bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen starvation in a Saccharomyces cerevisiae strain deleted in the trehalose‐6‐phosphate synthase complex
Authors: Fernandes Patricia M. B. , Trugo Luiz C. , Panek Anita D. 
Published: July 2007

AbstractLittle is known about the mechanisms by which nutrient limitation leads to G1 arrest in Saccharomyces cerevisiae. We have shown that mutant cells deleted in the trehalose‐6‐phosphate synthase gene able to grow on glucose, when starved for nitrogen, did not arrest in the G1 phase of the cell cycle. We attribute this effect to an increase in the activity of cAMP‐dependent protein kinase. When grown on maltose without nitrogen they arrested properly in G1. Tests with a mutant cell deleted in the specific trehalose phosphatase proved that the presence of the trehalose precursor, trehalose‐6‐phosphate, was sufficient to trigger the negative sign during nitrogen starvation, leading the cells to arrest in the G1 phase of the cell cycle.
Effect of detergent treatment on the cross‐linking of purified chromaffin granule membranes with F‐actin
Authors: Morita Kyoji , Pollard Harvey B. 
Published: July 2007

AbstractChromaffin granule‐microfilament interaction has previously been proposed to play a potential role in the regulation of dopamine uptake into the granules as well as catecholamine secretion in the adrenal medullary cell. However, the microfilament‐binding site on the granule surface has not yet been identified. To establish the conditions for solubilization of the binding site, the effects of different‐type detergents on the cross‐linking of chromaffin granule membranes with F‐actin were examined. The cross‐linking activity was abolished by treatment of the granule membranes with deoxycholate (DOC), but not Triton X‐100 (TX100) and CHAPS. The addition of DOC‐extract decreased the viscosity of F‐actin solution, suggesting that solubilized proteins bind to F‐actin, but not cause the cross‐linking of actin filaments. These results indicate that the actin‐binding site can be solubilized from chromaffin granule membranes by DOC treatment.
Regional heterogeneity of plasma membrane proteins in rat brain
Authors: Babu Phanithi Prakasa 
Published: July 2007

AbstractPlasma membranes separated and purified from rat cerebral cortex and cerebellum showed varying protein profiles on SDS‐PAGE scanning densitometry. Using highly sensitive two‐dimensional gel electrophoresis these proteins were further resolved and an apparent regional heterogeneity of plasma membrane associated proteins was demonstrated. These proteins might be involved in region specific structural and functional aspects in the brain.
Effect of n‐3 fatty acids on VLDL production by hepatocytes is mediated through prostaglandins
Authors: Anil K. , Jayadeep A. , Sudhakaran P. R. 
Published: July 2007

AbstractThe mechanism of the hypolipidemic effect of n‐3 fatty acids was studied using isolated rat hepatocytes maintained in culture. EPA and DHA caused a significant reduction in the incorporation of 3[H]‐leucine into apoB associated with the VLDL produced by hepatocytes in culture when compared to that in presence of palmitic acid. Presence of indomethacin, an inhibitor of cyclo‐oxygenase reversed the effect of EPA on VLDL synthesis while diethyl carbamazine an inhibitor of lipoxygenase did not show any effect suggesting that the effect of EPA may be mediated through prostaglandins. This was further tested by invivo experiments where animals were fed fish oil containing diet with and without aspirin, which inhibits formation of prostaglandins. The incorporation of 3[H] ‐leucine into apo B and 14[C]‐ acetate into cholesterol of VLDL produced by heypatocytes from aspirin treated animals were significantly high. The reversal of the effect of n‐3 fatty acids by agents which inhibit the formation of prostaglandin suggests that the n‐3 fatty acids may exert their effect on VLDL production by liver cells through prostaglandins.
The effects of a selection of alkaloids on the invertase activity of some higher plants
Authors: Rojo Hebe P. , Quiroga Emma N. , Vattuone Marta A. , Sampietro Antonio R. 
Published: July 2007

AbstractThe effects of several alkaloids on the invertase activities of Ricinus communis, Solanum tuberosum, Oryza sativa and Carica papaya were studied. The following alkaloids: caffeine, berberine, strychnine, morphine, ethyl‐narceine and nomicotine, have different inhibitory effects on invertase activity. Kinetic studies of the alkaloid inhibition revealed that different alkaloids exhibited diverse types of inhibition of invertase. It was found that alkaloids form reversible complexes with invertases. However cocaine and potato glycoalkaloids were activators of some invertase. The sugar moiety of potato glycoalkaloids were also activators. It is concluded that alkaloids may be effectors of higher plant invertase activity.
Aziridinyl steroid‐induced lesions in DNA and apoptosis in promyelocytic leukemia cells
Authors: Quadri Shafat A. , Qadri Ariful N. , Ahmad Masood , Islam Shabana 
Published: July 2007

AbstractVariety of synthetic steroids are reported to be mutagenic as well as carcinogenic. The mutagenic and carcinogenic nature of these compounds have been related to their potential of being reactive to genetic material and production of reactive oxygen species. Here we have analyzed the action of aziridinyl steroid on calf thymus DNA and human promyelocytic leukemia cell line HL‐60 under in vitro conditions. Calf thymus DNA when treated with various doses of aziridinyl steroid induced a high degree of strand separation and sensitivity/susceptibility to S1 nuclease hydrolysis. The treatment also induced an increasing number of strand breaks per molecule of DNA as determined by alkaline unwinding assay. Relatively higher doses of steroid, however, displayed a reduced susceptibility to S1 nuclease hydrolysis and did not increase the number of strand breaks in DNA. Moreover, the high dose treatments result increased melting temperature and an enhanced rate of reanealing after thermal denaturation, indicating that interstrand crosslinks are induced at higher doses of steroid treatment. Moreover, steroid treatment caused cell death in human promyelocytic leukemia cell line HL‐60 and induced DNA degradation, characteristic of apoptosis. The test steroid has the ability to produce reactive oxygen intermediates (ROI) as determined by chemical methods. Incorporation of oxygen radical scavengers into the system blocked the damaging effect of steroid in calf thymus DNA and HL‐60 cells. These observations strongly suggest that aziridinyl steroid, a pharmaceutical, damages mammalian DNA and induces apoptosis by the production of ROI in the test system.
Epitope analysis of monoclonal antibodies to human Gc globulin (vitamin D‐binding protein)
Authors: Osawa M. , Kimura A. , Yukawa N. , Seto Y. , Saito T. , Tsuji T. , Takeichi S. 
Published: July 2007

AbstractGc globulin, also called vitamin D‐binding protein, is human 56 kD plasma protein. Antigenic epitopes of the protein recognized by 12 different monoclonal antibodies (MoAbs), including the previously prepared MoAb E12 of which binding to Gc is inhibited by actin, were analyzed in relation to the functional domains of the protein. To map the epitopes recognized by the respective antibody, the reactivities of the MoAbs were tested by immunoblotting against the recombinant Gc fragments expressed in E. coli cells, and then a competitive ELISA was performed. The results showed that the antibodies were classified into at least six groups. Furthermore, in addition to E12, actin inhibited the reactivity of MoAb 21, of which the epitope was located within residues Asp320 to Glu379, in an ELISA in the presence of the ligand. This result must indicate that this antibody‐binding site is near the site that interacts with actin. In contrast, no inhibitory effect by 25‐hydroxyvitamin D to any antibodies was observed. Furthermore, all antibodies, including E12 and 21, reacted with membrane‐bound Gc of lymphocytes by an immunofluorescence study, suggesting that Gc is unlikely to bind to the plasma membrane in its interaction with actin.
Isolation of thermostable phosphatase from the hyperthermophilic archaeon Thermococcus pacificus by immobilized metal affinity chromatography
Authors: Bannikova Galina E. , Varlamov Valery P. , Miroshnichenko Margarita L. , Bonch‐Osmolovskaya Elizaveta A. 
Published: July 2007

AbstractPhosphatase was isolated from cells of the hyperthermophilic marine archaeon Thermococcus pacificus by a procedure including chromatography on Butyl‐Fractogel TSK‐650 and Ni2+‐iminodiacetic‐agarose. Enzyme activity is maximal at 90°C, and the enzyme half‐life time at this temperature is 1 h. The pH optimum of phosphatase activity is 6.0. Electrophoresis under denaturating conditions yielded a subunit molecular weight of 45 kDa. On gel‐filtration on Sephacryl S‐300 HR three peak corresponding to 295, 85 and 45 kDa were observed, suggesting that the enzyme is a homohexamer.
Efects of deleting A19 tyrosine form insulin
Authors: Du Xin , Tang Jian‐Guo 
Published: July 2007

AbstractA mutant proinsulin gene was constructed through PCR mediated mutagenesis. The code of A19Tyr was deleted. The mutant proinsulin, (ΔY)19‐lys‐proinsulin [(ΔY)19KPI], was expressed in E. coli and purified. After treatment with trypsin and carboxypeptidase B, and ResourceTM Q separation, (ΔY)19‐human insulin [(ΔY)19HI] was obtained. It retains 63.6% of receptor binding activity but only 2.2% of immune activity, and shows a longer retaining time on reverse‐phase FPLC and a slower mobility by native PAGE analysis. These results suggest that the deletion of A19Tyr causes some conformational changes on insulin, which plays a minor role on the affinity of insulin to its receptor, and a major role on immunegenicity of the hormone.
Molecular cloning of a novel chemokine receptor‐like gene from early stage chick embryos
Authors: Gupta Shalley K. , Pillarisetti Kodandaram , Gray Samantha L. , Stadel Jeffrey M. 
Published: July 2007

AbstractProliferation, differentiation and regulated trafficking of cells are the hallmarks of development and embryogenesis. This led us to speculate a role for chemokines and their receptors in this process. Here, we report the molecular cloning of AvCRL1, a novel member of the G‐protein coupled receptor family from early stage 3 days old chick embryos. While the function and ligand for this receptor remain unknown, its sequence and gene structure indicates that it is most related to the family of chemokine receptors, with highest homology to the virally induced human BLR‐1 and the CXCR3 or γIP‐10/Mig‐1 receptors.
PP7, a plant phosphatase representing a novel evolutionary branch of eukaryotic protein Ser/Thr phosphatases
Authors: Andreeva Alexandra V. , Evans David E. , Hawes Chris R. , Bennett Nelly , Kutuzov Mikhail A. 
Published: July 2007

AbstractWe describe a novel protein Ser/Thr phosphatase from Arabidopsis thaliana, PP7, which is only 27‐32% identical in amino acid sequence to the known phosphatases and is the most divergent member of the PPP (PP1/2A/2B) family for today. Some structural features suggest more close relationship of PP7 to the PP5/rdgC subfamily. PP7 contains all of the residues essential for the phosphatase activity and possesses three major insertions in its presumable C‐terminal subdomain, which suggest its unique regulation and/or optimisation of its structure for interaction with specific substrates or regulators. A phosphatase structurally related to PP7 is expressed in rice. PP7 conservation between mono‐ and dicotyledonous plants may point to its essential role in the plant cell.
Effect of lipids on the conformation of an antigenic determinant for experimental autoimmune neuritis
Authors: Shin Hang‐Cheol 
Published: July 2007

AbstractThe conformation of SP‐26, the synthetic peptide (residues 53‐78) of myelin P2 protein that causes experimental autoimmune neuritis (EAN) in the peripheral nervous system, has been studied in lipid environments and in water/trifluoroethanol (TFE) mixture using circular dichroism (CD) spectroscopy and Fourier transform infra‐red (FTIR) spectroscopy. SP‐26 becomes more structured on binding with micelles formed from anionic lipids and in the presence of TFE. On the other hand, zwitterionic lipids have a denaturing effect or no effect on the conformation of SP‐26. The present results suggest that the disease‐modulating effects of various lipids are closely related to their ability to induce conformational change in the antigenic region of P2 protein.
Purification and characterization of CD38/ADP‐ribosyl cyclase from rat lung
Authors: Khoo Keng Meng , Chang Chan Fong 
Published: July 2007

AbstractPurification and characterization of CD38/ADP‐ribosyl cyctase in the rat lung tissue was performed with microsomes solubilized in Triton X‐100 and the ADP‐ribosyl cyclase was then purified using sequential column chromatography. Partially purified rat lung ADP‐ribosyl cyclase was analyzed by immunoblotting using an antibody raised against a recombinant rat CD38 and showed the presence of monomer (42 kDa) and dimer (85 kDa) under non‐reducing conditions but under reducing conditions, only the monomer was detected. Both the monomer and dimer could be eluted out in a stable manner from SDS‐PAGE and the enzymatic activity was retained by the two different forms of CD38/ADP‐ribosyl cyclase. Immunohistochemical staining showed the presence of CD38 on the bronchial epithelium and the alveoli.
Involvement of available SH groups in the heterogeneity of hemoglobin from the tortoise Geochelone carbonaria
Authors: Torsoni M. A. , Souza‐Torsoni A. , Ogo S. H. 
Published: July 2007

AbstractGeochelone carbonaria hemoglobin (Hb) was analyzed by polyacrylamide gel electrophoresis (PAGE) and purified by ion exchange chromatography on CM‐cellulose. Seven fractions were obtained using fresh Hb preparations. CM‐cellulose chromatography of Hb reacted with iodoacetamide, showed one minor (HbI) and one major band (HbII). Analysis of the molecular masses of recently collected Hb and of aged solutions determined by gel filtration showed that polymerization increased with the duration of storage. The reaction with oxidized glutathione changed the electrophoretic pattern of Hb, and highlighted the bands corresponding to glutathionyl‐Hb. The presence of these bands in fresh Hb solutions and in alkylated preparations suggests that they may occur in vivo. PAGE under dissociating conditions showed that the hemolysate contained 3 different polypeptide chains (G1, G2 and G3). Both Hb components shared the G1 globin chain with HbI containing G1 and G2 and HbII, G1 and G3 chains.
Purification of swine serum angiotensin converting enzyme with high recovery of activity using lisinopril coupled to epoxy‐activated sepharose 6B
Authors: Quassinti Luana , Miano Antonino , Bramucci Massimo , Maccari Ennio , Amici Domenico 
Published: July 2007

AbstractThe Authors describe the purification of swine serum ACE to molecular homogeneity with high recovery of activity (40 %) in a few stepsl. The purification procedure consists of affinity chromatography, using commercial activated resin (epoxy‐activated sepharose 6B) and two steps of anion exchange chromatography (Resource Q) performed at different pH (pH 9.0 and pH 6.0). Furthermore, a specific and sensitive method for the accurate quantitation of ACE activity in biological fluids was developed, based on the hydrolysis of synthetic FAPGG (N‐[3‐(2‐furyl) acryloyl] L‐phenylalanyl glycyl glycine), as substrate and following the separation of prodcts by reversed‐phase HPLC. Some kinetic parameters were determined. The Km and Kcat values for FAPGG were 0.793±0.052 mM and 5830 s‐1, respectively, and the I50 values for captopril and lisinopril, two specific ACE inhibitors, are 5.7±0.67 nM and 1.0±0.29 nM, respectively.
DNA gyrase from Streptomyces noursei and comparison with gyrases from other sources: Gyr B subunit may affect the pH‐dependence of the enzymic activity
Authors: Simon Hannelore , Zimmer Christoph 
Published: July 2007

AbstractPurified subunits of DNA gyrase from Streptomyces noursei have been obtained with relatively high yield. By comparing the activity of the reconstituted enzyme (supercoiling and cleavage reaction) with other gyrase species and hybrid enzymes it is shown that the reactivity of gyrases in vitro may differ significantly with pH, an effect not previously reported. The pH‐effects on gyrase and hybrid enzyme activity seems to be largely determined by the Gyr B protein.
Steady state levels of D1 protein and psbA transcript during UV‐B inactivation of photosystem II in wheat
Authors: Chaturvedi R. , Shyam R. , Sane P. V. 
Published: July 2007

AbstractUV‐B induced alterations in the pigment composition and photosystem II (PS II) electron transport activity was studied in laboratory grown seedlings of wheat cv. RR21. Subsequent to UV‐B exposure, the chlorophyll, carotenoids, anthocyanin and flavonoids, showed an increase in their levels. A time dependent decrease in the photosystem II electron transport activity was evident in the UV‐B treated plants. Reduction in the steady state levels of transcript of the psbA gene and its translation product the D1 protein was concurrent with the loss of PS II activity in the wheat plants exposed to UV‐B.
Surface hydrophobicity and thermal aggregation of adenylate kinase
Authors: Yan‐Ling Zhang , Xian‐Ming Pan , Jun‐Mei Zhou 
Published: July 2007

AbstractThe fluorescence probe, 8‐anilinonaphthalene‐1 sulfonate (ANS), is used to study the thermal denaturation of adenylate kinase (AK). Native AK has one ANS binding site. With increasing temperature, the ANS binding fluorescence intensity increases, showing that the enzyme undergoes a thermally induced conformational change that causes the exposure of the hydrophobic surfaces. With the exposure of the hydrophobic surfaces, the partially denatured enzyme proceeds to aggregate. This result suggests that the formation of the aggregates may be correlated with increases in the surface hydrophobicity of the intermediates. The thermally unfolded AK become resistant to aggregation in the presence of ammonium sulfate or ethylene glycol. These observations are discussed in terms of a model where the ethylene glycol enhances the hydrophobicity of the solvent and increases the solubility of the intermediates.
Inhibition of epidermal growth factor‐induced stat1 activation by lysophosphatidic acid is mediated by pertussis toxin‐sensitive g proteins and tyrosine phosphatase in human epidermoid carcinoma A431 cells
Authors: Suzuki Yasuyuki , Ozawa Yasuhiro , Murakami Kazuo , Miyazaki Hitoshi 
Published: July 2007

AbstractWe previously reported that pretreatment of A431 cells with G protein‐coupled receptor agonists which activate phospholipase C, such as lysophosphatidic acid (LPA), inhibit epidermal growth factor (EGF)‐induced formation of Stat1‐DNA complex (SIF‐C). In this study, we examined the mechanism for this phenomenon. LPA inhibited EGF‐induced but not interferon‐γ‐induced SIF‐C formation. Ligand‐dependent tyrosine phosphorylation of the EGF receptor was markedly reduced by LPA, suggesting that the reduction of the receptor phosphorylation is probably responsible for LPA‐induced inhibition of SIF‐C formation. The LPA action was prevented by pertussis toxin and the tyrosine phosphatase inhibitor vanadate, but not by the phospholipase C inhibitor U‐73122. These results demonstrate that the inhibitory effect of LPA on EGF‐induced SIF‐C formation is mediated by Gi and/or Go proteins and tyrosine phosphatase, but not by Gq proteins coupling with a phospholipase C pathway.
Involvement of p21 in mitomycin C‐induced G2 arrest in LP1‐1 cells
Authors: Kang Kyung Hwa , Oh Won Jong , Kim Won Ho , Choi Kyung Hee 
Published: July 2007

Abstractp21, a protein kinase inhibitor, was known to play a major role in the induction of G1 arrest in response to DNA damaging agent, but its role in G2/M transition was poorly understood. In this study, we investigated the involvement of p21 in mitomycin C‐induced G2 arrest in LP1‐1 cells. Treatment of mitomycin C at early G2 phase of LP1‐1 cells was found to induce G2 arrest and inhibit cdc2 kinase activity. However, expression of cyclin B and cdc2 protein were not affected by mitomycin C and an alteration of tyrosine dephosphorylation of cdc2 kinase could not be observed in the cells. On the other hand, p21 mRNA and protein were induced by mitomycin C. The binding of p21 protein to cyelin B‐cdc2 complex was increased and it was accompanied with the inactivation of cdc2 kinase after treatment of mitomycin C. These results suggest that mitomycin C‐induced G2 arrest may be mediated via increment of p21 level, elevation of binding ability with cyclin B‐cdc2 complex, and a subsequent reduction of cdc2 kinase activity.
Differential expression of mRNAS for M31 and M32, murine homologues of Drosophila heterochromatin protein 1 (HP1), during murine embryogenesis
Authors: Miyado Kenji , Sato Masahiro , Kimura Minoru 
Published: July 2007

AbstractMice have two structural homologues of the Drosophila HP1 gene, termed M31 and M32, which have two structurally conserved domains, the chromo (C) and chromo shadow (CS) domains. In Drosophila, HP1 has been isolated as one of the components of conserved chromatin structure (heterochromatin) and is thought to bind DNA indirectly by mediating formation of a complex of nuclear proteins. However, little is known about the function of M31 and M32 in mammals. In order to assess the function of the M31 and M32 proteins, Northern blot analysis was performed in mice. M32 mRNA (with approximately 1,800 nucleotides (ntds)) was expressed strongly throughout embryonic stages examined and in TT2 embryonic stem (ES) cells, while expression of M31 mRNA (with approximately 2,300 and 1,100 ntds) was strong in embryos at embryonic day 8.5 (E8.5) and in TT2 cells, but was decreased at E12.5 and thereafter. In adults, expression of M32 mRNA was strongest in brain and brain stem among tissues examined, and was relatively weak in organs including kidney, stomach, intestine and testis. The two M31 transcripts were weakly but uniformly expressed throughout the organs examined in adults. These findings suggest that M31 and M32 may play different roles in murine embryogenesis, although they have the C and CS domains and are members of the same gene family.
Vaccinia virus‐induced changes in cytokine‐regulated acute phase plasma protein synthesis by hepatoma cells
Authors: Rokita H. , Branicki W. , Wronska D. , Borysiewicz L. K. , Koj A. 
Published: July 2007

AbstractHuman hepatoma cell line, HepG2, has been infected with vaccinia virus and synthesis of plasma proteins was determined by etectroimmunoassay and corresponding mRNA's measured by Northem blotting. The inhibitory effect of the virus was dose‐ and time‐ dependent. Electrophoretic mobility shift assay revealed a decrease in C/EBP binding activities in nuclear extracts isolated from the infected hepatoma cells. Supershift analysis of the C/EBP isoforms showed α and β subunit involvement in DNA binding. The treatment of the cells with interleukin‐1, interleukin‐6, and dexamethasone at the initital stage of infection appears to delay the virally induced inhibition of host cell protein synthesis. Thus, possible “protective” role of the acute phase cytokines in viral infection is proposed.