Locating the center of resistance in individual teeth via two- and three-dimensional radiographic data.

OBJECTIVES: The preferred reference point to describe the force-moment system exerted upon a tooth is its center of resistance (CR). Morphological data on the dentoalveolar complex can be used to locate this point either three-dimensionally (3D) with the finite element (FE) method, or two-dimensionally (2D) with a mathematical method calculating the centroid of the projected dental root. This study aimed to compare and appraise these two methods with regard to their accuracy and time requirements. METHODS: Three radiological datasets with permanent teeth were included. Each single 3D dataset was used in each of these patients to derive both a 3D and 2D morphological model of the upper right central incisor. CR levels were evaluated in percent, indicating the relative height as measured from the (averaged levels of the mesial and distal) bony ridge margin to the tooth's apex. RESULTS: Mean CR levels of 42.8% for distalization and 56.5% for lingual movement were obtained from the 3D FE simulations of initial tooth movement. The 2D mathematical model yielded a mean CR level of 44.5%. Compared to this mathematical approach, the 3D FE simulations were around 15 times more time-consuming, with an interactive requirement of around 15 h. CONCLUSION: Because they contain so much more morphological information, 3D FE simulations should offer superior predictability. In addition, they are the only method offering detailed CR identification for specific directions of tooth movement. Before this method can be used in clinical practice, however, there is still a major need to reduce time requirements via further automation of process steps and to investigate how it should be applied to different tooth types.

Small nucleolar RNP scleroderma autoantigens associate with phosphorylated serine/arginine splicing factors during apoptosis.

OBJECTIVE: Proteins that are phosphorylated during apoptosis are commonly precipitated by autoantibodies found in the sera of patients with systemic lupus erythematosus. We sought to determine whether scleroderma autoantigens such as small nucleolar RNPs (snoRNP) also associate with phosphoproteins in response to various cellular stressors. METHODS: We screened a panel of monoclonal antibodies derived from mice exposed to mercury, a well-characterized murine model of the anti-snoRNP autoimmune response, for the ability to selectively precipitate phosphoproteins from radiolabeled lysates prepared from Jurkat T cells subjected to stressful stimuli. RESULTS: Monoclonal antibodies reactive with snoRNPs precipitated a phosphoprotein complex (pp42, pp34, and pp23) from lysates prepared from apoptotic cells. Several novel phosphoproteins (pp62 and pp18) were also observed. The phosphorylation and/or recruitment of these proteins to the snoRNP complex is induced by multiple apoptotic stimuli (e.g., Fas ligation, anisomycin, or ultraviolet irradiation), an effect that is blocked by overexpression of Bcl-2. We were unable to demonstrate an association of the phosphoprotein complex with snoRNPs in cells treated with the xenobiotic agent mercury. The snoRNP-associated phosphoprotein complex is composed of serine/arginine (SR) splicing factors, including SRp40. CONCLUSION: The association of phosphorylated SR proteins with snoRNPs in cells undergoing apoptosis suggests that the immune response to fibrillarin that characterizes a subset of patients with scleroderma may be related to cell death induced by apoptotic stimuli (e.g., Fas ligation, irradiation, or chemical toxins), or by exposure to mercury.

The 72-kDa component of signal recognition particle is cleaved during apoptosis.

Proteins cleaved by apoptotic caspases are commonly recognized by autoantibodies found in the serum of patients with rheumatic disease. We report that the 72-kDa signal recognition particle (SRP) protein, a rare target of autoantibodies found in the serum of patients with dermatomyositis and systemic lupus erythematosus, is rapidly cleaved in Jurkat T cells treated with apoptotic (i.e. Fas ligation, treatment with gamma or ultraviolet radiation, or co-culture with anisomycin or staurosporine) but not proliferative (CD3 cross-linking) stimuli. Cleavage of SRP 72 produces a 66-kDa amino-terminal fragment and a 6-kDa carboxyl-terminal fragment that is selectively phosphorylated on serine residues. Cleavage of SRP 72 is prevented by chemical and peptide caspase inhibitors, and by overexpression of bcl-2, an inhibitor of apoptotic cell death. Analysis of the carboxyl terminus of SRP 72 has identified a putative cleavage site (SELD/A) for group III caspases, and carboxyl-terminal serine residues that are highly conserved in phylogeny. Both serine phosphorylation and caspase cleavage of SRP 72 are observed in cells derived from human, dog, rat, and mouse. Canine SRP 72 is cleaved in vitro by recombinant caspase 3 but retains the ability to mediate transport of a signal peptide-containing protein into the endoplasmic reticulum lumen. The 72-kDa component of the SRP joins a growing list of autoantigens that undergo post-translational modifications during programmed cell death.