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Biomedical subjects

A Petit

Publications and source records attributed to A Petit.

At least 37 records · Page 2Linked to original sources
PubMed2001

Structure and characterization of the crown gall opines heliopine, vitopine and ridéopine.

The crown gall opines heliopine from tumors induced by octopine type Agrobacterium tumefaciens strains A6, A136(pTiB6-806), E9, A652 and 1590-1 and vitopine from tumor induced by grapevine strains S4 and T2 are identical to synthetic N2-(1'R-carboxyethyl)-L-glutamine. Tumors produced by strains S4 and T2 do not contain octopine or lysopine, but they do contain heliopine and the new opine ridéopine identified as N-(4'-aminobutyl)-D-glutamic acid. Grapevine strains S4 and T2 grow normally on tumor heliopine or synthetic heliopine and on tumor and synthetic ridéopine as well as on ridéopine lactam as sole carbon source. While octopine strains A6 and A136(pTiB6-806) do not grow on heliopine, mutant colonies do appear after a few weeks. Heliopine catabolism by octopine strains is not induced by octopine.

Agrobacterium tumefaciens↗
PubMed2001

Apoptosis in interface membranes of aseptically loose total hip arthroplasty.

The terminal events leading to periprosthetic osteolysis are multifactorial in nature and modulation of this process after the stage of osteolytic mediator release has been futile. Recently, the demonstration of the ability of bisphosphonates to inhibit bone resorption that is mediated by particle-stimulated macrophages and their induction of osteoclast apoptosis suggests a potent area for modulation of osteolysis at the prosthesis-bone interface. The purpose of this study was to determine the mode of cell death that occurs at the osteolytic interface of failed total hip arthroplasty (THA). TUNEL staining, DNA laddering, and immunodetection of poly(ADP-ribose)polymerase (PARP) protein were used to identify the presence of apoptosis in interface membranes from 25 patients aged 28-88 years old (mean, 58 years) harvested at the time of hip revision surgery. Our results demonstrated positive TUNEL stain in 100% of specimens with an average 37% of cells (range 12-60%) positively stained for TUNEL whereas less than 8% of control tissue cells showed positive staining. DNA laddering, a characteristic feature of apoptotic cells, was observed in 82% (28/34) of specimens studied at both the acetabular and femoral side of aseptically loose THAs. No laddering was observed in control tissues. Finally, using Western blot analysis, we observed the appearance of the 89 kDa PARP fragment associated with apoptosis in 92% of specimens (30/33). Our results demonstrate the presence of apoptotic cell death in interface membranes of THAs suggesting that apoptosis-related events are indeed associated with periprosthetic osteolysis and could serve as a specific target point for therapeutic modulation.

Journal Article↗
PubMed2001

New protease inhibitors prevent gamma-secretase-mediated production of Abeta40/42 without affecting Notch cleavage.

We have designed new non-peptidic potential inhibitors of gamma-secretase and examined their ability to prevent production of amyloid-beta 40 (Abeta40) and Abeta42 by human cells expressing wild-type and Swedish-mutant beta-amyloid precursor protein (betaAPP). Here we identify three such agents that markedly reduce recovery of both Abeta40 and Abeta42 produced by both cell lines, and increase that of C99 and C83, the carboxy-terminal fragments of betaAPP that are derived from beta-and alpha-secretase, respectively. Furthermore, we show that these inhibitors do not affect endoproteolysis of endogenous or overexpressed presenilins. These inhibitors are totally unable to affect the mDeltaEnotch-1 cleavage that leads to generation of the Notch intracellular domain (NICD). These represent the first non-peptidic inhibitors that are able to prevent gamma-secretase cleavage of betaAPP without affecting processing of mDeltaEnotch-1 or endoproteolysis of presenilins. The distinction between these two proteolytic events, which are both prevented by disruption of presenilin genes, indicates that although they are intimately linked with betaAPP and Notch maturation, presenilins are probably involved in the control of maturation processes upstream of enzymes that cleave gamma-secretase and Notch.

Amyloid Precursor Protein Secretases↗
PubMed2001

Endogenous beta-amyloid production in presenilin-deficient embryonic mouse fibroblasts.

Genetic and biochemical evidence have led to the suggestion that presenilins could be the long-searched-for gamma-secretase, the proteolytic activity that generates the carboxy terminus of amyloid beta-peptides. This activity is also thought to be responsible for the release of the Notch intracellular domain (NICD) from Notch. Here, we report the production of endogenous secreted and intracellular 40- and 42-amino-acid Abeta peptides in mouse fibroblasts deficient in presenilin 1, presenilin 2 or both. We show that the endogenous production of Abeta40 and Abeta42 was not altered by presenilin deficiency. By contrast, inactivating presenilin genes fully abolished NICD production. These data indicate that Abeta and NICD production are distinct catabolic events. Also, even though NICD formation is indeed presenilin dependent, endogenous secreted and intracellular beta-amyloid peptides are still generated in absence of presenilins, indicating that there is a gamma-secretase activity distinct from presenilins, at least in murine fibroblasts.

Amyloid beta-Peptides↗
PubMed2001

[Magnetic resonance imaging of dilatation of the ascending aorta after repair of coarctation of the aorta].

The authors studied the risk factors for dilatation of the ascending aorta in patients operated for coarctation of the aorta. A prospective study of the diameters of the ascending aorta by magnetic resonance imaging was undertaken in 46 patients with an average age of 30 months (range 6 days to 11 years) at surgery, and 10 years of age (6 months to 31 years) at the time of the investigation. The diameters were measured at the level of the sinus of Valsalva, at the sino-tubular junction, and compared with reference tables with respect to body surface area. Twenty six per cent of patients had dilatation of the ascending aorta. The predisposing factors were investigated. Age, type of surgery, postoperative hypertension. Doppler gradient in the isthmic region, anatomical appearances of the repair observed by MRI were not predictive of this complication. On the other hand, age of patients at MRI and bicuspid aortic valves (present in 66% of cases) (p < 0.05) were significant risk factors. These results indicate that regular follow-up by echocardiography or MRI of the diameter of the ascending aorta is necessary in patients operated for coarctation of the aorta and with bicuspid aortic valves.

Age Factors↗
PubMed2000

Lupine leghemoglobin I: expression in transgenic Lotus and tobacco tissues.

The proximal parts of the promoters of the genes for symbiotic-type hemoglobins are generally conserved, but the promoter of the lbI gene of lupine (LulbI) shows some unusual structural features. It lacks typical organ-specific elements characteristic of all the leghemoglobin gene promoters described thus far. We have analysed its functional activity in transgenic Lotus corniculatus. A fusion construct between the lbI promoter and the GUS reporter gene was expressed mainly in the central zone of the root nodule, but the product was also detected in the non-nodule root zone and in roots in tissue culture. In roots of transgenic tobacco, the activity of the promoter was only 24% lower than in Lotus nodules. LulbI promoter activity was also detected in tobacco leaves. Lupine hemoglobin I has a higher sequence identity to symbiotic-type hemoglobins and thus it groups within the "Class II" hemoglobins.

Base Sequence↗
PubMed2000

Early secondary acute myelogenous leukemia in breast cancer patients after treatment with mitoxantrone, cyclophosphamide, fluorouracil and radiation therapy.

BACKGROUND: The topoisomerase II-targeted drugs, epipodophyllotoxins and anthracyclines, have been shown to induce therapy-related AML (t-AML) characterized by a short latency period after chemotherapy, the absence of prior myelodysplastic syndrome and stereotyped chromosome aberrations. Few reports have been published on patients treated with the anthracenedione mitoxantrone which also targets topoisomerase II. We observed 10 cases of such t-AML over a 7-year-period in breast cancer patients treated with mitoxantrone combined with fluorouracil, cyclophosphamide and regional radiotherapy, and in three cases with vindesine. PATIENTS AND METHODS: We retrospectively analyzed patients referred to our hospital for AML with a past history of polychemotherapy for breast cancer, including mitoxantrone, either as adjuvant (8 patients)/neoadjuvant (1 patient) therapy or for metastatic disease (1 patient). We studied the probability of developing t-AML in a prospective series of 350 patients treated with an adjuvant FNC regimen (mitoxantrone, fluorouracil, cyclophosphamide) and radiation therapy. RESULTS: The median age was 45 years (range 35-67). t-AML developed 13-36 months (median 16) after beginning chemotherapy for breast cancer, and 4-28 months (median 10.5) after ending treatment. As described in t-AML following treatment with epipodophyllotoxins or anthracyclines, we found a majority of FAB M4, M5 and M3 phenotypes (7 of 10), and characteristic karyotype abnormalities that also can be found in de novo AML: breakpoint on chromosome 11q23 (3 patients), inv(16)(p13q22) (2 patients), t(15;17)(q22;q11) (1 patient), t(8;21)(q22;q22) (1 patient) and del(20q)(q11) (1 patient). The prognosis was poor. All patients died of AML shortly after diagnosis. Since two patients had been enrolled in a prospective trial for the treatment of breast cancer which included 350 patients, the probability of developing t-AML was calculated to be 0.7% from 25-40 months, using the Kaplan-Meier method (95%, confidence interval (95% CI): 0.1-4.5). CONCLUSIONS: The combination of mitoxantrone with cyclophosphamide, fluorouracil, and radiation therapy can induce t-AML, as with other topoisomerase II-targeted drugs. Despite a low incidence, the prognosis appears to be poor.

Adult↗
PubMed2000

Novel proline endopeptidase inhibitors do not modify Abeta40/42 formation and degradation by human cells expressing wild-type and swedish mutated beta-amyloid precursor protein.

Previous studies have suggested that proline endopeptidase (PE) could participate to the catabolism of the beta-amyloid peptide (Abeta) or to the physiopathological maturation of the beta-amyloid protein precursor (betaAPP). We have examined the putative ability of human purified PE to catabolize Abeta40 and Abeta42 and the possible contribution of this enzyme to the generation of Abeta40 and Abeta42 in human HEK293 cells. We show first that purified human PE does not degrade synthetic Abeta40 and Abeta42, in vitro. We establish that HEK293 cell homogenates exhibit a Z-Gly-Pro-7AMC-cleaving enzyme, the activity of which is inhibited by Z-Pro-Prolinal and S17092 and S19825, two novel PE inhibitors, with affinities similar to those displayed on the purified human PE. These inhibitors also penetrate cells and achieve a full inhibition of endogenous proline endopeptidase in human cells. By means of selective antibodies directed towards the C-terminal of Abeta40 and Abeta42, we assessed the effect of PE inhibitors on the recovery of both Abeta species. This was examined in HEK293 cells stably overexpressing the wild-type and the familial Alzheimer's disease-related Swedish mutated beta-APP. We establish that none of these inhibitors affected Abeta40 or Abeta42 production in these transfected cells. Overall, our study indicates that human PE does not degrade Abeta40 and Abeta42. Furthermore, PE does not contribute to Abeta40 and Abeta42 formation in HEK293 cells. Therefore, PE does not appear to contribute to the Abeta-related aetiology of Alzheimer's disease.

Amyloid beta-Peptides↗
PubMed2000

Characterization of plasmid-borne and chromosome-encoded traits of Agrobacterium biovar 1, 2, and 3 strains from France.

We collected 111 Agrobacterium isolates from galls of various origins (most of them from France) and analyzed both their plasmid-borne and chromosome-encoded traits. Phenotypic analysis of these strains allowed their classification in three phena which exactly matched the delineation of biovars 1, 2, and 3. A fourth phenon was identified which comprises three atypical strains. The phenotypic analysis has also allowed us to identify 12 additional characteristics which could be used to identify the three biovars of Agrobacterium. Our results also suggest that biovar 1 and 2 represent distinct species. Analysis of plasmid-borne traits confirmed that tartrate utilization is a common feature of biovar 3 strains (now named Agrobacterium vitis) and of Agrobacterium grapevine strains in general. Among pathogenic strains of Agrobacterium, several exhibited unusual opine synthesis and degradation patterns, and one strain of biovar 3 induced tumors containing vitopine and a novel opine-like molecule derived from putrescine. We have named this compound ridéopine.

Chromosome Mapping↗
PubMed1999

S 17092-1, a highly potent, specific and cell permeant inhibitor of human proline endopeptidase.

Several lines of evidence indicate that proline endopeptidase (PE) could participate to the symptomatology and/or etiology of Alzheimer's disease. Thus, proline endopeptidase appears to contribute to the degradation of neuropeptides involved in learning and memory and could also control the production of the amyloidogenic peptide Abeta. Therefore the design of potent, selective and permeant inhibitors of human PE should lead to potential probes to assess the genuine contribution of this enzyme in Alzheimer's pathology. A novel perhydroindol carboxylic derivative, S17092-1 inhibits the hydrolysis of Z-Gly-Pro-7AMC-hydrolysing activity present in human brain nuclei with a high affinity (Ki = 1 nM) and behaves as a highly potent (Ki = 1.5 nM) inhibitor of partially purified human PE. By contrast, S17092-1 is unable to affect a series of other peptidases including aminopeptidases B and M, dipeptidylaminopeptidase IV, endopeptidases 3.4.24.11, 3.4.24.15, 3.4.24.16, calpains and angiotensin-converting enzyme. Furthermore, we show that the embryonic human kidney 293 cell line displays an intracellular PE-like activity that is blocked after preincubating cells with S17092-1, indicating that this inhibitor penetrates in HEK293 cells and could affect intracellular human PE. Altogether, we establish that S17092-1 behaves as a highly potent, specific and cell permeant inhibitor of human proline endopeptidase and can be seen as a probe to examine PE contribution in Alzheimer's disease.

Alzheimer Disease↗
PubMed1999

Induction of macrophage apoptosis by ceramic and polyethylene particles in vitro.

The purpose of this study was to investigate in vitro the presence of apoptotic cell death after macrophage stimulation with different ceramic (Al2O3 and ZrO2) and high density polyethylene (HDP) particles. We also analyzed the effects of particle size, concentration, and composition. The J774 mouse macrophage cell line was exposed to commercial particles of different sizes (up to 4.5 microm) and concentrations (up to 500 particles per macrophage). Fluorescence microscopy and DNA laddering were used to investigate the presence of apoptosis in cell cultures after 24 h of incubation. Fluorescence microscopy of propidium iodide stained cells showed two characteristic morphological features that occur in apoptotic cells, namely nuclear condensation and heterogeneity of stain uptake. The effect of ceramic particles on apoptotic nuclear morphology was size- and concentration-dependent and reached a plateau above 150 particles per macrophage at 1.3 microm. With regards to composition, we did not find any difference in cell morphology between Al2O3 and ZrO2. Ceramic and HDP particles induced DNA fragmentation into oligonucleosomes as evidenced by DNA laddering, another characteristic of apoptosis. The induction of DNA laddering was size- and concentration-dependent whereas particle composition (Al2O3 vs. ZrO2 and Al2O3 vs. HDP) had no effect. In conclusion, our results demonstrated that ceramic and HDP particles induce macrophage apoptotic cell death in vitro and open doors for possible modulation of debris-induced periprosthetic osteolysis.

Aluminum Oxide↗
PubMed1999

Cytotoxicity and macrophage cytokine release induced by ceramic and polyethylene particles in vitro.

Although the response of macrophages to polyethylene debris has been widely studied, it has never been compared with the cellular response to ceramic debris. Our aim was to investigate the cytotoxicity of ceramic particles (Al2O3 and ZrO2) and to analyse their ability to stimulate the release of inflammatory mediators compared with that of high-density polyethylene particles (HDP). We analysed the effects of particle size, concentration and composition using an in vitro model. The J774 mouse macrophage cell line was exposed to commercial particles in the phagocytosable range (up to 4.5 microns). Al2O3 was compared with ZrO2 at 0.6 micron and with HDP at 4.5 microns. Cytotoxicity tests were performed using flow cytometry and macrophage cytokine release was measured by ELISA. Cell mortality increased with the size and concentration of Al2O3 particles. When comparing Al2O3 and ZrO2 at 0.6 micron, we did not detect any significant difference at the concentrations analysed (up to 2500 particles per macrophage), and mortality remained very low (less than 10%). Release of TNF-alpha also increased with the size and concentration of Al2O3 particles, reaching 195% of control (165 pg/ml v 84 pg/ml) at 2.4 microns and 350 particles per cell (p < 0.05). Release of TNF-alpha was higher with HDP than with Al2O3 particles at 4.5 microns. However, we did not detect any significant difference in the release of TNF-alpha between Al2O3 and ZrO2 at 0.6 micron (p > 0.05). We saw no evidence of release of interleukin-1 alpha or interleukin-1 beta after exposure to ceramic or HDP particles.

Aluminum Oxide↗
PubMed1999

Intracellular calcium stores are involved in growth hormone-releasing hormone signal transduction in rat somatotrophs.

In rat pituitary somatotrophs, the stimulation of growth hormone secretion by growth hormone-releasing hormone (GHRH) is a Ca(2+)-dependent event involving Ca2+ influx. The presence of calcium-induced calcium release (CICR) Ca2+ stores has been suggested in these cells. The aim of our study was to demonstrate the presence of CICR stores in rat somatotrophs and to determine their function in GHRH Ca2+ signalling. To this end we measured cytosolic free Ca2+ concentration ([Ca2+]i), using indo-1 in purified rat somatotrophs in primary culture, while altering intracellular Ca2+ stores. Ionomycin (10 ttM) or 4-bromo-A23187 (10 ItM), used to mobilise organelle-bound Ca2+, raised [Ca2+]i in the absence of extracellular Ca2+. Caffeine (5 to 50 mM), used to mobilise Ca2+ from CICR stores, transiently raised [Ca2+]i in 65% of cells tested. The response to 40 mM caffeine was abolished when Ca2+ stores were depleted, with 1 microM thapsigargin or with 10 microM ryanodine. All cells that responded to 40 mM caffeine responded to 10 nM GHRH. The [Ca2+]i response to 10 nM GHRH was reversible and repeatable. However, the second response was 38% smaller than the first. Ryanodine treatment abolished the reduction in the second [Ca2+]i response, while thapsigargin increased the reduction by 67%. We conclude that rat somatotrophs possess CICR Ca2+ stores and that they account for 30-35% of the GHRH-induced increase in [Ca2+]i, and that their partial depletion is involved in somatotroph desensitization.

Animals↗
PubMed1998

Flow cytometric analysis of macrophage response to ceramic and polyethylene particles: effects of size, concentration, and composition.

Using the J774 macrophage cell line, we designed an in vitro model to analyze by flow cytometry the effects of size, concentration, and composition of ceramic (Al2O3 and ZrO2) and high density polyethylene (HDP) particles on phagocytosis and cell mortality. Inflammatory mediator (TNF-alpha) also was measured by ELISA. Kinetic studies revealed that phagocytosis of the particles begins very early after cell exposure, increasing with time and particle concentration and reaching a plateau after 15 h. This implies that the optimum period to evaluate cellular response to particulate debris is between 15 and 24 h of incubation. Results also showed that phagocytosis increases with concentration for particles up to 2 microns. For larger particles (up to 4.5 microns), phagocytosis seems to reach a plateau independent of size and concentration, which suggests a saturation of phagocytosis that is most likely dependent on overall particle volume ingested. We did not detect any significant difference in phagocytosis between Al2O3 and ZrO2 at 0.6 microns. Al2O3 seems to be more easily phagocytosed than HDP at the same size (4.5 microns) and concentrations. Cytotoxicity studies revealed that macrophage mortality increases with particle size and concentration for sizes greater than 2 microns. Smaller particles (0.6 microns) cause cell mortality only at higher concentrations (from 1,250 particles per cell), but the mortality is still very low (10%). No significant difference in cell mortality and TNF-alpha release was found between Al2O3 and ZrO2. Effects of Al2O3 and HDP at 4.5 microns were compared by measuring TNF-alpha release. Results showed that TNF-alpha release increases with particle concentrations and is higher with HDP than with Al2O3.

Aluminum Oxide↗
PubMed1998

Expression of human placental D2-dopamine receptor during normal and abnormal pregnancies.

Previous studies have demonstrated the presence of D2-dopamine binding sites in the human placenta, and that dopamine (DA), via these D2-like receptors, inhibits both basal- and hormone-stimulated secretion of human placental lactogen (hPL) from trophoblastic cells. However, nothing is known about the ontogenesis of this placental D2-dopamine receptor (D2R) during pregnancy. Therefore, the aim of this study was to analyse the expression of these receptors throughout gestation in placentae from normal as well as abnormal pregnancies. Western and Northern blot analysis were performed on membrane protein and messenger RNA (mRNA) preparations of human placentae from various weeks of gestation as well as from pregnancies complicated by pre-eclampsia of hydatidiform mole. The autoradiographs of both proteins and mRNA showed differential expression of placental D2R during normal pregnancy. When the relative levels of D2R proteins were analysed throughout pregnancy, there was a significant but transient decrease of approximately 23 per cent of D2R content at 9-16 weeks of gestation with a return to baseline levels at 17-18 weeks. An increase in mRNA levels began at week 19 of gestation and reached a maximum value at term. During the first half of gestation, the relative levels of D2R mRNA (2.5 kb) showed an inverse pattern of expression when compared to D2R protein content. Specifically, the levels of D2R mRNA increased by approximately 26 per cent between weeks 9 and 16 of pregnancy in comparison with the values observed at 7-8 weeks, and returned to baseline levels at 17-18 weeks of gestation. The D2R relative protein levels subsequently increased from 19 to 30 weeks of gestation, and then remained stable. The autoradiographs of both proteins and mRNA showed significantly decreased expressions in placentae from both pre-eclamptic (approximately 45 per cent inhibition) and molar (approximately 0-70 per cent inhibition) pregnancies. Moreover, there was important variability in the expression of placental D2R from hydatidiform moles. Using immunological and molecular biology techniques, the present study confirms the presence of D2R in human placenta. The variations of placental D2R expression during normal and abnormal pregnancies argue for an important role of DA in human placental function, although this remains to be investigated further.

Autoradiography↗