bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metabolism of Tentoxin by Hepatic Cytochrome P‐450 3A Isozymes
Authors: Delaforge Marcel , Andre François , Jaouen Maryse , Dolgos Hugues , Benech Henri , Gomis Jean‐Marie , Noel Jean‐Pierre , Cavelier Florine , Verducci Jean , Aubagnac Jean‐Louis , Liebermann Bernd 
Published: June 2004

The interaction between rat and human liver cytochrome P‐450 with tentoxin, a natural phytotoxic cyclotetrapeptide having chlorotic properties, was studied by difference ultraviolet visible spectroscopy. Tentoxin interacted with rat liver microsomes and the difference spectrum was characteristic of binding to a protein site close to the heme. The intensity of this spectrum was clearly dependent on the amounts of P‐450 3A in the microsomes and was optimal in dexamethasone‐treated rat microsomes. Tentoxin exhibited a high affinity for P‐450 3A (Ks approximately 10 μM). Similar results were observed with human P‐450 isozymes expressed in yeast. Only P‐450 3A4 and 3A5 were able to give spectral interactions with tentoxin.Liver microsomes from rats pretreated with dexamethasone, a specific inducer of P‐450 3A, were found to be particularly active for the oxidation of tentoxin, which occurs mainly on its Ala(Me) function leading to demethylation. Yeast‐expressed P‐450 3A also exhibited high activity to metabolize tentoxin.The metabolites were identified by their ultraviolet and mass spectra in fast atom bombardment and collision‐activated dissociation modes. In addition to the major N‐demethylated metabolite, other hydroxylated metabolites were formed.Preliminary analysis showed that as tentoxin, some metabolites were still efficient chloroplast ATPase inhibitors, while at least one of them exhibited even at low concentration stimulatory effects.
SP‐22 is a Thioredoxin‐Dependent Peroxide Reductase in Mitochondria
Authors: Watabe Shoji , Hiroi Tomoko , Yamamoto Yoshimi , Fujioka Yoko , Hasegawa Hiroyuki , Yago Nagasumi , Takahashp Susumu Y. 
Published: June 2004

SP‐22 is a mitochondrial antioxidant protein in bovine adrenal cortex. The protein is homologous to thioredoxin peroxidase and other antioxidant proteins. It protects radical‐sensitive enzymes from oxidative damage by a radical‐generating system (Fe2+/dithiothreitol) in the presence of a small amount of serum. In this study we purified a second mitochondrial protein with M, 11 777, which cooperates with SP‐22 to protect glutamine synthetase and other proteins from Fe2+/dithiothreitol‐mediated damage. Without SP22, the protein had no protecting activity. We determined amino acid and nucleotide sequences of the protein and its cDNA, respectively, and found that it was a protein of the thioredoxin family. The protein, designated as mt‐Trx (mitochondrial thioredoxin), had a presequence composed of 59 amino acids that seemed to be a mitochondrial targeting signal.Mitochondrial extract prepared from adrenal cortex contained NADPH‐dependent 5,5’dithiobis(2‐ni‐trobenzoic acid) (Nbs2) reductase activity. The enzyme was thought to have thioredoxin reductase activity, since the Nbs2‐reducing activity was stimulated by mt‐Trx. We partially purified the Nbs2 reductase from bovine adrenocortical mitochondria. In the presence of the partially purified reductase, mt‐Trx, and NADPH, SP‐22 showed the activity to protect oxyhemoglobin against ascorbate‐induced damage. Furthermore, with the three protein components (Nbs2 reductase, mt‐Trx, and SP‐22) NADPH was oxidized in the presence of hydrogen peroxide or tert‐butyl hydroperoxide. The oxidation of NADPH was concomitant with the disappearance of an equimolar amount of hydrogen peroxide. Without any one of the protein components no hemoglobin‐protecting and peroxide‐dependent NADPH‐oxidizing activities were observed. From these results we concluded that SP‐22 is thioredoxin‐dependent peroxide reductase or so‐called thioredoxin peroxidase in mitochondria from the adrenal cortex.
The TATA‐Box‐Binding Protein (TBP) of Halobacterium Salinarum
Authors: Soppa Jorg , Link Thomas A. 
Published: June 2004

The TATA‐box binding protein (TBP) is a basal transcription factor involved in transcription initiation in Eucarya and Archaea. Using a tbp‐specific probe, a 4.5‐kbp genomic fragment from Halobacterium salinarum was cloned and sequenced. It contained the tbp gene and the 5’‐ends of two additional open reading frames, but surprisingly, 70% of the cloned fragment (3.2 kbp) was devoid of coding capacity or similarity to database sequences.The deduced halobacterial TBP exhibits sequence similarities to other archaeal (41–43%) as well as to eucaryal (27–38%) TBP. A comparative analysis showed that the archaeal and eucaryal TBP form two related monophylic protein families, and the archaeal TBP possess features which separate them from eucaryal TBP. Compared with the other TBP, the halobacterial TBP is unique in having a high excess of negatively charged residues.A histidine‐tagged version of the halobacterial TBP was produced in Escherichia coli in a denatured conformation and purified by means of Ni‐chelating chromatography. CD spectroscopy was used to monitor TBP secondary structure and the conditions necessary for folding it into a native conformation. In the absence of denaturating agents, the folded as well as the unfolded state were found to be stable over a wide range of salt concentrations. Properly folded TBP was shown to bind to a halobacterial TATA‐box‐containing DNA fragment, indicating that the fusion protein can be used to characterize DNA recognition by the halobacterial TBP.
Differential Splicing of Pre‐Messenger RNA Produces Multiple Forms of Mature Caprine αs1‐Casein
Authors: Ferrant Pasquale , Added Francesco , Malorni Antonio , Chianese Lina , Leroux Christine , Martin Patrice 
Published: June 2004

The identity of multiple forms of caprine αs1‐casein in variants A, B, and C has been determined by structural characterisation using mass spectrometry, automated Edman degradation and peptide mapping. Mature goat αs1‐casein exists as a mixture of at least four molecular species which differ in peptide chain length. The main component corresponds to the 199‐residues form already described. The other three, in lesser amounts, were shorter forms of αs1‐casein and differed for the deleted peptides 141–148, as shown previously for ovine αs1‐casein, peptide 110–117, or Gln78. Analysis of αs1‐casein mRNA from milk somatic cells demonstrated that these forms originated from skipping events at the level of exon 13 (codifying for peptide 110–117) and 16 (codifying for peptide 141–148) and from the presence of a cryptic splice site within exon 11 (whose first CAG triplet encodes Gln78) during primary transcript processing. The finding of these splicing abnormalities in the three common variants A, B, and C suggests that this is a general feature of αs1‐casein in goat.A further source of heterogeneity of caprine αs1‐casein was identified in the discrete phosphorylation of seryl residues. Eight serine residues (at positions 44, 46, 64 to 68 and 75) are fully phosphorylated (except in variant A because of the replacement Glu77→Gln which prevents phosphorylation of Ser75). Conversely, Ser115 and Ser41 are phosphorylated only to about 50% and 20%, respectively. Ser12, although located in a consensus triplet, is never phosphorylated, similarly to the ovine αs1‐casein variants.These results confirm that there are stabilised mechanisms of simultaneous synthesis of αs1‐casein at different length and of post‐translational modification in both caprine and ovine species.
Effect ofEscherichia coliHeat‐labile Enterotoxin on the Myoelectric Activity of the Duodenum in Weaned Pigs
Authors: Yao G. , Woliński J. , Zabielski R. 
Published: June 2004

SummaryThe objective of the present study was to elucidate the effect of subclinical doses ofEscherichia coliheat‐labile enterotoxin (LT) on the antro‐duodenal myoelectric activities of weaned pigs. Twelve weaned pigs were surgically implanted with three pairs of electrodes on the antrum 3 cm before the pylorus, 5 and 20 cm after the pylorus on the duodenum, respectively. An infusion cannula was inserted into the duodenum between duodenal electrodes. Using a wireless telemetry recording system, an electromyography (EMG) tracing lasting at least 24 h was recorded as the control, then another 24‐h EMG recording was performed with a bolus intraduodenal infusion of LT (0.1 and 0.5 μg/kg b.w.). After a 1‐ to 2‐day break, a 5‐fold higher dose of LT was administered using the same protocol. In the antrum, LT administration barely modified the EMG signal. However, in the duodenum it prolonged the duration of phase II and the migrating myoelectric complex (MMC) cycle when compared with the control. The number of duodenal MMC cycles was also significantly diminished. Moreover, the migrating velocity of phase III was increased. The migrating action potential complex (MAPC) was present both without and with LT, but occurred more frequently following LT administration. In conclusion, LT caused a dose‐dependent, lagged alteration in the duodenal MMC in weaned pigs, involving a reduction of the MMC number by lengthening phase II, increased phase III migration velocity, and increased MAPC frequency. The disturbances did not, however, result in diarrhoea and may reflect the induction of a local protection mechanism of the gut to expel unwanted foreign content from the lumen of the upper gut.
Tissue Doppler Imaging and Echo‐Doppler Findings Associated with a Mitral Valve Stenosis with an Immobile Posterior Valve Leaflet in a Bull Terrier
Authors: Tidholm A. , Nicolle A. P. , Carlos C. , Gouni V. , Caruso J. L. , Pouchelon J. L. , Chetboul V. 
Published: June 2004

SummaryA mitral valve stenosis was diagnosed in a 2‐year‐old female Bull Terrier by use of two‐dimensional (2‐D) and M‐mode echocardiography, colour‐flow imaging and spectral Doppler examinations. Tissue Doppler Imaging was also performed to assess the segmental radial myocardial motion. The mitral valve stenosis was characterized by a decreased mitral orifice area/left ventricle area ratio (0.14), an increased early diastolic flow velocity (E wave = 1.9 m/s), a prolonged pressure half‐time (106 ms) and a decreased E‐F slope (4.5 cm/s) on pulsed‐wave Doppler examination. This mitral stenosis was associated with an immobile posterior leaflet, as seen on 2‐D and M‐mode echocardiography. Immobility of the posterior mitral leaflet is considered to be a rare finding in humans and, to our knowledge, has not been precisely documented in dogs with mitral valve stenosis.
Metabolic Profiles and Bile Acid Extraction Rate in the Liver of Cows with Fasting‐induced Hepatic Lipidosis
Authors: Mohamed T. , Oikawa S. , Iwasaki Y. , Mizunuma Y. , Takehana K. , Endoh D. , Kurosawa T. , Sato H. 
Published: June 2004

SummaryThis study was designed to monitor lipid profile in the portal and hepatic blood of cows with fasting‐induced hepatic lipidosis, and to compare the results with those in the jugular blood. The work was also carried out to investigate bile acid (BA) in these vessels, and further to investigate BA extraction rate in the liver. Five cows were equipped with catheters in the portal, hepatic and jugular veins (day 0), fasted for 4 days (day 1–day 4) and then refed (day 5–day 11). Before morning feeding, blood was sampled before, during and after fasting from the catheterized vessels. In the portal blood, the concentration of non‐esterified fatty acids (NEFA) showed a progressive increase and at day 5 there was an approximate twofold rise. Increased NEFA concentrations were also found similarly in the other two veins. At day 5,β‐hydroxybutyrate (BHBA) in the portal, hepatic and jugular blood rose to 197, 190 and 186% of the pre‐fasting value, respectively. However, the concentrations of NEFA and BHBA in the three veins gradually returned to pre‐fasting concentration during the refeeding period. Compared with the pre‐fasting value at day 0, the content of liver triglyceride (TG) increased significantly at day 5 (P < 0.01). In the liver, the hepatic extraction rate of BA dropped from 3.1 times pre‐fasting to 2.2 times during fasting. There were no significant differences in the concentrations of glucose, TG, total cholesterol, cholesterol esters, free cholesterol and phospholipids. The results of the current study show that metabolic alterations occur in the portal, hepatic and jugular veins during induction of hepatic lipidosis in cows, and mostly metabolites, with exception of BA concentration, run parallel. The decreased BA extraction rate in the liver of fasted cows was considered to reflect hepatic cell impairment caused by TG accumulation. Hopefully, the findings, at least in part, contribute to the explanation of the pathophysiology of hepatic lipidosis in dairy cows.
Comparison of Plasma/Serum Urea and Creatinine Concentrations in the Dog: A 5‐Year Retrospective Study in a Commercial Veterinary Clinical Pathology Laboratory
Authors: Médaille C. , Trumel C. , Concordet D. , Vergez F. , Braun J. P. 
Published: June 2004

SummarySerum/plasma urea (S/P‐urea) and creatinine (S/P‐creatinine) concentrations are routinely assayed as indirect markers of glomerular filtration rate and have been reported to be highly correlated. The aim of this study was to evaluate the relationship between the two analytes in a large number of unselected samples submitted to a commercial laboratory. In 4799 pairs of results, the correlation was high (r = 0.795) and was not affected by sex or age. The relationship between the two analytes was best represented by a second‐order polynomial equation. However, the dispersion of results was large and there was a high percentage of cases (27.5%) where S/P‐urea was increased and S/P‐creatinine normal (≤120 μmol/l for this laboratory), while there was a low percentage of cases where S/P‐creatinine (1.6%) was increased and S/P‐urea normal (≤8 mmol/l for this laboratory). The discrepancy between increases in S/P‐urea and S/P‐creatinine might not only reflect a high incidence of non‐renal factors of variation for S/P‐urea but also an effect of the size or muscle mass of the dogs on the limit of decision for S/P‐creatinine. In dogs with normal S/P‐urea, there was a significant effect of the size on the 0.975 quantile of S/P‐creatinine, ranging from 106 μmol/l in very small dogs to 133 μmol/l in large and very large dogs. This study shows that isolated increases in S/P‐urea could be misleading for the diagnosis of renal diseases and that the reference intervals of S/P‐creatinine should be re‐evaluated according to breed or muscle mass of dogs.
Evaluation of cyclooxygenase‐1 and cyclooxygenase‐2 expression and the effect of cyclooxygenase inhibitors in canine prostatic carcinoma
Authors: Sorenmo K. U. , Goldschmidt M. H. , Shofer F. S. , Goldkamp C. , Ferracone J. 
Published: June 2004

AbstractProstatic carcinoma occurs primarily in older castrated male dogs and is typically a fatal disease (most dogs die within few months after the initial diagnosis). Surgery, i.e., total prostatectomy, or radiation therapy is often not pursued due to risks of complications and a high rate of distant metastasis. Cyclooxygenase‐2 (Cox‐2) expression has been documented in several malignancies, including canine prostatic carcinoma. Cox‐2 inhibition has been reported to have preventative effects on several human malignancies and has therapeutic effects on both laboratory and spontaneous tumour models. The purpose of this retrospective study was to evaluate Cox expression and the effects of Cox inhibitors on survival in dogs with prostatic carcinoma. 94.1 and 88.2% of the tumours expressed Cox‐1 and Cox‐2, respectively. Furthermore, dogs treated with Cox inhibitors (piroxicam or carprofen) lived significantly longer than untreated dogs, 6.9 versus 0.7 months (P < 0.0001), suggesting that Cox inhibitors may have an important role in canine prostate cancer therapy.
Calponin expression and myoepithelial cell differentiation in canine, feline and human mammary simple carcinomas
Authors: De Las Mulas J. Martín , Reymundo C. , De Los Monteros A. Espinosa , Millán Y. , Ordás J. 
Published: June 2004

AbstractCalponin is a 34‐kDa smooth muscle‐specific protein that has been shown to be a highly sensitive marker of myoepithelial cells in canine, feline and human mammary tissue and tumours. The expression of calponin was studied in 15 canine, 32 feline and 28 human simple mammary carcinomas using a monoclonal mouse antihuman calponin antibody and the avidin–biotin peroxidase complex (ABC) immunohistochemical technique. Calponin expression was compared with the expression of cytokeratin 14, a marker of normal mammary myoepithelial cells in the three species. Four different types of calponin‐positive cells were identified: (1) Type 1: cytokeratin‐14‐positive pre‐existing myoepithelial cells forming a continuous layer with images of focal disruptions; (2) Type 2: cytokeratin‐14‐positive isolated nests of fusiform, polygonal or round cells without atypia; (3) Type 3: cytokeratin‐14‐positive atypical cells indistinguishable from non‐reactive atypical cells, which should have never been detected in haematoxylin and eosin‐stained sections and (4) Type 4: cytokeratin‐14‐negative stromal fusiform cells around the neoplastic growth or cell nests, identified as myofibroblasts. Calponin‐negative and cytokeratin‐14‐positive atypical neoplastic cells were observed in three canine, 28 feline and two human carcinomas. The latter were indicative of altered expression of high‐molecular‐weight cytokeratins in luminal epithelial‐type simple carcinomas. Our findings show that calponin is a good marker of myoepithelial cell differentiation in feline, human and, particularly, canine simple carcinomas. The high number (six out of 15) of canine tumours with type 3 cells points to the need of both introducing calponin examination in the routine diagnostic schedule and performing further studies on its prognostic significance.
Antimalarial Quinolines and Artemisinin Inhibit Endocytosis in
Plasmodium falciparum
Authors: Hoppe Heinrich C. , van Schalkwyk Donelly A. , Wiehart Ursula I. M. , Meredith Sandra A. , Egan Joanne , Weber Brandon W. 
Published: June 2004

ABSTRACT

Endocytosis is a fundamental process of eukaryotic cells and fulfills numerous functions, most notably, that of macromolecular nutrient uptake. Malaria parasites invade red blood cells and during their intracellular development endocytose large amounts of host cytoplasm for digestion in a specialized lysosomal compartment, the food vacuole. In the present study we have examined the effects of artemisinin and the quinoline drugs chloroquine and mefloquine on endocytosis in
Plasmodium falciparum
. By using novel assays we found that mefloquine and artemisinin inhibit endocytosis of macromolecular tracers by up to 85%, while the latter drug also leads to an accumulation of undigested hemoglobin in the parasite. During 5-h incubations, chloroquine inhibited hemoglobin digestion but had no other significant effect on the endocytic pathway of the parasite, as assessed by electron microscopy, the immunofluorescence localization of hemoglobin, and the distribution of fluorescent and biotinylated dextran tracers. By contrast, when chloroquine was added to late ring stage parasites, followed by a 12-h incubation, macromolecule endocytosis was inhibited by more than 40%. Moreover, there is an accumulation of transport vesicles in the parasite cytosol, possibly due to a disruption in vacuole-vesicle fusion. This fusion block is not observed with mefloquine, artemisinin, quinine, or primaquine but is mimicked by the vacuole alkalinizing agents ammonium chloride and monensin. These results are discussed in the light of present theories regarding the mechanisms of action of the antimalarials and highlight the potential use of drugs in manipulating and studying the endocytic pathway of malaria parasites.
In Vitro and In Vivo Activities of E5700 and ER-119884, Two Novel Orally Active Squalene Synthase Inhibitors, against
Trypanosoma cruzi
Authors: Urbina Julio A. , Concepcion Juan Luis , Caldera Aura , Payares Gilberto , Sanoja Cristina , Otomo Takeshi , Hiyoshi Hironobu 
Published: June 2004

ABSTRACT

Chagas' disease is a serious public health problem in Latin America, and no treatment is available for the prevalent chronic stage. Its causative agent,
Trypanosoma cruzi
, requires specific endogenous sterols for survival, and we have recently demonstrated that squalene synthase (SQS) is a promising target for antiparasitic chemotherapy. E5700 and ER-119884 are quinuclidine-based inhibitors of mammalian SQS that are currently in development as cholesterol- and triglyceride-lowering agents in humans. These compounds were found to be potent noncompetitive or mixed-type inhibitors of
T. cruzi
SQS with
K

i

values in the low nanomolar to subnanomolar range in the absence or presence of 20 μM inorganic pyrophosphate. The antiproliferative 50% inhibitory concentrations of the compounds against extracellular epimastigotes and intracellular amastigotes were ca. 10 nM and 0.4 to 1.6 nM, respectively, with no effects on host cells. When treated with these compounds at the MIC, all of the parasite's sterols disappeared from the parasite cells. In vivo studies indicated that E5700 was able to provide full protection against death and completely arrested the development of parasitemia when given at a concentration of 50 mg/kg of body weight/day for 30 days, while ER-119884 provided only partial protection. This is the first report of an orally active SQS inhibitor that is capable of providing complete protection against fulminant, acute Chagas' disease.
Intracellular and Plasma Pharmacokinetics of Saquinavir-Ritonavir, Administered at 1,600/100 Milligrams Once Daily in Human Immunodeficiency Virus-Infected Patients
Authors: Ford Jennifer , Boffito Marta , Wildfire Adrian , Hill Andrew , Back David , Khoo Saye , Nelson Mark , Moyle Graeme , Gazzard Brian , Pozniak Anton 
Published: June 2004

ABSTRACTRitonavir-boosted saquinavir (SQV/r) is currently licensed as a twice-daily regimen. Reducing the pill burden with once-daily dosing may improve adherence. Intracellular concentrations of drugs must be related to the clinical efficacy of protease inhibitors. The aims of the study were to determine the cellular and plasma saquinavir and ritonavir concentrations, to determine the half-lives (t1/2s) of the drugs in each compartment, and to examine relationships between drug accumulation and lymphocyte subset P glycoprotein (P-gp) expression. Venous blood samples from 12 human immunodeficiency virus-infected patients receiving a hard-gel formulation of SQV/r (1,600/100 mg once daily) were collected at 2, 6, 12, and 24 h after dosing. Peripheral blood mononuclear cells were separated by density gradient centrifugation, and P-gp expression was measured by dual-color flow cytometry. Plasma and intracellular (cell-associated) drug concentrations were measured by high-performance liquid chromatography-tandem mass spectrometry. The ratio of the intracellular drug area under the concentration-time curve from 0 to 24 h (AUC0-24 h) to plasma drug AUC0-24 hwas calculated to determine cellular drug accumulation. The median (range) AUC0-24 hof saquinavir in plasma was 16.2 (5.7 to 39.3) mg · h · liter−1, and that in cells was 46.3 (24.7 to 114.6) mg · h · liter−1. Corresponding ritonavir values were 7.5 (1.5 to 14.6) mg · h · liter−1and 10.4 (3.2 to 13.7) mg · h · liter−1, respectively. The median accumulation ratios of cellular AUC to plasma AUC for saquinavir and ritonavir were 3.31 (range, 1.49 to 6.69) and 1.46 (range, 0.83 to 4.15), respectively. Significant differences between the plasma and intracellular saquinavirt1/2s (4.5 h [range, 2.5 to 9.3 h] and 5.9 h [range, 4.0 to 17.7 h];P= 0.034) and between the plasma and intracellular ritonavirt1/2s (4.1 h [range, 2.6 to 8.3 h] and 6.2 h [range, 3.9 to 18.6 h];P= 0.032) were observed. No relationship was observed between the accumulation of saquinavir or ritonavir and lymphocyte subset P-gp expression. The intracellulart1/2s of saquinavir and ritonavir were longer than the plasmat1/2s, indicating that intracellular drug may be available at a time when concentrations in plasma are below the minimum effective concentration.