No abstract available.
Electrodes*

BACKGROUND/AIMS: Gastric peristalsis begins in the orad corpus and propagates to the pylorus. Directionality of peristalsis depends upon orderly generation and propagation of electrical slow waves and a frequency gradient between proximal and distal pacemakers. We sought to understand how chronotropic agonists affect coupling between corpus and antrum. METHODS: Electrophysiological and imaging techniques were used to investigate regulation of gastric slow wave frequency by muscarinic agonists in mice. We also investigated the expression and role of cholinesterases in regulating slow wave frequency and motor patterns in the stomach. RESULTS: Both acetycholinesterase (Ache) and butyrylcholine esterase (Bche) are expressed in gastric muscles and AChE is localized to varicose processes of motor neurons. Inhibition of AChE in the absence of stimulation increased slow wave frequency in corpus and throughout muscle strips containing corpus and antrum. CCh caused depolarization and increased slow wave frequency. Stimulation of cholinergic neurons increased slow wave frequency but did not cause depolarization. Neostigmine (1 muM) increased slow wave frequency, but uncoupling between corpus and antrum was not detected. Motility mapping of contractile activity in gastric muscles showed similar effects of enteric nerve stimulation on the frequency and propagation of slow waves, but neostigmine (> 1 muM) caused aberrant contractile frequency and propagation and ectopic pacemaking. CONCLUSIONS: Our data show that slow wave uncoupling is difficult to assess with electrical recording from a single or double sites and suggest that efficient metabolism of ACh released from motor neurons is an extremely important regulator of slow wave frequency and propagation and gastric motility patterns.
Animals ; Cholinergic Neurons ; Cholinesterases* ; Metabolism ; Mice* ; Motor Neurons ; Muscarinic Agonists ; Muscle, Smooth ; Muscles ; Neostigmine ; Peristalsis ; Pylorus ; Stomach

BACKGROUND/AIMS: Several motility disorders are associated with disruption of interstitial cells of Cajal (ICC), which provide important functions, such as pacemaker activity, mediation of neural inputs and responses to stretch in the gastrointestinal (GI) tract. Restoration of ICC networks may be therapeutic for GI motor disorders. Recent reports have suggested that Kit+ cells can be restored to the GI tract via bone marrow (BM) transplantation. We tested whether BM derived cells can lead to generation of functional activity in intestines naturally lacking ICC. METHODS: BM cells from Kit(+/copGFP) mice, in which ICC are labeled with a green fluorescent protein, were transplanted into W/W(V) intestines, lacking ICC. After 12 weeks the presence of ICC was analyzed by immunohistochemistry and functional analysis of electrical behavior and contractile properties. RESULTS: After 12 weeks copGFP+ BM derived cells were found within the myenteric region of intestines from W/W(V) mice, typically populated by ICC. Kit+ cells failed to develop interconnections typical of ICC in the myenteric plexus. The presence of Kit+ cells was verified with Western analysis. BM cells failed to populate the region of the deep muscular plexus where normal ICC density, associated with the deep muscular plexus, is found in W/W(V) mice. Engraftment of Kit+-BM cells resulted in the development of unitary potentials in transplanted muscles, but slow wave activity failed to develop. Motility analysis showed that intestinal movements in transplanted animals were abnormal and similar to untransplanted W/W(V) intestines. CONCLUSIONS: BM derived Kit+ cells colonized the gut after BM transplantation, however these cells failed to develop the morphology and function of mature ICC.
Animals ; Bone Marrow Transplantation ; Bone Marrow* ; Colon* ; Electrophysiology ; Gastrointestinal Tract ; Immunohistochemistry ; Interstitial Cells of Cajal* ; Intestines* ; Mice ; Muscles ; Myenteric Plexus ; Negotiating

Smooth muscle layers of the gastrointestinal tract consist of a heterogeneous population of cells that include enteric neurons, several classes of interstitial cells of mesenchymal origin, a variety of immune cells and smooth muscle cells (SMCs). Over the last number of years the complexity of the interactions between these cell types has begun to emerge. For example, interstitial cells, consisting of both interstitial cells of Cajal (ICC) and platelet-derived growth factor receptor alpha-positive (PDGFRalpha+) cells generate pacemaker activity throughout the gastrointestinal (GI) tract and also transduce enteric motor nerve signals and mechanosensitivity to adjacent SMCs. ICC and PDGFRalpha+ cells are electrically coupled to SMCs possibly via gap junctions forming a multicellular functional syncytium termed the SIP syncytium. Cells that make up the SIP syncytium are highly specialized containing unique receptors, ion channels and intracellular signaling pathways that regulate the excitability of GI muscles. The unique role of these cells in coordinating GI motility is evident by the altered motility patterns in animal models where interstitial cell networks are disrupted. Although considerable advances have been made in recent years on our understanding of the roles of these cells within the SIP syncytium, the full physiological functions of these cells and the consequences of their disruption in GI muscles have not been clearly defined. This review gives a synopsis of the history of interstitial cell discovery and highlights recent advances in structural, molecular expression and functional roles of these cells in the GI tract.
Enteric Nervous System ; Gap Junctions ; Gastrointestinal Tract ; Giant Cells ; Interstitial Cells of Cajal ; Ion Channels ; Models, Animal ; Muscle, Smooth ; Muscles ; Myocytes, Smooth Muscle ; Neurons ; Receptor, Platelet-Derived Growth Factor alpha ; Receptors, Platelet-Derived Growth Factor

BACKGROUND/AIMS: Smooth muscle cells (SMCs) characteristically express serum response factor (SRF), which regulates their development. The role of SRF in SMC plasticity in the pathophysiological conditions of gastrointestinal (GI) tract is less characterized. METHODS: We generated SMC-specific Srf knockout mice and characterized the prenatally lethal phenotype using ultrasound biomicroscopy and histological analysis. We used small bowel partial obstruction surgeries and primary cell culture using cell-specific enhanced green fluorescent protein (EGFP) mouse lines to study phenotypic and molecular changes of SMCs by immunofluorescence, Western blotting, and quantitative polymerase chain reaction. Finally we examined SRF change in human rectal prolapse tissue by immunofluorescence. RESULTS: Congenital SMC-specific Srf knockout mice died before birth and displayed severe GI and cardiac defects. Partial obstruction resulted in an overall increase in SRF protein expression. However, individual SMCs appeared to gradually lose SRF in the hypertrophic muscle. Cells expressing low levels of SRF also expressed low levels of platelet-derived growth factor receptor alpha (PDGFRalphalow) and Ki67. SMCs grown in culture recaptured the phenotypic switch from differentiated SMCs to proliferative PDGFRalphalow cells. The immediate and dramatic reduction of Srf and Myh11 mRNA expression confirmed the phenotypic change. Human rectal prolapse tissue also demonstrated significant loss of SRF expression. CONCLUSIONS: SRF expression in SMCs is essential for prenatal development of the GI tract and heart. Following partial obstruction, SMCs down-regulate SRF to transition into proliferative PDGFRalphalow cells that may represent a phenotype responsible for their plasticity. These findings demonstrate that SRF also plays a critical role in the remodeling process following GI injury.
Animals ; Blotting, Western ; Fluorescent Antibody Technique ; Gastrointestinal Tract ; Heart ; Humans ; Mice ; Mice, Knockout ; Microscopy, Acoustic ; Muscle Cells ; Muscle, Smooth* ; Myocytes, Smooth Muscle ; Parturition ; Phenotype* ; Plastics ; Polymerase Chain Reaction ; Primary Cell Culture ; Receptors, Platelet-Derived Growth Factor ; Rectal Prolapse ; RNA, Messenger ; Serum Response Factor*

BACKGROUND/AIMS: Interstitial cells of Cajal (ICC) play important functions in motor activity of the gastrointestinal tract. The role of ICC as pacemakers is well established, however their participation in neurotransmission is controversial. Studies using mutant animals that lack ICC have yielded variable conclusions on their importance in enteric motor responses. The purpose of this study was to: (1) clarify the role of intramuscular ICC (ICC-IM) in gastric motor-neurotransmission and (2) evaluate remodeling of enteric motor responses in W/W(V) mice. METHODS: Kit immunohistochemistry and post-junctional contractile responses were performed on fundus muscles from wild-type and W/W(V) mice and quantitative polymerase chain reaction (qPCR) was used to evaluate differences in muscarinic and neurokinin receptor expression. RESULTS: Although ICC-IM were greatly reduced in comparison with wild-type mice, we found that ICC-IM persisted in the fundus of many W/W(V) animals. ICC-IM were not observed in W/W(V) group 1 (46%) but were observed in W/W(V) group 2 (40%). Evoked neural responses consisted of excitatory and inhibitory components. The inhibitory component (nitrergic) was absent in W/W(V) group 1 and reduced in W/W(V) group 2. Enhanced excitatory responses (cholinergic) were observed in both W/W(V) groups and qPCR revealed that muscarinic-M3 receptor expression was significantly augmented in the W/W(V) fundus compared to wild-type controls. CONCLUSIONS: This study demonstrates that ICC-IM mediate nitrergic inhibitory neurotransmission in the fundus and provides evidence of plasticity changes in neuronal responses that may explain discrepancies in previous functional studies which utilized mutant animals to examine the role of ICC-IM in gastric enteric motor responses.
Animals ; Enteric Nervous System ; Gastric Fundus* ; Gastrointestinal Tract ; Immunohistochemistry ; Interstitial Cells of Cajal* ; Mice* ; Motor Activity ; Motor Neurons* ; Muscle Relaxation ; Muscle, Smooth ; Muscles ; Neurons ; Plastics ; Polymerase Chain Reaction ; Synaptic Transmission

High-throughput RNA-seq has revolutionized the process of small RNA (sRNA) discovery, leading to a rapid expansion of sRNA categories. In addition to the previously well-characterized sRNAs such as microRNAs (miRNAs), piwi-interacting RNAs (piRNAs), and small nucleolar RNA (snoRNAs), recent emerging studies have spotlighted on tRNA-derived sRNAs (tsRNAs) and rRNA-derived sRNAs (rsRNAs) as new categories of sRNAs that bear versatile functions. Since existing software and pipelines for sRNA annotation are mostly focused on analyzing miRNAs or piRNAs, here we developed the sRNA annotation pipelineoptimized for rRNA- and tRNA-derived sRNAs (SPORTS1.0). SPORTS1.0 is optimized for analyzing tsRNAs and rsRNAs from sRNA-seq data, in addition to its capacity to annotate canonical sRNAs such as miRNAs and piRNAs. Moreover, SPORTS1.0 can predict potential RNA modification sites based on nucleotide mismatches within sRNAs. SPORTS1.0 is precompiled to annotate sRNAs for a wide range of 68 species across bacteria, yeast, plant, and animal kingdoms, while additional species for analyses could be readily expanded upon end users' input. For demonstration, by analyzing sRNA datasets using SPORTS1.0, we reveal that distinct signatures are present in tsRNAs and rsRNAs from different mouse cell types. We also find that compared to other sRNA species, tsRNAs bear the highest mismatch rate, which is consistent with their highly modified nature. SPORTS1.0 is an open-source software and can be publically accessed at https://github.com/junchaoshi/sports1.0.
Animals ; Gene Expression Profiling ; High-Throughput Nucleotide Sequencing ; Mice ; MicroRNAs ; chemistry ; metabolism ; Molecular Sequence Annotation ; RNA, Ribosomal ; chemistry ; metabolism ; RNA, Small Interfering ; chemistry ; metabolism ; RNA, Small Untranslated ; chemistry ; metabolism ; RNA, Transfer ; chemistry ; metabolism ; Sequence Analysis, RNA ; methods ; Software