Biomedical subjects

I A Hendry

Publications and source records attributed to I A Hendry.

At least 55 records · Page 3Linked to original sources

PubMed1993

Growth factor second messenger systems: oncogenes and the heterotrimeric GTP-binding protein connection.

We feel that there is now compelling evidence that the GTP-binding proteins play more than just a coordinating role in the actions of both tyrosine kinase and nontyrosine kinase receptor signal transduction. These similarities appear to represent just a small component of the convergence in the signaling pathways for structurally dissimilar receptor subsets. Future years will see further understanding of the intricacies of these G-protein-proto-oncogene interactions, and the extension into the potential role in growth factor action played by the expanding number of known members of this G-protein family.

Animals↗

PubMed1993

Gi alpha and Gi beta are part of a signalling complex in Balb/c3T3 cells: phosphorylation of Gi beta in growth-factor-activated fibroblasts.

Stimulation of division of Balb/c3T3 cells by epidermal growth factor (EGF) and/or insulin is inhibited by pertussis toxin. The G-protein involvement in this response includes the growth factor receptor-induced translocation of the alpha-subunit of Gi (Gi alpha) to the nucleus, where Gi alpha binds specifically to chromatin of dividing cells. This paper reports the first data of studies on the mode of interaction of tyrosine kinase growth factor receptors with Gi alpha, and the mechanism by which Gi affects cell proliferation. When Gi alpha was immunoprecipitated from Triton X-100 extracts of Balb/c3T3 cells, several other proteins were co-precipitated. The major proteins, of 110,000, 60,000 and 36,000 M(r), were not directly recognized by the Gi alpha antibody, showing that Gi alpha was in a complex with these proteins. The 36,000 M(r) protein was recognized by G beta-common antiserum, so confirming its identity as Gi beta. The 36,000 M(r) protein was phosphorylated in cells activated for 20 h with platelet-derived growth factor, epidermal growth factor and insulin, but not after 3 min or 1 h of stimulation. Both Gi alpha and G beta-common antibodies precipitated the phosphorylated 36,000 protein. Gi beta phosphorylation was similarly observed in response to activation by EGF alone for 20 h, but to a lesser extent. Phosphotyrosine antibodies also precipitated a 36,000 M(r) phosphorylated protein from growth factor-activated cells, suggesting that Gi beta may be phosphorylated on tyrosine. Therefore, Gi beta phosphorylation appears to represent a late event after activation of cells by tyrosine kinase growth factor receptors. We are currently examining the role of this event in signal transduction, particularly in relation to control of nuclear responses.

3T3 Cells↗

PubMed1993

Age-related changes in tyrosine hydroxylase and choline acetyltransferase in sympathetic ganglia of a rat strain with reduced sympathetic neuron numbers.

In Wistar rats, a subpopulation of sympathetic ganglionic neurons dies during ageing, but in the GH strain, these same neurons die during the period of perinatal maturation. We have compared tyrosine hydroxylase (TH) and choline acetyltransferase (ChAT) in superior cervical ganglia of GH and control rats at different ages. Ganglionic TH rose to near adult levels between postnatal weeks 1 and 2. No significant differences in TH values were seen between GH and control ganglia at any age, indicating that reduced neuron numbers are compensated for by increased cellular activity. Ganglionic ChAT rose initially in parallel with TH and then more slowly over postnatal weeks 3-4, reaching adult levels that were about 20% lower in GH than in normal ganglia. During ageing, TH remained constant but ChAT continued to rise slowly in GH ganglia, whereas ChAT in normal ganglia fell by about 10%. Both the strain difference in ChAT during development and the fall in ChAT during ageing in normal animals parallel the differences in ganglion cell numbers seen under these circumstances.

Aging↗

PubMed1993

Involvement of pertussis toxin-sensitive and -insensitive mechanisms in alpha-adrenoceptor modulation of noradrenaline release from rat sympathetic neurones in tissue culture.

1. Sympathetic neurones derived from superior cervical ganglia of neonatal rats and maintained in tissue culture were used to investigate the modulation of neurotransmitter release by presynaptic receptors. Three week old cultures of neurones were loaded with [3H]-noradrenaline to label endogenous neurotransmitter stores. Release of noradrenaline was evoked by depolarization with raised extracellular K+ in the presence of desipramine and corticosterone to prevent uptake of released catecholamine. 2. Potassium (55 mmol l-1) depolarization for 30 s caused more than a four fold increase in 3H overflow from basal levels but this increase was reduced by up to 40% in the presence of exogenous noradrenaline (1 mumol l-1). The inhibition by noradrenaline of depolarization-evoked overflow was blocked by the alpha 1/alpha 2-adrenoceptor antagonist, phentolamine. Phentolamine alone did not increase K(+)-evoked 3H overflow. 3. The alpha 2-adrenoceptor antagonist, yohimbine, produced a concentration-dependent block of the inhibition by noradrenaline of K(+)-evoked overflow, while the alpha 1-adrenoceptor antagonist, prazosin, was without effect at concentrations up to 0.1 mumol l-1. 4. The beta-adrenoceptor antagonist, propranolol, neither reduced K(+)-evoked overflow nor increased the degree of inhibition caused by the addition of 1 mumol l-1 noradrenaline. 5. The alpha 2-adrenoceptor agonist, clonidine (1 mumol l-1) was less effective than noradrenaline at inhibiting K(+)-evoked overflow, while the alpha 1-adrenoceptor agonist, phenylephrine (1 mumol l-1) had no significant effect. 6. The L-channel calcium blocker, nicardipine (1 mumol l-1) significantly inhibited 3H overflow evoked by K+. In the presence of L-channel block, however, noradrenaline still inhibited residual evoked overflow.7. In the presence or absence of nicardipine, pertussis toxin pretreatment (1 nmol 1-1) reduced, but did not prevent, the effect of noradrenaline (1 micromol 1-1). Pertussis toxin alone caused a significant enhancement of K+-evoked 3H overflow.8. The data indicate that on postganglionic neurones of cultured rat sympathetic ganglia there are alpha 2-adrenoceptors that modulate neurotransmitter release, but no functional beta-adrenoceptors that mediate an enhancement of transmitter release. The data suggest further that in this preparation the mechanism of alpha2-adrenoceptor modulation may involve pertussis toxin sensitive and insensitive G-proteins and effects on calcium channels other than L-type.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed1992

Neonatal nerve growth factor treatment alters the preganglionic innervation pattern of rat superior cervical ganglion.

We treated rat pups with nerve growth factor (10 micrograms/animal/day s.c.) over postnatal days 1-7. Subsequent adult neuron numbers and tyrosine hydroxylase content in superior cervical ganglion were normal, but preganglionic inputs, as gauged from ganglionic choline acetyltransferase, were reduced. In parallel, intraganglionic axon terminals containing calcitonin gene-related peptide, but not those containing substance P, were increased in number. We postulate that neonatal nerve growth factor stimulates sprouting of ingrowing axons that have entered the ganglion soon after birth and that this represses subsequent establishment of cholinergic preganglionic synapses.

Aging↗

PubMed1992

Ability of different chemically modified heparins to potentiate the biological activity of heparin-binding growth factor 1: lack of correlation with growth factor binding.

A range of chemically modified heparins was examined for their ability to bind heparin-binding growth factor 1 (HBGF-1; acidic fibroblast growth factor) and potentiate the in vitro mitogenic and neurotrophic activity of HBGF-1. It was found that carboxyl-reduced heparin bound HBGF-1 as effectively as the native heparin molecule. Totally desulfated heparin and N-desulfated heparin lack HBGF-1-binding capacity, and substitution of the exposed amino group with acetyl or acetoacetyl groups only partially restored binding capacity, indicating that N-sulfates only play a limited role in growth factor binding. However, the failure of totally desulfated, N-resulfated heparin to interact with HBGF-1 demonstrated that N-sulfates alone are insufficient and ester sulfates are absolutely essential for HBGF-1 binding. In contrast, the ability of the modified heparins to potentiate the mitogenic activity of HBGF-1 correlated only to a limited extent with their affinity for HBGF-1. Thus, the carboxyl-reduced molecule which displayed similar affinity for HBGF-1 as native heparin was consistently less potent in augmenting mitogenesis. Similarly, the N-acetylated and the N-acetoacetylated species, which had much lower affinity for HBGF-1 than the carboxyl-reduced molecule, conferred similar biological activity to HBGF-1 whereas N-desulfated heparin, which was unable to bind growth factor, potentiated the mitogenic activity of HBGF-1 for both 3T3 and HUVE cells. In contrast, the neurotrophic activity of HBGF-1 was potentiated by modified heparin species which failed to bind HBGF-1 and were without activity in the mitogenic assays.(ABSTRACT TRUNCATED AT 250 WORDS)

3T3 Cells↗

PubMed1992

Retrograde factors in peripheral nerves.

The relationship between the neuron and its target is explored and the possible mechanisms for achieving correct connections are analysed. The most plausible mechanism is the presence of a retrograde intra-axonal message from the target to the neuronal cell body. The molecular form of the message and the mechanisms to achieve this signal transduction are discussed and it is proposed that there are two types of neurotrophic factors. One has a short-acting second messenger, itself incapable of surviving for the time required for transport to the cell body and thus requiring the transport of the message-generating complex to the cell body. The other has a long-lasting second messenger complex which is well able to survive the transport to the cell body so that there is no need for the transport of the neurotrophic factor itself. Thus all neurotrophic factors do not themselves require retrograde axonal transport and such non-transportable factors may generate intricate messages due to associations of signal transduction molecules via binding sites such as phosphorylated tyrosines and the src homology domain 2.

Animals↗

PubMed1992

Binding and retrograde transport of leukemia inhibitory factor by the sensory nervous system.

Leukemia inhibitory factor (LIF), a peptide growth factor with multiple activities, has recently been shown to support the generation and survival of sensory neurons in cultures of mouse neural crest and dorsal root ganglia (DRG). We have conducted binding experiments with 125I-LIF on cultures of DRG to determine the receptor distribution for LIF on these cells and found that at least 60% of the sensory neurons in the cultures bound 125I-LIF, all of which could be eliminated by the addition of unlabeled LIF. The other cells in the culture, which morphologically appeared to be Schwann cells, did not bind appreciable quantities of 125I-LIF. In order to investigate whether LIF is retrogradely transported to sensory neurons in vivo, 125I-LIF was injected into the footpads and gastrocnemius muscles of newborn and adult mice, following sciatic nerve ligation. Radioactivity accumulated in the distal portion of the sciatic nerve, indicating retrograde transport of LIF. Subsequent experiments on mice with unligated sciatic nerves showed that 125I-LIF is specifically transported into the sensory neurons of the DRG. There was no apparent transport of 125I-LIF into motor neurons in the spinal cord. These experiments demonstrate that LIF can specifically bind to and be transported by sensory neurons and further support the idea that LIF acts as a target-derived neurotrophic factor, analogous to NGF.

Animals↗

PubMed1991

Retrograde axonal transport of the GTP-binding protein Gi alpha: a potential neurotrophic intra-axonal messenger.

When a neuronal target is to provide information to the nucleus of the neurone innervating it, it faces the problem of getting its message up the long length of axon separating the cell body from the site of receptor activation at the terminal. The retrograde axonal transport of the neurotrophic molecule, nerve growth factor (NGF), provided one possible mechanism for this information transfer in the sympathetic nervous system. However, some neurotrophic molecules are not retrogradely transported, indicating the message is carried back by a different mechanism. In this paper, we examined such a novel mechanism mediated by the retrograde axonal transport of the alpha subunit of the second messenger protein, Gi. It is proposed that some non-transported neurotrophic molecules may produce a stable second messenger that is itself transported to the nucleus to convey the target derived information for survival.

Animals↗

PubMed1991

Class 1 heparin binding growth factor promotes the differentiation but not the survival of ciliary neurones in vivo.

Molecules isolated from target tissues of various neuronal populations have been shown to enable the survival of those innervating neurones. A molecule derived from bovine heart which can support the survival of parasympathetic neurones of the chick embryo ciliary ganglion in vitro has been sequenced and identified as a member of the class 1 heparin binding growth factors (HBGF-1). When injected into developing chick embryos during the period of naturally occurring cell death in the ciliary ganglion, HBGF-1 failed to rescue those neurones which normally die. There was, however, a premature increase in the activity of choline acetyltransferase within the ganglion and a shift to the right in the size distribution of the neurones. We conclude that HBGF-1 may promote the differentiation of some subpopulation of neurones of the ciliary ganglion of the chick embryo but does not act in vivo as a survival molecule.

Amino Acid Sequence↗

PubMed1991

Retinoic acid potentiates the neurotrophic but not the mitogenic action of the class 1 heparin-binding growth factor (HBGF-1).

Retinoic acid promotes the neuronal survival properties of the class 1 heparin-binding growth factor (HBGF-1) on 8-day-old chick ciliary and sensory neurones. It has little or no effect on the survival promoting properties of class 2 heparin-binding growth factor (HBGF-2) on these cell types. Nerve growth factor (NGF) promoted survival of sympathetic and sensory neurones, and was unaffected at any concentration of retinoic acid. The mitogenic effect of both HBGF-1 and HBGF-2 was unaltered at any concentration of retinoic acid. It is suggested that naturally occurring gradients of retinoic acid, for example, as occur in the developing limb bud, could have a role in the development of normal innervation patterns through selective interaction with neurotrophic molecules.

Animals↗

PubMed1991

Co-activation of insulin-like growth factor-I receptors and protein kinase C results in parasympathetic neuronal survival.

We have studied the interaction between several growth factors to promote parasympathetic neuronal survival. Neither insulin nor insulin-like growth factor-I (IGF-I) had any effect on the survival of embryonic day 8 chick ciliary neurons in culture. Similarly, the protein kinase C activator phorbol dibutyrate (PdBu) had only a minor survival-promoting activity. In combination with PdBu, however, IGF-I or insulin, at concentrations sufficient to act through the IGF-I receptor, were highly synergistic. In a similar fashion, acidic fibroblast growth factor (aFGF)-induced neuronal survival was greatly enhanced by PdBu, as well as by insulin or IGF-I. When added alone, aFGF-induced cell survival required the presence of 1% serum. However, addition of aFGF, IGF-I, or insulin with PdBu under serum-free conditions replaced the serum requirement. That is, these agonist combinations could apparently induce the second messenger requirement for ciliary neuronal survival. Therefore, IGF-I must now be included in the list of candidate molecules responsible for directing parasympathetic nerve formation. The synergy between agonists observed in these experiments highlights the possibility that combinations of growth factors, rather than sole molecules, may dictate parasympathetic nervous system development in vivo.

Animals↗

PubMed1991

Intraspinal release of substance P and calcitonin gene-related peptide during opiate dependence and withdrawal.

The antibody microprobe technique was used to study the release of immunoreactive substance P and immunoreactive calcitonin gene-related peptide within the lower lumbar spinal cord of anaesthetized spinalized cats pretreated twice daily for 3.5 days with increasing doses of morphine hydrochloride (2-20 mg/kg, i.p.). Both peptides were released in the region of the substantia gelatinosa during noxious cutaneous thermal stimulation or high-intensity electrical stimulation of a hind limb nerve. Intravenous administration of naloxone increased the nociceptive excitation of lumbar dorsal horn neurons, but did not alter the evoked release of immunoreactive substance P or immunoreactive calcitonin gene-related peptide in the superficial gray matter dorsal to these neurons. In addition, the release of both peptides was not significantly different to that detected under similar experimental conditions in opioid-naive cats. The results suggest that alterations in neuropeptide release from the central terminals of nociceptive primary afferent neurons do not occur during states of opiate dependence and withdrawal, and thus do not contribute to the characteristic signs of these phenomena in dependent animals.

Animals↗

PubMed1991

Lack of retrograde axonal transport of the heparin-binding growth factors by chick ciliary neurones.

In view of the likelihood that the heparin-binding growth factors of fibroblast growth factors are neurotrophic for the neurones of the chick ciliary ganglion a study has been made of the retrograde axonal transport of the acidic and basic fibroblast growth factors by these neurones. No high capacity retrograde axonal transport of these molecules was seen. The amount of transport was equivalent to the low level seen with many proteins such as horse radish peroxidase or bovine serum albumin rather than the convincing transport seen for nerve growth factor in the sympathetic system. The iodinated proteins retained their ability to bind to neuronal receptors. Thus, if the fibroblast growth factors are neurotrophic in the ciliary ganglion, they may exert their action by mechanisms other than the retrograde axonal transport of the factor itself.

Animals↗

PubMed1990

Pertussis toxin inhibits EGF-, phorbol ester- and insulin-stimulated DNA synthesis in BALB/c3T3 cells: evidence for post-receptor activation of Gi alpha.

The contribution of the GTP-binding protein, Gi, to EGF, phorbol dibutyrate (PdBu)-, and insulin-stimulated DNA synthesis was examined in BALB/c3T3 cells. Pertussis toxin inhibited DNA synthesis by each agonist, particularly at suboptimal agonist concentrations, but the inhibition could be partially overcome with higher agonist concentrations and combinations of these agonists. This suggested that (1) some, but not all, of the mitogenic signals for all three agonists were transduced by Gi (2) Gi may be activated by post-receptor mechanisms involving protein kinase C. Gi alpha-specific antibodies and ADP-ribosylation by pertussis toxin using 32P-NAD each labelled a single protein band, representing one or more species of Gi alpha. Pertussis toxin treatment increased the synthesis of Gi alpha. These results are discussed in relation to possible direct effects of Gi alpha on nuclear control during division.

Animals↗

PubMed1990

Morphine and substance P release in the spinal cord.

In anaesthetised cats, antibody microprobes were used to measure the release of immunoreactive substance P (irSP) in the lumbar dorsal horn during noxious cutaneous stimulation or high-intensity electrical stimulation of a hind limb nerve. The major region of irSP release detected was centered on the substantia gelatinosa, with lesser release at the dorsal cord surface. Release at these sites was unchanged by systemic administration of morphine, or of morphine followed by naloxone. During superfusion of the dorsal cord surface with high concentrations of morphine, irSP release in the substantia gelatinosa region was slightly reduced and surface release was not observed, effects not reversed by systemic naloxone administration. The results suggest that the analgesic action of morphine does not involve reduced release of SP in the spinal cord.

Animals↗

PubMed1989

Somatostatin: evidence for a role in thermal nociception.

In barbiturate-anaesthetized spinalized cats, antibody microprobes were used to investigate the release of immunoreactive somatostatin (irSS) in the lumbar dorsal horn in response to cutaneous stimuli. In the absence of applied stimulation, a significant basal release of irSS was present in the region of the substantia gelatinosa. Such release was not increased by innocuous or noxious cutaneous mechanical stimuli nor by innocuous thermal stimuli, but was increased by noxious thermal stimulation. The magnitude of this noxious heat-evoked release was estimated by comparing in vivo microprobes with those used to detect known concentrations of somatostatin in vitro. Pairs of microprobes were used to detect simultaneous release of both irSS and immunoreactive substance P in the substantia gelatinosa. The results support the putative role of somatostatin in the spinal transmission of thermal nociceptive information.

Animals↗

PubMed1988

A monoclonal antibody to a parasympathetic neurotrophic factor causes immunoparasympathectomy in mice.

A monoclonal antibody capable of blocking the biological activity of the ciliary neurotrophic factor purified from bovine cardiac muscle has been produced. This antibody, when administered perinatally to mice, causes a failure of the normal development of the parasympathetic innervation of the iris as determined by assay for the activity of the cholinergic marker enzyme choline acetyltransferase. The same treatment has no effect on the adrenergic neuronal marker, tyrosine hydroxylase. This immunoparasympathectomy suggests that the ciliary neurotrophic factor has an essential role in regulating the development of the mammalian parasympathetic nervous system.

Age Factors↗