Human lower oesophageal sphincter relaxation is associated with raised cyclic nucleotide content

Article Abstract:

The contents of the stomach are extremely acidic, and reflux (backward flow) of gastric contents into the lower esophagus is normally prevented. This preventative action is accomplished by contraction of the lower esophageal sphincter, a ring of smooth muscle that separates the esophagus from the stomach. Functioning of the lower esophageal sphincter is controlled both by nerves within the walls of the gastrointestinal tract (enteric nerves) and by extrinsic nerves (the vagus nerve). In animal models, from which most of our knowledge concerning the biochemistry, physiology, and pharmacology of lower esophageal sphincter control comes, there is evidence that the molecular mechanisms involved in contraction and relaxation of the sphincter may differ from humans. One particular class of molecules (cyclic nucleotides) is involved in a wide range of physiological functions, including control of gastrointestinal smooth muscle contraction and relaxation. However, most of the particulars of what is known about the role of cyclic nucleotides in lower esophageal sphincter function come from studies in opossums and dogs. To determine whether or not human lower esophageal sphincter function has similar characteristics, tissue specimens from the human gastroesophageal junction (the site of the lower esophageal sphincter) were obtained from a national organ donor bank. The specimens were maintained in a physiological medium, and subjected to electrical stimulation and drug treatment. Electrical stimulation induced a dramatic relaxation of the muscle tissue, which was more pronounced with higher-frequency stimulation. Stimulation caused the muscle to produce higher levels of cyclic guanosine monophosphate (cGMP), while levels of cyclic adenosine monophosphate (cAMP) were unchanged. Administration of sodium nitroprusside, which induced muscular relaxation very similar to that induced by electrical stimulation, had the same effect on cyclic nucleotide levels. All of the effects seen were very similar to the profile reported in opossum and dog lower esophageal sphincter preparations, suggesting that these animal models are suitable experimental substitutes for human tissue. (Consumer Summary produced by Reliance Medical Information, Inc.)

Models, Nucleotides

---

Symptomatic gastro-oesophageal reflux, abnormal oesophageal acid exposure, and mucosal acid sensitivity are three separate, though related, aspects of gastro-oesophageal reflux disease

Article Abstract:

Gastroesophageal reflux disease is a condition in which the acidic contents of the stomach enter the esophagus, resulting in pain and sometimes inflammation of the esophageal mucosa (esophagitis). Conflicting definitions of gastroesophageal reflux have led to confusion in the medical literature concerning the causes, treatment, and outcome of cases. Patients with this condition may have abnormally high levels of acid in the esophagus and related symptoms, abnormal sensitivity to esophageal acid, physical damage to the esophageal mucosa, or any combination of these phenomena. Little is known about the relationships between these distinct aspects of the disease. Consequently, a study was carried out involving 50 consecutive patients referred with either noncardiac chest pain or suspected gastroesophageal reflux. Patients were given the following standard diagnostic tests for gastroesophageal reflux disease: the acid perfusion test (to determine esophageal sensitivity to increased acid), 23-hour ambulatory pH monitoring (to measure esophageal levels of acidity throughout the day); and endoscopic analysis of esophageal morphology. Symptomatic reflux was defined as the percentage of heartburn episodes and reflux events greater than 50 percent. Ten patients had symptomatic reflux; all 10 also had heightened sensitivity to esophageal acid. Patients with a negative acid perfusion test were unlikely to demonstrate symptomatic reflux. Patients with normal levels of esophageal acid exposure sometimes had positive acid perfusion tests or symptomatic reflux. Hence, the four symptoms of gastroesophageal reflux can occur individually or together; however, some combinations are more likely than others. (Consumer Summary produced by Reliance Medical Information, Inc.)

Inflammation, Esophagus, Gastric acid

---

Control of belching by the lower oesophageal sphincter

Article Abstract:

The mechanism by which gas flows backwards (refluxes) from the stomach into the esophagus, which is associated with belching, has not been well-studied. Stomach acid reflux is related to the temporary relaxation of the lower esophageal sphincter (muscular valve) in the absence of swallowing. To determine if a similar mechanism is associated with gas reflux, pressure and gas flow were studied following injection of carbon dioxide into the stomachs of 14 healthy subjects. The results suggest that distention of the stomach by gas or other substances leads to near-complete relaxation of the lower esophageal sphincter, which then allows gas reflux. This pattern was very similar to that observed with acid reflux, and was not associated with swallowing. Sphincter relaxation was regulated by posture, since it occurred more readily in the upright than in the supine position. These results should lead to better understanding of the causes of symptomatic reflux disease. (Consumer Summary produced by Reliance Medical Information, Inc.)

Similar abstracts:

• Abstracts: Interstitial pneumonitis associated with ifosfamide therapy. Ifosfamide is an inactive substance in the treatment of pancreatic carcinoma
• Abstracts: Alcoholics and liver transplantation. Successful liver transplantation in older patients raises new hopes, challenges, ethics questions
• Abstracts: Nosocomial sepsis associated with interleukin-2. Vaccine-associated measles pneumonitis in an adult with AIDS
• Abstracts: Reassessment of primary resection of the perforated segment for severe colonic diverticulitis. Proper timing of surgery for gallstone pancreatitis
• Abstracts: Partial splenectomy in sickle cell syndromes. Intradermal hepatitis B vaccination in thalassaemia. Partial splenectomy in homozygous beta thalassaemia

This website is not affiliated with document authors or copyright owners. This page is provided for informational purposes only. Unintentional errors are possible.