Mitochondrial content of choroid plexus epithelium

 The objective of the present study was to examine the apparent work capacity of one of the two separate membrane systems (the blood-cerebrospinal fluid barrier) that isolate the mammalian brain extracellular fluid (and cerebrospinal fluid, CSF) from plasma. Digitized analyses of electron-microscopic images provided estimates of mitochondrial volumes, which were expressed as a percentage of the cell cytoplasm. We recorded a high mitochondrial content of 12–15% in the cuboidal epithelium of primate choroid plexus, which was consistent in vervet, rhesus, and squirrel monkeys, as well as in baboons. Similarly high mitochondrial contents were observed in the rabbit, rat, and mouse choroid plexus. It has been postulated that the high mitochondrial content of brain endothelium is associated with maintaining the ionic gradients within the central nervous system. We observed that the mitochondrial content of the choroid plexus (where CSF is produced) was slightly higher than in (prior measurements of) the blood-brain barrier (BBB). In addition, surface areas at the apical borders of the choroid plexus epithelia (where the Na⁺K⁺ATPase activity has been localized) were increased 7- to 13-fold over the basal borders, in the primate species examined. The observation of high mitochondrial volumes in choroid plexus cells is consistent with the suggestion that increased mitochondrial densities seen in choroidal epithelia and BBB capillaries provide a metabolic work capability for both secretory activities and maintaining ionic gradients across blood-CSF barriers. Received: 25 February 1997 / Accepted: 2 May 1997     

Comparative immunohistochemical and lectin histochemical studies of ependymal cells and the epithelium of the choroid plexus

In a previous investigation we reported on the distribution of intermediate filaments in normal epithelium of choroid plexus and ependyma (Kasper et al. 1986). The present paper describes the results obtained with an enlarged panel of monoclonal antibodies against intermediate filaments and additionally with lectins. Ependymal cells contain GFAP and vimentin filaments, whereas epithelial plexus cells express cytokeratin, vimentin and neurofilament 200 KD. Using Concanavalin A, we found a strong cytoplasmatic staining of plexus epithelia and a reduced or failed reaction in ependymal cells. The differences in both cell types may find an explanation in their function or are determined during the ontogenic development.     

Human choroid plexus: Morphologic and histochemical alterations with age

The choroid plexus was studied in 217 necropsy specimens from human beings two months to 94 years of age. With advancing age, the height of the cuboidal epithelial cell gradually decreases, many becoming squamous. Cytoplasmic vacuoles increase in number. Focal stratification is not an artefact, and is evidence of proliferation. The proliferated cells eventually desquamate, becoming round, large and foamy as they accumulate intracytoplasmic lipid and degenerate. The findings indicate that cellular desquamation occurs during life. Filaments of mucopolysac-charides are common in the choroid plexus of old people. Stromal alterations associated with increased age consist of a gradual increase in the amount of connective tissue, in number of meningocytes and psammoma bodies, and in severity of hyalinization, fibrosis, fragmentation of connective tissue fibers and calcification. Most psammoma bodies are found in the glomus choroideum. Non-lamellar calcific foci occur mainly in the matrix of the choroidal villi and fronds. Formation of psammoma bodies is associated closely with the meningocytic whorls. Lipids, mucopolysaccharides and mucins are identified in both epithelial and stromal components of the choroid plexus. Lipids appear in the stroma later in life. It is suggested that lipid in the cytoplasm of desquamated choroidal eipthelial cells is one source of lipids in the cerebrospinal fluid.     

Structural organization of choroid plexus primordium in human telencephalon

Using the methods of light and electron microscopy and immunocytochemistry, the structure of choroid plexus primordium of telencephalon (epithelial plate) was studied in human embryos at weeks 5-6 of development. It was established that at this stage human choroid plexus primordium is an area of active morphogenesis. Rapid changes in its configuration in the course of choroid plexus formation are preceded by a suppression of proliferation and an activation of degenerative processes. Ultrastructural organization of choroid plexus primordium and specific structural features of its cells indicate that the tissue, forming the epithelial plate, substantially differs from the neuroepithelium that forms the primordia of hippocampus and neocortex, already at this very early stage of prenatal ontogenesis. Accumulation of p53 and bcl-2, proteins participating in apoptosis control, is the evidence of a special functional state of this morphogenetic zone, the detailed characteristic of which requires further research applying a wider spectrum of functional markers.     

大鼠侧脑室脉络丛的超微结构特征

脑和脊髓终生浸浴于一种液体，即脑脊液中。脉络丛位于第Ⅲ、Ⅳ及侧脑室内，一般认为是脑脊液产生的主要场所，也是血-脑脊液屏障的部位所在。有关脉络丛超微结构的研究，国外已有一些报道，但国内尚少见。本文利用扫描和透射电子显微镜观察法，对大鼠侧脑室脉络丛的超微结构进行了深入的研究，以期为进一步探讨其功能提供足够的超微形态学依据。     

Neuroinflammatory response of the choroid plexus epithelium in fatal diabetic ketoacidosis

A systemic inflammatory response (SIR) occurs prior to and during the treatment of severe diabetic ketoacidosis (DKA). IL-1beta, TNF-alpha and C5b-9 are components of SIR and have been speculated to be involved in the clinical brain edema (BE) of DKA. We studied IL-1beta, TNF-alpha, C5b-9, inducible nitric oxide (iNOS), ICAM-1, IL-10 and Hsp70 expression in the brains of two patients who died as the result of clinical BE during the treatment of DKA. IL-1beta was strongly expressed in the choroid plexus epithelium (CPE) and ependyma, and to a lesser extent in the hippocampus, caudate, white matter radiation of the pons, molecular layer of the cerebellum and neurons of the cortical gray matter. TNF-alpha was expressed to a lesser extent than IL-1beta, and only in the CP. C5b-9, previously shown to be deposited on neurons and oligodendrocytes, was found on CPE and ependymal cells. iNOS and ICAM-1 had increased expression in the CPE and ependyma. Hsp70 and IL-10 were also expressed in the CPE of the case with the shorter duration of treatment. Our data demonstrate the presence of a multifaceted neuroinflammatory cytotoxic insult of the CPE, which may play a role in the pathophysiology of the fatal brain edema of DKA.     

Increased aquaporin-1 expression in choroid plexus epithelium after systemic hyponatremia

The expression of aquaporin-1 (AQP1) protein, a water channel, in the choroid plexus epithelium was examined in the rat to determine the role of AQP1 in the pathophysiology of systemic hyponatremia. Systemic hyponatremia was produced by coadministration of 30 ml hypotonic dextrose solution (140 mM) intraperitoneally and 3 μg 1-deamino-8-d-arginine vasopressin (dDAVP) subcutaneously. This hydration protocol produced severe systemic hyponatremia: 2 h after drug administration, normonatremic serum osmolarity and Na⁺ concentration (296 ± 5 mOsm/L and 140 ± 5 mM) were reduced to 252 ± 5 mOsm/L and 117 ± 2 mM, respectively. AQP1 expression in the third ventricle choroid plexus epithelium was determined by using immunohistochemistry and quantitative immunoblot analysis. After 2 h of systemic hyponatremia, AQP1 expression was significantly increased by 28.2 ± 2.7% (n = 6, P < 0.05), whereas it was attenuated to 15.7 ± 2.2% (n = 6, P < 0.05) after 6 h of systemic hyponatremia. In addition, TUNEL staining revealed apoptotic granule cells in the dentate gyrus (DG) adjacent to the third ventricle with a peak measured 2 h after the start of the systemic hyponatremia protocol, while virtually no apoptotic granule cells left 6 h after the start of the hyponatremic treatment. These findings suggest that AQP1-mediated excessive water influx into the brain through the blood-cerebrospinal fluid barrier during systemic hyponatremia may elevate the intracranial pressure and result in the apoptotic brain cell death. Thus, AQP1 in the choroid plexus may play an important role in the pathogenesis of systemic hyponatremia.     

Novel localization of tenascin-X in adult mouse leptomeninges and choroid plexus

Tenascin-X (Tn-X) belongs to the tenascin family of glycoproteins and is clearly associated with the human connective tissue disorder Ehlers-Danlos syndrome. Recently, human single nucleotide polymorphism analyses showed that Tn-X is associated with schizophrenia. Tn-X-related central nervous system (CNS) disorder has been reported in recent years. However, details of Tn-X localization are not clear in the adult cerebral cortex and its meninges. Using immunohistochemical techniques, we found novel localizations of Tn-X in the leptomeningeal trabecula (TB) of adult mice and in the connective tissue of the choroid plexus (CP) in the brains of mice. Subsequent immunohistochemical studies showed complementary localization of Tn-X in the leptomeninges and CP. Localization of tenascin-C was not detected in the leptomeningeal TB or in the connective tissue of the CP. These results might provide insight into the role of Tn-X in the pathogenesis of disorders in the CNS.     

The choroid plexus of the mature and aging rat: The choroidal epithelium

The choroid plexus of mature and old rats has been examined by both scanning and transmission electron microscopy. It has been shown that the macrophages lying upon the ventricular surface of the choroid plexus have a close association with burr-like protrusions that extend from the apical surfaces of the choroidal epithelial cells. These protrusions have a dark cytoplasm filled with vesicles and tubules, and projecting from them are thin, shrunken microvilli. It is suggested that these protrusions are phagocytosed by the macrophages and that they are the source of some of the inclusions which become increasingly common within the cytoplasm of macrophages in older rats. The lateral surfaces of the choroidal epithelial cells have also been examined in the scanning electron microscope after exposure of the surfaces by dissection. In such preparations it is apparent that the elaborate interdigitations between adjacent cells are effected by irregular and vertically arranged folds confined to the basal portions of the lateral cell surfaces. Lastly, it has been shown that at the junction between the choroid plexus and the ependyma in the lateral ventricle, there are two modes of transition between the choroidal and ependymal epithelia. In one, typical choroidal and ependymal epithelial cells lie next to each other to produce a distinct and continuous boundary. In the other mode the boundary is also continuous, but there are modified ependymal cells present. These modified cells have short, relatively sparsely distributed microvilli and not more than one or two cilia.     

Proliferation of epithelial cells in the adult primate choroid plexus

An adult rhesus monkey was injected intraperitoneally with [H³] thymidine (2.3 μCi/gram body weight) and perfused 90 minutes later with a mixture of aldehydes. One and a half micrometer plastic sections were then cut and dipped into liquid emulsion for radioautography. Labeled cells were observed in the choroid plexus of the anterior lateral ventricle; cell identification was evaluated using electron micrographs taken from serial thin sections of reembedded. radioautographic 1.5-μm sections. The ultrastructure and location of both mitotic figures and labeled cells confirmed the presence of undifferentiated basal choroid plexus epithelial cells in the adult primate central nervous system.     

The choroid plexus of the mature and aging rat: the choroidal epithelium.

The choroid plexus of mature and old rats has been examined by both scanning and transmission electron microscopy. It has been shown that the macrophages lying upon the ventricular surface of the choroid plexus have a close association with burr-like protrusions that extend from the apical surfaces of the choroidal epithelial cells. These protrusions have a dark cytoplasm filled with vesicles and tubules, and projecting from them are thin, shrunken microvilli. It is suggested that these protrusions are phagocytosed by the macrophages and that they are the source of some of the inclusions which become increasingly common within the cytoplasm of macrophages in older rats. The lateral surfaces of the choroidal epithelial cells have also been examined in the scanning electron microscope after exposure of the surfaces by dissection. In such preparations it is apparent that the elaborate interdigitations between adjacent cells are effected by irregular and vertically arranged folds confined to the basal portions of the lateral cell surfaces. Lastly, it has been shown that at the junction between the choroid plexus and the ependyma in the lateral ventricle, there are two modes of transition between the choroidal and ependymal epithelia. In one, typical choroidal and ependymal epithelial cells lie next to each other to produce a distinct and continuous bondary. In the other mode the boundary is also continuous, but there are modified ependymal cells present. These modified cells have short, relatively sparsely distributed microvilli and not more than one or two cilia.     

The epithelium of the tongue of Ambystoma mexicanum. Ultrastructural and histochemical aspects.

The distribution pattern of taste buds and goblet cells and histochemical and ultrastructural aspects of the tongue epithelium of Ambystoma mexicanum are here described. This study is also concerned with the developmental stages and origins of the epithelial cells. Pavement cells and goblet cells of the stratum superficiale are replaced by basal cells of the stratum germinativum in larvae and neotenous adults. The pavement cells of the larvae are characterized by a marginal layer of mucin grana. Decompaction of the mucins occurs immediately before extrusion in the adult. The larval goblet cell type (type I), which is also present in the adult, contains unfused grana of irregular shape. At the tip of the tongue, a further type (type II) of goblet cells is found. In the type II cells the intracellular secretory grana fuse to a single homogeneous mass. Leydig cells of the tongue epithelium are discerned by light microscopy first in the semi-adult, apparently correlated with partial metamorphosis. In the course of ontogenesis and induced metamorphosis the secretion changes to neutral glycoconjugates. The mucins of the pavement cells change first followed by those of the goblet cells. The glands of the secondary tongue show a dorso-ventral pattern of varying secretory qualities. Taste buds are found at the anterior margin of the tongue and along the base of the gill clasps in the early larva. They are already distributed all over the tongue at the end of the early larval phase.     

Ultrastructural and histochemical changes of the mouse uterine epithelium on blastocyst activation for implantation

Summary An electron microscopic study was made of the changes of the trophoblast and the uterine epithelium at early implantation. During delay of implantation in mice, only a small amount of secretion was present in the uterine lumen, and the trophoblast-epithelial space was narrow. The luminal part of the uterine epithelial cells contained a 0.1 m deep layer of dense ground cytoplasm devoid of organelles and inclusions. Below this juxtaluminal layer many apical vesicles were seen. The luminal part of the trophoblast cells contained several endocytic vesicles, indicating that in spite of its low metabolic activity, the blastocyst is actively taking up substances at this stage. This also implies that the uterine epithelium is secreting, although at a low rate. At the luminal surface of the uterine epithelium, however, tests for alkaline phosphatase and glucose-6-phosphatase reactions were negative.During early oestrogen-induced activation for implantation, uterine secretion was present in a moderate amount in the lumen and the blastocyst lay separated from the epithelial surface. The apical vesicles of the epithelial cells now also occupied the juxtaluminal layer of cytoplasm, which had previously been free of vesicles. The luminal part of the trophoblast cells still contained many endocytic vesicles. A positive reaction to the alkaline phosphatase test was seen at the epithelial cell surface between 4 and 8 h after injection of oestrogen and still persisted at 16 h. No positive reaction indicating glucose-6-phosphatase was seen. One single implantation site was found at the 16-h stage and this showed a positive reaction to the alkaline phosphatase test at the trophoblast-epithelial border in the embryonal part, but not abembryonically.These findings suggest that a marked increase occurs in the secretory activity of the uterine epithelium only a few hours after initiation of blastocyst activation for implantation. Considering the mode of uterine control of blastocyst activity, the present results would seem to favour the view that the uterine control of implantation is dependent upon the amount and nutritional value of the uterine secretion made available to the blastocyst.     

Papillary carcinoma of choroid plexus

Summary Two cases of papillary carcinoma, one in a 23-month-old girl and the other in a 25-month-old boy who both died within a relatively short time after operation, were studied histologically and electron microscopically. Both tumors originated in the right trigone of the lateral ventricle and spread widely via the cerebrospinal fluid. Histologically, the tumors consisted mostly of a differentiated papillary architecture closely resembling choroid plexus papilloma. Some carcinoma cells, showing cellular atypism, displayed a multilayer arrangement. The amount and distribution of PAS-, Alcian blue- or orcein-positive substances on the cell surface and/or in the interstitial elements of the carcinomas differed from that of choroid papillomas examined in our laboratory. Electron microscopically, the carcinoma cells in some areas showed a loss of apical-basal polarity, and the formation of both microvilli and desmosome-like structures was indistinct. Papillary carcinoma is reviewed on the basis of the literature from 1906 till 1980.The authors thank Dr. S. Nagayoshi, Dr. N. Hirabayashi and Dr. I. Asamoto, who performed the autopsies, for their permission to publish.     

Telocytes in meninges and choroid plexus

Telocytes (TCs) are a recently identified type of interstitial cells present in a wide variety of organs in humans and mammals (www.telocytes.com). They are characterized by a small cell body, but extremely long cell processes - telopodes (Tp), and a specific phenotype. TCs establish close contacts with blood capillaries, nerve fibers and stem cells. We report here identification of TCs by electron microscopy and immunofluorescence in rat meninges and choroid plexus/subventricular zone, in the vicinity of putative stem cells. The presence of TCs in brain areas involved in adult neurogenesis might indicate that they have a role in modulation of neural stem cell fate.