[Computer-assisted manufacture of individual auricular framework and the experimental study for ear reconstruction].

OBJECTIVE: To manufacture the individual polyurethane (PUR) auricular framework using the rapid prototyping (RP) technique and to evaluate its feasibility in ear reconstruction. METHODS: 3-D models of the patient's auricle were reconstructed according to the computed tomography (CT) data. The supporting and drainage structures were created. Then the individual PUR auricular frameworks were manufactured using RP technique. The frameworks were tested for the fatigue strength and elasticity. The frameworks were also put at the subcutaneous layer of rat. At 1, 2, 4, 8, 12 weeks after operation, the shape of the reconstructed ears was observed and the histological examination was performed. RESULTS: The PUR framework had good elasticity and a much better fatigue strength than high density polyethylene (HDPE) framework. The shape of reconstructed ear matched the prototype very well. The around tissue grew into the implant pore and adhered tightly to the framework 2 weeks after implantation. Histologic examination showed integrated capsule four weeks later without lymphocytes infiltration. The shape kept very well twelve weeks later. CONCLUSIONS: PUR auricular framework manufactured by the 3D reconstruction and RP techniques has very good shape, intensity and elasticity. It can be selected to replace the autograft of rib cartilage framework.

Ultrastructure of electrical synapses between nociceptive and anterior pagoda neurons in the CNS of the leech (Whitmania pigra).

We have used electron microscopy to measure quantitatively the morphology of electrical synapses in a circuit that has been proposed to account for the positional discrimination of the leech. Injection of a presynaptic nociceptive sensory neuron and the postsynaptic anterior pagoda neuron with HRP showed gap junctions in the neuropil. After double labeling, La(3+)-treated ganglia revealed labeled gap junctions from 2.0 to 3.5 nm wide. Between the labeled axon terminals, there were innexons with diameters of 8 to 10 nm. The innexon's central pore diameter was 2 nm, and the mean of the center-to-center distance between two innexons was 30 nm. Except for the gap junction areas of nociceptive sensory neuron axon terminals, the other ultrastructural parameters measured by freeze fracture were similar to those of samples labeled with HRP and filled with La(3+). These data suggested that the gap width, innexon diameter, and its central pore do not on their own account for the mechanism of positional discrimination, which may depend rather on the differences in distribution and number of gap junctions.

Pressure sensation by an anterior pagoda neuron population distributed in multiple ganglia in the leech, Whitmania pigra.

Sensory processing of pressure signals in the central nervous system of the leech, Whitmania pigra, was studied through the interaction between pressure sensory neurons and anterior pagoda neurons. The responses of anterior pagoda neurons to one pulse or a train of pulses in pressure sensory neurons were characterized by the latency and amplitude of excitatory postsynaptic potentials. Here we show that each pressure sensory neuron is able to activate all the anterior pagoda neurons throughout the leech central nervous system. The response patterns of all anterior pagoda neurons were appropriate to the pressure location: in the longitudinal direction the anterior pagoda neuron further away from the pressure sensory neuron had a smaller response with longer latency; inside each ganglion, the anterior pagoda neuron on the contralateral side had a larger response with shorter latency than that on the ipsilateral side. All anterior pagoda neurons excited by pressure sensory neurons comprised a parallel system in which each anterior pagoda neuron was independent from the others. The location information of pressure stimuli was represented through the response of all 40 anterior pagoda neurons covering the whole leech body with a specific pattern of latency and amplitude.

Voltage-sensitive dye imaging of population neuronal activity in cortical tissue.

Voltage-sensitive dyes (VSDs) and optical imaging are useful for studying spatiotemporal patterns of population neuronal activity in cortical tissue. Using a photodiode array and absorption dyes we were able to detect neuronal activity in single trials before it could be detected by local field potential (LFP) recordings. Simultaneous electrical and optical recordings from the same tissue also showed that VSD and LFP signals have different waveforms during different activities, suggesting that they are sensitive to different aspects of the synchronization across the population. Noise, dye bleaching, phototoxicity and optical filter selection are important to the quality of the VSD signal and are discussed in this report. With optimized signal-to-noise ratio (S/N) and total recording time, we can optically monitor approximately 500 locations in an area of 1 mm(2) of cortical tissue with a sensitivity comparable to that of LFP electrodes. The total recording time and S/N of fluorescence and absorption dyes are also compared. At S/N of 8-10, absorption dye NK3630 allows a total recording time of 15-30 min, which can be divided into hundreds of 4-8 s recording trials over several hours, long enough for many kinds of experiments. In conclusion, the VSD method provides a reliable way for examining neuronal activity and pharmacological properties of synapses in brain slices.