Comparative cytomorphology of the avian adrenocortical tissue.

The histology and histochemistry of the interrenal gland of twenty avian species have been described in this report. The avian interrenal tissue, on the basis of nuclear orientation and other cytomorphic features, can be classified into six cytologically distinct types. Cytomorphic organization within the interrenal tissue of these avian species also indicates some regional demarcation into subcapsular and central zones. Zonal demarcation in the interrenal tissue of these birds has also been indicated from chemocytological investigation. Paradoxically not much of correspondence was noticed in the cytologic and cytochemical patterns. The cytological and cytochemical studies fail to indicate any phylogenetic trend within the interrenal tissue of the birds under investigation.     

Osmolality and volume factors in salt gland control of pekin ducks after adaptation to chronic salt loading

Summary Pekin ducks were adapted to permanent osmotic stress by rearing them on a NaCl solution of increasing concentration up to 2% as drinking water. Their salt and water balance was compared with that of non-adapted ducks maintained on tap water. Amounts and osmolalities of salt gland secretion and cloacal discharges, plasma osmolality and electrolytes were measured during stepwise osmotic loading by intravenous infusion of NaCl solution of about 740 mosm·kg^–1, at rates of 0.25, 0.45 and 0.65 ml·min^–1. Before loading, the plasma osmolality of the adapted ducks was about 22 mosm·kg^–1 higher than in non-adapted animals. The initial step of loading induced salt gland secretion in the adapted ducks after an average rise of plasma osmolality of 3.6 mosm·kg^–1 and in the non-adapted animals after a rise of 7.8 mosm·kg^–1. The method of osmotic loading enabled both groups of animals to balance their water input and output. However, only the adapted ducks were able to balance NaCl input and output, predominantly by salt gland secretion, thus maintaining a stable plasma osmolality. The nonadapted ducks retained 42% of the salt load which resulted in a rise of plasma osmolality of 49 mosm·kg^–1, more salt being excreted by the kidneys than by the salt glands.In the salt-adapted ducks, salt gland activity, plasma osmolality and Na⁺ concentration did not correlate during balanced states of salt input and output. The involvement of tonicity receptors in salt gland control was confirmed by the stimulating effects of various hypertonic solutions. On the other hand, continuous loading by a constant infusion of NaCl solution of 1,300 mosm·kg^–1 induced a steady salt gland secretion at a rising plasma osmolality and thus suggested that a volume factor is involved in salt gland control. Inhibition of salt gland activity by withdrawing blood and activation by blood infusion confirmed this assumption. While a direct cause and effect relationship between volume changes and salt gland secretion cannot be demonstrated, the results indicate that volume changes in one or more extracellular compartments do affect salt gland secretion.Supported by Deutsche Forschungsgemeinschaft (Si 320/2)     

The duct system of the avian salt gland as a transporting epithelium: structure and morphometry in the duck Anas platyrhynchos

Summary The duct system of the nasal salt gland of the duck comprises central canals, secondary ducts and main ducts. The secondary and main ducts consist of a layer of columnar cells overlying a layer of small cuboidal cells. The columnar cells have complex intercellular spaces showing evidence of Na⁺ K⁺ -ATPase at the apical regions. Approximately 70% of surface area of the duct system is external to the gland. During adaptation to salt water the duct system increases in size as does the gland. Although the components of the gland of adapted ducks, including the duct system within the gland, increase in size compared with normal ducks, the percentage volume densities of the components remain similar in both categories of ducks, i.e. the duct system increases in size in proportion to the glandular tissue. The volume of the duct system external to the gland is six to seven times larger than the volume within the gland. Thus, if ductal modification of secreted fluid occurs, it will be most likely to take place in the ducts external to the gland.Total surface areas of the duct system were measured from serial sections of glands and ducts from one normal and one adapted duck. These were used to calculate possible flux rates of water and sodium across the duct epithelium, assuming the occurrence of either water reabsorption or sodium secretion. Although these flux rates are high it is shown that they are similar to calculated flux rates across the luminal surface of the secretory tubules.     

Seasonal study of the adrenal gland of some Indian avian species.

Adrenal glands of eight Indian species of birds, namely Columba livia, Passer domesticus, Corvus splendens, Acridotheres tristis, Acridotheres ginginianus, Milvus migrans, Francolinus pondicerianus and Bubulcus ibis were examined during the sexually active and inactive phases of their annual reproductive cycles. Excepting A ginginianus and M. migrans, among members of either sex of the remaining six species the weight of the adrenal gland increases during the period of sexual activity. Histologically, the interrenal tissue of these birds could be divided into a peripheral subcapsular zone and a central zone. The cytochemical content of these two zones varies between sexual activity and inactivity. In sexually active birds of both sexes, interrenal cells of the central zone exhibit an increased concentration of alkaline phosphatase, glycogen, acid mucopolysaccharides and gross lipids, while in the subcapsular interrenal cells there is a prominent increase of ascorbic acid content. Cytochemical contents of chromaffin cells remain unchanged except acid phosphatase, which increases during the sexually active phase.     

Functional significance of interrenal cell zonation in the adrenal gland of the duck (Anas platyrhynchos)

Slices of whole adrenal gland tissue, incubated in vitro in the presence of ACTH for 1 h and 2 h produced corticosterone and aldosterone in constant ratio (16:1). Tangential slices taken from the region immediately below the connective tissue capsule and slices taken from deeper regions of the gland consisted primarily of cells conforming to the distinct structural characteristics of the subcapsular zone (SCZ) and inner zone (IZ) tissues respectively. When samples were incubated in the presence of ACTH for 1 h and 2 h, the interrenal cells of the SCZ produced relatively more aldosterone than cells taken from the IZ of the gland. The corticosterone: aldosterone ratio for the IZ after 1 h (68:1) and after 2 h (102:1) were ten times greater than the ratios for the SCZ after 1 h (7:1) and after 2 h (10:1). The SCZ slices were not more than 60 cells thick and consisted of cells arranged in cords. These cells contained irregular nuclei, mitochondria with shelf-like cristae and a moderate abundance of smooth endoplasmic reticulum. In contrast, the production of large amounts of corticosterone by the cells of the IZ was associated with tissue containing more vascular space than the SCZ and the cells contained large round nuclei surrounded by an abundance of smooth endoplasmic reticulum and the mitochondria had tubular rather than shelf-like cristae.     

Effect of ACTH and bilateral gonadectomy on the adrenocortical tissue of an air-breathing fish -- Heteropneustes fossilis (Bloch).

The mammalian ACTH (20 I.U.) injected in Heteropneustes fossilis (Bloch) caused hyperplasia of the adrenocortical tissue. The interrenal as well as chrome cells became vacuolated. The interrenal nuclear size increased by 15% as an average than the control fishes. The glycogen granules were found to be absent from the interrenal cells. The effect of bilateral gonadectomy in both sexes has been marked in the gradual decrease of the interrenal nuclear diameter which 12 weeks after the operation, recorded nearly 25% reduction in size. The glycogen content was reduced considerably. Removal of gonads during maturation period bringing inhibition of hyperplasia of the gland at the time of spawning possibly indicates action of gonadal steroids on the physiological alterations of the interrenal cells.     

Co-localization of vasoactive intestinal peptide (VIP) and enkephalins in chromaffin cells of the adrenal gland of amphibia. Stimulation of corticosteroid production by VIP

Recent studies have shown that biologically active peptides and monoaminergic neurotransmitters coexist in certain neuronal cell populations. Using the immunofluorescence technique, we have examined the localization of enkephalins, vasoactive intestinal peptide (VIP) and tyrosine hydroxylase in the adrenal gland of the frog Rana ridibunda. Most chromaffin cells which stained for tyrosine hydroxylase contained VIP-like immunoreactivity, whereas methionine- (Met-) and leucine- (Leu-) enkephalin-like immunoreactivity was detected in about 40% of the cells revealed by the anti-tyrosine hydroxylase serum. No VIP- or enkephalin-like immunoreactive nerve fibres were observed. Since in the frog, the chromaffin cells are in close contact with the adrenocortical (interrenal) tissue, a possible action of VIP and opiates on corticosteroidogenesis has been investigated. At doses 10(-6) and 10(-5) M, 20-min infusions of synthetic porcine or chicken VIP elicited a significant increase in corticosterone and aldosterone production by perifused frog adrenals, in a dose-dependent manner. As compared to ACTH, VIP was several orders of magnitude less effective in stimulating corticosteroid production. Morphine, Met- and Leu-enkephalins (10(-5) M) had no effect on spontaneous secretion of corticosteroids. In addition, Met- and Leu-enkephalins (10(-5) M) did not alter the production of corticosterone induced by ACTH. THese results suggest that VIP contained in the chromaffin cells of the frog adrenal gland may exert a local action in stimulating corticosteroid production by the interrenal tissue.     

Salt gland function in the common eider duck (Somateria mollissima)

The function of the supra-orbital salt gland was studied in the common eider duck (Somateria mollissima). The maximum salt-secreting capacity was determined in (1) wild ducks which had been living in a marine environment, (2) ducks reared in captivity on fresh water, and (3) ducks from group 2 adapted to salt water. The maximum secreting capacity was found by infusing a solution of NaCl (1000 mosmol·kg^-1) at increasing rates, from 0.691 to 1.671 mosmol·min^-1. Freshwater-adapted ducks secreted at a maximum rate of 0.785 mosmol·min^-1 (1500 mosmol·kg^-1). Adapted to salt water they increased their capacity, and the best duck secreted at a rate of 1215 mosmol·min^-1 (1600 mosmol·kg^-1). The best wild duck secreted at a rate of 1516 mosmol·min^-1. Ducks in group 3 were used to examine the response to a hyperosmotic or an isoosmotic infusion. The amount of salt (NaCl) given per unit time was the same. Given a hyperosmotic solution their salt glands secreted at a high rate: 30 min after the infusion had stopped the ducks had excreted 94% of the sodium infused, 92.9% via the salt gland. Given an isoosmotic solution they secreted at a rate about half the infusion rate: 30 min after cessation of infusion they had excreted 73% of the sodium, 42.9% via the salt gland and the rest by the kidneys.Abbreviations A II angiotensin II - AV I arginine vasotocin - ED freshwater-adapted ducks - FW fresh water - SD saltwater-adapted ducks - SW sea water - WD wild ducks     

Catecholamine hormones and the control of avian salt glands

Hypertonic saline loading (0.5 M NaCl, 15 ml.kg-1 i.v.) increased cardiac frequency and elicited nasal salt gland secretion in control ducks. Partial depletion of catecholamines by prior treatment with reserpine decreased body weight, lowered arterial pressure and abolished the tachycardiac responses to saline loading. Reserpine also increased plasma concentrations of Na, K and total osmolytes, yet altered neither the composition nor the flow rate of nasal fluid secretion. The preservation of the normal secretory responses to hypertonic stress in hypotensive, reserpine-treated ducks indicates that the nasal salt glands can function independently of changes in circulating catecholamine hormones.     

A light- and electron-microscopic investigation of gametogenesis in Typosyllis pulchra (Berkeley and Berkeley) (Polychaeta: Syllidae)

Summary The ultrastructure of the interrenal (adrenocortical) cells of trout (Salmo fario L.) was studied after dexamethasone treatment. A procedure for identifying and isolating interrenal tissue fragments from the surrounding head kidney tissue prior to their preparation for electron microscopy is described. The peripheral plasma cortisol concentrations were measured in order to evaluate the steroidogenic activity of this tissue.The interrenal cells of control animals contain numerous mitochondria with tubular cristae, and a well developed and highly organized smooth endoplasmic reticulum (SER). The scarcity, or absence, of lipid droplets contrasts markedly with the abundance of SER.Treatment with dexamethasone results in a decrease steroidogenic activity of the interrenal cells, as indicated by the fall in plasma cortisol concentrations. The interrenal cells are small, but still contain numerous mitochondria. The SER is poorly developed, but masses of densely intermeshed smooth cisternae subsist. Lipid droplets do not accumulate in these cells; this peculiarity is discussed in connection with the virtual absence of liposomes in teleost interrenal cells.     

Anteroposterior variation of the cell types in the interrenal gland of the male toad Rhinella arenarum (Amphibia,Anura)

The interrenal gland of anurans synthesizes the steroids aldosterone and corticosterone, but it is unknown whether these hormones are synthesized by the same cell type. In this work, we aim to elucidate whether there are different steroidogenic cell types and whether they have specific regionalization in the interrenal gland of the male toad Rhinella arenarum. We characterized all cell types using histological, immuhistochemical, and histochemical methods as well as transmission electron microscopy. Furthermore, we evaluated the organization of the cell types in the gland and anteroposterior variations in the synthesis of the steroids. We found evidence of five cell types: two morphologically different steroidogenic cells, type 1: polyhedral cells tightly attached to each other that have spherical euchromatic nuclei and type 2: retracted cells loosely attached to each other that have oval heterochromatic nuclei. Cell type 2 is mainly observed in the inner zone of the gland. In addition, we observed two types of chromaffin cells, called type 3 and 4 cells, randomly distributed throughout the interrenal gland, as well as type 5 cells, recognized as summer cells. Morphometric analyses of the cell types in the anterior and posterior zones of the interrenal showed that the ratio “area of type 2 cells/total interrenal area” is significantly lower in the posterior zone. In vitro incubations showed that the posterior portion of the gland produces significantly higher amounts of both corticosterone and aldosterone. Overall, our results suggest that the type 2 cells are less active to synthesize both aldosterone and corticosterone, compared to type 1 cells. Unlike most previous reports on the interrenal gland of anurans, in R. arenarum there is a zonation of the steroidogenic cell types, which implies that the organ is not anteroposterior or dorsoventrally homogeneous. © J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.     

The morphological study on the adrenal gland of African ostrich chicks

The morphology of the adrenal gland has been studied for a number of animal species all over the world, yet the detailed data about ostrich chick has not been reported. In the present study, the morphological features of the adrenal gland in African ostrich chicks were investigated by means of gross anatomy, light and electron microscope. Differences between the left and right adrenal glands were found in shape, size and location. The interrenal tissue and chromaffin cell interdigitated irregularly. The interrenal tissue was divided into a peripheral zone (PZ) and a central inner zone (CZ), and the PZ was further distinguished into an outer area (subcapsular zone, SCZ) and an inner area (IZ). The cellular arrangement in these zones showed evident zonation that resembled the mammalian. This phenomenon had been previously described only for the pelicanus. The cytoplasm of interrenal cells in SCZ was stained lightly than in IZ and CZ, and contained several vacuoles. Additionally, unlike CZ cells, SCZ cells appeared to contain more mitochondria and less lipid droplets. Two types of chromaffin cells: epinephrine cells and norepinephrine cells could be detected. The type 1 granules possessed a central core and a variable distance between membrane and core; the type 2 granules had an eccentric core, which leant to one side of granule and sticked to the membrane, giving a lager lacouna appearance in another side of the granule.     

Altered adrenal gland cholesterol metabolism in the apoE-deficient mouse

Previous studies suggest the hypothesis that apoE produced by adrenocortical cells modulates cellular cholesterol metabolism to enhance the storage of esterified cholesterol (EC) at the expense of cholesterol delivery to the steroidogenic pathway. In the present study, parameters of adrenal cholesterol metabolism and corticosteroid production were examined in wild type and apoE-deficient (apoe(-/-)) mice. Adrenal gland EC content and the EC/free cholesterol (FC) ratio in mice stressed by adrenocorticotropin (ACTH) treatment or saline injection were reduced in apoe(-/-) compared to apoe(+/+) mice. Relative to apoe(+/+) mice, apoE deficiency also resulted in increased levels of plasma corticosterone in the basal state, in response to acute or long-term ACTH treatment, and after a swim-induced neuroendocrine-directed stress test. Measurements of adrenal gland scavenger receptor class B, type I (SR-BI), LDL receptor, and LDL receptor related protein (LRP) levels and the activities of ACAT or HMG-CoA reductase showed no difference between genotypes. Apoe(-/-) and apoe(+/+) mice showed similar quantitative increases in LDL receptors, SR-BI, adrenal weight gain, and ACAT activities in response to ACTH, and both genotypes had similar basal plasma ACTH concentrations. These results suggest that the effects of apoE deficiency reflect events at the level of the adrenal gland and are specific to changes in cholesterol accumulation and corticosterone production. Further, these findings support the hypothesis that apoE acts to enhance adrenocortical EC accumulation and diminish corticosterone production.     

The effect of dehydration on the functional activity of the interrenal gland in adenohypophysectomized Rana catesbeiana frogs. A preliminary report

A significant increase of the content of corticosterone in the blood collected from intravenous cannula or by intracardiac punction has been detected using radioimmunoassay in non-operated and adenohypophysectomized frogs Rana catesbeiana subjected to dehydration in 6.2% mannitol solution during 24 hours. The osmolality of the blood plasma of these animals also increases although less significantly than the growth of plasma corticosterone content. There is a tendency to substantial increase of plasma arginine-vasotocin level prior to the growth of corticosterone level, already after 6 hours of dehydration. Based on the present results and literature data, it is suggested that in adenohypophysectomized frogs lacking endogenous ACTH just the increase of blood arginine-vasotocin level results in a substantial activation of corticosteroid-producing cells of the interrenal gland and in the growth of plasma content of corticosterone.     

Characterization and use of polyclonal antibody to Na+,K+-ATPase: immunocytochemical localization in salt glands of the duck

The amount of Na+,K+-ATPase of the avian salt gland increased concomitantly with plasma membrane surface area during salt feeding of ducklings (adaptation), and both enzyme content and membrane surface area decreased upon return to fresh water (deadaptation). In a further study of the enzyme, a marker for plasma membrane biogenesis, polyvalent antibodies were raised to the denatured alpha-subunit of the purified ATPase. Antisera did not inhibit enzymatic activity but immunoprecipitated the phosphorylated intermediate of the alpha-subunit. Furthermore, the alpha-subunit, which was not glycosylated, was immunoprecipitated from homogenates of tissue slices metabolically labelled with [35S]-methionine, using antisera raised against either duck salt gland or dog kidney alpha-subunit. The former antisera also recognized the alpha-subunit in the brain, heart, kidney, liver, intestine and skeletal muscle of the duck. Immunocytochemistry with the antisera raised to the duck salt gland alpha-subunit revealed reaction at basolateral as well as apical plasma membrane in the duck salt gland principal cells, with essentially no deposits on peripheral cells, fibroblasts, erythrocytes, endothelial cells and neural elements. Within the principal cells, immunolabelling was also detected on small vesicles, multivesicular bodies and lysosomes; deposits on extracellular debris and vesicles in the lateral and lumenal spaces were also apparent. The labelling patterns were qualitatively but not quantitatively similar in salt glands of control, adapted and deadapted ducklings, and are discussed in the context of a model for plasma membrane biogenesis and turnover in which degradative events may play a major role.     

Competitive protein-binding radioassay of corticosterone in the plasma of the frog, Rana esculenta L. (author's transl)]

1. Plasma corticosterone levels were measured in the plasma of the edible frog, Rana esculenta, by a competitive protein-binding radioassay method using baboon plasma as CBG source. 2. This technique was sensitive enough to make the assessment of corticosterone levels in 50 microliter plasma samples possible. The assay sensitivity threshold reached 0.5 ng per tube and the corticosterone rate assessment was correct between 0 and 5 ng. The specificity was tested, using 12 different steroids (fig. 2) : baboon CBG had very slight avidity for aldosterone, the second circulating steroid in frog plasma. 3. Using this technique, we have shown that plasma corticosterone underwent seasonal variations. Plasma corticosterone levels, in animals captured in nature during February and June, were 1.51 +/- 0.06 microgram/100 ml (n = 60) and 2.76 +/- 0.14 microgram/100 ml (n = 36), respectively, as appeared in table III. 4. It appeared that the interrenal gland of the frog was not totally dependent on pituitary ACTH, since total hypophysectomy reduced, but did not suppress, corticosterone secretion (table III).     

Interactions between vasotocin and other corticotropic factors on the frog adrenal gland

The adrenocortical cells of the amphibian interrenal (adrenal) gland are controlled by multiple factors including neuropeptides and classical neurotransmitters. In particular, it has recently been shown that vasotocin (AVT), the amphibian counterpart of vasopressin, is a potent stimulator of frog corticosteroidogenesis. In the present study, we have investigated the possible interactions between AVT and other regulatory factors on frog interrenal tissue. When AVT (10⁻⁹ M) and serotonin (10⁻⁶ M) were infused together, a strict addition of the individual effects was observed. Similar results were obtained with concomitant infusion of AVT and vasoactive intestinal peptide or AVT and ACTH. In contrast, when AVT (10⁻⁹ M) and acetylcholine (5 × 10⁻⁵ M) were added together, the increase in corticosteroid secretion was less than additive. Dopamine induced a significant reduction of AVT-evoked stimulation of corticosterone production. These results indicate that regulatory peptides or classical neurotransmitters which participate in the control of adrenal steroidogenesis may interact on their target cell to modulate the activity of their congeners.     

Comparisons of nine heavy metals in salt gland and liver of greater scaup (Aythya marila), black duck (Anas rubripes) and mallard (A. platyrhynchos)

Levels of nine heavy metals were measured in the livers and salt glands of greater scaup (Aythya marila), black duck (Anas rubripes) and mallard (A. platyrhynchos) from Raritan Bay, New Jersey to determine if the functioning avian salt gland concentrates heavy metals. Heavy metals examined were cadmium, cobalt, chromium, copper, lead, mercury, manganese, nickel and zinc. Heavy metal levels varied significantly by species and tissue for chromium, copper, lead, and manganese, and by tissue for cobalt, mercury, nickel and zinc. In comparing tissues cobalt was higher in the salt glands than in livers of all three species; chromium and nickel were higher in the salt gland than liver for mallard and black duck; and lead, manganese and zinc were higher in the liver than the salt gland in greater scaup. Generally metal levels were higher in the salt gland for mallard and black duck, and in the liver for greater scaup.     

Interrenal of a female gymnophione amphibian,Ichthyophis beddomei,during the annual reproductive cycle

The interrenal (adrenal) of Ichthyophis beddomei lies on the ventral side of the kidney, distributed in four zones. It is separated from the renal tissue by a thin layer of connective tissue and contains both adrenocortical and chromaffin cells. Adrenocortical tissue constitutes a major portion of the interrenal islets; the chromaffin tissue consists of a few cells located at the peripheries of the interrenal islets. Histochemical studies demonstrate the presence of Δ⁵3β-hydroxysteroid dehydrogenase, 17 β-hydroxysteroid dehydrogenase, glucose-6-phosphate dehydrogenase, succinate dehydrogenase, and sudanophilic lipids in the adrenocortical tissue, suggesting its steroidogenic potential. Annual histometric and histochemical studies show two peaks of interrenal activity: (1) during the breeding phase of the reproductive cycle (January and February) and (2) during the season of heavy monsoon rains (June and July) in the postbreeding phase.     

Fear and stress reactions in two species of duck and their hybrid

Susceptibility to fear and stress has often been studied in birds using selection experiments. Crosses between different species of the same genus have also been used to study the type of transmission observed for "fixed action patterns." In this experiment we used a cross between two species (male muscovy and female pekin ducks) to study the genetic transmission of various characteristics of fear reactions and adrenal activity. Males of the three genetic types (two parental species and the hybrid) were submitted to tonic immobility and fear of man tests. Blood was collected for corticosterone assay before and after physiological stress or injection of 5 microg/kg of immediate synacthen (ACTH agonist). The muscovy duck showed lower levels of fear reactions than the pekin duck in the majority of behavioral tests (six of eight). Corticosterone levels were also nearly always the lowest in muscovy ducks (five of six). Generally speaking, the muscovy duck appeared to be less fearful and less susceptible to stress than the pekin duck. The mule duck was similar to one parent, midway between the two, or showed heterosis for fear of man at 10 weeks of age (more fearful than the two parents). Corticosterone levels were midway between the two parents in the mule duck with only one exception, i.e., where the pekin duck was dominant. The existence of heterosis for fear is surprising, as this character is classically considered to be submitted to stabilizing selection. The transmission of corticosterone levels and other fear characteristics is, however, compatible with stabilizing selection. The results are discussed in terms of adaptability.