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Scanning electron microscopy study of the choroid plexus in the monkey (Cebus apella apella)

Estudo do plexo coróide no macaco (Cebus apella apella) ao microscópio eletrônico de varredura

Abstracts

The cells of the choroid plexus of the lateral ventricles of the monkey Cebus apella apella were examined through scanning electron microscopy at contributing to the description of such structures in primates. The animals were anesthetized previously with 3% hypnol intraperitoneally and after perfusion with 2.5% glutaraldehyde, samples of the choroid plexus were collected after exhibition of the central portion and inferior horn of the lateral ventricles. The ventricular surface of those cells presents globose form as well as fine interlaced protrusions named microvilli. Among those, it is observed the presence of some cilia. Resting on the choroid epithelial cells there is a variable number of free cells, with fine prolongations which extend from them. They are probably macrophages and have been compared to Kolmer cells or epiplexus cells, located on choroid epithelium. The choroid plexus of the encephalic lateral ventricles of the monkey Cebus apella apella at scanning electron microscopy is similar to that of other primates, as well as to that of other species of mammals mainly cats and rats, and also humans.

choroid plexus; monkey; scanning electron microscopy


As células do plexo coróide dos ventrículos laterais do macaco-prego (Cebus apella apella) foram examinadas ao microscópio eletrônico de varredura com o objetivo de melhor descrever e comparar este órgão ao de outras espécies de mamíferos, principalmente o homem. Inicialmente, os animais foram previamente anestesiados com hipnol a 3% intraperitonealmente e após perfusão com glutaraldeído 2,5%, amostras dos plexos coróides foram coletadas após exibição da porção central e corno inferior dos ventrículos laterais. A superfície ventricular dessas células apresenta forma globosa e a presença de finas protrusões entrelaçadas denominadas microvilosidades. Entre estas, observam-se alguns cílios. Repousando sobre as células epiteliais coróides está presente um número variável de células livres com finos prolongamentos que delas se estendem. São provavelmente macrófagos e têm sido comparadas com as células de Kolmer ou do epiplexo, localizadas sobre o epitélio coróide. O plexo coróide dos ventrículos encefálicos laterais do macaco Cebus apella apella ao microscópio eletrônico de varredura é similar ao de outros primatas, assim como de outras espécies de mamíferos, principalmente gatos e ratos, e também de humanos.

plexo coróide; macaco; microscópio eletrônico de varredura


SCANNING ELECTRON MICROSCOPY STUDY OF THE CHOROID PLEXUS IN THE MONKEY (CEBUS APELLA APELLA)

OISENYL JOSÉ TAMEGA* * Department of Anatomy, Institute of Biosciences (IB), State University of São Paulo (UNESP): Postgraduating; ** Professor. Aceite 22 maio 2000. , LUÍS FERNANDO TIRAPELLI** * Department of Anatomy, Institute of Biosciences (IB), State University of São Paulo (UNESP): Postgraduating; ** Professor. Aceite 22 maio 2000. , SIDNEI PETRONI** * Department of Anatomy, Institute of Biosciences (IB), State University of São Paulo (UNESP): Postgraduating; ** Professor. Aceite 22 maio 2000.

ABSTRACT - The cells of the choroid plexus of the lateral ventricles of the monkey Cebus apella apella were examined through scanning electron microscopy at contributing to the description of such structures in primates. The animals were anesthetized previously with 3% hypnol intraperitoneally and after perfusion with 2.5% glutaraldehyde, samples of the choroid plexus were collected after exhibition of the central portion and inferior horn of the lateral ventricles. The ventricular surface of those cells presents globose form as well as fine interlaced protrusions named microvilli. Among those, it is observed the presence of some cilia. Resting on the choroid epithelial cells there is a variable number of free cells, with fine prolongations which extend from them. They are probably macrophages and have been compared to Kolmer cells or epiplexus cells, located on choroid epithelium. The choroid plexus of the encephalic lateral ventricles of the monkey Cebus apella apella at scanning electron microscopy is similar to that of other primates, as well as to that of other species of mammals mainly cats and rats, and also humans.

KEY WORDS: choroid plexus, monkey, scanning electron microscopy.

Estudo do plexo coróide no macaco (Cebus apella apella) ao microscópio eletrônico de varredura

RESUMO - As células do plexo coróide dos ventrículos laterais do macaco-prego (Cebus apella apella) foram examinadas ao microscópio eletrônico de varredura com o objetivo de melhor descrever e comparar este órgão ao de outras espécies de mamíferos, principalmente o homem. Inicialmente, os animais foram previamente anestesiados com hipnol a 3% intraperitonealmente e após perfusão com glutaraldeído 2,5%, amostras dos plexos coróides foram coletadas após exibição da porção central e corno inferior dos ventrículos laterais. A superfície ventricular dessas células apresenta forma globosa e a presença de finas protrusões entrelaçadas denominadas microvilosidades. Entre estas, observam-se alguns cílios. Repousando sobre as células epiteliais coróides está presente um número variável de células livres com finos prolongamentos que delas se estendem. São provavelmente macrófagos e têm sido comparadas com as células de Kolmer ou do epiplexo, localizadas sobre o epitélio coróide. O plexo coróide dos ventrículos encefálicos laterais do macaco Cebus apella apella ao microscópio eletrônico de varredura é similar ao de outros primatas, assim como de outras espécies de mamíferos, principalmente gatos e ratos, e também de humanos.

PALAVRAS-CHAVE: plexo coróide, macaco, microscópio eletrônico de varredura.

The discovery of the choroid plexus of the encephalic ventricles was attributed by Galeno to Herophilus (335-280 a.C.) who named them "chorioid menix". Rufos of Ephesus suggested the term "chorioid tunic" to describe the ependyma as the choroid plexus 1. Later, the choroid plexus was studied at light and electron microscope levels in different animals and by several authors 2-13.

The choroid plexus consists of vascular folds from the piamater externally covered by an epithelium derived from the ependimary coating of the ventricles 12. Testut & Latarjet 14 refer to the choroid plexus of the lateral ventricles as J-shaped red and granular cords which successively occupy the sphenoidal and frontal portion of the lateral ventricles. More recently, the choroid plexus is histologically described as being formed by small amount of loose connective tissue derived from the piamater and covered by a cubic simple epithelium or a low columnar one originating from the neural tube 15. Since the last century, several authors (Faivre, 1853; Luschka, 1855; and Claisse & Levi, 1897)1,4 have attributed to the choroid plexus, among other functions, an outstanding participation in the production of cerebrospinal fluid (CSF) which surrounds the central nervous system. In spite of its important function and although it has been described thoroughly in several species of mammals, the choroid plexus is a structure which has not been studied in primates 16-18.

Thus, the objective of the present investigation was to examine the choroid plexus of the monkey Cebus apella apella by scanning electron microscopy for better describe and compare this organ to that of other species of mammals, mainly the human.

METHOD

Three adult male monkey (Cebus apella apella), from the Núcleo de Procriação de Primatas of the UNESP Araçatuba Campus, were used. The animals were anesthetized intraperitoneally with 3% hypnol. After perfusion with 2.5% glutaraldehyde, samples of the choroid plexus were collected after craniotomy and exhibition of the central portion and inferior horn of the lateral ventricles.

These structures were washed in 0.2 M sodium phosphate solution, pH 7.4 and immersed in 2.5% glutaraldehyde. After being fixed for 24 hours at room temperature, the samples were washed in 0.1 M sodium phosphate solution, pH 7.3. Afterwards they were post-fixed in 1% osmic tetroxide solution, for one hour in the same solution and again washed in phosphate solution. The dehydration was conducted in growing levels of ethanol, starting from 75% up to the absolute. The drying of the pieces was done by a Balzers CPD-020 critical point apparatus, using dioxide of liquid carbon. Afterwards they were mounted in metallic bases with silver glue covered with 10 nm of gold in Balzers MED-010 apparatus and examined in scanning electron microscopy SEM 515-Philips, under 15 Kv tension at the Center of Electronic Microscopy of IB/UNESP.

RESULTS

The surface of the choroid plexus of the lateral ventricles at low magnification is constituted by folds or crests in a kind of parallel way (Figs 1 and 2). These folds have varied dimensions, and at scanning electron microscopy, the surface shows apparently homogeneous projections similar to vesicles, each one representing a choroid cell (Figs 1 and 2). The diameter of the cells varies between 7 and 11 µm.



The areas that surround each one of the cellular projections are deeper and electron-dense (Figs 3 and 4), corresponding to junction sites among the adjacent choroid cells through luminal surface of its lateral walls which at this place are united by a junctional complex.



At higher magnification, it is visible at the surface of each epithelial choroid cells the presence of a tangling of fine and irregular projections named microvilli (Figs 3 and 4). It is observed some cilia among those (Fig 3).

It was observed the presence of cells close to the luminal surface of choroid epithelium. These prolonged cells present cytoplasmatic prolongations similar to the expansions of the perikaryon and are observed indented to the microvilli of the ependimary cellular surface. Firstly described by Kolmer (1921), they were named "cells of the epiplexus" or "Kolmer cells" (Figs 2, 5 and 6 ).

DISCUSSION

The choroid plexus of the encephalic lateral ventricles of the monkey Cebus apella apella at scanning electron microscopy is similar to that in other primates 18, as well as to that in other species of mammals mainly cats 9,16 and rats 11, and also humans 12.

According to the diameter of the choroid cells, similar values found in our study were also reported in the choroid plexus of the lateral ventricles of rats 11.

The microvilli and the presence of some cilia described in this species could also be observed in rats11 and in humans 12. These fine and irregular microvilli show their importance in the increase of the surface area of the cell, an important factor for their secretory activity, as well as other cellular characteristics.

However, the presence of cells with different appearance was described 11 which, instead of fine and long protrusions, were more swollen and with a foamy surface. Such cells could not be observed in this study.

Reported as leukocytes which infiltrate in the lateral ventricles, Kolmer cells still have their origin being contested by several authors 7,11,17-19. Those cells have their origin from cell elements of the estroma of connective tissue 19,20. Carpenter et al. 16 proposed that monocytes crossed the choroid blood vessels and then penetrate in the space of connective tissue, being then macrophages and consequently crossed the choroid epithelium to become "epiplexus cells".

In studies under electron microscopy scanning was observed 16,17 such cells resting in the microvilli of the choroid cells and sometimes showing their surface indented by the projections of the microvilli and cilia of those cells.

Studies about choroid plexus show that the "epiplexus cells" have their origin from monocytes16,18. This suggests the same origin for the "epiplexus cells" of the monkey, due to the presented morphologic similarity.

Studies in rats21 suggest that the "epiplexus cells" along with lysosomal activity of these choroid epithelial cells act as a protection and defense line, helped yet by the blood-CSF barrier.

Dr. Oisenyl José Tamega - Department of Anatomy, Institute of Biosciences, UNESP - 18618-000 Rubião Júnior SP - Brasil. FAX 14 821 3744. E-mail: anatomia@ibb.unesp.br

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  • *
    Department of Anatomy, Institute of Biosciences (IB), State University of São Paulo (UNESP):
    Postgraduating;
    **
    Professor. Aceite 22 maio 2000.
  • Publication Dates

    • Publication in this collection
      06 Dec 2000
    • Date of issue
      Sept 2000

    History

    • Accepted
      22 May 2000
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