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PubMed2004

Kinematic analysis of bipedal locomotion of a Japanese macaque that lost its forearms due to congenital malformation.

Spontaneously acquired bipedal locomotion of an untrained Japanese monkey (Macaca fuscata) is measured and compared with the elaborated bipedal locomotion of highly trained monkeys to assess the natural ability of a quadrupedal primate to walk bipedally. The subject acquired bipedalism by himself because of the loss of his forearms and hands due to congenital malformation. Two other subjects are performing monkeys that have been extensively trained for bipedal posture and locomotion. We videotaped their bipedal locomotion with two cameras in a lateral view and calculated joint angles (hip, knee, and ankle) and inertial angle of the trunk from the digitized joint positions. The results show that all joints are relatively more flexed in the untrained monkey. Moreover, it is noted that the ankle is less plantar flexed and the knee is more flexed in mid-to-late stance phase in the untrained monkey, suggesting that the trunk is not lifted up to store potential energy. In the trained monkeys, the joints are extended to bring the trunk as high as possible in the stance phase, and then stored potential energy is exchanged for kinetic energy to move forward. The efficient inverted pendulum mechanism seems to be absent in the untrained monkey's locomotion, implying that acquisition of such efficient bipedal locomotion is not a spontaneous ability for a Japanese monkey. Rather, it is probably a special skill that can only be acquired through artificial training for an inherently quadrupedal primate.

Animals↗

PubMed1982

The noise factor in railway locomotives.

This article concerns the problem of acoustic work conditions on railway locomotives. The objective results of sonometric surveys in locomotive cabins are compared with subject data received from locomotive crews obtained by means of a specific questionnaire 'The Subjective Estimation of Noise'. The analysis touched 9 type of locomotives; steam, diesel and electric engines. We asked drivers of different age groups and with varying lengths of professional service for their opinions The aim of the investigation was to determine the following points: 1. to analyse the drivers' subjective estimation of the noise in the locomotive cabins; 2. to define length of time for which the driver remains under the influence of the noise after finishing work; 3. to investigate the question of perception and understanding of sounds and vocal signals used in the locomotive. These problems are a small part of the general plan to improve work conditions on the Polish National Railways.

Journal Article↗

PubMed1996

Transfer of mechanical energy between ankle and knee joints by gastrocnemius and plantaris muscles during cat locomotion.

The purposes of this study were (1) to define and estimate the direction and amount of the energy transfer between the knee and ankle through gastrocnemius (GA) and plantaris (PL) muscles during cat locomotion, and (2) to test the assumption that the force and activity patterns of soleus (SO), GA, and PL are mechanically and physiologically advantageous for providing the transfer of energy between these joints. The direction, amount and rate of the energy transfer through a two-joint muscle were defined using a theoretical analysis of movements in two adjacent joints spanned by the two-joint muscle. The energy transferred between the ankle and the knee was calculated using the time integration of the difference between the power developed by the moments of SO, GA, and PL at the ankle joint and the total power of these muscles. The total power of SO, GA, and PL muscles, and the power of their movements about the ankle and knee, were obtained using the experimentally determined muscle forces, the rates of change in muscle length, and the angular velocities at the knee and ankle which were calculated from the kinematics and the geometry of the cat hindlimb. Muscular forces and hindlimb kinematics of the cats were recorded during normal walking and trotting on a treadmill at speeds of 0.4, 0.8, 1.2, 1.5, and 1.8 ms-1 using 'E'-shaped tendon transducers and high-speed video, respectively. It was found that during the early phase of support, there was a transfer of mechanical energy from the ankle to the knee through GA and PL. During the late phase of support, mechanical energy was transferred from the knee to the ankle. The amount of energy transferred increased with increasing speeds of locomotion. The energy transferred from the ankle to the knee was 3-60 mJ (7-22% of the negative work done by the moments of SO, GA, and PL at the ankle), and the energy transferred from the knee to the ankle was 10-67 mJ (7-14% of the positive work done by the moments of SO, GA, and PL at the ankle). The results of this study suggest that the activation and the forces of one-joint SO and multi-joint GA and PL are organized in such a way as to fit the features of the design of these ankle extensor muscles in order to provide locomotion efficiently. For example, the decrease in the contractile abilities of SO during the late phase of support at fast speeds of locomotion may be compensated for by the transfer of energy from the knee to the ankle through GA and PL. The design of GA and PL (a high percentage of fast-twitch muscle fibers, large angles of pinnation and short length of the fibers, long tendons, and the location about the ankle and knee joints) seems to be well suited for transferring mechanical energy between the ankle and knee at fast speeds of locomotion. Because of the design of GA and PL, their contractile abilities remain close to the maximum at fast speeds of locomotion. The design of GA and PL allows for extension of the ankle joint through the action of the knee extensor muscles during knee extension with a relatively small change in length of GA and PL.

Animals↗

PubMed1990

Midbrain areas required for locomotion initiated by electrical stimulation of the lateral hypothalamus in the anesthetized rat.

Locomotor stepping in the Nembutal-anesthetized rat was elicited by electrical stimulation of either of two sites in the right or left posterolateral hypothalamus. Essential midbrain loci were identified by reversibly blocking the elicited locomotion through local injections of the anesthetic procaine (15%, 0.5 microliter). Two types of critical midbrain sites were found. At ipsilateral block sites (n = 21), procaine blocked only that locomotion elicited by ipsilateral stimulation. These sites could be along the course of a direct descending ipsilateral pathway although a possible bidirectional pathway is not to be excluded. At bilateral block sites (n = 21), procaine blocked locomotion elicited by both ipsilateral and contralateral stimulation. These sites could be involved in functions prerequisite for the initiation of locomotion or in the generation of the stepping pattern. Procaine injections in 35 sites had no effect on locomotion. Ipsilateral and bilateral block sites were intermixed and generally located in regions ventral to the midbrain central gray: chiefly the anterior ventromedial midbrain, the pontis oralis nucleus and the pedunculopontine nucleus. Negative sites were located in both the dorsal and ventral midbrain. Ipsilateral block sites were relatively prevalent in the anterior midbrain, indicating that the locomotor initiation signals are lateralized at this level. Bilateral block sites were more prevalent in the posterior levels, suggesting that the initiation signals are proximal to, or interact with, circuits that have a bilateral influence on locomotion.

Animals↗

PubMed2001

Neural analysis of visual information during locomotion.

For most vertebrate species, vision is critical during locomotion. In this review, we survey what is known about neural mechanisms that might be involved in this visual analysis. Problems that such mechanisms are likely to solve include: (1) determination of heading (the discrepancy between an observer's direction of motion and direction of gaze); (2) detection of course changes; (3) setting of courses using goals and landmarks; (4) obstacle avoidance; (5) accurate foot placement. To understand how the visual system handles these tasks, we must first consider what neurons 'see' during locomotion: this is determined both by an observer's motion and by his gaze. We then review response properties of neurons in the cortical 'motion pathways' of the monkey and cat as they relate to problems encountered during locomotion. The most studied areas are the medial superior temporal area in the monkey, which has been linked to heading determination, and the lateral suprasylvian area in the cat, where many cells are sensitive to motion in depth, and some are selective for optic flow patterns generated during locomotion. A few subcortical populations have also been linked to visual analysis during locomotion. Most notable are cells in the pigeon's nucleus rotundus: these respond selectively to looming stimuli, some firing at a specific time before the stimulus collides with the bird. Another intriguing population is in the cat's visual pontine nucleus, where cells respond to large displays suggestive of optic flow during locomotion.

Animals↗

PubMed2000

Role of the laterodorsal tegmental nucleus in scopolamine- and amphetamine-induced locomotion and stereotypy.

Scopolamine (1.5 mg/kg; i.p.) or amphetamine (3 mg/kg; i.p.) increases locomotion and stereotyped behavior patterns in rats. Previous studies suggest that scopolamine acts via muscarinic receptors near the midbrain-pons border. In this study, unilateral microinjections in N-methyl-scopolamine (2.5-10 microg) into the laterodorsal tegmental nucleus (LDT) increased locomotion. Bilateral ibotenate lesions of the LDT attenuated scopolamine-induced locomotion by 68% 7 days postlesion, and by 35% 28 days postlesion. LDT lesions reduced scopolamine-induced stereotypy less than locomotion. The sensitization to amphetamine observed on repeated tests was attenuated by LDT lesions for stereotypy, but not for locomotion. These findings suggest that scopolamine induces locomotion largely, but not exclusively, by blocking muscarinic receptors in LDT.

Amphetamine↗

PubMed2003

Unilateral dorsal column and rubrospinal tract injuries affect overground locomotion in the unrestrained rat.

The purpose of this study was to determine the importance of the rubrospinal pathway and the ascending components of the dorsal column for overground locomotion in adult, unrestrained rats. The dorsal column (excluding the corticospinal tract), the rubrospinal tract or both were damaged unilaterally in rats at the level of the upper cervical spinal cord. Behavioural analysis consisted of skilled locomotion (an evaluation of footslips during ladder walking), a paw usage task and the assessment of ground reaction forces during unrestrained locomotion. All lesioned animals used the forepaw ipsilateral to the lesions less while rearing. Animals with dorsal column injuries used the forelimb contralateral to the spinal injury significantly more while rearing compared with uninjured animals. All lesioned animals produced more footfalls while crossing the ladder compared with uninjured animals. All injuries, regardless of the pathway affected, resulted in significant alterations in body weight support and reduced braking forces from the forelimb ipsilateral to the injury during overground locomotion. Animals typically bore less weight on the hindlimb ipsilateral to the lesion compared with the hindlimb contralateral to the spinal injury. Taken together with previously published work, our data indicate that the rubrospinal and dorsal column pathways are important for forelimb support while rearing and for skilled locomotion. Additionally, the ascending dorsal column pathways and the rubrospinal tract play a role during flat surface overground locomotion and combined damage to these pathways does not alter the acquired gait.

Animals↗

PubMed1993

TGF-beta 1 stimulation of cell locomotion utilizes the hyaluronan receptor RHAMM and hyaluronan.

TGF-beta is a potent stimulator of motility in a variety of cell types. It has recently been shown that hyaluronan (HA) can directly promote locomotion of cells through interaction with the HA receptor RHAMM. We have investigated the role of RHAMM and HA in TGF-beta-stimulated locomotion and show that TGF-beta triggers the transcription, synthesis and membrane expression of the RHAMM receptor and the secretion of HA coincident with the induction of the locomotory response. This was demonstrated by both incubating cells with exogenous TGF-beta 1 and by stimulating the production of bioactive TGF-beta 1 in tumor cells transfected with TGF-beta 1 under the control of the metallothionein promoter. TGF-beta 1-induced locomotion was suppressed by antibodies that prevented HA/RHAMM interaction, using polyclonal antibodies to either RHAMM fusion protein or RHAMM peptides, or mAbs to purified RHAMM. Peptides corresponding to the HA-binding motif of RHAMM also suppressed TGF-beta 1-induced increases in motility rate. Spontaneous locomotion of fibrosarcoma cells was blocked by neutralizing secreted TGF-beta with panspecific TGF-beta antibodies and by inhibition of TGF-beta 1 secretion with antisense oligonucleotides. Polyclonal anti-RHAMM fusion protein antibodies and peptide from the RHAMM HA-binding motif also suppressed the spontaneous motility rate of fibrosarcoma cells. These data suggest that fibrosarcoma cell locomotion requires TGF-beta, and the pathway by which TGF-beta stimulates locomotion uses the HA receptor RHAMM and HA.

Amino Acid Sequence↗

PubMed1999

The influence of different exercise regimens on the development of locomotion in the foal.

To study the influence of different exercise regimens on the development of locomotion, 40 Warmblood foals aged 1 week were subdivided into 3 groups: box-rest, training and pasture exercise. The box-rest group remained for 24 h a day in a box stall while the training group was housed similarly, but additionally received a 30 min workout with gallop sprints 6 times a week. The pasture group served as a control group and was kept at pasture for 24 h a day. After 5 months, the locomotion pattern at the trot of every foal was recorded overground with a 2-D MacReflex gait analysis system. A randomly selected group of 19 foals was recorded again at age 11 months after they had been kept in an open loose box with access to a small paddock without any specific training for 6 months duration. At 5 months of age the box-rest group moved with a more protracted forelimb, and more extended shoulder and elbow joints than the pasture group. Carpal and fetlock joint kinematics were rather similar in all groups. In the hindlimb, the box-rest foals were significantly different from the other 2 groups, reflected in a more retracted hindlimb, more hip extension, more flexed stifle and tarsal joints, and a larger maximal flexion of hip, stifle, tarsal and fetlock joints. In the simultaneous video recordings this locomotion pattern was visible as a hypermetric movement. The larger protraction in the forelimb and retraction in the hindlimb, as seen in the box-rest group, is opposite to the interlimb coordination of a superior moving horse. The pastured foals had a smaller range of motion of the shoulder and hip joint and less maximal step height of both fore and hind hooves, while the velocity and step length were similar between the 3 groups. Pastured foals could trot the same distance with less joint motion and therefore had a more efficient intralimb coordination. The training group moved in a way comparable with the box-rest group in the similar velocity box-rest foals trot with an abnormal, hypermetric and therefore inefficient and poorer locomotion pattern. When, superimposed on box-rest, exercise is provided in the form of gallop sprints, this will mainly improve the hindlimb locomotion. These induced differences in locomotion pattern of foals can be reversed when the foals afterwards are subjected to the same exercise regimen again.

Animals↗

PubMed1997

Reversal of fusimotor reflex responses during locomotion in the decerebrate cat.

The effect of brief trains of electrical stimulation, at 2, 3 and 20 x threshold (T), of cutaneous afferents in the medial plantar nerve on the discharges of single medial gastrocnemius static and dynamic gamma-efferents has been investigated at rest and during locomotion in a decerebrate cat preparation. The units were classified as dynamic (10 units) or static (10 units) indirectly on the basis of their resting and locomotor discharge characteristics. Responses were assessed by calculating the change in mean gamma-rate during the 100 ms after stimulus onset compared with a control period. At rest, most dynamic neurones were inhibited by stimulation at 2T (9 of 10 units) and above. In contrast, the resting responses of most static neurones were excitatory at 2T (9 of 10 units) and 3T, while 20T produced static gamma-effects that varied in sign. During locomotion the responses of both types of gamma-efferent were phase related. Two patterns were observed with dynamic units. For seven dynamic neurones, at stimulus levels of 2T (7 units) and above, responses during electromyogram (EMG) bursts were inhibitory while those between bursts were not significantly different from zero. However, for three other dynamic units, a phase-related reversal of reflex responses was observed at some stimulus intensities (always 2T, 3 units) comprising inhibition during, and excitation between, EMG bursts. For static neurones, inhibitory (never excitatory) responses occurred during walking at stimulus intensities of 2T (10 units) and above. The locomotor responses of static units were maximum during (3 units) or between (7 units) EMG bursts and were minimum in the opposite phase of EMG activity. A task-related reversal of reflex responses was thus generally apparent (9 of 10 units) to low intensity stimulation (2T) for static gamma-efferents during locomotion (inhibition) compared with rest (excitation). During locomotion there was a significant linear relation between the magnitude of response and the background gamma-rate for static units and those dynamic units that did not exhibit phase-related reflex reversal (total, 17 units). For dynamic gamma-efferents, inhibition at rest and during locomotion occurred at short (spinal) latencies which were not significantly different and are consistent with the involvement of the same interneuronal pathway. We conclude that pathways of opposite sign may dominate the responses of fusimotor neurones to low threshold cutaneous afferents from the plantar surface of the foot depending on behavioural context. Furthermore, the cutaneous reflex responses of both types of gamma-motoneurones during locomotion appear to vary with the source of the afferent input and do not constitute a general excitatory drive. The results are discussed in relation to the role and reflex control of the fusimotor system.

Animals↗

PubMed1983

Immediate changes in ventilation and respiratory pattern associated with onset and cessation of locomotion in the cat.

In high decerebrate unanaesthetized cats (pre-collicular/pre-mamillary) which developed spontaneous co-ordinated locomotor activity, ventilation, breathing pattern, phrenic nerve, external and internal intercostal electromyogram (e.m.g.) activities were examined. Locomotion was also induced by electrical stimulation of the subthalamic locomotor region and in a few cases the mesencephalic locomotor region. Quadriceps muscle e.m.g. was used to monitor locomotor activity. Spontaneous locomotor activity was associated with an immediate increase in ventilation and shift of the ventilatory CO2 response curve to the left. Tidal volume was smaller and respiratory rate larger at any given level of ventilation during spontaneous locomotion. Increases in respiratory rate were due to reductions in both inspiratory and expiratory duration. Upon cessation of locomotion, these changes abruptly returned to control values. Within the first one or two walking steps of spontaneous locomotor activity, the rate of rise of phrenic activity increased slightly while peak phrenic activity remained relatively constant; peak internal intercostal activity increased markedly while peak external intercostal activity decreased. Similar changes in ventilation, phrenic, external and internal intercostal activities were observed in association with locomotion induced by stimulation within the subthalamic or mesencephalic locomotor regions. In contrast to spontaneous locomotor activity, however, increases in both external and internal intercostal activities were often observed. Peak amplitudes of both external and internal intercostal activities increased linearly with increasing levels of end-tidal PCO2 during rest and during locomotion. However, at any given level of PCO2 peak external intercostal activity was smaller and peak internal intercostal activity larger during locomotion than at rest. With increasing peak quadriceps e.m.g. activity at a constant walking rate, external intercostal activity was progressively inhibited while internal intercostal activity was progressively enhanced. No consistent change in peak phrenic activity was observed with changes in peak quadriceps activity. With increasing walking rate at a constant peak quadriceps e.m.g., peak phrenic and peak internal intercostal activities progressively increased and peak amplitude of external intercostal activity (which was inhibited below the activity observed at rest) also progressively increased. The virtually simultaneous changes in quadriceps activity and respiratory motor activities suggest that the increase in ventilation at exercise onset is neurally mediated. Furthermore, these results suggest that the motor pathways to both the spinal locomotor pattern generators and the pattern-controlling mechanisms for respiration are driven in parallel to provide a quantitative relationship between respiratory motor output and locomotor activity. The functional significance of the alterations in respiratory pattern and participation of the different respiratory muscles is discussed.

Animals↗

PubMed2003

Arterial baroreflex control of muscle blood flow at the onset of voluntary locomotion in mice.

To assess the role of arterial baroreflex control in muscle blood flow (MBF) and voluntary locomotion, mean arterial pressure (MAP), MBF, and electromyograms (EMGs) were measured in freely moving mice before (CNT) and after blocking the afferent or efferent pathway of arterial baroreflexes, carotid sinus denervation (CSD), or intraperitoneal administration of phentolamine (BLK), respectively. MAP was measured through a catheter placed in the femoral artery. MBF was measured with a needle-type laser-Doppler flowmeter and recorded through a low-pass filter with an edge frequency of 0.1 Hz. The frequency and duration of locomotion were judged from EMG recordings in the hindlimb. These probes were implanted at least 2 days before the measurements. Muscle vascular conductance (MVC = MBF/MAP) in all groups started to rise within 1 s after the onset of locomotion, but the increasing rate in CSD and BLK was significantly higher than in CNT for the first 9 s (P < 0.001). MAP in CSD and BLK significantly decreased below the baseline within 1 s and this was highly correlated with the increase in MVC for the first 9 s (R2 = 0.842, P < 0.001), whereas MAP in CNT increased significantly 8 s after the onset of locomotion. Although the total period of movement in a free-moving state for 60 min was not significantly different between CNT and CSD (P > 0.1), the frequency of movement with a short duration of 0.1-0.4 min was higher in CSD than in CNT (P < 0.001), which was highly correlated with the reduction in MAP accompanying each period of movement (R2 = 0.883, P < 0.01). These results suggest that arterial baroreflexes suppress vasodilatation in contracting muscle to maintain MAP at the onset of voluntary locomotion, and are necessary to continue a given duration of locomotion in mice.

Adrenergic alpha-Antagonists↗

PubMed2000

Activity of reticulospinal neurons during locomotion in the freely behaving lamprey.

The reticulospinal (RS) system is the main descending system transmitting commands from the brain to the spinal cord in the lamprey. It is responsible for initiation of locomotion, steering, and equilibrium control. In the present study, we characterize the commands that are sent by the brain to the spinal cord in intact animals via the reticulospinal pathways during locomotion. We have developed a method for recording the activity of larger RS axons in the spinal cord in freely behaving lampreys by means of chronically implanted macroelectrodes. In this paper, the mass activity in the right and left RS pathways is described and the correlations of this activity with different aspects of locomotion are discussed. In quiescent animals, the RS neurons had a low level of activity. A mild activation of RS neurons occurred in response to different sensory stimuli. Unilateral eye illumination evoked activation of the ipsilateral RS neurons. Unilateral illumination of the tail dermal photoreceptors evoked bilateral activation of RS neurons. Water vibration also evoked bilateral activation of RS neurons. Roll tilt evoked activation of the contralateral RS neurons. With longer or more intense sensory stimulation of any modality and laterality, a sharp, massive bilateral activation of the RS system occurred, and the animal started to swim. This high activity of RS neurons and swimming could last for many seconds after termination of the stimulus. There was a positive correlation between the level of activity of RS system and the intensity of locomotion. An asymmetry in the mass activity on the left and right sides occurred during lateral turns with a 30% prevalence (on average) for the ipsilateral side. Rhythmic modulation of the activity in RS pathways, related to the locomotor cycle, often was observed, with its peak coinciding with the electromyographic (EMG) burst in the ipsilateral rostral myotomes. The pattern of vestibular response of RS neurons observed in the quiescent state, that is, activation with contralateral roll tilt, was preserved during locomotion. In addition, an inhibition of their activity with ipsilateral tilt was clearly seen. In the cases when the activity of individual neurons could be traced during swimming, it was found that rhythmic modulation of their firing rate was superimposed on their tonic firing or on their vestibular responses. In conclusion, different aspects of locomotor activity-initiation and termination, vigor of locomotion, steering and equilibrium control-are well reflected in the mass activity of the larger RS neurons.

Animals↗

PubMed1981

Inhibition of leukocyte locomotion by hyaluronic acid.

The effect of hyaluronate on neutrophil motility in vitro was studied by the micropore filter technique and by direct visual analysis of the locomotion of neutrophils on glass. Both directed and random locomotion of neutrophils was inhibited by physiological concentrations (0.5-6.0 mg ml(-1)) of hyaluronate in a dose- and molecular weight-dependent manner. Inhibition of cell movement was more pronounced for high molecular weight chemoattractants such as casein than for small chemotactic peptides such as f-Met-Leu-Phe. Chemotactic factor gradient formation in filter chambers was profoundly retarded by hyaluronate, which may partly explain the inhibitory effects of hyaluronate on directed neutrophil locomotion. In addition, hyaluronate inhibited the binding of chemotactic factor to the neutrophil surface. This effect, together with a reduction in cell-to-substratum adhesion, may provide an additional explanation for hyaluronate-induced inhibition of random neutrophil locomotion. Inhibition of locomotion by hyaluronate was easily reversed by washing the cells free of hyaluronate; thus competition by hyaluronate for cell-surface binding sites is unlikely, and physical effects such as steric exclusion or molecular sieving by the large hyaluronate polymer provide the most probable explanations of its inhibitory effect on cell locomotion. Since hyaluronate is a major constituent of tissue matrices, these results draw attention to the importance of the extracellular environment in regulating inflammatory cell movement in vivo.

Adult↗

PubMed1998

Underwater punting by an intertidal crab: a novel gait revealed by the kinematics of pedestrian locomotion in air versus water

As an animal moves from air to water, its effective weight is substantially reduced by buoyancy while the fluid-dynamic forces (e. g. lift and drag) are increased 800-fold. The changes in the magnitude of these forces are likely to have substantial consequences for locomotion as well as for resistance to being overturned. We began our investigation of aquatic pedestrian locomotion by quantifying the kinematics of crabs at slow speeds where buoyant forces are more important relative to fluid-dynamic forces. At these slow speeds, we used reduced-gravity models of terrestrial locomotion to predict trends in the kinematics of aquatic pedestrian locomotion. Using these models, we expected animals in water to use running gaits even at slow speeds. We hypothesized that aquatic pedestrians would (1) use lower duty factors and longer periods with no ground contact, (2) demonstrate more variable kinematics and (3) adopt wider stances for increased horizontal stability against fluid-dynamic forces than animals moving at the same speed on land. We tested these predictions by measuring the three-dimensional kinematics of intertidal rock crabs (Grapsus tenuicrustatus) locomoting through water and air at the same velocity (9 cm s-1) over a flat substratum. As predicted from reduced-gravity models of running, crabs moving under water showed decreased leg contact times and duty factors relative to locomotion on land. In water, the legs cycled intermittently, fewer legs were in contact with the substratum and leg kinematics were much more variable than on land. The width of the crab's stance was 19 % greater in water than in air, thereby increasing stability against overturning by hydrodynamic forces. Rather than an alternating tetrapod or metachronal wave gait, crabs in water used a novel gait we termed 'underwater punting', characterized by alternating phases of generating thrust against the substratum and gliding through the water.

Journal Article↗

PubMed2002

Loss of signal transduction and inhibition of lymphocyte locomotion in a ground-based model of microgravity.

Inflammatory adherence to, and locomotion through the interstitium is an important component of the immune response. Conditions such as microgravity and modeled microgravity (MMG) severely inhibit lymphocyte locomotion in vitro through gelled type I collagen. We used the NASA rotating wall vessel bioreactor or slow-turning lateral vessel as a prototype for MMG in ground-based experiments. Previous experiments from our laboratory revealed that when lymphocytes (human peripheral blood mononuclear cells [PBMCs]) were first activated with phytohemaglutinin followed by exposure to MMG, locomotory capacity was not affected. In the present study, MMG inhibits lymphocyte locomotion in a manner similar to that observed in microgravity. Phorbol myristate acetate (PMA) treatment of PBMCs restored lost locomotory capacity by a maximum of 87%. Augmentation of cellular calcium flux with ionomycin had no restorative effect. Treatment of lymphocytes with mitomycin C prior to exposure to MMG, followed by PMA, restored locomotion to the same extent as when nonmitomycin C-treated lymphocytes were exposed to MMG (80-87%), suggesting that deoxyribonucleic acid replication is not essential for the restoration of locomotion. Thus, direct activation of protein kinase C (PKC) with PMA was effective in restoring locomotion in MMG comparable to the normal levels seen in Ig cultures. Therefore, in MMG, lymphocyte calcium signaling pathways were functional, with defects occurring at either the level of PKC or upstream of PKC.

Chemotaxis, Leukocyte↗

PubMed2002

Locomotion of human granulocytes in viscous media.

BACKGROUND: Granulocytes must migrate to the infection site, where they phagocytose the infecting agents. Their ability to migrate depends on the rheological properties of the cells, which change along with the increased viscosity of the suspension medium. The purpose of this research was to study the influence of medium viscosity on granulocyte locomotion. MATERIAL/METHODS: The random locomotion of human granulocytes was investigated by means of an assay based on direct observation of individual cell trajectories. The study was performed in viscous media, ranging from 0.7 x 10(-3) to 370 x 10(-3) Pa x s (0.7-370 cP). Hanks solution, supplemented with methylcellulose in various concentrations, was used as a medium. The locomotion of several hundred granulocytes was studied, and about 7,000 cell track-sections (steps) were recorded. RESULTS: The mean granulocyte velocity decreases slowly with increasing medium viscosity. An increase in medium viscosity of ca. 500 times results in only a three-fold reduction in velocity. Granulocytes can migrate even at the viscosity of thick honey. They are capable of overcoming resistance forces on the order of 10(-11)N. The locomotion of granulocytes in dextran and ficoll media is also described. In these media both viscosity and osmotic pressure were variable. Granulocytes stop moving at very low viscosity, on the order of 10(-3) Pa x s. CONCLUSIONS: The locomotion of granulocytes is not stopped even in media of high viscosity. The observed decrease of granulocyte velocity is comparatively small. The studies in dextran and ficoll media indicate significant influence of osmotic pressure on granulocyte locomotion.

Cell Movement↗

PubMed1987

Inhibitory effect of K-562 malignant cells on locomotion of human neutrophils.

Certain tumor cells generate factors that inhibit neutrophil chemotaxis. The present study was designed to explore, in K-562 malignant cells, the release of such factors that may alter the neutrophil locomotion. The supernatant, separated from the K-562 malignant cells cultured in vitro for 48 hours, was lyophilised and extracted with ethanol 80%. This ethanol extract (SE-K562) inhibited neutrophil locomotion. Both random and locomotion induced either by formyl-methionyl-leucyl-phenylalanine (FMLP) or serum were inhibited. SE-K562 was partially purified by Sephadex chromatography and the analysis of the eluted active fraction by SDS electrophoresis led one band of about 8 kd. No one inhibitory effect was observed with appropriate controls. In conclusion, K562 malignant cells in culture release a low molecular weight factor (8 kd) that inhibits all forms of PMN locomotion i.e. random locomotion and locomotion induced either by FMLP or serum.

Cell Line↗