Further studies on cell adhesion based on Le(x)-Le(x) interaction, with new approaches: embryoglycan aggregation of F9 teratocarcinoma cells, and adhesion of various tumour cells based on Le(x) expression.

We previously proposed specific interaction of Le(x) (Gal beta 1-->4 [Fuc alpha 1-->3]-GlcNAc beta 1-->3Gal) with Le(x) as a basis of cell adhesion in pre-implantation embryos and in aggregation of F9 teratocarcinoma cells, based on several lines of evidence (Eggens et al., J. Biol Chem (1989) 264:9476-9484). We now present additional evidence for this concept, based on autoaggregation studies of plastic beads coated with glycosphingolipids (GSLs) bearing Le(x) or other epitopes, and affinity chromatography on Le(x)-columns of multivalent lactofucopentaose III (Le(x) oligosaccharide) conjugated with lysyllysine. Comparative adhesion studies of Le(x)-expressing tumour cells vs their Le(x)-non-expressing variants showed that only Le(x)-expressing cells adhere to Le(x)-coated plates and are involved in tumour cell aggregation, in analogy to F9 cell aggregation. The major carrier of Le(x) determinant in F9 cells is not GSL but rather polylactosaminoglycan ('embryoglycan'), and we demonstrated autoaggregation of purified embryoglycan in the presence of Ca2+, and reversible dissociation in the absence of Ca2+ (addition of EDTA). Defucosylated embryoglycan did not show autoaggregation under the same conditions. Thus, Le(x)-Le(x) interaction has been demonstrated on a lactosaminoglycan basis as well as a GSL basis. A molecular model of Le(x)-Le(x) interaction based on minimum energy conformation with involvement of Ca2+ is presented.

Common tetrasaccharide epitope NeuAc alpha 2-->3Gal beta 1-->3(Neu-Ac alpha 2-->6)GalNAc, presented by different carrier glycosylceramides or O-linked peptides, is recognized by different antibodies and ligands having distinct specificities.

A novel globo-series disialoganglioside, disialosyl galactosyl globoside (Structure 1 below), defined by new monoclonal antibody (mAb) RM2, was isolated and characterized as having terminal structure identical to that of ganglio-series ganglioside GD1 alpha (Structure 2) and a common mucin-type epitope (Structure 3) widely distributed in glycoproteins such as glycophorin A. While these three structures share a common nonreducing tetrasaccharide terminus, mAb RM2 showed strong specific reactivity only with Structure 1, not with Structures 2 or 3. Another mAb, QSH2, reacted strongly with Structure 3 but did not cross-react with Structures 1 or 2. Conformational molecular models based on minimum energy hard sphere exoanomeric calculations suggest that Structure 1 presents a unique surface topology distinct from that of Structures 2 or 3. Our findings suggest the novel concept that reactivity of a common carbohydrate epitope with different antibodies or ligands is highly dependent on the type of carrier glycosylceramide or carrier O-linked peptide. [formula: see text]

A comparative study of contrast agents for endoscopic retrograde pancreatography.

Pancreatitis is a major cause of morbidity and mortality secondary to endoscopic retrograde pancreatography (ERP). One factor that may cause post-ERP pancreatitis is the type of contrast media utilized during the procedure. The purpose of this prospective, double-blind, randomized study was to evaluate the effects of three contrast agents of differing osmolality and ionicity on changes between pre- and post-ERP chemical changes in serum amylase and lipase and development of clinical symptoms of acute pancreatitis. Our study of 53 patients showed that those who received Omnipaque a non-ionic, relatively iso-osmolar contrast agent, had a significantly lower serum amylase (p = 0.0038) and serum lipase (p = 0.0002) in post-ERP serological markers, compared with patients who received the ionic agents, Hypaque meglumine 60% or Hexabrix. In addition, the development of clinical symptoms of pancreatitis was less in patients who received Omnipaque than in those who received Hexabrix or Hypaque (1 vs. 3 vs. 4). No significant difference was found between patients who received ionic agents. No patient who received Omnipaque needed hospitalization, whereas one (6%) patient who received Hexabrix was hospitalized compared to three (20%) hospitalized patients who received Hypaque. When the initial cost and cost of hospitalization were compared, the non-ionic contrast medium was also found to be more cost-effective for the patient. In summary, the risk of post-ERP acute pancreatitis was significantly lower for patients who received the non-ionic contrast agent than for those who received the ionic agents.

Duodenal obstruction: a complication of percutaneous endoscopic gastrostomy tube migration.

Percutaneous endoscopic gastrostomy (PEG) is now a well-established technique for providing long-term enteral feeding. The procedure is being increasingly utilized and, although generally well tolerated, it may be associated with complications. We report two patients in whom a replacement Foley balloon tip catheter migrated into the small bowel and caused obstruction. The diagnosis, management, and preventive measures of tube migration are discussed.

Forceful balloon dilation: an outpatient procedure for achalasia.

The initial treatment of choice in patients with achalasia is balloon dilation. Heretofore, this procedure was performed on an in-hospital basis resulting in high patient cost. This study evaluated the safety and efficacy of pneumatic dilation as an outpatient procedure. Sixty-one procedures were performed on 50 patients at two centers. An overall treatment success rate of 95% (47 of 50 patients) was achieved. Two patients had elective surgical treatment and a third underwent surgery for perforation secondary to dilation. A total of three patients complained of post-procedure chest pain within 4 hours and were hospitalized. Two had perforations; one required surgical repair. The third patient had resolution of symptoms. We conclude that performing balloon dilation as an outpatient procedure is safe, efficacious, and cost effective.

Oxygen desaturation and changes in breathing pattern in patients undergoing colonoscopy and gastroscopy.

The respiratory effect of diagnostic colonoscopy and upper endoscopy were studied in 32 elderly patients. Twenty-two underwent colonoscopy and 10 upper endoscopy. In the group undergoing upper endoscopy, 4 of 10 patients experienced a decrease in oxygen desaturation greater than or equal to 4% during the medication period; an additional 2 patients desaturated during the procedure. In the group undergoing colonoscopy, 12 of 22 patients experienced oxygen desaturation during the medication period; 3 other patients desaturated during the procedure. Mean SaO2 for each group was lowest (p less than 0.05) during the medication period. Central apneas occurred in 13 of the patients undergoing colonoscopy during the medication period; however, only 8 of these patients with apneas experienced desaturation greater than or equal to 4% and the periods of desaturation did not correlate with the periods of apneas. Oxygen desaturation greater than or equal to 4% occurs frequently during both upper endoscopy and colonoscopy in this elderly population. This is related to the effects of sedation; the procedure itself worsened the desaturation in only 16% of the patients. Furthermore, the desaturation did not correlate with changes in the breathing patterns of the patients. Low-flow oxygen and/or close monitoring of patients during and subsequent to administration of medication is advised.