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Biomedical subjects

P M Galletti

Publications and source records attributed to P M Galletti.

At least 19 recordsLinked to original sources
PubMed1997

Controlled delivery of therapeutics from microporous membranes. I. Fabrication and characterization of microporous polyurethane membranes containing polymeric microspheres.

This paper describes a process for the inclusion of polymer microspheres in microporous polyurethane tubes and membranes. These composites were fabricated via a spray, phase-inversion technique using Cardiothane 51, a medical grade polyurethane, and either spray-dried poly(D,L-lactide-co-glycolide 50:50) microspheres or commercially available fluorescent polystyrene-latex microspheres. Characterization of the polyurethane membranes was performed using Fouriertransform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, hydraulic permeability testing, scanning electron microscopy, and visible and fluorescence light microscopy. The results indicated the feasibility of layering microspheres throughout the microporous membrane or wall of the microporous tube, and the potential of such composite structures for local delivery of bioactive substances.

Blood Vessel Prosthesis↗
PubMed1994

Gas transport in the intracorporeal oxygenator with woven tubes.

The woven tubes membrane oxygenator is a suitable configuration for the intracorporeal membrane oxygenator because of a high gas exchange performance and a compact packing of tubing. In this study the oxygen transfer performance of woven tubes was evaluated by an in vitro experiment with an external perfusion mode; the blood flow is outside of the tubes in order to reveal the feasibility of designing the intravascular oxygenator (IVOX) by the woven tubes. The oxygen transfer efficiency of the external perfusion mode is superior to that with the internal perfusion mode because of the larger convective mixing effect on the external surface of the tubes. Thus the use of the external perfusion mode results in the shorter necessary tube length for the rated condition, which enables making the oxygenator unit more compact. All of these features encourage the adoption of the woven tubes for use in the intravascular oxygenator.

Animals↗
PubMed1993

Cardiopulmonary bypass: a historical perspective.

Cardiopulmonary bypass in the clinical setting is barely 40 years old. Yet worldwide, it is used in the operating room in more than 500,000 cases a year. This broad acceptance is a tribute to the vision of gifted investigators who could see beyond the mere technical problems of perfused isolated organs. They integrated mechanical concepts, knowledge of materials, and sheer inventiveness with an appreciation of physiological issues to address the clinical needs of open-heart surgery.

Cardiac Surgical Procedures↗
PubMed1993

Very small-diameter polyurethane vascular prostheses with rapid endothelialization for coronary artery bypass grafting.

Two types of spongy polyurethane-polydimethylsiloxane blend (Cardiothane 51, Kontron Instruments, Inc., Everett, Mass.) vascular grafts with an internal diameter of 1.5 mm were fabricated by a spray, phase-inversion technique. Low-porosity grafts with hydraulic permeability of 2.7 +/- 0.4 ml/min per square centimeter and medium-porosity grafts with hydraulic permeability of 39 +/- 8 ml/min per square centimeter displayed good handling properties and suturability. Twelve straight low-porosity grafts, 17 straight medium-porosity grafts (1.5 to 2.0 cm in length), and one loop medium-porosity graft (10 cm in length) were implanted by the same surgeon end to end in the infrarenal aorta of 30 male Sprague-Dawley rats. Three months after implantation, patency was 8% for low-porosity grafts (1/12) and 76% for straight medium-porosity grafts (13/17). The loop medium-porosity graft was also patent. The sole patent low-porosity graft showed neointimal hyperplasia and incomplete endothelialization. All but one of the patent straight medium-porosity grafts showed a glistening and transparent neointima with complete endothelialization and no anastomotic hyperplasia. The loop medium-porosity graft displayed endothelialization from each anastomosis and in many islands in the middle portion of the graft, totalling 47% of the luminal surface by morphometric analysis. Thick mural thrombus, anastomotic hyperplasia, or aneurysm formation were not observed in any patent medium-porosity graft. These data indicate that in the rat aortic replacement model it is possible to achieve patency and a high degree of endothelialization in very small-diameter prostheses of appropriate porosity.

Animals↗
PubMed1992

Bioartificial organs.

Bioartificial organs combine the physical aspects of implantable prostheses with the biological advantages of organ transplantation. Enclosing live cells in a permselective, synthetic envelope avoids rejection by an immunoincompatible host while the geometric limitation of the closed polymer capsule prevents overgrowth of the transplanted material. As a tenet bioartificial organs widen the range of therapeutics based on the biological activity of cell transplants and open an alternative path to gene therapy.

Animals↗
PubMed1991

Development of small-diameter vascular prostheses which release bioactive agents.

A porous, distensible, tubular membrane which incorporates albumin and basic Fibroblast Growth Factor (bFGF), and is potentially utilizable as a bioactive small-diameter vascular prosthesis, was fabricated by a combined spraying, phase-inversion technique using a suspension of albumin and bFGF into a polyetherurethane-urea (Biomer) solution in dimethylacetamide (DMA). Scanning electron microscopy showed a material with an open-cell trabecular structure and small particles of albumin and/or bFGF entrapped in the bulk of the polyurethane trabeculae. The material released albumin and bFGF at an approximately constant rate for at least 2 weeks. The bFGF initially incorporated in the polymer remained biologically active as shown by in-vitro proliferation of human endothelial cells.

Albumins↗
PubMed1991

Gas transport in serpentine microporous tubes under steady and pulsatile blood flow conditions.

A serpentine gas exchange unit was built with cylindrical tubular microporous membranes featuring periodic arcs with a fixed curvature ratio (ratio of tube radius to radius of curvature) of 1/14 and circular angles between 30 and 360 deg. Oxygen transfer was measured under steady and pulsatile blood flow conditions in vitro and ex vivo to assess the design features which most effectively augment gas transfer. Under steady blood flow conditions, oxygen transfer increased with circular angles beyond 70 deg. Under pulsatile conditions, a wide range of geometrical and fluid mechanical parameters could be combined to enhance gas transfer performance, which eventually depended upon the secondary Reynolds number and the Womersley parameter.

Animals↗
PubMed1991

Bionic organs.

When a lizard loses its tail, a new caudal appendage soon grows to replace the one that is missing. But when a human loses a kidney, severs a peripheral nerve or worse, the spinal cord, that organ is lost forever. Such at least is conventional thinking. But imagine that the victim of an industrial accident with a paralyzed hand could achieve new levels of function by inducing axonal regrowth through a synthetic nerve guidance channel; or that a Parkinsonian patient's symptoms could be relieved by implanting in his brain neural tissue encased in a selectively permeable polymer envelope; or that the inexorable progression of the vascular complications of juvenile diabetes could be stopped, even reversed, by a membrane-protected xenograft of insulin-producing tissue. This is the dream of bionic organ science. It is predicated on two lines of technological achievement: the availability of ultra-thin, biocompatible, selectively permeable polymer membranes which can protect a transplant against immune rejection while allowing solute exchange between the graft and its environment; and the synthesis of novel materials, some biostable, some bioresorbable, which can serve as scaffolding or anchor for tissue regrowth in the geometrically and chemically controlled environment of an implant. The fabrication, growth and survival of composites of living tissues with synthetic polymers, often enhanced by the incorporation of specific cell growth factors or inhibitors, has been demonstrated at the tissue culture level, and extended in vivo to experimental models of human endocrine deficiency or neurological defects. The key to progress with bioartificial organs is the confluence of knowledge ranging from materials science to cell and molecular biology to experimental surgery. Obstacles to clinical implementation of this new therapeutic concept include: large scale procurement of specific tissue structures or isolated postmitotic cells from animal sources; demonstration of safety and efficacy of spontaneously occurring, bioactive tumor cell lines; verification of long-term stability and bio-acceptance of polymer implants; and industrialization of the fabrication process to meet quality control, shelf-life and commercial distribution requirements.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Effects of attachment substrates on the growth and differentiation of LLC-PK1 cells.

The growth and differentiation of an established renal epithelial cell line, LLC-PK1, on membrane bound mussel adhesive protein (MAP), collagen, and extracellular matrix (ECM) in serum-containing medium was studied. Cell attachment and growth on uncoated- vs. protein-coated cellulose nitrate and acetate membranes did not differ significantly, and confluence was achieved on all membranes. However, cells remained in a single monolayer only when plated on collagen or ECM. LLC-PK1 monolayers grown on ECM-coated membranes displayed the highest transepithelial D-glucose transport (333 +/- 22 ng.cm-2.min-1) whereas cells plated on collagen-coated membranes displayed the lowest (94 +/- 23 ng.cm-2.min-1). Glucose flux values increased with age of the culture, reaching a plateau at 28 d postseeding. These results indicate that the underlying substratum and cell age can affect differentiation of renal epithelial cells in vitro.

Aging↗
PubMed1989

Brain tissue reaction to permselective polymer capsules.

The brain tissue reaction to permselective polymer capsules implanted in rats was evaluated for 1 to 54 weeks. The polymer capsules were well tolerated in all animals and no recognizable neurological or behavioral deficits were associated with the implants. Necrosis at the brain/polymer interface, as assessed with Nissl stain, was not observed. Foreign body giant cells were consistently absent. Immunocytochemically identified reactive neuroglial cells showed a remarkably low-grade tissue response to the synthetic material beyond the first 2 weeks of observation. Immunolabeled cortical neurons revealed conserved columnar arrays around the implants. Transmission electron microscopy showed a minimal degree of collagen deposition compared to implants in peripheral sites, and normal synapses within a few micrometers from the brain/polymer interface, supporting the prospect of biocompatible, immunoisolated xenografts in the central nervous system.

Acrylic Resins↗
PubMed1989

Tissue reaction to intraperitoneal polymer implants: species difference and effects of corticoid and doxorubicin.

The peritoneal cavity is a convenient site for implantation of encapsulated hormone-secreting tissue. However, host tissue organization around such implants may affect solute exchange and viability of the encapsulated tissue. The reaction to polyvinyl chloride acrylic copolymer capsules implanted in the peritoneal cavity of rats and mice was therefore studied. Some animals received a slow release dexamethasone pellet, others were pretreated with doxorubicin, in an attempt to minimize the tissue reaction. The tissue reaction was significantly thicker in rats than in mice at both 2 and 6 weeks after implantation. In rats, corticoids decreased significantly the thickness of the reactive layer as compared to control at all time points studied, but doxorubicin had no effect. The tissue reaction in mice was not significantly affected by corticoid treatment. In both species the thickness of the tissue reaction did not increase significantly between 2 and 6 weeks. At 3 days the tissue reaction consisted of an interrupted single layer of macrophages in mice, whereas in rats the reaction consisted of two or three layers of macrophages and polymorphonuclear cells. At both 2 and 6 weeks, several cell layers surrounded the implants: a single layer of macrophages lying along the polymer, a variable number of layers of fibroblasts interspersed with collagen fibrils (fewer in mice than in rats, and fewer in corticoid treated rats than control rats) and an outer monolayer of mesothelial cells. We conclude that the intensity of tissue reaction to polymer implants in the peritoneal cavity is species dependent and can be decreased by the administration of corticoids but not doxorubicin.

Adrenal Cortex Hormones↗
PubMed1988

Blind-ended semipermeable guidance channels support peripheral nerve regeneration in the absence of a distal nerve stump.

The presence of a distal nerve segment is considered to be essential for peripheral nerve regeneration through impermeable synthetic guidance channels. The use of a perm-selective material may provide a more appropriate regenerating environment by allowing solute exchange across the wall of the channel. We compared perm-selective acrylic copolymer (AC) channels with impermeable silicone elastomer (SE) channels in terms of regeneration in the absence of a distal nerve stump. Cohorts of 6 animals received AC and SE channels for either 4 or 8 weeks, with the distal end of the polymer tube left open in half of the animals, and plugged with the same polymer ('capped') in the other half. Capped and uncapped AC channels contained regenerated nerve cables which extended fully to the distal end of the channel, whereas capped SE channels contained only 1 mm long granulomatous tissue cables, and uncapped SE channels showed small cables with only a few myelinated axons. The nerve cables regenerated in uncapped AC channels were smaller and contained fewer myelinated axons than those observed in capped AC channels. Capped AC channels sleeved with a tight-fitting silicone tube to render them impermeable, showed no regenerated tissue within their lumen. The use of a perm-selective channel may have allowed the influx of nutrients and growth factors from the external environment while concentrating factors released by the proximal nerve stump.

Acrylic Resins↗
PubMed1988

Transplantation of neural tissue in polymer capsules.

Neural tissue reaction to permselective polymer capsules and the feasibility of encapsulated neural tissue transplantation were evaluated in a rat model for a period of 1-12 weeks. Polymer implants in the central nervous system were generally well tolerated. The brain reaction to the synthetic material was minimal and did not disturb normal brain architectonics. Embryonic mouse mesencephalon enclosed in a polymer capsule remained morphologically intact for at least 12 weeks in the parietal cortex of rats. We conclude that the immunoprotection provided by a permselective polymer membrane encapsulating neural tissue is compatible with diffusional exchange of nutrients and metabolites. Polymer encapsulation may provide an alternative for the problem of immunorejection in transplantation of neural tissues.

Animals↗