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At least 487 records · Page 27Linked to original sources
PubMed2003

The odd-skipped family of zinc finger genes promotes Drosophila leg segmentation.

Notch signaling controls formation of joints at leg segment borders and growth of the developing Drosophila leg. Here, we identify the odd-skipped gene family as a key group of genes that function downstream of the Notch receptor to promote morphological changes associated with joint formation during leg development. odd, sob, drm, and bowl are expressed in a segmental pattern in the developing leg, and their expression is regulated by Notch signaling. Ectopic expression of odd, sob, or drm can induce invaginations in the leg disc epithelium and morphological changes in the adult leg that are characteristic of endogenous invaginating joint cells. These effects are not due to an alteration in the expression of other genes of the developing joint. While odd or drm mutant clones do not affect leg segmentation, and thus appear to act redundantly, bowl mutant clones do perturb leg development. Specifically, bowl mutant clones result in a failure of joint formation from the distal tibia to tarsal segment 5, while more proximal clones cause melanotic protrusions from the leg cuticle. Together, these results indicate that the odd-skipped family of genes mediates Notch function during leg development by promoting a specific aspect of joint formation, an epithelial invagination. As the odd-skipped family genes are involved in regulating cellular morphogenesis during both embryonic segmentation and hindgut development, we suggest that they may be required in multiple developmental contexts to induce epithelial cellular changes.

Animals↗
PubMed2003

Gene expression in spider appendages reveals reversal of exd/hth spatial specificity, altered leg gap gene dynamics, and suggests divergent distal morphogen signaling.

Leg development in Drosophila has been studied in much detail. However, Drosophila limbs form in the larva as imaginal discs and not during embryogenesis as in most other arthropods. Here, we analyze appendage genes in the spider Cupiennius salei and the beetle Tribolium castaneum. Differences in decapentaplegic (dpp) expression suggest a different mode of distal morphogen signaling suitable for the specific geometry of growing limb buds. Also, expression of the proximal genes homothorax (hth) and extradenticle (exd) is significantly altered: in the spider, exd is restricted to the proximal leg and hth expression extends distally, while in insects, exd is expressed in the entire leg and hth is restricted to proximal parts. This reversal of spatial specificity demonstrates an evolutionary shift, which is nevertheless compatible with a conserved role of this gene pair as instructor of proximal fate. Different expression dynamics of dachshund and Distal-less point to modifications in the regulation of the leg gap gene system. We comment on the significance of this finding for attempts to homologize leg segments in different arthropod classes. Comparison of the expression profiles of H15 and optomotor-blind to the Drosophila patterns suggests modifications also in the dorsal-ventral patterning system of the legs. Together, our results suggest alterations in many components of the leg developmental system, namely proximal-distal and dorsal-ventral patterning, and leg segmentation. Thus, the leg developmental system exhibits a propensity to evolutionary change, which probably forms the basis for the impressive diversity of arthropod leg morphologies.

Amino Acid Sequence↗
PubMed1997

Cardiopulmonary responses to exercise in swimmer using a swim bench and a leg-kicking ergometer.

There are few studies on the relative cardiopulmonary demands of the arm-stroke and the leg-kicking action in swimmers, mainly because of the absence of a suitable dry-land ergometer. Therefore, the purpose of this study was to compare the cardiopulmonary responses to exercise using a swim bench and a leg-kicking ergometer. Twelve highly-trained male swimmers with mean age of 20.3 +/- 1.9 (yrs), stature 1.77 +/- 0.04 (m) and body mass of 73.7 +/- 3.3 (kg) gave written informed consent and performed two separate incremental exercise tests on subsequent days. These tests used either a swim bench for assessment of arm-stroke or a specially designed front crawl leg-kicking ergometer. Oxygen consumption (VO2), heart rate (HR) and exercise intensity were recorded throughout both exercise tests. Peak oxygen consumption (VO2peak), peak heart rate (HRpeak) and peak exercise intensity (EIpeak) were also recorded. Furthermore, the relationships between submaximal heart rate and exercise intensity (HR/EI) and between oxygen consumption and exercise intensity (VO2/EI) for arm or leg exercise were explored. Mean values for VO2peak, HRpeak and EIpeak for a arm-stroke and leg-kick respectively were; 3.22 +/- 0.31 vs 3.76 +/- 0.42 (1 x min(-1); P=0.02), 170 +/- 3 vs 176 +/- 3 (b x min(-1); P=0.07) and 124.2 +/- 9.4 vs 141.3 +/- 12.7 (watts; P=0.01). The mean VO2peak and EIpeak for arm-stroke represented 85% and 88% respectively of the same measures for leg-kick. The HR/EI and VO2/EI relationships were shown to be linear (at least r=0.94, P<0.05 and r=0.96; P<0.01 respectively) and the differences in the gradients and elevations of these relationships for arm-stroke vs leg-kick were significant (at least P<0.05; ANCOVA). These results show that highly-trained swimmers can achieve similar peak levels of oxygen consumption when using the arms or the legs. The ability to assess the cardiopulmonary responses to front-crawl arm-stroking and leg-kicking relative to exercise intensity might be useful in understanding the importance of the arm and leg components of whole body metabolism in swimmers, especially during training programmes.

Adult↗
PubMed2006

Segmental dynamics of soccer instep kicking with the preferred and non-preferred leg.

Detailed time-series of the resultant joint moments and segmental interactions during soccer instep kicking were compared between the preferred and non-preferred kicking leg. The kicking motions of both legs were captured for five highly skilled players using a three-dimensional cinematographic technique at 200 Hz. The resultant joint moment (muscle moment) and moment due to segmental interactions (interaction moment) were computed using a two-link kinetic chain model composed of the thigh and lower leg (including shank and foot). The mechanical functioning of the muscle and interaction moments during kicking were clearly illustrated. Significantly greater ball velocity (32.1 vs. 27.1 m . s(-1)), shank angular velocity (39.4 vs. 31.8 rad . s(-1)) and final foot velocity (22.7 vs. 19.6 m . s(-1)) were observed for the preferred leg. The preferred leg showed a significantly greater knee muscle moment (129.9 N . m) than the non-preferred leg (93.5 N . m), while no substantial differences were found for the interaction moment between the two legs (79.3 vs. 55.7 N . m). These results indicate that the highly skilled soccer players achieved a well-coordinated inter-segmental motion for both the preferred and non-preferred leg. The faster leg swing observed for the preferred leg was most likely the result of the larger muscle moment.

Adolescent↗
PubMed2000

Inflammatory cells, motor weakness, and straight leg raising in transligamentous disc herniations.

STUDY DESIGN: Possible statistically significant relationships between inflammatory cells and either motor weakness or straight leg raising were determined. OBJECTIVES: To look for any clinically relevant links between inflammatory cells in disc herniations and signs of radiculopathy. SUMMARY OF BACKGROUND DATA: Many studies have during recent years shown a presence of various types of inflammatory cells in disc herniations, but their clinical relevance has been questioned. To be clinically relevant, a presence of inflammatory cells should show a clear relationship to clinical evidence of nerve root involvement. Macrophages repeatedly demonstrated in a high proportion of disc herniations studied are of particular interest. Their major role may be in disc herniations tissue resorption and not in sciatica. METHODS: A total of 96 disc herniations, all transligamentous, were analyzed by immunohistochemistry for presence of macrophages, T or B lymphocytes, and activated T lymphocytes separately. From recorded patient data, motor weakness and straight leg raising data were compared with a presence or absence of abundant (+ = at least 20 cells in a group) inflammatory cells. When not abundant, inflammatory cells were classified as "only few cells" (+) and grouped together with "no cells" (-). Patients with or without motor weakness were compared. Straight leg raising was compared for a positive (at <70 degrees ) or a negative test, and separately using the median as cut-off value. Groups were compared by chi-square analysis with the level of statistical significance set at P<0.05. RESULTS: None of the four inflammatory cell types showed any significant association with motor weakness. Nor was any association observed when comparing positive and negative straight leg raising. With the median (straight leg raising = 47.5 degrees ) as cut-off, only activated T cells showed a weak (chi2 = 4.40, P<0.05) relationship with tighter straight leg raising, but none of the other cell types did. Even when straight leg raising was < 47.5 degrees, three times more disc herniations lacked (n = 34) inflammatory cells than showed (n = 13) inflammation. In a subgroup of only sequestrated discs, the findings were similar. However, in the patients with a bilaterally positive straight leg raising (n = 25), the prevalence of at least one inflammatory cell type was much higher in sequestrated discs (80%) than in extrusions (33%). This may suggest more subtle interrelationships between type of disc herniation, straight leg raising, and inflammatory cells. CONCLUSIONS: The results of this study do not support a clinically relevant role for disc herniation inflammatory cells in sciatica. For the cells to be clinically relevant, a strong relationship between a presence of inflammatory cells and either or both of motor weakness and a tight straight leg raising should have been observed. The authors conclude that macrophages, which have been demonstrated in a high proportion of disc herniations in previous studies, are probably more important for disc tissue resorption processes than for producing sciatica. Other types of inflammatory cells are more rarely observed and may have no clinical meaning at all. However, more subtle interrelationships, considering the various types of disc herniations, should be further explored.

Adolescent↗
PubMed2003

Human hopping on damped surfaces: strategies for adjusting leg mechanics.

Fast-moving legged animals bounce along the ground with spring-like legs and agilely traverse variable terrain. Previous research has shown that hopping and running humans maintain the same bouncing movement of the body's centre of mass on a range of elastic surfaces by adjusting their spring-like legs to exactly offset changes in surface stiffness. This study investigated human hopping on damped surfaces that dissipated up to 72% of the hopper's mechanical energy. On these surfaces, the legs did not act like pure springs. Leg muscles performed up to 24-fold more net work to replace the energy lost by the damped surface. However, considering the leg and surface together, the combination appeared to behave like a constant stiffness spring on all damped surfaces. By conserving the mechanics of the leg-surface combination regardless of surface damping, hoppers also conserved centre-of-mass motions. Thus, the normal bouncing movements of the centre of mass in hopping are not always a direct result of spring-like leg behaviour. Conserving the trajectory of the centre of mass by maintaining spring-like mechanics of the leg-surface combination may be an important control strategy for fast-legged locomotion on variable terrain.

Biomechanical Phenomena↗
PubMed2004

Signals from load sensors underlie interjoint coordination during stepping movements of the stick insect leg.

During stance and swing phase of a walking stick insect, the retractor coxae (RetCx) and protractor coxae (ProCx) motoneurons and muscles supplying the thorax-coxa (TC)-joint generate backward and forward movements of the leg. Their activity is tightly coupled to the movement of the more distal leg segments, i.e., femur, tibia, and tarsus. We used the single middle leg preparation to study how this coupling is generated. With only the distal leg segments of the middle leg being free to move, motoneuronal activity of the de-afferented and -efferented TC-joint is similarly coupled to leg stepping. RetCx motoneurons are active during stance and ProCx motoneurons during swing. We studied whether sensory signals are involved in this coordination of TC-joint motoneuronal activity. Ablation of the load measuring campaniform sensilla (CS) revealed that they substantially contribute to the coupling of TC-joint motoneuronal activity to leg stepping. Individually ablating trochanteral and femoral CS revealed the trochanteral CS to be necessary for establishing the coupling between leg stepping and coxal motoneuron activity. When the locomotor system was active and generated alternating bursts of activity in ProCx and RetCx motoneurons, stimulation of the CS by rearward bending of the femur in otherwise de-afferented mesothoracic ganglion terminated ongoing ProCx motoneuronal activity and initiated RetCx motoneuronal activity. We show that cuticular strain signals from the trochanteral CS play a major role in shaping TC-joint motoneuronal activity during walking and contribute to their coordination with the stepping pattern of the distal leg joints. We present a model for the sensory control of timing of motoneuronal activity in walking movements of the single middle leg.

Action Potentials↗
PubMed1998

The roles of the homeobox genes aristaless and Distal-less in patterning the legs and wings of Drosophila.

In the leg and wing imaginal discs of Drosophila, the expression domains of the homeobox genes aristaless (al) and Distal-less (Dll) are defined by the secreted signaling molecules Wingless (Wg) and Decapentaplegic (Dpp). Here, the roles played by al and Dll in patterning the legs and wings have been investigated through loss of function studies. In the developing leg, al is expressed at the presumptive tip and a molecularly defined null allele of al reveals that its only function in patterning the leg appears to be to direct the growth and differentiation of the structures at the tip. In contrast, Dll has previously been shown to be required for the development of all of the leg more distal than the coxa. Dll protein can be detected in a central domain in leg discs throughout most of larval development, and in mature discs this domain corresponds to the distal-most region of the leg, the tarsus and the distal tibia. Clonal analysis reveals that late in development these are the only regions in which Dll function is required. However, earlier in development Dll is required in more proximal regions of the leg suggesting it is expressed at high levels in these cells early in development but not later. This reveals a correlation between a temporal requirement for Dll and position along the proximodistal axis; how this may relate to the generation of the P/D axis is discussed. Dll is required in the distal regions of the leg for the expression of tarsal-specific genes including al and bric-a-brac. Dll mutant cells in the leg sort out from wild-type cells suggesting one function of Dll here is to control adhesive properties of cells. Dll is also required for the normal development of the wing, primarily for the differentiation of the wing margin.

Alleles↗
PubMed2001

Stereotypic leg searching movements in the stick insect: kinematic analysis, behavioural context and simulation.

Insects are capable of efficient locomotion in a spatially complex environment, such as walking on a forest floor or climbing in a bush. One behavioural mechanism underlying such adaptability is the searching movement that occurs after loss of ground contact. Here, the kinematic sequence of leg searching movements of the stick insect Carausius morosus is analysed. Searching movements are shown to be stereotypic rhythmic movement sequences consisting of several loops. The typical loop structure allows the mean tarsus trajectory to be calculated using a feature-based averaging procedure. Thus, it is possible to describe the common underlying structure of this movement pattern. Phase relationships between joint angles, analysed for searching front legs, indicate a central role for the thorax-coxa joint in searching movements. Accordingly, the stereotyped loop structure of searching differs between front-, middle- and hindlegs, with leg-specific patterns being caused by differing protraction/retraction movements in the thorax-coxa joint. A simple artificial neural network that had originally been devised to generate simple swing movements allows two essential features of empirical searching trajectories to be simulated: (i) cyclic movements and (ii) the smooth transition into a search trajectory as a non-terminated swing movement. It is possible to generate several loops of a middle-leg search, but the precise size and shape of the loops fall short of a real-life approximation. Incorporation of front-leg retraction or hind-leg protraction during searching will also require an extension to the current model. Finally, front-leg searching occurs simultaneously with antennal movements. Also, because leg searching movements are a local behaviour, the legs remaining on the ground continue their stance phase, causing a forward shift of the body, including the searching leg. As a result of this shift, the centre of the searched space is close to the anterior extreme position of the tarsus during walking, representing the location of most likely ground contact according to past experience. Therefore, the behavioural relevance of searching movements arises from the combined actions of several limbs.

Animals↗
PubMed2006

Shaping leg muscles in Drosophila: role of ladybird, a conserved regulator of appendicular myogenesis.

Legs are locomotor appendages used by a variety of evolutionarily distant vertebrates and invertebrates. The primary biological leg function, locomotion, requires the formation of a specialised appendicular musculature. Here we report evidence that ladybird, an orthologue of the Lbx1 gene recognised as a hallmark of appendicular myogenesis in vertebrates, is expressed in leg myoblasts, and regulates the shape, ultrastructure and functional properties of leg muscles in Drosophila. Ladybird expression is progressively activated in myoblasts associated with the imaginal leg disc and precedes that of the founder cell marker dumbfounded. The RNAi-mediated attenuation of ladybird expression alters properties of developing myotubes, impairing their ability to grow and interact with the internal tendons and epithelial attachment sites. It also affects sarcomeric ultrastructure, resulting in reduced leg muscle performance and impaired mobility in surviving flies. The over-expression of ladybird also results in an abnormal pattern of dorsally located leg muscles, indicating different requirements for ladybird in dorsal versus ventral muscles. This differential effect is consistent with the higher level of Ladybird in ventrally located myoblasts and with positive ladybird regulation by extrinsic Wingless signalling from the ventral epithelium. In addition, ladybird expression correlates with that of FGF receptor Heartless and the read-out of FGF signalling downstream of FGF. FGF signals regulate the number of leg disc associated myoblasts and are able to accelerate myogenic differentiation by activating ladybird, leading to ectopic muscle fibre formation. A key role for ladybird in leg myogenesis is further supported by its capacity to repress vestigial and to down-regulate the vestigial-governed flight muscle developmental programme. Thus in Drosophila like in vertebrates, appendicular muscles develop from a specialised pool of myoblasts expressing ladybird/Lbx1. The ladybird/Lbx1 gene family appears as a part of an ancient genetic circuitry determining leg-specific properties of myoblasts and making an appendage adapted for locomotion.

Animals↗
PubMed1998

The relationship between isokinetic quadriceps strength test and hop tests for distance and one-legged vertical jump test following anterior cruciate ligament reconstruction.

Isokinetic measurements and functional tests are often used to assess function following knee ligament reconstruction using the opposite limb as a control. However, the question of whether the uninvolved leg may serve as a reference on functional tests has not been adequately answered. In particular, the one-legged rebound vertical jump has not been used to assess functional levels following surgery of the cruciate ligament. The purposes of this study were: 1) to determine whether the uninvolved leg is within normal range of an age- and weight-matched group, 2) to determine differences between the involved and uninvolved leg in patients after anterior cruciate ligament reconstruction, 3) to examine the relationship between knee extensor strength and four functional performance tests, and 4) to determine if the one-legged rebound vertical jump yields more information in the assessment of knee function than the other functional tests with respect to two time-frames. Fifty healthy subjects (group A, mean age = 28.1 years) and 55 anterior cruciate ligament patients (groups B and C) participated in dynamometric measurement, one-legged and two-legged vertical jump, and the single- and the triple-hop test. Mean time for testing was 13 weeks following surgery for group B (N = 30, mean age = 27.8 years) and 54 weeks following surgery for group C (N = 25, mean age = 29.9 years). Pearson product moment correlation coefficients between peak torque and single and triple hop were r = .45, r = .48, r = .51, and r = .55 for groups B and C, respectively. Pearson product moment correlation coefficients between peak torque and the height of the vertical jump was r = .51 for group C. Results for group A revealed limb symmetry indices of 95% or more on all functional performance and isokinetic tests. In group B, all patients showed a limb symmetry index of less than 85% on all tests. In group C, the index for the vertical jump was the only functional test that fell below the level of 85%. Regardless of whether the dominant or nondominant leg is involved, the uninvolved leg can be used adequately as a reference guide for outcome from rehabilitation using these measurements. The one-legged vertical jump test is capable of detecting functional limitations of the lower limb following knee ligament reconstruction up to 54 weeks postoperatively.

Adult↗
PubMed1976

[Adult leg development of Tenebrio molitor: I. Experimental analysis of the restoration process during morphogenesis (author's transl)].

The leg of the last instar larva, and especially the pharate pupa, of Tenebrio molitor (Coleoptera) shows considerable restoration ability. Restoration refers to the regeneration of leg structures removed during the last larval instar. This process involves only those tissues adjacent to the cut surface. At each level of the leg, amputation before a characteristic time leads to the restoration of a complete leg, but thereafter the new segments formed are hypomorphic or just lobes. After an amputation close to the pupal ecdysis, fragments are obtained, and these incomplete structures show that the restoration process has ceased. Just before the pupal ecdysis the leg is withdrawn from the cuticle, so a very late amputation does not effect the leg tissue and a complete pupal and adult leg is formed. The whole of the larval leg participates in adult leg morphogenesis, and histological techniques demonstrate a great correspondence between larval and adult leg segments. The larval trochanter, however, forms the adult trochanter and the proximal part of the femur. The larval tibia forms the adult tibia plus tarsus, except for the adult claws which develop from the larval tarsal claw.

Amputation, Surgical↗
PubMed1975

Difference in leg length in children with coxa plana during and after treatment using unilateral unloading.

In unilateral coxa plana a shortening of the affected leg can often be found. This shortening affects not only the caput-collum part of the femur but also the other parts of the femur and the tibia. In this study, however, the immobilization of the affected leg seemed to be the main reason for the observed difference in the leg length. Children who had not unloaded their affected leg as carefully as they should proved to have a smaller difference in leg length than those who had unloaded their affected leg according to the instructions. On the other hand compensatory growth of the affected leg was found when both legs were again taking weight. The difference in the leg length was significantly reduced one year after the completion of the treatment.

Child↗
PubMedDate not supplied

Large leg of superficial venous stasis, excluding disorders of the deep venous circulation.

Any abnormal increase in the volume of a lower member may be defined as "swollen leg", whether it is general and segmentary, or partial and local. This work concentrates on swollen legs caused by primary varicose disorders and does not deal with obstructions in the deep venous trunks. Swollen leg due to varicose disorder is marked by huge varices in clusters with total avalvulation. This constitutes a "phantom" swollen leg, for the evidence disappears when the patient lies down. It usually involves the long saphenous vein. It can be treated efficiently by surgery or sclerotherapy. Swollen leg of chronic venous stasis is due to vesperal oedema of complex character. Saphena insufficiency is to be observed, sometimes of the long saphenous vein, but usually of the saphena parva. Eventually large leg becomes permanent. Diagnosis is often difficult in swollen legs of deep venous stasis, and required venous functional investigations. Acute and painful forms may closely resemble ambulatory phlebitis. In all cases, lymphoedema ought to be considered, and the bruise test is conclusive. Sclerotherapy of the dilated saphenous trunks is often enough. Elastic stocking compression is sometimes necessary in order to obtain the best results, in conjunction with phlebotonics and crenotherapy. Swollen, inflammed legs are of two types: --Superficial thromboses, whether varicose or not, may be revelatory of underlying thromboembolic, cancerous, or hemopathic disease. This is the case for ascending phlebitis of the great saphenous vein which carries the risk of embolus, hyperuricemia, and, in the most localized forms, a risk of focal infection. --Phlebitis of the small saphenous vein, while rare, may be mistakenly taken to be deep lep phlebitis. The swollen legs seen in varicose trophic disorders are characterized by infectious or inflammatory edema, hypodermitis, and often, an ulcer. They may take on all of the clinical aspects of post-phlebitic disease, but functional vein studies will demonstrate patency of deep vein trunks. Active treatment and careful follow-up of venous and tissular lesions as well as suppression of aggravating factors should result in healing.

Diagnosis, Differential↗
PubMed1997

Cerebral generators involved in the pathogenesis of the restless legs syndrome.

The pathophysiology of periodic limb movements and sensory leg discomfort in the restless legs syndrome is unknown. With high-resolution functional magnetic resonance imaging, we localized for the first time cerebral generators associated with sensory leg discomfort and periodic limb movements in 19 patients with restless legs syndrome. During sensory leg discomfort there was mainly bilateral activation of the cerebellum and contralateral activation of the thalamus. During the combined periodic limb movement and sensory leg discomfort conditions, patients also showed activity in the cerebellum and thalamus. In contrast to the sensory leg discomfort condition alone, the combined condition was associated with additional activation in the red nuclei and brainstem close to the reticular formation. Voluntary imitation of periodic limb movements by patients and control subjects was not associated with brainstem activity, but with additional activation in the globus pallidus and motor cortex. These findings indicate that cerebellar and thalamic activation may occur because of sensory leg discomfort and that the red nucleus and brainstem are involved in the generation of periodic limb movements in patients with restless legs syndrome.

Aged↗
PubMed1986

Development of the apical ectodermal ridge in the chick leg bud and a comparison with the wing bud.

Histologic examination of the leg bud of stage-18 to stage-23 chick embryos was carried out with special reference to the development of the apical ectodermal ridge. The leg bud apical ectoderm, initially an irregular columnar epithelium with an overlying simple squamous periderm, began to thicken during stage 18 and was a pseudostratified epithelium by stage 19. A notch in the base of the thickened ectoderm was seen as early as stage 19. The notch represented the cross-sectional view of a groove, which developed in the base of the ridge. As development proceeded, the ridge and its associated groove lengthened. In addition, the groove became more prominent, and irregularities were seen in its width and depth along the apex. Ectodermal cell death was not consistently seen until stage 21 at which time most of the length of the thickened ectoderm had evidence of necrosis. Development of the leg bud ridge and wing bud ridge were compared. The temporal sequence of ectodermal thickening and ridge development was very similar in both the leg and wing buds with one exception; namely, that leg bud ridge development preceded wing bud ridge development by several hours. In addition, ectodermal cell death was not evident until stage 20 in the leg bud ridge, but could be seen at late stage 18 in the wing bud apical ectoderm. However, by stage 21, cell death was associated with most of the ridge in both the wing and leg buds. Finally, with respect to the axial line, the ridge with its associated groove extended further preaxially in the leg bud than in the wing bud, making the leg bud ridge more symmetrical.

Animals↗
PubMed1999

Increased dermal lymphatic density in the human leg compared with the forearm.

During orthostasis, capillary filtration pressure is higher in the leg than in the arm due to the effect of gravity. We investigated the possibility that the lymphatic network in leg skin might be adapted to cope with a greater fluid load. The dermal lymphatics of the forearm and lower leg were studied in white-skinned and brown-skinned men using fluorescence video microscopy. From video print lymphangiograms the following were determined: lymphatic length density at a series of radii from the centre of the lymphangiogram (LDr); maximum lymphatic density (LDmax); total length of lymphatic vessel (LL); maximum spread of lymphatic vessel; number and size of lymphatic rings (continuous circuits of vessel); and vessel diameter. There were no differences between the two racial types, but clear differences between the arm and leg. In the leg, mean (+/- SD) peak LDr (25.13 +/- 5.65 cm-1), LDmax (32.95 +/- 6.89 cm-1), LL (40.17 +/- 27.42 cm), and spread (1.39 +/- 0.08 cm) were all significantly higher than in the arm (18.03 +/- 5.48 cm-1, 23.91 +/- 7.21 cm-1, 11.76 +/- 5.47 cm, and 1.00 +/- 0.05 cm respectively, P </= 0.001). In the region of maximum lymphatic density there were 2.4 times more rings in the leg than in the arm, ring size being similar. Vessel image diameters were 89.6 +/- 26.3 micron (leg) and 94.8 +/- 10.9 micron (arm). Leg skin thus has a denser and more extensive lymphatic network than arm skin. This supports the hypothesis that lymph transport capacity in the leg is enhanced to compensate for a greater gravitational fluid loading.

Adult↗
PubMed2003

Blood volume changes are controlled centrally not locally--a near-infrared spectroscopy study of one legged aerobic exercise.

It is well known that blood flow increases in an exercising limb to match increases in oxygen consumption. However, it is less clear what effects occur in the opposite limb. We performed a one legged incremental cycling protocol and used near-infrared spectroscopy to measure changes in muscle blood volume and oxygenation in the exercising and non-exercising leg. As expected during exercise the exercising leg was deoxygenated relative to the non-exercising leg. However, there were similar increases in blood volume to both legs during the exercise, and during the post-exercise recovery period similar volume and oxygenation increases were seen in both legs. We conclude that blood volume increases may be signalled locally, but the effect is expressed globally. Previous studies have demonstrated a training effect in the non-exercising leg following one legged aerobic exercise. The large haemodynamic changes in the non-exercising leg observed here may be partially responsible for the cross-training effect.

Blood Volume↗