Computationally modelling cell proliferation: A review.

Cell proliferation is vital for the development and homeostasis of the human body. For such to occur, cells go through the cell cycle during which they replicate their genetic material and ultimately complete cellular division, when one cell divides into two new cells with equal genetic material. However, if there are some errors or abnormalities during the cell cycle that disrupt the balance between cell death and proliferation, severe problems can occur, such as tumour development, which is currently one of the leading causes of death in the world. Nowadays, mathematical and computational models are used to understand and study several biological mechanisms and processes, namely cellular proliferation. Over the last forty-five years, several models have attempted to describe cell proliferation and its regulation. Due to the complexity of the process, numerous assumptions and simplifications have been considered. This work presents a review of some of these models, focusing mainly on mammalian or generic eukaryotic models. Previously published continuum, discrete and hybrid approaches are presented and compared, in order to understand and highlight the relevance and capabilities of these models, their shortcomings and future challenges.

Computational simulation of cellular proliferation using a meshless method.

BACKGROUND AND OBJECTIVE: During cell proliferation, cells grow and divide in order to obtain two new genetically identical cells. Understanding this process is crucial to comprehend other biological processes. Computational models and algorithms have emerged to study this process and several examples can be found in the literature. The objective of this work was to develop a new computational model capable of simulating cell proliferation. This model was developed using the Radial Point Interpolation Method, a meshless method that, to the knowledge of the authors, was never used to solve this type of problem. Since the efficiency of the model strongly depends on the efficiency of the meshless method itself, the optimal numbers of integration points per integration cell and of nodes for each influence-domain were investigated. Irregular nodal meshes were also used to study their influence on the algorithm. METHODS: For the first time, an iterative discrete model solved by the Radial Point Interpolation Method based on the Galerkin weak form was used to establish the system of equations from the reaction-diffusion integro-differential equations, following a new phenomenological law proposed by the authors that describes the growth of a cell over time while dependant on oxygen and glucose availability. The discretization flexibility of the meshless method allows to explicitly follow the geometric changes of the cell until the division phase. RESULTS: It was found that an integration scheme of 6 × 6 per integration cell and influence-domains with only seven nodes allows to predict the cellular growth and division with the best balance between the relative error and the computing cost. Also, it was observed that using irregular meshes do not influence the solution. CONCLUSIONS: Even in a preliminary phase, the obtained results are promising, indicating that the algorithm might be a potential tool to study cell proliferation since it can predict cellular growth and division. Moreover, the Radial Point Interpolation Method seems to be a suitable method to study this type of process, even when irregular meshes are used. However, to optimize the algorithm, the integration scheme and the number of nodes inside the influence-domains must be considered.

Estudio retrospectivo del tiempo de erupción de caninos incluidos utilizando dos sistemas de tracción / No disponible

Introducción: El anclaje esquelético temporal es una incorporación relativamente reciente en los tratamientos de ortodoncia. El objetivo de este estudio fue comparar retrospectivamente el tiempo que tarda en asomar un canino maxilar incluido comparando el uso de minitornillos con el anclaje dentario convencional. Material y métodos: Se estudiaron un total de 31 pacientes con caninos maxilares incluidos, tratados en una clínica privada durante los últimos 15 años. El grupo test estaba formado por 15pacientes en los que se traccionó del canino incluido utilizando un minitornillo, y el grupo control estaba formado por 16 pacientes en los que se utilizó anclaje dentario. Resultados: A pesar de la reducción del tiempo de tracción utilizando minitornillos detectada clínicamente, no se encontraron diferencias estadísticamente significativas en el tiempo de erupción forzada en el grupo test comparado con el grupo control. Conclusiones: En este estudio retrospectivo comparativo no existe diferencia estadísticamente significativa entre los dos grupos, sugiriendo que dentro de los límites de este estudio, el tiempo de erupción forzada de un canino incluido no depende del sistema de tracción (AU)

Introduction: Temporal osseous anchorage is a recent technique that clinicians have incorporated to orthodontic treatments. The aim of this study was to compare retrospectively the time required to complete the canine forced eruption phase by using two different orthodontic devices. Subjects and methods: A total of 31 patients treated in a private office during the last 15 years were studied. Test group comprised15 patients on whom traction of the impacted canine was performed with a mini-screw, and control group comprised 16patients on whom traction of the impacted canine was performed from teeth. Results: In spite of a shorter time of traction detected in the mini-screw group there were no statistically significant differences between groups. Conclusions: In this retrospective comparative study no statistically significant differences could be observed between groups, suggesting that within the limits of this study, forced eruption time does not depend on the traction system (AU)

[Prevalence of dental caries and treatment needs in 6 to 12 year-old schoolchildren at public schools]. / Prevalência de cárie e necessidades de tratamento em escolares de 6 a 12 anos da rede pública de ensino.

OBJECTIVE: To assess dental caries prevalence and treatment needs of schoolchildren in the State of Goiás, Brazil. METHODS: The study population consisted of 6-12-yr-old schoolchildren (n=1,419), male and female, attending 25 public schools located in the urban area of 9 provincial cities in the State of Goiás. RESULTS: Percentage of caries-free schoolchildren was very low at all ages (4.4% at age 12). Mean DMF-T ranged from 0.41 at age 6 to 5.19 at age 12. Mean dmf-t in this age group ranged from 4.93 to 0.29. Treatment needs were higher than the proportion of treated teeth in both deciduous and permanent dentition. CONCLUSION: The high prevalence of dental caries found in schoolchildren in the provincial cities of Goiás suggests the need for oral health education and preventive programs targeted at the underlying causes of the disease on a population level.

[The prevalence of dental caries and necessary treatment in six to twelve year old schoolchildren in Goiânia, GO, Brazil, 1994]. / Prevalência de cárie e necessidades de tratamento em escolares de seis a doze anos de idade, Goiânia, GO, Brasil, 1994.

OBJECTIVE: The prevalence of dental caries and needs of treatment among schoolchildren in Goiânia-GO, middle-west of Brazil was assessed. METHODOLOGY: The study population consisted of 6-12-yr-old schoolchildren (n = 1,400) attending public schools located in the urban area of the city, where the water-supply had been fluoridated for 9 years. RESULTS: Mean dmf-t and DMF-T for the total sample were 2.19 and 2.86, respectively, showing a reduction of 57.1% in the DMF-T as compared to the regional data from the national survey carried out in 1986. At age 12 DMF-T was 4.59, which is above the acceptable level according to the FDI/WHO goal for the year 2000. Percentage of caries-free schoolchildren was very low at all ages (11% of the total sample). The most significant need was for restorative treatment in the treatment deciduous dentition at all ages and in the permanent dentition from age 9. CONCLUSION: It was concluded that the prevalence of dental caries among schoolchildren in Goiânia-GO is high, comparable to the situation in most Latin American countries and poor regions of developed countries. The results indicate the need for oral health education and preventive programs targeted at the underlying causes of the disease, in the population.