Analysis of LPS released from Salmonella abortus equi in human serum.

We investigated in which form lipopolysaccharide (LPS) is released from live bacteria incubated with human serum and whether the released LPS can interact with high density lipoprotein (HDL), the main transport protein for purified LPS in circulation. Live biotinylated Salmonella abortus equi bacteria were incubated with fresh serum (37 degrees C; 2 h). The released LPS was isolated by immunoprecipitation or immunoabsorption using specific anti-O antibodies. It was analysed and compared with purified LPS, also incubated with serum under identical conditions. Immunoprecipitation led to a 35% recovery and immunoabsorption to quantitative recovery of released or purified LPS. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and subsequent immunoblot analysis revealed that all molecular species present in the purified LPS were present in the released LPS. The rough fraction, which was co-isolated from serum together with the true smooth (O-polysaccharide-containing) molecules, exhibited S. minnesota rough mutant Rb antigenic specificity. In the immunoprecipitated material two forms of released LPS were identified. One represented LPS associated with a biotinylated bacterial component with an apparent molecular mass of 35-36 kDa, which was identified as OmpA, a major outer membrane protein. The OmpA-associated LPS was free of HDL. Another part of the released LPS was free of biotinylated bacterial components. This portion of LPS was associated with HDL, indicating that the interaction with HDL may also proceed with a part of LPS released from bacteria.     

Effect of biomaterial properties on bone healing in a rabbit tooth extraction socket model

In this work we sought to understand the effect of biomaterial properties upon healing bone tissue. We hypothesized that a hydrophilic polymer gel implanted into a bone tissue defect would impede the healing process owing to the biomaterial's prevention of protein adsorption and thus cell adhesion. To test this hypothesis, healing bone was investigated within a rabbit incisor extraction socket, a subcritical size bone defect that resists significant soft tissue invasion by virtue of its conformity. After removal of the incisor teeth, one tooth socket was left as an empty control, one was filled with crosslinked polymer networks formed from the hydrophobic polymer poly(propylene fumarate) (PPF), and one was filled with a hydrogel formed from the hydrophilic oligomer oligo(poly(ethylene glycol) fumarate) (OPF). At five different times (4 days as well as 1, 2, 4, and 8 weeks), jaw bone specimens containing the tooth sockets were removed. We analyzed bone healing by histomorphometrical analysis of hematoxylin and eosin stained sections as well as immunohistochemically stained sections. The proposed hypothesis, that a hydrophilic material would hinder bone healing, was supported by the histomorphometrical results. In addition, the immunohistochemical results reflect molecular signaling indicative of the early invasion of platelets, the vascularization of wound-healing tissue, the differentiation of migrating progenitor cells, and the formation and remodeling of bone tissue. Finally, the results emphasize the need to consider biomaterial properties and their differing effects upon endogenous growth factors, and thus bone healing, during the development of tissue engineering devices.     

In vitro degradation of polymeric networks of poly(propylene fumarate) and the crosslinking macromer poly(propylene fumarate)-diacrylate

Polymeric networks of poly(propylene fumarate) (PPF) crosslinked with poly(propylene fumarate)-diacrylate (PPF-DA) are currently being investigated as an injectable, biodegradable bone cement. This study examined the effect of crosslinking density, medium pH, and the incorporation of a beta-tricalcium phosphate (beta-TCP) filler on the in vitro degradation of PPF/PPF-DA. Cylindrical specimens were submerged in buffered saline at 37 degrees C and the change in weight, geometry, and compressive mechanical properties were monitored over a 52-week period. All formulations showed an initial increase in modulus and yield strength over the first 12 weeks, achieving maxima of 1307+/-101 and 51+/-3MPa, respectively, for the beta-TCP composite. PPF/PPF-DA networks with the lower crosslinking density demonstrated the greatest degradation with a 17% mass loss. Samples in the lower buffer pH 5.0 compared to physiological pH 7.4 did not show any differences in mass loss, but exhibited a faster decrease in the compressive strength over time. The beta-TCP composites maintained their mechanical properties at the level following their initial increase. These results show that the degradation of PPF/PPF-DA networks can be controlled by the crosslinking density, accelerated at a lower pH, and prolonged with the incorporation of the beta-TCP filler.     

Increased frequency of the rare PstI allele (P2) in a population of CAD patients in Northern Greece

Restriction fragment length polymorphisms (RFLPs) at the apolipoprotein AI-CIII-AIV gene cluster and their association with coronary artery disease (CAD) and lipid levels were studied in a Northern Greek population. Ninety-five patients with CAD and fifty-four normal controls, angio-graphically proven, were included in this study. Using genomic hybridization techniques, three polymorphic restriction sites were identified at this locus: the PstI at the 3' end of the apoAI gene, the SacI at the 3' non-coding region of the apoCIII gene and the PvuII at the intergenic region between the apoCIII-AIV genes. The rare allele (P2) arising from the absence of the PstI restriction site was observed with a significantly higher frequency (p<0.01) in patients compared to normals (0.11 vs 0.02). In contrast, the rare allele for the SacI polymorphic site had a similar distribution among patients and controls (0.12 vs 0.16). The same was observed for the PvuII RFLP (0.04 vs 0.05). Correlation of lipid and apolipoprotein AI levels with the three RFLPs revealed no significant association, although apo AI and HDL were lower in patients with the P2 allele. Thus, in this Greek population, only the PstI polymorphism, among the polymorphic restriction sites examined, appears to be associated with CAD.     

Colchicine prevents tumor necrosis factor-induced toxicity in vivo.

Tumor necrosis factor (TNF) toxicity was induced in vivo by intravenous administration of 15 micrograms of recombinant murine TNF-alpha per kg to galactosamine-sensitized mice. Within 8 h, the animals developed a fulminant hepatitis. Intravenous administration of 0.5 mg of colchicine per kg at 19 and 4 h prior to TNF challenge protected the animals against hepatitis. Lipopolysaccharide (LPS)-stimulated, bone marrow-derived macrophages from C3H/HeN mice released significant amounts of TNF in vitro. When such macrophages were intravenously given to LPS-resistant galactosamine-sensitized C3H/HeJ mice, these animals died within 24 h. Preincubation of these transferred macrophages with colchicine did not suppress the LPS-inducible TNF release from these cells. Concordantly, administration of macrophages exposed to colchicine in vitro resulted in full lethality. However, in vivo pretreatment of C3H/HeJ mice with colchicine 19 and 4 h prior to the transfer of LPS-stimulated macrophages prevented lethality. In LPS-responsive NMRI mice which had been protected against galactosamine-LPS-induced hepatitis by pretreatment with colchicine, TNF was still released into the blood. We conclude from our findings that the in vivo protection by colchicine is mediated by blocking TNF action on target cells while the effector cells of LPS toxicity, i.e., the macrophages, remain responsive.     

A 14,000 MW lipoprotein and a glycolipid-like structure of Borrelia burgdorferi induce proliferation and immunoglobulin production in mouse B cells at high frequencies.

Sonicated preparations of Borrelia burgdorferi are able to stimulate unselected resting BALB/c spleen cells to proliferate and to produce immunoglobulin in vitro. FACS analysis of target cells prestained with an integrated cell-surface marker as well as cell-depletion experiments demonstrate that the majority of responding lymphocytes are B cells. Limiting dilution analyses of resting B cells revealed high frequencies of cells producing IgM (F 1/11-1/62) or IgG (F 1/5-1/163) in response to B. burgdorferi sonicate (B.b. sonicate). These numbers were similar to those obtained with lipopolysaccharide (LPS) (IgM: F 1/20-1/84; IgG: F 1/14-1/85) or a synthetic lipopeptide of Braun's Escherichia coli lipoprotein (IgM: F 1/15, 1/19; IgG: F 1/148, 1/34). The mitogenic structure(s) expressed by B. burgdorferi is distinct from LPS, as similar proliferative responses were obtained with B cells from LPS-resistant (C57BL/10ScCr and C3H/HeJ) and LPS-susceptible (C57BL/10ScSn, C3H/HeN) mice. Furthermore, B-cell mitogenic properties were also found in two distinct fractions of a phenol-chloroform-petroleum ether extract of B. burgdorferi: they consisted of a lipoprotein distinct from the outer surface proteins (Osp) A and B and glycolipid-like structures, respectively. These data suggest that spirochetes express a multitude of distinct structures with mitogenic activity for B cells including various lipoproteins as well as glycolipid(s).     

Flow Perfusion Culture of Marrow Stromal Cells Seeded on Porous Biphasic Calcium Phosphate Ceramics

Calcium phosphate ceramics have been widely used for filling bone defects to aid in the regeneration of new bone tissue. Addition of osteogenic cells to porous ceramic scaffolds may accelerate the bone repair process. This study demonstrates the feasibility of culturing marrow stromal cells (MSCs) on porous biphasic calcium phosphate ceramic scaffolds in a flow perfusion bioreactor. The flow of medium through the scaffold porosity benefits cell differentiation by enhancing nutrient transport to the scaffold interior and by providing mechanical stimulation to cells in the form of fluid shear. Primary rat MSCs were seeded onto porous ceramic (60% hydroxyapatite, 40% β-tricalcium phosphate) scaffolds, cultured for up to 16 days in static or flow perfusion conditions, and assessed for osteoblastic differentiation. Cells were distributed throughout the entire scaffold by 16 days of flow perfusion culture whereas they were located only along the scaffold perimeter in static culture. At all culture times, flow perfused constructs demonstrated greater osteoblastic differentiation than statically cultured constructs as evidenced by alkaline phosphatase activity, osteopontin secretion into the culture medium, and histological evaluation. These results demonstrate the feasibility and benefit of culturing cell/ceramic constructs in a flow perfusion bioreactor for bone tissue engineering applications.     

Longitudinal study of antibody response to lipopolysaccharides during chronic Pseudomonas aeruginosa lung infection in cystic fibrosis.

Antibodies to Pseudomonas aeruginosa from 10 cystic fibrosis patients with chronic P. aeruginosa lung infections were quantitatively and qualitatively analyzed. The development of specific antibodies in patient serum was evaluated in a longitudinal study (1972 to 1987). The concentrations and specificities of immunoglobulin G (IgG) and IgM antibodies to purified lipopolysaccharides (LPS) from clinical isolates of P. aeruginosa and to a variety of other gram-negative bacteria were studied by immunoblotting and enzyme-linked immunosorbent assay techniques. Results were compared with the number of immunoprecipitates to P. aeruginosa whole-cell extracts detected by crossed immunoelectrophoresis. IgG, but not IgM, anti-Pseudomonas LPS concentrations increased significantly at the onset of chronic infection and continued to increase during the course of the infection. There was a good positive correlation between the concentration of IgG anti-Pseudomonas LPS antibodies and the number of crossed-immunoelectrophoresis precipitins. The increases in IgG anti-LPS antibody concentrations were much higher to Pseudomonas LPS than to other LPSs. Binding studies demonstrated an increase in binding of IgG anti-Pseudomonas LPS during infection, whereas the binding of other anti-LPS antibodies decreased. Immunoblotting studies confirmed that antibodies reacted strongly with Pseudomonas LPS and weakly with Escherichia coli core-lipid A. The specificity of the reaction with Pseudomonas LPS increased with the duration of infection. It is concluded that anti-LPS response in cystic fibrosis patients during chronic P. aeruginosa infection demonstrates a marked increase in IgG anti-Pseudomonas LPS antibody concentration, specificity, and affinity. The anti-LPS enzyme-linked immunosorbent assay is proposed as a routine test to diagnose and to follow the course of chronic P. aeruginosa lung infection in patients with cystic fibrosis.