The watermelon stomach: long-term outcome in patients treated with Nd:YAG laser therapy.

Watermelon stomach is an unusual cause of gastrointestinal bleeding and iron deficiency anemia. Its etiology is unknown, but it has been reported to be associated with a variety of diseases, including autoimmune disorders and cirrhosis. We report on the long-term outcome of 15 patients (13 women, 2 men) treated with neodymium-yttrium-aluminum-garnet (Nd:YAG) laser therapy. The mean age of patients at presentation was 71.6 years (range, 59 to 85 years). Fourteen patients were transfusion-dependent, requiring an average of 9.6 units of blood in the 12 months preceding diagnosis and treatment. Associated diseases included scleroderma (3 patients), mixed connective tissue disease (1 patient), history of cancer (3 patients), cryptogenic cirrhosis (3 patients), and chronic renal failure (3 patients). In 7 of 9 patients who had an antinuclear antibody test, an elevated titer greater than 1:160 in a speckled pattern was noted. Nd:YAG laser coagulation therapy was administered to all patients without complications and was successful in reducing bleeding in every case. Five patients died during the course of follow-up without signs of recurrent gastrointestinal bleeding. The remaining 10 patients have had both endoscopic and hematologic improvement during a mean follow-up period of 4.4 years from the time of initial diagnosis (range, 2 to 8 years). The 10 survivors are no longer transfusion-dependent and have stable hematocrits.

Effect of selenium on growth, S-adenosylmethionine and polyamine biosynthesis in human colon cancer cells.

Selenium metabolism and polyamine biosynthesis are linked in their common requirement for S-adenosylmethionine. The effects of selenium supplementation (0.1 to 6.0 ppm) on growth, polyamine biosynthesis and S-adenosylmethionine were examined in two human colon cancer cell lines, WiDr and HT29. WiDr cells were very sensitive to selenium with a significant decrease in 3H-thymidine incorporation and cell number to doses above 0.25 ppm. HT29 cells were less sensitive. In HT29 cells, ornithine decarboxylase activity and its product putrescine decreased in parallel with the growth inhibitory effects of selenium. Similar changes were not noted in WiDr cells. Spermidine and spermine content were conserved in both cell lines exposed to cytotoxic doses of selenium. S-adenosylmethionine was increased in HT29 cells at cytotoxic doses of selenium (1.0 to 6.0 ppm).

The biosynthesis, processing, and secretion of laminin by human choriocarcinoma cells.

Laminin, a glycoprotein component of basal laminae, is synthesized and secreted in culture by a human malignant cell line (JAR) derived from gestational choriocarcinoma. Biosynthetically labeled human laminin subunits A (Mr approximately 400,000) and B (Mr = 200,000 doublet) are glycoslyated with asparagine-linked high mannose oligosaccharides that are processed to complex oligosaccharides before the laminin molecule is externalized by the cell. The rate-limiting step in the processing of the asparagine-linked glycans of laminin is at the point of action of alpha-mannosidase I since the principal laminin forms that accumulate in JAR cells contain Man9GlcNAc2 and Man8GlcNAc2 oligosaccharide units. The combination of subunits to form the disulfide-linked laminin molecule (Mr approximately 950,000) occurs rapidly within the cell at a time when the subunits contain these high mannose oligosaccharides. The production of laminin is limited by the availability of the A subunit such that excess B subunit forms accumulate intracellularly as uncombined B and a disulfide-linked B dimer. Pulse-chase kinetic studies establish these B forms as intermediates in the assembly of the laminin molecule. The fully assembled laminin undergoes further oligosaccharide processing and translocation to the cell surface, but uncombined B and B dimer are neither processed nor secreted to any significant extent. Therefore, laminin subunit combination appears to be a prerequisite for intracellular translocation, processing, and secretion. The mature laminin that contains complex oligosaccharides does not accumulate intracellularly but is rapidly externalized upon completion, either secreted into the culture medium (25%) or associated with the cell surface (75%) as determined by susceptibility to degradation by trypsin. About one-third of the laminin molecules secreted or shed by JAR cells into the chase medium contain a smaller A subunit form that appears to have been modified by limited proteolytic cleavage. The putative proteolytic event is closely timed to the release of the laminin into the culture medium.

A kinetic comparison of the processing and secretion of the alpha beta dimer and the uncombined alpha and beta subunits of chorionic gonadotropin synthesized by human choriocarcinoma cells.

Human choriocarcinoma cells (JAR) synthesize the alpha and beta subunits of the glycoprotein hormone chorionic gonadotropin (hCG) (R.W. Ruddon, C.A. Hanson, A. H. Bryan, G.J. Putterman, E.L. White, F. Perini, K. S. Meade, and P.H. Aldenderfer (1980) J. Biol. Chem. 255, 1000-1007). In addition to the hCG dimer (alpha beta), JAR cells secrete uncombined alpha and beta subunits into the culture medium (L.A. Cole, R.J. Hartle, J.A. Laferla, and R.W. Ruddon (1983) Endocrinology 113, 1176-1178). Pulse-chase studies with [35S]methionine or [3H]mannose were carried out in order to compare free alpha, free beta, and the alpha beta dimer with regard to the kinetics of synthesis, N-linked oligosaccharide processing, and secretion and to determine the kinetics of alpha-beta subunit combination. A panel of three antisera was used to immunoprecipitate directly the free subunits and the alpha beta dimer sequentially from the same cell lysates and culture media. The alpha subunit of hCG was synthesized in a slight molar excess (1.2-1.5-fold) over the beta subunit, and alpha beta dimer was rapidly formed by combination of the intracellular alpha and beta precursors. Dimer formation was already apparent in JAR cells following a 10-min biosynthetic labeling incubation with [35S]methionine. The combination of subunits ceased by 30 min of chase even though 51% of alpha and 44% of beta remained free within the cells. Combination of the alpha and beta precursors had occurred before their N-linked oligosaccharides were processed beyond the Man8GlcNAc2 structure. The initial trimming of glucosyl and mannosyl units from the high-mannose oligosaccharides of the hCG precursors occurred more rapidly for free alpha and CG-alpha than for free beta and CG-beta. JAR cells accumulated alpha precursors bearing mostly Man8GlcNAc2 units and beta precursors bearing Man8GlcNAc2 units that represent the substrates of the rate-limiting step in the secretory pathway. In spite of the fact that their N-linked oligosaccharides were trimmed at different rates, free alpha, free beta, and alpha beta dimer were all secreted into the medium at the same rate, with a half-time of 35 min. The secreted hCG forms were stable in the chase medium between 4 and 8h, indicating that extracellular degradation, combination of free subunits to form dimer, or dissociation of dimer to form free subunits did not occur.(ABSTRACT TRUNCATED AT 400 WORDS)

The use of drugs to dissect the pathway for secretion of the glycoprotein hormone chorionic gonadotropin by cultured human trophoblastic cells.

Agents that affect intracellular cation and pH gradients and inhibit energy production have been tested for their ability to modulate the processing and secretion of the free alpha subunit and the alpha beta dimer of human chorionic gonadotropin (hCG) by cultured human trophoblastic cells (JAR). Incubation of JAR cells with monensin or nigericin, monovalent cation ionophores that produce equilibration of Na+ and K+ across cellular membranes, dicyclohexylcarbodiimide, an agent that inhibits intracellular membrane ATPases, and methylamine, which neutralizes intracellular pH gradients, produced similar effects on hCG processing and secretion. All these agents inhibited the processing of the asparagine-linked oligosaccharide chains of free alpha subunit and the alpha and beta subunits contained in the hCG dimer. Moreover, after treatment of JAR cells with these agents, there was an intracellular accumulation of precursor forms and an inhibition of secretion of "mature" forms of hCG. Monensin affected the processing and secretion of hCG subunits differently at different concentrations. At 5 X 10(-7) M, monensin inhibited the processing of the asparagine-linked oligosaccharides of hCG without altering the rate-limiting step in the secretory pathway or blocking hCG secretion. The intracellular hCG subunit precursors in both control and monensin-treated cells contained a similar array of high mannose oligosaccharides, predominantly of the Man8GlcNAc2 and Man9GlcNAc2 types. However, monensin-treated cells secreted hCG subunits that contained endo H-sensitive oligosaccharides of the high mannose (mostly Man5GlcNAc2) and hybrid types rather than the endo H-resistant complex chains synthesized by control cells. Nevertheless, a full complement of serine-linked oligosaccharides was added to the hCG-beta subunit in monensin-treated cells. These results indicate that the intracellular movement of hCG from the rough endoplasmic reticulum to the cell surface was not inhibited by monensin at a concentration that impaired Golgi-localized steps in the processing of asparagine-linked oligosaccharides. At 5 X 10(-6) M, monensin significantly inhibited secretion of hCG and created a new rate-limiting step in the processing pathway. hCG subunits bearing Man5GlcNAc2 units accumulated intracellularly, suggesting that the equilibration of intracellular Na+/K+ pools blocked oligosaccharide processing at an intra-Golgi point, perhaps by inhibiting movement of the glycoprotein hormone from the "cis" to the "trans" Golgi compartment. Since the other drugs mentioned above produced similar effects on hCG processing and secretion, it appears that maintenance of intracellular cation and pH gradients is necessary for the intra-Golgi transport of glycoprotein hormones.(ABSTRACT TRUNCATED AT 400 WORDS)

Detection of the free beta subunit of human chorionic gonadotropin (HCG) in cultures of normal and malignant trophoblast cells, pregnancy sera, and sera of patients with choriocarcinoma.

Immunoaffinity adsorption techniques, utilizing specific antisera for hCG and its subunits bound to Sepharose 4B, have been employed to separate hCG alpha beta dimer and free subunits of hCG. As previously reported by this and a number of other laboratories, trophoblast cells (in vivo and in vitro) produce free alpha subunit in addition to hCG dimer. We have now shown that cultured JAr choriocarcinoma cells also secrete free beta subunit: 37% of the total beta subunit (combined and free) secreted by JAr cells is in the free form. Moreover, in pooled sera from choriocarcinoma patients 15% of total beta subunit is free, and in media from placental explant cultures and in pooled first trimester pregnancy sera 11% and 6.5%, respectively, of total beta subunit are in the free form. The free beta s are all of similar mol wt to the combined forms, and associate with urinary hCG alpha to form hCG. Free alpha s, which are larger than the combined forms, are unable to associate with urinary hCG beta to form hCG. We propose that the supply of combinable alpha subunit, rather than beta, limits dimer formation.

Effect of dihydrostreptomycin on active transport in isolated bacterial membrane vesicles.

Membrane vesicles prepared from bacterial cells grown in the absence of dihydrostreptomycin but subsequently incubated in the presence of dihydrostreptomycin transported proline normally, but vesicles prepared from cells grown in media to which dihydrostreptomycin was added 30 min before harvesting had a greatly impaired ability to accumulate proline. The latter cells extruded protons normally but were unable to maintain a proton gradient as effectively as normal cells. These data indicated that metabolism was required for dihydrostreptomycin to exert an effect on the bacterial cell membrane.

Biosynthesis and secretion of chorionic gonadotropin subunits by organ cultures of first trimester human placenta.

The biosynthesis and secretion of human chorionic gonadotropin (hCG) have been studied by pulse-chase labeling techniques in organ cultures of normal first trimester placentae. As we previously reported for human malignant trophoblastic cells (Ruddon et al. (1981) J. Biol. Chem. 256, 5189-5196), first trimester placental tissue produces Mr = 18,000 and 15,000 intracellular forms of alpha subunit and Mr = 24,000 and 18,000 forms of beta subunit. In the placental tissue, there is a greater accumulation of mature subunit forms prior to secretion. The predominant intracellular form of alpha subunit in placental tissue is a high mannose, (Man)8(GlcNAc)2 oligosaccharide-containing form just as it is for malignant trophoblastic cells; however, in placenta there is evidence for a greater content of partially processed intermediates with oligosaccharides smaller than (Man)8(GlcNAc)2. Placental tissue secretes both a large free alpha subunit and an hCG-alpha subunit that is part of complete hCG, but there is a 3- to 6-fold greater secretion (on a molar basis) of free alpha than complete hCG. There is no evidence for the synthesis of high molecular weight prohormone forms that might be precursors to the secreted forms of hCG subunits.