Temporomandibular joint's reconstruction after segmental mandibulectomy in patients with primary and secondary tumors of the mandible

Background: Auto and allografts are used for segmental resection of the mandible with its exarticulation and simultaneous reconstruction. Endoprosthetic replacement of temporomandibular joint (TMJ) may bring good functional results. However, some complications, such as fracture of the fixing part of the endoprosthesis, migration of its head into the middle cranial fossa and prosthesis eruption, can occur in the long-term. The use of revascularized bone autografts allow for replacement of the mandibular defect and to restore TMJ function. Aim: To evaluate functional, aesthetic and oncological results after segmental resection of the mandible with its exarticulation and simultaneous reconstruction with allografts and revascularized bone autografts. Materials and methods: Thirty patients were enrolled into the study, 22 of them being with primary mandibular tumors and 8 with oral cancers originating from mucosa, with advanced involvement of the mandible. Segmental mandibulectomy with simultaneous reconstruction was performed in all patients, with 9 of them having the allograft and endoprosthesis of the articular head and 21 patients having revascularized bone or combined grafts. If only a defect of the mandibular ramus and articular head was to be replaced, we used an iliac free flap (n = 5), whereas for replacement of a defect of the mandibular ramus, body and articular head a fibular free flap was implanted (n = 16). Results: The use of allografts was associated with 4 (44.4%) complication events, such as plate fracture (n = 2) at 2 and 6 years and eruption of the plate. When revascularized grafts were used, complete necrosis was seen in 1 (4.7%) case. The iliac graft was formed with the size of the ramus defect (most often, up to the mandibular angle), and the articular head was formed from the distal part. At least one osteotomy was performed in the fibular graft at the angle, and the articular head was formed in the distal part. Twenty (66.7%) patients are currently disease-free. Six (33.3%) patients died of relapse at 1 to 5 years, and 4 (13.3%) patients died with lung metastases of osteogenic sarcoma of the mandible. Conclusion: Allotransplantation after segmental resection of the mandible gives good functional results, although with a high rate of late complications (44.4%). In patients with limited defects of the mandibular ramus and head, revascularized iliac grafts can be used. In those with large defects, the method of choice is a fibular graft. It is possible to make the articular head of the distal end of the graft with its subsequent adaptation to the functional load

Protein-free parallel triple-stranded DNA complex formation

A 14 nt DNA sequence 5′-AGAATGTGGCAAAG-3′ from the zinc finger repeat of the human KRAB zinc finger protein gene ZNF91 bearing the intercalator 2-methoxy,6-chloro,9-amino acridine (Acr) attached to the sugar–phosphate backbone in various positions has been shown to form a specific triple helix (triplex) with a 16 bp hairpin (intramolecular) or a two-stranded (intermolecular) duplex having the identical sequence in the same (parallel) orientation. Intramolecular targets with the identical sequence in the antiparallel orientation and a non-specific target sequence were tested as controls. Apparent binding constants for formation of the triplex were determined by quantitating electrophoretic band shifts. Binding of the single-stranded oligonucleotide probe sequence to the target led to an increase in the fluorescence anisotropy of acridine. The parallel orientation of the two identical sequence segments was confirmed by measurement of fluorescence resonance energy transfer between the acridine on the 5′-end of the probe strand as donor and BODIPY-Texas Red on the 3′-amino group of either strand of the target duplex as acceptor. There was full protection from OsO(4)-bipyridine modification of thymines in the probe strand of the triplex, in accordance with the presumed triplex formation, which excluded displacement of the homologous duplex strand by the probe–intercalator conjugate. The implications of these results for the existence of protein-independent parallel triplexes are discussed