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Biomedical subjects

Ariel Cohen

Publications and source records attributed to Ariel Cohen.

At least 19 recordsLinked to original sources
PubMed2006

Influence of pravastatin on carotid artery structure and function in dyslipidemic HIV-infected patients receiving antiretroviral therapy.

Forty-two pravastatin-treated HIV-positive patients and 42 sex, age, and smoking status-matched hypercholesterolemic HIV-positive patients not under lipid-lowering treatment were compared for differences in intima-media thickness (IMT) of the common carotid artery (CCA) and aortic stiffness. Pravastatin had no influence on carotid artery structure and function, or aortic stiffness. Age and body mass index were independent determinants of IMT of the CCA. Mean arterial pressure, age, duration of HIV infection and protease inhibitor exposure determined aortic stiffness.

Age Factors↗
PubMed2006

Variability and memory of protein levels in human cells.

Protein expression is a stochastic process that leads to phenotypic variation among cells. The cell-cell distribution of protein levels in microorganisms has been well characterized but little is known about such variability in human cells. Here, we studied the variability of protein levels in human cells, as well as the temporal dynamics of this variability, and addressed whether cells with higher than average protein levels eventually have lower than average levels, and if so, over what timescale does this mixing occur. We measured fluctuations over time in the levels of 20 endogenous proteins in living human cells, tagged by the gene for yellow fluorescent protein at their chromosomal loci. We found variability with a standard deviation that ranged, for different proteins, from about 15% to 30% of the mean. Mixing between high and low levels occurred for all proteins, but the mixing time was longer than two cell generations (more than 40 h) for many proteins. We also tagged pairs of proteins with two colours, and found that the levels of proteins in the same biological pathway were far more correlated than those of proteins in different pathways. The persistent memory for protein levels that we found might underlie individuality in cell behaviour and could set a timescale needed for signals to affect fully every member of a cell population.

Bacterial Proteins↗
PubMed2006

Experimental and theoretical analysis of neuron-transistor hybrid electrical coupling: the relationships between the electro-anatomy of cultured Aplysia neurons and the recorded field potentials.

Understanding the mechanisms that generate field potentials (FPs) by neurons grown on semiconductor chips is essential for implementing neuro-electronic devices. Earlier studies emphasized that FPs are generated by current flow between differentially expressed ion channels on the membranes facing the chip surface, and those facing the culture medium in electrically compact cells. Less is known, however, about the mechanisms that generate FPs by action potentials (APs) that propagate along typical non-isopotential neurons. Using Aplysia neurons cultured on floating gate-transistors, we found that the FPs generated by APs in cultured neurons are produced by current flow along neuronal compartments comprising the axon, cell body, and neurites, rather than by flow between the membrane facing the chip substrate and that facing the culture medium. We demonstrate that the FPs waveform generated by non-isopotential neurons largely depends on the morphology of the neuron.

Action Potentials↗
PubMed2006

Acetylcholinesterase-ISFET based system for the detection of acetylcholine and acetylcholinesterase inhibitors.

A bioelectronic hybrid system for the detection of acetylcholine esterase (AChE) catalytic activity was assembled by way of immobilizing the enzyme to the gate surface of an ion-sensitive field-effect transistor (ISFET). Photometric methods used to characterize bonded enzyme and linker layers on silicon substrates confirm the existence of a stable amino-cyanurate containing AChE monolayer. The transduction of the enzyme-functionalized ISFET, in ionic solutions, is detected in response to application of acetylcholine (ACh). Recorded sensitivity of the modified ISFET to ACh has reached levels of up to 10(-5)M. The Michaelis-Menten constant of the immobilized AChE is only moderately altered. Nevertheless, the maximum reaction velocity is reduced by over an order of magnitude. The ISFET response time to bath or ionophoretic application of ACh from a micropipette was in the range of a second. The catalytic activity of the immobilized AChE is inhibited in a reversible manner by eserine, a competitive inhibitor of AChE. We conclude that the immobilized enzyme maintains its pharmacological properties, and thus the described bioelectronic hybrid can serve as a detector for reagents that inhibit AChE activity.

Acetylcholine↗
PubMed2006

Dynamic proteomics in individual human cells uncovers widespread cell-cycle dependence of nuclear proteins.

We examined cell cycle-dependent changes in the proteome of human cells by systematically measuring protein dynamics in individual living cells. We used time-lapse microscopy to measure the dynamics of a random subset of 20 nuclear proteins, each tagged with yellow fluorescent protein (YFP) at its endogenous chromosomal location. We synchronized the cells in silico by aligning protein dynamics in each cell between consecutive divisions. We observed widespread (40%) cell-cycle dependence of nuclear protein levels and detected previously unknown cell cycle-dependent localization changes. This approach to dynamic proteomics can aid in discovery and accurate quantification of the extensive regulation of protein concentration and localization in individual living cells.

Bacterial Proteins↗
PubMed2006

Fatal cardiomyopathy associated with pegylated interferon/ribavirin in a patient with chronic hepatitis C.

We report the case of a 45-year-old man with HCV treated with pegylated interferon-alpha/ribavirin, in whom fatal cardiomyopathy occurred. Cardiomyopathy is a rare complication of high dose of standard interferon but has never been reported with pegylated interferon. The relationship between pegylated interferon-alpha/ribavirin and the development of cardiomyopathy is highly probable for the following reasons: (1) a cardiologist consultation with specific investigations had been performed before treatment excluding a pre-existing cardiomyopathy; (2) symptoms of advanced dilated cardiomyopathy appeared immediately after the end of treatment; (3) other causes of cardiomyopathy have been ruled out. In all except one of the 21 reported cases with standard interferon, cardiomyopathy was reversible. In our patient, fatal cardiomyopathy occurred with a usual dose of pegylated interferon-alpha. Clinicians should be aware of this potential complication when evaluating the ratio benefit/risk of treatment in patients with chronic hepatitis C infection.

Antiviral Agents↗
PubMed2006

Optimising stroke prevention in non-valvular atrial fibrillation.

Atrial fibrillation is associated with substantial morbidity and mortality. Pooled data from trials comparing antithrombotic treatment with placebo have shown that warfarin reduces the risk of stroke by 62%, and that aspirin alone reduces the risk by 22%. Overall, in high-risk patients, warfarin is superior to aspirin in preventing strokes, with a relative risk reduction of 36%. Ximelagatran, an oral direct thrombin inhibitor, was found to be as efficient as vitamin K antagonist drugs in the prevention of embolic events, but has been recently withdrawn because of abnormal liver function tests. The ACTIVE-W (Atrial Fibrillation Clopidogrel Trial with Irbesartan for Prevention of Vascular Events) study has demonstrated that warfarin is superior to platelet therapy (clopidogrel plus aspirin) in the prevention af embolic events. Idraparinux, a Factor Xa inhibitor, is being evaluated in patients with atrial fibrillation. Angiotensin-converting enzyme inhibitors and angiotensin II receptor-blocking drugs hold promise in atrial fibrillation through cardiac remodelling. Preliminary studies suggest that statins could interfere with the risk of recurrence after electrical cardioversion. Finally, percutaneous methods for the exclusion of left atrial appendage are under investigation in high-risk patients.

Adult↗
PubMed2006

[How to evaluate the cardiovascular and renal risk at the individual level?].

The cardiovascular impact of the non-steroidal anti-inflammatory drugs and the higher cardiovascular mortality during treatment of inflammatory rheumatism impose a rigorous evaluation of the cardiovascular risk of rheumatic patients. Large epidemiological studies have identified risk factors for cardiovascular diseases such as the age, male gender, family history (infarct, stroke), tobacco consumption, systolic arterial pressure, renal insufficiency, hypercholesterolemia, diabetes mellitis, sedentariness, obesity and "electric" ventricular hypertrophy. Some equations make it possible to evaluate the absolute cardiovascular risk at the individual level, which corresponds to the onset risk of a stroke in the 10 years to come in a subject according to the number and importance of each of his risk factors. It has been demonstrated that the correction of one or more risk factors reduce the overall cardiovascular risk justifying the strategies for evaluating this risk to define therapeutic intervention thresholds. The impact of a long-term anti-inflammatory treatment or an inflammatory disease such as rheumatoid arthritis has not been the subject of specific epidemiological study allowing these elements to be included in an equation of the estimation of the cardiovascular risk. However, the introduction of on anti-inflammatory treatment, likely to increase the cardiovascular risk of a patient, certainly justifies an evaluation of the absolute cardiovascular risk.

Adult↗
PubMed2005

Risk of embolism and death in infective endocarditis: prognostic value of echocardiography: a prospective multicenter study.

BACKGROUND: The incidence of embolic events (EE) and death is still high in patients with infective endocarditis (IE), and data about predictors of these 2 major complications are conflicting. Moreover, the exact role of echocardiography in risk stratification is not well defined. METHODS AND RESULTS: In a multicenter prospective European study, including 384 consecutive patients (aged 57+/-17 years) with definite IE according to Duke University criteria, we tested clinical, microbiological, and echocardiographic data as potential predictors of EE and 1-year mortality. Transesophageal echocardiography was performed in all patients. Embolism occurred before or after IE diagnosis (total-EE) in 131 patients (34.1%) and after initiation of antibiotic therapy (new-EE) in 28 patients (7.3%). Staphylococcus aureus and Streptococcus bovis were independently associated with total-EE, whereas vegetation length >10 mm and severe vegetation mobility were predictors of new-EE, even after adjustment for S aureus and S bovis. One-year mortality was 20.6%. In multivariable analysis, independently of the other predictors of death (age, female sex, creatinine serum >2 mg/L, moderate or severe congestive heart failure, and S aureus) and comorbidity, vegetation length >15 mm was a predictor of 1-year mortality (adjusted relative risk=1.8; 95% CI, 1.10 to 2.82; P=0.02). CONCLUSIONS: In IE, vegetation length is a strong predictor of new-EE and mortality. In combination with clinical and microbiological findings, echocardiography may identify high-risk patients who will need a more aggressive therapeutic strategy.

Adult↗
PubMed2005

Comparison of transesophageal echocardiographic identification of embolic risk markers in patients with lone versus non-lone atrial fibrillation.

Although transesophageal echocardiographically derived parameters, notably spontaneous echocardiographic contrast (SEC) in the left atrium or left atrial appendage (LAA), are known predictors of embolism in atrial fibrillation, their value is less well known in patients who have lone atrial fibrillation (LAF). This study describes transesophageal echocardiographic findings and identifies clinical predictors of SEC in the left atrium or LAA in a cohort of patients who had LAF. Eighty-two patients who had LAF and 289 patients who had non-LAF and underwent transesophageal echocardiography were enrolled from July 1998 to March 2002. LAA abnormality was defined as the presence of an LAA area >5 cm(2), emptying or filling LAA velocities <25 cm/s, or the presence of SEC or thrombus in the left atrium or LAA; LAA abnormalities were significantly less frequent in patients who had LAF than in those who had non-LAF. SEC in the left atrium or LAA was significantly less frequent in patients who had LAF than in those who had non-LAF (29.3% vs 49.8%, respectively, p <0.001). In patients who had LAF, SEC in the left atrium or LAA was significantly (p <0.05) less frequent in patients who were </=60 years old (17.9%) than in patients who were >60 years old (39.5%) and in patients who had paroxysmal LAF (5.9%) than in those who had persistent LAF (45.8%). On multivariate analysis, age and persistent LAF were the only clinical variables independently associated with SEC. Thus, transesophageal echocardiography detects thromboembolism risk markers in patients who have LAF. These abnormalities are less frequent in patients who have LAF than in those who are at low risk and have non-LAF; however, in patients who have LAF, older age and persistent atrial fibrillation are associated with these risk markers.

Aged↗
PubMed2004

Prognostic significance of renal insufficiency in patients presenting with acute coronary syndrome (the Prospective Multicenter SYCOMORE study).

This prospective, multicenter, observational study was designed to assess the in-hospital prognostic importance of renal insufficiency among patients presenting with acute coronary syndrome (ACS). One third of patients with ACS presented with renal insufficiency. After adjustment for potential confounders, decreasing renal function was independently associated with in-hospital death, bleeding, and contrast-induced nephropathy.

Contrast Media↗
PubMed2004

Depletion type floating gate p-channel MOS transistor for recording action potentials generated by cultured neurons.

We report the realization of electrical coupling between neurons and depletion type floating gate (FG) p-channel MOS transistors. The devices were realized in a shortened 0.5 microm CMOS technology. Increased boron implant dose was used to form the depletion type devices. Post-CMOS processing steps were added to expose the devices sensing area. The neurons are coupled to the polycrystalline silicon (PS) FG through 420A thermal oxide in an area which is located over the thick field oxide away from the transistor. The combination of coupling area pad having a diameter of 10 or 15 microm and sensing transistor with W/L of 50/0.5 microm results in capacitive coupling ratio of the neuron signal of about 0.5 together with relatively large transistor transconductance. The combination of the FG structure with a depletion type device, leads to the following advantages. (a) No need for dc bias between the solution in which the neurons are cultured and the transistor with expected consequences to the neuron as well as the silicon die durability. (b) The sensing area of the neuron activity is separated from the active area of the transistor. Thus, it is possible to design the sensing area and the channel area separately. (c) The channel area, which is the most sensitive part of the transistor, can be insulated and shielded from the ionic solution in which the neurons are cultured. (d) There is an option to add a switching transistor to the FG and use the FG also for the neuron stimulation.

Action Potentials↗
PubMed2004

Relation between randomized controlled trials published in leading general medical journals and the global burden of disease.

BACKGROUND: More than two-thirds of the world's population live in low-income countries, where health priorities are different from those of people living in more affluent parts of the world. We evaluated the relation between the global burden of disease and conditions or diseases studied in randomized controlled trials (RCTs) published in general medical journals. METHODS: A MEDLINE search identified 373 RCTs that had been published in 6 international peer-reviewed general medical journals in 1999. Manual review excluded non-RCTs, brief reports and trials in which the unit of randomization was not the patient; 286 RCTs remained eligible for analysis. We identified the RCTs that studied any of the 40 leading causes of the global burden of disease. Five of these conditions were considered unsuitable for study with an RCT design and were excluded from subsequent analysis. To provide a practical perspective, we asked 12 experts working with international health organizations to rate the relevance to global health of the articles that studied any of the top 10 causes of the global burden of disease, as measured by disability-adjusted life years (DALYs) and mortality, using a 5-point Likert scale. RESULTS: Among the 286 RCTs in our sample, 124 (43.4%) addressed 1 of the 35 leading causes of the global burden of disease. Of these, ischemic heart disease, HIV/AIDS and cerebrovascular disease were the most commonly studied conditions. Ninety articles (31.5%) studied 1 of the top 10 causes of the global burden of disease. The mean rating (and standard deviation) for international health relevance assigned by experts was 2.6 (1.5) out of 5. Only 14 (16%) of the 90 trials received a rating of 4 or greater, indicating high relevance to international health. Almost half of the 40 leading causes of the global burden of disease were not studied by any trial. INTERPRETATION: Many conditions or diseases common internationally are underrepresented in RCTs published in leading general medical journals. Trials published in these journals that studied one of these high-priority conditions were generally rated as being of little relevance to international health.

Bibliometrics↗
PubMed2004

[Antithrombotic therapy in atrial arrhythmia].

The principal complication of the atrial arrythmias is the thrombo-embolic accident, notably the cerebro-vascular accident. The efficacity of the oral anticoagulants in reducing cerebro-vascular accidents has been demonstrated in numerous studies. This is significantly superior to that obtained with the anti-platelet drugs. However, the anti-vitamin K drugs (warfarin) carry a risk of serious haemorrhage of around 5% per year. This restricts the proposal of this treatment to patients with an elevated risk of vascular accidents: age, diabetes, previous cerebro-vascular accidents, and cardiac failure are the risk factors. Nevertheless, the risk of haemorrhage is responsible for an under prescription of the anticoagulants in the elderly. This explains the interest aroused by alternative therapeutics: the results of trials on ximelagatran, a direct anti-thrombin, are promising. In patients with an arrythmia, cardioversion carries a thrombo-embolic risk of around 1%. This risk is reduced by prior anticoagulant treatment. The procedure for this treatment is orientated by a trans-oesophageal echocardiogram. The incertitude of the duration of anticoagulant therapy without cardioversion calls for respect of the arrythmia. The treatment of this is limited to control of the cardiac rhythm and anticoagulant treatment.

Atrial Fibrillation↗
PubMed2004

DECOPI (DEsobstruction COronaire en Post-Infarctus): a randomized multi-centre trial of occluded artery angioplasty after acute myocardial infarction.

AIM: To determine whether late recanalization of an occluded infarct artery after acute myocardial infarction is beneficial. METHODS AND RESULTS: Two hundred and twelve patients with a first Q-wave myocardial infarction (MI) and an occluded infarct vessel were enrolled. After coronary and left ventricular contrast angiography, patients were randomized to percutaneous revascularization (PTCA, n=109), carried out 2-15 days after symptom onset or medical therapy (n=103). The primary endpoint was a composite of cardiac death, non-fatal MI, or ventricular tachyarrhythmia. The majority had single-vessel disease and less than one-third had involvement of the left anterior descending artery. The use of pharmacological therapy was high in both groups. At six months, left ventricular ejection fraction was 5% higher in the invasive compared with the medical group (P=0.013) and more patients had a patent artery (82.8% vs 34.2%, P<0.0001). Restenosis was seen in 49.4% of patients in the PTCA group. At a mean of 34 months of follow-up, the occurrence of the primary endpoint was similar in the medical and PTCA groups (8.7% vs 7.3% respectively, P=0.68), but the overall costs were higher for PTCA. The secondary endpoint combining the primary endpoint with admission for heart failure was also similar between groups (12.6% vs 10.1% in the medical and PTCA groups, respectively, P=0.56). CONCLUSIONS: Systematic late PTCA of the infarct vessel was associated with a higher left ventricular ejection fraction at six months, no difference in clinical outcomes, and higher costs than medical therapy. These results must be interpreted with caution given the small size and low risk of the population.

Adult↗
PubMed2004

[Cardiotoxicity of 5-fluorouracil].

5-fluorouracil (5FU) is a largely employed antimetabolite, responsible for several well-known toxicities like hand-foot syndrome, diarrhoea, mucositis or leucopenia. Cardiotoxicity of 5-FU is known but uncommon and usually not life-threatening. The incidence has varied from 1.5 and 18%. The physiopathology is controversial, although more recent data suggest a myocardial toxicity. Clinical presentation include chest-pain, cardiac arrythmia, myocardial infarction or global cardiac failure. Electrocardiographic features are usually aspecific, with ischemic signs. The main treatment is to stop the 5-FU infusion and to introduce symptomatic cardiologic treatment. Although the prognosis is good, the mortality ranges between 2.2 and 13% in case of symptomatic cardiotoxicity. Secondary prophylaxis remains controversial.

Antimetabolites, Antineoplastic↗