A brief review of the debate over social inequalities in health

The effects of paraquat on rat brain were studied. Activities of complex I (NADH: ubiquinone oxidoreductase) in mitochondrial electron transport system, lipid peroxidation and the amount of catecholamines in rat brain were measured after acute paraquat exposure. Complex I activities were significantly lower and lipid peroxides were higher in the brains of a paraquat-treated group than in those of a control group. Lipid peroxide in rat serum, however, did not increase after paraquat exposure. A study of the time dependency of paraquat effects disclosed that mitochondrial complex I activities in rat brain as well as those in rat lung and liver gradually decreased prior to the appearance of respiratory dysfunction. As compared to controls, the dopamine in rat striatum was significantly lower in the paraquat-treated group. These results suggest that paraquat after crossing the blood-brain barrier might be reduced to the radical in rat brain, which may damage the brain tissue, especially dopaminergic neurons in striatum. We therefore propose that cerebral damage should be taken into consideration on paraquat exposure. Patients may therefore need to be followed up after exposure to high doses of paraquat.     

Young's moduli and shear moduli in cortical bone

Young's modulus and shear modulus are determined for cortical bone from mammals and birds and for antler bone, using three-point bending at a range of span-to-depth ratios between 25 and 10. Young's modulus is obtained by extrapolating the values for the flexural modulus Eapp to infinite span-to-depth ratios. The shear modulus is obtained from the dependance of Eapp on this ratio. The main determinant for the mechanical properties is the mineral content. For mammalian bone the frequency of Haversian systems correlates negatively with stiffness and resistance to shear. However, because Haversian systems have a lower mineral content than laminar bone (the main component), material and structural determinants can not be separated at present. The ratio of Young's modulus to shear modulus is of the order of 20:1. This high value is discussed in terms of the Cook-Gordon theory of controlled crack propagation as well as in its significance for protecting hollow bones from failing upon local impact.     

Effects of phase separating systems on lyophilized hemoglobin

Polymer liquid-liquid two-phase systems offer a unique opportunity to study the mechanisms of protein stabilization during freezing and freeze-drying. Fourier transform infrared spectroscopy was used to monitor the structural integrity of recombinant hemoglobin frozen and lyophilized in the separated phases of a polyethylene glycol (PEG)-dextran system. Protein in each phase of an equilibrated biphasic PEG-dextran system experiences similar levels of structural protection against freezing stresses despite large differences in polymer concentration. This result further demonstrates previous suggestions that proteins are protected during freezing by the preferential exclusion mechanism. There are, however, distinct differences in the level of structural protection that polymers in equilibrium phases provide to proteins during lyophilization, emphasizing that the mechanisms of protein protection during freezing and drying are fundamentally different. In addition, we provide evidence that phase separation per se occurring during the course of the lyophilization cycle can be detrimental to the structural stability of a protein.     

Autologous platelet concentrate as an adjunct in macular hole healing: a pilot study

PURPOSE: A pilot study was undertaken to assess the efficacy of autologous platelets in macular hole healing. PATIENTS AND METHODS: Eight eyes of eight patients with stage 3 or 4 macular holes, two of which had failed to heal after previous vitrectomy and gas tamponade, were included. The procedure consisted of pars plana vitrectomy with removal of posterior cortical vitreous, stripping of associated epimacular membranes, 15% perfluoroethane-air tamponade, and instillation of autologous platelet concentrate onto the posterior pole. Strict postoperative facedown positioning was observed for 12 days. Postoperative evaluation included visual acuity measurement, biomicroscopic macular appearance and scanning laser ophthalmoscope examination. The follow-up period ranged from 3 to 13 months (mean, 7 months). RESULTS: Of eight eyes, flattening of the surrounding retina and closure of the hole were achieved in seven (87.5%). Visual acuity improved two lines or more in four eyes (50%) Four eyes (50%) reached a postoperative visual acuity of 20/50 or more. Increased nuclear sclerosis was observed in six eyes (75%), and retinal detachment occurred in two eyes (25%). CONCLUSIONS: Autologous platelet concentrate administered peroperatively in full-thickness macular holes seems to be a safe and effective adjunct to vitrectomy with removal of posterior hyaloid and gas tamponade. A larger multicenter randomized prospective study is underway to verify these encouraging results before advocating the use of autologous platelets in macular hole surgery.     

The appearance of family themes in the speech of schizophrenics--a comprehensive analysis

Through comprehensive analysis, the authors reflect about the emergence of family thematic in the speeches of the individuals denominate schizophrenics who are out of crisis. Using phenomenology as a methodological way, the study intends to show how these subjects focuse the family in their talk.     

Serologic diagnosis of canine and equine borreliosis: use of recombinant antigens in enzyme-linked immunosorbent assays

A key regulatory enzyme of the C4-photosynthetic pathway is stromal pyruvate,orthophosphate dikinase (PPDK, EC 2.7.9.1). As a pivotal enzyme in the C4 pathway, it undergoes diurnal light-dark regulation of activity which is mediated by a single bifunctional regulatory protein (RP). RP specifically inactivates PPDK in the dark by an ADP-dependent phosphorylation of an active-site Thr residue (Thr-456 in maize). Conversely, RP activates inactive PPDK in the light by phosphorolytic dephosphorylation of this target Thr-P residue. We have employed a His-tagged maize recombinant C4 PPDK for directed mutagenesis of this active-site regulatory Thr. Three such mutants (T456V, T456S, T456D) were analyzed with respect to overall catalysis and regulation by exogenous maize RP. Substitution with Val and Ser at this position does not affect overall catalysis, whereas Asp abolishes enzyme activity. With respect to regulation by RP, it was found that Ser can effectively substitute for the wild-type Thr residue in that mutant enzyme is phosphorylated and inactivated by RP. The T456V mutant, however, could not be phosphorylated and was, thus, resistant to ADP-dependent inactivation by RP.     

Molecular dynamics-derived conformation and intramolecular interaction analysis of the N-acetyl-9-O-acetylneuraminic acid-containing ganglioside GD1a and NMR-based analysis of its binding to a human polyclonal immunoglobulin G fraction with selectivity for O-acetylated sialic acids

The influence of 9-O-acetylation of GD1a, yielding GD1a (eNeu5,9Ac2) with a 9-O-acetylated sialic acid moiety linked to the outer galactose residue, on the spatial extension and mobility of the carbohydrate chain and on recognition by a natural human antibody is analysed. To study a potential impact of the O-acetyl group on the overall conformation of the carbohydrate chain, molecular dynamics (MD) simulations of oligosaccharide chain fragments of increasing length starting from the non-reducing end have been carried out for the first time in this study. They revealed a considerable loss in chain flexibility after addition of the internal N-acetylneuraminic acid onto the chain. Besides MD calculations with different dielectric constants, the conformational behaviour of the complete oligosaccharide chain of the 9-O-acetylated GD1a ganglioside was simulated in the solvents water and dimethyl sulfoxide. These solvents were also used in NMR measurements. The results of this study indicate that 9-O-acetylation at the terminal sialic acid does not influence the overall conformation of the ganglioside. An extended interaction analysis of energetically minimized conformations of GD1a (eNeu5,9Ac2) and GD1a, obtained during molecular dynamics simulations, allowed assessment of the influence of the different parts of the saccharide chains on spatial flexibility. Noteworthy energetic interactions, most interestingly between the 9-O-acetyl group and the pyranose ring of N-acetylgalactosamine, were ascertained by the calculations. However, the strength of this interaction does not force the ganglioside into a conformation, where the 9-O-acetyl group is no longer accessible. Binding of GD1a (eNeu5,9Ac2) to proteins, which are specific for 9-O-acetylated sialic acids, should thus at least partially be mediated by the presence of this group. To experimentally prove this assumption, a NMR study of 9-O-acetylated GD1a in the presence of an affinity-purified polyclonal IgG fraction from human serum with preferential binding to 9-O-acetylated sialic acid was performed. The almost complete disappearance of the intensity of the 9-O-acetyl methyl signal of the GD1a (eNeu5,9Ac2) clearly indicates that the assumed interaction of the 9-O-acetyl group with the human protein takes place.     

Structure of gel phase saturated lecithin bilayers: temperature and chain length dependence

Systematic low-angle and wide-angle x-ray scattering studies have been performed on fully hydrated unoriented multilamamellar vesicles of saturated lecithins with even chain lengths N = 16, 18, 20, 22, and 24 as a function of temperature T in the normal gel (L beta') phase. For all N, the area per chain Ac increases linearly with T with an average slope dAc/dT = 0.027 A2/degree C, and the lamellar D-spacings also increase linearly with an average slope dD/dT = 0.040 A/degree C. At the same T, longer chain length lecithins have more densely packed chains, i.e., smaller Ac's, than shorter chain lengths. The chain packing of longer chain lengths is found to be more distorted from hexagonal packing than that of smaller N, and the distortion epsilon of all N approaches the same value at the respective transition temperatures. The thermal volume expansion of these lipids is accounted for by the expansion in the hydrocarbon chain region. Electron density profiles are constructed using four orders of low-angle lamellar peaks. These show that most of the increase in D with increasing T is due to thickening of the bilayers that is consistent with a decrease in tilt angle theta and with little change in water spacing with either T or N. Because of the opposing effects of temperature on area per chain Ac and tilt angle 0, the area expansivity alpha A is quite small. A qualitative theoretical model based on competing head and chain interactions accounts for our results.