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PubMed1985

Leg movements of stick insects walking with five legs on a treadwheel and with one leg on a motor-driven belt. II. Leg coordination when step-frequencies differ from leg to leg.

Stick insects walking with five legs on a self-propelled treadwheel and with the left hindleg (L3) on a motor-driven belt may move the "belt" leg L3 and the "wheel" legs with different frequencies. When L3 made less steps than L2, that step of L2, which was performed during the swing phase of L3, is prolonged. The time interval between the end of swing phase of L3 and the onset of the following swing phase of L2 was remarkably constant. When L3 made more steps than L2, that step of L3, which was performed during the swing phase of L2, is prolonged. Again, the time interval between the end of swing phase of L3 preceding a L2 swing phase and the onset of the L2 swing phase was relatively constant. For both kinds of walking situations phase response curves were drawn. They show that two types of coordinating channels exist: An anteriorly directed type is more dependent on absolute time than on phase. A posteriorly directed type is phase-dependent. Both inhibit the transition from stance to swing for some time. The results are compared with the existing coordination models.

Animals↗

PubMed1988

Neural control of leg movements in a metamorphic insect: persistence of larval leg motor neurons to innervate the adult legs of Manduca sexta.

During metamorphosis of the hawkmoth Manduca sexta, the larval thoracic legs along with their associated sensory organs and muscles degenerate and new adult legs develop. The larval legs are small and relatively simple structures capable of lateral extension and medial flexion allowing them to grasp the substrate as the caterpillar crawls along. By contrast, the adult legs are used for walking with an alternating gait. They are much larger than the larval legs and articulate such that they are capable of movement in several directions. This change in form and function is accompanied by a reorganization of the neural circuits controlling leg movements. In a previous report (Kent and Levine: J. Comp. Neurol. 271:559-576, '88) we described motor neurons innervating the larval prothoracic legs, and here we describe motor neurons innervating the prothoracic legs of the adult. Using a combination of cobalt staining methods and the persistent fluorescent dye Fluoro-Gold, we have found that some, if not all, larval leg motor neurons are retained and innervate the new adult leg muscles. Moreover, we have been able to discover the fate of individual larval leg motor neurons by marking a single larval neuron with Fluoro-Gold and using a second fluorescent dye to double label the same neuron in the adult. Our results suggest that specific larval leg motor neurons innervate corresponding muscles in the adult stage, although their apparent function is significantly different. In addition, the motor neurons undergo significant remodeling of their dendritic branching patterns during metamorphosis, alterations which doubtless contribute to their new roles in adult behavior.

Animals↗

PubMed1985

Leg movements of stick insects walking with five legs on a treadwheel and with one leg on a motor-driven belt. I. General results and 1:1-coordination.

Five legs of a fixed stick insect walked on a double treadwheel. The left hindleg (L3) walked on a motor-driven belt. When the belt was slower than the wheels L3 made less steps than the other legs and when the belt was faster than the wheels it made more steps than the other legs. In the case of slowlier stepping of the "belt-leg", the motor neurons of the retractor coxae muscle of this leg showed a high activity when the leg was pulled backwards by the belt. This activity was modulated in the step rhythm of the "wheel-legs". When all legs showed the same stepping frequency (1:1-coordination) the protraction duration of L3 was almost independent of step-period, as well as the lag between onset of protraction of L3 and that of L2. In some cases only L3 could be made to step on the belt even when all other legs did not walk.

Animals↗

PubMed2000

Compression bandages and stockings for venous leg ulcers.

OBJECTIVES: To assess the effectiveness and cost-effectiveness of compression bandaging and stockings in the treatment of venous leg ulcers. SEARCH STRATEGY: Searches of 19 databases, hand searching of journals, conference proceedings and bibliographies. Manufacturers of compression bandages and stockings and an Advisory Panel were contacted for unpublished studies. SELECTION CRITERIA: Trials that evaluated compression bandaging or stockings, as a treatment for venous leg ulcers. There was no restriction on date or language. Ulcer healing was the primary endpoint. DATA COLLECTION AND ANALYSIS: Details of eligible studies were extracted and summarised using a data extraction sheet. Data extraction was verified by two reviewers independently. MAIN RESULTS: Twenty two trials reporting 24 comparisons were identified. Compression was more effective than no compression (4/6 trials). When multi-layered systems were compared, elastic compression was more effective than non-elastic compression (5 trials). There was no difference in healing rates between 4-layer bandaging and other high compression multi-layered systems (3 trials). There was no difference in healing rates between elastomeric multi-layered systems (4 trials). Multi-layered high compression was more effective than single layer compression (4 trials). Compression stockings were evaluated in two trials. One found a high compression stocking plus a thrombo stocking to be more effective than a short stretch bandage. The second small trial reported no difference between the compression stockings and Unna's boot. There was insufficient data to draw conclusion about the relative cost-effectiveness of different regimens. REVIEWER'S CONCLUSIONS: Compression increases ulcer healing rates compared with no compression. Multi-layered systems are more effective than single-layered systems. High compression is more effective than low compression but there are no clear differences in the effectiveness of different types of high compression.

Bandages↗

PubMed2000

Comparison of hand-to-leg and leg-to-leg bioelectric impedance devices in the assessment of body adiposity in prepubertal children. the STRIP study. Special Turku coronary Risk factor Intervention Project.

UNLABELLED: The body composition of 40 seven-year-old children and of 50 of their parents was measured using two bioelectric impedance devices, the Model 101, RJL Systems, USA (conventional hand-to-leg device) and TANITA body fat analyser, TBF 105, Tanita Co, Tokio, Japan (newer leg-to-leg device). There were strong correlations between impedances obtained by these two devices [r= 0.95, r = 0.93, r= 0.82, r = 0.81 for girls (n = 22), boys (n = 18), mothers (n = 27) and fathers (n = 23), respectively (p < 0.0001 for all)]. However, there was a clear difference in the absolute impedance values due to the fact that the devices measure different segments of the body. Fat percentages based on built-in equations of the two devices correlated in girls, mothers and fathers (r = 0.71, r = 0.94, r = 0.80, respectively; p < 0.001) but not in boys (r = 0.21, p = 0.41). Using the Bland-Altman comparison method, a large intraindividual difference was observed in the fat percentages by the two devices, independent of adiposity level. Both devices detected significant gender differences in fat percentages in 7-y-old girls and boys with similar BMIs. CONCLUSION: When using the Tanita 105 leg-to-leg bioelectric impedance device to assess adiposity in children there is an obvious need for revised equations. For this, comparative studies using more validated methods, i.e. densitometry or DEXA, as part of a multi-compartment model are needed.

Adipose Tissue↗

PubMed2003

Time course of arousal response during periodic leg movements in patients with periodic leg movements and restless legs syndrome.

OBJECTIVE: The temporal evolution of periodic leg movements (PLM) and the relationship of their arousing effect on sleep episode has not been extensively investigated. We studied the nocturnal evolution of PLM associated or not with microarousal (MA) and associated with slow wave activity (PLM with slow wave activity) in 23 patients with PLM and/or restless legs syndrome (RLS). METHODS: All subjects had PLM associated with MA or with slow wave activity as well as without MA and all slept for 4 sleep cycles. Spectral electroencephalogrpahic (EEG) analysis was done for the 4 sleep cycles to assess the nocturnal variation in slow wave activity (SWA). RESULTS: Sixty percent of PLM were associated with MA, 4% were associated with slow wave activity whereas 36% showed no EEG changes. There was a clear prevalence of PLM with MA in stages 1 and 2 while PLM without MA were prevalent in slow wave sleep. The night-time PLM index progressively declined from the first to the last sleep cycle (P<0.005), without differences between PLM types, or between PLM and RLS patients. The decline of PLM duplicated the temporal trend in SWA over consecutive sleep cycles. CONCLUSIONS: PLM showed a typical pattern of progressive decline throughout the night following the exponential decline in SWA. These over-time variations occurred independently of changes in the rate of PLM associated or not with MA or associated with slow wave activity, suggesting that variations in arousal threshold and sleep propensity did not affect the PLM arousing effect. The PLM-related arousal response might be affected by interaction of circadian and sleep stage influences with the addition of sleep oscillatory processes.

Adult↗

PubMedDate not supplied

Validity of the Leg-O-Meter, an instrument to measure leg circumference.

The objective of this study was to validate the Leg-O-Meter measure against the clinical assessment of edema made by physicians using data from a 1-year follow-up study of unselected patients with chronic venous disease of the leg (CVDL). The Leg-O-Meter consists of a tape measure fixed to a stand attached to a small board on which the patient is in standing position. Its reliability has been shown to be above 97%. Data from the Venous Insufficiency Epidemiologic and Economic Study (VEINES) were used: 1,521 patients from France, Belgium, Italy, and Quebec (Canada) who spontaneously consulted a physician between 1994 and 1995 with a complaint resulting from venous problems of the legs were included. Baseline variables included leg circumference measurements using the Leg-O-Meter; physicians were also asked to diagnose edema and report it as present or absent on each leg. Clinical edema and leg circumferences were assessed again 3 to 6 months after the baseline visit and 12 months after baseline. The tape measure of the Leg-O-Meter was fixed at 13 cm from the floor. The first and last assessments were used to evaluate the variation in edema during the follow-up period. Clinical variation in edema status was assessed as follows: improved, if edema was diagnosed at baseline but not at the final visit; unchanged, if edema was diagnosed at both visits; and worsened, if there was no diagnosis of edema at baseline but a diagnosis of edema was made at the final visit. Variation in measured edema was classified as improved if there was a decrease in leg circumference of more than 1 cm between baseline and final evaluation; unchanged, if the difference in leg circumference was between plus or minus 1 cm between the 2 assessments; and worsened, if there was an increase in leg circumference greater than 1 cm between the 2 assessments. Data-driven cut-off points were also used: 1.3 cm and 1.5 cm. Sensitivity and specificity of the Leg-O-Meter using physician diagnosis as "gold standard" were calculated. In addition, receiver operating characteristics (ROC) curves were calculated by using the 3 different leg circumference cut-off points in order to determine the accuracy of the Leg-O-Meter to detect changes in edema. The overall accuracy of the Leg-O-Meter was 0.84 (standard error (se) = 0.06). Accuracy was greater when 1.5 cm was used as a cut-point. The Leg-O-Meter is an objective, reliable, and standardized instrument to assess patients over time. A change of 1.5 cm between 2 measurements gives a valid estimate of improvement or worsening of edema, when compared to physicians' diagnosis. The Leg-O-Meter is also sensitive to any changes in leg circumferences, which is an advantage over the clinical evaluation of edema.

Anthropometry↗

PubMed1991

Perturbation of the motor system in freely walking cockroaches. I. Rear leg amputation and the timing of motor activity in leg muscles.

1. The effects of amputation of a rear leg on the pattern of motor activity in the legs of freely walking cockroaches (Periplaneta americana L.) were studied. 2. Amputation affected both the frequency and the timing (phase) of motor bursts during a stepping cycle. Bursts in the stump of an amputated rear leg and in the contralateral (intact) rear leg often occurred at two or three times the frequency of bursts in the other legs. The remaining legs also showed multiple bursting during some steps. 3. Amputation affected the phase of motor bursts in two different ways. First, for every leg pair, phase was more variable after amputation, whether or not the mean phase was affected. Second, for some leg pairs, the mean phase itself was altered. During most steps, the timing of motor bursts in the stump of the amputated leg was walking-speed-dependent relative to bursts in the anterior legs. In contrast, the timing of bursts in the stump relative to bursts in the legs across the body from it showed no such speed-dependent timing. Timing between bursts in pairs of intact legs also showed either speed-dependent or speed-independent effects, depending on the pair under consideration. 4. The effects of amputation were not consistent. After loss of a leg, bursts in some leg pairs occurred synchronously in some insects and alternately in others. Even in single insects there were cases in which the timing between bursts in two legs switched from one value to another during walking. 5. These effects of amputation were manifest during slow walking only. At higher speeds, the timing of motor bursts in different pairs of legs was consistently closer to that seen during walking in intact insects. 6. Three conclusions are drawn from these results. (i) During slow walking, sensory feedback from the legs helps maintain the timing of adjacent ipsilateral leg pairs, but has little influence on contralateral pairs. (ii) During slow walking, either sensory input is quite variable, or it has variable effects on the motor pattern. (iii) During fast walking, sensory input from the legs seems to play a minimal role, if any, in the timing of the motor pattern of walking.

Amputation, Surgical↗

PubMed1992

Effect of arm-cranking on leg blood flow and noradrenaline spillover during leg exercise in man.

Controversy exists whether recruitment of a large muscle mass in dynamic exercise may outstrip the pumping capacity of the heart and require neurogenic vasoconstriction in exercising muscle to prevent a fall in arterial blood pressure. To elucidate this question, seven healthy young men cycled for 70 minutes at a work load of 55-60% VO2max. At 30 to 50 minutes, arm cranking was added and total work load increased to (mean +/- SE) 82 +/- 4% of VO2max. During leg exercise, leg blood flow average 6.15 +/- .511 minutes-1, mean arterial blood pressure 137 +/- 4 mmHg and leg conductance 42.3 +/- 2.2 ml minutes-1 mmHg-1. When arm cranking was added to leg cycling, leg blood flow did not change significantly, mean arterial blood pressure increased transiently to 147 +/- 5 mmHg and leg vascular conductance decreased transiently to 33.5 +/- 3.1 ml minutes-1 mmHg-1. Furthermore, arm cranking doubled leg noradrenaline spillover. When arm cranking was discontinued and leg cycling continued, leg blood flow was unchanged but mean arterial blood pressure decreased to values significantly below those measured in the first leg exercise period. Furthermore, leg vascular conductance increased transiently, and noradrenaline spillover decreased towards values measured during the first leg exercise period. It is concluded that addition of arm cranking to leg cycling increases leg noradrenaline spillover and decreases leg vascular conductance but leg blood flow remains unchanged because of a simultaneous increase in mean arterial blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Aerobic capacity with two leg work versus one leg plus both arms work in men with peripheral vascular disease.

The purpose of this pilot study was to examine the correlation between ergometry in men with peripheral vascular disease exercising with both legs and with one leg and both arms. Fifteen men with peripheral vascular disease performed three symptom-limited exercise tests on an ergometer that could be operated from a wheelchair with both legs or with one leg and both arms. The three exercise conditions were both legs (arms stabilized), left leg plus both arms, and right leg plus both arms. The exercise parameters compared were maximum oxygen consumption, maximum heart rate, and duration of exercise. Blood pressure was monitored at two-minute intervals and oxygen saturation and electrocardiogram were monitored continuously. The mean VO2 max +/- standard deviation for both legs, right leg plus both arms, and left leg plus both arms were 14.36 +/- 6.15, 14.86 +/- 4.09, 14.01 +/- 4.14 ml O2/kg-min, respectively. The mean duration of exercise +/- standard deviation were 12.01 +/- 5.74, 10.94 +/- 4.68, and 9.81 +/- 4.70 minutes respectively. The mean maximum heart rate +/- standard deviation were 126 +/- 24, 137 +/- 23, 136 +/- 23, respectively for the same exercise conditions. The Pearson Correlation Coefficients for VO2 for both legs versus right leg plus both arms and left leg plus both arms were .639 and .873, respectively. The Pearson Correlation Coefficients for duration of exercise for both legs versus right leg plus both arms and left leg plus both arms were .837 and .877, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2000

Oxygen uptake in one-legged and two-legged exercise.

PURPOSE: The purpose of this study was to determine the primary factors causing the differential oxygen uptake (VO2) response at submaximal intensities between one-legged and two-legged exercise, and whether peak oxygen uptake (VO2peak) increases in proportion to the increase in active muscle mass. METHODS: Two different types of exercise were used for this experiment, each requiring a different movement, a different method of stabilizing posture, and, finally, a different limiting VO2peak. In experiment 1, nine male subjects performed one-legged cycling (OLC) and two-legged cycling exercise (TLC) at a pedaling rate of 80 rpm. The exercise intensity was first set at 80 W and was increased by 40 W every 3 min until exhaustion. In experiment 2, six healthy male subjects performed one-legged knee-extension (OKE) and two-legged knee-extension (TKE) exercise at a rate of 50 contractions per minute. The knee-extension exercise was done at constant work rates for a 3-min session in OKE or a 4-min session in TKE. The exercise bouts were performed intermittently at four to seven different submaximal intensities and VO2 was determined at each intensity in all exercises. RESULTS: At submaximal intensities, VO2 in relation to work rate of one-legged exercise was more steep than those of two-legged exercise, and the mean values of VO2 were significantly higher in one-legged exercise than those in two-legged exercise in both knee extension and cycling exercise. Mean values of VO2peak for two-legged exercise were significantly higher than that for one-legged exercise (P < 0.01); however, it was much lower than two times of that for one-legged exercise even in knee extension exercise where the VO2peak would be limited peripherally. CONCLUSION: The findings of this study suggest that the differential VO2 response between one-legged and two-legged exercise would be attributed not only to the difference in force application throughout the exercise movement and to the effect of a postural component but also to the inhibited circulatory response caused by the multiple limb exercise. In addition, it was supposed that VO2peak does not increase in proportion to the exercising muscle mass even during smaller muscle activity where the cardiac pumping capacity has not reached its upper limit.

Adult↗

PubMed1982

Lactate and glucose exchange across the forearm, legs, and splanchnic bed during and after prolonged leg exercise.

The net exchange of glucose and lactate across the leg and the splanchnic bed and the arterialdeep venous (A-DV) differences for these substrates in the forearm were determined in healthy subjects during 3-3.5 h of leg exercise (bicycle ergometer) at 58% maximum O(2) uptake and during a 40-min post-exercise recovery period. Leg glucose uptake rose 16-fold during exercise and throughout the exercise period exceeded splanchnic glucose output. The latter reached a peak increment (3.5 times basal) at 90 min and fell by 60% during the third hour. As a result, blood glucose declined 40%, reaching frank hypoglycemia (blood glucose, <45 mg/dl) in 50% of subjects at 3.5 h. Splanchnic lactate uptake rose progressively during exercise to values four times the basal rate at 3 h in association with a rise in arterial lactate to 1.5 mM. There was, however, no significant net output of lactate from the legs beyond 90 min of exercise. In contrast, the A-DV lactate difference in the forearm became progressively more negative throughout exercise, reaching values three times the basal level at 3.5 h. The rise in arterial lactate during exercise was proportional to the elevation in plasma epinephrine, which rose ninefold. During recovery, splanchnic lactate uptake rose further to values six times the basal rate, whereas lactate output by the legs was no greater than in the basal state. The A-DV lactate difference in the forearm became even more negative than during exercise, reaching values four times basal. During exercise as well as recovery, forearm uptake of blood glucose could account for no more than 25-67% of forearm lactate release. Leg glucose uptake during recovery was threefold to fivefold higher than in the basal state in the face of plasma insulin concentrations that were 60% below basal and in association with a respiratory exchange ratio of 0.7. We conclude that (a) during prolonged leg exercise at 58% maximum O(2) uptake an imbalance between splanchnic glucose production and leg glucose utilization results in a fall in blood glucose that may reach hypoglycemic levels in healthy subjects; (b) there is a marked increase in the uptake of lactate by the splanchnic bed that cannot be attributed to increased output of lactate from the exercising legs; (c) lactate is released by forearm muscle and, together with other relatively inactive muscle, may be an important source of the increased lactate turnover during and after prolonged leg exercise; (d) the increasingly negative A-DV lactate difference in the forearm cannot be accounted for by uptake of blood glucose, suggesting the breakdown of glycogen in forearm muscle during and after leg exercise; (e) increased glucose uptake by the legs in association with hypoinsulinemia during recovery suggests an increase in insulin sensitivity that permits glycogen repletion in previously exercising muscle in the absence of food ingestion; and (f) the evidence for increased lactate output in the forearm and augmented glucose uptake in the legs during recovery raises the possibility that after leg exercise glycogen stores are decreasing in muscle that was relatively inactive (e.g., that of the forearm) while increasing in the previously exercising leg muscles.

Adult↗

PubMed1997

Bioimpedance analysis: evaluation of leg-to-leg system based on pressure contact footpad electrodes.

Conventional single frequency bioimpedance analysis (BIA) systems require technician placement of arm and leg gel electrodes, a suitable location for recumbent measurements, and a separate measurement of body weight. The aim of this study was to evaluate a new single frequency 50 KHz leg-to-leg bioimpedance analysis (BIA) system combined with a digital scale that employs stainless steel pressure-contact foot pad electrodes for standing impedance and body weight measurements. Healthy adults were evaluated for 1) electrode validity and 2) potential for body component estimation. Pressure-contact foot-pad electrode measured impedance was highly correlated with (N = 9, r = 0.99, P < 0.001) impedance measured using conventional gel electrodes applied to the plantar surface of both lower extremities; mean (+/-SD) impedance was systematically higher by about 15 ohms for pressure contact electrodes (526 +/- 56 ohms vs 511 +/- 59 ohms; P < 0.001). Second, the relationship between stature-adjusted leg-to-leg impedance (H2/Z) measured by the new system and two body composition components (total body water by 3H2O dilution (N = 144); and fat-free body mass, by underwater weighing and dual x-ray absorptiometry (N = 231)) was modeled using multiple regression analysis. Correlation coefficients for H2/Z alone versus body composition components were lower for leg-to-leg BIA than for arm-to-leg BIA; correlation coefficients and SEEs became similar for the leg-to-leg and arm-to-leg BIA systems with addition of three covariates (age, gender, and waist/hip circumference ratio) to regression models. The leg-to-leg pressure contact electrode BIA system has overall performance characteristics for impedance measurement and body composition analysis similar to conventional arm-to-leg gel electrode BIA and offers the advantage of increased speed and ease of measurement.

Absorptiometry, Photon↗

PubMed1989

[The effects of leg elevation to reduce leg edema resulting from prolonged standing].

In order to find the most comfortable and effective posture to reduce lower leg edema, 31 young women working in Chang Gung Memorial Hospital, ages ranging from 20 to 40, were studied by the volumetric displacement method with leg placed in a specially designed container. The effects of five different angles of leg elevation on reduction of leg edema were separately evaluated in 5 days. For each evaluation, two measurements of volumetric displacement of lower leg edema were performed after prolong sitting or standing of more than 4 hours, and at the end of 15 minutes of supine lying (angle of leg elevation = 0 degrees), or after the leg was elevated in an angle of 30 degrees, 45 degrees, 60 degrees, or 90 degrees respectively. A good correlation was found between the displaced volume and increasing angle of leg elevation (regression line Y = 99.109-0.016X, r = -0.96). There was a significant difference between leg elevation of 90 degrees and supine lying (t = 3.01, p less than 0.01). The degree of comfort in leg elevation was in the order of 30 degrees, 45 degrees, 60 degrees, 0 degrees, 90 degrees. Many subjects complained of numbness and throbbing pain over the lower legs or pain at the buttocks in the upright leg elevation to 90 degrees posture, but felt rather comfortable in the 30 degrees posture. Seventeen of these subjects were further studied for the degree of comfort in leg elevation at 30 degrees for 30 minutes as compared with those of 30 degrees, 15 minutes and 90 degrees, 15 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Regional distribution of 201Tl during one-leg exercise: comparison with leg blood flow by plethysmography.

To validate the use of 201Tl distribution as an estimate of regional blood flow in the legs, 201Tl leg uptake was compared by whole body scintigraphy and simultaneously measured leg blood flow by plethysmography during one-leg exercise in 11 male subjects. 201Tl leg uptake ratio and leg blood flow ratio were also compared to exclude the effect of cardiac output variation in each subject. There was a good correlation between 201Tl leg uptake and leg blood flow (r = 0.85, P < 0.01, y = 0.28x + 1.00). Moreover, there was a highly linear correlation between these ratios (r = 0.98, P < 0.01, y = 0.75x + 0.13), although the 201Tl leg uptake ratio somewhat underestimated the leg blood flow ratio as exercise became strenuous. It is concluded that 201Tl leg uptake reflects regional blood flow in the legs during exercise.

Aged↗

PubMed1988

Neural control of leg movements in a metamorphic insect: sensory and motor elements of the larval thoracic legs in Manduca sexta.

During the metamorphosis of the hawkmoth Manduca sexta the larval thoracic legs degenerate to be replaced in the adult by legs of very different form and function. This change must be accompanied by a reorganization of the neural circuits controlling leg movements. As an initial step in the study of this reorganization we describe here the sensory and motor elements of this circuitry in the larval stage of life. Sensory neurons innervating mechanoreceptive hairs on the thoracic surface were stained individually with cobalt. Those innervating hairs on the general thoracic surface project topographically into two ventral regions of the segmental ganglia. Sensory neurons innervating leg sensilla also map topographically to the more ventral of these regions but in addition have arborizations in a midlateral region. The density of branching within this lateral "leg neuropil" is greatest for sensory neurons form sensilla on the more distal leg segments. Leg motor neurons were identified with intracellular recording and cobalt injection techniques. Those innervating muscles controlling distal leg segments have dense dendritic arbors in the lateral "leg neuropil," while motor neurons controlling more proximal segments and muscles of the ventral body wall have extensive arborizations in a dorsomedial region of the ganglion. In general, flexor motor neurons are excited by medial and inhibited by lateral leg sensilla, while the opposite is true of extensors. Distal segment motor neurons respond most strongly to sensory neurons from distal segments, thus suggesting some interaction within the lateral "leg neuropil." Thus, in the larval nervous system a highly ordered array of of sensory and motor elements underlies the specific behavioral responses of the legs to tactile stimulation.

Action Potentials↗

PubMed2000

Correlation of diversity of leg morphology in Gryllus bimaculatus (cricket) with divergence in dpp expression pattern during leg development.

Insects can be grouped into mainly two categories, holometabolous and hemimetabolous, according to the extent of their morphological change during metamorphosis. The three thoracic legs, for example, are known to develop through two overtly different pathways: holometabolous insects make legs through their imaginal discs, while hemimetabolous legs develop from their leg buds. Thus, how the molecular mechanisms of leg development differ from each other is an intriguing question. In the holometabolous long-germ insect, these mechanisms have been extensively studied using Drosophila melanogaster. However, little is known about the mechanism in the hemimetabolous insect. Thus, we studied leg development of the hemimetabolous short-germ insect, Gryllus bimaculatus (cricket), focusing on expression patterns of the three key signaling molecules, hedgehog (hh), wingless (wg) and decapentaplegic (dpp), which are essential during leg development in Drosophila. In Gryllus embryos, expression of hh is restricted in the posterior half of each leg bud, while dpp and wg are expressed in the dorsal and ventral sides of its anteroposterior (A/P) boundary, respectively. Their expression patterns are essentially comparable with those of the three genes in Drosophila leg imaginal discs, suggesting the existence of the common mechanism for leg pattern formation. However, we found that expression pattern of dpp was significantly divergent among Gryllus, Schistocerca (grasshopper) and Drosophila embryos, while expression patterns of hh and wg are conserved. Furthermore, the divergence was found between the pro/mesothoracic and metathoracic Gryllus leg buds. These observations imply that the divergence in the dpp expression pattern may correlate with diversity of leg morphology.

Animals↗

PubMed1993

Effect of one- and two-leg training on arm and two-leg maximum aerobic power.

The purpose of this study was to examine the effect of one- and two-leg training on arm and two-leg maximum aerobic power. Seven subjects cycle-trained both legs simultaneously for 30 min.day-1, 4 days.week-1 for 4 weeks. Nine subjects cycle-trained each leg 15 min.day-1, 4 days.week-1 for 4 weeks. Both groups trained at a heart rate equal to that measured at 75% of their two-leg maximum aerobic power. Thus, during each training session the groups performed 30 min of work at the same heart rate intensity. Five subjects served as a non-training control group. Arm and leg maximum oxygen uptake tests were conducted before and after training. Only two-leg training induced significant gains in arm aerobic power (P < 0.0003), whereas both modes of training resulted in significant increases in two-leg aerobic power (P < 0.0008). The data demonstrate that improvements in arm aerobic power were dependent on the quantity of leg muscle mass involved in the training, whereas gains in two-leg aerobic power occurred regardless of whether the legs were trained separately or simultaneously.

Adult↗