Oscillating hypercycles at the origin of life: A bifurcation analysis

A hypercycle is a dynamical system formed by different replicator macromolecules that catalyze the reproduction between them in a cyclic architecture. This type of structure is thought to be involved in the transition from simple systems to more complex ones, such as the ones that took place at the origin of life. We conduct a bifurcation study of 5-component asymmetric oscillating hypercycles, in order to see whether there exists a gap between the saddle-node bifurcation value of periodic orbits and the saddle-node bifurcation value of fixed points. To achieve this goal, we carry out both an analytical and a numerical study of the systems and find out that, indeed, there exists a gap, and this one gets larger when the asymmetry of the hypercycle grows

Bifurcation gaps in asymmetric and high-dimensional hypercycles

Hypercycles are catalytic systems with cyclic architecture. These systems have been suggested to play a key role in the maintenance and increase of information in prebiotic replicators. It is known that for a large enough number of hypercycle species (n>4 the coexistence of all hypercycle members is governed by a stable periodic orbit. Previous research has characterized saddle-node (s-n) bifurcations involving abrupt transitions from stable hypercycles to extinction of all hypercycle members, or, alternatively, involving the outcompetition of the hypercycle by so-called mutant sequences or parasites. Recently, the presence of a bifurcation gap between a s-n bifurcation of periodic orbits and a s-n of fixed points has been described for symmetric five-member hypercycles. This gap was found between the value of the replication quality factor Q from which the periodic orbit vanishes (QPO)and the value where two unstable (nonzero) equilibrium points collide (QSS). Here, we explore the persistence of this gap considering asymmetries in replication rates in five-member hypercycles as well as considering symmetric, larger hypercycles. Our results indicate that both the asymmetry in Malthusian replication constants and the increase in hypercycle members enlarge the size of this gap. The implications of this phenomenon are discussed in the context of delayed transitions associated to the so-called saddle remnants. Read More: https://www.worldscientific.com/doi/abs/10.1142/S021812741830001X Read More: https://www.worldscientific.com/doi/abs/10.1142/S021812741830001XPeer ReviewedPreprin

Estudio comparativo de herramientas SIG Libres aplicadas a contextos de cooperación al desarrollo

En la fase de formulación del programa hidrosanitario que ISF-ApD está llevando a cabo en diversos distritos de Tanzania, surgió la necesidad de una herramienta que facilitara el análisis, gestión, seguimiento y evaluación de toda la información disponible con incidencia sobre el territorio en el que se estaba trabajando. Generalmente, los Sistemas de Información Geográfica en materia de Cooperación al Desarrollo, ofrecen ventajas tanto en las fases iniciales como en las posteriores a la propia implementación técnica de los proyectos, permitiendo en todo momento conocer determinadas situaciones territoriales (calidad del agua, focos epidémicos, pobreza, localización de comités locales, riesgo sísmico…). No obstante, el SIG elegido debería de contar con cualidades específicas adicionales no necesariamente requeridas en otro tipo de contextos. Con el propósito de facilitar la elección de un software se inició desde la Universidad Politécnica de Cataluña un estudio comparativo de entre diversos SIG en el que desde el comienzo, se exigió a todos los candidatos que fueran software libre. Este estudio presenta una serie de alternativas sometidas a un extenso análisis basado en las necesidades de un proyecto en concreto (ya sean tecnológicas, legales e incluso aspectos relacionados con la divulgación). Sin embargo, incluso con un claro objetivo inicial, se espera que los resultados obtenidos sean lo suficientemente representativos como para permitir a otros proyectos tomar sus propias decisiones en el proceso de selección.Postprint (published version

Bifurcation gaps in asymmetric and high-dimensional hypercycles

Hypercycles are catalytic systems with cyclic architecture. These systems have been suggested to play a key role in the maintenance and increase of information in prebiotic replicators. It is known that for a large enough number of hypercycle species (n>4) the coexistence of all hypercycle members is governed by a stable periodic orbit. Previous research has characterized saddle-node (s-n) bifurcations involving abrupt transitions from stable hypercycles to extinction of all hypercycle members, or, alternatively, involving the outcompetition of the hypercycle by so-called mutant sequences or parasites. Recently, the presence of a bifurcation gap between a s-n bifurcation of periodic orbits and a s-n of fixed points has been described for symmetric five-member hypercycles. This gap was found between the value of the replication quality factor Q from which the periodic orbit vanishes (QPO) and the value where two unstable (nonzero) equilibrium points collide (QSS). Here, we explore the persistence of this gap considering asymmetries in replication rates in five-member hypercycles as well as considering symmetric, larger hypercycles. Our results indicate that both the asymmetry in Malthusian replication constants and the increase in hypercycle members enlarge the size of this gap. The implications of this phenomenon are discussed in the context of delayed transitions associated to the so-called saddle remnants

Ocean acidification affects pigment concentration and photoprotection of marine phytoplankton

Ocean acidification produces significant changes on phytoplankton physiology that can affect their growth and primary production. Among them, a downregulation of the enzymatic activity and the production of different cellular metabolites, including chlorophyll a (Chl a), has been observed in high CO2 cultures under stable conditions. However, the extent of how phytoplankton metabolism regulation under high CO2 conditions affects pigment pools and patterns is unknown. This study shows the effect of the atmospheric CO2 increase on pigment concentration of three important marine primary producers: Thalassiosira pseudonana, Skeletonema costatum, and Emiliania huxleyi. Cultures grown under saturating photosynthetically active radiation were aerated for at least 3 weeks with current concentrations of atmospheric CO2 (0.04% CO2 in air) and with CO2 concentrations expected for future scenarios of climate change (0.1% CO2 in air) to assess the effect of CO2 under acclimated metabolism and stable conditions. Moreover, cultures were also subjected to a perturbation (4 h without aeration) to assess responses under non-stable conditions. The results showed that light harvesting and photoprotective pigment concentrations (i.e., Chl a, Chl c2, ββ-carotene, diadinoxanthin, diatoxanthin, fucoxanthin, among others) decreased significantly under high CO2 and stable conditions, but the response reversed after the perturbation. The de-epoxidation state of xanthophylls, also showed similar patterns, indicating an increase in phytoplankton sensitivity under high CO2 and stable conditions. The results demonstrate the relevance of CO2 concentration and acclimation status for phytoplankton light absorption and photoprotective response. They also identify fucoxanthin and Chl c2 as suitable biomarkers of phytoplankton carbon metabolism under ocean acidification conditions.Ministerio de Economía y Competitividad | Ref. CTM2014-59345-RUniversidade de Vigo/CISU

Prolonged vs short-term infusion of β-lactam antibiotics for the treatment of febrile neutropenia: A systematic review and meta-analysis

Background: The optimisation of the use of beta-lactam antibiotics (BLA) via prolonged infusions in life-threatening complications such as febrile neutropenia (FN) is still controversial. This systematic review and meta-analysis aim to evaluate the efficacy of this strategy in onco-haematological patients with FN. Methods: A systematic search was performed of PubMed, Web of Science, Cochrane, EMBASE, World Health Organization, and ClinicalTrials.gov, from database inception until December 2022. The search included randomised controlled trials (RCTs) and observational studies that compared prolonged vs short-term infusions of the same BLA. The primary outcome was all-cause mortality. Secondary outcomes were defervescence, requirement of vasoactive drugs, length of hospital stay and adverse events. Pooled risk ratios were calculated using random effects models. Results: Five studies were included, comprising 691 episodes of FN, mainly in haematological patients. Prolonged infusion was not associated with a reduction in all-cause mortality (pRR 0.83; 95% confidence interval 0.47-1.48). Nor differences were found in secondary outcomes. Conclusions: The limited data available did not show significant differences in terms of all-cause mortality or significant secondary outcomes in patients with FN receiving BLA in prolonged vs. short-term infusion. High-quality RCTs are needed to determine whether there are subgroups of FN patients who would benefit from prolonged BLA infusion. (c) 2023 The Author(s). Published by Elsevier Ltd on behalf of The British Infection Association. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Auditory target and novelty processing in patients with unilateral hippocampal sclerosis: A current-source density study

The capacity to respond to novel events is crucial for adapting to the constantly changing environment. Here, we recorded 29-channel Event Related Brain Potentials (ERPs) during an active auditory novelty oddball paradigm and used for the first time Current Source Density-transformed Event Related Brain Potentials and associated time-frequency spectra to study target and novelty processing in a group of epileptic patients with unilateral damage of the hippocampus (N = 18) and in healthy matched control participants (N = 18). Importantly, we used Voxel-Based Morphometry to ensure that our group of patients had a focal unilateral damage restricted to the hippocampus and especially its medial part. We found a clear deficit for target processing at the behavioral level. In addition, compared to controls, our group of patients presented (i) a reduction of theta event-related synchronization (ERS) for targets and (ii) a reduction and delayed P3a source accompanied by reduced theta and low-beta ERS and alpha event-related synchronization (ERD) for novel stimuli. These results suggest that the integrity of the hippocampus might be crucial for the functioning of the complex cortico-subcortical network involved in the detection of novel and target stimuli

Effect of Combination Antibiotic Empirical Therapy on Mortality in Neutropenic Cancer Patients with Pseudomonas aeruginosa Pneumonia

To assess the effect of combination antibiotic empirical therapy on 30-day case-fatality rate in neutropenic cancer patients with Pseudomonas aeruginosa (PA) bacteremic pneumonia. This was a multinational, retrospective cohort study of neutropenic onco-hematological patients with PA blood stream infection (BSI) (2006–2018). The effect of appropriate empirical combination therapy, appropri ate monotherapy and inappropriate empirical antibiotic therapy [IEAT] on 30-day case-fatality was assessed only in patients with PA bacteremic pneumonia. Among 1017 PA BSI episodes, pneumonia was the source of BSI in 294 (28.9%). Among those, 52 (17.7%) were caused by a multidrug-resistant (MDR) strain and 68 (23.1%) received IEAT, mainly when the infection was caused by an MDR strain [38/52 (73.1%) vs. 30/242 (12.4%); p < 0.001]. The 30-day case-fatality rate was higher in patients with PA bacteremic pneumonia than in those with PA BSI from other sources (55.1% vs. 31.4%; p < 0.001). IEAT was associated with increased 30-day case-fatality (aHR 1.44 [95%CI 1.01–2.03]; p = 0.042), whereas the use of appropriate combination empirical treatment was independently associated with improved survival (aHR 0.46 [95%CI 0.27–0.78]; p = 0.004). Appropriate empiri cal monotherapy was not associated with improved overall survival (aHR 1.25 [95%CI 0.76–2.05]; p = 0.39). Combination antibiotic empirical therapy should be administered promptly in febrile neutropenic patients with suspected pneumonia as the source of infection

Particle size and cholesterol content of circulating HDL correlate with cardiovascular death in chronic heart failure

Evidence regarding any association of HDL-particle (HDL-P) derangements and HDL-cholesterol content with cardiovascular (CV) death in chronic heart failure (HF) is lacking. To investigate the prognostic value of HDL-P size (HDL-Sz) and the number of cholesterol molecules per HDL-P for CV death in HF patients. Outpatient chronic HF patients were enrolled. Baseline HDL-P number, subfractions and HDL-Sz were measured using 1H-NMR spectroscopy. The HDL-C/P ratio was calculated as HDL-cholesterol over HDL-P. Endpoint was CV death, with non-CV death as the competing event. 422 patients were included and followed-up during a median of 4.1 (0–8) years. CV death occurred in 120 (30.5%) patients. Mean HDL-Sz was higher in CV dead as compared with survivors (8.39 nm vs. 8.31 nm, p < 0.001). This change in size was due to a reduction in the percentage of small HDL-P (54.6% vs. 60% for CV-death vs. alive; p < 0.001). HDL-C/P ratio was higher in the CV-death group (51.0 vs. 48.3, p < 0.001). HDL-Sz and HDL-C/P ratio were significantly associated with CV death after multivariable regression analysis (HR 1.22 [95% CI 1.01–1.47], p = 0.041 and HR 1.04 [95% CI 1.01–1.07], p = 0.008 respectively). HDL-Sz and HDL-C/P ratio are independent predictors of CV death in chronic HF patients.Tis work was supported by Grants from Fundació La MARATÓ de TV3 (201502 and 201516 to AB-G, 201602- 30-31 to NA and JJ), Ministerio de Educación y Ciencia (SAF2014-59892 to AB-G), AdvanceCat (2014-2020 to AB-G), Ministerio de Economía y Competitividad (MINECO)—Instituto de Salud Carlos III (ISCIII) (PI17- 00232 to JJ, PI17-01362 to NA, PI15-00625 to DM, and RED2018-102799-T to JJ), and by CIBER on Cardiovascular Diseases (CIBERCV, CB16/11/00403) and CIBER for Diabetes and Associated Metabolic Diseases (CIBERDEM, CB15/00071 and CB07/08/0016) are an initiative from ISCIII, Spain with co-funding from the European Regional Development Fund (ERDF). JJ is supported by funds provided by ISCIII (Grant CPII18/00004, Miguel Servet II program)

Particle size and cholesterol content of circulating HDL correlate with cardiovascular death in chronic heart failure

Altres ajuts: Fundació la Marató de TV3: 201602-30-31; 201502Evidence regarding any association of HDL-particle (HDL-P) derangements and HDL-cholesterol content with cardiovascular (CV) death in chronic heart failure (HF) is lacking. To investigate the prognostic value of HDL-P size (HDL-Sz) and the number of cholesterol molecules per HDL-P for CV death in HF patients. Outpatient chronic HF patients were enrolled. Baseline HDL-P number, subfractions and HDL-Sz were measured using 1H-NMR spectroscopy. The HDL-C/P ratio was calculated as HDL-cholesterol over HDL-P. Endpoint was CV death, with non-CV death as the competing event. 422 patients were included and followed-up during a median of 4.1 (0-8) years. CV death occurred in 120 (30.5%) patients. Mean HDL-Sz was higher in CV dead as compared with survivors (8.39 nm vs. 8.31 nm, p < 0.001). This change in size was due to a reduction in the percentage of small HDL-P (54.6% vs. 60% for CV-death vs. alive; p < 0.001). HDL-C/P ratio was higher in the CV-death group (51.0 vs. 48.3, p < 0.001). HDL-Sz and HDL-C/P ratio were significantly associated with CV death after multivariable regression analysis (HR 1.22 [95% CI 1.01-1.47], p = 0.041 and HR 1.04 [95% CI 1.01-1.07], p = 0.008 respectively). HDL-Sz and HDL-C/P ratio are independent predictors of CV death in chronic HF patients