bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ehrlich ascites tumour cells become refractory to α‐difluoromethylornithine at a certain stage of growth
Authors: Anehus Siw , Oredsson Stina M. , Heby Olle 
Published: May 2005

AbstractWhen Ehrlich ascites tumour cells are induced to proliferate by serum stimulation, the ornithine decarboxylase (ODC) activity increases rapidly and reaches two to three peaks during the first 24 h. Inhibition of the first peak in ODC activity (occurring at 4 h) by adding α‐difluoromethylornithine (DFMO) within 2 h of serum stimulation, results in maximal growth inhibition. Under these conditions, similar degrees of polyamine depletion are achieved. When DFMO is added 3 h after seeding, however, enough polyamines have already accumulated during the initial burst in ODC activity to reduce the antiproliferative effect of the drug. The antiproliferative effect is further reduced when DFMO is added 6 h after seeding. When DFMO is added 23 h after seeding, i.e. after maximal accumulation of polyamines, there is no inhibition of cell proliferation. These findings are important to consider both when designing experimental as well as clinical regimens for this drug.
Immunofluorescent localization of transglutaminase in rat small intestine
Authors: Sharp Gaynor , Grindley Helen , Lorand L. , Peters Timothy J. 
Published: May 2005

AbstractThe distribution of intestinal transglutaminase was investigated by immunofluorescence microscopy using rabbit anti‐guinea pig transglutaminase immunoglobulin. Transglutaminase‐related antigen was demonstrated principally in the cytoplasm of villous core interstitial cells with some activity in the brush border region of the villous epithelial cells. Implications for the pathogenesis of coeliac disease are discussed.
Purine and pyridine nucleotides in rabbit red blood cells of different maturity
Authors: Werner Andreas , Siems Werner , Gerber Gerhard 
Published: May 2005

AbstractUsing reversed‐phase high‐performance liquid chromatography purine nucleotides, nucleosides and nucleobases as well as pyridine nucleotides were determined in extracts of reticulocytes and mature red blood cells of rabbits. The concentrations of almost all compounds measured decrease during the last phase of red blood cell maturation.These changes were interpreted with respect to the loss of mitochondria, accompanied by shifting the energy production from the preferentially oxidative mode to the exclusively glycolytic one and variations in the concentrations of purine compounds in blood plasma during reticulocytosis.
Phosphate transport across the basolateral membrane of chick kidney proximal tubule cells
Authors: Myint Sabai , Butterworth Peter J. 
Published: May 2005

AbstractCharacterization of the phosphate transport system across the basolateral membrane of renal proximal tubule has been attempted using isolated proximal tubule cells prepared from chicks. The Pi efflux system is independent of Na+ ions and is not influenced by the nature of the chief anion present in the bathing medium. Pi efflux is not sensitive to DIDS and it is concluded that a generalized anion transporter of band III type is not the chief agent for facilitating Pi exit from the cell across the basolateral membrane. Inhibition of efflux by vanadate is evidence for a specific carrier protein in the membrane. The carrier probably possesses thiol group(s) that are essential for activity. The carrier may effect electroneutral transport of Pi possibly in exchange for OH− ions. The activity of the transport process is not stimulated by depleting the cells of phosphate or inhibited by rearing the chicks on a vitamin D‐deficient diet. The system is unlikely to be of great importance for the expression of various regulatory mechanisms that act on the kidney to control the excretion of Pi. The activity declines as the chicks mature however.
A prostaglandin oligomeric derivative inhibits activities of phospholipase and protease: A possible mechanism of membrane protection during ischemia
Authors: Ohnishi S. Tsuyoshi , Katsuoka Masayuki , Hidaka Saburo 
Published: May 2005

AbstractA prostaglandin oligomeric derivative was synthesized by alkaline treatment of prostaglandin E1. This compound protected the perfused rat heart from global ischemia. This compound was found to inhibit several lipolytic and proteolytic enzymes in vitro. When phospholipase A2 from Naja naja venom was used as an enzyme and phosphatidylcholine was used as a substrate, 50 per cent inhibition was achieved at 50 μM of the prostaglandin derivative. When trypsin and casein were used as enzyme and substrate, 50 per cent inhibition was obtained at 80 μM. A possible mechanism of beneficial effect of this compound in protecting membranes during ischemia is discussed.
Clofibrate feeding increases cytoplasmic but not mitochondrial malic enzyme activity in rat kidney cortex
Authors: Żelewski Mateusz , Świerczyṅski Julian 
Published: May 2005

AbstractAdministration of clofibrate for 21 days to rats increased the malic enzyme activity in the kidney cortex by about 80 per cent. This effect seems to be specific since the drug did not alter significantly the activity either of lactate dehydrogenase, citrate synthase or total mitochondrial protein content in this organ.The increase in activity of malic enzyme in the 13 000 g supernatant (extramitochondrial) fraction in rats treated with the drug was about 80 per cent, whereas in the pellet (mitochondrial fraction) it was about 40 per cent. The specific activity of malic enzyme in the kidney cortex cytosol from clofibrate‐treated rats was about twice that in controls. In contrast clofibrate treatment did not affect its specific activity in isolated mitochondria.Calculations showed that 0·57 and 0·53 μmoles min−1 g−1 wet tissue of mitochondrial malic enzyme was obtained in control and clofibrate‐treated rats respectively. Thus, clofibrate feeding increases the amount of cytoplasmic but not mitochondrial malic enzyme activity.
Methotrexate: Studies on cellular metabolism. III.‐Effect on the transplasma‐membrane redox activity and on ferricyanide‐induced proton extrusion by HeLa cells
Authors: Oliveira Ma. Benigna M. , Campello Annibal P. , Klüppel Ma. Lúcia W. 
Published: May 2005

AbstractThe effect of methotrexate (MTX) on transplasma‐membrane electron transport and ferricyanide‐induced proton extrusion by HeLa cells was studied. Both systems were inhibited by MTX. It is suggested that inhibition of electron transport and proton extrusion caused by MTX could be associated with other metabolic alterations such as response to the increase in NADH levels and decrease in intracellular pH.
Effect of orally‐administered epidermal growth factor on intestinal iron absorption and mucosal permeability
Authors: Raja K. B. , Simpson R. J. , Gregory H. , Peters T. J. 
Published: May 2005

AbstractA progressive increase in intestinal 59Fe3+ absorption was observed on oral feeding of mice with physiological doses of EGF/UGO. Maximal changes were apparent after 3 d and appeared to be dose‐dependent. In addition to a small increase in intestinal cell proliferation, as reflected by increased ornithine decarboxylase activity, EGF/UGO‐feeding increased mucosal permeability (evaluated with [51Cr]‐EDTA): the latter could account for the increase in iron absorption. Sialodenectomy, to remove the major source of endogenous EGF/UGO, had no appreciable effect on the intestinal absorption of iron.
Effect of silybin dihemisuccinate on the ethanol metabolizing systems of the rat liver
Authors: Valenzuela Alfonso , Bustamante Juan C. , Videla Carlos , Guerra Ricardo 
Published: May 2005

AbstractSilybin dihemisuccinate produces a decrease in the ethanol metabolic rate of rats. This effect is ascribed to an inhibition of the microsomal ethanol oxidizing system (MEOS). Alcohol dehydrogenase activity, catalase activity and NADPH cytochrome c reductase activity are not affected by the flavonoid. It is proposed that the inhibition of MEOS by silybin dihemisuccinate is related to its antioxidant properties, acting as a scavenger of the free radicals involved in ethanol metabolism by this enzymatic system. This observation may have therapeutical implications because microsomal lipid peroxidation induced by hydroxyl free radicals has been related to the etiology of hepatic alcoholic disease.
Microsomal membrane fluidity and phosphatidylcholine synthesis in rabbit lung under high oxygen tension
Authors: Casals Cristina , Herrera Luz , Gasset Maria , Garcia‐Barreno Pedro , Municio Angel M. 
Published: May 2005

AbstractPhosphatidylcholine metabolism and membrane fluidity were studied in microsomes isolated from rabbit lung, which had been exposed to high oxygen tension for 30 min.In these microsomes the incorporation of [3H]‐palmitate into phosphatidylcholine increased whereas the incorporation of [14C]‐glycerol and [14C]‐choline from CDP‐[methyl‐14C]‐choline remained unchanged in comparison to the control microsomes. The enhanced [3H]‐palmitate incorporation may be explained by an increase of the specific activity of acyl‐CoA:lysophosphatidylcholine acyltransferase which was measured in microsomes from hyperoxic lung.Although microsomal parameters influencing membrane fluidity, such as the cholesterol/phospholipid molar ratio, unsaturation degree of phospholipid acyl chains and lipid/protein ratio, are altered after oxygen treatment in vivo, no change of fluorescence polarization (PDPH) and lipid structural order parameter (SDPH) could be measured. Probably, the membrane maintains its fluidity by counteracting effects on different factors on which the fluidity depends.
Balancing of energy‐consuming processes of rat hepatocytes
Authors: Schneider W. , Siems W. , Grune T. 
Published: May 2005

AbstractA method for the quantification of energy consuming processes described by Siems et al.6 for reticulocytes and by Müller et al.10 for ascites tumour cells was applied to balance the ATP‐consumption of isolated rat hepatocytes. On the basis of decreased coupled respiration rates following the specific inhibition of energy‐requiring reactions, the energy demands of protein turnover, nucleic acid synthesis, Na+/K+‐ATPase and Ca2+‐transport of hepatocytes in different incubation media were assessed. These processes together with urea synthesis account for about 60 per cent of the total energy consumption in a glucose and amino acid‐enriched Eagle/Borsook medium. The metabolic flux rates of total ATP‐consumption and ATP‐consumption of single energy‐requiring processes in hepatocytes are compared with those in reticulocytes and different tumour cell types.
Stimulus‐secretion coupling of arginine‐induced insulin release: Significance of changes in extracellular and intracellular pH
Authors: Malaisse Willy J. , Plasman Pierre O. , Blachier François , Herchuelz Andre , Sener Abdullah 
Published: May 2005

AbstractThe possible relevance of changes in extracellular and/or intracellular pH to the insulinotropic action of L‐arginine and L‐homoarginine was investigated in rat pancreatic islets. A rise in extracellular pH from 7·0 to 7·4 and 7·8 augmented the secretory response to these cationic amino acids whilst failing to affect the uptake of L‐arginine by islet cells and whilst decreasing the release of insulin evoked by D‐glucose. Under these conditions, a qualified dissociation was also observed between secretory data and 45Ca net uptake. Moreover, at high extracellular pH, the homoarginine‐induced increase in 86Rb outflow from prelabelled islets rapidly faded out, despite sustained stimulation of insulin release. The cationic amino acids failed to affect the intracellular pH of islet cells, whether in the absence or presence of D‐glucose and whether at normal or abnormal extracellular pH. These findings argue against the view that the secretory response to L‐arginine would be related to either a change in cytosolic pH or the accumulation of this positively charged amino acid in the β‐cell. Nevertheless, they suggest that the yet unidentified target for L‐arginine and its non‐metabolized analogue in islet cells displays pH‐dependency with optimal responsiveness at alkaline pH.
The assay of uridine diphosphoglucose dehydrogenase activity: Discrimination from xanthine dehydrogenase activity
Authors: Mehdizadeh S. , Bitensky Lucille , Chayen J. 
Published: May 2005

AbstractThe biochemical and quantitative cytochemical assays of the activity of uridine diphosphoglucose dehydrogenase (UDPG‐D) have produced perplexing results. It is now shown that the perplexity may be due to the possibility that the coenzyme (NAD) required for UDPG‐D activity, may be acting as a substrate for a second dehydrogenase, namely xanthine dehydrogenase, which may utilize NAD as its substrate. The activity of UDPG‐D can be distinguished selectively by the pH of its optimal activity and by decreasing the concentration of the coenzyme used in the assay.
Variation in the isoenzymes of N‐acetyl‐β‐D‐glucosaminidase and protein excretion in aminoglycoside nephrotoxicity in the rat
Authors: Sanchez‐Bernal C. , Vlitos M. , Cabezas J. A. , Price R. G. 
Published: May 2005

AbstractThree aminoglycosidic antibiotics: tobramycin, amikacin and sisomicin were administred to rats. There was an increase in the activity of N‐acetyl‐β‐D‐glucosaminidase (NAG) excreted in the urine and this was characterized by a change in the isoenzyme profiles eluted from DEAE–cellulose. The largest increase in NAG activity was observed following sisomicin administration due mainly to an increase in the B‐form of NAG with a concomitant fall in the intermediate (I‐form). Separation of urinary proteins by SDS‐polyacrylamide gel electrophoresis demonstrated a mixed tubular and glomerular proteinuria following administration of sisomicin. It is concluded that the separation of NAG isoenzymes and urinary proteins provides valuable additional information on the nature and severity of antibiotic nephrotoxicity.
Differentiation of human peripheral blood monocytes to macrophages is associated with changes in the cellular respiratory burst activity
Authors: Johansson Agneta , Dahlgren Claes 
Published: May 2005

AbstractWhen phagocytic leukocytes, e.g. neutrophils, monocytes and macrophages, interact with soluble or particulate stimuli, the cells respond with an increased production of reactive oxygen metabolites. This production can be measured with the luminol‐amplified chemiluminescence (CL) technique. In the present study, the CL reaction induced in monocyte‐derived macrophages was investigated and compared to the responses of neutrophils and monocytes. In systems without additives the CL response of macrophages to soluble stimuli (FMLP, PMA and ionomycin) was very low. Addition of a peroxidase (HRP) to the reaction mixtures resulted in a pronounced increase in CL activity. The cellular CL response in macrophages is thus limited by the amount of peroxidase available. The macrophage response differs qualitatively from the responses of neutrophils and monocytes, in that the intracellular phase of the response is missing.
The relation between the synergistic effect of cytostatics and metabolism of V 79B cells In Vitro
Authors: Hudáková A. , Horáková K. , Perényi T. 
Published: May 2005

AbstractA single‐dose simultaneous application of methotrexate (MTX; 0·002/μg ml−1) and cisplatin (cis‐Pt; 0·0002/μg ml−1) had a permanent synergistic effect on both synchronized and asynchronous cell populations of V 79B cells. Successive combination of the drugs was manifested synergistically when MTX was applied first. The synchronized cell population was more sensitive to the cytostatics than the asynchronous population.Treatment with MTX alone, or the combination of MTX–cis‐Pt, as well as their successive combination with the first drug being cis‐Pt, caused gluconeogenesis.
Neutrophil integrin assay for clinical studies
Authors: Bateman J. , Parida S. K. , Nash G. B. 
Published: May 2005

AbstractThe level of expression of neutrophil adhesion molecules may be a useful marker for neutrophil activation in clinical studies. We therefore determined neutrophil integrin expression under various experimental conditions using a Fluorescence Activated Cell Sorter (FACS) after the cells had been labelled with fluorescent conjugated antibodies to the integrin subunits CD11a, CD11b and CD18. Levels of labelled CD11b and CD18 increased after activation with the chemotactic peptide formyl‐methionyl‐leucyl phenylalanine (fMLP) in a dose‐ and time‐dependent manner, but CD11a did not, indicating that CD11a would not be a useful marker of neutrophil activation. The baseline expression of CD11b and CD18 on unstimulated neutrophils was similar in heparin and EDTA anti‐coagulated blood but the response to activation with fMLP was significantly less for the EDTA anti‐coagulated samples (p < 0·01 in paired t‐test). The labelling of integrins was significantly higher in unfixed whole blood samples compared to samples fixed with 1 per cent paraformaldehyde. However, the increase in labelling induced by fMLP was similar whether or not the samples were fixed after activation. Labelling of CD11b and CD18 was greater for preparations of isolated neutrophils than for neutrophils in whole blood, and the response to fMLP stimulation tended to be lower for the isolated cells. Our results indicate that heparin should be used as anti‐coagulant in clinical studies utilizing whole blood if subsequent activation of neutrophils is planned (e.g. to detect in vivo priming), although EDTA may be used if baseline expression alone is to be measured. Fixation of blood samples should not affect the ability to detect neutrophil activation.
Phospholipase A2 from Trypanosoma congolense: Characterization and haematological properties
Authors: Nok Andrew J. , Esievo King A. N. , Ibrahim Sani , Ukoha Agwu I. , Ikediobi Christopher O. 
Published: May 2005

AbstractPhospholipase A2 was isolated from Trypanosoma congolense and purified to electrophoretic homogeneity. The enzyme appeared to exist in a dimeric form with subunit molecular weights of 16 500 and 18 000. It had a pH optimum of 6·8. Kinetic analysis with different substrates, showed that the enzyme had exceptional specificity for 1,2,dimyristoyl‐sn‐phosphatidylcholine and 1,2,dioleoyl‐sn‐phosphatidylcholine with Km values of 1·85 × 10−3 M and 2·12 × 10−3 M respectively. The Arrhenius plot was linear with an activation energy of 5·8 kcal mol−1. Inhibition studies with parahydroxymercuribenzoate and tri‐butyltinoxide were positive thus implicating a thiol group at the catalytic site of the enzyme. The enzyme was stable to heat treatment and possessed haemolytic and anticoagulating properties.
Fructose 1,6‐bisphosphate prevents oxidative stress in the isolated and perfused rat heart
Authors: Rigobello Maria Pia , Galzigna Lauro , Bindoli Alberto 
Published: May 2005

AbstractRat hearts were perfused with the Langendorff technique at constant flux in the presence of the oxidizing agents hydrogen peroxide and diamide. Fructose 1,6‐bisphosphate strongly prevented the decline of heart contractility due to the infusion of these oxidizing agents. On the other hand, fructose 1,6‐bisphosphate had no effect on the release of total glutathione into the perfusate but prevented the loss of lactate dehydrogenase indicating a protective effect on cell membranes. Comparing the cytosolic and mitochondrial loss of glutathione, fructose 1,6‐bisphosphate exerted a beneficial action only on the mitochondrial fraction. Several mechanisms of action have been considered to explain the protective action of frutose 1,6‐bisphosphate. In our experimental conditions fructose 1,6‐bisphosphate might stimulate its own production giving rise to dihydroxyacetone phosphate, that, after reduction to glycerol 3‐phosphate, can permeate the mitochondrial membrane with the final production of energy.
Reduced 4‐hydroxynonenal degradation in hearts of spontaneously hypertensive rats during normoxia and postischemic reperfusion
Authors: Grune T. , Schönheit K. , Blasig I. , Siems W. 
Published: May 2005

Abstract4‐Hydroxynonenal (HNE) degradation was investigated in isolated perfused rat hearts of the WKY and SHR strains before and after ischemia. HNE (10 μmoles l−1) were infused and the concentration of HNE in the effluent was determined. The rate of initial consumption was about 50 nmoles min−1 g−1 wet weight in hearts of both the WKY and SHR rats. In the WKY rat hearts, this rate of HNE degradation did not change during several minutes of HNE infusion and also remained constant during postischemic reperfusion. In the hearts of the SHR rats the HNE degradation rate declined within 5 min to 25 nmoles min−1 g−1 wet weight. Also during postischemic reperfusion, there was a lower HNE degradation rate in the SHR rat hearts than in the WKY rat hearts. The influence of hypertrophy on the rate of HNE degradation is discussed. It is suggested that the low degradation of the cytotoxic lipid peroxidation product, HNE, in hypertrophic hearts may contribute to reduced antioxidant defence in those hearts.
Hyaluronan‐mediated protective effect against cell damage caused by enzymatically produced hydroxyl (OH·) radicals is dependent on hyaluronan molecular mass
Authors: Presti Donatella , Scott John E. 
Published: May 2005

AbstractHyaluronan (HA) protected tendon fibroblasts against cell damage mediated by hydroxyl radicals (OH·) as demonstrated by release of 51Cr from labelled cells. Protection afforded by high molecular mass (Mr) HA (1218 kDa) was much more effective than that provided by lower (176 kDa and 668 kDa) Mr HA.OH· was generated by coupling H2O2 produced by glucose oxidase: glucose to [Fe2+‐EDTA] chelate in a Fenton‐type system. The flux of OH· was measured by a spectrofluorimetric assay of salicylate produced by the reaction of benzoate with OH·. Cell damage caused by the OH· generating system was prevented in the presence of catalase, which destroyed H2O2. Damage caused in a standard incubation time increased with increased amounts of glucose oxidase.Protection against OH·‐mediated cell damage increased with increasing concentration of HA. The presence of HA did not interfere with the enzyme‐Fenton system, as monitored by production of gluconate. On the other hand, HA scavenged OH· produced by the enzyme‐Fenton system, as shown by competition with benzoate, which produced less salicylate in the spectrofluorimetric assay in the presence of HA.The reaction of OH· with HA was measured directly by a pulse radiolysis technique in which a hydrated electron (e) produced OH· by the reaction with nitrous oxide. Second order rate constants obtained in distilled H2O or in phosphate buffer showed no dependence on HA Mr. Similarly, fluorimetric assay of the flux of in the enzyme‐Fenton system confirmed that HA competed with benzoate, thus lowering salicylate production, and the flux was also independent of the molecular mass of HA.These results demonstrate that part of the HA‐mediated protection against enzyme‐Fenton produced OH· and other reactive oxygen‐derived toxic species was not a consequence of either the primary or secondary structure of HA, but rather depends on higher order HA organization. Some aspects of the formation of the HA meshwork (tertiary structure) are Mr dependent. We therefore propose that cell‐anchored HA meshworks excluded relatively large enzyme molecules from the immediate environment of the cell, thus reducing the flux of OH· etc. at the cell surface and diminishing cell damage.