摘要:

AbstractOxidation–reduction reactions which can destroy high current‐density metalstimulating electrodes are avoided when using capacitive electrodes. The results ofin vitroandin vivotesting of anodized, high surface area, sintered tantalum electrodes are presented. The corrosion response of the electrodes is excellent; there is no evidence of dissolution of the electrode. A deposit forms on the surface of the electrodes, but has little effect on the voltage response to constant current stimulation. The physiological and histopathological results indicate the capacitive tantalum electrode to be the safest yet tes

ISSN:0021-9304    

DOI:10.1002/jbm.820110502

出版商:John Wiley&Sons, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractLaboratory tests carried out by means of body environment simulators have proved to be very important for the evaluation of endoprostheses potentially useful for implantation. The present paper examines the problems connected with the design of such a simulator. The results obtained with an initial, very primitive simulator concerning the outlines of the phenomena of wear, corrosion, and friction and some wear properties of commercially available hip endoprostheses are presented. From these results, the motivation that led to the design of a more advanced simulator is presented. This latter simulator is also described.

ISSN:0021-9304    

DOI:10.1002/jbm.820110503

出版商:John Wiley&Sons, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractThe peak temperature reached during the polymerization of a bone cement was reduced by addition of solidN‐vinylcarbazole to the powder component. It was also necessary to saturate the liquid component withN‐vinylcarbazole to prevent dissolution from the modified powder component on mixing. It is believed that this technique is generally applicable and opens up the possibility of achieving temperature control of bone cements with choice from a range of crystalline monom

ISSN:0021-9304    

DOI:10.1002/jbm.820110504

出版商:John Wiley&Sons, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractThe effect of collagen modification on the magnitude of stress‐generated potentials has been studied. A whole bone model has been developed for determining the effects of collagen crosslinking on the electrical signals. Increased crosslinking results in larger electrical signals, and such increases result whetherin vivoorin vitrochanges in the collagen are mad

ISSN:0021-9304    

DOI:10.1002/jbm.820110505

出版商:John Wiley&Sons, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractBonding between porcelain and dental ceramic alloys is thought to be dependent upon the establishment of a continous electron structure across the ceramicmetal interface (Pask,Proc. Procelain Enamel Inst.,33, 1, 1971). Such a structure most likely results from the compatibility of metal ions at the metal surface saturated in an oxide form with the complex oxide structure of the ceramic matrix. Reaction zone compounds are expected to play a prominent role in the strength of the ceramic–metal bonds but thus far none have been detected or identified.The present study was centered on the determination of possible adherence zone compounds in four composite ceramic–metal couples examined by x‐ray energy analysis. Elemental analysis of four couples revealed the presence of a predominant AlCr interaction resulting from the formation of an AlCrO compound or mixed oxide complex. The Cr ions were supplied by the Cr2O3oxide layer at the metal surface and the Al was provided by the initial bonding‐

ISSN:0021-9304    

DOI:10.1002/jbm.820110506

出版商:John Wiley&Sons, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractThis study determined the difference in rate of degradation between pure polymers of lactic acid (PLA), glycolic acid (PGA), and various ratios of copolymers of these two substances. Fast‐cured and slow‐cured polyglycolide was compared with copolymers of glycolide/lactide intermixed in ratios of 75:25, 50:50, and 25:75, as well as pure polylactide. A total of 420 rats were implanted with carbon‐14 and tritium‐labeled polymers in bone and soft tissue. At intervals of 1, 2, 3, 5, 7, 9, and 11 months, groups of five animals with the implants in bone and five with the implants in the abdominal wall were sacrificed. The implant area as well as tissue from the liver, spleen, kidney, lung and some muscle tissue was analyzed for radioactivity along with the urine and feces collected throughout the experiment. Half‐lives of the different polymers and copolymers were calculated from the radioactivity present in the implant area for each time interval. Half‐life of the polymers and copolymers decreased from 5 months for 100% PGA to 1 week with 50:50 PGA:PLA copolymer and rapidly increased to 6.1 months for 100% PLA. Fast‐cured PGA had a half‐life in tissue of 0.85 months. No difference in rate of degradation was seen in soft tissue or bone. No significant radioactivity was detected in urine, feces, or tissue samples. From this study, it is concluded that control of degradation rate of the implant could best be attained by varying the composition of PLA and PGA between 75% and 100% PLA along with a corresponding 25% to 0% PGA. This would provide a half‐life range of the implant of from 2

ISSN:0021-9304    

DOI:10.1002/jbm.820110507

出版商:John Wiley&Sons, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractTheoretical as well as practical–clinical applications of one form of collagen (collagen sponge) as a biodegradable material is reviewed. The role of porosity of the sponge and surface characteristics of the meshwork in relation to cell ingrowth are considered essential features of collagen sponge. Rate of resorption and antigenicity could be controlled by graded crosslinking of collagenous framework. Four basic examples of clinical use of collagen sponge are presented: as wound (burn) dressing material, as a matrix for bone and cartilage repair, as an intravaginal contraceptive diaphragm, and as surgical tampon

ISSN:0021-9304    

DOI:10.1002/jbm.820110508

出版商:John Wiley&Sons, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractCarbamoylphosphate synthetase (EC 2.7.2.5) and ornithine carbamoyl‐transferase (EC 2.1.3.3) extracted from frog liver were successfully immobilized on CNBr‐activated Sepharose 4B. The immobilized preparation had a better stability towards heat. The apparent Michaelis constant values forN‐acetyl‐glutamate, ammonia, and ATP were not significantly changed by immobil

ISSN:0021-9304    

DOI:10.1002/jbm.820110509

出版商:John Wiley&Sons, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractArgininosuccinate synthetase (EC 6.3.4.5) was immobilized on CNBr‐activated Sepharose 4B. Properties of the immobilized enzyme are described and compared with those of the native enzyme. The immobilized enzyme was much more stable than the native enzyme at 37°C. It was further stabilized in the presence of the assay reagents. The optimum pH of the immobilized enzyme shifted towards alkalinity (approximately 0.5 unit). The apparent Michaelis constants measured for the immobilized enzyme were not greatly different from those measured for the native enzyme.Urea formation from citrulline was confirmed in a continuous column reactor by the coimmobilized argininosuccinate synthetase, argininosuccinate lyase (EC 4.3.2.1), and arginase (EC 3.5.3.

ISSN:0021-9304    

DOI:10.1002/jbm.820110510

出版商:John Wiley&Sons, Inc.    

年代:1977

数据来源: WILEY

摘要:

AbstractThe feasibility of preventing platelet adhesion to porous foreign surfaces in contact with blood by passing (perfusing) a physiologic fluid through the pores into the blood was tested. Porous‐walled tubes of Teflon (Gore‐tex) and aluminosilicate ceramic were perfused with lactated Ringer's solution at rates between 3.13 and 0.3 cc/min per cm2of perfused surface and exposed to heparinized and unheparinized flowing human whole blood for periods of 3–6 min. Under these conditions, with 0.159 cm I.D. tubes and a mean blood flow rate of 8.3 cm/sec, the adhesion of all blood cells was prevented, compared with the adhesion of 1 to 8 × 106platelets/cm2on the nonperfused controls. The adhesion of plasma proteins was also markedly reduced as determined by bromophenol blue staining.The critical perfusion rate to prevent platelet adhesion to Gore‐tex (0.5 μ pore size, 60% pore volume) was found to be between 0.04 and 0.3 cc/ (min · cm2). The boundary layer produced by a perfused segment of porous tubing prevented platelet adhesion for several centimeters downstream from the perfusing segment under experimental condi

ISSN:0021-9304    

DOI:10.1002/jbm.820110511

出版商:John Wiley&Sons, Inc.    

年代:1977

数据来源: WILEY