Biocompatibility studies of the Anaconda stent-graft and observations of nitinol corrosion resistance.

PURPOSE: To validate the deployment, in vivo performance, biostability, and healing capacity of the Anaconda self-expanding endoprosthesis in a canine aortic aneurysm model. METHODS: Aneurysms were surgically created in 12 dogs by sewing a woven polyester patch onto the anterior side of the thoracic or abdominal aorta. Anaconda prostheses were implanted transfemorally for prescheduled periods (1 or 3 months). Aneurysm exclusion and stent-graft patency were monitored angiographically. Healing was assessed with histological analysis and scanning electron microscopy (SEM). Textile analysis determined the physical and chemical stability of the woven polyester material, while the biostability of the nitinol wires was evaluated with SEM and spectroscopy. RESULTS: All prostheses were intact at explantation. After 1 month, endothelial-like cells were migrating in a discontinuous manner both proximally and distally over the internal collagenous pannus at the device-host boundary. After 3 months, endothelialization had reached the midsections of the devices, with a thicker collagenous internal capsule. Patches of endothelial-like cells were sharing the luminal surface with thrombotic deposits. However, the wall of the device at the level of the aneurysm was generally poorly healed, with multiple thrombi scattered irregularly over the luminal surface. The polyester fabric was intact except for some filaments that were ruptured adjacent to the sutures and some abrasion caused by the nitinol wires. No evidence of corrosion was found on the nitinol stents. CONCLUSIONS: This Anaconda stent-graft has demonstrated its ability to exclude arterial aneurysms. The device used in this study was an experimental prototype, and the manufacturer has incorporated new immobilization features into the model for clinical use. The constituent materials appear to be suitable in terms of biocompatibility, biofunctionality, and short-term durability.     

Structural variations of DNA + Mn2+ complexes during helix-coil transition

The helix-coil transition in Phage T2 DNA in the presence of 6,4 · 10^?3 mol/l Mn²⁺ is studied using light scattering and UV spectroscopy. The transition range is about 0,5°C. Near the temperature of the end of melting T_f the molecular weight M_w and the radius of gyration R_z of the complex are observed to decrease to about one half. At a temperature 0,1–0,25°C higher than T_f, M_w and R_z pass through a minimum, which implies that aggregation is preceded by unwinding of DNA strands. Thus, rise in temperature rather than Mn²⁺ -induced aggregation causes DNA + Mn²⁺ melting.     

Morphologic changes in the walls of the internal saphenous vein used as an arterial bypass]

Long saphenous vein (LSV) is considered an optimal plastic material for arterial reconstructions in revascularization of the myocardium and in the femoral-popliteal segment. The authors analyze the results from the investigation of the operation material from 12 patients with obliterating atherosclerosis of the lower limbs in which reversed LSV has been previously used for arterial bypass grafts. Material is taken during the second operation performed between two days and 18 months after the first reconstruction. In the early period after LSV implantation into the arterial blood flow there is a prevalence of destructive alterations which are mainly manifested in the intima and internal layers of the media. In later periods a massive layer is formed growing into the venous vascular lumen designated as "néo-intima". Investigations of its structure and of mechanisms of its formation could enable the regulation of this process by clinicists.     

Effect of nimodipine in treatment of experimental focal cerebral ischaemia

Abstract

Despite the voluminous current literature the potential of nimodipine to modify the outcome in experimental cerebral ischaemia remains a controversial matter. The authors have evaluated in controlled double blind experiments the influence of a continuous i.v. infusion of the drug (1 ¼g kg^-1 min^-1) upon infarct size, histopathology and neurological outcome in rats with permanent middle cerebral artery (MCA) occlusion. The infusion was started 20 min before induction of ischaemia and continued 4 hours thereafter. The nimodipine treated animals were subdivided into hypotensive (MABP lower than 85 mmHg for more than 5 min after arterial occlusion) and normotensive groups. Infarction size, documented by TTC, H&E and Nissl staining was significantly smaller (p < 0.001) in nimodipine normotonic rats than the lesions in placebo and saline treated ratsas well compared with hypotonic nimodipine animals (largest infarction). These differences were found to be entirely at the expense of the cortical (frontoparietal) component of the lesion, suggesting ‘penumbra’ action of the drug. Moreover, nimodipine normotonic rats displayed lower cortical neuronal injury in the periinfarct zone. These findings were corroborated by corresponding better neurological scores. Our results indicate that nimodipine is effective in reducing focal cerebral ischaemia, provided the MABP is maintained higher than 85 mmHg.     

Some possibilities for application of "Pfizer" medicines--Prostin 15m, Prostin E2, Prepidil gel, Dostinex, Synarel--in the obstetrician practice

The authors make a clinical and pharmacological overview of the possibilities of application in the obstetrician practice of part of the medicines of the company Pfiser. Some of these medicines have no analogue in Bulgaria--i.e. Prostin 15M. The authors outline the advantages of the Pfiser medicines in comparison with other medicines with similar action.     

Pharyngo-esophageal reconstruction using pectoralis major cutaneous muscular flap after total laryngopharyngectomy

Using the pectoralis major myocutaneous flap is a good opportunity for one-stage reconstruction of the removed hypopharynx after total laryngopharyngectomy. The authors share their experience with five patients who underwent this kind of operation for T4 cancer of the hypopharynx and discuss their results.     

Extra-neoplastic epithelial changes in cancer of the vulva

A retrospective morphological research is made on the material of 78 cases from vulva for a three years period of time. They are identified 35 cases with invasive carcinoma, 2 c. with noninvasive carcinoma, 19 c. with vulvar dystrophia and squamous intraepithelial neoplasia (VIN). The invasive carcinomas are divided: keratinizing squamous cell carcinoma--31 c.; nonkeratinizing squamous cell carcinoma--3 c; adenoid squamous cell carcinoma--1. In all operated patients are examined the changes in the tissues surrounding the tumor and in the underlying tissue. They are divided in: lichen sclerosus, squamous cell hyperplasia, mixed dystrophia and squamous intraepithelial neoplasia. The morphological variants of squamous carcinoma, the epithelial changes and the patient's age are paralleled.