The cerebellum contains a hexadecapeptide, termed cerebellin, that is conserved in sequence from human to chicken. Three independent, overlapping cDNA clones have been isolated from a human cerebellum cDNA library that encode the cerebellin sequence. The longest clone codes for a protein of 193 amino acids that we term precerebellin. This protein has a significant similarity (31.3% identity, 52.2% similarity) to the globular (non-collagen-like) region of the B chain of human complement component Clq. The region of relatedness extends over =145 amino acids located in the carboxyl terminus of both proteins. Unlike Clq B chain, no collagen-like motifs are present in the amino-terminal regions of precerebellin. The amino terminus of precerebellin contains three possible N-linked glycosylation sites. Although hydrophobic amino acids are clustered at the amino terminus, they do not conform to the classical signal-peptide motif, and no other obvious membrane-spanning domains are predicted from the cDNA sequence. The cDNA predicts that the cerebellin peptide is flanked by Val-Arg and Glu-Pro residues. Therefore, cerebellin is not liberated from precerebellin by the classical dibasic amino acid proteolytic-cleavage mechanism seen in many neuropeptide precursors. In Northern (RNA) blots, precerebellin transcripts, with four distinct sizes (1.8, 2.3, 2.7, and 3.0 kilobases), are abundant in cerebellum. These transcripts are present at either very low or undetectable levels in other brain areas and extraneural structures. A similar pattern of cerebellin precursor transcripts are seen in rat, mouse, and human cerebellum. Furthermore, a partial genomic fragment from mouse shows the same bands in Northern blots as the human cDNA clone. During rat development, precerebellin transcripts mirror the level of cerebellin peptide. Low levels of precerebellin mRNA are seen at birth. Levels increase modestly from postpartum day 1 to 8, then increase more dramatically between day 5 and 15, and eventually reach peak values between day 21 and 56. Because cerebellin-like immunoreactivity is associated with Purki'ije cell postsynaptic structures, these data raise interesting possibilities concerning the function of the cerebellin precursor in synaptic physiology.

A nonapeptide Thr-Ile-Ile-Asn-Val-Lys-Cys-Thr-Ser (NTX1-9) and a decapeptide Met-Asn-Gly-Lys-Cys-Lys-Cys-Tyr-Asn-Asn (NTX30-39) corresponding to the N-terminal and C-terminal sequences respectively of Noxiustoxin (NTX) were synthesized by the solid phase method of Merrifield (1963). The first synthetic peptide (NTX1-9) was shown to be toxic to mice independently of the route of administration: intraperitoneally, subcutaneously or intraventricularly (100-200 micrograms/20 g mouse weight). The second (NTX30-39) was not toxic even at higher dose (400 micrograms/20 g mouse). When the effects of the peptide NTX1-9 and of the authentic toxin (Noxiustoxin) were studied on the liberation of [3H] 4-aminobutyric acid (3H-GABA) from mouse synaptosomes, both gave essentially the same results, except that peptide NTX1-9 was needed at higher concentration. Synthetic peptide NTX30-39 had no effect in the same preparation at even higher doses. The GABA release produced by toxic peptide NTX1-9 was not affected by tetrodotoxin but was completely abolished by the presence of the K+ ionophore valinomycin, mimicking the effect of native NTX in the same system (Sitges et al., 1986). These results indicate that the toxic active site of Noxiustoxin is possibly located in or near the N-terminal amino acid portion of the molecule.

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The identity of the neurotransmitter(s) in the mammalian retinogeniculate pathway is unclear. To investigate the possibility that some amino acids and certain dipeptides, such as N-acetyl-aspartyl-glutamate (NAAG), fulfill this function, changes in their concentration were measured in the optic tract, and the parvocellular and magnocellular segments of the LGNd of six monkeys (Macaca fascicularis), seven days after right optic tractotomy. The LGNd was studied also in two additional macaques, three months after occipital lobectomy. Tissue was frozen within five minutes of death, regions were dissected with the micropunch technique, and substances were analyzed by HPLC. Optic tractotomy induced significant, large reductions in NAAG, glutamate and aspartate in the optic tract distal to the lesion. Significant decreases in NAAG were also measured in the LGNd, and these changes were apparent in both the parvocellular and magnocellular segments. A small reduction in glutamate reached significance in the parvocellular laminae, and that of aspartate only approached significance in the magnocellular division. Occipital lobectomy produced large declines in aspartate and glutamate in the LGNd. The results of optic tractotomy support the role of NAAG as a neurotransmitter candidate in the monkey retinogeniculate pathways; its significant decrease in both geniculate segments suggests that both P- and M- retinal axons utilize this substance. Although at times the reductions in glutamate or aspartate failed to reach significance, their role cannot be excluded. The findings after occipital lobectomy strongly favor these latter substances as corticogeniculate and/or geniculocortical transmitters.

Activation of immediate-early gene expression has been associated with mitogenesis, differentiation, nerve cell depolarization, and recently, terminal differentiation processes and programmed cell death. Previous evidence also suggested that immediate-early genes play a role in the physiology of the lungs (J. I. Morgan, D. R. Cohen, J. L. Hempstead, and T. Curran, Science 237:192-197, 1987). Therefore, we analyzed c-fos expression in adult and developing lung tissues. Seizures elicited by chemoconvulsants induced expression of mRNA for c-fos, c-jun, and junB and Fos-like immunoreactivity in lung tissue. The use of pharmacological antagonists and adrenalectomy indicated that this increased expression was neurogenic. Interestingly, by using a fos-lacZ transgenic mouse, it was shown that Fos-LacZ expression in response to seizure occurred preferentially in clusters of epithelial cells at the poles of the bronchioles. This was the same location of Fos-LacZ expression detected during early lung development. These data imply that pharmacological induction of immediate-early gene expression in adult mice recapitulates an embryological program of gene expression.