Studies on the mechanical resistance of human erythrocytes under in-vitro conditions

Hemolysis and resistance of erythrocytes were studies in-vitro in experiments on human ACD fresh blood and on heparinized fresh blood after oxygen dispersion, resp. mixed oxygen and carbon dioxide dispersion, and subsequent treatment in the hemoresistometer. Blood alkalinity increases under oxygen dispersion, acidity increases under dispersion with mixed gases. The length of the period of dispersion is more important for hemolysis than the change of pH. The hematocrit value influences the behavior of blood resistance. High values imply enhanced hemolysis. There is no significant difference of actual hemolysis values between oxygen and oxygen/carbon dioxide dispersion. A different behavior appears in the calculation of difference value of hemolysis after treatment in resistometer and the respective actual hemolysis.     

Comprehension of familiar and unfamiliar native accents under adverse listening conditions.

This study aimed to determine the relative processing cost associated with comprehension of an unfamiliar native accent under adverse listening conditions. Two sentence verification experiments were conducted in which listeners heard sentences at various signal-to-noise ratios. In Experiment 1, these sentences were spoken in a familiar or an unfamiliar native accent or in two familiar native accents. In Experiment 2, they were spoken in a familiar or unfamiliar native accent or in a nonnative accent. The results indicated that the differences between the native accents influenced the speed of language processing under adverse listening conditions and that this processing speed was modulated by the relative familiarity of the listener with the native accent. Furthermore, the results showed that the processing cost associated with the nonnative accent was larger than for the unfamiliar native accent. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Friction of composite cushion bearings for total knee joint replacements under adverse lubrication conditions

Conventional joint replacements consist of a polished metallic or ceramic component articulating against a layer of polyethylene. Although the friction in the contact between these articulating surfaces is low, polyethylene wear is produced as a result of a boundary/mixed lubrication regime. Wear debris is generated by direct asperity contact, abrasion, adhesion and fatigue, and has been shown to cause adverse tissue reactions which can lead to joint failure. The introduction of soft compliant materials, similar in stiffness to articular cartilage, has shown that with cyclic loading and relative motion between the articulating surfaces typical of normal walking, a fluid film can be maintained through combined entraining and squeeze-film actions, and hence wear can be minimized. For 95 per cent of the time, however, we are not walking but standing still or moving slowly. A pendulum simulator has been used in the present study to investigate the effect of adverse tribological conditions which may lead to fluid film breakdown, such as severe cyclic loading, particularly in the swing phase, reduced sliding velocity, reduced stroke length and start-up after a period of constant loading. Friction of a model composite cushion knee bearing, manufactured from a graded modulus (20-1000 MPa) layer of polyurethane, sliding against a polished metal cylinder has been measured for various lubricants and the results have been analysed using a Stribeck assessment. Severe cyclic loading, decreased sliding velocity and decreased stroke length have been found to limit the degree of fluid entrainment previously allowed during the swing phase of normal walking, thus allowing breakdown of fluid films and elevated levels of friction and surface damage. Soft layer joint replacements must therefore be designed to operate with thick elastohydrodynamic fluid films to provide some degree of protection when tribological conditions become severe, or alternatively incorporate alternative boundary or mixed lubrication mechanisms. This study quantifies a potential limitation of the cushion bearing concept.     

Morphological changes of the corpus callosum in schizophrenia

Asthma and allergic disorders have been on the increase in recent decades, especially among children living in affluent countries; some aspects of the "Western" way of life may explain this trend. We evaluated the relation of aeroallergen skin test reactivity with socioeconomic status, number of siblings, and respiratory infections in early life. We examined a total of 2,226 schoolchildren, ages 7-11 years, in three areas of Lazio, Italy. Skin prick tests were performed to assess atopic status, and self-administered questionnaires were completed by the parents. The prevalence of prick test positivity was greater among children whose fathers were in the highest educational level than among those in the lowest [prevalence ratio (PR) = 1.58; 95% confidence interval (CI) = 1.21-2.06]. There was also a lower prevalence of atopy among larger sibships (PR = 0.38 for subjects with four or more siblings vs those without siblings; 95% CI = 0.14-0.99). A history of bronchitis or bronchiolitis before age 2 years was weakly associated with an increased risk of atopy, whereas a history of pertussis or pneumonia was not. Both the effect of father's education and the influence of larger sibship size remained when we adjusted for several potential confounding factors, including respiratory infections in early life. We infer that higher socioeconomic status and lower sibling number are determinants of atopy in this Italian population. Protection arising from early severe respiratory infections does not explain this association, although we cannot exclude a role for other viral infections.     

Developmental changes of tetrahydrobiopterin in rat and human erythrocytes

In the present study, we investigated the developmental changes of (1) plasma and erythrocyte tetrahydrobiopterin (BH4); (2) erythrocyte GTP cyclohydrolase (the rate-limiting enzyme of BH4 biosynthesis); (3) the permeability of erythrocyte membrane to BH4; and (4) plasma phenylalanine, both in healthy human subjects and Wistar rats. In vitro experiments demonstrated passive transport of BH4 into erythrocytes. In humans, BH4 levels as well as the other parameters were fairly consistent across all age groups. In contrast, Wistar rats showed significant developmental changes in erythrocyte BH4, which were not simply correlated to either GTP cyclohydrolase, permeability to BH4 or plasma phenylalanine levels. This may suggest the existence of other factors regulating the homeostasis of BH4, such as BH4-binding capacity in plasma and/or erythrocytes. These species/age differences in erythrocyte characteristics may influence the pharmacological behavior and clinical efficacy of BH4 in humans and experimental animals.     

Morphological changes during reduction of magnetite compacts

Magnetite superconcentrate compacts were reduced to wustite and iron at various temperatures (1173-1423 K) and the morphological changes occurring at various stages of reduction were observed under the scanning electron microscope. It has been demonstrated that considerable pitting and fragmentation occur during solid state reduction of Fe₃O₄ to FeO by solid iron. During the reduction of FeO the iron nuclei formed have a tetrahedral shape. At low reduction temperatures (1173 K) the large number of iron nuclei formed on wustite sinter together forming a dense iron layer. At high temperatures sustained growth of nuclei in the vertical direction leads to a sinuous porosity. Genesis of porosity creation has also been explained in terms of formation of holes, slits, cracks and fragmentation in magnetite and wustite and growth and sintering of iron nuclei.     

Immune changes induced by exercise in an adverse environment

Both physical activity and exposure to environmental stressors such as cold, heat, and high altitudes modify various components of immune function: T cell counts, natural killer (NK) cell counts, and cytolytic activity, cytokine secretion, lymphocyte proliferation and immunoglobulin levels. Light physical activity or a moderate level of environmental stress stimulate the immune response, but exhausting physical activity or more severe environmental stress have a suppressant effect, manifested by a temporary increase in susceptibility to viral infections. Combinations of physical activity and environmental stress generally have at least an additive effect. Thus, an intensity of physical activity or of environmental stress that is beneficial in itself can readily cause immunosuppression if the body is challenged by the two stimuli simultaneously.     

t-Butyl hydroperoxide-induced changes in the physicochemical properties of human erythrocytes

Treatment of human erythrocytes with micromolar concentrations of t-butyl hydroperoxide causes a variety of changes in the physical properties of the cells. Red cells exposed to concentrations of t-butyl hydroperoxide of less than 750 microM for 15 min exhibited significant decreases in cellular and membrane deformability, increases in membrane-associated protein cross-linking, osmotic fragility and the viscosity of the intracellular hemoglobin solution. No changes in the volume or density of the cells were observed. Changes in cellular deformability are probably attributable solely to changes in the mechanical properties of the cell membrane. Conversely, when red cells are exposed to t-butyl hydroperoxide concentrations in excess of 750 microM for 15 min they exhibited decreases in cellular deformability which may be related to increases in cell volume as well as membrane rigidity.     

Ultrastructural and biochemical changes of hepatocytes during ether and fluothane anesthesia under experimental conditions

A study was made of a possibility of using Soviet made membranes "Vladipor" with a pore diameter of 16--17 nm for the purpose of concentration and purification of antigenic extracts from stab cultures of S. typhi obtained by the action of typsin, hydrogen peroxide and detergents. Preparations, complete by antigenic structure, were obtained by ultrafiltration, with a good yield. The maximal rate of ultrafiltration was noted in case of "peroxide" antigenic preparations. The use of diafiltration provided a significant reduction of the ash content in the end products.