Pairs Of Limbs Research Articles

Comparison of Normograde and Retrograde Intramedullary Pinning of Feline Tibias

This study evaluated the effects of normograde and retrograde intramedullary pinning of mid-diaphyseal fractures of the feline tibia on the anatomical structures of the stifle joint. Using the paired pelvic limbs from five mature feline cadavers, a transverse, mid-diaphyseal osteotomy was performed, and each tibia was pinned in a normograde or retrograde fashion. The stifle joints were examined to determine the pin exit site and measure the distance from the exit site to pertinent anatomical structures of the stifle joint. Neither normograde nor retrograde intramedullary pinning resulted in damage to the cruciate ligaments, menisci, intermeniscal ligament, femoral condyles, or joint capsule. The patellar tendon was penetrated in all five tibias during retrograde pin insertion.

Compensatory load redistribution of horses with induced weightbearing hindlimb lameness trotting on a treadmill

The compensatory mechanisms of horses with weightbearing hindlimb lameness are still not fully understood. That weightbearing, unilateral hindlimb lameness would not only alter stride characteristics to diminish structural stress in the affected limb but also induce compensatory load adjustments in the other supporting limbs. To document the load and time shifting mechanisms of horses with unilateral weightbearing hindlimb lameness. Reversible lameness was induced in 8 clinically sound horses by applying a solar pressure model. Three degrees of lameness (subtle, mild and moderate) were induced and compared with the nonlame (sound) control measurement. Vertical ground reaction forces were recorded for all 4 limbs simultaneously on an instrumented treadmill. Compared to the sound situation, moderate hindlimb hoof lameness induced a decrease in stride duration (-3.3%) and stride impulse (-3.1%). Diagonal impulse decreased selectively in the lame diagonal stance (-7.7%). Within the diagonal limb pair, vertical impulse was shifted to the forelimb during the lame diagonal stance (+6.5%) and to the hindlimb during the sound diagonal stance (+3.2%). Peak vertical force and vertical impulse decreased in the lame limb (-15%), but only vertical impulse increased in the contralateral hindlimb (+5.7%). Stance duration was prolonged in both hindlimbs (+2.5%). Suspension duration was reduced to a greater extent after push-off of the lame diagonal limb pair (-21%) than after the sound diagonal limb pair (-9.2%). Four compensatory mechanisms could be identified that served to reduce structural stress, i.e. peak vertical force on the affected limb: 1) reduction of the total vertical impulse per stride; 2) diagonal impulse decreased selectively in the lame diagonal; 3) impulse was shifted within the lame diagonal to the forelimb and in the sound diagonal to the hindlimb; and 4) the rate of loading and peak forces were reduced by prolonging the stance duration. Load shifting mechanisms are not only effective in diminishing peak forces in the affected limb, but also suppress compensatory overload in other limbs. Selected force and time parameters allow the unequivocal identification of the lame limb. Future studies have to examine how far these compensatory mechanisms may be generalised for other defined orthopaedic problems in the hindlimb.

The larval development of an Australian limnadiid clam shrimp (Crustacea, Branchiopoda, Spinicaudata), and a comparison with other Limnadiidae

The adult morphology of the Australian Limnadopsis shows some remarkable differences to that of other Limnadiidae. These differences are not reflected in its larval development. In Limnadopsis parvispinus, larval development comprises six stages. In stages I and II only the three naupliar appendages are present: the antennule as a small bud, the biramous antenna as the main swimming organ, and the mandible. The antennal protopod bears two endites, the proximal naupliar process and a more distal endite. In stage III a bifid naupliar process (in earlier stages not bifid) and the first signs of the carapace and trunk limb anlagen (undifferentiated rudiments) appear. In stage IV the carapace anlagen become more pronounced. The number of trunk limb anlagens increases to five, and differentiation has commenced. In stage V the first five pairs of trunk limbs are differentiated to varying degrees. The anterior-most four pairs of trunk limbs are subdivided into five endites, a small endopod, an exopod and an epipod. The bivalved carapace covers the anterior-most limbs. In larval stage VI the carapace is larger and the trunk limbs are further differentiated. A general pattern in the sequence of larval stages is the increasing number of sensilla on the antennules. From the last larval to the first postlarval stage, a significant change in morphology takes place. The trunk limbs are now used for swimming. Typical larval organs are much smaller than in the last larval stage. A comparison with other representatives of the Limnadiidae shows a high degree of correspondence, with most differences explained by the heterochronous appearance of characters during development. Five to seven stages are described for all studied Limnadiidae, including one particular stage in which four fully developed setae, a bifid naupliar process and the first signs of carapace anlagen are present. These characters are found in stage III in L. parvispinus, Limnadia stanleyana, Eulimnadia texana, and Imnadia yeyetta but in stage IV in E. braueriana and L. lenticularis. Based on a comparison of the larval stages of six limnadiid and one cyzicid species, we conclude that at least six naupliar stages belong to the limnadiid ground pattern.

Larval development of Japanese ‘conchostracans’: part 2, larval development of Caenestheriella gifuensis (Crustacea, Branchiopoda, Spinicaudata, Cyzicidae), with notes on homologies and evolution of certain naupliar appendages within the Branchiopoda

As part of a larger project examining and comparing the ontogeny of all major taxa of the Branchiopoda in a phylogenetic context, the larval development of Caenestheriella gifuensis (Ishikawa, 1895), a Japanese spinicaudatan ‘conchostracan’, is described by scanning electron microscopy. Seven different larval stages are recognised, in most cases based on significant morphological differences. They range in length from about 200 to 850 μm. Nauplius 1 has a plumb and lecithotrophic appearance with a rounded hind body and a labrum with an incipient medial spine. Limb segmentation is mostly unclear but the second antennae have more putative segments delineated than are expressed in the later stages. Feeding structures such as the mandibular coxal process and antennal coxal spine are only weakly developed. Nauplius 2 is very different from nauplius 1 and has three large spines on the labral margin and two long caudal spines. Feeding structures such as the mandibular coxal process and various spines and setae are developed, but whether feeding begins at this stage was not determined. The mandible has developed an ‘extra’ seta on endopod segment 1, absent in Nauplius 1. The segmentation of the second antenna has changed significantly due to fusions of various early segments. Nauplius 3 is like nauplius 2 in morphological detail, but larger and more elongate. Nauplius 4 has developed a pair of small anlagen of the carapace and rudiments of the first five pairs of trunk limbs, and the coxal spine of the antenna has become distally bifid. Nauplius 5 has a larger carapace anlage, externally visible enditic portions of the elongate trunk limbs, and a pair of primordial dorsal telson setae. Nauplius 6 has a larger and partly free carapace and better-developed, partly free trunk limbs with incipient enditic, endopodal, and exopodal setation. A pair of caudal spines, dorsal to the large caudal spines, has appeared. Nauplius 7 is quite similar to nauplius 6 but is larger and has slightly longer caudal and labral spines; also, the setation of the most anterior trunks limbs is better developed. The larval development is largely similar to that of other spinicaudatans. The larval mandible, which is evolutionarily conservative within the Branchiopoda, reveals a setation pattern similar to that of the Anostraca and Notostraca (two setae on mandibular endopod segment 1). Most other spinicaudatans and all examined laevicaudatans share another setal pattern (one seta on mandibular endopod segment 1), which could indicate a close relationship among these taxa. The second antenna undergoes a special development, which provides an insight into the evolution of this limb within the Branchiopoda. In nauplius 1 the basipod, endopod, and exopod are all superficially divided into a relatively high number of segments. In later nauplii some of these have fused, forming fewer but larger segments. We suggest that this ontogeny reflects the evolution of antennae in the conchostracans. Various aspects of the morphology of the antennae are discussed as possible synapormorphies for either the Diplostraca or subgroups of the Conchostraca.

Strength analysis of intraosseous wire fixation for avulsion fractures of the fifth metatarsal base

The objective of this study was to gather pilot data of the pullout strength of intraosseous wire for fixation of fifth metatarsal avulsion fractures and to compare intraosseous wire fixation with tension-band wiring. Osteotomies consistent with fifth metatarsal avulsion fractures were created in 5 matched pairs of cadaver limbs. One limb of each pair underwent fixation with intraosseous wiring and the other with tension band wiring. Metatarsals were then loaded to failure, defined as the maximum force achieved before the slope of the load curve moved from a positive to a negative value. Tension-band wiring showed a mean strength of 164.5 ± 103.7 N compared with a mean strength of 113.7 ± 46.6 N for intraosseous wiring. No significant difference in strength was shown between methods of fixation. Although the power of this data is small (.143), the data indicate that intraosseous wiring shows similar pullout strength when compared with tension-band wiring for fixation of fifth metatarsal avulsion fractures.

Redescription of the Chengjiang arthropod Squamacula clypeata Hou and Bergström, from the Lower Cambrian, south‐west China

The anatomy of the arthropod Squamacula clypeata Hou and Bergström, 1997 from the Lower Cambrian Chengjiang Lagersta¨tte is redescribed based on four newly excavated specimens. The new material was collected from localities recently discovered in the Kunming area, Yunnan Province, south‐west China, and preserves remarkable details of the ventral morphology, revealed by preparation. Squamacula clypeata is dorsoventrally flattened and rounded in outline. The cephalon was covered by a wide, short shield, with a large doublure and a pair of uniramous antennae on the ventral side. The thorax consists of nine somites, each protected by a tergite and carrying at least one pair of biramous limbs. The pygidium is covered with a small rounded tergum. The endopod is segmented, equipped with short spines on the inner margin of the coxa and a claw‐like structure distally, and the exopod flap‐like, fringed with setae. The limbs in the pygidium are like those in the thorax in shape. Squamacula was most probably a nektobenthic predator. The spinose endopod could walk, grasp and grind. The large flap‐like exopod was adapted for swimming and respiration. Its affinities lie with the Arachnomorpha, but the relationships with other known taxa remain ambiguous.

A new ‘great‐appendage’ arthropod from the Lower Cambrian of China and homology of chelicerate chelicerae and raptorial antero‐ventral appendages

The uniramous ‘great appendages’ of several arthropods from the Early to Middle Cambrian are a characteristic pair of pre-oral limbs, which served for prey capture. It has been assumed that the morphological differences between the ‘great-appendage’ arthropods indicate that raptorial antero-ventral and anteriorly pointing appendages evolved more than once in arthropod phylogeny. One set of Cambrian ‘great-appendage’ arthropods has, however, very similar short antero-ventral appendages with a peduncle of two segments angled against each other (elbowed) and with stout distally or medio-distally directed spines or long flexible flagellate spines on each of the four distal segments. Moreover, the head appendages of all these forms comprise the ‘great appendages’ and three pairs of biramous limbs. To this set of taxa we can add a new form from the Lower Cambrian Maotianshan Shale of southern China, Haikoucaris ercaiensis n. gen. and n. sp. It is known from three specimens, possibly being little abundant in the faunal community. It can be distinguished from all other taxa by the prominence of the proximal claw segment of its ‘great appendages’ and by only three distal spines (one on each of the distal segments). The similarity of the short, spiky ‘great appendages’ of Haikoucaris with the chelicera of the Chelicerata leads us to hypothesize that this particular type of ‘great appendages’ was the actual precursor of the chelicera. Homeobox gene and developmental data recently demonstrated the homology between the antenna of ateloceratans and the antennula of crustaceans on one side and the chelicera of chelicerates on the other. To this we add palaeontological evidence for the homology between the chelicerae of chelicerates and the ‘short great appendages’ of certain Cambrian arthropods, which leads us to hypothesize that the evolutionary path went from the ‘short great appendages’, by progressive compaction, toward the chelicera with only a two-spined chela. The new form from China is regarded as the possible latest offshoot, whereas the other ‘great appendages’ arthropods with similar short grasping limbs were derivatives of the stem lineage of the crown-group Chelicerata. Consequently, the chelicera with a chela with one fixed and one mobile finger is an autapomorphy of the crown group of Chelicerata, whereas a raptorial, but more limb-like antenna, with more distal spine-bearing segments, characterized the ground pattern of Chelicerata. Further taxa having ‘great appendages’, including the large Anomalocarididae, are also discussed in the light of their possible affinities to the Chelicerata and possible monophyly of all of these arthropods with raptorial anterior appendages.

AnIn VitroBiomechanical Comparison of a Prototype Intramedullary Pin‐Plate with a Dynamic Compression Plate for Equine Metacarpophalangeal Arthrodesis

To compare the biomechanical properties of a prototype intramedullary pin-plate (IMPP) implant specifically designed for equine metacarpophalangeal (MCP) arthrodesis with a dynamic compression plate (DCP) system. In vitro biomechanical testing of paired cadaveric equine forelimbs with a simulated traumatic disruption of the suspensory apparatus, stabilized by one of two methods for MCP arthrodesis. Twenty-one pairs of adult equine cadaveric forelimbs. Each forelimb had the distal sesamoidean ligaments severed to create a disrupted suspensory apparatus. For each forelimb pair, the MCP joint was stabilized with the IMPP in one limb, and a DCP in the other limb. Seven matching limb pairs were tested in axial compression in a single cycle to failure, 7 matching limb pairs were tested in torsion in a single cycle to failure, and 7 matching limb pairs were fatigued tested in axial compression. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05. The mean yield load, yield stiffness, and failure load (axial compression, torsional loading) was significantly greater for the IMPP compared with the DCP system. Mean cycles to failure for axial compression was significantly greater for the IMPP compared with the DCP system. Significance in all tests was P<.0001. The IMPP was superior to the DCP system in resisting the biomechanical forces most likely to cause failure of MCP joint arthrodesis. The IMPP implant should be considered for MCP arthrodesis in horses with traumatic disruption of the suspensory apparatus. The specific design of the IMPP implant may facilitate equine MCP arthrodesis and avoid convalescent complications related to cyclic fatigue.

Fgf Signaling Controls the Number of Phalanges and Tip Formation in Developing Digits

Tetrapods have two pairs of limbs, each typically with five digits, each of which has a defined number of phalanges derived from an archetypal formula [1]. Much progress has been made in understanding vertebrate limb initiation and the patterning processes that determine digit number in developing limb buds, but little is known about how phalange number is controlled. We and others previously showed that an additional phalange can be induced in a chick toe if sonic hedgehog protein is applied in between developing digit primordia [2, 3]. Here we show that formation of an additional phalange is associated with prolonged Fgf8 expression in the overlying apical ridge and that an Fgf Receptor inhibitor blocks its formation. The additional phalange is produced by elongation and segmentation of the penultimate phalange, suggesting that the digit tip forms when Fgf signaling ceases by a special mechanism, possibly involving Wnt signaling. Consistent with this, Fgfs inhibit tip formation whereas attenuation of Fgf signaling induces tip formation prematurely. We propose that duration of Fgf signaling from the ridge, responsible for elongation of digit primordia, coupled with a characteristic periodicity of joint formation, generates the appropriate number of phalanges in each digit. We also propose that the process that generates the digit tips is independent of that which generates more proximal phalanges. This has implications for understanding human limb congenital malformations and evolution of digit diversity.

Crocodilian bone-tendon and bone-ligament interfaces

We investigated bone-tendon (27 sites) and bone-ligament (12 sites) interfaces in six pairs of crocodile limbs and girdles under light microscopy. These crocodilian interfaces often included a direct, unmediated insertion in which the tendon or ligament fibers inserted directly into the bone itself without fibrocartilaginous mediation. This was quite different from the usual direct insertion known in mammals and lizards. Fibrocartilaginous tissue at the bone-tendon interface is generally believed to protect tendon fibers against shear stress. Other types of insertions were found in the crocodilian epiphyses, namely, hyaline cartilage and pseudofibrocartilaginous insertions. Notably, a thick periosteum/perichondrium and subchondral layer was involved at both interfaces. The thick periosteum/perichondrium seemed to form along the epiphyseal hyaline cartilage and might function in replacement of fibrocartilaginous tissues. Crocodilian thick periosteum/perichondrium would be expected to reinforce the limb and girdle bones--especially their epiphyses, in which secondary centers of ossification are absent. The subchondral layer--a kind of fibrocartilaginous tissue--seemed to play the role of the growth plate in compensating for the absence of secondary centers of ossification. Therefore, we hypothesized that the crocodile-specific bone-tendon interfaces were the result of these specializations of bone development and growth. In crocodiles, the disadvantages of the single ossification center are effectively compensated for by specialized morphologies, including these interfaces. Specialized bone growth provides the crocodile with the largest body size of the recent reptiles and an extremely fast method of locomotion.

Postembryonic development in the pycnogonid Austropallene cornigera (Family Callipallenidae)

Summary This paper describes the postembryonic development of Austropallene cornigera (Family Callipallenidae), an Antarctic pycnogonid, with emphasis on the previously undescribed larval instars. Comparisons are made where feasible with the development of Propallene longiceps (Family Callipallenidae), a related species with a similar mode of development which was described in detail by Nakamura (1981). Although the development of both species is very similar, there are differences when the instars leave the parent and begin a free-living existence and there are several differences in the development of the walking legs. The P. longiceps larvae leave the parent and begin feeding immediately after becoming a fourth instar while A. cornigera larvae remain on the adult through one more molt. During leg development, both species add a new walking leg pair at each molt, but the new limb lacks either one (P. longiceps) or two (A. cornigera) segments. At each subsequent molt, the previously added walking leg gains the missing segment(s) and the next limb pair appears, complete except for the missing segment(s). This process continues until all four pairs of walking legs have appeared and have acquired the adult number of segments.

Sexual difference in modes of selection on the pleopods of crayfish (Decapoda: Astacoidea) revealed by the allometry of developmentally homologous traits

Crayfish have five pairs of abdominal limbs called pleopods. In males, the first and second pairs of pleopods are used for transferring spermatophores to the female during copulation. The remaining pleopods in males have no obvious function. Female crayfish use their pleopods to carry eggs. Accordingly, it is expected that the selection pressures that act on the pleopods differ between males and females. To test this hypothesis, we estimated modes of selection on pleopods in two species of crayfish (Procambarus clarkii and Pacifastacus trowbridgii) by comparing allometric relationships in functional and nonfunctional pleopods. Since pleopods are serially homologous traits, developmental constraints on these traits appear to be minimal. The lengths of the first male pleopods, used in copulation, showed lower allometric values and less dispersion around the regression line, suggesting that they have been under stabilizing selection. This likely occurs because the major selective force is the ability of males to copulate with females of various sizes. The pleopods of females showed higher allometric values than pleopods of males without an assigned function. This suggests that the pleopods of females have been under directional selection, most likely because they are longer and can therefore carry more eggs.

Extraosseous blood supply of the tibia and the effects of different plating techniques: a human cadaveric study.

To describe the extraosseous blood supply of the tibia and how the blood supply of the distal tibia is influenced by different plating techniques. Microdissection of cadaveric adult hip disarticulation specimens following sequential arterial injections of india ink and Ward's Blue Latex was performed. Readily identifiable arterioles measured approximately 0.5 mm in diameter. Their artery of origin was identified, and their position along the medial, lateral, and posterior aspects of the tibia was documented relative to the tibial plafond. Additionally, six matched pairs of limbs were used to assess the effects of different plating techniques on the extraosseous blood supply along the medial aspect of the distal tibia. University anatomy laboratory. Nine matched pairs ( = 18) of randomly obtained, adult cadaveric hip disarticulation specimens. India ink followed by Ward's Blue Latex was injected into the superficial femoral artery at the level of the inguinal crease after cleansing of the arterial system. The skin, subcutaneous tissue, and muscles were dissected from the leg, exposing the arterial system and the extraosseous vessels of the tibia. MEAN OUTCOME MEASUREMENTS: The extraosseous blood supply of each aspect of the tibial diaphysis was determined. Each extraosseous arteriole was identified, and the locations of each documented relative to the tibial plafond. Changes in the filling of these vessels along the medial aspect of the distal tibia were documented in a separate group of specimens ( = 12), which had undergone two different plating techniques. The proximal metaphysis of the tibia was found to have a rich extraosseous blood supply provided primarily from vessels from the popliteal artery, the anterior tibial artery (ATA) laterally, and the posterior tibial artery (PTA) medially. In comparison, the tibial diaphysis was found to have relatively few extraosseous vessels and a considerably hypovascular region, posteriorly. Branches of the ATA were found to supply the posterior aspect of the diaphysis with these branches passing through the interosseous membrane. The diaphysis also received a variable contribution from the PTA. The lateral aspect of the diaphysis was supplied by branches of the ATA. An anastomotic network of arteries from the ATA and PTA formed the rich extraosseous blood supply of the medial distal aspect of the tibia. Open plating of the medial aspect of the distal tibia caused a statistically significant ( < 0.05) greater disruption of the extraosseous blood supply of the metaphyseal region than did percutaneously applied plates. In each specimen, open plating prevented filling of each periosteal vessel in the region as opposed to percutaneous plates, which permitted filling of the extraosseous vessels up to the edge of the plate. The proximal and distal metaphyseal areas of the tibia have a rich extraosseous blood supply provided primarily by branches of the ATA and the PTA. Open plating of the medial aspect of the distal tibia caused a greater disruption of this extraosseous blood supply than did percutaneously applied plates. Disruption of these extraosseous vessels following fracture and subsequent operative stabilization may slow healing and increase the risk of delayed union and nonunion. These findings support current efforts to develop less invasive methods and implants for operative stabilization of distal tibia fractures.

Phylogenetic analysis of anostracans (Branchiopoda: Anostraca) inferred from nuclear 18S ribosomal DNA (18S rDNA) sequences

The nuclear small subunit ribosomal DNA (18S rDNA) of 27 anostracans (Branchiopoda: Anostraca) belonging to 14 genera and eight out of nine traditionally recognized families has been sequenced and used for phylogenetic analysis. The 18S rDNA phylogeny shows that the anostracans are monophyletic. The taxa under examination form two clades of subordinal level and eight clades of family level. Two families the Polyartemiidae and Linderiellidae are suppressed and merged with the Chirocephalidae, of which together they form a subfamily. In contrast, the Parartemiinae are removed from the Branchipodidae, raised to family level (Parartemiidae) and cluster as a sister group to the Artemiidae in a clade defined here as the Artemiina (new suborder). A number of morphological traits support this new suborder. The Branchipodidae are separated into two families, the Branchipodidae and Tanymastigidae (new family). The relationship between Dendrocephalus and Thamnocephalus requires further study and needs the addition of Branchinella sequences to decide whether the Thamnocephalidae are monophyletic. Surprisingly, Polyartemiella hazeni and Polyartemia forcipata (“Family” Polyartemiidae), with 17 and 19 thoracic segments and pairs of trunk limb as opposed to all other anostracans with only 11 pairs, do not cluster but are separated by Linderiella santarosae (“Family” Linderiellidae), which has 11 pairs of trunk limbs. All appear to be part of the Chirocephalidae and share one morphological character: double pre-epipodites on at least part of their legs. That Linderiella is part of the Polyartemiinae suggests that multiplication of the number of limbs occurred once, but was lost again in Linderiella. Within Chirocephalidae, we found two further clades, the Eubranchipus–Pristicephalus clade and the Chirocephalus clade. Pristicephalus is reinstated as a genus.

ARE PLEOPODS JUST “MORE LEGS”? THE FUNCTIONAL MORPHOLOGY OF SWIMMING LIMBS IN EURYTHENES GRYLLUS (AMPHIPODA)

Abstract Amphipods, like most swimming crustaceans, employ a drag-based mechanism to produce thrust. The propulsors are paddle-shaped pleopods that move parallel to the direction of motion. These paired abdominal limbs generate both the propulsive thrust and the respiratory currents that bathe the thoracic gills. This study addresses the basic kinematics of motion and the pleopodal skeletomusculature of the deep-sea scavenger Eurythenes gryllus. The limb beat cycle consists of a power stroke where the three pleopod pairs, with their setal fan outstretched, swing sequentially through an arc parallel to the body axis, and then return anteriorly in a collapsed and bent configuration. The joint connecting the body to the muscular peduncle is complex, allowing promotion and remotion along the main body axis. Several hard plates for extrinsic muscle attachment are surrounded by arthrodial membrane. The extrinsic musculature is proportioned accordingly, with a large mass of muscles controlling the power stroke a...

Effect of Duration of Upper- and Lower-Extremity Rehabilitation Sessions and Walking Speed on Recovery of Interlimb Coordination in Hemiplegic Gait

The effects of different durations of rehabilitation sessions for the upper extremities (UEs) and lower extremities (LEs) on the recovery of interlimb coordination in hemiplegic gait in patients who have had a stroke were investigated. Fifty-three subjects who had strokes involving their middle cerebral arteries were assigned to rehabilitation programs with (1) an emphasis on the LEs, (2) an emphasis on the paretic UE, or (3) a condition in which the paretic arm (UE) and leg (LE) were immobilized with an inflatable pressure splint (control treatment). The 3 treatment regimens were applied for 30 minutes, 5 days a week, during the first 20 weeks after onset of stroke. All subjects also participated in a rehabilitation program 5 days a week that consisted of 15 minutes of UE exercises and 15 minutes of LE exercises in addition to a weekly 11/2-hour session of training in activities of daily living. A repeated-measures design was used. Differences among the 3 treatment regimens were evaluated in terms of comfortable and maximal walking speeds. In addition, mean continuous relative phase (CRP) between paretic arm and leg (PAL) movements and nonparetic arm and leg (NAL) movements and standard deviations of CRP of both limb pairs as a measurement of stability (variability) were evaluated. Comfortable walking speed improved in the group that received interventions involving the LEs compared with the group that received interventions involving the UEs and the group that received the control treatment. No differences among the 3 treatment conditions were found for the mean CRP of NAL and PAL as well as the standard deviation of CRP of both limb pairs. With the exception of an improved comfortable walking speed as a result of a longer duration of rehabilitation sessions, no differential effects of duration of rehabilitation sessions for the LEs and UEs on the variable we measured related to hemiplegic gait were found. Increasing walking speed, however, resulted in a larger mean CRP for both limb pairs, with increased stability and asymmetry of walking, indicating that walking speed influences interlimb coordination in hemiplegic gait.

A Larval Sea Spider (Arthropoda: Pycnogonida) from the Upper Cambrian ‘orsten’ of Sweden, and the Phylogenetic Position of Pycnogonids

Among a set of small, secondarily phosphatised larval arthropods from the Upper Cambrian ‘Orsten’ of Sweden, described by Müller and Walossek in 1986, one form bears a remarkable resemblance to the hatching protonymph larva of extant Pantopoda. This ‘larva D’ shares with protonymphs their gross body form, the anteroventral mouth on a slightly off‐set forehead region, the cheliceral morphology, two homeomorphic pairs of post‐cheliceral limbs, and further detailed similarities. It is described herein as Cambropycnogon klausmuelleri gen. et sp. nov. and is proposed as the oldest unequivocal record of both Pycnogonida and Chelicerata. Plesiomorphic features such as a pair of rudimentary pre‐cheliceral limbs and the gnathobasic basipods of the two post‐cheliceral limbs distinguish it from all known larvae of extant Pantopoda and lead us to propose a phylogeny of the Pycnogonida of the form (Cambropycnogon klausmuelleri+ (Palaeoisopus+ (Palaeopantopus+ Pantopoda))). The fossil may help to resolve the long debate about the relationships of Pycnogonida to other Arthropoda and supports a (Pycnogonida + Euchelicerata) relationship within the Chelicerata. The pre‐cheliceral limbs in this fossil support traditional morphological studies in which the chelicera represent the second (a2) head appendage, corresponding to the crustacean ‘second antennae’, and contradict recent data based on homeobox genes implying that the chelicerae are the first (a1) head appendages homologous with crustacean first antennae.

Fin development in a cartilaginous fish and the origin of vertebrate limbs.

Recent fossil finds and experimental analysis of chick and mouse embryos highlighted the lateral fin fold theory, which suggests that two pairs of limbs in tetrapods evolved by subdivision of an elongated single fin. Here we examine fin development in embryos of the primitive cartilaginous fish, Scyliorhinus canicula (dogfish) using scanning electron microscopy and investigate expression of genes known to be involved in limb positioning, identity and patterning in higher vertebrates. Although we did not detect lateral fin folds in dogfish embryos, Engrailed-1 expression suggests that the body is compartmentalized dorso-ventrally. Furthermore, specification of limb identity occurs through the Tbx4 and Tbx5 genes, as in higher vertebrates. In contrast, unlike higher vertebrates, we did not detect Shh transcripts in dogfish fin-buds, although dHand (a gene involved in establishing Shh) is expressed. In S. canicula, the main fin axis seems to lie parallel to the body axis. 'Freeing' fins from the body axis and establishing a separate 'limb' axis has been proposed to be a crucial step in evolution of tetrapod limbs. We suggest that Shh plays a critical role in this process.

Biomechanical Effect of Cyclic Loading on the Reconstructed Posterior Cruciate Ligament: Comparison between Inlay and Transtibial Technique

Purpose : To compare differences in the biomechanical characteristics of posterior cruciate ligament (PCL) reconstructed by the inlay and transtibial techniques. Materials and Methods : PCL reconstruction was performed in 12 pairs of porcine hindlimbs using the inlay and transtibial techniques. Cyclic load testing was carried out in three steps. The first step was 750 cycles at 35-350 N, the second 10,000 cycles at 35-350 N, and the third 10,000 cycles at 45-450 N. Length changes of the reconstructed PCLs were measured and the sites of rupture observed. Results : Among the 10 pairs of limbs that completed the test procedure, the graft ruptured before step 3 in all specimens except one in the transtibial group, and seven specimens completed step 3 testing in the inlay group. Comparing the load elongation curves obtained in step 2 tests, more elongation of the graft was evident in the transtibial group (p

Limb excursion during quadrupedal walking: how do primates compare to other mammals?

AbstractPrimate quadrupeds are said to use relatively large limb excursions for mammals of their body size. Until recently, this claim was based on a comparison of hindlimb excursion data derived from small samples of primates and non‐primates. Using video recordings collected at zoos and primate research centres, the present study documents this contrast on much wider samples of quadrupedal mammals. The results indicate that while on average hindlimb excursion is relatively larger in quadrupedal primates, this contrast is somewhat less dramatic than first reports suggested. Comparisons between the data reported here and previously collected forelimb excursion data reveal a surprising asymmetry between the fore‐ and hind excursions for most mammalian species. Most commonly, forelimb excursion exceeds that of the hindlimb. We suggest that this is related to a complementary asymmetry in limb length (forelimbs shorter than hind) for the purpose of achieving equal step lengths for both pairs of limbs. Relatively large hindlimb excursions in primates have been related to a mechanism that reduces stresses on the forelimbs and then recovers mechanical energy during gait. We suggest that large excursions of both the fore‐ and hindlimbs are linked to other alterations in gait parameters, such as step length, contact time, and limb compliance, that have been adopted in quadrupedal primates to facilitate locomotion along slender arboreal substrates.