EXPERIMENTAL
AND
MOLECULAR
Morphological
Studies
RONALD
22, 294-301
PATHOLOGY
of the Ventricular
Wall
F. DODSON, YUKIO TAGASHIRA,
Departments of Baylor-Methodist Received
Neurology Center October
and Pathology, for Cerebrovascular 10, 1974,
( 1975 :
AND
in Cerebral LENA
Infarction
WAI-FONG
Baylor College of Medicine, Research, Houston, Texas
and in revised
form
November
’
CHU and 77025
the
13, 1974
The morphological changes in the ependymal lining of the lateral ventricle at the level of the caudate nucleus were studied following periods of ischemia. Ischemia was produced by transorbital occlusion of the middle cerebral artery for periods of one-half, one, two, three, or four hours, respectively. Six animals were studied from each period of occlusion. Two animals per occlusive period were perfused with 3% glutaraldehyde moval of the clip, two were additional animals were perfused
and subependymal
for
electron
microscopy
immediately
perfused at the end of a three-day one week
after
occlusion.
Changes
after
period,
the
re-
and two
in the ependymal
layer were found as early as two hours after occlusion.
These
changes and those seen in the other groups consisted of intracellular vacuolization of the ependymal layer and edematous involvement within the subependymal (astrocytic) layer. The supraependymal (neural) structures appeared less susceptible to ischemia than the ependymal and subependymal layers.
Ventricular cavities of the brain are separated from brain parenchyma by a lining which is morphologically subdivided into supraependymal, ependymal, and subependymal layers (Privat and Leblond, 1972; Lorez and Richards, 1973; Millhouse, 1972). As recently described in the squirrel monkey (Dodson and Chu, 1974), the subependymal region is composed of many astrocytic fibers, some vascular components and fibers of either neuronal or ependymal origin. The ependymal layer is composed of a heterogeneous layer of ependymal cells and tanycytes. The supraependymal elements are composed of nerve fibers or terminals. The ependymal lining is significantly involved in metabolic and functional activities between the parenchymal elements and the cerebrospinal fluid (Dawson, 1967). This association results in the ependymal components being considered as a major portion of the cerebrospinal fluid (liquor)-brain barrier. The functional qualities of this “barrier” are shown to be inferior to that of the blood-brain barrier, particularly with regard to the ‘passage of certain protein tracers ( Bowsher, 1957; Brightman 1965; Brightman, 1967a; Brightman, 196713). Ultrastructural responses in brain parenchyma and microvasculature have been studied following middle cerebral artery occlusion (Dodson et al., 1973; Dodson et al., 1974; Hudgins and Garcia, 1970; Garcia et al., 1971); however, the ultrastructural changes in the ependymal linings have been disregarded until this time. In the present paper, we wish to determine the ultrastructural response of the ependyma on the side subjected to ischemia as well as in the contralateral ependyma. 1 This
work
was
supported
in part
by
U.S.
Public
294 Copyright 0 1975 by Academic Press, Inc. All rights ot reproduction in any form reserved.
Health
Service
Grant
#NS09287.
EPENDYMAL
CHANGES
FOLLOWING
CEREBRAL
INFARCTION
295
The area of ependyma selected for evaluation lines the lateral ventricle at the level of the anterior portion of the caudate nucleus. The susceptibility of the underlying brain #parenchyma to periods of ischemia is reported in both acute studies (Dodson et al., 1973) and at longer postischemic periods following intervals of reflow (Dodson et al., 1974). In the present communication, we will present the morphological response of the ependyma at comparable periods following the original ischemic insult. METHODS The adult squirrel monkeys used in this experiment were lightly anesthetized (sodium pentobarbital) and surgically prepared for transorbital occlusion of the right middle cerebral artery as described by Hudgins and Garcia ( 1970). The animals were divided into groups according to the periods of arterial occlusion: one-half hour, one hour, two hours, three hours, or four hours, respectively. Arterial clips were removed at the termination of each selected time interval. Two animals from each group were perfused immediately after removal of the clip and provided the acute data. Two other animals from each occlusive period were maintained for three days, and two additional animals for a one-week postocclusive ,period. All animals were prepared by whole ,body intracardiac perfusion with a 3% glutaraldehyde/O.l M phosphate system. The selected area of the ependymal lining was dissected from both the right and left sides, postfixed in osmium tetroxide/phosphate buffer, dehydrated in ethanol and embedded in Spurr embedding medium ( Spurr, 1969). Semithin plastic sections were prepared from each block, stained with a polychromatic procedure (Ghidoni et al., 1968) and evaluated by light microscopy. Thin sections prepared with an LKB Ultratome III were stained with 3.5% uranyl acetate/lead citrate (Reynolds, 1963) and examined with an RCA EMU-4 electron microscope. RESULTS The findings for each group of animals will be reported according to the individual periods of vascular occlusion. One-haif Hour Occlusion No changes were apparent in the ependymal linings of those animals perfused immediately after the one-half hour occlusion or in those prepared after three days. Animals studied after a period of one week had involvement within the ependymal layer from the right hemisphere limited to increased intracellular vacuolization within the ependymal layer (Fig. 1). The supraependymal nerve bundles did not demonstrate morphological change. The subependymal (astrocytic) layer contained scattered edematous fibers (Fig. 1). One Hour Occlu&m No abnormalities were seen in the ependymal components of acute animals. Those studied at three days postocclusion contained no changes in the lining from the left side; however, ependymal samples from the right side contained
296
DODSOK,
FIG. I. The ependymal cells Normal organelles, mitochondria lying fibrous layer (f) contains (arrow) in adjacent parenchyma. Inter. X 6,933.
TACASHIRA
AND
CHU
( E ) in this field contain a few vacuolar structures (v). (m), cilia (c), and microvilli (mv) are shown. The underminimal changes; however, perivascular edema is evident Right side, one-half hour occhlsion and perfused one week
EPENDYMAL
CHANGES
FOLLOWING
CEREBRAL
INFARCTION
297
numerous intracellular vacuoles as well as some edema of astrocytic fibers in the subependymal region (Fig. 2). The animals studied at the end of one week contained an a,pparently normal left ventricular wall while changes in the right side were comparable to those seen in the animals studied at three days postocclusion. Invaginated nuclei were commonly seen in the three-day and the one-week groups ( Fig. 3). Two Hour Occlusion Changes in the acute group were limited to vacuolization within the ependymal cells and the underlying fibrous layer of the right side. Lysosomal elements were also usually observed in the ependymal cells. Further vacuolization of ependymal and subependymal elements were observed in the three-day and oneweek animals (Fig. 4). Vacuolization involved endoplasmic reticulum as well as Golgi complexes. Mitochondria usually appeared morphologically intact (Fig. 4). Numerous invaginated nuclei were also intact in the ne-week animals. The left wall appeared morphologically stable, as did the cilia and supraependymal neural elements of the right side. Three Hour Occlzlsion Data from the acute, three-day and one-week animals were comparabIe to that reported in the two-hour group. Four Hour Occlwion The ependymal and subependymal areas from the right side contained no greater involvement than that seen in comparable areas in acute, three-day, and one-week periods of the two-hour groups. However, unlike in the other groups, some tissue changes in the contralateral side were evident in the four-hour occluded/one-week animals. These ,changes were limited to the ependymal layer and consisted of an intracellular increase in number of vacuolar structures (Fig. 5). As in the right ependymal layer, the majority of these vacuoles were derived from distended elements of the endoplasmic reticulum and vesicles associated with the Golgi complexes. Tissue from both sides contained morphologically normal mitochondria. Of particular interest in this group as well as in the animals with shorter periods of occlusion was stability of the supraependymal/neural elements. In only the four-hour occluded/one-week animals were morphological changes observed. These were noted on the right side and consisted of the formation of myelin bodies withm the nerve terminals (Fig. 6). Mitochondrial structures as well as both clear-cored and dense-cored vesicles were still readily identifiable (Fig. 6) within the altered terminals. As in other groups, no morphological changes were observed in either the cilia or microvilli of the ependymal cells (Fig. 6).
FIG. 2. The lining from the right side of this one-hour occluded animal week, contains limited vacuolar response in the ependymal layer (x) cytoplasmic density within some astrocytic fibers (y) in the subependymal
perfused at one-half and a reduction of layer. X 5,100.
298
DODSON,
FIG. 3. The ependymal cell within which is a membranous clumping (arrows) is evident
TAGASHIRA
AND
CHU
(E ) sh own in this micrograph contains a large vacuole (V) swirl (X). This plane shows nuclear invagination. Chromatin adjacent to the invaginated envelope. The cytoplasm within
EPENDYMAL
CHANGES
FOLLOWING
CEREBRAL
INFARCTION
299
DISCUSSION The ventricular lining at the level of the caudate nucleus is susceptible to ischemia. Greater changes are found within the ependymal layer proper and in the subependymal-fibrous layer than in the supraependymal layer. Morphological changes are noted to be less severe than the changes reported in the underlying portion of caudate nucleus for the same duration of occlusion and at the same postocclusive interval (Dodson et al., 1973; Dodson et al., 1974). As reported (Dodson et al., 1973), the earliest tissue response following &hernia induced by Hudgins’ transorbital model results in involvement of perivascular fibers of the astrocytes. Ischemic changes within the subependymal layer which consisted of numerous astrocytic fibers are com,parable to those changes reported in intraparenchymal, nonperivascular astrocytic fibers at the same period of occlusion, and postocclusion (Dodson et al., 1973; Dodson et al., 1974). Morphological changes within the ependymal layer are observed in the acute animal after two-hour occlusion. These changes consist of increased vacuolization of the intracellular membranous systems. Vacuoles are derived from distended vesicles associated with smooth endoplasmic reticulum, rough endoplasmic reticulum, Golgi complexes, a few mitochondria, and/or cellular membrane invaginations. The alterations in these anabolically important organelles, invagination of the nuclear envelope, the increase in the number of catabolic organelles ( lysosomes ), and the inclusions indicate an involvement which would be expected to change the ability of the cell to function. Since changes in the ventricular wall were seen on the ischemic right side with one exception, we consider the morphological response to result directly or secondarily from the ischemia. In the group which did contain left-sided involvement (four hours occlusion, one-week group), those changes were less than the changes in the ependymal layer on the right side. The changes on the left side are most likely induced by the influence of intraventricular neurotransmitters or metabolites released from the more damaged right side rather than by the direct effect of ischemia on the ependymal tissue. This concept is supported in that ependymal ‘changes on the left were greater than the changes in underlying parenchyma of the brain (Dodson et al., 1973), whereas the changes in the ependymal complex on the right side consistently were not as advanced as those in the underlying ischemic brain tissue. The stability of the supraependymal elements suggest that they are derived from neurons which are located in the regions of reduced involvement. ACKNOWLEDGMENTS The authors express their appreciation to Dr. John Stirling Meyer and Dr. for their helpful suggestions during the completion of this project, and to Mrs. for her assistance in the preparation of the manuscript.
Jack L. Titus Kathy Tucker
the invagination contains several vacuoles (v). A large lysosomal body ( L) is present within the cytoplasm of the adjacent cell. Right side, one hour occlusion, perfused at one week. x 7,064. FIG. 4. The tissue from the right wall of this two-hour occluded animal maintained for one week, contains numerous vacuoles (v) and lysosomes (1). Many nonswollen and morphologically intact mitochondria (m) are present, Microvilh (mv) and cilia (c) are normal in appearance. X 7,480.
FIG. 5. Changes which occurred on the left side of the four-hour occluded animals after one week consist of vacuolar structures (v) within the ependymal layer. Mitochondria (m), cilia ( c), microvilli ( mv), as well as supraependymal neural elements (arrows) are unchanged. X 15,002.
EPENDYMAL
CHANGES
FOLLOWING
CEREBRAL
INFARCTION
301
REFERENCES DAWSON, H. ( 1967). “Physiology of the Cerebrospinal Fluid.” Little, Brown and Company, Boston, Mass. BOWSHER, D. (1957). Pathways of adsorption of protein from cerebrospinal fluid: an autoradiographic study in the cat. Anat. Rec. 218, 23-40. BRIGHTMAN, M. W. ( 1965). The distribution within the brain of ferritin-injected into cerebrospinal fluid compartments. I. Ependymal distribution. J. CeZZ Biol. 26, 99-123. BRIGHTMAN, M. W. ( 1967a). Movement within the brain of ferritin-injected into the cerebrospinal fluid compartment. In “Brain Edema,” (I. Klatzo and F. Seitelberger Eds.), pp. 271284. Springer-Verlag, Inc., N.Y. BRIGHTMAN, M. W. (1967b). The intracerebral movement of proteins injected into blood and cerebrospinal fluid of mice. In “Progress in Brain Research,” (A. Lajtha and D. H. Ford Eds.), pp. 19-37. Elsevier Publishing Co., Amsterdam. DODSON, R. F., KAWAMURA, Y., AOYAGI, M., HARTMANN, A., and CHEUNG, L. W. (1973). A comparative evaluation of the ultrastructural changes following induced cerebral infarction in the squirrel monkey and baboon. Cytobios 8, 175-182. D~DSON, R. F., TAGASHIRA, Y., KAWAMURA, Y., and CHU, L. W. (1974). Mor.phological responses of cerebral tissues following temporary ischemia. Submitted. HUDGINS, W. R., and GARCIA, J. H. (1970). Transorbital approach to the middle cerebral artery of the squirrel monkey: a technique for experimental cerebral infarction applicable to ultrastructural studies. Stroke 1, 107-111. SPURR, A. R. ( 1969). A low-viscosity epoxy resin embedding medium for electron microscopy. J. Vltrastruct. Res. 26,31-43. GHIWNI, J. J., CAMPBELL, M. M., ADAMS, J. G., THOMAS, H., and RAMOS, E. E. (1968). A new multicolor staining procedure for one-micron sections of epoxy embedment. Proc. Electr. Micros. Sot. Amer., 240-241. REYNOLDS, E. S. (1963). The use of lead citrate at high pH .as an electron opaque stain in electron microscopy. 1. CeZZ Bid. 17, 209-212. GARCIA, J. H., Cox, J. V., and HUDGINS, W. R. ( 1971). Ultrastructure of the microvasculature in experimental cerebral infarction, Acta NeUTOpUth. 18, 273-285. DODSON, R. F., and CHU, L. W. ( 1974). Ultrastructure of ependymal and subependymal cells in the lateral ventricle of the squirrel monkey. Cytobios, in press. PRIVAT, A., and LEBLOND, C. P. ( 1972). The subependymal layer and neighboring region in the brain of the young rat. J. Comp. NWTO~. 146, 277302. LOREZ, H. P., and RICHARDS, J. G. (1973). Distribution of indolealkylamine nerve terminals in the ventricles of the rat brain. 2. Zellforsch. 144, 511-522. MILLHOUSE, 0. E. ( 1972). Light and electron microscopic studies of the ventricular wall, Z. Zellforsch. 127, 149-174.
FIG. week, neural terminals. within adjacent
6. Changes on the right side of the four-hour occluded animals perfused after one consist of increased vacuolar (v) content, but involvement of the supraependymal elements (N) is more significant. Dense myelin figures (MF) are seen within the Clear cored (cc), dense cored (dc), and mixed vesicles could still be recognized such terminals as well as normal appearing mitochondria (m). Cilia (c) in the area appear normal. X 52,755.
AND
MOLECULAR
Morphological
Studies
RONALD
22, 294-301
PATHOLOGY
of the Ventricular
Wall
F. DODSON, YUKIO TAGASHIRA,
Departments of Baylor-Methodist Received
Neurology Center October
and Pathology, for Cerebrovascular 10, 1974,
( 1975 :
AND
in Cerebral LENA
Infarction
WAI-FONG
Baylor College of Medicine, Research, Houston, Texas
and in revised
form
November
’
CHU and 77025
the
13, 1974
The morphological changes in the ependymal lining of the lateral ventricle at the level of the caudate nucleus were studied following periods of ischemia. Ischemia was produced by transorbital occlusion of the middle cerebral artery for periods of one-half, one, two, three, or four hours, respectively. Six animals were studied from each period of occlusion. Two animals per occlusive period were perfused with 3% glutaraldehyde moval of the clip, two were additional animals were perfused
and subependymal
for
electron
microscopy
immediately
perfused at the end of a three-day one week
after
occlusion.
Changes
after
period,
the
re-
and two
in the ependymal
layer were found as early as two hours after occlusion.
These
changes and those seen in the other groups consisted of intracellular vacuolization of the ependymal layer and edematous involvement within the subependymal (astrocytic) layer. The supraependymal (neural) structures appeared less susceptible to ischemia than the ependymal and subependymal layers.
Ventricular cavities of the brain are separated from brain parenchyma by a lining which is morphologically subdivided into supraependymal, ependymal, and subependymal layers (Privat and Leblond, 1972; Lorez and Richards, 1973; Millhouse, 1972). As recently described in the squirrel monkey (Dodson and Chu, 1974), the subependymal region is composed of many astrocytic fibers, some vascular components and fibers of either neuronal or ependymal origin. The ependymal layer is composed of a heterogeneous layer of ependymal cells and tanycytes. The supraependymal elements are composed of nerve fibers or terminals. The ependymal lining is significantly involved in metabolic and functional activities between the parenchymal elements and the cerebrospinal fluid (Dawson, 1967). This association results in the ependymal components being considered as a major portion of the cerebrospinal fluid (liquor)-brain barrier. The functional qualities of this “barrier” are shown to be inferior to that of the blood-brain barrier, particularly with regard to the ‘passage of certain protein tracers ( Bowsher, 1957; Brightman 1965; Brightman, 1967a; Brightman, 196713). Ultrastructural responses in brain parenchyma and microvasculature have been studied following middle cerebral artery occlusion (Dodson et al., 1973; Dodson et al., 1974; Hudgins and Garcia, 1970; Garcia et al., 1971); however, the ultrastructural changes in the ependymal linings have been disregarded until this time. In the present paper, we wish to determine the ultrastructural response of the ependyma on the side subjected to ischemia as well as in the contralateral ependyma. 1 This
work
was
supported
in part
by
U.S.
Public
294 Copyright 0 1975 by Academic Press, Inc. All rights ot reproduction in any form reserved.
Health
Service
Grant
#NS09287.
EPENDYMAL
CHANGES
FOLLOWING
CEREBRAL
INFARCTION
295
The area of ependyma selected for evaluation lines the lateral ventricle at the level of the anterior portion of the caudate nucleus. The susceptibility of the underlying brain #parenchyma to periods of ischemia is reported in both acute studies (Dodson et al., 1973) and at longer postischemic periods following intervals of reflow (Dodson et al., 1974). In the present communication, we will present the morphological response of the ependyma at comparable periods following the original ischemic insult. METHODS The adult squirrel monkeys used in this experiment were lightly anesthetized (sodium pentobarbital) and surgically prepared for transorbital occlusion of the right middle cerebral artery as described by Hudgins and Garcia ( 1970). The animals were divided into groups according to the periods of arterial occlusion: one-half hour, one hour, two hours, three hours, or four hours, respectively. Arterial clips were removed at the termination of each selected time interval. Two animals from each group were perfused immediately after removal of the clip and provided the acute data. Two other animals from each occlusive period were maintained for three days, and two additional animals for a one-week postocclusive ,period. All animals were prepared by whole ,body intracardiac perfusion with a 3% glutaraldehyde/O.l M phosphate system. The selected area of the ependymal lining was dissected from both the right and left sides, postfixed in osmium tetroxide/phosphate buffer, dehydrated in ethanol and embedded in Spurr embedding medium ( Spurr, 1969). Semithin plastic sections were prepared from each block, stained with a polychromatic procedure (Ghidoni et al., 1968) and evaluated by light microscopy. Thin sections prepared with an LKB Ultratome III were stained with 3.5% uranyl acetate/lead citrate (Reynolds, 1963) and examined with an RCA EMU-4 electron microscope. RESULTS The findings for each group of animals will be reported according to the individual periods of vascular occlusion. One-haif Hour Occlusion No changes were apparent in the ependymal linings of those animals perfused immediately after the one-half hour occlusion or in those prepared after three days. Animals studied after a period of one week had involvement within the ependymal layer from the right hemisphere limited to increased intracellular vacuolization within the ependymal layer (Fig. 1). The supraependymal nerve bundles did not demonstrate morphological change. The subependymal (astrocytic) layer contained scattered edematous fibers (Fig. 1). One Hour Occlu&m No abnormalities were seen in the ependymal components of acute animals. Those studied at three days postocclusion contained no changes in the lining from the left side; however, ependymal samples from the right side contained
296
DODSOK,
FIG. I. The ependymal cells Normal organelles, mitochondria lying fibrous layer (f) contains (arrow) in adjacent parenchyma. Inter. X 6,933.
TACASHIRA
AND
CHU
( E ) in this field contain a few vacuolar structures (v). (m), cilia (c), and microvilli (mv) are shown. The underminimal changes; however, perivascular edema is evident Right side, one-half hour occhlsion and perfused one week
EPENDYMAL
CHANGES
FOLLOWING
CEREBRAL
INFARCTION
297
numerous intracellular vacuoles as well as some edema of astrocytic fibers in the subependymal region (Fig. 2). The animals studied at the end of one week contained an a,pparently normal left ventricular wall while changes in the right side were comparable to those seen in the animals studied at three days postocclusion. Invaginated nuclei were commonly seen in the three-day and the one-week groups ( Fig. 3). Two Hour Occlusion Changes in the acute group were limited to vacuolization within the ependymal cells and the underlying fibrous layer of the right side. Lysosomal elements were also usually observed in the ependymal cells. Further vacuolization of ependymal and subependymal elements were observed in the three-day and oneweek animals (Fig. 4). Vacuolization involved endoplasmic reticulum as well as Golgi complexes. Mitochondria usually appeared morphologically intact (Fig. 4). Numerous invaginated nuclei were also intact in the ne-week animals. The left wall appeared morphologically stable, as did the cilia and supraependymal neural elements of the right side. Three Hour Occlzlsion Data from the acute, three-day and one-week animals were comparabIe to that reported in the two-hour group. Four Hour Occlwion The ependymal and subependymal areas from the right side contained no greater involvement than that seen in comparable areas in acute, three-day, and one-week periods of the two-hour groups. However, unlike in the other groups, some tissue changes in the contralateral side were evident in the four-hour occluded/one-week animals. These ,changes were limited to the ependymal layer and consisted of an intracellular increase in number of vacuolar structures (Fig. 5). As in the right ependymal layer, the majority of these vacuoles were derived from distended elements of the endoplasmic reticulum and vesicles associated with the Golgi complexes. Tissue from both sides contained morphologically normal mitochondria. Of particular interest in this group as well as in the animals with shorter periods of occlusion was stability of the supraependymal/neural elements. In only the four-hour occluded/one-week animals were morphological changes observed. These were noted on the right side and consisted of the formation of myelin bodies withm the nerve terminals (Fig. 6). Mitochondrial structures as well as both clear-cored and dense-cored vesicles were still readily identifiable (Fig. 6) within the altered terminals. As in other groups, no morphological changes were observed in either the cilia or microvilli of the ependymal cells (Fig. 6).
FIG. 2. The lining from the right side of this one-hour occluded animal week, contains limited vacuolar response in the ependymal layer (x) cytoplasmic density within some astrocytic fibers (y) in the subependymal
perfused at one-half and a reduction of layer. X 5,100.
298
DODSON,
FIG. 3. The ependymal cell within which is a membranous clumping (arrows) is evident
TAGASHIRA
AND
CHU
(E ) sh own in this micrograph contains a large vacuole (V) swirl (X). This plane shows nuclear invagination. Chromatin adjacent to the invaginated envelope. The cytoplasm within
EPENDYMAL
CHANGES
FOLLOWING
CEREBRAL
INFARCTION
299
DISCUSSION The ventricular lining at the level of the caudate nucleus is susceptible to ischemia. Greater changes are found within the ependymal layer proper and in the subependymal-fibrous layer than in the supraependymal layer. Morphological changes are noted to be less severe than the changes reported in the underlying portion of caudate nucleus for the same duration of occlusion and at the same postocclusive interval (Dodson et al., 1973; Dodson et al., 1974). As reported (Dodson et al., 1973), the earliest tissue response following &hernia induced by Hudgins’ transorbital model results in involvement of perivascular fibers of the astrocytes. Ischemic changes within the subependymal layer which consisted of numerous astrocytic fibers are com,parable to those changes reported in intraparenchymal, nonperivascular astrocytic fibers at the same period of occlusion, and postocclusion (Dodson et al., 1973; Dodson et al., 1974). Morphological changes within the ependymal layer are observed in the acute animal after two-hour occlusion. These changes consist of increased vacuolization of the intracellular membranous systems. Vacuoles are derived from distended vesicles associated with smooth endoplasmic reticulum, rough endoplasmic reticulum, Golgi complexes, a few mitochondria, and/or cellular membrane invaginations. The alterations in these anabolically important organelles, invagination of the nuclear envelope, the increase in the number of catabolic organelles ( lysosomes ), and the inclusions indicate an involvement which would be expected to change the ability of the cell to function. Since changes in the ventricular wall were seen on the ischemic right side with one exception, we consider the morphological response to result directly or secondarily from the ischemia. In the group which did contain left-sided involvement (four hours occlusion, one-week group), those changes were less than the changes in the ependymal layer on the right side. The changes on the left side are most likely induced by the influence of intraventricular neurotransmitters or metabolites released from the more damaged right side rather than by the direct effect of ischemia on the ependymal tissue. This concept is supported in that ependymal ‘changes on the left were greater than the changes in underlying parenchyma of the brain (Dodson et al., 1973), whereas the changes in the ependymal complex on the right side consistently were not as advanced as those in the underlying ischemic brain tissue. The stability of the supraependymal elements suggest that they are derived from neurons which are located in the regions of reduced involvement. ACKNOWLEDGMENTS The authors express their appreciation to Dr. John Stirling Meyer and Dr. for their helpful suggestions during the completion of this project, and to Mrs. for her assistance in the preparation of the manuscript.
Jack L. Titus Kathy Tucker
the invagination contains several vacuoles (v). A large lysosomal body ( L) is present within the cytoplasm of the adjacent cell. Right side, one hour occlusion, perfused at one week. x 7,064. FIG. 4. The tissue from the right wall of this two-hour occluded animal maintained for one week, contains numerous vacuoles (v) and lysosomes (1). Many nonswollen and morphologically intact mitochondria (m) are present, Microvilh (mv) and cilia (c) are normal in appearance. X 7,480.
FIG. 5. Changes which occurred on the left side of the four-hour occluded animals after one week consist of vacuolar structures (v) within the ependymal layer. Mitochondria (m), cilia ( c), microvilli ( mv), as well as supraependymal neural elements (arrows) are unchanged. X 15,002.
EPENDYMAL
CHANGES
FOLLOWING
CEREBRAL
INFARCTION
301
REFERENCES DAWSON, H. ( 1967). “Physiology of the Cerebrospinal Fluid.” Little, Brown and Company, Boston, Mass. BOWSHER, D. (1957). Pathways of adsorption of protein from cerebrospinal fluid: an autoradiographic study in the cat. Anat. Rec. 218, 23-40. BRIGHTMAN, M. W. ( 1965). The distribution within the brain of ferritin-injected into cerebrospinal fluid compartments. I. Ependymal distribution. J. CeZZ Biol. 26, 99-123. BRIGHTMAN, M. W. ( 1967a). Movement within the brain of ferritin-injected into the cerebrospinal fluid compartment. In “Brain Edema,” (I. Klatzo and F. Seitelberger Eds.), pp. 271284. Springer-Verlag, Inc., N.Y. BRIGHTMAN, M. W. (1967b). The intracerebral movement of proteins injected into blood and cerebrospinal fluid of mice. In “Progress in Brain Research,” (A. Lajtha and D. H. Ford Eds.), pp. 19-37. Elsevier Publishing Co., Amsterdam. DODSON, R. F., KAWAMURA, Y., AOYAGI, M., HARTMANN, A., and CHEUNG, L. W. (1973). A comparative evaluation of the ultrastructural changes following induced cerebral infarction in the squirrel monkey and baboon. Cytobios 8, 175-182. D~DSON, R. F., TAGASHIRA, Y., KAWAMURA, Y., and CHU, L. W. (1974). Mor.phological responses of cerebral tissues following temporary ischemia. Submitted. HUDGINS, W. R., and GARCIA, J. H. (1970). Transorbital approach to the middle cerebral artery of the squirrel monkey: a technique for experimental cerebral infarction applicable to ultrastructural studies. Stroke 1, 107-111. SPURR, A. R. ( 1969). A low-viscosity epoxy resin embedding medium for electron microscopy. J. Vltrastruct. Res. 26,31-43. GHIWNI, J. J., CAMPBELL, M. M., ADAMS, J. G., THOMAS, H., and RAMOS, E. E. (1968). A new multicolor staining procedure for one-micron sections of epoxy embedment. Proc. Electr. Micros. Sot. Amer., 240-241. REYNOLDS, E. S. (1963). The use of lead citrate at high pH .as an electron opaque stain in electron microscopy. 1. CeZZ Bid. 17, 209-212. GARCIA, J. H., Cox, J. V., and HUDGINS, W. R. ( 1971). Ultrastructure of the microvasculature in experimental cerebral infarction, Acta NeUTOpUth. 18, 273-285. DODSON, R. F., and CHU, L. W. ( 1974). Ultrastructure of ependymal and subependymal cells in the lateral ventricle of the squirrel monkey. Cytobios, in press. PRIVAT, A., and LEBLOND, C. P. ( 1972). The subependymal layer and neighboring region in the brain of the young rat. J. Comp. NWTO~. 146, 277302. LOREZ, H. P., and RICHARDS, J. G. (1973). Distribution of indolealkylamine nerve terminals in the ventricles of the rat brain. 2. Zellforsch. 144, 511-522. MILLHOUSE, 0. E. ( 1972). Light and electron microscopic studies of the ventricular wall, Z. Zellforsch. 127, 149-174.
FIG. week, neural terminals. within adjacent
6. Changes on the right side of the four-hour occluded animals perfused after one consist of increased vacuolar (v) content, but involvement of the supraependymal elements (N) is more significant. Dense myelin figures (MF) are seen within the Clear cored (cc), dense cored (dc), and mixed vesicles could still be recognized such terminals as well as normal appearing mitochondria (m). Cilia (c) in the area appear normal. X 52,755.
