Ventral Limbs Research Articles

Focal Proliferative Eosinophilic Dermatitis of the External Ear Canal in Four Dogs

Dermatitides with marked tissue eosinophilia are commonly occurring lesions in the cat, and two distinct entities are described: feline eosinophilic plaque characterized histologically by a hyperplastic superficial and deep perivascular to diffuse eosinophilic dermatitis with intraepidermal eosinophilic microabscesses, and feline eosinophilic granuloma, which is a granulomatous eosinophilic dermatitis with multifocal flame figure^.^ A similar granulomatous lesion occurs in hor~es .~ Eosinophilic granuloma has been reported in the dog as a rare lesion of the skin and oral Although it has been described in dogs of all ages, breeds, and sexes, dogs under 3 years of age, Siberian Huskies, and males appear to be at risk. The most common site of canine eosinophilic granuloma is the oral cavity, and the lesions are characterized by vegetative and ulcerated lingual or palatine masse~.~.~.~. l l Multiple cutaneous nodules and raised plaques on the ventral abdomen, prepuce, flanks, and limbs have also been reported.5.8Jo One case involved the nasal skin.' The cutaneous lesions are non-pruritic and non-painful. Peripheral blood eosinophilia is occasionally observed. Although the blood and tissue eosinophilia and the response to corticosteroid therapy suggest that cutaneous hypersensitivity may be inv o l ~ e d , ~ the cause of canine eosinophilic granuloma is still not clear. In this report, we describe an unusual location of focal,

Development and diversity of the suspensorium of trichomycterids and comparison with loricarioids (Teleostei: Siluriformes).

Studies of ontogenetic series of trichomycterids and other catfishes reveal that the suspensorium of siluroids is highly specialized; several synapomorphies separate siluroids from other teleosts. In siluroids, the palatoquadrate is divided into pars autopalatina and pars pterygoquadrata and both are usually connected by the autopaiatine-metapterygoid ligament. The pterygoquadrate is broadly joined to the dorsal limb of the hyoid arch, forming a cartilaginous hyomandibular-symplectic-pterygoquadrate plate in early ontogeny. This produces a special alignment of the hyomandibula and quadrate which is characteristic of siluroids. A symplectic bone is absent. The interhyal is absent in trichomycterids and astroblepids. Dorsal and ventral limbs of the hyoid arch are connected by a ligament. A rudimentary interhyal and this ligament are present in primitive siluroids such as diplomystids and nematogenyids as well as loricariids. The metapterygoid arises as an anterior ossification of the pars pterygoquadrata in siluroids. The formation and position of the metapterygoid exhibit two patterns: (1) the metapterygoid develops as an ossification of a cartilaginous projection positioned between the future hyomandibula and quadrate in primitive catfishes (e.g., Diplomystes) as well as in Nematogenys, callichthyids, loricariids, and astroblepids; (2) the metapterygoid arises as an ossification of the cartilaginous projection (pterygoid process) positioned just above the articular facet of the quadrate for the lower jaw. An ossified anterior chondral pterygoid process of the complex quadrate is present in trichomycterids, whereas the process is absent (simple quadrate) in catfishes such as diplomystids, nematogenyids, callichthyids, and loricariids. The anterior membranous process of the quadrate of Astroblepus is non-homologous with the chondral pterygoid process of trichomycterids; both structures arose independently within the loricarioids. Despite topological relationships, the origin and development of bones reveal the presence of a chondral hyomandibula which develops a large meinbranous outgrowth during ontogeny and a chondral metapterygoid in trichomycterids. The presence of a compound hyomandibula + metapterygoid or a compound metapterygoid + ectopterygoid + entopterygoid have no developmental support in trichomycterines or other siluroids. The "entopterygoid" of Nematogenys and Diplomystes arises as an ossification of a ligament. The dermal entopterygoid of other ostariophysans and the "entopterygoid" are homologous. An ectopterygoid or tendon bone "ectopterygoid" is absent in loricarioids. The suspensorium is an important structural system which has significant evolutionary transformations which characterize loricarioid subgroups; however, no character, of the suspensorium supports the monophyly of the loricarioids.

Three new Indo-Australian species of the sciaenid genusAtrobucca, with a reevaluation of generic limit

Three new species of the sciaenid genusAtrobucca are described:A. kyushini from off Borneo, differs from all known congeners in having no swimbladder appendages enveloplng the bladder, no forward directed branches from the ventral limbs of the appendages, a long tube-like last appendage parallel to the bladder wall and a pale mouth lining;A. brevis from off northern Australia and Papua New Guinea, is distinguished by its short pectoral fin (less than 23% SL) and pleural rib on the 11th vertebra;A. adusta from Papua New Guinea, is distinctive in having a low dorsal soft ray number (23–24) and long caudal peduncle (27–30% SL).Atrobucca Chu, Lo et Wu is redefined to accommodate the new species: the genus is principally characterized by the swimbladder appendages divided into developed dorsal and ventral limbs, and the only slightly curved sulcus tail of the sagitta. A key and diagnoses are provided for all known species ofAtrobucca.

Regeneration from half lower arms in the axolotl

A technique involving grafting of pieces of skin from the head onto the limb in order to isolate halves of the limb is described. This technique was used to isolate posterior, anterior, dorsal and ventral halves of the lower arm. All halves produced regenerates but no part of the limb was able to produce a high proportion of regenerates with a complete pattern of skeletal structures. Posterior half stumps regenerated limbs with a mean digit number of 2.7 and had a normal dorsoventral muscle pattern. Anterior half stumps produced a high proportion of single-digit regenerates and had a mean digit number of 1.3. Dorsal and ventral half stumps regenerated limbs with a mean digit number of 2.8 and 2.3 respectively. Hypomorphic regenerates from dorsal and ventral half stumps often had only dorsal or ventral muscle. These results are in contrast to those from the upper arm (Wigmore & Holder, 1985) where a complete skeletal and muscular pattern regenerated from posterior and dorsal halves and hypomorphic regenerates were obtained from anterior and ventral half limbs.

The regeneration of double dorsal and double ventral limbs in the axolotl

Surgically made double dorsal and double ventral upper arms, comprising double extensor and double flexor muscles respectively, were amputated immediately following operation; both limb types regenerated. In terms of skeletal anatomy, a range of limb types was found. These included four-digit limbs of normal cartilage pattern, and hypomorphic limbs having from one to three digits. All of the double dorsal and the majority of the double ventral limbs were symmetrical in the dorsal-ventral axis. This was detected by analysing their muscle patterns at carpal and mid-forearm level, and muscle and epidermal characteristics in the metacarpal region are discussed in terms of the significance of healing time and stump pattern on the regenerative ability of surgically created limb regions.

Structure of the Spicules and Caudal Sensory Equipment in the Male of Aphelenchoides Blastophthorus (Nematoda: Tylenchida, Aphelenchina)

The spicules of Aphelenchoides blastophthorus are thorn-shaped, with a large dorsal and a smaller ventral limb, and a flattened base embedded in the tail tissues. When retracted, the spicule tips are not exposed through the cloacal opening as they are in some other genera. The large spicular nerve runs along the dorsal limb. Within the nerve a single dendritic process is differentiated and this passes to the outer edge of the dorsal limb, running just beneath the surface towards the tip, where there is a single pore. The spicules do not form an enclosed tube; the ventral limbs abut but the dorsal limbs gape open when extended. Two innervated cuticular processes from the wall of the cloacal sac are exposed when the spicule tips are protruded. These are probably mechanoreceptors. Three pairs of caudal papillae, in adanal, mid-tail and terminal positions, are probably chemosensory as the sensilla open to the exterior through a pore. The relationship between the morphology of spicules and accessory sensory structures and mating behaviour is discussed.

Supernumerary limbs in amphibians: Experimental production in Notophthalmus viridescens and a new interpretation of their formation

The formation of supernumerary limbs was studied in the adult newt, Notophthalmus viridescens. Forelimb blastemas at the stages of medium bud and early digits were either transplanted to the contralateral forelimb with their dorsal-ventral axis opposed to that of the limb stump, or removed, rotated through 180°, and replaced on the same limb stump with both dorsal-ventral and anterior-posterior axes opposed to those of the stump, or as a control, removed, and replaced in normal orientation. Supernumerary limbs were produced in both experimental series, but not in the controls. Following contralateral transplantation, supernumerary limbs arose close to the graft junction at the two positions where dorsal limb tissue was in contact with ventral limb tissue. Both dorsal and ventral supernumerary limbs were of the same handedness as the limb stump and they were mirror-images of the regenerate developing directly from the transplanted blastema. Following 180° rotation, supernumerary limbs arose close to the graft junction at those positions where anterior-ventral and posterior-dorsal limb tissues were in contact. The supernumerary limb which arose in the posterior-dorsal position with respect to the limb stump was a mirror-image of the transplant, and was therefore of opposite handedness to both transplant and stump. The supernumerary limb which arose in the anterior-ventral position was of the same handedness as both transplant and stump. A new model of pattern regulation in epimorphic fields which can account for these results and which has retrospective value in the interpretation of earlier experiments on developing limbs is discussed.