Plantar Pad Research Articles

The differentiation of the skin and its appendages. II. Altered development of papillary ridges following neuralectomy.

In order to test the hypothesis that the nervous system is an important determinant of skin differentiation, deletions of the left lumbosacral dorsal root ganglia (DRGs), the sources of cutaneous afferents to the left hindpaw, were performed on opossum pups at day 1 when hindpaws have just begun to be innervated. At birth, each lumbosacral DRG measures about 200 microns rostrocaudally and a deletion measuring 1 mm would span 4-5 DRGs. Following survival periods of 5-24 days, serial sections through the trunk documented partial left lumbosacral DRG deletion and a variable degree of spinal cord destruction. The blood supply to the trunk and hindpaws was preserved. Bilateral enlargement of residual DRGs was observed and regenerating skin at the site of the deletion was hyperplastic and hyperinnervated. The skin of the plantar pads of the hindpaws was studied following the neuralectomies. Statistically significant differences were observed between the left (experimental) and right (control) hindpaws. The density of innervation of the left hindpaw was reduced compared to the right hindpaw, development of papillary ridges was retarded by 3-4 days, and non-innervated Merkel cells were hypogranulated. This period of delay in ridge development is probably a reflection of the expansion of residual DRGs into the peripheral domains of deleted DRGs. The present study confirms a role for afferent nerves in the timing of cutaneous differentiation and a mutual trophic dependence between cutaneous nerves and Merkel cells in the epidermis.

Hallux sesamoid bones. Anatomical observations with special reference to osteoarthritis and hallux valgus.

The normal characteristics of the hallux sesamoid bones were studied in 200 toes (100 dissections and 100 radiographs from patients with hallux valgus), and pathological changes were recorded. Normally each sesamoid articulated with a separate groove on the plantar surface of the first metatarsal head. A bony ridge on the head separated these grooves. Bipartite sesamoids were found in 4% of the toes. Osteoarthritic changes manifested by deformity, irregularity, lipping, cysts in the sesamoids and in the heads of the first metatarsal, and erosions in the articular surfaces were present in 32% of the dissected toes. Fusion of the sesamoids was found in 6%. Ankylosis between the sesamoids and the head of the metatarsal was observed in 4%. In the toes affected by hallux valgus the sesamoids, together with the plantar pad and the tendon of the flexor hallucis brevis, were displaced laterally to a variable degree. In severe deformities the lateral sesamoid was dislocated lateral to the first metatarsal head and the medial sesamoid occupied the groove originally corresponding to the lateral sesamoid, while the metatarsal ridge separating the two sesamoids tended to disappear. Osteoarthritis of the metatarsophalangeal joint frequently accompanied hallux valgus.

Peripheral and central control of flexor digitorum longus and flexor hallucis longus motoneurons: the synaptic basis of functional diversity.

The two long toe flexor muscles in the cat, flexor digitorum longus (FDL) and flexor hallucis longus (FHL), have essentially identical mechanical actions, yet are used very differently during locomotion (O'Donovan et al. 1982). We attempted to identify the origin of the synaptic drive responsible for this functional differentiation. The organization of peripheral and central synaptic drive to FDL and FHL motoneurons was examined using two basic paradigms. (1) In animals anesthetized with chloralose or after ischemic destruction of the brain, peripheral reflex circuits were studied by recording intracellular responses from alpha-motoneurons produced by electrical stimulation of muscular and cutaneous nerves. (2) "Fictive locomotion", the centrally generated rhythmic synaptic drive produced in paralyzed, decerebrate animals by stimulation of the mesencephalic locomotor region or intravenous injection of L-DOPA and Nialamide, was monitored by recording electroneurograms from the central end of cut motor nerves. Despite their functional dissimilarity, FDL and FHL motoneurons received monosynaptic EPSPs from both FDL and FHL la afferents. Ipsilateral cutaneous afferents in the sural nerve and from the central plantar pad produced multiphasic PSPs which were not different in FDL and FHL cells. However afferents from the saphenous and superficial peroneal nerves did exert differential effects: the first component of the multiphasic PSP in most FDL cells was an EPSP, which was not present in most FHL cells. The central latency of this early EPSP in FDL motoneurons (0.8-1.5 ms) strongly suggests a disynaptic linkage. Cutaneous afferents from the ipsilateral forelimb produced IPSPs in most FHL cells but in only one of 18 FDL cells. Since some peripheral reflex circuits exerted differential effects on FDL and FHL cells, but others did not, the intracellular data did not demonstrate that the functional differences between FDL and FHL could be explained by differences in reflex organization. During fictive locomotion elicited by electrical or pharmacological stimulation, FHL motoneurons were coactive with ankle extensors during the extension phase of the fictive step cycle. In contrast, FDL motoneurons were most consistently activated in a brief burst at the onset of the flexion phase, showing much weaker and more variable coactivity with ankle extensors. These patients were essentially identical to those reported for FDL and FHL motor pools during treadmill locomotion by O'Donovan et al. (1982). We conclude that the central pattern generator (CPG) for locomotion produces distinct and highly differentiated sets of instructions for FDL and FHL motoneurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Technical report: a method for recovering the palmar and plantar pads of small primate cadaver specimens for dermatoglyphic analysis.

A method for recovering dermatoglyphic data from tamarin cadavers is described. The method involves the complete removal of the palmar and plantar pads with no destruction to the underlying skeletal elements. Once recovered, the pads are stored in a formalin solution. The stored pads of 213 individuals have remained in a good state of preservation for dermatoglyphic analysis for over four years.

Structure of the plantar sweat glands of the Bank vole Clethrionomys glareolus

The plantar pads of the hind feet of 15 male and female, young and old Clethrionomys glareolus (Rodentia–family Muridae) were examined for the presence of tubular glands. Groups of eight or nine coiled glands were found in all of the 11 plantar pads. The secretory portion of the gland lies deep in the fatty hypodermis and communicates with the plantar surface by a coiled duct whose lining cells merge with those of the stratum basale of the undersurface of the foot. Groups of shallow depressions mark the site of the duct openings. They are not associated with any hairs.Although light microscopy shows only one cell type, electron microscopy reveals two morphologically different cell types. Neither conform directly to the light and dark secretory cells of the human sweat glands although similarities exist. Myoepithelial cells surround the secretory cells, but do not appear to be present around the duct cells.

Regeneration of the plantar skin in mammals

Two posterior plantar pads together with the surrounding skin were removed from the hind limb in rats, and one plantar pad each without the surrounding skin was removed from the hind and fore limbs of hedgehogs. As a result of healing of the skin wounds in the rats and hedgehogs, areas of regeneration were formed with the typical stratum papillare of plantar skin. In hedgehogs the regenerating skin covered the restored plantar pad. In rats the plantar pads were not restored.

Different degrees of morbidity, in the white mouse, induced by Nocardia brasiliensis, Nocardia asteroides and Nocardia caviae.

The respective degrees of morbidity induced by 6 strains each of Nocardia brasiliensis, N. asteroides and N. caviae were investigated by the method of inoculation in the plantar pad of the white mouse, using a suspension of these nocardiae at a concentration of 10 mg/0-1 ml., and inspecting the animals one month, two months and three months following inoculation. All of the strains of N. brasiliensis produced attack greater and more consistent than that of the other species, N. caviae and N. asteroides showing patterns of attack similar to each other, but substantially lower than those obtained with N. brasiliensis. The 6 strains of N. brasiliensis showed different rates of infection at different times of observation, but it was constantly high for all of them; on the other hand, the infectiousness of the different strains of N. caviae and N. asteroides was low, and there were no substantial differences between them. To sum up, these results with 6 strains of each species confirm those that were published in 1973 which dealt with only one strain of each species.

Mouse Foot Screen for the Inhibition of Sweating by Anticholinergic Drugs

Mice have been utilized to develop a simple, rapid, inexpensive, quantitative screening procedure for sweat inhibition by anticholinergic agents. Graded doses of anticholinergic drugs are injected with a microliter syringe subcutaneously under the plantar foot pads of one hind foot of mice. Both hind feet are then coated with a suspension of starch and castor oil, and the mice are stimulated to sweat by an intraperitoneal injection of 10 mg/kg of pilocarpine HCI. Sweating on the treated foot is judged to be inhibited or not inhibited relative to the contralateral untreated foot. The median inhibitory concentrations and 95% confidence limits are determined by a simple, approximate method. The relative potencies of test compounds are expressed in terms of their ratios to a standard, scopolamine HBr. Compounds representing a wide range of potencies have been screened, and significant differences in their sweat inhibiting potencies have been demonstrated. These compounds include, in order of decreasing activity: tridihexethyl chloride and (2-[2-methyl-1-pyrrol- idyl ]ethylphenylcyclopentylacetate) HCI, which have similar potencies, 3, 3-diphenyl-N- dimethylpropylamine HCI and hydroxyzine HCI.

Primary afferent depolarization and flexion reflexes produced by radiant heat stimulation of the skin.

1. The reflex effects of pulses of intense radiant heat applied to the skin of the central plantar pad have been studied in unanaesthetized (decerebrate) spinal cats.2. Pad heat pulses produced flexion of the ipsilateral hind limb and increased ipsilateral flexor monosynaptic reflexes, due to post-synaptic excitation of flexor alpha motoneurones. These effects were accompanied by reduction of extensor monosynaptic reflexes and post-synaptic inhibition of extensor motoneurones.3. Ipsilateral (and contralateral) pad heat pulses consistently evoked negative dorsal root potentials (DRPs) as well as increased excitability of both cutaneous and group Ib muscle afferent terminals. The excitability of group Ia afferents was sometimes also increased during pad heat pulses, but to a lesser extent.4. Pad heat pulses produced negative DRPs in preparations in which positive DRP components could be demonstrated following electrical stimulation of both skin and muscle nerves.5. The motor and primary afferent effects of heat pulses always accompanied one another, beginning after the pad surface temperature had reached rather high levels (usually 48-55 degrees C).6. Negative DRPs increased excitability of cutaneous and group Ib afferents, and motoneurone activation produced by pad heat pulses was essentially unmodified when conduction in large myelinated afferents from the central plantar pad was blocked by cooling the posterior tibial nerve trunk.7. It is concluded that adequate noxious activation of cutaneous afferents of small diameter produces primary afferent depolarization in a variety of large diameter afferent fibres, as well as post-synaptic effects in alpha motoneurones.

Primary afferent depolarization evoked by a painful stimulus.

Pulses of intense radiant heat applied to the plantar pad of unanesthetized spinal cats produced negative dorsal root potentials, increased excitability of cutaneous A fibers, and marked activation of ipsilateral flexor motoneurons. The same effects were obtained during cold block of A fiber conduction in the appropriate peripheral nerve. We conclude that adequate noxious activation of cutaneous C fibers depolarizes cutaneous A fibers.

Apocrine Sweat Glands in the Angulus Oris of Microtine Rodents

Coiled, tubular glands of the apocrine, sudoriferous type occur in the angulus oris of microtine rodents ( Synaptomys cooperi , Clethrionomys occidentalis , Microtus californicus and M. mexicanus ) and are described here for the first time. This glandular tissue is similar in amount and structure in the three genera examined. The glands open into hair follicles and have dilated secretory tubules lined with cells that frequently exhibit an apocrine mode of secretory activity. They differ from the sudoriferous glands of the palmar and plantar pads of the same animals ( Microtus californicus ) not only in these features but also in their cytoplasmic content of lipid droplets. Glycogen granules and pigment (lipofuscin ?) are present in some secretory cells; ferric iron was not demonstrable. The structure of the glands is typical of the apocrine glands of some other mammalian Orders and is simpler and perhaps more generalized than that of the special dorsal and anal sudoriferous glands of some sciurids. The small number (2 to 3 per side) of the glands negates functional significance in thermoregulation but not the possibility of use in olfactory communication.

The anatomy of hallux valgus.

1. The anatomy of the forefoot in hallux valgus is compared with the normal, with a review of the literature and descriptions of anatomical preparations, observations at operation and radiographs. 2. The early and essential lesions are stretching of the ligaments on the medial side of the metatarso-phalangeal joint that attach the medial sesamoid and basal phalanx to the metatarsal, and erosion of the ridge that separates the grooves for the sesamoids on the metatarsal head. 3. In established hallux valgus a sagittal groove, formed where the cartilage is free from pressure by either the phalanx or the ligaments, cuts off a medial eminence, which articulates with the stretched ligaments, from a restricted area for the phalanx. 4. Apart from osteophytic lipping which squares off the outline of the eminence as it is seen in radiographs and a small amount of lipping of the ridge on the metatarsal there is no evidence of new bone growth. In chronic cases the eminence may degenerate or disappear. 5. The articular surfaces at the cuneo-metatarsal joint become adapted to the changed positions of the metatarsal without gross pathological change. 6. The four deep transverse ligaments that bind together the five plantar pads of the metatarso-phalangeal joints are not unduly stretched, so that as the metatarsals spread it is the ligaments that bind the pads to the heads of the metatarsals that give way. 7. The plantar metatarsal artery to the first space pursues a tortuous course between the two heads of the flexor hallucis brevis. In hallux valgus the course becomes still more tortuous and part of the pain experienced may be due to ischaemic effects.

Investigations on Foot-and-Mouth Disease by Means of Experiments with Small Animals During 1926–27.

1. Attempts to transfer the plantar pad of a guinea-pig by grafting to another part of the body were unsuccessful. 2. The hairy skin of the guinea-pig when put in the position of the plantar pad which had been removed, developed vesicles when foot-and-mouth disease virus was inoculated intradermally or intramuscularly, although lesions on the hairy skin elsewhere in the body have very seldom been observed. 3. Vesicles have been produced in places not usually affected by subjecting these parts to the irritation of pressure. 4. Fixation of a guinea-pig's hind leg so that the animal does not walk or rest on it inhibits, to a large extent, the growth of the virus in the pad and prevents the occurence of lesions on it when the guinea-pig is infected by I.M. inoculation with a large dose of foot-and-mouth virus, which causes vesiculation on the other leg. 5. No evidence of the propagation of foot-and-mouth disease virus in muscle has been obtained. An important factor in determining the presence of virus in muscle is the use of a buffer solution sufficiently strong to keep a constant pH in spite of the acid produced in grinding the muscle to make an emulsion. 6. Virus has been found in trachea, lung, liver, spleen, and kidney, but not in the heart muscle of guinea-pigs infected with foot-and-mouth disease. The amount of highly infective blood present may account for the virus being found in the organs in some instances. On the other hand, the buffer solution used in grinding the tissues with sand may not have been sufficient to maintain a favourable pH for the virus. 7. A guinea-pig's plantar pad on which a foot-and-mouth disease vesicle has previously occurred is more resistant to an inoculation of this virus than one in the same animal which has not been affected before. This may be due to a specific local immunity to the virus or merely to the result of the injury. 8. No substance harmful to the virus in vitro has been extracted by grinding the pads of immune guinea-pigs with sand in phosphate. This is the case whether the pads have or have not previously been the seat of lesions.