Morphological observations of small granule-containing (chromaffin) cells in the celiac ganglion of the guinea pig, with emphasis on cell contacts.

Utilizing electron microscopic observation, several contacts between small, granule-containing cells (SGC) and postganglionic neurons (PGN) in the celiac ganglion of the guinea pig have been observed. A SGC in very close association with a PGN was seen to receive a distinct synaptic contact that contained many vesicles with dense cores. This contact was morphologically unlike cholinergic synapses previously reported on chromaffin cells. Because the SGC and PGN were clearly separated by a thin rim of satellite cell cytoplasm mutual to both cells, it is not known how or if the SGC would possibly exert a synaptic or paracrine effect on the PGN. Also, intraganglion SGC existed as large well-vascularized islands within the celiac ganglion. These intraganglion clusters sometimes contained more than 50 cells and perhaps could be considered to function as localized neuroendocrine components within the ganglion by secreting granule products into the nearby blood vessels for local or distant effects, although this certainly is not known. This work reports a unique synaptic ending upon a single-occurring SGC, which, in turn, closely approximates a ganglion neuron in a soma-somatic relationship. In addition, a very close association (but no actual contact) was observed between granule-containing processes, presumably emanating from the intraganglion clusters, and PGN. Whatever the function of ganglionic SGC may be, the exact relationship between SGC and PGN presumably would be of great interest and potential importance.

Mitotic cell division in the extraadrenal chromaffin system of various species.

Mitotic activity often has been reported in embryonic and fetal sympathetic neuroblasts, principal sympathoblasts, and primitive sympathetic cells in various species at different stages of development. Postnatal adrenal medullary cells also are known to undergo mitosis, but such dividing capabilities rarely have been observed in the true postnatal extraadrenal chromaffin system. Although few in number, this work nevertheless has clearly identified such cells in varying stages of the mitotic cycle in the young dog, Syrian hamster, mouse, rabbit, and rat. The dividing cells were noted in paraaortic chromaffin organs, paraganglia, and within the inferior mesenteric ganglion as well. They displayed the morphological character usually associated with their adrenal medullary catecholaminergic counterparts, including numerous dense-cored vesicles known to be the harbingers of catecholamines and various peptides. Nerve endings were not noticed upon the mitotic cells. The phenomenon of dividing extraadrenal chromaffin cells augments existing data and perhaps suggests that these cells are more endocrine than neural in type and subservient to the adrenal medulla in its classic endocrine function.

Immunohistochemical evidence for the occurrence of vasoactive intestinal polypeptide (VIP)-containing nerve fibres in human fetal abdominal paraganglia.

The abdominal paraganglia in man represent a major source of catecholamines, and perhaps peptide hormones, during the fetal period. The nature of the innervation of the abdominal paraganglia was studied immunohistochemically by utilising antibodies to vasoactive intestinal polypeptide, enkephalin, substance-P and somatostatin. The paraganglia showed an abundant network of VIP-immunoreactive fibres, and similar nerve fibres were found within nerve bundles of the preaortic sympathetic plexus. Occasionally, VIP-immunoreactive fibres were seen within the prevertebral ganglia, but stained cell bodies were never observed. It may be suggested that VIP-containing nerves could regulate a secretory response from fetal human abdominal paraganglia.

Autoradiographic localization of alpha-bungarotoxin-binding sites in the carotid body of the rat.

Radioiodinated alpha-bungarotoxin (alpha-Bgt) was used to localize alpha-Bgt-acetylcholine receptors in the carotid body of the rat. The gamma spectrometer analyses indicated a high uptake of [125I] alpha-Bgt in carotid bodies incubated in vitro (1.51 fmole per organ). Incorporation of the isotope was effectively blocked by pretreatment of carotid bodies with d-tubocurarine and unlabeled alpha-Bgt, but not by atropine. Light microscopic autoradiography showed a heavy labeling of some parenchymal cells. Electron-microscopic autoradiography revealed that labeling was localized along the interface between parenchymal cells, especially where their cytoplasmic processes engage in complex interdigitations. The silver grain counts on electron-microscopic autoradiographs suggest that labelings are preferentially associated with the plasma membrane of certain Type I cells. It is suggested that these Type I cells in the rat's carotid body probably are provided with nicotinic acetylcholine receptors on their plasma membranes.

A glutaraldehyde/potassium dichromate tracing method for the localization and preservation of abdominal extra-adrenal chromaffin tissues.

The present work introduces a method for the localization in situ of the abdominal paraganglia. After treating retroperitoneal tissue blocks with a near-neutral glutaraldehyde/potassium dichromate solution following routine glutaraldehyde perfusion, intra- and extraadrenal chromaffin tissues develop a pronounced brown color from the interaction of glutaraldehyde/potassium dichromate with amines. In this manner, visualization of the abdominal extra-adrenal chromaffin organs is enhanced at the same time that cellular ultrastructure is preserved. Subsequent examination of the dichromate-reacted tissues with the electron microscope confirms that they represent the amine-rich paraganglia. This method offers an effective alternative to extensive sampling of plastic-embedded blocks for localizing peripheral chromaffin tissue and has been used to define the exact distribution of abdominal paraganglia in the rabbit.