["Elastic osteosynthesis" with autocompression plates of carbon fiber reinforced thermoplastic material].
The problem of atrophic bone that occurs in osteosynthesis employing rigid plates is first depicted. Attempts at fabricating "simirigid" plates, which, however, have so far failed to gain any practical importance are then discussed. The reason for this seems to be that made of duroplastics cannot be molded during the operation and the thermoplastics do not have sufficient strength. The production of semirigid plates made of thermoplastic Polyethersulfon (PES), reinforced with 20% short carbon fibres, results in plates which are made moldable by heating in a small oven, white retaining sufficient static strength, although only limited fatigue strength. Biomechanical examinations revealed that with appropriate dimensioning of the plates, "elastic osteosynthesis" results in less loss of mechanical function of the stabilized bones, so that less atrophy of the bone may be expected. During more pronounced exercise loading, a reversible "springiness" of the fracture results, which might stimulate callus formation and improved stability.
Verträglichkeit implantatgeeigneter alloplastischer Werkstoffe im Organismus
Die Bedeutung von Implantaten zur Wiederherstellung von Korperfunktionen, die durch Krankheit, naturliche Abnutzung oder Unfall verlorengegangen sind, nimmt stetig zu und last sich am einfachsten anhand des grosen Bedarfs ermessen. Jahrlich werden mehr als 1 500 000 Personen mit Gefasprothesen versorgt, in 100 000 Fallen werden kunstliche Herzklappen eingesetzt, etwa 220 000 Patienten erhalten einen implantierbaren Herzschrittmacher. Fur die extrakorporale Zirkulation bei Operationen am Herzen werden jahrlich etwa 600 000 Oxygenatoren benotigt. Der Jahresbedarf an kunstlichen Nieren nahert sich der Zahl 1 000 000. Beim Gelenkersatz steht die Huftprothese mit ca. 350 000 Implantationen an erster Stelle vor dem Ersatz des Finger-, Knie-, Schulter- und Ellenbogengelenks. Implantierbare Materialien fur die rekonstruktive Chirurgie haben den Umfang vieler Tonnen erreicht. Einen Eindruck von den vielfaltigen Einsatzgebieten moderner Kunststoffe vermittelt Tabelle 1.
Two distinct mechanisms for bilirubin glucuronide transport by rat bile canalicular membrane vesicles. Demonstration of defective ATP-dependent transport in rats (TR-) with inherited conjugated hyperbilirubinemia.
Bilirubin is conjugated with glucuronic acid in hepatocytes and subsequently secreted in bile. The major conjugate is bilirubin diglucuronide. Using sealed vesicles which are primarily derived from the canalicular (CMV) and sinusoidal (SMV) membrane vesicle domains of the plasma membrane of hepatocytes, we demonstrated that bilirubin glucuronides are transported by CMV by both ATP- and membrane potential-dependent transport systems. In CMV from normal rats, these processes are additive. In CMV from TR- rats, which have an autosomal recessively inherited defect in biliary secretion of nonbile acid organic anions, ATP-dependent transport of bilirubin diglucuronide was absent whereas the membrane potential driven system was retained. Other canalicular ATP-dependent transport systems, which were previously described for organic cations and bile acids, are functionally retained in TR- rats. Our study indicates that bilirubin glucuronides are primarily secreted into the bile canaliculus by an ATP-dependent mechanism which is defective in an animal model of the human Dubin-Johnson syndrome.