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Biomedical subjects

F Lévy

Publications and source records attributed to F Lévy.

At least 55 records · Page 3Linked 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↗
PubMed1995

Naltrexone delays the onset of maternal behavior in primiparous parturient ewes.

Previous studies indicate that morphine facilitates the induction of maternal behavior in nonpregnant multiparous ewes but has no effect in nulliparous females. Naltrexone (NAL) has the opposite effect. The aim of the present experiment was to investigate whether this also applied at parturition in ewes lambing for the first time. We studied the behavior of parturient ewes that received either saline (n = 9) or 50 mg (n = 7) or 150 mg (n = 8) of naltrexone, intravenously, at the first signs of lambing. either dose of naltrexone was found to reduce significantly the duration of maternal licking of the neonate and the emission of low-pitched bleats during the first 30 min following parturition (p < 0.005). The proportion of mothers failing to display an immediate onset of maternal care (in < 5 min) was also significantly higher in NAL-treated ewes (six of 15 vs. none of nine; p = 0.05). On the other hand, there was no indication that NAL affected the establishment of selectivity or that it facilitated the manifestation of postpartum estrus. Our results therefore tend to confirm that opiates have a role in the facilitation of maternal behavior at parturition in the ewe.

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

The retinal pigment epithelial membrane receptor for plasma retinol-binding protein. Isolation and cDNA cloning of the 63-kDa protein.

Retinol, a metabolic precursor of retinal and retinoic acid, is transported in plasma by the plasma retinol-binding protein (RBP). The cellular uptake of retinol from RBP is believed to involve a specific membrane receptor for RBP. In retinal pigment epithelium the RBP receptor appears to be an oligomeric protein complex, and we have previously identified a 63-kDa membrane protein as part of this receptor. The 63-kDa protein (p63) has now been isolated, and we have cloned the corresponding cDNA. In a data base search no sequences similar to p63 were identified. Hydropathy analyses of the 533 amino acids deduced from the cDNA sequence did not indicate an N-terminal signal sequence or obvious transmembrane regions. In vitro translation of synthetic mRNA encoding p63, in the presence of heterologous microsomes, verified that p63 does not become cotranslationally membrane-inserted. Transcripts for p63 are abundantly expressed in retinal pigment epithelium with no detectable expression in several other tissues. Southern blotting analysis of bovine and human genomic DNA revealed several hybridizing fragments suggesting a complex organization of the corresponding genes.

Amino Acid Sequence↗
PubMed1993

Early events in the assembly of MHC class I antigens.

The MHC class I heavy chain and beta 2-microglobulin are cell surface proteins, and are synthesized on membrane bound ribosomes. They are co-translationally inserted into the endoplasmic reticulum (ER) membrane and assemble with antigenic peptides in the lumen of this compartment. These peptides are believed to be generated in the cytosol, and must be protected from degradation prior to translocation across the ER membrane. Putative peptide transporters (TAP1 and 2) belonging to the ABC transporter family of proteins, have been suggested to function in this process, and have been shown to be essential for MHC class I antigen assembly. The finding that peptides were translocated across the ER membrane in microsomes prepared from cells lacking the TAP genes has challenged this view. In this review we discuss the different events leading to correct assembly of MHC class I antigens. We suggest the TAP molecules to be part of a complex, which function to select peptides, protect them from degradation, and facilitate their translocation by targeting them to the ER membrane.

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↗
PubMed1993

Effects of parturition and maternal experience on noradrenaline and acetylcholine release in the olfactory bulb of sheep.

Acetylcholine (ACh) and noradrenaline (NA) release in the olfactory bulb (OB) of ewes was monitored using microdialysis. Both ACh and NA release increased at parturition in multiparous but not in primiparous ewes. However, vaginocervical stimulation performed 6 hr postpartum induced an increase of ACh and NA release in both primiparous and multiparous ewes, indicating that a maturation process had occurred. Finally, pharmacological challenges to the ACh and NA inputs revealed differential responsiveness between nulliparous and multiparous nongestant ewes. These results suggest that the first parturition induces changes in neural circuitry involving ACh and NA inputs to the OB.

Acetylcholine↗