Healing of onlay mandibular bone grafts covered with collagen membrane or bovine bone substitutes: a microscopical and immunohistochemical study in the sheep.

The objective of this study was to evaluate the role of collagen membrane and Bio-Oss coverage in healing of an onlay graft to the mandible. Twelve adult sheep each received an onlay bone graft (experiment 1), bone graft+Bio-Gide (experiment 2), and bone graft+Bio-Oss/Bio-Gide (experiment 3) on the lateral surface of the mandible. The animals were euthanized at 4, 8, 12 or 16 weeks after surgery, and findings were analysed by routine microscopy and immunohistochemistry for proliferation (Ki67) and apoptotic (Caspase-3) markers. Grafts were fully incorporated in all specimens. Pronounced resorption was observed in experiment 1. Minimal loss of graft volume was seen in experiment 2 specimens without membrane displacement. A remarkable increase in the augmented region of the mandible was observed in experiment 3. A high number of osteoclasts were expressed within the grafts during the early healing period, and thereafter declined markedly. Osteoblasts within the grafts expressed a moderate level of Ki67 at 8 weeks, which thereafter declined markedly. The strongest expression of Caspase-3 on the bone surface was observed after 16 weeks. In conclusion, the effect of collagen membrane coverage on bone graft volume maintenance was dependent on membrane stability during healing. An autogenous bone graft covered with Bio-Oss particles resulted in a remarkable increase in augmented lateral surface of the mandible. The late stage of bone graft healing was associated with a high apoptotic induction pathway of osteoblasts lining the surfaces of the new bone, demonstrated by strong positive Caspase-3 immunoreactivity.

A case of chronic calcium pyrophosphate dihydrate crystal disease (tophaceous pseudogout) in the temporomandibular joint.

Pseudogout is a rare joint disease which is characterized by the presence of calcium pyrophosphate dihydrate crystals in the intraarticular and periarticular tissue. The crystals tend to attach to fibrocartilage tissue. Pseudogout principally affects the knee and wrist joints. Involvement of the temporomandibular joint (TMJ) is very rare. There have been <20 cases reported world-wide. Both acute and chronic manifestations have been described. We present here an unusual case that necessitated a high condylectomy.

Chemoprevention of oral squamous cell carcinomas.

Among individuals with a history of head and neck cancer and tobacco abuse the risk of second primary cancers in the upper aerodigestive tract is high. Chemoprevention of oral squamous cell carcinomas is based on two conditions: Premalignant mucosa lesions are treated with chemopreventive agents in order to prevent malignant conversion (primary prevention). In secondary prevention of oral cancer, after curative therapy patients are treated by chemoprevention in order to reduce the rate of second primaries. This paper presents a comprehensive clinical review of oral cancer prevention studies, highlighting the agents mostly used, such as beta-carotene, alpha-tocopherol, ascorbic acid, and retinoids. Although most intervention trials showed good overall response with these substances, high relapse rates and serious side effects, in most cases related to the retinoid compounds were noticed. In addition, in all prospective randomized chemoprevention trials (CARET, ATBC and PHS) no significant evidence of benefit for supplementation with alpha-tocopherol, beta-carotene or retinyl palmitate was reported.

Model of maltose-binding protein/chemoreceptor complex supports intrasubunit signaling mechanism.

The Tar protein of Escherichia coli is unique among known bacterial chemoreceptors in that it generates additive responses to two very disparate ligands, aspartate and maltose. Aspartate binds directly to the periplasmic (extracytoplasmic) domain of Tar. Maltose first binds to maltose-binding protein (MBP). MBP then assumes a closed conformation in which it can interact with the periplasmic domain of Tar. MBP residues critical for binding Tar were identified in a screen of mutations that cause specific defects in maltose chemotaxis. Mutations were introduced into a plasmid-borne malE gene that encodes a mutant form of MBP in which two engineered Cys residues spontaneously generate a disulfide bond in the oxidizing environment of the periplasmic space. This disulfide covalently crosslinks the NH3-terminal and COOH-terminal domains of MBP and locks the protein into a closed conformation. Double-Cys MBP confers a dominant-negative phenotype for maltose taxis, and we reasoned that third mutations that relieve this negative dominance probably alter residues that are important for the initial interaction of MBP with Tar. The published three-dimensional structures of MBP and the periplasmic domain of E. coli Tar were docked in a computer simulation that juxtaposed the residues in MBP identified in this way with residues in Tar that have been implicated in maltose taxis. The resulting model of the MBP-Tar complex exhibits good complementarity between the surfaces of the two proteins and supports the idea that aspartate and MBP may each initiate an attractant signal through Tar by inducing similar conformational changes in the chemoreceptor.

Self-regulation of slow cortical potentials in completely paralyzed human patients.

The study was intended to answer the question whether self-regulation of brain activity can be operantly learnt when the brain is disconnected from motor periphery. Two neurological patients with nearly complete motor paralysis learned bi-directional control of their slow cortical potentials (SCP) at vertex. After 4-6 weeks training both patients could reliably differentiate between SCP shifts in a negative versus positive direction. With one patient, training has been continued for a subsequent 4 months, which resulted in precise self-control, i.e. the patient was able to produce positive SCP shifts on command with an accuracy of about 95%. This indicates that self-regulation of cortical excitability (as manifested in the SCP) does not require feedback loops from the periphery. Although we cannot rule out that healthy subjects may employ behavioral strategies such as muscle contractions or changes in breathing, obviously humans can also control their SCP without using these strategies.

An assay for the quantitation of Photofrin in tissues and fluids.

A method for determining the concentration of Photofrin in tissues and biological fluids was developed. The procedure is based on the dissolution of biological material with Solvable, a commercially available tissue solubilizer, followed by porphyrin-specific fluorescence detection and measurement. It was found necessary to use a quadratic standard curve for the estimation of unknown Photofrin concentrations. While this method is limited to compounds that are stable in strong base, it has the advantages of being sensitive, rapid and low cost.

Partnering: a closer look at one group's programs.

The word "partner" brings to mind myriad thoughts and ideas: an association, a sharing relationship, joint interests, marriage. "Partnering" is arguably the most overused term in health care purchasing so far in the 1990s; nonetheless, it represents a change in how business is being conducted and an effective way to lower costs. The following is a representation of how one of the nation's leading group purchasing organizations (GPOs) uses partnerships with a variety of associates to provide opportunities for health care providers to lower costs.