Mitotic waves in an import-diffusion model with multiple nuclei in a shared cytoplasm.

Nuclei import and export proteins, including cell cycle regulators. These import-export processes are modulated periodically by the cell cycle, for example due to the periodic assembly and breakdown of the nuclear envelope. As such, replicated DNA can be segregated between the two daughter cells and the proteins that were localized in the nucleus are free to diffuse throughout the cytoplasm. Here, we study a mathematical import-diffusion model to show how proteins, i.e. cell cycle regulators, could be redistributed in the cytoplasm by nuclei that periodically toggle between interphase and mitosis. We show that when the cell cycle period depends on the local concentration of regulators, the model exhibits mitotic waves. We discuss how the velocity and spatial origin of these mitotic waves depend on the different model parameters. This work is motivated by recent in vitro experiments reporting on mitotic waves in cycling cell-free extracts made with Xenopus laevis frog eggs, where multiple nuclei share the same cytoplasm. Such experiments have shown that nuclei act as pacemakers for the cell cycle and thus play an important role in collectively defining the spatial origin of mitotic waves.

Synchronization in reaction-diffusion systems with multiple pacemakers.

Spatially extended oscillatory systems can be entrained by pacemakers, regions that oscillate with a higher frequency than the rest of the medium. Entrainment happens through waves originating at a pacemaker. Typically, biological and chemical media can contain multiple pacemaker regions, which compete with each other. In this paper, we perform a detailed numerical analysis of how wave propagation and synchronization of the medium depend on the properties of these pacemakers. We discuss the influence of the size and intrinsic frequency of pacemakers on the synchronization properties. We also study a system in which the pacemakers are embedded in a medium without any local dynamics. In this case, synchronization occurs if the coupling determined by the distance and diffusion is strong enough. The transition to synchronization is reminiscent of systems of discrete coupled oscillators.

Titanium orthodontic appliances for allergic patients.

AIM: The aim of our study was to assess the use of orthodontic appliances made in titanium for patients with an allergy to resin and nickel. We aim to highlight the resolution of problems such as stomatitis and peri-labial dermatitis, which generally manifest in patients who use traditional orthodontic appliances in acrylic resin and steel. METHODS: A total of 120 patients of ages between ten and fifteen undergoing orthodontic treatment requiring a rapid palatal expander or a mobile appliance were evaluated and two patch sensitivity tests were done to assess the presence of allergies. RESULTS: The biocompatibility of a material is directly dependent on its corrosion effect. If a metal does not allow the release of ions it will not have a damaging action or cause destruction on the cellular DNA. The oxidation status of an ion is related to the reactivity of the ion itself and thus may give the latter a carcinogenic effect. Titanium appliances used for this study have obtained excellent results due to their ability to form superficial oxides, which block the oxidation phenomenon and thus corrosion. CONCLUSION: We have noticed a total regression of the symptoms after the use of titanium appliances in patients who had a sensitivity reaction.

Pycnodysostosis: review and case report.

AIM: Aim of the present study was to present a case report of a patient suffering from pycnodysostosis and assess how it may manifest and affect the dental/ orthodontic treatment. METHODS: An 11-year-old patient who was diagnosed with pycnodysostosis at the age of 18 months, attended the orthodontics department requiring treatment for extensive carious lesions, periodontal disease and severe crowding. RESULTS: After an accurate radiographic, clinical and orthodontic assessment of the patient taking into consideration the severity of the condition and the patient's necessities, we have formulated a treatment plan, which was accepted by both the patient and parents. We took into consideration the risks and benefits of the options available and the requests of the patient. CONCLUSION: We have decided to opt for the extraction of teeth to relieve the crowding as this was impeding good oral hygiene and hence increasing the risk of caries and periodontal disease. Such patients must be placed under an oral hygiene prevention scheme, a treatment plan must be accurately designed and the patient must be constantly motivated.

Qualitative and quantitative assessment of plaque bacteria in pediatric patients, patients undergoing orthodontic treatment, combined orthdontic-surgical treatment and implant-prosthetic rehabilitation.

AIM: The aim of this paper was to describe the qualitative and quantitative changes occurring within the oral bacterial flora of several groups of patients following oral prevention protocols during the stages of the dental treatment they required. METHODS: Three hundred patients were enrolled in the study. The selected patients were categorized into different groups to receive preventive strategies according to their needs and treatment required. Plaque samples from each patient were collected at different intervals according to the treatment they were undergoing. These were then assessed under a microscope to carry out a quantitative and qualitative assessment of the plaque. RESULTS: The Mean Plaque Index Score of most patients generally decreased during the various treatment phases and hence the overall bacterial count. However, we noticed a slight increase in the plaque index in patients undergoing orthodontic surgery after placement of the orthodontic appliance and patients undergoing combined orthodontic-surgical treatment during the intermaxillary fixation phase. We generally found that the coccoidal bacterial form was the most prevalent. CONCLUSION: Patients who were adequately instructed and motivated through oral hygiene prevention strategies, showed a significant decrease in the plaque levels and in the overall bacterial components between the first visit and the successive sample taking. Even though we noticed a slight increase in the plaque index in patients undergoing the intermaxillary fixation phase, this decreased immediately once the phase ended and the patients managed to return to the routine oral hygiene care. This highlights the importance of constant motivation and oral hygiene instruction reinforcement.