Biomedical subjects

F Lévy

Publications and source records attributed to F Lévy.

At least 19 recordsLinked to original sources

PubMed2007

Influence of the mother in the development of flavored-food preference in lambs.

The aim of the study was to determine the influence of the mother in the development of flavored-food preference in lambs. First, we demonstrated that lambs that ate flavored food in the presence of their mothers before weaning ate more of this food 1 month after weaning than lambs that ate flavored food with other ewes or lambs exposed to nonflavored food with their mothers. Second, lambs that could only see their mothers eating the flavored food and had access to the food's olfactory cues before weaning, showed similar preference for flavored food 1 month after weaning to lambs that ate the flavored food with their mothers. However, lambs that were separated from their mothers while their mothers consumed flavored food did not reveal a preference for it. Overall these results suggest that development of food preference in lambs depends mainly on observation of the mother, provided there is also access to olfactory cues characterizing the food.

Animal Feed↗

PubMed2006

Superconductivity in doped cubic silicon.

Although the local resistivity of semiconducting silicon in its standard crystalline form can be changed by many orders of magnitude by doping with elements, superconductivity has so far never been achieved. Hybrid devices combining silicon's semiconducting properties and superconductivity have therefore remained largely underdeveloped. Here we report that superconductivity can be induced when boron is locally introduced into silicon at concentrations above its equilibrium solubility. For sufficiently high boron doping (typically 100 p.p.m.) silicon becomes metallic. We find that at a higher boron concentration of several per cent, achieved by gas immersion laser doping, silicon becomes superconducting. Electrical resistivity and magnetic susceptibility measurements show that boron-doped silicon (Si:B) made in this way is a superconductor below a transition temperature T(c) approximately 0.35 K, with a critical field of about 0.4 T. Ab initio calculations, corroborated by Raman measurements, strongly suggest that doping is substitutional. The calculated electron-phonon coupling strength is found to be consistent with a conventional phonon-mediated coupling mechanism. Our findings will facilitate the fabrication of new silicon-based superconducting nanostructures and mesoscopic devices with high-quality interfaces.

Journal Article↗

PubMed2006

Forebrain structures specifically activated by conditioned taste aversion.

This study investigates which forebrain structures show Fos protein expression during conditioned taste aversion (CTA) acquisition and whether Fos expression depends on the aversion strength. A novel taste paired with an intraperitoneal injection of a low dose of the malaise-inducing agent lithium chloride (LiCl) induced a weak CTA, whereas associating this novel taste with a high dose of LiCl induced a strong CTA. Increasing the strength of the gastric malaise alone enhanced Fos expression in central, basal, and lateral amygdala nuclei and decreased Fos expression in the nucleus accumbens core. Taste-malaise association induced specific Fos activation in the insular cortex (with both the low and the high doses of LiCl) and the nucleus accumbens shell (with the high LiCl dose only). No significant variation of Fos expression was measured in the perirhinal cortex. Several forebrain areas may be sites of taste-malaise convergence during CTA acquisition depending on the strength of the aversion.

Analysis of Variance↗

PubMed2005

Heart failure due to left ventricular systolic dysfunction: treatment at discharge from hospital and at one year.

BACKGROUND: The treatment of heart failure (HF) due to left ventricular systolic dysfunction has been defined in recent guidelines, but these guidelines are not always applied in routine clinical practice. One of the objectives of the ETICS study was to evaluate medical treatment at discharge and after 1 year in patients hospitalised for a first episode of congestive HF due to left ventricular systolic dysfunction in 2000. METHODS: One hundred and seventy nine patients (63% males, mean age of 69+/-13 years) with an ejection fraction < or = 40% were prospectively included. The main aetiology was ischaemic heart disease (44%). RESULTS: The drugs prescribed at discharge and at one year, respectively, were loop diuretics in 95% and 91% of cases, angiotensin-converting enzyme (ACE) inhibitors in 82% and 75%, spironolactone in 35% and 37%, beta-blockers in 25% and 41%, digitalis glycosides in 34% and 30% of cases, and nitrates in 20% and 16% of cases. ACE inhibitors were prescribed at discharge and at 1 year at dosages reaching 64+/-29% and 72+/-30% of the recommended doses, respectively, and beta-blockers were prescribed at 26+/-16% and 35+/-25% of recommended doses, respectively. CONCLUSION: Diuretics and ACE inhibitors are largely prescribed in HF due to left ventricular systolic dysfunction, followed by spironolactone. Beta-blockers are still underused both in terms of the rate of patients receiving them and the daily doses. These results highlight the value of continuing to widely circulate official practice guidelines in order to improve the management of HF due to left ventricular systolic dysfunction.

Adrenergic beta-Antagonists↗

PubMed2005

Magnetic field-induced superconductivity in the ferromagnet URhGe.

In several metals, including URhGe, superconductivity has recently been observed to appear and coexist with ferromagnetism at temperatures well below that at which the ferromagnetic state forms. However, the material characteristics leading to such a state of coexistence have not yet been fully elucidated. We report that in URhGe there is a magnetic transition where the direction of the spin axis changes when a magnetic field of 12 tesla is applied parallel to the crystal b axis. We also report that a second pocket of superconductivity occurs at low temperature for a range of fields enveloping this magnetic transition, well above the field of 2 tesla at which superconductivity is first destroyed. Our findings strongly suggest that excitations in which the spins rotate stimulate superconductivity in the neighborhood of a quantum phase transition under high magnetic field.

Journal Article↗

PubMed2005

Estradiol receptor-alpha expression in hypothalamic and limbic regions of ewes is influenced by physiological state and maternal experience.

The influence of estrus, pregnancy, parturition, and maternal experience on the expression of estrogen receptor-alpha (ERalpha) was investigated in hypothalamic and limbic regions of the sheep brain, using immunocytochemistry. Four days before parturition, previous maternal experience was associated with a higher density of ERalpha-labeled neurons in the paraventricular and supraoptic nuclei, the medial preoptic area, and the medial amygdala, but not in the mediobasal hypothalamus. Furthermore, an interaction was found between physiological state and experience in the peripartum period as the effect of experience existing 4 days prepartum was not found at parturition, when densities were lowest both in primiparous and in multiparous ewes. An additional effect of physiological state was also observed between parturition and estrus, densities being significantly lower at parturition than at estrus in the SON, PVN, and MPOA, but not in the medial amygdala. These results indicate that in sheep ERalpha expression is influenced by previous physiological and/or maternal experience at specific times of the reproductive cycle. They are also congruent with the higher ability of multiparous than nulliparous ewes to show maternal behavior several days prepartum.

Amygdala↗

PubMed2005

[When should one operate for severe asymptomatic aortic stenosis?].

The most common cause of aortic stenosis is degenerative and progression of the disease is slow. Deciding to proceed to aortic valve replacement in an asymptomatic patient is always difficult. Only a minority will require valve replacement after repeated work-ups including stress testing and serial echographic examinations. In the future, stress echocardiography and BNP measurements may prove helpful in decision making.

Aortic Valve Stenosis↗

PubMed2005

Mapping of brain networks involved in consolidation of lamb recognition memory.

In sheep, ewes at parturition are responsive to any newborn lamb, but within less than 1 h, mothers learn to recognize the odor of their lamb and restrict maternal care to their own offspring (maternal selectivity). In a first experiment, we investigated the long-term retention of maternal selectivity after various mother-young contact and separation durations. After 4 h of contact, 36 h of separation leads to a total loss of selectivity. Increasing contact duration to 7 days prior to this separation maintains selectivity. These data suggest that lamb memory after going through an initial labile state after parturition, is consolidated over time into a more stable long-term memory. Fos immunohistochemistry reveals that reintroduction of the lamb after 4 h of mother-young contact and 3 h of separation activates different maternal brain regions than reintroduction of the lamb after 7 days of mother-young contact and 3 h of separation. While the piriform cortex shows an enhanced activation at both times, a selective enhancement of activation is observed in the frontal medial and orbitofrontal cortices only after 7 days of mother-young contact. These data suggest that as consolidation occurs, the neurobiological networks sustaining lamb memory involve different structures.

Animals↗

PubMed2004

[Anaesthesia and intensive care for cardiac surgery in France: results of the three days national survey realised in 2001 by the club of Anaesthesia, Intensive Care and Technics in Cardiac Surgery (ARTECC)].

OBJECTIVES: Ageing of the surgical population and the evolution in anaesthetic techniques have led the Club d'anesthésie-réanimation et techniques en chirurgie cardiaque (ARTECC) to conduct a survey among French cardiac surgery centers. The aim was to profile patient population undergoing cardiac surgery and perioperative techniques employed. STUDY: National prospective study including all adult patients undergoing cardiac surgery on January 23rd, 24th and 25th, 2001. Data were collected during the first 48 postoperative hours. MATERIAL AND METHODS: Seven referent centers drafted a record form. Sixty-one centers sent back 425 patient forms, 399 were analyzed. The following were statistically studied: type of surgery, patient characteristics, preoperative treatment, monitoring, anaesthesia, cardio-pulmonary bypass (CPB) characteristics, duration of mechanical ventilation, length of stay in intensive care unit, postoperative complications. RESULTS: Patient mean age was 64.3 +/- 13.3 years. Patients over 80-year-old represented 2.5% of the population. Beating heart coronary aortic bypass grafts (13% surgery) and preoperative transoesophagal echography were not frequent. Propofol and sufentanil were the main anaesthetic agents used. There was a marked trend for fast-track procedures. CONCLUSIONS: The ARTECC study pointed out some reserve in practices and that the impact of new techniques seems limited. Regular use of studies of that kind will provide an effective tool to compare national practices.

Adult↗

PubMed2004

Olfactory regulation of maternal behavior in mammals.

In mammals, olfactory cues are extensively used in many aspects of maternal care to ensure the coordination of mother-infant interactions and consequently the normal development of the offspring. Outside the period of parturition and lactation, when the young are not a behavioral priority, olfactory cues play an inhibitory role on maternal responsiveness since in most mammalian species studied so far, nonpregnant females find the odor of young aversive. On the contrary at the time of parturition, a shift in the hedonic value of infantile odors occurs so that the young now become a very potent stimulus and this sensorial processing constitutes an important part of the maternal motivational system. Moreover, infants' odors provide a basis for individual recognition by their mothers and some species (ungulates) have developed highly specialized mechanisms for processing of the infant signals. Perception of the smell of the young also regulates various aspects of maternal behavior. Dodecyl propionate, a compound released by of pup's preputial glands, has been shown to influence anogenital licking behavior, a fundamental pattern of maternal behavior in rodents. While there is no functional specificity of either the main or the accessory olfactory systems in the development of maternal behavior amongst species, it appears that only the main olfactory system is implicated when individual odor discrimination of the young is required. Neural structures, such as the main olfactory bulb, undergo profound changes when exposed to offspring odors at parturition. These changes in synaptic circuitry contribute both to maternal responsiveness to these odors, to their memorization, and to effects of long-term maternal experience.

Animals↗

PubMed2003

Complete maternal deprivation affects social, but not spatial, learning in adult rats.

The effects of maternal deprivation on learning of social and spatial tasks were investigated in female adult rats. Pups were reared artificially and received "lickinglike" tactile stimulation (AR animals) or were reared with their mothers (MR animals). In adulthood, subjects were tested on paradigms of spatial learning and on paradigms involving learning of social cues. Results showed that maternal deprivation did not affect performance on spatial learning, but it did impair performance on the three social learning tasks. The AR animals made no distinction between a new and a previously presented juvenile conspecific. AR animals also responded less rapidly than MR animals at test for maternal behavior 2 weeks after a postpartum experience with pups. Finally, AR animals did not develop a preference for a food previously eaten by a familiar conspecific whereas MR animals did. This study indicates that animals reared without mother and siblings show no deficits in spatial tasks while showing consistent deficits in learning involving social interactions.

Animals↗

PubMed2002

Twenty-four-hour-old lambs rely more on maternal behavior than on the learning of individual characteristics to discriminate between their own and an alien mother.

Lambs can discriminate their own mother from an alien dam on the first day of life, suggesting the recognition of individual physical characteristics of the mother. Alternatively, their choice may depend on behavioral differences existing between the ewes because of their maternal selectivity. To clarify this, the ability of 24-hr-old lambs to discriminate between their own and an alien mother, that were either intact and accept only their own lamb at nursing (i.e., selective, n = 19) or anosmic, which nurse indiscriminately alien lambs as well as their own (i.e., nonselective, n = 24), was assessed by a 5-min, two-choice test. With intact dams, lambs spent significantly more time next to their own mother whereas this was not so in the presence of anosmic dams. Furthermore, in the intact group, the vocal activity by their own mother differed from that by the alien dam while this was not so in anosmic ewes. We conclude that 24-hr-old lambs rely more on the behavior of the ewes to select their dam than on their individual physical characteristics.

Animals↗

PubMed2002

[Aortic stenosis with left ventricular dysfunction].

Patients affected by aortic stenosis with severe systolic left ventricular dysfunction have a poor spontaneous prognosis. The results of valvular replacement are globally good, at the price of an acceptable operative mortality. The existence of surgical failure has however prompted much work aimed at better definition of prognostic factors and for proposing new methods of specifying surgical indications. In this article based on a review of the literature, we discuss the physiopathology of left ventricular dysfunction, predictive factors for operative risk and survival, and the elements to be taken into account in order to adjust therapeutic decisions in these severe cases.

Aortic Valve Stenosis↗

PubMed2001

Control of cell cycle progression in human mesothelioma cells treated with gamma interferon.

Recombinant human interferon gamma (r-hu-IFNgamma) exerts both antitumoral activity in the early stages of human malignant mesothelioma and a cytostatic effect in human mesothelioma (HM) cell lines in vitro. The antiproliferative effect of interferons (IFNs) reported in a variety of cells has been attributed to several mechanisms. In order to progress in the understanding of HM cell growth modulation by r-hu-IFNgamma, modifications of cell cycle progression and expression of key cell cycle regulator proteins in response to r-hu-IFNgamma were examined. Nine HM cell lines were studied, including one resistant to the antiproliferative effect of r-hu-IFNgamma. Except in the resistant cell line r-hu-IFNgamma produced an arrest in the G1 and G2-M phases of the cell cycle, associated with a reduction in both cyclin A and cyclin dependent kinase inhibitors (CDKIs) expression. Moreover cyclin B1/cdc2 activity was decreased. The present study provides the first evidence of a G2-arrest in r-hu-IFNgamma-treated HM cell lines and indicates that HM cell lines, despite their tumorigenic origin still support cell cycle control. The cell cycle arrest induced by r-hu-IFNgamma seems to depend on cyclin regulation through p21(WAF1/CIP1)- and p27(Kip1)-independent mechanisms and is not directly related to the induced DNA damage.

Antineoplastic Agents↗

PubMed2001

Lack of tumor recognition by hTERT peptide 540-548-specific CD8(+) T cells from melanoma patients reveals inefficient antigen processing.

Telomerase is a ribonucleoprotein complex responsible for the maintenance of the length of the telomeres during cell division, which is active in germ-line cells as well as in the vast majority of tumors but not in most normal tissues. The wide expression of the human telomerase catalytic subunit (hTERT) in tumors makes it an interesting candidate vaccine for cancer. hTERT-derived peptide 540-548 (hTERT(540)) has been recently shown to be recognized in an HLA-A*0201-restricted fashion by T cell lines derived from peptide-stimulated peripheral blood mononuclear cells (PBMC) from healthy donors. As a first step to the inclusion of this peptide in immunotherapy clinical trials, it is crucial to assess hTERT(540)-specific T cell reactivity in cancer patients as well as the ability of hTERT-specific CD8(+) T lymphocytes to recognize and lyse hTERT-expressing target cells. Here, we have analyzed the CD8(+) T cell response to peptide hTERT(540) in HLA-A*0201 melanoma patients by using fluorescent HLA-A*0201/hTERT(540) peptide tetramers. HLA-A*0201/hTERT(540) tetramer(+) CD8(+) T cells were readily detected in peptide-stimulated PBMC from a significant proportion of patients and could be isolated by tetramer-guided cell sorting. hTERT(540)-specific CD8(+) T cells were able to specifically recognize HLA-A*0201 cells either pulsed with peptide or transiently transfected with a minigene encoding the minimal epitope. In contrast, they failed to recognize hTERT-expressing HLA-A*0201(+) target cells. Furthermore, in vitro proteasome digestion studies revealed inadequate hTERT processing. Altogether, these results raise questions on the use of hTERT(540) peptide for cancer immunotherapy.

Antigen Presentation↗

PubMed2001

Neuroendocrine consequences of very early weaning in swine.

An experiment was conducted to investigate the consequences of very early weaning of piglets on neuroendocrine variables and growth. Sixty piglets from eight litters were either weaned on Postnatal Day 6 (early weaning, or EW piglets) or left with their dam until normal weaning at Day 28 (control piglets, or C). At Days 5, 7, 11, 14, and 19, urine was collected between 7:00 and 8:00 a.m. for the measurement of catecholamines, glucocorticoids, and creatinine. Compared with C, EW piglets displayed a transient increase in urinary cortisol on the day following separation from their dam (Day 7) (P<.05). Urinary norepinephrine (NE) was three times lower in EW compared to C piglets from Day 7 until Day 14 (P<.01) but there was no difference between the two groups on Day 19. Urinary epinephrine (EPI) did not differ between C and EW piglets on the day after weaning. Thereafter, EW piglets displayed a three times drop in urinary EPI as compared to C piglets until the end of the period (P<.01). Weaning induced an immediate reduction in food intake and growth rate and at Day 28, the body weight of EW piglets was 1.60 kg lower than that of C piglets (P<.0001). In conclusion, weaning of 6-day-old piglets results in a marked and prolonged suppression of the release of catecholamines. This result likely reflects physiological responses to insufficient energy intake after weaning, as reflected also by changes in thermoregulatory behavior. The transient increase in cortisol excretion in weanlings may be caused by both emotional distress and acute food deprivation.

Aging↗

PubMed2001

Distribution and co-localization of choline acetyltransferase and p75 neurotrophin receptors in the sheep basal forebrain: implications for the use of a specific cholinergic immunotoxin.

The basal forebrain cholinergic system is involved in different forms of memory. To study its role in social memory in sheep, an immunotoxin, ME20.4 immunoglobulin G (IgG)-saporin, was developed that is specific to basal forebrain cholinergic neurons bearing the p75 neurotrophin receptor. The distribution of sheep cholinergic neurons was mapped with an antibody against choline acetyltransferase. To assess the localization of the p75 receptor on basal forebrain cholinergic neurons, the distribution of p75 receptor-immunoreactive neurons with ME20.4 IgG was examined, and a double-labeling study with antibodies against choline acetyltransferase and p75 receptor was undertaken. The loss of basal forebrain cholinergic neurons and acetylcholinesterase fibers in basal forebrain projection areas was assessed in ewes that had received intracerebroventricular injections of the immunotoxin (50, 100 or 150 microg) alone, as well as, in some of the ewes treated with the highest dose, with bilateral immunotoxin injections in the nucleus basalis (11 microg/side). Results indicated that choline acetyltransferase- and p75 receptor-immunoreactive cells had similar distributions in the medial septum, the vertical and horizontal limbs of the band of Broca, and the nucleus basalis. The double-labeling procedure revealed that 100% of the cholinergic neurons are also p75 receptor positive in the medial septum and in the vertical and horizontal limbs of the band of Broca, and 82% in the nucleus basalis. Moreover, 100% of the p75 receptor-immunoreactive cells of these four nuclei were cholinergic. Combined immunotoxin injections into ventricles and the nucleus basalis produced a near complete loss (80-95%) of basal forebrain cholinergic neurons and acetylcholinesterase-positive fibers in the hippocampus, olfactory bulb and entorhinal cortex. This study provides the first anatomical data concerning the basal forebrain cholinergic system in ungulates. The availability of a selective cholinergic immunotoxin effective in sheep provides a new tool to probe the involvement of basal forebrain cholinergic neurons in cognitive processes in this species.

Animals↗

PubMed2001

Extensive immunolesions of basal forebrain cholinergic system impair offspring recognition in sheep.

The involvement of the basal forebrain cholinergic system has been extensively investigated in instrumental learning but little is known of its participation in social memory, especially in the memorization of individual traits of a conspecific. The present study tested in sheep its contribution to both instrumental learning and individual offspring recognition. Six weeks before parturition, ewes received injections of a specific cholinergic immunotoxin (ME20.4 IgG-saporin) into the lateral ventricles (150 microg) and in some cases additional immunotoxin injections into the nucleus basalis (11 microg/side). After 3 weeks of recovery, ewes were trained on a classical instrumental visual discrimination task known to be sensitive to cholinergic deficits. The formation of memory of offspring was assessed through both olfactory and visual/auditory recognition tasks. Olfactory recognition was tested by presenting at suckling successively an alien and the familiar lamb at 2 and 4 h after parturition. Visual/auditory recognition of the lamb was performed using a non-olfactory discrimination test between the familiar and an alien lamb after 12 h of mother-young contact. The lesion extent was assessed by counting choline acetyltransferase-immunopositive neurons in the basal forebrain and measuring the density of acetylcholinesterase fibers in different target areas. Results showed that immunotoxic lesions delayed acquisition of the instrumental visual discrimination. Moreover, olfactory recognition of the lamb was severely impaired while visual/auditory lamb recognition was marginally altered. There was no evidence for sensorimotor or motivational deficits. Importantly, impairment was observed in animals for which loss of basal forebrain cholinergic neurons and their efferent fibers was higher than 75%, while striatal cholinergic neurons and Purkinje cells were unaffected. This study provides evidence that the basal forebrain cholinergic system contributes not only to instrumental but also to social learning. In addition, the cholinergic modulation seems of importance for processing visual and olfactory modalities. However, since only extensive lesions affect performance, this indicates that the basal forebrain cholinergic system possesses substantial reserve capacity to sustain cognitive functions.

Acetylcholine↗