Epithelial Fluid Transport is Due to Electro-osmosis (80%), Plus Osmosis (20%).

Epithelial fluid transport, an important physiological process shrouded in a long-standing enigma, may finally be moving closer to a solution. We propose that, for the corneal endothelium, relative proportions for the driving forces for fluid transport are 80% of paracellular electro-osmosis, and 20% classical transcellular osmosis. These operate in a cyclical process with a period of 9.

Chemokine and cytokine levels in osteoarthritis and rheumatoid arthritis synovial fluid.

To develop a method of the assay of chemokine and cytokine signaling in synovial fluid from patients suffering from osteoarthritis (OA) or rheumatoid arthritis (RA) and evaluate the effect of heterophilic antibodies on the reliability of the data. 21 synovial fluid samples from OA and 16 synovial fluid samples from RA patients were analyzed using a unique 2 step dot sandwich ELISA based micro-well protein array designed to detect heterophilic antibody signaling in the presence or absence of an effective heterophilic blocking reagent with assays carried out for Eotaxin, hGROa, interleukin (IL)-8, IP10, MCP-1, MCP-2, MIG, RANTES, TARC and IL-6. Array analysis reveals that the selective presence of heterophilic antibodies interferes with the accurate assay of synovial fluid samples from a minority of RA patients but not OA synovia.

Pro-inflammatory cytokines in glaucomatous aqueous and encysted Molteno implant blebs and their relationship to pressure.

Purpose: To ascertain the presence of additional pro-inflammatory cytokines in glaucomatous aqueous, and their relationship with IOP.

Methods: To quantify the levels of 23 pro-inflammatory cytokines, and correlate levels with IOP, aqueous humor samples were analyzed from 23 eyes with open angle glaucoma (OAG) undergoing glaucoma filtration procedures, and from 24 Molteno blebs during the hypertensive phase. Control aqueous was derived from 13 eyes without glaucoma undergoing cataract removal.

DPOFA, a Cl⁻/HCO₃⁻ exchanger antagonist, stimulates fluid absorption across basolateral surface of the retinal pigment epithelium.

Background: Retinal detachment is a disorder of the eye in which sensory retina separates from the retinal pigment epithelium (RPE) due to accumulation of fluid in subretinal space. Pharmacological stimulation of fluid reabsorption from subretinal space to choroid across the RPE has been suggested as a treatment strategy for retinal detachment. DPOFA, (R)-(+)-(5,6-dichloro 2,3,9,9a-tetrahydro 3-oxo-9a-propyl-1H-fluoren-7-yl)oxy]acetic acid, is an abandoned drug capable of inhibiting Cl⁻/HCO₃⁻ exchanger activity.

Comparative permeabilities of the paracellular and transcellular pathways of corneal endothelial layers.

Layers of rabbit corneal endothelial cells were cultured on permeable inserts. We characterized the diffusional permeability of the cell layer to nonelectrolyte and charged molecules and compared the diffusional and filtration permeabilities of the paracellular and transcellular pathways. We determined the rates of diffusion of (3)H- and (14)C-labeled nonelectrolyte test molecules and estimated the equivalent pore radius of the tight junction.

Profile of lipid and protein autacoids in diabetic vitreous correlates with the progression of diabetic retinopathy.

Objective: This study was aimed at obtaining a profile of lipids and proteins with a paracrine function in normal and diabetic vitreous and exploring whether the profile correlates with retinal pathology.

Research Design And Methods: Vitreous was recovered from 47 individuals undergoing vitreoretinal surgery: 16 had nonproliferative diabetic retinopathy (NPDR), 15 had proliferative diabetic retinopathy, 7 had retinal detachments, and 9 had epiretinal membranes. Protein and lipid autacoid profiles were determined by protein arrays and mass spectrometry-based lipidomics.

Corneal endothelium transports fluid in the absence of net solute transport.

The corneal endothelium transports fluid from the corneal stroma to the aqueous humor, thus maintaining stromal transparency by keeping it relatively dehydrated. This fluid transport mechanism is thought to be driven by the transcellular transports of HCO(3)(-) and Cl(-) in the same direction, from stroma to aqueous. In parallel to these anion movements, for electroneutrality, there are paracellular Na(+) and transcellular K(+) transports in the same direction.

Functional and molecular characterization of multiple K-Cl cotransporter isoforms in corneal epithelial cells.

The dependence of regulatory volume decrease (RVD) activity on potassium-chloride cotransporter (KCC) isoform expression was characterized in corneal epithelial cells (CEC). During exposure to a 50% hypotonic challenge, the RVD response was larger in SV40-immortalized human CEC (HCEC) than in SV40-immortalized rabbit CEC (RCEC). A KCC inhibitor-[(dihydroindenyl)oxy] alkanoic acid (DIOA)-blocked RVD more in HCEC than RCEC.

Modulation of tight junction properties relevant to fluid transport across rabbit corneal endothelium.

Paracellular junctions could play an important role in corneal endothelial fluid transport. In this study we explored the effects of different reagents on the tight junctional barrier by assessing the translayer specific electrical resistance (TER) across rabbit corneal endothelial preparations and cultured rabbit corneal endothelial cells' (CRCEC) monolayers, the paracellular permeability (Papp) for fluorescein isothiocyanate (FITC) dextrans across CRCEC, and fluid transport across de-epithelialized rabbit corneal endothelial preparations. Palmitoyl carnitine (PC), poly-L-lysine (PLL), adenosine triphosphate (ATP), and dibutyryl adenosine 3',5'-cyclic monophosphate (dB-cAMP) were used to modulate corneal endothelial fluid transport and tight junctions (TJs).

Lack of threshold for anisotonic cell volume regulation.

Most cells possess mechanisms that are able to detect cellular volume shifts and to signal the initiation of appropriate volume regulatory responses. However, the identity and characteristics of the detecting mechanism remain obscure. In this study, we explored the influence of hypertonic and hypotonic challenges of varying magnitude on the characteristics of the ensuing regulatory volume increase (RVI) and regulatory volume decrease (RVD) of cultured bovine corneal endothelial cells (CBCECs).

Regulation of Na-K-2Cl cotransport in cultured bovine corneal endothelial cells.

We have previously demonstrated the presence of a Na(+)-K(+)-2Cl cotransporter in cultured bovine corneal endothelial cells (CBCEC) and determined that this cotransporter is located in the basolateral membrane. This transporter may contribute to volume regulation and transendothelial fluid transport. We have now investigated factors regulating the activity of the cotransporter.

A single amino acid residue can determine the sensitivity of SERCAs to artemisinins.

Artemisinins are the most important class of antimalarial drugs. They specifically inhibit PfATP6, a SERCA-type ATPase of Plasmodium falciparum. Here we show that a single amino acid in transmembrane segment 3 of SERCAs can determine susceptibility to artemisinin.

Predicting the three-dimensional structure of the human facilitative glucose transporter glut1 by a novel evolutionary homology strategy: insights on the molecular mechanism of substrate migration, and binding sites for glucose and inhibitory molecules.

The glucose transporters (GLUT/SLC2A) are members of the major facilitator superfamily. Here, we generated a three-dimensional model for Glut1 using a two-step strategy: 1), GlpT structure as an initial homology template and 2), evolutionary homology using glucose-6-phosphate translocase as a template. The resulting structure (PDB No.

Intracellular [Na+], Na+ pathways, and fluid transport in cultured bovine corneal endothelial cells.

The mechanism of fluid transport across corneal endothelium remains unclear. We examine here the relative contributions of cellular mechanisms of Na+ transport and the homeostasis of intracellular [Na+] in cultured bovine corneal endothelial cells, and the influence of ambient Na+ and HCO3- on the deturgescence of rabbit cornea. Bovine corneal endothelial cells plated on glass coverslips were incubated for 60 min with 10 microm of the fluorescent Na+ indicator SBFI precursor in HCO3- HEPES (BH) Ringer's solution.

Fluid transport across cultured layers of corneal endothelium from aquaporin-1 null mice.

We explored the role of AQP1, the only known aquaporin in corneal endothelium, on active fluid transport and passive osmotic water movements across corneal endothelial layers cultured from AQP1 null mice and wildtype mice. AQP1 null mice had grossly transparent corneas, just as wildtype mice. Endothelial cell layers grown on permeable supports transported fluid at rates of (in microl h(-1) cm(-2), n = 9 mean+/-s.

Functional studies of threonine 310 mutations in Glut1: T310I is pathogenic, causing Glut1 deficiency.

We have previously reported on a patient with the Glut1 deficiency syndrome (Online Mendelian Inheritance in Man number 606777) carrying a heterozygous T310I missense mutation in the GLUT1 gene (Klepper, J., Wang, D., Fischbarg, J.

Mutational analysis of the hexose transporter of Plasmodium falciparum and development of a three-dimensional model.

Plasmodium falciparum infection kills more than 1 million children annually. Novel drug targets are urgently being sought as multidrug resistance limits the range of treatment options for this protozoan pathogen. PfHT1, the major hexose transporter of P.

Changes in glucose transport and water permeability resulting from the T310I pathogenic mutation in Glut1 are consistent with two transport channels per monomer.

We studied glucose and water passage across wild type (WT) glucose transporter Glut1 and its T310I pathogenic mutant, expressing them in Xenopus laevis oocytes. We found that the T310I mutation produced a 8-fold decrease in glucose transport (zero-trans influx, 13 +/- 2% compared with WT), accompanied by a 2.8-fold increase in the osmotic water permeability (P(f) 280 +/- 40% compared with WT), and no change in the diffusional water permeability (P(d)).