bluuebunny/crossref_metadata_2025_split huggingface dataset:
Human placenta cytidine deaminase: proton‐linked enzyme activity and substrate binding
Authors: Vincenzetti Silvia , Angeletti Mauro , Lupidi Giulio , Cambi Alessandra , Natalini Paolo , Vita Alberto 
Published: July 2007

AbstractIn this work we focused our attention on some catalytic site requirements for human placenta cytidine deaminase (CDA). The effect of pH on substrate binding and catalysis was studied between pH 3.0 and pH 11.0. The results could be discussed postulating the presence of two classes of ionizable groups in the active site of CDA. The kinetic parameters pH‐dependence has been discussed considering the presence of four zinc atoms per each enzyme tetramer. Furthermore fluorescence studies on the enzyme and on enzyme‐inhibitor complexes, examined by using polar and non polar quenchers, allowed to define the substrate(inhibitor)‐dependent accessibility of the tryptophan‐containing pocket on each CDA monomer.
Heat treated myosin does not bind ATPase ‐ inhibiting antibodies
Authors: Gröschel‐Stewart Ute , Christian Anna‐Luise , Mestan Jürgen 
Published: July 2007

AbstractPolyclonal antibodies to native chicken pectoral fast‐twitch myosin are directed to all subfragments of the molecule (S1, S2 and LMM), as seen in the ELISA and Western blotting techniques. The antibodies inhibit the Ca2+‐activated myosin ATPase. Absorption of the antibodies with native myosin abolishes these reactions. Heat treatment of myosin for 2h at 40°C will inactivate myosin ATPase and alter its antibody binding pattern: the binding of antibodies to the rod fractions is reduced, that to the globular head (S1) completely abolished. Thus, these antibodies are useful as sensitive probes for the structural integrity of the myosin head.
Heterogeneous nuclear RNP protein A1‐arginine methylation during HCT‐48 cell cycle
Authors: Park Seung Hee , Park Gil Hong , Gu Hyunmin , Hwang Woo‐Ik , Lim In Kyoung , Paik Woon Ki , Kim Sangduk 
Published: July 2007

AbstractProtein methylase I (protein‐arginine N‐methyltransferase) was examined in HCT‐48 cells, synchronized by serum deprivation and hydroxyurea treatment. The enzyme activity to methylate the added hnRNP protein A1 increased about 2‐fold from G0 to S phase, and then decreased during G2/M phase. The enzymatically [methyl‐3H]‐labeled hnRNP protein A1 was identified by SDS‐PAGE/fluorography, and the products were identified as NG‐monomethylarginine and NG,NG‐dimethyl‐(asymmetric)arginines by HPLC. Among endogenous proteins, the 20‐kDa species in the extract was most intensely [methyl‐3H]‐labeled. This 20‐kDa methylation was markedly inhibited by the addition of exogenous hnRNP protein A1, indicating that these two substrates compete for the same protein methylase. The possible role of this post‐translational modification has been discussed.
The activity of branched‐chain α‐keto acid dehydrogenase complex in rat digestive tracts: Effects of dietary protein and exercise
Authors: Tsukamura Midoriko , Goto Hidemi , Arisawa Tomiyasu , Hayakawa Tetsuo , Kobayashi Rumi , Nakai Naoya , Murakami Taro , Sugiyama Satoru , Shimomura Yoshiharu 
Published: July 2007

AbstractBranched‐chain α‐keto acid dehydrogenase complex is the rate limiting enzyme in catabolism of branched‐chain amino acids. In this study, we examined effects of dietary protein and exercise on the complex activity in digestive tracts (stomach, small intestine and colon) of rats. Rats were fed a high (30%) or low (8%) protein diet for 3 weeks and a half of rats in each diet group was exercised by 85 min running just prior to sacrifice on the final day of the experiment. Total and actual (active form) activities of the complex were markedly high in stomach compared to other two tissues and the actual activity in stomach was significantly elevated by exercise only in rats fed the high protein diet. Both total and actual activities in colon were only a few percentage of those in stomach, and those in small intestine was further less. These results suggest that rat stomach is the tissue active in catabolism of branched‐chain amino acids, which is promoted by combination of high protein diet and exercise.
The structural analysis of the O‐glycans of the jacalin‐bound rabbit immunoglobulin G
Authors: Kabir S. , Gerwig G. J. 
Published: July 2007

AbstractRabbit immunoglobulin G (IgG) is a sialoglycoprotein (2.4% carbohydrate), containing both N‐glycolyl (Neu5Gc) and N‐acetyl (Neu5Ac) neuraminic acids in a ratio of 87:13. A small fraction of rabbit IgG (about 25% of total IgG) bound to jacalin as demonstrated by affinity chromatography. The jacalin‐bound rabbit IgG contained O‐linked glycans which were liberated from the protein by β‐elimination and isolated. Two O‐glycan structures were determined by 1H‐NMR spectroscopy, as being Neu5Gc(α2‐3)‐Gal (β31‐3)‐GalNAc‐ol and Neu5Ac(α2‐3)‐Gal(β1‐3)‐GalNAc‐ol in a ratio of 83…n17.
The priming effects of some human interleukins on the production of leukotrienes by calcium ionophore stimulated leukocytes
Authors: Mansour Mahmoud , EL‐Ahmady Omar , Motawi Tarek 
Published: July 2007

AbstractThis study demonstrates the changing levels of leukotrieneB4 (LTB4) and leukotrieneC4 (LTC4) generated by human white blood cells primed with different human interleukins IL‐3, IL‐5, IL‐6, IL‐8 and with human hematopoietic growth factor granulocyte‐macrophage colony stimulating factor (GM‐CSF). Preincubation of white blood cells at 37°C for 30 min with different human interleukins significantly increased leukotriene production in white blood cells preincubated with diluent control while IL‐3 was without priming effects. Addition of exogenous arachidonic acid to non primed white blood cells increased the production of leukotrienes in response to the calcium ionophore (A23187). The enhancement of the leukotrienes production by white blood cells stimulated by A23187 was only observed when the cells stimulated for periods of 2 min or less. The results reveal that GM‐CSF, IL‐4, IL‐6 and IL‐8 belong to particular set of cytokines with potent modulating effect on inducing inflammatory mediators released by white blood cells, while IL‐3 was ineffctive.
Nucleotide sequence of cDNA fragments coding for the FAD‐, glycerophosphate‐ and calcium‐binding domains of human islet mitochondrial glycerophosphate dehydrogenase
Authors: Novials Anna , Franco Carmen , Malaisse Willy J. , Gomis Ramon 
Published: July 2007

AbstractThe cDNA fragments coding for the FAD‐, glycerophosphate‐ and calcium‐ binding domains of mitochondrial glycerophosphate dehydrogenase (mGDH were synthetized using RNA extracted from freshly isolated pancreatic islets of a normal subject and two‐non‐insulin‐dependent diabetic patients. Single strand conformation polymorphism analysis of the PCR products yielded the same mobility as control cDNA probes. Likewise, the nucleotide sequence and corresponding amino acid sequence were identical to the normal gene bank sequence. These findings argue against the presence, in pancreatic islets, of an mGDH isoform distinct from that previously characterized in extrapancreatic organs.
Diminished response to food deprivation of the rat brown adipose tissue mitochondrial uncoupling system with age
Authors: Garcia‐Palmer Francisco J. , Pericas Jordi , Matamala Juan C. , Puigserver Pere , Bonet María L. , Palou Andreu , Gianotti Magdalena 
Published: July 2007

AbstractThe aim of the present work is to investigate the effect of starvation on brown adipose tissue thermogenic activity with aging. Interscapular brown adipose tissue from female Wistar rats of different ages was used; half of them were fed and the other half were starved for 24 hours. Mitochondria were isolated and mitochondrial protein content, GDP‐binding, Cytochrome‐c Oxidase activity and uncoupling protein levels were measured. Results show a decrease of all studied parameters, indicating a diminished thermogenic activity with age. The response to starvation is almost the same in all the parameters studied: a general reduction with starvation and a progressive disappearance of this response to starvation with aging. On the whole, these results would indicate a deficient regulation of brown adipose tissue thermogenic activity in old animals, as it happens in other animal models with an alterated thermogenesis.
Catalytic and physico‐chemical characteristics of goat spleen cathepsin B
Authors: Agarwal Sudhir K. , Choudhury Santanu D. , Lamsal Madhav , Khan M. Yahiya 
Published: July 2007

AbstractTo improve the level of purity of cathepsin B, we have modified the published procedure [Agarwal, S.K. and Khan, M.Y. (1987) Biochem. Int. 15, 785‐792] by incorporating CM‐Sephadex ion exchange chromatography and chromatofocusing. The enzyme thus isolated could be resolved into one 26 kDa major and a minor 27 kDa protein bands on SDS‐PAGE. The two components, however, could not be separated by gel filtration and they eluted, in a single peak corresponding to a molecular mass of 28.1 kDa . Among the various substrates tested, Z‐Phe‐Arg‐MCA with a Km of 0.058 mM and hemoglobin with a Km of 1.449 μM were the most preferred synthetic and protein substrates respectively. It was found to be a glycoprotein with an acidic pI of 4.8. The enzyme was activated by various thiol‐reducing reagents and inhibited by cysteine proteinase inhibitors, divalent cations, lysyl group modifiers, anti‐inflammatory drug and denaturing agents. The hydrodynamic behaviour of cathepsin B suggested a compact and globular conformation. Immunodiffusion studies with anti‐goat cathepsin B indicated a tissue/species dependence.
Modulation of the electrophoretic ATP‐induced K ‐transport in yeast mitochondria by ΔpH
Authors: Roucou Xavier , Manon Stéphen , Guérin Martine 
Published: July 2007

AbstractThe modulation of the ATP‐induced K+‐transport pathway of the yeast inner mitochondrial membrane by ΔpH was investigated in two ways. First, the inhibitory effect of phosphate was compared to the effect of other permeant acids, demonstrating that a part of the effect of phosphate was linked to its electroneutral transport down ΔpH. However, an additional effect specific for phosphate also occured inside the matrix. Second, the stimulation of the respiration by ATP in the presence of K+ was compared to the effects of the protonophore C1CCP2 and of the K+‐ionophore valinomycin. Quite unexpectedly, the effect of ATP looked more like the effect of CICCP than the effect of valinomycin. This and previous results (Manon et al., Biochimica et Biophysica Acta 1231, 282‐288 (1995)) show that the rate of electrophoretic K+‐entry is limited by the rate of electroneutral K+‐exit via the K+/H+ exchange and is therefore ΔpH‐dependent.
Determination of 8‐hydroxy‐deoxyguanosine formation in rat organs: Assessment of paraquat‐evoked oxidative DNA damage
Authors: Tokunaga Itsuo , Kubo Shin‐ichi , Mikasa Hiroaki , Suzuki Yasuo , Morita Kyoji 
Published: July 2007

AbstractParaquat has previously been shown to cause the oxidative damage to DNA in variety of cells and tissues. However, although paraquat‐evoked strand breaks has been extensively studied to assess the DNA damage, the effect of paraquat on base modifications, another marker for the oxidative damage, has not yet been investigated. To further characterize paraquat‐evoked DNA damage, the effect of paraquat on 8‐hydroxy‐deoxyguanosine (8‐OH‐dG) formation in various rat organs was examined. Paraquat markedly increased 8‐OH‐dG contents in various organs, particularly in brain, lung and heart, and this increase reached the maximum levels at 5 days after the drug administration. In contrast, the formation of 8‐hydroxy‐guanosine (8‐OH‐G), a marker for the oxidative damage to RNA, was not significantly affected by paraquat. These results indicate that paraquat causes base modifications as well as strand breaks as a consequence of the oxidative damage to DNA.
A study of the Na /H antiport in the archaeon Methanobacterium thermoautotrophicum strain ΔH
Authors: Majernik Alan , Smigán Peter , Greksák Miloslav 
Published: July 2007

AbstractThe ability of the cells of Mb. thermoautotrophicum strain ΔH to generate a proton gradient (driven by a concentration gradient of sodium ions) at pH 6.8 as well as at pH 8 was demonstrated. The electrogenic Na+/H+ antiport responsible for this process was shown to be inhibited by EIPA and also by DCCD. Artificially increasing of intracellular concentration of Ca2+ in these cells enhanced the Na+/H+ antiport activity, while the lowering of external Ca2+ by EGTA significantly decreased this activity. The apparent Km values for Na+ about 14 and 3 mM at pH 6.8 and 8, respectively, and Vmax about 214 (pH 6.8) and 155 (pH 8) ΔQ/min per mg of cell proteins, respectively, were calculated. It is concluded that the described processes are mediated by the Na+/H+ antiporter which might be a clue to the adaptive bioenergetic behaviour of the cells of Mb. thermoautotrophicum strain ΔH under the different physiological conditions.
Potentiation by its esterification of the inhibitory action of 2‐deoxy‐D‐glucose on D‐glucose metabolism and insulinotropic action
Authors: Vanhoutte C. , Kadiata M. M. , Sener A. , Malaisse W. J. 
Published: July 2007

AbstractIt was recently reported that selected esters of D‐glucose are more efficiently metabolized and display a greater insulinotropic action in pancreatic islets than the unesterified hexose. Likewise, in the present study, the inhibitory action of 2‐deoxy‐D‐glucose tetraacetate upon D‐glucose metabolism in rat erythrocytes and pancreatic islets was found to be more pronounced than that of unesterified 2‐deoxy‐D‐glucose. At a concentration of 10 mM, the ester also inhibited more severely than unesterified 2‐deoxy‐D‐glucose the release of insulin evoked by D‐glucose in isolated islets. It is proposed that 2‐deoxy‐D‐glucose tetraacetate represents a useful tool to facilitate the intracellular delivery of the glucose analog and to increase its efficiency as a potential therapeutic agent.
Sphingomyelinase increases 2‐deoxyglucose uptake and glucose metabolism of human platelets
Authors: Vasta Valeria , Meacci Elisabetta , Romiti Elena , Farnararo Marta , Bruni Paola 
Published: July 2007

AbstractRecent studies have shown that the sphingomyelinase (SMase)‐catalyzed hydrolysis of sphingomyelin (SM) represents an important cell signalling pathway. Control of SMase activity appears to be crucial for the regulation of multiple biological events in different cell systems; in particular, SMase activity appears to be involved in the control of vascular functions and in atherogenic events. Here we report that SMase treatment of human platelets significantly increases 2‐deoxyglucose uptake by decreasing Km value of sugar transport and increasing sugar diffusion. In addition SMase treatment enhances basal glycolytic flux of platelets as well as the stimulation of the flux induced by suboptimal concentration of thrombin. The present study demonstrates that exposure of platelets to SMase, which may take place in vivo in physiological and/or in pathological conditions, modifies biochemical parameters of resting and stimulated platelets which are essential for cell physiological role.
High affinity bradykinin binding to human inflammatory cells
Authors: Rajasekariah Poornima , Warlow Robert S. , Walls Ronald S. 
Published: July 2007

AbstractSpecific direct bradykinin (BK) binding and competitive inhibition was detected in human neutrophil and peripheral blood mononuclear cell (PBMC) detergent solubilized extracts and purified plasma membranes using in vitro radioreceptor ligand binding. Scatchard analyses of [125I]‐BK binding revealed an equilibrium dissociation constant (Kd) of 2.9×10‐11 M for neutrophils and 5.6×10‐11 M for PBMC using [des‐arg9]‐BK a B1 agonist; 2.6×10‐11 M for neutrophils, 6.2×10‐11 M for PBMC with BK a B2 agonist; 5.4×10‐11 M for PBMC using Lys‐BK a B2 agonist. The number of binding sites (Bmax) was calculated to be 0.113 fM/μg protein (720 receptors per cell) for neutrophils and 0.200 fM/μg protein (1289 receptors per cell) for PBMC with the B1 agonist while with the B2 agonists the values were 0.128 fM/μg protein (818 receptors per cell) for neutrophils and 0.157 fM/μg protein (1005 receptors per cell) for PBMC with BK, and 0.293 fM/μg protein (1870 receptors per cell) with Lys‐BK for PBMC. In a competitive binding inhibition assay using neutrophil and PBMC glycerol purified plasma membranes, high affinity binding in the nanomolar range was detected to Lys‐BK and BK but with [des‐arg9]‐BK a 10‐100 fold lower order affinity was observed this being indicative of pharmacologically defined B2 characteristics.
Inhibition of platelet aggregation by L‐arginine and polyamines in alloxan treated rats
Authors: Méndez J. D. , Zarzoza E. 
Published: July 2007

AbstractThe antiaggregating effect of L‐arginine and polyamines (putrescine, spermidine and spermine) was studied in platelets of normal and diabetic rats (120 mg/Kg alloxan, i.p.). This effect was compared with insulin. The assays of platelet aggregation were carried out using platelet‐rich plasma (PRP) obtained from both groups of animals. The platelet aggregation test were first standardized by using PRP obtained from human health donors. 2.5 μmoles/ml ADP, 250 μmoles/ml epinephrine and 0.4 U/ml of thrombin were used as inductors of platelet aggregation. 60% of inhibition was observed with 10 μM of L‐arginine or polyamines in PRP of normal rats, and 50% with PRP of diabetic rats when thrombin was used as an agonist. These results show that L‐arginine and the polyamines putrescine, spermidine and spermine have an antagonist action in platelet aggregation. In addition, we demonstrated the platelet arginase activity not only in rat platelets but also in human, was less under hyperglycaemia. The activity of this enzyme has been associated with polyamine synthesis, required to regulate platelet function.
Sucrose‐phosphate synthase in tree species: light/dark regulation involves a component of protein turnover in Prosopis juliflora (SW DC)
Authors: Sinha Alok K. , Shirke P. A. , Pathre Uday , Sane P. V. 
Published: July 2007

AbstractLight dependent modulation of sucrose‐phosphate synthase activity (SPS; EC 2.4.1.14) was studied in a tree species, namely Prosopis juliflora. In this paper we demonstrate that cycloheximide, an inhibitor of cytoplasmic protein synthesis, when fed to detached leaves of P. juliflora through transpiration stream in the dark or in light completely prevents in vivo light activation of Vlim and Vmax activities of SPS. In case of spinach, however, cycloheximide feeding affects only Vlim activity while Vmax activity remained unchanged. In contrast, chloramphenicol, an inhibitor of protein synthesis in chloroplast has no effect on the light activation of SPS in Prosopis. The treatment with cycloheximide showed slight reduction in the rate of O2 evolution indicating that cycloheximide had very little effect on overall photosynthesis. These results indicate that short term protein turnover of the SPS protein and some other essential component(s) (e.g., a putative protein that modifies SPS activity) is one of the primary steps in a complex and unique regulatory cascade effecting the reversible light activation of SPS.
Metabolic inhibitors as tools to delineate participation of distinct intracellular pathways in enhancement of lactose‐induced dissociation of neutrophil and thymocyte aggregates formed by mediation of a plant lectin
Authors: Timoshenko A. V. , Gorudko I. V. , Kaltner H. , Cherenkevich S. N. , Gabius H. ‐J. 
Published: July 2007

AbstractSignaling processes in the course of the formation of the lectin‐mediated aggregates may partake in conveying enhanced stability to the cell clusters. To prove the validity of this reasoning in a model, we have studied the impact of addition of three metabolic inhibitors (N‐ethylmaleimide, nordihydroguaiaretic acid, and trifluoperazine on lactose‐dependent dissociation of cell aggregates, formed in the presence of the galactoside‐binding mistletoe lectin. Using both human neutrophils and rat thymocytes to avoid measurement of responses restricted to a single cell type, an enhanced dissociation of lectin‐formed cell aggregates was observed, when lactose and an inhibitor were present. Among the tested inhibitors, nordihydroguaiaretic acid and N‐ethylmateimide were more potent enhancers of cell dissociation than trifluoperazine. These results suggest that biosignaling pathways connected with lipoxygenase activity as well as the level of intracellular sulfhydryl groups confer further stability to lectin‐dependent cell aggregates. The systematic evaluation of inhibitors for defined activities is thus suggested as a tool to disclose the nature and the contribution of individual signaling mechanisms to post‐binding effects following lectin‐initiated cell contact formation.
Isolation and characterization of anti morphine analgesic peptide from canine brain
Authors: Chert ShuJuan , Chen YuZhen , Wang JingYan 
Published: July 2007

AbstractThe anti‐morphine peptide from canine brain which is homologous to α subunit of hemoglobin of canine, has been isolated and characterized. The canine brain was homogenized and extracted in 0.1 M acetic acid. The supernatant was collected, and purified by chromatography of Sephadex G‐50 and ion‐exchange and RP‐HPLC. A polypeptide was then obtained, which is termed as AMP5. It shows prominent anti‐morphine analgesic activity. AMP5 has an apparent molecular mass of 10.23kD. The isoelectric point was estimated to be around pH 6.7 by IEF. The amino acid composition of AMP5 and sequence of the N‐terminal 50 amino acid residues was determined.
Unusual AMP‐deaminase solubilization from teleost fish white muscle
Authors: Lushchak Voiodymyr I. , Smirnova Yulia D. , Storey Kenneth B. 
Published: July 2007

AbstractA previous study described an unusual influence of neutral salts on the behavior of trout muscle AMP‐deaminase (AMPD) in its interactions with subcellular particulate matter (Lushchak and Storey 1994, Fish Physiol. Biochem. 13: 356‐368). The present study shows that this behavior is also shared by the muscle enzyme of two other fish species, sea scorpion (Scorpaena porcus) and corb (Sciena umbra), indicating that this describes a principle for AMPD interaction with cellular particulate material. AMPD binding to particulate matter increased with increasing KC1 concentration through the physiological range (100‐200 mM), but at higher salt concentrations the amount of bound enzyme was reduced. The pattern of binding was not influenced by hydrophobic interactions since addition of the nonionic detergents, Triton X‐100 or Tween‐80, did not alter the distribution of bound versus free enzyme although both detergents, at low concentrations, enhanced enzyme maximal activity. AMPD binding to particulate matter was also influenced by pH, the amount of free enzyme rising by nearly 3‐fold as pH fell within the physiological range from 7.5 to 6.5. It is concluded that neither electrostatic nor hydrophobic forrces alone can account for the unusual solubilization of AMPD from fish muscle and it is possible that the effect is also related to ion‐induced conforlnational changes in the structure of AMPD and/or of the myosin to which the enzyme binds.
Characterization of a helicase, DHEL III, from Drosophila melanogaster embryonic nuclei
Authors: Ristic Dejan , Todorovic Vesna , Kojic Snezana , Stefanovic Dragana 
Published: July 2007

AbstractNuclear extracts prepared from Drosophila preblastoderm embryos contain a nucleoside 5′‐triphosphate‐dependent helicase that unwinds circular or linear partial duplex DNA substrates and moves along the DNA in 3′ to 5′ direction. The helicase reaction is supported with both nucleoside and deoxynucleoside 5′‐triphosphates and requires divalent cations. Optimum activity in vitro is achieved with dATP or ATP and with MgCl2. In glycerol density gradients, embryonic enzyme migrates as a single peak of around 90kDa and it is the most prominent DNA‐unwinding activity detectable in nuclear extracts prepared from embryos 0‐2 hours after egg laying. In embryos collected 2‐4 hours after egg laying this DNA unwinding activity increases and then gradually decreases in embryos collected 4‐8 and 8‐16 hours after egg laying.