Carla M. A. Pinto

Fractional model for malaria transmission under control strategies

We study a fractional model for malaria transmission under control strategies. We consider the integer order model proposed by Chiyaka et al. (2008) in [15] and modify it to become a fractional order model. We study numerically the model for variation of the values of the fractional derivative and of the parameter that models personal protection, b. From observation of the figures we conclude that as b is increased from 0 to 1 there is a corresponding decrease in the number of infectious humans and infectious mosquitoes, for all values of @a. This means that this result is invariant for variation of fractional derivative, in the values tested. These results are in agreement with those obtained in Chiyaka et al. (2008) [15] for @a=1.0 and suggest that our fractional model is epidemiologically well-posed.

A brainstem-like modulation approach for gait transition in a quadruped robot

The ability to traverse a wide variety of terrains while walking is basically a requirement for performing useful tasks in our human centric world. In this article, we propose a bio-inspired robotic controller able to generate locomotion and to easily switch between different type of gaits. In order to improve the robot stability and response while locomoting, we adjust both the duty factor and the interlimb phase relationships, according to the velocities. We extend previous work, by applying nonlinear oscillators to generate the rhythmic locomotor movements for a quadruped robot, similarly to the biological counterparts. The generated trajectories are modulated by a drive signal, that modifies the oscillator frequency, amplitude and the coupling parameters among the oscillators, proportionally to the drive signal strength. By increasing the drive signal, locomotion can be elicited and velocity increased while switching to the appropriate gaits. This drive signal can be specified according to sensory information or set a priori. The implementation of the central pattern generator network and the activity modulation layer is shown in simulation and in an AIBO robot.

No significant role for beta tubulin mutations and mismatch repair defects in ovarian cancer resistance to paclitaxel/cisplatin

BackgroundThe mechanisms of chemoresistance in ovarian cancer patients remain largely to be elucidated. Paclitaxel/cisplatin combination is the standard chemotherapeutic treatment for this disease, although some patients do not respond to therapy. Our goals were to investigate whether TUBB mutations and mismatch repair defects underlie paclitaxel and cisplatin resistance.MethodsThirty-four patients with primary ovarian carcinomas (26 serous and eight clear cell carcinomas) treated with paclitaxel/cisplatin were analysed. TUBB exon 4 was analysed by nested PCR after a first round PCR using intronic primers. Microsatellite analysis was performed with the quasimonomorphic markers BAT 26 and BAT 34.ResultsTwenty-two of the 34 ovarian cancers (64.7%) presented residual tumour after surgery, seven of which (7/22; 31.8%) were shown to be chemoresistant (five serous and two clear cell tumours). Sequence analysis did not find any mutation in TUBB exon 4. Microsatellite instability was not detected in any of the ovarian carcinomas.ConclusionWe conclude that TUBB exon 4 mutations and mismatch repair defects do not play a significant role in paclitaxel/cisplatin resistance.

Complex-order forced van der Pol oscillator

In this paper we consider a complex-order forced van der Pol oscillator. The complex derivative D α ± ȷ β , with α, β ∈ ℝ+, is a generalization of the concept of an integer derivative, where α = 1, β = 0. The Fourier transforms of the periodic solutions of the complex-order forced van der Pol oscillator are computed for various values of parameters such as frequency ω and amplitude b of the external forcing, the damping μ, and parameters α and β. Moreover, we consider two cases: (i) b = 1, μ = {1.0, 5.0, 10.0}, and ω = {0.5, 2.46, 5.0, 20.0}; (ii) ω = 20.0, μ = {1.0, 5.0, 10.0}, and b = {1.0, 5.0, 10.0}. We verified that most of the signal energy is concentrated in the fundamental harmonic ω0. We also observed that the fundamental frequency of the oscillations ω0 varies with α and μ. For the range of tested values, the numerical fitting led to logarithmic approximations for system (7) in the two cases (i) and (ii). In conclusion, we verify that by varying the parameter values α and β of the complex-order derivative in expression (7), we accomplished a very effective way of perturbing the dynamical behavior of the forced van der Pol oscillator, which is no longer limited to parameters b and ω.

New findings on the dynamics of HIV and TB coinfection models

Abstract In this paper we study a model for HIV and TB coinfection. We consider the integer order and the fractional order versions of the model. Let α ∈ [ 0.78 , 1.0 ] be the order of the fractional derivative, then the integer order model is obtained for α = 1.0 . The model includes vertical transmission for HIV and treatment for both diseases. We compute the reproduction number of the integer order model and HIV and TB submodels, and the stability of the disease free equilibrium. We sketch the bifurcation diagrams of the integer order model, for variation of the average number of sexual partners per person and per unit time, and the tuberculosis transmission rate. We analyze numerical results of the fractional order model for different values of α , including α = 1 . The results show distinct types of transients, for variation of α . Moreover, we speculate, from observation of the numerical results, that the order of the fractional derivative may behave as a bifurcation parameter for the model. We conclude that the dynamics of the integer and the fractional order versions of the model are very rich and that together these versions may provide a better understanding of the dynamics of HIV and TB coinfection.

Immunohistochemical Studies of Epithelial Cell Proliferation and p53 Mutation in Bovine Ocular Squamous Cell Carcinoma

Bovine ocular squamous cell carcinoma (OSCC) is the second most common cause of rejection due to neoplasia in slaughterhouses on Sao Miguel Island, Azores, and accounts for significant economic losses. To obtain a better insight into the genesis and neoplastic transformation process of bovine OSCC, abnormal protein expression and proliferation index were assessed by the immunohistochemical evaluation of p53 and Ki67, respectively. OSCC samples were collected from 15 bovines and were classified histologically according to the degree of differentiation into three categories: poorly, moderately, and well differentiated. Immunohis-tochemistry using polyclonal anti-human p53 antibody and polyclonal anti-human Ki67 antibody was performed. Ten of 15 tumors tested were immunoreactive for p53. Twelve tumors demonstrated Ki67 expression. As in human squamous cell carcinoma, p53 overexpression is frequent in bovine OSCC, providing support for a possible role of the protein in the pathogenesis of this neoplasia. No correlation between the percentage of p53 stained nuclei and the degree of differentiation was observed, although different patterns of staining were seen according to the degree of keratinization of the tumor cells. With the exception of the moderately differentiated OSCC group, Ki67 index showed significant correlation with the histologic pattern, increased proliferation being found in poorly differentiated OSCC (P = 0.013).

Fractional complex-order model for HIV infection with drug resistance during therapy

We propose a fractional complex-order model for drug resistance in HIV infection. We consider three distinct growth rates for the CD4+ T helper cells. We simulate the model for different values of the fractional derivative of complex order Dα±jβ, where α,β ∈  R +, and for distinct growth rates. The fractional derivative of complex order is a generalization of the integer-order derivative where α = 1 and β = 0. The fractional complex-order system reveals rich dynamics and variation of the value of the complex-order derivative sheds new light on the modeling of the intracellular delay. Additionally, fractional patterns are characterized by time responses with faster transients and slower evolutions towards the steady state.

Genomic characterization of two large Alu-mediated rearrangements of the BRCA1 gene

To determine whether a large genomic rearrangement is actually novel and to gain insight about the mutational mechanism responsible for its occurrence, molecular characterization with breakpoint identification is mandatory. We here report the characterization of two large deletions involving the BRCA1 gene. The first rearrangement harbored a 89 664-bp deletion comprising exon 7 of the BRCA1 gene to exon 11 of the NBR1 gene (c.441+1724_oNBR1:c.1073+480del). Two highly homologous Alu elements were found in the genomic sequences flanking the deletion breakpoints. Furthermore, a 20-bp overlapping sequence at the breakpoint junction was observed, suggesting that the most likely mechanism for the occurrence of this rearrangement was nonallelic homologous recombination. The second rearrangement fully characterized at the nucleotide level was a BRCA1 exons 11–15 deletion (c.671-319_4677-578delinsAlu). The case harbored a 23 363-bp deletion with an Alu element inserted at the breakpoints of the deleted region. As the Alu element inserted belongs to a still active AluY family, the observed rearrangement could be due to an insertion-mediated deletion mechanism caused by Alu retrotransposition. To conclude, we describe the breakpoints of two novel large deletions involving the BRCA1 gene and analysis of their genomic context allowed us to gain insight about the respective mutational mechanism.

A latency fractional order model for HIV dynamics

We study a fractional order model for HIV infection where latent T helper cells are included. We compute the reproduction number of the model and study the stability of the disease free equilibrium. We observe that the reproduction number varies with the order of the fractional derivative . In terms of epidemics, this suggests that varying induces a change in the patients epidemic status. Moreover, we simulate the variation of relevant parameters, such as the fraction of uninfected CD4+ T cells that become latently infected, and the CTLs proliferation rate due to infected CD4+ T cells. The model produces biologically reasonable results.

The role of synaptic transmission in a HIV model with memory

A fractional order model for HIV with two transmission modes and treatment is proposed.Global stability of the disease-free equilibrium is analyzed.Cell-to-cell transmission has a strong impact in the value of the reproduction number.Increasing drug efficacy decreases the infectiousness of the disease. We propose a mathematical model with memory for the dynamics of HIV epidemics, where two transmission modes, cell-to-cell and virus-to-cell, and drug resistance are considered. Systems with memory, or fractional order systems, have largely been applied to the modeling of several real life phenomena. Here, we consider a fractional model where the order of the non-integer derivative takes values in the interval 0.5, 1.0. We prove the local and global stability of the disease-free equilibrium. We study the role of the cell-to-cell transmission probability on the dynamics of the model, and on the value of the reproduction number, R0, for distinct values of the fractional order derivative, α. Moreover, we show evidence of an improvement of HIV infected patients quality of life, due to the increase of the drug efficacy. In the end, important inferences are drawn.