Morphology and ultrastructure of the adrenal gland in Bactrian camels (Camelus bactrianus)

In the present study, we examined the morphological features of the adrenal gland in Bactrian camel by means of digital anatomy, light and electron microscopy. Our findings testified that the gland was divided into three parts, capsule, cortex and medulla from outside to inside as other mammals, and the cortex itself was further distinguished into four zones: zona glomerulosa, zona intermedia, zona fasciculate and zona reticularis. Notably, the zona intermedia could be seen clearly in the glands from females and castrated males, whereas it was not morphologically clear in male. There was a great deal of lipid droplets in the zona fasciculate, while it was fewer in the zona glomerulosa and zona reticularis. The cytoplasm of adrenocortical cell contained rich mitochondria and endoplasmic reticulum. The adrenal medulla was well-developed with two separations of external and internal zones. The most obvious histological property of adrenal medulla cells were that they contained a huge number of electron-dense granules enveloped by the membrane, and so medulla cells could be divided into norepinephrine cells and epinephrine cells. Moreover, the cortical cuffs were frequently present in adrenal gland. Results of this study provides a theoretical basis necessary for ongoing investigations on Bactrian camels and their good adaptability in arid and semi-arid circumstances.     

Morphological evidence for a close interaction of chromaffin cells with cortical cells within the adrenal gland

Summary The adrenal medulla appears to exert a regulatory influence on adrenocortical steroidogenesis. We have therefore studied the morphology of rat, porcine and bovine adrenals in order to characterize the contact zones of adrenomedullary and adrenocortical tissues. The distribution of chromaffin cells located within the adrenal cortex and of cortical cells located within the adrenal medulla was investigated. Chromaffin cells were characterized by immunostaining for synaptophysin and chromogranin A, both being considered specific for neuroendocrine cells. Cortical cells were characterized by immunostaining for 17-hydroxylase, an enzyme of the steroid pathway. Cellular contacts of chromaffin cells and cortical cells were examined at the electron microscopical level. In rat and porcine adrenals, rays of chromaffin cells, small cell clusters and single chromaffin cells or small invaginations from the medulla could be detected in all three zones of the cortex. Chromaffin cells often spread in the subcapsular space of the zona glomerulosa. In porcine and bovine adrenals, 17-hydroxylase immunoreactive cells were localized within the medulla. Single cortical cells and small accumulations of cells were spread throughout this region. At the ultrastructural level, the chromaffin cells located within the cortex in pig and rat adrenals formed close cellular contacts with cortical cells in all three zones. Our morphological data provide evidence for a possible paracrine role of chromaffin cells; this may be important for the neuroregulation of the adrenal cortex.     

Immunohistochemical localization of 3 beta-hydroxysteroid/delta 5-delta 4-isomerase, tyrosine hydroxylase and phenylethanolamine N-methyl transferase in adrenal glands of sheep fetuses throughout gestation and in neonates.

Immunoreactive 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4-isomerase (3 beta-HSD) was localized in adrenal glands of sheep fetuses in cortical-type cells, but not in medullary-type cells, from day 43 of gestation to term and in 2-4-day-old neonates. From day 54 of gestation, the formation of distinct zones within the adrenal cortex was apparent and immunoreactive 3 beta-HSD was found in cortical cells in the zona fasciculata and in groups and cords of cortical cells within the developing medulla, with weak positive staining in the zona glomerulosa. At this stage, most medullary cells were positive for immunoreactive tyrosine hydroxylase, and some of these cells with a juxtacortical distribution also stained positively for immunoreactive phenylethanolamine N-methyl transferase (PNMT). Between days 65 and 130, the adrenal medulla increased in size with little change in the width of the cortex. Organization and zonation of immunoreactive 3 beta-HSD staining cells were evident in the zona fasciculata and in groups of cells in the medulla. Between day 130 and term, uniform immunoreactive 3 beta-HSD staining was found throughout the zona fasciculata, and there was also staining in single cells and small clusters of cells throughout the medulla. At this stage, immunoreactive tyrosine hydroxylase was distributed in most cells throughout the medulla, but in two distinct patterns: cells staining intensely for immunoreactive tyrosine hydroxylase in the central region of the medulla, and cells exhibiting weaker staining for immunoreactive tyrosine hydroxylase localized in a juxta-cortical position. These juxta-cortical cells were also positive for immunoreactive PNMT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Immunohistochemical localization of adrenal ferredoxin and distribution of adrenal ferredoxin and cytochrome P-450 in the rat adrenal

Adrenal ferredoxin, the iron-sulfur protein associated with cytochromes P-450 in adrenocortical mitochondria, has been localized immunohistochemically at the light microscopic level in rat adrenals by employing rabbit antiserum to bovine adrenal ferredoxin in both an unlabeled antibody peroxidase-antiperoxidase method and an indirect fluorescent antibody method. When sections of rat adrenals were exposed to the adrenal ferredoxin antiserum in both procedures, positive staining for adrenal ferredoxin was observed in parenchymal cells of the three cortical zones but not in medullary chromaffin cells. Marked differences in the intensity of staining, however, where observed among the three cortical zones: the most intense staining being found in the zona fasciculata, less in the zona reticularis, and least in the zona glomerulosa. Furthermore, differences in staining intensity were also observed among cells within both the zona fasciculata and the zona reticularis. In agreement with these immunohistochemical observations, determinations of adrenal ferredoxin contents by electron paramagnetic resonance (EPR) spectrometry in homogenates prepared from capsular and decapsulated rat adrenals revealed that the concentration of adrenal ferredoxin in the zona glomerulosa was lower than that in the zona fasciculata-reticularis. Similar results were obtained when the contents of cytochrome P-450 were determined in capsular adn decapsulated rat adrenal homogenates. These observations indicate that adrenal ferrodoxin and cytochrome P-450 are not distributed uniformly throughout the rat adrenal cortex.     

Immunohistochemical localization of adrenal ferredoxin in bovine adrenal cortex.

Adrenal ferredoxin, the iron-sulfur protein associated with cytochrome P-450 in adrenocortical mitochondria, has been localized at the light microscopic level in bovine adrenal cortex. Localization was achieved through the use of rabbit antiserum to bovine adrenal ferrodoxin in an unlabeled antibody peroxidase-antiperoxidase method. When sections of bovine adrenal glands were exposed to the adrenal ferredoxin antiserum, intense staining was observed in parenchymal cells of the three cortical zones. Staining for adrenal ferredoxin was not detected in the medullary chromaffin cells. The presence of adrenal ferredoxin in the three cortical zones was verified by electron paramagnetic resonance spectrometry. These determinations also revealed that while the zona fasciculata and the zona reticularis contained approximately equal concentrations of adrenal ferredoxin, the concentration of the iron-sulfur protein in the zona glomerulosa was considerably lower. Similar results were obtained when the levels of cytochrome P-450 were determined in the three cortical zones. These results represent the first immunohistochemical localization within an intact tissue or cell of any component of an NADPH-dependent electron transport sequence which is responsible for the reduction of cytochrome P-450.     

Immunohistochemical localization of oxytocin and vasopressin in the adrenal glands of rat,cow, hamster and guinea pig

Summary The distribution of oxytocin and vasopressin in the adrenals of rat, cow, hamster and guinea pig has been studied by use of immunohistochemical techniques. In all the species studied the adrenal cortex contained both peptides; the staining in the zona glomerulosa being more intense than that in zona fasciculata or zona reticularis. The medulla, however, showed considerable species variation. In the cow, both peptides appear to be present in the adrenergic and noradrenergic cells, though staining was particularly prominent in cortical islands interspersed within the medullary tissue. In the rat, groups of medullary cells positive for both peptides were found, though it was not possible to associate these groups with particular chromaffin cell types. In the hamster oxytocin was present only in adrenaline-containing cells, whereas vasopressin was present in all medullary cells. The guinea pig medulla, which contains only adrenaline-secreting cells, was positive for both peptides. The possibilities that vasopressin and oxytocin have an autocrine or paracrine role in functioning of the adrenal gland is discussed.     

Histochemical localization of monoamine oxidase types A and B in the adrenal gland

Summary The distribution of monoamine oxidase types A and B within the adrenal galdn was studied in several mammals by histochemical methods. Controls showed that the methods were valid. The bovine adrenal medulla contained mostly the B type enzyme, distributed heterogeneously, with some A type associated with endothelium, nerves, and cells surrounding the nerves. The bovine adrenal cortex showed a marked zonation of the two types of monoamine oxidase. The zona glomerulosa contained the B type enzyme and the zona fasciculata and zona reticularis contained the type A enzyme. The adrenal medulla of the dog, cat, and rat demonstrated relatively little enzyme activity and it appeared to be both type A and B. The adrenal cortex of these animals appeared to contain mostly the B type enzyme, except the canine zona reticularis, which contained some A type monoamine oxidase as well.     

Morphometric and histological studies on the adrenal glands of the camel Camelus dromedarius

The adrenal gland of the camel consists of an outer cortex and an inner medulla. The general disposition of the cortex and medulla, however, differs occasionally from that of other mammals. Extensions of medulla could reach as far as the periphery of the cortex. Islet of medullary tissue may be found in sections of the cortex and cortical tissue consisting of all zones of the cortex may occur around arteries or nerves in the medulla. The medulla may be separated from the cortex by connective tissue especially in old camels. The arrangement of noradrenaline-secreting cells is different from that in other ruminants; they are found in groups scattered between the adrenaline-secreting cells. Bundles of smooth muscle occur in venules at the corticomedullary interface. Accessory adrenal glands are found embedded in the renal fat. They are similar in structure to the adrenal gland. The adrenal cortex forms 74% of the volume of the gland and the ratio of the cortex to medulla is 4:1. The zona glomerulosa, fasciculata and reticularis constitute about 13%, 53%, and 29% by volume of the cortex, respectively.     

Alteration of Subcapsular Adrenocortical Zonation in Humans with Aging: The Progenitor Zone Predominates over the Previously Well-Developed Zona Glomerulosa after 40 Years of Age

Few studies have examined functional adrenal zonation throughout human life. Adrenals from 61 surgical/autopsy patients from 1 day old to 92 years old who had no clinical endocrinological/mineralocorticoid abnormalities were assessed for immunohistochemically defined adrenal zonation. The zona glomerulosa (zG) was well developed in all 11 patients ranging in age from newborn to the 30s. After 40 years of age, however, the zG occupied less than one-quarter of the adrenal circumference, suggestive of zG involution. The other subcapsular areas were occupied by the progenitor zone (zP), which expressed neither cytochrome P450_aldo nor P450_11β but 3β-hydroxysteroid dehydrogenase and P450scc, although some autopsy cases had adrenals with zG zonation because of secondary aldosteronism, and others who had experienced severe stresses showed subcapsular zona fasciculata (zF). In conclusion, the adrenal cortex consists of homogeneous zG-topped columns from birth to adolescence. Subsequently, in the fifth decade of life, the cortex is reconstituted by integration of three types of cortical columns: scattered zG-topped columns and zonal zP-topped columns, the latter having the ability for bidirectional differentiation into either zG-topped columns or zF-topped columns, according to secondary aldosteronism or the presence of severe stresses. Such adrenocortical remodeling is ascribed to high-sodium/low-potassium diets.     

Ultrastructural study on the hypothalamic-hypophysial-adrenal axis in fetal rats

Summary The adrenal glands of decapitated and encephalectomized fetal rats were investigated electron microscopically and compared to those of normal intact fetal rats. Although the adrenal cortices did not show three zones (zona glomerulosa, fasciculata, and reticularis) on the 16.5th day of gestation when the decapitation or encephalectomy was carried out in utero, the zonation was recognized in fetuses operated on the 21.5th day of gestation. The same was true for normal control fetuses. However, cytoplasmic characteristics suggesting steroidogenesis in the cortical cells were reduced to various degrees in the encephalectomized or decapitated fetuses, especially in the latter ones. The change in cytoplasmic appearance was more conspicuous in the inner portion of the cortex. This result suggests that for the maintenance of normal adrenocortical function the hypothalamus may be indispensable even during the prenatal life of rats.     

Nuclear roles in the postconjugant development of the ciliated protozoan Euplotes aediculatus. 1. Evidence for sequential roles of the differentiating macronucleus in exconjugant development

Thin-section and freeze-fracture data retrieved from developing fetal adrenals of mouse, rabbit, and rat reveal that gap junctions which appear as cortical and medullary cells morphogenetically assort themselves. In the presumptive zona fasciculata and reticularis communicating junctions develop between neighboring cells just prior to the onset of steroidogenesis. In the rodents, gap junctions assemble in large, particle-free formation plaques 1 day before the proliferation of smooth endoplasmic reticulum and the vesiculation of mitochondria (morphological features which are indicative of steroidogenesis). Similar observations have been obtained in fetal rabbits, but here gap junctions apparently develop in the absence of formation plaques. In each species, gap junctions apparently develop 1 or 2 days prior to a surge in corticosteroid production, suggesting that the formation of communicating junctions during the early phases of adrenal cortical differentiation may provide an avenue to coordinate steroidogenesis in the developing fetal cortex.     

Immunohistochemical studies on electron transport proteins associated with cythochromes P-450 in steroidogenic tissues II. Microsomal NADPH-cytochrome c reductase in the rat adrenal

NADPH-cytochrome c reductase (NADPH : ferricytochrome oxido-reductase, EC 1.6.2.4), the flavoprotein which mediates the NADPH-dependent reduction of cytochromes P-450 in adrenocortical microsomes, has been localized immunohistochemically at the light microscopic level in rat adrenal glands. Localization was achieved through the use of sheep antiserum procued against purified, trypsin-solubilized rat hepatic microsomal NADPH-cytochrome c reductase in both an unlabeled antibody peroxidase-antiperoxidase techniques and an indirect fluorecent antibody method. The sheep antibody to rat hepatic microsomal NADPH-cytochrome c reductase concomitantly inhibited the NADPH-cytochrome c reductase and progesterone 21-hydroxylase activities catalyzed by isolated rat adrenal microsomes. When sections of rat adrenal glands were exposed to the reductase antiserum in both immunohistochemical procedures, positive staining for NADPH-cytochrome c reductase was observed in parenchymal cells of the three cortical zones but not in medullary chromaffin cells. The intensity of staining, however, was found to differ among the three cortical zones, with the most intense staining being found in the zona fasciculata and the least in the zona glomerulosa. The intensity of staining was also found differ among cells within the zona fasciculata. These immunohistochemical observations demonstrate that microsomal NADPH-cytochrome c reductase is not distributed uniformly throughout the rat adrenal cortex.     

Light and electron microscopic evidences of the presence of c-fos-like immunoreactivity in the rat adrenal cortex

The presence and localization of c-fos-like immunoreactivity in the rat adrenal cortex has been demonstrated by immunocytochemical methods at both light and electron microscopic level. C-fos-like immunoreactivity was detected in the zona fasciculata and the zona reticulata, but not in the zona glomerulosa. Ultrastructurally, all products of c-fos-like immunoreaction were localized exclusively in the regions associated with the euchromatin in the nucleus of the immunoreactive cells. Moreover, a higher density of the immunoreactive cells in the adrenal cortex of pregnant rats was found with quantitative immunocytochemistry as compared to the non-pregnant. The characteristic zonation of c-fos-like immunoreactivity in the adrenal cortex suggest that the c-fos protein is involved in the normal function of the glucocorticoid-producing cells of mammalian adrenals. The numerical increase in the immunoreactive cells in pregnant rats implies that basal expression of the c-fos-like protein may vary with the functional state of the cortical cells.     

Light and electron microscopic evidences of the presence of c-fos-like immunoreactivity in the rat adrenal cortex

Summary The presence and localization of c-fos-like immunoreactivity in the rat adrenal cortex has been demonstrated by immunocytochemical methods at both light and electron microscopic level. C-fos-like immunoreactivity was detected in the zona fasciculata and the zona reticulata, but not in the zona glomerulosa. Ultrastructurally, all products of c-fos-like immunoreaction were localized exclusively in the regions associated with the euchromatin in the nucleus of the immunoreactive cells. Moreover, a higher density of the immunoreactive cells in the adrenal cortex of pregnant rats was found with quantitative immunocytochemistry as compared to the non-pregnant. The characteristic zonation of c-fos-like immunoreactivity in the adrenal cortex suggest that the c-fos protein is involved in the normal function of the glucocorticoid-producing cells of mammalian adrenals. The numerical increase in the immunoreactive cells in pregnant rats implies that basal expression of the c-fos-like protein may vary with the functional state of the cortical cells.     

Development of zonular patterns in the human adrenal gland

Microscopic studies of human adrenal glands from 58 autopsy specimens, ranging in age from one month gestation to 69 years, revealed a pertinent developmental pattern in the establishment of definitive zonation. This pattern was established using the following criteria: (1) relationship of age to the developing zones; (2) times of formation of definitive zonation; and (3) the morphological determination of developmental patterns based on staining characteristics. Using these criteria, development was divided into five phases: (1) condensation of coelomic epithelium; (2) secondary proliferation of coelomic epithelium; (3) finding of PAS-positive material within the fetal cortex; (4) decline and disappearance of the fetal cortex; and (5) establishment and stabilization of the definitive zonular patterns. Significant features occurring in this development were: (1) the origin of both permanent and fetal cortex from proliferation of coelomic epithelium; (2) the appearance of PAS-positive granules surrounding a homogenous mass in the fetal cortex and the zona reticularis during maturation and organization; and (3) the gradual establishment of definitive zones by proliferation of the permanent cortex, maturation of the fetal cortex, and growth of the medulla; with the adult structure of the adrenal gland achieved by the eleventh to fifteenth year without any apparent major involution or hemorrhage.     

Sex differences in adrenocortical structure and function

Summary The zonation and cellular composition of the adrenal cortex of intact mature male and female rats of different strains (Chbb Thomm, CFY) and three strains of Wistar rats (W1, W2 and W3) at the age of 84–90 days were compared using morphometry.Both absolute and relative adrenal gland weights were higher in female than male rats. Rats of W3 and Chbb Thomm strains had the largest adrenals. These differences depended upon the higher volume of the zona fasciculata (ZF) and zona reticularis (ZR) in the W3 and Chbb Thomm strains than in the remaining animals. Females had larger adrenocortical zones than corresponding males. The average volume of the ZF cell ranged in males from 1589 m³ (W1 strain) to 2111 m³ (Chbb Thomm) and in females from 2249 m³ (W1 strain) to 2894 m³ (W3 strain). The average nuclear volume of the ZF cells was higher in female rats whereas there were no strain-and sex-differences in the size of zona glomerulosa (ZG) and ZR cells.The total number of parenchymal cells per pair of adrenals varied markedly among the studied strains, with the highest number in W3 and Chbb Thomm females. W3, Chbb Thomm and CFY females had larger number of parenchymal cells than males; the reverse was true for W1 strain whereas no differences were found among W2 male and female rats.     

Regional responsiveness of renal perfusion to activation of the renal nerves

We tested for regional differences in perfusion responses, within the renal medulla and cortex, to renal nerve stimulation in pentobarbital sodium-anesthetized rabbits. Laser-Doppler flux (LDF) was monitored at various depths below the cortical surface (1-15 mm). Basal cortical LDF (1-3 mm, approximately 200-450 U) was greater than medullary LDF (5-15 mm, approximately 70-160 U), but there were no statistically significant differences in basal LDF within these regions. The background LDF signal during aortic occlusion was similar in the cortex (2 mm, 31 U) and outer medulla (7 mm, 31 U), but slightly greater in the inner medulla (12 mm, 44 U). During electrical stimulation of the renal nerves (0.5-8 Hz), cortical LDF and total renal blood flow were similarly progressively reduced with increasing stimulus frequency. Medullary LDF (measured between 5 and 15 mm) was overall less responsive than cortical LDF. For example, 4-Hz stimulation reduced inner medullary LDF (9 mm) by 19 +/- 6% but reduced cortical LDF (1 mm) by 54 +/- 11%. However, medullary LDF responses to nerve stimulation were similar at all depths measured. Our results indicate that while the vascular elements controlling medullary perfusion are less sensitive to the effects of electrical stimulation of the renal nerves than are those controlling cortical perfusion, sensitivity within these vascular territories appears to be relatively homogeneous.     

Immunohistochemical localization of the somatostatin receptor subtype 2A in the rat adrenal gland

The immunohistochemical localization of the somatostatin receptor subtype sst2A was investigated in the rat adrenal gland using SS-800 polyclonal antibody. The sst2A immunopositivity was found in all adrenocortical zones and in adrenal medulla, the reaction being slightly more intense in zona glomerulosa and medulla. The administration of the potent agonist of sst2 receptors - octreotide - resulted in the enhancement of the immunopositivity in zona glomerulosa and medulla, whereas chronic exposure of the rats to diethylstilbestrol led to enhancement of the immunopositivity in zona glomerulosa and in the external part of zona fasciculata.     

Effect of Oxotremorine on Ornithine Decarboxylase Activity of the Adrenal Gland in Rat

Abstract: In this work we have studied the mechanism for the increase of adrenal ODC (ornithine decarboxylase, EC 4.1.1.17) activity provoked by oxotremorine, a muscarinic agonist. 1. Oxotremorine increased medullary ODC activity maximally at 2 h. Cortical enzyme responded much more slowly. 2. Blockade of peripheral muscarinic receptors with methylatropine partially reduced the response to oxotremorine in the medulla, but not cortex. 3. Hy-pophysectomy abolished the cortical, but not the medullary, responses to oxotremorine. Methylatropine reduced the effect of oxotremorine on medullary ODC in hypophysectomized rats. 4. In unilaterally splanchnicotomized rats oxotremorine caused an increase of ODC activity of the denervated adrenal gland relative to control value; activities in both medulla and cortex were significantly lower than those observed in the innervated gland. Evidence was obtained for a compensatory increase of ODC activity of the adrenal cortex (but not medulla) on the intact side of unilaterally operated rats. 5. Surgical intervention, in the form of a sham operation for transection of the spinal cord, leads to an increase of ODC activity in both parts of the adrenal gland. Transection of the cord attenuates these increases. 6. The additional increase of medullary ODC activity owing to the administration of oxotremorine to sham-operated rats is partially reduced in the adrenal medulla by muscarinic blockade, and completely in the cortex. This effect of methylatropine in regard to cortical ODC activity was not apparent in the other experiments with intact or unilaterally splanchnicotomized (unoperated side) rats. The results with unilaterally splanchnicotomized rats and those with transected spinal cord suggest that oxotremorine-induced modifications of adrenal ODC activity are centrally mediated, above the level of origin of the splanchnic nerves in the spinal cord (T_8–10). Experiments with hypophysectomized rats show that the response of the adrenal cortex to oxotremorine is entirely mediated by the hypophysis.