Plasticity of aged perivascular axons following exogenous NGF: analysis of catecholamines.

The present study investigated the atrophy of aged perivascular sympathetic axons and the response of these cerebrovascular neurons to the neurotrophin nerve growth factor (NGF). Using high performance liquid chromatography coupled with electrochemical detection (HPLC-ECD) to quantify catecholamines and immunohistochemical methods to quantify the density of TH immunoreactive fibers, we found a significant decrease in norepinephrine (NE) and TH in aged sympathetic axons. However, following in vivo administration of exogenous neurotrophin, aged neurons exhibited a robust response to NGF that was similar to the young adult, suggesting little decline in the capability of aged neurons to utilize exogenous neurotrophin. These results suggest that the age-related atrophy of aged sympathetic axons may result primarily from reduced availability of target-derived neurotrophin rather than from intrinsic alterations of neuronal function.

Structure and expression of the antigen 5-related gene of Drosophila melanogaster.

The Agr gene of Drosophila melanogaster was localized to the X chromosome 12F region between the Netrin B and rutabaga genes. A P1 clone containing this area was identified, and restriction sites within this clone were mapped. The entire Agr gene and some flanking region were sequenced, and the transcription start site was determined. The gene was 938 bp in length and included a 108 bp intron, dividing the coding region into a 140 bp 5' exon and a 690 bp 3' exon. The 5' untranslated region (UTR) was 23 bp in length and the 3' UTR 36 bp. Gene expression was initiated during late embryogenesis and was also observed during the larval, prepupal, and adult stages. Expression was found only in the outer layer of the proventriculus, a structure located at the fore- and midgut junction. Deletion of the Agr gene had no effect on proventricular morphogenesis in embryos. The Agr expression pattern within the proventriculus suggests that it encodes a component of the peritrophic matrix, a tubular envelope produced by the proventriculus and which lines the midgut. Sequences similar to the Agr coding region were detected in other dipteran species. suggesting that the function of the Agr gene product is conserved.