Lower Swimming Research Articles

Mu and delta opioid receptor analgesia, binding density, and mRNA levels in mice selectively bred for high and low analgesia

The present study examined mu and delta opioid analgesia, receptor binding, and receptor mRNA levels in lines of mice from two selective breeding projects of relevance to opioid analgesia. Large differences were observed in the analgesic potency of [ d-Ala 2, NMPhe 4, Gly-ol]enkephalin (DAMGO), [ d-Pen 2,5]enkephalin (DPDPE), and [ d-Ala 2]deltorphin II (DELT), selective mu, delta 1, and delta 2 opioid receptor agonists, respectively, in mice selectively bred for high (HA) and low (LA) swim stress-induced analgesia (SIA). HAR and LAR mice, selectively bred for high and low levorphanol analgesia, respectively, display equally large differences in their analgesic sensitivity to DAMGO, modest differences in sensitivity to DPDPE, and no differences in sensitivity to DELT. These sizable genotypic differences in analgesic potency were accompanied by HA/LA and HAR/LAR differences in whole-brain homogenate [ 3 H ]DPDPE and/or [ 3 H ]DELT, but paradoxically not [ 3 H ]DAMGO, binding. Solution hybridization of mRNA extracts encoding mu (MOR-1) or delta (DOR-1) opioid receptors indicated some regional differences in gene expression between high and low lines. Surprisingly, differences in these in vitro markers were often in the direction of LAR>HAR. The present data indicate that selection for either SSIA or levorphanol analgesia produces differential effects on mu and delta opioid analgesia that are accompanied by alterations on in vitro assays, the significance of which remains to be determined. The data are discussed with regard to the utility of in vitro biological markers and genetic models of analgesia.

Distribution patterns and feeding success of anchovy, <i>Engraulis anchoita</i>, larvae off southern Brazil

Feeding success and changes in horizontal patchiness relative to size were studied for anchovy, Engraulis anchoita, larvae caught with a Bongo net off southern Brazil. Results show higher feeding success rates during winter, when the combined effect of enrichment, stability and retention mechanisms seems to create optimal conditions for larval feeding. Under optimal feeding conditions larvae of more than 10 mm have higher feeding success rates than smaller size classes. With a simple body structure and low swimming capabilities, larvae of up to 10 mm show a low level of patchiness, low evasion rate of the sampling gear and feeding on small food particles only. Results corroborate the hypothesis of a critical period between two important ontogenic phases: the beginning of exogenous feeding and the onset of active swimming, gas gland buoyancy and school forming behavior.

Acute morphine dependence in mice selectively-bred for high and low analgesia

Acute morphine dependence was compared in mice selectively-bred for high (HA) and low (LA) swim stress-induced analgesia and high (HAR) and low (LAR) levorphanol analgesia by counting the number of naloxone-precipitated jumps. Whereas LAR mice displayed greater acute morphine dependence than HAR mice, HA and LA mice did not differ. No genotypic differences were observed in non-dependent mice, discounting possible differences in basal naloxone sensitivity and/or opioid peptide levels. Thus, the two selection projects, while both producing lines exhibiting highly divergent sensitivity to morphine analgesia, have not had analogous effects on all opioid measures, supporting the notion of independent genetic mediation of opioid analgesia and dependence. Further, these data suggest that analgesic sensitivity may not predict sensitivity to morphine dependence.

Muscular buffering capacity of the parr and smolts in Oncorhynchus masou

Evidence suggests that muscular buffering capacity is important in control of the intracellular pH in white muscle during anaerobic burst swimming for prey capture or to escape from predators. The goal of this study was to compare the buffering capacity in the muscle of Oncorhynchus masou parr and smolts from a variety of sources. Levels of anserine, histidine and inorganic phosphate in the muscle, compounds that have strong buffering capacities, within the physiological pH range, and the buffering capacities of the white muscle between parr and smolts were compared. The anserine levels were significantly higher in smolts (19.5–22.5 μmol/g muscle) than in parr (11.5–18.5 μmol/g), while the histidine levels were lower in smolts (0.5–2.6 μmol/g) than in parr (3.2–5.0 μmol/g), within each source. The smolts tended to have higher levels of muscular inorganic phosphate (50.3–66.4 μmol/g) than the parr (47.2–61.5 μmol/g). The overall difference in the levels of these substances between the smolts and parr was reflected in their muscular buffering capacities, the white muscle of smolts having a significantly stronger buffering capacity than that of parr. These results suggest that the burst swimming ability might be enhanced in smolts compared to parr, or that the muscular buffering capacity of smolts may be elevated for coping with the recruitment of anaerobic energy production even at low swimming speed resulting from poor aerobic swimming ability.

Swimming behavior and predator avoidance in three populations of Fundulus heteroclitus larvae after embryonic and/or larval exposure to methylmercury

We determined effects of embryonic and/or larval exposure to methylmercury (MeHg) on swimming behavior and predator avoidance ability in larval mummichogs ( Fundulus heteroclitus) from a site polluted with heavy metals and organic materials (Piles Creek (PC), NJ) and two reference sites (Tuckerton (TK), NJ and East Hampton (EH), NY). Mummichog eggs and sperm were stripped from ripe females and males captured from the field, and their embryos and larvae were raised in clean sea water or MeHg solution. After hatching, larval spontaneous activity, swimming performance and predator avoidance were tested periodically. Embryonic and/or larval exposure sometimes caused hyperactivity in PC or EH larvae, hypoactivity in TK larvae, and depression of swimming performance in all the three populations. Embryonic and/or larval exposure also increased vulnerability to predation by yearling mummichogs, but the effects of embryonic exposure were transitory. Among the three populations, TK was the least vulnerable to predation by blue crabs (i.e. most resistant to MeHg), which may have been associated with their lower swimming activity induced by MeHg, making them less conspicuous to the predator. The higher prey susceptibility in PC or EH larvae was correlated with their MeHg-induced hyperactivity.

Repeat swimming performance of mature sockeye salmon following a brief recovery period: a proposed measure of fish health and water quality

Measurements of swimming ability, such as critical swimming speed (Ucrit), have commonly been used as indicators of the effects of environmental challenges on the general health of fish. In this study, we introduce repeat swimming performance as a particularly sensitive means to assess fish health and the effects of environmental stressors. Adult sockeye salmon (Oncorhynchus nerka) performed two Ucrit tests separated by a 40-min recovery period. When recovery ability was expressed as a ratio of Ucrit values in the first and second swim challenges (Ucrit,2/Ucrit,1), control fish exhibited recovery ratios of unity (0.98 ± 0.01 (mean ± SEM)). In contrast, the recovery of fish pre-exposed to between 0.12 and 0.77 mg·L-1 dehydroabietic acid (DHA) for 8-14 h, and swimming in either hypoxia or normoxia, was impaired. These fish had recovery ratios significantly lower than unity (0.92 ± 0.02) despite swimming to a similar initial Ucrit as control fish. The effect of pre-exposure to DHA was also evident in measurements of oxygen consumption and plasma lactate concentration. Unhealthy fish exhibited significantly lower initial and second Ucrit values than control fish. To account for the low initial swimming performance of these fish, a normalized recovery ratio was introduced ((Ucrit,1/Ucrit,1(control) + Ucrit,2/Ucrit,1)/2). This index of recovery (0.65 ± 0.08) identified the poor physical status of these fish.

Feeding behaviour of cod,Gadus morhua: activity rhythm and chemically mediated food search

I studied the feeding behaviour of cod in late spring in a fjord in northern Norway by means of a stationary positioning system. The activity rhythm of eight cod tagged with acoustic transmitters was observed continuously for 3–8 days in terms of swimming speed and size of area occupied. I studied responses to food odour by setting a line with mackerel baits in the experimental area. The cod had a diurnal rhythm of swimming activity with a slightly lower swimming speed during a 5-h period at night, indicating that they searched more actively for food during the day. A shift towards a larger proportion of active prey taken in the day, accompanied by a change in hunting strategy where vision became more important, may explain this rhythmicity in feeding behaviour. The diurnal rhythm in the range of area occupied varied more than the swimming activity rhythm and there was no significant difference in range between day and night indicating that factors other than the diel light cycle also influenced periodicity in activity. A higher proportion of fish encountered by the bait odour plume located baits than that of fish that were out of range of the odour plume, indicating the importance of chemically mediated food searching in this species. The cod detected a food odour source from a distance of several hundred metres, and responded immediately to the odour plume by carrying out a rheotactic search at a moderately higher swimming speed.

Acute toxicity of organotin compounds to the larvae of the rock shell, Thais clavigera, the disk abalone, Haliotis discus discus and the giant abalone, Haliotis madaka

Acute toxicity tests of tributyltin (TBT) and triphenyltin (TPT) were conducted on hte larvae of the rock shell, Thais clavigera, the disk abalone, Haliotis discus discus and the giant abalone, Haliotis madaka. For the rock shell larvae, the LC 50 values (based on the nominal concentrations) were 8.4 μg (24 h) and 5.6 μg (48 h) TBT/IL; 8.6 μg (24 h) and 4.6 μg (48 h) TPT/L. For the disk abalone larvae, the 48 h LC 50 values were 5.4 μg TBT/L and 1.4 μg TPT/L. For the giant abalone larvae, the LC 50 values were 3.9 μg (24 h) and 1.2 μg (48 h) TBT/L; 2.4 μg (24 h) and 1.5 μg (48 h) TPT/L. Some effects on swimming behavior (e.g. unusual swimming behavior or low swimming activity) and irregular movement of cilia due to atrophy of velum compared to that in the control, as well as stripping out of the larvae from the shell, were observed even at lower concentrations than the LC 50 values. From these experimental results and actual organotin concentrations in Japanese inshore waters, TBT pollution may have adversely affected the recruitment of the rock shell, the disk abalone and the giant abalone in heavily polluted areas.

The impact of endurance training on arterial plasma K+ levels and swimming performance of rainbow trout

Arterial plasma K+ and lactate concentrations ([K+]a and [lactate]a), as well as blood oxygenation status, were measured in relation to increasing swimming speeds in rainbow trout Oncorhynchus mykiss. Neither [K+]a nor [lactate]a changed at swimming speeds below 1.5 BL s-1, where BL is total body length. Between 1.5 and 2.0 BL s-1, [K+]a started to increase, and above 2.0 BL s-1 both [K+]a and [lactate]a increased with swimming speed. Training shifted the onset of these increases to higher swimming speeds and increased the critical swimming speed (Ucrit) from 2.4 to 3.0 BL s-1. Blood oxygen content showed no changes in control fish, whereas in trained fish it increased by 22 % at the final swimming speed. From the [K+]a data, we suggest that no loss of K+ occurred from the working muscle at low swimming speeds, allowing an unlimited endurance, whereas moderate and higher speeds were probably associated with a loss of K+ from the working muscles, indicating a limited endurance. <P>

Repeat swimming performance of mature sockeye salmon following a brief recovery period: a proposed measure of fish health and water quality

Measurements of swimming ability, such as critical swimming speed (Ucrit), have commonly been used as indicators of the effects of environmental challenges on the general health of fish. In this study, we introduce repeat swimming performance as a particularly sensitive means to assess fish health and the effects of environmental stressors. Adult sockeye salmon (Oncorhynchus nerka) performed two Ucrit tests separated by a 40-min recovery period. When recovery ability was expressed as a ratio of Ucrit values in the first and second swim challenges (Ucrit,2/Ucrit,1), control fish exhibited recovery ratios of unity (0.98 ± 0.01 (mean ± SEM)). In contrast, the recovery of fish pre-exposed to between 0.12 and 0.77 mg·L-1 dehydroabietic acid (DHA) for 8-14 h, and swimming in either hypoxia or normoxia, was impaired. These fish had recovery ratios significantly lower than unity (0.92 ± 0.02) despite swimming to a similar initial Ucrit as control fish. The effect of pre-exposure to DHA was also evident in measurements of oxygen consumption and plasma lactate concentration. Unhealthy fish exhibited significantly lower initial and second Ucrit values than control fish. To account for the low initial swimming performance of these fish, a normalized recovery ratio was introduced ((Ucrit,1/Ucrit,1(control) + Ucrit,2/Ucrit,1)/2). This index of recovery (0.65 ± 0.08) identified the poor physical status of these fish.

Epidemiological characteristics of Schistosoma mansoni infection in rural and urban endemic areas of Minas Gerais, Brazil.

To compare the epidemiological profile and socioeconomic factors associated to the infection by Schistosoma mansoni in a rural and an urban endemic area a cross-sectional study was performed in Agua Branca de Minas (rural area) and Bela Fama (urban area), both situated in the State of Minas Gerais, Brazil. Two hundred and eighty eight individuals were surveyed in the rural area and 787 in the urban area. Water contact and socioeconomic questionnaires were used to identify risk factors for the infection. The prevalences of 38.8% and 9.7% and the geometric mean of eggs per gram of faeces of 117.8 and 62.3 were found in the rural and urban areas, respectively. By multivariate statistical analysis age groups over nine years old and previous specific treatment were associated with the infection in rural area. In urban area age over nine years old, low quality housing, weekly fishing and swimming were associated after adjustment by logistic regression.

Metabolic correlates of selection for swim stress-induced analgesia in laboratory mice.

The upper limits of metabolic rates and the links between maximal and resting metabolic rates in vertebrates have recently received a lot of attention, mainly due to their possible relationship to the evolution of endothermy. We measured peak metabolic rates during 3 min swimming in 20 degrees C water (Vo2swim), maximal metabolic rate (Vo2max) in -2.5 degrees C Helox, and basal metabolic rate (BMR) in two lines of mice selected for high (HA) and low (LA) swim stress-induced analgesia (SSIA). We found that exercise combined with heat loss used for producing SSIA also acted as a selection agent, resulting in a 15% HA/LA line difference in Vo2swim. Core body temperature of HA mice (characterized by lower Vo2swim) was also on average 3.2 degrees C lower than that of LA mice. Furthermore, Vo2max of HA mice was lower than that of LA mice by 8% and accompanied by larger hypothermia. Thus mice with exceptionally high (or low) Vo2max tended to have exceptionally high (or low) Vo2swim, resulting in a positive correlation between Vo2swim and Vo2max. All these suggest that selection for SSIA produced genetically correlated responses in both Vo2swim and Vo2max. However, we did not observe HA/LA differences in BMR. Hence, changes in resting and maximum metabolic rates are not necessarily correlated. We hypothesize that the lack of such a correlation was partially due to the modulation of metabolic responses by SSIA.

東京湾シャコ小型底曳網における魚種分離効率

A separator-trawl used for a mantis shrimp catch in Tokyo Bay has a separator panel and two codends; separator net-panel (100mm stretched mesh length) on part of the top of the first codend (62mm mesh length) which is covered with the second codend (33.6mm mesh length). The fishermen hoped mantis shrimp as a main target species would be caught in the second codend and be separated from starfishes retained in the first codend, because large amounts of starfishes cause difficulty in fishermen's hand-sorting on deck. Separation efficiencies of the trawl were obtained from the catch numbers in the two codends in a fishing experiment. Separation efficiency between species i and j is defined as γi+γj-1, where γi is the recovery ratio in the codend for i-species, that is, a proportion of the i-species catch number in the i-species codend. While the recovery ratio for starfish in the first codend was 0.96, that for mantis shrimp in the second codend was 0.66 which was not so high as expected. Thus, separation efficiency between mantis shrimp and starfish was 0.62. Although the separator net-panel has enough large mesh size for small animals, e.g. small crab Carcinoplax vestina, some species of low swimming ability failed to pass through the separator panel and were retained in the first codend. This implies that separation performance of the separator-trawl depends on the swimming ability of each species in the net as well as mesh selectivity of the separator net panel.

Differential sensitivity of mice bred for stress-induced analgesia to morphine and ACEA-1011 in the formalin test

The antinociceptive effect of morphine, an opioid receptor agonist, and ACEA-1011, a novel NMDA receptor/glycine site antagonist, was examined in the formalin test in mice selectively bred for high (HA) and low (LA) swim stress-induced analgesia (SSIA). A subcutaneous (SC) injection of formalin produced a biphasic nociceptive response in both lines. HA mice spent more time licking the injected paw than the LA mice in both phases of the formalin test. Morphine was equally potent in the early phase in both lines, but it was more potent in HA mice than in LA mice in the tonic late phase of the formalin test. Similarly, ACEA-1011 produced an equally potent antinociceptive effect in the early phase in both lines; however, the compound was more potent in LA mice than in HA mice in the tonic late phase of the formalin test. These data suggest that in HA mice antinociception in the tonic late phase of the formalin test is mediated largely by an opioid-mediated mechanism, whereas in the opioid-deficient LA line at least a nonopioid-mediated mechanism involving the NMDA receptor is also implicated.

Do three-spined sticklebacks avoid consuming copepods, the first intermediate host ofSchistocephalus solidus? — an experimental analysis of behavioural resistance

SUMMARYMany parasites that use intermediate hosts are transmitted to the next host through predation. If the next host's fitness is strongly reduced by the parasite, it is under selection either to recognize and avoid infected intermediate hosts or to exclude that prey species from its diet when alternative prey are available. We investigated the predator-prey interaction between laboratory bred three-spined sticklebacks (Gasterosteus aculeatus), the second intermediate host of the cestodeSchistocephalus solidus, from 2 parasitized and 1 unparasitized population, and different prey types: infected and uninfected copepods and size-matchedDaphniaas alternative prey. Copepods with infective procercoids were more active, had a lower swimming ability and were easier to catch than uninfected controls. The sticklebacks preferred moving copepods. Therefore parasitized copepods were preferentially attacked and consumed. There was no effect of the sticklebacks' parent population being parasitized or not. The sticklebacks switched fromDaphniato (uninfected) copepods in the course of a hunting sequence; this switch occurred earlier in smaller fish. With this strategy the fish maximized their feeding rate:Daphniawere easier to catch than copepods but increasingly difficult to swallow when the stomach was filling up especially for smaller fish. However, there was no indication that sticklebacks from infected populations either consumedDaphniarather than copepods or switched later in the hunting sequence to consuming copepods than fish from an uninfected population. Thus, sticklebacks did not avoid parasitized prey althoughS. solidususually has a high prevalence and causes a strong fitness reduction in its stickleback host.

Oligogenic determination of morphine analgesic magnitude: a genetic analysis of selectively bred mouse lines.

Two ongoing selective breeding projects have produced mice that display divergent analgesic responses to morphine. These two projects have selected for similar phenotypes: high and low levorphanol analgesia (HAR/LAR lines; Portland, OR) and high and low swim stress-induced analgesia (HA/LA lines; Jastrzebiec, Poland). Evidence suggests genetic commonalities between mice of the two projects. Using a Mendelian breeding protocol, we have recently found that one or two genetic loci predominantly determine the high morphine analgesia exhibited by HA mice. In the present study we demonstrate that the differential morphine analgesia (5 mg/kg, i.p.) displayed by HAR and LAR mice is similarly oligogenic, predominantly determined by two unlinked loci. A complementation analysis, in which the analgesic responses to morphine of the recessive homozygotes of each project (HAR and HA) were compared to those of their hybrid offspring (HAR x HA), revealed that different genetic loci have been fixed in each project. An intriguing bimodal distribution was observed in the HAR x HA population: Some HAR x HA hybrids displayed greater morphine analgesia than either HAR or HA mice, whereas others displayed minimal analgesia. LAR x LA hybrids displayed less analgesia than either LAR or LA mice. The analgesic responses of HAR x LA and LAR x HA mice were comparable to those of their low-line parents. These findings indicate not only that different loci were responsible for producing high morphine responders in each selection project but that these distinct loci can interact synergistically to produce "superhigh" and "superlow" responders.

One or two genetic loci mediate high opiate analgesia in selectively bred mice

The analgesic responses of humans and laboratory animals are characterized by substantial individual differences. The genetic basis of this variability can be studied experimentally in rodents using a program of selective breeding. One such program selected for high (HA) and low (LA) swim stress-induced analgesia (SSIA) on the hot-plate (56°C) test in Swiss-Webster mice. These lines, which have been selectively bred for more than 25 generations, display markedly divergent opioid-mediated SSIA (3-min swims in 38°C water), morphine analgesia (10 mg/kg, i.p.), and analgesia to the κ-receptor agonist, U-50,488H (30 mg/kg, i.p.). The present study investigated the mode of inheritance of these opioid analgesias in HA and LA mice, using Mendelian genetic analyses. We report that the differential sensitivity of HA and LA mice to each of these analgesic manipulations appears to be determined oligogenically, by one or at the most two major genetic loci. The loci associated with each type of analgesia do not co-segregate, however, indicating that three distinct oligogenic effects have been identified. These findings suggest that the genetic determination of analgesic mechanisms may have simple components and as such may be amenable to further analysis using molecular genetic techniques.

3種類の水温下での低強度長時間水泳に対するホルモンおよび代謝応答

3種類の水温下での低強度長時間水泳に対するホルモンおよび代謝応答

Swimming behaviour of developmental stages of the calanoid copepod Temora longicornis at different food concentrations

The swimming behaviour of developmental stages of the marine calanoid copepod Temora longicornis was studied using 2-dimensional observations under a microscope and a 3-dimensional filming technique to analyze swimming mode, swimming speed and swimming trajectories under different food concentrations. The nauplii swam intermittently in a stop-and-go fashion. The swimming behaviour of the smallest feeding stage (N2) did not change with different food concentrations. The largest nauplius stages reacted to an increased food concentration by increasing the percentage of time spent swimming. All copepodid stages swam continuously their mouthparts moving nearly 100% of the time. Copepodids can therefore only increase their feeding effort by increasing their limb beat frequency. Adult females showed low swimming speeds at very low food concentrations, higher swimming speeds at intermediate concentrations and low swimming speeds at very high food concentrations. This agreed with expectations based on the optimal foraging theory. Males behaved differently from the females. Not only was the average swimming speed of males higher at similar food conditions, but they also maintained a very high swimming speed at very high food concentrations. This increased swimming activity in the males may be linked to a mate seeking strategy. Neither males nor females showed any obvious differences in turning behaviour at different food concentrations.

Exercise intensity during long-distance swimming in the sea in two groups with higher and lower swimming ability.

Exercise intensity during long-distance swimming in the sea in two groups with higher and lower swimming ability.