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Results for “Fluorocarbon Polymers”

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At least 91 records · Page 5Linked to original sources
PubMed2002

Impact of rigid gas-permeable contact lens extended wear on corneal epithelial barrier function.

PURPOSE: To measure the effect of hypoxia and eye closure on epithelial permeability to fluorescein (P(dc)) during rigid lens extended wear (EW). METHODS: Central corneal thickness (CT) and P(dc) were measured in 42 subjects with an optical pachometer and automated scanning fluorophotometer, respectively. All subjects had been successfully wearing rigid gas-permeable (RGP) lenses on a 6-night EW regimen, and each individual was randomized to wear either medium- or high-oxygen-permeable (Dk) RGP lenses (two types of siloxane-fluorocarbon polymer lenses with Dk of 49 and 92). CT and P(dc) measurements were performed at an afternoon visit (baseline) and were repeated in the morning after 8 hours of overnight wear. Subjects slept with a patch over the right eye. The patch was not removed until immediately before the morning measurement. RESULTS: The mean overnight swelling response for subjects in the medium-Dk group was greater than that in the high-Dk group. Results of a paired t-test indicate that the eye wearing the medium-Dk lens with a patch overnight had a significant increase in epithelial permeability. Results of mixed-effect models suggest that eye closure and lens-induced hypoxia are significant factors in altering P(dc). CONCLUSIONS: The results indicate that corneal epithelial permeability increases with hypoxic dose and that epithelial barrier function is impaired by overnight rigid lens wear.

Adult↗
PubMed1975

Perfluoro compounds as artificial erythrocytes.

Some liquid perfluoro compounds dissolve relatively large amounts of oxygen and can be used in dispersed form as substitutes for erythrocytes. The commonly used perfluoro compounds contain about the same amount of oxygen as do equal volumes of erythrocytes when equilibrated with 100% oxygen. However, when equilibrated with alveolar air, the perfluoro compounds contain much less oxygen than erythrocytes. The dispersed fluorochemicals are adequate substitutes for perfusion of isolated preparations of mammalian brain, heart kidney, lung and liver. However, when put into the circulation of the intact animal, the dispersed fluorochemicals tends to produce lesions of the lungs, dilation of the right heart, and ultimately fatal hypoxia. It is suggested that the course of events following intravenous injection of dispersed fluorochemical is initiated by an interaction of the perfluoro particles with blood platelets or blood clotting factors. The ensuing intravascular clotting could then cause the changes in the lungs which lead to a marked increase in pulmonary artery pressure and dilation of the right heart. These events would terminate in fatal hypoxia due to pulmonary pathology and heart failure.

Animals↗
PubMed1976

The effect of myocardial infarction on the cardiac sensitization potential of certain halocarbons.

We have previously shown that many halocarbons and hydrocarbons are capable of producing cardiac sensitization. Briefly, the test method involved exposure of healthy, unanesthetized, beagle dogs to various inspired levels of sensitizing agent, followed by an intravenous dose (8 mug/kg) of epinephrine. Along, this epinephrine dose produces only mild ECG alterations, but, at threshold levels of a sensitizing agent, may induce a serious cardiac arrhythmia and sometimes death. Using the same test protocol, dogs with experimentally-induced myocardial infarctions were used to determine whether this type of heart condition might significantly lower the threshold for cardiac sensitization. Test results on three halocarbons showed no greater potential for cardiac sensitization among dogs having recovered from myocardial infarction as compared to normal, healthy animals.

Animals↗
PubMed1975

[Action of the fluorocarbons, 12 (difluorodichloromethane) and 11 (monofluorotrichloromethane), on smooth muscle].

We have studied the action of difluorodichloromethane (F12) and monofluorotrichloromethane (F11) on the rat isolated uterine muscle and the rabbit isolated duodenum. Both gases in the nutritive solution after the functioning of these organs in a way which is, moreover, non identical. On the uterus both gases show an inhibitory effect against the spontaneous contractions. On the duodenum, both gases inhibit the phasic contractions but the basal tonus is strongly increased by F12, and on the contrary reduced by F11. The action is a musculotrop one and quite reversible in every case. Both gases do not modify the action of acetylcholin, epinephrin and histamin.

Acetylcholine↗
PubMed1975

Fluorocarbon emulsions and cerebral microcirculation.

Mice were exchange transfused with a fluorocarbon emulsion (FC-80). Their hemotocrits were reduced to levels of 10-15. They were examined within 1 hour of completion of normal or slightly accelerated in the majority of the mice. Acceleration may have been due to reduced "blood" viscosity. All mice with normal or reduced transit times displayed reversible increases in brain NADH levels when they were exposed to room air or 100% N-2 for brief periods, rather than to the atmosphere of 100%O-2 used to support life in these mice. A small group of mice with prolonged fluorescein transit tended to display NADH levels that failed to rise when O-2 was reduced in the inspired air. In this small subgroup, microcirculatory failure had apparently produced anoxia and maximal NADH levels even before the supply of inhaled O-2 was reduced. Many FC-80 mice displayed reversible decreases in brain pO-2 levels when inspired O-2 was reduced. Pentylenetetrazol activated the EEG of FC-80 mice. The EEG activity was reversibly reduced when the animals were briefly exposed to room air or N-2. These data suggest that fluorocarbon emulsions can support brain microcirculation, oxygenation, and electrical activity in vivo, a result which is consonant with the observations of others who have performed in vitro experiments, or observed long-term survival.

Animals↗
PubMed1985

[Vascularization and resorption of different supporting tissues by the greater omentum in the formation of compound microvascular transplants].

In former investigations the author described the use of omentum majus in building microsurgical compound island flaps employing supporting tissue. Now different kinds of hard tissue, such as autogenous bone and cartilage, allogenous bone and cartilage (preserved by Cialit-solution), Teflon-Fluorocarbon Polymer (Proplast) and tri-calcium phosphate were presented in omentum-sandwich flaps in a histological investigation. We paid special attention to resorption and vascularisation of hard tissue. Allogenous cartilage grafts or artificial materials like Proplast were the most suitable to put into a compound omental island flap. There was good vascularisation with no resorption, especially with Proplast.

Animals↗
PubMed1988

"Proplast" for keratoprosthesis.

'Proplast,' a Teflon fluorocarbon polymer and carbon fiber composite, was used as support for a polymethyl-methacrylate cylinder in a keratoprosthesis that was implanted in rabbit corneas with successful retention for up to 3 years.

Animals↗
PubMed1980

The acceptance of a vitreous carbon alloplastic material, Proplast, in the rabbit eye.

Proplast, a vitreous, carbon-Teflon, fluorocarbon polymer, was tested in rabbits for corneal tolerance and acceptance. Toxicity, vascularization, epithelialization, infection, and extrusion were studied clinically and histologically. Four techniques were used: implantation of irregular-shaped pieces of material in an interlamellar corneal pocket, lamellar graft implantation with one exposed surface, full-thickness corneal implants in a manner similar to penetrating keratoplasty, and full-thickness implants covered by a conjunctival flap. Results showed that Proplast allows fibrovascular ingrowth and stabilization without a significant foreign body response or encapsulation for a period of observation from 6 weeks to 4 months. Evidence of epithelial coverage and epithelial ingrowth was also found. Coverage of the Proplast with conjunctiva or corneal tissue was essential to prevent extrusion and infection.

Animals↗