Effects of dietary protein contents and habitual endurance exercise on supplemental leucine oxidation in mice

The effects of dietary protein contents and regular exercise on the oxidation of supplemented leucine were examined. In the short-term study, male BALB/cCrSlc mice were fed diets containing 0, 10, 20, 35, and 60% protein: energy ratios for 1 week. In the long-term study, exercised and sedentary mice were fed diets containing 20, 35, and 60% protein ratios for 9 weeks. After the feeding periods, the mice were a bolus administered oral supplements of l-[1-¹³C] leucine. Expired gas was analyzed, and oxidized leucine was expressed as a relative ¹³CO₂/¹²CO₂ ratio. In the short-term study, the peak ¹³CO₂/¹²CO₂ ratio significantly increased with diet protein concentrations. Moreover, the long-term study also showed that the peak ¹³CO₂/¹²CO₂ ratio was significantly increased by high protein diets in both exercised and sedentary mice. Our results indicate that supplemental leucine oxidation is associated with consumption of a high-protein diet, irrespective of exercise status.

Abbreviations: AUC: area under the curve; EX: exercise; RQ: respiratory quotient; SED: sedentary; VO₂/W: oxygen uptake per body weight     

Mechanical understanding of hunting waves generated by killer whales

The wave wash hunting employed by Orcinus orca, also known as killer whales, is unique in that the prey is hunted outside of the water by generating waves. To quantitatively analyze the specific mechanism of the wave wash, data were obtained using computational fluid dynamics (CFD), and wave theory was introduced as the theoretical background to clarify the mechanism. The relationships between the swimming characteristics and wave parameters are defined in this paper. The results obtained by numerical investigation revealed that the wavelength increased with the swimming speed. Additionally, the wave height increased as the swimming speed increased and the swimming depth became shallower, and subsequently converged to a maximum of 2.42 m. The success of hunting is determined by two wave parameters, which indicate the intensity of the wave wash: the wave height and force exerted on the prey. The metabolic rate and the drag force are considered to evaluate the efficiency of the locomotion, which varied according to the swimming speed (V) and swimming depth (d) of the whales. To generate hunting waves efficiently, the optimal ranges of V and d were estimated to be 3 ~ 5 m/s and 0.5 m ~ 1.1 m respectively.     

Distribution, abundance, behavior and metabolism of Periphylla periphylla, a mesopelagic coronate medusa in a Norwegian fjord

The distribution, behavior and metabolism of the mesopelagic jellyfish, Periphylla periphylla (Péron & Lesueur), were investigated in Lurefjorden, Norway. Field studies, conducted in 1998–1999 with plankton nets and a remotely operated vehicle, indicated that 80-90% of the dense (up to 2.5 m^–3) population migrated 200–400 m vertically each day throughout the year. In situ observations with red light revealed that swimming rates and feeding activity varied with age and time of day. Detection of turbulence and contact with surfaces caused this medusa to conceal one or all of its tentacles in the stomach or to shed nematocyst-laden tissue from the tentacles. Stomachs of medusae collected with nets were often full of prey entangled with the sloughed tissue. Stomachs of medusae captured individually with ROV samplers were empty or contained only a few prey in their stomachs (typically, 1–4 copepods Calanus spp. or chaetognaths Eukrohnia hamata Möbius per medusa). Low rates (0.4–5.6 l O₂ mg C^–1 h^–1) of oxygen consumption of P. periphylla suggested that this species was sustained by relatively few (1–34) prey d^–1.     

A comparison of electrical activity in the triceps surae at maximum isometric contraction with the knee and ankle at various angles

The purpose of this study was to test the endurance of the soleus muscle, and to examine the joint position at which it is most active, while simultaneously suppressing the activity of the gastrocnemius. Ten young males performed maximum isometric contraction of the triceps surae for 100 s, and the endurance and plantar flexion torque of this muscle were measured at various angles of the knee and ankle joints. The electromyogram was measured simultaneously and subsequently converted into integrated electromyogram (IEMG) values. With the knee flexed at 130 degrees, the rate of change in IEMG values for the soleus (0.454% x s(-1)) with the ankle in a neutral position was significantly higher than that for the medial and lateral gastrocnemius. Both with the ankle dorsiflexed at 10 degrees and in the neutral position, the rate of change in IEMG for the soleus was significantly higher with the knee flexed at 90 degrees and 130 degrees than with the knee fully extended. With the knee flexed at 90 degrees and 130 degrees, the IEMG activity of the soleus during the initial (5-10 s) and final 5 s tended to be higher than those for the medial and lateral gastrocnemius, regardless of the ankle joint position. We conclude that the position in which the soleus acts most selectively during a sustained maximum isometric contraction of the triceps surae is with the ankle in a neutral position and the knee flexed at 130 degrees.     

Exposure and Health Risk from Swimming in Outdoor Pools Contaminated by Trichloroethylene

A method was developed that evaluated the exposure and health risk to children from swimming in outdoor pools filled with contaminated water. It was found that dermal absorption of trichloroethylene (TCE) was significantly larger than the inhalation component of the exposures. It was estimated that the inhalation route accounted for only 1% of the total exposure, whereas accidental ingestion was 7% of the child's total intake and the dermal absorbed dose was 92% of the total exposure. The relative percentage of the total exposure estimated for each exposure route indicated that the dermal exposure route and accidental ingestion of pool water should not be ignored for volatile compounds when evaluating exposure.

The method utilized was simple enough to use computer spreadsheets for the calculations and can be easily adapted to various swimming scenarios and age groups. This method also included an assessment of the uncertainty in the exposure and risk estimates. The range of estimated exposures was 40 μ g to 442 μ g of TCE per swimming season. All values in this range were below the health benchmark for both non-carcinogenic and carcinogenic endpoints.     

The Effects of Hypoxia on Three Sympatric Shark Species: Physiological and Behavioral Responses

Behavioral and physiological responses to hypoxia were examined in three sympatric species of sharks: bonnethead shark Sphyrna tiburo, blacknose shark, Carcharhinus acronotus, and Florida smoothhound shark, Mustelus norrisi, using closed system respirometry. Sharks were exposed to normoxic and three levels of hypoxic conditions. Under normoxic conditions (5.5–6.4mg l^–1), shark routine swimming speed averaged 25.5 and 31.0cm s^–1 for obligate ram-ventilating S. tiburo and C. acronotus respectively, and 25.0cm s^–1 for buccal-ventilating M. norrisi. Routine oxygen consumption averaged about 234.6 mg O₂kg^–1h^–1 for S. tiburo, 437.2mg O₂kg^–1h^–1 for C. acronotus, and 161.4mg O₂ kg^–1 h^–1 for M. norrisi. For ram-ventilating sharks, mouth gape averaged 1.0cm whereas M. norrisi gillbeats averaged 56.0 beats min^–1. Swimming speeds, mouth gape, and oxygen consumption rate of S. tiburo and C. acronotus increased to a maximum of 37–39cm s^–1, 2.5–3.0cm and 496 and 599mg O₂ kg^–1 h^–1 under hypoxic conditions (2.5–3.4mg l^–1), respectively. M. norrisi decreased swimming speeds to 16cm s^–1 and oxygen consumption rate remained similar. Results support the hypothesis that obligate ram-ventilating sharks respond to hypoxia by increasing swimming speed and mouth gape while buccal-ventilating smoothhound sharks reduce activity.     

Involvement of monoaminergic system in the antidepressant-like effect of the hydroalcoholic extract of Siphocampylus verticillatus

The antidepressant-like effect of the hydroalcoholic extract obtained from aerial parts of Siphocampylus verticillatus, a Brazilian medicinal plant, was investigated in two models of depression in mice and against synaptosomal uptake of serotonin, noradrenaline and dopamine. The immobility times in the forced swimming test (FST) and in the tail suspension test (TST) were significantly reduced by the extract (dose range 100-1000 mg/kg, i.p.), without accompanying changes in ambulation when assessed in an open-field. In addition when given orally the extract was also effective in reducing the immobility time in the TST. The efficacy of extract in the TST was comparable to that of the tricyclic antidepressant imipramine (15 mg/kg, i.p.) and with fluoxetine (32 mg/kg, i.p.). The anti-immobility effect of the extract (600 mg/kg, i.p.) assessed in the TST was not affected by pre-treatment with naloxone (1 mg/kg, i.p., a non-selective opioid receptor antagonist) or L-arginine (750 mg/kg, i.p., a nitric oxide precursor). In contrast, the extract (600 mg/kg, i.p.) antidepressant-like effect was significantly reduced by pre-treatment of animals with p-chlorophenylalanine (PCPA, 100 mg/kg, i.p., an inhibitor of serotonin synthesis), sulpiride (50 mg/kg, i.p., a selective D2 receptor antagonist), prazosin (62.5 microg/kg, i.p., an alpha1 adrenoreceptor antagonist) or by guanosine 5'-monophosphate (GMP, 250 mg/kg, i.p., a nucleotide known to block some actions elicited by NMDA). The biochemical data show that the extract of S. verticillatus inhibited in a graded manner the uptake of monoamines. However, at the IC50 level, the extract was approximately 3.2 to 3.4-fold more potent and also more efficacious in inhibiting the synaptosomal uptake of noradrenaline and serotonin than dopamine. Taken together these data demonstrate that the extract of S. verticillatus elicited a significant antidepressant-like effect, when assessed in the TST and FST in mice. Its action seems to involve an interaction with adrenergic, dopaminergic, glutamatergic and serotonergic systems.     

Effects of zinc deficiency and supplementation on malondialdehyde and glutathione levels in blood and tissues of rats performing swimming exercise

The aim of the study was to investigate the effects of zinc deficiency and supplementation on lipid peroxidation and glutathione levels in blood and in some tissues of rats performing swimming exercise. Forty adult male Sprague-Dawley rats were divided into four groups: group 1, zinc-deficient consisted of swimming rats; group 2 consisted of zinc-supplemented swimming rats; groups 3 and 4 were the swimming and nonswimming controls, respectively. The levels of malondialdehyde and glutathione were measured after 4 wk of zinc-deficient or zinc-supplemented diet and 30 min of swimming exercise daily. The erythrocyte glutathione levels of groups 2 and 4 were significantly higher than those of groups 1 and 3 (p<0.01). The plasma malondialdehyde level of group 1 was significantly higher than all other groups. The glutathione levels in liver, kidney, striated muscle, and testes of group 2 were higher than in the other groups (p<0.01) and higher in kidney and striated muscle of group 3 than in groups 1 and 4 (p<0.01). The tissue malondialdehyde levels of striated muscle, liver, kidney, and testes of group 1 were significantly higher than for all other groups (p<0.01). Our findings suggest that both swimming exercise and zinc deficiency result in an increase of lipid peroxidation in tissues and that zinc supplementation prevents these alterations by the activation of the antioxidant system.     

Testosterone, endurance, and Darwinian fitness: natural and sexual selection on the physiological bases of alternative male behaviors in side-blotched lizards

The mechanistic bases of natural and sexual selection on physiological and behavioral traits were examined in male morphs of three colors of the side-blotched lizard, Uta stansburiana. Orange-throated males are aggressive and defend large territories with many females. Blue-throated males defend smaller territories with fewer females; however, blue-throated males assiduously mate guard females on their territory. Yellow-throated males do not defend a territory, but patrol a large home range. They obtain secretive copulations from females on the territories of dominant males. Males with bright orange throats had higher levels of plasma testosterone (T), endurance, activity, and home range size and concomitantly gained greater control over female home ranges than blue- or yellow-throated males. Experimentally elevating plasma T in yellow- and blue-throated males increased their endurance, activity, home range size, and control over female territories to levels that were seen in unmanipulated orange-throated males that had naturally high plasma T. However, the enhanced performance of orange-throated males is not without costs. Orange-throated males had low survival compared to the other morphs. Finally, some yellow-throated males transformed to a partial blue morphology late in the season and the endurance of these transforming yellow-throated males increased from early to late in the season. In addition, yellow-throated males that transformed to blue also had significantly higher plasma T late in the season compared to the plasma T earlier in the season. T appears to play an important role in the physiological changes that all three color morphs undergo during the process of maturation. In some yellow males, T plays an additional role in plastic changes in behavior and physiology late in the reproductive season. We discuss natural and sexual selection on physiological and behavioral traits that leads to the evolution of steroid regulation in the context of alternative male strategies.     

PREDISPOSED TO ADAPT? CLADE‐LEVEL DIFFERENCES IN CHARACTERS AFFECTING SWIMMING PERFORMANCE IN DAMSELFLIES

Previous studies have shown that two or three lineages of Enallagma damselflies, which historically co-existed with fish, recently invaded and adapted to living with large dragonfly predators in fishless waters. In adapting to live with these new predators, lineages shifted behaviorally to using swimming as an evasive tactic against attacking predators, evolved morphological features that made them faster swimmers, and evolved biochemical features to increase refueling strenuous activities like swimming. However, these habitat shifts have occurred in only one of the two primary clades within the genus in North America. Here, I show that clade-level differences exist among species in the ancestral, fish-lake habitat that should make habitat shifts easier to accomplish in the clade in which they have occurred. Specifically, fish-lake species in the clade in which habitat shifts occurred have much higher propensities to swim in the laboratory, swim faster when they do swim, and have higher mass-specific activities for arginine kinase than do species in the other primary clade, in which no extant species are found in fishless waters. These results are discussed in the context of the dynamics of founder events and the potential implications for community structure.