In vivo study of polyurethane-coated Gianturco-Rosch biliary Z-stents

PURPOSE

Prototypes of Gianturco-Rosch Z-stents coated with polycarbonate urethane (PCU) were placed in the biliary tree of pigs, in order to test their biomechanical behavior, stability, and biocompatibility.

METHODS

The stents were surgically implanted in the common bile duct of three pairs of pigs, which were killed after 1, 3, and 6 months respectively. Explanted livers from pigs of the same race, age, and size were used to provide comparative data. The bile ducts were radiologically and histopathologically examined; the stents were processed and examined by scanning electron microscopy.

RESULTS

No complications occurred and the animals showed a normal weight gain. The main bile duct appeared radiologically and macroscopically dilated, but the stents proved to be in place. Histologically, the bile duct epithelium was destroyed, but neither hyperplastic nor inflammatory fibrotic reactions of the wall were evident. Both the metallic structure and the polymeric coating of the stents were intact. A layer of organic material with a maximum thickness of approximately 3 micron was evident on the inner surface of the stents.

CONCLUSION

The present in vivo study demonstrates the biocompatibility, efficacy, and stability of PCU-coated Gianturco-Rosch stents in the biliary environment.

Evaluation of temperature distribution during hyperthermic treatment in biliary tumors: a computational approach

A computational approach is adopted to predict the temperature distribution in the biliary tissue during hyperthermic treatments in biliary tumors. Two different models are developed: an axisymmetric model and a three-dimensional model. In the first model the Pennes bioheat transfer equation is applied. It is aimed at simulating the thermoregulatory effect of the capillary bed and it can also give a pressure criterion to determine whether the blood perfusion term should be included in the mathematical model. The second model is aimed at simulating the convective effect of the large hepatic vessels: A constant Nusselt number is assumed on the sides of the vessels. The simulations of the three-dimensional model have been carried out with and without capillary perfusion in the tissue, i.e., respectively in the worst case and in the best case that may occur during heating. The results show that it is possible to obtain therapeutic temperature values in the tissue for time intervals considered acceptable by physicians. Moreover, the model is able to give more precise information about the volumes of tumoral tissue heated above therapeutic temperatures with the hyperthermic technique considered.

Comparative in vitro sensitivity of human cholangiocarcinoma and colon adenocarcinoma cells to anticancer agents

We comparatively investigated the sensitivity of a human cholangiocarcinoma cell line (SG231) and an adenocarcinoma cell line (WiDr) to mitoxantrone (MX), taxol (TX), mitomycin C (MMC), doxorubicin (DX), cisplatin (CDDP) and 5-fluorouracil (5FU) by the sulforhodamine B assay. The lower susceptibility of SG231 to SFU, to CDDP, to DX and to MMC than WiDr was observed, whereas the sensitivity of the two cell lines to MX and TX was similar. We also investigated the ability of a chemical modulator, lonidomine (LND), and hyperthermia to enhance the cytotoxic activity of the different drugs in the SG231 cell line. No potentiation of MX or CDDP activity was observed after a 2 hours treatment in hyperthermic conditions (42 degrees C). Conversely, a slight potentiation of a 2 hours pretreatment with MX and DX was obtained by a 24 hours post treatment with LND.

Branched structures in the intracellular DNA of herpes simplex virus type 1

Herpes simplex virus type 1 (HSV-1) replication produces large intracellular DNA molecules that appear to be in a head-to-tail concatemeric arrangement. We have previously suggested (A. Severini, A.R. Morgan, D.R. Tovell, and D.L.J. Tyrrell, Virology 200:428-435, 1994) that these DNA species may have a complex branched structure. We now provide direct evidence for the presence of branches in the high-molecular-weight DNA produced during HSV-1 replication. On neutral agarose two-dimensional gel electrophoresis, a technique that allows separation of branched restriction fragments from linear fragments, intracellular HSV-1 DNA produces arches characteristic of Y junctions (such as replication forks) and X junctions (such as merging replication forks or recombination intermediates). Branched structures were resolved by T7 phage endonuclease I (gene 3 endonuclease), an enzyme that specifically linearizes Y and X structures. Resolution was detected by the disappearance of the arches on two-dimensional gel electrophoresis. Branched structures were also visualized by electron microscopy. Molecules with a single Y junction were observed, as well as large tangles containing two or more consecutive Y junctions. We had previously shown that a restriction enzyme which cuts the HSV-1 genome once does not resolve the large structure of HSV-1 intracellular DNA on pulsed-field gel electrophoresis. We have confirmed that result by using sucrose gradient sedimentation, in which both undigested and digested replicative intermediates sediment to the bottom of the gradient. Taken together, our experiments show that the intracellular HSV-1 DNA is held together in a large complex by frequent branches that create a network of replicating molecules. The fact that most of these branches are Y structures suggests that the network is held together by frequent replication forks and that it resembles the replicative intermediates of bacteriophage T4. Our findings add complexity to the simple model of rolling-circle DNA replication, and they pose interesting questions as to how the network is formed and how it is resolved for packaging into progeny virions.

Polyurethane-coated, self-expandable biliary stent: an experimental study

RATIONALE AND OBJECTIVES

We describe a self-expanding metallic biliary Gianturco-Rösch stent coated with polymeric material. The coating was designed to prevent the growth of neoplastic and reactive tissue within the biliary ducts.

METHODS

The stents were coated with a solvent-casting technique, which consists of dissolving polyurethane (polyether urethane or polycarbonate urethane) pellets in a solvent (dimethylacetamide), dipping the stent in the solution, and completely evaporating the solvent. In vitro mechanical characterization of the stent was performed to determine the adhesion of the coating to the metallic cage, the best introducer caliber for implantation of the device, and the relationship between the stent's diameter and radial stress.

RESULTS

Reports in the literature on the biostability of polycarbonate urethane compared with polyether urethane prompted us to use the former material to coat the stents. The solvent technique gives a smooth internal surface of the stent wall, leaving in relief the coated structure of the stent on the external surface. The functional tests demonstrated that the coating did not compromise the original characteristics of the stent in terms of self-expandability, axial flexibility, and increased radial rigidity of the device.

CONCLUSION

Functional tests verified coating stability and device handling, which are the first steps toward in vivo experimentation.

Suprapubic cystotomy as treatment for severe hemorrhagic cystitis after bone marrow transplantation

We analyzed the success of suprapubic cystotomy in patients with severe hemorrhagic cystitis after bone marrow transplantation. Seventy-three out of 963 patients developed severe hemorrhagic cystitis which resulted in urinary tract obstruction after high-dose cytoreductive therapy. Eleven patients (15%) failed medical treatment and required emergency suprapubic cystotomy. Three of these patients died of other complications prior to resolution of HC. Of the remaining 8 patients who underwent surgery, 4 are alive. The mortality rate was significantly higher in patients who required surgery than in those who responded to medical therapy. Patients whose HC required surgery also had a greater transfusion requirement than those who responded to medical therapy. We conclude that surgical treatment of severe HC should be undertaken only after failure of medical therapy.

Mechanism of inhibition of duck hepatitis B virus polymerase by (-)-beta-L-2',3'-dideoxy-3'-thiacytidine

We have used the endogenous reverse transcriptase reaction of viral core particles from duck liver to elucidate the mechanism of inhibition of duck hepatitis B virus (DHBV) replication by the nucleoside analog (-)-beta-L-2',3'-dideoxy-3'-thiacytidine (3TC). As is the case in human immunodeficiency virus replication, 3TC-5'-triphosphate (3TC-TP) acts as a chain terminator for the DNA polymerase activities. The results of several different experiments support this conclusion, which explains the potent activity of 3TC against the hepadnaviruses. In isolated DHBV core particles, 3TC-TP inhibited the reverse transcriptase in a manner that resembled competitive inhibition with respect to dCTP. However, the kinetics of inhibition was not linear on a double-reciprocal plot for the highest concentrations of 3TC-TP and the lowest concentration of dCTP. This anomaly would be expected if binding to the nucleotide site was followed by DNA chain termination. Calculations that used only the linear part of the curve yielded a Ki of 0.78 +/- 0.10 microM 3TC-TP. The inhibition of core particles incubated in vitro with 3TC-TP was not reversed by removal of the free inhibitor. 3TC-TP inactivated the reverse transcriptase activity in a concentration-dependent manner. The Km of the chain termination reaction was calculated at 0.71 +/- 0.05 microM. Similar competitive kinetics and irreversible inhibition were also obtained on the endogenous DNA polymerase from viral particles from serum, suggesting that 3TC-TP also acts as a chain terminator of the DNA-directed DNA polymerase of DHBV replication.(ABSTRACT TRUNCATED AT 250 WORDS)

[Transcutaneous radiotherapy combined with low dose intraluminal brachytherapy in the treatment of non-operable neoplastic stenoses of the bile ducts]

Percutaneous biliary drainage is an excellent method to relieve the acute symptoms related to neoplastic stenoses of extrahepatic bile ducts. However, survival rates are low and the quality of life of these patients is poor. High dose irradiation--combined with external beams (ERT) and intraluminal brachytherapy (BRT) through percutaneous drainage--allows effective disease control and, therefore, not only higher survival rates but also a much better quality of life when drainage can be removed after bile duct stenosis resolution. March, 1990, through March, 1993, eleven patients (8 with extrahepatic cholangiocarcinomas and 3 with extrinsic tumors) were treated with combined ERT (40-60 Gy, 6-15 MV X-rays) and intraluminal BRT (6-25 Gy, 192Ir wire, LDR). In 8 patients the biliary stenosis was resolved, completely (CR) in 5 and partially (PR) in 3, as shown by posttreatment cholangiography. In 5 patients biliary drainage could be removed for an average 9 months' period; 3 of 11 patients did not respond to treatment at all (NR). Average overall survival was 14 months: 11 months for NR patients and 16.5 months for CR+PR patients. Treatment complications were acceptable: in two patients only treatment had to be discontinued, both during BRT. Two cases of high grade postirradiation stenosis were observed, both resolved with percutaneous cholangioplasthy.

[Use of safety catheter after removal of Kehr's tube in liver transplant patients]

The authors report on the use of a safety catheter when removing the T-tube in the patients with choledocho-choledochal biliary reconstruction after liver transplantation. After T-tube removal, bile may leak into the peritoneal cavity through the catheter insertion site in the biliary wall. Biliary peritonitis, bilomas, subhepatic collections may develop, which are difficult to treat in immunodepressed patients. The safety catheter is used to allow the external drainage of the biliary outflow, if present, and to prevent the complications due to bile collecting in the peritoneal cavity. Moreover, the catheter allows cholangiography and interventional procedures to be performed when necessary. A soft guidewire is inserted into the distal bile duct through the T-tube and pushed into the duodenum. After removing the T-tube, an 8.3-F all-purpose catheter (APD) is placed on the guidewire with the tip just outside the biliary wall. The APD is then connected to a drainage bag allowing the amount of bile eliminated daily to be checked. This maneuver was performed in 24 transplant recipients and the safety catheter correctly positioned in 22 of them (91.6%). The APD was removed 48 hours after insertion in 15 patients with no biliary leakage. In the remaining 7 patients the catheter was left in situ up to 8 days, since biliary leakage was observed (range: 50-400 ml/day). No early or late complications related to this technique were observed.

[Self-expanding metal stents in the treatment of neoplastic esophageal stenosis. The technic and preliminary results]

Self-expanding metal stents have been recently used for the treatment of neoplastic esophageal stenoses. In our series, nitinol Strecker stents were implanted in ten patients with malignant esophageal intrinsic or extrinsic strictures, as a definitive palliation. Thirteen stents in all were used: two stents were positioned in three patients to recanalize the esophagus. The prostheses could always be inserted in the treated patients and in all of them swallowing was markedly improved. No major early complications were observed after stent insertion. All the stents but one were patent until the patient's death. Two patients are alive and bearing well-functioning stents. Self-expanding metal stents are to be preferred to plastic endoscopic tubes because their caliber is smaller at the time of insertion and they do not require general anesthesia, as endoscopic tubes sometimes require. Moreover, their complication rate is lower for both early and late complications. Tumor ingrowth through the stent mesh with stent occlusion is the major pitfall of these prostheses, together with the impossibility to use them when esophageal fistulas are present: these limitations will be soon overcome when silicone-coated expandable stents are on the market.

Study of the structure of replicative intermediates of HSV-1 DNA by pulsed-field gel electrophoresis

DNA from HSV-1-infected cells was separated by pulsed-field gel electrophoresis into two virus-specific bands: one that migrated as the linear monomer genome (152 kb) and another that remained at the origin of the gel. The latter band contained the replicating HSV-1 DNA, as determined by pulse-labeling with [3H]thymidine. To investigate the structure of this "gel origin" DNA, we constructed a HSV-1 KOS mutant bearing a unique PacI restriction site (HSV-1 PAC1DTK). Partial digestion of gel origin PAC1DTK DNA at late times postinfection (24-48 hr) demonstrated the presence of linear concatemers on pulsed-field gel electrophoresis. Within each concatemer, the long (L) regions of adjacent monomer genomes were found in the two possible orientations. In addition, shorter-than-unit-size fragments that corresponded in size to the left end fragments of the viral genome were detected with the UL region in the two possible orientations. At early times postinfection (8-12 hr), digestion with PacI released only a trace of linear fragments, and most of the gel origin DNA did not migrate on pulsed-field gel electrophoresis. Multiple cuts with EcoRI (a restriction enzyme that cuts the HSV-1 KOS genome 12 times) were necessary to release linear fragments that migrated from the origin of the gel. These results indicate that replicative intermediates of HSV-1 DNA are linked in a large network that needs to be unraveled before packaging takes place. This network may be composed of linear molecules linked together by frequent recombination events or of products of a mode of replication other than simple rolling circle (e.g., theta replication).

[Digital fluorography in gastroenterological radiology]

The clinical value of two digital fluoroscopy systems not connected to a PACS was investigated and compared with that of conventional radiology. Some critical variables were considered: image intensifier diameter, image definition, examination time, acquisition speed, patient exposure and finally film consumption. The main problems in the use of the digital techniques consisted in the limited size of the examination fields, which was not big enough to demonstrate the whole colon during double contrast enema, and in the difficult representation of the actual size on the image printed on the laser films. Definition was considered as sufficient for GI examinations. The main advantages consisted in acquisition speed, allowing detailed examinations of cervical esophagus, cardias and fistulous tracts, reduced patient dose and finally the real time visualization of the acquired image on the TV monitor.

The outcome of cholangitis after percutaneous biliary drainage in neoplastic jaundice

The purpose of this paper is to evaluate factors affecting the outcome of cholangitis after PTBD in jaundiced cancer patients. Twenty nine patients with neoplastic jaundice (male/female ratio 13/16, median age 55 years) with full clinical data, were treated by PTBD and developed cholangitis at a median of 9 days later. Four patients (14%) died of biliary sepsis a median of one month after PTBD while the other 25 survived a median of 6 months, with one week median duration of cholangitis. The probability of the cholangitis resolving was analyzed by time to resolution and it was found that 50% and 100% of the recoveries occurred 5 and 9 months respectively from the onset of the complication. The series was analyzed to determine the role of several variables (disease/patient/treatment related) in the resolution of cholangitis. Only a low stricture site, a large initial drainage catheter (10F) and a temperature increase exceeding 39 degrees C were correlated with a positive outcome. We conclude that PTBD-related cholangitis has, in our experience, a good chance of cure, low mortality rate and satisfactory 6 months median survival.

[Percutaneous gastrostomy]

Percutaneous gastrostomy was developed over the last years as an alternative method to surgical and endoscopic procedures, either for enteral feeding or for drainage of secretions or fluid collections communicating with the upper gastrointestinal (GI) tract. January 1990 through January 1992, 15 percutaneous gastrostomies and 2 percutaneous jejunostomies were performed at the Gastroenterologic Radiology Division of INT, Milan, Italy. The catheters were always inserted under local anesthesia, generally using special gastrostomy sets. Catheter insertion was possible in all the patients who underwent the procedure: in 12 cases gastrostomy allowed enteral feeding till the patients died and in 1 case the catheter is still working. In 2 cases the procedure was performed for drainage of gastroenteric secretions and the catheter was left in situ as a definitive palliation. In 1 patient the catheter was removed after draining a collection due to an anastomotic fistula. No major complications were observed in 17 procedures. In our experience, the indication according to which percutaneous gastrostomies and jejunostomies were performed for enteral feeding was always affected by the presence of a stenosis, in the upper GI tract. Other indications to the procedure, for enteral feeding, are functional swallowing disorders. Finally, it must be emphasized that when tight stenoses of the upper GI tract are present, percutaneous gastrostomy is the sole alternative to surgery.

Diagnostic accuracy of the double-contrast enema for colonic polyps in patients with or without diverticular disease

The accuracy of the double-contrast enema for the diagnosis of polypoid lesions in the presence or absence of diverticula was evaluated by retrospectively reviewing the medical records of 202 patients subjected to examination and endoscopy. Analysis of the data on 215 polypoid lesions showed that (a) the diagnostic accuracy of the examination is not affected significantly by the presence of diverticula; (b) the sensitivity of the examination is highly dependent on the size of the polyps (smaller or larger than 0.5 cm) but not on the form (sessile or pedunculated); and (c) the positive predictive value is higher in patients without diverticula. The double-contrast enema was confirmed to be a valid method for the diagnosis of polypoid lesions.

[Prognostic factors after percutaneous transhepatic biliary drainage]

The authors reviewed the clinical charts and the radiographic files of 93 patients with obstructive jaundice--in 86 cases due to neoplasm--treated with PTBD. The test of differences from survival curves was used to identify the clinical parameters predictive of short survival after PTBD. The difference in survival curves was significant relative to serum indirect bilirubin (cut point: 7.6 mg%), to serum cholinesterase (cut point: 1290 mU/ml), to white blood cell counts (cut point: 8600/mm3), to blood urea nitrogen (BUN) levels (cut point: 60 mg%). Because of the marked negative prognostic value of high BUN levels, our data seem to indicate that PTBD should not be performed when severe renal insufficiency is present. Other parameters correlated with a short survival after PTBD were the histotype of metastasis (in comparison with the other ones), and large neoplastic volume (in comparison with a small and a medium ones). Through pre-PTBD radiological and laboratory data analysis, a group of patients can be selected in whom the procedure will increase neither well-being nor survival, as plotted against those patients who are likely to benefit from biliary drainage.

An assay for proteinases and their inhibitors based on DNA/ethidium bromide fluorescence

Proteinases and their inhibitors have become the subject of intense research interest recently, since they control a multitude of very important biological processes, from the development of lambda phage to hypertension in humans. We have developed a simple and sensitive assay for detecting the activity of proteinases and of their proteinase inhibitors. The assay is based on ethidium bromide fluorescence, according to the following principles: (i) Ethidium bromide increases its fluorescence by 25-fold when it intercalates between base pairs of double-stranded DNA. (ii) Histones prevent this large increase in fluorescence by binding with high affinity to DNA thus blocking ethidium bromide intercalation. (iii) A proteinase that digests histones will make more DNA available for ethidium bromide intercalation, thereby producing an increase of fluorescence. Proteinase activity can easily be determined, in the presence of a DNA/histone complex, from the rate of ethidium fluorescence increase. In contrast, activity of a proteinase inhibitor is quantitated by the inhibition of fluorescence gain in the presence of a known amount of proteinase. This assay is rapid, simple, inexpensive, and, at the same time, accurate and sensitive enough to allow quantitation of nanogram amounts of various broad-specificity proteinases and their inhibitors. We show some possible applications of the assay (i) in testing column fractions during protein purifications, (ii) quantitation of alpha 1-antitrypsin in human serum, and (iii) detection of proteinase activity in cell extracts.

Double contrast small bowel enema in a case of selective duodeno-jejunal amyloidosis

Double contrast small bowel enema in a patient with selective amyloidosis of the duodenum and jejunum revealed an unusual radiologic pattern, mimicking multiple polyposis. Many submucosal polypoid lesions, sessile or pedunculated, were scattered throughout the duodenum and proximal jejunum. The lesions had smooth borders and did not show any retraction at the base. Other typical radiologic patterns of intestinal amyloidosis described in the literature were not observed in the present case. Differential diagnosis from multiple polyposis and diffuse lymphoproliferative neoplastic diseases is discussed.

[Use of Severini's coaxial catheters in gastrointestinal interventional radiology]

The growing importance of gastrointestinal interventional radiology has led to the development of new instruments and materials for the different proposed purposes. The authors present a set consisting of two coaxial catheters which was created for percutaneous transhepatic biliary drainage (Severini set). Its easy handling, adaptability and tolerability make it a versatile instrument in the hands of interventional radiologists for positioning large-calibre catheter (9-14 F) in deep sites. Hereafter are reported the results in 29 patients treated with different therapeutic aims and the use of the set for different pathologies. The catheters allowed a complete resolution of the collections communicating with the gastrointestinal tract in 4 of 5 patients. The catheter was inserted as a feeding tube in 22 patients. Finally, it was used as a gastrostomy catheter in 2 patients. Neither early nor late complications due to insertion or use of this set were observed.

Interconversion of replication and recombination structures: implications for terminal repeats and concatemers

Replication and recombination structures can be interconverted by branch-migration. Using this simple concept a novel mechanism is proposed for generating concatemers through an initial single-strand DNA invasion into a duplex. Only DNAs with terminal repeats can form concatemers, and Herpes Simplex Virus DNA replication is considered in detail. The model is more parsimonious than other models such as Watson's for concatemer formation.