Experimental esophagitis in a rabbit model. Clinical relevance

Esophagitis occurs in patients with excessive acid and/or alkaline gastroesophageal reflux. This observation prompted us to develop a continuously perfused in vivo rabbit esophageal model to examine the potential for different endogenous injurious agents to cause H+ back diffusion and morphologic evidence of esophagitis. We found that HCl at physiologic pH values did not break the mucosal barrier to H+ back diffusion or cause esophagitis. Bile salts at physiologic concentrations in both an acid or alkaline perfusate broke the mucosal barrier and caused H+ back diffusion, but failed to cause a morphologic injury consistent with clinical reflux esophagitis. Instead, proteolytic enzymes, such as pepsin in an acid environment and trypsin in an alkaline environment, caused a severe hemorrhagic erosive esophagitis consistent with that seen clinically. We feel new therapeutic strategies for the treatment of reflux esophagitis should be directed at proteolytic enzymes rather than only HCl or bile salts. Finally, we showed sucralfate to be a mucosal protectant against the acid-pepsin injury.

Development of the 24-hour intraesophageal pH monitoring composite scoring system

We describe in detail our logic for deriving a system to score 24-hour intraesophageal pH records of patients with gastroesophageal reflux. This system uses a uniform scoring unit and pH monitoring parameters taken from both the day and nighttime segments of the pH record. The score quantitates the degree of departure that a patient's reflux pattern exceeds physiologic reflux found in asymptomatic control volunteers, and directly correlates with the degree of reactive epithelial change characteristic of reflux esophagitis. Even though the scoring system was derived over 11 years ago, its logic and scoring principles are consistent with new concepts that concern the pathophysiology of gastroesophageal reflux disease.

Rumination, heartburn, and daytime gastroesophageal reflux. A case study with mechanisms defined and successfully treated with biofeedback therapy

A 31-year-old man with a 19-year history of rumination developed frequent episodes of heartburn and regurgitation associated with acid gastroesophageal reflux that occurred predominantly during the day. This reflux and its attendant symptoms resulted from abdominal muscle contractions at the time of gastroesophageal pressure equilibration (i.e., common cavity phenomena) consistent with the egress of air from the stomach to the esophagus. A voluntary pharyngeal maneuver unassociated with swallowing but simultaneous with the abdominal contraction resulted in a decrease in upper esophageal sphincter pressure. This lowered pressure facilitated acid esophagopharyngeal regurgitation at a velocity of 100 cm/s. Biofeedback therapy directed at relaxing the abdominal muscles during eating and avoiding the pharyngeal maneuver resulted in a decrease in reflux and marked improvement in symptoms.

Thymidylate synthase overproduction and gene amplification in fluorodeoxyuridine-resistant human cells

Cytotoxicity to 5-fluoro-2'-deoxyuridine (FdUrd) derives from its conversion to 5-fluorodeoxyuridine-5'-monophosphate, which binds to and inhibits thymidylate synthase (TS) in the presence of the cofactor, 5,10-methylenetetrahydrofolate. We have selected FdUrd-resistant variants of the human cell line HEp-2 following adaptation to stepwise increases in drug concentration. In the initial selection, maximal drug resistance was associated with a 26-fold increase in the cellular level of TS. Greater TS overproduction (80-fold) was obtained by selection for FdUrd resistance in the presence of 10 microM folinic acid and 100 microM deoxyinosine. The latter agents were included to expand the folate pool to ensure adequate levels of cofactor during the selection process. Using cDNA plasmid pMTS-4, which is complementary to mouse TS mRNA, we show that TS overproduction in the HEp-2 variants is accompanied by a 100-fold increase in TS mRNA and a 100-fold amplification of the TS structural gene. Thus, TS overproduction and gene amplification is a mechanism of resistance to FdUrd in human cells.

Control of thymidylate synthase mRNA content and gene transcription in an overproducing mouse cell line

We studied the content and metabolism of thymidylate synthase mRNA in cultured mouse fibroblasts that were undergoing a serum-induced transition from the resting to growing state. The studies were performed with a 5-fluorodeoxyuridine-resistant 3T6 cell line (LU3-7) that over produces the enzyme and its mRNA about 50-fold and that regulates the expression of the thymidylate synthase gene in the same manner as the parental cell line. We have previously shown that the rate of synthesis of thymidylate synthase increases at least ninefold when the serum-stimulated cells traverse the S phase. Here we show, by Northern blot analysis, that thymidylate synthase mRNA increased 20- to 40-fold as cells progressed from resting to late S phase. About 85% of poly(A)+ thymidylate synthase mRNA was associated with polysomes at all times. The increase in thymidylate synthase poly(A)+ mRNA content was the result of an eightfold increase in the rate of production of this species, as shown by pulse-labeling studies. Pulse-chase analysis revealed that the half-life of thymidylate synthase poly(A)+ mRNA was similar in resting (9 h) and growing (7 h) cells. The rate of transcription of the thymidylate synthase gene, as determined in isolated nuclei, increased only by a factor of three to four during the S phase. Since the content of the message increased to a much greater extent than the rate of transcription of the gene, posttranscriptional controls must also play a role in regulating the content of thymidylate synthase mRNA under these conditions. Our results suggest that the cell may regulate the distribution of thymidylate synthase mRNA between a relatively stable poly(A)+ RNA species and a labile poly(A)- RNA species.

Post-transfusion hepatitis: fatal outcome in two cases with underlying alcoholic liver disease

Two patients with underlying alcoholic liver disease who were doing well before receiving multiple blood transfusions for gastrointestinal bleeding died after developing post-transfusion hepatitis (PTH). This hepatitis was associated with an uncharacteristic disparity between transaminase levels.

Cimetidine for prevention and treatment of gastroduodenal mucosal lesions in patients in an intensive care unit

The efficacy of cimetidine in the prevention and treatment of stress-induced gastroduodenal lesions was evaluated in a randomized, double-blind, placebo-controlled study in which serial endoscopy was used to examine patients without clinical evidence of bleeding who were admitted to a medical intensive care unit. Endoscopy showed that 14 of 21 patients treated with cimetidine, compared with 5 of 18 patients treated with placebo, had normal or improved gastroduodenal mucosa (p less than 0.05). Endoscopic signs of bleeding cleared or did not develop in 20 patients treated with cimetidine and in 11 patients treated with placebo (p less than 0.01). Significantly fewer blood transfusions were given to patients with endoscopic signs of bleeding in the cimetidine-treated group (0.5 +/- 0.3 [SE] units) than in placebo-treated patients (4.5 +/- 1.5 units; p less than 0.05). The mortality rate was not statistically different between treatment groups. By preventing established gastroduodenal stress lesions from progressing in severity, cimetidine diminished both bleeding and the need for transfusions.

Thymidylate synthase gene amplification in fluorodeoxyuridine-resistant mouse cell lines

We have previously isolated fluorodeoxyuridine-resistant mouse fibroblast (LU3-7) and neuroblastoma (FUdR-R) cell lines that overproduce thymidylate synthase and the mRNA for this enzyme up to 50-fold as compared to the parental cell lines. We have also cloned cDNA corresponding to mouse thymidylate synthase mRNA into pBR322. In the present study, we used this cloned cDNA as a hybridization probe in Southern blot analysis of DNA from the parental and overproducing cell lines. These analyses showed that the thymidylate synthase gene is amplified 50-100 fold in LU3-7 cells and about 30-fold in FUdR-R cells when compared to the respective parental cells. The sizes of the restriction fragments were the same in the parental and overproducing cells of each type, suggesting that extensive rearrangements have not occurred in the vicinity of the thymidylate synthase gene during the amplification process. However, not all of the fragments in the parental cells were amplified in the overproducing cells, suggesting that there may be multiple genes or pseudogenes for the enzyme. Restriction fragment length polymorphisms were detected when analyzing DNA from several different mouse cell lines. When LU3-7 cells were grown in the absence of selective pressure, the level of thymidylate synthase overproduction and the number of copies of the thymidylate synthase gene decreased in parallel.

Taurodeoxycholate modulates the effects of pepsin and trypsin in experimental esophagitis

Pepsin and trypsin cause erosive, hemorrhagic lesions in our rabbit model of experimental esophagitis. Since the gastroduodenal contents of patients with reflux esophagitis may also contain bile salts, we used our model to determine the effect that a bile salt, taurodeoxycholate (TDC), would have on the esophageal mucosa when combined with either pepsin in an acid perfusate (pH 2) or trypsin in an alkaline perfusate (pH 7.5). Indexes of esophageal injury included gross appearance of the mucosa, microscopic examination, and mucosal barrier integrity as determined by permeability to hydrogen ion. We found that when 5 mM TDC was combined with pepsin (0.3 mg/ml), the gross and microscopic changes of esophagitis, as well as net hydrogen ion flux, were diminished when compared with those observed with pepsin exposure alone. When increasing concentrations of TDC (2 to 10 mM) were added to pepsin, the morphologic degree of injury as well as hydrogen ion flux decreased in a dose-dependent manner. In contrast, when 5 mM TDC was combined with trypsin (1000 U/ml) in the alkaline perfusate, the gross and microscopic changes of esophagitis and the net of hydrogen ion flux were increased when compared with either bile salt or trypsin alone. These effects were also dose dependent. These data demonstrate that bile salts present in the gastroduodenal contents of patients with reflux esophagitis have the capacity to modulate the effects of pepsin and trypsin on the esophageal mucosa.

Hemobilia and liver flukes in a patient from Thailand

A patient from Southeast Asia presented with abdominal pain, fever, jaundice, and upper gastrointestinal bleeding of unknown origin. Opisthorchis viverrini eggs were found in the stool and multiple hepatic filling defects were noted on liver scan and sonogram. Endoscopic retrograde cholangiopancreatography revealed cholelithiasis and crescent-like filling defects in the biliary system. At surgery, the gallbladder was filled with clotted blood and pigmented stones. During T-tube drainage of the common bile duct, small elliptical flukes (4 X 3 mm) identified as O. viverrini were recovered. Despite adequate biliary drainage, the patient continued to have high fevers. On the 53rd postoperative day, a larger fluke (2.8 X 0.8 cm) identified as a Fasciola hepatica migrated down the T-tube. Institution of therapy with bithional resulted in complete clinical resolution within 3 wk. Six years later the patient returned with fever, jaundice, and right upper quadrant pain. Two large pigmented stones were found in the common bile duct and were removed after endoscopic sphincterotomy. The stones had developed even though there was no evidence of recurrent helminthic infection.

Palliative dilation of esophageal carcinoma

The authors' experience with palliative dilation of 46 consecutive patients evaluated for squamous cell carcinoma of the esophagus was retrospectively reviewed. Thirty-nine of 46 patients (85%) underwent dilation in order to palliate symptoms, enable endoscopy and biopsy, or prepare for placement of an esophageal prosthesis. Thirty-two of the 46 patients (70%) were treated with radiation therapy and seven (15%) underwent placement of an esophageal prosthesis. Thirty-five of the 39 patients dilated (90%) noted improvement in swallowing, allowing resumption of a soft or regular diet. Complications were noted in three of the 39 patients dilated (8%). The authors conclude that peroral dilation is a safe, effective, and probably underutilized method of palliation in patients with squamous cell esophageal carcinoma.

Sucralfate prevents experimental peptic esophagitis in rabbits

Sucralfate was tested in a rabbit model for its ability to prevent experimental esophagitis. Esophagitis was assessed by gross appearance and microscopic examination by an uninformed observer. In addition, the permeability of the esophagus to a number of probe molecules was measured to assess barrier function. Animals were exposed for 1 h to either acid alone (HCl at pH 2), acid plus pepsin (0.8 mg/ml), or acid plus taurocholic acid (5 mM), as well as to the same injurious agents with the addition of 1 g of sucralfate. At the completion of this hour, the perfusate was removed and all animals were again perfused for 1 h with HCl at pH 2 while mucosal permeability was assessed by measuring erythritol, glucose, potassium, and sodium fluxes. The animals were then killed. Sucralfate significantly diminished esophagitis and the attendant mucosal permeability changes induced by pepsin. The viscous sucralfate gel was shown to adhere tenaciously to the esophageal mucosa, but this characteristic of sucralfate was found not to be critical for its protective action because a clear sucrose sulfate solution with no gel present was also protective. Hence, it was not necessary for the gel to be present for the drug to be effective. Several in vitro tests suggested that the clear sucrose sulfate solution, like the sucralfate gel, probably acts through a topical protectant effect, rather than through pepsin inactivation. Although the degree of esophagitis induced by the bile acid was significantly less than that observed with pepsin, the mucosal permeability changes were comparable. Sucralfate did not significantly reduce the flux rates of glucose, potassium, and sodium nor did it affect the morphology of the mucosa after exposure to taurocholic acid. In conclusion, the binding of sucralfate to pepsin substrates in tissue results in this agent being very effective in preventing experimental peptic esophagitis.

Regulation of thymidylate synthase enzyme synthesis in 5-fluorodeoxyuridine-resistant mouse fibroblasts during the transition from the resting to growing state

Thymidylate synthase (TS) activity is very low in resting mouse 3T6 fibroblasts but increases sharply in growth-stimulated cells at about the same time the cells enter S phase. To study the mechanism responsible for the increase in TS level, we isolated a 5-fluorodeoxyuridine (5-FdUrd)-resistant cell line (LU3-7) that overproduces TS and its mRNA about 50-100-fold. In this paper we show that the LU3-7 cells were able to rest in the G0 state of the cell cycle when maintained in medium containing 0.5% serum. When the serum concentration was increased to 10%, the resting cells reentered the cell cycle and began DNA replication about 12 hr later. TS activity remained at the resting level until DNA replication began, then increased at later times. The increase was not affected when the cells were stimulated in the presence of DNA synthesis inhibitors. The rate of synthesis of TS (as determined in a pulse-labeling experiment) remained at the resting level for the first 10 hr following stimulation, then increased 8-9-fold by 25 hr following serum stimulation. The half-life of TS in growing LU3-7 cells was measured in a pulse-chase experiment and found to be greater than 24 hr. Therefore the increase in TS activity was primarily due to an increase in the rate of synthesis of the enzyme. Since TS gene expression appears to be regulated in a similar manner in LU3-7 cells and in the parental 3T6 cells, the LU3-7 cells should be a good model system for detailed analysis of the mechanism for regulating TS gene expression in mammalian cells.

Lithium chloride: protective and antisecretory properties in rats

Lithium chloride was evaluated as a potential protective agent against ethanol-induced hemorrhagic gastritis in rats. Rats received lithium chloride intragastrically (30, 60, or 90 mg/kg i.g.) or subcutaneously (3, 5, 10, 15, 20, 30, 60, or 90 mg/kg s.c.), or a placebo (H2O i.g. or 0.9% NaCl s.c.). Ninety minutes later 1 cm3 of 95% ethanol was administered intragastrically. After 30 min, the rats were killed and their stomachs were removed and visually scored for gross hemorrhagic gastritis. Lithium chloride at all doses less than 3 mg/kg significantly improved hemorrhagic gastritis when compared with the placebo. Moreover, rats treated with lithium chloride intragastrically had significantly less hemorrhagic gastritis than those treated subcutaneously even though serum lithium levels were similar. To determine if lithium's protective properties related to acid inhibition, pylorus-ligated and gastric fistula rats were studied. The median effective dose for lithium chloride was 20-30 mg/kg and the nonantisecretory dose was 3 mg/kg. No difference in hemorrhagic gastritis was noted between controls and animals receiving the nonantisecretory dose. However, at higher doses (LiCl 30, 60, and 90 mg/kg), lithium's protective properties persisted in spite of adding 150 mM HCl to the intragastrically administered ethanol (p less than 0.001). To determine further if lithium chloride stimulated endogenous prostaglandins, indomethacin, a prostaglandin inhibitor, was administered. Indomethacin did not alter lithium chloride's protective properties. In fact, when compared with exogenously administered 16,16-dimethyl prostaglandin E2 (5 and 500 micrograms/kg), high-dose LiCl (30, 60, or 90 mg/kg) resulted in significantly more protection against ethanol-induced injury (p less than 0.001). In contrast, when both nonantisecretory doses were compared, 16,16-dimethyl prostaglandin E2 (5 micrograms/kg) gave significantly better protection than LiCl (3 mg/kg). These data indicate that LiCl is a potent gastric antisecretory and protective agent. The protective properties of LiCl appear to be related to acid inhibition and be independent of endogenous prostaglandins, although other protective mechanisms may be present at higher LiCl doses. Additionally, this study indicates that LiCl may have clinical application in protecting the gastric mucosa against hemorrhagic gastritis.

Hiccups associated with reflux esophagitis

A 67-yr-old man with protracted hiccups, as well as reflux esophagitis and a stricture, was found to have heartburn and water brash only during episodes of hiccups. Intraesophageal pH monitoring showed acid gastroesophageal reflux increased during these episodes and decreased with cessation of hiccups. After all attempts failed to relieve his hiccups, a Nissen fundoplication relieved heartburn, healed the esophagitis, and stopped excessive reflux of acid gastric juice, even though the hiccups persisted. These observations showed that reflux provoked by prolonged hiccups could either have adversely affected preexistent reflux esophagitis and stricture or conceivably could have caused these complications.

Molecular cloning of DNA sequences complementary to mouse thymidylate synthase messenger RNA

We describe the isolation of recombinant cDNA clones containing sequences corresponding to mouse thymidylate synthase mRNA. Double-stranded cDNA was made from poly(A+) RNA isolated from the 5-fluoro-2'-deoxyuridine-resistant mouse cell line LU3 -7 that overproduces thymidylate synthase 50- to 100-fold as compared to the parental mouse 3T6 fibroblasts. The cDNA was inserted into pBR322 using the poly(dC)-poly(dG) tailing procedure and transformed into Escherichia coli HB101. A library of 30,000 colonies was screened for thymidylate synthase cDNA sequences by differential colony hybridization. Plasmid DNA was purified from a colony that gave a positive signal. RNA corresponding to this plasmid was isolated by hybridization and translated in vitro to yield a protein that coelectrophoresed with authentic thymidylate synthase. The identity of the translation product was confirmed by immunoprecipitation with thymidylate synthase antiserum and by peptide analysis. A restriction fragment from this plasmid was used to rescreen the library to give a collection of thymidylate synthase cDNA plasmids with overlapping restriction maps. Several plasmids contained cDNA inserts greater than 1 kilobase pair in length. The size and content of thymidylate synthase mRNA in the overproducing and parental cell lines was determined by RNA blot analysis. Multiple thymidylate synthase mRNA species were identified. The predominant species was 1.3 kilobase pairs in length. Thymidylate synthase mRNA was 50 times more abundant in LU3 -7 than in 3T6 cells.

Effect of sleep on swallowing, esophageal peristalsis, and acid clearance

Recent studies have shown that impaired esophageal clearance of refluxed material during the sleeping interval plays a major role in the pathogenesis of esophagitis. The present investigation compares esophageal responses to both acid and water infusions during sleep in asymptomatic subjects. Fourteen healthy individuals were studied. The subjects were studied for two nights in the sleep laboratory. Each night involved four to six infusions of 15 ml of either sterile water or 0.1 N HCl. A similar infusion was conducted during the presleep waking interval. Acid clearance time was shown to decrease as a function of increasing wakefulness during the acid clearing interval. Arousal responses were significantly greater with acid infusions during sleep (p less than 0.05). Awakenings from sleep with acid infusions were associated with significantly greater swallowing rates than those associated with water infusions (p less than 0.01). Peristaltic parameters of amplitude, velocity, and duration were not differentially affected by acid versus water infusions or by sleep versus waking.