Expression of a drug resistance gene in human neuroblastoma cell lines: modulation by retinoic acid-induced differentiation.

Expression of a multidrug resistance gene (mdr1) and its protein product, P-glycoprotein (Pgp), has been correlated with the onset of multidrug resistance in vitro in human cell lines selected for resistance to chemotherapeutic agents derived from natural products. Expression of this gene has also been observed in normal tissues and human tumors, including neuroblastoma. We therefore examined total RNA prepared from human neuroblastoma cell lines before and after differentiation with retinoic acid or sodium butyrate. An increase in the level of mdr1 mRNA was observed after retinoic acid treatment of four neuroblastoma cell lines, including the SK-N-SH cell line. Western blot (immunoblot) analysis demonstrated concomitant increases in Pgp. However, studies of 3H-vinblastine uptake failed to show a concomitant Pgp-mediated decrease in cytotoxic drug accumulation. To provide evidence that Pgp was localized on the cell surface, an immunotoxin conjugate directed against Pgp was added to cells before and after treatment with retinoic acid. Incorporation of [3H]leucine was decreased by the immunotoxin in the retinoic acid-treated cells compared with the undifferentiated cells. These results demonstrate that whereas expression of the mdr1 gene can be modulated by differentiating agents, increased levels of expression are not necessarily associated with increased cytotoxic drug accumulation.

Adenylate cyclase activity of NIH 3T3 cells morphologically transformed by ras genes.

The observed homology between G-proteins which regulate adenylate cyclase and ras proteins and the suggested role of ras in the regulation of adenylate cyclase in yeast prompted us to examine the regulation of adenylate cyclase in three cell lines: (i) NIH 3T3 cells, (ii) NIH 3T3 cells transformed by high levels of the normal rasH gene product and (iii) NIH 3T3 cells transformed by a mutated rasH gene product. We found that the regulation of adenylate cyclase by G-proteins is identical in the three cell lines, although the response of the transformed NIH 3T3 cells to agonists is strongly attenuated. Our data suggest that mammalian ras products do not interact directly with adenylate cyclase, although their increased expression may indirectly inhibit the interaction of adenylate cyclase stimulatory receptors with G-proteins.

The gastric bladder: a continent reservoir for urinary diversion.

A continent reservoir ("gastric bladder") has been developed as an alternative to ileal conduits after urinary diversion procedures. The reservoir is fashioned from vagally denervated gastric fundus and has antireflux ureterogastric anastomoses and a continent "neourethra," the latter which is easily catheterized to empty the contents; the main stomach retains vagal innervation. Continent reservoirs were prepared in six dogs, and Heidenhain pouches (without urinary diversion) were prepared in six control dogs. Effects of short-term and long-term exposure of gastric mucosa to urine and 1M, 2M and 4M urea solutions were studied. Basal and food-stimulated acid outputs were unaffected by prolonged exposure. Mucosal permeability to H+, Na+, K+ and Cl- after exposure to urine remained unaltered, but 4M urea solutions produced a temporary increase in permeability. Mucosal blood flow was unchanged. Reservoir capacity rapidly increased up to 2,000 ml without any change in serum electrolytes. No precipitation of uric acid occurred. No histologic differences were noted between the main stomach and the reservoir. Because gastric mucosa (especially when acidified) is relatively impermeable to ions, secretes rather than absorbs Cl-, and is unaffected by prolonged exposure to urine, a gastric pouch may be useful as a continent urinary reservoir while allowing the maintenance of normal serum electrolytes.

Influence of a synthetic prostaglandin analog on pancreatic secretion.

Effects of a synthetic prostaglandin analog-16--16-dimethyl prostaglandin E2, methyl ester (16-diMe-PGE2)--on pancreatic secretion were evaluated in seven dogs with chronic duodenal fistulas. Graded doses of 16-diMe-PGE2 were administered intravenously (0.1, 0.3, 0.5, and 1.0 mug per kilogram, intraduodenally, or intragastrically (15, 30, 50, 100 mug per kilogram) with the pancreas in the resting state or in response to (1) secretin and (2) secretin with cholecystokinin-pancreozymin. Profound and prolonged inhibition of volume and bicarbonate concentration of secretion occurred in the resting and stimulated gland. ED50 was 0.31 mug per kilogram intravenously (1/75 the ED50 for PGE1) and 25 mug per kilogram intraduodenally. As with PGE1, stimulation of enzymes occurred, even with doses that were subthreshold for inhibition of volume and HCO3. Like PGE1, 16-diMe-PGE2 has a dual action on the intact canine pancreas (stimulation of enzymes and inhibition of volume and electrolytes), but is much more potent, has a prolonged action, and is active intraduodenally and intragastrically. Nonsteroid inhibitors of endogenous prostaglandin synthesis did not alter these effects.

Preperitoneal herniorrhaphy: adjunct to cesarean section.

A case of inguinal hernia repair at the time of repeat cesarean section is described. The success of the repair and the patient's uneventful recovery suggest that these procedures can be combined conveniently and safely in select cases.

Dysphagia and lower esophageal sphincter abnormalities after proximal gastric vagotomy.

We studied 96 patients subjected to elective proximal gastric vagotomy for intractable duodenal ulceration. Dysphagia was a frequent finding and occurred in 32 percent. It appeared in the immediate postoperative period and usually lasted for 1 to 2 months without any abnormalities in lower esophageal sphincter function. In five patients, dysphagia was severe and, although transient, was associated with changes in lower esophageal function simulating those observed in achalasia. The mechanism of these motor abnormalities is probably due to a reversible neuromuscular dysfunction of the lower esophageal sphincter.

Effect of emulsions of medium and long chain triglyceride on human adipose tissue prostaglandin production in vitro.

Preliminary in vitro studies have been performed to assess the effect of experimental lipid emulsions of varying fatty acid composition on human adipose tissue metabolism. Subcutaneous human adipose tissue was obtained during elective surgery and placed in tissue culture. Physical mixtures of long chain triglyceride (LCT) and/or medium chain triglyceride (MCT) were added to the tissue culture medium so that the final concentration was 400 mg/dl. After a 3-day incubation period the tissue was harvested, placed in buffer and used to determine in vitro production of the prostaglandins prostacyclin I2 (measured as its stable endproduct 6-keto PGF1 alpha), thromboxane A2 (measured as TXB2), and prostaglandin E2. Measurements of the fatty acid profile found in the neutral- and phospholipid fraction of the adipose tissue and fat cell size were also made. The results demonstrate that samples incubated in 100% MCT had the most significant increase in prostaglandin production whereas those incubated in 100% LCT had the most significant decrease in activity of the three prostaglandins assayed, when compared to controls. The addition of LCT to MCT caused a dose-related decrease in adipose tissue prostaglandin production. There were no significant changes in the profile of fatty acids found in the neutral- or phospholipid fraction of adipose tissue. The results indicate that the relative level of MCT/LCT incubated with human adipose tissue has a significant effect on prostaglandin production.

Pseudocysts of the pancreas involving the spleen.

Three case reports of direction extension of pancreatic pseudocysts into the spleen are presented. This unusual complication can occur in both emergent and nonemergent settings. The most useful diagnostic procedures to assess whether there is an intrasplenic pseudocyst are sonograms, CAT scans, splenic scan, and occasionally angiography. The best treatment for this condition is a prompt distal pancreatectomy.