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  • 1
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Fibrovascular tissue ingrowth into poly(vinyl alcohol) (PVA) sponges of different pore sizes was investigated by incorporating basic fibroblast growth factor (bFGF) into the sponges. The average pore size of PVA sponges used in this study was 30, 60, 110, 250, 350, and 700 μm and gelatin microspheres were employed as release carrier of bFGF. The sponges were subcutaneously implanted into the back of mice after incorporating free bFGF or gelatin microspheres containing bFGF into the sponges. Fibrovascular tissue infiltrated with time into the sponge pores and the extent of fibrous tissue ingrowth showed a maximum at a pore size around 250 μm 1 and 6 weeks after implantation. Significant promotion of the growth of fibrous tissue by bFGF was observed only at 3 weeks post-implantation (p 〈 0.05). New capillaries were formed in the tissue at any time, as long as bFGF was given to the sponges. Both empty gelatin microspheres and phosphate buffered solution neither promoted tissue ingrowth nor induced capillary formation in the sponges. It was concluded that bFGF was essential to induce the fibrovascular tissue ingrowth into the pores of PVA sponges. ©2000 Kluwer Academic Publishers
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  • 2
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: This study was undertaken to examine the osseous tissue compatibility of polylactic acid (PLA) with properties of bioabsorbability and plasticity. Two kinds of granular PLA with different molecular weight (PLA-H: 28 000 MW, PLA-L: 10 600 MW) were implanted into rat tibiae and light microscopic sections were prepared at 1, 2, 4, 8, 16, and 24 weeks following surgery. The tissue compatibility of the PLAs was compared with that of hydroxyapatite (HAP) which is a non-absorbable biocompatible material. After implantation, both PLAs were gradually absorbed and replaced by marrow tissue at 24 weeks. PLA-H degraded slower than PLA-L. New bone formation was observed around each PLA by 4 weeks, and a vast amount of bone deposited on PLA-H at 16 weeks. Phagocytic reactions to the PLAs were noted, however, severe inflammation was not seen. HAP was not absorbed and bone surrounded it throughout the experiment. These results indicate good tissue compatibility of PLA as a bioabsorbable material at the skeletal site.
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  • 3
    ISSN: 1573-904X
    Keywords: interferon ; pullulan conjugation ; liver targeting ; 2-5A synthetase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose of this study was to actively target interferon (IFN) to the liver through its chemical conjugation with pullulan, a water-soluble polysaccharide with a high affinity for the liver. Methods. Chemical conjugation of IFN with pullulan was achieved by a cyanuric chloride method. Following intravenous injection of the conjugates to mice, their body distribution and the activity of an IFN-induced enzyme, 2′,5′-oligoadenylate (2-5A) synthetase in the liver and other organs, were evaluated. Results. The cyanuric chloride method enabled us to prepare an IFN-pullulan conjugate that retained approximately 7–↑9 % of the biological activity of IFN. Pullulan conjugation enhanced the liver accumulation of IFN and the retention period with the results being reproducible. When injected intravenously to mice, the IFN-pullulan conjugate enhanced the activity of 2-5A synthetase in the liver. The activity could be induced at IFN doses much lower than those of free IFN injection. In addition, the liver 2-5A synthetase induced by conjugate injection was retained for 3 days, whereas it was lost within the first day for the free IFN-injected mice. Conclusions. IFN-pullulan conjugation was promising for IFN targeting to the liver with efficient exertion of its antiviral activity therein.
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  • 4
    ISSN: 1573-904X
    Keywords: polylactide microspheres ; macrophage ; phagocytosis ; antitumor activation ; gelatin ; immunopotentiator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Biodegradable microspheres containing a lipophilic muramyl dipeptide, MDP-B30, were prepared from a L-lactic acid–glycolic acid copolymer. The effect of precoating the microspheres with water-soluble polymers including proteins on the antitumor activity of mouse peritoneal macrophages (Mφ) was investigated. Macrophages activated by phagocytosis of the microspheres exhibited growth inhibitory activity toward Meth-A tumor cells. The activity correlated with the extent of Mφ phagocytosis of the microspheres. Mφ phagocytosis was greatly augmented by gelatin precoating of the microspheres, resulting in a significant increase of in vitro antitumor activity of Mφ by the microspheres. However, potentiation of Mφ activity by gelatin precoating was minimal after intraperitoneal injection of the microspheres, but cross-linking of the coated gelatin with glutaraldehyde afforded potentiation of the antitumor activity in vivo.
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  • 5
    ISSN: 1573-904X
    Keywords: hydrogel ; poly vinyl alcohol ; rectal administration ; indomethacin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In order to evaluate an indomethacin poly vinyl alcohol (PVA) hydrogel for rectal administration, the in vitro release characteristics of indomethacin from the hydrogel and indomethacin plasma concentrations after rectal administration were examined. The PVA hydrogel containing indomethacin was prepared by a low-temperature crystallization method. The release of indomethacin from the PVA hydrogel agreed with the Fickian diffusion model for 10 hr. Rectal administration of indomethacin hydrogels to rats yielded high indomethacin plasma concentrations, without producing a sharp peak, and a sustained-release effect. In dogs, the indomethacin hydrogel produced a similar sustained-release effect; however, the indomethacin plasma concentration was relatively low compared with that of an indomethacin suppository.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 32 (1997), S. 5533-5543 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In an attempt to synthesize hydroxyapatite (HAP)/polymer composites, HAP crystallization was investigated in solution in the presence of ionic synthetic polymers. The side groups of the polymers used include carboxylate, dihydrogen phosphate, sulfate, and primary amine. Spontaneous HAP precipitation and amorphous–crystalline transformation occurring in both the presence or absence of ionic polymers were studied by measuring the solution turbidity change and titrating the released protons, respectively. The rates of HAP nucleation and growth were determined from an induction period before onset of crystallization and the subsequent propagation of HAP crystallites. The added anionic and cationic polymers, were found to suppress the crystallization in a concentration-dependent manner. An exception was a concentrated poly(acrylic acid), which was precipitated by calcium ion binding to accelerate the nucleation and the growth of HAP crystallites. These results suggest that a molecular interaction is operative between the ionic polymer chains and the growing HAP crystallites. Infrared spectroscopy and X-ray diffraction analysis revealed that the HAP precipitated in the presence of ionic polymers incorporated the polymer chains in the HAP microcrystalline aggregates. Based on these findings, HAP/poly(acrylic acid) composites were prepared through in situ HAP crystallization in the presence of poly(acrylic acid). Tensile testing of the composites and electron microscopic observation of their fractured surfaces revealed that the composite prepared through this wet process was superior to that obtained by simple physical mixing with respect to the wet state mechanical properties and homogeneity in mixing.
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  • 7
    ISSN: 1619-0904
    Keywords: Dura mater ; Dual substitute ; Creutzfeldt-Jakob disease ; biodegradable polymer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Synthetic dural substitutes composed of bioabsorbable polymers were used in 20 patients during neurosurgical operation. Clinical manifestations such as operative wound features, white blood cell counts, C-reactive protein, and computed tomography were evaluated after neurosurgical operations. Transient subcutaneous collection of cerebrospinal fluid was observed in three patients. No other significant complication was observed. This preliminary report indicates the effectveness of the bioabsorbable artifical dura mater without risking virally transmitted infection when compared with a cadaveric dura mater graft.
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  • 8
    ISSN: 1619-0904
    Keywords: Tissue engineering ; Bioprosthesis ; Biomaterial ; Cardiovascular surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract Various vascular and valvlular grafts are commonly used in the treatment of cardiovascular disease. Current prosthetic or bioprosthetic materials lack growth potential, and therefore, subsequent replacement further defeats the concept of primary repair early in pediatric cardiac patients. Tissue engineering is a new discipline that offers the potential to create replacement structures from autologous cells and biodegradable polymer scaffolds. Because tissue-engineering constructs contain living cells, they may have the potential for growth, self-repair, and self-remodeling. Cardiac valve leaflets and large conduits in the pulmonary ciruulation have been made with this tissue-engineering approach in lambs. Venous conduits were also created in dogs. Mixed cell populations of endothelial cells and fibroblasts were isolated from explanted peripheral arteries or vein. A synthetic biodegradable scaffold con-sisting of polyglactin and polyglycolic acid fibers was seeded in vitro with mixed cultured cells. After one week, these autologous cell/polymer constructs were reimplanted in animals. Each animal was then followed periodically by echocardiography and angiography. The animals were sacrificed, and the implanted tissues were examined histologically, biochemically, and biomechanically. A 4-hydroxyproline assay was performed to evaluate the collagen content. The implanted conduit diameters increased as the animals grew during the study period. Histologically, the biodegradable polymer scaffold was completely degraded. Collagen analysis of the constructs showed the development of an extracellular matrix. Immunohistochemical staining demonstrated elastin fiber in the matrix and factor VIII on the inner surface of the conduits. In conclusion, a tissue-engineering approach to constructing cardiovascular structures is feasible using cells of either arterial or venous origin. In these tissue-engineered autografts, transplanted autologous cells generated the proper matrix over the polymer scaffold under physiologic conditions.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 8 (1991), S. 1292-1296 
    ISSN: 1573-904X
    Keywords: DL-lactide-ε-caprolactone copolymer ; biodegradable polymer ; cisplatin ; MD-805 ; sustained drug release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Poly(DL-lactic acid) (PLA), poly(ε-caprolactone) (PCL), and their copolymers (PLA-CL) with various monomer compositions were synthesized, and their properties as matrix for the sustained release of drugs were evaluated. The copolymerization technique produced very soft films which incorporated the drugs without deterioration of the elastic properties. Cisplatin and MD-805 were loaded in the films by casting the polymer solution containing the drugs. Fractions of the drugs released from the PLA-CL films were governed by the initial loading, the film thickness, and the polymer molecular weight. The drug release profiles obeyed the classical Fickian diffusion equation at least in the early stage, but significant hydrolytic degradation of the matrix polymers occurred in the later stage, influencing the kinetics of drug release. The monomer composition of copolymer affected the release profile more strongly than the initial molecular weight of the copolymer.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 6 (1989), S. 422-427 
    ISSN: 1573-904X
    Keywords: gelatin microspheres ; macrophages ; phagocytosis ; degradation ; interferon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Gelatin microspheres with a diameter less than 2 µm were synthesized by means of cross-linking with glutaraldehyde. When the microspheres were subjected to degradation in phosphate-buffered saline solution containing collagenase, the digestion of microspheres was found to decrease with increasing cross-linking. Interferon was incorporated in the microspheres at a high trapping efficiency, and the rate of interferon release from the microspheres was regulated by the extent of cross-linking with glutaraldehyde. Gelatin microspheres incorporating interferon-α were readily phagocytosed by macrophages, regardless of the extent of cross-linking, and the phagocytosed microspheres were observed to be degraded gradually in the interior of macrophages, resulting in the slow release of the incorporated interferon in the cells.
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