Diffeomorphic Surface Modeling for MRI-Based Characterization of Gastric Anatomy and Motility

Wang, Xiaokai; Cao, Jiayue; Han, Kuan; Choi, Minkyu; She, Yushi; Scheven, Ulrich M.; Avci, Recep; Du, Peng; Cheng, Leo K.; Natale, Madeleine R Di; Furness, John B.; Liu, Zhongming

doi:10.1109/tbme.2023.3234509

Cited by 4 publications

References 38 publications

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Magnetic Resonance Imaging of Gastric Motility in Conscious Rats

Wang,

Alkaabi,

Cornett

et al. 2024

Preprint

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IntroductionGastrointestinal (GI) magnetic resonance imaging (MRI) can simultaneously capture gastric peristalsis, emptying, and intestinal filling and transit. Performing GI MRI with animals requires anesthesia, which complicates physiology and confounds interpretation and translation from animals to humans. This study aims to enable MRI in conscious rats, and for the first time, characterize GI motor functions in awake versus anesthetized conditions.MethodsWe acclimated rats to remain awake, still, and minimally stressed during MRI. We scanned 14 Sprague-Dawley rats in both awake and anesthetized conditions after voluntarily consuming a contrast-enhanced test meal.ResultsAwake rats remained physiologically stable during MRI, showed gastric emptying of 23.7±1.4% after 48 minutes, and exhibited strong peristaltic contractions propagating through the antrum with a velocity of 0.72±0.04 mm/s, a relative amplitude of 40.7±2.3%, and a frequency of 5.1±0.1 cycles per minute. In the anesthetized condition, gastric emptying was about half of that in the awake condition, likely due to the effect of anesthesia in halving the amplitudes of peristaltic contractions rather than their frequency (not significantly changed) or velocity. In awake rats, the intestine filled more quickly and propulsive contractions were more occlusive.ConclusionWe demonstrated the effective acquisition and analysis of GI MRI in awake rats. Awake rats show faster gastric emptying, stronger gastric contraction with a faster propagation speed, and more effective intestinal filling and transit, compared to anesthetized rats. Our protocol is expected to benefit future preclinical studies of GI physiology and pathophysiology.

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Magnetic Resonance Imaging of Gastric Motility in Conscious Rats

Wang,

Alkaabi,

Cornett

et al. 2024

Preprint

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Mapping the rat gastric slow-wave conduction pathway: bridging in vitro and in vivo methods, revealing a loosely coupled region in the distal stomach

Athavale,

Di Natale,

Avci

et al. 2024

American Journal of Physiology-Gastrointestinal and Liver Physi

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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. In this study, the validity of extracellular recording was demonstrated in vitro with simultaneous intracellular and extracellular recordings and by pharmacological inhibition of slow waves. The conduction pathway was determined by in vivo extracellular recordings while considering the effect of motion. Slow wave characteristics (mean (SD)) varied regionally, having higher amplitude in the antrum than the distal corpus (1.03 (0.12) mV vs 0.75 (0.31) mV; n = 7; p = 0.025 paired t-test) and faster propagation near the greater curvature than the lesser curvature (1.00 (0.14) mm s-1 vs 0.74 (0.14) mm s-1; n = 9 GC, 7 LC; p = 0.003 unpaired t-test). Notably, in some subjects, separate wavefronts propagated near the lesser and greater curvatures with a loosely-coupled region occurring in the area near the distal corpus midline, at the interface of the two wavefronts. This region had either the greater or lesser curvature wavefront propagating through it in a time-varying manner. The conduction pattern suggests that slow waves in the rat stomach form annular wavefronts in the antrum and not the corpus. This study has implications for interpretation of the relationship between slow waves, the interstitial cells of Cajal network structure, smooth muscles, and gastric motility.

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Characterization of neuromuscular transmission and projections of muscle motor neurons in the rat stomach

Di Natale,

Hunne,

Stebbing

et al. 2024

American Journal of Physiology-Gastrointestinal and Liver Physi

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The stomach is the primary reservoir of the gastrointestinal tract, where ingested content is broken down into small particles. Coordinated relaxation and contraction is essential for rhythmic motility and digestion, but how the muscle motor innervation is organized to provide appropriate graded regional control is not established. In this study, we recorded neuromuscular transmission to the circular muscle using intracellular microelectrodes to investigate the spread of influence of intrinsic motor neurons. In addition, microanatomical investigations of neuronal projections and pharmacological analysis were conducted to investigate neuromuscular relationships. We found that inhibitory neurotransmission to the circular muscle is graded with stimulus strength and circumferential distance from the stimulation site. The influence of inhibitory neurons declined between 1 and 11 mm from the stimulation site. In the antrum, corpus and fundus the declines at 11 mm were about 20%, 30%, and 50% respectively. Stimulation of inhibitory neurons elicited biphasic hyperpolarizing potentials often followed by prolonged depolarizing events in the distal stomach, but only hyperpolarizing events in the proximal stomach. Excitatory neurotransmission influence varied greatly between proximal stomach, where depolarizing events occurred, and distal stomach, where no direct electrical effects in the muscle were observed. Structural studies utilizing microlesion surgeries confirmed a dominant circumferential projection. We conclude that motor neuron influences extend around the gastric circumference, that the effectiveness can be graded by the recruitment of different numbers of motor neuron nerve terminals to finely control gastric motility, and that the ways in which the neurons influence the muscle differ between anatomical regions.

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Diffeomorphic Surface Modeling for MRI-Based Characterization of Gastric Anatomy and Motility

Cited by 4 publications

References 38 publications

Magnetic Resonance Imaging of Gastric Motility in Conscious Rats

Magnetic Resonance Imaging of Gastric Motility in Conscious Rats

Mapping the rat gastric slow-wave conduction pathway: bridging in vitro and in vivo methods, revealing a loosely coupled region in the distal stomach

Characterization of neuromuscular transmission and projections of muscle motor neurons in the rat stomach

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