Two bacterial type II l-asparaginases, from Escherichia coli and Dickeya chrysanthemi, have played a critical role for more than 40 years as therapeutic agents against juvenile leukemias and ...lymphomas. Despite a long history of successful pharmacological applications and the apparent simplicity of the catalytic reaction, controversies still exist regarding major steps of the mechanism. In this report, we provide a detailed description of the reaction catalyzed by E. coli type II l-asparaginase (EcAII). Our model was developed on the basis of new structural and biochemical experiments combined with previously published data. The proposed mechanism is supported by quantum chemistry calculations based on density functional theory. We provide strong evidence that EcAII catalyzes the reaction according to the double-displacement (ping-pong) mechanism, with formation of a covalent intermediate. Several steps of catalysis by EcAII are unique when compared to reactions catalyzed by other known hydrolytic enzymes. Here, the reaction is initiated by a weak nucleophile, threonine, without direct assistance of a general base, although a distant general base is identified. Furthermore, tetrahedral intermediates formed during the catalytic process are stabilized by a never previously described motif. Although the scheme of the catalytic mechanism was developed only on the basis of data obtained from EcAII and its variants, this novel mechanism of enzymatic hydrolysis could potentially apply to most (and possibly all) l-asparaginases.
Sign language serves as a vital means of communication for individuals with hearing impairments, yet recognition resources for the over 100 distinct sign languages are severely lacking. In response, ...we present our work on sign language recognition using transfer learning and the domain adaptation method TA3N, which utilizes the Temporal Relational Network (TRN) module for aligning multi-scale temporal relations. Our findings highlight the superior performance of Domain Adaptation to neural network-based transfer learning, particularly in improving recognition of American Sign Language (ASL). Our research also identifies the effectiveness of aligning shorter-term temporal features between source and target domains. In addition to using RGB, we conducted experiments using Optical Flow mode for the sign language samples, ultimately determining that RGB outperforms Optical Flow in the majority of cases. Our work aims to improve accessibility and communication for individuals who rely on sign language as their primary mode of communication.
Fabry Disease (FD) is a systemic disorder that can result in cardiovascular, renal, and neurovascular disease leading to reduced life expectancy. FD should be considered in the differential of all ...patients with unexplained left ventricular hypertrophy (LVH). We therefore performed a prospective screening study in Edmonton and Hong Kong using Dried Blood Spot (DBS) testing on patients with undiagnosed LVH. Participants found to have unexplained LVH on echocardiography were invited to participate and subsequently subjected to DBS testing. DBS testing was used to measure α-galactosidase (α-GAL) enzyme activity and for mutation analysis of the α-galactosidase (GLA) gene, both of which are required to make a diagnosis of FD. DBS testing was performed as a screening tool on patients (n = 266) in Edmonton and Hong Kong, allowing for detection of five patients with FD (2% prevalence of FD) and one patient with hydroxychloroquine-induced phenocopy. Left ventricular mass index (LVMI) by GLA genotype showed a higher LVMI in patients with IVS4 + 919G > A mutations compared to those without the mutation. Two patients were initiated on ERT and hydroxychloroquine was discontinued in the patient with a phenocopy of FD. Overall, we detected FD in 2% of our screening cohort using DBS testing as an effective and easy to administer screening tool in patients with unexplained LVH. Utilizing DBS testing to screen for FD in patients with otherwise undiagnosed LVH is clinically important due to the availability of effective therapies and the value of cascade screening in extended families.
The T‐cell receptor (TCR) locus undergoes programmed rearrangements that frequently generate premature termination codons (PTCs). The PTC‐bearing transcripts derived from such nonproductively ...rearranged genes are dramatically downregulated by the nonsense‐mediated decay (NMD) pathway. Here, we show that depletion of the NMD factor UPF3b does not impair TCRβ NMD, thereby distinguishing it from classical NMD. Depletion of the related factor UPF3a, by itself or in combination with UPF3b, also has no effect on TCRβ NMD. Mapping experiments revealed the identity of TCRβ sequences that elicit a switch to UPF3b dependence. This regulation is not a peculiarity of TCRβ, as we identified many wild‐type genes, including one essential for NMD, that transcribe NMD‐targeted mRNAs whose downregulation is little or not affected by UPF3a and UPF3b depletion. We propose that we have uncovered an alternative branch of the NMD pathway that not only degrades aberrant mRNAs but also regulates normal mRNAs, including one that participates in a negative feedback loop controlling the magnitude of NMD.
A methodology is given for modeling the dynamics of discrete-event stochastic systems as optimization problems. The intent is to provide a means to utilize the rich mathematical theory and algorithms ...of optimization in the study of this important class of systems. A procedure for mapping a simulation event relationship graph into a mixed-integer program is presented, along with examples of queueing networks and manufacturing systems that illustrate the approach. Several potential applications are examined, including automatic constraint generation for optimal resource scheduling, representations of max-plus algebra models for queueing system dynamics, response gradient estimation, and an unconventional technique for simulating queueing systems using virtual resources that are identified from the optimization models for these systems.
We investigated the influence of native defects on the adsorption and photocatalytic degradation of anionic and cationic dyes for different ZnO nanoparticles. We found that there was no relationship ...between the dye adsorption onto ZnO nanoparticles and their photocatalytic activity. Fast photocatalytic degradation could be observed for samples having a low concentration of nonradiative defects (and thus low recombination losses of photogenerated carriers), regardless of the amount of dye adsorbed onto the surface. While the absorption of cationic dyes was not significantly affected by ZnO nanoparticle properties, dye adsorption of several anionic dyes was strongly affected by native defects in ZnO. The defects involved in the dye adsorption are likely shallow donor centers exhibiting an electron spin resonance peak at g ≈ 1.957, resulting in positively charged sites at the surface.
The phenotypic instability of adult tissue‐derived Schwann cell‐like cells (SCLCs) as revealed upon withdrawal of glia‐inducing culture supplements limits their clinical utility for cell therapy and ...disease modelling. We previously overcame this limitation by co‐culturing bone marrow‐derived SCLCs with neurons purified from developing rat and subsequently human sensory neurons such that direct contact between cell types accomplished the cell‐intrinsic switch to the Schwann cell fate. Here, our search for juxtacrine instructive signals found both Notch ligands and neuregulin‐1 type III localized on the surface of DRG neurons via live cell immunocytochemistry. Bypassing ligand‐induced release of the Notch intracellular domain (NICD) by transient transfection of SCLCs with the pAdlox/V5‐His‐NICD construct was shown to upregulate ErbB2/3. Interaction of ErbB2/3 with neuregulin‐1 type III (NRG1 type III) as presented on neurons then mediated the switch to the Schwann cell fate as demonstrated by expression of S100β/p75/ Sox10/Krox20. In contrast, treatment of cocultures with γ‐secretase inhibitor perturbed Notch signalling in SCLCs and consequently deterred both upregulation of ErbB2/3 and the transition to the Schwann cell fate. Taken together, juxtacrine signalling via Notch is key to the upregulation of ErbB receptors for neuregulin‐driven commitment of SCLCs to the Schwann cell fate.
Bone marrow stromal cells (BMSCs) differentiate into Schwann cell‐like cells (SCLCs) following culture supplementation with gliogenic factors. We demonstrate that subsequent coculture with purified dorsal root ganglia (DRG) neurons direct SCLCs to fate commitment by means of Notch‐mediated upregulation of ErbB receptors. Formation of intact ErbB2/B3 then allows for neuregulin‐driven maturation.
Recent research in silicon photonic chips has made huge progress in optical computing owing to their high speed, small footprint, and low energy consumption. Here, we employ nanostructured 2×2 ...optical processors in an optical neural network for implementing a binary classification task efficiently. The proposed optical neural network is composed of five linear layers including ten optical processors in each layer, and nonlinear activation functions. 2×2 optical processors are designed based on digitized meta-structures which have an extremely compact footprint of 1.6×4 μm 2 . A brand-new end-to-end design strategy based on Deep Q-Network is proposed to optimize the optical neural network for classifying a generated ring data set with better generalization, robustness, and operability. A high-efficient transfer matrix multiplication method is applied to simplify the calculation process in traditional optical software. Our numerical results illustrate that the maximum and mean accuracy on the testing data set can reach 90.5% and 87.8%, respectively. The demonstrated optical processors with a significantly compact area, and the efficient optimization method exhibit high potential for large-scale integration of whole-passive optical neural network on a photonic chip.
Information sharing during emergency events often takes place through popular social messaging apps. An emergency response area of increasing concern in recent times is that of mass attacks on school ...campuses yet work studying information sharing systems in these situations is scarce. In this exploratory work, we used data from various sources to construct an agent-based simulation of a hypothetical knife attack on a university campus in southern China. We model the information sharing system after WeChat and evaluate the impact of group and individual messages on attack response and outcome. Evaluation metrics such as how students become alerted to the attack, the maintenance of accurate information, and casualty levels, are tracked. Results suggest that group messages may be most helpful despite being perceived as less trustworthy, and that the presence and structure of information sharing systems has a significant effect on response to campus attack events. Future work in the area is suggested.
Anti-mitosis has been a key strategy of anti-cancer therapies, targeting at a fundamental property of cancer cells, their non-controllable proliferation due to overactive mitotic divisions. For ...improved anti-cancer therapies, it is important to find out whether cancer cells can proliferate independent of mitosis and become resistant to anti-mitotic agents.
In this study, live-cell imaging was applied to both primary-cultures of tumor cells, and immortalized cancer cell lines, to detect aberrant proliferations. Cells isolated from various malignant tumors, such as Grade-III hemangiopericytoma, atypical meningioma, and metastatic brain tumor exhibit distinct cellular behaviors, including amoeboid sequestration, tailing, tunneling, nucleic DNA leakage, as well as prokaryote-like division such as binary fission and budding-shedding, which are collectively referred to and reported as 'non-mitotic proliferation' in this study. In contrast, benign tumors including Grade-I hemangiopericytoma and meningioma were not obvious in such behaviors. Moreover, when cultured in medium free of any anti-cancer drugs, cells from a recurrent Grade-III hemangiopericytoma that had been subjected to pre-operation adjuvant chemotherapy gradually shifted from non-mitotic proliferation to abnormal mitosis in the form of daughter number variation (DNV) and endomitosis, and eventually regular mitosis. Similarly, when treated with the anti-cancer drugs Epirubicin or Cisplatin, the cancer cell lines HeLa and A549 showed a shift from regular mitosis to abnormal mitosis, and further to non-mitosis as the dominant mode of proliferation with increasing drug concentrations. Upon removal of the drugs, the cells reversed back to regular mitosis with only minor occurrences of abnormal mitosis, accompanied by increased expression of the stem cell markers ALDH1, Sox, Oct4 and Nanog.
The present study revealed that various types of malignant, but not benign, cancer cells exhibited cellular behaviors indicative of non-mitotic proliferation such as binary fission, which was typical of prokaryotic cell division, suggesting cell level atavism. Moreover, reversible transitions through the three modes of proliferation, i.e., mitosis, abnormal mitosis and non-mitosis, were observed when anticancer drug concentrations were grossly increased inducing non-mitosis or decreased favoring mitosis. Potential clinical significance of non-mitotic proliferation in cancer drug resistance and recurrence, and its relationship with cancer stem cells are worthy of further studies.
PDF
