Vagal afferent innervation of rat abdominal paraganglia as revealed by anterograde DiI-tracing and confocal microscopy

Abdominal vagal afferent fibers were selectively labeled by injecting the fluorescent carbocyanine dye DiI into the left nodose ganglion of rats. Almost all paraganglia that were distributed along the five major abdominal vagal branches and their subbranches were found to be innervated by labeled vagal afferents. Laser scanning confocal microscopy with its single optical sectioning and three-dimensional reconstruction capabilities were used to analyze this innervation in more detail for paraganglia near the vagal hepatic branch and liver hilus. Furthermore, in double-labeling studies, it was demonstrated that a large percentage of the vagally innervated glomus cells were capable of catecholamine synthesis on the basis of their positive staining for tyrosine hydroxylase antibody. These findings support the concept of a chemoreceptive function for the abdominal paraganglia.

The presence of paraganglia in the human ascending aortic fold: histological and ultrastructural studies

Light and electron microscopic features of the human ascending aortic fold are described. Histological examination showed the characteristic epicardial structures continuous with a stroma of abundant adipose tissue. In addition, randomly distributed tissue resembling the carotid body was observed by both light and electron microscopy throughout postnatal life, from a fullterm stillborn fetus to the oldest subject (65 y). The size of the paraganglionic cell nests was variable at all ages. The presence of paraganglia in the aortic fold raises the possibility that they are concerned with chemoreception.

The glomus tympanicum: a middle ear chemoreceptor?

Negative pressure in the middle ear has been identified as an important factor in the pathogenesis of middle ear disease. Unfortunately, to date, the physiological mechanisms that control middle ear pressure are poorly understood. Recent interest has focused on the possible role of carotid body-like tissue in the middle ear (the glomus tympanicum) as a chemoreceptor for changes in the gas composition of the middle ear. From the few anatomical studies of normal glomus tissue in the temporal bone it would seem that glomus bodies may not be consistently present in the middle ear. In this study, glomus bodies were sought in histological preparations of the promontory mucosa and tympanic plexus. It was found that the glomus tympanicum is only occasionally present in the middle ear mucosa, and thus a chemoreceptor role specific to the middle ear is unlikely.

Ultrastructural morphometric observations on the extramural aortico-pulmonary bodies of the domestic fowl

The extramural aortico-pulmonary bodies of the domestic fowl were analysed in electron micrographs by point-counting morphometry. The Type I cell constituted about 34% of the total volume of the parenchyma, whereas the supporting cells (Type II cells, pericytes and Schwann cells) constituted about 26%. The blood capillaries occupied the lowest volume density of about 5%. The mitochondria and the dense-cored vesicles occupied about the same volume (8%) of the Type I cell cytoplasm. The results obtained in the present study are compared with other similar studies on the aortic and carotid bodies of mammals.

Paraganglia of the superior laryngeal nerve of the rat

Paraganglia were consistently found at the bifurcation of the superior laryngeal nerve of the rat. Ultrastructurally the paraganglionic cells resembled the type I and type II cells of the carotid body. The dense-cored vesiculated type I cell was found most frequently, whereas the type II cell represented 10-25% of the cell population. The volume density of the dense-cored vesicles was found to be 3.5 +/- 0.5, which is about half as much as that found in the recurrent laryngeal nerve and about twice of that found in the carotid body. A total of 24,634 dense-cored vesicles were measured, and the mean diameter was calculated to be 113.8 +/- 4.9 nm. Based on the median vesicle profile diameter, only one type of dense-cored vesicle cell was found.

Aortico-pulmonary bodies in the domestic fowl: ultrastructure, innervation and secretion

In adult and immature domestic fowl, aggregations of large pale-staining cells were found in the wall of the aorta, and of the pulmonary trunk and arteries, in modified regions typified by interruption or loss of elastic laminae and smooth muscle cells. Encapsulated extramural aggregations of similar cells were identified either on the actual surface or well outside the arterial wall of the aorta, and pulmonary trunk and arteries. The electron microscope revealed that the pale cells in these intramural and extramural structures were granular cells characterised by dense-cored vesicles typically about 60-140 nm in diameter. Supporting cells partly invested the granular cells. These intramural and extramural structures are interpreted as aortico-pulmonary bodies. The extramural and to a lesser extent the intramural cells were associated with many axonal endings and fenestrated blood capillaries. The axonal endings formed presumptive afferent, efferent and reciprocal synapses with the granular cells. Both intra- and extramural granular cells displayed evidence of exocytosis and were also shown by autoradiography to handle amines. It is concluded that the ultrastructural features of these aortico-pulmonary bodies resemble those of the carotid body. It is therefore suggested that the aortico-pulmonary bodies of the domestic fowl have a chemoreceptor function similar to that of the carotid body. It is also suggested that they may have a general secretory function.

Quantitative studies of the aortic bodies of the cat. I. Point-counting analysis of tissue components

Electron micrographs of cat aortic bodies were submitted to point-counting analysis to determine the volume/volume densities (vv%) of general tissue components. Paraganglia, enclosed by a perineural sheath (endoneural paraganglia), exhibit a significantly higher density of specific tissue elements (type-I cells, type-II cells, nerves) than those which covered by fibroblasts (exoneural paraganglia). Additional criteria which allowed distinction of these types of aortic bodies were not evident in this study. On average, type-I cells occupied 27.8 vv% if related to the entire organ, or 35.6 vv% if related to the blood vessel-free space. Comparing our data with those reported for the carotid body, we found an about twofold amount of type-I cells within aortic bodies. The relevance of this finding is discussed with respect to the known different electrophysiological properties of carotid and aortic body arterial chemoreceptors.

The paraganglion supracardiale vagi: an intravagal paraganglion in the rat

In the Ham-Wistar rat, a paraganglion was found within the vagus nerve at the site of branching of the recurrent laryngeal nerve. Due to its location the name "paraganglion supracardiale vagi" is suggested. Fluorescence microscopy of the paragangkionic cells displays an intense yellow-green fluorescence indicating the presence of biogenic amines. Ultrastructurally, chief cells containing dense-core vesicles form three kinds of synaptic contacts (afferent, efferent and reciprocal) with enlarged. mitochondria-rich nerve endings.

Spontaneous neurite outgrowth and vasoactive intestinal peptide-like immunoreactivity of cultures of human paraganglioma cells from the glomus jugulare

The chief cells of paraganglionic tissues have morphological and functional similarities to adrenal chromaffin cells, and both cell types are derived from the neural crest. In the present investigation cells from two glomus jugulare paragangliomas were studied in culture. Approximately 50% of the cells from one tumor, and 7% from the other spontaneously formed neurite-like processes. Numerous granular and agranular synaptic-like vesicles also appeared in the process-forming cells. In contrast to findings with normal and neoplastic adrenal chromaffin cells, addition of nerve growth factor (NGF) to the culture medium had no major effects on proportion of cells with processes. Dexamethasone caused only a small decrease in process length. Culturing of the tumors also appeared to promote production of material with VIP-like immunoreactivity. It is concluded that the phenotype of paraganglioma as well as pheochromocytoma cells may be altered in vitro. Responsiveness to specific factors such as NGF or steroids, however, may vary for related tumor cell types in different anatomic locations.

Location and size of carotid body-like organs (paraganglia) revealed in rats by the permeability of blood vessels to Evans blue dye

We determined the number, distribution size, and morphology of paraganglia near the glossopharyngeal, vagus, and sympathetic nerves of rats. The location of paraganglia was revealed by a method that takes advantage of the comparatively high permeability of their blood vessels to Evans blue dye. Rats were fixed by vascular perfusion of glutaraldehyde 2 min after receiving an intravenous injection of Evans blue dye. Paraganglia appeared as circumscribed, intensely blue structures that were readily distinguished from unstained nerves associated with them. Similarly, some groups of small intensely fluorescent (SIF) cells in autonomic and sensory ganglia were surrounded by Evans blue at a time that other portions of the ganglia contained little detectable dye. An average of 92.5 (range 41-134) paraganglia and 41 (range 17-68) blue spots in ganglia were found in the neck, thorax and abdomen of each of 10 rats. Carotid bodies had a mean length of 601 +/- 123 micrometer, width of 275 +/- 65 micrometer, and volume of 25.1 +/- 11.2 micrometer 3 X 10(6). Other paraganglia had an average length of 168 +/- 108 micrometer, width of 77 +/- 41 micrometer, and volume of 0.87 +/- 1.55 micrometer 3 X 10(6). The total volume of paraganglion tissue averaged 128 micrometer 3 X 10(6) (range 62-215 micrometer 3 X 10(6)), 59% of which was due to paraganglia other than the carotid bodies. By using fluorescence microscopy, we verified that small catecholamine-containing cells, visible because of their yellow-green fluorescence induced by formaldehyde gas, were located in regions along nerves and within ganglia that contained extravascular dye, visible because of its red fluorescence. Electron-microscopic studies confirmed that blue-stained organs (presumptive paraganglia) associated with the superior laryngeal nerve and other branches of the vagus nerve contained cells morphologically similar to glomus cells of the carotid body. Celiac ganglia contained, in addition, some cells similar to chromaffin cells of the adrenal medulla. Paraganglia (but not in SIF cells in ganglia) were encapsulated by layers of perineurium, which may constitute a barrier to diffusion. Tortuous thin-walled blood vessels, some with a fenestrated endothelium, were present in all paraganglia examined and were near most groups of SIF cells in ganglia. Neural connections of the small catecholamine-containing cells varied. Most nerve terminals on cells in paraganglia resembled sensory nerve endings on glomus cells of the carotid body, although some were morphologically similar to preganglionic nerves on chromaffin cells of the adrenal medulla.

Ultrastructure of the gallbladder paraganglia

The ultrastructure of the paraganglia in the gallbladder is identical to that of other nonchromaffin paraganglia featuring granule-bearing chief cells with many axons ensheathed by supporting cells. Synapses between axons, chief cells, and axons and chief cells are common. Ultrastructural similarities to the carotid body, proven to be a chemoreceptor, support a similar function for these paraganglia. An endocrine function is also suggested by the partial similarity of their structure to that of Zuckerkandl's organ.

The neuroendocrine nature of the glomus cells: an experimental, ultrastructural, and histochemical tissue culture study

Although the carotid body is an established chemoreceptor, there is considerable evidence also for its possessing a secretory function. While adrenergic neuroendocrine cells of neuroectodermal derviation exist in the central and autonomic nervous systems, the exact histogenesis of the mammalian carotid body is unsettled. The normal human carotid body and glomus jugulare tumor have been grown in tissue culture and their constituent cells have been observed to transform from epithelial to neuronoid appearing cells with extensive dendritic processes. This conversion has been further enhanced by the addition of nerve growth factor, a polypeptide specific for neural tissue. Electron microscopy confirmed that these culus cell. Histofluorescence revealed that these in vitro cells continued to synthesize and store biogenic monoamines in culture. Comparison of the morphologic, ultrastructural and histochemical features of the glomus cell with established neuroendocrine cells (central nervous system neurons, sympathetic ganglia cells, chromaffin cells) shows striking similarities. On the basis of these findings it is concluded that the glomus cell is a modified neuron of neural crest origin. The embryology, electron microscopy and histochemistry of the carotid body and related glomera and their tumors are reviewed.

Paraganglion cells mimicking metastatic clear cell carcinoma

Four patients are presented whom normal paraganglion cells simulated metastases of clear cell carcinomas of the urogenital tract. The cells, located within and near the lumbar sympathetic ganglia, were initially interpreted by the pathologist as metastatic, but a later examination showed them to be normal paraganglion cells. One ganglion was also examined electron microscopically. Normal ganglion cells were seen, as were cells with intracytoplasmic osmophilic neurosecretory granules, confirming their paraganglionic origin. Awareness of the appearance of paraganglion cells in some instances is essential to avoid their misinterpretation as metastases of clear cell carcinomas.

An ultrastructural stereological analysis of the aortic body chief cell of adult rabbits

The chief cells of the aortic body (subclavian body) of adult New Zealand white rabbits were examined by ultrastructural stereological analysis. The chief cell nuclei occupy 26.5% of the total volume. Dense-core vesicles account for 16.5% of the cytoplasmic volume, followed by mitochondria (11.6%), endoplasmic reticulum (3.3%), and Golgi apparatus (0.6%). The dense-core vesicles measure approximately 131.6 nm in diameter (corrected) and exhibit a heterogeneous size distribution. Both perivascular adrenergic nerve terminals and presumptive afferent terminals presynaptic to the chief cells are observed. The mean synaptic vesicle size of the terminals adjacent to chief cells is 54 nm. The heterogeneous size distribution of the dense-core vesicles of chief cells may indicate the storage of different biogenic amines and/or different secretion or maturation states within the chief cells.

Hyperplasia of vagal and carotid body paraganglia in patients with chronic hypoxemia

Vagal and carotid body paraganglia were obtained from 43 randomly selected autopsies performed at the National Naval Medical Center. In each case, tissue from both sides was step sectioned and comparatively studied. The mean combined weight of carotid bodies in 37 control patients was 25.9 mg. There was good correlation between size and number of separate paraganglia comprising the vagal body (seven left, six right). Lobules were closely related to the ganglion nodosum and were actually within it in three instances. Tissue resembling parathyroid was encountered within 4 of the 86 resected vagus nerves. Lymphocytic infiltration occurred in carotid and vagal body paraganglia of 28% and 16% of patients, respectively. There was Schwann cell proliferatation in carotid body lobules of 2 patients; in another patient, talc emboli were present. The mean combined weight of carotid bodies in 6 patients with chronic hypoxemia was 47.6 mg, significantly greater than in the control group; in each case, lobules were enlarged. Chief cell hyperplasia occurred in vagal body paraganglia of 2 patients; in two other patients, lobules were large with equal proliferation of constituent cells. These morphologic findings indicate that in patients with chronic hypoxemia some vagal body paraganglia can be ascribed a chemoreceptor role similar to but probably less important than that of the carotid body.

Morphometric study of the aortic body type I cell

The subclavian glomus (aortic body) of New Zealand white rabbits was examined ultrastructurally using stereological morphometric analysis. The Type I cells of the glomus possess numerous electron-opaque vesicles which occupy approximately 12% of the cytoplasmic volume of the cells. The amine-containing vesicles comprise a heterogeneous population of vesicles with a mean caliper diameter of 113.5 nm. Differences in vesicle diameters may indicate the storage of different biogenic amines, different secretion or maturation states between glomera and/or additional physiological functions for the glomera.

Structure of cells and nerve endings in abdominal vagal paraganglia of the rat

The abdominal vagal paraganglia of the rat consist of small groups of cells, interspersed by blood vessels and nerve bundles and lying close to, or within, the vagus nerve or its branches. Each cell group consists of 2-10 Type I cells incompletely invested by 1-3 satellite cells. Type I cells are characterised by the presence of numerous dense-cored vesicles in their cytoplasm and may exhibit 'synaptic'-like contact with each other. Small efferent nerve endings make synaptic contacts with Type I cells. Larger cup-shaped afferent nerve endings also make synaptic contacts of two kinds with Type I cells. Nerve-nerve synapses are often seen within or close to paraganglia. Attention is drawn to the close similarity of fine structure of abdominal vagal paraganglia, carotid body and small intensely fluorescent cells of the superior cervical ganglion in rats. Possible functional implications of this morphological similarity are discussed.

Light, fluorescence and electron microscopic studies of rabbit subclavian glomera

The subclavian glomera (aortic bodies) of young New Zealand white rabbits were studied with the light, fluorescence, and electron microscopes. Two cell types were identified: type I, granule-containing (chief) cells, and type II, agranular (sustentacular) cells. The type I cells possessed large nuclei, the normal complement of cytoplasmic organelles and numerous electron-opaque cytoplasmic granules. The type II cells were agranular with attenuated cytoplasmic processes which partially or completely ensheathed the type I cells. The glomera were well vascularized. Capillary endothelial cells contained numerous pinocytotic vesicles, but few fenestrae. Two profiles of nerve terminals were observed. One, apposing the type I cells, contained numerous electron-lucent vesicles, several dense-cored vesicles, mitochondria and possessed membrane specializations resembling those usually observed in synaptic zones. The other profile contained abundant mitochondria and a few electron-lucent and dense-cored vesicles. Structural specializations were not observed on the apposed membranes of these terminals or adjacent to type II cells. Fluorescence histochemistry revealed an intense yellow-green fluorescence in the glomera, which indicated the presence of biogenic amines, possibly primary catecholamines or an indolamine. The electron-opaque granules observed in the type I cells were believed to be the storage sites for these amines. The subclavian glomera were found to be morphologically similar to the carotid body which is a known chemoreceptor.