Biomedical subjects
Publications and source records attributed to A Leahy.
Popliteal and femoral aneurysms can be treated by endoluminal graft stenting, instead of conventional surgery. Results in four cases suggest, however, that long-term results do not justify an endovascular approach.
OBJECTIVES: intimal hyperplasia (IH) is a major cause of re-stenosis post-vascular intervention. Induction of heat shock proteins (HSPs), by thermal pre-conditioning, reduces IH. Our aim was to investigate the effect of the pharmacological HSP inducer herbimycin A on IH in the rat carotid balloon injury model. MATERIALS AND METHODS: thirty male Sprague-Dawley rats were randomized into three groups. All groups underwent balloon injury to the left carotid artery. Stress proteins were induced 18 h pre-operatively by heat shock or herbimycin A. Two weeks post-operatively, animals were sacrificed and carotid intima/media area ratio (I/M ratio) calculated using computerized planimetry. Neo-intimal proliferation was assessed immunohistochemically with PCNA (proliferating cell nuclear antigen). Western blot and immunohistochemistry for arterial HSP70 and HSP27 were performed. RESULTS: heat stress and herbimycin significantly reduced the I/M ratio (p < 0.05 vs balloon injury alone). Neo-intimal proliferation was significantly reduced in the heat stress and herbimycin groups (p < 0.05 vs balloon injury alone). Heat stress induced arterial HSP70 and HSP27. Herbimycin A increased arterial HSP27. CONCLUSION: herbimycin A significantly attenuates IH after balloon injury. HSP27 may be the HSP involved in mediating this response. Pharmacological inducers of HSPs may have a therapeutic role to play in preventing re-stenosis post-vascular intervention.
INTRODUCTION: Endothelial dysfunction is an early manifestation of the atheromatous process and is evident without overt clinical signs or symptoms of the disease. Cigarette smoking has been shown to be associated with endothelial dysfunction in otherwise healthy adults. Although cessation of smoking is the ideal objective, it is not always attainable, and therefore any strategy to prevent early endothelial dysfunction is desirable. Folic acid is currently under review as a rational therapeutic agent in hyperhomocysteinemia. However, folic acid may modify endothelial function independent of its effect on homocysteine. We therefore investigated the effect of folic acid on endothelial function in young otherwise healthy cigarette smokers. METHODS: Volunteer cigarette smokers (n = 10) and control lifelong nonsmokers were enrolled in the study. Baseline folate, vitamin B12, homocysteine, and cholesterol levels were analyzed. Flow-mediated dilatation, an endothelial-dependent phenomenon, was assessed using ultrasonography. This scan was performed at baseline and following 4 weeks of folic acid supplementation (5 mg/day). RESULTS: There were no significant differences in the baseline hematological investigations between the groups. Homocysteine levels were within normal limits in both groups and did not change following folic acid supplementation. Cigarette smokers demonstrated significant endothelial dysfunction compared to controls (P < 0.005). This difference was significantly attenuated by folic acid supplementation (P < 0.005). CONCLUSION: Folic acid significantly improves endothelial function in otherwise healthy cigarette smokers. This provides a potential therapeutic tool in attenuating the atheromatous process in this group.
BACKGROUND: An increased plasma level of homocysteine has been proposed as an independent risk factor for atherosclerosis; this review examines the evidence. METHODS: A Medline search was undertaken for English language articles on homocysteine and vascular disease. Further papers were identified by cross-referencing from the reference lists of relevant major articles. RESULTS: Although much interest has been generated about homocysteine and atherosclerotic disease, contradictory data exist regarding its role in disease progression. There is insufficient current evidence to regard increased homocysteine level as a causative factor in atherosclerotic disease. CONCLUSION: It is not known whether lowering plasma homocysteine concentration will reduce cardiovascular risk in the long term. Until such data become available, there is no evidence for the widespread use of folic acid therapy to reduce cardiovascular disease risk.
Explore the source record for details and available documents.
An early event in endotoxin-induced tissue injury is adhesion and migration of leukocytes through the endothelium. This is a three-stage process, initially low-grade selectin-mediated adhesion, seen as a decrease in rolling velocity, followed by integrin-mediated adhesion and transmigration. Thermotolerance has been shown to reduce tissue injury and mortality induced by endotoxin. The aim of this study was to investigate the effect of thermotolerance on leukocyte-endothelial interactions. Intravital video microscopy was used to examine hemodynamic parameters, leukocyte rolling, adhesion, and migration in rat mesenteric postcapillary venules. Sprague-Dawley rats were randomized into control, lipopolysaccharide (LPS), and thermotolerance + LPS groups. Thermotolerance was induced 18 h prior to administration of LPS by elevating core body temperature to 41 + 0.5 degrees C for 15 min. LPS (055:B5 15 mg/kg) was administered via the jugular vein after baseline recording. Leukocyte rolling velocity and the number of adherent and migrated leukocytes were measured by intravital microscopy at baseline 0 min and 10, 30, 60, and 90 min after LPS administration. Heat shock protein 72 (HSP72) expression in tissues was determined by Western immunoblotting. The results indicated that LPS administration significantly decreased leukocyte rolling velocity during endotoxemia and increased leukocyte adhesion (10.3 +/- 1.67, 13.2 +/- 1.40, and 10.0 +/- 1.57/100 microm) and migration (5.7 +/- 1.02 and 8.3 +/- 1.76/field) at 30, 60, and 90 min after LPS injection (P < 0.01 vs baseline and control group). Thermotolerance maintained leukocyte rolling velocity and significantly reduced leukocyte adhesion (5.7 +/- 0.88 and 4.0 +/- 0.68/100 microm) and migration (2.8 +/- 0.32 and 3.0 +/- 0.68/field) at 30 and 60 min after LPS administration (P < 0.01 and 0.05 vs LPS group). Expression of HSP72 was induced in mesentery, gut, and lung by thermotolerance. This study indicates that thermotolerance attenuated LPS-induced microvascular injury by decreasing leukocyte-endothelial adhesion and migration.
BACKGROUND: Renal dysfunction due to ischemia-reperfusion (IR) injury is a common problem following renovascular surgery or kidney transplantation. There is a lot of emerging evidence that statins, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors, have anti-inflammatory properties and exert direct beneficial effects on the vascular endothelium. The aim of this study was to determine if pretreatment with pravastatin would attenuate the acute renal dysfunction that occurs following IR injury in an experimental model. MATERIALS AND METHODS: Male Sprague-Dawley rats were randomized into four groups (n = 7 per group): control, uninephrectomy, IR group, and IR group pretreated with pravastatin (0.4 mg/kg/day for the preceding 5 days). Following a left nephrectomy the IR injury was induced by cross-clamping the right vascular pedicle for 30 min followed by reperfusion for 2 h. In a separate experiment (n = 6 per group) renal function was assessed 12 and 24 h after reperfusion. RESULTS: IR injury causes significant renal dysfunction characterized by oliguria, 0.11 (0.05) ml/h, decreased glomerular filtration rate (GFR), 0.02 (0.01) ml/min; and marked protein leakage, 7.21 (1.3) g/L, 2 h postreperfusion. This renal dysfunction was also evident 12 and 24 h postreperfusion. This was in contrast to values of 0.61 (0.13) ml/h, 0.23 (0.01) ml/min, and 1.67 (0.12) g/L in the uninephrectomy-only group and values of 2 ml/h, 7.3 ml/min, and 0.72 g/L for uninjured time-matched controls. Pretreatment with pravastatin significantly attenuated IR-induced renal injury, improving urine production to 0.62 (0.2) ml/h and GFR to 0.14 (0.02) ml/min and diminishing protein leakage to 3.76 (0.7) g/L at the 2-h time point. This renoprotective effect was also evident 12 and 24 h postreperfusion. This renal protection was associated with an upregulation of constitutive endothelial nitric oxide synthase in the pravastatin-treated group. CONCLUSION: These results show that pravastatin may play a role in modulating renal impairment following aortic or transplantation surgery, allowing earlier recovery from an IR injury.
Vascular endothelial growth factor (VEGF) has neurotrophic and neuroprotective as well as angiogenic properties, but the pathways involved in VEGF-mediated neuronal survival have not been identified. We found previously that VEGF protects cultured neural cells from death induced by serum withdrawal or hypoxia via the activation of VEGF-2/fetal liver kinase-1 receptors, phosphatidylinositol 3'-kinase, Akt and nuclear factor-kappa B. We now report that in mouse cortical neuron cultures subjected to hypoxia, the neuroprotective effect of VEGF involves suppression of cell-death pathways mediated by caspase-3. Exposure to hypoxia for 24 h caused the death of 71+/-4% of cultured neurons; this was reduced to 40+/-1% by VEGF (n=3, P<0.005) and to 44+/-1% by the caspase-3 inhibitor benzyloxycarbonyl-DEVD-fluoromethyl ketone (n=3, P<0.005). VEGF inhibited the activation of caspase-3 as measured by the 17-20-kDa caspase-3 cleavage product, and immunolocalization of VEGF and activated caspase-3 showed segregated expression in separate neuronal populations. An antisense, but not sense, oligodeoxyribonucleotide directed against VEGF increased the proportion of neurons expressing activated caspase-3, and correspondingly reduced the viability of hypoxic neurons by 37+/-2% (n=3, P<0.005). These findings suggest that VEGF protects neurons from hypoxic injury by inhibiting the activation of caspase-3, and could therefore act as an endogenous neuroprotective factor in cerebral ischemia.
In a double-blind, placebo-controlled study, we examined the effects of nicotine (2 mg administered by inhalator) on the cognitive performance of male and female non-smoking students and on mood changes following a moderately stressful task. The groups were matched for age and IQ, and did not differ in pre-test measures of anxiety, depression, extroversion and neuroticism or in their weekly alcohol or daily caffeine intake. Nicotine did not change performance in tests of attention and memory. Exposure to moderate stress significantly increased ratings of anxiety, discontent and aggression and nicotine blocked these mood changes in females, but enhanced them in males. This suggests that young women may start regular smoking as a form of stress self-medication, which implies that preventative and smoking cessation programmes would be more successful in women if they addressed issues of stress and anxiety, which may be core factors underlying initiation and maintenance of regular smoking.
OBJECTIVES: in patients with occluded internal carotid arteries the carotid stump is a potential source of microemboli resulting in the persistence of retinal or cerebral ischaemic symptoms. We report 25 patients who had persistent cerebral and retinal ischaemic symptoms with an occluded ipsilateral ICA and a carotid stump who underwent surgical exclusion of the stump. METHODS: between January 1988 and January 1998, 332 patients underwent carotid endarterectomy. Twenty-five patients (20 males: five females; mean age 58.9 (range 44-78 years)) had carotid stump exclusion. Indications for surgery were transient ischaemic attack (22), amaurosis fugax (eight) and cerebrovascular accident (13). Three patients had undergone contralateral carotid endarterectomy and 12 had significant contralateral stenosis. Twenty patients were being treated with aspirin and four with warfarin at the time of presentation. RESULTS: the diagnosis of carotid stump was made in 22 patients by angiography. In the remaining three patients duplex alone was diagnostic in two patients. In the third case duplex was combined with magnetic resonance angiography (MRA) to confirm the diagnosis. Stump exclusion was carried out by oversewing the ICA origin. All but one patient remained symptom free at follow-up. CONCLUSION: carotid stump syndrome should be considered as a likely clinical entity in patients with an occluded ICA and persisting cerebral and retinal microembolic symptoms. Surgical exclusion of the carotid stump is a safe and effective method of treatment.
AIM: To investigate gastric pacemaker activity in gastro-oesophageal reflux disease using the electrogastrogram. PATIENTS: Forty patients with gastro-oesophageal reflux disease (20 with acid reflux, 20 with the additional symptom of food regurgitation) and 30 asymptomatic controls. METHODS: Patients were studied using an electrogastrogram, oesophageal manometry, and 24 hour ambulatory oesophageal pH analysis. RESULTS: An abnormal electrogastrogram was recorded in two (7%) controls, two (10%) patients with acid reflux, and 10 (50%) patients with food regurgitation. Food regurgitators had significantly more gastric dysrhythmias (tachygastrias) both before (p<0.02) and after (p<0.01) a test meal. Gastric pacemaker activity was also significantly less stable following the test meal in food regurgitators (p<0.003). Patients with food regurgitation and an abnormal electrogastrogram had higher oesophageal acid exposure than those with a normal electrogastrogram (p<0.05). CONCLUSIONS: The electrogastrogram is usually normal in gastro-oesophageal reflux disease but an abnormal rhythm occurred in half of our patients with the additional symptom of food regurgitation. Furthermore, an abnormal electrogastrogram is associated with increased oesophageal acid exposure.
Explore the source record for details and available documents.
BACKGROUND: The formation of prostacyclin (PGI(2)), thromboxane (TX) A(2), and isoprostanes is markedly enhanced in atherosclerosis. We examined the relative contribution of cyclooxygenase (COX)-1 and -2 to the generation of these eicosanoids in patients with atherosclerosis. METHODS AND RESULTS: The study population consisted of 42 patients with atherosclerosis who were undergoing surgical revascularization. COX-2 mRNA was detected in areas of atherosclerosis but not in normal blood vessel walls, and there was evidence of COX-1 induction. The use of immunohistochemical studies localized the COX-2 to proliferating vascular smooth muscle cells and macrophages. Twenty-four patients who did not previously receive aspirin were randomized to receive either no treatment or nimesulide at 24 hours before surgery and then for 3 days. Eighteen patients who were receiving aspirin were continued on a protocol of either aspirin alone or a combination of aspirin and nimesulide. Urinary levels of 11-dehydro-TXB(2) and 2,3-dinor-6-keto-PGF(1alpha), metabolites of TXA(2) and PGI(2), respectively, were elevated in patients with atherosclerosis compared with normal subjects (3211+/-533 versus 679+/-63 pg/mg creatinine, P<0.001; 594+/-156 versus 130+/-22 pg/mg creatinine, P<0.05, respectively), as was the level of the isoprostane 8-iso-PGF(2alpha). Nimesulide reduced 2, 3-dinor-6-keto-PGF(1alpha) excretion by 46+/-5% (378.3+/-103 to 167+/-37 pg/mg creatinine, P<0.01) preoperatively and blunted the increase after surgery. Nimesulide had no significant effect on 11-dehydro-TXB(2) before (2678+/-694 to 2110+/-282 pg/mg creatinine) or after surgery. The levels of both products were lower in patients who were taking aspirin, and no further reduction was seen with the addition of nimesulide. None of the treatments influenced urinary 8-iso-PGF(2alpha) excretion. CONCLUSIONS: Both COX-1 and -2 are expressed and contribute to the increase in PGI(2) in patients with atherosclerosis, whereas TXA(2) is generated by COX-1.
Ischemia/reperfusion (I/R) results in endothelial dysfunction, seen as loss of endothelium-dependent vasodilatation. In prolonged ischemia, this can result in marked vasospasm or no reflow in the microvasculature. Thermotolerance (T) attenuates I/R-induced microvascular injury. The aim of this study was to investigate the effect of thermotolerance on I/R-induced vasomotor changes and "no reflow." Sprague-Dawley rats were randomized into an ischemia/reperfusion group (I/R group) and a group in which thermotolerance (41 + 0.5 degrees C for 15 min 18 h prior to I/R) was induced (T + I/R group). IR injury was established by occlusion of the superior mesenteric and celiac vascular pedicle for 30 min, followed by 60 min of reperfusion. Vasomotor function [arteriolar constriction:dilatation (C:D) ratio] measured by response to acetylcholine (endothelium-dependent) and sodium nitroprusside (endothelium-independent) and "no-reflow" phenomenon were determined in mesenteric arterioles by intravital microscopy. Data are expressed as means +/- SEM and were analyzed using ANOVA and chi(2) test. I/R caused a significant decrease in endothelium-dependent vasodilatation (C:D = 1.37+/-0.31 in IR group vs. 2.06+/-0.20 in baseline, P<0.01) and no reflow in arterioles in 16 of 28 unheated rats. Endothelium-independent dilatation was not altered by I/R. Thermotolerance attenuated this impairment of endothelium-dependent dilatation (P<0.01 vs. IR; C:D = 1.95+/-0.19) and reduced no-reflow phenomenon to 4 of 16 rats (P<0.05 vs. IR). This study demonstrated that thermotolerance preserves endothelial vasomotor function and markedly reduces "no reflow" in arterioles.
Mouse embryonic stem cells are pluripotent cells that are derived from the inner cell mass of blastocysts. When induced to synchronously enter a program of differentiation in vitro, they form embryoid bodies that contain cells of the mesodermal, hematopoietic, endothelial, muscle, and neuronal lineages. Here, we used a panel of marker genes with early expression within the germ layers (oct-3, Brachyury T, Fgf-5, nodal, and GATA-4) or a variety of lineages (flk-1, Nkx-2.5, EKLF, and Msx3) to determine how progressive differentiation of embryoid bodies in culture correlated with early postimplantation development of mouse embryos. Using RNA in situ hybridization, we found that the temporal and spatial relationships existing between these marker genes in vivo were maintained also in vitro. Studying the onset of marker gene expression allowed us also to determine the time course of differentiation during the formation of embryoid bodies. Thus, stages equivalent to embryogenesis between implantation and the beginning of gastrulation (4.5-6.5 d.p.c.) occur within the first two days of embryoid body differentiation. Between days 3 and 5, embryoid bodies contain cell lineages found in embryos during gastrulation at 6.5 to 7.0 d.p.c., and after day 6 in culture, embryoid bodies are equivalent to early organogenesis-stage embryos (7.5 d.p.c.). In addition, we demonstrate that the panel of developmental markers can be applied in a screen for stage- or lineage-specific genes. Reporter gene expression from entrapment vector insertions can be co-localized with expression of specific markers within the same cell during embryoid body formation as well as during embryogenesis. Our results thus demonstrate the power of embryoid body formation as an in vitro model system to study early lineage determination and organogenesis in mammals, and indicate that they will prove to be useful tools for identifying developmental genes whose expression is restricted to particular lineages.
Using retroviral entrapment vectors, we identified a novel mouse gene whose expression is restricted to vascular endothelial cells and their precursors in the yolk sac blood islands. A 3.68-kb cDNA corresponding to the endogenous transcript was isolated using genomic DNA flanking the entrapment vector insertion as a probe. We have named this gene Vezf1 for vascular endothelial zinc finger 1. Vezf1 encodes a protein with a predicted molecular mass of 56 kDa and that contains six putative zinc finger domains and shows high homology to a previously identified human gene, DB1, that is believed to be involved in regulating expression of cytokine genes such as interleukin-3. In situ hybridization analysis revealed the onset of expression in advanced primitive streak-stage embryos being located in the extraembryonic mesodermal component of the visceral yolk sac and in the anteriormost mesoderm of the embryo proper. During head-fold and somite stages, expression was restricted to vascular endothelial cells that arise during both vasculogenesis and angiogenesis. Vezf1-related sequences were found to be highly conserved among higher vertebrate species that have acquired extraembryonic yolk sac membranes during evolution. The Vezf1 locus mapped to the proximal part of mouse chromosome 2, a region which has homology to human chromosome 9q. Vezf1 expression correlates temporally and spatially with the early differentiation of angioblasts into the endothelial cell lineage and the proliferation of endothelial cells of the embryonic vascular system. Thus, Vezf1 may play an important role in the endothelial lineage determination and may have an additional role during later stages of embryonic vasculogenesis and angiogenesis.
Organic anion transporters play an essential role in eliminating a wide range of organic anions including endogenous compounds, xenobiotics, and their metabolites from kidney, thereby preventing their potentially toxic effects within the body. The goal of this study was to extend our previous study on the functional characterization and post-translational modification of a mouse kidney organic anion transporter (mOAT), in a mammalian cell system, COS-7 cells. The transporter-mediated p-aminohippurate (PAH) uptake was saturable, probenecid-sensitive, and inhibited by a wide range of organic anions including vitamins, anti-hypertensive drugs, anti-tumor drugs, and anti-inflammatory drugs. Tunicamycin, an inhibitor of asparagine-linked glycosylation, significantly inhibited the transport activity. Immunofluorescence provided evidence that most of the protein remained in the intracellular compartment in tunicamycin-treated cells. Diethyl pyrocarbonate (DEPC), a histidine residue-specific reagent, completely blocked PAH transport. The inhibitory effect by DEPC was significantly protected (90%) by pretreating the cells with excess unlabeled PAH, suggesting that the histidine residues may be close to the PAH binding sites. Finally, in situ mRNA localization was studied in postnatal mouse kidney. The expression was observed in proximal tubules throughout development. We conclude that COS-7 cells may be useful in pharmacological and molecular biological studies of this carrier. The carbohydrate moieties are necessary for the proper trafficking of mOAT to the plasma membrane, and histidine residues appear to be important for the transport function.
We have characterized a retroviral promoter-trap insertion into a novel mammalian septin gene, Sep3. Its predicted amino acid sequence shares significant homology to that of Saccharomyces cerevisiae CDC3, CDC10, CDC11, CDC12, the Drosophila genes Pnut, Sep1, Sep2, and the mammalian genes BH5, CDC10, Nedd5, Diff6, and Sep2, which are implicated in cytokinesis and cell polarity. Sep3 encodes a protein of 465 amino acids, and contains an evolutionary conserved ATP/GTP-binding motif, two coiled-coil domains, and a highly hydrophobic domain at the C terminus. Alkaline phosphatase reporter gene expression in transgenic embryos was first detected at E8.5 in the neural fold, and high levels of expression continued throughout embryogenesis in the neural tube and brain. In addition, a low level of transient expression was detected in the somites, gut, and branchial arches of mouse embryos. Overall, reporter gene expression recapitulated Sep3 mRNA expression during mouse embryogenesis. In adults, Sep3 transcripts were only detected in the brain and testis. Zoo blot analysis revealed that Sep3-related sequences exist in several vertebrate species including zebrafish, frog, chicken, mouse and human. Consistent with the retroviral insertion into the 3' UTR of the Sep3 gene, no obvious phenotypes associated with the promoter trap were detected in transgenic embryos or adult mice. In summary, we report the first isolation of a novel full-length Sep3 cDNA and extensive characterization of its expression during mouse embryogenesis and in adult tissues.