Spatiotemporal regulation of liver development by the Wnt/β- catenin pathway

While the Wnt/β-catenin pathway plays a critical role in the maintenance of the zonation of ammonia metabolizing enzymes in the adult liver, the mechanisms responsible for inducing zonation in the embryo are not well understood. Herein we address the spatiotemporal role of the Wnt/β-catenin pathway in the development of zonation in embryonic mouse liver by conditional deletion of Apc and β-catenin at different stages of mouse liver development. In normal development, the ammonia metabolising enzymes carbamoylphosphate synthetase I (CPSI) and Glutamine synthetase (GS) begin to be expressed in separate hepatoblasts from E13.5 and E15.5 respectively and gradually increase in number thereafter. Restriction of GS expression occurs at E18 and becomes increasingly limited to the terminal perivenous hepatocytes postnatally. Expression of nuclear β-catenin coincides with the restriction of GS expression to the terminal perivenous hepatocytes. Conditional loss of Apc resulted in the expression of nuclear β-catenin throughout the developing liver and increased number of cells expressing GS. Conversely, conditional loss of β-catenin resulted in loss of GS expression. These data suggest that the Wnt pathway is critical to the development of zonation as well as maintaining the zonation in the adult liver

How global biodiversity hotspots may go unrecognized: Lessons from the North American Coastal Plain

© 2014 John Wiley & Sons Ltd. Biodiversity hotspots are conservation priorities. We identify the North American Coastal Plain (NACP) as a global hotspot based on the classic definition, a region with \u3e 1500 endemic plant species and \u3e 70% habitat loss. This region has been bypassed in prior designations due to misconceptions and myths about its ecology and history. These fallacies include: (1) young age of the NACP, climatic instability over time and submergence during high sea-level stands; (2) climatic and environmental homogeneity; (3) closed forest as the climax vegetation; and (4) fire regimes that are mostly anthropogenic. We show that the NACP is older and more climatically stable than usually assumed, spatially heterogeneous and extremely rich in species and endemics for its range of latitude, especially within pine savannas and other mostly herbaceous and fire-dependent communities. We suspect systematic biases and misconceptions, in addition to missing information, obscure the existence of similarly biologically significant regions world-wide. Potential solutions to this problem include (1) increased field biological surveys and taxonomic determinations, especially within grassy biomes and regions with low soil fertility, which tend to have much overlooked biodiversity; (2) more research on the climatic refugium role of hotspots, given that regions of high endemism often coincide with regions with low velocity of climate change; (3) in low-lying coastal regions, consideration of the heterogeneity in land area generated by historically fluctuating sea levels, which likely enhanced opportunities for evolution of endemic species; and (4) immediate actions to establish new protected areas and implement science-based management to restore evolutionary environmental conditions in newly recognized hotspots

Pharmacologic and Clinical Considerations of Nalmefene, a Long Duration Opioid Antagonist, in Opioid Overdose

Opioid use disorder is a well-established and growing problem in the United States. It is responsible for both psychosocial and physical damage to the affected individuals with a significant mortality rate. Given both the medical and non-medical consequences of this epidemic, it is important to understand the current treatments and approaches to opioid use disorder and acute opioid overdose. Naloxone is a competitive mu-opioid receptor antagonist that is used for the reversal of opioid intoxication. When given intravenously, naloxone has an onset of action of approximately 2 min with a duration of action of 60–90 min. Related to its empirical dosing and short duration of action, frequent monitoring of the patient is required so that the effects of opioid toxicity, namely respiratory depression, do not return to wreak havoc. Nalmefene is a pure opioid antagonist structurally similar to naltrexone that can serve as an alternative antidote for reversing respiratory depression associated with acute opioid overdose. Nalmefene is also known as 6-methylene naltrexone. Its main features of interest are its prolonged duration of action that surpasses most opioids and its ability to serve as an antidote for acute opioid overdose. This can be pivotal in reducing healthcare costs, increasing patient satisfaction, and redistributing the time that healthcare staff spend monitoring opioid overdose patients given naloxone

On the Influence of Alloy Composition on the Additive Manufacturability of Ni-Based Superalloys

The susceptibility of nickel-based superalloys to processing-induced crack formation during laser powder-bed additive manufacturing is studied. Twelve different alloys—some of existing (heritage) type but also other newly-designed ones—are considered. A strong inter-dependence of alloy composition and processability is demonstrated. Stereological procedures are developed to enable the two dominant defect types found—solidification cracks and solid-state ductility dip cracks—to be distinguished and quantified. Differential scanning calorimetry, creep stress relaxation tests at 1000 °C and measurements of tensile ductility at 800 °C are used to interpret the effects of alloy composition. A model for solid-state cracking is proposed, based on an incapacity to relax the thermal stress arising from constrained differential thermal contraction; its development is supported by experimental measurements using a constrained bar cooling test. A modified solidification cracking criterion is proposed based upon solidification range but including also a contribution from the stress relaxation effect. This work provides fundamental insights into the role of composition on the additive manufacturability of these materials

E-cadherin can limit the transforming properties of activating β-catenin mutations

Wnt pathway deregulation is a common characteristic of many cancers. But only Colorectal Cancer predominantly harbours mutations in APC, whereas other cancer types (hepatocellular carcinoma, solid pseudopapillary tumours of pancreas) have activating mutations in β-catenin (CTNNB1). We have compared the dynamics and the potency of β-catenin mutations in vivo. Within the murine small intestine (SI), an activating mutation of β-catenin took much longer to achieve a Wnt deregulation and acquire a crypt-progenitor-cell (CPC) phenotype than Apc or Gsk3 loss. Within the colon, a single activating mutation of β-catenin was unable to drive Wnt deregulation or induce the CPC phenotype. This ability of β-catenin mutation to differentially transform the SI versus the colon correlated with significantly higher expression of the β-catenin binding partner E-cadherin. This increased expression is associated with a higher number of E-cadherin:β-catenin complexes at the membrane. Reduction of E-cadherin synergised with an activating mutation of β-catenin so there was now a rapid CPC phenotype within the colon and SI. Thus there is a threshold of β-catenin that is required to drive transformation and E-cadherin can act as a buffer to prevent β-catenin accumulation

Activation Energy for Grain Growth in Bismuth Coatings

The knowledge of both activation energy and diffusion coefficient is needed for a predictive processing of grain size in coatings. However, for metals as Bismuth there is insufficient information available in the literature for these parameters. To determine these values, a method is adopted wherein an examination of the grain size is conducted for coatings deposited isothermally. The exponent for grain growth with time is determined, thereby enabling quantification of the activation energy and diffusion coefficient. Bismuth coatings that range from 10 {micro}m to 1 mm thick are deposited using electron-beam evaporation onto temperature-controlled substrate surfaces of glass and lithium fluoride. The grain size of each coating is measured upon examination of the microstructure in cross-section using the intercept method. Ideal grain growth is observed over the experimental range of deposition temperatures examined from 317 to 491 K. The activation energy (Q) for grain growth in bismuth is fit as 0.47 eV {center_dot} atom{sup -1} with a diffusion coefficient (D{sub 0}) of 3.3 x 10{sup -4} cm{sup 2} {center_dot} sec{sup -1}

Instantons and unitarity in quantum cosmology with fixed four-volume

We find a number of complex solutions of the Einstein equations in the so-called unimodular version of general relativity, and we interpret them as saddle points yielding estimates of a gravitational path integral over a space of almost everywhere Lorentzian metrics on a spacetime manifold with topology of the "no-boundary" type. In this setting, the compatibility of the no-boundary initial condition with the definability of the quantum measure reduces reduces to the normalizability and unitary evolution of the no-boundary wave function \psi. We consider the spacetime topologies R^4 and RP^4 # R^4 within a Taub minisuperspace model with spatial topology S^3, and the spacetime topology R^2 x T^2 within a Bianchi type I minisuperspace model with spatial topology T^3. In each case there exists exactly one complex saddle point (or combination of saddle points) that yields a wave function compatible with normalizability and unitary evolution. The existence of such saddle points tends to bear out the suggestion that the unimodular theory is less divergent than traditional Einstein gravity. In the Bianchi type I case, the distinguished complex solution is approximately real and Lorentzian at late times, and appears to describe an explosive expansion from zero size at T=0. (In the Taub cases, in contrast, the only complex solution with nearly Lorentzian late-time behavior yields a wave function that is normalizable but evolves nonunitarily, with the total probability increasing exponentially in the unimodular "time" in a manner that suggests a continuous creation of new universes at zero volume.) The issue of the stability of these results upon the inclusion of more degrees of freedom is raised.Comment: 32 pages, REVTeX v3.1 with amsfonts. (v2: minor typos etc corrected.

A Compensatory Mutation Provides Resistance to Disparate HIV Fusion Inhibitor Peptides and Enhances Membrane Fusion

Fusion inhibitors are a class of antiretroviral drugs used to prevent entry of HIV into host cells. Many of the fusion inhibitors being developed, including the drug enfuvirtide, are peptides designed to competitively inhibit the viral fusion protein gp41. With the emergence of drug resistance, there is an increased need for effective and unique alternatives within this class of antivirals. One such alternative is a class of cyclic, cationic, antimicrobial peptides known as θ-defensins, which are produced by many non-human primates and exhibit broad-spectrum antiviral and antibacterial activity. Currently, the θ-defensin analog RC-101 is being developed as a microbicide due to its specific antiviral activity, lack of toxicity to cells and tissues, and safety in animals. Understanding potential RC-101 resistance, and how resistance to other fusion inhibitors affects RC-101 susceptibility, is critical for future development. In previous studies, we identified a mutant, R5-tropic virus that had evolved partial resistance to RC-101 during in vitro selection. Here, we report that a secondary mutation in gp41 was found to restore replicative fitness, membrane fusion, and the rate of viral entry, which were compromised by an initial mutation providing partial RC-101 resistance. Interestingly, we show that RC-101 is effective against two enfuvirtide-resistant mutants, demonstrating the clinical importance of RC-101 as a unique fusion inhibitor. These findings both expand our understanding of HIV drug-resistance to diverse peptide fusion inhibitors and emphasize the significance of compensatory gp41 mutations. © 2013 Wood et al

Adjuvant drugs for peripheral nerve blocks: The role of nmda antagonists, neostigmine, epinephrine, and sodium bicarbonate

The potential for misuse, overdose, and chronic use has led researchers to look for other methods to decrease opioid consumption in patients with acute and chronic pain states. The use of peripheral nerve blocks for surgery has gained increasing popularity as it minimizes peripheral pain signals from the nociceptors of local tissue sustaining trauma and inflammation from surgery. The individualization of peripheral nerve blocks using adjuvant drugs has the potential to improve patient outcomes and reduce chronic pain. The major limitations of peripheral nerve blocks are their limited duration of action and dose-dependent adverse effects. Adjuvant drugs for peripheral nerve blocks show increasing potential as a solution for postoperative and chronic pain with their synergistic effects to increase the duration of action and decrease the required dosage of local anesthetic. N-methyl-d-aspartate (NMDA) receptor antagonists are a viable option for patients with opioid resistance and neuropathic pain due to their affinity to the neurotransmitter glutamate, which is released when patients experience a noxious stimulus. Neostigmine is a cholinesterase inhibitor that exerts its effect by competitively binding at the active site of acetylcholinesterase, which prevents the hydrolysis of acetylcholine and subsequently retaining acetylcholine at the nerve terminal. Epinephrine, also known as adrenaline, can potentially be used as an adjuvant to accelerate and prolong analgesic effects in digital nerve blocks. The theorized role of sodium bicarbonate in local anesthetic preparations is to increase the pH of the anesthetic. The resulting alkaline solution enables the anesthetic to more readily exist in its un-ionized form, which more efficiently crosses lipid membranes of peripheral nerves. However, more research is needed to show the efficacy of these adjuvants for nerve block prolongation as studies have been either mixed or have small sample sizes