Publications by authors named "Mark Santos"

Article Synopsis
  • Aging leads to loss of muscle mass and function, resulting in poorer health outcomes, decreased quality of life, and increased mortality risk among older adults.
  • Small extracellular vesicles (sEV), which can be isolated from body fluids and contain specific biomarkers, offer a minimally invasive way to assess muscle health.
  • Research on vervet monkeys showed that sEV from different age groups can reveal molecular changes related to muscle metabolism and regulation, suggesting they may serve as effective biomarkers for muscle health monitoring.
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Background: The nursing workforce comprises multiple generations, each with unique values, beliefs, and expectations that can influence communication, work ethic, and professional relationships. In Qatar, the generational gap between nurses and nurse managers poses challenges to effective communication and teamwork, impacting job satisfaction and patient outcomes.

Aim: This study investigates the generational gap between nurses and nurse managers in Qatar, aiming to identify strategies to enhance collaboration and create a positive work environment.

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The current study analyzed the intersecting biophysical, biochemical, and functional properties of extracellular particles (EPs) with the human immunodeficiency virus type-1 (HIV-1) beyond the currently accepted size range for HIV-1. We isolated five fractions (Frac-A through Frac-E) from HIV-infected cells by sequential differential ultracentrifugation (DUC). All fractions showed a heterogeneous size distribution with median particle sizes greater than 100 nm for Frac-A through Frac-D but not for Frac-E, which contained small EPs with an average size well below 50 nm.

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Extracellular vesicles (EVs) appear to play an important role in intercellular communication in various physiological processes and pathological conditions such as cancer. Like enveloped viruses, EVs can transport their contents into the nucleus of recipient cells, and a new intracellular pathway has been described to explain the nuclear shuttling of EV cargoes. It involves a tripartite protein complex consisting of vesicle-associated membrane protein-associated protein A (VAP-A), oxysterol-binding protein (OSBP)-related protein-3 (ORP3) and late endosome-associated Rab7 allowing late endosome entry into the nucleoplasmic reticulum.

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HIV in the UK is concentrated in a few key populations, and African migrants are among them. To date, there has been no documented record of the personal experiences of this group to accompany the significant amount of epidemiological data on these communities. There is no record celebrating the contribution, resilience and lived experience of Africans living with HIV in the UK, their allies and their response to the epidemic.

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End-stage renal disease (ESRD) poses a significant health challenge, with hemodialysis (HD) being the most prevalent therapy. Patients undergoing HD must comply with a strict therapeutic regimen, including dietary control, fluid restriction, and medication adherence. Successful disease management and improved outcomes rely on patients' involvement and participation in their care.

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Background: The incidence of melanoma is increasing worldwide. Since metastatic melanoma is highly aggressive, it is important to decipher all the biological aspects of melanoma cells. In this context, we have previously shown that metastatic FEMX-I melanoma cells release small (< 150 nm) extracellular vesicles (EVs) known as exosomes and ectosomes containing the stem (and cancer stem) cell antigenic marker CD133.

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Aim: Extracellular vesicles (EVs) are small particles released by all cells, including virally infected cells, into the extracellular space. They play a role in various cellular processes, including intercellular communication, signaling, and immunity, and carry several biomolecules like proteins, lipids, and nucleic acids that can modulate cellular functions mostly by releasing their cargo inside the target cells via the endocytic pathway. One of the most exciting aspects of EV physiology is its potential in liquid biopsy as a diagnostic and prognostic marker.

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The mechanism of human immunodeficiency virus 1 (HIV-1) nuclear entry, required for productive infection, is not fully understood. Here, we report that in HeLa cells and activated CD4 T cells infected with HIV-1 pseudotyped with VSV-G and native Env protein, respectively, Rab7 late endosomes containing endocytosed HIV-1 promote the formation of nuclear envelope invaginations (NEIs) by a molecular mechanism involving the VOR complex, composed of the outer nuclear membrane protein VAP-A, hyperphosphorylated ORP3 and Rab7. Silencing VAP-A or ORP3 and drug-mediated impairment of Rab7 binding to ORP3-VAP-A inhibited the nuclear transfer of the HIV-1 components and productive infection.

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Dysregulated inflammation within the central nervous system (CNS) contributes to neuropathology in infectious, autoimmune, and neurodegenerative disease. With the exception of microglia, major histocompatibility complex (MHC) proteins are virtually undetectable in the mature, healthy central nervous system (CNS). Neurons have generally been considered incapable of antigen presentation, and although interferon gamma (IFN-γ) can elicit neuronal MHC class I (MHC-I) expression and antigen presentation in vitro, it has been unclear whether similar responses occur in vivo.

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Background: Metastatic disease is the major cause of cancer-related deaths. Increasing evidence shows that primary tumor cells can promote metastasis by preparing the local microenvironment of distant organs, inducing the formation of the so-called "pre-metastatic niche". In recent years, several studies have highlighted that among the tumor-derived molecular components active in pre-metastatic niche formation, small extracellular vesicles (sEVs) play a crucial role.

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Intercellular communication between cancer cells themselves or with healthy cells in the tumor microenvironment and/or pre-metastatic sites plays an important role in cancer progression and metastasis. In addition to ligand-receptor signaling complexes, extracellular vesicles (EVs) are emerging as novel mediators of intercellular communication both in tissue homeostasis and in diseases such as cancer. EV-mediated transfer of molecular activities impacting morphological features and cell motility from highly metastatic SW620 cells to non-metastatic SW480 cells is a good in vitro example to illustrate the increased malignancy of colorectal cancer leading to its transformation and aggressive behavior.

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Progressive cognitive decline in Alzheimer's disease correlates closely with the spread of tau protein aggregation across neural networks of the cortical mantle. We tested the hypothesis that heritable factors may influence the rate of propagation of tau pathology across brain regions in a model system, taking advantage of well-defined genetically diverse background strains in mice. We virally expressed human tau locally in the hippocampus and the entorhinal cortex neurons and monitored the cell-to-cell tau protein spread by immunolabelling.

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In patients with acute ischemic stroke, pial collaterals play a key role in limiting neurological disability by maintaining blood flow to ischemic penumbra. We hypothesized that patient with poor pial collaterals will have greater corneal nerve and endothelial cell abnormalities. In a cross-sectional study, 35 patients with acute ischemic stroke secondary to middle cerebral artery (MCA) occlusion with poor (n = 12) and moderate-good (n = 23) pial collaterals and 35 healthy controls underwent corneal confocal microscopy and quantification of corneal nerve and endothelial cell morphology.

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Extracellular vesicles (EVs) are mediators of intercellular communication under both healthy and pathological conditions, including the induction of pro-metastatic traits, but it is not yet known how and where functional cargoes of EVs are delivered to their targets in host cell compartments. We have described that after endocytosis, EVs reach Rab7 late endosomes and a fraction of these enter the nucleoplasmic reticulum and transport EV biomaterials to the host cell nucleoplasm. Their entry therein and docking to outer nuclear membrane occur through a tripartite complex formed by the proteins VAP-A, ORP3 and Rab7 (VOR complex).

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Extracellular membrane vesicles (EVs) are emerging as new vehicles in intercellular communication, but how the biological information contained in EVs is shared between cells remains elusive. Several mechanisms have been described to explain their release from donor cells and the initial step of their uptake by recipient cells, which triggers a cellular response. Yet, the intracellular routes and subcellular fate of EV content upon internalization remain poorly characterized.

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Introduction: Recurrent ischemic strokes (IS) make up to one-third of all strokes. Nine out of 10 strokes are due to modifiable risk factors. Thus, it seems that standard management strategies of modifiable risk factors are yet to improve.

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Alzheimer's disease (AD) causes unrelenting, progressive cognitive impairments, but its course is heterogeneous, with a broad range of rates of cognitive decline. The spread of tau aggregates (neurofibrillary tangles) across the cerebral cortex parallels symptom severity. We hypothesized that the kinetics of tau spread may vary if the properties of the propagating tau proteins vary across individuals.

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Article Synopsis
  • Alzheimer's disease, an incurable condition, shows significant neuroinflammation but the role of the adaptive immune response is not well understood.
  • Recent research identified specific changes in both peripheral blood and brain immune responses, including an increase in certain CD8 T cells linked to cognitive decline in Alzheimer's patients.
  • Advanced techniques revealed clonally expanded CD8 T cells in the cerebrospinal fluid that specifically recognize Epstein-Barr virus antigens, indicating a targeted immune response connected to this neurodegenerative disease.
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The intercellular communication mediated by extracellular vesicles (EVs) has gained international interest during the last decade. Interfering with the mechanisms regulating this cellular process might find application particularly in oncology where cancer cell-derived EVs play a role in tumour microenvironment transformation. Although several mechanisms were ascribed to explain the internalization of EVs, little is our knowledge about the fate of their cargos, which are crucial to mediate their function.

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Stroke attacks were found to be present at a younger age in patients from Southeast Asia (SE) and the Middle East (ME) resident in the state of Qatar. Extracellular vesicles (EVs), which are small membrane vesicles with pro-thrombotic properties, may contribute to the high risk of stroke in this population. Thus, total and cell-specific medium size EVs were counted by flow cytometry in platelet-free plasma from healthy volunteers and patients with transient ischemic attacks (TIA) and acute ischemic stroke (AIS) from SE and ME.

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The diagnostic approach to thyroid cancer is one of the most challenging issues in oncology of the endocrine system because of its high incidence (3.8% of all new cancer cases in the US) and the difficulty to distinguish benign from malignant non-functional thyroid nodules and establish the cervical lymph node involvement during staging. Routine diagnosis of thyroid nodules usually relies on a fine-needle aspirate biopsy, which is invasive and often inaccurate.

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Background: Atrial fibrillation is an important risk factor for stroke but there are limited data on atrial fibrillation-related stroke from the Middle East.

Methods: We interrogated the Qatar Stroke Database to establish the occurrence, clinical features, and outcomes of atrial fibrillation-related stroke at Hamad General Hospital, the sole provider of acute stroke care in Qatar.

Results: A total of 4079 patients (81.

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