Reduced intracellular oxidative metabolism promotes firm adhesion of human polymorphonuclear leukocytes to vascular endothelium under flow conditions

The interaction of polymorphonuclear leukocytes (PMN) with the vascular endothelium and their subsequent extravasation to the tissues is a key step during different physiological and pathological processes. In certain of these pathologies the oxygen tension becomes very low, leading to reduced cellular oxidative status. To evaluate the effect of lowering the intracellular redox status in the interaction of PMN with the endothelium, exposure to hypoxic conditions as well as treatment with different antioxidant agents was carried out. PMN exposure to hypoxia enhanced beta2 integrin-dependent adhesion to intercellular adhesion molecule-1-coated surfaces, concomitant with a decrease in the intracellular redox status of the cell. As occurs with hypoxia, treatment with antioxidants produced a decrease in the oxidation state of PMN. These agents enhanced adhesion of PMN to human umbilical vein endothelial cells stimulated with tumor necrosis factor-alpha (TNF-alpha), and this effect was also mediated by beta2 integrins LFA-1 and Mac-1. Adhesion studies under defined laminar flow conditions showed that the antioxidant treatment induced an enhanced adhesion mediated by beta2 integrins with a decrease in the fraction of PMN rolling on TNF-alpha-activated endothelial cells. The up-regulated PMN adhesion was correlated to an increase in the expression and activation of integrin Mac-1, without loss of L-selectin surface expression. Altogether, these results demonstrate that a reduction in the intracellular oxidative state produces an enhanced beta2 integrin-dependent adhesion of PMN to stimulated endothelial cells under conditions of flow.     

The influence of yttrium on the Oxidation behaviour of Ni-23Co-19Cr-12Al alloy at high temperatures

The effect of 0.6 wt.% yttrium addition on the oxidation behaviour of the coating material Ni-23Co-19Cr-12Al was studied under isothermal and thermal cycling conditions in air at 1373 and 1473 K. The reaction was followed thermogravimetrically while the SEM, EDX, EPMA and X-ray diffraction techniques were used to characterise the starting materials and the oxidized samples. Intensive spalling and the formation of a deep internal oxidation zone were observed in the case of the yttrium-free alloy. Yttrium strongly improved the oxidation resistance by substantial suppression of scale spalling and considerable reduction of internal oxidation.     

Morphometric study of the placental vessels and its correlation with umbilical artery Doppler flow

OBJECTIVE: To determine the changes in the vessel-wall thickness and the radius of the lumen in tertiary-stem villi of the placenta with advancing gestational duration and their relationship to umbilical artery Doppler flow studies. METHODS: Placentas from 63 miscarriages and preterm and term deliveries (between 19 and 40 weeks) were used for morphometric study of the tertiary-stem villi vessels. Each woman had undergone Doppler flow study of the umbilical artery. The resistance index (RI) was determined from the Doppler flow velocity waveform. Placental paraffin sections of 4-micron thickness were stained with hematoxylin and eosin and with periodic acid-Schiff reagents. The tertiary-stem villi and their vessels were examined microscopically and assessed morphometrically using a personal computer with math co-processor and a touch-sensitive screen overlying a video monitor. The monitor received microscopic images from a video camera that was mounted on a microscope. We determined vessel-wall thickness by tracing the outer and inner circumferences of digitized vessel-wall images. RESULTS: Wall thickness, but not lumen size, of the tertiary-stem villi vessels decreased significantly overall at a rate of 0.63micron/week (P < .001). The rate of decrease was 0.64micron/week (P < .001) during the second trimester and 0.50micron/week (P < .001) during the third trimester. There was a significant correlation between the decrease in thickness and in RI (r = 0.83 [P < .001], r = 0.78 [P < .001] in the second and third trimesters, respectively). Resistance indices were all within normal limits. CONCLUSIONS: Placental tertiary-stem villi vessel-wall thickness decreases with advancing gestational age. There is a correlation between the changes in RI of the umbilical artery Doppler flow and the changes in mean wall thickness of the placental vessels.     

Guidelines for nonspecific bronchial provocation tests

This study evaluated the effects of a predialysis patient education programme on functioning and well-being in 28 uraemic patients. The programme consisted of four group sessions with the following themes: renal disease and dietary restriction, active renal replacement therapy, physical exercise, and the impact of chronic renal failure on economy, family and social life. Three to 9 months after having started dialysis the patients were evaluated regarding symptoms, perceived health (Health Index), functional (SIP) and emotional (STAI) status. Twenty-eight patients already on dialysis treatment informed according to conventional routines constituted the comparison group. There were no significant differences between the groups regarding age, sex, educational or social background, duration of kidney disease, choice of dialysis treatment, cause of renal disease and laboratory tests except for s-urea. The patients who participated in the education programme scored significantly better mood, less mobility problems (HI), less functional disabilities (SIP) and lower levels of anxiety (STAI) compared to the comparison group. There were no significant differences between the two groups regarding symptoms and overall health. The differences between the groups prevailed during the first 6 months on dialysis treatment, after which the differences disappeared. In the comparison group age correlated significantly to anxiety and overall SIP, which was not the case in the experimental group. In conclusion, the experimental group that participated in a predialysis patient education programme, showed better functional and emotional well-being than the non-educated comparison group. The positive effects of participating in an education programme prevailed during the first 6 months of dialysis treatment. Moreover, the younger patients seemed especially to benefit from participation in a predialysis patient education programme. It is suggested that patient education should be ongoing for patients with end-stage renal failure initiated during the predialysis stage and continued after maintenance dialysis has been established.     

Effect of hot pressing densification on the cellular structure of black agglomerated cork board

Samples of black cork agglomerate boards were observed by scanning electron microscopy, prior and after different densifications. These boards were densified under conditions previously defined, and were observed in two directions, parallel and perpendicular to the compression axis. The relationship between the average cell wall distance and the compression applied was studied and it was found that the maximum densification is achieved with a pressure of ca. 3 MPa. Some aspects of the influence of densification treatments on the chemical composition of the material were also broached.     

A Comparison of Three Methods of Estimating Displacement on an Instrumented Single Punch Machine

In this paper a determination of the possible sources of experimental errors of displacement measurements by an instrumented single-punch machine and their repercussion in compression parameters has been accomplished. Also, elastic deformation of punches and other parts of the machine was evaluated using three different methods. One of these, based on the strain gauge response as measure of punch deformation it is proposed as a novel method to correct displacement measurements by instrumented machines.     

Rhodium complexes as catalysts for hydrosilylation crosslinking of silicone rubber

Vulcanization of silicon rubber compound based on polysiloxanes containing vinyl and Si–H groups catalyzed by [RhCl(CO)₂]₂, [RhCl(C₂H₄)₂]₂, [RhCl(1,5-COD)]₂, [RhCl(NBD)]₂, RhCl[P(C₆H₅)₃]₃, and Rh(acac)₃ (1,5-COD = 1,5-cyklooktadiene, NBD = norbornadiene, acac = acetylacetonate) has been studied in dependence on the catalyst, solvent, and reaction conditions. The course of vulcanization as well as the crosslinking density of the vulcanizate and the content of sol indicate that the above catalysts are comparable to and in some cases even better than the widely used hexachloroplatinic acid.     

Relevant aspects in the clinical applications of NiTi shape memory alloys

NiTi shape memory alloys showing pseudoelastic behaviour have great potential in dental and orthopaedic applications where constant correcting loads may be required. In most of the clinical applications the device may have been heat treated and during its life in service it will be cyclically deformed. It is therefore important to investigate the effect of cyclic straining and heat treatments upon the transformation stresses and temperatures of the material. The aim of this work is to study the thermal and mechanical ageing of a pseudoelastic NiTi shape memory alloy, as well as the environmental in vitro degradation of the alloy due to the effect of artificial saliva.This paper was accepted for publication after the 1995 Conference of the European Society of Biomaterials, Oporto, Portugal, 10–13 September.