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PubMed1975

Thermodynamic aspect of the interaction of dichlorotetrafluoroethane with bovine albumin-1.

Binding of dichlorotetrafluoroethane (F 114) with bovine albumin was studied at 37, 20.5 and 5 C. It was found that at the total concentration of 0.4 x 10-3 M of F 114 in the 5-percent protein solution, 50, 51 and 55% of them, respectively, were in bound form at the temperatures indicated above. The termodynamic data found for the F 114-bovine albumin interaction in the temperature range studied were: deltaG = -3.44 to -4.11 Kcal/mol. deltaS =20.40 to 20.45 e.u., and deltaH =2.23 Kcal/mol. It is postulated that the large positive entropic change associated with a sizable positive enthalpy change indicates that the breaking of iceberg water stucture and slight unfolding of albumin molecule are involved in the interaction.

Aerosol Propellants↗
PubMed2003

Constitutive model development and micro-structural topology optimisation for nafion hydrogel membranes with ionic clustering.

The deployment of electroactive ionic polymer hydrogel-metal composites in artificial muscle and BioMEMS applications has recently been intensively investigated. In order to analyse their electromechanical responses to externally applied electrical fields, it is critical to develop a constitutive model linking the macro-mechanical moduli with the micro-mechanical characteristics, and to determine the geometric size and shape of the micro-structural cluster and investigate the effect of cluster morphology on the effective electro-elastic moduli of the polymer hydrogels. As a typical ionic polymer-based hydrogel, the Nafion membrane is studied in this work. Based on the Biot poroelasticity theory, a multi-scale constitutive model which includes both macro and micro characteristics is developed using an asymptotic homogenisation method. The effect of water-volume fraction on the effective elastic moduli of the hydrogel membrane is examined for different equivalent weights. Numerical investigations show that the simulated effective constitutive moduli agree well with experimental data. The presently developed constitutive model is thus validated. In order to determine the micro-structural shape of the polymer skeleton subject to fluid pressure, a representative volume element (RVE) is designed by topology optimisation of the periodic microstructures of the Nafion hydrogels, through the minimisation of the electro-elastic interaction energy between the polymer-based fluorocarbon matrix and the surrounding fluid. This optimal RVE correctly predicts the geometric shapes of the clusters.

Compressive Strength↗
PubMed2002

Genistein attenuates postischemic depressed myocardial function by increasing myofilament Ca2+ sensitivity in rat myocardium.

The present study investigated whether genistein, a broad-spectrum tyrosine kinase inhibitor, could increase the myofilament Ca(2+) sensitivity and partially reverse postischemic depressed myocardial function. Left ventricular papillary muscles were isolated from adult Wistar rats and loaded with the Ca2+ indicator, aequorin. The use of fluorocarbon immersion with hypoxia simulated a model of ischemia. Myofilament responsiveness to Ca2+ was evaluated from force-[Ca2+]i relationship recorded during tetani in papillary muscles. Protein levels of troponin I (TnI) were measured in postischemic papillary muscles with the Western blot technique. Isometric contraction was depressed during the period of ischemia and remained low after 60 min of reoxygenation without a corresponding significant change of peak [Ca2+]i in the control group (n = 7). In contrast, the depression of isometric contraction was ameliorated during ischemia in muscle preparations in the presence of genistein (2 micro M; n = 8), and postischemic depressed myocardial contractility partially recovered after a 60-min reperfusion. The myofilament Ca2+ responsiveness was significantly increased in papillary muscles in the presence of genistein. Protein levels of TnI were reduced in postischemic papillary muscles, whereas genistein partially restored decreased protein levels of TnI. Our results reveal that genistein produces an effective attenuation of postischemic depressed myocardial function and improves myofibrillar Ca2+ responsiveness in rat myocardium.

Actin Cytoskeleton↗
PubMed1976

Gaseous exchange and acid-base balance in premature lambs during liquid ventilation since birth.

Nine distressed premature lambs were studied before, during, and after ventilation with fluorocarbon liquid (FC-80). It was found that premature lambs, delivered by cesarean section, could be adequately ventilated with oxygenated liquid for period up to 3 hr. Using fluarocarbon liquid in conjunction with the described liquid breathing system, it was possible to maintain remarkably good pulmonary gas exchange and acid-base balance during normothermic conditions. In addition, peak intratracheal pressures measured during recovery from liquid ventilation were significanly reduced (P is less than 0.001) as compared with preliquid ventilation values. This improvement in lung function is in direct contrast to the deterioration in that of the adult animal following liquid ventilation as reported previously.

Acid-Base Equilibrium↗
PubMed1977

Frontal sinus trauma: experimental reconstruction with proplast.

Trauma has become the most common pathologic entity requiring operative intervention in the frontal sinus. Treatment has evolved from simple open drainage to ablation with reconstruction at a later date. Methyl-methacrylate, currently the most widely used alloplastic material, has inherent disadvantages such as two-stage reconstruction, difficulty in handling and molding, and susceptibility to trauma. The present investigation evaluates Proplast, a biocompatible Teflon fluorocarbon polymer implant, in one and two-stage frontal reconstruction following traumatic defects to the canine frontal sinus. Following the loss of anterior or posterior frontal bone, Proplast provided excellent cosmetic reconstruction over a period of one year. Resistance to infection was good, reaction with dura and brain was absent, and cerebrospinal fluid leaks sealed rapidly. In contrast to other alloplastic materials, rapid vascularization and collagen ingrowth lead to stabilization rather than sequestration. Several advantages over alloplastic and metallic implants may give Proplast a unique potential in operative cranioplasty.

Animals↗
PubMed1980

The use of synthetic implant material in osteoplastic frontal sinusotomy.

The use of homologous fat in obliterating frontal sinus operations has proved to be a satisfactory technique. It does entail, however, a separate procedure to obtain the graft. Furthermore, the implanted fat has a tendency to shrink or absorb in varying degrees. Proplast has been used in a series of osteoplastic frontal sinus operations. The implant block is a highly porous preparation of Teflon fluorocarbon polymer and vitrous carbon fibers. It can be easily carved into desired shapes or it may be implanted in peices. The porosity of the substance permits in-growth of connective tissue. Eight obliterating frontal sinus procedures using the osteoplastic flap technique and implanting the synthetic material are reported. There have been no failures to date after 1 to 5 years follow-up.

Adult↗
PubMed2006

Replication of continuous-profiled micro-optical elements for silicon integration.

A novel scheme for the integration of diffractive optical elements onto silicon is presented. The processing is made in reverse order, meaning that the process of structuring the optical elements on the wafer precedes the silicon microstructuring. The first processing step on the wafer is the hot embossing of the optical microstructures into an amorphous fluorocarbon polymer spin coated on the wafer. The cured polymer forms a highly stable material with excellent optical properties. The remaining silicon processing is thus performed with the diffractive optical elements already in place. Two different diffractive structures were used in the development of the method-a (Fresnel) lens with a rather low f-number and a diffractive element producing a fan-out of a large number of paraxial beams.

Journal Article↗
PubMed1976

Liquid ventilation of primates.

Three adult monkeys were anesthetized with ketamine and ventilated with fluorocarbon liquid [perfluoro bis (1, 4-isopropoxy) butane (Caroxin-D)] at 1 atmosphere on two separate occasions. During five runs, liquid ventilation was continued for 60 minutes. The sixth run was continued for ten minutes. Arterial blood gas levels during and after liquid ventilation were adequate for survival. Three years after the first period of liquid ventilation, the animals were killed. Approximately 0.001 mg of fluorocarbon per gram of tissue was present in the kidney, liver, brain, spleen, muscle, and heart. Fat contained approximately seven to nine times this amount, and the lung and pulmonary lymph nodes contained approximately 1,000 times this amount. In no case was it clinically evident that the monkeys had undergone periods of liquid ventilation. We conclude that primates can be ventilated successfully with liquid fluorocarbon on at least two separate occasions and can return to breathing air without obvious deleterious effects, but fluorocarbon is retained in small amounts for at least three years.

Adipose Tissue↗
PubMed1975

The effect of fluorocarbon FC 43 on the metabolism of steroids during perfusion of the isolated rat liver.

The influence of fluorocarbon FC 43 on the metabolism of oestrogens in the isolated perfused rat liver was investigated. In comparative once-through perfusions with FC 43 emulsion or albumin solution as perfusion medium, the clearance rates of oestrone and its metabolites were determined. In perfusions with FC 43, the clearance of oestrone was lower, and the metabolites formed in the liver were more concentrated in the outflowing medium than in perfusions without fluorocarbon. This can be explained by the high affinity, even of conjugated oestrogens, to FC 43, which is established by equilibrium dialysis and partition coefficient. The results presented here show that the fluorocarbon has a strong influence of its own on the metabolism of steroids in the isolated perfused liver. Therefore, this solvent should be avoided as medium when the metabolism of steroids is studied in perfusion experiments.

Albumins↗
PubMed1981

Intestinal cannulation of cattle and sheep with a T-shaped cannula designed for total digesta collection without externalizing digesta flow.

An intestinal cannula was prepared that was designed to have the advantages of a reentrant cannula without permanently exteriorizing digesta flow or adding significantly to the resistance of digesta flow. The cannula was fabricated in the shape of a T from a Teflon fluorocarbon polymer. Total passage of digesta through the lumen of the cannula was accomplished by suturing a support boot around the outside of the intestine at the cannulation site. The support boot prevented the intestine from stretching away from the cannula. Digesta leakage around the barrel of the cannula was eliminated by a special peritoneal ring attached to the cannula in a position that interrupted the continuity of the tubular scar tissue that formed from the intestine alongside the barrel to the skin. The cannula was supported by an outer ring held in place by a simple stainless steel retaining ring. The low external profile of the cannula minimized mechanical disturbance of the cannula and cannula site. Diet consumption and growth rates were normal, and no blockage was encountered in either the duodenal or the ileal cannula with a wide variety of diets, indicating that the cannula added no significant resistance to digesta flow. Total digesta collection or simultaneous collection and addition were easily accomplished with special collection gates. The cannula preparation has a long functional life; in one case, the cannula remained functional for more than 2 1/2 years.

Animals↗
PubMed1976

Proplast implant in Tenon's capsule after excision of the eye.

Hitherto implants used after enucleation have generally been extruded because of infection or tissue rejection. Proplast, an inert alloplastic material prepared from a combination of Teflon fluorocarbon polymer and vitreous carbon fibres, is a grey felt-like material which, when wholly implanted, is invaded by fibrous tissue and not rejected. Hemispherical implants of Proplast have been used in sixteen cases, no rejection has occurred to date (18 months), and movement of the implant has been good. At operation, the obliques are sutured posterior to the implant so as to hold it forwards and increase movement. The rectus muscles are sutured anterior to the implant in cruciate fashion. Tenon's capsule and the conjunctiva are closed separately.

Carbon↗
PubMed1975

Fluorocarbons: properties and syntheses.

The paper discusses custom syntheses of fluorocarbons for potential use as artificial blood substitutes. The term "fluorocarbon" designates a perfluorinated carbon compound which does not contain another halogen or hydrogen. Prominent requirements of an artificial blood substitute are: 1) efficient oxygen/carbon dioxide transport, 2) biological inertness, 3) low vapor pressure, 4) dispersibility to form emulsion. Fluorocarbons are superior to other liquids in dissolving oxygen and carbon dioxide. The most biologically inert halogenated alkanes are fully fluorinated. Introduction of another halogen or unsaturation decreases biological inertness. Boiling points of fluoroalkanes can be estimated from the Kinney equation. The most common method of fluorination, namely electrofluorination, is briefly described and applied to several types of organic compounds. Hydrocarbons give low yields of perfluoroalkanes. Alternatively, perfluoroalkanes may be prepared through reaction of functionalized substrates. Innert perfluorocyclic ethers are obtained from substrate ethers or acid fluorides. All types of amines perfluorinate but only perfluorotertiary amines are inert. Divalent organo-sulfur compounds afford inert perfluorinated products with sulfur in the hexavalent state. Sulfonyl fluorides give perfluorosulfonyl fluorides which can be pyrolytically coupled producing perfluoroalkanes. The Schoniger combustion method and neutron activation are described as analytical means for determining fluorine content.

Animals↗
PubMed1975

Emulsions of perfluorinated solvents for intravascular gas transport.

During the past several years we have progressed from the use of perfluorinated substances, which were good gas solvents but often produced unexpected physiological reactions, to a point where emulsions of pure perfluorinated substances can be made in a reproducible way. A standardized method of making emulsions has now been developed. The physical properties of the perfluorinated substances needed to make useful emulsions have been defined. Specifically, perfluorinated substances having vapor pressures above about 40 torr must be avoided as they produce pulmonary gas embolism; also lower boiling components having vapor pressures above about 40 torr must be excluded. The relationship between chemical structure and several physiological and pharmacological effects has been delineated. Perfluorinated substances containing only carbon and fluorine, or those containing carbon, fluorine, and either bromine or iodine have reasonably short dwell times in the liver. Perfluorinated iodo- and bromo-compounds dissolve oxygen and are radiopaque. Present iodo-perfluorinates are unstable in the presence of light. Perfluorodecalin can enter and leave the liver without changing the liver's ultrastructure. Both egg phospholipid and Pluronic F68 are useful in making perfluorodecalin emulsions. Perfluorodimethyladamantane makes a fine-particle stable emulsion. There is a bright future for perfluorinated substances in a number of areas of research in biology and medicine.

Animals↗
PubMed1975

Preparation of perfluorodecalin emulsion, an approach to the red cells substitute.

The major problems unsolved in fluorocarbon emulsions have been the long lasting retention of the substance in tissues of organs and acute shock symptom in animals receiving "coarse" emulsion with particles larger then 0.2 mum. This report offers a new, stable and sterile preparation of 25% "fine" perfluorodecalin emulsion with yolk phospholipid that is eliminated from liver, spleen and other organs within a few weeks, and whose acute and subacute toxicity is as low as perfluorotributylamine/Pluronic F68 emulsion. Effects of the perfluorodecalin emulsion thus prepared for maintaining contractile force of isolated guinea pig heart by perfusion and survival of animals receiving repeated circulatory exchange proved similar to perfluorotributylamine/Pluronic F68 emulsion.

Animals↗
PubMed1975

Studies on isolated rat liver perfused by perfluoro-compound emulsion.

Isolated rat livers were perfused for 6 hours by different types of cell-free synthetic media. Some of the media included perfluoro-compounds as an oxygen carrier. The value of the perfusion medium as blood substitute was judged on the basis of observations and measurements of a number of parameters. These were: secretion of bile, fluid pressure in the portal vein, the level of GPT (ALAT) transaminase, urea nitrogen, and glucose in the perfusate. The rate of albumin synthesis and the rate of 14-C-lysine incorporated into circulating proteins were also measured. It was found that perfusion of the isolated rat liver with the TC-199 Difco medium containing the perfluoro-compound FC-80 emulsion maintained the liver in a good condition demonstrated, among other things, by the synthesis of albumin and other proteins. The liver could be kept in a good functional condition during 6 hours perfusion with this cell-free medium. With all the other types of perfusate tested the liver did not synthesize proteins. The isolated rat liver seems to be both convenient and advantageous for testing the perfusion media with respect to their capacity to maintain important metabolic functions.

Albumins↗
PubMed1975

Evaluation of fluorochemicals for liquid membrane oxygenation.

An attempt is being made to develop an oxygenator utilizing gaseous oxygen bubbles completely encapsulated with fluorochemical, thereby avoiding the detrimental changes induced by a blood-gas interface. After the feasibility of this method of oxygenation had been proved, the biocompatibility of the fluorochemicals was investigated. No significant changes in human red blood cells, fibrinogen, or platelets were induced by chronic in vitro contact with fluorochemical over a 24-hour peroid. There is no evidence that the fluorochemicals tested extract lipids from plasma. A device which allowed continuous formation of a blood-fluorochemical interface was utilized in vitro with human blood and in vivo with dogs. No significant alterations were induced by fluorochemicals in the human or animal blood or in the canine organs at autopsy. A prototype oxygenator is now undergoing evaluation. A method of analyzing for fluorochemical in blood and other protein solutions is presented.

Blood Chemical Analysis↗
PubMed1975

Effect of fluorocarbon emulsions on the mechanical fragility of normal and sickle cells: in vitro studies.

Mechanical fragility measurements have been made in vitro on fluorocarbon emulsions mixed with normal and sickle cells in plasma to determine the effect of fluorocarbon. Emulsions of FC-80 with Pluronic F-68 were added to give final solutions of 0, 1, 5, 10, and 20% fluorocarbon emulsion. The effect of the fluorocarbon emulsion was observed in the presence and absence of oxygen. In the presence of oxygen, there was no effect of the fluorocarbon emulsion on the mechanical fragility of normal or sickle cells. In deoxygenated systems, however, there was significantly less hemoglobin in the plasma during the mechanical fragility test with fluorocarbon emulsion added to sickle cell blood. The normal blood was not affected by the fluorocarbon emulsion in the deoxygenated system. Five percent of fluorocarbon emulsion was required for a significant effect on the deoxygenated sickle cells. Since the effect of the fluorocarbon emulsion was in a deoxygenated condition, the effect is due to the presence of the fluorocarbon emulsion and not its oxygen carrying capability.

Anemia, Sickle Cell↗