Effect of Coulomb blockade, gold resistance, and thermal expansion on the electrical resistance of ultrathin gold films

Controlling the electrical resistance of granular thin films is of great importance for many applications, yet a full understanding of electron transport in such films remains a major challenge. We have studied experimentally and by model calculations the temperature dependence of the electrical resistance of ultrathin gold films at temperatures between 2 K and 300 K. Using sputter deposition, the film morphology was varied from a discontinuous film of weakly coupled meandering islands to a continuous film of strongly coupled coalesced islands. In the weak-coupling regime, we compare the regular island array model, the cotunneling model, and the conduction percolation model with our experimental data. We show that the tunnel barriers and the Coulomb blockade energies are important at low temperatures and that the thermal expansion of the substrate and the island resistance affect the resistance at high temperatures. At low temperatures our experimental data show evidence for a transition from electron cotunneling to sequential tunneling but the data can also be interpreted in terms of conduction percolation. The resistivity and temperature coefficient of resistance of the meandering gold islands are found to resemble those of gold nanowires. We derive a simple expression for the temperature at which the resistance changes from non-metal-like behavior into metal-like behavior. In the case of strong island coupling, the total resistance is solely determined by the Ohmic island resistance.

Blockade of PD-1/PD-L1 promotes adoptive T-Cell immunotherapy in a tolerogenic environment

Adoptive cellular immunotherapy using in vitro expanded CD8+ T cells shows promise for tumour immunotherapy but is limited by eventual loss of function of the transferred T cells through factors that likely include inactivation by tolerogenic dendritic cells (DC). The coinhibitory receptor programmed death-1 (PD-1), in addition to controlling T-cell responsiveness at effector sites in malignancies and chronic viral diseases is an important modulator of dendritic cell-induced tolerance in naive T cell populations. The most potent therapeutic capacity amongst CD8+ T cells appears to lie within Tcm or Tcm-like cells but memory T cells express elevated levels of PD-1. Based on established trafficking patterns for Tcm it is likely Tcm-like cells interact with lymphoid-tissue DC that present tumour-derived antigens and may be inherently tolerogenic to develop therapeutic effector function. As little is understood of the effect of PD-1/PD-L1 blockade on Tcm-like CD8+ T cells, particularly in relation to inactivation by DC, we explored the effects of PD-1/PD-L1 blockade in a mouse model where resting DC tolerise effector and memory CD8+ T cells. Blockade of PD-1/PDL1 promoted effector differentiation of adoptively-transferred Tcm-phenotype cells interacting with tolerising DC. In tumour-bearing mice with tolerising DC, effector activity was increased in both lymphoid tissues and the tumour-site and anti-tumour activity was promoted. Our findings suggest PD-1/PD-L1 blockade may be a useful adjunct for adoptive immunotherapy by promoting effector differentiation in the host of transferred Tcmlike cells. © 2015 Blake et al.

Blockade of estrogen synthesis with an aromatase inhibitor affects luteal function of the pseudopregnant rat

The luteotropic action of estrogen (E) was investigated using immature pseudopregnant rat as the model and CGS 16949A (Fadrozole hydrochloride), a potent aromatase inhibitor (AI), to block E synthesis. Aromatase activity could be inhibited by administering CGS 16949A (50 mu g/day/rat) via a mini osmotic Alzet pump (model 2002) for 3 days during pseudopregnancy. This resulted in significant reduction of serum (40%, P < 0.05) and intraovarian (70.6%, P < 0.001) estradiol-17 beta (E(2)) levels. The serum and intraovarian progesterone (P-4) levels as analyzed on day 4 of pseudopregnancy were also reduced by greater than or equal to 50% (for both, P < 0.01). Simultaneous administration of estradiol-3-benzoate (E(2)B) via an Alzet pump during the Al: treatment period at a dose of 1 mu g/day could completely reverse the Al induced reduction in P-4 secretion. The luteal cells of experimental rats depleted of E in vivo showed a significantly reduced response upon incubation with hCG or dbcAMP in vitro (P < 0.05 and 0.001, respectively). Addition of E(2) (500 pg/tube) at the time of in vitro incubation was able to partially increase the responsiveness to hCG. The luteal cell LH/hCG receptor content and the affinity of hCG binding to the receptor remained unchanged following AI treatment in vivo. Both esterified and total cholesterol content of luteal cells of rats treated with Al in vivo was significantly high (P < 0.05) suggesting that E lack results in an impairment in cholesterol utilization for steroidogenesis. The results clearly show that E regulates luteal function in the pseudopregnant rat by acting at a non-cAMP mediated event and this perhaps involves facilitation of cholesterol utilization at the mitochondrial level for P-4 synthesis.

VIP blockade leads to microcephaly in mice via disruption of Mcph1-Chk1 signaling

Autosomal recessive primary microcephaly (MCPH) is a genetic disorder that causes a reduction of cortical outgrowth without severe interference with cortical patterning. It is associated with mutations in a number of genes encoding protein involved in mitotic spindle formation and centrosomal activities or cell cycle control. We have shown previously that blocking vasoactive intestinal peptide (VIP) during gestation in mice by using a VIP antagonist (VA) results in microcephaly. Here, we have shown that the cortical abnormalities caused by prenatal VA administration mimic the phenotype described in MCPH patients and that VIP blockade during neurogenesis specifically disrupts Mcph1 signaling. VA administration reduced neuroepithelial progenitor proliferation by increasing cell cycle length and promoting cell cycle exit and premature neuronal differentiation. Quantitative RT-PCR and Western blot showed that VA downregulated Mcph1. Inhibition of Mcph1 expression led to downregulation of Chk1 and reduction of Chk1 kinase activity. The inhibition of Mcph1 and Chk1 affected the expression of a specific subset of cell cycle-controlling genes and turned off neural stem cell proliferation in neurospheres. Furthermore, in vitro silencing of either Mcph1 or Chk1 in neurospheres mimicked VA-induced inhibition of cell proliferation. These results demonstrate that VIP blockade induces microcephaly through Mcph1 signaling and suggest that VIP/Mcph1/Chk1 signaling is key for normal cortical development.

Pharmacological Blockade of Cannabinoid CB1 Receptors in Diet-Induced Obesity Regulates Mitochondrial Dihydrolipoamide Dehydrogenase in Muscle

Cannabinoid CB1 receptors peripherally modulate energy metabolism. Here, we investigated the role of CB1 receptors in the expression of glucose/pyruvate/tricarboxylic acid (TCA) metabolism in rat abdominal muscle. Dihydrolipoamide dehydrogenase (DLD), a flavoprotein component (E3) of alpha-ketoacid dehydrogenase complexes with diaphorase activity in mitochondria, was specifically analyzed. After assessing the effectiveness of the CB1 receptor antagonist AM251 (3 mg kg(-1), 14 days) on food intake and body weight, we could identified seven key enzymes from either glycolytic pathway or TCA cycle-regulated by both diet and CB1 receptor activity-through comprehensive proteomic approaches involving two-dimensional electrophoresis and MALDI-TOF/LC-ESI trap mass spectrometry. These enzymes were glucose 6-phosphate isomerase (GPI), triosephosphate isomerase (TPI), enolase (Eno3), lactate dehydrogenase (LDHa), glyoxalase-1 (Glo1) and the mitochondrial DLD, whose expressions were modified by AM251 in hypercaloric diet-induced obesity. Specifically, AM251 blocked high-carbohydrate diet (HCD)-induced expression of GPI, TPI, Eno3 and LDHa, suggesting a down-regulation of glucose/pyruvate/lactate pathways under glucose availability. AM251 reversed the HCD-inhibited expression of Glo1 and DLD in the muscle, and the DLD and CB1 receptor expression in the mitochondrial fraction. Interestingly, we identified the presence of CB1 receptors at the membrane of striate muscle mitochondria. DLD over-expression was confirmed in muscle of CB1-/- mice. AM251 increased the pyruvate dehydrogenase and glutathione reductase activity in C2C12 myotubes, and the diaphorase/oxidative activity in the mitochondria fraction. These results indicated an up-regulation of methylglyoxal and TCA cycle activity. Findings suggest that CB1 receptors in muscle modulate glucose/pyruvate/lactate pathways and mitochondrial oxidative activity by targeting DLD.

Coulomb blockade double-dot Aharonov-Bohm interferometer: Giant fluctuations

Electron transport through two parallel quantum dots is a kind of solid-state realization of double path interference We demonstrate that the inter-clot Coulomb correlation and quantum coherence would result in strong current fluctuations with a divergent Fano factor at zero frequency. We also provide physical interpretation for this surprising result, which displays its generic feature and allows us to recover this phenomenon in more complicated systems. (C) 2009 Elsevier B.V. All rights reserved.

Coulomb blockade double-dot Aharonov-Bohm interferometer: Harmonic decomposition of the interference pattern

For the solid-state double-dot interferometer, the phase shifted interference pattern induced by the interplay of inter-dot Coulomb correlation and multiple reflections is analyzed by harmonic decomposition. Unexpected result is uncovered, and is discussed in connection with the which-path detection and electron loss. (C) 2009 Elsevier B.V. All rights reserved.

Full counting statistics of transport through two-channel Coulomb blockade systems

A mesoscopic Coulomb blockade system with two transport channels is studied in terms of full counting statistics. It is found that the shot noise and skewness are crucially affected by the quantum mechanical interference. In particular, the super-Poisson behavior can be induced as a consequence of constructive interference, and can be understood by the formation of effective fast-and-slow transport channels. Dephasing and finite temperature effects are carried out together with physical interpretations.

A comprehensive description of the competencies required for the performance of an ultrasound-guided axillary brachial plexus blockade

We addressed four research questions, each relating to the training and assessment of the competencies associated with the performance of ultrasound-guided axillary brachial plexus blockade (USgABPB). These were: (i) What are the most important determinants of learning of USgABPB? (ii) What is USgABPB? What are the errors most likely to occur when trainees learn to perform this procedure? (iii) How should end-user input be applied to the development of a novel USgABPB simulator? (iv) Does structured simulation based training influence novice learning of the procedure positively? We demonstrated that the most important determinants of learning USgABPB are: (a) Access to a formal structured training programme. (b) Frequent exposure to clinical learning opportunity in an appropriate setting (c) A clinical learning opporunity requires an appropriate patient, trainee and teacher being present at the same time, in an appropriate environment. We carried out a comprehensive description of the procedure. We performed a formal task analysis of USgABPB, identifying (i) 256 specific tasks associated with the safe and effective performance of the procedure, and (ii) the 20 most critical errors likely to occur in this setting. We described a methodology for this and collected data based on detailed, sequential evaluation of prototypes by trainees in anaesthesia. We carried out a pilot randomised control trial assessing the effectiveness of a USgABPB simulator during its development. Our data did not enable us to draw a reliable conclusion to this question; the trail did provide important new learning (as a pilot) to inform future investigation of this question. We believe that the ultimate goal of designing effective simulation-based training and assessment of ultrasound-guided regional anaesthesia is closer to realisation as a result of this work. It remains to be proven if this approach will have a positive impact on procedural performance, and more importantly improve patient outcomes.

Training in and assessment of the procedural skills required to perform peripheral nerve blockade

The training and ongoing education of medical practitioners has undergone major changes in an incremental fashion over the past 15 years. These changes have been driven by patient safety, educational, economic and legislative/regulatory factors. In the near future, training in procedural skills will undergo a paradigm shift to proficiency based progression with associated requirements for competence-based programmes, valid, reliable assessment tools and simulation technology. Before training begins, the learning outcomes require clear definition; any form of assessment applied should include measurement of these outcomes. Currently training in a procedural skill often takes place on an ad hoc basis. The number of attempts necessary to attain a defined degree of proficiency varies from procedure to procedure. Convincing evidence exists that simulation training helps trainees to acquire skills more efficiently rather than relying on opportunities in their clinical practice. Simulation provides a safe, stress free environment for trainees for skill acquisition, generalization and transfer via deliberate practice. The work described in this thesis contributes to a greater understanding of how medical procedures can be performed more safely and effectively through education. The effect of feedback, provided to novices in a standardized setting on a bench model, based on knowledge of performance was associated with an increase in the speed of skill acquisition and a decrease in error rate during initial learning. The timing of feedback was also associated with effective learning of skill. A marked attrition of skills (independent of the type of feedback provided) was demonstrable 24 hrs after they have first been learned. Using the principles of feedback as described above, when studying the effect of an intense training program on novices of varied years of experience in anaesthesia (i.e. the present training programmes / courses of an intense training day for one or more procedures). There was a marked attrition of skill at 24 hours with a significant correlation with increasing years of experience; there also appeared to be an inverse relationship between years of experience in anaesthesia and performance. The greater the number of years of practice experience, the longer it required a learner to acquire a new skill. The findings of the studies described in this thesis may have important implications for the trainers, trainees and training bodies in the design and implementation of training courses and the formats of delivery of changing curricula. Both curricula and training modalities will need to take account of characteristics of individual learners and the dynamic nature of procedural healthcare.

Reciprocal in vivo regulation of myocardial G protein-coupled receptor kinase expression by beta-adrenergic receptor stimulation and blockade.

BACKGROUND: Impaired myocardial beta-adrenergic receptor (betaAR) signaling, including desensitization and functional uncoupling, is a characteristic of congestive heart failure. A contributing mechanism for this impairment may involve enhanced myocardial beta-adrenergic receptor kinase (betaARK1) activity because levels of this betaAR-desensitizing G protein-coupled receptor kinase (GRK) are increased in heart failure. An hypothesis has emerged that increased sympathetic nervous system activity associated with heart failure might be the initial stimulus for betaAR signaling alterations, including desensitization. We have chronically treated mice with drugs that either activate or antagonize betaARs to study the dynamic relationship between betaAR activation and myocardial levels of betaARK1. METHODS AND RESULTS: Long-term in vivo stimulation of betaARs results in the impairment of cardiac +betaAR signaling and increases the level of expression (mRNA and protein) and activity of +betaARK1 but not that of GRK5, a second GRK abundantly expressed in the myocardium. Long-term beta-blocker treatment, including the use of carvedilol, improves myocardial betaAR signaling and reduces betaARK1 levels in a specific and dose-dependent manner. Identical results were obtained in vitro in cultured cells, demonstrating that the regulation of GRK expression is directly linked to betaAR signaling. CONCLUSIONS: This report demonstrates, for the first time, that betaAR stimulation can significantly increase the expression of betaARK1 , whereas beta-blockade decreases expression. This reciprocal regulation of betaARK1 documents a novel mechanism of ligand-induced betaAR regulation and provides important insights into the potential mechanisms responsible for the effectiveness of beta-blockers, such as carvedilol, in the treatment of heart failure.