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Biomedical subjects

F Lévy

Publications and source records attributed to F Lévy.

At least 19 recordsLinked to original sources
PubMed1995

Oxytocin and vasopressin release in the olfactory bulb of parturient ewes: changes with maternal experience and effects on acetylcholine, gamma-aminobutyric acid, glutamate and noradrenaline release.

Maternal behaviour and the ewe's ability to recognize her lamb depend on olfactory cues and parturition, and are facilitated by maternal experience. Parturition induces a variety of neurochemical changes in the brain and, in particular, oxytocin (OT) release. This peptide injected centrally induces maternal behaviour. Oxytocin release occurs in the olfactory bulb (OB) at parturition and yet this structure is involved in the process of selective bonding with lamb. The present study therefore investigated the possibility that oxytocin release in the OB might modulate the release of classical transmitters that are known to be important in controlling selective recognition and whether maternal experience has any effect on this. We have first used in vivo microdialysis to measure OT release, as well as that of the related peptide, arginine-vasopressin (AVP), in the OB of maternally experienced and inexperienced ewes during parturition. While OT release significantly increased in both primiparous and multiparous ewes at parturition this increase was significantly greater in multiparous ewes. No significant change of AVP release was observed in either group. However, vagino-cervical stimulation (VCS) performed at 6 h post-partum caused similar increases in OT but not AVP release in both primiparous and multiparous ewes suggesting that the first birth experience potentiates the ability of VCS to evoke OT release within 6 h of parturition. Using retrodialysis, either OT (10 microM) or AVP (10 microM) were infused into the OB of multiparous and nulliparous ewes and their effects on modulating acetylcholine (ACh), noradrenaline (NA), glutamate and gamma-aminobutyric acid (GABA) release were monitored. Both peptides produced an increase of ACh and NA in multiparous animals and this effect was either absent or less pronounced in nulliparous animals. OT, but not AVP, also increased GABA release equivalently in nulliparous and multiparous animals. Glutamate release was not altered in response to OT or AVP infusion. These results suggest that OT release in the OB at parturition may facilitate the recognition of lamb odours by modulating NA, ACh and GABA release which are of primary importance for olfactory memory. The reduced release of OT in the OB of primiparous ewes at parturition, together with its reduced ability to modulate NA and ACh release, might also partly explain why maternally inexperienced animals require a longer period to selectively bond with their lambs.

Acetylcholine↗
PubMed1995

Synthesis of poly(ADP-ribose) in asbestos treated rat pleural mesothelial cells in culture.

To investigate the origin of DNA repair in rat pleural mesothelial cells (RPMC) exposed to asbestos fibers, poly(ADP-ribose) polymerase (PARP) activity was measured in the asbestos-treated cells. As bleomycin has been shown to activate poly(ADP-ribose) synthesis in several cell systems, the response to bleomycin with regard to PARP assay was first investigated. Bleomycin produced a dose-dependent increase of poly(ADP-ribose) synthesis in RPMC. Likewise both chrysotile and crocidolite fibers produced a concentration-dependent PARP activation indicating that the formation of DNA strand breaks is one type of damage produced by asbestos in RPMC. Enhancement of DNA repair, assessed by the measurement of [3H] methylthymidine incorporation in growth arrested cells, was not detectable in the presence of 3-methoxybenzamide (3-MBA), a PARP inhibitor, confirming a relation between PARP activation and DNA repair. The participation of DNA breakage in asbestos toxicity on RPMC was determined by the colorimetric 3-4(5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. There was no relationship between DNA breakage and cytotoxicity since the use of PARP inhibitors did not change cell viability. These results indicate that asbestos produce DNA damage that is repaired in RPMC.

Animals↗
PubMed1995

Involvement of the main but not the accessory olfactory system in maternal behavior of primiparous and multiparous ewes.

The respective roles of the main and accessory olfactory systems in the development of maternal behavior and selective suckling were investigated in parturient primiparous and multiparous ewes. Vomeronasal nerve section before parturition did not disturb either maternal behavior or maternal selectivity at suckling. By contrast, anosmia induced by zinc sulphate infusion had significant effects on the onset of maternal behavior in primiparous ewes. The onset of licking and of suckling were delayed and licking times and maternal bleats were reduced. Such disturbances were not observed in multiparous anosmic ewes, indicating that experience can compensate for the loss of olfactory information. On the other hand, anosmia prevented selective care regardless of maternal experience. Our results underline the importance of the main olfactory system for the development of adequate maternal behavior in sheep.

Animals↗
PubMed1994

Role of oxygen derivatives in the cytotoxicity and DNA damage produced by asbestos on rat pleural mesothelial cells in vitro.

The role of reactive oxygen metabolites in the toxic effects of asbestos on pleural mesothelial cells is not well defined. We exposed rat pleural mesothelial cells (RPMC) to chrysotile and crocidolite fibers (0-40 micrograms/cm2) in the presence or absence of catalase and superoxide dismutase (SOD). Cell injury was measured using the colorimetric 3-4 (5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and DNA damage was evaluated in terms of unscheduled DNA synthesis (UDS). Catalase (100 U/ml) and SOD (250 U/ml) protected RPMC against asbestos-induced cytotoxicity and DNA damage. However, the inactivated enzymes and bovine serum albumin also showed some protection, suggesting that the effect of antioxidant enzymes may be partly related to their protein nature. These results suggest that oxygen derivatives are partly involved in the toxic effects of asbestos on cultures of RPMC. The presence of extracellular proteins may also decrease asbestos-produced toxicity by reducing the degree of RPMC-fiber interaction.

Animals↗
PubMed1993

Influence of birth and maternal experience on olfactory bulb neurotransmitter release.

The ewe's ability to selectively recognize her lamb depends upon vaginocervical feedback to the brain stimulating an interest in lamb odours. This process is facilitated by previous maternal experience. We have used in vivo microdialysis to measure changes in the release of intrinsic transmitters in the olfactory bulb (glutamate, dopamine and GABA) at parturition to determine if their release profiles differ depending upon the ewe's past maternal olfactory experience. Glutamate and GABA release increased significantly at parturition in multiparous but not primiparous ewes. Dopamine release increased in both groups but mean basal levels of this transmitter were significantly higher in primiparous ewes during the pre-partum period and the first few hours postpartum. The changes in the underlying neural circuitry which determine these differences are established within 6 h of parturition, as revealed by artificial stimulation of the reproductive tract. This procedure renders the system plastic enabling adoption of strange lambs and, contingent, on this, the release of intrinsic transmitters no longer differs between the two groups of ewes. Pharmacological challenges to the olfactory bulb using retrodialysis in nulliparous and multiparous (maternally inexperienced and experienced) ewes produced significant differences between the groups for induction of glutamate and GABA release, but not that of dopamine. K+ challenges produced greater increases in glutamate and GABA release in multiparous than in nulliparous ewes, while dopamine release did not differ with experience. Glutamate receptor blockade produced increases in glutamate ase without changing GABA release.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Autoradiographic detection of vasopressin binding sites, but not of oxytocin binding sites, in the sheep olfactory bulb.

Oxytocin facilitates maternal behaviour in sheep. In the present study, we searched for the presence of oxytocin and vasopressin binding sites in the sheep olfactory bulb, a brain area which is thought to be involved in specific bond formation between the ewe and its lamb. Using in vitro autoradiography, we observed binding of tritiated vasopressin to the glomerular layer of the olfactory bulb. Competition studies performed with structural analogues and the use of a 125I-labelled linear vasopressin antagonist suggested that sites which bind vasopressin are V1 type receptors. In contrast, specific binding sites for oxytocin in the olfactory bulb could be detected neither in control females, nor in ovariectomized females treated with estradiol nor in postparturient ewes, although such sites were present in the uterus.

Animals↗
PubMed1992

Changes in the sensory processing of olfactory signals induced by birth in sheep.

After giving birth, sheep and many other species form a selective bond with their offspring based on the sense of smell. Processing of olfactory signals is altered to allow the animals to perform this selective recognition. Lamb odors have little effect on either neurotransmitter release or electrical activity of neurons in the olfactory bulb before birth. However, after birth there is an increase in the number of mitral cells, the principal cells of the olfactory bulb, that respond to lamb odors, which is associated with increased cholinergic and noradrenergic neurotransmitter release. Selective recognition of lambs is accompanied by increased activity of a subset of mitral cells and release of glutamate and gamma-aminobutyric acid (GABA) from the dendrodendritic synapses between the mitral and granule cells. The relation between the release of each transmitter after birth also suggests an increased efficacy of glutamate-evoked GABA release.

Animals↗
PubMed1992

Intracerebral oxytocin is important for the onset of maternal behavior in inexperienced ewes delivered under peridural anesthesia.

Measurement of cerebrospinal concentrations of oxytocin (OT) in intact and peridural-anesthetized ewes showed that central release of OT during parturition is inhibited by this anesthesia. Also, observations of maternal behavior and attraction to amniotic fluid (AF) in inexperienced peridural-anesthetized parturient ewes after intracerebroventricular injections of either OT (2 x 10 micrograms) or saline showed that OT infusions increased the proportion of maternal females (2/17 vs. 10/20; p = .01) and attraction to AF. This study confirms that in sheep vaginocervical stimulation activates the oxytocinergic system, which induces the onset of maternal behavior, and that this action is not limited to maternally experienced females.

Anesthesia, Epidural↗
PubMed1991

ATP is required for in vitro assembly of MHC class I antigens but not for transfer of peptides across the ER membrane.

We have translated the HLA-B27 heavy chain in vitro and studied its assembly with beta 2-microglobulin and peptide in microsomes from human cells. The assembly process requires ATP. However, the translocation of peptide across the endoplasmic reticulum (ER) membrane does not require ATP, and binding of biotinylated peptide to BiP, an ER luminal protein, occurs after ATP depletion. Proteinase K treatment of the microsomes does not block peptide translocation. Thus, ATP is required in the lumen of the ER for efficient assembly to occur. Microsomes prepared from Raji and T1 cells show similar levels of assembly, whereas assembly in T2 microsomes is 10-fold lower. This difference remains after peptide stimulation of assembly. The inefficient assembly in T2 microsomes is not due to impaired peptide translocation across the ER membrane, as no difference was found compared with microsomes from T1 cells. Instead, the defect seems to reside in the lumen of the ER.

Adenosine Triphosphate↗
PubMed1991

Individual olfactory signatures as major determinants of early maternal discrimination in sheep.

Responses of recently parturient ewes to their familiar versus separated (i.e., unfamiliar) twin lambs were observed in an attempt to elucidate further the characteristics of the phenotypic traits (signatures) mediating maternal recognition and bonding. Ewes responded more positively to their familiar lamb than to its twin that had been isolated at birth. Nonetheless, those same mothers also discriminated between their separated twin and unfamiliar alien lambs. Alien lambs elicited similar rejection behavior regardless of whether they had been housed with their own mother or in isolation prior to testing. Lambs appear to have individually distinct (olfactory) signatures; however, the signatures of twin siblings may be sufficiently similar to enable the mother to detect a resemblance. No evidence suggests that acquired maternal labels play a role in either the acceptance of the ewe's own lamb(s) or rejection of aliens.

Animals↗
PubMed1991

Importance of vaginocervical stimulation for the formation of maternal bonding in primiparous and multiparous parturient ewes.

The importance of vaginocervical stimulation for the formation of the maternal bond between a ewe and its lambs was investigated by studying the ability of artificial mechanical vaginocervical stimulation to induce adoption of an alien lamb after the selective bond with the ewe's own lambs had been formed. Results showed that for both multiparous and primiparous ewes, 5 min of mechanical VCS (using a hand) was effective in inducing complete acceptance of an alien lamb (6-48 h old) between 6.5 and 7.5 h postpartum in the majority of animals (8/10 multiparous, 8/9 primiparous) without interfering with the bond between the ewe and its own lambs. In a second group of multiparous animals, 6 out of 7 animals were also induced to completely accept an alien lamb between 26.5 and 27.5 h postpartum. It was found that the most critical aspect of the VCS was pressure on, and stretching the neck of, the cervix. Results show that VCS is not only important for the stimulation of maternal behavior, but also for the formation of the selective maternal bond. The ability of VCS to trigger the formation of a new maternal bond extends for at least 27.5 h post-partum.

Animals↗
PubMed1991

Translocation of peptides through microsomal membranes is a rapid process and promotes assembly of HLA-B27 heavy chain and beta 2-microglobulin translated in vitro.

We have translated major histocompatibility complex (MHC) class I heavy chains and human beta 2-microglobulin in vitro in the presence of microsomal membranes and a peptide from the nucleoprotein of influenza A. This peptide stimulates assembly of HLA-B27 heavy chain and beta 2-microglobulin about fivefold. By modifying this peptide to contain biotin at its amino terminus, we could precipitate HLA-B27 heavy chains with immobilized streptavidin, thereby directly demonstrating class I heavy chain-peptide association under close to physiological conditions. The biotin-modified peptide stimulates assembly to the same extent as the unmodified peptide. Both peptides bind to the same site on the HLA-B27 molecule. Immediately after synthesis of the HLA-B27 heavy chain has been completed, it assembles with beta 2-microglobulin and peptide. These interactions occur in the lumen of the microsomes (endoplasmic reticulum), demonstrating that the peptide must cross the microsomal membrane in order to promote assembly. The transfer of peptide across the microsomal membrane is a rapid process, as peptide binding to heavy chain-beta 2-microglobulin complexes is observed in less than 1 min after addition of peptide. By using microsomes deficient of beta 2-microglobulin (from Daudi cells), we find a strict requirement of beta 2-microglobulin for detection of peptide interaction with the MHC class I heavy chain. Furthermore, we show that heavy chain interaction with beta 2-microglobulin is likely to precede peptide binding. Biotin-modified peptides are likely to become a valuable tool in studying MHC antigen interaction and assembly.

Amino Acid Sequence↗
PubMed1990

Unscheduled DNA synthesis in rat pleural mesothelial cells treated with mineral fibres.

Unscheduled DNA synthesis (UDS) was studied in confluent rat pleural mesothelial cells (RPMCs) arrested in G0/G1 with hydroxyurea (HU) and treated with various fibre types, i.e., chrysotile, crocidolite or attapulgite. In addition, the effects of UV light and of benzo[a]pyrene were determined as references. Using autoradiography after [3H]thymidine incorporation ([3H]dThd), RPMCs treated with 4 micrograms/cm2 of chrysotile fibres exhibited a low but significant enhancement of net grains compared to untreated cells. Treatment with higher doses of chrysotile was not possible because of the impairment of microscopic observation due to the presence of the fibres. Using liquid scintillation counting, RPMCs treated with chrysotile or crocidolite showed a significant dose-dependent increase in [3H]dThd incorporation compared to untreated cells. In contrast, attapulgite did not enhance [3H]dThd incorporation compared to untreated cells. Treatment of RPMCs with 1, 2 or 4 micrograms/ml of benzo[a]pyrene resulted in a significant increase in [3H]dThd incorporation. In order to discount a possible role of S cells in the augmentation of [3H]dThd incorporation, despite the presence of 5 mM HU, S cells were counted by autoradiography. Results indicated that the percentage of S cells was similar in asbestos-treated and untreated cultures. Stimulation of the S phase also seems unlikely because treatment of RPMCs with asbestos fibres in the absence of HU resulted in a reduction of [3H]dThd incorporation attributed to an impairment of the S phase by the fibres. 1-4 micrograms/ml benzo[a]pyrene or 10-50 J/m2 UV light resulted in an approximate doubling of [3H]dThd incorporation. The effects of inhibitors of DNA repair were determined in chrysotile-treated RPMCs. [3H]dThd incorporation was inhibited by cytosine arabinoside and nalidixic acid. These results show that asbestos produces UDS in RPMCs.

Animals↗
PubMed1990

Importance of beta-noradrenergic receptors in the olfactory bulb of sheep for recognition of lambs.

Within a 4-hr period after parturition, the ewe learns the odor of her lamb that will allow later recognition of her offspring from alien lamb. This study investigated the importance of the activation of olfactory bulb (OB) beta-noradrenergic receptors in establishing this olfactory memory. Pregnant ewes (n = 24) were cannulated bilaterally in the OB. Two days before parturition, OB were perfused continuously (10 microliters/hr) with either a solution containing the selective beta-noradrenergic antagonist propranolol (10(-3) M) or vehicle. The results showed that, although 8 of 9 control ewes were still able to bond selectively to their lambs, only 7 of 15 propranolol-treated animals were able to bond (p = .04). These results suggest that activation of beta-noradrenergic receptors in the OB during the period surrounding parturition is required to establish olfactory recognition of the lamb.

Animals↗
PubMed1990

Co-expression of the human HLA-B27 class I antigen and the E3/19K protein of adenovirus-2 in insect cells using a baculovirus vector.

We have expressed the human MHC class I HLA-B27 antigen, human beta 2-microglobulin, and the E3/19K protein of adenovirus-2 in Spodoptera frugiperda insect cells (Sf9) by using the Autographa californica nuclear polyhedrosis virus. All genes were inserted under the strong polyhedrin promoter in the vector pVL941. The proteins were expressed at high levels, ranging from 1 to 8 mg protein per 3 x 10(9) cells. Both a full-length and a truncated form of HLA-B27 were expressed. The latter was terminated at the border of the membrane-spanning segment at the extracellular side of the membrane. The HLA-B27 antigens and the E3/19K protein showed considerable heterogeneity with respect to glycosylation. Only a small fraction of HLA-B27 was assembled (less than 5%) with beta 2-microglobulin. Nevertheless, we were able to find the heavy chain at the cell surface, and by co-infection with the recombinant virus for beta 2-microglobulin we observed an increase in cell surface expression. The E3/19K protein of adenovirus-2 blocks cell surface expression of HLA class I antigens in human cells and has a similar effect in insect cells. In contrast to beta 2-microglobulin it assembles efficiently to the heavy HLA-B27 chain, both the full-length and truncated forms. The E3/19K protein does not stimulate assembly of HLA-B27-beta 2-microglobulin. Due to these problems of assembly and the heterogeneity of glycosylation we predict that it will be difficult to use HLA antigens produced in insect cells for X-ray crystallographic studies.

Adenovirus E3 Proteins↗
PubMed1990

Requirements for the association of adenovirus type 2 E3/19K wild-type and mutant proteins with HLA antigens.

The E3/19K protein of human adenovirus type 2 is a resident of the endoplasmic reticulum (ER). Immediately after synthesis, it associates with major histocompatibility complex class I antigens and prevents their intracellular transport and cell surface expression. We have generated several C-terminal deletion mutants of the E3/19K protein that are preterminated at various positions on both sides of the membrane-spanning segment of the protein. One of these mutants is terminated at the luminal side of the membrane (M310), and two are terminated in the hydrophobic segment (M374 and M392), whereas mutant M621 is terminated on the cytoplasmic side of the ER membrane. The M310, M374, and M392 mutants are soluble proteins. They do not associate with HLA antigens in transfected 293 cells, and they are, to some extent, secreted into the medium. The M621 mutant protein is integrated in the ER membrane, associates immediately after its synthesis with HLA antigens, and exits from the ER. By using either an in vitro translation system supplemented with microsomes or overexpression in insect cells, we showed that M374 and E3/19K are able to associate with HLA antigens. These results indicate that the conformation of the luminal part of the E3/19K protein is not grossly altered by the mutations. Rapid transport of the M374 mutant out of the ER and partial degradation of this protein may prevent the interaction with HLA class I antigens in transfected 293 cells.

Adenovirus Early Proteins↗
PubMed1988

Genital, olfactory, and endocrine interactions in the development of maternal behaviour in the parturient ewe.

This article reviews current understanding of the physiological control of maternal behaviour in parturient ewes. Estradiol is an important endocrine factor which stimulates maternal responsiveness, both in nonpregnant and in parturient ewes. However, its action depends on previous maternal experience, and other factors are also necessary for the rapid manifestation of maternal behaviour. Olfactory cues play a major role in the normal development of the mother-young relationship. Genital stimulation (GS) is a key factor influencing various aspects of maternal responsiveness in sheep. GS acts in synergy with peripheral hormones to induce the rapid onset of licking and immediate acceptance of a neonate at the udder in nonpregnant ewes. It also influences the attraction of amniotic fluid at parturition and reduces aggressive behaviour towards lambs. Deprivation of GS by peridural anesthesia disturbs maternal behaviour in parturient ewes, especially in primiparae. And, additional GS in postparturient ewes allows the formation of a new bond with an alien neonate in mothers which had already established a selective relationship with their own lambs. Some of these positive effects of GS are mediated through modifications of olfactory function (attraction of amniotic fluid, establishment of a selective bond), whereas this may not be the case for other effects (stimulation of licking, reduction of aggressive behaviour). Studies of the neural mechanisms involved will be necessary to specify the modes of action of GS. The first results suggest GS may act in at least two ways at the level of the brain. Stimulation of maternal behaviour could depend on the liberation of oxytocin within the brain, since intracerebroventricular injections of this hormone facilitate maternal responses. Also, GS can influence olfactory function through the activation of afferent noradrenergic pathways in the olfactory bulbs. Further studies need to be developed to specify the relationships between the various structures involved as well as the level at which estradiol exerts its facilitatory action.

Animals↗