Mutations in and Expression of the Tumor Suppressor Gene p53 in Egg-Type Chickens Infected With Subgroup J Avian Leukosis Virus.

To investigate the molecular mechanisms of the oncogenic effects of avian leukosis virus subgroup J (ALV-J), we examined mutations in and the expression of p53 in the myelocytomas distributed in the liver, spleen, trachea, and bone marrow, as well as in fibrosarcomas in the abdominal cavity and hemangiomas in skin from chickens that were naturally or experimentally infected with ALV-J. Two types of mutations in the p53 gene were detected in myelocytomas of both the experimentally infected and the naturally infected chickens and included point mutations and deletions. Two of the point mutations have not been reported previously. Partial complementary DNA clones with a 122-bp deletion in the p53 gene ORF and a 15-bp deletion in the C-terminus were identified in the myelocytomas. In addition, moderate expression of the mutant p53 protein was detected in the myelocytomas that were distributed in the liver, trachea, spleen, and bone marrow. Mutant p53 protein was not detected in the subcutaneous hemangiomas or in the abdominal fibrosarcomas associated with natural and experimental ALV-J infection, respectively. These results identify mutations associated with abnormal expression of p53 in ALV-J-associated myelocytomas, suggesting a role in tumorigenesis.

Introduction of gelatin microspheres into an injectable calcium phosphate cement.

For tissue engineered bone constructs, calcium phosphate cement (CPC) has a high potential as scaffold material because of its biocompatibility and osteoconductivity. However, in vivo resorption and tissue ingrowth is slow. To address these issues, microspheres can be incorporated into the cement, which will create macroporosity after in situ degradation. The goal of this study was to investigate the handling properties and degradation characteristics of CPC containing gelatin microspheres. Setting time and injectability were determined and an in vitro degradation study was performed. Samples were assayed on mass, compression strength, E-modulus, and morphology. A supplementary degradation test with gelatin microspheres was performed to investigate the influence of physical conditions inside the cement on microsphere stability. The gelatin microsphere CPCs were easy to inject and showed initial setting times of less than 3 min. After 12-weeks in vitro degradation no increase in macroporosity was observed, which was supported by the small mass loss and stabilizing mechanical strength. Even a clear densification of the composite was observed. Explanations for the lack of macroporosity were recrystallization of the cement onto or inside the gelatin spheres and a delayed degradation of gelatin microspheres inside the scaffold. The supplementary degradation test showed that the pH is a factor in the delayed gelatin microsphere degradation. Also differences in degradation rate between types of gelatin were observed. Overall, the introduction of gelatin microspheres into CPC renders composites with good handling properties, though the degradation characteristics should be further investigated to generate a macroporous scaffold.

Formation of a bone apatite-like layer on the surface of porous hydroxyapatite ceramics.

Phosphoric acid solution was used to react with commercial hydroxyapatite (HA) powders to demonstrate the possibility of converting HA to non-stoichiometric apatite and thus to treat porous HA ceramics, to form a thin bone-apatite like layer on the HA ceramic surface. Such a carbonate-containing non-stoichiometric apatite "bioceramic" would be more efficient in bone bonding or bone formation, due to its analogy to natural bone apatite.

Relationship between the colour change of hydroxyapatite and the trace element manganese.

Hydroxyapatite containing the trace element manganese turns blue after sintering at high temperature in an oxidizing atmosphere. This phenomenon is related to the oxidation of manganese ions in the special crystal structure of hydroxyapatite. Combination of the crystal structure with electron spin resonance spectra gives an explanation for this oxidation of Mn2+ ions at Ca(l) sites into Mn5+ ions and the formation of MnO4(3-) ions at PO4(3-) sites, corresponding to the colour change of hydroxyapatite.