Luis Sepulveda

Interactions of neutral molecules with ionic micelles

The interactions of neutral molecules with ionic micelles are analyzed. The cell and mass action models are presented in order to provide a semi-quantitative description of the solubilization process. Both approaches are discussed from a thermodynamic and kinetic point of view and the different definitions of solute incorporation constants are also discussed and compared. An extensive compilation of standard free energies of transfer from water to micelles is provided and the basis of the employed methods to obtain them is presented. Several aspects of the solubilization process such as its dynamics, the effect of additives, the probe microenvironment and its dependence with the solute mean occupation number are reviewed and critically discussed. The effect of solute incorporation upon the micelle shape and size is also briefly reviewed.

Absorbances of solutions of cationic micelles and organic anions

Abstract The absorbances in the uv region of sodium p -toluene sulfonate, sodium toluate, sodium benzene sulfonate and sodium phenyl phosphate have been measured in the presence of increasing amounts of cetyl trimethyl ammonium bromide (CTA). The addition of CTA to the aqueous solutions of the organic salts changed their absorbances until a point was reached at which they remained constant. It is demonstrated that the change is due to the lower dielectric constant of the core of the micelles in which the anion is incorporated. The results are quantitatively examined by assuming that the micelles are composed of a certain number of sites, each of which is accessible to one molecule of the corresponding anion.

High viscosities of cationic and anionic micellar solutions in the presence of added salts

Abstract Viscosities of micelles of cetyltrimethylammonium salts (CTAX, X = tosylate (TOS−), Cl−, Br−, NO3−) in the presence of Cl−, Br−, NO3−, benzene sulfonate (BS−), and TOS−, of cetylpyridinium chloride (CpyC) in the presence of Cl−, Br−, and NO3−, and of sodium dodecyl sulfate (SDS) in the presence of Na+ and H+ counterions have been measured at 25 ± 0.01 °C. Viscosities were determined using a conventional Ubbelohde viscometer connected to a wide U-Shaped tube containing water, which allowed measurement of the viscosities under different pressure and, consequently, at different flow rates; the viscosities reported here correspond to the values extrapolated to zero rate of flow because the solutions were highly non-Newtonian. The viscosity values exhibit the order TOS− > NO3− > Br− > Cl− in CTAX and Na+ > H+ in SDS micellar solutions; i.e., the more strongly bound counterions produce the more viscous solution. The high viscosities observed in these systems are interpreted in terms of a micellar sphere-to-rod transition which occurs over a certain range of concentration of either surfactant or added salt. The length of the rod-shaped micelles was estimated from the intrinsic viscosities at zero rate of flow.

Successful percutaneous closure of paraprosthetic aorto-right ventricular leak using the Amplatzer duct occluder.

A 55‐year‐old male with persisting aorto‐right ventricular paraprosthetic leak after mitroaortic valve replacement was hospitalized for recurrent heart failure. Depressed left ventricular ejection fraction and severe pulmonary hypertension with increased right and left ventricular filling pressures were associated with significant left to right shunting through the leak. Elective closure of the leak was obtained with a 6–4 mm Amplatzer duct occluder. No complications were observed, and the patient experienced complete resolution of heart failure symptoms, with NYHA class I heart failure 12 months after discharge.

Counterion association in mixed micelles of cationic and nonionic detergents

Abstract A study of a mixed micellar system formed by mixing a cationic surfactant(cetyltrimethylammonium bromide) with a nonionic surfactant (polioxiethylene (23) Lauryl Ether, Brij 35) is presented. The variation of the micellar surface charge density with the composition of the mixed micelles and its influence upon some micellar surface properties has been obtained. These effects are observed for the decomposition of uncharged substrates such as 2,4-dinitrochlorobenzene and p-nitrophenyldiphenyl phosphate. The measured quenching produced by bromide ions upon the fluorescence of biphenyl adsorbed by micelles was used to obtain the concentration of the bromide counterions. The variation of the specific conductance and the critical micelle concentration as a function of the composition of the surfactant mixtures are also reported. The results are discussed in terms of a minimum ionic surfactant composition necessary to form a Stern layer in the mixed micelle.

Effects of trimetazidine in nonischemic heart failure: a randomized study.

OBJECTIVES Heart failure (HF) is associated with changes in myocardial metabolism that lead to impairment of contractile function. Trimetazidine (TMZ) modulates cardiac energetic efficiency and improves outcomes in ischemic heart disease. We evaluated the effects of TMZ on left ventricular ejection fraction (LVEF), cardiac metabolism, exercise capacity, O2 uptake, and quality of life in patients with nonischemic HF. METHODS AND RESULTS Sixty patients with stable nonischemic HF under optimal medical therapy were included in this randomized double-blind study. Patients were randomized to TMZ (35 mg orally twice a day) or placebo for 6 months. LVEF, 6-minute walk test (6MWT), maximum O2 uptake in cardiopulmonary exercise test, different markers of metabolism, oxidative stress, and endothelial function, and quality of life were assessed at baseline and after TMZ treatment. Left ventricular peak glucose uptake was evaluated with the use of the maximum standardized uptake value (SUV) by 18-fluorodeoxyglucose positron emission tomography ((18)FDG-PET). Etiology was idiopathic in 85% and hypertensive in 15%. Both groups were similar in age, functional class, LVEF, and levels of N-terminal pro-B-type natriuretic peptide at baseline. After 6 months of TMZ treatment, no changes were observed in LVEF (31 ± 10% vs 34 ± 8%; P = .8), 6MWT (443 ± 25 m vs 506 ± 79 m; P = .03), maximum O2 uptake (19.1 ± 5.0 mL kg(-1) min(-1) vs 23.0 ± 7.2 mL kg(-1) min(-1); P = .11), functional class (percentages of patients in functional classes I/II/III/IV 10/3753/0 vs 7/40/50/3; P = .14), or quality of life (32 ± 26 points vs 24 ± 18 points; P = .25) in TMZ versus placebo, respectively. In the subgroup of patients evaluated with (18)FDG-PET, no significant differences were observed in SUV between both groups (7.0 ± 3.6 vs 8.2 ± 3.4 respectively; P = .47). CONCLUSIONS In patients with nonischemic HF, the addition of TMZ to optimal medical treatment does not result in significant changes of LVEF, exercise capacity, O2 uptake, or quality of life.

Interactions between alkyl xanthates and cationic micelles

Abstract Interactions between methyl, ethyl, n-buthyl, n-amyl, and n-hexyl xanthates with monomers and micelles of cetyltrimethylammonium bromide CTAB were studied. Xanthates have a pronounced absorbance peak at 301 nm which is shifted to 306 nm when in presence of CTAB micelles. A maximum difference in absortivities between the micellar bound and free xanthates was found at 313 nm. This wavelength was used to measure the amount of xanthate associated to micelles. An insoluble ion pair formed between xanthates and CTA monomers which is gradually redissolved by increasing amounts of CTAB was detected. Association constants of xanthates to CTAB micelles as well as ionic exchange constants between xanthates and added Br− ions in presence of CTAB micelles were calculated and from their values the transfer free energies Δμx0 of the methyl and methylene groups of the alkyl chain of xanthates were calculated from both the association and ionic exchange constants.

Properties of aqueous mixed micelles formed by hexadecyltrimethylammonium bromide and polyoxyethylene 23-lauryl ether obtained by ion selective electrodes

Surface properties of aqueous mixed micelles formed by hexadecyltrimethylammonium bromide (CTABr) and the nonionic surfactant polyoxyethylene 23 lauryl ether (Brij 35) have been studied. The Br− and CTA+ intermicellar activities have been measured by using specific electrodes for both ionic species. When log(aCTA+) are plotted vs log(aBr−) linear relations are obtained and the slopes of the plots are used to calculate the degree of dissociation (β) for the different molar fractions of the CTABr-Brij 35 mixed micelles. Surface micellar potentials (Ψ0) were also calculated, compared with reported values, and related with the experimental β values. β was found to be an almost linear function of Ψ0. Mean activities for the intermicellar CTA+ and Br− ions were also calculated. The obtained mean activities suggest that the CTA+ monomers are preferentially sorbed by micelles richer in the nonionic surfactant. CMCs of the mixed micelles, calculated from the electromotive force of the CTA+ electrode are in very good agreement with CMCs values reported for the same systems.

Relationship between mechanical and metabolic dyssynchrony with left bundle branch block: evaluation by 18-fluorodeoxyglucose positron emission tomography in patients with non-ischemic heart failure.

BACKGROUND Ventricular dyssynchrony is a common finding in patients with heart failure (HF), especially in the presence of conduction delays. The loss of ventricular synchrony leads to progressive impairment of contractile function, which may be explained in part by segmental abnormalities of myocardial metabolism. However, the association of these metabolic disarrangements with parameters of ventricular dyssynchrony and electrocardiography (ECG) findings has not yet been studied. METHODS Our aim was to determine the correlation between the presence of left bundle branch block (LBBB) with left ventricular (LV) mechanical synchrony assessed by multiple-gated acquisition scan (MUGA) and with patterns of 18-fluorodeoxyglucose (18FDG) uptake in patients with non-ischemic heart failure. Twenty-two patients with non-ischemic cardiomyopathy, LV ejection fraction (LVEF) ≤45% and New York Heart Association (NYHA) Functional Class II or III symptoms under standard medical therapy were included, along with 10 healthy controls matched for age and gender. A 12-lead ECG was obtained to measure the length of the QRS. Mechanical LV synchrony was assessed by MUGA using phase analysis. All patients and controls underwent positron emission tomography with 18FDG to determine the distribution of myocardial glucose uptake. The standard deviation of peak (18)FDG uptake was used as an index of metabolic heterogeneity. Students t-test and Pearsons correlation were used for statistical analysis. RESULTS The mean age of the patients with HF was 54 ± 12 years and 72% were male. The length of the QRS was 129 ± 31 milliseconds and LBBB was present in 9 patients. Patients with HF had decreased LV 18FDG uptake compared with controls (7.56 ± 3.36 vs. 11.63 ± 4.55 standard uptake value; p = 0.03). The length of the QRS interval correlated significantly with glucose uptake heterogeneity (r = 0.62; p = 0.002) and mechanical dyssynchrony (r = 0.63; p = 0.006). HF patients with LBBB showed marked glucose uptake heterogeneity compared with HF patients without LBBB (41.4 ± 10 vs 34.7 ± 4.9 ml/100 g/min, respectively; p = 0.01). CONCLUSIONS Patients with non-ischemic heart failure exhibit a global decrease in myocardial glucose uptake. Within this group, subjects who also have LBBB exhibit a marked heterogeneity in segmental glucose uptake, which directly correlates with QRS duration.

Acute effect of iloprost inhalation on right atrial function and ventricular dyssynchrony in patients with pulmonary artery hypertension.

Right atrium function and ventricular function have significant prognostic value in pulmonary arterial hypertension patients. Acute changes in right ventricular synchrony and right atrium function postiloprost inhalation have not been evaluated.