Geochemical approach to the Bou Hadjar hydrothermal system (NE Algeria)

The Bou Hadjar low-temperature hydrothermal system is located in northeast Algeria. The four main thermal springs that are the subject of the study emerge ith temperatures between 32 and 60°C from allochthonous formations. The reservoir temperature has been estimated from chemical compositions by utilizing simultaneously the silica, gas and sulfate-water oxygen isotope geothermometers, fluid-mineral equilibrium calculations, and a mixing model. According to these thermometric methods, the most probable subsurface temperature is in the range 75–106°C. The mixing model suggests a temperature of 125°C for the parent water.     

Loss of substance of the lateral region of the face

The cardiovascular effects of a partially purified extract of fish oil, enriched in the n-3 series fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were studied in stroke-prone spontaneously hypertensive rats (SHR-SP) fed with high- and low-sodium diets during 5 weeks. Addition of salt to the low-salt control diet at a level commonly found in human food items (6% NaCl of the dry weight of the diet) produced a remarkable rise in blood pressure, an increase in left ventricular weight-to-body weight ratio (LVH-index) and an increase in kidney weight-to-body weight ratio (RH-index). Fish oil (20% of the dry weight of the diet) did not significantly influence the blood pressure or LVH-index or RH-index during the low-salt control diet. However, fish oil completely prevented the remarkable rise in blood pressure and clearly antagonized the rise of both LVH- and RH-indices, induced by the high-salt diet. The fish oil supplementation increased the levels of the polyunsaturated fatty acids of the n-3 series and decreased those of the n-6 series in plasma and kidney, irrespective of the salt content of the diet. Fish oil lowered serum thromboxane B2 concentration by approximately 75%. During the high-salt diet, fish oil markedly decreased water intake and urine volume, and increased urinary sodium concentration by about 60%. Our findings show that, in addition to an antihypertensive effect, fish oil also decreases LVH and RH. These effects appear to be due to an improved ability to excrete sodium and could be explained by the observed changes in the fatty acid composition and metabolism.     

Patellar instability in children

Current work on disease states involving the patella has led to increased interest in patellar instability. We reviewed a series of patellar luxations. True trauma-induced luxations are rare. Most cases are recurrent luxations in subjects with a morphological anomaly of the knee extensor system. Because of the growth cartilages, selective therapeutic techniques are needed to stabilize the patella. Recurrent or permanent luxations of the patella result from congenital malformations of the muscles or skeleton. A complete MRI study is highly indicated. The patella can be correctly realigned by surgical release. In cases with femoropatellar dysplasia, which is not specific for children, well conducted rehabilitation therapy often leads to favourable outcome.     

Activation of the anti-cancer drug ifosphamide by rat liver microsomal P450 enzymes

The NADPH-dependent metabolism of ifosphamide catalyzed by rat liver microsomes was investigated in order to identify individual P450 enzymes that activate this anti-cancer drug and to ascertain their relationship to the P450 enzymes that activate the isomeric drug cyclophosphamide. Pretreatment of rats with phenobarbital or clofibrate increased by up to 8-fold the activation of both ifosphamide and cyclophosphamide catalyzed by isolated liver microsomes. Studies using P450 form-selective inhibitory antibodies demonstrated that constitutively expressed P450s belonging to subfamily 2C (forms 2C11/2C6) make significant contributions to the activation of both oxazaphosphorines in uninduced male rat liver microsomes, while the phenobarbital-inducible P450 2B1 was shown to be a major catalyst of these activations in phenobarbital-induced microsomes. Pretreatment of rats with dexamethasone increased liver microsomal activation of ifosphamide approximately 6-fold without a corresponding effect on cyclophosphamide activation rates. Ifosphamide activation catalyzed by dexamethasone-induced liver microsomes was minimally inhibited by anti-P450 2B or anti-P450 2C antibodies, but was selectively inhibited by anti-P450 3A antibodies. Selective inhibition of liver microsomal ifosphamide activation was also effected by the macrolide antibiotic triacetyloleandomycin, an inhibitor of several dexamethasone-inducible 3A P450s. These studies establish that a dexamethasone-inducible family 3A P450 can make an important contribution to rat liver microsomal ifosphamide activation, and suggest that dexamethasone pretreatment might provide a useful approach for modulation of ifosphamide metabolism in order to improve its therapeutic efficacy in cancer patients.     

Role of cholesterol in regulating apolipoprotein B secretion by the liver

The review examines the evidence that the supply of cholesterol available for incorporation into nascent lipoprotein particles exerts a regulatory influence on apolipoprotein (apo) B secretion by the liver. Support for this hypothesis comes both from in vitro experiments and from recent observations in normal subjects and patients with dyslipidemia associated with familial hypercholesterolemia, obesity, noninsulin dependent diabetes mellitus, growth hormone deficiency and cholesteryl ester storage disease. The findings do not negate a role for triglyceride synthesis in determining apoB secretion in very low density lipoprotein, but the inhibitory effects on the latter process of pharmacological blockade of cholesterol synthesis or esterification suggest that it is conditional upon an adequate supply of cholesteryl ester.     

Thermal stability in bulk cryomilled ultrafine-grained 5083 Al alloy

Thermal stability in bulk ultrafine-grained (UFG) 5083 Al that was processed by gas atomization followed by cryomilling, consolidation, and extrusion, and that exhibited an average grain size of 305 nm, was investigated in the temperature range of 473 to 673 K (0.55 to 0.79 T _m , where T _m is the melting temperature of the material) for different annealing times. Appreciable grain growth was observed at temperatures > 573 K, whereas there was limited grain growth at temperatures < 573 K even after long annealing times. The values of the grain growth exponent, n, deduced from the grain growth data were higher than the value of 2 predicted from elementary grain growth theories. The discrepancy was attributed to the operation of strong pinning forces on boundaries during the annealing treatment. An examination of the microstructure of the alloy suggests that the origin of the pinning forces is most likely related to the presence of dispersion particles, which are mostly introduced during cryomilling. Two-grain growth regimes were identified: the low-temperature region (<573 K) and the high-temperature region (>573 K). For temperatures lower than 573 K, the activation energy of 25 ± 5 kJ/mol was determined. It is suggested that this low activation energy represents the energy for the reordering of grain boundaries in the UFG material. For temperatures higher than 573 K, an activation energy of 124 ± 5 kJ/mol was measured. This value of activation energy, 124 ± 5 kJ/mol, lies between that for grain boundary diffusion and lattice diffusion in analogous aluminum polycrystalline systems. The results show that the strength and ductility of bulk UFG 5083 Al, as obtained from tensile tests, correlate well with substructural changes introduced in the alloy by the annealing treatment.