A Rule of Thumb Derivation of Born-Infeld Action for D-branes

A rule of thumb derivation of the Dirac-Born-Infeld action for D-branes is studied \`a la Fradkin and Tseytlin, by simply integrating out of the superstring coordinates in a narrow strip attached to the D-branes. In case of superstrings, the coupling of Ramond-Ramond fields as well as the Dirac-Born-Infeld type coupling of the Neveu Schwarz-Neveu Schwarz fields come out in this way.Comment: 9 pages, Latex, minor correction

Rapidly Destructive Arthrosis of Bilateral Humeral Heads Caused by Subchondral Insufficiency Fracture

The bilateral shoulder pain of an 81-year-old Japanese woman due to falls persisted despite celecoxib treatment, and plain X-rays later showed bilateral collapsed humeral heads. After ruling out osteoarthritis, infectious arthritis, crystal-induced arthritis, neuropathic arthropathy, and osteonecrosis, we diagnosed bilateral shoulder joint rapidly destructive arthrosis (RDA). Lumbar bone mineral density showed very low T-score (−4.1). Primary osteoporosis was observed. Histology of biopsied humeral head indicated the features of fracture healing process: callus formation and osteoclasts without empty lacunae. Her history thus included an insufficiency fracture due to severe osteoporosis. Bilateral humeral head replacement was performed; her shoulder joint function improved. This case is extremely rare in that RDA was caused by simultaneous bilateral shoulder joint collapse within a very short time, with minimal or low mechanical stress and severe osteoporosis

Sacral Stress Fracture Complicated by L5 Radiculopathy in a Patient with Rheumatoid Arthritis

A 60-year-old Japanese woman with severe osteoporosis presented with a history of right buttock pain and right lateral lower leg pain in an L5 distribution. She had been treated with methotrexate and methylprednisolone for rheumatoid arthritis (RA) and interstitial pneumonia. Computed tomography demonstrated a sacral stress fracture in the right sacral ala. The right L5 nerve root was compressed by the fracture site. This case is rare in that L5 radiculopathy was complicated by a sacral stress fracture. Clinicians should suspect sacral stress fractures when RA or osteoporosis is present in women who experiences lumbar pain and lumbar radiculopathy

Mechanical Stress Activates Smad Pathway through PKCδ to Enhance Interleukin-11 Gene Transcription in Osteoblasts

BACKGROUND: Mechanical stress rapidly induces ΔFosB expression in osteoblasts, which binds to interleukin (IL)-11 gene promoter to enhance IL-11 expression, and IL-11 enhances osteoblast differentiation. Because bone morphogenetic proteins (BMPs) also stimulate IL-11 expression in osteoblasts, there is a possibility that BMP-Smad signaling is involved in the enhancement of osteoblast differentiation by mechanical stress. The present study was undertaken to clarify whether mechanical stress affects BMP-Smad signaling, and if so, to elucidate the role of Smad signaling in mechanical stress-induced enhancement of IL-11 gene transcription. METHODOLOGY/PRINCIPAL FINDINGS: Mechanical loading by fluid shear stress (FSS) induced phosphorylation of BMP-specific receptor-regulated Smads (BR-Smads), Smad1/5, in murine primary osteoblasts (mPOBs). FSS rapidly phosphorylated Y311 of protein kinase C (PKC)δ, and phosphorylated PKCδ interacted with BR-Smads to phosphorylate BR-Smads. Transfection of PKCδ siRNA or Y311F mutant PKCδ abrogated BR-Smads phosphorylation and suppressed IL-11 gene transcription enhanced by FSS. Activated BR-Smads bound to the Smad-binding element (SBE) of IL-11 gene promoter and formed complex with ΔFosB/JunD heterodimer via binding to the C-terminal region of JunD. Site-directed mutagenesis in the SBE and the AP-1 site revealed that both SBE and AP-1 sites were required for full activation of IL-11 gene promoter by FSS. CONCLUSIONS/SIGNIFICANCE: These results demonstrate that PKCδ-BR-Smads pathway plays an important role in the intracellular signaling in response to mechanical stress, and that a cross-talk between PKCδ-BR-Smads and ΔFosB/JunD pathways synergistically stimulates IL-11 gene transcription in response to mechanical stress

ICTP and vulnerable plaque

Evaluation of atherosclerotic plaques depends on invasive intravascular ultrasonography (IVUS). Carboxy-terminal telopeptide of type I collagen (ICTP) is produced by matrix metalloproteinase (MMP)-dependent digestion of type I collagen. Because vulnerable plaques are rich in type I collagen and MMPs from macrophages, we examined the association between serum ICTP and coronary plaques in patients with coronary disease. We recruited 46 men and 17 women without renal failure or bone diseases affecting serum ICTP, who underwent coronary IVUS. Serum ICTP levels were higher in patients with coronary plaques containing more than 10% necrotic core area than in patients with less than 10% necrotic core area. A positive correlation was found between serum ICTP and necrotic core area. Only serum ICTP was positively correlated with necrotic core area by multivariate analysis (p<0.05). These results suggest that serum ICTP can be used as a non-invasive marker of vulnerable plaques in atherosclerotic patients