Basic fibroblast growth factor (FGF) in the central nervous system: identification of specific loci of basic FGF expression in the rat brain

Basic fibroblast growth factor in the hypoglossal system: specific retrograde transport, trophic, and lesion-related responses

To further clarify the function of basic fibroblast growth factor (bFGF) in the nervous system, we have examined its distribution, lesion-dependent regulation, retrograde transport, and trophic roles on rat hypoglossal neurons. In adult rats, bFGF-like immunoreactivity is localized in hypoglossal motoneurons, drastically reduced 2 days after axotomy, and re-expressed by 11 days. Neuron numbers and morphology assessed by Nissl staining are not affected by the lesion. 125J bFGF is specifically retrogradely transported by hypoglossal motoneurons from their peripheral nerve terminals. Moreover, bFGF stimulates the in vitro survival of hypoglossal neurons (ED50 2 ng/ml). In vivo administration of bFGF prevents lesion-induced motoneuron death to 14% in 7 day old rats and to 60% in 18 day old rats, but not the axotomy-induced decrease of choline acetyltransferase activity in the hypoglossal nucleus of adult rats. These results are consistent with a neurotrophic role of bFGF in the hypoglossal system.

Basic fibroblast growth factor-like immunoreactivity in the trigeminal proprioceptive and motor systems

Basic fibroblast growth factor (bFGF) isolated from the brain and pituitary, has been shown to induce cell divisions in a variety of cell types. It also acts as a potent stimulator of angiogenesis, and it is important in the survival of several types of cultured neurons. Despite considerable information on the functions of bFGF, there is incomplete knowledge about the ways in which it reaches remote tissues and its subcellular localization in the adult brain. Here we report our findings that a certain population of neurons with free ribosomes and rough endoplasmic reticulum immunoreactive for bFGF in the mesencephalic nucleus of the trigeminal nerve sends proprioceptive fibers to muscle spindles in the masseter muscle, and immunoreactive axons to the trigeminal motor nucleus to form synapses with the bFGF-containing motoneurons whose axons further constitute myoneural junctions in the periphery. Moreover, some bFGF neurons contain electron dense immunoreaction deposits in the euchromatin but not in the heterochromatin of the nucleus. These findings suggest that endogenous bFGF is transported within nerve processes and functions in mature neuronal circuits subserving the masseteric reflex arcs, and that bFGF is produced in free ribosomes and/or rough endoplasmic reticulum and is transported into the genetically active euchromatin as well.

Co-localization of basic fibroblast growth factor-like immunoreactivity and its receptor mRNA in the rat spinal cord and the dorsal root ganglion

In the present study, we examined the localizations of basic fibroblast growth factor-like immunoreactivity (bFGF-LI) and its receptor mRNA in the spinal cord and the dorsal root ganglion of the rat. Anti-bFGF peptide antibody and cRNA probe were employed to visualize the localizations of bFGF-LI and FGF receptor (FGF-R) mRNA, respectively. In the spinal cord, we observed that a number of neurons including the motor neurons and interneurons were positive for both substances. In the dorsal root ganglion (DRG), the large neurons preferentially showed co-localization of bFGF-LI and FGF-R mRNA, while the small neurons were not always positive for both. Given the fact that FGF-R is a membrane-spanning protein, these findings suggest the following two possibilities: (1) bFGF acts on the neurons of the spinal cord and the DRG in an autocrine and/or paracrine manner; (2) FGF-R mRNA-positive neurons take up bFGF from innervating neurons and/or surrounding glias in a receptor-mediated fashion.

Characterization of a neurotrophic factor produced by cultured astrocytes involved in the regulation of subcortical cholinergic neurons

When dissociated subcortical cells were cultured in the presence of conditioned medium of relatively differentiated astrocytes (ACM), a marked increase was observed in the expression of choline acetyltransferase (ChAT), an enzyme required for the synthesis of the neurotransmitter acetylcholine. Astrocytes from the target regions of subcortical neurons, the hippocampus and the cerebral cortex, produced neurotrophic factor consistently more than those derived from the nontarget region, the cerebellum. The production of cholinergic trophic activity was increased with the maturation of astrocytes. Even though, nerve growth factor (NGF) and ciliary neurotrophic factor (CNTF) are known cholinergic trophic compounds produced by astrocytes in vitro, a large part of the neurotrophic activity in our ACM was not related to either of these 2 factors. This is because (i) ACM and NGF produced an additive effect on ChAT activity, (ii) only a small proportion of the cholinergic trophic activity in ACM was abolished by anti-NGF antibody, and (iii) treatment with CNTF had no effect on ChAT activity of basal forebrain cholinergic neurons. On the other hand, when cholinergic neurons are cultured on a preformed layer of astrocytes, addition of basal fibroblast growth factor (bFGF) failed to increase further the ChAT activity. Similarly the effects of ACM and bFGF were not additive. A large proportion of the cholinergic trophic activity in ACM was neutralized by anti-bFGF antibody. These findings would suggest that the trophic activity on septal cholinergic neurons in our ACM was due to bFGF or a bFGF-like compound.

Basic fibroblast growth factor in cells derived from Dupuytren's contracture: synthesis, presence, and implications for treatment of the disease

Dupuytren's contracture (DC) is associated with fibroblast and endothelial cell proliferation. We have identified a fibroblast and endothelial cell mitogen, basic fibroblast growth factor (FGF), in cells derived from this tissue and characterized the effects of this growth factor on DC cells. Northern blot analysis of DC cells reveals the presence of basic FGF mRNA species, and the DC cells coexpress multiple forms of basic FGF. Radioreceptor assays establish that the DC cells have high-affinity binding sites for basic FGF and proliferate in response to exogenous recombinant basic FGF. Furthermore, a conjugate between saporin (a ribosome-inactivating protein) and basic FGF, which is cytotoxic to cells possessing the basic FGF receptor, is also cytotoxic to DC cells. The possibility that basic FGF-saporin could be a potential therapeutic agent for prevention of recurrence of the disease after surgery is discussed.

Interactions of FGFs with target cells

Growth factors play a key role in cellular communication, a necessary step for the development of pluricellular organisms. The fibroblast growth factors (FGF) are among these polypeptides and have seven known members: FGF 1 to FGF 7 which are also known as acidic FGF, basic FGF, translation products of oncogenes hst, int 2, FGF 5, FGF 6 and FGF 7 or keratinocyte growth factor (KGF) respectively [1]. The best known and the most abundant in normal adult tissues are acidic and basic FGFs, or FGF 1 and 2 respectively, which have been subjected to extensive studies both in vitro and in vivo. These two factors have almost ubiquitous distribution and a wide spectrum of biological activity including action on cellular proliferation and differentiation, as well as neurotrophic and angiogenic properties [1]. These different activities are induced by triggering specific receptors present at the surface of the target cell. Following this interaction, the FGF-receptor complexes are internalized and activate intracellular pathways. An important effort of investigations has been produced to characterize these receptors and intracellular pathways. It is the purpose of this review to present this work which will focus on FGFs 1 and 2. The existence of two classes of interactions has been reported as early as 1987 [52, 53, 54] suggesting the presence of high and low affinity receptors for FGFs.

A role for fibroblast growth factor in oligodendrocyte development

The differentiation of oligodendrocyte-type 2 astrocyte (O-2A) glial progenitor cells into myelin-forming oligodendrocytes is influenced by several polypeptide growth factors. Exposure of O-2A progenitors to basic fibroblast growth factor (bFGF) promotes their sustained proliferation, blocks their differentiation, and maintains both a high level of platelet-derived growth factor (PDGF) alpha-receptors and PDGF sensitivity. Exposure to PDGF, in contrast, promotes only a limited number of cell divisions prior to their differentiation and triggers progenitor cell migration. In the continued presence of bFGF the cells have a stellate morphology with short processes. Upon addition of PDGF these stellate cells become bipolar with long processes, and on removal of PDGF their morphology reverts back to stellate. Thus the phenotype of O-2A progenitor cells in response to these growth factors is plastic. Our studies suggest that bFGF (or a related ligand) in the CNS may sensitize O-2A progenitors to PDGF and thereby initiate their ability to migrate into white matter tracts prior to the onset of myelination.

Developmental expression of the basic fibroblast growth factor gene in rat brain

Basic fibroblast growth factor (bFGF) is a trophic factor for a variety of neuronal/glial cell populations. The RNase protection assay, with a cRNA complementary to the coding region of bFGF mRNA, was used to investigate the brain distribution and developmental regulation of bFGF mRNA expression. In adult rats bFGF mRNA is distributed throughout the brain, the highest levels being observed in cerebral cortex, hippocampus and spinal cord. The levels of bFGF mRNA in all the brain structures are low in newborn rats, increase thereafter to reach a peak of expression around postnatal day 21. bFGF mRNA levels are significantly different between various brain structures during the first and second postnatal week. Adult and aged rats (Fisher 344) express the same levels of bFGF mRNA in the various brain regions. The onset of bFGF mRNA expression suggests that this growth factor is important for the maturation as well as for the maintenance of different cell populations of the central nervous system.

Acidic fibroblast growth factor in the developing rat embryo

Compared to basic fibroblast growth factor (bFGF), a widely distributed, broad spectrum mitogen and mesoderm inducer, acidic fibroblast growth factor (aFGF) is reported to have an essentially neural distribution and to be undetectable in the early embryo. In the present investigation, we used immunoblotting and immunochemistry to assess the cellular and tissue distributions of aFGF and bFGF in 11-20-d rat embryos. Immunoblotting of crude and heparin-bound embryo extracts revealed faint bands at the expected 17-18-kD and predominant bands at an apparent molecular mass of 26 to 28-kD (despite reducing conditions) using multiple specific antibodies for aFGF and bFGF. Pretreatment with 8 M urea yielded 18-20-kD aFGF and bFGF and some 24-26-kD bFGF. Immunoreactivity for both aFGF and bFGF was positive and similar in the cytoplasm, nuclei, and extracellular matrix of cells of neuroectodermal and mesodermal origin, while it was negative in endoderm-derived cells. The distribution of immunoreactive aFGF and bFGF also showed changes during development that were associated with the process of cellular and tissue differentiation. For example, intensity and extent of immunoreactivity for both peptides progressively increased in the middle layer of the spinal cord with increasing differentiation of the neural cells. The immunostaining patterns were very similar for aFGF and bFGF for each organ and at each stage. In conclusion, high molecular mass forms of immunoreactive aFGF and bFGF are present in the rat embryo. Acidic FGF and bFGF are both widely distributed in tissues of neuroectodermal and mesodermal origin, and their distribution was very similar.

Basic fibroblast growth factor regulates the ability of astrocytes to support hypothalamic neuronal survival in vitro

The putative neurotrophic effects of basic fibroblast growth factor (bFGF) were tested on embryonic hypothalamic neurons in dissociated cell culture. Basic FGF dramatically increased the survival of embryonic hypothalamic astrocytes plated on a poly-L-lysine (PLL) substrate. Basic FGF treatment also increased the number of hypothalamic neurons surviving in vitro; however, no neurotrophic effects were observed when astrocyte proliferation was prevented by using serum-free N2 medium or by using the mitotic inhibitor cytosine arabinoside. In contrast to effects when PLL was used as a substrate, bFGF reduced the survival of hypothalamic neurons plated on a confluent, contact-inhibited monolayer of astrocytes. This effect appears to be due to the direct actions of bFGF on astrocytes: treatment of confluent astrocytes with 5 ng/ml bFGF caused the protoplasmic astrocytes to develop a fibrillar morphology and reduced the ability of the astrocyte monolayer to promote neuronal survival after a further 24 hr in bFGF-free medium. It is concluded that in addition to its mitogenic effects, bFGF acts as a differentiation factor for protoplasmic astrocytes in vitro, and these morphological and functional changes may reflect the process of normal astrocytic development and response to brain injury in vivo.

Tissue- and development-specific expression of HBGF-1 mRNA

The gene for heparin-binding growth factor-1 (HBGF-1) encodes a 15.5-18 kDa polypeptide that affects the proliferation and differentiation of a broad range of mammalian cells and is widely distributed among normal adult tissues. In this study, we show that normal tissues of the adult rat express HBGF-1 transcripts in one of three patterns: a 4.4 kb mRNA was the predominant HBGF-1 transcript in brain, heart and lung; a 1.4 kb mRNA was the predominant transcript in the liver; approximately equal levels of the 1.4 and 4.4 kb mRNAs were found in the kidney. HBGF-1 expression was localized in two tissues: central nervous system expression of HBGF-1 was significantly higher in the brain stem compared to the cerebrum and cerebellum; renal expression of HBGF-1 was significantly higher in the medulla compared to the cortex. Analysis of the postnatal changes in HBGF-1 expression using the newborn rat kidney revealed that the level of HBGF-1 mRNA is low at birth and does not rise to adult levels until the seventh postnatal day. These findings demonstrate that HBGF-1 expression is specific for tissue type and stage of development.

Basic fibroblast growth factor and somatomedin C in human medulloepithelioma

Two published cases of medulloepithelioma, a rare malignant pediatric brain tumor composed of a mixture of primitive neuroepithelium and its differentiated neuronal and glial descendants, were examined by immunohistochemical staining for the presence of growth factors. From a panel of antibodies, those identifying basic fibroblast growth factor and insulin-like growth factor I, formerly known as somatomedin C, were strongly immunoreactive within the neuroepithelial cell population of the tumors. Immunoblots of purified recombinant basic fibroblast growth factor and insulin-like growth factor I showed antibody specificity without cross-reactivity. In controls, immunostaining of tissue sections was abolished by preabsorption of primary antibodies with the appropriate growth factor polypeptide antigen. Preabsorption with inappropriate growth factor did not reduce the intensity or alter the distribution of staining. The congruent histologic patterns of immunoreactivities suggest that more than one type of growth factor may be produced by the neuroepithelial component of medulloepithelioma. These growth factors may stimulate proliferation and differentiation of tumor cells by autocrine molecular mechanisms.

Temporal, differential and regional expression of mRNA for basic fibroblast growth factor in the developing and adult rat brain

The expression of basic fibroblast growth factor (bFGF) mRNA and bFGF receptor mRNA was investigated in developing rat brain. In embryonic rat brain days 13-21 (E13-E21), an abundant 1.8 kb bFGF mRNA was detected. Expression of 1.8 kb bFGF mRNA was the highest at E17 to E19 and was relatively undetectable 20 days after birth. However, very little mitogenic activity was associated with prenatal brain. On the other hand, multiple bFGF mRNA species of 6.0, 3.7, 2.5, 1.8, 1.6, 1.4 and 1.0 kb were detected in total adult rat brain and a significant amount of mitogenic activity was present. Differential and spatial bFGF mRNA expression was found in different parts of developing rat brain. Embryonic hypothalamus was found to contain the 1.8 kb bFGF mRNA while the 6.0 kb bFGF mRNA transcript was predominant in adult hypothalamus. Adult pituitary and cortex transcribed the lower molecular weight mRNAs but not the 6.0 kb mRNA. Expression of high-affinity bFGF receptor (flg) mRNA was found to be temporally regulated. flg 4.3 kb mRNA expression was high in embryonic rat brain (E13-E19). There appears to be coordinate expression between the 1.8 kb bFGF mRNA and flg. These results suggest that the expression of basic FGF mRNA is complex since it is both temporally and differentially regulated with different species being expressed at different times in development.

Localization of basic fibroblast growth factor and its mRNA after CNS injury

Basic fibroblast growth factor (FGF) mRNA is increased 4 h after cortical brain injury. In situ hybridization reveals that the increased mRNA persists for at least 2 weeks and that, in areas adjacent and ipsilateral to the lesion, the expression of basic FGF mRNA is also modified. As an example, at three days distal from the lesion, mRNA can be detected in ependymal cells of the lateral ventricle and in selected cells of the hippocampus and cortex. Endothelial cells also synthesize basic FGF mRNA. The increase in basic FGF mRNA is paralleled by similar changes in the localization of the basic FGF protein. Both the intensity and number of cells which stain for basic FGF are increased when they are compared to staining in either the contralateral side or to comparable areas of unlesioned brains. The pattern of mRNA expression is similar from 4 hours to 14 days. Early in the response (4 h to 3 days) on the border of the lesion, the presence of basic FGF is most obvious within the MAC-1-immunopositive population (macrophages and/or microglia). From 7 days to 2 weeks, there has been extensive hypertrophy of the reactive astrocytes which stain intensely for anti-basic FGF(1-24). We conclude that there is increased basic FGF as a function of injury to the CNS. In view of the observation that it is an early and persistent response, the possibility that it plays multiple functions in the regenerative capacity of the CNS is discussed.

Expression of basic fibroblast growth factor and its receptor in the rat subfornical organ

Basic fibroblast growth factor (FGF), its mRNA and the mRNA that encodes for its receptor have all been localized in the rat subfornical organ (SFO). Basic FGF is widely distributed throughout the SFO; it is present in neurons, in the vascular basement membrane of lateral blood vessels (but not those within the SFO) and in ependymal cells surrounding the SFO. Results of in situ hybridization show that the expression of basic FGF mRNA is detected throughout the organ. Similarly, the expression of flg, the gene for the putative basic FGF receptor, can also be detected in the SFO. The results all support the possibility that this growth factor may modulate the known physiological functions of the SFO.

Developmental changes of acidic fibroblast growth factor (aFGF) transcription and expression in mouse brain

In order to increase our knowledge of the in vivo role of acidic fibroblast growth factor (aFGF) in the central nervous system, we have examined aFGF levels during mouse brain development. Using a specific polyclonal antibody raised against aFGF, we measured levels of aFGF-immunoreactive material (IRMaFGF) in extract of total mouse brain taken at different days of development. We found that the level of measurable IRMaFGF remained low and without significant variation during fetal brain development (0.2 ng/mg of extracted proteins). During the first 11 days postnatal (P0 to P11), IRMaFGF increased from 0.5 to 1.5 ng/mg. Between P11 and P14 IRMaFGF levels went up more rapidly, reaching 5 ng/mg. From P30 to adulthood a constant value of 2.5 ng/mg was measured, aFGF content in the different brain extracts was further characterized by its affinity for heparin-Sepharose, its elution at 1 M NaCl from this column and its capacity to induce thymidine incorporation in quiescent fibroblasts. These results were confirmed at the mRNA level. Northern blot analyses of poly A+ mRNA from brains with a specific riboprobe for bovine aFGF, revealed a major 4.5-Kb transcript and a minor 2.7-Kb transcript detectable only in postnatal brains. A similar pattern to that observed for IRMaFGF was seen with these mRNA transcripts, indicating that these aFGFmRNA are translated in the mouse brain. Our results suggest that aFGF may act in the postnatal phases of brain maturation.

trkB, a neural receptor protein-tyrosine kinase: evidence for a full-length and two truncated receptors

We have screened an adult rat cerebellar cDNA library in search of novel protein tyrosine-kinase (PTK) cDNAs. A cDNA for a putative PTK, trkB, was cloned, and its sequence indicates that it is likely to be derived from a gene for a ligand-regulated receptor closely related to the human trk oncogene. Northern (RNA) analysis showed that the trkB gene is expressed predominantly in the brain and that trkB expresses multiple mRNAs, ranging from 0.7 to 9 kb. Hybridization of cerebral mRNAs with a variety of probes indicates that there are mRNAs encoding truncated trkB receptors. Two additional types of cDNA were isolated, and their sequences are predicted to encode two distinct C-terminally truncated receptors which have the complete extracellular region and transmembrane domain, but which differ in their short cytoplasmic tails.

PDGF B-chain in neurons of the central nervous system, posterior pituitary, and in a transgenic model

Platelet-derived growth factors (PDGFs) are growth-regulatory molecules that stimulate chemotaxis, proliferation, and increased metabolism of primarily connective tissue cells. In a survey of normal tissues, we found specific immunostaining for PDGF B-chain in neurons, principal dendrites, some axons, and probable terminals throughout the brain, in the dorsal horn of the spinal cord, and in the posterior pituitary of a nonhuman primate (Macaca nemestrina). PDGF activity was extracted from brain cortex and posterior pituitary, and ubiquitous expression of transcripts for the two chains of PDGF and both PDGF receptors was detected throughout the brain and posterior pituitary. A transgenic model was also evaluated in which the chloramphenicol acetyltransferase gene was placed under transcriptional control of the PDGF B-chain promoter. The transgene was preferentially expressed within neural cell bodies in the cortex, hippocampus, and cerebellum. PDGF may act as a neuronal regulatory agent. Neuronal release of PDGF could contribute to nerve regeneration and to glial proliferation that leads to gliosis and scarring.

trkB, a neural receptor protein-tyrosine kinase: evidence for a full-length and two truncated receptors

We have screened an adult rat cerebellar cDNA library in search of novel protein tyrosine-kinase (PTK) cDNAs. A cDNA for a putative PTK, trkB, was cloned, and its sequence indicates that it is likely to be derived from a gene for a ligand-regulated receptor closely related to the human trk oncogene. Northern (RNA) analysis showed that the trkB gene is expressed predominantly in the brain and that trkB expresses multiple mRNAs, ranging from 0.7 to 9 kb. Hybridization of cerebral mRNAs with a variety of probes indicates that there are mRNAs encoding truncated trkB receptors. Two additional types of cDNA were isolated, and their sequences are predicted to encode two distinct C-terminally truncated receptors which have the complete extracellular region and transmembrane domain, but which differ in their short cytoplasmic tails.

Biologically active basic fibroblast growth factor migrates at 27 kD in "non-denaturing" SDS-polyacrylamide gel electrophoresis

Using mild conditions of SDS-PAGE, i.e. no heating of the sample, and the PhastSystem (Pharmacia), we found that bFGF, either natural bovine or recombinant human migrated at a 27 kD position in addition to the classical 18 kD one. By the cell-blot technique, we found that the biological activity toward rat astroblasts and 3T3 mouse fibroblasts was always restricted to the 27 kD band. Partial heat denaturation experiments revealed a close correlation between the remaining biological activity of bFGF in solution and the ratio of the 27 kD band versus the 18 kD band seen on SDS gels. These observations suggest that the bFGF which is biologically active in solution migrates at an apparent Mr of 27 kD in our conditions of electrophoresis, keeping its biological activity after electrophoresis, and the molecules which are inactive (denatured) in solution migrate at 18 kD and remain inactive. These experimental conditions, in which the biological activity appears to be preserved, could be referred to as "non-denaturing SDS-polyacrylamide gel electrophoresis" and could be useful, associated to cell-blot, for the search and characterization of new growth factors active on cells in culture.

Transforming growth factor beta isoforms in the adult rat central and peripheral nervous system

The distribution of transforming growth factor-beta isoforms 1, 2 and 3 and transforming growth factor-beta 2 and 3 mRNAs in adult rat central and peripheral nervous system was examined using Northern blotting and isoform specific antibodies for immunocytochemistry. Transforming growth factor-beta 2 and 3 mRNA were present in all brain areas including cerebral cortex, hippocampus, striatum, cerebellum and brainstem. In sciatic nerve, transforming growth factor-beta 3 mRNA was highly expressed, but transforming growth factor-beta 2 mRNA was not detectable. Transforming growth factor-beta 1-like immunoreactivity was confined to meninges and choroid plexus in the brain and connective tissue in peripheral ganglia and nerves. Transforming growth factor-beta 2 and 3 immunoreactivity entirely overlapped and, in general, were found in large multipolar neurons. Highest densities of immunoreactive neuronal perikarya were present in spinal cord and brainstem motor nuclei, hypothalamus, amygdaloid complex, hippocampus and cerebral cortical layers II, III and V. Most thalamic nuclei, superior colliculi, periaqueductal gray and striatum were almost devoid of transforming growth factor-beta 2- and 3-immunoreactive neurons. Fibrous astrocytes in white matter areas were intensely immunostained. Most dorsal root ganglionic neurons, their satellite cells and Schwann cells in peripheral nerves were also labeled. Transforming growth factor-beta 2- and 3-immunoreactive neurons were localized in brain regions that have been shown to contain neurons synthesizing and/or storing basic fibroblast growth factor suggesting possible opposing or synergistic effects of these peptide growth factors. However, the precise functions of local synthesis and storage of the transforming growth factor-beta isoforms in the nervous system are as yet unknown.

Basic fibroblast growth factor in Alzheimer's disease

We have examined the presence of basic fibroblast growth factor (FGF) in normal and in Alzheimer brains, studied the distribution of the mitogen by immunohistochemical techniques, measured the quantities of growth factor in selected areas of the brain (Brodmann areas 10/11 and 20/21), characterized the molecular forms by Western blotting and determined its sites of synthesis by in situ hybridization. Although the same molecular forms of basic FGF are found in control and Alzheimer brains, basic FGF is increased in the brains of Alzheimer's patients. Furthermore, basic FGF is not distributed in an identical fashion to normal and Alzheimer brains, but is found in association with the lesions that characterize this disease. In normal controls (n = 5), basic FGF was found to be widely distributed throughout the three brain regions examined (prefrontal cortex, hippocampus, and hypothalamus). Immunoreactivity was observed within astrocytes in both the grey and white matter, as well as within neuronal perikarya. Brain tissues that were obtained from Alzheimer patients (N = 4) showed a substantial increase in the overall specific staining of astrocytes and neurons, particularly in areas of reactive gliosis. Focal concentration of immunoreactive basic FGF was evident within the neuritic plaques, and could be clearly seen in association with the neurofibrillary tangles present within neuronal perikarya. The possibility that basic FGF expression in the CNS is linked to the pathogenesis of the disease is discussed.