A novel interaction of the myosin light chain phosphatase with the regulatory subunits of protein kinase A in platelets

Platelet activation initiates a series of events, such as shape change, degranulation and aggregation, which results in the formation of a haemostatic plug and arrest of blood loss at the sites of vascular damage. Shape change is accompanied by remodelling of the actin cytoskeleton and formation of an acto-myosin contractile ring. This process is regulated by phosphorylation of the myosin light chain (MLC), which in turn is controlled by the relative activities of myosin light chain kinase (MLCK) and phosphatase (MLCP). MLCP is a target of both inhibitory and activatory signalling molecules. Here we focussed on the control of MLCP activation by the cyclic adenosine 3', 5’ monophosphate (cAMP) signalling pathway. cAMP signalling is a major inhibitory pathway that inhibits platelet function through its effector protein kinase A (PKA). One of the downstream targets of PKA is MLCP. In vascular smooth muscle cells cAMP activates MLCP to dephosphorylate MLC and regulate cytoskeletal rearrangement. However, the relationship between cAMP signalling, MLCP and platelet function is unclear. Here we investigated the molecular and biochemical regulation of MLCP by cAMP signalling.We found that MYPT1, the targeting subunit of MLCP, is phosphorylated in platelets in response to cAMP elevating agents, suggesting that the phosphatase is a direct target for cAMP signalling. Our data suggests the possibility of at least two different splice variants of MYPT1 in platelets, but only one splice variant, possibly full length, was phosphorylated downstream of cAMP signalling. Using co-immunoprecipitation, cAMP pull-down assays and GST pull-down approaches we found that MYPT1 and PKA are part of the same complex and MYPT1 interacts with all four regulatory subunits of PKA (PKA-R) in platelets. Using a series of truncated proteins in HEK cells the interaction of MYPT1 and PKA-R was mapped to the central region of MYPT1 (aa501-706). Moreover, co-sedimentation assays with recombinant proteins confirmed the direct association of MYPT1 (aa501-706) with PKA-R. The conserved dimerisation and docking (D/D) domain of PKA-R, which facilitates interactions with A-kinase anchoring proteins (AKAP) was not required for the interaction. Consistent with this observation, the AKAP disruptor peptide Ht31 did not disrupt the interaction, indicating that the interaction of MYPT1 with PKA-R does not occur in an AKAP modus.These results were complemented with immunohistochemistry studies showing that MYPT1 co-localised with all four PKA regulatory subunits in both non-activated and spread platelets. In summary, our data identify MYPT1 as a novel PKA binding protein in platelets. The interaction of MYPT1 with PKA emerges as an important component of the signalling pathways that protect platelets from a hyperreactive state and may constitute a target towards preventing thrombogenic disorders

ESSAYS ON EVASION AND ENFORCEMENT IN VALUE ADDED TAX (VAT)

Value added tax (VAT) based on credit invoice system is the most common consumption tax in the world. Despite its self-regulating nature, VAT faces challenges in developing countries who have limited state capacity to check evasion and enforce tax on informal sectors of the economy. The tax authorities introduce policy interventions that can target the evasive behavior of firms interacting with informal sectors. My dissertation seeks to provide insight into three such policy reforms in Pakistan’s VAT regime. Therefore, this dissertation is composed of three essays. In first essay of my dissertation, titled “Using Computerization to enforce VAT: Evidence from Pakistan”, I study a policy intervention which empowered a computerized system to check invoices and reject input tax claims based on risk-based criteria. I use administrative tax data for the universe of VAT returns filed in Pakistan from tax year 2009 to 2016 to estimate the impact of this reform on the firms operating domestically. Using the exporters not subject to the reform as a control group, I find that the input tax claims fell by 2.36 million Pak Rs. per treated firm, representing a decline in input tax claims to the tune of Pak Rs. 86 billion. Firm heterogeneity analysis by business activity and firm structure shows a decline ranging from 30% to 90%. Surprisingly, the corporations and partnerships also show significant reduction in input tax claims from 50-70%. Contrary to the expectations, the huge volume of evasion shows that VAT implementation in limited tax capacity regimes may not yield the expected revenue efficiency gains. Second essay of my dissertation titled, “Is Minimum the Maximum? Tax Burden on Informal Sector in VAT: Evidence from Pakistan”, analyzes another policy reform. In developing countries, a substantial amount of revenue at import stage is now collected from VAT instead of traditional import tariffs. This modern approach assumes negligible VAT evasion at post-importation stage. I test this assumption through universe of monthly VAT returns filed in Pakistan for tax years 2009 to 2016 to estimate evasion by firms exclusively engaged in imports. I utilize kinks produced by minimum value addition thresholds to estimate evasion of VAT post-importation. I estimate an average evasion rate of nearly 78%. Using changes in thresholds over years, I provide evidence that this minimum tax collection is the best-case scenario for revenue efficiency. The firms show strong bunching at or below threshold with about 40-60% of the firms showing bunching behavior. My results support the view that, absent deviations from standard, replacing high import tariffs with VAT would decrease welfare. Third essay of my dissertation titled, “The Deterrence Value of Tax Audits: Estimates from a Randomized Audit Program”, analyzes a randomized audit program. It is a joint project with Michael Best and Mazhar Waseem. In modern tax systems audit is the sole instrument through which the tax authority can detect noncompliance and create deterrence. We exploit a national program of randomized audits covering the entire population of VAT filers from Pakistan to study how much evasion audit uncovers and how much evasion it prevents by changing behavior. While audit uncovers a substantial amount of evasion (the evasion rate among firms in the bottom three size quartiles is more than 100%), it does not deter future cheating. Examining more than ten intensive and extensive margin outcomes, we detect no effect of audit on proximate or distant firm behavior. Our results suggest audits are sub optimally utilized in checking mechanical violations of law instead of creating deterrence against evasion

What Can Practitioners Learn from the Narratives of Young Refugees?

Abstract Current dominant discourses around refugees in the UK focus on one of two viewpoints. The first positions refugees as “the other”, distinctly different from the general British population and subsequently less entitled to help, support and resources. The alternative discourse positions refugees as “helpless”, in need and deserving of support. A significant body of academic literature in this area focuses on past, traumatic and adverse experiences of refugees. In positioning refugees as vulnerable, it could be argued that the literature detracts from the individual aspirations of refugees and the barriers they may face to resettlement in the UK. This research aimed to explore the narratives of young refugees about their journey from their home countries into the UK, with a particular focus on post-migration factors. This research adopted a social constructionist perspective and used a narrative approach in its inquiry. In doing so, it aimed to prioritise voice and empower the narrators to embrace their subjective experience and interpretations of their journey and resettlement in the UK. The narrators included five young people aged fourteen to seventeen who came to the UK as refugees. Co-constructed narratives were facilitated during semi-structured interviews. Rich interpretations were sought from within as well as across narratives. Overlapping themes included: language as an integral part of helping resettlement, experience of racism as a hindering factor, and the role of family and other protective factors. Potential implications of the research are discussed alongside an exploration of their relevance for the profession of Educational Psychology. Key terms: Refugees, young people, transition, identity, narrative, Educational Psychology. Research supervisor: Dr Anthony William

Association of hypoadiponectemia with smokeless/dipping tobacco use in young men

Background: Low levels of adiponectin, an adipocytokine with anti-diabetic, antiatherogenic and cardioprotective properties, is associated with increased risk of coronary disease in young men. Previous studies have demonstrated that smokeless tobacco is linked with a reduction of plasma adiponectin levels. However, the influence of smokeless tobacco (dipping tobacco) on plasma adiponectin levels still remains unknown. This study was conducted to assess the plasma adiponectin levels in young men who were using dipping tobacco. Methods: This was a community based study, which consisted of 186 young lean healthy males aged 20 to 35 years. Among these, 96 men were dipping tobacco users (BMI = 23.07 ± 2.68) and 90 were non-dipping tobacco users (BMI = 23.67 ± 1.46). Serum adiponectin levels were assessed by Enzyme Linked ImmunoSorbent Assay (ELISA). Results: A statistically significant difference in the mean adiponectin level between tobacco dipper and non-dipper groups was observed (p = 0.0001). A significant difference between the two groups was also observed in baseline parameters including triglyceride and random blood sugar levels (p < 0.05). However, no significant difference was observed between the two groups in other clinical parameters. Conclusions: Findings of this study suggest that dipping tobacco use was significantly associated with low level of adiponetin in community dwelling young males. This emphasizes the importance of developing community intervention to reduce the use of dipping tobacco, which will reduce the tobacco associated disease burden in the community and will improve public health

QoS-based routing over software defined networks

Quality of Service (QoS) relies on the shaping of preferential delivery services for applications in favour of ensuring sufficient bandwidth, controlling latency and reducing packet loss. QoS can be achieved by prioritizing important broadband data traffic over the less important one. Thus, depending on the users’ needs, video, voice or data traffic take different priority based on the prevalent importance within a particular context. This prioritization might require changes in the configuration of each network entity which can be difficult in traditional network architecture. To this extent, this paper investigates the use of a QoS-based routing scheme over a Software-Defined Network (SDN). A real SDN test-bed is constructed using Raspberry Pi computers as virtual SDN switches managed by a centralized controller. It is shown that a QoS-based routing approach over SDN generates enormous control possibilities and enables automation

Policy-based QoS management framework for software-defined networks

With the emerging trends of virtualization of cloud computing and big data applications, network management has become a challenging problem for optimizing the network state while satisfying the applications’ Quality of Service (QoS) requirements. This paper proposes a policy-based management framework over Software-Defined Networks (SDN) for QoS provisioning. The proposed approach monitors the QoS parameters of the active flows and dynamically enforces new decisions on the underlying SDN switches to adapt the network state to the current demanded high-level policies. Moreover, the proposed solution makes use of Neural Networks to identify the violating flows causing the network congestion. Upon detection of a policy violation two route management techniques are implemented, such as: rerouting and rate limiting. The proposed framework was implemented and evaluated within an experimental test bed setup. The results indicate that the proposed PBNM-based SDN framework enables QoS provisioning and outperforms the default SDN in terms of throughput, packet loss rate and latency

LearnSDN: optimizing routing over multimedia-based 5G-SDN using machine learning

With the advent of 5G networks and beyond, there is an increasing demand to leverage Machine Learning (ML) capabilities and develop new and innovative solutions that could achieve efficient use of network resources and improve users' Quality of Experience (QoE). One of the key enabling technologies for 5G networks is Software Defined Networking (SDN) as it enables fine-grained monitoring and control of the network. Given the variety of dynamic networking conditions within 5G-SDN environments and the diversity of routing algorithms, an intelligent control of these strategies should exist to maximize the Quality of Service (QoS) provisioning of multimedia traffic with more stringent requirements without penalizing the performance of the background traffic. This paper proposes LearnSDN, an innovative ML-based solution that enables QoS provisioning over multimedia-based 5G-SDN environments. LearnSDN uses ML to learn the most convenient routing algorithm to be employed on the background traffic based on the dynamic network conditions in order to cater for the QoS requirements of the multimedia traffic. The performance of the proposed LearnSDN solution is evaluated under a realistic emulation-based SDN environment. The results indicate that LearnSDN outperforms other state-of-the-art solutions in terms of QoS provisioning, PSNR and MOS

LearnQoS: a learning approach for optimizing QoS over multimedia-based SDNs

As video-based services become an integral part of the end-users’ lives, there is an imminent need for increase in the backhaul capacity and resource management efficiency to enable a highly enhanced multimedia experience to the endusers. The next-generation networking paradigm offers wide advantages over the traditional networks through simplifying the management layer, especially with the adoption of Software Defined Networks (SDN). However, enabling Quality of Service (QoS) provisioning still remains a challenge that needs to be optimized especially for multimedia-based applications. In this paper, we propose LearnQoS, an intelligent QoS management framework for multimedia-based SDNs. LearnQoS employs a policy-based network management (PBNM) to ensure the compliance of QoS requirements and optimizes the operation of PBNM through Reinforcement Learning (RL). The proposed LearnQoS framework is implemented and evaluated under an experimental setup environment and compared with the default SDN operation in terms of PSNR, MOS, throughput and packet loss