Comparison of a new type of polytetrafluoroethylene patch (Mycro Mesh) and polypropylene prosthesis (Marlex) for repair of abdominal wall defects.

Background: Two types of prosthetic material used for repairing hernial defects of the abdominal wall were compared: Mycro Mesh and Marlex. Mycro Mesh (MM) is a new polytetrafluoroethylene product of layered, microporous structure. Macroscopically, it presents regularly distributed, 2-mm orifices that perforate the biomaterial.

Modifications induced by atherogenic diet in the capacity of the arterial wall in rats to respond to surgical insult.

A study was made of events occurring in the arterial wall of the rat after administration of an atherogenic calcification-inducing diet and of vascular response in a model of combined metabolic aggression (atherogenic, calcification-inducing diet) and surgical aggression (adventitial resection). Female Sprague-Dawley rats were fed an atherogenic, calcification-inducing diet for 24 consecutive days, after which half the rats returned to standard diet (group I, n = 12) and the other half (group II) underwent resection of the adventitia on a segment of common iliac artery on day 25 before returning to standard diet. Normolipemic rats and rats that underwent adventitial resection without the atherogenic, calcification-inducing diet were used as the control groups.

Similarity in behavior of polytetrafluoroethylene (ePTFE) prostheses implanted into different interfaces.

The biomaterial ePTFE is widely used in the clinical environment for vascular replacement or bypass, as well as in the repair of tissue defects, especially those involving the abdominal wall. The objective of this study was to evaluate the healing response to ePTFE prostheses implanted into a circulatory interface and a tissue interface, each in a different animal species. For vascular implants, the Sprague-Dawley rat (n = 60) was used, while the New Zealand white rabbit (n = 20) was used in the tissue replacement model.

Hepatic resuscitation after warm anoxia: one approach for increasing the donor pool for liver transplantation.

The deleterious effects of warm anoxia on the liver are seen to be irreversible if cooling and transplantation (LT) follow immediately after. The aim of our study is to demonstrate that livers subjected to anoxia may be suitable for LT if a period of resuscitation is interposed before the cooling process. Forty female Large White pigs were used.

Cyclosporin A delays the presentation of intimal hyperplasia in an experimental model of arterial autograft.

A study was made of the effect of cyclosporin A on intimal hyperplasia in an experimental model of arterial autograft. Fifty female Sprague-Dawley rats weighing 250-300 g were employed. Using a microsurgical technique, an arterial autograft measuring approximately 5 mm in length was implanted in right common iliac artery.

Use of a fibroblastic matrix improves the results of mesothelial-cell seeding on vascular prostheses of polytetrafluoroethylene.

Mesothelial cells (MC) obtained from the human omentum are a good alternative to the use of endothelial cells (EC) as a covering for vascular prostheses of polytetrafluoroethylene (PTFE), given the antithrombogenic properties and good behavior in vitro of mesothelial cells. We studied the behaviour of mesothelial cells seeded on PTFE prostheses with an interposed fibroblastic matrix for seeding. The mesothelial cells were extracted from 30-40 g fragments of human omentum by enzymatic digestion with collagenase.

Assessment of cyclosporine A-induced ultrastructural changes in vascular wall using an experimental arterial autograft model.

The objective of this ultrastructural study was to assess the effects of cyclosporine A (CsA) in an experimental model of arterial autograft. Fifty female Sprague-Dawley rats weighing 250-300 g were employed. Using a microsurgical technique, an arterial autograft measuring approximately 5 mm in length was placed in the right common iliac artery.

Behavior of cryopreserved endothelial cells in different phases: their application in the seeding of vascular prostheses.

Various methods of cryopreservation of human endothelial cells (EC) were studied to determine their viability and behavior when seeded onto vascular prostheses made of polytetrafluoroethylene (PTFE). Three different protocols were used: (1) cyropreservation of whole umbilical vein, (2) cyropreservation of freshly extracted umbilical EC in suspension, and (3) cryopreservation of EC derived from a first subculture. Fresh EC and EC from a first subculture were used as controls.

Integration of biomaterials implanted into abdominal wall: process of scar formation and macrophage response.

The behaviour of two biomaterials polytetrafluoroethylene (PTFE) and polypropylene (PL) has been studied, focussing especially on the macrophage response to the implant, as well as on certain aspects of the process of scar formation. A total of 24 animals (white New Zealand rabbits) received prostheses implanted into the anterior abdominal wall in such a way as to involve every layer over an area of 7 cm x 5 cm. The interfaces formed with the visceral peritoneum, subcutaneous tissue layer and the recipient muscle-aponeurotic tissue were assessed.

Adhesion and stability of fibronectin on PTFE before and after seeding with normal and synchronized endothelial cells: in vitro study.

The possible influence of the cell cycle on the efficacy of endothelial cell (EC) seeding onto the surface of polytetrafluoroethylene (PTFE) prostheses was studied. Likewise the ideal fibronectin concentration and optimal incubation time to guarantee the binding of this protein to the prosthetic surface have been calculated. Synchronized ECs, previously labeled with 3H-thymidine, were used, and the loss of radioactivity was determined at several times throughout the study.

Arterial autografts and PTFE vascular microprostheses: similarities in the healing process.

A comparative study has been carried out dealing with the vascular healing process in two experimental vascular graft models to determine the differences or similarities between the two. One of the models consisted of the use of arterial autografts and the other of the implantation of vascular microprostheses of polytetrafluoroethylene (PTFE). The common iliac artery of female Sprague-Dawley rats was used.

Coatings for vascular prostheses: mesothelial cells express specific markers for muscle cells and have biological activity similar to that of endothelial cells.

The use of human omentum as an alternative to veins as a source of cells for seeding onto small-caliber vascular prostheses has awakened controversy as to the identification of the predominant cell type derived from this source. Mesothelial cells from omentum were extracted by collagenase digestion, and cultured until a monolayer was formed. These cells showed positivity for monoclonal antibodies specific for endothelial cells (anti-CD34 QBEND10), antibodies to intermediate filaments (anti-vimentin and anti-desmin) and anti-smooth muscle cell antibodies (anti-actin and anti-total actin).

Inhibition of the calcification of porcine valve tissue by selective lipid removal.

Since the development of cardiac prostheses, numerous chemical treatments have been assayed to prevent the process of their mineralization, causing 60% of the failures. The effect of the extraction of lipids from the tissue employed in porcine valves is assessed in a model of subcutaneous implantation in rats. Tissue from aortic and pulmonary porcine valves was treated with chloroform-methanol and 0.

Application of new coatings for vascular grafts based on polyacrylic systems with antiaggregating activity.

A study has been made of the behaviour of knitted and woven Dacron mesh used in the preparation of vascular grafts when coated with either a layer of poly(2-hydroxyethyl methacrylate) or co-polymers of 2-hydroxyethyl methacrylate with 5, 10 or 20 wt% of an acrylic derivative of salicylic acid, 2-methacryloyloxybenzoic acid. In vitro studies were carried out to quantify the loss of polymer under flow conditions, and ex vivo studies were done in dogs to quantify the deposition of 111In-oxine-labelled platelets. The treated materials showed a lesser deposition of platelet thrombi when compared with the control group.

Possible role of brown adipose tissue as a mediator during cyclosporine-A treatment.

Cyclosporine-A (CsA) is a potent immunosuppressor used successfully to control rejection in organ transplantation. According to the most recent evidence, this drug modifies the lipid metabolism of the patient, provoking a rise in the blood lipids, constituting an important risk factor for acceleration of the atherogenic process. Taking into account that brown adipose tissue (BAT) constitutes the major storage site for cholesterol and triglycerides in the rat, and given the apparent lack of references about the implications of CsA on this tissue in the literature, we proposed to study the possible morphological changes occurring in BAT following the administration of this drug.

Macrophage response to experimental implantation of polypropylene prostheses.

We have assessed the macrophage response to polypropylene mesh (Marlex) implanted into the abdominal wall of New Zealand white rabbits, using RAM-11, a monoclonal antibody specific for rabbit macrophages. The response diminishes during the course of the first 90 days after implantation, although the presence of other cell types typical of foreign-body reactions increases. We have also confirmed the high degree of integration of the biomaterial into the wall achieved after 9 weeks.

Endothelial cell seeding of polytetrafluoroethylene vascular prostheses coated with a fibroblastic matrix.

One of the most serious problems with endothelial cell (EC) seeding of prosthetic materials is the poor adhesion and stability of the cells. Although several substrates that improve the initial adhesion have been assayed, the EC are lost within a limited period of time. In this study we attempted to modify the hydrophobic conditions of expanded polytetrafluoroethylene (ePTFE) by treating it with ethanol prior to seeding.

Experimental neurocytomas.

Four ethyl-nitrosourea (ENU)-induced oligodendroglioma-like tumors of the rat showing large rosettes on haematoxylin-eosin stain were studied by means of immunohistochemistry and electron microscopy, and their features compared with six human intraventricular neurocytomas. The similarities between the experimental and human tumors studied support the hypothesis that most of the so-called ENU-induced oligodendrogliomas in the rat are primitive neuroectodermal tumors with the tendency to differentiate toward a neuronal phenotype, and also suggest that the ENU-model of neurocarcinogenesis is useful for the induction of experimental neurocytomas.

Lack of intimal hyperplasia response in an experimental model of non-endothelial vascular wall damage.

The endothelial and medial layers are generally presumed to play an important role in the appearance and development of intimal hyperplasia. We have carried out a short-, media- and long-term study of the morphological changes taking place in the common iliac artery of rats after surgical removal of the adventitial layer. Our aim has been to assess the likely role played by this layer in the development of intimal hyperplasia.

Seeding of expanded polytetrafluoroethylene (ePTFE) vascular grafts. A morphological study of porcine endothelial and fibroblast cells.

The need to improve clinical results with small and medium calibre grafts has led to extensive research on cell seeding of prosthetic materials. Numerous problems remain regarding identification, seeding, adhesion and survival of the cells attached. We have studied the behaviour of seedings of endothelial and fibroblast cells on ePTFE grafts.

Intimal thickening in arterial autografts. Role of the adventitial layer.

In the present work, the repairing response of the iliac arterial wall is studied after carrying out autografts in segments of these vessels. The formation of the intimal hyperplasia, which occurred in all the cases, was followed at the biochemical level (tritium thymidine incorporation) and with light and electron microscopy. The adventitial layer showed great activity during the repairing process.

Blood coagulation variations induced by carbon tetrachloride inhalation in Wistar rats.

Research into the development of chronic hepatic failure induced by CCl4 inhalation and the effect of this damage on blood coagulation was performed on Wistar rats. Exposure to CCl4 (325 ppm) consisted of the administration of 22, 26, 29, 31, 34, 39, 40, 45, and 49 doses, respectively. To determine and evaluate the nature and degree of CCl4-induced lesions at different stages of the treatment, histological alterations in liver samples were evaluated.

Influence of the conjoint administration of insulin and glucagon upon hepatic regeneration.

In noneviscerated rats, the influence of the conjoint administration of insulin and glucagon in the regenerative response triggered by 70 per cent hepatectomy using the incorporation of tritiated thymidine by nuclear deoxyribonucleic acid as a parameter has been demonstrated. The response was earlier and more intense in relation to animals not hormonally stimulated and stimulated only with glucagon (previously reported by us). Such a response has been comparatively greater both in the nonparenchymal cells and in the hepatocytes, especially in the latter, which are the main cause of the early peak of thymidine incorporation in the periportal zones indicating a greater regenerative activity than in the intermediate and centrolobular zones.