Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LOCOMOTION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1995

Low concentrations of nocodazole interfere with fibroblast locomotion without significantly affecting microtubule level: implications for the role of dynamic microtubules in cell locomotion.

The role of microtubules (MTs) in cell locomotion is uncertain: while MTs are not essential for motility of certain cells, MTs are necessary for the directed translocation of large cells such as fibroblasts, endothelial cells and neuronal growth cones. Based on previous studies, we hypothesize that cell locomotion may involve MTs in two possible ways: (1) the rate of cell locomotion is proportional to MT level; or (2) cell locomotion is not proportional to MT level but requires a critical level of MTs to proceed. To test these hypotheses, we measured the rate of locomotion of NRK fibroblasts migrating into an in vitro wound, before and after treatment with different concentrations of nocodazole to generate cells with different levels of MTs. Locomotion of cells was monitored directly using timelapse recording and analyzed with an Image-1 image analysis program. Addition of nocodazole (> or = 50 nM) resulted in a rapid reduction in locomotion to a new rate that was maintained for > 2 hours. We found that addition of as little as 100 nM nocodazole decreased the rate of locomotion by more than 60%; and that 300 nM nocodazole completely stopped cell locomotion. Although 100 nM nocodazole decreased locomotion over 60%, we detected no qualitative change in MT distribution by immunofluorescence. Quantitative analysis of MT fluorescence in immunofluorescently stained preparations showed that 100 nM nocodazole had no detectable effect on MT levels and that 300 nM nocodazole only decreased MT levels to approximately 40% of controls. Quantitative analysis of tubulin polymer levels by cell extraction and western blotting yielded results similar to those obtained by quantification of MT fluorescence. A comparison of the locomotion rate measurements with the MT level measurements indicated that over half of the cell locomotion rate could be blocked by nocodazole without significantly affecting MT levels in the cell; the remaining locomotion rate was reduced proportionally to MT levels. These results do not support the notion that a critical level of MTs is required for cell locomotion and suggest that only a portion (< 50%) of the speed of the cells is proportional to MT levels. Rather, by analogy with studies of MT antagonists on the mitotic spindle, they suggest a third possibility: that low concentrations of nocodazole interfere with MT dynamics and thus, MT dynamics are critical for the maximal speed of cell locomotion. This notion was further supported by analogous effects of taxol and vinblastine on cell locomotion: at concentrations that reportedly cause little change in the level of MTs, taxol and vinblastine also dramatically decreased the rate of locomotion of NRK cells. In summary, our results establish the relationship between microtubule levels and locomotion rate and suggest that dynamic MTs are rate-limiting for fibroblast locomotion.

Animals↗
PubMedDate not supplied

Performance limits of low-temperature, continuous locomotion are exceeded when locomotion is intermittent in the ghost crab.

Since a decline in temperature decreases aerobic capacity and slows the kinetics of exercise-to-rest transitions in ectotherms, we manipulated body temperature to better understand the performance limits of intermittent locomotion. Distance capacity (i.e., the total distance traveled before fatigue) of the ghost crab, Ocypode quadrata, was determined during acute exposure to 15 degrees C inside a treadmill-respirometer. Instead of exacerbating the near-paralyzing effects of low body temperature resulting from the frequent transitions, intermittent locomotion allowed animals to exceed the performance limits measured during steady-state locomotion. At low temperature, distance capacity for continuous locomotion at 0.04 m s(-1) (83% maximum aerobic speed) was 60 m. When 30 s of exercise at 0.08 m s(-1) (166% maximum aerobic speed) was alternated with 30 s of rest, distance capacity increased to 271 m, 4.5-fold greater than continuous locomotion at the same average speed (83% maximum aerobic speed). A 30-s pause following a 30-s exercise period was sufficient for maintaining low lactate concentrations in muscle and for partial resynthesis of arginine phosphate. A greater dependency on nonoxidative metabolism due to slowed oxygen uptake kinetics at low temperature resulted in a decreased duration of the critical exercise period, which increased performance relative to that measured at higher temperatures (30 s at 15 degrees C vs. 120 s at 24 degrees C). Despite the ghost crab's limited aerobic capacity at 15 degrees C, distance capacity during intermittent locomotion at low temperature can be comparable to that of a crab moving continuously at a body temperature 10 degrees C warmer. While endurance capacity is generally correlated with maximum aerobic speed, we have demonstrated that both locomotor behavior and body temperature must be considered when characterizing performance limits.

Acclimatization↗
PubMed1992

Reversal of interleg coupling in backward locomotion implies a prime role of the direction of locomotion.

Conventional descriptions of interleg coupling relate to anatomical definitions such as fore- or hindlegs, right or left legs (i.e. the body is the frame of reference). This convention is obvious for forward walking, where forelegs (in anatomical terms) are also the leading legs (in terms of direction). In backward locomotion, however, the leading legs in terms of direction are the hindlegs in terms of anatomy. What effects do the anatomy and direction of movement have on the sequence of stepping? Our observations on the locomotion of mole rats in a transparent acrylic tunnel revealed that, as in nature, mole rats moved both forwards and backwards. They typically employed a diagonal sequence of steps in forward walking, whereas in backward walking they typically employed a lateral sequence. However, when stepping was described with movement direction as the frame of reference, both forward and backward walking were made up of the same sequence of steps. The same invariant trend was recorded during backward galloping, but to a lesser extent than during walking. We suggest that the backward sequence is simply a reversal of the forward sequence: a hindleg during backward locomotion acts like a foreleg in forward locomotion, while a foreleg acts like a hindleg in forward locomotion. Interleg coupling therefore remains invariant in relation to the direction of locomotion.

Animals↗
PubMed1985

Ontogeny of human locomotor control. I. Infant stepping, supported locomotion and transition to independent locomotion.

Locomotor patterns of human infants were studied during stepping in the newborn period (first two months of life), during supported locomotion (6-12 months of age) and during independent locomotion in children who just were able to walk by themselves without external support (10-18 months of age). Leg movements, pattern of muscular activity and reaction forces were studied by a computerized system. The locomotor pattern during the newborn period lacked the specific functions that are unique for human plantigrade locomotion. There was no heel strike in front of the body; the foot was placed instead on its forepart straight under the body. Hip and knee joints were hyperflexed during the whole step cycle and flexed synchronously during swing. The specific knee-ankle coordination of human adults was missing. The ankle extensors were activated prior to touch down together with other extensor muscles. There was no propulsive force. A similar immature non-plantigrade pattern recurred after an inactive period. During the subsequent period of supported locomotion there was a gradual transformation of the infantile pattern towards the plantigrade pattern continuing after establishment of independent locomotion. It is suggested that innate pattern generators in the spinal cord produce the infant stepping and also generate the basic locomotor rhythm in adults, but that neural circuits specific for humans develop late in ontogeny and transform the original, non-plantigrade motor activity to a plantigrade locomotor pattern.

Biomechanical Phenomena↗
PubMed1976

Lymphocyte locomotion. I. The initiation, velocity, pattern, and path of locomotion in vitro.

The locomotive behaviour of human lymphocytes in coverslip preparations of clotted autoplasma was studied at +37 degrees C. Lymphocytes isolated from peripheral blood or from the tonsils did not move prior to membrane activation by means of incubation with phytohemagglutinin (PHA). After PHA stimulation the locomotion of 19 lymphocytes was analysed by time-lapse fliming. The locomotion was random, as evidenced by a median locomotive index of 0.64 (Q1-Q3 0.04-0.75) and comparatively slow, median velocity 15 mum/min (Q1-Q3 12-18). The locomotion of 5 other lymphocytes was studied at high magnification. It is suggested that the characteristic polarity of wandering lymphocytes, indicating the direction of movement, can be utilized in the analysis of the lymphocyte traffic in tissue sections of post-capillary high-endothelium venules.

Cell Movement↗
PubMed2003

Sensitised locomotion does not predict conditioned locomotion in cocaine-treated mice: further evidence against the excitatory conditioning model of context-dependent sensitisation.

The excitatory conditioning model of contextual sensitisation proposes that the progressive emergence of the locomotion-activating effect of cocaine (or any other stimulant drug) characterising that phenomenon is due to a growing conditioned response (the test context cues) that mimics the unchanging unconditioned response (the drug effect). The present study aimed at verifying whether the relationship between the amplitude of sensitisation and the size of the conditioned response was positive, a direct implication of that view. Sensitisation to the locomotion-activating effect of cocaine (10 mg/kg, s.c.) was firstly generated over 10 daily sessions in 25 mice (strain C57Bl/6J), another lot of 25 mice receiving the same dose of cocaine outside of the testing context. Conditioned locomotion was assessed 24 h later. No significant linear correlations were found between the magnitude of the conditioned response and the magnitude of the sensitised response (delta scores), the rate of sensitisation (individual regression coefficients) or the magnitude of the initial unconditioned response to cocaine (scores in the first session of sensitisation treatment). Accordingly, there was no significant correlation between the magnitude of the initial unconditioned response and the magnitude of the sensitised response or that of the initial unconditioned response. Therefore, the conditioned response is neither necessary nor sufficient for the development of context-dependent sensitisation of the locomotion-activating effect of cocaine, a conclusion that refutes the excitatory conditioning model of that chronic effect.

Animals↗
PubMed1997

Isolation, spreading, locomotion on various substrata, and the effect of hypotonicity on locomotion of fish keratinocytes.

The paper describes improved methods for the isolation of fish skin keratinocytes, which spread and locomote 15 min after trypsinization, in the absence of extracellular matrix proteins. The random locomotion of these keratinocytes under isotropic conditions on glass, plastic (polystyrene), and glass covered with poly-L-lysine or collagen IV was studied with computer-aided methods. Several methods for quantitative description of random cell locomotion were compared. The values of some parameters commonly computed showed non-Gaussian distribution. A comparison of keratinocyte locomotion under isotonic and hypotonic conditions revealed that the hypotonic conditions increased cell displacement (net migration) owing to the klinokinetic and not the orthokinetic effect.

Animals↗
PubMed1995

Uphill locomotion in mole rats: a possible advantage of backward locomotion.

Mole rats were videotaped while locomoting in a Plexiglas tube to evaluate the effects of inclination on locomotion. Animals moving uphill preferred to go backward using plantigrade foot postures, presumably to prevent sliding. Uphill backward locomotion also allowed animals to cope with changes in weight distribution between the hind and forelimbs without modifying footfall pattern relative to the direction of progression. When the animals did use uphill forward strides, they switched to asymmetrical gaits, which are associated with increased propulsive forces. These and prior results suggest that weight distribution and direction of progression can modify the natural pattern of stepping in mammalian quadrupeds.

Animals↗
PubMed1977

Apomorphine-induced locomotion and gnawing: evidence that the experimental design greatly influences gnawing while locomotion remains unchanged.

In a recent study we have shown that it was possible to recognize and record two independent behavioural patterns elicited by apomorphine (s.c.): one behaviour characterized by increased locomotion, sniffing and repetitive head and limb movements and another, characterized by compulsive gnawing. In the present study we have further characterized the gnawing and the locomotion patterns, their dependence on the experimental design and on the test environment. We found that the apomorphine-induced gnawing was easily modified by factors such as the design of the test-box and the habituation of the animal to the test-box. Locomotion, on the other hand was essentially independent of such factors and seemed more compulsive than the so-called "compulsive gnawing".

Animals↗
PubMed1983

Peripheral control of the cat's step cycle. II. Entrainment of the central pattern generators for locomotion by sinusoidal hip movements during "fictive locomotion.".

Acute low spinal and curarized cats injected with noradrenergic agonists i.v. can elicit an efferent burst pattern which can be recorded in muscle nerve filaments and can be referred to as "fictive locomotion". This study investigates the effect that feedback, arising from movements in the hip joint, can exert on the central network generating fictive locomotion. The central network is uncoupled from generating any active movements by curarization. The motor pattern could be entrained by applying sinusoidal hip movements, even when a very extensive denervation of the leg had been performed leaving only some of the muscles around the hip and the hip joint innervated. During flexion movements, efferents to different flexor muscles became active and during movements in the reverse direction (extension), efferents to extensors were active. With an increasing movement frequency the onsets of both flexor and extensor bursts were delayed in the movement cycle. The duration of the extensor bursts varied markedly with the movement cycle, whereas pure flexors changed less in burst duration. The frequency within which the efferent burst activity was entrained in a strict 1:1 relation to the movement varied between 5 to 70% above and below the resting burst period. In preparations with a narrow 1:1 range, a "relative coordination" was encountered outside this range. The flexor burst duration was in these cases dependent on where in the hip movement cycle the bursts appeared.

4-Aminopyridine↗
PubMed1996

Size influences on primate locomotion and body shape, with special emphasis on the locomotion of 'small mammals'.

The mechanical laws which make possible several characteristic and well-known modes of primate locomotion are reviewed. Biological requirements are fulfilled in small and in large primates by utilizing different mechanical principles. On the basis of the mechanics, special morphological traits can be identified which are advantageous for performing these locomotor modes, and which determine different life-styles. These morphological 'adaptations' consequently are different in larger and smaller primates. The divergence between large and small forms is clarified by the inclusion of non-primate mammals into the comparisons.

Animals↗
PubMed1988

The defect of lymphocyte locomotion in chronic lymphocytic leukaemia: studies of polarization and growth-dependent locomotion.

This paper reports a study of the locomotor behaviour of the lymphocytes from 17 patients with chronic lymphocytic leukaemia (CLL). The cells were studied both immediately after separation from blood and after culture for 24 to 48 h with a range of growth activators. Cells direct from blood were tested for polarization in fetal calf serum (FCS 20%), phorbol myristate acetate (PMA 10(-7)M) and colchicine (10(-5)M). The polarization of lymphocytes from CLL patients with high white cell (WBC) counts (greater than 10 X 10(9)/litre) was very poor in FCS and PMA, though the cells from about half of these patients responded well to colchicine. The response of cells from patients with low white cell counts was the same as that of controls. The growth activators, PHA (1 micrograms/ml), anti-CD3 antibody (OKT3 2.5 ng/ml), Cowan strain Staphylococcus aureus (SAC; 1.5 X 10(7)/ml) and PMA (10(-8)M) induced an increase in the proportion of locomotor lymphocytes from controls and from CLL patients with low white cell counts during 24 h of culture. Cells from patients with high white cell counts showed very little increase in locomotor forms in any activator including PMA and the B cell mitogen SAC. This defect was seen in both polarization assays and collagen gel invasion assays. The findings suggest that CLL lymphocytes have a defect of locomotion demonstrable at two levels: (a) the cells fail to respond by polarizing immediately upon stimulation; colchicine treatment reverses this defect in some cases; (b) they also fail to acquire locomotor capacity during culture with activators of growth.

Aged↗
PubMed1987

Morphometrics and niche metrics in prosimian locomotion: an approach to measuring locomotion, habitat, and diet.

Locomotor morphology, it is recognized, cannot be understood without an understanding of locomotor behavior. The interaction of locomotor anatomy and behavior has been successfully analyzed for single species and species pairs. Broader generalizations, however, require the demonstration of anatomical/behavioral associations for numerous sets of species. To accomplish this it is necessary to develop a method for the simultaneous quantitative description and comparison of many different parameters of the locomotor niche: locomotor behaviors, habitat usages, and diets. As a start towards achieving this we present a multidimensional approach to the description of functional parameters of the niche for prosimians. We derive quantitative evaluations of locomotor activity, habitat utilization, and diet for each of 27 species, using field data, film and video records, and the available literature. These parameters are then displayed graphically and clustered to provide profiles for comparisons both of species and variables. The multidimensional profiles reveal valuable information about activity, environment and diet, and their interactions. They permit closer comparisons with equivalent multidimensional information about prosimian structure, based on morphometric studies. The method gives useful graphical and statistical techniques for interspecific comparisons of morphometrics and niche metrics.

Animals↗