Photo-induced structural dynamics of o-nitrophenol by ultrafast electron diffraction.

The photo-induced dynamics of o-nitrophenol, particularly its photolysis, has garnered significant scientific interest as a potential source of nitrous acid in the atmosphere. Although the photolysis products and preceding photo-induced electronic structure dynamics have been investigated extensively, the nuclear dynamics accompanying the non-radiative relaxation of o-nitrophenol on the ultrafast timescale, which include an intramolecular proton transfer step, have not been experimentally resolved. Herein, we present a direct observation of the ultrafast nuclear motions mediating photo-relaxation using ultrafast electron diffraction. This work spatiotemporally resolves the loss of planarity which enables access to a conical intersection between the first excited state and the ground state after the proton transfer step, on the femtosecond timescale and with sub-Angstrom resolution. Our observations, supported by ab initio multiple spawning simulations, provide new insights into the proton transfer mediated relaxation mechanism in o-nitrophenol.

Rehybridization dynamics into the pericyclic minimum of an electrocyclic reaction imaged in real-time.

Electrocyclic reactions are characterized by the concerted formation and cleavage of both σ and π bonds through a cyclic structure. This structure is known as a pericyclic transition state for thermal reactions and a pericyclic minimum in the excited state for photochemical reactions. However, the structure of the pericyclic geometry has yet to be observed experimentally. We use a combination of ultrafast electron diffraction and excited state wavepacket simulations to image structural dynamics through the pericyclic minimum of a photochemical electrocyclic ring-opening reaction in the molecule α-terpinene. The structural motion into the pericyclic minimum is dominated by rehybridization of two carbon atoms, which is required for the transformation from two to three conjugated π bonds. The σ bond dissociation largely happens after internal conversion from the pericyclic minimum to the electronic ground state. These findings may be transferrable to electrocyclic reactions in general.

[Supply of sterile medical devices to an interventional technical platform via mobile RFID technology]. / Approvisionnement d'un plateau technique interventionnel en dispositifs médicaux stériles via la technologie RFID mobile.

This work presents the eight-month assessment of the mobile RFID (radio frequency identification) technology implementation for the management of sterile medical devices in an interventional cardiology department. Several indicators dedicated to stock management, organizational impact (within the pharmacy and the department) and economic impact were collected. The scope of MDS tracked by RFID was defined as well as the new supply circuit. In total, 297 (83%) references were managed by RFID. At eight months, the number of MDS units in stock has decreased by 35% and the number of overstocked references by more than 50%. The value of the inventory decreased by €30,196 (17%) in three months from an initial amount of €17,995. This decrease has been maintained at eight months. The average time spent by the pharmacy technician (PPH) was 66min/d. The paramedical team gained 180min/week. By integrating the cost of the equipment, the annual subscription and the PPH cost, the benefit is estimated at €9555 the first year (then €17,155 the following years). To conclude, RFID has allowed a significant reduction of the stock and its control over time while securing the supply circuit adjusted to the activity. The limits are the absence of interface between the dedicated software and the ordering software as well as the consequent time dedicated by the PPH to this new management mode.

Descripción de las tasas de egresos hospitalarios por psoriasis entre los años 2018 a 2021 en Chile / Psoriasis hospital discharge rates description from 2018 to 2021 in Chile

Introducción: La psoriasis es una enfermedad crónica con diversas manifestaciones cutáneas que presenta asociación con patologías cardiovasculares y reumatológicas y que puede requerir manejo hospitalizado. El objetivo de este estudio fue describir la tasa de egresos hospitalarios por psoriasis entre los años 2018-2021 en Chile. Metodología: Estudio descriptivo observacional, sobre egresos hospitalarios por psoriasis entre 2018-2021, Chile, según sexo y grupos etario (n=2463). Datos obtenidos del Departamento de estadística e información de Salud. Se calculó la Tasa de egreso hospitalario (TEH). No se requirió comité de ética. Resultados: El año 2020 y 2021 se presentó la menor TEH del periodo de estudio con 2.8 y 2.09/100.000 hab respectivamente. El sexo masculino presento la mayor TEH del periodo con 4.96, y el grupo etario de 45-64 años presento la mayor TEH con 6.97/100000 habitantes. Discusión: En el año 2020 y 2021 se evidenció una reducción de la tasa de egreso hospitalario, que coincide con la declaración de pandemia en el año 2020 producto del virus SARS-CoV-2 y esto puede deberse a una reconversión de camas, a camas respiratorias. El sexo femenino podría presentar menor TEH debido a que el estrógeno se reporta como un factor protector. La mayor TEH en el grupo etario 45-64 puede explicarse debido a que esta población presenta más comorbilidades que predisponen a la psoriasis. Conclusión: Se requieren más estudios a nivel nacional para profundizar en los resultados encontrados. Existe escasez de estadísticas nacionales de tasa de egreso de psoriasis siendo interesante aumentar el periodo de tiempo estudiado para profundizar los hallazgos reportados.

Introduction: Psoriasis is a chronic disease with a diversity of skin manifestations, whose etiology is multifactorial and associated with cardiovascular and rheumatological pathologies and that may require hospitalization. The objective of this study was to describe the rate of hospital discharges due to psoriasis between the years 2018-2021 in Chile. Methodology: Observational descriptive study on hospital discharges for psoriasis between 2018-2021 in Chile according to sex and age groups (n=2463).. The data was obtained from the Department of Statistics and Health Information (DEIS). The Hospital Discharge Rate (TEH) was calculated. No ethics committee was required. Results: The year 2020 and 2021 presented the lowest TEH of the study period with 2.8 and 2.09/100,000 habitants respectively. The male sex presented the highest TEH of the period with 4.96, and the age group of 45-64 years presented the highest TEH with 6.97/100,000 habitants. Discussion: In 2020 and 2021, there was a reduction in the hospital discharge rate, which coincides with the declaration of a pandemic in 2020 as a result of the SARS-CoV-2 virus and this may be due to a conversion of beds to respiratory beds. The female sex could present lower TEH because estrogen is reported as a protective factor. The higher TEH in the 45-64 age group can be explained by the fact that this population presents more comorbidities that predispose to psoriasis. Conclusion: More studies are required at a national level to deepen the results found. There is a scarcity of national statistics on the rate of discharge from psoriasis, and it is interesting to increase the period of time studied to deepen the reported findings.

Au and Pt Remain Unoxidized on a CeO2-Based Catalyst during the Water-Gas Shift Reaction.

The active forms of Au and Pt in CeO2-based catalysts for the water-gas shift (WGS) reaction are an issue that remains unclear, although it has been widely studied. On one hand, ionic species might be responsible for weakening the Ce-O bonds, thus increasing the oxygen mobility and WGS activity. On the other hand, the close contact of Au or Pt atoms with CeO2 oxygen vacancies at the metal-CeO2 interface might provide the active sites for an efficient reaction. In this work, using in situ X-ray absorption spectroscopy, we demonstrate that both Au and Pt remain unoxidized during the reaction. Remarkable differences involving the dynamics established by both species under WGS atmospheres were recognized. For the prereduced Pt catalyst, the increase of the conversion coincided with a restructuration of the Pt atoms into cuboctahedrical metallic particles without significant variations on the overall particle size. Contrary to the relatively static behavior of Pt0, Au0 nanoparticles exhibited a sequence of particle splitting and agglomeration while maintaining a zero oxidation state despite not being located in a metallic environment during the process. High WGS activity was obtained when Au atoms were surrounded by oxygen. The fact that Au preserves its unoxidized state indicates that the chemical interaction between Au and oxygen must be necessarily electrostatic and that such an electrostatic interaction is fundamental for a top performance in the WGS process.

Relación entre mielitis transversa y vacunas: actualización y revisión de la literatura

La mielitis transversa (MT) es un síndrome clínico caracterizado por una inflamación y desmielinización aguda de la médula espinal. Esta entidad tomó relevancia pública en septiembre de 2020 cuando fueron suspendidos los ensayos clínicos de la vacuna ChAdOx1 para SARS-CoV-2, desarrollada por AstraZeneca y la Universidad de Oxford, por casos de MT en tres participantes. Al respecto, esta investigación se plantea recopilar la información disponible que relacione casos de MT con vacunas a nivel mundial. En este sentido, se llevó a cabo una investigación descriptiva, con diseño documental, donde se efectuó la revisión sistemática de publicaciones disponibles en las bases de datos: "PubMed", "Redalyc" y "SciELO", desde el 01/2000 al 04/2021, que presentan casos clínicos de MT post vacunación. Se estudiaron 49 casos de MT posterior a la vacunación contra diferentes virus y bacterias, 81,8 % de los mismos sucedieron en el primer mes. Se argumenta que los antígenos de las vacunas o sus adyuvantes pueden propiciar complicaciones autoinmunes que explican este fenómeno. Sin embargo, los análisis estadísticos no encuentran relación causal clara, mientras que existe evidencia que sugiere que las vacunas pueden contribuir a que se manifieste un trastorno autoinmune subyacente. El riesgo de MT pos-vacunación parece ser muy pequeño o depender del azar, mientras que el beneficio derivado de la vacunación está demostrado, incluso para disminuir los trastornos autoinmunitarios. No obstante, es importante notificar y estudiar estos casos para la realización de estimaciones certeras en el futuro, contribuyendo al desarrollo de la medicina de precisión y personalizada

Transverse myelitis (TM) is a clinical syndrome characterized by acute inflammation and demyelination of the spinal cord. This entity gained public relevance in September 2020 when clinical trials of the ChAdOx1 vaccine for SARS-CoV-2, developed by AstraZeneca and the University of Oxford, were suspended due to possible cases of MT in three participants. For this reason, this research aims to compile the available information that relates MT cases to vaccinations worldwide. In this sense, a descriptive research with documentary design was carried out through a systematic review of the publications available in the databases "PubMed", "Redalyc" y "SciELO" that presented clinical cases of post-vaccination TM from 01/2000 to 04/2021. We studied 49 cases of post-vaccination MT for different viruses and bacteria, 81.8 % of which occurred in the first month. In this sense, It's argued that vaccine antigens or their adjuvants may promote autoimmune complications that explain this phenomenon. However, statistical analyses find no certain causal relationship, while there is evidence to suggest that vaccines may contribute to the development of an underlying autoimmune disorder. The risk of postvaccination MT appears to be very small or dependent on chance, whereas the benefit derived from vaccination is certain, including in decreasing autoimmune disorders. However, it is important to report and study these cases for accurate estimates in the future, contributing to the development of precise and personalized medicine

Conformer-specific photochemistry imaged in real space and time.

Conformational isomers (conformers) of molecules play a decisive role in biology and organic chemistry. However, experimental methods for investigating chemical reaction dynamics are typically not conformer-sensitive. We report on a gas-phase megaelectronvolt ultrafast electron diffraction investigation of α-phellandrene undergoing an electrocyclic ring-opening reaction. We directly imaged the evolution of a specific set of α-phellandrene conformers into the product isomer predicted by the Woodward-Hoffmann rules in real space and time. Our experimental results are in quantitative agreement with nonadiabatic quantum molecular dynamics simulations, which provide considerable detail of how conformation influences the time scale and quantum efficiency of photoinduced ring-opening reactions.

Matter-wave interference of a native polypeptide.

The de Broglie wave nature of matter is a paradigmatic example of quantum physics and it has been exploited in precision measurements of forces and fundamental constants. However, matter-wave interferometry has remained an outstanding challenge for natural polypeptides, building blocks of life, which are fragile and difficult to handle. Here, we demonstrate the wave nature of gramicidin, a natural antibiotic composed of 15 amino acids. Its center of mass is delocalized over more than 20 times the molecular size in our time-domain Talbot-Lau interferometer. We compare the observed interference fringes with a model that includes both a rigorous treatment of the peptide's quantum wave nature as well as a quantum chemical assessment of its optical properties to distinguish our result from classical predictions. The realization of quantum optics with this prototypical biomolecule paves the way for quantum-assisted measurements on a large class of biologically relevant molecules.

Oversedation Zero as a tool for comfort, safety and intensive care unit management. / Sobresedación Zero como herramienta de confort, seguridad y gestión en la unidades de cuidados intensivos.

Sedation is necessary in the management of critically ill patients, both to alleviate suffering and to cure patients with diseases that require admission to the intensive care unit. Such sedation should be appropriate to the patient needs at each timepoint during clinical evolution, and neither too low (undersedation) nor too high (oversedation). Adequate sedation influences patient comfort, safety, survival, subsequent quality of life, bed rotation of critical care units and costs. Undersedation is detected and quickly corrected. In contrast, oversedation is silent and difficult to prevent in the absence of management guidelines, collective awareness and teamwork. The Zero Oversedation Project of the Sedation, Analgesia and Delirium Working Group of the Spanish Society of Intensive and Critical Care Medicine and Coronary Units aims to offer a practical teaching and collective awareness tool for ensuring patient comfort, safety and management with a view to optimizing the clinical outcomes and minimizing the deleterious effects of excessive sedation. The tool is based on a package of measures that include monitoring pain, analgesia, agitation, sedation, delirium and neuromuscular block, keeping patients pain-free, performing dynamic sedation according to clinical objectives, agreeing upon the multidisciplinary protocol to be followed, and avoiding deep sedation where not clinically indicated.

Treatment with intravenous immunoglobulins in systemic lupus erythematosus: a single-center experience with 63 patients.

BACKGROUND: Intravenous immunoglobulin (IVIG) is prepared using purified human plasma. IVIG therapy has immunomodulatory effects on autoimmune diseases, including severe systemic lupus erythematosus (SLE). However, reports of its effects on large cohorts are scarce. METHODS: This single-center retrospective study included SLE patients treated with at least one IVIG cycle for SLE complications. Demographic data, indications, cycle numbers, and clinical improvement with IVIG were evaluated. SLE Disease Activity Index 2000 (SLEDAI-2K) scores were calculated at admission and after IVIG treatment in order to measure clinical improvement. RESULTS: Sixty-three SLE patients treated with IVIG (median age: 29 years; interquartile range 21-36 years; 84.13% female) were included, who received 2 g/kg IVIG for two to five days. Main indications were immune thrombocytopenia, hypogammaglobulinemia, infection during a SLE flare, bicytopenia, and immune hemolytic anemia. Seven patients received more than one IVIG cycle without severe adverse effects. Significant differences were found in SLEDAI-2K scores when the indications were immune thrombocytopenia and hypogammaglobulinemia, with a trend for hemolytic anemia. Patients with concomitant infection, myopathy, and gastrointestinal involvement showed a considerable reduction in their last SLEDAI-2K scores. Fourteen patients died during hospitalization, mainly due to septic shock and active SLE. CONCLUSIONS: IVIG showed adequate tolerance and effectiveness in selected severe SLE manifestations, mainly hematological involvement. It was useful for concomitant infection.

Mercury in sediment cores from the southern Gulf of Mexico: Preindustrial levels and temporal enrichment trends.

Spatial and temporal variability of mercury concentrations in sediments was evaluated in 210Pb-dated sediment cores from offshore and intertidal areas in the southern Gulf of Mexico. In offshore cores, mercury concentrations were comparable (11.2-69.2 ng g-1), and intermediate between concentrations in intertidal cores from the eastern (6.0-34.4 ng g-1) and the western (34.9-137.7 ng g-1) inlets of Términos Lagoon. The enrichment factor (EF) indicated minimal contamination (EF < 2) in most offshore cores, whereas in some intertidal cores steadily increasing mercury enrichment and fluxes were observed along the past century. No evidence of oil industry related mercury contamination was found, as the minor but increasing enrichment in intertidal cores is most likely related to land-derived sources such as catchment eroded soils and waste water runoff. Results highlight the importance to control catchment erosion and untreated sewage releases to reduce mercury loadings to the coastal zone.

Electrostatic Influence on Photoisomerization in Bacteriorhodopsin and Halorhodopsin.

Bacteriorhodopsin (bR) and halorhodopsin (hR) are both membrane proteins that transport ions across the cell membrane in halobacteria. Their ion transport function is triggered by photoactivated isomerization of the retinal protonated Schiff base (RPSB) chromophore. In spite of their similar structures, bR and hR exhibit widely differing RPSB isomerization rates and quantum yields (with bR being both faster and more efficient than hR). Previous simulations of photoisomerization in bR and hR using ab initio multiple spawning (AIMS) with QM/MM have successfully reproduced the experimentally observed ordering of quantum yields and isomerization rates, but the origin of these differences remains elusive. Here we investigate the role of electrostatic interactions in the protein pocket surrounding RPSB. We probe the influence of protein electrostatics by modifying the charge of the complex counterion in bR/hR to be more/less negative than the native state. We find that such modifications lead to bR-like behavior in hR and vice versa. This demonstrates the crucial role of electrostatic interactions in controlling the outcome of RPSB photoisomerization.

The photochemical ring-opening of 1,3-cyclohexadiene imaged by ultrafast electron diffraction.

The ultrafast photoinduced ring-opening of 1,3-cyclohexadiene constitutes a textbook example of electrocyclic reactions in organic chemistry and a model for photobiological reactions in vitamin D synthesis. Although the relaxation from the photoexcited electronic state during the ring-opening has been investigated in numerous studies, the accompanying changes in atomic distance have not been resolved. Here we present a direct and unambiguous observation of the ring-opening reaction path on the femtosecond timescale and subångström length scale using megaelectronvolt ultrafast electron diffraction. We followed the carbon-carbon bond dissociation and the structural opening of the 1,3-cyclohexadiene ring by the direct measurement of time-dependent changes in the distribution of interatomic distances. We observed a substantial acceleration of the ring-opening motion after internal conversion to the ground state due to a steepening of the electronic potential gradient towards the product minima. The ring-opening motion transforms into rotation of the terminal ethylene groups in the photoproduct 1,3,5-hexatriene on the subpicosecond timescale.

[Thyroid effects of treatment with biotin]. / Efectos tiroideos del tratamiento con biotina.

TITLE: Efectos tiroideos del tratamiento con biotina.

Large Impact of the Decay of Niobium Isomers on the Reactor ν[over ¯]_{e} Summation Calculations.

Even mass neutron-rich niobium isotopes are among the principal contributors to the reactor antineutrino energy spectrum. They are also among the most challenging to measure due to the refractory nature of niobium, and because they exhibit isomeric states lying very close in energy. The ß-intensity distributions of ^{100gs,100m}Nb and ^{102gs,102m}Nb ß decays have been determined using the total absorption γ-ray spectroscopy technique. The measurements were performed at the upgraded Ion Guide Isotope Separator On-Line facility at the University of Jyväskylä. Here, the double Penning trap system JYFLTRAP was employed to disentangle the ß decay of the isomeric states. The new data obtained in this challenging measurement have a large impact in antineutrino summation calculations. For the first time the discrepancy between the summation model and the reactor antineutrino measurements in the region of the shape distortion has been reduced.

Management of analgesia, sedation and delirium in Spanish Intensive Care Units: A national two-part survey. / Prácticas de analgosedación y delirium en Unidades de Cuidados Intensivos españolas: Encuesta 2013-2014.

OBJECTIVE: To know the real clinical practice of Spanish ICUs in relation to analgesia, sedation and delirium, with a view to assessing adherence to current recommendations. DESIGN: A descriptive cross-sectional study was carried out based on a national survey on analgesia, sedation and delirium practices in patients admitted to intensive care on 16 November, 2013 and 16 October, 2014. An on-line questionnaire was sent with the endorsement of the SEMICYUC. SETTING: Spanish ICUs in public and private hospitals. RESULTS: A total of 166 ICUs participated, with the inclusion of 1567 patients. The results showed that 61.4% of the ICUs had a sedation protocol, and 75% regularly monitored sedation and agitation - the RASS being the most frequently used scale. Pain was monitored in about half of the ICUs, but the behavioral scales were very little used. Delirium monitoring was implemented in few ICUs. Among the patients on mechanical ventilation, midazolam remained a very commonly used agent. CONCLUSIONS: This survey is the first conducted in Spain on the practices of analgesia, sedation and delirium. We identified specific targets for quality improvement, particularly concerning the management of sedation and the assessment of delirium.

Modelos anatómicos personalizados impresos en 3D como herramientas para el aprendizaje y la preparación de intervenciones / Custom 3D printed anatomical models as tools for learning and preparation of Interventions / Modelos anatômicos personalizados impressos em 3D como ferramentas para aprendizagem e preparação de intervenções

Objetivo: presentar un método de desarrollo basado en dos casos de modelos anatómicos personalizados impresos en 3D, el\r\nprimero una arteria cerebral y el segundo una estructura ósea del húmero humano, a fin de ejemplificar el uso de herramientas\r\nde visualización tridimensionales para planificar intervenciones quirúrgicas. Método: se seleccionaron imágenes médicas de\r\ntomografías computarizadas o imágenes de resonancia magnética de pacientes anónimos y la sección específica del órgano se\r\nsegmentó con el software 3D Slicer. El modelo se convirtió en mallas poligonales en tres dimensiones, se optimizó y se imprimió\r\nen 3D. La morfología del órgano representada en el modelo anatómico se validó con especialistas para determinar si son oportunas\r\npara planificar procedimientos médicos. Resultados: diversos modelos anatómicos de los mismos casos se elaboraron en dos laboratorios de fabricación digital, uno en la Universidad El Bosque y otro en el FabLab Valencia, con diferentes variables en su\r\nproceso técnico y características, dada la dificultad de morfologías y delicadeza de las estructuras presentes en el cuerpo humano.\r\nConclusiones: con el método presentado sí es posible realizar modelos anatómicos personalizados en 3D para visualizar y simular\r\nestructuras anatómicas de pacientes útiles en la planeación de cirugías y la enseñanza de anatomía, que podrían mejorar el éxito\r\nen las intervenciones y el entrenamiento de profesionales en áreas de la salud.

Objective: To present a method of development based on\r\ntwo cases of custom anatomical models printed in 3D; the\r\nfirst one a cerebral artery and the second a bone structure\r\nof the human humerus, to exemplify the use of three-dimensional\r\nvisualization tools to perform planning of surgical\r\noperations. Method: It consisted of: a) Searching CT or MRI\r\nimages of anonymous patients, b) Segmenting with the 3D\r\nSlicer software the specific section of the organ, c) Converting\r\nthe model into polygonal meshes in three dimensions, d)\r\nOptimizing and printing in 3D, e) Validating with specialists\r\nthe organ morphology to determine if they are pertinent to\r\nplanning medical procedures. Results: Models were made in\r\ntwo different manufacturing laboratories; El Bosque University\r\nand FabLab in Valencia, with various anatomical models\r\nmanufactured of the same case with different variables in their\r\nprocess and characteristics given the difficulty of morphologies\r\nand delicacy of the structures present in the human body.\r\nConclusion: The method presented does provide useful results\r\nas an example for the planning of surgeries and anatomy\r\nteaching of anatomical structures in different scenarios that\r\ncould improve the success in interventions and the training of\r\nprofessionals in health areas.

Objetivo: apresentar um método de desenvolvimento de\r\nmodelos anatômicos personalizados em 3D para exemplificar\r\no uso de ferramentas de visualização para realizar planificação\r\nde operações cirúrgicas. Realizaram-se dois modelos como\r\nexemplo; o primeiro uma artéria cerebral e o segundo uma\r\nestrutura óssea do úmero humano. Método: o método de\r\ntrabalho consistiu em a) Buscar imagens médicas realizadas\r\ncom CT ou MRI de pacientes anônimos, b) Segmentar com o\r\nsoftware 3D Slicer a seção específica do órgão, c) Converter o\r\nmodelo em malhas poligonais em três dimensões, d) Otimizar\r\ne imprimir em 3D, e) Validar com especialistas a morfologia do\r\nórgão para determinar se são pertinentes para planejar procedimentos\r\nmédicos. Resultados: fabricou-se em dois laboratórios\r\nde fabricação diferentes, um na Universidad El Bosque e outro\r\nno FabLab Valencia, diversos modelos anatômicos do mesmo\r\ncaso com diferentes variáveis em seu processo e características\r\ndada a dificuldade de morfologias e delicadeza das estruturas\r\npresentes no corpo humano. Conclusão: o método apresentado\r\nproporciona resultados úteis para o planejamento de\r\ncirurgias e ensino de anatomia de estruturas anatômicas em\r\ndiferentes cenários que poderiam melhorar o êxito das intervenções\r\ne o treinamento de profissionais na área de saúde.

Feed pellets containing chitosan nanoparticles as plasmid DNA oral delivery system for fish: In vivo assessment in gilthead sea bream (Sparus aurata) juveniles.

The aim of this study was the assessment of preloaded feed pellets as a delivery system for plasmid DNA (pDNA), with the purpose of evaluating the potential administration of DNA vaccines orally in aquacultured fish. Pellets were made up by usual feed ingredients, which were mixed with chitosan nanoparticles entrapping a model plasmid (pCMVß) expressible in eukaryotic cells before being elaborated. The plasmid is characterized by the insertion of the reporter gene lacZ, encoding for the bacterial enzyme ß-galactosidase (ß-gal). The possible in vivo expression of the exogenous gene was measured in different fish tissues of gilthead sea bream (Sparus aurata) juveniles by two different procedures. On the one hand, the activity of the enzyme ß-gal was detected and quantified in muscle, liver and intestine; on the other, specific IgM against ß-gal antigen was titrated in blood samples. Intramuscular (i.m.) injection of equal amounts of plasmid was also carried out for the purpose of comparison with oral administration. The expression of the reporter gene was detected in fish tissues following both oral and i. m. administration of pDNA up to 60 days. However, organ distribution of the gene expression was more evident after oral (ß-gal activity measured in gut, liver and muscle) than after parenteral administration (restricted to adjacent muscle tissues). In agreement, specific IgM titration indicated that humoral immune response was more intense and sustained throughout the experimental period after oral than after i. m. delivery of equal amounts of pDNA. These results suggest that feed pellets containing chitosan nanoparticles might enable efficient oral delivery of pDNA, a fact that might imply valuable applications in terms of on-farm mass immunization purposes, especially with regard to DNA-based vaccines and small size fish, in which i. m. administration remains unfeasible.