Nerve interactions and regenerative processes occurring in newt limbs fused end-to-end

Peripheral nerve interactions and regenerative phenomena were studied in newt forelimbs fused end to end. After simple fusion, one or two spikelike structures regenerated at the plane of fusion in 88% of the cases. When one of the limbs was denervated at the time of fusion, no regeneration occurred from the plane of fusion. If the limbs were fused and one was amputated at the shoulder more than 10 days after fusion, regeneration from the amputation surface did not occur. When the limbs were reamputated 30 days later, regeneration of left limbs from the proximodistally reversed right limb stumps followed. If one of the limbs was denervated at the time of fusion, and amputation was subsequently carried out through the formerly denervated limb, regeneration always took place after the first amputation. On the basis of these results it is postulated that when regenerating nerves of opposite proximodistal polarity meet head-on, the majority of fibers, at least, do not grow into territories occupied by the other nerve. These results have also demonstrated that full limb regeneration can occur at a greater distance from the midline than the end of a normal limb. These experiments also provide a technique for artificially elongating peripheral nerves.     

The evolutionary transformation of phyllopodous to stenopodous limbs in the Branchiopoda (Crustacea)--is there a common mechanism for early limb development in arthropods?

Arthropods and in particular crustaceans show a great diversity concerning their limb morphology. This makes the homologization of limbs and their parts and our understanding of evolutionary transformations of these limb types problematical. To address these problems we undertook a comparative study of the limb development of two representatives of branchiopod crustaceans, one with phyllopodous the other with stenopodous trunk limbs. The trunk limb ontogeny of a 'larger branchiopod', Cyclestheria hislopi ('Conchostraca') and the raptorial cladoceran Leptodora kindtii (Haplopoda) has been examined by various methods such as SEM, Hoechst fluorescent stain and expression of the Distal-less gene. The early ontogeny of the trunk limbs in C. hislopi and L. kindtii is similar. In both species the limbs are formed as ventrally placed, elongate, subdivided limb buds. However, in C. hislopi, the portions of the early limb bud end up constituting the endites and the endopod of the phyllopodous filtratory limb in the adult, whereas in L. kindtii, similar limb bud portions end up constituting the actual segments in the segmented, stenopodous, and raptorial trunk limbs of the adults. Hence, the portions of the limbs corresponding to the endites of the phyllopodous trunk limbs in C. hislopi (and other 'larger branchiopods') are homologous to the segments of the stenopodous trunk limbs in L. kindtii. It is most parsimonious to assume that the segmented trunk limbs in L. kindtii have developed from phyllopodous limbs with endites and not vice versa. This study has demonstrated at least one way in which segmented limbs have been derived from phyllopodous, multi-lobate limbs during evolution. Similar pathways can be assumed for the evolution of stenopodous, segmented and uniramous limbs in other crustaceans. Irrespective of the differences in the adult limb morphology, the early patterning of arthropod limbs seems to follow a similar principle.     

Limb morphogenesis in the branchiopod crustacean, Thamnocephalus platyurus, and the evolution of proximal limb lobes within Anostraca

Crustacean limbs exhibit highly diverse morphologies. One major route of diversification is in the number and position of branches arising from the proximal part of the limb. Here I describe development of larvae of the branchiopod crustacean, Thamnocephalus platyurus and describe in detail the development of the thoracic limbs. The thoracic limbs bear proximal branches both medially and laterally. The most proximal branches on either side (gnathobase and pre-epipod) show a similar developmental history: they develop via fusion of two rudiments into a single adult branch. However, phylogenetic analysis suggests that the developmental fusions have distinct evolutionary histories. In one case (gnathobase), the developmental rudiments reflect the ancestral adult morphology of two distinct branches. In the other (pre-epipod), the rudiments are an apparent novelty within the Anostraca and develop into two adult structures in only a single derived family.     

Vascular casts demonstrate microcirculatory insufficiency in acute frostbite

The use of vascular microcorrosion casts (vascular replicas) has made it possible to demonstrate the degree of damage to the microcirculation in experimentally induced frostbite. This approach provides a direct method for demonstrating vascular patency. Four groups of animals were used in this investigation. The left hind limbs of anesthetized rats were cooled to -10 degrees C in groups one and three and to -20 degrees C in groups two and four, as measured by needle thermocouples placed under the gastrocnemius muscles. Thermocouples were also placed in the left hind footpads of groups three and four. The sheathed limbs were cooled in an alcohol bath at approximately 1.1 degree C per minute. All limbs exposed to the cold bath were rewarmed to 37 degrees C in a 40 degree C water bath. The right hind limbs served as uninjured controls. The footpad temperatures recorded in groups three and four were used in conjunction with the temperatures recorded under the gastrocnemius muscles to characterize the footpad temperatures in groups one and two. Vascular microcorrosion casts were made from the left and right hind paws of groups one and two using Batson's modified methyl methacrylate. Scanning electron microscopic examination of the casts demonstrated dramatic differences between the vascular integrity of control paws and that of frozen paws. Exposure to the cold temperatures destroyed most of the microcirculation. In addition, the weights of the casts from the control paws were significantly different from the weights of the casts from the frozen paws. It was concluded that this model for evaluating frostbite injury accurately demonstrates the extent of microvascular damage and has significant potential as a method for evaluating therapeutic drug regimens.     

Natural variation in the limb skeletal pattern of the crested newt,Triturus carnifex (amphibia: Salamandridae)

The forelimb skeletal patterns of two geographically isolated populations of Triturus carnifex, one from northern Italy (Rosate, Milano) and one from central Italy (Bagnaia, Perugia) were studied. A total of 1,018 limbs were examined. Limb skeletal variants, generally consisting either of a reduced number of carpals and/or of an alternate phalangeal formula, were commonly observed, as has been reported for other amphibian species. The population from northern Italy showed a greater variability than that from central Italy. Skeletal variants were present in 34% and 12% of the limbs, respectively (i.e., in 48% and 20% of the newts). In the Rosate population, the majority of variants consisted of fusions of radiale and prepollicis and of the phalangeal formula 1-2-3-2. Severe skeletal defects were also found in 3% of the limbs of the newts from Rosate and in 1% of the limbs of those from Bagnaia. At present, no conclusion can be drawn about the evolutionary significance of the limb skeletal variation observed in the two populations, because of the paucity of data on intra- and interpopulation variations in other species of the genus Triturus. © 1992 Wiley-Liss, Inc.     

Estimation of the onset of bone atrophy

Disturbances of bone growth were investigated in the skeletal remains of two individuals. These two--unrelated--mature males possessed limbs with marked atrophy as a result of immobilization, while the non-affected limbs showed a massive hyper-robusticity of the bones. The atrophied bones were investigated metrically and histologically. We assessed the time of onset, the duration and the extent of the immobilization. Both males suffered from paralysis, whereby one was apparently paralyzed from the pelvis down, the other had both lower extremities and the right arm affected. It appears that the onset occurred during the juvenile period.     

Inhibition of antigen-driven proliferative responses and enhancement of antibody production during infection with Brugia pahangi

Long standing Brugia pahangi infections in seven dogs, restricted to one rear limb popliteal lymph node and its afferent ducts, were monitored with regard to proliferative responses and antibody production specific for a PBS extract of B. pahangi (BpA) by cells from infected and uninfected lymph nodes and by PBL. Five of 10 dogs were negative for proliferative responses to BpA in node cells from infected limbs, yet they had positive PBL responses, and another was negative in both node cells and PBL. Production of BpA-specific antibody was detected in cultures of node cells from infected limbs of 9 of 10 dogs, but only in two cultures of node cells from uninfected limbs and not at all in PBL cultures. Three dogs with responsive node cells produced the least amount of anti-BpA antibody in culture. Injections of B. pahangi adult worm excretory/secretory products (ES), totaling 1 mg over 48 h, into the limb of the original infections in seven dogs, resulted in inhibition of Ag-driven proliferation by cell populations previously responsive to BpA. There was a loss of PBL responsiveness by all but one infected dog and a loss of node cell response by the two dogs previously responsive in infected and uninfected nodes. This loss of responsiveness lasted at least 28 days in three dogs. There was no evidence of suppression of responses to mitogens either before or after ES injection. In contrast, BpA-specific antibody production was greatly increased in node cells from infected limbs injected with ES. Similar injections into the uninfected limbs of two infected dogs produced no change of proliferative responses or of antibody production in the uninfected node. These results indicate that ES can modulate immune cell, Ag-driven proliferation, and simultaneously enhance antibody production in previously infected nodes. This may promote parasite survival by inhibiting cellular attack based on delayed-type hypersensitivity while directing immune responses toward production of antibodies that are less damaging to the adult helminth.     

Injury, nerve, and wound epidermis related electrophoretic and fluorographic protein patterns in forelimbs of adult newts

Polyacrylamide slab gel electrophoresis and [35S]methionine fluorography were used to examine proteins in regenerating newt limbs, amputated denervated limbs, unamputated denervated limbs, and separated blastema mesodermal core and wound epidermis. A total of 27 protein electrophoretic bands were obtained from amputated limbs and 24 bands from unamputated limbs. Amputation resulted in the appearance of 4 new bands and the loss of 1 band as compared to unamputated limbs. These 5 banding differences were apparent on stained gels 3 days postamputation and were maintained through 10 weeks postamputation (complete regenerate stage). Only one band in unamputated limbs was always detectable on fluorographs, whereas virtually all of the stainable bands of amputated limbs were visible on fluorographs. Amputation clearly stimulated a marked, generalized increase in the synthesis of limb proteins. The 5 amputation induced changes were equally evident in stained gels of both innervated and denervated limbs. Amputated denervated limbs possessed a full set of fluorographic bands (including the 5 differences) through 18 days postamputation. However, denervation without amputation was not sufficient to alter the stainable banding pattern. Wound epidermis and mesodermal core both displayed the 5 banding differences and had identical banding patterns with the exception of one epidermal specific band. This band was also present in whole limb skin but was absent in unamputated mesodermal limb tissue. This was the only band of unamputated limbs that was consistently detectable by fluorography. It is concluded that amputation induces nerve independent changes in protein synthesis that are common to both mesodermal core and wound epidermis. These changes may represent preparation for cellular proliferation.     

Mechanics of the limbs of the walrus (Odobenus rosmarus) and the california sea lion (Zalophus californianus)

Moment arms and cross-sectional areas of muscles from the forelimbs and hind limbs of Odobenus and Zalophus were used to estimate relative torques associated with several locomotor movements. Odobenus uses predominantly the hind limbs for aquatic propulsion, while Zalophus only uses the forelimbs. Torques contributing to locomotor movements used during the power and recovery strokes were substantially greater for the hind limbs of Odobenus and for the forelimbs of Zalophus. Apparently, the lineages of these two genera shared an aquatic ancestor during the Miocene; therefore, they also shared a common method of aquatic propulsion. This common method of aquatic propulsion could have been either forelimb, hind limb, or both. Since the Miocene then, the method of aquatic propulsion and the mechanical characteristics of the limbs have diverged for at least one of these two lineages. A model is advanced to explain key mechanical differences between Odobenus and Zalophus that enable Odobenus to maneuver effectively in a head-down posture on the ocean floor.     

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.     

Interactions between irradiated and unirradiated tissues during supernumerary limb formation in the newt.

The interactions between irradiated and unirradiated blastemas and stumps in the newt forelimb were studied. Irradiated right blastemas at the stage of early digits were grafted to unirradiated left stumps and unirradiated left blastemas were grafted to irradiated right stumps. Grafts were oriented with their anterior-posterior axes opposed to that of the stumps. Supernumerary limbs ranging in completeness from one to four digits were found to arise predominantly on the anterior or posterior sides of the host limb. The graft developed well when the blastema was unirradiated and had reversed handedness with respect to the stump. Irradiated grafts developed poorly. On occasions, limbs with two supernumerary structures were found. The results are discussed in terms of the origin of the cells which comprise the supernumerary limbs and their bearing on a recently presented model concerned with pattern specification and regulation in epimorphic fields.     

Comparative morphology among trunk limbs of Caenestheriella gifuensis and Leptestheria kawachiensis (Crustacea: Branchiopoda: Spinicaudata)

Morphological differences among groups of the 24 trunk limbs of Caenestheriella gifuensis (Ishikawa, 1895) and differences between males and females are described and illustrated. A setose attenuate lobe located proximally near enditic lobe 1 and a discoid lobe covered with small setae proximal to enditic lobe 1 are newly described. The five ventral enditic lobes, endopod, exopod, and dorsal exite of traditional spinicaudatan morphology are redescribed. Trunk limbs 1–4 of females bear a palp on enditic lobe 5 and trunk limbs 1–15 of males bear a similar palp. A second, articulating palp is associated with the base of the endopod of trunk limbs 1–2 of males. The proximal part of trunk limbs 19–24, bearing enditic lobe 1, articulates by an arthrodial membrane with the remainder of the limb, and the exite is distal to this arthrodial membrane. Development of trunk limbs, ascertained through an examination of early juvenile instars of Leptestheria kawachiensis Uéno, 1927, includes an asetose limb followed in time by a series of setose limbs that increase in morphological complexity with age. The number of lobes on the asetose limb varies from seven (corresponding to five enditic lobes, an endopod, and an exopod) on anterior limbs to five on trunk limb 24, which lacks the lobes corresponding to enditic lobe 4 and the endopod; these two structures are added later to setose limbs. The attenuate lobe, the discoid lobe, the exite of all trunk limbs, and the palps of the anterior trunk limbs are added to the setose limbs. Development of anterior limbs is accelerated relative to that of posterior limbs, and development of the more posterior limbs is truncated relative to that of limbs immediately anterior to them. Enditic lobe 4 and the endopod of limbs like trunk limb 24 develop from, or are patterned by, enditic lobe 5; the articulating palp of male trunk limbs 1–2 also may be added in this way. A comparison of these observations with development of the copepod maxilliped suggests that the spinicaudatan trunk limb is composed of a praecoxa with three lobes, a coxa and a basis each with one lobe, and an endopod of three segments in females and four in males. This is similar to the homology scheme previously proposed by Hansen in 1925. A critique is given of attempts to homologize parts of arthropod limbs based on developmental gene expression patterns. Stenopodal to phyllopodal transformations of maxillipeds in copepods provide a model at least partly applicable to spinicaudatans, and a ‘multibranched’ interpretation of spinicaudatan (and by extension branchiopodan) limb morphology is rejected. There is nothing intrinsic to the structure of the adult trunk limbs suggesting that they are similar to the adult limbs of the ancestral branchiopod or the ancestral crustacean, but early developmental steps of more posterior limbs are good matches for the morphology of an ancestral crustacean biramal limb predicted by a hypothesis of duplication of the proximo‐distal axis. © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society, 2003, 139 , 547–564. No claim to original US government works.     

FFU complex: an analysis of 491 cases

A study of 491 patients with femur-fibula-ulna (FFU) complex is presented. The term FFU complex has been proposed for cases in which the femur, fibula and/or ulna show defects, which tend to be associated. These cases are usually sporadic. Some rare anomalies of the arms which are present are particularly frequent in FFU complex. These are amelia, peromelia of humerus, humeroradial synostosis and defect of ulna. In our study, 491 patients were investigated for involvement of limb malformations. Our results, showing nearly equal proportions of the most common malformations in four analysed groups (with one, two, three and four limbs affected) supports the hypothesis that even if one arm or one leg only is affected, the cases may still be classifiable as FFU complex. There is a striking asymmetry in presence and in degree. All malformations are more often unilateral than bilateral. Upper limbs are affected more often than lower limbs. The right side and the male sex are preferentially affected. The limb malformations present in the FFU complex are different from those seen in most other types of limb defects, so there is virtually no overlap between FFU and other limb malformations. Some arguments in favour of early somatic mutation as a cause are discussed.     

Homology of Holocene ostracode biramous appendages with those of other crustaceans: the protopod, epipod, exopod and endopod

Unambiguously biramous appendages with a proximal precoxa, well-defined coxa and basis, setose plate-like epipod originating on the precoxa, and both an endopod and exopod attached to the terminal end of the basis are described from several living Ostracoda of the order Halo-cyprida (Myodocopa). These limbs are proposed as the best choice for comparison of ostracode limbs with those of other crustaceans and fossil arthropods with preserved limbs, such as the Cambrian superficially ostracode-like Kunmingella and Hesslandona. The 2nd maxilla of Metapolycope (Cladocopina) and 1st trunk limb of Spelaeoecia, Deeveya and Thaumatoconcha (all Halocypridina) are illustrated, and clear homologies are shown between the parts of these limbs and those of some general crustacean models as well as some of the remarkable crustacean s.s. Orsten fossils. No living ostracodes exhibit only primitive morphology; all have at least some (usually many) derived characters. Few have the probably primitive attribute of trunk segmentation (two genera of halocyprid Myodocopa, one order plus one genus of Podocopa, and the problematic Manawa); unambiguously biramous limbs are limited to a few halo-cyprids. Homologies between podocopid limbs and those of the illustrated primitive myodocopid limbs are tentatively suggested. A setose plate-like extension, often attached basally to a podocopid protopod, is probably homologous to the myodocopid epipod, which was present at least as early as the Triassic. Somewhat more distal, less setose, and plate-like extensions, present on some podocopid limbs (e.g., mandible), may be homologous instead to the exopod (clearly present on myodocopid mandibles). The coxa (or precoxa) is by definition the most basal part of the limb. A molar-like tooth is present proximally on the mandibular protopod of many ostracodes; it is the coxal endite and projects medially from the coxa (or proximal protopod). The Ostracoda is probably a monophyletic crustacean group composed of Myodocopa and Podocopa. All have a unique juvenile (not a larva) initially with three or more limbs. Except that juveniles lack some setae and limbs, they are morphologially similar to the adult. Thus the following suite of characters in all instars may be considered a synapomorphy uniting all Ostracoda: (1) Each pair of limbs is uniquely different from the others. (2) The whole body is completely enclosed within a bivalved carapace that lacks growth lines. (3) No more than nine pairs of limbs are present in any instar. (4) The body shows little or no segmentation, with no more than ten dorsally defined trunk segments. No other crustaceans have this suite of characters. A probable synapomorphy uniting the Podocopa is a 2nd antenna with exopod reduced relative to the endopod.     

Renal anatomy in sparrows from different environments

The renal anatomy of three species of sparrows, two from mesic areas, the House Sparrow (Passer domesticus) and Song Sparrow (Melospiza melodia), and one salt marsh species, the Savannah Sparrow (Passerculus sandwichensis) was examined. Electron microscopy was used to describe the ultrastructure of the nephron. In addition, stereology was used to quantify the volumes of cortex, medulla, and major vasculature of the kidneys, and the volumes and surface areas occupied by individual nephron components. There appeared to be no differences in the ultrastructural anatomy of the nephrons among the sparrows. Proximal tubules contained both narrow and wide intercellular spaces filled with interdigitations of the basolateral membrane. The thin limbs of Henle contained very wide intercellular spaces which were absent in the thick limbs of Henle. The distal tubule cells contained short, apical microvilli and infoldings of the basolateral membrane. In cross section, the medullary cones of all birds display an outer ring of thick limbs of Henle which surround an inner ring of collecting ducts, which in turn surround a central core of thin limbs of Henle. The Savannah Sparrow has a significantly higher volume of medulla compared to the two more mesic species. Within the cortex, the Savannah Sparrow also has a significantly higher volume of proximal tubules but a significantly lower volume of distal tubules than the other species. Within the medulla, the Savannah Sparrow has a significantly higher volume and surface area of capillaries, and a significantly higher surface area of thick limbs of Henle and collecting ducts than the mesic species. These data suggest that the salt marsh Savannah Sparrow has the renal morphology necessary to produce a more highly concentrated urine than the mesic zone species.     

Évaluation lymphoscintigraphique d’éventuelles anomalies du système lymphatique au niveau des membres inférieurs de joueurs de football : à propos de six observations

In order to demonstrate possible abnormalities of the lymphatic system as consequence of soccer practice, lymphoscintigraphic investigations of the lower limbs have been performed (1) in five young male volunteers with at least ten years of soccer practice (kicking with one foot in the five cases; previous osteoarticular events involving the ankles in four: no clinical edema observed) and (2) in one professional female soccer player (also kicking with one foot) who presented with one bilateral distal edema of the lower limbs. After the subcutaneous injection of ^99mTc-labeled HSA nanosized colloids in the first interdigital space of the feet and the limbs being at rest during 30 min, the tracer did reach normally the first inguinal nodes in only three subjects (their kicking limbs), suggesting thus one functional insufficiency of the lymphatic system at the level of nine of the twelve limbs. With exercise (tip-toeing during 5 min), one (abnormal) functional asymmetry (activity reaching the inguinal nodes greater at the level of the kicking limb than at the level of the not-kicking one) was also observed. Finally, the female player with distal limb edemas showed at the end of the investigation the lowest values (within the group) of tracer disappearance at the level of the injection sites. Morphological abnormalities on the lymphatic system of the lower limbs (as dermal backflow, lymphostasis, …) were observed in none of the subjects at the end of the investigation, suggesting lesions at the level of the tissues injected and/or of the initial lymphatics of the feet rather than lesions at the level of the great lymphatic vessels of the limbs. To conclude and although based on a limited series of subjects, the results suggest the development of functional lymphatic abnormalities at the level of the feet in soccer players, abnormalities mostly without clinical manifestations but that can lead to clinically obvious edemas. These abnormalities would have to be confirmed on a larger series.     

Dorsal root ganglia grafts stimulate regeneration of denervated urodele forelimbs: timing of graft implantation with respect to denervation

Amphibian forelimb regeneration is a nerve-dependent process; nerves presumably release one or more neurotrophic factors that stimulate blastema cell division. To date several candidate molecules/factors have been shown to stimulate macromolecular synthesis and/or mitosis but sustained cell cycle activity and blastema development have not been achieved. Because dorsal root ganglia (DRG) implants are capable of promoting regeneration of denervated adult newt limbs (Kamrin & Singer, 1959), we have evaluated the DRG stimulation of regeneration in denervated limbs of adult newts and larval axolotls; two alternative timing strategies were tested as a step toward defining bioassay parameters that best reflect neurotrophic activity. The frequency of regeneration in denervated adult newt limbs was compared after providing DRG before or at the time of denervation (to maintain neurotrophic and cell cycle activity) versus DRG implantation at various postdenervation times (to resupply neurotrophic activity and restimulate suppressed cell cycle activity). The results show that denervated adult newt limbs regenerated most frequently using the maintenance strategy, but as the denervation interval was extended in the restimulation strategy, the frequency of regeneration declined. Larval axolotl limbs responded positively in both maintenance and restimulation DRG-grafting protocols. These results suggest that the efficacy of DRG stimulation of regeneration in adult newts was related to the relative number of blastema cells present at the time of denervation and the proliferative status of the blastema cells; bioassays with denervated adult newt limbs should be designed with these constraints in mind. Because such constraints are not as problematic with the larval axolotl, this species may provide the best opportunity for further defining bioassay parameters related to the neurotrophic stimulation of regeneration.     

An application of cineradiography to the study of locomotion in primates

The cineradiographic technique, whereby, at 64 frames/second, the successive positions of every bone segment of animals in motion can be accurately analyzed, was used to study the vertical leap of a Galago alleni from the ground position. This jump, 13 to 14 times the body length of the animal excluding the tail, is a record among primates challenged only by the tarsier. Such vertical leaps from the ground are a common mode of locomotion for the galago. Two different patterns were observed, a symmetrical and an asymmetrical jump. In the former, the two hind limbs move in the same manner and simultaneously; and the propulsive force is equally distributed in both limbs. In the latter (more frequent in our records), the animal shifts its weight onto one foot during the preparatory phase and lifts the other; thus, only one of the hind limbs is responsible for the launching. The angular variations of every knee and ankle articulation and the successive positions of the hind limb bones were measured and diagrammatically analyzed frame by frame. A short film was made to illustrate the cineradiographic technique; it cinematographically and cineradiographically records in successive sequence the galago's leap from the ground. The symmetrical and asymmetrical jumps are also schematically presented.     

Limb Loss and Regeneration in Two Grabs: The King Crab Paralithodes camtschatica and the Tanner Crab Chionoecetes bairdi

The incidence of limb loss and regeneration in two species of benthic Crustacea, the king crab Paralithodes camtschatica, an anomuran, and the tanner crab Chionoecoetes bairdi, a brachyuran, is surveyed in populations from the Bering Sea. 29.4 % of young juvenile P. camtschatica and 14.8 % of adults had lost at least one limb. The overall incidence of limb loss in C. bairdi was 38.8 %, with female adults less prone to damage than males and juveniles. Limb loss increases in frequency in more posterior limbs. Right hand limbs are lost more often than left in both species. This “right handedness” appears to be widespread in crabs and may be due to the greater vulnerability of leading limbs. The frequency distribution of limb regenerate lengths in a population of young juveniles suggests that at least four instars must be passed before limb symmetry is restored.     

Fibroblast growth factor-induced gene expression and cartilage pattern formation in chick limb bud recombinants

To clarify the roles of fibroblast growth factors (FGF) in limb cartilage pattern formation, the effects of various FGF on recombinant limbs that were composed of dissociated and reaggregated mesoderm and ectodermal jackets were examined. Fibroblast growth factor-soaked beads were inserted just under the apical ectodermal ridge (AER) of recombinant limbs and the recombinant limbs were grafted and allowed to develop. Control recombinant limbs without FGF beads formed one or two cartilage elements. Recombinants with FGF-4 beads formed up to five cartilage elements, which were aligned along the anteroposterior (AP) axis. Each cartilage element showed digit-like segmentation. In contrast, recombinants with FGF-2 beads showed formation of multiple thick and unsegmented cartilage rods, which elongated inside and outside the AP plane from the distal end of the recombinants. Recombinants with FGF-8 beads formed a truncated cartilage pattern and recombinants with FGF-10 beads formed a cartilage pattern similar to that of the control recombinants. The expression of the Fgf-8, Msx-1 and Hoxa-13 genes in the developing recombinant limbs were examined. FGF-4 induced extension of the length of the Fgf-8-positive epidermis, or AER, along the AP axis 5 days after grafting, at which time the digits are specified. FGF-2 induced expansion of the Msx-1-positive area, first in the proximal direction and then along the dorsoventral axis. The functions of these FGF in recombinant and normal limb patterning are discussed in this paper.