Erythropoietin treatment elevates haemoglobin concentration by increasing red cell volume and depressing plasma volume

[EN] Erythropoietin (Epo) has been suggested to affect plasma volume, and would thereby possess a mechanism apart from erythropoiesis to increase arterial oxygen content. This, and potential underlying mechanisms, were tested in eight healthy subjects receiving 5000 IU recombinant human Epo (rHuEpo) for 15 weeks at a dose frequency aimed to increase and maintain haematocrit at approximately 50%. Red blood cell volume was increased from 2933 +/- 402 ml before rHuEpo treatment to 3210 +/- 356 (P < 0.01), 3117 +/- 554 (P < 0.05), and 3172 +/- 561 ml (P < 0.01) after 5, 11 and 13 weeks, respectively. This was accompanied by a decrease in plasma volume from 3645 +/- 538 ml before rHuEpo treatment to 3267 +/- 333 (P < 0.01), 3119 +/- 499 (P < 0.05), and 3323 +/- 521 ml (P < 0.01) after 5, 11 and 13 weeks, respectively. Concomitantly, plasma renin activity and aldosterone concentration were reduced. This maintained blood volume relatively unchanged, with a slight transient decrease at week 11, such that blood volume was 6578 +/- 839 ml before rHuEpo treatment, and 6477 +/- 573 (NS), 6236 +/- 908 (P < 0.05), and 6495 +/- 935 ml (NS), after 5, 11 and 13 weeks of treatment. We conclude that Epo treatment in healthy humans induces an elevation in haemoglobin concentration by two mechanisms: (i) an increase in red cell volume; and (ii) a decrease in plasma volume, which is probably mediated by a downregulation of the rennin-angiotensin-aldosterone axis. Since the relative contribution of plasma volume changes to the increments in arterial oxygen content was between 37.9 and 53.9% during the study period, this mechanism seems as important for increasing arterial oxygen content as the well-known erythropoietic effect of Epo.

Photocatalytic activity of nanostructured anatase coatings obtained by cold gas spray

[EN] This article describes a photocatalytic nanostructured anatase coating deposited by cold gas spray (CGS) supported on titanium sub-oxide (TiO22x) coatings obtained by atmospheric plasma spray (APS) onto stainless steel cylinders. The photocatalytic coating was homogeneous and preserved the composition and nanostructure of the starting powder. The inner titanium sub-oxide coating favored the deposition of anatase particles in the solid state. Agglomerated nano-TiO2 particles fragmented when impacting onto the hard surface of the APS TiO22x bond coat. The rough surface provided by APS provided an ideal scenario for entrapping the nanostructured particles, which may be adhered onto the bond coat due to chemical bonding; a possible bonding mechanism is described. Photocatalytic experiments showed that CGS nano-TiO2 coating was active for photodegrading phenol and formic acid under aqueous conditions. The results were similar to the performance obtained by competitor technologies and materials such as dip-coating P25 photocatalysts. Disparity in the final performance of the photoactive materials may have been caused by differences in grain size and the crystalline composition of titanium dioxide.