The role of mechanical forces driving kidney epithelial fluid transport and morphogenesis in kidney diseases is unclear. Here, using a microfluidic platform to recapitulate fluid transport activity of kidney cells, we report that renal epithelial cells can actively generate hydraulic pressure gradients across the epithelium. The fluidic flux declines with increasing hydraulic pressure until a stall pressure, in a manner similar to mechanical fluid pumps. For normal human kidney cells, the fluidic flux is from apical to basal, and the pressure is higher on the basal side. For human Autosomal Dominant Polycystic Kidney Disease cells, the fluidic flux is reversed from basal to apical. Molecular and proteomic studies reveal that renal epithelial cells are sensitive to hydraulic pressure gradients, changing gene expression profiles and spatial arrangements of ion exchangers and the cytoskeleton in different pressure conditions. These results implicate mechanical force and hydraulic pressure as important variables during kidney function and morphological change, and provide insights into pathophysiological mechanisms underlying the development and transduction of hydraulic pressure gradients.

The number of people engaged in artisanal and small-scale mining (ASM) has grown rapidly in the past twenty years, but they continue to be an understudied population experiencing high rates of malnutrition, poverty, and food insecurity. This paper explores how characteristics of markets that serve ASM populations facilitate and pose challenges to acquiring a nutritious and sustainable diet. The study sites included eight markets across four mining districts in the Kankan Region in the Republic of Guinea. Market descriptions to capture the structure of village markets, as well as twenty in-depth structured interviews with food vendors at mining site markets were conducted. We identified three forms of market organization based on location and distance from mining sites. Markets located close to mining sites offered fewer fruit and vegetable options, as well as a higher ratio of prepared food options as compared with markets located close to village centers. Vendors were highly responsive to customer needs. Food accessibility and utilization, rather than availability, are critical for food security in non-agricultural rural areas such as mining sites. Future market-based nutrition interventions need to consider the diverse market settings serving ASM communities and leverage the high vendor responsiveness to customer needs.

Ketamine, a widely used anesthetic, is currently under renewed inquiry for its rapid and sustained antidepressant effects at sub anesthetic doses. Ketamine exerts its effects on the central nervous system (CNS) by blocking open Nmethyl-D-aspartate (NMDA) receptors with IC 50 = 1.0 uM. This overall effect is modulated regionally and temporally by dynamic variations in extracellular pH at synapses. An increase in extracellular proton concentrations decrease NMDA receptor open probability (Po) with IC 50 = 7.0 in an isoform dependent manner, and protonated forms of ketamine are more potent blockers of NMDA receptors. In an effort to separate the effects of proton inhibition and ketamine block on channel activity, we used GluN1-1b containing NMDA receptors with reduced proton sensitivity (IC 50 = 6.7) expressed in HEK293 cells and quantified the receptors' activation mechanism with kinetic modelling from on-cell single channel recordings. With this approach, we estimated rate constants for channel gating and for ketamine association and dissociation at pH 6.8, 7.2, and 7.6. The activation mechanism of protonated GluN1-1a and GluN1-1b isoforms were indistinguishable. As expected, ketamine reduced the channel mean open time with no changes in unitary conductance. Furthermore, ketamine increased the mean closed time and reduced the number of open components. These results quantify the distinct effects of protons and ketamine on NMDA receptor activity, and serve to better understand the complex modulatory actions of pharmacologic interventions.

Using a novel microfluidic platform to recapitulate fluid absorption activity of kidney cells, we report that renal epithelial cells can actively generate hydraulic pressure gradients across the epithelium.The fluidic flux declines with increasing hydraulic pressure until a stall pressure, at which the fluidic flux vanishes--in a manner similar to mechanical fluidic pumps. The developed pressure gradient translates to a force of 50-100 nanoNewtons per cell. For normal human kidney cells, the fluidic flux is from apical to basal, and the pressure is higher on the basal side. For human polycystic kidney disease (PKD) cells, the fluidic flux is reversed from basal to apical with a significantly higher stall pressure. Molecular studies and proteomic analysis reveal that renal epithelial cells are highly sensitive to hydraulic pressure gradients, developing different expression profiles and spatial arrangements of ion exchangers and the cytoskeleton in different pressure conditions. These results, together with data from osmotic and pharmacological perturbations of fluidic pumping, implicate mechanical force and hydraulic pressure as important variables during morphological changes in epithelial tubules, and provide further insights into pathophysiological mechanisms underlying the development of high luminal pressure within renal cysts.

Using a novel microfluidic platform to recapitulate fluid transport activity of kidney cells, we report that renal epithelial cells can actively generate hydraulic pressure gradients across the epithelium. The fluidic flux declines with increasing hydraulic pressure until a stall pressure, at which the flux vanishes--in a manner similar to mechanical fluidic pumps. The developed pressure gradient translates to a force of 50-100 nanoNewtons per cell. For normal human kidney cells, the fluidic flux is from apical to basal, and the pressure is higher on the basal side. For human Autosomal Dominant Polycystic Kidney Disease (ADPKD) cells, the fluidic flux is reversed from basal to apical with a higher stall pressure. Molecular studies and proteomic analysis reveal that renal epithelial cells are sensitive to hydraulic pressure gradients, developing different expression profiles and spatial arrangements of ion exchangers and the cytoskeleton in different pressure conditions. These results, together with data from osmotic and pharmacological perturbations of fluidic pumping, implicate mechanical force and hydraulic pressure as important variables during morphological changes in epithelial tubules, and provide further insights into pathophysiological mechanisms underlying the development of high luminal pressure within renal cysts.