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F Lévy

Publications and source records attributed to F Lévy.

At least 91 records · Page 5Linked to original sources
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↗
PubMed1987

Peridural anesthesia disturbs maternal behavior in primiparous and multiparous parturient ewes.

Several experiments were carried out to study the effects of peridural anesthesia (Sylvocaine, 6 ml between sacrum and 1st caudal vertebra) performed either at the first signs of birth (early peridural: EP), or little before expulsion (late peridural: LP). When performed late, peridural anesthesia altered maternal behavior only slightly when compared with controls. By contrast severe deficits were observed in the case of EP. Seven out of 8 primiparae failed to show interest for their lamb within 30 min of the birth of the young (vs. 1/9 in LP group, p less than 0.01). In multiparae these proportions were 8/27 and 0/22 respectively (p less than 0.01). Within the EP group the effects of the peridural were more marked in primiparous than in multiparous mothers (p less than 0.05). Even in EP multiparous ewes becoming maternal within 5 min after giving birth a reduction in duration of licking was noted, when compared with the LP group (p less than 0.05). On the other hand, these same ewes established normally a selective bond within 2 hours after giving birth, as did the LP or control ewes. These results confirm the importance of genital stimulation for the rapid onset of maternal behavior in parturient ewes. They failed however to clarify the role played by genital stimulation in the establishment of a selective maternal bond.

Afferent Pathways↗
PubMed1986

[Circadian rhythms of the so-called inflammation proteins in healthy subjects].

Circadian rhythms for the factors listed below were investigated in 14 subjects hospitalized in apparently good health: total proteins, albumin, pre-albumin, alpha-1-antitrypsin, orosomucoid, ceruloplasmin, C3, C-reactive protein, haptoglobin and transferrin. Seven venous blood samples were taken from each subject over a 24 hour period. A circadian rhythm was detected for the total proteins, prealbumin, alpha-1-antitrypsin, orosomucoid, ceruloplasmin and transferrin. The acrophases occurred at about 12 hour intervals and the authors research group are already investigating these rhythms for the "inflammation proteins" and the transport proteins in cancer and inflammatory processes.

Blood Proteins↗
PubMed1976

[New researches on protein synthesis inhibition under the action of aurintricarboxylic acid during cell cycle : Study on meristematic cells of Allium sativum L].

Aurin tricarboxylic acid, an inhibitor of protein synthesis, prevents cells from entering mitosis in Allium sativum L. root meristems. When the uptake of 3H-leucine comes back up to the control rate after removal of roots from the drug, mitotoic activity is resumed. Furthermore, the percent of labelled cells obtained by continuous labelling with H3-thymidine shows a reversible arrest of cell progress from G1 to S.

Aurintricarboxylic Acid↗
PubMed1976

[Study on a synchronized population of the antimitotic effect of cycloheximide at various phases of the cell cycle in Allium sativum L].

The effect on the entry in mitosis, induced in synchronized meristematic cells of Allium sativum L. by a treatment with cycloheximide (10 mug/ml-30 min) at different phases of the cell cycle has been investigated. In all cases cells enter mitosis after a long delay but it appears that the delay induced on G1 cells is longer. Incorporation of 3H leucine is immediately inhibited at any stage of the cell cycle.

Cell Division↗
PubMed1972

[Not Available].

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History, Ancient↗