Assessment of gastric emptying using a low fat meal: establishment of international control values

OBJECTIVE

The diagnosis of gastroparesis implies delayed gastric emptying. The diagnostic gold standard is scintigraphy, but techniques and measured endpoints vary widely among institutions. In this study, a simplified scintigraphic measurement of gastric emptying was compared to conventional gastric scintigraphic techniques and normal gastric emptying values defined in healthy subjects.

METHODS

In 123 volunteers (aged 19-73 yr, 60 women and 63 men) from 11 centers, scintigraphy was used to assess gastric emptying of a 99Tc-labeled low fat meal (egg substitute) and percent intragastric residual contents 60, 120, and 240 min after completion of the meal. In 42 subjects, additional measurements were taken every 10 min for 1 h. In 20 subjects, gastric emptying of a 99Tc-labeled liver meal was compared with that of the 99Tc-labeled low fat meal.

RESULTS

Median values (95th percentile) for percent gastric retention at 60, 120, and 240 min were 69% (90%), 24% (60%) and 1.2% (10%) respectively. A power exponential model yielded similar emptying curves and estimated T50 when using images only taken at 1, 2 and 4 h, or with imaging taken every 10 min. Gastric emptying was initially more rapid in men but was comparable in men and women at 4 h; it was faster in older subjects (p < 0.05) but was independent of body mass index.

CONCLUSIONS

This multicenter study provides gastric emptying values in healthy subjects based on data obtained using a large sample size and consistent meal and methodology. Gastric retention of >10% at 4 h is indicative of delayed emptying, a value comparable to those provided by more intensive scanning approaches. Gastric emptying of a low fat meal is initially faster in men but is comparable in women at 4 h; it is also faster in older individuals but is independent of body mass.

Electrogastrography: a document prepared by the gastric section of the American Motility Society Clinical GI Motility Testing Task Force

The objective of this document is to present the consensus opinion of the American Motility Society Clinical GI Motility Testing Task Force on the performance and clinical utility of electrogastrography (EGG). EGG is a non-invasive means of recording human gastric myoelectrical activity or slow waves from cutaneous leads placed over the stomach. In healthy volunteers, EGG tracings exhibit sinusoidal waveforms with a predominant frequency of 3 cycles per minute (cpm). Clinical studies have shown good correlation of these cutaneous recordings with those acquired from serosally implanted electrodes. The amplitude of the EGG waveform increases with ingestion of caloric or non-caloric meals. Some patients with nausea, vomiting, or other dyspeptic symptoms exhibit EGG rhythm disturbances or blunting of meal-evoked EGG signal amplitude increases. These abnormalities correlate to some degree with delayed gastric emptying of solids. In selected patients, EGG may be complementary to gastric emptying testing. To date, no therapies have convincingly demonstrated in controlled studies that correcting abnormalities detected by EGG improves upper gastrointestinal symptoms. Proposed clinical indications for performance of EGG in patients with unexplained nausea, vomiting and dyspeptic symptoms must be validated by prospective controlled investigations.

Effect of octreotide and erythromycin on idiopathic and scleroderma-associated intestinal pseudoobstruction

Treatment of chronic intestinal pseudoobstruction with prokinetic agents has been disappointing. Our study was designed to determine if octreotide and erythromycin would provide sustained relief from nausea, abdominal pain, and bloating in pseudoobstruction. Using gastrointestinal manometry, quantitative parameters of the activity front of the migrating motor complex at baseline and after prokinetic therapy with erythromycin and octreotide were determined in 14 patients with intestinal pseudoobstruction who had nausea, abdominal pain, and bloating. Patients were treated with erythromycin and octreotide for 20-33 weeks. Octreotide increased the frequency, duration, and motility index of activity fronts (AFs) from 1.2 +/- 0.3 AFs/4 hr, 2.7 +/- 0.7 min, and 85 +/- 23 min mm Hg to 4.1 +/- 0.8 AFs/4 hr, 5.5 +/- 0.7 min, and 152 +/- 24 min mm Hg, respectively (P < 0.05). Antral activity was decreased from 63 +/- 14 to 23 +/- 8% by octreotide (P < 0.05). Erythromycin induced antral activity; however, small intestinal motor activity was suppressed. While on erythromycin and octreotide, five patients had long-term improvement of nausea and abdominal pain. All responders had at least 5 AFs/4 hr induced by octreotide. We conclude that octreotide and erythromycin relieve abdominal pain and nausea in pseudoobstruction. Patients who have at least 5 AFs/4 hr after octreotide administration are most likely to clinically respond.

Gastric myoelectrical activity and gastric emptying in patients with functional dyspepsia

OBJECTIVES

The aims of this study were to investigate gastric myoelectrical activity and gastric emptying (GE) and their relationship in patients with functional dyspepsia.

METHODS

The study was conducted in 15 healthy volunteers (six women, nine men, mean age: 42 yr) and 15 patients (13 women, two men, mean age: 43 yr) with functional dyspepsia. Gastric myoelectrical activity was recorded using cutaneous electrogastrography (EGG) for 30 min in the fasting state and for 120 min simultaneously with GE monitoring after an isotope-labeled solid meal. The anterior/posterior images of the stomach were taken using a technetium scanner immediately after eating, and then at 1, 2, and 4 h to determine the percentage of gastric retention. The dominant frequency of the EGG, the change of the postprandial EGG peak power (deltaP), and the percentage of normal 2-4 cycles/min (cpm) slow waves during each recording session were calculated and compared between the patients and healthy subjects.

RESULTS

The patients had a significantly lower mean percentage of 2-4 cpm slow waves, both in the fed state and in the fasting state, than did healthy subjects. Compared to the EGG in the fasting state, a significant increase of the EGG dominant frequency in the fed state was observed in healthy subjects but not in the patients. The mean postprandial EGG power increase in the patients was substantially less than in the healthy subjects during the first postprandial hour but similar during the second postprandial hour. The mean percentage of gastric retention in patients is substantially higher than in the healthy subjects, both at 2 h after eating and at 4 h after eating. Of 15 patients, nine (60%) had delayed GE (gastric retention at 2 h >50%) and 10 (66%) had abnormal EGGs (percentage of 2-4 cpm <70% and/or deltaP < 0). Eight of these 10 patients (80%) with abnormal EGGs had delayed GE.

CONCLUSIONS

A high proportion of adult patients (60%) with functional dyspepsia have abnormally slow GE and abnormalities in gastric myoelectrical activity.

Anti-myenteric neuronal antibodies in patients with achalasia. A prospective study

Achalasia is a motility disorder of the esophagus characterized by the loss of inhibitory neurons in the distal esophagus. Although idiopathic in nature, autoimmune mechanisms have been proposed, and we set out to determine the presence of myenteric neuronal antibodies. We prospectively studied 18 patients with well-characterized achalasia (by clinical, x-ray, and manometric evidence), nine with gastroesophageal reflux disease, and analyzed the sera from 22 disease-free controls. Using double-label, indirect immunofluorescence techniques, rat esophageal and intestinal sections were double-labeled with sera (dilutions of 1:50 to 1:400) from the three groups and with neurofilament antibody to localize neurons. Seven of 18 achalasia patients had sera that stained the majority of neurons within plexi in the esophageal and intestinal sections, including both NADPH diaphorase (nitric oxide synthase) -positive and -negative neurons. None of the gastroesophageal reflux patients or the controls showed staining. Neuronal antibodies in achalasia provide an attractive hypothesis to explain this diffuse, possibly immune-based disorder.

Antimyenteric neuronal antibodies in scleroderma

The pathogenesis of gastrointestinal (GI) dysmotility in scleroderma is incompletely understood, although previous studies have proposed a neuropathic mechanism. We studied patients with scleroderma as compared with other connective tissue disease patients and normal controls for the presence of circulating antibodies to myenteric neurons. Serial dilutions of sera were overlaid on rat intestine, double-labeled with antineurofilament antibody as a myenteric plexus marker, and imaged using indirect immunofluorescence techniques. High titer sera (> or = 1:50) from 19 out of 41 scleroderma patients stained myenteric neurons, whereas none of 22 normals or 5 patients with idiopathic GI dysmotility were positive. Although 6 out of 20 SLE and 6 out of 10 mixed connective tissue disease patients' sera stained myenteric plexus neurons, when positive sera were absorbed with calf thymus extract to remove antinuclear antibody, 15 scleroderma sera, 0 SLE, and 2 mixed connective tissue disease patients retained positive staining of myenteric neurons. Western blotting using actin and neuronal intermediate filament preparations failed to show immunoreactivity with scleroderma sera containing antimyenteric neuronal antibodies. Paraneoplastic sera associated with GI dysmotility stained myenteric neurons in a different pattern than seen with scleroderma sera. A positive correlation between the presence of Raynaud's phenomenon and antimyenteric neuronal antibodies was observed in scleroderma patients. Our results indicate that IgG antibodies reacting with myenteric neurons are present in many patients with scleroderma. Although the neuronal antigen has not yet been identified, the presence of myenteric neuronal antibodies in patients with GI dysmotility and scleroderma suggests a neuropathic process.

Colchicine is an effective treatment for patients with chronic constipation: an open-label trial

Chronic constipation is a common clinical condition that frequently does not respond to routine therapeutic measures. We hypothesized that colchicine would be effective in this condition because we reported that it stimulates intestinal motility in rats and commonly causes diarrhea in patients taking the drug for either gouty arthritis or Familial Mediterranean fever. We prospectively studied seven patients with chronic constipation who were refractory to medical therapy and treated them with oral colchicine 0.6 mg per os three times a day for eight weeks in an open-label pilot study. During the study, the mean number of spontaneous bowel movements significantly increased (P < 0.05) from 1.7 +/- 0.5 noted during routine therapy of constipation with laxatives and enemas to 6.4 +/- 0.7 per week; mean colonic transit time significantly (P < 0.05) decreased from 58.1 +/- 2.5 to 47.1 +/- 5.0 hr; and symptoms of abdominal pain, nausea, and bloating significantly (P < 0.05) improved during therapy with colchicine. Oral colchicine (0.6 mg three times a day) therapy appears to be an a promising treatment for chronic constipation and a placebo-controlled trial is indicated to confirm these findings.

Myenteric neuronal antibodies in scleroderma: passive transfer evokes alterations in intestinal myoelectric activity in a rat model

Although the mechanism for neuropathic gastrointestinal motility disturbances in scleroderma is unknown, we have previously described anti-myenteric antibodies in some patients with scleroderma. The aim of this study was to screen patients with scleroderma who had gastrointestinal symptoms for the presence of anti-myenteric neuronal antibodies and then purify the immunoglobulin G (IgG) fraction from serum samples for passive immunization into a rat model and observe for intestinal motility effects. Patients with scleroderma were screened, a serum sample from a patient with high titer anti-myenteric neuronal antibodies was obtained, and IgG was purified. Using a rat model with chronic indwelling intestinal electrodes to measure intestinal myoelectric activity, we passively transferred the IgG from either control subjects or this patient with scleroderma. We immunosuppressed the rats and intraperitoneally injected IgG from control subjects and this patient with scleroderma daily for 7 days. Recordings of myoelectric activity in control injected rats revealed no difference from baseline, but a prolongation in the activity front duration and interval and a disruption were seen after scleroderma IgG injections. IgG from a patient with scleroderma with antimyenteric neuronal antibodies, when passively immunized into a rat model, evokes intestinal myoelectric activity alterations. We hypothesize that these antibodies could account for the gastrointestinal neuropathic motility disturbances seen in scleroderma.

The distribution of novel intermediate filament proteins defines subpopulations of myenteric neurons in rat intestine

BACKGROUND/AIMS

Recent studies with neurofilament antibodies as neuronal markers have shown subpopulations of myenteric neurons that do not contain neurofilament proteins. Novel neuronal intermediate filament proteins alpha-internexin, peripherin, and nestin have been identified. The aim of this study was to examine the distribution of these novel intermediate filaments in comparison with neurofilaments in myenteric plexus neurons.

METHODS

Using indirect immunofluorescence techniques in whole-mount cryostat sections from neonate and adult rat small intestine and in primary cultures of myenteric neurons, the distribution of neurofilaments, alpha-internexin, peripherin, and nestin was studied in comparison with the neuronal marker protein gene product (PGP) 9.5 in myenteric neurons.

RESULTS

Sixty-five percent of neurons contained neurofilament triplet proteins. alpha-Internexin and/or peripherin were found in the neurofilament-negative neurons. PGP 9.5 was present in 80% of the myenteric neurons. Of the neurons that were PGP negative, > 95% contained peripherin or alpha-internexin. Nestin was not found in either neonate or adult myenteric neurons but was seen in glial cells in culture.

CONCLUSIONS

The results suggest that a subpopulation of myenteric neurons lacks neurofilament triplet proteins but contains either peripherin, alpha-internexin, or both. This selective distribution of intermediate filaments in subpopulations of enteric neurons may support differential roles in these structurally unique neurons.

Colitis and interleukin 1beta up-regulate inducible nitric oxide synthase and superoxide dismutase in rat myenteric neurons

BACKGROUND & AIMS

Manganese superoxide dismutase (MnSOD) is rapidly induced in myenteric plexus neurons (MPNs) in acute colitis and may protect cells from nitric oxide toxicity. Inducible nitric oxide synthase (iNOS) regulation was examined in acute colitis, and MnSOD and iNOS were examined in primary cultures of MPNs.

METHODS

Acute colitis in rats was induced with 5% acetic acid. iNOS messenger RNA (mRNA) was analyzed by Northern analysis, and reduced nicotinamide adenine dinucleotide phosphate diaphorase was used to identify potential NO synthase activity. MnSOD and iNOS mRNA levels were evaluated in cultured MPNs after treatment with tumor necrosis factor alpha, interleukin (IL) 1beta, or IL-6. iNOS and MnSOD protein expression in control and IL-1beta-treated neurons was evaluated by immunofluorescence microscopy.

RESULTS

iNOS mRNA was detected in the mucosal and muscularis layers after the initiation of colitis. Reduced nicotinamide adenine dinucleotide phosphate diaphorase localized NO synthase activity to MPNs in controls and in epithelial cells and MPNs in the inflamed colon. In MPN cultures, tumor necrosis factor alpha and IL-1beta treatment resulted in induction of MnSOD, but only IL-1beta induced iNOS. Immunolocalization confirmed that the neurons were the primary source of iNOS and MnSOD.

CONCLUSIONS

Induction of MnSOD and iNOS are coordinated and may limit NO cytotoxicity. The function of iNOS in gut neurons remains to be delineated.

Erythromycin enhances gastric emptying in patients with gastroparesis after vagotomy and antrectomy

We studied the effect of erythromycin on gastric emptying in nine patients with gastroparesis following truncal vagotomy and antrectomy, and assessed their clinical response to chronic oral erythromycin. Gastric emptying was evaluated using a solid-phase radio-labeled meal. Patients were studied after erythromycin 200 mg intravenously (N = 9) and after an oral suspension of erythromycin 200 mg (N = 7) each given 15 min after ingestion of the meal. Three parameters of gastric emptying were analyzed: half-emptying time (T1/2), area under the curve, and percent gastric residual at 2 hr. Nine patients were subsequently placed on oral suspension erythromycin 150 mg three times a day before meals (range 125-250 mg three times a day) and symptoms of nausea, vomiting, postprandial fullness, and abdominal pain were assessed before and after erythromycin. Intravenous erythromycin markedly accelerated the gastric emptying (all three parameters studied) of solids (P < 0.01) in seven of nine patients with postsurgical gastroparesis [baseline T1/2 154 +/- 15 min; after intravenous erythromycin, T1/2 56 +/- 17 min (mean +/- SEM)]. Oral erythromycin enhanced (P < 0.05) the gastric emptying rate (T1/2, area under the curve) in five of seven patients (baseline T1/2 146 +/- 16 min; after oral erythromycin, T1/2 87 +/- 20 min). Of the nine patients who were placed on oral maintenance erythromycin, three showed clinical improvement after two weeks. In summary, erythromycin significantly enhances gastric emptying in many patients with vagotomy and antrectomy-induced gastroparesis; however, only a small subset of patients respond clinically to chronic oral erythromycin.

Systemic lupus erythematosus presenting initially with acute pancreatitis and a review of the literature

A patient with systemic lupus erythematosus is reported whose initial clinical presentation was that of acute pancreatitis, confirmed by pancreatic isoamylase elevation and pancreatic enlargement on computerized tomography. A lack of a correlation with steroid therapy and a need to document pancreatitis in a multisystem disease like lupus with radiographic evidence as well as pancreatic isoamylase elevations is emphasized.

Treatment of chronic constipation with colchicine: randomized, double-blind, placebo-controlled, crossover trial

OBJECTIVE

Refractory constipation is a common GI complaint seen by physicians in all practice settings. We have previously shown that p.d. colchicine (0.6 mg t.i.d.) increases the number of spontaneous bowel movements, hastens GI transit, and improves GI symptoms in patients with chronic constipation during an 8-wk, open-label therapeutic trial. The aim of this study was to determine if p.d. colchicine will increase spontaneous bowel movements and accelerate colonic transit in patients with idiopathic chronic constipation in a randomized, placebo-controlled, crossover trial.

METHODS

A total of 16 patients (15 women, one man) with a mean age of 47 yr (age range 25-89) with chronic idiopathic constipation who were refractory to standard medical therapy participated in the study. Patients randomly received either colchicine 0.6 mg p.o. t.i.d. or an identical placebo p.o. t.i.d. for a total of 4 wk in a double-blind, crossover fashion. Patients recorded their daily number of bowel movements and daily symptoms of daily nausea, abdominal pain, and bloating. Mean colonic transit was calculated at baseline, weeks 6 and 12.

RESULTS

Colchicine increased the number of bowel movements and accelerated colonic transit compared with baseline and placebo conditions. There were no significant differences between conditions on ratings of nausea and bloating. During colchicine administration, mean abdominal pain was greater than the baseline or placebo conditions, however, the pain decreased significantly by the last week the patient was on colchicine.

CONCLUSION

Colchicine increases the frequency of bowel movements and hastens colonic transit in patients with chronic constipation. Colchicine may be an effective agent available to practitioners to treat a subset of patients with chronic constipation who are refractory to standard medical therapy.

Effect of berberine on myoelectric activity and transit of the small intestine in rats

The motility of the small intestine in unanesthetized rats receiving berberine sulfate (0.2, 2.0, and 20.0 mg/kg i.p.) was investigated. Motility was determined by two methods: myoelectric activity was monitored with indwelling bipolar electrodes, and intestinal transit was measured by the movement of radiochromium (Na51CrO4). The 20.0-mg/kg dose caused a marked inhibition of spike activity for 21.8 +/- 7.0 min and disrupted activity fronts of the migrating myoelectric complex for 212.3 min. Berberine, 2.0 mg/kg i.p., disrupted migrating myoelectric complexes for 64.6 min but spike inhibition was not observed. Transit of the small intestine was significantly (p less than 0.001) delayed at 15 and 100 min after the highest dose of berberine. Naloxone blocked the spike inhibition noted with 20.0 mg/kg of berberine but failed to improve transit. Phentolamine blocked spike inhibition and was associated with a significantly earlier return of activity fronts of the migrating myoelectric complex. Animals pretreated with this antagonist tended toward a higher geometric center in transit studies than those injected with berberine alone. Berberine was also administered by various routes (intraperitoneal injection, intravenous injection, orogastric gavage, and intraluminal injection). An intraperitoneal injection was 10-fold more potent than an intravenous injection. Orogastric gavage and intraluminal administration of berberine did not alter intestinal motility. In summary, berberine sulfate significantly inhibits myoelectric activity and transit of the small intestine. This appears to be partially mediated by opioid and alpha-adrenergic receptors. The antidiarrheal properties of berberine may be mediated, at least in part, by its ability to delay small intestinal transit.

Presence of gonadotropin-releasing hormone (GnRH) receptor mRNA in rat myenteric plexus cells

Idiopathic neuromuscular disease of the gastrointestinal tract (functional bowel disease) is thought to result from the malfunction of neurons within the enteric nervous system. Gonadotropin-releasing hormone (GnRH) analogs have recently been shown to organize the disordered motility patterns typical in these patients and to produce significant, long-term symptomatic improvement. To determine whether GnRH analogs might bind to an endogenous enteric nervous system GnRH receptor, reverse transcription-polymerase chain reaction (RT-PCR) was performed using cultured neonatal rat enteric neuron RNA and rat GnRH receptor primers. A PCR product of the predicted size was cloned and nucleotide sequence analysis demonstrated that the myenteric plexus PCR product encoded a portion of the GnRH receptor sequence previously identified in rat pituitary. These results suggest that cells in the myenteric plexus express GnRH receptors that may bind exogenously administered GnRH analogs. The expression of GnRH receptors in enteric neurons would provide an explanation for the effectiveness of GnRH analogs in treatment of idiopathic neuromuscular disease of the gastrointestinal tract.

Neurofilament immunoreactivity in myenteric neurons differs from that found in the central nervous system

Neurofilaments are 10-nm diameter protein fibers found within neurons and are composed predominantly of a triplet of polypeptides usually referred to as low-, medium-, and high-molecular-weight subunits. We describe the results of a study of myenteric plexus neurons using a panel of neurofilament triplet protein antibodies and indirect immunofluorescence techniques. Polyclonal antibodies to each of the three neurofilament subunits reliably stained myenteric neurons and their processes, indicating the presence of all three proteins in these cells. However, several well-characterized monoclonal antibodies to epitopes on high- and medium-molecular-weight subunits showed immunoreactivity in brain tissue but not in myenteric neurons and their processes. Some of the antibodies that do not stain recognize only phosphorylated epitopes, indicating that the level of neurofilament phosphorylation is very low in enteric neurons. Other antibodies that are not thought to be sensitive to the level of neurofilament phosphorylation show reduced or no staining of enteric neurons, suggesting the presence of immunologically distinct neurofilaments in these cells. These results suggest the presence of modified neurofilament structures in enteric neurons, possibly reflecting their unique mechanical character within the moving intestinal wall.

Neurofilament and intermediate filament immunoreactivity in human intestinal myenteric neurons

It has been reported previously that rat myenteric neurons have neurofilament (NF) immunoreactivity that differs from the brain. Now the result of a study of neurofilaments and intermediate filament immunoreactivity in human colon and ileum using a panel of antibodies and indirect immunofluorescence techniques is reported here. Results with polyclonal neurofilament antisera showed positive immunoreactivity in subsets of myenteric neurons. Results with peripherin and alpha-internexin showed immunoreactivity in some neurons that contained neurofilaments and in many that were neurofilament negative, similar to our observations in rat. Some monoclonal antibodies to epitopes on NF-M and NF-H demonstrated weak or negative immunoreactivity in human myenteric neurons yet showed positive immunoreactivity in brain. Some of these antibodies are phosphorylation dependent, suggesting NF-M and NF-H epitopes in myenteric neurons are not as phosphorylated as in brain; other antibodies are phosphorylation independent, suggesting other differences or masking of epitopes. In summary, neurofilaments are present in a subset of myenteric neurons. In those human myenteric neurons that contain them, the neurofilaments appear immunologically distinct from those in the brain.

Differential increase in neuropeptide Y-like levels and myenteric neuronal staining in diabetic rat intestine

Neuropeptide Y is a regulatory peptide found in adrenergic and non-adrenergic neurons. Diabetes, which may cause autonomic neuropathy, induces an increase in hypothalamic neuropeptide Y (NPY) levels; thereby we measured the effects of chronic diabetes on neuropeptide Y in the intestine. Rats were injected with streptozotocin (65 mg/kg) and maintained for up to 20 weeks. Another group of rats was injected with 6-hydroxydopamine (50 mg/kg) x 2 to induce sympathectomy. Ileum and colon were harvested and both whole and microdissected intestine were (1) stained with antibodies to neuropeptide Y, vasoactive intestine polypeptide, and neurofilaments or (2) extracted for neuropeptide Y radioimmunoassay. Neuropeptide Y levels were similar under all conditions in the colon, but there was a trend toward an increase in the diabetic whole ileum. NPY levels were significantly increased in the dissected myenteric plexus ileal layer in diabetics. We noted an increase in the number of neuropeptide Y and vasoactive intestine polypeptide immunoreactive myenteric neurons in diabetics and after 6-hydroxydopamine-induced sympathectomy. Diabetes, and to a lesser extent sympathectomy, induced an increase in ileal neuropeptide Y levels and neuropeptide Y-staining myenteric but not submucosal neurons. Altered tissue levels of neuropeptide Y may account for certain of the gastrointestinal disturbances commonly seen in diabetes.

Myenteric plexus neurons have developmentally acquired differences in the medium molecular weight subunit of neurofilament protein

We have previously shown that neurofilaments in enteric neurons are immunologically distinct from those found in the central nervous system. In particular, one monoclonal antibody to the medium molecular weight neurofilament subunit, called NN18, stained the perikarya of enteric neurons very weakly, if at all, although other medium molecular weight neurofilament subunit antibodies clearly showed the presence of significant amounts of medium molecular weight neurofilament subunit. We have since located the epitope for NN18 in a peptide sequence at the carboxy terminal tail of medium molecular weight neurofilament subunit and have now looked for further neurofilament antibodies that stain the same region. We found two monoclonal antibodies, RMO1 and RMO59, that recognize the same peptide. These antibodies also show much reduced staining in myenteric neurons compared to those in the central nervous system, suggesting that this region of the medium molecular weight neurofilament subunit is specifically modified in certain cells. In the developing enteric nervous system, we found that all the antibodies show strong staining of enteric neurons in the neonatal rat, but that with NN18, RMO1, and RMO59, the staining intensity decreases during further development, and by postnatal day 21 all three demonstrate decreased or absent staining identical to the adult. These results indicate that myenteric neurons, in contrast to the brain, have a developmentally regulated modification in a specific region of the medium molecular weight neurofilament subunit, which may reflect adaptation to structural stress by myenteric neurons.

Update on acute colonic pseudo-obstruction

Acute colonic pseudo-obstruction is characterized by distention of the colon in the absence of mechanical obstruction. This presentation is typically related to recent surgery, severe illness, or medication. Nasogastric and rectal tube decompression and correction of electrolyte abnormalities are the standard of care. Colonoscopic decompression, performed in a number of these cases, was felt to be unwarranted in many situations and is associated with a high recurrence rate. Medical management beyond conservative measures has been limited. Medical therapy with pharmacologic agents such as erythromycin, metoclopromide, and cisapride was of limited use. Recent findings confirm that an older agent, neostigmine, provides excellent results, including colonic decompression and clinical improvement after administration. This suggests a new standard of care.

Evidence against impaired brain microtubule protein polymerization at high glucose concentrations or during diabetes mellitus

Previous studies suggest that brain microtubule protein exposed to high glucose levels or isolated from diabetic rats can become glucosylated and that this impairs GTP-induced microtubule polymerization. We set out to extend that investigation to define the mechanistic basis for inhibition of microtubule assembly during diabetes or on incubation at high glucose levels. Rat and bovine brain microtubule protein was purified by cycles of polymerization/depolymerization. When microtubules were incubated for 1 h in either buffer or buffer containing glucose (up to 165 mM), there was no difference in polymerization, a finding contrary to the earlier study. Other rats were injected with vehicle or streptozotocin (90 mg/kg) to induce diabetes as evidenced by serum glucose in excess of 300 mg%, and at 4 weeks, brain microtubule protein was isolated by the polymerization cycling method. Again, there was no difference in the amount or purity of isolated microtubule protein between control or diabetic rats. We also observed no increase in microtubule glucosylation, and GTP-induced polymerization in vitro was indistinguishable for protein derived from brains of normal rats and rats with diabetes as measured by turbidity or electron microscopy. Our results suggest that in vitro incubation with glucose or in vivo elevation of glucose during diabetes fails to impair microtubule polymerization, pointing to other mechanisms for the neuropathy associated with diabetes.

Chronic alterations in jejunal myoelectric activity in rats due to MPTP

Parkinsonian patients may have symptoms consistent with intestinal pseudo-obstruction, but a primary intestinal abnormality has not been shown. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), after conversion to a toxic metabolite via the monoamine oxidase system, can induce Parkinson's disease by destroying dopaminergic neurons in the substantia nigra in humans and primates. Rodents have some catecholamine depletion but much less so than primates. Using chronic bipolar electrodes on the proximal jejunum of Wistar rats, we show significant, chronic migrating myoelectric complex disruption (P less than 0.001) and prolongation of irregular spike activity (P less than 0.001). Pargyline (a monoamine oxidase inhibitor) pretreatment significantly blocked these myoelectric changes. Sinemet (L-dopa and carbidopa), given after MPTP to replete dopamine, decreased the MPTP-induced migrating myoelectric complex disruption. Jejunal myenteric plexus dopamine levels were significantly decreased (to 61% of control) after MPTP but after much higher doses than were required to disrupt migrating myoelectric complex activity (180 mg/kg total vs. 30 mg/kg). Dopamine in the central nervous system was not depleted. We conclude that MPTP causes intestinal myoelectric disruption (which can be blocked by pargyline and decreased by Sinemet) possibly through enteric, but not central, nervous system effects.