bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ethanol inhibits phosphatidylcholine and phosphatidylethanolamine biosynthesis in human leukemic monocyte‐like U937 cells
Authors: Chu Arthur J. , Nguyen Camtu T. 
Published: May 2005

AbstractThe effect of ethanol (ETOH) on the incorporation of [14C]oleic acid (18:1) into lipid in human monocyte‐like U937 cells was investigated. With increasing time of exposure to ETOH, the percentage of the label distributed into neutral lipid (NL) declined from 35 per cent (3 h) to 10 per cent (24 h) accompanied by increased incorporation into phospholipid (PL). [14C] 18 : 1 was preferentially incorporated into triglyceride (TG) and phosphatidylcholine (PC), comprising over 65 per cent and 50 per cent of the label associated with NL and PL, respectively. Low concentrations of ETOH (⩽ 1·0 per cent; v/v) had no effect. At concentrations greater than 1·5 per cent, there was enhanced incorporation into TG and diacylglycerol (DAG) in a 24‐h incubation period, while at 16 h the label in phosphatidylethanolamine (PE) was decreased.The effect of ETOH on the CDP‐choline or ethanolamine pathway was examined by monitoring the incorporation of [3H]choline or [14C]ethanolamine into PC or PE, respectively. At low concentrations ETOH had no effect on either choline uptake or the incorporation into PC. Higher concentrations (≥ 1·5 per cent) for 3 and 6 h resulted in a slightly decreased choline uptake, and the reduction (40–50 per cent) of incorporation into PC suggests that the CDP‐choline pathway was inhibited. There was a similar inhibition of the incorporation of [14C]ethanolamine into PE. When the cells were incubated for 3 h in the presence of 2 per cent ETOH and with labelled 18 : 1 and PL‐base, the ratios of incorporation (base/18 : 1) into PC and PE fractions decreased, indicating that the major inhibition lay in blockage of the availability of the base moiety for PL formation. Analysis of the distribution of the label into metabolites revealed that ETOH inhibited the conversion of [14C] ethanolamine into [14C]phosphorylethanolamine. The reduction in incorporation was not due to the enhanced breakdown of base‐labelled PL. Our results indicate that ETOH has an inhibitory effect on the CDP‐choline or ethanolamine pathway.
Effect of exogenous CDP‐choline on choline metabolism in isolated adult rat ventricular myocytes under normoxic and hypoxic conditions
Authors: Rabkin Simon W. 
Published: May 2005

AbstractThe purpose of this study was to examine the effect of exogenous CDP‐choline on choline metabolism and phosphatidylcholine biosynthesis in adult rat ventricular myocytes. Choline uptake and metabolism were examined, using [methyl3 H] choline. CDP‐choline in the medium produced a concentration dependent reduction in the amount of radio‐label in phosphocholine and phospholipid but it did not alter choline uptake into the myocytes. CDP‐choline also did not antagonize the effect of hypoxia on phosphatidylcholine synthesis; rather it accentuated the hypoxia‐induced reductions in cellular phosphocholine and phosphatidylcholine biosynthesis. These results indicate that the exogenous administration of CDP‐choline alters choline metabolism in the heart by reducing the formation of phosphocholine and phosphatidylcholine without altering choline uptake and suggest an effect of a CDP‐choline metabolite on choline metabolism which is not effective in opposing the effect of hypoxia on phosphatidylcholine biosynthesis.
Effect of cocaine and morphine on neutral endopeptidase activity of human peripheral blood mononuclear cells cultured with lectins
Authors: Leoni Lorenzo M. , Losa Gabriele A. 
Published: May 2005

AbstractWe have tested the effect of alkaloids (cocaine, morphine) and enkephalins on neutral endopeptidase of peripheral blood mononuclear cells activated by lectins. When treated with concanavalin A and cocaine, peripheral blood mononuclear cells showed an enhanced activity (+110 per cent) of the membrane neutral endopeptidase, which was not related to the expression of the common acute lymphoblastic leukemia antigen at the cell surface, although both molecules have the identical amino acid sequence. Phytohemagglutinin‐P, morphine and synthetic enkephalins did not induce the activity of neutral endopeptidase nor the expression of common acute lymphoblastic leukemia antigen. Our findings suggested that the drugs of abuse, cocaine and morphine, affected specific membrane constituents without altering proliferation, subcellular localization of membrane enzymes or the surface immune phenotype of peripheral blood mononuclear cells.
Thioglycollate stimulus modifies lymphocyte metabolism and proliferation. A comparison with lymphocyte activation by walker 256 tumour implantation
Authors: Rosa L. F. B. P. Costa , De Almeida A. F. , Safi D. A. , Curi R. 
Published: May 2005

AbstractKey enzyme activities of glycolysis, the pentose‐phosphate pathway, the Krebs' cycle and glutaminolysis were measured in lymphocytes obtained from the control (CC), thioglycollate‐injected (TG) and Walker 256 tumour‐implanted (WT) groups, non‐immune and immune inflammatory stimuli, respectively. The rates of incorporation of [2‐14C]‐thymidine and [5‐3H]‐uridine into cultured lymphocytes were also determined. The results indicated that the rates of both [2‐14C]‐thymidine and [5‐3H]‐uridine incorporation were enhanced in lymphocytes obtained from thioglycollate‐injected (by an average of 80 per cent) and tumour‐implanted animals (by 2·4‐fold) as compared to control rats. Lymphocyte hexokinase activity diminished both in the TG (23 per cent) and WT (61 per cent) groups, whereas glucose 6‐phosphate dehydrogenase activity was not altered due to the non‐immune inflammatory stimulus, being reduced (23 per cent) in WT rats as compared to CC. The activity of lymphocyte citrate synthase was lowered by thioglycollate (39 per cent) and tumour‐implantation (46 per cent). In contrast, glutaminase activity was augmented in lymphocytes from the TG (41 per cent) and was not modified in the WT groups. Taken as a whole, the presence of the Walker 256 tumour did not affect the capacity for glutamine utilization but depressed glucose metabolism in these cells. On the other hand, the non‐immune inflammatory stimulus suppressed the activities of glycolysis and the Krebs' cycle and enhanced that of glutaminolysis in lymphocytes.
Induction of differentiation by radiation and hyperthermia in neuroblastoma—glioma hybrid cells
Authors: Sugihara Masaki , Fujita Yasuhiko , Enomoto Koh‐Ichi , Maeno Takashi , Ishida Tetsuya 
Published: May 2005

AbstractThe effects of either radiation or hyperthermia on the differentiation potential of NG108‐15, a neuroblastoma‐glioma hybrid cell line, were studied. After radiation and hyperthermia, the outgrowth of neurites from NG108‐15 cells was potentiated, and polarizing current and voltage pulses induced a distinct action potential and a diphasic (inward following outward) current, respectively. An increase in the specific activity of acetylcholinesterase was also observed. In addition, both treatments induced an elevation of the concentration of intracellular calcium in some cells. The increase in intracellular calcium concentration caused by applying the calcium ionophore, A23187, induced differentiation. It is suggested that both the radiation‐ and the hyperthermia‐induced increases of electrical excitability and acetylcholinesterase activity may have originated from an increase in intracellular Ca2+ concentration.
Characterization of plasma membrane redox activity from ehrlich cells
Authors: Del Castillo‐Olivares Antonio , Márquez Javier , De Castro Ignacio Núñez , Medina Miguel Angel 
Published: May 2005

AbstractFerricyanide reductase activity of plasma membranes isolated from Ehrlich ascites tumour cells was very sensitive to trypsin treatment. The decreases of activity observed after treatment with different glycosidases suggests that ferricyanide reductase is a glycoprotein. The opposite effects of phospholipase A2 and phospholipase C on the redox activity indicate that the phospholipidic environment plays an important role in the function of ferricyanide reductase. Sodium ions at millimolar concentrations, and some divalent cations at micromolar concentrations (Ca2+, Mg2+, Sr2+, and Mn2+) behaved as stimulators of ferricyanide reductase activity.
Inositol lipid phosphorylation and breakdown in rat liver nuclei is affected by hydrocortisone blood levels
Authors: Santi Patrizia , Marmiroli S. , Falcieri E. , Bertagnolo V. , Capitani S. 
Published: May 2005

AbstractThe possibility that inositol lipid metabolism is related to nuclear events accompanying steroid hormone action has been investigated by comparing lipid phosphorylation and breakdown in normal rat liver nuclei and in hypo‐ and hypercortisolemic conditions. Lipid phosphorylation in vitro showed the presence of diacylglycerol (DAG)‐, phosphatidylinositol (PI)‐ and phosphatidylinositol‐4‐phosphate (PIP)‐kinase activity, with differences between total tissue homogenates and isolated nuclei, relevant to the treatment in vivo. Administration of hydrocortisone (HC) produced a marked decrease in the phosphorylated nuclear products without influencing the homogenate kinase activity. Under conditions which were optimal for the kinase activities, nuclear PIP‐kinase was strongly increased in presence of a high blood level of HC whereas PI‐kinase activity was reduced. From these observations it appears that the observed differences were due to specific modulation of kinase activities rather than to changes in the availability of substrates.The phosphoinositide‐specific phospholipase C (PLC) activity was also investigated. In the presence of a high HC blood level, the phosphodiesteratic cleavage of PIP strongly increased, while that of phosphatidylinositol bisphosphate (PIP2) was similar in normal and hypercortisolemic conditions. Nuclear phosphoinositide hydrolysis was affected by PLC, β and γ isoforms, which were equally represented in all the conditions investigated, indicating that the observed changes of activity were due to a modulation rather than to a change in the amount of enzyme.These results suggest that inositol lipid metabolism plays a role in the nuclear modifications accompanying steroid hormone induction of transcriptional activity.
Kinetics of the inhibition of acetylcholinesterase from pigeon brain by procaine hydrochloride
Authors: Al‐Jafari Abdulaziz A. , Duhaiman Ali S. 
Published: May 2005

AbstractThe kinetic parameters of the inhibition of pigeon brain acetylchlolinesterase (AChE) by procaine hydrochloride were investigated. Procaine (0·083–1·67 mM) reversibly inhibited AChE activity (15–83 percent) in a concentration dependent manner, the IC50 being about 0·38 mM. The Michaelis‐Menten constant (Km) for the hydrolysis of acetylthiocholine iodide was found to be 1·53 × 10−4 M and the Vmax was 1·06 μmol min−1 mg−1 protein. Dixon as well as Lineweaver‐Burk plots and their secondary replots indicated that the nature of the inhibition is of the linear mixed type which is considered to be a mixture of partial competitive and pure non‐competitive. The values of Ki(slope) and Ki (intercepts) were estimated as 0·14 mM and 0·22 mM respectively by the primary Dixon and by the secondary replots of the Lineweaver‐Burk plot. The Ki′/Ki ratio shows that procaine has a greater affinity of binding for the peripheral than for the active site.
Red blood cell phagocytosis following hexokinase inactivation
Authors: Chiarantini L. , Antonelli A. , Rossi L. , Fraternale A. , Magnani M. 
Published: May 2005

AbstractHexokinase inactivating antibodies were loaded into human erythrocytes using an encapsulation procedure based on hypotonic haemolysis, isotonic resealing and reannealing. Red blood cells loaded with anti‐hexokinase IgG showed 20 percent residual hexokinase activity and reduced glycolytic activity. 9Incubation of these cells in the presence of an oxidizing agent such as terbutyl hydroperoxide (TBH) and then in autologous plasma, promoted opsonization by autologous IgG and complement deposition, but not haemolysis. Furthermore, the antihexokinase IgG loaded cells treated with TBH were actively recognized and phagocytosed by macrophages. Thus, metabolic impairment of human erthrocytes promotes autologous IgG binding, C3 deposition and phagocytosis, a mechanism already reported for the removal of senescent erythrocytes.
A calcium‐dependent protein kinase is present in tetrahymena
Authors: Hegyesi Hargita , Csaba G. 
Published: May 2005

AbstractA Ca2+‐dependent protein kinase of Tetrahymena thermophila has been partially purified and characterized. The molecular mass of the enzyme is less than that of similar enzymes (for example protein kinase C), being about 55 kDa. After purification and in the presence of Ca2+ the enzyme activity increased. The promoter of protein kinase C (PKC) activity, phorbol myristate acetate (PMA), increased the activity while the protein kinase inhibitor H‐7 decreased the activity of the enzyme. The experiments demonstrate the presence, activity and similarity to vertebrate enzymes of a protein kinase at a low level of phylogeny.
Time‐dependent irreversible inhibition of bovine kidney alkaline phosphatase by oxidized adenosine. Use of this compound as a site‐directed inhibitor for studying uncompetitive inhibition
Authors: Butterworth Peter J. 
Published: May 2005

AbstractThe L/B/K type of mammalian alkaline phosphatase (ALP) is inhibited uncompetitively by nucleotides. A combination of adenosine and nicotinamide is more effective than either adenosine or nicotinamide alone, probably because a dinucleotide structure is necessary to trigger a conformational change accompanying binding of structures such as NADH. It has been suggested that a loop region containing residue 429 in the ALP polypeptide is important in the interaction of uncompetitive inhibitors with the enzyme. In the L/B/K isoenzyme, residue 429 is a histidine and is a potential target for modification. In an attempt to learn more about the molecular events accompanying inhibition of ALP by uncompetitive inhibitors, bovine kidney ALP was reacted with oxidized adenosine in the presence of nicotinamide to see if site‐directed modification occurs. Kidney ALP was irreversibly inactivated by oxidized adenosine but the reaction was slow. The site modified is likely to be close to the region of binding. Sequence data for the kidney enzyme shows that in the region of residue 429 there are no residues except His429 itself that is likely to react with oxidized adenosine.
Differential expression of nuclear HMG1, HMG2 proteins and H10 histone in various blood cells
Authors: Čabart Pavel , Kalousek Ivan , Jandová Danuše , Hrkal Zbyněk 
Published: May 2005

AbstractChanges in the levels of chromosomal high‐mobility group proteins HMG1, HMG2 and histone H10 were investigated in blood cells of various types, proliferation activity and stage of differentiation. The relative amounts of proteins HMG1, HMG2 and histone H10 were evaluated densitometrically by SDS‐PAGE of 5 per cent w/v perchloric acid extracts of blood cells. Concerning the HMG1 and HMG2, the main conclusions were: the expression of these HMG proteins was higher in malignant cells, namely leukemia cell lines, then in lymphocytes or granulocytes and the distribution of HMG1 and HMG2 was highly cell‐specific. In comparison with lymphoid cells, the levels of HMG1/2 were higher in myeloid cells. The results revealed that in myeloid cells HMG2 prevails over HMG1. There was no direct correlation between HMG1/2 expression and proliferation activity. The levels of HMG1/2 did not depend on the transcription of chromatin either. However, there was some connection between irreversibly differentiated nonproliferating cells and a loss of HMG1/2 proteins. Reversibly differentiated leukemic cells retain their HMG1/2 levels. Similarly to HMG1/2, H10 showed a strong cell specificity. The level of H10 was different in the various blood cell types. As compared with lymphoid cells, the level of H10 was several‐fold higher in myeloid cells, regardless of whether they were normal or malignant. Moreover, there was an accumulation of H10 in differentiating HL‐60 cells accompanied by only a slight decline in cell proliferation; this agrees with the idea that H10 expression is not directly associated with the inhibition of cell growth. Rather higher expression of H10 is related to changes during cell differentiation.
Effect of lipoproteins on macrophage superoxide generation
Authors: Mohan Pamarthi F. , Jacobson Marc S. 
Published: May 2005

AbstractSuperoxide production by macrophages and leukocytes may have an important role in atherogenesis. Whether lipoproteins modulate the superoxide production of these cells is not clear. Therefore, the effect of lipoproteins on the production of superoxide by rat peritoneal macrophages was tested. VLDL and LDL inhibited digitonin‐stimulated superoxide production in a dose‐dependent manner. Maximum inhibition was observed at 10 μg ml−1 of VLDL protein and 50 μg ml−1 of LDL protein respectively. In contrast, HDL (40 μg protein ml−1) enhanced digitoninstimulated superoxide production (by 47 per cent). Macrophage superoxide production induced by arachidonic acid was enhanced by both VLDL (130 per cent) and HDL (84 per cent), whereas LDL had no effect. The lipoproteins had no effect on macrophage superoxide stimulated by other agonists such as phorbol myristate 13‐acetate, sodium fluoride or the calcium ionophore, A23187. The effect of lipoproteins was also tested on human polymorphonuclear leukocyte superoxide generation, stimulated by digitonin and PMA. Ten μg of VLDL, 50 μg of LDL and 50 μg of HDL proteins ml−1, inhibited digitonin‐induced superoxide production by 50, 100 and 33 per cent respectively. Lipoproteins had no effect on PMA stimulated superoxide generation by human polymorphonuclear leukocytes. The stimulatory and inhibitory effects of lipoproteins on macrophage and neutrophil superoxide generation could be important in the understanding of oxidation‐mediated development of atherosclerosis.
Effect of hypo‐ and hyperthyroidism on the function and metabolism of macrophages in rats
Authors: Rosa L. F. B. P. Costa , Safi D. A. , Curi R. 
Published: May 2005

AbstractThe effect of thyroid hormones on monocyte migration, phagocytic capacity and hydrogen peroxide production by macrophages and the effect of these hormones on glutamine and glucose metabolism was investigated. The experiments were performed on resident, thioglycollate‐ and BCG‐stimulated cells from hypo‐ and hyperthyroid rats. High plasma levels of thyroid hormones suppressed the migration of monocytes and hydrogen peroxide production, whereas hypothyuroidism did not affect cell migration but rasied the phagocytic capacity and the hydrogen peroxide production. Hyperthyroidism increased the activities of glutaminase and hexokinase and the rates of decarboxylation of [U‐14C]‐glutamine and [U‐14C]‐glucose in inflammatory and activated cells. Hypothyroidism stimulated glucose metabolism and had only a slight effect on glutaminolysis. The activity of the TCA cycle was, however, diminished in the presence of high plasma levels of thyroid hormones and enhanced by the hypothyroid state. These findings suggest that the functional changes observed are more likely to be related to the activity of the TCA cycle rather than to glutaminolysis and glycolysis.
Bivascular liver perfusion in the anterograde and retrograde modes: Zonation of the response to inhibitors of oxidative phosphorylation
Authors: Constantin Jorgete , Ishii‐Iwamoto Emy , Suzuki‐Kemmelmeier Fumie , Yamamoto Nair S. , Bracht Adelar 
Published: May 2005

AbstractThe action of cyanide (500 μM), 2,4‐dinitrophenol (50 μM) and atractyloside (100 μM) on glycogen catabolism and oxygen uptake was investigated in the bivascularly perfused liver of fed rats. Cyanide, 2,4‐dinitrophenol and atractyloside were infused at identical rates into the hepatic artery in either the anterograde or retrograde perfusion. The accessible aqueous cell spaces were determined by means of the multiple‐indicator dilution technique. Glucose release, oxygen uptake and glycolysis were measured as metabolic parameters.Oxygen uptake changes per unit cell space caused by atractyloside (inhibition) and 2,4‐dinitrophenol (stimulation) were equal in the retrograde perfusion (periportal cells) and the anterograde perfusion (space enriched in perivenous cells); the decreases caused by cyanide were higher in the retrograde perfusion. Glucose release from periportal cells was not increased upon inhibition of oxidative phosphorylation, a phenomenon which was independent of the mechanism of action of the inhibitor. There were nearly identical changes in glycolysis in the periportal and perivenous cells.It was concluded that: (1) oxygen concentration in the perfused rat liver, if maintained above 100 μM, had little influence on the zonation of the respiratory activity; (2) in spite of the lower activities of the key enzymes of glycolysis in the periportal hepatocytes, as assayed under standard conditions, these cells were as effective as the perivenous ones in generating ATP in the cytosol when oxidative phosphorylation was impaired; (3) the key enzymes of glycogenolysis and glycolysis in periportal and perivenous cells responded differently to changes in the energy charge.
Citrinin affects the oxidative metabolism of BHK‐21 cells
Authors: Chagas Generoso M. , Campello Annibal P. , Kluppel Ma. Lúcia W. , Oliveira Ma. Benigna M. 
Published: May 2005

AbstractThe effects of citrinin on energy production along the respiratory chain and on glycolytic lactate production were examined in BHK‐21 cultured cells. Citrinin inhibited the oxygen consumption rate by about 45 per cent. The respiratory rate of digitonin‐treated cells energized with succinate, in the presence of ADP, was reduced by about 39 per cent. The mycotoxin inhibited the glucose utilization of BHK‐21 cells by about 86 per cent. Cells treated with citrinin produced a small quantity of pyruvate, but were unable to produce lactate. It is concluded that BHK‐21 cells cannot generate lactate when oxidative metabolism is inhibited by citrinin. The perturbations in BHK‐21 cells caused by citrinin are due to alterations in mitochondrial function and in the glycolytic anaerobic pathway.
Numerical deconvolution of gas chromatograph peaks using Jansson's method
Authors: Crilly Paul Benjamin 
Published: May 2005

AbstractSeverely overlapped gas chromatographic peaks can be resolved using Jansson's method. Jansson's method is an iterative nonlinear deconvolution technique and consists of Van Cittert's algorithm with the relaxation factor a function of the kth estimate of the peak shape. The maximum peak amplitude of the instrument and peak non‐negativity serve as constraints to improve the peak estimate. Super‐resolution is achieved without significantly degrading the chromatogram signal‐to‐noise ratio. The method only requires a knowledge of the instrument impulse response function and maximum peak height.