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Assessing leg length discrepancy after femoral fracture: clinical examination or computed tomography?

INTRODUCTION: Femoral shaft fractures treated with intramedullary nailing often heal with a leg length discrepancy (LLD). LLD is commonly evaluated by clinical examination and computed tomography (CT) scanogram. We assessed the correlation between these two techniques of calculating LLD. METHODS: We reviewed 35 skeletally mature patients who sustained a femoral shaft fracture between January 1997 and December 1999. Leg length was measured clinically with direct measurement and a block test. Each patient was asked whether they felt they walked with a limp and whether they felt they had a leg length discrepancy. Each patient underwent a CT scanogram to measure femoral and total leg length. The correlation between clinical examination and scanogram was analysed using the Pearson Product Moment Correlation. RESULTS: Of the 35 patients, 15 patients (43%) had a measurable LLD. There was a positive correlation between direct leg length measurement and the block test (P = 0.003), and between the block test and patient perception of limp and LLD. CT scanogram was performed on 29/35 patients. There was no correlation between CT scanogram and clinical measurement of leg length or between CT scanogram and patient perception of LLD or limp. DISCUSSION: Leg length discrepancy commonly occurs following treatment of femoral shaft fractures. We found that there was a strong correlation between direct leg length measurement and the block test, and between both methods of clinical leg length measurement and patient perception of a limp or LLD. Our study found no correlation between CT scanogram and clinical leg length measurement or patient perception of limp or LLD. CONCLUSION: Our study shows that physical examination (direct measurement and the block test) is more reliable and clinically relevant than CT scanogram measurement in the assessment of LLD after femoral fracture.

Adolescent↗

Pulsatile blood flow asymmetry in paired human legs.

Average leg blood flow has been extensively measured using non-invasive methods, but knowledge concerning pulsatile flow at specific leg cross-sections in normal or vascularly impaired limbs is quite limited. The present study used nuclear magnetic resonance flowmetry to address two fundamental questions; (1) to what extent are pulsatile flow differences present between paired-legs? and (2) is paired-leg flow symmetry affected by the presence of lower extremity arterial disease (LEAD)? Comparisons of left-right leg pulsatile blood flow (ml/min), perfusion (ml/min/100cc), and arterial status index at multiple leg sites showed highly significant correlations between legs (P < 0.001) in 57 normal and 37 patients with LEAD. To evaluate symmetry, the ratio of lower to higher paired-leg flow parameter values at five below-knee sites were averaged. Results showed all ratios significantly greater in normal subjects (P < 0.001). These findings establish the distribution and range of leg flow symmetry in vascularly normal individuals and show significant symmetry reductions accompanying bilateral LEAD. Although the cause of the asymmetry is presently unknown, non-uniform disease progression between paired legs may be involved. These initial findings provide a basis for subsequent research regarding the possible use of bilateral flow asymmetry assessment to further clarify the pathophysiological progression process and the possibility of using symmetry-based parameters to develop early markers of sub-clinical peripheral arterial disease progression.

Adult↗

Childhood leg length and adult mortality: follow up of the Carnegie (Boyd Orr) Survey of Diet and Health in Pre-war Britain.

OBJECTIVE: To investigate the relation between childhood height, its components--leg length and trunk length--and mortality in adulthood. DESIGN: Cohort study based on the Carnegie (Boyd Orr) Survey of diet and health in pre-war Britain, 1937-9. SETTING: The 14 centres in England and Scotland that participated in the Carnegie Survey and where children were examined. Scottish centres: Aberdeen, Dundee, West Wemyss, Coaltown of Wemyss, Hopeman, Methlick, Tarves, Barthol Chapel. English Centres: Liverpool, York-shire, Barrow in Furness, Wisbech, Fulham, and Bethnal Green. SUBJECTS: 2990 boys and girls aged between 2 years and 14 years 9 months when they were examined in 1937-9. These children were drawn from 1134 families who underwent a one week assessment of family diet and home circumstances. Of these, 2547 (85%) have been traced and flagged using the NHS Central Register. MAIN OUTCOME MEASURES: Age adjusted overall, coronary heart disease, and cancer mortality in men and women in relation to age and sex specific z scores for height, leg length, and trunk length. All analyses were adjusted for the possible confounding effects of childhood and adult socioeconomic circumstances and childhood diet. RESULTS: Leg length was the component of childhood height most strongly associated with socioeconomic and dietary exposures. There was no significant relation between childhood height and overall mortality. Height-mortality relations were observed in relation to both coronary heart disease (CHD) and cancer. Leg length was the component of height most strongly related to cause specific mortality. In men and women CHD mortality increased with decreasing childhood leg length. Men in the lowest leg length quintile had a relative risk (RR) of 2.5 (95% CI 1.0 to 6.2) compared to those with the longest legs (linear trend p = 0.14). Similarly, women in the lowest leg length quintile had a RR of 3.9 (95% CI 0.8 to 19.0; linear trend p < 0.01). Adjustment for childhood and adult socioeconomic circumstances had little effect on these trends. In men, but not women, those who as children had long legs experienced increased cancer mortality. The significant relations between anthropometry and both CHD and cancer mortality were restricted to those aged < 8 years when measured. CONCLUSIONS: These findings suggest that adverse diet and living conditions in childhood, for which leg length seems to be a particularly sensitive indicator, are associated with increased risk of CHD in adulthood and possibly reduced cancer risk. It is likely that these influences operate after birth, during the first few years of life.

Adolescent↗

Lower leg high-intensity resistance training and peripheral hemodynamic adaptations.

High-intensity resistance (HIR) training has been associated with muscle hypertrophy and decreased microvascular density that might produce a blood flow limitation. The effect of HIR training on lower leg maximal blood flow and minimum vascular resistance (Rmin) during reactive hyperemia were investigated in 7 healthy males. The gastrocnemius-soleus muscles of one leg were trained using maximal isokinetic concentric contractions for 4 weeks; the nontrained leg was the control. Lower leg blood flow was measured by venous occlusion plethysmography. Lower leg muscle volume was determined using magnetic resonance imaging. Peak isokinetic torque increased in both the trained (T) and nontrained (NT) legs (p < .05). Lower leg muscle volume increased by 2% in the T leg only (p < .05). In the T leg, maximal blood flow decreased and Rmin increased (p < .05); no hemodynamic change was detected in the NT leg. It is concluded that HIR training of the calf muscles is associated with a decrease in hyperemia-induced blood flow; thereby, indicating a blood flow limitation to the calf muscles.

Adaptation, Physiological↗

Why do arms extract less oxygen than legs during exercise?

To determine whether conditions for O2 utilization and O2 off-loading from the hemoglobin are different in exercising arms and legs, six cross-country skiers participated in this study. Femoral and subclavian vein blood flow and gases were determined during skiing on a treadmill at approximately 76% maximal O2 uptake (V(O2)max) and at V(O2)max with different techniques: diagonal stride (combined arm and leg exercise), double poling (predominantly arm exercise), and leg skiing (predominantly leg exercise). The percentage of O2 extraction was always higher for the legs than for the arms. At maximal exercise (diagonal stride), the corresponding mean values were 93 and 85% (n = 3; P < 0.05). During exercise, mean arm O2 extraction correlated with the P(O2) value that causes hemoglobin to be 50% saturated (P50: r = 0.93, P < 0.05), but for a given value of P50, O2 extraction was always higher in the legs than in the arms. Mean capillary muscle O2 conductance of the arm during double poling was 14.5 (SD 2.6) ml.min(-1).mmHg(-1), and mean capillary P(O2) was 47.7 (SD 2.6) mmHg. Corresponding values for the legs during maximal exercise were 48.3 (SD 13.0) ml.min(-1).mmHg(-1) and 33.8 (SD 2.6) mmHg, respectively. Because conditions for O2 off-loading from the hemoglobin are similar in leg and arm muscles, the observed differences in maximal arm and leg O2 extraction should be attributed to other factors, such as a higher heterogeneity in blood flow distribution, shorter mean transit time, smaller diffusing area, and larger diffusing distance, in arms than in legs.

Adult↗

Forces applied to cranks of a bicycle ergometer during one- and two-leg cycling.

An examination was made of the comparability of one- and two-leg exercise performed pedaling a stationary bicycle ergometer. The pattern of force exerted on both cranks was examined by means of a specially adapted ergometer which is described. The mean of the peak force in each cycle (MPF) was linearly related to work load (W) in both forms of exercise, and if account was taken of the doubled work output in two-leg cycling there was no significant difference between the MPF/W relationships; these are given by the equations one-leg: MPF (kg) = 11.23 + 0.065 (W in kpm/min) two-leg MPF (kg) = 10.76 + 0.032 (W in kpm/min). Calculation from the force records of the work performed on the cranks (WCR net) showed good agreement (r = 0.98, P less than 0.001) with the work load set on the ergometer. Analysis of the proportion of work done in leg extension and flexion phases of cycling revealed no differences between one- and two-leg exercise or between the right and left legs. The majority (approximately 80%) of Wer net being performed in leg extension is described by: Wer net (extension)) = 10.6 +/- 0.8 (W cr net total). In one-leg exercise (W greater than 900 kpm/min) the variation in rotation speed during a normal cycle ranged from +20 to --30% of the mean speed compared with +/- 10% in two-leg exercise.

Adult↗

Mutability of bifunctional thigh muscle activity in pedaling due to contralateral leg force generation.

Locomotion requires uninterrupted transitions between limb extension and flexion. The role of contralateral sensorimotor signals in executing smooth transitions is little understood even though their participation is crucial to bipedal walking. However, elucidating neural interlimb coordinating mechanisms in human walking is difficult because changes to contralateral sensorimotor activity also affect the ipsilateral mechanics. Pedaling, conversely, is ideal for studying bilateral coordination because ipsilateral mechanics can be independently controlled. In pedaling, the anterior and posterior bifunctional thigh muscles develop needed anterior and posterior crank forces, respectively, to dominate the flexion-to-extension and extension-to-flexion transitions. We hypothesized that contralateral sensorimotor activity substantially contributes to the appropriate activation of these bifunctional muscles during the limb transitions. Bilateral pedal forces and surface electromyograms (EMGs) from four thigh muscles were collected from 15 subjects who pedaled with their right leg against a right-crank servomotor, which emulated the mechanical load experienced in conventional two-legged coupled-crank pedaling. In one pedaling session, the contralateral (left) leg pseudo-pedaled (i.e., EMG activity and pedal forces were pedaling-like, but pedal force was not allowed to affect crank rotation). In other sessions, the mechanically decoupled contralateral leg was first relaxed and then produced rhythmic isometric force trajectories during either leg flexion or one of the two limb transitions of the pedaling leg. With contralateral force production in the extension-to-flexion transition (predominantly by the hamstrings), rectus femoris activity and work output increased in the pedaling leg during its flexion-to-extension transition, which occurs simultaneously with contralateral extension-to-flexion in conventional pedaling. Similarly, with contralateral force production in the other transition (i.e., flexion-to-extension; predominantly by rectus femoris), hamstrings activity and work output increased in the pedaling leg during its extension-to-flexion transition. Therefore rhythmic isometric force generation in the contralateral leg supported the ongoing bifunctional muscle activity and resulting work output in the pedaling leg. The results suggest that neural interlimb coordinating mechanisms fine-tune bifunctional muscle activity in rhythmic lower-limb tasks to ensure limb flexion/extension transitions are executed successfully.

Adult↗

Preserved alpha-adrenergic tone in the leg vascular bed of spinal cord-injured individuals.

BACKGROUND: Supraspinal sympathetic control of leg vascular tone is lost in spinal cord-injured individuals, but this does not result in a reduced leg vascular tone: Leg vascular resistance is even increased. The aim of this study was to assess the alpha-adrenergic contribution to the increased vascular tone in the lower extremity in patients without central sympathetic control of leg circulation. METHODS AND RESULTS: Upper-leg vascular resistance responses to local infusion of incremental doses of phentolamine (a competitive antagonist of the alpha-adrenoceptor) into the femoral artery were determined in 10 spinal cord-injured individuals (SCI) and 8 healthy age-matched control subjects during local beta-adrenergic receptor blockade with propranolol. Basal leg vascular resistance was higher in SCI than in control subjects (41+/-6 arbitrary units [AU] versus 24+/-4 AU; P=0.034). The same accounts for minimal leg vascular resistance, assessed during reactive hyperemia, which was higher in SCI compared with control subjects (6.9+/-1.0 AU versus 2.5+/-0.2 AU; P<0.01). The maximal phentolamine-induced reduction in leg vascular resistance normalized to each individual's minimal resistance did not differ between the groups (68+/-17% and 51+/-4% for SCI and control subjects, respectively; P>0.1). A decline in mean arterial pressure was observed in both groups with increasing dosage of phentolamine. In response, baroreceptor-mediated vasoconstriction was observed in the noninfused leg of the control subjects, whereas in SCI individuals this reaction was absent. CONCLUSIONS: These results indicate that the alpha-adrenoceptor-mediated vascular tone in the leg is preserved in spinal cord-injured individuals without sympathetic supraspinal control.

Adrenergic alpha-Antagonists↗

Testosterone dose-dependently increases maximal voluntary strength and leg power, but does not affect fatigability or specific tension.

Testosterone supplementation in men increases fat-free mass, but whether measures of muscle performance, such as maximal voluntary strength, power, fatigability, or specific tension, are improved has not been determined. Furthermore, the extent to which these measures of muscle performance are related to testosterone dose or circulating concentration is unknown. To examine the relationship between testosterone dose and muscle performance, 61 healthy, eugonadal young men (aged 18-35 yr) were randomized to 1 of 5 groups, each receiving a long-acting GnRH agonist to suppress endogenous testosterone production plus weekly injections of 25, 50, 125, 300, or 600 mg testosterone enanthate for 20 wk. These doses produced mean nadir testosterone concentrations of 253, 306, 542, 1345, and 2370 ng/dl, respectively. Maximal voluntary muscle strength and fatigability were determined by a seated leg press exercise. Leg power was measured using a validated leg power instrument. Specific tension was estimated by the ratio of one repetition maximum muscle strength to thigh muscle volume determined by magnetic resonance imaging. Testosterone administration was associated with a dose-dependent increase in leg press strength and leg power, but muscle fatigability did not change significantly during treatment. Changes in leg press strength were significantly correlated with total (r = 0.46; P = 0.0005) and free (r = 0.38; P = 0.006) testosterone as was leg power (total testosterone: r = 0.38; P = 0.007; free testosterone: r = 0.35; P = 0.015), but not muscle fatigability. Serum IGF-I concentrations were not significantly correlated with leg strength, power, or fatigability. Specific tension did not change significantly at any dose. We conclude that the effects of testosterone on muscle performance are specific; it increases maximal voluntary strength and leg power, but does not affect fatigability or specific tension. The changes in leg strength and power are dependent on testosterone dose and circulating testosterone concentrations and exhibit a log-linear relationship with serum total and free testosterone. Failure to observe a significant testosterone dose relationship with fatigability suggests that testosterone does not affect this component of muscle performance and that different components of muscle performance are regulated by different mechanisms.

Adolescent↗

[Leg ulcers and cancer. 6 case reports].

OBJECTIVE: It is estimated that 1 leg ulcer out of 300 is a carcinoma. In the literature ulceration of skin cancer is distinguished from chronic leg ulcers although this later category remains a subject of debate. We examined the clinical features of suspected malignant leg ulcers and discuss the notion of secondary malignant transformation of leg ulcers. PATIENTS AND METHODS: This study included patients attending the Vascular Clinic at the Saint-Joseph Hospital in Paris between 1991 and 1999 who were referred for leg ulcers and whose final diagnosis was cancerous ulceration. RESULTS: There were six patients, mean age 77 years who had squamous cell carcinomas (4 cases) and basocellular carcinomas (2 cases). We observed two distinct situations: leg carcinomas that ulcerated from onset (2 cases) and malignant transformation of a cicatrix, known as Marjolin's ulcer (4 cases). There were no cases of malignant transformation of chronic leg ulcers in this series. The clinical elements suggestive of a cancerous leg ulcer were the absence of a vascular etiology, the red, budding aspect of the ulcer with hard borders, and its development on a cicatrix. CONCLUSION: Malignant transformation of a vascular leg ulcer was not observed in our series, but has been reported in the literature although a critical analysis of reported data is only significant for squamous cell carcinoma. The frequency is probably overestimated. Our series enabled us to identify the clinical circumstances leading to an early diagnosis of carcinoma of the lower limbs. There are three essential criteria: analysis of the vascular status of the patient, the clinical characteristics of the leg ulcer, and its development on a cicatrix.

Aged↗

[Clinical assessment of phlebopathy severity by specification of leg heaviness symptom].

The paper presents the first attempt to differentiate phlebopathy severity on the basis of subjective information, which serves a key parameter of decompensation assessment reflecting individual range of daily living activity and functional load. Phlebopathy is defined as structural and functional insufficiency of venous wall, decreased ability to maintain stable volume both of particular veins and leg venous system as a whole during prolonged orthostasis. From 1995 to 2001 different forms of leg varices were diagnosed and treated in 583 patients. The most common complaint expressed by 567 patients (97.0%) was the heaviness and bursting pain in legs caused by daily orthostasis. Four clinical groups were clearly defined: 0 grade - no heaviness in legs; 1 grade - episodes of heaviness after excess daily load; 2 grade - regular heaviness in legs not demanding obligate evening rest with updrawn legs; 3 grade - permanent heaviness in legs demanding rest with legs updrawn. Permanent symptom (the last 2 groups) can be subdivided according to timing of symptom onset: a) in the afternoon, b) in the forenoon. The data analysis demonstrated that the symptom of leg heaviness during orthostasis caused by increased creep of venous walls was be a subjective equivalent to phlebopathy severity. The time of symptom onset and degree of manifestation correlated with the severity of venous wall incompetence. This method can be used to evaluate functional status of leg venous circulation both during initial assessment and for treatment or rehabilitation monitoring.

Female↗

Peak physiologic responses to arm and leg ergometry in male and female patients with airflow obstruction.

STUDY OBJECTIVE: To investigate differences in work capacity for the arms and legs in patients with moderate-to-severe COPD. DESIGN: Cross-sectional investigation. PATIENTS: One hundred twenty-four patients (90 men and 34 women) aged 45 to 81 years with moderate-to-very severe COPD. FEV(1) ranged from 0.70 to 2.79 L/min (FVC, 1.73 to 5.77 L; FEV(1)/FVC, 24 to 69%). All patients were in stable condition at the time of testing and receiving a stable drug regime. MEASUREMENTS: Each patient completed a demographic and medical history questionnaire, pulmonary function studies (spirometry, lung volumes, and diffusion capacity), peak exercise ergometry with gas exchange for the arms and legs; they also rated their subjective assessment of perceived dyspnea and extremity fatigue using Borg scores during exercise. RESULTS: Patients were of comparable age, with men taller and heavier than women. Smoking history was significantly less for women (47.9 pack-years vs 66.6 pack-years for men) even though each group presented with equivalent age (p > 0.05). Women were less obstructed than men, with FEV(1)/FVC (mean +/- SD) of 46.5 +/- 10.9% vs 40.2 +/- 9.3%, respectively. Ventilatory limitation during exercise was noted for all patients studied. Peak work capacity was greater for men, and leg peak responses were greater than arm values for each gender. As airway obstruction increased, work capacity became more limited. Peak arm work achieved was 38.9 +/- 19.6 W, oxygen uptake (VO(2)) was 903.9 +/- 263.5 mL/min, and minute ventilation (VE) was 33.7 +/- 9.5 L. Peak leg work value was 62.9 +/- 24.8 W, VO(2) was 1,091.4 +/- 321.5 mL/min, and VE was 39.3 +/- 12.0 L. Hence, arm values were 62%, 83%, and 85% of the measured leg values, respectively. Dyspnea and extremity effort scores were similar for men and women, and for arms and legs. Regression analysis was used to derive prediction equations for arm work from measured leg ergometry testing. For watts of work, a three-variable model emerged explaining 66% of the variance; VO(2) yielded a four-variable model with 80% of the variance explained; and VE yielded a three-variable model explaining 72% of the variance. CONCLUSION: Arm work is reduced by 38% that of the legs, while more modest reductions are noted for VO(2) and VE, suggesting greater mechanical efficiency for leg work as compared to arm work. These data also suggest greater metabolic demand for respiratory muscles and arm ergometry. Dyspnea and extremity Borg scores were equivalent for each modality and level of airway obstruction studied, suggesting that perception plays an important role in limiting exercise, and that a threshold for termination of exercise may exist. Further, peak leg ergometry results can be used with pulmonary function indexes to predict peak arm workload in watts, VO(2), and VE. These data may be used to assist the clinician in prescribing rehabilitation or estimating arm exercise ability when arm testing is unavailable.

Activities of Daily Living↗

Transcutaneous PO2 and laser Doppler blood flow measurements in 40 patients with venous leg ulcers.

The study included 40 patients with clinically venous leg ulcer(s) in one leg only and with a systolic toe blood pressure above 50 mmHg in both legs. Transcutaneous oxygen tension was measured on both lower legs at equivalent sites, on the affected leg immediately proximal to the ulcer(s). Similarly, skin blood flow was measured in both legs at a skin temperature of 32 degrees C and 44 degrees C by means of laser Doppler velocimetry, and for each leg the index of blood flow 44 degrees C/flow 32 degrees C was calculated to express the degree of blood flow increment following local hyperthermia. Transcutaneous oxygen tension measurements were significantly lower on affected legs (p less than 0.01) as was flow increment (p less than 0.01), mainly due to a high flow measurement at 32 degrees C on affected legs rather than to a low measurement at 44 degrees C. The results of our flow measurements suggest a state of (relative) hyperemia in the vicinity of venous leg ulcers, also confirmed by the clinical findings. This could be interpreted as an arteriolar response to lowered oxygen tension or (it could) be part of reactive reparative processes leading to increased O2 consumption in the tissues.

Aged↗

Clinical significance of leg-length inequality after total hip arthroplasty.

Sixty-eight patients were interviewed and examined after total hip arthroplasty (THA) to determine the clinical consequences (patient satisfaction, shoe lift use, gait abnormalities, etc) of leg-length inequality. No patient met clinical or radiographic criteria for revision THA. Minimum follow-up was 2 years, and average follow-up was 6.6 years (range, 2 to 20.5 years). A questionnaire, with specific questions about leg-length inequality, was completed by each patient. Leg-length inequality was determined by orthoroentgenography and compared with clinical measurements of leg length. The average inequality in this series of patients was 9.7 mm. A significant number (32%) of patients were aware of this inequality; the average leg-length inequality in this group was 14.9 mm. More than half of these patients were disturbed by the inequality. The magnitude of leg-length inequality closely correlated with awareness of the inequality, abnormal gait, use of ambulatory assistive devices, the need for a shoe lift, prior leg-length inequality, and revision THA. Clinical measures of leg-length inequality correlated poorly with values determined orthoroentgenographically. The high rate of dissatisfaction among patients with a leg-length inequality and the untoward results associated with this inequality indicate that surgeons performing THA should familiarize themselves with a reliable method for equalizing leg lengths intraoperatively.

Adult↗

[Leg volumetry: a precise method for quantification in phlebology].

UNLABELLED: Chronic venous insufficiency is usually quantified by venous pressure measurement, which is an invasive method. Air plethysmography has also been used, but it is expensive, time consuming and only suitable for sophisticated research laboratories. Leg volumetry might be suitable for routine use, as it is simple, inexpensive, fast, non invasive and can be performed by non medical personnel. Here, we only evaluated its practicability, accuracy and reproducibility. PATIENTS: The study group included 28 legs of 14 healthy volunteers, and 22 legs of 11 patients suffering from varicose veins. METHOD: The device used was a plexiglass boot, 50 cm high, 20 cm wide. It was filled with water at 24 +/- 2 degrees C. The leg was immersed and the volume of water displaced recorded. RESULTS: Normal legs displaced a volume of 2,449 +/- 153 ml (mean +/- SD), range: 2,080-2,720, and variability 6.2%. Patients' legs displaced a volume of 2,576 +/- 290, range: 2,110-3,120, (p = 0.05 vs normals) and variability 11.2%. Accuracy was 0.7%, as from 2 consecutive measurements of the same patients' legs by 2 different observers. Intra-individual variability was 1.3%, as recorded in 12 repeated measurements of the same leg on different mornings. In normal legs, the difference between morning and evening volumes was statistically significant (18 +/- 15 ml, p = 0.0001), a finding consistent with the deterioration of the venous function in normal extremities during daily activities. CONCLUSION: This simple, cheap, objective, non-invasive reproducible and accurate method of leg volume measurement might be useful in routine practice for chronic venous insufficiency quantification.

Adult↗

decapentaplegic overexpression affects Drosophila wing and leg imaginal disc development and wingless expression.

We have used the GAL4-UAS expression system to increase the level of expression of the Drosophila gene decapentaplegic (dpp) in a pattern approximating its normal pattern in leg and wing imaginal discs. Intermediate increases of dpp expression have little effect in wing discs but high levels of dpp overexpression lead to reduction of the scutellum and duplication of posterior wing structures. In leg discs intermediate increases cause supernumerary outgrowths of ventral leg structures in the anterior-ventral region. Greater increases of dpp expression cause the loss of ventral leg structures with the concomitant fusion of left and right dorsal forelegs. The defects observed in both legs and wings appear to arise through dose-dependent effects of dpp on wingless (wg) expression. A high level of dpp overexpression in the wing disc causes reduction of wg expression in the presumptive scutellar region, consistent with the subsequent reduction of the scutellum. An intermediate increase of dpp expression in leg discs induces the expansion of wg expression into the ventral outgrowths. At higher dpp expression levels, ventral wg expression in leg discs is eliminated, consistent with the loss of ventral leg cuticle. In the leg disc end knob and in the wing margin primordium, where wg and dpp cooperate in producing distal outgrowth, dpp overexpression has no detectable effect either on patterning or on wg expression. We propose that a critical role for dpp in other regions of the leg and wing discs is to reduce or block the expression of wg. This role of dpp is supported by the observation that ectopic wg expression is detected in imaginal discs where dpp signaling is compromised by lowering the activity of one of its receptors, tkv. This antagonism between dpp and wg expression may be critical to assigning only one disc region as the distal organizer.

Animals↗

The effect of one-legged sprint training on intramuscular pH and nonbicarbonate buffering capacity.

To determine the effect of one-legged sprint training on muscle pH and nonbicarbonate buffering capacity (BC), 9 subjects completed 15 to 20 intervals at 90 RPM, 4 days a week for 7 weeks on a bicycle ergometer adapted for one-legged pedaling. Needle biopsies from the vastus lateralis and blood samples from an antecubital vein were taken at rest and twice during recovery (1 and 4 minutes) from a 60 s one-legged maximal power test on a cycle ergometer. pH one minute after exercise in both the trained and untrained legs following the training period was not different but both were higher than before training. BC increased from 49.9 to 57.8 mumol HCl x g-1 x pH-1 after training (p less than 0.05). Blood lactate levels after exercise were significantly higher for the trained leg when compared to the untrained leg after spring training. Peak and average power output on the 60 s power test increased significantly after training. One-legged aerobic power (VO2max) was significantly increased in the untrained and trained legs. Two-legged VO2max also improved significantly after training. These data suggest that nonbicarbonate buffering capacity and power output can be enhanced with one-legged sprint training. Also, small but significant improvements in VO2max were also observed.

Adult↗

Development of adult thoracic leg muscles during metamorphosis of the hawk moth Manduca sexta.

During metamorphosis, the larval thoracic legs of the hawk moth Manduca sexta are replaced by a new set of adult legs. The larval leg motoneurons persist to innervate new adult muscles, and the motor terminals remain within the developing adult legs. Here we describe the fate of the larval leg muscles and the origin of new muscles within the adult legs. During the larval instars, large and small nuclei proliferate within leg muscle fibers. Near the end of the larval stage a subset of the small nuclei undergo a wave of proliferation, as indicated by the incorporation of 5-bromodeoxyuridine, whereas other nuclei die. However, none of the larval leg muscles fibers persist to serve as templates for adult muscle formation, and there was no evidence for persistence of larval myonuclei. Migrating myoblasts that are born within aggregate to form adult muscle anlagen at specific production sites within the developing imaginal legs. Intense nuclear proliferation occurs within the anlagen during the early pupal stage, followed by muscle fiber formation and striation. We conclude that adult leg muscles form mainly, if not exclusively, from migrating myoblasts that without the involvement of larval elements.

Animals↗