Micromanipulation of daughter cells for the study of cytokinetic abscission.

The last step of cytokinesis, abscission, consists in the severing of the intercellular bridge connecting the two daughter cells. Because daughter cells move randomly on regular cell culture substrates, the use of adhesive micropatterns facilitates the observation of the intercellular bridge and its severing. Here we propose general rules to design micropatterns optimized to study this process. In particular, these micropatterns allow a good stabilization of the daughter cells and a predictable positioning of the intercellular bridge. We suggest a series of micropatterns controlling various cellular parameters such as distance between daughter cells or daughter cells polarization. We give recommendations for videomicroscopy acquisition during cell division and propose automated image analysis methods using kymograph analysis or bridge detection. Finally, we detail methods to artificially cut the intercellular bridge using UV-based laser ablation or using two-photons laser ablation.

Incidence of class A extended-spectrum beta-lactamases in Champagne-Ardenne (France): a 1 year prospective study.

OBJECTIVES: To assess the frequency and diversity of extended spectrum beta-lactamases (ESBLs) in the Champagne-Ardenne region France, and to identify genetic elements associated with the bla(CTX-M) genes. METHODS: During 2004, all the non-duplicate isolates of Pseudomonas aeruginosa and Acinetobacter baumannii resistant to ceftazidime and of Enterobacteriaceae intermediate or resistant to ceftazidime and/or cefotaxime, screening samples excluded, were collected in 10 public hospitals and 3 private clinics. bla genes were sequenced and bla(CTX-M) environment characterized by PCR mapping. RESULTS: In Enterobacteriaceae (138/21 861; 0.6%), ESBLs were predominantly TEM-24 (n = 52; 37.7%) and CTX-M-15 (n = 37; 26.8%). Three new enzymes were identified, CTX-M-61 (CTX-M-1 group), TEM- and SHV-type. A. baumannii (n = 5) produced VEB-1 and P. aeruginosa (n = 2) SHV-2a. ISEcp1 was detected in 22/27 strains, disrupted in 7 of them. The IS903-like element was downstream of bla(CTX-M-14) and bla(CTX-M-16). ISCR1 was found upstream of bla(CTX-M-2) and bla(CTX-M-9), and ISCR1 and bla(CTX-M-2) were located on a sul1-type class 1 integron. In comparison with 2001-02, ESBL distribution among Enterobacteriaceae showed an increase in CTX-M-type (44.9% vs 3.7% P < 10(-7)) due to Escherichia coli CTX-M-15 and to the almost total disappearance of TEM-3 (0.9% vs 51.2%). E. coli was the most frequent species (50.0% vs 5.1% in 1998) despite a similar prevalence to that in 1998 (0.5% vs 0.2%). CONCLUSIONS: A careful detection of bla(CTX-M)-type spread to other species would help to anticipate clonal endemics such as those observed in Enterobacter aerogenes TEM-24.

Down-regulation of human granzyme B expression by glucocorticoids. Dexamethasone inhibits binding to the Ikaros and AP-1 regulatory elements of the granzyme B promoter.

The serine protease granzyme B is an essential component of the granule exocytosis pathway, a major apoptotic mechanism used by cytotoxic T lymphocytes and natural killer cells to induce target cell apoptosis. Granzyme B gene transcription is induced in activated lymphocytes upon antigenic stimulation, and several regulatory regions including CBF, AP-1, and Ikaros binding sites have been shown to be essential in the control of granzyme B promoter activation. Dexamethasone, a glucocorticoid that is widely used as an immunomodulatory and anti-inflammatory agent, inhibits granzyme B mRNA transcript in phytohemagglutinin-activated peripheral blood mononuclear cells. Transfection of a reporter construct containing the -148 to +60 region of the human granzyme B promoter demonstrated that this region was the target for dexamethasone repression. Mutation of Ikaros or AP-1 binding sites in the context of the granzyme B promoter demonstrated that both sites participate in dexamethasone-mediated inhibition of the granzyme B promoter activity. Electromobility shift assay revealed that dexamethasone abolished the binding of nuclear transcription factors to the Ikaros binding site and reduced AP-1 binding activity. These results indicate that dexamethasone is able to abrogate the transcriptional activity of the human granzyme B gene promoter by inhibiting the binding of nuclear factors at the AP-1 and Ikaros sites.

High sensitivity of laser-induced fluorescence detection in capillary gel electrophoresis for accurate apolipoprotein E genotyping.

Human apolipoprotein E (apoE) is a product of a polymorphic gene. In the general population, it shows two major mutations, which lead to the appearance of three common alleles encoding for three protein isoforms. This polymorphism is important in the regulation of lipid metabolism. Accurate apoE phenotyping or genotyping has become essential in clinical laboratories, since the epsilon 4 allele has been associated with cardiovascular and Alzheimer's diseases. Endonuclease restriction isotyping, followed by slab gel electrophoresis, is a rapid and convenient method for the investigation of common apoE genotypes. However, during the large-scale apoE genotyping of the STANISLAS cohort, we were confronted with a partial lack of sensitivity and resolution power of this traditional method, which sometimes leads to the misclassification of the genotypes epsilon 2/2 and epsilon 3/2. We have overcome this difficulty by separating the restriction fragments with capillary gel electrophoresis linked to laser-induced fluorescence detection. The baseline resolution was 2 bp, and the sensitivity limit attainable was similar to that by radioactive detection. The distinction between the epsilon 3/2 and the epsilon 2/2 genotypes became unequivocal, even when only low amounts of DNA were available for amplification.

Granzyme B and perforin lytic proteins are expressed in CD34+ peripheral blood progenitor cells mobilized by chemotherapy and granulocyte colony-stimulating factor.

Granzyme B and perforin are cytoplasmic granule-associated proteins used by cytotoxic T lymphocytes and natural killer (NK) cells to kill their targets. However, granzyme B gene expression has also been detected in a non-cytotoxic hematopoietic murine multipotent stem cell line, FDCP-Mix. The objective of the present study was to investigate whether granzyme B and perforin could be expressed in human hematopoietic CD34+ cells and if present, discover what their physiologic relevance could be. The primitive CD34+ human cell line KG1a was investigated first and was found to express granzyme B and perforin. Highly purified hematopoietic stem/progenitor cells were then selected using the CD34 surface antigen as marker. Steady-state bone marrow (BM) CD34+ cells did not contain these proteins. Peripheral blood (PB) CD34+ cells, which had been induced to circulate, were also analyzed. After chemotherapy (CT) and granulocyte colony-stimulating factor (G-CSF) treatment, CD34+ cells strongly expressed mRNAs and proteins of granzyme B and perforin. In contrast, CD34+ cells mobilized by G-CSF alone were negative. Western blot analysis further showed that granzyme B and perforin proteins were identical in CD34+ cells and activated PBLs. Such proteins might be implicated in the highly efficient migration of CD34+ stem/progenitor cells from BM to PB after CT and G-CSF treatment. The cellular adhesion mechanisms involved in the BM homing of CD34+ cells are disrupted at least temporarily after CT. The Asp-ase proteolytic activity of granzyme B on extracellular matrix proteins could be used by progenitor cells for their rapid detachment from BM stromal cells and perforin might facilitate their migration across the endothelial cell barrier.

Identification of human granzyme B promoter regulatory elements interacting with activated T-cell-specific proteins: implication of Ikaros and CBF binding sites in promoter activation.

Granzyme B serine protease is found in the granules of activated cytotoxic T cells and in natural and lymphokine-activated killer cells. This protease plays a critical role in the rapid induction of target cell DNA fragmentation. The DNA regulatory elements that are responsible for the specificity of granzyme B gene transcription in activated T-cells reside between nt -148 and +60 (relative to the transcription start point at +1) of the human granzyme B gene promoter. This region contains binding sites for the transcription factors Ikaros, CBF, Ets, and AP-1. Mutational analysis of the human granzyme B promoter reveals that the Ikaros binding site (-143 to -114) and the AP-1/CBF binding site (-103 to -77) are essential for the activation of transcription in phytohemagglutinin-activated peripheral blood lymphocytes, whereas mutation of the Ets binding site does not affect promoter activity in these cells.

Glucuronidation of hyodeoxycholic acid in human liver. Evidence for a selective role of UDP-glucuronosyltransferase 2B4.

Monospecific polyclonal antibodies were raised against a variable amino-terminal domain (amino acids 14-150) of a human liver form of UDP-glucuronosyl-transferase conjugating bile acids, UGT2B4 (Jackson, M. R., McCarthy, L. R., Harding, D., Wilson, S., Coughtrie, M. W., and Burchell, B. (1987) Biochem. J. 242, 581-588), expressed as a fusion protein in Escherichia coli. The antibodies were able to recognize the protein, stably expressed in a genetically engineered eukaryotic V79 cell line, against which they were directed. The specificity of these antibodies allowed their use for analyzing the substrate specificity of this isoform in human liver, as well as for determining its contribution to the total hepatic and extra-hepatic glucuronidation of hyodeoxycholic acid. Western blot analysis of microsomal proteins demonstrated the presence of UGT2B4 exclusively in human liver and not in human kidney. In human liver microsomes, the antibodies were able to inhibit and precipitate up to 90% of the total hyodeoxycholic acid 6-O-glucuronidation activity, but had no effect on activities toward several other substrates, such as phenols, bilirubin, or other bile acids, especially hyocholic acid and the steroids 4-hydroxyesterone and estriol. Moreover, Western blot analysis and immunoinhibition studies of human liver microsomes from healthy patients and from patients presenting liver diseases revealed a good correlation between the glucuronidation rate of hyodeoxycholic acid and the UGT2B4 expression level. The absence of immunoinhibition of hyodeoxycholic acid conjugation with UDP sugars other than UDP-glucuronic acid suggests the involvement of different enzymatic systems in the glucosidation and xylosylation of hyodeoxycholic acid. Altogether, the results provided strong evidence for the specific and predominant involvement of UGT2B4 in the 6-O-glucuronidation of this bile acid via a UDP-glucuronic acid-dependent mechanism.

Determination of the human liver UDP-glucuronosyltransferase 2B4 domains involved in the binding of UDP-glucuronic acid using photoaffinity labeling of fusion proteins.

The interactions between UDP-glucuronic acid and two human liver UDP-glucuronosyltransferase 2B4 peptides (14-150 and 299-446) purified from E. coli as Staphylococcus aureus protein A fusion proteins have been investigated. Photoaffinity labeling with azidonucleotides ([beta-32P]5N3UDP-Glucuronic acid and [beta-32P]5N3UDP-Glucose) and competition experiments with UDP-glucuronic acid and structurally related compounds emphasized the presence of a specific UDP binding site between amino acids 299 and 446. Moreover, competition experiments strongly suggested an interaction between the amino terminal part of the protein and glucuronic acid. It would involve an electrostatic bond in the binding of the cosubstrate via the carboxyl group of UDP-glucuronic acid and a positively charged amino acid of the N-terminal domain of the enzyme.

Purification and characterization of a catalytically active human liver UDP-glucuronosyltransferase expressed as a fusion protein in E. coli.

The purification and the characterization of functional human liver UDP-glucuronosyltransferase 2B4 produced as a Staphylococcus aureus protein A fusion protein in E. coli are described. The purified fusion protein was able to catalyze the glucuronidation of hyodeoxycholic acid, the major substrate described for this isoform to date. The effects of the amount and the nature of the phospholipids upon reconstitution into phospholipid micelles were investigated. Apparent determined Km values for hyodeoxycholic acid and UDP-glucuronic acid were 0.55 and 0.43 mM, respectively. Moreover, photoaffinity labelling of the fusion protein with a photoactivatable analog of UDP-glucuronic acid strongly suggested that this recombinant protein exhibited similar binding properties as the microsomal protein, which emphasizes its use for further structural analyses.

Oral contraceptives stimulate the excretion of clofibric acid glucuronide in women and female rats.

1. Glucuronidation of clofibric acid, the pharmacologically active form of the hypolipidemic drug clofibrate was investigated in a human population, either in vitro with liver homogenates from biopsies, or after ingestion of the drug and determination of the urinary metabolite. No difference in the glucuronidation rate according to age of the patients was observed. Bilirubin but not clofibric acid glucuronidation was significantly higher in women (106% increase), when expressed per gram of tissue. 2. The excretion of clofibryl glucuronide in women who took oral contraceptives was significantly enhanced by 25%. 3. In female rats, treatment with the contraceptive agent norethindrone also stimulated by 48% the formation of clofibrylglucuronide in liver microsomes.

PIP: The effect of oral contraceptive (OC) intake on the glucuronidation of clofibric acid was investigated both in vivo, by measuring the excretion of urinary clofibrylglucuronide in female Wistar rats, or in vitro, with liver biopsy homogenates from 69 health female volunteers. In both study groups norethindrone markedly enhanced glucuronidation of clofibric acid while the situation was modulated by the administration of ethinyl estradiol. Excretion of clofibric acid into urine averaged 142.1 + or - 38.4 mg in OC users compared to only 105.8 + or - 31.5 mg in non-users. When expressed per gram of tissue, bilirubin but not clofibric acid glucuronidation was significantly greater in human liver biopsies from OC users compared to non-users. In rats treated with norethindrone, the liver microsomal protein content was increased 28% over the average control value and formation of clofibylglucoride was stimulated by 48%. It is hypothesized that the stimulation of clofibylglucuronide in OC users results from the selective stimulation in the liver of the isoenzyme involved in the process of the glucuronidation of clofibric acid.

Glucuronidation of 2-arylpropionic acids pirprofen, flurbiprofen, and ibuprofen by liver microsomes.

Acylglucuronide formation from the 2-arylpropionic acids pirprofen, flurbiprofen, and ibuprofen, three nonsteroidal anti-inflammatory drugs (NSAIDs), was investigated in rat liver microsomes using an HPLC method and 14C-labeled UDP-glucuronic acid as co-substrate. Pirprofen was the best substrate of UDP-glucuronosyltransferase with a Vmax/Km of 45.4, as compared with 8.0 and 1.6 for flurbiprofen and ibuprofen, respectively. Glucuronidation of the drugs was significantly increased upon treatment of rats with phenobarbital; 3-methylcholanthrene or clofibrate failed to induce the activity. At the dose of 100 mg/kg body weight for 1, 3, and 5 days, pirprofen was unable to induce its own glucuronidation. However, this treatment caused a transient increase, after 1 day, of several isoform activities monitored with 4-nitrophenol, 1-naphthol, 4-methylumbelliferone, terpenes, and testosterone as substrates. After 3 and 5 days these activities were decreased, especially when glucuronidation of 4-nitrophenol and 4-methylumbelliferone was considered, glucuronidation of the terpenes cis-myrtanol, borneol, nopol, and of testosterone being similar to control values. By contrast to clofibrate, administration of pirprofen to rats decreased bilirubin UDP-glucuronosyltransferase in a time-dependent fashion with a maximal decrease of 59% after 5 days. Treatment of rats with pirprofen also decreased markedly the formation of flurbiprofen glucuronide. Comparison of NSAID glucuronidation between several species indicated that it was most potent in monkeys, dogs, and humans. Cats were also efficient in that respect. Gunn rats, which are genetically deficient in bilirubin glucuronidation, were able to form acylglucuronides from the drugs, thus indicating that these 2-arylpropionic acids were not substrates of the bilirubin isozyme.

Phenobarbital inducible UDP-glucuronosyltransferase is responsible for glucuronidation of 3'-azido-3'-deoxythymidine: characterization of the enzyme in human and rat liver microsomes.

Glucuronidation by liver microsomes of 3'-azido-3'-deoxythymidine (AZT) was characterized in human and in various animal species. The glucuronide isolated by HPLC, was identified by mass spectrometry (fast atom bombardment, desorption in chemical ionization), and beta-glucuronidase hydrolysis. AZT glucuronidation reaction in liver microsomes of human and monkey proceeded similarly with an apparent Vmax of 0.98 nmol/min/mg protein and apparent Km of 13 mM. Oleoyl lysophosphatidylcholine activated more than twofold the formation of the glucuronide. Human kidney microsomes could also biosynthesize AZT glucuronide, although to a lower extent (six times less than the corresponding liver). Probenecid, which is administered to AIDS patients, decreased hepatic AZT glucuronidation in vitro (I50 = 1.5 mM), whereas paracetamol did not exert any effect at concentrations up to 21.5 mM. Morphine also inhibited the reaction (I50 = 2.7 mM). AZT glucuronidation presented the highest rate in human and in monkey (0.50 nmol/min/mg protein); pig and rat glucuronidated the drug two and three times less, respectively. In Gunn rat, the specific activity in liver microsomes was similar (0.18 nmol/min/mg protein) to that of the congenic normal strain; this suggests that an isozyme other than bilirubin UDP-glucuronosyltransferase catalyzed the reaction. In rats, AZT glucuronidation was stimulated fourfold by phenobarbital; 3-methylcholanthrene or clofibrate failed to increase this activity. This result was consistent with the bulkiness of the AZT molecule (thickness 6.7 A), which is a critical structural factor for glucuronidation of the drug by phenobarbital-induced isozymes. Altogether, the results strongly indicate that UDP-glucuronosyltransferase (phenobarbital inducible forms) is responsible for AZT glucuronidation.

Urease-negative Nocardia asteroides causing cutaneous nocardiosis.

We report a case of cutaneous nocardiosis, caused by a urease-negative strain of Nocardia asteroides, in a patient who had undergone long-term corticosteroid therapy. The microbiological characteristics of the isolate were typical of N. asteroides except for the failure of the isolate to hydrolyze urea. During the course of routine identification, laboratory specialists should be aware of the occasional occurrence of atypical strains of N. asteroides.

Comparative study of clofibric acid and bilirubin glucuronidation in human liver microsomes.

Hepatic microsomal glucuronoconjugation of the hypolipidemic drug clofibric acid was characterized in human liver and compared to the acylglucuronide formation of an endogenous substrate, bilirubin. The affinity of UDP-glucuronosyltransferase for bilirubin was 15-fold higher than for clofibric acid; the Vmax for the transformation of the two substrates were similar. The analysis of the specific activity in 32 liver biopsies showed that glucuronidation of clofibric acid or bilirubin were comparable in man and in rat. However, UDP-glucuronosyltransferase activity towards clofibric acid exhibited a large interindividual variation in man. Sex or age did not influence the glucuronidation of bilirubin and clofibric acid. Among the drugs given to the patients only clofibrate was able to increase the bilirubin conjugation. No effect of alcohol or smoking on the conjugation of the two substrates was observed. The absence of correlation between UDP-glucuronosyltransferase activities towards clofibric acid and bilirubin together with the specific induction of bilirubin glucuronidation by clofibrate suggested that these arylcarboxylic substrates were conjugated by separate forms of UDP-glucuronosyltransferase in human.

Inhibition of bilirubin UDPglucuronosyltransferase activity by triphenylacetic acid and related compounds.

Bilirubin UDPglucuronosyltransferase of rat or human liver microsomes was inhibited, in vitro, by triphenylacetic acid and by structurally related arylcarboxylic acids. This inhibition appeared to be competitive towards bilirubin, and mixed-type towards UDPglucuronic acid. A decrease in the number of phenyl rings or the absence of the carboxyl group in the molecule gave structures which did not affect enzyme activity, showing that both the triphenyl moiety and the carboxyl group were necessary for the inhibition. On the other hand, successive additions of methylene groups in the aliphatic chain progressively increased inhibitory potency. Kappi,bilirubin for triphenylacetic acid was 96 microM compared with 5 microM for 7,7,7-triphenylheptanoic acid. The inhibition of bilirubin UDPglucuronosyltransferase was not due to displacement of bilirubin from albumin. On the basis of these results an attempt was made to delineate the molecular events leading to glucuronidation of bilirubin.