Neurons isolated from the lateral vestibular nucleus of young adult and senescent Fischer-344 rats were incubated with fluorescamine-labelled Concanavalin A (fl-Con A) alone, or following incubation in trypsin or Vibrio cholerae neuraminidase. They were then observed and photographed. Microdensitometric analysis of fluorescence micrographs showed that senescent rat neurons were significantly more fluorescent than those from young adult rats. Additionally, either patches or caps of fl-Con A were seen on the surface of neurons from senescent rats, while most young adult rat neurons bound fl-Con A uniformly. Pretreatment with trypsin or neuraminidase had no effect on the amount of fluorescence on the surface of senescent rat neurons, and only a slight effect on the surface distribution. Trypsin and neuronal plasma membranes of young adult rats and a rearrangement of the binding pattern in the majority of neurons observed.

The measurement of strain in materials using clad rod acoustic waveguides has been considered recently by several authors [R. T. Harrold and Z. N. Sanjana, Proc. Soc. Plastics Eng. Conf., Washington, DC (May 1985)]. In such waveguides, axisymmetric torsional, axisymmetric radial-longitudinal, and core-guided shear modes typically propagate if the velocity of plane shear waves in the clad exceeds that velocity the core. If instead the materials are reversed, these modes are not supported but an interface wave may propagate on the core-clad boundary. In principle, such waves may propagate without attenuation if the core and clad materials properties are suitably related. The theoretical sensitivity of the attenuation and mode conversion of such nonattenuating interface waves to strain-induced variations in the geometry and elastic constants of the waveguide materials are considered in this paper. Experimental measurements using strained glass-on-glass clad rods which approximately satisfy the assumed boundary conditions are reported. Potential applications in the internal monitoring of materials are suggested. [Work supported by NASA and Simmonds Precision.]