Mechanoreceptors and length of the patellar ligament after Ho-YAG laser treatment: a long-term follow-up in rabbits.

We studied the shortening and the number of mechanoreceptors in the patellar ligament up to 18 months after Ho-YAG irradiation of the ligament's surface in 35 rabbits. The ligaments shortened an average 13% immediately after irradiation. After treatment, we divided the rabbits into a mobilized or immobilized group. At 2 weeks and 12 months after treatment both groups showed no shortening of the ligament, as compared to the intact ligament while that in the mobilized group had elongated at 12 months. Fewer Pacinian and Ruffini corpuscles were found in the irradiated ligaments than in the intact ones at 2 weeks after treatment, but we found no difference between irradiated and intact ligaments at 18 months after treatment.

Deprivation and denervation differentially affect zinc-containing circuitries in the barrel cortex of mice.

In the neocortex, a population of glutamatergic synapses contains chelatable zinc that is released upon depolarization. The present study compares the effect of chronic tactile deprivation and vibrissectomy performed at different postnatal ages on the synaptic zinc distribution in the mouse barrel cortex. We found that a chronic unilateral tactile deprivation resulted in an increase of synaptic zinc in deprived barrels. Distribution and intensity of zinc staining in non-deprived barrels resembled the control situation. The increase of zinc staining was observed if chronic deprivation started in early postnatal life or in adolescent mice but not in 70-day-old animals. This suggests that a critical period exists for plasticity of zinc containing terminals in the barrel cortex. The alteration of zinc staining was localized to not only the thalamorecipient layers IV but also layer II/III, and upper layer V. Neonatal denervation of selected vibrissal rows resulted in rearrangement of synaptic zinc distribution following cytoarchitectonic alterations in the barrel field. However, no changes in the intensity of zinc staining were observed. Vibrissectomy performed after the critical period for barrel formation did not affect either the distribution or intensity of zinc staining. It appears that the integrity of vibrissa-barrel pathway is necessary to induce activity-dependent alterations in synaptic zinc.

Sensory recovery and Meissner corpuscle number after toe-to-hand transplantation.

This study investigated the possible relationship between sensory recovery and receptor number after toe-to-hand transplantation. Moving two-point discrimination was measured after a course of sensory re-education. Meissner corpuscle number was then quantified by light microscopic examination of multiple sections of glabrous skin obtained at pulp reduction and from site-matched normal toe and fingertip skin. Meissner corpuscle number per millimeter was 0.94 in normal toe skin (n = 4), and 0.37 after toe-to-hand transplantation (n = 34). A significant correlation existed between moving two-point discrimination and Meissner corpuscle number (r = -0.62; p < 0.001). No significant relationship was found between moving two-point discrimination and patient age or interval from injury to reconstruction. The results suggest that despite sensory re-education, there may be a level of receptor reinnervation below which good sensory recovery may not be obtained.

The relation between the response properties and the position of reinnervated periodontal ligament mechanoreceptors in the cat.

Electrophysiological recordings were made from functional single fibres teased from the inferior alveolar nerve 12 weeks after nerve section. The force thresholds, adaptation times and conduction velocities of 10 located periodontal ligament mechanoreceptors in 2 cats were recorded and compared with results for normal located receptors from a previous study using similar techniques. The relation of both threshold and the adaptation rate to the position of the reinnervated receptors was statistically significant and similar to the relation for normal units. These results support the hypothesis that the range of response characteristics of periodontal ligament mechanoreceptors depends on their position relative to the tooth's fulcrum.

Opponensplasty by extensor indicis and flexor digitorium superficialis tendon transfer

From 1977 to 1988, 166 patients with median nerve paralysis of varied aetiology underwent opponensplasty. In 50 of these the extensor indicis was used, and in 116 the flexor digitorum superficialis of the ring finger. An analysis of these hands showed that the EI opponensplasty was best in supple hands and FDS opponensplasty was more suitable for less pliable hands. There were fewer complications seen after FDS opponensplasty if the detachment of the donor tendon was done through a volar oblique incision rather than the conventional lateral incision.