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At least 1,675 records · Page 93Linked to original sources
PubMed1998

Self-propelled anguilliform swimming: simultaneous solution of the two-dimensional navier-stokes equations and Newton's laws of motion

Anguilliform swimming has been investigated by using a computational model combining the dynamics of both the creature's movement and the two-dimensional fluid flow of the surrounding water. The model creature is self-propelled; it follows a path determined by the forces acting upon it, as generated by its prescribed changing shape. The numerical solution has been obtained by applying coordinate transformations and then using finite difference methods. Results are presented showing the flow around the creature as it accelerates from rest in an enclosed tank. The kinematics and dynamics associated with the creature's centre of mass are also shown. For a particular set of body shape parameters, the final mean swimming speed is found to be 0.77 times the speed of the backward-travelling wave. The corresponding movement amplitude envelope is shown. The magnitude of oscillation in the net forward force has been shown to be approximately twice that in the lateral force. The importance of allowing for acceleration and deceleration of the creature's body (rather than imposing a constant swimming speed) has been demonstrated. The calculations of rotational movement of the body and the associated moment of forces about the centre of mass have also been included in the model. The important role of viscous forces along and around the creature's body and in the growth and dissolution of the vortex structures has been illustrated.

Journal Article↗
PubMed1999

Red muscle activation patterns in yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) tunas during steady swimming.

To learn about muscle function in two species of tuna (yellowfin Thunnus albacares and skipjack Katsuwonus pelamis), a series of electromyogram (EMG) electrodes was implanted down the length of the body in the internal red (aerobic) muscle. Additionally, a buckle force transducer was fitted around the deep caudal tendons on the same side of the peduncle as the electrodes. Recordings of muscle activity and caudal tendon forces were made while the fish swam over a range of steady, sustainable cruising speeds in a large water tunnel treadmill. In both species, the onset of red muscle activation proceeds sequentially in a rostro-caudal direction, while the offset (or deactivation) is nearly simultaneous at all sites, so that EMG burst duration decreases towards the tail. Muscle duty cycle at each location remains a constant proportion of the tailbeat period (T), independent of swimming speed, and peak force is registered in the tail tendons just as all ipsilateral muscle deactivates. Mean duty cycles in skipjack are longer than those in yellowfin. In yellowfin red muscle, there is complete segregation of contralateral activity, while in skipjack there is slight overlap. In both species, all internal red muscle on one side is active simultaneously for part of each cycle, lasting 0.18T in yellowfin and 0.11T in skipjack. (Across the distance encompassing the majority of the red muscle mass, 0.35-0.65L, where L is fork length, the duration is 0.25T in both species.) When red muscle activation patterns were compared across a variety of fish species, it became apparent that the EMG patterns grade in a progression that parallels the kinematic spectrum of swimming modes from anguilliform to thunniform. The tuna EMG pattern, underlying the thunniform swimming mode, culminates this progression, exhibiting an activation pattern at the extreme opposite end of the spectrum from the anguilliform mode.

Journal Article↗
PubMed1999

Daphnia pulex swims towards the most strongly polarized light - a response that leads to 'shore flight'

When Daphnia pulex are presented on one side of their visual field with diffuse, large-area linearly polarized light with a horizontal e-vector and on the other side of their visual field with large-area polarized light with a lower degree of polarization, they swim towards the place with the higher degree of polarization. The response is intensity-invariant: Daphnia pulex swim towards the place of maximal polarization regardless of which side of their visual field has the higher intensity of light. As a result of Rayleigh scattering in a pond, the light surrounding the Daphnia is polarized and has a horizontal e-vector. Near the shore, polarization is not homogeneous. The light seen in the direction of the open water has a higher degree of polarization than that seen in the direction towards the shore. Therefore, in a pond, swimming towards the place with the highest degree of polarization leads the Daphnia away from the shore. For Daphnia, this response explains a mechanism that underlies the well-known phenomenon of 'shore flight', the active departure of small pelagic crustaceans from shore zones.

Journal Article↗
PubMed1976

Spirillum swimming: theory and observations of propulsion by the flagellar bundle.

The hydrodynamics and energetics of helical swimming by the bacterium Spirillum sp. is analysed using observations from medium speed cine photomicrography and theory. The photographic records show that the swimming organism's flagellar bundles beat in a helical fashion just as other bacterial flagella do. The data are analysed according to the rotational resistive theory of Chwang & Wu (1971) in a simple-to-use parametric form with the viscous coefficients Cs and Cn calculated according to the method of Lighthill (1975). Results of the analysis show that Spirillum dissipated biochemical energy in performing work against fluid resistance to motion at an average rate of about 6 X 10(-8) dyne cm s-1 with some 62-72% of the power dissipation due to the non-contractile body. These relationships yield a relatively low hydromechanical efficiency which is reflected in swimming speeds much smaller than a representative eukaryote. In addition the Cn/Cs ratio for the body is shown to lie in the range 0-86-1-51 and that for the flagellar bundle in the range 1-46-1-63. The implications of the power calculations for the Berg & Anderson (1973) rotating shaft model are discussed and it is shown that a rotational resistive theory analysis predicts a 5-cross bridge M ring for each flagellum of Spirillum.

Energy Metabolism↗
PubMed1978

The effect of training on the swimming muscles of the goldfish (Carassius auratus).

Goldfish (Carassius auratus) were exercised continuously for periods of 28 days at swimming speeds of 1.5, 3.0 and 4.5 body lengths per second and their rates of growth were determined. Changes in muscle fibre size were examined, as were changes which occurred in the concentrations of the major chemical constituents of these cells. These fish, typical of the carp family in that they are found only in still or slowly moving water, did not adapt well to the flowing water environment at any swimming speed. They often grew less than the controls, although consuming much more food. Changes in the composition of the muscle fibres indicated that excess food was not being stored, and also indicated that the major fuel for swimming at all speeds was glycogen. The fish survived well at high speeds and it was suggested that this was due to the ability of the species to metabolize glycogen anaerobically without the production of lactic acid.

Animals↗
PubMed1985

Accumulation of adrenaline in sympathetic nerve endings in various organs of the rat exposed to swimming stress.

Swimming produced a marked increase in adrenaline content, but produced no change or slight decrease in noradrenaline content in the heart, spleen and submaxillary gland of the rat. Pretreatment with desmethylimipramine abolished the swimming-induced increase in adrenaline in the three organs. It was also found that the administration of 6-hydroxydopamine caused almost complete depletion of both adrenaline and noradrenaline from these organs of control and swimming-treated rats. Furthermore, a differential centrifugation study revealed that the microsomal fraction had the highest concentrations of both adrenaline and noradrenaline in the heart and spleen of control and stress-treated rats. These findings suggest that adrenaline, like noradrenaline, exists in sympathetic nerve endings in the peripheral organs of the rats under basal conditions, and the adrenaline contents in the nerve endings are increased under stress situations.

Animals↗
PubMed1988

Nuclear maturity and morphology of human spermatozoa selected by Percoll density gradient centrifugation or swim-up procedure.

The selection of motile human spermatozoa, from fertile and infertile semen samples was compared by using Percoll density gradient centrifugation or the swim-up procedure. Selected spermatozoa were evaluated according to their motility, % normal forms, nuclear maturity (aniline blue staining, acridine orange staining, ethidium bromide uptake and SDS nuclear decondensation). These methods showed differences between fertile and infertile men. The swim-up procedure, based on motility, resulted in greater proportions of motile spermatozoa and eliminated mainly tail abnormalities. Percoll gradient separation, based on density, selected oval-headed spermatozoa with good motility. Nuclear maturity level was improved by both methods but Percoll gradient separation generally resulted in spermatozoa with better nuclear maturity than those selected by the swim-up procedure.

Cell Nucleus↗
PubMed1999

The relationship between anxiety and depression in animal models: a study using the forced swimming test and elevated plus-maze.

The present study evaluated the correlation between the behavior of mice in the forced swimming test (FST) and in the elevated plus-maze (PM). The effect of the order of the experiments, i.e., the influence of the first test (FST or PM) on mouse behavior in the second test (PM or FST, respectively) was compared to handled animals (HAND). The execution of FST one week before the plus-maze (FST-PM, N = 10), in comparison to mice that were only handled (HAND-PM, N = 10) in week 1, decreased % open entries (HAND-PM: 33.6 +/- 2.9; FST-PM: 20.0 +/- 3.9; mean +/- SEM; P<0.02) and % open time (HAND-PM: 18.9 +/- 3.3; FST-PM: 9.0 +/- 1.9; P<0.03), suggesting an anxiogenic effect. No significant effect was seen in the number of closed arm entries (FST-PM: 9.5 (7.0-11.0); HAND-PM: 10.0 (4.0-14.5), median (interquartile range); U = 46.5; P>0.10). A prior test in the plus-maze (PM-FST) did not change % immobility time in the FST when compared to the HAND-FST group (HAND-FST: 57.7 +/- 3.9; PM-FST: 65.7 +/- 3.2; mean +/- SEM; P>0.10). Since these data suggest that there is an order effect, the correlation was evaluated separately with each test sequence: FST-PM (N = 20) and PM-FST (N = 18). There was no significant correlation between % immobility time in the FST and plus-maze indexes (% time and entries in open arms) in any test sequence (r: -0.07 to 0.18). These data suggest that mouse behavior in the elevated plus-maze is not related to behavior in the forced swimming test and that a forced swimming test before the plus-maze has an anxiogenic effect even after a one-week interval.

Animals↗
PubMed1983

Evaluation of a coaching strategy to reduce swimming stroke errors with beginning age-group swimmers.

A coaching strategy to decrease errors in swimming strokes with swimmers who had not improved under "standard" coaching procedures was investigated using a multiple baseline design across subjects and swimming strokes. The procedure resulted in a large decrease in errors on swimming strokes during sessions in a training pool. Stimulus generalization of improved performance to normal practice conditions in the regular pool was observed with all but one swimmer. This improvement was maintained during two maintenance phases lasting approximately 2 weeks, as well as under standard coaching conditions during at least a 2-week follow-up. For two swimmers, error rates on one of the strokes showed a gradual increase between the third and fifth week of follow-up, but brief remedial prompting sessions immediately corrected their performance. Some beneficial response generalization to other components of the stroke being trained was observed, but no improvements were found on untrained strokes. The error correction package did not disrupt practice, require excessive amounts of the coach's time, or necessitate the use of cumbersome apparatus. In addition, the coach and the swimmers considered the procedures to be effective, and expressed their willingness to participate in them again in the future.

Journal Article↗
PubMed1993

The health effects of swimming at Sydney beaches. The Sydney Beach Users Study Advisory Group.

OBJECTIVES: The purpose of the study was to determine the health risks of swimming at ocean beaches in Sydney, Australia. METHODS: From people attending 12 Sydney beaches in the period from December 5, 1989 to February 26, 1990, we recruited a cohort of 8413 adults who agreed to participate in this study. Of these, 4424 were excluded either because they had been swimming in the previous 5 days or because they reported a current illness. Of the remainder, 2839 successfully completed a follow-up telephone interview conducted within 10 days after recruitment. We recorded reported respiratory, gastrointestinal, eye, and ear symptoms and fever that occurred within the 10 days between initial interview on the beach and the follow-up interview. RESULTS: A total of 683 participants (24.0%) reported experiencing symptoms in the 10 days following initial interview. Of these, 435 (63.7%) reported respiratory symptoms. Swimmers were almost twice as likely as nonswimmers to report symptoms. There was a linear relationship between water pollution and all reported symptoms with the exception of gastrointestinal complaints. CONCLUSIONS: Swimmers at Sydney ocean beaches are more likely to report respiratory, ear, and eye symptoms than beachgoers who do not swim. The incidence of these symptoms increases slightly with increasing levels of pollution.

Adolescent↗
PubMedDate not supplied

Comparison of direct swim-up, mini-Percoll, and Sephadex G10 separation procedures.

A comparison was made of three sperm separation techniques--direct swim-up, mini-Percoll, and Sephadex G-10--on semen parameters, including count, % motility, forward progression, and hypoosmotic swelling (HOS) test scores. Overall, the best quality sperm (less debris, best % and quality motility, and best HOS scores) were noted with the direct swim-up procedure. Mini-Percoll resulted in the highest count, but the worst HOS score. Sephadex G-10 resulted in quality of semen specimen almost as good as the direct swim-up procedure, but did allow some noncellular debris and bacteria to filter through the column.

Cell Separation↗
PubMedDate not supplied

Correlation between sperm morphology using strict criteria in original semen and swim-up inseminate and human in vitro fertilization.

To study the value of sperm morphology using strict criteria in raw semen and in swim-up inseminate of human in vitro fertilization (IVF), 135 cycles of IVF with normal sperm concentration and motility were recruited. At least two mature oocytes were recovered in each cycle. The correlation between the percentages of normal forms and fertilization rates of mature oocytes was analyzed. The results demonstrate that the percentage of normal forms in both the raw semen and swim-up sample of patients with poor fertilization was significantly lower than in those with acceptable fertilization. The percentages of normal forms both in raw semen and in swim-up sample were significantly correlated with fertilization rates in vitro, however, the former seemed to have a better correlation (r = .51 and .19, respectively). Regarding the percentages of normal forms in raw semen, the fertilization rate in patients with normal forms < 4% was 6 +/- 11%, for 4-14% it was 58 +/- 36%, and for > 14% it was 88 +/- 20%. The fertilization rates were significantly different among these three groups of patients. The evaluation of sperm morphology using strict criteria in raw semen before IVF is predictive of fertilization outcome and may also help doctors to choose an optimal method of treatment for patients.

Female↗
PubMedDate not supplied

Comparison between swim-up and glass wool column filtration of human semen in a gamete intrafallopian transfer program.

This study compared swim-up and glass wool filtration in both pregnancy outcome and fertilization of excess oocytes in patients undergoing gamete intrafallopian transfer. Gamete intrafallopian transfer patients were retrospectively included in the study group (n = 52). The criteria for inclusion were as follows: Semen had to have been prepared by means of glass wool filtration and at least 2 metaphase II oocytes had to have been transferred. Each patient from this group was then carefully matched with another patient according to specific criteria (number of metaphase II oocytes aspirated and transferred, normal sperm morphology, wife's age, the absence of anti-sperm antibodies, semen preparation by means of the swim-up procedure). Fourteen patients were matched with themselves (groups A1 and A2) and 38 patients were matched with another patient (groups B and C). The results indicate that there was no significant difference in the fertilization and pregnancy probabilities of sperm prepared by means of glass wool filtration or swim-up procedure. The comparative pregnancy rates for the groups were A1 (7.1%) versus A2 (7.1%) and B (28.9%) versus C (31.6%). Factors other than fertilization and pregnancy potential may have a greater influence on choosing the optimum sperm preparation procedure.

Female↗
PubMedDate not supplied

Motility stimulant effects of prostasome inclusion in swim-up medium on cryopreserved human spermatozoa.

The chance of obtaining a fertilization and establishing a pregnancy increases with the number of motile spermatozoa that can reach and interact with the oocyte after the time of insemination. In an attempt to increase the recovery of freeze-thawed and motile spermatozoa, the swim-up medium was supplemented with prostasomes and some other effectors. Swim-up media supplemented with prostasomes were superior in comparison to the other effectors investigated in the recovery of motile spermatozoa for insemination. These results suggest that prostasome inclusion in swim-up medium might be of benefit in improving results in assisted reproductive technologies using freeze-thawed spermatozoa.

Aminopeptidases↗
PubMed1983

Enhanced glycogen repletion in liver and skeletal muscle with citrate orally fed after exhaustive treadmill running and swimming.

A possibility whether an oral feeding of citrate, which has been reported to inhibit phosphofructokinase in vitro, following exercise to exhaustion could increase the rate of glycogen repletion in liver and soleus muscle was tested in treadmill running trained (experiments 1 and 2) and swimming trained rats (experiment 3). An exhaustive running or swimming was loaded at the end of the experiments, resulting in a significant reduction in liver and soleus muscle glycogen stores. The feeding of 1.0 and 0.5 g of citrate per kg of body weight just after the exhaustive running could significantly increase the liver glycogen repletion during a 2-hr recovery period, but this was not observed in soleus muscle (experiment 1). As compared with a single feeding of 3.3 g of glucose per kg of body weight, a mixed feeding of 0.5 g of citrate and 3.0 g of glucose after an exhaustive running (experiment 2) and swimming (experiment 3) could significantly enhance the repletion of glycogen stores in both liver and soleus muscle. These results clearly indicate that the postexercise feeding of citrate can stimulate the glycogen repletion in liver and skeletal muscle during an early period of recovery.

Administration, Oral↗
PubMed1999

A newly designed underwater antenna and its application to underwater radio-telemetry for measuring electroencephalographic activity from the rainbow trout freely swimming in natural environments.

A novel underwater antenna (which we named an 'aquaerial') for telemetering the biological signals from freely swimming fish in freshwater natural environments is presented. It is designed for receiving a 90-100 MHz carrier wave and consists of plural unit receiving antennas (UAs). The plural UAs are placed underwater to cover the area where the target fish carrying the transmitter is swimming. The UAs are equally spaced and have a directional coupling amplifier to supply the signals received to the coaxial cable. The optimal length of the UA was found to be 16.5 cm (a half wavelength in water) and optimal spacing was 2 m (one wavelength along coaxial cable) when 95 MHz was used as the carrier frequency. Using this 'aquaerial', long-term monitoring of EEG signals from the olfactory bulb of the rainbow trout (Oncorhynchus mykiss) swimming freely in natural environments was achieved.

Animals↗
PubMed2001

Source water impact model (SWIM)--a watershed guided approach as a new planing tool for indirect potable water reuse.

The scope of this study was to develop a model to assess the impact of source water quality on reclaimed water used for indirect potable reuse. The source water impact model (SWIM) considered source water qualities, water supply distribution data, water use and the impact of wastewater treatment to calculate reclaimed water quality. It was applied for sulfate, chloride, and dissolved organic carbon (DOC) at four water reuse sites in Arizona and California. SWIM was able to differentiate between the amount of salts derived by drinking water sources and the amount added by consumers. At all sites, the magnitude of organic residuals in reclaimed water was strongly effected by the concentration of organics in corresponding water sources and effluent-derived organic matter. SWIM can be used as a tool to predict reclaimed water quality in existing or planned water reuse systems.

Arizona↗
PubMed2001

Prevention of adrenocortical hyperactivity by dietary casein in rats exposed to forced swimming stress.

Adrenal weight, adrenal hydroxysteroid dehydrogenase activity and serum corticosterone level were significantly higher in rats fed with 5% casein diet after 7 days of swimming stress (45 min/day) as compared to their controls. All the parameters were similar to their control levels in rats receiving 20% casein diet and exposed to swimming stress. The results suggest that casein can play an important role in preventing adrenocortical hyperactivity in swimming stressed rats.

3-Hydroxysteroid Dehydrogenases↗