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To test whether an observed age-related increase in the level of oxidized protein in rat liver is due to a decrease in the activity of the multicatalytic proteinase (MCP), this protease was isolated from liver of young (8-month-old) and old (24-month-old) male Fischer 344 rats. Three peptidase activities of the MCP were assayed using fluorogenic peptides: trypsin-like, chymotrypsin-like, and peptidylglutamyl-peptide hydrolase. Only peptidylglutamyl-peptide hydrolase activity declined with age, with protease from old animals exhibiting approximately 50% of the activity of that from young animals. Bidimensional gel electrophoresis and thermostability studies did not reveal age-related structural modifications of the MCP subunits. Peptidylglutamyl-peptide hydrolase activity and trypsin-like activity were sensitive to metal-catalyzed oxidation. In some preparations, a 95-kDa protein that has been identified as the heat shock protein 90 copurified with the MCP. In the presence of HSP 90, trypsin-like activity is protected from oxidative inactivation and chymotrypsin-like activity is slightly activated. Peptidylglutamyl-peptide hydrolase activity remained sensitive to oxidation in protease isolated from young rats, but that from old rats was resistant to oxidative inactivation. Furthermore, addition of rat HSP 90 to rat liver MCP (purified from 8-month-old animals and free of contaminating HSP 90) was found to protect trypsin-like activity from oxidative inactivation.

In this paper the radioresistance of human erythrocytes to radiation-induced haemolysis was studied by means of the split-dose technique. Human erythrocytes suspended in an isotonic Na-phosphatase buffer, pH7.4 were exposed under air to gamma radiation. Erythrocytes were irradiated with a single dose of 2.7kGy and with the same total dose split into two fractions with an interval between the subsequent exposures. It seems that postradiation processes initiated by the first radiation dose of definite magnitude can lead to an increase in the resistance of erythrocytes to haemolysis under the influence of subsequent dose. The maximal effect of the fractionation (50% decrease of haemolysis) was observed when the first fraction was equal to 0.3–0.4kGy and the interval between exposures was equal to 3h.

During aging cells accumulate altered forms of proteins, notably oxidatively modified proteins. The multicatalytic protease selectively degrades oxidized proteins, suggesting that the age-related accumulation of oxidized proteins might be a consequence of decreased activity of this protease, The protease activity of liver homogenates was assayed with an improved fluorimetric method, using oxidatively modified glutamine synthetase as substrate, Application of this assay to extracts from liver of Fischer 344 rats from both Japan and the United States demonstrated a marked preference for the oxidized substrate, as expected. Extracts from animals ages 8 to 26 months maintain both total proteolytic activity and the ability to distinguish between native and oxidized substrates. Oxidatively modified hepatocyte extracts were also employed as substrate, and older animals again maintained proteolytic activity. The multicatalytic protease was purified from liver of young and old rats, and the specific activity of the preparations were comparable when assayed with oxidatively modified glutamine synthetase. We conclude that the intrinsic neutral or alkaline proteolytic activity of rat liver is maintained during aging,

We consider the results for hadronic current correlators that we have obtained previously using a generalized Nambu-Jona-Lasinio (NJL) model. Given the nature of the NJL model, these results are expected to be valid for energies and momenta below some cutoff of about 1 Gev. However, the very high-energy behavior of such correlators can be calculated in perturbation theory. In this work, we use dispersion relations to interpolate between the known high-energy behavior of the correlators and the low-energy behavior that was obtained from the NJL model. The results of calculations made using the NJL model serve to fix various substraction constants in these dispersion relations. In this manner we obtain continuous curves for the correlation functions for all momenta. This procedure is defined such that the (low-energy) predictions of the NJL model are unchanged and such that the correlators have the correct high-energy behavior. In addition to the various results presented in terms of momentum-space variables, we also calculate the scalar-isoscalar correlation function in coordinate space.Copyright 1995, 1999 Academic Press, Inc.

The effects of interaction of ethanol, l‐butanol or t‐butanol peroxyl radicals with oxyhemoglobin (HbO2) were estimated using absorption spectroscopy in the visible range and tryptophan fluorescence. Peroxyl radicals were generated by gamma‐radiation. Alcohol peroxyl radicals showed the same effectiveness in oxidizing HbO2 iron as ‐OH radicals (GFe(III) = 1.8 for a dose 0.33 kGy). However, they degraded hemoglobin to hemichromes and cholehemichromes to a lesser degree than ‐OH radicals. In addition l‐ and t‐butanol peroxyl radicals were less effective than peroxyl ethanol radicals. Alcohol peroxyl radicals caused unfolding of protein to a much lesser degree than ‐OH radicals. Their contribution to the destruction of tryptophan residues was nearly matched by those obtained with the ‐OH radicals.

Alkalosis is a clinical complication resulting from various pathological and physiological conditions. Although it is well established that reducing the cellular proton concentration is lethal, the mechanism leading to cell death is unknown. Mitochondrial respiration generates a proton gradient and superoxide radicals, suggesting a possible link between oxidative stress, mitochondrial integrity, and alkaline-induced cell death. Manganese superoxide dismutase removes superoxide radicals in mitochondria, and thus protects mitochondria from oxidative injury. Cells cultured under alkaline conditions were found to exhibit elevated levels of mitochondrial membrane potential, reactive oxygen species, and calcium which was accompanied by mitochondrial damage, DNA fragmentation, and cell death. Overexpression of manganese superoxide dismutase reduced the levels of intracellular reactive oxygen species and calcium, restored mitochondrial transmembrane potential, and prevented cell death. The results suggest that mitochondria are the primary target for alkaline-induced cell death and that free radical generation is an important and early event conveying cell death signals under alkaline conditions.

The activity of rat liver glutaminase from sedimented fractions of freeze-thawed mitochondria is strongly affected by variation in pH over a physiologically relevant range at approximate physiological concentrations of activators. As pH increases from 7.1 to 7.7 at 0.7 mMammonium and 10 mMphosphate, the S0.5for glutamine decreases 3.5-fold, from 38 to 11 mM. This results in an 8-fold increase in reaction velocity at 10 mMglutamine. In addition, the M0.5for phosphate activation decreases from 21 to 8.9 mMas pH increases from 7.1 to 7.7. This apparent effect of pH on the affinity of glutaminase for phosphate is similar to previous reports of the pH effect on activation by ammonium (Verhoeven, A. J., Van Iwaarden, J. F., Joseph, S. K., and Meijer, A. J. (1983) Eur. J. Biochem.133, 241–244; McGivan, J. D., and Bradford, N. M. (1983) Biochim. Biophys. Acta159, 296–302). Glutaminase does not respond to variation in pH between 7.1 and 7.7 when phosphate and ammonium are saturating. The effects of the two modifiers are additive. Each is still effective, as is pH, when the other is saturating. Therefore, it appears that the effects of pH on the apparent affinity of the enzyme for ammonium and phosphate account for the enzyme's response to pH. These results may help explain previous reports of minimal effects of pH on glutaminase at saturating concentrations of related substances (McGivan, J. D., Lacey, J. H., and Joseph, K. (1980) Biochim. J.192, 537–542; Horowitz, M. L., and Knox, W. E. (1968) Enzymol. Biol. Clin.9, 241–255; McGivan, J. D., and Bradford, N. M. (1983) Biochim. Biophys. Acta759, 296–302). Glutaminase binds glutamine cooperatively with Hill coefficients ranging from 1.7 to 2.2, which suggests at least two and probably three or more interacting binding sites for glutamine. The strong response of liver glutaminase to pH and the fact that the reaction can supply metabolites for urea synthesis suggest a possible regulatory role of glutaminase in ureagenesis.

Incubation of glucose-6-phosphate dehydrogenase fromLeuconostoc mesenteroides with Fe2+ and citrate results in rapid O₂-dependent inactivation of the enzyme. Maximal rate of inactivation occurred at equimolar concentrations of Fe2+ and citrate. Loss of enzyme activity appears to be the result of selective oxidative modification, as evidenced by a corresponding increase in protein carbonyl content. Partially inactivated enzyme remained predominantly in the dimeric form with no change in the apparent affinity of the remaining active subunits for substrate. Modified Glu-6-PDH was, however, more susceptible to heat denaturation. Our results suggest that the Fe2+-citrate complex binds to the glucose 6-phosphate binding site and then undergoes reaction with H₂O₂ formed in solution leading to the oxidative modification of amino acids essential for enzyme activity.Copyright 1993, 1999 Academic Press

A spectrophotometric assay for glucosidase I using the synthetic trisaccharide α-D-Glc 1 → 2 α-D-Glc 1 → 3 α-D-Glc-O(CH2)8COOCH3is reported. The terminal glucose is released from the substrate by the enzyme and quantitated using glucose oxidase, peroxidase, and o-dianisidine. The trisaccharide is specific for glucosidase I and provides all the necessary structural features for correct interaction in the enzyme active site. The utility of the assay for monitoring enzyme activity during isolation and for use in kinetic and inhibition studies (i.e., with 1-deoxynorjirimycin) is demonstrated.

Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroidesis inactivated when exposed to metal-catalyzed oxidation or when modified by the lipid peroxidation product, 4-hydroxy-2-nonenal (HNE). Although in each case inactivation appears to be the result of the selective modification of an active site lysine residue, only the oxidized enzyme becomes more susceptible to proteolysis by purified rat liver multicatalytic protease, a multienzymatic proteolytic complex involved in the intracellular degradation of damaged proteins. The HNE-treated enzyme remains as resistant to proteolysis by the multicatalytic protease as the native enzyme. In contrast to the HNE-treated Glu-6-PDH, enzyme modified by Fe2+and citrate is more thermolabile and exhibits increased binding of the hydrophobic probe 8-anilino-1-naphtalene sulfonic acid (ANSA). Heat inactivation is characterized, in part, by dissociation of the dimer to inactive subunits. No change in the secondary structure and only small variations in the fluorescence and circular dichroism of the aromatic residues are observed for the two modified forms of the enzyme as compared with the native enzyme. The increased heat sensitivity, ANSA binding, and proteolytic susceptibility are likely related to a decrease in the structural stability of oxidatively modified Glu-6-PDH. Conversely, modification of Glu-6-PDH with HNE has no apparent effect on its structural stability or proteolytic susceptibility. This finding may have important implications for the accumulation of altered protein in vivo, a process that is believed to be involved in age- and disease-related impairment of cellular function.

Liver glutaminase is stimulated by an increase in NH4+ concentration and NH4+ is an absolute requirement for activity at approximate physiological concentrations of phosphate and glutamine. Increases in the concentration of NH4+ cannot, however, overcome the inhibitory effect of a decrease in pH. In addition, the concentration of NH4+ required for half-maximal rate decreases as pH increases. This decrease is the result of two factors: a direct effect of pH on the apparent affinity of the enzyme for NH4+, and an indirect effect of pH brought about by an increase in the apparent affinity of the enzyme for phosphate which results in a further decrease in the M0.5 for NH4+. In addition, liver glutaminase responds strongly to the concentration of citrate over a physiologically relevant range at approximate physiological concentrations of NH4+, phosphate, and glutamine. An increase in citrate concentration stimulates glutaminase by increasing the affinity of the enzyme for glutamine. The apparent affinity of the enzyme for citrate increases as pH increases. The strong response of liver glutaminase to pH, NH4+, and citrate and the fact that the hydrolysis of glutamine can supply metabolites and effectors for urea synthesis suggest a possible regulatory role of glutaminase in ureagenesis.

The adipose tissue stroma is a rich source of molecularly distinct stem and progenitor cell populations with diverse functions in metabolic regulation, adipogenesis, and inflammation. The ontology of these populations and the mechanisms that govern their behaviors in response to stimuli, such as overfeeding, however, are unclear. Here, we show that the developmental fates and functional properties of adipose platelet-derived growth factor receptor beta (PDGFRβ)+ progenitor subpopulations are tightly regulated by mitochondrial metabolism. Reducing the mitochondrial β-oxidative capacity of PDGFRβ+ cells via inducible expression of MitoNEET drives a pro-inflammatory phenotype in adipose progenitors and alters lineage commitment. Furthermore, disrupting mitochondrial function in PDGFRβ+ cells rapidly induces alterations in immune cell composition in lean mice and impacts expansion of adipose tissue in diet-induced obesity. The adverse effects on adipose tissue remodeling can be reversed by restoring mitochondrial activity in progenitors, suggesting therapeutic potential for targeting energy metabolism in these cells.

Electronics R&D is becoming prohibitively expensive and often the only way to continue to make progress is as part of a joint effort. Many companies have realised this and such technological alliances are making the news nearly every week. Sadly, just about all of these announcements concern chip R&D and prospects for solving the problems of packaging are as grim as ever. At this rate, multi-chip modules will have been just a minor diversion on the route to the single chip computer.

If we were to draw up a pecking order of semiconductors, we would undeniably rank silicon as pre-eminent. Gallium arsenide would come a good second - everyone has heard of gallium arsenide even if most don't know what it is and what it does. But what to place in third position? The answer is, of course, indium phosphide (InP). The status of this enigmatic material can be likened to that of Cinderella, step-sister of Si and GaAs, but it may come as a surprise to learn that it has an entire conference, a very succesful one I should add, devoted to it.

Readers will have noticed the presence of colour figures in Microelectronics journal recent issues. This is but the tip of an iceberg as your journal evolves in the computer-aided age. I thought that it would make an interesting editorial to pontificate on the impact that some of the various computer aided publishing processes are already having on this and other journals. As with all new things, there are advantages and disadvantages. Moreover, whenever these developments are implemented on the grounds of saving time and money, circumstances nearly always contrive to confound this expectation.

Results of incoherent light transient annealing of Mg implants in GaAs are reported and compared to conventional furnace anneals. Transient anneals produced better activations, with an optimum at an annealing temperature of 800°C, due apparently to reduced outdiffusion of Mg into the encapsulating silicon nitride layer.

Diffusion process determines the rate of chloride ions penetration in concrete and therefore diffusion coefficient values play a major role in the evaluation of protective properties in concrete with reference to reinforcement. This paper describes tests on protective properties of concrete cover made of ordinary concrete and different types of low alkali cement. The tests on four types of concrete mix which differed in a type of used cement was performed. The following types of cement were applied: in concrete C1 - cement CEM I 42.5 R characterised by high heat of hydration, rapid increase in strength and high early strength. In concrete C2 - cement CEM III/A 32.5 N-LH/HSR/NA characterised by high resistance to chemical aggression. In concrete C3 - cement CEM I 42.5 N/SR3/NA with high chemical resistance, particularly to sulphate corrosion, low content of Na2O alkali, tricalcium aluminate C3A and aluminium oxide Al2O3. In concrete C4 - cement CEM IV/B (V) 32.5 R - LH/NA characterised by a stable increase in strength, increased strength during longer stages of concrete curing. Protective properties of concrete cover for reinforcing steel were specified by determining values of chloride diffusion coefficients describing flow rate of chloride ions in wet concrete. Chloride diffusion coefficients were determined on the basis of the thermodynamic model of chloride flow in the electric field. Migration tests in the electric field were used to determine diffusion coefficients. Then, distribution of chloride concentrations in diffusion tests with the forecast distribution of chloride concentrations, taking into account the obtained values of chloride concentrations was compared. Consequently, reliable values of diffusion coefficients were determined. Also the forecast durability of concrete structure made of tested types of concrete was specified.

A possibility of diagnosing the welded joints in the components of powered roof supports used in longwall panels of hard coal mines is analysed. It was found that the magnetic-and-powder method is most useful for that purpose. Devices which facilitate assessment of technical condition of welded joints in canopies and bases are discussed. Design and principles of operation of welded joints liquid detector adapted for operation in industrial conditions are presented. Two ideas of a magnetic inductor for technical diagnosis of powered roof support components by the magnetic-and-powder method is discussed.

Protective properties of concrete for steel can be assessed with a diffusion coefficient. This method refers to steel exposed to chloride ions present in sea water or deicing agents. However, the aggressive environment with chlorides hinders the determination of diffusion coefficient as they enter into electrostatic interaction with other ions present in concrete pore water, adsorb hardened cement grout on the surface of hydrated minerals, and react with concrete components. But Fick's laws can be used to express chloride ion flow in concrete regardless of complex physical, chemical and electrostatic processes. Fick's laws are predominantly used to calculate values of that coefficient values with reference to methods defined by standards AASHTO T 259 and NT BUILD 443. The main disadvantage of such methods is their duration. Therefore, an electric field is used to speed up a flow of chloride ions. On the basis of obtained results, we can either calculate a passed charge or a migration coefficient. The determined coefficient of migration according to NT BUILD 492 characterized chlorides ingress into concrete when exposed to the electric field. But this method did not specify the time, after which the critical value of chloride ions was achieved at the reinforcement. Also, the method described in the standard ASTM C 1202-97 is only useful for comparing protective properties of concrete. However, the migration of chlorides could be analysed with the theoretical model, which was the base to derive the equation of migration. This paper presents experimentally determined averaged results and values of diffusion coefficients determined from migration tests. It also compares results from diffusion tests performed in accordance with standards AASHTO T 259 and NT BUILD443, and results from migration tests conducted in accordance with standards ASTM C 1202-97 and NT BUILD 492.

Prestressed hollow-core slabs are suitable for various span applications in different types of buildings. Such structures are quick to mount and do not require boarding system or assembly supports reducing deflection, which is an economic asset. The performed analysis included HC-500 slabs made of C50/60 concrete with w/c ratio of 0.31, with Portland cement CEM II 52.5 R. Strength of such structures is determined by, among other things, chloride ion concentration at the interface between the surface of prestressing tendons and concrete. Corrosion products, induced by chloride ions, will certainly reduce stress of adhesion to concrete, and consequently, second-order momentum in the structure. It may be difficult to draw firm conclusions about the predicted strength of analysed slabs on the basis of the obtained results. Therefore, we performed the static analysis including the changes in tendon adhesion to concrete caused by corrosion. We also analysed the bearing capacity of slabs according to concrete cover thickness of upper and lower tendons. The analyses included results from the accelerated tests on chloride ion penetration to cylindrical elements drilled directly from the top surface of prefabricated prestressed floor slabs HC500-19/R120. Those results were used to determine the diffusion coefficient of chloride ions into concrete, from which the analysed slabs were made. The value of diffusion coefficient ${\bar{D}}_{s}^{1}=0.72\cdot {10}^{-12}\,\,{\text{m}}^{2}/\text{s}$ for the tested concrete was used to illustrate results for changes in the bearing capacity over time. We determined times, after which those tendons could corrode, assuming that penetration of chloride ions is observed only at the surface of the upper floor slab. The obtained results were used to develop recommendations and draw conclusions for further tests.

Although the Sensititre Yeast-One (SYO) and Etest methods are widely utilized, interpretive criteria are not available for triazole susceptibility testing of Candidaor Aspergillusspecies. We collected fluconazole, itraconazole, posaconazole, and voriconazole SYO and Etest MICs from 39 laboratories representing all continents for (method/agent-dependent) 11,171 Candida albicans, 215 C. dubliniensis, 4,418 C. glabrataspecies complex, 157 C.guilliermondii(Meyerozyma guilliermondii), 676 C. krusei(Pichia kudriavzevii), 298 C.lusitaniae(Clavispora lusitaniae), 911 C.parapsilosissensu stricto, 3,691 C.parapsilosisspecies complex, 36 C.metapsilosis, 110 C.orthopsilosis, 1,854 C.tropicalis, 244 Saccharomyces cerevisiae, 1,409 Aspergillus fumigatus, 389 A.flavus, 130 A.nidulans, 233 A.niger, and 302 A.terreuscomplex isolates.