Environment and feeding change the ability of heart rate to predict metabolism in resting Steller sea lions (<Emphasis Type="Italic">Eumetopias jubatus</Emphasis>)

The ability to use heart rate (fh) to predict oxygen consumption rates ( [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} ) in Steller sea lions and other pinnipeds has been investigated in fasting animals. However, it is unknown whether established fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationships hold under more complex physiological situations, such as when animals are feeding or digesting. We assessed whether fh could accurately predict [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} in trained Steller sea lions while fasting and after being fed. Using linear mixed-effects models, we derived unique equations to describe the fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship for fasted sea lions resting on land and in water. Feeding did not significantly change the fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship on land. However, Steller sea lions in water displayed a different fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} relationship after consuming a 4-kg meal compared with the fasting condition. Incorporating comparable published fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} data from Steller sea lions showed a distinct effect of feeding after a 6-kg meal. Ultimately, our study illustrated that both feeding and physical environment are statistically relevant when deriving [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} from telemetered fh, but that only environment affects the practical ability to predict metabolism from fh. Updating current bioenergetic models with data gathered using these predictive fh: [(V)\dot]_\textO2 \dot{V}_{{{\text{O}}_{2} }} equations will yield more accurate estimates of metabolic rates of free-ranging Steller sea lions under a variety of physiological, behavioral, and environmental states.     

Cardiorespiratory responses to hypoxia in the African catfish, <Emphasis Type="Italic">Clarias gariepinus</Emphasis> (Burchell 1822), an air-breathing fish

The African catfish, Clarias gariepinus, possesses a pair of suprabranchial chambers located in the dorsal-posterior part of the branchial cavity having extensions from the upper parts of the second and fourth gill arches, forming the arborescent organs. This structure is an air-breathing organ (ABO) and allows aerial breathing (AB). We evaluated its cardiorespiratory responses to aquatic hypoxia. To determine the mode of air-breathing (obligate or accessory), fish had the respiratory frequency (f _R) monitored and were subjected to normoxic water (PwO₂ = 140 mmHg) without becoming hyperactive for 30 h. During this period, all fish survived without displaying evidences of hyperactivity and maintained unchanged f _R, confirming that this species is a facultative air-breather. Its aquatic O₂ uptake ( [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} ) was maintained constant down to a critical PO₂ (PcO₂) of 60 mmHg, below which [(V)\dot]\textO₂ \dot{V}{\text{O}}_{2} declined linearly with further reductions of inspired O₂ tension (PiO₂). Just above the PcO₂ the ventilatory tidal volume (V _T) increased significantly along with gill ventilation ( [(V)\dot]_\textG \dot{V}_{\text{G}} ), while f _R changed little. Consequently, the water convection requirement ( [(V)\dot]_\textG /[(V)\dot]\textO₂ ) \left( {\dot{V}_{\text{G}} /\dot{V}{\text{O}}_{2} } \right) increased steeply. This threshold applied to a cardiac response that included reflex bradycardia. AB was initiated at PiO₂ = 140 mmHg (normoxia) and air-breathing episodes increased linearly with more severe hypoxia, being significantly higher at PiO₂ tensions below the PcO₂. Air-breathing episodes were accompanied by bradycardia pre air-breath, to tachycardia post air-breath.     

AMP-activated protein kinase plays a role in initiating metabolic rate suppression in goldfish hepatocytes

In the present study, we test the hypothesis that AMP-activated protein kinase (AMPK) initiates metabolic rate suppression in isolated goldfish hepatocytes. To accomplish this, we attempted to pharmacologically activate AMPK in goldfish hepatocytes with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR) and the thienopyridone, A769662, to examine the effects of AMPK activation on eukaryotic elongation factor-2 (eEF2), protein synthesis, and cellular oxygen consumption rate ( [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} ). Goldfish hepatocytes treated with 1 mM AICAR under normoxic conditions (>200 μM O₂) showed a modest but significant 1.1-fold increase in AMPK phosphorylation, a 7.5-fold increase in AMPK activity, a 1.4-fold increase in eEF2 phosphorylation, and a 24% decrease in [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} . At physiologically relevant [O₂] (<40 μM O₂), the addition of 1 mM AICAR resulted in only a 13% decrease in cellular [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} with no change in sensitivity to [O₂] as assessed by estimates of cellular P₅₀ and P₉₀ values. The addition of compound C, a general protein kinase inhibitor, after AICAR incubation did not reverse the effects of AICAR on [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} in normoxia. Treatment of hepatocytes with ≤200 μM A769662 did not affect AMPK activity, AMPK phosphorylation, eEF2 phosphorylation, or cellular [(M)\dot]_{\textO 2} \dot{M}_{{{\text{O}}_{ 2} }} . These data suggest that A769662 is not an activator of AMPK in goldfish hepatocytes. Although our study provides support for the hypothesis that AMPK plays a role in initiating metabolic rate suppression in goldfish hepatocytes, this support must be viewed cautiously because of the known off-target effects of the pharmacological agents used.     

Oxygen-dependence of metabolic rate in the muscles of craniates

We present evidence that oxygen consumption (V_\textO2 ) (V_{{{\text{O}}_{2} }} ) is oxygen partial pressure (P_\textO2 ) (P_{{{\text{O}}_{2} }} ) dependent in striated muscles and P_\textO2 P_{{{\text{O}}_{2} }} -independent in the vasculature in representatives of three craniate taxa: two teleost fish, a hagfish and a rat. Blood vessel V_\textO2 V_{{{\text{O}}_{2} }} displayed varying degrees of independence in a P_\textO2 P_{{{\text{O}}_{2} }} range of 15–95 mmHg, while V_\textO2 V_{{{\text{O}}_{2} }} by striated muscle tissue slices from all species related linearly to P_\textO2 P_{{{\text{O}}_{2} }} between 0 and 125 mmHg, despite V_\textO2 V_{{{\text{O}}_{2} }} rates varying greatly between species and muscle type. In salmon red muscle, lactate concentrations fell in slices incubated at a P_\textO2 P_{{{\text{O}}_{2} }} of either 30 or 100 mmHg, suggesting aerobic rather than anaerobic metabolism. Consistent with this finding, potential energy, a proxy of ATP turnover, was P_\textO2 P_{{{\text{O}}_{2} }} -dependent. Our data suggest that the reduction in V_\textO2 V_{{{\text{O}}_{2} }} with falling P_\textO2 P_{{{\text{O}}_{2} }} results in a decrease in ATP demand, suggesting that the hypoxic signal is sensed and cellular changes effected. Viability and diffusion limitation of the preparations were investigated using salmon cardiac and skeletal muscles. Following the initial P_\textO2 P_{{{\text{O}}_{2} }} depletion, reoxygenation of the Ringer bathing salmon cardiac muscle resulted in V_\textO2 \texts V_{{{\text{O}}_{2} }} {\text{s}} that was unchanged from the first run. V_\textO2 V_{{{\text{O}}_{2} }} increased in all muscles uncoupled with p-trifluoromethoxylphenyl-hydrazone (FCCP) and 2,4-dinitrophenol (DNP). Mitochondrial succinate dehydrogenase activity, quantified by reduction of 3-(4,5-dimethylthiazol)-2,5-diphenyl-2H-tetrazolium bromide (MTT) to formazan, was constant over the course of the experiment. These three findings indicate that the tissues remained viable over time and ruled out diffusion-limitation as a constraint on V_\textO2 V_{{{\text{O}}_{2} }} .     

Effects of environmental oxygen on development and respiration of Australian lungfish (<Emphasis Type="Italic">Neoceratodus forsteri</Emphasis>) embryos

The effects of oxygen partial pressure ( P_\textO2 P_{{{\text{O}}_{2} }} ) on development and respiration were investigated in the eggs of the Australian lungfish, Neoceratodus forsteri. At 20°C, embryonic survival and development was optimal at 15 and 20.9 kPa. Development was slowed at 5 and 10 kPa and embryos did not survive 2 kPa. At lower P_\textO2 P_{{{\text{O}}_{2} }} , the rate of oxygen consumption also decreased. Embryos responded to hypoxia by hatching at an earlier age and stage of development, and hatching wet and dry gut-free masses were reduced. The role of oxygen conductance ( G_\textO2 G_{{{\text{O}}_{2} }} ) in gas exchange was also examined under selected environmental P_\textO2 P_{{{\text{O}}_{2} }} and temperatures. The breakdown of the vitelline membrane changed capsule geometry, allowed water to be absorbed into the perivitelline space and increased capsule G_\textO2 G_{{{\text{O}}_{2} }} . This occurred at embryonic stage 32 under all treatments and was largely independent of both P_\textO2 P_{{{\text{O}}_{2} }} and temperature (15, 20 and 25°C), demonstrating that capsule G_\textO2 G_{{{\text{O}}_{2} }} cannot adaptively respond to altered environmental conditions. The membrane breakdown increased capsule diffusive G_\textO2 G_{{{\text{O}}_{2} }} and stabilised perivitelline P_\textO2 P_{{{\text{O}}_{2} }} , but reduced the convective G_\textO2 G_{{{\text{O}}_{2} }} of the perivitelline fluid, as the large perivitelline volume and inadequate convective current resulted in a P_\textO2 P_{{{\text{O}}_{2} }} gradient within the egg prior to hatch.     

The effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis)

To investigate the effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis), we measured the following: (1) the resting oxygen consumption rate $ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{rest}}}} } \right) $ , critical swimming speed (U _crit) and active oxygen consumption rate $ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} } \right) $ of fish at acclimation temperatures of 10, 15, 20, 25 and 30 °C and (2) the $ \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $ , U _crit and $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ of both exercise-trained (exhaustive chasing training for 14 days) and control fish at both low and high acclimation temperatures (15 and 25 °C). The relationship between U _crit and temperature (T) approximately followed a bell-shaped curve as temperature increased: U _crit = 8.21/{1 + [(T ? 27.2)/17.0]²} (R ² = 0.915, P < 0.001, N = 40). The optimal temperature for maximal U _crit (8.21 BL s^?1) in juvenile qingbo was 27.2 °C. Both the $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ and the metabolic scope (MS, $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} - \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $ ) of qingbo increased with temperature from 10 to 25 °C (P < 0.05), but there were no significant differences between fish acclimated to 25 and 30 °C. The relationships between $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ or MS and temperature were described as $ {\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} = 1,214.29/\left\{ {1 + \left[ {\left( {T - 28.8} \right)/10.6} \right]^{2} } \right\}\;\left( {R^{2} = 0.911,\;P < 0.001,\;N = 40} \right) $ and MS = 972.67/{1 + [(T ? 28.0)/9.34]²} (R ² = 0.878, P < 0.001, N = 40). The optimal temperatures for $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ and MS in juvenile qingbo were 28.8 and 28.0 °C, respectively. Exercise training resulted in significant increases in both U _crit and $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ at a low temperature (P < 0.05), but training exhibited no significant effect on either U _crit or $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ at a high temperature. These results suggest that exercise training had different effects on swimming performance at different temperatures. These differences may be related to changes in aerobic metabolic capability, arterial oxygen delivery, available dissolved oxygen, imbalances in ion fluxes and stimuli to remodel tissues with changes in temperature.     

Transition from octahedral to tetrahedral geometry causes the activation or inhibition by Zn<Superscript>2+</Superscript> of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> phosphorylcholine phosphatase

Pseudomonas aeruginosa phosphorylcholine phosphatase (PchP) catalyzes the hydrolysis of phosphorylcholine, which is produced by the action of hemolytic phospholipase C on phosphatidylcholine or sphyngomielin, to generate choline and inorganic phosphate. Among divalent cations, its activity is dependent on Mg²⁺ or Zn²⁺. Mg²⁺ produced identical activation at pH 5.0 and 7.4, but Zn²⁺ was an activator at pH 5.0 and became an inhibitor at pH 7.4. At this higher pH, very low concentrations of Zn²⁺ inhibited enzymatic activity even in the presence of saturating Mg²⁺ concentrations. Considering experimental and theoretical physicochemical calculations performed by different authors, we conclude that at pH 5.0, Mg²⁺ and Zn²⁺ are hexacoordinated in an octahedral arrangement in the PchP active site. At pH 7.4, Mg²⁺ conserves the octahedral coordination maintaining enzymatic activity. The inhibition produced by Zn²⁺ at 7.4 is interpreted as a change from octahedral to tetrahedral coordination geometry which is produced by hydrolysis of the [ \textZn ²⁺ \textL ₂ ^{- 1} \textL ₂⁰ ( \textH ₂ \textO ) ₂ ] \left[ {{\text{Zn}}^{ 2+ } {\text{L}}_{ 2}^{ - 1} {\text{L}}_{ 2}^{0} \left( {{\text{H}}_{ 2} {\text{O}}} \right)_{ 2} } \right] complex.     

Oxygen removal from water versus arterial oxygen delivery: calibrating the Fick equation in Pacific salmon

While it is well known that O₂ is directly removed from the water by skin and gill tissues of fish, the mismatch between O₂ removal from water (O₂ uptake; \(\dot{V}{\text{O}}_{ 2}\) ) and the O₂ delivered to tissues by the primary circulation (O₂ consumption; \(\dot{V}{\text{aO}}_{ 2}\) ) has never been measured directly. Using data from four recent studies that simultaneously measured \(\dot{V}{\text{O}}_{ 2}\) and \(\dot{V}{\text{aO}}_{ 2}\) in 2–5 kg Pacific salmon, our analysis revealed that sockeye salmon can remove an additional 12–48 % more O₂ from the water than the primary circulation delivers to the systemic tissues. This percentage did not change significantly during swimming activity, a result that contradicts an earlier prediction that the difference should decrease when \(\dot{V}{\text{O}}_{ 2}\) increases during exercise. In resting Chinook salmon, a similar percentage difference in simultaneously measured \(\dot{V}{\text{O}}_{ 2}\) and \(\dot{V}{\text{O}}_{ 2}\) was observed, yet the difference tended to disappear during acute heat stress to a near lethal temperature. These results emphasize that caution should be exercised when using the Fick equation to estimate cardiac output because the overestimate of cardiac output that results from using the Fick equation in Pacific salmon is not small, may not be fixed and may exist in other teleosts.     

Energy requirements of Adélie penguin (Pygoscelis adeliae) chicks

Summary The energy requirements of Adélie penguin (Pygoscelis adeliae) chicks were analysed with respect to body mass (W, 0.145–3.35 kg, n=36) and various forms of activity (lying, standing, minor activity, locomotion, walking on a treadmill). Direct respirometry was used to measure O₂ consumption ( ) and CO₂ production. Heart rate (HR, bpm) was recorded from the ECG obtained by both externally attached electrodes and implantable HR-transmitters. The parameters measured were not affected by hand-rearing of the chicks or by implanting transmitters. HR measured in the laboratory and in the field were comparable. Oxygen uptake ranged from in lying chicks to at maximal activity, RQ=0.76. Metabolic rate in small wild chicks (0.14–0.38 kg) was not affected by time of day, nor was their feeding frequency in the colony (Dec 20–21). Regressions of HR on were highly significant (p< 0.0001) in transmitter implanted chicks (n=4), and two relationships are proposed for the pooled data, one for minor activities ( ), and one for walking ( ). Oxygen consumption, mass of the chick (2–3 kg), and duration of walking (T, s) were related as , whereas mass-specific O₂ consumption was related to walking speed (S, m·s^-1) as .Abbreviations bpm beats per minute - D distance walked (m) - ECG electrocardiogram - HR heart rate (bpm) - ns number of steps - RQ respiratory quotient - S walking speed (m·s^-1) - T time walked (s) - W body mass (kg)     

Genetic parameters and predicted selection responses for timber production traits in a Castanea sativa progeny trial: developing a breeding program

Total height, diameter, index volume, stem straightness, apical dominance, and survival were assessed at 8 years from seed in an open-pollinated progeny test of 36 families of European chestnut (Castanea sativa Miller) established at two sites in the Atlantic area of Galicia, Spain. Iterative spatial analysis was applied to eliminate the effect of the spatial dependence in the original data and to estimate accurately genetic parameters for evaluating the potential for selection of the measured trees. Spatial analysis was very beneficial for growth traits and survival, but less so if at all for form traits. Estimated individual heritabilities ranged from moderate to high for growth traits ([^(h)]_i² = 0.29 - 0.42 \widehat{h}_i^2 = 0.29 - 0.42 ) and stem straightness ([^(h)]_i² = 0.24 - 0.42 \widehat{h}_i^2 = 0.{24} - 0.{42} ). High coefficients of additive genetic variance were obtained for volume ( [^(\textC)]\textV_\textA = 36.5 - 41.5% \widehat{\text{C}}{{\text{V}}_{\text{A}}} = {36}.{5} - {41}.{5}\% ) and straightness ( [^(\textC)]\textV_\textA = 44.26 - 53.84% \widehat{\text{C}}{{\text{V}}_{\text{A}}} = {44}.{26} - {53}.{84}\% ). Phenotypic and estimated genetic correlations between growth traits were very high, and correlations between sites indicated that there was no important family × site interaction. No adverse correlations between traits were evident. The results indicate the ample potential for selection in the current progeny trial, where responses to within-family and combined selection for growth traits may be high. Accordingly, three selection scenarios were addressed with the aim to initiate the selection of individuals for implementing the Forest Breeding Plan of Galicia for European chestnut.     

Effects of ambient temperature and altitude on ventilation and gas exchange in deer mice (Peromyscus maniculatus)

Summary The effects of different ambient temperatures (T _a) on gas exchange and ventilation in deer mice (Peromyscus maniculatus) were determined after acclimation to low and high altitude (340 and 3,800 m).At both low and high altitude, oxygen consumption ( ) decreased with increasingT _a atT _a from –10 to 30 °C. The was 15–20% smaller at high altitude than at low altitude atT _a below 30 °C.Increased atT _a below thermoneutrality was supported by increased minute volume ( ) at both low and high altitude. At mostT _a, the change in was primarily a function of changing respiration frequency (f); relatively little change occurred in tidal volume (V _T) or oxygen extraction efficiency (O₂EE). AtT _a=0 °C and below at high altitude, was constant due to decliningV _T and O₂EE increased in order to maintain high .At high altitude, (BTP) was 30–40% higher at a givenT _a than at low altitude, except atT _a below 10 °C. The increased at high altitude was due primarily to a proportional increase inf, which attained mean values of 450–500 breaths/min atT _a below 0 °C. The (STP) was equivalent at high and low altitude atT _a of 10 °C and above. At lowerT _a, (STPD) was larger at low altitude.At both altitudes, respiratory heat loss was a small fraction (<10%) of metabolic heat production, except at highT _a (20–30 °C).Abbreviations EHL evaporative heat loss - f respiration frequency - HL _a heat loss from warming tidal air - HL _e evaporative heat loss in tidal air - HL total respiratory heat loss - MHP metabolic heat production - O ₂ EE oxygen extraction efficiency - RQ respiratory quotient - T _a ambient temperature - T _b body temperatureT _lc lower critical temperature - carbon dioxide production - evaporative water loss - oxygen consumption - minute volume - V _T tidal volume     

Influence of {\text{NH - }}{{\text{S}}^\gamma } bonding interactions on the structure and dynamics of metallothioneins

Mammalian metallothioneins ( \textM₇^\textIIMTs {\text{M}}_7^{\text{IIMTs}} ) show a clustered arrangement of the metal ions and a nonregular protein structure. The solution structures of Cd₃-thiolate cluster containing β-domain of mouse β-MT-1 and rat β-MT-2 show high structural similarities, but widely differing structure dynamics. Molecular dynamics simulations revealed a substantially increased number of \textNH - \textS^g {\text{NH - }}{{\text{S}}^\gamma } hydrogen bonds in β-MT-2, features likely responsible for the increased stability of the Cd₃-thiolate cluster and the enfolding protein domain. Alterations in the \textNH - \textS^g {\text{NH - }}{{\text{S}}^\gamma } hydrogen-bonding network may provide a rationale for the differences in dynamic properties encountered in the β-domains of MT-1, -2, and -3 isoforms, believed to be essential for their different biological function.     

Reactive oxygen species production and antioxidative defense system in pea root tissues treated with lead ions: the whole roots level

The lead absorbed by the roots induce oxidative stress conditions through the Reactive oxygen species (ROS) production for the pea plants cultivated hydroponically for 96 h on a Hoagland medium with the addition of 0.1 and 0.5 mM of Pb(NO₃)₂. The alterations in \textO₂ ^{- ·} {\text{O}}_{2}^{ - \cdot } and H₂O₂ concentrations were monitored spectrophotometrically which show a rapid increase in \textO₂ ^{- ·} {\text{O}}_{2}^{ - \cdot } production during the initial 2 h, and in case of H₂O₂, during the eighth hour of cultivation. The level of ROS remained higher at all the time points for the roots of the plants cultivated with Pb²⁺ and it was proportional to metal concentration. The production of \textO₂ ^{- ·} {\text{O}}_{2}^{ - \cdot } and H₂O₂ was visualized by means of fluorescence microscope technique. They are produced in nonenzymatic membrane lipid peroxidation and its final product is Malondialdehyde, the level of which increased together with the level of H₂O₂. As stress intensity raised (duration of treatment and Pb²⁺ concentration), so did the activities of superoxide dismutases, catalase and ascorbate peroxidase antioxidative enzymes and of low-molecular antioxidants, particularly glutathione (GSH), homoglutathione (h-GSH) and cysteine substrate toward their synthesis. The root cells redox state (GSH/GSSG) dropped proportionally to lead stress intensity.     

Average shear rate in three pneumatic bioreactors

A method proposed in recent literature was applied to evaluate the average shear rate ( [(g)\dot]_av ) \left( {\dot{\gamma }_{\rm av} } \right) in three pneumatic bioreactors of 5-dm³ working volume: bubble column, split airlift, and concentric-tube airlift. The volumetric oxygen transfer coefficient (k _L a) is the appropriate characteristic parameter to assess the average shear rate ( [(g)\dot]_av ) \left( {\dot{\gamma }_{\rm av} } \right) in this methodology. Correlations for [(g)\dot]_av \dot{\gamma }_{\rm av} as a function of superficial gas velocity in the riser region (U _GR) and rheological fluid properties (consistency index, K, and flow index, n) were obtained for each model of pneumatic bioreactor studied. The [(g)\dot]_av \dot{\gamma }_{\rm av} values estimated by the proposed methodology lay within the range of values calculated by classical correlations. The proposed correlations were utilized to predict the [(g)\dot]_av \dot{\gamma }_{\rm av} during the Streptomyces clavuligerus cultivations carried out at the same specific air flow rate (3.5 vvm) in the different types of pneumatic bioreactors. The lowest values of [(g)\dot]_av \dot{\gamma }_{\rm av} related to the highest values of consistency index (K) were found for the bubble column bioreactor, and the highest values of [(g)\dot]_av \dot{\gamma }_{\rm av} related to the lowest values of K were found for the concentric-tube airlift bioreactor. Intermediate values were found for the split airlift bioreactor. The results showed that high [(g)\dot]_av \dot{\gamma }_{\rm av} values affect the structural health of the mycelia by the rupture of the hipha.     

Changes in partial pressures of respiratory gases during submerged voluntary breath hold across odontocetes: is body mass important?

Odontocetes have an exceptional range in body mass spanning 10³ kg across species. Because, size influences oxygen utilization and carbon dioxide production rates in mammals, this lineage likely displays an extraordinary variation in oxygen store management compared to other marine mammal groups. To examine this, we measured changes in the partial pressures of respiratory gases ( P_\textO2 P_{{{\text{O}}_{2} }} , P_\textCO2 P_{{{\text{CO}}_{2} }} ), pH, and lactate in the blood during voluntary, quiescent, submerged breath holds in Pacific white-sided dolphins (Lagenorhynchus obliquidens), bottlenose dolphins (Tursiops truncatus), and a killer whale (Orcinus orca) representing a mass range of 96–3,850 kg. These measurements provided an empirical determination of the effect of body size on the variability in blood biochemistry during breath hold and experimentally determined aerobic dive limits (ADL) within one taxonomic group (odontocetes). For the species in this study, maximum voluntary breath-hold duration was positively correlated with body mass, ranging from 3.5 min in white-sided dolphins to 13.3 min for the killer whale. Variation in breath-hold duration was associated with differences in the rate of change for P_\textO2 P_{{{\text{O}}_{2} }} throughout breath hold; P_\textO2 P_{{{\text{O}}_{2} }} decreased twice as fast for the two smaller species (−0.6 mmHg O₂ min⁻¹) compared to the largest species (−0.3 mmHg O₂ min⁻¹). In contrast, the rate of increase in P_\textCO2 P_{{{\text{CO}}_{2} }} during breath hold was similar across species. These results demonstrate that large body size in odontocetes facilitates increased aerobic breath-hold capacity as mediated by decreased mass-specific metabolic rates (rates of change in P_\textO2 P_{{{\text{O}}_{2} }} served as a proxy for oxygen utilization). Indeed the experimentally determined 5 min ADL for bottlenose dolphins was surpassed by the 13.3 min maximum breath hold of the killer whale, which did not end in a rise in lactate. Rather, breath hold ended voluntarily as respiratory gases and pH fell within a narrow range for both large and small species, likely providing cues for ventilation.     

Thermoregulation,gas exchange,and ventilation in Adelie penguins (Pygoscelis adeliae)

Summary Adelie penguins (Pygoscelis adeliae) experience a wide range of ambient temperatures (T _a) in their natural habitat. We examined body temperature (T _b), oxygen consumption ( ), carbon dioxide production ( ), evaporative water loss ( ), and ventilation atT _a from –20 to 30 °C. Body temperature did not change significantly between –20 and 20°C (meanT _b=39.3°C).T _b increased slightly to 40.1 °C atT _a=30°C. Both and were constant and minimal atT _a between –10 and 20°C, with only minor increases at –20 and 30°C. The minimal of adult penguins (mean mass 4.007 kg) was 0.0112 ml/[g·min], equivalent to a metabolic heat production (MHP) of 14.9 Watt. The respiratory exchange ratio was approximately 0.7 at allT _a. Values of were low at lowT _a, but increased to 0.21 g/min at 30°C, equivalent to 0.3% of body mass/h. Dry conductance increased 3.5-fold between –20 and 30°C. Evaporative heat loss (EHL) comprised about 5% of MHP at lowT _a, rising to 47% of MHP atT _a=30°C. The means of ventilation parameters (tidal volume [VT], respiration frequency [f], minute volume [I], and oxygen extraction [ ]) were fairly stable between –20 and 10°C (VT did not change significantly over the entireT _a range). However, there was considerable inter- and intra-individual variation in ventilation patterns. AtT _a=20–30°C,f increased 7-fold over the minimal value of 7.6 breaths/min, and I showed a similar change. fell from 28–35% at lowT _a to 6% atT _a=30°C.Abbreviations C thermal conductance - EHL evaporative heat loss - oxygen extraction - f respiratory frequency - MHP metabolic heat production - evaporative water loss - LCT lower critical temperature - RE respiratory exchange ratio - T _a ambient temperature - T _b body temperature - rate of oxygen consumption - rate of carbon dioxide production - I inspiratory minute volume - VT tidal volume     

Changes in skeletal muscle oxygenation during incremental exercise measured with near infrared spectroscopy

To determine the change in muscle oxygenation in response to progressively increasing work rate exercise, muscle oxyhemoglobin + oxymyoglobin saturation was measured transcutaneously with near infrared spectroscopy in the vastus lateralis muscle during cycle ergometry. Studies were done in 11 subjects while gas exchange was measured breath-by-breath. As work rate was increased, tissue oxygenation initially either remained constant near resting levels or, more usually, decreased. Near the work rate and metabolic rate where significant lactic acidosis was detected by excess CO₂ production (lactic acidosis threshold, LAT), muscle oxygenation decreased more steeply. As maximum oxygen uptake ( ) was approached, the rate of desaturation slowed. In 8 of the 11 subjects, tissue O₂ saturation reached a minimum which was sustained for 1–3 min before was reached. The LAT correlated with both the (r = 0.95,P < 0.0001) and the work rate (r = 0.94,P < 0.0001) at which the rate of tissue O₂ desaturation accelerated. These results describe a consistent pattern in the rate of decrease in muscle oxygenation, slowly decreasing over the lower work rate range, decreasing more rapidly in the work rate range of the LAT and then slowing at about 80% of , approaching or reaching a minimum saturation at .     

Succinate accumulation in man during exercise

It has been demonstrated in several diving vertebrates that succinate, a component of the Krebs cycle, accumulates in blood during breath-hold dives. The production of succinate is thought to result from amino acid catabolism. Our purpose was to determine whether succinate accumulation occurs in man during muscular activity requiring anaerobic energy contribution. Experiments using an endurance athlete included apneic work on an underwater ergometer and treadmill running to exhaustion. During 1 min breath-hold [(V)\dot]\dot V O₂max, venous succinate increased from 42 [(V)\dot]\dot V O₂max and increased succinate from a similar resting value to 93 M×10^–6. Increases in alanine, lactate, and pyruvate were observed for both types of exercise. The findings confirm that succinate accumulation also occurs in man. It was suggested that amino acid catabolism may provide a source of anaerobic energy production in addition to glycolysis. However, the importance of the proposed energy pathway remains to be quantified.     

Times to exhaustion at 100% of velocity at [(V)\dot]\textO\text2 \dot V{\text{O}}_{\text{2}} max and modelling of the time-limit / velocity relationship in elite long-distance runners

The aim of this study was to measure running times to exhaustion (Tlim) on a treadmill at 100% of the minimum velocity which elicits _{max max} in 38 elite male long - distance runners _max = 71.4 ± 5.5 ml.kg^–1.min^–1 and _max = 21.8 ± 1.2 km.h^–1). The lactate threshold (LT) was defined as a starting point of accelerated lactate accumulation around 4 mM and was expressed in _max. Tlim value was negatively correlated with _max (r = -0.362, p< 0.05) and _max (r = –0.347, p< 0.05) but positively with LT (%v _max) (r = 0.378, p < 0.05). These data demonstrate that running time to exhaustion at _max in a homogeneous group of elite male long-distance runners was inversely related to _max and experimentally illustrates the model of Monod and Scherrer regarding the time limit-velocity relationship adapted from local exercise for running by Hughson et al. (1984) .