Search PubMed⌕ Search

Biomedical subjects

M Lyon

Publications and source records attributed to M Lyon.

At least 37 records · Page 2Linked to original sources
PubMed1999

Highly sensitive sequencing of the sulfated domains of heparan sulfate.

The heparan sulfates (HS) are hypervariable linear polysaccharides that act as membrane co-receptors for growth factors, chemokines, and extracellular matrix proteins. In most instances, the molecular basis of protein recognition by HS is poorly understood. We have sequenced 75% of the sulfated domains (S-domains) of fibroblast HS, including all of the major ones. This analysis revealed tight coupling of N- and 2-O-sulfation and a low frequency but precise positioning of 6-O-sulfates, which are required functional groups for HS-mediated activation of the fibroblast growth factors. S-domain sequencing was conducted using a novel and highly sensitive method based on a new way of reading the sequence from high performance liquid chromatography separation profiles of metabolically labeled HS-saccharides following specific chemical and enzymatic scission. The implications of the patterns seen in the sulfated domains for better understanding of the synthesis and function of HS are discussed.

3T3 Cells↗
PubMed1999

Differential regulation of hepatocyte growth factor/scatter factor by cell surface proteoglycans and free glycosaminoglycan chains.

Hepatocyte growth factor interacts with both heparan and dermatan sulphates, in addition to its specific signalling receptor, Met. However, the extent of glycosaminoglycan involvement in its biological activity remains uncertain. We have investigated the effects of exogenous glycosaminoglycan addition upon hepatocyte growth factor-stimulated motility of Madin-Darby canine kidney cells. Exogenous heparan/dermatan sulphate chains behave similarly as either potentiators or inhibitors of cell motility (depending upon the assay). Specific heparan sulphate oligosaccharides, of octasaccharide or larger, elicit similar effects, though with reduced potency. Additionally we have investigated the motility of cells made completely deficient in functional proteoglycans by metabolic inhibition of glycosaminoglycan sulphation, using chlorate. Such cells are completely unresponsive to hepatocyte growth factor, both in terms of downstream phosphorylation of mitogen-activated protein kinase and actual cell motility, though they do remain responsive to phorbol ester. Interestingly, although cell responsiveness to hepatocyte growth factor is not restored by exogenous heparan/dermatan sulphate chains, it is by an immobilised heparan sulphate proteoglycan substratum. These findings suggest that hepatocyte growth factor activity is not only critically dependent upon the presence of glycosaminoglycan, but specifically requires an intact proteoglycan structure located in close apposition to cell surface Met.

Absorption↗
PubMed1998

Hepatocyte growth factor/scatter factor binds with high affinity to dermatan sulfate.

We have demonstrated by affinity chromatography that hepatocyte growth factor/scatter factor (HGF/SF) binds strongly to dermatan sulfate (DS), with a similar ionic strength dependence to that previously seen with heparan sulfate (HS). Analysis of binding kinetics on a biosensor yields an equilibrium dissociation constant, KD, of 19.7 nM. This corresponds to a 10-100-fold weaker interaction than that with HS, primarily due to a faster dissociation rate of the complex. The smallest DS oligosaccharide with significant affinity for HGF/SF by affinity chromatography appears to be an octasaccharide. A sequence comprising unsulfated iduronate residues in combination with 4-O-sulfated N-acetylgalactosamine is sufficient for high affinity binding. The presence of 2-O-sulfation on the iduronate residues does not appear to be inhibitory. These observations concur with our previous suggestions, from analyses of HS binding (Lyon, M., Deakin, J. A., Mizuno, K., Nakamura, T., and Gallagher, J.T. (1994) J. Biol. Chem. 269, 11216-11223), that N-sulfation of hexosamines and 2-O-sulfation of iduronates are not absolute requirements for glycosaminoglycan binding to HGF/SF. This is the first described example of a high affinity interaction between a growth factor and DS, and is likely to have significant implications for the biological activity of this paracrine-acting factor.

3T3 Cells↗
PubMed1998

Heparan sulfate undergoes specific structural changes during the progression from human colon adenoma to carcinoma in vitro.

We report a detailed analysis of heparan sulfate (HS) structure using a model of human colon carcinogenesis. Metabolically radiolabeled HS was isolated from adenoma and carcinoma cells. The chain length of HS was the same in both cell populations (Mr 20,000; 45-50 disaccharides), and the chains contained on average of two sulfated domains (S domains), identified by heparinase I scission. This enzyme produced fragments of approximate size 7 kDa, suggesting that the S domains were evenly spaced in the intact HS chain. The degree of polymer sulfation and the patterns of sulfation were strikingly different between the two HS species. When compared with adenoma HS, the iduronic acid 2-O-sulfate content of the carcinoma-derived material was reduced by 33%, and the overall level of N-sulfation was reduced by 20%. However, the level of 6-O-sulfation was increased by 24%, and this was almost entirely attributable to an enhanced level of N-sulfated glucosamine 6-O-sulfate, a species whose data implied was mainly located in the mixed sequences of alternating N-sulfated and N-acetylated disaccharides. The results indicate that in the transition to malignancy in human colon adenoma cells, the overall molecular organization of HS is preserved, but there are distinct modifications in both the S domains and their flanking mixed domains that may contribute to the aberrant behavior of the cancer cell.

Adenoma↗
PubMed1997

Binding of perlecan to transthyretin in vitro.

Transthyretin is one of two specific proteins involved in the transport of thyroid hormones in plasma; it possesses two binding sites for serum retinol-binding protein. In the present study we demonstrate that transthyretin also interacts in vitro with [35S]sulphate-labelled material from the medium of HepG2 cells. By using the same strategy as for purifying serum retinol-binding protein, [35S]sulphate-labelled medium was specifically eluted from a transthyretin-affinity column. Ion-exchange chromatography showed that the material was highly polyanionic, and its size and alkali susceptibility suggested that it was a proteoglycan. Structural analyses with chondroitinase ABC lyase and nitrous acid revealed that approx. 20% was chondroitin sulphate and 80% heparan sulphate. Immunoprecipitation showed that the [35S]sulphate-labelled material contained perlecan. Further analysis by binding studies revealed specific and saturable binding of 125I-transthyretin to perlecan-enriched Matrigel. Because inhibition of sulphation by treating HepG2 cells with sodium chlorate increased the affinity of the perlecan for transthyretin, and [3H]heparin was not retained by the transthyretin affinity column, the binding is probably mediated by the core protein and is not a protein-glycosaminoglycan interaction. Because perlecan is released from transthyretin in water, the binding might be due to hydrophobic interactions.

Heparan Sulfate Proteoglycans↗
PubMed1997

The interaction of the transforming growth factor-betas with heparin/heparan sulfate is isoform-specific.

We have undertaken a comparative study of the interaction of the three mammalian transforming growth factor-betas (TGF-beta) with heparin and heparan sulfate. TGF-beta1 and -beta2, but not -beta3, bind to heparin and the highly sulfated liver heparan sulfate. These polysaccharides potentiate the biological activity of TGF-beta1 (but not the other isoforms), whereas a low sulfated mucosal heparan sulfate fails to do so. Potentiation is due to antagonism of the binding and inactivation of TGF-beta1 by alpha2-macroglobulin, rather than by modulation of growth factor-receptor interactions. TGF-beta2.alpha2-macroglobulin complexes are more refractory to heparin/heparan sulfate, and those involving TGF-beta3 cannot be affected. Comparison of the amino acid sequences of the TGF-beta isoforms strongly implicates the basic amino acid residue at position 26 of each monomer as being a vital binding determinant. A model is proposed in which polysaccharide binding occurs at two distinct sites on the TGF-beta dimer. Interaction with heparin and liver heparan sulfate may be most effective because of the ability of the dimer to co-operatively engage two specific sulfated binding sequences, separated by a distance of approximately seven disaccharides, within the same chain.

Amino Acid Sequence↗
PubMed1997

Presence of a unique parainfluenza virus 3 strain identified by RT-PCR in visna-maedi virus infected sheep.

The presence in farm sheep of a paramyxovirus closely related to parainfluenza virus type 3 (Pi3) from humans or cattle was confirmed using RT-PCR on RNA samples from lung cells from slaughtered animals. Sequencing and restriction enzyme patterns of the amplified fragment of the F gene confirms the distinctness of the isolate, and suitable PCR primers allow specific detection of the ovine virus. A study of the incidence of ovine Pi3 in samples from sheep with or without distinctive histopathological signs of maedi shows that it is uncommon in aged sheep with overt lentiviral disease, but it occurs at moderate frequency in lambs and may, in the presence of visna-maedi virus, contribute to early lesion formation.

Abattoirs↗
PubMed1997

Testing the hypothesis of the multidimensional model of anorexia nervosa in adolescents.

This study statistically tested six hypothesized risk factors of the model for anorexia nervosa. Forty-three adolescents with anorexia nervosa and 85 controls were administered the EAT, EDI, and FES. In addition, 43 parents of anorexics and 85 parents of controls completed the Family History Data Sheet, the FES, and the Perfect Child Questionnaire. Three of six hypothesized risk factors were confirmed: family history of depression, feelings of ineffectiveness, and poor interceptive awareness. Log-linear analysis indicated that the hierarchical model that best fit the data had significant two-way interactions with anorexia nervosa, G2 (11, N = 128) = 65.87, p < .001. In addition, alcohol and drug abuse or dependence figured prominently in the family history of patients with anorexia nervosa. The multidimensional model for anorexia nervosa holds up as an exploratory model of this condition in the adolescent age group.

Adolescent↗
PubMed1996

Morphologic changes in contralateral superior vestibulo-ocular neurons following labyrinthectomy in the cat.

Ultrastructural changes were measured in 22 contralateral superior vestibulo-ocular neurons (SVONs) from four cats painlessly sacrificed at 8 weeks and 25 contralateral SVONs from four cats sacrificed at 1 year following unilateral labyrinthectomy. The SVONs at 8 weeks showed a 43% decrease in somal size, a 34% loss in rough endoplasmic reticulum (RER), a 48% loss of ribosomes, and a 47% decrease in the number of synaptic profiles (SPs) contacting the soma. At 1 year the SVONs had a 31% decrease in size, a 43% decrease in RER, a 50% loss of ribosomes, and a 71% decrease in SPs. Synaptic vesicles (SVs) in both groups of SVONs showed no change in size or shape compared to control SVs. These findings resemble the contralateral SVON changes that occur following excision of the vestibular ganglion.

Animals↗
PubMed1995

Ovine aortic smooth muscle cells allow the replication of visna-maedi virus in vitro.

Visna-maedi virus induces in sheep an interstitial lung disease characterised by an accumulation of smooth muscle cells (SMC) or myomatosis. Infection by HIV-1 has been recently associated with disorders of the vessel-derived cells: primary pulmonary hypertension, coronary artery disease and smooth muscle tumors in humans. We hypothesized that, besides their regular targets (i.e. macrophages and lymphocytes), lentiviruses could infect smooth muscle cells. Smooth muscle cell cultures derived from ovine aorta were infected with visna-maedi virus strain K1514. The cultured cells were smooth muscle cells as demonstrated by their antigenic expression of alpha-actin and vimentin. The lentiviral infection of the smooth muscle cells was demonstrated by a typical cytopathic effect (syncytia), the expression of virus specific antigens, and the presence of genomic RNA detected by Northern blot analysis and RT PCR. The detection of a reverse transcriptase activity, the presence of viral RNA in supernatants of infected smooth muscle cells detected by RT PCR and their ability to infect ovine permissive fibroblasts demonstrated a productive infection. The ability of smooth muscle cells to be infected by lentiviruses may participate in the pathogenesis of the tissue damage associated with the lentiviruses such as myomatosis in sheep and vascular disease in humans.

Animals↗
PubMed1995

Sulphated proteoglycan is required for collecting duct growth and branching but not nephron formation during kidney development.

Kidney epithelia have separate origins; collecting ducts develop by ureteric bud growth and arborisation, nephrons by induced mesenchyme-epithelium transition. Both express sulphated glycosaminoglycans (GAGs) which are strikingly upregulated during nephron differentiation. However, sodium chlorate, an inhibitor of GAG sulphation, and the GAG-degrading enzymes heparitinase plus chondroitinase, did not prevent nephron development. In contrast, ureteric bud growth and branching were reversibly inhibited by the above reagents, the inhibition correlating quantitatively with sulphated GAG deprivation caused by a range of chlorate concentrations. Growth and branching could be independently restored during GAG deprivation by hepatocyte growth factor and phorbol-12-myristate acetate (PMA) respectively. Together these signalling effectors stimulated both branch initiation and growth. Thus growth and morphogenesis of ureteric bud involve distinct signalling pathways both regulated by GAGs.

Animals↗
PubMed1994

Violence research.

In the article "Carbon pools and flux of global forest ecosystems" by R. K. Dixon et al. (14 Jan., p. 185), the first sentence in column three on page 187 under the heading "Carbon sources and sinks" should have read, "The net C flux to the atmosphere from the world's forests caused by changes in land use, forest status, and forest C cycling processes was approximately -1.3 to -0.5 Pg year(-1), with a midpoint of -0.9 Pg year(-1) (Table 3)."

Humans↗
PubMed1994

Liver heparan sulfate structure. A novel molecular design.

The structure of rat liver heparan sulfate (HS) has been investigated using a combination of (a) chain scission with specific reagents, (b) disaccharide compositional analysis, and (c) end-referenced sequence analysis of the proximal, protein-linked region of the chain. This study reveals that the liver synthesizes a highly sulfated HS species (1.34 sulfates/disaccharide), particularly high in N-sulfation (60%) and 2-O-sulfate content (36%). Approximately half of the latter is found in trisulfated disaccharides, i.e. IdceA(2-OSO3) alpha 1-4GlcNSO3 (6-OSO3). End-referencing methodology established the existence of an extended, unmodified heparan (GlcUA beta 1-4GlcNAc) sequence, 8-11 disaccharides in length, attached to the linkage tetrasaccharide, similar to that found in a number of other HS species. Directly following this is a mixed HexUA1-4GlcNR(6-OSO3) (where GlcNR represents alpha-D-glucosamine with an unspecified N-substituent)-containing sequence of variable length, culminating in the appearance of the first IdceA(2-OSO3) residue approximately 20 disaccharides from the linkage region, i.e. approximately 40% along the length of the chain. The distal 60% of the polysaccharide is highly sulfated (approximately 2 sulfates/disaccharide) and mainly comprises three heparin-like domains, highly enriched in IdceA(2-OSO3) residues. Overall, liver HS qualifies as an extreme member of the HS family, with a considerable proportion of heparin-like structure asymmetrically concentrated to the distal part of the chain.

Animals↗
PubMed1994

Interaction of hepatocyte growth factor with heparan sulfate. Elucidation of the major heparan sulfate structural determinants.

We have demonstrated by affinity chromatography that hepatocyte growth factor (HGF) binds strongly to heparan sulfate (HS). This substantiates previous suggestions that cell-surface heparan sulfate proteoglycans constitute the so-called low affinity cellular binding sites for HGF. Using a recombinant human HGF affinity column, we have analyzed the effects of various specific chemical and enzymatic modifications/depolymerizations of HS on its affinity in order to elucidate the polysaccharide structural determinants. Interaction is shown to be only slightly affected by digestion with heparinase I or III or by replacement of N-sulfates with N-acetyl groups. This suggests a specific role for sulfated domains containing nonsulfated IdceA residues, with only a small contribution from N-sulfates and IdceA(2-OSO3) residues. In addition, disaccharide analyses of various HGF-binding oligosaccharides indicate that affinity is more closely associated with 6-O-sulfation of GlcNSO3 residues than with sulfation at any other position. Although interaction can be demonstrated with heparinase III-resistant oligosaccharides as small as hexasaccharides, the highest affinity was found with oligosaccharides containing a minimum of 10-12 monosaccharides. The structural specificity of the HGF-HS interaction is thus shown to be radically different from that previously described for the basic fibroblast growth factor-HS interaction.

Animals↗
PubMed1994

Investigations of fetal development models for prenatal drug exposure and schizophrenia. Prenatal d-amphetamine effects upon early and late juvenile behavior in the rat.

Recent evidence suggests that mid-pregnancy is a critical period for production of fetal abnormalities that cause behavioral and neuropathological changes in adult offspring. The present experiments provide an animal model of these effects by treating pregnant Sprague-Dawley rats during gestational days 11-14 with d-amphetamine (AM). Offspring were tested for neurological signs, foraging activity, reversal learning, and sensitivity to amphetamine challenge. In the Early Juvenile period, postnatal days (PND) 20-30, female AM offspring initially showed reductions in rearing, holepoking, and midfield activity. On later trials, and as young adults, AM females showed signs of locomotor hyperactivity despite continued poor foraging efficiency, and were also more sensitive to a 1.0 mg/kg d-amphetamine challenge. AM males showed initially slower and more perseverative responding than controls, but then developed excessive response switching. These changes continued during tests for Retention, Reversal, and Extinction in the Late Juvenile/Early Adult stage (PND 50-90), when both AM-exposed sexes showed increased eating time, significantly more perseverative lateral turning preference (right or left), and slower reversal learning than controls. Behavioral data were consistent with aberrations in thalamo-frontal and mesolimbic/nigrostriatal projection systems that have been reported in AM animals and which are also affected by maternal drug abuse and schizophrenia.

Animals↗
PubMed1994

The importance of temporal structure in analyzing schizophrenic behavior: some theoretical and diagnostic implications.

THEME, a new method for analyzing the temporal structure of responding on a two-choice task, is described. This method reveals the time relationships (temporal patterns) between all response events, even those not occurring in direct sequence. It selects those temporal patterns that are significantly different (p < 0.0001) from the patterns found in a random Poisson distribution of the same events. The method was applied to data from Lyon et al. (1986) in which n = 17 outpatient schizophrenics were compared with n = 17 age-, sex-, and education-matched normal control subjects. Results revealed that responding of schizophrenic outpatients, in comparison to control subjects, had a larger number of significant temporal patterns, more different types of patterns, and more branching (connectivity) of patterns at a higher level. The latter indicates a higher degree of internal structure. These results are not predicted by standard (DSM-III-R) diagnostic procedures, but are in agreement with studies of two-choice behavior in schizophrenia based on the Lyon-Robbins (1975) theory of behavioral change, which has possible relationship to dopamine/acetylcholine imbalance in the brain. Diagnostic procedures in schizophrenia might benefit from tests oriented toward these findings, which are also consistent with Bleuler's original descriptions of schizophrenic symptomatology.

Adult↗