. Nickel from NiCl2 strongly activated SOD activity. In vitro addition of nickel chloride to a crude lung preparation altered the KM for SOD without changing the Vmax. Nickel chloride produced increased enzyme affinity to the substrate, because decreased (O2-) concentration that yields half-maximal velocity. The combination of nickel and SOD may contribute to stabilization of the particular conformation of SOD responsible for maximal catalytically activity.

Increased oxygen radical and high-dietary-carbohydrate pancreatic damage.

These data suggest that an improved understanding of the relationship between high dietary carbohydrate and the rate of lipid peroxidation may give some insight into possible treatment modalities for pancreatic damages and may shed light on molecular mechanisms underlying certain pathological processes. High dietary carbohydrate lesions are age related and induced alterations on ceruloplasmin, phospholipids, total proteins, copper and zinc serum levels. Significantly increased serum and pancreatic amylase, and lipoperoxide determinations were observed in 20 month old rats. Cu-Zn superoxide dismutase was decreased in these animals. Daily injection of Cu-Zn superoxide dismutase conjugated with polyethylene glycol (SOD-PEG) prevented the serum and pancreatic changes, indicating that superoxide radical is an important intermediate to high dietary carbohydrate lesion.

Electrocardiographic evolution in cats from birth to 30 days of age

Further knowledge of feline physiology and neonatology is needed because the number of cats being kept as pets and used as experimental animals has increased. Few studies have been published on feline sequential electrocardiography. This study was conducted to determine the values of normal waves, complexes, and intervals of the electrocardiogram in clinically healthy feline neonates. Serial electrocardiography was performed in 15 female and 15 male neonates at 30 days of age. Parameters analyzed were heart rate and rhythm, duration and amplitude of electrocardiographic waves, duration of intervals, and the electrical axis of the heart. The results did not show differences between males and females. During the neonates' first 30 days of life, migration of the electrical axis from right to left was observed. There was a progressive increase in the R wave amplitude, while the S wave amplitude showed a progressive decrease. A sinus heart rhythm was predominant in the feline neonates.

Small-angle x-ray scattering study of the structural evolution of the drying of sonogels with the liquid phase exchanged by acetone

The structural evolution on the drying of wet sonogels of silica with the liquid phase exchanged by acetone, obtained from tetraethoxisilane sonohydrolysis, was studied in situ by small-angle x-ray scattering (SAXS). The periods associated to the structural evolution as determined by SAXS are in agreement with those classical ones established on basis of the features of the evaporation rate of the liquid phase in the obtaining of xerogels. The wet gel can be described as formed by primary particles (microclusters), with characteristic length a ∼ 0.67 nm and surface which is fractal, linking together to form mass fractal structures with mass fractal dimension D=2.24 in a length scale ξ∼6.7 nm. As the network collapses while the liquid/vapor meniscus is kept out of the gel volume, the mass fractal structure becomes more compacted by increasing D and decreasing ξ, with smoothing of the fractal surface of the microclusters. The time evolution of the density of the wet gels was evaluated exclusively from the SAXS parameters ξ, D, and a. The final dried acetone-exchanged gel presents Porod's inhomogeneity length of about 2.8 nm and apparently exhibits an interesting singularity D →3, as determined by the mass fractal modeling used to fit the SAXS intensity data for the obtaining of the parameters ξ and D.

Effect of lithium doping on the evolution of rheological and structural properties during gelation of siloxane-poly(oxypropylene) nanocomposites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Microstructure evolution during warm deformation of low carbon steel with dispersed cementite

The microstructure evolution and mechanical behavior during large strain of a 0.16%C-Mn steel has been investigated by warm torsion tests. These experiments were carried out at 685°C at equivalent strain rate of 0.1 s . The initial microstructure composed of a martensite matrix with uniformly dispersed fine cementite particles was attained by quenching and tempering. The microstructure evolution during tempering and straining was performed through interrupted tests. As the material was reheated to testing temperature, well-defined cell structure was created and subgrains within lath martensite were observed by TEM; strong recovery took place, decreasing the dislocation density. After 1 hour at the test temperature and without straining, EBSD technique showed the formation of new grains. The flow stress curves measured had a peculiar shape: rapid work hardening to a hump, followed by an extensive flow-softening region. 65% of the boundaries observed in the sample strained to ε = 1.0 were high angle grain boundaries. After straining to ε = 5.0, average ferrite grain size close to 1.5 μm was found, suggesting that dynamic recrystallization took place. Also, two sets of cementite particles were observed: large particles aligned with straining direction and smaller particles more uniformly dispersed. The fragmentation or grain subdivision that occurred during reheating and tempering time was essential for the formation of ultrafine grained microstructure.

The effect of eccentric strength training on heart rate and on its variability during isometric exercise in healthy older men

The purpose of this study was to investigate if chronic eccentric strength training (ST) affects heart rate (HR) and heart rate variability (HRV) during sub-maximal isometric voluntary contractions (SIVC). The training group (TG) (9 men, 62 ± 2) was submitted to ST (12 weeks, 2 days/week, 2 - 4 sets of 8-12 repetitions at 75-80% peak torque (PT). The control group (CG) (8 men, 64 ± 4) did not perform ST. The HR and the HRV (RMSSD index) were evaluated during SIVC of the knee extension (15, 30 and 40% of PT). ST increased the eccentric torque only in TG, but did not change the isometric PT and the duration of SIVC. During SIVC, the HR response pattern and the RMSSD index were similar for both groups in pre- and post-training evaluations. Although ST increased the eccentric torque in the TG, it did not generate changes in HR or HRV. © Springer-Verlag 2008.

Estresse oxidativo nos estágios finais da doença renal crônica em pequenos animais

The chronic kidney disease (CKD) it is characterized by irreversible structural lesions that can develop progressively for uremia and chronic renal failure (CRF). In the CRF it happens the incapacity of executing the functions of maintenance of the electrolyte balance and acid-base, catabolitos excretion and hormonal regulation appropriately. When the mechanism basic physiopathology of the renal upset is analyzed, it is observed that present factors, predispose to the unbalance oxidative. Most of the time, the renal patient comes badly nurtured, with lack in reservations of vitamins and minerals, what reduces the antioxidant defense mechanisms, what favors the installation of the renal oxidative stress, with the formation of species you reactivate of reactive oxygen species (ROS), substances these potentially harmful to the organism. The reduction of the glomerular filtration rate (GFR) in the evolution of CKD in dogs and cats is a component for the installation of the renal oxidative stress. The ROS possesses important action in the kidneys, and these substances are highly reactivate, and when presents in excess damage lipids, proteins, DNA and carbohydrate, driving functional and structural abnormalities taking the cellular apoptosis and necrosis. Against the harmful potential action of these substances you reactivate, she becomes fundamental a delicate control of his production and consumption in the half intracellular, in other words, a balance of his concentration intra and extracellular. That is possible due to the activity of the antioxidants. Like this, to present literature revision had as objective describes the participation of the oxidative stress in CRF, as well as the mechanisms defenses against the harmful action of those substances.

Continuous measurement of cerebral oxygen saturation (rSO 2) for assessment of cardiovascular status during hemorrhagic shock in a swine model

Background: Early trauma care is dependent on subjective assessments and sporadic vital sign assessments. We hypothesized that near-infrared spectroscopy-measured cerebral oxygenation (regional oxygen saturation [rSO 2]) would provide a tool to detect cardiovascular compromise during active hemorrhage. We compared rSO 2 with invasively measured mixed venous oxygen saturation (SvO2), mean arterial pressure (MAP), cardiac output, heart rate, and calculated pulse pressure. Methods: Six propofol-anesthetized instrumented swine were subjected to a fixed-rate hemorrhage until cardiovascular collapse. rSO 2 was monitored with noninvasively measured cerebral oximetry; SvO2 was measured with a fiber optic pulmonary arterial catheter. As an assessment of the time responsiveness of each variable, we recorded minutes from start of the hemorrhage for each variable achieving a 5%, 10%, 15%, and 20% change compared with baseline. Results: Mean time to cardiovascular collapse was 35 minutes ± 11 minutes (54 ± 17% total blood volume). Cerebral rSO 2 began a steady decline at an average MAP of 78 mm Hg ± 17 mm Hg, well above the expected autoregulatory threshold of cerebral blood flow. The 5%, 10%, and 15% decreases in rSO 2 during hemorrhage occurred at a similar times to SvO2, but rSO 2 lagged 6 minutes behind the equivalent percentage decreases in MAP. There was a higher correlation between rSO 2 versus MAP (R =0.72) than SvO2 versus MAP (R =0.55). Conclusions: Near-infrared spectroscopy- measured rSO 2 provided reproducible decreases during hemorrhage that were similar in time course to invasively measured cardiac output and SvO2 but delayed 5 to 9 minutes compared with MAP and pulse pressure. rSO 2 may provide an earlier warning of worsening hemorrhagic shock for prompt interventions in patients with trauma when continuous arterial BP measurements are unavailable. © 2012 Lippincott Williams & Wilkins.

On Hepatitis C Virus Evolution: The Interaction between Virus and Host towards Treatment Outcome

Background:Hepatitis C is a disease spread throughout the world. Hepatitis C virus (HCV), the etiological agent of this disease, is a single-stranded positive RNA virus. Its genome encodes a single precursor protein that yields ten proteins after processing. NS5A, one of the non-structural viral proteins, is most associated with interferon-based therapy response, the approved treatment for hepatitis C in Brazil. HCV has a high mutation rate and therefore high variability, which may be important for evading the immune system and response to therapy. The aim of this study was to analyze the evolution of NS5A quasispecies before, during, and after treatment in patients infected with HCV genotype 3a who presented different therapy responses.Methods:Viral RNA was extracted, cDNA was synthesized, the NS5A region was amplified and cloned, and 15 clones from each time-point were sequenced. The sequences were analyzed for evolutionary history, genetic diversity and selection.Results:This analysis shows that the viral population that persists after treatment for most non-responder patients is present in before-treatment samples, suggesting it is adapted to evade treatment. In contrast, the population found in before treatment samples from most end-of-treatment responder patients either are selected out or appears in low frequency after relapse, therefore changing the population structure. The exceptions illustrate the uniqueness of the evolutionary process, and therefore the treatment resistance process, in each patient.Conclusion:Although evolutionary behavior throughout treatment showed that each patient presented different population dynamics unrelated to therapy outcome, it seems that the viral population from non-responders that resists the treatment already had strains that could evade therapy before it started. © 2013 Bittar et al.

Ablation of the ability to control the right-to-left cardiac shunt does not affect oxygen uptake, specific dynamic action or growth in the rattlesnake Crotalus durissus

The morphologically undivided ventricle of the heart in non-crocodilian reptiles permits the mixing of oxygen-rich blood returning from the lungs and oxygen-poor blood from the systemic circulation. A possible functional significance for this intra-cardiac shunt has been debated for almost a century. Unilateral left vagotomy rendered the single effective pulmonary artery of the South American rattlesnake, Crotalus durissus, unable to adjust the magnitude of blood flow to the lung. The higher constant perfusion of the lung circulation and the incapability of adjusting the right-left shunt in left-denervated snakes persisted over time, providing a unique model for investigation of the long-term consequences of cardiac shunting in a squamate. Oxygen uptake recorded at rest and during spontaneous and forced activity was not affected by removing control of the cardiac shunt. Furthermore, metabolic rate and energetic balance during the post-prandial metabolic increment, plus the food conversion efficiency and growth rate, were all similarly unaffected. These results show that control of cardiac shunting is not associated with a clear functional advantage in adjusting metabolic rate, effectiveness of digestion or growth rates. © 2013. Published by The Company of Biologists Ltd.