A synthetic hydroxyapatite implant: the so-called counterfeit implant.

This article evaluates three generations of synthetic hydroxyapatite implants in a rabbit model. Fourteen New Zealand white rabbits received synthetic hydroxyapatite orbital implants (first, second, and third generation). The rabbits underwent enucleation of one eye and then received a 12-mm synthetic hydroxyapatite implant wrapped in Vicryl (polygalactin 910; Ethicon, Inc.) mesh or sclera. Magnetic resonance imaging was conducted to assess host fibrovascularization of the implant 4 and 12 weeks after implantation. Animals were killed at each of these times and the implant was removed for histopathologic examination. Enhancement on magnetic resonance imaging and extent of fibrovascularization by histopathologic examination were assessed. The first-generation synthetic hydroxyapatite (FCI, Issy-Les-Moulineaux, France) was not 100% hydroxyapatite as is the Bio Eye (Integrated Orbital Implants, Inc., San Diego, CA, U.S.A.). It contained 3.2% calcium oxide. The implant was heavier and much less porous than the original Bio Eye implant. Central vascularization eventually occurred but was not extensive. The second-generation implant was more porous than the first, with rapid central vascularization to the center of the implant by 4 weeks. However, the second-generation implant was very fragile and crumbled easily. The second-generation synthetic implant was chemically identical to the original Bio Eye implant with no calcium oxide. The third-generation implant was more porous than its predecessors. When compared side by side with the Bio Eye, a difference in pore uniformity and interconnectivity seems apparent. However, an early extensive vascularization pattern to the center of the implant is seen histopathologically, similar to that with the Bio Eye. Magnetic resonance imaging also shows extensive enhancement as is the case with the Bio Eye. The third-generation synthetic implant is not fragile as was the second-generation implant, and chemically it is identical to the Bio Eye with no calcium oxide present. The third-generation implant is approximately half the price of the original Bio Eye implant.

Toxicity of intravitreal interferon alpha-2b in the rabbit.

OBJECTIVE: To investigate the toxicity of single doses of intravitreally administered interferon alpha-2b in the New Zealand white albino rabbit. INTERVENTIONS: One eye each of six rabbits received an intravitreal injection of 1000, 10,000, 100,000, 500,000, 1 million or 2 million units of interferon alpha-2b reconstituted in 0.1 mL of balanced salt solution. The fellow eye of the first three rabbits received an intravitreal injection of the same volume of balanced salt solution. OUTCOME MEASURES: Media opacities, toxic effects to the retina, optic nerve or other ocular structures. RESULTS: The injection of 2 million units of interferon alpha-2b elicited an immediate dense vitreous haze that largely cleared within 24 hours as well as numerous intraretinal hemorrhages that were no longer visible 7 days after injection. Histopathological study of this eye 14 days after injection showed a diffuse mixed inflammatory cell infiltrate with retinal vacuolation and ganglion cell dropout. In the remaining eyes, to dosages of 1 million units, the agent produced no clinically or pathologically evident toxic ocular effects. CONCLUSIONS: Interferon alpha-2b appears to be safe and well tolerated up to dosages of 1 million units.

Vicryl-mesh wrap for the implantation of hydroxyapatite orbital implants: an animal model.

OBJECTIVE: To evaluate host fibrovascularization of hydroxyapatite orbital implants wrapped in sclera or in Vicryl (polyglactin 910) mesh in a rabbit model. NUMBERS: Eight adult New Zealand white rabbits that received hydroxyapatite orbital implants wrapped in homologous donor sclera (four animals) or Vicryl mesh (four animals). INTERVENTIONS: The rabbits had one eye enucleated and then received a 12-mm hydroxyapatite implant wrapped in sclera or Vicryl mesh. Magnetic resonance imaging (MRI) and bone scintigraphy were done to assess host fibrovascularization of the implant 4, 8, 12 and 20 weeks after implantation. Two animals (one in each group) were killed at each of these times, and the implant was removed for histopathological examination. MAIN OUTCOME MEASURES: Enhancement on MRI, uptake on bone scintigraphy, fibrovascularization seen on histopathological examination. RESULTS: The degree of fibrovascularization was substantial in all the specimens but appeared greater in the Vicryl-mesh-wrapped implants in the first 12 weeks after implantation on both histopathological and MRI studies. At 20 weeks these findings were similar in the two groups. A granulomatous foreign-body giant-cell reaction to both the Vicryl mesh and the implant itself was present up to 8 weeks after implantation. Bone scans showed only grade 1+ activity in all the implants. CONCLUSIONS: Host fibrovascularization in the rabbit appears to occur to a greater degree in Vicryl-mesh-wrapped hydroxyapatite implants than in those wrapped in donor sclera during the first 12 weeks after implantation. Vicryl mesh appears to be an acceptable alternative wrap for the hydroxyapatite implant, eliminating the need for donor sclera and its potential risks of transmissible diseases.

Effect on lipopolysaccharide structure of aeration during growth of a plum isolate of Pseudomonas syringae pv. morsprunorum.

The composition of lipopolysaccharide (LPS) extracted with aqueous phenol from a virulent English plum isolate of Pseudomonas syringae pv. morsprunorum varied according to the partial pressure of oxygen (pO2) in the culture medium at the time of harvest. When pO2 was low, the organism grew slowly and produced smooth LPS bearing rhamnan sidechains. As pO2 was raised, the rate of growth increased and smooth LPS was replaced by a rough species deficient in rhamnose, which co-extracted with a D-glucan. Organization of rhamnose and glucose into separate polymers was shown by the selective susceptibility of the rhamnose-containing polymer to hydrolysis by rhamnanase of the phage A7. By methylation analysis, GC-MS, and 1H- and 13C-NMR spectroscopy, the glucan was shown to consist of alpha (1-->4)-linked residues with alpha (1-->4,6)-branch points and non-reducing terminal residues in the approximate ratio 4:1:1, resembling glycogen in composition. A glucan which co-extracted with LPS using phenol/water from an avirulent plum isolate that was resistant to lysis by phages A1 and A7 was shown by methylation analysis to have a similar structure. Whether the effect on LPS composition was due directly to pO2, or was dependent on the rate of growth, has not been established. It is suggested that, because epiphytic growth would entail exposure to high pO2, English plum isolates growing on the surfaces of host plants might be unable to produce smooth LPS. Since cell surface composition affects virulence in plant-pathogenic pseudomonads, this effect could account for the observed failure of the English plum isolates to enter the host via leaf scars.

Structure of the sidechain of lipopolysaccharide from Pseudomonas syringae pv. morsprunorum C28.

The sidechain of the lipopolysaccharide from the phytopathogen Pseudomonas syringae pv. morsprunorum C28 was shown to be composed of D-rhamnose. Using 1H and 13C-NMR spectroscopy, methylation analysis, Smith degradation and optical rotation data, the repeat unit was found to have the structure: ----3)-D-Rhap-(alpha 1----3)-D-Rhap-(alpha 1----2)-D-Rhap-(alpha 1---- and a degree of polymerization of approximately 70. Attention is drawn to the possible prevalence of D-6-deoxyhexoses in the lipopolysaccharides of plant pathogenic bacteria.