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Certain neurons in the brain are specifically and intensely stained by a histochemical method which demonstrates nicotinamide adenine dinucleotide phosphate NADPH-diaphorase activity. The cell types containing this enzyme in certain areas of the rat forebrain were examined by combining NADPH-diaphorase histochemistry with the indirect immunofluorescence technique. Neurons containing somatostatin- or avian pancreatic polypeptide (APP)-like immunoreactivities were found throughout the forebrain including the striatum and neocortex. These two neuropeptides were also found to coexist in many telencephalic neurons. After photography, the sections processed for immunohistochemistry were stained for NADPH-diaphorase activity by a histochemical method. It was found that within the striatum all of the neurons that were selectively stained by this technique also contained both somatostatin- and APP-like immunoreactivities. Also in the neocortex NADPH-diaphorase was found only in those neurons displaying somatostatin- or APP-like immunoreactivity. In other brain regions such as the nucleus laterodorsalis tegmenti, NADPH-diaphorase-containing cells did not contain these neuropeptides. The results indicate that NADPH-diaphorase histochemistry provides a simple, reliable, histochemical method to demonstrate those striatal neurons in which somatostatin- and APP-like immunoreactivities coexist. The selective occurrence of this enzyme within these neurons may provide a useful target for pharmacological studies of these neuropeptide-containing cells.

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(Rcceiwd bcbrtiat-! 27. 19x4) ~ L J B 83 0215 Pancreatic polypeptide has been extracted and sequenced from a wide range of species. The 36-residue polypeptides have some hormonal characteristics, and show a high degree of sequence homology. Two recently isolated polypeptides, from porcine gut and brain, also show a high degree of sequence homology with the pancreatic polypeptides. It was proposed that these polypeptides were members of a related family.The X-ray determined structure of one member of the family, turkey pancreatic polypeptide, is known to high resolution, but there is no structural information for the others. Studies designed to give an insight into the tertiary structure of these related molecules have been carried out, including model building using interactive computer graphics, circular dichroic spectroscopy and secondary structure prediction using a variety of algorithms.The results indicate that a compact globular conformation, similar to that observed in turkey pancreatic polypeptide may be adopted by all molecules and that this may be more highly conserved than the individual amino acid sequences.Since the first identification of pancreatic polypeptide (PP) in the chicken pancreas [l], homologous peptides have been isolated from the alligator (Kimmel, unpublished results), the turkey [2], goose (Shen et al., unpublished results), ox, pig, sheep, dog and human [3]. These 36-residue polypeptides share a feature common to many gastroenteric hormones, a blocked. amidated carboxy terminus. Tatemoto and Mutt [4] used this feature to isolate possible hormonal peptides in tissue extracts and isolated, amongst others, two peptides, PYY from pig intestine [5] and NPY from pig brain tissue [6]. They showed that these polypeptides have considerable homology with the pancreatic polypeptides and proposed that PP, NPY and PYY form a newly recognised hormone family (see Table 1).The structure of one member of this family, turkey pancreatic polypeptide, has been determined by X-ray crystallography [2, 7, 81 and the analysis recently extended to very high resolution, d,,, = 98pm [9-111. The turkey PP protomer comprises of two segments of secondary structure: a polyproline type-I1 helix (residues 1-8) and an a-helix (residues 14-32). These helices, joined by a type-I1 fl-turn, interact via hydrophobic contacts to produce a compact and stable tertiary fold. The C-terminal region, residues 33 -36, extend away from the body of the molecule and display some flexibility in the crystal lattice. Further hydrophobic interactions are achieved by the formation of dimers in which a cage of aromatic residues, related by the crystallographic diad axis, is formed. In the crystal the dimers form extended oligomeric arrays via the coordination of a zinc ion. The zinc coordination involves His-34 Nt: of one, Asp-23 of another and the glycine nitrogen and carbonyl oxygen of a third dimer. The penta-,4hhrericr/ions. PP, pancreatic polypeptide; NPY, pig neuropolypcptide; PYY, pig intestinal polypeptide. coordinated site is c...