Electron microscopic radioautographic studies on DNA synthesis and the ultrastructure of the adrenal gland in aging mice

The changes in DNA synthesis of adrenal gland cells in aging mice from prenatal day 19 to postnatal 2 years were observed by electron microscopic radioautography. The percentages of labeled cells (labeling indices) in the zona glomerulosa, zona fasciculata and zona reticularis of the cortex and the medulla after³H-thymidine injection were at their maxima during the perinatal stage and then gradually decreased with age. The ultrastructural features of the cells at the late embryonic and early postnatal stages appeared undeveloped. Well-developed cell organelles, such as smooth surfaced endoplasmic reticulum, mitochondria with tubular or vesicular cristae and lipid droplets, were more frequently observed in the cytoplasm of the unlabeled cells than in the labeled cells in the three zones of the cortex. This paper was presented at the 28th Annual Meeting of the Clinical Electron Microscopy Society of Japan, Osaka, October 17–19, 1996.     

Ultrastructural Localization of Endothelin-1 in Nonneoplastic, Hyperplastic, and Neoplastic Adrenal Gland

Endothelin (ET)-1 is a 21-amino acid peptide with potent vasopressor and vasoconstrictive properties. Biochemical and recent histochemical studies have shown that this peptide is present in human adrenal cortex. This study was intended to determine ET-1 immunoreactivity in human adrenal cortex and cortical adenoma, and hyperplasia ultrastructurally. Light microscopical examination confirmed recent findings of ET-1 immunoreactivity in the three cortical zones (but not in the medulla) as well as in cortical adenoma and cortical hyperplasia. The immunoreactivity in the cortex and adenoma appeared in the cytoplasm in the form of vacuolar structures and grains. Focally, the cell membranes also showed immu-noreactive staining. Electronmicroscopical investigation revealed ET-1 immunoreactive products adjacent to the outer surface of the membrane of lipid bodies, in mitochondria and rough endoplasmic reticulum and focally on the cell membrane, but no immunolabeling was seen in the medulla. The localization of ET-1 in the endoplasmic reticulum indicates that this peptide is synthesized in the cortical cells. Its localization in the membrane of the lipid bodies and in the mitochondria suggests that it takes part in synthesis and/or secretion of steroid hormones. The focally immunolabeled cell membranes may be dependent on ET-1 binding to ET receptors.     

Ultrastructural morphometry of normal adrenal cortex and of hyperplastic adrenals in gushing’s disease

Surgical specimens of 4 normal adrenal glands and of 5 hyperplastic ones in Cushing’s disease were studied ultrastructurally. The ultrastructure of the three zones of each adrenal gland was morphometrically and statistically analyzed. Comparing the statistical data of the three zones of the normal gland, the development of smooth endoplasmic reticuium and rough endoplasmic reticuium showed an increase from the outer zona glomerulosa to the inner zona fasciculata and reticularis. Also, the mitochondria were more numerous in the inner zona reticularis than in the outer zones. In Cushing’s disease, the smooth endoplasmic reticuium, the rough endoplasmic reticuium, and the mitochondria were developed to a significantly higher degree than in normal human adrenal glands. The distribution of the cell organelles in the zona fasciculata and zona reticularis is almost alike in normal adrenal glands and in the adrenal cortex in Cushing’s disease, except that the smooth endoplasmic reticuium in the zona reticularis was less extensive than in the zona fasciculata. The volume percentages of lipid vacuoies in the hyperplastic zona fasciculata in Cushing’s disease was strongly and significantly decreased in comparison to normal adrenal glands. Our ultrastructural findings and the statistical data were in accordance with the results from animal experiments with adrenocorticotropic hormone (ACTH) stimulation and confirmed former qualitative ultrastructural findings concerning human adrenal gland changes in ACTH-dependent Cushing’s disease.     

Ultrastructure of the fetal rat adrenal gland at full-term and during prolonged gestation

The ultrastructure of the fetal rat adrenal gland is described at full-term (day 22) and during artificially prolonged gestation (days 23, 24, 25). The latter was achieved by daily subcutaneous injections of seven mg progesterone to gravid females from the twentieth through the twenty-fourth day. Cortical and medullary cells contained well developed organelles at all stages. Nonetheless, zonation of the gland was not yet distinct. Whereas the zona glomerulosa and zona fasciculata were fairly well delineated, the zona reticularis and medulla were as yet poorly defined. The latter regions were intermingled, and thus collectively referred to as the “zona reticulo-medullaris.” During prolonged gestation (days 24 and 25 only), many cells of the zona fasciculata and zona reticulo-medullaris contained dilated smooth endoplasmic reticulum and numerous enlarged mitochondria. Enlarged mitochondria were observed also in medullary cells concurrent with a paucity of catecholamine storage granules. Moreover, meconium staining, which is indicative of fetal stress, was also observed on days 24 and 25. The ultrastructural changes observed were interpreted to be an expression of response by the fetal adrenal gland to fetal stress produced by as yet undetermined factors arising during prolonged gestation.     

Organogenesis of the pituitary,adrenal, and lung at birth in the wallaby,Macropus rufogriseus

The ultrastructure of the pituitary, the adrenal, and the lung was examined in the newborn wallaby, Macropus rufogriseus. Tissue from six wallaby neonates (less than 8 hr of age), two near-term fetuses (26 days after removal of suckling pouch young [RPY]), and a two-day-old pouch young was examined; and tissue levels of cortisol in the adrenal glands of five neonates and a near-term fetus (26 days) were measured by radioimmunoassay. At birth the adenohypophysis comprised the bulk of the pituitary gland. The pars distalis was well vascularized and many cells contained electron-dense, membrane-bound granules. The adrenal glands lacked specific zones but comprised two distinct populations of cells. The cytoplasm of one cell type contained electron-dense, membrane-bound granules, similar to those observed inside catecholamine-secreting cells of the adrenal medulla; the other cell type possessed large amounts of smooth endoplasmic reticulum and mitochondria with tubulo-vesicular cristae. These features are characteristic of cells which are actively synthesizing steroid hormones. The concentration of cortisol was 0.58 ng/adrenal in the wallaby at birth. The fetal lungs near term were at the glandular stage of development, and epithelial differentiation of type I and type II pneumocytes was imminent although attenuation was not evident. The canalicular neonatal lung did not contain true alveoli, but type II pneumocytes contained osmiophilic lamellar inclusions of surfactant. The fetal pituitary and adrenal are functional at birth and are thus capable of initiating parturition and of influencing lung maturation in the fetus.     

ULTRASTRUCTURAL ZONATION OF THE HUMAN ADRENAL CORTEX

Electron microscopic observations of sections from adrenal cortex obtained from a twenty-four-year-old male with hypertension were made. In the zona glomerulosa the cells showed a large nuclear-cytoplasmic ratio. The mitochondria had a dark matrix and plate-like inner structure. The agranular endoplasmic reticulum revealed a close association with lipid granules. The Golgi apparatus was prominent and frequently accompanied by centrioles. Free ribosomes were abundant. The zona fasciculata can be subdivided into two layers. In the outer layer the cells are characterized by numerous large lipid granules. Two kinds of mitochondria are discernible; one with a pale matrix and tubulo-vesicular or vesicular inner structure and the other with a dark matrix and tubulo-vesicular or lamelllform cristae. In the inner zona fasciculata and reticularis there are two types of cells besides the dark cells. The type 1 cells have a compact cytoplasm, elliptic or irregularly shaped mitochondria with a dark matrix and tubulo-vesicular or vesicular internal structure. The type 2 cells are large and ovoid, having a clear transparent cytoplasm. The mitochondria are numerous having a clear matrix and almost exclusively vesicular inner elements. Abundance in agranular endoplasmic reticulum, decreased lipid granules, and cytoplasmic incisions are common in both the inner fasciculata and reticularis. In addition the zona reticularis is characterized by increased number of dark cells, numerous pigment bodies, and the appearance of huge mitochondria.
On the basis of these observation were discussed the significance of the organelles in steroid biosynthesis, mode of hormone secretion, and cyto-genesls in the adrenal cortex.     

The ultrastructural features of secretory cells of some endocrine glands in aging

In the electron microscopic investigation of the secretory cells of adenohypophysis, adrenal cortex, adrenal medulla and pancreatic islets from the adult and old Wistar male rats, certain age-related ultrastructural features have been found. Age changes appeared to be more pronounced in the thyrotrophs, somatotrophs and gonadotrophs of the adenohypophysis and in zona glomerulosa and zona reticularis spongiocytes of the adrenal cortex. They consisted of atrophy of the Golgi apparatus, appearance of the cytoplasmic vacuoles, lipid and lipofuscin granules, secondary lysosomes and damage of the inner mitochondrial membrane. Parallel to these, hypertrophy of the Golgi apparatus and rough endoplasmic reticulum, formation of giant mitochondria and presence of a great number of secretory cells in the cellular cytoplasm were noted in zona fasciculata spongiocytes and chromaffin cells of the adrenal medulla, and in beta cells of the pancreatic islets during aging thus evidencing for the adaptive changes in the ultrastructure of these cells. However, no appreciable age changes have been observed in the ultrastructure of the adrenocorticotropic cells of the adenohypophysis.     

The ultrastructure of the pituitary and the adrenal gland of three newborn marsupials (Dasyurus hallucatus, Trichosurus vulpecula and Isoodon macrourus)

Summary The ultrastructure of the pituitary glands of the newborn northern native cat, brushtail possum and the northern brown bandicoot and the adrenal glands of the former two marsupials were examined to determine whether these endocrine glands were functional at birth.The anterior pituitary of all three species was well vascularised and many cells contained electron-dense, membrane bound granules. The adrenal glands were composed of two distinct cell populations. One group of cells possessed dark staining granules, normally observed in catecholamine-secreting cells, and the second group contained large amounts of smooth endoplasmic reticulum and mitochondria with tubulovesicular cristae, indicative of steroid hormone secreting cells.The ultrastructure of the cells of the fetal pituitary and adrenal of all three species would suggest that these glands are functional at birth and, as with many eutherians, the marsupial pituitary and adrenal gland may play an important role in determining the length of gestation.     

Opossum adrenal medulla: II. Differentiation of the chromaffin cell

The ultrastructure of the opossum adrenal medulla was examined in its postnatal development. Maturation of chromaffin cells and genesis of chromaffin vesicles were of particular interest. The primitive sympathetic cell was seen to contain few organelles with no apparent polarity. Initial pheochro-moblasts contained more organelles with some polarity. Endoplasmic reticulum and the Golgi complex increased as the pheochromoblasts matured, which suggested increased synthetic activity. Structures resembling Golgi/endoplasmic reticulum/lysosome (GERL) systems were seen in the pheochromoblasts. It is suggested that some of the components of the chromaffin vesicle may be processed by the GERL while others come directly through the Golgi complex. It is stressed that the developing pheochromoblast in the opossum presents an interesting model in which to study the genesis of the chromaffin vesicle.     

Optical and ultrastructural studies of midgut and salivary glands of first instar of Dermatobia hominis (Diptera: Oestridae)

Midguts and salivary glands of newly hatched larvae (L1) of Dermatobia hominis (L., Jr.) were studied using light and electron microscopy. The larval midgut has a tubular, sinusoidal form and consists of a monolayer of epithelial cells with an underlying basement membrane and a surrounding layer of connective tissue. The fine structure of the midgut shows digestive cells with short microvilli, large nuclei, and cytoplasm containing few visible organelles (mitochondria, rough endoplasmic reticulum, and free ribosomes). In the basal region, the plasma membrane of the cells is folded into a labyrinth area. Hemidesmosomes link the basal surface to the basement membrane and septet junctions are present between adjacent cells. The connective tissue circling the basement membrane contains collagen fibrils, muscle fibers, and tracheal tubes. Prominent nuclei with evident nucleoli occur in the digestive cells. The salivary gland is simple and tubular. It has a monolayer of epithelial cells surrounded by basement membrane and connective tissue. The fine structure of the salivary gland shows epithelial cells, microvilli, secretion into the lumen, septate junctions at the lateral face and a basal labyrinth region. The cell nucleus is large and the cytoplasm contains rough endoplasmic reticulum, ribosomes and mitochondria.     

Effects of exogenous ACTH on the rat fetal adrenal cortex: a histochemical and electron-microscopical observation.

ACTH was administered subcutaneously to rat fetus directly at the late stage of fetal development and acute reaction on the fetal adrenal cortex was observed histochemically and electron microscopically. By administration of ACTH the adrenal cortex became remarkably hyperemic and there were swollen cells in all layers, particularly in the middle and inner layers (corresponding to the zona fasciculata and reticularis in adult rat). Marked reduction of lipid, enlarged mitochondria with increased vesicular cristae and increased smooth-surfaced endoplasmic reticulum (SER) were characteristic. The alterations of mitochondria preceded the change of SER, and thereafter mitochondria showed rapid degeneration. The outer layer (corresponding to the zona glomerulosa in adult rat) also showed similar changes by ACTH to those of the other two layers. These results indicated that the fetal adrenal cortex of rats was exogenous ACTH-reactive and its reaction which was different from that of adult cortical cells, seemed to be specifically related to the development and differentiation of the cells.     

胶体金法研究胎儿胸腺上皮网状细胞的细胞学观察

为了探讨胎儿胸腺上皮网状细胞发育过程的结构特点,用胶体金免疫组化法及电镜观察60例胎龄12～42周胸腺。结果表明:不同类型的上皮网状细胞中间丝有多寡之别并含有不同类型角蛋白;中间丝多者细胞器相对减少。角蛋白阳性反应细胞体积随胎龄增长而增大,但阳性细胞出现率与胎龄关系不大。角蛋白阴性反应细胞电镜下可见丰富的内质网、线粒体及核糖体,提示该细胞主要有分泌胸腺激素功能。     

The development of adrenal homolog of rainbow trout<Emphasis Type="Italic"> Oncorhynchus mykiss</Emphasis>: an immunohistochemical and ultrastructural study

In this work we describe the adrenal homolog of the rainbow trout Oncorhynchus mykiss during development. At the histological level, the interrenal primordium is clearly evident in larvae 25 days after fertilization (dpf), and the immunohistochemical reactions for tyrosine hydroxylase (TH) and phenylethanolamine-N-methyltransferase (PNMT), which mark the chromaffin cells, appear as early as 27 dpf. Both reactions are evident in cells localized in the head kidney and in some, probably migrating, cells close to the notochord. In 27-dpf larvae, the ultrastructural analysis shows the presence of the interrenal cells with mitochondria with tubulovesicular cristae, typical of steroidogenic cells, sometimes surrounded by smooth endoplasmic reticulum (SER) cisternae, indicating that in this stage the cells have the capacity for steroid synthesis and secretion. In the same stage the chromaffin cells are characterized by few and small membrane-bound granules containing cores of heterogeneous electron density. Both types of cells show large nuclei, numerous free or clumped ribosomes, developed rough endoplasmic reticulum (RER), and scarce SER. Rare nerve endings contacting chromaffin cells are present. In the subsequent developmental stages, a further differentiation of both types of cells is evidenced by modifications of cell organelles as mitochondria, chromaffin granules, RER, SER, and so on. A clear discrimination of the two types of catecholamine-containing cells, adrenaline and noradrenaline cells, is evident only 5 days after hatching. The presence of different interrenal cell types in larvae at 5 and 10 days after hatching probably indicates the activation of a physiological cellular cycle. The immunohistochemical and ultrastructural results are compared with those obtained by other authors in the same and other vertebrate species.     

EFFECTS OF EXOGENOUS ACTH ON THE RAT FETAL ADRENAL CORTEX: A HISTOCHEMICAL AND ELECTRON-MICROSCOPICAL OBSERVATION

ACTH was administered subcutaneously to rat fetus directly at the late stage of fetal development and acute reaction on the fetal adrenal cortex was observed histochemically and electron microscopically. By administration of ACTH the adrenal cortex became remarkably hyperemic and there were swollen cells in all layers, particularly in the middle and inner layers (corresponding to the zona fasciculata and reticularis in adult rat). Marked reduction of lipid, enlarged mitochondria with increased vesicular cristae and increased smooth-surfaced endoplasmic reticulum (SER) were characteristic. The alterations of mitochondria preceded the change of SER, and thereafter mitochondria showed rapid degeneration. The outer layer (corresponding to the zona glomerulosa in adult rat) also showed similar changes by ACTH to those of the other two layers. These results indicated that the fetal adrenal cortex of rats was exogenous ACTH-reactive and its reaction which was different from that of adult cortical cells, seemed to be speciflcally related to the development and differentiation of the cells. ACTA PATH. JAP. 27 : 477–484, 1977.     

ENDOTHELIAL TUBULORETICULAR STRUCTURES IN INTRACRANIAL GERMINOMAS

In studying three human intracranial germinomas tubuloreticular structures were observed within the cisterns of granular endoplasmic reticulum (RER), as well as occasionally within dilated perinuclear spaces of capillary endothelial cells. These tubuloreticular structures seen as a network of branching, convoluted, tubular profiles appear to originate from amorphous material. The development of these structures could be classified into three stages. In Stage I, the precursor substance appears as dense amorphous material within the cisterns of RER. Stage II is marked by the transformation of the amorphous material to coarse particulate material which aggregates to form tubular units. During the first and second stages, the distended RER that participates in the formation of these structures is accompanied by numerous attached ribosomes and is closely associated with mitochondria. In Stage III, the tubular units fuse with one another to form the tubuloreticular structure. In this third stage both ribosomes and mitochondria are almost absent. As a result of the almost complete disappearance of these organelles at this time, both the attached ribosomes and mitochondria may play an important role in the synthesis of the precursor substance as well as in its transformation to the tubuloreticular structure.     

Fluoride stimulation of the rat parathyroid gland: An ultrastructural study

The parathyroid glands of rats given 150 ppm fluoride in the drinking water for 10 weeks are evaluated ultrastructurally and compared to the parathyroid glands of untreated rats. As a result of fluoride ingestion, the majority of the parathyroid cells are dark chief cells, indicating that these cells are in the active stages of the secretory cycle. More significantly, in the fluoride-treated rats, the cytoplasmic organelles of the dark chief cells are even more developed that those seen in the dark chief cells of untreated rats. The dark cells contain an electron-dense cytoplasm with abundant lamellar arrays of rough endoplasmic reticulum, spiral aggregations of free ribosomes, multiple dilated Golgi complexes, and increased numbers of secretory granules. The cells are at a minimum dimension with maximum tortuosity of the plasma membranes; and, as a result, large intercellular spaces are often seen between contiguous cells. Based on these observations, it is suggested that, in the fluoride-treated rat, a type of secondary hyperparathyroidism develops resulting in an increase in the organelles involved in protein synthesis and secretion.     

Adrenal gland: structure, function, and mechanisms of toxicity

The adrenal gland is one of the most common endocrine organs affected by chemically induced lesions. In the adrenal cortex, lesions are more frequent in the zona fasciculata and reticularis than in the zona glomerulosa. The adrenal cortex produces steroid hormones with a 17-carbon nucleus following a series of hydroxylation reactions that occur in the mitochondria and endoplasmic reticulum. Toxic agents for the adrenal cortex include short-chain aliphatic compounds, lipidosis inducers, amphiphilic compounds, natural and synthetic steroids, and chemicals that affect hydroxylation. Morphologic evaluation of cortical lesions provides insight into the sites of inhibition of steroidogenesis. The adrenal cortex response to injury is varied. Degeneration (vacuolar and granular), necrosis, and hemorrhage are common findings of acute injury. In contrast, chronic reparative processes are typically atrophy, fibrosis, and nodular hyperplasia. Chemically induced proliferative lesions are uncommon in the adrenal cortex. The adrenal medulla contains chromaffin cells (that produce epinephrine, norepinephrine, chromogranin, and neuropeptides) and ganglion cells. Proliferative lesions of the medulla are common in the rat and include diffuse or nodular hyperplasia and benign and malignant pheochromocytoma. Mechanisms of chromaffin cell proliferation in rats include excess growth hormone or prolactin, stimulation of cholinergic nerves, and diet-induced hypercalcemia. There often are species specificity and age dependence in the development of chemically induced adrenal lesions that should be considered when interpreting toxicity data.     

Ultrastructural immunomorphology of antibody synthesis

An ultrastructural study of antibody formation in the lymphoid cells of the lymph glands was carried out in C3HA mice using horseradish peroxidase as the antigen. The perinuclear space and tubules of the granular endoplasmic reticulum are the primary zones of synthesis and accumulation of antibodies inside the immunocompetent cells. Much less activity of the reaction was observed in the lamellar component of the Golgi apparatus and on the ribosomes.     

Development of ultrastructural heterogeneity among hepatocytes in the mouse

Ultrastructural stereological analyses of periportal and centrilobular hepatocytes of newborn, 5- and 10-day-old, and adult male ddY mice were carried out to study the postnatal development of the morphologic heterogeneity among hepatocytes. In newborn animals, the periportal and centrilobular cells did not differ in the volume densities of the smooth and rough endoplasmic reticulum; in the volume and numerical densities of the mitochondria, lysosomes, peroxisomes, and lipid droplets; or in the shape (the axial ratio) of the mitochondria. In 5-day-old animals, the volume densities of the mitochondria and rough endoplasmic reticulum were greater in periportal cells than centrilobular cells, and the volume density of the smooth endoplasmic reticulum was greater in centrilobular cells than periportal cells. In 10-day-old animals, a further difference was seen in the numerical density of the mitochondria, which was greater in centribular cells than periportal cells. Adult hepatocytes showed also a difference in the axial ratio of the mitochondria, which was greater in centrilobular than periportal cells; there was no difference in the volume density of the rough endoplasmic reticulum. When the data were expressed as volume and number per hepatocyte, the patterns of sublobular distributions of these organelles differed from the patterns seen in the volume and numerical density data, mainly in adult animals. This difference was caused by the marked increase in hepatocyte volume between 10 days of age and adulthood, especially in centrilobular cells. The results show that, in general, the ultrastructural heterogeneity among hepatocytes, evident in adult animals, is not present in newborn animals but arises during postnatal development, and suggest the occurrence of a lobular gradient in postnatal development of hepatocyte functions.     

Ultrastructure of mouse egg-cylinder

Summary The mouse egg-cylinder prior to and after mesoderm formation was studied by means of electron microscopy. The ultrastructural appearance of the proximal entoderm of both embryonic and extraembryonic segments suggests an intensive absorptive and nutritional activity. Numerous pinocytotic vacuoles, microvilli, primary and secondary lysosomes and fair amounts of rough endoplasmic reticulum and free ribosomes were the most important characteristics of these cells. After mesoderm formation, the extraembryonic entoderm showed the aforementioned characteristics even more prominently, while the cells of embryonic entoderm became flattened and depleted of microvilli and of almost all organelles. The cells of the extraembryonic and embryonic ectoderm prior to and after mesoderm formation had the same ultrastructural appearance as mesodermal cells. The cytoplasm of these cells was replete with free ribosomes, but other organelles such as mitochondria and rough endoplasmic reticulum were few in number. The architecture of all cells of the egg-cylinder except those of the extraembryonic entoderm suggested a very low level of differentiation. The criteria and possibilities for the determination of the degree of differentiation on the ultrastructural level and possible differences in protein synthesis in extraembryonic entoderm as compared with other parts of the embryo are considered.