bluuebunny/crossref_metadata_2025_split huggingface dataset:
Potentiation and suppression of mouse liver cytochrome P‐450 isozymes during the acute‐phase response induced by bacterial endotoxin
Authors: STANLEY Lesley A. , ADAMS David J. , LINDSAY Robert , MEEHAN Richard R. , LIAO Warren , WOLF C. Roland 
Published: March 2005

Infection and inflammation are known to affect the metabolism and disposition of drugs and carcinogens. We report a detailed study of the effects of bacterial endotoxin on the constitutive and inducible expression and activities of cytochrome P‐450 isozymes from families P‐4501, P‐450IIB, P‐450IIC and P‐450III. In general high doses of high endotoxin caused very marked suppression of P‐450 isozymes and associated activities. However, this effect was differential, the expression of certain isozymes being only slightly reduced whereas others were suppressed to almost undetectable levels. Low doses of endotoxin also gave differential effects on cytochrome P‐450 expression. Of particular interest was the very marked potentiation of the inductive effect of both 3‐methylcholanthrene and phenobarbital. In the case of 3‐methylcholanthrene the 10‐fold induction of activity was increased to 24‐fold by concomitant endotoxin administration. In this regard it was interesting that 3‐methylcholanthrene was an effective inducer of a wide variety of acute‐phase proteins including metallothionein, serum amyloid A, fibrinogen and hemopexin.These data show that endotoxin, and therefore bacterial infection and inflammation, can have profound and differential effects on components of the cytochrome‐P‐450 monooxygenase system which could result in significant changes in susceptibility to the effects of drugs, chemical toxins and carcinogens.
Species differences in the molecular characteristics of vasoactive‐intestinal‐peptide receptors in the pancreas from rat and guinea‐pig
Authors: SVOBODA Michal , POLOCZEK Piotr , WINAND Jacques , ROBBERECHT Patrick , CHRISTOPHE Jean 
Published: March 2005

The receptors for vasoactive intestinal peptide (VIP) present in dispersed acini and membranes from rat and guinea‐pig pancreas differed in selectivity pattern, i.e. in the displacement of [125I]iodo‐VIP by parent peptides, as revealed by a VIP:secretin IC50 ratio at least ten times higher in rat than in guinea‐pig preparations. The molecular properties of these VIP receptors were therefore investigated.
When comparing six succinimidyl ester cross‐linkers, bis[2‐(succinimidooxycarbonyloxy)ethyl]sulfone proved to be the most universal [125I]iodo‐VIP cross‐linker for all pancreatic preparations.
In intact rat acini the main labeled peptide had an Mr of 80000, whereas the main labeled peptide in intact guinea‐pig acini was a smear of Mr 160000. In both rat and guinea‐pig pancreatic membranes, the main labeled peptide ([125I]iodo‐VIP–binding‐protein complex) had an Mr of 66000. In addition, variable proportions of an Mr‐80000 peptide and an Mr‐83000 peptide were visualized in, respectively, rat and guinea‐pig membranes. The labeling of all peptides was suppressed by VIP and by GTP. Reducing conditions allowed only a better resolution, making the presence of intermolecular disulfide bridges unlikely.
Taking into account the Mr of VIP it is thus plausible that the main native Mr‐77000 VIP‐binding site present in rat acini could be easily converted to an Mr‐63000 peptide during membrane preparation, while in guinea‐pig acini Mr‐80000 and/or Mr‐63000 VIP‐binding sites were often closely associated with another membrane component in the native state. These molecular differences between VIP receptors in intact rat and guinea‐pig acini are in keeping with functional differences.
13C‐NMR study of glycerol metabolism in rabbit renal cells of proximal convoluted tubules
Authors: JANS Arnold W. H. , WILLEM Rudolph 
Published: March 2005

Perchloric acid extracts of rabbit renal proximal convoluted tubular cells (PCT) incubated with [2‐13C]glycerol and [1,3‐13C]glycerol were investigated by 13C‐NMR spectroscopy. These 13C‐NMR spectra enabled us to determine cell metabolic pathways of glycerol in PCT cells. The main percentage of 13C‐label, arising from 13C‐enriched glycerol, was found in glucose, lactate, glutamine and glutamate. So far it can be concluded that glycerol is a suitable substrate for PCT cells and is involved in gluconeogenesis and glycolysis as well in the Krebs cycle intermediates.Label exchange and label enrichment in 13C‐labelled glucose, arising from [2‐13C]glycerol and [1,3‐13C]glycerol, is explained by label scrambling through the pentose shunt and a label exchange in the triose phosphate pool. From relative enrichments it is estimated that the ratio of the pyruvate kinase flux to the gluconeogenetic flux is 0.97:1 and that the ratio of pyruvate carboxylase activity relative to pyruvate dehydrogenase activity is 2.0:1. Our results show that 13C‐NMR spectroscopy, using 13C‐labelled substrates, is a powerful tool for the examination of renal metabolism.
Regeneration after cardiotoxin injury of innervated and denervated slow and fast muscles of mammals
Authors: d'ALBIS Anne , COUTEAUX René , JANMOT Chantal , ROULET Agnès , MIRA Jean‐Claude 
Published: March 2005

The regeneration of adult rat and mouse slow (soleus) and fast (sternomastoid) muscles was examined after the degeneration of myofibers had been achieved by a snake venom cardiotoxin, under experimental conditions devised to spare as far as possible the satellite cells, the nerves, and the blood vessels of the muscles.Three days after the injury, no myosin was detectable in selected portions of the muscles. New myosins of embryonic, neonatal, and adult types started to be synthesized during the following two days. Adult myosins thus appeared more precociously than in development, which implies that the synthesis of myosin isoforms during regeneration does not entirely ‘recapitulate’ the sequence of myosin transitions observed during normal development.Two weeks after the injury, the isomyosin electrophoretic pattern displayed by regenerated muscles was already the same as that of control muscles; the normal adult pattern was therefore expressed more rapidly in regenerating than in developing muscles.Except for the synthesis of the slow isoform which was generally inhibited in denervated muscles, the same types of myosins were expressed during the early stages of regeneration in denervated as in innervated muscles; long‐term denervation prevented however the qualitative and quantitative recovery of the normal myosin pattern.
The protection by ascorbate and glutathione against microsomal lipid peroxidation is dependent on vitamin E
Authors: WEFERS Heribert , SIES Helmut 
Published: March 2005

Lipid peroxidation of rat liver microsomal fractions was monitored by its low‐level chemilunminescence in preparations from controls and vitamin‐E‐deficient animals. Measurements were made (a) of the duration of the lag phase τ0 after initiation with NADPH/iron‐ADP and (b) of the slope of the chemiluminescence increase.In microsomes with normal vitamin E (α‐tocopherol) level the lag phase τ0 was substantially increased by ascorbate; in contrast, even an enhanced peroxidation was observed with ascorbate in vitamin‐E‐deficient microsomes. Therefore, the ascorbate‐mediated protection of microsomal membranes against lipid peroxidation is dependent on vitamin E in the membrane. In vitamin E deficiency the pro‐oxidant effect of ascorbate was abolished when glutathione (GSH) was present.Likewise, GSH does not prolong the lag phase τ0 in vitamin E deficiency. However, GSH (but not cysteine) exerts an antioxidant effect both in controls and in vitamin E deficiency by decreasing the slope of the chemiluminescence increase during lipid peroxidation. The involvement of GSH in an enzyme‐dependent mechanism is suggested.
The dihydrolipoyltransacetylase component of the pyruvate dehydrogenase complex from Azotobacter vinelandii
Authors: HANEMAAIJER Roeland , JANSSEN Anja , de KOK Arie , VEEGER Cees 
Published: March 2005

The gene encoding the dihydrolipoyltransacetylase component (E2) of the pyruvate dehydrogenase complex from Azotobacter vinelandii has been cloned in Escherichia coli. A plasmid containing a 2.8‐kbp insert of A. vinelandii chromosomal DNA was obtained and its nucleotide sequence determined.The gene comprises 1911 base pairs, 637 codons excluding the initiation codon GUG and stop codon UGA. It is preceded by the gene encoding the pyruvate dehydrogenase component (E1) of pyruvate dehydrogenase complex and by an intercistronic region of 11 base pairs containing a good ribosome binding site. The gene is followed downstream by a strong terminating sequence. The relative molecular mass (64913), amino acid composition and N‐terminal sequence are in good agreement with information obtained from studies on the purified enzyme. Approximately the first half of the gene codes for the lipoyl domain. Three very homologous sequences are present, which are translated in three almost identical units, alternated with non‐homologous regions which are very rich in alanyl and prolyl residues. The N‐terminus of the catalytic domain is sited at residue 381. Between the lipoyl domain and the catalytic domain, a region of about 50 residues is found containing many charged amino acid residues. This region is characterized as a hinge region and is involved in the binding of the pyruvate dehydrogenase and lipoamide dehydrogenase components. The homology with the dihydrolipoyltransacetylase from E. coli is high: 50% amino acid residues are identical.
Studies of a novel repetitive sequence family in the genome of mice
Authors: DECOVILLE Martine , MALFOY Bernard , LOCKER Daniel 
Published: March 2005

A new middle repetitive sequence is described in the mouse genome. It has been revealed with a recombinant clone isolated from a Mus musculus BamHI gene library constructed in pBR322 and containing an insertion of 1.73 kb. When digests of genomic DNA were subjected to Southern blot hybridization, using the 1.73‐kb insert as probe, we obtained a light smear and discrete bands, indicating a dispersion in the mouse genome of this sequence. This 1.73‐kb sequence seems to be a part of a greater repetitive sequence at least 6 kb in length.The sizes of the bands hybridizing with the 1.73‐kb insert are similar when compared between different laboratory strains but differ remarkably between the two species M. musculus and Mus caroli. We have shown also a great variation in the copy number of the sequence studied between these two species. When rat DNA is probed with the 1.73‐kb insert, no hybridization is observed.Subcloning of the 1.73‐kb sequence in three fragments has pointed out that the reiteration was not homogeneous along the 1.73‐kb sequence.The 1.73‐kb clone was sequenced and compared with other interspersed repetitive sequences, previously described in the rodent genome, and no homology was found.
Uptake and intracellular transport in rat liver of formaldehyde‐treated bovine serum albumin labelled with 125I‐tyramine‐cellobiose
Authors: MISQUITH Sandra , CONINCK Simone WATTIAUX‐DE , WATTIAUX Robert 
Published: March 2005

Endocytosis of formaldehyde‐treated bovine serum albumin by rat liver sinusoidal cells has been followed by injecting rats with the protein labelled with 125I‐tyramine cellobiose (125I‐TCfBSA). 125I‐TCfBSA is quickly taken up by the liver; the radioactivity present in the organ reaches a plateau 5–10 min after injection and is maintained for up to at least 180 min. During the first 5 min most of radioactivity remains acid‐precipitable. After which, labelled acid‐soluble components are produced at a constant rate for up to 30–40 min.
Differential centrifugation shows that radioactivity is first recovered mainly in the microsomal fraction. Within a few minutes it exhibits a distribution pattern similar to that of lysosomal enzymes, being chiefly located in the mitochondrial fractions.
Isopycnic centrifugation in a sucrose gradient of the microsomal fraction isolated 1 min after injection indicates a similar distribution for radioactivity and alkaline phosphodiesterase. Later, the microsomal radioactivity distribution curve is shifted towards higher densities and becomes distinct from that of the plasma‐membrane enzyme. After isopycnic centrifugation in a sucrose gradient of the total mitochondrial fraction a considerable overlapping of acid‐precipitable and acid‐soluble radioactivity distributions is observed without significant changes with time. The same is observed in a Percoll gradient except that after a relatively long time (> 30 min) of injection a marked shift of radioactivity distribution towards higher densities occurs.
A pretreatment of rats with Triton WR 1339, a density perturbant of liver lysosomes, causes a striking shift of acid‐soluble radioactivity distribution in a sucrose gradient towards lower densities while having markedly less influence on the acid‐precipitable distribution. As a result, a distinction between the distribution of both kinds of radioactivity becomes clearly apparent. A preinjection of yeast invertase, modifies the acidsoluble distribution without having a significant effect on the acid‐precipitable distribution up to 30 min after 125I‐TCfBSA injection.
Glycyl‐1‐phenylalanine‐2‐naphthylamide largely releases acid‐soluble radioactivity associated with the mitochondrial fraction, whatever the time after 125I‐TCfBSA injection. On the other hand the proportion of acid‐precipitable radioactivity present in the fraction that can be released is almost zero at 10 min after injection, and it later increases.
The results presented here are best explained by supposing that, after being trapped in small pinocytic vesicles, 125I‐TCfBSA is quickly delivered to the endosomes. It is then transferred at a constant rate from these organelles to a first population of secondary lysosomes, where it is rapidly hydrolysed. In a later step the hydrolysis products and a small proportion of labelled compounds that remain acid‐precipitable accumulate in a second population of lysosomes.
Studies on the mechanism of translational enhancement by the 5′‐leader sequence of tobacco mosaic virus RNA
Authors: SLEAT David E. , HULL Roger , TURNER Philip C. , WILSON T. Michael A. 
Published: March 2005

Translation of foreign mRNAs is enhanced by a cis‐acting derivative (Ω′) of the 5′‐leader sequence (Ω) of tobacco mosaic virus RNA (vulgarestrain). To explain this effect we have conducted several experimentsin vitro.The presence of various 5′‐terminal sequences, including Ω′, did not significantly increase the half‐lives of chloramphenicol acetyltransferase (CAT) or neomycin phosphotransferase (NPTII) mRNAs in wheat‐germ extract. Also, a long leader sequence, unrelated to Ω', did not enhance expression of NPTII mRNAin vitro.The ability of several leader sequences, including Ω′, to form multiple initiation complexes with 80S (wheat germ) ribosomes was examined using CAT or NPTII mRNAs incubated in the presence of sparsomycin. Formation of disome complexes was unrelated to the capacity of a 5′‐leader sequence to enhance translation.Expression of CAT mRNA in both wheat germ extract and messenger‐dependent rabbit reticulocyte lysate was less susceptible to inhibition by increasing salt concentration when a 5′‐proximal Ω′ sequence was present. This effect was less marked when the CAT mRNA was capped. Conversely at high salt concentrations, capping was less stimulatory for mRNA with a 5′‐proximal Ω′ sequence. These data suggest that Ω′ and the cap enhance translation, at least in part, by a similar mechanism. We propose that both features reduce RNA secondary structure, thereby rendering the 5′ terminus more accessible to scanning by 40s ribosomal subunits and/or interaction with associated initiation factors. This conclusion was supported by computer‐based secondary‐structure analyses of our SP6 RNA polymerase transcript sequences.The ability of 5′ leader sequences from brome mosaic virus RNA 3, alfalfa mosaic virus RNA 4, and the genomic RNAs of turnip yellow mosaic virus, Rous sarcoma virus or tobacco mosaic virus (tomato strain) to enhance mRNA translation in eukaryotic systems may also be correlated with their respective secondary structures.A different mechanism probably accounts for the Ω′‐dependent enhancement of mRNA expression inEscherichia colior inE. colicell‐free systems.
3‐Methyladenine, an inhibitor of autophagy, has multiple effects on metabolism
Authors: CARO L. Heleen P. , PLOMP Peter J. A. M. , WOLVETANG Ernst J. , KERKHOF Christine , MEIJER Alfred J. 
Published: March 2005

3‐Methyladenine is generally used as an inhibitor of autophagy [P. 0. Seglen & P. B. Gordon (1982) Proc. Natl Acad. Sci. USA 79, 1889–1892]. Using isolated hepatocytes, we observed that 3‐methyladenine has other effects as well.

3‐Methyladenine promoted glycogen breakdown and inhibited flux through phosphofructokinase and pyruvate kinase. These effects proved to be unrelated to inhibition of autophagic proteolysis and were caused by CAMP, which slightly increased in the presence of 3‐methyladenine.
Addition of 3‐methyladenine to intact hepatocytes increased the intralysosomal pH and caused a lower density of the lysosomal population upon centrifugation in a Percoll density gradient. No increase in the intralysosomal pH was effected by 3‐methyladenine in isolated lysosomes.
Insulin and phorbol ester stimulate phosphorylation of acetyl‐CoA carboxylase at similar sites in isolated adipocytes
Authors: HAYSTEAD Timothy A. J. , HARDIE D. Grahame 
Published: March 2005

The phorbol ester 12‐0‐tetradecanoyl phorbol 13‐acetate (TPA) stimulates fatty acid synthesis from glucose in isolated adipocytes with a half‐maximal effect at 0.72 μM. In seven batches of cells, the maximal effects of TPA and insulin were 8.5 ± 1.1‐fold and 27.1 ± 2.1‐fold respectively. Insulin also stimulated fatty acid synthesis from acetate 8.9 ± 0.5‐fold (three experiments), but TPA did not significantly increase fatty acid synthesis from this precursor.
In contrast to insulin, TPA treatment of isolated adipocytes did not produce an activation of acetyl‐CoA carboxylase which was detectable in crude cell extracts.
The total phosphate content of acetyl‐CoA carboxylase, isolated from adipocytes in the presence of protein phosphatase inhibitors, was estimated by 32P‐labelling experiments to be 2.6 ± 0.1 (5), 3.4 ± 0.2 (5), and 3.8 ± 0.2 (3) mol/mol subunit for enzyme from control, insulin‐and TPA‐treated cells respectively. Insulin and TPA stimulated phosphorylation within the same two tryptic peptides.
Purified acetyl‐CoA carboxylase is phosphorylated in vitro by protein kinase C at serine residues which are recovered in three tryptic peptides, i.e. peptide T1, which appears to be identical with the peptide Ser‐Ser(P)‐Met‐Ser‐Gly‐Leu‐His‐Leu‐Val‐Lys phosphorylated by cyclic‐AMP‐dependent protein kinase, and peptides Ta and Tb, which have the sequences Ile‐Asp‐Ser(P)‐Gln‐Arg and Lys‐Ile‐Asp‐Ser(P)‐Gln‐Arg respectively, and which appear to be derived from a single site by alternative cleavages. None of these correspond to the peptides whose 32P‐labelling increase in response to insulin or TPA. Peptides Ta/Tb are not significantly phosphorylated in isolated adipocytes, even after insulin or TPA treatment. Peptide T1 is phosphorylated in isolated adipocytes, but this phosphorylation is not altered by insulin or TPA.
These results show that TPA mimics the effect of insulin on phosphorylation, but not activation, of acetyl‐CoA carboxylase, i.e. that these two events can be dissociated. In addition, phorbol ester stimulates phosphorylation of acetyl‐CoA carboxylase in isolated adipocytes, but this is not catalyzed directly by protein kinase C, and acetyl‐CoA carboxylase does not appear to be a physiological substrate for this kinase.
Glycosylation of three molecular forms of human α1‐acid glycoprotein having different interactions with concanavalin A
Authors: BIERHUIZEN Marti F. A. , DE WIT Moniek , GOVERS Carin A. R. L. , FERWERDA Wijnholt , KOELEMAN Carolien , POS Odette , VAN DIJK Willem 
Published: March 2005

Human αl‐acid glycoprotein (AGP) was separated into a non‐bound (AGP‐A; 46%), a retarded (AGP‐B; 39%) and a bound fraction (AGP‐C; 150%) using concanavalin A (ConA)‐Sepharose chromatography. The apparent molecular masses, as determined by SDS‐PAGE, of the three fractions were 43.5, 42.3 and 41.2 kDa, respectively.The occurrence of N‐linked di‐, tri‐ and tetraantennary glycans on these three molecular forms (AGP‐A, ‐B, and ‐C) was studied by sequential lectin‐affinity chromatography of the 14C‐labelled glycopeptides. These were obtained by extensive pronase treatment followed by N‐[14C]acetylation of the peptide moieties.The glycopeptides of AGP‐A did not bind to ConA‐Sepharose whereas for AGP‐B and AGP‐C 18% and 44%, respectively, of the glycopeptides were bound as diantennary structures. Glycopeptide fractions of all three forms of AGP which were not bound to ConA‐Sepharose were shown to contain equal amounts of both tri‐ and tetraantennary glycans by chromatography with Phaseolus vulgaris leukoagglutinating lectin (L‐PHA).With the assumption that each molecule contains five glycosylation sites, it could be shown that AGP‐A contains no diantennary structures whereas AGP‐B and AGP‐C contain one and two diantennary structures, respectively. In addition each of the molecular forms contains equal amounts of tri‐ and tetraantennary structures on the remaining glycosylation sites. The results of this study, therefore, exclude a uniformity of glycan chains in the three molecular forms of AGP.The degree of sialylation of each of the molecular forms was investigated by chromatography on L‐PHA‐agarose and Ricinus communis agglutinin‐I‐agarose both before and after desialylation of the glycopeptides. It was shown that about 90% of the biantennary glycans of both AGP‐B and AGP‐C were disialylated while the remainder were monosialylated. The degree of sialylation of the tri‐ and tetraantennary glycans was identical for the three molecular forms. In each case, one or more terminal galactose residues occurred on at least 20% of the tri‐ and 65% of the tetraantennary chains.It is suggested that the decrease in the exposure of galactose residues from AGP‐A to AGP‐C is related to the concomittant decrease in branching of the glycans of the three molecular forms. The relevance of these findings to studies on the function of AGP during inflammatory and liver diseases is discussed.
Prokaryotic hopanoids: the biosynthesis of the bacteriohopane skeleton
Authors: FLESCH Gérard , ROHMER Michel 
Published: March 2005

Incorporation of 13C‐labelled acetate into the hopanoids of the purple non‐sulfur bacteria Rhodopseudomonas palustris and Rhodopseudomonas acidophila and the facultative methylotroph Methylobacterium organophilum showed that the bacteriohopane skeleton is built from an unique carbon/carbon linkage between the triterpenic hopane moiety and the C‐5 carbon of a d‐ribose derivative arising from the non‐oxidative pentose phosphate pathway.Furthermore a probable compartmentation of the acetate metabolism could be observed in these bacteria. Whereas exogenous acetate was directly incorporated into the glucose derivatives and poly‐(3‐hydroxybutyrate), the isoprenic units were apparently solely synthesized from two acetate units arising from the glyoxylate cycle and a third one issued either from the glyoxylate cycle or from the Entner‐Doudoroff pathway of glucose catabolism. Although an unknown biosynthetic pathway different from that usually proposed for isoprenoid biosynthesis can not be excluded, the former hypothesis explained all labelling patterns observed on the triterpenic skeleton.