The distribution of nicotinic acetylcholine receptors (AChR) in the rat and mouse central nervous system has been mapped in detail using monoclonal antibodies to receptors purified from chicken and rat brain. Initial studies in the chicken brain indicate that different neuronal AChRs are contained in axonal projections to the optic lobe in the midbrain from neurons in the lateral spiriform nucleus and from retinal ganglion cells. Monoclonal antibodies to the chicken and rat brain AChRs also label apparently identical regions in all major subdivisions of the central nervous system of rats and mice, and this pattern is very similar to previous reports of 3H-nicotine binding, but quite different from that of alpha-bungarotoxin binding. In several instances, the immunohistochemical evidence has strongly indicated that neuronal AChR undergoes axonal transport. The clearest example of this has been in the visual system, where labeling was observed in the retina, the optic nerve and tract, and in all of the major terminal fields of the optic nerve except the ventral suprachiasmatic nucleus. This was confirmed in unilateral enucleation experiments in the rat, where labeling was greatly reduced in the contralateral optic tract, ventral lateral geniculate nucleus, pretectal nuclei receiving direct visual input, superficial layers of the superior colliculus, and medical terminal nucleus, and was significantly reduced in the dorsal lateral geniculate nucleus. Clear neuronal labeling was also observed in dorsal root ganglion cells and in cranial nerve nuclei containing motoneurons that innervate branchial arch-derived muscles, although the possibility that neuronal AChR undergoes axonal transport in the latter cells was not tested experimentally.(ABSTRACT TRUNCATED AT 250 WORDS)

Preproenkephalin mRNA production by efferent neurons projecting to the gerbil inner ear was assessed using combined in situ hybridization and retrograde labeling with fluorescent tracers. Virtually all vestibular efferent neurons were positive for preproenkephalin mRNA. Of the cochlear efferents, one-half of the medial olivocochlear neurons were positive for enkephalin. All lateral olivocochlear neurons were negative for enkephalin. The results suggest that there are two, biochemically distinct subpopulations of medial olivocochlear efferents in the gerbil.

The use of glutaraldehyde (GTA) for cross‐linking biological tissue implants has a number of undesirable side effects, including cytotoxicity and induction of calcification. In an attempt to find an improved cross‐linking agent for tissue implants, we have evaluated a number of cross‐linking procedures shown previously to be effective with pure collagen or collagenous substrates, including GTA, succinic anhydride, cyanamide, 1‐ethyl‐3‐(dimethylaminopropyl)carbodi‐imide, dimethyl suberimidate, ascorbate‐copper, glucose‐lysine and acyl azide treatments. Apart from GTA, only acyl azide treatment significantly cross‐linked human dermis, the degree of cross‐linking being better than that seen after treatment of dermis with 1 mM GTA. Acyl azide treatment of thicker vascular tissue (porcine aorta) also resulted in a significantly cross‐linked tissue. Preliminary cytotoxicity studies suggested that acyl azide treatment was not toxic, and, therefore, coupled with its cross‐linking ability, this treatment is worthy of further investigation and may prove to be an alternative to GTA for the treatment of bioprostheses.

Australian populations of the widespread Emex australis and the more restricted E. spinosa were tested for subspecific variation. The plants were grown for two generations in a glasshouse from seed collected from field populations. The results from growing the first generation showed that two groupings of E. australis could be made on the basis of hierarchical grouping analysis, but the populations were much more similar in the second generation and such groupings could not be made. There were no marked differences between E. australis populations from Australia and South Africa, although one from Hawaii was less vigorous than the others. Amongst Australian populations of E. spinosa, one from Western Australia was less vigorous than the others. It was also found that Australian populations of E. spinosa were generally similar to those from Portugal and slightly more vigorous than those from Morocco.