Presence Of PS Research Articles

Differential efficacy of a chlorine dioxide-containing sanitizer against single species and binary biofilms of a dairy-associated Bacillus cereus and a Pseudomonas fluorescens isolate.

Daily exposure to 100 p.p.m. chlorine dioxide of single species and binary biofilms of dairy-associated Bacillus cereus DL5 and Pseudomonas fluorescens M2, attached to stainless steel surfaces in a laboratory flow system, was studied. Surfaces were sampled daily before and after sanitizer treatment and cells and spores dislodged and enumerated by standard methods. Duplicate surfaces were prepared for confocal scanning laser microscopy (CSLM) and scanning electron microscopy. Higher counts of Ps. fluorescens M2 were obtained in single species biofilms, microcolonies stained green (viable) in CSLM images and were closely packed on attachment surfaces. By contrast, higher counts of B. cereus DL5 were obtained in binary biofilms, microcolonies stained green in CSLM images, but were more spread out. Lower spore counts were obtained for B. cereus DL5 in binary biofilms. The survival of Ps. fluorescens M2 cells after exposure to chlorine dioxide was apparently enhanced by the presence of B. cereus DL5 in binary biofilms. By contrast, B. cereus DL5 showed increased susceptibility to sanitizer treatment in the presence of Ps. fluorescens M2. Co-cultured bacteria in biofilms influence each other with respect to attachment capabilities and sanitizer resistance/susceptibility. Binary biofilms endemic in food-processing industries can survive sanitation regimes and may represent reservoirs of product contamination leading to subsequent spoilage and/or food safety risks.

The migration of Proteus mirabilis and other urinary tract pathogens over Foley catheters

Objective To examine the ability of organisms that infect the catheterized urinary tract to migrate over the surfaces of Foley catheters. Materials and methods In a simple laboratory model, organisms were challenged to migrate across sections of hydrogel‐coated latex, hydrogel/silver‐coated latex, silicone‐coated latex and all‐silicone catheters. The sections (1 cm long) were placed as bridges in channels between blocks of agar and the test organisms inoculated onto the agar adjacent to one side of each bridge. The plates were incubated at 37 °C for 24 h and examined for growth of the test organisms on the agar on the other side of the bridges. A collection of swarming, swimming and nonmotile species were tested in the model. The relative mobilities of the test organisms were expressed as migration indices, calculated as the percentage of tests in which bacterial migration was observed over each type of catheter bridge. Results The swarmer cells of Proteus mirabilis and P. vulgaris migrated successfully (migration indices of 73–100) over all four types of catheter. The migration index of Serratia marcescens swarmers was reduced to 33 over the silver‐coated catheters, but these cells crossed over the other catheter surfaces with ease (indices of 100). Pseudomonas aeruginosa was the most mobile of the swimming, non‐swarming organisms with indices of 70–22, but this group was less capable of migration than the swarmers. Indices were 0–33 for nonmotile organisms. The mean migration indices for the nine species for each type of catheter were 57 (hydrogel‐coated latex), 49 (silver/hydrogel‐coated latex), 41 (silicone‐coated latex) and 35 (all‐silicone). The swarmer cells of P. mirabilis moved through populations of Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus and Enterococcus faecalis, and then migrated over sections of hydrogel‐coated latex catheters with little or no reduction in migration index. They were also capable of transporting the nonmotile cells of K. pneumoniae and S. aureus over the catheters. The migration index of P. mirabilis swarmers was substantially reduced in the presence of Ps. aeruginosa and S. marcescens. Conclusions Hydrogel coatings facilitate the migration of urinary tract pathogens over catheter surfaces. With the exception of S. marcescens, the incorporation of silver into the hydrogel did not inhibit migration. Swarmer cells were particularly effective at moving over catheters and P. mirabilis swarmers were also capable of transporting other species. This suggests that inhibitors of swarming could be useful in controlling catheter‐associated infection and the complications resulting from the spread of bacterial biofilm over catheters.

The migration of Proteus mirabilis and other urinary tract pathogens over Foley catheters.

To examine the ability of organisms that infect the catheterized urinary tract to migrate over the surfaces of Foley catheters. In a simple laboratory model, organisms were challenged to migrate across sections of hydrogel-coated latex, hydrogel/silver-coated latex, silicone-coated latex and all-silicone catheters. The sections (1 cm long) were placed as bridges in channels between blocks of agar and the test organisms inoculated onto the agar adjacent to one side of each bridge. The plates were incubated at 37 degrees C for 24 h and examined for growth of the test organisms on the agar on the other side of the bridges. A collection of swarming, swimming and nonmotile species were tested in the model. The relative mobilities of the test organisms were expressed as migration indices, calculated as the percentage of tests in which bacterial migration was observed over each type of catheter bridge. The swarmer cells of Proteus mirabilis and P. vulgaris migrated successfully (migration indices of 73-100) over all four types of catheter. The migration index of Serratia marcescens swarmers was reduced to 33 over the silver-coated catheters, but these cells crossed over the other catheter surfaces with ease (indices of 100). Pseudomonas aeruginosa was the most mobile of the swimming, non-swarming organisms with indices of 70-22, but this group was less capable of migration than the swarmers. Indices were 0-33 for nonmotile organisms. The mean migration indices for the nine species for each type of catheter were 57 (hydrogel-coated latex), 49 (silver/hydrogel-coated latex), 41 (silicone-coated latex) and 35 (all-silicone). The swarmer cells of P. mirabilis moved through populations of Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus and Enterococcus faecalis, and then migrated over sections of hydrogel-coated latex catheters with little or no reduction in migration index. They were also capable of transporting the nonmotile cells of K. pneumoniae and S. aureus over the catheters. The migration index of P. mirabilis swarmers was substantially reduced in the presence of Ps. aeruginosa and S. marcescens. Hydrogel coatings facilitate the migration of urinary tract pathogens over catheter surfaces. With the exception of S. marcescens, the incorporation of silver into the hydrogel did not inhibit migration. Swarmer cells were particularly effective at moving over catheters and P. mirabilis swarmers were also capable of transporting other species. This suggests that inhibitors of swarming could be useful in controlling catheter-associated infection and the complications resulting from the spread of bacterial biofilm over catheters.

Effects of steroids on NMDA receptors and excitatory synaptic transmission in neonatal motoneurons in rat spinal cord slices.

The effect of steroids on NMDA receptors and excitatory postsynaptic transmission was studied in fluorescence-labelled motoneurons in thin spinal cord slices. In outside-out patches, NMDA-induced responses were potentiated by 79% in the presence of 20-oxopregn-5-en-3beta-yl sulfate (PS), while in the presence of 20-oxo-5alpha-pregnan-3alpha-yl sulfate (3alpha5alphaS) and 20-oxo-5beta-pregnan-3alpha-yl sulfate (3alpha5betaS) they were diminished by 57% and 66%, respectively. PS and 3alpha5betaS had no effect on the amplitude of single NMDA receptor channel openings, however, both compounds altered relative distribution of the openings to individual conductance levels. In control cases, the most frequent openings of the NMDA receptor channels were at the 70 pS conductance level, while in the presence of PS or 3alpha5betaS, the most frequent openings were at the 55 pS conductance level. Analysis of the mean current transferred by NMDA receptor channel openings at individual conductance levels indicated that in the presence of PS, the mean current induced by 55 pS conductance openings was significantly increased. In the presence of 3alpha5betaS, the mean currents induced by 55 pS and 70 pS conductance openings were significantly decreased. The amplitude of NMDA receptor-mediated EPSCs was potentiated by 54% in the presence of PS and the deactivation kinetics slowed. Neither the amplitude nor the kinetics of NMDA receptor-mediated EPSCs was significantly changed in the presence of 3alpha5betaS. The results of our experiments indicate that neurosteroids affect NMDA receptors in motoneurons. The effect appears to be influenced by the receptor subunit composition.

Effect of different copolymers (hydrogenated and non-hydrogenated, with different molecular weights and different content of styrene) in the compatibilization of PS + PP (80+20) polyblend

We have studied the effect of the addition of different compositions of several styrene / butadiene / styrene (SBS) triblock copolymers, hydrogenated and non-hydrogenated, with different molecular weights and different content of styrene, on the PS + PP (80+20) polyblend. We have determined the influence of these parameters on thermal and mechanical properties as well as on the observed morphology. As the composition of the hydrogenated copolymer or the copolymer with a similar content of styrene and butadiene was increased, the dispersion of particles increased, lowering remarkably their size and producing this way a better interfacial adhesion in the blend. Excluding the copolymer with similar content of styrene and butadiene in its structure, the rest of the copolymers show a strong tendency to form micelles or mesophases in the matrix as the amount of copolymer increases, improving some mechanical properties such as impact strength but deteriorating others like the yield and break stresses. On the other hand, the presence of compatibilizers, at any composition, does not have any effect on the thermal parameters of the blend. Nevertheless, the presence of PS, amorphous and the majority component in the blend, affects the crystallization process of PP, enhancing in a wide temperature range (from 125 °C to 40 °C) its crystallization process.

Cytochrome b6/f complex as an indigenous photodynamic generator of singlet oxygen in thylakoid membranes.

Possible association of photodynamic sensitization by cytochrome b6/f complex (cyt b6/f) via singlet oxygen (1O2) mechanism with photoinhibition damage to photosystem II (PS II) was studied using such subthylakoid preparations as photosystem I (PS I) particles, PS II core complex and cyt b6/f from spinach leaves. Upon exposure to bright light, PS II core complex lost photosynthetic electron transport activity to a certain extent, whose-spectral dependence implied that pheophytin a is likely involved in photoinactivation of PS II core complex in itself. The presence of PS I particles exerted virtually no effect on PS II core photoinactivation. However, the inclusion of cyt b6/f in samples resulted in a marked exacerbation of the photoinactivation, particularly in UV-A and blue light. Such effect of cyt b6/f was suppressed by azide and enhanced by the medium deuteration. Photogeneration of 1O2 from cyt b6/f was confirmed by ESR and spectrophotometry, chemically trapping 1O2. Action spectra for both 1O2 photoproduction and PS II core photoinactivation by cyt b6/f bore a close resemblance to each other, seemingly carrying the absorption characteristics of the Rieske Fe-S protein. A complex deficient in the Rieske protein prepared from intact cyt b6/f showed virtually no generation of 1O2 in light, whereas an efficient photoformation of 1O2 was seen in the Rieske protein preparation. The results suggest that cyt b6/f, rather specifically the Rieske center, may play a prominent role in photoinhibition processes through type II photosensitization in thylakoids.

Cytochrome b6/f Complex as an Indigenous Photodynamic Generator of Singlet Oxygen in Thylakoid Membranes

Possible association of photodynamic sensitization by cytochrome b6/f complex (cyt b6/f) via singlet oxygen (1O2) mechanism with photoinhibition damage to photosystem II (PS II) was studied using such subthylakoid preparations as photosystem I (PS I) particles, PS II core complex and cyt b6/f from spinach leaves. Upon exposure to bright light, PS II core complex lost photosynthetic electron transport activity to a certain extent, whose spectral dependence implied that pheophytin a is likely involved in photoinactivation of PS II core complex in itself. The presence of PS I particles exerted virtually no effect on PS II core photoinactivation. However, the inclusion of cyt b6/f in samples resulted in a marked exacerbation of the photoinactivation, particularly in UV-A and blue light. Such effect of cyt b6/f was suppressed by azide and enhanced by the medium deuteration. Photogeneration of 1O2 from cyt b6/f was confirmed by ESR and spectrophotometry, chemically trapping 1O2. Action spectra for both 1O2 photoproduction and PS II core photoinactivation by cyt b6/f bore a close resemblance to each other, seemingly carrying the absorption characteristics of the Rieske Fe-S protein. A complex deficient in the Rieske protein prepared from intact cyt b6/f showed virtually no generation of 1O2 in light, whereas an efficient photoformation of 1O2 was seen in the Rieske protein preparation. The results suggest that cyt b6/f, rather specifically the Rieske center, may play a prominent role in photoinhibition processes through type II photosensitization in thylakoids.

Brefeldin A Inhibited Activity of the Sec7 Domain of p200, a Mammalian Guanine Nucleotide-exchange Protein for ADP-ribosylation Factors

A brefeldin A (BFA)-inhibited guanine nucleotide-exchange protein (GEP) for ADP-ribosylation factors (ARF) was purified earlier from bovine brain cytosol. Cloning and expression of the cDNA confirmed that the recombinant protein (p200) is a BFA-sensitive ARF GEP. p200 contains a domain that is 50% identical in amino acid sequence to a region in yeast Sec7, termed the Sec7 domain. Sec7 domains have been identified also in other proteins with ARF GEP activity, some of which are not inhibited by BFA. To identify structural elements that influence GEP activity and its BFA sensitivity, several truncated mutants of p200 were made. Deletion of sequence C-terminal to the Sec7 domain did not affect GEP activity. A protein lacking 594 amino acids at the N terminus, as well as sequence following the Sec7 domain, also had high activity. The mutant lacking 630 N-terminal amino acids was, however, only 1% as active, as was the Sec7 domain itself (mutant lacking 697 N-terminal residues). It appears that the Sec7 domain of p200 contains the catalytic site but additional sequence (perhaps especially that between positions 595 and 630) modifies activity dramatically. Myristoylated recombinant ARFs were better than non-myristoylated as substrates; ARFs 1 and 3 were better than ARF5, and no activity was detected with ARF6. Physical interaction of the Sec7 domain with an ARF1 mutant was demonstrated, but it was much weaker than that of the cytohesin-1 Sec7 domain with the same ARF protein. Effects of BFA on p200 and all mutants with high activity were similar with approximately 50% inhibition at </=50 microM. The inactive BFA analogue B36 did not inhibit the Sec7 domain or p200. Thus, the Sec7 domain of p200, like that of Sec7 itself (Sata, M., Donaldson, J. G., Moss, J., and Vaughan, M. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 4204-4208), plays a role in BFA inhibition as well as in GEP activity, although the latter is markedly modified by other structural elements.

Influence of a fine talc on the properties of composites with high density polyethylene and polyethylene/polystyrene blends

Fine talc filled high density polyethylene (HDPE) and HDPE/polystyrene (PS) blends were extruded, injection moulded and characterized. Some of the mechanical properties of the talc filled HDPE and talc filled 75/25 HDPE/PS blend were deduced from stress–strain measurements. A comparison between the effect of the talc on the properties of the filled HDPE and filled 75/25 HDPE/PS blend showed that the mineral filler had the same effect on both systems provided that its array in the organic matrix is almost the same in both cases. In fact, the rheological results proved that the dispersion of talc in the HDPE matrix was not really affected by the presence of PS. The study particularly focused on the effect of talc on the ultimate tensile strength of the filled HDPE and that of the filled blend. It has been noted that the brittle nature of PS neutralizes, to a certain extent, the degrading effect of talc on this property. Furthermore, both PS and talc have a complementary effect on the stiffness and the resilience of HDPE/PS/talc blend composites.

Receptor-mediated Ribosome Binding to Liposomes Depends on Lipid Composition

Ribosome binding to the endoplasmic reticulum has been traditionally studied using an in vitro assay in which potential ribosome receptors have been purified, incorporated into synthetic liposomes, and tested for activity. One such receptor (180 kDa; "p180") has been shown to bind ribosomes with high affinity in such a system when purified to homogeneity. This result has been challenged by data generated in other laboratories, and as a result, doubt has lingered as to the authenticity of p180 as a ribosome receptor. The contribution of the major difference between these studies, the lipid composition of the liposomes used in the in vitro assays, was assessed when identical fractions of rough endoplasmic reticulum-specific membrane proteins were incorporated into liposomes composed of only phosphatidylcholine (as used in other laboratories), a 50:50 mix of phosphatidylcholine and phosphatidylserine (as used in our original studies), or lipids derived from canine pancreatic microsomes (as a physiologically relevant control). The presence of PS was found to be crucial for the incorporation into and ribosome binding activity of p180 in liposomes. These observations are compatible with published studies on the importance of acidic phospholipids in ribosome binding to intact microsomes and reconcile the apparently conflicting in vitro results surrounding the assignment of p180 as a ribosome receptor.

The effects of hydrogen bonding on the miscibility, complexation and crystallization in blends of crystalline and amorphous components

AbstractThe miscibility and crystallization of blends of poly{styrene‐co‐[p‐(2,2,2‐trifluoro‐1‐hydroxy‐1‐trifluoromethyl)ethyl‐a‐methylstyrene]} (PS(OH)) and polycaprolactone (PCL) have been investigated by viscometry and differential scanning calorimetry. With increasing the hydroxyl content in PS(OH), the transitions from immiscibility to miscibility and then to complexation can be realized. Depending on the states in which the blends exist, a different behavior of PCL crystallization is observed. Crystallization in the immiscible blends, is almost not affected by the presence of PS(OH). In the miscible blends, an apparent depression of crystallization is observed. Particularly, for the blends with a hydroxyl content larger than 8 mol‐% in PS(OH), complete depression of PCL crystallization is found, which can be attributed to a complex formed by pairing segments of PCL and PS(OH).

Effect of Sodium Poly(styrene sulfonate) on Acid Dyeing of Nylon with C.I. Acid Orange 7.

The effect of sodium poly (styrene sulfonate) (PS) on acid dyeing of nylon with C. I. Orange 7 was investigated. Sodium ethylbenzene sulfonate (EB) was used for comparison. Both of PS and EB is found to be effective as retardant of acid dyeing of nylon. The retarding effect of EB is more remarkable than one of PS. PS is adsorbed only on the surface of nylon due to the large molecular size, while EB is diffused into the nylon substrate. A model of nylon dyeing in the presence of PS or EB is presented.

Autoproteolysis or Plasmin-mediated Cleavage of Factor Xaα Exposes a Plasminogen Binding Site and Inhibits Coagulation

Blood coagulation factor Xa (FXa) has recently been shown to function as a plasminogen receptor in the presence of procoagulant phospholipid (phosphatidylserine; PS) and Ca2+. In the current work, the possible effect of autoproteolytic and plasmin-mediated cleavage of FXa on complex formation with plasminogen was investigated. 125I-plasminogen binding to derivatives of FXa electrotransferred to polyvinylidene difluoride revealed that the autoproteolytic conversion of FXaalpha to FXabeta was required for the expression of a plasminogen binding site. In the presence of PS and Ca2+, plasmin was shown to convert FXaalpha to a FXabeta-like species at least 3 orders of magnitude faster than the autoproteolytic mechanism. This also resulted in the exposure of a plasminogen binding site. Further processing by plasmin generated a fragment (33 kDa) due to cleavage at Gly331 in the FXa heavy chain. Production of this species enhanced apparent plasminogen binding compared with FXabeta and resulted in the loss of FXa amidolytic and clotting activity. In the absence of either PS or Ca2+, the plasmin-mediated fragmentation of FXaalpha was altered to include a FXabeta-like molecule and a species (40 kDa) with intact beta-heavy chain disulfide linked to a COOH-terminal fragment of the light chain starting at Tyr44. Neither of these products was observed to interact with plasminogen. The 40-kDa species had amidolytic activity comparable with FXaalpha but inhibited clotting activity. Cumulatively the data provide the first evidence for a functional difference between the FXa subforms and suggest a mechanism where autoproteolysis and plasmin-mediated cleavage modulate the function of FXaalpha from a procoagulant enzyme to a profibrinolytic plasminogen receptor.

Field‐aligned currents associated with spatially periodic X ray structures in the morningside auroral oval

On February 9, 1992, the Atmospheric X ray Imaging Spectrometer (AXIS) on the Upper Atmosphere Research Satellite (UARS) observed spatially periodic structures in X ray luminosity from the top of the atmosphere during a pass over the dawnside auroral oval. The patches of luminosity were several hundred kilometers in size and separated by a mean distance of about 700 km. As many as a dozen distinct patches could be identified extending from local times just after midnight to the noon meridian. The characteristics of the precipitating electrons responsible for the patches were determined from the measured X ray fluxes. Peak electron energy fluxes were between 4 and 10 ergs cm−2 s−1 with e‐folding energies of 10–25 keV. In situ magnetic field data from the onboard magnetometer were used to model the field‐aligned currents associated with two of the patches. The model that best fit the data had upward currents in the western portions of the patches and more intense downward currents confined to the eastern edges. The modeling also indicated that these small‐scale currents were embedded within the large‐scale region 2 field‐aligned current sheet. Data from a ground‐based magnetometer near the satellite ground track indicated the presence of Ps 6 pulsations. We have interpreted the observations in terms of eastward‐drifting current patch systems. Under this assumption, the patches moved at 1.7 km s−1, the drift speed of ∼30‐keV electrons. This motion, and the correlation with Ps 6 pulsations suggests that the X ray patches were associated with omega bands that are seen in the morning sector during geomagnetically active times.

Roles of the membrane-interactive regions of factor VIIa and tissue factor. The factor VIIa Gla domain is dispensable for binding to tissue factor but important for activation of factor X.

The roles of the putative membrane-interactive regions of factor VIIa (fVIIa) and tissue factor (TF) have been examined. Enzymatic removal of the 4-carboxyglutamic acid (Gla) domain of fVIIa had no effect on hydrolysis of a tripeptidyl chromogenic substrate in the absence or presence of TF. Additionally, Gla-domainless fVIIa (GdVIIa) was similar to native fVIIa in activating factor X in the absence of TF and phospholipid. However, GdVIIa in complex with recombinant soluble TF (sTF) was 76-fold less efficient in factor X activation than was fVIIa.sTF. The difference increased to 740-fold using TF relipidated in vesicles composed of 80% phosphatidylcholine and 20% phosphatidylserine (TF/PCPS). While Gla domain deletion produced a 10(3)-fold increase in the Kd for binding to TF/PCPS, the Kd for binding to TF/PC increased only 20-fold, and that for sTF in the absence of phospholipid increased 10-fold. Kd values for GdVIIa binding to TF/PCPS, TF/PC, or sTF were nearly identical. Thus, most of the binding energy required for formation of the fVIIa.TF complex was present even after Gla domain deletion. Both fVIIa and GdVIIa were capable of binding sTF in the presence of excess divalent metal-ion chelator, suggesting Ca(2+)-independent binding or the presence of a novel very high affinity Ca2+ binding site in fVIIa. The results demonstrate that the effect of the Gla domain on the Kd is apparent only in the presence of PS, and that interactions involving the fVIIa Gla domain and phospholipid are critical for efficient proteolysis of factor X on a membrane surface.

Exposure of phosphatidylserine in the outer leaflet of human red blood cells. Relationship to cell density, cell age, and clearance by mononuclear cells.

Human red blood cells (RBC) were separated by density on self-forming Percoll gradients into five distinct populations. The transbilayer movement and equilibrium distribution of 1-oleoyl-2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4- yl)aminocaproyl)phosphatidylserine (NBD-PS) was slower in dense cells and equilibrated in the inner leaflet of these cells to a lesser degree than in light cells. Conversely, the outward movement of the lipid was slower in light cells. Assessment of endogenous PS in the cells' outer leaflet by the prothrombinase activity of externalized PS revealed an increase in its presence at the cell surface with increasing cell density. The presence of PS on the cell surface directly correlated with the propensity of the RBC to bound by autologous monocytes. To determine whether increased cell density is associated with increased cell age, the in vivo clearance of density-separated murine RBC was monitored in syngeneic mice. The T1/2 of circulation of light cells was about twice that of dense cells. The majority of the cleared cells localized in the spleen. Studies carried out in antibody-deficient SCID mice indicated that RBC were cleared via a mechanism that was independent of antibody. These data suggest that cell age is related to cell density and that cells of increasing age and density display higher amounts of PS in their outer leaflet.

A study of the incidence of different fluorescent Pseudomonas species and biovars in the microflora of fresh and spoiled meat and fish, raw milk, cheese, soil and water

Of 182 various foodstuffs and environmental samples examined, 86% had microflora containing fluorescent Pseudomonas in differing proportions. A computer-aided technique was used to identify most of the 445 fluorescent strains. Pseudomonas fluorescens biovar V-1 was most frequently isolated (24%); it either predominated or was present in all types of samples. Other strains, belonging to the other subgroups of biovar V (V-2, V-4, V-5, V-6 and V-7), together represented 14.3%. We also identified Ps. fluorescens biovars I-1 and I-2 (13.9%), II-1 and II-3 (3.6%), III-1 and III-2 (8.7%), IV-2 (0.7%); Ps. putida A and B (11%); Ps. lundensis (10.3%); group B3 (2%) and Ps. aeruginosa (0.7%). Unidentified strains accounted for 10.6% of the flora, many resembling Ps. fluorescens biovar V. Although the presence of Ps. fluorescens V-1 was often marked, other taxa predominated or were present in large quantities in some particular samples, such as Ps. fluorescens I-1 in raw milk and cheese, Ps. lundensis in spoiled meat and Ps. fluorescens III-1 in spoiled fish. Pseudomonas putida A and B were evident in environmental rather than in food samples.

Photooxidation of blends of polystyrene and poly (vinyl methyl ether)

AbstractPhotooxidation of blends of polystyrene and poly (vinyl methyl ether) was studied at 30°C. The oxygen uptake by PS was negligible but PVME oxidized readily. The induction period of oxidation of PVME was prolonged by the presence of PS. The steady state rate of oxidation of the blend was strongly influenced by the segmental mobility of the blend which also governed the kinetics and morphology of phase separation. The molecular weight of PVME decreased more slowly in the blend as PS content increased. It was believed that the reaction between PVME radicals and PS resulted in less reactive PS radicals which retarded oxidation. The PS radicals eventually underwent chain scission reactions.

Inactivation of the Water-Oxidizing Complex by Exogenous Reductants in PS II Membranes Depleted of Extrinsic Proteins

We have studied the inactivation of the water-oxidizing complex by exogenous, «general», reductants in various types of PS II membrane. Extraction of the 33, 23 and 17 kDa proteins from PS II membranes rendered the functional Mn susceptible to rapid solubilization by reductants such as hydroquinone, benzidine and ascorbate, while water analogs, such as NH 2 OH, inactivated the complex regardless of the presence of PS II extrinsic proteins (...)

Activation of human neutrophil NADPH-oxidase in vitro by the catalytic fragment of protein kinase-C

Phorbol ester treatment of intact neutrophils both stimulates protein kinase C (PK-C) and causes the rapid proteolytic conversion to a cytosolic, cofactor independent fragment, protein kinase M (PK-M). In intact neutrophils, phorbol ester treament activates the NADPH-oxidase, the enzyme responsible for the oxidative burst. Addition of purified PK-M to resting neutrophil light density membranes activated the NADPH-oxidase in the presence of PS, ATP and Mg 2+. A 3.5-fold greater stimulation of oxidase (ca. 25 nmoles O 2 − /min/mg membrane protein) was obtained with comparable PK-M concentrations to that observed with the reconstituted PK-C system, and approximately 1 3 that obtained with arachidonic acid (AA) or SDS. In contrast to the reconstituted system using PK-C, PMA and Ca ++ were neither required nor affected activity. The effect of PS was unexpected, since PK-M does not require phospholipids for enzymatic activity, and likely represents the action of PS on the oxidase itself or on another component in the plasma membrane fraction. Our studies demonstrate for the first time that purified PK-M permits reconstitution of a physiologic phorbol ester response