bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ability of different hepatoma cells to metabolize 4‐hydroxynonenal
Authors: Canuto R. A. , Muzio G. , Maggiora M. , Poli G. , Biasi F. , Dianzani M. U. , Ferro M. , Bassi A. M. , Penco S. , Marinari U. M. 
Published: May 2005

Abstract4‐Hydroxynonenal (4‐HNE), produced during the oxidative lipid breakdown of biological membranes, modulates various biochemical processes in normal liver and in hepatoma cells. It is very probable that the effects of 4‐HNE are related to the quantity formed in the cells and the cells' ability to metabolize it. Aldehyde catabolism takes place within the cells through oxidative and reductive enzymes, and through conjugation with intracellular glutathione. In this paper, the various enzymatic pathways involved in the metabolism of 4‐HNE were studied in normal hepatocytes and in hepatoma cells. The hepatocyte pathway undergoes a complex variety of change during neoplastic transformation.In hepatoma cells, generally, 4‐HNE metabolism was due mainly to aldehyde dehydrogenases, whereas in normal hepatocytes 4‐HNE metabolism was mainly due to alcohol dehydrogenase and glutathione‐S‐transferase. The increase in oxidative enzymes compared to normal tissue was not the same in all types of hepatoma: in HTC hepatoma cells, the enzyme levels were considerably higher; in AH‐130 hepatoma cells of Yoshida, they were lower in subcellular particles and similar in the cytosol. Indeed, consumption of externally‐added 4‐HNE in hepatoma cells was proportional to their content of 4‐HNE metabolizing enzymes.
Propranolol has direct antithyroid activity: Inhibition of iodide transport in cultured thyroid follicles
Authors: Murakami Saburo , Nasu Michiyo , Fukayama Harushisa , Krishnan Lalita , Sugawara Masahiro 
Published: May 2005

AbstractThe effect of propranolol on the process of thyroid hormone formation was studied in a physiological culture system. Porcine thyroid follicles were preincubated with propranolol for 24 h. Iodide transport, iodine organification, and de novo thyroid hormone formation were measured by incubating these follicles with the mixture of carrier‐free 0·1 μCi Na 125I and 50 nM NaI for 2 to 6 h at 37°C. A concentration of propranolol greater than 100 μM inhibited iodide transport in a dose‐dependent manner; this inhibition was non‐competitive with iodide and independent of thyrotropin (TSH). Reduced iodine organification and thyroid hormone formation was seen with 150 μM propranolol or greater. The inhibitory action of propranolol was not caused by beta‐blocking activity, since D‐propranolol (devoid of beta‐blocking activity) inhibited iodide transport, and other beta‐blockers (metoprolol, atenolol, and labetalol) did not inhibit iodide transport. The inhibition of iodide transport was most likely caused by membrane stabilizing activity since quinidine, which possess the same membrane stabilizing activity as propranolol, also inhibited iodide transport. TSH‐mediated cAMP generation and Na +K+ ATPase activity, membrane functions for iodide transport, were unaffected by propranolol.Our study has shown, for the first time, that propranolol has a direct antithyroid action, namely inhibition of iodide transport in the intact thyroid follicle.
Isolation and cloning by a polymerase chain reaction of a genomic DNA fragment of the human slow skeletal troponin (TNNT1) gene
Authors: Novelli G. , Gennarelli M. , Sangiuolo F. , D'Agruma L. , Cicero S. Lo , Melchionda S. , Dallapiccola B. 
Published: May 2005

AbstractThe genomic 3′ structure of the gene coding for the human slow skeletal troponin T (TNNT1) gene, is reported. An intron of 912 nucleotides containing an Alu‐element has been identified and characterized. The complexity of the sequenced region suggests an alternative exon use. The present results may be valuable for further studies on the gene structure of TNNT1 and the related troponin gene family.
Intracellular calcium mobilization is triggered by clustering of membrane glycoproteins in concanavalin A‐stimulated platelets
Authors: Ramaschi Giuseppe , Torti Mauro , Sinigaglia Fabiola , Balduini Cesare 
Published: May 2005

AbstractStimulation of human platelets with concanavalin A resulted in a significant increase in the concentration of cytoplasmic free Ca2+. This effect was due to two different processes: Ca2+ mobilization from internal stores and Ca2+ influx from the extracellular medium. Kinetic analysis revealed that the release of Ca2+ from internal storage sites occurred sooner than the opening of plasma membrane Ca2+ channels. The ability of concanavalin A to induce a sustained increase in cytoplasmic Ca2+ concentration was antagonized and reversed by methyl ∝‐D‐mannopyranoside, demonstrating that it was promoted by the interaction of the lectin with cell surface glycoproteins. Succinyl–concanavalin A, a dimeric derivative of the lectin, that does not promote patching/capping of the receptor, was able to bind to the platelet surface, and antagonized the effects of native concanavalin A. In addition, succinyl–concanavalin A, per se, was unable to induce Ca2+ mobilization in human platelets. Therefore, the action of the native concanavalin A was mediated by receptor clustering events. Concanavalin A mobilized Ca2+ from the same internal stores from which Ca2+ was mobilized in response to strong platelet agonists, such as thrombin and arachidonic acid. However, while thrombin was ineffective in inducing Ca2+ release after stimulation of platelets with Con A, Con A was able to cause a full discharge of Ca2+ from internal stores even in platelets previously stimulated with thrombin. These results demonstrate for the first time that the clustering of specific membrane glycoproteins can trigger platelet activation. The physiological implications during platelet aggregation are discussed.
PTH induces modification of transductive events in otosclerotic bone cell cultures
Authors: Fanó G. , Venti‐Donti G. , Belia S. , Paludetti G. , Antonica A. , Donti E. , Maurizi M. 
Published: May 2005

AbstractWe studied the effect of PTH (10–100 nM) on transductive mechanisms (adenylate cyclase activity, Ca2+ metabolism, IP3 levels) in cell cultures derived from normal and otosclerotic human bone fragments. The cultured cells were osteoblast‐like but with calcitonin‐receptors still present and with PTH receptors coupled with the adenylate cyclase system.The results showed that PTH activated adenylate cyclase and increased the intracellular Ca2+ levels with qualitative and quantitative differences between the two cellular populations. In particular, otosclerotic cells responded less to hormone stimulation, which is in accord with the current hypothesis of a desensitization of the receptor/enzyme complex associated with the pathological status.
Estimation of metabolic flux rates in liver purine catabolism of tumour‐bearing mice by computer simulation of radioactive tracer experiments
Authors: Siems Werner G. , Schwendel Anke , Grune Tilman , Holzhütter Hermann‐Georg , Uhlig Rolf 
Published: May 2005

AbstractMouse hepatocytes from healthy control mice and from Ehrlich ascites tumour‐bearing mice were used for tracer‐kinetic studies of purine catabolism of liver cells during different periods of tumour growth. The dynamics of the radioactive tracers were modelled mathematically by a system of differential equations. Computer simulations, i.e. direct fitting of numerical solutions of these equations to the observed time‐courses of metabolites and specific radioactivites, enables one to estimate unknown kinetic parameters of a simplified model of pathways of hepatic purine catabolism in tumour‐bearing mice.There occurred great differences of metabolic flux rates between control hepatocytes, hepatocytes of mice during the proliferating period of tumour growth (6th day after inoculation of the tumour) and hepatocytes of mice during the resting period of tumour growth (12th day after inoculation of the tumour). The final purine degradation of hepatocytes prepared during the proliferating period was lower in comparison with that of control hepatocytes, but it was markedly higher in hepatocytes prepared during the resting period of tumour growth. The changes in hepatocyte purine catabolism during the proliferating period of tumour growth argue for transitions which aim at the maintenance of high purine nucleotide levels in the liver itself rather than for an increased nucleoside and nucleobase supply for the tumour. This suggestion is in accordance with the increased ATP level of the liver during the proliferating phase of tumour growth. The drastic acceleration of the final steps of hepatic purine catabolism forming uric acid and allantoin during the resting period of tumour growth was predominantly due to increased flux rate from xanthosine and guanine in accordance with increased catabolism of monophosphorylated nucleotides.
The preparation and kinetic properties of multiple forms of chicken brain acetylcholinesterase
Authors: Al‐Jafari Abdulaziz A. , Kamal M. A. 
Published: May 2005

AbstractA method for preparing various forms of acetylcholinesterase (A ChE) from chicken brain has been developed and they have been characterized in terms of kinetic parameters such as Km, rate constant (k), turnover number (kp), specificity constant (ksp), Vmax and half‐life (t1/2). The solubility experiments show that, there are two major forms of A ChE i.e. water‐soluble and membrane‐bound A ChE (MBA ChE). The MBA ChE shows several subforms, and on the basis of percentage activity only three MBA ChE forms have been selected for complete characterization by various kinetic parameters. It was found that these three forms of MBA ChE demonstrate significant differences in their kinetic properties.
No discrete complexes containing DNA polymerase α activity can be solubilized from the heat‐stabilized nuclear matrix prepared from HeLa S3 cells
Authors: Martelli Alberto M. , Cocco Lucio 
Published: May 2005

AbstractMost of the DNA polymerase α activity, bound to the heat‐stabilized nuclear matrix prepared from HeLa S3 cells, was released as a matrix extract by sonication. When the extract was centrifuged in a 5–20 per cent linear sucrose gradient no definite peaks of activity could be identified. Most of the activity sedimented to the bottom of the tube under all the conditions tested, whilst the remaining activity was associated with matrix fragments of various and irregular size. No 10 S complexes, containing polymerase activity, were seen after incubation of the extract for 16 h before centrifugation. Other solubilization procedures (i.e. treatment of the matrix with chelating agents, high pH associated with reducing agents, ionic and nonionic detergents) failed to produce release of matrix‐bound DNA polymerase α activity. In contrast, we released 10 S complexes, containing polymerase activity, from the matrix prepared from nuclei not exposed to heat. We conclude that a 37°C incubation of isolated nuclei before extraction with 2 M NaCl and DNase I digestion causes DNA polymerase α to bind to the nuclear matrix in a form that cannot subsequently be released as discrete components, at variance with previous results obtained with the matrix prepared from regenerating rat liver.
Testing Drugs on Human Osteoarthritic Articular Cartilage
Authors: Chayen J. , Bitensky Lucille , Mehdizadeh S. , Dunham Jane , Older J. 
Published: May 2005

AbstractNew drugs are generally developed against animal models of the human disease. Before they are subjected to clinical trials it might be helpful to be able to test whether they are as effective against the disease in human tissue as they were in animals. It is proposed that this can be achieved by the use of organ maintenance culture of the human diseased tissue, the relevant biochemical parameters being measured by quantitative cytochemistry. In the present studies differences between the effect of indomethacin and of the ‘chondroprotective’ drug diclofenac sodium, on human osteoarthritic cartilage, have been measured.
Modulatory effect of dexamethasone on ornithine decarboxylase activity and gene expression: A possible post‐transcriptional regulation by a neutral metalloprotease
Authors: Nguyen‐Ba Giao , Robert Sophie , Dhalluin Stephane , Tapiero Haim , Hornebeck William 
Published: May 2005

AbstractThe intracellular effect of dexamethasone (DXME) on the activity and gene expression of ornithine decarboxylase (ODC) was studied in Syrian hamster embryo cells (SHE). The ODC activity (expressed as nmoles decarboxylated ornithine mg−1 protein h−1) was 4·61 ± 0·14 in untreated cells, whereas it increased to 14·38 ± 0·26 after 5h treatment with 1·6 × 10−7 M TPA. In contrast, DXME (2·5 × 10−5 M) reduced the ODC activity by 50 per cent to 2·35 ± 0·22. In cells co‐treated for 5 h with TPA and DXME, ODC acitivity decreased to the level of the untreated cells. However, when DXME was added 3 h after TPA treatment for 2 h, in the continuous presence of TPA, the ODC activity unexpectedly increased further to 16·44 ± 1·05. The modulation of ODC activity correlated partly with the level of ODC mRNA. Thus when cells were treated with TPA, and ODC mRNA increased threefold, whereas it decreased by 30 per cent when the cells were exposed to DXME. In TPA–DXME co‐treated cells, as in TPA pretreated cells followed by DXME for 2 h, a decrease (31·25 per cent and 12·5 per cent respectively) was observed in ODC mRNA. In turnover studies, DXME was found to increase the stability of ODC; the discrepancy between ODC activity and ODC mRNA levels could result from an inhibitory effect of the corticoid on proteolysis of ODC.Studies of lysosomal protease showed that the activities of cathepsins L, B and H decreased following TPA treatment. DXME also inhibited cathepsin L and B activities, but stimulated cathepsin H. Analysis of neutral cytosolic protease activity by gelatin and casein zymograms showed that TPA strongly stimulated the activity of a 70 kDa gelatinase. DXME was able to inhibit the induction of such cytosolic proteases under all the treatment conditions. When the cytosolic protein was incubated in vitro, at 37°C, in the presence of 2 mM CaCl2, the ODC activity decreased by 50 per cent after 30 min incubation. Further decrease was achieved when p‐amino‐phenylmercuric acetate, a protease activator, was added. Proteolytic activity was not inhibited after the addition of 10 μg ml−1 of TIMP‐1. In contrast, the addition of EDTA restored the ODC activity completely.We postulate that modification of the 70 kDa cytosolic metalloprotease activity could interact with the post‐transcriptional regulation of ODC.
Catalytic properties of DNA polymerase α activity associated with the heat‐stabilized nuclear matrix prepared from HeLa S3 cells
Authors: Martelli Alberto M. , Bareggi Renato , Narducci Paola 
Published: May 2005

AbstractWe have investigated whether or not ATP or other nucleoside di‐ and trisphosphates (including some nonhydrolysable ATP analogues) can stimulate the activity and/or the processivity of DNA polymerase α associated with the nuclear matrix obtained from HeLa S3 cell nuclei that had been stabilized at 37°C prior to subfractionation, as has been reported previously for DNA polymerase α bound to the nuclear matrix prepared from 22‐h regenerating rat liver. We have found that HeLa cell matrix‐associated DNA polymerase α activity could not be stimulated at all by ATP or other nucleotides, a behaviour which was shared also by DNA polymerase α activity that solubilizes from cells during the isolation of nuclei and that is thought to be a form of the enzyme not actively engaged in DNA replication. Moreover, the processivity of matrix‐bound DNA polymerase α activity was low (< 10 nucleotides). These results were obtained with the matrix prepared with either 2M NaCl or 0·25 M (NH4)2SO4 and led us to consider that a 37° incubation of isolated nuclei renders resistant to high‐salt extraction a form of DNA polymerase α which is unlikely to be involved in DNA replication in vivo.
Glycogen synthase, glycogen phosphorylase and α‐amylase activity in homogenates of islets of GK rats: Comparison with hepatic and pancreatic extracts
Authors: Zhang Tie‐Mei , Östenson Claes‐Göran , Malaisse Willy J. 
Published: May 2005

AbstractGlycogen accumulation in pancreatic islet cells in situations of sustained hyperglycaemia may participate in the phenomenon of so‐called B‐cell glucotoxicity. Unexpectedly, however, previously little if any glycogen was found in islet cells of non‐insulin‐dependent diabetic Goto‐Kakizaki rats (GK rats). Therefore, the activities of glycogen synthase, glycogen phosphorylase and α‐amylase were measured in islets of control and GK rats. No significant difference in enzymatic activity was observed between the control and diabetic animals. In the liver, the activity of glycogen synthase appeared even somewhat higher in GK rats than in control animals. It is concluded that the diabetic syndrome in the GK rats does not involve any major anomaly of glycogen synthase and glycogen phosphorylase activity in the liver of these animals, as well as α‐amylase, in pancreatic islets.
Taxol causes rapid gross structural rearrangement of a native microtubule bundle
Authors: Hunt Cherryl , Stebbings Howard 
Published: May 2005

AbstractTaxol is an anti‐mitotic agent now being used in the treatment of some cancers, although the manner of its interaction with the microtubular components of the cytoskeleton is still not fully characterized. Here we report the effects of taxol upon a huge, naturally occurring and experimentally amenable aggregate of parallel microtubules from the ovaries of hemipteran insects. Within seconds of exposure to taxol, the microtubule aggregate began to twist upon itself. After a few minutes this movement was complete, the drug having brought about a gross rearrangement of the microtubules, involving coiling on a massive scale. The final form assumed by the microtubule array was influenced by pH and by the presence of microtubule‐associated proteins, salt, cations, and both hydrolysable and non‐hydrolysable nucleotides. The possible mechanisms leading to this rapid structural change are considered.
Uric acid synthesis by rat liver supernatants from purine bases, nucleosides and nucleotides. Effect of allopurinol
Authors: Bleisch Siegfried , Sillero Maria A. Günther , Torrecilla Amparo , Sillero Antonio 
Published: May 2005

AbstractThe synthesis of uric acid from purine bases, nucleosides and nucleotides has been measured in reaction mixtures containing rat liver supernatant and each one of the following compounds at 1 mM concentration (except xanthine, 0·5 mM and guanosine and guanine, 0·1 mM). The rates of the reaction, expressed as nanomoles of uric acid synthesized g−1 of wet liver min−1 were: ATP, 10; ADP, 37; AMP, 62; adenosine, 108; adenine 6; adenylo‐succinate, 9; IMP 32; inosine, 112; hypoxanthine, 50; GTP, 19; GDP, 19; GMP, 27; guanosine, 34; guanine, 72; XMP, 10; xanthosine, 24; xanthine, 144. These figures divided by 55 correspond to nanomoles of uric acid synthesized min−1 per mg−1 of protein. The rate of synthesis of uric acid obtained with each one of those compounds at 0·1 and 0·05 mM concentrations was also determined. ATP (1 nM) strongly inhibited uric acid synthesis from 0·05 mM AMP (91 per cent) and from 0·05 mM ADP (88 per cent), but not from adenosine. CTP or UTP (1 mM) also inhibited (by more than 90 per cent) the synthesis of uric acid from 0·05 mM AMP. Xanthine oxidase was inhibited by concentrations of hypoxanthine higher than 0·012 mM. The results favour the view that the level of uric acid in plasma may be an index of the energetic state of the organism. Allopurinol, besides inhibiting uric acid synthesis, reduced the rate of degradation of AMP. The ability of crude extracts to catabolize purine nucleotides to uric acid is an important factor to be considered when some enzymes related to purine nucleotide metabolism, particularly CTP synthase, are measured in crude liver extracts.
Glucocorticoid‐induced changes in liver: Effect of dexamethasone administration on DNA topoisomerase I and II activities and distribution of histone H1 subtypes
Authors: Goodlad George A. J. , Clark Catherine M. 
Published: May 2005

AbstractThe activities of DNA topoisomerase I and II and the relative proportions of the histone H1 subtypes were investigated in rat liver which was undergoing hypertrophy and exhibiting increased transcriptional activity following the administration of dexamethasone. There was a rise in the level of activity of DNA topoisomerase I and a slight fall in that of DNA topoisomerase II. The relative proportions of the H1 subtypes were altered due to a preferential increase in H1.1. The results are discussed in relation to the effect of glucocorticoids on the transcription and replication of hepatic DNA.
Activation of phosphoinositide‐specific phospholipase C of rat neutrophils by the chemotactic aldehydes 4‐hydroxy‐2,3‐trans‐nonenal and 4‐hydroxy‐2,3‐trans‐octenal
Authors: Rossi Maria Armida , Di Mauro Clelia , Esterbauer Hermann , Fidale Fulvio , Dianzani Mario Umberto 
Published: May 2005

AbstractA comparison has been made between the effects of 4‐hydroxy‐2,3‐trans‐nonenal (HNE) and 4‐hydroxy‐2,3‐trans‐octenal (HOE), two lipid peroxidation products, on the basal and GTPgammaS‐stimulated activities of phosphoinositide‐specific phospholipase C (PL‐C) of rat polymorphonuclear leukocytes. PL‐C activity was determined in vitro by measuring the hydrolysis of [3H] phosphatidylinositol‐4,5‐bis‐phosphate (PtdIns‐P2) added as exogenous substrate to neutrophil plasma membranes. PL‐C was activated by concentrations of HNE ranging from 10−8 to 10−6 M both in the presence and in the absence of 2 × 10−5 M GTPgammaS; HOE stimulated the enzymatic activity between 10−11 and 10−8 M; maximal stimulation was given by 10−11 M HOE plus GTPgammaS. The aldehyde concentrations able to accelerate PtdIns‐P2 breakdown displayed a good correspondence with those which have been reported to stimulate the oriented migration of rat neutrophils. Pretreatment of neutrophils with pertussis toxin prevented the stimulation of PL‐C by 10−11 M HOE and by HOE plus GTPgammaS. Our results suggest that the chemotactic action of HNE and HOE might depend on the activation of PL‐C; furthermore a regulatory G protein appears to be involved in the acceleration of PtdIns‐P2 turnover by HOE.
Release of arachidonic acid via Ca2+ increase stimulated by pyrophosphonucleotides and bradykinin in mammary tumour cells
Authors: Enomoto Koh‐ichi , Furuya Kishio , Yamagishi Shunichi , Oka Takami , Maeno Takashi 
Published: May 2005

AbstractThe relationship between the increase of intracellular Ca2+ and the release of arachidonic acid by bradykinin and pyrophosphonucleotides was studied in cultured mammary tumour cells, MMT060562. Bradykinin, ATP, UTP and UDP induced an increase of intracellular Ca2+ and the release of arachidonic acid from phospholipids into the extracellular fluid. Release of arachidonic acid was also induced by the application of the Ca2+ ionophore, A23187. Liberation of arachidonic acid by bradykinin and ATP was reduced by mepacrine, a blocker of phospholipase A2 and W‐7, a calmodulin antagonist.It is suggested that the increase in cytosolic Ca2+‐induced release of arachidonic acid occurs through activation of calmodulin‐dependent phospholipase A2.
Increase of cyclin B by overexpression of cystatin α
Authors: Hiwasa Takaki , Ma Jun , Ike Yoshimasa , Katunuma Nobuhiko , Sakiyama Shigeru 
Published: May 2005

AbstractDegradation of cyclin B was effectively suppressed when cells were treated with ALLN (N‐acetylleucylleucylnorleucinal) which inhibits proteasome, calpain and cysteine proteinase cathepsins. In order to examine which protease degrades cyclin B, the effect of a cathepsin inhibitor, cystatin α, was investigated. The cystatin α gene was inserted into an inducible expression vector, pMSG, and transfected into NIH3T3 mouse fibroblasts. The expression of cystatin α was induced effectively in the transfected cells after treatment with dexamethasone. Overexpression of cystatin α resulted in an increase of the amount of cyclin B, suggesting that cysteine proteinase cathepsins might be involved in the degradation of cyclin B.