Control systems of gastrointestinal motility are immature at birth in dogs

Stem Cell Factor/Kit Signal Insufficiency Contributes to Hypoxia-Induced Intestinal Motility Dysfunctions in Neonatal Mice

BACKGROUND

Gastrointestinal (GI) motility disorders represent a group of problems that more constantly encountered in preterm infants. However, whether hypoxia exposure contributes to the GI dysfunctions is still unclear.

METHODS

Newborn mice were exposed to hypoxia (10%) from P1 to P7. Intestinal motilities were examined by a strain gauge transducer. The proliferation of ICCs was detected by using immunostaining for BrdU, Ki67, Kit, Ano1, and insulin-like growth factor 1 receptor (IGF-1R+). Smooth muscle cells and enteric neurons were revealed by immunostaining for α-SMA and NF200, respectively. Apoptosis was assessed by TUNEL assay. Kit signal pathway was examined by western blot and qPCR.

RESULTS

Intestinal motilities were found weakened significantly in the hypoxic small intestines as compared to controls on P8. Kit+ or Ano1+ interstitial cells of Cajal (ICCs) were found obviously decreased in the myenteric ICCs (ICC-MY) of neonatal mice after exposed to hypoxia. A large number of ICC progenitors (IGF-1R+) were found highly mitotic (BrdU+ Ki67+) to populate ICC during early postnatal development in the normoxic mice. We found the ICC proliferation was significantly inhibited upon hypoxia exposure, without increasing apoptosis (TUNEL+). We next identified that Kit phosphorylation was inhibited 3 days after hypoxia exposure. The inhibition of Kit signaling was largely due to decreased the expression of the ligand of Kit receptor, stem cell factor (SCF), in the intestinal walls. Exposure to imatinib, a Kit receptor inhibitor, for 3 days from P4 phenocopied the effect of hypoxia on the neonatal pups that resulted in inhibited intestinal motilities and decreased Kit+ ICC numbers.

CONCLUSION

All together, our findings indicate the SCF/Kit signaling insufficiency may contribute to the underdevelopment of ICCs and intestinal motility dysfunction upon hypoxia exposure. The decease in ICC density is likely due to the cell cycle arrest of ICC progenitor cells.

Evaluation of changes in oral drug absorption in preterm and term neonates for Biopharmaceutics Classification System (BCS) class I and II compounds

AIMS

Evidence suggests that the rate of oral drug absorption changes during early childhood. Yet, respective clinical implications are currently unclear, particularly for preterm neonates. The objective of this study was to evaluate changes in oral drug absorption after birth for different Biopharmaceutics Classification System (BCS) class I and II compounds to better understand respective implications for paediatric pharmacotherapy.

METHODS

Two paradigm compounds were selected for BCS class I (paracetamol (acetaminophen) and theophylline) and II (indomethacin and ibuprofen), respectively, based on the availability of clinical literature data following intravenous and oral dosing. A comparative population pharmacokinetic analysis was performed in a step-wise manner in NONMEM® 7.2 to characterize and predict changes in oral drug absorption after birth for paracetamol, theophylline and indomethacin.

RESULTS

A one compartment model with an age-dependent maturation function for oral drug absorption was found appropriate to characterize the pharmacokinetics of paracetamol. Our findings indicate that the rate at which a drug is absorbed from the GI tract reaches adult levels within about 1 week after birth. The maturation function for paracetamol was found applicable to theophylline and indomethacin once solubility limitations were overcome via drug formulation. The influence of excipients on solubility and, hence, oral bioavailability was confirmed for ibuprofen, a second BCS class II compound.

CONCLUSIONS

The findings of our study suggest that the processes underlying changes in oral drug absorption after birth are drug-independent and that the maturation function identified for paracetamol may be generally applicable to other BCS class I and II compounds for characterizing drug absorption in preterm as well as term neonates.

Cricopharyngeal achalasia in children: botulinum toxin injection as a tool for diagnosis and treatment

OBJECTIVES/HYPOTHESIS

Characteristics and outcomes of pediatric patients undergoing cricopharyngeus injection with botulinum toxin for the treatment of cricopharyngeal achalasia were reviewed. A parental telephone survey was performed to assess improvement and satisfaction.

STUDY DESIGN

Retrospective review of patients who underwent injection of the cricopharyngeus with botulinum toxin for cricopharyngeal achalasia. A prospective survey of postoperative symptoms and parental satisfaction was also performed.

METHODS

After institutional review board approval, children with cricopharyngeal achalasia who underwent injection with botulinum toxin were identified. Specific parameters were recorded for each patient. A survey of the parents' satisfaction and subjective improvement was then conducted.

RESULTS

Six children were identified with cricopharyngeal achalasia, with an age range of 3 months to 10 years. Symptoms varied and five of the six children required some form of altered nutrition. Preoperative studies varied, and the number of injections ranged from one to three per patient. One child had transient worsening of aspiration. Two children benefited from injections and went on to myotomy, while four children did not require myotomy and their symptoms were treated with injections alone. A parental survey was performed via telephone. All parents were satisfied with the procedure. Three children were symptom-free, and three children still exhibit some dysphagia.

CONCLUSIONS

Botulinum toxin injection is a useful tool to help diagnose and treat pediatric cricopharyngeal achalasia. More research is needed to elucidate optimal dosing, frequency of injections, and when to move on to surgical intervention.

LEVEL OF EVIDENCE

4.

Congenital cricopharyngeal achalasia in a 4.5-year-old managed by cervical myotomy: a case report

INTRODUCTION

Congenital cricopharyngeal achalasia (CCA) is a rare disorder in children characterized by inappropriate contraction of the cricopharyngeus muscle, resulting in the inability to relax the upper esophageal sphincter during deglutition. We report the diagnostic process and management of a relatively older patient who underwent cricopharyngeal myotomy at the age of 4.5 years.

METHODS

A retrospective review of the case and clinical follow-up was performed.

RESULTS

This young patient had a long history of dysphagia, choking, nasal reflux and recurrent pneumonia and croup since birth and was diagnosed with CCA at 22 months of age. She underwent balloon dilation of the cricopharyngeus muscle shortly thereafter with only transient relief of her symptoms of feeding difficulty (choking and aspiration). The parents were reluctant for her to undergo further interventions until 2 years later when they consented to cricopharyngeal myotomy. She underwent transcervical myotomy at age 4.5 years and had complete relief of her symptoms. She had no post-operative complications and has done well for nearly 12 months following myotomy.

DISCUSSION

Our patient is one of the oldest children reported to have undergone myotomy, recovered quickly, and had no difficulty swallowing at any time following surgery. We suggest transcervical cricopharyngeal myotomy as the preferred treatment due to its lasting effects and repeated success in relieving dysphagia in young patients with CCA.

The preterm piglet - a model in the study of oesophageal development in preterm neonates

AIM

Preterm infants have difficulty in attaining independent oral feeding. This can ensue from inadequate sucking, swallowing and/or respiration. In impeding bolus transport, immature oesophageal motility may also be a cause. As studies on the development of oesophageal motility are invasive in preterm infants, the preterm piglet was investigated as a potential research model.

METHODS

Oesophageal motility (EM) of term (n = 6) and preterm (n = 15) piglets were monitored by manometry for 10 min immediately following bottle feeding on days 1-2 and 3-4 of life.

RESULTS

Piglets' oral feeding performance and EM were similar to those of their human counterparts. Term piglets readily completed their feeding, whereas their preterm counterparts did not. They also presented with greater peristaltic activity and propagating velocity. Peristaltic activity remained unchanged over time in preterm piglets, but an increase in synchronous and decrease in incomplete motor activity were noted. Preterm piglets that developed symptoms analogous to necrotizing enterocolitis (NEC) demonstrated uncharacteristic oesophageal activity.

CONCLUSION

Immature EM may cause oral feeding difficulties. NEC-like symptoms may adversely affect EM. The piglet is a valid research model for studying human infant oral feeding and oesophageal development.

Maturation of gastric electrical activity, gastric emptying and intestinal permeability in preterm newborns during the first month of life

INTRODUCTION

Immaturity of motility, intestinal epithelial barrier function and absorptive capacity may play a role in the pathophysiology of intestinal diseases in preterms. We determined the gastric electrical activity and emptying, and intestinal permeability, in preterm newborns to verify if a maturation pattern exists in preterm newborns during the first month of life.

PATIENTS AND METHODS

Eighteen preterm newborns (median 34 wks, range 2 wks) completed the study. They underwent the recording of gastric electrical activity by means of cutaneous electrogastrography, the ultrasound examination of gastric emptying, and the lactulose-to-mannitol ratio from permeability-absorption test on days 3, 7, 15, and 30 after birth.

RESULTS

Gastric electrical activity and emptying showed only slight changes between day 3 and day 7. On the contrary, an evident maturation in permeability, expressed as L/Mratio, was evident over time (Friedman Repeated Measures Analysis, p = 0.004).

CONCLUSION

In preterm healthy newborns of 34 weeks gestational age, electrical and motor activity are completely developed at birth whilst the intestinal epithelial barrier clearly improves during the first week of life.

Enteric nervous system and developmental abnormalities in childhood

ENS consists of a complex network of neurons, organised in several plexuses, which interact by means of numerous neurotransmitters. It is capable of modulating the intestinal motility, exocrine and endocrine secretions, microcirculation and immune and inflammatory responses within the gastrointestinal tract, independent of the central nervous system. Though the embryological development of various plexuses are completed by mid-way of gestation, the maturation of neurons and nerve plexuses appear to continue well after birth. Therefore, any histological or functional abnormalities related to the gastrointestinal function must be investigated with the ongoing maturational processes in mind.

The effects of endogenous and exogenous nitric oxide on gut motility in zebrafish Danio rerio embryos and larvae

Using motion analysis, the ontogeny of the nitrergic control system in the gut was studied in vivo in zebrafish Danio rerio embryos and larvae. For the first time we show the presence of a nitrergic tonus,modulating both anterograde and retrograde contraction waves in the intestine of developing zebrafish. At 4 d.p.f. (days post fertilisation), the nitric oxide synthase (NOS) inhibitor l-NAME (three boluses of 50–100 nl, 10–3 mol l–1) increased the anterograde contraction wave frequency by 0.50±0.10 cycles min–1. Subsequent application of the NO donor sodium nitroprusside (SNP; three boluses of 50–100 nl, 10–4mol l–1) reduced the frequency of propagating anterograde waves (–0.71±0.20 cycles min–1). This coincided with the first appearance of an excitatory cholinergic tonus, observed in an earlier study. One day later, at 5 d.p.f., in addition to the effect on anterograde contraction waves, application of l-NAME increased(0.39±0.15 cycles min–1) and following SNP application reduced (–1.61±0.36 cycles min–1) the retrograde contraction wave frequency. In contrast, at 3 d.p.f., when no spontaneous motility is observed, application of l-NAME did not induce contraction waves in either part of the gut, indicating the lack of a functional inhibitory tonus at this early stage. Gut neurons expressing NOS-like immunoreactivity were present in the distal and middle intestine as early as 2 d.p.f., and at 1 day later in the proximal intestine. In conclusion, the present study suggests that a nitrergic inhibitory tonus develops shortly before or at the time for onset of exogenous feeding.

Co-contribution of IP3R and Ca2+ influx pathways to pacemaker Ca2+ activity in stomach ICC

Intracellular Ca2+ oscillations in interstitial cells of Cajal (ICCs) are thought to be the primary pacemaker activity in the gut. In the present study, the authors prepared small tissues of 100-to 300-microm diameter (cell cluster preparation) from the stomach smooth muscle (including the myenteric plexus) of mice by enzymatic and mechanical treatments. After 2 to 4 days of culture, the intracellular Ca2+ concentration ([Ca2+]i) was measured. In the presence of nifedipine, a dihydropyridine Ca2+ channel antagonist, spontaneous [Ca2+]i oscillations were observed within limited regions showing positive c-Kitimmunoreactivity, a maker for ICCs. In the majority of cell cluster preparations with multiple regions of [Ca2+]i oscillations, [Ca2+]i oscillated synchronously in the same phase. A small number of cell clusters (8 of 53) showed multiple regions of [Ca2+]i oscillations synchronized but with a considerable phase shift. Neither tetrodotoxin (250 nM) nor atropine (10 microM) significantly affected [Ca2+]i oscillations in the presence of nifedipine. Low concentrations (40 microM) of Ni2+ had little effect on the spontaneous [Ca2+]i oscillation, but SK&F96365 (40 microM) and Cd2+ (120 microM) terminated it. Applications of either 2-aminoethoxydiphenyl borate (10 microM) or xestosponginC(10 microM) completely and rather rapidly (approximately 2 min) abolished the spontaneous [Ca2+]i oscillations. The results suggest that pacemaker [Ca2+]i oscillations in ICCs are produced by close interaction of intracellular Ca2+ release channels, especially inositol 1,4,5-trisphosphate receptor (InsP3R) and Ca2+ influx pathways, presumably corresponding to store-operated type channels. Reverse transcription polymerase chain reaction examinations revealed expression of TRPC2, 4, and 6, as well as InsP3R1 and 2 in ICCs.

Effect of erythromycin on gastroduodenal contractile activity in developing neonates

BACKGROUND

The occurrence of phase III of migrating motor complexes in neonates is inversely related to gestational age, and it can be triggered in some infants by the motilin receptor agonist erythromycin. After intragastric erythromycin, the authors determined 1) the occurrence and characteristics of phase III of migrating motor complexes, 2) the antral and duodenal motor responses, and 3) the dose-response relation among preterm and full-term infants.

METHODS

Using an unbalanced, repeated measures design, 25 preterm and term infants were given two of three doses of intragastric erythromycin: 0.75, 1.5, and 3.0 mg/kg. Motor activity was recorded 3 hours before and 2 hours after each dose using a continuous water perfusion manometry system.

RESULTS

Erythromycin failed to induce phase III of migrating motor complexes in infants younger than 31 weeks' gestation; however, it induced phase III in a dose-dependent manner among infants whose gestational ages were 32 weeks and older ( P < 0.05). Erythromycin significantly increased the amplitude and frequency of antral contractions in term infants and significantly increased the duodenal contraction amplitude in older preterm and term infants, but these effects were absent in younger preterm infants.

CONCLUSIONS

The ontogenic emergence of the motilin receptor-mediated induction of phase III occurs by 32 weeks' gestation, whereas the non-motilin-mediated response of increased antroduodenal motor activity is not observed until term. Therefore, early use of erythromycin as a prokinetic agent may not be useful in very preterm infants, partially useful in older preterm infants, and useful in full-term infants.

Physiology and pathophysiology of the interstitial cell of Cajal: from bench to bedside. III. Interaction of interstitial cells of Cajal with neuromediators: an interim assessment

Interstitial cells of Cajal (ICC) control gastrointestinal motility; some pace slow waves and others act in enteric neurotransmission. This review asks the question, does either class of ICC receive and respond to messages carried by neuromediators from these nerves? Relevant evidence includes the presence of receptors or responses to exogenous neuromediators and responses to endogenous neuromediators. Some pacemaking ICC networks have receptors for or respond to some exogenous neuromediators. None is known to respond to endogenous neuromediators. Intramuscular ICC have receptors for and respond to some neuromediators and are required in mice for responses to the exogenous and endogenous neuromediators nitric oxide and acetylcholine. The mechanisms underlying this requirement remain unclear. ICC pathologies exist, but their origins are unknown.

Physiology and pathophysiology of the interstitial cell of Cajal: from bench to bedside. II. Gastric motility: lessons from mutant mice on slow waves and innervation

The stomach harbors a network of interstitial cells of Cajal (ICC) associated with Auerbach's plexus as well as intramuscular ICC within the muscle layers that make close apposition contact with nerve varicosities. ICC are critical for slow-wave generation, making ICC the pacemaker cells of the gut, allowing rhythmic peristaltic motor patterns in the mid- and distal stomach. ICC also play a role in neurotransmission, but its importance relative to direct muscle innervation is still under investigation. The role of ICC in many control functions of gastric motility in humans needs further examination. The pathophysiology of ICC in disease can be partially assessed by immunohistochemistry and electron microscopy on tissue samples. Electrogastrogram measurements may also play a role, but this technique needs further refinement. Communication between ICC and muscle may involve electrical coupling, metabolic coupling through gap junctions, or secretion of nitric oxide or carbon monoxide.