Electron microscope immunohistochemical localization of neurophysin in the rat hypothalamus and pituitary

In order to identify the organelles associated with neurophysin in neurosecretory neurons and axons, an electron microscopic immunohistochemical localization of this protein has been performed in the rat hypothalamus and posterior pituitary gland. Rabbit antiserum to human neurophysin II (which shows a cross-reaction with rat neurophysin) was used as antibody and the complex peroxidase-rabbit antiperoxidase (PAP) as the marker with unlabelled antirabbit globulin. PAP molecules indicating the presence of neurophysin were detected in the secretory neurons of both supraoptic and paraventricular nuclei, in axons of the internal layer of the median eminence and in the nerve terminals of the posterior pituitary gland. The reaction product was observed only over the secretory granules, all other organelles being negative. In the positive cells and axons, all the secretory granules present were usually labelled. These results demonstrate for the first time that neurophysin is associated with neurosecretory granules which also contain presumably either vasopressin or oxytocin.     

Exocytosis of Neurosecretory Granules in Small Cell Undifferentiated Carcinoma

The tumor cells in the pleural effusions of a case of small cell undifferentiated carcinoma have been studied by light microscopy and by thin section and freeze-fracture electron microscopy. Evidence of exocytosis of neurosecretory granules from the tumor cells is presented. The tumor cells form clumps, with the cells joined by focal tight junctions and small desmosomes. These findings are discussed with reference to the neuroendocrine origin of these tumors and the role of the junctional complexes in the formation of tumor cell aggregates.     

Paraventricular neurosecretory neurons: synaptic inputs from the ventrolateral medulla in rats

Effects of electrical stimulation of the ventrolateral medulla on discharge activity of neurosecretory neurons in the paraventricular nucleus (PVN) were studied in male rats anesthetized with urethane-chloralose. Among 35 phasically firing neurosecretory neurons, stimulation of the lateral reticular nucleus and its vicinity produced excitation in 10 and inhibition in 2. The stimulation also enhanced the activity of 40% of the PVN neurosecretory neurons that fired continuously (n = 81); of these responsive neurons, half of the neurons tested (n = 12) were inhibited by i.v. administration of phenylephrine. The result suggests that both vasopressin- and oxytocin-secreting neurons in the PVN receive mainly excitatory synaptic inputs from the ventrolateral medulla.     

Immunocytochemical demonstration of a homology in peptidergic neurosecretory cells in the suboesophageal ganglion of a beetle and a locust with antisera to bovine pancreatic polypeptide, FMRFamide, vasopressin and alpha-MSH

In the suboesophageal ganglion of the Colorado potato beetle and the migratory locust three types of peptidergic neurosecretory cells were identified immunocytochemically with antisera to bovine pancreatic polypeptide, FMRFamide, vasopressin and alpha-MSH. Their locations and immunocytochemical reactions are similar, which suggests that these peptidergic cells in both insect species are homologous and perhaps have similar functions.     

Primary Neuroendocrine Carcinoma of the Liver

A case of primary neuroendocrine carcinoma in an unusual location, the liver, is reported. The neoplasm was composed of small, uniform cells that had distinct borders and grew in strands, ribbons and nests; its appearance resembled that of a carcinoid. Electron microscopy and special staining of the neoplastic cells confirmed the neuroendocrine nature of the tumor, and the cells showed immunoreactivity for gastrin and pancreatic polypeptide by the PAP. The recent literature is reviewed, and the possible histogenesis of hepatic neuroendocrine carcinoma is discussed.     

Heterogeneity of neurons in the crustacean X-organ as revealed by intracellular recording and injection of horseradish peroxidase

The intracellular injection technique of HRP with simultaneous recordings of intracellular potential was applied to the crab X-organ-sinus gland peptidergic neurosecretory neurons. At least two classes of neurons were discriminated from the usual type of neurosecretory neurons morphologically as well as electrophysiologically. Possible roles of those neurons were suggested as the modulation and coordination of activities of the neurosecretory system.     

The efferent projections of the subfornical organ of the rat: A circumventricular organ within a neural network subserving water balance

The efferent projections of the subfornical organ (SFO) of rats were traced using the autoradiographic method of following anterograde transport of labelled proteins through axons.The efferents of the SFO go to two different areas. The first is the anteroventral third ventricular area of the preoptic region and the second is the hypothalamus particularly the neurosecretory, magnocellular nuclei. Specifically, the apparent terminal fields in the first area are in the nucleus medianus of the medial preoptic area (NM), the organum vasculosm of the lamina terminalis (OVLT), and the anterior periventricular area (PeV). Many efferent fibers to this area emerge from the rostral SFO, pass anteriorly over the anterior commissure in the midline and either descend along the anterior border of the NM or enter the PeV dorsally just beneath the anterior commissure. The apparent terminal fields within the hypothalamus are in the anterior and tuberal supraoptic nuclei (SON_a and SON_t), the paraventricular nucleus (PVN) including its rostral accessory cluster, the nucleus circularis (NC), the dorsal perifornical area (PFd), and in both the lateral preoptic area and lateral hypothalamus adjacent to the SON. Many efferent fibers to the hypothalamus emerge from the rostral SFO and enter the columns of the fornix, diverge with the ventral stria medullari to disperse medially and laterally over the columns of the fornix and along their dorsal border at the anterior dorsal level of the columns trajectory through the hypothalamus.These findings are discussed in terms of the SFO's role within a neural network mediating water balance behaviorally and physiologically.     

Histological,histochemical, and immunohistochemical studies of hippocampus in male New Zealand rabbits

The present study aims to give detailed histomorphological features of the hippocampus of adult male New Zealand rabbits. Both histological and histochemical specimens were prepared to be examined microscopically by using a light microscope. The hippocampus appeared as C-shaped hippocampal proper, dentate gyrus, and subiculum. The hippocampal proper subdivided along its length according to the density and size of its major constituent pyramidal cells into four distinct regions named Cornu Ammonis (CA1, CA2, CA3, and CA4). With the histochemical preparations, each of these regions consisted of five layers, stratum alveolus, stratum oriens, stratum pyramidale, stratum radiatum, and stratum lacunosum-moleculare. The stratum pyramidale constituted the middle dark zone and contained the principal excitatory neurons and a few interneurons. Histochemically, the pyramidal neurons along all regions of the CA reacted positively to Grimelius silver impregnation, lead hematoxylin, Gomori's aldehyde fuchsin, aldehyde thionine, Gomori's chrome alum hematoxylin, and performic acid alcian blue stains. Immunohistochemically, the pyramidal neurons reacted positively to anti-NSE antibodies. The dentate gyrus was formed of three distinct layers. The subiculum was formed of proper subiculum, presubiculum, and parasubiculum.     

Cytology of brain stem neurons projecting to the caudal neurosecretory complex: An HRP-electron microscopic study

Brain stem projections to the neurons in the caudal neurosecretory complex (CNC) of Poecilia sphenops (molly) have been studied with HRP retrograde tracing. Using light microscopic procedures, HRP-labelled neurons were located in the reticular nucleus of the medulla (RMN) and in the vicinity of the nucleus of the medial longitudinal fascicle (NMLF). The present study was undertaken to examine the cytology of the brain stem neurons that project to the caudal neurosecretory complex using combined HRP-electron microscopic methods. Cells in the midbrain NMLF containing HRP-filled profiles were located bilaterally close to the midline and just beneath the ependyma. HRP reaction product was found additionally in the neurosecretory cells of the midbrain dorsal tegmental magnocellular nucleus (DTMN) located dorsal to the NMLF. Cells containing HRP-labelled profiles were also seen in the RMN and in neurons dorsal-lateral to the RMN. This latter group of neurons contained small dense core vesicles in addition to HRP labelled dense bodies.     

Ultrastructural localization of inhibin β- and somatostatin-28-immunoreactivities in the paraventricular and supraoptic nuclei

Recent studies have supported the existence of projections to the paraventricular and supraoptic nuclei of the hypothalamus that arise from non-catecholaminergic neurons in the nucleus of the solitary tract, whose terminal distribution is suggestive of interactions with both parvocellular and magnocellular neurosecretory neurons. Pre-embedding immunolabeling methods were used to compare and characterize the termination patterns of axons immunoreactive for two putative markers for this projection system, inhibin β and somatostatin-28, at the ultrastructural level. Axon terminal profiles stained fro either peptide were found to form symmetric or asymmetric junctions predominantly with the shafts of unlabeled dendrites of varying caliber. A small percentage of peptidergic terminals was found in both hypothalamic nuclei to engage in so-called ‘shared synapses’, where a single terminal profile contacted two postsynaptic elements. Axo-somatic terminations were relatively rarely seen in the supraoptic nucleus, but were somewhat more abundant in the paraventricular nucleus. These comprised principally symmetric junctions onto the somatic membranes of an ostensibly mixed population of cells, some of which bore apparent neurosecretory specializations. Combined immunoperoxidase and immuno-autoradiographic staining methods were used to estimate the extent to which either terminal type interacts with oxytocin neurons. Oxytocin stained elements comprised a minority of the postsynaptic targets of both peptidergic terminal types in the paraventricular nucleus, and a scant majority of those in the supraoptic nucleus. These results support the view that peptidergic neurons in the caudal nucleus of the solitary tract interact synaptically with multiple cell types in the parvocellular division of the paraventricular nucleus, and preferentially with oxytocinergic elements in the magnocellular neurosecretory system.