Publications by authors named "Walcott G"

Background: When human induced pluripotent stem cells (hiPSCs) that CCND2-OE (overexpressed cyclin-D2) were differentiated into cardiomyocytes (hiPSC-CMs) and administered to the infarcted hearts of immunodeficient mice, the cells proliferated after administration and repopulated >50% of the scar. Here, we knocked out human leukocyte antigen class I and class II expression in hiPSC-CMs (hiPSC-CMs) to reduce the cells' immunogenicity and then assessed the therapeutic efficacy of hiPSC-CMs for the treatment of myocardial infarction.

Methods: hiPSC-CM and wild-type hiPSC-CM (hiPSC-CM) spheroids were differentiated in shaking flasks, purified, characterized, and intramyocardially injected into pigs after ischemia/reperfusion injury; control animals were injected with basal medium.

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Article Synopsis
  • Developed an experimental platform that combines optogenetic stimulation with simultaneous imaging of membrane potential (Vm) and calcium transients (CaT) in cardiac spheroids made from human induced pluripotent stem cells.
  • Utilized a genetically encoded optogenetic actuator (CheRiff) and a calcium indicator (jRCaMP1b), along with an organic dye (RH237) to monitor bioelectrical activity without cross-talk, while achieving different signal qualities based on the excitation light used.
  • This innovative system allows for independent tissue stimulation, making it a valuable tool for studying interactions between engineered tissue grafts and host tissue in biomedical research.
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Gastric peristalsis is governed by electrical "slow waves" generally assumed to travel from proximal to distal stomach (antegrade propagation) in symmetric rings. Although alternative slow-wave patterns have been correlated with gastric disorders, their mechanisms and how they alter contractions remain understudied. Optical electromechanical mapping, a developing field in cardiac electrophysiology, images electrical and mechanical physiology simultaneously.

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Targeting Meis1 and Hoxb13 transcriptional activity could be a viable therapeutic strategy for heart regeneration. In this study, we performd an in silico screening to identify FDA-approved drugs that can inhibit Meis1 and Hoxb13 transcriptional activity based on the resolved crystal structure of Meis1 and Hoxb13 bound to DNA. Paromomycin (Paro) and neomycin (Neo) induced proliferation of neonatal rat ventricular myocytes in vitro and displayed dose-dependent inhibition of Meis1 and Hoxb13 transcriptional activity by luciferase assay and disruption of DNA binding by electromobility shift assay.

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Article Synopsis
  • - Gastric rhythmic contractions are controlled by slow waves (SW), and irregular SW activity can lead to digestive disorders; gastric pacing aims to normalize this activity but has inconsistent results and unclear mechanisms.
  • - The study utilized optical mapping, typically used in heart research, to visualize how pacing affects the stomach by revealing virtual electrode polarization patterns where areas of tissue become depolarized or hyperpolarized.
  • - It was discovered that most SWs (15 out of 16 times) originated from the depolarized regions during pacing, marking the first direct observation of these patterns in the stomach, which could enhance our understanding of gastric pacing as a treatment option.
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Cardiac optical mapping has traditionally been performed in ex-vivo, motion-arrested hearts. Recently, in-situ cardiac optical mapping has been made possible by both motion correction techniques and long-wavelength voltage sensitive dyes (VSDs). However, VSDs have been observed to wash out quickly from blood-perfused in-situ hearts.

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This article presents a case study of an innovative culturally based therapeutic approach using collective poiesis to improve the functioning of a youth sports team in Jamaica. In recent decades, Jamaica has endured high levels of violence and corruption, and has been ranked among the top four countries in the world in terms of murder rate per capita. We conjecture that a high prevalence of personality disorder linked to the legacy of slavery and colonialism often impedes Jamaicans from achieving success in diverse fields, including sports.

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Optical mapping has been widely used in the study of cardiac electrophysiology in motion-arrested, ex vivo heart preparations. Recent developments in motion artifact mitigation techniques have made it possible to optically map beating ex vivo hearts, enabling the study of cardiac electromechanics using optical mapping. However, the ex vivo setting imposes limitations on optical mapping such as altered metabolic states, oversimplified mechanical loads, and the absence of neurohormonal regulation.

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Background: Experiments in mammalian models of cardiac injury suggest that the cardiomyocyte-specific overexpression of CCND2 (cyclin D2, in humans) improves recovery from myocardial infarction (MI). The primary objective of this investigation was to demonstrate that our specific modified mRNA translation system (SMRTs) can induce CCND2 expression in cardiomyocytes and replicate the benefits observed in other studies of cardiomyocyte-specific CCND2 overexpression for myocardial repair.

Methods: The CCND2-cardiomyocyte-specific modified mRNA translation system (cardiomyocyte SMRTs) consists of 2 modRNA constructs: one codes for CCND2 and contains a binding site for L7Ae, and the other codes for L7Ae and contains recognition elements for the cardiomyocyte-specific microRNAs miR-1 and miR-208.

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The efficacy of psilocybin and other psychedelics as modes of treatment have been demonstrated through clinical trials and other studies in the management of a number of mental illnesses, including some treatment resistant cases. In Psychedelic Assisted Psychotherapy (PAP), psychedelics catalyze or enhance the experience fostered by psychotherapeutic methods. Psychohistoriographic Brief Psychotherapy, conceptualized by the late Professor Frederick Hickling in the 1970's in Kingston, Jamaica, offers a pathway for exploration in the Jamaican context.

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Single-cell RNA sequencing (scRNAseq) enables researchers to identify and characterize populations and subpopulations of different cell types in hearts recovering from myocardial infarction (MI) by characterizing the transcriptomes in thousands of individual cells. However, the effectiveness of the currently available tools for processing and interpreting these immense datasets is limited. We incorporated three Artificial Intelligence (AI) techniques into a toolkit for evaluating scRNAseq data: AI Autoencoding separates data from different cell types and subpopulations of cell types (cluster analysis); AI Sparse Modeling identifies genes and signaling mechanisms that are differentially activated between subpopulations (pathway/gene set enrichment analysis), and AI Semisupervised Learning tracks the transformation of cells from one subpopulation into another (trajectory analysis).

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Introduction: The wearable cardioverter defibrillator (WCD) is used to protect patients at risk for sudden cardiac arrest. We examined defibrillation efficacy and safety of a biphasic truncated exponential waveform designed for use in a contemporary WCD in three animal studies and a human study.

Methods: Animal (swine) studies: #1: Efficacy comparison of a 170J BTE waveform (SHOCK A) to a 150J BTE waveform (SHOCK B) that approximates another commercially available waveform.

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Introduction: tobacco smoking remains a significant threat to public health. This paper sought to examine the prevalence, perceived risk and the associated factors of current tobacco use amongst Jamaican adults.

Methods: this study is a secondary data analysis of the Jamaican National Household Survey 2016.

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The neonatal swine heart possesses an endogenous ability to regenerate injured myocardium through the proliferation of pre-existing cardiomyocyte (CM) populations. However, this regenerative capacity is lost shortly after birth. Normal postnatal developmental processes and the regenerative capacity of mammalian hearts are tightly linked, but not much is known about how the swine cardiac proteome changes throughout postnatal development.

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Ectopic activation during early acute regional ischemia may initiate fatal reentrant arrhythmias. However, the origin of this ectopy remains poorly understood. Studies suggest that systolic stretch arising from dyskinesia in ischemic tissue may cause ectopic depolarization due to cardiac mechanosensitivity.

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Background: In Latin America and the Caribbean, there is a dearth of research exploring polysubstance use. This study aims to determine the prevalence, varying combinations and associated sociodemographic characteristics of polysubstance use in Jamaica.

Methods: This study involved a secondary data analysis of the Jamaica National Drug Prevalence Survey 2016 dataset where 4,623 participants between the age of 12 and 65 years from each household were randomly selected as respondents.

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BACKGROUND Although improving, survival after pig orthotopic heart transplantation (OHTx) in baboons has been mixed and largely poor. The causes for the high incidence of early failure remain uncertain. MATERIAL AND METHODS We have carried out pig OHTx in 4 baboons.

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Background: Mortality for infants on the heart transplant waitlist remains unacceptably high, and available mechanical circulatory support is suboptimal. Our goal is to demonstrate the feasibility of utilizing genetically engineered pig (GEP) heart as a bridge to allotransplantation by transplantation of a GEP heart in a baboon.

Methods: Four baboons underwent orthotopic cardiac transplantation from GEP donors.

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Background: Both gap junctional remodeling and interstitial fibrosis have been linked to impaired electrical conduction velocity (CV) and fatal ventricular arrhythmias in nonischemic heart failure (HF). However, the arrhythmogenic role of the ventricular gap junctional Cx43 in nonischemic HF remains in debate. Here, we assessed this in a newly developed arrhythmogenic canine model of nonischemic HF.

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Background: Human induced pluripotent stem cells with normal (wild-type) or upregulated (overexpressed) levels of CCND2 (cyclin D2) expression were differentiated into cardiomyocytes (CCND2CMs or CCND2CMs, respectively) and injected into infarcted pig hearts.

Methods: Acute myocardial infarction was induced by a 60-minute occlusion of the left anterior descending coronary artery. Immediately after reperfusion, CCND2CMs or CCND2CMs (3×10 cells each) or an equivalent volume of the delivery vehicle was injected around the infarct border zone area.

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Introduction: Mechanical chest compression devices allow for variation in chest compression (CCs) characteristics from moment to moment, enabling therapy that is not feasible for manual CCs. Effects of varying compressions over time have not been studied. In a randomized trial in an experimental model of prolonged cardiac arrest, we compared time-varying CPR (TVCPR), alternating between 100 and 200 compressions per minute (cpm) every 6 s, to guidelines CPR (Control).

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There is a critical shortage of deceased human donor organs for transplantation. The need is perhaps most acute in neonates and infants with life-threatening congenital heart disease, in whom mechanical support devices are largely unsuccessful. If orthotopic (life-supporting) heart transplantation (OHTx) were consistently successful in the genetically engineered pig-to-nonhuman primate (NHP) model, a clinical trial of bridging with a pig heart in such patients might be justified.

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