Ana R.M. Carvalho

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.

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.

Analysis of Cardamonin by Square Wave Voltammetry

INTRODUCTION Several biochemical studies have already shown that cardamonin has health promoting properties, such is in agreement with typical characteristics of chalcones. Although being a very promising compound for the nutraceutical field there is a lack of studies concerning its electroanalytical properties. OBJECTIVE To develop an electroanalytical methodology for the quantification of cardamonin in cardamom. METHODOLOGY Cardamonin was analysed electrochemically by means of a hanging mercury drop electrode (HMDE) using square wave voltammetry (SWV). It was extracted from cardamom spice and quantified thereafter using the standard additions method to overcome matrix effects. RESULTS A limit of detection (LOD) of 0.15 mg/L and good linearity (r²  = 0.9998) were obtained. Decoction using ethanol as the extraction solvent appears to be the simplest extraction technique. Spectrophotometric analysis (maximum absorbance peak was found in ethanol at 344 nm with a value of molar extinction coefficient of (2.8 ± 0.1) × 10⁴  L mol⁻¹ cm⁻¹) and mass spectrometry analysis by electrospray in the positive ion mode were also performed. CONCLUSION Cardamonin was detected voltammetrically. The LOD and limit of quantification (LOQ) of the proposed voltammetric methodology are adequate for trace analysis of this compound in several phytochemical matrices.

A coinfection model for HIV and HCV

We study a mathematical model for the human immunodeficiency virus (HIV) and hepatites C virus (HCV) coinfection. The model predicts four distinct equilibria: the disease free, the HIV endemic, the HCV endemic, and the full endemic equilibria. The local and global stability of the disease free equilibrium was calculated for the full model and the HIV and HCV submodels. We present numerical simulations of the full model where the distinct equilibria can be observed. We show simulations of the qualitative changes of the dynamical behavior of the full model for variation of relevant parameters. From the results of the model, we infer possible measures that could be implemented in order to reduce the number of infected individuals.

Novel application of square-wave adsorptive-stripping voltammetry for the determination of xanthohumol in spent hops.

This paper reports the development of a novel electrochemical assay for xanthohumol (XN) by square-wave adsorptive-stripping voltammetry (SWAdSV) with a hanging mercury drop electrode. The method showed good repeatability (CV < 2%) and linearity (between 10 and 250 μg L(-1)), as well as suitable limits of detection (2.6 μg L(-1)) and quantification (8.8 μg L(-1)). The method was applied for the quantification of this compound in spent hops, and the results obtained were compared with the HPLC-UV method. XN contents determined by the SWAdSV method were 16 ± 1 and 100 ± 4 μg L(-1) for aqueous and methanolic extracts, respectively. The developed new methodology considerably reduces the analysis time, approximately from 25 min (HPLC-UV method) to 7 min, enabling a high sample throughput. In addition, the detection and quantification limits were approximately 5-fold lower than those obtained with the chromatographic method.

The impact of pre-exposure prophylaxis (PrEP) and screening on the dynamics of HIV

Abstract We analyse the impact of pre-exposure prophylaxis (PrEP) and screening effects on HIV dynamics in infected patients. Our model incorporates condom use, the number of sexual partners, and treatment for HIV. Numerical simulations are performed and the model is fitted to data on the cumulative HIV and AIDS cases in Portugal. Moreover, critical epidemiological parameters are also varied. Inferences are made concerning the epidemiological consequences of the model’s predictions on public HIV/AIDS planning. The order of the fractional derivative is suggested to have a powerful role in the drama of HIV epidemics.

Fractional dynamics of a model for HIV and TB coinfection

In this paper we study a fractional order model for HIV and TB coinfection. We consider vertical transmission for HIV and treatment for both diseases. We analyze numerical results of the proposed model for different values of the order of the fractional derivative. The results are in agreement with the integer order model and reveal that we can extend the dynamical evolution up to new types of transients.

Diagnóstico laboratorial de doença renal crônica em adultos: visão geral dos hospitais inseridos no Sistema Nacional de Saúde de Portugal

Introduction: The laboratory diagnosis of chronic kidney disease (CKD) is a simple and cost-effective procedure that allows the detection of early stages of the disease, which is essential to avoid kidney damage and a life threateaning event. It consists of measuring serum creatinine concentration, urinary albumin concentration and calculating the estimated glomerular filtration rate (eGFR). In 2012, the guidelines for laboratory evaluation of the CKD were published by the Kidney Disease: Improving Global Outcomes (KDIGO). Objectives: This study aimed to evaluate whether the laboratories in hospitals of the Portuguese National Health System follow these guidelines and provide a correct diagnosis of CKD. Material and method: A questionnaire composed of 32 questions was sent to the Clinical Pathology Services of all hospitals inserted in the System. Results: All 49 labs responded that measure serum creatinine, 18 reported measurering eGFR. Ten reported measuring eGFR only if specifically ordered. Forty-four measure total protein and albumin in the urine, three only protein, one albumin alone, and one measure none of them. The type of samples, methods, reagents, equipment, expression units of results and reference intervals varied. Conclusion: There is great variability among laboratories in relation to the methodology of measuring serum creatinine, albumin and total protein in the urine. There are wide variations in the release of results. Most laboratories do not follow the guidelines recommended by the KDIGO 2012. This work indicates that there is a need to develop education and alignment processes in the laboratory diagnosis of CKD in the laboratories installed in hospitals inserted in the Portuguese National Health System.

A Delay Mathematical Model for HIV Dynamics in HIV-Specific Helper Cells

In this paper we study a delay mathematical model for the dynamics of HIV in HIV-specific CD4+ T helper cells. We modify the model presented by Roy and Wodarz in 2012, where the HIV dynamics is studied, considering a single CD4+ T cell population. Non-specific helper cells are included as alternative target cell population, to account for macrophages and dendritic cells. In this paper, we include two types of delay: (1) a latent period for the interval of time for cells, with contact with the virus, to be infected by the virions, released by them; (2) a virion production period for the virions to be produced and released to the bloodstream from the infected cells. We compute the reproduction number of the model, R 0, and the stability of the disease-free equilibrium. We find that for values of R 0 < 1, the model approaches asymptotically the disease-free equilibrium. We present numerical simulations of this fact. These results suggest that the model is mathematically and epidemiologically well posed.