Covered and uncovered self-expandable metallic Hanarostents are equally efficacious in the drainage of extrahepatic malignant strictures. Results of a double-blind randomized study

BACKGROUND

Self-expandable metallic stents (SEMS) placement is a standard treatment for inoperable malignant bile duct strictures. Covered SEMS have been introduced to avoid stent occlusion by tumor ingrowth. The aims were to compare covered and uncovered stents in terms of patency, efficacy and complication rate.

MATERIAL AND METHODS

Consecutive patients with inoperable malignant distal biliary strictures were included in the study and randomized to receive a covered (n = 34) or uncovered (n = 34) Hanaro SEMS. Follow-up was performed by nurses after 18 h, 48 h, 2 weeks and thereafter every month until stent dysfunction or the patient died. Outcomes were measured as follows: the patients reported urine and stool color, presence of fever and abdominal pain. Liver function tests and CRP were analyzed each time. The procedure time and complications were monitored. The follow-up was blinded to stent type.

RESULTS

The median patient age was 79 years (IQR: 66-83, R: 54-92), 59% were female and 85% had the gallbladder in situ. There was no difference between covered and uncovered stents in terms of procedure time (median: 30 min (20-38, R: 12-90) vs. 30 min (IQR: 20-42, R: 12-70)), stent patency (median: 153 days (IQR: 65-217; R: 20-609) vs. median of 127 days (IQR: 70-196; R: 18-486)) or patient survival (median: 154 days (IQR: 65-217; R: 21-609) vs 157 days (IQR: 70-273, R: 20-690)). Eighty-seven percent died with a patent covered and 83% with an uncovered stent (n.s.). Two early complications occurred (sepsis; pancreatitis), both with covered stents.

CONCLUSION

There is no clinical difference between covered and uncovered biliary Hanaro SEMS. Both types are easily inserted with low complication rate and have long-term patency.

Decreasing ratios of phosphocreatine to beta-ATP correlates to progressive acute rejection in a concordant mouse heart to rat xenotransplantation model

Biopsies are difficult to perform in rodent heart transplant models without compromising the graft function and therefore other means to evaluate the grafts repeatedly and noninvasively are warranted. The goal of the present study was to measure changes in ratios of high energy phosphorus containing metabolites detected with in vivo 31Phosphorous Magnetic Resonance Spectroscopy ((31)P MRS) in a xenotransplantation model and to investigate if these ratios correlated to histological signs of acute xenograft rejection. Thirty-five heart transplantations were performed (NMRI-mice to Lewis (RT1(1)) rats). Thirteen heart transplants underwent repeated daily in vivo (31)P MRS measurements and 22 grafts were measured on any of 4 postoperative days and thereafter sacrificed for histology. A modified scoring system based on Billingham's criteria was used to stage the rejection process. The median graft survival was 3.0 +/- 0.44 (median +/- SD) days (n = 17). Significant differences, both overall and interday, could be calculated for the phosphocreatine (PCr)/beta-adenosine triphosphate (beta-ATP) ratios and for the rejection score. The decreases in PCr/beta-ATP ratios correlated significantly to the progressive acute rejection process in the sacrificed grafts (P = 0.01). Further studies are indicated to establish the potential of (31)P MRS in immunosuppressed recipients of vascularized xenotransplants with prolonged graft survival.

Characterization of Forssman and other antigen/antibody systems in vascularized mouse heart to rat xenotransplantation

In the present study, the nature of hyperacute xenograft rejection was closely studied in a vascularized mouse-to-rat transplantation model. Antibodies against mouse heart, erythrocytes and lymphocytes and against the Forssman antigen were raised in the rat. Upon heterotopic heart transplantation the respective antisera were intravenously (i.v.) injected. Passive transfer of antiheart, antierythrocyte or antilymphocyte serum resulted in hyperacute rejection of the transplanted mouse heart. Subfractionation of the antiheart serum showed that the capacity to induce hyperacute rejection was carried by the immunoglobulin (Ig)G fraction. When antierythrocyte serum adsorbed with mouse erythrocytes was administered the cardiac grafts remained beating. To the contrary, antilymphocyte serum adsorbed with erythrocytes still had the capacity to induce hyperacute rejection. None of the rats that had previously been challenged with the Forssman antigen rejected their grafts hyperacutely. Subsequent investigations by electron microscopy revealed that the Forssman antigen is expressed on dendritic cells (DC) adjacent to the vessels, but not on the vascular endothelium, thus explaining the inability of the anti-Forssman serum to induce hyperacute rejection. Taken together, we have demonstrated the existence of several xenoantigens that can be targets for antibody-mediated rejection, suggesting that more than one relevant xenoantigen exists also in more distantly related combinations, such as the pig-to-human combination.

Leb glycolipids present in the lumen of the gastrointestinal tract of rats do not enter the plasma compartment

We orally administered to rats several times more Leb glycolipids than is proportionally found in the gastrointestinal tract of humans. This was done in an effort to study two potential phenomena: the possibility that glycolipids in plasma may originate from glycolipids derived from the lumen of the gastrointestinal tract, and to investigate the potential to secondarily modify in vivo the glycolipid profile of gastrointestinal tract epithelial cells, a phenomenon clearly established for human erythrocytes, leukocytes, and platelets. We were able to establish that some of the orally administered glycolipids can be detected at the surface of the upper region mucosa of the gastrointestinal tract for more than 24 hours and are essentially excreted intact in stools in less than 72 hours. Some fecal degradation of the Leb glycolipids into Lea and H type 1 did occur. Although we clearly established that the glycolipids were present in the mucus layer adherent to the cell surface, we could not conclusively establish if the glycolipids had inserted into the epithelial cell membrane. This, however, could not be excluded. The fact that the fed glycolipids remained in the mucus layer of the upper region of the gastrointestinal tract for at least 24 hours may have some pharmacological value. Using sensitive techniques, including red cell serology, immunohistology, and immunochemistry of glycolipids isolated from plasma and red cells, there was no evidence that the fed Leb glycolipids reached the plasma compartment, thus suggesting that glycolipids present in the lumen of the gastrointestinal tract cannot reach the circulation.

Anti-carbohydrate antibodies associated with hyperacute rejection in a vascularized mouse heart-to-rat xenotransplantation model

Specificity of immune reactions has always been sought, because it facilitates intervention with unwanted mechanisms. Specific carbohydrate antigens have been proposed to be targets of antibodies in early immune responses in pig-to-man xenografts. This work was undertaken to determine carbohydrate structure for antibody response in the experimental xenograft model mouse-to-rat. Glycolipids were prepared from nine different mouse organs and separated for carbohydrate size on thin layer plates. Sera taken from normal untreated rats showed only weak or absent IgM antibody-binding to the separated mouse glycolipids. This is in accordance with the observation that mouse heart grafts are not hyperacutely rejected by the rat. However, sera taken from mouse heart xenografted rats show clear IgG and IgM antibody binding to neutral glycolipids migrating in the five-sugar region of the thin-layer plate. These rats have previously been reported to hyperacutely reject a second xenograft. Glycolipids with this particular mobility and immunostaining properties are the dominant ones in the mouse caval vein preparation, which probably represents a rather pure vascular structure. The target antigen structure was identified, by mass spectrometry and proton nuclear magnetic resonance spectroscopy, to be the Forssman pentaglycosylceramide. A commercial monoclonal antibody directed toward the Forssman antigen bound the same biochemical structure as the antibodies derived from the mouse heart-xenografted rats. Most of the IgM activity, but very little of the IgG activity was adsorbed using the Forssman terminal disaccharide solid phase.

Two families of murine carbohydrate ligands for E-selectin

In search of endogenous oligosaccharide ligands for the endothelial adhesion molecule E-selectin in mouse, glycolipids from tissues and the neutrophilic cell line 32D c13 were tested for E-selectin binding. Kidneys of BALB/c and NMRI mice (but not CBA) and the 32D c13 cells were found to contain minor glycolipid populations that support strongly the binding of murine E-selectin. By chromatogram binding experiments and in situ liquid secondary ion mass spectrometry (LSIMS) with neoglycolipids derived from their endoglycoceramidase-released oligosaccharides, in conjunction with compositional and linkage analyses, one of the glycolipid ligands in kidney was identified as the Le(x)-active extended globo-glycolipid: [formula: see text] Neoglycolipids enriched for the ligand structures were obtained from oligosaccharides released by endo-beta-galactosidase from the 32D c13 cells. By TLC-LSIMS and antibody binding, the main E-selectin binding determinant on these was identified as sialyl-Le(a).

Structural and immunochemical identification of Leb glycolipids in the plasma of a group O Le(a-b-) secretor

Total non-acid glycosphingolipids were isolated from the plasma of a healthy red blood cell group O Le(a-b-) salivary ABH secretor individual. Glycolipids were fractionated by HPLC and combined into eight fractions based on chromatographic and immunoreactive properties. These glycolipid fractions were analysed by thin-layer chromatography and tested for Lewis activity with antibodies reactive to the type 1 precursor (Le(c)), H type 1 (Le(d)), Le(a) and Le(b) epitopes. Fractions were structurally characterized by mass spectrometry (EI-MS and LSIMS) and proton NMR spectroscopy. Expected blood group glycolipids, such as H type 1, (Fuc alpha 1-2Gal beta 1-3GlcNac beta 1-3Gal beta 1-4Glc beta 1-1Cer) were immunochemically and structurally identified. Inconsistent with the red cell phenotype and for the first time, small quantities of Le(b) blood group glycolipids (Fuc alpha 1-2Gal beta 1-3(Fuc alpha 1-4)GlcNAc beta 1-4Glc beta 1-1Cer) were immunochemically and structurally identified in the plasma of a Lewis-negative individual. These findings confirm recent immunological evidence suggesting the production of small amounts of Lewis antigens by Lewis negative individuals.

The blood group B type-4 heptaglycosylceramide is a minor blood group B structure in human B kidneys in contrast to the corresponding A type-4 compound in A kidneys. Structural and in vitro biosynthetic studies

Blood group A glycolipid antigens have been found based upon at least four different core saccharides (types 1 to 4). The biological significance of this structural polymorphism is not known, although the successful outcome of transplantations of blood group A2 kidneys to blood group O individuals have been partly explained by the low expression of A type-3 and -4 chain glycolipid antigens in A2 kidneys. If graft rejection due to ABO incompatibility is, in any way, correlated to the expression of type-3 and -4 chain blood group glycolipids, it is of interest to identify possible blood group B structures based on these core saccharides. In a non-acid glycosphingolipid fraction isolated from human blood group B kidneys, mass spectrometry, high-temperature gas chromatography-mass spectrometry and probing of thin-layer chromatograms with Gal alpha 1-4Gal-specific Escherichia coli and monoclonal anti-B antibodies provided evidence for minute amounts of a Gal alpha 1-3(Fuc alpha 1-2)Gal beta-HexNAc-Gal alpha 1-4Gal beta-Hex-Ceramide structure consistent with a B type-4 chain heptaglycosylceramide. In contrast, blood group A kidneys have the corresponding A type-4 chain heptaglycosylceramide as the predominant blood group A glycolipid. No, or very low activity of the blood group B gene enzyme on the type-4 chain blood group H hexaglycosylceramide precursor was found by biosynthetic experiments in vitro, which might explain the low expression of type-4 chain blood group B heptaglycosylceramides in human blood group B kidneys.