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Biomedical subjects

E R Mohler

Publications and source records attributed to E R Mohler.

At least 19 recordsLinked to original sources
PubMed2001

Bone formation and inflammation in cardiac valves.

BACKGROUND: For nearly a century, the mechanical failure of calcified heart valves was attributed to a passive degenerative process. Recently, several case reports described bone formation in surgically excised heart valves and suggested an unexpected process of tissue repair. METHODS AND RESULTS: We studied the prevalence and pathology of heterotopic ossification in 347 surgically excised heart valves (256 aortic, 91 mitral) in 324 consecutive patients (182 men, 142 women; mean age 68 years) who underwent cardiac valve replacement surgery between 1994 and 1998. The valves were examined microscopically to determine the prevalence and features of bone formation and remodeling. Two hundred eighty-eight valves (83%) had dystrophic calcification. Mature lamellar bone with hematopoietic elements and active bone remodeling were present in 36 valves (13%) with dystrophic calcification. Endochondral bone formation, similar to that seen in normal fracture repair, was identified in 4 valves. Microfractures were present in 92% of all valves with ossification. Neoangiogenesis was found in all valves with ossification. Bone morphogenetic proteins 2 and 4 (BMP 2/4), potent osteogenic morphogens, were expressed by myofibroblasts and preosteoblasts in areas adjacent to B- and T-lymphocyte infiltration in valves where ossification was identified. Mast cells were present in calcified and ossified valves and were especially prominent in atheromatous regions. CONCLUSIONS: Heterotopic ossification consisting of mature lamellar bone formation and active bone remodeling is a relatively common and unexpected finding in end-stage valvular heart disease and may be associated with repair of pathological microfractures in calcified cardiac valves.

Adult↗
PubMed2001

Safety and effectiveness of Niaspan when added sequentially to a statin for treatment of dyslipidemia.

Niaspan, when added to a stable dose of a statin in 66 subjects, was found to be safe and highly effective in improving lipid parameters. Subgroup analyses demonstrated its effectiveness in lowering low-density lipoprotein cholesterol in persons not at the National Cholesterol and Education Program low-density lipoprotein cholesterol target and in raising high-density lipoprotein cholesterol in persons with levels < 40 mg/dl.

Adult↗
PubMed2001

Matrix metalloproteinase-2 is associated with tenascin-C in calcific aortic stenosis.

We previously showed that the expression of tenascin (TN-C), an extracellular matrix glycoprotein found in developing bone and atherosclerotic plaque, and matrix metalloproteinase-2 (MMP-2) are coordinated and interdependent in cultured vascular smooth muscle cells. In this study, we hypothesized that TN-C and MMP-2 are mechanistically involved in the pathobiology of calcific aortic stenosis. Human calcific aortic stenosis cusps demonstrated immunohistochemically prominent deposition of TN-C, MMP-2, and alkaline phosphatase activity, as well as MMP-2 gelatinolytic activity. Although far lesser amounts of TN-C were noted in several of the grossly non-calcified valve cusps, MMP-2 and AP were never detected. Further, when aortic valve interstitial cells (both sheep and human) were cultivated on collagen supplemented with TN-C, both MMP-2 mRNA expression and MMP-2 gelatinolytic activity (both pro and active forms), were up-regulated compared to control. These observations support the view that accumulation of first TN-C and then MMP-2 are associated with progression of calcification. The residual presence of these proteins in severe calcifications is indicative of their involvement in the pathogenesis.

Animals↗
PubMed2001

Effects of cilostazol on resting ankle pressures and exercise-induced ischemia in patients with intermittent claudication.

During exercise, patients with intermittent claudication (IC) have decreased limb arterial blood pressure that recovers during rest. A novel method for assessing dynamic recovery of function is measurement of the hemodynamic response after exercise. Cilostazol (Pletal), a new agent for the treatment of IC, increases walking distance and may decrease ischemic burden. The objective of this study was to assess the effect of cilostazol versus placebo on hemodynamic measurements after exercise-induced ischemia in patients with IC. Two double-blind, placebo-controlled studies with similar inclusion/exclusion criteria and duration (24 weeks) were pooled. Patients walked on a treadmill at 2.0 miles/h (3.2 km/h) on a 12.5% grade until the claudication-limited maximal walking distance (MWD) was reached. Anterior and posterior tibial pressures were measured with Doppler ultrasound at baseline and at 1, 5, and 9 min during recovery. Area under the curve (AUC), a measure of the time course of recovery of systolic pressure after exercise-induced ischemia, and ankle-brachial index (ABI) were calculated and compared using analysis of variance (ANOVA). All three treatment groups (308 patients randomized to cilostazol 100 mg bid, 303 to cilostazol 50 mg bid, and 299 to placebo) had similar baseline characteristics. Mean post-exercise AUC for cilostazol 100 mg and 50 mg bid versus placebo increased by 0.31 (p = 0.001) and 0.26 (p = 0.004), respectively. Mean resting ABI increased by 0.03 (p = 0.0039) and 0.04 (p = 0.0001) in the cilostazol 100 mg and 50 mg bid groups, respectively. In conclusion, following 24 weeks of treatment, cilostazol increased the ABI at rest and improved the recovery time of ankle pressures post-exercise.

Aged↗
PubMed2001

Therapeutic thrombin injection of pseudoaneurysms: a multicenter experience.

The standard non-invasive treatment of pseudoaneurysms has been ultrasound-guided compression (UGC). Problems with UGC include pain at the site of compression, long compression times and incomplete closure. Each of these difficulties is exacerbated with large pseudoaneurysms. Recently, ultrasound-guided injection of pseudoaneurysms with thrombin has gained popularity. The goal of this study was to report a multicenter registry using this technique and in so doing detail the clinical utility and safety of this emerging procedure. The medical records of all patients diagnosed with pseudoaneurysm in the vascular laboratory who underwent thrombin injection over the past year were reviewed for patient characteristics and clinical outcome. There were 91 patients (55 male) with a mean age of 69 years. Three patients also had an arteriovenous fistula. The majority of patients were receiving one or more antiplatelet agents and/or anticoagulants. All patients underwent pseudoaneurysm injection with bovine thrombin. The mean aneurysm diameter was 3.3 cm, with a range of 1.5-6.3 cm. Successful thrombosis of the pseudoaneurysm was achieved in 89/91 (98%) of cases. Anticoagulation with heparin was used in one of the unsuccessful cases. In two cases, UGC was used to close a small active region that did not completely thrombose after thrombin injection. There were two patients who had recurrence of pseudoaneurysm the day after successful injection and thrombosis of the pseudoaneurysm. There were no local complications after injection; however, one patient suffered a pulmonary embolus that was thought to be unrelated to the procedure. In conclusion, thrombin injection for the treatment of pseudoaneurysms is safe and effective, even in patients receiving anticoagulation. This procedure should be considered as the initial therapeutic approach for peripheral pseudoaneurysms.

Adult↗
PubMed2001

Cilostazol: treatment of intermittent claudication.

OBJECTIVE: To review the pharmacology and clinical utility of cilostazol, an antiplatelet and vasodilator agent approved for the management of intermittent claudication. DATA SOURCES: Primary literature on cilostazol was identified from a comprehensive MEDLINE literature search (1980-February 2000). Selected meeting abstracts and manufacturer literature were also used as source material. Indexing terms included cilostazol, intermittent claudication, platelet inhibitors, and restenosis. STUDY SELECTION: Human clinical, pharmacokinetic and randomized comparative trials performed in the US and Asia were reviewed. Selected in vitro, ex vivo, and animal studies were evaluated when human data were not available. DATA SYNTHESIS: Intermittent claudication, defined as reproducible discomfort of a muscle group induced by exercise and relieved by rest, is the most common clinical manifestation of peripheral arterial disease (PAD). Cilostazol, a specific inhibitor of cyclic adenosine monophosphate phosphodiesterase in platelets and vascular smooth-muscle cells, is a potent antiplatelet agent and vasodilator that reduces vascular proliferation and has lipid-lowering effects in vivo. Recent multicenter, randomized, placebo-controlled trials have led to approval of cilostazol by the Food and Drug Administration for relief of intermittent claudication in patients with stable PAD. Cilostazol doubled walking distances and improved quality of life compared with placebo in these studies. One trial found that cilostazol was more effective than pentoxifylline, the only alternative pharmacologic therapy for claudication. Although frequent (approximately 50%) minor adverse effects, including headache, diarrhea, and palpitations, may occur in clinical practice, cilostazol has not been associated with major adverse events or increased mortality. Small, nonblind studies suggest that cilostazol may prove useful in preventing thrombosis and restenosis following percutaneous coronary interventions, although these remain unlabeled uses. CONCLUSIONS: The unique combination of antiplatelet, vasodilatory, and antiproliferative effects of cilostazol appear to make it an attractive agent for use in patients with PAD. Clinical trials demonstrating a significant improvement in walking distances with cilostazol therapy suggest that it will be an important tool in improving symptoms and quality of life in patients with intermittent claudication.

Cilostazol↗
PubMed2001

Electron beam computed tomography for the quantification of aortic valvular calcification.

BACKGROUND AND AIM OF THE STUDY: Calcific aortic stenosis is common in the elderly; indeed, 30-60% of patients with mild 'senile' aortic stenosis will progress to severe obstruction. Nonetheless, predictors of progression are incompletely defined, and non-invasive technologies capable of quantifying aortic valve calcium are needed. The reliability of electron beam computed tomography (EBCT) was evaluated for quantification of aortic valve calcium content. METHODS: Nineteen patients with and without restrictive valve calcification underwent EBCT scanning. Separate calcium scores, 30 s apart, were obtained in all patients, and the Spearman correlation coefficient was calculated between measurements. The relationship between dichotomized mean calcium score and aortic valve area was also investigated. RESULTS: There was excellent correlation between calcium scores (R = 0.99, p = 0.0001), as well as a significant inverse relationship between calcium scores in the upper and lower ranges and aortic valve area (p = 0.002). CONCLUSION: EBCT can be used for reproducible quantitation of aortic valve calcification. While at their extremes, calcium scores are inversely related to aortic valve area, further evaluation is needed to define the precise nature of this relationship throughout the spectrum of stenosis severity. EBCT holds promise in the longitudinal assessment of valvular calcification progression and its response to potential medical therapies.

Adult↗
PubMed2000

Trial of a novel prostacyclin analog, UT-15, in patients with severe intermittent claudication.

Prostacyclin is an endothelially derived vasodilator and inhibitor of platelet aggregation. Despite its therapeutic potential for peripheral arterial disease, the short half-life and chemical instability are barriers to routine therapy. Accordingly, prostacyclin analogs are being evaluated in patients with peripheral arterial disease. State-of-the-art non-invasive ultrasonography allows for serial testing of the hemodynamic effects of vasoactive drugs. The safety, efficacy and hemodynamic effects of UT-15, a novel, long-acting prostacyclin analog, were studied in patients with severe intermittent claudication. A total of eight patients with stable severe intermittent claudication, Fontaine classes IIb-III, were admitted to the hospital for intravenous infusion of UT-15. A symptom-limited, dose-escalation protocol was instituted, beginning with placebo and then with increasing dosage at 60-min intervals, followed by a 2-h period of maintenance dose at the maximum well-tolerated infusion rate. The hemodynamic response in the lower limbs was assessed with serial ultrasonography, segmental arterial pressures and pulse volumes. Blood flow in the common femoral artery increased 29% (p = 0.003) by the end of the maintenance period and remained above baseline throughout the washout period (p = 0.044). Blood velocity in the lower limb increased in most of the peripheral arteries. These increases achieved statistical significance in the common femoral artery (p = 0.025) and anterior tibial artery (p = 0.019), and approached significance in the popliteal artery (p = 0.062). In two of four patients in whom blood flow was undetectable before the infusion, arterial blood flow at the ankle level became apparent on ultrasonography during maintenance infusion. UT-15 infusion improved the pulse volume recording (p = 0.016) but the ankle/brachial index did not change significantly. Common side effects at peak dose included headache and nausea. There were no serious adverse events attributable to UT-15 treatment. In most patients, the optimal infusion rate was 10-20 ng/kg per min. In conclusion, ultrasonography is a novel approach for assessing the hemodynamic response to vasoactive agents. UT-15 is well tolerated when given for up to 2 h and increases arterial blood flow and velocity in patients with severe intermittent claudication.

Aged↗
PubMed2000

Hirudin therapy during thrombolysis for venous thrombosis in heparin-induced thrombocytopenia.

Heparin-induced thrombocytopenia (HIT) is the most common drug-related thrombocytopenia. Thromboembolic complications occur in approximately 50% of patients with HIT and result in limb amputation and death in up to 20% and 30% respectively. Because patients with a history of HIT may require future intravenous anticoagulation but have a high-risk of thromboembolism if re-challenged with heparin, alternative therapies are necessary when further anticoagulation is indicated. The use of direct thrombin inhibitors in HIT patients who also require thrombolytic therapy offers unique challenges to anticoagulant monitoring and safety. We present a case of progressive ileofemoral deep venous thrombosis in a patient with a history of HIT in order to review the combined use of hirudin and thrombolysis in this setting.

Anticoagulants↗
PubMed1999

The effect of tea consumption on oxidative stress in smokers and nonsmokers.

While the anticarcinogenic effects of tea in animal models have been reported by several groups, human epidemiological studies examining tea consumption and cancer prevention have produced equivocal results. The beneficial properties of tea to human health may be related to the antioxidant properties of tea components. However, little evidence has been provided that tea consumption can either increase the antioxidant capacity or decrease oxidative stress in humans. In the present study, the effects of tea treatment (green tea) on biomarkers of oxidative stress were investigated in smokers and nonsmokers in two volunteer study groups (one in China and the other in United States). Green tea consumption in both study groups decreased oxidative DNA damage (8-OHdG in white blood cells and urine), lipid peroxidation (MDA in urine), and free radical generation (2, 3-DHBA in urine) in smokers. Nonsmokers (US study group) also exhibited a decrease in overall oxidative stress.

3,4-Methylenedioxyamphetamine↗
PubMed1999

Statins and cerebrovascular disease: plaque attack to prevent brain attack.

Stroke is the third leading cause of death in the USA and in the developed world. The beneficial role of cholesterol reduction in decreasing stroke has been uncertain. However, recent data indicate that statin treatment in patients with a history of myocardial infarction not only reduces the risk of a second myocardial infarction, coronary heart disease, revascularization procedures and death, but also significantly reduces the risk of stroke. However, the mechanism(s) by which statins reduce stroke remain uncertain. Thus, the therapeutic armamentarium for the reduction of stroke in secondary prevention now includes cholesterol reduction with statins.

Adult↗
PubMed1999

Identification and characterization of calcifying valve cells from human and canine aortic valves.

BACKGROUND AND AIM OF THE STUDY: Cardiac valve calcification is the predominant pathology in patients needing valve replacement. The aim of this study was to determine if aortic valve cells calcify spontaneously and, if so, to characterize the nodular complex and response to growth factors. METHODS: Aortic valves were obtained from humans undergoing surgical valve replacement, and from female dogs. The valvular endothelium was removed and explants cultured in medium. RESULTS: A population of valvular interstitial cells spontaneously formed distinct calcified nodules containing hydroxyapatite within two to three weeks in canine and within six weeks in human aortic valves. The nodules contained an inner ring of dead cells surrounded by an outer ring of living cells. Cells associated with nodules had osteoblast-like characteristics and stained positively for extracellular bone matrix proteins. Incubating canine cells with potential calcifying stimuli tested the stimulus for calcification. The rate of nodule formation was increased with transforming growth factor beta-1 (+25 nodules), 25-hydroxycholesterol (+9 nodules) and bone morphogenetic protein 2 (+4 nodules) as compared with vehicle control (+3 nodules) over 25 days. CONCLUSIONS: We identified a population of valvular interstitial cells with osteoblast-like characteristics that spontaneously form calcific nodules in cell culture. In addition, the rate of calcific nodule formation was increased with transforming growth factor beta-1 and 25-hydroxycholesterol. Further study of these 'calcifying valve cells' may yield a new in vitro model for testing therapy aimed at preventing calcific valve stenosis.

Animals↗
PubMed1998

Clinical utility of troponin T levels and echocardiography in the emergency department.

We investigated the clinical utility of cardiac troponin T (TnT) and echocardiography in the emergency department to predict subsequent in-hospital diagnosis and adverse cardiac events. TnT is a cardiac-specific protein released during cell injury such as that following acute myocardial inFarction (MI). Unlike creatine kinase-MB isoenzymes, TnT is increased in a subset of patients with unstable angina, and these may be at higher risk for subsequent cardiac events. Echocardiography is a useful noninvasive imaging technique for the assessment of ischemic heart disease in acute care settings because of its mobility and rapid results. Serial TnT determinations and echocardiographic images were prospectively evaluated in 100 patients with chest discomfort and admitted to the hospital. Serum was obtained for CKMB and TnT on presentation to the emergency department and 4, 8, 16 and 24 hours later. TnT was considered increased when at values greater than 0.1 microg/L. Echocardiograms were recorded on videotape in the emergency department and images reviewed in a blinded fashion for wall-motion abnormalities. When available, current echocardiographic results were compared with previous results to determine whether a new wall-motion abnormality was present. Of the 100 patients (57 men, 43 women), TnT was increased in 21 of 21 with acute MI and 15 of 41 with unstable angina. One of the 38 patients with stable angina had an increased TnT value and died 5 months later of a noncardiac cause. Ninety percent of patients who sustained acute MI had a TnT increase detected within 4 hours of presentation. Fifteen of 18 patients with acute MI and 9 of 37 patients with unstable angina had a new wall-motion abnormality on echocardiography. The combination of TnT levels with echocardiography yielded a positive predictive value of 84% and a negative predictive value of 90% for adverse cardiac events in the follow-up population, which was more accurate than either test analyzed separately. TnT and echocardiography are useful tests in emergency department triage of unstable coronary syndromes. Both tests are predictive of discharge diagnosis and follow-up events. However, the combined utility of TnT levels and echocardiographic imaging is a more powerful predictor of adverse cardiac events than isolated results.

Angina, Unstable↗
PubMed1998

Role of 8-epi PGF2alpha, 8-isoprostane, in H2O2-induced derangements of pulmonary artery endothelial cell barrier function.

The non-enzymatic peroxidation product of arachidonic acid, 8-epi-PGF2alpha or 8-isoprostane (8-IP) was measured in H2O2-exposed cultured pulmonary artery endothelial cell (PAEC) monolayers using a commercially-available enzyme immunoassay kit. H2O2 (50 microM for 1-30 min) significantly increased 8-IP production in a time-dependent fashion. Treatment with higher H2O2 concentrations (100 or 250 microM) failed to further increase 8-IP generation. Determinations of thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides (LOOH) were not sufficiently sensitive to detect lipid peroxidation in PAEC exposed to 50 microM H2O2 for 15 min. 8-IP (100 pM-500 nM for 2 h) caused PAEC monolayer barrier dysfunction measured as the transmonolayer clearance of albumin without causing significant PAEC cytotoxicity (measured as intracellular lactate dehydrogenase release). This is the first report to provide evidence that 8-IP generated in H2O2-exposed PAEC contributes to oxidant-mediated alterations in monolayer barrier function at non-cytotoxic concentrations.

Animals↗
PubMed1997

Characterization of signal transduction events stimulated by 8-epi-prostaglandin(PG)F2 alpha in rat aortic rings.

One of the most abundant F2 isoprostanes formed under pathological conditions is 8-epi-prostaglandin F2 alpha (8-epi-PGF2 alpha), a potent vasoconstrictor. The purpose of this study was to determine the signal transduction events initiated by 8-epi-PGF2 alpha-induced vasoconstriction. Isolated arterial rings from male Sprague-Dawley rats were suspended in tissue baths containing Krebs-Henseleit salt solution, stretched to optimal resting tension and stimulated. 8-epi-PGF2 alpha induced concentration-dependent contractions in pulmonary arteries (EC50: 7.7 +/- 2.1 microM; n = 3) and aortas (EC50: 0.9 +/- 0.1 microM; n = 4) which were blocked by the TXA2 receptor antagonists SQ29548, L657925 and L657926. The contractile response to 8-epi-PGF2 alpha was significantly (*p < 0.05; n = 4) diminished by: 1) indomethacin and ibuprofen; 2) Ca++ free media; 3) verapamil, a voltage gated Ca++ channel blocker; 4) flunarizine, a T-type Ca++ channel blocker; and 5) calphostin C, a protein kinase C inhibitor. These data suggest that the contractile response to 8-epi-PGF2 alpha is: 1) mediated via activation of TXA2 receptors; 2) partially dependent on the synthesis and release of other cyclooxygenase derived products; 3) dependent on an influx of extracellular Ca++ possibly via Ca++ channels; and 4) may be PKC dependent.

Animals↗
PubMed1997

Role of cytokines in the mechanism of action of amlodipine: the PRAISE Heart Failure Trial. Prospective Randomized Amlodipine Survival Evaluation.

OBJECTIVES: We sought to determine whether the beneficial effects of amlodipine in heart failure may be mediated by a reduction in tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) levels. We postulated that TNF-alpha and IL-6 levels may also have predictive value in patients with congestive heart failure (CHF). BACKGROUND: The molecular mechanism for progression of CHF may involve cytokine overexpression. The effect of amlodipine on cytokine levels in patients with CHF is unknown. METHODS: In the Prospective Randomized Amlodipine Survival Evaluation (PRAISE) trial, we used enzyme-linked immunosorbent assay to measure plasma levels of TNF-alpha in 92 patients and IL-6 in 62 patients in New York Heart Association functional classes III and IV randomized to receive amlodipine (10 mg/day) or placebo. Blood samples were obtained for cytokine measurement at baseline and at 8 and 26 weeks after enrollment. RESULTS: The baseline amlodipine and placebo groups did not differ in demographics and cytokine levels. Mean (+/- SD) plasma levels of TNF-alpha were 5.69 +/- 0.32 pg/ml, and those of IL-6 were 9.23 +/- 1.26 pg/ml at baseline. These levels were elevated 6 and 10 times, respectively, compared with those of normal subjects (p < 0.001). Levels of TNF-alpha did not change significantly over the 26-week period (p = 0.69). However, IL-6 levels were significantly lower at 26 weeks in patients treated with amlodipine versus placebo (p = 0.007 by the Wilcoxon signed-rank test). An adverse event-CHF or death-occurred more commonly in patients with higher IL-6 levels. CONCLUSIONS: Amlodipine lowers plasma IL-6 levels in patients with CHF. The beneficial effect of amlodipine in CHF may be due to a reduction of cytokines such as IL-6.

Aged↗