Expandable metal stents for the treatment of colonic obstruction: techniques and outcomes

Modulation of CD8(+) T-cell responses specific for an exogenous antigen by epitope variants would be advantageous to develop a novel means of antigen-specific immune regulation. We have analyzed CD8(+) T-cell responses to single amino acid-substituted variants of a peptide corresponding to residues 142-149 (p142-149; LAYFYPEL) of alphas1-casein, a major milk allergen, which is a dominant determinant restricted by H-2Kb. An analog peptide L142I with a substitution of Ile for Leu at the nonanchor N-terminal residue induced more IFN-gamma secretion than p142-149 from specific CD8(+) T cells. Furthermore, L142I could prime CD8(+) T cells more efficiently in vivo, and these L142I-primed cells secreted more IFN-gamma than p142-149-primed CD8(+) T cells upon stimulation with p142-149 in vitro. These findings are mainly explained by the greater ability of L142I to form stable Kb-peptide complexes. These findings indicate that appropriate analog peptides may be useful as efficient inducers of CD8(+) T cells which recognize the parent peptide and secrete IFN-gamma, a potent inhibitor of Th2-dependent events, including IgE production.     

Iliofemoral venous stenoses: effectiveness of treatment with metallic endovascular stents

PURPOSE: To assess effectiveness of metallic endovascular stents in treatment of venous stenoses and occlusions. MATERIALS AND METHODS: Stents were placed intravenously in 56 patients (59 stenoses or occlusions) over a 6-year period. Stent sites included the inferior vena cava (n = 10) and common iliac (n = 31), external iliac (n = 46), common femoral (n = 27), and superficial femoral veins (n = 4). Indications for stent placement included stenoses from pelvic malignancy and its treatment; trauma, surgery, or pregnancy; and idiopathic stenoses. Patients underwent anticoagulation therapy for 3-6 months after stent placement. Follow-up was performed with duplex ultrasound. RESULTS: With use of life-table analysis, overall primary and secondary 1-year patency rates were 50% and 81%, respectively. Primary and secondary 4-year patency rates were and 50% and 75%, respectively. Five patients died of primary disease progression within 6 months after stent placement. Major complications occurred in 6.8% of cases. One-year secondary patency rates were statistically significantly lower (P = .05) for patients with malignant disease, although primary patency rates were comparable. Overall sustained decrease in symptoms (P < .0001) was observed 1 year later. CONCLUSION: Endovascular stent placement is a nonsurgical alternative for reestablishment of venous flow and sustained relief of symptoms in patients with malignant or benign pelvic venous disease.     

Metal stents in patients with malignant and benign esophageal stenoses

The authors used between October 1993 and January 1997 in 131 patients with inoperable malignant or benign stenosis of the oesophagus an expansible metal stent. In 25 patients the stenosis was in the upper third of the oesophagus, in 44 in the medium part, in 53 in the lower third of the oesophagus and in 9 patients in the area of the anastomosis. All patients suffered at the time when the stent was introduced from marked dysphagia (stage 3-4 according to the international classification). In 45 patients the authors introduced more than one stent. 112 patients suffered from malignant stenosis (67 squamous cell carcinoma, 27 adenocarcinoma, 9 pulmonary or bronchogenic carcinoma, in two instances lymphoma, in two instances leiomyosarcoma and in five patients another type of tumour). Seventeen patients suffered from benign stenosis (8 complications of reflux oesophagitis, 3 stenosis in the anastomosis, in two instances corrosion by acid, 2 cases of epidermolysis bullosa oesophagi and one post-radiation stenosis). In these patients repeatedly before introduction of the stent dilatation of the stenosis by means of a balloon dilatation catheter was attempted. In two instances the etiology of the stenosis was obscure. Complications related to the procedure proper or after insertion of the stent were recorded in 49 patients-dislocation of the stent 23x, occlusion of the stent 17x, development of a fistula 6x, ulceration 16x, haemorrhage 4x, hyperplasia of the mucosa 21x, ileus 2x, inadequate expansion of the stent 8x.     

An endoscopic treatment method for postoperative stenoses

A 68-year-old-male was admitted to our hospital with the chief complaint of macrohematuria. He was diagnosed with malignant lymphoma at 63 years old. Cystoscopy and computerized tomography revealed a non-papillary and broad based tumor at the anterior wall of the urinary bladder and partial cystectomy was done. Pathological diagnosis was collision tumor between squamous cell carcinoma and malignant lymphoma. To our knowledge, this is the 13th case of collision tumor associated with genitourinary organs in the literature.     

Prolonged tracheal intubation in an infant with tracheomalacia secondary to a vascular ring. A useful adjunct to treatment?

We report a case in which the trachea of a 3-week-old infant with a double aortic arch and secondary tracheomalacia was intubated for nearly 10 months prior to tracheal surgery. Postoperatively no complications relating to surgery or intubation were seen.     

Palliative treatment of malignant esophageal stenosis: experience with plastic versus metal stents

BACKGROUND/AIMS: We report on the palliative treatment of 44 patients with malignant dysphagia by placement of plastic (Celestin tubes, n = 24) vs metal stents (Wall stents, Nitinol stents, Gianturco stents, n = 20). METHODOLOGY: Prior to stent insertion, esophageal stenosis was dilated stepwise to 16 mm (plastic tube) and to 10 mm (metal stent). RESULTS: Stent insertion was technically successful in all cases and led to a reduction of dysphagia. Risk of perforation was comparable in both groups (n = 1 in each group). Most of the plastic stents were placed when the tumor was localized in the proximal part of the esophagus close to the upper esophageal sphincter, when esophageal-bronchial fistula was present and in the risk of fistula development after radiation. During follow-up, tumor ingrowth (TI) and stent migration (SM) were the major complications. Whereas tumor ingrowth predominantly occurred in metal stents (TI after 6 weeks, 45% vs. SM, 10%) that required repeated argon beamer therapy, tube migration and bolus impaction (BI) often occurred in patients with plastic stents (TI, 0% vs. SM, 16%; BI, 4%). CONCLUSIONS: The findings of the study suggest that the decision whether plastic tubes or metal stents used should be taken individually considering tumor localization, axis deviation and the presence of esophago-respiratory fistulas. When stepwise dilation of malignant stenoses is performed carefully, perforation risk appears not to be different between placement of plastic prostheses and metal stents.     

Tissue compatibility and biodegradation of new absorbable stents for tracheal stabilization: an experimental study

Although visceral and cutaneous leishmaniasis are important clinical and public health problems worldwide, these diseases are not endemic in Singapore and the medical profession here has little opportunity to diagnose and manage these conditions. We report our experience with two patients with culture-proven visceral leishmaniasis and one with histologically-proven cutaneous leishmaniasis. The patients with kala-azar were migrant workers from countries in which the disease is endemic. The patient with proven cutaneous leishmaniasis (and another who was diagnosed to have the condition clinically) had entered the jungles of an endemic area. With increasing travel on the part of Singaporeans along less well-trodden paths to exotic destinations as well as the burgeoning traffic of migrant workers from less developed countries, doctors in Singapore will continue to see diseases such as leishmaniasis.     

Palliative treatment of malignant esophagorespiratory fistulas with Gianturco-Z stents. A prospective clinical trial and review of the literature on covered metal stents

OBJECTIVE: Esophagorespiratory fistulas, especially in the upper third of the esophagus, are a complication of malignant esophageal tumors, which are difficult to manage. The efficacy of polyurethane-covered, self-expanding metal stents for palliation of malignant esophagorespiratory fistulas was investigated prospectively. METHODS: Eleven patients with malignant esophagorespiratory fistulas resp. perforations were treated with Gianturco-Z stents. In five patients the lesion was located in the proximal part of the esophagus. Because of the fistula all patients suffered from dysphagia even for liquids. RESULTS: No technical problems during the implantation procedure of the stents occurred. In the control radiography with water-soluble contrast media, the fistulas were completely sealed in 10 of 11 patients. Therefore the dysphagia score improved from 3.0 to 0.6. Nearly all Gianturco-Z stents (10/11) showed a sufficient expansion within 24 h after placement. Severe early or late complications were not encountered, with the exception of tumor overgrowth in one patient about 9 months after stent placement. In five patients, short term (3-6 days) retrosternal pain was observed, and one patient complained of slight foreign body sensation. By August 1997 all 11 patients had died of advanced disease, with a median survival time of 121 days (range, 22-300 days). CONCLUSIONS: Gianturco-Z stents are highly effective for palliative treatment of esophagorespiratory fistula resp. perforations and have a low complication rate. Due to the fact that this stent shows no retraction during the release, a precise positioning is possible, especially in the case of tumors and fistulas in the upper third of the esophagus. It seems that use of the Gianturco-Z stent can be considered a good therapeutic method for palliative endoscopic treatment of this high risk patient group.     

Aortopexy as a surgical treatment method in infantile congenital tracheo-chondrohypoplasia and tracheomalacia

In 1994 we reported on a small series of 3 children with malignant, marker-positive pineal nongerminomatous germ cell tumors treated with a 'sandwich' protocol. Here, we report on the long-term survival of these children. Preoperative chemotherapy consisted of two courses of bleomycin, etoposide, and cisplatin. En bloc resection of the tumors via the supracerebellar, infratentorial route was performed immediately after decline of tumor marker levels. Postoperatively, two courses of vinblastine, ifosfamide, and cisplatin were applied, followed by craniospinal irradiation. The patients showed no major neurological deficits and no evidence (neuroradiologically or with regard to tumor marker levels) of recurrence of disease after 66, 71, and 78 months, respectively. We propose this regimen for children with tumors of the pineal region in whom the tumor markers are positive. It should be started without histological classification of the tumor to avoid possible spillage of malignant tumor cells to the cerebrospinal fluid.     

Comparison of tissue reactions in the tracheal mucosa surrounding a bioabsorbable and silicone airway stents

BACKGROUND: Treatment of tracheobronchial stenosis is problematic. Conservative methods include stenting the stenotic area, but an ideal stent has not yet been developed. Bioabsorbable airway stents offer benefits; the extraction of the device is unnecessary, and the airway preserves its normal function after stent resorption. The aim of this study was to examine the suitability of self-reinforced poly-L-lactide as a material for an airway stent. METHODS: A spiral airway stent made of 0.7-mm wire of self-reinforced poly-L-lactide was implanted operatively in 9 rabbits intratracheally; silicone stents served as controls. RESULTS: Silicone stents had a tendency to become stenosed with encrustation material and to develop a hyperplastic polyp at both ends. Self-reinforced poly-L-lactide stents were well tolerated and caused no foreign body reaction, and they had a tendency to penetrate into the tracheal wall. They had disappeared at the end of the follow-up of 10 months. CONCLUSIONS: This experimental study showed that bioabsorbable self-reinforced poly-L-lactide is a promising material for an airway stent for treatment of airway stenosis.     

Nitinol alloy endotracheal stent for treatment of tracheal stenosis

OBJECTIVE: To treat inoperable tracheal stenosis by using nitinol endotracheal stent and to solve some problems facing endotracheal stenting with other kinds of stents. METHODS: The stent was made of nitinol wire. It can be deformed to smaller size in iced water. With a self-made introducer, the stent was placed in the location of stenosis. After hot water was injected into the introducer, the stent resumed its original form and anchored there itself. RESULTS: Altogether, 5 patients with severe tracheal stenosis received this treatment. Dyspnea was relieved immediately after implantation of stents in all patients. Long-term follow-up also showed satisfactory results. CONCLUSION: Nitinol stent has some remarkable advantages as compared with other tracheal stents. It can be used as a new endoprosthesis in treating narrowed trachea.     

CO2 laser and Gianturco stent for endoscopic treatment of tracheal stenosis

Spectroscopic studies of antibody-antigen interactions can provide useful information about the interactive motifs and energetics involved in the intermolecular association process. In this study we used absorption spectroscopy to examine the interactions between five different monoclonal antibodies (mAb) and four superpotent ligand sweeteners. Quantitative changes in the absorption spectra in the wavelength range of 230-800 nm were utilized for the determination of intrinsic association constants and thermodynamic parameters of the mAb-ligand complexes. The intrinsic association constants for the mAb-ligand complexes were found to be in the range of 10(7)-10(5) lM-1 and were in agreement with previous radioimmunoassay determinations. For two mAb, qualitative changes in the spectra in the 340 nm range could be identified and were related to the presence of charge-transfer interaction between the guanidinium ligand and aromatic residues in the binding site of the mAb. A charge transfer spectra was observed in mAb NC10.8 with two different sweetener ligands. The thermodynamic parameters of the ligand-mAb interactions were analyzed by van't Hoff plots and in almost all cases the reactions were found to be enthalpically driven. The determinations of intrinsic affinity and thermodynamic parameters may be useful in computer-aided molecular modelling studies of the antibody binding pocket and predicted ligand docking orientations. Antibody NC6.8 was found to react with this set of sweetener ligands in a rank order that is related to their sweetness potencies and the spectroscopic findings for NC6.8 are in agreement with the X-ray diffraction data of the Fab-ligand crystal structures.(ABSTRACT TRUNCATED AT 250 WORDS)     

The use of urethral stents for the treatment of urethral strictures

Three types of urethral stents can be used in the treatment of recurrent strictures: Urolume/Wallstent is a self-expanding mesh which is incorporated into the urethral epithelium; the ASI Titanium stent is a short rigid mesh of Titanium wire which is also incorporated into the urethra; Nitinol is a flexible spring in one or two parts connected by a steel wire. It remains endoluminal. The Urolume/Wallstent has been used since 1987. It is indicated in iatrogenic strictures. No statistical results are presented. The ASI stent should be reserved for strictures of the prostatic and posterior urethra. The Niticol UroCoil system can be used at all levels of the urethra; two models are available: simple or twin. The author has inserted 65 stents in 56 patients. The stent was removed after one year in 41 patients. The use of these stents has considerably decreased the number of repeated dilatations and urethrotomies.     

Effect on intimal hyperplasia of dexamethasone released from coated metal stents compared with non-coated stents in canine femoral arteries

Previous studies suggest that esthetic Caucasian profiles exhibit fuller lips than the norm for their race, while esthetic African American profiles are similar to those of esthetic Caucasians. The present study was undertaken to compare the profiles of female Caucasian and African American models and their nonmodel counterparts. Four groups of 30 subjects were evaluated: Caucasian models [CM], Caucasian controls [CC], African American models [AM], and African American controls [AC]. The models' profiles were photographed from current fashion magazines, the photos were scanned, and 17 landmarks were digitized. Each profile was standardized for size and oriented along the N'-Sn' line on a Macintosh 6115CD computer. Control photographs were processed in a similar manner. Twenty-six variables were measured for each profile. Means, ranges, and standard deviations were computed along with unpaired, two-tailed Student's t-tests (p<0.05) to evaluate group differences. The results showed that for the AM and AC profiles, all but two of the 26 variable were similar. For the CM and CC profiles, eight variables demonstrated significant differences. Between-race comparisons demonstrated greater numbers of parameters that were significantly different: CM/AM with 18 and CM/AC, CC/AC, and CC/AM with 22 each. Most of the differences involved the lips. Vertical soft tissue proportions for the four groups did not follow a 40/20/40 ratio. Caucasian and African American models displayed significantly different profile characteristics. The African American models and controls showed similar profile features, whereas greater differences were observed between Caucasian models and controls. Based on our study, the African American profile currently presented in the mass media is not "Caucasian-like." In fact, it appears that Caucasian models display more ethnic features than African American models do Caucasian features, suggesting that previously held concepts of facial beauty may no longer apply.     

3-D simulation of metal forming processes with automatic mesh generation

The numerical simulation of industrial metal forming processes requires robust and feasible solution methods. In this context, any solution procedure must be able to handle three-dimensional problems with general contact conditions and severe deformations. The latter condition necessitates automatic mesh-generation abilities. At the same time, the simulation tool must be economical and user-friendly. In this paper, a solution procedure is introduced which is able to perform the numerical simulation of complex industrial metal forming processes without any interference. The procedure is based on the rigid-plastic finite element method and is primarily suited to the analysis of bulk metal-forming processes. To ensure a real automatic simulation, the numerical procedure is made robust by using Euler time integration, a Newton-Raphson solver which is coupled with a direct iteration solver, a linear contact algorithm and, finally, a completely automatic hexahedral mesh generation scheme. The method is implemented in the ANSI-C programming language. To demonstrate the effectiveness of the method an industrial application has been simulated: A spider produced from a cylindrical initial workpiece by cold radial-extrusion.