Localization of mu class glutathione-S-transferase in the forebrains of neonatal and young rats: implications for astrocyte development.

The Yb (Mu class) isoform of glutathione-S-transferase has recently been localized in ependymal cells, subependymal cells, and astrocytes in the forebrains of rats 3 weeks to adult in age. It was not known, however, at what age Mu might first be observed during postnatal development and whether the first cells in which it was found would be immature astrocytes or some less differentiated glial precursor cell, if the latter were present in vivo. Tissue sections from the forebrains of neonatal to 16 day old rats were immunostained with antibodies against Mu. In neonates Mu was observed in vimentin-positive cells and their processes adjacent to the lateral ventricles, and in the corpus striatum. The colocalization with vimentin suggested that these were subependymal cells and radial glia. In the corpus striatum the radial glia, while still vimentin-positive, rapidly lost Mu from their radial cell processes, whereas the cell-bodies remained Mu-positive. During the first postnatal week the Mu-positive, glial-fibrillary-acidic-protein (GFAP)-positive cell bodies of immature astrocytes appeared in the corpus striatum. The earliest Mu-positive cells in the immature white matter of the corpus callosum were vimentin-positive and had striking longitudinal processes that also were vimentin- and Mu-positive. Like the processes of radial glia, the longitudinal processes lost their Mu-immunoreactivity, only later and more gradually. Mu-positive, GFAP-positive cells appeared later in the corpus callosum than in the corpus striatum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Carbonic anhydrase in distinct precursors of astrocytes and oligodendrocytes in the forebrains of neonatal and young rats.

Carbonic anhydrase is present in oligodendrocytes and astrocytes in the mature rat brain. Whereas carbonic anhydrase-positive oligodendrocyte precursors had been identified during the first postnatal week, no information was available about the earliest occurrence of carbonic anhydrase in the astrocytic cell line, nor had carbonic anhydrase been detected in astrocytes in neonatal rat brains. Beginning on the first postnatal day, rat brains were double immunostained with anti-carbonic anhydrase II and respective 'markers' for immature and mature astrocytes and oligodendrocytes. During the first postnatal week there were intensely carbonic anhydrase-positive cells which were ovoid or had broad processes. On the basis of their shapes and antigen contents these were considered to be precursors of oligodendrocytes. Beginning on the first postnatal day carbonic anhydrase II was also observed in some vimentin-positive radial glia and in other vimentin-positive cells that differed in their appearance from the immature oligodendrocytes. The vimentin-positive, carbonic anhydrase-positive cells were less smooth-surfaced, and had much finer processes, than the oligodendrocyte precursors. By the third postnatal day there appeared carbonic anhydrase-positive, glial fibrillary acidic protein (GFAP)-positive cells that resembled the vimentin-positive cells. It is concluded that the latter are immature astrocytes and that carbonic anhydrase is in distinct precursors of oligodendrocytes and astrocytes as early as the first postnatal day.     

Embryonic divergence of oligodendrocyte and astrocyte lineages in developing rat cerebrum

Oligodendrocyte and astrocyte lineages were traced in rat forebrain sections using single- and double-label immunoperoxidase and indirect immunofluorescent techniques. Antibodies were directed against antigenic markers, the expressions of which overlapped in time: GD3 ganglioside in immature neuroectodermal cells; vimentin in radial glia; glial fibrillary acidic protein (GFAP) in astrocytes; and carbonic anhydrase (CA) and galactocerebroside (GC) in oligodendrocytes. A histochemical stain for iron was also used as a marker of oligodendrocytes. Small cells of the subventricular zone (SVZ) were stained with anti-GD3 but not with the other antibodies. By 16 d of gestation (E16), the SVZ generated large, round cells and thick, process-bearing cells that were GD3+/CA+/iron+. These cells then appeared in the cingulum and, with time, increased in numbers and extended thick processes as they filled the subcortical white matter. These cells eventually lost their reactivity to anti-GD3 but became GC+/CA+ with processes extending to myelin sheaths. At E15 radial glia were stained with the anti-vimentin antibody but were negative for GFAP. At birth, only the vimentin+ radial glia midline between the 2 ventricles were GFAP+, but with time more vimentin+ cells became GFAP+. By 7 d of postnatal age all the vimentin+ cells were GFAP+ and had converged predominately on the cingulum. With time these cells condensed and took on characteristic shapes of astrocytes. The embryonic separation of the oligodendrocyte and the astrocyte lineage is supported by four pieces of evidence: (1) GD3+ cells were double labeled with anti-CA, and then went on to become GC+; (2) vimentin+ and GFAP+ cells were not also GD3+; (3) ultrastructural localization of anti-GD3 was confined to cells with characteristics consistent with developing oligodendrocytes; and (4) the shapes of GD3+, CA+, GC+, or iron+ cells did not resemble those of the vimentin+ or GFAP+ cells.     

Glial responses to neonatal hypoxic–ischemic injury in the rat cerebral cortex

Neurogenesis is nearly completed after birth, whereas gliogenic activities remain intense during the postnatal period in the developing rat cortex. These include involution of radial glia, proliferation of astrocytes and oligodendrocytes and myelin formation. Little is known about the effects of hypoxic–ischemic (HI) injury on these critical postnatal processes. Here we explored the glial reactions to mild HI injury of the neonatal rat cerebral cortex at P3. We show that the HI lesion results in disruption of the normal radial glia architecture, which was paralleled by an increase in GFAP immunopositive reactive astrocytes. The morphology of these latter cells and the fact that they were immunolabelled for both nestin and GFAP suggest an accelerated transformation of radial glia into astrocytes. In addition, BrdU/GFAP immunostaining revealed a significant increase of double-labelled cells indicating an acute proliferation of astrocytes after HI. This enhanced proliferative activity of astrocytes persisted for several weeks. We found an elevated number and increased mitotic activity of both NG2-positive oligodendrocyte progenitors and RIP-positive oligodendrocytes after injury. These findings imply that glial responses are central to cortical tissue remodelling following neonatal ischemia and represent a potential target for therapeutic approaches.     

Prenatal exposure to ethanol alters the postnatal development and transformation of radial glia to astrocytes in the cortex

Postmitotic neurons migrate from a zone(s) near the ventricles to the neocortex. During this migration, neurons associate with radial glia. After serving their role as guides for neuronal migration, the radial glia transform into astrocytes. Prenatal exposure to ethanol causes abnormal neuronal migration. We examined the effects of gestational exposure to ethanol on radial glia and astrocytes. Radial glia were stained immunohistochemically with the antibody RAT-401, and astrocytes were labeled with an antibody directed against glial-fibrillary acidic protein (GFAP). The subjects were the offspring of rats fed an ethanol-containing liquid. diet (Et), pair-fed a liquid control diet (Ct), or fed chow and water (Ch). During the first postnatal week, radial glial fibers (in Et-treated rats and controls) stretched from the ventricular surface through the developing. cerebral wall to the pial surface. In the Et-treated rats, the radial processes were less dense and more poorly fasciculated than they were in the Ch-and Ct-treated rats. Moreover, by postnatal day (P) 5, there was a significant reduction in RAT-401 immunostaining in the Et-treated rats, particularly in the superficial cortex. A similar reduction in control rats did not begin until P10. In all three treatment groups, GFAP-immunoreactive astrocytes were in the cortex throughout the period from P1 to P45. In neonates, GFAP-positive cells were distributed in the marginal zone (layer I) and the intermediate zone (the white matter). The number of GFAP-positive cells in the cortical plate increased steadily with time so that, by P26, GFAP-immunoreactive astrocytes were distributed evenly through all cortical laminae. Interestingly, between P5 and P12, the number of astrocytes was significantly greater in Et-treated rats than in controls. Thus prenatal exposure to ethanol induces the premature loss of RAT-401-positive processes and the precocious increase in GFAP immunostaining. These ethanol-induced changes in glial development indicate that ethanol accelerates the transformation of radial glia into astrocytes. Moreover, the ethanol-induced premature degradation of the network of radial glial fibers may underlie the migration of late-generated neurons to ectopic sites. © 1993 Wiley-Liss, Inc.     

Astroglial changes in the cerebral cortex of AIDS brains: a morphometric and immunohistochemical investigation

Astroglial changes in the cerebral cortex of AIDS brains were analysed by means of morphometry. Astrocytes with and without immunoreactivity for glial acidic protein (GFAP) were counted and their size was measured. In the two investigated cortical areas (frontal and parietal), a similar reaction pattern of astroglia was observed. The total number of astrocytes (i.e. GFAP-positive and GFAP-negative astrocytes) did not differ between control and AIDS brains. However, the number of GFAP-positive astrocytes was significantly increased in AIDS brains, while the number of GFAP-negative cells was significantly reduced. Nuclear size of GFAP-negative and GFAP-positive astrocytes was significantly increased. The reaction pattern of cortical astrocytes in AIDS seems to be characterized by GFAP production in protoplasmic astroglia as well as by hypertrophy of all astrocytes.     

Expression of 48-kilodalton intermediate filament-associated protein in differentiating and in mature astrocytes in various regions of the central nervous system

In this paper we present evidence that the 48-kD intermediate filament-associated protein (IFAP) is expressed relatively late in maturation of astrocytes, after they have acquired the glial fibrillary acidic protein (GFAP). In the astrocytes of white matter in the cerebellum the GFAP is detected at P3, whereas the 48-kD IFAP is detected only at P11. In the periventricular region and the hippocampus the 48-kD IFAP was detected at P6, long after the appearance of GFAP. In adult mice the 48-kD IFAP was observed in GFAP-positive astrocytes in the white matter of cerebellum, spinal cord, brainstem, and corpus callosum as well as in GFAP-positive cells in the grey matter of cerebral cortex and spinal cord. The 48-kD IFAP was not, however, detected in radial glia and their derivatives, in Bergmann glia or in Müller glia. Thus, not all the GFAP-positive astroglia express the 48-kD IFAP. Similarly, 48-kD IFAP was not detected in cells which were GFAP-negative.     

Glial responses to neonatal hypoxic-ischemic injury in the rat cerebral cortex.

Neurogenesis is nearly completed after birth, whereas gliogenic activities remain intense during the postnatal period in the developing rat cortex. These include involution of radial glia, proliferation of astrocytes and oligodendrocytes and myelin formation. Little is known about the effects of hypoxic-ischemic (HI) injury on these critical postnatal processes. Here we explored the glial reactions to mild HI injury of the neonatal rat cerebral cortex at P3. We show that the HI lesion results in disruption of the normal radial glia architecture, which was paralleled by an increase in GFAP immunopositive reactive astrocytes. The morphology of these latter cells and the fact that they were immunolabelled for both nestin and GFAP suggest an accelerated transformation of radial glia into astrocytes. In addition, BrdU/GFAP immunostaining revealed a significant increase of double-labelled cells indicating an acute proliferation of astrocytes after HI. This enhanced proliferative activity of astrocytes persisted for several weeks. We found an elevated number and increased mitotic activity of both NG2-positive oligodendrocyte progenitors and RIP-positive oligodendrocytes after injury. These findings imply that glial responses are central to cortical tissue remodelling following neonatal ischemia and represent a potential target for therapeutic approaches.     

Survival and migration of transplanted male glia in adult female mouse brains monitored by a Y-chromosome-specific probe.

A Y-chromosome-specific probe and in situ hybridization technology have been used to monitor the survival and migration of neonatal male glia isografted to the left cerebral hemisphere of adult female mice. More than 95% of the cultured donor glia were glial fibrillary acidic protein (GFAP)-positive astrocytes. By 4 weeks, large numbers of transplanted glia were found in both cerebral hemispheres; the extent of glial migration was greatest in white matter tracts. This method provides a new way of identifying all surviving donor cells within the brains of immunologically compatible hosts.     

Development of glial cells in the cerebral wall of ferrets: direct tracing of their transformation from radial glia into astrocytes

Coronal sections of the cerebral wall from developing ferrets (newborn to adult) were double-stained with antibodies to vimentin and glial fibrillary acidic protein (GFAP). At birth, the dominant glial population was radial glia and these cells labeled only for vimentin. A small population of immature astrocytes in the cortical plate was double labeled for GFAP and vimentin. In successive days, the number of vimentin-positive radial glia gradually decreased and they disappeared entirely at about 21 days. During this same period, the double-stained astrocytes increased in number and were distributed throughout the cortical plate and intermediate zone. After 6 weeks of age the astrocytes were mostly confined to the developing white matter. Around this time they gradually lost their vimentin staining, and in the adult no vimentin-positive elements were seen except at the ependymal surface. In newborn ferrets single radial glial cells were also visualized by applying the carbocyanine dye DiI onto the pial surface of fixed brains. While most radial glia extended from the ventricular zone to the pial surface, a substantial fraction of them had lost their contact to the ventricular zone. Their somata were displaced into the subventricular zone and lower portion of the intermediate zone. The possibility that radial glia transform into astrocytes was directly tested by injecting fluorescent dyes under the pial surface of newborn ferrets at a time when virtually no GFAP-positive astrocytes are present. The tracer, which was taken up in the upper portion of the cortical plate, stained the radial glial cell somata in the ventricular zone in a similar way as the dye DiI did in the fixed brains. As the radial glial cells disappeared at successively longer survival times, the tracer was ultimately found within newly formed GFAP-positive astrocytes. These results provide strong support for the hypothesis that radial glia cells are the immature form of astrocytes (Choi and Lapham: Brain Res. 148:295-311, '78; Schmechel and Rakic: Anat. Embryol. (Berl.) 156:115-152, '79), and also show that, at least in the ferret cortex, the transformation is accompanied by a change in the expression of intermediate filament protein.     

Palisading pattern of subpial astroglial processes in the adult rodent brain: relationship between the glial palisading pattern and the axonal and astroglial organization

The architectural organization of the subpial astrocyte processes was examined near the brain surface by single immunostaining methods. The astroglial processes were stained on brain sections made parallel to the pial surface. The astroglial glial fibrillary acid protein (GFAP) antigen was used as a specific marker. We show that these subpial astrocyte processes present a well organized palisading pattern in the adult mouse and rat spinal cord, medulla and pons. This adult astrocyte palisading pattern is compared to the palisading radial glia organization we previously demonstrated in the fetal mouse brain. The observed analogies afford a new and strong argument in favor of a derivation of the subpial astrocytes from radial glia. Double immunostaining methods, using GFAP and neurofilament antigens as glial and neuronal markers respectively, show the close relationship existing between the trajectories of axonal and glial processes. Beside the colinearity already observed between the axon trajectories and the glial palisades we demonstrate a new kind of axon/glia relationship. Axons are closely intermingled, within the palisading glial tufts, with the peripheral processes of the subpial astrocytes progressing to the pial surface. The findings suggest that fetal radial glia organization has a direct and indirect influence on the adult astroglial and perhaps the axonal pattern.     

Regionally specific properties of midbrain glia: I. Interactions with midbrain neurons

Regional astrocyte cultures were obtained by dissecting and dissociating medial and lateral sectors of the midbrain from 14-day Swiss mouse embryos. Once confluent, these cultures were tested by glial fibrillary acidic protein (GFAP) immunocytochemistry to confirm their astrocyte composition and for 2′-3′ cyclic nucleotide 3′-phosphohydrolase (CNPase) and microtubule-associated protein 2 (MAP₂) immunocytochemistry to rule out oligodendroglial and neuronal components, respectively. In confluent astrocyte cultures from either sector, virtually all cells were GFAP-positive elements, most of which were flat cells accompanied by smaller numbers of flat cells with processes. Confluent astrocyte cultures, derived from medial (M) or lateral (L) sectors, were used as substrata for culturing dissociated cells from medial (m) or lateral (1) sectors of 14-day embryonic midbrains. Fixed cocultures (LI, Lm, Mm, MI) were stained with an anti-MAP₂ antibody to verify neuronal aggregation and neuritic morphology. In spite of the morphological constancy of glia substrata at plating, MAP₂-positive cells in cocultures showed differences in the aggregation of somata and in the length, caliber, and branching of neurites. These differences, which depend mostly on the sector of origin of astrocytes, suggest that the substrata may differ in adhesiveness and/or growth-promoting vs. growth-interfering properties. Together with evidence for sectorial heterogeneity in brainstem radial glia, the present results raise the possibility that cultured astrocytes have properties that reflect the roles played by their parent radial glia in the developing brain. © 1995 Wiley-Liss, Inc.     

The development of ependyma in the human fetal brain: an immunohistological and electron microscopic study

The stratified inner layer of the embryonic fetal brain, the ventricular zone (VZ), contains glial fibrillary acidic protein (GFAP)-positive cell bodies of radial glia. The adult cerebral ventricle is lined by a single layer of cuboidal, ciliated common ependymal cells which are, immunohistologically, GFAP negative. In late gestation, the ventricular lining is formed by tanycytes, ependymal cells with short, intensely GFAP-positive basal fibres. The development of ependyma was examined, morphologically and immunohistologically, in human fetal brain from between 11 weeks gestation to 6 months post-term to determine the relationship between the radial glia cell, tanycyte and common ependymal cell. This study was not able to show whether tanycytes were formed from radial glia or were formed from a previously uncommitted population of VZ cells. The study did show, however, that tanycytes probably mature into common ependymal cells following acquisition of cilia and loss of basal fibres. Electron microscopic data indicate that tanycytes have features suggestive of a secretory and/or transport function.     

Interactions between meningeal cells and astrocytes in vivo and in vitro.

At the interface between the meninges and the central nervous system there is a characteristic structure known as the glia limitans, consisting of many fine interdigitating astrocyte processes which contain both GFAP and vimentin, and a basal lamina. A similar structure is set up after brain injury where meningeal cells invade the lesion. We have experimentally put astrocytes and meningeal cells in contact with one another, both in vivo and in vitro, to see whether this results in the formation of a glia limitans. Cultured meningeal cells were injected into the hippocampus of adult rats, and from 1 to 12 weeks later brains were stained were stained for GFAP and vimentin. One week after injection there was a widespread astrocytic reaction stretching up to 2 mm from the injection, the cells being stained intensely for both GFAP and vimentin. Over the next 4-6 weeks this widespread reaction subsided, the only remaining vimentin stained astrocytes, apart from those at the normal glia limitans, being in contact with the injected meningeal cells, or with meningeal cells which had migrated into the injection needle track. In vitro a structure reminiscent of the glia limitans formed where patches of astrocytes abutted meningeal cells; the astrocytes formed a layer of fine interdigitating processes all running parallel to the interface between the two cell types, and there was heavy staining for laminin and fibronectin. We conclude that a glia limitans forms wherever astrocytes and meningeal cells come into contact.     

Localization of glial cell antigens in the brains of young normal mice and the dysmyelinating mutant mice, jimpy and shiverer

Tissue sections from the brains of normal, jimpy, and shiverer mice were immunostained by the peroxidase antiperoxidase method for carbonic anhydrase (CA) and the putative astrocytic "markers" glutamine synthetase (GS) and glial fibrillary acidic protein (GFAP). The cells in normal gray matter that immunostained with anti-CA and anti-GS were similar to one another in size and process elaboration. In the normal gray matter there were relatively few GFAP-positive astrocytes. When present, these cells resembled the CA- and GS-positive cells; however, the GFAP appeared to be concentrated in the astroglial processes, as distinguished from the cell bodies. Glial cell processes, immunostained for CA or GS, surrounded blood vessels and unstained neurons in the normal gray matter. The glial cells in shiverer gray matter were similar to those in the normal gray matter. When stained for GS or GFAP, the glial cells in the jimpy gray matter appeared to be somewhat hypertrophied, and when the glial cells in this mutant were stained for CA, the nuclei appeared to be swollen. It was concluded that some of the CA-positive cells in the gray matter of the normal and of each mutant mouse brain could be astrocytes. The patterns of immunostaining in the white matter emphasized the different complements of glial cells in the mutants. In the normal and shiverer mouse corpus callosum, CA, in particular, was detected only in the oligodendrocytes, their processes, and myelin. However, the data concerning the jimpy mouse suggested that the few CA-positive cells in the corpus callosum of that mutant could be astrocytes.     

The distribution of glial fibrillary acidic protein and vimentin in postnatal marmoset (Callithrix jacchus) brain

Antisera to glial fibrillary acidic protein (GFAP) and vimentin were used to elucidate the distribution of these intermediate filament proteins in postnatal marmoset brains of various ages. The ependyma of the lateral ventricles was unique in being equally immunoreactive for both GFAP and vimentin at all ages. Vimentin alone was consistently demonstrated in endothelial and leptomeningeal cells at all ages. In neonates, vimentin immunoreactivity greatly exceeded that of GFAP and was located primarily in radial glia in the subependymal plate of the anterior cerebrum. Their vimentin-positive processes formed thick fascicles in the corpus callosum but separated into fine fibres on entering the cortex. GFAP immunoreactivity in these cells and processes was very limited. With age, GFAP-positive cells increased in number and displayed the typical stellate appearance of astroglia. The vimentin-positive radial glial population decreased considerably during this period and by 6 months had virtually disappeared. The GFAP reaction in adult brain was even more widespread, largely due to the increased number of positive astrocytes in the white matter. Vimentin immunoreactivity in the adult was greatly diminished and positive radial glia were not detectable. A major change in intermediate filament protein expression, therefore, occurs in the early postnatal period and probably reflects phases in the differentiation of radial glial precursors into astrocytes.     

Glial fibrillary acidic protein and vimentin immunohistochemistry in the developing and adult midbrain of the lizard Gallotia galloti

The distribution of glial fibrillary acidic protein (GFAP)- and vimentin-containing cells was studied by immunohistochemistry in the midbrain of the lizard Gallotia galloti. At embryonic stage 32 (E32), vimentin immunoreactivity appeared first in cell bodies located in the ventricular walls, in radial fibers, and subpial end-feet and increased in these structures until E34/E35. Faint GFAP immunoreactivity gradually appeared in the same structures between E34 and E37, and this increased until adulthood, whereas vimentin immunoreactivity decreased after E35, becoming limited to a few end-feet and fibers in the adult, mainly in the tegmentum. Thus, in developing Gallotia midbrain a shift from vimentin-containing to GFAP-containing intermediate filaments begins around E36 or E37. At E40, in addition to the cell bodies in the ependymal area, dispersed GFAP-positive cells, possibly immature astrocytes appeared. These cells showed the same shift. In the adult lizard, GFAP-positive radial glia are still present and coexist with GFAP-positive astrocytes, which are prefentially located in the marginal optic tract and the oculomotor nuclei, but are absent in the fasciculus longitudinalis medialis. Optic tectum, pretectum, tegmentum, and isthmic nuclei are the areas richest in GFAP-positive radial fibers: these were much less abundant in the deep mesencephalic nuclei. Thus, in this lizard, GFAP-positive astrocytes display a clear cut regional distribution: they are present in mesencephalon, whereas they are absent in telencephalon.     

Degeneration and proliferation of astrocytes in the mouse dentate gyrus after pilocarpine-induced status epilepticus

Astrocytes are relatively resistant to injury compared to neurons and oligodendrocytes. Here, we report transient region-specific loss of astrocytes in mice early after pilocarpine-induced status epilepticus (SE). In the dentate hilus, immunoreactivity for glial acidic fibrillary protein (GFAP) was decreased, and the number of healthy appearing GFAP- or S100beta-positive cells was significantly reduced (> or =65%) 1 and 3 days after pilocarpine-induced SE. Many remaining GFAP-positive cells were shrunken, and 1 day after SE electron microscopy revealed numerous electron-dense degenerating astrocyte processes and degenerating glial somata in the hilus. Degeneration of GFAP-expressing cells may be linked to hilar neuronal death, because we did not observe loss of astrocytes after kainate-induced SE, after which hilar neurons remained intact. Ten days after SE, hilar GFAP immunoreactivity had returned, partially from GFAP-positive cells in the hilus. Unlike control mice, many GFAP-positive hilar processes originated from cell bodies located in the subgranular zone (SGZ). To investigate whether proliferation contributes to hilar repopulation, we injected 5-bromo-2'-deoxyuridine (BrdU) 3 days after SE. Five hours later and up to 31 days after SE, many BrdU/GFAP colabeled cells were found in the hilus and the SGZ, some with hilar processes, indicating that proliferation in both areas contributes to generation of hilar astrocytes and astrocyte processes. In contrast to pilocarpine-induced SE in mice, astrocyte degeneration was not found after pilocarpine-induced SE in rats. These findings demonstrate astrocyte degeneration in the mouse dentate hilus specifically in the mouse pilocarpine epilepsy model, followed by astrogenesis leading to hilar repopulation.     

Immunocytochemical detection of the microsomal glucose-6-phosphatase in human brain astrocytes

Using an antibody raised against the catalytic subunit of glucose-6-phosphatase, this enzyme was immuno-localized in many astrocytes in 20 normal human brains. Double immunofluorescence studies showed co-localization of glial fibrillary acidic protein (GFAP) with glucose-6-phosphatase in astrocytes. However, not all GFAP-positive cells were also glucose-6-phosphatase positive, indicating that some astrocytes do not contain demonstrable expression of this enzyme. Reactive astrocytes in a variety of abnormal brains were strongly glucose-6-phosphatase positive, but neoplastic astrocytes were often only weakly positive. Expression of the enzyme could not be demonstrated in radial glia, neurons or oligodendroglia. Astrocytes normally contain glycogen and the demonstration that some astrocytes also contain glucose-6-phosphatase indicates that they are competent for both glycogenolysis and gluconeogenesis, which may be critical for neuronal welfare.     

Immunohistochemical Study on Glial Cells in Brains with Periventricular Leukomalacia

The lesions in periventricular leukomalacia (PVL) comprise necrosis and a glial reaction in the deep cerebral white matter of fetuses and neonates. The purpose of this study was to elucidate the role of glial cells in the formation of the lesions in PVL. Ten PVL brains and 22 control brains were immunohistochemically compared using anti-glial fibrillary acidic protein (GFAP) and anti-ferritin antibodies, and lectin-Ricinus communis agglutinin (RCA-1). The numbers of GFAP-positive glia and RCA-1 positive glia increased in the whole white matter and the periventricular white matter, respectively. Ferritin was predominantly stained in the cytoplasm of oligodendrocytes, and the number of ferritin-positive oligodendrocytes gradually increased with age in normal brains. However, ferritin was stained in microglia and partially reactive astrocytes, instead of ferritin-positive oligodendrocytes, in PVL brains. A relationship of the glial cellular reaction with the time scale of histologic change in PVL was shown by the appearance of RCA-1-positive microglia around fresh necrotic regions, accumulation of RCA-1-positive macrophages in necrotic regions, and then proliferation of GFAP-positive reactive astrocytes with long processes outside the microglial reaction sites. On cavity formation, the end-stage of PVL, rough walls of moderately dense gliosis consisted of slightly GFAP-positive fibrillary astrocytes. PVL involves glial cellular reactions not only in regional necrotic lesions, but also in the whole cerebral white matter. The decrease in ferritin-positive oligodendrocytes in PVL brains may be related to the delayed myelination in the brains of long-surviving infants with PVL.