Nanosilver: a nanoproduct in medical application.

https://www.farm.ucl.ac.be/Full-texts-FARM/des-Rieux-2006-1.pdf

Nanoparticles as potential oral delivery systems of proteins and vaccines: a mechanistic approach.

Electroneutral cation-Cl− cotransporters compose a family of solute carriers in which cation (Na+ or K+) movement through the plasma membrane is always accompanied by Cl− in a 1:1 stoichiometry. Se...

https://www.physiology.org/doi/pdf/10.1152/physrev.00011.2004

Molecular Physiology and Pathophysiology of Electroneutral Cation-Chloride Cotransporters

The ability of an epithelium to prevent permeation of noxious agents has not been well studied except in the gastrointestinal tract where exclusion of H+ has clinical significance. This article reviews the permeation routes across epithelia both as elucidated in the extensive electrophysiological work done in recent years and as demonstrated in morphological studies. We thus place concepts about gastrointestinal barrier function into the framework of transport physiology. Both the permeability and permselectivity of epithelial barriers are reviewed here. The effects of physical agents (pressure and electric current), polyvalent cations, organic compounds with both specific (channel blocking) and nonspecific (detergent) membrane properties, cyclic nucleotides, microfilament-active agents, and particularly H+ on both the barrier function (permeability and permselectivity) and transport function of epithelia are considered. Based on the available data, an important role for active Na+ transport in the maintenance of the epithelial barrier function can be postulated.

https://www.physiology.org/doi/pdf/10.1152/ajpgi.1981.241.4.G275

Barrier function of epithelia

The role that mechanical factors deriving from blood flow play in the growth of blood vessels was most probably mentioned for the first time by John Hunter in his “Treatise on the Blood Flow, Inflammation and Gunshot Wounds,” published in 1794. Hunter was an anatomist who kept a deer herd in Richmond Park. He described enlargement of the carotid arteries in deer, coincident with the development of new antlers, which is known to involve intensive vascular growth. Almost a century later, Thoma (1) demonstrated that ontogenetic growth of vessels is caused by a combination of hemodynamic forces — increased blood flow, blood pressure, and wall tension — and mechanical stretch of vessels owing to the growth of the surrounding tissue. The importance of flow for capillary development was later shown in tadpole tails by Clark (2), who exposed to observation under the microscope the same site over many days, and in wound healing in the rabbit ear chamber (3). Today, the roles in angiogenesis of mechanical factors such as shear stress, circumferential stress, stretch, or physical forces owing to modification of the extracellular matrix are widely studied in tissue culture.

Angiogenesis in skeletal and cardiac muscle

M cells are specialized structures in the Peyer's patch follicle-associated epithelium capable of taking up bacteria, viruses and other pathogens for later presentation to the gut-associated lymphoid tissue. The present work studies how coating microspheres with different proteins affects their ability to be taken up by M cells under near physiological conditions in vivo. The later appearance of microspheres in intestinal lymph has also been measured by flow cytometry. The protein preparations used in these experiments included bovine serum albumin (bSA), human immunoglobulin G (hIgG), secretory immunoglobulin A (hIgA), bovine growth hormone (bGH) and bGH complexed with an IgG antibody raised against bGH (bGH-Ab). Selectivity in binding of these microspheres to M cells, determined by confocal microscopy, was bGH < bSA < hIgG (mice) and bGH < bGH-Ab (rats and mice). A similar selectivity was seen for microsphere entry into M cells (bGH < bSA < hIgG; bGH < bGH-Ab). The appearance of protein-coated microspheres in rat mesenteric lymph showed a similar selectivity to that found for binding and entry into M cells (bGH < bGH-Ab). This latter selectivity was also found for hIgA-coated microspheres (bSA < hIgA). Preservation of transport selectivity throughout transcytosis highlights the unique importance of the M cell surface as being the primary site determining which type of antigen can be presented subsequently to the gut immune system. The possibility that this is a transient or phasic property of the M cell surface and that this could have physiological relevance is also discussed.

Selective transport of microparticles across Peyer's patch follicle‐associated M cells from mice and rats

Latex beads coated with secretory immunoglobulin (IgA) instilled into mouse intestinal loops are taken up by M cells present in Peyer's patch follicle-associated epithelial tissue. Bead adsorption and uptake is greater at the edge compared with the apex of follicle domes. Coating beads with bovine serum albumin (BSA) causes a fourfold reduction in adsorption and a twentyfold reduction in uptake. Results demonstrate selectivity between adsorption and uptake and between the ability of different proteins to facilitate uptake.

Confocal analysis of fluorescent bead uptake by mouse Peyer's patch follicle-associated M cells.

The intracellular potential in gallbladder epithelial cells is about −59 mV with respect to both mucosal and serosal media.

Transcellular ion route in rabbit gallbladder. Electric properties of the epithelial cells.

The reported experiments demonstrate that in rabbit gallbladder epithelium:

a)

The mucosa-cell Na+ and Cl− influxes (45 sec long) are reduced in Cl−-free and Na+-free bathing solutions respectively; transconcentration effects are observed.




b)

Cell Cl− labelling through the luminal membrane, with36Cl− (1 hr incubation), is nearly abolished if a Na+-free bathing solution is used; but cell Na+ labelling with22Na+ in the lumen (1 hr incubation) does not change if a Cl−-free bathing solution is employed.




c)

Cell Na+ and Cl− labelling through the basolateral membrane (1 hr incubation) is negligible; some Cl− labelling is obtained only when the intracellular electrical potential is artificially reduced.




d)

SO42− is found to abolish net water transport, to cross the epithelium, but not to enter the cell.

Na+ and Cl- transepithelial routes in rabbit gallbladder: tracer analysis of the transports.

1. Both electrophysiological properties and unidirectional Na and Cl fluxes have been determined across distal colons taken from pigs during early post-natal development. 2. The transmural potential difference (Vms) was 5 mV in the new-born and 10 mV in the 4 day old colon. The short circuit current (Scc) showed a three to sixfold increase during the first 10 days of post-natal life. The microvillar membrane potential (Vm) fell from about -45 mV in the new-born to -40 mV in the 4 day old colon. 3. Amiloride had no effect on Vms, Scc or Vm, measured in the new-born animal. It reduced Vms and Scc, caused a hyperpolarization of Vm and increased the microvillar membrane/basolateral membrane resistance ratio (Rm/Rs) in colons taken from older animals. 4. The Scc of distal colons taken from new-born and 1 day old pigs was only half that predicted from unidirectional measurements of Na flux. This discrepancy, which could not be completely accounted for by net CL absorption, disappeared in the older animals. 5. Net transport of Na doubled during the first 24 h of post-natal life. Part of this transport took place through an amiloride sensitive, non-electrogenic, pathway. 6. It is suggested that Na uses mainly a non-electrogenic pathway to cross the mucosa of the new-born pig. This pathway is replaced by an electrogenic amiloride sensitive mechanism in older animals. Aldosterone is thought to initiate these changes in Na tranport.

Dario Cremaschi

Papers

Selective transport of microparticles across Peyer's patch follicle‐associated M cells from mice and rats

Confocal analysis of fluorescent bead uptake by mouse Peyer's patch follicle-associated M cells.

Transcellular ion route in rabbit gallbladder. Electric properties of the epithelial cells.

Na+ and Cl- transepithelial routes in rabbit gallbladder: tracer analysis of the transports.

Post-natal development of amiloride sensitive sodium transport in pig distal colon.