Renal function in transgenic rats expressing an angiotensin-(1-7)-producing fusion protein

Transgenic rats [TGR(A1-7)3292] present a chronic 2.5-fold increase in plasma Angiotensin-(1-7) [Ang-(1-7)] concentration. In the present study, we investigated the effects of this chronic elevation on renal function, vasopressin levels, kidney morphology, expression of Ang-(1-7) and vasopressin receptors in TGR(A1-7)3292. Urine volume and water intake were measured for 24 h. At the end of this period, plasma and urine samples were collected to evaluate renal function parameters and circulating vasopressin levels. Expression of renal V(2) receptors and Mas was assessed by ribonuclease protection assay. Renal slices were processed for histological analysis. The urine flow of TGR(A1-7)3292 was significantly lower in comparison with Sprague-Dawley rats. The reduced urine volume of TGR(A1-7)3292 was accompanied by a significant increase in urinary osmolality and decrease free water clearance. Glomerular filtration rate, urinary sodium and potassium excretion were similar in both strains. No significant changes were observed in vasopressin levels as well as in V(2) receptor and Mas mRNA expression in renal tissue. No changes in kidney structure of TGR(A1-7)3292 were detected. These data suggest that changes in circulating renin-angiotensin system produced by chronic increase of Ang-(1-7) levels can lead to adjustments in the water balance that are independent of vasopressin release and V(2) receptor expression

Mechanical strength of thermoplastics and composite thermoplastics welded by laser – a review

Thermoplastic welding is currently well implemented in the market, with several competitive and suitable processes, ranging from simple hot plate to ultrasonic welding. By its side, laser welding of plastics is still in a relatively early stage of research. This process is one of the most recent in the welding of thermoplastics and of great interest in the market. The welding technique is based on heating the thermoplastics by transmitting heat in the form of radiation. This is due to the ability of certain plastics to absorb the beam. Usually, one of the parts to be welded must be transparent and the other opaque to radiation. These two parts are kept under pressure as the laser beams are transmitted through the transparent part. The laser beam is concentrated in the joint area of the opaque part, heating and melting it. There are relatively few scientific studies on the joining of thermoplastics by laser and, in the case of thermoplastic matrix composites, there are even fewer. The main conclusion is that the mechanical strength of a laser welded joint is in the range of 30-50 MPa, a value that is frankly weak when compared to the value that the base material can handle and which is usually more than double for thermoplastics and 10 times for composites. Although the fusion process is contactless, one of the great limitations of laser welding of plastics is the need to exert pressure on the joint, which conditions and complicates the execution of a weld. However, despite everything, it is certain that laser welding presents mechanical strength values superior to those of a bonded connection and the processing time is much shorter, therefore, it is clear the interest on the process.info:eu-repo/semantics/publishedVersio

Angioprotectin: an angiotensin II-like peptide causing vasodilatory effects

The family of angiotensin peptides has been steadily growing in recent years. Most are fragments of angiotensin II (Ang II) with different affinities to the known angiotensin receptors. Here, we describe a novel endogenous Ang II-like octapeptide in plasma from healthy humans and patients with end-stage renal failure, which acts as a stronger agonist at Mas receptors than Ang 1-7. Chromatographic purification and structural analysis by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight (MALDI-TOF/TOF) revealed an Ang II-like octapeptide, angioprotectin, with the sequence Pro-Glu-Val-Tyr-Ile-His-Pro-Phe, which differs from Ang II in Pro(1) and Glu(2) instead of Asp(1) and Arg(2). Pro-Glu-Val-Tyr-Ile-His-Pro-Phe in angioprotectin is most likely generated enzymatically from Ang II. Angioprotectin antagonized the contractile actions of Ang II on rat aortic rings. The physiological antagonism of vasoconstrictor actions of Ang II by angioprotectin is mediated by the Mas receptor. Angioprotectin has a stronger affinity to the Mas receptor than Ang-1-7. Plasma concentrations were ~15% of plasma Ang II concentrations in healthy volunteers and up to 50% in patients with renal failure. A commercially available Ang II antibody did not discriminate between angioprotectin and Ang II; thus, angioprotectin can contribute to Ang II concentrations measured by antibody-based assays. This novel peptide is likely to be a relevant component of the human renin-angiotensin-system