1,25-Dihydroxyvitamin D3 receptor as a marker of human colon carcinoma cell line differentiation and growth inhibition.

The antiproliferative action of 1,25-dihydroxyvitamin D3 in osteosarcoma, breast carcinoma, and colon carcinoma cell lines has been described. In this study, the level of vitamin D receptor was analyzed in a panel of colon adenoma and adenocarcinoma cell lines and the receptor level was correlated with the response to treatment with 1,25-dihydroxyvitamin D3. Ribonuclease protection and ligand-binding assays quantitated the level of vitamin D receptor mRNA expression and the level of functional receptors, respectively. The more well-differentiated cell lines, such as VACO 330, showed higher levels of vitamin D receptor than less-differentiated cell lines, such as SW620. Proliferation assay, clonogenic assay, and growth curve study in HT29 and SW620 cell lines assessed the antiproliferative effect of 1,25-dihydroxyvitamin D3 at concentrations ranging from 10(-11) to 10(-6) M. HT29 showed significant (P < 0.05) growth inhibition at 10(-9) to 10(-6) M concentrations, but growth of SW620 remained unchanged. The amount of vitamin D receptor in 12 malignant colonic tumors was compared with that of adjacent normal tissue, and in 9 cases, the tumor expressed a lower vitamin D receptor level. Our results suggest that the level of vitamin D receptor correlates with the degree of differentiation in human colon cancer cell lines and may serve as a useful biological marker in predicting clinical outcome in patients.

Growth inhibition of HT-29 human colon cancer cells by analogues of 1,25-dihydroxyvitamin D3.

The use of 1,25-dihydroxyvitamin D3 as an antiproliferative agent in the treatment of cancer is limited by its hypercalcemic effects. Analogues with equivalent or greater antiproliferative activities but smaller hypercalcemic effects have been developed. The antiproliferative effects of 1,25-dihydroxyvitamin D3 and four analogues were studied in HT-29 and SW620 human colon cancer cell lines, moderate and low expressors of the vitamin D receptor, respectively. HT-29 is a primary, moderately differentiated, cell line, while SW620 is metastatic and poorly differentiated. Growth curve studies, proliferation assays, and clonogenic assays were used to assess the antiproliferative effects of 1,25-dihydroxyvitamin D3, 1,25-dihydroxy-16-ene-23-yne-D3, 1,25-dihydroxy-26,27-hexafluoro-16-ene-23-yne-D3, 1,25-dihydroxy-16,23E-diene-26,27-hexafluoro-D3, and 1,25-dihydroxy-16,23Z-diene-26,27-hexafluoro-D3. Growth of HT-29 cells was significantly inhibited by all four analogues at 10(-8) M (P < 0.05). Analogues 1,25-dihydroxy-26,27-hexafluoro-16-ene-23-yne-D3, 1,25-dihydroxy-16,23E-diene-26,27-hexafluoro-D3, and 1,25-dihydroxy-16,23Z-diene-26,27-hexafluoro-D3 were 2 times as potent as analogue 1,25-dihydroxy-16-ene-23-yne-D3 and 1,25-dihydroxyvitamin D3. SW620 cells did not show any growth inhibition with any of the compounds tested. The affinities of the three most potent analogues for the vitamin D receptor were similar to that of 1,25-dihydroxyvitamin D3, while that of analogue 1,25-dihydroxy-16-ene-23-yne-D3 was lower. These results demonstrate that, as in leukemic cells, analogues of 1,25-dihydroxyvitamin D3 are potent antiproliferative agents in colon cancer cells and this activity is most likely mediated through the vitamin D receptor.

Interferon enhancement of radioimmunotherapy for colon carcinoma.

Recombinant human gamma-interferon (IFN-gamma) has recently been shown to enhance localization of radiolabeled monoclonal antibodies (MAb) to human colon carcinoma xenografts in athymic mice. The present study investigates the ability of gamma-interferon to enhance radioimmunotherapy of a low carcinoembryonic antigen-expressing human colon cancer (WiDr) in athymic mice. Growth curve analysis, antibody localization, and dose estimation studies were performed. A significant tumor growth delay, measured as the time to reach 1.0 g, was noted for animals receiving specific anti-carcinoembryonic antigen 90Y-MAb (ZCE025, 120 microCi) plus IFN-gamma (61.8 days) as compared to animals that received specific 90Y-MAb with phosphate-buffered saline (34.9 days; P less than 0.005). IFN-gamma (100,000 units) was given i.p. every 8 h for 2 days before and 4 days after 90Y-MAb therapy. The time required to reach 1.0 g for animals treated with nonspecific 90Y-MAb (ZME018) was significantly less either with (38.3 days) or without (34.4 days) IFN-gamma. The difference was more apparent when compared to animals receiving IFN-gamma alone (30.0 days) or phosphate-buffered saline alone (28.9 days; P less than 0.001). Increased antibody localization in the tumors of animals treated with IFN-gamma plus specific 90Y-MAb (43.2% injected dose/g) was seen in comparison to animals treated with specific 90Y-MAb without IFN-gamma (18.2% injected dose/g). The estimate of radiation dose delivered to the tumors, based on biodistribution data over time, revealed significantly higher levels in animals treated with specific 90Y-MAb with IFN-gamma (2477 cGy) compared to animals treated without IFN-gamma (1217 cGy). These results provide support for the use of gamma-interferon as an immunomodulating agent prior to radioimmunotherapy.

The effect of extracellular calcium on colonocytes: evidence for differential responsiveness based upon degree of cell differentiation.

Calcium supplementation decreases the incidence of colon cancer in animal models and may prevent colon cancer in man. Potential mechanisms include binding of mitogens and direct effects of calcium on colonic epithelial cells. In this study, the effects of extracellular calcium on epithelial cell growth and differentiation were studied in three colon carcinoma and two colonic adenoma cell lines. The characteristics studied included morphology, cell cycle kinetics, [Ca2+]IC (intracellular calcium concentration), proliferation, and expression of differentiation markers such as carcinoembryonic antigen (CEA) and alkaline phosphatase (AP). Sodium butyrate (NaB) and 1,25-dihydroxyvitamin D3 were used as controls in the latter three assays as these two agents are known differentiating agents. Alteration of [Ca+2]EC (extracellular calcium concentration) did not affect carcinoembryonic antigen (CEA) or alkaline phosphatase (AP) expression. NaB enhanced the expression of AP three-fold and CEA five-fold. This effect was augmented by increasing [Ca2+]EC. The exposure of cells to 1,25-(OH)2-Vitamin D3 increased CEA but not AP. [Ca2+]IC increased in response to 1,25-(OH)2-vitamin D3 and NaB but not with variation in [Ca2+]EC. Increased [Ca2+]EC inhibited proliferation of well-differentiated cells, but had no effect on poorly-differentiated cells. Morphological studies showed that extracellular calcium was necessary for normal cell-cell interactions. These studies have demonstrated direct effects of calcium on colonic epithelial cells which may contribute to the protective effects of dietary calcium against colon cancer. Loss of responsiveness to the antiproliferative effects of [Ca2+]EC with de-differentiation suggests that calcium supplementation may be most beneficial prior to the development of neoplastic changes in colonic epithelium.

Carcinoma of the stomach following the Chernobyl nuclear accident.

Medical consequences of many nuclear accidents on humans are well studied, but the results pertaining to gastric cancer patients who were exposed to radiation as a result of the Chernobyl nuclear accident have not been analysed. In this study, the outcome of the surgical treatment of 68 gastric cancer patients who were exposed to radiation as a result of the Chernobyl nuclear accident was compared with that of 117 consecutive gastric cancer patients from uncontaminated areas of the Ukraine. Patients in the study group was significantly younger than that of the control group. Comparative analysis showed the same frequency of regional metastases (65.7% versus 71.1%, P > 0.05), but a smaller number of distant metastases (23.8% versus 38.1%, P < 0.05) in the study group. 41.2% of patients in the study group underwent total gastrectomy compared to 19.6% of patients in the control group (P = 0.002). Postoperative complications developed in 13.2% of patients in the study group, while postoperative mortality in the study group was 7.3% compared to 1.7% in the control group. A significant decrease in CD16 cells was noted in patients from the study group following the operative procedure. Young age, invasive tumours with smaller number of distant metastases, frequent necessity for total gastrectomy and combined operations with adjacent organs, a higher level of postoperative morbidity and mortality and low levels of natural killer cells (CD16+) with a tendency to decrease after surgery are characteristic of patients with carcinoma of the stomach affected by the Chernobyl accident.

Comparison of radioimmunotherapy and external beam radiotherapy in colon cancer xenografts.

Radioimmunotherapy and external beam radiotherapy were compared in a nude mouse human colon cancer model. Radioimmunotherapy was delivered by intraperitoneal injection of 90Y-labeled anticarcinoembryonic antigen monoclonal antibody (anti-CEA MAB). Single fraction external beam radiotherapy was delivered using a 60Co teletherapy unit. Control groups received saline, unlabeled anti-CEA monoclonal antibody and labeled nonspecific monoclonal antibody. Subcutaneous CEA-expressing LS174T human colon carcinoma tumors were measured over time. Tumor growth suppression was expressed as delay to reach 2g compared to saline controls. Unlabeled anti-CEA monoclonal antibody and labeled nonspecific monoclonal antibody had no effect. External beam radiotherapy of 300, 600, 1000 and 2000 cGy produced growth delays of 3, 12, 17, and 22 days, respectively. Radioimmunotherapy with 120 microCi, 175 microCi, and 225 microCi resulted in growth delays of 20, 34, and 36 days. Estimated absorbed tumor dose was 1750 cGy in the 120 microCi group. Similar comparisons were done with the more radioresistant WiDr human colon carcinoma cell line. External beam radiotherapy doses of 400, 800, 1200, and 1600 cGy resulted in growth delays of 6, 21, 36 and 48 days, respectively. Radioimmunotherapy of 120 microCi and 175 microCi resulted in growth delays of 9 and 19 days, respectively. The 120 microCi dose delivered an estimated absorbed tumor dose of 1080 cGy to WiDr tumors. In summary, for the radiosensitive LS174T line, radioimmunotherapy produced biologic effects that were comparable to a similar dose of single fraction external beam radiotherapy. For the more radioresistant WiDr tumor, radioimmunotherapy produced a biologic effect which was less than a similar dose of single fraction external beam radiotherapy. These studies suggest that a tumor's response to radioimmunotherapy relative to that of external beam radiotherapy is, in part, dependent on tumor radiosensitivity and repair capacity.

The antiproliferative effect of vitamin D analogs on MCF-7 human breast cancer cells.

We analyzed the antiproliferative effect of 1,25-dihydroxyvitamin D3 and four vitamin D analogs on MCF-7, a human breast cancer cell line known to express the vitamin D receptor. Growth curve studies and [3H]thymidine incorporation assays were used to assess the antiproliferative effect of 1,25-dihydroxyvitamin D3 (vitamin D), Ro 23-7553, Ro 24-5531, Ro 25-5317, and Ro 24-5583. Growth of MCF-7 cells was significantly inhibited by 1,25-dihydroxyvitamin D3 and all four analogs at 10(-8) M (P < 0.05). MCF-7 cells treated with analog had significantly less [3H]thymidine incorporation than cells treated with 1,25-dihydroxyvitamin D3 (P < 0.05). The affinity of the analogs for the vitamin D receptor was similar to that of 1,25-dihydroxyvitamin D3. These results demonstrate that analogs of 1,25-dihydroxyvitamin D3 are potent antiproliferative agents on human breast cancer cells and that this activity is likely mediated through the vitamin D receptor.

Modulation of vitamin D receptor and estrogen receptor by 1,25(OH)2-vitamin D3 in T-47D human breast cancer cells.

1,25(OH)2-Vitamin D3 inhibits breast cancer cell proliferation through interaction with the vitamin D receptor (VDR). Regulation of VDR is under the influence of several factors which include the functional ligand for this receptor (1,25(OH)2-vitamin D3) as well as heterologous steroid hormones. We evaluated the nature of homologous regulation in T-47D human breast cancer cells with a radiolabelled ligand binding assay and a ribonuclease protection assay for VDR. Significant VDR up-regulation, as measured by hormone binding assays, occurred with pre-incubations with 10(-9)M through 10(-6)M 1,25(OH)2-vitamin D3 (P < 0.05). A 7-fold VDR up-regulation with 10(-8)M 1,25(OH)2-vitamin D3 occurred at 4 h treatment and was not associated with an increase in VDR mRNA expression on ribonuclease protection assay. This supports the hypothesis that up-regulation of VDR is probably the result of ligand-induced stabilization of pre-existing receptor. All-trans-retinoic acid, the progesterone analog R-5020, and prednisone were found to induce heterologous up-regulation of the VDR. We then determined with ligand binding assays whether 1,25(OH)2-vitamin D3 could influence receptor levels for another hormone in a manner analogous to the heterologous regulation of VDR. Regulation of estrogen receptor (ER) by 1,25(OH)2-vitamin D3 was studied in T-47D and MDA-MB-231 breast cancer cells. Incubation of T-47D cells, which are ER (+), with 10(-8)M 1,25(OH)2-vitamin D3 did not result in up-regulation of ER. Yet estrogen binding was significantly up-regulated in a cell line that is ER(-), MDA-MB-231. The increased estrogen binding was associated with a shift in binding affinity and ribonuclease protection assay showed absence of ER mRNA in these cells, suggesting an up-regulation of estrogen binding proteins and not of the ER itself.

Radioimmunotherapy of human colon cancer in nude mice.

Nude mice bearing subcutaneous human colon cancer xenografts (LS174T) were treated with 120 microCi of yttrium 90-labeled anti-carcinoembryonic antigen monoclonal antibodies (specific therapy), 120 microCi of 90Y-labeled anti-melanoma monoclonal antibodies (nonspecific therapy), or phosphate-buffered saline solution (no treatment control). Mean (+/- SD) tumor growth rates (percent increase per day) over the first 30 days of the study were as follows: 0.6% +/- 0.2% per day (specific therapy); 17.7% +/- 5.7% per day (nonspecific therapy); and 30.5% +/- 4.2% per day (control). In all three groups, tumors over 1 g had similar doubling times (5.74 +/- 0.71 d). Specific therapy caused a lag in tumor growth corresponding to a 3-logarithm cell kill. Estimated tumor dose of radiation obtained by tissue analysis was 34 and 14 Gy for specific and nonspecific therapy, respectively. In conclusion, 120 microCi of 90Y-labeled anti-carcinoembryonic antigen monoclonal antibodies was effective in suppressing growth of human colon cancer xenografts. Clinical studies with this preparation are recommended.

Intraoperative gamma detection probe with presurgical antibody imaging in colon cancer.

In this study, presurgical gamma camera imaging and an intraoperative gamma detection probe were used in 12 consecutive patients 6 to 22 days after infusion with indium 111-labeled anticarcinoembryonic antigen monoclonal antibody (111In-MoAb). In three of 11 patients who underwent laparotomy, clinical management was affected by the probe findings: localization of occult retroperitoneal disease, identification of an occult cecal lesion, and localization of residual disease at a site of local recurrence. Of all intra-abdominal lesions seen using any method, the probe identified 18 (86%) of 21, compared with 14 (67%) of 21 with the 111In-MoAb scan, 10 (48%) of 21 by computed tomographic scan, and 16 (76%) of 21 after surgical exploration. Uptake of 111In-MoAb in the portal (n = 3) and mediastinal (n = 3) lymph nodes was not associated with histologic findings of malignant neoplasms. For all pathologically confirmed extrahepatic and nonportal sites of cancer, the probe localized nine of nine, compared with five of nine by 111In-MoAb scan, two of nine by computed tomographic scan, and six of nine by surgical exploration. Important clinical uses of the intraoperative probe included occult lesion identification, localization of areas with 111In uptake shown with MoAb scanning, and verification of complete resection of areas with 111In-MoAb uptake.

Effect of mitomycin C, verapamil, and hyperthermia on human gastric adenocarcinoma.

The purpose of this study was to assess the efficacy of verapamil (20 microM) and hyperthermia (42 degrees C) as modifiers of mitomycin C (MMC), used at different concentrations, in inhibiting the growth of human gastric adenocarcinoma (AGS) cells. Combined verapamil and hyperthermia treatment resulted in a significant decrease in cell count by 72.2% as compared with the control value. Verapamil drastically enhanced the growth-inhibitory activity of MMC at high concentration against AGS cells by 67.5% and had no effect at intermediate and low concentrations. Hyperthermia did not enhance the effect of MMC on AGS cells. The modalities analyzed in this study require further investigation and may have potential for in vivo studies on gastric cancer therapy in the near future.

Antitumour activity of 5-fluorouracil, verapamil and hyperthermia against human gastric adenocarcinoma cell (AGS) in vitro.

The purpose of this study was to assess the efficacy of verapamil (20 microM) and hyperthermia (42 degrees C) as modifiers of 5-fluorouracil (5-FU), used at different concentrations, in inhibiting the growth of gastric adenocarcinoma cells. Combined verapamil and hyperthermia treatment showed a significant decrease in cell count when compared to control (72.2%), hyperthermia alone (68.4%), or verapamil alone (65%). At a high concentration of 5-FU (50 micrograms/ml), verapamil and hyperthermia had an additive growth inhibitory effect over a 4-day period when compared to control. A combination of 5-FU at low concentration (0.5 microgram/ml) with verapamil significantly suppressed growth by 31.2% in comparison to control--with this effect being independent of the duration of treatment. The modalities analysed in this study require further investigation and have potential for clinical applicability to gastric cancer therapy in the future.

Intensive preoperative radiotherapy with local hyperthermia for the treatment of gastric carcinoma.

In order to devitalize maximally tumour tissue and improve the prognosis of gastric cancer patients, a method employing preoperative intensive radiotherapy with local hyperthermia as adjuvant treatment was evaluated. In order to estimate the effectiveness of preoperative intensive radiation and radiation with local microwave hyperthermia in radical gastric cancer treatment, 293 patients were randomized into three respective treatment groups: surgery alone, surgery preceded by preoperative radiation; and surgery followed by preoperative radiation and hyperthermia. Preoperative radiation therapy to a total dose of 20 Gy in four 5 Gy fractions did not improve 3- or 5-year survival in gastric cancer patients in comparison with surgery alone. Local hyperthermia in combination with radiation therapy followed by surgery produced a significant improvement in 3-year survival of 22.1% (from 35.5 +/- 4.9% to 57.6 +/- 6.3%, P < 0.05) and 5-year survival of 21.3% (from 30.1 +/- 4.7 to 51.4 +/- 6.6%, P < 0.05). In unresectable gastric cancer patients, radiation therapy and radiation therapy with hyperthermia both increase mean survival. In conclusion; intensive preoperative radiation therapy in total dose 20 Gy plus local microwave hyperthermia significantly improved 3- and 5-year survival in comparison with surgery alone. Further development and evaluation of equipment to produce reliable and safe delivery systems for hyperthermia is needed.

Apoptosis of human primary and metastatic colon adenocarcinoma cell lines in vitro induced by 5-fluorouracil, verapamil, and hyperthermia.

Combined verapamil(V) and hyperthermia(HT) showed a significant decrease in HT29 and SW-620 cell counts by 61.5% and 77.6%, respectively, when compared to control. V in conjunction with 5-FU significantly reduced HT-29 count by 37% in comparison to 5-FU alone, and did not enhance the growth inhibitory effect of 5-FU on SW-620. HT did not enhance the growth inhibition seen with 5-FU treatment alone on HT-29, while this combination significantly decreased SW-620 cell count by 28.9% in comparison to administration of 5-FU alone. Joint administration of V and HT with 5-FU appeared to have a possible synergistic effect and reduced HT-29 count by 90% when compared to control. 5-FU alone or in different combinations with V and HT, as well as combination V+HT, results in apoptosis.

Hyperthermia and verapamil inhibit the growth of human colon cancer xenografts in vivo through apoptosis.

BACKGROUND: The long-term goal of this work is to develop a new therapeutic regimen for the treatment of colon cancer in humans which will include hyperthermic intraperitoneal perfusion of verapamil as an alternative to administration of chemotherapy. METHODS AND RESULTS: Hyperthermia and verapamil caused a significant inhibition of the growth of human colon cancer (HT-29) xenografts. Both apoptosis detection assays, TUNEL and H and E staining, have shown that approximately 50% of human colon cancer cells underwent apoptosis after hyperthermia and verapamil administration. The TUNEL assay has demonstrated that DNA strand breaks appeared fairly rapidly and maximum breakage occurred at 2 hours after the treatment. Histopathological assay has showed maximum apoptotic morphological changes at 12 hours after treatment. CONCLUSION: Thus, the results of our in vivo experiments confirmed our previously obtained in vitro data concerning the significant ability of the combination of hyperthermia and verapamil to inhibit human colon cancer cell growth through programmed cell death.

Extended surgical resection in T4 gastric cancer.

BACKGROUND: Some physicians still consider invasion of adjacent organs by the carcinoma of stomach as a sign of incurable disease. METHODS: This retrospective study has been done with particular reference to 353 T4 gastric cancer patients who underwent combined gastrectomies with adjacent organs. RESULTS: Subtotal gastrectomy was performed in 237 (67.1%) patients and total gastrectomy was performed in 116 (32.9%) patients. Organs most commonly resected with the stomach were the transverse colon in 159 (45%) cases, the tail of pancreas and spleen in 150 (42.5%), the left lobe of liver in 101 (28.5%), and the head of pancreas in 37 (10.5%) patients. A total of 110 postoperative complications occurred in this subset of patients corresponding to a complication rate of 31.2%. A total of 48 postoperative deaths occurred in this subset of patients corresponding to a mortality rate of 13.6%. The 5-year survival rate for all patients who underwent combined gastrectomy with adjacent organs was 25%. Of the node-negative T4 gastric cancer resections, 37% survived 5 years whereas the T4 node-positive resections have only a 15% 5-year survival. CONCLUSIONS: Patients who present with T4 gastric cancer (about 20% of the patient population) will benefit from aggressive en bloc surgical resection and should not be considered unresectable.

Postoperative complications requiring relaparotomies after 700 gastretomies performed for gastric cancer.

BACKGROUND: Prevention of fatal postoperative complications and improved management of patients with complications are important means of increased survival in gastric cancer patients. PATIENTS AND METHODS: A study of 700 patients undergoing gastrectomy was performed to examine factors that contributed to a high rate of postoperative complications. RESULTS: Of 700 patients undergoing gastrectomy for adenocarcinoma, 40 (5.7%) underwent reexploration because of serious complications. The frequency of the relaparotomies varied from 2.1% and 4.4% after regular subtotal and total gastrectomies, respectively, to 20% and 30.4% after palliative and conventional total gastrectomies, respectively. The complications that required reexploration most frequently were anastomotic leakage and incompetence of sutures (11, 27.5%), intra-abdominal abscesses (8, 20%), and pancreatic necrosis (7, 17.5%). A combination of preventive measures allowed the attainment of low rates of esophagojejunal anastomotic leakage (0.8%). CONCLUSION: We believe that the decision to perform an urgent reexploration, based on clinical findings, should generally be made by a group of experienced surgeons (not only the primary surgeon). Timely relaparotomy prevented death in 37.5% of the patients with serious acute postoperative complications.

Radical treatment of locally recurrent gastric cancer.

Locally recurrent gastric cancer develops in 45 per cent of resected patients. This study assessed the impact of an aggressive search for recurrence after radical operations and the use of reoperative and adjuvant therapy in this setting. From 1983 to 1990, 75 patients were explored for regionally recurrent gastric cancer. Resection was possible in 40 (53.5%), and palliative bypass was possible in 19 (25.3%); exploration only was performed in 16 (21.4%). Among resectable patients, gastrectomy was performed in 22 (55%) and gastrectomy with adjacent organ resection in 18 (45%) with an overall operative mortality of 15% (6 patients). Mean duration of life after bypass was 3.1 months; after exploration 4.5 months. Fifteen (40.6%) were not candidates for radiation or chemotherapy, 13 (31.2%) received preoperative radiotherapy (20 Gy), and 12 (28.2%) received postoperative systemic chemotherapy. Two-year survival after radical treatment was as follows: surgery alone 20%; radiotherapy and surgery 31.3%; surgery and chemotherapy 66.4%. These preliminary results indicate that re-excision benefits selected patients with recurrent gastric cancer. Patients receiving radiotherapy and chemotherapy tended toward improved survival.

Multiple duplications of the small intestine.

A case of coexistent cystic and tubular duplications of the small intestine is presented. Staged resection resulted in maximal preservation of small intestinal length. Intraoperative radionuclide scanning is suggested as a technique to assure complete removal of ectopic gastric mucosa. The literature regarding multiple duplications is reviewed and the management of duplications involving long segments of the small intestine is discussed.

An antireflux procedure for use with the reversed gastric tube.

A study was undertaken to determine whether reflux could be reduced or prevented by creation of a nipple valve at the distal end of a reversed gastric tube. The gastric tube was constructed in standard fashion in six adult dogs. The tube was placed through a substernal tunnel to a cutaneous ostomy in the neck. An antireflux valve was then created by invaginating the lower end of the tube into the gastric remnant. The following observations were made before and after creation of the valve: (1) gastric distending pressure required to produce efflux of saline from the ostomy; (2) manometric pressure at the stomach-tube junction; and (3) 2-hour pH monitoring within the tube after acid infusion into the stomach. The valve shortened the gastric tube by 2.0 to 2.5 cm. It did not obstruct antegrade flow of saline. Prior to creation of the valve, reflux of saline out of the cutaneous ostomy occurred at an average pressure of 62 cm H2O (range 25 to 80). The antireflux procedure prevented reflux with distending pressures up to 200 cm H2O. Manometry revealed an average pressure of 18 cm H2O (range 5 to 25) at the lower end of the tube before creation of the valve. The antireflux procedure raised this high pressure zone to 60 cm H2O (Range 50 to 65) (P less than 0.05). Spontaneous reflux was rarely observed in the anesthetized dog when acid was infused into the stomach and the pH was monitored in the gastric tube. Acid reflux could easily be produced by application of minimal manual pressure to the closed abdomen.(ABSTRACT TRUNCATED AT 250 WORDS)