PubMed Health⌕ Search

Biomedical subjects

A Keren

Publications and source records attributed to A Keren.

At least 19 recordsLinked to original sources
PubMed2006

Invited for debate: is virus persistence a determinant for disease progression?

Evidence-based medicine is not based on assumptions or extrapolations from experimental data in animal models but on solid evidence obtained from randomized clinical trials. There is today experimental and clinical proof of the capability of viruses to invade, persist, and replicate in the myocardium, where they can induce chronic damage. However, the pathogenetic role of viruses detected on endomyocardial biopsies is not clear, and clinical observational data published in the literature on the prognostic implications of this finding are non-uniform and need further elucidation in randomized trials, such as the currently ongoing Betaferon in Chronic Viral Cardiomyopathy (BICC) study. This is the first large randomized trial that evaluates the importance of antiviral therapy in patients with inflammatory cardiomyopathy with presence of viral genome in the myocardium. The results of the BICC trial might supply the needed scientific evidence for the clinical use of a targeted antiviral therapy for prevention of the progression of myocardial dysfunction and reversal of myocardial damage.

Animals↗
PubMed2006

Late humoral rejection in a cardiac transplant recipient treated with the anti-CD20 monoclonal antibody rituximab.

Humoral or vascular rejection results from a B cell-mediated production of immunoglobulin (Ig) G antibody against a transplanted organ, producing immune complex deposition on the vascular endothelium, activation of the complement cascade, generation of endothelial dysfunction, and regional ischemic injury. Antibody-mediated rejection, which may be accompanied by hemodynamic compromise, is associated with reduced long-term graft survival. Patients believed to be at an increased risk of developing humoral rejection include women, particularly those with high levels of panel reactive antibodies, cytomegalovirus seropositivity, and positive cross matches, and subjects with prior sensitization to OKT3. Treatment options for humoral rejection include plasmapheresis to lower the circulating immunoglobulin levels followed by high-dose cyclophosphamide to reduce the B-cell population. Other modalities include total lymphoid irradiation, photophoresis, splenectomy, and, for treatment failures, retransplantation. Rituximab is a chimeric humanized monoclonal antibody directed against the pan B-cell surface molecule, CD20. It is approved for the treatment of low-grade B-cell non-Hodgkin's lymphoma. It has also been used successfully for the treatment of posttransplant B-cell lymphoproliferative disease. We report a case of late humoral rejection successfully treated with rituximab.

Antibodies, Monoclonal↗
PubMed2006

Sense of coherence and its impact on quality of life of patients with systemic lupus erythematosus.

The sense of coherence (SOC) construct refers to a global orientation, which significantly determines the link between stressors, coping with disease and health. The aim of this work was to assess possible associations between SOC and quality of life (QOL) scores among women with SLE. Sixty consecutive SLE women and 88 healthy women were included in the study. QOL was assessed using the SF-36 and the WHO QOL-Bref scales. The SOC has three main sub-scales: comprehensibility, manageability and meaningfulness. Regression analyses were used to study associations between various parameters of SF-36, WHO QOL-Bref, SOC, SLEDAI, indices of end organ damage (SDI), and demographic variables. Mean SLEDAI and SDI scores were 4.5 (SD = 5.6) and 1.29 (SD=2). SLE patients had significantly lower scores for all individual and summary sub-scales in the two QOL questionnaires compared with controls. SLE patients had significantly lower scores for the general, comprehensibility and meaningfulness sub-scales of SOC. No significant correlation was seen between SOC scores and measures of disease activity or end-organ damage. A strong linear correlation was seen between the scores of SOC, general WHO QOL-Bref, and the mental and physical component summary (MCS & PCS) scores of SF36. Age, SOC and SDI significantly affected the PCS score. SOC was the only variable independently associated with MCS. Education and SOC were significantly associated with the general WHO QOL-Bref. Age, education, SDI and SOC were independently associated with QOL of women with SLE.

Adult↗
PubMed2004

Muon spin relaxation measurements of NaxCoO2.yH2O.

Using the transverse field muon spin relaxation technique, we measure the temperature dependence of the magnetic field penetration depth lambda, in the NaxCoO2.yH(2)O system. We find that lambda, which is determined by the superfluid density n(s) and the effective mass m*, is very small and on the edge of the TF-microSR sensitivity. Nevertheless, the results indicate that this system obeys the Uemura relation. By comparing lambda with the normal state electron density, we conclude that m* of the superconductivity carrier is 70 times larger than the mass of bare electrons. Finally, the order parameter in this system cannot be described by a complete gap over the entire Fermi surface.

Journal Article↗
PubMed2004

Dynamic properties of a diluted pyrochlore cooperative paramagnet (Tb(p)Y(1-p))2Ti2O7.

Investigations of the spin dynamics of the geometrically frustrated pyrochlore (Tb(p)Y(1-p))2Ti2O7, using muon spin relaxation and neutron spin echo, as a function of magnetic coverage p, have been carried out. Our major finding is that paramagnetic fluctuations prevail as T-->0 for all values of p, and that they are sensitive to dilution, indicating a cooperative spin motion. However, the percolation threshold pc is not a critical point for the fluctuations. We also find that the low temperature spectral density has a 1/f behavior, and that dilution slows down the spin fluctuations.

Journal Article↗
PubMed2003

Muon spin relaxation and susceptibility studies of the pure and diluted spin 1/2 kagomé-like lattice system (CuxZn(1-x))3V2O7(OH2) 2H2O.

Muon spin relaxation and magnetic susceptibility measurements have been performed on the pure and diluted spin 1/2 kagomé system (CuxZn(1-x))3V2O7(OH)2 2H2O. In the pure x=1 system we found a slowing down of Cu spin fluctuations with decreasing temperature towards T approximately 1 K, followed by slow and nearly temperature-independent spin fluctuations persisting down to T=50 mK, indicative of quantum fluctuations. No indication of static spin freezing was detected in either of the pure (x=1.0) or diluted samples. The observed magnitude of fluctuating fields indicates that the slow spin fluctuations represent an intrinsic property of kagomé network rather than impurity spins.

Journal Article↗
PubMed2003

Local magnetic susceptibility of the positive muon in the quasi-one-dimensional S=1/2 antiferromagnet dichlorobis (pyridine) copper (II).

We report muon spin rotation measurements of the local magnetic susceptibility around a positive muon in the paramagnetic state of the quasi-one-dimensional spin 1/2 antiferromagnet dichlorobis (pyridine) copper (II). Signals from three distinct sites are resolved and have a temperature dependent frequency shift which is significantly different than the magnetic susceptibility. This difference is attributed to a muon induced perturbation of the spin 1/2 chain. The obtained frequency shifts are compared with transfer matrix density-matrix renormalization-group numerical simulations.

Journal Article↗
PubMed2001

Frustration driven lattice distortion: an NMR investigation of Y(2)Mo(2)O(7).

We have investigated the (89)Y NMR spectrum and spin lattice relaxation, T(1), in the magnetically frustrated pyrochlore Y(2)Mo(2)O(7). We find that upon cooling the spectrum shifts, and broadens asymmetrically. A detailed examination of the low T spectrum reveals that it is constructed from multiple peaks, each shifted by a different amount. We argue that this spectrum is due to discrete lattice distortions and speculate that these distortions relieve the frustration and reduce the system's energy.

Journal Article↗
PubMed2001

The peripheral vascular response to exercise is impaired in patients with risk factors for coronary artery disease.

BACKGROUND: Abnormal coronary and brachial artery responses have been described in individuals with risk factors for coronary artery disease (CAD). Peripheral arterial tonometry (PAT), a newly developed digital plethysmographic technique was used to assess peripheral vascular response to exercise in healthy controls and individuals with risk factors. METHODS AND RESULTS: Continuous finger PAT during Bruce protocol exercise test was performed in 30 subjects with risk factors for CAD and 30 healthy individuals. Compared with baseline, the PAT wave amplitude at peak exercise decreased in the subjects but increased in the controls: 83 +/- 28% vs. 114 +/- 40% respectively, p < 0.01. CONCLUSIONS: A different pattern of systemic vascular response to exercise was found in individuals with risk factors for atherosclerosis. Since the vascular behavior in these patients is probably related to endothelial dysfunction, it may be that peripheral arterial tonometry can be used as a simple, readily available technique to assess endothelial function.

Adult↗
PubMed2000

Ga NMR study of the local susceptibility in Kagome-based SrCr8Ga4O19: pseudogap and paramagnetic defects

We present the first Ga(4f ) NMR study of the Cr susceptibility in the archetype of kagome-based frustrated antiferromagnets, SrCr8Ga4O19. Our major finding is that the susceptibility of the frustrated lattice goes through a maximum around 50 K. Our data also support the existence of paramagnetic "clusters" of spins, responsible for the Curie behavior observed in the macroscopic susceptibility at low T. These results set novel features for the constantly debated physics of geometrically frustrated magnets.

Journal Article↗
PubMed2000

Magnetic dilution in the geometrically frustrated SrCr(9p)Ga(12-9p)O19 and the role of local dynamics: A muon spin relaxation study

We investigate the spin dynamics of SrCr(9p)Ga(12-9p)O19 for p below and above the percolation threshold p(c) using muon spin relaxation. Our major findings are as follows: (i) At T-->0 the relaxation rate is T independent and approximately p(3), (ii) the slowing down of spin fluctuation is activated with an energy U, which is also a linear function of p(3) and lim U as p-->0 = 8 K; this energy scale could stem only from a single ion anisotropy, and (iii) the p dependence of the dynamical properties is identical below and above p(c), indicating that they are controlled by local excitation.

Journal Article↗
PubMed1999

[Use of abciximab (Reopro) in the catheterization laboratory and in unstable coronary syndromes].

Blockage of platelet glycoprotein IIb/IIIa receptor by Reopro (c7E3 Fab-abciximab) has been shown to reduce markedly ischemic complications during and following elective and high-risk coronary intervention (CI). Between July '96 and February '98, 120 consecutive patients (85 men and 34 women, aged 34-90--mean 62) received Reopro (20 mg bolus, followed by 10 micrograms/min for 12-48 hours). 100 were treated with Reopro in the catheterization laboratory, in 76 as prophylactic treatment preceding high-risk CI and in 24 as bailout treatment for acute complications during CI. 20 additional patients were treated in the CCU for acute coronary syndromes, 17 of whom underwent CI 6-48 hours later. Coronary angiography demonstrated multivessel disease in 66 (56%), and the target lesions were LAD--77, RCA--41, LCX--22, SVG--6, and 2 unprotected LMCA (total: 148 lesions dilated in 117 patients). Of the 117 CI, 44 were PTCA alone, and 73 included stenting. Indications for prophylactic Reopro for high risk CI were: acute MI (< or = 48 hours), early post-MI angina, unstable AP, and/or complex anatomy with visible thrombus. In this high-risk population the overall success rate (open artery, no MI, discharged alive, no need for urgent re-vascularization) was 97% when Reopro was given prophylactically prior to CI. The success rate was lower (87.5%) when Reopro was given in bailout situations. In 20 patients with acute coronary syndromes treated in the CCU while receiving maximal combined conventional therapy (including full-dose heparin), all symptoms and dynamic ischemic ECG changes disappeared within minutes following Reopro. 17 underwent successful CI during hospitalization and 3 were treated medically. Reopro given prior to high risk CI was associated with a very low rate of complications. In a few cases with acute coronary syndromes, Reopro given in the CCU cases immediate relief of myocardial ischemia and reduced the need for urgent coronary intervention.

Abciximab↗
PubMed1998

Cardiovascular safety of transdermal nicotine patches in patients with coronary artery disease who try to quit smoking.

Nicotine patches are commonly used by people who try to quit smoking. Because high doses of nicotine may increase heart rate and potentiate cardiac arrhythmia or ischemia, its use in patients with coronary artery disease was investigated. The objective was to assess the cardiovascular safety of nicotine patches in patients with coronary artery disease (CAD) who try to quit smoking. The study was conducted in a double-blind, placebo-controlled, randomized fashion over a 2-week period. One hundred and six patients with CAD who wished to stop smoking and were taking part in a smoking cessation program were included. Fifty-two patients received nicotine patches (Nicotinell) and 54 received placebo patches. The cardiovascular effects of nicotine patches were assessed by repeated ambulatory ECG monitoring (AEM) and exercise testing. There were no changes in the resting heart rate and in the systolic or diastolic blood pressure between the screening and the two phases of the study in both the Nicotinell and placebo groups. Repeated 48-hour AEM revealed that there were no significant changes in the number and duration of ischemic episodes in both groups. There was no change in the frequency of atrial or ventricular arrhythmias. Exercise duration and time to 1-mm ST-segment depression increased in both groups during the double-blind treatment phase. More patients in the Nicotinell group claimed tobacco abstinence compared with the placebo group (27% vs. 13%). The use of nicotine patches did not cause aggravation of myocardial ischemia or arrhythmia in coronary patients and therefore can be used as a method to promote smoking cessation in this high-risk group.

Administration, Cutaneous↗
PubMed1997

Relation of coronary artery disease to atherosclerotic disease in the aorta, carotid, and femoral arteries evaluated by ultrasound.

This prospective study was conducted to correlate the presence of angiographically significant coronary artery disease (CAD) and atherosclerotic disease in the aorta, carotid, and femoral arteries as measured by ultrasound. One hundred two consecutive patients admitted for coronary angiography for suspected CAD participated in the study. All patients underwent transesophageal echocardiography for the evaluation of thoracic aortic atherosclerosis and B-mode ultrasound for evaluation of carotid and femoral atherosclerosis. Intimal-medial thickness > 1 mm in the thoracic aorta or peripheral vessels was considered as evidence of atherosclerosis. Patients with CAD (n = 64) had a significantly higher incidence of atherosclerotic plaques in the thoracic aorta, carotid, and femoral arteries than subjects with normal coronary arteries: 91%, 72%, 77% vs 31%, 47% and 42%, respectively. Extracoronary plaque was a stronger predictor of CAD than conventional risk factors. Evidence of plaque in patients younger than median age (64 years) had a higher specificity than in patients above median age (77% vs 40%, respectively, p <0.0001). Plaque score of the extracardiac vessels was significantly higher in patients with multivessel CAD than in patients with 1-vessel CAD disease and in subjects with normal coronary arteries (p <0.001). Thus, atherosclerotic plaques in the aortic and femoral arteries and, to a lesser extent, in the carotid arteries are strong predictors of CAD.

Adult↗
PubMed1997

Frequency and distribution of atherosclerotic plaques in the thoracic aorta as determined by transesophageal echocardiography in patients with coronary artery disease.

The frequency, distribution, and severity of thoracic aortic plaques were evaluated by transesophageal echocardiography in 152 consecutive patients undergoing coronary arteriography. Coronary artery disease (CAD) was defined as > or = 50% stenosis of > or = 1 major branch. Atherosclerotic plaques were detected in the aorta in 90 of the 97 patients (93%) with CAD, but in only 12 of the 55 patients (22%) with normal coronary arteries. Atherosclerotic plaques in patients with CAD were found predominantly in the descending aorta (in 93%) and in the aortic arch (in 80%), whereas the ascending aorta was the least involved (in 37%). In the descending aorta, 58% of the plaques were complex (>3 mm thick, ulcerated, mobile, or calcified), and in the aortic arch, 40% of the plaques were so classified. Complex plaques were not found in the ascending aorta. The presence of an atherosclerotic plaque in the descending aorta had a sensitivity and a specificity for the prediction of CAD of 93% and 78%, respectively. In the ascending aorta, the sensitivity was lower (37%) but the specificity was higher (100%). The sensitivity of aortic plaques for the prediction of CAD was high in all age groups. Its specificity in subjects >63 years was lower than in younger subjects: 64% versus 90%, respectively. Multivariate logistic regression analysis showed that aortic plaques were a stronger predictor of CAD than were conventional risk factors.

Adult↗