Modulation of M(2) muscarinic receptor-receptor interaction by immunoglobulin G antibodies from Chagas' disease patients.

Circulating immunoglobulin (Ig)G antibodies against M(2) muscarinic acetylcholine receptors (M(2) mAChR) have been implicated in Chagas' disease (ChD) pathophysiology. These antibodies bind to and activate their target receptor, displaying agonist-like activity through an unclear mechanism. This study tested the ability of serum anti-M(2) mAChR antibodies from chronic ChD patients to modulate M(2) muscarinic receptor-receptor interaction by bioluminescence resonance energy transfer (BRET). Human embryonic kidney (HEK) 293 cells co-expressing fusion proteins M(2) mAChR-Renilla luciferase (RLuc) and M(2) mAChR-yellow fluorescent protein (YFP) were exposed to the serum IgG fraction from ChD patients, and BRET between RLuc and YFP was assessed by luminometry. Unlike serum IgG from healthy subjects and conventional muscarinic ligands, ChD IgG promoted a time- and concentration-dependent increase in the BRET signal. This effect neither required cellular integrity nor occurred as a consequence of receptor activation. Enhancement of M(2) receptor-receptor interaction by ChD IgG was receptor subtype-specific and mediated by the recognition of the second extracellular loop of the M(2) mAChR. The monovalent Fab fragment derived from ChD IgG was unable to reproduce the effect of the native immunoglobulin. However, addition of ChD Fab in the presence of anti-human Fab IgG restored BRET-enhancing activity. These data suggest that the modulatory effect of ChD IgG on M(2) receptor-receptor interaction results from receptor cross-linking by bivalent antibodies.

Interaction of human chagasic IgG with human colon muscarinic acetylcholine receptor: molecular and functional evidence.

BACKGROUND AND AIMS: Gastrointestinal disorders is one of the clinical manifestations of chronic Chagas' disease. The pathogenesis seems to be associated with autonomic dysfunction. Here, we consider the muscarinic cholinoceptor mediated alteration in distal colon function in chagasic megacolon. PATIENTS: Patients were divided into four groups: group I, chronic chagasic patients with megacolon; group II, chronic chagasic patients without megacolon; group III, non-chagasic patients with megacolon; and group IV, normal healthy volunteers (control). METHODS: Binding assay and immunoblot of cholinoceptors from human and rat colon and enzyme immunoassay (ELISA) using a synthetic 24mer peptide corresponding to the second extracellular loop of human M2 muscarinic acetylcholine receptors (mAChR) were used to detect the presence of serum antibodies. The effect of antibodies on basal tone and 3',5'-cyclic monophosphate (cAMP) production of human and rat distal colon strips were also tested. RESULTS: Group I but not the other groups had circulating antibodies capable of interacting with human colon activating M2 mAChR, as they competed with binding of specific radioligand to mAChR and interacted with the second extracellular loop of human M2 mAChR. Moreover, affinity purified anti-M2 peptide IgG from group I, in common with monoclonal antihuman M2 mAChR, recognised bands with a molecular weight corresponding to colon mAChR. This antibody also displayed an agonist-like activity, increasing basal tone and decreasing cAMP accumulation. Both effects were blunted by AF-DX 116 and neutralised by the synthetic peptide. CONCLUSIONS: In chagasic patients with megacolon there are antibodies that can recognise and activate M2 mAChR. The implications of these autoantibodies in the pathogenesis of chagasic megacolon is discussed.

On the first-order Rao-Scott correction of the Umesh-Loughin-Scherer statistic.

Decady and Thomas (2000, Biometrics 56, 893-896) propose a first-order corrected Umesh-Loughin-Scherer statistic to test for association in an r x c contingency table with multiple column responses. Agresti and Liu (1999, Biometrics 55, 936-943) point out that such statistics are not invariant to the arbitrary designation of a zero or one to a positive response. This paper shows that, in addition, the proposed testing procedure does not hold the correct size when there are strong pairwise associations between responses.

Functional implications of circulating muscarinic cholinergic receptor autoantibodies in chagasic patients with achalasia.

BACKGROUND & AIMS: Autoantibodies against M(2)-muscarinic acetylcholine receptors (M(2) mAChR) have been reported in patients with chronic Chagas' disease who have cardiac dysautonomia. The aim of this study was to investigate the presence of such antibodies in chronic chagasic and non-chagasic patients with esophageal achalasia and their ability to activate M(2) mAChR in the isolated esophagus. METHODS: Enzyme-linked immunosorbent assay was used to detect serum immunoglobulin (Ig) G antibodies against a synthetic 24-mer peptide corresponding to the second extracellular loop of human M(2) mAChR. The effects of both total serum IgG and affinity-purified antipeptide antibodies on the contractile activity and adenosine 3', 5'-cyclic monophosphate (cAMP) production in rat esophageal strips were also tested. RESULTS: Circulating IgG antibodies from chagasic achalasia patients recognized the M(2)-peptide more often than those from non-chagasic achalasia patients (P < 0.0005) and normal subjects (P < 0.0001). A strong association between the existence of circulating anti-M(2) mAChR antibodies and the presence of achalasia in chagasic patients was found (P < 0.01). Both the total IgG fraction and anti-M(2)-peptide antibodies increased the basal tone, reduced the relaxant effect of isoproterenol, and decreased cAMP accumulation in esophageal strips, displaying a muscarinic agonist-like activity on M(2) mAChR. CONCLUSIONS: Patients with chronic Chagas' disease have circulating autoantibodies against M(2) mAChR. These antibodies could be involved in the pathophysiological mechanism of chagasic achalasia.

Colonic motility in man: features in normal subjects and in patients with chronic idiopathic constipation.

The human colon is still a relatively unknown viscus, especially concerning its motor activity. However, in recent years, techniques have been perfected that allow a better understanding of colonic motility, especially through prolonged recording periods. In this way, it has been demonstrated that the viscus contracts according to a circadian trend, is responsive to physiological stimuli (meals, sleep), and features high amplitude, propulsive contractions that are part of the complex dynamic of the defecatory process. These physiological properties and their alterations in patients with chronic idiopathic constipation are reviewed in this article.

Effect of bolus volume on the response of the human esophagus to a viscous bolus.

It is well known that increasing the volume of a non-viscous bolus has no significant effect on esophageal peristalsis. Viscous boluses, however, tend to remain more compact during passage through the esophagus; we therefore sought to determine whether increasing the volume of a viscous bolus would significantly affect esophageal peristalsis. Intraluminal pressure events were measured with a low-compliance-infused catheter system, and lower esophageal sphincter (LES) pressure was monitored continuously with a Dent sleeve. Each subject was given a series of 10 swallows of a water bolus (viscosity, 0.89 centipoise) and of a viscous bolus (syrup; viscosity, 102 centipoise). The volume of each bolus varied (5, 10, 15, 20 ml), and the order of administration of each set of swallows was randomized. Tracings were coded and analyzed blindly. Increasing the volume of the non-viscous bolus had no significant effects of esophageal peristalsis. Additionally, the viscous bolus at each volume was associated with significant (p less than 0.05) reductions in peristaltic wave velocity and significant (p less than 0.05) increments in durations of contraction and LES relaxation. However, increasing the volume of the viscous bolus did not significantly alter variables of esophageal peristalsis. It is concluded that altering the volume of a viscous bolus has no incremental effect on esophageal peristalsis over the effect of viscosity alone.

Effect of bolus osmolality on human esophageal function.

The effect of bolus osmolality on human esophageal function is undefined. We sought to define the response of the human esophagus to boluses with a wide range of osmolalities in 10 healthy male volunteers. Intraluminal pressure events were measured with an infused catheter system, and lower esophageal sphincter pressure was monitored continuously with a Dent sleeve. Each subject was given a series of 10 swallows of each of seven boluses, which consisted of water, mannitol solutions with osmolalities of 142, 296, 449, 704, and 1481 mOsm/kg, and orange juice (585 mOsm/kg), in a randomized fashion. Tracings were coded and analyzed blindly. Alterations in bolus osmolality did not elicit any significant changes in amplitude and duration of contraction, velocity of wave propagation, or the duration of relaxation of the lower esophageal sphincter. We conclude that bolus osmolality does not play a significant role in the control of human esophageal motility, and that this lack of effect is explained by consideration of esophageal muscle mechanics.

Esophageal motility in chagasic patients

Se estudió la motilidad esofágica en 16 individuos normales y 59 pacientes chagásicos crónicos. En éstos se realizaron estímulos con dosis submáximas de betanecol y pentagastrina con el objeto de estudiar si existe daño esofágico motor. Se obtuvieron los siguiéntes resultados: 1) no se encontraron diferencias en los trazados electromanométricos basales entre chagásicos y normales; 2) al utilizar estímulo colinérgico y hormonal, los trazados correspondientes a los pacientes chagásicos evidenciaron un significativo aumento de la presión de la zona de alta presión; 3) en los pacientes chagásicos se demostró un significativo incremento de la presión del cuerpo esofágico después del estímulo con betanecol y pentagastrina, así como un aumento en la duración de la onda peristáltica, y 4) no se detectaron alteraciones en los porcentajes de la velocidad de propagación de la onda peristáltica ni en la relajación cardial. Concluimos que en este grupo de pacientes chagásicos crónicos, procedentes de áreas endémicas argentinas, hallamos un comportamiento anormal de la motilidad esofágica sugestivo de daño neuronal precoz

Esophageal motility in chagasic patients

Se estudió la motilidad esofágica en 16 individuos normales y 59 pacientes chagásicos crónicos. En éstos se realizaron estímulos con dosis submáximas de betanecol y pentagastrina con el objeto de estudiar si existe daño esofágico motor. Se obtuvieron los siguiéntes resultados: 1) no se encontraron diferencias en los trazados electromanométricos basales entre chagásicos y normales; 2) al utilizar estímulo colinérgico y hormonal, los trazados correspondientes a los pacientes chagásicos evidenciaron un significativo aumento de la presión de la zona de alta presión; 3) en los pacientes chagásicos se demostró un significativo incremento de la presión del cuerpo esofágico después del estímulo con betanecol y pentagastrina, así como un aumento en la duración de la onda peristáltica, y 4) no se detectaron alteraciones en los porcentajes de la velocidad de propagación de la onda peristáltica ni en la relajación cardial. Concluimos que en este grupo de pacientes chagásicos crónicos, procedentes de áreas endémicas argentinas, hallamos un comportamiento anormal de la motilidad esofágica sugestivo de daño neuronal precoz (AU)

Progesterone as therapy for retroperitoneal fibrosis

Se presenta un caso de fibrosis retroperitoneal con obstrucción ureteral e infiltración vesical con remisión completa después del tratamiento con progesterona. La exploración abdominal y retroperitoneal, en una segunda laparatomía por un tumor inflamatorio apendicular, permitió constatar la ausencia de fibrosis. Cuatro años después de la última laparotomía, el paciente se encuentra asintomático y con estudios radiológicos y de laboratorio normales

Progesterone as therapy for retroperitoneal fibrosis

Se presenta un caso de fibrosis retroperitoneal con obstrucción ureteral e infiltración vesical con remisión completa después del tratamiento con progesterona. La exploración abdominal y retroperitoneal, en una segunda laparatomía por un tumor inflamatorio apendicular, permitió constatar la ausencia de fibrosis. Cuatro años después de la última laparotomía, el paciente se encuentra asintomático y con estudios radiológicos y de laboratorio normales (AU)