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Somatostatin is produced by gastrointestinal endocrine cells that have long, nonluminal, cytoplasmic processes. Such processes terminate on other cell types, including gastrin-producing and hydrochloric acid-producing cells, whose functions are profoundly affected by somatostatin. The findings suggest that somatostatin cells control the functions of other cells through local release of the peptide by way of cytoplasmic processes. Also, certain other types of gastrointestinal endocrine cells have similar cytoplasmic prolongations, which may have analogous local (paracrine) regulatory functions.

The localization of the vasoactive intestinal polyptide (VIP) has been studied with immunohistochemistry and radioimmunoanalysis. VIP immunoreactivity is present in gastrointestinal nerves, which constitute a quantitatively important nerve population that may be intrinsic to the gut wall. VIP-immunoreactive neurons are also found within the ventromedial hypothalamus and give off processes that travel lateral to the third ventricle. Results of radioimmunoanalysis strongly indicate that the immunoreactive material represents true VIP. Thus VIP, at present a gastrointestinal hormone candidate, appears to represent a new neuronal peptide occurring in both the central and peripheral nervous system. Vasoactive intestinal polypeptide (VIP), a potent hypotensive and vasodilatory agent, has been isolated from the porcine small intestine and shown to have an amino acid sequence related to that of secretin, glucagon, and gastric inhibitory polypeptide (1-3). The corresponding polypeptide has also been isolated from chicken intestine and its structure has been determined (4, 5). The almost complete inactivation of VIP reported to occur in the liver has led to the suspicion that its actions are confined to the gut (6). In contrast to a recent report on the exclusive localization of immunoreactive VIP in a population of endocrine-like cells of the gut (7), we wish to report that VIP immunoreactivity occurs mainly in neurons of both the central and peripheral nervous system. MATERIALS AND METHODSAntisera. Antisera were raised in rabbits to highly purified porcine VIP (generous gift from Prof. V. Mutt) covalently coupled to bovine serum albumin. Each rabbit received 30 nmol of the antigen emulsified in Freund's complete adjuvant subcutaneously at multiple sites with 8 week intervals. Sera collected after the third immunization were used for radioimmunoassay and immunohistochemistry.Tissue Sources. Material was collected from adult human, pig, cat, rat, and mouse. Three rats underwent bilateral abdominal vagotomy 2 weeks prior to sacrifice and three mice received 6-hydroxydopamine (100 mg/kg intravenously) (chemical sympathectomy) 24 hr before sacrifice. Specimens of apparently normal human gut and pancreas were collected at surgery (for carcinoma or peptic ulcer). Material from pig was obtained immediately after death. Cats were killed by an overdose of mebumal (Nembutal) and rats and mice with diethyl ether.Radioimmunoassay. Tissue material was immediately frozen on dry ice, crushed, and homogenized in acidified ethanol (i.e., 70% ethanol containing 0.74% hydrochloric acid).Solids were removed by centrifugation and the supernatant was decanted and dried in vacuo. The samples were reconstituted in 0.04 M sodium phosphate buffer at pH 7.4 containing 58 ,M human serum albumin and 100 mM sodium chloride. Each sample was assayed in triplicate in three different dilutions. Antiserum no. 5601 was routinely used. '25I-Labeled VIP was prepared by a chloramine-T method and highly purified porcine VIP was used as standard. Separ...

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The invasively growing and metastasizing Lewis lung carcinoma consistently contained urokinase-type plasminogen activator (u-PA) enzyme activity. When investigated immunocytochemically with antibodies against u-PA, different parts of individual tumors showed a pronounced heterogeneity in staining intensity. Strong staining was found in areas with invasive growth and degradation of surrounding normal tissue, while other areas were completely devoid of staining. Immunoreactivity occurred both with a perinuclear cytoplasmic localization in tumor cells and associated with apparently extracellular material. SDS PAGE of tumor extracts, under both reducing and nonreducing conditions, followed by immunoblotting, showed only one immunocytochemically stainable band with an electrophoretic mobility corresponding to that of purified proenzyme to u-PA, while no two-chain u-PA was detected. This indicates that the major part of the activator in Lewis lung carcinoma is present as one-chain pro-u-PA.

Brain mast cells were studied in mice, rats, rabbits, hamsters, guinea pigs, cats, cows, monkeys, and humans with use of a variety of techniques. They were localized by staining with Astrablau or by toluidine blue-induced metachromasia and characterized by their ultrastructural appearance and by the presence of histochemically demonstrable histamine (o-phthaldiadehyde fluorescence method). The identity of the fluorophore was secured by microspectrofluorometry. Mast cells in brain usually had a perivascular localization but were also found scattered in the parenchyma. The regional variations in the number of mast cells agreed with the histamine concentration as measured fluorometrically. The variation was in the order leptomeninges greater than hypothalamus greater than cerebral cortex = mesencephalon greater than cerebellum = brain stem. In addition to histamine, murine mast cells stored serotonin, whereas bovine mast cells contained dopamine, visualized histochemically by the formaldehyde technique.

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