Ultrastructural studies of vagal paraganglia in Syrian hamsters

Morphology and morphometry of the vagus nerve in male and female spontaneously hypertensive rats

The vagus nerve is an important component of the efferent arm of the baroreflex. Blood pressure levels as well as baroreflex control of circulation are significantly different in male and female spontaneously hypertensive rats (SHR). We proposed to investigate the morphometric differences between genders using the vagus nerve of SHR. Adult animals (20 weeks old) were anesthetized and had their arterial pressure (AP) and heart rate (HR) recorded by a computerized system. The rats were then systemically perfused with a fixative solution and had their cervical vagi nerves prepared for light microscopy. Proximal and distal segments of the left and right vagi nerves were evaluated for morphometric parameters including fascicle area and diameter, myelinated fiber number, density, area and diameter. Comparisons were made between sides and segments on the same gender as well as between genders. Differences were considered significant when p<0.05. Male SHR had significantly higher AP and HR. Morphometric data showed no differences between the same levels of both sides and between segments on the same side for male and female rats. In addition, no significant morphometric differences were observed when genders were compared. This is the first description of vagus nerve morphometry in SHR indicating that gender differences in AP and HR cannot be attributed to dissimilarities in vagal innervation of the heart. These data provide a morphological basis for further studies involving functional investigations of the efferent arm of the baroreflex in hypertension.

Carotid body and glomus cells distributed in the wall of the common carotid artery in the bird

In the bird the carotid body is located between the distal (nodose) ganglion of the vagus nerve and the recurrent laryngeal nerve at the beginning of the common carotid artery, that is, the organ is located at the cervicothoracic border. The chicken carotid body receives numerous branches from the vagus and the recurrent laryngeal nerves. In addition, dense networks of the peptidergic nerve fibers immunoreactive for substance P, calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide (VIP), galanin, and neuropeptide Y (NPY) are distributed in and around the carotid body parenchyma. The substance P- and CGRP-immunoreactive fibers are derived from both the superior and inferior ganglia of the vagus nerve. The VIP-, galanin-, and NPY-immunoreactive fibers originate from the 14th cervical ganglion of the sympathetic trunk. The endocrine organs including the thyroid gland, parathyroid glands, carotid body, and ultimobranchial gland are situated as a continuous series along the common carotid artery. The organs are supplied with arteries arising as one trunk from the common carotid artery. Glomus cells are widely distributed not only in the carotid body but also in the wall of the common carotid artery and around the common trunk and its branches. The glomus cells of the chicken carotid body exhibit intense immunoreactivity for serotonin, tyrosine hydroxylase, and chromogranin A. The cells located in the wall of the common carotid artery further express NPY mRNA and peptide. In the chickens exposed to isocapnic hypoxia for 35 days, 3-4-fold increase of the carotid body volume is induced and the carotid body glomus cells show enhanced synthetic and secretory activities. On the other hand, the cells in the wall of the common carotid artery display little changes after the long-term hypoxia, having different functions from the carotid body. The carotid body rudiment is formed in the lateral wall of the third branchial artery. The neural cells immunoreactive for TuJ1, PGP 9.5, and HNK-1, which are continuous with the inferior vagal (nodose) ganglion, first surround and then invade both the carotid body rudiment and the other portions of the third branchial artery, becoming glomus cells.

Accessory carotid body within the parathyroid gland III of the chicken

In the chicken, the cranial and caudal parathyroid glands (parathyroid gland III and IV), which are connected to each other, are located adjacent to the carotid body. In the present study, we found that a mass of glomus cells surrounded by a thick layer of connective tissue was frequently distributed within the parathyroid gland III. The glomus cells in the parathyroid III, as well as those of the carotid body, expressed intense immunoreactivity for serotonin, chromogranin A, and tyrosine hydroxylase but no immunoreactivity for neuropeptide Y. The cells possessed long cytoplasmic processes containing dense-cored vesicles of 70-220 nm in diameter, and were in close association with sustentacular cells. In and around the glomus cell clusters of the parathyroid III, dense networks of varicose fibers showed immunostaining with the monoclonal antibody TuJ1 to a neuron-specific class III beta-tubulin isotype, c beta 4. Furthermore, the distribution was also detected of numerous galanin-, vasoactive intestinal peptide (VIP)-, substance P-, and calcitonin gene-related peptide (CGRP)-immunoreactive fibers.

Chemosensitivity, plasticity, and functional heterogeneity of paraganglionic cells in the rat coeliac-superior mesenteric complex

Chemosensitivity and plasticity of paraganglionic cells in the rat coeliac-superior mesenteric complex (CSMC) were investigated at a basal state of normoxia (21% O2) and after long-term moderate hypoxia (10% O2, 14 days). Chemical sympathectomy previous to hypoxia was performed to destroy principal ganglionic neurons and thus to allow measurement of the norepinephrine and dopamine content of paraganglionic cells. At the basal state, the CSMC contained dopaminergic (TH+/DBH-) and noradrenergic (TH+/DBH+) paraganglionic cells, the majority being of the noradrenergic type. After 14 days of hypoxia, this ratio was reversed and dopaminergic cells predominated, as indicated by a twofold increase of TH+ cells and a twofold decrease of DBH+ cells. Biochemically, hypoxia produced an increase in the content (1.6-fold) and utilization (1.4-fold) of dopamine as well as a smaller increase in the content of norepinephrine, with no change in its utilization rate. The dopaminergic activation induced by hypoxia persisted after sympathectomy with guanethidine. It is concluded that paraganglionic cells in the CSMC display a chemosensitive function. Furthermore, our findings indicate that paraganglionic cells are differentially affected by hypoxia, depending on their distribution and the nature of their neuromodulators. The alterations induced by hypoxia point out the phenotypic plasticity developed by paraganglionic cells in adaptation to hypoxia and further demonstrate the functional heterogeneity of this autonomic cell population in the rat CSMC.

An anterograde tracing study of the vagal innervation of rat liver, portal vein and biliary system

In order to investigate the distribution and structure of the vagal liver innervation, abdominal vagal afferents and efferents were selectively labeled by injecting WGA-HRP or Dil into the nodose ganglia, and DiA into the dorsal motor nucleus, respectively. Vagal afferent fibers produced characteristic terminal-like structures at three locations in the liver hilus: 1. Fine varicose endings preferentially surrounding, but not entering, the numerous peribiliary glands in the larger intra and extrahepatic bile ducts 2. Large, cup-shaped terminals in almost all paraganglia 3. Fine varicose endings in the portal vein adventitia. No fibers and terminals were found in the hepatic parenchyma. While about two thirds of the vagal afferent fibers that originate in the left nodose ganglion, and are contained in the hepatic branch, bypass the liver hilus area on their way to the gastroduodenal artery, a significant number (approx. 10% of the total) of vagal afferents that do innervate the area, originates from the right nodose ganglion, and projects to the periarterial plexus of the common hepatic artery and liver pedicle most likely through the dorsal celiac branch. Varicose vagal efferent fibers were present within the fascicles of the vagal hepatic branch and fine terminal-like structures in a small fraction of the paraganglia. No efferents were found to terminate in the hepatic parenchyma or on the few neurons embedded in nerves or paraganglia. In contrast to the paucity of vagal terminals in the hepatic parenchyma, an abundance of vagal efferent and afferent fibers and terminals with distinctive distribution patterns and structural characteristics was present in esophagus and gastrointestinal tract.(ABSTRACT TRUNCATED AT 250 WORDS)

Vagal paraganglia of the rat

Paraganglia are associated with every branch of the rat vagus nerve except the pharyngeal branch. Some of the paraganglia closely resemble the glomus caroticum, whereas others appear like small, intensely fluorescent (SIF) cells of autonomic ganglia. The paraganglionic cells of SIF cell-like bodies (SLB) store catecholamines (the most abundant is probably noradrenaline) and in some cases neurotensin. The innervation pattern of SLB is variable and their physiological role remains unclear. Paraganglionic cells of glomus-like bodies (GLB) predominantly store dopamine and probably also to a lesser extent noradrenaline. These putative chemoreceptor organs receive sensory innervation from nodose ganglion neurons as revealed by degeneration experiments and by anterograde neuronal tracing. Substance P- and calcitonin gene-related peptide-immunoreactive fibres seen in the region of vascular entry into the GLB may account for some of these sensory fibres, but the peptide/classical transmitter stored in sensory terminals synapsing on paraganglionic cells is unknown. Ultrastructural immunocytochemistry revealed vasoactive intestinal polypeptide (VIP)-immunoreactive fibres lying in the interstitial space between paraganglionic cells and large capillaries. These fibres may originate from VIP-immunoreactive neurons, being frequently attached to GLB. The major difference between GLB and the glomus caroticum concerns their blood supply and related innervation: Arteries and arterioles do not penetrate into GLB and, accordingly, noradrenaline- and neuropeptide Y-containing nerve fibres are lacking within GLB. This peculiar arrangement of paraganglionic parenchyma and arterial blood supply may be one of the reasons for the different physiological properties of vagal and carotid arterial chemoreceptors.

Occurrence of calcitonin-positive C cells within the distal vagal ganglion and the recurrent laryngeal nerve of the chicken

The chicken ultimobranchial glands are richly supplied with nerve fibers originating from both the main trunk of the vagus nerve and its branch--the recurrent laryngeal nerve. C cells immunoreactive for calcitonin were invariably found in the large nerve bundles distributed throughout the ultimobranchial glands. In addition, these cells were often present within the distal vagal ganglia and the recurrent laryngeal nerves. The frequency of occurrence and the pattern of distribution of the C cells in the distal vagal ganglia and the recurrent laryngeal nerves were determined in chickens of various ages by means of an immunoperoxidase method with anticalcitonin and antineurofilament antisera. The left and right sides of the ultimobranchial region were asymmetrical. The left ultimobranchial gland was in close contact with the vagus nerve trunk, especially with the distal vagal ganglion, but it was separated from the recurrent laryngeal nerve. The right gland contacted the recurrent laryngeal nerves, its medial edge being frequently penetrated by the nerve, but the gland was separated from the distal vagal ganglion. On the left side, C cells were found in 25 out of 39 distal vagal ganglia but they were not distributed in the recurrent laryngeal nerve. On the right side, the cells were present in 28 out of 43 recurrent laryngeal nerves but absent in the distal vagal ganglia. The results indicate that the C cells secreting a hormone calcitonin can enter into nerves, but their occurrence is restricted to the nerves in close proximity to the ultimobranchial glands. Electron microscopic studies revealed that C cells in the nerves received numerous axon clusters enveloped with Schwann cell cytoplasm. Naked axons regarded as axon terminals were found in direct contact with the surface of C cells. They were mainly composed of efferent-type nerve endings showing the accumulation of numerous small clear vesicles and a few large dense-cored vesicles. In addition, C cells were partly covered with the long cytoplasmic processes of Schwann cells and were also in contact with the Schwann cell perikarya. The C cells in nerves appear to be controlled by neural stimulation.

Intra and juxtavagal paraganglia: a topographical, histochemical, and ultrastructural study in the human

The topographical, ultrastructural, and histochemical features of 23 human vagal paraganglia were analyzed. Nineteen of the 23 paraganglia were found in previously unreported sites; 18 of the 19 were in the cervical part of the nerve, between the carotid bifurcation and the superior thoraco-cervical inlet, and one paraganglion was located in the retrothyroidal part of the left inferior laryngeal nerve. The results of ultrastructural studies (2 cases), the histochemical and formaldehyde-induced-fluorescence studies (3 cases), and specific acetylcholinesterase activity (one case) demonstrate that these structures fulfill many of the modern criteria for paraganglionic tissue. In addition to paraganglia, single, isolated neurons or true micro-ganglia were always found along the trunk and branches of the vagus nerve when multiple sections were examined.

Respiratory effects of sectioning the carotid sinus glossopharyngeal and abdominal vagal nerves in the awake rat

Normoxic and hypoxic respiration has been measured in awake rats after denervation procedures designed to eliminate the regulatory input from the carotid bodies, from all chemosensory tissue supplied by the glossopharyngeal nerve (n. IX), and from abdominal chemoreceptors. Studies were made 1 day after section of the carotid sinus nerve (c.s.n.), n. IX (at a level including c.s.n.), the abdominal vagus (n. Xa) and combinations of these nerves. Results were compared with those found in normal controls. C.s.n. section led to hypoventilation in both normoxia and hypoxia, reductions in respiratory frequency being consistent and substantial, and reductions in tidal volume varying with the degree of hypoxia. By comparison, section of n. IX produced significantly greater reductions of both normoxic and hypoxic ventilation. Section of n. Xa produced no significant change in normoxic ventilation but in hypoxia produced a significant small reduction in ventilation, mostly from an effect on tidal volume. Denervation of all the associated chemosensory tissue by combined section of n. IX and n. Xa demonstrated a summation of effects but left two distinct residual responses, one to mild hypoxia, and one to severe hypoxia, both associated mainly with increases of tidal volume. The experiments demonstrate that glomus tissues at different sites in the rat produce significant and distinct contributions to respiratory regulation. Denervation of all known receptors shows that significant ventilatory responses to hypoxia are still produced, either by unrevealed peripheral chemoreceptors, or by central neural mechanisms.

A light and fluorescence cytochemical and electron microscopic study of granule-containing cells in the intrapulmonary ganglia of Pseudemys scripta elegans

In the lung of the red-eared turtle, large numbers of intramural ganglia located in the intraparenchymal connective tissue are demonstrated. Numerous cells in close proximity to the principal ganglionic neurons displayed a bright blue-white formaldehyde-induced fluorescence. Microspectrofluorometric analysis revealed the presence of dopamine (DA) in all cells measured. Subsequent light histochemical staining of the fluorescent sections showed the DA-containing cells to display argentaffinity. Electron microscopy of serial sections revealed cells characterized by dense-cored vesicles corresponding to the intensely formaldehyde-induced fluorescent cells. The argentaffin technique performed directly on ultrathin sections selectively stained the dense-cored vesicles. After fixation with glutaraldehyde followed by dichromate, x-ray microanalysis showed the chromium to be incorporated into the dense granules. Cholinergic-type nerve endings formed axosomatic synaptic contacts with the DA-containing cells, which can therefore be considered as intrinsic postganglionic elements. No efferent synapses from the granule-containing cells to the principal ganglionic neurons could be observed. The granule-containing cells occurred solitarily and in clusters, partially invested with satellite cells, and usually located near fenestrated capillaries; they displayed cytoplasmic processes and indicated emiocytotic granule release. Adjacent granule-containing cells were separated by spaces about 20 nm wide, gradually widening to form intercellular channels with apically projecting microvilli and primary cilia. It is concluded that the intrapulmonary granule-containing cells of the red-eared turtle belong to the APUD system. Furthermore, morphologically these cells appeared to possess a special sensory apparatus which designates them as paraneurons. The possible physiological significance of these intrapulmonary granule-containing cells is discussed.

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.

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.

Arterial chemoreceptor-like activity in the abdominal vagus of the rat

1. Centripetal activity in fibres in the ventral abdominal vagus nerve of the rat has been studied by recording from fine strands of the divided nerve within the abdomen. 2. In the starved animal, few spontaneously active fibres were located. A proportion of these, however, showed changes in activity in response to changes in F1 oxygen which were typical of arterial chemoreceptor afferent nerves. The resting discharge in these preparations was 0.8-8.0 impulses/sec. In response to extreme hypoxic hypoxia, histotoxic hypoxia or acetylcholine, this discharge increased markedly, with a maximum mean activity of up to 25 impulses/sec. 3. Both the mean/S.D. ratio and statistical comparison with a 'noise' equation were used to assess the apparent random nature of the spike intervals. The former indicated that the spike intervals were random but the latter test was inconclusive. 4. We suggest that this chemoreceptor-like activity originates from the abdominal vagal paraganglia and that these structures may be part of a more generally distributed chemoreceptor system.

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.

A nonfunctioning paraganglioma of vagus nerve: an ultrastructural study

The clinical, histological, and ultrastructural aspects of a cervical paraganglioma of the vagus nerve, in a 66-year-old white man, have been discussed in detail. Ultrastructurally, the tumor chief cells contained characteristic membrane-bound and dense-cored neurosecretory granules which ranged in size from 85 millimicron to 190 millimicron. Unlike earlier ultrastructural reports, the present study showed the presence of sustentacular or supporting cells. These cells were smaller, darker, polymorphic, and were commonly located at the periphery of a single or group of chief cells. Furthermore, unlike earlier reports on vagal paragangliomas, nonmyelinated nerve fibers and an occasional axon were identified in the present fine structure study.

The distribution and endocrine nature of the abdominal paraganglia of adult man

The paraganglia of adult man were studied using the formaldehyde-induced fluorescence (FIF) method for histochemical characterization of biogenic monoamines. Microspectrofluorimetry was used to record the emission spectra and fluorescence intensities of the paraganglionic cells. The study of samples from six patients showed that well vascularized paraganglia were widely distributed throughout the retroperitoneal spaces. The paraganglia exhibited strong FIF with the spectral characteristics of monamines. Treatment with HC1 caused an increase in the fluorescence intensity of the paraganglia and a simultaneous shift of the emission maximum from 480--495 nm. This change suggests the presence of high concentrations of tryptophyl-containing peptides and is not due to monoamines. The possibility of a dual endocrine function for the paraganglia is discussed.

Polypoid nonchromaffin paraganglioma of the duodenum

A polypoid tumor was surgically removed from the second part of the duodenum of a 56-year-old male. The main body consisted of large epithelioid cells arranged in an adenoma like pattern of strands and nests. These cells were argyrophil and had marked nonspecific esterase activity. Unmyelinated nerves with proliferated Schwann cells accompanied these epithelioid cells together with scattered gangliocyte like elements. Ultramicroscopically, the epithelioid cells were seen to contain round electron dense granules, 150 nm in diameter on average. The tumor is considered to be a nonchromaffin paraganglioma, as it probable developed from paraganglion cells associated with small arteries or branches of the vagus nerve, or from the undifferentiated pluripotent APUD cells of the duodenum.

The ultrastructure of paraganglia associated with the inferior mesenteric ganglia in the guinea-pig

The paraganglia of the inferior mesenteric ganglia in the guinea-pig are composed of small chromaffin cells containing an abundance of granule-containing vesicles. The chromaffin cells are almost completely surrounded by satellite cells. In areas in which satellite cell processes do not intervene, the membranes of adjacent chromaffin cells are closely apposed and often form specialized attachment zones. The paraganglia contain a dense capillary network, the endothelial cells of which are often extremely attenuated and show areas of fenestration. The processes of chromaffin cells approach close to the capillary walls and are often bare of satellite cells covering on the side facing the capillary. Evidence has been obtained for the exocytotic release of the contents of chromaffin cell vesicles into pericapillary spaces. Synapses of cholinergic and noradrenergic axons are seen on the chromaffin cells. The cholinergic axons degenerate when the praganglia are decentralized, but the noradrenergic axons, which appear to arise from the local inferior mesenteric ganglia, remain intact. The results suggest that the paraganglia have an endocrine function.

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.

An electron microscopic study on the effects of reserpine on the subclavian glomera of the rabbit

Young male and female New Zealand white rabbits were given a daily subcutaneous injection of reserpine (Serpasil, Ciba; 3 mg/kg) for two days and were sacrificed 24 hours after the last injection. The subclavian glomera (aortic bodies) were processed for electron microscopy to determine the effects of this biogenic amine depleting agent on the electron-opaque cytoplasmic granules of the parenchymal type I cells. Observations of glutaraldehyde-osmium tetroxide fixed glomera from reserpinized animals showed a slight decrease in granule density of the type I cells. Glomera fixed in glutaraldehyde and incubated in potassium dichromate (pH 4.1) demonstrated a reduction in granule opacity following reserpine treatment. Control glomera incubated in potassium dichromate displayed electron-opaque granules. These results indicate that reserpine does deplete the amines without granule disappearance or changes in granule population. The positive reaction of the control tissue granules to potassium dichromate incubation suggests that the predominant biogenic amines in the electron-opaque granules are unsubstituted monoamines. Persistence of the opaque granules following reserpinization and glutaraldehyde-osmium tetroxide double fixation, may be due to amine-binding protein within the granules. The mode of granule depletion could not be ascertained with certainty.

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.

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.

Reflex apnea, bradycardia, and hypotension produced by serotonin and phenyldiguanide acting on the nodose ganglia of the cat

Five to 20 µg of phenyldiguanide or serotonin (5-HT) injected into the common carotid arteries of cats (anesthetized with chloralose and urethan) elicited an immediate apnea, usually accompanied by bradycardia and hypotension. The response persisted after ligation of the external carotid and lingual arteries. Since the internal carotid is occluded in the cat, the receptors must be in the distribution of the occipital or ascending pharyngeal arteries. Denervation of the carotid sinus and carotid body, removal of the superior cervical ganglion, section of the vagosympathetic trunk below the nodose ganglion, and extracranial section of cranial nerves IX, XI, and XII did not diminish the response. Section or procaine block of the extracranial supranodose vagus or removal of the nodose ganglion usually abolished the apnea and bradycardia; hypotension still occurred in many cats. Examination of the nodose ganglion by fluorescence microscopy revealed nests of intensely fluorescent cells similar to type 1 carotid body cells. Although previous investigators have reported that veratrnm alkaloids or acetylstrophanthidin causes vomiting or bradycardia by an action on the nodose ganglion, this is the first demonstration that a naturally occurring substance (5-HT) stimulates receptors in the nodose ganglion, causing reflex apnea and hypotension in addition to bradycardia.