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At least 1,621 records · Page 90Linked to original sources
PubMed2006

Na(+) and flagella-dependent swimming of alkaliphilic Bacillus pseudofirmus OF4: a basis for poor motility at low pH and enhancement in viscous media in an "up-motile" variant.

Flagella-based motility of extremely alkaliphilic Bacillus species is completely dependent upon Na(+). Little motility is observed at pH values < approximately 8.0. Here we examine the number of flagella/cell as a function of growth pH in the facultative alkaliphile Bacillus pseudofirmus OF4 and a derivative selected for increased motility on soft agar plates. Flagella were produced by both strains during growth in a pH range from 7.5 to 10.3. The number of flagella/cell and flagellin levels of cells were not strongly dependent on growth pH over this range in either strain although both of these parameters were higher in the up-motile strain. Assays of the swimming speed indicated no motility at pH < 8 with 10 mM Na(+), but significant motility at pH 7 at much higher Na(+) concentrations. At pH 8-10, the swimming speed increased with the increase of Na(+) concentration up to 230 mM, with fastest swimming at pH 10. Motility of the up-motile strain was greatly increased relative to wild-type on soft agar at alkaline pH but not in liquid except when polyvinylpyrrolidone was added to increase viscosity. The up-motile phenotype, with increased flagella/cell may support bundle formation that particularly enhances motility under a subset of conditions with specific challenges.

Alkalies↗
PubMed1991

Effect of inhalation anesthetics on swimming activity of artemia salina.

The swimming movement of artemia salina in the artificial sea water was measured by using the video camera system in the absence and presence of anesthetics, i.e. enflurane, halothane, and isoflurane. The movement of artemia looked random at a glance but the obtained distribution curve for the swimming speed was skewed toward the high speed side somewhat resembling a Maxwellian distribution curve seen in the statistics of ideal gases. When anesthetic were added, the distribution curve became sharpened and shifted to the low speed side, which is similar to a behavior of ideal gases when they are cooled down. The mean swimming-speed was decreased eventually leading to an irreversible death with increasing the anesthetic dose. The activity was analyzed by using the hydrodynamic equation. The ED(50), which is a dose that causes a 50% reduction in the activity, of all anesthetics used in this study was quite similar to the MAC values for human. It was also suggested that an interaction between anesthetics and artemia was highly cooperative since the larger Hill coefficients were obtained for all three anesthetics used.

Journal Article↗
PubMed1984

Intersegmental coordination of leech swimming: comparison of in situ and isolated nerve cord activity with body wall movement.

Recordings of motoneuron activity during swimming, obtained from leech ventral nerve cords in situ, were compared with films of swimming leeches and with recordings of motoneuron activity from isolated nerve cords. It was found that the intersegmental phase lag in body movement is greater than the phase lag of in situ neuronal activity, which is in turn greater than the phase lag of isolated nerve cord activity. We conclude that peripheral neuronal or mechanical effects, as well as sensory feedback to the central pattern generator, contribute to the movement pattern of the intact swimming leech.

Animals↗
PubMed1993

Antidepressant-like effect of LY228729 as measured in the rodent forced swim paradigm.

The novel 5-HT1A receptor agonist, LY228729, was tested to see if it would produce antidepressant-like behavioural effects in the rodent forced swim model. The tricyclic antidepressant, imipramine, as well as the 5-HT1A receptor agonists, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and gepirone, produced dose-related decreases in immobility in the forced swim test following subchronic treatment in rats. LY228729, when given over a three injection course, as with the other compounds, significantly reduced immobility at doses of 1 and 3 mg/kg. Subsequent analysis of locomotor activity revealed no increases in behavior, so that general changes in activity could not account for the reduction in immobility time in the forced swim. These results suggest that LY228729 may have clinical antidepressant efficacy.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1991

Involvement of histamine in naloxone-resistant and naloxone-sensitive models of swim stress-induced antinociception in the mouse.

The antinociceptive activity of histamine in male mice has been demonstrated using chemical and thermal noxious stimuli and its involvement in naloxone-sensitive and naloxone-insensitive models of stress-induced antinociception investigated. In the abdominal constriction test, histamine and dimaprit but not histidine, induced antinociception. Compound 48/80 and H1 antagonists (diphenhydramine, mepyramine and promethazine) and large doses of H2 antagonists (cimetidine and zolantidine) produced antinociception in this test. Antinociception induced by histamine was refractory to mepyramine, metiamide and naloxone. Histamine and non-antinociceptive doses of its antagonists had no influence on the naloxone-resistant warm water swim stress-induced antinociception. In the hot-plate test, histamine agonists, except the H3 agonist (R) alpha-methyl histamine (alpha-MeHA), were antinociceptive but all these agents augmented the naloxone-sensitive room temperature swim stress-induced antinociception, after either intraperitoneal or intraventricular injection. The antinociceptive action of dimaprit was not antagonized by zolantidine which, like other histamine antagonists excluding metiamide, also produced antinociception and enhanced room temperature swim stress-induced antinociception. These findings suggest that histamine is involved in pathways mediating antinociception in the mouse and that such pathways are activated in a naloxone-sensitive model of stress-induced antinociception but not in a naloxone-insensitive model.

Animals↗
PubMed1992

Effects of chronic forced swimming and exposure to alarm substance: physiological and behavioral consequences.

Rats tested for 7 consecutive days in the forced swim test in fresh water were more immobile than those tested in soiled water on all days. Animals in both water conditions increased their immobility times slightly over days, but animals tested in soiled water, which presumably contained an alarm substance, never attained the immobility times of those tested in fresh water. When animals were switched between fresh and soiled water, they behaved exactly like animals in the water condition to which they were switched. Prior inescapable forced swimming in either water condition affected subsequent escape in a Morris water maze, but more so for animals tested only in fresh water. A second study corroborated the escape results. Serum corticosterone and relative adrenal weights were increased as a result of forced swimming but escape performance differences could not be attributed to differences in the stress-provoking consequences of the two water conditions.

Animals↗
PubMed1988

Potentiation of opioid and nonopioid forms of swim analgesia by cimetidine.

Antagonism of the H-2 receptor with cimetidine and other histaminergic receptor antagonists has been used to differentiate nonopioid and opioid forms of footshock analgesia which are mediated by neural mechanisms. Cimetidine reduces nonopioid footshock analgesia while potentiating an opioid form of this analgesia. The present study examined whether cimetidine altered the nonopioid, neurohormonal analgesia induced by either continuous cold-water swims (CCWS: 2 degrees C for 3.5 min) or the opioid analgesia induced by intermittent cold-water swims (ICWS: 2 degrees C, 18 10-sec swims, 18 10-sec recovery periods). Vehicle or cimetidine (10, 50, 100 mg/kg) injections were administered alone or paired with either CCWS or ICWS; tail-flick latencies, jump thresholds and core body temperatures were then measured. Cimetidine (100 mg/kg) significantly potentiated CCWS and ICWS analgesia and hypothermia, while having minimal effects upon basal thresholds. Lower cimetidine doses produced transitory effects on these measures. These data demonstrate dissociations between neural and neurohormonal forms of nonopioid analgesia following cimetidine treatment. The latter effect may be attributed to changes in stress responsiveness or thermoregulation rather than pain inhibition.

Animals↗
PubMed1990

Antidepressant-like action of nicardipine, verapamil and hemicholinium-3 injected into the anterior hypothalamus in the rat forced swim test.

Male Wistar rats, chronically implanted with cannulas into the anterior hypothalamus, were acutely injected with the calcium channel inhibitors, diltiazem, nicardipine and verapamil, or the choline uptake blocker hemicholinium-3 and tested in the forced swim test. Hemicholinium-3, nicardipine and verapamil markedly increased the duration of active swimming. This antidepressant-like effect did not appear to reflect merely a hyperactive state as the drug-treated rats did not differ from vehicle-injected controls in their open field motility scores. Diltiazem failed to influence rats' performance in either test. Since nicardipine and verapamil, but not diltiazem, share choline uptake property with hemicholinium-3, it seems that this action plays a role in the antidepressant-like effect of all three drugs in the forced swim test.

Animals↗
PubMed1992

Relationships between the results of a modified sperm penetration test and a swim-up technique and the fertility of ram semen.

Two relatively simple techniques for the objective measurement of semen quality, and which are easy to apply in the field or laboratory, have been developed: a modified sperm penetration test read by the naked eye and a colorimeter-based swim-up technique. Both the modified sperm penetration and swim-up methods produced promising results in prediction of ram fertility; the modified sperm penetration test was correlated (P<0.05) with a 48-day nonreturn rate and a 60-day conception rate; the correlation between a swim-up velocity and the 60-day conception rate approached significance (r=0.483; 0.1>P>0.05).

Journal Article↗
PubMed1991

Effect of different restraint schedules on the immobility in the forced swim test: modulation by an opiate mechanism.

The present research was conducted to evaluate the influence of different stress schedules on behaviors displayed during both phases of the forced swim test (FST). In addition, the involvement of an opiate mechanism in the behavioral consequences of chronic restraint was investigated. Exposure to a single, but not to chronic, restraint event induced an increase in the immobility score obtained during the 10-min initial swimming exposure (initial test) of the FST. Animals submitted to a previous regime of repeated restraint showed a significant increase in immobility during the 5-min second swimming exposure (retest period) of this behavioral task. However, naloxone (NAL) administered before each of the seven restraint events, blocked the higher immobility observed in chronically stressed rats during the retest period suggesting the involvement of an opiate mechanism. Results concerning the effect of chronic stress on the behavior displayed during the FST were discussed with reference to previous reports which have proposed that immobility performed during the retest period of the FST represents an efficient adaptive response in this inescapable aversive experience.

Adaptation, Physiological↗
PubMed2005

[Isokinetic dynamometer measurement of shoulder rotational strength in healthy elite athletes (swimming, volley-ball, tennis): comparison between dominant and nondominant shoulder].

OBJECTIVE: To compare lateral rotator (LR) and medial rotator (MR) muscle strength of both shoulders in a sport involving asymmetrical movements (tennis), symmetrical movements (swimming), and symmetrical and asymmetrical movements (volley-ball). MATERIALS AND METHODS: Retrospective study of 42 healthy elite athletes (18 women: 14 tennis players, 19 swimmers and 9 volleyball players. We evaluated the strength of LR and MR of both shoulders by Cybex Norm isokinetic dynamometer, in the concentric mode, in the modified Davies position, at 2 different speeds (60 degrees and 180 degrees s(-1)) and analysed peak torque of LR and MR and LR/MR ratios. RESULTS: TENNIS: The MR peak torque of the dominant shoulder was significantly higher than that of the non-dominant shoulder. The LR/MR ratio of the dominant shoulder was significantly lower than the non dominant shoulder in women. SWIMMING: The LR strength and LR/MR ratio of the dominant shoulder was higher than the non dominant side in men at 60 degrees/second. Both shoulders showed comparable strength in women. VOLLEYBALL: Shoulder muscular strength was symmetrical. CONCLUSION: The higher strength of MR muscles in the dominant shoulder of tennis players (asymmetrical movements) has been reported in the literature. Athletes show asymmetrical shoulder strength in swimming, a symmetrical sport and similar LR and MR strength in both shoulders in volleyball, a sport with asymmetrical movements. To our knowledge, these results have never been reported before.

Adult↗
PubMed2004

The relationship between body size and the field potentials generated by swimming crayfish.

Aquatic animals generate electrical field potentials which may be monitored by predators or conspecifics. Many crustaceans use rapid, forceful contractions of the flexor and extensor muscles to curl and extend their abdomens during swimming in escape and locomotion. When crayfish swim they generate electrical field potentials that can be recorded by electrodes nearby in the water. In general, it is reasonable to assume that larger bodied crayfish will generate signals of greater amplitude because they have larger muscles. It is not known, however, how activity in particular muscles and nerves combines to produce the compound electrical waveform recorded during swimming. We therefore investigated the relationship between abdominal muscle, body size and the amplitude of nearby tailflip potentials in the freshwater crayfish (Cherax destructor). We found that amplitude was correlated positively with abdominal muscle mass. The mean amplitude recorded from the five smallest and five largest individuals differed by 440 microV, a difference sufficiently large to be of significance to predators and co-inhabitants in the wild.

Abdominal Muscles↗
PubMed2005

Spiroplasma swim by a processive change in body helicity.

Microscopic organisms must rely on very different strategies than their macroscopic counterparts to swim through liquid. To date, the best understood method for prokaryotic swimming employs the rotation of flagella. Here, we show that Spiroplasma, tiny helical bacteria that infect plants and insects, use a very different approach. By measuring cell kinematics during free swimming, we find that propulsion is generated by the propagation of kink pairs down the length of the cell body. A processive change in the helicity of the body creates these waves and enables directional movement.

Methylcellulose↗
PubMed1982

Motility analysis of circularly swimming bull spermatozoa by quasi-elastic light scattering and cinematography.

The Rayleigh-Gans-Debye approximation is used to predict the electric field autocorrelation functions of light scattered from circularly swimming bull spermatozoa. Using parameters determined from cinematography and modeling the cells as coated ellipsoids of semiaxes a = 0.5 micrometers, b = 2.3 micrometers, and c = 9.0 micrometers, we were able to obtain model spectra that mimic the data exactly. A coat is found to be a necessary attribute of the particle. It is also clear that these model functions at 15 degrees may be represented by the relatively simple function used before by Hallett et al. (1978) to fit data from circularly swimming cells, thus giving some physical meaning to these functional shapes. Because of this agreement the half-widths of experimental functions can now be interpreted in terms of an oscillatory frequency for the movement of the circularly swimming cell. The cinematographic results show a trend to chaotic behavior as the temperature of the sample is increased, with concomitant decrease in overall efficiency. This is manifested by a decrease in oscillatory frequency and translational speed.

Animals↗
PubMed1998

Origins of individual swimming behavior in bacteria.

Cells in a cloned population of coliform bacteria exhibit a wide range of swimming behaviors--a form of non-genetic individuality. We used computer models to examine the proposition that these variations are due to differences in the number of chemotaxis signaling molecules from one cell to the next. Simulations were run in which the concentrations of seven gene products in the chemotaxis pathway were changed either deterministically or stochastically, with the changes derived from independent normal distributions. Computer models with two adaptation mechanisms were compared with experimental results from observations on individuals drawn from genetically identical populations. The range of swimming behavior predicted for cells with a standard deviation of protein copy number per cell of 10% of the mean was found to match closely the experimental range of the wild-type population. We also make predictions for the swimming behaviors of mutant strains lacking the adaptational mechanism that can be tested experimentally.

Bacteria↗
PubMed1998

Spatial sensing of stimulus gradients can be superior to temporal sensing for free-swimming bacteria.

Predictions of the minimal size an organism must have to swim along stimulus gradients were used to compare the relative advantages of sensory systems employing spatial (simultaneous) and temporal (sequential) gradient detection mechanisms for small free-swimming bacteria, leading to the following conclusions: 1) there are environmental conditions where spatial detection mechanisms can function for smaller organisms than can temporal mechanisms, 2) temporal mechanisms are superior (have a smaller size limit) for the difficult conditions of low concentration and shallow gradients, but 3) observed bacterial chemotaxis occurs mostly under conditions where spatial mechanisms have a smaller size limit, and 4) relevant conditions in the natural environment favor temporal mechanisms in some cases and spatial mechanisms in others. Thus, sensory ecology considerations do not preclude free-swimming bacteria from employing spatial detection mechanisms, as has been thought, and microbiologists should be on the lookout for them. If spatial mechanisms do not occur, the explanation should be sought elsewhere.

Bacterial Physiological Phenomena↗
PubMed1999

Bacterial swimming strategies and turbulence.

Most bacteria in the ocean can be motile. Chemotaxis allows bacteria to detect nutrient gradients, and hence motility is believed to serve as a method of approaching sources of food. This picture is well established in a stagnant environment. In the ocean a shear microenvironment is associated with turbulence. This shear flow prevents clustering of bacteria around local nutrient sources if they swim in the commonly assumed "run-and-tumble" strategy. Recent observations, however, indicate a "back-and-forth" swimming behavior for marine bacteria. In a theoretical study we compare the two bacterial swimming strategies in a realistic ocean environment. The "back-and-forth" strategy is found to enable the bacteria to stay close to a nutrient source even under high shear. Furthermore, rotational diffusion driven by thermal noise can significantly enhance the efficiency of this strategy. The superiority of the "back-and-forth" strategy suggests that bacterial motility has a control function rather than an approach function under turbulent conditions.

Bacteria↗
PubMedDate not supplied

Swimming of spermatozoa in a linear viscoelastic fluid.

A modified resistive force theory is developed for a spermatozoon swimming in a general linear viscoelastic fluid. The theory is based on a Fourier decomposition of the flagellar velocity, which leads to solving the Stokes flow equations with a complex viscosity. We use a model spermatozoon with a spherical head which propagates small amplitude sinusoidal waves along its flagellum. Results are obtained for the velocity of propulsion and the rate of working for a free swimming spermatozoon and the thrust on a fixed spermatozoon. There is no change in propulsive velocity for a viscoelastic fluid compared to a Newtonian fluid. The rate of working does change however, decreasing with increasing elasticity of the fluid, for a Maxwell fluid. Thus the theory predicts that a spermatozoon can swim faster in a Maxwell fluid with the same expenditure of energy for a Newtonian fluid.

Animals↗