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  • 1
    Electronic Resource
    Electronic Resource
    Polyurethane-polydimethylsiloxane (PU-PDMS) tubular membranes for pancreatic islet transplantation. Permselectivity and diffusion studies (1992)
    Springer
    Journal of materials science 3 (1992), S. 371-376 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Transplantation of immuno-protected xenogenic islets of Langerhans by a permselective synthetic membrane represents an intriguing possibility to treat the diabetic disease. In this study, polymeric tubular membrane with a porous wall structure and an internal permselective layer (skin) were fabricated by a combination of spraying and phase-inversion of a thermodynamically unstable solution of a biocompatible PU (90%)-PDMS (10%) blend (Cardiothane™ 51) over a sliding and rotating mandrel. Segments of tubular membranes were capped at both extremities according to the “macroencapsulation” technique. Reference compounds of different molecular masses were used to evaluate capsules permselectivity characteristics, while glucose, insulin and porcine islets of Langerhans were used to study the diffusion properties. The results of these studies showed the capsules to be impermeable to compounds with a molecular mass higher than approximately 40 000 Da, but permeable to glucose and insulin. Pancreatic islets entrapped within the capsules released, over a 2 h period, insulin proportionally to the glucose concentration in the medium without a significant difference in comparison with the amount of insulin released by non-encapsulated islets. Finally, potential drawbacks deriving from an inaccurate capsules sealing and from the severity of the host tissue reaction versus the structural material are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00705370
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation and characterization of permselective, biocompatible membranes for the macroencapsulation of pancreatic islets (1994)
    Springer
    Journal of materials science 5 (1994), S. 887-890 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Polymeric membranes were prepared by mixing poly (vinyl alcohol) (PVA) and poly (acrilic acid) (PAA) solutions (10/90 weight ratio), freeze-drying and crosslinking under vacuum. The membranes were then coated with alginic acid sodium salt, and gelation was accomplished by calcium chloride. The resulting membrane structure was essentially trabecular, with pore size ranging from 50 to 100 μm. Glucose and insulin diffusions reached a plateau at 2 and 32 min, respectively. Immunoglobulins and red blood cells did not cross the membranes. Gelpermeation HPLC showed that the membrane wall was impermeable to compounds with a molecular weight higher than 100 000 D. Biocompatibility of the membranes was demonstrated by showing minimal fibrotic reaction at 3 weeks after intraperitoneal implantation into mice. Porcine islets were placed into the membranes and cultured at 37°C for 7 days, at which time the incapsulated were shown to release insulin in response to glucose. These results support the use of PVA/PAA membranes for bioartificial pancreas studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01172031
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Androgen receptors and hormone sensitivity of a human prostatic cancer cell line (PC-3) are modulated by natural beta-interferon (1994)
    Springer
    Urological research 22 (1994), S. 33-38 
    Details
    ISSN: 1434-0879
    Keywords: Androgen receptors ; Hormone sensitivity ; Hydroxyflutamide ; Interferon ; Prostatic cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Androgen recptors are expressed at a low level in the cell line PC-3, which does not respond to either androgens or antiandrogens. If these cells are exposed to natural beta-interferon (β-IFN) a reduction in cell growth and an increase in androgen receptors, evaluated by both biochemical and immunocytochemical techniques, occur. This increase seems not to be related to a selective block of PC-3 in any phase of the cell cycle. Pretreatment with β-IFN determines in PC-3 cells a partial responsiveness to the androgen dihydrotestosterone as reflected by the increase in cell number. Moreover, the antiandrogen hydroxyflutamide shows agonistic properties by increasing the cell number of PC-3 cells pre-exposed to β-IFN. When the antiandrogen is tested in combination with interferon, it produces a reduction in the β-IFN-induced inhibition of cell growth. It is not known whether these unexpected effects are due to the increase in androgen receptors or to other mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00431546
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  • 4
    Electronic Resource
    Electronic Resource
    Raman and infrared spectroscopic study of the molecular characterization of the biocompatibility of prosthetic biomaterials (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 25 (1994), S. 109-114 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Raman spectra were obtained directly in a non-destructive and non-invasive way from the biomaterials PMMA [poly(methyl methacrylate)], HDPE (high-density polyethylene), α-Al2O3 (alumina) and HA (hydroxyapatite) constituting the components (bone cement, acetabular cup, ball and stem coated with ceramic) of a hip prosthesis. The aim was to give an objective contribution at a molecular level to predict their biocompatibility. In particular, Raman spectra of explanted PMMA bone cements do not show the 1640 cm-1 band due to the stretching mode of C=C unsaturated centres. Moreover, conformational changes of PMMA following the implant appear in the spectra in the range 1100-500 cm-1, where conformational marker bands at 985, 968, 601 and 565 cm-1 are present. The limited number of HDPE explanted acetabular cups did not allow unequivocal Raman results to be obtained by means of band deconvolution in the region between 1500 and 1000 cm-1, regarding the changes in the crystalline, amorphous and interfacial contents of the acetabular cup surfaces following the implant. α-Al2O3 proved to be a ceramic with good biocompatibility as a biomaterial constituting a hip prosthesis. As regards the stem coating, Raman and Fourier transform IR spectra of HA pre-coating and HA coating on metal implants show spectroscopic modifications due to structural and chemical changes with formation of other calcium phosphates. The development of new bioactive coatings containing precursors of bone growth and able to promote osteogenesis is outlined.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250250116
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    Paper (German National Licenses)
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