Publications by authors named "Doris Chen"

This chapter describes the computational pipeline for the processing and visualization of Protec-Seq data, a method for purification and genome-wide mapping of double-stranded DNA protected by a specific protein at both ends. In the published case, the protein of choice was Saccharomyces cerevisiae Spo11, a conserved topoisomerase-like enzyme that makes meiotic double-strand breaks (DSBs) to initiate homologous recombination, ensuring proper segregation of homologous chromosomes and fertility. The isolated DNA molecules were thus termed double DSB (dDSB) fragments and were found to represent 34 to several hundred base-pair long segments that are generated by Spo11 and are enriched at DSB hotspots, which are sites of topological stress.

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Article Synopsis
  • * The study investigates how advanced glycation endproducts (AGEs) and their precursor, methylglyoxal (MG), negatively affect synaptic mitochondria, leading to reduced mitochondrial function and increased oxidative stress in aging brains.
  • * Enhancing the expression of the detoxifying enzyme glyoxalase 1 (GLO1) in neuronal cells helps eliminate AGEs, which improves mitochondrial health and cognitive function by restoring synaptic plasticity and transmission.
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Electrophilic halogenation is a widely used tool employed by medicinal chemists to either pre-functionalize molecules for further diversity or incorporate a halogen atom into drugs or drug-like compounds to solve metabolic problems or modulate off-target effects. Current methods to increase the power of halogenation rely on either the invention of new reagents or activating commercially available reagents with various additives such as Lewis or Brønsted acids, Lewis bases and hydrogen-bonding activators. There is a high demand for new reagents that can halogenate otherwise unreactive compounds under mild conditions.

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Meiotic recombination is of central importance for the proper segregation of homologous chromosomes, but also for creating genetic diversity. It is initiated by the formation of double-strand breaks (DSBs) in DNA catalysed by evolutionarily conserved Spo11, together with additional protein partners. Difficulties in purifying the Spo11 protein have limited the characterization of its biochemical properties and of its interactions with other DSB proteins.

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Introduction: Little is known about which conditions seen in primary care are appropriate for video visits. This study evaluated video visits compared to office visits for six conditions: abdominal pain, joint pain, back pain, headache, chest pain, and dizziness.

Methods: Six hundred charts of adult patients from our institution's same-day outpatient clinic were reviewed in this study.

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Mitochondrial dysfunction is an early pathological feature of Alzheimer disease and plays a crucial role in the development and progression of Alzheimer's disease. Strategies to rescue mitochondrial function and cognition remain to be explored. Cyclophilin D (CypD), the peptidylprolyl isomerase F (PPIase), is a key component in opening the mitochondrial membrane permeability transition pore, leading to mitochondrial dysfunction and cell death.

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Background: There is increasing evidence that people with hallucinations overweight perceptual beliefs relative to incoming sensory evidence. Past work demonstrating prior overweighting has used simple, nonlinguistic stimuli. However, auditory hallucinations in psychosis are often complex and linguistic.

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Introduction: Hepatocellular carcinoma (HCC) patients at advanced stages receive immunotherapy or treatment with tyrosine kinase inhibitors (TKIs) such as Sorafenib (Sora) or Lenvatinib in frontline as well as Regorafenib (Rego) or Cabozantinib in second-line. A major hindrance of TKI therapies is the development of resistance, which renders drug treatment futile and results in HCC progression.

Methods: In this study, we addressed the impact of the receptor tyrosine kinase Axl binding to its ligand Gas6 in acquiring refractoriness to TKIs.

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Headache is an ancient problem plaguing a large proportion of the population. At present, headache disorders rank third among the global causes of disability, accounting for over $78 billion per year in direct and indirect costs in the United States. Given the prevalence of headache and the wide range of possible etiologies, the goal of this document is to help clarify the most appropriate initial imaging guidelines for headache for eight clinical scenarios/variants, which range from acute onset, life-threatening etiologies to chronic benign scenarios.

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Chronic shoulder pain is an extremely common presenting complaint. Potential pain generators include the rotator cuff tendons, biceps tendon, labrum, glenohumeral articular cartilage, acromioclavicular joint, bones, suprascapular and axillary nerves, and the joint capsule/synovium. Radiographs are typically the initial imaging study obtained in patients with chronic shoulder pain.

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Article Synopsis
  • Activation of the Axl receptor by Gas6 is linked to aggressive behavior in hepatocellular carcinoma (HCC) and worse patient outcomes, but the specific genes influenced by this signaling are not fully understood.
  • Researchers used RNA sequencing and various studies to identify PRAME as a key target of the Gas6/Axl signaling pathway, which is connected to increased cancer cell movement and invasiveness.
  • Higher levels of PRAME in HCC patients reflect a more aggressive tumor phenotype and correlate with worse survival rates, highlighting its potential as a therapeutic target in HCC.*
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Willin/ has been reported as a potential Alzheimer's disease (AD) risk gene in a series of genome-wide association and neuroimaging studies; however, the mechanisms underlying its potential role in AD pathogenesis remain unknown. Here, we demonstrate the direct effects of Aβ on Willin/FRMD6 expression and position mitochondrial oxidative stress as a novel potential mechanism underlying the role of Willin/FRMD6 in AD pathogenesis. Specifically, using mouse hippocampal HT-22 cells and primary mouse neurons, we show that Aβ induces downregulation of Willin/FRMD6 protein expression.

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Herein, a SnCl -catalyzed intramolecular, interrupted homo-Nazarov cascade biscyclization to access angular (hetero)aryl-fused polycycles is reported. Subsequent decarboxylation of the readily enolizable products afforded the angular products in up to 71 % yield over two steps, with the trans-diastereomers as the major products. The cyclopropyl homo-Nazarov cyclization precursors were formed using a scalable and modular synthetic route that, ultimately, offers access to 6,6,6-, 6,6,5-, 6,5,6-, 6,6,5,6-, and 6,6,6,5-fused angular polycyclic products.

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The FERM domain-containing protein 6 (FRMD6), also known as Willin, is an upstream regulator of Hippo signaling that has recently been shown to modulate actin cytoskeleton dynamics and mechanical phenotype of neuronal cells through ERK signaling. Physiological functions of Willin/FRMD6 in the nervous system include neuronal differentiation, myelination, nerve injury repair, and vesicle exocytosis. The newly established neuronal role of Willin/FRMD6 is of particular interest given the mounting evidence suggesting a role for Willin/FRMD6 in Alzheimer's disease (AD), including a series of genome wide association studies that position Willin/FRMD6 as a novel AD risk gene.

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Meiotic recombination is essential for chromosome segregation at meiosis and fertility. It is initiated by programmed DNA double-strand breaks (DSBs) introduced by Spo11, a eukaryotic homologue of an archaeal topoisomerase (Topo VIA). Here we describe previously uncharacterized Spo11-induced lesions, 34 to several hundred base pair-long gaps, which are generated by coordinated pairs of DSBs termed double DSBs.

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Mitochondrial dysfunction is one of the early pathological features of Alzheimer's disease (AD). Accumulation of cerebral and mitochondrial Aβ links to mitochondrial and synaptic toxicity. We have previously demonstrated the mechanism by which presequence peptidase (PITRM1)-mediated clearance of mitochondrial Aβ contributes to mitochondrial and cerebral amyloid pathology and mitochondrial and synaptic stress in adult transgenic AD mice overexpressing Aβ up to 12 months old.

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Aging is a strong risk factor for brain dementia and cognitive decline. Age-related accumulation of metabolites such as advanced glycation end products (AGEs) could serve as danger signals to initiate and accelerate disease process and neurodegeneration. The underlying causes and consequences of cerebral AGEs accumulation remain largely unknown.

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In a recent methodological study investigating the synthesis of -alkoxyazomethine ylides, an unexpected aminal byproduct was generated during our attempt to isolate -benzyl--((trimethylsilyl)methyl)hydroxylamine. After a strategic investigation, silica gel was discovered to be the cause of the byproduct formation. Through the mechanistic insight from control and trapping experiments, we propose the formation of a methaniminium ion via a novel aza-Peterson reaction, which ultimately triggers a sequential iminium ion cascade sequence.

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Willin/FRMD6 is part of a family of proteins with a 4.1 ezrin-radixin-moesin (FERM) domain. It has been identified as an upstream activator of the Hippo pathway and, when aberrant in its expression, is associated with human diseases and disorders.

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: There is a lack of research regarding whether prolonged use of cocaine would lead to increase of coronary plaque burden. : To study the effects of cocaine use on the coronary artery plaque volume. We hypothesize the longer the cocaine use, the greater the plaque burden.

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Transcription elongation is a highly regulated process affected by many proteins, RNAs and the underlying DNA. Here we show that the nascent RNA can interfere with transcription in human cells, extending our previous findings from bacteria and yeast. We identified a variety of Pol II-binding aptamers (RAPs), prominent in repeat elements such as ACRO1 satellites, LINE1 retrotransposons and CA simple repeats, and also in several protein-coding genes.

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Background: Advanced glycation end products (AGEs) are an important risk factor for the development of cognitive decline in aging and late-onset neurodegenerative diseases including Alzheimer's disease. However, whether and how dietary AGEs exacerbate cognitive impairment and brain mitochondrial dysfunction in the aging process remains largely unknown.

Objective: We investigated the direct effects of dietary AGEs on AGE adducts accumulation, mitochondrial function, and cognitive performance in mice.

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Objectives: To assess the effectiveness of a clinical decision support tool consisting of an electronic medical record best practice alert (BPA) on the frequency of lumbar imaging in patients with acute low back pain in the ambulatory care setting, and to explore why providers order imaging outside of clinical guidelines.

Methods: On March 23, 2016, we implemented a BPA pop-up alert that informed the ordering physician of the Choosing Wisely recommendation to not order imaging within the first 6 weeks of low back pain in the absence of red flags. We calculated imaging rates 1 year before and after implementation of the BPA.

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Article Synopsis
  • - Recurrent gain-of-function mutations in transcription factors are prevalent in hematopoietic malignancies, particularly in mature T-cell and natural killer-cell neoplasms like peripheral T-cell lymphoma (PTCL), which currently lack targeted therapies
  • - Researchers created transgenic mice with heightened STAT5A or STAT5B activity, and only those with high levels developed a fatal disease similar to human PTCL, characterized by extensive CD8 T-cell expansion and organ infiltration
  • - Analysis showed that increased STAT5 activity correlates with different PTCL subtypes, suggesting that JAK/STAT pathways are promising therapeutic targets, as both JAK inhibitors and selective STAT5 inhibitors effectively induced cell death in T-cell neoplasia*.
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