The effect of L-arginine or L-citrulline supplementation on biochemical parameters and the vascular aortic wall in high-fat and high-cholesterol-fed rats.

The aim of the present study is to investigate the potential role of L-arginine or L-citrulline in rats fed high-fat and high-cholesterol (HFC) diet. HFC feeding increased significantly serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities, urea and all lipid profiles and decreased significantly serum high-density lipoprotein-cholesterol (HDL-c) and non significantly serum nitric oxide levels. L-arginine or L-citrulline administration reversed the increase in serum AST and ALT activities, urea and all lipid profiles. These effects were associated with a concomitant increase in HDL-c and nitric oxide levels. In general, rats fed HFC diet and orally treated with L-arginine or L-citrulline had higher relative percentage of 18:0, 20:0 and 22:6 and lower 16:0 fatty acids than rats fed HFC diet. Light and transmission electron microscopic findings of the thoracic aorta confirmed the biochemical results and demonstrated structural changes in the endothelial cells of the intimal layer, medial smooth muscle cells as well as in the adventitial layer in HFC fed-animals. However, these findings indicate little structural alterations in animals supplemented with L-arginine or L-citrulline along with HFC feeding. In the present study, L-arginine or L-citrulline was effective hypocholesterolemic and hypolipidemic agents in rats.

The effects of palm oil tocotrienol-rich fraction supplementation on biochemical parameters, oxidative stress and the vascular wall of streptozotocin-induced diabetic rats.

OBJECTIVE: This study examined the effects of palm oil tocotrienol-rich fractions on streptozotocin-induced diabetic rats. METHODS: Animals were divided into three groups: (i) normal non-diabetic (NDM), (ii) diabetic treated (tocotrienol-rich fractions - TRF) and (iii) diabetic untreated (non-TRF). The treatment group received oral administration of tocotrienol-rich fractions (200 mg/kg body weight) daily for eight weeks. The normal non-diabetic and the diabetic untreated groups were fed standard rat feed. Blood glucose and lipid profiles, oxidative stress markers and morphological changes of the thoracic aorta were evaluated. RESULTS: Tocotrienol-rich fractions treatment reduced serum glucose and glycated hemoglobin concentrations. The tocotrienol-rich fractions group also showed significantly lower levels of plasma total cholesterol, low-density lipoprotein cholesterol, and triglyceride, as compared to the untreated group. The tocotrienol-rich fractions group had higher levels of high-density lipoprotein cholesterol, as compared to the untreated group. Superoxide dismutase activity and levels of vitamin C in plasma were increased in tocotrienol-rich fractions-treated rats. The levels of plasma and aorta malondealdehyde + 4-hydroxynonenal (MDA + 4-HNE) and oxidative DNA damage were significant following tocotrienol-rich fractions treatment. Electron microscopic examination showed that the normal morphology of the thoracic aorta was disrupted in STZ-diabetic rats. Tocotrienol-rich fractions supplementation resulted in a protective effect on the vessel wall. CONCLUSION: These results show that tocotrienol-rich fractions lowers the blood glucose level and improves dyslipidemia. Levels of oxidative stress markers were also reduced by administration of tocotrienol-rich fractions. Vessel wall integrity was maintained due to the positive effects mediated by tocotrienol-rich fractions.

Effect of alpha lipoic acid on oxidative stress and vascular wall of diabetic rats.

UNLABELLED: PREMISES AND OBJECTIVES: Antioxidant plays an important role in preventing the progression of diabetes mellitus (DM) complications. The aim of the present study was to investigate the effect of alpha lipoic acid (ALA) supplementation on plasma lipid, oxidative stress and vascular changes in diabetic rats. MATERIAL AND METHODS: Diabetes was induced by a single intravenous injection of streptozotocin (STZ) (50 mg/kg). The diabetic rats were divided into two groups: (i) supplemented group with ALA (100 mg/kg/day) and (ii) non-supplemented group without ALA. Non-diabetic rats (NDM) formed the control group, which received saline injection. RESULTS: Following eight weeks of supplementation, fasting blood glucose (FBG) and glycosylated hemoglobin (HBA1c) in ALA-supplemented rats was found to be significantly lower than the non-supplemented group. ALA-supplementation also improved dyslipidemia that occurred in diabetic rats. ALA-supplementation also significantly increased plasma superoxide dismutase (SOD) activity and vitamin C level as compared to the No Suppl group. The increase in plasma and aorta malondealdehyde + 4-hydroxynonenal (MDA + 4-HNE) levels were also inhibited and the levels of oxidative DNA damage of peripheral lymphocytes were significantly reduced. Electron microscopic examination of thoracic aorta revealed that normal tissue organization was disrupted in STZ-diabetic rats with ALA-supplementation reducing the changes in the vascular morphology. CONCLUSIONS: It is concluded that ALA has the potential in preventing the alteration of vascular morphology in diabetic rats probably through the improvement of glycemic status and dyslipidemia as well as its antioxidant activities.

The effects of palm oil tocotrienol-rich fraction supplementation on biochemical parameters, oxidative stress and the vascular wall of streptozotocin-induced diabetic rats

OBJECTIVE: This study examined the effects of palm oil tocotrienol-rich fractions on streptozotocin-induced diabetic rats. METHODS: Animals were divided into three groups: (i) normal non-diabetic (NDM), (ii) diabetic treated (tocotrienol-rich fractions - TRF) and (iii) diabetic untreated (non-TRF). The treatment group received oral administration of tocotrienol-rich fractions (200 mg/kg body weight) daily for eight weeks. The normal non-diabetic and the diabetic untreated groups were fed standard rat feed. Blood glucose and lipid profiles, oxidative stress markers and morphological changes of the thoracic aorta were evaluated. RESULTS: Tocotrienol-rich fractions treatment reduced serum glucose and glycated hemoglobin concentrations. The tocotrienol-rich fractions group also showed significantly lower levels of plasma total cholesterol, low-density lipoprotein cholesterol, and triglyceride, as compared to the untreated group. The tocotrienol-rich fractions group had higher levels of high-density lipoprotein cholesterol, as compared to the untreated group. Superoxide dismutase activity and levels of vitamin C in plasma were increased in tocotrienol-rich fractions-treated rats. The levels of plasma and aorta malondealdehyde + 4-hydroxynonenal (MDA + 4-HNE) and oxidative DNA damage were significant following tocotrienol-rich fractions treatment. Electron microscopic examination showed that the normal morphology of the thoracic aorta was disrupted in STZ-diabetic rats. Tocotrienol-rich fractions supplementation resulted in a protective effect on the vessel wall. CONCLUSION: These results show that tocotrienol-rich fractions lowers the blood glucose level and improves dyslipidemia. Levels of oxidative stress markers were also reduced by administration of tocotrienol-rich fractions. Vessel wall integrity was maintained due to the positive effects mediated by tocotrienol-rich fractions.

[Effects of herb therapy for benefiting qi and removing blood stasis on ultrastructure of vascular endothelial cells and vascular smooth muscle cells of uterine endometrium in rabbits with copper intrauterine device].

OBJECTIVE: To observe the effects of herb therapy for benefiting qi and removing blood stasis on ultrastructure of vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs) of uterine endometrium in rabbits with copper intrauterine device. METHODS: Fifty-six rabbits were randomly divided into seven groups, which were normal control group, sham-operation group, untreated group, indomethacin-treated group and low-, medium- and high-dose Gonghuan Zhixueling Recipe (GHZXLR)-treated groups. The rabbits in the last five groups were operated with copper IUD insertion and then orally given distilled water, indomethacin and low-, medium- and high-dose GHZXLR respectively for at least one week. Rabbits in the normal control group and sham-operation group were given distilled water orally. The ultrastructure of VECs and VSMCs of uterine endometrium in rabbits was observed by transmission electron microscopy. RESULTS: The morphological changes of VSMCs revealed intracellular edema, organelle disintegration and decrease of organelle amount, or cell atrophy and vacuolar degeneration of mitochondria in the untreated group, and the amount of collagen fibers also increased outside the VSMCs. Local interstitial edema in subendothelial substance and vacuolar degeneration of mitochondria in VECs were both observed. The ultrastructural damages to the mitochondria, Golgi bodies and myofilament of VECs and VSMCs and the intercellular substance in GHZXLR-treated groups were slighter than those in the untreated group, while these damages had no significant differences as compared with those in the indomethacin-treated group. CONCLUSION: The Chinese herb therapy for benefiting qi for removing blood stasis has the protective effect on VECs of uterine endometrium in the rabbits with copper intrauterine device. It appears to be a good treatment for menorrhagia induced by copper IUD insertion.

The effect of zinc on endothelium-dependent relaxation of blood-vessels and on the ultrastructure of endothelial cells under immobilization stress.

We investigated the effects of zinc on the function and ultrastructure of endothelial cells in the case of a 48-day immobilization stress provoked in Chinchilla male rabbits (n=18) by placing them in metal hutches. Half of those rabbits (n=9) received an daily oral supplement of zinc at a dose of 0.3 mg/kg body weight (in the form of zinc acetate). The control rabbits had no intervention and received no supplement of zinc. The relaxation of smooth muscles from thoracic aorta as mediated by acetylcholine at concentrations from 10(-8) mol/L to 10(-4) mol/L was determined in isometric regime. Responses were expressed as the percentage of relaxation to prostaglandin F2alpha (2.10(-5) mol/L)-induced precontraction. The ultrastructure of endothelial cells was evaluated by electron microscopy. The level of total cholesterol and zinc in the blood serum was determined by an enzymatic method and by atomic absorption spectrometry, respectively. In rabbits receiving no zinc supplement, the relaxation of smooth muscles under the influence of acetylcholine concentrations from 10(-8) mol/L to 10(-4) mol/L was significantly (P < 0.05-0.01) lower than in rabbits receiving a supplement of zinc and lower than in control rabbits. Also, in the rabbits not receiving the zinc supplement, the level of total blood serum cholesterol was increased, but the concentration of zinc decreased. In rabbits receiving the zinc supplement, the contractility of the smooth muscles effected by acetylcholine did not change as compared with control rabbits, and we found a normal structure of endothelial cells and a normal level of total cholesterol and zinc in their blood serum. Thus, zinc played an important role in the maintenance of the normal ultrastructure and function of the endothelial cells in the rabbits receiving zinc under immobilization stress.

Ultrastructural examination of rabbit aortic wall following high-fat diet feeding and selenium supplementation: a transmission electron microscopy study.

Experiments were carried out to examine the changes occurring in the wall of rabbit aortae following high-fat diet (HFD) feeding as well as HFD + selenium supplementation. Male New Zealand White rabbits were divided into three groups-control, HFD-fed and HFD + Se supplementation-and were treated for three months. The study depicted that levels of serum total cholesterol and triglycerides were markedly increased in the HFD-fed group as compared with control animals. However, in the HFD + Se-fed group, these levels were markedly suppressed vis-à-vis animals fed on HFD only. Development of atherogenic and atheromatic plaques has been shown at the light microscopy level in HFD-fed rabbits, whereas these developments were not visible in the HFD + Se-fed rabbits. Transmission electron microscopy findings indicated altered ultrastructure in the endothelial cells of the intimal layer as well as smooth-muscle cells of the medial layer in HFD-fed animals. However, these findings indicated normal ultrastructure in most of the cells, with little ultrastructural alterations from animals supplemented with Se along with HFD feeding. The study on the whole depicted the ability of Se to inhibit the onset of progression of aortic disease and hence has relevance to its therapeutic potential.

Apoptosis and glomerular injury after prolonged nitric oxide synthase inhibition in spontaneously hypertensive rats.

This study was designed to investigate the relationship between apoptosis and glomerular injury in spontaneously hypertensive rats (SHR) with hypertensive disease that was exacerbated by inhibition of NO synthesis. Development of glomerular cell apoptosis was evaluated by assessment of renal hemodynamics, glomerular morphometric changes, and participation of the renin-angiotensin system. Three groups of 20-week-old SHR were investigated: control male SHR and 2 similar groups given 2 doses of N(G)-nitro-L-arginine methyl ester (L-NAME, 50 or 80 mg/L, respectively) for 3 weeks. Mean arterial pressure and renal vascular resistance increased, whereas effective renal plasma flow and glomerular filtration rate were diminished by L-NAME. The small artery wall/lumen ratio increased as the glomerular-tuft area diminished. Renal cortical tissue levels of angiotensin II increased in response to the L-NAME, thereby inducing afferent arteriolar injury. Apoptosis and proliferative index (PCNA) of nonsclerotic glomeruli were induced by the low-dose L-NAME as the glomerular cell number decreased. In contrast, the PCNA index was downregulated with the high-dose L-NAME. These results indicate that angiotensin II activation, induced by L-NAME, was related to glomerular cell deletion and apoptosis together with the pathophysiological changes of severe nephrosclerosis and impaired renal dynamics.

Reduction of vein graft disease using photodynamic therapy with motexafin lutetium in a rodent isograft model.

BACKGROUND: Motexafin lutetium (Lu-Tex) is a photosensitizer that targets atheromatous plaque. Subsequent photoactivation (photodynamic therapy [PDT]) induces local cytotoxic effects. The aim of the present study was to investigate whether Lu-Tex targets vein graft intimal hyperplasia and whether subsequent photoactivation attenuates the disease process. METHODS AND RESULTS: The subcellular localization of Lu-Tex and postillumination viability were studied in cultured human vein graft smooth muscle cells. Inferior vena cava-grafted rats were injected with Lu-Tex (10 mg/kg) 4 or 12 weeks after grafting. Biodistribution was assessed in a subgroup 24 hours after administration. Light therapy (742 nm) was performed 24 hours after Lu-Tex injection by illuminating intraperitoneally placed isografts using a laparotomy. Animals were divided into the following 4 groups: PDT (n=15), Lu-Tex injection and laparotomy (n=13), light treatment (n=14), and laparotomy only (n=13). Grafts were harvested 14 days after treatment for histochemical analysis. Lu-Tex localized within subcellular organelles of smooth muscle cells, and subsequent photoactivation induced cell death via apoptosis. The Lu-Tex concentrations present in the vein grafts were 9.3 times higher than those in the normal inferior vena cava. Postoperative PDT at 4 weeks after surgery significantly reduced the intima/media ratio, whereas treatment at 12 weeks did not reduce the intima/media ratio. Activated macrophages were observed 4 weeks after grafting; however, a significant reduction occurred in these cells by 12 weeks. The mechanism by which PDT works may be related to the presence of activated macrophages. CONCLUSIONS: PDT significantly reduces the intima/media ratio in the early phase of vein graft disease. Lu-Tex-mediated PDT may be a viable method for the attenuation of atherosclerotic disease in vein grafts.

Differences in the effects of HMG-CoA reductase inhibitors on proliferation and viability of smooth muscle cells in culture.

We investigated the influence of lovastatin, simvastatin and pravastatin on proliferation and viability of vascular smooth muscle cells (SMC) in vitro and studied the effects of lovastatin on a mouse SMC line transgenic for a temperature-sensitive mutant of SV40 large T antigen (TAg), known to inhibit the function of p53 and pRb family members. We found that lovastatin and simvastatin inhibited cell proliferation by provoking G0/G1 phase arrest with concomitant depression of the proliferation antigen Ki-67/MIB-1. Lovastatin at high concentrations of 20 micromol/l caused cell death in the presence of serum but not under serum starved conditions, which was verified on the basis of increased DNA strand breaks, decreased DNA content and morphological alterations seen by electron microscopy. Cell death was also found for simvastatin, whereas pravastatin did not exhibit antiproliferative or cytotoxic effects. Mouse SMC transgenic for TAg did not show any impaired sensitivity to the antiproliferative and cell death inducing effect of lovastatin, but both effects could be antagonized by the supplementation of mevalonate. The data indicate that antiproliferative and cytotoxic effects of lovastatin are caused by the using up of products of mevalonate metabolism and do not require the presence of p53 or pRb.

Proliferation and differentiation of stromal-vascular cells in primary culture differ between neonatal pigs consuming maternal or formula milk.

Proliferation and differentiation of preadipocytes from 7-d-old pigs consuming maternal or formula milk were examined in primary culture of stromal-vascular (s-v) cells derived from subcutaneous adipose tissue. Unsuckled pigs were bottle-fed isoenergetically with colostrum and then sow's milk (SM) or with formula milk alone (F) from birth to 7 d. Isolated cells were exposed to serum-supplemented medium and serum-free medium to determine proliferation and differentiation, respectively. Proliferation estimated between d 3 and 4 of culture was higher (P<0.05) in cells from F than SM pigs. In addition, the number of s-v cells isolated from 1 g of adipose tissue was higher (P<0.01) in F than SM pigs. Variables assessing differentiation were also affected. The percentage of differentiating cells and lipoprotein lipase (LPL) activity were lower (P<0.05) in F than SM pigs, whereas malic enzyme (ME) activity did not differ significantly between the two groups. In conclusion, formula milk increased the number of s-v cells and their capacity for proliferation, whereas the potential for cell differentiation was lower compared with cells from the maternal milk group. Further studies are required to identify the growth and/or nutritional factors that are implicated in the observed differences and to determine whether subsequent development of adipose tissue is affected.

The significance of programmed cell death or apoptosis and matrix vesicles in atherogenesis.

Programmed cell death or its current synonym, apoptosis, is considered a genetically controlled biological process of cell deletion complementary to cell replication. Apoptosis is most likely a self-regulatory mechanism whereby a genetically determined biochemical pathway to death is initiated in cells sustaining irreparable damage particularly of DNA. Initiating factors in each instance need to be established. Identified in arteries, apoptosis correlates with the localization and severity of atherosclerosis. Granulovesicular disintegration of vascular smooth muscle cells leads to abundant vesicular debris mostly in the intima and increasing with age and hypertension and such matrix vesicle production is a major pathogenetic feature of atherosclerosis. The abundant debris produced accumulates lipid and minerals as usually occurs in non-phagocytosed cell debris. Similar vesiculation in erythrocytes under haemodynamic stress supports the contention that vascular cells under haemodynamic biomechanical stresses in spontaneous and experimental atherosclerosis degenerate due to depletion of cytoplasm, DNA fragmentation and oxidative damage with some cells inevitably undergoing terminal apoptosis. Evaluation of apoptosis must take into account the concomitant changes in the whole vessel wall and its matrix. Currently generalizations about therapeutic or pathogenetic roles for apoptosis in any disease are speculative and unwarranted.

Local effects of nitric oxide supplementation and suppression in the development of intimal hyperplasia in experimental vein grafts.

OBJECTIVES: The universal response of vein grafts after insertion into the arterial circulation is the development of intimal hyperplasia; smooth muscle cell proliferation and connective tissue deposition, which may be modulated in part by dysfunctional endothelial nitric oxide (NO) metabolism. This study examines the effects of single dose, local application by pluronic gel of a NO donor, S-nitroso-N-acetylpenicillamine (SNAP) and an NO synthase inhibitor nitro-L-arginine methyl ester (L-NAME) on the formation of intimal hyperplasia. MATERIALS: Forty New Zealand white rabbits underwent jugular vein interposition grafting of the common carotid artery. DESIGN: Ten animals were controls, 10 animals had the outer surface of the vein graft coated with 30% pluronic gel (2.5 ml), and 10 each were immersed for 15 min prior to insertion in Ringer lactate containing 10(-3) M of SNAP or L-NAME and then had their vein grafts coated with 2.5 ml of gel containing either SNAP (10(-3) M) or L-NAME (10(-3) M), which allows for sustained delivery for up to 6 h. On the 28th post operative day, the animals were sacrificed and vein grafts were harvested for morphology by electron microscopy (SEM and TEM) and dimensional analysis by videomorphometry. RESULTS: All vein grafts developed intimal hyperplasia. On SEM the vein grafts had a confluent layer of endothelial cells with multiple layers of smooth muscle cells representing intimal hyperplasia in TEM. There were no demonstrable morphological differences between the four groups. Local treatment with SNAP produced a significant 36% decrease in mean intimal thickness (72 +/- 4 microns vs. 45 +/- 4 microns; mean +/- S.E.M.; p < 0.01) without a change in medial thickness compared to gel-only treated groups (58 +/- 6 microns vs. 61 +/- 7 microns; p = ns). Inhibition of NO synthase by L-NAME had no effect on the development of intimal hyperplasia (72 +/- 4 microns vs. 79 +/- 10 microns; p = ns); medial thickness was also unchanged. CONCLUSION: These data confirm the protective effect of NO in vascular injury and suggest that NO synthase activity is either absent or reduced to such a level that further inhibition in this short time course is not relevant to the pathophysiology of vein graft intimal hyperplasia.

[Experimental study of vascular smooth muscle cell apoptosis induced by Huotong Capsule].

OBJECTIVE: To explore the anti-atherogenic mechanism of Huotong Capsule (HTC) on vascular smooth muscle cell (VSMC) apoptosis. METHODS: VSMC proliferation model of cultured human embryonal thoracic aorta was established by stimulating VSMC with interleukin-1 (IL-1) and HTC was applied to observe the apoptosis inducing effect by transmission electron microscopy, DNA gel electrophoresis and flow cytometry. RESULTS: Typical apoptotic cellular changes were found after HTC treatment, the VSMC shrinked, the nuclei disappeared after chromatin agglutination, cellular membrane projected and wrapped the organelle to form apoptotic body. DNA gel electrophoresis showed "ladder" strand of DNA, a special phenomenon of cellular apoptosis. And an Ap peak of degraded DNA could be seen by flow cytometry, which widened and heightened when the concentration of HTC increased. The above-mentioned changes were not found in the blank control and untreated model group. CONCLUSION: HTC could induce apoptosis of human proliferated VSMC.

Confocal analysis of primary cilia structure and colocalization with the Golgi apparatus in chondrocytes and aortic smooth muscle cells.

Detyrosinated and acetylated alpha-tubulins represent a stable pool of tubulin typically associated with microtubules of the centrosome and primary cilium of eukaryotic cells. Although primary cilium-centrosome and centrosome-Golgi relationships have been identified independently, the precise structural relationship between the primary cilium and Golgi has yet to be specifically defined. Confocal immunohistochemistry was used to localize detyrosinated (ID5) and acetylated (6-11B-1) tubulin antibodies in primary cilia of chondrocytes and smooth muscle cells, and to demonstrate their relationship to the Golgi complex identified by complementary lectin staining with wheat germ agglutinin. The results demonstrate the distribution and inherent structural variation of primary cilia tubulins, and the anatomical interrelationship between the primary cilium, the Golgi apparatus and the nucleus. We suggest that these interrelationships may form part of a functional feedback mechanism which could facilitate the directed secretion of newly synthesized connective tissue macromolecules.

Microfibrils provide non-linear elastic behaviour in the abdominal artery of the lobster Homarus americanus.

1. Microfibrils are becoming increasingly recognized as an important component of the extra-cellular matrix. However, almost nothing is known about their mechanical role in the diversity of tissues in which they are found. 2. Microfibrils form the principal structural component in the wall of the abdominal artery of the lobster Homarus americanus. We have used previous estimates of the mechanical properties of these microfibrils, estimates of the fraction of the aorta wall volume occupied by the microfibrils, and their angular distribution as a function of strain in a numerical model that predicts the macroscopic mechanical properties of the whole tissue. 3. Microfibrils alone, when their reorientation and deformation are accounted for, characterize the stress-strain behaviour of the vessel. Evidence of the evolutionary conservation of fibrillin between medusans, echinoderms and vertebrates implies that the mechanical properties of lobster microfibrils may apply to microfibrillar function in other taxa. This will have profound implications on the perceived roles of microfibrils in development, physiology and disease.

Inhibitory effect of a novel orally active GP IIb/IIIa inhibitor, SC-54684A on intimal thickening in the guinea pig femoral artery.

The inhibitory effect of a novel orally active platelet membrane glycoprotein receptor complex IIb/IIIa (GP IIb/IIIa) inhibitor, SC-54684A is studied on intimal thickening in the guinea pig femoral artery. A segment of the femoral artery was occluded by a platelet-rich thrombus induced by photochemical reaction between systemically administered Rose Bengal and transluminal green light which causes endothelial injury followed by platelet adhesion and aggregation at the site of photochemical reaction. Three weeks after successful thrombolysis by tissue-type plasminogen activator, intimal thickening occurred at the irradiated site. SC-54684A (30 mg/kg), administered 2 h before photochemical reaction, significantly (P < 0.05) prolonged the time to occlusion of the femoral artery; in this respect aspirin (100 mg/kg) was ineffective. A combination of SC-54684A and recombinant tissue-type plasminogen activator (rt-PA) increased the frequency of reopening and significantly (P < 0.05) prolonged the duration of reflow compared with rt-PA alone. Further, SC-54684A administered orally twice a day for 3 weeks significantly (P < 0.05) inhibited intimal thickening but aspirin, administered orally once a day for 3 weeks, was ineffective. Scanning electron microscopy revealed extensive platelet adhesion and aggregation on the denuded vessel walls in the untreated group 24 h after successful thrombolysis. In separate experiments, SC-54684A markedly inhibited platelet aggregation ex-vivo. Inhibition of platelet adhesion and aggregation at the site of endothelial injury by SC-54684A (via GPIIb/IIIa inhibition) may account for its inhibitory effect on intimal thickening.

The modulus of elasticity of lobster aorta microfibrils.

The presence of elastic fibres in the extracellular matrix (ECM) provides physiologically important elastic properties for many tissues. Until recently, microfibrils, one component of the ECM, were thought primarily to serve as a scaffolding on which elastin is deposited during development to form elaunin fibres [1]. The most prominent protein that forms mammalian microfibrils is fibrillin. It is known that mutations in the fibrillin gene cause a heterogenous connective tissue disease called Marfan syndrome [2], so information on mechanical properties of microfibrils or their role in tissue function would be useful. Microfibrils are also found in the ECM of some invertebrate tissues, and there is growing evidence that the protein forming the structure is homologous to mammalian fibrillin [3,4]. It has been shown that the microfibril-based arterial wall of the lobster has viscoelastic properties [5], and we have now utilized this primitive artery to measure the modulus of elasticity of microfibrils. It is similar to that of the rubber-like protein elastin.

Nucleotide receptor P2u partially mediates ATP-induced cell cycle progression of aortic smooth muscle cells.

mRNA of the P2u purinoceptor (or nucleotide receptor) is detected both by polymerase chain reaction or Northern blot analyses in cultured aortic smooth muscle cells. When added to the culture medium of these cells, UTP, a specific ligand of the P2u receptor, induces an increased expression of both immediate-early and delayed-early cell cycle-dependent genes. This induction demonstrates similar features (kinetics, concentration dependence) to those obtained after stimulation of aortic smooth cells by exogenous ATP, a common ligand for most P2 purinoceptors. In contrast, 2-methylthioATP, a preferential ligand for P2y purinoceptors, induces only a significant increase of immediate-early genes but not of delayed-early genes. Moreover, the 2-methylthioATP-induced responses (c-fos mRNA increase, free intracellular calcium transient) are lower than those induced by ATP or UTP and are complementary to those of UTP. These results demonstrate that functional P2u receptors are present on cultured aortic smooth muscle cells and suggest that the bulk of responses induced by extracellular ATP on cell cycle progression are mediated via P2u purinoceptors, a hypothesis confirmed by cytofluorometric studies. Since some ATP- or UTP-induced genes code for chemotactic proteins (monocyte chemoattractant protein-1 and osteopontin), this study suggests that these nucleotides may contribute to vascular or blood cell migration and proliferation and consequently to the genesis of arterial diseases.