Biomedical subjects

I A Hendry

Publications and source records attributed to I A Hendry.

At least 37 records · Page 2Linked to original sources

PubMed1999

The regulation of the retrograde axonal transport of (125)I-beta nerve growth factor is independent of calcium.

Calcium has been shown to play a major role in the regulation of endocytosis and exocytosis of synaptic vesicles and retrograde axonal transport of proteins. The role of calcium in the regulation of neurotrophin retrograde axonal transport is unknown. This study aimed to determine if calcium plays a role in the uptake and retrograde axonal transport of (125)I-beta nerve growth factor ((125)I-betaNGF) within sympathetic neurons innervating the iris by comparing it with (125)I-anti-dopamine beta hydroxylase (anti-DBH). The nonspecific voltage-sensitive calcium channel (VSCC) antagonists, cadmium (200 nmol/eye) and nickel (100 nmol/eye) reduced the amount of (125)I-anti-DBH retrograde axonal transport by 90 and 70%, respectively. In contrast, cadmium (200 nmol/eye) had no effect on (125)I-betaNGF retrograde axonal transport, while nickel (100 nmol/eye) caused a significant increase in the amount transported to the ganglia. The L-type VSCC antagonist nifedipine (10 nmol/eye) and N-type VSCC antagonist omega-conotoxin (1.5 nmol/eye) both had no effect on (125)I-anti-DBH retrograde axonal transport which suggests that these types of calcium channels are not involved in the exocytosis/endocytosis of anti-DBH containing vesicles. Thapsigargin (0.2 nmol/eye), an inhibitor of sarcoplasmic reticulum Ca(2+)-ATPases also significantly inhibited (125)I-anti-DBH transport but had no effect on (125)I-betaNGF retrograde transport. This suggests that (125)I-anti-DBH and (125)I-betaNGF are internalized into different vesicle types and that the endocytosis and retrograde axonal transport of (125)I-betaNGF are not dependent upon calcium.

Animals↗

PubMed1999

Differential mRNA expression and subcellular locations of PI3-kinase isoforms in sympathetic and sensory neurons.

Phosphatidylinositol 3-kinase (PI3-kinase) enzymes are key signalling molecules in the PC12 and neuronal cell survival pathway and are also involved in the regulation of retrograde axonal transport of nerve growth factor (NGF), with sympathetic neurons more sensitive to the effects of wortmannin/LY294002 than sensory neurons (Bartlett et al. [1997]; Brain Res. 761:257-262; Reynolds et al. [1998] Brain Res. 798:67-74). In this article, we characterized the mRNA expression of PI3-kinase isoforms in mouse sympathetic superior cervical ganglia (SCG) and sensory trigeminal ganglia (TGG) and examined the subcellular locations of immunoreactivity of the PI3-kinase isoforms in mouse cultured SCG and dorsal root ganglion (DRG) neurons. Both the SCG and the TGG express mRNA for the p110alpha, beta, gamma, delta, and vps34p PI3-kinase isoforms, but the TGG and not the SCG express mRNA for the p170 PI3-kinase isoform. In cultured SCG and DRG neurons, p110alpha, beta, and gamma immunoreactivity is in the SCG and DRG growth cones, and predominantly in puncta throughout the growth cone varicosity. However, in the cell bodies immunoreactivity varied, p110alpha is localized predominantly at the plasma membrane, while p110beta and gamma is localized in the perinuclear region of the cells. In addition, unlike other cell types, wortmannin has little effect on actin filament polymerization in either mouse cultured SCG or DRG neurons.

Actins↗

PubMed1999

A technique for 125I-labelling of neurotrophins and the use of retrograde axonal transport as a bioassay.

The protocol presented here details a technique which enables the neurotrophins nerve growth factor (NGF), neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), and brain-derived neurotrophic factor (BDNF) to be labelled using 125I and the bioactivity of these labelled proteins determined using an in vivo bioassay. We have found that the simplest and most effective method for 125I-labelling of neurotrophic factors is the IODO-GEN method. Following the iodination of neurotrophins it must be established that the labelling procedure has not affected the biological activity of the protein. Traditional methods of assaying the bioactivity of 125I-labelled neurotrophins have several disadvantages and a much easier protocol to use is the retrograde axonal transport of these proteins in sympathetic and sensory neurons of adult mice. High specific activity 125I-labelled neurotrophin, to which known amounts of unlabelled neurotrophin are added, is injected into the right anterior eye chamber of adult mice under anaesthetic and the animals are left to recover for 16 h, after which they are sacrificed and both superior cervical ganglia (SCG) and trigeminal ganglia (TGG) are removed. The accumulated radioactivity in each ganglion is determined using a gamma-counter and the amount of neurotrophin transported is calculated by subtracting the counts obtained on the non-injected side from those present on the injected side. By comparing the amount of protein injected with the amount transported, the specific activity of the bioactive labelled neurotrophin can be determined.

Animals↗

PubMed1999

Evidence for phosphatidylinositol 4-kinase and actin involvement in the regulation of 125I-beta-nerve growth factor retrograde axonal transport.

The signaling events regulating the retrograde axonal transport of neurotrophins are poorly understood, but a role for phosphatidylinositol kinases has been proposed. In this study, we used phenylarsine oxide (PAO) to examine the participation of phosphatidylinositol 4-kinases in nerve growth factor (NGF) retrograde axonal transport within sympathetic and sensory neurons. The retrograde transport of 125I-labeled betaNGF was inhibited by PAO (0.5-2 nmol/eye), and this effect was diminished by dilution. Coinjection of 2,3-dimercaptopropanol with PAO reduced its ability to inhibit 125I-betaNGF retrograde transport. PAO (20 nM to 200 microM) also inhibited NGF-dependent survival of both sympathetic and sensory neuronal populations. F-actin staining in sympathetic and sensory neuronal growth cones was disrupted by PAO at 10 and 2 nM, respectively, and occurred within 5 min of exposure to the drug. The actin inhibitor latrunculin A also rapidly affected F-actin staining in vitro and reduced 125I-betaNGF retrograde axonal transport in vivo to the same extent as PAO. These results suggest that both phosphatidylinositol 4-kinase isoforms and the actin cytoskeleton play significant roles in the regulation of 125I-betaNGF retrograde axonal transport in vivo.

1-Phosphatidylinositol 4-Kinase↗

PubMed1998

Signalling events regulating the retrograde axonal transport of 125I-beta nerve growth factor in vivo.

The molecular mechanisms regulating the retrograde axonal transport of nerve growth factor (NGF) are currently unknown. This study identifies some of the signalling events involved. The phosphoinositide 3-kinase (PI3-kinase) inhibitor wortmannin (1 nmol/eye) irreversibly inhibits the amount of 125I-betaNGF retrogradely transported in both sensory and sympathetic neurons. Another PI3-kinase inhibitor LY294002 (100 nmol/eye) also inhibited 125I-betaNGF retrograde transport in sensory neurons. The pp70S6K inhibitor rapamycin (1 micromol/eye) had the same effect, inhibiting 125I-betaNGF transport only in sensory neurons. The cPLA2 inhibitor AACOCF3 (10 nmol/eye) had no effect on 125I-betaNGF transport in either sensory or sympathetic neurons. The TrkA receptor tyrosine kinase inhibitor AG-879 (10 nmol/eye) reduced 125I-betaNGF transport by approximately 50% in both sensory and sympathetic neurons. Cytochalasin D (2 nmol/eye), a disruptor of actin filaments and the dynein ATPase inhibitor erythro-9-[3-(2-hydroxynonyl)]adenine (EHNA) both inhibited 125I-betaNGF retrograde transport. These results demonstrate that in vivo TrkA tyrosine kinase activity, actin filaments and dynein are involved in the retrograde transport of NGF. In addition, different PI3-kinase isoforms may be recruited within different neuronal populations to regulate the retrograde transport of NGF. Potentially, these isoforms could activate alternative signalling pathways, such as pp70S6K in sensory neurons.

Animals↗

PubMed1998

Developmental expression of messenger RNA levels of the alpha subunit of the GTP-binding protein, Gz, in the mouse nervous system.

There has been recent evidence that Gz may play a role in the transmission of the neurotrophic signal from nerve terminals to the cell bodies [Johanson, S.O., Crouch, M.F., Hendry, I.A., Signal transduction from membrane to nucleus: the special case for neurons, Neurochem. Res. 21 (1996) 779-785]. We examined the developmental expression of the alpha subunit of Gz (Gzalpha) in the peripheral and central nervous systems of the mouse. Our laboratory has developed a quantitative reverse transcription-polymerase chain reaction (RT-PCR) for Gzalpha which makes use of a fragment of the PCR product shortened by 107 base pairs creating a standard which mimics the original RNA. Serial dilutions of the mouse RNA with a constant concentration of mimic RNA were made and the point where equal amounts of product are formed allows accurate measurement of Gzalpha mRNA in the tissue. We have demonstrated that in the developing mouse superior cervical ganglion (SCG), dorsal root ganglion (DRG) and trigeminal ganglion the expression of Gzalpha mRNA is highest perinatally. From 3 weeks of age, in all tissues with the exception of the SCG, Gzalpha mRNA levels fall to lower levels in the adult animal. The developmental pattern of expression of Gzalpha in both the cerebellum and the brain differs from the peripheral nervous system. In the cerebellum, Gzalpha mRNA expression is highest around birth and in the brain it is highest around third postnatal week and then the levels decline as adulthood is approached. These results suggest that the highest level of Gzalpha mRNA is expressed at the time when target tissue innervation is occurring. This further strengthens the hypothesis that Gzalpha is important in the transfer of information from target tissues to the innervating nerve cells.

Animals↗

PubMed1998

Retrograde axonal transport of neurotrophins: differences between neuronal populations and implications for motor neuron disease.

During development, neurons die if they do not receive neurotrophin support from the target cells they are innervating. Neurotrophins are delivered from the target to the cell bodies of the innervating neurons by interacting with specific receptors located on the nerve terminals and then together are retrogradely transported to the cell body. This process consists of a number of distinct events including endocytosis of neurotrophin and its receptor into coated vesicles; vesicle sorting followed by retrograde axonal transport to the cell body, where interaction of the activated receptor initiates a signalling cascade at the cell body that causes the survival response. It has recently been shown that the signalling molecules associated with retrograde transport differ between neuronal populations. In sympathetic but not sensory neurons, a wortmannin-sensitive molecule (phosphatidylinositol kinase) is essential for the retrograde transport of neurotrophins. In sensory but not sympathetic neurons, a rapamycin-sensitive molecule (pp70S6K) is associated with retrograde transport of neurotrophins. This is strong evidence that sympathetic and sensory neurons utilize different signalling pathways to perform the same cellular function; retrograde transport. These findings may provide clues to understanding neurological diseases, such as motor neuron disease, in which axonal transport is impaired specifically in motor neurons.

Animals↗

PubMed1997

In sympathetic but not sensory neurones, phosphoinositide-3 kinase is important for NGF-dependent survival and the retrograde transport of 125I-betaNGF.

The way in which the same ligands and receptors have different functional effects in different cell types must depend on subtle differences in the second messenger cascades. Sensory and sympathetic neurones both retrogradely transport nerve growth factor (NGF) and depend on NGF for their developmental survival. NGF binding to the high affinity tyrosine kinase (TrkA) receptors initiates second messenger signalling cascades, one of which includes the activation of phosphoinositide-3 kinase (PI3-kinase). We demonstrate that 100-fold higher concentrations of the PI3-kinase inhibitor, Wortmannin, are required to inhibit the survival effects and retrograde axonal transport of NGF in sensory neurones than in sympathetic neurones. Similarly, although less potently than Wortmannin, the PI3-kinase inhibitor LY294002 required a 10-fold higher concentration to inhibit the survival effects of NGF in sensory than in sympathetic neurones. Inhibitors of other second messengers, including staurosporine, pertussis and cholera toxins, failed to have an effect on the transport of the NGF receptor complex in both cell types. Also, Wortmannin did not affect the structural integrity of the sympathetic nerve terminals. As PI3-kinase is present in both neuronal populations, this suggests that the Wortmannin sensitive isoform of PI3-kinase (p110) is essential in sympathetic neurones both for survival and for NGF-TrkA receptor complex trafficking. As sensory neurones also depend on NGF for their developmental survival and endocytose and retrogradely transport the NGF-TrkA receptor complex, this population of neurones may either recruit a different isoform of PI3-kinase or utilize PI3-kinase independent signalling pathways for these cellular functions.

1-Phosphatidylinositol 4-Kinase↗

PubMed1997

Identifying the G protein, Gz alpha, and its associated proteins in nervous tissue using mass spectrometry and microsequencing techniques.

The signaling pathway associated with pertussis and cholera toxin sensitive G proteins have been extensively investigated. In contrast, the function and associated signal transduction cascade for the pertussis toxin insensitive G protein, Gz alpha have remained elusive. Therefore, the aim of this study was to identify the signal transduction pathway associated with Gz alpha by using the protein identification techniques of matrix assisted laser desorption ionization-time of flight mass spectroscopy and N-terminal Edman sequencing. We have chosen this technique to identify proteins that Gz alpha associates with and to gain insights into the potential role this G protein plays in cells. As Gz alpha is predominantly localized in neuronal tissues, homogenates of whole brain tissue were used. Gz alpha and its associated proteins were immunoprecipitated from brain tissue and identified. The immunoprecipitation of four proteins (140, 46, 41 and 36 kDa) was shown to be inhibited in the presence of the Gz alpha peptide. These proteins were subsequently identified as phospholipase C (PLC)-gamma, beta or gamma-actin, Gz alpha and G beta, the beta subunit of heterotrimeric G proteins, respectively. These results suggest that Gz alpha exists in a protein complex with the actin cytoskeleton and an important intracellular signalling enzyme, PLC-gamma. These methods are powerful techniques for determining protein-protein interactions, and provide the first step to the identification of signalling proteins that Gz alpha associates with. However further experimentation will be required to determine the biological relevance of these protein interactions.

Amino Acid Sequence↗

PubMed1996

Signal transduction from membrane to nucleus: the special case for neurons.

Neurons have a unique problem with signal transduction from the membrane in the region of their terminals back to the cell body and nucleus. This distance may be several meters in some nerves in some species, so there is a requirement for some mechanism to stabilize the signal. This review examines two complementary mechanisms for this signal transduction, either by the retrograde axonal transport of the neurotrophic factor together with its receptor, or the transport of a stable activated second messenger molecule. Extrapolation of studies on the fibroblast signal transduction pathway, where it has been shown that G1 can translocate from the membrane to the nucleus, has led to the demonstration of the retrograde axonal transport of several putative signaling molecules. The alpha subunits of both G1 and Gz are retrogradely transported and Gz alpha or possibly the intact heterotrimeric Gz subsequently accumulates in dorsal root ganglia nuclei. Thus Gz1 Gi1 and potentially other G-proteins and distinct signaling molecules may provide additional signal transduction pathways to that of the neurotrophins from terminal to nucleus.

Animals↗

PubMed1995

Retrograde axonal transport of the alpha subunit of the GTP-binding protein Gz to the nucleus of sensory neurons.

Nerve cells are exquisitely sensitive to target tissue derived factors and the discovery that nerve growth factor could be retrogradely transported in axons suggested that the physical translocation of proteins along the axon could be a mechanism to convey this signal. This message is not due to the neurotrophic factor itself but rather due to second messengers generated by interaction with receptors. We have previously demonstrated the retrograde axonal transport of the alpha subunits of two putative second messenger molecules Gi and Gz. We have investigated more thoroughly the transport of the alpha subunit of Gz (Gz alpha) and in order to be more certain that the immunoreactivity seen is due to Gz alpha, we have made antibodies to peptides from both the N- and C-terminal regions of Gz alpha, which recognise the same 41 kDa band on Western blots of brain and sciatic nerve extracts. This band is eliminated when the antibodies are previously incubated with the specific peptide to which they were made. Using these antibodies for immunohistochemical localisation for Gz alpha, we now report that the GTP-binding protein Gz, is not only retrogradely transported in axons but that it translocates to the neuronal nucleus. Furthermore, the levels seen in the nuclear compartment decline after axotomy or ligation of the mice under ether anaesthetic, suggesting it is the retrogradely transported Gz alpha that is accumulating in the nucleus after activation at the nerve terminal.

Amino Acid Sequence↗

PubMed1995

Retrograde axonal transport of signal transduction proteins in rat sciatic nerve.

Neurons require a mechanism to transmit stable signals over the large distance from the nerve growth cone or terminal to the cell body, in order that information from the target tissue can be relayed to the cell body where it is required. Nerve growth factor (NGF), a target-derived neurotrophic factor, is thought to signal over this distance by receptor mediated internalization of NGF, followed by retrograde axonal transport of the NGF-receptor complex. In this paper we show, by immunohistochemistry of rat sciatic nerve, accumulation of phosphotyrosine immunoreactivity only on the distal side of a nerve crush, suggesting axonal transport of tyrosine kinases and/or tyrosine phosphorylated proteins primarily in a retrograde direction. Furthermore, we also show retrograde axonal transport of phosphoinositide 3-kinase, ERK, MEK and MEK kinase, of which all but MEK kinase are known to be activated downstream of tyrosine receptor kinase activation. The retrograde transport of these proteins suggests that they may be involved in transmission of signals along the axon, relaying neurotrophic factor receptor activation at the nerve terminal to the nerve cell body.

Animals↗

PubMed1995

Acidic and basic fibroblast growth factor bind with differing affinity to the same heparan sulfate proteoglycan on BALB/c 3T3 cells: implications for potentiation of growth factor action by heparin.

Heparan sulfate proteoglycans on the cell surface act as low affinity binding sites for acidic and basic fibroblast growth factor (FGF) [Moscatelli (1987): J Cell Physiol 131:123-130] and play an important role in the interaction of FGF with the FGF receptor (FGFR). In this study, several aspects of the interaction of FGFs with cell surface heparan sulfate proteoglycans were examined. Reciprocal cross blocking studies demonstrated that acidic FGF (aFGF) and basic FGF (bFGF) bind to identical or closely associated heparan sulfate motifs on BALB/c 3T3 cell surface heparan sulfate proteoglycans. However, the binding affinity of the two growth factors for these heparan sulfate proteoglycans differs considerably, competition binding data indicating that aFGF has a 4.7-fold lower affinity than bFGF for 3T3 heparan sulfate proteoglycan. Subsequent studies of dissociation kinetics demonstrated that bFGF dissociates from the FGFR at least 10-fold slower than aFGF, whereas, following removal of cell surface heparan sulfate proteoglycans by heparinase treatment, the dissociation rate of both FGFs is similar and rapid. These results support the concept that cell surface heparan sulfate proteoglycans stabilize the interaction of FGF with FGFR, possibly by the formation of a ternary complex.

3T3 Cells↗

PubMed1995

Evidence that carboxyl-reduced heparin fails to potentiate acidic fibroblast growth factor activity due to an inability to interact with cell surface heparin receptors.

Recently we reported that carboxyl-reduced heparin (CR-heparin), despite binding acidic fibroblast growth factor (aFGF) as effectively as native heparin, was much less potent at augmenting aFGF-induced mitogenesis. This paper describes experiments which examined this phenomenon in more detail in the hope that it would shed light on the mechanism by which heparin potentiates aFGF activity. Initial studies confirmed that heparin, with 60% of its carboxyl groups reduced, although binding aFGF with the same affinity as native heparin (Kd 35 +/- 5 nM), was a poor potentiator of aFGF-induced mitogenic activity. Proteolysis protection experiments also revealed that CR-heparin was as effective as native heparin at protecting aFGF from proteolytic degradation. In contrast, CR-heparin was considerably less effective than native heparin at enhancing the binding of aFGF to the fibroblast growth factor receptor (FGFR) on 3T3 cells. Furthermore, CR-heparin only bound to a subset (approximately 1/3) of heparin receptors on 3T3 cells. Based on these data, it is proposed that CR-heparin is less efficient than heparin at facilitating the formation of a quaternary complex among aFGF, the FGFR, and cell surface heparin receptors.

3T3 Cells↗

PubMed1995

Developmental signalling.

1. In investigating the communication paths between target tissue and neurons we have been led to propose two classes of neurotrophic factors. One comprises the factors which transport themselves, the other factors relying on the transport of a second messenger. The former may have labile second messenger systems necessitating the translocation of agonist and receptor from the nerve terminal to the cell body and the latter must possess a stable second messenger system that itself is sufficiently robust to survive the transport to the cell body. 2. One such class of stable messengers may be the GTP-binding protein family and it has been shown that the alpha subunits of both Gi alpha and Gz alpha can be retrogradely transported in the mouse sciatic nerve. 3. Examination of the cell bodies in the dorsal root ganglia revealed that Gz alpha accumulated in the nucleus of cells with intact axons but that 24 h after axonal ligation this immunoreactivity decreased. 4. It is suggested that Gz is activated at the nerve terminal and it, or at least its alpha subunit, undergoes retrograde transport to the cell body where it accumulates in the nucleus.

Animals↗

PubMed1995

Interaction of the GTP-binding protein Gi2 with a protein kinase A-like kinase in mouse fibroblasts.

We have previously shown that the GTP-binding protein, Gi2 of mouse Balb/c3T3 cells is linked to a serine kinase which phosphorylates the alpha-subunit of Gi itself. In this report we show that Gi is coupled to a second protein kinase. This kinase does not phosphorylate G but phosphorylates another protein bound non-covalently to G. Phosphorylation of the Gi-linked protein induces its release from Gi. Kinase activity is slightly enhanced by GTPyS, suggesting that this kinase may be physiologically regulated by Gi. In an attempt to identify the kinase we have examined the effect of peptide substrates and inhibitors on kinase activity. We found that the protein kinase A inhibitory peptide, PK1 5-24, inhibited the kinase activity, but at concentrations above those usually required to block protein kinase A. The protein kinase A substrate peptide, kemptide, acted as a substrate of the kinase, and was an inhibitor of the phosphorylation of the Gi-linked protein. However, a protein kinase A, catalytic subunit antibody failed to react with any proteins linked to Gi., A protein kinase C inhibitory peptide had no effect on phosphorylation of the Gi-linked protein. Thus, the identity of this kinase has not been resolved, but it may form part of the signalling system of activated Gi in fibroblasts.

Animals↗

PubMed1994

Retrograde axonal transport of the alpha-subunit of the GTP-binding protein GZ in mouse sciatic nerve: a potential pathway for signal transduction in neurons.

We have utilized antibodies against the alpha subunit of GZ in fluorescence immunohistochemistry to determine whether this GTP-binding protein can translocate along nerves by intra-axonal transport. After ligation of the mouse sciatic nerve we found an increase in GZ-like immunoreactivity on the proximal and distal side with time, suggesting that the alpha subunit undergoes orthograde axonal transport and also returns to the cell body by retrograde axonal transport in the sciatic nerve. Unlike the retrograde transport of Gi alpha, shown in a previous study to be present in most sciatic axons, GZ alpha only accumulated in a subpopulation of axons, suggesting that different G-proteins could convey information specific to neuronal subtypes. These results support our proposal that GZ may play a second messenger role in communicating information from the terminals back to cell bodies. Gi alpha and GZ alpha may be representative of relatively stable signalling molecules by which the signal from some neurotrophic molecules can be translocated from the neuron periphery to the cell body without the need for the retrograde transport of the neurotrophic factor itself.

Amino Acid Sequence↗

PubMed1993

Investigation of the ability of several naturally occurring and synthetic polyanions to bind to and potentiate the biological activity of acidic fibroblast growth factor.

The ability of several animal, plant, and bacterial derived polyanions (PAs) as well as synthetic PAs to compete with heparin for the binding of acidic fibroblast growth factor (aFGF) was correlated with their ability to potentiate the mitogenic and neurotrophic actions of this factor. Dextran sulphate, kappa-carrageenan, pentosan sulphate, polyanethole sulfonate, heparin, and fucoidin competed for the heparin binding site on aFGF at relatively low concentrations (< 50 micrograms/ml). lambda-carrageenan, iota-carrageenan, and polyvinyl sulphate exhibited lower affinity for aFGF, whereas hyaluronic acid, dermatan sulphate, chondroitin-6-sulphate, chondroitin-4-sulphate, and uncharged dextran displayed very low or no demonstrable affinity. Potentiation of the mitogenic action of aFGF for Balb/c 3T3 fibroblasts tended to be in general agreement with the aFGF binding affinity of the PAs. However, polyanethole sulfonate, the carrageenans, polyvinyl sulphate, fucoidin, and pentosan sulphate exerted a mitogenic action on the 3T3 cells that was independent of, and in addition to, the ability of these GAGs to potentiate the action of aFGF. The ability to potentiate the neurotrophic action of aFGF for E8 chick ciliary neurons was a general property of those PA with low or no activity in the mitogen assay. Thus hyaluronic acid, dermatan sulphate, chondroitin-4-sulphate, chondroitin-6-sulphate, and even unchanged dextran all potentiated aFGF induced neuronal survival. The differential effects of these PA in potentiating the biological activities of aFGF are discussed in relation to their ability to compete for the heparin-binding site of aFGF.

3T3 Cells↗