Biomedical subjects
Publications and source records attributed to J Draffehn.
Dispersions of fluorocarbons (PFC's) made with phospholipids have unusual properties, e.g. very high stability, due to the formation of thermodynamically stable vesicles. They can be used for high PFC concentrations as well as e.g. for ESR imaging.
Although perfluorocarbons (PFC) are chemically inert, toxic reactions are observed on using them as fluorocarbon emulsions in blood substitutes. Six to twelve hours after exchanging about half of the circulating blood of conscious rats pathobiochemical reactions occur despite a high interarterial oxygen pressure. They indicate the disturbance of intracellular energy generation, which is characterized by a decrease in ATP, increase in ADP, inorganic phosphate and potassium, increase in NADH and lactate. Impurities of perfluorocarbons and effects of the surfactant were excluded to be causes of this disturbance. The following hypotheses were proposed: Storing of perfluorocarbons in the mitochondrial membrane decreases the ATP-forming proton gradient on the membrane and the electron transport in cytochromes is disturbed, respectively.
Besides a number of other characteristic features the colloidal osmotic pressure of blood substitutes is of importance, since it regulates the physiological balance between the intra- and extravascular fluid content. The colloidal osmotic pressure in blood is determined predominantly by the albumin fraction. The entropy increase on diluting albumin which, can't pass semipermeable vascular walls of the intravascular substances are used in blood substitutes to maintain the colloidal osmotic pressure. Their selection and appropriate are of great importance for the efficiency of blood substitutes.
Oxygen uptake and desoxygenation in blood take place in the capillary system of the organism so that flow characteristics of blood substitutes should be adapted to that of microcirculation. Therefore, appropriate viscosity of blood substitutes is required. In addition to this, studies on the viscosity of blood substitutes made on the basis of perfluorocarbons are also of interest for considering the deemulsificability during circulation. Viscosity measurements carried out on highly polymerized dextran solutions determining the colloid osmotic pressure in blood substitutes, perfluorocarbon emulsions as oxygen carriers, blood as well as mixtures of these components showed that the rheological behaviour of blood substitutes examined did not lead to organic disorders.
Perfluorocarbons are insoluble in water. For being used as oxygen carriers in blood substitutes they therefore have to be emulsified. Using surfactants in the living organism a compromise on the emulsifying effect and toxicity is to be made, since good emulsifiers do also affect biological membranes. The influence of molecule parameters of surfactants on toxicity was studied in this paper.
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The activities of the alkaline and the acid bone phosphatases as well as the concentrations of calcium and phosphorus were measured in the periimplantal tissue of the rat femur bone after implantation of the vitroceramic Ap 40, the metal oxide stabilized vitroceramics Ap 40 A and Ap 40 Z, as well titanium after 2, 10, and 15 weeks. The incorporation of the vitroceramic Ap 40 turns out like a primary bone fracture healing. The implants Ap 40 A and Ap 40 Z are a compromise with a higher stability and the osteogenesis induced effect is preserved, but is belated in contrast to Ap 40.
A method for testing the bioactivity of hard tissue implants is described by analysis of the periimplantary enzyme activities of the alkaline and the acid phosphatase in the femur of rats. Bioactive materials cause an increase of the activity of the alkaline phosphatase in the periimplantal bone tissue. An increase of the activity of the acid phosphatase is a measure for the biodepressive effect of the implant material.
The steroidal estrogens ethinylestradiol, mestranol and the synthetic "impeded" estrogen derivatives STS 456, STS 593 and J 628 were studied for their postcoital antifertility activity and estrogenicity in mice, rats and rabbits. Results of these studies suggest a positive relationship between these two biological endpoints with the exception of the findings in rats. As seen in uterotrophic--anti-implantation ratio, in view of only one species it is possible to dissociate the interceptive and the unwanted uterotrophic activities. The profound species differences in the effects of exogenous estrogens on the nidation phase are discussed.
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