Phase uncertainty and loss of interference: A general picture.
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Journal Article↗
Biomedical subjects
A Stern
Publications and source records attributed to A Stern.
Kringle 1 domain of human tissue-type plasminogen activator is a functional module mediating fibrinogen-stimulated plasminogenolytic activity.
The functions of the finger and kringle-2 (K2) domains of human tissue-type plasminogen activator (t-PA) in mediating fibrin-stimulated plasminogenolytic activity are well documented. Contradictory results have been reported for the kringle-1 (K1) domain with respect to this property. To clarify this issue we have deleted the finger and the K2 domains of t-PA according to the exon-intron organization of the gene by site-directed mutagenesis. The resulting derivative (GK1L) was constitutively expressed in permanent clones of Chinese hamster ovary cells. The secreted proteins have been partially purified and characterized by Western blotting. Since the plasminogenolytic activity of GK1L is stimulated by fibrin, the K1 domain of t-PA must be a functional domain in this context.
Animals↗
Effects of 1,4-naphthoquinone derivatives on red blood cell metabolism.
The effect on red blood cell metabolism of a series of substituted 1,4-naphthoquinones has been investigated. 2-Methoxy-1,4-naphthoquinone was found to be a potent oxidative compound, generating hydrogen peroxide in erythrocytes and causing both methemoglobin formation and glutathione depletion in the absence of glucose. Flux of glucose through both glycolysis and the hexose monophosphate shunt was stimulated. 2-Hydroxy- and 2,3-dihydroxy-1,4-naphthoquinone were less oxidative. Both compounds caused oxidation of glutathione and formation of hydrogen peroxide with corresponding stimulation of the hexose monophosphate shunt, but did not cause methemoglobin formation. 2-Hydroxy-3-alkyl-1,4-naphthoquinones were not oxidative but did increase the flux of glucose through glycolysis, possibly reflecting membranal damage. The in vitro oxidative effects of these substances do not correlate with their hemolytic activity in rats, indicating that factors other than oxidative damage are important in mediating the in vivo toxicity of these substances.
Animals↗
Tetravalent vanadium mediated oxidation of low density lipoprotein.
1. Tetravalent vanadium causes oxidation of low density lipoprotein (LDL) as manifest by protein degradation and lipid peroxidation. 2. Oxidative modification of the apolipoprotein B-100 is paralleled by the formation of thiobarbituric acid reactive substance and fluorescent chromolipid production. 3. The metal chelators ethylenediamine tetracetic acid and desferrioxamine, and the alcohols, ethanol and isopropanol inhibit the oxidation of LDL by tetravalent vanadium. No inhibition is observed with superoxide dismutase, catalase or mannitol. 4. The data suggest that aldehydes formed during the process of lipid peroxidation induced by tetravalent vanadium react with the proteins in LDL to form fluorescent chromolipids and that the oxidative process originates within the hydrophobic domain of LDL.
1-Propanol↗
Desferrioxamine protects human red blood cells from hemin-induced hemolysis.
Hemin binding to red cell membranes, its effect on red cell hemolysis, and it interaction with desferrioxamine (DFO) in these processes were investigated. DFO interacted with hemin via the iron moiety. Blockage of the binding groups in DFO prevented interaction of DFO with hemin, implying the importance of the hydroxamic acid groups in DFO-hemin interactions. Since hemolysis is a result of hemin association with the membrane components, its binding in the presence and absence of DFO was studied. DFO strongly inhibited hemin-induced lysis in a concentration-dependent manner. With 50 microM hemin, 1 mM DFO completely inhibited lysis. Preincubation of ghost membranes with DFO (1 mM) inhibited binding of hemin (50 microM) to membranes by 42%. After ghost membranes were preincubated with hemin (50 microM), the addition of DFO (1 mM) removed 20% of the membrane-bound hemin. It is suggested that DFO may have an important role in alleviating the hemin-induced deleterious effects on the red cell membrane, especially in hemolytic anemias associated with unstable, autoxidized hemoglobins.
Deferoxamine↗
The Arthus reaction in cats deficient in Hageman factor (factor XII).
A study was made of the Arthus reaction in an animal model of Hageman-factor deficiency, namely Hageman trait cats, and in control cats with normal Hageman-factor activity. At three time points, there was a significant decrease (P less than 0.01) in the size of the cutaneous Arthus reaction to chicken red blood cells in biopsies from Hageman trait cats compared with the reaction in biopsies from control animals. Injection of a positive control, histamine, and a negative control, phosphate-buffered saline, produced no significant differences between the two groups. Hageman trait cats had a significant decrease (P less than 0.001) in the number of neutrophils in the skin lesions compared with controls. When Hageman trait cats were injected intravenously with purified cat Hageman factor, Arthus reactions were similar to those observed in control cats.
Animals↗
Properties of a novel plasminogen activator (BM 06.022) produced in Escherichia coli.
Since currently available thrombolytics still show disadvantages, such as administration by infusion, occurrence of intracranial hemorrhage, major hemorrhagic complications, allergic reactions, and high price, a novel tissue plasminogen activator has been developed. BM 06.022 is a t-PA mutant produced in Escherichia coli by DNA technology. It has no oligosaccharide side-chains and comprises the kringle 2- and protease domains of t-PA. Like t-PA, the enzymatic activity of BM 06.022 can be stimulated by fibrin. However, BM 06.022 binds to neither endothelial cells nor fibrin. Despite this, BM 06.022 demonstrates the same fibrin selectivity in vivo as t-PA. Investigation of the pharmacokinetic properties in rats, rabbits, dogs, and primates reveals, depending on species, a 4.5- - 10.4-fold longer dominant half-life and 3- - 8.4-fold slower plasma clearance than t-PA (alteplase). In spite of its lower specific activity in vitro, BM 06.022 has a thrombolytic potency which is 4.6 - 11.5 times higher in vivo than that of alteplase in the rabbit model of venous thrombosis and the canine model of coronary artery thrombosis. BM 06.022 achieves reperfusion significantly more rapid than long-acting anistreplase. Therefore, because of its improved pharmacokinetic properties, BM 06.022 might be administered to infarct patients by i.v. injection in the pre-hospital phase to achieve rapid lysis. Due to its lack of fibrin- and endothelial-cell-binding, combined with retained fibrin selectivity, BM 06.022 further promises to induce fewer hemorrhagic complications than either t-PA or streptokinase.
Animals↗
Antimicrobial management of postoperative infections in abdominal surgery: single or combination regimen?
In a prospective, controlled, randomized study, the clinical and bacteriologic efficacy of imipenem/cilastatin was compared with that of a standard combination of an aminoglycoside, amoxicillin, and clindamycin in patients with serious postoperative infections. Doses used were imipenem/cilastatin 1 gm q 8 hr, amoxicillin 2 gm q 8 hr, and clindamycin 0.6 gm q 6 hr. Aminoglycoside doses were individualized and monitored six times weekly with serum concentration assays. Sixty-three patients were entered into the study: 31 in the imipenem/cilastatin group and 32 in the combination group. Diagnoses included pneumonia (ten in the imipenem/cilastatin group and seven in the combination group), peritonitis (eight in the imipenem/cilastatin group and 15 in the combination group), and septicemia (eight in the imipenem/cilastatin group and three in the combination group). The two groups were comparable with respect to sex, age, underlying diseases, and duration of antibiotic therapy. In the imipenem/cilastatin group, 26 patients were cured and one improved (87%). In the combination group, 21 were cured and five improved (81%). Four patients receiving imipenem/cilastatin and six receiving the combination therapy failed to respond to treatment. Eighty percent of the bacterial isolates were eradicated, and 15% were suppressed in the imipenem/cilastatin group. Corresponding frequencies in the combination group were 84% and 11%, respectively. Isolated pathogens persisted in 5% of the patients in each group. It is concluded that imipenem/cilastatin appears to be an effective and well-tolerated alternative to a triple antibiotic combination in the treatment of serious postoperative infections.(ABSTRACT TRUNCATED AT 250 WORDS)
Abdomen↗
Magnetic field modulation effects on the microwave transmission through superconducting thin films of Y-Ba-Cu-O.
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Journal Article↗
Effect of oxidative stress on membrane phospholipid and protein organization in human erythrocytes.
Membrane phospholipid and protein organization was studied in intact human erythrocytes exposed to phenylhydrazine, an oxidative agent inducer. The evaluation of the membrane phospholipid and protein organization was carried out in terms of asymmetric distribution across the membrane bilayer for the phospholipids, and in terms of accessibility of cleavable sites present on the outer membrane surface for the proteins. Treatment of phenylhydrazine-exposed erythrocytes either with bee venom phospholipase A2 or with trinitrobenzenesulfonic acid indicated that phosphatidylserine (PS), which is the only phospholipid not formally present on the outer leaflet of the membrane, was translocated to the outer surface of the cell membrane. The extent of this phenomenon was directly proportional to the concentration of the oxidant having a peak value at 0.1 mM. Phosphatidylcholine and phosphatidylethanolamine conserved their original distribution across the erythrocyte membrane throughout the study. The oxidant, at a dose which did not induce any modification of the sodium dodecyl sulfate-polyacrylamide gel electrophoresis cytoskeleton membrane protein pattern, did not provoke any alteration of the membrane protein surface architecture, although the translocation of PS to the membrane outer leaflet in intact erythrocytes was present.
Analysis of Variance↗
Functional topology of human tissue-type plasminogen activator: characterization of two deletion derivatives and of a duplication derivative.
Three types of permanent Chinese hamster ovary (CHO) cell lines with different amplified expression constructs that abundantly secrete derivatives of human tissue-type plasminogen activator (t-PA) were established. The first one expresses a deletion derivative in which the kringle 2 domain (K2) has been removed (FGK1L). In the second derivative, the growth-factor-homologous domain (G) has also been deleted (FK1L); a third line expresses a duplication derivative of K2 (FK2K2L) lacking the (G) and kringle 1 (K1). All deletion derivatives were constructed according to the exon-intron organization of the gene. We have analyzed the secreted proteins and the fibrinogen-stimulated plasminogenolytic activity as a function of different culturing conditions (fetal calf serum, aprotinin) of the cells. The specific activities of the two deletion derivatives (FGK1L and FK1L) were only 10-20% of the specific activity of t-PA. Surprisingly, the specific activity of the K2-duplication derivative, FK2K2L, was three times higher than that of t-PA. These data were correlated with the morphological properties of CHO cells constitutively secreting the described derivatives under different culturing conditions. CHO cells secreting the deletion derivatives (FGK1L and FK1L) remained attached to the surface of the petri dishes. Cell lines secreting the duplication derivative FK2K2L detached from the surface even in the presence of the protease inhibitor aprotinin.
Animals↗
Glucose metabolism and hemoglobin reactivity in human red blood cells exposed to the tryptophan metabolites 3-hydroxyanthranilate, quinolinate and picolinate.
Glucose metabolism and hemoglobin reactivity in intact human erythrocytes were assessed in the presence of the tryptophan metabolites, 3-hydroxyanthranilate (3-HAT), quinolinate and picolinate. Of these compounds, only 3-HAT altered red cell oxidative status by inducing, in a dose-dependent manner, formation of methemoglobin and non-functional oxidation products of hemoglobin, and by increasing both net glycolytic flux and flux through the hexose monophosphate shunt. 3-HAT also decreased the normal lactate to pyruvate production ratio with pyruvate accumulating at the expense of lactate. These findings are consistent with the auto-oxidative reactivity of quinolinate, picolinate, and 3-HAT in that only 3-HAT undergoes base-catalyzed auto-oxidation (Dykens et al., Biochem Pharmacol 36: 211-217, 1987). Lactate and pyruvate added to the medium in physiologic concentrations uncoupled oxidative glycolysis from reductive glycolysis, resulting in accumulation of pyruvate in the presence of 3-HAT with little increase in total glycolytic flux. Superoxide dismutase (SOD), which accelerates 3-HAT auto-oxidation in vitro (Dykens et al., Biochem Pharmacol 36: 211-217, 1987), exacerbated HAT-mediated oxidative insult by increasing methemoglobin formation, hexose monophosphate shunt flux, and pyruvate accumulation. Persistence of 3-HAT-induced red cell metabolic responses and oxidative damage in the presence of SOD, DETAPAC (diethylenetriaminepentaacetic acid) and formate suggests that an organic-based radical, perhaps the anthranilyl radical produced during 3-HAT auto-oxidation, is the proximate agent exerting oxidative stress. Slow rates of auto-oxidation indicate that 3-HAT may be useful as a probe of antioxidant mechanisms in normal and diseased red blood cells.
3-Hydroxyanthranilic Acid↗
Canonical quantization of chiral bosons.
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Journal Article↗
Toxicity of aromatic thiols in the human red blood cell.
Thiophenol and 4-aminothiophenol were used to study levels of toxicity in human red blood cells. Thiophenols caused conversion of oxyhemoglobin to methemoglobin. Reduction of corresponding disulfides by intracellular glutathione caused cyclic reduction/oxidation reactions, resulting in increased oxidative flux. Three levels of oxidative stress were observed in these experiments: the lowest level resulted from incubation with 0.25 mM thiophenol; the intermediate level with 0.50 mM thiophenol or 0.25 mM 4-aminothiophenol; the highest levels with 0.50 mM 4-aminothiophenol. Methemoglobin formation increased with increasing level of oxidative stress. Glycolysis and the hexose monophosphate shunt were inhibited at the intermediate and highest levels of stress, respectively. Above the highest level of stress non-intact hemoglobin was formed and cell lysis occurred. These metabolic responses were reflected in cellular levels of NADH, NADPH and reduced glutathione. At the lowest level of oxidative stress, both glycolysis and hexose monophosphate shunt were increased such that near-normal levels of NADH, NADPH and reduced glutathione were maintained and methemoglobin formation was kept to a minimum. The response of red cells to 0.25 mM thiophenol appears to represent a level of oxidative stress to which the cell is capable of adaptive metabolic response. Glycolysis contributes approximately one-quarter of the total reducing equivalents from glucose metabolism in response to the oxidative challenge by thiophenol. The results suggest that the metabolic response to autoxidation of endogenous thiols is thiol exchange with glutathione and reduction of resulting glutathione disulfide by the hexose monophosphate shunt.
Erythrocytes↗
Vanadate-mediated oxidation of NADH: description of an in vitro system requiring ascorbate and phosphate.
Oxidation of NADH has been observed in an in vitro system requiring NADH, vanadate, ascorbate, and phosphate. Similar results were observed with NADPH. Ascorbate provides the reducing equivalents necessary to reduce vanadate to vanadyl. Vanadyl autoxidizes producing superoxide which initiates a free radical chain reaction resulting in oxidation of NADH. Oxidation is inhibited by superoxide dismutase but not by catalase or ethanol. Ascorbate functions to initiate the free radical chain reaction but is not required in stoichiometric concentrations. At higher concentrations, ascorbate inhibits NADH oxidation. Inorganic phosphate was required for NADH oxidation. Dialysis of phosphate buffers against solutions containing apoferritin or conalbumin or addition of transition metal cations or chelators to the reaction medium did not alter dependence on phosphate. Phosphate and vanadate were interchangeable in their effects on kinetic parameters of NADH oxidation except that vanadate was 100 times more potent than phosphate. Vanadate participates directly in the initiating and propagating redox reactions of NADH oxidation. Phosphate may be important in lowering the energy of activation for the necessary transfer of hydronium ion and water in the transition state between vanadate anion and vanadyl cation.
Ascorbic Acid↗
Prooxidant and antioxidant effects of ascorbate on tBuOOH-induced erythrocyte membrane damage.
1. t-Butylhydroperoxide (tBuOOH) a lipoperoxide analog, causes rapid and considerable sulphydryl (SH) oxidation but almost no lipid peroxidation in red blood cell membranes (ghosts) containing no detectable haemoglobin. 2. tBuOOH, in the presence of ascorbate, produces significant lipid peroxidation the level of which is proportional to the ascorbate concentration. The initiation of lipid peroxidation is thought to occur by the reactive tBuO (butoxyl) species via the reductive decomposition of tBuOOH by ascorbate. 3. Ascorbate protects ghost membranes from the tBuOOH-induced SH oxidation in a dose-dependent fashion. 4. There is no parallelism between lipid peroxidation and SH oxidation in these systems. This suggests that the two processes occur independently of each other. 5. These findings indicate that, simultaneously, ascorbate can have both a protective and a prooxidant action in different membrane components under the same oxidative stress.
Antioxidants↗
Agranulocytosis associated with T-gamma-lymphocytosis: no improvement of peripheral blood granulocyte count with human-recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF).
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Agranulocytosis↗
Human red cells enhance the formation of 5-lipoxygenase-derived products by neutrophils.
Upon activation, human neutrophils generate 5-lipoxygenase products which are involved in inflammation as well as other physiological and pathophysiological processes. We have examined the influence of red cells on the generation of lipoxygenase-derived products by neutrophils utilizing high pressure liquid chromatography system which permitted quantitation of 5-HETE, leukotriene B4 (and its isomers) and the omega oxidation products of leukotriene B4 (20-hydroxyleukotriene B4, 20-carboxyleukotriene B4) within the same sample. Co-incubation of red cells with neutrophils (50:1, red cells:neutrophils) resulted in a 722 percent increase in 5-hydroxyeicosatetraenoic acid production and a slight increase in leukotriene B4 and its omega oxidation products which were not accompanied by increases in 15-hydroxyeicosatetraenoic acid production. The role of the sulfhydryl status of the red cell and its ability to scavenge hydrogen peroxide were assessed in relationship to the interaction of red cells on the neutrophil-derived lipoxygenase products. Together, these findings indicate that red cells can regulate the levels of lipid-derived mediators produced by neutrophils. Moreover, they suggest that red cell-neutrophil interactions may be of importance in inflammatory reactions.
Arachidonate 15-Lipoxygenase↗