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197 result(s) for "Leão, Ricardo"
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Mechanisms of human telomerase reverse transcriptase (hTERT) regulation: clinical impacts in cancer
Background Limitless self-renewal is one of the hallmarks of cancer and is attained by telomere maintenance, essentially through telomerase (h TERT ) activation. Transcriptional regulation of h TERT is believed to play a major role in telomerase activation in human cancers. Main body The dominant interest in telomerase results from its role in cancer. The role of telomeres and telomere maintenance mechanisms is well established as a major driving force in generating chromosomal and genomic instability. Cancer cells have acquired the ability to overcome their fate of senescence via telomere length maintenance mechanisms, mainly by telomerase activation. h TERT expression is up-regulated in tumors via multiple genetic and epigenetic mechanisms including h TERT amplifications, h TERT structural variants, h TERT promoter mutations and epigenetic modifications through h TERT promoter methylation. Genetic (h TERT promoter mutations) and epigenetic (h TERT promoter methylation and miRNAs) events were shown to have clinical implications in cancers that depend on h TERT activation. Knowing that telomeres are crucial for cellular self-renewal, the mechanisms responsible for telomere maintenance have a crucial role in cancer diseases and might be important oncological biomarkers. Thus, rather than quantifying TERT expression and its correlation with telomerase activation, the discovery and the assessment of the mechanisms responsible for TERT upregulation offers important information that may be used for diagnosis, prognosis, and treatment monitoring in oncology. Furthermore, a better understanding of these mechanisms may promote their translation into effective targeted cancer therapies. Conclusion Herein, we reviewed the underlying mechanisms of h TERT regulation, their role in oncogenesis, and the potential clinical applications in telomerase-dependent cancers.
Reduction in mitochondrial ATP synthesis mimics the effect of low glucose in depolarizing neurons from the subpostremal nucleus of the solitary tract of rats
Neurons of the subpostremal nucleus of the solitary tract (NTS) respond to changes in extracellular glucose with alterations in membrane potential with both depolarization and hyperpolarization. From 5 mM glucose, a rapid shift to 0.5 mM glucose produces a membrane depolarization by an unknown mechanism in most neurons. However, the mechanism involved in this response needs to be known. Here, we investigated if the low glucose-induced depolarization could be mimicked by reducing ATP synthesis and possible mediators of this effect. We showed that applying the mitochondrial uncoupler CCCP (1 µM) reproduced the effects of low glucose depolarizing the membrane, generating an inward current, and decreasing membrane resistance. On the other hand, activation of AMPK did not alter these parameters. To test if low glucose and CCCP could depolarize the membrane by affecting the ionic gradient, we inhibited the electrogenic Na/K pump with 10 µM of ouabain. We observed a similar membrane depolarization but not a decrease in membrane resistance. We conclude that perfusion of neurons of the subpostremal NTS with a low glucose solution depolarizes the membrane by probably reducing intracellular ATP, but not by activating AMPK or decreasing the ionic gradient across the membrane.
Increased hippocampal GABAergic inhibition after long-term high-intensity sound exposure
Exposure to loud sounds is related to harmful mental and systemic effects. The hippocampal function can be affected to either high-intensity sound exposure or long-term sound deprivation. We previously showed that hippocampal long-term potentiation (LTP) is inhibited after ten days of daily exposure to 2 minutes of high-intensity noise (110 dB), in the hippocampi of Wistar rats. Here we investigated how the glutamatergic and GABAergic neurotransmission mediated by ionotropic receptors is affected by the same protocol of high-intensity sound exposure. We found that while the glutamatergic transmission both by AMPA/kainate and NMDA receptors in the Schaffer-CA1 synapses is unaffected by long-term exposure to high-intensity sound, the amplitude of the inhibitory GABAergic currents is potentiated, but not the frequency of both spontaneous and miniature currents. We conclude that after prolonged exposure to short periods of high-intensity sound, GABAergic transmission is potentiated in the hippocampal CA1 pyramidal neurons. This effect could be an essential factor for the reduced LTP in the hippocampi of these animals after high-intensity sound exposure. We conclude that prolonged exposure to high- intensity sound could affect hippocampal inhibitory transmission and consequently, its function.
Biomarkers for Bladder Cancer Diagnosis and Surveillance: A Comprehensive Review
Bladder cancer (BC) ranks as the sixth most prevalent cancer in the world, with a steady rise in its incidence and prevalence, and is accompanied by a high morbidity and mortality. BC is a complex disease with several molecular and pathological pathways, thus reflecting different behaviors depending on the clinical staging of the tumor and molecular type. Diagnosis and monitoring of BC is mainly performed by invasive tests, namely periodic cystoscopies; this procedure, although a reliable method, is highly uncomfortable for the patient and it is not exempt of comorbidities. Currently, there is no formal indication for the use of molecular biomarkers in clinical practice, even though there are several tests available. There is an imperative need for a clinical non-invasive testing for early detection, disease monitoring, and treatment response in BC. In this review, we aim to assess and compare different tests based on molecular biomarkers and evaluate their potential role as new molecules for bladder cancer diagnosis, follow-up, and treatment response monitoring.
Editorial: Cellular and molecular mechanisms of synaptic plasticity at hippocampal and cortical synapses
[...]many neurological diseases and neuropsychiatric disorders are today interpreted as alterations in plasticity mechanisms. Using in vivo recordings and genetic manipulations, they show that cortical plasticity accompanying behavioral habituation occurs across seconds, minutes, and days of repeated stimulus experience. [...]they characterized the role of NMDA receptors and parvalbumin-positive interneurons in such processes, identifying a range of mechanistically separable forms of plasticity occurring at different timescales in the same learning mouse. dos Santos Cardoso et al., focus on the analysis of the potentially beneficial effect of photobiomodulation (transcranial near-infrared laser treatment) on the aging brain. By investigating the expression and activation of distinct intracellular signaling proteins in the cerebral cortex and hippocampus of aged rats treated with the transcranial near-infrared laser, they identify that this experimental approach improves intracellular signaling pathways linked to cell survival, memory, and glucose metabolism.
Profiling of urinary extracellular vesicle protein signatures from patients with cribriform and intraductal prostate carcinoma in a cross-sectional study
Prognostic tests and treatment approaches for optimized clinical care of prostatic neoplasms are an unmet need. Prostate cancer (PCa) and derived extracellular vesicles (EVs) proteome changes occur during initiation and progression of the disease. PCa tissue proteome has been previously characterized, but screening of tissue samples constitutes an invasive procedure. Consequently, we focused this study on liquid biopsies, such as urine samples. More specifically, urinary small extracellular vesicle and particles proteome profiles of 100 subjects were analyzed using liquid chromatography coupled to high-resolution mass spectrometry (LC–MS/MS). We identified 171 proteins that were differentially expressed between intraductal prostate cancer/cribriform (IDC/Crib) and non-IDC/non-Crib after correction for multiple testing. However, the strong correlation between IDC/Crib and Gleason Grade complicates the disentanglement of the underlying factors driving this association. Nevertheless, even after accounting for multiple testing and adjusting for ISUP (International Society of Urological Pathology) grading, two proteins continued to exhibit significant differential expression between IDC/Crib and non-IDC/non-Crib. Functional enrichment analysis based on cancer hallmark proteins disclosed a clear pattern of androgen response down-regulation in urinary EVs from IDC/Crib compared to non-IDC/non-Crib. Interestingly, proteome differences between IDC and cribriform were more subtle, suggesting high proteome heterogeneity. Overall, the urinary EV proteome reflected partly the prostate pathology.
Liquid Biopsies in the Clinical Management of Germ Cell Tumor Patients: State-of-the-Art and Future Directions
Liquid biopsies constitute a minimally invasive means of managing cancer patients, entailing early diagnosis, follow-up and prediction of response to therapy. Their use in the germ cell tumor field is invaluable since diagnostic tissue biopsies (which are invasive) are often not performed, and therefore only a presumptive diagnosis can be made, confirmed upon examination of the surgical specimen. Herein, we provide an overall review of the current liquid biopsy-based biomarkers of this disease, including the classical, routinely used serum tumor markers—the promising microRNAs rapidly approaching the introduction into clinical practice—but also cell-free DNA markers (including DNA methylation) and circulating tumor cells. Finally, and importantly, we also explore novel strategies and challenges for liquid biopsy markers and methodologies, providing a critical view of the future directions for liquid biopsy tests in this field, highlighting gaps and unanswered questions.
Clinical Validation of a Urine Test (Uromonitor-V2®) for the Surveillance of Non-Muscle-Invasive Bladder Cancer Patients
The costly and burdensome nature of the current follow-up methods in non-muscle-invasive bladder cancer (NMIBC) drives the development of new methods that may alternate with regular cystoscopy and urine cytology. The Uromonitor-V2® is a new urine-based assay in the detection of hotspot mutations in three genes (TERT, FGFR3, and KRAS) for evaluation of disease recurrence. The aim of this study was to investigate the Uromonitor-V2®’s performance in detecting NMIBC recurrence and compare it with urine cytology. From February 2018 to September 2019 patients were enrolled. All subjects underwent a standard-of-care (SOC) cystoscopy, either as part of their follow-up for NMIBC or for a nonmalignant urological pathology. Urine cytology was performed in NMIBC patients. Out of the 105 patients enrolled, 97 were eligible for the study. Twenty patients presented nonmalignant lesions, 29 had a history of NMIBC with disease recurrence, and 49 had a history of NMIBC without recurrence. In NMIBC, the Uromonitor-V2® displayed a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 93.1%, 85.4%, 79.4%, and 95.3%, respectively. Urine cytology was available for 52 patients, and the sensitivity, specificity, PPV, and NPV were 26.3%, 90.9%, 62.5%, and 68.2%, respectively. With its high NPV of 95.3%, the Uromonitor-V2® revealed promising properties for the follow-up of patients with NMIBC.
Extracellular Vesicle Proteome in Prostate Cancer: A Comparative Analysis of Mass Spectrometry Studies
Molecular diagnostics based on discovery research holds the promise of improving screening methods for prostate cancer (PCa). Furthermore, the congregated information prompts the question whether the urinary extracellular vesicles (uEV) proteome has been thoroughly explored, especially at the proteome level. In fact, most extracellular vesicles (EV) based biomarker studies have mainly targeted plasma or serum. Therefore, in this study, we aim to inquire about possible strategies for urinary biomarker discovery particularly focused on the proteome of urine EVs. Proteomics data deposited in the PRIDE archive were reanalyzed to target identifications of potential PCa markers. Network analysis of the markers proposed by different prostate cancer studies revealed moderate overlap. The recent throughput improvements in mass spectrometry together with the network analysis performed in this study, suggest that a larger standardized cohort may provide potential biomarkers that are able to fully characterize the heterogeneity of PCa. According to our analysis PCa studies based on urinary EV proteome presents higher protein coverage compared to plasma, plasma EV, and voided urine proteome. This together with a direct interaction of the prostate gland and urethra makes uEVs an attractive option for protein biomarker studies. In addition, urinary proteome based PCa studies must also evaluate samples from bladder and renal cancers to assess specificity for PCa.
Ih Equalizes Membrane Input Resistance in a Heterogeneous Population of Fusiform Neurons in the Dorsal Cochlear Nucleus
In a neuronal population, several combinations of its ionic conductances are used to attain a specific firing phenotype. Some neurons present heterogeneity in their firing, generally produced by expression of a specific conductance, but how additional conductances vary along in order to homeostatically regulate membrane excitability is less known. Dorsal cochlear nucleus principal neurons, fusiform neurons, display heterogeneous spontaneous action potential activity and thus represent an appropriate model to study the role of different conductances in establishing firing heterogeneity. Particularly, fusiform neurons are divided into quiet, with no spontaneous firing, or active neurons, presenting spontaneous, regular firing. These modes are determined by the expression levels of an intrinsic membrane conductance, an inwardly rectifying potassium current (IKir). In this work, we tested whether other subthreshold conductances vary homeostatically to maintain membrane excitability constant across the two subtypes. We found that Ih expression covaries specifically with IKir in order to maintain membrane resistance constant. The impact of Ih on membrane resistance is dependent on the level of IKir expression, being much smaller in quiet neurons with bigger IKir, but Ih variations are not relevant for creating the quiet and active phenotypes. Finally, we demonstrate that the individual proportion of each conductance, and not their absolute conductance, is relevant for determining the neuronal firing mode. We conclude that in fusiform neurons the variations of their different subthreshold conductances are limited to specific conductances in order to create firing heterogeneity and maintain membrane homeostasis.