Osteolipoma of the knee

AbstractA case of a right knee intra-articular osteolipoma in a 64-year-old man is reported. The patient presented for evaluation of a 1-year history of nontraumatic, mechanically-exacerbated, medial-sided right knee pain. Radiographs demonstrated a partially calcified 3.0 cm mass anterior to the distal medial femur at the suprapatellar fossa. Magnetic resonance imaging examination confirmed a 4.0 × 3.6 cm well-circumscribed mass deep to the medial patellofemoral ligament, with predominantly fat characteristics on T1-weighted and T2-weighted sequences. The mass had irregular ossification superiorly with surrounding heterogeneous enhancement. Histologic examination of an excisional biopsy showed the lesion to be an osteolipoma. Osteolipoma is a rare histologic variant of lipoma with osseous metaplasia, but should be considered in the differential of a fat-containing neoplasm with ossification

Osteolipoma of the knee

A case of a right knee intra-articular osteolipoma in a 64-year-old man is reported. The patient presented for evaluation of a 1-year history of nontraumatic, mechanically-exacerbated, medial-sided right knee pain. Radiographs demonstrated a partially calcified 3.0 cm mass anterior to the distal medial femur at the suprapatellar fossa. Magnetic resonance imaging examination confirmed a 4.0 × 3.6 cm well-circumscribed mass deep to the medial patellofemoral ligament, with predominantly fat characteristics on T1-weighted and T2-weighted sequences. The mass had irregular ossification superiorly with surrounding heterogeneous enhancement. Histologic examination of an excisional biopsy showed the lesion to be an osteolipoma. Osteolipoma is a rare histologic variant of lipoma with osseous metaplasia, but should be considered in the differential of a fat-containing neoplasm with ossification

A Critical Role of Ser26 Hydrogen Bonding in Aβ42 Assembly and Toxicity.

Amyloid β-protein (Aβ) assembly is a seminal process in Alzheimer's disease. Elucidating the mechanistic features of this process is thought to be vital for the design and targeting of therapeutic agents. Computational studies of the most pathologic form of Aβ, the 42-residue Aβ42 peptide, have suggested that hydrogen bonding involving Ser26 may be particularly important in organizing a monomer folding nucleus and in subsequent peptide assembly. To study this question, we experimentally determined structure-activity relationships among Aβ42 peptides in which Ser26 was replaced with Gly, Ala, α-aminobutryic acid (Abu), or Cys. We observed that aliphatic substitutions (Ala and Abu) produced substantially increased rates of formation of β-sheet, hydrophobic surface, and fibrils, and higher levels of cellular toxicity. Replacement of the Ser hydroxyl group with a sulfhydryl moiety (Cys) did not have these effects. Instead, this peptide behaved like native Aβ42, even though the hydropathy of Cys was similar to that of Abu and very different from that of Ser. We conclude that H bonding of Ser26 is the factor most important in its contribution to Aβ42 conformation, assembly, and subsequent toxicity

A Critical Role of Ser26 Hydrogen Bonding in Aβ42 Assembly and Toxicity.

Amyloid β-protein (Aβ) assembly is a seminal process in Alzheimer's disease. Elucidating the mechanistic features of this process is thought to be vital for the design and targeting of therapeutic agents. Computational studies of the most pathologic form of Aβ, the 42-residue Aβ42 peptide, have suggested that hydrogen bonding involving Ser26 may be particularly important in organizing a monomer folding nucleus and in subsequent peptide assembly. To study this question, we experimentally determined structure-activity relationships among Aβ42 peptides in which Ser26 was replaced with Gly, Ala, α-aminobutryic acid (Abu), or Cys. We observed that aliphatic substitutions (Ala and Abu) produced substantially increased rates of formation of β-sheet, hydrophobic surface, and fibrils, and higher levels of cellular toxicity. Replacement of the Ser hydroxyl group with a sulfhydryl moiety (Cys) did not have these effects. Instead, this peptide behaved like native Aβ42, even though the hydropathy of Cys was similar to that of Abu and very different from that of Ser. We conclude that H bonding of Ser26 is the factor most important in its contribution to Aβ42 conformation, assembly, and subsequent toxicity