Publications by authors named "Leo Cheng"

Diagnosing and classifying central nervous system tumors such as gliomas or glioblastomas pose a significant challenge due to their aggressive and infiltrative nature. However, recent advancements in metabolomics and magnetic resonance spectroscopy (MRS) offer promising avenues for differentiating tumor grades both in vivo and ex vivo. This study aimed to explore tissue-based metabolic signatures to classify/distinguish between low- and high-grade gliomas.

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Article Synopsis
  • Contractions of the uterus are important for menstruation and fertility, and problems with these contractions can cause diseases like endometriosis.
  • Researchers used a special imaging technique called micro-computed tomography to look at the entire uterus of non-pregnant rats to understand its muscle structure better.
  • The study found that this imaging method effectively measured muscle thickness and could create 3D models of the uterus, showing a strong connection between their measurements and those from traditional methods.
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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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Rhythmic electrical events, termed slow waves, govern the timing and amplitude of phasic contractions of the gastric musculature. Extracellular multielectrode measurement of gastric slow waves can be a biomarker for phenotypes of motility dysfunction. However, a gastric slow-wave conduction pathway for the rat, a common animal model, is unestablished.

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The motility of the gastrointestinal tract is coordinated in part by rhythmic slow waves, and disrupted slow-wave patterns are linked to functional motility disorders. At present, there are no treatment strategies that primarily target slow-wave activity. This study assessed the use of pacing to suppress glucagon-induced slow-wave dysrhythmias in the small intestine.

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The uterus exhibits intermittent electrophysiological activity in vivo. Although most active during labor, the non-pregnant uterus can exhibit activity of comparable magnitude to the early stages of labor. In this study, two types of flexible electrodes were utilized to measure the electrical activity of uterine smooth muscle in vivo in anesthetized, non-pregnant rats.

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Background: The National Cancer Institute issued a Request for Information (RFI; NOT-CA-23-007) in October 2022, soliciting input on using and reusing metabolomics data. This RFI aimed to gather input on best practices for metabolomics data storage, management, and use/reuse.

Aim Of Review: The nuclear magnetic resonance (NMR) Interest Group within the Metabolomics Association of North America (MANA) prepared a set of recommendations regarding the deposition, archiving, use, and reuse of NMR-based and, to a lesser extent, mass spectrometry (MS)-based metabolomics datasets.

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Pacing has been proposed as a therapy to restore function in motility disorders associated with electrical dysrhythmias. The spatial response of bioelectrical activity in the small intestine to pacing is poorly understood due to a lack of high-resolution investigations. This study systematically varied pacing parameters to determine the optimal settings for the spatial entrainment of slow wave activity in the jejunum.

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Thermochromism, the change in color of a material with temperature, is the fundamental basis of optical thermometry. A longstanding challenge in realizing sensitive optical thermometers for widespread use is identifying materials with pronounced thermometric optical performance in the visible range. Herein, it is demonstrated that single crystals of indium selenium iodide (InSeI), a 1D van der Waals (vdW) solid consisting of weakly bound helical chains, exhibit considerable visible range thermochromism.

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Swallowing is a primary and complex behaviour that transports food and drink from the oral cavity, through the pharynx and oesophagus, into the stomach at an appropriate rate and speed. To understand this sophisticated behaviour, a tremendous amount of research has been carried out by utilising the in vivo approach, which is often challenging to perform, poses a risk to the subjects if interventions are undertaken and are seldom able to control for confounding factors. In contrast, in silico (computational) and in vitro (instrumental) methods offer an alternate insight into the process of the human swallowing system.

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Soft gastric simulators are biomimetic modules that can reproduce the antral contraction waves (ACWs). Along with providing information concerning stomach contents, stomach simulators enable experts to evaluate the digestion process of foods and drugs. Traditionally, open-loop control approaches were implemented on stomach simulators to produce ACWs.

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Neural regulation of gastric motility occurs partly through the regulation of gastric bioelectrical slow waves (SWs) and phasic contractions. The interaction of the tissues and organs involved in this regulatory process is complex. We sought to infer the relative importance of cellular mechanisms in inhibitory neural regulation of the stomach by enteric neurons and the interaction of inhibitory and excitatory electrical field stimulation.

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Gastrointestinal (GI) sphincters provide critical roles in regulating the transport of contents along the GI tract. Dysfunctions of GI sphincters are associated with a range of major digestive disorders. Despite their importance, the microstructures of GI sphincters are not well investigated.

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The primary function of the duodenum is to undertake chemical digestion by ensuring that the partially digested food received from the stomach is well-mixed with the enzymes and chemicals secreted into it. However, little is known about the anatomical variations in the shape of the duodenum within humans, and thus the effect of duodenum shape on the flow and mixing occurring within the lumen has not been studied. In this work, a methodology for analyzing shape variations in the normal duodenal anatomy has been developed and applied to a publicly available dataset of abdominal CT images.

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Postoperative ileus and chronic intestinal pseudo-obstruction are intestinal motility disorders that can compromise bowel function resulting in a significant reduction in quality of life and prolonged hospital stays. While medication and nutritional support provides relief for some patients, a significant patient population remains untreated. Therefore, alternative treatment options are required.

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A framework to simulate the flow in the stomach using subject-specific motility patterns and geometries was developed. Dynamic 2D magnetic resonance images (MRIs) were obtained. Motility parameters such as contraction speed and occlusion were quantified, and 3D stomach geometries were reconstructed using a semi-automated approach.

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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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Swallowing involves the precise coordination of a large number of muscles. This coordination can be quantified non-invasively by electromyographic (EMG) time-series analysis of swallowing events. The temporal alignment of swallow events is critical for defining coordination patterns.

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Cervical vagus nerve stimulation (cVNS) is a promising neuromodulation therapy for treating symptoms of disease in peripheral organs. The rat is a common animal model for studying and trialing new applications of cVNS therapy, but the stomach and its activity in rats is less well characterized than other animals, such as pigs. We sought to investigate the effects of acute, in vivo cVNS on gastric bioelectrical activity as an intermediate step to computational modeling of the effects of cVNS on gastric smooth muscle electromechanical coupling.

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  • Untargeted metabolomics is a method that effectively analyzes small molecules in biological systems but faces challenges in data quality evaluation; using pooled quality control (QC) samples can help monitor and correct analytical variance during experiments.!* -
  • A literature review of 109 published studies shows that the metabolomics community has widely adopted pooled QC samples across various biological types, but many studies fail to report their effectiveness in improving data quality.!* -
  • The review reveals missing or unclear details in the QC framework, which hampers the ability to fully understand the quality control steps taken in these studies, indicating both strengths and areas for improvement in the field's reporting practices.!*
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Objective: Bioelectrical 'slow waves' regulate gastrointestinal contractions. We aimed to confirm whether the pyloric sphincter demarcates slow waves in the intact stomach and duodenum.

Methods: We developed and validated novel anatomically-specific electrode cradles and analysis techniques which enable high-resolution slow wave mapping across the in vivo gastroduodenal junction.

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Intestinal motility is governed in part by bioelectrical slow-waves and spike-bursts. Mesenteric ischemia is a substantial clinical challenge, but its electrophysiological and contractile mechanisms are not well understood. Simultaneous high-resolution bioelectrical and video mapping techniques were used to capture the changes in slow-waves, spike-bursts, and contractile activity during baseline, ischemia, and reperfusion periods.

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Background: Renal cell carcinoma (RCC) is a metabolic disease, with subtypes exhibiting aberrations in different metabolic pathways. Metabolomics may offer greater sensitivity for revealing disease biology. We investigated the metabolomic profile of RCC using high-resolution magic angle spinning (HRMAS) proton magnetic resonance spectroscopy (HMRS).

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Stickland-fermenting preferentially ferment amino acids to generate energy and anabolic substrates for growth. In gut ecosystems, these species prefer dual redox substrates, particularly mucin-abundant leucine. Here, we establish how theronine, a more prevalent, mucinabundant substrate, supports dual redox metabolism in the pathogen .

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Article Synopsis
  • Smart capsules are rapidly evolving technologies designed to diagnose and monitor gut health, originating from early 2000s endoscopic prototypes and now measuring various physiological parameters like temperature and pH.* ! -
  • Recent advancements include the development of robotic capsules capable of collecting tissue biopsies and gut microbiota samples, which may significantly enhance diagnostic capabilities.* ! -
  • The review discusses the technical and clinical challenges these smart devices face, and emphasizes their potential to transform healthcare by improving understanding of gut responses under different conditions.* !
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