Paraganglia of the rat recurrent laryngeal nerve after long-term hypoxia: A morphometric and biochemical study

Summary Paraganglia of the recurrent laryngeal nerve of rats exposed to hypoxia (10±0.5% O₂) for 3 weeks became enlarged in volume by 2.6-fold. The volume densities of blood vessel lumen and endothelial cells were unchanged. The enlargement of the paraganglia was mainly attributed to hypertrophy of the dense-cored vesicle-containing cell. Concerning the profile diameter of the vesicle, a unimodal distribution of dense-cored vesicle cells was found in both control and hypoxic paraganglia. The vesicle diameter increased by about 19%, whereas the numerical density of dense-cored vesicles and the vesicle volume density were unaltered after hypoxia.Recurrent laryngeal nerves assayed by a sensitive high performance liquid chromatography technique contained an average of 1.9pmol dopamine and 1.3pmol norepinephrine. Exposure to 2 weeks of hypoxia increased the dopamine level to 4.9pmol, whereas the norepinephrine content was unchanged. It is suggested from this study that the catecholamines determined are housed in the paraganglia of the recurrent laryngeal nerve.     

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

Summary 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 m, width of 275 ± 65 m, and volume of 25.1 ± 11.2,m³ × 10⁶. Other paraganglia had an average length of 168 ± 108m, width of 77 ± 41 m, and volume of 0.87 ± 1.55 m³ × 10⁶. The total volume of paraganglion tissue averaged 128 m³ × 10⁶ (range 62–215 m³ × 10⁶), 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 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.     

Catecholamines of endoneurial laryngeal paraganglia in the rat

The catecholamines in the recurrent and superior laryngeal nerves of the rat were assayed by high performance liquid chromatography. The nerves were shown to contain high levels of dopamine (1.9 ± 0.6 and 2.3 ± 0.4 pmol, respectively) and noradrenaline (1.3 ± 0.3 and 0.9 ± 0.2 pmol, respectively). No adrenaline could be detected in any of the nerves. Reserpine markedly depleted the stores of these amines in both nerves. A significant increase in dopamine level was seen in the superior laryngeal nerve after treatment with a monoaminoxidase inhibitor, but not in the recurrent laryngeal nerve. The high levels of dopamine detected are presumably derived from endoneurial paraganglia which were demonstrated by glyoxylic acid-induced fluorescence. The source of noradrenaline is less evident, but noradrenaline is probably stored in both endoneurial paraganglia and in sympathetic nerve endings.,     

Ultrastructure of the primate carotid body: a morphometric study of the glomus cells and nerve endings in the monkey (Macaca fascicularis)

Summary The carotid body of the monkey (Macaca fascicularis) was studied at both the light and electron microscopic levels in an effort to provide a detailed quantitative characterization of this chemoreceptor organ in the primate. Structurally, the monkey carotid body was organized into lobules of from three to eight glomus cells (in section) and their ensheathing supporting cells. Interspersed among the lobules was abundant connective tissue stroma, fibroblasts and mast cells. Fenestrated capillaries, small arterioles and venules also permeated the organ. Each supporting cell partially ensheathed about three glomus cells and could be easily differentiated from glomus cells by their darker cytoplasmic staining, lack of dense-core vesicles and angular nuclear profile. Glomus cells exhibited an intense catecholamine histofluorescence and contained abundant dense-core vesicles. On the basis of dense-core vesicle size, shape and numerical density, four types of glomus cells were identified. The most common type (62% of all glomus cells) contained vesicles with an average diameter of 219 nm and a density of 8 vesicles per m² of cytoplasm. The second type possessed larger vesicles (264 nm in diameter) and accounted for about 14% of all glomus cells. A third type of glomus cell contained smaller (167 nm) and fewer (5 vesicles per m²) dense-core vesicles. The fourth type of glomus cell contained pleomorphic-shaped vesicles with a maximal diameter of 232 nm. Each of these last two types accounted for about 12% of all glomus cells. All four types of glomus cells were innervated, averaging 1.43 nerve endings per glomus cell (in sections). Nerve endings were primarily of the bouton-like variety averaging 2 m² in sectional area and containing 34.3 clear-core synaptic vesicles (average size 73.5 nm in diameter) per m² of cytoplasm. Of the 57 nerve endings examined in single sections, 16% displayed junctions typical of synaptic specializations and most of these were presynaptic to glomus cells. Glomus cell-glomus cell synapses were not observed. Based on these quantitative observations and on previous studies of carotid body cytoarchitecture in other laboratory species, it appears that the primate organ most closely resembles the cat carotid body, although several differences exist.     

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.     

Intimate apposition of the glomus and smooth muscle cells (g-s connection) in the carotid labyrinth of juvenile bullfrogs

Summary Intimate apposition of the glomus and smooth muscle cells (g-s connection) was found in almost all glomus cells of the carotid labyrinths in juvenile bullfrogs, Rana catesbeiana. There were three types of g-s connection: between thin processes (0.1–0.2 m in width) without dense-cored vesicles of glomus cells and smooth muscle cells; between thick processes (1.0–1.5 m in width) with dense-cored vesicles of glomus cells and smooth muscle cells; and between the tonguelike projections of smooth muscle cells and the flat surface of the glomus cell. In some cases, a single glomus cell made g-s connections with several smooth muscle cells. Exocytosis often occurs at the g-s connection. Afferent and efferent synapses were found on the glomus cells with g-s connections. Reciprocal synapses were also observed. On the basis of these findings, the second and third types of g-s connection are presumed to participate in vascular regulation.     

Dopamine beta-hydroxylase-like immunoreactivity in the rat and cat carotid body: a light and electron microscopic study

Summary Immunocytochemical localization of dopamine -hydroxylase (DBH) was used to study the synthesis and storage sites of norepinephrine (noradrenaline) in the rat and cat carotid bodies. In the rat carotid body some parenchymal cells exhibited strong DBH-like immunoreactivity (DBH-I), while others displayed only faint DBH-I. In a typical parenchymal cell cluster, most cells with strong DBH-I were irregular in shape and appeared to partially surround those with weak DBH-I which usually were rounded in contour. In the cat carotid body most parenchymal cells showed a strong to moderate DBH-I. In both the rat and cat carotid bodies varicose nerve fibres with DBH-I were associated primarily with blood vessels. All autonomic ganglion cells examined, which were associated with the rat carotid body, showed DBH-I. Electron microscopy revealed that most DBH-I in the strongly positive cells of the rat carotid body was associated with dense granules (possibly corresponding to dense-cored vesicles of various sizes), although some was found in other sites. In oval cells with less DBH-I, reactivity resided in some of the large granules. In the cat carotid body the glomus cells contained more granules of various sizes and shapes than did those of the rat carotid body. Most of the cat glomus cell granules exhibited DBH-I activity. Our results indicate that some of glomus cells in the rat and most of the glomus cells in the cat contain DBH and therefore may be sites of norepinephrine synthesis.     

Expression of catecholamine-synthesizing enzymes in paraganglionic and ganglionic cells in the laryngeal nerves of the rat

Summary The rat recurrent and superior laryngeal nerves with adjacent connective tissue were examined by immunohistochemical techniques for localization of the catecholamine-synthesizing enzymes tyrosine hydroxylase, dopamine--hydroxylase and phenylethanolamine-n-methyltransferase. Most of the cells in the paraganglia of the recurrent and superior laryngeal nerves showed an intense tyrosine hydroxylase-like immunoreactivity. A few paraganglionic cells exhibited dopamine--hydroxylase-like immunoreactivity while none of the cells displayed phenylethanolamine-n-methyltransferase-like immunoreactivity. Some of the ganglionic cells in the recurrent and superior laryngeal nerves showed dopamine--hydroxylase-like immunoreactivity whilst these cells never showed tyrosine hydroxylase- or phenylethanolamine-N-methyltransferase-like immunoreactivity. The arterioles were supplied with plexuses of nerve fibres showing tyrosine hydroxylase- and dopamine--hydroxylase-like immunoreactivity. The results indicate that dopamine is the major catecholamine located in the laryngeal nerve paraganglia and show that ganglionic cells in the recurrent and superior laryngeal nerves show immunolabelling for one of the enzymes in the catecholamine synthetic pathway, dopamine--hydroxylase.     

Ultrastructure of the glomus cells in the carotid body of chronically hypoxic rats: With special reference to the similarity of amphibian glomus cells

The ultrastructural characteristics of the glomus cells in the rat carotid body exposed to extremely long-term hypoxia (10–12 weeks) were investigated. The glomus cells could be classified into four distinct types according to the shape of dense-cored vesicles in the glomus cell cytoplasm: (1) small vesicle cells (SVCs, 50 nm in mean diameter), (2) large vesicle cells (LVCs, 80 nm in mean diameter), (3) dilated eccentric vesicle cells (EVCs, 400–800 nm in diameter), and (4) mixed vesicle cells (MVCs, large and eccentric vesicles). Many clusters of glomus cells were found to contain all four categories of cell types. The appearance of EVCs was a unique and common characteristic of glomus cells in this long-term hypoxia model. We also noted other ultrastructural features with chronic hypoxia which are characteristic of the amphibian carotid labyrinth glomus cells: (1) incomplete covering of glomus cells with the supporting cell missing over a wide area, (2) long thin cytoplasmic projections in the intervascular stroma, and (3) intimate apposition of the glomus cells and pericytes (g-p connection), endothelial cells (g-e connection), plasma cells, and fibrocytes. Because arterial PO₂ is generally low in amphibia, these may be general features of hypoxic adaptation and facilitate both uptake of oxygen from blood and release of catecholamine into the blood. The g-p and g-e connections may take part in the regulation of the microcirculation in the enlarged carotid body. © 1993 Wiley-Liss Inc.     

Norepinephrine-containing glomus cells in the rabbit carotid body. I. Autoradiographic and morphometric study after tritiated norepinephrine uptake

Summary Rabbit carotid bodies were investigated by autoradiography at both the light and electron microscope levels following tritiated norepinephrine administration eitherin vivo orin vitro. Two kinds of labelled structures were found: nerve fibres (absent in sympathectomized carotid bodies) and some type I glomus cells. Desipramine (a specific norepinephrine uptake inhibitor) prevented labelling. Most of the labelled cells differed from unlabelled ones by the presence of (i) large dense-cored vesicles characterized by a large halo between the membrane and an eccentric dense core; (ii) a nucleus showing a more electron dense chromatin and a more irregular shape; and (iii) relatively abundant glycogen particles. A few weakly-labelled cells were characterized by a pyknotic nucleus and very swollen dense-cored vesicles, and were presumed to be degenerating.Dense core diameters of dense-cored vesicles were distributed according to a unimodal distribution in labelled cells as in unlabelled ones but with an extension towards both large and very small diameters in labelled cells. The mean diameter was higher in labelled cells than in unlabelled ones (127 nm versus 113 nm,P < 0.01). The labelling intensity (as estimated by the number of silver grains per unit of cytoplasmic area) was maximum in cells having dense-cored vesicles whose mean diameter was between 130 and 170 nm, but decreased for cells with mean diameter of dense cores smaller than 130 nm, or larger than 170 nm.Thus, in the rabbit carotid body, some glomus cells differ from others by their ability to take up tritiated norepinephrine and by the presence of larger dense-cored vesicles. However, this distinction is not clearcut and there are many intermediates. The observations suggest a phenomenon of evolution deriving from a unique cell type and typified by both metabolic norepinephrine uptake ability, glycogen accumulation) and morphologic changes (increase in diameter of dense-cored vesicles). It seems, therefore, more appropriate to consider these results in terms of different functional states rather than different types of glomus cells.     

Effects of 5-hydroxydopamine and 6-hydroxydopamine on the ultrastructure of type I cells in paraganglia of the rat recurrent laryngeal nerve.

The ultrastructure of the Type I cells in paraganglia of rat recurrent laryngeal nerve (RLN) was studied after the administration of 5-hydroxydopamine (5-OHDA) and 6-hydroxydopamine (6-OHDA). Normal Type I cells of RLN-paraganglia contained abundant organelles and their cytoplasm was characterized by the presence of numerous membrane-bounded dense-cored vesicles (DCVs). The DCVs were round in profile (diameter 107.67 +/- 0.06 nm, all values expressed as mean +/- s.e.m. in the present study) and possessed dense cores of moderate to low electron density. After 5-OHDA treatment (single injection, 100 mg/kg b.w., i.v.), the majority of DCVs were filled with a material of high electron density. No significant difference was observed between the profile diameter of the DCVs in 5-OHDA-treated rats (104.96 +/- 0.06 nm) and that in normal rats. After 6-OHDA treatment (three injections, 100 mg/kg b.w. each at 12 h intervals i.p.), no significant alteration in the electron density of the core was noted. However, most of the DCVs were enlarged and round, elliptical or irregular in profile (190.57 +/- 2.77 nm x 130.34 +/- 2.09 nm). The dense core of DCVs was centrally or eccentrically located in DCVs. The results of the present study indicate that: 1) there is only one type of granulated glomus cell (i.e., Type I cells) in the rat RLN-paraganglia under normal physiological condition; and 2) since the ultrastructural morphology of DCVs in Type I cells of rat RLN-paraganglia is altered after 5-OHDA or 6-OHDA treatment, these cells may possess mechanisms for the uptake of false adrenergic neurotransmitter and/or neurotoxin.     

The effect of pro-inflammatory cytokines on the discharge rate of vagal nerve paraganglia in the rat

Vagal paraganglia resemble the carotid body and are chemosensitive to reduction in the partial pressure of oxygen (P_O2$P_{{\text{O}}_2}$) (O’Leary et al., 2004). We hypothesised that they may also mediate communication between the immune system and the central nervous system and more specifically respond to the pro-inflammatory cytokines: interleukin-1 beta (IL-1β) and tumour necrosis factor-α (TNF-α). We recorded axonal firing rate of isolated superfused rat glomus cells – located at the bifurcation of the superior laryngeal nerve – to IL-1β or TNF-α at concentrations of 0.5 ng/ml, 5 ng/ml and 50 ng/ml. Twenty-three successful single fibre recordings were obtained from 10 animals. IL-1β and TNF-α had no statistically significant effect on the frequency of action potentials observed (p = 0.39 and 0.42, respectively, repeated measures ANOVA). The activity of both cytokines was tested by observing translocation of P65-NFκB from cytoplasm to nucleus in cultured HELA cells. In conclusion, an immune role for SLN paraganglia has not been established.     

Type I cells of carotid body from rats treated with 5-OH-Dopa and L-Dopa: an electron microscopical study

Summary The ultrastructure of the Type I cells in rat carotid bodies was studied after treatment with 5-OH-Dopa and L-Dopa. Type I cells from the L-Dopa treated rats were also analysed by morphometric methods.After 5-OH-Dopa treatment, the majority of dense-cored vesicles of the Type I cells were almost completely filled withvery electron-dense material. The vesicles were mainly distributed close to the plasma membrane.After L-Dopa treatment, the ultrastructure of the Type I cells resembled that after 5-OH-Dopa treatment, except that the increase in electron density of the vesicle content was less pronounced. The morphometric analysis revealed, as previously described for normal carotid bodies, two subclasses of Type I cells, small vesicle cells (SVC) and large vesicle cells (LVC). Compared to those of normal rats, the mean profile diameter of the vesicles in theL-Dopa treated rat carotid bodies were enlarged (for SVC from 47 to 55 nm and for LVC from 63 to 76–78 nm). Furthermore, the volume density of vesicles in both SVC and LVC was increased. The mean volume of the SVC was markedly increased after L-Dopa treatment for 60 h.These observations indicate that the Type I cells possess mechanisms for uptake of amine precursors and synthesis of monoamines. Though the vesicle may be involved in an endocrine-like function, they may also be related to the chemoreceptor function of the carotid body.     

Immunohistochemical characteristics of human paraganglion cells and sensory corpuscles associated with the urinary bladder. A developmental study in the male fetus, neonate and infant

Triple label immunohistochemistry was used to study the coexistence of the catecholamine-synthesising enzymes dopamine beta-hydroxylase (DBH) and tyrosine hydroxylase (TH) and several neuropeptides including neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP), substance P (SP), calcitonin gene-related peptide (CGRP), somatostatin (SOM) and galanin (GAL) as well as nitric oxide synthase (NOS) in developing pelvic paraganglion cells in a series of human male fetal, neonatal and infant specimens ranging in age from 13 wk of gestation to 3 y postnatal. 13–20 wk old fetal specimens possessed large clusters of paraganglion cells lying lateral to the urinary bladder and prostate gland which were intensely DBH-immunoreactive (-IR) but lacked TH, NOS and the neuropeptides investigated. With increasing fetal age small clusters of paraganglion cells were observed in the muscle coat of the urinary bladder. At 23 wk of gestation occasional paraganglion cells were NOS or NPY-IR while at 26 wk of gestation the majority of paraganglion cells were TH-IR and a few were SOM or GAL-IR. Some postnatal paraganglia within the bladder musculature contained cells which were all VIP, SP or CGRP-IR while others displayed coexistence of NOS and NPY, SP and CGRP, or NPY and VIP. The presence of NOS in certain paraganglion cells indicates their capacity to generate nitric oxide (NO). These results show that human paraganglion cells develop different phenotypes possibly dependent upon their location within the bladder wall. A delicate plexus of branching varicose nerves was observed in the fetal paraganglia which increased in density with increasing gestational age. The majority of these nerves were VIP-IR while others were CGRP, SP, NPY, NOS or GAL-IR. The presence of nerve terminals adjacent to the paraganglion cells implies a neural influence on the functional activity of the paraganglia. Some paraganglia in the late fetal and early postnatal specimens contained Timofeew's sensory corpuscles, resembling pacinian corpuscles in their morphology. The central nerve fibre of these corpuscles displayed immunoreactivity for SP, CGRP and NOS, the latter indicating a possible role for NO in afferent transmission from the urinary bladder. In addition, a few corpuscles were penetrated by a noradrenergic nerve fibre immunoreactive for NPY and TH, which may have a modulatory role on the sensory receptor.     

Norepinephrine-containing glomus cells in the rabbit carotid body. II. Immunocytochemical evidence of dopamine-beta-hydroxylase and norepinephrine.

Summary The presence of noradrenergic glomus cells in the rabbit carotid body was investigated at the light and electron microscope levels, using dopamine-ß-hydroxylase and norepinephrine immunocytochemistry as well as the chromaffin reaction.Frozen and semi-thin plastic sections showed some dopamine-ß-hydroxylase immunoreactive glomus cells either isolated in the connective tissue or, more frequently, mixed with unreactive cells. At the ultrastructural level, immunopositive cells differed from immunonegative ones by the larger size of most of their dense-cored vesicles. Similar observations were made after using anti-norepinephrine antibodies. Immunoreactive cells to anti-dopamine-ß-hydroxylase and anti-norepinephrine antibodies were relatively few although their number varied from carotid body to carotid body. The immunolabelling intensity was very variable from cell to cell. Consecutive frozen sections processed for norepinephrine- and dopamine-immunocytochemistry showed many cell clusters containing both norepinephrine and dopamine-immunoreactive glomus cells.Some chromaffin glomus cells were clearly identifiable by the very strong electron opacity of their dense-cored vesicles; most of these vesicles were characterized by their large size, as the dense-cored vesicles observed in dopamine-ß-hydroxylase- and norepinephrine-immunopositive cells.These results demonstrated that dopamine-ß-hydroxylase and norepinephrine-immunopositive, as well as chromaffin cells, were identical to the cells which take up exogeneous norepinephrine, described in part I of this study. However, many intermediate levels were found between norepinephrine-immunonegative and strongly norepinephrine-immunopositive glomus cells, suggesting that the distinction between these two kinds of cells is not clearcut.     

Fine structure of the carotid body of the midterm human fetus

Summary The human fetal carotid body was studied using both histochemical and electron microscopic methods. The glomus cells of a mid term fetal carotid body evidently contain catecholamines. This was demonstrated both by formaldehyder-induced fluorescence of the cells and by the presence of typical dense-cored vesicles (diameter 1430–3200 Å) in the cytoplasm of the chief cells. The glomus cells were densely innervated and the synapses found on their surface were probably cholinergic in type, containing agranular synaptic vesicles measuring 400–700 Å in diameter with a few dense-cored vesicles measuring 900 to 1300 Å. Synapses were not found in any other cell type within the glomus caroticum. The prominent feature of the glomus cell cytoplasm was the presence of the dense-cored vesicles. The density of the vesicular core varied only slightly from cell to cell. There were no perceptible differences in vesicular size between the different cells. The glomus cells were mostly surrounded by the processes of the sustentacular cells, which usually also surrounded the capillary walls. No glomus cells were ever found in direct contact with the capillary wall. The capillaries were wide and very numerous over the restricted area of the organ. They formed sinusoidal loops, probably anastomosing with each other. Finally, the features of the fine structure are discussed, correlating the present findings with our knowledge about the adult functional carotic body.     

Anatomical basis of the risk of injury to the right laryngeal recurrent nerve during thoracic surgery

Purpose

Despite the intrathoracic part being short, the right laryngeal recurrent nerve is often injured during thoracic surgery. The aim of this cadaver study was to understand the mechanisms of right laryngeal recurrent nerve injuries during thoracic surgery and to describe anatomical landmarks for its preservation.

Methods

Dissections were performed on 10 fresh human cadavers. A right anterolateral thoracic wall segment was removed, preserving the first rib. Dissections were carried out to identify the following structures: first rib, esophagus, trachea, right main bronchus, right brachiocephalic and subclavian vessels, azygos vein, phrenic nerve, vagus nerve, and right laryngeal recurrent nerve.

Results

The distance between the origin of the right laryngeal recurrent nerve and its adjacent structures was assessed. Moderate traction of the thoracic part of the vagus nerve resulted in a downward translation of the right laryngeal recurrent nerve’s origin. In such conditions, the right laryngeal recurrent nerve’s origin was distant of 14.8?mm (±2.89?mm) from the subclavian artery.

Conclusions

Intraoperative incidence of right laryngeal recurrent nerve direct injury could be decreased by understanding the detailed course of its intrathoracic part. Moreover, traction on the intrathoracic part of the right vagus nerve may result in indirect lesions of the right laryngeal recurrent nerve: stretch induced lesions and nerve vasculature’s lesions.     

Ultrastructural characteristics of glomus cells in the external carotid artery during larval development and metamorphosis in bullfrogs,Rana catesbeiana

Electron microscopic observations of the external carotid artery in the larvae of the bullfrog, Rana catesbeiana, showed that glomus cells are present in the subendothelial stroma of the septum between the expanded region of the external carotid artery and the carotid arch. There were some differences in the ultrastructure of the glomus cells at each stage of larval development. At the early stages (stages I, III, V, X), most glomus cells were isolated and free from the covering of a supporting cell. The cytoplasm of the glomus cells contained fewer dense-cored vesicles. No synaptic junctions were observed. At the middle stages (stages XV, XX, XXI), some glomus cells showed a tendency to form small clusters. Between adjacent cells in a cluster, gap junctions were often observed. The number of dense-cored vesicles increased remarkably. Intimate apposition of the glomus and smooth muscle cells (g-s connection) was also observed. Nerve terminals containing clear vesicles were observed in synaptic contact with glomus cells at this phase. At the metamorphic climax (stages XXII–XXV), in addition to g-s connections, the glomus cells made intimate apposition to the cells around the glomus cells. The afferent synapses described in other amphibians were not encountered in this study. These findings suggest that the glomus cells at the early stages of development are nonfunctional, the vascular regulation via the g-s connection starts at the middle stages, and the chemoreception starts after metamorphosis. © 1992 Wiley-Liss, Inc.     

The occurrence of melanosomes in the newt glomus cell

Combined light and electron microscopic observations of the carotid labyrinth of the newt, Cynops pyrrhogaster, revealed the occurrence of glomus cells with melanosomes (MG cells), a finding so far unreported in the amphibian carotid labyrinth. These melanosomes, which derived from melanophores, were electron-dense and usually oval (250-700 nm in diameter). They occurred in groups enclosed by a limiting membrane, and the diameter of clusters was approximately 1.5 microns. These clusters were surrounded by a large number of dense-cored vesicles (60-100 nm in diameter), which were predominantly located in the glomus cell cytoplasm. The density of dense-cored vesicles in MG cells was higher than that in regular glomus cells (G cells).     

The effect of aging on extra-adrenal catecholamine storing cells of the rat

Cell number and catecholamine histofluorescence were determined in three extra-adrenal chromaffin tissues: the abdominal paraganglia, the carotid body and SIF (small intensely fluorescent)-cells, of male Fischer-344 rats at different ages. Catecholamines were demonstrated using the formaldehyde-induced fluorescence method. The number of paraganglia cells in the retroperitoneal area increased 13.6 fold between 3 and 33 months of age, and the volume of abdominal paraganglia approached 65% of the volume of one adrenal medulla. The emission color of some paraganglia cells shifted from greenish-yellow to yellowish-brown with aging, but differences were not observed in cell number of fluorophore color in the carotid body, a chemoreceptor type of paraganglion. The number of SIF cells (an intraganglionic variant of extra-adrenal chromaffin tissue) in the hypogastric ganglion increased significantly between 3 and 33 months. The pronounced increase of the volume of the paraganglia in aged rats may contribute to elevated concentrations of circulating catecholamines in these animals.