Immunophenotyping and spatio-temporal distribution of aortic cell clusters in the bovine embryo.

In the present study the temporal and spatial appearance of aortic cell clusters in bovine embryos is described. Aorta-associated c-kit-positive cell clusters can be observed first in 23 days post inseminationem (dpi) bovine embryos and disappear after 34 dpi. For the first time, it was shown that the immunophenotype of these aortic cluster cells changes during embryonic development. Aortic cell clusters are c-kit+/CD45-/STA-, when they are first detected in the 23 dpi embryo, and acquire a c-kit+/CD45+/STA- phenotype in 27-29 embryos and a c-kit+/CD45+/STA+ immunophenotype in 32-34-day-old specimens. Cell clusters are most prominent in the vicinity of lateral and ventral aortic branches, but rare in omphalomesenteric arteries and absent in Aa. umbilicales. Free c-kit-positive cells in an intravasal position are common, suggesting separation from the clusters in order to colonize subsequent hematopoietic organs, i.e., the liver and the mesonephros. Transmission electron microscopic analysis reveals the existence of primitive desmosomes between the clusters cells and adjacent endothelial cells as well as a fine basal lamina as a demarcation between the cluster cells and underlying mesenchymal cells. Material resembling extracellular matrix is found in large vacuoles in cluster cells of 23 dpi embryos. Immunocytochemistry reveals an intense accumulation of heparan sulfate proteoglycan and collagen IV in the aortic wall at the sites where cell clusters are attached. These observations suggest that the hematopoietic cell clusters induce the formation of a specific microenvironment within the aortic wall.

Unusual metastasis of malignant aortic body tumor to multiple bones in a dog.

Unusual metastasis of malignant aortic body tumor to multiple bones was detected in a 5-year-old female English Setter dog. Radiographs exhibited an abnormal mass in the base of heart and osteolytic lesions in the bodies of T11 and L2 vertebrates, body of right femur, right proximal humoral epiphysis and infraspinous fossa near to the neck of right scapula. At necropsy, multiple tumor masses of various sizes were observed also in the bones as well as the heart base and tracheobronchial lymph node. Tumor masses of L2 and T11 protruded into the vertebral canal and compressed corresponding sites of spinal cord, leading to paraplegia. Histopathologically, the tumor cells, arranged in sheets or nests, were polyhedral, lightly eosinophilic, finely granular cytoplasm with mostly round to oval nucleus and had scattered bizarre giant cells. Ultrastructural study revealed the characteristic findings that tumor cells contained a large number of small, electron-dense, membrane-limited secretory granules in cytoplasm. This is thought to be an extremely rare case having multiple bone metastases of a malignant aortic body tumor.

Spatial relationships of enteric nerve fibers to vagal motor terminals and the sarcolemma in motor endplates of the rat esophagus: a confocal laser scanning and electron-microscopic study.

Enteric co-innervation of motor endplates in the rat esophagus was studied with confocal laser scanning and electron microscopy. Enteric fibers were demonstrated with immunocytochemistry for nitric oxide synthase, vasoactive intestinal peptide or NADPH-diaphorase histochemistry. Vagal motor terminals were identified with calcitonin gene-related peptide (CGRP) immunocytochemistry. Teloglia was stained with immuno- cytochemistry for S100, and TRITC-tagged alpha-bungarotoxin was used to delineate endplate areas in immmunofluorescence preparations. Both confocal imaging and electron microscopy revealed intimate relationships between enteric and vagal terminals on the one hand, and enteric terminals and the sarcolemma on the other. In addition, electron microscopy could point out direct apposition of a significant proportion of enteric varicosities to vagal motor terminals without intervening teloglial processes. These morphological data are compatible with pre- and postsynaptic modulatory effects of enteric neurons on vagal neuromuscular transmission in striated esophageal muscle.

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.

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.

Aortic body chemoreceptor responses to dopamine, haloperidol, and pargyline.

Aortic chemoreceptor activity, from single- or few-fiber afferent nerve preparations, was measured in response to dopamine and a dopaminergic blocker, haloperidol, in 18 anesthetized cats. In six of these cats the effect of dopamine was assessed before and after inhibiting monoamine oxidase (MAO) by pargyline. Intravenous dopamine infusion (7-14 microgram X kg-1 X min-1) had a generally inhibitory effect on aortic chemoreceptor activity, but the magnitude of this effect varied with arterial partial pressure of O2 (Pao2) levels. The inhibitory effect of dopamine increased as Pao2 levels fell, and at severely hypoxic Pao2 levels (below 30 Torr) exogenous dopamine had no significant effect. The inhibitory effect of dopamine also increased during hyperoxic hypercapnia. Blockade of dopamine receptors in the aortic body by haloperidol-stimulated chemoreceptor activity significantly during hypoxia, suggesting an O2-dependent release of dopamine from the aortic body as Pao2 falls. Inhibition of MAO by pargyline had no significant effect on the control rate of activity at any level of Pao2 but augmented the inhibitory effect of exogenously administered dopamine. These data indicate that MAO is not significantly involved in the degradation of endogenous dopamine at the aortic receptor sites, but may participate in the degradation of exogenous dopamine.

Aortic body tumours and hyperplasia in the rat.

The histologic features of aortic body neoplasia, hyperplasia, and normal aortico-pulmonary paraganglia were described for a series of 56 rats of several strains. Argyrophilic cytoplasmic granules were demonstrated in chief cells of the aortic body lesions, and electron microscopic examination disclosed the presence of electron-dense, membrane-bound granules in these cells. In a series of ageing rats, hyperplasia and neoplasia of the aortico-pulmonary paraganglia occurred more frequently in female WAG/Rij rats than in males of that strain, and more frequently than in males and females of the BN/Bi strain or of the (WAG X BN)F1 hybrid. No apparent causal relationship to chronic hypoxia could be shown, in that no correlation between the development of aortic body neoplasia or hyperplasia and cardiopulmonary disease was found. Aortic body lesions did not appear to occur as part of a multiple endocrinopathy syndrome, although hyperplasia and neoplasia of various endocrine organs occurred relatively frequently in the WAG/Rij strain.

Calcium binding sites in the vesicles of the carotid and aortic body chief cells.

Chief cells of the carotid and aortic body chemoreceptors possess numerous cytoplasmic dense-core vesicles which are known to contain primarily dopamine. Following fixation in solutions containing 50 mM CaCl2, a 20--30 nm electron-dense particle (EDP) is often observed eccentrically located in many of the vesicles. Approximately 44% of the carotid body and 16% of the aortic body vesicles contain an EDP. The EDP probably represents the Ca++ binding site critical to the stimulus-secretion coupling events culminating in exocytosis of these vesicles. The presence of Ca++ in the cytoplasmic vesicles was verified by electron probe X-ray microanalysis.

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.

Development of type I cells of the rabbit subclavian glomera (aortic bodies): a light, fluorescence and electron microscopic study.

The embryogenesis of the subclavian glomera (aortic bodies) is controversial. Past investigators have attributed the development of the Type I cells to mesodermal and/or neural elements. Based on the results of the present light microscopic, fluorescence histochemical and electron microscopic study of rabbit aortic bodies from 16 days of gestation (term:31 days) to four days postpartum, it appears that the Type I glomus cell are derived from cells of neural crest origin. The subclavian anlage is associated with cells of neural crest origin. The subclavian glomus anlage is associated with cells of vagal origin throughout its development. Evidence of Type I cell development from pre-existing mesodermal condensations is not observed. Type I cells exhibit formaldehyde-induced-fluorescence by the twentieth day of gestation. Dense-cored cytoplasmic vesicles are apparent by the sixteenth day of gestation. The number of cytoplasmic vesicles increases steadily, but the greatest increase of vesicles is observed between the twenty-eighth day of gestation and birth. Primitive Type I glomus cells exhibit abundant polysomes and rough endoplasmic reticulum indicative of synthetic activity. Nerve terminals are apparent adjacent to Type I cells by the twentieth day of gestation, but synaptogenesis does not occur until sometime between the twenty-fourth and twenty-eighth days of gestation. Abundant vascularity, characteristic of chemosensory glomera, is not achieved until the twenty-eighth day of gestation.

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.

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.

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.