Well-developed Cell Organelles Research Articles

Characteristics of pericytes in diethylstilbestrol (DES)-induced pituitary prolactinoma in rats.

Prolactinomas are the most common tumor of the human pituitary. They result in excessive prolactin secretion and important changes in the vasculature. Pericytes are perivascular cells associated with capillaries and have crucial roles in physiological and pathological neovascularization. We previously reported that pericytes produce type I and III collagens in the anterior pituitary of adult rats. In addition, pituitary pericytes contained well-developed cell organelles and actively synthesized collagens during early postnatal development. However, the characteristics of pericytes in pituitary tumors are unclear. In this study, we used diethylstilbestrol (DES)-treated rats as an animal model of prolactinoma. Using five common pericyte markers, more pericytes were observed in rats treated with DES for 3 months (prolactinoma) compared to the control. Transmission electron microscopy revealed that attached and semidetached pericytes exhibited active cell organelles. Moreover, we identified pericyte migration between capillaries. Although the fine structure of pituitary pericytes was active in prolactinoma, expressions of type I and III collagen mRNAs were greatly diminished. In sum, the characteristics and functions of pericytes were altered in pituitary tumors. This study is the first to clarify fine structural changes of pericytes in rat prolactinomas and improves our understanding of the function of pericytes under pathological conditions.

Changes in fine structure of pericytes and novel desmin-immunopositive perivascular cells during postnatal development in rat anterior pituitary gland

Pericytes are perivascular cells associated with capillaries. We previously demonstrated that pericytes, identified by desmin immunohistochemistry, produce type I and III collagens in the anterior pituitary gland of adult rats. In addition, we recently used desmin immunoelectron microscopy to characterize a novel type of perivascular cell, dubbed a desmin-immunopositive perivascular cell, in the anterior pituitary. These two types of perivascular cells differ in fine structure. The present study attempted to characterize the morphological features of pituitary pericytes and novel desmin-immunopositive perivascular cells during postnatal development, in particular their role in collagen synthesis. Desmin immunostaining revealed numerous perivascular cells at postnatal day 5 (P5) and P10. Transmission electron microscopy showed differences in the fine structure of the two cell types, starting at P5. Pericytes had well-developed rough endoplasmic reticulum and Golgi apparatus at P5 and P10. The novel desmin-immunopositive perivascular cells exhibited dilated cisternae of rough endoplasmic reticulum at P5-P30. In addition, during early postnatal development in the gland, a number of type I and III collagen-expressing cells were observed, as were high expression levels of these collagen mRNAs. We conclude that pituitary pericytes and novel desmin-immunopositive perivascular cells contain well-developed cell organelles and that they actively synthesize collagens during the early postnatal period.

Histochemical and immunocytochemical study of hard tissue formation in dental pulp during the healing process in rat molars after tooth replantation

Dental pulp is assumed to possess the capacity to elaborate both bone and dentin matrix under the pathological conditions following tooth injury. This study was undertaken to clarify the mechanism inducing bone formation in the dental pulp by investigating the pulpal healing process, after tooth replantation, by micro-computed tomography (mu-CT), immunocytochemistry for heat-shock protein (HSP)-25 and cathepsin K (CK), and histochemistry for both alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP). Under deep anesthesia, the upper right first molar of 4-week-old Wistar rats was extracted and immediately repositioned in the original socket. In control teeth at this age, the periphery of the coronal dental pulp showed intense ALP-positive and HSP-25-positive reactions, whereas there were no TRAP-positive or CK-positive cells. Tooth replantation weakened or terminated ALP-positive and HSP-25-positive reactions in the pulp tissue at the initial stages. At 3-7 days after operation, the ALP-positive region recovered from the root apex to the coronal pulp followed by HSP-25-positive reactions in successful cases showing tertiary dentin formation. In other cases, TRAP-positive and CK-positive cells appeared in the pulp tissue of the replanted tooth at postoperative days 5-10 and remained associated with the bone tissue after 12-60 days. Immunoelectron microscopy clearly demonstrated that CK-positive osteoclast-lineage cells made contact with mesenchymal cells with prominent nucleoli and well-developed cell organelles. These data suggest that the appearance of TRAP-positive and CK-positive cells is involved in the induction of bone tissue formation in dental pulp.

Fine structure of the semicompact formation of the nucleus ambiguus of the rat.

We investigated the fine structure of the semicompact formation of the nucleus ambiguus (AmS), which was identified by retrogradely labeled pharyngeal (PH) motoneurons. When cholera toxin subunit B-conjugated horseradish peroxidase was injected into the lower pharyngeal muscle, many retrogradely labeled PH neurons were found throughout the AmS. Besides the PH neurons, two types of neurons were recognized in the AmS: unlabeled medium-sized neurons and unlabeled small neurons. The PH neuron was large (27.6 x 44.1 microm) and polygonal, and contained many Nissl bodies and well-developed cell organelles with a prominent spherical nucleus. The medium-sized neuron was dark and oval (19.3 x 33.2 microm), and contained many free ribosomes and much swollen rough endoplasmic reticulum with a distorted oval nucleus. The small neuron was spindle-shaped (12.3 x 20.2 microm), and had poorly developed cell organelles with an irregularly shaped nucleus. The average number of axosomatic terminals in a sectional plane was largest in the PH neurons (32.8), smaller in the medium-sized neurons (23.1), and smallest in the small neurons (6.3). The number of axo-somatic terminals containing round vesicles (Gray's type I) was almost equal to that of terminals containing pleomorphic vesicles (Gray's type II) in the PH neuron, and slightly smaller in the small and the medium-sized neurons. About 60% of the axodendritic terminals were Gray's type I, and 40% were type II. These results indicate that there are two different types of interneurons besides the PH motoneurons in the AmS.

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.

Ultrastructural characterization of pharyngeal and esophageal motoneurons in the nucleus ambiguus of the rat.

The viscerotopic organization of the upper alimentary tract has been established in the nucleus ambiguus, but there is little information about the morphology of the individual neurons innervating the pharynx and esophagus. We studied the ultrastructure of pharyngeal (PH), cervical esophageal (CE), and subdiaphragmatic esophageal (SDE) motoneurons labeled by retrogradely transported wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) in the compact formation of the nucleus ambiguus. WGA-HRP was injected into the lower pharynx, or the cervical and subdiaphragmatic esophagus of male rats. The retrogradely labeled PH neurons in the rostral portion of the compact formation were large (26.1 x 50.1 microns, 906.7 microns2), polygonal, and contained well-developed cell organelles with a round nucleus. Subsurface cisterns connected with rough endoplastic reticulum were often present near the postsynaptic membrane. Both CE and SDE neurons in the compact formation were medium-sized, round or oval, and contained well-developed cell organelles, although the SDE neuron was significantly larger than the CE neuron (24.9 x 33.6 microns, 593.0 microns2 in the SDE neuron, and 19.5 x 30.2 microns, 440.3 microns2 in the CE neuron). The average number of axosomatic terminals in a sectional plane was largest in PH neurons (29.0), smaller in CE neurons (7.9), and smallest in SDE neurons (4.2). The number of axosomatic terminals containing round vesicles (Gray's type I) was almost equal to that of terminals containing pleomorphic vesicles (Gray's type II) in PH and CE neurons, but there were few Gray's type II axosomatic terminals in SDE neurons. Desmosome-like junctions at somato-somatic or somato-dendritic apposition were often present in the area surrounding SDE neurons. There were also small unlabeled neurons (9.5 x 18.1 microns, 131.8 microns2) in the compact formation of the nucleus ambiguus. The small neurons contained poorly developed cell organelles and an irregular shaped nucleus with invaginated nuclear membrane, and had no Nissl bodies. These results indicate that PH neurons have the characteristics of somatic motoneurons, and that CE and SDE neurons are similar to visceral motoneurons.

Pituitary adenylate cyclase-activating polypeptide (PACAP)-like immunoreactive neuronal elements in rat hypothalamus and median eminence with special reference to morphological background of its effect on anterior pituitary — light and electron microscopic immunocytochemistry

Pituitary adenylate cyclase-activating polypeptide-like immunoreactive (PACAP-LI) neuronal elements in the rat hypothalamus including the median eminence (ME) were investigated by light and electron microscopic immunocytochemistry. PACAP-LI neuronal perikarya with well-developed cell organelles and dense granules were distributed mainly in the magnocellular portion of the paraventricular nucleus and throughout the entire supraoptic nucleus. In the ME, numerous PACAP-LI neuronal processes were found in the internal layer (IL), and immunoreactive terminals containing dense granules, vesicles and mitochondria were detected around portal capillaries which penetrated into the IL from the external layer. Thereafter, PACAP is released into the portal capillaries in the IL, transported to the anterior pituitary and plays a role in the stimulation of adenylate cyclase of anterior pituitary cells.

Effects of perfluorooctanoic acid — a potent peroxisome proliferator in rat — on Morris hepatoma 7800C1 cells, a rat cell line

In this study, Morris hepatoma 7800C1 cells (from rat) were exposed to 500 μM perfluorooctanoic acid (PFOA) in the culture medium for 7 days. This treatment resulted in inductions of catalase, lauroyl-CoA oxidase (which catalyzes the first step in peroxisomal β-oxidation) and of cytochrome P-450IVA (specialized for omega-and omega-1 hydroxylation of fatty acids). Northern blot analysis revealed that the level of mRNA for peroxisomal fatty acyl-CoA oxidase was enhanced in cells treated with PFOA. Inductions of the enzymes mentioned above are generally connected with peroxisome proliferation in vivo. This work also includes a comparison between the activities of catalase, lauroyl-CoA oxidase, DT-diaphorase and glutathione transferase in rat liver homogenate and 7800C1 cells in order to investigate to what extent this cell line differs from the situation in vivo. The findings suggest that the cells selectively lost most of their peroxisomes during transformation into a cell line and subsequent propagation. The control activities of catalase and lauroyl-CoA oxidase (marker enzymes for peroxisomes) were only about 2% of the corresponding enzyme activities in rat liver. In addition, a morphological study revealed that the frequency of peroxisomes in 7800C1 cells is very low. The control activity of glutathione transferase in 7800C1 cells was 11% of the corresponding activity in rat liver homogenate, whereas the level of DT-diaphorase was virtually the same in 7800C1 cells as in rat liver. Electron microscopic investigation of the control cultures revealed all signs of viable cells, with well-developed cell organelles. Treatment of 7800C1 cells with 500 μM PFOA has little effect on cellular morphology.

Influence of exogenously administered oxytocin on prolactin-producing cells in adult male rats as revealed by immuno-electron microscopy.

Prolactin-producing cells (PRL cells) identified by immuno-electron microscopy were studied in male rats with chronic intraperitoneal injection of synthetic oxytocin (OT). The PRL cells are usually classified into three types: the immature type containing round secretory granules about 100 nm in diameter with poorly developed cell organelles; the intermediate type containing medium-sized (150-250 nm in diameter) secretory granules with moderately developed cell organelles; and mature type containing large pleomorphic secretory granules ranging from 300 to 700 nm in diameter with well-developed cell organelles. In male rats, the intermediate type comprises typical PRL cells that constitute about 50% of all immunoreactive PRL cells. Chronic intraperitoneal OT administration to rats caused morphologically hypertrophic and hyperfunctioning PRL cells which are identified as mature type PRL cells. The frequency of occurrence of the mature type PRL cells increased after treatment. The contents of pituitary and serum PRL as measured by radioimmunoassay essentially paralleled the morphological results. These data indicate that OT may play a physiological role in PRL secretion as a releasing factor, and that OT administration causes the interconversion of the three types of PRL cells, indicating the mature type to be at the most activated state of secretory function.

Fine Structure of Tyrosine Hydroxylase-like Immunoreactive Neurons and Terminals of the Hypothalamic Arcuate Nucleus and Median Eminence in Young and Aged Rats

Tyrosine hydroxylase (TH)-like immunoreactive neurons, fibers, and terminals in the hypothalamic arcuate nucleus and median eminence of young (8 weeks old) and aged (24 months old) rats were investigated at light and electron microscopic levels by means of the peroxidase anti-peroxidase (PAP) method. In the arcuate nucleus, TH-like immunoreactive neuronal perikarya of young animals contained well-developed cell organelles such as rough-surfaced endoplasmic reticulum (rER), mitochondria, Golgi apparatus, polysomes, as well as dense granules. Immunoreactive neuronal elements appeared as both presynaptic and postsynaptic elements. In aged rats, TH-like immunoreactive neuronal perikarya as well as non-immunoreactive ones were found to include many lysosomes or inclusions, and many neuronal elements with degradative changes were observed. In the external layer of the median eminence of young animals, many immunoreactive nerve endings were found around the pericapillary spaces of portal vessels and often terminated adjacent to the basement membranes of the pericapillary spaces. Immunoreactive fibers having close contact with non-immunoreactive fibers were also observed. In aged animals, degradative changes such as axons with swollen and watery appearance and myelin figures were observed in the neuronal elements, although many immunoreactive nerve endings were seen around the pericapillary spaces.

Microvascular Changes in the Stroma of Human Colorectal Carcinomas: Ultrastructural Histochemical Study

Ultrastructural histochemical studies were performed using Ulex europaeus agglutinin‐I lectin (UEA‐I) and anti‐endothelial monoclonal antibody BMA 120 in order to morphologically characterize the microvasculature of human colorectal carcinomas. In the normal mucosa, UEA‐I and BMA 120 were bound to luminal plasma membrane of endothelial cells, usually continuously. Capillaries in the stroma of invasive adenocarcinomas showed remarkable structural changes such as swelling of endothelial cells with well‐developed cell organelles and narrowing of the lumen. Reaction products for UEA‐I and BMA 120 were both observed along the luminal plasma membrane of endothelial cells, usually discontinuously, partially retaining the features of normal capillaries. Furthermore, we have confirmed an occurrence of solid capillary buds composed of a strand of large endothelial cells with a trace of lumen. They showed almost no reactivity to UEA‐I and BMA 120. Conventional electron microscopy revealed that they were present frequently in invasive carcinomas, but infrequently in intramucosal carcinomas and inflammatory lesions. Our results suggest that the stroma of invasive colorectal carcinomas abounds in immature capillaries and their precursors, which may indicate active tumor‐induced angiogenesis.

Light and electron microscopic immunocytochemistry of neurotensin-like immunoreactive neurons in the rat hypothalamus

Neurotensin-like immunoreactive neuronal perikarya, fibers and terminals in the rat hypothalamus, particularly in the arcuate nucleus, the paraventricular nucleus and the median eminence, were investigated by light and electron microscopic immunocytochemistry. The main distributional areas of immunoreactive neuronal perikarya were found to be the arcuate nucleus, the periventricular nucleus and the paraventricular nucleus by light microscopic immunocytochemistry. Immunoreactive neuronal perikarya showed a characteristic distributional pattern in the arcuate nucleus. In the paraventricular nucleus they were distributed in both the magnocellular and parvocellular portions. A large number of immunoreactive terminals were observed throughout the external layer of the median eminence, particularly its lateral portion. A moderate number of immunoreactive terminals were also observed in the internal layer of the median eminence. By electron microscopic immunocytochemistry immunoreactive neuronal perikarya both in the arcuate and paraventricular nuclei showed generally well-developed cell organelles such as mitochondria, r-ER, and Golgi complex. In addition, immunoreactive dense granules were dispersed throughout the perikarya. A large number of immunoreactive terminals containing immunoreactive dense granules, clear vesicles and mitochondria were observed in the vicinity of pericapillary spaces of the external layer of the median eminence. This observation strongly suggests that neurotensin-like immunoreactive substance is released into the portal capillaries.

Formation and disintegration of lipid droplets associated with cell organelles, especially smooth-surfaced endoplasmic reticulum in the white adipose cell

Although a number of ultrastructural studies on the white adipose cell have been reported, not a few unsolved problems still remain on the morphological and functional relationships between formation or disintegration of lipid droplets and cell organelles in those cells. In order to re-examine such the points, we have made electron microscopical studies on the epididymal adipose cells from normal and starved Wistar adult rats, and on these cells from rats refed ordinary animal food or given only lipid without carbohydrate after a period of starvation. Additionally, for the same purpose we have observed the ultrastructure of developing and differentiating fat cells in the epididymal adipose tissue of rats ranging from newborn to 5 weeks old.The adipose cell from normal adult rats shows that the peripheral cytoplasm which envelopes a central large lipid mass contains well-developed cell organelles and occasionally small lipid droplets. These lipid droplets have no limiting membrane, but are often observed to be closely encircled by fenestrated profiles of smooth-surfaced endoplasmic reticulum (SER) which connects with a part of rough-surfaced endoplasmic reticulum (RER) in places (Fig. 1).

INTERSTITIAL GLAND TISSUE OF MAMMALIAN OVARY

ABSTRACT The interstitial gland cells of the mammalian ovary originate from the theca interna and surrounding stromal elements of degenerating follicles and are simultaneously vascularized, and hypertrophied (or luteinized). They form a specific feature of the mammalian ovary, and are invariably present in the ovaries of young and adult mammals. The interstitial gland cells show several variations in their amount and distribution in different mammals. They also show cycles of abundance and differentiation correlated with the reproductive age and ovarian cycles. The interstitial gland cells possess the cytological, histochemical and biochemical features of well-established steroid-secreting cells. These features are: a) abundant diffuse lipids (lipoproteins) in the cytoplasm, which apparently derive from the abundant ultrastructural agranular endoplasmic reticulum; b) well-developed cell organelles, especially the pleomorphic mitochondria with complex system of internal cristae that are predominantly tubular; c) the development of diffuse lipoproteins (or membranes of smooth reticulum), closely accompanied by the appearance of enzyme activities indicative of the biosynthesis of steroid hormones; d) under certain physiological situations, stored lipid droplets in the cytoplasm, which consist of phospholipids, triglycerides, and cholesterol and/or its esters; and e) the capacity to form steroid hormones in biochemical experiments in vitro and in vivo. The physiological significance of these various features, which do not show any appreciable development in the compressed, relatively embryonic stromal elements of the general ovarian stroma, has been discussed in relation to steroid hormone synthesis in the interstitial gland cells. In general, the results of the cytological, histochemical and biochemical studies agree well with each other and are compatible with their endocrine function. After stimulation with endogenous gonadotrophins, the interstitial gland cells undergo conspicuous cytological, histochemical and biochemical changes, which have been correlated to the accelerated production of steroid hormones. The formation of androgenic steroids seems to be the principal product of interstitial gland cells; in some mammalian species, oestrogens and progestins are also formed. Further comparative studies on the interstitial gland cells in different mammalian species are suggested to determine the nature and physiological significance of their steroid secretions under different physiological situations. Interstitial gland cells of different mammals show several variations with regard to their permanency, apparently depending on some gonadotrophic stimulation. After persisting for some time, they gradually lose their cytoplasm and lipids, and ultimately revert to the relatively embryonic, compressed stromal tissue from which they are originally derived. This cytoplasmic change is closely accompanied by the loss of blood vascularity, which may be providing the gonadotrophic hormone and other nutrient substances to the functional interstitial gland cells. Some interstitial gland cells show degenerative cytoplasmic changes, and ultimately become refractory to gonadotrophic stimulation.