An Exploratory Study of Sleep-Wake Differences of Autonomic Activity in Patients with Mild Cognitive Impairment: The Role of Melatonin as a Modulating Factor

Carolina Abulafia,1,2 María F Vidal,3 Natividad Olivar,4 Andrea Odzak,5 Ignacio Brusco,4– 6 Salvador M Guinjoan,7 Daniel P Cardinali,8 Daniel E Vigo1,9 1Laboratory of Chronophysiology, Institute for Biomedical Research (BIOMED), Pontifical Catholic University of Argentina (UCA) and CONICET, Buenos Aires, Argentina; 2Facultad de Psicología, Universidad de Buenos Aires, Buenos Aires, Argentina; 3Servicio de Psiquiatría, Departamento de Neurología, Fleni, Buenos Aires, Argentina; 4Hospital de Clínicas “José de San Martín”, Universidad de Buenos Aires, Buenos Aires, Argentina; 5Servicio de Clínica Médica, Hospital Argerich, Buenos Aires, Argentina; 6CONICET, Buenos Aires, Argentina; 7Laureate Institute for Brain Research, Tulsa, OK, USA; 8Facultad de Ciencias Médicas, Universidad Católica Argentina, Buenos Aires, Argentina; 9Faculty of Psychology and Educational Sciences, Katholieke Universiteit Leuven, Leuven, BelgiumCorrespondence: Daniel E Vigo, Instituto de Investigaciones Biomédicas, Pontificia Universidad Católica Argentina, Alicia Moreau de Justo 1500, 4° piso, Buenos Aires, C1107AAZ, Argentina, Tel +54 0810-2200-822 ext 1152, Email [email protected]; [email protected]: The objective of the present study was to assess sleep-wake differences of autonomic activity in patients with mild cognitive impairment (MCI) compared to control subjects. As a post-hoc objective, we sought to evaluate the mediating effect of melatonin on this association.Patients and Methods: A total of 22 MCI patients (13 under melatonin treatment) and 12 control subjects were included in this study. Sleep-wake periods were identified by actigraphy and 24hr-heart rate variability measures were obtained to study sleep-wake autonomic activity.Results: MCI patients did not show any significant differences in sleep-wake autonomic activity when compared to control subjects. Post-hoc analyses revealed that MCI patients not taking melatonin displayed lower parasympathetic sleep-wake amplitude than controls not taking melatonin (RMSSD − 7 ± 1 vs 4 ± 4, p = 0.004). In addition, we observed that melatonin treatment was associated with greater parasympathetic activity during sleep (VLF 15.5 ± 0.1 vs 15.1 ± 0.1, p = 0.010) and in sleep-wake differences in MCI patients (VLF 0.5 ± 0.1 vs 0.2 ± 0.0, p = 0.004).Conclusion: These preliminary findings hint at a possible sleep-related parasympathetic vulnerability in patients at prodromal stages of dementia as well as a potential protective effect of exogenous melatonin in this population.Keywords: heart rate variability, actigraphy, circadian rhythms, wavelet

Use of DGT to measure cadmium speciation in solutions with synthetic and natural ligands : comparison with model predictions.

The performance of the technique of diffusive gradients in thin films (DGT) was characterized in well-defined systems containing cadmium with chloride and nitrate ions, simple organic ligands (nitrilotriacetic acid and diglycolic acid), and Suwannee river fulvic acid for the pH range 5−8. Cd was fully labile in all Cd, Cl-, and NO3- solutions tested (I = 0.1 and 0.01 M), even at very low Cd concentrations (10 nM), consistent with there being no binding of Cd to the diffusive gel. Diffusion coefficients of Cd−nitritotriacetic acid (NTA) and Cd−diglycolic acid (DGA) species were measured and found to be ca. 25−30% lower than the equivalent coefficient for free metal ions. These values were used to calculate concentrations of labile Cd from DGT measurements in solutions of Cd with NTA or DGA. Cd−NTA and Cd−DGA species were found to be fully DGT-labile. DGT devices that used a diffusive gel with a reduced pore size, which retarded the passage of fulvic acid species through the gel, were used to estimate the proportion of Cd complexed by fulvic acid. These results were compared with predictions of the solution speciation from models with default parameter values. ECOSAT, incorporating the NICA−Donnan model, correctly predicted the magnitude of the binding and its pH dependence, while predictions from WHAM V (with humic ion binding model V) and WHAM 6 (with humic ion binding model VI) were less satisfactory at predicting the pH dependence. Reasonable fits to the data could be obtained from WHAM 6 when the effective binding constant log KMA was changed from 1.6 to 1.5, the value of ΔLK1 from 2.8 to 1.0 to minimize the dependence on pH, and the value of ΔLK2 from 1.48 to1.0 to decrease the strength of the strong bidentate and tridentate binding sites

Zeolite- and MgO-Supported Molecular Iridium Complexes: Support and Ligand Effects in Catalysis of Ethene Hydrogenation and H-D Exchange in the Conversion of H2 + D2

[EN] Zeolite- and MgO-supported mononuclear iridium diethene complexes were formed by the reaction of Ir(C2H4)2(acac) (acac = acetylacetonate, C5H7O2¿) with each support. Changes in the ligand environment of the supported iridium complexes were characterized by infrared, X-ray absorption near edge structure, and extended X-ray absorption fine structure spectroscopies as various mixtures of H2, C2H4, and CO flowed over the samples. In contrast to the nonuniform metal complexes anchored to metal oxides, our zeolite-supported metal complexes were highly uniform, allowing precise determinations of the chemistry, including the role of the support as a macroligand. Zeolite- and MgO-supported Ir(C2H4)2 complexes are each rapidly converted to Ir(CO)2 upon contact with a pulse of CO, and the ¿CO frequencies indicate that the iridium is more electron-deficient when the support is the zeolite. The Ir(CO)2 complex supported on MgO was highly stable in the presence of various combinations of CO, C2H4, and helium. In contrast, the zeolite-supported Ir(CO)2 complex was found to be highly reactive, forming Ir(CO)3, Ir(CO)(C2H4), Ir(CO)2(C2H4), and Ir(CO)(C2H4)2. The ¿-bonded ethene ligands of the zeolite-supported Ir(C2H4)2 in H2 were facilely converted to ¿-bonded ethyl when treated. However, the stability of the ethene ligands was markedly increased when the support was changed to MgO or when a CO ligand was simultaneously bonded to the iridium. The rates of catalytic ethene hydrogenation and H2/D2 exchange in the presence of a catalyst initially consisting of Ir(C2H4)2 on the zeolite were found to be more than an order of magnitude higher than when MgO was the support. The iridium complexes containing one or more CO ligands were found to be inactive for H2/D2 exchange reactions when the support was MgO, but they were moderately active when it was the zeolite. The effects of the MgO and zeolite supports on reactivity and catalytic activity are attributed to their differences as ligands donating or withdrawing electrons, respectively.Lu, J.; Serna Merino, PM.; Gates, BC. (2011). Zeolite- and MgO-Supported Molecular Iridium Complexes: Support and Ligand Effects in Catalysis of Ethene Hydrogenation and H-D Exchange in the Conversion of H2 + D2. ACS CATALYSIS. 1(11):1549-1561. doi:10.1021/cs200397rS1549156111