bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of dibutyryl cyclic AMP and theophylline on lipoprotein lipase secretion by human monocyte‐derived macrophages
Authors: Gardette J. , Margelin D. , Maziere J.C. , Bertrand J. , Picard J.
Published: July 2002

The effect of dibutyryl cyclic AMP and theophylline on lipoprotein lipase secretion was investigated after a 24 h pretreatment of human monocyte‐derived macrophages. Both the effectors decreased in a dose‐dependent manner the enzyme activity recovered in the culture medium. The decrease in lipoprotein lipase activity appeared to be related to reduced enzyme synthesis without apparent modification of its stability and half‐life and was conversely associated with an increase of lysosomal acid hydrolase activities. This effect was reversible on removal of the nucleotide. The present findings suggest that cyclic AMP may play a role in lipoprotein lipase expression in human macrophages and therefore may participate in the regulation of lipoprotein uptake by these cells, which are strongly implicated in the atherogenic process.
Determination of covalently bound myo‐inositol in bovine erythrocyte acetylcholinesterase and porcine kidney alkaline phosphatase
Authors: Taguchi Ryo , Kawase Mamoru , Ikezawa Hiroh
Published: July 2002

Bovine erythrocyte acetylcholinesterase and porcine kidney alkaline phosphatase were purified to a homogeneous state. By using gas chromatography‐mass spectrometry, we demonstrated the presence of covalently bound myo‐inositol in these purified enzymes. The quantitative data suggest that one molecule of myo‐inositol is bound to each subunit of these enzyme proteins. The covalently bound inositol was removed from these enzyme molecules by deamination with nitrous acid, suggesting the possibility that myo‐inositol is directly bound to amino sugar.
Ultrasonic studies of proton‐transfer reactions at the catalytic site of α‐chymotrypsin
Authors: Rogez Daniel , Cerf Roger , Andrianjara Razafindrabe , Salehi Seyed-Taghi , Fouladgar Hossein
Published: July 2002

Ultrasonic relaxation measurements for α‐chymotrypsin in phosphate, sulfite and arsenate buffers exhibit a high peak of absorption at neutral pH. The analysis is based on: (i) comparison of the relaxation measurements for the enzyme and for the zymogen and inhibited enzyme; (ii) X‐ray and neutron diffraction data, and high‐resolution NMR data. The ultrasonic relaxation is shown to result mainly from a proton‐transfer reaction that involves the histidine at the catalytic site (His‐57). The question is raised of whether the enhanced ultrasonic effect observed in the enzyme is indicative of a property that plays a part in the catalytic activity.
Cloning of Alu‐containing cDNAs from human fibroblasts and identification of small Alu+ poly(A)+ RNAs in a variety of human normal and tumor cells
Authors: Limborska Svetlana A. , Korneev Sergei A. , Maleeva Natalia E. , Slominsky Petr A. , Jincharadze Appolon G. , Ivanov Pavel L. , Ryskov Alexei P.
Published: July 2002

Two clones have been selected from a human fibroblast cDNA bank. By DNA sequencing the clones were shown to contain Alu elements located near the ends of the cDNA inserts. DNA of the clones was used for Northern blot hybridization analysis of a number of poly(A)‐containing RNAs from normal human tissues (brain, stomach, uterus, spleen, fibroblasts) and tumors (neurinoma, glioma, neuroblastoma, liposarcoma, adrenal cortex adenocarcinoma). All RNA samples reveal a heterodisperse distribution of Alu transcripts with discrete bands in the region of 7‐12 S RNA. The majority of these small poly(A)+ Alu+ RNAs contain Alu sequences only in one (canonical) orientation with functional signals including the split promoter for RNA polymerase III.
Electrochemical characteristics of platinum electrodes coated with cytochrome b5‐phospholipid monolayers
Authors: Zaba B.N. , Wilkinson M.C. , Taylor D.M. , Lewis T.J. , Laidman D.L.
Published: July 2002

Platinum electrodes can be coated with cytochrome b
5‐phospholipid monolayers by the Langmuir‐Blodgett technique. Cyclic voltammetry of a series of dyes shows that the coated electrodes become selective for certain electroactive species. The electron transfer reactions of negatively charged species are inhibited at the modified electrode, whereas positively charged species show enhanced reactivity compared with that at a bare metal electrode.
Counteraction by 20‐hydroxyecdysone of the effect of juvenile hormone on phosphorylation of ribosomal protein S6
Authors: Itoh Kohji , Ueno Kohji , Natori Shunji
Published: July 2002

Phosphorylation of ribosomal protein S6, induced when the fat body of Sarcophaga peregrina (flesh‐fly) larvae was incubated in vitro in the presence of 32P, was found to be suppressed by juvenile hormone. This suppressive effect of juvenile hormone was counteracted by a physiological concentration of 20‐hydroxyecdysone. Since 20‐hydroxyecdysone is known to induce phosphorylation of S6 in vivo, this reaction was suggested to be regulated by the balance of the effects of ecdysone and juvenile hormone.
The structure of the 5 S ribosomal RNA of a member of the phylum of green non‐sulfur bacteria and relatives
Authors: Van den Eynde Hilde , Stackebrandt Erko , De Wachter Rupert
Published: July 2002

The 5 S rRNA sequence was determined for the bacterium Herpetosiphon strain Senghas Wie 2. It is the first 5 S RNA sequence reported for a member of the eubacterial phylum defined by green non‐sulfur bacteria. The sequence fits into a consensus secondary structure model for eubacterial 5 S RNA. At four positions, the sequence shows substitutions with respect to strongly conserved nucleotides found in other hitherto examined eubacterial 5 S RNAs.
A plausible mechanism for large‐scale chromosomal DNA amplification in streptomycetes
Authors: Young Michael , Cullum John
Published: July 2002

Recent advances in our understanding of the structure of highly amplified DNA sequences in Streptomyces fradiae and lividans have enabled us to formulate a possible mechanism by which amplification may occur. An essential feature of the model is the generation of an amplification precursor, which comprises a circularised copy of the DNA to be amplified, attached to one arm of the chromosome by a replication fork. Multiple copies of the amplifiable DNA are generated by rolling circle replication. The model adequately accounts for many features of gene amplification in these two species, including the tendency for deletions to occur to one side, but not the other, of the amplified DNA.
Interaction of Sendai virions with resealed human erythrocyte ghosts Lateral mobility of the viral glycoproteins in the cell membrane following fusion
Authors: Henis Yoav I. , Gutman Orit
Published: July 2002

Two independent methods demonstrated that resealed human erythrocyte ghosts undergo Sendai virus‐mediated cell‐cell fusion to a much lower degree (about 4%) than intact erythrocytes, in spite of similar levels of viral envelope‐cell fusion in the two preparations. Fluorescence photobleaching recovery (FPR) showed similar lateral mobilities of the viral glycoproteins following fusion with either ghosts or whole erythrocytes. It is suggested that although viral glycoprotein mobilization in the cell membrane is essential for cell‐cell fusion, the target cell properties are also important; in the absence of the required cellular parameters, the mobilization may not be a sufficient condition.
Induction of eIF‐4E phosphorylation by the addition of L‐pyrroline‐5‐carboxylic acid to rabbit reticulocyte lysate
Authors: Mick Steven J. , Abramson Richard D. , Ray Bimal K. , Merrick William C. , Thach Robert E. , Hagedorn Curt H.
Published: July 2002

Addition of L‐pyrroline‐5‐carboxylic acid to reticulocyte lysates inhibits protein synthesis and induced phosphoproteins of 25 and 14 kDa. The 25 kDa phosphoprotein had the same M
r and pI as phosphorylated eIF‐4E. Incubation of lysates with L‐pyrroline‐5‐carboxylic acid did not alter the crosslinking of eIF‐4E to reovirus mRNA caps. These results suggest that modifications of the translational apparatus other than eIF‐4E phosphorylation may mediate the inhibitory effect seen with L‐pyrroline‐5‐carboxylic acid and/or that phosphorylation of eIF‐4E may effect functions subsequent to its interaction with the mRNA cap such as protein‐protein interactions with other cap‐specific translation factors.
EPR studies of a 9 kDa polypeptide with an iron‐sulfur cluster(s) isolated from photosystem I complex by n‐butanol extraction
Authors: Oh-oka H. , Takahashi Y. , Matsubara H. , Itoh S.
Published: July 2002

A 9 kDa polypeptide was isolated with an iron‐sulfur cluster(s) from spinach photosystem I complex [(1988) J. Biochem., in press]. Its EPR spectrum indicated that this protein was an iron‐sulfur protein similar to bacterial‐type ferredoxins. The reduction profiles and temperature dependence of its EPR signals suggested the existence of at least two iron‐sulfur clusters: the one with a lower redox potential shows similar characteristics to those of center B, while the other seems to be a degradation product of center A (or B).
The Kluyveromyces lactis KEX1 gene encodes a subtilisin‐type serine proteinase
Authors: Tanguy-Rougeau Christine , Wésolowski-Louvel Micheline , Fukuhara Hiroshi
Published: July 2002

KEX1 is a chromosomal gene required for the production of the killer toxin encoded by the linear DNA plasmid pGKL‐1 of Kluyveromyces lactis. The nucleotide sequence of the cloned KEX1 gene has been determined. The deduced structure of the KEX1 protein, 700 amino acids long, indicated that it contained an internal domain with a striking homology to the sequences of the subtilisin‐type proteinases, and a probable transmembrane domain near the carboxyl terminus. The results confirm the hypothesis that the product of the gene KEX1 of K. lactis is a proteinase involved in the processing of the toxin precursor.
Binding characteristics of complementary fibronectin fragments on artificial substrata
Authors: Lewandowska Kristine , Kaetzel Charlotte S. , Zardi Luciano , Culp Lloyd A.
Published: July 2002

Various properties have been evaluated for the binding to tissue culture substrata of proteolytic fragments of human plasma or cellular fibronectins containing complementary sequences from the individual and alternatively spliced chains, since related fragments are known to yield differing adhesive responses from cells. These studies utilize ELISA methods and a polyclonal antiserum directed to human pFN for direct measurement or an occupancy test utilizing anti‐albumin. Very related fragments (with or without an extra type III homology unit or extra domaina or b) have significantly different properties in substratum binding and such differences provide a partial explanation for alteration of cellular adhesive responses on such fragments.
Geranylpyrophosphate synthase from cell cultures of Lithospermum erythrorhizon
Authors: Heide Lutz
Published: July 2002

A prenyltransferase (EC 2.5.1.1) was isolated and partially purified from cell cultures of Lithospermum erythrorhizon. The product of the enzymatic reaction is geranyl pyrophosphate rather than farnesyl pyrophosphate.
The effect of pepstatin A, an inhibitor of the pro‐opiomelanocortin (POMC)‐converting enzyme, on POMC processing in mouse intermediate pituitary
Authors: Loh Y.Peng
Published: July 2002

In our previous studies, we have purified a unique, paired basic residue‐specific, prohormone‐converting enzyme from pituitary intermediate lobe secretory vesicles. This enzyme, an aspartyl protease, was shown to cleave the intermediate lobe prohormone, pro‐opiomelanocortin (POMC), to adrenocorticotropin, β‐endorphin and a 16 kDa NH2‐terminal glycopeptide, in vitro [(1985) J. Biol. Chem. 260, 7194–7205]. To provide some evidence that this enzyme plays a role in prohormone conversion in the intact cell, the ability of pepstatin A, an aspartyl protease inhibitor, to block POMC processing in the mouse intermediate pituitary was investigated. By the use of a radioactive pulse‐chase paradigm, [3H]POMC processing was found to be inhibited by 36.4% in pepstatin A‐treated intermediate lobes. This result is consistent with the inactivation of pro‐opiomelanocortin‐converting enzyme by pepstatin A in the intact pituitary and further supports a role of this enzyme in POMC processing in vivo.
Demonstration of Na+‐selective channels in the luminal‐membrane vesicles isolated from pars recta of rabbit proximal tubule
Authors: Jacobsen Christian , Røigaard-Petersen Hans , Sheikh M.Iqbal
Published: July 2002

Characteristics of 22Na+ fluxes through Na+ channels in luminal‐membrane vesicles isolated from either pars recta or pars convoluta of rabbit proximal tubule were studied. In NaCl‐loaded vesicles from pars recta, transient accumulation of 22Na+ is observed, which is inhibited by amiloride. The isotope accumulation is driven by an electrical diffusion potential as shown in experiments using either these membrane vesicles loaded with different anions, or an outwardly directed K+ gradient with a K+ ionophore valinomycin. The vesicles containing the channel show a cation selectivity with the order Li+ > Na+ > K+. The amiloride‐sensitive 22Na+ flux is dependent on intravesicular Ca2+. In NaCl‐loaded vesicles from pars convoluta, no overshoot for 22Na+ uptake is observed. Furthermore, addition of amiloride to the incubation medium did not influence the uptake of 22Na+ in these vesicle preparations. It is concluded that Na+ channels are only present in pars recta of rabbit proximal tubule.
PAF‐acether decreases low density lipoprotein degradation and alters lipid metabolism in cultured human fibroblasts
Authors: Mazière Jean-Claude , Mazière Cécile , Auclair Martine , Mora Liliana , Polonovski Jacques
Published: July 2002

A 24 h pretreatment of human cultured fibroblasts with PAF‐acether (PAF) induced a decrease in LDL degradation and a correlative accumulation of undegraded LDL. LDL binding was not significantly affected. Sterol and triacylglycerol synthesis from sodium acetate was enhanced whereas phospholipid synthesis decreased. Oleic acid incorporation into cholesteryl ester was markedly inhibited, whereas incorporation into triacylglycerols was increased. A decrease in the percentage of phosphatidylcholine and an increase in the percentage of phosphatidylethanolamine were found using sodium [32P]orthophosphate as precursor. These effects of PAF on LDL and lipid metabolism could be related to perturbations in membrane structure characteristics, leading to a delay in LDL delivery to lysosomes, and to modification of the activity of some key enzymes of lipid metabolism.
Reconstitution of the photosystem I complex from the P700 and Fx‐containing reaction center core protein and the FA/FB polypeptide
Authors: Golbeck John H. , Mehari Tetemke , Parrett Kevin , Ikegami Isamu
Published: July 2002

Complete restoration of electron flow from P700 to FA/FB was achieved by incubating a P700 and Fx‐containing photosystem (PS) I core protein from Synechococcus sp. 6301 with the 8.9 kDa, FA/FB polypeptide from spinach. The ESR spectrum of the reconstituted PS I complex shows nearly equal photochemical reduction of FA and FB when frozen in darkness and illuminated at 16 K. When illuminated during freezing, both FA and FB are quantitatively reduced and the spectrum is nearly indistinguishable from FA and FB in the control PS I complex. In the reconstituted PS I complex Fx is photochemically reduced only in the presence of F−
A and F−
B, and the high‐field resonance appears indistinguishable from Fx in the control PS I complex. Optical flash photolysis after extensive washing confirms the complete restoration of the P700+ [FA/FBI‐back‐reaction, indicating quantitative rebinding of the 8.9 kDA polypeptide. This procedure represents the first reconstitution of the PS I complex from a purified PS I core protein and an isolated 8.9 kDa, FA/FB polypeptide, and makes possible independent manipulation of the two subunits that carry the entire electron acceptor system of PS I.
The tertiary structure of Aspergillus saitoi minor ribonuclease (Ms) predicted from the structure of RNase T1
Authors: Flögel Rainer , Zielenkiewicz Piotr , Saenger Wolfram
Published: July 2002

Ribonuclease Ms from Aspergillus saitoi is a small acidic protein (11 714 Da) containing 106 amino acids of known sequence. Unlike other enzymes belonging to the RNase T1 family this ribonuclease is base‐unspecific. Using interactive computer graphics and energy minimisation we predicted the structure of RNase Ms on the basis of sequence homology to RNase T1 of known structure. In this report the predicted structure of this protein is presented and characterised.
Activation of c‐Ki‐ras coexists with c‐myc amplification in cells from a nude mouse tumor induced by the human breast carcinoma cell line SW 613‐S
Authors: Carloni Guido , Champ Brigitte , Vilarem Marie-Jose´ , Lavialle Christian , Cassingena Roland
Published: July 2002

In vitro transfection experiments have shown that cooperation between two different oncogenes can confer a fully malignant phenotype to primary rodent cells. We have previously reported that SW 613‐Tul cells, derived from a tumor induced in a nude mouse by the human breast carcinoma cell line SW 613‐S, showed a 30‐fold amplification of the c‐ myc gene. In the present work, we show that these cells also harbor an activated c‐Ki‐ras gene capable of inducing the formation of foci upon transfection of NIH 3T3 cells with SW 613‐Tul genomic DNA. Our results suggest that both the c‐myc and c‐Ki‐ras oncogenes, activated by two different mechanisms, may cooperate in the full expression of the tumorigenic phenotype of SW 613‐Tul cells.
Structural studies on improved crystals of the photosystem I reaction centre from Phormidium laminosum
Authors: Ford Robert C. , Pauptit Richard A. , Holzenburg Andreas
Published: July 2002

Improved crystallization methods led to the growth of large single crystals of the photosystem I reaction centre isolated from the thermophilic cyanobacterium Phormidium laminosum. Although the crystals exhibited a high degree of mosaicity, some preliminary X‐ray diffraction studies were performed. The highest order reflections found correspond to interplanar spacings of approx. 0.8 nm. In conjunction with electron microscopy of thin three‐dimensional crystals, a triclinic or monoclinic crystal system with unit cell dimensions 30 × 18 × 18 nm was assigned. In addition, our data suggest the presence of four trimeric complexes per unit cell, which may be organised as two face‐to‐face pairs.
Spectroscopic characterization of reaction center crystals from the carotenoid‐containing wild‐type strain Rhodobacter sphaeroides Y
Authors: Reiss-Husson F. , Mäntele W.
Published: July 2002

Thin three‐dimensional crystals of the photochemical reaction center from Rhodobacter sphaeroides wild‐type strain Y were investigated with microspectrophotometric methods. Absorbance and linear dichroism spectra were obtained for two crystal forms with the same type of unit cell, but grown in different morphological forms. High dichroism was found for the Qx and the Qy transitions of the bacteriopheophytin as well as for the Qy transitions of the accessory bacteriochlorophylls and the bacteriochlorophylls forming the primary electron donor. Low absorption and dichroism of the carotenoid transitions in the plane of the crystal suggests a large component out of the crystal plane. Photoactivity of the crystal was demonstrated by light‐induced charge separation. The analysis of the rates of charge recombination indicates that almost all reaction centers in the crystal (> 90%) contain the secondary electron acceptor QB.
Photo‐CIDNP study of the interaction between lac repressor headpiece and lac operator DNA
Authors: Stob S. , Scheek R.M. , Boelens R. , Kaptein R.
Published: July 2002

Lac repressor headpiece (HP) and intact lac repressor have been studied using the photo‐CIDNP method. At neutral pH histidine 29, tyrosines 7, 12 and 17 and methionine 1 are polarised. His‐29 polarisations are weaker and broader in HP59 than in HP51 indicating that the C‐terminal octapeptide in HP59 adopts a conformation that allows an interaction with His‐29. The photo‐CIDNP spectra of intact lac repressor and HP51 are very similar, showing that the same residues are accessible to the photo‐excited flavin. An equimolar mixture of HP51 and a 14 base pair lac operator fragment strongly suppresses the photo‐CIDNP effect of tyrosines 7 and 17 and abolishes the His‐29 polarisations. The results are compared with earlier photo‐CIDNP measurements on a complex of headpiece with poly[d(AT)] and with a model derived from a 2D NMR study on a lac headpiece‐operator complex.
Adenylate cyclase activity of ν‐ras‐k transformed rat epithelial thyroid cells
Authors: Colletta Giulia , Corda Daniela , Schettini Gennaro , Cirafici Anna Maria , Kohn Leonard D. , Consiglio Eduardo
Published: July 2002

The regulation of adenylate cyclase has been analyzed in normal rat thyroid cells as well as in the same cells transformed by the ν‐ras‐k oncogene. In both cell types the adenylate cyclase complex consists of the two GTP‐binding proteins, Gi and Gs, as demonstrated by the specific ADP‐ribosylation induced by pertussis and cholera toxin, respectively. The response of adenylate cyclase of the transformed cells to forskolin, pertussis toxin and cholera toxin is attenuated with respect to the control cell line. The thyrotropic hormone (TSH), that acts on normal thyroid cells in culture as a growth factor by stimulating the adenylate cyclase activity, is not able to induce DNA synthesis nor does it stimulate adenylate cyclase in ν‐ras‐k transformed cells.
Antibodies against the human cellular 3,3′,5‐triiodo‐L‐thyronine‐binding protein (p58)
Authors: Obata Toru , Fukuda Takaaki , Cheng Sheue-yann
Published: July 2002

High‐titer antibodies against a cellular thyroid hormone‐binding protein (M
r 58 000, p58) were developed by a special immunization method. To enhance immune responses, this method uses a boosting protocol in which repeated injections of small amounts of antigen are administered at 2‐day intervals. Antibodies were detected 1 week after the last injection of antigen by ELISA, Western dot blotting and immunoprecipitation. The anti‐p58 antibodies recognize p58 which is bound to the thyroid hormone. With the availability of anti‐p58 antibodies, it has become possible to study cellular localization and function.
Evidence that muscarinic potentiation of insulin release is initiated by an early transient calcium entry
Authors: Sánchez-Andrés J.V. , Ripoll Cristina , Soria Bernat
Published: July 2002

The increased insulin release induced by carbamoylcholine (CbCh) in pancreatic islets requires the presence of extracellular Ca2+. Intracellular recordings demonstrate that CbCh produces a transient increase in Ca2+ channel activity lasting from 30 to 60 s. Thereafter activity decreased to levels lower than in controls. When extracellular Ca2+ was present during this initial period, the stimulatory effects of CbCh were not different from those in which Ca2+ was present throughout. These experiments suggest that during muscarinic potentiation of insulin release extracellular calcium is only needed in the first minute.
Sex‐related difference in oxidative metabolism of testosterone and erythromycin by hamster liver microsomes
Authors: Miura Toshiaki , Komori Masayuki , Iwasaki Miyuki , Kurozumi Kimikazu , Ohta Kazuhide , Ohmori Shigeru , Kitada Mitsukazu , Kamataki Tetsuya
Published: July 2002

The activities of testosterone hydroxylases and erythromycin N‐demethylase were significantly higher in liver microsomes from female hamsters than in the male counterparts. SDS‐polyacrylamide gel electrophoresis revealed a difference in protein composition between male and female liver microsomes in the molecular mass region comprising cytochrome P‐450. Western blot analysis showed further that antibodies to rat male‐specific cytochrome P‐450 crossreacted with at least two proteins in both male and female hamster microsomes, but one of the female proteins had a different molecular mass from that of the male proteins. It is concluded that sex difference in liver microsomal cytochrome P‐450 is not restricted to rats and mice, as has previously been believed.
Human ubiquitin genes: One member of the UbB gene subfamily is a tetrameric non‐processed pseudogene
Authors: Cowland Jack B. , Wiborg Ove , Vuust Jens
Published: July 2002

The human ubiquitin gene family consists of three subfamilies. One of these, the UbB subfamily, includes a functional gene coding for a polyubiquitin protein that contains three ubiquitin copies tandemly repeated, as well as three pseudogenes of the processed type. We have now isolated a fifth human UbB type gene, different from any of the previously identified ones. This newly isolated gene is a tetrameric pseudogene which has presumably arisen by unequal crossing‐over of two ancestral trimeric alleles. Southern blotting data indicate that all members of the human UbB gene subfamily are now accounted for.
Functional residues at the active site of horse liver phosphopantothenoylcysteine decarboxylase
Authors: Scandurra R. , Consalvi V. , Politi L. , Gallina C.
Published: July 2002

Horse liver phosphopantothenoylcysteine decarboxylase (EC 4.1.1.36) is rapidly inactivated by N‐acetoacetylation with diketene following a pseudo‐first‐order kinetics: the presence of substrate quantitatively protects against this inactivation. Histidine photo‐oxidation with methylene blue or rose bengal brings about the total loss of activity. These results indicate the presence of functional lysyl and histidyl groups at the active site of the enzyme. The substrate sulphydryl group is essential for enzyme activity. Enzymatic decarboxylation is proposed to result from a combined action of the keto group of the enzyme‐bound pyruvate protonated by an essential histidine and a protonated amino group of a lysine.
Effect of structure of the initiator codon on translation in E. coli
Authors: Khudyakov Yu.E. , Neplyueva V.S. , Kalinina T.I. , Smirnov V.D.
Published: July 2002

A set of plasmids carrying different initiator codons ‐ either AUG, or GUG, or UUG, or CUG (as a control) in the hybrid gene lacIZ ‐ was constructed by using synthetic oligonucleotides. GUG and UUG codons were demonstrated to be 2–3‐times less effective than AUG in translation initiation. Furthermore, the correlation between the efficiencies of different initiator codons in translation initiation proved to vary, depending on the phase of bacterial growth. The rarely occurring usage in nature of the initiator codons GUG and UUG is supposed to be due to the particular role played by the initiator triplets in regulation of gene expression.
Glucose transporters in chromaffin cells: Subcellular distribution and characterization
Authors: Delicado E.G. , Torres M. , Miras-Portugal M.T.
Published: July 2002

The glucose transporter was identified and characterized by cytochalasin B binding in subcellular membrane fractions of chromaffin tissue. The binding was saturable with a K
d of about 0.3 μM for each subcellular fraction. The B
max capacity was 12–16 pmol/mg protein for enriched plasma membrane fractions, 6.3 pmol/mg protein for microsomal membrane preparations and 5.4 pmol/mg protein for chromaffin granule membranes. Irreversible photoaffinity labelling of the glucose‐protectable binding sites with [3H]cytochalasin B followed by solubilization and polyacrylamide gel electrophoresis from enriched plasma membrane preparations demonstrated the presence of three molecular species: 97±10, 51.5±6 and 30±4 kDa. The chromaffin granule membranes showed only a molecular species of 80±10 kDa.
Polyunsaturated fatty acids alter sterol transbilayer domains in LM fibroblast plasma membrane
Authors: Sweet William D. , Schroeder Friedhelm
Published: July 2002

Sterols are asymmetrically distributed between the leaflets of animal cell plasma membranes. Although transbilayer migration of sterols is extremely rapid, s to min, previous experimental manipulations have not altered their transmembrane steady‐state distribution. However, the effect of polyunsaturated fatty acids has not been reported. When cultured in a lipid‐free, chemically defined culture medium, LM fibroblasts do not synthesize polyunsaturated fatty acids but will incorporate polyunsaturated fatty acids into their plasma membranes if supplied in the medium. Sterol transbilayer distribution in LM plasma membranes was determined from quenching of fluorescence of dehydroergosterol by trinitrophenyl groups selectively attached to the exofacial leaflet. When cells are cultured in lipid‐free media, 28.1% of the plasma membrane sterol is located in the exofacial (outside) leaflet. In contrast, when cells are cultured with linoleate‐ or linolenate‐supplemented medium, 71.8% and 75.5% of the plasma membrane sterol is exofacial, respectively.
Occurrence of glucose polymer in undifferentiated PC12 cells
Authors: Rasilo Maija-Liisa , Yamagata Tatsuya
Published: July 2002

A large glucose polymer was found, following pronase digestion, in PC12 pheochromocytoma cells metabolically labeled with [1‐3H]galactose. The polymer was excluded from a Bio‐Gel A‐0.5 m column and adsorbed by immobilized concanavalin A‐Sepharose from which it was eluted with 10 mM α‐methylmannoside. Glucose was found to be the sole component monosaccharide. Except for those capable of degrading glycogen, no exo‐ or endo‐glycosidases cleaved the polymer. This is the first report on the occurrence of a glucose polymer in undifferentiated PC12 cells.
Methanol oxidation under physiological conditions using methanol dehydrogenase and a factor isolated from Hyphomicrobium X
Authors: Dijkstra Maarten , Frank jzn Johannes , Duine Johannes A.
Published: July 2002

Anion‐exchange chromatography of a cell‐free extract from Hyphomicrobium X yielded a cytochrome c
H‐containing methanol dehydrogenase (MDH) preparation only when all manipulations were carried out under anaerobic conditions. The properties of MDH in this preparation were unusual since significant activity could be detected in the absence of an artificial activator (NH+
4‐salts) and the absorption spectrum was clearly different from that of MDH isolated in the usual way (aerobically). After gel filtration, the activator independency was lost, but reappeared when the front fractions (containing activator‐dependent MDH) were combined with the low molecular mass fractions. Although the compound in these fractions (factor X) could replace the artificial activator in an assay at pH 9.0, it is clearly not an NH+
4‐salt. In addition, it could not be replaced by coenzyme A, tetrahydrofolate, reduced glutathione, ubiquinone Q‐9 or a number of divalent metal ions. Inactivation of factor X occurred in the presence of oxygen and cytochrome c. Using ferricytochrome c
L and MDH at pH 7.0, it was shown that factor X stimulates the methanol oxidation rate under this physiological condition.
Characterization of mouse reticulocyte free globin mRNP
Authors: Rairkar Asha , Lockard Raymond E.
Published: July 2002

Globin messenger ribonucleoprotein particles (free and polysomal) from mouse reticulocyte lysates were characterized for their mRNA composition, translational activity as well as the proteins in direct contact with them. In contrast to the homogeneous single‐peak distribution of rabbit and duck reticulocyte free mRNPs, mouse free mRNP particles were heterogeneously dispersed on the sucrose density gradient into two major domains called region I and region II. Region I appeared enriched with α‐globin mRNP and region II with β‐globin mRNP. mRNP from both regions was translationally active. Examination of lysates prepared from β‐thalassemic mice revealed a reduction of translatable βminor mRNP within region I, supporting the hypothesis of a compensatory recruitment of βminor free mRNP into polysomes in β‐thalassemic mice.
Effects of ATP depletion on the mechanism of hexose transport in intact human erythrocytes
Authors: May James M.
Published: July 2002

Depletion of ATP is known to inhibit glucose transport in human erythrocytes, but the kinetic mechanism of this effect is controversial. Selective ATP depletion of human erythrocytes by 10 μg/ml A23187 in the presence of extracellular calcium inhibited 3‐O‐methylglucose influx noncompetitively and efflux competitively. ATP depletion also decreased the ability of either equilibrated 3‐O‐methylglucose or extracellular maltose to inhibit cytochalasin B binding in intact cells, whereas neither total high‐affinity cytochalasin B binding nor its K
d was affected. Under the one‐site model of hexose transport these data indicate that ATP depletion decreases both the affinity of the inward‐facing glucose carrier for substrate and its ability to reorient outwardly in intact cells.
Phenotypic changes in 3T3 cells associated with the change of sphingolipid synthesis by a ceramide analog, 2‐decanoylamino‐3‐morpholino‐1‐phenylpropanol (compound RV538)
Authors: Okada Yoshio , Radin Norman S. , Hakomori Sen-itiroh
Published: July 2002

A culture of BALB/c 3T3 cells grown in the presence of 40 μM of the ceramide analog compound RV538 (2‐decanoylamino‐3‐morpholino‐1‐phenylpropanol) for several passages caused a substantial decrease in the level of all glycosphingolipids and an accumulation of ceramide and sphingomyelin. Associated with these chemical changes of sphingolipid composition and metabolism, the following phenotypic changes were observed: (i) loss of the cobblestone appearance at cell density saturation and development of fibroblastic appearance with partial overlapping of cells; (ii) reduction of cell growth rate; (iii) enhanced production of lactic acid; (iv) enhanced rate of glucose transport; and (v) higher incidence of large colony formation with infiltrating appearance in soft agar. Cell morphology changes, lactate pruduction, and enhanced sugar uptake were reversed by co‐culturing cells with gangliosides, particularly trisialogangliosides. Thus, these phenotypic changes mimicking those of oncogenically transformed cells are closely related to the blocked synthesis of glycolipids in these cells, whereas other changes may be caused by an accumulation of ceramide and sphingomyelin.
Comparative study on the evolution of chloroplast ribosomal 5 S RNA of a living fossil plant, Cycas revoluta Thunb
Authors: Zhou Xue-qiong , Liu Wang-yi , Wang Ming-qi
Published: July 2002

The complete nucleotide sequence of Cycas revoluta Thunb chloroplast 5 S rRNA was determined. It consists of 122 nucleotides. This is the only known 5 S rRNA sequence in Gymnospermae. It is highly homologous with chloroplast 5 S rRNA of higher plants (92–97%), but less homologous (about 54%) with those of lower plants. There is however 67% homology between Cycas and a procaryote A. nidulans. The chloroplast 5 S rRNAs of Angiospermae are nearly identical with each other (95–97%). S. oligorhize and L. minor have 100% homology among themselves. We have constructed a phylogenic tree of 5 S rRNA sequences from fifteen plant chloroplasts. The result suggests that the emergence of algae occurred at an early stage of plant chloroplast evolution and that green plants originated from green algae. This is in agreement with the classical view and other theories of molecular evolution. However there is no common ancestor in the case of Bryophyta and ferns. Among the Angiospermae, a precise evolutionary process cannot be deduced because the K
nuc values among the species are very close to each other.
Isolation of pterocarpan synthase, the terminal enzyme of pterocarpan phytoalexin biosynthesis in cell suspension cultures of Cicer arietinum
Authors: Bleß Wolfgang , Barz Wolfgang
Published: July 2002

Chickpea (Cicer arietinum L.) cell suspension cultures transferred into a medium containing yeast extract as elicitor accumulate the phytoalexins medicarpin and maackiain. Concomitant with the accumulation of the pterocarpans, a new enzyme activity is induced which catalyses the conversion of the 2′‐hydroxyisoflavanone vestitone to the pterocarpan medicarpin. Maximum enzyme activity was reached 12 h after transfer of cells and then activity declined. The soluble enzyme was partially purified and characterized as pterocarpan synthase.
Leukotriene B4 increases the lymphocyte binding to endothelial cells
Authors: Renkonen Risto , Mattila Pirkko , Leszczynski Dariusz , Häyry Pekka
Published: July 2002

Leukotrienes are potent mediators of local microvascular environment. Leukotriene B4 treatment of cultured endothelium increases the binding of lymphocytes to endothelial cell monolayers within minutes. This effect is dose‐dependent and reversible upon removal of the leukotriene. Pretreatment of lymphocytes slightly decreases the binding and pretreatment of both lymphocytes and endothelium with leukotriene B4 prior to the adherence assay did not alter the binding. These results suggest that leukotriene B4 regulates exclusively the vascular side, but not the white cell side of this interaction.
Differences in the organization of adenovirus E1A promoters are not important for their full activity
Authors: Leite José Paulo G. , D'Halluin Jean-Claude
Published: July 2002

The 5′‐E1A control regions of adenovirus (Ad) types 2, 3 and 12 were cloned upstream from the cat gene. Each serotype was characterized by unique organization of the 5′‐E1A non‐coding region. All three 5′‐non‐coding E1A regions were able to stimulate the cat gene transcription in HeLa cells. Hybrid plasmids between Ad2/Ad3 and Ad2/Ad12 revealed the same level of CAT activity as the native plasmids but the optimum activity of promoter was achieved only when its organization was not modified. These observations suggest that various nuclear factors take part in the activation process of each promoter.
Complete amino acid sequence of protein B
Authors: Rühlmann J. , Wittmann-Liebold B. , Jürgens D. , Fehrenbach F.J.
Published: July 2002

The complete amino acid sequence of protein B (= CAMP factor) of Streptococcus agalactiae has been determined. The sequence data were obtained mainly by manual sequencing of peptides derived from digestion with lysyl‐peptidase, clostripain ans Staphylococcus aureus protease and by solid phase sequencing of cyanogen bromide fragments. The protein contains 226 amino acids and has an M
r of 25 263. The sequence was compared with sequences of other Fc‐binding proteins and partial sequence homology was found between protein B and the Fc‐binding region of protein A.
The effect of inhibition of both diacylglycerol metabolism and phospholipase A2 activity on superoxide generation by human neutrophils
Authors: Muid Robert E. , Twomey Breda , Dale M.Maureen
Published: July 2002

A ‘cocktail’ consisting of an inhibitor of diacylglycerol kinase (R59022, 10 μM), an inhibitor of diacylglycerol lipase (RHC80267, 10 μM), and an inhibitor of phospholipase A2 (either 100 μM indomethacin, or 100 μM sodium meclofenamate) markedly enhanced superoxide production by human neutrophils stimulated with post‐receptor stimuli, fluoride and γ‐hexachlorocyclohexane. On the other hand, the response to the C3b/Fc receptor stimulus, opsonized zymosan, was marginally decreased whilst that to the Fc receptor stimulus, aggregated IgG, was virtually unaffected. Since the inhibitors used are deemed to inhibit the main routes of arachidonate production, these results call into question the role of arachidonate in the transduction of O−
2 generation by post‐receptor stimuli, but support a role for arachidonate in receptor‐mediated transduction.
Subunit‐specific phosphorylation of pyruvate kinase in medullary thyroid carcinomas of the rat
Authors: Rijksen Gert , van der Heijden Margreet C.M. , Oskam Ralph , Staal Gerard E.J.
Published: July 2002

Pyruvate kinase from anaplastic medullary thyroid carcinomas contains predominantly K‐type subunits, whereas pyruvate kinase from differentiated medullary thyroid carcinomas consist of M‐ and K‐type subunits in about equal proportion. In order to analyse the incorporation of phosphate in the respective isozymes after endogenous phosphorylation of cytosolic extracts with [32P]ATP, homotetrameric isozymes as well as heterotetrameric hybrids of differentiated0 tumors were resolved by affinity chromatography on Blue‐Sepharose CL‐6B and, if necessary, further purified by immunoprecipitation. SDS‐polyacrylamide gel electrophoresis of purified isozymes and subsequent autoradiography showed the incorporation of phosphate in the K4‐type isozymes, but not in the other isozymes. The phosphorylation appeared to be cAMP‐independent and occurred on a serine residue.
Phosphorylation of threonine residues on cloned fragments of the Dictyostelium myosin heavy chain
Authors: Wagle Gertrud , Noegel Angelika , Scheel Jochen , Gerisch Günther
Published: July 2002

A tail fragment of Dictyostelium discoideum myosin has been cloned and expressed as a fusion protein with the N‐terminal region of MS‐2 polymerase. The cloned fragment was phosphorylated with myosin heavy chain kinase II from aggregation‐competent D.discoideum cells that specifically phosphorylate threonine residues on the myosin tail. Phosphopeptide maps showed the same site specificity of phosphorylation with the fusion protein as a substrate as with native myosin. An improved assay for the kinase was developed in which the fusion protein is precipitated with a monoclonal antibody that inhibits polymerization of the myosin tails without preventing their phosphorylation. Sites of phosphorylation were tentatively localized to a sequence in the C‐terminal region of the heavy chain where four threonine residues are found.
Surface enhanced resonance Raman study of phenobarbital‐induced rabbit liver cytochrome P‐450 LM2
Authors: Hildebrandt Peter , Greinert Rüdiger , Stier Anton , Stockburger Manfred , Taniguchi Hisaaki
Published: July 2002

Surface enhanced resonance Raman (SERR) spectroscopy has been used to study the vibrational spectra of the heme of purified rabbit liver cytochrome P‐450 LM2 which was adsorbed on colloidal silver suspensions or on a silver electrode. Based on a comparison with the resonance Raman (RR) spectra of the ‘solute’ species the high sensitivity of the SERR technique is demonstrated. Two different features were chosen in order to determine the structural and functional integrity of the adsorbed P‐450. Both, substrate‐induced spin state changes on the oxidized P‐450 and the effect of the thiolate ligand on the oxidation state marker band ν4 in the reduced P‐450 could be observed in the SERR spectra of the adsorbed as well as in the RR spectra of the dissolved enzyme. These findings indicate that the protein structure near the substrate binding site and the coordination by thiolate are not affected by the interaction with the metal surface. Both structural elements are crucial for the function of P‐450. Thus the elementary processes of the enzymatic action of P‐450 can be investigated by this highly sensitive version of RR spectroscopy.
Steroid receptors in health and disease An Oakland University‐Serono Symposia, USA Conference, September 20–23, 1987, Meadow Brook Hall, Rochester. MI 48309‐9908, USA
Authors: Moudgil V.K.
Published: July 2002

Steroid hormones are widely known to influence expression of the hormone‐responsive genes in target cells. The action of steroid hormones is known to be mediated by their initial binding to specific ‘receptor’ proteins. The exact sequence of events, which follow hormone binding and lead to a cellular response, has remained unclear. This timely meeting has provided a forum for discussion of the recent advances in the field, which explore the structure and function of steroid receptors in health and disease.
Identification and isolation of core histones from Schizosaccharomyces pombe
Authors: Whiteside Stephen G. , Plocke Donald J.
Published: July 2002

Core histones have been isolated from Schizosaccharomyces pombe and compared electrophoretically to core histones from Saccharomyces cerevisiae and rat liver. The molecular masses of all cognate histones examined were found to be very similar as determined by SDS gel electrophoresis. Histones H3, H2A and H2B from Sch. pombe migrated almost identically to their respective counterparts from S. cerevisiae as determined by acid/urea gel electrophoresis. Two‐dimensional gel electrophoresis with a Triton X‐100 acid/urea gel in the first dimension followed by an SDS gel in the second dimension was used to separate Sch. pombe histones from contaminating ribosomal proteins.
Three actin‐binding proteins are developmentally regulated in rat liver plasma membranes
Authors: Keresztes Margit
Published: July 2002

Actin‐binding membrane proteins (linking microfilaments to the cell membrane) are involved in cytoskeleton‐membrane interactions which are supposed to undergo profound changes during cell proliferation and development. In this study 8 polypeptides were shown to bind F‐actin directly in the liver cell membranes of mature rats. From these, the abundance of three polypeptides, of 130, 50 and 36 kDa, was observed to increase considerably during postnatal development, which indicates a developmental change in the cytoskeleton‐membrane interactions.
The release of nitric oxide from denitrifying cells of Paracoccus denitrificans by an uncoupler is the basis for a new oscillator
Authors: Kučera Igor
Published: July 2002

Micromolar concentrations of the uncoupler 3‐chlorophenylhydrazonepropanedinitrile caused the release of nitric oxide from the cells of Paracoccus denitrificans respiring nitrite. At the same time, a new component with an absorption maximum at 573 nm could be observed in the difference spectra. Damped oscillations of the concentrations of the cytochrome c‐NO complex were observed during the trapping of released NO by added mammalian cytochrome c; reduced cytochrome c accumulated simultaneously in the reaction mixture.
GTP‐dependent and ‐independent activation of superoxide producing NADPH oxidase in a neutrophil cell‐free system
Authors: Ishida Kiyoshi , Takeshige Koichiro , Takasugi Shin-ichiro , Minakami Shigeki
Published: July 2002

GTP and GTP‐γ‐S enhanced several‐fold the NADPH‐dependent superoxide production induced by sodium dodecyl sulfate in a cell‐free system of pig neutrophils consisting of the membrane fraction and two cytosolic fractions separated by gel filtration. The enhanced activity was decreased by the addition of GDP in a dose‐dependent manner, but 70% of the activity in the absence of GTP remained even at 1 mM GDP. Only one cytosol fraction besides the membrane fraction was required for the activation in the presence of GTP. The cytosol fraction was analyzed by chromatography on 2′,5′‐ADP agarose and two components responsible for the GTP‐dependent and independent activation were separated. These results suggest that at least two pathways are available for the activation of superoxide production in the cell‐free system of pig neutrophils.
The expression of genes coding for positive acute‐phase proteins in the reproductive tract of the female rat
Authors: Thomas Tim , Schreiber Gerhard
Published: July 2002

High levels of ceruloplasmin mRNA were measured in the uterus of both pregnant and non‐pregnant rats. No mRNA for α2‐macroglobulin and α1‐acid glycoprotein could be detected in the uterus in contrast to the high levels of those two mRNAs found in the decidua in the mid‐gestation period. Synthesis of plasma proteins with a protective function in the decidua or uterus may be important in maintaining homeostasis at different stages of reproduction. In addition, ceruloplasmin synthesis by the uterus may be part of a system transporting copper to the fetus.