Search PubMed⌕ Search

PubMed · 9312704

[Resorbable bone cements].

Abstract

Bone cements are used to treat compression fractures, fill bone defects and improve implant fixation in osteoporotic patients through reinforcement of weak bone. When the fracture repair is complete the bone cement ideally should degrade. In general, calcium-phosphate bone cements are biodegradable and can fulfill this temporary function. Several research groups have developed calcium-phosphate bone cements in the last years which have a chemical structure similar to that of the apatite of bone. However the conditions for processing the cement intraoperatively, as well as the mechanical properties and degradation characteristic of the various products show great variations. Clinical long-term studies have not yet been reported so far. Whether these new types of bone cements fulfill all the requirements for clinical application is still not certain and remains to be determined in future studies.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

L Claes, I Hoellen, A Ignatius. 1997. [Resorbable bone cements].. https://doi.org/10.1007/s001320050112

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

The pH-dependent biphasic release of azidothymidine from a layered composite of PVA disks and P(MMA/MAA) spheres.

A composite device was developed to provide a biphasic drug release using poly(vinyl alcohol) (PVA) and poly(methylmethacrylate-co-methacrylic acid) (P(MMA/MAA)) spheres. Azidothymidine (AZT), an anti-HIV agent with a short biological half-life, was used as the model drug. Dynamic and equilibrium swelling of the polymers, and kinetics of AZT release from these polymers were determined in pH 1.2 and 6.8 buffer solutions. The swelling of PVA and release of AZT from PVA disks were fast and nearly pH-independent, whereas the swelling behavior and drug release kinetics of P(MMA/MAA) spheres were strongly pH-dependent. A swelling interface number for the spheres at pH 6.8 was determined to be Sw&z.Lt;1 and time dependent. Nevertheless, Fickian diffusion might also contribute to the drug release in this system. The composite disks consisting of PVA matrix and P(MMA/MAA) spheres provided prolonged (over 20 h) and more steady release profiles, differing profoundly from individual components. Such release profiles resulted from the second phase release at pH 6.8 and the presence of PVA layer. The relative drug loading in the matrix could be tailored to produce release profiles varying from a distinct bimodal release to a pseudo zero-order release with an initial burst.

Absorption↗

Hybrid polar compounds produce a positive shift in the surface dipole potential of self-assembled phospholipid monolayers.

Hybrid polar compounds (HPCs) are powerful inducers of terminal differentiation of various types of tumors, including Friend murine erythroleukemia cells (MELCs). They are known to act synergistically with an increase in the extracellular concentration of cations, which causes a positive shift in the negative value of the ionic surface potential. Two HPCs, hexamethylenebisacetamide (HMBA) and suberoylanilide hydroxamic acid (SAHA), were adsorbed on self-assembled phospholipid monolayers supported on a mercury drop and the shift in the surface dipole potential chi of the lipid film due to their adsorption was estimated from charge measurements. At their optimal concentrations for inducing MELC terminal differentiation (5 mM for HMBA and 2.6 microM for SAHA), these HPCs cause a chi shift of about 15-20 mV, positive toward the hydrocarbon tails, both on neutral phosphatidylcholine films and on negatively or positively charged phosphatidylserine films. This strongly suggests that the nonspecific effect of HPCs of different structure in inducing cancer cells to rescue their differentiation program is related to a positive chi shift on the extracellular side of the cell membrane.

Absorption↗

ELISA to evaluate plasma anti-asparaginase IgG concentrations in patients with acute lymphoblastic leukemia.

The development of antibodies to asparaginase may attenuate the pharmacologic effect of asparaginase treatment, may be associated with hypersensitivity reactions, and may necessitate switching to a different commercial asparaginase preparation for current or future therapy. Thus, development of an ELISA for measurement of anti-asparaginase antibody levels is important in the clinical setting. An anti-asparaginase antibody reference was established by screening 65 plasma samples from six patients with acute lymphoblastic leukemia (ALL) who had recently developed a hypersensitivity reaction to Escherichia coli or Erwinia chrysanthemi asparaginase therapy. Twenty-one plasma samples were selected for the anti-asparaginase antibody reference pool. Five micrograms per milliliter of commercial E. coli and Erwinia asparaginase and 10 microg/ml of E. coli asparaginase conjugated with polyethylene glycol (PEG asparaginase) were found to be optimal as coating antigen concentrations. Anti-asparaginase antibody concentrations were determined using a commercial polyclonal goat anti-human IgG horseradish peroxidase conjugate. The antibody reference curves were linear in a range of absorbance from 0.1 to 1. 5 O.D. units for dilutions from 1:1600 to 1:51,200. Inter-assay coefficients of variation were 9.04, 14.7 and 13.0%, and intra-assay coefficients of variation were 1.44, 4.43 and 3.28% for antibodies against E. coli, Erwinia, and PEG L-asparaginase, respectively. The cut-off for positivity in plasma was determined as mean+2 S.D. of the optical density values for plasma from untreated healthy volunteers. Measurement of specific IgG by this ELISA allows for the evaluation of plasma anti-asparaginase antibody concentrations in patients receiving one or more of the multiple commercial L-asparaginase preparations.

Absorption↗