Biomedical subjects

M Aubert

Publications and source records attributed to M Aubert.

At least 19 recordsLinked to original sources

PubMed2006

A cellular automaton model for the migration of glioma cells.

We present a study of in vitro cell migration in two dimensions as a first step towards understanding the mechanisms governing the motility of glioma cells. Our study is based on a cellular automaton model which aims at reproducing the kinetics of a lump of glioma cells deposited on a substrate of collagen. The dynamical effects of cell attraction and motion inertia are introduced through adequate automaton rules. We compare the density profiles given by the model to those obtained experimentally. The result of the best fit indicates a substantial cell-cell attraction due to cell-cell communication through gap junctions (or chemotaxis) and negligible inertia effects during migration. Tracking of individual migrating cells indicates highly convoluted cell trajectories.

Algorithms↗

PubMed2006

Tetracycline residues in honey after hive treatment.

Tetracyclines are used to control bacterial diseases such as European and American foulbrood, which may cause severe losses in the honey bee population and honey production. By using 24 hives randomly distributed into four groups of six hives, this study was performed to measure the occurrence of tetracycline hydrochloride (TC) residues in honey following two types of TC application. Two groups of colonies were treated three times with 0.5 g TC in 1 litre syrup (group S) or in 10 g powdered sugar (group P). Six hives of a first control group (C) fed with untreated syrup were installed at 20 and 45 m from groups S and P, respectively. A second control group (DC) was set up 3 km away. Honey was sampled at different times from all hives, and honey artificially contaminated with TC was stored in the laboratory at 4, 20 and 35 degrees C; all samples were analysed by ELISA and HPLC methods. One day after the last application, the mean TC concentration in brood chamber honey was ten times higher in group S (40.7 mg kg(-1)) than in group P (4.34 mg kg(-1)). After 8 days, TC residues were detected in all hives of group C. After 146 days, the mean TC concentration in harvested honey was 1.54, 0.35 and 0.15 mg kg(-1) for groups S, P and C, respectively. The control group C had been contaminated with TC by drifting. In all hives of group DC, no residues were detected at any time during the study. The honey collected at day 504 did not contain any detectable TC residues, except in one super from group C (0.026 mg kg(-1)). The half-life of TC in honey from supers was similar in groups C, S and P: 65 days. This duration was twice lower than in honey stored in laboratory in similar conditions: at 35 degrees C in the dark (t(1/2) = 121 days). In honey stored at 20 degrees C, TC was quite stable and its half-life was 242 days. The data from these experiments indicate levels of TC residues in honey after a treatment in hives, their persistence and diffusion into the apiary. These results show that the TC must be used with precaution in honey production.

Animals↗

PubMed2004

Elimination of terrestrial rabies in Western European countries.

Since the late 1930s, the red fox (Vulpes vulpes) has been the main vector of rabies in Europe. Practically, decimation of fox population did not prevent the spread of the disease. The only efficient method to control wildlife rabies consisted in using oral vaccination by depositing vaccine baits containing a capsule or a plastic sachet filled with an attenuated anti-rabies liquid vaccine throughout fox habitats. Several live virus vaccines have been and are currently being used: the SAD B19 and SAD P5/88 are rabies strains attenuated in cell culture, the SAG1 and SAG2 strains are apathogenic mutants of an already attenuated rabies strain, and the VRG vaccine is an attenuated vaccinia virus recombinant coding for the rabies glycoprotein gene. These vaccines have different residual pathogenicity. SAG1 and SAG2 are pathogenic only for suckling mice inoculated by intracerebral and oral routes. VRG presents absolutely no rabies risk to humans and the environment and the residual pathogenicity of the vaccinia vector virus is very low even for humans. Other parameters such as the thermostability of the vaccine and the melting point of the bait casing are of utmost importance to guarantee the success of oral vaccination campaigns. Additionally, VRG is the only vaccine that did not interfere with maternal immunity in fox cubs, an important issue for spring campaigns. Successes and failure of national programmes confirm that whatever the ecological conditions, the same rules must be strictly followed to ensure the success of rabies elimination programmes: (i) considering the strategy, any rabies vaccination programme must be organised with the support of a national scientific team specially designated for the task that will have to apply the only methods that have already been proved successful elsewhere in Europe, including rabies surveillance, bait distribution calendar and pattern, and monitoring of this distribution; (ii) vaccination must be pursued for at least two years after the last reported case of rabies in the area; (iii) the choice of a low cost but poorly efficient and poorly stable vaccine does not prove to be cost-beneficial for successful elimination of rabies. Several European countries have become rabies-free: Belgium, Luxembourg, France, Italy, Switzerland, Finland and the Netherlands. Since the European Union is going comprise 25 countries from May 2004, all the scientific knowledge is available for establishing efficient and adapted oral programmes aimed at eliminating terrestrial rabies from this area.

Animals↗

PubMed2003

Echinococcus multilocularis: secondary poisoning of fox population during a vole outbreak reduces environmental contamination in a high endemicity area.

This paper describes the role of fox population level on Echinococcus multilocularis infection in foxes in a highly endemic area in eastern France. Fox population level was monitored by spotlight survey at Le Souillot from 1989 to 2000, and from 1992 to 2000 at Chemin, a control site located in a low endemic area. The infection level of the fox population was estimated at Le Souillot from winter 1995 to winter 1999 using a coproantigen ELISA performed on faeces collected in the field. Population biomass of intermediate hosts (Microtus arvalis and Arvicola terrestris) was monitored using index methods from 1995 to 1999. At Le Souillot, a significant decline in the fox population level was recorded after spring 1997 (P<0.001), and the population level remained low until 2000. The decline occurred when 31% of the grassland area was treated with bromadiolone, an anticoagulant used at a large scale for the control of A. terrestris population outbreaks. No decline of population was recorded at Chemin, where bromadiolone was not used for rodent control. Significant differences among ELISA OD distributions in fox faeces were recorded for the five winters under study at Le Souillot (P=0.0004). The median of ELISA OD distribution was 0.209 and 0.207 before the population decline (winter 1995 and 1996, respectively), significantly increased to 0.306 just after the decline (winter 1997), and then significantly decreased to 0.099 and 0.104 afterwards (winter 1998 and 1999, respectively). Therefore, the decrease in infection level occurred during winter 1998, 1 year after the population decline, when the intermediate host biomass in the field was at its highest. These results suggest a complex dependence between the fox population level and E. multilocularis infection in a high endemicity area. Alternative ways to control fox population as a way to reduce E. multilocularis transmission in a given area are discussed.

4-Hydroxycoumarins↗

PubMed2003

Measurement of CTL-induced cytotoxicity: the caspase 3 assay.

Cytotoxic T lymphocytes (CTL) are critical effector cells of the immune system. Measurement of target cell damage has historically been an important measure of CTL function. CTL kill their target cells predominantly by inducing programmed cell death, or apoptosis. The gold standard for CTL-mediated cytotoxicity has been the (51)Cr release assay. However, measurement of target cell lysis by (51)Cr release does not provide mechanistic information on the fate of target cells, especially at the single cell level. Given the recent advances in our understanding of programmed cell death, newer assays are required which evaluate the status of the apoptotic pathways in target cells. We have developed a flow cytometry-based assay for CTL-mediated cytotoxicity based on specific binding of antibody to activated caspase 3 in target cells. Our assay is convenient and more sensitive than the (51)Cr release assay. The use of this assay should allow mechanistic studies of the intracellular events resulting from CTL attack.

Animals↗

PubMed2003

Viral oncoapoptosis of human tumor cells.

Many cancer cells refractory to radiation treatment and chemotherapy proliferate because of loss of intrinsic programmed cell death (apoptosis) regulation. Consequently, the resolution of these cancers are many times outside the management capabilities of conventional therapeutics. We now report that replication-defective delta27 herpes simplex virus (rd delta27) triggers apoptosis in three representative transformed human cell lines. Susceptibility to virus-induced cell death is dependent on the abundance and distribution of modified p53 protein in the tumor cells indicating specific targeting of the treatment. Primary human and mouse fibroblast cells that produce modified p53 are resistant to rd delta27 killing but not to apoptosis induced by nonviral environmental factors. These results suggest that induction of apoptosis by nonreplicating virus is a feasible genetic therapy approach for killing human cancer cells. Our findings may have important implications in designing novel virus-based anticancer strategies in appropriate animal model systems.

Animals↗

PubMed2003

Neutralising antibody titration in 25,000 sera of dogs and cats vaccinated against rabies in France, in the framework of the new regulations that offer an alternative to quarantine.

Regulations governing international movements of domestic carnivores from rabies-infected to rabies-free countries have recently been loosened, with the adoption of a system that combines vaccination against rabies and serological surveillance (neutralising antibody titration test with a threshold of 0.5 UI/ml). Since 1993, the Research Laboratory for Rabies and Wild Animal Pathology in Nancy, France, has analysed over 25,000 sera from dogs and cats using a viral seroneutralisation technique. The statistical analyses performed during this time show that cats respond better than dogs. Although no significant difference in titres was observed between primovaccinated and repeat-vaccinated cats, repeat-vaccinated dogs had titres above 0.5 IU/ml more frequently. In primovaccinated dogs, monovalent vaccines offered a better serological conversion rate than multivalent ones. Finally, the results of these analyses showed a strong correlation between antibody counts and the time that elapsed between the last vaccination and the blood sampling.

Animals↗

PubMed2001

Maximal exercise and muscle energy metabolism after recovery from exercise hyperthermia syndrome.

Muscle energy metabolism was studied in 30 subjects after recovery from exercise hyperthermia syndrome (EHTS subjects) and 15 healthy men with identical physical activities. Blood lactate, free fatty acid (FFA), serum creatine kinase activity (CK), and glycerol and the temperature in the auditory duct (T(c)) and on the thumb pad (T(sk)) were measured at rest and during and after maximal exercise on a cycloergometer. The EHTS subjects had a limitation of physical performance, with lowered values for maximal oxygen uptake (VO(2max), P < 0.0005), maximal workload (P < 0.05), and ventilatory threshold (V(t), P < 0.0005). The discrepancy between high plasma concentrations of FFA and the lack of decrease in respiratory ratio (RR) suggests that, in EHTS subjects, a very active release of FFA was not balanced by a proportional increase in catabolism. The increased skin temperature was smaller in EHTS subjects (P < 0.05 at 180 and 200 W). At the end of exercise, auditory duct temperature increase was higher in EHTS subjects than in control subjects (P < 0.05). This study thus showed an impairment of muscle metabolism and an abnormality of thermoregulatory mechanisms. These results may provide insight into the underlying physiopathological disturbance.

Adult↗

PubMed2001

Sub-MAC concentrations of desflurane do not inhibit hypoxic pulmonary vasoconstriction in anesthetized piglets.

PURPOSE: In vitro, halogenated agents reduce the pulmonary vasoconstrictor response to alveolar hypoxia in isolated perfused lungs. However, studies in intact animals have been less convincing. The aim of the present study was to assess the effect of sub-MAC concentrations of desflurane on hypoxic pulmonary vasoconstriction (HPV) in anesthetized piglets using the pressure/cardiac output relationship (P/Q). METHODS: Eleven large white piglets were anesthetized and ventilated mechanically, alternatively in hyperoxia (FIO2=0.4) and in hypoxia (FIO2=0.12). Multipoint plots of pulmonary arterial pressure (PAP), or differences between PAP and left atrial pressure (LAP) against Q were generated by gradual inflation of a balloon advanced into the inferior vena cava. P/Q relationships were established in hyperoxia and in hypoxia at baseline, and then with gradual concentrations of desflurane. RESULTS: In hypoxia, pressure gradients (PAP-LAP) increased significantly at every level of Q, demonstrating active pulmonary vasoconstriction. Desflurane did not affect these P/Q relationships either in hyperoxia, or in hypoxia, when compared with baseline. CONCLUSION: Desflurane at a clinically relevant dose has no significant effect on HPV in anesthetized piglets.

Anesthesia↗

PubMed2001

Modulation of apoptosis during herpes simplex virus infection in human cells.

Human herpes simplex virus (HSV) is cytolytic and has profound impacts on its host cells. Consequences of HSV infection include the induction of apoptosis and the concomitant synthesis of proteins which act to block this process. We review recent evidence showing how this important human pathogen modulates the fundamental cell death process.

Apoptosis↗

PubMed2001

An endogenous adrenoceptor ligand potentiates excitatory synaptic transmission in cultured hippocampal neurons.

Noradrenergic inputs modulate hippocampal function via distinct receptors. In hippocampal neuronal cultures, mRNA expression of adrenoceptor subtypes is maintained from 1 day in vitro (DIV) to 22 DIV. Noradrenaline dose-dependently stimulates phosphoinositide (PI) breakdown in both immature and mature cultures through the activation of alpha1 receptors. At 22 DIV, basal PI breakdown depends on excitatory synaptic activity since it is decreased by tetrodotoxin or glutamate receptor antagonists. At 22 DIV, a similar decrease of basal PI breakdown is also observed with alpha1, alpha2 or beta adrenoceptor antagonists. These effects are not additive with that produced by tetrodotoxin. Adrenergic antagonists also strongly reduce spontaneous excitatory post-synaptic currents (sEPSC) as evidenced by whole cell recording. Therefore, in hippocampal cultures, excitatory transmission is modulated by a tonic activation of adrenoceptors probably produced by an endogenous ligand. Indeed, (i) the depletion of catecholamine pools by reserpine also decreases both basal PI metabolism and sEPSC; (ii) hippocampal neurons possess both tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase mRNAs, encoding enzymes required for catecholamine synthesis; and (iii) some hippocampal neurons show TH-immunoreactivity. TH-positive cells are also detected in E18 hippocampal sections. Thus, cultured hippocampal neurons synthesize and release an adrenergic-like ligand, which tonically potentiates excitatory synaptic transmission in mature cultures.

Adrenergic Uptake Inhibitors↗

PubMed2001

A noninvasive investigation of muscle energetics supports similarities between exertional heat stroke and malignant hyperthermia.

Exertional heat stroke (EHS) is usually triggered by strenuous exercise performed under hot and humid environmental conditions. Although the pathogenesis of an EHS episode differs from that of a clinical malignant hyperthermia (MH) crisis, both conditions share some similarities in symptoms, such as the abnormal increase in core temperature. By use of (31)P magnetic resonance spectroscopy, we analyzed the muscle energetics of 26 post-EHS subjects for whom in vitro halothane/caffeine contracture tests were abnormal and investigated possible similarities with subjects susceptible to MH. An early decrease of pH was noted during the first minute of exercise in EHS subjects as compared with controls. EHS subjects were divided into two subgroups according to the diagnostic score previously developed for MH subjects. The 19 subjects (73%) with a score higher than 2 displayed significantly larger caffeine-induced and earlier ryanodine-induced contractures on muscle biopsies as compared with the rest of the group (7 subjects). The results demonstrate that muscle energetics are abnormal in subjects who have experienced EHS and suggest a possible link between MH and EH, although all EHS cannot be considered as MH.

Anesthetics, Inhalation↗

PubMed2001

Accumulation of herpes simplex virus type 1 early and leaky-late proteins correlates with apoptosis prevention in infected human HEp-2 cells.

We previously reported that a recombinant ICP27-null virus stimulated, but did not prevent, apoptosis in human HEp-2 cells during infection (M. Aubert and J. A. Blaho, J. Virol. 73:2803-2813, 1999). In the present study, we used a panel of 15 recombinant ICP27 mutant viruses to determine which features of herpes simplex virus type 1 (HSV-1) replication are required for the apoptosis-inhibitory activity. Each virus was defined experimentally as either apoptotic, partially apoptotic, or nonapoptotic based on infected HEp-2 cell morphologies, percentages of infected cells with condensed chromatin, and patterns of specific cellular death factor processing. Viruses d27-1, d1-5, d1-2, M11, M15, M16, n504R, n406R, n263R, and n59R are apoptotic or partially apoptotic in HEp-2 cells and severely defective for growth in Vero cells. Viruses d2-3, d3-4, d4-5, d5-6, and d6-7 are nonapoptotic, demonstrating that ICP27 contains a large amino-terminal region, including its RGG box RNA binding domain, which is not essential for apoptosis prevention. Accumulations of viral TK, VP16, and gD but not gC, ICP22, or ICP4 proteins correlated with prevention of apoptosis during the replication of these viruses. Of the nonapoptotic viruses, d4-5 did not produce gC, indicating that accumulation of true late gene products is not necessary for the prevention process. Analyses of viral DNA synthesis in HEp-2 cells indicated that apoptosis prevention by HSV-1 requires that the infection proceeds to the stage in which viral DNA replication takes place. Infections performed in the presence of the drug phosphonoacetic acid confirmed that the process of viral DNA synthesis and the accumulation of true late (gamma(2)) proteins are not required for apoptosis prevention. Based on our results, we conclude that the accumulation of HSV-1 early (beta) and leaky-late (gamma(1)) proteins correlates with the prevention of apoptosis in infected HEp-2 cells.

Animals↗

PubMed2000

Peritoneal colonization by human pancreatic cancer cells is inhibited by antisense FUT3 sequence.

Several alpha(1,3/1,4) fucosyltransferases expressed in human pancreatic cancer cells can participate in the biosynthesis of cell surface sialyl-Lewis a and sialyl-Lewis x antigens that contribute to hematogenous metastatis. Previously, we observed a significant increase of the alpha(1,4) fucosyltransferase activity in tumoral pancreatic cell lines, suggesting that FUT3 could be involved in the sialyl-Lewis antigen expression. Therefore, we invalidated the expression of FUT3 by expressing FUT3 antisense sequence in the human pancreatic tumor BxPC-3 cell line, which expresses the alpha(1,4) fucosyltransferase activity and harbors the cell surface sialyl-Lewis antigens. The decrease of FUT3 transcript after transfection of antisense cDNA of FUT3 in these cells results in a substantial reduction of sialyl-Lewis antigen expression on cell surface. This decreased antigen expression was associated with an inhibition of adhesive properties to E-selectin and a decrease of metastatic power of FUT3 antisense-transfected BxPC-3 cells as tested in nude mice. Our study provides evidence that the expression level of FUT3 may regulate the expression of sialyl-Lewis a and sialyl-Lewis x surface antigens and consequently could play an important role in metastatic properties of human pancreatic cancer cells.

Animals↗

PubMed2000

Restoration of alpha(1,2) fucosyltransferase activity decreases adhesive and metastatic properties of human pancreatic cancer cells.

The expression of alpha(1,2) fucosyltransferases that catalyze the fucose transfer to galactose of the N-acetyl(iso)lactosamine chain is decreased in human metastatic pancreatic cancer cells. alpha(2,3) Sialyltransferases catalyze the transfer of sialic acid to the same substrate to form, with alpha(1,3/1,4) fucosyltransferases, sialyl-Lewis a and sialyl-Lewis x determinants on cell surface that are involved in pancreatic metastatic invasion. The aim of this study was to determine whether this decrease of alpha(1,2) fucosyltransferase expression can favor the alpha(2,3) sialyltransferase activity to form metastatic sialyl-Lewis antigens. Restoration of alpha(1,2) fucosyltransferase activity in the human pancreatic cancer cell line BxPC-3 was obtained by selecting stable transfectants expressing FUT1. Overexpression of FUTI in BxPC-3 cells resulted in a substantial reduction of sialyl-Lewis antigen expression that correlated with an increase of expression of Lewis y and H-type antigens on cell surface. The modified oligosaccharide structures were preferentially restricted to three major glycoproteins, which could in part be related to mucin-type glycoproteins. The reduction of sialyl-Lewis antigen expression was associated with an inhibition of adhesive properties to E-selectin and a decrease of gastrointestinal metastatic power of BxPC-3 cells after xenograft transplantation into nude mice. This study provides evidence that the expression level of alpha(1,2) fucosyltransferase may regulate the expression of sialyl-Lewis a and sialyl-Lewis x antigens and consequently could play an important role in metastatic properties of human pancreatic cancer cells.

Animals↗

PubMed1999

Immunization of dogs with a DNA vaccine induces protection against rabies virus.

Rabies is a fatal encephalomyelitis which is transmitted to man, mostly by dogs in developing countries. This zoonosis can be prevented by vaccination of humans before or after exposure. However, a more radical approach is possible, involving the elimination of the principal vector/reservoir by vaccinating dogs. The vaccine must be effective, safe and inexpensive. Mass production of plasmids is possible and DNA-based immunization with a plasmid encoding the antigen responsible for inducing protection seems to be more cost-effective than classical techniques involving cell culture. Beagles were immunized by intramuscular (i.m.) injection with a plasmid encoding the rabies virus (PV strain) glycoprotein. Neutralizing antibodies against both wild-type rabies virus and European Bat Lyssaviruses (EBL1 and EBL2) were detected after a single injection and a boost, but levels of neutralizing antibodies against EBL1 were low. Moreover, all vaccinated dogs were protected against a lethal challenge with a wild-type dog rabies strain. This is one of the first studies to demonstrate that dogs can be protected by DNA vaccines, and opens important perspectives for rabies control.

Animals↗

PubMed1999

Opposite regulation by glucocorticoids of the alpha 1B- and alpha 2A-adrenoreceptor mRNA levels in rat cultured anterior hypothalamic slices.

In this study we investigated whether the expression of alpha1B- and alpha2A-adrenoreceptor mRNAs is differently modulated by glucocorticoids in rat cultured anterior hypothalamus slices. Using a semi-quantitative reverse transcription-polymerase chain reaction assay, the level of the alpha1B-adrenoreceptor mRNA was significantly reduced in slices cultured in steroid free-medium when compared with that measured in standard medium (i.e. containing basal adrenosteroid plasma concentrations). In contrast, the expression of the alpha2A-adrenoreceptor mRNA was markedly increased. Finally, the ratio of alpha1B- versus alpha2A-mRNA levels was about 1.7 and 0.7 in standard and steroid-free medium, respectively. These responses were completely reversed by supplementation with corticosterone. These findings provide the first evidence that in vitro glucocorticoids may regulate, in an opposite manner, the expression of the alpha1B-and alpha2A-adrenoreceptor mRNAs in the hypothalamus. This kind of regulation could be related to steroid-dependent changes in the noradrenergic control of neuroendocrine secretions.

Animals↗

PubMed1999

Induction and prevention of apoptosis in human HEp-2 cells by herpes simplex virus type 1.

Cultured human epithelial cells infected with an ICP27 deletion strain of herpes simplex virus type 1 (HSV-1) show characteristic features of apoptotic cells including cell shrinkage, nuclear condensation, and DNA fragmentation. These cells do not show such apoptotic features when infected with a wild-type virus unless the infections are performed in the presence of a protein synthesis inhibitor. Thus, both types of virus induce apoptosis, but the ICP27-null virus is unable to prevent this process from killing the cells. In this report, we show that this ICP27-deficient virus induced apoptosis in human HEp-2 cells through a pathway which involved the activation of caspase-3 and the processing of the death substrates DNA fragmentation factor and poly(ADP-ribose) polymerase. The induction of apoptosis by wild-type HSV-1 occurred prior to 6 h postinfection (hpi), and de novo viral protein synthesis was not required to induce the process. The ability of the virus to inhibit apoptosis was shown to be effective between 3 to 6 hpi. Wild-type HSV-1 infection was also able to block the apoptosis induced in cells by the addition of cycloheximide, staurosporine, and sorbitol. While U(S)3- and ICP22-deficient viruses showed a partial prevention of apoptosis, deletion of either the U(L)13 or vhs gene products did not affect the ability of HSV-1 to prevent apoptosis in infected cells. Finally, we demonstrate that in UV-inactivated viruses, viral binding and entry were not sufficient to induce apoptosis. Taken together, these results suggest that either gene expression or another RNA metabolic event likely plays a role in the induction of apoptosis in HSV-1-infected human cells.

Animals↗