Arterial pharmacokinetics in a patient-specific atherosclerotic artery-a simulation study

Of concern in the paper is a numerical study of endovascular drug delivery in a patient-specific atherosclerotic artery through a mathematical model in which the luminal flow is governed by an incompressible vis- cous Newtonian fluid, and the transport of luminal as well as tissue concentration is modeled as an unsteady convection-diffusion process. An image processing technique has been successfully adopted to detect the edges of the computational domain extracted from an asymmetric (about the centerline of the artery) patient-specific atherosclerotic artery. Considering each pixel as a control volume, the Marker and Cell (MAC) method has been leveraged to get a quantitative insight of the model considered by exploiting physiologically realistic initial, boundary as well as interface conditions. Simulated results reveal that the number as well as the length of separation zone does increase with increasing Re, and the near-wall velocity contour might be important for estimating the near-wall residence time for the pool of drug molecules available for tissue uptake. Results also show that the more the tissue porosity and interface roughness do not necessarily imply the more the effective- ness of delivery, even though they enhance the averaged concentration in the tissue domains, and also the area under concentration diminishes with increasing Peclet number. Thus, the tissue porosity, the Peclet number and various geometrical shapes (interface roughness) play a pivotal role in the dispersion and the effectiveness of drug delivery. GANITJ. Bangladesh Math. Soc.41.1 (2021) 62-77

Modeling invasion patterns in the glioblastoma battlefield

Glioblastoma is the most aggressive tumor of the central nervous system, due to its great infiltration capacity. Understanding the mechanisms that regulate the Glioblastoma invasion front is a major challenge with preeminent potential clinical relevances. In the infiltration front, the key features of tumor dynamics relate to biochemical and biomechanical aspects, which result in the extension of cellular protrusions known as tumor microtubes. The coordination of metalloproteases expression, extracellular matrix degradation, and integrin activity emerges as a leading mechanism that facilitates Glioblastoma expansion and infiltration in uncontaminated brain regions. We propose a novel multidisciplinary approach, based on in vivo experiments in Drosophila and mathematical models, that describes the dynamics of active and inactive integrins in relation to matrix metalloprotease concentration and tumor density at the Glioblastoma invasion front. The mathematical model is based on a non-linear system of evolution equations in which the mechanisms leading chemotaxis, haptotaxis, and front dynamics compete with the movement induced by the saturated flux in porous media. This approach is able to capture the relative influences of the involved agents and reproduce the formation of patterns, which drive tumor front evolution. These patterns have the value of providing biomarker information that is related to the direction of the dynamical evolution of the front and based on static measures of proteins in several tumor samples. Furthermore, we consider in our model biomechanical elements, like the tissue porosity, as indicators of the healthy tissue resistance to tumor progression.

Immunocytochemical demonstration of cell wall components related to tissue compartments in the globoid galls induced by Clinodiplosis sp. (Cecidomyiidae) on Croton floribundus Spreng. (Euphorbiaceae)

The dynamics of cell wall components during gall development are related to structural specialization to meet the defensive or nutritional requirements of gall tissues. Cell wall features have been studied mostly in galls induced by hemipterans (Psylloidea), while galls induced by Cecidomyiidae have been little explored. We applied monoclonal antibodies to epitopes of proteins and pectins in the cell walls of non-galled leaves and galls induced by Clinodiplosis sp. (Diptera; Cecidomyiidae) on Croton floribundus Spreng. (Euphorbiaceae). The complexity of tissue zonation in Clinodiplosis galls reflected the impairment of the activity of the pectin-methylesterases during development. The labeling of the epitopes of extensins in young galls denoted cell enlargement with resistant cell walls, while the labeling of epitopes of the arabinogalactan proteins in senescent galls indicated the involvement of these proteins with programmed cell death, at the end of cell cycles at the gall development site. We conclude that the cell wall profile in Clinodiplosis galls implies an imbalance between tissue porosity, cell-to-cell signaling, and resistance linked to tissue structural and functional compartments. Current data confirm the presence of the epitopes of extensins in young galls, and the compartmentalization of homogalacturonans and rhamnogalacturonan I in galls as an independent taxon feature.

Contrasting oxygen dynamics in Limonium narbonense and Sarcocornia fruticosa during partial and complete submergence

Terrestrial saltmarsh plants inhabiting flood-prone habitats undergo recurrent and prolonged flooding driven by tidal regimes. In this study, the role of internal plant aeration in contrasting hypoxic/anoxic conditions during submergence was investigated in the two halophytes Limonium narbonense Mill. and Sarcocornia fruticosa (L.) A.J. Scott. Monitoring of tissue O2 dynamics was performed in shoots and roots using microelectrodes under drained conditions, waterlogging, partial and complete submergence, in light or darkness. For both species, submergence in darkness resulted in significant declines in tissue O2 status and when in light, in rapid O2 increases first in shoot tissues and subsequently in roots. During partial submergence, S. fruticosa benefitted from snorkelling and efficiently transported O2 to roots, whereas the O2 concentration in roots of L. narbonense declined by more than 90%. Significantly thinner leaves and articles were recorded under high degree of flooding stress and both species showed considerably high tissue porosity. The presence of aerenchyma seemed to support internal aeration in S. fruticosa whereas O2 diffusion in L. narbonense seemed impeded, despite the higher porosity (up to 50%). Thus, the results obtained for L. narbonense, being well adapted to flooding, suggests that processes other than internal aeration could be involved in better flooding tolerance e.g. fermentative processes, and that traits resulting in flooding tolerance in plants are not yet fully understood.

Cartilage Dysfunction in ALS Patients as Side Effect of Motion Loss: 3D Mechano-Electrochemical Computational Model

Amyotrophic lateral sclerosis (ALS) is a debilitating motor neuron disease characterized by progressive weakness, muscle atrophy, and fasciculation. This fact results in a continuous degeneration and dysfunction of articular soft tissues. Specifically, cartilage is an avascular and nonneural connective tissue that allows smooth motion in diarthrodial joints. Due to the avascular nature of cartilage tissue, cells nutrition and by-product exchange are intermittently occurring during joint motions. Reduced mobility results in a change of proteoglycan density, osmotic pressure, and permeability of the tissue. This work aims to demonstrate the abnormal cartilage deformation in progressive immobilized articular cartilage for ALS patients. For this aim a novel 3D mechano-electrochemical model based on the triphasic theory for charged hydrated soft tissues is developed. ALS patient parameters such as tissue porosity, osmotic coefficient, and fixed anions were incorporated. Considering different mobility reduction of each phase of the disease, results predicted the degree of tissue degeneration and the reduction of its capacity for deformation. The present model can be a useful tool to predict the evolution of joints in ALS patients and the necessity of including specific cartilage protectors, drugs, or maintenance physical activities as part of the symptomatic treatment in amyotrophic lateral sclerosis.