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Biomedical subjects

Julie H Campbell

Publications and source records attributed to Julie H Campbell.

At least 19 recordsLinked to original sources
PubMed2006

Mechanics of cellular adhesion to artificial artery templates.

We are using polymer templates to grow artificial artery grafts in vivo for the replacement of diseased blood vessels. We have previously shown that adhesion of macrophages to the template starts the graft formation. We present a study of the mechanics of macrophage adhesion to these templates on a single cell and single bond level with optical tweezers. For whole cells, in vitro cell adhesion densities decreased significantly from polymer templates polyethylene to silicone to Tygon (167, 135, and 65 cells/mm(2)). These cell densities were correlated with the graft formation success rate (50%, 25%, and 0%). Single-bond rupture forces at a loading rate of 450 pN/s were quantified by adhesion of trapped 2-microm spheres to macrophages. Rupture force distributions were dominated by nonspecific adhesion (forces <40 pN). On polystyrene, preadsorption of fibronectin or presence of serum proteins in the cell medium significantly enhanced adhesion strength from a mean rupture force of 20 pN to 28 pN or 33 pN, respectively. The enhancement of adhesion by fibronectin and serum is additive (mean rupture force of 43 pN). The fraction of specific binding forces in the presence of serum was similar for polystyrene and polymethyl-methacrylate, but specific binding forces were not observed for silica. Again, we found correlation to in vivo experiments, where the density of adherent cells is higher on polystyrene than on silica templates, and can be further enhanced by fibronectin adsorption. These findings show that in vitro adhesion testing can be used for template optimization and to substitute for in-vivo experiments.

Animals↗
PubMed2005

Cholestanol: a serum marker to guide LDL cholesterol-lowering therapy.

Statins have been the mainstay of lipid-lowering therapy since their introduction. However, as lower LDL cholesterol targets are sought, adjunct therapies are becoming increasingly important. Few patients reach new targets with statin monotherapy. We propose that the cholestanol:cholesterol ratio can be used to guide lipid-lowering therapy and result in greater numbers of patients reaching target LDL cholesterol. By determining whether a patient is mainly a synthesizer or absorber of cholesterol, customized regimens can be used and are expected to improve patient outcomes and minimize costs of treatment.

Anticholesteremic Agents↗
PubMed2005

Establishment of metanephros transplantation in mice highlights contributions by both nephrectomy and pregnancy to developmental progression.

BACKGROUND: It has been demonstrated that embryonic kidneys (metanephroi) xenotransplanted into the omentum of adult recipients continue to develop and display immune protection due to their more naïve immune presentation. To date, this has been achieved using rat, pig and human metanephroi, with unilateral nephrectomy (UNX) of recipient rats a requisite of renal development. The aim of this study was to adapt this approach for use in mice and examine the parameters affecting successful onward development in this species. METHODS: Metanephroi at embryonic age (E) 13.5 were transplanted either onto the body wall, abdominal fat pads or omentum of recipient isogenic C57/Bl6 mice using either sutures or polyglycolic acid mesh. Having established greatest success with polyglycolic acid mesh on the body wall, E12.5 and 15.5 days metanephroi from C57/Bl6 mice were then transplanted onto the body wall of control (non-pregnant non-UNX), UNX or 12.5 days post-coitum pregnant isogenic recipients. After 7 days, implanted tissue was harvested and examined using histology and immunohistochemistry for markers of renal maturation. The mean number of S-shaped bodies and glomeruli per section were recorded and statistically analysed for significant differences between all recipient groups and untransplanted metanephroi. The degree of development was scored qualitatively. RESULTS: Transplanted E12.5 metanephroi developed S-shaped bodies and glomeruli in all recipient groups, although there were statistically higher numbers of S-shaped bodies in UNX (n = 2) and pregnant recipients (n = 9) than in control recipients (n = 4). Continued development, as indicated by mature vascularized glomeruli, was only observed in those E15.5 metanephroi transplanted into pregnant recipients (n = 11) with a 15.5-fold increase in S-shaped bodies and 4-fold increase in glomeruli compared with control transplants (n = 12). CONCLUSIONS: We have successfully established metanephros transplantation in mice and demonstrated enhancement of onward development of E12.5 metanephroi in response to both pregnancy and UNX. Using E15.5 metanephroi, continued development only occurred in pregnant recipients, implying pregnancy provides an environment conducive to continued organogenesis. This murine assay, when coupled with transgenically-tagged strains of mice, will allow the investigation of the relative contribution of donor and recipient cells to this process.

Animals↗
PubMed2005

Rho and vascular disease.

The Rho family GTPases are regulatory molecules that link surface receptors to organisation of the actin cytoskeleton and play major roles in fundamental cellular processes. In the vasculature Rho signalling pathways are intimately involved in the regulation of endothelial barrier function, inflammation and transendothelial leukocyte migration, platelet activation, thrombosis and oxidative stress, as well as smooth muscle contraction, migration, proliferation and differentiation, and are thus implicated in many of the changes associated with atherogenesis. Indeed, it is believed that many of the beneficial, non-lipid lowering effects of statins occur as a result of their ability to inhibit Rho protein activation. Conversely, the Rho proteins can have beneficial effects on the vasculature, including the promotion of endothelial repair and the maintenance of SMC differentiation. Further identification of the mechanisms by which these proteins and their effectors act in the vasculature should lead to therapies that specifically target only the adverse effects of Rho signalling.

Atherosclerosis↗
PubMed2005

S18886, a selective TP receptor antagonist, inhibits development of atherosclerosis in rabbits.

OBJECTIVE: To investigate the effect of S18886, a novel TP (thromboxane A2 and prostaglandin endoperoxide) receptor antagonist, on the development of aortic fatty streaks and advanced lesions in a rabbit model of atherosclerosis and restenosis. METHODS AND RESULTS: The right iliac artery of 96 rabbits (8 groups, n=12/group) was balloon injured, then the animals were fed a cholesterol-enriched diet for 6 weeks. In Groups 1-4, concomitant oral administration of S18886 at 5 mg/kg/day over the 6-week-period reduced the intima to media ratio of lesions in the uninjured aorta and injured iliac artery, the accumulation of macrophages and the expression of ICAM-1 compared with 1 mg/kg/day S18886, 30 mg/kg/day aspirin and placebo, with no effect on body weight or plasma cholesterol levels. In Groups 5-8, 2 weeks of treatment with 5 mg/kg/day S18886 reduced the intima to media ratio of restenosing lesions when pre-formed iliac artery lesions underwent a second balloon injury at week 6. The smaller lesions resulting from S18886 treatment correlated with a significant decrease in the neointimal area occupied by macrophages, as well as in ICAM-1 expression, with no effect on the smooth muscle component. Aspirin treatment had no significant effect on the neointimal smooth muscle component, but partially inhibited macrophage infiltration, without inhibiting ICAM-1 expression. CONCLUSION: Inhibition of the TP receptor using S18886 causes a significant decrease in the recruitment of monocyte/macrophages within fatty streaks in the uninjured aorta and within primary and restenosing atherosclerotic lesions in the iliac artery of rabbits. Since TP receptor agonists, such as thromboxane A2, prostanoid endoperoxides and isoprostanes participate in vessel wall inflammation and are localized and increased in atherosclerotic plaques, treatment with S18886 may enhance atherosclerotic lesion stability by attenuating inflammatory processes that ultimately lead to plaque rupture.

Animals↗
PubMed2005

Tissue-engineered blood vessels: alternative to autologous grafts?

Although vascular bypass grafting remains the mainstay for revascularization for ischemic heart disease and peripheral vascular disease, many patients do not have healthy vessels suitable for harvest. Thus, prosthetic grafts made of synthetic polymers were developed, but their use is limited to high-flow/low-resistance conditions because of poor elasticity, low compliance, and thrombogenicity of their synthetic surfaces. To fill this need, several laboratories have produced in vivo or in vitro tissue-engineered blood vessels using molds or prosthetic or biodegradable scaffolds, but each artificial graft has significant problems. Recently, conduits have been grown in the peritoneal cavity of the same animals in which they will be grafted, ensuring no rejection, in the short time of 2 to 3 weeks. Remodeling occurs after grafting such that the tissue is almost indistinguishable from native vessels. This conduit is derived from cells of bone marrow origin, opening new possibilities in vascular modeling and remodeling.

Animals↗
PubMed2005

Vascular engineering for bypass surgery.

Since the introduction of synthetic vascular grafts in the 1960s, only two-stage endothelial cell seeding has demonstrated any significant improvement over conventional vascular grafts, and its benefits have yet to be demonstrated on a large scale. Tissue engineering is a rapidly expanding field with great potential, but efforts to construct tissue-engineered arterial grafts have, to date, yielded little clinical success. This review explores the latest approaches to the construction of a superior vascular graft, along with its potential for use in the clinic in the future.

Animals↗
PubMed2004

Conjugation of an antibody to cross-linked fibrin for targeted delivery of anti-restenotic drugs.

There is an urgent need to treat restenosis, a major complication of the treatment of arteries blocked by atherosclerotic plaque, using local delivery techniques. We observed that cross-linked fibrin (XLF) is deposited at the site of surgical injury of arteries. An antibody to XLF, conjugated to anti-restenotic agents, should deliver the drugs directly and only to the site of injury. An anti-XLF antibody (H93.7C.1D2/48; 1D2) was conjugated to heparin (using N-succinimidyl 3-(2-pyridyldithio)propionate), low molecular weight heparin (LMWH) (adipic acid dihydrazide) and rapamycin (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide), and the conjugates purified and tested for activity before use in vivo. Rabbits had their right carotid arteries de-endothelialised and then given a bolus of 1D2-heparin, 1D2-LMWH or 1D2-rapamycin conjugate or controls of saline, heparin, LMWH, rapamycin or 1D2 (+/-heparin bolus) and sacrificed after 2 or 4 weeks (12 groups, n=6/group). Rabbits given any of the conjugates had minimal neointimal development in injured arteries, with up to 59% fewer neointimal cells than those given control drugs. Rabbits given 1D2-heparin or 1D2-LMWH had an increased or insignificant reduction in luminal area, with positive remodelling, while the medial and total arterial areas of rabbits given 1D2-rapamycin were not affected by injury. Arteries exposed to 1D2-heparin or 1D2-rapamycin had more endothelial cells than rabbits given control drugs. Thus, XLF-antibodies can site-deliver anti-restenotic agents to injured areas of the artery wall, where the conjugates can influence remodelling, re-endothelialisation and neointimal cell density, with reduced neointimal formation.

Animals↗
PubMed2004

In vivo engineering of blood vessels.

The inadequacy of conventional synthetic grafts has led to efforts to construct a superior vascular graft. In vivo tissue engineering is one approach to this problem that has been investigated for half a century and enables the construction of autogenous vascular prostheses. Three types of in vivo engineering are explored: remodelling of implanted scaffolds, fibrocollagenous tubes, and the artificial artery generated in the peritoneal cavity. Scaffolds designed to be remodelled may be synthetic or biological and have been remodelled in animal models to form vasoactive neoarteries with arterial morphology. The differences in vascular remodelling ability, particularly spontaneous endothelialisation, between animal models and humans may impair the effectiveness of this approach in the clinic. Fibrocollagenous tubes such as the Sparks Mandril have demonstrated poor performance in the clinic and are prone to aneurysm formation. The artificial artery generated in the peritoneal cavity is a novel addition to the ranks of in vivo engineered vascular prostheses and combines many of the best features of scaffolds designed to be remodelled and fibrocollagenous tubes. However, understanding and manipulating the vascular remodelling process will be the key to producing the ideal arterial prosthesis.

Animals↗
PubMed2004

Rho expression and activation in vascular smooth muscle cells.

Phenotypic modulation of smooth muscle cells (SMC) involves dramatic changes in expression and organization of contractile and cytoskeletal proteins, but little is known of how this process is regulated. The present study used a cell culture model to investigate the possible involvement of RhoA, a known regulator of the actin cytoskeleton. In rabbit aortic SMC seeded into primary culture at moderate density, Rho activation was high at two functionally distinct time-points, first as cells modulated to the "synthetic" phenotype, and again upon confluence and return to the "contractile" phenotype. Rho expression increased with time, such that maximal expression occurred upon return to the contractile state. Transient transfection of synthetic state cells with constitutively active RhoA (Val14RhoA) caused a reduction in cell size and reorganization of cytoskeletal proteins to resemble that of the contractile phenotype. Actin and myosin filaments were tightly packed and highly organised while vimentin localised to the perinuclear region; focal adhesions were enlarged and concentrated at the cell periphery. Conversely, inhibition of endogenous Rho by C3 exoenzyme resulted in complete loss of contractile filaments without affecting vimentin distribution; focal adhesions were reduced in size and number. Treatment of synthetic state SMC with known regulators of SMC phenotype, heparin and thrombin, caused a modest increase in Rho activation. Long-term confluence and serum deprivation induced cells to return to a more contractile phenotype and this was augmented by heparin and thrombin. The results implicate RhoA for a role in regulating SMC phenotype and further show that activation of Rho by heparin and thrombin correlates with the ability of these factors to promote the contractile phenotype.

Animals↗
PubMed2004

Targeted delivery of heparin and LMWH using a fibrin antibody prevents restenosis.

This study investigates a stent-less local delivery system for anti-restenotic agents utilizing antibodies to cross-linked fibrin (XLF). Heparin and low molecular weight heparin (LMWH) were conjugated to an antibody to cross-linked fibrin D-dimer (1D2). Rabbit right carotid arteries were injured with a balloon catheter, then the animals were given a bolus injection of 40 microg/kg 1D2-heparin (26-70 microg/kg heparin) or 1D2-LMWH (29-80 microg/kg LMWH) conjugates or controls of saline (0.5 ml/kg), heparin (150 U/kg), LMWH (2 mg), or 1D2 (40 microg/kg), with or without a heparin bolus and sacrificed after 2 weeks (8 groups, n = 6/group). The injured artery of rabbits given 1D2-heparin or 1D2-LMWH conjugates had reduced neointimal development, with decreased luminal narrowing and positive remodelling compared with animals given control drugs. Animals given 1D2-heparin conjugate (with a heparin bolus) had three to five times more endothelial cells than the rabbits given saline or unconjugated heparin, while rabbits given 1D2-LMWH conjugate had up to 59% fewer neointimal cells than those given unconjugated drugs. There was little difference in extracellular matrix organization or composition. Thus cross-linked fibrin-antibodies can site-deliver anti-restenotic agents to injured areas of the artery wall where they influence wall remodelling and endothelial and neointimal cell number, reducing neointimal formation without systemic complications. Local delivery of anti-restenotic agents should minimise systemic effects, bleeding complications and potentially the cost of treatment due to a single, lower dose.

Animals↗
PubMed2004

Dog peritoneal and pleural cavities as bioreactors to grow autologous vascular grafts.

OBJECTIVE: The purpose of this study was to grow "artificial blood vessels" for autologous transplantation as arterial interposition grafts in a large animal model (dog). METHOD AND RESULTS: Tubing up to 250 mm long, either bare or wrapped in biodegradable polyglycolic acid (Dexon) or nonbiodegradable polypropylene (Prolene) mesh, was inserted in the peritoneal or pleural cavity of dogs, using minimally invasive techniques, and tethered at one end to the wall with a loose suture. After 3 weeks the tubes and their tissue capsules were harvested, and the inert tubing was discarded. The wall of living tissue was uniformly 1-1.5 mm thick throughout its length, and consisted of multiple layers of myofibroblasts and matrix overlaid with a single layer of mesothelium. The myofibroblasts stained for alpha-smooth muscle actin, vimentin, and desmin. The bursting strength of tissue tubes with no biodegradable mesh scaffolds was in excess of 2500 mm Hg, and the suture holding strength was 11.5 N, both similar to that in dog carotid and femoral arteries. Eleven tissue tubes were transplanted as interposition grafts into the femoral artery of the same dog in which they were grown, and were harvested after 3 to 6.5 months. Eight remained patent during this time. At harvest, their lumens were lined with endothelium-like cells, and wall cells stained for alpha-actin, smooth muscle myosin, desmin and smoothelin; there was also a thick "adventitia" containing vasa vasorum. CONCLUSION: Peritoneal and pleural cavities of large animals can function as bioreactors to grow myofibroblast tubes for use as autologous vascular grafts.

Animals↗
PubMed2003

Blockade of vascular smooth muscle cell proliferation and intimal thickening after balloon injury by the sulfated oligosaccharide PI-88: phosphomannopentaose sulfate directly binds FGF-2, blocks cellular signaling, and inhibits proliferation.

Percutaneous transluminal coronary angioplasty is a frequently used interventional technique to reopen arteries that have narrowed because of atherosclerosis. Restenosis, or renarrowing of the artery shortly after angioplasty, is a major limitation to the success of the procedure and is due mainly to smooth muscle cell accumulation in the artery wall at the site of balloon injury. In the present study, we demonstrate that the antiangiogenic sulfated oligosaccharide, PI-88, inhibits primary vascular smooth muscle cell proliferation and reduces intimal thickening 14 days after balloon angioplasty of rat and rabbit arteries. PI-88 reduced heparan sulfate content in the injured artery wall and prevented change in smooth muscle phenotype. However, the mechanism of PI-88 inhibition was not merely confined to the antiheparanase activity of this compound. PI-88 blocked extracellular signal-regulated kinase-1/2 (ERK1/2) activity within minutes of smooth muscle cell injury. It facilitated FGF-2 release from uninjured smooth muscle cells in vitro, and super-released FGF-2 after injury while inhibiting ERK1/2 activation. PI-88 inhibited the decrease in levels of FGF-2 protein in the rat artery wall within 8 minutes of injury. PI-88 also blocked injury-inducible ERK phosphorylation, without altering the clotting time in these animals. Optical biosensor studies revealed that PI-88 potently inhibited (Ki 10.3 nmol/L) the interaction of FGF-2 with heparan sulfate. These findings show for the first time the capacity of this sulfated oligosaccharide to directly bind FGF-2, block cellular signaling and proliferation in vitro, and inhibit injury-induced smooth muscle cell hyperplasia in two animal models. As such, this study demonstrates a new role for PI-88 as an inhibitor of intimal thickening after balloon angioplasty. The full text of this article is available online at http://www.circresaha.org.

Angioplasty, Balloon↗
PubMed2003

Leukaemia inhibitory factor retards the progression of atherosclerosis.

OBJECTIVE: Our previous studies showed that the pleiotropic cytokine leukaemia inhibitory factor (LIF) inhibits the de novo formation of experimental atherosclerotic lesions. The present study examined whether LIF also inhibits progression of pre-existing atheroma. METHODS: Balloon angioplasty was performed on the right carotid arteries of 18 rabbits immediately before placing animals on a cholesterol-enriched diet. After 4 weeks, at which time the intima:media ratio (I:M) was 0.99+/-0.12 (n=6), osmotic minipumps containing LIF (n=6) or saline control (n=6) were inserted into the peritoneal cavity of each of the remaining rabbits for a further 4 weeks. Arteries were then harvested for analysis. RESULTS: Continuous administration of LIF for the final 4 weeks of an 8-week cholesterol-enriched diet completely inhibited lesion progression in injured carotid arteries (I:M 1.05+/-0.16) compared with the saline-treated group at 8 weeks (1.62+/-0.13; P<0.05). Similarly in contralateral uninjured carotid arteries, LIF treatment prevented an increase in I:M from a baseline of 0.11+/-0.01 at 4 weeks to 0.15+/-0.02 at 8 weeks compared with 0.40+/-0.04 for the saline-treated group at 8 weeks (P<0.05). LIF reduced the number of macrophages in the neointima of uninjured arteries, but had no effect on the cellular composition of injured arteries. LIF treatment normalised smooth muscle-dependent vasoreactivity to phenylephrine and sodium nitroprusside in both injured and uninjured arteries. Expression and activity of inducible nitric oxide synthase (iNOS) were up-regulated in response to hypercholesterolemia with levels further increased following endothelial denudation. With LIF treatment, iNOS expression was increased in uninjured arteries but marginally reduced in injured arteries. LIF receptors were expressed in both uninjured and injured arteries, with LIF treatment having no significant effect on expression levels. CONCLUSION: LIF prevents progression of pre-formed atherosclerotic plaques, affecting lesion size and vascular reactivity. LIF treatment has differential effects within the artery wall, depending on the presence or absence of de-endothelialisation injury.

Acetylcholine↗
PubMed2003

A casein variant in cow's milk is atherogenic.

Casein is a major protein in cow's milk that occurs in several variant forms, two of which are beta-casein A1 and beta-casein A2. The levels of these two proteins vary considerably in milk dependent on the breed of cow, and epidemiology studies suggest that there is a relationship between their consumption and the degree of atherosclerosis. In the present study, the direct effect of consumption of beta-casein A1 vs beta-casein A2 on atherosclerosis development was examined in a rabbit model. Sixty rabbits had their right carotid artery balloon de-endothelialised at t=0, divided randomly into 10 groups (n=6 per group), then for 6 weeks fed a diet containing 0, 5, 10 or 20% casein isolate, either beta-casein variant A1 or A2, made up to 20% milk protein with whey. Some groups had their diets supplemented with 0.5% cholesterol. Blood samples were collected at t=0, 3 and 6 weeks and rabbits were sacrificed at t=6 weeks. In the absence of dietary cholesterol, beta-casein A1 produced significantly higher (P<0.05) serum cholesterol, LDL, HDL and triglyceride levels than whey diet alone, which in turn produced higher levels than beta-casein A2. Rabbits fed beta-casein A1 had a higher percent surface area of aorta covered by fatty streaks than those fed beta-casein A2 (5.2+/-0.81 vs 1.1+/-0.39, P<0.05) and the thickness of the fatty streak lesions in the aortic arch was significantly higher (0.04+/-0.010 vs 0.00, P<0.05). Similarly, the intima to media ratio (I:M) of the balloon injured carotid arteries in A1 fed animals (0.77+/-0.07) was higher than in those that consumed A2 (0.57+/-0.04) or whey (0.58+/-0.04), but this did not reach significance. In the presence of 0.5% dietary cholesterol, the thickness of the aortic arch lesions was higher (P<0.05) in 5, 10 and 20% casein A1 fed animals compared with their A2 counterparts, while other parameters were not significantly different. It is concluded that beta-casein A1 is atherogenic compared with beta-casein A2.

Animals↗
PubMed2002

Macrophages, myofibroblasts and neointimal hyperplasia after coronary artery injury and repair.

Macrophages participate in the restenosis process through the release of cytokines, metalloproteinases and growth factors. Studies of peritoneal granulation tissue suggest that macrophages may be precursors of myofibroblasts. This study examined the contribution of monocyte/macrophage lineage cells to neointimal cellular mass in a porcine model of thermal vascular injury. Thermal coronary artery injury caused medial smooth muscle cell necrosis and transformation of the media into an extracellular matrix barrier. The neointimal hyperplasia that developed over the injury sites was evaluated by light microscopy, electron microscopy and immunohistochemistry. At day 3, blood monocytes were adhered to the vessel wall and infiltrated the fibrotic media. At day 14, 42+/-3.9% of neointimal cells had a monocytic nuclear morphology and expressed macrophage-specific antigen SWC3 (identified by monoclonal antibody DH59B). Moreover, 9.2+/-1.8% of neointimal cells co-expressed SWC3 and alpha-smooth muscle actin and had ultrastructural characteristics intermediate between macrophages and myofibroblasts. At day 28, 10.5+/-3.5% of cells expressed SWC3 and 5.2+/-1.8% of cells co-expressed SWC3 and alpha-smooth muscle actin. This study indicates that hematopoietic cells of monocyte/macrophage lineage abundantly populate the neointima in the process of lesion formation and may be precursors of neointimal myofibroblasts after thermal vascular injury.

Analysis of Variance↗
PubMed2002

Cloning of a differentially expressed tropomyosin isoform from cultured rabbit aortic smooth muscle cells.

The four known tropomyosin genes have highly conserved DNA and amino acid sequences, and at least 18 isoforms are generated by alternative RNA splicing in muscle and non-muscle cells. No rabbit tropomyosin nucleotide sequences are known, although protein sequences for alpha- and beta-tropomyosin expressed by rabbit skeletal muscle have been described. Subtractive hybridisation was used to select for genes differentially expressed in rabbit aortic smooth muscle cells (SMC), during the change in cell phenotype in primary culture that is characterised by a loss of cytoskeletal filaments and contractile proteins. This led to the cloning of a tropomyosin gene predominantly expressed in rabbit SMC during this change. The full-length cDNA clone, designated "rabbit TM-beta", contains an open reading frame of 284 amino acids, 5' untranslated region (UTR) of 117 base pairs and 3' UTR of 79 base pairs. It is closely related to the beta-gene isoforms in other species, with the highest homology in DNA and protein sequences to the human fibroblast isoform TM-1 (91.7% identity in 1035 bp and 93.3% identity in the entire 284 amino acid sequence of the protein). It differs from rabbit skeletal muscle beta-tropomyosin (81.7% homology at the protein level) mainly in two regions at amino acids 189-213 and 258-283 suggesting alternative splicing of exons 6a for 6b and 9d for 9a. Since this TM-beta gene was the only gene strongly enough expressed in SMC changing phenotype to be observed by the subtractive hybridisation screen, it likely plays a significant role in this process.

Amino Acid Sequence↗