Glial Fibrillary Acidic Protein Reactivity Research Articles

Immunocytochemical localization of basic fibroblast growth factor and glial fibrillary acidic protein after laser photocoagulation in the Royal College of Surgeons rat

Argon laser photocoagulation slows photoreceptor degeneration in the Royal College of Surgeons (RCS) rat, as does intravitreal injection of basic fibroblast growth factor (bFGF). We hypothesize that up-regulation of retinal bFGF is a consequence of laser lesioning in RCS rats. Therefore, we examined the localization of bFGF after laser and correlated this with Mailer cell glial fibrillary acidic protein (GFAP) expression, which is known to increase after injury. A total of 34 RCS rats at postnatal day 23 were anaesthetized (ketamine 40 mg/kg) and their retinas were irradiated with a grid pattern of 40 non-overlapping argon green lesions with a power of 120 mW for 0.2 s using a 50 microm spot size. At 0, 6, 12, 24 and 48 h and 7, 14 and 21 days post-lesion, rats were anaesthetized and their eyes were enucleated and cryostat sectioned and the sections were processed using either an antibody to bFGF or GFAP using the standard avidin-biotinylated peroxidase complex method. Five age-matched RCS rats without laser lesions served as controls. Basic fibroblast growth factor immunoreactivity (IR) was normally located within cells in the ganglion cell layer inner nuclear layer and in retinal pigment epithelium cells and in the extracellular matrix/cell membranes of the outer nuclear layer (ONL). In lasered retinas, there was elevated bFGF-IR in the coagulated outer segments for the first 24 h. Retinal blood vessels/Müller cells/astrocytes were moderately labelled in and near each lesion immediately after lesion and became more intense after 48 h and persisted for at least 21 days. There was an elevation of bFGF-IR in the ONL on the lesion flanks at 14 days. Muller cell GFAP-IR was first detected at 6 h post-lesion and spread for a considerable distance beyond the lesion site. At 7 and 14 days, Müller cells at the lesion site had sprouted, while those on the flanks were still GFAP-IR. Following laser lesion there was an increase in bFGF at the lesion core only for the first 24 h. However, elevated levels of bFGF were observed in the ONL at 14 days, which extended into the lesion flanks for a similar distance to that over which increased photoreceptor survival is found. These results provide support for the hypothesis that laser lesions induce bFGF and this may be the mechanism whereby photoreceptors are spared. Müller cell activation is consistent with growth factor stimulation, but was more widespread than the bFGF changes in ONL. However, blood vessel labelling was similarly widespread and so the responses may be linked between Müller cell GFAP reaction and blood vessel bFGF localization after laser lesions.

Blockade of basic fibroblast growth factor retards recovery from motor cortex injury in rats.

The endogenous expression of basic fibroblast growth factor (bFGF) was blocked by neutralizing antibodies following unilateral suction lesions of the motor cortex. Rats with control treatment (saline, goat IgG) after motor cortex lesions showed slow recovery of forelimb manipulatory abilities. Rats with blockade of bFGF expression showed little recovery. Anatomically, the control-treated lesioned rats showed an acute increase in bFGF and glial fibrillary acidic protein (GFAP) reactivity, and chronically they had normal dendritic arborization and spine density in layer V pyramidal cells in the remaining motor cortex. In contrast, rats treated with antibodies to bFGF showed little bFGF reactivity, normal GFAP reactivity, and atrophy of dendritic arbor and decreased spine density in layer V pyramidal cells. These results demonstrate the importance of endogenous bFGF release in processes related to functional recovery after cortical injury.

Overexpression of nestin and vimentin in ependymal cells in hydrocephalus.

In order to elucidate the immunohistochemical features of hydrocephalic ependyma, immunohistochemical examination was undertaken in 11 normal, postmortem brains (age range, 11 weeks' postconception to 6 months after birth) and 12 hydrocephalic brains (three cases each of congenital aqueductal stenosis, Dandy-Walker malformation, Arnold-Chiari type II malformation and posthemorrhagic hydrocephalus) by using antisera to nestin, vimentin and glial fibrillary acidic protein (GFAP). In normal brains, nestin was predominantly expressed in neuroepithelial cells and radial glial fibers during the period of neuronal migration. Vimentin immunoreactivity was principally detected in immature ependymal cells and their basal fibers after the period of neuronal migration, then partly replaced by GFAP reactivity during late gestation. In hydrocephalus, the areas of ependymal disruption were covered with nestin- or vimentin-positive cells. Nestin and vimentin were also expressed in immature ependymal cells or their basal processes in anatomical regions such as the roof or floor plate of the fourth ventricle or the cerebral aqueduct, and the ventral part of the third ventricle. These results suggest that the overexpression of nestin and vimentin in hydrocephalus follows two patterns: a reactive pattern of proliferating immature glial cells associated with ependymal cell loss and an abnormal developmental pattern of immunopositivity associated with anatomical regions in the midline mesencephalon.

Chapter 5 Astrocytes in the mammalian circadian clock: putative roles

The rhythmic modification seems specific to the circadian clock and suggests that the astrocytic population is implicated in its oscillating manifestations. Cells immunoreactive for glial fibrillary acidic protein (GFAP), a specific astrocyte structural protein, have also been identified in the suprachiasmatic nucleus (SCN). The GFAP reaction product is distributed throughout the whole SCN, delineating its margins more clearly from the surrounding hypothalamic areas that appear almost devoid of any GFAP immunoreactivity (GFAP-ir). From these observations several hypothesis promoting neuron–glia interactions in the understanding of the clock function can be proposed. Two main issues are addressed (i) the cellular counterparts of events mediating glial fibrillary acidic protein(GFAP) variation and its functional signification and (ii) the effect of GFAP variation that driven in the suprachiasmatic nuclei. From the data reviewed, it seems obvious that astrocytes do not constitute the core of the circadian clock although the role of astrocytes is essential to the comprehensive understanding of the cellular mechanisms of the clock. Two main aspects of their participation to the clock functioning can be considered.

Ultrastructural characteristics of glial fibrillary acidic protein expression in epoxy resin-embedded human brain tumors.

Thirteen surgically removed, epoxy resin (Durcupan ACM or Epon 812)-embedded human brain tumors were examined for glial fibrillary acidic protein (GFAP) content in semithin and ultrathin sections with the immunogold-silver staining method. Mild aldehyde fixation and the hydrophobic resin embedding did not interfere with the antigenicity, since silver intensification of the immunogold marker provided excellent visualization of the reaction on both light microscopic and ultrastructural levels. The GFAP reaction was usually localized on the glial intermediate filament bundles, usually correlating well with the amount of filaments. The unstained filamental regions of two ependymomas might correspond to the vimentin expression revealed by double labeling in semithin sections. Occasional GFAP immunopositivity without filamental appearance was observed in one of the oligodendrogliomas, as patchy electron-dense cytoplasmic corpuscules, in Rosenthal fibers and in some mainly necrobiotic tumor cells, reflecting a possible connection with glial filaments.

Immunoelectron microscopy of Rosenthal fibers.

Seventeen intracerebral gliomas containing Rosenthal fibers (RF) were studied by an immunoperoxidase method for localization of ubiquitin (UB), glial fibrillary acidic protein (GFAP), desmin and vimentin (VIM). The majority of RF showed an immunohistochemically negative core surrounded by a ring of overlapping reactions for UB, GFAP and VIM. Many RF were entirely negative for UB and intermediate filaments (IF). Immunoelectron microscopic localization of UB and GFAP was performed on seven selected tumors. UB was found in all RF and on IF in the proximity of RF. GFAP reaction was localized on astrocytic IF, including those trapped within RF, and within the granular component of some RF. In contrast to the light microscopic studies, neither GFAP- nor UB-negative RF were found on immunoelectron microscopy. VIM reaction on IF and a few RF was demonstrated in one tumor processed at low temperature into Lowicryl; it was much weaker than that for GFAP. Many cells with RF contained lysosome-like inclusions with material displaying electron density similar to adjacent RF; few of these inclusions were reactive for UB. It is concluded that RF formation is associated with ubiquitination of astrocytic IF. GFAP- and VIM-immunoreactive IF and products of their disintegration contribute to RF material. It is also suggested that the lysosomal system of astrocytes partially degrades RF.

Heterogeneous astroglial response in the rat spinal cord to long‐term portacaval shunt: An immunohistochemical study

Glial fibrillary acidic protein (GFAP) immunoreactivity has been used to study the astroglial response in the rat spinal cord to long-term portacaval shunt (PCS). The astroglial response in PCS rats is heterogeneous. In general, astrocytes show a loss of GFAP immunoreactivity, as well as shrinking and pyknosis in their nuclei; however, while GFAP reactivity was unchanged in the periependymal region, it was strongly increased in the dorsolateral region of the spinal cord (lateral spinal nucleus, dorsal root entry zone, and the most dorsal region of the dorsal horn). Three possibilities are postulated to explain how astrocytes, in the periependymal and dorsolateral regions, can support the effects of PCS: a) astrocytes related to glutamatergic pathways ought to possess a more efficient ammonia uptake and detoxification system, b) long-term PCS can activate nociceptive pathways (substancePergic fibers), and c) astrocytes located in periependymal and dorsolateral regions can be exposed to lower concentrations of ammonia because of its diffusion into the cerebro-spinal fluid close to these regions.

Glial fibrillary acidic protein and βA4 protein deposits in temporal lobe of aging brain and senile dementia of the Alzheimer type: Relation with the cognitive state and with quantitative studies of senile plaques and neurofibrillary tangles

The aim of this study was to compare brain glial fibrillary acidic protein (GFAP) levels to the modifications of cognitive functions (Blessed test score [BTS]), the density of the main neuropathological lesions (senile plaques [SP] and neurofibrillary tangles [NFT]), and the density of the two main subtypes of beta A4 deposits (classic plaques and diffuse deposits) in a series of patients with normal aging and senile dementia of the Alzheimer type of various degrees of severity. GFAP levels (enzyme-linked immunosorbent assay [ELISA] technique) and the densities of changes were measured in the temporal lobe of 12 women over 75 years of age. Under these conditions, the ELISA assay could determine GFAP in brain homogenates (aqueous-Triton buffer soluble extract) in a range from 2.5 ng to 600 ng per assay. Least affected patients (with a BTS of 19 and over) all ranged below 60 micrograms/mg protein. Most affected patients (with a BTS under 6) ranged above 150 micrograms/mg protein. However, interindividual variations were wide. A significant correlation between the BTS and the amount of GFAP could be found only when using the non parametric test of Spearman. There was a significant positive correlation between the amount of GFAP and the density of 1) SP, 2) NFT both revealed by Bodian's silver stain, and 3) classic beta A4 plaques shown by immunocytochemistry. On the contrary, no correlation was observed with diffuse beta A4 deposits. One case with very large amounts of diffuse beta A4 deposits without SP or NFT showed no associated GFAP reactivity. This suggests that GFAP production is a critical event in the formation of classic SP.

Characterization of the origins of astrocyte response to injury using the dopaminergic neurotoxicant, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

We used the dopaminergic neurotoxicant, 1-methyl-1,2,3,6-tetrahydropyridine (MPTP), as a tool to characterize the origins of astroglial response to injury. Radioimmunoassay of the astrocyte protein, glial fibrillary acidic protein (GFAP), was used to quantify the astrocyte reaction to MPTP. Assays of neuron-localized proteins and of dopamine were used to assess neuronal damage caused by MPTP. A single administration of MPTP (12.5 mg/kg, s.c.) to the C57BL/6J mouse resulted in more than a 3-fold increase in striatal GFAP within 48 h, followed by a decline to baseline at 3 weeks. A decrease in the amount of striatal tyrosine hydroxylase (TH), a marker of dopaminergic neurons, preceded the rise in GFAP. The concentration of striatal DARPP-32, a phosphoprotein enriched in neurons receiving dopaminergic input, was not affected by MPTP. Protecting the dopaminergic neurons from the neurotoxic metabolite of MPTP, 1-methyl-4-phenylpyridinium (MPP +), either by blocking its formation or by preventing its uptake into dopaminergic neurons, completely blocked the increase in GFAP. MPTP did not appear to disrupt the blood-brain barrier, therefore, blood-borne elements probably did not mediate the increase in GFAP. In addition, immunoblot data indicated that brain-derived interleukin 1, an astrocyte growth factor, also did not play a role in MPTP-induced gliosis. Together, these findings suggest that diffusible factors derived from damaged dopaminergic neurons initiate the astrocyte response to MPTP and that large increases in GFAP can be induced without the participation of serum-derived growth factors. Because the transient nature of GFAP reaction to MPTP coincides with the rapid elimination of the active toxicant, MPP +, suggests that maintenance of reactive gliosis, in general, may require the continued presence of the damage-inducing insult.

Increased Glial Fibrillary Acidic Protein Immunoreactivity in Astrocytes within the Lateral Vestibular Nucleus of the Cat following Labyrinthectomy and Vestibular Neurectomy

Unilateral vestibular injury evokes a characteristic pattern of acute disorganization of posture, locomotion, and eye movements. Following this acute stage, functional recovery occurs. In the present study, unilateral labyrinthectomy and vestibular neurectomy were performed in cats. The lateral vestibular nucleus (LVN) and vestibular nerve root entry zone on both sides of the brain stem were examined 24 hours, 3 days, and 8 weeks after operation by use of an immunochemical astrocyte marker, glial fibrillary acidic protein (GFAP). The results demonstrate extensive GFAP immunoreactivity within the ipsilateral nerve root following neurectomy, but not after labyrinthectomy. Prominent GFAP-immunoreactive astrocytic processes were detected in the LVN both ipsilateral and contralateral to neurectomy and labyrinthectomy. Within the ipsilateral LVN, the intensity of GFAP immunoreactivity was greater following neurectomy than after labyrinthectomy, but the pattern of GFAP reactivity remained similar. In the contralateral LVN, GFAP reactivity was noted exclusively in the dorsal-rostral region corresponding to the zone of cerebellar afferents to the LVN. The results of the present study suggest that reactive astroglia may play an important role in the mechanism that leads to vestibular compensation.

Expression of vimentin and glial fibrillary acidic protein in human developing spinal cord

Expression of intermediate filament proteins was studied in human developing spinal cord using immunoperoxidase and double-label immunofluorescence methods with monoclonal antibodies to vimentin and glial fibrillary acidic protein (GFAP). Vimentin was found in the processes of radial glial cells in 6-week embryos, while GFAP appeared in vimentin-positive astroglial cells at 8-10 weeks. GFAP and vimentin were present in approximately equal amounts in differentiating astrocytes in 23-week spinal cord. In 30-week fetuses, astrocytes reacted strongly for GFAP, while both the reaction intensity and the number of vimentin-positive cells fluctuated predominantly in the grey matter. No clear-cut transition from vimentin to GFAP was noticed during the development of astrocytes. The majority of ependymal cells in 23-week fetuses contained vimentin but only a few of them reacted for GFAP. The expression of vimentin continued during the whole development of the ependymal layer, in contrast to the reactivity for GFAP which disappeared between the 30th week and term.

An Immunohistochemical Study of Canine Tissues with Vimentin, Desmin, Glial Fibrillary Acidic Protein, and Neurofilament Antisera

In a wide range of canine tissues the immunoreactivity with commercially available antisera against intermediate filament antigens viz. vimentin, desmin, glial fibrillary acidic protein (GFAP) and neurofilament proteins, was studied. In addition, the results of formalin and Carnoy fixation were compared. Carnoy fixation appeared to result in optimal reactivity for all antisera. Epithelial cells did not react with any of the antisera, with exception of ovarian surface epithelium, which showed staining with the vimentin and desmin antisera. The vimentin antiserum induced staining of several cell types viz. fibroblasts, endothelial cells, chondrocytes, Schwann cells, ependymal cells, astrocytes, Leydig cells, synovial cells, podocytes and some parietal cells of Bowman's capsule. Sertoli cells showed a faint staining reaction. Muscle cells in various tissues reacted with the desmin antiserum. In the kidney a varying number of parietal cells appeared to react as did a restricted number of epithelial cells of proximal tubules and loops of Henle. GFAP reactivity was confined to glial cells, predominantly fibrous astrocytes, Schwann cells and axons. Additionally, some neuronal cell bodies in peripheral ganglia showed staining of varying intensity. Neurofilament staining was restricted to axons and some neurons. The immunoreactivity of canine tissues with these antisera is compared to findings in other species. The results confirm a broad interspecies cross-reactivity of these antisera. They can be used in studying the nature of canine tissues.

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.

Immunocytochemical demonstration of glial fibrillary acidic protein in imprint smears of human brain tumors.

Papanicolaou-destained imprint smears from 24 brain tumors were investigated by means of avidin-biotin-peroxidase complex method (ABC) with the use of monoclonal antibodies against glial fibrillary acidic protein (GFAP). Positive staining reaction to GFAP antibody has been demonstrated in cells from the following tumors: astrocytoma, anaplastic astrocytoma, glioblastoma multiforme, mixed glioma, and ependymoma. The reaction for GFAP was negative for the following tumors: medulloblastoma, neurilemmoma, melanoma, hemangioblastoma, and metastatic tumors. In astrocytoma, the cell bodies and processes were positive with delicate fibrillary patterns; in anaplastic astrocytoma, cytoplasm and the processes were intensively stained. In glioblastoma multiforme, the staining patterns were also mixed, and the short, thickened processes were characteristic. Use of both a smear preparation and the immunoperoxidase staining technique is of great value in diagnosis of tumors of the central nervous system.

Expression of S-100 protein, glial fibrillary acidic protein, neuron-specific enolase, and keratin in mixed tumors of skin.

Mixed tumors of sweat gland in the skin were stained by the peroxidase antiperoxidase (PAP) method using antibodies to S-100 protein, glial fibrillary acidic protein (GFAP), neuron-specific enolase (NSE), and keratin proteins, in order to evaluate possible histogenesis of the tumors. Secretory coiled cells in normal eccrine glands were moderately positive for S-100 protein, markedly positive for NSE, and negative for GFAP, and they displayed variably intense staining with anti-keratin antibodies. In mixed tumors of the skin, the round, oval or polygonal cells located in the outer zone of tubular or duct-like structures, were usually strongly positive for S-100 protein, gave reactions of varied intensity for NSE, and were generally negative or very weakly positive for GFAP. Spindle-shaped cells were negative or very slightly positive for S-100 protein and strongly positive for NSE; but the reaction for GFAP varied. Tumor cells located on the luminal side of tubular or duct-like structures were uniformly positive for KLl (molecular weight 55-57 Kdaltons keratin) and PKKl (molecular weight 41-56 Kdaltons keratin). From the present study, it is suggested that mixed tumors of the skin may be differentiated from either transitional portion or myoepithelial cells of the eccrine glands.

Immunohistochemical Evidence for the Presence of S-100 Protein in Stromal Cells of Cerebellar Hemangioblastomas

The histogenesis of the stromal cells in cerebellar hemangioblastomas is still a subject of controversy. In this study, 13 cerebellar hemangioblastomas were examined immunohistochemically for S-100 protein, glial fibrillary acidic protein (GFAP), and human factor VIII-related antigen in an attempt to elucidate the histogenesis of the stromal cells in these tumors. An unequivocally positive immunoperoxidase reaction for S-100 protein was observed in most of the stromal cells in 10 of the 13 cerebellar hemangioblastomas examined, whereas GFAP and human factor VIII-related antigen assays were essentially negative. The positive GFAP reaction occurred sporadically, in what we thought to be astrocytes trapped within the tumor. Human factor VIII-related antigen was positive exclusively in the capillary endothelial cells of the tumor. Thus, our results suggest that the stromal cells are derived from either vestigial cells of the neural crest or histiocytic cells of the reticuloendothelial system, which potentially produce S-100 protein. Our results, considered in light of certain previous observations, imply that the stromal cells are the principal neoplastic cells of hemangioblastoma and are associated with the proliferation of vascular channels, possibly as a secondary effect of this tumor.

Factor VIII related antigen and glial fibrillary acidic protein immunoreactivity in the differential diagnosis of central nervous system hemangioblastomas.

Nineteen hemangioblastomas, nine angioblastic meningiomas, ten metastases to the brain (including five renal cell carcinomas), and five primary renal cell carcinomas were studied using the immunoperoxidase method for Factor VIII related antigen and glial fibrillary acidic protein (GFAP). All tumor types showed Factor VIII immunoreactivity confined to endothelial cells. Factor VIII immunostaining revealed a distinct, though probably nondiagnostic, vascular pattern for hemangioblastomas as compared with metastatic carcinomas and angioblastic meningiomas. Most of the hemangioblastomas and metastases showed numerous GFAP-reactive cells with unequivocal astrocytic morphology primarily at the interface with brain parenchyma but also occasionally deep within the tumor. Within metastases these cells often were associated with penetrating fibrovascular septa. In a minority of hemangioblastomas and metastatic carcinomas there were rare GFAP immunoreactive cells that were indistinguishable from stromal or metastatic tumor cells, respectively. Angioblastic meningiomas showed no GFAP reactivity. It is concluded that the presence of GFAP-reactive cells alone is not helpful in differentiating between hemangioblastomas and intra-axial lesions. The lack of stromal cell immunoreactivity in angioblastic meningiomas and the rare staining of stromal cells in hemangioblastomas, seen also in central nervous system (CNS) metastases, suggest that except for the endothelial cells lining vessels, these primary CNS lesions are not antigenically closely related to either endothelial cells or astroglia. Furthermore, in the evaluation of tumors within the CNS, the significance of rare GFAP-positive tumor cells must be interpreted with caution.

Immunocytochemical study of the glial fibrillary acidic protein in human neoplasms of the central nervous system

The distribution of the glial fibrillary acidic protein (GFAP) was investigated in sections of 131 paraffin-embedded brain neoplasms obtained at surgery or at autopsy. The unlabeled antibody immunoperoxidase (peroxidase-antiperoxidase, PAP) method was used. Equally good results were obtained from 17-year-old material and from recent material derived at surgery or autopsy and fixed with Bouin fluid or phosphate-buffered formalin. The perikaryons and processes of reactive astrocytes showed the most intense stain for GFAP. Positive reaction to antibody against GFAP of varying intensity was demonstrated in astrocytomas of various grades of malignancy (32 of 32), glioblastoma multiforme (10 of 10), subependymal giant cell astrocytoma (1 of 1), ependymoma (2 of 10), subependymoma (4 of 4), and astrocytes in mixed neoplasms (8 of 8). In two neoplasms diagnosed as malignant astrocytomas and in four neoplasms diagnosed as glioblastoma multiforme, GFAP stain was limited to a few neoplastic cells. Usually the stain was more intense over processes than in perikaryons, with the exception of gemistocytic astrocytomas and the giant cells in glioblastoma multiforme, which showed an equally intense stain over perikaryons and processes. The periphery of Rosenthal fibers was intensely positive for GFAP. In astrocytic neoplasms the number of GFAP-positive cells and the intensity of the stain were inversely proportional to the degree of malignancy. In the following neoplasms the reaction for GFAP was negative: oligodendroglioma (3), oligodendroblastoma (1), medulloblastoma (3), medulloepithelioma (1), neuroblastoma (1), pineocytoma (1), typical teratoma of the pineal (1), fibrosarcoma (1), pituitary adenoma (2), craniopharyngioma (1), chordoma (1), chemodectoma of globus jugulare (1), metastatic carcinoma (17), and lymphoma (8). In one of 18 meningiomas, endogenous peroxidase activity was seen in mast cells. All meningiomas studied were negative for GFAP. In one of six neurinomas a positive reaction for GFAP was detected over processes. The authors concluded that the immunostain for GFAP is useful in the diagnoses of astrocytic neoplasms and of mixed gliomas.

The role of glutamine synthetase in the diagnosis of cerebral tumours.

Glutamine synthetase (GS) was studied in a range of human brain tumours and compared with results obtained by staining for glial fibrillary acidic protein (GFAP) using the indirect immunoperoxidase and peroxidase-anti-peroxidase methods. All astrocytomas showed positive staining with GS, the degree of which was related to the extent of differentiation and the amount of cytoplasm of the constituent cells. Ependymomas were only weakly positive, although a dense GFAP reaction was detected around blood vessels; possibly due to the presence of astrocyte foot processes. Medulloblastomas showed signs of astrocytic differentiation by the presence of clusters of positively staining cells amongst undifferentiated neoplastic cells. Oligodendrocytomas and meningiomas were generally negative apart from occasional astrocytes within the former neoplasms. GS and GFAP staining corresponded in virtually all cases; however, GS demonstrated poorly-fibrillated cells better than GFAP, but did not show cell processes so clearly. Although GS appears to be cell-specific in the central nervous system for normal, reactive and neoplastic astrocytes, it is not organ-specific and therefore also stains cells of other tissues, e.g. liver. GS offers a practical alternative to GFAP as an astrocyte specific marker in human cerebral tumours and may be of diagnostic value in cases where poorly-differentiated astrocytic tumours have been found negative to conventional histological stains for glial fibres or demonstrate a weak positive reaction to GFAP.

Immunofluorescent staining of frozen sections for glial fibrillary acidic protein.

Immunofluorescent staining for glial fibrillary acidic protein (GFAP) has been used as part of the diagnostic evaluation of eleven patients and compared with routine special stains. In one case, a difficult fibrillary neoplasm of the spinal cord, this diagnostic procedure provided rapid, positive identification of the glial nature of the tumor. In all cases, the GFAP reactivity was consistent with staining properties of PTAH and more rapid than PTAH.