Goedel-type Universes and the Landau Problem

We point out a close relation between a family of Goedel-type solutions of 3+1 General Relativity and the Landau problem in S^2, R^2 and H_2; in particular, the classical geodesics correspond to Larmor orbits in the Landau problem. We discuss the extent of this relation, by analyzing the solutions of the Klein-Gordon equation in these backgrounds. For the R^2 case, this relation was independently noticed in hep-th/0306148. Guided by the analogy with the Landau problem, we speculate on the possible holographic description of a single chronologically safe region.Comment: Latex, 21 pages, 1 figure. v2 missing references to previous work on the subject adde

Parasite-derived microRNAs in host serum as novel biomarkers of helminth infection.

BACKGROUND: MicroRNAs (miRNAs) are a class of short non-coding RNA that play important roles in disease processes in animals and are present in a highly stable cell-free form in body fluids. Here, we examine the capacity of host and parasite miRNAs to serve as tissue or serum biomarkers of Schistosoma mansoni infection. METHODS/PRINCIPAL FINDINGS: We used Exiqon miRNA microarrays to profile miRNA expression in the livers of mice infected with S. mansoni at 7 weeks post-infection. Thirty-three mouse miRNAs were differentially expressed in infected compared to naïve mice (>2 fold change, p<0.05) including miR-199a-3p, miR-199a-5p, miR-214 and miR-21, which have previously been associated with liver fibrosis in other settings. Five of the mouse miRNAs were also significantly elevated in serum by twelve weeks post-infection. Sequencing of small RNAs from serum confirmed the presence of these miRNAs and further revealed eleven parasite-derived miRNAs that were detectable by eight weeks post infection. Analysis of host and parasite miRNA abundance by qRT-PCR was extended to serum of patients from low and high infection sites in Zimbabwe and Uganda. The host-derived miRNAs failed to distinguish uninfected from infected individuals. However, analysis of three of the parasite-derived miRNAs (miR-277, miR-3479-3p and bantam) could detect infected individuals from low and high infection intensity sites with specificity/sensitivity values of 89%/80% and 80%/90%, respectively. CONCLUSIONS: This work identifies parasite-derived miRNAs as novel markers of S. mansoni infection in both mice and humans, with the potential to be used with existing techniques to improve S. mansoni diagnosis. In contrast, although host miRNAs are differentially expressed in the liver during infection their abundance levels in serum are variable in human patients and may be useful in cases of extreme pathology but likely hold limited value for detecting prevalence of infection

Alcohol-induced damage to the fimbria/fornix reduces hippocampal-prefrontal cortex connection during early abstinence

[EN] IntroductionAlcohol dependence is characterized by a gradual reduction in cognitive control and inflexibility to contingency changes. The neuroadaptations underlying this aberrant behavior are poorly understood. Using an animal model of alcohol use disorders (AUD) and complementing diffusion-weighted (dw)-MRI with quantitative immunohistochemistry and electrophysiological recordings, we provide causal evidence that chronic intermittent alcohol exposure affects the microstructural integrity of the fimbria/fornix, decreasing myelin basic protein content, and reducing the effective communication from the hippocampus (HC) to the prefrontal cortex (PFC). Using a simple quantitative neural network model, we show how disturbed HC-PFC communication may impede the extinction of maladaptive memories, decreasing flexibility. Finally, combining dw-MRI and psychometric data in AUD patients, we discovered an association between the magnitude of microstructural alteration in the fimbria/fornix and the reduction in cognitive flexibility. Overall, these findings highlight the vulnerability of the fimbria/fornix microstructure in AUD and its potential contribution to alcohol pathophysiology.Fimbria vulnerability to alcohol underlies hippocampal-prefrontal cortex dysfunction and correlates with cognitive impairment.The authors acknowledge funding from the European Union Horizon 2020 research and innovation program under Grant Agreement No. 668863 (SyBil-AA), and the Spanish Ministerio de Ciencia e Innovación, Agencia Estatal de Investigación (PID2021-128158NB-C21 [to S.C.] and PID2021-128909NA-I00 [to S.D.S.]) and Programs for Centres of Excellence in R&D Severo Ochoa (CEX2021-001165-S [to S.C. and S.D.S.]), the Spanish Generalitat Valenciana Government (PROMETEO/2019/015 [to SC] and CIDEGENT/2021/015 [to SDS]), the Spanish Ministerio de Sanidad, Servicios Sociales e Igualdad (#2021I082). W.H.S., F.K. and P.K. further acknowledge funding by the Deutsche Forschungs Gesellschaft through the Collaborative research Center grant TRR265 EnCoDe [138]. F.K. and P.K. also acknowledge funding by the Deutsche Forschungs Gesellschaft through the Collaborative Research Center SFB636 (Project D6). Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.Pérez-Cervera, L.; De Santis, S.; Marcos, E.; Ghorbanzad-Ghaziany, Z.; Trouvé-Carpena, A.; Selim, MK.; Pérez-Ramírez, Ú.... (2023). Alcohol-induced damage to the fimbria/fornix reduces hippocampal-prefrontal cortex connection during early abstinence. Acta Neuropathologica Communications. 11(1):1-21. https://doi.org/10.1186/s40478-023-01597-812111

Simultaneous genome sequencing of symbionts and their hosts

Second-generation sequencing has made possible the sequencing of genomes of interest for even small research groups. However, obtaining separate clean cultures and clonal or inbred samples of metazoan hosts and their bacterial symbionts is often difficult. We present a computational pipeline for separating metazoan and bacterial DNA in silico rather than at the bench. The method relies on the generation of deep coverage of all the genomes in a mixed sample using Illumina short-read sequencing technology, and using aggregate properties of the different genomes to identify read sets belonging to each. This inexpensive and rapid approach has been used to sequence several nematode genomes and their bacterial endosymbionts in the last year in our laboratory and can also be used to visualize and identify unexpected contaminants (or possible symbionts) in genomic DNA samples. We hope that this method will enable researchers studying symbiotic systems to move from gene-centric to genome-centric approaches

Criteria for the differentiation between young and old Onchocerca volvulus filariae

Drugs exist that show long-lasting inhibition of embryogenesis and microfilaria production or macrofilaricidal activity against Onchocerca volvulus. Therefore, the patients have to be followed-up for several years. Clinical drug trials have to be performed in areas with ongoing transmission to assess the efficacy on younger worms. In addition, future vaccine trials may also require demonstrating efficacy against establishment of new worms. For the evaluation of the efficacy, it is necessary to differentiate between older worms, which were exposed to the drug, and younger worms newly acquired after drug treatment or vaccination. Here, we describe criteria for the differentiation between young and old filariae based on histological studies of worms with a known age from travellers, or from children, or patients living in areas with interrupted transmission in Burkina Faso, Ghana or Uganda. Older worms were larger and presented degenerated tissues. Gomori's iron stain showed that the worms accumulated more iron with increasing age, first in the gut and later in other organs. Using an antibody against O. volvulus lysosomal aspartic protease, the gut of young worms was stained only weakly; whereas, it was stronger labelled in older worms, accompanied by additional staining of hypodermis and epithelia. Using morphological and immunohistological criteria, it was possible to differentiate young (1–3 years old) from older females and to identify young males

Resistance to mesenchymal reprogramming sustains clonal propagation in metastatic breast cancer

The acquisition of mesenchymal traits is considered a hallmark of breast cancer progression. However, the functional relevance of epithelial-to-mesenchymal transition (EMT) remains controversial and context dependent. Here, we isolate epithelial and mesenchymal populations from human breast cancer metastatic biopsies and assess their functional potential in vivo. Strikingly, progressively decreasing epithelial cell adhesion molecule (EPCAM) levels correlate with declining disease propagation. Mechanistically, we find that persistent EPCAM expression marks epithelial clones that resist EMT induction and propagate competitively. In contrast, loss of EPCAM defines clones arrested in a mesenchymal state, with concomitant suppression of tumorigenicity and metastatic potential. This dichotomy results from distinct clonal trajectories impacting global epigenetic programs that are determined by the interplay between human ZEB1 and its target GRHL2. Collectively, our results indicate that susceptibility to irreversible EMT restrains clonal propagation, whereas resistance to mesenchymal reprogramming sustains disease spread in multiple models of human metastatic breast cancer, including patient-derived cells in vivo

Interaction of developmental factors and ordinary stressful life events on brain structure in adults

An interplay of early environmental and genetic risk factors with recent stressful life events (SLEs) in adulthood increases the risk for adverse mental health outcomes. The interaction of early risk and current SLEs on brain structure has hardly been investigated. Whole brain voxel-based morphometry analysis was performed in N = 786 (64.6% female, mean age = 33.39) healthy subjects to identify correlations of brain clusters with commonplace recent SLEs. Genetic and early environmental risk factors, operationalized as those for severe psychopathology (i.e., polygenic scores for neuroticism, childhood maltreatment, urban upbringing and paternal age) were assessed as modulators of the impact of SLEs on the brain. SLEs were negatively correlated with grey matter volume in the left medial orbitofrontal cortex (mOFC, FWE p = 0.003). This association was present for both, positive and negative, life events. Cognitive-emotional variables, i.e., neuroticism, perceived stress, trait anxiety, intelligence, and current depressive symptoms did not account for the SLE-mOFC association. Further, genetic and environmental risk factors were not correlated with grey matter volume in the left mOFC cluster and did not affect the association between SLEs and left mOFC grey matter volume. The orbitofrontal cortex has been implicated in stress-related psychopathology, particularly major depression in previous studies. We find that SLEs are associated with this area. Important early life risk factors do not interact with current SLEs on brain morphology in healthy subjects

Anti-relapse neurons in the infralimbic cortex of rats drive relapse-suppression by drug omission cues

Drug addiction is a chronic relapsing disorder of compulsive drug use. Studies of the neurobehavioral factors that promote drug relapse have yet to produce an effective treatment. Here we take a different approach and examine the factors that suppress – rather than promote – relapse. Adapting Pavlovian procedures to suppress operant drug response, we determined the anti-relapse action of environmental cues that signal drug omission (unavailability) in rats. Under laboratory conditions linked to compulsive drug use and heightened relapse risk, drug omission cues suppressed three major modes of relapse-promotion (drug-predictive cues, stress, and drug exposure) for cocaine and alcohol. This relapse-suppression is partially driven by omission cue-reactive neurons, which constitute small subsets of glutamatergic and GABAergic cells, in the infralimbic cortex. Future studies of such neural activity-based cellular units (neuronal ensembles/memory engram cells) for relapse-suppression can be used to identify alternate targets for addiction medicine through functional characterization of anti-relapse mechanisms