Growing evidence indicates that the mammalian microbiome can affect behaviour, and several symbionts even produce neurotransmitters. One common explanation for these observations is that symbionts ...have evolved to manipulate host behaviour for their benefit. Here, we evaluate the manipulation hypothesis by applying evolutionary theory to recent work on the gut-brain axis. Although the theory predicts manipulation by symbionts under certain conditions, these appear rarely satisfied by the genetically diverse communities of the mammalian microbiome. Specifically, any symbiont investing its resources to manipulate host behaviour is expected to be outcompeted within the microbiome by strains that do not manipulate and redirect their resources into growth and survival. Moreover, current data provide no clear evidence for manipulation. Instead, we show how behavioural effects can readily arise as a by-product of natural selection on microorganisms to grow within the host and natural selection on hosts to depend upon their symbionts. We argue that understanding why the microbiome influences behaviour requires a focus on microbial ecology and local effects within the host.
Various two dimensional quantum gravity theories of Jackiw-Teitelboim (JT) form have descriptions as random matrix models. Such models, treated nonperturbatively, can give an explicit and tractable ...description of the underlying "microstate" degrees of freedom, which play a prominent role in regimes where the smooth geometrical picture of the physics is inadequate. This is shown using a natural tool, a Fredholm determinant det ( 1 − K ) , which can be defined explicitly for a wide variety of JT gravity theories. To illustrate the methods, the statistics of the first several energy levels of a nonperturbative definition of JT gravity are constructed explicitly using numerical methods, and the full quenched free energy FQ(T) of the system is computed for the first time. These results are also of relevance to quantum properties of black holes in higher dimensions.
•Oxytocin and vasopressin systems exhibit conserved properties.•Receptor expression patterns reflect species-specific sociosensory pathways.•Diversity in receptors expression contributes to diversity ...in social behavior.•Oxytocin and vasopressin modulate widely distributed brain networks.•Oxytocin is a potential target for improving social cognition in autism.
Oxytocin- and vasopressin-related systems are present in invertebrate and vertebrate bilaterian animals, including humans, and exhibit conserved neuroanatomical and functional properties. In vertebrates, these systems innervate conserved neural networks that regulate social learning and behavior, including conspecific recognition, social attachment, and parental behavior. Individual and species-level variation in central organization of oxytocin and vasopressin systems has been linked to individual and species variation in social learning and behavior. In humans, genetic polymorphisms in the genes encoding oxytocin and vasopressin peptides and/or their respective target receptors have been associated with individual variation in social recognition, social attachment phenotypes, parental behavior, and psychiatric phenotypes such as autism. Here we describe both conserved and variable features of central oxytocin and vasopressin systems in the context of social behavioral diversity, with a particular focus on neural networks that modulate social learning, behavior, and salience of sociosensory stimuli during species-typical social contexts.
A
bstract
Recent work has shown that certain deformations of the scalar potential in Jackiw-Teitelboim gravity can be written as double-scaled matrix models. However, some of the deformations exhibit ...an apparent breakdown of unitarity in the form of a negative spectral density at disc order. We show here that the source of the problem is the presence of a multi-valued solution of the leading order matrix model string equation. While for a class of deformations we fix the problem by identifying a first order phase transition, for others we show that the theory is both perturbatively and non-perturbatively inconsistent. Aspects of the phase structure of the deformations are mapped out, using methods known to supply a non-perturbative definition of undeformed JT gravity. Some features are in qualitative agreement with a semi-classical analysis of the phase structure of two-dimensional black holes in these deformed theories.
The shape of the light-curve peak of radioactive-powered core-collapse ‘stripped-envelope’ supernovae constrains the ejecta mass, nickel mass and kinetic energy by the brightness and diffusion time ...for a given opacity and observed expansion velocity. Late-time light curves give constraints on the ejecta mass and energy, given the gamma-ray opacity. Previous work has shown that the principal light-curve peaks for SN IIb with small amounts of hydrogen and for hydrogen/helium-deficient SN Ib/c are often rather similar near maximum light, suggesting similar ejecta masses and kinetic energies, but that late-time light curves show a wide dispersion, suggesting a dispersion in ejecta masses and kinetic energies. It was also shown that SN IIb and SN Ib/c can have very similar late-time light curves, but different ejecta velocities demanding significantly different ejecta masses and kinetic energies. We revisit these topics by collecting and analysing well-sampled single-band and quasi-bolometric light curves from the literature. We find that the late-time light curves of stripped-envelope core-collapse supernovae are heterogeneous. We also show that the observed properties, the photospheric velocity at peak, the rise time and the late decay time, can be used to determine the mean opacity appropriate to the peak. The opacity determined in this way is considerably smaller than common estimates. We discuss how the small effective opacity may result from recombination and asymmetries in the ejecta.
Over the past two decades, electrospinning has emerged as an enabling nanotechnology to produce nanofiber materials for various biomedical applications. In particular, therapeutic/cellloaded ...nanofiber scaffolds have been widely examined in drug delivery, wound healing, and tissue repair and regeneration. However, due to the insufficient porosity, small pore size, noninjectability, and inaccurate spatial control in nanofibers of scaffolds, many efforts have been devoted to exploring new forms of nanofiber materials including expanded nanofiber scaffolds, nanofiber aerogels, short nanofibers, and nanofiber microspheres. This short review discusses the preparation and potential biomedical applications of new forms of nanofiber materials.
Natural bone constitutes a complex and organized structure of organic and inorganic components with limited ability to regenerate and restore injured tissues, especially in large bone defects. To ...improve the reconstruction of the damaged bones, tissue engineering has been introduced as a promising alternative approach to the conventional therapeutic methods including surgical interventions using allograft and autograft implants. Bioengineered composite scaffolds consisting of multifunctional biomaterials in combination with the cells and bioactive therapeutic agents have great promise for bone repair and regeneration. Cellulose and its derivatives are renewable and biodegradable natural polymers that have shown promising potential in bone tissue engineering applications. Cellulose-based scaffolds possess numerous advantages attributed to their excellent properties of non-toxicity, biocompatibility, biodegradability, availability through renewable resources, and the low cost of preparation and processing. Furthermore, cellulose and its derivatives have been extensively used for delivering growth factors and antibiotics directly to the site of the impaired bone tissue to promote tissue repair. This review focuses on the various classifications of cellulose-based composite scaffolds utilized in localized bone drug delivery systems and bone regeneration, including cellulose-organic composites, cellulose-inorganic composites, cellulose-organic/inorganic composites. We will also highlight the physicochemical, mechanical, and biological properties of the different cellulose-based scaffolds for bone tissue engineering applications.
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•Cellulose and its derivatives are renewable and biodegradable natural polymers that with great potential for bone tissue engineering.•Cellulose-based materials can be used various therapeutics directly to the bone to achieve bone regeneration.•Bioinks made of cellulose-based materials hold great promise to develop patient specific solutions for bone repair using 3D printing.•Challenges associated with inaccuracies in existing preclinical models, sterilization regulatory barriers still need to be addressed before clinical translation.
The Carnot heat engine sets an upper bound on the efficiency of a heat engine. As an ideal, reversible engine, a single cycle must be performed in infinite time, and so the Carnot engine has zero ...power. However, there is nothing, in principle, forbidding the existence of a heat engine whose efficiency approaches that of Carnot while maintaining finite power. Such an engine must have very special properties, some of which have been discussed in the literature, in various limits. While recent theorems rule out a large class of engines from maintaining finite power at exactly the Carnot efficiency, the approach to the limit still merits close study. Presented here is an exactly solvable model of such an approach that may serve as a laboratory for exploration of the underlying mechanisms. The equations of state have their origins in the extended thermodynamics of electrically charged black holes.
Significance
This work shows that, under strong immune pressure, SARS-CoV-2 can use mutations in both the N-terminal domain and the receptor-binding domain to escape potent polyclonal neutralizing ...responses. Indeed, after a long period under immune selective pressure, SARS-CoV-2 evolved to evade the immunity of a potent polyclonal serum from a COVID-19 convalescent donor. Only three mutations were sufficient to generate this escape variant. The new virus was resistant to 70% of the neutralizing antibodies tested and had a decreased susceptibility to all convalescent sera. Our data predict that, as the immunity in the population increases, following infection and vaccination, new variants will emerge, and therefore vaccines and monoclonal antibodies need to be developed to address them.
To investigate the evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the immune population, we coincupi bated the authentic virus with a highly neutralizing plasma from a COVID-19 convalescent patient. The plasma fully neutralized the virus for seven passages, but, after 45 d, the deletion of F140 in the spike N-terminal domain (NTD) N3 loop led to partial breakthrough. At day 73, an E484K substitution in the receptor-binding domain (RBD) occurred, followed, at day 80, by an insertion in the NTD N5 loop containing a new glycan sequon, which generated a variant completely resistant to plasma neutralization. Computational modeling predicts that the deletion and insertion in loops N3 and N5 prevent binding of neutralizing antibodies. The recent emergence in the United Kingdom, South Africa, Brazil, and Japan of natural variants with similar changes suggests that SARS-CoV-2 has the potential to escape an effective immune response and that vaccines and antibodies able to control emerging variants should be developed.
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