Biomedical subjects

N G Honduvilla

Publications and source records attributed to N G Honduvilla.

8 recordsLinked to original sources

PubMed2001

Optical aggregometry versus the PFA-100: experimental studies in pigs treated with propofol.

An experimental study of platelet aggregation was performed in 22 male Landrace x Large-White crossbred pigs treated with propofol at different doses, to compare the results of optical aggregometry with those of the PFA-100 (Dade Int., Miami, FL, USA), a new platelet function analyzer. Platelet aggregation was analyzed in basal blood samples by both methods, after which the pigs were divided into three groups: G1, anaesthetic induction with propofol (2 mg/kg intravenously (i.v.)); G2, anaesthetic induction with propofol (2 mg/kg i.v.), followed by a second dose of 1.5 mg/kg; and G3, anaesthetic induction with propofol (2 mg/kg i.v.), followed by 1 h of continuous i.v. infusion at 13 mg/kg/h. Four minutes after propofol injection, blood samples were again taken from each group and studied by both methods. In groups G2 and G3, both methods showed reduced platelet aggregation, while in group G1 neither evidenced an anti-aggregating effect of propofol. Under our experimental conditions: (1) the propofol effect on platelet aggregation depends on the plasma concentration; (2) the results obtained with the two methods are comparable; (3) PFA-100 may provide an alternative to optical aggregometry for detecting the effects of anaesthetic agents ex vivo.

Adenosine Diphosphate↗

PubMed1999

New resorbable polymeric systems with antithrombogenic activity.

The synthesis and application as resorbable coatings of vascular grafts of a new polyacrylic derivative of Triflusal (2-acetyloxy-4-trifluoromethyl)benzoic acid, a commercial drug with antithrombogenic properties, are described. The high-molecular-weight polyacrylic system is rather stable in physiological conditions and provides a chemical support for the slow release of the pharmacologically active compound, Triflusal, or its main metabolite (2-hydroxy-4-trifluoromethyl)benzoic acid (HTB). Experiments of deposition and retention of platelets in static basal conditions using plasma-rich medium from blood of sheep, seem to indicate that the polymeric coating of the polyacrylic derivative of Triflusal improves the antiaggregating character for platelets of the surface of small-diameter vascular grafts without the application of other antithrombogenic drugs.

Journal Article↗

PubMed1997

Study of biochemical substrate and role of metalloproteinases in fascia transversalis from hernial processes.

The aim of this study was to examine the fascia transversalis (FT) from patients with direct and indirect hernia in an attempt to identify possible differences between each type of hernia. FT samples were obtained from 36 patients presenting inguinal hernia (23 indirect hernia and 13 direct hernia) who underwent surgery. We have analysed the ultrastructure of the fascia surrounding the hernial lesions, the proline and lysine hydroxylation in the tissue, the type I-type III collagen ratio and the presence of metalloproteinases. We have not detected ultrastructural differences in the collagen fibrils from FT in direct and indirect hernias. However, the interfibrillar matrix was more abundant in direct hernias, showing abundant electron-dense particles. No differences in proline hydroxylation were observed between each type of hernia. A small decrease in lysine hydroxylation was detected in patients with direct hernia. Enzyme-linked immunosorbent assays (ELISAs) showed no statistically significant differences in the type I-type III collagen absorbance ratios. Immunohistochemistry revealed no differences in the expression of matrix metalloproteinase-1. FT from patients presenting direct hernia showed a very strong staining vs. metalloproteinase-2 when compared with that observed in indirect hernia.

Collagen↗

PubMed1996

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. Two groups were established: group I (control), consisting of 25 animals subjected only to arterial autograft, and group II (preoperative cyclosporin A), also consisting of 25 animals, which received a daily subcutaneous dose of 5 mg/kg cyclosporin A (Sandimmun, Sandoz) for 4 days before the surgical procedure. The animals were sacrificed on postoperative days 7, 14, 21, 30 or 50. Specimens were studied by optical microscopy, transmission and scanning electron microscopy, autoradiography, and morphometry. Endothelialization of the graft zone was slow in the cyclosporin-treated group. Hyperplasia was delayed notably, but at 30 days the hyperplastic process had improved and at 50 days it was similar to that of the control group. In the cyclosporin-treated group, thymidine was not taken up by the medial layer; the absence of medial thymidine uptake correlated with ultrastructural evidence of medial degeneration with lipid vacuolization of the smooth muscle cells and the presence of macrophages. These results suggest that cyclosporin A does not inhibit intimal hyperplasia but instead delays its occurrence, probably because of the drug's toxicity for smooth muscle cells.

Animals↗

PubMed1995

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. The viability and growth of these cells in culture media were studied, and basal prostacyclin levels were determined. The cells were assessed morphologically after they were seeded onto PTFE discs. Our results showed that the cryopreservation method that maintained the greatest viability was that in which previously cultured EC were used. Basal prostacyclin levels were significantly different following cyropreservation. However, when these cells were seeded onto PTFE discs their behavior was similar to that of fresh EC.

Blood Vessel Prosthesis↗

PubMed1995

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. The results showed a progressive loss of cells on the prosthetic surface similar to that occurring with the seeding of unsynchronized ECs. The optimal concentration of fibronectin was 20 micrograms/ml, and the optimal incubation time was 1 h.

Adsorption↗

PubMed1994

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. The length of the grafts in both models was 5 mm. A microsurgical technique was employed, and anticoagulant and antibiotic therapies were not used. The results were studied using light microscopy, transmission and scanning electron microscopies, autoradiography, and immunohistochemistry. A patency of 100% was obtained in the arterial autografts, and 87.6% in the PTFE implants. The histopathological findings were as follows: a) the mechanisms of immediate postgrafting response were similar, with marked presence of fibrin and platelet deposition in the form of a nonthrombogenic monolayer; b) a "neoadventitia" formed over the implant in both models; c) the endothelialisation was complete in both types of grafts 2 to 3 weeks after implantation; d) an intimal hyperplastic response appeared in both, although at different times (in the first week in the autografts and at one month with the PTFE); e) white cell accumulation was significantly greater on the PTFE luminal surface than on the autograft. The intimal hyperplasia was formed mainly by secretory myocytes in the autografts, while in the PTFE implants, fibrosis predominated.

Animals↗

PubMed1993

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. In addition, we created a fibroblastic matrix that was also fixed by ethanol to the prosthetic material. In vitro studies were carried out at intervals of 24 hours and 15 days after seeding. EC from umbilical cord vein and fibroblasts from skin were seeded onto disks of PTFE with a porosity of 30 microns. The results obtained show that treatment of ePTFE with ethanol prior to EC seeding modified its permeability, preventing cellular adhesion. The seeding of fibroblasts onto ePTFE allows a coating to form at 24 hours. The EC seeded onto this matrix adhere to it, forming a monolayer that persisted throughout the entire study period. The fibroblastic matrix allows the long-term survival of the EC on ePTFE.

Blood Vessel Prosthesis↗