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1.
Sensors (Basel) ; 24(5)2024 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-38474967

RESUMO

This paper presents the integration of a sensing layer over interdigitated electrodes and an electronic circuit on the same flexible printed circuit board. This integration provides an effective technique to use this design as a wearable gas measuring system in a target application, exhibiting high performance, low power consumption, and being lightweight for on-site monitoring. The wearable system proves the concept of using an NFC tag combined with a chemoresistive gas sensor as a cumulative gas sensor, having the possibility of holding the data for a working day, and completely capturing the exposure of a person to NO2 concentrations. Three different types of sensors were tested, depositing the sensing layers on gold electrodes over Kapton substrate: bare graphene, graphene decorated with 5 wt.% zinc oxide nanoflowers, or nanopillars. The deposited layers were characterized using FESEM, EDX, XRD, and Raman spectroscopy to determine their crystalline structure, morphological and chemical compositions. The gas sensing performance of the sensors was analyzed against NO2 (dry and humid conditions) and other interfering species (dry conditions) to check their sensitivity and selectivity. The resultant-built wearable NFC tag system accumulates the data in a non-volatile memory every minute and has an average low power consumption of 24.9 µW in dynamic operation. Also, it can be easily attached to a work vest.

2.
ACS Omega ; 9(11): 13028-13040, 2024 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-38524411

RESUMO

In this paper, we develop high-performance gas sensors based on heteroatom-doped and -codoped graphene oxide as a sensing material for the detection of NO2 at trace levels. Graphene oxide (GO) was doped with nitrogen and boron by a chemical method using urea and boric acid as precursors. The prepared samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The obtained results proved the successful reduction of graphene oxide by doping effects, leading to the removal of some oxygen functional groups and restoration of an sp2 carbon structure. New bonds in honeycombs, such as pyridinic, pyrrolic, graphitic, B-C3, B-C2-O, and B-O, were created. Compared to the nondoped GO, the N/B-rGO materials exhibited enhanced responses toward low concentrations of NO2 (<1 ppm) at 100 °C. Particularly, the N-rGO-based device showed the highest sensitivity and lowest limit of detection.

3.
Int J Mol Sci ; 24(14)2023 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-37511060

RESUMO

Adipocytes play a critical role in maintaining a healthy systemic metabolism by storing and releasing energy in the form of fat and helping to regulate glucose and lipid levels in the body. Adipogenesis is the process through which pre-adipocytes are differentiated into mature adipocytes. It is a complex process involving various transcription factors and signaling pathways. The dysregulation of adipogenesis has been implicated in the development of obesity and metabolic disorders. Therefore, understanding the mechanisms that regulate adipogenesis and the factors that contribute to its dysregulation may provide insights into the prevention and treatment of these conditions. RNA-binding motif single-stranded interacting protein 1 (RBMS1) is a protein that binds to RNA and plays a critical role in various cellular processes such as alternative splicing, mRNA stability, and translation. RBMS1 polymorphism has been shown to be associated with obesity and type 2 diabetes, but the role of RBMS1 in adipose metabolism and adipogenesis is not known. We show that RBMS1 is highly expressed during the early phase of the differentiation of the murine adipocyte cell line 3T3-L1 and is significantly upregulated in the adipose tissue depots and adipocytes of high-fat-fed mice, implying a possible role in adipogenesis and adipose metabolism. Knockdown of RBMS1 in pre-adipocytes impacted the differentiation process and reduced the expression of some of the key adipogenic markers. Transcriptomic and proteomic analysis indicated that RBMS1 depletion affected the expression of several genes involved in major metabolic processes, including carbohydrate and lipid metabolism. Our findings imply that RBMS1 plays an important role in adipocyte metabolism and may offer novel therapeutic opportunity for metabolic disorders such as obesity and type 2 diabetes.


Assuntos
Adipócitos , Adipogenia , Animais , Camundongos , Células 3T3-L1 , Adipócitos/metabolismo , Adipogenia/genética , Diferenciação Celular/genética , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Metabolismo dos Lipídeos/genética , Obesidade/metabolismo , Proteômica , Transcriptoma
4.
Biology (Basel) ; 12(3)2023 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-36979108

RESUMO

Heat stroke is among the most hazardous hyperthermia-related illnesses and an emerging threat to humans from climate change. Acute brain injury and long-lasting brain damage are the hallmarks of this condition. Hyperthermic neurological manifestations are remarkable for their damage correlation with stress amplitude and long-term persistence. Hyperthermia-induced protein unfolding, and nonspecific aggregation accumulation have neurotoxic effects and contribute to the pathogenesis of brain damage in heat stroke. Therefore, we generated heat-induced, dose-responsive extreme and mild proteotoxic stress models in medulloblastoma [Daoy] and neuroblastoma [SH-SY5Y] and differentiated SH-SY5Y neuronal cells. We show that heat-induced protein aggregation is associated with reduced cell proliferation and viability. Higher protein aggregation in differentiated neurons than in neuroblastoma precursors suggests a differential neuronal vulnerability to heat. We characterized the neuronal heat shock response through RT-PCR array analysis of eighty-four genes involved in protein folding and protein quality control (PQC). We identify seventeen significantly expressed genes, five of which are Hsp70 chaperones, and four of their known complementing function proteins. Protein expression analysis determined the individual differential contribution of the five Hsp70 chaperones to the proteotoxic stress response and the significance of only two members under mild conditions. The co-expression analysis reveals significantly high co-expression between the Hsp70 chaperones and their interacting partners. The findings of this study lend support to the hypothesis that hyperthermia-induced proteotoxicity may underlie the brain injury of heat stroke. Additionally, this study presents a comprehensive map of the Hsp70 network in these models with potential clinical and translational implications.

5.
J Physiol ; 601(12): 2407-2423, 2023 06.
Artigo em Inglês | MEDLINE | ID: mdl-36951421

RESUMO

An evolutionary heat shock response (HSR) protects most living species, including humans, from heat-induced macromolecular damage. However, its role in the pathogenesis of heat stroke is unknown. We examined the whole genome transcriptome in peripheral blood mononuclear cells of a cohort of subjects exposed to the same high environmental heat conditions, who developed heat stroke (n = 19) versus those who did not (n = 19). Patients with heat stroke had a mean rectal temperature at admission of 41.7 ± 0.8°C, and eight were in deep coma (Glasgow Coma Score = 3). The transcriptome showed that genes involved in more than half of the entire chaperome were differentially expressed relative to heat stress control. These include the heat shock protein, cochaperone, and chaperonin genes, indicating a robust HSR. Differentially expressed genes also encoded proteins related to unfolded protein response, DNA repair, energy metabolism, oxidative stress, and immunity. The analysis predicted perturbations of the proteome network and energy production. Cooling therapy attenuated these alterations without complete restoration of homeostasis. We validated the significantly expressed genes by a real-time polymerase chain reaction. The findings reveal the molecular signature of heat stroke. They also suggested that a powerful HSR may not be sufficient to protect against heat injury. The overwhelming proteotoxicity and energy failure could play a pathogenic role. KEY POINTS: Most living species, including humans, have inherent heat stress response (HSR) that shields them against heat-induced macromolecular damage. The role of the HSR in subjects exposed to environmental heat who progressed to heat stroke versus those that did not is unknown. Our findings suggest that heat stroke induces a broad and robust HSR of nearly half of the total heat shock proteins, cochaperones, and chaperonin genes. Heat stroke patients exhibited inhibition of genes involved in energy production, including oxidative phosphorylation and ATP production. Significant enrichment of neurodegenerative pathways, including amyloid processing signalling, the Huntington's and Parkinson's disease signalling suggestive of brain proteotoxicity was noted. The data suggests that more than a powerful HSR may be required to protect against heat stroke. Overwhelming proteotoxicity and energy failure might contribute to its pathogenesis.


Assuntos
Golpe de Calor , Transcriptoma , Humanos , Coma , Leucócitos Mononucleares , Resposta ao Choque Térmico/genética , Proteínas de Choque Térmico/genética , Golpe de Calor/genética
6.
Cells ; 12(3)2023 01 19.
Artigo em Inglês | MEDLINE | ID: mdl-36766718

RESUMO

G protein-coupled receptors (GPCRs) are expressed essentially on all cells, facilitating cellular responses to external stimuli, and are involved in nearly every biological process. Several members of this family play significant roles in the regulation of adipogenesis and adipose metabolism. However, the expression and functional significance of a vast number of GPCRs in adipose tissue are unknown. We used a high-throughput RT-PCR panel to determine the expression of the entire repertoire of non-sensory GPCRs in mouse white, and brown adipose tissue and assess changes in their expression during adipogenic differentiation of murine adipocyte cell line, 3T3-L1. In addition, the expression of GPCRs in subcutaneous adipose tissues from lean, obese, and diabetic human subjects and in adipocytes isolated from regular chow and high-fat fed mice were evaluated by re-analyzing RNA-sequencing data. We detected a total of 292 and 271 GPCRs in mouse white and brown adipose tissue, respectively. There is a significant overlap in the expression of GPCRs between the two adipose tissue depots, but several GPCRs are specifically expressed in one of the two tissue types. Adipogenic differentiation of 3T3-L1 cells had a profound impact on the expression of several GPCRs. RNA sequencing of subcutaneous adipose from healthy human subjects detected 255 GPCRs and obesity significantly changed the expression of several GPCRs in adipose tissue. High-fat diet had a significant impact on adipocyte GPCR expression that was similar to human obesity. Finally, we report several highly expressed GPCRs with no known role in adipose biology whose expression was significantly altered during adipogenic differentiation, and/or in the diseased human subjects. These GPCRs could play an important role in adipose metabolism and serve as a valuable translational resource for obesity and metabolic research.


Assuntos
Adipócitos , Obesidade , Humanos , Camundongos , Animais , Adipócitos/metabolismo , Obesidade/metabolismo , Diferenciação Celular/genética , Tecido Adiposo Marrom/metabolismo , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo
7.
Cureus ; 14(10): e30005, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36348889

RESUMO

Coronavirus disease 2019 (COVID-19) has a wide range of clinical manifestations, affecting multiple organ systems. Cardiovascular manifestations of COVID-19 that have been reported include arrhythmias, myocarditis, and an increased predisposition to acute myocardial infarction. Takotsubo cardiomyopathy (TCM), which is characterized by apical ballooning of the heart leading to acute left ventricular dysfunction, is scarcely seen in COVID-19 patients. We present a case of COVID-19-associated TCM in a 68-year-old man.  A 68-year-old man with no significant past medical history presented with sudden-onset midsternal pressure-like chest pain at rest, associated with diaphoresis and shortness of breath. This occurred ten days after diagnosis of COVID-19 with mild symptoms, with no other recent physical or emotional stressors. At presentation, he was afebrile (98.5 °F), hypertensive (177/108 mmHg), tachycardic (HR 118 bpm), and saturating 100% on room air. Labs were significant for leukocytosis with 15.1 × 103 WBCs/mcL, elevated creatinine (1.46 g/dL), brain natriuretic peptide (BNP) of 156, troponin of 4 ng/mL that peaked at 16.28 ng/mL. The rapid COVID-19 test was positive. EKG showed anterolateral ST elevation and QTc interval of 446 ms. Echo showed severe hypokinesis of mid and apical segments and severely decreased left ventricular ejection fraction (LVEF)of <30%. Emergent left heart catheterization showed 75% mid left anterior descending coronary artery (LAD) stenosis and moderate right coronary artery (RCA) disease, while the ventriculogram showed a left ventricular ejection fraction of 35% with anteroapical and inferoapical akinesia suggestive of Takotsubo cardiomyopathy. The patient was placed on aspirin, ticagrelor, and atorvastatin, carvedilol, and lisinopril. EKG the next day showed a prolonged QTc of 526 ms with T-wave inversion and no ST elevations. The patient had no findings consistent with myocarditis or pheochromocytoma. He was discharged two days later. Within the next few weeks, his symptoms improved, and a follow-up echo confirmed normalization of left ventricular function.  There has been an increased incidence of Takotsubo cardiomyopathy during the COVID-19 pandemic compared to the pre-pandemic period. There is only a slight female preponderance in COVID-19-induced TCM, possibly because males are predominantly affected by COVID-19. Our patient satisfied all four Mayo Clinic criteria required for the diagnosis of TCM. Pathophysiology of TCM in COVID-19 is linked with cytokine storm and consequent catecholamine surge. Most patients improve within succeeding weeks or months. Nonetheless, the case fatality rate is high 36.5%, which is significantly higher compared to TCM patients without COVID-19. COVID-19 has a multisystem involvement with various clinical presentations. New cardiomyopathy in COVID-19 patients should raise suspicion among clinicians regarding stress-induced cardiomyopathy.

8.
Curr Issues Mol Biol ; 44(10): 4748-4768, 2022 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-36286039

RESUMO

Placenta-derived stem cells (PDSCs), due to unique traits such as mesenchymal and embryonic characteristics and the absence of ethical constraints, are in a clinically and therapeutically advantageous position. To aid in stemness maintenance, counter pathophysiological stresses, and withstand post-differentiation challenges, stem cells require elevated protein synthesis and consequently augmented proteostasis. Stem cells exhibit source-specific proteostasis traits, making it imperative to study them individually from different sources. These studies have implications for understanding stem cell biology and exploitation in the augmentation of therapeutic applications. Here, we aim to identify the primary determinants of proteotoxic stress response in PDSCs. We generated heat-induced dose-responsive proteotoxic stress models of three stem cell types: placental origin cells, the placenta-derived mesenchymal stem cells (pMSCs), maternal origin cells, the decidua parietalis mesenchymal stem cells (DPMSCs), and the maternal-fetal interface cells, decidua basalis mesenchymal stem cells (DBMSCs), and measured stress induction through biochemical and cell proliferation assays. RT-PCR array analysis of 84 genes involved in protein folding and protein quality control led to the identification of Hsp70 members HSPA1A and HSPA1B as the prominent ones among 17 significantly expressed genes and with further analysis at the protein level through Western blotting. A kinetic analysis of HSPA1A and HSPA1B gene and protein expression allowed a time series evaluation of stress response. As identified by protein expression, an active stress response is in play even at 24 h. More prominent differences in expression between the two homologs are detected at the translational level, alluding to a potential higher requirement for HSPA1B during proteotoxic stress response in PDSCs.

9.
Cells ; 11(4)2022 02 21.
Artigo em Inglês | MEDLINE | ID: mdl-35203397

RESUMO

Fatty acids (FFAs) are important biological molecules that serve as a major energy source and are key components of biological membranes. In addition, FFAs play important roles in metabolic regulation and contribute to the development and progression of metabolic disorders like diabetes. Recent studies have shown that FFAs can act as important ligands of G-protein-coupled receptors (GPCRs) on the surface of cells and impact key physiological processes. Free fatty acid-activated receptors include FFAR1 (GPR40), FFAR2 (GPR43), FFAR3 (GPR41), and FFAR4 (GPR120). FFAR2 and FFAR3 are activated by short-chain fatty acids like acetate, propionate, and butyrate, whereas FFAR1 and FFAR4 are activated by medium- and long-chain fatty acids like palmitate, oleate, linoleate, and others. FFARs have attracted considerable attention over the last few years and have become attractive pharmacological targets in the treatment of type 2 diabetes and metabolic syndrome. Several lines of evidence point to their importance in the regulation of whole-body metabolic homeostasis including adipose metabolism. Here, we summarize our current understanding of the physiological functions of FFAR isoforms in adipose biology and explore the prospect of FFAR-based therapies to treat patients with obesity and Type 2 diabetes.


Assuntos
Tecido Adiposo , Diabetes Mellitus Tipo 2 , Ácidos Graxos não Esterificados , Receptores Acoplados a Proteínas G , Tecido Adiposo/metabolismo , Ácidos Graxos não Esterificados/metabolismo , Humanos , Ligantes , Obesidade , Receptores Acoplados a Proteínas G/metabolismo
10.
Int J Mol Sci ; 22(11)2021 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-34072007

RESUMO

Adrenergic receptor ß3 (ADRß3) is a member of the rhodopsin-like G protein-coupled receptor family. The binding of the ligand to ADRß3 activates adenylate cyclase and increases cAMP in the cells. ADRß3 is highly expressed in white and brown adipocytes and controls key regulatory pathways of lipid metabolism. Trp64Arg (W64R) polymorphism in the ADRß3 is associated with the early development of type 2 diabetes mellitus, lower resting metabolic rate, abdominal obesity, and insulin resistance. It is unclear how the substitution of W64R affects the functioning of ADRß3. This study was initiated to functionally characterize this obesity-linked variant of ADRß3. We evaluated in detail the expression, subcellular distribution, and post-activation behavior of the WT and W64R ADRß3 using single cell quantitative fluorescence microscopy. When expressed in HEK 293 cells, ADRß3 shows a typical distribution displayed by other GPCRs with a predominant localization at the cell surface. Unlike adrenergic receptor ß2 (ADRß2), agonist-induced desensitization of ADRß3 does not involve loss of cell surface expression. WT and W64R variant of ADRß3 displayed comparable biochemical properties, and there was no significant impact of the substitution of tryptophan with arginine on the expression, cellular distribution, signaling, and post-activation behavior of ADRß3. The obesity-linked W64R variant of ADRß3 is indistinguishable from the WT ADRß3 in terms of expression, cellular distribution, signaling, and post-activation behavior.


Assuntos
Predisposição Genética para Doença , Variação Genética , Obesidade/genética , Obesidade/metabolismo , Receptores Adrenérgicos beta 3/genética , Receptores Adrenérgicos beta 3/metabolismo , Agonistas de Receptores Adrenérgicos beta 3/farmacologia , Alelos , Substituição de Aminoácidos , Linhagem Celular , Expressão Gênica , Estudos de Associação Genética , Humanos , Mutação , Polimorfismo Genético , Transporte Proteico
11.
Immun Ageing ; 18(1): 1, 2021 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-33390183

RESUMO

The disease (COVID-19) novel coronavirus pandemic has so far infected millions resulting in the death of over a million people as of Oct 2020. More than 90% of those infected with COVID-19 show mild or no symptoms but the rest of the infected cases show severe symptoms resulting in significant mortality. Age has emerged as a major factor to predict the severity of the disease and mortality rates are significantly higher in elderly patients. Besides, patients with underlying conditions like Type 2 diabetes, cardiovascular diseases, hypertension, and cancer have an increased risk of severe disease and death due to COVID-19 infection. Obesity has emerged as a novel risk factor for hospitalization and death due to COVID-19. Several independent studies have observed that people with obesity are at a greater risk of severe disease and death due to COVID-19. Here we review the published data related to obesity and overweight to assess the possible risk and outcome in Covid-19 patients based on their body weight. Besides, we explore how the obese host provides a unique microenvironment for disease pathogenesis, resulting in increased severity of the disease and poor outcome.

12.
Cureus ; 12(7): e9407, 2020 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-32864236

RESUMO

Tracheobronchopathia osteochondroplastica (TBPO) is a rare benign disease of unknown cause, in which multiple cartilaginous or bony submucosal nodules project into the trachea and proximal bronchi. It usually occurs in men in their fifth decade and can cause airway obstruction, bleeding and chronic cough; patients are more prone to post-obstructive pneumonia and chronic lung infection in some instances. We report a case of a 69-year-old female who presented with shortness of breath and lower extremity swelling over the past couple of weeks. Echocardiography (ECHO) was consistent with heart failure with preserved ejection fraction, and she was treated with diuretics accordingly. Imaging revealed persistent pleural effusions bilaterally, more pronounced on the right side. During the course of her hospitalization, the patient coded once and had to be resuscitated. She had bronchoscopy done and pathology was consistent with TBPO. In this condition, there are numerous osseous or cartilaginous submucosal nodules in the trachea and the main bronchus and nodules are formed due to the deposition of calcium phosphate that results in the proliferation of osseous and cartilaginous structures resulting in the obstruction of large airways. Treatment for the most part is supportive and resolves around bronchodilators for symptomatic relief.

13.
Pathogens ; 9(9)2020 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-32825438

RESUMO

The COVID-19 pandemic, in the first seven months, has led to more than 15 million confirmed infected cases and 600,000 deaths. SARS-CoV-2, the causative agent for COVID-19, has proved to be a great challenge for its ability to spread in asymptomatic stages and the diverse disease spectrum it has generated. This has created a challenge of unimaginable magnitude, not only affecting human health and life but also potentially generating a long-lasting socioeconomic impact. Both medical sciences and biomedical research have also been challenged, consequently leading to a large number of clinical trials and vaccine initiatives. While known proteins of pathobiological importance are targets for these therapeutic approaches, it is imperative to explore other factors of viral significance. Accessory proteins are one such trait that have diverse roles in coronavirus pathobiology. Here, we analyze certain genomic characteristics of SARS-CoV-2 accessory protein ORF8 and predict its protein features. We have further reviewed current available literature regarding its function and comparatively evaluated these and other features of ORF8 and ORF8ab, its homolog from SARS-CoV. Because coronaviruses have been infecting humans repeatedly and might continue to do so, we therefore expect this study to aid in the development of holistic understanding of these proteins. Despite low nucleotide and protein identity and differentiating genome level characteristics, there appears to be significant structural integrity and functional proximity between these proteins pointing towards their high significance. There is further need for comprehensive genomics and structural-functional studies to lead towards definitive conclusions regarding their criticality and that can eventually define their relevance to therapeutics development.

14.
J Family Med Prim Care ; 9(10): 5381-5383, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33409221

RESUMO

Hemifacial spasm (HFS) is characterized by involuntary synchronous contractions or spasms of one side of the face, usually beginning around the eye. They are typically brief, irregular clonic movements but are occasionally tonic. We present a case of a 41-year-old female who presented to the neurology clinic with complaints of recurrent right facial spasms. These involuntary spontaneous movements had affected her quality of life. The neuroimaging revealed the vascular malformation right cranial nerves (CN) VII/VIII complex. It was considered to be responsible for the patient's HFSs. The patient responded well symptomatically to the botox injections without any neurovascular decompression.

15.
Curr Mol Med ; 20(6): 488-493, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31840614

RESUMO

BACKGROUND: G protein-coupled receptors (GPCRs) represent the largest family of surface proteins and are involved in the regulation of key physiological processes. GPCRs are characterized by seven transmembrane domains, an extracellular N-terminus and an intracellular C-terminus. Cellular response of these receptors to their ligands is largely determined by their surface expression and postactivation behavior including expression, desensitization and resensitization. OBJECTIVE: To develop a quantitative fluorescence Microscopy assay to study ß2- Adrenergic receptor expression and desensitization. METHOD: ß2-Adrenergic receptor cDNA was engineered to put an HA tag at the extracellular N-terminus and GFP Tag at the intracellular C-terminus. GFP fluorescence serves as a measure of total cellular expression; whereas staining with CY3 conjugated anti-HA antibodies without permeabilizing the cells represents the surface expression of ß2-AR. The images are quantified and amount of CY3 (surface) and GFP (total) fluorescence for each cell determined using image processing software. RESULTS: The method is sensitive and allows for the simultaneous measurement of surface and total expression of ß2-AR. CONCLUSION: A highly accurate method is described for measuring ß2-AR surface and total expression based on single-cell quantitative immunofluorescence. The method can be used to determine agonist-induced desensitization and resensitization process as well as receptor kinetics like endocytosis and exocytosis of ß2-Adrenergic receptor and can be applied to essentially any other GPCR.


Assuntos
Receptores Adrenérgicos beta 2/metabolismo , Animais , Humanos , Microscopia de Fluorescência , Receptores Adrenérgicos beta 2/genética , Transdução de Sinais/genética , Transdução de Sinais/fisiologia , Análise de Célula Única , Software
16.
J Am Chem Soc ; 141(47): 18851-18861, 2019 11 27.
Artigo em Inglês | MEDLINE | ID: mdl-31693361

RESUMO

5-Methylcytosine (mC) is an epigenetic mark that is written by methyltransferases, erased through passive and active mechanisms, and impacts transcription, development, diseases including cancer, and aging. Active DNA demethylation involves TET-mediated stepwise oxidation of mC to 5-hydroxymethylcytosine, 5-formylcytosine (fC), or 5-carboxylcytosine (caC), excision of fC or caC by thymine DNA glycosylase (TDG), and subsequent base excision repair. Many elements of this essential process are poorly defined, including TDG excision of caC. To address this problem, we solved high-resolution structures of human TDG bound to DNA with cadC (5-carboxyl-2'-deoxycytidine) flipped into its active site. The structures unveil detailed enzyme-substrate interactions that mediate recognition and removal of caC, many involving water molecules. Importantly, two water molecules contact a carboxylate oxygen of caC and are poised to facilitate acid-catalyzed caC excision. Moreover, a substrate-dependent conformational change in TDG modulates the hydrogen bond interactions for one of these waters, enabling productive interaction with caC. An Asn residue (N191) that is critical for caC excision is found to contact N3 and N4 of caC, suggesting a mechanism for acid-catalyzed base excision that features an N3-protonated form of caC but would be ineffective for C, mC, or hmC. We also investigated another Asn residue (N140) that is catalytically essential and strictly conserved in the TDG-MUG enzyme family. A structure of N140A-TDG bound to cadC DNA provides the first high-resolution insight into how enzyme-substrate interactions, including water molecules, are impacted by depleting the conserved Asn, informing its role in binding and addition of the nucleophilic water molecule.


Assuntos
Citosina/análogos & derivados , Timina DNA Glicosilase/metabolismo , Citosina/metabolismo , Modelos Moleculares , Ligação Proteica , Conformação Proteica , Timina DNA Glicosilase/química
17.
J Am Chem Soc ; 141(12): 4952-4962, 2019 03 27.
Artigo em Inglês | MEDLINE | ID: mdl-30841696

RESUMO

A broad range of proteins employ nucleotide flipping to recognize specific sites in nucleic acids, including DNA glycosylases, which remove modified nucleobases to initiate base excision repair. Deamination, a pervasive mode of damage, typically generates lesions that are recognized by glycosylases as being foreign to DNA. However, deamination of 5-methylcytosine (mC) generates thymine, a canonical DNA base, presenting a challenge for damage recognition. Nevertheless, repair of mC deamination is important because the resulting G·T mispairs cause C → T transition mutations, and mC is abundant in all three domains of life. Countering this threat are three types of glycosylases that excise thymine from G·T mispairs, including thymine DNA glycosylase (TDG). These enzymes must minimize excision of thymine that is not generated by mC deamination, in A·T pairs and in polymerase-generated G·T mispairs. TDG preferentially removes thymine from DNA contexts in which cytosine methylation is prevalent, including CG and one non-CG site. This remarkable context specificity could be attained through modulation of nucleotide flipping, a reversible step that precedes base excision. We tested this idea using fluorine NMR and DNA containing 2'-fluoro-substituted nucleotides. We find that dT nucleotide flipping depends on DNA context and is efficient only in contexts known to feature cytosine methylation. We also show that a conserved Ala residue limits thymine excision by hindering nucleotide flipping. A linear free energy correlation reveals that TDG attains context specificity for thymine excision through modulation of nucleotide flipping. Our results provide a framework for characterizing nucleotide flipping in nucleic acids using 19F NMR.


Assuntos
DNA Glicosilases/metabolismo , Espectroscopia de Ressonância Magnética , Nucleotídeos/metabolismo , DNA/química , DNA/metabolismo , DNA Glicosilases/química , Cinética , Modelos Moleculares , Conformação de Ácido Nucleico , Conformação Proteica , Especificidade por Substrato , Timina/metabolismo
18.
Cureus ; 11(12): e6338, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31938626

RESUMO

Abdominal hiccups are often masked by abdominal epilepsy (AE) in clinical settings. Spontaneous arrhythmic muscular movements sometimes raise the suspicion for abdominal myoclonus as well. AE is an atypical and rare cause of seizure disorder. It is a manifestation of different transient abdominal complaints correlating with abnormal electroencephalogram (EEG) changes and adequate response to anti-epileptic drugs. We present a case of an 80-year-old female who presented with an episode of tonic-clonic seizure that lasted for almost 10 minutes. The patient was confused and had a facial droop. She had another episode of seizure with a perseverative speech followed by left facial drooping and left upper extremity weakness. She continued having fluctuating mental status and left-sided hemiparesis with intermittent abdominal twitching. She was getting more bradykinetic than bradyphrenic. The computed tomography (CT) scan of the head and magnetic resonance imaging (MRI) of the brain showed a parietal lobe mass that was confirmed on biopsy as malignant glioma. The long-term video monitoring EEG report showed the occurrence of persistent right parietal spikes with background slowing. The brain mass was later treated with radiation therapy and surgery.

19.
Biomed Rep ; 8(3): 275-282, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29564125

RESUMO

The 'Therapeutics discovery: From bench to first in-human trials' conference, held at the King Abdullah International Medical Research Center (KAIMRC), Ministry of National Guard Health Affairs (MNGHA), Kingdom of Saudi Arabia (KSA) from October 10-12, 2017, provided a unique opportunity for experts worldwide to discuss advances in drug discovery and development, focusing on phase I clinical trials. It was the first event of its kind to be hosted at the new research center, which was constructed to boost drug discovery and development in the KSA in collaboration with institutions, such as the Academic Drug Discovery Consortium in the United States of America (USA), Structural Genomics Consortium of the University of Oxford in the United Kingdom (UK), and Institute of Materia Medica of the Chinese Academy of Medical Sciences in China. The program was divided into two parts. A pre-symposium day took place on October 10, during which courses were conducted on clinical trials, preclinical drug discovery, molecular biology and nanofiber research. The attendees had the opportunity for one-to-one meetings with international experts to exchange information and foster collaborations. In the second part of the conference, which took place on October 11 and 12, the clinical trials pipeline, design and recruitment of volunteers, and economic impact of clinical trials were discussed. The Saudi Food and Drug Administration presented the regulations governing clinical trials in the KSA. The process of preclinical drug discovery from small molecules, cellular and immunologic therapies, and approaches to identifying new targets were also presented. The recommendation of the conference was that researchers in the KSA must invest more fund, talents and infrastructure to lead the region in phase I clinical trials and preclinical drug discovery. Diseases affecting the local population, such as Middle East Respiratory Syndrome and resistant bacterial infections, represent the optimal starting point.

20.
Cureus ; 9(7): e1503, 2017 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-28948123

RESUMO

Hospital-acquired multidrug-resistant (MDR) Klebsiella infection is posing a significant challenge to physicians all around the world. The spread of multiple antibiotic resistance among various members of bacteria continues to be a significant clinical threat. Antibiotic susceptibility testing is the initial step in optimizing the appropriate antibiotic therapy for infections with MDR Klebsiella. We report a case of MDR Klebsiella urinary tract infection (UTI) in a patient following a trimalleolar fracture, which was appropriately treated with a combination of amikacin and meropenem.

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