Person:
Sánchez Jiménez, Abel

First Name

Abel

Last Name

Sánchez Jiménez

URI

https://hdl.handle.net/20.500.14352/74359

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Biológicas

Department

Biodiversidad, Ecología y Evolución

Area

Matemática Aplicada

Identifiers

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Search Results

Now showing 1 - 10 of 26

Project number: 235
Programa piloto de uso del portafolio como herramienta docente en el Grado de Biología
(2020) Delgado Sáez, Juan Antonio; Jiménez Escobar, María Dolores; Pias Couso, María Beatriz; Herrero De Jáuregui, Cristina; Pérez Tris, Javier; Sánchez Jiménez, Abel; González Martín, Antonio; Saura Álvarez, María; Rodríguez Sousa, Antonio Alberto; Pardos Martínez, Fernando; Sánchez De Dios, Rut; Gutiérrez López, Mónica; Schmitz García, María Fe; Ramírez García, Álvaro; Vergara Carretero, Susana; Pulido Delgado, Francisco; Santos Martínez, Tomas; Acosta Gallo, Belén; Panetsos Petrova, Fivos; Arriero Higueras, Elena; Almodovar Pérez, Ana María; López De Pablo, Carlos Tomas; Alonso Campos, Germán; Miguel Garcinuño, José Manuel De; Gabriel Y Galán Moris, José María; Hernández Pazmiño, Nathalia
Memoria final del proyecto de Innovación educativa "Programa piloto de uso del portafolio como herramienta docente en el Grado de Biología"
Rain-fed granite rock pools in a national park: extreme niches for protists
(Limnetica, 2021) Pérez Uz, María Blanca; Velasco González, Ismael; Murciano, Antonio; Sánchez Jiménez, Abel; García-Rodriguez, M.; Centeno Carrillo, Juan de Dios; Montero González, Esperanza; Muñoz Araújo, Benito; Olmedo Salinas, Cristina; Quintela Alonso, Pablo; Refoyo Román, Pablo; Williams, Richard Alexander John; Martín Cereceda, María Mercedes
Rain-fed granite rock pools are geological landforms with a worldwide distribution. However, their role as habitats for microorganisms has been barely explored. We carried out a detailed morphological inventory of the ciliated protists in the sediments of three granite rain-fed rock pools from a Spanish National Park. The ciliate seed bank in the rock pools comprised 54 morphospecies. The species number inferred for each pool by rarefaction analysis was similar to that observed by microscopy. The most representative species were small bacterivorous ciliates, although the distribution of ciliate groups was significantly different in each rock pool. Testate amoebae were also found to be rich in species. This study demonstrates the existence of a diverse ciliate community adapted to persist in these ephemeral and extreme rock pool habitats through species resistance structures, many of which have not been described previously. The presence of competitive species in dormant stages prevents local extinctions through a sequential excystation over time. Our results provide a benchmark for studying protist and microbial biodiversity within rain-fed granite rock pools, a unique habitat that merits bio- and geo- conservation.
Necessary conditions for signal processing by resonant neurons
(2001) Villacorta Atienza, José Antonio; Sánchez Jiménez, Abel; Panetsos Petrova, Fivos
We study a mathematical model for information processing and coding by means of groups of resonant neurons. We conclude that incoming signals can be expressed by means of their Fourier series which coefficients are represented by the value of the membrane potential of the resonant neurons.
Project number: 63
Diseño e implementación de la metodología Flipped Classroom en la asignatura de “Estadística aplicada a la Biología”. Uso de dispositivos móviles para la evaluación del alumnado
(2020) Juan Llamas, María del Carmen; Murciano Cespedosa, Antonio; Sánchez Jiménez, Abel; Villacorta Atienza, José Antonio
Static internal representation of dynamic situations reveals time compaction in human cognition
(Journal of Advanced Research, 2020) Villacorta-Atienza, José Antonio; Calvo Tapia, Carlos; Díez-Hermano, Sergio; Sánchez Jiménez, Abel; Lobov, Sergei; Krilova, Nadia; Murciano Cespedosa, Antonio; López-Tolsa, Gabriela E.; Pellón, Ricardo; Makarov Slizneva, Valeriy
Introduction: The human brain has evolved under the constraint of survival in complex dynamic situations. It makes fast and reliable decisions based on internal representations of the environment. Whereas neural mechanisms involved in the internal representation of space are becoming known, entire spatiotemporal cognition remains a challenge. Growing experimental evidence suggests that brain mechanisms devoted to spatial cognition may also participate in spatiotemporal information processing. Objectives: The time compaction hypothesis postulates that the brain represents both static and dynamic situations as purely static maps. Such an internal reduction of the external complexity allows humans to process time-changing situations in real-time efficiently. According to time compaction, there may be a deep inner similarity between the representation of conventional static and dynamic visual stimuli. Here, we test the hypothesis and report the first experimental evidence of time compaction in humans. Methods: We engaged human subjects in a discrimination-learning task consisting in the classification of static and dynamic visual stimuli. When there was a hidden correspondence between static and dynamic stimuli due to time compaction, the learning performance was expected to be modulated. We studied such a modulation experimentally and by a computational model. Results: The collected data validated the predicted learning modulation and confirmed that time compaction is a salient cognitive strategy adopted by the human brain to process time-changing situations. Mathematical modelling supported the finding. We also revealed that men are more prone to exploit time compaction in accordance with the context of the hypothesis as a cognitive basis for survival. Conclusions: The static internal representation of dynamic situations is a human cognitive mechanism involved in decision-making and strategy planning to cope with time-changing environments. The finding opens a new venue to understand how humans efficiently interact with our dynamic world and thrive in nature.
Phytoestrogen Metabolism by Adult Human Gut Microbiota
(Molecules, 2016) Gaya, Pilar; Medina, Margarita; Sánchez Jiménez, Abel; Landete, José María
Phytoestrogens are plant-derived polyphenols with a structure similar to human estrogens. The three main groups of phytoestrogens, isoflavones, ellagitannins, and lignans, are transformed into equol, urolithins, and enterolignans, respectively, by bacteria. These metabolites have more estrogenic/antiestrogenic and antioxidant activities than their precursors, and they are more bioavailable. The aim of this study was to analyze the metabolism of isoflavones, lignans and ellagitannins by gut microbiota, and to study the possible correlation in the metabolism of these three groups of phytoestrogens. In vitro fermentation experiments were performed with feces samples from 14 healthy adult volunteers, and metabolite formation was measured by HPLC-PAD and HPLC-ESI/MS. Only the microbiota of one subject produced equol, while most of them showed production of O-desmethylangolensin (O-DMA). Significant inter-subject differences were observed in the metabolism of dihydrodaidzein and dihydrogenistein, while the glucoside isoflavones and their aglycones showed less variability, except for glycitin. Most subjects produced urolithins M-5 and E. Urolithin D was not detected, while uroltithin B was found in half of the individuals analyzed, and urolithins A and C were detected in two and four subjects, respectively. Enterolactone was found in all subjects, while enterodiol only appeared in five. Isoflavone metabolism could be correlated with the metabolism of lignans and ellagitannins. However, the metabolism of ellagitannins and lignans could not be correlated. This the first study where the metabolism of the three groups together of phytoestrogen, isoflavones, lignans, and ellagitannins by gut microbiota is analyzed.
Computational study of resonant neural behaviour in the presence of continuous signals
(2001) Sánchez Jiménez, Abel; Villacorta Atienza, José Antonio; Panetsos Petrova, Fivos; Pérez de Vargas, Antonio; Rattay, Frank
The resonant behaviour and the response preference to input signals of specific frequencies are well known properties of many neurons of the Central Nervous System. In the present communication we computationally evaluate a theoretical model of oscillating neurons and we prove that ensembles of neurons with a reduced variety of channels could make use of the fluctuations of their membrane potential to perform signal analysis.
Complexity of river ciliate communities at a national park highlights the need for microbial conservation
(Aquatic Conservation: Marine and Freshwater Ecosystems, 2018) Quintela Alonso, Pablo; Pérez‐Uz, Blanca; Sánchez Jiménez, Abel; Murciano Cespedosa, Antonio; Centeno, Juan D.; García-Rodríguez, Manuel; Montero, Esperanza; Muñoz Araújo, Benito; Olmedo Salinas, Cristina; Refoyo Román, Pablo; Velasco González, Ismael; Martín Cereceda, María Mercedes
1.Microorganisms play pivotal roles in aquatic ecosystems. Free‐living protists are the main components of the eukaryotic microbial communities at the base of freshwater ecosystems. Ciliate grazing channels a large proportion of organic matter into multicellular organisms. Surprisingly, ciliates and other microorganisms are neglected in global conservation schemes. 2. Interstitial ciliates were sampled in three sites of varying human pressure on the River Manzanares (La Pedriza National Park, Spain). Abundances of trophic groups and species were adjusted to a generalized linear model (GLM Poisson regression). 3.Ciliate communities were rich in species (74 morphotypes) and although traditional microscopy retrieved a high number of species that appeared only once or in low numbers, rarefaction analyses estimated much larger species richness. These results illustrate that rarefaction assays are a useful first step for exploring the extent of the ciliate cryptic diversity in freshwater ecosystems. 4.Benthic ciliate communities changed significantly, both spatially and at a short temporal scale. The fluctuating nature of the community was manifested by the presence of many ephemeral species at the same river site, revealing a complex and transient community structure. No significant short‐term changes were observed in the physical–chemical properties. Therefore, even slight differences in the abiotic variables may cause rapid shifts of ciliate species. 5.Overall, human pressure had an effect on the interstitial (or benthic) ciliates that resulted in a reduction of species richness and their abundance.
Influencia de la temperatura sobre la asimetría de pilancones en ambiente granítico. Aplicación de un modelo de regresión lineal
(Boletín de la Sociedad Geológica Mexicana, 2017) García Rodríguez, Manuel; Sánchez Jiménez, Abel; Murciano Cespedosa, Antonio; Pérez Uz, María Blanca; Martín Cereceda, María Mercedes
Las pilas representan un tipo de forma presente en casi todos los ambientes climáticos. El trabajo estudia el papel de los ciclos térmicos como un agente importante del modelado y asimetría que presentan las paredes de las pilas en un clima Mediterrá- neo templado - frío. El estudio se ha realizado en el macizo granítico de la Pedriza de Manzanares, zona protegida de gran valor ambiental, incluida en el Parque Nacional de la Sierra de Guadarrama (Madrid, España). El análisis de la variabilidad térmica mediante modelos de regresión perió- dica múltiple, pone de manifiesto la influencia de los ciclos diario y anual en función de las orientaciones norte y sur de las paredes de las pilas. Un modelo matemático de regresión lineal muestra cómo la variabilidad térmica diaria influye en la alteración de las paredes de las pilas, generando superficies planas o de concavidad más o menos pronunciada. El trabajo también establece relaciones entre el grado de alteración de las diferentes partes de las pilas, con la presencia de líquenes y dureza relativa de la roca. Los resultados avalan la hipótesis de relación causal entre la variabilidad térmica y alteración de las paredes de las pilas según su orientación norte o sur.
Rain-Fed Granite Rock Basins Accumulate a High Diversity of Dormant Microbial Eukaryotes
(Microbial Ecology, 2019) Velasco González, Ismael; Sánchez Jiménez, Abel; Singer, David; Murciano Cespedosa, Antonio; Díez-Hermano, Sergio; Lara, Enrique; Martín-Cereceda, Mercedes
Rain fed granite rock basins are ancient geological landforms of worldwide distribution and structural simplicity. They support habitats that can switch quickly from terrestrial to aquatic along the year. Diversity of animals and plants, and the connexion between communities in different basins have been widely explored in these habitats, but hardly any research has been carried out on microorganisms. The aim of this study is to provide the first insights on the diversity of eukaryotic microbial communities from these environments. Due to the ephemeral nature of these aquatic environments, we predict that the granitic basins should host a high proportion of dormant microeukaryotes. Based on an environmental DNA diversity survey, we reveal diverse communities with representatives of all major eukaryotic taxonomic supergroups, mainly composed of a diverse pool of low abundance OTUs. Basin communities were very distinctive, with alpha and beta diversity patterns non-related to basin size or spatial distance respectively. Dissimilarity between basins was mainly characterised by turnover of OTUs. The strong microbial eukaryotic heterogeneity observed among the basins may be explained by a complex combination of deterministic factors (diverging environment in the basins), spatial constraints, and randomness including founder effects. Most interestingly, communities contain organisms that cannot coexist at the same time because of incompatible metabolic requirements, thus suggesting the existence of a pool of dormant organisms whose activity varies along with the changing environment. These organisms accumulate in the pools, which turns granitic rock into high biodiversity microbial islands whose conservation and study deserve further attention.