Morphological and histological studies of the adrenal gland in the Japanese quail (Coturnix japonica)

The adrenal gland is a vital endocrine gland that secretes many important hormones in everyday bird life. The adrenal gland of the Japanese quail is grossly located ventromedially the corresponding kidney and has a creamy to yellow color. The quail gland is surrounded by a capsule and contains some ganglionic cells, and the capsule is characterized by the presence of chromaffin cells. The adrenal gland is subdivided into three concentric zones: subcapsular, peripheral, and central. The parenchyma consists of interrenal tissue, chromaffin islets, and blood sinusoids. The interrenal cells contain lipid droplets, are arranged in cords, and rest on the basement membrane. Chromaffin cells are categorized as two types: epinephrine (E) and norepinephrine (NE) cells. These cells contain the granules, and are characterized by the presence of lipid droplets. In this study, the interrenal tissue was found to have a higher proportion of chromaffin cells in quail as compared with other birds, which is attributed to the fact that the Japanese quail is a migratory bird. Therefore, the present investigation aims to provide a detailed study on the adrenal gland in the Japanese quail to help physiologists understand the gland's function and the pathologist to determine the implications for the differential diagnosis of adrenal gland tumors. HIGHLIGHTS: The adrenal gland is subdivided into three concentric zones: subcapsular, peripheral, and central. The interrenal cells contain lipid droplets, are arranged in cords. Chromaffin cells are categorized as two types: epinephrine (E) and norepinephrine (NE) cells. These cells contain the granules, and are characterized by the presence of lipid droplets. The interrenal tissue was found to have a higher proportion of chromaffin cells in quail because it is a migratory bird.

Adrenal Aging and Its Implications on Stress Responsiveness in Humans

Normal aging results in subtle changes both in ACTH and cortisol secretion. Most notable is the general increase in mean daily serum cortisol levels in the elderly, without a noteworthy alteration in the normal circadian rhythm pattern. Glucocorticoid excess seen in the elderly population can have serious consequences in both the structural and functional integrity of various key areas in the brain, including the hippocampus, amygdala, prefrontal cortex, with consequent impairment in normal memory, cognitive function, and sleep cycles. The chronically elevated glucocorticoid levels also impinge on the normal stress response in the elderly, leading to an impaired ability to recover from stressful stimuli. In addition to the effects on the brain, glucocorticoid excess is associated with other age-related changes, including loss of muscle mass, hypertension, osteopenia, visceral obesity, and diabetes, among others. In contrast to the increase in glucocorticoid levels, other adrenocortical hormones, particularly serum aldosterone and DHEA (the precursor to androgens and estrogens) show significant decreases in the elderly. The underlying mechanisms for their decrease remain unclear. While the adrenomedullary hormone, norephinephrine, shows an increase in plasma levels, associated with a decrease in clearance, no notable changes observed in plasma epinephrine levels in the elderly. The multiplicity and complexity of the adrenal hormone changes observed throughout the normal aging process, suggests that age-related alterations in cellular growth, differentiation, and senescence specific to the adrenal gland must also be considered.

The Human Adrenal Gland Proteome Defined by Transcriptomics and Antibody-Based Profiling

The adrenal gland is a composite endocrine organ with vital functions that include the synthesis and release of glucocorticoids and catecholamines. To define the molecular landscape that underlies the specific functions of the adrenal gland, we combined a genome-wide transcriptomics approach using messenger RNA sequencing of human tissues with immunohistochemistry-based protein profiling on tissue microarrays. Approximately two-thirds of all putative protein coding genes were expressed in the adrenal gland, and the analysis identified 253 genes with an elevated pattern of expression in the adrenal gland, with only 37 genes showing a markedly greater expression level (more than fivefold) in the adrenal gland compared with 31 other normal human tissue types analyzed. The analyses allowed for an assessment of the relative expression levels for well-known proteins involved in adrenal gland function but also identified previously poorly characterized proteins in the adrenal cortex, such as the FERM (4.1 protein, ezrin, radixin, moesin) domain containing 5 and the nephroblastoma overexpressed (NOV) protein homolog. We have provided a global analysis of the adrenal gland transcriptome and proteome, with a comprehensive list of genes with elevated expression in the adrenal gland and spatial information with examples of protein expression patterns for corresponding proteins. These genes and proteins constitute important starting points for an improved understanding of the normal function and pathophysiology of the adrenal glands.

A simple and sensitive method for the demonstration of norepinephrine-storing adrenomedullary chromaffin cells

The medulla of the adrenal gland is a neuroendocrine tissue in which catecholamine-storing chromaffin cells exist. The chromaffin cells are derived from neural crest cells and distinctly differentiated into two types of cells, epinephrine (E) (adrenaline)-storing and norepinephrine (NE) (noradrenaline)-storing cells. Using histochemical or immunostaining methods, the two types of chromaffin cells have been differentially distinguished. However, difficulties and/or drawbacks of the procedures have somewhat restricted the progress of research in differential functions of E-storing and NE-storing cells. Here, we show a new method for the differential demonstration of these two cell types. We found that mouse and rat adrenomedullary cells are heterogeneously stained with Harris hematoxylin after treatment with citrate buffer at pH 6. The cell clusters stained with hematoxylin were positive for tyrosine hydroxylase, which is an enzyme involved in catecholamine biosynthesis. Furthermore, the cell clusters were negative for phenylethanolamine-N-methyl transferase, which is an enzyme responsible for the conversion from NE to E and expresses in E-storing chromaffin cells. Moreover, we found that the cell clusters stained with hematoxylin can also be stained with nitroblue tetrazolium at pH 11, using Hopsu and Mäkinen's method by which NE-storing chromaffin cells are stained. These observations indicate that the cytoplasm of NE-storing chromaffin cells is specifically stained with hematoxylin after treatment with citrate buffer at pH 6. This method will allow us to facilitate cell-type specific research of chromaffin cells. Indeed, this method revealed that α-synuclein selectively expresses in E-storing chromaffin cells, but not in NE-storing chromaffin cells.

A non-mammalian type opsin 5 functions dually in the photoreceptive and non-photoreceptive organs of birds

A mammalian type opsin 5 (neuropsin) is a recently identified ultraviolet (UV)-sensitive pigment of the retina and other photosensitive organs in birds. Two other opsin 5-related molecules have been found in the genomes of non-mammalian vertebrates. However, their functions have not been examined as yet. Here, we identify the molecular properties of a second avian opsin 5, cOpn5L2 (chicken opsin 5-like 2), and its localization in the post-hatch chicken. Spectrophotometric analysis and radionucleotide-binding assay have revealed that cOpn5L2 is a UV-sensitive bistable pigment that couples with the Gi subtype of guanine nucleotide-binding protein (G protein). As a bistable pigment, it also shows the direct binding ability to agonist all-trans-retinal to activate G protein. The absorption maxima of UV-light-absorbing and visible light-absorbing forms were 350 and 521 nm, respectively. Expression analysis showed relatively high expression of cOpn5L2 mRNA in the adrenal gland, which is not photoreceptive but an endocrine organ, while lower expression was found in the brain and retina. At the protein level, cOpn5L2 immunoreactive cells were present in the chromaffin cells of the adrenal gland. In the brain, cOpn5L2 immunoreactive cells were found in the paraventricular and supraoptic nuclei of the anterior hypothalamus, known for photoreceptive deep brain areas. In the retina, cOpn5L2 protein was localized to subsets of cells in the ganglion cell layer and the inner nuclear layer. These results suggest that the non-mammalian type opsin 5 (Opn5L2) functions as a second UV sensor in the photoreceptive organs, while it might function as chemosensor using its direct binding ability to agonist all-trans-retinal in non-photoreceptive organs such as the adrenal gland of birds.