65 results on '"Valdes, D."'
Search Results
2. Experimental and numerical evaluation of multi-pass scratch on borided ARMCO iron
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Vidal-Torres, J., Ocampo-Ramírez, A., Rodríguez-Castro, G.A., Fernández-Valdés, D., Meneses-Amador, A., and Campos-Silva, I.
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- 2024
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3. Evaluation of adhesive damage in a nitrided stainless steel under cyclic contact loading
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Fernández-Valdés, D., Vidal-Torres, J., López-Liévano, A., Meneses-Amador, A., López-García, C., and Rodríguez-Castro, G.A.
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- 2023
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4. Competitive growth of Sb2Se3 and GeSe2 crystals in pseudobinary (GeSe2)x(Sb2Se3)1-x glass-forming materials
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Barták, J., Valdés, D., Martinková, S., Shánělová, J., and Koštál, P.
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- 2023
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5. Experimental and numerical evaluation of the contact fatigue resistance of AlCrN, FexN and AlCrN/FexN coatings on AISI 4140 steel
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Ballesteros-Arguello, A., Ramírez-Reyna, F.O., Rodríguez-Castro, G.A., Meneses-Amador, A., Fernández-Valdés, D., and Reyes-Carcaño, O.
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- 2021
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6. A numerical-experimental study of AISI 316L borided steels under cyclic contact loading
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Fernández-Valdés, D., Vasquez-De la Rosa, O., Rodríguez-Castro, G.A., Meneses-Amador, A., López-Liévano, A., and Ocampo-Ramírez, A.
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- 2021
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7. Use of liver grafts from cadaveric donors: Implementation impact of a local evaluation and procurement team in Mexico
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Zamora-Valdés, D., Leal-Leyte, P., Arvizu-Tachiquin, P.C., Cárdenas-Rodríguez, R.F., Ávila-Armendáriz, J.A., and Luévano-González, A.
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- 2021
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8. FEM-based evaluation of friction and initial imperfections effects on sandwich pipes local buckling
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Fernández-Valdés, D., Vázquez-Hernández, A.O., Ortega-Herrera, J.A., Ocampo-Ramírez, A., and Hernández, D.
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- 2020
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9. Standing contact fatigue behavior of nitrided AISI 316L steels
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Fernández-Valdés, D., Meneses-Amador, A., Rodríguez-Castro, G.A., Arzate-Vázquez, I., Campos-Silva, I., and Nava-Sánchez, J.L.
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- 2019
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10. Spatial organization of the impulse response in a karst aquifer
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Delbart, C., Valdés, D., Barbecot, F., Tognelli, A., and Couchoux, L.
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- 2016
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11. Spatial heterogeneity of high-resolution Chalk groundwater geochemistry – Underground quarry at Saint Martin-le-Noeud, France
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Barhoum, S., Valdès, D., Guérin, R., Marlin, C., Vitale, Q., Benmamar, J., and Gombert, P.
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- 2014
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12. Incisional Hernia: Plastic Aspects, Component Separation, Technical Details & Pediatrics
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Kenchadze, G., Pipia, I., Demetrashvili, Z., Botezatu, A., Marakutsa, E., Raileanu, R., Trischuk, V., Elzakaky, N., Elkayal, E., Shawky, A., Elgendi, A., Espinosa-De-Los-Monteros, A., Arista-De La Torre, L., Avendaño-Peza, H., Zamora-Valdes, D., Gomez-Arcive, Z., Elnecave-Olaiz, A., Yap, Y., Lee, H. J., Nallathamby, V., Ong, W. C., Lim, J., Lim, T. C., Dunn, R., Figy, S., Shkreta, A., Karam, A., Cahan, M., Shepetko, E., Fomin, P., Garmash, D., Kurbanov, A., Yanyuk, S., Kozak, Y., Fischer, J., Basta, M., Wink, J., Kovach, S., Szotek, P., Megha, R., Stanton, K., Ziegler, M., Fecher, A., Streib, E., Lysenko, R., Kryshchuk, N., Verhelst, J., de Goede, B., van Kempen, B. J. H., Langeveld, H. R., Kazemier, G., Lange, J. F., Wijnen, R. H. M., Lee, S., Shen, Y. M., Yang, S., Chen, J., Liu, S. J., Wang, M. G., Boume, M., Milhued-Agbolan, K. A., Akakpo-Numado, G. K., Tekou, H. A., Alkassem/Farhan, S., Yahya/Ibrahim, A., Algaddar, K., Shewrif, H., Salem, A., Ekheil, M., Akakpo-Numado, G., Boume, M. A., Mihluedo-Agbolan, K. A., Sanni, Y. S., Adabra, K., Tekou, H., Hounnou, G., Sogbo, D. H. O., Houessou, G. F., Bara, J. E., and Agossou-Voyeme, A. K.
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- 2015
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13. Sliding wear analysis in borided AISI 316L steels
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Fernández-Valdés, D., Meneses-Amador, A., López-Liévano, A., and Ocampo-Ramírez, A.
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- 2021
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14. Nutrient dynamics as indicators of karst processes: Comparison of the Chalk aquifer (Normandy, France) and the Edwards aquifer (Texas, U.S.A.)
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Mahler, B.J., Valdes, D., Musgrove, M., and Massei, N.
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- 2008
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15. Investigating transport properties and turbidity dynamics of a karst aquifer using correlation, spectral, and wavelet analyses
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Massei, N., Dupont, J.P., Mahler, B.J., Laignel, B., Fournier, M., Valdes, D., and Ogier, S.
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- 2006
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16. Endocannabinoid receptor CB2 in nonalcoholic fatty liver disease
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Mendez-Sanchez, N., Zamora-Valdes, D., Pichardo-Bahena, R., Barredo-Prieto, B., Ponciano-Rodriguez, G., Bermejo-Martínez, L., Chavez-Tapia, N. C., Baptista-González, H. A., and Uribe, M.
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- 2007
17. Characterization and analysis of polymorphs by near-infrared spectrometry
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Blanco, M, Valdés, D, Bayod, M.S, Fernández-Marı́, F, and Llorente, I
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- 2004
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18. NOX4 and TNF-α Govern and perpetuate the atherosclerotic damage in patients with chronic limb-threatening ischemia: Molecular insights from the ghas trial
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Valdés, D. Caicedo, Múgica, J. Devesa, and Villamarin, C. V. Álvarez
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- 2021
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19. Investigating possible links between the North Atlantic Oscillation 3 and rainfall variability in northwestern France 4 over the past 35 years
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Massei, Nicolas, Durand, A., Deloffre, Julien, Dupont, Jean-Paul, Valdes, D., Laignel, Benoît, Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), and Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)
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[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology - Abstract
In this paper, the temporal dynamics of precipitation in northwestern France in 8 relation to the dominant climatic pattern in Europe were investigated. The general trends 9 and the nonstationary behavior of the North Atlantic Oscillation (NAO) were described 10 using fractal analysis and Fourier spectral and continuous wavelet analysis of a NAO 11 index time series over the 1865–2004 period. The 44-year and 8-year multidecadal 12 components showed a clear increasing power during the second half of the last century. 13 The possible link between rainfall variability and the NAO was then investigated. The 14 links between the NAO and rainfall were not as obvious, as NAO-like components were 15 not easily retrieved in the precipitation records: Relationships between the NAO and 16 rainfall were very likely at certain timescales but were not systematically very obvious. 17 For instance, the characteristic quasi-biennal oscillation (QBO) of the NAO was barely 18 detected in precipitation, but a 6-year fluctuation beginning in the 90s was found to be 19 statistically significant at a 95% confidence limit After investigating a possible link 20 with the Southern Oscillation Index, the occurrence of this fluctuation in the beginning of 21 the 90s could be related to the observed shift of the QBO toward slightly higher 22 frequencies in the NAO time series. On the other hand, a modulation of the QBO by a 23 6-year interannual fluctuation would suggest the existence of a 6-year climate pattern 24 that could affect precipitation and, to a lesser extent, the NAO. Cross-wavelet analysis 25 between the NAO and precipitation revealed a loss in correlation across the 1970–2005 26 period, which seemed to be the fact of a QBO-like fluctuation. This loss of correlation 27 was related to the above-mentioned shift of the QBO and 6-year rainfall interannual 28 band since the 90s.
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- 2007
20. Azimuth-dependent Auger neutralization of He+ on Ag(111) and (110) surfaces
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Valdes, D., Blanco, J.M., Esaulov, V.A., Monreal, R.C., Geurts, Mireille, Laboratoire des collisions atomiques et moléculaires (LCAM), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Département de Physique, and Universidad Autonoma de Madrid (UAM)
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ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2007
21. Investigating of karst hydrodynamics and organization using autocorrelations and T- Curves
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Valdes, D., Dupont, Jean-Paul, Massei, Nicolas, Laignel, Benoît, Rodet, J., Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), and Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)
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resuspension ,autocorrelation ,dissolved phase ,Transport ,Karst ,suspended solids ,[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology ,deposition - Published
- 2006
22. Investigation of karst hydrodynamics and organization using autocorrelations and T-[Delta]C curves, Journal of Hydrology
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Valdes, D., Dupont, Jean-Paul, Massei, Nicolas, Laignel, Benoît, Rodet, J., Casado-Malaizé, Valérie, Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), and Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS)
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[SDU.STU.GM] Sciences of the Universe [physics]/Earth Sciences/Geomorphology ,[SDU.STU.GM]Sciences of the Universe [physics]/Earth Sciences/Geomorphology - Abstract
International audience; In karst systems, rain events often result in a decrease in conductivity (a tracer of dissolved phase transport) and an increase in turbidity (a tracer of suspended solids transport) at wells and springs. We investigated the response to rain events at five karst outlets (three springs and two wells) discharging from the cretaceous chalk aquifer of the Haute-Normandie region, France. As the input signal (rainfall) is relatively homogeneous spatially, the differences in the responses at the sites provide information on the internal organization of the karst systems and their hydrodynamic functioning. We used autocorrelation functions and turbidity-conductivity (T-[Delta]C) hysteresis curves to analyze the responses. At short time scales, autocorrelation functions allow estimation of the inertia of the conduit flow system. The T-[Delta]C curves reflect the processes of deposition, resuspension, and direct transport of suspended solids within the karst network. The results show that: (i) a long memory effect for conductivity indicates storage of water in the karst network and deposition of suspended solids, and the transport of the dissolved phase and suspended solids is not the same; (ii) a short memory effect for conductivity indicates that transport of the dissolved phase and suspended solids is synchronous and direct. On the basis of the results at the five sites, we propose three conceptual models of hydrodynamic functioning.
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- 2006
23. Role of d-electrons in Auger neutralization at metal surfaces
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Valdes, D., Blanco, J.M., Esaulov, V.A., Monreal, R.C., Laboratoire des collisions atomiques et moléculaires (LCAM), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Département de Physique, Universidad Autonoma de Madrid (UAM), and Geurts, Mireille
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ComputingMilieux_MISCELLANEOUS - Abstract
International audience
- Published
- 2006
24. Late Choledochojejunostomy Dysfunction After Liver Transplantation for Primary Sclerosing Cholangitis
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Zamora-Valdes, D., Rosen, C.B., Heimbach, J.K., and Taner, T.
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- 2016
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25. Investigating possible links between the North Atlantic Oscillation and rainfall variability in northwestern France over the past 35 years.
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Massei, N., Durand, A., Deloffre, J., Dupont, J. P., Valdes, D., and Laignel, B.
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- 2007
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26. PAF receptor and PAF acetylhydrolase expression in the endosalpinx of the human Fallopian tube: possible role of embryo-derived PAF in the control of embryo transport to the uterus.
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Velasquez, L. A., Maisey, K., Fernandez, R., Valdes, D., Cardenas, H., Imarai, M., Delgado, J., Aguilera, J., and Croxatto, H. B.
- Abstract
Background: Prostaglandin-E(2) and platelet-activating factor (PAF) are embryonic-derived signals that time embryo passage into the uterus in the mare and hamster respectively. PAF-like activity is detectable in the spent media of preimplantation human embryos and it has been suggested that PAF may be the embryonic signal that controls embryo transport to the uterus in our species. The actions of PAF are regulated at the level of its synthesis and degradation as well as the expression of a specific cell surface receptor (PAFr). The enzyme PAF acetylhydrolase (PAF-AH) degrades PAF. This study was undertaken to examine whether or not PAFr and PAF-AH are expressed in the human Fallopian tube and to identify the cell types in which they are expressed.Methods: The presence of PAFr mRNA in tissue extracts was investigated using reverse transcription-polymerase chain reaction. We amplified the predicted amplicon for PAFr mRNA from RNA samples extracted from Fallopian tubes. The expression of PAF-AH was detected by Western blot and the localization of PAFr and PAF-AH proteins was detected by immunohistochemistry.Results: Utilizing antibodies against PAFr and PAF-AH, co-localization of the two proteins in the epithelium and stromal cells were demonstrated.Conclusions: These observations show that the human Fallopian tube expresses PAFr and PAF-AH at a location compatible with the proposed paracrine role of early embryo-derived PAF. [ABSTRACT FROM AUTHOR]- Published
- 2001
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27. Transfer of trace organic compounds in an operational soil-aquifer treatment system assessed through an intrinsic tracer test and transport modelling.
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Guillemoto, Q., Picot-Colbeaux, G., Valdes, D., Devau, N., Mathurin, F.A., Pettenati, M., Kloppmann, W., and Mouchel, J.-M.
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- 2022
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28. Investigation of young water inflow in karst aquifers using SF6–CFC–3H/He–85Kr–39Ar and stable isotope components.
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Delbart, C., Barbecot, F., Valdes, D., Tognelli, A., Fourre, E., Purtschert, R., Couchoux, L., and Jean-Baptiste, P.
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KARST , *STABLE isotope analysis , *AQUIFERS , *WATER transfer , *SULFUR hexafluoride , *CHLOROFLUOROCARBONS , *GEOCHEMISTRY - Abstract
Karst aquifers are known for their wide distribution of water transfer velocities. From this observation, a multiple geochemical tracer approach seems to be particularly well suited to provide a significant assessment of groundwater flows, but the choice of adapted tracers is essential. In this study, several common tracers in karst aquifers such as physicochemical parameters, major ions, stable isotopes, and δ 13 C to more specific tracers such as dating tracers – 14 C, 3 H, 3 H– 3 He, CFC-12, SF 6 and 85 Kr, and 39 Ar – were used, in a fractured karstic carbonated aquifer located in Burgundy (France). The information carried by each tracer and the best sampling strategy are compared on the basis of geochemical monitoring done during several recharge events and over longer time periods (months to years). This study’s results demonstrate that at the seasonal and recharge event time scale, the variability of concentrations is low for most tracers due to the broad spectrum of groundwater mixings. The tracers used traditionally for the study of karst aquifers, i.e., physicochemical parameters and major ions, efficiently describe hydrological processes such as the direct and differed recharge, but require being monitored at short time steps during recharge events to be maximized. From stable isotopes, tritium, and Cl − contents, the proportion of the fast direct recharge by the largest porosity was estimated using a binary mixing model. The use of tracers such as CFC-12, SF 6 , and 85 Kr in karst aquifers provides additional information, notably an estimation of apparent age, but they require good preliminary knowledge of the karst system to interpret the results suitably. The CFC-12 and SF 6 methods efficiently determine the apparent age of baseflow, but it is preferable to sample the groundwater during the recharge event. Furthermore, these methods are based on different assumptions such as regional enrichment in atmospheric SF 6 , excess air, and flow models among others. 85 Kr and 39 Ar concentrations can potentially provide a more direct estimation of groundwater residence time. Conversely, the 3 H– 3 He method is inefficient in the karst aquifer for dating due to 3 He degassing. [ABSTRACT FROM AUTHOR]
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- 2014
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29. Gallium oxide (Ga2O3) energy dependent scintillation response to fast neutrons and flash gamma-rays.
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Valdes DJ, Miller S, Leak C, Haque S, Gunthoti K, Wender SA, Paneru S, Lee HY, Vogel SC, and Sun KX
- Abstract
Gallium oxide is a newly emerged ultrawide bandgap (4.9 eV) semiconductor that is suitable as a combined electronics and radiation detection platform. We have experimentally demonstrated fast neutron and gamma-ray scintillation from Czochralski-grown β-Ga2O3 in a recent series (October 2023) of experiments at the unmoderated pulsed neutron spallation source located at the Los Alamos Neutron Science Center. Using the neutron time-of-flight (TOF) technique and a fast-gated intensified CCD camera, we observed energy-dependent neutron scintillation for neutron energies ranging from 1 to 400 MeV, including the 14.1 MeV neutron energy relevant to D-T fusion. Neutron flux is quantified and calibrated by cascading the scintillator after the fission chamber, enabling a detailed analysis of temporal and energy-dependent characteristics of the scintillation events. A pronounced scintillation signal from the spallation gamma flash with a temporal full width of half maximum of ∼4 ns is indicative of the material's rapid response. Neutron energy dependent scintillation is observed using the TOF method at a 22.6-m distance from the neutron source. These results highlight the possibility of developing a Ga2O3 based fusion neutron diagnostic platform integrated with both scintillation and electronics functions on the integrated chip scale., (© 2024 Author(s). Published under an exclusive license by AIP Publishing.)
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- 2024
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30. A retrospective study suggests 55 days of persistence of SARS-CoV-2 during the first wave of the pandemic in Santiago de Chile.
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Acuña-Castillo C, Vidal M, Vallejos-Vidal E, Luraschi R, Barrera-Avalos C, Inostroza-Molina A, Molina-Cabrera S, Valdes D, Schafer C, Maisey K, Imarai M, Vera R, Vargas S, Rojo LE, Leiva-Salcedo E, Escobar A, Reyes-Cerpa S, Gaete A, Palma-Vejares R, Travisany D, Torres C, Reyes-López FE, and Sandino AM
- Abstract
Background: As the COVID-19 pandemic persists, infections continue to surge globally. Presently, the most effective strategies to curb the disease and prevent outbreaks involve fostering immunity, promptly identifying positive cases, and ensuring their timely isolation. Notably, there are instances where the SARS-CoV-2 virus remains infectious even after patients have completed their quarantine., Objective: Understanding viral persistence post-quarantine is crucial as it could account for localized infection outbreaks. Therefore, studying and documenting such instances is vital for shaping future public health policies., Design: This study delves into a unique case of SARS-CoV-2 persistence in a 60-year-old female healthcare worker with a medical history of hypertension and hypothyroidism. The research spans 55 days, marking the duration between her initial and subsequent diagnosis during Chile's first COVID-19 wave, with the analysis conducted using RT-qPCR., Results: Genomic sequencing-based phylogenetic analysis revealed that the SARS-CoV-2 detected in both Nasopharyngeal swab samples (NPSs) was consistent with the 20B clade of the Nextstrain classification, even after a 55-day interval., Conclusion: This research underscores the need for heightened vigilance concerning cases of viral persistence. Such instances, albeit rare, might be pivotal in understanding sporadic infection outbreaks that occur post-quarantine., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Published by Elsevier Ltd.)
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- 2024
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31. A content analysis on the perceptions of LGBTQ+ (centred) health care on Twitter.
- Author
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Van Diepen C and Rosales Valdes D
- Subjects
- Humans, Disclosure, Delivery of Health Care, Social Media, Sexual and Gender Minorities
- Abstract
Background: LGBTQ+ individuals have experienced many barriers to receiving quality health care, but the worldwide implementation of person-centred care should make a positive change. However, as forthright disclosures are difficult to find using traditional methods, novel approaches should be utilized to uncover opinions and experiences on LGBTQ+ health care. Twitter could be a place where people post on this topic., Aim: This study aimed to explore tweets mentioning LGBTQ+ (centred) health care., Methods: The methods consisted of an explorative qualitative content analysis of tweets. The tweets were collected between 26 February and 30 March 2021, resulting in 2524 tweets of which 659 were relevant for content analysis., Results: The results showed an excess of political tweets involving LGBTQ+ health care. Many tweets included general statements on the need for LGBTQ+ health care. The few tweets on personal experiences in LGBTQ+ health care showed the overwhelming need for quality care that has been made difficult by political developments., Conclusion: Most tweets were made to inform others of the necessity of quality health care for LGBTQ+ individuals, but the utilization of person-centred care is hardly noticeable., Public Contribution: This study was conducted with the involvement of a public partner (second author) who contributed to the design, data analyses and writing of the paper. Moreover, this study involves the analysis of data provided by the public and published on social media., (© 2022 The Authors. Health Expectations published by John Wiley & Sons Ltd.)
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- 2022
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32. Epidemiological characteristics of Omicron and Delta SARS-CoV-2 variant infection in Santiago, Chile.
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Mella-Torres A, Escobar A, Barrera-Avalos C, Vargas-Salas S, Pirazzoli M, Gonzalez U, Valdes D, Rojas P, Luraschi R, Vallejos-Vidal E, Imarai M, Sandino AM, Reyes-López FE, Vera R, and Acuña-Castillo C
- Subjects
- Humans, Chile epidemiology, Pandemics, SARS-CoV-2, COVID-19 epidemiology
- Abstract
The variant of concern (VOC) SARS-CoV-2 Omicron (B.1.1529) has been described as a highly contagious variant but less virulent than the current variant being monitored (VBM) Delta (B.1.617.2), causing fewer cases of hospitalizations, symptomatology, and deaths associated with COVID-19 disease. Although the epidemiological comparison of both variants has been previously reported in other countries, no report indicates their behavior and severity of infection in Chile. In this work, we report for the first time the effect of the Omicron and Delta variants in a cohort of 588 patients from the Hospital de Urgencia Asistencia pública (HUAP), a high-complexity health center in Santiago, Chile. This report is framed at the beginning of Chile's third wave of the COVID-19 pandemic, with a marked increase in the Omicron variant and a decrease in the circulating Delta variant. Our results indicated a similar proportion of patients with a complete vaccination schedule for both variants. However, the Delta variant was associated with a higher prevalence of hospitalization and more significant symptomatology associated with respiratory distress. On the other hand, our data suggest that vaccination is less effective in preventing infection by the Omicron variant. This antecedent, with a low severity but high contagiousness, suggests that the Omicron variant could even collapse the primary health care service due to the high demand for health care., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Mella-Torres, Escobar, Barrera-Avalos, Vargas-Salas, Pirazzoli, Gonzalez, Valdes, Rojas, Luraschi, Vallejos-Vidal, Imarai, Sandino, Reyes-López, Vera and Acuña-Castillo.)
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- 2022
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33. Socioeconomic differences in help seeking for colorectal cancer symptoms during COVID-19.
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Sexton V, Dale J, Hillman S, Hoverd E, Leach H, MacGregor B, McLoughlin B, Paule A, Shariff Z, Spencer R, Thomas N, Valdes D, Watson E, Navarathnage SW, and Atherton H
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- Humans, Patient Acceptance of Health Care, Qualitative Research, Socioeconomic Factors, United Kingdom, COVID-19, Colorectal Neoplasms diagnosis
- Published
- 2022
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34. Global evidence on the rapid adoption of telemedicine in primary care during the first 2 years of the COVID-19 pandemic: a scoping review protocol.
- Author
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Valdes D, Alqazlan L, Procter R, and Dale J
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- Communicable Disease Control, Humans, Pandemics prevention & control, Primary Health Care, Review Literature as Topic, COVID-19 epidemiology, Telemedicine
- Abstract
Background: Before the declaration of the COVID-19 pandemic in March 2020, primary care in most countries relied on face-to-face consultations, with relatively limited use of telemedicine. Lockdowns and social distancing measures during the early stages of the pandemic led to rapid, widely spread telemedicine adoption in healthcare settings. The rapid uptake that occurred following the onset of these pandemic-induced measures in countries such as the UK, Canada and New Zealand prompts questions around the drivers, extent and sustainability of this transformation in clinical practice at the global level, as the research in this area is still emerging. The purpose of this scoping review is to explore the global evidence surrounding the rapid adoption of telemedicine in primary care settings during the first 2 years of the COVID-19 pandemic through three lenses: patient experience, health inequalities and patient-clinician trust, with the purpose of identifying elements contributing to the sustainability of this innovation., Methods: A draft protocol was tested through an initial search on Ovid Medline, Web of Science and Google Scholar with additional searches on the Cochrane Database. This informed the final selection of terms which will be used to search Ovid, Web of Science, Google Scholar, PROSPERO, Cochrane Library and others, filtering for studies from the pandemic declaration onwards. Additional grey literature reports will be sourced through simplified searches on Google in widely spoken languages. Duplicates will be removed by screening titles. Abstracts and grey literature text extracts will be screened based on pre-set eligibility criteria by two researchers. Abstracts (and extracts in the case of grey literature) will be mapped against the domains of the Non-adoption, Abandonment, and challenges to Scale-up, Spread and Sustainability (NASSS) framework by two researchers. Data will be presented in table format., Discussion: This review will map the current literature to identify current gaps in evidence related to the adoption of telemedicine after the declaration of the pandemic in March 2020. The use of simplified searches in the several spoken languages in the world is aimed at capturing more immediate non-academic reflections and experiences on this major service change at a global level., Systematic Review Registration: The study has been registered on Open Science Framework and can be accessed through the following URL: https://osf.io/4z5ut/., (© 2022. The Author(s).)
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- 2022
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35. First Identification of Reinfection by a Genetically Different Variant of SARS-CoV-2 in a Homeless Person from the Metropolitan Area of Santiago, Chile.
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Acuña-Castillo C, Vidal M, Inostroza-Molina A, Vallejos-Vidal E, Luraschi R, Figueroa M, Barrera-Avalos C, Vera R, Vargas S, Valdes D, Maisey K, Imarai M, Leiva-Salcedo E, Escobar A, Reyes-Cerpa S, Gaete A, Palma-Vejares R, Travisany D, Rojo LE, Reyes-López FE, and Sandino AM
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- COVID-19 Testing, Chile epidemiology, Humans, Pandemics, Reinfection, SARS-CoV-2 genetics, COVID-19 epidemiology, Ill-Housed Persons
- Abstract
The identification and tracking of SARS-CoV-2 infected patients in the general population are essential components of the global strategy to limit the COVID-19 viral spread, specifically for maintaining traceability and suppressing the resurgence of local outbreaks. Public health programs that include continuous RT-qPCR testing for COVID-19 in the general population, viral sequencing, and genomic surveillance for highly contagious forms of the virus have allowed for the identification of SARS-CoV-2 infections and reinfections. This work identified SARS-CoV-2 reinfection in a homeless person, which occurred 58 days after the first COVID-19 diagnosis. Genomic sequencing identified a different Nextstrain classification clade (20A and 20B) and PANGO lineage, with a divergence of 4 single nucleotide variants (SNVs) in S and ORF1ab genes, suggesting reinfection by different viral variants. This study is the first from the great metropolitan area of Santiago, Chile, one of the top ten countries in the world to live during the COVID-19 pandemic. We support the importance of performing intensive genomic surveillance programs in the whole population and high-risk groups, such as homeless people, nearly 20 thousand people in Chile, and have limited access to health care services and poor viral traceability., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Claudio Acuña-Castillo et al.)
- Published
- 2022
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36. Living Donor Liver Transplantation for Perihilar Cholangiocarcinoma: Outcomes and Complications.
- Author
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Tan EK, Rosen CB, Heimbach JK, Gores GJ, Zamora-Valdes D, and Taner T
- Subjects
- Adult, Cholangiocarcinoma diagnosis, Female, Follow-Up Studies, Graft Survival, Humans, Incidence, Male, Middle Aged, Retrospective Studies, United States epidemiology, Bile Duct Neoplasms surgery, Cholangiocarcinoma surgery, Liver Transplantation methods, Living Donors, Postoperative Complications epidemiology
- Abstract
Background: Neoadjuvant therapy and liver transplantation is an effective treatment for perihilar cholangiocarcinoma (pCCA). Living donor liver transplantation (LDLT) addresses the problem of organ shortage, but has higher risk of technical complication that can be aggravated by radiotherapy. We investigated the incidence of vascular and biliary complication in pCCA compared with non-pCCA patients and their impact on patient and graft survival., Study Design: All consecutive LDLTs (n = 247) performed between 2000 and 2017 were reviewed, including demographics, donor variables, operative details, and postoperative outcomes. Logistic regression models were used to investigate the relationship between variables and outcomes., Results: Seventy-four LDLTs (30.0%) were performed for pCCA and 173 for other indications. Forty-nine patients (66.2%) had primary sclerosing cholangitis-associated pCCA; the remainder had de novo pCCA. LDLT for pCCA was associated with nonstandard arterial (p = 0.001) or portal vein reconstruction (p < 0.001) and Roux-en-Y choledochojejunostomy (p < 0.001). The incidence of early hepatic artery thromboses was similar (5.4% vs 7.6%; p = 0.54). Late hepatic artery (18.9% vs 4.1%; p < 0.001) and portal vein (37.8% vs 8.7%; p < 0.001) complication was more common in the pCCA group. Anastomotic biliary complications occurred in 39.2% vs 54.1% (p = 0.032) of patients. Overall survival for pCCA at 1, 5, and 10 years was 84.9%, 66.5%, and 55.6%, respectively. Cancer recurred in 12.3%. Residual tumor on explant prognosticated inferior survival (hazard ratio 5.69; 95% CI, 1.97 to 16.35) and vascular and biliary complications did not., Conclusions: Late vascular complication is common after LDLT for pCCA, but do not adversely affect long-term survival. LDLT provides excellent survival, particularly for patients with no residual disease at the time of transplantation., (Copyright © 2020 American College of Surgeons. Published by Elsevier Inc. All rights reserved.)
- Published
- 2020
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37. Rapid SPE - LC MS/MS analysis for atrazine, its by-products, simazine and S metolachlor in groundwater samples.
- Author
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Blanchoud H, Alliot F, Chen N, and Valdes D
- Abstract
A rapid analysis of pesticides using on-line Solid phase extraction LC MS/MS (Agilent Technology) was performed using only 2-mL water samples. SPE cartridge PLRP-s was used for the pre-concentration sample with methanol elution in back flush. Sensitive transitions and mass spectrometry conditions were optimized by direct infusion of individual standard solutions in a positive electrospray mode. Water samples were spiked with internal standards to compensate the matrix effect. The limit of quantification was calculated to be 20 ng L
-1 using the standard deviation of blank analysis injected ten times and uncertainties were estimated at less than 20% on concentrations. This method was validated to study leaching water samples for which only small quantities of water were available.•Only 2 mL water sample was used.•Samples were filtered at 0.2 µm and spiked with individual standard.•Compounds were separated in an 18.5-min elution time using the dynamic MRM program., Competing Interests: Authors declare no conflict of interest., (© 2020 The Authors. Published by Elsevier B.V.)- Published
- 2020
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38. Transfer and degradation of the common pesticide atrazine through the unsaturated zone of the Chalk aquifer (Northern France).
- Author
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Chen N, Valdes D, Marlin C, Ribstein P, Alliot F, Aubry E, and Blanchoud H
- Subjects
- Atrazine analysis, France, Groundwater chemistry, Lakes analysis, Nitrates analysis, Atrazine analogs & derivatives, Herbicides analysis, Pesticides analysis, Water Pollutants, Chemical analysis
- Abstract
Groundwater in the Chalk aquifer is an important water resource whose quality has degraded due to fertilizer and pesticide use. Atrazine, classified as a priority substance, has been one of the most applied pesticides and also one of the most frequently detected pesticides in groundwater. The present study investigated the transfer and degradation of atrazine in the unsaturated zone of the Chalk aquifer in Northern France. The study was conducted in an underground quarry (Saint-Martin-le-Noeud), which provides a direct access to the water table and intercepts the unsaturated zone at different depths. The lake and the ceiling percolation of 16 sites throughout the quarry were followed. For 16 sites, the percolating flow rate and lake level were measured and the lake water was sampled for nitrate, atrazine and deethylatrazine (DEA, main degradation product of atrazine) analysis over 2.5 years. High spatial variations in hydrodynamics (percolating flow rate and lake level) and in lake water quality (atrazine between 55±11 and 202±40 ng L
-1 and DEA between 269±53 and 1727±345 ng L-1 ) indicate that the properties of the unsaturated zone influence the transfer and the degradation of atrazine. A counterclockwise hysteresis characterizes the relationship between the lake level and atrazine concentration. Temporal variation shows that the atrazine is transferred through the matrix and fractures with a delay caused by the sorption process that differs in atrazine and DEA. The layer of clay-with-flints is shown to favor the degradation of atrazine near the surface. Preferential pathways may be created below clay-with-flints, through which the transfer of atrazine is quicker., (Copyright © 2019 Elsevier Ltd. All rights reserved.)- Published
- 2019
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39. Water, nitrate and atrazine transfer through the unsaturated zone of the Chalk aquifer in northern France.
- Author
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Chen N, Valdes D, Marlin C, Blanchoud H, Guerin R, Rouelle M, and Ribstein P
- Abstract
The water quality of the Chalk aquifer is degrading due to fertilizers and pesticides use which are classified as toxic to public health. The study aims to provide a better understanding of the transfer processes in the unsaturated zone of the Chalk aquifer using different environmental tracers (nitrate, atrazine and tritium). The study was conducted in an underground quarry in northern France (St. Martin le Noeud). The quarry provides direct access to the lower part of the unsaturated zone of the Chalk at a depth of 18-30 m. Fifteen sites throughout the quarry display percolation directly from the unsaturated zone. Since percolation intensity is heterogeneous at one site, a comparison was made between the variation of geochemical properties of ten samples from one site and the spatial variation of samples from 15 sites throughout the quarry. Using the Siegel-Tukey and Wilcoxon tests, we found that the variation between the sites is higher than the variation within one site. Therefore, one percolation sample can be used to represent one site. The transfer time of nitrate and atrazine is estimated based on its use in the cultivated fields. Pore water with no contamination indicates water infiltrated before the use of contaminants at the surface, and pore water with a high concentration of contaminants indicates water infiltrated during the use of contaminants at the surface. The transfer time of water molecules is estimated using the time series of tritium. Transfer velocities were computed for each environmental tracer (nitrate, atrazine and tritium) by dividing the estimated transfer time by the depth of each site. Two transfer velocity ranges are determined: (1) <0.32 ± 0.02 m/year and (2) between 0.72 ± 0.14 and 2.15 ± 0.43 m/year, showing most water transfer through the matrix but also a mixture of water with different velocities., (Copyright © 2018 Elsevier B.V. All rights reserved.)
- Published
- 2019
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40. Long-term outcomes of patients undergoing simultaneous liver transplantation and sleeve gastrectomy.
- Author
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Zamora-Valdes D, Watt KD, Kellogg TA, Poterucha JJ, Di Cecco SR, Francisco-Ziller NM, Taner T, Rosen CB, and Heimbach JK
- Subjects
- Adult, Aged, Body Mass Index, Body Weight, Female, Follow-Up Studies, Gastrectomy adverse effects, Humans, Liver Diseases epidemiology, Liver Diseases etiology, Liver Transplantation methods, Male, Middle Aged, Obesity complications, Quality of Life, Survival Rate, Treatment Outcome, Weight Loss, Gastrectomy methods, Liver Transplantation adverse effects, Obesity surgery, Weight Reduction Programs methods
- Abstract
Obesity is increasingly common before and after liver transplantation (LT), yet optimal management remains unclear. The aim of this study was to analyze the long-term outcomes for obese patients undergoing LT, including a noninvasive weight loss program and combined LT and sleeve gastrectomy (SG). Since 2006, all patients referred for LT with a body mass index (BMI) ≥35 kg/m
2 were enrolled. Patients who achieved weight loss (BMI <35) underwent LT alone, and those who did not underwent simultaneous LT + SG. Analysis of long-term outcomes for patients ≥3 years posttransplant was performed. Since 2006, there were 36 in the weight loss intervention (LT cohort) and 13 in the LT + SG cohort with >3 years of follow-up, whereas overall, a total of 29 patients underwent LT + SG. Patients in the LT cohort had less severe obesity at enrollment (40.0 ± 2.7 vs. LT + SG cohort 46.0 ± 4.5; P < 0.001). In the LT cohort, 83.3% (30 of 36) achieved >10% loss in total body weight (TBW) pre-LT. Three years posttransplant, 29.4% of patients in the LT cohort maintained >10% loss in TBW, whereas 100% of the LT + SG patients did (P < 0.001). Patients who underwent LT + SG maintained a significantly higher percentage of total body weight loss after 3 years of follow-up (LT cohort 3.9 ± 13.3% vs. LT + S G cohort 34.8 ± 17.3%; P < 0.001). Patients in the LT + SG also had a lower prevalence of hypertension, insulin resistance, and hepatic steatosis and required fewer antihypertensive medications and lipid agents at last follow-up., Conclusion: Whereas weight loss before transplantation was achieved by obese patients, weight regain was common in the LT cohort. Combined LT + SG resulted in more effective and more durable weight loss, as well as fewer metabolic complications at last follow-up. (Hepatology 2018)., (© 2018 by the American Association for the Study of Liver Diseases.)- Published
- 2018
- Full Text
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41. Mobile Decision Support Tool for Emergency Departments and Mass Casualty Incidents (EDIT): Initial Study.
- Author
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Boltin N, Valdes D, Culley JM, and Valafar H
- Abstract
Background: Chemical exposures pose a significant threat to life. A rapid assessment by first responders and emergency nurses is required to reduce death and disability. Currently, no informatics tools exist to process victims of chemical exposures efficiently. The surge of patients into a hospital emergency department during a mass casualty incident creates additional stress on an already overburdened system, potentially placing patients at risk and challenging staff to process patients for appropriate care and treatment efficacy. Traditional emergency department triage models are oversimplified during highly stressed mass casualty incident scenarios in which there is little margin for error. Emerging mobile technology could alleviate the burden placed on nurses by allowing the freedom to move about the emergency department and stay connected to a decision support system., Objective: This study aims to present and evaluate a new mobile tool for assisting emergency department personnel in patient management and triage during a chemical mass casualty incident., Methods: Over 500 volunteer nurses, students, and first responders were recruited for a study involving a simulated chemical mass casualty incident. During the exercise, a mobile application was used to collect patient data through a kiosk system. Nurses also received tablets where they could review patient information and choose recommendations from a decision support system. Data collected was analyzed on the efficiency of the app to obtain patient data and on nurse agreement with the decision support system., Results: Of the 296 participants, 96.3% (288/296) of the patients completed the kiosk system with an average time of 3 minutes, 22 seconds. Average time to complete the entire triage process was 5 minutes, 34 seconds. Analysis of the data also showed strong agreement among nurses regarding the app's decision support system. Overall, nurses agreed with the system 91.6% (262/286) of the time when it came to choose an exposure level and 84.3% (241/286) of the time when selecting an action., Conclusions: The app reliably demonstrated the ability to collect patient data through a self-service kiosk system thus reducing the burden on hospital resources. Also, the mobile technology allowed nurses the freedom to triage patients on the go while staying connected to a decision support system in which they felt would give reliable recommendations., (©Nicholas Boltin, Diego Valdes, Joan M. Culley, Homayoun Valafar. Originally published in JMIR Mhealth and Uhealth (http://mhealth.jmir.org), 22.06.2018.)
- Published
- 2018
- Full Text
- View/download PDF
42. Liver Transplant for Cholangiocarcinoma.
- Author
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Zamora-Valdes D and Heimbach JK
- Subjects
- Bile Duct Neoplasms etiology, Bile Duct Neoplasms therapy, Bile Ducts, Intrahepatic, Cholangiocarcinoma etiology, Cholangiocarcinoma therapy, Cholangitis, Sclerosing complications, Disease-Free Survival, Humans, Neoadjuvant Therapy, Survival Rate, Bile Duct Neoplasms surgery, Cholangiocarcinoma surgery, Liver Transplantation, Patient Selection
- Abstract
Liver transplant (LT) for perihilar cholangiocarcinoma (CCA) offers an opportunity for survival among patients with early-stage but anatomically unresectable disease. The 5-year survival rate after LT is 65% to 70%, higher among patients with primary sclerosing cholangitis, who are often diagnosed earlier, and lower among patients with de novo CCA. The results of LT for hilar CCA, along with recent limited data suggesting favorable survival among patients with very early intrahepatic CCA (ICC), have reignited interest in the subject. This article discusses LT following neoadjuvant therapy for CCA and the early data on LT alone for ICC., (Copyright © 2018 Elsevier Inc. All rights reserved.)
- Published
- 2018
- Full Text
- View/download PDF
43. Fighting Mortality in the Waiting List: Liver Transplantation in North America, Europe, and Asia.
- Author
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Zamora-Valdes D, Leal-Leyte P, Kim PT, and Testa G
- Subjects
- Age Factors, Asia, Donor Selection, End Stage Liver Disease diagnosis, Europe, Humans, Liver Transplantation adverse effects, Liver Transplantation mortality, Living Donors, North America, Risk Factors, Time Factors, Treatment Outcome, End Stage Liver Disease mortality, End Stage Liver Disease surgery, Health Services Accessibility, Liver Transplantation methods, Waiting Lists mortality
- Abstract
Liver disease is a major cause of mortality worldwide. Liver transplantation (LT) is the most effective treatment for end stage liver disease. Available resources and social circumstances have led to different ways of implementing LT around the world. The experience with pediatric LT corroborates the hypothesis that a combination of surgical strategies can be beneficial. The goal of this manuscript is to describe the strategies used by LT centers in North America, Europe and Asia and how these strategies can be applied to reduce waitlist mortality and increase access to LT.
- Published
- 2017
- Full Text
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44. Surgical Treatment of Hepatocellular Carcinoma.
- Author
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Zamora-Valdes D, Taner T, and Nagorney DM
- Subjects
- Carcinoma, Hepatocellular pathology, Female, Humans, Liver Neoplasms pathology, Male, Carcinoma, Hepatocellular surgery, Liver Neoplasms surgery
- Abstract
Hepatocellular carcinoma (HCC) is a major cause of cancer-related death worldwide. In select patients, surgical treatment in the form of either resection or transplantation offers a curative option. The aims of this review are to (1) review the current American Association for the Study of Liver Diseases/European Association for the Study of the Liver guidelines on the surgical management of HCC and (2) review the proposed changes to these guidelines and analyze the strength of evidence underlying these proposals. Three authors identified the most relevant publications in the literature on liver resection and transplantation for HCC and analyzed the strength of evidence according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) classification. In the United States, the liver allocation system provides priority for liver transplantation to patients with HCC within the Milan criteria. Current evidence suggests that liver transplantation may also be indicated in certain patient groups beyond Milan criteria, such as pediatric patients with large tumor burden or adult patients who are successfully downstaged. Patients with no underlying liver disease may also benefit from liver transplantation if the HCC is unresectable. In patients with no or minimal (compensated) liver disease and solitary HCC ≥2 cm, liver resection is warranted. If liver transplantation is not available or contraindicated, liver resection can be offered to patients with multinodular HCC, provided that the underlying liver disease is not decompensated. Many patients may benefit from surgical strategies adapted to local resources and policies (hepatitis B prevalence, organ availability, etc). Although current low-quality evidence shows better overall survival with aggressive surgical strategies, this approach is limited to select patients. Larger and well-designed prospective studies are needed to better define the benefits and limits of such approach.
- Published
- 2017
- Full Text
- View/download PDF
45. Cell-Autonomous and Non-Cell-Autonomous Regulation of a Feeding State-Dependent Chemoreceptor Gene via MEF-2 and bHLH Transcription Factors.
- Author
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Gruner M, Grubbs J, McDonagh A, Valdes D, Winbush A, and van der Linden AM
- Subjects
- Animals, Animals, Genetically Modified, Basic Helix-Loop-Helix Transcription Factors biosynthesis, Binding Sites, Caenorhabditis elegans genetics, Caenorhabditis elegans growth & development, Caenorhabditis elegans Proteins biosynthesis, Gene Expression Regulation, Developmental, Receptors, Neuropeptide biosynthesis, Receptors, Pituitary Hormone-Regulating Hormone biosynthesis, Sensory Receptor Cells metabolism, Signal Transduction genetics, Transcription Factors biosynthesis, Basic Helix-Loop-Helix Transcription Factors genetics, Caenorhabditis elegans Proteins genetics, Chemoreceptor Cells metabolism, Receptors, Neuropeptide genetics, Receptors, Pituitary Hormone-Regulating Hormone genetics, Transcription Factors genetics
- Abstract
Food and feeding-state dependent changes in chemoreceptor gene expression may allow Caenorhabditis elegans to modify their chemosensory behavior, but the mechanisms essential for these expression changes remain poorly characterized. We had previously shown that expression of a feeding state-dependent chemoreceptor gene, srh-234, in the ADL sensory neuron of C. elegans is regulated via the MEF-2 transcription factor. Here, we show that MEF-2 acts together with basic helix-loop-helix (bHLH) transcription factors to regulate srh-234 expression as a function of feeding state. We identify a cis-regulatory MEF2 binding site that is necessary and sufficient for the starvation-induced down regulation of srh-234 expression, while an E-box site known to bind bHLH factors is required to drive srh-234 expression in ADL. We show that HLH-2 (E/Daughterless), HLH-3 and HLH-4 (Achaete-scute homologs) act in ADL neurons to regulate srh-234 expression. We further demonstrate that the expression levels of srh-234 in ADL neurons are regulated remotely by MXL-3 (Max-like 3 homolog) and HLH-30 (TFEB ortholog) acting in the intestine, which is dependent on insulin signaling functioning specifically in ADL neurons. We also show that this intestine-to-neuron feeding-state regulation of srh-234 involves a subset of insulin-like peptides. These results combined suggest that chemoreceptor gene expression is regulated by both cell-autonomous and non-cell-autonomous transcriptional mechanisms mediated by MEF2 and bHLH factors, which may allow animals to fine-tune their chemosensory responses in response to changes in their feeding state.
- Published
- 2016
- Full Text
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46. Is There a Role for Desmopressin in Liver Transplantation? A Case Report.
- Author
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Gonzales MM, Valdes DZ, Helmick R, Taner T, and Vasdev G
- Subjects
- Humans, Liver blood supply, Liver drug effects, Liver Transplantation methods, Male, Middle Aged, Postoperative Hemorrhage etiology, Reperfusion Injury etiology, Deamino Arginine Vasopressin therapeutic use, Hemostatics therapeutic use, Liver Transplantation adverse effects, Postoperative Hemorrhage drug therapy, Reperfusion Injury drug therapy
- Abstract
Living donor liver transplantation reduces time and mortality on the waiting list. Bleeding is a serious complication; however, "overcorrection" of coagulopathy may lead to hepatic artery thrombosis. We report a case where desmopressin (DDAVP) was used in the management of persistent postreperfusion bleeding (44 red blood cell units transfused). After 1 dose of DDAVP, bleeding improved significantly and the recipient had an unremarkable recovery. DDAVP should be considered for persisting bleeding after correcting common coagulation abnormalities where complexity of the anastomosis may preclude the use of more aggressive procoagulant drugs in liver transplantation., (Copyright © 2015 Elsevier Inc. All rights reserved.)
- Published
- 2015
- Full Text
- View/download PDF
47. Growth hormone-releasing hormone agonists reduce myocardial infarct scar in swine with subacute ischemic cardiomyopathy.
- Author
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Bagno LL, Kanashiro-Takeuchi RM, Suncion VY, Golpanian S, Karantalis V, Wolf A, Wang B, Premer C, Balkan W, Rodriguez J, Valdes D, Rosado M, Block NL, Goldstein P, Morales A, Cai RZ, Sha W, Schally AV, and Hare JM
- Subjects
- Animals, Cicatrix pathology, Creatine Kinase, MB Form blood, Creatine Kinase, MM Form blood, Female, Growth Hormone-Releasing Hormone therapeutic use, Magnetic Resonance Imaging, Myocardial Infarction drug therapy, Myocardium pathology, Sermorelin therapeutic use, Swine, Troponin I blood, Ventricular Remodeling drug effects, Cicatrix drug therapy, Growth Hormone-Releasing Hormone agonists, Myocardial Infarction complications, Myocardial Ischemia drug therapy, Sermorelin analogs & derivatives
- Abstract
Background: Growth hormone-releasing hormone agonists (GHRH-As) stimulate cardiac repair following myocardial infarction (MI) in rats through the activation of the GHRH signaling pathway within the heart. We tested the hypothesis that the administration of GHRH-As prevents ventricular remodeling in a swine subacute MI model., Methods and Results: Twelve female Yorkshire swine (25 to 30 kg) underwent transient occlusion of the left anterior descending coronary artery (MI). Two weeks post MI, swine were randomized to receive injections of either 30 μg/kg GHRH-A (MR-409) (GHRH-A group; n=6) or vehicle (placebo group; n=6). Cardiac magnetic resonance imaging and pressure-volume loops were obtained at multiple time points. Infarct, border, and remote (noninfarcted) zones were assessed for GHRH receptor by immunohistochemistry. Four weeks of GHRH-A treatment resulted in reduced scar mass (GHRH-A: -21.9 ± 6.42%; P=0.02; placebo: 10.9 ± 5.88%; P=0.25; 2-way ANOVA; P=0.003), and scar size (percentage of left ventricular mass) (GHRH-A: -38.38 ± 4.63; P=0.0002; placebo: -14.56 ± 6.92; P=0.16; 2-way ANOVA; P=0.02). This was accompanied by improved diastolic strain. Unlike in rats, this reduced infarct size in swine was not accompanied by improved cardiac function as measured by serial hemodynamic pressure-volume analysis. GHRH receptors were abundant in cardiac tissue, with a greater density in the border zone of the GHRH-A group compared with the placebo group., Conclusions: Daily subcutaneous administration of GHRH-A is feasible and safe in a large animal model of subacute ischemic cardiomyopathy. Furthermore, GHRH-A therapy significantly reduced infarct size and improved diastolic strain, suggesting a local activation of the GHRH pathway leading to the reparative process., (© 2015 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.)
- Published
- 2015
- Full Text
- View/download PDF
48. Bone marrow mesenchymal stem cells stimulate cardiac stem cell proliferation and differentiation.
- Author
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Hatzistergos KE, Quevedo H, Oskouei BN, Hu Q, Feigenbaum GS, Margitich IS, Mazhari R, Boyle AJ, Zambrano JP, Rodriguez JE, Dulce R, Pattany PM, Valdes D, Revilla C, Heldman AW, McNiece I, and Hare JM
- Subjects
- Animals, Biopsy, Bone Marrow Cells cytology, Bone Marrow Cells metabolism, Cell Communication physiology, Cell Differentiation physiology, Cell Division physiology, Cells, Cultured, Coculture Techniques, Coronary Vessels cytology, Coronary Vessels physiology, Culture Media, Conditioned pharmacology, Female, Green Fluorescent Proteins genetics, Mesenchymal Stem Cells metabolism, Myocytes, Cardiac metabolism, Proto-Oncogene Proteins c-kit metabolism, Regeneration physiology, Sus scrofa, Mesenchymal Stem Cell Transplantation, Mesenchymal Stem Cells cytology, Myocardial Infarction pathology, Myocardial Infarction therapy, Myocytes, Cardiac cytology
- Abstract
Rationale: The regenerative potential of the heart is insufficient to fully restore functioning myocardium after injury, motivating the quest for a cell-based replacement strategy. Bone marrow-derived mesenchymal stem cells (MSCs) have the capacity for cardiac repair that appears to exceed their capacity for differentiation into cardiac myocytes., Objective: Here, we test the hypothesis that bone marrow derived MSCs stimulate the proliferation and differentiation of endogenous cardiac stem cells (CSCs) as part of their regenerative repertoire., Methods and Results: Female Yorkshire pigs (n=31) underwent experimental myocardial infarction (MI), and 3 days later, received transendocardial injections of allogeneic male bone marrow-derived MSCs, MSC concentrated conditioned medium (CCM), or placebo (Plasmalyte). A no-injection control group was also studied. MSCs engrafted and differentiated into cardiomyocytes and vascular structures. In addition, endogenous c-kit(+) CSCs increased 20-fold in MSC-treated animals versus controls (P<0.001), there was a 6-fold increase in GATA-4(+) CSCs in MSC versus control (P<0.001), and mitotic myocytes increased 4-fold (P=0.005). Porcine endomyocardial biopsies were harvested and plated as organotypic cultures in the presence or absence of MSC feeder layers. In vitro, MSCs stimulated c-kit(+) CSCs proliferation into enriched populations of adult cardioblasts that expressed Nkx2-5 and troponin I., Conclusions: MSCs stimulate host CSCs, a new mechanism of action underlying successful cell-based therapeutics.
- Published
- 2010
- Full Text
- View/download PDF
49. Natural and technical factors in faecal contamination incidents of drinking water in small distribution networks, France, 2003-2004: a geographical study.
- Author
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Beaudeau P, Valdes D, Mouly D, Stempfelet M, and Seux R
- Subjects
- Ecosystem, Environmental Monitoring, France, Geography, Time Factors, Water Pollution, Water Supply, Feces microbiology, Water Microbiology
- Abstract
This geographical study aimed to show natural or water-processing-related factors of faecal contamination incidents (FCIs) of drinking water in continental France. We defined a FCI as the occurrence of at least 20 colony-forming Escherichia coli or enterococci among all the 100 mL samples collected for regulatory purpose within one day from a given drinking water supply zone (SZ). We explored correlations between the standardized number of FCIs per département (N_Pols) and various indicators related to weather, land cover, topography, geology and water management for three SZ size sub-classes. In 2003-2004, 2,739 FCIs occurred in SZs supplying fewer than 2,000 people, mainly with simply disinfected groundwater. N_Pols correlates with four covariates: (1) precipitation; (2) the extension of the karst outcrops; (3) the extent of disinfection; and (4) catchment protection. One hundred millimetres of yearly excess in precipitation increases the pollution risk by 28-37%, depending on the sub-class. A 10% extension of the karst areas, a 10% increase of unprotected resources, or of SZs with no disinfection, could entail a higher risk of FCI by about 10%. The correlations are reproducible over the three sub-classes and corroborate expert appraisals. These results encourage the ongoing effort to generalize disinfection and catchment protection.
- Published
- 2010
- Full Text
- View/download PDF
50. Allogeneic mesenchymal stem cells restore cardiac function in chronic ischemic cardiomyopathy via trilineage differentiating capacity.
- Author
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Quevedo HC, Hatzistergos KE, Oskouei BN, Feigenbaum GS, Rodriguez JE, Valdes D, Pattany PM, Zambrano JP, Hu Q, McNiece I, Heldman AW, and Hare JM
- Subjects
- Actins metabolism, Animals, Bone Marrow Cells, Cell Differentiation, Cell Survival, Female, GATA4 Transcription Factor metabolism, Homeobox Protein Nkx-2.5, Homeodomain Proteins metabolism, Male, Placebos, Swine, Swine, Miniature, Transcription Factors metabolism, Cardiomyopathies pathology, Ischemia pathology, Mesenchymal Stem Cells cytology, Y Chromosome metabolism
- Abstract
The mechanism(s) underlying cardiac reparative effects of bone marrow-derived mesenchymal stem cells (MSC) remain highly controversial. Here we tested the hypothesis that MSCs regenerate chronically infarcted myocardium through mechanisms comprising long-term engraftment and trilineage differentiation. Twelve weeks after myocardial infarction, female swine received catheter-based transendocardial injections of either placebo (n = 4) or male allogeneic MSCs (200 million; n = 6). Animals underwent serial cardiac magnetic resonance imaging, and in vivo cell fate was determined by co-localization of Y-chromosome (Y(pos)) cells with markers of cardiac, vascular muscle, and endothelial lineages. MSCs engrafted in infarct and border zones and differentiated into cardiomyocytes as ascertained by co-localization with GATA-4, Nkx2.5, and alpha-sarcomeric actin. In addition, Y(pos) MSCs exhibited vascular smooth muscle and endothelial cell differentiation, contributing to large and small vessel formation. Infarct size was reduced from 19.3 +/- 1.7% to 13.9 +/- 2.0% (P < 0.001), and ejection fraction (EF) increased from 35.0 +/- 1.7% to 41.3 +/- 2.7% (P < 0.05) in MSC but not placebo pigs over 12 weeks. This was accompanied by increases in regional contractility and myocardial blood flow (MBF), particularly in the infarct border zone. Importantly, MSC engraftment correlated with functional recovery in contractility (R = 0.85, P < 0.05) and MBF (R = 0.76, P < 0.01). Together these findings demonstrate long-term MSC survival, engraftment, and trilineage differentiation following transplantation into chronically scarred myocardium. MSCs are an adult stem cell with the capacity for cardiomyogenesis and vasculogenesis which contribute, at least in part, to their ability to repair chronically scarred myocardium.
- Published
- 2009
- Full Text
- View/download PDF
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