Immunocytochemical analysis of proenkephalin-derived peptides in the amphibian hypothalamus and optic tectum

[Met5]-Enkephalin-, [Met5]-enkephalin-Arg6-, [Met5]-enkephalin-Arg6-Phe7-, metorphamide- and BAM 22P-like peptides could be localized in the amphibian brain by immunocytochemistry. However, a [Met5]-enkephalin-Arg6-Gly7-Leu8-like peptide could not be detected in the brain of any anuran species with an antiserum that was capable of detecting this octapeptide in mammalian brain. A synenkephalin-like peptide also could not be detected in the anuran brain with an antiserum that was capable of detecting the antigen in bovine and porcine brain. Although the intensity of proenkephalin-like immunoreactivity depended on the antiserum used, its distribution appeared to be identical with all of the effective antisera. Antisera directed against somatostatin and corticotropin-releasing factor stained perikarya, nerve fibers and terminals in the anuran brain with a distribution that was different from antisera directed against proenkephalin-derived peptides. The distribution of proenkephalin-containing perikarya and nerve fibers in the regions of the anuran brain selected for study showed many similarities to the distribution of proenkephalin-containing perikarya and nerve fibers in the same regions of the amniote brain.

Glutamate-positive neurons in the somatic sensory cortex of rats and monkeys

The morphology and laminar distribution of neurons labeled with an antiserum prepared against glutamic acid (Glu) conjugated to keyhole limpet hemocyanin have been studied in the somatic sensory cortex of rats and monkeys. In both species, the vast majority of immunostained neurons are pyramidal; some nonpyramidal neurons are also present. Positive neurons are observed in all cortical layers, although variations are found in the percentage of Glu-positive neurons in the different layers. In rats they are most numerous in layer V (36%), followed by layer II (33%), layer III (32%), and layer VI (29%). In layer IV, 13% of all neurons are positive. Immunoreactive neurons are very sparse in layer I. In monkeys, Glu-positive neurons represent 51% of all neurons in layer V, 49% in layer III, 40% in layers II and VI, and 19% in layer IV. No differences are evident in the laminar distribution of Glu-positive neurons among cytoarchitectonic areas 3a, 3b, 1, and 2. As in rats, Glu-positive neurons are very sparse in layer I. Since Glu and GABA metabolisms are closely related, double-labeling experiments were performed in which thin, adjacent paraffin sections were stained alternately with the anti-Glu serum and with an anti-GABA serum. The 2 populations are almost completely segregated, even though a small fraction of neurons (less than 5%) are labeled by the antisera against both antigens.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistologic localization of corticotrophin-releasing hormone in human tumors

The authors investigated formalin-fixed, paraffin-embedded human tissues for the presence of corticotrophin-releasing hormone (CRH) using the avidin-biotin-peroxidase technic. Immunopositivity was demonstrated in nontumorous hypothalami, 1 of 8 hypothalamic gangliocytomas, 3 of 9 bronchial endocrine tumors, 1 of 30 small cell lung carcinomas, 1 of 8 ileal endocrine neoplasms, 2 of 20 pancreatic endocrine tumors, 2 of 10 medullary thyroid carcinomas, and 1 of 3 small cell prostate carcinomas. Of the tumors containing immunoreactivity, most were associated with Cushing's syndrome; the ileal and thyroid tumors were not. Adrenocorticotrophic hormone was immunohistochemically localized in two bronchial and one pancreatic tumor, which contained CRH-like immunoreactivity. No CRH was detected in nontumorous extrahypothalamic tissues from which the CRH-containing tumors derived, two mediastinal endocrine carcinomas, six endocrine tumors of the stomach/duodenum/appendix, eight pheochromocytomas, one Merkel cell tumor, and 32 squamous and adenocarcinomas of the lung/gut. CRH-like immunoreactivity may be found in tumors composed of peptide-hormone-producing endocrine cells; hypersecretion of CRH by those neoplasms may be significant in the development of Cushing's syndrome.

Immunocytochemical localization of proenkephalin-derived peptides in the central nervous system of the rat

Most of the early studies on the immunohistochemical distribution of enkephalin pentapeptide-like immunoreactivity used antisera that stained both proenkephalin- and prodynorphin-containing neurons. The present study used the peroxidase-antiperoxidase method, thick Vibratome sections and antisera specific for the carboxyl termini of [Met]enkephalin, [Met]enkephalyl-Arg6-Phe7, [Met]enkephalyl-Arg6-Gly7-Leu8, and metorphamide and for BAM 22P in order to obtain a detailed description of the distribution of authentic proenkephalin-containing perikarya and nerve processes. The peroxidase-antiperoxidase reaction product was intensified by the selective deposition of silver crystals in order to display the morphology of proenkephalin-containing neurons with great fidelity. The results indicate that the magnocellular perikarya in the supraoptic and paraventricular nuclei contain prodynorphin rather than proenkephalin as had been suggested by earlier investigators. The coarse fibers in the internal zone of the median eminence and the granule cell-mossy fiber pathway in the hippocampus also contain prodynorphin rather than proenkephalin. The number of proenkephalin-containing perikarya and/or the density of proenkephalin-containing nerve terminals in several other areas of the brain, e.g. the substantia nigra, the central amygdaloid nucleus, the periaqueductal gray and the parabrachial nuclei, were overestimated by earlier investigators. The distribution of authentic proenkephalin-containing perikarya and nerve processes is, despite these errors, similar to the distribution of enkephalin pentapeptide-like immunoreactivity described by earlier investigators. Proenkephalin-containing perikarya were identified for the first time in the medial and lateral habenular nuclei of the adult rat. Antisera specific for [Met]enkephalin, [Met]enkephalyl-Arg6-Phe7, [Met]enkephalyl-Arg6-Gly7-Leu8 and BAM 22P stain perikarya and nerve terminals with a similar distribution. The metorphamide antiserum also stains the same perikarya and nerve terminals; however, it also stains magnocellular perikarya in the zona incerta and the lateral hypothalamus that are not stained by any of the other proenkephalin-specific antisera.

Central and peripheral distribution of corticotropin-releasing factor

Corticotropin-releasing factor (CRF) is widely distributed in the central nervous system and is associated with nuclei and pathways that control the release of adrenocorticotropin and beta-endorphin from the pituitary, and others that mediate central and peripheral autonomic responses to stress. Major concentrations of CRF immunoreactive neurons have been described in the hypothalamus, parts of the limbic system, several nuclei of the basal forebrain and brain stem, and the cerebral cortex. Recent data on the distribution of CRF immunoreactive perikarya and fibers in the preoptic-septal area, the thalamus, and the spinal cord are reviewed. Outside the nervous system, CRF-like immunoreactivity has been shown to occur in endocrine cells of the pancreas and gastrointestinal system, and in the liver, pituitary, adrenal, lung, placenta, and several endocrine tumors. However, the chemical identity of this "peripheral CRF" has not been determined.

Corticotropin releasing factor (CRF): origin and course of afferent pathways to the median eminence (ME) of the rat hypothalamus

8-10 days after making various lesions in the rat hypothalamus, the presence of corticotropin releasing factor (CRF) immunoreactive neural structures was studied in paraffin and vibratome sections with CRF immunocytochemistry. Bilateral anterolateral deafferentation of the medial basal hypothalamus (MBH) caused complete disappearance of CRF immunoreactivity from the median eminence (ME) in brains where the posterior edge of the cut reached the level of the pituitary stalk. A shorter cut resulted in positive immunostaining caudal to the caudal edge of the cut. Unilateral deafferentation of the MBH caused significant decrease in CRF immunostaining in the ipsilateral ME. Unilateral posterolateral deafferentation of the MBH caused no changes in CRF immunostaining in the rostral ME, while fewer CRF-containing processes were observed in the more caudal regions. A horizontal cut ventral to the paraventricular nuclei (PVN) caused a slight decrease in the number of CRF-immunoreactive profiles in the ME. A wider and complete unilateral horizontal cut resulted in a significant decrease in CRF immunoreactivity on the operated side. Following various surgical interventions, hormone accumulation in cell bodies was detected in the paraventricular, periventricular preoptic, dorsomedial, periventricular, lateral and posterior hypothalamic, and premammillary nuclei. Fibers arising from most of these nuclei formed a fan-like projection to the ME. The majority of the CRF-fibers ran through the lateral tract of the fan, and reached the ME by the lateral-basal retrochiasmatic area (LBRCA). Scattered fibers were detected in the lateral-basal hypothalamus as far caudally as the level of the pituitary stalk. Unilateral anterolateral and horizontal cuts did not result in complete disappearance of CRF immunoreactivity from the ipsilateral ME, indicating the existence of CRF-fibers of contralateral origin in the ME.

Gonadotropin-releasing hormone (GnRH) neurons and pathways in the rat brain

Gonadotropin-releasing hormone (GnRH) neurons and their pathways in the rat brain were localized by immunocytochemistry in 6- to 18-day-old female animals, by use of thick frozen or vibratome sections, and silver-gold intensification of the diaminobenzidine reaction product. GnRH-immunoreactive perikarya were observed in the following regions: olfactory bulb and tubercle, vertical and horizontal limbs of the diagonal band of Broca, medial septum, medial preoptic and suprachiasmatic areas, anterior and lateral hypothalamus, and different regions of the hippocampus (indusium griseum, Ammon's horn). In addition to the known GnRH-pathways (preoptico-terminal, preoptico-infundibular, periventricular), we also observed GnRH-immunopositive processes in several major tracts and areas of the brain, including the medial and cortical amygdaloid complex, stria terminalis, stria medullaris thalami, fasciculus retroflexus, medial forebrain bundle, indusium griseum, stria longitudinalis medialis and lateralis, hippocampus, periaqueductal gray of the mesencephalon, and extracerebral regions, such as the lamina cribrosa, nervus terminalis and its associated ganglia. By use of the silver-gold intensification method we present Golgi-like images of GnRH perikarya and their pathways. The possible distribution of efferents from each GnRH cell group is discussed.

Immunohistochemical techniques and their applications in the histopathology of the respiratory system

Subsequent to the first report in the 1940s on incubation of tissue sections with fluorescein-conjugated antibodies for localization of antigens, a great number of modifications were introduced to improve the validity of immunohistochemistry which has become a growingly popular tool. The use of immunoenzymatic techniques eliminates the need for expensive fluorescence microscopy equipment, the lack of permanency of preparations and the lack of electron density required in ultrastructural localization of antigens. Regardless of the technique, it is also important to choose a correct fixation which allows the proper preservation of antigens and morphology and the penetration of antibodies through the entire thickness of the preparation. A variety of immunohistochemical techniques have been applied to study several components of the lung, such as collagen, surface active material, lung specific antigens, and enzymes and the detection of tumor markers, immunoglobulins and infectious agents in the respiratory system which is reviewed. The large surface area and the multiplicity of cell types provided by the respiratory tract epithelium of humans for exposure to microbial as well as toxic substances in the environment make this organ system very vulnerable but a good early indicator of adverse health effects. Immunohistochemistry provides valuable information complementary to the immunochemical and biochemical characterization of this barrier.

Immunocytochemical localization of growth hormone-releasing factor in the rat hypothalamus

The distribution of GRF-immunoreactive structures in the rat hypothalamus was studied after colchicine treatment with peroxidase-antiperoxidase immunocytochemistry in vibratome sections. The majority of the GRF-immunoreactive cell bodies were found in the arcuate nucleus and the medial perifornical region of the lateral hypothalamus. Scattered cells were seen in the lateral basal hypothalamus, the medial and lateral portions of the ventromedial nucleus, and the dorsomedial and paraventricular nuclei. Fibers from the perifornical cell bodies formed a fan-like projection to the median eminence, where a dense accumulation of GRF-containing processes and terminals was found. GRF terminals were located in the central regions of the median eminence. The localization of GRF-immunoreactive structures in the hypothalamus and median eminence reinforces the view that GRF plays a physiological role in the regulation of pituitary function.

Corticotropin-releasing factor (CRF)-like immunoreactivity in the gastro-entero-pancreatic endocrine system

CRF has been detected in the endocrine pancreas by immunocytochemistry with an antiserum that recognizes mainly the C-terminal portion of CRF-41. CRF-containing cells have been shown to be present in the pancreas of representative species of fishes, amphibians, reptiles, birds, and mammals including man. Light and electron microscopic observations indicate that the CRF-containing cells in the endocrine pancreas are similar to glucagon (A) cells both in their morphology and distribution. Individual CRF-containing cells are also found scattered in the exocrine pancreas in all species studied. In addition, CRF-containing cells have been identified in the human, monkey, cat, and rat stomach and small intestine. Recent reports also indicate that CRF-like immunoreactivity is present in the circulating blood, the adrenal medulla, and the placenta. Finally, several peripheral (pancreas, stomach, colon, lung and thyroid) tumors which produced corticotropin-releasing substances have been described by others. Although the peripheral actions of CRF are not yet known, these observations indicate that it is widely distributed in peripheral tissues and it may also represent a new tumor marker.

Preferential immunohistochemical localization of vasoactive intestinal polypeptide (VIP) in the sacral spinal cord of the cat: light and electron microscopic observations

In the present study we have employed immunoperoxidase techniques to investigate the distribution of vasoactive intestinal polypeptide (VIP)-like immunoreactivity in the spinal cord and sensory ganglia of the cat. The spinal distribution of VIP-containing neuronal processes was also compared with that of substance P (SP), somatostatin (SOM), and cholecystokinin-8 (CCK) at lumbar, sacral, and coccygeal levels. At sacral levels, VIP was found to be contained in small and medium-sized primary sensory neurons and in dorsal rootlets. Deafferentation, by either ganglionectomy or dorsal rhizotomy, resulted in a nearly complete loss of VIP immunoreactivity in the spinal cord. The spinal distribution of VIP fibers and terminals was most dense and extensive in sacral segments. Forming a thin shell around the dorsal horn, collaterals, apparently originating from Lissauer's tract, projected either medially or laterally through lamina I. Laterally, many VIP axons terminated in lateral laminae V to VII. Others projected further through the neck of the dorsal horn to medial lamina V and the gray matter near the central canal. Medially, VIP axons descended through lamina I to expand into terminal fields in the posterior commissure and medial lamina V. At the ultrastructural level, VIP-like immunoreactivity was found in dense core vesicles within axonal enlargements containing both large dense core and smaller clear round vesicles. Synaptic connections were infrequently observed but, when encountered, were of the simple axodendritic type. The spinal distribution of VIP-containing fibers was remarkably similar to that reported for pelvic nerve visceral afferents, both in termination patterns within the spinal gray matter and in localization to the sacral cord. The density of SP-, SOM-, and CCK-containing fibers and terminals was constant at all levels examined (L4 to Co4). In marked contrast, the distribution of VIP fibers, much like that of pelvic nerve afferents, was mostly confined to sacral segments. Thus, although SP, SOM, and CCK may be contained within a population of sacral visceral afferents, they must be common to afferent systems in other segments as well. VIP, however, appears to be preferentially contained within pelvic visceral afferent fibers confined mostly to sacral segments.

Immunocytochemical localization of corticotropin releasing factor (CRF) in the rat spinal cord

The presence of corticotropin releasing factor (CRF)-immunoreactive nerve fibers and cell bodies in the spinal cord is demonstrated. Immunopositive fibers were found in the lateral column of the white matter, in laminae I, V-VII, X, and in the intermediolateral column of the spinal cord. Complete transection of the spinal cord showed that the majority of the fibers in the lateral funiculus formed an ascending pathway; however, a few descending fibers were also detected. Hypophysectomy resulted in enhanced immunoreactivity of the fibers and staining of CRF-immunoreactive cell bodies in laminae V-VII, X, and in the intermediolateral sympathetic column. The results suggest that CRF is not merely an ACTH releasing factor, but also a regulatory peptide which may be involved in several stress-related neural responses.

Corticotropin-releasing factor (CRF)-like immunoreactivity in the vertebrate endocrine pancreas

The light microscopic immunocytochemical localization of corticotropin-releasing factor (CRF) is described in the endocrine pancreas of several species representing the major classes of vertebrates: fishes (channel catfish, Ictalurus punctatus), amphibians (African clawed toad, Xenopus laevis), reptiles (chameleon, Anolis carolinensis), birds (chicken, Gallus domesticus), and several mammals (rat, mouse, cat, rhesus monkey, and man). The CRF-containing cells are scattered over the entire islet tissue in primates and cat, whereas in rat and mouse they are located at the periphery of the islets. In the chicken and catfish, the CRF-containing cells are found in a central location within islets and form larger clusters or cords. Single cells with CRF-like immunoreactivity are interspersed between acinar cells of the exocrine pancreas in all species studied. The CRF cells show a substantial topographical overlap with glucagon cells, but their precise identity and function remain to be determined.

The paraventriculo-infundibular corticotropin releasing factor (CRF) pathway as revealed by immunocytochemistry in long-term hypophysectomized or adrenalectomized rats

The immunocytochemical localization of corticotropin releasing factor (CRF)-containing pathways projecting from the paraventricular nucleus (PVN) to the external layer of the median eminence (ME) in long-term hypophysectomized or adrenalectomized rats is described. Immunocytochemistry was followed by silver intensification of the diaminobenzidine end-product. In comparison with untreated control rats, both hypophysectomy and adrenalectomy resulted in a dramatic increase in immunostaining of the CRF-containing perikarya and fibers, particularly those originating from the PVN and terminating in the ME. The staining was more intense in adrenalectomized than in hypophysectomized rats. The CRF-positive fibers emerging from the PVN form a medial, an intermediate and a lateral fiber pathway. The lateral and intermediate CRF tracts leave the dorsolateral part of the PVN and course laterally and medially of the fornix, respectively, then ventrally toward the optic tract. Just dorsal to the optic tract they turn in caudal direction and run parallel with and very close to the basal surface of the hypothalamus; individual fibers then turn medially to terminate in the external layer of the ME. Only a few fibers originate from the medial-ventral part of the PVN (medial pathway). These fibers run in ventral direction along the walls of the 3rd ventricle and terminate in the ME. Thus the majority of CRF fibers, similarly to other peptidergic systems, reach the medial basal hypothalamus from the anterolateral direction.

The ultrastructure and synaptic connections of serotonin-immunoreactive terminals in spinal laminae I and II

In order to study the synaptic relationships of serotonin (5-HT)-containing axons, boutons in laminae I and II of the cat spinal cord were labeled for serotonin with peroxidase-antiperoxidase immunocytochemistry. Labeled boutons were examined with the light microscope and recut into serial ultrathin sections for examination with the electron microscope. Labeled axons exhibiting boutons were sagittally oriented, and were most numerous in lamina I and outer lamina II (IIo) and least numerous in inner lamina II (IIi). Two types of labeled boutons were observed ultrastructurally. A relatively rare, large, scalloped or egg-shaped bouton, which contained many mitochondria and dense core vesicles, was found in laminae I and IIo. A smaller dome-shaped bouton, which contained fewer dense core vesicles and round or pleomorphic, clear vesicles, was found throughout laminae I and II. Both types commonly established symmetrical synaptic contacts with the distal portion of a dendritic tree, rarely with proximal portions or cell somas, and never with axon terminals. The results suggest that there are heterogeneous serotonergic systems that may selectively modify different inputs postsynaptically to functionally different types of neurons in the superficial dorsal horn of the spinal cord.

Immunocytochemical localization of corticotropin-releasing factor (CRF) in the rat brain

The immunocytochemical localization of neurons containing the 41 amino acid peptide corticotropin-releasing factor (CRF) in the rat brain is described. The detection of CRF-like immunoreactivity in neurons was facilitated by colchicine pretreatment of the rats and by silver intensification of the diaminobenzidine end-product. The presence of immunoreactive CRF in perikarya, neuronal processes, and terminals in all major subdivisions of the rat brain is demonstrated. Aggregates of CRF-immunoreactive perikarya are found in the paraventricular, supraoptic, medial and periventricular preoptic, and premammillary nuclei of the hypothalamus, the bed nuclei of the stria terminalis and of the anterior commissure, the medial septal nucleus, the nucleus accumbens, the central amygdaloid nucleus, the olfactory bulb, the locus ceruleus, the parabrachial nucleus, the superior and inferior colliculus, and the medial vestibular nucleus. A few scattered perikarya with CRF-like immunoreactivity are present along the paraventriculo-infundibular pathway, in the anterior hypothalamus, the cerebral cortex, the hippocampus, and the periaqueductal gray of the mesencephalon and pons. Processes with CRF-like immunoreactivity are present in all of the above areas as well as in the cerebellum. The densest accumulation of CRF-immunoreactive terminals is seen in the external zone of the median eminence, with some immunoreactive CRF also present in the internal zone. The widespread but selective distribution of neurons containing CRF-like immunoreactivity supports the neuroendocrine role of this peptide and suggests that CRF, similarly to other neuropeptides, may also function as a neuromodulator throughout the brain.

Origin and distribution of cholecystokinin-containing nerve terminals in the lumbar dorsal horn and nucleus caudalis of the cat

Immunohistochemical bridge methods were used to localize cholecystokinin (CCK)-like immunoreactivity in the lumbar dorsal horn (DH) and nucleus caudalis (NC) of the cat. The CCK-positive structures were either dot- or fiber-like. The distribution of CCK-like immunoreactivity in the DH and NC was narrower than substance P (SP)-like immunoreactivity in adjacent sections. CCK- and SP-like immunoreactivity in the DH and NC was severely depleted 7--10 days following rhizotomy of either the dorsal roots or the 5th, 9th and 10th cranial nerves, respectively; enkephalin-like immunoreactivity in adjacent sections was unaffected. Cervical hemisection had no effect on either CCK- or SP-like immunoreactivity in the DH.

Serotonin immunocytochemistry in the adult and developing rat brain: methodological and pharmacological considerations

An antiserum has been raised in rabbits against serotonin (5-HT) conjugated to the invertebrate protein hemocyanin (HC). This antiserum was characterized with respect to its cross-reactivity with related compounds and its immunocytochemical staining properties in brains of adult and developing rats and in animals pretreated with various pharmacological regimens. When compared to an antiserum raised against 5-HT/bovine serum albumin (BSA) conjugates [59], the 5-HT/HC conjugate elicited a more profound immune response which resulted in the production of a specific, high titer antiserum that could be used directly for immunocytochemistry without removal of antibodies to the invertebrate carrier molecule, HC. Immunoabsorption experiments to assess the specificity of this antiserum demonstrated a small degree of cross-reactivity with dopamine (which was greater than that with norepinephrine or epinephrine). However, no staining of catecholaminergic neurons was found in untreated adult or developing animals, nor in animals pretreated with L-DOPA or L-DOPA + the MAO inhibitor nialamide, indicating that this cross-reactivity is not manifested under normal staining conditions. No cross-reactivity of the 5-HT/HC antiserum was observed for any 5-HT precursors or metabolites tested, although both this antiserum and the 5-HT/BSA antiserum did exhibit a high degree of cross-reactivity to the related indoleamines 5-methoxytryptamine (5-MT) and tryptamine. However, based on the immunocytochemical staining patterns observed, and the fact that both 5-MT and tryptamine are found in very low quantities in the normal rat brain, it appears that 5-HT is the predominant indoleamine stained by both of these antisera in the untreated rat brain. In animals pretreated with L-tryptophan + nialamide, some light staining was found in the dopaminergic A9 and A10 cell groups using either antiserum. However, since this staining was not observed in L-DOPA + nialamide treated animals it is not thought to be due to cross-reactivity with dopamine. Rather, since the staining could be inhibited by pretreatment with the catecholaminergic uptake blocker desmethylimipramine, it is postulated that this effect may be due to either (1) the non-specific uptake of 5-HT or 5-hydroxytryptophan (5-HTP) into the dopaminergic cells of A9 and A10 due to elevated levels of these substances in the dense serotonergic axonal plexus passing through this region or (2) to an increased uptake of circulating L-tryptophan by these A9 and A10 cells followed by conversion of this amino acid to tryptamine by aromatic amine decarboxylase, an enzyme common to both 5-HT and dopaminergic neurons. This latter possibility suggests that caution should be exercised when interpreting immunocytochemical staining patterns obtained in animals pretreated with L-tryptophan + nialamide using 5-HT antisera, since other cross-reactive indoleamines could be elevated by this pharmacological manipulation.

In vivo and in vitro development of serotonergic neurons

The monoamines are one of the earliest developing neurotransmitter systems in the mammalian brain. The first part of this paper describes the normal ontogeny of the serotonergic (5-HT) system in the rat brain as studied using long survival 3H-thymidine autoradiography (time of neuronal genesis, time of origin) and the Falck-Hillarp histofluorescence method, electron microscopy, and immunocytochemistry (anti-5-HT). Due to their early ontogeny relative to other brain regions, 5-HT neurons (as well as monoamine neurons in general) have been suggested to exert some type of "trophic" influence on brain development. Results of pharmacological experiments designed to inhibit 5-HT synthesis in the embryonic rat brain by maternal treatment with p-chlorophenylalanine (pCPA) at a time when this monoamine might exert such an influence are discussed with regard to effects on the time course of neuronal genesis (time of origin) of 5-HT neurons and their target cells. These results, which prompted us to propose that 5-HT might act as a "differentiation signal" for certain of its target cells, are now discussed in light of our more recent immunocytochemical-autoradiographic studies (anti-5-HT, 3H-thymidine) which morphologically demonstrate close associations between developing 5-HT neurons and proliferating neuroepithelial cells in the embryonic brain. Postnatal studies using this immunocytochemical-autoradiographic method also provide evidence for interactions of 5-HT axons with proliferating glioblasts in the developing cerebellum and with immature granule cells and their precursors in the hippocampus. These findings, in conjunction with the results of our pCPA experiments, further enhance the possibility that 5-HT neurons could exert an epigenetic influence on the development of less differentiated cells with which they come into contact. Finally, preliminary studies using dissociated cell cultures containing 5-HT neurons suggest that interactions between 5-HT neurons and glial elements may be important for the differentiation of these neurons in vitro. Whether 5-HT neurons in turn influence the development of glial or neuronal cells in these cultures remains to be determined. These studies are evaluated with regard to a possible pre-transmission role for 5-HT during key phases of neuronal and glial genesis.

Transferrin in the rat prostate Dunning tumor

A major protein of the rat Dunning prostate tumor has been purified. It has physicochemical properties and an amino acid composition similar to that of transferrin. Furthermore, the isolated tumor protein reacts with antiserum to authentic rat transferrin. Immunoperoxidase staining with rabbit anti-rat transferrin localizes transferrin within tumor acinar glands. Rocket immunoelectrophoresis indicates that transferrin constitutes 30 to 40% of tumor fluid protein, but accounts for only approximately 9% of total serum protein. In normal rat prostate cytosols, the level of transferrin is at least 200 times lower than in tumor cytosol. Nevertheless, dorsal and lateral prostate show variable peroxidase staining indicating the presence of immunoreactive transferrin within acinar glands of these normal tissues. While intense staining for transferrin was found in the interstium of all regions of the normal prostate, transferrin was not detected within acinar glands of coagulating gland, ventral prostate, or seminal vesicle. Immunocytochemical localization of albumin indicates a distribution similar to that of transferrin in normal and neoplastic rat prostate. However, unlike transferrin, the albumin content was lower in tumor fluid than in serum. It is suggested that the high level of transferrin in tumor fluid may be due to selective uptake by the tumor from serum.

Four unlabeled antibody bridge techniques: a comparison

Four unlabeled antibody immunocytochemical techniques, the "single bridge" (Avrameas S: Immunocytochemistry 6:825, 1969; Mason TE, Phifer RF, Spicer SS, Swallow RS, Dreskin RD: J Histochem Cytochem 17:190, 1969a; Sternberger LA, Cuculis JJ: 1969), the "single peroxidase-antiperoxidase (PAP)" (Sternberger LA, Hardy PH Jr, Cuculis JJ, Meyer HG: J Histochem Cytochem 18:315, 1970), the "double PAP" (Vacca LL, Rosario SL, Zimmerman EA, Tomashefsky P, Ng P-Y, Hsu KC: J Histochem Cytochem 23:208, 1975) and the "double bridge" (Ordronneau P, Petrusz P: Am J Anat 158:491, 1980) were compared at both the light and electron microscopic levels. The "double" procedures involved repeating incubations with the bridge antibody, in this case, sheep anti-rabbit gamma globulin, followed either by a second PAP step for the "double PAP" or a second anti-horseradish peroxidase step and a single incubation in horseradish peroxidase for the "double bridge." At both the light and electron microscopic levels the staining intensity was greater with the "double" techniques than with the "single" ones. This is probably due to amplification achieved with the second sheep anti-rabbit gamma globulin step, permitting an increase in the number of horseradish peroxidase molecules bound for each molecule of tissue-bound primary antibody. Also, the quality of the various commercial PAP preparations tested was variable. With the weaker ones the staining intensity could be increased by performing an incubation in fresh horseradish peroxidase after the PAP step. Finally, in electron microscopic studies, the reaction products formed in both the bridge and PAP procedures were identical in shape and size.