Hydroxyapatite from Natural Sources for Medical Applications

The aim of this work is to study the physical-chemical, mechanical, and biocompatible properties of hydroxyapatite obtained by hydrothermal synthesis, at relatively low temperatures and high pressures, starting from natural sources (Rapana whelk shells), knowing that these properties influence the behavior of nanostructured materials in cells or tissues. Thus, hydroxyapatite nanopowders were characterized by chemical analysis, Fourier-transform infrared spectroscopy (FT-IR), dynamic light scattering (DLS), scanning electron microscopy (SEM), and X-ray diffraction (XRD). In vitro studies on osteoblast cell lines (cytotoxicity and cell proliferation), as well as preliminary mechanical tests, have been performed. The results showed that the obtained powders have a crystallite size below 50 nm and particle size less than 100 nm, demonstrating that hydrothermal synthesis led to hydroxyapatite nanocrystalline powders, with a Ca:P ratio close to the stoichiometric ratio and a controlled morphology (spherical particle aggregates). The tensile strength of HAp samples sintered at 1100 °C/90 min varies between 37.6–39.1 N/mm². HAp samples sintered at 1300 °C/120 min provide better results for the investigated mechanical properties. The coefficient of friction has an appropriate value for biomechanical applications. The results of cell viability showed that the cytotoxic effect is low for all tested samples. Better cell proliferation is observed for osteoblasts grown on square samples.     

Theoretical investigation of photon partial pathlengths in multilayered turbid media

Functional near infrared spectroscopy (fNIRS) is a valuable tool for assessing oxy- and deoxyhemoglobin concentration changes (Δ[HbO] and Δ[HbR], respectively) in the human brain. To this end, photon pathlengths in tissue are needed to convert from light attenuation to Δ[HbO] and Δ[HbR]. Current techniques describe the human head as a homogeneous medium, in which case these pathlengths are easily computed. However, the head is more appropriately described as a layered medium; hence, the partial pathlengths in each layer are required. The current way to do this is by means of Monte Carlo (MC) simulations, which are time-consuming and computationally expensive. In this work, we introduce an approach to theoretically calculate these partial pathlengths, which are computed several times faster than MC simulations. Comparison of our approach with MC simulations show very good agreement. Results also suggest that these analytical expressions give much more specific information about light absorption in each layer than in the homogeneous case.     

Targeting angiogenesis in ovarian cancer

Results of standard chemotherapy in ovarian cancer are hampered by the development of drug resistance leading to disease recurrence. This prompted interest in the development of therapies targeting critical pathways responsible for tumor progression. Angiogenesis is a key process that enables ovarian cancer growth and metastasis in the peritoneal space. Its regulation relies on signaling mechanisms initiated by the vascular endothelial growth factor, the platelet-derived growth factor, the fibroblast growth factor, angiopoietins, and others. These pathways are not only important to the modulation of the tumor microenvironment and vasculature, but also control cancer cell proliferation and survival. In this review, we discuss preclinical evidence supporting the rationale for inhibiting these pathways and provide an overview for the clinical development of agents targeting them. Clinical trials evaluating such agents alone and in combination with chemotherapy are ongoing. Early clinical results position antiangiogenic therapy at the forefront of change to the standard treatment of difficult to treat ovarian cancer.     

High risk for sleep apnea in the Berlin questionnaire and coronary artery disease

Introduction  

Obstructive sleep apnea (OSA) affects up to 30% of the adult population and is a risk factor for coronary artery disease (CAD). The diagnostic process, involving polysomnography, may be complex. Berlin questionnaire (BQ) is a validated and economical screening tool.     

A case of myopericarditis associated to Campylobacter jejuni infection in the Southern Hemisphere

Myopericarditis is an infrequent complication of acute diarrheal illness due to Campylobacter jejuni, and it has been mainly reported in developed nations. The first case detected in Chile – an upper-middle income country –, that is coincidental with the increasing importance of acute gastroenteritis associated to this pathogen, is described. Recognition of this agent in stools requires special laboratory techniques not widely available, and it was suspected when a young patient presented with acute diarrhea, fever, and chest pain combined with electrocardiogram (EKG) abnormalities and elevated myocardial enzymes. C. jejuni myopericarditis can easily be suspected but its detection requires dedicated laboratory techniques.