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Biomedical subjects

M Moreau

Publications and source records attributed to M Moreau.

At least 109 records · Page 6Linked to original sources
PubMed1996

Meiosis reinitiation in Ruditapes philippinarum (Mollusca): involvement of L-calcium channels in the release of metaphase I block.

Prophase-arrested oocytes of Ruditapes philippinarum cannot be fertilised or stimulated by excess KCl, in contrast to the situation found in other bivalve species such as Barnea and Spisula. However, these oocytes can be triggered to reinitiate meiosis following treatment by serotonin or several pharmacological agents (calcium ionophores, thapsigargin, weak bases) which promote an intracellular calcium surge. Ruditapes oocytes further arrest in metaphase I, at which stage they can be activated either by sperm or by excess KCl. This suggests that functional voltage-operated calcium channels are expressed in this species during the course of maturation. Using pharmacological tools and direct binding of specific dihydropyridines, we demonstrate that these channels are L-type calcium channels which become functional after serotonin stimulation, their number increasing before germinal vesicle breakdown. Moreover we establish that: (1) the addition of 20 microM S(-)BayK8644, an agonist of L-type calcium channels, to metaphase-arrested oocytes releases them from metaphase block; (2) incubating these oocytes with PN200-110, a potent blocker of L-type calcium channels, inhibits their activation by both excess KCl and fertilisation. Taken together these data suggest that the absence of L-type calcium channels in the membrane of prophase-arrested oocytes of Ruditapes may account for their inability to be fertilised.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1996

Nocardiosis: a rare cause of pleuropulmonary disease in the immunocompromised host.

We report a case of acute pleuropulmonary nocardial infection in a 24-year-old woman suffering from systemic lupus erythematosus. In most instances, No-cardia asteroides is an opportunistic pathogen. In our patient, the infection was facilitated by systemic lupus erythematosus and chronic use of corticosteroids and immunosuppressive drugs. N. asteroides was cultured from both pleural effusion and blood. No extrathoracic location was found and the patient improved upon intravenous antibiotics and pleural drainage. Owing to the poor tolerance of trimethoprim/sulfamethoxazole, the patient was treated successfully with imipenem. The predisposing factors, the clues to the diagnosis and the therapy of nocardiosis are briefly reviewed.

Adult↗
PubMed1996

The spatiotemporal development of innervation in spinal ligaments of chickens.

The development of the innervation of both central and lateral (intertransverse) spinal ligaments was investigated in chickens between the time of hatching and 13 wk of age. A total of 36 White Leghorn chickens in 4 groups of 9 at ages 0, 2, 7, and 13 wk were used. The spinal ligaments were dissected, serially sectioned and labelled with a monoclonal antibody against neurofilament protein and observed using either conventional fluorescence or confocal microscopy. Only a few nerve elements were found in the ligaments at hatching and these consisted simply of single nerve fibres and small nerve bundles. The number of nerve elements increased rapidly up to 7 wk of age when large nerve bundles and Ruffini corpuscles were also found. The number of nerve elements decreased between 7 and 13 wk birds when the ligaments had begun to ossify and the amount of collagenous ligamentous tissue was significantly reduced. The fluctuation in numbers of neural elements was due to changes in numbers of single nerve fibres and small nerve bundles rather than large nerve bundles and Ruffini corpuscles which remained constant. In contrast to this significant increase in numbers of nerve elements, the innervation density of the ligaments decreased because of the overwhelming increase of the ligament volume due to growth. There were no differences between ligaments on the left and right sides of the body, but there was an unequal distribution of the neural elements within the ligaments; most were found in the cranial third of the intertransverse ligaments. These results show that significant changes in innervation of spinal ligaments occur during development and reflect the possibility that damage to the ligaments during this time could produce significant and permanent damage, especially in relation to the maintenance of an erect spine.

Animals↗
PubMed1995

Leukaemia Inhibitory Factor derived from rat colon carcinoma cells increases host susceptibility to tumour growth.

We have tested Leukaemia Inhibitory Factor (LIF) production by 12 rat colon tumour clones isolated from a single cell line that display various degrees of tumorigenicity. A highly significantly relationship was found between levels of soluble LIF produced by the clones and their in vivo tumorigenicity. Such results suggested a role for LIF as a tumour facilitating agent. To test this hypothesis, the highly tumorigenic and LIF producing PROb clone was transfected with the LIF cDNA in antisense orientation in order to decrease LIF production. Conversely, REGb, a low LIF producer that is rejected by syngeneic animals, as well as nude mice, was transfected with the LIF cDNA to increase its production. PROb cells transfected with antisense cDNA were shown to have decreased LIF production along with decreased tumorigenicity. LIF-transfected REGb cells expressing high LIF levels still regressed in syngeneic rats, but could form progressive tumours in nude mice. We did not detect LIF receptors on PROb or REGb cells and their in vitro proliferation was not modified by the addition of exogenous LIF. Therefore, LIF was not an autocrine growth regulator for PROb and REGb cells. Instead, LIF appears to facilitate in vivo tumour growth, without being an immunosuppressive factor sufficient on its own to allow growth of immunogenic cells in fully immunocompetent hosts.

Adenocarcinoma↗
PubMed1995

In vivo labelling of L-type Ca2+ channels by fluorescent dihydropyridine: correlation between ontogenesis of the channels and the acquisition of neural competence in ecotderm cells from Pleurodeles waltl embryos.

The ability of the ectodermal cells to be induced and to differentiate toward neural tissue, called neural competence, is acquired shortly before gastrulation and lost during late gastrula stages in Pleurodeles waltl embryos. We have examined ectodermal cells' neural competence in relation to the evolution of the density of L-type calcium channels using the fluorescent labelled dihydropyridine probe (STBodipy-DHP). We find that the appearance of dihydropyridine sensitive calcium channels (L-type Ca2+ channels) is correlated with the acquisition of neural competence by the ectoderm cells. The highest density of these channels is reached when competence of the ectoderm is optimal. Conversely, the decrease of L-type Ca2+ channel density occurs simultaneously with the normal loss of competence. In addition, we show that these channels are functional since stimulation by S(-)-Bay K 8644 triggered an increase in [Ca2+]i revealed by fluorescence measurements using Fluo-3. This increase in [Ca2+]i is a function of the L-type Ca2+ channels' density. We propose that the molecular basis of the gain and loss of neural competence is linked to the presence of L-type Ca2+ channels in ectodermal cell membranes of Pleurodeles waltl embryos.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1995

Progressive development of gap junctions during growth of human pancreatic duct cells (Capan-1) in vitro and in vivo.

Among their numerous functions, gap junctions play a crucial role in proliferation, differentiation and secretion processes, although their existence and potential role in ion secretion in human pancreatic ducts have yet to be established. To investigate the morphogenesis and the role of gap junctions in human pancreatic duct cells, the Capan-1 cell line maintained in culture or heterotransplanted into nude mice was employed as model system. Capan-1 cells polarize during their growth in vivo and in vitro forming duct-like structures. Furthermore in culture, after confluence, these cells form domes, which is indicative of ion exchange processes. After treatment with tannic acid and freeze-fracture, gap junctions were observed along the basolateral membranes of Capan-1 cells on electron microscopic examination. The presence of alkaline phosphatases on gap junctions was demonstrated cytoenzymatically. In addition, cell-to-cell communication was visualized by microinjection of Lucifer yellow. During differentiation of Capan-1 cells in culture, the frequency of intercellular communications increased markedly over the period (days 11-13) when the cells form duct-like structures. The increase in gap junctions was demonstrated by analysis of the polarized cells organized in duct-like structures that are commonly observed in the tumors formed by heterotransplantation of Capan-1 cells into nude mice. Furthermore, gap junctions associated with tight junctions were also observed in the cells forming such structures. The role of gap junctions in ion exchange was evaluated by counting the number of domes in cultures treated with heptanol. Heptanol (an uncoupling agent of gap junction communication) completely inhibited dome formation in a reversible way, and reduced the frequency of intracellular communications by 44%. These results suggest that the gap junctions expressed by Capan-1 cells are involved in ion secretion by the human cancerous pancreatic duct cell line, Capan-1. In the present study, we show that: i) the expression of gap junctions is linked to development of the spatial conformation of the cells; and ii) gap junctions may be involved in ion secretion.

Adenocarcinoma↗
PubMed1995

Quantitative investigation of in vitro flow using three-dimensional colour Doppler ultrasound.

A quantitative in vitro flow study was performed by using a three-dimensional colour Doppler imaging system. This system was based on a clinical ultrasound instrument with its transducer mounted on a motor-driven translation stage. A vascular and tissue-mimicking phantom containing two wall-less vessels, one normal and another stenotic, was used to quantify the measurement accuracy of the flow velocity and the flow field. Steady state flows, having Reynolds numbers ranging between 460 and 1300, were generated by a computer-controlled positive displacement pump. Effects of the parameter settings of the ultrasound instrument on results of the estimation of flow field were also studied. Experimental results show that our three-dimensional colour Doppler system's velocity accuracy was better than 7% of the Nyquist velocity and its spatial accuracy was better than 0.5 mm. The system showed a good correlation (r = 0.999) between the estimated and the true mean flow velocity, and a good correlation (r = 0.998) between the estimated maximum and the true mean flow velocity. This study is our first step toward validating the measurement of the three-dimensional velocity and wall shear stress distributions by using three-dimensional colour Doppler ultrasound

Blood Flow Velocity↗
PubMed1995

Increased plasma levels of human interleukin for DA1.a cells/leukemia inhibitory factor in sepsis correlate with shock and poor prognosis.

Animal study results have suggested a role in sepsis for human interleukin for DA1.a cells/leukemia inhibitory factor (HILDA/LIF). HILDA/LIF and interleukin-6 (IL-6) levels were prospectively studied by serial ELISAs in 34 septic patients. HILDA/LIF was detected in 11 of 34 patients at plasma levels of 100-37,000 pg/mL. Peak HILDA/LIF levels correlated with increased temperature and creatinine and IL-6 and with decreased arterial CO2 (P < .05). Multivariate analysis showed that shock and decreased arterial CO2 accounted for 75% of peak HILDA/LIF plasma variations (R2 = .753). Fatal outcome was most often associated with detectable HILDA/LIF (> 56 pg/mL) and peak IL-6 plasma levels > 850 pg/mL (sensitivity, 83%; specificity, 87%), but both (at respective levels of > 480 and > 850 pg/mL) were associated with fatal outcome. HILDA/LIF was detected in septic patients exhibiting shock, and its levels correlated with higher mortality and shorter survival.

APACHE↗
PubMed1995

Tissue factor pathway inhibitor activity associated with LDL is inactivated by cell- and copper-mediated oxidation.

Human plasma contains a multivalent, Kunitz-type proteinase inhibitor termed tissue factor pathway inhibitor (TFPI), which is a specific inhibitor of the action of the factor VII(a)-tissue factor complex in coagulation. A major fraction of plasma TFPI is transported in association with LDL. Because LDL may undergo oxidation in the arterial wall during atherogenesis, we examined the effect of copper- and cell-mediated oxidative modification on TFPI activity associated with LDL. Oxidation mediated by copper ions resulted in a significant inactivation of LDL-associated TFPI (60% to 72% at 24 hours with 2.5 mumol/l CuCl2). The inactivation of TFPI was strongly negatively correlated with both an increase in the net electrical charge of LDL (r = -.80, P < or = .0001) and with the production of thiobarbituric acid-reactive substances (r = -.78, P < or = .0001) and lipid peroxides (r = -.80, P < or = .0001). Cell-mediated oxidation, involving incubation of LDL for 48 hours with either monocyte-like THP1 cells or human monocytes in Ham's F-10 medium, effected a significant decrease (64% and 75%, respectively) in LDL-associated TFPI activity. By contrast, prolonged exposure of LDL to purified soybean lipoxygenase (5000 U/mL) was less effective in inactivating TFPI (47% reduction after incubation for 72 hours at 37 degrees C). We subsequently investigated the mechanism(s) that may underlie such inactivation. Oxidation of LDL is accompanied by the generation of various aldehydes, including malondialdehyde and 4-hydroxynonenal. Chemical modification with these aldehydes revealed a significant inverse correlation between the progressive loss of TFPI activity and both the increase in net electrical charge (r = -.90, P < or = .0001) and the derivatization of free amino acid residues of LDL (r = -.90, P < or = .0001). Specific chemical modification of lysine amino groups by acetylation similarly led to inactivation of LDL-associated TFPI activity. TFPI activity was almost totally abolished (< 1.4%) when the TNBS reactivities of acetylated LDL, malondialdehyde-modified LDL, and 4-hydroxynonenal-modified LDL were 31%, 21%, and 43% that of native LDL, respectively. Our data demonstrate that expression of LDL-associated anticoagulant activity is markedly decreased as a consequence of the oxidative process, and suggest that the progressive aldehydic derivatization of apo B of LDL, and of the associated TFPI protein, may contribute to this phenomenon. Because tissue factor is overexpressed in the atheromatous plaque, it may exert a marked local procoagulant effect.(ABSTRACT TRUNCATED AT 400 WORDS)

Blood Coagulation↗
PubMed1995

4-aminopyridine acts as a weak base and a Ca2+ mobilizing agent in triggering oocyte meiosis reinitiation and activation in the Japanese clam Ruditapes philippinarum.

Ovarian oocytes of the prosobranch mollusc Patella vulgata and the pelecypod Ruditapes philippinarum are arrested during prophase of the first maturation division. Release from this blockade, which is revealed by germinal vesicle breakdown, drives these oocytes to a second arrest in metaphase I, at which time the oocytes become fertilizable. The respective roles of Ca2+ and H+ ion movements during this early step in meiosis reinitiation has not been fully established yet. In this work we reveal the presence of acidic vesicles and report that bafilomycin A1 and N,N'-dicyclohexylcarbodiimide, two inhibitors of the vacuolar-type H(+)-ATPase, applied to Ruditapes oocytes, produce a significant inhibition of their response to the natural neurohormone serotonin. Since sodium deprivation did not affect this response, this suggests that a v-type ATPase pump, possibly located in the membrane of these acidic vesicles, may play a subtle role in the cascade of events that releases oocytes from their prophase block. We then describe how 4-aminopyridine, a drug reputed to be a K+ channel antagonist, triggers both meiosis reinitiation and activation of Patella and Ruditapes oocytes. This agent acts as a weak base, its effect depending on external pH. Moreover, using the fluorescent probes BCECF and Fluo-3/AM, we observe that this drug both alkalinizes the endoplasm and promotes an intracellular Ca2+ surge. This dual effect may explain why Ruditapes oocytes no longer stop in metaphase under these conditions and behave like other bivalve species which are directly fertilizable at the germinal vesicle stage.

4-Aminopyridine↗
PubMed1995

A comparison of spinal ligaments--differences between bipeds and quadrupeds.

Following dissection, the spinal ligaments were observed in a selection of bipedal, pseudobipedal and quadrupedal animals during a search for an appropriate animal model for investigating the innervation of these ligaments. Midline spinal ligaments were found in all animals while lateral spinal ligaments could only be observed in bipedal (human) and pseudobipedal (avian) species. The presence of lateral spinal ligaments in these animals and their absence in quadrupeds suggests that the development of the lateral ligaments reflects a mechanical challenge unique to the erect spine and that these lateral spinal ligaments are fundamental to the stability of an erect posture.

Animals↗
PubMed1995

Regulation of Na+, K+ ATPase activity during meiotic maturation of Pleurodeles waltl oocytes. Role of calcium.

Changes in activity of the Na+, K+ ATPase of maturing Pleurodeles waltl were followed by measuring the resting potential in presence or absence of the specific inhibitor dihydroouabain. Corresponding currents were measured in voltage clamp conditions to eliminate the differences in resting potential at the origin and at the end of the meiotic maturation process. Our data confirm previous results obtained on Xenopus, indicating that the Na+,K+ pump activity disappears from the plasma membrane during progesterone-induced maturation and can be reactivated by an increase in internal Ca2+ triggered by ionomycin. Moreover we show by ultrastructural histochemistry that these modulations are likely to depend on the internalization and reinsertion of the transporter into the plasma membrane.

Animals↗
PubMed1995

Thimerosal triggers meiosis reinitiation in oocytes of the Japanese clam Ruditapes philippinarum by eliciting an intracellular Ca2+ surge.

Ovarian oocytes of the bivalve mollusc Ruditapes philippinarum are arrested during first meiotic prophase. Release from this blockade is triggered by the neurohormone serotonin (5HT or 5-hydroxytryptamine), which promotes germinal vesicle breakdown and drives these oocytes to a second arrest in metaphase I. 5HT action involves binding to a specific G protein-coupled receptor which results in a transient rise in IP3 and in the intracellular free Ca2+ concentration. Here we analyze the cytological effects and mode of action of the sulphydryl reagent thimerosal which could also trigger meiosis reinitiation in Ruditapes. No metaphase I spindle formed under these conditions since thimerosal was found to be able to preclude or reverse tubulin polymerization when applied to prophase- or to metaphase-arrested oocytes, respectively. Our results strongly suggest that the common final target for 5HT and thimerosal actions consists in a transient rise in internal free Ca2+ level that we could follow using Fluo3/AM as a probe. The effect of thimerosal in promoting oocyte maturation and increasing intracellular free Ca2+ concentration was improved by excess KCI. In addition, thimerosal, but not KCI, was found to facilitate 5HT-induced maturation at subthreshold hormone concentrations which, by themselves, did not produce an intracellular Ca2+ surge. These data suggest that thimerosal may inhibit Ca2+ pumps of the endoplasmic reticulum and unmask the plasma membrane voltage-sensitive Ca2+ channels which also appear after 5HT-induced GVBD.

Aniline Compounds↗