Anomalous Stochastic Transport of Particles with Self-Reinforcement and Mittag–Leffler Distributed Rest Times

We introduce a persistent random walk model for the stochastic transport of particles involving self-reinforcement and a rest state with Mittag–Leffler distributed residence times. The model involves a system of hyperbolic partial differential equations with a non-local switching term described by the Riemann–Liouville derivative. From Monte Carlo simulations, we found that this model generates superdiffusion at intermediate times but reverts to subdiffusion in the long time asymptotic limit. To confirm this result, we derived the equation for the second moment and find that it is subdiffusive in the long time limit. Analyses of two simpler models are also included, which demonstrate the dominance of the Mittag–Leffler rest state leading to subdiffusion. The observation that transient superdiffusion occurs in an eventually subdiffusive system is a useful feature for applications in stochastic biological transport.

PHYSIOLOGY OF ARTAVAVAHA SROTASA: A REVIEW

Ayurvedic classics proclaim Srotasa as the system of channels designed as biological transport system performing divergent functions. Indeed, it is a generic term indicating all the macro and micro channels and pathways operat- ing in the living organism. Broadly Srotasa are classified in two categories: Bahirmukha and Antarmukha. Ar- tavavaha Srotasa is enumerated as one of the Antarmukha Srotasa by Sushruta, playing an important role in transformation of Artava and Artava Chakra, and Garbhotpatti, having Garbhasaya and Artavavahi Dhamani as its Moolasthana. Keywords: Antarmukha, Artavavaha, Garbhotpatti, Moolasthana, Srotasa

Effect of A 2-HP-β-Cyclodextrin Formulation on the Biological Transport and Delivery of Chemotherapeutic PLGA Nanoparticles

Background: The aim of this work was to develop a novel and feasible modification strategy by utilizing the supramolecular effect of 2-hydroxypropyl-beta-cyclodexrin (2-HP-β-CD) for enhancing the biological transport efficiency of paclitaxel (PTX)-loaded poly(lactide-co-glycolide)(PLGA) nanoparticles.Methods: PTX-loaded 2-HP-β-CD-modified PLGA nanoparticles (2-HP-β-CD/PLGA NPs) were prepared using the modified emulsion method. Nano-characteristics, drug release behavior, in vitro cytotoxicity, cellular uptake profiles and in vivo bio-behavior of the nanoparticles were then characterized. Results: Compared with the plain PLGA NPs, 2-HP-β-CD/PLGA NPs exhibited smaller particle sizes (151.03±1.36 nm), increased entrapment efficiency (~49.12% increase) and sustained drug release. When added to A549 human lung cancer cells, compared with PLGA NPs, 2-HP-β-CD/PLGA NPs exhibited higher cytotoxicity in MTT assays and improved cellular uptake efficiency. Pharmacokinetic analysis showed that the AUC value of 2-HP-β-CD/PLGA NPs was 2.4-fold higher than commercial Taxol® and 1.7-fold higher than plain PLGA NPs. In biodistribution assays, 2-HP-β-CD/PLGA NPs exhibited excellent stability in the circulation.Conclusions: The results of this study suggest that formulation contains 2-HP-β-CD can prolong PTX release, enhance drug transpot efficiency and serve as a potential tumor targeting system for PTX.

A two-lane mechanism for selective biological ammonium transport

The transport of charged molecules across biological membranes faces the dual problem of accommodating charges in a highly hydrophobic environment while maintaining selective substrate translocation. This has been the subject of a particular controversy for the exchange of ammonium across cellular membranes, an essential process in all domains of life. Ammonium transport is mediated by the ubiquitous Amt/Mep/Rh transporters that includes the human Rhesus factors. Here, using a combination of electrophysiology, yeast functional complementation and extended molecular dynamics simulations, we reveal a unique two-lane pathway for electrogenic NH4+ transport in two archetypal members of the family, the transporters AmtB from Escherichia coli and Rh50 from Nitrosomonas europaea. The pathway underpins a mechanism by which charged H+ and neutral NH3 are carried separately across the membrane after NH4+ deprotonation. This mechanism defines a new principle of achieving transport selectivity against competing ions in a biological transport process.

A two-lane mechanism for selective biological ammonium transport

The transport of charged molecules across biological membranes faces the dual problem of accommodating charges in a highly hydrophobic environment while maintaining selective substrate translocation. A particular controversy has existed around the mechanism of ammonium exchange by the ubiquitous Amt/Mep/Rh transporter family, an essential process in all kingdoms of life. Here, using a combination of SSME electrophysiology, yeast functional complementation, and extended molecular dynamics simulations, we reveal a unique two-lane pathway for electrogenic NH4+transport in two archetypal members of the family. The pathway underpins a mechanism by which charged H+and neutral NH3 are carried separately across the membrane after NH4+deprotonation. This mechanism defines a new principle of achieving transport selectivity against competing ions in a biological transport process.

The Biophysical Modeling of the Transport Phenomena in the Living Systems

This article describes the principles of biological transport. The transport phenomena mean the variation in time and space of generalized forces when they generate flows for which conservation laws apply. After we describes: mass-, impulse-, energy- and electric-charge-transport and their mathematical characteristic equations. It emphasizes the physical aspects of transport and examines the assumptions and concepts underlying the equations most widely used to characterize transport. In the living organisms, flows are not generated only by the conjugated generalized forces, but also by the simultaneous action of other forces, so appears the cross-effects. The biophysical modeling offer a „language” of quantitative and qua­litative process­sing of experimental data, being compatible and adequate to the laws of biology.