Induction of porphobilinogen oxygenase and porphobilinogen deaminase in rat blood under conditions of erythropoietic stress

Porphobilinogen is the substrate of two enzymes: porphobilinogen deaminase and porphobilinogen-oxygenase. The first one transforms it into the metabolic precursors of heme and the second diverts it from this metabolic pathway by oxidizing porphobilinogen to 5-oxopyrrolinones. Rat blood is devoid of porphobilinogen-oxygenase under normal conditions while it carries porphobilinogen-deaminase activity. When the rats were submitted to hypoxia (p_O2 = 0.42 atm) for 18 days, the activity of porphobilinogen-oxygenase appeared at the tenth day of hypoxia and reached the maximum at the 14–16th day. It decreased to a half after 2 days (half-life of the enzyme) and disappeared after 4 days of return to normal oxygen pressure. Porphobilinogen-deaminase activity increased after the first day of hypoxia, reached a maximum at the 14–16th day and did not decrease to normal values until the 15th day after return to normal oxygen pressure. The activities of both prophobilinogen-oxygenase and porphobilinogen-deaminase were induced by administration of erythropoietin. When rats were made anaemic with phenylhydrazine, porphobilinogen-oxygenase activity also appeared in the blood cells. Although the reticulocyte concentration was higher when compared to that obtained under hypoxia, the activities of the oxygenase obtained under both conditions were comparable. Porphobilinogen-deaminase activity was always closely related to the reticulocyte content. The appearance of porphobilinogen-oxygenase under the described erythropoietic conditions was due to a de novo induction of the enzyme, as shown by its inhibition with actinomycin D and cycloheximide. Porphobilinogen-oxygenase as well as porphobilinogen-deaminase were present in the rat bone marrow under normal conditions. Their activities increased in phenylhydrazine treated rats. The properties and kinetics of porphobilinogen-oxygenase from the rat blood and bone marrow were determined and found to differ in several aspects.     

Quantitative EMG analysis to investigate synergistic coactivation of ankle and knee muscles during isokinetic ankle movement. Part 2: time frequency analysis.

Fundamental to intralimb coordination in the lower extremity, ankle-knee synergy induced by motor irradiation has long been employed to secure facilitation of paralyzed muscles. This study, a companion research subsequent to the time amplitude analysis of surface electromyography in part 1, was to investigate the recruitment strategy of irradiated muscles and prime movers during ankle isokinetic contraction at different contraction speeds (30, 60, 120 and 240 degrees/s) with time frequency analysis. The results indicated the recruitment strategies of the major irradiated muscles (ipsilateral rectus femoris/ipsilateral biceps femoris) and prime movers (anterior tibialis/gastrocnemius) were time-dependent and significantly different in terms of the instantaneous median frequency. In general, the prime movers for ankle isokinetic concentric contraction demonstrated a similar recruitment strategy, irrespective of different contraction speeds. This finding is consistent with the idea of generalized motor programs that speed is one of the constraint parameters supplied to motor programs. Nevertheless, the recruitment strategies of the irradiated muscles were highly inconsistent, varying across trials at different contraction speeds, and were not relevant to those of the prime movers. In addition, the recruitment in the irradiated muscles seemly limited to motor units of low threshold, in spite of maximal voluntary contraction of the prime movers.     

Denitrification with methanol in the presence of high salt concentrations and at high pH levels

Summary In the combined ion exchange/biological denitrification process for nitrate removal from ground water, in which nitrate is removed by ion exchange, the resins are regenerated in a closed circuit by a biological denitrification reactor. This denitrification reactor eliminates nitrate from the regenerant. Methanol is used as electron donor for biological denitrification. To obtain sufficient regeneration of the resins within a reasonable time, high NaCl or NaHCO₃ concentrations (10–30 g/l) in the regenerant are necessary. High NaHCO₃ concentrations affected the biological denitrification in three ways: a) a slight decrease in denitrification capacity (30%) was observed; b) the yield coefficient and CH₃OH/NO₃ ^-–N ratio decreased. When high NaHCO₃ concentrations (above 10g NaHCO₃/l) were used, the yield coefficient was 0.10–0.13 g VSS/g NO₃ ^-–N and the CH₃OH/NO₃ ^-–N ratio was 2.00–2.03 g/g; c) high NaHCO₃ concentrations influenced nitrite production. Nitrite is an intermediate product of biological denitrification and with rising NaHCO₃ concentrations nitrite accumulation was suppressed. This was explained by the effect of high NaHCO₃ concentrations on the pH in the microenvironment of the denitrifying organisms. High NaCl concentrations also resulted in a slight decrease in denitrification capacity, but the second and third effects were not observed in the presence of high NaCl concentrations.Although the pH in the regenerant will rise as a result of biological denitrification, the capacity of a denitrification reactor did not decrease significantly when a pH of 8.8–9.2 was reached.     

Assembly of a chemically synthesized peptide of Escherichia coli type 1 fimbriae into fimbria-like antigenic structures.

Escherichia coli type 1 fimbriae are composed of subunits, each of which comprises 158 amino acids. We synthesized a copy of a 13-residue peptide, located near the NH2 terminus of the fimbrial subunit, that assumed some of the properties of type 1 fimbriae. At pH 5.5 the synthetic peptide autoassembled into fibrillar structures that resembled type 1 fimbriae except that they appeared less rigid and rodlike. A quaternary structure-specific monoclonal antibody against type 1 fimbriae recognized the synthetic peptide in the assembled but not the unassembled state. Furthermore, when the synthetic peptide was injected in its fimbrial conformation into rabbits, it evoked antibodies that reacted with type 1 fimbriae isolated from E. coli.     

The in vitro cellular immune response to quartz

It is known that macrophages release into medium in vitro biologically active substances which modulate immune response. In recent years, increase attention has been directed towards the role of prostaglandin in macrophage function. Guinea pig splenic lymphocytes and peritoneal macrophage cultures were incubated with quartz (DQ12), Corundum and aspirin as prostaglandin inhibitor. Lymphocyte proliferation measured by 3H-thymidine incorporation, and lymphokine release by Bendixen-Soborg capillary test (MIF) were applied. EA rosetting and phagocytosis were determined for macrophage function assessment. Quartz suppressed the immune response evidenced by reduced 3H-thymidine incorporation and decreased lymphokine production. Aspirin (as a specific prostaglandin synthesis inhibitor) restored the affected by quartz immunological parameters. This observation gives support to the hypothesis that the immunological response to quartz involves macrophage prostaglandin release, presumably as a first step of lipid peroxidation.     

Isotype restriction during infection of mice with the cestode Mesocestoides corti: role of immune suppression

Mice infected with the parasite Mesocestoides corti produce a vigorous antibody response that is restricted to the IgM and IgG1 heavy chain classes. The isotypic restriction observed is apparently associated with active infection and is not a unique characteristic of responses to M. corti antigens. Thus, animals immunized with intact but nonviable parasites respond with the production of a variety of antibody isotypes in addition to IgM and IgG1. To delineate immunoregulatory mechanisms involved in the isotypic restriction of antibody responses to M. corti, an in vitro lymphocyte suspension culture was established. The data indicate that there are two cell subsets in the spleens of infected mice that contribute to an overall suppression of the in vitro antibody response. Thus, both Lyt-2+ cells and G-10-adherent cells must be removed to maximize antibody production. However, the anti-parasite response obtained in vitro after depletion of Lyt-2+ cells and G-10-adherent cells is restricted to the IgM and IgG1 isotypes as observed in vivo, indicating that suppression is not actively involved in the IgM, IgG1 dominance of the response. The cellular regulation associated with this restriction was then studied by using isolated helper T cells derived from parasite-infected animals to stimulate B cells from uninfected animals. The antibody produced was again restricted to IgM and IgG1, indicating that the helper T cells were regulating the preferential expression of the IgM and IgG1 antibody classes.     

Immunochemical studies on the contribution of NADPH cytochrome P-450 reductase to the cytochrome P-450-dependent metabolism of arachidonic acid

We have studied the role of NADPH cytochrome P-450 reductase in the metabolism of arachidonic acid and in two other monooxygenase systems: aryl hydrocarbon hydroxylase and 7-ethoxyresorufin-o-deethylase. Human liver NADPH cytochrome P-450 reductase was purified to homogeneity as evidenced by its migration as a single band on SDS gel electrophoresis, having a molecular weight of 71,000 Da. Rabbits were immunized with the purified enzyme and the resulting antibodies were used to evaluate the involvement of the reductase in cytochrome P-450-dependent arachidonic acid metabolism by bovine corneal epithelial and rabbit renal cortical microsomes. A highly sensitive immunoblotting method was used to identify the presence of NADPH cytochrome P-450 reductase in both tissues. We used these antibodies to demonstrate for the first time the presence of cytochrome c reductase in the cornea. Anti-NADPH cytochrome P-450 reductase IgG, but not anti-heme oxygenase IgG, inhibited the NADPH-dependent arachidonic acid metabolism in both renal and corneal microsomes. The inhibition was dependent on the ratio of IgG to microsomal protein where 50% inhibition of arachidonic acid conversion by cortical microsomes was achieved with a ratio of 1:1. A higher concentration of IgG was needed to achieve the same degree of inhibition in the corneal microsomes. The antibody also inhibited rabbit renal cortical 7-ethoxyresorufin-o-deethylase activity, a cytochrome P-450-dependent enzyme. However, the anti-NADPH cytochrome P-450 reductase IgG was much less effective in inhibiting rabbit cortical aryl hydrocarbon hydroxylase. Thus, the degree of inhibition of monooxygenases by anti-NADPH cytochrome P-450 reductase IgG is variable. However, with respect to arachidonic acid, NADPH cytochrome P-450 reductase appears to be an integral component for the electron transfer to cytochrome P-450 in the oxidation of arachidonic acid.