A low-cost prosthetic orbital simulation model for endoscopic anterior ethmoid artery ligation

OBJECTIVE

This study aimed to develop and evaluate a low-cost orbital prosthesis for simulation of endoscopically assisted intra-orbital anterior ethmoidal artery ligation.

METHODS

A low-cost orbital prosthesis was built and evaluated by ENT surgical trainees. Feedback was given following the assessment in the form of a face validity questionnaire.

RESULTS

Results were scored on a Likert scale of 1-7 (low to high). Trainees had limited exposure to the procedure (40 per cent) and predominantly low levels of confidence (mean, 3.67) that correlated with a lack of first-hand experience. The anatomy and likeness to human tissue of the prosthesis were both ranked highly, with mean scores of 5.0 and 4.93, respectively.

CONCLUSION

The results of this study support the idea that a simple anatomical prosthesis for the simulation of endoscopic anterior ethmoidal artery ligation can be created with potential value to otolaryngology surgical training. To the authors' knowledge, this is the first documentation of simulated surgical epistaxis management using an artificial anatomical model.

Characterization of the Electrophysiological Characteristics of Chronic Atrial Fibrillation for Efficient Simulations

Atrial biophysical simulations have the potential to enhance outcomes by enabling the simulation of pharmacological and ablative strategies. However, the high computational times associated with such simulations render them unsuitable for diagnostic purposes. To address this challenge, discrete models such as cellular automata (CA) have been developed, which consider a finite number of states, thus significantly reducing computational times. Yet, there is a pressing need to determine whether CA can replicate pathological simulations with accuracy. The analysis of simulations under different degrees of electrical remodeling shows an expected increase of Action Potential Duration (APD) with the previous Diastolic Interval (DI) interval, indicating short-term memory of atrial cardiomyocytes: shorter APD0 provoked shorter APD+1, and previous DI has a similar effect on APD+1. Independent prediction using both APD0 and DI was found to provide a far better estimation of APD+1 values, compared to relying on DI alone (p<<0.01). Finally, the CA models were able to replicate reentrant patterns and cycle lengths of different states of atrial remodeling with a high degree of accuracy when compared to biophysical simulations. Overall, the use of atrial CA with short-term memory allows accurate reproduction of arrhythmic behavior in pathological tissue within a clinically relevant timeframe.Clinical Relevance- Discrete electrophysiological models simulate pathological self-sustained arrhythmias in diagnostic times.

Assessment of Risk for Ventricular Tachycardia based on Extensive Electrophysiology Simulations

Patients that have suffered a myocardial infarction are at high risk of developing ventricular tachycardia. Patient stratification is often determined by characterization of the underlying myocardial substrate by cardiac imaging methods. In this study, we show that computer modeling of cardiac electrophysiology based on personalized fast 3D simulations can help to assess patient risk to arrhythmia. We perform a large simulation study on 21 patient digital twins and reproduce successfully the clinical outcomes. In addition, we provide the sites which are prone to sustain ventricular tachycardias, i.e, onset sites around the scar region, and validate if they colocalize with exit sites from slow conduction channels.Clinical relevance- Fast electrophysiological simulations can provide advanced patient stratification indices and predict arrhythmic susceptibility to suffer from ventricular tachycardia in patients that have suffered a myocardial infarction.

Morphometry and comparative histology of sinus and atrioventricular nodes in humans and pigs and their relevance in the prevention of nodal arrhythmias

The cardiac conduction system is a network structure that allows the initiation and fast propagation of electrical impulses that trigger the electrical depolarization of the myocardial tissue. The purpose of this work is to study the histological and morphometric characteristics of the different components of the sinus and atrioventricular nodes in humans and pigs and their relationship with supraventricular arrhythmias. In this study, we describe the morphometry of the sinus and atrioventricular nodes of 10 adult humans and 10 pig hearts. A computerized morphometric study has been carried out, where we determined the number of cells that compose the nodes as well as different parameters related to their shape and size. The sinus node in human and pig is a compact structure, whose shape is oblong. Their cells (nodal and transitional cells) are pale and located in the center and the periphery, respectively. The atrioventricular node has also a shape oblong. P cells are pale in both species, but in humans, they are smaller than cardiomyocytes. The T cells are small and pale in both species, identified by hematoxylin-eosin and desmin stains. We have observed through a morphometric profile that the structure of sinus and atrioventricular nodes of pigs and humans show few differences. Pigs can be used as models for hemodynamic applications and experimental studies that include atrial electrical conduction and, in this way, prevent the presentation of arrhythmias that can generate sudden deaths in humans and pigs.

Transferrin-Conjugated Docetaxel-PLGA Nanoparticles for Tumor Targeting: Influence on MCF-7 Cell Cycle

Targeted drug delivery systems are commonly used to improve the therapeutic index of anti-cancer drugs by increasing their selectivity and reducing systemic distribution and toxicity. Ligand-conjugated nanoparticles (NPs) can be effectively applied for active chemotherapeutic targeting to overexpressed receptors of tumor cells. In this study, transferrin (Tf) was successfully conjugated with poly-l-lactic-co-glycolic acid (PLGA) using ethylene diamine confirmed by NMR, for the loading of docetaxel trihydrate (DCT) into PLGA nanoparticles (NPs). The DCT-loaded Tf-conjugated PLGA NPs were produced by an emulsion-solvent evaporation technique, and a 3² full factorial design was used to optimize the nanoparticle formulations. The DCT-loaded Tf-conjugated PLGA NPs were characterized by FTIR spectroscopy, differential scanning calorimetry, powder X-ray diffraction (PXRD), TEM, particle size, and zeta potential analysis. In vitro release kinetics confirmed that release of DCT from the designed formulations followed a zero-order kinetics and a diffusion controlled non-Fickian release profile. The DCT-loaded Tf-conjugated PLGA NPs were evaluated in vitro in MCF-7 cells for bioactivity assessment. Cytotoxicity studies confirmed that the Tf-conjugated PLGA NPs were more active than the non-conjugated counterparts. Cell uptake studies re-confirmed the ligand-mediated active targeting of the formulated NPs. From the cell cycle analysis, the anti-cancer activity of DCT-loaded Tf-conjugated PLGA NPs was shown to occur by arresting the G₂/M phase.

A quantitative structural and morphometric analysis of the Purkinje network and the Purkinje-myocardial junctions in pig hearts

The morpho-functional properties of the distal section of the cardiac Purkinje network (PN) and the Purkinje-myocardial junctions (PMJs) are fundamental to understanding the sequence of electrical activation in the heart. The overall structure of the system has already been described, and several computational models have been developed to gain insight into its involvement in cardiac arrhythmias or its interaction with implantable devices, such as pacemakers. However, anatomical descriptions of the PN in the literature have not enabled enough improvements in the accuracy of anatomical-based electrophysiological simulations of the PN in 3D hearts models. In this work, we study the global distribution and morphological properties of the PN, with special emphasis on the cellular and architectural characterization of its intramural branching structure, mesh-like sub-endocardial network, and the PMJs in adult pig hearts by both histopathological and morphometric evaluation. We have defined three main patterns of PMJ: contact through cell bodies, contact through cell prolongations either thick or piliform, and contact through transitional cells. Moreover, from hundreds of micrographs, we quantified the density of PMJs and provided data for the basal/medial/apical regions, anterior/posterior/septal/lateral regions and myocardial/sub-endocardial distribution. Morphometric variables, such as Purkinje cell density and thickness of the bundles, were also analyzed. After combining the results of these parameters, a different septoanterior distribution in the Purkinje cell density was observed towards the cardiac apex, which is associated with a progressive thinning of the conduction bundles and the posterolateral ascension of intramyocardial terminal scattered fibers. The study of the PMJs revealed a decreasing trend towards the base that may anatomically explain the early apical activation. The anterolateral region contains the greatest number of contacts, followed by the anterior and septal regions. This supports the hypothesis that thin distal Purkinje bundles create a junction-rich network that may be responsible for the quick apical depolarization. The PN then ascends laterally and spreads through the anterior and medial walls up to the base. We have established the first morphometric study of the Purkinje system, and provided quantitative and objective data that facilitate its incorporation into the development of models beyond gross and variable pathological descriptions, and which, after further studies, could be useful in the characterization of pathological processes or therapeutic procedures.

Current Insights into the role of HIF-1 in cutaneous wound healing

Hypoxia Inducible Factor-1 (HIF-1) is considered the major coordinator of the cellular adaptive response to hypoxia. Over recent years, its activity in the context of wound healing has been the object of increasing investigation. On the molecular level, HIF-1 transcriptional target products have been shown to regulate the process of endothelial cell survival, migration and proliferation (VEGF, ANGPT-1, ANGPT-2, ANGPT-4, FGF-2, PlGF, PDGF-B, RGC-32), vascular smooth muscle cell migration and proliferation (FGF-2, EGF, PDGF, thrombospondin) and mobilization of Circulating Angiogenic Cells to the periphery (SFD-1/CXCR4). Studies on the effect of HIF-1 on the expression and activity of extracellular cell matrix modifying enzymes, such as MMPs and prolidase, have been conducted in the context of tumor angiogenesis and metastasis, and have resulted in controversial findings. A growing body of evidence suggests that HIF-1 also affects reepithelialization of the wound bed, through increasing keratinocyte migration, but decreasing their proliferation. Diminished HIF-1 levels and activity have been documented in conditions of impaired wound healing, such as wound healing in aged and in diabetic mice. The increasing number of studies on the role of HIF-1 in wound healing, apart from answering certain questions, has also raised an equal number, if not more. Clarifying the topics that still remain unclear could introduce a new era of HIF-1 targeted management of a wide range of problematic wounds.

Inter-model consistency and complementarity: learning from ex-vivo imaging and electrophysiological data towards an integrated understanding of cardiac physiology

Computational models of the heart at various scales and levels of complexity have been independently developed, parameterised and validated using a wide range of experimental data for over four decades. However, despite remarkable progress, the lack of coordinated efforts to compare and combine these computational models has limited their impact on the numerous open questions in cardiac physiology. To address this issue, a comprehensive dataset has previously been made available to the community that contains the cardiac anatomy and fibre orientations from magnetic resonance imaging as well as epicardial transmembrane potentials from optical mapping measured on a perfused ex-vivo porcine heart. This data was used to develop and customize four models of cardiac electrophysiology with different level of details, including a personalized fast conduction Purkinje system, a maximum a posteriori estimation of the 3D distribution of transmembrane potential, the personalization of a simplified reaction-diffusion model, and a detailed biophysical model with generic conduction parameters. This study proposes the integration of these four models into a single modelling and simulation pipeline, after analyzing their common features and discrepancies. The proposed integrated pipeline demonstrates an increase prediction power of depolarization isochrones in different pacing conditions.

Age-related trends in the timeliness and prediction of medical visits, hospitalizations and deaths due to pneumonia and influenza, British Columbia, Canada, 1998-2004

The influenza immunization program in North America has been primarily designed to provide direct benefit to vaccinated individuals at highest risk of serious influenza outcomes. Some evidence suggests that immunization of certain age groups may also extend indirect protective benefit to vulnerable populations. Our goal was to identify age groups associated earliest with seasonal influenza activity and who may have the greatest indirect impact at the population level. We examined age-based associations between influenza medical visits and population-wide hospitalization/mortality due to pneumonia & influenza (P&I) using administrative datasets in British Columbia, Canada. A peak week was identified for each age group based on the highest rates observed in a given week for that study year. Mean rates at the peak week were averaged over the study years per age group. Timeliness (T) was defined as the mean difference in days between the first peak in influenza medical visits and population-wide P&I hospitalizations/deaths. Poisson regression was applied to calculate prediction (Pr) as the average proportion of deviance in P&I explained by influenza medical visits. T and Pr were derived by age group, and the product (T x Pr) was used as a summary measure to rank potential indirect effects of influenza by age group. Young children (0-23 months) and the elderly (> or = 65 years) had the highest peak rates of P&I hospitalization. Children < 6m and the elderly had the highest peak rates of P&I mortality. We found no significant differences by age for influenza medical visits in predicting population-wide P&I hospitalizations or deaths. School-aged children (5-19 years) showed the best relative combination of T x Pr, followed by preschool-aged children (2-4 years). We conclude that the very young and old suffer the greatest morbidity due to P&I, and an indirect role for school-aged children in anticipating the risk to others warrants further evaluation.

Granulometric analysis of corneal endothelium specular images by using a germ-grain model

Specular microscopy is widely used to study the human corneal endothelium status in vivo. In this paper, the corneal endothelium is represented as a binary image composed of the cell inscribed circles. The granulometric distribution function of the complement of this image is used as a functional descriptor, which provides information about the shape, size and spatial arrangement of cells. Experimental evaluation using bootstrap techniques shows its ability to discriminate between controls and pathological cases. It represents a reliable and graphical alternative to the classical indices (cell density, hexagonality and coefficient of variation of cell areas), which behave poorly when detecting subtle abnormalities.

Stress on the Farm and Its Association with Injury

The objectives of this study were to examine associations between perceived psychosocial stress and farm injury among men and women in Ontario, Canada. Cross-sectional data from the Ontario Farm Family Health Study were used to investigate perceived levels of stress, farm injuries and their interrelationships. Age-standardized rates of injury were 13.3/100/year and 3.8/100/year for men and women, respectively. The most common types of injury were strains/sprains/torn ligaments and cuts/lacerations. Approximately 18% of men and 11% of women reported that their lives were "very stressful." Common sources of stress were money worries and feeling overworked. The risk for farm injury increased with level of stress. For men, the adjusted odds ratios for injury were: 1.00 (referent), 1.02 (95% CI: 0.72, 1.42), and 1.61 (95% CI: 1.08, 2.41)for lowest to highest stress levels, respectively. For women, adjusted odds ratios were: 1.00 (referent), 1.43 (95% CI: 0.83, 2.47), and 2.73 (95% CI: 1.38, 5.39). These risks were especially pronounced among women who were not employed off the farm. This study represents a novel quantitative analysis examining associations between perceived psychological stress and farm injury. Future research should investigate these associations in other farm populations, confirm their temporal directions, and further explore the effect of gender on the strength of these associations.

The multicultural sensitivity of physician assistant students

Using a specially designed instrument, the authors examined physician assistant students' multicultural sensitivity at four points before, during, and after the 30 months of a master's degree program. The students (n = 19) were found to have become more multiculturally sensitive by the end of the program, even in the absence of specific relevant instruction. The greatest improvement followed the end of clerkship rotations, where the students had experiences with low-income patients of other racial/ethnic backgrounds. The authors suggest that increasing such experiences during training may enhance students' multicultural sensitivity.