Unpacking the homeostasis core concept in physiology: an Australian perspective.

Australia-wide consensus was reached on seven core concepts of physiology, which included homeostasis, a fundamental concept for students to understand as they develop their basic knowledge of physiological regulatory mechanisms. The term homeostasis is most commonly used to describe how the internal environment of mammalian systems maintains relative constancy. The descriptor "the internal environment of the organism is actively regulated by the responses of cells, tissues, and organs through feedback systems" was unpacked by a team of three Australian Physiology educators into 5 themes and 18 subthemes arranged in a hierarchy. Using a five-point Likert scale, the unpacked concept was rated by 24 physiology educators from 24 Australian Universities for level of importance and level of difficulty for students. Survey data were analyzed using a one-way ANOVA to compare between and within concept themes and subthemes. There were no differences in main themes for level of importance, with all ratings between essential or important. Theme 1: the organism has regulatory mechanisms to maintain a relatively stable internal environment, a process known as homeostasis was almost unanimously rated as essential. Difficulty ratings for unpacked concept themes averaged between slightly difficult and moderately difficult. The Australian team concurred with published literature that there are inconsistencies in the way the critical components of homeostatic systems are represented and interpreted. We aimed to simplify the components of the concept so that undergraduates would be able to easily identify the language used and build on their knowledge.NEW & NOTEWORTHY The homeostasis core concept of physiology was defined and unpacked by an Australian team with the goal of constructing a resource that will improve learning and teaching of this core physiology concept in an Australian Higher Education context.

Establishing consensus for the core concepts of physiology in the Australian higher education context using the Delphi method.

A set of core concepts ("big ideas") integral to the discipline of physiology are important for students to understand and demonstrate their capacity to apply. We found poor alignment of learning outcomes in programs with physiology majors (or equivalent) from 17 Australian universities and the 15 core concepts developed by a team in the United States. The objective of this project was to reach Australia-wide consensus on a set of core concepts for physiology, which can be embedded in curricula across Australian universities. A four-phase Delphi method was employed, starting with the assembling of a Task Force of physiology educators with extensive teaching and curriculum development expertise from 25 Australian universities. After two online meetings and a survey, the Task Force reached agreement on seven core concepts of physiology and their descriptors, which were then sent out to the physiology educator community across Australia for agreement. The seven core concepts and their associated descriptions were endorsed through this process (n = 138). In addition, embedding the core concepts across the curriculum was supported by both Task Force members (85.7%) and educators (82.1%). The seven adopted core concepts of human physiology were Cell Membrane, Cell-Cell Communication, Movement of Substances, Structure and Function, Homeostasis, Integration, and Physiological Adaptation. The core concepts were subsequently unpacked into themes and subthemes. If adopted, these core concepts will result in consistency across curricula in undergraduate physiology programs and allow for future benchmarking.NEW & NOTEWORTHY This is the first time Australia-wide agreement has been reached on the core concepts of physiology with the Delphi method. Embedding of the core concepts will result in consistency in physiology curricula, improvements to teaching and learning, and benchmarking across Australian universities.

Virtual delivery: a panacea for the financial and ethical challenges associated with physiology laboratory classes?

There has been a gradual shift in the delivery of physiology laboratory classes over the last 30 years. For many, wet-lab demonstrations using animal tissues have been reduced or replaced with student-led investigations where students are both subjects and researchers. Despite these changes, expectations remain that physiology courses should include a practical component to encourage deeper and higher-order learning. Wet-lab tissue experiments and student-based group research formats can be expensive to run, associated with various ethical constraints, and, as discovered in these times of COVID-19, difficult to operate while adhering to physical distancing. We address the proposition that online and/or remote delivery of laboratory classes using digital technologies may provide a solution to both financial and ethical constraints of on-campus laboratory classes. Our discussions, as an international group of 10 physiologists from the United States, the United Kingdom, Canada, and Australia, revealed that although some of the financial and ethical constraints of using animal tissues and student-led investigations were addressed by the introduction of online alternatives, the construction and maintenance of online delivery modes could also be expensive and ethical issues, not previously considered, included digital equity and student data security. There was also a collective perception that if face-to-face laboratory classes were changed to an entirely virtual mode there was a risk that some intended learning outcomes would not be met. It was concluded that the "ideal" approach is likely a hybrid model whereby student attendance in face-to-face, on-campus classes is supported with interactive digital content either developed in house or obtained through third-party providers.

Identification of a novel distension-evoked motility pattern in the mouse uterus.

The dynamic changes in uterine contractility in response to distension are incompletely understood. Rhythmic, propagating contractions of nonpregnant uterine smooth muscle occur in the absence of nerve activity (i.e., myogenic), events that decline during pregnancy and reemerge at parturition. We therefore sought to determine how myogenic contractions of the nonpregnant uterus are affected by distension, which might provide mechanistic clues underlying distension-associated uterine conditions such as preterm birth. Uteri isolated from nulliparous adult female mice in proestrus were video imaged to generate spatiotemporal maps, and myoelectrical activity simultaneously recorded using extracellular suction electrodes. Motility patterns were examined under basal conditions and following ramped intraluminal distension with fluid to 5 and 10 cmH2O. Intraluminal distension caused pressure-dependent changes in the frequency, amplitude, propagation speed, and directionality of uterine contractions, which reversed upon pressure release. Altered burst durations of underlying smooth muscle myoelectric events were concurrently observed, although action potential spike intervals were unchanged. Voltage-gated sodium channel blockade [tetrodotoxin (TTX); 0.6 µM] attenuated both the amplitude of contractions and burst duration of action potentials, whereas all activity was abolished by L-type calcium channel blockade (nifedipine; 1 µM). These data suggest that myogenic motility patterns of the nonpregnant mouse uterus are sensitive to changes in intraluminal pressure and, at high pressures, may be modulated by voltage-gated sodium channel activity. Future studies may investigate whether similar distension-evoked changes occur in the pregnant uterus and the possible pathophysiological role of such activity in the development of preterm birth.

International educators' attitudes, experiences, and recommendations after an abrupt transition to remote physiology laboratories.

The COVID-19 pandemic triggered university lockdowns, forcing physiology educators to rapidly pivot laboratories into a remote delivery format. This study documents the experiences of an international group of 10 physiology educators surrounding this transition. They wrote reflective narratives, framed by guiding questions, to answer the research question: "What were the changes to physiology laboratories in response to the COVID-19 pandemic?" These narratives probed educators' attitudes toward virtual laboratories before, during, and after the transition to remote delivery. Thematic analysis of the reflections found that before COVID-19 only a few respondents had utilized virtual laboratories and most felt that virtual laboratories could not replace the in-person laboratory experience. In response to university lockdowns, most respondents transitioned from traditional labs to remote formats within a week or less. The most common remote delivery formats were commercially available online physiology laboratories, homemade videos, and sample experimental data. The main challenges associated with the rapid remote transition included workload and expertise constraints, disparities in online access and workspaces, issues with academic integrity, educator and student stress, changes in learning outcomes, and reduced engagement. However, the experience generated opportunities including exploration of unfamiliar technologies, new collaborations, and revisiting the physiology laboratory curriculum and structure. Most of the respondents reported planning on retaining some aspects of the remote laboratories postpandemic, particularly with a blended model of remote and on-campus laboratories. This study concludes with recommendations for physiology educators as to how they can successfully develop and deliver remote laboratories.

Morphological identification of thoracolumbar spinal afferent nerve endings in mouse uterus.

Major sensory innervation to the uterus is provided by spinal afferent nerves, whose cell bodies lie predominantly in thoracolumbar dorsal root ganglia (DRG). While the origin of the cell bodies of uterine spinal afferents is clear, the identity of their sensory endings has remained unknown. Hence, our major aim was to identify the location, morphology, and calcitonin gene-related peptide (CGRP)-immunoreactivity of uterine spinal afferent endings supplied by thoracolumbar DRG. We also sought to determine the degree of uterine afferent innervation provided by the vagus nerve. Using an anterograde tracing technique, nulliparous female C57BL/6 mice were injected unilaterally with biotinylated dextran into thoracolumbar DRG (T13-L3). After 7-9 days, uterine horns were stained to visualize traced nerve axons and endings immunoreactive to CGRP. Whole uteri from a separate cohort of animals were injected with retrograde neuronal tracer (DiI) and dye uptake in nodose ganglia was examined. Anterogradely labeled axons innervated each uterine horn, these projected rostrally or caudally from their site of entry, branching to form varicose endings in the myometrium and/or vascular plexus. Most spinal afferent endings were CGRP-immunoreactive and morphologically classified as "simple-type." Rarely, uterine nerve cell bodies were labeled in nodose ganglia. Here, we provide the first detailed description of spinal afferent nerve endings in the uterus of a vertebrate. Distinct morphological types of spinal afferent nerve endings were identified throughout multiple anatomical layers of the uterine wall. Compared to other visceral organs, uterine spinal afferent endings displayed noticeably less morphological diversity. Few neurons in nodose ganglia innervate the uterus.

Spinal Glial Adaptations Occur in a Minimally Invasive Mouse Model of Endometriosis: Potential Implications for Lesion Etiology and Persistent Pelvic Pain.

Glial adaptations within the central nervous system are well known to modulate central sensitization and pain. Recently, it has been suggested that activity of glial-related proinflammatory cytokines may potentiate peripheral inflammation, via central neurogenic processes. However, a role for altered glial function has not yet been investigated in the context of endometriosis, a chronic inflammatory condition in women associated with peripheral lesions, often manifesting with persistent pelvic pain. Using a minimally invasive mouse model of endometriosis, we investigated associations between peripheral endometriosis-like lesions and adaptations in central glial reactivity. Spinal cords (T13-S1) from female C57BL/6 mice with endometriosis-like lesions (ENDO) were imaged via fluorescent immunohistochemistry for the expression of glial fibrillary acidic protein (GFAP; astrocytes) and CD11b (microglia) in the dorsal horn (n = 5). Heightened variability ( P = .02) as well as an overall increase ( P = .04) in the mean area of GFAP immunoreactivity was found in ENDO versus saline-injected control animals. Interestingly, spinal levels showing the greatest alterations in GFAP immunoreactivity appeared to correlate with the spatial location of lesions within the abdominopelvic cavity. A subtle but significant increase in the mean area of CD11b immunostaining was also observed in ENDO mice compared to controls ( P = .02). This is the first study to describe adaptations in nonneuronal, immune-like cells of the central nervous system attributed to the presence of endometriosis-like lesions.

The HER3 pathway as a potential target for inhibition in patients with biliary tract cancers.

INTRODUCTION: Expression of human epidermal growth factor receptor (HER)2 and HER3 have been investigated in small BTC studies using variable scoring systems. METHODS: HER2 and HER3 overexpression/amplification were explored following internationally agreed guidelines using immunohistochemistry (IHC) and fluorescent in-situ hybridisation (FISH), respectively. Logistic regression and survival analysis (Kaplan Meier, Log rank test and Cox Regression) were used for statistical analysis. RESULTS: Sixty-seven eligible patients with Stage I/II (31.3%) or III/IV (68.7%) disease at diagnosis were included. Membrane HER2 overexpression/amplification was identified in 1 patient (1%). HER3 overexpression was predominantly cytoplasmic; the rate of overexpression/amplification of HER3 in membrane and cytoplasm was 16% [ampullary cancer (AMP) (1/13; 8%), gallbladder cancer (GBC) (1/10; 10%), intra-hepatic cholangiocarcinoma (ICC) (6/26; 23%), extra-hepatic cholangiocarcinoma (ECC) (3/18; 17%)] and 24% [AMP (1/13; 8%), GBC (1/10; 10%), ICC (10/26; 38%), ECC (4/18; 22%)], respectively. CONCLUSIONS: A significant subset of patients with BTC expressed HER3. Inhibition of HER3 warrants further investigation. A better understanding of the downstream effects of HER3 in BTC requires further mechanistic investigations to identify new biomarkers and improve patient selection for future clinical trials.

Colonic migrating motor complexes are inhibited in acute tri-nitro benzene sulphonic acid colitis.

BACKGROUND: Inflammatory Bowel Disease (IBD) is characterized by overt inflammation of the intestine and is typically accompanied by symptoms of bloody diarrhea, abdominal pain and cramping. The Colonic Migrating Motor Complex (CMMC) directs the movement of colonic luminal contents over long distances. The tri-nitrobenzene sulphonic acid (TNBS) model of colitis causes inflammatory damage to enteric nerves, however it remains to be determined whether these changes translate to functional outcomes in CMMC activity. We aimed to visualize innate immune cell infiltration into the colon using two-photon laser scanning intra-vital microscopy, and to determine whether CMMC activity is altered in the tri-nitro benzene sulphonic (TNBS) model of colitis. METHODS: Epithelial barrier permeability was compared between TNBS treated and healthy control mice in-vitro and in-vivo. Innate immune activation was determined by ELISA, flow cytometry and by 2-photon intravital microscopy. The effects of TNBS treatment and IL-1ß on CMMC function were determined using a specialized organ bath. RESULTS: TNBS colitis increased epithelial barrier permeability in-vitro and in-vivo. Colonic IL-1ß concentrations, colonic and systemic CD11b+ cell infiltration, and the number of migrating CD11b+ cells on colonic blood vessels were all increased in TNBS treated mice relative to controls. CMMC frequency and amplitude were inhibited in the distal and mid colon of TNBS treated mice. CMMC activity was not altered by superfusion with IL-1ß. CONCLUSIONS: TNBS colitis damages the epithelial barrier and increases innate immune cell activation in the colon and systemically. Innate cell migration into the colon is readily identifiable by two-photon intra-vital microscopy. CMMC are inhibited by inflammation, but this is not due to direct effects of IL-1ß.

Differential effect of morphine on gastrointestinal transit, colonic contractions and nerve-evoked relaxations in Toll-Like Receptor deficient mice.

Toll-like receptors (TLRs) are expressed in enteric neurons, glia, gastrointestinal (GI) smooth muscle and mucosa, yet their functional roles in the GI tract are not fully understood. TLRs have been linked to many of the undesirable central effects of chronic opioid administration including hyperalgesia and dependence via activation of central microglia. Opioid-induced bowel dysfunction (OIBD) remains a primary reason for the reduction or withdrawal of opioid analgesics. Morphine-induced inhibition of colonic motility was assessed in vivo by GI transit studies and in vitro using isolated colons from wildtype (WT) and TLR deficient mice. Morphine slowed movement of ingested content in WT but this retardation effect was attenuated in TLR4 -/- and TLR2/4 -/- . In isolated colons, morphine reduced amplitude and frequency colonic migrating motor contractions in both WT and TLR2/4 -/- . Electrical field stimulation elicited distal colon relaxation that was potentiated by morphine in WT but not in TLR2/4 -/- . Inhibitory junction potentials were of similar amplitude and kinetics in WT and TLR2/4 -/- distal colon and not altered by morphine. Enteric nerve density and proportion of nitrergic nerves were similar in WT and TLR2/4 -/- distal colon. These data suggest an involvement of TLRs in opioid pharmacodynamics and thus a potential interventional target for OIBD.

Identifying unique subtypes of spinal afferent nerve endings within the urinary bladder of mice.

Spinal afferent neurons are responsible for the transduction and transmission of noxious (painful) stimuli and innocuous stimuli that do not reach conscious sensations from visceral organs to the central nervous system. Although the location of the nerve cell bodies of spinal afferents is well known to reside in dorsal root ganglia (DRG), the morphology and location of peripheral nerve endings of spinal afferents that transduce sensory stimuli into action potentials is poorly understood. The individual nerve endings of spinal afferents that innervate the urinary bladder have never been unequivocally identified in any species. We used an anterograde tracing technique developed in our laboratory to selectively label only spinal afferents. Mice were anesthetized and unilateral injections of dextran-amine made into lumbosacral DRGs (L5-S2). Seven to nine days postsurgery, mice were euthanized, the urinary bladder removed, then fresh-fixed and stained for immunoreactivity to calcitonin-gene-related-peptide (CGRP). Four distinct morphological types of spinal afferent ending in the bladder were identified. Three types existed in the detrusor muscle and one major type in the sub-urothelium and urothelium. Most nerve endings were located in detrusor muscle where the three types could be identified as having: "branching", "simple", or "complex" morphology. The majority of spinal afferent nerve endings were CGRP-immunoreactive. Single spinal afferent axons bifurcated many times upon entering the bladder and developed varicosities along their axon terminal endings. We present the first morphological identification of spinal afferent nerve endings in the mammalian urinary bladder.

Lesion development is modulated by the natural estrous cycle and mouse strain in a minimally invasive model of endometriosis.

Many rodent models of endometriosis are invasive, involving surgery to implant donor endometrial tissue into recipient animals. Moreover, few studies have compared and contrasted lesions between rodent strains and estrous stages without exogenous hormone manipulation. This is despite extensive data demonstrating that genetic and hormonal factors can influence endometriosis progression. Here, we have refined a minimally invasive model of endometriosis using naturally cycling mice (donor and recipient matched for cycle phase) to investigate lesion development in two different strains (C57BL/6 and BALB/c), induced in estrous stages of high and low estrogen (proestrus or estrus, respectively), and with varying amounts of donor endometrial tissue (7.5-40 mg), injected intraperitoneally. The overall probability of developing endometriosis-like lesions was higher in proestrus than estrus, and increased with greater masses of donor tissue. Similarly, the total number of lesions (0-3) increased from 7.5 to 40 mg, and was significantly greater in proestrus C57BL/6 mice but not BALB/cs. The dominant lesion type also differed between mouse strains; C57BL/6 mice were more likely to develop dense-type lesions, whereas BALB/c mice developed a greater proportion of cystic type. These data further support a role for estrogen in the development of endometriosis, and that genetic variance can influence the degree and characteristics of lesions. Our minimally invasive model would be beneficial for studies with outcome measurements particularly sensitive to incisional injury, such as pain, or alterations to sex hormones, including fertility.

Inhibitory responses mediated by vagal nerve stimulation are diminished in stomachs of mice with reduced intramuscular interstitial cells of Cajal.

Intramuscular interstitial cells of Cajal (ICC-IM) are closely associated with enteric motor nerve terminals and electrically coupled to smooth muscle cells within the gastric musculature. Previous studies investigating the role of ICC-IM in motor neurotransmission have used indiscriminate electric field stimulation of neural elements within the gastric wall. To determine the role of ICC-IM in transduction of vagally-mediated motor input to gastric muscles electrical and mechanical responses to selective electrical vagal stimulation (EVS) were recorded from gastric fundus and antral regions of wild type and W/WV mice, which lack most ICC-IM. EVS evoked inhibitory junction potentials (IJPs) in wild type muscles that were attenuated or abolished by L-NNA. IJPs were rarely evoked in W/WV muscles by EVS, and not affected by L-NNA. EVS evoked relaxation of wild type stomachs, but the predominant response of W/WV stomachs was contraction. EVS applied after pre-contraction with bethanechol caused relaxation of wild type gastric tissues and these were inhibited by the nitric oxide synthase inhibitor L-NNA. Relaxation responses were of smaller amplitude in W/WV muscles and L-NNA did not attenuate relaxation responses in W/WV fundus muscles. These data suggest an important role for ICC-IM in vagally-mediated nitrergic relaxation in the proximal and distal stomach.

Different types of spinal afferent nerve endings in stomach and esophagus identified by anterograde tracing from dorsal root ganglia.

In visceral organs of mammals, most noxious (painful) stimuli as well as innocuous stimuli are detected by spinal afferent neurons, whose cell bodies lie in dorsal root ganglia (DRGs). One of the major unresolved questions is the location, morphology, and neurochemistry of the nerve endings of spinal afferents that actually detect these stimuli in the viscera. In the upper gastrointestinal (GI) tract, there have been many anterograde tracing studies of vagal afferent endings, but none on spinal afferent endings. Recently, we developed a technique that now provides selective labeling of only spinal afferents. We used this approach to identify spinal afferent nerve endings in the upper GI tract of mice. Animals were anesthetized, and injections of dextran-amine were made into thoracic DRGs (T8-T12). Seven days post surgery, mice were euthanized, and the stomach and esophagus were removed, fixed, and stained for calcitonin gene-related peptide (CGRP). Spinal afferent axons were identified that ramified extensively through many rows of myenteric ganglia and formed nerve endings in discrete anatomical layers. Most commonly, intraganglionic varicose endings (IGVEs) were identified in myenteric ganglia of the stomach and varicose simple-type endings in the circular muscle and mucosa. Less commonly, nerve endings were identified in internodal strands, blood vessels, submucosal ganglia, and longitudinal muscle. In the esophagus, only IGVEs were identified in myenteric ganglia. No intraganglionic lamellar endings (IGLEs) were identified in the stomach or esophagus. We present the first identification of spinal afferent endings in the upper GI tract. Eight distinct types of spinal afferent endings were identified in the stomach, and most of them were CGRP immunoreactive. J. Comp. Neurol. 524:3064-3083, 2016. © 2016 Wiley Periodicals, Inc.

Uterine Contractility in the Nonpregnant Mouse: Changes During the Estrous Cycle and Effects of Chloride Channel Blockade.

Mechanisms involved in the generation of spontaneous uterine contractions are not fully understood. Kit-expressing interstitial cells of Cajal are pacemakers of contractile rhythm in other visceral organs, and recent studies describe a role for Ca(2+)-activated Cl(-) currents as the initiating conductance in these cells. The existence and role of similar specialized pacemaker cells in the nonpregnant uterus remains undetermined. Spontaneous contractility patterns were characterized throughout the estrous cycle in isolated, nonpregnant mouse uteri using spatiotemporal mapping and tension recordings. During proestrus, estrus, and diestrus, contraction origin predominated in the oviduct end of the uterus, suggesting the existence of a dominant pacemaker site. Propagation speed of contractions during estrus and diestrus were significantly slower than in proestrus and metestrus. Five major patterns of activity were predominantly exhibited in particular stages: quiescent (diestrus), high-frequency phasic (proestrus), low-frequency phasic (estrus), multivariant (metestrus), and complex. Kit-immunopositive cells reminiscent of pacemaking ICCs were not consistently observed within the uterus. Niflumic acid (10 µM), anthracene-9-carboxylic acid (0.1-1 mM), and 5-nitro-2-(3-phenylpropylamino)benzoic acid (10 µM) each reduced the frequency of spontaneous contractions, suggesting involvement of Cl(-) channels in generating spontaneous uterine motor activity. It is unlikely that this conductance is generated by the Ca(2+)-activated Cl(-) channels, anoctamin-1 and CLCA4, as immunohistochemical labeling did not reveal protein expression within muscle or pacemaker cell networks. In summary, these results suggest that spontaneous uterine contractions may be generated by a Kit-negative pacemaker cell type or uterine myocytes, likely involving the activity of a yet-unidentified Cl(-) channel.

Characterization of primary afferent spinal innervation of mouse uterus.

The primary afferent innervation of the uterus is incompletely understood. The aim of this study was to identify the location and characteristics of primary afferent neurons that innervate the uterine horn of mice and correlate the different morphological types of putative primary afferent nerve endings, immunoreactive to the sensory marker, calcitonin gene related peptide (CGRP). Using retrograde tracing, injection of 5-10 µL of 1,1'-didodecyl-3,3,3,3'-tetramethylindocarbocyanine perchlorate (DiI) into discrete single sites in each uterine horn revealed a biomodal distribution of sensory neurons in dorsal root ganglia (DRG) with peak labeling occurring between T13-L3 and a second smaller peak between L6-S1. The mean cross sectional area of labeled cells was 463 µm(2) ± s.e.m. A significantly greater proportion of labeled neurons consisted of small cell bodies (<300 µm(2)) in the sacral spinal cord (S2) compared with peak labeling at the lumbar (L2) region. In both sections and whole mount preparations, immunohistochemical staining for CGRP revealed substantial innervation of the uterus by CGRP-positive nerve fibers located primarily at the border between the circular and longitudinal muscle layers (N = 4). The nerve endings were classified into three distinct types: "single," "branching," or "complex," that often aligned preferentially in either the circular or longitudinal axis of the smooth muscles. Complex endings were often associated with mesenteric vessels. We have identified that the cell bodies of primary afferent neurons innervating the mouse uterus lie primarily in DRG at L2 and S1 spinal levels. Also, the greatest density of CGRP immunoreactivity lies within the myometrium, with at least three different morphological types of nerve endings identified. These findings will facilitate further investigations into the mechanisms underlying sensory transduction in mouse uterus.

Control of intrinsic pacemaker frequency and velocity of colonic migrating motor complexes in mouse.

The mechanisms that control the frequency and propagation velocity of colonic migrating motor complexes (CMMCs) in mammals are poorly understood. Previous in vitro studies on whole mouse colon have shown that CMMCs occur frequently (~every 1-3 min) when the colon is devoid of all fecal content. Consequently, these studies have concluded that the generation of CMMCs and the frequency which they occur does not require the presence of fecal content in the lumen. However, in these studies, stimuli have always been unavoidably applied to these empty colonic preparations, facilitating recordings of CMMC activity. We tested whether CMMCs still occur in empty whole colonic preparations, but when conventional recording methods are not used. To test this, we used video imaging, but did not utilize standard recording methods. In whole isolated colons containing multiple endogenous fecal pellets, CMMCs occurred frequently (1.9 ± 0.1/min) and propagated at 2.2 ± 0.2 mm/s. Surprisingly, when these preparations had expelled all content, CMMCs were absent in 11/24 preparations. In the remaining preparations, CMMCs occurred rarely (0.18 ± 0.02/min) and at reduced velocities (0.71 ± 0.1 mm/s), with reduced extent of propagation. When conventional recording techniques were then applied to these empty preparations, CMMC frequency significantly increased, as did the extent of propagation and velocity. We show that in contrast to popular belief, CMMCs either do not occur when the colon is free of luminal contents, or, they occur at significantly lower frequencies. We believe that previous in vitro studies on empty segments of whole mouse colon have consistently demonstrated CMMCs at high frequencies because conventional recording techniques stimulate the colon. This study shows that CMMCs are normally absent, or infrequent in an empty colon, but their frequency increases substantially when fecal content is present, or, if in vitro techniques are used that stimulate the intestine.

AqF026 is a pharmacologic agonist of the water channel aquaporin-1.

Aquaporin-1 (AQP1) facilitates the osmotic transport of water across the capillary endothelium, among other cell types, and thereby has a substantial role in ultrafiltration during peritoneal dialysis. At present, pharmacologic agents that enhance AQP1-mediated water transport, which would be expected to increase the efficiency of peritoneal dialysis, are not available. Here, we describe AqF026, an aquaporin agonist that is a chemical derivative of the arylsulfonamide compound furosemide. In the Xenopus laevis oocyte system, extracellular AqF026 potentiated the channel activity of human AQP1 by >20% but had no effect on channel activity of AQP4. We found that the intracellular binding site for AQP1 involves loop D, a region associated with channel gating. In a mouse model of peritoneal dialysis, AqF026 enhanced the osmotic transport of water across the peritoneal membrane but did not affect the osmotic gradient, the transport of small solutes, or the localization and expression of AQP1 on the plasma membrane. Furthermore, AqF026 did not potentiate water transport in Aqp1-null mice, suggesting that indirect mechanisms involving other channels or transporters were unlikely. Last, in a mouse gastric antrum preparation, AqF026 did not affect the Na-K-Cl cotransporter NKCC1. In summary, AqF026 directly and specifically potentiates AQP1-mediated water transport, suggesting that it deserves additional investigation for applications such as peritoneal dialysis or clinical situations associated with defective water handling.

A study of gata3 and phox2b expression in tumors of the autonomic nervous system.

Autonomic neurons and chromaffin cells, which constitute the autonomic nervous system, are derived from a common progenitor from the neural crest, and its development is controlled by a network of transcription factors, including the master regulator, Phox2b, and its downstream, Gata3. Anti-Phox2b and anti-Gata3 antibodies were applied to a total of 77 autonomic nervous system tumors, including 35 paragangliomas, 21 pheochromocytomas, 9 neuroblastomas, 4 ganglioneuroblastomas, and 8 ganglioneuromas, as well as their potential morphologic mimics, including tumors of the small round cell tumor group, neuroendocrine carcinomas of lung and gastrointestinal tract (carcinoid tumors/neuroendocrine tumors, large cell neuroendocrine carcinomas, and small cell carcinomas), Merkel cell carcinomas, benign and malignant tumors of thyroid, parathyroid, and adrenal cortex, and malignant melanomas. A variety of nonendocrine/neuroendocrine carcinomas were also studied. Gata3 expression was seen in 89% of paragangliomas, 95% of pheochromocytomas, and all neuroblastomas, ganglioneuroblastomas, and ganglioneuromas, as well as in all parathyroid tumors, a majority of urothelial and mammary carcinomas, and a subset of squamous cell carcinomas, but all other tumors were negative. Phox2b expression was seen in all neuroblastomas, ganglioneuroblastomas, and ganglioneuromas and in 40% of paragangliomas, but pheochromocytomas and all other tumors were negative. Gata3 is a highly reliable marker for paragangliomas, pheochromocytomas, and neuroblastic tumors to distinguish from their simulators. This is an additional utility for this marker, which is used for the diagnosis of urothelial and mammary carcinomas. Phox2b is also highly specific, but its low sensitivity to paragangliomas and pheochromocytomas would limit the utility only to neuroblastic tumors.